title: Activating and Inhibitory Functions of WNT/β-Catenin in the Induction of Cytochromes P450 by Nuclear Receptors in HepaRG Cells.
abstract: The WNT/β-catenin signaling pathway has been identified as an important endogenous regulator of hepatic cytochrome P450 (P450) expression in mouse liver. In particular, it is involved in the regulation of P450 expression in response to exposure to xenobiotic agonists of the nuclear receptors constitutive androstane receptor (CAR), aryl hydrocarbon receptor (AhR), and Nrf2. To systematically elucidate the effect of the WNT/β-catenin pathway on the regulation and inducibility of major human P450 enzymes, HepaRG cells were treated with either the WNT/β-catenin signaling pathway agonist, WNT3a, or with small interfering RNA directed against β-catenin, alone or in combination with a panel of activating ligands for AhR [2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)], CAR [6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde-O-(3,4-dichlorobenzyl)oxime (CITCO)], pregnane X receptor (PXR) [rifampicin], and peroxisome proliferator-activated receptor (PPAR) α [4-chloro-6-(2,3-xylidino)-2-pyrimidinylthioacetic acid (WY14,643)]. Assessment of P450 gene expression and enzymatic activity after downregulation or activation of the WNT/β-catenin pathway revealed a requirement of β-catenin in the AhR-, CAR-, and PXR-mediated induction of CYP1A, CYP2B6 and CYP3A4 (for CAR and PXR), and CYP2C8 (for PXR) gene expression. By contrast, activation of the WNT/β-catenin pathway prevented PPARα-mediated induction of CYP1A, CYP2C8, CYP3A4, and CYP4A11 genes, suggesting a dominant-negative role of β-catenin in PPARα-mediated regulation of these genes. Our data indicate a significant effect of the WNT/β-catenin pathway on the regulation of P450 enzymes in human hepatocytes and reveal a novel crosstalk between β-catenin and PPARα signaling pathways in the regulation of P450 expression.
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, and University of Tuebingen, Tuebingen, Germany (M.T., C.B., U.H., U.M.Z.); Department of Toxicology, Institute of Experimental and Clinical Pharmacology and Toxicology, University of Tübingen, Tübingen, Germany (S.V., M.S.); and Department of Food Safety, Federal Institute for Risk Assessment, Berlin, Germany (A.B.) maria.thomas@ikp-stuttgart.de.
authors.forename: Maria
authors.initials: M
authors.lastname: Thomas
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, and University of Tuebingen, Tuebingen, Germany (M.T., C.B., U.H., U.M.Z.); Department of Toxicology, Institute of Experimental and Clinical Pharmacology and Toxicology, University of Tübingen, Tübingen, Germany (S.V., M.S.); and Department of Food Safety, Federal Institute for Risk Assessment, Berlin, Germany (A.B.).
authors.forename: Christine
authors.initials: C
authors.lastname: Bayha
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, and University of Tuebingen, Tuebingen, Germany (M.T., C.B., U.H., U.M.Z.); Department of Toxicology, Institute of Experimental and Clinical Pharmacology and Toxicology, University of Tübingen, Tübingen, Germany (S.V., M.S.); and Department of Food Safety, Federal Institute for Risk Assessment, Berlin, Germany (A.B.).
authors.forename: Silvia
authors.initials: S
authors.lastname: Vetter
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, and University of Tuebingen, Tuebingen, Germany (M.T., C.B., U.H., U.M.Z.); Department of Toxicology, Institute of Experimental and Clinical Pharmacology and Toxicology, University of Tübingen, Tübingen, Germany (S.V., M.S.); and Department of Food Safety, Federal Institute for Risk Assessment, Berlin, Germany (A.B.).
authors.forename: Ute
authors.initials: U
authors.lastname: Hofmann
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, and University of Tuebingen, Tuebingen, Germany (M.T., C.B., U.H., U.M.Z.); Department of Toxicology, Institute of Experimental and Clinical Pharmacology and Toxicology, University of Tübingen, Tübingen, Germany (S.V., M.S.); and Department of Food Safety, Federal Institute for Risk Assessment, Berlin, Germany (A.B.).
authors.forename: Michael
authors.initials: M
authors.lastname: Schwarz
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, and University of Tuebingen, Tuebingen, Germany (M.T., C.B., U.H., U.M.Z.); Department of Toxicology, Institute of Experimental and Clinical Pharmacology and Toxicology, University of Tübingen, Tübingen, Germany (S.V., M.S.); and Department of Food Safety, Federal Institute for Risk Assessment, Berlin, Germany (A.B.).
authors.forename: Ulrich M
authors.initials: UM
authors.lastname: Zanger
authors.affiliation: Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, and University of Tuebingen, Tuebingen, Germany (M.T., C.B., U.H., U.M.Z.); Department of Toxicology, Institute of Experimental and Clinical Pharmacology and Toxicology, University of Tübingen, Tübingen, Germany (S.V., M.S.); and Department of Food Safety, Federal Institute for Risk Assessment, Berlin, Germany (A.B.).
authors.forename: Albert
authors.initials: A
authors.lastname: Braeuning
mesh_terms: D006528:Carcinoma, Hepatocellular; D045744:Cell Line, Tumor; D000090702:Constitutive Androstane Receptor; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis; D008113:Liver Neoplasms; D047493:PPAR alpha / Q000378:metabolism*; D000077297:Pregnane X Receptor; D034741:RNA, Small Interfering / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D011987:Receptors, Steroid / Q000378:metabolism*; D015398:Signal Transduction; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D000090702:Constitutive Androstane Receptor; D007527:Isoenzymes; D047493:PPAR alpha; D000077297:Pregnane X Receptor; D034741:RNA, Small Interfering; D018336:Receptors, Aryl Hydrocarbon; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D051153:Wnt Proteins; D051176:beta Catenin; D003577:Cytochrome P-450 Enzyme System