基于钙稳态失调研究NMDAR在抑郁致室性心律失常中的作用及其机制

Depression has been generally recognized as an important cause of ventricular arrhythmias and sudden cardiac death, but often neglected in clinic and the mechanisms remain unknown. Our preliminary studies found N-methyl-D-aspartate receptor (NMDAR) involving in ventricular arrhythmias induced by depression. The depression rats showed increased susceptibility of ventricular tachycardia and up-regulation of NMDAR, however, specific inhibition of NMDAR could block these changes. NMDAR is an ionic glutamate receptor which widely distributed in the central nervous system and peripheral tissues, abnormal calcium signal transduction in glutamate neurons mediated by NMDAR is an important mechanism of depression. Besides, chronic activation of NMDAR leaded to increased spontaneous calcium release and induced ventricular arrhythmias in a normal heart. Therefore, we consider that NMDAR-mediated calcium homeostasis may play a pivotal role in ventricular arrhythmias induced by depression. To prove the above hypothesis, we aim to study the effect of the regulation of NMDAR and knockout of GR1N1 gene on Ca2+ homeostasis, ventricular electrophysiological properties and susceptibility of ventricular arrhythmias in an animal model of depression. To identify the pathogenesis of ventricular arrhythmias induced by depression, and to open up new targets for prevention and treatment of psycho-cardiology disease and sudden cardiac death.

抑郁是室性心律失常和心脏性猝死的重要病因，易被临床忽视，且机制未明。我们前期研究发现，N-甲基-D-天门冬氨酸受体（NMDAR）是抑郁致室性心律失常的潜在靶点：抑郁动物室速/室颤发生率显著增加，心室肌NMDAR上调，特异性阻断NMDAR可抑制室速/室颤发生。NMDAR是广泛分布在中枢神经系统和外周组织中的离子型谷氨酸受体，其介导的谷氨酸能神经细胞钙信号转导异常是抑郁的重要机制。我们前期研究还证实，在正常动物中，特异性激活NMDAR导致心室肌细胞自发性钙释放增加，并促发室速/室颤。据此，本课题组认为：NMDAR介导的钙稳态失调是抑郁致室性心律失常的关键机制。为证明该假设，本课题通过调控NMDAR和敲除GR1N1基因，研究其对抑郁动物心室肌细胞钙稳态、心室电生理性质、室性心律失常发生的影响。藉此明确抑郁致室性心律失常的机制，为防治“双心（心理-心脏）”疾病和心脏性猝死提供新思路。

抑郁是室性心律失常和心脏性猝死的重要诱因，属于双心（心理-心脏）疾病范畴，越来越受到临床重视，但机制未明，防治困难。本课题首先制作抑郁模型，通过双向调节NMDAR受体，探讨NMDAR在抑郁相关性室性心律失常中的作用及其机制。通过实验，首先我们采用4周慢性温和刺激诱导抑郁模型，旷场实验和糖水偏好实验证实该模型模拟出抑郁、焦虑样情绪，并出现自主活动下降，为下一步实验研究提供了适宜的动物。其次，电生理实验发现（1）抑郁动物自发室性心律失常-频发室性早搏、室早二联律，提示抑郁显著增加室性心律失常的发生率；（2）抑郁显著降低动物的心率变异性，而NMDAR抑制剂MK-801干预使动物的心率变异性（HRV）恢复正常，心房和心室的有效不应期、不应期离散度恢复正常，与正常对照组（CTL组）无显著差异；（3）离体心脏测试结果表明，抑郁显著增加心房肌、心室肌的电活动异质性，导致电交替阈值下降，室速诱发率达100%，其中持续性室速诱发率达75%。而用MK-801一致NMDAR后，和使抑郁动物心脏电活动稳定，室速诱发率为25%，持续性室速诱发率为0。最后机制研究发现：（1）通过激光共聚焦实验发现，抑郁诱发心室肌细胞自发性钙释放活动明显增加，而MK-801显著降低自发性钙释放，差异具有统计学意义；（2）生化实验显示，抑郁组的NMRAR1、p-CaMKII/CaMKII的表达量显著增加，而MK-801使上述蛋白表达正常。上述结果表明抑郁导致NMDAR受体激活开放，引起钙稳态失调，包括自发性钙活动增加、钙运作相关蛋白表达升高，是抑郁致心室肌电活动紊乱和室性心律失常易感性增加的重要机制。该研究明确NMDAR介导的钙运作紊乱为抑郁致室性心律失常和心脏性猝死关键机制，有望成为治疗双心疾病的新靶点。