ascorbic-acid and Asphyxia

Asphyxial cardiac arrest (CA) is a significant cause of death and disability in children. Using juvenile Osteogenic disorder Shionogi (ODS) rats that, like humans, do not synthesize ascorbate, we tested the effect of ascorbate deficiency on functional and histological outcome after CA.. Postnatal day 16-18 milk-fed ODS and wild-type Wistar rats underwent 9-min asphyxial CA (n = 8/group) or sham surgery (n = 4/group). ODS mothers received ascorbate in drinking water to prevent scurvy. Levels of ascorbate and glutathione (GSH) were measured in plasma and hippocampus at baseline and after CA. Neurologic deficit score (NDS) was measured at 3, 24, and 48 h and hippocampal neuronal counts, neurodegeneration, and microglial activation were assessed at day 7.. ODS rats showed depletion of plasma and hippocampal ascorbate, attenuated hippocampal neurodegeneration and microglial activation, and increased CA1 hippocampal neuron survival vs. Wistar rats while NDS were similar. Hippocampal GSH levels were higher in ODS vs. Wistar rats at baseline and 10 min, whereas hypoxia-inducible factor-1α levels were higher in Wistar vs. ODS rats at 24 , after CA.. Ascorbate-deficient juvenile ODS rats appear resistant to neurodegeneration produced by asphyxia CA, possibly related to upregulation of the endogenous antioxidant GSH in brain.. Like humans and unlike other rodents, osteogenic disorder Shionogi (ODS) rats do not synthesize ascorbate, and thus may serve as a useful model for studying the role of ascorbate in human disease. Conflicting evidence exists regarding ascorbate's protective versus detrimental effects in animal models and clinical studies. Ascorbate-deficient ODS rats are resistant to neurodegeneration after experimental cardiac arrest.

Topics: Animals; Ascorbic Acid; Asphyxia; Heart Arrest; Hippocampus; Rats; Rats, Wistar

Nitrite acts as an ischemic reservoir of nitric oxide (NO) and a potent S-nitrosating agent which reduced histologic brain injury after rat asphyxial cardiac arrest (ACA). The mechanism(s) of nitrite-mediated neuroprotection remain to be defined. We hypothesized that nitrite-mediated brain mitochondrial S-nitrosation accounts for neuroprotection by reducing reperfusion reactive oxygen species (ROS) generation. Nitrite (4 μmol) or placebo was infused IV after normothermic (37°C) ACA in randomized, blinded fashion with evaluation of neurologic function, survival, brain mitochondrial function, and ROS. Blood and CSF nitrite were quantified using reductive chemiluminescence and S-nitrosation by biotin switch. Direct neuroprotection was verified in vitro after 1 and 4 h neuronal oxygen glucose deprivation measuring neuronal death with inhibition studies to examine mechanism. Mitochondrial ROS generation was quantified by live neuronal imaging using mitoSOX. Nitrite significantly reduced neurologic disability after ACA. ROS generation was reduced in brain mitochondria from nitrite- versus placebo-treated rats after ACA with congruent preservation of brain ascorbate and reduction of ROS in brain sections using immuno-spin trapping. ATP generation was maintained with nitrite up to 24 h after ACA. Nitrite rapidly entered CSF and increased brain mitochondrial S-nitrosation. Nitrite reduced in vitro mitochondrial superoxide generation and improved survival of neurons after oxygen glucose deprivation. Protection was maintained with inhibition of soluble guanylate cyclase but lost with NO scavenging and ultraviolet irradiation. Nitrite therapy results in direct neuroprotection from ACA mediated by reductions in brain mitochondrial ROS in association with protein S-nitrosation. Neuroprotection is dependent on NO and S-nitrosothiol generation, not soluble guanylate cyclase.

Topics: Animals; Ascorbic Acid; Asphyxia; Brain Chemistry; Cell Survival; Free Radical Scavengers; Glucose; Guanylate Cyclase; Heart Arrest; Male; Mitochondria; Neurons; Neuroprotection; Neuroprotective Agents; Nitric Oxide; Nitrites; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Superoxides; Survival Analysis

Free radicals seem to be involved in the development of cerebral white matter damage after asphyxia in the premature infant. The immature brain may be at increased risk of free radical mediated injury, as particularly the preterm infant has a relative deficiency in brain antioxidants systems, such as superoxide dismutase and glutathione peroxidase. In vitro studies show that immature oligodendrocytes express an intrinsic vulnerability to reactive oxygen species and free radical scavengers are able to protect immature oligodendrocytes from injury. The aim of this study was to examine the formation of ascorbyl radicals as a marker of oxidative stress in the preterm brain in association with cerebral white matter injury after intrauterine asphyxia. Fetal sheep at 0.65 gestation were chronically instrumented with vascular catheters and an occluder cuff around the umbilical cord. A microdialysis probe was placed in the periventricular white matter. Fetal asphyxia was induced by occlusion of the umbilical cord for 25 min (n = 10). Microdialysis samples were collected for 72 h and analyzed for ascorbyl radicals using electron spin resonance. Five instrumented fetuses served as controls. Three days after the insult, fetal brains were examined for morphologic injury. Umbilical cord occlusion resulted in prolonged and marked increase in ascorbyl radical production in the brain in connection with white matter injury, with activation of microglia cells in periventricular white matter and axonal injury. These data suggest that reperfusion injury following asphyxia in the immature brain is associated with marked free radical production.

Topics: Animals; Antioxidants; Ascorbic Acid; Asphyxia; Brain; Dehydroascorbic Acid; Electron Spin Resonance Spectroscopy; Female; Free Radicals; Glucose; Glutathione Peroxidase; Lactic Acid; Lectins; Oxygen; Pregnancy; Pregnancy, Animal; Reactive Oxygen Species; Regression Analysis; Reperfusion Injury; Risk; Sheep; Superoxide Dismutase; Time Factors

An electron spin resonance technique was used to measure cerebral antioxidant activity during asphyxial cardiac arrest and reperfusion. There were significant decreases in ascorbate (48%), glutathione (44%), total thiols (42%), protein thiols (38%) and alpha-tocopherol (26%) in the hippocampus 10 min after reperfusion (p < 0.05 vs respective baselines) but not during asphyxial cardiac arrest. The levels of antioxidants returned to baseline values by 120 min after reperfusion. The results support the hypothesis that reperfusion from asphyxial cardiac arrest, but not arrest alone, produced a significant oxidative stress as reflected by a depletion of both water and lipid soluble antioxidants. Furthermore, antioxidant depletion was transient, with normal antioxidant levels observed 120 min, 24 h and 72 h after reperfusion.

Topics: Analysis of Variance; Animals; Antioxidants; Ascorbic Acid; Asphyxia; Carbon Dioxide; Consciousness; Cranial Nerves; Electron Spin Resonance Spectroscopy; Glutathione; Heart Arrest; Hippocampus; Monophenol Monooxygenase; Myocardial Ischemia; Myocardial Reperfusion; Nerve Tissue Proteins; Oxidative Stress; Oxygen; Partial Pressure; Rats; Rats, Sprague-Dawley; Respiration; Sulfhydryl Compounds; Time Factors; Vitamin E

Levels of ascorbic acid (AA) in the plasma, brain, and adrenal gland of rats were determined after 15 min of hypoxia (PaO2 less than 25 mm Hg) and following asphyxia. In rabbits, AA plasma levels were followed up to 75 min of reoxygenation following 15 min of hypoxia of the same severity. A significant increase (approximately 70%) in AA levels was found in plasma of rats and rabbits after hypoxia and asphyxia. This increase was found to be transient, with a return to normal levels within 1 h after resumption of normal oxygenation. Pretreatment with dexamethasone reduced the increase in AA level in both rabbits and rats. Adrenalectomy in rats, performed 24 h before the experiment, abolished the response to hypoxia. Ascorbate levels in the cerebral cortex, hypothalamus, and adrenal gland of awake rats subjected to hypoxia or asphyxia were found to be the same as in normoxic rats. Our results suggest that the observed changes in plasma AA levels are probably mediated through adrenocorticotropic hormone and that the adrenal gland is the major source of ascorbate efflux into the circulation during oxygen deprivation.

Topics: Adrenal Glands; Adrenocorticotropic Hormone; Animals; Ascorbic Acid; Asphyxia; Cerebral Cortex; Guinea Pigs; Hypothalamus; Hypoxia; Male; Oxygen; Rabbits; Rats

Topics: Adrenal Glands; Aging; Animals; Animals, Newborn; Ascorbic Acid; Asphyxia; Brain; Brain Stem; Cerebellum; Female; Fetus; Guinea Pigs; Liver; Male; Nutrition Disorders; Pregnancy; Rats; Starvation

Topics: Ascorbic Acid; Asphyxia; Carbohydrate Metabolism; Glutathione; Hypothermia; Hypothermia, Induced

Topics: Adrenal Glands; Animals; Ascorbic Acid; Asphyxia; Carbohydrate Metabolism; Rats; Shock

Topics: Ascorbic Acid; Asphyxia; Conditioning, Classical; Reflex

Topics: Adrenal Cortex; Ascorbic Acid; Asphyxia; Conditioning, Classical; Nervous System Physiological Phenomena; Reflex