染色质重塑对房颤心房肌肥大基因转录调控影响的研究

Atrial fibrillation is one of the important causes leading to circulation embolism and cerebrovascular accident with high morbidity and mortality. After cardioversion of atrial fibrillation within one year，recurrence rate is still high. therefore, to study the onset and basis of atrial fibrillation, to find the fundamental method of prevention and cure has become the current hot topics in the study of treatment of atrial fibrillation. This topic proposed by examining patients with atrial fibrillation: surface area of atrial myocyte, protein expression and chromatin histone acetylation level of hypertrophy gene. Confirmed the existence of hypertrophy in atrial myocyte、expression of hypertrophic gene and acetylation modification in chromatin histone; Incubation atrial myocyte in vitro using AngII ，hypertrophic myocyte model was constructed.By detecting the friability of chromatin structure、the ability of raising acetylation of histone acetyltransferase and enzyme、acetylated modification of chromatin histone lysine、the ability of raising transcription factor，confirm that hypertrophic stimulus can promote acetylated modification of specific lysine loci in hypertrophy genome, induce chromatin remodeling of hypertrophy gene：tend to be loose and open, thus increase the combination of transcription factors with promoter sequences, activate the transcription of hypertrophy gene, promote the process of atrial fibrillation.The research is a new exploration for pathogenesis of atrial fibrillation in the field of epigenetics. It provides new targets for intervention of atrial fibrillation in clinical treatment.

心房颤动是导致循环栓塞和脑血管意外的最常见、最重要原因之一，有极高的致残率和致死率。房颤的治疗一直未获突破性进展，归其原因主要在于对房颤发病机制仍然认识不够深入，启动、维持房颤的关键因素不清楚。因此，研究房颤的发病基础、对其进行干预，寻找根本的防治方法已成为当前房颤治疗研究的热点。本课题拟通过检测房颤病人：心房肌细胞表面积、肥大基因蛋白表达和染色质组蛋白乙酰化水平，证实房颤时存在心房肌细胞肥大、肥大基因再表达和染色质组蛋白乙酰化修饰；利用AngII体外诱导心房肌细胞，构建肥大细胞模型，检测心房肌肥大基因：染色质结构松散度、染色质组蛋白特定赖氨酸位点乙酰化修饰、募集转录因子能力等的变化，证实肥大刺激能够通过诱导肥大基因启动子序列染色质重塑，促进转录因子与启动子结合，启动肥大基因转录，促进房颤的进程。此课题是在表观遗传学领域对房颤发病机制的新探索，能够为临床治疗房颤动提供新的干预靶点。

背景：欧洲心律协会通过专家共识，根据心房心肌病的组织病理学特征，将其定义、特征化和分类为四个亚型，一型和三型的主要病理特征是心房心肌细胞肥大。本研究旨在探讨心房心肌病心肌细胞肥大的表观遗传学转录调控机制。.主要研究内容和方法：对8例慢性持续性房颤患者和7例窦性心律患者进行心脏手术治疗过程中收集右心耳样本，进行酶联免疫吸附试验和RNA测序（RNA-seq）分析。原代新生大鼠心房心肌细胞原代培养用于细胞分子检测。.试验结果：房颤患者心房肌组织中血管紧张素Ⅱ、心肌细胞增强因子2（MEF-2）、组蛋白H4、H3K27乙酰化水平较窦性心律患者升高，肥大相关基因表达上调，去乙酰化酶-4和-5与肥大相关基因的启动子结合减少。在原代心房肌细胞培养实验中，血管紧张素II诱导肥大相关基因的表达增加，促进去乙酰化酶-4和-5的磷酸化，并诱导了它们的出核转运。RNA测序分析提示血管紧张素II显著上调心肌能量和结构重构基因的表达。染色质免疫共沉淀结果提示：心肌肥大基因启动子序列染色质结合的MEF-2，染色质组蛋白乙酰化水平修饰的增加与在肥大相关基因启动子上的富集的去乙酰化酶丰度降低有关。此外，这些由血管紧张素II诱导的促肥大效应均可被氯沙坦部分抑制。.结论：房颤患者对心房肥大的易感性增加，肥大相关基因转录激活的表观遗传学特质增加。MEF2可作为平台通过交换组蛋白乙酰转移酶和去乙酰化酶对正或负向转录调控信号作出应答。血管紧张素II诱导的去乙酰化酶出核转运及由此引发的组蛋白乙酰化修饰增加可能是一种新的心房肥大调节机制，为心房心肌病的治疗提供新的治疗策略。