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.

Activation of the Steroid and Xenobiotic Receptor (Human Pregnane X Receptor) by Nontaxane Microtubule-Stabilizing Agents

“…Epothilone A and epothilone B had only a minimal effect on CYP3A expression. Docetaxel (IC 50 , >10 Amol/L) at 5 Amol/L resulted in a 3.5-fold induction of CYP3A4; however, paclitaxel showed a 4.3-fold induction compared with DMSO-treated control cells. As expected, rifampicin, a known inducer of CYP3A4 in mammalian cells, increased the level of CYP3A4 protein, whereas cisplatin as expected had no effect on CYP3A4 abundance when compared with DMSO-treated control cells (Fig.…”

“…We have assessed activity of these drugs in their ability to inhibit cell proliferation as well as in their ability to induce stable microtubule polymers. Although there does not seem to be a clear and direct link between microtubule stabilization and activation of hPXR, the ability of hPXR to translocate from the cytoplasm to the nucleus may be influenced by altered signaling cascades emanating from the formation of stable tubulin polymers (50,54).…”

“…Statistical analysis was done with Analyze-It software using the nonparametric Mann-Whitney test (22,23). 50 , 10 Amol/L) at a concentration of 5 Amol/L resulted in a 3.7-and 5.8-fold increase in CYP3A4 levels, respectively, compared with DMSOtreated controls. Epothilone A and epothilone B had only a minimal effect on CYP3A expression.…”

Transcription Factor and Drug-Metabolizing Enzyme Gene Expression in Lymphocytes from Healthy Human Subjects

“…The different TF influence mutually their relative expression. CAR and PXR are regulated, at least in part, by the GR, and a signal transduction cascade GR-[CAR-PXR]-P450 exists at least for CYP3A4 and CYP2C9 (Dvorak et al, 2003) and maybe CYP2C19 (Chen et al, 2003). In addition, VDR probably regulates CYP3A4, CYP2C9, and CYP2B6 (Drocourt et al, 2002).…”

Lack of an effect of CYP3A4 and MDR1 gene polymorphisms on colchicine pharmacogenetics in the treatment of Familial Mediterranean fever

“…The main route of colchicine elimination is via hepatobiliary excretion (Ferron et al, 1996;Tateishi et al, 1997;Dvorak et al, 2003) and with the feces (Tateishi et al, 1997;Dvorak et al, 2003). Kidneys contribute to <20% of clearance (Lange et al, 2001;Molad, 2002;Niel and Shermann, 2006).…”