Effects of secretory leukocyte protease inhibitor on expression of inflammation mediators in normal human bronchial epithelial cells induced by cigarette smoke extract

OBJECTIVE: To study the effect of secretory leukocyte protease inhibitor (SLPI) on the expression of MMP-9 and IL-8 in normal human bronchial epithelial (NHBE) cells induced by cigarette smoke extract (CSE), and therefore to explore the mechanisms of SLPI for protecting the local airways of chronic inflammatory diseases. METHODS: The experiments of cultured airway epithelia cells in vivo were randomly divided into 4 groups, including a control group, a CSE group, a SLPI group, and a SLPI + CSE group. The expression level of IL-8 in NHBE cell supernatant was examined by ELISA. The expression level of MMP-9 protein in NHBE cells was evaluated by using immunocytochemical stain method. One way analysis of variance was employed in significance test of different groups, followed by SNK test with equal variances and Dunnett3 test with unequal variances. RESULTS: A small quantities of MMP-9 and IL-8 expression were observed in the control group NHBE cells. The mean integral expression of MMP-9 protein was (3.1 +/- 0.5), and the concentration of IL-8 in NHBE cell supernatant was (4.9 +/- 0.6) ng/L. After exposure to CSE for different times, the expression of MMP-9 and IL-8 in NHBE cells of the CSE group was higher than those of in control group. The expression levels of MMP-9 and IL-8 were dependent on CSE exposure time within certain limits. The highest expression was observed at the time of 24 h exposure to CSE. The mean integral expression of MMP-9 protein was 6.6 +/- 0.4, and the concentration of IL-8 in NHBE cell supernatant was (17.7 +/- 1.9) ng/L. But subsequently the levels decreased significantly in 36 h. When NHBE cells were exposed to 10 microg/L SLPI, the expression levels of MMP-9 and IL-8 were inhibited. The integral expression of MMP-9 protein was 0.8 +/- 0.5, and the concentration of IL-8 in NHBE cell supernatant was (0.7 +/- 0.6) ng/L. CONCLUSION: SLPI inhibited the expression of MMP-9 and IL-8 in NHBE cells induced by cigarette smoking extract.