Department of Pharmacy Practice, College of Pharmacy, University of Illinois at Chicago, Chicago, IL 60612, USA.
Biochem Pharmacol. 2012 Jul 1;84(1):93-103. doi: 10.1016/j.bcp.2012.03.016. Epub 2012 Mar 30.
Pregnancy alters the rate and extent of drug metabolism, but little is known about the underlying molecular mechanism. We have found that 17β-estradiol (E2) upregulates expression of the major drug-metabolizing enzyme CYP2B6 in primary human hepatocytes. Results from promoter reporter assays in HepG2 cells revealed that E2 activates constitutive androstane receptor (CAR) and enhances promoter activity of CYP2B6, for which high concentrations of E2 reached during pregnancy were required. E2 triggered nuclear translocation of CAR in primary rat hepatocytes that were transiently transfected with human CAR as well as in primary human hepatocytes, further confirming transactivation of CAR by E2. E2-activated estrogen receptor (ER) also enhanced CYP2B6 promoter activity. The DNA-binding domain of ER was not required for the induction of CYP2B6 promoter activity by E2, suggesting involvement of a non-classical mechanism of ER action. Results from deletion and mutation assays as well as electrophorectic mobility shift and supershift assays revealed that two AP-1 binding sites (-1782/-1776 and -1664/-1658 of CYP2B6) are critical for ER-mediated activation of the CYP2B6 promoter by E2. Concurrent activation of both ER and CAR by E2 enhanced CYP2B6 expression in a synergistic manner. Our data demonstrate that at high concentrations reached during pregnancy, E2 activates both CAR and ER that synergistically induce CYP2B6 expression. These results illustrate pharmacological activity of E2 that would likely become prominent during pregnancy.
妊娠改变了药物代谢的速度和程度，但对于潜在的分子机制知之甚少。我们发现 17β-雌二醇（E2）上调了原代人肝细胞中主要药物代谢酶 CYP2B6 的表达。HepG2 细胞中的启动子报告基因检测结果显示，E2 激活了组成型雄烷受体（CAR），并增强了 CYP2B6 的启动子活性，而妊娠期间达到的高浓度 E2 是必需的。E2 在瞬时转染人 CAR 的原代大鼠肝细胞和原代人肝细胞中触发了 CAR 的核易位，进一步证实了 E2 对 CAR 的转录激活。E2 激活的雌激素受体（ER）也增强了 CYP2B6 启动子活性。ER 的 DNA 结合域对于 E2 诱导 CYP2B6 启动子活性不是必需的，这表明 ER 作用的非经典机制的参与。通过缺失和突变检测以及电泳迁移率变动和超迁移检测，结果表明，两个 AP-1 结合位点（CYP2B6 的-1782/-1776 和-1664/-1658）对于 E2 介导的 ER 激活 CYP2B6 启动子是至关重要的。E2 同时激活 ER 和 CAR 以协同方式增强 CYP2B6 的表达。我们的数据表明，在妊娠期间达到的高浓度下，E2 激活了 CAR 和 ER，它们协同诱导 CYP2B6 的表达。这些结果说明了 E2 的药理学活性，这在妊娠期间可能会变得更为突出。
