Objective To investigate the effect of autophagy on histone-mediated apoptosis of human proximal tubular endothelial cells(HK-2).Methods To investigate the effect of histones on the autophagy and apoptosis,HK-2 cells were treated with increasing concentrations of histones.The rate of apoptosis and the expressions of autophagy-related protien LC3Ⅱ and Beclin1 in HK-2 cells were detected by using flow cytometry and immunoblotting assay,respectively.To further confirm the effect of autophagy on apoptosis of HK-2 cells,cells were incubated with histones after one hour pretreatment with 10 mmol/L 3-MA,a pharmacological inhibitor.The rate of apoptosis and the activity of caspase-3 of HK-2 cells were detected separately by using flow cytometry and immunoblotting assay.Results Histones significantly enhanced apoptosis of HK-2 cells in a dose-dependent manner,with the increased expressions of LC3Ⅱ and Beclin1.Blockage of autophagy by 3-MA significantly increased the apoptosis of HK-2 cells and the activity of caspase3.Conclusion Autophagy in proximal tubules protects against apoptosis induced by histones,with potential value in acute kidney injury (AKI).