Implication of N-methyl-D-aspartate receptor In Homocysteine Induced Age related Macular Degeneration
Abstract Background: Age related macular degeneration (AMD) is a leading cause of vision loss in old people. Elevated homocysteine (Hcy), known as Hyperhomocysteinemia (HHcy) was reported in association with AMD. We previously reported that HHcy induces AMD like features. The current study suggests activation of N-Methyl-D-aspartate receptor (NMDAR) in retinal pigment epithelium (RPE) cells as a mechanism for HHcy-induced AMD. Serum Hcy and cystathione-β-synthase enzyme (CBS) were assessed by ELISA in AMD patients. The involvement of NMDAR in Hcy’s induced AMD features were evaluated 1)-In-vitro using ARPE-19 cells, primary RPE isolated from mice model of HHcy (CBS) and mouse choroidal endothelial cells (MCEC). 2)-In-vivo using wild type mice and mice deficient in RPE cells NMDAR (NMDARR -/-) with/without intravitreal injection of Hcy. Expression of retinal isolectin-B4, Ki67, HIF-1α, VEGF, NMDAR1 and albumin were assessed by immunofluorescence (IF), Western blot (WB), Optical coherence tomography (OCT), and fluorescein angiography (FA) to evaluate retinal structure, fluorescein leakage and development of choroidal neovascularization (CNV) in living mice. Results: Serum of the neovascular AMD patients showed significant increase in Hcy and decrease in CBS levels. Moreover, Hcy significantly increased angiogenic markers; HIF-1α, VEGF and NMDAR in RPE cells and Ki67 in MCEC. Hcy-injected WT mice showed disrupted retinal morphology and development of CNV. Knocking down NMDAR in RPE improved retinal structure and CNV induction.Conclusion: Our findings underscore the potential role for NMDAR in RPE cells in mediating Hcy-induced features of AMD and CNV induction, thus NMDAR inhibition could provide a promising therapeutic target for AMD.