Nav1.8: 雷诺嗪治疗心肌梗死后室性心律失常的新靶点

Antiarrhythmic drugs (AADs) play very important roles in the treatment of post-myocardial infarction ventricular arrhythmia which has an extremely high mortality. The Nav1.8 sodium channel, encoded by gene SCN10A, usually expressed only in neurons while cardiac sodium channels are dominantly Nav1.5 that is encoded by SCN5A gene. However, under pathological situations like myocardial infarction, expression of Nav1.8 both in neurons and cardiac myocytes will increase; as a consequence will enhance the late sodium current and facilitate the development of ventricular arrhythmia. Ranolazine, an anti-ischemic medication, can exert an anti-arrhythmic effect by blocking the Nav1.8 and inhibiting late sodium current. We hypothesize that post-infarction neural remodeling will lead to an increasing expression of SCN10 in neuronal cells and cardiac myocytes. This study is designed to investigate how these changes will alter electrophysiological properties of ventricular myocardium and its pro-arrhythmic mechanisms. Effects of Ranolazine and specific Nav1.8 inhibitor on the prevention of ventricular arrhythmia will also be studied. It is expected that this study will further our understanding on the mechanism of post-infarction ventricular arrhythmia and provide novel target to develop next generation AADs.

抗心律失常药物（AAD）在治疗病死率极高的心梗后室性心律失常中仍有不可替代的重要地位。生理情况下SCN10A编码的NaV1.8钠通道主要表达于神经元，而心肌组织内以SCN5A编码的NaV1.8钠通道占主导地位。但在心梗等病理状态下在神经元和心肌细胞的NaV1.8表达均有增加/功能增强，使晚钠电流增大，从而参与心律失常的发生和维持。抗心肌缺血药雷诺嗪或可通过阻滞Nav1.8通道、抑制晚钠电流发挥抗心律失常作用。本课题将从分子-细胞-组织-整体四个层次展开研究，观察心梗后神经元形态、细胞因子与神经递质分泌、神经元和心肌细胞内SCN10A表达及功能改变及其对心肌细胞电生理特性的影响和致心律失常机制；以及雷诺嗪和Nav1.8特异性阻滞剂的干预效果。本课题的预期结果有助于进一步理解心梗后室性心律失常的发生机制，并以雷诺嗪的干预效应为借鉴，为研发新型AAD提供思路和实验依据。

根据课题《申请书》和《计划书》的安排，本课题于 2018年完成在体实验部分，包括制作大鼠心梗模型，观察大鼠心梗后及假手术组3个月，6个月，通过大体标本、HE染色、Masson染色查看心梗模型情况；于 2019 年利用心肌模型，开始组织免疫荧光染色Nav1.8和神经酪氨酸羟化酶免疫染色分布情况；检测各组大鼠心肌组织NGF和GAP-43 。同时提取各组的大鼠心肌组织的RNA进行SCN10A基因表达量的检测。观察各组大鼠SCN10A基因表达量的差异；于 2020年完善各组心肌组织的留取并进行Nav1.8蛋白的Western Blot检测查看各组蛋白表达量差别。利用心梗模型并急性分离的心肌细胞，同步记录各组心室肌细胞钠通道表达的类型和分布，进行Nav1.8和Nav1.5细胞免疫荧光染色。于 2021 年继续心梗模型并急性分离的心肌细胞，同步记录各组心室肌细胞钠电流情况，并观察雷诺请药物干预后对于Na电流的干预情况。同步记录各组大鼠在体模型中心电图记录，并给与电生理检查（EPS）刺激，观察室性心律失常的诱发情况，并给与雷诺嗪干预后对于室性心律失常诱发情况的改善，分析和总结研究成果。本课题研究按照计划安排稳步进展，并顺利完成所研究内容。