Effect of Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) on IL-6, IL-8, and MCP-1 Expression in Human Retinal Pigment Epithelial Cell Line

Abstract

Purpose: To examine pituitary adenylate cyclase–activating polypeptide (PACAP) receptors (PAC1, VPAC1, and VPAC2) mRNA and the effect of PACAP on interleukin-6 (IL-6), interleukin-8 (IL-8), and monocyte chemotactic protein-1 (MCP-1) expression in human retinal pigment epithelial cell line (ARPE-19) stimulated with interleukin-1β (IL-1β). Methods: Expression of PACAP receptor mRNA was examined by reverse transcription polymerase chain reaction (RT-PCR). PACAP and IL-1β were added to serum-free medium. IL-6, IL-8, and MCP-1 mRNA were measured by real-time PCR. IL-6, IL-8, and MCP-1 protein concentrations were measured using enzyme-linked immunosorbent assay. Nuclear factor κB (NF-κB) translocation was examined by immunofluorescence. Results: PAC1 and VCAP1 receptors mRNA were expressed in unstimulated cells. VCAP2 mRNA was expressed in cells stimulated with IL-1β. IL-1β stimulated IL-6, IL-8, and MCP-1 mRNA expression and protein levels. PACAP (10− 7 to 10− 6 M) inhibited IL-1β –stimulated IL-6, IL-8, and MCP-1 mRNA and protein levels. Immunofluorescence of NF-κB in the nucleus was dense 30 min after stimulation with IL-1β, and it was decreased by PACAP. Conclusions: ARPE-19 cells had PACAP receptors mRNA. PACAP inhibited IL-6, IL-8, and MCP-1 expression and protein secretion. Possibly, the effect on cytokines may be via suppression of NF-κB translocation.