Antioxidant intervention attenuates myocardial neovascularization in hypercholesterolemia

Background - Hypercholesterolemia (HC) and atherosclerosis can elicit oxidative stress, coronary endothelial dysfunction, and myocardial ischemia, which may induce growth-factor expression and lead to myocardial neovascularization. We tested the hypothesis that chronic antioxidant intervention in HC would attenuate neovascularization and preserve the expression of hypoxia-inducible factor (HIF)-1alpha and vascular endothelial growth factor (VEGF). Methods and Results - Three groups of pigs (n = 6 each) were studied after 12 weeks of normal or 2% HC diet or HC + antioxidant supplementation ( 100 IU/kg vitamin E and 1 g vitamin C daily). Myocardial samples were scanned ex vivo with a novel 3D micro-CT scanner, and the spatial density and tortuosity of myocardial microvessels were determined in situ. VEGF mRNA, protein levels of VEGF and VEGF receptor-1, HIF-1alpha, nitrotyrosine, and superoxide dismutase ( SOD) were determined in myocardial tissue. The HC and HC+ antioxidant groups had similar increases in serum cholesterol levels. HC animals showed an increase in subendocardial spatial density of microvessels compared with normal (160.5 +/- 11.8 versus 95.3 +/- 8.2 vessels/cm(2), P < 0.05), which was normalized in HC+ antioxidant (92.5 +/- 20.5 vessels/cm(2), P < 0.05 versus HC), as was arteriolar tortuosity. In addition, HC induced upregulation of VEGF, HIF-1alpha, and nitrotyrosine expression and decreased SOD expression and activity, all of which were preserved by antioxidant intervention. Conclusions - Changes in myocardial microvascular architecture invoked by HC are accompanied by increases in HIF-1alpha and VEGF expression and attenuated by antioxidant intervention. This underscores a role of increased oxidative stress in modulating myocardial microvascular architecture in early atherogenesis.