salicylates and Hypoxia-Ischemia--Brain

The implementation and clinical efficacy of hypothermia in neonatal hypoxic-ischemic (HI) encephalopathy are limited, in part, by the delay in instituting hypothermia and access to equipment. In a piglet model of HI, half of the neurons in putamen already showed ischemic cytopathology by 6 hours of recovery. We tested the hypothesis that treatment with the superoxide dismutase-catalase mimetic EUK-134 at 30 minutes of recovery provides additive neuronal protection when combined with 1 day of whole-body hypothermia implemented 4 hours after resuscitation.. Anesthetized piglets were subjected to 40 minutes of hypoxia (10% inspired oxygen) followed by 7 minutes of airway occlusion and resuscitation. Body temperature was maintained at 38.5°C in normothermic groups and at 34°C in hypothermic groups. All groups were mechanically ventilated, sedated, and received muscle relaxants during the first day of recovery. Neuropathology was assessed by profile and stereological cell-counting methods.. At 10 days of recovery, neuronal viability in putamen of a normothermic group treated with saline vehicle was reduced to 17% ± 6% (±95% confidence interval) of the value in a sham-operated control group (100% ± 15%). Intravenous infusion of EUK-134 (2.5 mg/kg at 30 minutes of recovery + 1.25 mg/kg/h until 4 hours of recovery) with normothermic recovery resulted in 40% ± 12% viable neurons in putamen. Treatment with saline vehicle followed by delayed hypothermia resulted in partial protection (46% ± 15%). Combining early EUK-134 treatment with delayed hypothermia also produced partial protection (47% ± 18%) that was not significantly greater than single treatment with EUK-134 (confidence interval of difference: -15% to 29%) or delayed hypothermia (-16% to 19%). Furthermore, no additive neuroprotection was detected in caudate nucleus or parasagittal neocortex, where neuronal loss was less severe.. We conclude that early treatment with this antioxidant does not substantially enhance the therapeutic benefit of delayed hypothermia in protecting highly vulnerable neurons in HI-insulted newborns, possibly because basal ganglia neurons are already undergoing irreversible cell death signaling by the time EUK-134 is administered or because this compound and hypothermia attenuate similar mechanisms of injury.

Topics: Animals; Animals, Newborn; Antioxidants; Hypothermia, Induced; Hypoxia-Ischemia, Brain; Male; Neuroprotective Agents; Organometallic Compounds; Salicylates; Swine

Striatal neurons are highly vulnerable to hypoxia-ischemia (HI) in term newborns. In a piglet model of HI, striatal neurons develop oxidative stress and organelle disruption by 3-6 h of recovery and ischemic cytopathology over 6-24 h of recovery. We tested the hypothesis that early treatment with the antioxidants EUK-134 (a manganese-salen derivative that acts as a scavenger of superoxide, hydrogen peroxide, nitric oxide or NO and peroxynitrite) or edaravone (MCI-186, a scavenger of hydroxyl radical and NO) protects striatal neurons from HI. Anesthetized newborn piglets were subjected to 40 min of hypoxia and 7 min of airway occlusion. At 30 min after resuscitation, the piglets received vehicle, EUK-134 or edaravone. Drug treatment did not affect arterial blood pressure, blood gases, blood glucose or rectal temperature. At 4 days of recovery, the density of viable neurons in the putamen of vehicle-treated piglets was 12 ± 6% (±SD) of sham-operated control density. Treatment with EUK-134 increased viability to 41 ± 17%, and treatment with edaravone increased viability to 39 ± 19%. In the caudate nucleus, neuronal viability was increased from 54 ± 11% in the vehicle group to 78 ± 15% in the EUK-134 group and to 73 ± 13% in the edaravone group. Antioxidant drug treatment accelerated recovery from neurologic deficits and decreased oxidative and nitrative damage to nucleic acids. Treatment with EUK-134 reduced the HI-induced formation of protein carbonyl groups and tyrosine nitration at 3 h of recovery. We conclude that systemic administration of antioxidant agents by 30 min after resuscitation from HI can reduce oxidative stress and salvage neurons in the highly vulnerable striatum in a large-animal model of neonatal HI. Therefore, oxidative stress is an important mechanism for this injury, and antioxidant therapy is a rational, mechanism-based approach to neuroprotection in the newborn brain.

Topics: Animals; Animals, Newborn; Antioxidants; Antipyrine; Corpus Striatum; Edaravone; Free Radical Scavengers; Hypoxia-Ischemia, Brain; Nerve Degeneration; Neuroprotective Agents; Organometallic Compounds; Oxidative Stress; Salicylates; Swine

Although oxygen/glucose deprivation (OGD) has been widely used as a model of ischemic brain damage, the mechanisms underlying acute neuronal death in this model are not yet well understood. We used OGD in acute hippocampal slices to investigate the roles of reactive oxygen species and of the mitogen-activated protein kinases (MAPKs) in neuronal death. In particular, we tested the neuroprotective effects of two synthetic superoxide dismutase/catalase mimetics, EUK-189 and EUK-207. Acute hippocampal slices prepared from 2-month-old or postnatal day 10 rats were exposed to oxygen and glucose deprivation for 2 h followed by 2.5 h reoxygenation. Lactate dehydrogenase (LDH) release in the medium and propidium iodide (PI) uptake were used to evaluate cell viability. EUK-189 or EUK-207 applied during the OGD and reoxygenation periods decreased LDH release and PI uptake in slices from 2-month-old rats. EUK-189 or EUK-207 also partly blocked OGD-induced ATP depletion and extracellular signal-regulated kinases 1 and 2 (ERK1/2) dephosphorylation, and completely eliminated reactive oxygen species generation. The MEK inhibitor U0126 applied together with EUK-189 or EUK-207 completely blocked ERK1/2 activation, but had no effect on their protective effects against OGD-induced LDH release. U0126 alone had no effect on OGD-induced LDH release. EUK-207 had no effect on OGD-induced p38 or c-Jun N-terminal kinase dephosphorylation, and when the p38 inhibitor SB203580 was applied together with EUK-207, it had no effect on the protective effects of EUK-207. SB203580 alone had no effect on OGD-induced LDH release either. In slices from p10 rats, OGD also induced high-LDH release that was partly reversed by EUK-207; however, neither OGD nor EUK-207 produced significant changes in ERK1/2 and p38 phosphorylation. OGD-induced spectrin degradation was not modified by EUK-189 or EUK-207 in slices from p10 or 2-month-old rats, suggesting that their protective effects was not mediated through inhibition of calpain activation. Thus, both EUK-189 and EUK-207 provide neuroprotection in acute ischemic conditions, and this effect is related to elimination of free radical formation and partial reversal of ATP depletion, but not mediated by the activation or inhibition of the MEK/ERK or p38 pathways, or inhibition of calpain activation.

Topics: Adenosine Triphosphate; Animals; Animals, Newborn; Calpain; Catalase; Cell Death; Enzyme Inhibitors; Free Radicals; Hippocampus; Hypoxia-Ischemia, Brain; L-Lactate Dehydrogenase; MAP Kinase Signaling System; Molecular Mimicry; Neuroprotective Agents; Organ Culture Techniques; Organometallic Compounds; Oxidative Stress; Phosphorylation; Rats; Rats, Sprague-Dawley; Salicylates; Superoxide Dismutase; Superoxide Dismutase-1