title: Colchicine down-regulates cytochrome P450 2B6, 2C8, 2C9, and 3A4 in human hepatocytes by affecting their glucocorticoid receptor-mediated regulation.
abstract: The xenobiotic-mediated induction of three major human liver cytochrome P450 genes, CYP2B6, CYP2C9, and CYP3A4, is known to be regulated by the constitutive androstane receptor (CAR) and the pregnane X receptor (PXR). CAR and PXR are regulated, at least in part, by the glucocorticoid receptor (GR) and the hypothesis of a signal transduction cascade GR-[CAR/PXR]-P450 has been proposed. This study was aimed at testing this hypothesis in primary human hepatocytes by using the tubulin network disrupting agent colchicine. Colchicine (COL) decreased both basal and rifampicin- and phenobarbital-inducible expression of CYP2B6, CYP2C8/9, and CYP3A4. A parallel down-regulation of mRNA expression of CAR, PXR, and tyrosine aminotransferase, a prototypic gene directly regulated by GR, was observed. COL affected neither the level of GR mRNA nor ligand binding to GR. To evaluate the effect of colchicine on GR-mediated gene transactivation, HeLa cells stably or transiently transfected with a GR-responsive element-dependent luciferase reporter gene were used. COL decreased the dexamethasone-induced luciferase expression in stably transfected cell line by 50%, whereas GR transactivation in transiently transfected cells was not affected by COL. In contrast, ligand-dependent GR translocation in the human embryonic kidney 293 cell line transiently transfected with GFP-GR was inhibited by COL. We conclude that alteration of the signal transduction mediated through the GR-[CAR/PXR]-P450 cascade by colchicine is responsible for the down-regulation of CYP2C9 and CYP3A4, implicating cytoskeleton as necessary for correct functioning of this cascade under physiological conditions.
authors.affiliation: Institute of Medical Chemistry and Biochemistry, Medical Faculty, Palacký University Olomouc, Olomouc, Czech Republic.
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Dvorak
authors.forename: Martin
authors.initials: M
authors.lastname: Modriansky
authors.forename: Lydiane
authors.initials: L
authors.lastname: Pichard-Garcia
authors.forename: Patrick
authors.initials: P
authors.lastname: Balaguer
authors.forename: Marie-Jose
authors.initials: MJ
authors.lastname: Vilarem
authors.forename: Jitka
authors.initials: J
authors.lastname: Ulrichová
authors.forename: Patrick
authors.initials: P
authors.lastname: Maurel
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Pascussi
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis; D001692:Biological Transport / Q000187:drug effects; D019556:COS Cells; D002478:Cells, Cultured; D003078:Colchicine / Q000494:pharmacology*; D065702:Cytochrome P-450 CYP2B6; D065727:Cytochrome P-450 CYP2C8; D065729:Cytochrome P-450 CYP2C9; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D004790:Enzyme Induction / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D010089:Oxidoreductases, N-Demethylating / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis / Q000187:drug effects; D011965:Receptors, Glucocorticoid / Q000187:drug effects / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D003577:Cytochrome P-450 Enzyme System; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; C585599:CYP2B6 protein, human; C450259:CYP2C8 protein, human; C104464:CYP3A protein, human; D065702:Cytochrome P-450 CYP2B6; D065727:Cytochrome P-450 CYP2C8; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D010089:Oxidoreductases, N-Demethylating; D003078:Colchicine