Involvement of Nox2 NADPH oxidase in retinal neovascularization

The proliferation of new blood vessels in the retina is a leading cause of vision impairment. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) is involved in cell signaling for ischemia-induced angiogenesis, but its role in retinal neovascularization is unclear. We have analyzed the dependence of retinal neovascularization on the Nox2 isoform in oxygen-induced retinopathy (OIR) in mice.

Neonatal C57BL/6 mice aged 7 days (P7) were placed in a hyperoxic chamber (75% O2) for 5 days, followed by 5 days of exposure to room air. Eyes were harvested on P8 and P17 for the quantification of retinal vaso-obliteration and neovascularization, respectively. The retinal expression of Nox2 and VEGF-A were measured by RT-PCR, while superoxide generation was detected by in situ dihydroethidium (DHE) staining of fresh frozen sections.

In wild type (WT) mice, OIR was characterized by central retinal vaso-obliteration at P8 and neovascularization at P17, which was associated with increases in Nox2 and VEGF-A gene expression, superoxide generation, and accumulation of Iba-1 positive cells in the inner retina. In contrast, Nox2 knockout mice exhibited markedly less retinal neovascularization and VEGF-A mRNA expression at P17, despite showing comparable vaso-obliteration at P8. These changes were accompanied by reductions in DHE fluorescence and Iba-1-positive cell accumulation in the hypoxic retina.

The Nox2-generated reactive oxygen species (ROS) facilitate the retinal expression of VEGF-A and neovascularization in this mouse model of OIR. Therapies targeting Nox2 could be of value to reduce aberrant retinal neovascularization in retinopathy of prematurity, diabetes, and other disease processes driven by VEGF.