Abstract 864: Hypoxia/Reoxygenation-Induced Myocardial Angiogenesis: Role of NADPH Oxidase Derived Reactive Oxygen Species (ROS)
NADPH oxidase is the major source of reactive oxygen species (ROS) in the cardiovascular system and plays a critical role in the pathogenesis of many cardiovascular diseases such as hypertension, diabetes and atherosclerosis. Our previous studies, and data from other investigators, suggest that NADPH oxidase has a requisite role in regulating angiogenic signaling cascades and angiogenesis. In the present study, we further investigate the potential role of endothelial NADPH oxidase in hypoxia/reoxygenation (H/R)-induced myocardial angiogenic growth factors expression and angiogenesis. Our data reveal that exposure porcine coronary artery endothelial cells (PCAECs) to hypoxia for 2 hours followed by 1 hours reoxygenation led to a significant increase in ROS and superoxide formation. PCAECs pretreated with NADPH oxidase inhibitors, DPI (10 μM) or apocynin (200 and 600 μM) significantly suppressed H/R-induced ROS and superoxide formation. In addition, exposure PCAECs to H/R caused a significant increase in Akt phosphorylation, angiogenic growth factors vascular endothelial growth factor (VEGF) and angiopoietin-2 (Ang-2) expression, and pretreatment with NADPH oxidase inhibitors attenuated H/R-induced Akt phosphorylation, VEGF and Ang-2 expression. Inhibition of NADPH oxidase also resulted in significantly suppression of H/R-induced sprouts from endothelial spheroids and mouse aortic rings. Using MHMECs from wild type mice (WT) and mice deficient in NADPH oxidase subunit p47phox (p47phox−/ −), we further found that while H/R-stimulated intracellular ROS, VEGF, Ang-2 expression, and endothelial spheroids sprouting in WT cells; the responses were strikingly suppressed in cells from the p47phox −/ − mice. Furthermore, exposure of aortic rings from NADPH oxidase p47phox−/ − mice to H/R showed strikingly less vessel sprouts than seen in rings from WT mice. Our data indicate that endothelial NADPH oxidase and ROS are necessary and require for the H/R-induced myocardial angiogenic growth factors expression and angiogenesis.
Supported by a grant from the American Heart Association (0565196B) and DK074995.