Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu 210029, China.
Nanjing Jinling Hospital, 210002.
Biochem Pharmacol. 2012 Sep 1;84(5):701-711. doi: 10.1016/j.bcp.2012.06.010. Epub 2012 Jun 21.
In this study, we provided molecular evidences that interleukin-6 (IL-6) contributed to the decreased capacity of oxidative biotransformation in human liver by suppressing the expression of cytochrome P450 3A4 (CYP3A4). After human hepatocytes were treated with IL-6, differentially expressed in chondrocytes 1 (DEC1) expression rapidly increased, and subsequently, the CYP3A4 expression decreased continuously. Furthermore, the repression of CYP3A4 by IL-6 occurred after the increase of DEC1 in primary human hepatocytes. In HepG2 cells, knockdown of DEC1 increased the CYP3A4 expression and its enzymatic activity. In addition, it partially abolished the decreased CYP3A4 expression as well as its enzymatic activity induced by IL-6. Consistent with this, overexpression of DEC1 markedly reduced the CYP3A4 promoter activity and the CYP3A4 expression as well as its enzymatic activity. Using sequential truncation and site directed mutagenesis of CYP3A4 proximal promoter with DEC1 construct, we showed that DEC1 specifically bound to CCCTGC sequence in the proximal promoter of CYP3A4, which was validated by EMSA and ChIP assay. These findings suggest that the repression of CYP3A4 by IL-6 is achieved through increasing the DEC1 expression in human hepatocytes, the increased DEC1 binds to the CCCTGC sequence in the promoter of CYP3A4 to form CCCTGC-DEC1 complex, and the complex downregulates the CYP3A4 expression and its enzymatic activity.
在这项研究中，我们提供了分子证据，表明白细胞介素 6（IL-6）通过抑制细胞色素 P450 3A4（CYP3A4）的表达，导致人肝氧化生物转化能力下降。人肝细胞用 IL-6 处理后，差异表达在软骨细胞 1（DEC1）的表达迅速增加，随后 CYP3A4 的表达持续下降。此外，在原代人肝细胞中 DEC1 增加后，IL-6 对 CYP3A4 的抑制作用发生。在 HepG2 细胞中，DEC1 的敲低增加了 CYP3A4 的表达及其酶活性。此外，它部分消除了由 IL-6 诱导的 CYP3A4 表达及其酶活性的降低。与此一致的是，DEC1 的过表达显著降低了 CYP3A4 启动子活性以及 CYP3A4 的表达及其酶活性。使用 DEC1 构建体对 CYP3A4 近端启动子进行连续截短和定点突变，我们表明 DEC1 特异性结合 CYP3A4 近端启动子中的 CCCTGC 序列，这通过 EMSA 和 ChIP 测定得到了验证。这些发现表明，IL-6 对 CYP3A4 的抑制作用是通过增加人肝细胞中 DEC1 的表达来实现的，增加的 DEC1 结合到 CYP3A4 启动子中的 CCCTGC 序列上，形成 CCCTGC-DEC1 复合物，该复合物下调 CYP3A4 的表达及其酶活性。
