Abstract
Abstract: :
Purpose: Metalloproteinases (MMPs) have been known to modulate corneal wound healing and corneal neovascularization. We investigated the regulatory effects of cytokines on the expression of MMPs in cultured rabbit corneal epithelium. Methods: Subconfluent primary cultures of rabbit corneal epithelial cells were switched to serum-free media for 24 hours before treatment. Each one of the cytokines including IL-1ß, TNF-α, TGF-ß1, bFGF and VEGF, at a concentration of 10 ng/ml, was added alone to the serum-free media for 4 or 24 hours. Total RNA was extracted from 4-hour treated cells and subjected to semi-quantitative RT-PCR for gene expression of MMPs with GAPDH as a control. The conditioned media were collected from 24-hour treated cultures for MMP bioassays. The activities of MMP-1 and MMP-13 were determined by a Biotrak MMP activity assay. Gelatin zymography was used to determine the activities of MMP-2 and MMP-9. Results: The regulation of three major groups of MMPs, including gelatinases (MMP-2 and -9), collagenases (MMP-1, and -13) and stromelysins (MMP-3, -10 and -11), by rabbit corneal epithelial cells was evaluated. IL-1ß markedly up-regulated the mRNA and protein expressions of MMP-9, MMP-1, MMP-13, and MMP-10. TNF-α and TGF-ß1 increased the mRNA and/or protein of MMP-2, MMP-9 and MMP-13. In addition, TGF-ß1 markedly stimulated expression of the stromelysins, MMP-3 and -10. In contrast, bFGF slightly increased MMP-2, -9 and -13, while VEGF only slightly upregulated MMP-10 and -13 in rabbit corneal epithelial cells. Interestingly, all these five cytokines upregulated MMP-13 transcript and protein, which was barely detectable in the normal untreated cells. Conclusion: The results indicate that inflammatory cytokines, i.e. IL-1ß, TNF-α and TGF-ß1 can selectively up-regulate the MMP expressions by rabbit corneal epithelial cells and may indirectly modulate the process of corneal wound healing or corneal neovascularization via MMPs.
Keywords: 372 cornea: epithelium • 380 cytokines/chemokines • 631 wound healing