Abstract
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 a, PGJ 2, 15-deoxy-? 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. Phagocy tis -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-? 12,14 -PGJ 2 elevated ROS-phagocytosis-induced, but not basal, expression of tis-1 mRNA expression. PGF 2a 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 2a, when added to the medium at 1-µM 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.