Background:Oxidative and inflammatory damage have been suggested to play an important role in cerebral ischemic pathogenesis,and provide a promising therapeutic strategies for stroke.Nuclear factor-erythroid 2-related factor 2 (Nrf2),a pleiotropic transcription factor,has been shown to play a key role in protecting cells against oxidative injury in cerebral ischemia.Methods:In this study,we demonstrated the hypothesis that ursolic acid (UA),a natural pentacyclic triterpenoid acid,isolated from edible plants in the Oleaceae family,a well-known anti-oxidative and anti-inflammatory reagent,protects the brain against ischemic injury by activating Nrf2 pathway.Methods:Nrf2-/-and Wild-type (WT) mice were induced into focal cerebral ischemia by transient middle cerebral artery occlusion (MCAO),and received UA treatment immediately after MCAO.The behavioral dysfunction,infarct size,and the expression of Nrf2,HO-I and inflammatory factors (TLR4 and NF-K B) in ischemic brain were measured at 24 h af t er stroke.Results:UA treatment significantly improved neurological deficit and reduced infarct size in WT mice after MCAO.Administration of UA also decreased the product of lipid peroxidation,promoted the activation of Nrf2 pathway and decreased the expression of TLR4 and NFKB after stroke in WT mice.However,Nrf2-/-mice demonstrated more severe neurologic deficits,infarct size and inflammatory damage after MCAO,and did not benefit from the protective effect of UA.Conclusion:The results indicated that UA protected the brain against ischemic injury in mice by antioxidative and anti-inflammatory effects after MCAO.Activation of Nrf2 pathway contributes to the neuroprotective effects induced by UA in cerebral ischemia.