MODULATION OF LENS EPITHELIAL-CELL PROLIFERATION BY ENHANCED PROSTAGLANDIN SYNTHESIS AFTER UVB EXPOSURE

Purpose. The goals of this investigation were to examine the synthesis of prostaglandins after UVB exposure of lens epithelial cells and to investigate their role in cell proliferation. Methods. Cultured rabbit lens epithelial cells (cell line N/N1003A) were exposed to low levels of UV radiation. Prostaglandins were assayed by radioimmunoassay; products of arachidonic acid metabolism were analyzed by thin-layer chromatography and mass spectroscopy. Cell proliferation was measured by [H-3]thymidine incorporation and proliferative autoradiography. Results. Cultured lens epithelial cells exposed to WB radiation showed a dose-dependent increase in basal prostaglandin synthesis measured 24 hours after UV exposure. At an optimal dose (250 J/m(2)) of UVB, prostaglandin E(2) (PGE(2)) synthesis was enhanced tenfold. Product identity was confirmed using thin-layer chromatography and mass spectroscopy with authentic standards. Incubation of irradiated cells with exogenous arachidonic acid followed by extraction and thin-layer chromatography revealed that the cultures produced PGE(2), prostaglandin I-2 (measured as 6-keto-prostaglandin F-1 alpha), prostaglandin F-2 alpha, and hydroxyeicosatetraenoic acid. The synthesis of all of these products was enhanced threefold in cells exposed to 250-J/ m(2) UVB. Indomethacin pretreatment eliminated the synthesis of prostaglandins, further confirming their identity. To discover the relationship between PGE(2) synthesis and irradiation-induced cell proliferation, [H-3]thymidine incorporation into DNA was determined 24 or 48 hours after exposure. These experiments revealed a fivefold increase in incorporation induced by UVB exposure. UVB-enhanced incorporation of thymidine was eliminated by pretreatment of cultures with indomethacin to eliminate PG synthesis. However, when 100 nM PGE(2) was added to the indomethacin-treated irradiated cultures, incorporation of the label was restored toward the level detected in the UVB-stimulated cells. Addition of other prostaglandins to the cultures was ineffective.