p300/Ahnak1参与衰老相关心房肌细胞L型钙电流下调的机制研究

Atrial fibrillation (AF) is a kind of aging disease, its incidence increased with age. With the aging of the population, patients with AF in China will increase year by year, and the treatment of AF is still far from idea, especially for elderly patients; The aging of cardiomyocytes is involved in the pathological process of many cardiovascular diseases including AF; There are a variety of ion current changes in the aging atrial myocytes, which will lead to AF electrical remodeling, but its mechanism has not been elucidated; Our previous studies have shown that the expression of co-transcriptional activators and acetyltransferase p300 and its downstream signal Ahnak1 were increased in left atrial tissues from the aging patients with AF and sinus rhythm than in young patients. Ahnak1 is involved in the regulation of ICa,L by interacting with Cavβ2, and the over-expression of Ahnak1 will downregulate the Cyclin and lead to aging; So in this study we will investigate if p300 is involved in the aging of atrial myocytes and aging-related atrial electrical remodeling through the upregulation of Ahnak1, and subsequent senescence and Cavβ2-mediated inhibition of ICa,L, in human tissues, p300 knockout mice and aging mice and in vitro cultured atiral myocytes. The results will help us to elucidate the pathological mechanism of AF caused by aging.

房颤（Atrial fibrillation，AF）是一种老年病，随着我国人口的老龄化，AF患者逐年增加，但治疗效果仍不理想，其发病机制值得深入研究。心肌细胞衰老参与AF的病理过程，衰老的心房肌细胞可出现多种离子流改变，导致心房电重塑，但机制不明；我们的前期研究显示，辅转录激活因子和乙酰转移酶p300和其下游效应子Ahnak1在老龄AF和窦性患者左心房中表达均明显升高；而近期有研究发现心肌细胞中Ahnak1可通过与Cavβ2相互作用，参与ICa,L的调控；另外，随着年龄的增加，人骨骼肌中Ahnak表达增加，提示其参与衰老；因此本研究中我们拟在人体心房组织标本，心肌特异性敲除p300和衰老小鼠模型以及体外培养的心房肌细胞中，观察p300是否通过上调Ahnak1，激活其下游通路，参与衰老以及衰老相关的ICa,L下调，导致心房电重塑，以进一步阐明衰老导致AF的病理机制。

衰老是房颤（Atrial fibrillation，AF）独立危险因素，老龄AF患者逐年增加而治疗仍远未理想，需寻找新的防治策略；以心房肌细胞ICa,L减少和有效不应期缩短为主要特征的心房电重塑是AF的重要发病机制。本研究中，我们发现老龄AF患者左心房组织中辅转录激活因子和乙酰转移酶p300表达明显升高，同时衰老信号通路蛋白p53/p21，p16表达明显升高，而Cav1.2及心房肌细胞ICa,L明显下降。且与年轻小鼠相比，18月龄小鼠AF可诱发率明显升高。且老龄小鼠心房组织中p300，p53/p21和p16的表达明显升高，而Cav1.2和CyclinD1明显降低。心房肌细胞ICa,L明显下降，且APD缩短。给予姜黄素处理或p300+/-老龄小鼠，可明显降低老年小鼠的AF可诱发率，以及改善心房组织中上述因子的表达和心房肌细胞电重塑。予氧化应激诱导心房肌细胞株（HL-1细胞）衰老，可使细胞内p300，p16高表达，而Cav1.2和CyclinD1明显降低。提示氧化应激主要激活p16诱导心房肌细胞衰老。而给予姜黄素或p300 siRNA干预p300，可明显改善衰老和钙通道蛋白的表达改变。提示p300参与心房肌细胞的衰老和钙通道蛋白的调控。此外老年AF患者和老龄小鼠心房组织以及衰老HL-1细胞中Ahnak1和Cavβ2的表达明显增加。p300+/-老龄小鼠心房组织和衰老HL-1细胞中上述蛋白改变改善。而过表达p300，可使HL-1细胞Ahnak1和Cavβ2表达上调。且心房肌细胞中Ahnak1和Cavβ2存在共定位。HL-1细胞敲除Ahnak1可降低Cavβ2和p16的表达和升高CyclinD1的表达。提示Ahnak1通过调控p16/CyclinD1和Cavβ2参与心房肌细胞衰老相关电重塑，并受p300调控。本研究进一步阐明了衰老导致AF的病理机制，为AF的防治提供了新的治疗靶点。