Aim To understand the mechanism of Chinese medicine ligustrazini against thrombosis and the effects of ligustrazini on plasminogen activator inhibitor type-1(PAI-1)expression in normal endothelial cells(EC)and EC exposed to lipopolysaccharide(LPS).Methods Human umbilical umbilical vein endothelial cells (HUVEC)were cultured by trypsin digestion method.PAI-1 protein in HUVEC conditioned medium was measured by sandwich enzyme-linked immunosorbent assay(ELISA),and PAI-1 mRNA expression was de-termined by Northern blot analysis.HUVEC nuclear factor-kappa B(NF-kB)nuclear translocation was as-sessed by electrophoretic mobility shift assay (EMSA).Results LPS treatment of cultured HUVEC result-ed in a significant increase in PAI-1 protein and mRNA expression by these cells.However,when HUVEC were incubated with LPS plus ligustrazini,the upregu-lation of PAI-1 by LPS was abated.Moreover ligus-trazini was able to decrease the basal level of PAI-1protein and mRNA as compared to control.Nuclear extracts prepared from LPS stimulated stimulated HUVEC demonstrated increased binding to the NF-kB oligonu-cleotide as compared to unstimulated cells,but ligus-trazini did not change those binding in the absence or presence of LPS.Conclusion Ligustrazini inhibited both basal and LPS-induced PAI-1 protein and mRNA expression in EC,and the modulation of PAI-1 in HUVEC by ligus-trazini might have other mechanisms rather than NF-kB pathway.