低氧训练预防心肌细胞横管系统损伤的研究

A characteristic feature of striated muscle cells is the presence of deep invaginations of the plasma membrane (sarcolemma), most commonly referred to as T-tubules or the sarcolemmal transverse-axial tubular system (TATS). T-tubules accounted for 50% of membrane area. TATS mediates the rapid spread of the electrical signal (action potential) to the cell core, ultimately inducing myofilament contraction (excitation–contraction coupling).The loss and disorganization of T-tubules found in a number of pathological conditions and lead to abnormal excitation–contraction coupling. In our previous study, we analyzed the subcellular localization pattern of REEP5 in the cardiomyocyte and found that REEP5 is predominantly concentrated at T-tubules. REEP5-KO rats are susceptible to cardiac contractile dysfunction and lethal cardiac arrhythmias. The expression of REEP5 increased in myocardium of HT-treated rats, while the occurrence of cardiac arrhythmias in HT-treated rats is decreased. We assume that: HT can prevent transverse-axial tubular system from impairment by increasing the expression of REEP5, and reduce the occurrence of arrhythmia. Using the techonology of the cell biology and electrophysiology and myocardial ischemic injury animal model of REEP5 knockout rats, we explore the function of HT in the prevention of ischemic TATS imparement.This project will identify the potential molecular pathway. Our study is expected to find TATS protection strategy and to provide new potential targets for prevention and intervention of arrhythmia.

肌膜沿肌纤维横轴方向内陷形成横管。心肌细胞横管占肌膜面积的50%，形成密部心肌细胞的横管系统。横管是心肌细胞兴奋-收缩偶联的关键结构基础。横管损伤可以导致心脏电活动和机械活动异常。我们前期研究发现：受体表达增强蛋白5（REEP5）特异性定位于横管，REEP5缺陷导致横管结构紊乱和致命性心律失常发生；在经过低氧训练（HT）后的大鼠心肌组织中，REEP5的表达量显著增多；HT明显降低大鼠心律失常易感性。我们假设：HT通过增加REEP5表达，防治心肌细胞横管损伤，降低心律失常发生。本研究拟采用细胞生物学、电生理学和缺血性心肌损伤实验动物模型等技术，探索HT在防治缺血性横管损伤中的作用，并借助既有的REEP5基因敲除大鼠模型等，鉴定介导HT防治横管损伤的潜在的分子通路，阐明HT防治横管损伤的机制。我们的研究有望发现横管损伤的保护策略，并为心律失常防治提供新的潜在的干预靶点。

心律失常是心脏活动的起源和（或）传导障碍导致的心脏搏动的频率和（或）节律异常，是临床上最常见的一大类重大心血管病。横管是心肌细胞膜的重要组成部分，是心肌细胞兴奋收缩偶联的结构基础。在本项目的资助下，我们项目组聚焦于横管系统损伤与心肌兴奋收缩偶联失衡，采用细胞生物学、分子生物学、生物信息学、细胞电生理学及模式生物等方面的技术，从整体、器官、组织和细胞水平探索了横管损伤的影响及机制。我们发现受体表达增强蛋白5（Reep5）敲除REEP5-KO大鼠心肌细胞中的肌质网与横管系统之间的弯曲度减少。进一步的定量分析显示，REEP5-KO大鼠心肌细胞中的肌质网与横管系统的连接长度明显减少，提示REEP5控制肌质网膜成形以及肌质网与横管系统的空间连接。对REEP5-KO大鼠心肌细胞钙电流与钙瞬变的分析发现，REEP5-KO大鼠心肌细胞钙电流无明显改变，而钙瞬变幅度明显下降，导致兴奋收缩偶联下降。值得注意的是，这种肌质网钙释放缺陷与肌质网钙处理蛋白如RyR2、SERCA2a和CASQ2的表达水平无明显相关性。结果显示，REEP5缺陷导致的肌质网膜重塑是肌质网钙释放异常进而影响心肌细胞兴奋收缩偶联的主要原因。我们的发现从新的视角揭示了心律失常和心力衰竭的发生机制，为其治疗提供了潜在重要的干预靶点或者干预理念。本项目合计发表标注受项目资助的SCI论文5篇，代表性研究成果发表在《JAHA》、《Int J Caridiol》等领域内权威刊物上。