AIM:To explore the influences of semaphorin 3A (Sema 3A) on hydrogen peroxide (H2O2)-induced injury in human umbilical vein endothelial cells (HUVECs).METHODS:Sema 3A over-expression vectors were constructed and transfected into the HUVECs by Lipofectamine 2000, and the over-expression effect was verified by qPCR and Western blot.The HUVECs in different groups were treated with or without 200 μmol/L H2O2 for 4 h.The levels of inflammatory cytokines were measured by qPCR.The levels of lactic dehydrogenase (LDH), superoxide dismutase (SOD) and malondialdehyde (MDA) were detected by corresponding colorimetry.The cell viability was measured by MTT assay.The cell apoptosis was analyzed by flow cytometry.The levels of apoptosis-related proteins cleaved caspase-3 and Bcl-2 were determined by Western blot.RESULTS:H2O2 induced inflammatory cytokine secretion, increased the levels of LDH and MDA, decreased SOD activity and cell viability, and increased cell apoptosis in the HUVECs.Over-expression of Sema 3A enhanced the above processes.No injury effect of Sema 3A over-expression on HUVECs without H2O2 treatment was observed, indicating that the injury effects of Sema 3A on HUVECs depended on H2O2.CONCLUSION:Sema 3A markedly enhances H2O2-induced injury in the HUVECs, which depends on H2O2.Sema 3A may promote oxidative stress-caused endothelial cell injury.