Up regulation of VEGF gene expression by PGE₂ stimulation in cultured rat muller cells

Purpose. Neovascular disease of the retina is a major cause of blindness. Vascular endothelial growth factor (VEGF) is a potent, specific mitogen for vascular endothelial cells and promotes neovascularization in vivo. PGE₂ is a pathogenetic mediator in the central nervous system and has been recently reported inducing VEGF expression in osteoblasts. To determine whether PGE₂ induces VEGF gene expression in Müller cells, we performed Northern blot analysis and found that PGE₂ up-regulated VEGF expression in cultured rat Müller cells, and this occurs through activation of protein kinase C (PKC). Methods. Müller cells from 1-3 day Sprague-Dawley rats were isolated and cultured with Eagle MEM+10% FCS. Cells at passage1-4 were treated with PGE₂, PKC inhibitor H-7, adenylate cyclase inhibitor SQ₂₂₅₃₆. Northern blot analysis was performed to determine VEGF mRNA levels. Results. Cells were identified by immunocytochemistry with antibodies against Müller cell markers: vimentin, carbonic anhydrase C, and glutamine synthetase. The PGE₂-induced up-regulation of VEGF mRNA increased by 1.5, 1.8, 2.0, and 2.5-fold at concentrations of 0.1, 1.0, 10, and 100 μM respectively. The time course of induction revealed a 1.7-fold increase in VEGF mRNA 1 hr after PGE₂ treatment, which reached 2.3-fold by 2 hr, then declined to 1.8-fold by 4 br. The PGE₂-induced up-regulation of VEGF mRNA was completely blocked by the PKC inhibitor H-7, while not by the adenylate cyclase inhibitor SQ₂₂₅₃₆. Conclusions: Our results indicate that PGE₂ induces VEGF expression in cultured Müller cells and the induction seems to be through PKC activation. These findings raise the possibility that PGE₂ may be involved in neovascular disease of the retina by simulating Müller cell VEGF expression.