Mohamed Ali Behzadian

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The purpose of these experiments was to determine the specific role of reactive oxygen species (ROS) in the blood-retinal barrier (BRB) breakdown that characterizes the early stages of vascular dysfunction in diabetes. Based on our data showing that high glucose increases nitric oxide, superoxide, and nitrotyrosine formation in retinal endothelial cells, we(More)
PURPOSE To determine transforming growth factor (TGF) beta effects on matrix metalloproteinases (MMPs) as a potential cause of the blood-retinal barrier breakdown at the onset of angiogenesis. Previously, glial cells were shown to play a role in the angiogenesis process and to express the angiogenic regulating factor TGF-beta, which becomes active under(More)
Retinal neovascularization and macular edema are central features of diabetic retinopathy, the major cause of blindness in the developed world. Current treatments are limited in their efficacy and are associated with significant adverse effects. Characterization of the molecular and cellular processes involved in vascular growth and permeability has led to(More)
The modulation of angiogenic signaling by reactive oxygen species (ROS) is an emerging area of interest in cellular and vascular biology research. We provide evidence here that peroxynitrite, the powerful oxidizing and nitrating free radical, is critically involved in transduction of the VEGF signal. We tested the hypothesis that VEGF induces peroxynitrite(More)
Retinal neovascularization and macular edema are central features of diabetic retinopathy, a major cause of blindness in working age adults. The currently established treatment for diabetic retinopathy targets the vascular pathology by laser photocoagulation. This approach is associated with significant adverse effects due the destruction of neural tissue(More)
Vasculogenesis is the formation of blood-vessels by differentiation of vascular precursor cells. Experiments using retinal models were designed to test the hypothesis that astrocytes influence this process by effects on the composition of the extracellular matrix. Retinal vasculogenesis was studied in relation to the migration of astrocytes and expression(More)
Our previous in vivo analyses have suggested that astrocytes play a key role in retinal vascularization by inducing endothelial cell differentiation. Here we demonstrate that medium conditioned by cultured rat brain astrocytes (ACM) contains factors, including transforming growth factor-beta (TGF-beta), that inhibit endothelial cell growth. Serum-free(More)
Because oxidative stress has been strongly implicated in up-regulation of vascular endothelial growth factor (VEGF) expression in ischemic retinopathy, we evaluated the role of NAD(P)H oxidase in causing VEGF overexpression and retinal neovascularization. Dihydroethidium imaging analyses showed increased superoxide formation in areas of retinal(More)
Vascular endothelial growth factor/vascular permeability factor (VEGF) has been implicated in blood/tissue barrier dysfunctions associated with pathological angiogenesis, but the mechanisms of VEGF-induced permeability increase are poorly understood. Here, the role of VEGF-induced extracellular proteolytic activities on the endothelial cell permeability(More)
PURPOSE To determine the cellular route by which vascular endothelial cell growth factor (VEGF) increases the permeability of cultured retinal endothelial cells and to test whether nitric oxide (NO) production by NO synthase (NOS) is involved in signaling VEGF's permeability enhancing effects. METHODS Cultured bovine retinal microvascular endothelial(More)