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

Purpose. To explore the role of prostaglandins (PGs) as modulators of retin al pigment epithelium (RPE) rod outer segment (ROS)-phagocytosis and ROS-ph agocytosis- 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 (stab le analog of thromboxane A(2)), and fed with a suspension of ROS. Expressio n of zif-268 and tis-1 mRNA was determined by Northern blotting. DNA-bindin g 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 countin g of double-immunostained bound and ingested ROS. Results. PGE(2), the most potent of PGs, strongly elevated both basal and R OS-phagocytosis- induced levels of tis-1 mRNA, while significantly inhibiti ng 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-ind uced 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 th e 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-phago cytosis. Conclusions. PGs act as selective regulators of phagocytosis-induced transc ription 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 tr ansduction in RPE cells.