Kamiyama Yoshiteru, Matsubara Tsutomu, Yoshinari Kouichi, Nagata Kiyoshi, Kamimura Hidetaka, Yamazoe Yasushi
Division of Drug Metabolism and Molecular Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
Drug Metab Pharmacokinet. 2007 Aug;22(4):287-98. doi: 10.2133/dmpk.22.287.
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.
肝细胞核因子4α（HNF4α）是肝脏基因表达中的一种重要转录因子。在此，我们使用表达人HNF4α小干扰RNA（hHNF4α-siRNA）的腺病毒，研究了HNF4α在人肝细胞中药物代谢酶和转运体表达中的作用。hHNF4α-siRNA以浓度依赖的方式有效降低了hHNF4α的mRNA和核蛋白水平。hHNF4α-siRNA还降低了CYP2A6、CYP2B6、CYP2C8、CYP2C9、CYP2C19、CYP2D6、CYP3A4、UGT1A1、UGT1A9、SULT2A1、ABCB1、ABCB11、ABCC2、OATP1B1和OCT1以及PXR和CAR的mRNA水平。为了明确这些核受体的作用，我们用hHNF4α-siRNA和表达PXR或CAR的腺病毒共同感染肝细胞。除CYP2B6 mRNA水平外，hHNF4α-siRNA诱导的酶和转运体mRNA水平的降低未恢复，通过过表达CAR可将其恢复到对照水平。此外，尽管hHNF4α-siRNA对CYP诱导剂处理后CYP2B6、CYP2C8、CYP2C9或CYP3A4 mRNA水平的诱导倍数没有显著影响，但与对照相比，hHNF4α抑制细胞中的水平显著下降。这些结果表明，HNF4α在人肝细胞中药物代谢酶和转运体的表达中起主导作用，并且HNF4α表达水平可能是这些酶和转运体表达个体间差异的一个决定因素。
