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Carazo A, Mladěnka P, Pávek P. Marine Ligands of the Pregnane X Receptor (PXR): An Overview. Mar Drugs 2019; 17:md17100554. [PMID: 31569349 PMCID: PMC6836225 DOI: 10.3390/md17100554] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 09/27/2019] [Accepted: 09/27/2019] [Indexed: 02/06/2023] Open
Abstract
Pregnane X Receptor (PXR) is a ligand-activated transcription factor which binds many structurally different molecules. The receptor is able to regulate the expression of a wide array of genes and is involved in cancer and different key physiological processes such as the metabolism of drugs/xenobiotics and endogenous compounds including lipids and carbohydrates, and inflammation. Algae, sponges, sea squirts, and other marine organisms are some of the species from which structurally new molecules have been isolated that have been subsequently identified in recent decades as ligands for PXR. The therapeutic potential of these natural compounds is promising in different areas and has recently resulted in the registration of trabectedin by the FDA as a novel antineoplastic drug. Apart from being potentially novel drugs, these compounds can also serve as models for the development of new molecules with improved activity. The aim of this review is to succinctly summarize the currently known natural molecules isolated from marine organisms with a proven ability to interact with PXR.
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Affiliation(s)
- Alejandro Carazo
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovského 1203, Hradec Králové 500 05, Czech Republic.
| | - Přemysl Mladěnka
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovského 1203, Hradec Králové 500 05, Czech Republic.
| | - Petr Pávek
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovského 1203, Hradec Králové 500 05, Czech Republic.
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Chen H, Zhang X, Feng Y, Rui W, Shi Z, Wu L. Bioactive components of Glycyrrhiza uralensis mediate drug functions and properties through regulation of CYP450 enzymes. Mol Med Rep 2014; 10:1355-62. [PMID: 24939038 DOI: 10.3892/mmr.2014.2331] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 04/14/2014] [Indexed: 11/06/2022] Open
Abstract
Glycyrrhiza uralensis (G. uralensis) is a common medicinal plant that has mainly been used to modulate the pharmaceutical activity of herbal medicines. Although G. uralensis has been shown to affect the expression and activity of the key metabolic enzyme cytochrome P450 (CYP450), the detailed mechanism of this process has yet to be elucidated. The present study aimed to elucidate the effects of bioactive components of G. uralensis on different isoforms of CYP450 and determine the ability of these components to modulate drug properties. In the present study, mRNA levels of CYP1A2, CYP2D6, CYP2E1, and CYP3A4 were investigated by quantitative polymerase chain reaction (qPCR) in HepG2 cells following treatment with the major bioactive compounds of G. uralensis. The activity of CYP450 enzymes was investigated in human liver microsomes using the cocktail probe drug method, and the metabolites of specific probes were detected by UPLC‑MS/MS. The effects of G. uralensis on CYP450 were assessed using bioinformatics network analysis. Several compounds from G. uralensis had various effects on the expression and activity of multiple CYP450 isoforms. The majority of the compounds analysed the inhibited expression of CYP2D6 and CYP3A4. Several CYP isoforms were differentially modulated depending on the specific compound and dose tested. In conclusion, the present study suggested that G. uralensis influenced the expression and activity of CYP450 enzymes. Therefore, caution should be taken when G. uralensis is co‑administered with drugs that are known to be metabolized by CYP450. This study contributed to the knowledge of the mechanisms by which this medicinal plant, commonly known as licorice, modulates drug efficacy.
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Affiliation(s)
- Hao Chen
- Department of Pharmacy, Qilu Hospital of Shandong University, Jinan, Shandong 250012, P.R. China
| | - Xiaomei Zhang
- Center Laboratory, Guangdong Pharmaceutical University, Guangzhou, Guangdong 510006, P.R. China
| | - Yifan Feng
- Center Laboratory, Guangdong Pharmaceutical University, Guangzhou, Guangdong 510006, P.R. China
| | - Wen Rui
- Center Laboratory, Guangdong Pharmaceutical University, Guangzhou, Guangdong 510006, P.R. China
| | - Zhongfeng Shi
- Center Laboratory, Guangdong Pharmaceutical University, Guangzhou, Guangdong 510006, P.R. China
| | - Lirong Wu
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances, Guangdong Pharmaceutical University, Guangzhou, Guangdong 510006, P.R. China
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Prigent L, Robineau M, Jouneau S, Morzadec C, Louarn L, Vernhet L, Fardel O, Sparfel L. The aryl hydrocarbon receptor is functionally upregulated early in the course of human T-cell activation. Eur J Immunol 2014; 44:1330-40. [PMID: 24549985 DOI: 10.1002/eji.201343920] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 01/14/2014] [Accepted: 01/24/2014] [Indexed: 11/08/2022]
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that mediates immunosuppression caused by a variety of environmental contaminants, such as polycyclic aromatic hydrocarbons or dioxins. Recent evidence suggests that AhR plays an important role in T-cell-mediated immune responses by affecting the polarization and differentiation of activated T cells. However, the regulation of AhR expression in activated T cells remains poorly characterized. In the present study, we used purified human T cells stimulated with anti-CD3 and anti-CD28 Abs to investigate the effect of T-cell activation on AhR mRNA and protein expression. The expression of AhR mRNA increased significantly and rapidly after T-cell activation, identifying AhR as an immediate-early activation gene. AhR upregulation occurred in all of the T-cell subtypes, and is associated with its nuclear translocation and induction of the cytochromes P-450 1A1 and 1B1 mRNA expression in the absence of exogenous signals. In addition, the use of an AhR antagonist or siRNA-mediated AhR knockdown significantly inhibited IL-22 expression, suggesting that expression and functional activation of AhR is necessary for the secretion of IL-22 by activated T cells. In conclusion, our data support the idea that AhR is a major player in T-cell physiology.
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Affiliation(s)
- Laurie Prigent
- UMR INSERM U1085, Institut de Recherche sur la Santé, l'Environnement et le Travail (IRSET), Université de Rennes 1, Rennes, France
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Fardel O, Kolasa E, Le Vee M. Environmental chemicals as substrates, inhibitors or inducers of drug transporters: implication for toxicokinetics, toxicity and pharmacokinetics. Expert Opin Drug Metab Toxicol 2011; 8:29-46. [DOI: 10.1517/17425255.2012.637918] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Cheng J, Ma X, Gonzalez FJ. Pregnane X receptor- and CYP3A4-humanized mouse models and their applications. Br J Pharmacol 2011; 163:461-8. [PMID: 21091656 DOI: 10.1111/j.1476-5381.2010.01129.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Pregnane X receptor (PXR) is a pivotal nuclear receptor modulating xenobiotic metabolism primarily through its regulation of CYP3A4, the most important enzyme involved in drug metabolism in humans. Due to the marked species differences in ligand recognition by PXR, PXR-humanized (hPXR) mice, and mice expressing human PXR and CYP3A4 (Tg3A4/hPXR) were established. hPXR and Tg3A4/hPXR mice are valuable models for investigating the role of PXR in xenobiotic metabolism and toxicity, in lipid, bile acid and steroid hormone homeostasis, and in the control of inflammation.
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Affiliation(s)
- Jie Cheng
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
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Pinel-Marie ML, Louarn L, Desmots S, Fardel O, Sparfel L. Aryl hydrocarbon receptor-dependent induction of the IgA receptor FcαRI by the environmental contaminant benzo(a)pyrene in human macrophages. Toxicology 2011; 290:89-95. [PMID: 21911031 DOI: 10.1016/j.tox.2011.08.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 08/24/2011] [Accepted: 08/25/2011] [Indexed: 12/14/2022]
Abstract
Polycyclic aromatic hydrocarbons (PAHs), such as benzo(a)pyrene (BaP), are widely distributed toxic environmental contaminants well known to regulate gene expression through activation of the aryl hydrocarbon receptor (AhR). In the present study, we demonstrated that the IgA receptor FcαRI/CD89 constitutes a molecular target for PAHs. Indeed, in vitro exposure to BaP markedly increased mRNA and protein expression of FcαRI in primary human macrophages; intratracheal instillation of BaP to rats also enhanced mRNA expression of FcαRI in alveolar macrophages. BaP concomitantly increased activity of the previously uncharacterized -1734 to -42 fragment of the FcaRI promoter that we subcloned in a luciferase reporter vector. Three-methylcholanthrene, a PAH known to activate AhR like BaP, induced FcαRI expression, in contrast to benzo(e)pyrene, a PAH known to poorly interact with AhR. Moreover, FcαRI induction in BaP-exposed human macrophages was fully prevented by down-regulating AhR expression through small interference RNA transfection. In addition, BaP increased nuclear protein binding to a consensus AhR-related xenobiotic-responsive element found in the FcαRI gene promoter, as revealed by electrophoretic mobility shift assay. Overall, these data highlight an AhR-dependent up-regulation of FcαRI in response to BaP, which may contribute to the deleterious effects of environmental PAHs toward the immune/inflammatory response and which also likely emphasizes the role played by AhR in the regulation of genes involved in immunity and inflammation.
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Affiliation(s)
- Marie-Laure Pinel-Marie
- Institut de Recherche sur la Santé, l'Environnement et le Travail (IRSET), EA-4427 Signalisation et Réponses aux Agents Infectieux et Chimiques (SeRAIC), Université de Rennes 1, 2 avenue du Professeur Léon Bernard, 35043 Rennes, France.
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Pinel-Marie ML, Sparfel L, Desmots S, Fardel O. Aryl hydrocarbon receptor-dependent induction of the NADPH oxidase subunit NCF1/p47 phox expression leading to priming of human macrophage oxidative burst. Free Radic Biol Med 2009; 47:825-34. [PMID: 19559082 DOI: 10.1016/j.freeradbiomed.2009.06.025] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Revised: 06/10/2009] [Accepted: 06/18/2009] [Indexed: 10/20/2022]
Abstract
Polycyclic aromatic hydrocarbons such as benzo(a)pyrene (BaP) are toxic environmental contaminants known to regulate gene expression through activation of the aryl hydrocarbon receptor (AhR). In the present study, we demonstrated that acute treatment by BaP markedly increased expression of the NADPH oxidase subunit gene neutrophil cytosolic factor 1 (NCF1)/p47(phox) in primary human macrophages; NCF1 was similarly up-regulated in alveolar macrophages from BaP-instilled rats. NCF1 induction in BaP-treated human macrophages was prevented by targeting AhR, through its chemical inhibition or small interference RNA-mediated down-modulation of its expression. BaP moreover induced activity of the NCF1 promoter sequence, containing a consensus AhR-related xenobiotic-responsive element (XRE), and electrophoretic mobility shift assays and chromatin immunoprecipitation experiments indicated that BaP-triggered binding of AhR to this XRE. Finally, we showed that BaP exposure resulted in p47(phox) protein translocation to the plasma membrane and in potentiation of phorbol myristate acetate (PMA)-induced superoxide anion production in macrophages. This BaP priming effect toward NADPH oxidase activity was inhibited by the NADPH oxidase specific inhibitor apocynin and the chemical AhR inhibitor alpha-naphtoflavone. These results indicated that BaP induced NCF1/p47(phox) expression and subsequently enhanced superoxide anion production in PMA-treated human macrophages, in an AhR-dependent manner; such an NCF1/NADPH oxidase regulation by polycyclic aromatic hydrocarbons may participate in deleterious effects toward human health triggered by these environmental contaminants, including atherosclerosis and smoking-related diseases.
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Affiliation(s)
- Marie-Laure Pinel-Marie
- INSERM U620-EA4427 SeRAIC, IFR140, Université de Rennes I, 2 Avenue du Pr Léon Bernard, 35043 Rennes, France
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Biswas A, Mani S, Redinbo MR, Krasowski MD, Li H, Ekins S. Elucidating the 'Jekyll and Hyde' nature of PXR: the case for discovering antagonists or allosteric antagonists. Pharm Res 2009; 26:1807-15. [PMID: 19415465 DOI: 10.1007/s11095-009-9901-7] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Accepted: 04/16/2009] [Indexed: 12/15/2022]
Abstract
The pregnane X receptor belongs to the nuclear hormone receptor superfamily and is involved in the transcriptional control of numerous genes. It was originally thought that it was a xenobiotic sensor controlling detoxification pathways. Recent studies have shown an increasingly important role in inflammation and cancer, supporting its function in abrogating tissue damage. PXR orthologs and PXR-like pathways have been identified in several non-mammalian species which corroborate a conserved role for PXR in cellular detoxification. In summary, PXR has a multiplicity of roles in vivo and is being revealed as behaving like a "Jekyll and Hyde" nuclear hormone receptor. The importance of this review is to elucidate the need for discovery of antagonists of PXR to further probe its biology and therapeutic applications. Although several PXR agonists are already reported, virtually nothing is known about PXR antagonists. Here, we propose the development of PXR antagonists through chemical, genetic and molecular modeling approaches. Based on this review it will be clear that antagonists of PXR and PXR-like pathways will have widespread utility in PXR biology and therapeutics.
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Affiliation(s)
- Arunima Biswas
- Albert Einstein Cancer Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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Kiyosawa N, Kwekel JC, Burgoon LD, Williams KJ, Tashiro C, Chittim B, Zacharewski TR. o,p'-DDT elicits PXR/CAR-, not ER-, mediated responses in the immature ovariectomized rat liver. Toxicol Sci 2007; 101:350-63. [PMID: 17984292 DOI: 10.1093/toxsci/kfm275] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Technical-grade dichlorodiphenyltrichloroethane (DDT) is an agricultural pesticide and malarial vector control agent that has been designated a potential human hepatocarcinogen. The o,p'-enantiomer exhibits estrogenic activity that has been associated with the carcinogenicity of DDT. The temporal and dose-dependent hepatic estrogenicity of o,p'-DDT was investigated using complementary DNA microarrays in immature ovariectomized Sprague-Dawley rats with complementary histopathology and tissue-level analysis. Animals were gavaged with 300 mg/kg o,p'-DDT either once or once daily for 3 consecutive days. Liver samples were examined 2, 4, 8, 12, 18, or 24 h after a single dose or following three daily doses. For dose-response studies, a single dose of 3, 10, 30, 100, or 300 mg/kg body weight o,p'-DTT was administered for 3 consecutive days. Genes associated with drug metabolism (Cyp2b2 and Cyp3a2), the nuclear receptors constitutive androstane receptor (CAR) and pregnane X receptor (PXR), cell proliferation (Ccnd1, Ccnb1, Ccnb2, and Stmn1), and oxidative stress (Gclm and Hmox1) were significantly induced. Cyp2b2 exhibited dose-dependent regulation and was significantly induced across all time points, while cell proliferation- and oxidative stress-related genes exhibited transient induction. The induction of Cyp2b2 and Cyp3a2 mRNA levels suggest PXR/CAR activation, consistent with expression of genes associated with oxidative stress. Few genes known to be estrogen receptor (ER) regulated were differentially expressed when compared to the hepatic gene expression profile elicited by ethynyl estradiol in immature ovariectomized C57BL/6 mice using the same study design and analysis methods. These data indicate that o,p'-DDT elicits PXR/CAR-, not ER-, mediated gene expression in the rat liver. Based on the species-specific differences in CAR regulation, the extrapolation of rodent DDT hepatocarcinogenicity to humans warrants further investigation.
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Affiliation(s)
- Naoki Kiyosawa
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA
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Plant N. The human cytochrome P450 sub-family: Transcriptional regulation, inter-individual variation and interaction networks. Biochim Biophys Acta Gen Subj 2007; 1770:478-88. [PMID: 17097810 DOI: 10.1016/j.bbagen.2006.09.024] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Accepted: 09/28/2006] [Indexed: 11/26/2022]
Abstract
The Cytochrome P450 super-family is a fundamental requirement for the viability of most life, with Cytochrome P450 proteins having been identified in organisms ranging from bacteria to man. These enzymes may be subdivided into those that metabolise purely endogenous chemicals, and those that are involved in xenobiotic metabolism. Of the latter group it can be argued that CYP3A sub-family members rank as the most important; their high expression in the liver and wide substrate specificity mean that they are clinically important in the metabolism of many therapeutic drugs, and alteration in their activity is central to many clinically-relevant drug-drug interactions. In this review I will examine the human CYP3A enzymes, discussing their genome structure, common allelic variants and, in greatest detail, their transcriptional regulation. Through examination of these characteristics we will see both striking similarities and differences between the four human CYP3A enzymes, which may have important impacts on inter-individual response to chemical exposure. Finally, the role of nuclear receptors in regulating CYP3A gene expression, and indeed that of many other proteins involved in drug metabolism, will be examined: Such an examination will show the need to utilize a systems biology approach to understand fully how the human body responds to chemical exposure.
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Affiliation(s)
- Nick Plant
- School of Biomedical and Molecular Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK.
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Anapolsky A, Teng S, Dixit S, Piquette-Miller M. The role of pregnane X receptor in 2-acetylaminofluorene-mediated induction of drug transport and -metabolizing enzymes in mice. Drug Metab Dispos 2005; 34:405-9. [PMID: 16381673 DOI: 10.1124/dmd.105.006197] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of the pregnane X receptor (PXR) mediates the induction of several drug transporters and -metabolizing enzymes. In vitro studies have reported that several of these genes are induced after exposure to the hepatocarcinogen, 2-acetylaminofluorene (2-AAF). Thus, we hypothesized that PXR may play a role in the in vivo induction of gene expression by 2-AAF. We examined the expression of the drug-metabolizing enzymes CYP1A2 and CYP3A11 and the drug transporters breast cancer resistance protein (BCRP), MRP2, and OATP2. Wild-type (PXR+/+) and PXR-null (PXR-/-) C57BL/6 mice were injected daily for 7 days with 150 or 300 mg/kg 2-AAF suspended in corn oil (i.p.), whereas the control group received corn oil vehicle. Levels of mRNA isolated from liver were measured by reverse transcription-polymerase chain reaction and normalized to beta-actin. Treatment of PXR+/+ mice resulted in a dose-dependent 2- to 4-fold induction (p<0.001) of MRP2, OATP2, BCRP, CYP3A11, and CYP1A2, but no induction was observed in PXR-/- mice. Induction of PXR mRNA was observed in the 2-AAF-treated PXR+/+ mice. Furthermore, a dose-dependent increase in CYP3A4 promoter construct activity was observed in HepG2 cells cotransfected with human or rat PXR, indicating that 2-AAF does indeed activate PXR. These results suggest that PXR is responsible for 2-AAF-mediated induction of drug efflux transporters and biotransformation enzymes in the liver. Moreover, novel findings demonstrate that PXR plays a role in regulation of the drug efflux transporter, BCRP, in mice.
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Affiliation(s)
- Alexander Anapolsky
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, 19 Russell Street, Toronto, Ontario, Canada, M5S 2S2
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Sun G, Thai SF, Tully DB, Lambert GR, Goetz AK, Wolf DC, Dix DJ, Nesnow S. Propiconazole-induced cytochrome P450 gene expression and enzymatic activities in rat and mouse liver. Toxicol Lett 2005; 155:277-87. [PMID: 15603923 DOI: 10.1016/j.toxlet.2004.10.006] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2004] [Revised: 10/14/2004] [Accepted: 10/14/2004] [Indexed: 11/21/2022]
Abstract
Propiconazole is a N-substituted triazole used as a fungicide on fruits, grains, seeds, hardwoods, and conifers. In the present study, propiconazole was examined for its effects on the expression of hepatic cytochrome P450 genes and on the activities of P450 enzymes in male Sprague-Dawley rats and male CD-1 mice. Rats and mice were administered propiconazole by gavage daily for 14 days at doses of 10, 75, and 150 mg/kg body weight/day. Quantitative real time RT-PCR assays of rat hepatic RNA samples from animals treated at the 150 mg/kg body weight/day dose revealed significant mRNA overexpression of the following genes compared to control: CYP1A2 (1.62-fold), CYP2B1 (10.8-fold), CYP3A1/CYP3A23 (2.78-fold), and CYP3A2 (1.84-fold). In mouse liver, propiconazole produced mRNA overexpression of Cyp2b10 (2.39-fold) and Cyp3a11 (5.19-fold). mRNA expression of CYP1A1 was not detected in liver tissues from treated or controls animals from either species. Propiconazole significantly induced both pentoxyresorufin O-dealkylation (PROD) and methoxyresorufin O-dealkylation (MROD) activities in both rat and mouse liver at the 150 mg/kg body weight/day and 75 mg/kg body weight/day doses. In summary, these results indicated that propiconazole induced CYP1A2 in rat liver and CYP2B and CYP3A families of isoforms in rat and mouse liver.
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Affiliation(s)
- Guobin Sun
- National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA
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Yueh MF, Kawahara M, Raucy J. High volume bioassays to assess CYP3A4-mediated drug interactions: induction and inhibition in a single cell line. Drug Metab Dispos 2004; 33:38-48. [PMID: 15466163 DOI: 10.1124/dmd.104.001594] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Exposure to certain xenochemicals can alter the catalytic activity of the major drug-metabolizing enzyme, CYP3A4, either by enhancing expression of this cytochrome P450 or inhibiting its activity. Such alterations can result in adverse consequences stemming from drug-drug interactions. A simplified and reliable tool for detecting the ability of candidate drugs to alter CYP3A4 levels or inhibit catalytic activity was developed by stable integration of human pregnane X receptor and a luciferase vector harboring the CYP3A4 enhancers. Treatment of stable transformants, namely DPX-2, with various concentrations of inducers including rifampicin, mifepristone, troglitazone, methoxychlor, and kava produced dose-dependent increases in luciferase expression (between 2- and 40-fold above dimethyl sulfoxide-treated cells). Northern blot analyses of CYP3A4 mRNA in DPX-2 cells exhibited a good correlation to results generated with the reporter gene assay (r(2) = 0.5, p < 0.01). Induction of CYP3A4 protein was examined by measuring catalytic activity with the CYP3A4 substrate, luciferin 6' benzyl ether (luciferin BE). Metabolism of luciferin BE by DPX-2 cells was enhanced 5.2-fold above dimethyl sulfoxide-treated cells by treatment with rifampicin. Constitutive androstane receptor-mediated regulation of CYP3A4 protein was addressed by measuring catalytic activity in a separate cell line over-expressing this receptor. Phenobarbital and dexamethasone produced 1.5- and 2.0-fold increases, respectively, above control in luciferin BE metabolism. To determine the utility of DPX-2 cells for identifying inhibitors of CYP3A4 catabolism, luciferin BE activity was measured in the presence of various concentrations of ketoconazole, erythromycin, or kava. These agents exhibited dose-dependent decreases in CYP3A4 activity with IC(50) values of 0.3 microM for ketoconazole, 108 microM for erythromycin, and 15.5 microg/ml for kava. Collectively, DPX-2 cells were used to identify xenobiotics that induce or inhibit CYP3A4 in a high throughput manner, demonstrating their applicability to early-stage drug development.
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Affiliation(s)
- Mei-Fei Yueh
- Dept. of Molecular and Cellular Toxicology, California Toxicology Research Institute, 1989 Palomar Oaks Way, Suite B, Carlsbad, CA 92009, USA
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