Role of SIRT6 in calcific aortic valve disease

描述(申请人提供)：衰老与心血管钙化的进行性增加有关1。血流动力学显着的主动脉瓣狭窄影响3%的65岁以上人群。即使是中度主动脉瓣狭窄(峰值速度为3-4m/s)的患者，5年无事件存活率也不到40%，唯一被批准的治疗方法是瓣膜置换手术。然而，最近的工作描述了钙化的主动脉瓣中存在成骨样细胞、破骨细胞样细胞和骨基质，这表明瓣膜钙化是一个活跃的、潜在的可改变的过程。我们小组的初步数据表明，钙化的主动脉瓣细胞中存在大量的表观遗传修饰。具体地说，sirtuin 6在狭窄瓣膜中的表达显著降低，并与蛋白质和组蛋白乙酰化的增加密切相关。实验上，SIRT6在小鼠中的全局缺失导致了戏剧性的孕激素表型，并且孕激素综合征患者有更大的心血管钙化发展倾向。由于瓣膜钙化的许多危险因素与氧化应激增加有关，我们还试图确定氧化应激增加与组蛋白乙酰化/sirtuin活性之间是否存在联系。因此，目前应用的目的是通过实验确定：1)氧化应激增加组蛋白乙酰化并加速主动脉瓣钙化和狭窄的进展，2)改变SIRT6水平加速或减缓高胆固醇血症小鼠主动脉瓣狭窄的进展，以及3)血管内皮细胞或神经沟来源的细胞(即形成主动脉瓣的细胞)中SIRT6的缺失 和流出道)加速CAV的进展。我们将使用新的体内动物模型和体外方法相结合的方法来确定氧化应激和SIRT6影响主动脉瓣成骨细胞/成骨样细胞分化和活性的机制。通过使用这些方法来确定减缓钙化性主动脉瓣疾病进展的机制，我们希望找到既能延长人类寿命又能改善人类健康状况的治疗方法。

DESCRIPTION (provided by applicant): Aging is associated with progressive increases in cardiovascular calcification1. Hemodynamically significant aortic valve stenosis affects 3% of the population over age 65. Patients with even moderate aortic valve stenosis (peak velocity of 3-4 m/sec) have a 5 year event-free survival of less than 40%, with the only approved treatment being valve replacement surgery. Recent work, however, described the presence of osteoblast-like cells, osteoclast-like cells, and bone matrix in calcified aortic valves, which suggests that valve calcification is an active, potentially modifiable process. Preliminary data from our group suggest that there are substantial epigenetic modifications present in cells from calcified aortic valves. Specifically, expression of sirtuin 6 is markedly reduced in stenotic valves and strongly associated with increases in protein and histone acetylation. Experimentally, global deletion of SIRT6 in mice results in a dramatic progeroid phenotype, and patients with progeroid syndromes have a much greater propensity for development of cardiovascular calcification. As many risk factors for valve calcification are associated with increases in oxidative stress, we also sought to determine whether there is a link between increases in oxidative stress and histone acetylation/sirtuin activity. Thus, the aims of the current application is to experimentall determine whether: 1) increases in oxidative stress increase histone acetylation and accelerate progression of aortic valve calcification and stenosis, 2) altering SIRT6 levels accelerates or slows progression of aortic valve stenosis in hypercholesterolemic mice, and 3) deletion of SIRT6 in vascular endothelium or neural crest-derived cells (i.e., cells that form the aortic valve and outflow tract) accelerate progression of CAVS. We will use a combination of novel in vivo animal models and in vitro methods to identify mechanisms whereby oxidative stress and SIRT6 impact osteoblast/osteoblast-like cell differentiation and activity in aortic valves. By using thes approaches to identify mechanisms that slow the progression of calcific aortic valve disease, we hope to identify therapies that will improve both the lifespan and health span of humans.