Neurobiology of hypoxic-ischemic injury in the developing brain

Neural stem cell therapies and hypoxic-ischemic brain injury

Hypoxic-ischemic brain injury is a significant cause of morbidity and mortality in the adult as well as in the neonate. Extensive pre-clinical studies have shown promising therapeutic effects of neural stem cell-based treatments for hypoxic-ischemic brain injury. There are two major strategies of neural stem cell-based therapies: transplanting exogenous neural stem cells and boosting self-repair of endogenous neural stem cells. Neural stem cell transplantation has been proved to improve functional recovery after brain injury through multiple by-stander mechanisms (e.g., neuroprotection, immunomodulation), rather than simple cell-replacement. Endogenous neural stem cells reside in certain neurogenic niches of the brain and response to brain injury. Many molecules (e.g., neurotrophic factors) can stimulate or enhance proliferation and differentiation of endogenous neural stem cells after injury. In this review, we first present an overview of neural stem cells during normal brain development and the effect of hypoxic-ischemic injury on the activation and function of endogenous neural stem cells in the brain. We then summarize and discuss the current knowledge of strategies and mechanisms for neural stem cell-based therapies on brain hypoxic-ischemic injury, including neonatal hypoxic-ischemic brain injury and adult ischemic stroke.

Methylcyclopentadienyl manganese tricarbonyl increases cell vulnerability to oxidative stress on rat thymocytes

Methylcyclopentadienyl manganese tricarbonyl (MMT) is used as a gasoline antiknock additive. However, the toxic effect of MMT is currently not well understood. In this study, we investigated the toxic effect of MMT on rat thymocytes using a flow cytometer and fluorescent probes. MMT at 100-300 µM significantly increased the population of cells exhibiting propidium fluorescence, i.e., the population of dead cells. The intensity of BES-So-AM fluorescence significantly increased when using 100 µM MMT. In addition, the intensity of oxonol fluorescence in rat thymocytes increased with the treatment with MMT in a concentration-dependent manner (10-100 µM). The toxic effect of MMT was inhibited by quercetin, antioxidant flavonoid. Moreover, co-treatment with 30-100 µM MMT and 100 µM H₂O₂ increased the cell lethality further. These results indicate that MMT increases cell vulnerability to oxidative stress on rat thymocytes. This study provides insight into the toxic effect of MMT on the immune system.

Pretreatment with Human Chorionic Gonadotropin Protects the Neonatal Brain against the Effects of Hypoxic-Ischemic Injury

INTRODUCTION

Though the human fetus is exposed to placentally derived human chorionic gonadotropin (hCG) throughout gestation, the role of hCG on the fetal brain is unknown. Review of the available literature appears to indicate that groups of women with higher mean levels of hCG during pregnancy tend to have offspring with lower cerebral palsy (CP) risk. Given that newborn cerebral injury often precedes the development of CP, we aimed to determine whether hCG may protect against the neurodegenerative effects of neonatal brain injury.

METHODS

We utilized the Rice-Vannucci model of neonatal cerebral hypoxia-ischemia (HI) in postnatal day 7 mice to examine whether intraperitoneal administration of hCG 15-18 h prior, 1 h after or immediately following HI decrease brain tissue loss 7 days after injury. We next studied whether hCG has pro-survival and trophic properties in neurons by exposing immature cortical and hippocampal neurons to hCG in vitro and examining neurite sprouting and neuronal survival prior and after glutamate receptor-mediated excitotoxic injury.

RESULTS

We found that intraperitoneal injection of hCG 15 h prior to HI, but not at or 1 h after HI induction, resulted in a significant decrease in hippocampal and striatal tissue loss 7 days following brain injury. Furthermore, hCG reduced N-methyl-d-aspartate (NMDA)-mediated neuronal excitotoxicity in vitro when neurons were continuously exposed to this hormone for 10 days or when given at the time and following neuronal injury. In addition, continuous in vitro administration of hCG for 6-9 days increased neurite sprouting and basal neuronal survival as assessed by at least a 1-fold increase in MAP2 immunoreactivity and a 2.5-fold increase in NeuN + immunoreactivity.

CONCLUSION

Our findings suggest that hCG can decrease HI-associated immature neural degeneration. The mechanism of action for this neuroprotective effect may partly involve inhibition of NMDA-dependent excitotoxic injury. This study supports the hypothesis that hCG during pregnancy has the potential for protecting the developing brain against HI, an important CP risk factor.

Neuroprotective effects of orientin on oxygen-glucose deprivation/reperfusion-induced cell injury in primary culture of rat cortical neurons

Orientin (luteolin-8-C-glucoside) is a phenolic compound found abundantly in millet, juice, and peel of passion fruit and has been shown to have antioxidant properties. In the present study, we explored the effects of orientin on oxygen-glucose deprivation/reperfusion (OGD/RP)-induced cell injury in primary culture of rat cortical neurons using an in vitro model of neonatal ischemic brain injury. The reduced cell viability and elevated lactate dehydrogenase leakage were observed after OGD/RP exposure, which were then reversed by orientin (10, 20, and 30 µM) pretreatment in a dose-dependent manner. Additionally, OGD/RP treatment resulted in significant oxidative stress, accompanied by enhanced intracellular reactive oxygen species (ROS) generation, and obvious depletion in the activities of intracellular Mn-superoxide dismutase, catalase, and glutathione peroxidase antioxidases. However, these effects were dose dependently restored by orientin pretreatment. We also found that orientin pretreatment dose dependently suppressed [Ca²⁺]_i increase and mitochondrial membrane potential dissipation caused by OGD/RP in primary culture of rat cortical neurons. Western blot analysis showed that OGD/RP exposure induced a distinct decrease of Bcl-2 protein and a marked elevation of Bax, caspase-3, and cleaved caspase-3 proteins; whereas these effects were dose dependently reversed by orientin incubation. Both the caspase-3 activity and the apoptosis rate were increased under OGD/RP treatment, but was then dose dependently down-regulated by orientin (10, 20, and 30 µM) incubation. Moreover, orientin pretreatment dose dependently inhibited OGD/RP-induced phosphorylation of JNK and ERK1/2. Notably, JNK inhibitor SP600125 and ERK1/2 inhibitor PD98059 also dramatically attenuated OGD/RP-induced cell viability loss and ROS generation, and further, orientin failed to protect cortical neurons with the interference of JNK activator anisomycin or ERK1/2 activator FGF-2. Taken together, these results demonstrated that orientin has significant neuroprotective effects against OGD/RP-induced cell injury via JNK and ERK1/2 signaling pathways in primary culture of rat cortical neurons. Impact statement Orientin has been used in traditional eastern medicine and reported to possess antioxidant properties. However, the effects of orientin on neonatal ischemic brain injury and the underlying mechanisms involved have not been studied. Our results showed that orientin exerts significant neuroprotective effects on cell injury caused by oxygen-glucose deprivation/reperfusion via the JNK and ERK1/2 signaling pathways in primary culture of rat cortical neurons, implying the potential therapeutic application of orientin via the suppression of oxidative stress and cell apoptosis. This research suggested that orientin may be used as a therapeutic and preventive option for newborn cerebral ischemia/reperfusion injury.

Blood Glutamate Reducing Effect of Hemofiltration in Critically Ill Patients

Glutamate toxicity plays a well-established role in secondary brain damage following acute and chronic brain insults. Previous studies have demonstrated the efficacy of hemodialysis and peritoneal dialysis in reducing blood glutamate levels. However, these methods are not viable options for hemodynamically unstable patients. Given more favorable hemodynamics, longer treatment, and less needed anticoagulation, we investigated whether hemofiltration could be effective in lowering blood glutamate levels. Blood samples were taken from 10 critically ill patients immediately before initiation of hemofiltration and after 1, 2, 4, 6, and 12 h, for a total of 6 blood samples. Samples were sent for determination of glutamate, glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), hemoglobin, hematocrit, urea, creatinine, glucose, sodium, potassium, platelet, and white blood cell (WBC) levels. There was a statistically significant reduction in blood glutamate levels at all time points compared to baseline levels. There was no difference in levels of GOT or GPT. Hemofiltration can be a promising method of reducing blood glutamate levels, especially in critically ill patients where hemodialysis and peritoneal dialysis may be contraindicated.

A comparison of blood and cerebrospinal fluid cytokines (IL-1β, IL-6, IL-18, TNF-α) in neonates with perinatal hypoxia

Perinatal hypoxia-ischemia is a specific and important pathological event in neonatal care practice. The data on relationship between the concentrations of cytokines in blood and cerebrospinal fluid (CSF) and perinatal brain injury are scarce. The aim of this study is to evaluate changes in interleukin (IL-1β, IL-6, and IL-18) and tumor necrosis factor alpha (TNF-α) levels in newborns with perinatal hypoxia (PNH). CSF and serum samples of 35 term and near-term (35-40 weeks) newborns with PNH, at the age of 3-96 hours, were analyzed using enzyme-linked immunosorbent assay. Control group consisted of 25 non-asphyxic/non-hypoxic infants of the same age sampled for clinically suspected perinatal meningitis, but proven negative and healthy otherwise. The cytokine values in CSF and serum samples were determined in relation to initial hypoxic-ischemic encephalopathy (HIE) staged according the Sarnat/Sarnat method, and compared with neurological outcome at 12 months of age estimated using Amiel-Tison procedure. The concentrations of IL-6 and TNF-α in serum of PNH patients were significantly higher compared to control group (p = 0.0407 and p = 0.023, respectively). No significant difference between average values of cytokines in relation to the stage of HIE was observed. Significantly higher levels of IL-6 and IL-18 corresponded to a mildly abnormal neurological outcome, while higher levels of IL-6 and TNF-α corresponded to a severely abnormal neurological outcome, at 12 months of age. Elevated serum levels of IL-6 and TNF-α better corresponded with hypoxia/ischemia compared to CSF values, within 96 hours of birth. Also, higher serum levels of IL-6, TNF-α, and IL-18 corresponded better with abnormal neurological outcome at 12 months of age, compared to CSF values.

A Controversial Medicolegal Issue: Timing the Onset of Perinatal Hypoxic-Ischemic Brain Injury

Perinatal hypoxic-ischemic brain injury, as a result of chronic, subacute, and acute insults, represents the pathological consequence of fetal distress and birth or perinatal asphyxia, that is, “nonreassuring fetal status.” Hypoxic-ischemic injury (HII) is typically characterized by an early phase of damage, followed by a delayed inflammatory local response, in an apoptosis-necrosis continuum. In the early phase, the cytotoxic edema and eventual acute lysis take place; with reperfusion, additional damage should be assigned to excitotoxicity and oxidative stress. Finally, a later phase involves all the inflammatory activity and long-term neural tissue repairing and remodeling. In this model mechanism, loss of mitochondrial function is supposed to be the hallmark of secondary injury progression, and autophagy which is lysosome-mediated play a role in enhancing brain injury. Early-induced molecules driven by hypoxia, as chaperonins HSPs and ORP150, besides common markers for inflammatory responses, have predictive value in timing the onset of neonatal HII; on the other hand, clinical biomarkers for HII diagnosis, as CK-BB, LDH, S-100beta, and NSE, could be useful to predict outcomes.

Neuroprotective Effect of Chitosan Oligosaccharide on Hypoxic-Ischemic Brain Damage in Neonatal Rats

Neonatal hypoxic-ischemic brain damage (HIBD) is one of the leading causes of neonatal mortality and permanent neurological disability worldwide and the effective treatment strategies are not yet available. It has been demonstrated that Chitosan oligosaccharide (COS) exerts protective effect in vitro ischemic brain injury. However, no information is available on possible effects of COS on neonatal HIBD. To investigate the hypothesis of the potential neuroprotective effect of COS on the brain injury due to HIBD, 7-day-old Sprague-Dawley rats were treated with left carotid artery ligation followed by exposure to 8% oxygen (balanced with nitrogen) for 2.5 h at 37 °C. After COS treatment, the cerebral damage was measured by behavior tasks, 2,3,5-triphenyltetrazolium chloride(TTC), Hematoxyline-Eosin(HE), Nissl and Fluoro-Jade B(FJB)staining. In addition, the oxidative stress were assayed with ipsilateral hemisphere homogenates. Immunofluorescence staining were used to examine the activation of the astrocyte and microglia. Expression of inflammatory-related proteins were analyzed by western-blot analysis. In this study we found that administration of COS ameliorated early neurological reflex behavior, significantly reduce brain infarct volume and attenuated neuronal cell injury and degeneration. Furthermore, COS markedly decreased the level of MDA, lactic acid and increased SOD, GSH-Px and T-AOC. COS attenuated hypoxic-ischemic induced up-regulation of expressions of interleukin-1β (IL-1β), tumor necrosis factor alpha (TNF-α), meanwhile it dramatically increased the interleukin-10 (IL-10). These results suggest that COS exerts neuroprotection on hypoxic-ischemic brain damage in neonatal rats, it implies COS might be a potential therapeutic for the treatment of HIBD.

Transient receptor potential melastatin 2 channels (TRPM2) mediate neonatal hypoxic-ischemic brain injury in mice

Transient receptor potential melastatin 2 (TRPM2), a calcium-permeable non-selective cation channel, is reported to mediate brain damage following ischemic insults in adult mice. However, the role of TRPM2 channels in neonatal hypoxic-ischemic brain injury remains unknown. We hypothesize that TRPM2^+/- and TRPM2^-/- neonatal mice have reduced hypoxic-ischemic brain injury. To study the effect of TRPM2 on neonatal brain damage, we used 2,3,5-triphenyltetrazolium chloride (TTC) staining to assess the infarct volume and whole brain imaging to assess morphological changes in the brain. In addition, we also evaluated neurobehavioral outcomes for sensorimotor function 7days following hypoxic-ischemic brain injury. We report that the infarct volumes were significantly smaller and behavioral outcomes were improved in both TRPM2^+/- and TRPM2^-/- mice compared to that of wildtype mice. Next, we found that TRPM2-null mice showed reduced dephosphorylation of GSK-3β following hypoxic ischemic injury unlike sham mice. TRPM2^+/- and TRPM2^-/- mice also had reduced activation of astrocytes and microglia in ipsilateral hemispheres, compared to wildtype mice. These findings suggest that TRPM2 channels play an essential role in mediating hypoxic-ischemic brain injury in neonatal mice. Genetically eliminating TRPM2 channels can provide neuroprotection against hypoxic-ischemic brain injury and this effect is elicited in part through regulation of GSK-3β.

Expression of apoptosis-regulatory genes in the hippocampus of rat neonates born to mothers with diabetes

Diabetes during pregnancy impairs the development of the central nervous system (CNS) and causes cognitive and behavioral abnormalities in offspring. However, the exact mechanism by which the maternal diabetes affects the development of the brain remains to be elucidated. The aim of the present study was to investigate the effects of maternal diabetes in pregnancy on the expression of Bcl-2 and Bax genes and the numerical density of degenerating dark neurons (DNs) in the hippocampus of offspring at the first postnatal two weeks. Wistar female rats were maintained diabetic from a week before pregnancy through parturition and male offspring was sacrificed at P0, P7, and P14. Our findings demonstrated a significant down-regulation in the hippocampal expression of Bcl-2 in the diabetic group newborns (P < 0.05). In contrast, the mRNA expression of Bax was markedly up-regulated in the offspring born to diabetic dams at all of studied time-points (P < 0.05). Moreover, we found a striking increase in the numerical density of DNs in the various subfields of hippocampus of diabetic group pups (P < 0.05). The results of the present study revealed that maternal hyperglycemia during gestational period may result in disturbances in the expression of Bcl-2 and Bax genes as two important genes in neuronal apoptosis regulation and induces the production of DNs in the developing hippocampus of neonatal rats. These disturbances may be a reason for the cognitive, structural, and behavioral anomalies observed in offspring born to diabetic mothers. Furthermore, the control of maternal glycaemia by insulin administration in most cases normalized these negative impacts.

Neuroprotective Role of Exogenous Brain-Derived Neurotrophic Factor in Hypoxia-Hypoglycemia-Induced Hippocampal Neuron Injury via Regulating Trkb/MiR134 Signaling

Hypoxic-ischemic brain injury is an important cause of neonatal mortality and morbidity. Brain-derived neurotrophic factor (BDNF) has been reported to play a neuroprotective role in hypoxic-ischemic brain injury; however, the specific effects and mechanism of BDNF on hypoxic-hypoglycemic hippocampal neuron injury remains unknown. The current study investigated the action of BDNF in regulating cerebral hypoxic-ischemic injury by simulating hippocampal neuron ischemia and hypoxia. We found that BDNF, p-Trkb, and miR-134 expression levels decreased, and that exogenous BDNF increased survival and reduced apoptosis in hypoxic-hypoglycemic hippocampal neurons. The results also show that BDNF inhibits MiR-134 expression by activating the TrkB pathway. Transfection with TrkB siRNA and pre-miR-134 abrogated the neuroprotective role of BDNF in hypoxic-hypoglycemic hippocampal neurons. Our results suggest that exogenous BDNF alleviates hypoxic-ischemic brain injury through the Trkb/MiR-134 pathway. These findings may help to identify a potential therapeutic agent for the treatment of hypoxic-ischemic brain injury.

Short-term outcome of functional integrity of the auditory brainstem in term infants who suffer perinatal asphyxia

OBJECTIVES

To assess short-term outcome of impaired functional integrity of the auditory brainstem in term infants who suffer perinatal asphyxia.

METHODS

Maximum length sequence brainstem auditory evoked response (MLS BAER) was recorded and analyzed at a mean age of 3months in term infants after perinatal asphyxia. The data were compared with age-matched normal term infants.

RESULTS

The infants after asphyxia showed an increase in the latency of MLS BAER wave III at 91, 455 and 910/s, and wave V at all click rates of 91-910/s. The interpeak intervals in the infants after asphyxia were increased at almost all click rates. The IV and I-III intervals were increased at all click rates, and the III-V interval was increased at 455 and 910/s. These increases were generally more significant at higher than at lower click rates. The amplitudes of waves I, III and V in the infants after asphyxia were reduced at all click rates. The V/I amplitude ratio was increased at 91-455/s clicks. The slope of III-V interval-rate function was abnormally increased. 17.1% of the infants after asphyxia had an abnormal increase in IV intervals.

CONCLUSIONS

MLS BAER was moderately abnormal at 3months of age in term infants after perinatal asphyxia, suggesting moderate impairment in the functional integrity of the auditory brainstem. The impairment occurs in 17.1% of the infants. Compared with that found at term, the impairment has improved, but not completely recovered.

Neuroprotection by Estrogen and Progesterone in Traumatic Brain Injury and Spinal Cord Injury

In recent years there has been a growing body of clinical and laboratory evidence demonstrating the neuroprotective effects of estrogen and progesterone after traumatic brain injury (TBI) and spinal cord injury (SCI). In humans, women have been shown to have a lower incidence of morbidity and mortality after TBI compared with age-matched men. Similarly, numerous laboratory studies have demonstrated that estrogen and progesterone administration is associated with a mortality reduction, improvement in neurological outcomes, and a reduction in neuronal apoptosis after TBI and SCI. Here, we review the evidence that supports hormone-related neuroprotection and discuss possible underlying mechanisms. Estrogen and progesterone-mediated neuroprotection are thought to be related to their effects on hormone receptors, signaling systems, direct antioxidant effects, effects on astrocytes and microglia, modulation of the inflammatory response, effects on cerebral blood flow and metabolism, and effects on mediating glutamate excitotoxicity. Future laboratory research is needed to better determine the mechanisms underlying the hormones' neuroprotective effects, which will allow for more clinical studies. Furthermore, large randomized clinical control trials are needed to better assess their role in human neurodegenerative conditions.

Inflammation in epileptogenesis after traumatic brain injury

Background

Epilepsy is a common and debilitating consequence of traumatic brain injury (TBI). Seizures contribute to progressive neurodegeneration and poor functional and psychosocial outcomes for TBI survivors, and epilepsy after TBI is often resistant to existing anti-epileptic drugs. The development of post-traumatic epilepsy (PTE) occurs in a complex neurobiological environment characterized by ongoing TBI-induced secondary injury processes. Neuroinflammation is an important secondary injury process, though how it contributes to epileptogenesis, and the development of chronic, spontaneous seizure activity, remains poorly understood. A mechanistic understanding of how inflammation contributes to the development of epilepsy (epileptogenesis) after TBI is important to facilitate the identification of novel therapeutic strategies to reduce or prevent seizures.

Body

We reviewed previous clinical and pre-clinical data to evaluate the hypothesis that inflammation contributes to seizures and epilepsy after TBI. Increasing evidence indicates that neuroinflammation is a common consequence of epileptic seizure activity, and also contributes to epileptogenesis as well as seizure initiation (ictogenesis) and perpetuation. Three key signaling factors implicated in both seizure activity and TBI-induced secondary pathogenesis are highlighted in this review: high-mobility group box protein-1 interacting with toll-like receptors, interleukin-1β interacting with its receptors, and transforming growth factor-β signaling from extravascular albumin. Lastly, we consider age-dependent differences in seizure susceptibility and neuroinflammation as mechanisms which may contribute to a heightened vulnerability to epileptogenesis in young brain-injured patients.

Conclusion

Several inflammatory mediators exhibit epileptogenic and ictogenic properties, acting on glia and neurons both directly and indirectly influence neuronal excitability. Further research is required to establish causality between inflammatory signaling cascades and the development of epilepsy post-TBI, and to evaluate the therapeutic potential of pharmaceuticals targeting inflammatory pathways to prevent or mitigate the development of PTE.

Neonatal Hypoxic-ischemic Encephalopathy: A Radiological Review

Neonatal hypoxic-ischemic encephalopathy (HIE) is a devastating condition that may result in death or severe neurologic deficits in children. Neuroimaging with cranial ultrasound (US), computed tomography and magnetic resonance imaging are valuable tools in the workup of patients with HIE. The pattern of brain injury depends on the severity and duration of hypoxia and degree of brain maturation. Mild to moderate HI injury results in periventricular leukomalacia and germinal matrix bleed in preterm neonates, and parasagittal watershed infarcts in full-term neonates. Severe HI injury involves deep gray matter in both term and preterm infants. Treatment of HIE is largely supportive. The current article reviews the etiopathophysiology and clinical manifestations of HIE, role of imaging in the evaluation of the condition, patterns of brain injury in term and preterm neonates, the treatment and the prognosis.

Selective cerebral perfusion prevents abnormalities in glutamate cycling and neuronal apoptosis in a model of infant deep hypothermic circulatory arrest and reperfusion

Deep hypothermic circulatory arrest is often required for the repair of complex congenital cardiac defects in infants. However, deep hypothermic circulatory arrest induces neuroapoptosis associated with later development of neurocognitive abnormalities. Selective cerebral perfusion theoretically provides superior neural protection possibly through modifications in cerebral substrate oxidation and closely integrated glutamate cycling. We tested the hypothesis that selective cerebral perfusion modulates glucose utilization, and ameliorates abnormalities in glutamate flux, which occur in association with neuroapoptosis during deep hypothermic circulatory arrest. Eighteen infant male Yorkshire piglets were assigned randomly to two groups of seven (deep hypothermic circulatory arrest or deep hypothermic circulatory arrest with selective cerebral perfusion for 60 minutes at 18℃) and four control pigs without cardiopulmonary bypass support. Carbon-13-labeled glucose as a metabolic tracer was infused, and gas chromatography-mass spectrometry and nuclear magnetic resonance were used for metabolic analysis in the frontal cortex. Following 2.5 h of cerebral reperfusion, we observed similar cerebral adenosine triphosphate levels, absolute levels of lactate and citric acid cycle intermediates, and carbon-13 enrichment among three groups. However, deep hypothermic circulatory arrest induced significant abnormalities in glutamate cycling resulting in reduced glutamate/glutamine and elevated γ-aminobutyric acid/glutamate along with neuroapoptosis, which were all prevented by selective cerebral perfusion. The data suggest that selective cerebral perfusion prevents these modifications in glutamate/glutamine/γ-aminobutyric acid cycling and protects the cerebral cortex from apoptosis.

Mitochondrial DNA Sequence and Lack of Response to Anoxia in the Annual Killifish Austrofundulus limnaeus

The annual killifish Austrofundulus limnaeus inhabits ephemeral ponds in regions of Venezuela, South America. Permanent populations of A. limnaeus are maintained by production of stress-tolerant embryos that are able to persist in the desiccated sediment. Previous work has demonstrated that A. limnaeus have a remarkable ability to tolerate extended periods of anoxia and desiccating conditions. After considering temperature, A. limnaeus embryos have the highest known tolerance to anoxia when compared to any other vertebrate yet studied. Oxygen is completely essential for the process of oxidative phosphorylation by mitochondria, the intracellular organelle responsible for the majority of adenosine triphosphate production. Thus, understanding the unique properties of A. limnaeus mitochondria is of great interest. In this work, we describe the first complete mitochondrial genome (mtgenome) sequence of a single adult A. limnaeus individual and compare both coding and non-coding regions to several other closely related fish mtgenomes. Mitochondrial features were predicted using MitoAnnotator and polyadenylation sites were predicted using RNAseq mapping. To estimate the responsiveness of A. limnaeus mitochondria to anoxia treatment, we measure relative mitochondrial DNA copy number and total citrate synthase activity in both relatively anoxia-tolerant and anoxia-sensitive embryonic stages. Our cross-species comparative approach identifies unique features of ND1, ND5, ND6, and ATPase-6 that may facilitate the unique phenotype of A. limnaeus embryos. Additionally, we do not find evidence for mitochondrial degradation or biogenesis during anoxia/reoxygenation treatment in A. limnaeus embryos, suggesting that anoxia-tolerant mitochondria do not respond to anoxia in a manner similar to anoxia-sensitive mitochondria.

Preliminary case control study to establish the correlation between novel peroxidation biomarkers in cord serum and the severity of hypoxic ischemic encephalopathy

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) has deleterious neurological consequences. To identify patients at risk of neuronal damage deserving implementation of neuroprotective strategies clinicians have relied on prenatal sentinel events, postnatal clinical assessment (Apgar score), and blood gas analysis. This feasibility study aimed to assess if lipid peroxidation byproducts associated with neuronal damage correlated with cord blood metabolic acidemia in patients with HIE.

POPULATION AND METHODS

This is a case/control study in which cases were newborn infants with severe acidemia (pH<7.00; base excess ≥12mmol/L) while control babies exhibited normal gases (pH=7.20-7.40; base excess=-4 to +4mmol/L) in the first cord blood analysis performed immediately after birth. Concomitantly, lipid peroxidation byproducts were determined using ultra performance liquid chromatography coupled to mass spectrometry in the same cord blood sample.

RESULTS

A total of 19 controls and 20 cases were recruited. No differences in gestational characteristics were present. However, cases exhibited profound metabolic alterations as compared to controls (Cases vs.

CONTROL

pH=6.90±0.1 vs. 7.33±0.03; base excess=-15±3 vs. -1±2mmol/L), 85% were admitted to the NICU, and 50% developed symptoms of HIE. 8-iso-15(R)-PGF2α (P=0.01) and total isoprostanes (P=0.045) presented statistically significant differences between cases and control groups and correlated with level of HIE.

CONCLUSIONS

The 8-iso-15(R)-PGF2α and isoprostanes reflecting oxidative damage are significantly increased in severe postnatal acidemia. Follow up studies with adequate power are necessary to confirm if these biomarkers measured in cord blood serum could be predictive of neonatal encephalopathy.

Differential Changes in Peripheraland Central Components of the Brain Stem Auditory Evoked Potentials during the Neonatal Period Interm Infants after Perinatal Hypoxia-Ischemia

To identify any differences in dynamic changes between peripheral and central hearing after perinatal hypoxia-ischemia, we studied 80 term infants during the neonatal period by serially recording brain stem auditory evoked potentials (BAEPs) at 60 dB normal hearing level. All BAEP wave latencies and the I-V interval increased significantly on day 1 (analysis of variance, all p < .001). Thereafter, the wave I latency decreased gradually with some variation. The wave V latency and the I-V interval increased further on day 3 and then decreased progressively. On day 30, neither the latencies nor the I-V interval differed significantly from those of normal controls, but the wave v latency and the I-V interval still tended to increase slightly. These results suggest that hearing is impaired shortly after hypoxia-ischemia. Peripheral hearing gradually recovers after day 1, whereas central impairment progresses during the first 3 days and then starts to recover. We conclude that peripheral impairment recovers sooner than central impairment after perinatal hypoxia-ischemia.

Plasticity in the Neonatal Brain following Hypoxic-Ischaemic Injury

Hypoxic-ischaemic damage to the developing brain is a leading cause of child death, with high mortality and morbidity, including cerebral palsy, epilepsy, and cognitive disabilities. The developmental stage of the brain and the severity of the insult influence the selective regional vulnerability and the subsequent clinical manifestations. The increased susceptibility to hypoxia-ischaemia (HI) of periventricular white matter in preterm infants predisposes the immature brain to motor, cognitive, and sensory deficits, with cognitive impairment associated with earlier gestational age. In term infants HI causes selective damage to sensorimotor cortex, basal ganglia, thalamus, and brain stem. Even though the immature brain is more malleable to external stimuli compared to the adult one, a hypoxic-ischaemic event to the neonate interrupts the shaping of central motor pathways and can affect normal developmental plasticity through altering neurotransmission, changes in cellular signalling, neural connectivity and function, wrong targeted innervation, and interruption of developmental apoptosis. Models of neonatal HI demonstrate three morphologically different types of cell death, that is, apoptosis, necrosis, and autophagy, which crosstalk and can exist as a continuum in the same cell. In the present review we discuss the mechanisms of HI injury to the immature brain and the way they affect plasticity.

Preterm Hypoxic-Ischemic Encephalopathy

Hypoxic-ischemic encephalopathy (HIE) is a recognizable and defined clinical syndrome in term infants that results from a severe or prolonged hypoxic-ischemic episode before or during birth. However, in the preterm infant, defining hypoxic-ischemic injury (HII), its clinical course, monitoring, and outcomes remains complex. Few studies examine preterm HIE, and these are heterogeneous, with variable inclusion criteria and outcomes reported. We examine the available evidence that implies that the incidence of hypoxic-ischemic insult in preterm infants is probably higher than recognized and follows a more complex clinical course, with higher rates of adverse neurological outcomes, compared to term infants. This review aims to elucidate the causes and consequences of preterm hypoxia-ischemia, the subsequent clinical encephalopathy syndrome, diagnostic tools, and outcomes. Finally, we suggest a uniform definition for preterm HIE that may help in identifying infants most at risk of adverse outcomes and amenable to neuroprotective therapies.

Clinics in diagnostic imaging (153). Severe hypoxic ischaemic brain injury

A 58-year-old Indian woman presented with asystole after an episode of haemetemesis, with a patient downtime of 20 mins. After initial resuscitation efforts, computed tomography of the brain, obtained to evaluate neurological injury, demonstrated evidence of severe hypoxic ischaemic brain injury. The imaging features of hypoxic ischaemic brain injury and the potential pitfalls with regard to image interpretation are herein discussed.

Neuroplasticity for spontaneous functional recovery after neonatal hypoxic ischemic brain injury in rats observed by functional MRI and diffusion tensor imaging

For infants and children, an incredible resilience from injury is often observed. There is growing evidence that functional recovery after brain injury might well be a consequence of the reorganization of the neural network as a process of neuroplasticity. We demonstrate the presence of neuroplasticity at work in spontaneous recovery after neonatal hypoxic ischemic (HI) injury, by elucidating a precise picture in which such reorganization takes place using functional MRI techniques. For all 12 siblings, 6 rats were subjected to severe HI brain injury and 6 rats underwent sham operation only. Severe HI brain injury was induced to postnatal day 7 (p7) Sprague-Dawley rats according to the Rice-Vannucci model (right carotid artery occlusion followed by 150min of hypoxia with 8% O2 and 92% of N2). Brain activation maps along with anatomical and functional connectivity maps related to the sensory motor function were obtained at adult (p63) using blood oxygen level dependent (BOLD)-functional MRI (fMRI), resting state-functional MRI (rs-fMRI) and diffusion tensor imaging (DTI); each of these MRI data was related to sensory motor functional outcome. In-depth investigation of the functional MRI data revealed: 1) intra-hemispheric expansion of BOLD signal activation in the contralesional undamaged hemisphere for ipsilesional forepaw stimuli to include the M2 and Cg1 in addition to the S1 and M1 wide spreading in the anterior and posterior directions, 2) inter-hemispheric transfer of BOLD signal activation for contralesional forepaw stimuli, normally routed to the injured hemisphere, to analogous sites in the contralesional undamaged hemisphere, localized newly to the M1 and M2 with a reduced portion of the S1, 3) inter-hemispheric axonal disconnection and axonal rewiring within the undamaged hemisphere as shown through DTI, and 4) increased functional interactions within the cingulate gyrus in the HI injured rats as shown through rs-fMRI. The BOLD signal amplitudes as well as DTI and rs-fMRI data well correlate with behavioral tests (tape to remove). We found that function normally utilizing what would be the injured hemisphere is transferred to the uninjured hemisphere, and functionality of the uninjured hemisphere remains not untouched but is also rewired in an expansion corresponding to the newly formed sensorimotor function from both the contralesional and the ipsilesional sides. The conclusion drawn from the data in our current study is that enhanced motor function in the contralesional hemisphere governs both the normal and damaged sides, indicating that active plasticity with brain laterality was spontaneously generated to overcome functional loss and established autonomously through normal experience via modification of neural circuitry for neonatal HI injured brain.

Neuroprotective Strategies after Neonatal Hypoxic Ischemic Encephalopathy

Neonatal hypoxic ischemic encephalopathy (HIE) is a devastating disease that primarily causes neuronal and white matter injury and is among the leading cause of death among infants. Currently there are no well-established treatments; thus, it is important to understand the pathophysiology of the disease and elucidate complications that are creating a gap between basic science and clinical translation. In the development of neuroprotective strategies and translation of experimental results in HIE, there are many limitations and challenges to master based on an appropriate study design, drug delivery properties, dosage, and use in neonates. We will identify understudied targets after HIE, as well as neuroprotective molecules that bring hope to future treatments such as melatonin, topiramate, xenon, interferon-beta, stem cell transplantation. This review will also discuss some of the most recent trials being conducted in the clinical setting and evaluate what directions are needed in the future.

Efficacy, safety, and outcomes in 17 pediatric cases treated with the free radical scavenger edaravone

SUBJECTS

Edaravone is a free radical scavenger with brain protection properties and is recommended by "The Japanese Guidelines for the Management of Stroke 2009" for administration to adult patients, in whom it has been shown to improve neurological deficits after cerebral infarction. However, its dosage and effects have not yet been established in children.

METHODS

Seventeen pediatric patients with cerebral ischemia were administered edaravone at a dose based on body weight from the standard dose given to adults. Functional outcomes were evaluated using mRS and PSOM (modified ranking scale and pediatric stroke outcome scale, respectively).

RESULTS

Immediate post-treatment results were mostly positive, with no liver or renal complications. In some cases, neurological symptoms markedly improved after the administration of edaravone.

CONCLUSIONS

The efficacy of edaravone has not yet been examined in pediatric patients. The results of the present study suggest that edaravone has potential in the treatment of children safely with promising results similar to those in adults.

Leigh syndrome: neuropathology and pathogenesis

Leigh syndrome (LS) is the most common pediatric presentation of a defined mitochondrial disease. This progressive encephalopathy is characterized pathologically by the development of bilateral symmetrical lesions in the brainstem and basal ganglia that show gliosis, vacuolation, capillary proliferation, relative neuronal preservation, and by hyperlacticacidemia in the blood and/or cerebrospinal fluid. Understanding the molecular mechanisms underlying this unique pathology has been challenging, particularly in view of the heterogeneous and not yet fully determined genetic basis of LS. Moreover, animal models that mimic features of LS have only been created relatively recently. Here, we review the pathology of LS and consider what might be the molecular mechanisms underlying its pathogenesis. Data from a wide range of sources, including patient samples, animal models, and studies of hypoxic-ischemic encephalopathy (a condition that shares features with LS), were used to provide insight into the pathogenic mechanisms that may drive lesion development. Based on current data, we suggest that severe ATP depletion, gliosis, hyperlacticacidemia, reactive oxygen species, and potentially excitotoxicity cumulatively contribute to the neuropathogenesis of LS. An intimate understanding of the molecular mechanisms causing LS is required to accelerate the development of LS treatments.

Nitric oxide induces hypoxia ischemic injury in the neonatal brain via the disruption of neuronal iron metabolism

We have recently shown that increased hydrogen peroxide (H₂O₂) generation is involved in hypoxia–ischemia (HI)-mediated neonatal brain injury. H₂O₂ can react with free iron to form the hydroxyl radical, through Fenton Chemistry. Thus, the objective of this study was to determine if there was a role for the hydroxyl radical in neonatal HI brain injury and to elucidate the underlying mechanisms. Our data demonstrate that HI increases the deposition of free iron and hydroxyl radical formation, in both P7 hippocampal slice cultures exposed to oxygen–glucose deprivation (OGD), and the neonatal rat exposed to HI. Both these processes were found to be nitric oxide (NO) dependent. Further analysis demonstrated that the NO-dependent increase in iron deposition was mediated through increased transferrin receptor expression and a decrease in ferritin expression. This was correlated with a reduction in aconitase activity. Both NO inhibition and iron scavenging, using deferoxamine administration, reduced hydroxyl radical levels and neuronal cell death. In conclusion, our results suggest that increased NO generation leads to neuronal cell death during neonatal HI, at least in part, by altering iron homeostasis and hydroxyl radical generation.

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HI increases the deposition of free iron and hydroxyl radical formation in the neonatal brain.

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Both these processes are NO dependent.

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Increased iron deposition is mediated via increased TfR and decreased ferritin expression.

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These processes are involved in the neuronal cell death associated with neonatal HI.

Some of the experimental and clinical aspects of the effects of the maternal diabetes on developing hippocampus

Diabetes mellitus during pregnancy is associated with an increased risk of multiple congenital anomalies in progeny. There are sufficient evidence suggesting that the children of diabetic women exhibit intellectual and behavioral abnormalities accompanied by modification of hippocampus structure and function. Although, the exact mechanism by which maternal diabetes affects the developing hippocampus remains to be defined. Multiple biological alterations, including hyperglycemia, hyperinsulinemia, oxidative stress, hypoxia, and iron deficiency occur in pregnancies with diabetes and affect the development of central nervous system (CNS) of the fetus. The conclusion from several studies is that disturbance in glucose and insulin homeostasis in mothers and infants are major teratogenic factor in the development of CNS. Insulin and Insulin-like growth factor-1 (IGF-1) are two key regulators of CNS function and development. Insulin and IGF-1 receptors (IR and IGF1R, respectively) are distributed in a highly specific pattern with the high density in some brain regions such as hippocampus. Recent researches have clearly established that maternal diabetes disrupts the regulation of both IR and IGF1R in the hippocampus of rat newborn. Dissecting out the mechanisms responsible for maternal diabetes-related changes in the development of hippocampus is helping to prevent from impaired cognitive and memory functions in offspring.

Cerebroplacental ratio in prediction of adverse perinatal outcome and fetal heart rate disturbances in uncomplicated pregnancy at 40 weeks and beyond

INTRODUCTION

The aim of the study was to determine the usefulness of Doppler velocimetry, based on cerebroplacental ratio (C/U) evaluation, in predicting intrapartum fetal heart rate abnormalities and adverse neonatal outcome in uncomplicated pregnancies at 40 weeks and beyond.

MATERIAL AND METHODS

One hundred and forty-eight women in uncomplicated pregnancies, between 40 and 42 completed weeks, were divided into control and study groups: with the absence (n = 79) and with the presence of a fetal brain-sparing effect (n = 69), respectively. Pulsatility and resistance indices in the middle cerebral, the umbilical artery and the C/U ratio were evaluated daily by Doppler ultrasonography. C/U < 1.1 was reported as suggestive of a brain-sparing effect. Abnormal flow indices were analyzed and compared to adverse pregnancy and neonatal outcome determinants.

RESULTS

In the abnormal C/U group the abnormal CTG records were significantly more frequently observed (62.3%) than in normal C/U group (19.0%) (p = 0.0001). The comparison of selected Doppler indices revealed that C/U showed the highest sensitivity in prediction of both the intrapartum abnormal FHR (74.1%) and the adverse neonatal outcome (87.8%).

CONCLUSIONS

The C/U index shows the highest sensitivity in prediction of FHR abnormalities and adverse neonatal outcome in uncomplicated pregnancies at 40 weeks and beyond. The C/U index is useful in clinical practice in antenatal monitoring of these women in order to select those at high risk of intra- and postpartum complications.

Thioredoxin 1 and glutaredoxin 2 contribute to maintain the phenotype and integrity of neurons following perinatal asphyxia

BACKGROUND

Thioredoxin (Trx) family proteins are crucial mediators of cell functions via regulation of the thiol redox state of various key proteins and the levels of the intracellular second messenger hydrogen peroxide. Their expression, localization and functions are altered in various pathologies. Here, we have analyzed the impact of Trx family proteins in neuronal development and recovery, following hypoxia/ischemia and reperfusion.

METHODS

We have analyzed the regulation and potential functions of Trx family proteins during hypoxia/ischemia and reoxygenation of the developing brain in both an animal and a cellular model of perinatal asphyxia. We have analyzed the distribution of 14 Trx family and related proteins in the cerebellum, striatum, and hippocampus, three areas of the rat brain that are especially susceptible to hypoxia. Using SH-SY5Y cells subjected to hypoxia and reoxygenation, we have analyzed the functions of some redoxins suggested by the animal experiment.

RESULTS AND CONCLUSIONS

We have described/discovered a complex, cell-type and tissue-specific expression pattern following the hypoxia/ischemia and reoxygenation. Particularly, Grx2 and Trx1 showed distinct changes during tissue recovery following hypoxia/ischemia and reoxygenation. Silencing of these proteins in SH-SY5Y cells subjected to hypoxia-reoxygenation confirmed that these proteins are required to maintain the normal neuronal phenotype.

GENERAL SIGNIFICANCE

These findings demonstrate the significance of redox signaling in cellular pathways. Grx2 and Trx1 contribute significantly to neuronal integrity and could be clinically relevant in neuronal damage following perinatal asphyxia and other neuronal disorders.

Genetic deletion of neuronal pentraxin 1 expression prevents brain injury in a neonatal mouse model of cerebral hypoxia-ischemia

Neonatal hypoxic-ischemic (HI) brain injury is a leading cause of mortality and morbidity in infants and children for which there is no promising therapy at present. Previously, we reported induction of neuronal pentraxin 1 (NP1), a novel neuronal protein of the long-pentraxin family, following HI injury in neonatal brain. Here, we report that genetic deletion of NP1 expression prevents HI injury in neonatal brain. Elevated expression of NP1 was observed in neurons, not in astrocytes, of the ipsilateral cortical layers (I-IV) and in the hippocampal CA1 and CA3 areas of WT brains following hypoxia-ischemia; brain areas that developed infarcts (at 24-48 h), showed significantly increased numbers of TUNEL-(+) cells and tissue loss (at 7 days). In contrast, NP1-KO mice showed no evidence of brain infarction and tissue loss after HI. The immunofluorescence staining of brain sections with mitochondrial protein COX IV and subcellular fractionation analysis showed increased accumulation of NP1 in mitochondria, pro-death protein Bax activation and NP1 co-localization with activated caspase-3 in WT, but not in the NP1-KO brains; corroborating NP1 interactions with the mitochondria-derived pro-death pathways. Disruption of NP1 translocation to mitochondria by NP1-siRNA in primary cortical cultures significantly reduced ischemic neuronal death. NP1 was immunoprecipitated with activated Bax [6A7] proteins; HI caused increased interactions of NP1 with Bax, thereby, facilitating Bax translocation to mitochondrial and neuronal death. To further delineate the specificity of NPs, we found that NP1 but not the NP2 induction is specifically involved in brain injury mechanisms and that knockdown of NP1 only results in neuroprotection. Furthermore, live in vivo T2-weighted magnetic resonance imaging (MRI) including fractional anisotropy (FA) mapping showed no sign of delayed brain injury or tissue loss in the NP1-KO mice as compared to the WT at different post-HI periods (4-24 weeks) examined; indicating a long-term neuroprotective efficacy of NP1 gene deletion. Collectively, our results demonstrate a novel mechanism of neuronal death and predict that inhibition of NP1 expression is a promising strategy to prevent hypoxic-ischemic injury in immature brain.

Critical role of extracellularly secreted neuronal pentraxin 1 in ischemic neuronal death

Background

Developing brain is highly susceptible to hypoxic-ischemic injury leading to severe neurological disabilities in surviving infants and children. Previously we reported induction of neuronal pentraxin 1 (NP1) in hypoxic-ischemic injury in neonatal brain and NP1 co-localization with the excitatory AMPA receptors GluR1 at the synaptic sites. However, how NP1 contributes to hypoxic-ischemic neuronal injury is not completely understood.

Results

Here we report that extracellular secretion of NP1 is required for ischemic neuronal death. Primary cortical neurons at days in vitro (DIV) 12 were subjected to oxygen glucose deprivation (OGD), an in vitro model of ischemic stroke, for different time periods (2–8 h). Oxygen glucose deprivation showed characteristic morphological changes of dying cells, OGD time-dependent induction of NP1 (2-4-fold) and increased neuronal death. In contrast, the NP1-KO cortical neurons were healthy and showed no sign of dying cells under similar conditions. NP1gene silencing by NP1-specific small interfering RNA (NP1-siRNA) protected cortical neurons from OGD-induced death. Conditioned media (CM) collected from OGD exposed WT cortical cultures caused neurotoxicity when added to a subset of DIV 12 normoxia control WT cortical cultures. In contrast, CM from OGD-exposed NP1-KO cultures did not induce cell toxicity in control WT cultures, suggesting a role for extracellular NP1 in neuronal death. However, NP1-KO neurons, which showed normal neuronal morphology and protection against OGD, sustained enhanced death following incubation with CM from WT OGD-exposed cultures. Western blot analysis of OGD exposed WT CM showed temporal increase of NP1 protein levels in the CM. Most strikingly, in contrast to NP1-KO CM, incubation of normal cortical cultures with CM from OGD exposed NP2-KO cultures showed neurotoxicity similar to that observed with CM from OGD exposed WT neuronal cultures. Western immunoblotting further confirmed the increased presence of NP1 protein in OGD-exposed NP2-KO CM. Live immunofluorescence analysis show intense cell surface clustering of NP1 with AMPA GluR1 receptors.

Conclusions

Collectively, our results demonstrate that extracellular release of NP1 promote hypoxic-ischemic neuronal death possibly via surface clustering with GluR1 at synaptic sites and that NP1, not its family member NP2, is involved in the neuronal death mechanisms.

Mild hypothermia combined with neural stem cell transplantation for hypoxic-ischemic encephalopathy: neuroprotective effects of combined therapy

Neural stem cell transplantation is a useful treatment for ischemic stroke, but apoptosis often occurs in the hypoxic-ischemic environment of the brain after cell transplantation. In this study, we determined if mild hypothermia (27-28°C) can increase the survival rate of neural stem cells (1.0 × 10(5)/μL) transplanted into neonatal mice with hypoxic-ischemic encephalopathy. Long-term effects on neurological functioning of the mice were also examined. After mild hypothermia combined with neural stem cell transplantation, we observed decreased expression levels of inflammatory factor nuclear factor-kappa B and apoptotic factor caspase-3, reduced cerebral infarct volumes, increased survival rate of transplanted cells, and marked improvements in neurological function. Thus, the neuroprotective effects of mild hypothermia combined with neural stem cell transplantation are superior to those of monotherapy. Moreover, our findings suggest that the neuroprotective effects of mild hypothermia combined with neural stem cell transplantation on hypoxic-ischemic encephalopathy are achieved by anti-inflammatory and anti-apoptotic mechanisms.

Hypoxic preconditioning differentially affects GABAergic and glutamatergic neuronal cells in the injured cerebellum of the neonatal rat

In this study we examined cerebellar alterations in a neonatal rat model of hypoxic-ischemic brain injury with or without hypoxic preconditioning (Pc). Between postnatal days 7 and 15, the cerebellum is still undergoing intense cellular proliferation, differentiation and migration, dendritogenesis and synaptogenesis. The expression of glutamate decarboxylase 1 (GAD67) and the differentiation factor NeuroD1 were examined as markers of Purkinje and granule cells, respectively. We applied quantitative immunohistochemistry to sagittal cerebellar slices, and Western blot analysis of whole cerebella obtained from control (C) rats and rats submitted to Pc, hypoxia-ischemia (L) and a combination of both treatments (PcL). We found that either hypoxia-ischemia or Pc perturbed the granule cells in the posterior lobes, affecting their migration and final placement in the internal granular layer. These effects were partially attenuated when the Pc was delivered prior to the hypoxia-ischemia. Interestingly, whole nuclear NeuroD1 levels in Pc animals were comparable to those in the C rats. However, a subset of Purkinje cells that were severely affected by the hypoxic-ischemic insult—showing signs of neuronal distress at the levels of the nucleus, cytoplasm and dendritic arborization—were not protected by Pc. A monoclonal antibody specific for GAD67 revealed a three-band pattern in cytoplasmic extracts from whole P15 cerebella. A ∼110 kDa band, interpreted as a potential homodimer of a truncated form of GAD67, was reduced in Pc and L groups while its levels were close to the control animals in PcL rats. Additionally we demonstrated differential glial responses depending on the treatment, including astrogliosis in hypoxiated cerebella and a selective effect of hypoxia-ischemia on the vimentin-immunolabeled intermediate filaments of the Bergmann glia. Thus, while both glutamatergic and GABAergic cerebellar neurons are compromised by the hypoxic-ischemic insult, the former are protected by a preconditioning hypoxia while the latter are not.

Factors associated with hemispheric hypodensity after subdural hematoma following abusive head trauma in children

Abusive head trauma (AHT) is a unique form of pediatric TBI with increased mortality and neurologic sequelae. Hemispheric hypodensity (HH) in association with subdural blood after AHT has been described. Though risk factors for HH are not understood, we hypothesized that risk factors could be identified. We retrospectively enrolled children under 5 years with TBI secondary to AHT (child advocacy diagnosis) who had undergone initial and interval brain imaging. Records were interrogated for prearrival and in-hospital physiologic and radiographic findings. HH was determined by a blinded observer. Twenty-four children were enrolled and 13 developed HH. HH was not significantly associated with age, initial Glascow Coma Scale, or mortality. Pediatric Intensity Level of Therapy (PILOT) scores (p=0.01) and daily maximal intracranial pressure (ICPmax; p=0.037) were higher in HH. Hypoxia, hypotension, cardiopulmonary arrest, need for blood transfusion, and daily blood glucoses tended to be greater in HH. Whereas all children with HH had acute subdural hematoma (SBH), many children without HH also had subdural blood; the presence of skull fracture was more likely in the children who did not develop HH (p=0.04), but no other intracranial radiographic pattern of injury was associated with HH. Surgical intervention did not appear to protect against development of HH. A variety of insults associated with ischemia, including intracranial hypertension, ICP-directed therapies, hypoxia, hypotension, and cardiac arrest, occurred in the children who developed HH. Given the morbidity and mortality of this condition, larger studies to identify mechanisms leading to the development of HH and mitigating clinical approaches are warranted.

Current status of hypothermia for hypoxemic ischemia of the newborn

This article reviews the pathophysiology of hypoxic-ischemic brain injury, and the impact of hypothermia as neuroprotection in the clinical setting. The results of trials performed in well resourced and mid and low resourced countries is presented. Infant and childhood outcome following hypothermia is provided. Biomarkers of outcome that are clinical, electrophysiological and imaging which will be helpful to clinicians are noted. Management of infants with encephalopathy, including safety of hypothermia is reviewed. The article concludes with knowledge gaps in neuroprotection and the future of hypothermia therapy.

Correlation between clinical and histologic findings in the human neonatal hippocampus after perinatal asphyxia

Hypoxic ischemic encephalopathy after perinatal asphyxia is a major cause of mortality and morbidity in infants. Here, we evaluated pathologic changes in the hippocampi of a cohort of 16 deceased full-term asphyxiated infants who died from January 2000 to January 2009. Histochemical and immunocytochemical results for glial and neuronal cells were compared between cases with or without seizures and to adult and sudden infant death syndrome cases (n = 3 each). All asphyxiated infants displayed neuronal cell damage and reactive glial changes. Strong aquaporin-4 immunoreactivity was seen on astroglial cells within hippocampi in 50% of cases. In patients with seizures, the expression of metabotropic glutamate receptors was increased in glial cells. Cases with seizures displayed increased microglial activation and greater expression of the inflammatory markers interleukin 1β and complement 1q compared with those in cases without seizures. All cases with seizures displayed alterations in the blood-brain barrier, as assessed by immunohistochemistry for albumin. These findings confirm the complex cascade of cellular and molecular changes occurring in the human neonatal hippocampus after perinatal asphyxia. These changes may contribute to seizure development leading to secondary brain damage. These data may aid in the development of therapeutic targets for neonatal seizures.

Cell size anomalies in the auditory thalamus of rats with hypoxic-ischemic injury on postnatal day 3 or 7

Children born prematurely (<37 weeks gestational age) or at very low birth weight (VLBW; <1500g) are at increased risk for hypoxic ischemic (HI) brain injuries. Term infants can also suffer HI from birth complications. In both groups, blood/oxygen delivery to the brain is compromised, often resulting in brain damage and later cognitive delays (e.g., language deficits). Literature suggests that language delays in a variety of developmentally impaired populations (including specific language impairment (SLI), dyslexia, and early HI-injury) may be associated with underlying deficits in rapid auditory processing (RAP; the ability to process and discriminate brief acoustic cues). Data supporting a relationship between RAP deficits and poor language outcomes is consistent with the "magnocellular theory," which purports that damage to or loss of large (magnocellular) cells in thalamic nuclei could underlie disruptions in temporal processing of sensory input, possibly including auditory (medial geniculate nucleus; MGN) information This theory could be applied to neonatal HI populations that show subsequent RAP deficits. In animal models of neonatal HI, persistent RAP deficits are seen in postnatal (P)7 HI injured rats (who exhibit neuropathology comparable to term birth injury), but not in P1-3 HI injured rodents (who exhibit neuropathology comparable to human pre-term injury). The current study sought to investigate the mean cell size, cell number, and cumulative probability of cell size in the MGN of P3 HI and P7 HI injured male rats that had previously demonstrated behavioral RAP deficits. Pilot data from our lab (Alexander, 2011) previously revealed cell size abnormalities (a shift toward smaller cells) in P7 but not P1 HI injured animals when compared to shams. Our current finding support this result, with evidence of a significant shift to smaller cells in the experimental MGN of P7 HI but not P3 HI subjects. P7 HI animals also showed significantly fewer cells in the affected (right) MGN as compared P3 HI and shams animals. Moreover, cell number in the right hemisphere was found to correlate with gap detection (fewer cells=worse performance) in P7 HI injured subjects. These findings could be applied to clinical populations, providing an anatomic marker that may index potential long-term language disabilities in HI injured infants and possibly other at-risk populations.

Brain to blood glutamate scavenging as a novel therapeutic modality: a review

It is well known that abnormally elevated glutamate levels in the brain are associated with secondary brain injury following acute and chronic brain insults. As such, a tight regulation of brain glutamate concentrations is of utmost importance in preventing the neurodegenerative effects of excess glutamate. There has been much effort in recent years to better understand the mechanisms by which glutamate is reduced in the brain to non-toxic concentrations, and in how to safely accelerate these mechanisms. Blood glutamate scavengers such as oxaloacetate, pyruvate, glutamate-oxaloacetate transaminase, and glutamate-pyruvate transaminase have been shown to reduce blood glutamate concentrations, thereby increasing the driving force of the brain to blood glutamate efflux and subsequently reducing brain glutamate levels. In the past decade, blood glutamate scavengers have gained increasing international interest, and its uses have been applied to a wide range of experimental contexts in animal models of traumatic brain injury, ischemic stroke, subarachnoid hemorrhage, epilepsy, migraine, and malignant gliomas. Although glutamate scavengers have not yet been used in humans, there is increasing evidence that their use may provide effective and exciting new therapeutic modalities. Here, we review the laboratory evidence for the use of blood glutamate scavengers. Other experimental neuroprotective treatments thought to scavenge blood glutamate, including estrogen and progesterone, beta-adrenergic activation, hypothermia, insulin and glucagon, and hemodialysis and peritoneal dialysis are also discussed. The evidence reviewed here will hopefully pave the way for future clinical trials.

Involvement of the subplate zone in preterm infants with periventricular white matter injury

Studies of periventricular white matter injury (PWMI) in preterm infants suggest the involvement of the transient cortical subplate zone. We studied the cortical wall of noncystic and cystic PWMI cases and controls. Non-cystic PWMI corresponded to diffuse white matter lesions, the predominant injury currently detected by imaging. Glial cell populations were analyzed in post-mortem human frontal lobes from very preterm [24–29 postconceptional weeks (pcw)] and preterm infants (30–34 pcw) using immunohistochemistry for glial fibrillary acidic protein (GFAP), monocarboxylate transporter 1(MCT1), ionized calcium-binding adapter molecule 1 (Iba1), CD68 and oligodendrocyte lineage (Olig2). Glial activation extended into the subplate in non-cystic PWMI but was restricted to the white matter in cystic PWMI. Two major age-related and laminar differences were observed in non-cystic PWMI: in very preterm cases, activated microglial cells were increased and extended into the subplate adjacent to the lesion, whereas in preterm cases, an astroglial reaction was seen not only in the subplate but throughout the cortical plate. There were no differences in Olig2-positive pre-oligodendrocytes in the subplate inPWMI cases compared with controls. The involvement of gliosis in the deep subplate supports the concept of the complex cellular vulnerability of the subplate zone during the preterm period and may explain widespread changes in magnetic resonance signal intensity in early PWMI.

Effects of caffeine on neuronal apoptosis in neonatal hypoxic-ischemic brain injury

OBJECTIVE

Hypoxia-ischemia (HI) in rat pups leads to strong activation of apoptosis, and apoptosis contributes significantly to cerebral damage in the perinatal period. Caffeine displays a broad array of actions on the brain. The aim of this study was to investigate the effects of caffeine on neuronal apoptosis in a hypoxic-ischemic neonatal model.

METHODS

Twenty-four seven-day-old Wistar rat pups were subjected to right common carotid artery ligation and hypoxia for 2 h. Sham group (n = 8) had a median neck incision, but the rats were not subjected to ligation or hypoxia. The pups were treated with 20 mg/kg/day caffeine citrate (n = 8) or saline (n = 8) immediately before HI and at 0, 24, 48 and 72 h post-hypoxia. Neuronal apoptosis was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) and caspase-3 in the hippocampus and parietal cortex of both hemispheres.

RESULTS

The numbers of apoptotic cells in the hippocampus and parietal cortex were significantly higher in the saline group than they were in the sham group (p < 0.0001). The number of apoptotic cells in the hippocampus (p < 0.0001) and parietal cortex (p < 0.0001, TUNEL and p = 0.001, caspase-3) were higher in the caffeine-treated group than they were in the sham group, but the number of apoptotic cells decreased significantly in the caffeine-treated group compared with the saline group in the hippocampus (p < 0.0001, TUNEL and p = 0.001, caspase-3) and parietal cortex (p = 0.001, TUNEL and p = 0.002, caspase-3).

CONCLUSIONS

We show that caffeine administration in hypoxic-ischemic brain injury reduces neuronal apoptosis in the developing brain. We suggest that caffeine may be effective in reducing brain injury.

Mechanism of metabolic stroke and spontaneous cerebral hemorrhage in glutaric aciduria type I

Background

Metabolic stroke is the rapid onset of lasting central neurological deficit associated with decompensation of an underlying metabolic disorder. Glutaric aciduria type I (GA1) is an inherited disorder of lysine and tryptophan metabolism presenting with metabolic stroke in infancy. The clinical presentation includes bilateral striatal necrosis and spontaneous subdural and retinal hemorrhages, which has been frequently misdiagnosed as non-accidental head trauma. The mechanisms underlying metabolic stroke and spontaneous hemorrhage are poorly understood.

Results

Using a mouse model of GA1, we show that metabolic stroke progresses in the opposite sequence of ischemic stroke, with initial neuronal swelling and vacuole formation leading to cerebral capillary occlusion. Focal regions of cortical followed by striatal capillaries are occluded with shunting to larger non-exchange vessels leading to early filling and dilation of deep cerebral veins. Blood–brain barrier breakdown was associated with displacement of tight-junction protein Occludin.

Conclusion

Together the current findings illuminate the pathophysiology of metabolic stroke and vascular compromise in GA1, which may translate to other neurometabolic disorders presenting with stroke.

Hypothermia for hypoxic-ischemic encephalopathy

Moderate to severe hypoxic-ischemic injury in newborn infants, manifested as encephalopathy immediately or within hours after birth, is associated with a high risk of either death or a lifetime with disability. In recent multicenter clinical trials, hypothermia initiated within the first 6 postnatal hours has emerged as a therapy that reduces the risk of death or impairment among infants with hypoxic-ischemic encephalopathy. Prior to hypothermia, no therapies directly targeting neonatal encephalopathy secondary to hypoxic-ischemic injury had convincing evidence of efficacy. Hypothermia therapy is now becoming increasingly available at tertiary centers. Despite the deserved enthusiasm for hypothermia, obstetric and neonatology caregivers, as well as society at large, must be reminded that in the clinical trials more than 40% of cooled infants died or survived with impairment. Although hypothermia is an evidence-based therapy, additional discoveries are needed to further improve outcome after HIE. In this article, we briefly present the epidemiology of neonatal encephalopathy due to hypoxic-ischemic injury, describe the rationale for the use of hypothermia therapy for hypoxic-ischemic encephalopathy, and present results of the clinical trials that have demonstrated the efficacy of hypothermia. We also present findings noted during and after these trials that will guide care and direct research for this devastating problem.

Two-year follow-up study on neurodevelopmental outcomes after term intrapartum asphyxia using age and stages questionnaire

Birth asphyxia is one of the multiple causes of neonatal encephalopathy. The objective of this study was to evaluate neurodevelopmental outcomes of newborn term infants with definitive asphyxia. Thirty infants met study criteria for asphyxia. The 5-year incidence of asphyxia was estimated to be 5.5 in 1000. According to the Age and Stage Questionnaire, 10.5% of 6-month-old infants, 14.3% of 12- and 18-month-old infants, and 5.3% of 24-month-old infants had neurodevelopmental delay in gross motor function in the absence of cerebral palsy. In 7.3% of 18-month-old infants, neurodevelopmental delay in problem-solving ability was observed. Higher values of Apgar score and bicarbonate levels were associated with higher Age and Stage Questionnaire total score. Delivery type, maternal age, gravidity of mother, and existence of mother disease during pregnancy were also associated with lower Age and Stage Questionnaire total score in different stages of life.

Thioredoxins, glutaredoxins, and peroxiredoxins--molecular mechanisms and health significance: from cofactors to antioxidants to redox signaling

Thioredoxins (Trxs), glutaredoxins (Grxs), and peroxiredoxins (Prxs) have been characterized as electron donors, guards of the intracellular redox state, and "antioxidants". Today, these redox catalysts are increasingly recognized for their specific role in redox signaling. The number of publications published on the functions of these proteins continues to increase exponentially. The field is experiencing an exciting transformation, from looking at a general redox homeostasis and the pathological oxidative stress model to realizing redox changes as a part of localized, rapid, specific, and reversible redox-regulated signaling events. This review summarizes the almost 50 years of research on these proteins, focusing primarily on data from vertebrates and mammals. The role of Trx fold proteins in redox signaling is discussed by looking at reaction mechanisms, reversible oxidative post-translational modifications of proteins, and characterized interaction partners. On the basis of this analysis, the specific regulatory functions are exemplified for the cellular processes of apoptosis, proliferation, and iron metabolism. The importance of Trxs, Grxs, and Prxs for human health is addressed in the second part of this review, that is, their potential impact and functions in different cell types, tissues, and various pathological conditions.

Early neural disruption and auditory processing outcomes in rodent models: implications for developmental language disability

Most researchers in the field of neural plasticity are familiar with the "Kennard Principle," which purports a positive relationship between age at brain injury and severity of subsequent deficits (plateauing in adulthood). As an example, a child with left hemispherectomy can recover seemingly normal language, while an adult with focal injury to sub-regions of left temporal and/or frontal cortex can suffer dramatic and permanent language loss. Here we present data regarding the impact of early brain injury in rat models as a function of type and timing, measuring long-term behavioral outcomes via auditory discrimination tasks varying in temporal demand. These tasks were created to model (in rodents) aspects of human sensory processing that may correlate-both developmentally and functionally-with typical and atypical language. We found that bilateral focal lesions to the cortical plate in rats during active neuronal migration led to worse auditory outcomes than comparable lesions induced after cortical migration was complete. Conversely, unilateral hypoxic-ischemic (HI) injuries (similar to those seen in premature infants and term infants with birth complications) led to permanent auditory processing deficits when induced at a neurodevelopmental point comparable to human "term," but only transient deficits (undetectable in adulthood) when induced in a "preterm" window. Convergent evidence suggests that regardless of when or how disruption of early neural development occurs, the consequences may be particularly deleterious to rapid auditory processing (RAP) outcomes when they trigger developmental alterations that extend into subcortical structures (i.e., lower sensory processing stations). Collective findings hold implications for the study of behavioral outcomes following early brain injury as well as genetic/environmental disruption, and are relevant to our understanding of the neurologic risk factors underlying developmental language disability in human populations.

The role of hypothermia in the regulation of blood glutamate levels in naive rats

BACKGROUND

The exact mechanism of hypothermia-induced neuroprotection has not been determined yet; however, we hypothesized that it may be mediated by a blood glutamate-scavenging effect. Here, we examine the effect of hypothermic conditions (mild, moderate, and deep) on blood glutamate levels in naive rats. To identify the mechanism of hypothermia-induced glutamate reduction, we also measured concentrations of glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT), the primary regulators of glutamate concentration in blood.

METHODS

Rats were anesthetized with isoflurane, and their rectal temperature was maintained for 6 hours at 36 to 37°C, 33 to 36°C, 30 to 32°C, 18 to 22°C, or was not maintained artificially. At 6 hours, active cooling was discontinued and rats were allowed to rewarm. There were 12 rats in each group for a total of 60 rats. Blood samples were drawn at 0, 3, 6, 12, 24, and 48 hours for the determination of blood glutamate, GOT, and GPT levels.

RESULTS

A strong correlation between body temperature and blood glutamate levels was observed (P<0.001). Mild (33 to 36°C) and moderate (30 to 32°C) hypothermia led to reduced blood glutamate levels (P<0.001). Deep hypothermia (18 to 22°C) was associated with significant elevations in blood glutamate levels (P<0.001). Hypothermia, irrespective of the degree, led to elevations in GOT in plasma (P<0.001).

CONCLUSIONS

Mild and moderate hypothermia led to a reduction in blood glutamate levels in rats, whereas deep hypothermia was associated with a significant elevation in blood glutamate levels. We further demonstrated an elevation of GOT and GPT levels, supporting their involvement in reducing blood glutamate by the conversion of glutamate to 2-ketoglutarate. We suggest that the neuroprotective properties of hypothermia may be partially because of a blood glutamate-scavenging mechanism.

Ca²⁺/calmodulin-dependent protein kinase II contributes to hypoxic ischemic cell death in neonatal hippocampal slice cultures

We have recently shown that p38MAP kinase (p38MAPK) stimulates ROS generation via the activation of NADPH oxidase during neonatal hypoxia-ischemia (HI) brain injury. However, how p38MAPK is activated during HI remains unresolved and was the focus of this study. Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) plays a key role in brain synapse development, neural transduction and synaptic plasticity. Here we show that CaMKII activity is stimulated in rat hippocampal slice culture exposed to oxygen glucose deprivation (OGD) to mimic the condition of HI. Further, the elevation of CaMKII activity, correlated with enhanced p38MAPK activity, increased superoxide generation from NADPH oxidase as well as necrotic and apoptotic cell death. All of these events were prevented when CaMKII activity was inhibited with KN93. In a neonatal rat model of HI, KN93 also reduced brain injury. Our results suggest that CaMKII activation contributes to the oxidative stress associated with neural cell death after HI.