Purchase this article with an account.
M. El-Shabrawey, N. Tsai, R.B. Caldwell; Upregulation of Vascular NADPH-Oxidase Contributes to Retinal Angiogenesis . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2914.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Recent studies have implicated over-expression of the reactive oxygen species-generating NADPH oxidase enzyme family in the induction of VEGF expression during tumor angiogenesis. The NADPH oxidase catalytic subunit gp91phox is thought to function as an oxygen sensor and may therefore participate in intracellular signaling pathways leading to hypoxia-induced expression of VEGF. Thus, we hypothesized that upregulation of gp91phox could be involved in hypoxia-induced retinal angiogenesis. Method: This was tested by experiments in the developing mouse retina and in a mouse model of oxygen-induced retinopathy (OIR) in which newborn mice are maintained in hyperoxia for 5 days (P7-P12) followed by 5 days of normoxia (P12-P17). The hyperoxia exposure causes retinal vaso-obliteration, which leads to ischemia and relative hypoxia during the normoxia exposure. This results in pathological angiogenesis within the retina and vitreous cavity. We used a combination of immunolocalization and Western blotting techniques to analyze gp91phox expression in relation to retinal angiogenesis. NADPH oxidase activity in forming superoxide anion was determined by hydroethidine imaging. Morphometric methods were used to determine the effects of inhibiting NADPH oxidase activity on retinal angiogenesis during OIR. Results: Immunolocalization analysis in developing retinas of normal mice showed that gp91phox co-localizes exactly with the forming retinal vessels during the angiogenic phase of retinal development (P7-P9), but disappears as the vessels differentiate (P12 and later). Western analyses in the OIR model of pathological angiogenesis showed a significant, time-dependent increase in gp91phox protein levels during retinal neovascularization. Immunolocalization studies showed that gp91phox co-localizes precisely with the proliferating vessels in the retinas of the OIR model, whereas the normal vessels in the control retinas are negative. Dihydroethidine image analyses showed that retinal angiogenesis is associated with substantial increases in superoxide formation within the retinal vasculature. Treatment with the specific NADPH oxidase inhibitor apocynin (IP injection, 4 or 10 mg/kg/day) caused a dose-dependent reduction in vitreoretinal neovascularization in the OIR model. Conclusions: These results suggest that superoxide generation by NADPH oxidase plays a key role in the induction of both normal and pathological retinal angiogenesis.
This PDF is available to Subscribers Only