title: Inhibition of CYP3A4 expression by ketoconazole is mediated by the disruption of pregnane X receptor, steroid receptor coactivator-1, and hepatocyte nuclear factor 4alpha interaction.
abstract: BACKGROUND
  Earlier studies have shown that ketoconazole inhibits CYP3A4 expression through pregnane X receptor (PXR)-mediated transcription and coactivator interaction. The involvement of other nuclear receptors remains to be elucidated. It was recently reported that hepatocyte nuclear receptor 4alpha (HNF4alpha), a master regulator of several nuclear receptors, associates with PXR thus regulates the expression of CYP3A4 under rifampin treatment. We therefore focused on the role of PXR-HNF4alpha interaction in the transcriptional regulation of CYP3A4 under rifampin-mediated ketoconazole inhibition.
  
  
  RESULTS
  Several approaches were used to characterize this role and to investigate the relation between the regulatory function of the PXR-HNF4alpha complex and CYP3A4 expression, including a mammalian two-hybrid system, DNA affinity precipitation assay, co-immunoprecipitation, and HNF4alpha silencing by RNA interference. Here, we report that HNF4alpha plays a critical role in CYP3A4 promoter activation, and the interaction between PXR and HNF4alpha, which is closely related to the expression of CYP3A4, might be involved in ketoconazole-mediated inhibition of CYP3A4 gene expression. These observations indicate that the inhibition of the interaction of PXR with HNF4alpha is likely an important mechanism of drug-drug interaction.
authors.affiliation: Department of Pharmacology, Medical College, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Yun-Ping
authors.initials: YP
authors.lastname: Lim
authors.forename: Sheng-Chun
authors.initials: SC
authors.lastname: Kuo
authors.forename: Ming-Liang
authors.initials: ML
authors.lastname: Lai
authors.forename: Jin-Ding
authors.initials: JD
authors.lastname: Huang
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology; D001483:Base Sequence; D002460:Cell Line; D051544:Cytochrome P-450 CYP3A / Q000235:genetics*; D065692:Cytochrome P-450 CYP3A Inhibitors; D017931:DNA Primers / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006367:HeLa Cells; D051557:Hepatocyte Nuclear Factor 4 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D051548:Histone Acetyltransferases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007654:Ketoconazole / Q000494:pharmacology*; D008024:Ligands; D056920:Nuclear Receptor Coactivator 1; D010597:Pharmacogenetics; D000077297:Pregnane X Receptor; D011401:Promoter Regions, Genetic; D054730:Protein Interaction Domains and Motifs; D034622:RNA Interference; D011987:Receptors, Steroid / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D012293:Rifampin / Q000494:pharmacology; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D000935:Antifungal Agents; D065692:Cytochrome P-450 CYP3A Inhibitors; D017931:DNA Primers; C496592:HNF4A protein, human; D051557:Hepatocyte Nuclear Factor 4; D008024:Ligands; D000077297:Pregnane X Receptor; D011987:Receptors, Steroid; D011994:Recombinant Proteins; D014157:Transcription Factors; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; D056920:Nuclear Receptor Coactivator 1; D007654:Ketoconazole; D012293:Rifampin