气温变化在哮喘发病中扮演重要角色，但具体机制尚未阐明。NEDD4样E3泛素蛋白连接酶（Nedd4-2）及其底物气道上皮钠离子通道（ENaC）表达异常参与哮喘的发病过程。课题组前期发现：同37℃比，低温（29℃）引起肺上皮细胞Nedd4-2表达下降。鉴于文献报道气道上皮细胞的温度敏感型钙离子通道香草素受体4（TRPV4）可能参与调控Nedd4-2表达。本课题假设冷刺激通过抑制TRPV4影响胞内钙离子水平，引起Nedd4-2表达下降、ENaC膜滞留增加，继而驱动气道脱水和炎症反应。本研究拟以TRPV4条件敲除性小鼠和肺上皮细胞作为研究对象，结合TRPV4抑制剂、激动剂、钙离子螯合剂及钙离子成像等工具，探索低温下TRPV4抑制对Nedd4-2表达的调控作用和分子机制，有望从钙离子通道调控的角度阐明冷刺激对哮喘发病的影响，为从环境因素角度干预哮喘提供理论依据。

The molecular mechanisms underlying low temperature-induced asthma has not been fully clarified. Nedd4-2 (Nedd4 like E3 ubiquitin protein ligase) and its substrate ENaC (epithelial sodium channel) has been proposed to play important roles in driving asthma. Our previous results show that the mRNA expression of Nedd4-2 in lung epithelial cells was downregulated under low temperature (29℃). TRPV4 (transient receptor potential vanilloid 4) is a type of thermosensitive Ca2+ channel which is expressed in airway epithelial cells. Studies have shown that the expression of Nedd4-2 can be regulated by intracellular Ca2+ ([Ca2+]i). We thus hypothesize that temperature change may affect the expression of Nedd4-2 through TRPV4-mediated Ca2+ influx, and cold stress could lead to inhibition of TRPV4, which in turn decreases [Ca2+]i and affect levels of ENaC through Nedd4-2-mediated ubiquitination to drive the progress of airway dehydration and inflammation. In this study, we plan to examine the possible role and mechanism of TRPV4 in the regulation of Nedd4-2 in asthma induced by low temperature exposure, by using conditioned-TRPV4 knockout mice and lung epithelial cells combined with TRPV4 inhibitor, TRPV4 agonist, Ca2+ chelator, shRNA knockout, and calcium imaging tools, to clarify possible mechanisms of asthma in response to environmental risk factors.