title: Role of human hepatocyte nuclear factor 4alpha in the expression of drug-metabolizing enzymes and transporters in human hepatocytes assessed by use of small interfering RNA.
abstract: Hepatocyte nuclear factor 4alpha (HNF4alpha) is an important transcription factor in hepatic gene expression. Here, we have investigated the role of HNF4alpha in the expression of drug-metabolizing enzymes and transporters in human hepatocytes using an adenovirus expressing human HNF4alpha-small interfering RNA (hHNF4alpha-siRNA). The hHNF4alpha-siRNA effectively reduced the mRNA and nuclear protein levels of hHNF4alpha in a concentration-dependent manner. The hHNF4alpha-siRNA also decreased the mRNA levels of CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP3A4, UGT1A1, UGT1A9, SULT2A1, ABCB1, ABCB11, ABCC2, OATP1B1 and OCT1, as well as those of PXR and CAR. To discern the role of these nuclear receptors, we co-infected hepatocytes with hHNF4alpha-siRNA and PXR- or CAR-expressing adenovirus. The hHNF4alpha-siRNA-induced reductions of the enzyme and transporter mRNA levels were not restored except CYP2B6 mRNA levels, which were returned to the control level by overexpressing CAR. Furthermore, although hHNF4alpha-siRNA did not significantly affect the fold-induction of CYP2B6, CYP2C8, CYP2C9, or CYP3A4 mRNA levels following treatment with CYP inducers, the levels in hHNF4alpha-suppressed cells fell significantly compared to the control. These results suggest that HNF4alpha plays a dominant role in the expression of drug-metabolizing enzymes and transporters in human hepatocytes, and that HNF4alpha expression levels is a possible determinant for inter-individual variations in the expression of these enzymes and transporters.
authors.affiliation: Division of Drug Metabolism and Molecular Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
authors.forename: Yoshiteru
authors.initials: Y
authors.lastname: Kamiyama
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Matsubara
authors.forename: Kouichi
authors.initials: K
authors.lastname: Yoshinari
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Nagata
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Kamimura
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Yamazoe
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D004790:Enzyme Induction / Q000187:drug effects* / Q000235:genetics; D005822:Genetic Vectors; D051557:Hepatocyte Nuclear Factor 4 / Q000502:physiology*; D022781:Hepatocytes / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D000089762:Multidrug Resistance-Associated Protein 2; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D000077297:Pregnane X Receptor; D034741:RNA, Small Interfering / Q000494:pharmacology*; D011987:Receptors, Steroid / Q000187:drug effects / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics; D014162:Transfection; D015262:Xenobiotics / Q000494:pharmacology