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.
Methods and 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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Antifungal Agents / pharmacology
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Base Sequence
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Cell Line
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Cytochrome P-450 CYP3A / genetics*
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Cytochrome P-450 CYP3A Inhibitors*
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DNA Primers / genetics
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Gene Expression Regulation, Enzymologic / drug effects
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HeLa Cells
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Hepatocyte Nuclear Factor 4 / antagonists & inhibitors*
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Hepatocyte Nuclear Factor 4 / genetics
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Hepatocyte Nuclear Factor 4 / metabolism
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Histone Acetyltransferases / antagonists & inhibitors*
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Histone Acetyltransferases / metabolism
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Humans
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In Vitro Techniques
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Ketoconazole / pharmacology*
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Ligands
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Nuclear Receptor Coactivator 1
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Pharmacogenetics
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Pregnane X Receptor
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Promoter Regions, Genetic
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Protein Interaction Domains and Motifs
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RNA Interference
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Receptors, Steroid / antagonists & inhibitors*
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Receptors, Steroid / metabolism
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Recombinant Proteins / antagonists & inhibitors
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Rifampin / pharmacology
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Transcription Factors / antagonists & inhibitors*
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Transcription Factors / metabolism
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Two-Hybrid System Techniques
Substances
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Antifungal Agents
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Cytochrome P-450 CYP3A Inhibitors
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DNA Primers
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HNF4A protein, human
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Hepatocyte Nuclear Factor 4
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Ligands
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Pregnane X Receptor
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Receptors, Steroid
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Recombinant Proteins
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Transcription Factors
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Cytochrome P-450 CYP3A
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CYP3A4 protein, human
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Histone Acetyltransferases
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NCOA1 protein, human
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Nuclear Receptor Coactivator 1
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Ketoconazole
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Rifampin