ABSTRACT
<p><b>OBJECTIVE</b>To study the expressions of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) in the airway of bronchiectasis (BE) patients, and evaluate the effect of pseudomonas aeruginosa (PAE) on the expression of TIMP-1 and MMP-9.</p><p><b>METHODS</b>In this case-control study, subjects were divided into BE group and control group, and the BE group was further divided into PAE group and other bacteria group based on the culture results of bronchoalveolar lavage fluid (BALF). BALF was obtained by bronchoscopy, the expressions of MMP-9 and TIMP-1 were determined by ELISA, then the ratio of TIMP-1/MMP-9 was calculated. Furthermore, the tissue of bronchic endomembrane was obtained by transbronchial biopsy and the expressions of MMP-9 and TIMP-1 were determined using immunohistochemical method.</p><p><b>RESULTS</b>The levels of MMP-9 in the BALF of PAE group and other bacteria group were significantly higher than that in control group (P=0.0000 both), and the expressions of MMP-9 in bronchic endomembrane of PAE group and other bacteria group were also significantly higher (P=0.0421 and 0.0003, respectively). The level of TIMP-1 in BALF of PAE group was significantly lower than that in other bacteria group (P=0.0324). The ratio of TIMP-1/MMP-9 in BALF of BE group was significantly lower than that in control group(P=0.0000), and this ratio of PAE group was significantly lower than those in both other bacteria group and control group (P=0.0026 and 0.0000, respectively).</p><p><b>CONCLUSION</b>PAE infection in BE patients can suppress the expression of TIMP-1 and stimulate the expression of MMP-9, and thus make the disease even worse.</p>