Abstract 4909: Nox2-Containing NADPH Oxidase Deficiency Protects Against Age-Dependent Inhibition of Neovascularization

Abstract

Background: We have previously shown that aging is associated with an impaired angiogenic response following ischemia. Because aging leads to an increased generation of reactive oxygen species (ROS), here we investigated the role of Nox2-containing NADPH oxidase ROS generation for the modulation of neovascularization by aging. Methods: Hindlimb ischemia was surgically induced by femoral artery removal in young (5–7 weeks) and older (9 months) Nox2 −/− and control (Nox2 +/+ ) mice. Results: We found that blood flow recovery is significantly reduced in older compared to younger mice at day 21 after surgery (Doppler flow ratios: 0.51± 0.05 vs. 0.72± 0.05; p<0.05). At the microvascular level, capillary density was also significantly reduced in ischemic muscles of older animals (53.4± 6.3 capillaries/field vs. 82.5± 4.9 capillaries/field; p<0.001). This was associated with a significant increase of oxidative stress levels (nitrotyrosine immunostaining) in ischemic tissues of older animals. Importantly, we found that Nox2 deficiency reduces oxidative stress levels in ischemic tissues and restores blood flow recuperation in older animals. Endothelial progenitor cells (EPCs) have been shown to have an important role for postnatal neovascularization. Here we found that the functional activities of EPCs (adhesion to HUVECs, migration) are significantly impaired in old compared to young mice. However, Nox2 deficiency rescues EPCs functional activities in older animals. We also demonstrate an age-dependent pathological increase of oxidative stress levels (DCF-DA, DHE) in EPCs that is not present in Nox2-deficient animals. Conclusion: Nox2-containing NADPH oxidase deficiency protects against age-dependent impairment of neovascularization. Potential mechanisms include reduced ROS generation in ischemic tissues and preserved angiogenic activities of EPCs.