上调Smyd1表达抑制内质网应激在有氧运动改善心梗大鼠心功能中的作用

Myocardial infarction (MI) results in ischemia and hypoxia in heart muscle, produces persistent endoplasmic reticulum stress (ERS), which lead to cardiomyocytes apoptosis and necrosis, finally, induce heart failure. Smyd1, a member of histone methyltransferases, plays an important role in the heart development and normal physiological function. It has been reported that aerobic exercise could inhibit ERS and improve cardiac function in infarcted heart. However, whether up-regulation of Smyd1 expression could inhibit ERS reaction and its role in the exercise-induced improvement of cardiac function in infarcted heart are not well known. In this project, we intend to use rat MI model, smyd1 knockout zebrafish and H9C2 cell to detect the role of inhibition of endoplasmic reticulum stress by Smyd1 in aerobic exercise-induced improvement of cardiac function in rats with myocardial infarction. The main contents include: detect ERS and Smyd1 expression in MI rat; use smyd1 knockout zebrafish model with or without hypoxia intervention to test whether Smyd1 could regulate ERS reaction; use smyd1 knockout and overexpression H9C2 cell model with or without hypoxia intervention, to test whether Smyd1 could regulate the expression of SERCA2, Hsp90, and TRB3, reduce ERS reaction; use exercise model of MI rat and H9C2 cell stimulated with AMPK agonist to detect whether aerobic exercise could up-regulate Smyd1 expression, inhibit ERS reaction, reduce the level of myocardial cell apoptosis and improve cardiac function in infarcted rats. In this project, we aim to detect the target of exercise-induced protection effect in infarcted heart, and give possible targets and new ideas for the MI treatment.

心梗致心肌缺血缺氧，产生持久性内质网应激（ERS），心肌细胞凋亡坏死，诱发心衰。组蛋白甲基转移酶Smyd1在心脏发育和成体功能维持中作用重大。有氧运动可降低心梗心脏ERS水平，改善心功能。但上调Smyd1是否抑制ERS反应及其在运动改善心梗心功能中的作用尚不清楚。本项目利用大鼠-斑马鱼-细胞模型，从整体心功能、器官组织、蛋白和基因调控等方面进行探索。主要内容包括：检测心梗大鼠心脏ERS和Smyd1的表达变化；利用斑马鱼smyd1基因敲除与低氧干预模型研究Smyd1与ERS反应的调控关系；检测H9C2细胞敲除/过表达smyd1是否调节SERCA2、Hsp90和TRB3表达，调控低氧诱导的ERS反应；利用心梗大鼠运动干预和H9C2细胞的AMPK激动剂干预（模拟运动效应）模型，探讨有氧运动上调Smyd1表达抑制ERS反应，改善心功能及其机制。为探索运动改善心衰病理进程作用机制与靶点筛选提供依据。

心梗致心肌缺血缺氧，产生持久性内质网应激（ERS），心肌细胞凋亡坏死，诱发心衰。组蛋白甲基转移酶Smyd1在心脏发育和成体功能维持中作用重大。有氧运动可降低心梗心脏ERS水平，改善心功能。但上调Smyd1是否抑制ERS反应及其在运动改善心梗心功能中的作用尚不清楚。本项目基于大鼠-小鼠-斑马鱼-细胞模型，研究Smyd1对内质网应激（endoplasmic reticulum stress, ERS）相关蛋白表达的影响，探讨Smyd1调节ERS反应在运动改善心梗心脏功能中的可能作用。结果发现Smyd1表达随心梗病理进程的发展而发生变化。低氧可下调斑马鱼心脏smyd1b基因表达，上调ERS相关基因表达；敲除smyd1b导致斑马鱼心跳停止，胸腔水肿，上调unc45、hsp90、ERS和细胞凋亡相关基因表达。高浓度H2O2可抑制Smyd1表达，诱发ERS反应；而抑制smyd1表达可降低H9C2细胞肥大程度和正常ERS反应，增加TRB3蛋白表达，过表达smyd1改善H2O2诱导的ERS反应。不同运动方式均可有效改善心梗后心功能和心肌纤维化水平，中等强度的持续有氧运动更为安全。运动可上调Smyd1蛋白表达，改善心梗心脏ERS水平，降低氧化应激损伤和细胞凋亡，提升心功能；NRG1和Trx1上调心梗心脏Smyd1表达可能是运动改善ERS水平和细胞凋亡，提升心功能的重要机制之一。心梗导致骨骼肌ERS水平增加，细胞发生凋亡，肌肉质量减少；运动上调骨骼肌NRG1和Trx1蛋白表达，降低氧化应激水平，缓解ERS反应和细胞凋亡，降低蛋白泛素化降解过程，抑制心梗后的骨骼肌质量减少。本项目证实心梗后损伤微环境的改善和调控Smyd1的表达是运动保护心梗后心功能的重要切入点，为运动保护效应的分子机制研究和作用靶点筛选提供实验依据。