Objective To investigate the protective effects of rhein lysinate (RHL)on the blood vessel damage induced by oxidative stress in the mice,and to explore its mechanism.Methods The mouse models of oxidative damage were established by intraperitoneal injection of paraquat.30 C57 mice were randomly divided into control, paraquat model,and RHL prevention groups.The mice in RHL prevention group were given RHL by gavage for one week before performing model.The mice in other two groups were given equal volume of distilled water.For making model,paraquat was intraperitoneally injected in the mice in paraquat model and RHL prevention groups once a week for two weeks.The activities of superoxide dismutase (SOD)and glutathione peroxidase (GSH-Px) and the content of serum malonaldehyde (MDA) of the mice were detected 2 weeks after modeling. The pathological profile of blood vessel was observed by hematoxylin and eosin (HE)staining and the level of reactive oxygen species was observed by DCFH-DA staining.The expressions of genes related to blood vessel damage were detected by Western blotting method.Results Compared with control group,the activities of SOD and GSH-Px were decreased and the content of MDA was increased in paraquat model group (P < 0.05 ). Compared with paraquat model group,the activities of SOD and GSH-Px were increased and the content of MDA was decreased in RHL prevention group (P <0.05).The pathological examination indicated the structure of blood vessel of the mice was damaged and the level of reactive oxygen species of blood vessel was increased (P <0.05)in paraquat model group.The pathological changes were significantly improved and the level of reactive oxygen species of blood vessel of the mice was decreased (P < 0.05 )in RHL prevention group. The Western blotting analysis showed that compared with control group,the expression levels of nitric oxide endothelial synthase (eNOS)and caspase-3 of the mice in paraquat model group were decreased (P < 0.05),however the expression level of cleaved fragment of caspase-3 was increased (P < 0.05).Compared with paraquat model group,the expression levels of eNOS and caspase-3 of the mice in RHL prevention group were increased (P < 0.05 )and the expression level of cleaved fragment of caspase-3 was decreased (P <0.05).Conclusion Paraquat could induce vascular cell damage in vivo through increasing the levels of reactive oxygen species, and RHL could antagonize the effects of paraquat by scavenging reactive oxygen species, and up-regulating the eNOS expression and reducing the expression of the cleaved fragment of caspase-3.