The rat canalicular conjugate export pump (Mrp2) is downregulated in intrahepatic and obstructive cholestasis
The rat canalicular conjugate export pump (Mrp2) is downregulated in intrahepatic and obstructive cholestasis
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DOI：
10.1016/s0016-5085(97)70103-3
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发表时间：
1997-07-01
期刊：
影响因子：
29.4
通讯作者：
Boyer, JL
中科院分区：
文献类型：
--
作者：
Trauner, M;Arrese, M;Boyer, JL
背景与目的：多种有机阴离子排泄到胆汁中是由三磷酸腺苷依赖的偶联输出泵介导的，该泵已被确定为多药耐药蛋白（Mrp2）的管状异构体。Mrp2在肝内和梗阻性胆汁淤积的各种实验模型中功能受损，但其潜在的分子机制尚不清楚。本研究的目的是探讨这些分子机制。方法：采用Northern blotting、Western blot和组织免疫荧光法检测内毒素、乙炔雌二醇和胆总管结扎（CBDL）对大鼠肝脏Mrp2蛋白、mRNA表达和Mrp2组织定位的影响。为了评估Mrp2的变化是否特异性，我们还检测了小管外腺苷三磷酸酶（外腺苷三磷酸酶）和mdr p -糖蛋白（P-gp）的表达。结果：三种胆汁淤积模型均导致Mrp2蛋白显著降低（P < 0.01），其在小管膜的组织定位明显降低。内毒素处理（P < 0.0005）和CBDL处理（P < 0.05）后，Mrp2 mRNA水平显著降低，而乙炔雌二醇处理后，Mrp2 mRNA水平无明显变化。与Mrp2相比，内毒素和炔雌醇处理动物的外泌atp酶和P-gp蛋白表达保持不变，而CBDL后P-gp水平升高（P < 0.05）。结论：Mrp2表达下调可能解释了在这些胆汁淤积模型中两亲性阴离子偶联物的胆汁排泄受损。
Background & Aims: The excretion of various organic anions into bile is mediated by an adenosine triphosphate-dependent conjugate export pump, which has been identified as the canalicular isoform of the multi-drug resistance protein (Mrp2). Mrp2 function is impaired in various experimental models of intrahepatic and obstructive cholestasis, but the underlying molecular mechanisms ave unclear. The aim of this study was to investigate these molecular mechanisms. Methods: The effects of endotoxin, ethinylestradiol, and common bile duct ligation (CBDL) on Mrp2 protein, messenger RNA (mRNA) expression, and Mrp2 tissue localization were determined in rat livers by Northern blotting, Western analysis, and tissue immunofluorescence. To assess whether changes were specific for Mrp2, we also examined the expression of canalicular ecto-adenosine triphosphatase (ecto-ATPase) and mdr P-glycoproteins (P-gp). Results: All three cholestatic models resulted in a marked decrease in Mrp2 protein (P < 0.01) and its tissue localization at the canalicular membrane. Mrp2 mRNA levels diminished profoundly after endotoxin (P < 0.0005) and CBDL (P < 0.05), but did not change after ethinylestradiol. In contrast to Mrp2, protein expression of ecto-ATPase and P-gp remained unchanged in endotoxin- and ethinylestradiol-treated animals, whereas P-gp levels increased after CBDL (P < 0.05). Conclusions: Down-regulation of Mrp2 expression may explain impaired biliary excretion of amphiphilic anionic conjugates in these models of cholestasis.