Abstract 89: Nitrite After Cardiac Arrest Has Mitochondrial Antioxidant Effects Reducing Reperfusion Cerebral Hyperemia
Background: Nitrite confers neuroprotection after asphyxial cardiac arrest (ACA) through uncertain mechanisms though others have demonstrated antioxidant effects and improved blood flow after ischemia. We hypothesized that nitrite would modulate reperfusion blood flow and reduce reactive oxygen species (ROS).
Methods: Adult male SD rats were intubated and catheterized. Cardiac output (CO) was measured using an ultrasonic flow probe (ascending aorta), cortical blood flow (CBF) was measured using laser speckle imaging (5mm craniotomy). 5m post-ROSC from 8m ACA, animals were randomized to a 500 ul 10m infusion of 8 uM nitrite or plasmalyte placebo. Physiology was measured for 1h and normalized to pre-arrest baseline. Brains were removed at 1h and homogenized for ascorbate measurement (ac-TEMPO). Separately, brains removed 15m post-ROSC had mitochondria isolated by Percoll gradient. Respiration was measured using a Clark electrode and ROS generation quantified by Amplex Red fluorescence +/- UV pretreatment to lyse S-nitrosothiols. Pyruvate/malate or succinate +/- ADP were the substrates.
Results: Animals had similar baseline physiology. In placebo animals, post-RSOC hypertension resulted in significant increases in CBF (187%) compared to nitrite treated animals (136%; p<0.01; Figure): This difference persisted until 20 min after ROSC at which point groups converged. Nitrite treated animals had significantly higher levels of ascorbate (33.09 nmol/mg protein) compared to placebo treated animals (26.17; p=0.027). ROS generation with pyruvate substrate was reduced with nitrite therapy with minimal effects on respiration (Figure ). This difference was reversed with UV pretreatment and not present with succinate.
Conclusion: Nitrite is antioxidant after ROSC, preserving ascorbate, reducing mitochondrial ROS generation at complex I presumably via S-nitrosation and blunting loss of autoregulation and hyperemia.
- © 2013 by American Heart Association, Inc.