Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, 20 Penn Street, Baltimore, Maryland, 21201, USA.
Key Laboratory of Pharmacology of Ministry of Education, Zunyi Medical University, Zunyi, China.
Pharm Res. 2020 Jan 6;37(2):26. doi: 10.1007/s11095-019-2753-x.
The bile salt export pump (BSEP), a key player in hepatic bile acid clearance, has been the center of research on drug-induced cholestasis. However, such studies focus primarily on the direct inhibition of BSEP, often overlooking the potential impact of transcriptional repression. This work aims to explore the disruption of bile acid efflux caused by drug-induced BSEP repression.
BSEP activity was analyzed in human primary hepatocytes (HPH) using a traditional biliary-clearance experiment and a modified efflux assay, which includes a 72-h pretreatment prior to efflux measurement. Relative mRNA and protein expressions were examined by RT-PCR and Western blotting, respectively.
Metformin concentration-dependently repressed BSEP expression in HPH. Although metformin did not directly inhibit BSEP activity, longer metformin exposure reduced BSEP transport function in HPH by down-regulating BSEP expression. BSEP repression by metformin was found to be AMP-activated protein kinase-independent. Additional screening of 10 reported cholestatic non-BSEP inhibitors revealed that the anti-cancer drug tamoxifen also markedly repressed BSEP expression and reduced BSEP activity in HPH.
Repression of BSEP alone is sufficient to disrupt hepatic bile acid efflux. Metformin and tamoxifen appear to be prototypes of a class of BSEP repressors that may cause drug-induced cholestasis through gene repression instead of direct BSEP inhibition.
胆汁盐输出泵（BSEP）是肝脏胆汁酸清除的关键因素，一直是药物性胆汁淤积研究的中心。然而，此类研究主要集中在 BSEP 的直接抑制上，往往忽略了转录抑制的潜在影响。本研究旨在探讨药物诱导的 BSEP 抑制引起的胆汁酸外排中断。
采用传统的胆汁清除实验和改良的外排实验分析人原代肝细胞（HPH）中的 BSEP 活性，外排测量前进行 72 小时预处理。通过 RT-PCR 和 Western blot 分别检测相对 mRNA 和蛋白表达。
二甲双胍浓度依赖性地下调 HPH 中的 BSEP 表达。尽管二甲双胍本身并没有直接抑制 BSEP 活性，但较长时间的二甲双胍暴露通过下调 BSEP 表达降低了 HPH 中的 BSEP 转运功能。二甲双胍对 BSEP 的抑制作用与 AMP 激活的蛋白激酶无关。对 10 种已报道的致胆汁淤积非 BSEP 抑制剂的进一步筛选发现，抗癌药物他莫昔芬也显著下调了 HPH 中的 BSEP 表达并降低了 BSEP 活性。
仅抑制 BSEP 就足以破坏肝脏胆汁酸外排。二甲双胍和他莫昔芬似乎是一类 BSEP 抑制剂的原型，它们可能通过基因抑制而不是直接抑制 BSEP 引起药物性胆汁淤积。
