HCN通道介导钙内流在心房颤动中电重构的作用研究

Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with increased morbidity and mortality in the general population. It has been considered that Ca2+ handing abnormalities and atrial remodeling played the important role in the genesis and maintenance of AF. Novel studies have been showed that increased expression and dysfunction of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are associated with AF closely. Meanwhile, increased calcium influx controls multi-pathophysiological processes mediated by HCN channels, but the mechanism of electrical remodeling induced by calcium influx through HCN channels is not clear during AF. The aim of this study is to investigate systematically the correlation between the change in expression of HCN channels, augmented calcium influx through HCN channels and Ca2+ handing abnormalities, using by techniques of electrophysiology, molecular biology and laser scanning confocal Ca2+ imaging system, and elucidate the mechanism of effect of calcium influx on electrical remodeling by interfering the expression and function of HCN channels. We try hard to indicate novel direction in combined therapy of AF focusing this target.

心房颤动是临床上最常见一种心律失常，具有较高的发病率及死亡率。目前认为胞钙调控紊乱及心房重构在房颤的发生和维持中起着重要作用。最近研究发现超极化激活环核苷酸门控（HCN）通道的表达及功能异常与房颤密切相关，且HCN通道对钙离子的通透性显著增大参与调控多种致病过程。但是HCN通道及其介导的钙内流在房颤状态下心房电重构的机制仍未清楚。本项目旨在联合运用电生理学、分子生物学、激光共聚焦钙成像技术手段，以建立快速心房起搏房颤犬模型为研究对象，系统研究房颤状态下HCN通道表达上调及其介导的钙内流异常与胞内钙调控紊乱之间的关系，并通过干预HCN通道表达及功能阐明其在心房电重构过程中的机制，力图以此为靶点为临床上房颤的系统治疗指出新的方向。

既往研究表明伊伐布雷定，一种高选择性HCN通道阻滞剂，可治疗或诱发心律失常，但其作用机制仍未阐明。本项目发现HCN通道阻滞剂——伊伐布雷定可显著增加心房各部位AERP；可明显降低快速心房起搏模型房颤诱发率及持续时间；可对抗快速心房起搏诱导心房组织HCN亚基mRNA及蛋白水平的过表达，可以显著阻滞单个心房肌细胞上If，功能性抑制起搏电流。并在细胞水平采用快速电刺激模拟快速房颤模型显示快速心房刺激可以显著性增加HCN通道功能性的表达，并诱导心房细胞凋亡发生。但伊伐布雷定可明显抑制细胞凋亡并降低HCN亚基的表达及一致性下调If幅度电导。同时快速电刺激可上调miR-1及miR-133的表达量，而伊伐布雷定可逆转这种改变。本项目证实伊伐布雷定在心房快速起搏模型上可有效逆转房颤介导的急性心房重构的发生并显著降低房颤的诱发率，逆转HCN通道的离子通道重构。