Modulation of early response gene expression by prostaglandins in cultured rat retinal pigment epithelium cells

Purpose. To explore the role of prostaglandins (PGs) as modulators of retinal pigment epithelium (RPE) rod outer segment (ROS)-phagocytosis and ROS-phagocytosis- induced gene expression. Methods. RPE cells in primary cell culture were pre-incubated with PGE(2), PGD(2), PGF(2)alpha, PGJ(2), 15-deoxy-Delta (12,14)-PGJ(2) or U-46619 (stable analog of thromboxane A(2)), and fed with a suspension of ROS. Expression of zif-268 and tis-1 mRNA was determined by Northern blotting. DNA-binding activity of TIS-1 protein was assessed by electrophoretic mobility shift assay. Concentration of PGE(2) and PGD(2) in the tissue culture medium was measured by enzyme immuno-assay. Phagocytis-tosis was quantified by counting of double-immunostained bound and ingested ROS. Results. PGE(2), the most potent of PGs, strongly elevated both basal and ROS-phagocytosis- induced levels of tis-1 mRNA, while significantly inhibiting both basal and phagocytosis-induced expression of zif-268 mRNA. PGD(2), PGJ(2) and 15-deoxy-Delta (12,14)-PGJ(2) elevated ROS-phagocytosis-induced, but not basal, expression of tis-1 mRNA expression. PGF(2 alpha) super-induced both phagocytosis-induced and basal tis-1 mRNA expression. U-46619 and carbaprostacyclin had no effect on expression of tis-1 mRNA. PGE(2) was the only PG to affect zif-268 expression. Exogenous PGE(2), PGD(2) and PGF(2), when added to the medium at 1-muM concentrations, significantly inhibited ingestion of ROS, with PGE(2) being the most potent PG affecting ROS-phagocytosis. Conclusions. PGs act as selective regulators of phagocytosis-induced transcription factor gene expression in RPE cells, as well as of ROS-phagocytosis itself. This modulation may help to ensure specificity in the differential activation of target genes by ROS-phagocytosis receptor-mediated signal transduction in RPE cells.