疏水性胆盐(HBS)在移植肝缺血型胆管病的发生中起重要作用，但其作用途径及分子机制仍不清楚。最新研究显示，胆管细胞分泌的碳酸氢根离子(HCO3-)可抑制HBS质子化而阻止其细胞内渗透，对保护胆管细胞免受HBS损伤具有重要意义。而阴离子交换蛋白AE2是胆管细胞分泌HCO3-的关键分子。因此，结合前期实验结果，我们提出，肝移植后AE2表达及功能的减低可能通过降低HCO3-分泌，促进胆盐细胞内渗透，从而在HBS介导的移植肝胆管损伤中起重要作用。我们拟以体外培养的人胆管上皮细胞和小鼠肝移植模型为实验对象，首先利用同位素示踪技术证明AE2表达及功能降低对胆盐细胞内渗透积聚的作用，并分析其与胆管细胞损伤及胆管周围纤维化的关系；然后，我们利用基因沉默、荧光素酶报告基因分析等技术阐明肝移植后胆管细胞AE2表达及活性降低的分子机制。本项目将为移植肝缺血型胆管病变防治策略的设计提供新的理论依据。

Hydrophobic bile salts (HBS) play an important role in the pathogenesis of ischemia-type biliary lesions (ITBL) after liver transplantation. However, the exact action pathways for bile salts and its molecular mechanism remain unclear. Recent study shows that HCO3- secreted by cholangiocytes is essential for protection of biliary epithelial cells from HBS toxicity by inhibiting the protonation and subsequent intracellular permeation of HBS. Meanwhile, Anion exchanger type 2 (AE2) is the key molecule responsible for HCO3- secretion. Thus, Given the latest reports and our preliminary results, we tentatively propose that the downregulation and inactivation of AE2 were responsible for the HBS-mediated biliary epithelial damage through the decrease of HCO3- secretion and subsequent facilitation of the intracellular permeation of HBS. With the in vitro cultured human bile duct epithelial cells and mouse liver transplant model, we will first use the isotopic tracer technique to verify the role of AE2-mediated bile salt permeation and intracellular accumulation in the bile duct injury and peribiliary fibrosis,and then investigate the mechanism of downregulation and inactivation of AE2 after liver transplantation using gene silencing, luciferase gene reporter assay and other molecular biology techniques. This study will provide new theoretical basis for designing efficient prevention and treatment strategy of ITBL after liver transplantation.