上皮细胞钠通道（ENaC）在寒冷暴露诱导血管内皮功能障碍中的作用及机制研究

The epithelial sodium channel (ENaC) plays an important role in maintenance Na+ homeostasis and the regulation of blood pressure. Our preliminary work suggests that the activity of ENaC in rat mesenteric endothelial cells can be strongly stimulated by cold exposure, which is followed the blood pressure alteration. Alteration of ENaC activity contributes to reduced endothelial-dependent vascular relaxation. Based upon our recent work, we hypothesis that cold exposure stimulates expression and activity of ENaC via reactive oxygen species and intracellular signaling molecules, and subsequently causes reduced eNOS phosphorylation and NO production, imbalance the vascular homeostasis; H2S may prevent cold exposure-induced endothelial dysfunction through inhibition of ENaC. We will use Spraque-Dawlye (SD) rats, the primary cultured endothelial cells isolated from the animal models combined with electrophysiological recording in split-open arteries, wire myograph, immunofluorescence and molecular biology to address our hypothesis; we will determine whether cold exposure regulates ENaC and mechanisms by which ENaC up-regulation contributes to dysfunction of endothelial cells and the development of vascular dysfunction; we will test whether H2S exerts a protective effects on pathophysiological processes through inhibition of ENaC. The results obtained by proposed studies will gain our knowledge in understanding ENaC in cold induced hypertension. Our results also may provide new insight and intervention targets for the cold region residents suffering hypertension disease.

上皮细胞钠通道（ENaC）在维持机体钠离子平衡和调控血压方面具有重要作用。我们前期实验表明，寒冷暴露2周后，SD大鼠的血压明显升高，血管舒张功能发生障碍；血管内皮细胞ENaC的活性随着寒冷暴露时间的延长而升高，并且参与了寒冷诱导的血管舒张功能障碍。因此，我们假设：寒冷暴露可引起氧化应激水平升高而调节ENaC表达和活性的改变，进而影响细胞内Na+水平和细胞硬度变化，从而降低eNOS磷酸化和NO产生，最终诱发血管功能障碍；并进一步探索小分子气体H2S对寒冷诱发的血管功能障碍是否具有保护作用。我们拟采用寒冷诱导高血压模型检测血管内皮ENaC的表达及活性的变化规律；采用膜片钳、血管环、共聚焦显微镜和分子生物学等实验技术验证上述假设并阐明其调节机制。本项目首次探讨内皮ENaC在寒冷诱导高血压中的调节作用，为解决寒冷地域居民承受高血压疾病的困扰提供新的理论依据和干预靶点。

我们既往研究表明上皮细胞钠通道（ENaC）在血压调节中具有重要作用，然而，在寒冷暴露诱导高血压的发展过程中，ENaC是否发挥作用还未知。本研究旨在探索大鼠肠系膜动脉内皮ENaC在寒冷性高血压中的作用。我们将大鼠置于4℃环境中进行寒冷暴露，应用尾套法和血管环检测大鼠血压变化和血管功能，结果发现寒冷暴露两周后，大鼠血压明显升高，且血管内皮依赖性舒张功能障碍。我们应用血管开放式膜片钳技术，检测大鼠肠系膜动脉内皮ENaC活性，结果发现：寒冷暴露导致ENaC活性呈时间依赖性升高，且内皮NO生成降低，而在挽救实验中，给予寒冷组大鼠ENaC阻断剂和醛固酮受体拮抗剂后，血压明显下降，并改善血管舒张功能。其机制涉及：寒冷诱导血浆醛固酮水平升高，继而激活下游sgk1/nedd4-2/ENaC信号通路，ENaC活性升高引起血管内皮NO水平降低，进而导致血管舒张功能下降，诱发高血压。本研究为治疗寒冷性高血压提供了新的治疗方式。