心律失常发生的新机制—lncRNA-MIAT靶向miR-194-5p/221/222调控心肌电重构

Myocardial infarction is one of the most common cardiovascular disease. Arrhythmias and sudden cardiac death results from ion channel remodeling in myocardial infarction. Prevention and treatment of electrical remodeling and arrhythmias is a key research topic. Our studies have shown that lncRNAs are associated with myocardial hypertrophy and heart infarction. But whether they are involved in arrhythmias has not been elucidated. Accordingly, we hypothesize that upregulation of MIAT in myocardial infarction regulates calcium and potassium channel expression via miR-194-5p/221/222-mediated NFATc3 signaling, and causes ion channel remodeling and electrical remodeling, and subsequently increases the susceptibility of infarcted hearts to arrhythmia. This study will employ patch-clamp, luciferase assay and molecule cloning technique, etc. to determine if lncRNA-MIAT is involved in cardiac calcium and potassium channel remodeling, further clarify if miR-194-5p/221/222 is involved in lncRNA-MIAT induced ion channel remodeling, and identify if lncRNA-MIAT will be a predictor and therapeutic target for arrhythmias. This study will provide new insights into the treatment of cardiac arrhythmias.

心肌梗死是最常见的心血管疾病之一，梗死边缘区心肌因离子通道失衡而导致心律失常和心源性猝死的发生。如何防治心肌电重构及心源性猝死是目前心律失常研究领域的难点。我们团队发现长链非编码RNAs（lncRNAs）与心肌肥厚、心肌梗死发生相关，但其是否参与了心梗后心律失常的发生尚不清楚。我们提出假设：心梗时上调的lncRNA-MIAT通过miR-194-5p/221/222调控NFATc3通路，进而抑制钙通道、钾通道，引起心肌电重构，增加心律失常易感性。本课题拟运用膜片钳、Luciferase及分子克隆等技术研究（1）LncRNA-MIAT是否调控了梗死边缘区心肌钙通道和钾通道重构；（2）miR-194-5p/221/222是否介导了LncRNA-MIAT诱导的离子通道失衡；（3）LncRNA-MIAT是否可以成为心律失常的预警因子及治疗新靶点。本研究将为临床心肌梗死后心律失常的防治提供新思路。

心肌梗死后心脏电重构和结构性重构是引起心律失常、心源性猝死及心衰发生和进展的关键因素，但其上游分子调控机制及潜在药物治疗靶点尚未被完全揭示。本项目通过整体动物和离体细胞水平揭示lncRNAs通过介导离子通道失衡诱发心律失常的作用和机制，以及探究梗死后心脏结构性重构的发生机理和药物防治策略。本项目的主要发现包括：（1）缺血心肌组织中表达上调的lncRNA-MIAT作为ceRNA竞争性的结合miR-194，使miR-194的活性降低，解除其对下游靶基因NFATc3的靶向抑制作用，从而增加NFATc3的表达；NFATc3转录抑制离子通道Cav1.2、KV4.2和KV4.2蛋白表达水平，进而减少Ica和Ito电流强度，增加心律失常易感性；敲减lncRNA-MIAT可以纠正心肌缺血致上述离子通道表达和功能失衡，进而发挥抗心律失常作用。lncRNA-MIAT/miR-194/NFATc3信号轴有望成为心律失常和心源性猝死的防治新靶点。（2）QT间期延长是导致恶性心律失常发生的高风险因素，也是AS2O3致心脏毒性中最为常见的节律异常表型。我们发现AS2O3诱导小鼠心脏QT间期延长，同时伴有离子通道蛋白KvLQT1和lncRNA Kcnq1ot1表达下调；进一步实验发现沉默lncRNA Kcnq1ot1可以减少KvLQT1表达，延长动作电位时程和QT间期，从而证实了lncRNA Kcnq1ot1是AS2O3致QT间期延长的关键调节分子。（3）发现Dectin-1作为炎症调节因子通过激活NLRP3炎症小体，加重缺血性心肌细胞死亡和心脏重构的作用及机制。（4）我们还开展了抗心肌缺血损伤的药物研究，证实我们自主合成的化合物-康乐欣具有减轻心肌梗死面积和改善心脏功能的作用，为缺血性心脏病的治疗提供新策略。