Inhibition of NAD(P)H Oxidase Activity Blocks Vascular Endothelial Growth Factor Overexpression and Neovascularization during Ischemic Retinopathy

• Published in: The American journal of pathology Vol. 167; no. 2; pp. 599 - 607
• Main Authors: Al-Shabrawey, Mohamed, Bartoli, Manuela, El-Remessy, Azza B., Platt, Daniel H., Matragoon, Sue, Behzadian, M. Ali, Caldwell, Robert W., Caldwell, Ruth B.
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 01.08.2005; ASIP; American Society for Investigative Pathology
• Subjects: Acetophenones - pharmacology; Animals; Biological and medical sciences; Cattle; Cells, Cultured; Endothelium, Vascular - metabolism; Endothelium, Vascular - pathology; Enzyme Inhibitors - pharmacology; Hypoxia; Investigative techniques, diagnostic techniques (general aspects); Ischemia; Medical sciences; Membrane Glycoproteins - metabolism; Mice; Mice, Inbred C57BL; NADPH Oxidase 2; NADPH Oxidases - antagonists & inhibitors; NADPH Oxidases - metabolism; Ophthalmology; Original Research Paper; Oxygen; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Retina - cytology; Retina - metabolism; Retina - pathology; Retinal Diseases - etiology; Retinal Diseases - pathology; Retinal Diseases - prevention & control; Retinal Neovascularization - prevention & control; Retinal Vessels - pathology; Retinopathies; Superoxides - metabolism; Up-Regulation; Vascular Endothelial Growth Factor A - metabolism; NAD; Eye disease; Anatomic pathology; Vascular endothelium growth factor; Retinopathy; Enzymatic activity; Ischemia; Gene overexpression; Cardiovascular disease; Inhibitor; Inhibition; Neovascularization
• DOI: 10.1016/S0002-9440(10)63001-5
• ISSN: 0002-9440

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 neovascularization associated with relative retinal hypoxia in a mouse model for oxygen-induced retinopathy. The effect of hypoxia in stimulating superoxide formation in retinal vascular endothelial cells was confirmed by in vitro chemiluminescence assays. The superoxide formation was blocked by specific inhibitors of NAD(P)H oxidase activity (apocynin, gp91ds-tat) indicating that NAD(P)H oxidase is a major source of superoxide formation. Western blot and immunolocalization analyses showed that retinal ischemia increased expression of the NAD(P)H oxidase catalytic subunit gp91phox, which localized primarily within vascular endothelial cells. Treatment of mice with apocynin blocked ischemia-induced increases in oxidative stress, normalized VEGF expression, and prevented retinal neovascularization. Apocynin and gp91ds-tat also blocked the action of hypoxia in causing increased VEGF expression in vitro , confirming the specific role of NAD(P)H oxidase in hypoxia-induced increases in VEGF expression. In conclusion, NAD(P)H oxidase activity is required for hypoxia-stimulated increases in VEGF expression and retinal neovascularization. Inhibition of NAD(P)H oxidase offers a new therapeutic target for the treatment of retinopathy.