DOCSLIB.ORG

Evolutionary Recruitment of a Flavin-Dependent Monooxygenase for the Detoxification of Host Plant-Acquired Pyrrolizidine Alkaloi

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Evolutionary Recruitment of a Flavin-Dependent Monooxygenase for the Detoxification of Host Plant-Acquired Pyrrolizidine Alkaloi Evolutionary recruitment of a flavin-dependent monooxygenase for the detoxification of host plant-acquired pyrrolizidine alkaloids in the alkaloid-defended arctiid moth Tyria jacobaeae Claudia Naumann, Thomas Hartmann, and Dietrich Ober* Institut fu¨r Pharmazeutische Biologie der Technischen Universita¨t Braunschweig, Mendelssohnstrasse 1, D-38106 Braunschweig, Germany Edited by May R. Berenbaum, University of Illinois at Urbana-Champaign, IL, and approved February 26, 2002 (received for review December 17, 2001) Larvae of Tyria jacobaeae feed solely upon the pyrrolizidine alkaloid- effects of PAs because of high levels of N-oxide forming FMO containing plant Senecio jacobaea. Ingested pyrrolizidine alkaloids activity and low levels of bioactivating P450 (9). (PAs), which are toxic to unspecialized insects and vertebrates, are Herbivorous insects also can cope with xenobiotics by means of efficiently N-oxidized in the hemolymph of T. jacobaeae by sene- P450s, as evidenced by resistance to commercial insecticides (15). cionine N-oxygenase (SNO), a flavin-dependent monooxygenase However, during evolutionary adaptation to their food plants, (FMO) with a high substrate specificity for PAs. Peptide microse- herbivorous insects have developed specific mechanisms to tolerate quences obtained from purified T. jacobaeae SNO were used to clone specific plant defense chemicals, often involving P450s. In one the corresponding cDNA, which was expressed in active form in example, Papilio polyxenes, the black swallowtail, feeds on Apiaceae Escherichia coli. T. jacobaeae SNO possesses a signal peptide charac- species containing phototoxic furanocoumarins, which are effi- teristic of extracellular proteins, and it belongs to a large family of ciently detoxified in the insect by a P450 monooxygenase. This mainly FMO-like sequences of mostly unknown function, including enzyme not only shows high substrate specificity for the furano- two predicted Drosophila melanogaster gene products. The data coumarins occurring in the host plant (16), but it also is specifically indicate that the gene for T. jacobaeae SNO, highly specific for toxic induced by these compounds (17) by means of the xanthotoxin- pyrrolizidine alkaloids, was recruited from a preexisting insect-spe- response element, which was identified in the promoter region of cific FMO gene family of hitherto unknown function. The enzyme this inducible P450 enzyme (18). In another example, Drosophila allows the larvae to feed on PA-containing plants and to accumulate mettleri, one of four Drosophila species endemic to the Sonoran predation-deterrent PAs in the hemolymph. desert in the southwestern United States, lives and breeds in soils soaked by rot exudate of the saguaro cactus, which contains toxic EVOLUTION N-oxidation ͉ alkaloid sequestering insects ͉ insect adaptation ͉ chemical isoquinoline alkaloids that accumulate in the soil because of water defense ͉ gene recruitment evaporation (19). D. mettleri’s unique isoquinoline alkaloid resis- tance involves a cytochrome P450 monooxygenase that is specifi- cally induced by isoquinolines from saguaro (20), but not from other arvae of the European cinnabar moth Tyria jacobaeae are cacti (20). Thus, P. polyxenes and D. mettleri each possess at least one Lspecialized to tansy ragwort (Senecio jacobaea L.) as food P450 enzyme whose substrate specificity and inducibility evolved in plant. Pyrrolizidine alkaloids (PAs) present in this plant are response to specific plant defense compounds (‘‘secondary metab- sequestered by the larvae and are retained during all stages of olites’’) present in the respective host plant. metamorphosis (1, 2). PAs are typical plant secondary com- Tyria jacobaeae larvae do not simply detoxify PAs by N-oxidation, pounds thought to play an important role as defensive chemicals but store the nontoxic N-oxides as predation deterrents (Fig. 1; 21). in the plant and its adapted insect herbivores (3). PAs are The larvae advertise their toxic PAs by a striking yellow-black hepatotoxic and carcinogenic to vertebrates and mutagenic or warning coloration. N-oxidation is only one of the different, re- genotoxic to insects and even to yeast (4); they also show strong cently identified strategies insects developed in evolution to safely antifeedant activity against various herbivores (5). In species of handle plant-acquired PAs for their own defense (22, 23). The the genus Senecio (Asteraceae), senecionine N-oxide is synthe- enzyme responsible for the N-oxidation of tertiary PAs in Tyria is sized in the roots as common PA-backbone structure, which senecionine N-oxygenase (SNO), which is a reduced nicotinamide- subsequently is transported to other organs and tissues where it adenine dinucleotide phosphate (NADPH)-dependent flavin is chemically modified into the species-specific PA patterns (6). monooxygenase (FMO), not a cytochrome P450 enzyme (21). In In the gut of mammalian herbivores feeding on PA-containing contrast to the intensively studied mammalian multisubstrate plants, the PA N-oxides are easily reduced, yielding the respec- FMOs (24), the Tyria enzyme is strictly substrate specific. It tive free bases, which are passively absorbed and thus become N-oxidizes only protoxic PAs, i.e., PAs with structural features accessible to the bioactivating microsomal cytochrome P450- dependent monooxygenases (P450) of liver. These enzymes are part of xenobiotic metabolism in vertebrates (7, 8) and transform This paper was submitted directly (Track II) to the PNAS office. the tertiary PAs to unstable pyrroles, which are highly reactive Abbreviations: PA, pyrrolizidine alkaloid; P450, cytochrome P450-dependent monooxy- alkylating agents. N-oxidation was shown to be a second pathway genase; NADPH, nicotinamide-adenine dinucleotide phosphate; FMO, flavin-dependent monooxygenase; SNO, senecionine N-oxygenase; RACE, rapid amplification of cDNA ends. of PA metabolism in mammals, catalyzed by flavin-dependent Data deposition: The sequence reported in this paper has been deposited in the EMBL monooxygenases (FMOs; ref. 9) or by an isoform of P450s (10, Nucleotide Sequence Database (accession no. AJ420233). 11). The potentially toxic tertiary PAs are oxidized to their *To whom reprint requests should be addressed. E-mail: [email protected]. N-oxides, which no longer serve as substrates for bioactivating The publication costs of this article were defrayed in part by page charge payment. This P450s (10, 12). In contrast to most mammals, guinea pigs, sheep, article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. and hamsters (9, 13, 14) exhibit a high resistance against the toxic §1734 solely to indicate this fact. www.pnas.org͞cgi͞doi͞10.1073͞pnas.082674499 PNAS ͉ April 30, 2002 ͉ vol. 99 ͉ no. 9 ͉ 6085–6090 Downloaded by guest on September 23, 2021 jacobaeae was recruited from a preexisting family of FMO-like proteins of hitherto unknown functions. Materials and Methods Radiochemicals. [N-Methyl-3H]atropine (87 Ci͞mmol) was pur- chased from DuPont. Pyrrolizidine alkaloids applied as enzyme substrates were obtained as described (21). Purification and Microsequencing of SNO. SNO was purified from hemolymph of T. jacobaeae as described (21). The purified enzyme was transferred to a poly(vinylidene difluoride) mem- brane (Millipore) and was subjected to microsequencing. Pep- tides of purified SNO obtained by digestion with trypsin were separated by means of HPLC on a Vydac C18 column (4.6 mm ϫ 150 mm) and sequenced according to ref. 26. RNA Isolation and cDNA Synthesis. Total RNA was isolated by using the RNeasy Mini Kit (Qiagen) from one-week-old larvae of T. jacobaeae and of the larvae and adults of D. melanogaster frozen in liquid nitrogen. Total RNA (2 ␮g) was reverse-transcribed by Superscript II (Invitrogen) in a total volume of 50 ␮l by using an ␮ oligo(dT)17 primer (0.1 M; Table 1). PCR with Degenerate Primers. Degenerate primers (P1–6) were constructed according to peptides resulting from partial sequencing Fig. 1. PA N-oxides ingested from plants are reduced in the gut. In their of the SNO protein (Table 1). Amplification of 1 ␮l of cDNA was tertiary form as lipophilic free bases, they permeate passively the membrane performed with Taq DNA Polymerase (Qiagen, Chatsworth, CA) and are trapped in the hemolymph by efficient re-N-oxidation catalyzed by in a total volume of 25 ␮l by using all possible combinations of SNO of T. jacobaeae (A). SNO is an NADPH-dependent monooxygenase (B). ␮ forward and reverse primers (2.0 M each), including oligo(dT)17 primer (1.0 ␮M). A touch-down protocol with decreasing annealing temperatures from 60°Cto45°C(0.5°C per cycle, 45°C constant for required by substrates of the bioactivating cytochrome P450 en- 20 further cycles) was used for the temperature program . With zymes, indicating that the major function of SNO is to maintain primers P5 and oligo(dT)17, a 554-bp fragment was amplified, which sequestered protoxic PAs as nontoxic N-oxides. No functionally subsequently was electrophoretically purified, subcloned by using characterized FMO is known from insects (15, 25). To trace the the TOPO TA cloning kit (Invitrogen) according to the manufac- evolutionary origin of SNO, we have obtained peptide sequences turer’s instructions, and sequenced. from the purified T. jacobaeae enzyme, cloned the cDNA, ex- pressed the active protein in E. coli and investigated its gene Amplification of the 5؅-cDNA End of SNO. For identification of the phylogeny. The data indicate that the PA-specific SNO of T.
Load more

Recommended publications
  • Clinical Biochemistry of Hepatotoxicity
    linica f C l To o x l ic a o n r l o u g Singh, J Clinic Toxicol 2011, S:4 o y J Journal of Clinical Toxicology DOI: 10.4172/2161-0495.S4-001 ISSN: 2161-0495 ReviewResearch Article Article OpenOpen Access Access Clinical Biochemistry of Hepatotoxicity Anita Singh1, Tej K Bhat2 and Om P Sharma2* 1CSK Himachal Pradesh, Krishi Vishva Vidyalaya, Palampur (HP) 176 062, India 2Biochemistry Laboratory, Indian Veterinary Research Institute, Regional Station, Palampur (HP) 176 061, India Abstract Liver plays a central role in the metabolism and excretion of xenobiotics which makes it highly susceptible to their adverse and toxic effects. Liver injury caused by various toxic chemicals or their reactive metabolites [hepatotoxicants) is known as hepatotoxicity. The present review describes the biotransformation of hepatotoxicants and various models used to study hepatotoxicity. It provides an overview of pathological and biochemical mechanism involved during hepatotoxicity together with alteration of clinical biochemistry during liver injury. The review has been supported by a list of important hepatotoxicants as well as common hepatoprotective herbs. Keywords: Hepatotoxicity; Hepatotoxicant; In Vivo models; In Vitro production of bile thus leading to the body’s inability to flush out the models; Pathology; Alanine aminotransferase; Alkaline phosphatase; chemicals through waste. Smooth endoplasmic reticulum of the liver is Bilirubin; Hepatoprotective the principal ‘metabolic clearing house’ for both endogenous chemicals like cholesterol, steroid hormones, fatty acids and proteins, and Introduction exogenous substances like drugs and alcohol. The central role played by liver in the clearance and transformation of chemicals exposes it to Hepatotoxicity refers to liver dysfunction or liver damage that is toxic injury [4].
    [Show full text]
  • Hepatic Veno-Occlusive Disease As a Result of a Traditional Remedy: Confirmation of Toxic Pyrrolizidine Alkaloids As the Cause
    676 ORIGINAL ARTICLE J Clin Pathol: first published as 10.1136/jcp.55.9.676 on 1 September 2002. Downloaded from Hepatic veno-occlusive disease as a result of a traditional remedy: confirmation of toxic pyrrolizidine alkaloids as the cause, using an in vitro technique M Zuckerman, V Steenkamp, M J Stewart ............................................................................................................................. J Clin Pathol 2002;55:676–679 See end of article for Background/Aims: A child presented with hepatic veno-occlusive disease after having been adminis- authors’ affiliations tered a short course of treatment with a traditional herbal remedy. The child subsequently died. Post- ....................... mortem liver histology confirmed the diagnosis. This study aimed to investigate the hypothesis that the Correspondence to: herbal remedy was the cause of veno-occlusive disease. Dr M J Stewart, Department Methods: Extracts of the traditional remedy were analysed by colorimetry and gas chromatography/ of Chemical Pathology, mass spectrometry. Cultured hepatocytes were treated with an extract of the plant material and exam- University of the ined for morphological changes. Witwatersrand Medical Results: The screening analyses indicated the presence of toxic pyrrolizidine alkaloids, which were School, 7 York Road, Parktown 2193, Gauteng, later confirmed by gas chromatography/mass spectrometry. The cell studies indicated dose related South Africa; toxicity, with necrosis at high concentrations and apoptosis and abnormalities of the cytoskeleton at [email protected] lower concentrations. Accepted for publication 5 Conclusions: The simple screening techniques used allowed rapid confirmation of the presence of September 2001 toxic pyrrolizidines in the remedy. The in vitro method confirmed the toxicity of herbal extracts to hepa- ......................
    [Show full text]
  • TOX-27: Riddelliine (CASRN 23246-96-0)
    National Toxicology Program Toxicity Report Series Number 27 NTP Technical Report on Toxicity Studies of Riddelliine (CAS No. 23246-96-0) Administered by Gavage to F344/N Rats and B6C3F1 Mice Po C. Chan, PhD, Study Scientist National Toxicology Program Post Office Box 12233 Research Triangle Park, NC 27709 NIH Publication 94-3350 December 1993 United States Department of Health and Human Services Public Health Service National Institutes of Health Note to the Reader The National Toxicology Program (NTP) is made up of four charter agencies of the United States Department of Health and Human Services (DHHS): • the National Cancer Institute (NCI) of the National Institutes of Health; • the National Institute of Environmental Health Sciences (NIEHS) of the National Institutes of Health; • the National Center for Toxicological Research (NCTR) of the Food and Drug Administration; and • the National Institute for Occupational Safety and Health (NIOSH) of the Centers for Disease Control. In July 1981, the Carcinogenesis Bioassay Testing Program was transferred from NCI to NIEHS. NTP coordinates the relevant Public Health Service programs, staff, and resources that are concerned with basic and applied research and with biological assay development and validation. NTP develops, evaluates, and disseminates scientific information about potentially toxic and hazardous chemicals. This knowledge is used for protecting the health of the American people and for the primary prevention of disease. To carry out its mission, NTP designs and conducts studies to characterize and evaluate the toxicologic potential of selected chemicals in laboratory animals (usually two species, rats and mice). Chemicals selected for NTP toxicology studies are chosen primarily on the bases of human exposure, level of production, and chemical structure.
    [Show full text]
  • D. SENECIO SPECIES and RIDDELLIINE 1. Exposure Data
    D. SENECIO SPECIES AND RIDDELLIINE 1. Exposure Data 1.1 Origin, type and botanical data (Molyneux et al., 1991) Senecio riddellii (Asteraceae) (Riddell groundsel) is a grey-white half-shrub, 30–90 cm tall with pinnatifid and relatively hairless leaves, revealing its bright green leaf colour. It has bright yellow flowers on the stems at about the same height above the ground. This gives the plant a flat-topped appearance when in bloom. It produces flowers in late summer to early autumn and dies back to ground level after the first frost. It grows in dry, sandy soils and its roots are long and about as thick as a lead pencil. Senecio longilobus (also known as woolly groundsel and thread-leaf groundsel) is a shrubby, erect, branched, leafy plant, 30–60 cm tall. It has narrowly linear leaves which are thick, white, and occasionally pinnately lobed, up to 10 cm long. The composite yellow flower heads contain numerous clusters. In North America, this is a common plant with a range extending from Colorado to Utah, south to Texas and Mexico (Kingsbury, 1964). 1.2 Use The ‘bush tea’ used in Jamaica to treat children for a cold an a herbal tea that is popular in the south-west USA, gordolobo yerba, may contain riddelliine (Stillman et al., 1977a; Huxtable, 1980; National Toxicology Program, 2002). 1.3 Chemical constituents The plants (ragworts) from which riddelliine and other pyrrolizidine alkaloids are isolated are found in the rangelands of the western USA. Cattle, horses and, less commonly, sheep that ingest these plants can succumb to their toxic effects (called pyrro- lizidine alkaloidosis).
    [Show full text]
  • In Vitro Biotransformation of Pyrrolizidine Alkaloids in Different Species
    Archives of Toxicology https://doi.org/10.1007/s00204-017-2114-7 TOXICOKINETICS AND METABOLISM In vitro biotransformation of pyrrolizidine alkaloids in different species. Part I: Microsomal degradation Franziska Kolrep1 · Jorge Numata1 · Carsten Kneuer1 · Angelika Preiss‑Weigert1 · Monika Lahrssen‑Wiederholt1 · Dieter Schrenk2 · Anja These1 Received: 20 September 2017 / Accepted: 8 November 2017 © The Author(s) 2017. This article is an open access publication Abstract Pyrrolizidine alkaloids (PA) are secondary metabolites of certain flowering plants. The ingestion of PAs may result in acute and chronic effects in man and livestock with hepatotoxicity, mutagenicity, and carcinogenicity being identified as predominant effects. Several hundred PAs sharing the diol pyrrolizidine as a core structure are formed by plants. Although many congeners may cause adverse effects, differences in the toxic potency have been detected in animal tests. It is generally accepted that PAs themselves are biologically and toxicologically inactive and require metabolic activation. Consequently, a strong relationship between activating metabolism and toxicity can be expected. Concerning PA susceptibility, marked differences between species were reported with a comparatively high susceptibility in horses, while goat and sheep seem to be almost resistant. Therefore, we investigated the in vitro degradation rate of four frequently occurring PAs by liver enzymes present in S9 fractions from human, pig, cow, horse, rat, rabbit, goat, and sheep liver. Unexpectedly, almost no metabolic degradation of any PA was observed for susceptible species such as human, pig, horse, or cow. If the formation of toxic metabolites represents a crucial bioactivation step, the found inverse conversion rates of PAs compared to the known susceptibility require further investigation.
    [Show full text]
  • Pyrrolizidine Alkaloids: Biosynthesis, Biological Activities and Occurrence in Crop Plants
    molecules Review Pyrrolizidine Alkaloids: Biosynthesis, Biological Activities and Occurrence in Crop Plants Sebastian Schramm, Nikolai Köhler and Wilfried Rozhon * Biotechnology of Horticultural Crops, TUM School of Life Sciences Weihenstephan, Technical University of Munich, Liesel-Beckmann-Straße 1, 85354 Freising, Germany; [email protected] (S.S.); [email protected] (N.K.) * Correspondence: [email protected]; Tel.: +49-8161-71-2023 Academic Editor: John C. D’Auria Received: 20 December 2018; Accepted: 29 January 2019; Published: 30 January 2019 Abstract: Pyrrolizidine alkaloids (PAs) are heterocyclic secondary metabolites with a typical pyrrolizidine motif predominantly produced by plants as defense chemicals against herbivores. They display a wide structural diversity and occur in a vast number of species with novel structures and occurrences continuously being discovered. These alkaloids exhibit strong hepatotoxic, genotoxic, cytotoxic, tumorigenic, and neurotoxic activities, and thereby pose a serious threat to the health of humans since they are known contaminants of foods including grain, milk, honey, and eggs, as well as plant derived pharmaceuticals and food supplements. Livestock and fodder can be affected due to PA-containing plants on pastures and fields. Despite their importance as toxic contaminants of agricultural products, there is limited knowledge about their biosynthesis. While the intermediates were well defined by feeding experiments, only one enzyme involved in PA biosynthesis has been characterized so far, the homospermidine synthase catalyzing the first committed step in PA biosynthesis. This review gives an overview about structural diversity of PAs, biosynthetic pathways of necine base, and necic acid formation and how PA accumulation is regulated. Furthermore, we discuss their role in plant ecology and their modes of toxicity towards humans and animals.
    [Show full text]
  • Current Knowledge and Perspectives of Pyrrolizidine Alkaloids in Pharmacological Applications: a Mini-Review
    molecules Review Current Knowledge and Perspectives of Pyrrolizidine Alkaloids in Pharmacological Applications: A Mini-Review Xianqin Wei 1,*, Weibin Ruan 1 and Klaas Vrieling 2 1 Institute of Entomology, College of Life Sciences, Nankai University, Tianjin 300071, China; [email protected] 2 Plant Science and Natural Products, Institute of Biology, Leiden University, Sylviusweg 72, P.O. Box 9505, 2300 RA Leiden, The Netherlands; [email protected] * Correspondence: [email protected] or [email protected] Abstract: Pyrrolizidine alkaloids (PAs) are a widespread group of secondary metabolites in plants. PAs are notorious for their acute hepatotoxicity, genotoxicity and neurological damage to humans and animals. In recent decades, the application of PAs for beneficial biological activities to cure disease has drawn greater attention. Here, we review the current knowledge regarding the pharmacological properties of PAs and discuss PAs as promising prototypes for the development of new drugs. Keywords: plant secondary metabolites; pharmacy; alkaloids; herb medicine; defense; regulations 1. Introduction Pyrrolizidine alkaloids (PAs) are an important group of secondary metabolites in Citation: Wei, X.; Ruan, W.; Vrieling, plants [1,2]. More than 500 different PAs were identified in more than 6000 plant species K. Current Knowledge and to date [1,3]. PAs have been identified in Apocynaceae (Alafia, Aristeguietia, Brachyglottis, Perspectives of Pyrrolizidine Cacalia, Eupatorium, Ligularia, Pittocaulon, Senecio and Tephroseris), Boraginaceae (Anchusa, Alkaloids in Pharmacological Borago, Cynoglossum, Echium, Heliotropium, Lithospermum, Onosma, Rindera and Solenanthus), Applications: A Mini-Review. Convolvulaceae (Argyreia), Fabaceae (Castanospermum and Crotalaria), Hyacinthaceae (Mus- Molecules 2021, 26, 1970. https:// cari and Scilla), Orchidaceae (Cremastra and Liparis), and Santalaceae (Amphorogyne and doi.org/10.3390/molecules26071970 Osyris)[4–6].
    [Show full text]
  • Chemical Ecology Example 1. Pyrrolizidine Alkaloids (Pas)
    Alkaloids Part 2 Chemical Ecology p. 1 Alkaloids Part 2: Chemical Ecology Example 1. Pyrrolizidine Alkaloids (PAs) - Senecionine-N-oxides Background - basic structural type, but many variations - occurrence in plants in Compositae, Boragincaceae, Orchidaceae - extremely toxic to both mammals and insects but complex interactions - documented co-evolution with specialist insects, and sophisticated use of plant defenses by insects Biosynthesis Senecionine-N-oxide synthesized from two separate pathways/moieties - necine moiety, from arginine via putrescine (decarboxylate, condense, cyclize) - dicarboxylic acid moiety, from isoleucine => both form the macrocyclic diester = senecionine - key enzyme: homospermine synthase. Evolved independently at least four time - different plant families - from deoxyhypusine synthase, and enzyme of primary metabolism (activates eukaryotic translation initiation factor eIF5A) - five distinct structural types, that vary in macrocyclic diester bridge component Pyrrolizidine alkaloid localization and transport - root synthesis of senecionine, then transported to shoot - final accumulation of alkaloids is in flowers and shoot apex - further biochemical elaboration and structural diversification (decoration of macrocycle) occurs in shoot - population differentiation (diverse mixtures of pyrrolizidine alkaloids in different plant populations) - > variable target for pests. Pyrrolizidine Alkaloid Toxicity and its Avoidance - PA-containing plants are generally avoided by herbivores ( bitter taste, toxicity) - N-oxide
    [Show full text]
  • The Food Contaminants Pyrrolizidine Alkaloids Disturb Bile Acid Homeostasis Structure-Dependently in the Human Hepatoma Cell Line Heparg
    foods Article The Food Contaminants Pyrrolizidine Alkaloids Disturb Bile Acid Homeostasis Structure-Dependently in the Human Hepatoma Cell Line HepaRG Josephin Glück 1, Marcus Henricsson 2, Albert Braeuning 1 and Stefanie Hessel-Pras 1,* 1 Department of Food Safety, German Federal Institute for Risk Assessment, Max-Dohrn-Straße 8-10, 10589 Berlin, Germany; [email protected] (J.G.); [email protected] (A.B.) 2 Wallenberg Laboratory, Department of Molecular and Clinical Medicine, Institute of Medicine, University of Gothenburg, 413 45 Gothenburg, Sweden; [email protected] * Correspondence: [email protected]; Tel.: +49-30-18412-25203 Abstract: Pyrrolizidine alkaloids (PAs) are a group of secondary plant metabolites being contained in various plant species. The consumption of contaminated food can lead to acute intoxications in humans and exert severe hepatotoxicity. The development of jaundice and elevated bile acid concentrations in blood have been reported in acute human PA intoxication, indicating a connection between PA exposure and the induction of cholestasis. Additionally, it is considered that differences in toxicity of individual PAs is based on their individual chemical structures. Therefore, we aimed to elucidate the structure-dependent disturbance of bile acid homeostasis by PAs in the human hepatoma cell line HepaRG. A set of 14 different PAs, including representatives of all major structural characteristics, namely, the four different necine bases retronecine, heliotridine, otonecine and platynecine and different grades of esterification, was analyzed in regard to the expression of genes Citation: Glück, J.; Henricsson, M.; Braeuning, A.; Hessel-Pras, S. The involved in bile acid synthesis, metabolism and transport.
    [Show full text]
  • Occurrence of Nine Pyrrolizidine Alkaloids in Senecio Vulgaris L
    plants Article Occurrence of Nine Pyrrolizidine Alkaloids in Senecio vulgaris L. Depending on Developmental Stage and Season Jens Flade 1,2,3 , Heidrun Beschow 1, Monika Wensch-Dorendorf 4, Andreas Plescher 2 and Wim Wätjen 3,* 1 Plant Nutrition, Institute of Agricultural and Nutritional Sciences, Martin-Luther-University Halle-Wittenberg, Betty-Heimann-Strasse 3, 06120 Halle/Saale, Germany; [email protected] (J.F.); [email protected] (H.B.) 2 PHARMAPLANT Arznei- und Gewürzpflanzen Forschungs- und Saatzucht GmbH, Am Westbahnhof 4, 06556 Artern, Germany; [email protected] 3 Biofunctionality of Secondary Plant Compounds, Institute of Agricultural and Nutritional Sciences, Martin-Luther-University Halle-Wittenberg, Weinbergweg 22, 06120 Halle/Saale, Germany 4 AG Biometrie und Agrarinformatik, Institute of Agricultural and Nutritional Sciences, Martin-Luther-University Halle-Wittenberg, Karl-Freiherr-von-Fritsch-Strasse 4, 06120 Halle/Saale, Germany; [email protected] * Correspondence: [email protected]; Tel.: +49-345-5522380 Received: 16 January 2019; Accepted: 19 February 2019; Published: 5 March 2019 Abstract: The contamination of phytopharmaceuticals and herbal teas with toxic plants is an increasing problem. Senecio vulgaris L. is a particularly noxious weed in agricultural and horticultural crops due to its content of toxic pyrrolizidine alkaloids (PAs). Since some of these compounds are carcinogenic, the distribution of this plant should be monitored. The amount of PAs in S. vulgaris is affected by various factors. Therefore, we investigated the occurrence of PAs depending on the developmental stage and season. A systematic study using field-plot experiments (four seasons, five developmental stages of the plants: S1 to S5) was performed and the PA concentration was determined via LC-MS/MS analysis.
    [Show full text]
  • An Important Mechanism of Herb-Induced Hepatotoxicity: to Produce Rms Based on Active Functional Groups-Containing Ingredients from Phytomedicine by Binding Cyp450s
    Chinese Herbal Medicines 11 (2019) 239–257 Contents lists available at ScienceDirect Chinese Herbal Medicines journal homepage: www.elsevier.com/locate/chmed Review An important mechanism of herb-induced hepatotoxicity: To produce RMs based on active functional groups-containing ingredients from phytomedicine by binding CYP450s ∗ Xin He a,b, , Zi-jun Wu a, Li-li Wang a, Xue Gao a,b, Yue Hai a, Wen-li Liu a, Le-mei Du a, Lei Zhang a, Ai-hong Yang a, Nan-nan Huang a a School of Chinese Materia Medica, Tianjin University of Traditional Chinese Medicine, Tianjin 300193, China b School of Traditional Chinese Medicine, Guangdong Pharmaceutical University, Guangzhou 510 0 06, China a r t i c l e i n f o a b s t r a c t Article history: Reactive metabolites (RMs) generated by hepatic metabolism are thought to play an important role in the Received 22 December 2018 pathogenesis of drug-induced liver injury (DILI). Like many synthetic drugs undergoing metabolic activa- Revised 15 March 2019 tion to form RMs which are often associated with drug toxicity, it is recognized that some herbal compo- Accepted 18 April 2019 nents may be also converted to toxic, or even mutagenetic and carcinogenic metabolites by cytochrome Available online 9 July 2019 P450s (CYP450s). This review focuses on the metabolic activation of herbal components and its liver Keywords: toxicological implications. By summarizing references, we found that hepatotoxic herbal components via active functional groups producing RMs have some certain structural dependence. There is a correlation
    [Show full text]
  • Pyrrolizidine Alkaloids in Food
    Risk Assessment Studies Report No. 56 Chemical Hazard Evaluation Pyrrolizidine Alkaloids in Food January 2017 Centre for Food Safety Food and Environmental Hygiene Department The Government of the Hong Kong Special Administrative Region This is a publication of the Centre for Food Safety of the Food and Environmental Hygiene Department (FEHD) of the Government of the Hong Kong Special Administrative Region. Under no circumstances should the research data contained herein be reproduced, reviewed, or abstracted in part or in whole, or in conjunction with other publications or research work unless a written permission is obtained from the Centre for Food Safety. Acknowledgement is required if other parts of this publication are used. Correspondence: Risk Assessment Section Centre for Food Safety Food and Environmental Hygiene Department 43/F, Queensway Government Offices, 66 Queensway, Hong Kong. Email: [email protected] ii Contents Page Executive Summary 1 Objectives 6 Background 6 Chemistry of Pyrrolizidine Alkaloids (PAs) 7 Sources of PAs 10 Sources of Dietary Exposure 10 Toxicity 12 Health-Based Guidance Values (HBGVs) 17 Regulatory Control 17 Scope of Study 18 Methodology and Laboratory Analysis 19 Methodology 19 Laboratory Analysis 20 Treatment of Analytical Values Below the Limit of Detection 21 (LOD) Results and Discussion 21 Total PAs in Different Food Groups 21 Dietary Exposure to PAs 24 Major Food Contributors 26 Food Items Not Covered by Exposure Estimation 28 Limitations of the Study 30 Conclusions and Recommendations 31 References 34 Appendices 39 Appendix 1: Sum of twenty-eight 1,2 PAs ( µg/kg) in food groups and 39 food items Appendix 2: Lower Bound (LB) and Upper Bound (UB) Dietary 41 Exposure to the sum of 1,2 unsaturated PAs by Age-Gender Group (Average and High Consumer of the Population) iii EXECUTIVE SUMMARY This study aims to determine the total sum of 1,2-unsaturated pyrrolizidine alkaloids (PAs) in selected food items, to estimate the dietary exposure to PAs of the Hong Kong adult population and to assess the associated health risks.
    [Show full text]