Proinflammatory cytokines induce RANTES and MCP-1 synthesis in human corneal keratocytes but not in corneal epithelial cells. Beta-chemokine synthesis in corneal cells.

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Abstract

PURPOSE: To determine whether human corneal epithelial cells and keratocytes produce chemokines regulated upon activation, normal T-cell expressed and secreted (RANTES) protein and monocyte chemotactic protein-1 (MCP-1) after exposure to proinflammatory cytokines interleukin-1 alpha (IL-1 alpha) and tumor necrosis factor-alpha (TNF-alpha). METHODS: Pure cultures of human corneal epithelial cells and keratocytes were exposed to increasing concentrations of either human recombinant IL-1 alpha or TNF-alpha. At selected time intervals after exposure, culture supernatants were removed and assayed for RANTES and MCP-1 by the enzyme-linked immunosorbent assay. Total RNA was extracted from the cell cultures, and steady state mRNA levels were measured by reverse transcriptase-polymerase chain reaction. RESULTS: Exposure to keratocytes to either IL-1 alpha or TNF-alpha resulted in > 100-fold increases in RANTES protein secretion and > 150-fold increases in MCP-1 protein secretion, as well as in rapid sustained increases in intracellular levels of their corresponding mRNAs. Exposure of corneal epithelial cells to IL-1 alpha and TNF-alpha did not stimulate MCP-1 secretion nor intracellular levels of MCP-1 mRNA. Epithelial cells also failed to secrete RANTES protein even through the two inducing cytokines did stimulate increased expression of RANTES mRNA. CONCLUSIONS: These results suggest that RANTES and MCP-1 gene expression in human keratocytes differs markedly from their expression in human corneal epithelial cells and that the stroma of the cornea may be more important than the epithelium in recruitment of mononuclear leukocytes responsible for cell-mediated immunity.