PROSTAGLANDIN E-2 INDUCES VASCULAR ENDOTHELIAL GROWTH-FACTOR AND BASIC FIBROBLAST GROWTH-FACTOR MESSENGER-RNA EXPRESSION IN CULTURED RAT MULLER CELLS

PURPOSE. To investigate the induction of vascular endothelial growth f actor (VEGF) and, basic fibroblast growth factor (bFGF) gene expressio n by prostaglandin E-2 (PGE(2)) in cultured rat Muller cells and to st udy the mechanism of the induction. METHODS. Muller cells were obtaine d from neonatal Sprague-Dawley rat retinas and cultured in essential m odified Eagle's medium supplemented with 10% fetal calf serum for up t o four passages. Cells were treated with PGE(2), protein kinase A (PKA ) inhibitors H-89 or SQ 22536, protein kinase C (PKC) inhibitors calph ostin C or GF 109203X, PKC activator phorbol 12-myristate 13-acetate ( PMA), or the PKA activator forskolin. Northern blot analysis was perfo rmed to determine the levels of VEGF and bFGF mRNA. RESULTS. PGE(2) in duced VEGF and bFGF mRNA expression in a dose-and time-dependent manne r. VEGF and bFGF mRNA reached peaks of 2- and 3.5-fold at 10 mu M PGE( 2). No further increases were observed at 100 mu M PGE(2). When treate d with 10 mu M PGE(2), the increases in VEGF and bFGF mRNA reached max imum by 2 hours, then slowly declined toward the control level within 24 hours of PGE(2) treatment. The inductions of VEGF and bFGF mRNA exp ression by PGE(2) were blocked by the specific PKA inhibitors H-89 (30 mu M) or SQ 22536 (500 mu M, 1000 mu M). Forskolin (10 mu M), a cycli c adenosine monophosphate activator, also stimulated VEGF and bFGF mRN A expression. However, the effects of forskolin and PGE, on VEGF gene expression were not additive, whereas forskolin enhanced the effect of PGE(2) on bFGF mRNA expression. The specific PKC inhibitors, GF 10920 3X (2 mu M) and calphostin C (1 mu M), did not inhibit PGE(2)-induced VEGF gene expression, whereas PGE(2)-induced bFGF expression was block ed by the PKC inhibitor GF 109203X. In addition, downregulation of PKC by PMA (0.8 mu M) treatment did not block the induction of VEGF gene expression, whereas it did inhibit the induction of bFGF mRNA expressi on. CONCLUSIONS. These results indicate that PGE(2) stimulates VEGF an d bFGF mRNA expression in cultured rat Muller cells. The induction of VEGF seems to occur through activation of the PKA pathway, whereas tha t of bFGF occurs through PKA and PKC activation. These findings raise the possibility that endogenous PGE(2) stimulates VEGF and bFGF mRNA e xpression in Muller cells in vivo under conditions in which PGE(2) pro duction is increased, such as in injury.