Effect of Alpha-Melanocyte-Stimulating Hormone on Interleukin 8 and Monocyte Chemotactic Protein 1 Expression in a Human Retinal Pigment Epithelial Cell Line

Abstract

Purpose: To examine melanocortin receptor (from MC-1 to MC-5) mRNA and the effect of α-melanocyte-stimulating hormone (α-MSH) on interleukin 8 (IL-8) and monocyte chemotactic protein 1 (MCP-1) expression in a human retinal pigment epithelial cell line (ARPE-19) stimulated with IL-1β or tumor necrosis factor α (TNF-α). Methods: Expressions of MC-1 to MC-5 mRNA were examined by semiquantitative reverse transcription polymerase chain reaction (RT-PCR). α-MSH and IL-1β or TNF-α were added to serum-free medium. IL-8 and MCP-1 mRNA were measured by real-time PCR. IL-8 and MCP-1 protein concentrations were measured using enzyme-linked immunosorbent assay. Nuclear factor ĸB (NF-ĸB) translocation was examined by immunofluorescent staining/microscopy. Results: MC-1 to MC-5 receptor mRNA was expressed in unstimulated cells. IL-1β stimulated IL-8 and MCP-1 mRNA at 6 h. TNF-α stimulated IL-8 and MCP-1 mRNA expression at 1.5 and 3 h. α-MSH (10^–14 to 10^–10M) inhibited IL-8 and MCP-1 mRNA expression in the cells stimulated with IL-1β or TNF-α. α-MSH inhibited IL-1β or TNF-α-stimulated IL-8 and MCP-1 protein levels in the media. Immunofluorescent staining/microscopy of NF-ĸB in the nucleus was dense 30 min after stimulation with IL-1β or TNF-α and was decreased by α-MSH. Conclusions: ARPE-19 cells had MC-1 mRNA. α-MSH inhibited IL-8 and MCP-1 expression and protein secretion. Possibly, the effect on chemotactic factors may be via suppression of NF-ĸB translocation.