The effects of SIRT1/FoxO1 on LPS induced INS-1 cells dysfunction

Oxidative stress is one of the key mechanisms of sepsis related organ dysfunction including stress hyperglycemia. Silent mating type information regulation 2 homolog 1 (SIRT1) could regulate glucose metabolism through its deacetylase activity. In this study, we aimed to investigate the role of SIRT1/forkhead box protein 1 (FoxO1) pathway on lipopolysaccharide (LPS) induced INS-1 cells dysfunction from aspects of oxidative stress and apoptosis. After being treated with 1 mg/L LPS together with or without SIRT1 activator resveratrol (RSV) or SIRT1 inhibitor EX527, cell viability, ROS generation, malondialdehyde (MDA), superoxide, insulin secretion, and activity of superoxide dismutase (SOD) in INS-1 cells were measured by specific assays. Protein expression of SIRT1, FoxO1, toll-like receptor 4 (TLR4), and acetylated FoxO1 (ac-FoxO1) were detected by western blot analysis. Nuclear and cytoplasmic protein was extracted respectively to analyze SIRT1 and FoxO1 redistribution. Mitochondrial potentials and apoptosis were detected by flow cytometry or observed under fluorescence microscope. Results showed that LPS decreased cell viability and insulin secretion, increased ROS, MDA, and superoxide generation, whereas inhibited SOD activity and FoxO1 nuclear transportation. Activation of SIRT1 by RSV down-regulated TLR4 expression, SIRT1 and FoxO1 nuclear protein expression increased after RSV pretreatment. Additionally, LPS induced decreased mitochondrial membrane potentials and structural abnormalities, which could be partially reversed by RSV. SIRT1/FoxO1 may be one of potential targets which could resist against LPS-induced INS-1 cells from oxidative stress damage and mitochondrial dysfunction.