Polyethylene glycol-superoxide dismutase prevents endotoxin-induced cardiac dysfunction

Rationale: Sepsis produces significant mitochondrial and contractile dysfunction in the heart, but the role of superoxide-derived free radicals in the genesis of these abnormalities is not completely understood. Objectives: The studywas designed to test the hypothesis that superoxide scavenger administration prevents endotoxin-induced cardiac mitochondrial and contractile dysfunction. Methods: Four groups of rats were studied, and animals were injected with either saline, endotoxin, endotoxin plus polyethylene glycol-adsorbed-superoxide dismutase (PEG-SOD; a free-radical scavenger), or PEG-SOD alone. Animals were killed 48 h after injections. We then measured cardiac mitochondrial generation of reactive oxygen species (ROS), formation of free-radical reaction products (protein carbonyls, lipid aldehydes, nitrotyrosine), mitochondrial function, and cardiac contractile function. Measurements and Main Results: Endotoxin elicited increases in cardiac mitochondrial ROS formation (p < 0.001), increases in cardiac levels of free-radical reaction products, reductions in mitochondrial ATP generation (p < 0.001), and decrements in cardiac pressure-generating capacity (p < 0.01). Administration of PEG-SOD blocked formation of free-radical reaction products, prevented mitochondrial dysfunction, and preserved cardiac contractility. For example, mitochondrial ATP generation was 923 ± 50, 392 ± 32, 753 ± 25, and 763 ± 36 nmol/min/mg, respectively, for control, endotoxin, endotoxin + PEG-SOD, and PEG-SOD groups (p < 0.001). In addition, cardiac systolic pressure generation at a diastolic pressure of 15 mm Hg averaged 110 ± 11, 66 ± 7, 129 ± 10 and 124 ± 5 mmHg, respectively, for control, endotoxin, endotoxin + PEG-SOD, and PEG-SOD groups (p < 0.01). Conclusion: These data indicate that superoxide-derived oxidants play a critical role in the development of cardiac mitochondrial and contractile dysfunction in endotoxin-induced sepsis.