A microplate reader was used to measure the absorbance at 450 nm. that specific activation of SIRT1 suppresses senescence. And the Akt-FoxO1 pathway, as the upstream of SIRT1, might be involved in the regulation of H2O2-induced senescence of rat NP cells by affecting Trelagliptin the expression of SIRT1. In addition, the resveratrol played an anti-senescence role in rat NP cells, which might impact the Akt-FoxO1-SIRT1 axis. Conclusion: SIRT1 ameliorated oxidative stress-induced senescence of rat NP cell which was regulated by Akt-FoxO1 pathway, and resveratrol exerted anti-senescence effects by affecting this signaling axis. [7], but the process of H2O2-induced premature senescence of NP cells needs further verification. silent information regulator 1 (SIRT1) is usually a member of the silent information regulator 2 protein family. It is a highly conserved nicotinamide (NAD+)-dependent deacetylases and has been found to be associated with age-related diseases, malignancy and degenerative disorders [8,9]. SIRT1 has been shown to regulate cellular oxidative stress burden and its toxicity, while cellular redox status can also affect SIRT1 level and activity through multiple manners [10]. Although previous study has shown that oxidative stress led to a reduction of SIRT1 large quantity and transcription Trelagliptin in lung epithelial cells, endothelial cells and macrophages, the SIRT1 expression was significantly elevated in an early degeneration stage [11,12]. Thus, the expression of SIRT1 in NP cells modulated by oxidative stress is controversial. In addition, SIRT1 is able to regulate the expressions of p53 and p16 by deacetylation in NP and other type cells to relieve the progress Fst of senescence [13C15]. Trelagliptin However, the role of SIRT1 in senescent NP cells has not been well analyzed. Transcription factor FoxO family members (and FoxO1 in particular) also play important roles in aging, cell metabolism, insulin resistance and oxidative stress resistance [16]. FoxO1, as a transcription factor, binds to a large set of target gene promoters and has been shown to regulate the transcription of genes even in the absence of direct DNA binding [17]. And it has been shown that FoxO1 could bind directly to the SIRT1 promoter through insulin receptor substrate-1 and forkhead (FKHD)-L sites and to positively regulate its transcription [18]. However, whether this regulatory relationship between FoxO1 and SIRT1 exists in senescence NP cells induced by oxidative stress has not been verified. Besides, the best characterized of all FoxO regulatory pathways is the phosphatidylinositol-3-kinase (PI3K)/Akt-mediated suppression of FoxO activity. Functionally, active FoxO1 protein is mainly localized in the cell nucleus, where its transcriptional functions can be executed. Conversely, the activation of PI3K/Akt pathway phosphorylates FoxO1 in the nucleus, creating a docking site for 14-3-3 proteins that translocate FoxO1 to the cytoplasm and inactivate them [19,20]. At physiologic levels, ROS signaling is frequently associated with growth factorCreceptor activation and activation of cellular metabolism and growth through the PI3K/Akt pathway. And previous study had found that Akt activation induced premature senescence by increasing intracellular ROS through increased oxygen consumption and inhibiting the expression of ROS scavengers downstream of FoxO [21]. Akt, FoxO1 and SIRT1 play important functions in regulating oxidative stress and senescence, but their relationship and function in oxidative stress-induced premature NP cells are poorly characterized. In the present study, we exhibited that SIRT1 played a crucial role in oxidative stress-induced senescent rat NP cells, and Akt-FoxO1 pathway was involved in the regulation of SIRT1 expression. Additionally, we found that resveratrol, a known plant-derived polyphenol antioxidant and activator of SIRT1 [22,23], shown an anti-senescence effect via suppressing the activity of Akt and activating the FoxO1-SIRT1 pathway. It is suggested that Akt-FoxO1-SIRT1 axis might be a potential therapeutic approach to relieve chronic disc degeneration. Materials and methods Reagents and antibodies SRT1720 HCL (S1129), a selective activator of SIRT1 was purchased from Selleck (Houston, TX, U.S.A.) [24]. AS1842856 (HY-100596), a potent and cell-permeable Foxo1 inhibitor was purchased from MedChem Express (MCE) (Princeton, NJ, U.S.A.) [25]. MK-2206 dihydrochloride (T1952), a highly specific inhibitor of Akt1/2/3 [26], was purchased from TargetMol (Boston, MA, U.S.A.). Resveratrol (R5010), a phenolic phytoalexin found in grape skin and other plants was purchased from SigmaCAldrich (St. Louis, MO, U.S.A.). The antibodies against Collagen II (ab34712), p53 (ab26), p21 (ab80633), p16 (ab51243) and SIRT1 (ab110304) were purchased from Abcam (Cambridge, MA, U.K.). The antibodies against -actin (4970S), Phospho-Histone H2A.X (Ser139) (9718S), Phospho-Rb (Ser807/811) (8516S), Akt (4691S), Phospho-Akt (Ser473) (4060S), FoxO1 (2880S) and Phospho-FoxO1 (Ser256) (9461S) were purchased from Cell Signaling Technology (CST, Danvers, MA, U.S.A.). Isolation of rat.
