TRPV4在心房颤动发病中的作用及其分子机制研究

Abnormal electrical activity, loss of Ca2+ homeostasis and fibrosis play very important role in the pathogenesis of atrial fibrillation (AF).TRPV4 belongs to a family of nonselective cation channels. Activation of TRPV4 increases [Ca2+]i, affects electrical activity, Ca2+ homeostasis and fibrosis. However, whether TRPV4 channel involved in pathology of AF has remained unknown. Our preliminary studies found that: TRPV4 expression in the atria increased in patients with AF as well as AF model of rats with sterile pericarditis (SP) and the channel was translocated to the cell membrane. Therefore, we propose that the activation of TRPV4 involves in pathogenesis of AF through affecting electrical activates, inducing loss of Ca2+ homeostasis and promoting fibrosis. We will firstly study the changes of TRPV4 functional expression in the SP mice/ rats and effects of TRPV4 blockage/activation on the induction of AF; secondly explore whether activation of TRPV4 in the pathogenesis of ⑴ abnormal electrical activity via changing ITRPV4, INa, IK, ICa,L as well as function and distribution of Cx, ⑵ loss of Ca2+ homeostasis by altering RyR2, SERCA2a, PLB and INCX, ⑶ fibrosis via modulating MAPK/ERK signaling pathway; finally create the computer model to simulate the role and mechanism of TRPV4 in the pathophysiology of AF. The results are expected to provide a new target for the clinic treatment of AF.

电活动异常、钙稳态失调和纤维化在心房颤动（房颤）发病中起重要作用。TRPV4是一种非选择性的阳离子通道，激活后升高 [Ca2+]i，影响细胞电活动、钙稳态及纤维化。然而 TRPV4 是否参与房颤发病未见报道。我们预实验发现：房颤患者及无菌性心包炎（SP）房颤大鼠心房TRPV4表达上调，且向细胞膜转位。因此我们推测： TRPV4上调可通过改变心房电活动、诱导钙稳态失调、促进心房纤维化等机制参与房颤的发病。本项目首先研究TRPV4在SP鼠中的功能表达，阻断/激动TRPV4对房颤发作的影响；阐明激活TRPV4是否通过⑴ ITRPV4、INa、IK、ICa,L、Cx功能及分布引起心房肌电活动异常，⑵ RyR2、SERCA2a、PLB及INCX诱导心房肌钙稳态失调，⑶ MAPK/ERK等信号通路介导心房肌纤维化；最后建立计算机模型，模拟TRPV4在房颤发病中的作用和机制；为临床防治房颤提供新靶点。

TRPV4激活后升高 [Ca2+]i，影响细胞电活动，触发钙稳态失调，促进纤维化，然而TRPV4是否参与心房颤动（房颤）以及机制尚未见报道。本项目首先制备无菌性心包炎(SP)大鼠和小鼠模型留取SP术后1-14天心房组织以及房颤患者的心房组织，检测瞬时感受器电位香草酸受体4(TRPV4)的蛋白水平，发现TRPV4表达显著增多，而阻断TRPV4能显著减少SP大/小鼠房颤的诱发。此后我们利用荧光标测、膜片钳、分子生物学等技术进一步证实了TRPV4活化可通过抑制瞬时外向钾电流（Ito）以及持续外向钾电流（Iss），延长动作电位时程(APD)并增加APD在心房表明分布异质性，促进触发和折返活动，增加对房颤的易感性；抑制肌浆网上雷诺啶受体(RyR)和钙泵(SEACA)功能引起心房钙稳态失调；通过P38、AKT以及STAT3信号分子促进心房成纤维细胞的增殖和分化，参与心房纤维化，通过ERK/NF-κB信号通路激活NLRP3炎症小体进而促进炎症反应；此外，我们还构建了大鼠心房细胞、成纤维细胞的电生理模型，发现TRPV4通道电流及耦合成纤维细胞的数目可显著影响电动势时常，并呈非线性特征。因此，TRPV4活化可通过促进心房电重构、钙稳态失调、纤维化以及炎症等机制参与房颤的发生和发展，而阻断TRPV4有望用于房颤的防治。