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Ekiciler A, Chen WLK, Bo Y, Pugliano A, Donzelli M, Parrott N, Umehara K. Quantitative Cytochrome P450 3A4 Induction Risk Assessment Using Human Hepatocytes Complemented with Pregnane X Receptor-Activating Profiles. Drug Metab Dispos 2023; 51:276-284. [PMID: 36460477 DOI: 10.1124/dmd.122.001132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 11/14/2022] [Accepted: 11/23/2022] [Indexed: 12/05/2022] Open
Abstract
Reliable in vitro to in vivo translation of cytochrome P450 (CYP) 3A4 induction potential is essential to support risk mitigation for compounds during pharmaceutical discovery and development. In this study, a linear correlation of CYP3A4 mRNA induction potential in human hepatocytes with the respective pregnane-X receptor (PXR) activation in a reporter gene assay using DPX2 cells was successfully demonstrated for 13 clinically used drugs. Based on this correlation, using rifampicin as a positive control, the magnitude of CYP3A4 mRNA induction for 71 internal compounds at several concentrations up to 10 µM (n = 90) was predicted within 2-fold error for 64% of cases with only a few false positives (19%). Furthermore, the in vivo area under the curve reduction of probe CYP substrates was reasonably predicted for eight marketed drugs (carbamazepine, dexamethasone, enzalutamide, nevirapine, phenobarbital, phenytoin, rifampicin, and rufinamide) using the static net effect model using both the PXR activation and CYP3A4 mRNA induction data. The liver exit concentrations were used for the model in place of the inlet concentrations to avoid false positive predictions and the concentration achieving twofold induction (F2) was used to compensate for the lack of full induction kinetics due to cytotoxicity and solubility limitations in vitro. These findings can complement the currently available induction risk mitigation strategy and potentially influence the drug interaction modeling work conducted at clinical stages. SIGNIFICANCE STATEMENT: The established correlation of CYP3A4 mRNA in human hepatocytes to PXR activation provides a clear cut-off to identify a compound showing an in vitro induction risk, complementing current regulatory guidance. Also, the demonstrated in vitro-in vivo translation of induction data strongly supports a clinical development program although limitations remain for drug candidates showing complex disposition pathways, such as involvement of auto-inhibition/induction, active transport and high protein binding.
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Affiliation(s)
- Aynur Ekiciler
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Basel, Switzerland (A.E., A.P., M.D., N.P., K.U.) and Roche Pharmaceutical Research and Early Development, China Innovation Center of Roche, Shanghai, China (W.L.K.C., Y.B.)
| | - Wen Li Kelly Chen
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Basel, Switzerland (A.E., A.P., M.D., N.P., K.U.) and Roche Pharmaceutical Research and Early Development, China Innovation Center of Roche, Shanghai, China (W.L.K.C., Y.B.)
| | - Yan Bo
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Basel, Switzerland (A.E., A.P., M.D., N.P., K.U.) and Roche Pharmaceutical Research and Early Development, China Innovation Center of Roche, Shanghai, China (W.L.K.C., Y.B.)
| | - Alessandra Pugliano
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Basel, Switzerland (A.E., A.P., M.D., N.P., K.U.) and Roche Pharmaceutical Research and Early Development, China Innovation Center of Roche, Shanghai, China (W.L.K.C., Y.B.)
| | - Massimiliano Donzelli
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Basel, Switzerland (A.E., A.P., M.D., N.P., K.U.) and Roche Pharmaceutical Research and Early Development, China Innovation Center of Roche, Shanghai, China (W.L.K.C., Y.B.)
| | - Neil Parrott
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Basel, Switzerland (A.E., A.P., M.D., N.P., K.U.) and Roche Pharmaceutical Research and Early Development, China Innovation Center of Roche, Shanghai, China (W.L.K.C., Y.B.)
| | - Kenichi Umehara
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Basel, Switzerland (A.E., A.P., M.D., N.P., K.U.) and Roche Pharmaceutical Research and Early Development, China Innovation Center of Roche, Shanghai, China (W.L.K.C., Y.B.)
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2
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Shinohara M, Arakawa H, Oda Y, Shiraki N, Sugiura S, Nishiuchi T, Satoh T, Iino K, Leo S, Kato Y, Araya K, Kawanishi T, Nakatsuji T, Mitsuta M, Inamura K, Goto T, Shinha K, Nihei W, Komori K, Nishikawa M, Kume S, Kato Y, Kanamori T, Sakai Y, Kimura H. Coculture with hiPS-derived intestinal cells enhanced human hepatocyte functions in a pneumatic-pressure-driven two-organ microphysiological system. Sci Rep 2021; 11:5437. [PMID: 33686099 PMCID: PMC7940409 DOI: 10.1038/s41598-021-84861-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 02/16/2021] [Indexed: 12/31/2022] Open
Abstract
Examining intestine-liver interactions is important for achieving the desired physiological drug absorption and metabolism response in in vitro drug tests. Multi-organ microphysiological systems (MPSs) constitute promising tools for evaluating inter-organ interactions in vitro. For coculture on MPSs, normal cells are challenging to use because they require complex maintenance and careful handling. Herein, we demonstrated the potential of coculturing normal cells on MPSs in the evaluation of intestine-liver interactions. To this end, we cocultured human-induced pluripotent stem cell-derived intestinal cells and fresh human hepatocytes which were isolated from PXB mice with medium circulation in a pneumatic-pressure-driven MPS with pipette-friendly liquid-handling options. The cytochrome activity, albumin production, and liver-specific gene expressions in human hepatocytes freshly isolated from a PXB mouse were significantly upregulated via coculture with hiPS-intestinal cells. Our normal cell coculture shows the effects of the interactions between the intestine and liver that may occur in vivo. This study is the first to demonstrate the coculturing of hiPS-intestinal cells and fresh human hepatocytes on an MPS for examining pure inter-organ interactions. Normal-cell coculture using the multi-organ MPS could be pursued to explore unknown physiological mechanisms of inter-organ interactions in vitro and investigate the physiological response of new drugs.
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Affiliation(s)
- Marie Shinohara
- Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
| | - Hiroshi Arakawa
- Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan
| | - Yuuichi Oda
- Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
- Department of Mechanical Engineering, School of Engineering, Tokai University, Kanagawa, Japan
| | - Nobuaki Shiraki
- School of Life Science and Technology, Tokyo Institute of Technology, Kanagawa, Japan
| | - Shinji Sugiura
- Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
| | - Takumi Nishiuchi
- Advanced Science Research Centre, Kanazawa University, Kanazawa, Japan
| | - Taku Satoh
- Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
| | - Keita Iino
- School of Life Science and Technology, Tokyo Institute of Technology, Kanagawa, Japan
| | - Sylvia Leo
- School of Life Science and Technology, Tokyo Institute of Technology, Kanagawa, Japan
| | - Yusuke Kato
- School of Life Science and Technology, Tokyo Institute of Technology, Kanagawa, Japan
| | - Karin Araya
- Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan
| | - Takumi Kawanishi
- Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan
| | - Tomoki Nakatsuji
- Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan
| | - Manami Mitsuta
- Department of Chemical System Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Kosuke Inamura
- Department of Chemical System Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Tomomi Goto
- Department of Mechanical Engineering, School of Engineering, Tokai University, Kanagawa, Japan
| | - Kenta Shinha
- Department of Mechanical Engineering, School of Engineering, Tokai University, Kanagawa, Japan
| | - Wataru Nihei
- Department of Mechanical Engineering, School of Engineering, Tokai University, Kanagawa, Japan
| | - Kikuo Komori
- Department of Chemical System Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Masaki Nishikawa
- Department of Chemical System Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Shoen Kume
- School of Life Science and Technology, Tokyo Institute of Technology, Kanagawa, Japan
| | - Yukio Kato
- Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan
| | - Toshiyuki Kanamori
- Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
| | - Yasuyuki Sakai
- Department of Chemical System Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Hiroshi Kimura
- Institute of Industrial Science, The University of Tokyo, Tokyo, Japan.
- Department of Mechanical Engineering, School of Engineering, Tokai University, Kanagawa, Japan.
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3
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Toporova L, Grimaldi M, Boulahtouf A, Balaguer P. Assessing the Selectivity of FXR, LXRs, CAR, and RORγ Pharmaceutical Ligands With Reporter Cell Lines. Front Pharmacol 2020; 11:1122. [PMID: 32792956 PMCID: PMC7394005 DOI: 10.3389/fphar.2020.01122] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 07/10/2020] [Indexed: 01/01/2023] Open
Abstract
To characterize human nuclear receptor (NR) specificity of synthetic pharmaceutical chemicals we established stable cell lines expressing the ligand binding domains (LBDs) of human FXR, LXRα, LXRβ, CAR, and RORγ fused to the yeast GAL4 DNA binding domain (DBD). As we have already done for human PXR, a two-step transfection procedure was used. HeLa cells stably expressing a Gal4 responsive gene (HG5LN cell line) were transfected by Gal4-NRs expressing plasmids. At first, using these cell lines as well as the HG5LN PXR cells, we demonstrated that the basal activities varied from weak (FXR and LXRs), intermediate (PXR), to strong (CAR and RORγ), reflecting the recruitment of HeLa co-regulators in absence of ligand. Secondly, we finely characterized the activities of commercially available FXR, LXRα, LXRβ, CAR, RORγ, and PXR agonists/antagonists GW4064, feraxamine, DY268, T0901317, GW3965, WAY252623, SR9238, SR9243, GSK2033, CITCO, CINPA1, PK11195, S07662, SR1078, SR0987, SR1001, SR2211, XY018, clotrimazole, dabrafenib, SR12813, and SPA70, respectively. Among these compounds we revealed both, receptor specific agonists/antagonists, as well as less selective ligands, activating or inhibiting several nuclear receptors. FXR ligands manifested high receptor selectivity. Vice versa, LXR ligands behaved in non-selective manner, all activating at least PXR. CAR was selectively influenced by their ligands, while it also responded to several LXR ligands. Finally, although PXR was quite selectively activated or antagonized by its own ligands, it responded to several NRs ligands as well. Thus, using these reporter cell lines enabled us to precisely characterize the selectivity of pharmaceutical ligands for different nuclear receptors.
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Affiliation(s)
- Lucia Toporova
- Institut de Recherche en Cancérologie de Montpellier (IRCM), INSERM U1194, ICM, Univ Montpellier, Montpellier, France
| | - Marina Grimaldi
- Institut de Recherche en Cancérologie de Montpellier (IRCM), INSERM U1194, ICM, Univ Montpellier, Montpellier, France
| | - Abdelhay Boulahtouf
- Institut de Recherche en Cancérologie de Montpellier (IRCM), INSERM U1194, ICM, Univ Montpellier, Montpellier, France
| | - Patrick Balaguer
- Institut de Recherche en Cancérologie de Montpellier (IRCM), INSERM U1194, ICM, Univ Montpellier, Montpellier, France
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4
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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: 4] [Impact Index Per Article: 0.7] [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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5
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Li J, Tan H, Zhou X, Zhang C, Jin H, Tian Y, Zhao X, Li X, Sun X, Duan M, Zhang D. The Protection of Midazolam Against Immune Mediated Liver Injury Induced by Lipopolysaccharide and Galactosamine in Mice. Front Pharmacol 2019; 9:1528. [PMID: 30670973 PMCID: PMC6331471 DOI: 10.3389/fphar.2018.01528] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 12/13/2018] [Indexed: 01/23/2023] Open
Abstract
Objectives: Liver macrophages agitated by Lipopolysaccharide (LPS) can enhance immuno-inflammatory responses in the liver which mediate liver injury and result in dysfunction. Midazolam has been reported to have inhibitory effects on activated immunity and escalated inflammation, however, what the effects of midazolam on the liver injury caused by excessive immuno-inflammatory response in sepsis, and what influence it will exert on inflamed liver macrophages need to be elucidated. Methods: In the present study, LPS and galactosamine-induced acute liver injury mice were used to observe the effect of midazolam in vivo. LPS-stimulated bone marrow cells were used to evaluate the influence of midazolam on monocytes in vitro. Results: Midazolam prevented liver tissue injury and decreased serum alanine transaminase (ALT) level in LPS plus galactosamine treated mice. Mechanistically, midazolam suppressed tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) produced by LPS stimulated liver macrophages in vivo and bone marrow monocytes in vitro, and reduced the expression of major histocompatibility complex class II (MHC II), cluster of differentiation 40 and 86 (CD40 and CD86) on the cell surface. These results could be reversed by PK-11195, a peripheral benzodiazepine receptor (PBR) blocker. Conclusion: Midazolam can prevent liver from LPS-induced immune mediated liver injury by inhibiting inflammation and immune activation in liver macrophages.
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Affiliation(s)
- Jian Li
- Department of Intensive Care Unit, Beijing Friendship Hospital, Capital Medical University, Beijing, China.,Beijing Clinical Research Institute, Beijing, China.,Beijing Key Laboratory of Tolerance Induction and Organ Protection in Transplantation, Beijing, China
| | - Hong Tan
- Beijing Key Laboratory of Tolerance Induction and Organ Protection in Transplantation, Beijing, China.,Department of Anesthesiology, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Xiaona Zhou
- Beijing Key Laboratory of Tolerance Induction and Organ Protection in Transplantation, Beijing, China.,General Surgery Department, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Chunpan Zhang
- Beijing Clinical Research Institute, Beijing, China.,Beijing Key Laboratory of Tolerance Induction and Organ Protection in Transplantation, Beijing, China.,Experimental and Translational Research Center, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Hua Jin
- Beijing Clinical Research Institute, Beijing, China.,Beijing Key Laboratory of Tolerance Induction and Organ Protection in Transplantation, Beijing, China.,Experimental and Translational Research Center, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Yue Tian
- Beijing Clinical Research Institute, Beijing, China.,Beijing Key Laboratory of Tolerance Induction and Organ Protection in Transplantation, Beijing, China.,Experimental and Translational Research Center, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Xinyan Zhao
- Beijing Clinical Research Institute, Beijing, China.,Beijing Key Laboratory of Tolerance Induction and Organ Protection in Transplantation, Beijing, China
| | - Xinmin Li
- Beijing Clinical Research Institute, Beijing, China.,Beijing Key Laboratory of Tolerance Induction and Organ Protection in Transplantation, Beijing, China.,Experimental and Translational Research Center, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Xuelian Sun
- Beijing Clinical Research Institute, Beijing, China.,Department of Emergency Medicine, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Meili Duan
- Department of Intensive Care Unit, Beijing Friendship Hospital, Capital Medical University, Beijing, China.,Beijing Clinical Research Institute, Beijing, China.,Beijing Key Laboratory of Tolerance Induction and Organ Protection in Transplantation, Beijing, China
| | - Dong Zhang
- Beijing Clinical Research Institute, Beijing, China.,Beijing Key Laboratory of Tolerance Induction and Organ Protection in Transplantation, Beijing, China.,Experimental and Translational Research Center, Beijing Friendship Hospital, Capital Medical University, Beijing, China.,National Clinical Research Center for Digestive Diseases, Beijing, China
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6
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Mackowiak B, Li L, Welch MA, Li D, Jones JW, Heyward S, Kane MA, Swaan PW, Wang H. Molecular Basis of Metabolism-Mediated Conversion of PK11195 from an Antagonist to an Agonist of the Constitutive Androstane Receptor. Mol Pharmacol 2017; 92:75-87. [PMID: 28442602 PMCID: PMC5452073 DOI: 10.1124/mol.117.108621] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 04/20/2017] [Indexed: 12/19/2022] Open
Abstract
The constitutive androstane receptor (CAR) plays an important role in xenobiotic metabolism, energy homeostasis, and cell proliferation. Antagonism of the CAR represents a key strategy for studying its function and may have potential clinical applications. However, specific human CAR (hCAR) antagonists are limited and conflicting data on the activity of these compounds have been reported. 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide (PK11195), a typical peripheral benzodiazepine receptor ligand, has been established as a potent hCAR deactivator in immortalized cells; whether it inhibits hCAR activity under physiologically relevant conditions remains unclear. Here, we investigated the effects of PK11195 on hCAR in metabolically competent human primary hepatocytes (HPH) and HepaRG cells. We show that although PK11195 antagonizes hCAR in HepG2 cells, it induces the expression of CYP2B6 and CYP3A4, targets of hCAR and the pregnane X receptor (PXR), in HPH, HepaRG, and PXR-knockout HepaRG cells. Utilizing a HPH-HepG2 coculture model, we demonstrate that inclusion of HPH converts PK11195 from an antagonist to an agonist of hCAR, and such conversion was attenuated by potent CYP3A4 inhibitor ketoconazole. Metabolically, we show that the N-desmethyl metabolite is responsible for PK11195-mediated hCAR activation by facilitating hCAR interaction with coactivators and enhancing hCAR nuclear translocation in HPHs. Structure-activity analysis revealed that N-demethylation alters the interaction of PK11195 with the binding pocket of hCAR to favor activation. Together, these results indicate that removal of a methyl group switches PK11195 from a potent antagonist of hCAR to an agonist in HPH and highlights the importance of physiologically relevant metabolism when attempting to define the biologic action of small molecules.
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Affiliation(s)
- Bryan Mackowiak
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (B.M., L.L., M.A.W., D.L., J.W.J., M.A.K., P.W.S., H.W.); and Bioreclamation In Vitro Technologies, Halethorpe, Maryland (S.H.)
| | - Linhao Li
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (B.M., L.L., M.A.W., D.L., J.W.J., M.A.K., P.W.S., H.W.); and Bioreclamation In Vitro Technologies, Halethorpe, Maryland (S.H.)
| | - Matthew A Welch
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (B.M., L.L., M.A.W., D.L., J.W.J., M.A.K., P.W.S., H.W.); and Bioreclamation In Vitro Technologies, Halethorpe, Maryland (S.H.)
| | - Daochuan Li
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (B.M., L.L., M.A.W., D.L., J.W.J., M.A.K., P.W.S., H.W.); and Bioreclamation In Vitro Technologies, Halethorpe, Maryland (S.H.)
| | - Jace W Jones
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (B.M., L.L., M.A.W., D.L., J.W.J., M.A.K., P.W.S., H.W.); and Bioreclamation In Vitro Technologies, Halethorpe, Maryland (S.H.)
| | - Scott Heyward
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (B.M., L.L., M.A.W., D.L., J.W.J., M.A.K., P.W.S., H.W.); and Bioreclamation In Vitro Technologies, Halethorpe, Maryland (S.H.)
| | - Maureen A Kane
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (B.M., L.L., M.A.W., D.L., J.W.J., M.A.K., P.W.S., H.W.); and Bioreclamation In Vitro Technologies, Halethorpe, Maryland (S.H.)
| | - Peter W Swaan
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (B.M., L.L., M.A.W., D.L., J.W.J., M.A.K., P.W.S., H.W.); and Bioreclamation In Vitro Technologies, Halethorpe, Maryland (S.H.)
| | - Hongbing Wang
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland (B.M., L.L., M.A.W., D.L., J.W.J., M.A.K., P.W.S., H.W.); and Bioreclamation In Vitro Technologies, Halethorpe, Maryland (S.H.)
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7
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Lee K, You H, Choi J, No KT. Development of pharmacophore-based classification model for activators of constitutive androstane receptor. Drug Metab Pharmacokinet 2016; 32:172-178. [PMID: 28366619 DOI: 10.1016/j.dmpk.2016.11.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 09/21/2016] [Accepted: 11/10/2016] [Indexed: 10/20/2022]
Abstract
Constitutive androstane receptor (CAR) is predominantly expressed in the liver and is important for regulating drug metabolism and transport. Despite its biological importance, there have been few attempts to develop in silico models to predict the activity of CAR modulated by chemical compounds. The number of in silico studies of CAR may be limited because of CAR's constitutive activity under normal conditions, which makes it difficult to elucidate the key structural features of the interaction between CAR and its ligands. In this study, to address these limitations, we introduced 3D pharmacophore-based descriptors with an integrated ligand and structure-based pharmacophore features, which represent the receptor-ligand interaction. Machine learning methods (support vector machine and artificial neural network) were applied to develop an in silico model with the descriptors containing significant information regarding the ligand binding positions. The best classification model built with a solvent accessibility volume-based filter and the support vector machine showed good predictabilities of 87%, and 85.4% for the training set and validation set, respectively. This demonstrates that our model can be used to accurately predict CAR activators and offers structural information regarding ligand/protein interactions.
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Affiliation(s)
- Kyungro Lee
- Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, South Korea
| | - Hwan You
- Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, South Korea
| | - Jiwon Choi
- Bioinformatics & Molecular Design Research Center, Yonsei University, Seoul 03722, South Korea
| | - Kyoung Tai No
- Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, South Korea; Bioinformatics & Molecular Design Research Center, Yonsei University, Seoul 03722, South Korea.
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8
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Selvaraj V, Tu LN. Current status and future perspectives: TSPO in steroid neuroendocrinology. J Endocrinol 2016; 231:R1-R30. [PMID: 27422254 DOI: 10.1530/joe-16-0241] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 07/15/2016] [Indexed: 12/21/2022]
Abstract
The mitochondrial translocator protein (TSPO), previously known as the peripheral benzodiazepine receptor (PBR), has received significant attention both as a diagnostic biomarker and as a therapeutic target for different neuronal disease pathologies. Recently, its functional basis believed to be mediating mitochondrial cholesterol import for steroid hormone production has been refuted by studies examining both in vivo and in vitro genetic Tspo-deficient models. As a result, there now exists a fundamental gap in the understanding of TSPO function in the nervous system, and its putative pharmacology in neurosteroid production. In this review, we discuss several recent findings in steroidogenic cells that are in direct contradiction to previous studies, and necessitate a re-examination of the purported role for TSPO in de novo neurosteroid biosynthesis. We critically examine the pharmacological effects of different TSPO-binding drugs with particular focus on studies that measure neurosteroid levels. We highlight the basis of key misconceptions regarding TSPO that continue to pervade the literature, and the need for interpretation with caution to avoid negative impacts. We also summarize the emerging perspectives that point to new directions that need to be investigated for understanding the molecular function of TSPO, only after which the true potential of this therapeutic target in medicine may be realized.
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Affiliation(s)
- Vimal Selvaraj
- Department of Animal ScienceCornell University, Ithaca, New York, USA
| | - Lan N Tu
- Department of Animal ScienceCornell University, Ithaca, New York, USA
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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: 1.7] [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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Carazo Fernández A, Smutny T, Hyrsová L, Berka K, Pavek P. Chrysin, baicalein and galangin are indirect activators of the human constitutive androstane receptor (CAR). Toxicol Lett 2015; 233:68-77. [DOI: 10.1016/j.toxlet.2015.01.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 01/22/2015] [Accepted: 01/23/2015] [Indexed: 11/30/2022]
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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: 1.0] [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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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: 0.6] [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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Huang L, Huang M, Li YH, Li RM, Zeng Y, Kuang SY, Zhang L, Wang YT, Bi HC. Up-regulatation of CYP3A expression through pregnent X receptor by praeruptorin D isolated from Peucedanum praeruptorum Dunn. JOURNAL OF ETHNOPHARMACOLOGY 2013; 148:596-602. [PMID: 23702042 DOI: 10.1016/j.jep.2013.05.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2012] [Revised: 03/10/2013] [Accepted: 05/01/2013] [Indexed: 06/02/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Qianhu, the dried roots of Peucedanum praeruptorum DUNN (Umbelliferae), is a well-known traditional Chinese medicinal herb which was officially listed in the Chinese Pharmacopoeia. Praeruptorin D (PD) is one of the major active constituents of Peucedanum praeruptorum Dunn (Qianhu). The Pregnane X receptor (PXR) is an orphan nuclear receptor and plays a pivotal role in the activation of human cytochrome P450 3A4 (CYP3A4) gene. AIM OF THE STUDY The purpose of this study was to investigate the effect of PD on the PXR-mediated transactivation of CYP3A4, and thus to predict potential herb-drug interactions between PD, Qianhu, and the other co-administered drugs that metabolized by CYP3A4. MATERIALS AND METHODS The effect of PD on the Cyp3a11, mPXR mRNA expression in mice primary hepatocytes was measured using real-time PCR. The gene expression, protein expression, and catalytic activity of CYP3A4 in the LS174T cells after transfected with PXR expression plasmids were determined by real-time PCR, Western blot analysis, and LC-MS/MS based CYP3A4 substrate assay. RESULTS The results revealed that the level of Cyp3a11 gene expression in mice primary hepatocytes was significantly increased by PD, but PD cannot induce the mPXR gene expression. On the other hand, CYP3A4 mRNA, protein expression and functional activity in PXR-over-expression LS174T cells were significantly increased by PD through PXR-mediated pathway; conversely, no significant change was found in the untransfected cells. CONCLUSIONS These findings suggest that PD can significantly up-regulate CYP3A4 expression and activity via the PXR-mediated pathway and this should be taken into consideration to predict any potential herb-drug interactions when PD and Peucedanum praeruptorum Dunn are co-administered with other drugs.
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Affiliation(s)
- Ling Huang
- School of Pharmaceutical Sciences, Sun Yat-sen University, 132# Waihuan Dong Road, University City, Guangzhou 510006, China
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Avoiding PXR and CAR Activation and CYP3A4 Enzyme Induction. TOPICS IN MEDICINAL CHEMISTRY 2013. [DOI: 10.1007/7355_2013_24] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Ogawa T, Kumagai N, Shibasaki M. Catalytic Asymmetric Conjugate Addition of Thiols to α,β‐Unsaturated Thioamides: Expeditious Access to Enantioenriched 1,5‐Benzothiazepines. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201204365] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Takanori Ogawa
- Institute of Microbial Chemistry, Tokyo, 3‐14‐23 Kamiosaki, Shinagawa‐ku, Tokyo 141‐0021 (Japan) http://www.bikaken.or.jp/research/group/shibasaki/shibasaki‐lab/index_e.html
| | - Naoya Kumagai
- Institute of Microbial Chemistry, Tokyo, 3‐14‐23 Kamiosaki, Shinagawa‐ku, Tokyo 141‐0021 (Japan) http://www.bikaken.or.jp/research/group/shibasaki/shibasaki‐lab/index_e.html
| | - Masakatsu Shibasaki
- Institute of Microbial Chemistry, Tokyo, 3‐14‐23 Kamiosaki, Shinagawa‐ku, Tokyo 141‐0021 (Japan) http://www.bikaken.or.jp/research/group/shibasaki/shibasaki‐lab/index_e.html
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Ogawa T, Kumagai N, Shibasaki M. Catalytic Asymmetric Conjugate Addition of Thiols to α,β‐Unsaturated Thioamides: Expeditious Access to Enantioenriched 1,5‐Benzothiazepines. Angew Chem Int Ed Engl 2012; 51:8551-4. [DOI: 10.1002/anie.201204365] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Indexed: 11/12/2022]
Affiliation(s)
- Takanori Ogawa
- Institute of Microbial Chemistry, Tokyo, 3‐14‐23 Kamiosaki, Shinagawa‐ku, Tokyo 141‐0021 (Japan) http://www.bikaken.or.jp/research/group/shibasaki/shibasaki‐lab/index_e.html
| | - Naoya Kumagai
- Institute of Microbial Chemistry, Tokyo, 3‐14‐23 Kamiosaki, Shinagawa‐ku, Tokyo 141‐0021 (Japan) http://www.bikaken.or.jp/research/group/shibasaki/shibasaki‐lab/index_e.html
| | - Masakatsu Shibasaki
- Institute of Microbial Chemistry, Tokyo, 3‐14‐23 Kamiosaki, Shinagawa‐ku, Tokyo 141‐0021 (Japan) http://www.bikaken.or.jp/research/group/shibasaki/shibasaki‐lab/index_e.html
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Ramel F, Sulmon C, Serra AA, Gouesbet G, Couée I. Xenobiotic sensing and signalling in higher plants. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:3999-4014. [PMID: 22493519 DOI: 10.1093/jxb/ers102] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Anthropogenic changes and chemical pollution confront plant communities with various xenobiotic compounds or combinations of xenobiotics, involving chemical structures that are at least partially novel for plant species. Plant responses to chemical challenges and stimuli are usually characterized by the approaches of toxicology, ecotoxicology, and stress physiology. Development of transcriptomics and proteomics analysis has demonstrated the importance of modifications to gene expression in plant responses to xenobiotics. It has emerged that xenobiotic effects could involve not only biochemical and physiological disruption, but also the disruption of signalling pathways. Moreover, mutations affecting sensing and signalling pathways result in modifications of responses to xenobiotics, thus confirming interference or crosstalk between xenobiotic effects and signalling pathways. Some of these changes at gene expression, regulation and signalling levels suggest various mechanisms of xenobiotic sensing in higher plants, in accordance with xenobiotic-sensing mechanisms that have been characterized in other phyla (yeast, invertebrates, vertebrates). In higher plants, such sensing systems are difficult to identify, even though different lines of evidence, involving mutant studies, transcription factor analysis, or comparative studies, point to their existence. It remains difficult to distinguish between the hypothesis of direct xenobiotic sensing and indirect sensing of xenobiotic-related modifications. However, future characterization of xenobiotic sensing and signalling in higher plants is likely to be a key element for determining the tolerance and remediation capacities of plant species. This characterization will also be of interest for understanding evolutionary dynamics of stress adaptation and mechanisms of adaptation to novel stressors.
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Affiliation(s)
- Fanny Ramel
- Université de Rennes 1, Centre National de la Recherche Scientifique, UMR 6553 ECOBIO, Campus de Beaulieu, bâtiment 14A, F-35042 Rennes Cedex, France
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Abass K, Lämsä V, Reponen P, Küblbeck J, Honkakoski P, Mattila S, Pelkonen O, Hakkola J. Characterization of human cytochrome P450 induction by pesticides. Toxicology 2012; 294:17-26. [DOI: 10.1016/j.tox.2012.01.010] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 01/17/2012] [Accepted: 01/19/2012] [Indexed: 01/25/2023]
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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] [MESH Headings] [Grants] [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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