Cardiac mitochondrial damage and loss of ROS defense after burn injury: the beneficial effects of antioxidant therapy

Mechanisms of burn-related cardiac dysfunction may involve defects in mitochondria. This study determined 1) whether burn injury alters myocardial mitochondrial integrity and function; and 2) whether an antioxidant vitamin therapy prevented changes in cardiac mitochondrial function after burn. Sprague- Dawley rats were given a 3 burn over 40% total body surface area and fluid resuscitated. Antioxidant vitamins or vehicle were given to sham and burn rats. Mitochondrial and cytosolic fractions were prepared from heart tissues at several times postburn. In mitochondria, lipid peroxidation was measured to assess oxidative stress, mitochondrial outer membrane damage and cytochrome-c translocation were determined to estimate mitochondrial integrity, and activities of SOD and glutathione peroxidase were examined to evaluate mitochondrial antioxidant defense. Cardiac function was measured by Langendorff model in sham and burn rats given either vitamins or vehicle. Twenty-four hours postburn, mitochondrial outer membrane damage was progressively increased to similar to 50%, and cytosolic cytochrome-c gradually accumulated to approximately three times more than that measured in shams, indicating impaired mitochondrial integrity. Maximal decrease of mitochondrial SOD activity occurred 8 h postburn ( similar to 63.5% of shams), whereas maximal decrease in glutathione peroxidase activity persisted 2 - 24 h postburn ( similar to 60% of shams). In burn animals, lipid peroxidation in cardiac mitochondria increased 30 - 50%, suggesting burn-induced oxidative stress. Antioxidant vitamin therapy prevented burn- related loss of membrane integrity and antioxidant defense in myocardial mitochondria and prevented cardiac dysfunction. These data suggest that burn- mediated mitochondrial dysfunction and loss of reactive oxygen species defense may play a role in postburn cardiac dysfunction.