Abstract 1952: NADPH Oxidase-derived Superoxide Generation Contributes To Venous Endothelial Dysfunction In Human Heart Failure
Venous endothelial dysfunction contributes to the pathophysiology of human heart failure, for example by altering venous capacitance, vascular volume and ventricular preload. The aim of this study was to compare venous endothelial function in human subjects with and without heart failure and to investigate potential underlying mechanisms. Segments of saphenous vein were obtained from consecutive patients undergoing CABG, of whom 18 had heart failure diagnosed by conventional criteria and 34 had preserved left ventricular function (Control). Vascular function was assessed in organ baths from the vasomotor dose-response curves to acetylcholine and sodium nitroprusside (endothelium-dependent and independent agonists, respectively). The mRNA expression of NADPH oxidase components (Nox1, Nox2, Nox4, p47, p67) and eNOS in venous segments was quantified by real-time PCR using the SYBR Green and standard curve method. Superoxide production in venous homogenates was measured by lucigenin (5 μM)-enhanced chemiluminescence. All patients had measurement of blood lipids, glucose, CRP, interleukin 6 and TNF-alpha levels. Patients with heart failure had greater endothelial dysfunction than controls (16±3 vs 40±8%; P<0.05), increased CRP levels (8.2±2.6 vs 2.6±0.4 mg/L; P<0.05), and increased NADPH-dependent superoxide generation in venous homogenates (4.2±0.8 vs 2.1±0.3 Integrated Light Units; P<0.05; n=32). The latter was attributable to NADPH oxidase rather than uncoupled NO synthase or xanthine oxidase. No significant differences were found in mRNA expression between groups although there was a trend towards increased Nox2 expression in the heart failure group. The level of superoxide production was positively correlated with heart failure NYHA class (r=0.623, P<0.05) and CRP levels (r=0.478, P<0.05, n=30). In conclusion, this study shows for the first time that venous endothelial dysfunction in human heart failure is associated with increased NADPH oxidase-derived superoxide generation. The correlation of superoxide levels with CRP and NYHA class suggests that inflammatory mechanisms may be responsible for increasing NADPH oxidase-derived ROS generation in human heart failure.