细胞核受磷蛋白重构调控HFpEF室性心律失常的机制研究

Ventricular arrhythmia is the most common mode of exodus in patients with heart failure and preserved ejection fraction (HFpEF). However, the arrhythmogenesis mechanisms of HFpEF are not fully understood. Phospholamban (PLB) is the major regulator of sarcoplasmic reticulum (SR) calcium-ATPase (SERCA). We recently reported that the levels of PLB are higher in the nuclear envelope than in the SR of the normal ventricular cardiomyocytes. By regulating nuclear calcium uptake, PLB modulates the initiation of spontaneous calcium waves (SCWs) from the nuclei. However, whether nuclear PLB remodeling plays a role in generating SCWs in failing ventricular cardiomyocytes remains unclear. In this grant proposal, we hypothesize that nuclear PLB remodeling in HFpEF creates an imbalanced nuclear calcium handling, which increases the frequency of SCWs originated from the nuclei. We take advantage of the Dahl salt-sensitive rats to create a model of HFpEF. By using confocal calcium imaging, optical mapping, patch clamp and nuclei isolation, et. al., we aim to elucidate that the nuclear PLB is remodeled during HFpEF, with decreased total protein expression, heightened phosphorylation and blunted responses to β-adrenergic stimulation. Such remodeling in HFpEF facilitates the nuclei-initiated, whole-cell propagated SCWs, which trigger the delayed afterdepolarization and the triggered activities, thus participating in the ventricular arrhythmias. This study will demonstrate the importance of nuclear PLB and nuclear calcium dynamics in the arrhythmogenesis in HFpEF. It may also suggest novel approaches for treating HFpEF-related ventricular arrhythmias by targeting nuclear PLB and calcium handling.

室性心律失常是射血分数保留的心衰（HFpEF）最严重的并发症之一，但其心律失常机制尚不明确。受磷蛋白（PLB）是心肌钙泵的调节蛋白。我们前期研究发现，在正常心肌细胞中，PLB在核膜较肌浆网更加浓聚，并调控起源于细胞核的自发钙波。据此我们假设，细胞核PLB在HFpEF时发生重构，调控室性心律失常的发生。本研究拟应用Dahl盐敏感大鼠构建HFpEF模型，通过共聚焦钙显像、光学标测、膜片钳和细胞核单离等技术阐明：细胞核PLB在HFpEF时蛋白表达量下降、磷酸化水平增加和对外源性β-肾上腺素反应钝化。细胞核PLB的重构有利于形成细胞核起源、全细胞传导的自发钙波，诱发晚期后除极和触发活动，导致室性心律失常的发生。本研究旨在明确细胞核PLB在HFpEF室性心律失常中的关键作用，证实细胞核钙活动异常可作为晚期后除极和触发活动的诱因。本研究能为HFpEF室性心律失常的机制研究和临床诊疗提供新思路和新线索。

射血分数保留的心衰（HFpEF）是最常见的心衰类型，而室性心律失常是射血分数保留的心衰（HFpEF）最严重的并发症之一，但其心律失常机制尚不明确。受磷蛋白（PLB）是心肌钙泵的调节蛋白。本研究发现，在正常心肌细胞中，PLB在核膜较肌浆网更加浓聚，并调控起源于细胞核的自发钙波。细胞核PLB在HFpEF时发生重构，调控室性心律失常的发生。本研究应用Dahl盐敏感大鼠构建HFpEF模型，通过共聚焦钙显像、光学标测、膜片钳和细胞核单离等技术阐明：细胞核PLB在HFpEF时蛋白表达量下降、磷酸化水平增加和对外源性β-肾上腺素反应钝化。细胞核PLB的重构有利于形成细胞核起源、全细胞传导的自发钙波，诱发晚期后除极和触发活动，通过兴奋-收缩偶联，导致室性心律失常的发生。本研究明确了细胞核PLB在HFpEF室性心律失常中的关键作用，证实细胞核钙活动异常可作为晚期后除极和触发活动的诱因。本研究能为HFpEF室性心律失常的机制研究和临床诊疗提供新思路和新线索。