MCP-1和MCPIP在增龄性心房颤动心房纤维化和心肌细胞凋亡中的作用及机制

The prevalence rate of atrial fibrillation(AF) generally increases with age, thus aging is an independent risk factor of AF. It has already been demonstrated in our previous studies that aging causes atrial physiological changes and decrease the density of L - type calcium current which is known as the important mechanism of occurrence and maintenance of age-related AF. Furthermore , histological changes of myocardial fibrosis and apoptosis are found in age-related AF, but the exact mechanism still remains unclear. It has been shown that monocyte chemoattractant protein-1(MCP-1) promotes the myocardial fibrosis, monocyte chemotactic protein-1 induced protein (MCPIP) is involved in myocardial apoptosis. In this study, an experimental in vivo canine model with age-related AF and in vitro cell culture will be performed, by using the technical approaches such as cardiac electrophysiology, patch clamp, flow cytometry, cellular and molecular biology. We will observe the difference in the expression of MCP-1 and MCPIP, atrial electrophysiological changes, ion channel currents, extent of atrial fibrosis and cellular apoptosis in different canine group. We aim to reveal the relationship between MCP-1, MCPIP and the occurrence of age-related AF, atrial fibrosis , atrial cellular apoptosis, to illustrate the pathological mechanism which atrial fibrosis and myocardial apoptosis induced by MCP-1 as well as MCPIP are involved in atrial remodeling and ion channel remodeling in age-related AF. All mentioned above will bring new ideas and will provide the theoretical foundation for the mechanism of atrial remodeling in age-related AF and also for the therapy.

心房颤动（房颤）患病率随年龄增长而增加，增龄是房颤的独立危险因素。本课题组前期的研究表明，增龄引起的心房电生理改变和L-型钙电流密度降低是增龄性房颤发生和维持的重要机制，且增龄性房颤存在心肌纤维化和细胞凋亡的组织形态改变，但这一改变参与增龄性房颤的确切机制尚未阐明。已知MCP-1可促进心肌纤维化，MCPIP参与心肌细胞凋亡。本研究拟通过增龄性房颤犬模型的体内试验和体外细胞培养，利用心电生理、膜片钳、流式细胞术、细胞与分子生物学等技术，观察各组犬MCP-1和MCPIP表达、心房电生理改变、离子通道电流、心房纤维化程度、细胞凋亡等的差异，揭示MCP-1和MCPIP与增龄性房颤、心房纤维化、心房细胞凋亡间的关系，阐明MCP-1和MCPIP诱导的心房纤维化和心肌细胞凋亡参与增龄性房颤心房电重构、离子通道重构发生发展的病理机制，为增龄性房颤的心房重构机制和治疗提供新的思路和理论依据。

心房颤动（简称房颤）是心血管疾病中最为常见和复杂的心律失常之一，有很高的致残率和致死率。增龄是发生房颤的独立危险因素。炎症是房颤中引起心房纤维化的重要机制，炎症因子MCPIP和MCP-1在房颤的发生发展中可能有重要作用。目的：我们旨在探讨MCP-1和MCPIP与增龄、房颤、心房纤维化之间的关系，阐明MCP-1促进心房纤维化及MCPIP导致心肌细胞凋亡的机制。主要研究内容：1.将24只比格犬根据年龄随机4组，分别为老年房颤组，老年窦律组，成年房颤组和成年窦律组，每组各6只。房颤组植入起搏器，持续左心耳起搏8周，窦律组植入起搏器不起博。结果：通过快速起搏能够成功建立慢性房颤犬模型；增龄使房颤犬的有效不应期延缩短，有效不应期离散度随刺激周长的延长而增加，校正窦房结恢复时间增加。老年犬更易诱发出房颤，且持续时间更长。老年房颤犬心房内径的增加更明显，心房纤维化程度更重，心肌细胞凋亡比例更高；老年房颤犬的外周血MCPIP、MCP-1、CCR2水平高于成年房颤组，其外周血和心肌组织中的纤维化及凋亡相关指标的表达高于成年房颤组和老年对照组。老年房颤犬心房组织中内质网应激过程中的关键酶IRE1的表达也上调。2.分离犬心房成纤维细胞和H9c2细胞，分别进行MCP-1不同浓度、不同时间点干预。结果：MCP-1可影响犬原代成纤维细胞增殖、活化、分泌功能。干扰MCP-1/CCR2途径可减少肌成纤维细胞活化功能。MCP-1/CCR2/TGF-β1途径之间存在反馈环路影响成纤维细胞活化及分泌。H9c2细胞可在MCP-1的影响下，分泌MCP-1及MCPIP。而CCR2拮抗剂可抑制MCPIP的分泌，对MCP-1的影响不大。MCP-1表达增加可引起心肌细胞生存率下降，细胞凋亡增加，CCR2拮抗剂的加入可抑制这种作用。MCP-1/MCPIP可引起心肌细胞凋亡或自噬增加，内质网应激发生，这些作用是通过CEBPβ和PPAR-γ通路起作用的。结论：MCP-1/CCR2途径可通过对成纤维细胞的作用影响心肌纤维化过程。MCPIP的表达在老年房颤犬中更多，且变化趋势与心肌凋亡水平一致。MCP-1/MCPIP可引起心肌细胞凋亡或自噬增加，内质网应激发生，这些作用是通过CEBPβ和PPAR-γ通路起作用的。