Neuroprotection by Selective Nitric Oxide Synthase Inhibition at 24 Hours After Perinatal Hypoxia-Ischemia

Background and Purpose—Perinatal hypoxia-ischemia is a major cause of neonatal morbidity and mortality. Until now no established neuroprotective intervention after perinatal hypoxia-ischemia has been available. The delay in cell death after perinatal hypoxia-ischemia creates possibilities for therapeutic intervention after the initial insult. Excessive nitric oxide and reactive oxygen species generated on hypoxia-ischemia and reperfusion play a key role in the neurotoxic cascade. The present study examines the neuroprotective properties of neuronal and inducible but not endothelial nitric oxide synthase inhibition by 2-iminobiotin in a piglet model of perinatal hypoxia-ischemia. Methods—Twenty-three newborn piglets were subjected to 60 minutes of hypoxia-ischemia, followed by 24 hours of reperfusion and reoxygenation. Five additional piglets served as sham-operated controls. On reperfusion, piglets were randomly treated with either vehicle (n12) or 2-iminobiotin (n11). At 24 hours after hypoxia-ischemia, the cerebral energy state, presence of vasogenic edema, amount of apparently normal neuronal cells, caspase-3 activity, amount of terminal deoxynucleotidyl transferase–mediated dUTP-biotin in situ nick end labeling (TUNEL)–positive cells, and degree of tyrosine nitration were assessed. Results—A 90% improvement in cerebral energy state, 90% reduction in vasogenic edema, and 60% to 80% reduction in apoptosis-related neuronal cell death were demonstrated in 2-iminobiotin–treated piglets at 24 hours after hypoxiaischemia. A significant reduction in tyrosine nitration in the cerebral cortex was observed in 2-iminobiotin–treated piglets, indicating decreased formation of reactive nitrogen species. Conclusions—Simultaneous and selective inhibition of neuronal and inducible nitric oxide synthase by 2-iminobiotin is a promising strategy for neuroprotection after perinatal hypoxia-ischemia. (Stroke. 2002;33:2304-2310.)