NLRP3炎性小体介导的肌浆网钙漏流在心衰时KChIP2表达降低和瞬间外向钾通道（Ito)重构中的作用和机制研究

瞬间外向钾通道（Ito）结构功能重构是心衰心律失常发生的重要原因。心衰时Ito下调与其β亚基KChIP2表达降低密切相关，其机制尚待查明。心衰的一个重要病理改变是肌浆网(SR)钙释放通道RyR2稳定性降低，引起钙火花介导的SR钙漏流增强，进而激活相关基因表达导致心脏结构功能重构。预实验发现，LPS刺激心肌细胞引起SR钙漏流，减少KChIP2表达，降低Ito电流；抑制钙漏流恢复Ito。因此，提出心衰时SR钙漏流引起心脏KChIP2表达降低导致心律失常发生的设想。本研究拟采用Confocal、膜片钳、ChIP等技术从分子、细胞和整体水平研究：1.心衰时SR钙漏流引起Ito通道重构的作用；2.和机制：NF-KB和/或H3K4me3对KChIP2基因表达的调节作用；3.心衰时NLRP3炎性小体引起SR钙漏流导致Ito通道重构的作用和机制，旨在阐明心衰心律失常发生的新机制，为治疗提供新靶点。

Downregulation of transient outward K+ channel (Ito) contributes to the pathogenesis of ventricular arrhythmia in heart failure (HF). It is well established that the downregulation of Ito is largely attributed to the reduction of KChIP2 expression, the beta subunit of Ito. However, the mechanisms underlying the downregulation of KChIP2 expression in HF are poorly understood. Many studies revealed that enhancement of sarcoplasmic reticulum (SR) Ca2+ leakage mediated by the increased activity of ryanodine receptors (RyRs) is a prominent feature of HF. Recent studies demonstrate that the enhancement of SR Ca2+ leak leads to left ventricular injury in HF by inducing structural and functional remodeling. The structural and functional remodeling is tightly related to changes of the expression of related genes. However, the role of SR Ca2+ leak in Ito remodeling and the resulting cardiac arrhythmia in HF remains unknown. Our preliminary data demonstrated the role of SR Ca2+ leak in inducing the downregulation of Ito in LPS-stimulated cardiomyocytes, where LPS induced enhancement of SR Ca2+ leak and decreased the transcription and expression of KChIP2 and thus Ito currents, preventing SR Ca2+ leak upregulated Ito in LPS-treated cardiomyocytes. Based on the evidence, we proposed that SR Ca2+ leakage contributed to Ito channel remodeling, inducing ventricular arrhythmia in HF. We will apply multiple advanced technologies, including manipulation of gene expression, confocal Ca2+ imaging of local Ca2+ signal (Ca2+ sparks), patch clamp recording of ion channels, chromatin immunoprecipitation (ChIP) and producing HF animal model, to testify our hypothesis. Furthermore, we will investigate the possible underlying mechanisms relating to NF-kB pathway and/or H3K4me3 regulation of the expression of Ito subunits. Given the critical role of NLRP3 inflammasome in the pathogenesis of HF and in inducing SR Ca2+ leak, we will testify the hypothesis that activation of NLRP3 inflammasome enhances sarcoplasmic reticulum (SR) Ca2+ leak and consequently leads to decreased KChIP2 expression and Ito remodeling and the development of cardiac arrhythmia in HF. At last, we will explore the therapeutic effect of inhibition of SR calcium leakage with RyR stabilizer, JTV519, on the treatment of Ito remodeling induced by SR Ca2+ leak. These efforts are expected to enrich our understanding of the mechanisms underlying the increased susceptibility to ventricular arrhythmia of failing hearts and shed new lights on the therapeutic strategies against cardiac arrhythmia in HF.