心外膜脂肪对心肌细胞钙瞬变的影响及其介导非体外循环冠脉搭桥术后新发房颤的机制研究

Post-operative atrial fibrillation (PoAF) is a commonly encountered arrhythmia and occurs in up to 40% of patients after coronary artery bypass surgery (CABG).Knowledge of the mechanism underlying PoAF is scarce.A growing body of data from epidemiological and clinical studies has demonstrated that epicardial adipose tissue（EAT)is consistently associated with AF.The relationship between PoAF after off-pump CABG and EAT remain unclear.We have confirmed in previous work that EATV is strong associated with PoAF after off-pump CABG.Local inflammation, oxidative stress may play important role in PoAF.EAT is a source of inflammatory mediators and ROS.In summary we suggest a hypothesis"EAT effect the PoAF after off-pump CABG through a local inflammation and oxidative stress way".We intended to detect the local inflammatory mediators and ROS in the post-CABG EAT,learn the relationship between PoAF and the local inflammation and oxidative stress of EAT.Then we will prepare conditioned media (CM) generated from EAT to investigate the effect of epicardial fat on Ca2+ transient and SR Ca2+ leak of cardiomyocytes,learn the mechanism of that how epicardial fat affecting cardiomyocytes electrophysiology.

新发房颤是非体外循环冠脉搭桥（off-pump CABG）术后最常见的并发症之一，其发生机制不明。我们的前期工作证实心外膜脂肪组织(EAT)体积与off-pump CABG术后新发房颤的发病率呈正相关，心肌脂质含量与局部炎性介质水平正相关。我们提出假设“EAT 通过局部炎症反应和氧化应激介导off-pump CABG术后新发房颤”。本项目拟1.分析off-pump CABG手术患者EAT样本局部炎性介质和活性氧族（ROS）含量与术后新发房颤的相关性；2.探寻EAT条件培养基对心肌细胞Ca2+瞬变和肌浆网Ca2+释放（SR Ca2+ leak）等电生理活动的影响；3.明确EAT局部炎症反应和氧化应激水平的时间变化趋势，对照术后房颤的常见发生时点。在人体组织、细胞、动物实验三个水平上验证EAT介导off-pump CABG术后新发房颤的机制，为临床提供新的治疗策略。

心肌重构广泛存在于心梗，房颤等心脏疾病中，其病理表现为心肌肥大和纤维化。本研究中，我们在 MI 大鼠模型中观察到明显的心外膜脂肪组织 (EAT)堆积，且 EAT 含量与 MI后 2 周和 4 周组的心肌细胞大小和心肌纤维化面积呈正相关。将大鼠心肌细胞系H9C2和原代大鼠心脏成纤维细胞在由MI 4周组（EAT-CM）制备的条件培养基中培养。结果发现EAT-CM 通过提高细胞内活性氧 (ROS) 水平来扩大 H9C2 细胞的细胞表面积并增强心脏成纤维细胞向肌成纤维细胞的活化。机制上，miR-134-5p 在 H9C2 细胞和原代大鼠心脏成纤维细胞中均被 EAT-CM 上调。 miR-134-5p 敲低通过上调赖氨酸乙酰转移酶 7 （KAT-7）的表达来促进锰超氧化物歧化酶和过氧化氢酶的组蛋白 H3K14 乙酰化，从而降低 ROS 水平。体内研究表明，敲低 miR-134-5p 可限制 MI 大鼠模型中的不良心肌重塑，表现为减轻心肌细胞肥大和纤维化。我们的研究阐明了一种涉及 EAT/miRNA 轴的病理机制，证实 MI 后发生的不良心肌重塑与EAT密切相关。