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Li Z, Kwon SM, Li D, Li L, Peng X, Zhang J, Sueyoshi T, Raufman JP, Negishi M, Wang XW, Wang H. Human constitutive androstane receptor represses liver cancer development and hepatoma cell proliferation by inhibiting erythropoietin signaling. J Biol Chem 2022; 298:101885. [PMID: 35367211 PMCID: PMC9052153 DOI: 10.1016/j.jbc.2022.101885] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 03/22/2022] [Accepted: 03/24/2022] [Indexed: 12/13/2022] Open
Abstract
The constitutive androstane receptor (CAR) is a nuclear receptor that plays a crucial role in regulating xenobiotic metabolism and detoxification, energy homeostasis, and cell proliferation by modulating the transcription of numerous target genes. CAR activation has been established as the mode of action by which phenobarbital-like nongenotoxic carcinogens promote liver tumor formation in rodents. This paradigm, however, appears to be unrelated to the function of human CAR (hCAR) in hepatocellular carcinoma (HCC), which remains poorly understood. Here, we show that hCAR expression is significantly lower in HCC than that in adjacent nontumor tissues and, importantly, reduced hCAR expression is associated with a worse HCC prognosis. We also show overexpression of hCAR in human hepatoma cells (HepG2 and Hep3B) profoundly suppressed cell proliferation, cell cycle progression, soft-agar colony formation, and the growth of xenografts in nude mice. RNA-Seq analysis revealed that the expression of erythropoietin (EPO), a pleiotropic growth factor, was markedly repressed by hCAR in hepatoma cells. Addition of recombinant EPO in HepG2 cells partially rescued hCAR-suppressed cell viability. Mechanistically, we showed that overexpressing hCAR repressed mitogenic EPO-EPO receptor signaling through dephosphorylation of signal transducer and activator of transcription 3, AKT, and extracellular signal-regulated kinase 1/2. Furthermore, we found that hCAR downregulates EPO expression by repressing the expression and activity of hepatocyte nuclear factor 4 alpha, a key transcription factor regulating EPO expression. Collectively, our results suggest that hCAR plays a tumor suppressive role in HCC development, which differs from that of rodent CAR and offers insight into the hCAR-hepatocyte nuclear factor 4 alpha-EPO axis in human liver tumorigenesis.
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Affiliation(s)
- Zhihui Li
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, USA
| | - So Mee Kwon
- Laboratory of Human Carcinogenesis, and Liver Cancer Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Daochuan Li
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, USA
| | - Linhao Li
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, USA
| | - Xiwei Peng
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, USA
| | - Junran Zhang
- Department of Radiation Oncology, The Ohio State University James Comprehensive Cancer Center and College of Medicine, Ohio, USA
| | - Tatsuya Sueyoshi
- Pharmacogenetics Section, Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, USA
| | - Jean-Pierre Raufman
- Division of Gastroenterology and Hepatology, University of Maryland School of Medicine, Baltimore, Maryland, USA; Office of Research and Development, Biomedical Laboratory Research and Development, VA Maryland Healthcare System, Baltimore, Maryland, USA
| | - Masahiko Negishi
- Pharmacogenetics Section, Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, USA
| | - Xin Wei Wang
- Laboratory of Human Carcinogenesis, and Liver Cancer Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Hongbing Wang
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, USA.
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Honkakoski P. Searching for CAR modulators. Drug Metab Dispos 2022; 50:1002-1009. [DOI: 10.1124/dmd.121.000482] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 02/01/2022] [Indexed: 11/22/2022] Open
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Lin YS, Thummel KE, Thompson BD, Totah RA, Cho CW. Sources of Interindividual Variability. Methods Mol Biol 2021; 2342:481-550. [PMID: 34272705 DOI: 10.1007/978-1-0716-1554-6_17] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The efficacy, safety, and tolerability of drugs are dependent on numerous factors that influence their disposition. A dose that is efficacious and safe for one individual may result in sub-therapeutic or toxic blood concentrations in others. A significant source of this variability in drug response is drug metabolism, where differences in presystemic and systemic biotransformation efficiency result in variable degrees of systemic exposure (e.g., AUC, Cmax, and/or Cmin) following administration of a fixed dose.Interindividual differences in drug biotransformation have been studied extensively. It is recognized that both intrinsic factors (e.g., genetics, age, sex, and disease states) and extrinsic factors (e.g., diet , chemical exposures from the environment, and the microbiome) play a significant role. For drug-metabolizing enzymes, genetic variation can result in the complete absence or enhanced expression of a functional enzyme. In addition, upregulation and downregulation of gene expression, in response to an altered cellular environment, can achieve the same range of metabolic function (phenotype), but often in a less predictable and time-dependent manner. Understanding the mechanistic basis for variability in drug disposition and response is essential if we are to move beyond the era of empirical, trial-and-error dose selection and into an age of personalized medicine that will improve outcomes in maintaining health and treating disease.
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Affiliation(s)
- Yvonne S Lin
- Department of Pharmaceutics, University of Washington, Seattle, WA, USA.
| | - Kenneth E Thummel
- Department of Pharmaceutics, University of Washington, Seattle, WA, USA
| | - Brice D Thompson
- Department of Pharmaceutics, University of Washington, Seattle, WA, USA
| | - Rheem A Totah
- Department of Medicinal Chemistry, University of Washington, Seattle, WA, USA
| | - Christi W Cho
- Department of Medicinal Chemistry, University of Washington, Seattle, WA, USA
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Zhang X, Meng R, Wang H, Xing J. Differential Effects of Components in Artemisia annua Extract on the Induction of Drug-Metabolizing Enzyme Expression Mediated by Nuclear Receptors. PLANTA MEDICA 2020; 86:867-875. [PMID: 32557519 DOI: 10.1055/a-1178-0852] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Artemisia annua tea is a popular dosage form used to treat and prevent malaria in some developing countries. However, repeated drinking leads to an obviously decreased efficacy, which may be related to the induction of metabolizing enzymes by artemisinin. In the present study, the ability of different components in A. annua to activate the pregnane X receptor and constitutive androstane receptor was evaluated by the dual luciferase reporter gene system. The changes in mRNA and protein expression of CYP3A4 and CYP2B6 were determined by quantitative real-time PCR and Western blotting. Results showed that in the pregnane X receptor-mediated CYP3A4 reporter gene system, chrysosplenetin and arteannuin B exhibited a weak induction effect on pregnane X receptor wt, while arteannuin A had a strong induction effect on pregnane X receptor wt and pregnane X receptor 370 and a weak induction effect on pregnane X receptor 163. In the pregnane X receptor-mediated CYP2B6 reporter gene system, arteannuin A had a moderate induction effect on pregnane X receptor wt and pregnane X receptor 379, and a weak induction effect on pregnane X receptor 403, while arteannuin B had a weak induction effect on pregnane X receptor wt and pregnane X receptor 379. Arteannuin A had a strong induction effect on constitutive androstane receptor 3 in constitutive androstane receptor-mediated CYP3A4/2B6 reporter gene systems, while arteannuin B showed a weak induction effect on constitutive androstane receptor 3 in the constitutive androstane receptor-mediated CYP2B6 reporter gene system. The mRNA and protein expressions of CYP3A4 and CYP2B6 were increased when the pregnane X receptor or constitutive androstane receptor was activated. Various components present in A. annua differentially affect the activities of pregnane X receptor isoforms and the constitutive androstane receptor, which indicates the possibility of a drug-drug interaction. This partly explains the decline in efficacy after repeated drinking of A. annua tea.
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Affiliation(s)
- Xueli Zhang
- School of Pharmaceutical Sciences, Shandong University, Jinan, R. P. China
| | - Ran Meng
- School of Pharmaceutical Sciences, Shandong University, Jinan, R. P. China
| | - Haina Wang
- School of Pharmaceutical Sciences, Shandong University, Jinan, R. P. China
| | - Jie Xing
- School of Pharmaceutical Sciences, Shandong University, Jinan, R. P. China
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Lin W, Bwayi M, Wu J, Li Y, Chai SC, Huber AD, Chen T. CITCO Directly Binds to and Activates Human Pregnane X Receptor. Mol Pharmacol 2020; 97:180-190. [PMID: 31882411 PMCID: PMC6978709 DOI: 10.1124/mol.119.118513] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 12/23/2019] [Indexed: 12/12/2022] Open
Abstract
The xenobiotic receptors pregnane X receptor (PXR) and constitutive androstane receptor (CAR) are activated by structurally diverse chemicals to regulate the expression of target genes, and they have overlapping regulation in terms of ligands and target genes. Receptor-selective agonists are, therefore, critical for studying the overlapping function of PXR and CAR. An early effort identified 6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde-O-(3,4-dichlorobenzyl)oxime (CITCO) as a selective human CAR (hCAR) agonist, and this has since been widely used to distinguish the function of hCAR from that of human PXR (hPXR). The selectivity was demonstrated in a green monkey kidney cell line, CV-1, in which CITCO displayed >100-fold selectivity for hCAR over hPXR. However, whether the selectivity observed in CV-1 cells also represented CITCO activity in liver cell models was not hitherto investigated. In this study, we showed that CITCO: 1) binds directly to hPXR; 2) activates hPXR in HepG2 cells, with activation being blocked by an hPXR-specific antagonist, SPA70; 3) does not activate mouse PXR; 4) depends on tryptophan-299 to activate hPXR; 5) recruits steroid receptor coactivator 1 to hPXR; 6) activates hPXR in HepaRG cell lines even when hCAR is knocked out; and 7) activates hPXR in primary human hepatocytes. Together, these data indicate that CITCO binds directly to the hPXR ligand-binding domain to activate hPXR. As CITCO has been widely used, its confirmation as a dual agonist for hCAR and hPXR is important for appropriately interpreting existing data and designing future experiments to understand the regulation of hPXR and hCAR. SIGNIFICANCE STATEMENT: The results of this study demonstrate that 6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde-O-(3,4-dichlorobenzyl)oxime (CITCO) is a dual agonist for human constitutive androstane receptor (hCAR) and human pregnane X receptor (hPXR). As CITCO has been widely used to activate hCAR, and hPXR and hCAR have distinct and overlapping biological functions, these results highlight the value of receptor-selective agonists and the importance of appropriately interpreting data in the context of receptor selectivity of such agonists.
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Affiliation(s)
- Wenwei Lin
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee
| | - Monicah Bwayi
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee
| | - Jing Wu
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee
| | - Yongtao Li
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee
| | - Sergio C Chai
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee
| | - Andrew D Huber
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee
| | - Taosheng Chen
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee
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Annalora AJ, Marcus CB, Iversen PL. Alternative Splicing in the Nuclear Receptor Superfamily Expands Gene Function to Refine Endo-Xenobiotic Metabolism. Drug Metab Dispos 2020; 48:272-287. [DOI: 10.1124/dmd.119.089102] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 12/31/2019] [Indexed: 12/20/2022] Open
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Li L, Welch MA, Li Z, Mackowiak B, Heyward S, Swaan PW, Wang H. Mechanistic Insights of Phenobarbital-Mediated Activation of Human but Not Mouse Pregnane X Receptor. Mol Pharmacol 2019; 96:345-354. [PMID: 31436536 PMCID: PMC6701513 DOI: 10.1124/mol.119.116616] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Accepted: 07/07/2019] [Indexed: 12/12/2022] Open
Abstract
Phenobarbital (PB), a broadly used antiseizure drug, was the first to be characterized as an inducer of cytochrome P450 by activation of the constitutive androstane receptor (CAR). Although PB is recognized as a conserved CAR activator among species via a well-documented indirect activation mechanism, conflicting results have been reported regarding PB regulation of the pregnane X receptor (PXR), a sister receptor of CAR, and the underlying mechanisms remain elusive. Here, we show that in a human CAR (hCAR)-knockout (KO) HepaRG cell line, PB significantly induces the expression of CYP2B6 and CYP3A4, two shared target genes of hCAR and human PXR (hPXR). In human primary hepatocytes and hCAR-KO HepaRG cells, PB-induced expression of CYP3A4 was markedly repressed by genetic knockdown or pharmacological inhibition of hPXR. Mechanistically, PB concentration dependently activates hPXR but not its mouse counterpart in cell-based luciferase assays. Mammalian two-hybrid assays demonstrated that PB selectively increases the functional interaction between the steroid receptor coactivator-1 and hPXR but not mouse PXR. Moreover, surface plasmon resonance binding affinity assay showed that PB directly binds to the ligand binding domain of hPXR (KD = 1.42 × 10-05). Structure-activity analysis further revealed that the amino acid tryptophan-299 within the ligand binding pocket of hPXR plays a key role in the agonistic binding of PB and mutation of tryptophan-299 disrupts PB activation of hPXR. Collectively, these data reveal that PB, a selective mouse CAR activator, activates both hCAR and hPXR, and provide novel mechanistic insights for PB-mediated activation of hPXR.
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Affiliation(s)
- Linhao Li
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (L.L., M.A.W., Z.L., B.M., P.W.S., H.W.); and BioIVT, Halethorpe, Maryland (S.H.)
| | - Matthew A Welch
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (L.L., M.A.W., Z.L., B.M., P.W.S., H.W.); and BioIVT, Halethorpe, Maryland (S.H.)
| | - Zhihui Li
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (L.L., M.A.W., Z.L., B.M., P.W.S., H.W.); and BioIVT, Halethorpe, Maryland (S.H.)
| | - Bryan Mackowiak
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (L.L., M.A.W., Z.L., B.M., P.W.S., H.W.); and BioIVT, Halethorpe, Maryland (S.H.)
| | - Scott Heyward
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (L.L., M.A.W., Z.L., B.M., P.W.S., H.W.); and BioIVT, Halethorpe, Maryland (S.H.)
| | - Peter W Swaan
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (L.L., M.A.W., Z.L., B.M., P.W.S., H.W.); and BioIVT, Halethorpe, Maryland (S.H.)
| | - Hongbing Wang
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (L.L., M.A.W., Z.L., B.M., P.W.S., H.W.); and BioIVT, Halethorpe, Maryland (S.H.)
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8
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Keminer O, Windshügel B, Essmann F, Lee SML, Schiergens TS, Schwab M, Burk O. Identification of novel agonists by high-throughput screening and molecular modelling of human constitutive androstane receptor isoform 3. Arch Toxicol 2019; 93:2247-2264. [PMID: 31312845 DOI: 10.1007/s00204-019-02495-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 06/17/2019] [Indexed: 11/28/2022]
Abstract
Prediction of drug interactions, based on the induction of drug disposition, calls for the identification of chemicals, which activate xenosensing nuclear receptors. Constitutive androstane receptor (CAR) is one of the major human xenosensors; however, the constitutive activity of its reference variant CAR1 in immortalized cell lines complicates the identification of agonists. The exclusively ligand-dependent isoform CAR3 represents an obvious alternative for screening of CAR agonists. As CAR3 is even more abundant in human liver than CAR1, identification of its agonists is also of pharmacological value in its own right. We here established a cellular high-throughput screening assay for CAR3 to identify ligands of this isoform and to analyse its suitability for identifying CAR ligands in general. Proof-of-concept screening of 2054 drug-like compounds at 10 µM resulted in the identification of novel CAR3 agonists. The CAR3 assay proved to detect the previously described CAR1 ligands in the screened libraries. However, we failed to detect CAR3-selective compounds, as the four novel agonists, which were selected for further investigations, all proved to activate CAR1 in different cellular and in vitro assays. In primary human hepatocytes, the compounds preferentially induced the expression of the prototypical CAR target gene CYP2B6. Failure to identify CAR3-selective compounds was investigated by molecular modelling, which showed that the isoform-specific insertion of five amino acids did not impact on the ligand binding pocket but only on heterodimerization with retinoid X receptor. In conclusion, we demonstrate here the usability of CAR3 for screening compound libraries for the presence of CAR agonists.
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Affiliation(s)
- Oliver Keminer
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Schnackenburgallee 114, 22525, Hamburg, Germany
| | - Björn Windshügel
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Schnackenburgallee 114, 22525, Hamburg, Germany.
| | - Frank Essmann
- Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Auerbachstrasse 112, 70376, Stuttgart, Germany.,University of Tübingen, Tübingen, Germany
| | - Serene M L Lee
- Biobank of the Department of General, Visceral, and Transplant Surgery, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Tobias S Schiergens
- Biobank of the Department of General, Visceral, and Transplant Surgery, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Matthias Schwab
- Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Auerbachstrasse 112, 70376, Stuttgart, Germany.,Departments of Clinical Pharmacology, Pharmacy and Biochemistry, University of Tübingen, Tübingen, Germany
| | - Oliver Burk
- Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Auerbachstrasse 112, 70376, Stuttgart, Germany. .,University of Tübingen, Tübingen, Germany.
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McMahon M, Ding S, Jimenez LA, Terranova R, Gerard MA, Vitobello A, Moggs J, Henderson CJ, Wolf CR. Constitutive androstane receptor 1 is constitutively bound to chromatin and 'primed' for transactivation in hepatocytes. Mol Pharmacol 2019; 95:97-105. [PMID: 30361333 PMCID: PMC6277922 DOI: 10.1124/mol.118.113555] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 10/19/2018] [Indexed: 12/15/2022] Open
Abstract
The constitutive androstane receptor (CAR) is a xenobiotic sensor expressed in hepatocytes that activates genes involved in drug metabolism, lipid homeostasis, and cell proliferation. Much progress has been made in understanding the mechanism of activation of human CAR by drugs and xenobiotics. However, many aspects of the activation pathway remain to be elucidated. In this report, we have used viral constructs to express human CAR, its splice variants, and mutant CAR forms in hepatocytes from Car-/- mice in vitro and in vivo. We demonstrate CAR expression rescued the ability of Car-/- hepatocytes to respond to a wide range of CAR activators including phenobarbital. Additionally, two major splice isoforms of human CAR, CAR2 and CAR3, were inactive with almost all the agents tested. In contrast to the current model of CAR activation, ectopic CAR1 is constitutively localized in the nucleus and is loaded onto Cyp2b10 gene in the absence of an inducing agent. In studies to elucidate the role of threonine T38 in CAR regulation, we found that the T38D mutant was inactive even in the presence of CAR activators. However, the T38A mutant was activated by CAR inducers, showing that T38 is not essential for CAR activation. Also, using the inhibitor erlotinib, we could not confirm a role for the epidermal growth factor receptor in CAR regulation. Our data suggest that CAR is constitutively bound to gene regulatory regions and is regulated by exogenous agents through a mechanism which involves protein phosphorylation in the nucleus.
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Affiliation(s)
- Michael McMahon
- School of Medicine, Jacqui Wood Cancer Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom (M.M., S.D., L.A.J., C.J.H., C.R.W.) and Preclinical Safety, Translational Medicine, Novartis Institutes for BioMedical Research, Basel, Switzerland (R.T., M.-A.G., A.V., J.M.)
| | - Shaohong Ding
- School of Medicine, Jacqui Wood Cancer Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom (M.M., S.D., L.A.J., C.J.H., C.R.W.) and Preclinical Safety, Translational Medicine, Novartis Institutes for BioMedical Research, Basel, Switzerland (R.T., M.-A.G., A.V., J.M.)
| | - Lourdes Acosta Jimenez
- School of Medicine, Jacqui Wood Cancer Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom (M.M., S.D., L.A.J., C.J.H., C.R.W.) and Preclinical Safety, Translational Medicine, Novartis Institutes for BioMedical Research, Basel, Switzerland (R.T., M.-A.G., A.V., J.M.)
| | - Remi Terranova
- School of Medicine, Jacqui Wood Cancer Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom (M.M., S.D., L.A.J., C.J.H., C.R.W.) and Preclinical Safety, Translational Medicine, Novartis Institutes for BioMedical Research, Basel, Switzerland (R.T., M.-A.G., A.V., J.M.)
| | - Marie-Apolline Gerard
- School of Medicine, Jacqui Wood Cancer Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom (M.M., S.D., L.A.J., C.J.H., C.R.W.) and Preclinical Safety, Translational Medicine, Novartis Institutes for BioMedical Research, Basel, Switzerland (R.T., M.-A.G., A.V., J.M.)
| | - Antonio Vitobello
- School of Medicine, Jacqui Wood Cancer Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom (M.M., S.D., L.A.J., C.J.H., C.R.W.) and Preclinical Safety, Translational Medicine, Novartis Institutes for BioMedical Research, Basel, Switzerland (R.T., M.-A.G., A.V., J.M.)
| | - Jonathan Moggs
- School of Medicine, Jacqui Wood Cancer Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom (M.M., S.D., L.A.J., C.J.H., C.R.W.) and Preclinical Safety, Translational Medicine, Novartis Institutes for BioMedical Research, Basel, Switzerland (R.T., M.-A.G., A.V., J.M.)
| | - Colin J Henderson
- School of Medicine, Jacqui Wood Cancer Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom (M.M., S.D., L.A.J., C.J.H., C.R.W.) and Preclinical Safety, Translational Medicine, Novartis Institutes for BioMedical Research, Basel, Switzerland (R.T., M.-A.G., A.V., J.M.)
| | - C Roland Wolf
- School of Medicine, Jacqui Wood Cancer Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom (M.M., S.D., L.A.J., C.J.H., C.R.W.) and Preclinical Safety, Translational Medicine, Novartis Institutes for BioMedical Research, Basel, Switzerland (R.T., M.-A.G., A.V., J.M.)
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Hyrsova L, Vanduchova A, Dusek J, Smutny T, Carazo A, Maresova V, Trejtnar F, Barta P, Anzenbacher P, Dvorak Z, Pavek P. Trans-resveratrol, but not other natural stilbenes occurring in food, carries the risk of drug-food interaction via inhibition of cytochrome P450 enzymes or interaction with xenosensor receptors. Toxicol Lett 2018; 300:81-91. [PMID: 30394306 DOI: 10.1016/j.toxlet.2018.10.028] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 09/03/2018] [Accepted: 10/08/2018] [Indexed: 01/27/2023]
Abstract
Resveratrol (RSV) is a stilbene phytochemical common in food and red wine. RSV inhibits cytochrome P450 CYP3A4 activity and interacts with the pregnane X receptor (PXR), the central regulator of drug/xenobiotic metabolizing enzyme expression. In this work, we comprehensively examined the effects of 13 stilbenes (trans- and cis-resveratrol, trans- and cis-piceatannol, oxyresveratrol, pterostilbene, pinostilbene, a,b-dihydroresveratrol, trans- and cis-trismethoxyresveratrol, trans-3,4,5,4'-tetramethoxystilbene, trans-2,4,3',5'-tetramethoxystilbene, trans-4-methoxystilbene), on CYP3A4 and CYP2B6 mRNA induction, and on CYP3A4/5, CYP2C8/9/19, CYP2D6, CYP2A6, CYP2E1, CYP1A2 and CYP2B6 cytochrome P450 enzyme activities. Expression experiments in five different primary human hepatocyte preparations, reporter gene assays, and ligand binding assays with pregnane X (PXR) and constitutive androstane (CAR) receptors were performed. Inhibition of cytochrome P450 enzymes was examined in human microsomes. We found that only polymethoxylated stilbenes are prone to significantly induce CYP2B6 or CYP3A4 in primary human hepatocytes via pregnane X receptor (PXR) interaction. Natural resveratrol derivatives such as trans- and cis-RSV, oxyresveratrol, pinostilbene and pterostilbene significantly inhibit CYP3A4/5 enzymatic activities; however, only trans-RSV significantly inhibits CYP3A4/5 activity (both testosterone 6β-hydroxylation and midazolam 1´-hydroxylation) in micromolar concentrations by a non-competitive mechanism, suggesting a potential risk of food-drug interactions with CYP3A4/5 substrates.
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Affiliation(s)
- Lucie Hyrsova
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovskeho 1203, Hradec Kralove, CZ500 05, Czech Republic
| | - Alena Vanduchova
- Department of Pharmacology, Faculty of Medicine and Dentistry, Palacky University in Olomouc, Hnevotinska 3, CZ775 15, Olomouc, Czech Republic; Institute of Molecular and Translational Medicine (IMTM), Faculty of Medicine and Dentistry, Palacky University in Olomouc, Hnevotinska 3, CZ775 15, Olomouc, Czech Republic
| | - Jan Dusek
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovskeho 1203, Hradec Kralove, CZ500 05, Czech Republic
| | - Tomas Smutny
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovskeho 1203, Hradec Kralove, CZ500 05, Czech Republic
| | - Alejandro Carazo
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovskeho 1203, Hradec Kralove, CZ500 05, Czech Republic; Institute of Molecular and Translational Medicine (IMTM), Faculty of Medicine and Dentistry, Palacky University in Olomouc, Hnevotinska 3, CZ775 15, Olomouc, Czech Republic
| | - Veronika Maresova
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovskeho 1203, Hradec Kralove, CZ500 05, Czech Republic
| | - Frantisek Trejtnar
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovskeho 1203, Hradec Kralove, CZ500 05, Czech Republic
| | - Pavel Barta
- Department of Biophysics and Physical Chemistry, Faculty of Pharmacy, Charles University, Heyrovskeho 1203, Hradec Kralove, CZ500 05, Czech Republic
| | - Pavel Anzenbacher
- Department of Pharmacology, Faculty of Medicine and Dentistry, Palacky University in Olomouc, Hnevotinska 3, CZ775 15, Olomouc, Czech Republic
| | - Zdenek Dvorak
- Department of Cellular Biology and Genetics, Faculty of Sciences, Palacky University in Olomouc, Slechtitelu 27, 783 71, Olomouc, Czech Republic
| | - Petr Pavek
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Charles University, Heyrovskeho 1203, Hradec Kralove, CZ500 05, Czech Republic.
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11
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Pinne M, Ponce E, Raucy JL. Transactivation Assays to Assess Canine and Rodent Pregnane X Receptor (PXR) and Constitutive Androstane Receptor (CAR) Activation. PLoS One 2016; 11:e0164642. [PMID: 27732639 PMCID: PMC5061317 DOI: 10.1371/journal.pone.0164642] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 09/28/2016] [Indexed: 11/21/2022] Open
Abstract
The pregnane X receptor (PXR/SXR, NR1I2) and constitutive androstane receptor (CAR, NR1I3) are nuclear receptors (NRs) involved in the regulation of many genes including cytochrome P450 enzymes (CYPs) and transporters important in metabolism and uptake of both endogenous substrates and xenobiotics. Activation of these receptors can lead to adverse drug effects as well as drug-drug interactions. Depending on which nuclear receptor is activated will determine which adverse effect could occur, making identification important. Screening for NR activation by New Molecular Entities (NMEs) using cell-based transactivation assays is the singular high throughput method currently available for identifying the activation of a particular NR. Moreover, screening for species-specific NR activation can minimize the use of animals in drug development and toxicology studies. With this in mind, we have developed in vitro transactivation assays to identify compounds that activate canine and rat PXR and CAR3. We found differences in specificity for canine and rat PXR, with the best activator for canine PXR being 10 μM SR12813 (60.1 ± 3.1-fold) and for rat PXR, 10 μM dexamethasone (60.9 ± 8.4 fold). Of the 19 test agents examined, 10 and 9 significantly activated rat and canine PXR at varying degrees, respectively. In contrast, 5 compounds exhibited statistically significant activation of rat CAR3 and 4 activated the canine receptor. For canine CAR3, 50 μM artemisinin proved to be the best activator (7.3 ± 1.8 and 10.5 ± 2.2 fold) while clotrimazole (10 μM) was the primary activator of the rat variant (13.7 ± 0.8 and 26.9 ± 1.3 fold). Results from these studies demonstrated that cell-based transactivation assays can detect species-specific activators and revealed that PXR was activated by at least twice as many compounds as was CAR3, suggesting that there are many more agonists for PXR than CAR.
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Affiliation(s)
- Marija Pinne
- Puracyp, Inc., Carlsbad, California, United States of America
- * E-mail:
| | - Elsa Ponce
- Puracyp, Inc., Carlsbad, California, United States of America
| | - Judy L. Raucy
- Puracyp, Inc., Carlsbad, California, United States of America
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12
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Laurenzana EM, Coslo DM, Vigilar MV, Roman AM, Omiecinski CJ. Activation of the Constitutive Androstane Receptor by Monophthalates. Chem Res Toxicol 2016; 29:1651-1661. [PMID: 27551952 DOI: 10.1021/acs.chemrestox.6b00186] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Humans in industrialized areas are continuously exposed to phthalate plasticizers, prompting concerns of their potential toxicities. Previous studies from our laboratory and others have shown that various phthalates activate several mammalian nuclear receptors, in particular the constitutive androstane receptor (CAR), the pregnane X receptor (PXR), and the peroxisomal proliferator-activated receptors (PPARs), although often at concentration levels of questionable relevance to human exposure. We discovered that di(2-ethylhexyl) phthalate (DEHP) and di-isononyl phthalate (DiNP), two of the highest volume production agents, were potent activators of human CAR2 (hCAR2), a unique human CAR splice variant and, to a lesser degree, human PXR (hPXR). These diphthalates undergo rapid metabolism in mammalian systems, initially to their major monophthalate derivatives MEHP and MiNP. Although MEHP and MiNP are reported activators of the rodent PPARs, with lower affinities for the corresponding human PPARs, it remains unclear whether these monophthalate metabolites activate hCAR2 or hPXR. In this investigation, we assessed the relative activation potential of selected monophthalates and other low molecular weight phthalates against hCAR, the most prominent hCAR splice variants, as well as hPXR and human PPAR. Using transactivation and mammalian two-hybrid protein interaction assays, we demonstrate that these substances indeed activate hCARs and hPXR but to varying degrees. MEHP and MiNP exhibit potent activation of hCAR2 and hPXR with higher affinities for these receptors than for the hPPARs. The rank order potency for MEHP and MiNP was hCAR2 > hPXR > hPPARs. Results from primary hepatocyte experiments also reflect the MEHP and MiNP upregulation of the respective human target genes. We conclude that both di- and monophthalates are potently selective hCAR2 activators and effective hPXR activators. These results implicate these targets as important mediators of selective phthalate effects in humans. The striking differential affinities for these compounds between human and rodent nuclear receptors further implies that biological results obtained from rodent models may be of only limited relevance for interpolating phthalate-mediated effects in humans.
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Affiliation(s)
- Elizabeth M Laurenzana
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University , 101 Life Sciences Building, University Park, Pennsylvania 16802, United States
| | - Denise M Coslo
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University , 101 Life Sciences Building, University Park, Pennsylvania 16802, United States
| | - M Veronica Vigilar
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University , 101 Life Sciences Building, University Park, Pennsylvania 16802, United States
| | - Anthony M Roman
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University , 101 Life Sciences Building, University Park, Pennsylvania 16802, United States
| | - Curtis J Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University , 101 Life Sciences Building, University Park, Pennsylvania 16802, United States
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13
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Smutny T, Nova A, Drechslerová M, Carazo A, Hyrsova L, Hrušková ZR, Kuneš J, Pour M, Špulák M, Pavek P. 2-(3-Methoxyphenyl)quinazoline Derivatives: A New Class of Direct Constitutive Androstane Receptor (CAR) Agonists. J Med Chem 2016; 59:4601-10. [PMID: 27145071 DOI: 10.1021/acs.jmedchem.5b01891] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Constitutive androstane receptor (CAR) is a key regulator of xenobiotic and endobiotic metabolism. Together with pregnane X (PXR) and aryl hydrocarbon (AHR) receptors, it is referred to as "xenobiotic receptor". The unique properties of human CAR, such as its high constitutive activity, both direct (ligand-binding domain-dependent) and indirect activation have hindered the discovery of direct selective human CAR ligands. Herein, we report a novel class of direct human CAR agonists in a group of 2-(3-methoxyphenyl)quinazoline derivatives. The compounds are even more potent activators of human CAR than is prototype 6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde O-(3,4-dichlorobenzyl)oxime (CITCO). The three most potent ligands are at the same time extremely potent activators of the other xenobiotic or hormonal receptors, namely PXR, AHR, and vitamin D receptor, which regulate major xenobiotic-metabolizing enzymes and efflux transporters. Thus, the novel CAR ligands can be also considered as constituting the first class of potent pan-xenobiotic receptor ligands that can serve as potential antidotes boosting overall metabolic elimination of xenobiotic or toxic compounds.
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Affiliation(s)
| | - Alice Nova
- Institute of Molecular and Translation Medicine, Faculty of Medicine, Palacky University in Olomouc , Hnevotinska 5, CZ-779 00 Olomouc, Czech Republic
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14
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Inouye Y. [Structure and Function of the Nuclear Receptor Constitutive Androstane Receptor]. YAKUGAKU ZASSHI 2016; 136:297-308. [PMID: 26831808 DOI: 10.1248/yakushi.15-00215] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Animal defense mechanisms against both endogenous and exogenous toxic compounds function mainly through receptor-type transcription factors, including the constitutive androstane receptor (CAR). Following xenobiotic stimulation, CAR translocates into the nucleus and transactivates its target genes including oxygenic and conjugative enzymes and transporters in hepatocytes. We identified subcellular localization signals in the rat CAR: two nuclear localization signals (NLS1 and 2); two nuclear export signals (NES1 and 2); and a cytoplasmic retention region. The nuclear import of CAR is regulated by the importin-Ran system and microtubule network. Five splice variants (SV1-5) were identified in rat liver in addition to wild-type CAR. When expressed in immortalized cells, their artificial transcripts were inactive as transcription factors. A CAR mutant with three consecutive alanine residues inserted into the ligand-binding domain of CAR showed ligand-dependent activation of target genes in immortalized cells, which is in marked contrast to the constitutive transactivating nature of wild-type CAR. Using this assay system, androstenol and clotrimazole, both of which are inverse agonists of CAR, were classified as an antagonist and weak agonist, respectively. A member of the DEAD box DNA/RNA helicase family (DP97) and protein arginine methyltransferase 5 (PRMT5) were found to be gene (or promotor)-specific coactivators of CAR. The expression of the CAR gene might be under the control of clock genes mediated by the nuclear receptor Rev-erb-α.
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15
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Rondini EA, Duniec-Dmuchowski Z, Kocarek TA. Nonsterol Isoprenoids Activate Human Constitutive Androstane Receptor in an Isoform-Selective Manner in Primary Cultured Mouse Hepatocytes. ACTA ACUST UNITED AC 2016; 44:595-604. [PMID: 26798158 DOI: 10.1124/dmd.115.068551] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Accepted: 01/20/2016] [Indexed: 12/26/2022]
Abstract
Our laboratory previously reported that accumulation of nonsterol isoprenoids following treatment with the squalene synthase inhibitor, squalestatin 1 (SQ1) markedly induced cytochrome P450 (CYP)2B1 mRNA and reporter activity in primary cultured rat hepatocytes, which was dependent on activation of the constitutive androstane receptor (CAR). The objective of the current study was to evaluate whether isoprenoids likewise activate murine CAR (mCAR) or one or more isoforms of human CAR (hCAR) produced by alternative splicing (SPTV, hCAR2; APYLT, hCAR3). We found that SQ1 significantly induced Cyp2b10 mRNA (∼3.5-fold) in primary hepatocytes isolated from both CAR-wild-type and humanized CAR transgenic mice, whereas the 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor pravastatin had no effect. In the absence of CAR, basal Cyp2b10 mRNA levels were reduced by 28-fold and the effect of SQ1 on Cyp2b10 induction was attenuated. Cotransfection with an expression plasmid for hCAR1, but not hCAR2 or hCAR3, mediated SQ1-induced CYP2B1 and CYP2B6 reporter activation in hepatocytes isolated from CAR-knockout mice. This effect was also observed following treatment with the isoprenoid trans,trans-farnesol. The direct agonist CITCO increased interaction of hCAR1, hCAR2, and hCAR3 with steroid receptor coactivator-1. However, no significant effect on coactivator recruitment was observed with SQ1, suggesting an indirect activation mechanism. Further results from an in vitro ligand binding assay demonstrated that neither farnesol nor other isoprenoids are direct ligands for hCAR1. Collectively, our findings demonstrate that SQ1 activates CYP2B transcriptional responses through farnesol metabolism in an hCAR1-dependent manner. Further, this effect probably occurs through an indirect mechanism.
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Affiliation(s)
- Elizabeth A Rondini
- Institute of Environmental Health Sciences, Wayne State University, Detroit, Michigan
| | | | - Thomas A Kocarek
- Institute of Environmental Health Sciences, Wayne State University, Detroit, Michigan
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16
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Cherian MT, Chai SC, Chen T. Small-molecule modulators of the constitutive androstane receptor. Expert Opin Drug Metab Toxicol 2015; 11:1099-114. [PMID: 25979168 DOI: 10.1517/17425255.2015.1043887] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
INTRODUCTION The constitutive androstane receptor (CAR) induces drug-metabolizing enzymes for xenobiotic metabolism. AREAS COVERED This review covers recent advances in elucidating the biological functions of CAR and its modulation by a growing number of agonists and inhibitors. EXPERT OPINION Extrapolation of animal CAR function to that of humans should be carefully scrutinized, particularly when rodents are used in evaluating the metabolic profile and carcinogenic properties of clinical drugs and environmental chemicals. Continuous efforts are needed to discover novel CAR inhibitors, with extensive understanding of their inhibitory mechanism, species selectivity, and discriminating power against other xenobiotic sensors.
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Affiliation(s)
- Milu T Cherian
- Postdoctoral fellow, St. Jude Children's Research Hospital, Department of Chemical Biology and Therapeutics , 262 Danny Thomas Place, Memphis, TN 38105 , USA
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17
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Cherian MT, Lin W, Wu J, Chen T. CINPA1 is an inhibitor of constitutive androstane receptor that does not activate pregnane X receptor. Mol Pharmacol 2015; 87:878-89. [PMID: 25762023 PMCID: PMC4407736 DOI: 10.1124/mol.115.097782] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 03/11/2015] [Indexed: 11/22/2022] Open
Abstract
Constitutive androstane receptor (CAR) and pregnane X receptor (PXR) are xenobiotic sensors that enhance the detoxification and elimination of xenobiotics and endobiotics by modulating the expression of genes encoding drug-metabolizing enzymes and transporters. Elevated levels of drug-metabolizing enzymes and efflux transporters, resulting from CAR activation in various cancers, promote the elimination of chemotherapeutic agents, leading to reduced therapeutic effectiveness and acquired drug resistance. CAR inhibitors, in combination with existing chemotherapeutics, could therefore be used to attenuate multidrug resistance in cancers. Interestingly, all previously reported CAR inverse-agonists are also activators of PXR, rendering them mechanistically counterproductive in tissues where both these xenobiotic receptors are present and active. We used a directed high-throughput screening approach, followed by subsequent mechanistic studies, to identify novel, potent, and specific small-molecule CAR inhibitors that do not activate PXR. We describe here one such inhibitor, CINPA1 (CAR inhibitor not PXR activator 1), capable of reducing CAR-mediated transcription with an IC50 of ∼70 nM. CINPA1 1) is a specific xenobiotic receptor inhibitor and has no cytotoxic effects up to 30 µM; 2) inhibits CAR-mediated gene expression in primary human hepatocytes, where CAR is endogenously expressed; 3) does not alter the protein levels or subcellular localization of CAR; 4) increases corepressor and reduces coactivator interaction with the CAR ligand-binding domain in mammalian two-hybrid assays; and 5) disrupts CAR binding to the promoter regions of target genes in chromatin immunoprecipitation assays. CINPA1 could be used as a novel molecular tool for understanding CAR function.
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Affiliation(s)
- Milu T Cherian
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee
| | - Wenwei Lin
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee
| | - Jing Wu
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee
| | - Taosheng Chen
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee
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18
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Sharma D, Lau AJ, Sherman MA, Chang TKH. Differential activation of human constitutive androstane receptor and its SV23 and SV24 splice variants by rilpivirine and etravirine. Br J Pharmacol 2015; 172:1263-76. [PMID: 25363652 DOI: 10.1111/bph.12997] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 10/22/2014] [Accepted: 10/27/2014] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND AND PURPOSE Rilpivirine and etravirine are second-generation non-nucleoside reverse transcriptase inhibitors (NNRTIs) indicated for the treatment of HIV/AIDS. The constitutive androstane receptor (CAR) regulates the expression of genes involved in various biological processes, including the transport and biotransformation of drugs. We investigated the effect of rilpivirine and etravirine on the activity of the wild-type human CAR (hCAR-WT) and its hCAR-SV23 and hCAR-SV24 splice variants, and compared it with first-generation NNRTIs (efavirenz, nevirapine, and delavirdine). EXPERIMENTAL APPROACH Receptor activation, ligand-binding domain (LBD) transactivation, and co-activator recruitment were investigated in transiently transfected, NNRTI-treated HepG2 cells. Nuclear translocation of green fluorescent protein-tagged hCAR-WT and CYP2B6 gene expression were assessed in NNRTI-treated human hepatocytes. KEY RESULTS Rilpivirine and etravirine activated hCAR-WT, but not hCAR-SV23 or hCAR-SV24, and without transactivating the LBD or recruiting steroid receptor coactivators SRC-1, SRC-2, or SRC-3. Among the first-generation NNRTIs investigated, only efavirenz activated hCAR-WT, hCAR-SV23, and hCAR-SV24, but none of them transactivated the LBD of these receptors or substantively recruited SRC-1, SRC-2, or SRC-3. Rilpivirine, etravirine, and efavirenz triggered nuclear translocation of hCAR-WT and increased hCAR target gene (CYP2B6) expression. CONCLUSION AND IMPLICATIONS NNRTIs activate hCAR-WT, hCAR-SV23, and hCAR-SV24 in a drug-specific and isoform-selective manner. The activation occurs by a mechanism that does not appear to involve binding to the LBD or recruitment of SRC-1, SRC-2, or SRC-3.
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Affiliation(s)
- Devinder Sharma
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada
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19
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Lau AJ, Chang TKH. Indirect activation of the SV23 and SV24 splice variants of human constitutive androstane receptor: analysis with 3-hydroxyflavone and its analogues. Br J Pharmacol 2014; 170:403-14. [PMID: 23809009 DOI: 10.1111/bph.12284] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Revised: 04/17/2013] [Accepted: 06/20/2013] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND AND PURPOSE Naturally occurring splice variants of human CAR (hCAR), including hCAR-SV23 (insertion of amino acids SPTV) and hCAR-SV24 (APYLT), have been shown to be expressed in liver. However, little is known regarding how hCAR-SV23 and hCAR-SV24 are activated. Therefore, we investigated the mode of activation of these hCAR splice variants. EXPERIMENTAL APPROACH Cell-based reporter gene assays, including ligand-binding domain transactivation assays and coactivator recruitment assays, were conducted on cultured HepG2 cells transfected with various constructs and treated with 3-hydroxyflavone or a hydroxylated (galangin, datiscetin, kaempferol, morin, quercetin or myricetin) or methylated (isorhamnetin, tamarixetin, or syringetin) analogue. KEY RESULTS Among the flavonols investigated, only 3-hydroxyflavone increased hCAR-SV23 and hCAR-SV24 activities. 3-Hydroxyflavone did not transactivate the ligand-binding domain of these isoforms or recruit steroid receptor coactivators (SRC-1, SRC-2, or SRC-3). By comparison, 3-hydroxyflavone, galangin, datiscetin, kaempferol, quercetin, isorhamnetin and tamarixetin activated hCAR-WT, whereas none of the flavonols activated hCAR-SV25 (both SPTV and APYLT insertions). The flavonols 3-Hydroxyflavone, galangin, quercetin and tamarixetin transactivated the ligand-binding domain of hCAR-WT, but only 3-hydroxyflavone recruited SRC-1, SRC-2 and SRC-3 to the receptor. CONCLUSION AND IMPLICATIONS hCAR-SV23 and hCAR-SV24 can be activated by a mechanism that does not involve the ligand-binding domain of the receptor or recruitment of SRC-1, SRC-2, or SRC-3. 3-Hydroxyflavone and its structural analogues activated hCAR in an isoform-selective and chemical-specific manner. Overall, our study provides insight into a novel mode of ligand activation of hCAR-SV23 and hCAR-SV24.
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Affiliation(s)
- Aik Jiang Lau
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC, Canada
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20
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Lynch C, Pan Y, Li L, Heyward S, Moeller T, Swaan PW, Wang H. Activation of the constitutive androstane receptor inhibits gluconeogenesis without affecting lipogenesis or fatty acid synthesis in human hepatocytes. Toxicol Appl Pharmacol 2014; 279:33-42. [PMID: 24878338 DOI: 10.1016/j.taap.2014.05.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 05/07/2014] [Accepted: 05/16/2014] [Indexed: 12/23/2022]
Abstract
OBJECTIVE Accumulating evidence suggests that activation of mouse constitutive androstane receptor (mCAR) alleviates type 2 diabetes and obesity by inhibiting hepatic gluconeogenesis, lipogenesis, and fatty acid synthesis. However, the role of human (h) CAR in energy metabolism is largely unknown. The present study aims to investigate the effects of selective hCAR activators on hepatic energy metabolism in human primary hepatocytes (HPH). METHODS Ligand-based structure-activity models were used for virtual screening of the Specs database (www.specs.net) followed by biological validation in cell-based luciferase assays. The effects of two novel hCAR activators (UM104 and UM145) on hepatic energy metabolism were evaluated in HPH. RESULTS Real-time PCR and Western blotting analyses reveal that activation of hCAR by UM104 and UM145 significantly repressed the expression of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase, two pivotal gluconeogenic enzymes, while exerting negligible effects on the expression of genes associated with lipogenesis and fatty acid synthesis. Functional experiments show that UM104 and UM145 markedly inhibit hepatic synthesis of glucose but not triglycerides in HPH. In contrast, activation of mCAR by 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene, a selective mCAR activator, repressed the expression of genes associated with gluconeogenesis, lipogenesis, and fatty acid synthesis in mouse primary hepatocytes, which were consistent with previous observations in mouse model in vivo. CONCLUSION Our findings uncover an important species difference between hCAR and mCAR in hepatic energy metabolism, where hCAR selectively inhibits gluconeogenesis without suppressing fatty acid synthesis. IMPLICATIONS Such species selectivity should be considered when exploring CAR as a potential therapeutic target for metabolic disorders.
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Affiliation(s)
- Caitlin Lynch
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, USA
| | - Yongmei Pan
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, USA
| | - Linhao Li
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, USA
| | - Scott Heyward
- Bioreclamation In Vitro Technologies, Baltimore, MD 21227, USA
| | - Timothy Moeller
- Bioreclamation In Vitro Technologies, Baltimore, MD 21227, USA
| | - Peter W Swaan
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, USA
| | - Hongbing Wang
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, USA.
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21
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Pinne M, Raucy JL. Advantages of cell-based high-volume screening assays to assess nuclear receptor activation during drug discovery. Expert Opin Drug Discov 2014; 9:669-86. [DOI: 10.1517/17460441.2014.913019] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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22
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Wahlang B, Falkner KC, Clair HB, Al-Eryani L, Prough RA, States JC, Coslo DM, Omiecinski CJ, Cave MC. Human receptor activation by aroclor 1260, a polychlorinated biphenyl mixture. Toxicol Sci 2014; 140:283-97. [PMID: 24812009 DOI: 10.1093/toxsci/kfu083] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Polychlorinated biphenyls (PCBs) are persistent environmental toxicants, present in 100% of U.S. adults and dose-dependently associated with obesity and non-alcoholic fatty liver disease (NAFLD). PCBs are predicted to interact with receptors previously implicated in xenobiotic/energy metabolism and NAFLD. These receptors include the aryl hydrocarbon receptor (AhR), pregnane xenobiotic receptor (PXR), constitutive androstane receptor (CAR), peroxisome proliferator-activated receptors (PPARs), liver-X-receptor (LXRα), and farnesoid-X-receptor (FXR). This study evaluates Aroclor 1260, a PCB mixture with congener composition mimicking that of human adipose tissue, and selected congeners, as potential ligands for these receptors utilizing human hepatoma-derived (HepG2) and primate-derived (COS-1) cell lines, and primary human hepatocytes. Aroclor 1260 (20 μg/ml) activated AhR, and PCB 126, a minor component, was a potent inducer. Aroclor 1260 activated PXR in a simple concentration-dependent manner at concentrations ≥10 μg/ml. Among the congeners tested, PCBs 138, 149, 151, 174, 183, 187, and 196 activated PXR. Aroclor 1260 activated CAR2 and CAR3 variants at lower concentrations and antagonize CAR2 activation by the CAR agonist, CITCO, at higher concentrations (≥20 μg/ml). Additionally, Aroclor 1260 induced CYP2B6 in primary hepatocytes. At subtoxic doses, Aroclor 1260 did not activate LXR or FXR and had no effect on LXR- or FXR-dependent induction by the agonists T0901317 or GW4064, respectively. Aroclor 1260 (20 μg/ml) suppressed PPARα activation by the agonist nafenopin, although none of the congeners tested demonstrated significant inhibition. The results suggest that Aroclor 1260 is a human AhR, PXR and CAR3 agonist, a mixed agonist/antagonist for CAR2, and an antagonist for human PPARα.
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Affiliation(s)
| | - K Cameron Falkner
- Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition
| | - Heather B Clair
- Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, Kentucky 40202
| | | | - Russell A Prough
- Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, Kentucky 40202
| | | | - Denise M Coslo
- Center for Molecular Toxicology, Penn State University, University Park, Pennsylvania 16802
| | - Curtis J Omiecinski
- Center for Molecular Toxicology, Penn State University, University Park, Pennsylvania 16802
| | - Matthew C Cave
- Department of Pharmacology and Toxicology Department of Medicine, Division of Gastroenterology, Hepatology and Nutrition The Robley Rex Veterans Affairs Medical Center, Louisville, Kentucky 40206
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Mathäs M, Burk O, Gödtel-Armbrust U, Herlyn H, Wojnowski L, Windshügel B. Structural and functional similarity of amphibian constitutive androstane receptor with mammalian pregnane X receptor. PLoS One 2014; 9:e96263. [PMID: 24797902 PMCID: PMC4010427 DOI: 10.1371/journal.pone.0096263] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 04/04/2014] [Indexed: 11/19/2022] Open
Abstract
The nuclear receptors and xenosensors constitutive androstane receptor (CAR, NR1I3) and pregnane X receptor (PXR, NR1I2) induce the expression of xenobiotic metabolizing enzymes and transporters, which also affects various endobiotics. While human and mouse CAR feature a high basal activity and low induction upon ligand exposure, we recently identified two constitutive androstane receptors in Xenopus laevis (xlCARα and β) that possess PXR-like characteristics such as low basal activity and activation in response to structurally diverse compounds. Using a set of complementary computational and biochemical approaches we provide evidence for xlCARα being the structural and functional counterpart of mammalian PXR. A three-dimensional model of the xlCARα ligand-binding domain (LBD) reveals a human PXR-like L-shaped ligand binding pocket with a larger volume than the binding pockets in human and murine CAR. The shape and amino acid composition of the ligand-binding pocket of xlCAR suggests PXR-like binding of chemically diverse ligands which was confirmed by biochemical methods. Similarly to PXR, xlCARα possesses a flexible helix 11’. Modest increase in the recruitment of coactivator PGC-1α may contribute to the enhanced basal activity of three gain-of-function xlCARα mutants humanizing key LBD amino acid residues. xlCARα and PXR appear to constitute an example of convergent evolution.
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Affiliation(s)
- Marianne Mathäs
- Department of Pharmacology, University Medical Center, Mainz, Germany
| | - Christian Nußhag
- Department of Pharmacology, University Medical Center, Mainz, Germany
| | - Oliver Burk
- Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart, Germany
| | | | - Holger Herlyn
- Institute of Anthropology, Johannes Gutenberg-University, Mainz, Germany
| | - Leszek Wojnowski
- Department of Pharmacology, University Medical Center, Mainz, Germany
| | - Björn Windshügel
- Centre for Bioinformatics, University of Hamburg, Hamburg, Germany
- European ScreeningPort GmbH, Hamburg, Germany
- * E-mail:
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Proteasomal interaction as a critical activity modulator of the human constitutive androstane receptor. Biochem J 2014; 458:95-107. [PMID: 24224465 DOI: 10.1042/bj20130685] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The CAR (constitutive androstane receptor; NR1I3) is a critical xenobiotic sensor that regulates xenobiotic metabolism, drug clearance, energy and lipid homoeostasis, cell proliferation and development. Although constitutively active, in hepatocytes CAR is normally held quiescent through a tethering mechanism in the cytosol, anchored to a protein complex that includes several components, including heat-shock protein 90. Release and subsequent nuclear translocation of CAR is triggered through either direct binding to ligand activators such as CITCO {6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde O-(3,4-dichlorobenzyl)oxime} or through indirect chemical activation, such as with PB (phenobarbital). In the present study, we demonstrate that proteasomal inhibition markedly disrupts CAR function, repressing CAR nuclear trafficking, disrupting CAR's interaction with nuclear co-activators and inhibiting induction of CAR target gene responses in human primary hepatocytes following treatment with either PB or CITCO. Paradoxically, these effects occur following accumulation of ubiquitinated hCAR (human CAR). Furthermore, a non-proteolytic function was indicated by its interaction with a SUG1 (suppressor for Gal1), a subunit of the 26S proteasome. Taken together, these data demonstrate that the proteasome complex functions at multiple levels to regulate the functional biology of hCAR activity.
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Lau AJ, Chang TKH. Fetal bovine serum and human constitutive androstane receptor: evidence for activation of the SV23 splice variant by artemisinin, artemether, and arteether in a serum-free cell culture system. Toxicol Appl Pharmacol 2014; 277:221-30. [PMID: 24721719 DOI: 10.1016/j.taap.2014.03.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 03/08/2014] [Accepted: 03/26/2014] [Indexed: 10/25/2022]
Abstract
The naturally occurring SV23 splice variant of human constitutive androstane receptor (hCAR-SV23) is activated by di-(2-ethylhexyl)phthalate (DEHP), which is detected as a contaminant in fetal bovine serum (FBS). In our initial experiment, we compared the effect of dialyzed FBS, charcoal-stripped, dextran-treated FBS (CS-FBS), and regular FBS on the basal activity and ligand-activation of hCAR-SV23 in a cell-based reporter gene assay. In transfected HepG2 cells cultured in medium supplemented with 10% FBS, basal hCAR-SV23 activity varied with the type of FBS (regular>dialyzed>CS). DEHP increased hCAR-SV23 activity when 10% CS-FBS, but not regular FBS or dialyzed FBS, was used. With increasing concentrations (1-10%) of regular FBS or CS-FBS, hCAR-SV23 basal activity increased, whereas in DEHP-treated cells, hCAR-SV23 activity remained similar (regular FBS) or slightly increased (CS-FBS). Subsequent experiments identified a serum-free culture condition to detect DEHP activation of hCAR-SV23. Under this condition, artemisinin, artemether, and arteether increased hCAR-SV23 activity, whereas they decreased it in cells cultured in medium supplemented with 10% regular FBS. By comparison, FBS increased the basal activity of the wild-type isoform of hCAR (hCAR-WT), whereas it did not affect the basal activity of the SV24 splice variant (hCAR-SV24) or ligand activation of hCAR-SV24 and hCAR-WT by 6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde O-(3,4-dichlorobenzyl)oxime (CITCO). The use of serum-free culture condition was suitable for detecting CITCO activation of hCAR-WT and hCAR-SV24. In conclusion, FBS leads to erroneous classification of pharmacological ligands of hCAR-SV23 in cell-based assays, but investigations on functional ligands of hCAR isoforms can be conducted in serum-free culture condition.
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Affiliation(s)
- Aik Jiang Lau
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Thomas K H Chang
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, Canada.
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Su S, Yang X, Omiecinski CJ. Intronic DNA elements regulate Nrf2 chemical responsiveness of the human microsomal epoxide hydrolase gene (EPHX1) through a far upstream alternative promoter. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1839:493-505. [PMID: 24704207 DOI: 10.1016/j.bbagrm.2014.03.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 03/16/2014] [Accepted: 03/26/2014] [Indexed: 10/25/2022]
Abstract
In humans, microsomal epoxide hydrolase (mEH) contributes important biological functions that underlie both detoxification and bioactivation fates arising from exposures to foreign chemicals. Previously, we discovered that human mEH gene transcription is initiated from alternative promoters. The respective transcripts are programmed with tissue specificity and the upstream E1b promoter contributes predominantly to mEH expression. The results presented demonstrate that exposures to the Nrf2 activators, sulforaphane (SFN) and tert-butylhydroquinone (tBHQ), markedly activate E1b transcription in human lung and liver cells. Genomic analyses identified two major DNase I hypersensitive regions (HS-1 and HS-2) within the ~15 kb intervening sequence separating E1b from the downstream E1 promoter. In BEAS-2B cells, the Nrf2 effectors, SFN and tBHQ, selectively activated the more distal HS-2 through an antioxidant response element (ARE). An activator protein 1/12-O-tetradecanoylphorbol-13-acetate interaction was further identified within the HS-2 enhancer that functioned to additionally contribute to ARE-mediated induction responsiveness of the E1b promoter. The results demonstrate that ARE modulation, integrated with additional transcriptional complexes, regulates the tissue-specific expression of mEH and that these processes likely coordinate both the protective and bioactivation functions contributed by mEH activities in human tissues.
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Affiliation(s)
- Shengzhong Su
- Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, 101 Life Sciences Bldg, University Park, PA 16802, USA
| | - Xi Yang
- Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, 101 Life Sciences Bldg, University Park, PA 16802, USA
| | - Curtis J Omiecinski
- Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, 101 Life Sciences Bldg, University Park, PA 16802, USA.
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Luisier R, Lempiäinen H, Scherbichler N, Braeuning A, Geissler M, Dubost V, Müller A, Scheer N, Chibout SD, Hara H, Picard F, Theil D, Couttet P, Vitobello A, Grenet O, Grasl-Kraupp B, Ellinger-Ziegelbauer H, Thomson JP, Meehan RR, Elcombe CR, Henderson CJ, Wolf CR, Schwarz M, Moulin P, Terranova R, Moggs JG. Phenobarbital induces cell cycle transcriptional responses in mouse liver humanized for constitutive androstane and pregnane x receptors. Toxicol Sci 2014; 139:501-11. [PMID: 24690595 DOI: 10.1093/toxsci/kfu038] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The constitutive androstane receptor (CAR) and the pregnane X receptor (PXR) are closely related nuclear receptors involved in drug metabolism and play important roles in the mechanism of phenobarbital (PB)-induced rodent nongenotoxic hepatocarcinogenesis. Here, we have used a humanized CAR/PXR mouse model to examine potential species differences in receptor-dependent mechanisms underlying liver tissue molecular responses to PB. Early and late transcriptomic responses to sustained PB exposure were investigated in liver tissue from double knock-out CAR and PXR (CAR(KO)-PXR(KO)), double humanized CAR and PXR (CAR(h)-PXR(h)), and wild-type C57BL/6 mice. Wild-type and CAR(h)-PXR(h) mouse livers exhibited temporally and quantitatively similar transcriptional responses during 91 days of PB exposure including the sustained induction of the xenobiotic response gene Cyp2b10, the Wnt signaling inhibitor Wisp1, and noncoding RNA biomarkers from the Dlk1-Dio3 locus. Transient induction of DNA replication (Hells, Mcm6, and Esco2) and mitotic genes (Ccnb2, Cdc20, and Cdk1) and the proliferation-related nuclear antigen Mki67 were observed with peak expression occurring between 1 and 7 days PB exposure. All these transcriptional responses were absent in CAR(KO)-PXR(KO) mouse livers and largely reversible in wild-type and CAR(h)-PXR(h) mouse livers following 91 days of PB exposure and a subsequent 4-week recovery period. Furthermore, PB-mediated upregulation of the noncoding RNA Meg3, which has recently been associated with cellular pluripotency, exhibited a similar dose response and perivenous hepatocyte-specific localization in both wild-type and CAR(h)-PXR(h) mice. Thus, mouse livers coexpressing human CAR and PXR support both the xenobiotic metabolizing and the proliferative transcriptional responses following exposure to PB.
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Affiliation(s)
- Raphaëlle Luisier
- Preclinical Safety, Novartis Institutes for Biomedical Research, CH-4057 Basel, Switzerland
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Zamek-Gliszczynski MJ, Mohutsky MA, Rehmel JLF, Ke AB. Investigational Small-Molecule Drug Selectively Suppresses Constitutive CYP2B6 Activity at the Gene Transcription Level: Physiologically Based Pharmacokinetic Model Assessment of Clinical Drug Interaction Risk. Drug Metab Dispos 2014; 42:1008-15. [DOI: 10.1124/dmd.114.057018] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Abstract
The efficacy, safety, and tolerability of drugs are dependent on numerous factors that influence their disposition. A dose that is efficacious and safe for one individual may result in sub-therapeutic or toxic blood concentrations in other individuals. A major source of this variability in drug response is drug metabolism, where differences in pre-systemic and systemic biotransformation efficiency result in variable degrees of systemic exposure (e.g., AUC, C max, and/or C min) following administration of a fixed dose.Interindividual differences in drug biotransformation have been studied extensively. It is well recognized that both intrinsic (such as genetics, age, sex, and disease states) and extrinsic (such as diet, chemical exposures from the environment, and even sunlight) factors play a significant role. For the family of cytochrome P450 enzymes, the most critical of the drug metabolizing enzymes, genetic variation can result in the complete absence or enhanced expression of a functional enzyme. In addition, up- and down-regulation of gene expression, in response to an altered cellular environment, can achieve the same range of metabolic function (phenotype), but often in a less reliably predictable and time-dependent manner. Understanding the mechanistic basis for drug disposition and response variability is essential if we are to move beyond the era of empirical, trial-and-error dose selection and into an age of personalized medicine that brings with it true improvements in health outcomes in the therapeutic treatment of disease.
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Affiliation(s)
- Kenneth E Thummel
- Department of Pharmaceutics, University of Washington, Seattle, WA, USA
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Su S, Omiecinski CJ. Sp1 and Sp3 transcription factors regulate the basal expression of human microsomal epoxide hydrolase (EPHX1) through interaction with the E1b far upstream promoter. Gene 2013; 536:135-44. [PMID: 24315822 DOI: 10.1016/j.gene.2013.11.053] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 10/28/2013] [Accepted: 11/18/2013] [Indexed: 11/24/2022]
Abstract
Microsomal epoxide hydrolase (mEH, EPHX1) is a critical biotransformation enzyme, catalyzing the metabolism of many xenobiotics. Human mEH is transcribed using alternative promoters. The upstream E1 promoter is active in liver while the far upstream E1b promoter drives the expression of mEH in all tissues, including liver. Although several liver-specific transcription factors have been identified in the regulation of E1 transcription, little is known regarding the mechanisms of E1b transcriptional regulation. Genome-wide mapping of DNase I hypersensitive sites revealed an open chromatin region between nucleotide -300 upstream and +400 downstream of E1b. This area coincides with a previously described promoter region responsible for maintaining high basal promoter activity. In silico analysis of this location revealed several Sp1/Sp3 binding sites. Site-directed mutagenesis of these motifs suppressed the transactivation activity of the E1b proximal promoter, indicating their importance as contributors to E1b promoter regulation. Further, E1b promoter activities were increased significantly following Sp1 and Sp3 overexpression, while Mithramycin A, a selective Sp1 inhibitor, reduced the promoter activities. EMSA studies demonstrated that Sp1 bound to two putative Sp1/Sp3 binding sites. ChIP analysis confirmed that both endogenous Sp1 and Sp3 were bound to the proximal promoter region of E1b. Knockdown of Sp1 expression using siRNA did not alter the endogenous E1b transcriptional level, while knockdown of Sp3 greatly decreased E1b expression in different human cell lines. Taken together, these results support the concept that Sp1 and Sp3 are functionally involved as transcriptional integrators regulating the basal expression of the derived mEH E1b variant transcript.
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Affiliation(s)
- Shengzhong Su
- Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, 101 Life Sciences Bldg, University Park, PA 16802, USA
| | - Curtis J Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, 101 Life Sciences Bldg, University Park, PA 16802, USA.
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Yang H, Garzel B, Heyward S, Moeller T, Shapiro P, Wang H. Metformin represses drug-induced expression of CYP2B6 by modulating the constitutive androstane receptor signaling. Mol Pharmacol 2013; 85:249-60. [PMID: 24252946 DOI: 10.1124/mol.113.089763] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Metformin is currently the most widely used drug for the treatment of type 2 diabetes. Mechanistically, metformin interacts with many protein kinases and transcription factors that alter the expression of numerous downstream target genes governing lipid metabolism, cell proliferation, and drug metabolism. The constitutive androstane receptor (CAR, NR1i3), a known xenobiotic sensor, has recently been recognized as a novel signaling molecule, in that its activation could be regulated by protein kinases in addition to the traditional ligand binding. We show that metformin could suppress drug-induced expression of CYP2B6 (a typical target gene of CAR) by modulating the phosphorylation status of CAR. In human hepatocytes, metformin robustly suppressed the expression of CYP2B6 induced by both indirect (phenobarbital) and direct CITCO [6-(4-chlorophenyl)imidazo[2,1-b]1,3thiazole-5-carbaldehyde O-(3,4-dichlorobenzyl)oxime] activators of human CAR. Mechanistic investigation revealed that metformin specifically enhanced the phosphorylation of threonine-38 of CAR, which blocks CAR nuclear translocation and activation. Moreover, we showed that phosphorylation of CAR by metformin was primarily an AMP-activated protein kinase- and extracellular signal-regulated kinase 1/2-dependent event. Additional two-hybrid and coimmunoprecipitation assays demonstrated that metformin could also disrupt CITCO-mediated interaction between CAR and the steroid receptor coactivator 1 or the glucocorticoid receptor-interacting protein 1. Our results suggest that metformin is a potent repressor of drug-induced CYP2B6 expression through specific inhibition of human CAR activation. Thus, metformin may affect the metabolism and clearance of drugs that are CYP2B6 substrates.
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Affiliation(s)
- Hui Yang
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland (H.Y., B.G., P.S., H.W.); and Bioreclamation In Vitro Technologies (S.H., T.M.), Baltimore, Maryland
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Kanno Y, Tanuma N, Takahashi A, Inouye Y. TO901317, a potent LXR agonist, is an inverse agonist of CAR. J Toxicol Sci 2013; 38:309-15. [PMID: 23665929 DOI: 10.2131/jts.38.309] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The basal transcriptional activity of unliganded human constitutive androstane receptor (hCAR) was shown to be repressed by the potent liver X receptor (LXR) agonist, TO901317, in a concentration-dependent manner using a reporter assay in cultured cells. TO901317 also repressed the basal transcriptional activity of both mouse and rat CAR. The certified hCAR agonist, CITCO, partially reversed this repressive effect of TO901317 on hCAR basal activity. Unlike hCAR, a three alanine insertion mutant and the splice variant 2 of hCAR require agonists, such as CITCO, to become transcriptionally active and the CITCO-induced reporter activity was repressed by TO901317. As has been previously shown for the typical hCAR inverse agonist, PK11195, TO901317 blocked the interaction of hCAR with steroid receptor co-activator 1 (SRC1). In contrast, the interaction between hCAR and nuclear receptor corepressor 1 (NCoR1) was promoted by PK11195 and TO901317. Furthermore, the hCAR-mediated basal induction of endogenous cytochrome P450 2B6 (CYP2B6) mRNA was adversely affected by co-treatment with TO901317.
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Lynch C, Pan Y, Li L, Ferguson SS, Xia M, Swaan PW, Wang H. Identification of novel activators of constitutive androstane receptor from FDA-approved drugs by integrated computational and biological approaches. Pharm Res 2013; 30:489-501. [PMID: 23090669 PMCID: PMC3554869 DOI: 10.1007/s11095-012-0895-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 10/04/2012] [Indexed: 10/27/2022]
Abstract
PURPOSE The constitutive androstane receptor (CAR, NR1I3) is a xenobiotic sensor governing the transcription of numerous hepatic genes associated with drug metabolism and clearance. Recent evidence suggests that CAR also modulates energy homeostasis and cancer development. Thus, identification of novel human (h) CAR activators is of both clinical importance and scientific interest. METHODS Docking and ligand-based structure-activity models were used for virtual screening of a database containing over 2000 FDA-approved drugs. Identified lead compounds were evaluated in cell-based reporter assays to determine hCAR activation. Potential activators were further tested in human primary hepatocytes (HPHs) for the expression of the prototypical hCAR target gene CYP2B6. RESULTS Nineteen lead compounds with optimal modeling parameters were selected for biological evaluation. Seven of the 19 leads exhibited moderate to potent activation of hCAR. Five out of the seven compounds translocated hCAR from the cytoplasm to the nucleus of HPHs in a concentration-dependent manner. These compounds also induce the expression of CYP2B6 in HPHs with rank-order of efficacies closely resembling that of hCAR activation. CONCLUSION These results indicate that our strategically integrated approaches are effective in the identification of novel hCAR modulators, which may function as valuable research tools or potential therapeutic molecules.
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Affiliation(s)
- Caitlin Lynch
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland 21201
| | - Yongmei Pan
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland 21201
| | - Linhao Li
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland 21201
| | | | - Menghang Xia
- NIH Chemical Genomics Center, National Institutes of Health, Bethesda, Maryland 20892
| | - Peter W. Swaan
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland 21201
| | - Hongbing Wang
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland 21201
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Raucy JL, Lasker JM. Cell-based systems to assess nuclear receptor activation and their use in drug development. Drug Metab Rev 2013; 45:101-9. [DOI: 10.3109/03602532.2012.737333] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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35
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Burk O, Piedade R, Ghebreghiorghis L, Fait JT, Nussler AK, Gil JP, Windshügel B, Schwab M. Differential effects of clinically used derivatives and metabolites of artemisinin in the activation of constitutive androstane receptor isoforms. Br J Pharmacol 2013; 167:666-81. [PMID: 22577882 DOI: 10.1111/j.1476-5381.2012.02033.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND AND PURPOSE Widespread resistance to antimalarial drugs requires combination therapies with increasing risk of pharmacokinetic drug-drug interactions. Here, we explore the capacity of antimalarial drugs to induce drug metabolism via activation of constitutive androstane receptors (CAR) by ligand binding. EXPERIMENTAL APPROACH A total of 21 selected antimalarials and 11 major metabolites were screened for binding to CAR isoforms using cellular and in vitro CAR-coactivator interaction assays, combined with in silico molecular docking. Identified ligands were further characterized by cell-based assays and primary human hepatocytes were used to elucidate induction of gene expression. KEY RESULTS Only two artemisinin derivatives arteether and artemether, the metabolite deoxyartemisinin and artemisinin itself demonstrated agonist binding to the major isoforms CAR1 and CAR3, while arteether and artemether were also inverse agonists of CAR2. Dihydroartemisinin and artesunate acted as weak inverse agonists of CAR1. While arteether showed the highest activities in vitro, it was less active than artemisinin in inducing hepatic CYP3A4 gene expression in hepatocytes. CONCLUSIONS AND IMPLICATIONS Artemisinin derivatives and metabolites differentially affect the activities of CAR isoforms and of the pregnane X receptor (PXR). This negates a common effect of these drugs on CAR/PXR-dependent induction of drug metabolism and further provides an explanation for artemisinin consistently inducing cytochrome P450 genes in vivo, whereas arteether and artemether do not. All these drugs are metabolized very rapidly, but only artemisinin is converted to an enzyme-inducing metabolite. For better understanding of pharmacokinetic drug-drug interaction possibilities, the inducing properties of artemisinin metabolites should be considered.
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Affiliation(s)
- O Burk
- Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and University of Tübingen, Germany.
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Imai J, Yamazoe Y, Yoshinari K. Novel Cell-based Reporter Assay System Using Epitope-tagged Protein for the Identification of Agonistic Ligands of Constitutive Androstane Receptor (CAR). Drug Metab Pharmacokinet 2013; 28:290-8. [DOI: 10.2133/dmpk.dmpk-12-rg-112] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Wallace BD, Redinbo MR. Xenobiotic-sensing nuclear receptors involved in drug metabolism: a structural perspective. Drug Metab Rev 2012; 45:79-100. [PMID: 23210723 DOI: 10.3109/03602532.2012.740049] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Xenobiotic compounds undergo a critical range of biotransformations performed by the phase I, II, and III drug-metabolizing enzymes. The oxidation, conjugation, and transportation of potentially harmful xenobiotic and endobiotic compounds achieved by these catalytic systems are significantly regulated, at the gene expression level, by members of the nuclear receptor (NR) family of ligand-modulated transcription factors. Activation of NRs by a variety of endo- and exogenous chemicals are elemental to induction and repression of drug-metabolism pathways. The master xenobiotic sensing NRs, the promiscuous pregnane X receptor and less-promiscuous constitutive androstane receptor are crucial to initial ligand recognition, jump-starting the metabolic process. Other receptors, including farnesoid X receptor, vitamin D receptor, hepatocyte nuclear factor 4 alpha, peroxisome proliferator activated receptor, glucocorticoid receptor, liver X receptor, and RAR-related orphan receptor, are not directly linked to promiscuous xenobiotic binding, but clearly play important roles in the modulation of metabolic gene expression. Crystallographic studies of the ligand-binding domains of nine NRs involved in drug metabolism provide key insights into ligand-based and constitutive activity, coregulator recruitment, and gene regulation. Structures of other, noncanonical transcription factors also shed light on secondary, but important, pathways of control. Pharmacological targeting of some of these nuclear and atypical receptors has been instituted as a means to treat metabolic and developmental disorders and provides a future avenue to be explored for other members of the xenobiotic-sensing NRs.
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Affiliation(s)
- Bret D Wallace
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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Zhang YKJ, Lu H, Klaassen CD. Expression of human CAR splicing variants in BAC-transgenic mice. Toxicol Sci 2012; 132:142-50. [PMID: 23152187 DOI: 10.1093/toxsci/kfs321] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The nuclear receptor constitutive androstane receptor (CAR) is a key regulator for drug metabolism in liver. Human CAR (hCAR) transcripts are subjected to alternative splicing. Some hCAR splicing variants (SVs) have been shown to encode functional proteins by reporter assays. However, in vivo research on the activity of these hCAR SVs has been impeded by the absence of a valid model. This study engineered an hCAR-BAC-transgenic (hCAR-TG) mouse model by integrating the 8.5-kbp hCAR gene as well as 73-kbp upstream and 91-kbp downstream human genomic DNA into the genome of CAR-null mice. A series of experiments demonstrate that (1) the expression of major hCAR mRNA SVs, SV0-4, in livers of hCAR-TG mice is comparable to that in human livers; (2) the hCAR SVs are predominantly expressed in liver, which resembles the tissue distribution of CAR in humans, but diverges from that in mice; and (3) major hCAR mRNA SVs increase markedly in postnatal livers of hCAR-TG mice, which mimics the ontogeny of CAR mRNA in humans. Thus, the transgene likely contains all the functional regulatory elements controlling proper spatial and temporal expression of the hCAR gene. Moreover, hCAR-TG mice respond to the hCAR-specific agonist 6-(4-chlorophenyl)imidazo[2,1-b] [1,3]thiazole-5-carbaldehyde O-(3,4-dichlorobenzyl)oxime instead of the mouse CAR agonist 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene, as well as the common CAR activator, phenobarbital, suggesting that hCAR is fully functional in livers of transgenic mice. In summary, the hCAR-TG mice developed by this study represent a valid model for studying in vivo function and regulation of hCAR and its splicing variants.
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Affiliation(s)
- Yu-Kun Jennifer Zhang
- Department of Pharmacology, University of Kansas Medical Center, Kansas City, KS, USA
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Laurenzana EM, Chen T, Kannuswamy M, Sell BE, Strom SC, Li Y, Omiecinski CJ. The orphan nuclear receptor DAX-1 functions as a potent corepressor of the constitutive androstane receptor (NR1I3). Mol Pharmacol 2012; 82:918-28. [PMID: 22896671 DOI: 10.1124/mol.112.080721] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Regulation of gene transcription is controlled in part by nuclear receptors that function coordinately with coregulator proteins. The human constitutive androstane receptor (CAR; NR1I3) is expressed primarily in liver and regulates the expression of genes involved in xenobiotic metabolism as well as hormone, energy, and lipid homeostasis. In this report, DAX-1, a nuclear receptor family member with corepressor properties, was identified as a potent CAR regulator. Results of transaction and mutational studies demonstrated that both DAX-1's downstream LXXLL and its PCFQVLP motifs were critical contributors to DAX-1's corepression activities, although two other LXXM/LL motifs located nearer the N terminus had no impact on the CAR functional interaction. Deletion of DAX-1's C-terminal transcription silencing domain restored CAR1 transactivation activity in reporter assays to approximately 90% of control, demonstrating its critical function in mediating the CAR repression activities. Furthermore, results obtained from mammalian two-hybrid experiments assessing various domain configurations of the respective receptors showed that full-length DAX-1 inhibited the CAR-SRC1 interaction by approximately 50%, whereas the same interaction was restored to 90% of control when the DAX-1 transcription silencing domain was deleted. Direct interaction between CAR and DAX-1 was demonstrated with both alpha-screen and coimmunoprecipitation experiments, and this interaction was enhanced in the presence of the CAR activator 6-(4-chlorophenyl)imidazo[2,1-b]thiazole-5-carbaldehyde O-(3,4-dichlorobenzyl)oxime (CITCO). Results obtained in primary human hepatocytes further demonstrated DAX-1 inhibition of CAR-mediated CITCO induction of the CYP2B6 target gene. The results of this investigation identify DAX-1 as a novel and potent CAR corepressor and suggest that DAX-1 functions as a coordinate hepatic regulator of CAR's biological function.
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Affiliation(s)
- Elizabeth M Laurenzana
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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40
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Koh KH, Jurkovic S, Yang K, Choi SY, Jung JW, Kim KP, Zhang W, Jeong H. Estradiol induces cytochrome P450 2B6 expression at high concentrations: implication in estrogen-mediated gene regulation in pregnancy. Biochem Pharmacol 2012; 84:93-103. [PMID: 22484313 PMCID: PMC3376749 DOI: 10.1016/j.bcp.2012.03.016] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 03/21/2012] [Accepted: 03/22/2012] [Indexed: 12/19/2022]
Abstract
Pregnancy alters the rate and extent of drug metabolism, but little is known about the underlying molecular mechanism. We have found that 17β-estradiol (E2) upregulates expression of the major drug-metabolizing enzyme CYP2B6 in primary human hepatocytes. Results from promoter reporter assays in HepG2 cells revealed that E2 activates constitutive androstane receptor (CAR) and enhances promoter activity of CYP2B6, for which high concentrations of E2 reached during pregnancy were required. E2 triggered nuclear translocation of CAR in primary rat hepatocytes that were transiently transfected with human CAR as well as in primary human hepatocytes, further confirming transactivation of CAR by E2. E2-activated estrogen receptor (ER) also enhanced CYP2B6 promoter activity. The DNA-binding domain of ER was not required for the induction of CYP2B6 promoter activity by E2, suggesting involvement of a non-classical mechanism of ER action. Results from deletion and mutation assays as well as electrophorectic mobility shift and supershift assays revealed that two AP-1 binding sites (-1782/-1776 and -1664/-1658 of CYP2B6) are critical for ER-mediated activation of the CYP2B6 promoter by E2. Concurrent activation of both ER and CAR by E2 enhanced CYP2B6 expression in a synergistic manner. Our data demonstrate that at high concentrations reached during pregnancy, E2 activates both CAR and ER that synergistically induce CYP2B6 expression. These results illustrate pharmacological activity of E2 that would likely become prominent during pregnancy.
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MESH Headings
- Adult
- Aryl Hydrocarbon Hydroxylases/genetics
- Aryl Hydrocarbon Hydroxylases/metabolism
- Binding Sites
- Cell Nucleus/metabolism
- Chromatin Immunoprecipitation
- Chromatography, High Pressure Liquid
- Constitutive Androstane Receptor
- Cytochrome P-450 CYP2B6
- Dose-Response Relationship, Drug
- Electrophoretic Mobility Shift Assay
- Estradiol/blood
- Estradiol/pharmacology
- Estrogens/blood
- Estrogens/pharmacology
- Female
- Gene Expression Profiling
- Gene Expression Regulation, Enzymologic/drug effects
- Genes, Reporter
- Hep G2 Cells
- Hepatocytes/drug effects
- Hepatocytes/enzymology
- Humans
- Luciferases/genetics
- Middle Aged
- Nuclear Proteins/metabolism
- Oligonucleotide Array Sequence Analysis
- Oxidoreductases, N-Demethylating/genetics
- Oxidoreductases, N-Demethylating/metabolism
- Pregnancy/blood
- Pregnancy/genetics
- Promoter Regions, Genetic
- Real-Time Polymerase Chain Reaction
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Estrogen/genetics
- Receptors, Estrogen/metabolism
- Tandem Mass Spectrometry
- Transcription Factor AP-1/genetics
- Transcription Factor AP-1/metabolism
- Transcriptional Activation
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Affiliation(s)
- Kwi Hye Koh
- Department of Pharmacy Practice, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Steve Jurkovic
- Department of Biopharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Kyunghee Yang
- Department of Pharmacy Practice, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Su-Young Choi
- Center for Pharmaceutical Biotechnology, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Jin Woo Jung
- Department of Molecular Biotechnology, Institute of Biomedical Science and Technology, Konkuk University, Seoul 143-701, South Korea
| | - Kwang Pyo Kim
- Department of Molecular Biotechnology, Institute of Biomedical Science and Technology, Konkuk University, Seoul 143-701, South Korea
| | - Wei Zhang
- Department of Pediatrics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Hyunyoung Jeong
- Department of Pharmacy Practice, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA
- Department of Biopharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA
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41
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Wang D, Wang H. Oxazaphosphorine bioactivation and detoxification The role of xenobiotic receptors. Acta Pharm Sin B 2012; 2. [PMID: 24349963 DOI: 10.1016/j.apsb.2012.02.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Oxazaphosphorines, with the most representative members including cyclophosphamide, ifosfamide, and trofosfamide, constitute a class of alkylating agents that have a broad spectrum of anticancer activity against many malignant ailments including both solid tumors such as breast cancer and hematological malignancies such as leukemia and lymphoma. Most oxazaphosphorines are prodrugs that require hepatic cytochrome P450 enzymes to generate active alkylating moieties before manifesting their chemotherapeutic effects. Meanwhile, oxazaphosphorines can also be transformed into non-therapeutic byproducts by various drug-metabolizing enzymes. Clinically, oxazaphosphorines are often administered in combination with other chemotherapeutics in adjuvant treatments. As such, the therapeutic efficacy, off-target toxicity, and unintentional drug-drug interactions of oxazaphosphorines have been long-lasting clinical concerns and heightened focuses of scientific literatures. Recent evidence suggests that xenobiotic receptors may play important roles in regulating the metabolism and clearance of oxazaphosphorines. Drugs as modulators of xenobiotic receptors can affect the therapeutic efficacy, cytotoxicity, and pharmacokinetics of coadministered oxazaphosphorines, providing a new molecular mechanism of drug-drug interactions. Here, we review current advances regarding the influence of xenobiotic receptors, particularly, the constitutive androstane receptor, the pregnane X receptor and the aryl hydrocarbon receptor, on the bioactivation and detoxification of oxazaphosphorines, with a focus on cyclophosphamide and ifosfamide.
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42
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Berthier A, Oger F, Gheeraert C, Boulahtouf A, Le Guével R, Balaguer P, Staels B, Salbert G, Lefebvre P. The novel antibacterial compound walrycin A induces human PXR transcriptional activity. Toxicol Sci 2012; 127:225-35. [PMID: 22314385 DOI: 10.1093/toxsci/kfs073] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The human pregnane X receptor (PXR) is a ligand-regulated transcription factor belonging to the nuclear receptor superfamily. PXR is activated by a large, structurally diverse, set of endogenous and xenobiotic compounds and coordinates the expression of genes central to metabolism and excretion of potentially harmful chemicals and therapeutic drugs in humans. Walrycin A is a novel antibacterial compound targeting the WalK/WalR two-component signal transduction system of Gram (+) bacteria. Here, we report that, in hepatoma cells, walrycin A potently activates a gene set known to be regulated by the xenobiotic sensor PXR. Walrycin A was as efficient as the reference PXR agonist rifampicin to activate PXR in a transactivation assay at noncytotoxic concentrations. Using a limited proteolysis assay, we show that walrycin A induces conformational changes at a concentration which correlates with walrycin A ability to enhance the expression of prototypic target genes, suggesting that walrycin A interacts with PXR. The activation of the canonical human PXR target gene CYP3A4 by walrycin A is dose and PXR dependent. Finally, in silico docking experiments suggest that the walrycin A oxidation product Russig's blue is the actual ligand for PXR. Taken together, these results identify walrycin A as a novel human PXR activator.
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Fucoxanthin attenuates rifampin-induced cytochrome P450 3A4 (CYP3A4) and multiple drug resistance 1 (MDR1) gene expression through pregnane X receptor (PXR)-mediated pathways in human hepatoma HepG2 and colon adenocarcinoma LS174T cells. Mar Drugs 2012; 10:242-257. [PMID: 22363234 PMCID: PMC3280533 DOI: 10.3390/md10010242] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Revised: 01/10/2012] [Accepted: 01/16/2012] [Indexed: 01/11/2023] Open
Abstract
Pregnane X receptor (PXR) has been reported to regulate the expression of drug-metabolizing enzymes, such as the cytochrome P450 3A (CYP3A) family and transporters, such as multiple drug resistance 1 (MDR1). Fucoxanthin, the major carotenoid in brown sea algae, is a putative chemopreventive agent. In this study, we determined whether fucoxanthin could overcome drug resistance through attenuation of rifampin-induced CYP3A4 and MDR1 gene expression by PXR-mediated pathways in HepG2 hepatoma cells. We found that fucoxanthin (1–10 μM) significantly attenuated rifampin (20 μM)-induced CYP3A4, MDR1 mRNA and CYP3A4 protein expression at 24 h of incubation. Mechanistically, fucoxanthin strongly attenuated the PXR-mediated CYP3A4 promoter activity in HepG2 cells. In addition, fucoxanthin attenuated constitutive androstane receptor (CAR)- and rPXR-mediated CYP3A4 promoter activity in this cell line. Using the mammalian two-hybrid assay, we found that fucoxanthin significantly decreased the interaction between PXR and SRC-1, a PXR co-activator. Thus, fucoxanthin can decrease rifampin-induced CYP3A4 and MDR1 expression through attenuation of PXR-mediated CYP3A4 promoter activation and interaction between PXR and co-activator. These findings could lead to potentially important new therapeutic and dietary approaches to reduce the frequency of adverse drug reactions.
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44
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Li L, Sinz MW, Zimmermann K, Wang H. An insulin-like growth factor 1 receptor inhibitor induces CYP3A4 expression through a pregnane X receptor-independent, noncanonical constitutive androstane receptor-related mechanism. J Pharmacol Exp Ther 2011; 340:688-97. [PMID: 22171088 DOI: 10.1124/jpet.111.188854] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Inhibition of insulin-like growth factor-1 receptor (IGF-1R) signaling represents an attractive therapeutic strategy for cancer treatment. A first-generation IGF-1R inhibitor (R)-4-(3-(3-chlorophenyl)-3-hydroxypropyl)-3-(4-methyl-6-morpholino-1H-benzo[d]imidazol-2-yl)pyridin-2(1H)-one (BMS-536924), however, was associated with potent CYP3A4 induction mediated by pregnane X receptor (PXR; NR1I2) transactivation. Structural activity-based modification led to the synthesis of 4-(1-(2-(4-((2-(4-chloro-1H-pyrazol-1-yl)ethyl)amino)-2-oxo-1,2-dihydropyridin-3-yl)-4-methyl-1H-benzo[d]imidazol-6-yl)piperidin-4-yl) piperazine-1-carboxylate (BMS-665351) with no PXR activity while maintaining its ability to inhibit IGF-1R. However, BMS-665351 significantly induces CYP3A4 expression in human primary hepatocytes (HPHs). Here, we report a novel nonclassical constitutive androstane receptor (CAR; NR1I3)-related pathway of BMS-665351-mediated CYP3A4 induction. BMS-665351 treatment resulted in the significant induction of CYP3A4 in HPHs and HepG2 cells, but failed to activate either PXR or CAR in cell-based reporter assays. Moreover, BMS-665351 at concentrations that induce CYP3A4 expression was unable to translocate human CAR from the cytoplasm to the nucleus of HPHs, which represents the initial step of CAR activation. Nevertheless, quantitative polymerase chain reaction analysis demonstrated that BMS-665351 significantly enhanced the expression of CYP3A4 in CAR- but not PXR-transfected HepG2 and Huh7 cells. It is noteworthy that BMS-665351 selectively induced the expression of CAR but not PXR in all tested hepatic cell systems. Synergistic induction of CYP3A4 was observed in HPHs cotreated with BMS-665351 and prototypical activators of CAR but not PXR. In summary, our results indicate that BMS-665351-mediated induction of CYP3A4 is CAR-dependent, but BMS-665351 itself is not a typical activator of either CAR or PXR, rather it functions as a selective inducer of CAR expression and increases CYP3A4 through a noncanonical CAR-related mechanism.
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Affiliation(s)
- Linhao Li
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, 20 Penn Street, Baltimore, MD 21201, USA
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45
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Küblbeck J, Laitinen T, Jyrkkärinne J, Rousu T, Tolonen A, Abel T, Kortelainen T, Uusitalo J, Korjamo T, Honkakoski P, Molnár F. Use of comprehensive screening methods to detect selective human CAR activators. Biochem Pharmacol 2011; 82:1994-2007. [DOI: 10.1016/j.bcp.2011.08.027] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Revised: 08/30/2011] [Accepted: 08/31/2011] [Indexed: 01/20/2023]
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46
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Lau AJ, Yang G, Chang TKH. Isoform-selective activation of human constitutive androstane receptor by Ginkgo biloba extract: functional analysis of the SV23, SV24, and SV25 splice variants. J Pharmacol Exp Ther 2011; 339:704-15. [PMID: 21862659 DOI: 10.1124/jpet.111.186130] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Naturally occurring splice variants of human constitutive androstane receptor (hCAR) exist, including hCAR-SV23 (insertion of amino acids SPTV), hCAR-SV24 (APYLT), and hCAR-SV25 (SPTV and APYLT). An extract of Ginkgo biloba was reported to activate hCAR-SV24 and the wild type (hCAR-WT). However, it is not known whether it selectively affects hCAR splice variants, how it activates hCAR isoforms, and which chemical is responsible for the effects of the extract. Therefore, we evaluated the impact of G. biloba extract on the functionality of hCAR-SV23, hCAR-SV24, hCAR-SV25, and hCAR-WT and compared it with that of phenobarbital, di-(2-ethylhexyl)phthalate (DEHP), 6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde O-(3,4-dichlorobenzyl)oxime (CITCO), and 1,4-bis-[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) in cell-based reporter gene assays. Among the hCAR splice variants investigated, only hCAR-SV23 was activated by G. biloba extract, and this required cotransfection of a retinoid X receptor α (RXRα) expression plasmid. The extract activated hCAR-SV23 to a lesser extent than hCAR-WT, but ginkgolide A, ginkgolide B, ginkgolide C, ginkgolide J, and bilobalide were not responsible for the effects of the extract. CITCO activated hCAR-SV23, hCAR-SV24, and hCAR-WT. By comparison, phenobarbital activated hCAR-WT, whereas DEHP activated hCAR-SV23, hCAR-SV24 (with exogenous RXRα supplementation), and hCAR-WT. TCPOBOP did not affect the activity of any of the isoforms. G. biloba extract and phenobarbital did not bind or recruit coactivators to the ligand-binding domains of hCAR-WT and hCAR-SV23, whereas positive results were obtained with the controls (CITCO for hCAR-WT and DEHP for hCAR-SV23). In conclusion, G. biloba extract activates hCAR in an isoform-selective manner, and hCAR-SV23, hCAR-SV24, and hCAR-WT have overlapping, but distinct, sets of ligands.
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Affiliation(s)
- Aik Jiang Lau
- Faculty of Pharmaceutical Sciences, The University of British Columbia, 2146 East Mall, Vancouver, British Columbia, V6T 1Z3, Canada
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47
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Omiecinski CJ, Coslo DM, Chen T, Laurenzana EM, Peffer RC. Multi-species analyses of direct activators of the constitutive androstane receptor. Toxicol Sci 2011; 123:550-62. [PMID: 21778469 DOI: 10.1093/toxsci/kfr191] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The constitutive androstane receptor (CAR; NR1I3) is a member of the nuclear receptor superfamily and functions as an important xenochemical sensor and transcriptional modulator in mammalian cells. Upon chemical activation, CAR undergoes nuclear translocation and heterodimerization with the retinoid X receptor subsequent to its DNA target interaction. CAR is unusual among nuclear receptors in that it possesses a high level of constitutive activity in cell-based assays, obscuring the detection of ligand activators. However, a human splice variant of CAR, termed CAR3, exhibits negligible constitutive activity. In addition, CAR3 is activated by ligands with similar specificity as the reference form of the receptor. In this study, we hypothesized that similar CAR3 receptors could be constructed across various mammalian species' forms of CAR that would preserve species-specific ligand responses, thus enabling a more sensitive and differential screening assessment of CAR response among animal models. A battery of CAR3 receptors was produced in mouse, rat, and dog and comparatively evaluated with selected ligands together with human CAR1 and CAR3 in mammalian cell reporter assays. The results demonstrate that the 5-amino acid insertion that typifies human CAR3 also imparts ligand-activated receptor function in other species' CAR while maintaining signature responses in each species to select CAR ligands. These variant constructs permit in vitro evaluation of differential chemical effector responses across species and coupled with in vivo assays, the species-selective contributions of CAR in normal physiology and in disease processes such as hepatocarcinogenesis.
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Affiliation(s)
- Curtis J Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, Penn State University, University Park, Pennsylvania 16802, USA.
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48
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Anderson LE, Dring AM, Hamel LD, Stoner MA. Modulation of constitutive androstane receptor (CAR) and pregnane X receptor (PXR) by 6-arylpyrrolo[2,1-d][1,5]benzothiazepine derivatives, ligands of peripheral benzodiazepine receptor (PBR). Toxicol Lett 2011; 202:148-54. [PMID: 21315811 PMCID: PMC3086002 DOI: 10.1016/j.toxlet.2011.02.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Revised: 02/02/2011] [Accepted: 02/03/2011] [Indexed: 12/31/2022]
Abstract
Constitutive androstane receptor (CAR) and pregnane X receptor (PXR) regulate xenobiotic sensing and metabolism through interactions with multiple exogenous and endogenous chemicals. Compounds that activate CAR are often ligands of PXR; attention is therefore given to discovery of new, receptor-specific chemical entities that may be exploited for therapeutic and basic research purposes. Recently, ligands of the peripheral benzodiazepine receptor (PBR), PK11195 and FGIN-1-27, were shown to modulate both CAR and PXR. PBR is a mitochondrial transport protein responsible for multiple regulatory functions, including heme biosynthesis, a major component in cytochrome P450 (CYP) enzymes. To investigate possible new roles for PBR involvement in metabolic regulation, expression of the CAR and PXR target genes, CYP2B6 and CYP3A4, was measured in human hepatocytes following treatment with a targeted PBR ligand set. Luciferase reporter assays with transiently expressed wild-type CAR (CAR1), splice variant CAR3, or PXR in HuH-7 cells were used to further study activation of these receptors. Four structurally related PBR ligands (benzothiazepines) differentially modulate CAR1, CAR3 and PXR activity. Benzothiazepine NF49 is an agonist ligand of CAR3, a partial agonist of PXR, exhibits greater inverse agonist activity on CAR1 than does PK11195, and is a new tool for studying these closely related nuclear receptors.
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Affiliation(s)
- Linnea E Anderson
- Department of Biomedical and Pharmaceutical Sciences, and Center for Molecular Toxicology, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, United States
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49
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Omiecinski CJ, Vanden Heuvel JP, Perdew GH, Peters JM. Xenobiotic metabolism, disposition, and regulation by receptors: from biochemical phenomenon to predictors of major toxicities. Toxicol Sci 2011; 120 Suppl 1:S49-75. [PMID: 21059794 PMCID: PMC3145385 DOI: 10.1093/toxsci/kfq338] [Citation(s) in RCA: 242] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 11/01/2010] [Indexed: 02/07/2023] Open
Abstract
To commemorate the 50th anniversary of the Society of Toxicology, this special edition article reviews the history and current scope of xenobiotic metabolism and transport, with special emphasis on the discoveries and impact of selected "xenobiotic receptors." This overall research realm has witnessed dynamic development in the past 50 years, and several of the key milestone events that mark the impressive progress in these areas of toxicological sciences are highlighted. From the initial observations regarding aspects of drug metabolism dating from the mid- to late 1800's, the area of biotransformation research witnessed seminal discoveries in the mid-1900's and onward that are remarkable in retrospect, including the discovery and characterization of the phase I monooxygenases, the cytochrome P450s. Further research uncovered many aspects of the biochemistry of xenobiotic metabolism, expanding to phase II conjugation and phase III xenobiotic transport. This led to hallmark developments involving integration of genomic technologies to elucidate the basis for interindividual differences in response to xenobiotic exposures and discovery of nuclear and soluble receptor families that selectively "sense" the chemical milieu of the mammalian cell and orchestrate compensatory changes in gene expression programming to accommodate complex xenobiotic exposures. This review will briefly summarize these developments and investigate the expanding roles of xenobiotic receptor biology in the underlying basis of toxicological response to chemical agents.
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Affiliation(s)
- Curtis J Omiecinski
- Department of Veterinary and Biomedical Sciences, Center for Molecular Toxicology and Carcinogenesis, Penn State University, University Park, Pennsylvania 16802, USA.
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50
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Abstract
Interindividual differences in drug transporter expression can result in variability in drug response. This variation in gene expression is determined, in part, by the actions of nuclear hormone receptors that act as xenobiotic- and endobiotic-sensing transcription factors. Among the ligand-activated nuclear receptors, signaling through the pregnane X receptor (PXR), constitutive androstane receptor (CAR), farnesoid X receptor (FXR), and vitamin D receptor (VDR) constitute major pathways regulating drug transporter expression in tissues. Hence, these endobiotic- and xenobiotic-sensing nuclear receptors are intrinsically involved in environmental influences of drug response. Moreover, because nuclear receptor genes are polymorphic, these transcription factors are also thought to contribute to heritability of variable drug action. In this chapter, the molecular aspects of drug transporter gene regulation by ligand-activated nuclear receptors will be reviewed including their clinical relevance.
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