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Y.-G. He, D. Liao, B. Zhao, J. Owens, J. M. Johnston; Evidence for a Role of Platelet-Activating Factor (PAF) in the Pathogenesis of Age-Related Macular Degeneration (AMD). Invest. Ophthalmol. Vis. Sci. 2007;48(13):2200.
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Much of severe vision loss in AMD is due to exudative complications such as choroidal neovascular membranes (CNV). Advances in AMD therapy have targeted vascular endothelial group factor (VEGF) in late stages of the disease. However, earlier steps in the pathogenesis of AMD are unclear. We have previously shown that PAF, a potent pro-inflammatory phospholipid, is present in cultured human retinal pigment epithelial (ARPE) cells and that its receptor is expressed in human eyes. We now show that PAF production by RPE cells can be stimulated and that its agonist and antagonist modulate VEGF production by RPE cells. We have also measured the effect these agents on RPE cell proliferation and apoptosis.
Human RPE cells were maintained in culture and exposed to PAF receptor (PAF-R) agonist carbamyl-PAF (C-PAF), PAF-R antagonist WEB 2086. The presence of PAF was demonstrated by HPLC and tandem mass spectrometry. The Ca++ ionophore A23187 was employed to stimulate PAF biosynthesis in human RPE cells. VEGF levels in the media were the analyzed by ELISA. To measure cellular proliferation, RPE cells were exposed to C-PAF, WEB 2086, or vehicle and then thiazolyl blue tetrazolium bromide. Proliferation was assessed by colorimetric assay. Apoptosis was measured using an Annexin V protocol.
A 10-fold increase in PAF was found in cells treated with the Ca++ ionophore. PAF-R agonist caused a statistically significant increase in VEGF production while PAF-R antagonist caused a statistically significant decrease. PAF-R agonist and antagonist caused modest increases in cell proliferation but no effect on apoptosis.
Our previous work has shown the presence of PAF-R both in human eye and ARPE cells. We now show that ARPE cells are capable of producing PAF and that its agonist and antagonist modulate VEGF production. These findings point towards a role for PAF in the early pathogenesis of exudative AMD.
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