血管内皮上皮细胞钠通道（ENaC）在糖尿病内皮功能障碍中的作用及机制研究

Diabetes is a kind of endocrine and metabolic disease characterized by the increase of chronic blood glucose. Vascular endothelial cell dysfunction is one of the originating factors in diabetic patients with vascular complications. Recent studies have shown that the epithelial sodium channel (ENaC) was expressed in vascular endothelial cells. We confirmed that ENaC could form the functional ion channel in the endothelial cells. The endothelial ENaC activity was significantly increased in diabetic mice model. However, its regulatory mechanism remains to be elucidated. Therefore, we proposed the hypothesis that the level of 20-hydroxyeicosatetraenoic was increased in diabetic mice. It could significantly upregulate the expression and activity of ENaC via intracellular signal pathway, thereby affecting the sodion level and NO synthesis/release in endothelial cells, eventually resulting in vascular endothelial dysfunction. The wild type and diabetic mice were used in the experiment. The effects of ENaC in diabetes induced endothelial cells dysfunction were explored by various research methods. The molecular mechanisms of diabetes mediated increase of vascular endothelial ENaC activity and increased expression were investigated. The purpose of the paper was to investigate the regulatory role of ENaC in vascular endothelial cells dysfunction, so as to provide a new theoretical basis for the pathogenesis of diabetic vascular dysfunction.

糖尿病是一种以血糖慢性增高为特点的内分泌代谢疾病，血管内皮细胞功能障碍是糖尿病患者血管并发症的始发因素之一。近年研究发现上皮细胞钠通道（ENaC）在血管内皮细胞中表达，我们证实ENaC在内皮上形成功能性的离子通道，在糖尿病小鼠模型中，内皮ENaC活性显著升高，但其调控机制有待阐明。因此我们提出假设：在糖尿病中，20-羟-二十烷四烯酸水平升高，其通过细胞内信号通路显著上调ENaC表达和活性，进而影响内皮细胞内钠离子水平和 NO 合成/释放，最终导致血管内皮功能障碍。我们将应用野生型和糖尿病模型小鼠及内皮细胞系，采用多种研究方法，研究ENaC在糖尿病引起内皮功能障碍中的作用，阐明糖尿病介导血管内皮ENaC活性升高和表达增加从而导致内皮功能障碍的分子机制。本项目探讨血管内皮细胞 ENaC 在血管内皮功能障碍中的调节作用，为糖尿病性血管功能异常发生机制提供新的理论依据。

上皮钠离子通道（Epithelial Sodium Channel,ENaC）可以调节钠离子的转运，但是该通道在糖尿病引起的内皮功能紊乱中的作用及机制尚未被揭示。本课题采用分子生物学、电生理记录技术、激光共聚焦等实验手段，围绕糖尿病的危险因子对血管内皮ENaC活性的调控和机制及小分子化合物的潜在治疗靶点展开研究。课题首次发现：1.糖尿病代谢产物棕榈酸可以异常激活ENaC活性，其机制为棕榈酸通过引起细胞内钙升高，激活NADPH酶，引起细胞内ROS水平升高，升高PI3K活性，进而激活ENaC活性；2. 小分子气体H2S可以通过氧化还原缓解棕榈酸引起的ENaC活性异常升高。3.首次发现在小鼠血管内皮上形成功能性ENaC离子通道蛋白；4.发现糖尿病代谢产物氧化性低密度脂蛋白（ox-LDL）可以通过激活瘦素样氧化型低密度脂蛋白受体（LOX-1），进而激活NADPH， 引起细胞内ROS升高，从而激活ENaC活性；4. 抑制ENaC活性可以缓解ox-LDL引起的血管内皮舒张功能障碍；5.硝普钠（NO供体）可以通过sGC/PKG信号通路缓解ox-LDL引起的ENaC异常激活。6.应用benzamile（ENaC抑制剂）可以缓解高脂喂养的LDLr-/-小鼠的血管动脉粥样硬化。我们的研究揭示ENaC在调节内皮功能紊乱中具有重要作用，以上研究结果为探索血管内皮细胞上的离子通道异常调节参与糖尿病血管病变调控提供理论依据，为防治糖尿病血管病变提供新靶点和潜在治疗药物。