Epidermal growth factor and insulin inhibit cell death in pancreatic beta cells by activation of P13-kinase/Akt signaling pathway under oxidative stress

Production of reactive oxygen species (ROS) during islet purification by enzymatic digestion as well as during warm and cold ischemia causes islet cell damage. Recent reports have shown that activated Akt, the downstream protein after phosphatidylinositol (PI) 3-kinase, is involved in cell survival by phosphorylating several proteins that mediate apoptosis. We analyzed the role of PI3-kinase/Akt pathway activation using insulin or epidermal growth factor (EGF) on islet beta cell survival during oxidative stress. Canine islets and murine beta cell line (BTC) were cultured in the presence of hydrogen peroxide (H2O2) for 12 to 20 hours. Viability and cell death were measured by MTT assay. Maximum cell damage was observed with as little as 100 mumol/L of H2O2. Pretreatment with 100 ng/mL of insulin significantly decreased cell damage. Meanwhile, the protective effect of insulin was partially blocked with an inhibitor of PI3-kinase, LY294002, suggesting the utilization of PI3-kinase/Akt signaling pathway for the observed cytoprotective effect. Similar to insulin, EGF also protected beta cells from oxidative stress. Our results suggest that PI3-kinase/Akt activation by insulin or EGF is beneficial for islet beta cell protection.