Piezo1介导牵张激活内向电流对慢性心力衰竭后机械牵张致恶性室性心律失常的影响和作用机制

Chronic heart failure(CHF) associated malignant ventricular arrhythmias(VA) is among the most common causes of death in cardiovascular disease. Our previous and other researches demonstrate that myocardial stretch elicits HF associated malignant VA, in which stretch-activated inward current (Is) plays an important role by decreasing the ventricular electrophysiological stability and ventricular fibrillation threshold. Our preliminary experiment results showed that Piezo1 mRNA expression was increased significantly in the ventricular wall of rats with HF, and Piezo1-mediated Is was elicited by stretching the ventricular myocytes of rats. Is was diminished in myocytes treated with siRNA against Piezo1. There is no report about the role of Piezo1 in stretch-induced arrhythmias. Therefore, we suppose that Piezo1 decreases the ventricular electrophysiological stability and ventricular fibrillation threshold via Piezo1-mediated Is, and participates in the induction of malignant VA associated with stretch-induced HF. To verify this hypothesis, this study detects Piezo1 expressions and distributions in the ventricle of HF rat model by up-regulating and down-regulating Piezo1 in rat's ventricular myocardia with respective pGC-Piezo1-EGFP vector and Piezo1-shRNA lentiviral vector, investigates the subsequent changes of ventricular cardioelectrophysiological stability, ventricular fibrillation threshold and incidence of malignant ventricular arrhythmias by optical mapping and monophasic action potential recording during stretching Langendorff-perfusion HF rats' hearts. Our study will demonstrate the possible functions and electrophysiological mechanisms of Piezo1 in the induction of malignant VA associated with stretch-induced HF. And so this study will provide clues to develop new ways to prevent and treat the malignant cardiac arrhythmias and sudden cardiac death in patients with CHF.

慢性心力衰竭（CHF）后恶性室性心律失常（VA）是心血管疾病常见死亡原因。我们前期和国内外研究表明机械牵张引起CHF后恶性VA，牵张激活内向电流（Is）降低心室肌电生理稳定性和室颤阈值是其关键。预实验结果发现Piezo1在CHF大鼠心室肌中显著增强并产生Is。Piezo1是否参与及如何参与CHF后机械牵张致恶性VA发生，迄今尚无报导。基于我们前期和国内外研究，我们提出Piezo1介导Is降低心室肌电生理稳定性和室颤阈值参与CHF后机械牵张致恶性VA的科学假设。本实验拟通过pGC-FU-Piezo1-EGFP及Piezo1-shRNA重组慢病毒分别上调和下调心室肌Piezo1，探讨Piezo1在CHF后恶性VA发生中的作用及Piezo1介导Is对心室肌电生理稳定性和室颤阈值的影响，明确Piezo1在CHF后机械牵张致恶性VA中的作用和电生理机制，为临床防治CHF后恶性VA奠定基础。

Piezo 1作为新近被明确的机械牵张激活离子通道，是否通过感受机械牵张刺激在心血管疾病的发生以及发展中起到重要促进作用，特别是慢性心衰后心律失常的发生，目前仍未见报道。我们的研究首先发现Piezo1表达于大鼠心脏以及人体心房组织，并定位于心肌细胞以及成纤维细胞的细胞膜以及内质网膜。在心肌梗死后慢性心衰大鼠模型中，随着心衰进展，心室肌组织Piezo1表达显著增加，并且血管紧张素受体抑制剂losartan可以抑制Piezo 1的表达。细胞实验发现，血管紧张素II通过激活AT1-Erk1/2信号通路上调心室肌细胞Piezo1的表达。该研究结果表明AngⅡ通过激活AT1-Erk1/2信号通路上调心肌组织Piezo 1表达，从而引起慢性心衰大鼠心室组织Piezo 1离子通道的重构，ARBs治疗可有效抑制Piezo1的上调。通过全细胞膜片钳技术证实Piezo1通过感受机械牵张刺激引起大鼠心室肌细胞牵张激活内向电流（Is）的产生，提示慢性心衰大鼠心室Piezo1的重构可能通过感受机械牵张刺激产生Is，在心衰后心律失常的发生中起到重要促进作用。此外，我们的研究发现房颤患者心房组织Piezo 1的表达水平显著增高，且与心房纤维化相关。Piezo 1可以介导机械牵张刺激引起成纤维细胞活化成肌成纤维细胞和纤维化，其具体的机制可能是通过引起成纤维细胞内钙离子调控异常而激活成纤维细胞。我们针对Piezo1在心衰后心律失常的发生以及房颤心房纤维化方面进行了初步研究，为后续进一步探讨Piezo1在心血管疾病的发生发展中的作用奠定了实验基础。