Objective: To investigate the effect of urokinase on the expression of Matrix metalloproteinase 9 (MMP-9) in human endothelial cell and its mechanism. Methods: The human umbilical vein endothelial cell cultured in normal condition were divided into five groups: the first group was blank control

the second group was given urokinase

the third

fourth and fifth groups were treated with MEK inhibitor PD98059

NF-κB inhibitor PDTC

and AP-1 inhibitor Curcumin

respectively before urokinase was added in. The expression of MMP- 9 mRNA and protein in all the groups were detected by RT-PCR and Laser-Confocus respectively. Results: The mRNA and protein expression of MMP-9 in the second group were increased obviously

as compared with the first group. Compared with the second group

the mRNA and protein expression of MMP-9 in the third

fourth

and fifth groups were decreased significantly. Conclusion: Urokinase can upregulate the MMP-9 mRNA and protein expression of human endothelial cell. The mechanism is related to the Ras-Raf-MEK1/2-ERK1/2 signal transduction pathway

also to NF-κB and AP-1.