Primary biliary cholangitis (PBC) is a chronic cholestatic liver disease associated with autoimmune phenomena targeting intrahepatic bile duct cells (cholangiocytes). Although its etiopathogenesis remains obscure, development of antimitochondrial autoantibodies against pyruvate dehydrogenase complex E2 is a common feature. MicroRNA (miR) dysregulation occurs in liver and immune cells of PBC patients, but its functional relevance is largely unknown. We previously reported that miR‐506 is overexpressed in PBC cholangiocytes and directly targets both Cl–/ HCO3− anion exchanger 2 and type III inositol 1,4,5‐trisphosphate receptor, leading to cholestasis. Here, the regulation of miR‐506 gene expression and its role in cholangiocyte pathophysiology and immune activation was studied. Several proinflammatory cytokines overexpressed in PBC livers (such as interleukin‐8 [IL8], IL12, IL17, IL18, and tumor necrosis factor alpha) stimulated miR‐506 promoter activity in human cholangiocytes, as revealed by luciferase reporter assays. Experimental overexpression of miR‐506 in cholangiocytes dysregulated the cell proteomic profile (by mass spectrometry), affecting proteins involved in different biological processes including mitochondrial metabolism. In cholangiocytes, miR‐506 (1) induced dedifferentiation with down‐regulation of biliary and epithelial markers together with up‐regulation of mesenchymal, proinflammatory, and profibrotic markers; (2) impaired cell proliferation and adhesion; (3) increased oxidative and endoplasmic reticulum stress; (4) caused DNA damage; and (5) sensitized to caspase‐3‐dependent apoptosis induced by cytotoxic bile acids. These events were also associated with impaired energy metabolism in mitochondria (proton leak and less adenosine triphosphate production) and pyruvate dehydrogenase complex E2 overexpression. Coculture of miR‐506 overexpressing cholangiocytes with PBC immunocytes induced activation and proliferation of PBC immunocytes. Conclusion: Different proinflammatory cytokines enhance the expression of miR‐506 in biliary epithelial cells; miR‐506 induces PBC‐like features in cholangiocytes and promotes immune activation, representing a potential therapeutic target for PBC patients. (Hepatology 2018;67:1420‐1440)

中文翻译：

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miRNA-506 促进胆管细胞的原发性胆汁性胆管炎样特征和免疫激活


原发性胆汁性胆管炎（PBC）是一种慢性胆汁淤积性肝病，与针对肝内胆管细胞（胆管细胞）的自身免疫现象相关。尽管其发病机制仍不清楚，但针对丙酮酸脱氢酶复合物 E2 的抗线粒体自身抗体的产生是一个共同特征。 PBC 患者的肝脏和免疫细胞中存在 MicroRNA (miR) 失调，但其功能相关性很大程度上未知。我们之前报道，miR-506 在 PBC 胆管细胞中过度表达，并直接靶向 Cl-/HCO3- 阴离子交换剂 2 和 III 型肌醇 1,4,5-三磷酸受体，导致胆汁淤积。在此，研究了 miR-506 基因表达的调控及其在胆管细胞病理生理学和免疫激活中的作用。荧光素酶报告基因检测显示，PBC 肝脏中过表达的几种促炎细胞因子（例如白介素-8 [IL8]、IL12、IL17、IL18 和肿瘤坏死因子 α）刺激人胆管细胞中的 miR-506 启动子活性。胆管细胞中 miR-506 的实验性过度表达导致细胞蛋白质组谱失调（通过质谱分析），影响参与包括线粒体代谢在内的不同生物过程的蛋白质。在胆管细胞中，miR-506 (1) 诱导去分化，下调胆管和上皮标记物，同时上调间充质、促炎症和促纤维化标记物； (2)细胞增殖和粘附受损； (3)氧化应激和内质网应激增加； (4)造成DNA损伤； (5) 对细胞毒性胆汁酸诱导的 caspase-3 依赖性细胞凋亡敏感。 这些事件还与线粒体能量代谢受损（质子泄漏和三磷酸腺苷产量减少）和丙酮酸脱氢酶复合物 E2 过度表达有关。过表达 miR-506 的胆管细胞与 PBC 免疫细胞共培养可诱导 PBC 免疫细胞的激活和增殖。结论：不同促炎细胞因子增强胆管上皮细胞中miR-506的表达； miR-506 在胆管细胞中诱导 PBC 样特征并促进免疫激活，是 PBC 患者的潜在治疗靶点。（肝病学 2018；67：1420‐1440）