A Thesis
entitled
Regulatory Mechanisms of Cardiotonic Steroids in Chronic Kidney Disease
by
Subhanwita Ghosh
Submitted to the Graduate Faculty as partial fulfillment of the requirements for the
Master of Science Degree in
Bioinformatics & Proteomics/Genomics
______Dr. David J. Kennedy, Committee Chair
______Dr. Sadik Khuder, Committee Member
______Dr. Levison Bruce, Committee Member
______Dr. Amanda Bryant-Friedrich, Dean College of Graduate Studies
The University of Toledo
August, 2017
Copyright 2017, Subhanwita Ghosh
This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author. An Abstract of
Regulatory Mechanisms of Cardiotonic Steroids in Chronic Kidney Disease
by
Subhanwita Ghosh
Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Bioinformatics & Proteomics/Genomics
The University of Toledo
August, 2017
Introduction: Cardiotonic steroids (CTSs) are steroid hormones which are elevated in chronic kidney disease (CKD). The 2-pyrone ring structure of CTS is critical for its binding to the Na+/K+-ATPase and subsequent initiation of profibrotic signaling which promotes tissue fibrosis and organ dysfunction underlying cardiac and renal disease.
Paraoxonases (PONs) are a family of hydrolytic enzymes which can regulate levels of 2- pyrone structures like those found in CTS, and we have recently discovered that the activity of these enzymes is diminished in setting such as CKD where CTSs are elevated.
Hypothesis: We hypothesized that dysregulated expression in the PON gene family is associated with renal disease and that PONs, via their hydrolytic activity, participate in the metabolism and regulation of CTSs.
Methods/ Results: We used molecular, biochemical, and bioinformatic approaches to study how PONs regulate CTSs in the setting of renal disease. We first performed a meta- analysis (accessed from NCBI’s Gene Expression Omnibus (GEO) Datasets) of normalized PON isoform gene expression from whole genome microarray data of both peripheral blood mononuclear cells (PBMC’s, n=4 studies, 174 total patients) and renal
iii biopsy samples (n=4 studies, 207 total patients), in case-control studies of patients with chronic kidney disease (CKD stage 2-5) and the respective non-CKD controls. From these studies, we noted that PON-1 gene expression was significantly decreased in
PBMCs of CKD (Stage 2-3) patients vs non-CKD controls (0.8±0.03 vs 1.0±0.03, p<0.05), however in renal biopsy specimens PON-1 (2.7±0.42 vs 1.0±0.02, p<0.05) and
PON-2 (1.5±0.06 vs 1.0±0.04, p<0.01) was significantly increased in CKD (Stage 2-3) patients vs non-CKD controls. We also searched for the genes which are highly correlated such as GADD45B, STK26, IFITM2///IFITM1, ZNF418, etc. with PON genes in the setting of chronic kidney disease. Next, we measured circulating PON-1 protein
(ELISA) and activity (as measured with 7-hydroxycoumarin, a specific fluorogenic substrate of PON lactonase/2-pyronase activity) in CKD patients (n=31) and non-CKD controls (n=15). Here we found that PON-1 circulating protein was significantly lower compared to non-CKD controls (p<0.001), and that PON lactonase/2-pyronase activity was also significantly decreased in CKD patients (p<0.0001). Finally, we developed an
LC-MS-MS based assay to monitor the potential metabolism of CTSs by PONs.
Incubation of the CTS telocinobufagin (TCB) with PON-1 overexpressing HEPG2 cells led to a 2-fold decrease in the intact 2-pyrone form of TCB vs control (p=0.0054).
Conclusion: While PON-1 and PON-2 gene expression is increased in renal biopsy samples of CKD patients, PON-1 gene expression is decreased in PBMC’s of CKD patients’ vs controls. Furthermore, circulating levels of PON1 and lactonase activity of
PON1are decreased in CKD patients. There are numbers of genes that are differentially expressed in chronic kidney disease which are correlated with PON gene expression including GADD45B, STK26, IFITM2///IFITM1, ZNF418, GDAP1, etc. Furthermore,
iv
CTS appear to be physiologic substrates for PON’s hydrolytic lactonase/2-pyronase activity and this may represent a novel regulatory mechanism for CTS.
v
Acknowledgements
I express my deepest appreciation to my Master’s thesis adviser, Dr. David J. Kennedy for his invaluable help and guidance throughout my research work. Having him as an adviser is an honor. I also express my heartfelt thanks to my committee members, Dr.
Levison Bruce and Dr. Sadik Khuder for their assistance with this thesis. Without their immense help and insightful comments this work could not be completed. My sincere thanks to Dr. Haller for useful suggestions during the research lab meetings that helped in improving this thesis.
I also express my sincere thanks to my fellow labmates for stimulating ideas and discussions. It was a great fun to work in Dr. Kennedy’s lab.
Finally, I express my sincere gratitude to my family for always being supportive.
vi
Table of Contents
Abstract ...... iii
Acknowledgements ...... vi
Table of Contents ...... vii
List of Tables ...... x
List of Figures ...... xi
List of Abbreviations ...... xiii
1 Introduction ………………...... 1
2 The Paraoxonase gene family ...... 6
3 Methods
3.1 Bioinformatics approaches...... 9
3.1.1 Study of PON gene expressions in different tissues in human body ...... 9
3.1.2 PON genes dysregulation is related to heart and kidney disease ...... 9
3.1.3 Comparison of PON gene expressions in renal biopsy samples and peripheral blood samples taken from CKD patients and non-CKD controls ...... 10
3.1.4 An approach to look at the regulatory network of genes that may involve in
CKD...... 15
3.2 Biochemical and molecular biology approaches ...... 17
3.2.1 Animal tissue culture ...... 17
3.2.2 Method development to measure protein level expression of PON1 in tissue culture samples and human plasma/ serum ...... 19
vii 3.2.3 Method development to measure PON1 lactonase activity in human plasma and tissue culture sample ...... 24
3.2.4 Measurement of PON1 protein expression in CKD vs non-CKD human plasma…………………………………………………………………………..………. 30
3.2.5 Measurement of PON1 lactonase activity in CKD vs non-CKD human plasma…………………………………………………….………………….…………. 31
3.2.7 Measurement of PON1 protein expression in tissue culture ...... 33
3.2.8 Measurement of PON1 lactonase activity in tissue culture ...... 34
3.2.9 Method development for measuring TCB by LC-MS ...... 35
3.2.10 Making Standard curve for TCB standards ...... 37
3.2.11 Measuring CTS degradation by tissue culture that produce PON1……….37
4 Results
4.1 Bioinformatics approaches...... 39
4.1.1 Studying the PON genes using bioinformatics tools provided in www.ncbi.nlm.nih.gov ...... 39
4.1.2 Study of PON gene expressions in different tissue in human body ...... 42
4.1.3 Comparison of PON gene expressions in renal biopsy samples and peripheral blood samples taken from CKD patients and non-CKD controls ...... 44
4.1.4 An approach to look at the highly correlated genes that may involve in
CKD...... …………………………………………………………………...…….46
4.2 Biochemical and molecular biology approaches ...... 51
4.2.1 Method development to measure PON1 protein expression in human plasma samples………………………………………………………………………51
viii 4.2.2 Method development to measure PON1 lactonase activity in human plasma samples…………………………………………………………………………. 51
4.2.3 Measurement of PON1 protein expression in CKD vs non-CKD human plasma………...... 51
4.2.4 Measurement of PON1 lactonase activity in CKD vs non-CKD human plasma…………………………………………………….…………………...… 52
4.2.5 Measurement of PON1 protein expression in tissue culture ...... 52
4.2.6 Measurement of PON1 lactonase activity in tissue culture ...... 53
4.2.7 Method development for measuring TCB by LC-MS ...... 53
4.2.8 Making Standard curve to measure TCB ...... 53
4.2.9 Measuring CTS degradation by tissue culture that produce PON1 ..54
Conclusion ...... 57
References ...... 58
A The R-code to find out the correlated genes and save the corresponding values in
*.csv files ...... 62
B The correspondence values of differentially expressed genes ...... 64
C The ELISA report of CKD patients’ vs non-CKD control plasma ...... 70
D The lactonase activity assay CKD patients’ vs non-CKD control plasma...... 71
ix
List of Tables
2.1 PON genes and their position in chromosome 7 ...... 6
3.1 GFR value distribution at different stages of CKD ...... 14
3.2 Data matrix of studies with PBMC samples ...... 15
3.3 Data matrix of studies with renal biopsy samples ...... 15
3.4 Experiment design for lactonase activity assay method development ...... 27
4.1 Correspondence values of differentially expressed genes with PON genes in study with PBMC samples ...... 46
4.2 Correspondence values of differentially expressed genes with PON genes in study with renal biopsy samples ...... 49
4.3 TCB standards measured by LC-MS ...... 53
4.4 TCB degradation by PON produced by high -PON-HEPG2 ...... 55
B.1 Correspondence value from GSE 15072 (CKD vs non-CKD) ...... 64
B.2 Correspondence value from GSE 15072 (CKD vs non-CKD) ...... 65
B.3 Correspondence value from GSE43484...... 67
B.4 Correspondence value from GSE32591...... 68
B.5 Correspondence value from GSE66494...... 69
C.1 ELISA report of CKD patients’ and non-CKD controls’ plasma ...... 70
D.1 Lactonase activity assay of CKD patients’ and non-CKD controls’ plasma ...... 71
E.1 The lactonase activity of high PON recombinant cells …………….……...... 72
x
List of Figures
1-1 Balance between natriuretic effect and CTS and the “trade-off” ...... 2
1-2 Binding of CTS with Na/K-ATPase triggers fibrosis in tissues ...... 3
1-3 Closed ring and open ring structure of CTS such as TCB ...... 4
2-1 PON genes position in human chr7 ...... 6
2-2 Nucleotide BLAST of PON genes ...... 6
2-3 Protein BLAST of PON protein ...... 7
3-1 NCBI nucleotide search ...... 9
3-2 Selecting data for analysis from a data set ...... 14
3-3 PON1 expression values from a study ...... 15
4-1 The conserved domain of PON1 protein ...... 40
4-2 The conserved domain of PON2 protein ...... 41
4-3 The conserved domain of PON3 protein ...... 42
4-4 Tissue specific expression of PON1 in human body ...... 42
4-5 Tissue specific expression of PON2 in human body ...... 43
4-6 Tissue specific expression of PON3 in human body ...... 43
4-7 Comparison of PON gene expression in heart, kidney and liver ...... 44
4-8 PON gene expression in PBMC from CKD and non-CKD ...... 44
4-9 PON gene expression in renal biopsy from CKD and non-CKD ...... 45
4-10 Network of PON1 with differentially expressed genes in PBMC samples ...... 47
xi 4-11 Network of PON2 with differentially expressed genes in PBMC samples ...... 48
4-12 Network of PON3 with differentially expressed genes in PBMC samples ...... 48
4-13 Network of PON1 with differentially expressed genes in renal biopsy samples ...50
4-14 Network of PON3 with differentially expressed genes in renal biopsy samples ...50
4-15 PON1 protein expression in CKD and non-CKD plasma samples ...... 51
4-16 PON1 lactonase activity in CKD and non-CKD plasma samples ...... 52
4-17 PON1 expression by high PON-CHO cell lines ...... 52
4-18 PON1 expression by high PON-HEPG2 vs HEPG2 parental cell lines ...... 52
4-19 PON1 lactonase activity by recombinant high-PON cell lines…………………. 53
4-20 Chromatogram of 10ng/ml TCB ...... 54
4-21 Chromatogram of 5ng/ml TCB ...... 54
4-22 TCB standard curve ...... 54
4-23 TCB degradation by PON produced by high PON-HEPG2 cells ...... 56
B-1 Network with PON1 (GSE15072) ...... 65
B-2 Network with PON2 (GSE15072) ...... 66
B-3 Network with PON3 (GSE15072) ...... 66
B-4 Network with PON3 (GSE43484) ...... 68
B-5 Network with PON3 (GSE32591) ...... 69
B-6 Network with PON3 (GSE66494) ...... 70
xii
List of Abbreviations
APCI………………… Atmospheric Pressure Chemical Ionization
BLAST………………. Basic Local Alignment Search Tool
CE……………………. Capillary Electrophoresis CHO………………… Chinese hamster ovary CKD…………………. Chronic Kidney Disease CTS…………………. Cardiotonic Steroids
DMSO………………. Dimethyl sulfoxide DNA…………………. Deoxyribonucleic Acid
EDTA………………. Ethylenediaminetetraacetic acid eGFR………………...Estimated Glomerular Filtration Rate ELISA………………. Enzyme-Linked Immunosorbent Assay EMEM………………. Eagle's Minimum Essential Medium ESI…………………… Electrospray Ionization Ex/Em……………… Excitation/Emission
FBS………………….Fetal Bovine Serum
GEO…………………Gene Expression omnibus
HD……………………Hemodialysis HDL…………………. High Density Lipid HEPG2……………… Human Liver Cancer Cell Line HRP…….……………Horseradish peroxidase HT……………………Hypertensive
LC-MS………………. Liquid Chromatography–Mass Spectrometry LDL…………………...Low Density Lipid LRE……………………Luciferin-Regenerating
xiii
Na/K ATPase…………. Sodium-Potassium Adenosine Triphosphatase NCBI………….………. National Center for Biotechnology Information
PBMC……………… Peripheral Blood Mononuclear Cell PBS………………… Phosphate-Buffered Saline PC…………………. Positive Control pH…………………. Potential of Hydrogen PON…………………Paraoxonase
QI……………………. Quadrupole Ion
RefSeq ………………. Reference Sequence RIPA………………… Radioimmunoprecipitation Assay RNA…………………. Ribonucleic Acid
SGL…………………...SMP-30/Gluconolaconase/LRE SMP-30………………. Senescence Marker Protein 30 Src…………………… Sarcoma viral oncogene kinase Str_Synth………………Strictosidine synthase
TCB…………………. Telocinobufagin
xiv
xv Chapter 1
Introduction
The maladaptation of the body’s ability to handle sodium (salt) and volume (water) loads is linked with devastating diseases of heart failure and renal failure. This process includes an elegant regulatory system composed of effector steroid hormones – known as cardiotonic steroids (CTS) – and their receptor complex, the sodium-potassium adenosine triphosphatase (Na+/K+ ATPase). CTS are ligands of the Na+/K+ ATPase. The production of these hormones are a compensatory mechanism for natriuresis. Natriuresis is excretion of sodium in the urine via action on the Na+/K+ ATPase in the kidney and vascular tone in volume-expanded states such as salt-sensitive hypertension and chronic kidney disease, as well as edematous states like heart failure and pre-eclampsia.
Chronic stimulation of Na+/K+ ATPase signaling by CTS has important implications which are not limited to the natriuretic response to increased salt and water load. There is a “trade-off” pathological adaptation to volume expansion, that includes hypertension, hypertrophy, and fibrosis (23). It has been evident that the pro-inflammatory and pro- fibrotic pathways initiated by these steroid hormones in both cardiac and renal tissue and that makes them attractive therapeutic targets for researches in cardiac and renal disease.
Natriuresis is the natural process to excrete Na+ from our body. If Na+ is not removed 1
from our body it causes different kind of problems related to sodium homeostasis such as hypertension. This ultimately cause adverse cardiovascular outcomes. The increased sodium load can be balanced by increased production of CTS. But when there is an excess of CTS in our body it binds with Na+/K+ ATPase and that activates Src (Sarcoma viral oncogene kinase). Activation of Src leads the downstream pro-fibrotic and pro- inflammatory signals in our important organs like heart and kidney.
Figure 1-1: Illustration of the balance between the natriuretic effect of cardiotonic steroids (CTS) and trade-off of inducing Na+/K+ ATPase -mediated signal transduction leading to cardiac and renal fibrosis, eventually contributing to the development of hypertension and adverse cardiovascular outcomes.
Progressive cardiac and renal compromise (referred to as “cardio-renal syndrome”) in patients with heart failure and chronic kidney disease are very common and leading to recurrent hospitalizations and clinical deterioration. The contemporary therapies of neurohormonal blockade fail to adequately address cardio-renal syndrome. The progression and regulation of CTS in volume-expanded states such as heart failure and chronic kidney disease is unknown. Thus, the understanding of a fundamental, integrated,
2
and mechanistic understanding of the CTS- Na+/K+ ATPase effector/receptor complex is very much important.
One of the common structural features of CTS is the presence of a lactone ring which is critical for its binding to the Na+/K+ ATPase and subsequent signaling. The unique δ- lactone ring structure of CTS such as TCB binds with the Na+/K+ ATPase, which leads
Src activation and cause profibrotic and proinflammatory signal in kidney, heart and circulatory systems. As the δ-lactone ring is necessary to bind with the Na+/K+ ATPase and producing profibrotic and pro-inflammatory signals in kidney and heart tissue, our goal is to determine if lactonase enzymes can hydrolyze the δ-lactone ring and thus render the CTS unable to bind with the Na+/K+ ATPase.
TCB
Profibrotic and proinflammatory signals
Figure 1-2: The binding of TCB with the Na+/K+ ATPase, leads profibrotic and proinflammatory signal in kidney, heart and circulatory systems.
Paraoxonases (PON) can function as antioxidant enzymes and due to this ability, they have been a topic of interest in cardiovascular research over the past two decades. 3
Besides this recent point of interest, PON’s initially were subject of toxicology studies in the field of organophosphate poisoning in the post-World War II era and were identified as an organophosphate hydrolyzing enzymes (15). The organophosphates were first synthesized as insecticides in the 1930s. These insecticides have direct neurotoxic effect.
This discovery led to the subsequent identification of PON in human serum in 1953 (2).
PON1 is produced in liver and excreted attached to HDL.
HDL is known to carry important detoxifying enzymes like PON which have lactonase activities. The liver makes PON which is eventually attached to HDL and thus confers important antioxidant properties to HDL.
In these studies, we have attempted to address the following topics: While circulating
PON lactonase activity is decreased in CKD and is associated with increased mortality in this setting, little is known about what causes this decreased activity (e.g. is it due to either decreased PON expression levels or dysfunctional PON protein)? Further, while decreased PON lactonase activity is associated with increased levels of lactone containing CTS in CKD, does this group of hydrolytic enzymes regulate CTS? This would represent the first known native physiologic substrate for these enzymes.
Figure 1-3: Closed lactone ring
structure of CTS such as TCB and
its hydrolyzed structure
In 2014 Kennedy et al found that the enzymatic activity of the HDL associated PON protein was decreased in patients with chronic kidney disease, and that those with low
PON activity have significantly worse survival rates and cardiovascular outcomes (11). 4
As CTS are elevated in these settings where PON activity is diminished, we sought to determine if there was a potential role for PON lactonase activity in regulating CTS levels.
The hydrolysis of CTS may be useful to prevent CTS from binding to the Na+/K+
ATPase. If PON demonstrates the ability to hydrolyze CTS, it may be useful therapeutically. In this current study, we hypothesized that genetic polymorphisms in the
PON gene family are associated with cardiovascular and renal disease; and PON’s, via their enzymatic lactonase/hydrolytic activity, participate in the metabolism and regulation of cardiotonic steroids (CTS). In this current study, we tested two hypotheses. The first one tests if PON activity is associated with decreased PON expression in the setting of renal disease and second one tests if PON’s, via their hydrolytic activity, participate in the metabolism and regulation of CTS.
5
Chapter 2
The Paraoxonase Gene Family
The PON gene family includes 3 members: PON1, PON2, and PON3. PON genes are located as cluster in human chromosome 7. They are Calcium-dependent esterases with approximate molecular mass of 40-45 kDa. PON reflects the ability to hydrolyze paraoxon, though it is the substrate primarily for PON1. Lactones are substrate for all three isoforms. PON1 has been shown to protect lipoproteins (not only LDL but also
HDL) from lipid peroxidation by degrading specific oxidized cholesteryl esters and phospholipids. On a per microgram basis, PON3 is protecting LDL against oxidation and in lactonase activity, approximately 100 times more active than PON1 (18).
Table 2.1: PON genes and their positions in human chromosome 7
Symbol Gene ID Map Start End
PON1 5444 7q21.3 95,297,676 95,297,698
PON2 5445 7q21.3 95,404,863 95,435,329
PON3 5446 7q21.3 95,359,944 95,396,368
6
Figure 2-1: PON genes position in chromosome 7 by Illumina genome browser
Paraoxonases have over 80% similarity at the nucleotide level. PON2 is 93% identical to
PON3 and 84% identical to PON1. Query cover is very low in both cases.
Figure 2-2: BLAST result comparing the nucleic acid sequence of PON1 and PON3 with that of PON2 showing over 80% similarity in DNA sequence level.
Paraoxonases have over 66% similarity at the protein level. Both PON1 and PON3 are
66% identical to PON2. It covers 100% of the query sequence and that signifies very similar structure of the PON proteins.
7
Figure 2-3: BLAST result of PON1 and PON3 showing 66% similarity at protein sequence level
In 2013, Martinelli and cowrokers published the multifunctional role of PON enzymes.
Initially they were characterized for the ability to hydrolyze organophosphates. The name
PON reflects its ability to hydrolyze paraoxon, a metabolite of the insecticide parathion, as well as hydrolyzing several other insecticides and nerve agents, though PON1 is the one to act on organophosphates like paraoxon. PON2 and PON3 are not able to degrade paraoxon. PON1, PON2, and PON3 also share an ability to hydrolyze aromatic and long- chain aliphatic lactones, and thus the term “lactonase” may be more appropriate, but native physiologic substrate is not well established. Aromatic esters are another common substrate for all three (14, 18)
8
Chapter 3
Methods
3.1 Bioinformatics approaches
3.1.1 Studying the PON genes using bioinformatics tools provided in www.ncbi.nlm.nih.gov:
PON1: PON1 is searched under nucleotide option and the search is limited by choosing homo sapiens as species, genomic DNA/RNA as molecular type and RefSeq as source database. The PON1 DNA has the NCBI reference number NG_008779.1.
Figure 3-1: The NCBI search result on human PON1 nucleotide (DNA)
3.1.2 Study of PON gene expressions in different tissues in human body:
BioGPS is a bioinformatic tool to accumulate tissue specific mRNA expression data by using customized oligonucleotide array to analyze samples from 79 human and 61 mouse tissues. This database is based on an experiment done by Su AI et. Al., with name “A
9
gene atlas of the mouse and human protein-encoding transcriptomes” (21). BioGPS is described as an extensive gene query tool by Wu et. Al in 2009 (22).
For this current study, we used the gene names (PON1, PON2 and PON3) as queries in the search box for tissue specific expression.
3.1.3 Comparison of PON gene expressions in renal biopsy samples and peripheral blood samples taken from CKD patients and non-CKD controls:
Geo Datasets from NCBI: GEO (Gene expression omnibus) is an international public repository that archives and freely distributes microarray, next-generation sequencing, and other forms of high-throughput functional genomics data submitted by the research community. The GEO Datasets database stores original submitter-supplied records
(Series, Samples and Platforms) as well as curated Datasets
(https://www.ncbi.nlm.nih.gov/geo/info/datasets.html).
Goal: To study the PON gene expression in CKD vs non-CKD subjects
Studies:
1. We selected 4 studies related to CKD that are using peripheral blood samples:
GSE15072, GSE37171, GSE43484, GSE70528
2. We also selected 4 studies related to CKD that are using renal biopsy samples:
GSE12682, GSE20602, GSE32591, GSE66494
Study designs:
1. Studies with peripheral blood samples from CKD vs non-CKD controls
10
a) GSE15072: This is a combined study comprising two studies. The study included
8 healthy subjects (NORM), 9 patients with Chronic kidney disease (CKD) at
stage II-III (CKD II-III) (mean±SD of estimated GFR by MDRD formula:
41.4±4.3 ml/min) and 17 patients undergoing hemodialysis treatment (HD). All
HD patients were under stable treatment, for at least 1 year, three times a week (4-
5 hours per session) and synthetic membrane dialyzers were used. No CKD
patients received dialysis treatment. The patients were screened for infectious
diseases, diabetes, chronic lung diseases, neoplasm, or inflammatory diseases and
patients receiving antibiotics, corticosteroids, or nonsteroidal anti-inflammatory
agents and were excluded. No patients had symptomatic coronary artery diseases
or a family history of premature cardiovascular diseases. 20 ml of whole blood
were collected from each patient. For HD patients, the blood samples were
obtained at the beginning of the second HD session of the week. Total RNA was
isolated from PBMC’s by RNeasy mini kit (Qiagen, Oslo Norway) from a
minimum of 5 million cryopreserved PBMC. Next, the isolated RNA was,
processed and hybridized to the GeneChip Human Genome Plus 2.0 or U133A
oligonucleotide microarray (Affymetrix, Santa Clara, CA, USA) (7, 24). b) GSE37171: This study was conducted at the University of British Columbia and
approved by the human ethics research board. The gene expression in patients
with CKD and healthy controls was compared by a 3:1 case-control design. A
group of Patients with stage 5 renal disease aged 18 to 75 years were involved.
The patients were clinically stable awaiting renal transplantation, and were not
receiving immunosuppressive medications. They all provided written informed 11
consent and those that were enrolled into the study were treated per Canadian
Guidelines for Chronic Kidney Disease. Normal controls served as comparators,
they were selected based on comparable age and gender matched to the patients
who were screened to ensure freedom from known illness and medical therapy
(19). c) GSE43484: This study was performed in patients with CKD who have
significantly increased morbidity and mortality resulting from infections and
cardiovascular diseases. Here the gene expression profile in PBMC was explored
and to identify differences in activated pathways in monocytes relevant to the
pathophysiology of atherosclerosis and increased susceptibility to infections. The
peripheral blood from CKD patients (stages 4 and 5, eGFR <20 ml/min x 1.73
m2) and healthy donors were collected to isolate monocytes. Genespring software
and Panther tools website were used to interpret the Microarray gene expression
profile data (1). d) GSE70528: This study involved RNA microarray analysis in 19 patients without
diabetes and they were divided into three groups: HT group (8 hypertension
patients with eGFR of >60 mL/min/1.73 m2), CKD group (7 patients not on
dialysis with eGFR of <60 mL/min/1.73 m2) and HD group (4 HD patients). (12)
2. Studies with renal biopsy samples from CKD vs non-CKD controls a) GSE12682: 42 kidney samples from healthy living transplant donors,
nephrectomies and from diagnostic kidney biopsies were collected. The tissue
samples were grouped based on the histological readings of the kidney biopsies. 12
Samples with evidence of glomerular and tubulo-interstitial fibrosis were selected
into the diseased group. The tissue from glomerular and tubulointerstitial fractions
were micro-dissected and expression arrays were performed separately (20).
b) GSE20602: There were 14 human kidney biopsies of patients with
nephrosclerosis and 4 human kidney biopsies of patients with tumor nephrectomy.
Samples were used for RNA extraction and hybridization on Affymetrix
microarrays. Gene expression data was then analyzed using Genepattern and
Genomatix software (17).
c) GSE32591: This study used glomeruli and tubulointerstitial compartments to
extract RNA. The RNAs were then processed for hybridization on Affymetrix
microarrays (4).
d) GSE66494: Renal biopsy specimens were used to explore gene expression
profiles in human chronic kidney disease. Two independent sets …………
discovery set and validation set were performed (16).
Method:
1. 8 studies are selected for Bioinformatic meta-analysis. The studies are
accessed from NCBI’s Gene Expression Omnibus (GEO) Datasets).
2. PON expression from whole genome microarray data of both peripheral
blood mononuclear cells (PBMC’s, n=4 studies) and renal biopsy (n=4
studies) in patients with chronic kidney disease (CKD stage 2-5) and the
respective non-CKD controls are retrieved.
13
Figure3-2: Selecting CKD and non-CKD samples from data set
3. PON gene expressions from each sample are retrieved from gene
expression profile of each studies by using the ID’s of PON genes
Figure 3-3: PON1 expression of each samples in a study
4. The PON expressions are normalized and plotted.
5. CKD stages are classified according to the glomerular filtration rate
(GFR).
Table 3.1: GFR value distribution in different stages of CKD
CKD Stages for grouping: Stage 1 with normal or high GFR (GFR > 90 mL/min) Stage 2 Mild CKD (GFR = 60-89 mL/min) Stage 3A Moderate CKD (GFR = 45-59 mL/min) Stage 3B Moderate CKD (GFR = 30-44 mL/min) Stage 4 Severe CKD (GFR = 15-29 mL/min) Stage 5 End Stage CKD (GFR <15 mL/min) 6. The data matrix made from the studies is as follows…………………….
14
Table 3.2: Data matrix of the studies with PBMC samples from CKD patents and non-
CKD controls
Table 3.3: Data matrix of the studies with renal biopsy samples from CKD patents and non-CKD controls.
3.1.4 An approach to look at the highly correlated of genes that may affect PON1:
Goal: To determine genes which are highly correlated with PON genes regulation
Materials: The same studies as above are used for the analysis. R-program is used with c3net, bc3net and igraph packages are used in this analysis (3,6,10).
Target file:
1. The data sets are analyzed by GEO2R provided in the Web site Bonferroni method is
used to select the top 250 significantly differentially expressed genes.
2. The raw values of each genes are retrieved along with PON1, PON2, PON3.
3. The same method is followed for all eight studies.
15
Method:
1. The target files are saved as *.txt files and the following R-code is used to find
out highly correlated genes with PON genes
2. Filtering the target files: Some of the genes are duplicated in the target files
because of different IDs with same genes in the microarray chip. The flowing
code is used to find out the duplications. Only gene ID’s with lowest probability
are kept for each of the duplicated genes in the target files.
R-code :
expmat = read.csv("GSE15072-HD.csv", header=T)
table(expmat[,1])
3. The duplication of gene names are removed on the basis of the filtering process.
Now the target files are ready to be used to find out the genes with higher
correspondence values with PON genes.
4. The R-code shown in Appendix A is used to find out the correlated genes and
saved in *.csv files. In this code bc3net, c3net and igraph packages are used.
5. In some cases, 0.25 value is not enough to obtain correlations of PON genes with
other genes by the code………….
expmat = expmat[avgexp > quantile(avgexp, prob=0.25),]
In that cases, different values (<0.25) are examined.
6. Selecting the correlated genes: the correlated genes are having higher
corresponding values with PON genes in both a negative and positive way, that
means the positive values shows direct correlation and negative values shows
16
reverse correlation. We are selecting the values which are higher than 0.4 and
higher than -0.4.
7. Differentially expressed genes that are with higher correspondence values are
searched through “Lens”, a tool for enrichment and network studies of proteins.
This tool is developed by Adam Handen and Madhavi K Ganapathiraju and
published in BMC Medical Genomics in 2015 (8).
3.2 Biochemical and molecular biology approaches
3.2.1 Animal tissue culture
Goal: Expanding cell lines storage for future use and further experiments.
Materials:
Materials:
1. Cell lines:
a. High PON-CHO: These are recombinant Chinese hamster
ovarian cell line expressing PON genes (5).
b. High PON-HEPG2: These are recombinant hepatic cell
lines over expressing PON genes (9).
2. Media: EMEM with 10% FBS and 1% penicillin + streptavidin solution
3. Container for culture: T-75 flasks, Cryo tubes
Media preparation:
We are using EMEM media for this purpose. The media is opened only under hood and 10% FBS and 1% penicillin-streptavidin solution is added to it. Normally we
17
make 500 ml media and add 50ml FBS and 5ml penicillin-streptavidin. We filtered this media to sterilize.
Method:
1. 30ml fresh media 1 in two t-75 flasks was poured.
2. cells in cryo tube were thawed down and 1ml fresh media was
added and mixed thoroughly.
3. 1ml of suspended cells in each flask was added. The flask with
passage number was marked and was incubated at 37C
incubator
4. The media was changed when cells were 60% confluent and
incubated until 80-90% confluent
5. When the cells are 80-90% confluent, they are ready to be
stored or to be used for other experiments.
6. For storing the cells, the old media was sucked out and washed
with 4ml sterile PBS.
7. After washing with PBS, 4ml trypsin 1X was added to the flask.
The cells were incubated for 4-5 mins with trypsin.
8. After 4-5mins incubation the cells were detached from the flask
surface by vigorous shaking and 5ml fresh media was added to
eliminate the trypsin effect.
9. The detached cells were taken out in sterile tube and centrifuged
at 200Xg for 5mins at room temperature
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10. The supernatant was sucked out carefully without disturbing the
cell Pilate.
11. 100μl sterile DMSO with 900μl FBS was added to re-suspend
the cells.
12. The cells in were transferred in cryo and was stored at -80◦C
and latter transfer in liquid nitrogen
3.2.2 Method development to measure protein level expression of PON1 in tissue culture samples and human plasma/ serum
Goal: To identify the sample concentration to be used for assay
Materials:
1. PBS- 137 mM NaCl, 2.7 mM KCl, 8.1 mM Na2HPO4,
1.5mM KH2PO4, pH 7.2-7.4, 0.2μM filtered.
2. Wash Buffer- 0.05% Tween 20 in PBS, pH 7.2- 7.4 (R&D
Systems, Catalog #WA126).
3. Block Buffer- 1% BSA, 0.05% NaN3, in PBS, pH7.2-7.4
4. IC Diluent #1- 1% BSA in PBS, pH 7.2-7.4, 0.2μm filtered
5. IC Diluent #4- 1mM EDTA, 0.5% Triton X-100 in PBS, pH
7.2-7.4
6. Lysis Buffer- 1mM EDTA, 0.5% Triton X-100, 10ug/mL
Leupeptin, 10 μg/ml Pepstatin, 100μM PMSF, 3μgmL
Aprotinin in PBS, pH 7.2-7.4
7. Total PON1 capture antibody- rat anti-human PON1
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8. Total PON1 Detection antibody- goat anti-human PON1
9. Total PON1 standard- recombinant human PON1
10. Streptavidin-HRP- streptavidin conjugated to horseradish-
peroxidase
Reagent preparation: All reagents were purchased from R&D systems. The reagents are described below with the catalog numbers…………………...
1. Wash buffer: WA126 was used to make wash buffer. For
1 liter wash buffer 1 pouch of WA126 is dissolved in 1
liter of DD water and NaN3 is added to get 0.05% final
concentration.
2. IC diluent#1: 10X DY995 is diluted to 1X concentration
by adding DD water.
3. IC diluent#4: 5X DYC001 is diluted to 1X concentration
by adding DD water.
4. Block Buffer: 10% NaN3 is added to IC diluent 1 to get
final 0.05% NaN3 concentration
5. Substrate solution: DY999 contains two types of vials
marked as A and B. vial A and B were used in 1:1
20
concentration to get substrate solution. The substrate
solution was made right before applying to the plate.
6. Stop Solution: DY994 is the stop solution and contains
Acid.
7. Capture antibody: The Total Human PON1 ELISA duo
Kit from R&D system provides capture antibody in
powder form. Each vail gives 360ug/ml capture antibody
when reconstituted with 200ul PBS. This can be stored in
-20C. The working concentration 2μg/ml is achieved by
further dilution as required.
8. Detection Antibody: The Total Human PON1 ELISA
duo Kit from R&D system provides detection antibody
in powder form. Each vail gives 21.6μg/ml capture
antibody when reconstituted with 1ml IC diluent 1. This
can be stored in -20C. The working concentration
600ng/ml is achieved by further dilution as required.
9. PON1 standards: The Total Human PON1 ELISA duo
Kit from R&D system provides recombinant PON1 in
powder form. Each vial contains 140ng/ml recombinant
PON1 protein when reconstituted with 500ul of IC
diluent 4. Further dilutions are required for the assay.
Sample preparation: Human plasma samples are diluted as follows…………….
21
1. 10 % sample: 100μl plasma in 900μl IC diluent#4
2. 1% sample: 10μl plasma in 990μl IC diluent#4
3. 0.1% sample: 1μl plasma in 999μl IC diluent#4
Conditioned media and the cell lysate are used in undiluted form.
Method:
Plate preparation
1. The capture Antibody was diluted to working concentration
of 2.0μg/ml in PBS, without carrier protein. 100μL per well
of the diluted Capture Antibody was used immediately to
coat a 96-well microplate with. The plate was sealed and
incubated overnight at room temperature.
2. Each well was aspirated and washed with Wash Buffer,
repeating the process two times for a total of 3 washes. The
process was done by 96well plate washer (auto washer) by
400μL wash buffer in each well. Any remaining was
removed by aspirating.
3. The plate was blocked by adding 300μL of Block Buffer to
each well and incubated at room temperature for 1-2 hours.
4. step 2 was repeated. The plates are now ready for sample
addition.
22
Assay Procedure
1. 100uL of sample or standards in IC Diluent#4 per well was
added. IC Diluent#4 is used as the zero standard. The plate
was sealed and incubated for 2 hours at room temperature.
Note: A seven-point standard curve using 2-fold serial dilutions and a high standard of
10,000 pg/mL is recommended.
2. Aspiration/wash step was repeated.
3. Detection Antibody was diluted to a working concentration
of 600ng/mL in IC diluent # 1 before use. 100μL of the
diluted Detection Antibody was added to each well. The
plate was sealed with a new plate sealer and incubated for 2
hours at room temperature.
4. Aspiration/wash step was repeated.
5. Immediately before use, the Streptavidin-HRP was diluted
to the working concentration specified on the vial label
using IC Diluent #1. 100μL of the diluted Streptavidin-
HRP was applied to each well and incubated for 20 minutes
at room temperature in dark.
6. Aspiration/wash step was repeated. 7. 100 μL of Substrate Solution was added to each well and
incubated for 20 minutes at room temperature in dark.
23
8. 50μL of Stop Solution was added to each well and the plate
is gently tapped to ensure thorough mixing.
9. The optical density of each well was measured
immediately, using a microplate reader set to 450nm.
3.2.3 Method development to measure PON1 lactonase activity in human plasma and tissue culture sample
Goal: Developing method to measure PON1 lactonase activity
Materials:
1. Paraoxonase assay buffer
2. Fluorescence standard
3. PON1 inhibitor (2-hydroxyquinoline)
4. PON1 substrate
5. Paraoxonase Positive Control
6. Samples (cell lysate, human serum/plasma - without
EDTA)
7. Anhydrous DMSO
8. Black 96-well plates
Storing: Kit should be stored at -20◦C and protect from direct light. Reconstituted fluorescence standard, PON1 inhibitor and PON1 substrate should be stored at -20◦C as well. Reconstituted paraoxonase positive control is aliquoted and stored at -80◦C.
24
Reagent preparation:
1. Fluorescence standard: a flouregenic standard is used
for this assay. It has a similar 2-pyrone ring as CTS.
This standard is provided in PON1 activity assay kit
(should be stored in -20C) by BioVision. Each vial of
standard gives 50mM stck when reconstituted with
55ul of DMSO
2. PON1 inhibitor: 2-hydroxyquinoline is a PON
inhibitor. A vial of this compound is also included in
the above assay kit. Each vial gives 50mM stock
when reconstituted with 110ul of DMSO. To get
2mM working concentration we need to dilute 40ul
stock with 960ul of distilled water yielding 1ml work
solution. The stock can be stored in -20C and is good
for 3 freeze/ thaw cycles
3. PON1 substrate: PON1 substrate is available in the kit
as powder. It gives 250X stock when reconstituted
with 44ul of DMSO. The stock is diluted to 5X
working concentration before adding to the wells.
4. Paraoxonase positive control: It is the recombinant
PON enzyme and should be reconstituted with 110 ul
of assay buffer provided in the kit. This positive
25
control should be aliquoted and stored in -80 C for
further use.
Sample preparation:
Undiluted portions of samples are used for lactonase activity assay.
For Plasma, samples should be EDTA or Ca+2 chelating coagulant free.
Method:
Standard curve preparation:
1. The fluorescence standard was diluted to working
concentration by adding 10μl of the 5mM stock to 990μl
Paraoxonase Assay Buffer to obtain a 50 pmol/ul
Standard solution. 0, 2, 4, 6, 8, 12, 16, and 20μl of the 50
pmol/μl solution into a series of wells in a black 96-well
plate was added and the volume of each well was
adjusted to 100 μl with Paraoxonase Assay Buffer,
yielding 0, 100, 200, 300, 400, 600, 800, and
1000pmol/well Fluorescence Standard.
Sample preparation:
2. Plasma samples are collected by standard methods and
store at -80◦C. Samples should be heparinized for
storing. No EDTA or Ca+2 chelating anticoagulants are
usable as PON1 is Ca+2 dependent enzyme. The cell
26
lysate and conditioned media can be collected fresh or
can be stored at -20C for future use.
3. Assay reaction wells were prepared according to the
table below. In addition to the sample wells, a
background control (no enzyme) well was prepared to
correct for potential non-enzymatic substrate hydrolysis.
For verification of PON1 specific activity, I examined
the PON 1 inhibition, using the 2-hydroxyquinoline
Positive control (PC) and PC+ inhibitor wells using the
reconstituted Paraoxonase positive Control were also
investigated. The volume of all reaction wells to 80
μl/well were adjusted by assay buffer.
Table 3.4: Experiment design for lactonase activity assay method development
Test + PON1 Background +ve PC+inhibitor
sample inhibitor control
Samples (serum/ plasma) 2-10μl 2-10μl ------
Paraoxonase +ve control ------10μl 10μl
2-hydroxyquinoline ---- 10μl ------10μl solution (10X)
Paraoxonase assay buffer 78-70μl 68-60μl 80μl 70μl 60μl
Total 80μl 80μl 80μl 80μl 80μl
27
Reaction mix:
4. The plate was preincubated for 10min at 37◦C to pe-
warm samples and allow the the inhibitor to interact with
sample PON1. During the preincubation, a 5X
concentrated PON1 substrate solution was prepared by
diluting the reconstituted 250X PON1 Substrate stock
solution at a 1:50 ratio with the assay buffer.
5. The reaction was started by adding 20ul of 5X PON1
Substrate solution to each reaction well using a
multichannel pipette, yielding a final volume of
100ul/well. The Substrate solution was not added to the
standard curve wells.
Measurement:
6. Immediately (within 1 min) the fluorescence at
Ex/Em=368/460 nm is measured for 60 min at 37◦C.
The readings were taken at specific time interval for 1
hour. Ideal measurement time for linear range may vary
depending upon the sample. The standard curve wells
may be read in endpoint mode (EX/EM=368/460nm).
Calculations:
7. For the fluorescence, standard curve, the zero standard
(0 pmole/well) reading from the standard readings was
28
subtracted, background-subtracted values are plotted and
the slope of the standard curve is calculated.
8. For the reaction wells (including background control),
two time points (t1 and t2) in the linear phase of the
reaction progress curves were identified and the
corresponding fluorescence values at those points
(RFU1 and RFU2) were selected to determine the
change in fluorescence over the time interval:
ΔF=RFU2-RFU1.
9. The specific fluorescence (Cs) was calculated by
subtracting the background control from each sample:
Cs=ΔFs-ΔFBC. Paraoxonase activity was obtained by
applying the Cs values to the fluorescence standard
curve to get B pmol of substrate metabolized during the
reaction time.