Abstract:Aim Previous study demonstrated that tetramethylpyrazine(TMP)had an inhibitory effect on the TF expression induced by thrombin in human umbilical vein endothelium derived cell line human umbilical vascular endothelial cells(HUVEC).However,its mechanisms were not fully understood.In this study,we observed the role of nitric oxide(NO)and transcription factor NF-κB in the regulation of TMP on tissue factor(TF)expression.Methods HUVEC were cultured in RPMI-1640.TF activity was determined with one-stage clotting assay measuring total cellular pro-coagulant activity(PCA).TF mRNA was examined by semi-quantitative reverse transcription polymerase chain reaction(RT-PCR).Immunohistochemical analysis was performed to evaluate the translocation of NF-κB.Results NG-nitro-L-arginine methylate(L-NAME)is an inhibitor of nitric oxide synthase(NOS),and it alone had no marked effects on PCA and TF mRNA in HUVEC,but L-NAME significantly decrease the inhibitory effects of TMP on PCA increment induced by thrombin(P<0.05).Immunohistochemical analysis demonstrated that NF-κB translocation from cytoplasm to the nucleus was found after treatment of endothelial cells with thrombin.TMP inhibited thrombin-induced NF-κB translocation from cytoplasm to the nucleus.Conclusion NO pathway participates in the inhibitory effect of TMP on the expression of TF induced by thrombin.TMP can inhibit TF expression induced by thrombin through suppressing NF-κB activation.