SIRT1 Protects Human Lens Epithelial Cells Against Oxidative Stress by Inhibiting p53-Dependent Apoptosis

Purpose: This study aims to test the hypothesis that sirtuin type 1 (SIRT1) plays a role in modulating resistance against oxidative stress in lens epithelial cells (LECs), and to determine its mechanism if this hypothesis is found to be true.Methods: Cultured LECs were treated with resveratrol (RES, an activator of SIRT1) or nicotinamide (NAM, a SIRT1 inhibitor) and incubated with H2O2. Changes in SIRT1, p53, and acetyl-p53 expressions were measured. Cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay. TUNEL assay was used to evaluate apoptosis. Pifithrin- (PFT-) was applied to block the p53 pathway.Results: SIRT1 expressions significantly increased with H2O2 treatment and further increased with RES treatment in a dose-dependent manner. RES eliminated cellular morphological changes related to H2O2 treatment, increased cell proliferation, and inhibited apoptosis under oxidative stress. In contrast, NAM enhanced cell apoptosis under oxidative stress and decreased cell proliferation. RES caused a dose-dependent decrease in acetyl-p53 levels under oxidative stress, while NAM increased p53 acetylation. Under oxidative conditions, PFT-, a p53 pathway inhibitor, eliminated the destructive effect of NAM. PFT- decreased the morphological changes in LECs compared to NAM treatment and increased cell proliferation and inhibited apoptosis.Conclusions: SIRT1 protected LECs from oxidative stress via the inhibition of the p53 pathway. SIRT1 or SIRT1 activators could potentially be used to prevent ocular aging and cataract in the future.