Objective: We examined the effect of lipopolysaccharide (LPS), a component of the outer wall of gram-negative bacteria, on expression of the neutrophil chemoattractant interleukin-8 (IL-8) and the effects of IL-8 treatment on release of matrix metabolizing enzymes in human cervical smooth muscle cells (CSMCs).
Methods: Human CSMCs were exposed to Escherichia coli LPS, and the expression of IL-8 mRNA was analyzed by Northern blotting. The IL-8 promoter activity was examined by dual luciferase assay, and the IL-8 concentration was assessed by enzyme-linked immunosorbent assay. We also treated the CSMCs with human IL-8 and examined the expression of matrix-degrading enzymes.
Results: E coli LPS (100 ng/mL) increased the expression of IL-8 mRNA 12.8-fold after 3 hours. This up-regulation was maintained for up to 24 hours. Lipopolysaccharide treatment produced a fivefold increase in IL-8 promoter activity in CSMCs transfected with an IL-8 promoter-reporter construct. IL-8 concentrations in conditioned medium of CSMC cultures treated with E coli LPS increased approximately 18-fold compared with the control cultures. Northern blot analysis and zymography revealed that exogenous human IL-8 had no significant effect on the expression of matrix metalloproteinase (MMP)-1, -3, and tissue inhibitor of metalloproteinase (TIMP)-1 mRNAs, and on the secretion MMP-2 and -9 in CSMCs.
Conclusion: We conclude that CSMCs respond to LPS with increased expression of IL-8 mRNA and secreted IL-8, and that expression of matrix metabolizing enzymes in CSMCs is not directly affected by IL-8. IL-8 produced by CSMCs in response to gram-negative infection may promote neutrophil invasion, and release of neutrophil matrix-degrading enzymes may participate in the matrix remodeling associated with parturition.