The Role of Sirtl in Vascular Senescence and Funcrion

酵母Sir2在基因沉默、抗逆性和长寿中起着至关重要的作用。哺乳动物Sirt1 NAD（+）依赖性蛋白去乙酰化酶是与Sir2最接近的同源物，通过与p53等多种生物分子的功能相互作用，调控细胞周期、细胞衰老、细胞凋亡和代谢。为了研究Sirt1在内皮功能障碍和过早衰老中的作用，我们检测了Sirt1抑制对人脐静脉内皮细胞（HUVEC）的影响。sirtinol或siRNA抑制Sirt1诱导的过早衰老样表型，通过衰老相关的β -半乳糖苷酶（sa - β -gal）活性增加、持续生长停滞和治疗后10天细胞形态变大变平来判断。sirtinol或Sirt1 siRNA抑制Sirt1增加PAI-1表达，降低eNOS蛋白表达和活性。sirtinol或Sirt1 siRNA治疗增加了p53的乙酰化，而p53的表达没有改变。受损表皮生长因子诱导的丝裂原活化蛋白激酶的激活与Sirt1抑制诱导的衰老样生长停滞有关。相反，Sirt1的过表达可阻止过氧化氢诱导的sa - β -gal活性、形态学改变和PAI-1和eNOS的紊乱表达。接下来，我们发现磷酸二酯酶3抑制剂西洛他唑对HUVEC过早衰老样表型具有保护作用，no依赖性Sirt1表达在其作用中起关键作用。我们得出结论，Sirt1可能通过防止应激诱导的过早衰老而对内皮功能障碍发挥保护作用。

Yeast Sir2 plays critical roles in gene silencing, stress resistance and longevity. Mammalian Sirt1 NAD (+)-dependent protein deacetylase, the closest homolog of Sir2, regulates cell cycle, cellular senescence, apoptosis and metabolism, by functional interactions with a number of biological molecules such as p53. To investigate a role of Sirt1 in endothelial dysfunction and premature senescence, we examined the effects of Sirt1 inhibition in human umbilical vein endothelial cells (HUVEC). Sirt1 inhibition by sirtinol or siRNA for Sirt1-induced premature senescence-like phenotype, as judged by increased senescence-associated beta-galactosidase (SA-beta-gal) activity, sustained growth arrest and enlarged and flattened cell morphology at 10 days after the treatment. Sirt1 inhibition by sirtinol or Sirt1 siRNA increased PAI-1 expression and decreased both protein expression and activity of eNOS. Treatment with sirtinol or Sirt1 siRNA increased acetylation of p53, while p53 expression was unaltered. Impaired epidermal growth factor-induced activation of mitogen-activated protein kinases was associated with Sirt1 inhibition-induced senescence-like growth arrest. Conversely, overexpression of Sirt1 prevented hydrogen peroxide-induced SA-beta-gal activity, morphological changes and deranged expression of PAI-1 and eNOS. Next, we found that cilostazol, a phosphodiesterase 3 inhibitor, exerted protective effects against premature senescence-like phenotype of HUVEC, and NO-dependent Sirt1 expression plays a key role in its effects. We conclude that Sirt1 may exert protective effects against endothelial dysfunction by preventing stress-induced premature senescence.