Free radicals, mitochondria, and hypoxia-ischemia in the developing brain

Nicotinamide prevents the down-regulation of MEK/ERK/p90RSK signaling cascade in brain ischemic injury

Nicotinamide attenuates neuronal cell death related to focal cerebral ischemic injury. This study investigated whether nicotinamide exerts a neuroprotective effect through the activation of Raf- mitogen-activated protein kinase kinase (MEK)-ERK and its downstream targets, including p90 ribosomal S6 kinase (p90RSK) and Bad. Adult male Sprague-Dawley rats were treated with nicotinamide (500 mg/kg) or vehicle 2 hr after the onset of middle cerebral artery occlusion (MCAO). Brains were collected 24 hr after MCAO. In the present study, nicotinamide significantly reduces the volume of infarct regions and decreases the number of positive cells by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining in the cerebral cortex. Nicotinamide prevents injury-induced decrease in Raf-1, MEK1/2, and ERK1/2 phosphorylation. As part of the downstream cascade, nicotinamide inhibits the injury-induced decrease in p90RSK and Bad phosphorylation. Moreover, nicotinamide prevents the injury-induced increase in cleaved caspase-3 levels. These findings suggest that nicotinamide protects neuronal cells against cerebral ischemic injury and that MEK-ERK-p90RSK cascade activation by nicotinamide contributes to these neuroprotective effects.

Superoxide scavenging and xanthine oxidase inhibiting activities of copper-β-citryl-L-glutamate complex

β-Citryl-L-glutamate (β-CG) is a unique compound initially isolated from developing brains, which also appears in high concentrations during the period characterized by growth and differentiation of neurons in developing animals, and then decreases with maturation. However, its functional roles remain unclear. The stability constant obtained in our previous pH titration studies showed that β-CG forms relatively strong complexes with copper. Reactive oxygen species (ROS) and nitric oxide (NO) have been suggested to act as mediators of the cell death that occurs in neurons during development of the nervous system. However, regulation of ROS and NO formation by Cu in the developing brain remains poorly understood. The activity of superoxide dismutase (SOD), a key superoxide scavenging enzyme, is low in the developing brain. Furthermore, xanthine oxidase (XO) has been implicated in diverse pathological situations due to its capability of generating both ROS and NO. Therefore, we examined the effects of β-CG and its Cu-complex on SOD and XO activities. We found that the [Cu(II)(β-CG)] complex had SOD activity and a strong competitive inhibition of XO, while reduced glutathione caused concentration-dependent decreases of the XO inhibitory activities in the [Cu(II)(β-CG)] complex.

Striatal neuroprotection from neonatal hypoxia-ischemia in piglets by antioxidant treatment with EUK-134 or edaravone

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.

Treatment advances in neonatal neuroprotection and neurointensive care

Knowledge of the nature, prognosis, and ways to treat brain lesions in neonatal infants has increased remarkably. Neonatal hypoxic-ischaemic encephalopathy (HIE) in term infants, mirrors a progressive cascade of excito-oxidative events that unfold in the brain after an asphyxial insult. In the laboratory, this cascade can be blocked to protect brain tissue through the process of neuroprotection. However, proof of a clinical effect was lacking until the publication of three positive randomised controlled trials of moderate hypothermia for term infants with HIE. These results have greatly improved treatment prospects for babies with asphyxia and altered understanding of the theory of neuroprotection. The studies show that moderate hypothermia within 6 h of asphyxia improves survival without cerebral palsy or other disability by about 40% and reduces death or neurological disability by nearly 30%. The search is on to discover adjuvant treatments that can further enhance the effects of hypothermia.

Overweight worsens apoptosis, neuroinflammation and blood-brain barrier damage after hypoxic ischemia in neonatal brain through JNK hyperactivation

BACKGROUND

Apoptosis, neuroinflammation and blood-brain barrier (BBB) damage affect the susceptibility of the developing brain to hypoxic-ischemic (HI) insults. c-Jun N-terminal kinase (JNK) is an important mediator of insulin resistance in obesity. We hypothesized that neonatal overweight aggravates HI brain damage through JNK hyperactivation-mediated upregulation of neuronal apoptosis, neuroinflammation and BBB leakage in rat pups.

METHODS

Overweight (OF) pups were established by reducing the litter size to 6, and control (NF) pups by keeping the litter size at 12 from postnatal (P) day 1 before HI on P7. Immunohistochemistry and immunoblotting were used to determine the TUNEL-(+) cells and BBB damage, cleaved caspase-3 and poly (ADP-ribose) polymerase (PARP), and phospho-JNK and phospho-BimEL levels. Immunofluorescence was performed to determine the cellular distribution of phospho-JNK.

RESULTS

Compared with NF pups, OF pups had a significantly heavier body-weight and greater fat deposition on P7. Compared with the NF-HI group, the OF-HI group showed significant increases of TUNEL-(+) cells, cleaved levels of caspase-3 and PARP, and ED1-(+) activated microglia and BBB damage in the cortex 24 hours post-HI. Immunofluorescence of the OF-HI pups showed that activated-caspase 3 expression was found mainly in NeuN-(+) neurons and RECA1-(+) vascular endothelial cells 24 hours post-HI. The OF-HI group also had prolonged escape latency in the Morris water maze test and greater brain-volume loss compared with the NF-HI group when assessed at adulthood. Phospho-JNK and phospho-BimEL levels were higher in OF-HI pups than in NF-HI pups immediately post-HI. JNK activation in OF-HI pups was mainly expressed in neurons, microglia and vascular endothelial cells. Inhibiting JNK activity by AS601245 caused more attenuation of cleaved caspase-3 and PARP, a greater reduction of microglial activation and BBB damage post-HI, and significantly reduced brain damage in OF-HI than in NF-HI pups.

CONCLUSIONS

Neonatal overweight increased HI-induced neuronal apoptosis, microglial activation and BBB damage, and aggravated HI brain damage in rat pups through JNK hyperactivation.

Neuronal death and oxidative stress in the developing brain

The developing brain is particularly vulnerable to reactive oxygen and reactive nitrogen species-mediated damage because of its high concentrations of unsaturated fatty acids, high rate of oxygen consumption, low concentrations of antioxidants, high content of metals catalyzing free radical formation, and large proportion of sensitive immature cells. In this review, we outline the dynamic changes of energy resources, metabolic requirements, and endogenous free radical scavenging systems during physiologic brain development. We further discuss the involvement of oxidative stress in the pathogenesis of neuronal death after exposure of the infant brain to hyperoxia, hypoxia/ischemia, sedative drugs, ethanol, and mechanical trauma. Several approaches have been developed to combat oxidative stress, but neuroprotective treatment strategies are limited in the clinical setting.

Exploring uncoupling proteins and antioxidant mechanisms under acute cold exposure in brains of fish

Exposure to fluctuating temperatures accelerates the mitochondrial respiration and increases the formation of mitochondrial reactive oxygen species (ROS) in ectothermic vertebrates including fish. To date, little is known on potential oxidative damage and on protective antioxidative defense mechanisms in the brain of fish under cold shock. In this study, the concentration of cellular protein carbonyls in brain was significantly increased by 38% within 1 h after cold exposure (from 28°C to 18°C) of zebrafish (Danio rerio). In addition, the specific activity of superoxide dismutase (SOD) and the mRNA level of catalase (CAT) were increased after cold exposure by about 60% (6 h) and by 60%–90% (1 and 24 h), respectively, while the specific glutathione content as well as the ratio of glutathione disulfide to glutathione remained constant and at a very low level. In addition, cold exposure increased the protein level of hypoxia-inducible factor (HIF) by about 50% and the mRNA level of the glucose transporter zglut3 in brain by 50%–100%. To test for an involvement of uncoupling proteins (UCPs) in the cold adaptation of zebrafish, five UCP members were annotated and identified (zucp1-5). With the exception of zucp1, the mRNA levels of the other four zucps were significantly increased after cold exposure. In addition, the mRNA levels of four of the fish homologs (zppar) of the peroxisome proliferator-activated receptor (PPAR) were increased after cold exposure. These data suggest that PPARs and UCPs are involved in the alterations observed in zebrafish brain after exposure to 18°C. The observed stimulation of the PPAR-UCP axis may help to prevent oxidative damage and to maintain metabolic balance and cellular homeostasis in the brains of ectothermic zebrafish upon cold exposure.

Electrophysiological analysis of vulnerability to experimental ischemia in neonatal rat spinal ventral horn neurons

To clarify the vulnerability of spinal motoneurons to excitotoxicity, we analyzed the agonal current induced by experimental ischemia in ventral lamina IX neurons of spinal cord slices from neonatal rats by using whole-cell patch-clamp. Ischemia was simulated in vitro by oxygen/glucose deprivation. Superfusion with ischemia-simulating medium elicited an agonal inward current, which was initially slow and then became rapid. We compared 8-, 9-, 10-, 11-, and 12-day postnatal rats and found age-dependent shortening of the latency of the rapid inward current. Furthermore, the membrane capacitance (Cm) and resting membrane potential (RMP) of the lamina IX neurons demonstrated significant negative correlations with the latency of the rapid inward current. Logistic regression analysis showed that postnatal age, Cm, and RMP were independent contributing factors to ischemic vulnerability. These results suggest that not only cell volume and ionic balance but also early postnatal maturation of the intracellular environment is vital for developing vulnerability to excitotoxicity.

Chronic fetal hypoxia produces selective brain injury associated with altered nitric oxide synthases

OBJECTIVE

The purpose of this study was to investigate the impact of chronic hypoxia on the nitric oxide synthase isoenzymes in specific brain structures.

STUDY DESIGN

Time-mated pregnant guinea pigs were exposed to 10.5% molecular oxygen for 14 days (animals with chronic fetal hypoxia; HPX) or room air (control animals; NMX); L-N6-(1-iminoethyl)-lysine (L-NIL; an inducible nitric oxide synthase inhibitor, 1 mg/kg/d) was administered to HPX group for 14 days (L-NIL + HPX). Fetal brains were harvested at term. Multilabeled immunofluorescence was used to generate a brain injury map. Laser capture microdissection and quantitative polymerase chain reaction were applied; cell injury markers, apoptosis activation, neuron loss, total nitric oxide, and the levels of individual nitric oxide synthase isoenzymes were quantified.

RESULTS

Chronic hypoxia causes selective fetal brain injury rather than global. Injury is associated with differentially affected nitric oxide synthases in both neurons and glial cells, with inducible macrophage-type nitric oxide synthase up-regulated at all injury sites. L-NIL attenuated the injury, despite continued hypoxia.

CONCLUSION

These studies demonstrate that chronic hypoxia selectively injures the fetal brain in part by the differential regulation of nitric oxide synthase isoenzymes in an anatomic- and cell-specific manner.

Docosahexaenoic acid: brain accretion and roles in neuroprotection after brain hypoxia and ischemia

PURPOSE OF REVIEW

With important effects on neuronal lipid composition, neurochemical signaling and cerebrovascular pathobiology, docosahexaenoic acid (DHA), a n-3 polyunsaturated fatty acid, may emerge as a neuroprotective agent against cerebrovascular disease. This paper examines pathways for DHA accretion in brain and evidence for possible roles of DHA in prophylactic and therapeutic approaches for cerebrovascular disease.

RECENT FINDINGS

DHA is a major n-3 fatty acid in the mammalian central nervous system and enhances synaptic activities in neuronal cells. DHA can be obtained through diet or to a limited extent via conversion from its precursor, α-linolenic acid (α-LNA). DHA attenuates brain necrosis after hypoxic ischemic injury, principally by modulating membrane biophysical properties and maintaining integrity in functions between presynaptic and postsynaptic areas, resulting in better stabilizing intracellular ion balance in hypoxic-ischemic insult. Additionally, DHA alleviates brain apoptosis, by inducing antiapoptotic activities such as decreasing responses to reactive oxygen species, upregulating antiapoptotic protein expression, downregulating apoptotic protein expression, and maintaining mitochondrial integrity and function.

SUMMARY

DHA in brain relates to a number of efficient delivery and accretion pathways. In animal models DHA renders neuroprotection after hypoxic-ischemic injury by regulating multiple molecular pathways and gene expression.

Glutathione biosynthesis via activation of the nuclear factor E2-related factor 2 (Nrf2)--antioxidant-response element (ARE) pathway is essential for neuroprotective effects of sulforaphane and 6-(methylsulfinyl) hexyl isothiocyanate

Oxidative stress plays pivotal roles in aging, neurodegenerative disease, and pathological conditions such as ischemia. We investigated the effect of sulforaphane and 6-(methysulfinyl) hexyl isothiocyanate (6-HITC), a naturally occurring isothiocyanate, on oxidative stress-induced cytotoxicity using primary neuronal cultures of rat striatum. Pretreatment with sulforaphane and 6-HITC significantly protected against H(2)O(2)- and paraquat-induced cytotoxicity in a concentration-dependent manner. Sulforaphane and 6-HITC induced the translocation of nuclear factor E2-related factor 2 (Nrf2) into the nucleus and increased the expression of γ-glutamylcysteine synthetase (γ-GCS), a rate-limiting enzyme in glutathione synthesis, and the intracellular glutathione content. Treatment with reduced glutathione (GSH) and N-acetyl-L-cysteine, a substance for glutathione synthesis, significantly prevented the cytotoxicity induced by H(2)O(2) and paraquat. Moreover, exposure to L-buthionine-sulfoximine, an irreversible inhibitor of γ-GCS, suppressed the protective effects of sulforaphane and 6-HITC. In contrast, sulforaphane and 6-HITC increased heme oxygenase-1 (HO-1) expression in neurons. However, zinc-protophorphyrin IX, a competitive inhibitor of HO-1, did not influence the protective effects of sulforaphane and 6-HITC. These results suggest that sulforaphane and 6-HITC prevent oxidative stress-induced cytotoxicity in rat striatal cultures by raising the intracellular glutathione content via an increase in γ-GCS expression induced by the activation of the Nrf2-antioxidant response element pathway.

Toxicity biomarkers among US children compared to a similar cohort in France: a blinded study measuring urinary porphyrins

The purpose of this blinded study was to evaluate potential environmental toxicity in a cohort of neurotypical children (n = 28) living in a suburban area of north-central Texas in the United States (US) with a comparable age- and gender-matched cohort of neurotypical children (n = 28) living in a suburban area of southeastern France using urinary porphyrin testing: uroporphyrin (uP), heptacarboxyporphyrin (7cxP), hexacarboxyporphyrin (6cxP), pentacarboxyporphyrin (5cxP), precoproporphyrin (prcP), and coproporphyrin (cP). Results showed significantly elevated 6cxP, prcP (an atypical, mercury-specific porphyrin), and cP levels, and increasing trends in 5cxP levels, among neurotypical children in the USA compared to children in France. Data suggest that in US neurotypical children, there is a significantly increased body-burden of mercury (Hg) compared to the body-burden of Hg in the matched neurotypical children in France. The presence of lead contributing to the higher levels of cP also needs to be considered. Further, other factors including genetics can not be completely ruled out.

Regional characterization of energy metabolism in the brain of normal and MPTP-intoxicated mice using new markers of glucose and phosphate transport

The gibbon ape leukemia virus (GALV), the amphotropic murine leukemia virus (AMLV) and the human T-cell leukemia virus (HTLV) are retroviruses that specifically bind nutrient transporters with their envelope glycoproteins (Env) when entering host cells. Here, we used tagged ligands derived from GALV, AMLV, and HTLV Env to monitor the distribution of their cognate receptors, the inorganic phosphate transporters PiT1 and PiT2, and the glucose transporter GLUT1, respectively, in basal conditions and after acute energy deficiency. For this purpose, we monitored changes in the distribution of PiT1, PiT2 and GLUT1 in the cerebellum, the frontal cortex, the corpus callosum, the striatum and the substantia nigra (SN) of C57/BL6 mice after administration of 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridinium (MPTP), a mitochondrial complex I inhibitor which induces neuronal degeneration in the striato-nigral network.The PiT1 ligand stained oligodendrocytes in the corpus callosum and showed a reticular pattern in the SN. The PiT2 ligand stained particularly the cerebellar Purkinje cells, while GLUT1 labelling was mainly observed throughout the cortex, basal ganglia and cerebellar gray matter. Interestingly, unlike GLUT1 and PiT2 distributions which did not appear to be modified by MPTP intoxication, PiT1 immunostaining seemed to be more extended in the SN. The plausible reasons for this change following acute energy stress are discussed.These new ligands therefore constitute new metabolic markers which should help to unravel cellular adaptations to a wide variety of normal and pathologic conditions and to determine the role of specific nutrient transporters in tissue homeostasis.

Anti-amnesic effect of Chong-Myung-Tang on scopolamine-induced memory impairments in mice

AIM OF THE STUDY

Chong-Myung-Tang (CMT) consisted of Acorus gramineus Soland, Polygala tenuifolia Willdenow, and Poria cocos Wolf is one of the traditional Korean herbal medicines used for the therapy of learning and memory improvement. The present study was investigated the effect of CMT on learning and memory functions in SCOP-induced memory deficits mice.

MATERIALS AND METHODS

The cognitive-enhancing effect of CMT on amnesic mice induced by SCOP was investigated by assessing the passive avoidance test and the Morris water maze test. In order to confirm the underlying mechanisms of memory enhancing effects of CMT, activities of AChE, choline acetyltransferase (ChAT), and antioxidant enzymes were measured.

RESULTS

Administration of CMT significantly restored memory impairments induced by SCOP in the passive avoidance test and also reduced escape latency during trial sessions in the Morris water maze test. The increased AChE activity produced by SCOP was significantly inhibited by CMT. CMT significantly enhanced ChAT activity. Moreover, treatment with CMT to the amnesic mice induced by SCOP considerably decreased malondialdehyde levels and restored activities of superoxide dismutase and catalase to the control values.

CONCLUSIONS

These results suggest that CMT may be useful for the cognitive improvement via regulation of cholinergic marker enzyme activities and the antioxidant defense system.

Extracellular amino acids and lipid peroxidation products in periventricular white matter during and after cerebral ischemia in preterm fetal sheep

It is widely hypothesized that accumulation of excitatory amino acids, and oxygen free radicals during or after exposure to hypoxia-ischemia play a pivotal role in preterm periventricular white matter injury; however, there is limited evidence in the intact brain. In preterm fetal sheep (0.65 gestation; term 147 days) we found no significant increase in extracellular levels of excitatory amino acids measured by microdialysis in the periventricular white matter during cerebral ischemia induced by bilateral carotid occlusion. There was no significant change in 8-isoprostane or malondialdehyde levels in the early phase of recovery after occlusion. In contrast, there was a significant delayed increase in most amino acids and in malondialdehyde (but not 8-isoprostane) that was maximal approximately 2-3 days after occlusion. The increase in glutamate was significantly correlated with a secondary increase in cortical impedance, an index of cytotoxic edema, and with white matter damage 3 days post-insult. In conclusion, no significant accumulation of cytotoxins was found within immature white matter during cerebral ischemia. Although a minority of fetuses showed a delayed increase in some cytotoxins, this occurred many days after ischemia, in association with secondary cytotoxic edema, strongly suggesting that these changes are mainly a consequence of evolving cell death.

Timing of appearance of late oligodendrocyte progenitors coincides with enhanced susceptibility of preterm rabbit cerebral white matter to hypoxia-ischemia

Emerging evidence supports that premature infants are susceptible to both cerebral white and gray matter injury. In a fetal rabbit model of placental insufficiency, preterm rabbits at embryonic day 22 (E22) exhibited histologic evidence of gray matter injury but minimal white matter injury after global hypoxia-ischemia (H-I). We hypothesized that the dissociation between susceptibility to gray and white matter injury at E22 was related to the timing of appearance of late oligodendrocyte progenitors (preOLs) that are particularly vulnerable in preterm human white matter lesions. During normal rabbit oligodendrocyte (OL) lineage progression, early OL progenitors predominated at E22. PreOL density increased between E24 and E25 in major forebrain white matter tracts. After H-I at E22 and E25, we observed a similar magnitude of cerebral H-I, assessed by cortical microvascular blood flow, and gray matter injury, assessed by caspase activation. However, the increased preOL density at E25 was accompanied by a significant increase in acute white matter injury after H-I that coincided with enhanced preOL degeneration. At E29, significant white matter atrophy developed after H-I at E25 but not E22. Thus, the timing of appearance of preOLs coincided with onset of a developmental window of enhanced white but not gray matter susceptibility to H-I.

Prolyl hydroxylase domain inhibitors: a route to HIF activation and neuroprotection

Abstract Ischemic stroke is a major cause of death worldwide, and current therapeutic options are very limited. Preconditioning with an ischemic or hypoxic insult is beneficial in experimental models of ischemic stroke. Ischemia/hypoxia results in activation of numerous transcription factors, including hypoxia inducible factor (HIF), which is a master regulator of oxygen homeostasis. HIF activation induces a diverse range of target genes, encompassing a wide variety of cellular processes; including angiogenesis, energy metabolism, cell survival, radical production/scavenging, iron metabolism, stem cell homing, and differentiation. Inhibition of HIF prolyl hydroxylase domain (PHD) enzymes results in activation of HIF and is likely to mimic, at least in part, the effects of hypoxia preconditioning. A caveat is that not all consequences of HIF activation will be beneficial and some could even be deleterious. Nevertheless, PHD inhibitors may be therapeutically useful in the treatment of stroke. Prototype PHD inhibitors have shown promising results in preclinical models.

trans-Resveratrol as a neuroprotectant

Epidemiological evidence indicates that nutritionally-derived polyphenols such as resveratrol (RES) have neuroprotective properties. Administration of RES to culture media protects a wide variety of neuronal cell types from stress-induced death. Dietary supplementation of RES can ameliorate neuronal damage and death resulting from both acute and chronic stresses in rodents. The specific molecular mechanisms by which RES acts at the cellular level remain incompletely understood. However, many experimental data indicate that RES reduces or prevents the occurrence of oxidative damage. Here we discuss possible mechanisms by which RES might exert protection against oxidative damage and cell death. Evidence suggesting that RES’s chemical antioxidant potential is not sufficient explanation for its effects is discussed. Putative biological activities, including interactions with estrogen receptors and sirtuins are critically discussed. We provide a synthesis of how RES’s phytoestrogenic properties might mediate the neuronal stress resistance underlying its observed neuroprotective properties.

Simultaneous analysis of expression of multiple redox-sensitive and apoptotic genes in hypothalamic neurons exposed to cholesterol secoaldehyde

Oxidative stress and apoptotic cell death are two important processes that occur under several disease states and in conditions of toxicant insult. Traditionally, investigators have chosen a variety of analytical methods to detect and/or quantify oxidative stress and apoptosis. The approach has proven less satisfying, however, when applied to complex systems with many unknown influences. Such areas of study could benefit from the development and application of new and more powerful analytical tools. Microarray-based approach has been developed for analyzing various cellular phenomena at the level of gene expression. These gene arrays are hybridization chips that are capable of simultaneous analysis of the expression of thousands of genes. Often, this approach warrants examining a multitude of unrelated genes which can greatly impede the interpretation of results. The real-time RT-PCR-based methodology presented here allows simultaneous detection and analysis of as many as 84 well-characterized genes associated with either oxidative stress or apoptosis in hypothalamic neuronal cells exposed to cholesterol secoaldehyde, an "ozone-/singlet oxygen-specific" oxidation product of cholesterol that has been shown to be present at the inflammatory sites including the arterial plaque and the brain specimens of patients with Alzheimer's disease. This pathway-specific analysis of the expression of the well-defined chosen set of genes offers ways of convenient and reliable interpretation of results that often corroborate well with the results obtained from other standard biochemical analytical approaches.

Ethyl pyruvate protects against hypoxic-ischemic brain injury via anti-cell death and anti-inflammatory mechanisms

Ethyl pyruvate (EP) is protective in experimental models of many illnesses. This study investigates whether EP can protect against neonatal hypoxic-ischemic (H-I) brain injury. Pre-treatment with EP significantly reduced brain damage at 7 days post-H-I, with 50 mg/kg EP achieving over 50% recovery in tissue loss compared to vehicle-treated animals. Delayed treatment with EP until 30 min after H-I was still neuroprotective. EP-afforded brain protection, together with neurological function improvement, was observed up to 2 months after H-I. We further demonstrated an inhibitory effect of EP on cell death, both in an in vivo model of H-I and in in vitro neuronal cultures subjected to OGD, by reducing calpain activation and calcium dysregulation. Moreover, EP exerted an anti-inflammatory effect in microglia by inhibiting NF-kappaB activation and subsequent release of inflammatory mediators. Taken together, our results suggest that EP confers potent neuroprotection against neonatal H-I brain injury via its anti-cell death and anti-inflammatory actions. EP is a potential novel therapeutic agent for neonatal H-I brain injury.

Oxygen glucose deprivation model of cerebral stroke in PC-12 cells: glucose as a limiting factor

Optimum time points for oxygen-glucose deprivation (OGD) and re-oxygenation have been identified to suggest the suitability of PC-12 cells as rapid and sensitive in vitro model of cerebral stroke. Further, the precise role of glucose as one of the limiting factors was ascertained. PC-12 cells were subjected to receive OGD of 1-8 h followed by re-oxygenation for 6 to 96 h in medium having glucose 0-10 mg/ml. Loss of cell viability was assessed using trypan blue dye exclusion and MTT assays. The significant (p < 0.05) reduction in percent viable cell count was started at 2 h of OGD (80.7 +/- 2.0) and continued in further OGD periods (3, 4, 5, 6, 7, and 8 h), i.e. 65.7 +/- 3.5, 59.7 +/- 4.6, 54.3 +/- 3.2, 44.7 +/- 2.9, 20.3 +/- 4.3, 5.7 +/- 2.0 of counted cells, respectively. Cells growing in glucose-free medium have shown a gradual (p < 0.001) decrease in cell viability throughout the re-oxygenation. Re-oxygenation of 24 h was found to be first statistically significant time point for all the glucose concentrations. Glucose concentration during re-oxygenation was found to be one of the key factors involved in the growth and proliferation in PC-12 cells. The OGD of 6 h followed by a re-oxygenation period of 24 h with 4-6 mg/ml glucose concentration could be recorded as optimum conditions under our experimental conditions.

Hypoxic-ischemic encephalopathy in the term infant

Hypoxia-ischemia in the perinatal period is an important cause of cerebral palsy and associated disabilities in children. There has been significant research progress in hypoxic-ischemic encephalopathy over the last 2 decades, and many new molecular mechanisms have been identified. Despite all these advances, therapeutic interventions are still limited. In this article the authors discuss several molecular pathways involved in hypoxia-ischemia, and potential therapeutic targets.

Evaluation of Salicornia herbacea as a potential antioxidant and anti-inflammatory agent

In this study, the antioxidant and anti-inflammatory activities of Salicornia herbacea were evaluated. The crude CH(2)Cl(2)/methanol extract of S. herbacea showed 52% and 86% scavenging activities of the authentic ONOO(-) and ONOO(-) from 3-morpholinosydnomimine (SIN-1) at a concentration of 50 microg/mL, respectively, and was subjected to a further fractionation with n-hexane, 85% aqueous methanol, n-butanol, and water. Additional purification of the n-butanol fraction revealed that the most potent scavenging activity led to the isolation of isorhamnetin 3-O-beta-d-glucopyranoside as the active principle. The structure of isorhamnetin 3-O-beta-d-glucopyranoside was elucidated by extensive two-dimensional nuclear magnetic resonance experiments such as (1)H correlation spectroscopy nuclear Overhauser effect spectroscopy, heteronuclear single quantum correlation, and heteronuclear multiple-bond correlation as well as by comparison with the published spectral data. Isorhamnetin 3-O-beta-d-glucopyranoside exhibited dose-dependent scavenging activities of the authentic ONOO(-) and ONOO(-) from SIN-1. The electron spin resonance spin-trap techniques confirmed that reactive oxygen species, including the hydroxyl, superoxide, carbon-centered, and 1,1-diphenyl-2-picrylhydrazyl radicals, were actively quenched by addition of isorhamnetin 3-O-beta-d-glucopyranoside. In addition, isorhamnetin 3-O-beta-d-glucopyranoside suppressed the lipopolysaccharide-induced nitric oxide production and the expression of cytokines such as inducible nitric oxide synthase, tumor necrosis factor-alpha, and interleukin-1beta in Raw 264.7 cells. Findings from this study should underscore the nutraceutical value of S. herbacea-derived isorhamnetin 3-O-beta-d-glucopyranoside as a potent antioxidative and anti-inflammatory agent via alleviation of radical-induced toxicities and pro-inflammatory responses.

FORT and FORD: two simple and rapid assays in the evaluation of oxidative stress in patients with type 2 diabetes mellitus

The aim of the study was to evaluate the levels of free oxygen radicals and free oxygen radicals defense in patients with newly diagnosed type 2 diabetes mellitus (T2DM). The disease seems to be involved strongly in the production of reactive oxygen species. Forty-five patients with newly diagnosed T2DM and 20 apparently healthy individuals (control group) were included in the study. Reactive oxygen species were determined using the free oxygen radicals (FORT) test, which is based on the Fenton reaction. In this method, the hydroperoxides reacted with the transition metal ions liberated from the proteins and were converted to alkoxy and peroxy radicals. The radical species produced by the reaction, which are directly proportional to the quantity of lipid peroxides, interact with an additive that forms a radical molecule. Similarly, the free oxygen radicals defense (FORD) test uses preformed stable and colored radicals and determines the decrease in absorbance that is proportional to the blood antioxidant concentration. We found that (a) FORT levels were increased in diabetic patients (2.86 +/- 0.56 mmol/L H(2)O(2)) compared with controls (1.87 +/- 0.26 mmol/L H(2)O(2)) (P < .0001) and (b) FORD levels were lower in diabetic patients (1.23 +/- 0.18 mmol/L Trolox) compared with controls (1.34 +/- 0.14 mmol/L Trolox) (P < .01). The intraassay and interassay coefficients of variation were 3.7% and 6.2%, respectively, for FORT and 4.2% and 6.6%, respectively, for FORD. Determination of free oxygen radicals and free oxygen radicals defense seems to play an important role in the generation and evaluation of oxidative stress, an imbalance between oxidants and antioxidants that can lead to oxidative damage and is involved in the pathogenesis of several diseases, such as T2DM.

Endoplasmic reticulum stress, inflammation, and perinatal brain damage

Inflammation seems to play a role in the pathogenesis of perinatal brain damage in fetuses/infants born much before term. We raise the possibility that noninflammatory phenomena induce endoplasmic reticulum stress, which, in turn, leads to the unfolded protein response, which is followed by apoptosis-promoting processes and inflammation. Perhaps by these events, noninflammatory stimuli lead to perinatal brain damage.

Nutritional and exercise-based interventions in the treatment of amyotrophic lateral sclerosis

BACKGROUND & AIMS

Disease pathogenesis in amyotrophic lateral sclerosis (ALS) involves a number of interconnected mechanisms all resulting in the rapid deterioration of motor neurons. The main mechanisms include enhanced free radical production, protein misfolding, aberrant protein aggregation, excitotoxicity, mitochondrial dysfunction, neuroinflammation and apoptosis. The aim of this review is to assess the efficacy of using nutrition- and exercise-related interventions to improve disease outcomes in ALS.

METHODS

Studies involving nutrition or exercise in human and animal models of ALS were reviewed.

RESULTS

Treatments conducted in animal models of ALS have not consistently translated into beneficial results in clinical trials due to poor design, lack of power and short study duration, as well as differences in the genetic backgrounds, treatment dosages and disease pathology between animals and humans. However, vitamin E, folic acid, alpha lipoic acid, lyophilized red wine, coenzyme Q10, epigallocatechin gallate, Ginkgo biloba, melatonin, Cu chelators, and regular low and moderate intensity exercise, as well as treatments with catalase and l-carnitine, hold promise to mitigating the effects of ALS, whereas caloric restriction, malnutrition and high-intensity exercise are contraindicated in this disease model.

CONCLUSIONS

Improved nutritional status is of utmost importance in mitigating the detrimental effects of ALS.

Changes in the expression of insulin-like growth factor 1 variants in the postnatal brain development and in neonatal hypoxia-ischaemia

Insulin-like growth factor-1 (IGF-1) is a multifunctional peptide of which numerous isoforms exist. The predominant form, IGF-1Ea is involved in physiological processes while IGF-1Ec (mechano-growth factor, MGF) is expressed in response to a different set of stimuli. We have identified specific changes in the expression patterns of these IGF-1 variants in brain development in normal rats and following neonatal hypoxia-ischaemia (HI). Both IGF-1Ea and IGF-1Ec are expressed during normal postnatal brain development, albeit with highly specific temporal distributions. In contrast, HI produced increased and prolonged expression of the IGF-1Ec isoform only. Importantly, hypoxia alone stimulated the expression of IGF-1Ec as well. Thus, IGF-1Ec may play a role in HI pathology. Neonatal hypoxia-ischaemia occurs in approximately 1:4000-1:10,000 newborns and causes neurological deficits in approximately 75% of those affected. Unfortunately, no specific treatment is available. IGF-1 is known to have neuroprotective activity and its IGF-1Ec variant appears to be an endogenous protective factor in hypoxia-ischaemia. Therefore, IGF-1Ec could potentially be developed into a therapeutic modality for the attenuation or prevention of neuronal damage in this and related disorders.

Lipopolysaccharide preconditioning reduces neuroinflammation against hypoxic ischemia and provides long-term outcome of neuroprotection in neonatal rat

Hypoxic ischemia (HI) in newborns causes long-term neurologic abnormalities. Systemic lipopolysaccharide (LPS) is neuroprotective in neonatal rats when injected 24 h before HI. However, the effect on HI-induced neuroinflammation and the long-term outcome of LPS preconditioning in neonatal rats have not been examined. In a rat-pup HI model, compared with normal saline (NS), 0.3 mg/kg of LPS injected 24 h before HI greatly increased microglial cell and macrophage activation and up-regulated TNF-alpha and inducible NOS expression 12-h postinjection and resulted in high mortality during HI. In contrast, 0.05 mg/kg of LPS elicited very little microglia and macrophage activation and TNF-alpha and inducible NOS expression and resulted in low mortality. Given 24 h before HI, low-dose (0.05 mg/kg) LPS greatly reduced microglia and macrophage activation, TNF-alpha expression, and reactive oxygen species production 24-h post-HI compared with NS-treated rats. Rats in the low-dose LPS group also showed significantly better learning and memory and less brain damage in adulthood. Learning and memory performance among the LPS-HI, LPS, and NS groups was not significantly different. We conclude that low-dose LPS preconditioning in neonatal rats greatly reduces HI-induced neuroinflammation and provides long-term neuroprotection against behavioral and pathologic abnormalities.

Apoptotic mechanisms in the immature brain: involvement of mitochondria

Brain injury after hypoxic-ischemic encephalopathy often develops with delayed appearance, opening a therapeutic window. Clinical studies in newborns show that post-hypoxic-ischemic hypothermia improves outcome. This has generated renewed interest in the molecular mechanisms of hypoxic-ischemic brain injury. In this brief review, we propose that mitochondrial permeabilization is crucial for injury to advance beyond the point of no return. We suggest that excitatory amino acids, nitric oxide, inflammation, trophic factor withdrawal, and an increased pro- versus antiapoptotic Bcl-2 protein ratio will trigger Bax-dependent mitochondrial outer membrane permeabilization. Mitochondrial outer membrane permeabilization, in turn, elicits mitochondrial release of cytochrome C, apoptosis-inducing factor, second mitochondria-derived activator of caspase/Diablo, and HtrA2/Omi. Cytochrome C efflux activates caspase-9/-3, leading to DNA fragmentation. Apoptosis-inducing factor interacts with cyclophilin A and induces chromatinolysis. Blockage of mitochondrial outer membrane permeabilization holds promise as a strategy for perinatal brain protection.

Vitamin K prevents oxidative cell death by inhibiting activation of 12-lipoxygenase in developing oligodendrocytes

Oxidative mechanisms of injury are important in many neurological disorders. Developing oligodendrocytes (pre-OLs) are particularly sensitive to oxidative stress-mediated injury. We previously demonstrated a novel function of phylloquinone (vitamin K(1)) and menaquinone 4 (MK-4; a major form of vitamin K2) in protecting pre-OLs and immature neurons against glutathione depletion-induced oxidative damage (Li et al. [ 2003] J. Neurosci. 23:5816-5826). Here we report that vitamin K at nanomolar concentrations prevents arachidonic acid-induced oxidative injury to pre-OLs through blocking the activation of 12-lipoxygenase (12-LOX). Arachidonic acid metabolism is a potential source for reactive oxygen species (ROS) generation during ischemia and reperfusion. Exposure of pre-OLs to arachidonic acid resulted in oxidative cell death in a concentration-dependent manner. Administration of vitamin K (K(1) and MK-4) completely prevented the toxicity. Consistent with our previous findings, inhibitors of 12-LOX abolished ROS production and cell death, indicating that activation of 12-LOX is a key event in arachidonic acid-induced pre-OL death. Vitamin K(1) and MK-4 significantly blocked 12-LOX activation and prevented ROS accumulation in pre-OLs challenged with arachidonic acid. However, vitamin K itself did not directly inhibit 12-LOX enzymatic activity when assayed with purified 12-LOX in vitro. These results suggest that vitamin K, or likely its metabolites, acts upstream of activation of 12-LOX in pre-OLs. In summary, our data indicate that vitamin K prevents oxidative cell death by blocking activation of 12-LOX and ROS generation.

Mitochondrial mechanisms of cell death and neuroprotection in pediatric ischemic and traumatic brain injury

There are several forms of acute pediatric brain injury, including neonatal asphyxia, pediatric cardiac arrest with global ischemia, and head trauma, that result in devastating, lifelong neurologic impairment. The only clinical intervention that appears neuroprotective is hypothermia initiated soon after the initial injury. Evidence indicates that oxidative stress, mitochondrial dysfunction, and impaired cerebral energy metabolism contribute to the brain cell death that is responsible for much of the poor neurologic outcome from these events. Recent results obtained from both in vitro and animal models of neuronal death in the immature brain point toward several molecular mechanisms that are either induced or promoted by oxidative modification of macromolecules, including consumption of cytosolic and mitochondrial NAD(+) by poly-ADP ribose polymerase, opening of the mitochondrial inner membrane permeability transition pore, and inactivation of key, rate-limiting metabolic enzymes, e.g., the pyruvate dehydrogenase complex. In addition, the relative abundance of pro-apoptotic proteins in immature brains and neurons, and particularly within their mitochondria, predisposes these cells to the intrinsic, mitochondrial pathway of apoptosis, mediated by Bax- or Bak-triggered release of proteins into the cytosol through the mitochondrial outer membrane. Based on these pathways of cell dysfunction and death, several approaches toward neuroprotection are being investigated that show promise toward clinical translation. These strategies include minimizing oxidative stress by avoiding unnecessary hyperoxia, promoting aerobic energy metabolism by repletion of NAD(+) and by providing alternative oxidative fuels, e.g., ketone bodies, directly interfering with apoptotic pathways at the mitochondrial level, and pharmacologic induction of antioxidant and anti-inflammatory gene expression.

Post-ischemic hypothermia for 24h in P7 rats rescues hippocampal neuron: association with decreased astrocyte activation and inflammatory cytokine expression

Hypothermia is an effective method for reducing the neuronal damage induced by hypoxia-ischemia (HI) but the underlying mechanism remains unclear. To investigate the effects of post-HI hypothermia on the developing brain, 7-day-old rats were subjected to left carotid artery ligation followed by 8% oxygen for 2h. They were divided into a hypothermia group (rectal temperature 32-33 degrees C for 24h) and a normothermia group (36-37 degrees C for 24h) immediately after hypoxia-ischemia. Animals were sacrificed at 12, 24 and 72 h for gene analysis and 0, 1, 3 and 7 days for protein analysis after HI. There was a significant decrease in infarct volume in the hypothermia group at 7 days after HI compared with that in the normothermia group. The hypothermia group had more neuronal nuclei (NeuN) positive neurons and lower levels of glial fibrillary acidic protein (GFAP) mRNA and immunoreactivity in the hippocampus CA1 region than the normothermia group. Real-time PCR showed no significant difference in glial cell line-derived neurotrophic factor (GDNF) mRNA expression in the hippocampus in the two groups at various time points after HI. However, GDNF protein level was significantly increased in the hypothermia group. On the other hand, mRNA and protein levels of the inflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6) were dramatically decreased in the hypothermia compared with the normothermia group. The present findings highlight an apparent association between inhibition of hippocampal neuron loss by hypothermia and decreased astrocytosis and inflammatory cytokine release after hypoxia-ischemia in the developing brain.

CREB activation in the rapid, intermediate, and delayed ischemic preconditioning against hypoxic-ischemia in neonatal rat

Ischemic preconditioning (IP) is a defense program in which exposure to sublethal ischemia followed by a period of reperfusion results in subsequent resistance to severe ischemic insults. Very few in vivo IP models have been established for neonatal brain. We examined whether rapid, intermediate, and delayed IP against hypoxic-ischemia (HI) could be induced in neonatal brain, and if so, whether the IP involved phosphorylation of cAMP response element-binding protein (pCREB) after HI. Postnatal day 7 rat pups were subjected to HI at 2 h (2-h IP), 6 h (6-h IP), or 22 h (22-h IP) after IP. We found all three IP groups had significantly reduced neuronal damage and TUNEL-(+) cells 24 h post-HI than no-IP group. Compared with control, the no-IP group had significant decreases of pCREB and mitochondria Bcl-2 levels in the ipsilateral cortex 24 h post-HI. In contrast, the three IP groups had increased pCREB and mitochondria Bcl-2 levels, and significant differences were found between three IP and no-IP groups. The increases of cleavage of caspase-3 and poly (ADP-ribose) polymerase and of cells with nuclear apoptosis inducing factor post-HI in no-IP group were all significantly reduced in three IP groups. The increases of caspase-3 and calpain-mediated proteolysis of a-spectrin post-HI were significantly reduced only in 22-h IP group. Furthermore, all three IP groups had long-term neuroprotection at behavioral and pathological levels compared with no-IP group. In conclusion, IP, rapid, intermediate, or delayed, in neonatal rat brain activates CREB, up-regulates Bcl-2, induces extensive brakes on caspase-dependent and -independent apoptosis after HI, and provides long-term neuroprotection.

Room air or 100% oxygen for resuscitation of infants with perinatal depression

PURPOSE OF REVIEW

The International Liaison Committee on Resuscitation (ILCOR) recommends initiating neonatal resuscitation with concentrations of oxygen between 21 and 100%. This wide range of oxygen concentrations recommended for resuscitation highlights the lack of evidence supporting either 21 or 100% O2. The purpose of this review is to analyze the efficacy of reoxygenation with 100% O2 or room air on rates of return of spontaneous circulation--the main goal of cardiopulmonary resuscitation.

RECENT FINDINGS

Clinical studies suggest that reoxygenation initiated with room air is effective in depressed neonates born with a preserved circulation. Reoxygenation with room air in these infants is associated with lower levels of circulating markers of oxidative stress than reoxygenation with 100% oxygen. However, there is no evidence that resuscitation with room air is as effective as that with 100% oxygen in restoration of an arrested circulation. In fact, animal studies indicate that, in comparison with 100% oxygen, reoxygenation with room air results in more sluggish restoration of depressed cerebral and systemic circulations.

SUMMARY

Prior to a revision of current neonatal resuscitation guidelines it must be determined whether resuscitation initiated with room air results in the same rate of return of spontaneous circulation as resuscitation initiated with 100% oxygen.

Oxygen in health and disease: regulation of oxygen homeostasis--clinical implications

Oxygen is critical for multicellular existence. Its reduction to water by the mitochondrial electron transport chain helps supply the metabolic demands of human life. The incompletely reduced, reactive oxygen byproducts of this reaction, however, can be quite toxic. In this review, we explore the mechanisms responsible for maintaining oxygen homeostasis and the consequences of their dysfunction. With an eye toward defining clinical care guidelines for the management of critically ill neonates, we present evidence describing the role of physiologic hypoxia during development and the adverse consequences of hyperoxia in-term as well as preterm infants.

Postischemic oxidative stress promotes mitochondrial metabolic failure in neurons and astrocytes

Oxidative stress and mitochondrial dysfunction have been closely associated in many subcellular, cellular, animal, and human studies of both acute brain injury and neurodegenerative diseases. Our animal models of brain injury caused by cardiac arrest illustrate this relationship and demonstrate that both oxidative molecular modifications and mitochondrial metabolic impairment are exacerbated by reoxygenation of the brain using 100% ventilatory O(2) compared to lower levels that maintain normoxemia. Numerous molecular mechanisms may be responsible for mitochondrial dysfunction caused by oxidative stress, including oxidation and inactivation of mitochondrial proteins, promotion of the mitochondrial membrane permeability transition, and consumption of metabolic cofactors and intermediates, for example, NAD(H). Moreover, the relative contribution of these mechanisms to cell injury and death is likely different among different types of brain cells, for example, neurons and astrocytes. In order to better understand these oxidative stress mechanisms and their relevance to neurologic disorders, we have undertaken studies with primary cultures of astrocytes and neurons exposed to O(2) and glucose deprivation and reoxygenation and compared the results of these studies to those using a rat model of neonatal asphyxic brain injury. These results support the hypothesis that release and or consumption of mitochondrial NAD(H) is at least partially responsible for respiratory inhibition, particularly in neurons.

Combination of deferoxamine and erythropoietin: therapy for hypoxia-ischemia-induced brain injury in the neonatal rat?

Deferoxamine (DFO) and erythropoietin (EPO) have each been shown to provide neuroprotection in neonatal rodent models of brain injury. In view of the described anti-oxidative actions of DFO and the anti-apoptotic and anti-inflammatory effects of EPO, we hypothesized that the combination of DFO and EPO would increase neuroprotection after neonatal hypoxic-ischemic brain injury as compared to single DFO or EPO treatment. At postnatal day 7 rats underwent right common carotid artery occlusion followed by a 90-min exposure to 8% oxygen. Rats were treated intraperitoneally with DFO (200mg/kg), recombinant human EPO (1 kU/kg), a combination of DFO-EPO or vehicle at 0, 24 and 48 h after hypoxia-ischemia (HI) and were sacrificed at 72 h. DFO-EPO administration reduced the number of cleaved caspase 3-positive cells in the ipsilateral cerebral cortex. Early neuronal damage was assessed by staining for microtubuli-associated protein (MAP)-2. In our model 63+/-9% loss of ipsilateral MAP-2 was observed after HI, indicating extensive brain injury. DFO, EPO or DFO-EPO treatment did not improve neuronal integrity as defined by MAP-2. Cerebral white matter tracts were stained for myelin basic protein (MBP), a constituent of myelin. Hypoxia-ischemia strongly reduced MBP staining which suggests white matter damage. However, DFO, EPO and DFO-EPO treatment had no effect on the loss of MBP staining. Finally, HI-induced loss of striatal tyrosine hydroxylase staining was not attenuated by DFO, EPO or DFO-EPO. Although DFO-EPO treatment reduced the number of cleaved caspase 3(+) cells, treatment with DFO, EPO, or with the combination of DFO and EPO did not protect against gray or white matter damage in the experimental setting applied.

Intrauterine resuscitation during labor: should maternal oxygen administration be a first-line measure?

Intrauterine resuscitation techniques are often used during labor when the fetal heart rate pattern is nonreassuring. These techniques have not been well studied; common practices are based on classic studies many years old. Models of intrauterine resuscitation using one (or more) technique as a first-line intervention and adding others in a specific series or clinical algorithm based on fetal response have not been tested. Maternal oxygen therapy is often used; however, recent evidence suggests potential risks to the mother and fetus or newborn. Even small increases in maternal and fetal pO(2) as a result of maternal oxygen administration can produce oxygen free radical activity in mothers and fetuses. The potential long-term effects are unknown. Caution should be exercised when considering maternal oxygen administration as a first-line intrauterine resuscitation measure until more data are available, reserving its use after other measures have been unsuccessful in resolving the nonreassuring fetal heart rate pattern.

Ischemia enhances activation by Ca2+ and redox modification of ryanodine receptor channels from rat brain cortex

Cerebral ischemia stimulates Ca2+ influx and thus increases neuronal intracellular free [Ca2+]. Using a rat model of cerebral ischemia without recirculation, we tested whether ischemia enhances the activation by Ca2+ of ryanodine receptor (RyR) channels, a requisite feature of RyR-mediated Ca2+-induced Ca2+ release (CICR). To this aim, we evaluated how single RyR channels from endoplasmic reticulum vesicles, fused into planar lipid bilayers, responded to cytoplasmic [Ca2+] changes. Endoplasmic reticulum vesicles were isolated from the cortex of rat brains incubated without blood flow for 5 min at 37 degrees C (ischemic) or at 4 degrees C (control). Ischemic brains displayed increased oxidative intracellular conditions, as evidenced by a lower ratio (approximately 130:1) of reduced/oxidized glutathione than controls (approximately 200:1). Single RyR channels from ischemic or control brains displayed the same three responses to Ca2+ reported previously, characterized by low, moderate, or high maximal activity. Relative to controls, RyR channels from ischemic brains displayed with increased frequency the high activity response and with lower frequency the low activity response. Both control and ischemic cortical vesicles contained the RyR2 and RyR3 isoforms in a 3:1 proportion, with undetectable amounts of RyR1. Ischemia reduced [3H]ryanodine binding and total RyR protein content by 35%, and increased at least twofold endogenous RyR2 S-nitrosylation and S-glutathionylation without affecting the corresponding RyR3 endogenous levels. In vitro RyR S-glutathionylation but not S-nitrosylation favored the emergence of high activity channels. We propose that ischemia, by enhancing RyR2 S-glutathionylation, allows RyR2 to sustain CICR; the resulting amplification of Ca2+ entry signals may contribute to cortical neuronal death.

Rapidly increased neuronal mitochondrial biogenesis after hypoxic-ischemic brain injury

BACKGROUND AND PURPOSE

Mitochondrial biogenesis is regulated through the coordinated actions of both nuclear and mitochondrial genomes to ensure that the organelles are replenished on a regular basis. This highly regulated process has been well defined in skeletal and heart muscle, but its role in neuronal cells, particularly when under stress or injury, is not well understood. In this study, we report for the first time rapidly increased mitochondrial biogenesis in a rat model of neonatal hypoxic/ischemic brain injury (H-I).

METHODS

Postnatal day 7 rats were subjected to H-I induced by unilateral carotid artery ligation followed by 2.5 hours of hypoxia. The relative amount of brain mitochondrial DNA (mtDNA) was measured semiquantitatively using long fragment PCR at various time points after H-I. HSP60 and COXIV proteins were detected by Western blot. Expression of three genes critical for the transcriptional regulation of mitochondrial biogenesis, peroxisome proliferator-activated receptor coactivator-1 (PGC-1), nuclear respiratory factor-1 (NRF-1), and mitochondrial transcription factor A (TFAM), were examined by Western blot and RT-PCR.

RESULTS

Brain mtDNA content was markedly increased 6 hours after H-I, and continued to increase up to 24 hours after H-I. Paralleling the temporal change in mtDNA content, mitochondrial number and proteins HSP60 and COXIV, and citrate synthase activity were increased in neurons in the cortical infarct border zone after H-I. Moreover, cortical expression of NRF-1 and TFAM were increased 6 to 24 hours after H-I, whereas PGC-1 was not changed.

CONCLUSIONS

Neonatal H-I brain injury rapidly induces mitochondrial biogenesis, which may constitute a novel component of the endogenous repair mechanisms of the brain.