In Vivo Choroidal Neovascularization and Macrophage Studies Provide Further Evidence for a Broad Role of Prostacyclin in Angiogenesis

Purpose: The purpose of these studies was (1) to investigate the ability of human M1 phenotype macrophages to secrete vascular endothelial growth factor (VEGF) and the influence of prostacyclin receptor (IP) stimulation (2) to evaluate the contribution of the proangiogenic prostanoid prostacyclin to experimental choroidal neovascularization Methods: Human macrophages derived from primary blood mononuclear cells were functionally biased toward the M1 phenotype by using tumor necrosis factor alpha (TNF alpha). Experimental choroidal neovascularization was produced by laser photocoagulation. Antagonist drugs RO-3244794 (IP antagonist) and GW 627368 (EP4 antagonist) were administered according to an optimal dosing regimen that was predetermined by bioavailability studies. Results: IP receptor stimulation had diametrically opposed effects on VEGF release compared with reported data on cytokine/chemokine secretion from human macrophages. For example, the IP agonist cicaprost stimulated VEGF secretion although it inhibits monocyte chemoattractant protein-1 (MCP-1) secretion: both would favor a proangiogenic effect. The IP receptor antagonist RO-3244794 produced an similar to 20% statistically significant reduction in the neovascularized lesion area in the choroidal neovascularization model, which was a similar level to that produced by the EP4 antagonist GW 627368. Combining the 2 drugs produced a statistically significant reduction in neovascularization but only of slightly greater magnitude than that obtained with each antagonist administered alone. Conclusions: IP receptor stimulation potently and highly efficaciously promoted VEGF release from human M1 macrophages, indicating a possible contribution of the M1 macrophage subtype to VEGF-induced choroidal neovascularization. Studies in living animals suggest that prostacyclin and its target IP receptor contribute to choroidal neovascularization, although to a more modest extent than might have been expected.