Objective: To investigate the protective effect of snake venom tripeptide pENW on the injury of human umbilical vein endothelial cells (HUVECs) induced by lipopolysaccharide (LPS) in vitro and to explore its underlying mechanism. Method: HUVECs were treated with pENW (10-4

10-5

10-6 mol · L-1) and nitric oxide synthase(NOS) inhibitor L-NMMA (5×10-4 mol · L-1)

then induced with LPS (1 mg · L-1) for 24 h. The cell viability was evaluated by MTT assay. Nitric oxide (NO) content was measured by Griess Reagent. The nitric-oxide synthase (NOS) activity was assessed by commercially available kits. The NOS expression was measured by Western blot. Result: Compared with normal control group

vascular endothelial cells were obviously damaged and NO release increased by LPS

which could be protected by pENW in a concentration-dependent manner (P<0.05

P<0.01). L-NMMA and pENW could increase the cell viability rates and decrease NO production (P<0.05

P<0.01). Meanwhile

iNOS activity and protein expression were inhibited by pENW(P<0.05

P<0.01). However

there was no significant effect on eNOS activity and protein expression. Conclusion: The results showe that pENW has protective effect on HUVECs induced by LPS. Its mechanism may be related to the suppression of iNOS expression along with decreasing levels of NO and iNOS activity.