Abstract: AIM:To investigate the expression of matrix metalloproteinase-9(MMP-9)in blood polymorphonuclear leukocyte(PMN)and the effect of dexamethasone on them in rat asthma models.To explore the relationship between MMP-9 in PMN and its inhibitor matrix metallo-proteinase inhibitor-1(TIMP-1). METHODS:The rat models of asthma were randomly divided into asthma group (group A), control group (group C)and dexamethasone treated group (group C).Blood PMN was isolated and purified.The expression of MMP-9was detected by immunocytochemical method in blood PMN.The concentration of TIMP-1protein was detected by ELISA.RESULTS:The levels of MMP-9 in PMN in group A (OD=0.196± 0.011)and in group D(OD=0.135±0.008)were significantly higher than those in group C(OD=0.100±0.010)(P<0.01).The levels of MMP-9 in PMN in group D were significantly lower than those in group A.The levels of TIMP-1protein in group A[(34.96± 4.54)ng/mL] were significantly higher than those in group C [(26.14±3.43)ng/mL] and in group D [(29.89±3.43)ng/mL] (P<0.01).The levels of TIMP-1protein in group D were significantly higher than those in group C(P<0.05).There was significant positive correlation between bloodMMP-9 in PMN protein expression level and concentration of TIMP-1protein(n=29, r=0.741, P<0.01).CONCLUSION:MMP-9 protein can be synthesized by PMN, and expression levels of MMP-9 are increased in rat asthma.PMN are involved in asthmatic inflammation and maybe by increasing synthesis of MMP-9.But this function of PMN can be inhibited by dexamethasone. MMP-9 and its inhibitor TIMP-1may take part in the pathogenesis of asthma exacerbation.

Key words: asthma, matrix metalloproteinase-9, polymorphonuclear leukocyte, TIMP-1, immunocytochemical method, rat