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Ozcagli E, Kubickova B, Jacobs MN. Addressing chemically-induced obesogenic metabolic disruption: selection of chemicals for in vitro human PPARα, PPARγ transactivation, and adipogenesis test methods. Front Endocrinol (Lausanne) 2024; 15:1401120. [PMID: 39040675 PMCID: PMC11260640 DOI: 10.3389/fendo.2024.1401120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Accepted: 06/10/2024] [Indexed: 07/24/2024] Open
Abstract
Whilst western diet and sedentary lifestyles heavily contribute to the global obesity epidemic, it is likely that chemical exposure may also contribute. A substantial body of literature implicates a variety of suspected environmental chemicals in metabolic disruption and obesogenic mechanisms. Chemically induced obesogenic metabolic disruption is not yet considered in regulatory testing paradigms or regulations, but this is an internationally recognised human health regulatory development need. An early step in the development of relevant regulatory test methods is to derive appropriate minimum chemical selection lists for the target endpoint and its key mechanisms, such that the test method can be suitably optimised and validated. Independently collated and reviewed reference and proficiency chemicals relevant for the regulatory chemical universe that they are intended to serve, assist regulatory test method development and validation, particularly in relation to the OECD Test Guidelines Programme. To address obesogenic mechanisms and modes of action for chemical hazard assessment, key initiating mechanisms include molecular-level Peroxisome Proliferator-Activated Receptor (PPAR) α and γ agonism and the tissue/organ-level key event of perturbation of the adipogenesis process that may lead to excess white adipose tissue. Here we present a critical literature review, analysis and evaluation of chemicals suitable for the development, optimisation and validation of human PPARα and PPARγ agonism and human white adipose tissue adipogenesis test methods. The chemical lists have been derived with consideration of essential criteria needed for understanding the strengths and limitations of the test methods. With a weight of evidence approach, this has been combined with practical and applied aspects required for the integration and combination of relevant candidate test methods into test batteries, as part of an Integrated Approach to Testing and Assessment for metabolic disruption. The proposed proficiency and reference chemical list includes a long list of negatives and positives (20 chemicals for PPARα, 21 for PPARγ, and 11 for adipogenesis) from which a (pre-)validation proficiency chemicals list has been derived.
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Li Y, Lin W, Chai SC, Wu J, Annu K, Chen T. Design and Optimization of 1 H-1,2,3-Triazole-4-carboxamides as Novel, Potent, and Selective Inverse Agonists and Antagonists of PXR. J Med Chem 2022; 65:16829-16859. [PMID: 36480704 PMCID: PMC9789209 DOI: 10.1021/acs.jmedchem.2c01640] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The pregnane X receptor (PXR) is a key regulator of drug metabolism. Many drugs bind to and activate PXR, causing adverse drug responses. This suggests that PXR inhibitors have therapeutic value, but potent PXR inhibitors have so far been lacking. Herein, we report the structural optimization of a series of 1H-1,2,3-triazole-4-carboxamides compounds that led to the discovery of compound 85 as a selective and the most potent inverse agonist and antagonist of PXR, with low nanomolar IC50 values for binding and cellular activity. Importantly, compound 89, a close analog of 85, is a selective and pure antagonist with low nanomolar IC50 values for binding and cellular activity. This study has provided novel, selective, and most potent PXR inhibitors (a dual inverse agonist/antagonist and a pure antagonist) for use in basic research and future clinical studies and also shed light on how to reduce the binding affinity of a compound to PXR.
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Affiliation(s)
- Yongtao Li
- Department of Chemical Biology and Therapeutics, St. Jude Children’s Research Hospital, Memphis, TN, 38105, USA
| | - Wenwei Lin
- Department of Chemical Biology and Therapeutics, St. Jude Children’s Research Hospital, Memphis, TN, 38105, USA
| | - Sergio C. Chai
- Department of Chemical Biology and Therapeutics, St. Jude Children’s Research Hospital, Memphis, TN, 38105, USA
| | - Jing Wu
- Department of Chemical Biology and Therapeutics, St. Jude Children’s Research Hospital, Memphis, TN, 38105, USA
| | - Kavya Annu
- Department of Chemical Biology and Therapeutics, St. Jude Children’s Research Hospital, Memphis, TN, 38105, USA
| | - Taosheng Chen
- Department of Chemical Biology and Therapeutics, St. Jude Children’s Research Hospital, Memphis, TN, 38105, USA
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3
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Interactions governing transcriptional activity of nuclear receptors. Biochem Soc Trans 2022; 50:1941-1952. [DOI: 10.1042/bst20220338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 11/29/2022] [Accepted: 12/01/2022] [Indexed: 12/23/2022]
Abstract
The key players in transcriptional regulation are transcription factors (TFs), proteins that bind specific DNA sequences. Several mechanisms exist to turn TFs ‘on’ and ‘off’, including ligand binding which induces conformational changes within TFs, subsequently influencing multiple inter- and intramolecular interactions to drive transcriptional responses. Nuclear receptors are a specific family of ligand-regulated TFs whose activity relies on interactions with DNA, coregulator proteins and other receptors. These multidomain proteins also undergo interdomain interactions on multiple levels, further modulating transcriptional outputs. Cooperation between these distinct interactions is critical for appropriate transcription and remains an intense area of investigation. In this review, we report and summarize recent findings that continue to advance our mechanistic understanding of how interactions between nuclear receptors and diverse partners influence transcription.
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Haque N, Tischkau SA. Sexual Dimorphism in Adipose-Hypothalamic Crosstalk and the Contribution of Aryl Hydrocarbon Receptor to Regulate Energy Homeostasis. Int J Mol Sci 2022; 23:ijms23147679. [PMID: 35887027 PMCID: PMC9322714 DOI: 10.3390/ijms23147679] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 07/08/2022] [Accepted: 07/09/2022] [Indexed: 11/16/2022] Open
Abstract
There are fundamental sex differences in the regulation of energy homeostasis. Better understanding of the underlying mechanisms of energy balance that account for this asymmetry will assist in developing sex-specific therapies for sexually dimorphic diseases such as obesity. Multiple organs, including the hypothalamus and adipose tissue, play vital roles in the regulation of energy homeostasis, which are regulated differently in males and females. Various neuronal populations, particularly within the hypothalamus, such as arcuate nucleus (ARC), can sense nutrient content of the body by the help of peripheral hormones such leptin, derived from adipocytes, to regulate energy homeostasis. This review summarizes how adipose tissue crosstalk with homeostatic network control systems in the brain, which includes energy regulatory regions and the hypothalamic–pituitary axis, contribute to energy regulation in a sex-specific manner. Moreover, development of obesity is contingent upon diet and environmental factors. Substances from diet and environmental contaminants can exert insidious effects on energy metabolism, acting peripherally through the aryl hydrocarbon receptor (AhR). Developmental AhR activation can impart permanent alterations of neuronal development that can manifest a number of sex-specific physiological changes, which sometimes become evident only in adulthood. AhR is currently being investigated as a potential target for treating obesity. The consensus is that impaired function of the receptor protects from obesity in mice. AhR also modulates sex steroid receptors, and hence, one of the objectives of this review is to explain why investigating sex differences while examining this receptor is crucial. Overall, this review summarizes sex differences in the regulation of energy homeostasis imparted by the adipose–hypothalamic axis and examines how this axis can be affected by xenobiotics that signal through AhR.
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Affiliation(s)
- Nazmul Haque
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL 62702, USA;
| | - Shelley A. Tischkau
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL 62702, USA;
- Department of Medical Microbiology, Immunology and Cell Biology, Southern Illinois University School of Medicine, Springfield, IL 62702, USA
- Correspondence:
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5
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Chen K, Zhong J, Hu L, Li R, Du Q, Cai J, Li Y, Gao Y, Cui X, Yang X, Wu X, Yao L, Dai J, Wang Y, Jin H. The Role of Xenobiotic Receptors on Hepatic Glycolipid Metabolism. Curr Drug Metab 2019; 20:29-35. [PMID: 30227815 DOI: 10.2174/1389200219666180918152241] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 03/13/2018] [Accepted: 08/20/2018] [Indexed: 01/14/2023]
Abstract
Background:
PXR (Pregnane X Receptor) and CAR (Constitutive Androstane Receptor) are termed as
xenobiotic receptors, which are known as core factors in regulation of the transcription of metabolic enzymes and
drug transporters. However, accumulating evidence has shown that PXR and CAR exert their effects on energy metabolism
through the regulation of gluconeogenesis, lipogenesis and β-oxidation. Therefore, in this review, we are
trying to summary recent advances to show how xenobiotic receptors regulate energy metabolism.
Methods:
A structured search of databases has been performed by using focused review topics. According to conceptual
framework, the main idea of research literature was summarized and presented.
Results:
For introduction of each receptor, the general introduction and the critical functions in hepatic glucose and
lipid metabolism have been included. Recent important studies have shown that CAR acts as a negative regulator of
lipogenesis, gluconeogenesis and β -oxidation. PXR activation induces lipogenesis, inhibits gluconeogenesis and
inhabits β-oxidation.
Conclusion:
In this review, the importance of xenobiotic receptors in hepatic glucose and lipid metabolism has been
confirmed. Therefore, PXR and CAR may become new therapeutic targets for metabolic syndrome, including obesity
and diabetes. However, further research is required to promote the clinical application of this new energy metabolism
function of xenobiotic receptors.
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Affiliation(s)
- Ke Chen
- Department of Hepatobiliary Surgery, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Jinwei Zhong
- Department of Gastroenterology, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Lin Hu
- Pi-wei Institute, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Ruliu Li
- Pi-wei Institute, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Qun Du
- Pi-wei Institute, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Jiazhong Cai
- Pi-wei Institute, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Yanwu Li
- Pi-wei Institute, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Yong Gao
- Pi-wei Institute, Guangzhou University of Chinese Medicine, Guangzhou, China
| | - Xiaona Cui
- Department of Pathogenic Biology and Immunology, Jiangsu Key Laboratory of Immunity and Metabolism, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Xiaoying Yang
- Department of Pathogenic Biology and Immunology, Jiangsu Key Laboratory of Immunity and Metabolism, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Xiaojie Wu
- Department of Immunology, Binzhou Medical University, Yantai, Shangdong, China
| | - Lu Yao
- Jilin Medical University, Jilin, China
| | - Juji Dai
- School of Basic Medical Sciences, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Yan Wang
- Department of Otolaryngology, The Second Affiliated Hospital & Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Haiyong Jin
- Department of Otolaryngology, The Second Affiliated Hospital & Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
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Liu H, Tang S, Zheng X, Zhu Y, Ma Z, Liu C, Hecker M, Saunders DMV, Giesy JP, Zhang X, Yu H. Bioaccumulation, biotransformation, and toxicity of BDE-47, 6-OH-BDE-47, and 6-MeO-BDE-47 in early life-stages of zebrafish (Danio rerio). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:1823-33. [PMID: 25565004 DOI: 10.1021/es503833q] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
2,2',4,4'-Tetrabromodiphenyl ether (BDE-47), 6-hydroxy-tetrabromodiphenyl ether (6-OH-BDE-47), and 6-methoxy-tetrabromodiphenyl ether (6-MeO-BDE-47) are the most detected congeners of polybrominated diphenyl ethers (PBDEs), OH-BDEs, and MeO-BDEs, respectively, in aquatic organisms. Although it has been demonstrated that BDE-47 can interfere with certain endocrine functions that are mediated through several nuclear hormone receptors (NRs), most of these findings were from mammalian cell lines exposed in vitro. In the present study, embryos and larvae of zebrafish were exposed to BDE-47, 6-OH-BDE-47, and 6-MeO-BDE-47 to compare their accumulation, biotransformation, and bioconcentration factors (BCF) from 4 to 120 hpf. In addition, effects on expression of genes associated with eight different pathways regulated by NRs were investigated at 120 hpf. 6-MeO-BDE-47 was most bioaccumulated and 6-OH-BDE-47, which was the most potent BDE, was least bioaccumulated. Moreover, the amount of 6-MeO-BDE-47, but not BDE-47, transformed to 6-OH-BDE-47 increased in a time-dependent manner, approximately 0.01%, 0.04%, and 0.08% at 48, 96, and 120 hpf, respectively. Expression of genes regulated by the aryl hydrocarbon receptor (AhR), estrogen receptor (ER), and mineralocorticoid receptor (MR) was affected in larvae exposed to 6-OH-BDE-47, whereas genes regulated by AhR, ER, and the glucocorticoid receptor (GR) were altered in larvae exposed to BDE-47. The greatest effect on expression of genes was observed in larvae exposed to 6-MeO-BDE-47. Specifically, 6-MeO-BDE-47 affected the expression of genes regulated by AhR, ER, AR, GR, and thyroid hormone receptor alpha (TRα). These pathways were mostly down-regulated at 2.5 μM. Taken together, these results demonstrate the importance of usage of an internal dose to assess the toxic effects of PBDEs. BDE-47 and its analogs elicited distinct effects on expression of genes of different hormone receptor-mediated pathways, which have expanded the knowledge of different mechanisms of endocrine disrupting effects in aquatic vertebrates. Because some of these homologues are natural products, assessments of risks of anthropogenic PBDE need to be made against the background of concentrations from naturally occurring products. Even though PBDEs are being phased out as flame retardants, the natural products remain.
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MESH Headings
- Animals
- Anisoles/pharmacokinetics
- Anisoles/toxicity
- Biotransformation
- Embryo, Nonmammalian/drug effects
- Embryo, Nonmammalian/metabolism
- Endocrine Disruptors/pharmacokinetics
- Endocrine Disruptors/toxicity
- Flame Retardants/pharmacokinetics
- Flame Retardants/toxicity
- Gene Expression Regulation, Developmental/drug effects
- Halogenated Diphenyl Ethers/pharmacokinetics
- Halogenated Diphenyl Ethers/toxicity
- Larva/drug effects
- Larva/genetics
- Larva/metabolism
- Polybrominated Biphenyls/pharmacokinetics
- Polybrominated Biphenyls/toxicity
- Receptors, Androgen/genetics
- Receptors, Aryl Hydrocarbon/genetics
- Receptors, Estrogen/genetics
- Receptors, Glucocorticoid/genetics
- Receptors, Mineralocorticoid/genetics
- Receptors, Thyroid Hormone/genetics
- Water Pollutants, Chemical/pharmacokinetics
- Water Pollutants, Chemical/toxicity
- Zebrafish/embryology
- Zebrafish/genetics
- Zebrafish/metabolism
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Affiliation(s)
- Hongling Liu
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing, Jiangsu 210023, China
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7
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Muriach B, Carrillo M, Zanuy S, Cerdá-Reverter JM. Characterization of sea bass FSHβ 5' flanking region: transcriptional control by 17β-estradiol. FISH PHYSIOLOGY AND BIOCHEMISTRY 2014; 40:849-864. [PMID: 24271878 DOI: 10.1007/s10695-013-9891-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 11/13/2013] [Indexed: 06/02/2023]
Abstract
The sea bass follicle-stimulating hormone 5' flanking region (sbFSHβ 5' FR) was cloned and characterized in order to study the molecular mechanisms underlying transcriptional regulation of the sbFSHβ gene. Analysis of the ~3.5 kb of this region revealed the presence of several putative cis-acting elements, including steroid hormone response elements, cAMP response elements, pituitary-specific transcription factor response elements, activator protein-1 response elements and TATA sequence. Deleted constructs containing ~3.5 kb of the sbFSHβ 5' FR fused to a luciferase reporter gene were transiently transfected into human embryonic kidney (HEK 293) and mouse mature gonadotrope (LβT2) cell lines. The sbFSHβ 5' FR was efficiently expressed under basal conditions in LβT2 but not in HEK 293, pointing to both positive and negative regulatory elements. In order to elucidate the estrogen-mediated sbFSHβ transcriptional activity, in vitro treatments with 17β-estradiol were carried out on primary cultures of pituitary cells and LβT2 cells transiently expressing luciferase under the control of sbFSHβ 5' FR. Overall, these results demonstrate that 17β-estradiol inhibits sbFSHβ gene expression directly at the level of the pituitary. However, it was also shown that estrogen did not induce changes of the sbFSH promoter-directed luciferase activity, suggesting that sbFSHβ 5'FR (~3.5 kb) activity is cell type dependent and its estrogen regulation could require cis-acting elements located upstream of the promoter region, which is characterized in this article.
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Affiliation(s)
- Borja Muriach
- Department of Fish Physiology and Biotechnology, Instituto de Acuicultura de Torre de la Sal (IATS), CSIC, Torre de la Sal, 12595 Ribera de Cabanes, Castellón, Spain
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8
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Abstract
The pregnane X receptor (PXR) and constitutive androstane receptor (CAR), 2 closely related and liver-enriched members of the nuclear receptor superfamily, and aryl hydrocarbon receptor (AhR), a nonnuclear receptor transcription factor (TF), are major receptors/TFs regulating the expression of genes for the clearance and detoxification of xenobiotics. They are hence defined as "xenobiotic receptors". Recent studies have demonstrated that PXR, CAR and AhR also regulate the expression of key proteins involved in endobiotic responses such as the metabolic homeostasis of lipids, glucose, and bile acid, and inflammatory processes. It is suggested that the functions of PXR, CAR and AhR may be closely implicated in the pathogeneses of metabolic vascular diseases, such as hyperlipidemia, atherogenesis, and hypertension. Therefore, manipulation of the activities of these receptors may provide novel strategies for the treatment of vascular diseases. Here, we review the pathophysiological roles of PXR, CAR and AhR in the vascular system.
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Affiliation(s)
- Lei Xiao
- Cardiovascular Research Center, School of Medicine, Xi'an Jiaotong University
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9
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Šíma M, Netíková I, Slanař O. Pregnane xenobiotic receptors and their effect on drug elimination from the organism. Prague Med Rep 2014; 114:205-13. [PMID: 24485337 DOI: 10.14712/23362936.2014.9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Nuclear receptors are intracellular proteins which, having been activated by their more or less specific ligands, regulate (usually increase) the transcription of target genes. They thus participate in a regulation of a number of physiologic functions. Some of them - especially pregnane xenobiotic receptors - serve primarily as protection of the organism from the xenobiotic intoxication. This is because many xenobiotics activate their function which consists in increasing the gene expression of enzymes involved in the metabolism of xenobiotics and detoxication drug transporters. Clarification of these mechanisms enabled the understanding of the substance of many drug-drug interactions observed in the clinical practice. Polymorphism of the nuclear receptors appears to be one of the causes of the interindividual variability in response to drug administration.
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Affiliation(s)
- M Šíma
- Institute of Pharmacology, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | - I Netíková
- Institute of Pharmacology, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | - O Slanař
- Institute of Pharmacology, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech RepublicInstitute of Pharmacology, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
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10
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Long M, Ghisari M, Bonefeld-Jørgensen EC. Effects of perfluoroalkyl acids on the function of the thyroid hormone and the aryl hydrocarbon receptor. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2013; 20:8045-56. [PMID: 23539207 DOI: 10.1007/s11356-013-1628-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Accepted: 03/11/2013] [Indexed: 05/03/2023]
Abstract
Perfluoroalkyl acids (PFAAs) are perfluorinated compounds that widely exist in the environment and can elicit adverse effects including endocrine disruption in humans and animals. This study investigated the effect of seven PFAAs on the thyroid hormone (TH) system assessing the proliferation of the 3,3',5-triiodo-L-thryonine (T3)-dependent rat pituitary GH3 cells using the T-screen assay and the effect on the aryl hydrocarbon receptor (AhR) transactivation in the AhR-luciferase reporter gene bioassay. A dose-dependent impact on GH3 cells was observed in the range 1×10(-9)-1×10(-4) M: seven PFAAs (perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), perfluorooctanoic acid, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnA), and perfluorododecanoic acid (PFDoA)) inhibited the GH3 cell growth, and four PFAAs (PFOS, PFHxS, PFNA, and PFUnA) antagonized the T3-induced GH3 cell proliferation. At the highest test concentration, PFHxS showed a further increase of the T3-induced GH3 growth. Among the seven tested PFAAs, only PFDoA and PFDA elicited an activating effect on the AhR. In conclusion, PFAAs possess in vitro endocrine-disrupting potential by interfering with TH and AhR functions, which need to be taken into consideration when assessing the impact on human health.
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Affiliation(s)
- Manhai Long
- Centre for Arctic Health and Unit of Cellular and Molecular Toxicology, Department of Public Health, Aarhus University, Bartholins Alle 2, Building 1260, 8000, Aarhus C, Denmark,
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11
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Scientific Opinion on the hazard assessment of endocrine disruptors: Scientific criteria for identification of endocrine disruptors and appropriateness of existing test methods for assessing effects mediated by these substances on human health and the environment. EFSA J 2013. [DOI: 10.2903/j.efsa.2013.3132] [Citation(s) in RCA: 154] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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12
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Long M, Krüger T, Ghisari M, Bonefeld-Jørgensen EC. Effects of selected phytoestrogens and their mixtures on the function of the thyroid hormone and the aryl hydrocarbon receptor. Nutr Cancer 2012; 64:1008-19. [PMID: 22966911 DOI: 10.1080/01635581.2012.711419] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Phytoestrogens (PEs) are natural plant components, which can induce biologic responses in vertebrates by mimicking or blocking the actions of natural hormones or influencing the hormone production in the body. This study investigated the effect of different mixtures composed of food-relevant PEs on the thyroid hormone (TH) system assessing the proliferation of the 3,3',5-triiodi-L-thryonine (T3) dependent rat pituitary GH3 cells using the T-screen assay, and the effect on the aryl hydrocarbon receptor (AhR) transactivation using an AhR-luciferase reporter gene assay. Most tested PEs and their mixtures showed effect on both the TH and AhR system. Single isoflavonoid metabolites and their mixture and coumestrol induced GH3 cell growth and AhR transactivity dose-dependently. Isoflavonoid metabolites elicited an additive effect on the T3-dependent GH3 cell growth, and a synergistic effect on the AhR transactivity. In conclusion, nutrition-relevant PEs, alone and in mixture may possess endocrine-disrupting potential by interfering with TH and AhR functions, which need to be considered when assessing the effects on human health.
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Affiliation(s)
- Manhai Long
- Centre for Arctic Health & Unit of Cellular and Molecular Toxicology, Department of Public Health, Aarhus University, Aarhus, Denmark.
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13
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Development of in silico filters to predict activation of the pregnane X receptor (PXR) by structurally diverse drug-like molecules. Bioorg Med Chem 2012; 20:5352-65. [PMID: 22560839 DOI: 10.1016/j.bmc.2012.04.020] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Revised: 03/28/2012] [Accepted: 04/07/2012] [Indexed: 01/22/2023]
Abstract
The pregnane X receptor (PXR), a member of the nuclear hormone superfamily, regulates the expression of several enzymes and transporters involved in metabolically relevant processes. The significant induction of CYP450 enzymes by PXR, in particular CYP3A4, might significantly alter the metabolism of prescribed drugs. In order to early identify molecules in drug discovery with a potential to activate PXR as antitarget, we developed fast and reliable in silico filters by ligand-based QSAR techniques. Two classification models were established on a diverse dataset of 434 drug-like molecules. A second augmented set allowed focusing on interesting regions in chemical space. These classifiers are based on decision trees combined with a genetic algorithm based variable selection to arrive at predictive models. The classifier for the first dataset on 29 descriptors showed good performance on a test set with a correct classification of both 100% for PXR activators and non-activators plus 87% for activators and 83% for non-activators in an external dataset. The second classifier then correctly predicts 97% activators and 91% non-activators in a test set and 94% for activators and 64% non-activators in an external set of 50 molecules, which still qualifies for application as a filter focusing on PXR activators. Finally a quantitative model for PXR activation for a subset of these molecules was derived using a regression-tree approach combined with GA variable selection. This final model shows a predictive r(2) of 0.774 for the test set and 0.452 for an external set of 33 molecules. Thus, the combination of these filters consistently provide guidelines for lowering PXR activation in novel candidate molecules.
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14
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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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Ribecco C, Baker ME, Šášik R, Zuo Y, Hardiman G, Carnevali O. Biological effects of marine contaminated sediments on Sparus aurata juveniles. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2011; 104:308-316. [PMID: 21658360 DOI: 10.1016/j.aquatox.2011.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Revised: 04/28/2011] [Accepted: 05/07/2011] [Indexed: 05/30/2023]
Abstract
Chemical analysis of the compounds present in sediment, although informative, often is not indicative of the downstream biological effects that these contaminants exert on resident aquatic organisms. More direct molecular methods are needed to determine if marine life is affected by exposure to sediments. In this study, we used an aquatic multi-species microarray and q-PCR to investigate the effects on gene expression in juvenile sea bream (Sparus aurata) of two contaminated sediments defined as sediment 1 and 2, respectively, from marine areas in Northern Italy. Both sediments affected gene expression as evidenced by aquatic multi-species microarray analysis and q-PCR. Exposure of S. aurata juveniles to sediment 1 and sediment 2 altered expression of genes that are biomarkers for endocrine disruption. There were differences between the effects of sediment 1 and sediment 2 on gene expression in S. aurata juveniles indicating that the chemicals in the two sediments had different physiological targets. These results suggest that the classification of sediment solely on the basis of specific chemical profiles is inadequate, and not a true indicator of its potential to cause harmful effects. Our data also indicate that integration of physiochemical analysis and bioassays for monitoring the downstream harmful effects on aquatic organisms are required to gain a complete understanding of the effects of sediment on aquatic life.
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Affiliation(s)
- C Ribecco
- Dipartimento di Scienze del Mare, Università Politecnica delle Marche, 60131 Ancona, Italy
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16
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Jogalekar AS, Reiling S, Vaz RJ. Identification of optimum computational protocols for modeling the aryl hydrocarbon receptor (AHR) and its interaction with ligands. Bioorg Med Chem Lett 2010; 20:6616-9. [DOI: 10.1016/j.bmcl.2010.09.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Revised: 09/02/2010] [Accepted: 09/07/2010] [Indexed: 10/19/2022]
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17
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Yoshikawa E, Miyagi S, Dedachi K, Ishihara-Sugano M, Itoh S, Kurita N. Specific interactions between aryl hydrocarbon receptor and dioxin congeners: Ab initio fragment molecular orbital calculations. J Mol Graph Model 2010; 29:197-205. [DOI: 10.1016/j.jmgm.2010.06.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2010] [Revised: 06/16/2010] [Accepted: 06/17/2010] [Indexed: 11/30/2022]
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18
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Boobis A, Watelet JB, Whomsley R, Benedetti MS, Demoly P, Tipton K. Drug interactions. Drug Metab Rev 2009; 41:486-527. [PMID: 19601724 DOI: 10.1080/10837450902891550] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Drugs for allergy are often taken in combination with other drugs, either to treat allergy or other conditions. In common with many pharmaceuticals, most such drugs are subject to metabolism by P450 enzymes and to transmembrane transport. This gives rise to considerable potential for drug-drug interactions, to which must be added consideration of drug-diet interactions. The potential for metabolism-based drug interactions is increasingly being taken into account during drug development, using a variety of in silico and in vitro approaches. Prediction of transporter-based interactions is not as advanced. The clinical importance of a drug interaction will depend upon a number of factors, and it is important to address concerns quantitatively, taking into account the therapeutic index of the compound.
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Affiliation(s)
- Alan Boobis
- Department of Experimental Medicine and Toxicology, Division of Medicine, Imperial College London, Hammersmith Campus, London.
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19
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Shukla SJ, Nguyen DT, Macarthur R, Simeonov A, Frazee WJ, Hallis TM, Marks BD, Singh U, Eliason HC, Printen J, Austin CP, Inglese J, Auld DS. Identification of pregnane X receptor ligands using time-resolved fluorescence resonance energy transfer and quantitative high-throughput screening. Assay Drug Dev Technol 2009; 7:143-69. [PMID: 19505231 DOI: 10.1089/adt.2009.193] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The human pregnane X nuclear receptor (PXR) is a xenobiotic-regulated receptor that is activated by a range of diverse chemicals, including antibiotics, antifungals, glucocorticoids, and herbal extracts. PXR has been characterized as an important receptor in the metabolism of xenobiotics due to induction of cytochrome P450 isozymes and activation by a large number of prescribed medications. Developing methodologies that can efficiently detect PXR ligands will be clinically beneficial to avoid potential drug-drug interactions. To facilitate the identification of PXR ligands, a time-resolved fluorescence resonance energy transfer (TR-FRET) assay was miniaturized to a 1,536-well microtiter plate format to employ quantitative high-throughput screening (qHTS). The optimized 1,536-well TR-FRET assay showed Z'-factors of >or=0.5. Seven- to 15-point concentration-response curves (CRCs) were generated for 8,280 compounds using both terbium and fluorescein emission data, resulting in the generation of 241,664 data points. The qHTS method allowed us to retrospectively examine single concentration screening datasets to assess the sensitivity and selectivity of the PXR assay at different compound screening concentrations. Furthermore, nonspecific assay artifacts such as concentration-based quenching of the terbium signal and compound fluorescence were identified through the examination of CRCs for specific emission channels. The CRC information was also used to define chemotypes associated with PXR ligands. This study demonstrates the feasibility of profiling thousands of compounds against PXR using the TR-FRET assay in a high-throughput format.
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Affiliation(s)
- Sunita J Shukla
- NIH Chemical Genomics Center, National Institutes of Health, Bethesda, Maryland, USA
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20
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Characterization of the region of the aryl hydrocarbon receptor required for ligand dependency of transactivation using chimeric receptor between Drosophila and Mus musculus. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2009; 1789:477-86. [PMID: 19560568 DOI: 10.1016/j.bbagrm.2009.06.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Revised: 06/17/2009] [Accepted: 06/17/2009] [Indexed: 02/08/2023]
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-activated transcriptional factor. Although 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is high affinity and toxic to many vertebrate animals, invertebrate AhRs including Drosophila melanogaster AhR (spineless) have no ability to bind exogenous chemicals as ligands. To analyze the ligand-binding domain (LBD) of AhR, we used chimeras between mouse and Drosophila AhR. The chimeric AhR revealed that the LBD determines constitutive transactivation in Drosophila AhR or ligand-dependent activation in mouse AhR. The LBD was further divided into three blocks that corresponded to amino acids 230-300, 301-361, and 361-420 of the mouse sequence. Six chimeric proteins clarified that amino acids 291-350 of the Drosophila LBD, i.e. the middle region, were required to keep the protein in the active form in the absence of ligand binding, whereas in the mouse AhR, this region was required to maintain the protein in the inactive form in the absence of ligand. Furthermore, Arg346 in the middle region of the mouse LBD, was identified as amino acids that were critical for AhR activation by site-directed mutagenesis.
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21
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Hosohata K, Masuda S, Yonezawa A, Katsura T, Oike F, Ogura Y, Takada Y, Egawa H, Uemoto S, Inui KI. MDR1 haplotypes conferring an increased expression of intestinal CYP3A4 rather than MDR1 in female living-donor liver transplant patients. Pharm Res 2009; 26:1590-5. [PMID: 19267185 DOI: 10.1007/s11095-009-9867-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2008] [Accepted: 02/26/2009] [Indexed: 01/11/2023]
Abstract
PURPOSE This study investigated whether haplotypes in the multidrug resistance 1 (MDR1) gene had effects on mRNA expression levels of MDR1 and cytochrome P450 (CYP) 3A4, and on the pharmacokinetics of tacrolimus in living-donor liver transplant (LDLT) patients, considering the gender difference. METHODS Haplotype analysis of MDR1 with G2677T/A and C3435T was performed in 63 de novo Japanese LDLT patients (17 to 55 years; 44.4% women). The expression levels of MDR1 and CYP3A4 mRNAs in jejunal biopsy specimens were quantified by real-time PCR. RESULTS Intestinal CYP3A4 mRNA expression levels (amol/microg total RNA) showed significantly higher values in women carrying the 2677TT-3435TT haplotype (median, 10.7; range, 5.92-15.2) than those with 2677GG-3435CC (3.03; range 1.38-4.68) and 2677GT-3435CT (median, 4.31; range, 0.07-9.42) (P = 0.022), but not in men (P = 0.81). However, MDR1 haplotype did not influence mRNA expression levels of MDR1 nor the concentration/dose ratio [(ng/mL)/(mg/day)] of oral tacrolimus for the postoperative 7 days, irrespective of gender. CONCLUSION MDR1 haplotype may have a minor association with the tacrolimus pharmacokinetics after LDLT, but could be a good predictor of the inter-individual variation of intestinal expression of CYP3A4 in women.
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Affiliation(s)
- Keiko Hosohata
- Department of Pharmacy, Kyoto University Hospital, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
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22
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Piña B, Boronat S, Casado M, Olivares A. Recombinant Yeast Assays and Gene Expression Assays for the Analysis of Endocrine Disruption. THE HANDBOOK OF ENVIRONMENTAL CHEMISTRY 2009. [DOI: 10.1007/978-3-540-36253-1_4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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23
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A comparison of the effects of soya isoflavonoids and fish oil on cell proliferation, apoptosis and the expression of oestrogen receptors alpha and beta in the mammary gland and colon of the rat. Br J Nutr 2008; 102:29-36. [PMID: 19079816 DOI: 10.1017/s0007114508137862] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Isoflavonoids and fish oil may be protective against colorectal cancer, but the evidence in relation to breast cancer risk is ambiguous. In the present study, we have investigated the impact of soya-derived isoflavonoids and n-3 fatty acids from fish oil, both individually and in combination, on apoptosis, cell proliferation and oestrogen receptor (ER) expression in the colon and mammary gland of the rat. Female rats were fed diets high in n-3 fatty acids (80 g/kg diet) or soya protein (765 mg/kg diet isoflavones) for 2 weeks, and then killed before the removal of the colon and mammary glands. Cell proliferation and apoptosis were quantified morphologically in whole crypts and terminal end buds. The expressions of ERalpha and ERbeta were measured in colon tissue scrapes and the mammary gland. Fish oil significantly increased apoptosis and decreased mitosis in both tissues, an effect associated with a decrease in the expressions of ERalpha and ERbeta. Soya had no effect on apoptosis in either tissue, but reduced mitosis in the colon (P < 0.001) while increasing it in the mammary gland (P = 0.001). The changes in proliferation were associated with contrasting changes in the ER expression such that fish oil significantly decreased both ERbeta and ERalpha, while soya increased ERalpha and decreased ERbeta. The results may provide a novel mechanism by which n-3 fatty acids could reduce cancer risk, but the interpretation of the results in relation to soya consumption and breast cancer risk requires further investigation.
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24
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Ma X, Idle JR, Gonzalez FJ. The pregnane X receptor: from bench to bedside. Expert Opin Drug Metab Toxicol 2008; 4:895-908. [PMID: 18624678 DOI: 10.1517/17425255.4.7.895] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND The pregnane X receptor (PXR; NR1I2), a member of the nuclear receptor superfamily, regulates the expression of metabolic enzymes and transporters involved in the response of mammals to their chemical environment. OBJECTIVE To summarize the functions and clinical implications of PXR. METHODS In the current review, the clinical implications of PXR are discussed, and the use of genetically engineered PXR mouse models is highlighted. RESULTS/CONCLUSION Recent advances in mouse models, including Pxr-null and PXR-humanized mice, provide in vivo tools for evaluating the physiological functions of PXR and its role in controlling xenobiotic metabolism and transport. By using the PXR knockout and humanized mouse models, PXR was found to influence drug-drug interactions, hepatic steatosis, and the homeostasis of vitamin D, bile acids, and steroid hormones. PXR was also shown to influence inflammatory bowel diseases.
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Affiliation(s)
- Xiaochao Ma
- National Cancer Institute, Laboratory of Metabolism, Center for Cancer Research, National Institutes of Health, Bethesda, MD 20892, USA
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25
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Alessandri JM, Extier A, Langelier B, Perruchot MH, Heberden C, Guesnet P, Lavialle M. Estradiol Favors the Formation of Eicosapentaenoic Acid (20:5n-3) and n-3 Docosapentaenoic Acid (22:5n-3) from Alpha-Linolenic Acid (18:3n-3) in SH-SY5Y Neuroblastoma Cells. Lipids 2007; 43:19-28. [PMID: 17912567 DOI: 10.1007/s11745-007-3117-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Accepted: 08/27/2007] [Indexed: 01/25/2023]
Abstract
Whether neurosteroids regulate the synthesis of long chain polyunsaturated fatty acids in brain cells is unknown. We examined the influence of 17-beta-estradiol (E2) on the capacity of SH-SY5Y cells supplemented with alpha-linolenic acid (ALA), to produce eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). Cells were incubated for 24 or 72 h with ALA added alone or in combination with E2 (ALA + E2). Fatty acids were analyzed by gas chromatography of ethanolamine glycerophospholipids (EtnGpl) and phosphatidylcholine (PtdCho). Incubation for 24 h with ALA alone increased EPA and DPA in EtnGpl, by 330 and 430% compared to controls (P < 0.001) and DHA by only 10% (P < 0.05). Although DHA increased by 30% (P < 0.001) in ALA + E2-treated cells, the difference between the ALA and ALA + E2 treatments were not significant after 24 h (Anova-1, Fisher's test). After 72 h, EPA, DPA and DHA further increased in EtnGpl and PtdCho of cells supplemented with ALA or ALA + E2. Incubation for 72 h with ALA + E2 specifically increased EPA (+34% in EtnGpl, P < 0.001) and DPA (+15%, P < 0.001) compared to ALA alone. Thus, SH-SY5Y cells produced membrane EPA, DPA and DHA from supplemental ALA. The formation of DHA was limited, even in the presence of E2. E2 significantly favored EPA and DPA production in cells grown for 72 h. Enhanced synthesis of ALA-elongation products in neuroblastoma cells treated with E2 supports the hypothesis that neurosteroids could modulate the metabolism of PUFA.
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Affiliation(s)
- Jean-Marc Alessandri
- Unit of Lipid Nutrition and Regulation of Brain Functions, Nu.Re.Li.Ce, INRA, Jouy-en-Josas, France.
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26
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Petersen SL, Krishnan S, Hudgens ED. The aryl hydrocarbon receptor pathway and sexual differentiation of neuroendocrine functions. Endocrinology 2006; 147:S33-42. [PMID: 16690800 DOI: 10.1210/en.2005-1157] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Historically, much of the research on health effects of environmental pollutants focused on ascertaining whether compounds were carcinogenic. More recent findings show that environmental contaminants also exert insidious effects by disrupting hormone action. Of particular concern are findings that developmental exposure to dioxins, chemicals that act through the aryl hydrocarbon receptor pathway, permanently alters sexually differentiated neural functions in animal models. In this review, we focus on mechanisms through which dioxins disrupt neuroendocrine development as exemplified by effects on a brain region critical for ovulation in rodents. We also provide evidence that dysregulation of GABAergic neural development may be a general mechanism underlying a broad spectrum of effects seen after perinatal dioxin exposure.
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Affiliation(s)
- Sandra L Petersen
- Department of Biology, University of Massachusetts-Amherst, Amherst, Massachusetts 01003 USA.
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27
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Noguerol TN, Boronat S, Casado M, Raldúa D, Barceló D, Piña B. Evaluating the interactions of vertebrate receptors with persistent pollutants and antifouling pesticides using recombinant yeast assays. Anal Bioanal Chem 2006; 385:1012-9. [PMID: 16705413 DOI: 10.1007/s00216-006-0476-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2005] [Revised: 03/31/2006] [Accepted: 04/06/2006] [Indexed: 10/24/2022]
Abstract
The development of in vitro methods for screening potentially harmful biological activities of new compounds is an extremely important way to increase not only their intrinsic environmental safety, but also the public perception of the safety standards associated with them. In this work we use two yeast systems to test the ability of different chemicals to bind and activate two vertebrate receptors which are intimately related to adverse biological effects of pollution in exposed fauna: the estrogen receptor (ER) and the aryl hydrocarbon receptor (AhR). The panel of compounds analysed here includes well-known pollutants, like PCBs, pp'-DDT and hexachlorobenzene, together with the less-known, emerging putative pollutants, such as Sea-Nine, Irgarol and diuron. Results show the ability of some of these compounds to interact with one or both receptors, provide hints about the relationship between structure and activity, and suggest mechanistic explanations for the biological activities already described in whole-animal experiments. In addition, we show that AhR may have an intrinsic ligand promiscuity comparable to that of ER, a feature not fully appreciated in the past due to the technical difficulties involved with testing highly lipophilic substances in yeast-based assays.
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Affiliation(s)
- Tania-Noelia Noguerol
- Department of Molecular Biology, Institut de Biologia Molecular de Barcelona, CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain
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28
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Windshügel B, Jyrkkärinne J, Vanamo J, Poso A, Honkakoski P, Sippl W. Comparison of homology models and X-ray structures of the nuclear receptor CAR: assessing the structural basis of constitutive activity. J Mol Graph Model 2006; 25:644-57. [PMID: 16831563 DOI: 10.1016/j.jmgm.2006.05.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2005] [Revised: 04/28/2006] [Accepted: 05/02/2006] [Indexed: 12/31/2022]
Abstract
The constitutive androstane receptor (CAR) possesses an intrinsic basal activity whose structural basis has been analysed during the last decade. Recently, we published a homology model of the CAR ligand binding domain (LBD) based on the X-ray structures of the closely related pregnane X (PXR) and vitamin D (VDR) receptor. A detailed analysis of the homology model and molecular dynamics (MD) simulations afforded us to propose a potential mechanism underlying the constitutive activity of CAR. Almost simultaneously, X-ray structures of human and mouse CAR LBD were released. In the present study, a detailed analysis and comparison of homology model and X-ray structures is carried out in order to evaluate the quality and reliability of our homology modelling procedure. The hypothesis of the constitutive activity which we proposed on the basis of our modelling results was tested for consistency with the crystal structures. In addition, the features stated to be essential for the basal activity based on the X-ray data were investigated by means of molecular dynamics simulations. Our results show that the homology modelling procedure was able to predict the CAR LBD structure with high accuracy. Structural features that have been revealed as critical for constitutive activity in the model are also observed in the X-ray structures. Furthermore, the MD simulations of the CAR X-ray structures and a detailed analysis of other NRs clarify the role of distinct structural features that have been assigned an important role for the constitutive activity.
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Affiliation(s)
- Björn Windshügel
- Institute of Pharmaceutical Chemistry, Martin-Luther-University Halle-Wittenberg, Wolfgang-Langenbeck-Str. 4, 06120 Halle (Saale), Germany.
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29
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Amacher DE. A Toxicologist's Guide to the Preclinical Assessment of Hepatic Microsomal Enzyme Induction. Toxicol Mech Methods 2006; 16:385-94. [PMID: 20021012 DOI: 10.1080/15376510600783791] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The assessment of hepatic microsomal enzyme induction at the completion of preclinical toxicology studies in rodents and large mammals provides a wealth of information to the toxicologist and pharmacokineticist regarding how the drug-metabolizing system of the hepatocyte endoplasmic reticulum responded to high-dose levels of a xenobiotic designed for a specific pharmacological target in any of several target organs. The interpretation of these data can be greatly enhanced by a clear understanding of how this system functions and what the immediate and long-term ramifications are to organs and organ systems. This review focuses on how drugs modify the hepatic cytochrome P450 system, how those modifications are detected, the various consequences of these modifications, and some differences in the induction response among species.
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Affiliation(s)
- David E Amacher
- World-Wide Safety Sciences, Mail Stop 8274-1227, Pfizer Global Research and Development, Groton Laboratories, Groton, Connecticut
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30
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Pellequer JL, Chen SWW, Keum YS, Karu AE, Li QX, Roberts VA. Structural basis for preferential binding of non-ortho-substituted polychlorinated biphenyls by the monoclonal antibody S2B1. J Mol Recognit 2005; 18:282-94. [PMID: 15880452 DOI: 10.1002/jmr.740] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Polychlorinated biphenyls (PCBs) are a family of 209 isomers (congeners) with a wide range of toxic effects. In structural terms, they are of two types: those with and those without chlorines at the ortho positions (2, 2', 6 and 6'). Only 20 congeners have no ortho chlorines. Three of these are bound by the aryl hydrocarbon receptor and are one to four orders of magnitude more toxic than all others. A monoclonal antibody, S2B1, and its recombinant Fab have high selectivity and nanomolar binding affinities for two of the most toxic non-ortho-chlorinated PCBs, 3,4,3',4'-tetrachlorobiphenyl and 3,4,3',4',5'-pentachlorobiphenyl. To investigate the basis for these properties, we built a three-dimensional structure model of the S2B1 variable fragment (Fv) based on the high-resolution crystallographic structures of antibodies 48G7 and N1G9. Two plausible conformations for the complementarity-determining region (CDR) H3 loop led to two putative PCB-binding pockets with very different shapes (models A and B). Docking studies using molecular mechanics and potentials of mean force (PMF) indicated that model B was most consistent with the selectivity observed for S2B1 in competition ELISAs. The binding site in model B had a deep, narrow pocket between V(L) and V(H), with a slight constriction at the top that opened into a wider pocket between CDRs H1 and H3 on the antibody surface. This binding site resembles those of esterolytic antibodies that bind haptens with phenyl rings. One phenyl ring of the PCB fits into the deep pocket, and the other ring is bound in the shallower one. The bound PCB is surrounded by the side chains of TyrL91, TyrL96 and TrpH98, and it has a pi-cation interaction with ArgL46. The tight fit of the binding pocket around the ortho positions of the bound PCBs indicates that steric hindrance of ortho chlorines in the binding site, rather than induced conformational change of the PCBs, is responsible for the selectivity of S2B1.
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Affiliation(s)
- Jean-Luc Pellequer
- Département d'Ingenierie et d'Etudes des Proteines, Service de Biochimie Post-Génomique et Toxicologie Nucléaire, Commissariat à L'Energie Atomique, Centre de Marcoule, BP17171, 30207 Bagnols Sur Cèze, France.
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31
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Tsuchiya Y, Nakajima M, Yokoi T. Cytochrome P450-mediated metabolism of estrogens and its regulation in human. Cancer Lett 2005; 227:115-24. [PMID: 16112414 DOI: 10.1016/j.canlet.2004.10.007] [Citation(s) in RCA: 416] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2004] [Accepted: 10/07/2004] [Indexed: 11/18/2022]
Abstract
Estrogens are eliminated from the body by metabolic conversion to estrogenically inactive metabolites that are excreted in the urine and/or feces. The first step in the metabolism of estrogens is the hydroxylation catalyzed by cytochrome P450 (CYP) enzymes. Since most CYP isoforms are abundantly expressed in liver, the metabolism of estrogens mainly occurs in the liver. A major metabolite of estradiol, 2-hydroxyestradiol, is mainly catalyzed by CYP1A2 and CYP3A4 in liver, and by CYP1A1 in extrahepatic tissues. However, CYP1B1 which is highly expressed in estrogen target tissues including mammary, ovary, and uterus, specifically catalyzes the 4-hydroxylation of estradiol. Since 4-hydroxyestradiol generates free radicals from the reductive-oxidative cycling with the corresponding semiquinone and quinone forms, which cause cellular damage, the specific and local formation of 4-hydroxyestradiol is important for breast and endometrial carcinogenesis. Changes in the expression level of estrogen-metabolizing CYP isoforms not only alter the intensity of the action of estrogen but may also alter the profile of its physiological effect in liver and target tissues. Generally, many CYP isoforms are induced by the substrates themselves, resulting in enhanced metabolism and elimination from the body. Of particular interest is a novel finding that human CYP1B1 is regulated by estradiol via the estrogen receptor. This fact suggests that the regulation of CYP enzymes involved in estrogen metabolism by estrogen itself would be physiologically significant for the homeostasis of estrogens at local organs. In this mini-review, we discuss the CYP-mediated metabolism of estrogens and the regulation of the estrogen-metabolizing CYP enzymes in relation to the risk of cancer.
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Affiliation(s)
- Yuki Tsuchiya
- Drug Metabolism and Toxicology, Division of Pharmaceutical Sciences, Graduate School of Medical Science, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
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32
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Janosek J, Hilscherová K, Bláha L, Holoubek I. Environmental xenobiotics and nuclear receptors--interactions, effects and in vitro assessment. Toxicol In Vitro 2005; 20:18-37. [PMID: 16061344 DOI: 10.1016/j.tiv.2005.06.001] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2004] [Revised: 05/19/2005] [Accepted: 06/13/2005] [Indexed: 11/18/2022]
Abstract
A group of intracellular nuclear receptors is a protein superfamily including arylhydrocarbon AhR, estrogen ER, androgen AR, thyroid TR and retinoid receptors RAR/RXR as well as molecules with unknown function known as orphan receptors. These proteins play an important role in a wide range of physiological as well as toxicological processes acting as transcription factors (ligand-dependent signalling macromolecules modulating expression of various genes in a positive or negative manner). A large number of environmental pollutants and other xenobiotics negatively affect signaling pathways, in which nuclear receptors are involved, and these modulations were related to important in vivo toxic effects such as immunosuppression, carcinogenesis, reproduction or developmental toxicity, and embryotoxicity. Presented review summarizes current knowledge on major nuclear receptors (AhR, ER, AR, RAR/RXR, TR) and their relationship to known in vivo toxic effects. Special attention is focused on priority organic environmental contaminants and experimental approaches for determination and studies of specific toxicity mechanisms.
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Affiliation(s)
- J Janosek
- RECETOX, Masaryk University Brno, Kamenice 3, 625 00 Brno, Czech Republic.
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Huang THW, Kota BP, Razmovski V, Roufogalis BD. Herbal or natural medicines as modulators of peroxisome proliferator-activated receptors and related nuclear receptors for therapy of metabolic syndrome. Basic Clin Pharmacol Toxicol 2005; 96:3-14. [PMID: 15667590 DOI: 10.1111/j.1742-7843.2005.pto960102.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The use of herbal or natural medicines for the treatment of various disorders has a long and extensive history. Many of these herbal medicines are finding their way onto the world market as alternatives to prescribed drugs currently available to treat various disorders/ailments. In particular, hyperlipidaemia is a major risk factor for atherosclerotic coronary vascular disease, which can culminate in mortality in diabetes mellitus. There is overwhelming evidence that patients with type 2 diabetes mellitus often have metabolic syndrome and require a multifactorial intervention including aggressive treatment of arterial hypertension and dyslipidaemia to prevent cardiovascular complications. One of the most active areas of metabolic research into potential treatments is in the role of nuclear receptors as therapeutic targets for both glucose and lipid metabolism. The purpose of this review is to highlight the recent advances made by pharmaceutical and research organizations in identifying biologically active compounds from natural plant products capable of modulating nuclear receptors such as peroxisome proliferator-activated receptors and, to a lesser extent, liver X receptor and farnesoid X receptor. The specific features presented by these receptors provide an in-depth insight into the pathogenesis of metabolic disease and thus, a means of establishing potential mechanisms of action with traditional medicine. In hindsight, the review offers valuable information for rational drug design using known active compounds of plant origin. Further research may ultimately lead to a reduction in both the chronic microvascular complications of type 2 diabetes mellitus and the risk of cardiovascular disease and metabolic syndrome with the use of traditional medicine.
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Affiliation(s)
- Tom Hsun-Wei Huang
- Pharmaceutical Chemistry Discipline and Herbal Medicines Research and Education Centre, Faculty of Pharmacy, University of Sydney, NSW, Australia
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34
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Windshügel B, Jyrkkärinne J, Poso A, Honkakoski P, Sippl W. Molecular dynamics simulations of the human CAR ligand-binding domain: deciphering the molecular basis for constitutive activity. J Mol Model 2004; 11:69-79. [PMID: 15616833 DOI: 10.1007/s00894-004-0227-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2004] [Accepted: 11/02/2004] [Indexed: 10/26/2022]
Abstract
The constitutive androstane receptor (CAR) belongs to the superfamily of nuclear-hormone receptors that function as ligand-activated transcription factors. CAR plays an essential role in the metabolism of xenobiotics and shows--in contrast to related receptors--constitutive activity. However, the molecular basis for the constitutive activity remains unclear. In the present study, homology models of the ligand binding domain (LBD) were generated based on the crystal structures of the related pregnane X (PXR) and the vitamin D receptor (VDR). The models were used to investigate the basal activity of CAR and the effect of coactivator binding. Molecular dynamics (MD) simulations of complexed and uncomplexed receptor revealed a hypothesis for the activation mechanism. The suggested mechanism is supported by experimental results from site-directed mutagenesis. The basal activity of CAR can be explained by specific van-der-Waals interactions between amino acids on the LBD and its C-terminal activation domain (AF-2). Docking studies with the GOLD program yielded the interaction modes of structurally diverse agonists, giving insight into mechanisms by which ligands enhance CAR activity.
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Affiliation(s)
- Björn Windshügel
- Department of Pharmaceutical Chemistry, Martin-Luther-University, Halle-Wittenberg, Wolfgang-Langenbeck-Str. 4, 06120 Halle, Saale, Germany.
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Seidlová-Wuttke D, Jarry H, Wuttke W. Pure estrogenic effect of benzophenone-2 (BP2) but not of bisphenol A (BPA) and dibutylphtalate (DBP) in uterus, vagina and bone. Toxicology 2004; 205:103-12. [PMID: 15458795 DOI: 10.1016/j.tox.2004.06.042] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
UNLABELLED Contradictory results whether the endocrine disrupters (ED) benzophenone-2 (BP2), bisphenol A (BPA) and dibutylphtalate (DBP) exert estrogenic effects have been published. Selective estrogen receptor modulators (SERMs) exert estrogenic effects in some but not in all organs and ED may be SERMs. Therefore, we studied their binding properties to recombinant ERalpha and ERbeta protein and their effects in the uterus, vagina and bone of ovariectomized rats. BP2 bound to both receptor subtypes, while BPA had a relatively high ERbeta selectivity. DBP did not bind to ERalpha but with a low affinity to ERbeta. In the uterus, only E2 and BP2 increased uterine weight and the complement C3 but decreased ERbeta gene expression. Discrete effects of BPA and DBP in the uterus were found upon histological examination. In the vagina, BP2 but not BPA and DBP had clear estrogenic effects. E2 and BP2 had antiosteoporotic effects in the metaphysis of the tibia. The serum surrogate parameters of bone metabolism, i.e. osteocalcin and the cross (rat) laps were significantly reduced by E2, an effect shared with BP2 but not by the two other EDs. THE CONCLUSION BP2 acts as ERalpha and ERbeta agonist mimicking effects of E2, while the effects of BPA and DBP are not pure estrogenic.
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Affiliation(s)
- D Seidlová-Wuttke
- Abt. Klin. und Exp. Endokrinologie, Universitäts-Frauenklinik Göttingen, Robert-Koch-Strasse 40, D-37075 Göttingen, Germany.
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36
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Abstract
In silico or computational tools could be used more effectively in endocrine disruptor risk assessment for prescreening potential endocrine disruptors, improving experimental in vitro screening assay design and facilitating more thorough data analyses. The in silico tools reviewed here are three-fold and include the use of: (1) nuclear receptor (NR) crystal structures and homology models to examine potential modes of ligand binding by different representative compounds; (2) multivariate principal component analyses (PCA) techniques to select best predicted cell lines for endocrine disrupting chemicals (EDC) risk assessment purposes; (3) NR quantitative structure-activity relationships (QSARs) that can be constructed from varied biological data sources, using multivariate partial least squares (PLS) techniques and specific descriptors. The cytosolic and NR examples discussed here include the Ah receptor, (AhR), the human oestrogen receptor alpha (hERalpha) and the human pregnane X receptor (PXR). The varied biological data sets can be compared to give a more integrated dimension to receptor cross talk mechanisms, with further support from molecular modelling studies.
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Affiliation(s)
- M N Jacobs
- School of Biomedical and Molecular Sciences, University of Surrey, Guildford, Surrey, UK.
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37
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Jyrkkärinne J, Windshügel B, Mäkinen J, Ylisirniö M, Peräkylä M, Poso A, Sippl W, Honkakoski P. Amino acids important for ligand specificity of the human constitutive androstane receptor. J Biol Chem 2004; 280:5960-71. [PMID: 15572376 DOI: 10.1074/jbc.m411241200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The human constitutive androstane receptor (CAR, NR1I3) is an important ligand-activated regulator of oxidative and conjugative enzymes and transport proteins. Because of the lack of a crystal structure of the ligand-binding domain (LBD), wide species differences in ligand specificity and the scarcity of well characterized ligands, the factors that determine CAR ligand specificity are not clear. To address this issue, we developed highly defined homology models of human CAR LBD to identify residues lining the ligand-binding pocket and to perform molecular dynamics simulations with known human CAR modulators. The roles of 22 LBD residues for basal activity, ligand selectivity, and interactions with co-regulators were studied using site-directed mutagenesis, mammalian co-transfection, and yeast two-hybrid assays. These studies identified several amino acids within helices 3 (Asn(165)), 5 (Val(199)), 11 (Tyr(326), Ile(330), and Gln(331)), and 12 (Leu(343) and Ile(346)) that contribute to the high basal activity of human CAR. Unique residues within helices 3 (Ile(164) and Asn(165)), 5 (Cys(202) and His(203)), and 7 (Phe(234) and Phe(238)) were found control the selectivity for CAR activators and inhibitors. A single residue in helix 7 (Phe(243)) appears to explain the human/mouse species difference in response of CAR to 17alpha-ethynyl-3,17beta-estradiol.
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Affiliation(s)
- Johanna Jyrkkärinne
- Department of Pharmaceutics, University of Kuopio, P. O. Box 1627, FIN-70211 Kuopio, Finland
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Meng G, Zhao Y, Nag A, Zeng M, Dimri G, Gao Q, Wazer DE, Kumar R, Band H, Band V. Human ADA3 binds to estrogen receptor (ER) and functions as a coactivator for ER-mediated transactivation. J Biol Chem 2004; 279:54230-40. [PMID: 15496419 DOI: 10.1074/jbc.m404482200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have recently identified the hADA3 protein, the human homologue of yeast transcriptional coactivator yADA3, as a novel HPV16 E6 target. Using ectopic expression approaches, we further demonstrated that hADA3 directly binds to the 9-cis retinoic acid receptors alpha and beta, and functions as a coactivator for retinoid receptor-mediated transcriptional activation. Here, we examined the role of endogenous hADA3 as a coactivator for estrogen receptor (ER), an important member of the nuclear hormone receptor superfamily. We show that ADA3 directly interacts with ER alpha and ER beta. Using the chromatin immunoprecipitation assay, we also show that hADA3 is a component of the activator complexes bound to the native ER response element within the promoter of the estrogen-responsive gene pS2. Furthermore, using an ER response element-luciferase reporter, we show that overexpression of ADA3 enhances the ER alpha- and ER beta-mediated sequence-specific transactivation. Reverse transcription-PCR analysis showed an ADA3-mediated increase in estrogen-induced expression of the endogenous pS2 gene. More importantly, using RNA interference against hADA3, we demonstrate that inhibition of endogenous hADA3 inhibited ER-mediated transactivation and the estrogen-induced increase in the expression of pS2, cathepsin D, and progesterone receptor, three widely known ER-responsive genes. The HPV E6 protein, by targeting hADA3 for degradation, inhibited the ER alpha-mediated transactivation and the protein expression of ER target genes. Thus, our results demonstrate that ADA3 directly binds to human estrogen receptor and enhances the transcription of ER-responsive genes, suggesting a broader role of mammalian hADA3 as a coactivator of nuclear hormone receptors and the potential role of these pathways in HPV oncogenesis.
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Affiliation(s)
- Gaoyuan Meng
- Department of Radiation Oncology, New England Medical Center, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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Ma Y, Sachdeva K, Liu J, Ford M, Yang D, Khan IA, Chichester CO, Yan B. Desmethoxyyangonin and dihydromethysticin are two major pharmacological kavalactones with marked activity on the induction of CYP3A23. Drug Metab Dispos 2004; 32:1317-24. [PMID: 15282211 DOI: 10.1124/dmd.104.000786] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Kava kava (Piper methysticum), an herbal remedy, is widely used for the treatment of mild to moderate cases of anxiety. The therapeutic activity is presumably achieved through multiple constituents called kavalactones. Recently, kava extracts were shown to induce CYP3A4 and activate human pregnane X receptor (PXR). This study was undertaken to test the ability of purified kavalactones to induce CYP3A23 and activate PXR. Rat hepatocytes were treated with desmethoxyyangonin, dihydrokawain, dihydromethysticin, kawain, methysticin, or yangonin, and the expression of CYP3A23 was monitored. Among the kavalactones, only desmethoxyyangonin and dihydromethysticin markedly induced the expression of CYP3A23 (approximately 7-fold). A similar magnitude of induction was detected with combined six kavalactones at a noninductive concentration when individually used. The induced expression, however, was markedly reduced or completely abolished if dihydromethysticin, desmethoxyyangonin, or both were excluded from the mixtures. Interestingly, regardless of whether dihydromethysticin or desmethoxyyangonin was used alone or together with other kavalactones, similar amounts of total kavalactones were needed to produce comparable induction, suggesting that the inductive activity of dihydromethysticin and desmethoxyyangonin is additively/synergistically enhanced by other kavalactones. In addition, treatment with dihydromethysticin, desmethoxyyangonin, or pregnenolone 16alpha-carbonitrile (PCN) markedly increased the levels of CYP3A23 mRNA, and inhibition of mRNA synthesis abolished the induction. In contrast to PCN, dihydromethysticin and desmethoxyyangonin only slightly activated rat or human PXR. These findings suggest that the induction of CYP3A23 by dihydromethysticin and desmethoxyyangonin involves transcription activation, probably through a PXR-independent or PXR-involved indirect mechanism.
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Affiliation(s)
- Yuzhong Ma
- Department of Biomedical Sciences, University of Rhode Island, 41 Lower College Road, Kingston, RI 02881, USA
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40
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Knockaert M, Blondel M, Bach S, Leost M, Elbi C, Hager GL, Nagy SR, Han D, Denison M, Ffrench M, Ryan XP, Magiatis P, Polychronopoulos P, Greengard P, Skaltsounis L, Meijer L. Independent actions on cyclin-dependent kinases and aryl hydrocarbon receptor mediate the antiproliferative effects of indirubins. Oncogene 2004; 23:4400-12. [PMID: 15077192 DOI: 10.1038/sj.onc.1207535] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Indirubin, a bis-indole obtained from various natural sources, is responsible for the reported antileukemia activity of a Chinese Medicinal recipe, Danggui Longhui Wan. However, its molecular mechanism of action is still not well understood. In addition to inhibition of cyclin-dependent kinases and glycogen synthase kinase-3, indirubins have been reported to activate the aryl hydrocarbon receptor (AhR), a cotranscriptional factor. Here, we confirm the interaction of AhR and indirubin using a series of indirubin derivatives and show that their binding modes to AhR and to protein kinases are unrelated. As reported for other AhR ligands, binding of indirubins to AhR leads to its nuclear translocation. Furthermore, the apparent survival of AhR-/- and +/+ cells, as measured by the MTT assay, is equally sensitive to the kinase-inhibiting indirubins. Thus, the cytotoxic effects of indirubins are AhR-independent and more likely to be linked to protein kinase inhibition. In contrast, a dramatic cytostatic effect, as measured by actual cell counts and associated with a sharp G1 phase arrest, is induced by 1-methyl-indirubins, a subfamily of AhR-active but kinase-inactive indirubins. As shown for TCDD (dioxin), this effect appears to be mediated through the AhR-dependent expression of p27(KIP1). Altogether these results suggest that AhR activation, rather than kinase inhibition, is responsible for the cytostatic effects of some indirubins. In contrast, kinase inhibition, rather than AhR activation, represents the main mechanism underlying the cytotoxic properties of this class of promising antitumor molecules.
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Affiliation(s)
- Marie Knockaert
- C.N.R.S., Cell Cycle Group and UPS-2682, Station Biologique, BP 74, 29682 ROSCOFF cedex, Bretagne, France
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41
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Abstract
The nuclear orphan receptor CAR is active in the absence of ligand with the unique capability to be further regulated by activators. A number of these activators, including phenobarbital, do not directly bind to the receptor. Considered a xenobiotic sensing receptor, CAR transcriptionally modifies the expression of genes involved in the metabolism and elimination of xenobiotics and steroids in response to these compounds and other cellular metabolites. Its hepatic expression pattern endows the liver with the ability to protect against not only exogenous but also endogenous insults. The mechanism of CAR activation is complex, involving translocation from the cytoplasm to the nucleus in the presence of activators, followed by further activation steps in the nucleus. Although this mechanism remains under investigation, we have summarized here the cellular signaling pathways elucidated so far and speculate on the mechanism by which CAR activators regulate gene expression through this network.
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Affiliation(s)
- Karen Swales
- Pharmacogenetics Section, Laboratory of Reproductive and Developmental Toxicology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
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42
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Frank C, Molnár F, Matilainen M, Lempiäinen H, Carlberg C. Agonist-dependent and agonist-independent transactivations of the human constitutive androstane receptor are modulated by specific amino acid pairs. J Biol Chem 2004; 279:33558-66. [PMID: 15151997 DOI: 10.1074/jbc.m403946200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The constitutive androstane receptor (CAR) is an interesting member of the nuclear receptor superfamily because of its exceptionally high constitutive activity due to ligand-independent interaction of the ligand-binding domain with co-activator proteins. This study compares the agonist-dependent and agonist-independent activities of human CAR with those of mouse CAR and the vitamin D receptor and demonstrates that the constitutive activity of CAR is mediated by at least three contacts between the amino acids of helix 12, partner amino acids in helices 4 and 11, and a charge clamp between helices 12 and 3. The stabilization of helix 12 by a contact between its C terminus and the lysine of helix 4 has the same impact in human and mouse CARs. In addition, the charge clamp between the glutamate in helix 12 and the lysine in helix 3 is also important for the constitutive activity of both receptor orthologs but less critical for the agonist-dependent stabilization of their respective helices 12. Interestingly, Cys-357 in mouse CAR has significantly more impact on the stabilization of helix 12 than does the orthologous position Cys-347 in human CAR. This deficit appears to be compensated by a more dominant role of Ile-330 in human CAR over Leu-340 in mouse CAR because it is more efficient than Cys-347 in controlling the flexibility of helix 12 in the presence of an agonist. The constitutive activity of other members of the nuclear receptor superfamily could be explained by a homologous hydrophobic interaction between large, non-polar amino acids of helices 11 and 12.
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Affiliation(s)
- Christian Frank
- Department of Biochemistry, University of Kuopio, FIN-70211 Kuopio, Finland
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43
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Terasaka S, Aita Y, Inoue A, Hayashi S, Nishigaki M, Aoyagi K, Sasaki H, Wada-Kiyama Y, Sakuma Y, Akaba S, Tanaka J, Sone H, Yonemoto J, Tanji M, Kiyama R. Using a customized DNA microarray for expression profiling of the estrogen-responsive genes to evaluate estrogen activity among natural estrogens and industrial chemicals. ENVIRONMENTAL HEALTH PERSPECTIVES 2004; 112:773-81. [PMID: 15159206 PMCID: PMC1241992 DOI: 10.1289/ehp.6753] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We developed a DNA microarray to evaluate the estrogen activity of natural estrogens and industrial chemicals. Using MCF-7 cells, we conducted a comprehensive analysis of estrogen-responsive genes among approximately 20,000 human genes. On the basis of reproducible and reliable responses of the genes to estrogen, we selected 172 genes to be used for developing a customized DNA microarray. Using this DNA microarray, we examined estrogen activity among natural estrogens (17beta-estradiol, estriol, estrone, genistein), industrial chemicals (diethylstilbestrol, bisphenol A, nonylphenol, methoxychlor), and dioxin. We obtained results identical to those for other bioassays that are used for detecting estrogen activity. On the basis of statistical correlations analysis, these bioassays have shown more sensitivity for dioxin and methoxychlor.
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Affiliation(s)
- Shunichi Terasaka
- Research Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
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Walgren JL, Jollow DJ, McMillan JM. Induction of peroxisome proliferation in cultured hepatocytes by a series of halogenated acetates. Toxicology 2004; 197:189-97. [PMID: 15033542 DOI: 10.1016/j.tox.2004.01.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2003] [Revised: 01/01/2004] [Accepted: 01/05/2004] [Indexed: 11/26/2022]
Abstract
Trichloroacetate (TCA) and dichloroacetate (DCA) are hepatocarcinogenic metabolites of the environmental pollutant trichloroethylene (TCE) and are common water contaminants. Induction of peroxisome proliferation via activation of the peroxisome proliferator-activated receptor alpha (PPARalpha) has been proposed as a mechanism for their hepatocarcinogenic action. However, it is unclear whether these compounds are direct ligands of PPARalpha or whether activation occurs by a ligand-independent process. The present studies were undertaken to determine whether a primary rat hepatocyte model system could be used to examine structure-activity relationships of haloacetates for the induction of peroxisomal palmitoyl-CoA oxidation. The haloacetates tested differed in both type (iodo, bromo, chloro and fluoro) and extent (mono, di and tri) substitution. Significant differences were observed in both potency and efficacy. Potency varied over about two orders of magnitude, in the order of mono > di = tri. Within the monohalo-substituted series, the order of potency was iodo > bromo > chloro, with the fluoro analog being essentially inactive. The monoiodo- and monobromo-derivatives showed significant induction at 50 and 100 microM, respectively, but cytotoxicity precluded obtaining full concentration-response curves. The dihalo- and trihalo-acetates had generally similar potency, and, with the exception of the diflouro- and dibromoacetates, showed a maximal induction of two- to three-fold. Difluoroacetate and dibromoacetate induced palmitoyl-CoA oxidation by nine- and six-fold, respectively, approaching the effectiveness of Wy-14,643 (50 microM) in this system. Of interest, the slopes of the concentration-dependence lines of the difluoro- and dibromo-acetates were markedly dissimilar from the other di- and tri-haloacetates, suggesting either a marked difference in the way they activate the PPARalpha receptor or a substantial difference in the way they are metabolized or transported by the hepatocytes.
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Affiliation(s)
- Jennie L Walgren
- Department of Cell and Molecular Pharmacology, P.O. Box 250505, 173 Ashley Avenue, Medical University of South Carolina, Charleston, SC 29425, USA
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Abstract
Nuclear orphan receptors represent a large and diverse subgroup in the nuclear receptor superfamily. Although putative ligands for these orphan members remain to be identified, some of these receptors possess intrinsic activating, inhibitory, or dual regulatory functions in development, differentiation, homeostasis, and reproduction. In particular, gene-silencing events elicited by chicken ovalbumin upstream promoter-transcription factors (COUP-TFs); dosage-sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome, gene 1 (DAX-1); germ cell nuclear factor (GCNF); short heterodimer partner (SHP); and testicular receptors 2 and 4 (TR2 and TR4) are among the best characterized. These orphan receptors are critical in controlling basal activities or hormonal responsiveness of numerous target genes. They employ multiple and distinct mechanisms to mediate target gene repression. Complex cross-talk exists between these orphan receptors at their cognate DNA binding elements and an array of steroid?nonsteroid hormone receptors, other transcriptional activators, coactivators and corepressors, histone modification enzyme complexes, and components of basal transcriptional components. Therefore, perturbation induced by these orphan receptors at multiple levels, including DNA binding activities, receptor homo- or heterodimerization, recruitment of cofactor proteins, communication with general transcriptional machinery, and changes at histone acetylation status and chromatin structures, may contribute to silencing of target gene expression in a specific promoter or cell-type context. Moreover, the findings derived from gene-targeting studies have demonstrated the significance of these orphan receptors' function in physiologic settings. Thus, COUP-TFs, DAX-1, GCNF, SHP, and TR2 and 4 are known to be required for multiple physiologic and biologic functions, including neurogenesis and development of the heart and vascular system steroidogenesis and sex determination, gametogenesis and embryonic development, and cholesterol?lipid homeostasis.
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MESH Headings
- Animals
- COUP Transcription Factor I
- COUP Transcription Factors
- DAX-1 Orphan Nuclear Receptor
- DNA-Binding Proteins/metabolism
- Gametogenesis/physiology
- Gene Expression/physiology
- Gene Silencing/physiology
- Humans
- Models, Molecular
- Nuclear Receptor Subfamily 2, Group C, Member 1
- Nuclear Receptor Subfamily 6, Group A, Member 1
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Cytoplasmic and Nuclear/physiology
- Receptors, Retinoic Acid/metabolism
- Receptors, Steroid/metabolism
- Receptors, Thyroid Hormone/metabolism
- Repressor Proteins/metabolism
- Transcription Factors/metabolism
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Affiliation(s)
- Ying Zhang
- Section on Molecular Endocrinology, Endocrinology, and Reproduction Research Branch, National Institutes of Health, Bethesda, Maryland 20892, USA
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46
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Abstract
Induction of drug metabolism was described more than 40 years ago. Progress in understanding the molecular mechanism of induction of drug-metabolizing enzymes was made recently when the important roles of the pregnane X receptor (PXR) and the constitutive androstane receptor (CAR), two members of the nuclear receptor superfamily of transcription factors, were discovered to act as sensors for lipophilic xenobiotics, including drugs. CAR and PXR bind as heterodimeric complexes with the retinoid X receptor to response elements in the regulatory regions of the induced genes. PXR is directly activated by xenobiotic ligands, whereas CAR is involved in a more complex and less well understood mechanism of signal transduction triggered by drugs. Most recently, analysis of these xenobiotic-sensing nuclear receptors and their nonmammalian precursors such as the chicken xenobiotic receptor suggests an important role of PXR and CAR also in endogenous pathways, such as cholesterol and bile acid biosynthesis and metabolism. In this review, recent findings regarding xenosensors and their target genes are summarized and are put into an evolutionary perspective in regard to how a living organism has derived a system that is able to deal with potentially toxic compounds it has not encountered before.
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Affiliation(s)
- Christoph Handschin
- Division of Pharmacology/Neurobiology, Biozentrum of the University of Basel, Klingelbergstrasse 50-70, CH-4056 Basel, Switzerland
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