Pharmacological Characterization of Platycodin D and Cimicoxib in Terms of Their

Home , Cimicoxib

A Dissertation for the Degree of Doctor of Philosophy

Dynamic and Kinetic Profiles

Department of Veterinary Medicine

Graduate School

Chungnam National University

Tae-Won Kim

Advisor Hyo-In Yun & Mario Giorgi

August, 2014

Pharmacological Characterization of Platycodin D and Cimicoxib in Terms of Their Dynamic and Kinetic Profiles

Advisor Hyo-In Yun & Mario Giorgi

Submitted to the Graduate School in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy

April, 2014

Department of Veterinary Medicine

Graduate School

Chungnam National University

Tae-Won Kim

To Approve the Submitted Dissertation for the Degree of Doctor of Philosophy

By Tae-Won Kim

Title: Pharmacological Characterization of Platycodin D and Cimicoxib in Terms of Their Dynamic and Kinetic Profiles

June, 2014

Committee Chair ______

Committee ______

Graduate School Chungnam National University

CONTENTS

Part I

General introduction ------1

Chapter 1. Anti-hepatitis C viral activity and hepatoprotective effect of standardized Platycodon grandiflorum extract on chemical-induced hepatotoxicity in mice

Abstract ------5 Introduction ------6 Materials and methods ------9 Chemicals and reagents ------9 Preparation of PG ------9 Gastric degradation simulation ------10 HPLC-ELSD analysis ------11 Anti-HCV activity in the HCV replicon model of PG ------11 Cytotoxicity of PG ------13 Polyphenolic content and DPPH radical scavenging activity ------13 Animals and treatments ------14 Serum and hepatic biochemical examination ------15 Histopathological examination ------16 Statistical analysis ------16 Results ------17 HPLC-ELSD fingerprint-analysis ------17 Total phenol content and DPPH radical scavenging activity ------18 Anti-HCV activity of PG ------20

i Effect of PG on serum liver enzymes ------21 Hepatic levels of GSH, TBARS, NO and SOD ------24 Histopathological observations ------27 Discussion ------31 References ------37

Chapter 2. Protective effect of the standardized aqueous extract from the root of Platycodon grandiflorum on bile duct ligation-induced hepatic injury

Abstract ------43 Introduction ------45 Materials and methods ------48 Chemicals and reagents ------48 Animals and treatments ------49 Serum biochemical examination ------51 Oxidant and antioxidant parameters ------51 Measurement of plasma TGF-β1 levels ------51 Histopathological examination ------52 Statistical analysis ------52 Results ------53 Assessment of serum hepatic enzyme activities ------53 Effect of PG on GSH, SOD, TBARS, NO values ------56 Histopathological findings ------59 Serum TGF- β level ------63 Discussion ------64 References ------69

ii Chapter 3. Platycodin D attenuates bile duct ligation-induced hepatic injury and fibrosis in mice

Abstract ------75 Introduction ------76 Materials and methods ------77 Chemicals and reagents ------77 Animals and treatments ------78 Serum biochemical examination ------79 Determination of hepatic GSH, SOD, TBARS, and NO levels ------80 Histopathological examination ------80 Immunohistochemical analysis ------81 Statistical analysis ------82 Results ------82 Serum hepatic enzyme activity ------82 Evaluation of hepatic GSH, SOD, TBARS, and NO levels ------84 Histopathological findings ------86 Immunohistochemical analysis ------89 Discussion ------92 References ------97

Chapter 4. Platycodin D-induced apoptosis in CT26 cells and its synergistic effect with cisplatin on tumor bearing mice

Abstract ------101 Introduction ------102 Materials and methods ------103 Chemicals and reagents ------103 In vitro study ------104

iii Determination of combination index ------104 Cell cycle analysis ------105 Apoptosis assay ------106 Western blot analysis ------107 In vivo study ------107 Animals and treatments ------107 Determination of synergistic index ------109 Serum biochemical examination ------109 Oxidative status in liver and kidney tissue ------110 Pharmacokinetic study ------110 Statistical analysis ------112 Results ------112 In vitro study ------112 Synergism assay ------112 Cell cycle and apoptosis analysis ------115 Western blot analysis ------118 In vivo study ------119 Determination of synergistic index ------119 Serum biochemical examination ------121 Evaluation of GSH, SOD, TBARS, and NO levels ------123 Pharmacokinetic analysis ------125 Discussion ------127 References ------132

General conclusion ------138

iv Part II

General Introduction ------140

Chapter 1. Pharmacokinetic profiles of the novel COX-2 selective inhibitor cimicoxib in dogs

Abstract ------165 Introduction ------166 Materials and methods ------168 Chemical and reagents ------168 Animal studies ------169 Study 1. cimicoxib 2 mg/kg administration (precise dose) ------169 Study 2. cimicoxib 80 mg/dog administration (variation on recommended dose) ------170 Chromatographic conditions ------171 Quantification ------172 PK evaluation ------173 Determination of cimicoxib dosage regimens ------173 Statistical analysis ------174 Results ------174 Study 1. cimicoxib 2 mg/kg administration (precise dose) ------174 Study 2. cimicoxib 80 mg/dog administration (variation on recommended dose) ------177 Determination of cimicoxib dosage regimens ------181 Discussion ------183 References ------189

v Chapter 2. The pharmacokinetics and ex vivo cyclooxygenase selectivity of cimicoxib in fasted and fed horses

Abstract ------193 Introduction ------194 Materials and methods ------196 Chemicals and reagents ------196 Animal studies ------197 Pharmacokinetic evaluation ------199 Chromatographic analysis ------200 Pharmacodynamic assay ------200 Statistical methods ------201 Results ------202 Pharmacokinetics ------202 Pharmacodynamics ------208 Discussion ------210 References ------217

Chapter 3. Pharmacokinetics of the novel COX-2 inhibitor cimicoxib in donkeys

Abstract ------223

Inroduction ------224 Materials and methods ------225 Animal study ------225 Pharmacokinetic analysis ------226 Statistical anaysis ------227 Results ------228

vi Discussion ------230 References ------233

General conclusion ------236

Related publications ------237

vii Part I

General introduction

The root of Platycodon grandiflorum has been used as a traditional folk

remedy for various respiratory diseases such as bronchitis, asthma, pulmonary tuberculosis and inflammation in East Asia (Takagi and Lee,

1972). It was reported to contain carbohydrates (at least 90%), protein

(2.4%), lipids (0.1%) and ash (1.5%) (Lee, 1973). Recently, it has been

reported that the polysaccharides isolated from the root of Platycodon

grandiflorum prevent obesity, hypecholesterolemia, hypertension, diabetes

and hyperlipidemia (Kim et al., 1995; Han et al., 2001; Lee et al., 2011; Lim

et al.,2011). The inulin-type polysaccharides from the roots of Platycodon

grandiflorum demonstrated the selective immune-modulating effects on B

cells and macrophages (Lee et al., 2008). More than 20 triterpenoid saponins

have been found in the roots of Platycodon grandiflorum including

platycosides (A, B, C, D, E and F), platycodins (A, D, D2 and D3),

polygalacin (D and D2) and platyconic acid A (Kim et al., 2001; Dinda et al.,

2010). Triterpenoid saponins from Platycodon grandiflorum have been

shown to exhibit a variety of pharmacological activities, such as anti-

inflammatory, anti-cancer, immune enhancing and hepatoprotective effects

1 (Kim et al., 2001; Khanal et al., 2009; Lee et al., 2008; Xie et al., 2009; Yu and Kim, 2010).

The aim of the present studies was to assess protective effect of the standardized aqueous extract of Platycodon grandiflorum (PG) against liver injury using various chemical and surgical animal models. Moreover, additional studies were performed to confirm the protective effect of platycodin D, which is the most potent saponin in terms of its effect on radical-scavenging activity and various other pharmacological effects.

2 References

Dinda B, Debnath S, Mohanta BC, Harigaya Y. 2010. Naturally occurring triterpenoid saponins. Chem Biodivers. 7: 2327-2580.

Han SB, Park SH, Lee KH, Lee CW, Lee SH, Kim HC, Kim YS, Lee HS, Kim HM. 2001. Polysaccharide isolated from the radix of Platycodon grandiflorum selectively activates B cells and macrophages but not T cells. Int Immunopharmacol. 1: 1969-1978.

Lee JC, Chen WC, Wu SF, Tseng CK, Chiou CY, Chang FR, Hsu SH, Wu YC. 2011. Anti-hepatitis C virus activity of Acacia confusa extract via suppressing cyclooxygenase-2. Antiviral Res 89: 35-42.

Khanal T, Choi JH, Hwang YP, Chung YC, Jeong HG. 2009. Saponins isolated from the root of Platycodon grandiflorum protect against acute ethanol-induced hepatotoxicity in mice. Food Chem. Toxicol. 47: 530-535.

Kim KS, Ezaki O, Ikemoto S, Itakura H. 1995. Effects of Platycodon grandiflorum feeding on serum and liver lipid concentrations in rats with diet-induced hyperlipidemia. J Nutr Sci Vitamino.l 41: 485-491.

Kim YP, Lee EB, Kim SY, Li D, Ban HS, Lim SS, Shin KH, Ohuchi K. 2001. Inhibition of prostaglandin E2 production by platycodin D isolated from the root of Platycodon grandiflorum. Planta Med. 67, 362-364.

Lee EB. 1973. Pharmacological studies on Platycodon grandiflorum A. DC. IV. A comparison of experimental pharmacological effects of crude platycodin with clinical indications of platycodi radix (author’s transl). Yakugaku Zasshi. 93: 1188-1194.

3 Lee KJ, Choi JH, Kim HG, Han EH, Hwang YP, Lee YC, Chung YC, Jeong HG. 2008. Protective effect of saponins derived from the roots of Platycodon grandiflorum against carbon tetrachloride induced hepatotoxicity in mice. Food Chem. Toxicol. 46: 1778-1785.

Lim JH, Kim TW, Park SJ, Song IB, Kim MS, Kwon HJ, Cho ES, Son HY, Lee SW, Suh JW, Kim JW, Yun HI. 2011. Protective effects of Platycodon grandiflorum aqueous extract on thioacetamide-induced fulminant hepatic failure in mice. J Toxicol Pathol. 24: 223-228.

Takagi K, Lee EB. 1972. Pharmacological studies on Platycodon grandiflorum A. DC. 3. Activities of crude platycodin on respiratory and circulatory systems and its other pharmacological activities. Yakugaku Zasshi. 92, 969-973.

Xie Y, Sun HX, Li D. 2009. Platycodin D is a potent adjuvant of specific cellular and humoral immune responses against recombinant hepatitis B antigen. Vaccine 27, 757-764.

Yu JS, Kim AK. 2010. Platycodin D induces apoptosis in MCF-7 human breast cancer cells. J Med Food. 13: 398-305.

4 Chapter 1. Anti-hepatitis C viral activity and hepatoprotective effect of the standardized Platycodon grandiflorum extract on chemical-induced hepatotoxicity in mice

Abstract

The present study aims to evaluate the anti-hepatitis C virus (HCV) activity of standardized aqueous extract from Platycodon grandiflorum (PG) with HCV genotype 1b subgenomic replicon system and investigate its hepatoprotective activity on thioacetamide (TA) and carbon tetrachloride

(CCl4)-induced acute liver damage in mice. PG produced significant hepatoprotective effects against TA and CCl4-induced acute hepatic injury by

decreasing the activities of serum enzymes, nitric oxide and lipid

peroxidation. Histopathological studies further substantiated the protective

effect of PG. Furthermore, PG inhibited the HCV RNA replication with an

EC50 value and selective index (CC50/EC50) of 2.82 µg/mL and above 35.46,

respectively. However, digested PG using a simulated gastric juice showed

poor protective effect against CCl4-induced hepatotoxicity in mice and decreased anti-HCV activity as compared to the intact PG. Although further studies are necessary, PG may be a beneficial agent for the management of acute hepatic injury and chronic HCV infection.

5 Introduction

Polysaccharides obtained from many natural sources represent a

structurally diverse class of macromolecules, and are known to affect a

variety of biological responses. Recently, it has been reported that the polysaccharides isolated from the root of Platycodon grandiflorum prevent obesity, hypecholesterolemia, hypertension, diabetes, immune modulation and hyperlipidemia (Han et al., 2001; Kim et al., 1995; Lee et al., 2011; Lim et al.,2011). Triterpenoid saponins, such as platycodins (A, D, D2 and D3), 2

and 3-O-acetyl polygalacin D2, platyconic acid and platycosides (A, B, C, D,

E and F), were also found in the roots of the Platycodon grandiflorum

(Dinda et al., 2010). These saponins are believed to have a wide range of

health benefits and to prevent chemicals-induced hepatotoxicity (Lee et al.,

2001 and 2008). Although the beneficial effect of Platycodon graniflorum on

acute hepatic failure using various chemical induced hepatic injury models

has been widely studied, little is known about the preventative effect of

Platycodon grandiflorum decoction on thioacetamide (TA) and carbon

tetrachloride (CCl4)-induced acute hepatic injury in mice. In addition,

information on its stability in the stomach has not been investigated and this

information may be important to contribute to the development of

Platycodon grandiflorum extract, which can later be directed to consumers with an increased knowledge of the content and biological activity of this

6 medicinal herb.

The liver plays a central role in transforming and clearing xenobiotics, and

is susceptible to their toxicity (Brattin et al., 1985). An animal model of fulminant hepatic failure induced by the TA and CCl4 has been described

previously (Domitrovic et al., 2009; McCay et al., 1984; Recknagel et al.,

1989; Tunon et al., 2009; Wang et al., 2004). Within a short period of

administration, TA is converted to thioacetamide sulfoxide (TASO) by the

oxidase system. It is further metabolized by cytochrome P450

monooxygenases to thioacetamide sulfone (TASO2), a highly reactive

electrophilic metabolite. Covalent binding of this polar product to cellular

macromolecules exerts hepatotoxicity, leading to generation of reactive

oxygen species (ROS) (Chilakapati et al., 2005; Hunter et al., 1977; Kang et

al., 2008). CCl4 is a potent hepatotoxicant and a single exposure to it can

rapidly lead to severe centrizonal necrosis and steatosis (Brattin et al., 1985;

Domitrovic et al., 2009). During its metabolization, an unstable

trichloromethyl free radical (CCl3) is formed and rapidly converted to

trichloromethyl peroxide (Recknagel et al., 1989; Domitrovic et al., 2009).

These free radical result in the peroxidation of fatty acids found in the phospholipids making up the cell membranes. Lipid peroxide radicals, lipid hydroperoxides and lipid breakdown products develop in this process and

7 each constitutes an active oxidizing agent. Consequently, cell membrane

structures and intracellular organelle membrane structures are completely

broken down (Brattin et al., 1985; Recknagel et al., 1989; Domitrovic et al.,

2009).

Hepatitis C virus (HCV) infection is a major healthcare problem around

the world (Alter, 2007). HCV infection usually runs a chronic infection in an

estimated 70% of HCV patients. Approximately 170 million subjects are

chronically infected with HCV (Feld and Hoofnagle, 2005; Fried et al.,

2002). A chronic HCV infection leads to cirrhosis and hepatocellular

carcinoma and causes 300,000 deaths per year (Alter, 2007). Current

treatment is based on a combination of pegylated interferon (IFN)-α and

ribavirin, which directly inhibits HCV replication and causes progressive

infected cell clearance through intricate and only partly understood

mechanisms (Fried et al., 2002; Feld and Hoofnagle, 2005). Among natural antiviral agents, recent investigations have reconsidered the interest of phyto- polysaccharides, which act as potent inhibitors of different viruses (Ikeda et al., 2006; Seeff et al., 2008; Wagoner et al., 2010).

In the present study, the standardized hot water extract from Platycodon grandiflorum (PG) was tested for its antiviral properties using a cell-based

HCV subgenomic replicon system. We also investigated its protective effect

8 on chemical-induced acute hepatic injury in mice.

Materials and methods

Chemicals and reagents

Thiobarbituric acid reactive substances (TBARS), glutathione (GSH), and nitric oxide (NO) assay kits were purchased from BioAssay Systems

(Hayward, CA, USA). Serum alanine aminotransferase (ALT), aspartate

aminotransferase (AST), blood urine nitrogen (BUN) and creatinine (CRE) test kits were obtained from IDEXX Laboratories (Westbrook, ME, USA).

The superoxide dismutase (SOD) assay kit was obtained from Cayman (Ann

Arbor, MI, USA). CCl4, TA, Folin-Ciocalteu phenol reagent, 2,2-diphenyl-1-

picrylhydrazyl (DPPH) and other chemicals were purchased from Sigma

Chemicals (St. Louis, MO, USA). Acetonitrile and methanol as High-

performance liquid chromatography (HPLC)-grade were obtained from

Mallinckrodt Baker (Phillipsburg, NJ, USA).

Preparation of PG

The standardized Platycodon grandiflorum aqueous extract (PG) was

9 manufactured by SkyHerb Pharmaceuticals (Zhejiang, China) in accordance

with good manufacturing practices (GMP). Briefly, the dried roots of

Platycodon grandiflorum (100 g) were cut into slices and extracted in

distilled water with occasional shaking at 60-90 °C for 6-10 h. The aqueous

extract was then filtered, concentrated under reduced pressure in a rotary evaporator and spray-dried into powder (36 g). It has previously been reported that the aqueous extracts of the roots of Platycodon grandiflorum contain an inulin-type polyfructose, (1→2)-β-D-fructan2,3,13. It also includes deapio-platycoside E, platycoside E, deapio-platycodin D3, platycodin D3, deapio-platycodin D, platycodin D, polygalacin D, 3″-O- acetyl polygalacin D, platycodin A and 2″-O-acetyl polygalacin D. PG was standardized in reference to platycodin D (at least 0.8%) using a validated

HPLC-evaporative light scattering detector (ELSD) method.

Gastric degradation simulation

Simulated gastric juices were prepared by suspending pepsin (1 : 10,000,

ICN) in sterile saline (0.5% w/v) to a final concentration of 3 mg/mL and adjusting to pH 2, and PG was incubated for 2 h at 37°C for preparation of digested PG

10 HPLC-ELSD analysis

HPLC analysis of PG was carried out as previously described (Kim et al.,

2007). In brief, HPLC analysis of PG was performed on a Younglin ACME

9000 (Seoul, Korea) equipped with a Sedex 55 evaporative light scattering detector (ELSD; SEDERE, Alfortville, France). Sample separation was achieved in a Gemini C18 column (100 mm×4.6 mm, 3 µm particle size;

Phenomenex, Torrance, CA, USA) with a precolum (C18, 3.5µm, 2×20 mm) at room temperature. The mobile phase consisted of 0.1% formic acid / methanol / acetonitrile (75: 5: 20, v/v/v; A) and 0.1% formic acid / methanol

/ acetonitrile (70: 5: 25, v/v/v; B) and gradient runs programed as follows: 0-

10 min (0% B), 10-17 min (0-50% B), 25-34 min (50-80% B), 42-52 min

(100% B) and then equilibration with 0% B for 10 min at a flow rate of 1 mL/min. The injection volume was 20 µL. The ELSD was set to a probe temperature of 70°C, a gain of 7, and the nebulizer gas nitrogen adjusted to

2.5 bar.

Anti-HCV activity in the HCV replicon model of PG

The plasmid pNNeo/3-5B replicon of Ikeda et al. (2002) contains the sequence of a similar HCV replicon in which almost all of the NS3-NS5B

11 sequence comprising the 3′cistron is derived from an infectious molecular

clone of the genotype 1b virus, HCV-N (GenBank accession no. AF139594).

It was kindly provided by Prof. Soon-bong Hwang (Ilsong Institute of Life

Science, Hanllym University, Anyang, Korea). An expression vector

harboring HCV replicon proceeded to in vitro transcription and the obtained

HCV replicon was transfected into the Huh7 cells by electroporation. To

select only those cells having the HCV replicon, Huh7 cells were cultured

with Dulbecco’s modified Eagle’s medium (Invitrogen, Carlsbad, CA, USA)

supplemented with 10% of fetal bovine serum, 1% nonessential amino acids,

and 500 µg/mL of geneticin.

HCV replicon-harboring cells were seeded at a low density of 1×104 cells

per well in a 96-well plate and maintained at 37°C and 5% CO2. The next

day, the culture medium was replaced with medium containing serially

diluted compounds in the presence of 2% FBS and 0.1% DMSO. After the

cells were treated for 72 h, total RNA was extracted using a CellAmp Direct

RNA Prep Kit (Korea Biomedical, Seoul, Korea). The HCV RNA levels

were quantified by a quantitative real-time polymerase chain reaction assay using an IQ5 real time PCR detection system (Bio-Rad, Hercules, CA, USA) with HCV-specific primers (5′-GACACTCCACCATAGATCACTC-3′and 5′-

CCCAACACTACTCGGCTAG-3′) and probe (5′-FAM-

12 CCCAAATCTCCAGGCATTGAGCGG-3′BHQ-1). Results were normalized to glyceraldehyde-3-phosphate dehydrogenase gene (GAPDH). Each data point represents the average of at least 3 replicates in cell culture. Relative

HCV RNA reduction was assessed by comparing the level of HCV RNA in compound treated cells to control cells treated with 0.1% DMSO.

Cytotoxicity of PG

The cytotoxicity of PG on Huh7 cells was determined. Cell viability was then assessed with a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay. The 50% cytotoxic concentration (CC50),

defined as the compound concentration that inhibited proliferation of

exponentially growing cells by 50%, was calculated.

Polyphenolic content and DPPH radical scavenging activity

The total phenolic content was determined according to the method

described by Slinkard and Singleton (1977). The sample was accurately weighed and dissolved in a 100 mL brown volumetric flask with distilled water. The standard solution of gallic acid (0-0.06 mg/mL) was prepared.

The standard and the sample (0.40 mL each) were mixed with the Folin-

13 Ciocalteu phenol reagent (0.5 mL) and 20% of Na2CO3 (1.5 mL). The absorbance at 760 nm was measured 20 min after incubation at 30°C using an ultraviolet-visible spectrophotometer.

The free radical scavenging activity of PG was measured using the stable radical DPPH (Blois, 1958). A solution of DPPH (0.1 mM) in ethanol was prepared, and 900 µL of this solution was added to 100 µL of PG solution at different concentrations (0.05-5 mg/mL). The resulting solution was thoroughly mixed by vortexing and left in the dark, and then the absorbance was measured at 517 nm at different times until the reaction reached a steady state. The scavenging activity was determined by comparing the absorbance with that of the blank. When the reaction reached a plateau, the IC50 value of

PG was calculated from the results.

Animals and treatments

Male ICR mice (5-6 week, 32-36 g) were used for this study. They were

obtained from OrinetBio (Sungnam, Korea) and acclimated for 1 week

before experiments. Healthy ICR mice were randomly allocated into 5

groups (n=6) for each model. For TA model, one group served as a control to

orally receive distilled water. The others were orally administered with PG (0,

14 1, 5 and 10 mg/kg) for 3 consecutive days. For CCl4 model, one group served as a control to orally receive distilled water and the others were administered PG (0, 1 and 5 mg/kg bodyweight) and digested PG with simulated gastric juice (10 mg as PG/ kg bodyweight) for 3 consecutive days.

At 3 h after the last treatment, both model mice were intraperitoneally injected with 200 mg/kg of TA (saline for control) or 50% of CCl4 (1 mL/kg

in olive oil; olive oil for control). After 24 h of TA or CCl4 inmjection, mice

were killed by cardiac puncture after being anesthetized lightly with carbon

dioxide. Collected blood samples were separated by centrifuging at 800×g

for 15 min and the serum samples were subjected to biochemical

investigations. Liver samples from each mouse were removed for

histopathological and biochemical examination. The experimental protocols

were approved by the Institutional Animal Care and Use Committee of

Chungnam National University (Daejeon, Korea).

Serum and hepatic biochemical examination

The serum ALT, AST, BUN and CRE activities were determined on a dry chemistry system, the Vettest 8008 blood chemistry analyzer (IDEXX

Laboratories). The content of malondialdehyd (MDA), a terminal product of lipid peroxidation, was measured with the thiobarbituric acid reduction

15 method using a commercially available kit (Quatichrom TBARS assay kit,

Bioassay Systems). The hepatic GSH levels were determined using the

improved DTNB (5,5′-dithiobis-(2-nitrobenzoic acid)) method

(QuantiChrom GSH Assay kit; BioAssay Systems). The hepatic SOD levels were also evaluated using the superoxide dismutase assay kit (Cayman).

Histopathological examination

The liver slices were made from a part of the left lobe and fixed immediately in a 10% buffered formalin phosphate solution, embedded in paraffin, and sectioned at 5 µm. The serial sections were stained with hematoxylin and eosin (H&E) to evaluate the portal inflammation, hepatocellular necrosis and Kupffer cell hyperplasia. To quantify the degree

(%) of hepatic necrosis, liver H&E sections were digitally photographed, and the percentage of necrotic areas was quantified as the mean of 10 randomly selected fields within each slide.

Statistical analysis

Results were expressed as mean ± standard error (SE). The significances of differences among experimental groups were determined using one-way

16 analysis of variance (ANOVA) or the corresponding non-parametric Kruskal-

Wallis test, as required. Where significant effects were found, post-hoc analysis using Turkey’s multiple comparison test or the Mann-Whitney U- test was performed and p<0.05 was considered to be statistically significant.

Results

HPLC-ELSD fingerprint-analysis

On the basis of fingerprint analysis of PG, it contained a large group of oleanane-type triterpenoid saponins, such as deapioplatycoside E, platycoside E, platycodinD3, platycodin D2, platycodin D, platycodin A,

polygalacin D, 3″-O-acetyl polygalacin D, 2″-O-acetyl platycodin D (Fig. 1).

Among these triterpenoid saponins, platycodin D is the major and potent

constituent of triterpenoid saponin found in the root of Platycodon

grandiflorum. Thus, PG was standardized in reference to platycodin D (at

least 0.8%) A number of other non-saponin chemical constituents have been

identified from Platycodon grandiflourm, including α-spinasterol, α-

spinasteryl-β-glucoside, stigmasterol, inulin-type polyfructose, and pectin

(Che, 1992; Oka et al., 1992).

Fig. 1. Representative HPLC chromatograms of triterpenoids from extract of Platycodon grandiflorum and PG. (A), PG; (B), simulated gastric digestion of PG with pepsin-HCl (pH 2.0) for 2 h. The numbers indicate each platycoside: 1, deapio-platycoside E; 2, platycoside

E; 3, platycodinD3; 4, deapio-platycodin D; 5, platycodin D; 6, polygalacin D; 7, 3″-O- acetyl polygalacin D; 8, platycodin A; 9, 2″-O-acetyl polygalacin D.

18 Total phenol content and DPPH radical scavenging activity

The DPPH free radical scavenging activity of PG is shown in Fig. 2 and the calculated EC50 of PG was 0.91 mg/mL. Simulated gastric digestion of

PG with pepsin-HCl (pH 2.0) for 2 h did not show any difference of phenolic content, whereas DPPH radical scavenging activity was significantly decreased in gastric digestion of PG (p<0.05, Fig. 2). Triterpenoids in PG after 2 h of digestion with pepsin under acidic conditions were also slightly decreased to approximately 92.24±4.32% of intact PG, based on the relative amount of platydodin D.

Fig. 2. Total phenolic content and DPPH free radical scavenging activity of PG. (A) total phenolic content of PG before and after gastric digestion with pepsin-HCl (pH 2.0) for 2 h at 37°C. The total phenolic contents were expressed as mg of gallic acid equivalent (GAE) per g of PG. (B) changes in DPPH free radical scavenging activity of PG (500 µg/mL) before and after gastric digestion with pepsin-HCl (pH 2.0) for 2 h at 37°C. Vitamin C (10 µg/mL) served as a positive control for DPPH free radical scavenging activity. Values are expressed as means±SE. *p < 0.05, a significant difference in comparison with gastric digestion of PG (500 µg/mL) with pepsin-HCl (pH 2.0) for 2 h.

19 Anti-HCV activity of PG

The anti-HCV activity of PG was evaluated in Huh7 cells harboring the

HCV genotype 1b replicon. PG caused a dose-dependent inhibition of HCV

RNA replication without affecting cell viability or cell growth. The calculated EC50 of PG was 2.82 µg/mL (Fig. 3). However, the anti-HCV

activity of digested PG with simulated gastric juice significantly decreased

(p<0.05). Cytotoxicity of PG on Huh7 cells was also studied. The CC50

value of PG was above 100 µg/mL and the selective index (CC50/EC50) of

PG in vitro was more than 35.46.

Fig. 3. Suppressive effect of PG on HCV RNA replication. Huh7 cells harboring the HCV genotype 1b replicon were treated with different concentrations (1, 2, 5, 10 and 20 µg/mL) of PG (A) before and after simulated gastric digestion of PG (10 µg/mL) with pepsin-HCl (pH 2.0) for 2 h (B). Treatment with 0.1% DMSO served as a mock control for anti-HCV activity. Total RNA of PG treated Huh7 cells was extracted to quantify HCV RNA levels by RT-qPCR. Cytotoxicity was simultaneously evaluated by MTT assay. Values are expressed as means±SE for triplicate experiments. *p <0.05, a significant difference in comparison with gastric digestion of PG (10 µg/mL) with pepsin-HCl (pH 2.0) for 2 h.

20 Effect of PG on serum liver enzymes

After TA injection, marked increases in the levels of ALT, AST, BUN and

CRE were shown in TA alone treated mice (Table 1). This increase was attenuated in mice that received PG in a dose-dependent manner. Moreover, the group treated with 10 mg/kg of PG showed reduced liver enzyme and renal function marker (BUN and CRE) levels to a greater extent than the positive control group (p<0.05).

In CCl4 model, the CCl4 alone treated group showed increased serum ALT

and AST as compared to the negative control group (p<0.05, Fig. 4). The

elevated levels of serum ALT and AST were reduced in the group treated

with 5 mg/kg bodyweight of PG (p<0.05). Treatment with PG decreased

ALT and AST levels in CCl4 treated mice in a dosedependent manner (Fig. 4).

21 Table 1. Effect of PG on serum biochemical parameters in TA-induced fulminant hepatic failure in mice

AST ALT ALP BUN CRE Groups (Unit/L) (Unit/L) (Unit/L) (mg/dL) (mg/dL)

Negative 97.3±21* 71.5±8.6* 106.8±9.0* 15.4±1.5* 0.3±0.09* control

TA alone 4308.3±246 8351.6±890 167.5±42.5 72.5±12.5 0.8±0.17

TA+ PG 3425.8±722 7465.0±700 166.2±9.4 57.5±17.5 0.6±0.11 (1 mg/kg)

TA+ PG 2912.5±435* 7275.0±1130 150.0±10.8 46.2±10.2* 0.5±0.06* (5 mg/kg)

TA+ PG 2301.1±510* 6312.5±1351* 156.2±11.4 32.5±12.5* 0.4±0.05* (10 mg/kg)

Values are expressed as means ± SEM. The mice in the negative and positive control groups were orally given distilled water. The others were orally administered PG (1, 5, and 10 mg/kg) for three consecutive days. At 3 h after the last oral administration, mice were intraperitoneally injected saline or 200 mg/kg of TA. * Significantly different compared with the positive control group (p < 0.05).

Fig. 4. Effect of PG on liver function in CCl4-induced acute hepatic injury. Mice were given orally PG (0, 1 and 5 mg/kg bodyweight) once daily for 3 consecutive days prior to intraperitoneal injection of 50% CCl4 (1 mL/kg bodyweight in olive oil) or olive oil. Mice in the digested PG with a stimulated gastric juice treated group were given orally digested PG (10 mg/kg bodyweight) once daily for 3 consecutive days prior to intraperitoneal injection of

50% CCl4 (1 mL/kg in olive oil). Values are expressed as means±SE (in surviving animals). ap<0.05, a significant difference in comparison with the control group. bp<0.05, a significant difference in comparison with the CCl4 alone treated group.

23 Hepatic levels of GSH, TBARS, NO and SOD

In TA model, the liver homogenate from the TA alone treated group showed significantly reduced activities of GSH and SOD, whereas increased levels of NO and TBARS (Fig. 5). The hepatic TBARS level in the positive control group was significantly increased by 1.9-fold compared with the level in the negative control group after TA injection (p<0.05). PG attenuated the increased TBARS level in PG pretreated group at 5 and 10 mg/kg

(p<0.05). The level of hepatic NO was remarkably decreased by PG pretreatment in dose-dependent manners, compared with the positive control group. Moreover, the significant decrease in hepatic GSH, which was observed in the positive control group as compared with the negative control group, was significantly reversed by PG pretreatment (p<0.05).

As in TA model, similarly, CCl4 alone treated group showed significant reduced activities of GSH and SOD, whereas increased levels of NO and lipid peroxidation (Fig. 6). The administration of PG showed an increase in

GSH and SOD levels with decreased levels of NO and lipid peroxidation

(Fig. 6). However, for digested PG with stimulated gastric juice under acidic conditions for 2 h, the antioxidant activity was decreased if compared to intact PG (5 mg/kg) treated groups.

Fig. 5. Effect of PG on TBARS (A), NO (B), GSH (C) and SOD (D) content in the TA- induced fulminant hepatic failure. The mice in the negative and positive control groups were orally given distilled water. The others were orally administered with PG (1, 5, and 10 mg/kg) for three consecutive days. At 3 h after the last oral administration, mice were intraperitoneally injected saline or 200 mg/kg of TA. Values are expressed as means ± SEM. *Significantly different compared with the positive control group (p <0.05).

Fig. 6. Effect of PG on TBARS (A), NO (B), GSH (C) and SOD (D) content on CCl4- induced acute hepatic injury. Mice were given orally PG (0, 1 and 5 mg/kg bodyweight)

once daily for 3 consecutive days prior to intraperitoneal injection of 50% CCl4 (1 mL/kg bodyweight in olive oil) or olive oil. Mice in the digested PG with a stimulated gastric juice treated group were given orally digested PG (10 mg/kg bodyweight) once daily for 3 consecutive days prior to intraperitoneal injection of 50% CCl4 (1 mL/kg bodyweight in olive oil). Values are expressed as means±SEM. ap<0.05, a significant difference in comparison with the control group. bp<0.05, a significant difference in comparison with the

CCl4 alone treated group.

26 Histopathological observations

The livers from the negative control group in both TA and CCl4 models

had normal hepatic cells with well- preserved cytoplasm, a prominent nucleus, a nucleolus and visible central veins (Fig. 7 and 8).

The TA alone treated mice showed severe hepatic injury characterized by

centrilobular necrosis, periportal hepatocytic vacoulation and infiltration of inflammatory cells (Fig. 7). Most of the parenchyma of the liver was destroyed in this group of mice, resulting in hepatic failure. Confluent submassive necrosis was noted around the central vein in positive control group mice. Also, numerous neutrophil infiltrations were seen adjacent to necrotic areas. The lower dose of PG (1 mg/kg) did not prevent the toxic effect of TA, with large necrotic areas still present. The other doses of PG (5 and 10 mg/kg) produced a more or less normal lobular pattern with a mild degree of hepatic injury. Scattered spotty necrosis was found, and some inflammatory cells surrounded spotty necrotic foci in mice treated with 5 and

10 mg/kg of PG (Fig. 7). The necrotic area was significantly reduced in PG- treated mice in a dose-dependent manner compared to the positive control group mice (Fig. 7).

In CCl4 model, CCl4 alone treated mice showed extensive, mainly

pericentral necrosis with loss of hepatic architecture, vacuolar fatty change

27 and mild inflammatory cell infiltration comprised predominantly of mononuclear cells and macrophages (Fig. 8).The lower dose of PG (1 mg/kg) did not prevent the toxic effect of CCl4 with large necrotic areas still present.

However, the high dose of PG (5 mg/kg) showed a more or less normal lobular pattern with mild degree of fatty degenerations and necrosis (Fig. 8).

Fig. 7. The histopathological changes in the liver stained with hematoxyline and eosin in the TA-induced hepatotoxicity (×200). The mice in the negative and positive control groups were orally given distilled water. The others were orally administered with PG (1, 5, and 10 mg/kg) for three consecutive days. At 3 h after the last oral administration, mice were intraperitoneally injected saline or 200 mg/kg of TA. In the positive control mice, widespread destruction of the liver architecture was characterized by massive necrosis around the central vein and hemorrhage as well as infiltration of inflammatory cells adjacent to necrotic areas. In contrast, the group of mice treated with TA+10 mg/kg of PG displayed only a mild scattered spotty necrosis and inflammation. (A) Negative control group, (B) positive control group, (C) TA+1 mg/kg of PG group, (D) TA+5 mg/kg of PG group, (E) TA+10 mg/kg of PG group.

Fig. 8. The histopathological changes in liver stained with hematoxyline & eosin in CCl4- induced hepatotoxicity (×200). Mice were given orally PG (0, 1 and 5 mg/kg bodyweight) once daily for 3 consecutive days prior to intraperitoneal injection of 50% CCl4 (1 mL/kg bodyweight in olive oil) or olive oil. Mice in the digested PG with a stimulated gastric juice treated group were given orally digested PG (10 mg/kg bodyweight) once daily for 3 consecutive days prior to intraperitoneal injection of 50% CCl4 (1 mL/kg in olive oil). A, non-treated negative control; B, CCl4 alone treated group; C, CCl4+1 mg/kg of PG treated group; D, CCl4+5 mg/kg of PG treated group; E, CCl4+10 mg/kg of digested PG treated group.

30 Discussion

TA and CCl4 is a centrilobular hepatotoxicant, widely used as a model

compound to induce acute and chronic liver diseases (Kang et al., 2008; Lee

et al., 2008). Both chemicals bioactivated by hepatic microsomal CYP2E1 to

produces hepatotoxic metabolites (Brattin et al., 1985; Brautbar and

Williams, 2002; Kang et al., 2008; Ledda-Columbano et al., 1991). The

covalent binding of the free radical to the cell proteins is considered to be the

initial step in a chain of events that eventually lead to cell necrosis

(Domitrovic et al., 2009; Kang et al., 2008). The results of the present study

showed that chemical injection caused severe acute liver damage in mice,

demonstrated by remarkable elevation of serum AST and ALT levels. The

increased serum levels of AST and ALT are attributed to the damaged

structural integrity of the liver.

CYP2E1 metabolizes a large number of low-molecular-weight compounds, many of which are industrial solvents, chemical additives and drugs (Lieber,

1997; Tanaka et al., 2000). An inhibition of CYP2E1 was associated with a

decrease in toxicity induced by some chemicals, such as acetaminophen, benzene, CCl4 and chloroform (Lee et al., 1996; Tanaka et al., 2000). In

previous studies, a crude saponin extract from Platycodon grandiflorum

resulted in a significant decrease in the CYP2E1-dependent hydroxylation of

31 aniline and showed a hepatoprotective effects on CCl4-induced hepatic injury in mice (Lee et al., 2008). Thus, these results suggest that PG would attenuate the chemical-induced hepatic injury in mice by suppression of

CYP2E1 and the same evidence has been reported by Kang et al. (2008). In addition, this assumption was also confirmed by histological observation.

Perivenous cells contained a higher level of CYP2E1 compared to periportal cells, which reflected zonal differences toxicity (Lee et al., 1996; Tanaka et al., 2000). In the histopathogical examination, perivenous cells were much more severely damaged than periportal cells in positive control group mice, whereas the pretreatment with PG produced only a very mild degree of liver injury in a dose-dependent manner.

GSH is the major non-enzymatic antioxidant and regulator of intracellular redox homeostasis, ubiquitously present in all cell types (Valko et al., 2007).

The detoxification mechanism in chemical-induced hepatotoxicity involves

GSH conjugation of the free radical (Brattin et al., 1985; Brautbar and

Williams, 2002). It was reported that, administration of TA and CCl4 leads to

a significant decrease in the glutathione level (Akhtar and Sheikh, 2013;

Kwak et al., 2011). In addition, lipid peroxidation has been implicated in the

pathogenesis of hepatic injury by the free radical derivatives and is

responsible for cell membrane damage and the consequent release of marker

32 enzymes of hepatotoxicity (McCay et al., 1984; Domitrovic et al., 2009). In this study, pretreatment with PG prior to chemical-induced hepatic injury inhibited lipid peroxidation and reduced chemical-induced hepatic GSH depletion, as well as restoring hepatic Cu/Zn SOD activities in the liver. In addition, administration of PG prevented chemical-induced elevation of lipid peroxidation in a dosedependent manner, indicating its hepatoprotective effect. A sufficient regenerative response of PG by reducing the intensity of liver damage could be also expected.

The current standard care for patients with chronic hepatitis C is combination therapy with pegylated IFN-α and ribavirin (Alter, 2007; Feld and Hoofnagle, 2005; Fried et al., 2002). It is effective in approximately 80% of patients with HCV genotype 2 or 3 infection, but less than 50% of patients with HCV genotype 1, by far the most frequent HCV genotype worldwide

(Feld and Hoofnagle, 2005; Fried et al., 2002). In addition, the combination

therapy is prolonged, costly, and may be associated with adverse effects that

are difficult for many patients to tolerate (Fried et al., 2002). Thus, more

effective, more tolerable, and/or more tailored therapies are required.

Numerous studies recently showed that plant extracts exhibit an inhibitory

effect on HCV enzyme and replication and they have demonstrated their

utility in eradicating chronic hepatitis C through a multitude of

33 hepatoprotective functions in initial trials (Ikeda et al., 2006; Lee et al., 2011;

Seeff et al., 2008; Wagoner et al., 2010; Zuo et al., 2007). Ma et al. (2002) reported that 27 of 44 medicinal herbs showed potent or moderate antiviral activities against respiratory syncytical virus (RSV). Among them,

Platycodon grandiflorum extract exhibited an inhibitory effect against RSV with an IC50 value of 44.1 mg/mL an SI index of 8.0 (Ma et al., 2002). In the

present study, we showed that PG strongly inhibited HCV genotype 1b

replicon replication in Huh7 cells with an EC50 of 2.82 µg/mL and an SI

index of >35.46, although the detailed mechanism has not been clearly

defined. PG may be considered as a potential source of new bioactive

compounds against HCV infection.

There is still debate about the stability and absorption of plant-derived

compounds comprising a wide range of bioactive constituents under

gastrointestinal conditions. Inulin is a polysaccharide with β (2-1) linkages

by which D-fructose is polymerized. Inulin is widely distributed throughout

the plant kingdom and exists as a reserve substance in the tuber or tuberous

roots of plants including Platycodon grandiflorum (Che, 1992; Oka et al.,

1992). Plant-origin inulin is resistant to hydrolysis by pancreatic amylase and

saccharidase in the upper gastrointestinal tract and it reaches the large

intestine unabsorbed and is utilized as a carbohydrate substrate for the

34 growth of indigenous bifidobacteria (Che, 1992; Oka et al., 1992). However, from many other studies on the degradation and metabolization of β- glycosides of plant origin, it is known that the metabolization proceeds mainly via degradation processes already occurring in the gastrointestinal tract (Tawab et al., 2003). Moreover, Shimizu et al. reported that saikosaponins in Bupleurum species converted into their corresponding structural isomers of diene derivatives with acidic treatment or in gastric juice with low pH (Shimizu et al., 1985). Under acidic conditions, ginsenoside Re was mainly hydrolyzed to yield Rg2 and then ginsenoside

Rg2 was transformed to 20(R)-Rg2 by epimerization, or changed to ginsenoside F4 and Rg6 via a dehydration reaction (Kong et al., 2009). In the present study, the treatment group with digested PG using a simulated gastric juice showed poor protective activity against CCl4-induced hepatotoxicity in mice and anti-HCV activity in HCV genotype 1b subgenomic replicon RNA containing Huh7 cells as compared to the PG. On the basis of these results, active ingredients of PG having the anti-HCV and hepatoprotective activity may be not stable in human gastric juice. Thus, PG for clinical use in humans may require a specific drug delivery system such as an enteric coated tablet formulation to minimize the degradation of its active ingredient by low gastric pH and to improve its bioavailability.

35 In conclusion, PG attenuates the chemical-induced acute hepatotoxicity in mice and inhibits HCV RNA replication in Huh7 cells harboring the HCV genotype 1b replicon. Although further studies are necessary, PG may be a beneficial agent for the management of acute hepatic injury and chronic

HCV infection.

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42 Chapter 2. Protective effect of the standardized aqueous extract from the root of Platycodon grandiflorum on bile duct ligation-induced hepatic injury

Abstract

The root of Platycodon grandiflorum (Jacq.) A. DC. (Campanulaceae) has

been widely studied for its hepatoprotective effects against various

hepatotoxicants. The present study evaluated the protective effect of the

standardized aqueous extract of Platycodon grandiflorum (PG) on acute and

chronic cholestasis-induced hepatic injury. For shot-term bile duct ligation

(BDL) model, the mice were allocated into five groups as follows: Sham-

operated, BDL alone, and BDL with PG (1, 5, and 10 mg/kg) treated group.

PG was given for 3 consecutive days before BDL operation and sacrificed

post-24 h of BDL. For long-term BDL model, the rats were divided into four groups as follows: Sham-operated, bile duct ligation (BDL) alone, and BDL

with PG (10 and 50 mg/kg) treated group. PG was given for consecutive 28

days after BDL operation. Both in short- and long-term BDL model,

increased serum alanine aminotransferase (ALT) and aspartate

aminotransferase (AST) in BDL alone group were decreased in PG treated

group in a dose-dependent manner. Especially in short-term BDL model, the

43 10 mg/kg of PG-treated mice showed a 77% decrease of ALT and 56% of

AST as compared with BDL alone. Decreased antioxidant enzyme, glutathione and superoxide dismutase, levels in BDL alone group were elevated in PG-treated groups. PG treatment also attenuated malondialdehyde and nitric oxide levels as compared with BDL alone. In addition, in the long-term BDL model, PG treatment significantly reduced the serum level of fibrogenic cytokine, TGF-b1. Histopathological studies further substantiated the protective effect of PG on long-term BDL-induced hepatic fibrosis in rat. PG may have beneficial effects not only on hepatic injury in acute cholestasis but also on hepatic fibrosis development in patients with chronic hepatic disease.

44 Introduction

Biliary obstruction causes acute hepatocellular injury and leads to

progressive fibrogenesis. It is also characterized by portal tract expansion,

leukocyte infiltration, bile duct and septal proliferation, liver fibrosis and

eventually cirrhosis. Although the pathogenesis of cholestatic liver disease is

uncertain, several studies reported that free radicals may play a role in

cholestatic liver injury (Montilla et al., 2001; Pastor et al., 1997). Bile acids

enhanced the release of free radicals from activated polymorphonuclear and inflammatory cells in cholestatic liver lesions (Dahm et al., 1988).

Furthermore, accumulated lipophilic bile acid during cholestasis impairs the activity of the electron transport chain in the liver mitochondria and reduces its antioxidant capacity (Dueland et al., 1991). Cholestasis has been shown to stimulate the expression of collagen gene transcripts (Lee et al., 1995; Lyons and Schwarz, 1984; Shimizu et al., 1999). Antioxidants have been shown to block stellate cell activation via type I collagen in hepatic fibrogenesis (Lee et al., 1995). Endogenous antioxidant defense mechanisms could play a central role in preventing extensive injury in cholestatic livers

(Neuschwander-Tetri et al., 1996).

The key pathological feature of hepatic fibrosis is the accumulation of extracellular matrix protein. It is well known that the fibrogenic cytokine

45 transforming growth factor-beta (TGF-β) plays a pivotal role in the

development of hepatic fibrosis and cirrhosis through its stimulatory effect

on matrix protein generation and its inhibitory effect on matrix protein

removal (Friedman, 2000; Gressner et al., 2002). Therefore, an approach involving the inhibition of TGF-b1, a key member of the TGF-b superfamily, has been used in several therapeutic approaches to prevent hepatic fibrosis.

However, there is no clinically effective treatment for liver fibrosis, and an effective therapeutic approach against the development of hepatic fibrosis is needed (Breitkopf et al., 2005).

Recently, a report described that Sho-saiko-to, the most popular herbal medicine for the treatment of chronic liver disease in China and Japan, and silymarin, a hepatoprotectant with anti-hepatitis C virus (HCV) activity, significantly reduced the expression of TGF-b1, and platelet-derived growth factor inhibited hematopoietic stem cell (HSC) proliferation and activation in a bile duct ligation (BDL) model of cirrhosis (Chen et al., 2005; Jia et al.,

2001). Herbal therapies and products derived from natural compounds such as silymarin and Sho-saiko-to may well prove to be of use as adjunctive measures in the care of patients with HCV, but there have not yet been any adequately designed clinical trials to support this assumption (Teixeira et al.,

2007; Wagoner et al., 2010).

46 Triterpenoid saponins in the roots of the Platycodon grandiflorum are believed to prevent chemically induced hepatotoxicity (Lee et al., 2004 and

2008). In our previous study, a standardized aqueous extract of Platycodon grandiflorum attenuated thioacetamide-induced fulminant hepatic failure in mice (Lim et al., 2011). Furthermore, the extract attenuated carbon tetrachloride (CCl4)-induced acute hepatotoxicity in mice and inhibited HCV

RNA replication in Huh7 cells harboring the HCV genotype 1b replicon

(Kim et al., 2011). Although the beneficial effect of Platycodon grandiflorumon acute hepatic failure has been widely studied using various chemically induced hepatic injury models, little is known about its ability to prevent hepatic fibrosis in BDL-induced cholestasis. Cholestasis is a common pathological condition that can be reproduced in rodents by surgical ligation of the common bile duct.

The aim of the current study was to investigate the beneficial effects of the standardized Platycodon grandiflorum aqueous extract (PG) on BDL- induced oxidative stress and hepatic fibrosis.

47 Materials and methods

Chemicals and reagents

Assay kits for thiobarbituric acid reactive substances (TBARS), glutathione (GSH) and nitric oxide (NO) were purchased from BioAssay

Systems (Hayward, California, USA). The assay kit for superoxide dismutase (SOD) was obtained from Cayman Chemical (Ann Arbor,

Michigan, USA). Test kits for serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN) and total bilirubin (TBIL) were obtained from IDEXX (Westbrook, Maine, USA).

TGF-b1 enzyme-linked immunosorbent assay (ELISA) kit was purchased from R&D systems (Minneapolis, Minnesota, USA). Other chemicals were obtained from Sigma chemicals (St Louis, Missouri, USA). High- performance liquid chromatography (HPLC)-grade acetonitrile and methanol were obtained from Mallinckrodt Baker (Phillipsburg, New Jersey, USA).

The standardized Platycodon grandiflorum aqueous extract (PG) was manufactured from SkyHerb Pharmaceuticals (Zhejiang, China) in accordance with good manufacturing practices. PG was standardized with reference to its platycodin D content (at least 0.8%) using a validated HPLC assay as described previously (Kim et al., 2007).

48 Animals and treatments

Male Crl:CD1(ICR) mice (5-6 weeks; 32-36 g) and Sprague-Dawley (SD)

rats (7-8 week; 250-300 g) were used for short- and long-term BDL study, respectively. They were obtained from Orient Bio (Seongnam, Korea) and acclimated for 1 week before experiments. They were housed under standard

laboratory conditions (12 h light/dark cycle, 22-23°C) with standard mouse

food pellet and water ad libitum. For short-term BDL study, mice were

randomly allocated into 5 groups as follows: Group 1 (sham-operated, n = 5),

Group 2 (BDL alone, n = 5), Group 3 (BDL and 1 mg/kg of PG treated, n =

5), Group 4 (BDL and 5 mg/kg of PG treated, n = 5), and Group 5 (BDL and

10 mg/kg of PG treated, n = 5). The sham-operated group and BDL alone

group were orally administered distilled water, and the others were orally

administered with PG (1, 5, and 10 mg/kg) for 3 consecutive days before

BDL operation. At 3 h after the last treatment, common BDL was performed

under anesthesia with intraperitoneal injection of zolazepam and tiletamine

combination (Zoletil 50®, Virbac, Carros, France). After midline laparotomy,

the duodenum was retracted, and common bile duct was carefully double

ligated with a 6-0 nylon suture and dissected. Sham-operated mice received

an identical laparotomy and isolation of the common bile duct without

ligation. After 24 h of BDL, mice were sacrificed by cardiac puncture under

49 CO2 anesthesia.

For long-term model, rats were randomly allocated into 4 groups as

follows: Group 1 (sham-operated, n = 6), Group 2 (BDL alone, n = 6), Group

3 (BDL and 10 mg/kg of PG treated, n = 6), and Group 4 (BDL and 50

mg/kg of PG treated, n = 6). After anesthetization, the common bile duct was

ligated using double ligatures with 4-0 silk in all group except for sham-

operated group. After surgery, BDL rats orally received distilled water or PG

(10 and 50 mg/kg/day) for 28 consecutive days. PG was dissolved in distilled

water. Sham-operated rats (n = 6) were also operated by making an

abdominal incision without a ligation and were given distilled water orally

for 4 weeks. Twenty eight days after the BDL operation, the rats were killed

by cardiac puncture after being anesthetized lightly with carbon dioxide.

Blood samples were collected and serum was separated by centrifuging at

800 g for 15 min, and the serum samples were subjected to biochemical

investigations. Liver samples from each mouse were taken for

histopathological and biochemical examinations. Left lobes of liver were

fixed immediately with 10% buffered formalin phosphate solution. Serum samples and other parts of livers were stored at -70°C until analysis. The experimental protocols were approved by the Institutional Animal Care and

Use Committee of Chungnam National University (Daejeon, Korea).

50 Serum biochemical examination

The serum levels of ALT, AST, BUN and TBIL were determined using a

dry chemistry system, VetTest 8008 blood chemistry analyzer (IDEXX,

Westbrook, Maine, USA).

Oxidant and antioxidant parameters

The level of SOD was measured by using the tetrazolium salt assay

(Superoxide Dismutase Assay Kit, Cayman Chemical Company, Ann Arbor,

MI, USA). The content of malondialdehyde, a terminal product of lipid

peroxidation, was measured with the thiobarbituric acid reduction method

using a commercially available kit (QuatiChrom TBARS Assay kit). The

hepatic GSH level was determined using the improved DTNB (5,5’- dithiobis-[2-nitrobenzoic acid]) method (QuantiChrom GSH Assay kit). NO was measured by improved Griess method (QuantiChrom NO Assay kit).

Measurement of plasma TGF-β1 levels

Plasma TGF-β1 levels were measured using an ELISA kit (R&D systems) according to the manufacturer’s guidelines.

51 Histopathological examination

Liver slices were obtained from a part of the left lobe and fixed immediately in a 10% buffered formalin phosphate solution, embedded in

paraffin and cut into 5 μm sections. Four random samples of each liver

sample were stained with hematoxylin and eosin (H&E). Additionally,

Masson’s trichrome staining was performed to facilitate the evaluation of periportal fibrotic bands. The degree of fibrosis was scored according to a

modified histological activity index (HAI) (Ishak et al., 1995; Knodell et al.,

1981), which included portal inflammation, focal necrosis, confluent

necrosis, piecemeal necrosis, apoptosis, focal inflammation and fibrosis. The

number of biliary canals in five portal sites for each section was also noted.

The samples were examined without prior knowledge of the clinical

information and biochemical results.

Statistical analysis

Results were expressed as mean ± SEM. The significance of the

differences among the experimental groups was determined using one-way

analysis of variance or the corresponding nonparametric (Kruskal-Wallis)

test, as required. Where significant effects were found, post hoc analysis was

52 performed using Tukey’s multiple comparison test or Mann-Whitney U test, and p<0.05 was considered statistically significant.

Results

Assessment of serum hepatic enzyme activities

In short-term BDL study, the levels of serum ALT and AST in the BDL alone group significantly increased to 395.2 ± 90.0 and 266.0 ± 45.6 Unit/L compared with the sham-operated group (Fig. 1; p<0.05). However, PG (1, 5, and 10 mg/kg) pretreatment dose-dependently attenuated these BDL-induced elevations in serum ALT and AST levels up to 77% and 56%, respectively

(Fig. 1). In addition, in long-term BDL study, liver injury was assessed by determining the serum levels of liver enzymes including ALT, AST, CRE and

TBIL (Table 1). As shown in Table 1, the serum levels of AST, ALT, CRE and TBIL were significantly higher in BDL rats than in sham-operated rats

(p<0.05) and PG treatment at a dose of 50 mg/kg to the BDL group reduced these values (p<0.05).

Fig. 1. Effect of PG on liver function in the bile duct ligation (BDL)-induced acute hepatic injury. Mice were given orally PG (0, 1, 5, and 10 mg/kg) once daily for 3 consecutive days prior to BDL. Values are expressed as means ± standard error (SEM). *p < 0.05, a significant difference in comparison with the positive control group.

54 Table 1. Effect of PG on serum biochemical parameters in BDL-induced cholestasis in rats.

Groups ALT (U/L) AST (U/L) AST/ALT ratio BUN (mg/dL) TBIL (mg/dL)

Sham-operated 65.50 + 7.6a 60.75 + 9.5a 0.93 + 0.09a 10.75 + 0.48a 0.52 + 0.05a

BDL alone 112.00 + 5.3b 541.75 + 94.0b 4.75 + 0.65b 12.25 + 0.25b 7.25 + 0.64b

BDL + PG (10 mg /kg) 116.50 + 13.6b 540.50 + 92.9b 4.57 + 0.35b 11.75 + 0.48b 5.63 + 0.34b

BDL + PG (50 mg /kg) 89.33 + 4.6a,b 315.33 + 25.8a,b 3.52 + 0.17a,b 10.25 + 0.85 3.48 + 0.57a,b

ALT: alanine aminotransferase; BDL: bile duct ligation; AST: aspartate aminotransferase; BUN: blood urea nitrogen; TBIL: total bilirubin. Values are expressed as means + SEM (in survival animals). After BDL operation, the rats in PG-treated groups were orally given PG (0, 10 and 50 mg/kg) once a day for 4 weeks. The sham-operated groups were orally given the same volume of saline as the BDLtreated animals that received PG. ap < 0.05, a significant difference when compared with the group treated with BDL alone. bp < 0.05, a significant difference when compared with the sham-operated group.

55 Effect of PG on GSH, SOD, TBARS, NO values

To evaluate the possible effects of PG on oxidative stress status, lipid peroxidation products, GSH and SOD, were measured in liver homogenates.

In short-term BDL study, the BDL alone group, significantly reduced

activities of GSH and SOD were shown, whereas the levels of NO and

TBARS were increased as compared with the sham-operated group (Fig. 3; p<0.05). Decreased GSH values by BDL were increased to 5.6 ± 0.94, 5.9 ±

1.36, and 6.7 ± 0.17 nmole/mg of protein in the PG-treated group at 1, 5 and

10 mg/kg, respectively. Similarly, SOD levels were also increased in the PG- treated group in a dose-dependent fashion. The level of hepatic NO was remarkably decreased, ranging from 32 to 50%, by PG pretreatment. PG also attenuated the increased TBARS level in PG-treated group. As in short-term study, long-term BDL group showed significantly reduced GSH and SOD activity, together with increased levels of NO and TBARS in the group treated with BDL alone (Fig. 4). The hepatic TBARS level in the positive control group was significantly increased by 1.9-fold than that in the sham- operated group (p<0.05). PG (50 mg/kg) attenuated the increased TBARS level in the BDL group (p<0.05). Hepatic NO levels remarkably decreased by PG treatment and PG also significantly ameliorated the significant decrease in hepatic GSH levels, which were observed in the group treated

56 with BDL alone (p<0.05).

Fig. 3. Effect of PG on the hepatic GSH (A), SOD (B), lipid peroxidation (C) and NO (D) content in the bile duct ligation (BDL)-induced acute hepatic injury. Mice were given orally PG (0, 1, 5 and 10 mg/kg) once daily for 3 consecutive days prior to BDL. Values are expressed as means ± SEM. *p<0.05, a significant difference in comparison with the positive control group.

Fig. 4. Effect of PG on TBARS (A), NO (B), GSH (C) and SOD (D) content in the BDL- induced cholestasis. After BDL operation, the rats in PG-treated groups were orally given PG at 0, 10 and 50 mg/kg body weight/day for 4 weeks. The sham-operated groups were orally given with the same volume of saline as the BDL-treated animals that received PG. Values are expressed as mean ± SEM. ap < 0.05, a significant difference when compared with the sham-operated group. bp < 0.05, a significant difference when compared with the group treated with BDL alone. TBARS: thiobarbituric acid reactive substances; NO: nitric oxide; GSH: glutathione; SOD: superoxide dismutase; BDL: bile duct ligation.

58 Histopathological findings

In short-term study, sham-operated animals, there were no microscopic

structural changes of liver from normal hepatic architecture (Fig. 5). The

liver from the BDL alone group showed significant histopathological

alteration of liver, such as mild ductal proliferation, polymorphic nucleus,

hepatocyte necrosis, and inflammatory cell infiltration. In the low dose, PG

(1 mg/kg) did not reduce the BDLinduced histopathlogical alteration, with

mild ductal proliferation and inflammatory cell infiltration still present. The

higher dose PG (5 and 10 mg/kg) treated groups showed much less necrosis of hepatocyte and infiltration of inflammatory cell than the BDL alone group.

The HAI scores for long-term BDL liver of the different experimental

groups are summarized in Table 2. The livers of the animals in the sham-

operated group had normal hepatic cells with well-preserved cytoplasm, a

prominent nucleus, a nucleolus and visible central veins. In contrast, the

livers collected from BDL-operated rats showed typical histological changes,

which were characterized by bridge fibrosis formation in the portal area

prominent ductular proliferation, edema and mild-to-moderate polymorphonuclear leukocyte and lymphocyte infiltration in the periportal region (Fig. 6). The long-term BDL rats that were treated with PG (50 mg/kg) had markedly reduced histological collagen accumulation, ductular

59 proliferation, edema and inflammation than did the group treated with BDL

alone (Fig. 6).

Fig. 5. Histopathological changes of the liver stained with hematoxyline and eosin on the bile duct ligation (BDL)-induced liver injury (×100). Mice were given orally PG (0, 1, 5, and 10 mg/kg) once daily for 3 consecutive days prior to BDL. (A) nontreated sham- operated group; (B) nontreated BDL group; (C) PG (1 mg/kg) treated BDL group; (D) PG (5 mg/kg) treated BDL group; (E) PG (10 mg/kg) treated BDL group. Arrows indicate the bile duct proliferation and hepatocyte necrosis.

60 Table 2. Scores for necor inflammation (focal necrosis, confluent necrosis, piecemeal necrosis, focal and portal inflammation and apoptosis) and fibrosis using modified HAI grading system.

Groups Inflammation Fibrosis Number of biliary canals

Sham-operated 0.75 + 0.48a 0.00 + 0.00a 36.75 + 3.75a

BDL alone 10.75 + 1.25b 4.00 + 0.41b 352.00 + 38.08b

BDL + PG (10 mg /kg) 9.50 + 0.96b 3.75 + 0.48b 322.75 + 40.38b

BDL + PG (50 mg /kg) 6.00 + 0.91a,b 2.00 + 0.41a,b 268.50 + 22.51

BDL: bile duct ligation; HAI: histological activity index. Values are expressed as means ± SEM (in survival animals). After BDL operation, the rats in PG-treated groups were orally given PG at 0, 10 and 50 mg/kg body weight/day for 4 weeks. The sham-operated groups were orally given the same volume of saline as the BDL-treated animals that received PG. ap < 0.05, a significant difference when compared with the group treated with BDL alone. bp < 0.05, a significant difference when compared with the sham-operated group.

Fig. 6. The histopathological changes in the liver in BDL-induced cholestasis stained with H&E and Masson’s trichrome stain (×40). After BDL operation, the rats in PG-treated groups were orally given PG at 0, 10 and 50 mg/kg body weight/day for 4 weeks. The sham-operated groups were orally given with the same volume of saline as the BDL-treated animals that received PG. The livers of the sham-operated rats had normal histological features of liver, but the livers collected from BDL-operated rats showed typical histological changes, which were characterized by bridge fibrosis formation in the portal area prominent ductular proliferation (thin arrows), mild-to-moderate PNL and lymphocyte infiltration (thin arrows) and piecemeal necrosis (thick arrows) in the periportal region. Asterisk indicates bridge fibrosis by ductular proliferation and collagen accumulation in portal area. BDL: bile duct ligation; H&E: hematoxylin and eosin; PNL: polymorphonuclear leukocyte.

62 Serum TGF- β level

The plasma fibrogenic cytokines, TGF-β, which play important roles in

the activation of hepatic stellate cells, were significantly increased by 2.2-

fold in the group treated with BDL alone (Fig. 7). However, TGF- β1

production was significantly reduced in PG-treated BDL rats than in the rats

treated with BDL alone.

Fig. 7. Serum level of TGF-b1 in the BDL-induced cholestasis. After BDL operation, the rats in PG-treated groups were orally given PG at 0, 10 and 50 mg/kg body weight/day for 4 weeks. The sham-operated groups were orally given the same volume of saline as the BDL- treated animals that received PG. Values are expressed as means ± SEM. ap < 0.05, a significant difference when compared with the sham-operated group. bp < 0.05, a significant difference when compared with the group treated with BDL alone. TGF-β1: transforming growth factor-beta 1; BDL: bile duct ligation.

63 Discussion

One of the standard animal models for research on cholestasis is the total

ligation of the common BDL model (Georgiev et al., 2008). During bile duct

obstruction and the subsequent cholestasis, increased concentrations of bile

acids and toxins in the liver result in the activation of Kupffer and hepatic

stellate cells (Gaillard et al., 1991). In the early stage of BDL, even 8 h after

BDL, the liver presented clusters of injured hepatocytes and initiation of

cholangiocellular proliferation in the large bile duct (Georgiev et al., 2008;

Portincasa et al., 2007). In the present study, levels of serum liver enzymes in the short-term BDL alone group were significantly increased by BDL in comparison with the sham-operated group, and these elevated enzyme levels

were decreased by pretreatment of PG. Serum levels of ALT, AST and TBIL

are classical markers of obstructive cholestasis in the clinical setting.

Clinically, the AST to ALT ratio is significantly elevated in patients with

advanced fibrosis (Su et al., 2009). In long-term BDL study, elevated serum

levels of ALT, AST and TBIL, together with the AST/ALT ratio were

observed in rats treated with long-term BDL alone, but these elevations were

ameliorated in the PG-treated BDL groups.

BDL induces a type of liver fibrosis that etiologically and pathogenically

resembles the biliary fibrosis in human (Serviddio et al., 2004). The bile

64 stasis and backpressure that occur because of the obstruction induce proliferation of the duct epithelial cells and looping and reduplication of the ducts, which is termed ‘‘bile duct proliferation’’. The hepatocellular degeneration and death observed in cholestasis have been reported to be related to the retention of toxic bile salts, which leads to oxidative stress via the entry of nicotinamide adenine dinucleotide phosphate oxidase isoforms into the immune activation pathway (Trauner et al., 1998). It has been suggested that hepatocyte apoptosis and/or necrosis may be associated with the activation of Kupffer cells, which release TGF-β and tumor necrosis factor-a (Friedman, 2000; Gressner et al., 2002; Lee et al., 1995).

Furthermore, TGF-β is upregulated in liver fibrosis and known to cause hepatic satellite cell proliferation and the production of collagen (Gressner et

al., 2002). Increased TGF-β expression has been reported in bile duct-

obstructed liver tissue and it leads to the pathological accumulation of

extracellular matrix protein (Canbakan et al., 2009; Reyes-Gordillo K et al.,

2008). Intracellular oxidative stress is a major contributor to fibrogenesis,

and recent studies have shown the induction of profibrogenic TGF-β1 by

peroxide radicals, thereby providing a rationale for the use of intracellular

antioxidants as adjunctive antifibrotic agents (Breitkopf et al., 2005; Teixeira

et al., 2007). Several promising drugs derived from plants may be useful in

antifibrotic combination therapy. Silibinin from milk thistle (Silybum

65 marianum) was shown to reduce hepatic collagen accumulation in rat biliary

fibrosis secondary to bile duct occlusion and baicalein from Sho-saiko-to

also showed antifibrotic properties in activated hepatic satellite cell in vitro

(Chen et al., 2005; Jia et al., 2001; Shimizu et al., 1999).

PG ameliorated hepatotoxic chemical-induced hepatic injury, which inhibited the production of excessive ROS and strongly inhibited HCV genotype 1b replicon replication in Huh7 cells (Lim et al., 2011; Kim et al.,

2011). In addition, triterpenoid saponins from Platycodon grandiflorum

significantly prevented the elevation of hepatic alpha1 (I) procollagen

messenger RNA and alpha-smooth muscle actin expressions via HSC

inactivation in CCl4-intoxicated rats.

Recent findings suggest that the Wnt/b-catenin pathway is strongly

involved in the normal activation and proliferation of adult hepatic

progenitor cells in both acute and chronic human liver diseases (Spee et al.,

2010). Canonical Wnt/b-catenin signaling also suppresses the expression and

promoter activation of peroxisome proliferator-activated receptor γ (PPARγ)

in HSC transdifferentiation. Moreover, PPARγ agonists inhibit HSC

activation and counteract liver fibrosis in models of cholestasis (Fiorucci et

al., 2005; Galli et al., 2002; Yang et al., 2006). In addition, some studies

have shown that PPARγ agonist, such as rosiglitazone, improves steatosis

66 and transaminase levels, which is an effect related to an improvement in insulin sensitivity (Galli et al., 2002). It was recently reported that

Platycodon grandiflorum extract and its triterpenoid saponins enhanced hepatic and adipocyte insulin sensitivity, possibly by activating the PPARγ

(Galli et al., 2002; Kim et al., 2009; Kwon et al., 2009 and 2012). Kwon et al. (2012) reported that triterpenoid saponins including platycoside E, platycodin D2, platycodin D3, platyconic acid and platycodin D may be

potential PPARγ activators and possible agonists and reduce triglyceride

accumulation in the liver by enhancing hepatic insulin sensitivity (Kwon et al., 2012). In addition, Platycodon grandiflorum extracts improved nonalcoholic steatohepatitis mediating the anti-steatohepatitis action of the

PPARγ (Kim et al., 2009; Noh et al., 2010). In accordance with the previous

data, PG in the present study inhibited lipid peroxidation and reduced BDL-

induced hepatic GSH depletion as well as restored hepatic Cu/Zn SOD

activities in the liver. The level of TGF-β1 was significantly increased in the

group treated with BDL alone, whereas it was significantly ameliorated in

the BDL group treated with PG. Consistently, many histopathological

features of cholestasis such as extensive bile duct proliferation, the formation

of periportal fibrosis, focal necrosis, confluent necrosis, piecemeal necrosis,

focal and portal inflammation, bile duct proliferation and fibrosis were

observed in the group treated with BDL alone. These histopathological

67 features associated with cholestasis were attenuated by PG, although PG did

not significantly decrease the number of bile ducts among the BDL groups.

In conclusion, the protective effect of PG against BDL-induced hepatic

fibrosis may be mainly associated with the ability of this extract to attenuate oxidative stress and to inhibit TGF-β1. The capacity of PG to attenuate oxidative stress and suppress the release of TGF-β1, and the advantage of it being a nontoxic natural product are important factors that make this extract an interesting candidate for preventing and treating human hepatic fibrosis and cirrhosis.

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74 Chapter 3. Platycodin D attenuates bile duct ligation-induced hepatic injury and fibrosis in mice

Abstract

Platycodin D (PD) is the major triterpene saponin in the root of

Platycodon grandiflorum. The aim of the present study was to evaluate the

protective effects of PD on bile duct ligation (BDL)-induced cholestasis in

mice. Mice were allocated to five groups: sham, BDL alone, and BDL with

PD treatment at 1, 2, and 4 mg/kg. PD was administered to the mice for 28 consecutive days after the BDL operation. PD treatment of BDL-operated

mice decreased serum alanine aminotransferase, serum aspartate

aminotransferase, and total bilirubin levels by up to 37%, 31%, and 41%,

respectively, in comparison with the levels in mice that underwent BDL

alone. PD treatment attenuated oxidative stress, as evidenced by an increase

in antioxidative enzyme levels glutathione and superoxide dismutase

together with a decrease in lipid peroxidation and oxidative stress indices

levels of malondialdehyde and nitric oxide. Histopathological studies further

confirmed the protective effects of PD on cholestasis-induced hepatic injury

and liver fibrosis in mice. In addition, nuclear factor-kappa B and inducible

nitric oxide synthase levels significantly decreased after PD treatment, as did

75 the levels of hepatocyte apoptosis. Taken together, these results suggest that

PD treatment might be beneficial in cholestasis-induced hepatotoxicity.

Introduction

Cholestasis can be defined as bile flow impairment resulting from the obstruction of the bile duct or a functional defect in bile formation (Arrese and Trauner, 2003; Clavien et al., 2007). In the early stages of cholestasis, toxic bile salts damage hepatocytes due to their surfactant properties and the damaged hepatocytes generate reactive oxygen species (ROS) (Copple et al.,

2010). ROS not only amplify inflammation, but also stimulate hepatic stellate cells to promote fibrosis by lipid peroxidation. Therefore, reduction of oxidative stress can play an essential role in the treatment of obstructive cholestasis. Demirbilek et al. (2007) reported that, 3-hydroxy-

3methylglutarly coenzyme A (HMG-Co-A) reductase inhibitor, a statin that is present in cholesterol-lowering drugs and has an antioxidant effect, can be useful in cholestasis patients (Demirbilek et al., 2007).

Triterpenoid saponins from Platycodon grandiflorum have been shown to exhibit a variety of pharmacological activities (Khanal et al., 2009; Kim et al., 2001; Lee et al., 2008; Xie et al., 2009; Yu and Kim, 2010). Among these

76 terpenoid saponins, platycodin D (PD) is the most potent in terms of its

effect on peroxyl radical-scavenging activity and various other

pharmacological effects (Kim et al., 2001; Ryu et al., 2012). In addition, PD

has been reported to inhibit HMG-Co-A reductase, a key enzyme that catalyzes the ratelimiting step in the cholesterol biosynthetic pathway (Wu et

al., 2011).

The present study investigated the hepatoprotective effect of PD on chronic cholestasis-induced hepatic injury and fibrosis in bile duct ligation

(BDL)-operated mice.

Materials and methods

Chemicals and reagents

PD (approximately 98% purity) from Platycodon grandiflorum roots was purchased from Innoten (Seoul, Korea). The assay kits for superoxide dismutase (SOD), thiobarbituric acid reactive substances (TBARS), and glutathione (GSH) were obtained from Cayman (Ann Arbor, MI, USA). The assay kit for nitric oxide (NO) was purchased from BioAssay Systems

(Hayward, CA, USA). Serum alanine aminotransferase (ALT), aspartate

aminotransferase (AST) and total bilirubin (TBIL) test kits were obtained

77 from IDEXX (Westbrook, ME, USA). The terminal deoxynucleotidyl

transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL)

staining and immunostaining kits were purchased from Millipore (Billerica,

MA, USA) and Vector Laboratories (Burlingame, CA, USA), respectively.

The anti-nuclear factor-kappa B (NF-κB) p65 and anti-inducible nitric oxide synthase (iNOS) antibodies were purchased from Abcam (Cambridge, UK).

All other reagents were from Sigma Chemicals (St. Louis, MO, USA).

Animals and treatments

Male Crl:CD-1 (ICR) mice (6-7 week) were obtained from Orient Bio

(Seongnam, Korea) and acclimated for 1 week before the experiments. The

mice were housed under a 12 h light/dark cycle (22-23°C) and provided with standard mice food pellets and water ad libitum. The mice were randomly allocated into 5 groups as follows: group 1 (sham, n = 5), group 2 (BDL alone, n = 5), group 3 (BDL and 1 mg/kg of PD, n = 5), group 4 (BDL and 2 mg/kg of PD, n = 5), and group 5 (BDL and 4 mg/kg of PD, n = 5). BDL was performed under anesthesia with an intraperitoneal injection of a combination of zolazepam and tiletamine (Zoletil 50; Virbac, Carros, France).

After midline laparotomy the duodenum was retracted, and the common bile duct was carefully double-ligated with a 6-0 nylon suture and dissected.

78 Sham group mice received an identical laparotomy and isolation of the common bile duct without ligation. After the BDL operation, the sham and

BDL alone groups were orally administered distilled water and the other groups were orally administered PD (1, 2, and 4 mg/kg) for 28 consecutive days. PD was dissolved in distilled water and the dosing volume was 5 mL/kg body weight. Twenty eight days after the BDL operation, the mice were sacrificed by cardiac puncture under anesthesia with carbon dioxide.

Blood was collected and the serum was separated by centrifugation at 800 g for 15 min for the biochemical investigations. Liver samples were taken from each mouse for the histopathological and biochemical examinations. The left lobes of the liver were fixed immediately with a 10% buffered formalin phosphate solution. The serum samples and the other parts of the liver were stored at -70°C until analysis. The experimental protocols were approved by the Institutional Animal Care and Use Committee of Chungnam National

University (Daejeon, Korea).

Serum biochemical examination

The serum ALT, AST and TBIL activities were determined on a dry chemistry system: the VetTest 8008 blood chemistry analyzer (IDEXX).

79 Determination of hepatic GSH, SOD, TBARS, and NO levels

The hepatic GSH level was determined using the improved DTNB [5,50- dithiobis-(2-nitrobenzoic acid)] method. The SOD level was measured using the tetrazolium salt assay. The levels of malondialdehyde (MDA), the terminal product of lipid peroxidation, were measured with the thiobarbituric acid reduction method using a commercially available kit. NO levels were measured by the improved Griess method. All assays were performed according to the manufacturer’s protocols.

Histopathological examination

Liver slices were taken from a part of the left lobe in each group, fixed in a 10% buffered formalin phosphate solution, and embedded in paraffin. The block was cut into 5 µm sections and stained with hematoxylin and eosin

(H&E) and Masson’s trichrome stain. The typical histopathological alterations such as portal inflammation, focal necrosis, piecemeal necrosis, ductular proliferation, edema and fibrosis were evaluated with H&E stained liver section. The degree of fibrosis were evaluated and graded with

Masson’s trichrome stained liver sections according to the modified Ishak system as follows: 0, no fibrosis; 1, fibrous expansion of some portal tracts,

80 with or without short fibrous septa; 2, fibrous expansion of most portal tracts,

with or without short fibrous septa; 3, fibrous expansion of portal tracts with

occasional portal to portal bridging; 4, fibrous expansion of portal tracts with

marked portal to portal bridging as well as portal to central; 5, marked

bridging portal to portal and/or portal to central with occasional nodules; 6,

cirrhosis, probable or definite (Ishak et al., 1995; Knodell et al., 1981).

Immunohistochemical analysis

Apoptotic nuclei were detected with the TUNEL method using an

apoptosis detection kit (ApopTag Peroxidase In Situ Apoptosis Detection Kit;

Millipore). Immunostaining for NF-κB p65 and iNOS was performed with

anti-NF-κB p65 and anti-iNOS antibodies (Abcam, Cambridge, UK) using

the Vectastain Elite ABC Rabbit IgG Kit (Vector Laboratories) according to

the manufacturer’s protocol. The color development steps were carried out

using 3,30-diaminobenzidine (DAB) as a chromogen which produces a dark

brown color in positive staining. The immunostaining for NF-κB was scored according to its intensity: 0, no specific staining (no cytoplasmic and nuclear staining); 1, weakly positive (mild cytoplasmic staining and no nuclear staining); 2, moderately positive (moderate cytoplasmic staining and present or absent nuclear staining); and 3, strongly positive (severe cytoplasmic and

81 nuclear staining) (Demirbilek et al., 2007). Image analysis for the

quantification of TUNEL-positive stained cell number and relative intensity

of iNOS staining was performed using Image J (National Institutes of Health,

Bethesda, MD, USA) in 10 randomly selected microscopic fields per

specimen.

Statistical analysis

The results were expressed as the mean ± standard error (SEM).

Significant differences among the experimental groups were determined using the one-way analysis of variance (ANOVA) test or the non-parametric

Kruskal-Wallis test. Where significant effects were found, post-hoc analyses

using the Tukey’s test or Mann-Whitney U-test were test was performed and p<0.05 was considered statistically significant.

Results

Serum hepatic enzyme activity

Serum ALT and AST levels significantly increased to 271.4 ± 16.88 and

307 ± 10.29 U/L in mice that received BDL alone group animals (p < 0.05;

82 Table 1). PD administration reduced the cholestasis-induced increase in ALT

and AST levels in a dosedependent manner. Similarly, BDL alone mice also showed a significant elevation in their TBIL concentration in comparison

with the levels in the sham-treated group (p<0.05; Table 1). The levels of

TBIL in the PD-treated groups (1, 2, and 4 mg/kg) were markedly lower than

those in the group that received BDL alone (26%, 31%, and 41%

respectively; p < 0.05; Table 1).

Table 1. Effect of PD on serum enzyme in the BDL-induced liver injury (n = 5/group). Mice were given orally PD (0, 1, 2 and 4 mg/kg) once daily for 28 consecutive days after BDL.

Group ALT AST TBIL

Sham 12.25 ± 0.85 b** 13.33 ± 1.66 b** 4.27 ± 2.56 b**

BDL-alone 271.40 ± 16.88 a** 307.60 ± 10.29 a** 243.44 ± 10.46 a**

PD 1 mg/kg 248.40 ± 32.07 a** 241.33 ± 15.94 a** 179.02 ± 9.38 a**, b*

PD 2 mg/kg 193.75 ± 28.25 a** 232.20 ± 45.53 a** 167.04 ± 8.62 a**, b*

PD 4 mg/kg 170.60 ± 29.73 a**, b* 210.20 ± 11.29 a**, b* 141.62 ± 14.01 a**, b** Values are expressed as means ± SEM. ‘‘a’’ denotes statistically significant difference in comparison with the sham group and ‘‘b’’ denotes statistically significant difference in comparison with the BDL-alone group (*p < 0.05; **p < 0.01; one-way ANOVA followed by Tukey’s post hoc test).

83 Evaluation of hepatic GSH, SOD, TBARS, and NO levels The obstruction of the bile duct in the group that received BDL alone caused a significant decrease in the levels of antioxidant enzymes (GSH and

SOD), but treatment with PD partially restored these levels (p<0.05). The indices of oxidative stress (the levels of NO and TBARS) increased by approximately 93% and 121% in the group that received BDL alone compared with the levels in the sham-treated group, while the PD-treated group showed markedly reduced levels of these enzymes compared with the levels in the group that received BDL alone (up to 34% and 27% reductions, respectively; p<0.05; Fig. 1).

Fig. 1. Effect of PD on GSH, SOD, TBARS and NO in the BDL-induced liver injury (n = 5/group). Mice were given orally PD (0, 1, 2 and 4 mg/kg) once daily for 28 consecutive days after BDL. Values are expressed as means ± SEM. ‘‘a’’ denotes statistically significant difference in comparison with the sham group and ‘‘b’’ denotes statistically significant difference in comparison with the BDL-alone group (*p < 0.05; **p < 0.01; one-way ANOVA followed by Tukey’s post hoc test).

85 Histopathological findings

The liver tissue architecture in the sham-operated mice remained intact with no morphological alterations, while hepatocyte necrosis, polymorphic nuclei and broad ductular proliferation were observed in the mice that

received BDL alone (Fig. 2). Massive bridging fibrosis around the portal and central vein was also observed in the mice that received BDL alone (Fig. 3).

The low dose of PD (1 mg/kg) did not prevent this histological alteration, with bridging fibrosis observed in the portal area and ballooning degeneration of the hepatocyte also present (Fig. 3). The mice that were

treated with 4 mg/kg PD, however, had markedly decreased ductular

proliferation, fibrosis, edema, and inflammation (Fig. 3).

Fig. 2. Effect of PD on histopathological alteration in the BDL-induced liver injury (n = 5/group). The histopathological changes of the liver stained with hematoxylin and eosin (×200). Mice were given orally PD (0, 1, 2 and 4 mg/kg) once daily for 28 consecutive days after BDL. (A) Sham group; (B) BDL-alone group; (C) PD (1 mg/kg) treated group; (D) PD (2 mg/kg) treated group; (E) PD (4 mg/kg) treated group. In the sham group, livers show normal morphology with intact cytoplasm. In the BDL-alone group, livers show massive ductular proliferation around portal area and feathery degeneration of hepatocyte. These alterations were markedly decreased in the PD (4 mg/kg) treated group. Arrows indicate ductular proliferation area and ballooning degeneration of hepatocyte (CV, central vein; PV, portal vein).

Fig. 3. Effect of PD on fibrosis in the BDL-induced liver injury (n = 5/group). The fibrosis of the liver stained with Masson’s trichrome (×100). Mice were given orally PD (0, 1, 2 and 4 mg/kg) once daily for 28 consecutive days after BDL. (A) Sham group; (B) BDL-alone group; (C) PD (1 mg/kg) treated group; (D) PD (2 mg/kg) treated group; (E) PD (4 mg/kg) treated group. Broad fibrosis and fibrous bridge were present in the BDL-alone group (Grade 4-5). Fibrosis areas were markedly decreased in the PD treated group (Grade 1-2). ‘‘a’’ denotes statistically significant difference in comparison with the sham group and ‘‘b’’ denotes statistically significant difference in comparison with the BDLalone group (*p < 0.05; Kruskal-Wallis test using Mann-Whitney U post-hoc test).

88 Immunohistochemical analysis

Evaluation of NF-κB immunoreactivity showed that the degree of

hepatocyte NF-κB activation in the group that received BDL alone was

significantly higher than that in the sham-operated group (p<0.05; Fig 4).

NF-κB activation appeared scattered at the parenchyma, predominantly adjacent to the inflamed portal tracts. The expression of iNOS was also increased in the group that received BDL alone compared with that in the sham-treated group (Fig. 4). However, the expression levels of NF-κB p65 and iNOS were markedly attenuated by PD treatment (p<0.05). In

histological evaluation of apoptosis, the number of TUNEL-positive cells increased significantly in the ductal proliferation areas of the group that received BDL alone, whereas it was decreased by 18%, 40%, and 49% in the groups treated with PD at 1, 2, and 4 mg/kg, respectively (p<0.05; Fig. 5).

Fig. 4. Effect of PD on NF-κB (×200) and iNOS (×100) expression in the BDL-induced liver injury (n = 5/group). Mice were given orally PD (0, 1, 2 and 4 mg/kg) once daily for 28 consecutive days after BDL. (A) Sham group; (B) BDL-alone group; (C) PD (1 mg/kg) treated group; (D) PD (2 mg/kg) treated group; (E) PD (4 mg/kg) treated group. Staining score for NF-jB and relative intensity for iNOS are expressed as means ± SEM. ‘‘a’’ denotes statistically significant difference in comparison with the sham group and ‘‘b’’ denotes statistically significant difference in comparison with the BDL-alone group (*p < 0.05; **p < 0.01; Kruskal-Wallis test using Mann-Whitney U post-hoc test).

Fig. 5. The effects of PD on apoptotic cells in the BDL-induced liver injury (n = 5/group). The apoptotic cells were showed in TUNEL stained livers (×200). Mice were given orally PD (0, 1, 2 and 4 mg/kg) once daily for 28 consecutive days after BDL. (A) Sham group; (B) BDL-alone group; (C) PD (1 mg/kg) treated group; (D) PD (2 mg/kg) treated group; (E) PD (4 mg/kg) treated group. Arrows indicate apoptotic cells. The presence of TUNEL-positive cells were measured by the image analyzer. Values are expressed as means ± SEM. adenotes statistically significant difference in comparison with the sham group and bdenotes statistically significant difference in comparison with the BDL alone group (*p < 0.05; **p <

0.01; one-way ANOVA followed by Tukey’s post hoc test).

91 Discussion

Several studies have revealed terpenoid saponins from the root of

Platycodon grandiflorum to have a protective effect against chemically induced hepatotoxicity (Khanal et al., 2009; Lee et al., 2001; Lim et al.,

2011). Based on these findings, the present study aimed to examine the protective effect of PD, which has the most potent biological activity of all the terpenoid saponins from Platycodon grandiflorum against chronic cholestasis-induced hepatotoxicity.

In the present study, we used the mice BDL model to assess the protective effect of PD against cholestasis. Bile duct ligation is a good model to evaluate for the protective or curative effect of certain compounds against cholestasis-induced liver injury. Furthermore, mice develop bile duct and

septal proliferations with leukocyte infiltration and liver fibrosis similar to

human. In addition, the presence of gallbladder in mice helps to confirm the

proper ligation as against rats with no gallbladder (Aller et al., 2008;

Georgiev et al., 2008; Heinrich et al., 2010). Georgiev et al. (2008) reported

that during 42 days of BDL, only nine out of 63 mice became moribund. In

the present study, there was no mortality during 28 days of experiments.

During the experiment period, all BDL-operated mice showed clinical

symptoms of jaundice by BDL-induced cholestasis such as a yellowish

92 pigmentation of skin and mucous membrane, and dark urine. In necropsy, all

the operated mice had markedly dilated gallbladder, which means the confirmation of the BDL operation.

During cholestasis, accumulated bile salts cause damage to the hepatocytes and elevate serum ALT and AST levels. In addition, the increased TBIL that is observed in cholestasis reflects the obstruction- induced deficiency of the bile duct at excreting bilirubin. In the present study, the serum ALT, AST, and TBIL levels in the group that received BDL alone significantly increased after BDL, which indicated that the common bile duct was completely ligated. These elevated serum enzymes levels markedly decreased by PD treatment in a dose-dependent manner. Obstruction of the bile duct causes the generation of massive oxidative stress and the depletion of antioxidant enzymes during cholestasis. Pastor et al. (1997) reported that prooxidant/antioxidant balances shifted towards lipid peroxidation under the conditions of BDL (Pastor et al., 1997). In the group that received BDL alone, the cholestasis-induced depletion of antioxidant enzymes such as GSH and SOD was markedly increased in contrast with the effect on the lipid peroxidation indices TBARS and NO. In this study, treatment of BDL-

operated mice with PD inhibited lipid peroxidation and reduced

cholestasisinduced hepatic GSH depletion, and also restored hepatic SOD

93 activities in the liver.

Under normal condition, NO has several beneficial effects, such as antimicrobial, anti-viral, and anti-tumor activities (Bogdan, 2001). However, excessive NO production due to the overexpression of iNOS can be detrimental to normal tissue, both directly and indirectly through its interaction with ROS, which forms the cytotoxic oxidizing agent peroxynitrite (Davis et al., 2001). The expression of iNOS is regulated by

NF-κB activation, which may result in a sustained high level of NO (Xie et al., 1994). Lin et al. reported an anti-fibrotic effect of a herbal extract alongside reduced expression of NF-κB and iNOS (Lin et al., 2008). In addition, Ahn et al. (2005) reported that PD downregulated iNOS and COX

II via suppression of NF-κB in RAW 264.7 cells (Ahn et al., 2005). In the present study, the group that received BDL alone showed activation of NF-

κB accompanied by increased iNOS levels. The PD-treated group exhibited ameliorated NF-κB and iNOS expression. Consistent with the results for iNOS and NF-κB expression, the decrease in hepatic NO levels as a result of

PD treatment probably resulted from the inhibited NF-κB expression via the suppression of iNOS.

Cholestasis-induced apoptosis of liver cells was detected using TUNEL staining. In the present study, hepatocyte apoptosis was related to oxidative

94 stress status; the group that received BDL alone treatment showed an increase in the number apoptotic cells accompanied by elevated levels of

ROS, whereas PD treatment ameliorated both ROS and the hepatic apoptosis.

Even though several factors may be involved in hepatocyte apoptosis during cholestasis, the generation of ROS plays a key role in the apoptosis of liver cells by altering the liver’s redox status (Maillette de Buy Wenniger and

Beuers, 2010). Therefore, the reduction in the number of apoptotic cells in the PD-treated group may have resulted from an improvement of the redox status in cholestasis-induced hepatic injury.

Obstruction of the biliary system induces retention of bile. Chronic bile retention causes bile duct dilatation and proliferation, activate hepatic stellate cells to produce collagen, and eventually leads to periportal and perineoductular fibrosis (Copple et al., 2010), which were confirmed by trichrome staining in the present study. The liver tissue from mice that received BDL alone showed broad ductal proliferation and the formation of a fibrous connective tissue bridge between the portal tracts. Treatment with PD significantly reduced the proliferation of the bile duct and fibrosis. These results were consistent with the results of a previous study on statins, a class of hypolipidemic drugs, in the BDL model. According to previous study, bile acids were formed as a result of hydroxylation of endogenous cholesterol;

95 thus lowering cholesterol levels can promote the downregulation of

enterohepatic bile acid circulation (Staels and Fonseca, 2009). It was

reported that statins might improve hypercholesterolemia and bile acid

accumulation in primary biliary cirrhosis patients by down-regulating HMG-

CoA reductase, the enzyme that is responsible for the production of

cholesterol (Demirbilek et al., 2007; Kolouchova et al., 2011). PD has been

shown to effectively lower cholesterol levels in hypercholesterolemic mice

with HMG-CoA inhibitor activity (Wu et al., 2011; Zhao et al., 2006).

Furthermore, Zhao et al. (2006) reported that PD showed a human acyl- coenzyme A: cholesterol acyltransferase inhibitory activity, which was attributable to the lowering of hepatic cholesterol storage (Zhao et al., 2006).

Therefore, the cholesterol-decreasing activity of PD likely partially

contributed to the ameliorated TBIL level in the serum and the decreased

ductular proliferation in the present study.

Taken together, these results indicate that treatment with PD reduced

oxidative stress and ameliorated apoptosis and tissue fibrosis in a cholestasis-

induced hepatotoxic liver. Although further studies should be performed

prior to the clinical use of PD, these results suggest that PD treatment might

be beneficial to patients who undergo complication with chronic cholestasis.

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100 Chapter 4. Platycodin D-induced apoptosis acin CT26 cells and its synergistic effect with cisplatin on tumor bearing mice

Abstract

There has been growing interest in natural anti-cancer compounds due to

their relative safety. Platycodin D (PD) is a triterpenoid saponin with various pharmacological activities. We aimed to assess anti-cancer effect of PD and its synergistic effect with cisplatin against CT26 cells using in vitro and in vivo study. In vitro study, the IC50 of PD and cisplatin in CT26 cells were 8.2

and 1.2 μM, respectively, and the combination of both compounds showed a

synergistic effect (CI<1). In addition, PD treatment induced apoptosis in

CT26 cells in a dose- and time-dependent manner with increased

phosphorylation of extracellular-signal-regulated kinase and c-Jun N- terminal kinase. In vivo study, CT26 cells were injected into the right frank of the mice and the mice were treated for 4 weeks with single PD and cisplatin and their combination. The combination treatment showed a synergistic effect on tumor growth inhibition and decreased cisplatin-induced oxidative stress in the liver and kidney tissue. Taken together, PD can be a candidate for combination therapy with chemotherapeutic agents after careful safety assessment study.

101 Introduction

Anticancer drugs exert their therapeutic effect by killing rapidly dividing tumor cells. However, the tumor cells have multiple survival pathways to resist chemotherapeutic agents. Cisplatin (cis-diamminedichloroplatinum II) is one of the most potent platinum-containing anticancer drug used for many types of cancer, including testicular, ovarian and cervical carcinoma (Pabla and Dong, 2008). Despite its effective chemotherapeutic properties, dose- related side effects limit its clinical application, such as nausea and vomiting, ototoxicity and nephrotoxicity (Arany and Safirstein, 2003; Pabla and Dong,

2008). Although the nephrotoxicity is regarded as the most frequent and severe side effect, high dose cisplatin was reported to induce additional hepatotoxicity (Iraz et al., 2006; İşeri et al., 2007). Oxidative stress, inflammation and apoptosis are main factors for the cisplatin-induced damage (Yao et al., 2007).

A number of studies so far reported that co-administration of dietary or pharmaceutical antioxidants with chemotherapeutic agents decreased anticancer treatment-related side-effects (Pace et al., 2003; Sieja, 2000).

Moreover, drug combinations are assumed to enhance therapeutic efficacy compared to single drugs (Chiu et al., 2009; Koppikar et al., 2010; Sandler et al., 2006; Webb et al., 2007).

102 The root of Platycodon grandiflorum has been traditionally used as a

medicine for various respiratory diseases, including bronchitis, asthma and

pulmonary tuberculosis in East Asian countries (Takagi and Lee, 1972). The

triterpenoid saponins from Platycodon grandiflorum exhibited a variety of

pharmacological activities, such as anti-inflammatory, anti-cancer and

immune enhancing effects (Kim et al., 2008a; Shin et al., 2009; Xie et al.,

2009). In our previous study, platycodin D (PD) ameliorated cisplatin-

induced nephrotoxicity in mice with dose-dependent manners (Kim et al.,

2012). Furthermore, the PD from Platycodon grandiflorum was reported to

exhibit growth inhibition properties in several types of cancer cells (Chun et

al., 2013; Kim et al., 2008a; Yu and Kim, 2010). To our knowledge, there

has been no report on the anticancer activity of PD and its combined effect

with cisplatin against CT26 cells. The aim of the present study was to

evaluate the efficacy of the PD as an anticancer agent and its combined effect

with cisplatin using in vitro and in vivo as well. We also assessed antioxidant properties of PD in long-term cisplatin treated tumor bearing mice.

Materials and methods

Chemicals and reagents

103 PD (approximately 98% purity) was purchased from Innoten (Seoul,

Korea). Assay kits for glutathione (GSH), superoxide dismutase (SOD) and thiobarbituric acid (TBARS) were obtained from Cayman (Ann Arbor, MI,

USA). The Nitric oxide (NO) kit was from BioAssay Systems (Hayward, CA,

USA). Serum alanine aminotransferase (ALT), aspartate aminotransferase

(AST), creatinine (CRE) and blood urea nitrogen (BUN) test kits were obtained from IDEXX (Westbrook, ME, USA). Extracellular-signal- regulated kinase (ERK), p-ERK, c-Jun N-terminal kinase (JNK) and p-JNK antibody was purchased from Cell Signalling Technology (Danvers, MA,

USA). All other reagents were from Sigma Chemicals (St. Louis, MO, USA).

In vitro study

Determination of combination index

The viability of CT26 cell was examined using resazurin assay. CT26 cells

(Colon carcinoma; KCBL. 80009; Korean Cell Line Bank; 5 x 103 cells/well) were plated for 24 h into 96-well tissue culture plates with DMEM containing 10% v/v fetal bovine serum (FBS) and 1% penicillin- streptomycin. The cell viability assay was performed with serial

concentration of cisplatin (0, 0.3, 0.6, 1.2, 2.5, 5.0, 10.0 and 20.0 μM), PD (0,

104 3.0, 3.3, 5.5, 6.0, 6.5, 11.0, 12.0, 13.0, 22.0, 24.0 and 26.0 μM). After 24, 48

and 72 h of incubation, 10 μL resazurin solution was added into medium and

incubated cells for 3 h at 37°C. Absorbance was measured at 570 nm and 600

nm using a micro-titer plate reader.

For synergism assay, serial concentration of the drug, either as a single agent or in combination of both cisplatin and PD were added to the wells.

After 48 h of incubation, the viability of cell was assessed using resazurin

assay. The type of drug interaction was assessed by the combination index

(CI) according to the method of Chou and Talalay (1984). Interactions

between cisplatin and PD were assessed using isobologram analyses

(CalcuSyn Software, Biosoft, Ferguson, MO, USA). A combined index (CI)

<1 was regard as synergism, CI=1 indicating additive interactions, and CI>1

representing antagonism. All assays were performed in triplicates.

Cell cycle analysis

Cell cycle distribution was monitored by flow-cytometry. Cells were

seeded at the density of 1 × 105 per well in 6-well plates. After 24 h, cells were treated with 20 μM of PD for 24, 48 and 72 h. Control and treated cells were harvested, washed twice with PBS, and fixed in 70% ethanol overnight

105 at -20°C. Fixed cells were washed twice with PBS, incubated with 1 mL of

propidium iodide (PI) solution (0.1% Triton X-100, 10 μg/mL PI, and 100

μg/mL DNase-free RNase A in PBS) for 30 min at 37°C. Stained cells were

analysed using a FACS Canto II and Cell Quest software (Becton Dickinson).

Apoptosis assay

Apoptosis was determined using Annexin V-FITC/ PI double staining.

Cells were seeded at the density of 1 × 106 per well in 6-well plates. After 24 h, cells were treated with 0, 10, 20 and 40 μM of PD for 48 h. After incubation, cells were washed cells twice with PBS. Cells were resuspended in 1×binding buffer at a concentration of 1 × 106 cells/mL and 100 μL of

suspended cells were incubated in the dark at room temperature with 5 µL of

FITC Annexin V and 5 µL of PI. After 20 min of incubation, 400 µL of

1×binding buffer was added to each tube. The samples were analysed within

1 h. Data were analysed by flow-cytometry using the FACS Canto II and

Cell Quest software (Becton Dickinson).

106 Western blot analysis

Cells were seeded at the density of 1 × 105 per well in 6-well plates. After

24 h, cells were treated with 0, 20 and 40 μM of PD for 24, 48 and 72 h.

After incubation, the cells were lysed with lysis buffer (20 mM Tris-HCl pH

8, 150 mM NaCl) containing a protease inhibitor cocktail. After protein quantification, 20 µg of protein were separated using a 12% SDS-PAGE. The proteins were transferred onto a nitrocellulose membrane in a Semi-Dry

Transfer system from Hoefer (Holliston, MA, USA). The membrane was blocked with 5% (w/v) dry milk in 1X TBS with 20% TWEEN-20 (TBS-T) and incubated with aliquot volume of anti-primary antibody. Horseradish peroxidase-conjugated anti-rabbit and mouse IgG (1:5000) was used.

Immunoreactivity was visualized using an enhanced chemiluminescence detection (ECL) kit (Amersham Pharmacia Biotech, Piscataway, NJ, USA).

In vivo study

Animals and treatments

Balb/c mice (5-6 week; 32-36 g) were obtained from Orient Bio

(Seongnam, Korea) and housed with standard chow (Charles River Inc.,

Richmond, IN, USA) and water ad libitum under the standard room

107 temperature (25°C) and 12 h light/dark cycle. After one week of acclimation,

CT26 cells (2 x 105) were injected into the right frank of all healthy mice except for normal group. To explore the therapeutic efficacy of cisplatin and

PD, the mice were treated 2 weeks after CT26 cell implantation (around 5 mm of diameter). All mice were randomly allocated into 5 groups as follows:

Group 1 (normal, n=7), group 2 (CT26 injected control, n=7), group 3 (CT26

+ cisplatin, n=7), group 4 (CT26 + PD, n=7) and group 5 (CT26+ cisplatin

and PD, n=7). PD (5 mg/kg) and cisplatin (5 mg/kg) were administered via

oral and intraperitoneal route for 4 weeks, respectively. Normal and CT26

injected control mice were treated with saline (0.9%). The body weight and

the tumor volume were monitored 3 day interval. Tumor volume was

measured by longest (length) and shortest (width) dimension using a dial caliper. Tumor volume was calculated by the following formula: tumor volume (mm3) = 0.52 × length (mm) × width (mm) × width (mm). At the end of the experiment, the surviving mice were sacrificed by cardiac puncture after being anaesthetized lightly with carbon dioxide. Blood was collected and serum was separated by centrifuging at the 800 g for 15 min, and the serum samples were subjected to biochemical examination. Liver and kidney samples were taken from each mouse for the biochemical examinations and stored at -70°C until analysis. The experimental protocols

108 were approved by the Institutional Animal Care and Use Committee of

Chungnam National University (Daejeon, Korea).

Determination of synergistic index

In vivo synergism between cisplatin and PD was assessed using a relative

ratio of tumor volume (RRTV) as a synergistic index (Dings et al., 2003).

RRTV and expected relative ratio of the combination were calculated as follows; RRTV = mean tumor volume experimental/mean tumor volume control; Expected combination ratio = Mean RRTV of cisplatin × mean

RRTV of PD.

The synergistic index was obtained by dividing the expected relative ratio by the observed relative ratio. A synergistic index of >1 indicates a synergistic effect; an index of <1 indicates a less than additive effect.

Serum biochemical examination

The serum ALT, AST, CRE and BUN activities were determined on a dry chemistry system, the Vettest 8008 blood chemistry analyzer (IDEXX

Laboratories, Westbrook, ME, USA).

109 Oxidative status in liver and kidney tissue

After homogenate liver and kidney tissue, all assays were performed using commercially available kits according to the manufacturer’s protocols. The

GSH level was determined using the improved DTNB [5,50-dithiobis-(2- nitrobenzoic acid)] method. The SOD level was monitored using the tetrazolium salt. The levels of malondialdehyde (MDA), the terminal product of lipid peroxidation, were measured with the thiobarbituric acid reduction method. NO levels were measured by the improved Griess reaction method.

Pharmacokinetic study

Ten healthy male Sprague-Dawley (SD) rats (6-7 week, 180-200 g) were used in this study. All rats were randomly divided into two groups (n=5/each).

The first group received 2 mg/kg of PD via intravenous (IV) route and the second group was treated with 35 mg/kg of PD using oral administration.

Blood samples (0.2 mL) were collected from the tail-vein of SD rats into heparinized tubes at 0, 0.08, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8 and 12 h after dosing.

After centrifugation, the plasma samples (50 µL) were mixed with 10 µL of the internal standard (IS; dexamethasone, 20 μg/mL) and 90 µL of acetonitrile was then added for extraction. The mixture was vortexed for 10

110 min and then centrifugated at 1,200 g for 10 min. After centrifugation, the

supernatant (10 μL) was injected into LC/MS.

Extracted plasma samples were analysed on the Agilent 1100 series

LC/MSD system. Separation was achieved on the XTerraMS® C18 reverse phase column (2.5μm, 3×50 mm, Waters, USA) at ambient temperature. The mobile phase consisted of 0. 1% formic acid in water (A) and 0.1% formic acid in acetonitrile (B) and the gradient flow was as follows: 20 % (v/v) B for 3 min, then increased to 100% B over 13 min, held for 3 min, then returned to initial condition 20% B and equilibrated for 5 min before the next injection. The flow rate was 0.4 mL/min. The electrospray ionization (ESI)-

MS analysis was performed on an Agilent 5989 mass spectrometer with an

ESI interface fitted with a hexapole ion guide. The optimal condition for the analysis of PD and IS employed pneumatic nebulization with nitrogen (45 p.s.i.) and a counterflow of nitrogen (9 L/min) heated to 350°C for the nebulization and desolvation of the introduced liquid. Mass spectrometer was performed using the negative ion mode and the selected ion monitoring

(SIM), detecting at m/z 1224.3 for PD and m/z 391.4 for IS with a dwell time of 300 ms.

111 Statistical analysis

Results were expressed as mean ± standard error (SEM). The significances

of differences among experimental groups were determined using the one

way analysis of variance (ANOVA) test or the non-parametric Kruskal-

Wallis test. Where significant effects were found, post hoc analysis using the

Tukey’s multiple comparison test or Mann-Whitney U-test was performed and p<0.05 was considered to be statistically significant.

Results

In vitro study

Synergism assay

The viability of CT26 after PD and cisplatin treatment was shown in Fig. 1

(A and B). The viability levels of CT26 cells decreased in a dose- and time- dependent manner with increasing doses of both PD and cisplatin treatment.

After 48 h of incubation, the viability of CT26 cells decreased from 91% to

8.7% with increasing doses (3-22 μM) of the PD, from 98% to 0.1% with increasing dose (0.3-10 μM) of cisplatin. The half maximal inhibitory concentration (IC50) of cisplatin and PD were 1.22±0.10 and 8.21±0.51 μM,

respectively, after 48 h incubation. To determine whether the combined

112 effects of the PD and cisplatin were synergistic, the CI value was calculated.

The median effect plot, dose effect curve and fa-CI plot were shown in Fig. 1

(C, D and E). The combination treatment showed higher dose-effect plot than that of single treated cells (Fig. 1 C and D). The fa-CI indicates that the PD and the cisplatin combination yielded synergistic effects with CI values ranging from 0.99 to 0.46 at different effect levels (Fig. 1 E).

113

Fig. 1. The effect of PD, cisplatin and its combination on CT26 cell viability. Cell viability was measured using resazurin assay. CT26 cells were treated with serial concentration of PD (A; 0, 3.0, 3.3, 5.5, 6.0, 6.5, 11.0, 12.0, 13.0, 22.0, 24.0 and 26.0 μM) and cisplatin (B; 0, 0.3, 0.6, 1.2, 2.5, 5.0, 10.0 and 20.0 μM) for 24, 48 and 72 h. For combination assay, CT26 cells were incubated with PD (3.0, 3.3, 5.5, 6.0 and 6.5 μM), cisplatin (0.3, 0.6, 1.2, 2.5 and 5.0 μM) and its 1 to 1 combined mixture for 48 h(C, D, E).

114 Cell cycle and apoptosis analysis

The CT26 cells were treated with 20 μM of PD for 0, 24, 48 and 72 h. The cell population in sub-G1 was gradually increased after PD treatment in a time-dependent manner (Fig. 2). In addition, time-dependent decrement in the G0/G1 phase population (67%-24%) was observed as compared with a negative control (70%). However, significant cell-cycle arrest was not observed at all phases in different treatment (Table 1).

To confirm PD induced apoptosis, Annexin V-FITC/PI double staining was conducted (Fig. 3). The CT26 cells were treated with different concentration of PD (0, 10, 20 and 40 μM) for 48 h. The apoptosis was induced in CT26 cells after exposure to 10 μM of PD (22.6%). In 20 μM of

PD treated cells indicated 25.2% of early and late apoptosis (lower right and upper right quandrants). Some propidium iodide only stained cells were also noted, indicating very late stage apoptosis or necrosis.

115

Fig. 2. The effects of PD on CT26 cell cycle. The sub-G0/G1 apoptotic, G0/G1, S and G2/M phase of CT26 cells were quantified by flow-cytometry using propidium iodide stain. CT26 cells were analysed after treatment of PD (20 μM) for 24, 48 and 72 h.

Table 1. Effect of PD on cell cycle distribution in CT26 cells.

Control (%) 24 h(%) 48 h(%) 72 h(%) Sub G0/G1 2.0±1.0 3.2±1.0 11.5±1.5 49.8±2.2 G0/G1 70.9±3.2 67.9±2.5 56.0±3.3 24.8±1.9 S 11.1±2.1 12.2±2.4 13.1±2.1 15.2±3.2 G2/M 16.0±0.9 16.7±0.7 19.2±1.1 10.0±0.5 Cell cycle was analysed after treatment of PD (20 μM) for 24, 48 and 72 h using flow- cytometry with propidium iodide stain. Values were expressed as mean±SD of triplicated experiment.

116

Fig. 3. PD induced apoptosis in CT26 cells. The apoptosis was measured by Annexin V- FITC/ propidium iodide (PI) staining. CT26 cells were treated with 0 (A), 10 (B), 20 (C) and 40 (D) μM of PD for 48 h, and analyzed with flow-cytometry. The horizontal and vertical axes represent labeling with annexin V-FITC and PI, respectively. Lower right represents early apoptotic cells, upper right represents late apoptotic cells. Lower left represents normal live cells and upper left represents necrotic cells.

117 Western blot analysis

The CT26 cells were treated with 0, 20 and 40 μM of PD for 24, 48 and 72 h. The protein expression levels were determined using Western blot analysis

(Fig. 4). The phosphorylation of JNK and ERK were significantly increased after PD treatment compared to control cells.

Fig. 4. The effect of PD on protein expression in the CT26 cell. The CT26 cells were treated with 0, 20 and 40 μM of PD for 24, 48 and 73 h. The protein expression levels were determined using Western blot analysis.

118 In vivo study

Determination of synergistic index

The combination effect of PD and cisplatin on the growth of CT26 in

BALB/c mice was assessed (Fig. 5). Even though, the tumor volume was gradually increased in all group, tumor volume assay showed that either PD

or cisplatin individually resulted in effective suppression of tumor growth

with 59% and 43% of that in control mice at day 23, respectively. In

combination treated mice showed significantly smaller tumor volume (30%

of control mice) if compared to control mice. In table 2, the RRTV of the

combination group showed an synergistic effect about 32 days after tumor

cell transplantation.

119

Fig. 5. Tumor volume in PD, cisplatin and combination treated mice (n=7/each group). Male Balb/c mice were transplanted subcutaneously with CT26 cells (2x105) into the right frank. The mice were treated 2 week after CT26 cell implantation. PD (5 mg/kg) and cisplatin (5 mg/kg) were administered via oral and intraperitoneal route for 4 weeks, respectively. Normal and CT26 injected control mice were treated with saline (0.9%). Body weight and tumor volume was monitored 3 day interval. Tumor volume was measured by longest (length) and shortest (width) dimension using a dial caliper. Tumor volume was calculated by the following formula: tumor volume (mm3) = 0.52 × length (mm) × width (mm) × width (mm).

120 Serum biochemical examination

To assess liver and kidney function, serum enzymes were monitored in

different treatment group. As shown in Fig. 6, only serum AST was

significantly increased after CT26 transplantation. In addition, PD treated group showed similar serum enzyme levels compared with control group mice. In cisplatin alone treated group, cisplatin administration caused impairment in the liver and renal functions, as characterized by increase in all serum ALT, AST, BUN and CRE levels by 2.3, 1.1, 6.4 and 2.1 times than those in the control group, respectively (p < 0.05). Meanwhile, combination treated group showed mildly ameliorated serum enzyme levels in the ALT and AST levels, as well as in the BUN and CRE levels.

121

Fig. 6. Effect of cisplatin, PD and its combination therapy on serum ALT, AST, BUN and CRE in the CT26 tumor bearing mice (n=7/group). PD (5 mg/kg) and cisplatin (5 mg/kg) were administered via oral and intraperitoneal route for 4 weeks, respectively. Normal and CT26 injected control mice were treated with saline (0.9%). Values are expressed as means ± SEM. ap<0.05, a significant difference when compared with the normal group. bp<0.05, a significant difference when compared with the control group. cp<0.05, a significant difference when compared with the group treated with the cisplatin treated group.

122 Evaluation of GSH, SOD, TBARS, and NO levels

The CT26 cells transplanted control group mice showed similar oxidative status compared with normal group mice both in liver and kidney tissue, except NO value (Fig. 7). The NO value in control group was almost 4 times higher than that of normal group mice (p<0.05). The cisplatin alone treatment caused a decrease in the levels of GSH and SOD, but combination treated group showed restored antioxidant enzyme levels (p<0.05).

Meanwhile, the level of TBARS increased in the cisplatin treated group compared with the level in the control group, while the combination treatment slightly reduced level of TBARS enzymes compared with the level in the cisplatin treated group both in liver and kidney tissue (p<0.05; Fig. 6).

123

Fig. 7. Effect of cisplatin, PD and its combination therapy on GSH, SOD, TBARS and NO in the CT26 tumor bearing mice (n=7/group). PD (5 mg/kg) and cisplatin (5 mg/kg) were administered via oral and intraperitoneal route for 4 weeks, respectively. Normal and CT26 injected control mice were treated with saline (0.9%). Values are expressed as means ± SEMValues are expressed as means ± SEM. ap<0.05, a significant difference when compared with the normal group. bp<0.05, a significant difference when compared with the group treated with the control group. cp<0.05, a significant difference when compared with the group treated with the cisplatin treated group.

124 Pharmacokinetic analysis

The mean time concentration curve for the rats given PD is shown in Fig.

8. A non-compartmental model best fitted the plasma concentrations both in

IV and PO group. As shown in table 2, the half-life of PD was 3.05±0.55 and

3.34±0.01 h after IV and PO administration, respectively. After PO

administration, PD reached 0.31±0.02 μg/mL of Cmax at 1 hafter

administration. The bioavailability was 0.991 % after PO administration.

Fig. 8. Mean plasma concentrations of PD vs. time curves in SD rat after IV (2 mg/kg) and PO (35 mg/kg) administration (n=5/group).

125 Table 2. Main pharmacokinetic parameters of PD in the SD rat

Parameters (unit) IV (2 mg/kg, n=5) PO (35 mg/kg, n=5) T (h) 1/2λz 3.05±0.55 3.34±0.01 C0 (μg/mL) 13.78±2.79 - Tmax (h) - 1 Cmax (μg/mL) - 0.31±0.02

AUCINF (μg·h/mL) 8.69±1.58 1.60±0.088 Vz (L/kg) 1.02±0.18 - Cl (L/kg/h) 0.23±0.06 - MRT (h) 2.78±0.43 5.03±0.05 Vss (L/kg) 0.63±0.14 - F (%) - 0.991

T1/2λz, half-life; C0, initial concentration; Tmax, time of peak; Cmax, peak plasma concentration; AUCINF, area under the plasma concentration-time curve from 0 to infinite; Vz, volume of distribution of the terminal phase; Cl, clearance of the terminal phase; MRT, mean residual time; Vss, estimate of the volume of distribution at steady state; F, bioavailability.

126 Discussion

Chemotherapy improves overall survival rate but the side effect of chemotherapy is a serious problem in cancer patients, thereby requiring a potent agent with a minimum side effect (Wang et al., 2008). Recently, there has been a growing interest in the cancer treatments using combined agents with distinct molecular mechanisms which exert higher efficacy with lower toxicity (Sarkar and Li, 2006). Natural compounds are generally recognized as a relatively non-toxic agent compared to the chemical compounds. Several natural compounds exhibit excellent preventive effect in chemotherapy- induced toxicity with anti-oxidative effect (Block et al., 2007; Falsaperia et al., 2005; Wessner et al., 2007). In addition, it has been reported that the co- administration of natural compounds with a cytotoxic chemotherapeutic agent exhibit synergistic effects with ameliorated side-effect (Lee et al., 2008;

Sriganth and Premalatha, 1999). In the present study, we have evaluated the anticancer activity of PD, alone and in combination with cisplatin to explore its combination effect in vitro and in vivo. In vitro study, PD exhibited dose- and time-dependent growth inhibition effect in the CT26 cell by inducing apoptosis which was confirmed by flow-cytometry. Kim et al. (2008) reported that PD showed similar effects to that of paclitaxel, both of them causing mitotic arrest in the G2/M phase in human leukemia cells (Kim et al.,

127 2008a). Recently, PD-induced apoptosis was observed in AGC human gastric

cancer cells with markedly increased sub-G0/G1 ratio, a marker of apoptosis

(Chun et al. 2013). In the present study, sub-G0/G1 phase of PD treated

CT26 cells, even though different in cell type, also significantly increased

after 72 h of incubation. Moreover, the combination of PD with cisplatin

showed higher inhibition rate if compared to cisplatin alone treated CT26

cells.

In Western blot analysis, though the mechanism of PD-induced apoptosis

is not fully elucidated, phosphorylation of JNK and ERK were increased in

PD-treated CT26 cells compared to control cells. The JNK1 and JNK2 can

act as either tumor promoter or suppressor kinases in different cancer types,

thus the profile of both roles of JNKs in different tumors is responsible for

the therapeutic potential of JNK inhibition (Bubici and Papa, 2014). It has

been suggested that the JNKs suppresses tumor formation through their

apoptotic functions which is connected with the mitochondrial pathway

(Davis, 2000). Furthermore, Tournier et al. (2000) reported that murine

embryonic fibroblasts lacking in JNKs showed resistance to the apoptosis,

down-regulating pro-apoptotic molecules from mitochondria on UV

irradiation. The ERK signaling pathway plays a crucial role in cell functions

and mediates different anti-proliferative activity, including apoptosis,

128 autophagy and senescence, dependent on the cell type and the stimuli

(Cagnol and Chambard, 2010). Furthermore, ERK has been reported to

involve in cell death induced by various antitumor compounds, such as

resveratrol and quercetin (Kim et al., 2008b; Shih et al., 2002).

In vivo study, the mice from cisplatin alone and in combination with

platycodin D treated group showed decreased body weights (about 76% of

day 0). In CT26 cell transplanted control group, only serum AST level was

significantly increased if compared to the normal group. AST is found not

only in the liver as well as in many other organs such as heart, skeletal

muscle, kidneys, brain, and red blood cells, the elevation in AST levels might

derive from other organs as a result of cancer transplantation. In the present

study, 4 weeks of cisplatin treatment leads to the increased serum enzymes,

whereas combination treatment with PD decreased serum enzyme levels.

Combination treatment showed synergistic effect on tumor volume growth

inhibition as well as in vitro study,.

The pathogenesis of cisplatin-induced tissue damage have mainly focused

on the oxidative stress induced by direct toxicity of cisplatin (Santos et al.,

2008). Recently, it has been reported that natural compounds from plants with antioxidant capacity can attenuate the cisplatin-induced toxicity, such as quercetin, luteolin, and curcumin (Behling et al., 2006; Ilbey et al., 2009;

129 Kang et al., 2011). In addition, we reported that the PD ameliorated cisplatin-induced nephrotoxicity with recovered oxidative status (Kim et al,

2012). In line with our previous study, consecutive cisplatin treatment increased the TBARS level, a marker for malondialdehyde which is an end product of lipid peroxidation in kidney and especially in liver tissues.

Meanwhile, combination treatment with PD significantly suppressed the cisplatin derived increase in TBARS levels. In addition, the levels of NO in both liver and kidney were markedly increased after CT26 transplantation.

Many studies reported that NO involves in carcinogenesis including initiation, promotion, progression, metastasis, and tumor microcirculation and angiogenesis (Fukumura and Jain; 1998; Lala and Orucevic, 1998;

Thomsen and Miles, 1998). Combination treatment in this study decreased

NO levels compared to both control and single cisplatin treated groups.

Furthermore, combination treatment enhanced the levels of both GSH and

SOD compared to the single cisplatin treated group, both of them being an essential antioxidant preventing reactive oxygen species derived cellular damage (Kaplowitz, 1981).

Pharmacokinetic study was explored in SD rats after IV and PO administration of PD. The half-life was similar in both IV and PO administered rat, meanwhile, the oral bioavailability was significantly lower

130 with 0.9% value, indicating poor absorption of the compound. Interaction of herbal compounds with drugs could change its pharmacokinetic properties by altering its absorption, distribution, metabolism, or elimination of a conventional drug (Chavez et al., 2006). To expand possibility of the combination therapy in clinic, drug interaction in pharmacokinetic study between PD and cisplatin should be considered.

In conclusion, PD treatment induces apoptosis in CT26 cells in dose- and time- dependent manner. In addition, the PD inhibits the growth of CT26 cells and exerts synergistic effect with cisplatin in both in vitro and in vivo study. Moreover, combination treatment with PD attenuates cisplatin-induced oxidative stress. Further careful studies are requested to obtain safety profiles and therapeutic window.

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Yu JS, Kim AK. 2010. Platycodin D induces apoptosis in MCF-7 human breast cancer cells. J Med Food. 13: 298-305.

137 General conclusion

The protective effect of PG against liver injury was assessed using

chemical and surgical animal models. In chemical-induced hepatotoxicity study, PG produced hepato-protective effects against TA and CCl4-induced acute hepatic injury by decreasing the nitric oxide enzyme and lipid peroxidation. In addition, PG inhibited the HCV RNA replication with a

35.46 of selective index (CC50/EC50) in Huh7 cells harbouring the HCV genotype 1b replicon. However, PG was unstable in simulated gastric juice.

After incubation with gastric juice, digested PG showed poor hepatoprotective effect and decreased anti-HCV activity as compared to the intact

PG. In surgical model, we used both acute and chronic BDL-induced cholestasis model. After 28 days of PG treatment, BDL-induced hepatic injury and fibrosis were decreased with recovered oxidative status and inhibited TGF-β1 expression.

To confirm the phrmaceutical effect of saponin from Platycodon grandiflorum, PD was hired as a target compound. In the chronic BDL model,

PD reduced oxidative stress and ameliorated apoptosis and tissue fibrosis in a cholestasis-induced hepatotoxic liver. Moreover, the expression of NF-κB and inducible nitric oxide synthase in the liver tissue were significantly

138 decreased after PD treatment. In cancer model study, PD treatment induces apoptosis in CT26 cells in dose- and time- dependent manner. In addition, the PD inhibits the growth of CT26 cells and exerts synergistic effect with cisplatin in both in vitro and in vivo study and combination treatment with

PD attenuates cisplatin-induced oxidative stress. In this study, terpenoid saponin from Platycodon grandiflorum found to have pharmaceutical effect against various animal models. Further studies requested to secure safety profiles and therapeutic window before clinical application.

139 Part II

General Introduction

In basic terms, inflammation is a protective reaction of the body against external and internal stimuli. In the acute phase, it serves to remove triggering agents in addition to restoring tissue following damage. However, if the inflammatory process becomes overwhelming, it results in pain through activation of nociceptors by various inflammatory mediators and eventually it can become life threatening and requiring of clinical intervention (Dubin and Patapoutian, 2010).

The nonsteroidal anti-inflammatory drugs (NSAIDs) are used to treat pain, fever and inflammation in various diseases. Although the properties of

NSAIDs may vary slightly between the diverse classes and generations, the main mechanism of action involves inhibition of cyclo-oxygenase (COX) in various organs. COX is the enzyme that converts arachidonic acid (AA) to form prostanoids, which are essential biological mediators including prostaglandins (PG) and thromboxanes (TX). In 1990, two decades after the discovery of COX, it was revealed that COX exists as two isoforms, COX-1 and COX-2 (Meek et al., 2010; Vonkeman and Laar, 2010). In brief, COX-1 is a constitutive enzyme found in many organs under normal conditions,

140 while COX-2 is an enzyme up-regulated during inflammatory processes.

Additionally in 2002, the third COX isoform (COX-3) was discovered. It is

encoded by the same gene as COX-1, but COX-3, as a clinical target, is yet

to be fully understood (Botting, 2003; Perrone et al., 2010).

In general, COX-1 is thought to be beneficial to the body’s homeostasis with functions including maintenance of mucosal epithelium integrity, thus, its inhibition readily leads to gastric ulcers (Buvanendran, 2012). Inhibition of COX-2 only could decrease production of prostanoids such as PGE2 and

PGI2 that are just involved in inflammatory and pathological processes, as well as ameliorate pain generation (Agarwal et al., 2009). Therefore, many clinical trials with NSAIDs focus on the selective inhibition of COX-2 enzymes because of the superior safety profile resulting from the COX-1 sparing effect.

Nowadays, there is a growing interest in animal welfare. Owners consider their pets as members of their families. The changed breeding environment and extended life span of pets has meant that they are predisposed to an extended spectrum of diseases for which owners are demanding a higher level of care. These trends have been an impetus for the development of more effective and innovative veterinary therapies (Giorgi, 2012; Giorgi et al., 2012a; Giorgi and Yun, 2012). However, veterinarians still have a reduced drug armamentarium compared to their human counterparts, thus,

141 many studies have been conducted on the use of human medicine in the veterinary field (Giorgi et al., 2012b; Lavy et al., 2011). As use of selective

COX-2 inhibitors (coxibs) became more prominent in human medicine, it followed that many selective inhibitors were introduced into clinical use for the veterinary market. Nowadays, many pharmaceutical companies have their own coxib drugs and some of these active ingredients have been recently launched on the veterinary market.

However, animal species differences in factors such as the sensitivity and disposition of certain drugs could evoke unexpected results if they are used without any understanding of the drugs’ behaviour in the target species

(Toutain et al., 1997; Giorgi et al., 2011; Martignoni et al., 2006). In addition, to the best of the Authors’ knowledge, the cardiovascular effects of coxibs during protracted therapy have not described in animals. In contrast, in the human field, coxibs have been reported to produce adverse effects on cardiovascular system such as thrombotic disorders including cerebral vascular events and myocardial infarction (Cairns, 2007; Batlouni, 2010).

Furthermore, animals can be more sensitive to coxibs than humans due to differences in drug metabolism, absorption and enterohepatic recirculation

(Bergh and Budsberg, 2005). For these reasons, knowing the pharmacological properties, pharmacokinetic/pharmacodynamic and safety profile of each drug is essential in order to use veterinary coxibs

142 appropriately.

The coxibs are a subclass of NSAID which have a COX-1 sparing effects.

Because of steric hindrance, the COX-1 active site is smaller than that of

COX-2. The bulky structure of coxibs restricts their inhibition of COX-1 but

allows for complete inhibition of the COX-2 pathway. The classification of

NSAIDs is expressed as COX-2 selective, COX-2 specific, or COX-2

preferential. This indicates the drug selectivity for COX-2 and it is

determined through calculation of the inhibitory concentration (IC50) COX-

1:COX-2 ratio (Vane and Warner, 2000; Bergh and Budsberg, 2005).

However, these ratios have not been fully quantified and ratios for the same

compound can be inconsistent, as the assays used were considerably

different (Livingston, 2000; Pairet and Ryn, 1998).

Coxibs are regarded as a third generation of NSAIDs (Sternon, 2001). In

the human field, several coxibs have been launched. The first to be launched

were rofecoxib and celecoxib, these have been categorized as first generation.

The newest active ingredients (valdecoxib, parecoxib, etoricoxib and

lumiracoxib) have been classified as second generation and possess a

stronger selectivity for the COX-2 enzyme inhibition (Stichtenoth, 2004;

Andersohn et al., 2006). In veterinary medicine deracoxib (2002), firocoxib

(2007), mavacoxib (2008) and robenacoxib (2009) have been introduced for animal use (Bergh and Budsberg, 2005). Recently, cimicoxib (2011) has also

143 been introduced for the veterinary market from the human field (Emmerich,

2012).

Deracoxib (Deramaxx®; Novartis) was the first coxib to be approved in veterinary medicine (Papich, 2008). Deracoxib contains a sulfonamide moiety. Chemically it is a 4-[3-(difluoromethyl)-5-(3-fluoro-4-methoxyphenyl)-

1H-pyrazole-1-yl] benzenesulfonamide and its molecular weight is 397.38

g/moL. Deracoxib is categorized as a diarylheterocycle drug, these exert a

time-dependent pseudo-irreversible inhibition of COX-2 (Walker et al.,

2001). Deracoxib was initially approved for postoperative orthopedic pain in

dogs at 3-4 mg/kg by oral (PO) daily dose for a maximum of 7 days. In 2003,

deracoxib was also approved for chronic administration at a dosage of 1-2

mg/kg PO once daily (Smith, 2003).

In in vitro evaluations, among the coxibs, deracoxib was determined as a

highly selective COX-2 inhibitor with a COX-1/COX-2 ratio of 1275 in

purified enzymes assay (Gierse et al., 2002). However when tested using

canine whole blood, the COX-1/COX-2 ratio was only 12 (McCann et al.,

2004). This inconsistency resulted from the different types of cells with

different cell conditions being used in each assay (Vane and Botting, 1995).

In another study using dogs, deracoxib showed the same degree of COX-1

and COX-2 inhibition as carprofen (COX-2 preferential drug), despite a wide

variation of COX-1/COX-2 inhibitory ratios between the two drugs being

144 found in in vitro assays (Sessions et al., 2005). These discordance results between in vivo and in vitro studies suggest that the in vitro results do not provide a quantitative measure of difference in efficacy or safety (Papich,

2008).

In the pharmacokinetic evaluation after oral administration of deracoxib

(2~3 mg/kg) in dogs, deracoxib had a protein binding affinity of over 90%. It also underwent hepatic biotransformation with an elimination half-life of 3 h, using biliary excretion as a major excretion route (Smith, 2003). After high- dose administration (8 mg/kg) however, a non-linear elimination has been shown: deracoxib loses its COX-2 selectivity and starts to inhibit COX-1 also (DCT, 2003). The nonlinearity at high doses might result from saturation of the metabolizing enzymes. In other species treated with deracoxib including cats (1 mg/kg) and horses (1~2 mg/kg), a longer half-life (7.9 and

12 h, respectively) than dogs was reported (Davis et al., 2011; Gassel et al.,

2006). In cats and horses the hepatic enzymes, which participate in biotransformation of deracoxib, may be present at lower concentrations than in dogs and might therefore be saturated at lower concentrations, which leads to the longer half-life (Davis et al., 2011).

Clinical trials in dogs showed that deracoxib (1~2 mg/kg PO for 3 days) was able to reduce postoperative pain and inflammation after dental extraction surgery (Bienhoff et al., 2012). In addition, Millis et al. (2002)

145 reported that the administration of deracoxib (1, 3, or 10 mg/kg PO) was

more effective in reducing pain associated with urate crystal-induced synovitis than carprofen (2.2 mg/kg PO). Deracoxib treatment also showed no significant adverse effects (Millis et al., 2002).

After 28 days of once daily administration of deracoxib (1.6 mg/kg PO), it was shown to be safer than aspirin in regards to risk of gastric ulceration in healthy dogs (Sennello and Leib, 2006). In addition, long-term therapy of deracoxib for up to 6 months administered at the labeled dose, was found to be safe and well tolerated in dogs without any significant nephrotoxicity

(Roberts et al., 2009). On the contrary, at higher than labeled doses or when given with other NSAIDs or corticosteroids, deracoxib has been found to cause gastrointestinal perforations in dogs (Lascelles et al., 2005).

Even though there has been no significant instances of hypersensitivity reported thus far, the administration of sulfonamide coxibs in animals allergic to sulfonamides should be carefully considered. Indeed it might be likely a cross reaction with other sulfonamides such as antimicrobial or an evocation of hypersensitivity (Shapiro et al., 2003; Sanchez-Borges et al.,

2004; Bergh and Budsberg, 2005; Ayuso et al., 2013). The hypersensitivity of sulfonamide coxib such as deracoxib is yet to be confirmed.

Firocoxib (Previcox®; Meriel) was developed specially for the veterinary

field (for dogs and horses). It was found to be 350~430 fold more selective

146 for COX-2 than COX-1 in in vitro canine whole blood assays (McCann et al.,

2004). Chemically it is a 3-cyclopropymethoxy-5,5-dimethyl-4-[4-(methyl sulfonyl) phenyl]-2-(5H)-furanone and its molecular weight is 336.402 g/moL. The drug was launched several years ago and in this short time, the pharmacokinetic properties of firocoxib in dogs and horses have already been well established (Kvaternick et al., 2007a; 2007b; Letendre et al., 2008).

Firocoxib is available as a chewable tablet oral preparation which has been approved in the European Union for dogs at a once daily administration of 5 mg/kg. In addition, firocoxib, as an oral paste was approved by FDA for the control of pain and inflammation associated with osteoarthritis in horses at

0.1 mg/kg once daily (Kvaternick et al., 2007b). In dogs, following PO administration (5 mg/kg), firocoxib was well absorbed and eliminated by hepatic metabolism and fecal excretion with an elimination half-life of 8 h

(Kvaternick et al., 2007a). Firocoxib in horses (0.1 mg/kg) showed a bioavailability of 79% and an elimination half-life of 30 and 34 h for oral and intravenous administration, respectively. Due to its lipophilic and non- ionizable nature, firocoxib was widely distributed with a volume of distribution value of 1.7 L/kg after intravenous administration in horse.

Firocoxib showed a longer half-life compared with other NSAIDs, such as phenylbutazone and flunixin meglumine (Kahn and Line, 2010; Kvaternick et al., 2007b).

147 A clinical study including 1,000 dogs treated for a 40-day period, reported

that withdrawal rate due to development of gastrointestinal side effects was

only 2.9%. Over 90% of investigators and owners rated improved clinical scores after firocoxib treatment (Ryan et al., 2006). In a long-term study over

52 weeks of treatment, a slight increase in withdrawal rate (5.1%) was

reported due to GI signs (Autefage et al., 2011). Steagall et al. (2007)

evaluated the adverse effects of oral firocoxib in healthy dogs for 29 days

and found that a dose of 5.3±0.34 mg kg-1 of firocoxib did not cause any adverse effects on the GI tract or serum biochemical variables and was well

tolerated in terms of hematological signs including platelet aggregation and

buccal mucosal bleeding time index (Steagall et al., 2007). Firocoxib was

found to be effective in a 90 day long-term study performed on relatively

geriatric dogs (over 7 years) affected by osteoarthritis. The side effects

reported (minimal biochemical changes and diarrhea) were thought to be due

to age-related deterioration in liver and renal functions (Joubert, 2009).

Furthermore, in the sodium urate crystal-induced synovitis model, firocoxib treatment (5.3~6.49 mg/kg) resulted in reduced lameness and increased

weight-bearing at both 3 and 7 h post-treatment, as compared with carprofen.

Firocoxib efficacy was similar to dogs treated with vedaprofen but without any cardiovascular effects (Hazewinkel et al., 2008).

However, in developmental toxicity studies firocoxib showed embryotoxic

148 and foetotoxic effects in both rats and rabbits, inducing a variety of malformations and anomalies. Consequently firocoxib, as with other coxibs, is contraindicated for use during pregnancy and lactation in dogs.

Furthermore, firocoxib had a low safety margin in puppies compared to older dogs. Thus, like other drugs, its use in very young animals requires careful monitoring (EMEA, 2006).

Mavacoxib (Trocoxil®; Pfizer) is a long acting coxib which has a chemical

structure of 4-[5-(4-fluorophenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]- benzenesulfonamide, it has a molecular weight of 385 g/moL and it acts as a preferential rather than selective COX-2 inhibitor if compared with carprofen.

It is approved for the treatment of canine osteoarthritis requiring long-term treatment between 1 and 7 months EMEA, 2008. Mavacoxib is produced in a diverse range of tablets (6, 20, 30, 75 and 90 mg) as an oral chewable form.

Unlike other coxibs, mavacoxib is recommended for monthly administration at 2 mg/kg because of its long half-life. In order to achieve steady-state concentrations, it is recommended that mavacoxib is administered with a 2- week interval between the first and second dose with monthly dosing thereafter.

The pharmacokinetics profile of mavacoxib has been well described in

Beagle dogs (Cox et al., 2010). It showed significant low clearance rate (2.7 mL/h/kg) with a large volume of distribution (1.6 L⁄kg) in experimental

149 intravenous administration. Especially in terminal halflife, all PO treated

Beagle dogs (n = 63) showed an average value of 16.6 days with individual

values ranging from 7.9 to 38.8 days. The half-life differences between

individuals should be considered as a significant factor in the use of this drug.

In fact, in individuals demonstrating a poor elimination rate this drug could

evoke cumulative side effects. Moreover, it has been reported that food

intake significantly affects mavacoxib absorption. The administration of

mavacoxib (4 mg/kg) in fasted and fed dogs resulted in a bioavailability of

46.1 and 87.4% respectively. In field trials, mavacoxib showed a terminal

elimination plasma half-life of 44 days in the target population, however 5%

of dogs had an extended half-life of 80 days. In addition, most animals

treated with 2 mg/kg, maintained trough plasma mavacoxib concentrations

associated with efficacy (Cox et al., 2011).

As the safety profile has not been established in reproductive toxicity,

application of mavacoxib to pregnant or breeding animals should be avoided.

Furthermore, this kind of drug, which has a long half-life, should be carefully handled because of the potential for prolonged exposure.

Robenacoxib (Onsior®; Norvatis) is a coxib which has been developed

solely for use in veterinary medicine and is the only approved coxib in cats

available as a tablet as well as injectable form (King et al., 2009). It is

recommended at a dose of 1~2 mg/kg once daily for both species. It has a

150 chemical structure of 5-ethyl-2-[(2, 3, 5, 6-tetrafluorophenyl)amino]-phenyl

acetic acid and a molecular weight of 327.27. Robenacoxib is a weak acidic

drug (pKa 4.7) which has high protein-binding affinity (>98% in dogs) (Jung

et al., 2009). In the in vitro COX-2 selectivity comparative study in dogs

with whole blood assay, the IC50 ratio (COX-1:COX-2) was highest in

robenacoxib (128.8) when compared to other NSAID such as deracoxib

(48.5), nimesulide (29.2) and meloxicam (7.3) (King et al., 2010). In cats,

robenacoxib also showed more COX-2 selectiveness (32.2) compared with diclofenac (3.9) and meloxicam (2.7) (Schmid et al., 2010a).

Previous studies have revealed its pharmacokinetic properties via different administration routes including, intravenous, subcutaneous and oral administration in the dog and cat (Jung et al., 2009; Pelligand et al., 2012).

In dogs, robenacoxib showed good bioavailability after oral (84%) and subcutaneous (88%) administration with a short blood half-life of 1 h (Jung et al., 2009). In addition, Silber et al. (2010) revealed that robenacoxib remained longer in inflamed synovial joints than blood. The anatomically focused persistence of robenacoxib may be triggered by its weak acidity and high proteinbinding affinity. In an inflamed area, the blood supply is increased and pH has become mildly acidic. These alterations allow robenacoxib to enter cells more readily than under normal conditions. The ion-trapping due to the pH change slows release of the drug and as a result,

151 intracellular drug concentrations increase (Brune and Furst, 2007).

In a clinical study, Schmid et al. (2010b) reported that SC injection of robenacoxib exerted analgesic and antiinflammatory effects in the urate synovitis model at dosages of 0.25-4 mg/kg without COX-1 inhibition

(Schmid et al., 2010b). In comparison with carprofen, robenacoxib also demonstrated good efficacy in field trials when given once daily (Reymond et al., 2012). Furthermore, robenacoxib provided similar efficacy and tolerability to meloxicam in controlling perioperative pain and inflammation in dogs (Gruet et al., 2011). In cats after ovariohysterectomy surgery, SC injected robenacoxib (2 mg/kg) provided a greater analgesic effect for up to

24 h compared to buprenorphine (Staffieri et al., 2013). According to the study from King et al. (2012), as expected, robenacoxib had an excellent safety profile in young healthy cats when administered at daily dosages up to

10 mg/kg for 28 days and up to 20 mg/kg for 42 days (King et al., 2012).

Also in dogs, robenacoxib showed high safety index without any relevant toxicity with daily dosages as high as 40 mg/kg for one month and 10 mg/kg for 6 months (King et al., 2011). This proven safety of robenacoxib may result from its high COX-2 selectivity and rapid central compartment clearance with longer residence at inflamed sites (King et al., 2012).

However there is no data on reproductive toxicity and robenacoxib should not be used in pregnant or breeding animals.

152 Cimicoxib (Cimalgex®; Vetoquinol) is a novel imidazole derivative coxib

and a highly selective COX-2 inhibitor, that has recently been launched

(Emmerich, 2012). Chemically it is a 4-[4-Chloro-5-(3-fluoro-4- methoxyphenyl)-1H-imidazol-1-yl]benzenesulfonamide and its molecular weight is 381.809 g/moL. Although it was originally developed to treat depression and schizophrenia, this compound showed good oral activity when tested in experimental models of acute and chronic inflammation and pain (Haroon et al., 2012). After some years of human clinical studies on its anti-inflammatory and analgesic properties, cimicoxib was redirected from the human to the veterinary field.

Cimicoxib is available as chewable oral tablets licensed for dogs as a once daily administration given at a dose of 2 mg/kg. Due to its recent release, there is very little published data available. Recently an analytical method for cimicoxib pharmacokinetic study has been published (Giorgi et al., 2013).

Sorbera and Ramis (2004) found that cimicoxib was more metabolically stable than celecoxib. In humans, cimicoxib undergoes demethylation and a subsequent conjugation reaction, the demethylated metabolite of cimicoxib has been found to be inactive in both COX-1 and COX-2 activity assays. In rats after oral and i.v. administrations, biliary excretion was the major route of elimination. 70 and 30% of the Cimicoxib dose was excreted in the feces

153 and urine respectively. In Beagle dogs, the bioavailability was 75%

following oral administration (1 mg/kg) with tmax of 2 h and t1/2 of 7 h. Like

in rats, biliary/intestinal excretion was the major route of elimination in

Beagle dogs and cimicoxib was extensively metabolized, as <0.2%

unchanged drug was detected (Sorbera and Ramis, 2004). In an in vivo

inflammatory acute pain model study, 10 h after administration (2 mg kg-1) the plasma concentrations were above a level of 100 ng Ml-1 (the EC50/IC50

values varied between 216 and 452 ng/mL for different parameters) in six out

of ten animals. At 24 h, the concentrations are lower than the stated

EC50/IC50 values in all animals. Considering the estimated differences in bioavailability and correcting for non-linear PK, it appeared that the effect of cimicoxib lasted for approximately 10-14 h in the simulated inflammatory

acute pain model EMEA, 2009. In addition, the noninferiority study where it

was compared with firocoxib confirmed that cimicoxib reduced the clinical signs of disease including lameness, pain, locomotor disturbance and oedema in dogs with chronic osteoarthritis during the 90 days of the follow up study.

Furthermore, compared with carprofen, cimicoxib was also effective in peri-

operative pain control in orthopaedic or soft tissue surgery during the first 24

h after surgery (EMEA, 2009).

In a 26 week tolerance study with Beagle dogs, it was demonstrated that

adverse effects occur on the gastrointestinal tract and to a lesser extent the

154 kidney especially papillary necrosis at higher doses (10 mg/kg). However, there were no significant adverse signs in the recommended dose group (2 mg/kg) and notably, there were no cardiovascular events. The reproductive toxicity study with rabbits however, revealed that the cimicoxib affects fertility and fetal development. Since there are no data in pregnant bitches,

“caution” or “cimicoxib is contraindicated in” is needed in breeding, pregnant and lactating dogs (EMEA, 2009).

Several studies are available in the literature for most of coxib drugs in veterinary field. Among the coxib drugs in veterinary field, however, cimicoxib has a few peer-reviewed study on the pharmacokinetic profiles, due to its recent release. The aim of this study was to ubderstand the pharmacokinetic features of cimicoxib in several animal species including dog, horse and donky.

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164 Chapter 1. Pharmacokinetic profiles of the novel COX-2 selective inhibitor cimicoxib in dogs

Abstract

Cimicoxib is a novel imidazole derivative that is a cyclo-oxygenase

(COX)-2 selective non-steroidal anti-inflammatory drug and the latest COX-

2 selective inhibitor to be released for veterinary use. Currently there is limited information available on the pharmacokinetic (PK) properties of

Cimicoxib. The aim of the current study was to evaluate the PK features of cimicoxib after administration of the recommended dose and after administration of a more variable dose rate in the form of the commercially available tablet. In addition, the effects of food intake on the PK properties were also evaluated. In the first study, five healthy Beagle dogs received 2 mg/kg cimicoxib via the oral route following a period of fasting. The second study was conducted using six healthy Labrador retriever dogs which each received an 80 mg tablet (approximate dose 1.95-2.5 mg/kg) using a crossover design, both in the fasted and fed condition. The plasma concentrations of cimicoxib were detected by a validated HPLC method.

No adverse effects were observed in any dogs during the experiment. The results from the PK analysis were similar between the studies, regardless of

165 precision of dose and fasted and fed conditions. The mean peak

concentration of cimicoxib was 0.49 and 0.43 μg/mL under fasted and fed

conditions, respectively. The mean half-life was about 3 h after all treatments.

In addition, simulated multiple dosing data revealed that time over minimal effective concentration was similar after 1.95, 2.0 and 2.5 mg/kg dose administrations. These findings suggest that slight variation from the recommended dose should not alter the therapeutic outcome. In addition, cimicoxib can be administered to fed dogs without significantly affecting blood levels.

Introduction

For over a decade, osteoarthritis (OA) has been increasingly diagnosed in dogs (Moreau et al., 2005), mainly due to a more humanized life-style

(Hoffman and Perkins, 2008). Domesticated dogs are now living longer and, as a result, are more susceptible to age-related diseases such as cancer, arthritis, metabolic disorders, and obesity. Fortunately, the veterinary drug market continues to grow (Giorgi, 2012; Hoffman and Perkins, 2008) although available drugs for the veterinarian remains quite small.

Chronic pain management during inflammatory disease has become a priority in pets. Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit

166 cyclooxygenase (COX) enzymes, preventing the conversion of arachidonic acid to various prostaglandins and thromboxanes. COX-1 is considered to be

a housekeeping enzyme and COX-2 is best known for its local up-regulation

by pro-inflammatory stimuli, by production of prostaglandins involved in inflammatory responses and in the spinal cord facilitating transduction of painful stimuli (Vardeh et al., 2009). The analgesic and anti-inflammatory activity of NSAIDs is thought to be predominantly mediated through COX-2 inhibition (Seibert et al., 1994; Zhang et al., 1997).

Due to the severe side effects often associated with chronic NSAID use, there has been a boost in research in COX-2 selective inhibitor (coxib) drugs in human and veterinary medicine. In the last decade, five different COX-2 selective drugs have been launched on the veterinary market, namely, deracoxib (2002), firocoxib (2007), mavacoxib (2008), robenacoxib (2009) and the most recent, cimicoxib (2011). Several studies are available in the literature for most of these drugs (Autefage et al., 2011; Bienhoff et al., 2012;

Hanson et al., 2006; Kim and Giorgi, 2013; Reymond et al., 2012), and also for COX-2 inhibitor drugs labelled for human use and applied to veterinary medicine (Giorgi et al., 2012). However, there has been no peer-reviewed study on the pharmacokinetic (PK) profiles of cimicoxib in the dog. Recently, an analytical method for cimicoxib detection in dog plasma has been

167 developed and used to determine PK profile for a single dog (Giorgi et al.,

2013).

The objectives of this study were to determine the PK features of cimicoxib in healthy dogs after a single oral administration of (1) 2 mg/kg and (2) 80 mg to dogs in the fasting and fed state.

Materials and methods

Chemical and reagents

Pure cimicoxib and parecoxib (internal standard) powders (both >99.0% purity) were donated by Vetoquinol and Pfizer, respectively. High performance liquid chromatography (HPLC) grade acetonitrile (ACN),

methanol (MeOH), dichloromethane (CH2Cl2), and diethyl ether (Et2O) were

purchased from Merck. Analytical grade trifluoroacetic acid (CF3COOH)

was obtained from BDH. Sodium chloride (NaCl) and ammonium acetate

(AcONH4) were purchased from Carlo Erba. Distilled water was produced

by a Milli-Q Milli-pore Water System (Millipore). All other reagents and

materials were of analytical grade and supplied from commercial sources.

The LC mobile phases were filtered through 0.2 μm cellulose acetate

membrane filters (Sartorius Stedim Biotech) with a solvent filtration

168 apparatus.

Animal studies

Beagle and Labrador retriever dogs were used. Each dog was housed in a

single 3m × 2 m box and acclimatized for a minimum of 1 week. The

experiments, approved by the Lublin local Animal Research Ethical Board

(54/2012), were performed in accordance with the European Regulation on

Animal Welfare (Directive 2010/63/EU).

Study 1. cimicoxib 2 mg/kg administration (precise dose)

Five healthy male adult Beagles with a weight and age range of 9-12 kg

and 4-5 years, respectively, were used. The animals were considered

clinically healthy on the basis of a physical examination and complete

haematological analyses. The dogs were given cimicoxib (Cimalgex,

Vetoquinol) at a dose of 2 mg/kg orally, after 12 h of fasting overnight. Water

was provided ad libitum. The tailored doses were prepared by carefully partitioning and weighing the marketed chewable tablet.

A catheter was placed into the right cephalic vein to facilitate blood

169 sampling. Blood samples for PK analysis (2-3 mL) were collected at

intervals of 0, 0.25, 0.5, 0.75, 1, 2, 3, 4, 5, 6, 8, 10, and 24 h after cimicoxib

administration, and placed in collection tubes containing lithium heparin.

The blood samples were centrifuged at 400 g for 5 min within 30 min of

collection. The harvested plasma was stored at -20°C and used within 14

days of collection.

Study 2. cimicoxib 80 mg/dog administration (variation on recommended

dose)

Six healthy male Labrador retriever dogs weighing 32-41 kg and ranging in age between 2 and 4 years were used in this study. The dogs were considered clinically healthy on the basis of a physical examination and complete haematological analyses. Animals were randomly (drawn from a box) assigned to two treatment groups, using an open, paired, single-dose, two treatment, two-period, crossover design. Each dog received a single dose of 80 mg/subject cimicoxib (Cimalgex, Vetoquinol). The first group (n = 3) received the treatment in the morning, after fasting for 12 h overnight. The second group (n = 3) was treated with a single dose of 80 mg/subject cimicoxib in the morning, 15 min after the dogs had been fed canned meat dog food (250 g) with oatmeal (200 g) in a 20 cm squared container. After a

170 wash-out period of 2 weeks the groups were reversed and the treatments

repeated. A catheter was placed into the right cephalic vein to facilitate blood sampling. Both the collection times and the sample handling were as reported for Study 1.

Chromatographic conditions

The analysis procedure was performed according to Giorgi et al. (2013).

Briefly, plasma samples (500 μL) were added to internal standard (100 μL, 5

μg/mL) and 10% CF3COOH (100 μL). After vortexing for 30 s, NaCl (4 mg) was added and the samples were vortexed again. After vortexing, 600 μL of

CH2Cl2:Et2O (3:7, v/v) were added, then the samples were vortexed (30 s),

shaken (60 osc/min, 10 min) and centrifuged at 21,913 g (rotor radius 10 cm)

for 10 min at 10 °C. The supernatant (400 μL) was collected in a separate

snap cap vial. The organic phase was evaporated under a gentle stream of

nitrogen and reconstituted with 200 μL of mobile phase. Twenty microlitres

of this latter solution were injected onto the HPLC system which was

coupled to a fluorescence detector (HPLC-FL).

The plasma concentration of cimicoxib was determined by liquid

chromatography (LC Jasco) consisting of a quaternary gradient system (PU

171 980 plus) and an in line multi-lambda fluorescence detector (FL 2020 plus).

The chromatographic separation assay was performed with a Kinetex C18 analytical column (100 mm × 4.6 mm inner diameter, 2.6 lm particle size;

Phenomenex) preceded by a security guard column with the same stationary phase (Kinetex XB-C18; Phenomenex). The system was maintained at 25 °C.

The mobile phase consisted of acetonitrile:buffer (10 mM AcONH4, adjusted to pH 4.5 with AcOH) (35:65, v/v) at a flow rate of 1 mL/min with isocratic mode. Excitation and emission wavelengths for analysis were set at 268 and

430 nm, respectively.

Quantification

The calibration curve of peak area vs. concentration (0.01, 0.05, 0.1, 0.5 and 1 μg/mL) of cimicoxib was plotted. Least squares regression parameters for the calibration curve were calculated, and the concentrations of the test samples were interpolated from the regression parameters. Sample concentrations were determined by linear regression, using the formula Y = aX + b, where Y = peak area, X = concentration of the standard in lg/mL, a = the slope of the curve and b = the intercept with Y axis. The correlation coefficient of the calibration curve was >0.99. The cimicoxib recovery was

76 ± 5.6% with a coefficient of variation (CV) < 6.3%. The limit of

172 quantification was 25 ng/mL. The full method validation can be found

elsewhere (Giorgi et al., 2013).

PK evaluation

The PK calculations were carried out using WinNonLin v 5.3.1

(Pharsight). Maximum concentration (Cmax) of cimicoxib in plasma, and the time required to reach Cmax (Tmax) were predicted from the data. The area

under the concentration/time curve (AUC0-∞) was calculated using the linear

trapezoidal rule. According to Akaike value and to goodness of fit criteria,

changes in plasma concentrations of cimicoxib were best described using the

mono-compartmental analysis. The adequacy of the curve fitting was

assessed by the correlation coefficient and standard error of the estimated

parameters.

Determination of cimicoxib dosage regimens

Based on the PK analysis of pooled data, computer simulations

(WinNonlin 5.3) were performed to compare the time above minimal

effective concentration (MEC) after different oral doses (1.95, 2, and 2.5

mg/kg). The MEC was set 0.2 μg/mL according to the previous report (EMA,

173 2011).

Statistical analysis

The PK data between groups were assessed using ANOVA with

Bonferroni’s post hoc test. The results are reported as standard deviations of the mean values (±SD). All the analyses were conducted using GraphPad

InStat v.5.0. Differences were considered significant if the associated P value was <0.05.

Results

No visible adverse effects were observed in any dogs in either of the studies over the 24 h following drug administration.

Study 1. cimicoxib 2 mg/kg administration (precise dose)

The mean time concentration curve for the five Beagle dogs given 2 mg/kg cimicoxib is shown in Fig. 1. After oral administration, cimicoxib concentrations were detectable in plasma for up to 24 h in 2/5 dogs. A mono-

174 compartmental model best fitted the plasma concentrations. The Cmax and

Tmax were 0.52 (0.30-0.78) μg/mL and 2.98 (1.80-4.16) h, respectively. The distribution and disposition half-lives were 1.75 (0.58-2.89) h and 2.97

(2.68-3.43) h, respectively. Some variability in the PK parameters was shown.

The complete mean PK parameters are reported in Table 1.

Fig. 1. Mean plasma concentrations of cimicoxib vs. time curve in Beagle dogs (n = 5) following PO administration (2 mg/kg). Bars represent the standard deviations.

175 Table 1

Main pharmacokinetic parameters of cimicoxib (2 mg/kg) in the Beagle dogs (n = 5)

Parameters Unit Mean (Range) CV (%) R2 0.94 (0.92-0.99) 4.14

K01_HL h 1.75 (0.58-2.89) 69.49

K10_HL h 2.97 (2.68-3.43) 10.74

Tmax h 2.98 (1.80-4.16) 40.51

Cmax µg/mL 0.52 (0.30-0.78) 38.91 V_F mL/kg 2177 (936-3148) 42.26 CL_F mL/h/kg 495.9 (242.0-636.1) 35.38

AUC0-∞ h*µg/mL 4.67 (3.14-8.26) 51.72 2 R , correlation coefficient; K01_HL, distribution half-life; K10_HL, disposition half-life; Tmax, time of peak; Cmax, peak plasma concentration; V_F, volume of distribution of the terminal phase; CL_F, clearance of the terminal phase; AUC0-∞, area under the plasma concentration- time curve from 0 to infinite.

176 Study 2. cimicoxib 80 mg/dog administration (variation on recommended

dose)

The mean PK profiles of cimicoxib in fasted and fed states are shown in

Fig. 2. cimicoxib concentrations were detectable in plasma for up to 24 h in

3/6 dogs in both groups. Large intra- and inter-subject variability was noted.

Four dogs showed individual PK profiles that were almost identical in the fasted and fed states, while two subjects demonstrated variations in their PK profiles that were influenced by fasted/fed status (Fig. 3). Overall the mean

PK curves for fasted and fed status showed similar but not identical profiles and the difference was not significant. There was some variability with fasted/fed status reported for the PK parameters (Table 2) but, again, the differences were not significant. These parameters with the variable dose rates were not significantly different from the parameters computed in the 2 mg/kg study (Table 1).

177

Fig. 2. Mean plasma concentrations of cimicoxib vs. time curves in Labrador retriever dogs (n = 6) following PO administration (80 mg tablet/dog) after fasted (-○-) and fed (-●-) status. Bars represent the standard deviations.

178

Fig. 3. Individual plasma concentrations of cimicoxib vs. time curves in Labrador Retriever dogs following PO administration (80 mg tablet/dog) after fasted (-○-) and fed (-●-) status. In the graph area is reported the ID and the actual dose (mg/kg) administered for each subject.

179 Table 2

Pharmacokinetic parameters following a single PO administrations of 80 mg tablet/dog of cimicoxib in Labrador Retriever dogs (n = 6)

Fasted Fed

Parameters Unit Mean (Range) CV (%) Mean (Range) CV (%) R2 0.97 (0.94-0.99) 2.19 0.95 (0.90-0.98) 3.23

K01_HL h 2.53 (0.97-3.98) 49.61 3.10 (0.39-4.71) 48.95

K10_HL h 3.85 (1.71-5.41) 35.91 3.72 (2.68-4.71) 20.78

Tmax h 4.14 (2.59-5.83) 30.75 4.62 (1.47-6.80) 40.56

Cmax µg/mL 0.49 (0.31-0.61) 22.59 0.43 (0.29-0.81) 44.59 V_F mL/kg 2087 (1604-2557) 18.59 2310 (1820-2726) 40.56 CL_F mL/h/kg 413.9 (290.2-669.8) 35.67 441.5 (300.0-547.2) 19.77

AUC0-∞ h*µg/mL 5.94 (3.40-7.64) 28.42 5.27 (4.05-6.49) 18.04 2 R , correlation coefficient; K01_HL, distribution half-life; K10_HL, disposition half-life; Tmax, time of peak; Cmax, peak plasma concentration; V_F, volume of distribution of the terminal phase; CL_F, clearance of the terminal phase; AUC0-∞, area under the plasma concentration-time curve from 0 to infinite; CV, coefficient of variation.

180 Determination of cimicoxib dosage regimens

A compartmental open PK model was fitted to the pooled data from five

fasting Beagle dogs, and the model was used to simulate the concentration vs.

time profile for several dosage regimens after oral (PO) administration. The

parameters of this average model were V_F, K01 and K10, which were 2177 ±

920 (mL/kg), 0.63 ± 0.46 (1/h), and 0.23 ± 0.02 (1/h), respectively.

Following simulations of PO administration of cimicoxib at a daily dose of 2

mg/kg, plasma concentrations were greater than the assumed MEC value of

0.2 μg/mL for approximately 8.4 h. Simulation of PO administration of

cimicoxib at daily dose range of 1.95-2.5 mg/kg gave drug concentrations exceeding the MEC for 8.3-9.4 h (Fig. 4).

181

Fig. 4. Simulated concentration vs. time curves of cimicoxib after multiple once a day PO administrations at different doses. Each line indicates a different dose as follows: 1.95 mg/kg (- - -), 2 mg/kg (—) and 2.5 mg/kg (-··-). The horizontal dashed line represents the MEC (0.2 mg/mL).

182 Discussion

Cimicoxib is a second generation, highly selective COX-2 inhibitor that exhibits promising anti-inflammatory and analgesic activity. It was developed originally as a treatment for depression and schizophrenia

(Almansa et al., 2003) but showed oral activity comparable to other coxibs when tested in experimental models of acute and chronic inflammation and pain (Rigau et al., 2003; Sorbera and Ramis, 2004). After some years of clinical development as an antiinflammatory and analgesic agent in humans, cimicoxib has recently been launched on the market for veterinary use

(Emmerich, 2012). It is reported to have poor solubility in water, is widely distributed throughout the body after oral administration and is eliminated mainly via the faeces (75%) following biliary excretion (EMA, 2011).

In the present study, cimicoxib did not produce any apparent adverse

clinical signs in our experimental dogs which is in agreement with the high

safety margin with regard to cardiorespiratory, gastrointestinal and central

nervous system side effects previously reported (Rigau et al., 2003).

Additionally, a recent study fully investigated cimicoxib safety in dogs that

were given 2 mg/kg/day for 6 days and cimicoxib did not show any

difference in the incidence of adverse events compared with other drugs of

the same class (Grandemange et al., 2013). The rationale for the two

183 experimental studies described here was that in its marketed form, the same

dose of cimicoxib could be administered to a canine population with large variations in weight, breed, status conditions, etc. In order to investigate the extent of any influence of this variation, a specific dose (2 mg/kg) was

administered to Beagle dogs, a relatively genetically homogeneous

population, of similar ages, weights and life conditions. These results were

compared to those generated using a more variable dog population and a

more variable dose rate. Such an investigation is of value particularly for

drugs used to treat pain and inflammation, as treatments are often long-term and can be intermittent; convenient application is important, therefore, as is a low incidence of side effects.

Like other coxib drugs, cimicoxib is offered as an oral chewable tablet which allows owners to treat their pets themselves. Although the chewable tablet form has benefits in ease of administration, it has the disadvantage of not allowing precise dosing. With chewable tablets, exact dosing can only be achieved by splitting the tablets based on bodyweight, which can be a tedious and inaccurate process. Thus, it is common to treat animals in a range of weights with the same dose, achieving the approximate recommended dose. Our second study was designed to reflect the range in doses that dogs are likely to receive when their owners are administering the

184 treatment. Both the product information and a recent efficacy study

(Grandemange et al., 2013) on cimicoxib recommend a daily dose of 2 mg/kg and this dose was therefore selected for our PK study.

In the 2 mg/kg Beagle study, cimicoxib had Tmax and K10_HL values of

2.9 h for both parameters. Sorbera and Ramis (2004) reported that cimicoxib

(1 mg/kg) administered PO to a single Beagle had a similar Tmax (2 h) but a

longer K10_HL (7 h). This difference in half-life was also reported in the

cimicoxib EMA report (2011), where the K10_HL of cimicoxib was around

2.5-4 h, and over 8 h in Beagles with normal and slow metabolisms

respectively (EMA, 2011). It was suggested that the cimicoxib dosage should

be reduced in dogs with impaired liver function.

For the second experiment, the dogs were selected based on a bodyweight of around 30-40 kg. Dogs within this range of bodyweight would receive small variations on the recommended dose when administered a whole tablet

(80 mg). The results from the second study examining PK parameters that

are likely to result after client administered treatment under fasting

conditions are in close agreement with 2 mg/kg dose study 1 data.

Approximate dosing and a different dog breed did not result in significant differences in PK parameters.

The second experiment was also designed to examine the effect of

185 fed/fasted status on PK profile. It is well known that solid food decreases

gastric emptying rate, but gastrointestinal motility increases in the presence of food. Delayed arrival of the drug at the small intestine, where most drug absorption occurs, might result in a delayed onset with reduced absorption rate. On the other hand, increased intestinal motility also might increase the rate of transit of the drug through the intestine (Welling, 1977). The type of food may also affect the absorption of lipophilic drugs with bile flow alteration. Bile acts as a surfactant for dissolution of lipophilic drugs and improves the fat intake increasing drug absorption. Moreover, the secretion

of bile can be enhanced by a high fat diet (Dongowski et al., 2005).

A previous study using celecoxib showed that food can affect the PK profile of that coxib drug. It was found that a high-fat diet increases absorption of the drug compared to fasted control animals and compared also to a low fat diet (Paulson et al., 2001). In the present study, however, the meal was of the type that would normally be given to dogs in order to simulate the real-life situation. The AUC0-∞ in both fasted and fed treatments

was similar (P = 0.50). The lipid contents of the food might account for the

similar results. The mean values of Tmax and absorption half-life in the fed group were slightly delayed compared to the fasted group and Cmax was slightly decreased in the fed group (P = 0.74). However, these small

186 differences between groups were not significant. The rate of cimicoxib

absorption remained almost unchanged regardless of fed or fasted state.

Cimicoxib showed values for clearance and volume of distribution of one-

half and three-times the values for robenacoxib, respectively (Jung et al.,

2009) but were of the same order of magnitude to firocoxib (EMA, 2005).

Further studies are required to clarify if the drug can penetrate inflamed

tissues or synovial fluid at therapeutic concentrations.

Large differences have been found in both intra- and inter-subject PK profiles. A previous report revealed that polymorphism of one or both

metabolizing enzymes (CYP2D6 and CYP2C19) in Beagles might be

responsible for these variations (EMA, 2011). The CYP polymorphism might

also have affected the dogs used in the present study and in part explain the

inter-subject differences. However, the factors that evoked the intra-subject differences in two dogs (in study 2) are obscure and further studies will be needed to clarify this issue.

The MEC assumed in this study (0.2 μg/mL) had previously been reported

in dogs (EMA, 2011). The simulation of PO administration of cimicoxib at

1.95, 2.00 and 2.50 mg/kg showed a drug plasma concentration over the

MEC in the range 8.3-9.4 h. This value is shorter than the efficacy of

cimicoxib reported in rats (10-14 h) for pain relief (EMA, 2011) and the

187 difference might result from different assessment methods. Indeed the drug plasma concentration over the MEC and the efficacy in pain relief come from PK and pharmacodynamic (PD) evaluations, respectively. It is well known that for NSAIDs drugs, PK and PD are not in phase, accounting for a large anticlockwise hysteric loop (Toutain and Lees, 2004). Moreover it is recognised that there may be some discrepancy between plasma concentration and actual effect at the receptor level (Toutain and Lees, 2004) which may explain the lower value in the present study. In addition, species difference (dog vs. rat) could have affected the results. Notably in clinical subjects, the PK-PD hysteresis could be larger than in healthy patients, and parameters, such as the onset time and time over the MEC, should be verified with proper PK-PD studies.

In conclusion, the PK parameters of cimicoxib in dogs given precise (2 mg/kg) and approximate doses (ca. 1.95-2.5 mg/kg) were similar. In addition, there were no significant differences in PK values between the fasted and fed condition. Further studies are now required to investigate the true analgesic efficacy and actual effective plasma concentration in dogs.

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192 Chapter 2. The pharmacokinetics and ex vivo cyclooxygenase selectivity of cimicoxib in fasted and fed horses

Abstract

The aim of the present study was to evaluate pharmacokinetic and pharmacodynamic properties of cimicoxib, a novel selective cyclooxygenase-2 (COX-2) inhibitor, in fasted and fed horses. A pilot study was conducted through administration of cimicoxib intra-gastrically at 2 mg/kg (canine clinical dose) to three fasted and three fed horses. The full- scale study was an open, single-dose, two treatments, two-period, crossover design (n=6) with a 2 week interval before the cross over, an increased dose of 5 mg/kg was administered due to the low bioavailability shown in the pilot study. Following cimicoxib administration (5 mg/kg), the mean maximum plasma concentration was 0.16 ± 0.01 µg/mL and 0.14 ± 0.03

µg/mL in fasted and fed groups, respectively. The higher dose led to higher peak plasma concentrations and AUC than in the pilot study, though the increment of increase was not proportional to the dose. The mean time to maximum plasma concentration was delayed in the fed group (5.91 ± 3.23 h) compared with the fasted group (3.25 ± 1.17 h) without significant difference

(p=0.12). In the ex vivo pharmacodynamic assay, the mean maximal

193 inhibition rate of thromboxane B2 and prostaglandin E2 was about 60% and

70% respectively, in both fasted and fed groups. In the present study,

although the COX-2 selectivity of cimicoxib was not shown, relatively low

blood drug concentration of cimicoxib exhibited good COX-1 and -2 inhibitions in horses. Although further investigations are required, cimicoxib use in equine practice is not recommended.

Introduction

The molecule 4-[4-chloro-5-(3-fluoro-4-methoxyphenyl)imidazol-1-yl] benzenesulfonamide (cimicoxib) was discovered in the early 2000’s. In the early stages of its development, this novel imidazole derivative drug was studied in the context of depression and schizophrenia treatment in humans

(Almansa et al., 2003). After several years of research, the selective COX-2 inhibiting effect of cimicoxib was revealed, and this active ingredient was developed as an anti-inflammatory and analgesic agent (Rigau et al., 2003;

Sorbera and Ramis, 2004). Nowadays, it is the latest coxib drug to be approved for use in dogs and marketed in the veterinary field.

Joint disease is a common clinical problem in the horse and over 60% of lameness is related to osteoarthritis (OA) which hampers their abilities to

194 race, labor,...etc (Caron and Genovese, 2003; Caron, 2011). OA can be

triggered by various causes such as trauma and infection which may

contribute to the degenerative process in the articular space by releasing

enzymes, inflammatory mediators, and cytokines (McIlwraith, 1996).

Medical treatment is usually the preferred option in equine OA. Many drug types can be used such as systemic nonsteroidal anti-inflammatory drugs (NSAIDs), intra-articular steroids, visco supplementation and chondroprotectants (Goodrich and Nixon, 2006).

The use of NSAIDs is common due to their well recognised anti-

inflammatory and analgesic effects. However, the use of some NSAIDs in

horses can induce toxicity in the gastrointestinal or renal systems due to their

non-selective inhibition of cyclooxygenase (COX) (Snow et al., 1979,

Gunson and Soma, 1983). NSAIDs act by inhibiting both COX-1 and -2

pathways to prevent the conversion of arachidonic acid to various

prostaglandins and thromboxanes. The COX-1 enzyme is considered to be a housekeeping enzyme which is involved in normal physiologic processes and the COX-2 enzyme is regarded as one of the main targets in the inflammatory response (Hawkey, 2002). For these reasons, there has been an increase in research on COX-2 selective inhibitor drugs in the veterinary field. These drugs have a COX-1 sparing effect with a reduced incidence of

195 associated side effects. However, recent studies have shown that the COX-2 inhibitors may increase the possibility of cardiovascular event in humans

(Rao and Knaus, 2008). In addition there are some indications that PGE2 and

PGI2 derived from COX-2 pathways can play a protective role pertaining the oxidative damage (Adderley and FitzGerald, 1999). In the last decade, several COX-2 selective drugs have been launched on the veterinary market including deracoxib, firocoxib, mavacoxib, robenacoxib and most recently cimicoxib (Autefage et al., 2011; Bienhoff et al., 2012; Reymond et al., 2012;

Kim and Giorgi, 2013; Jeunesse et al., 2013). Among these coxib drugs, firocoxib is the only approved option for horse treatment. Due to the limited options currently available, there is a need for the testing of new drugs for use in horses. Moreover, there are no studies on the pharmacokinetic (PK) profiles of cimicoxib in horses in the veterinary literature, due to its recent release. The aim of the present study was to determine the PK features of cimicoxib in the horse and evaluate its suitability as a candidate for horse treatment using a pharmacodynamic (PD) study measuring the inhibition of the inflammatory mediator levels.

Materials and methods

Chemicals and reagents

196 The standard compound of cimicoxib and parecoxib (internal standard)

powders (both > 99.0% purity) were donated by Vetoquinol (Bertinoro, IT)

and Pfizer (Rome, IT), respectively. All other reagents and materials were of

analytical grade from Merck. Lipopolysaccharide (LPS) was obtained from

Sigma Aldrich. ELISA assay kits for prostaglandin E2 (PGE2) and

thromboxane B2 (TXB2) were obtained from My Biosource (California,

USA).

Animal studies

Six clinically healthy mares (7-12 years, 430-570 kg) were used in the present study. The mares were previously determined to be clinically healthy on the basis of a physical examination and full haematological analyses. The study protocol was approved by the ethics committee of the University of

Pisa (authorization n° 001 4896/2013) and transmitted to the Italian Ministry of Health. The full-scale study was preceded by a pilot study. For the pilot study, the animals were randomly assigned to two groups using six slips of paper marked with the numbers 1-6, selected blindly from a box. Each subject received 2 mg/kg cimicoxib (Cimalgex 80 mg/tablet, Vetoquinol) in the morning. The first group (n=3) was treated after fasting for 12 h overnight and the second group (n=3) received the drug 2 h after feeding.

197 Fed animals had a diet composed of a ground cereal mixture Equifioc

(Molitoria Val di Serchio, IT) in the afternoon and alfalfa hay in the morning.

The oral formulation of cimicoxib was given to all animals via nasogastric tube and consisted of split tablets in 500 mL of distilled water. After administration, the nasogastric tube was rinsed with 500 mL of distilled water to ensure complete delivery of the drug into the stomach. General physiological signs were assessed throughout the study (24 h) including blood pressure, heart rate, respiratory rate and body temperature. Findings of this study showed very low values in drug plasma concentrations, hence after a 2-week wash-out period, a full-scale study with a dose increment was performed. The animals were randomly allocated to two treatment groups, using an open, single-dose, two treatment, two-period, crossover design with a two week interval. All animals received 5 mg/kg of cimicoxib in the same manner as in the pilot study.

Following aseptic preparation, synovial fluid was collected from the radiocarpal joint of the forelimb using aseptic arthrocentesis. To protect horses from excessive stress and joint damage, the collection was only performed two times for each horse (2 and 10 h or 4 and 24 h) after cimicoxib administration. The rational for these collection points was extrapolated from the PK of cimicoxib in dogs early reported (Kim et al.,

198 2014a)

At the beginning of the experiments, a catheter for blood collection was

inserted into the right jugular vein and blood (10 mL) was collected at 0,

0.08, 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 6, 8, 10, and 24 h after cimicoxib

administration. The blood sample for PK analysis was placed in a lithium

heparin tube. The samples were then centrifuged at 400 g for 5 min within 30

min of collection, and the harvested plasma was stored at -20 °C until

analysis. For PD evaluation, an additional 10 mL of blood was collected at 0,

1, 4, 10, and 24 h, split evenly and stored in a sodium heparin tube (PGE2)

and non-heparinised glass tube (TXB2).

Pharmacokinetic evaluation

The Pharmacokinetic calculations were carried out using WinNonLin v

5.3.1 (Pharsight Corp). Maximum concentration (Cmax) of cimicoxib in

plasma, and the time required to reach Cmax (Tmax) were predicted from the

data. The area under the concentration/time curve (AUClast) was calculated using the linear trapezoidal rule. The non-compartmental analysis was used for plotting plasma concentrations of cimicoxib.

199 Chromatographic analysis

The HPLC analysis was carried out based on the Giorgi et al. (2013) method. The analytical method was shortly validated as follows. The standard curve was evaluated in addition to nine quality control samples with three different concentrations for each series of analyses. The intra- and inter-day repeatability was measured as coefficient of variation and was lower than 8.1%, whereas accuracy, measured as closeness to the concentration added on the same replicates, was lower than 6.2%. The limits of detection (LOD) and quantification (LOQ) were determined using signal- to-noise ratios of 3 and 10, respectively. These parameters resulted in concentrations of 0.5 ng/mL and 2 ng/mL, respectively.

Pharmacodynamic assay

The sample preparation was performed according to a previously described method (Giorgi et al., 2011). The non-heparinised whole blood (5 mL) in glass tubes was incubated for 1 h in a water bath (37 °C) for TXB2 production. Tubes were centrifuged at 400 g for 10 min at room temperature and the serum was stored at - 20 °C until analysis. For the PGE2 assay, 20 µL

(1 mg/mL) of LPS was added to sodium-heparinised blood (2 mL) and

200 incubated at 37 °C for 24 h to simulate PGE2 production from mononuclear

cells. In addition, PBS added to heparinised blood was used as a negative

control. After the incubation, blood was centrifuged at 400 g for 10 min and

a 100 µL aliquot of plasma was mixed with 400 µL of HPLC-grade MeOH to precipitate proteins. The mixture was centrifuged at 400 g for 10 min at room temperature; the supernatant was collected and stored at - 80 °C.

TXB2 and PGE2 analysis were performed using a commercial ELISA kit

(validated for horses) according to the manufacturer’s protocol. The samples

were diluted 15-, and 25-fold for TXB2 and PGE2 respectively, using the

assay buffer supplied with the kit.

Statistical methods

The Pharmacokinetic data between groups was assessed using the

ANOVA for a crossover study. The results are reported as mean ± SD. All the

analyses were conducted using GraphPad InStat v.5.0 (GraphPad Software).

In all the experiments, differences were considered significant if the

associated P value was < 0.05.

201 Results

During the entire experiment, there were no visible adverse effects in any

horses in either of the studies over the 24 h following drug administration.

Physiological signs and parameters were normal.

Pharmacokinetics

The plasma concentrations of cimicoxib vs. time after intra-gastric

administration of cimicoxib (2 mg/kg) in fasted and fed states are shown in

Fig. 1. In both plots, there was an initial rapid absorption up to 2 h followed

by a less rapid increase in concentration and the plasma concentrations of

cimicoxib were detectable for up to 24 h. The peak concentration time was

delayed about 5 h in the fed group compared to that of fasted group.

A non-compartmental model was used to calculate PK parameters of cimicoxib plasma concentration after intra-gastric administration (2 mg/kg).

The various PK parameters from both the fast and fed groups are

summarised in table 1. There were no significant differences between the

two treatment groups except in the Tmax value, though statistical significance

was not found due to large individual variation.

202

Fig. 1. Mean plasma concentrations of cimicoxib vs. time curves in fasted (-○-, n=3) and fed (-●-, n=3) horses following intra-gastric administration of Cimalgex (2 mg⁄kg). Bars represent the standard deviations.

203 Table 1

Pharmacokinetic parameters of cimicoxib (2 mg/kg) in fasted (n=3) and fed (n=3) horses

Mean ± SD Parameters Unit Fasted Fed Lambda_z 1/h 0.18 ± 0.05 0.21 ± 0.03 HL_Lambda_z h 4.12 ± 1.14 3.26 ± 0.57

Tmax h 3.66 ± 0.81 6.66 ± 2.42

Cmax µg/mL 0.12 ± 0.03 0.10 ± 0.01

AUClast h*µg/mL 1.08 ± 0.13 1.15 ± 0.18 Vz_F mL/kg 10436 ± 1683 8091 ± 1310 Cl_F mL/h/kg 1812 ± 268 1747 ± 337

AUMClast h*h*µg/mL 7.69 ± 1.21 9.07 ± 2.02

MRTlast h 7.03 ± 0.37 7.76 ± 0.64

Lambda_z, terminal phase rate constant; HL_Lambda_z, terminal half-life; Tmax, time of peak; Cmax, peak plasma concentration; AUClast, area under the plasma concentration-time curve up to the last measurable concentration; Vz_F, apparent volume of distribution; Cl_F, apparent plasma clearance; AUMClast, area under the moment curve computed to the last observation; MRTlast, mean residence time based on values up to the last measured concentration

204 The mean time concentration curve of horses administered with 5 mg/kg

cimicoxib is shown in Fig. 2. The concentration vs. time curve from the full-

scale study showed a similar tendency to the pilot study plot (Fig. 1). The

peak concentration point was shifted to the right side in the fed group vs. the

fasted group. The complete set of mean PK parameters from the full-scale

study are reported in table 2. Similarly to the pilot study, some variability in

the PK parameters was shown. A Cmax of 0.16 µg/mL at a Tmax of 3.25 h and

a Cmax 0.14 µg/mL at a Tmax of 5.91 h were obtained from horses in fasted and fed conditions, respectively. In addition, fasted and fed groups showed similar AUClast values with a 5 - 6 h range of elimination half-life.

In both the pilot and full-scale study, the concentration of cimicoxib in synovial fluid showed similar trends to plasma concentration. However, synovial fluid concentration of cimicoxib varied from that in the plasma at the same collection time by 1.6% to 20% (Fig. 3).

205 Table 2.

Pharmacokinetic parameters of cimicoxib (5 mg/kg) in fasted (n=6) and fed (n=6) horses

Lambda_z, terminal phase rate constant; HL_Lambda_z, terminal half-life; Tmax, time of Mean ± SD Parameters Unit Fasted Fed Lambda_z 1/h 0.12 ± 0.03 0.12 ± 0.02 HL_Lambda_z h 5.96 ± 1.79 5.63 ± 1.01

Tmax h 3.25 ± 1.17 5.91 ± 3.23

Cmax µg/mL 0.16 ± 0.01 0.14 ± 0.03

AUClast h*µg/mL 1.49 ± 0.60 1.61 ± 0.72 Vz_F_obs mL/kg 33340 ± 21790 34243 ± 30186 Cl_F_obs mL/h/kg 3879 ± 2225 4067 ± 3329

AUMClast h*h*µg/mL 10.96 ± 5.77 13.22 ±7.07

MRTlast h 6.85 ± 1.51 7.70 ± 1.48

peak; Cmax, peak plasma concentration; AUClast, area under the plasma concentration-time curve up to the last measurable concentration; Vz_F, apparent volume of distribution; Cl_F, apparent plasma clearance; AUMClast, area under the moment curve computed to the last observation; MRTlast, mean residence time based on values up to the last measured concentration

206

Fig. 2. Mean plasma concentrations of cimicoxib vs. time curves in fasted (-○-, n=6) and fed (-●-, n=6) horses following intra-gastric administration of Cimalgex (5 mg⁄kg). Bars represent the standard deviations.

Fig. 3. Mean synovial fluid concentrations of cimicoxib in fasted (-○-, n=6) and fed (-●-, n=6) horses following intra-gastric administration of Cimalgex (5 mg⁄kg). Bars represent the standard deviations.

207 Pharmacodynamics

The levels of TXB2 and PGE2 were evaluated in the 0, 1, 4, 10, and 24 h

time point samples. The inhibition rate for both mediators showed different

behavior. The inhibition rate of TXB2 was increased at 1 h and maintained up to 10 h after administration. Its mean maximal inhibition rate was 62.4 ±

13.8% and 54.6 ± 15.4% in fasted and fed conditions, respectively, without

significant difference (Fig. 4). On the other hand, the inhibition of PGE2

gradually increased and reached a maximal value at 10 h after administration

with a rate of about 70% in both fasted and fed states (Fig. 5).

208

Fig. 4. Ex vivo analysis of TXB2 inhibition rate in fasted (-○-, n=6) and fed (-●-, n=6) horses following intra-gastric administration of Cimalgex (5 mg⁄kg). Bars represent the standard deviations.

Fig. 5. Ex vivo analysis of PGE2 inhibition rate in fasted (-○-, n=6) and fed (-●-, n=6) horses following intra-gastric administration of Cimalgex (5 mg⁄kg). Bars represent the standard deviations.

209 Discussion

In the present study the PK and the ex vivo PD of cimicoxib in horses is reported for the first time. Cimicoxib did not show any apparent adverse clinical signs, even if administered at 2.5 times the recommended canine clinical dose. This was in line with a previous finding reporting the high safety margin of cimicoxib in the gastrointestinal, central nervous and

cardiorespiratory systems (Rigau et al., 2003).

At the beginning of the study horses were treated with 2 mg/kg cimicoxib.

This dose was selected according to both the product information and a

recent efficacy study on the recommend daily dose in dogs (Grandemange et

al., 2013).

An earlier study on dogs revealed that food in the form of canned meat did

not affect absorption of cimicoxib (Kim et al., 2014a). In both the pilot and

full-scale study, a delay was found when drug was given together with food

in line with a previous study (Maitho et al., 1986). However the difference in

Tmax values (in both pilot and full scale studies) but it was without

statistical significances due to large inter-subject variation. The shift in Tmax

might have resulted from the rough fibrous feed preventing tablet contact

with gastric secretions. However, the fibrous content did not affect drug

absorption which was determined by systemic exposure of drug, the AUC.

210 In the present study, following administration of cimicoxib at a dose of 2

mg/kg to six healthy horses, the average half-life was 4 h. This half-life was similar to that of dogs (Kim et al., 2014a). However, the mean Cmax in horses was about 0.1 µg/mL, which is relatively low compared to that in dogs (0.4 µg/mL) administered with the same dose (Kim et al., 2014a).

Moreover, the above mentioned Cmax from horses was only about 50% of the minimal effective concentration (MEC, 0.2 μg/mL) reported in dogs

(EMA report, 2011). Because of this low blood drug concentration, the administered dose of cimicoxib was increased to 5 mg/kg after the 2 week wash-out period. The data from the full-scale study showed both increased

Cmax and AUC values from those in the pilot study. However, these differences were not proportional to the increment of dose increase. Even with a dose that was 2.5 times higher (5 mg/kg), the horses did not achieve average plasma concentration levels as high as in dogs which indicates a relatively low bioavailability or a high plasma clearance. This trend was similar also in donkeys (Kim et al., 2014b). Concurrent experimental trials in dogs showed that the disposition of cimicoxib after an oral administration was not linear for doses ranging from 1 to 4 mg/kg due to the limited solubility of cimicoxib (Jeunesse et al., 2013). It is also in line with likely species differences: indeed drugs such as ampicillin and amoxicillin showed oral bioavailabilities of 0-1% and 5% in horses and 30% and 60-80% in dogs,

211 respectively (Ensink et al., 1992; Ensink et al., 1996; Kung et al., 1994;

Schulze et al., 2005). Unfortunately cimicoxib is not sold as injectable formulation because of its poor water solubility. That did not allowed to

perform an IV administration in order to assess its oral bioavailability.

There are several possible explanations for the low plasma concentration

of cimicoxib in horses. One reason might be high Cl/F value that reflects

both clearance and bioavailability. The observed plasma clearance of the

drug was much higher in the horses (1,812 mL/h/kg) compared to dogs

(413.9 mL/h/kg) after the same treatment. According to an earlier report,

cimicoxib is mainly eliminated via the faeces following processing via two

major metabolic pathways, glucuronidation and demethylation (EMA report

2011). The phase II reactions including glucuronidation, acetylation and

sulfation showed large variations among species and the horse has been

recognised as a species with a relatively high glucuronidating capacity

(Toutain et al, 2010). In addition, equine gastric pH levels have been

reported to be highly variable depending on region of the stomach, this might

result in poor absorption (accounting for a low F) depending on the drug pKa

value (Murray et al, 1989). The daily intake of highly fibrous feed could also

affect the small intestinal wall grooves reducing the drug absorption in

comparison to other animal species (Baggot and Brown, 1998). The

212 pharmaceutical formulation could also have affected the bioavailability.

Indeed the administered cimicoxib tablets are formulated specifically for dogs (containing lactose monohydrate, povidone K25, crospovidone, sodium laurylsulfate, macrogol 400, sodium stearyl fumarate and pork liver powder) which might have reduced the drug absorption in the horse. It is conceivable that different dissolution in the equine stomach may be responsible for any differences between the dog and horse for systemic availability of cimicoxib and variability in absorption following oral administration. However, additional studies on the dissolution of these tablets (designed for dogs) in equine gastric fluid might clarify a consistent and timely release of the active ingredient.

The scientific literature contains many reports of in vitro studies undertaken to determine the potency of a wide range of NSAIDs as inhibitors of COX isoforms. As discussed earlier (Lees et al., 2004; Warner et al. 1999), assay results are markedly dependent on experimental conditions, such as isolated enzymes, broken cell vs. intact cell assays, and diverse buffer solutions, and intact cell whole blood assays have yielded very disparate findings. Most investigators conducting in vitro assays have preferred to use whole blood, on the grounds of greatest physiological relevance. Such assays use a matrix which is a natural body fluid containing both platelets and

213 leucocytes and accounts for the very high degree of drug binding to plasma

protein, which characterises the great majority of NSAIDs (Pairet and Van

Ryn, 1998; Young et al., 1996). However, even optimised in vitro blood

assays can yield differing ratios to those obtained ex vivo and in vivo for

individual drugs. Indeed in this study, ex vivo assays were used to determine

TXB2 and PGE2 inhibition, these are representative parameters for the COX-

1 and COX-2 pathway respectively.

Although the Cmax is often lower than the MEC (from dog, 0.2 µg/mL), the 5 mg/kg administered to horses resulted in a PGE2 inhibition rate of over

70%. A diverse plasma protein binding between the animal species might

have triggered this difference. However, the tendency of inhibition rate vs.

time plots was not in phase with the concentration vs. time curve. The time

of maximal effect was observed about 6 h later than peak concentration time.

The drug blood concentration at certain points cannot be directly correlated

to effect, due to the time interval between Tmax (PK) and the maximal

inhibition time point (PD). This is in line with most NSAIDs drugs which

have been found to show a large anti-clockwise hysteresis PK-PD loop

(Pleuvry, 2005; Torres-López et al., 1997; Toutain, 2002). The PK and PD

are not in phase due to a hysteresis between plasma concentration and actual

effect at the receptor level (Toutain and Lee, 2004). This can also occur for

214 drugs such as aspirin, phenylbutazone and tepoxalin, which are converted to

active metabolites in vivo (Lees et al., 2004).

Unfortunately, TXB2 was also inhibited by cimicoxib treatment but with a

rate and trend that was different to that of PGE2. The inhibition rate was

lower than that of PGE2 and the TXB2 peak inhibition was found at 1 h after

cimicoxib administration. The reason for the time interval between COX-1

and -2 inhibition is obscure. Although dual inhibition of the COX isoforms in

unexpected in a molecule classified as coxib, it is important to point out that

the term “coxib” is used to denote a class of molecules possessing a tricyclic

ring and a methyl-sulfonic group, and it is often improperly associated with

COX-2 selective inhibition. The coxib class also includes molecules with

COX-1 selective inhibition such as the experimental compound SC-560

(Teng et al., 2003).

The animal species might have played a role in determining COX selectivity. Indeed it is not the first time that an anti-inflammatory drug is selective in one animal species and non-selective in others. Hence, the lack of selectivity might be due to the animal species being treated. Similar results have been shown for carprofen, although carprofen has not a coxib structure. According to Lee et al. (2004), carprofen may act as a non- selective drug in the horse rather than being a COX-2 preferential or

215 selective drug as it is in both the dog and cat. Meanwhile, from the previous report, phenylbutazone has a relatively high potency in horses compared to other species including dogs and humans (Gierse et al., 2002; Higgins and

Lees, 1983). Further studies to assess the selectivity of cimicoxib in horses are required. It is noteworthy that cimicoxib, even though its maximal plasma level was below the IC50 reported in dogs, has revealed a good activity against the markers for inflammation and pain in the horse.

In conclusion, cimicoxib pharmacokinetics were characterised by low plasma concentrations and further studies are needed to clarify this behavior.

Although the drug plasma concentration required to inhibit the COX enzymes was lower than the one reported in dogs, cimicoxib was found to be not COX-2 selective in the horse. At the light of these preliminary findings the use of cimicoxib in equine practice is not recommended.

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Giorgi M, Kim TW, Saba A, Rouini MR, Yun H, Ryschanova R, Owen H. 2013. Detection and quantification of cimicoxib, a novel COX-2 inhibitor, in canine plasma by HPLC with spectrofluorimetric detection: Development and validation of a new methodology. J Pharm Biomed Anal. 83: 28-33.

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221 Springer Berlin, DE.

222 Chapter 3. Pharmacokinetics of the novel COX-2 inhibitor cimicoxib in donkeys

Abstract

Cimicoxib is a novel cyclooxygenase 2 inhibitor drug approved for use in

dogs. Assessing pharmacokinetic profiles in target species is pivotal for

extra-label applications. The purpose of the present study was to evaluate the

pharmacokinetic profiles of cimicoxib after intragastric administration in six

healthy jennies. Plasma concentrations of cimicoxib were determined by

high performance liquid chromatography with fluorescence detector. A pilot study was carried out with two animal groups (n = 3) in fasted or fed conditions receiving 2 mg/kg of cimicoxib. Because of the relatively low

Cmax (0.03 μg/mL) from the pilot study, the dose was increased (5 mg/kg) for the subsequent full-scale crossover study. Single administration of 5

mg/kg did not show any adverse effects. However, the Cmax (0.02 μg/mL)

and area under the curve (0.14 h × mg/mL) values obtained after 5 mg/kg

administration were not dose dependent compared with those in the 2 mg/kg

pilot study. The results from this study could provide basic but essential information for the use of cimicoxib. Further pharmacodynamic studies are required to assess clinical efficacy in donkeys at these low plasma

223 concentrations.

Inroduction

Pain due to inflammatory processes is frequently a problem in equids.

Nonsteroidal anti-inflammatory drugs (NSAIDs) block pathologic processes by inhibiting cyclooxygenase (COX) enzymes. There is a trend for the replacement of NSAIDs with selective COX-2 inhibitors in treatment protocols to reduce the gastrointestinal and/or platelet disorders triggered by

COX-1 inhibition (Kim et al., 2013). Cimicoxib is a recently marketed selective COX-2 inhibitor drug for use in dogs (Anonymus, 2012). Because of its recent release, there are little background data in other species. There is a particular need for broadening of the veterinaryarmamentarium of diagnostics and treatments, especially the range of available drugs for use in different diseases and/or animal species. This was the impetus for evaluation of the extra-label application of coxib drugs in species such as horses and donkeys (Kvaternick et al.,2007 ).

Understanding pharmacokinetic (PK) properties is the first step in investigating the use of a particular drug in anew species. Few drugs used in donkeys have dosages based on evidence (Coakley et al., 1999; Matthews et al., 2001; Sinclair et al., 2006); most dosages are extrapolated from other

224 species (commonly horses). Thus, the aim of this study was to determine the

PK properties of cimicoxib in donkeys.

Materials and methods

Animal study

The animal experiment was approved by the ethics committee for animal welfare of the University of Pisa (protocol number 001 4896/2013). In the present study, six healthy jennies (6-9 years and 280-320 kg) were treated with two doses (2 and 5 mg/kg) of cimicoxib.

For the pilot study, a 2 mg/kg dose was administered based on the clinical dose in dogs (Anonymus, 2011). The animals were randomly assigned to two groups. The first group (n = 3) was treated after fasting for 12 h overnight and the second group (n = 3) received the drug 2 h after feeding. Oral formulation of cimicoxib (Cimalgex 80 mg; Vetoquinol, Lure, France) was ground into powder and suspended in 200 mL of distilled water (DW). The suspension was given to all donkeys via a nasogastric tube. After administration, the nasogastric tube was rinsed with 500 mL of DW to complete administration into the stomach. Before administration, a catheter was inserted into the right jugular vein and blood (5 mL) was collected at 0,

225 0.08, 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 6, 8, 10, and 24 h after cimicoxib administration. After a 2-week washout period, a second study was conducted with an increased dose of 5 mg/kg using an open, single dose, two treatments, two periods, and crossover design with 2 weeks of interval. The rationale for the increased dose was the low average cimicoxib plasma concentrations detected after the 2 mg/kg treatment. The jennies were treated in the same manner as the pilot study.

Pharmacokinetic analysis

Plasma concentrations of cimicoxib were determined by high performance liquid chromatography (HPLC) with fluorescence detector, as described elsewhere with slight modification (Giorgi et al., 2013). An extraction solvent composed by C2H2:Et2O (1:1, vol/vol) rather than C2H2:Et2O (3:7, vol/vol) was found to give a better cimicoxib recovery in plasma from donkey. The method was validated for plasma of jennies. The standard curve for analysis was linear from 0.01 to 2.5 mg/mL. The intra- and inter-day repeatability was < 6.9%, whereas accuracy was < 7.4%. The limits of detection and limits of quantification (LOQ) were 3 and 10 ng/mL, respectively.

Each donkey was analyzed singularly using the PK software WinNonlin

5.3 (Pharsight, St. Louis, MO). Donkeys having the same treatment were

226 grouped and averaged. Non-compartmental PK analysis was chosen as the best fitting model, according to the visual analysis of the plasma drug concentrations.

Statistical anaysis

The Pharmacokinetic data between groups was assessed using the

ANOVA for a crossover study. The results are reported as mean ± SD. All the analyses were conducted using GraphPad InStat v.5.0 (GraphPad Software).

In all the experiments, differences were considered significant if the associated P value was < 0.05.

227 Results

There were no adverse effects observed at any point during the study. The plasma concentrations of cimicoxib were below the limit of quantification 10 h after both the 2 and 5 mg/kg administrations (Fig. 1). There was no significant difference in PK profiles between the fasted and fed conditions in both the 2 and 5 mg/kg treated groups (Table 1).

Fig. 1. Mean plasma concentrations of cimicoxib versus time curve in donkeys after intragastric administration of (A) 2 mg/kg (n = 3) and (B) 5 mg/kg (n = 6) after fasted (open circle) and fed (filled circle) conditions. Bars represent the standard deviations.

228 Table 1.

Pharmacokinetic parameters of cimicoxib (2 mg/kg) in the donkey (n=6)

2 mg/kg (n = 3) 5 mg/kg (n = 6) Parameters Unit Fasted Fed Fasted Fed R2 0.92±0.051 0.96±0.015 0.90±0.034 0.80±0.137

Lambda_z 1/h 0.29±0.129 0.26±0.216 0.19±0.153 0.13±0.065 HL_Lambda_z h 2.72±1.391 5.17±5.385 5.28±3.494 5.89±2.486

Tmax h 1.66±2.020 1.55±0.500 1.00±0.433 1.66±0.577

Cmax µg/mL 0.03±0.003 0.03±0.009 0.02±0.005 0.02±0.004

AUClast h*µg/mL 0.13±0.045 0.10±0.020 0.14±0.056 0.15±0.034 Vz_F_obs mL/kg 46639±8379.2 75051±43458.8 175005±18814 195300±69291 Cl_F_obs mL/h/kg 13861±7147 13828±6435 32402±22358 24440±7648.0

AUMClast h*h*µg/mL 0.45±0.225 0.36±0.078 0.58±0.348 0.65±0.183

MRTlast h 3.11±0.808 3.33±0.448 3.90±0.929 4.29±0.328

AUClast, area under the plasma concentration-time curve up to the last measurable concentration; AUMClast, area under the moment curve computed to the last observation; Cmax, peak plasma concentration; Cl_F, systemic clearance per fraction adsorbed; HL_Lambda_z, terminal half-life; Lambda_z, terminal phase rate constant; MRTlast, mean residence time based on values up to the last measured concentration; R2, correlation coefficient; Tmax, time of peak; Vz_F, volume of distribution per fraction adsorbed.

229 Discussion

The 2 mg/kg treated group showed a low Cmax value and the Cmax was

achieved more rapidly than that in dogs administered with the same dose (0.5

mg/mL at 3 h) (Kim et al., 2014). According to the analysis of variance test

for a crossover study, higher clearance (Cl_F) of cimicoxib was observed in

donkeys (13,861 mL/h/kg) compared with dogs (495 mL/h/kg) (Kim et al.,

2014) and horses (1,812 mL/h/kg) (Kim et al., under review). In addition, the

volume of distribution (Vz_F) of cimicoxib in donkeys was 46,639 mL/kg, which was 20 times higher than that of dogs (Kim et al., 2014). However, as

clearance and volume of distribution after oral administration are linked to the functional dose (F), the different bioavailability of the drug in these animal species could have affected these two parameters.

A previous study reported that oral cimicoxib at 2 mg/kg showed similar efficacy and tolerability compared with carprofen in dogs (Grandemange at al., 2013). However, the present PK study reports lower average cimicoxib plasma concentration and AUC values (>20 fold) than those reported in dogs.

In the 5 mg/kg treated group, although the dosewas increased 2.5 times, the

Cmax (0.02 mg/mL) was not significantly different than that obtained from the 2 mg/kg treated donkeys. The minimal effective concentration of cimicoxib in dogs has been reported to be 0.2 mg/mL (Anonymus, 2011). It

230 is unlikely that the drug plasma concentrations achieved in this study would produce pain relief in donkeys.

Cimicoxb showed a small average area under the curve (AUC) value after intragastric administration in donkeys. In addition, drug distribution and elimination differed from that reported for horses (Kim et al., under review).

Most of the PK parameters correlated with absorption and AUC was relatively low compared with that in horses. This trend has previously been reported for many other NSAID drugs such as phenylbutazone, flunixine meglumine, and meloxicam (Coakley et al., 1999; Matthews et al., 2001;

Sinclair et al., 2006). Additionally, in the 5 mg/kg treated donkeys of the present study, the AUC and mean residual time (MRT) values were respectively 10 and 2 times lower than the AUC and MRT obtained from horses administered with 5 mg/kg of cimicoxib (1.5 h × mg/mL and 7 h)

(Kim et al., under review). The short MRT might be indicative of a substantial first-pass metabolism and true higher clearance, but the IV administration is required to clarify this issue. Unfortunately, slight water solubility of the drug did not enable us to test cimicoxib after IV route. In fact, no IV pharmaceutical formulation of cimicoxib is present on the market.

Differences in pharmacokinetics between horses and donkeys, although they are genetically related, may derive from different physiological

231 properties, which can affect absorption and distribution of the drug into the

body system (Grosenbaugh et al., 2011). Donkeys are known to be desert-

adapted animals and can maintain blood volume and function even when 20%

dehydrated, demonstrating a different fluid balance and body water

compartment partitioning compared with horses (Yousef et al., 1970). In

addition, hepatic metabolism in donkeys has been shown to be more rapid

with respect to horses for various drugs (Lees et al., 2004; Matthews et al.,

1997; Mealey et al., 1997). This study proved that interspecies variations can

affect the pharmacokinetics of cimicoxib. These differences should be

considered when extrapolating data from certain species to others (Giorgi ,

2012).

In conclusion, a single administration of cimicoxib did not evoke any

adverse effects even at doses as high as 5 mg/kg. However, after intragastric

administration, cimicoxib drug plasma concentrations were low. Further

pharmacodynamic studies are required to assess the efficacy of cimicoxib at

these plasma concentrations in donkeys.

232 References

Anonymus. EMA report. 2011. European Medicines Agency. Veterinary medicines and product data management (EMA/CVMP/513842/2011).

Anonymus. Emmerich IU. 2012. New drugs for small animals in 2011. Tierarztl Prax Ausg K Kleintiere Heimtiere. 40: 351-362.

Coakley M, Peck KE, Taylor TS, Matthews NS, Mealey KL. 1999. Pharmacokinetics of flunixin meglumine in donkeys, mules, and horses. Am J vet Res. 60:1441-1444.

Giorgi M. 2012. Veterinary pharmacology: is it still pharmacology’s cinderella? Clin Exp Pharmacol. 2: 2.

Giorgi M, Kim TW, Saba A, Rouini MR, Yun HI, Ryschanova R, Owen H. 2013. Detection and quantification of cimicoxib, a novel COX-2 inhibitor, in canine plasma by HPLC with spectrofluorimetric detection: development and validation of a new methodology. J Pharm Biomed Anal. 83: 28-33.

Grandemange E, Fournel S, Woehrle F. 2013. Efficacy and safety of cimicoxib in the control of perioperative pain in dogs. J Small Anim Pract. 54: 304-312.

Grosenbaugh DA, Reinemeyer CR, Figueiredo MD. 2011. Pharmacology and therapeutics in donkeys. Equine Vet Educ. 23: 523-530.

Kim TW, Lebkowska-Wieruszewska B, Owen H, Yun HI, Kowalski CJ, Giorgi M. 2014. Pharmacokinetic profiles of the novel COX-2 selective inhibitor cimicoxib in dogs. Vet J. 200: 77-81

233 Kim TW, Della Rocca G, Di Salvo A, Ryschanova R, Micaela S, Giorgi M. 2014. Pharmacokinetic and pharmacodynamic evaluation of cimicoxib after intra-gastric administration in fasted and fed horses. NZ Vet J. under review.

Kim TW, Giorgi M. 2013. A brief overview of the coxib drugs in the veterinary field. Am J Anim Vet Sci. 8: 89-97.

Kvaternick V, Pollimeier M, Fischer J, Hanson PD. 2007. Pharmacokinetics and metabolism of orally administered firocoxib, a novel second generation coxib, in horses. J vet Pharmacol Therap. 30: 208-217.

Lees P, Landoni MF, Giraudel J, Toutain PL. 2004. Pharmacodynamics and pharmacokinetics of nonsteroidal anti-inflammatory drugs in species of veterinary interest. J Vet Pharmacol Therap. 27: 479-490.

Matthews NS, Peck KE, Taylor TS, Mealey KL. 2001. Pharmacokinetics of phenylbutazone and its metabolite oxyphenbutazone in miniature donkeys. Am J vet Res. 62: 673-675.

Matthews NS, Peck KE, Mealey KL, Taylor TS, Ray AC. 1997. Pharmacokinetics and cardiopulmonary effects of guaifenesin in donkeys. J Vet Pharmacol Therap. 20: 442-446.

Mealey KL, Matthews NS, Peck KE, Ray AC, Taylor TS. 1997. Comparative pharmacokinetics of phenylbutazone and its metabolite oxyphenbutazone in clinically normal horses and donkeys. Am J Vet Res. 58: 53-55.

Sinclair MD, Mealey KL, Matthews NS, Peck KE, Taylor TS, Bennett BS. 2006. Comparative pharmacokinetics of meloxicam in clinically normal horses and donkeys. Am J vet Res. 67: 1082-1085.

234 Yousef MK, Dill DB, Mayes MG. 1970. Shifts in body fluids during dehydration in the burro, Equus asinus. J Appl Physiol. 29: 345-349.

235 General conclusion

The drug must be explored carefully based on a species differences to

secure its safe and effective clinical application. In dogs, the

pharmacokinetic parameters in precise and approximate doses were similar

in both fast and fed conditions. In horses and donkeys, the average serum

concentration of cimicoxib was lower than that of dogs after the same dosage

administration. In addition, cimicoxib was found to be not COX-2 selective

in the horse. It is complicated work to make firm distinctions between preferential and selective COX inhibition or between nonselective and preferential inhibition. This is because 1. Potency ratios (COX-1:COX-2) vary widely according to experimental conditions both within and between laboratories, 2. the ratio calculated may vary depending on whether it is based on 50, 80, 95 or some other percentage inhibition and 3. apparent species differences in inhibition ratios. Further in vivo studies with diverse end-points are requested to obtain optimal clinical dosage regimens in difference species before its clinical use.

236 Related publications

Kim TW, della Rocca G, Di Salvo A, Owen H, Sgorbini M, Giorgi M. 2014. Pharmacokinetics of the novel cyclooxygenase 2 inhibitor cimicoxib in donkeys. J Equine Vet Sci. In press.

Kim TW, Łebkowska-Wieruszewska B, Owen H, Yun HI, Kowalski CJ, Giorgi M. 2013. Pharmacokinetic profiles of the novel COX-2 selective inhibitor cimicoxib in dogs. Vet J. 200: 77-81.

Kim TW, Lee HK, Song IB, Lim JH, Cho ES, Son HY, Yun HI. 2013. Platycodin D attenuates bile duct ligation-induced hepatic injury and fibrosis in mice. Food Chem Toxicol. 51: 364-369.

Kim TW, Giorgi M. 2013. A brief overview of the coxib drugs in the veterinary field. Am J Vet Sci. 8:2.

Giorgi M, Kim TW, Saba A, Rouini MR, Yun HI, Ryschanova R, Owen H. 2013. Detection and quantification of cimicoxib, a novel COX-2 inhibitor, in canine plasma by HPLC with spectrofluorimetric detection: Development and validation of a new methodology. J Pharm Biomed Anal. 83: 28-33.

Lim JH, Kim TW, Song IB, Park SJ, Kim MS, Cho ES, Yun HI. 2013. Protective effect of the roots extract of Platycodon grandiflorum on bile duct ligation-induced hepatic fibrosis in rats. Hum and Exp Toxicol. 32: 1197-1205.

Kim TW, Lim JH, Song IB, Park SJ, Yang JW, Yun HI. 2012. Hepatoprotective and anti-hepatitis C viral activity of Platycodon grandiflorum extract on carbon tetrachloride-induced acute hepatic injury in

237 mice. J Nutr Sci Vitaminol. 58: 187-194.

Kim TW, Lee HK, Song IB, Kim MS, Hwang YH, Lim JH, Yun HI. 2012. Protective effect of the aqueous extract from the root of Platycodon grandiflorum on cholestasis-induced hepatic injury in mice. Pharm Biol. 50: 1473-1478.

Lim JH, Kim TW, Park SJ, Song IB, Kim MS, Kwon HJ, Yun HI. 2011. Protective effects of Platycodon grandiflorum aqueous extract on thioacetamide-induced fulminant hepatic failure in mice. J Toxicol Pathol. 24: 223-228.

238