Department of Pharmacology, School of Medicine, Sapporo Medical University, Sapporo, Japan.
PLoS One. 2013 Sep 11;8(9):e73875. doi: 10.1371/journal.pone.0073875. eCollection 2013.
Excessive reactive oxygen species (ROS) induce apoptosis and are associated with various diseases and with aging. SIRT1 (sirtuin-1), an NAD+-dependent protein deacetylase, decreases ROS levels and participates in cell survival under oxidative stress conditions. SIRT1 modulates the transcription factors p53, a tumor suppressor and inducer of apoptosis, and the forkhead O (FOXO) family, both of which play roles for cell survival and cell death. In this study, we aimed to know which is working greatly among p53 and FOXOs transcription factors in SIRT1's cell protective functions under oxidative stress conditions. The antimycin A-induced increase in ROS levels and apoptosis was enhanced by SIRT1 inhibitors nicotinamide and splitomicin, whereas it was suppressed by a SIRT1 activator, resveratrol, and a SIRT1 cofactor, NAD+. SIRT1-siRNA abolished the effects of splitomicin and resveratrol. p53-knockdown experiment in C2C12 cells and experiment using p53-deficient HCT116 cells showed that splitomicin and resveratrol modulated apoptosis by p53-dependent and p53-independent pathways. In p53-independent cell protective pathway, we found that FOXO1, FOXO3a, and FOXO4 were involved in SOD2's upregulation by resveratrol. The knockdown of these three FOXOs by siRNAs completely abolished the SOD2 induction, ROS reduction, and anti-apoptotic function of resveratrol. Our results indicate that FOXO1, FOXO3a and FOXO4, are indispensable for SIRT1-dependent cell survival against oxidative stress, although deacetylation of p53 has also some role for cell protective function of SIRT1.
过量的活性氧（ROS）诱导细胞凋亡，并与各种疾病和衰老有关。SIRT1（沉默调节蛋白 1）是一种 NAD+依赖性蛋白去乙酰化酶，可降低 ROS 水平，并参与氧化应激条件下的细胞存活。SIRT1 调节转录因子 p53（一种肿瘤抑制因子和凋亡诱导因子）和叉头 O（FOXO）家族，两者都在细胞存活和细胞死亡中发挥作用。在这项研究中，我们旨在了解在氧化应激条件下，SIRT1 的细胞保护功能中，p53 和 FOXO 转录因子哪个的作用更大。SIRT1 抑制剂烟酰胺和分裂霉素增强了抗霉素 A 诱导的 ROS 水平增加和细胞凋亡，而 SIRT1 激活剂白藜芦醇和 SIRT1 辅助因子 NAD+则抑制了这种作用。SIRT1-siRNA 消除了分裂霉素和白藜芦醇的作用。C2C12 细胞中的 p53 敲低实验和使用 p53 缺陷型 HCT116 细胞的实验表明，分裂霉素和白藜芦醇通过 p53 依赖和 p53 非依赖途径调节细胞凋亡。在 p53 非依赖的细胞保护途径中，我们发现 FOXO1、FOXO3a 和 FOXO4 参与了白藜芦醇对 SOD2 的上调。这些 FOXO 的 siRNA 敲低完全消除了白藜芦醇诱导的 SOD2、ROS 减少和抗凋亡作用。我们的结果表明，尽管 p53 的去乙酰化作用对 SIRT1 依赖的细胞对氧化应激的生存也有一定的作用，但 FOXO1、FOXO3a 和 FOXO4 对于 SIRT1 依赖的细胞生存是必不可少的。
