Endophilin A2参与肾脏纤维化调控及机制研究

Our recent study has revealed the expression of Endophilin A2 was reduced in the fibrotic kidney tissue. It suggested that Endophilin A2 downregulation may be the critical contributor to renal fibrosis. Our primary data showed that the fibrotic lesions of kidney was significantly reduced in Endophilin A2 transgene mice induced by unilateral ureteral occlusion when compared with wild type control mice. Endophilin A2 was mainly located in the proximal tulules in the cortex of kidney, and overexpression of Endophilin A2 inhibited the expression of extracellular matrix in renal tubular epithelial cells induced by injury factors. Moreover, Endophilin A2 can bind to TβR I. Our present study aimed to confirm the function of Endophilin A2 in renal fibrosis by increasing the amount of animal expriments based on these above data. Moreover, we aimed to further clarify the interaction of Endophilin A2 and TβR I and how this interaction interfered with the inhibition of TGF-β/smad signaling pathway, and found out the affect of Endophilin A2 in Epithelial-mesenchyma transition in renal tubular epithelial cells. This work will provide the evidence that modulation of Endophilin A2 expression may be a nove therapeutic stratagem for renal fibrosis.

我们最近的研究发现Endophilin A2（Endo A2）在纤维化病变的肾脏组织中表达显著减少，提示Endo A2可能是肾脏纤维化发生发展的关键调节因素。预实验结果发现：采用Endo A2转基因小鼠肾脏纤维化模型，发现转基因小鼠肾脏纤维化病变程度与野生型对照小鼠相比显著降低；Endo A2在肾脏主要表达于肾小管上皮细胞，上调Endo A2抑制损伤因素诱导的肾小管上皮细胞细胞外基质积累。Endo A2可直接结合TβR I。本研究拟在上述工作基础上，加大在体实验样品量，明确Endo A2对肾脏纤维化形成的抑制作用；阐明Endo A2结合TβR I进而调控TGF-β/smad信号通路的具体机制，并明确其对肾小管上皮细胞上皮间质转分化表型转化的影响。该工作将较系统地认识Endo A2调控肾脏纤维化的作用，为评估Endo A2是否可作为肾脏纤维化防治的新靶点提供实验室依据。

肾脏纤维化是慢性肾病的常见病例特征，发展到后期出现大量胶原沉积和积聚，导致终末期肾病。目前认为上皮间质转分化（EMT）是导致肾间质纤维化的重要原因。转化生长因子β1（TGF-β1）是诱导EMT的最强和最常见的刺激因子，其主要通过smad依赖性信号途径介导EMT。本研究主要探讨Endophilin A2对肾脏纤维化形成的作用。制备Endophilin A2转基因小鼠，通过单侧输尿管结扎（UUO）诱导小鼠形成肾脏纤维化模型。动物实验结果显示，体内过表达Endophilin A2可减少UUO诱导的小鼠肾脏FN、TGF-β1、Collagen I、Collagen III 和 Collagen IV的蛋白表达增加，以及减少Collagen I、Collagen III、Collagen IV和TGF-β1的mRNA表达增加，降低肾脏纤维化程度。培养人肾小管上皮细胞（HK2），转染Endophilin A2过表达腺病毒，结果显示，过表达Endophilin A2可抑制TGF-β1诱导的HK2细胞EMT，并抑制smad2和smad3磷酸化表达；过表达Endophilin A2还能减少TGF-β1诱导的HK2细胞TβR I表达；免疫共沉淀结果显示，Endophilin A2通过其PRD结构域与TβR I相互结合。以上结果显示，Endophilin A2通过其PRD结构域与TβR I相互结合，降低TβR I表达，从而抑制TGF-β/smad信号通路，减少TGF-β1诱导的HK2细胞转分化，最终减缓肾脏纤维化发生发展。该研究为Endophilin A2成为治疗肾脏纤维化的新靶点提供实验室依据。