ObjectiveTo investigate the influence of Ataxia-telangiectasia mutated (ATM) activation on cellular oxidative stress induced by high glucose in bovine retinal capillary endothelial cells(BRECs). Methods The BRECs were treated by different culture medium with various glucose concentrations (5 mmol/L glucose, 30 mmol/L glucose, 30 mmol/L glucose+10 μmol/L KU55933) as normal glucose group, high glucose group and treatment group respectively.After the cells incubated for 48 hours, the protein expression of ATM, P-ATM, Mitogen-Activated Protein Kinase P38(P38), P-P38, Extracellular signal-regulated kinases(ERKs), P-ERKs was detected by Western blot; cellular ROS level was detected by Reactive Oxygen Species Assay Kit; propidium iodide/Hoechst staining was used for analysis of apoptosis; the expression of vascular endothelial growth factor (VEGF) in the supernatant was determined by Enzyme-Linked Immunosorbent Assay (ELISA); the paracellular permeability between endothelium cells was detected by FITC-dextran. ResultsCompared with the protein level of P-ATM, P-P38 and P-ERKs in high glucose group increased. Especially, P-P38, P-ERKs expressed much more than in high glucose group. The secretion of VEGF in high glucose group was higher than that in the normal glucose group but less than that in treatment group. The same tendency existed in ROS assay, apoptosis assay and paracellular permeability measuring. ConclusionsHigh glucose induced altered activation of ATM which might play a protective role in cellular oxidative stress. Deficiency of ATM might lead to ROS explosion, cell apoptosis and dysfunction of endothelial barrier. The mechanism might be associated with P38, ERKs and VEGF.