Abstract： Objective To investigate the effects of Saussurea involucrata extract pretreatment on the expression of the Toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) in focal cerebral ischemia/reperfusion in mice and its possible neuroprotective mechanism.Methods Seventy-two Kunming mice were randomly divided into four groups:sham operation,saline,Saussurea involucrata extract,and edaravone groups (n =18 in each group).Saussurea involucrata extract 0.8 g/kg was given intraperitoneally in the Saussurea involucrata extract group; edaravone 3 mg/kg was given in the edaravone group; and the same volume of saline was given in the saline group.A model of middle cerebral artery occlusion (MCAO) was induced after 7 days of continuous injection.Cerebral infarct volume was determined by 2,3,5-triphenyltetrazolium staining.Immunohistochemical staining was used to detect TLR4-positive cells in ischemic brain tissue.Reverse transcriptase polymerase chain reaction was used to detect the expression of TLR4/NF-κB mRNA.Results The cerebral infarct volume in mice in the saline,Saussurea involucrata extract and edaravone groups was 131.55± 28.25 mm3,84.10 ±13.92 mm3 and 65.10 ± 6.78 mm3,respectively.There were significant difference (F =10.158,P =0.012).The infarct volume in the Saussurea involucrata extract group (P =0.020) and edaravone group (P0.005) was significantly less than that in the saline group,and there was no significantly difference between the 2 groups.The numbers of cortex and TLR4 positive cells in hippocampus area at the ischemic sides in the saline group were significantly more than those in the sham operation group (all P ＜0.001).The numbers of positive cells of cortex and TLR4 in the Saussurea involucrata extract group and the edaravone group were significantly decreased compared to the saline group (all P ＜ 0.05),and there was no significant differences between the Saussurea involucrata extract group and the edaravone group.The expressions of TLR4,p50,and p65 mRNA in the saline group were significantly up-regulated compared to the sham operation group (all P =0.000).Saussurea involucrata extract could significantly down-regulate the expressions of TLR4,p50,and p65 mRNA at 24 hours after ischemia/reperfusion (all P =0.000).Edaravone could significantly down-regulate the expressions of TLR4 and p65 mRNA (all P =0.000) and it had a down-regulated trend for the expression of p50 mRNA (P =0.053); while there was no significant difference in the expressions of TLR4 and p65 mRNA between the Saussurea involucrata extract group and the edaravone group.Conclusions Saussurea involucrata extract pretreatment may significantly reduce the cerebral infarct volume,down-regulate the expressions of TLR4 and NF-κB subunit,and play a neuroprotective effect by inhibiting inflammatory response after ischemia.