Telomere-p53-PGC轴对心房细胞电生理和胞内Ca2+的调控在房颤中的作用及分子机制研究

Atrial fibrillation (AF) is an aging-associated disease. Several recent studies have shown that telomere shortening is closely related to AF, but the mechanism is unknown. Our previous researches and other studies reported that increased intracellular Ca2+ and reduced ICa,L were the important mechanisms of atrial fibrillation. Researches show that Telomere-p53-PGC axis plays an important role in the process of aging. It is found that intracellular Ca2+ of myocardial cells is regulated by p53 and PGC. We establish the hypothesis that Ca2+ and cellular electrophysiology may be regulated in the atrial cell by telomere-p53-PGC axis, which is involved in AF. In this study, we will explore the change of Ca2+ and electrophysiology of atrial myocytes in the aging AF patients or the elderly atrial fibrillation mouse model, and the regulating role of telomere-p53-PGC axis. The regulating effects will be also investigated in the neonatal mouse with silence or over expression of the key molecules of axis and in TERT-/- mice respectively. The study aims to reveal the molecular mechanism of regulation of Ca2+ in atrial cell by telomere-p53-PGC axis, providing theoretical and experimental basis for the correlation between shortening of telomere length and atrial fibrillation, especially atrial fibrillation in the elderly.

房颤为典型的增龄性疾病。最新研究显示，衰老相关分子端粒长度缩短与房颤发病高度相关，但具体机制不详。我们前期研究和其他学者发现，胞内Ca2+增加和ICa,L降低是房颤发生的主要机制之一。Telomere-p53-PGC调节轴在心脏衰老过程中发挥重要作用，且p53和PGC均对胞内Ca2+有调控效应。据此假设Telomere-p53-PGC轴通过调节胞内Ca2+和细胞电生理导致房颤的发生。为此，本课题拟首先研究端粒长度和telomere-p53-PGC轴与老年房颤发生的相关性及对老年鼠心房细胞电生理和胞内Ca2+的调节作用，进一步在细胞水平通过对调节轴的关键分子沉默或过表达或应用药理学手段及在整体水平构建TERT基因敲除鼠等主动干预策略，观察心房细胞电生理和胞内Ca2+的变化，旨在从衰老和Telomere-p53-PGC轴调控的角度，阐释房颤特别是老年房颤的发生机制。

房颤为典型的增龄性疾病，衰老相关分子端粒长度缩短与房颤的发生密切相关。但迄今尚未对端粒缩短在房颤病程中的作用和机制进行深入研究。本研究以胞内钙和L-型钙电流（ICa,L）为房颤发生的主要电生理指标，探究了Telomere-p53-PGC轴在心脏衰老过程中对其调控效应。取得如下成果：首先通过临床研究，明确老年房颤患者的白细胞端粒长度明显缩短并与Telomere-p53-PGC轴密切相关；其次在细胞和动物水平，通过老年鼠房颤模型、细胞水平干预、TERT-/-模式动物等不同层面的研究策略，采用多项技术联合检测，发现老年鼠心房组织中端粒长度显著缩短、房颤易感性增加；端粒缩短可激活Telomere-p53-PGC轴并参与心房细胞电生理重构，具体表现为：（1）胞内钙超载引起DAD和TA的发生率显著增加；（2）细胞膜ICa,L降低导致APD缩短；（3）线粒体ROS和能量代谢异常；（4）发现肌浆网钙释放蛋白活性形式p-RyR2和线粒体钙离子处置蛋白MCU、MICU1和VDAC1蛋白表达下调；肌浆网钙摄取蛋白SERCA2a、PLB和细胞膜CaV1.2和NCX1.1表达下调。上述综合效应引起老年心房组织复极缩短、异位节律增加，最终诱发房颤。. 本研究对于阐明衰老引起的心房组织端粒缩短在房颤中的作用，促进对老年房颤发生的电重构机制认知有所脾益，为相关房颤发生的机制研究提供借鉴。