Neuroprotection by selective nitric oxide synthase inhibition at 24 hours after perinatal hypoxia-ischemia

2-iminobiotin, a selective inhibitor of nitric oxide synthase, improves memory and learning in a rat model after four vessel occlusion, mimicking cardiac arrest

Survivors of out-of-hospital cardiac arrest (OHCA) experience between 30% and 50% cognitive deficits several years post-discharge. Especially spatial memory is affected due to ischemia-induced neuronal damage in the hippocampus. Aim of this study was to investigate the potential neuroprotective effect of 2-iminobiotin (2-IB), a biotin analogue, on memory and learning in a four-vessel occlusion model of global ischemia using the Water Maze test. Sprague-Dawley rats were randomly assigned to either sham operation (n = 6), vehicle treatment (n = 20), 1.1 (n = 15), 3.3 (n = 14), 10 (n = 14), or 30 mg/kg/dose 2-IB treatment (n = 15). Treatment was subcutaneously (s.c.) administered immediately upon reperfusion, at 12h, and at 24h after reperfusion. Memory function on day 32 was significantly preserved in all doses of 2-IB rats compared to vehicle, as was the learning curve in the 1.1, 3.3 and 30 mg/kg dose group. Adult rats treated s.c. with 3 gifts of 2-IB every 12 h in a dose range of 1.1-30 mg/kg/dose directly upon reperfusion showed significant improved memory and learning after four vessel occlusion compared to vehicle-treated rats. Since 2-IB has already shown to be safe in a phase 1 clinical trial in adult human volunteers, it is a suitable candidate for translation to a human phase 2 study after OHCA.

Neuroprotection after cardiac arrest with 2-iminobiotin: a single center phase IIa study on safety, tolerability, and pharmacokinetics

Background

Brain injury is a serious problem in patients who survive out-of-hospital cardiac arrest (OHCA). Neuroprotective drugs could reduce hypoxic-ischemic reperfusion injury. The aim of this study was to investigate the safety, tolerability, and pharmacokinetics (PK) of 2-iminobiotin (2-IB), a selective inhibitor of neuronal nitric oxide synthase.

Methods

Single-center, open-label dose-escalation study in adult OHCA patients, investigating three 2-IB dosing schedules (targeting an AUC_0-24h of 600-1,200 ng*h/m in cohort A, of 2,100-3,300 ng*h/mL in cohort B, and 7,200-8,400 of ng*h/mL in cohort C). Safety was investigated by monitoring vital signs until 15 min after study drug administration and adverse events up to 30 days after admission. Blood sampling for PK analysis was performed. Brain biomarkers and patient outcomes were collected 30 days after OHCA.

Results

A total of 21 patients was included, eight in cohort A and B and five in cohort C. No changes in vital signs were observed, and no adverse events related to 2-IB were reported. A two-compartment PK model described data the best. Exposure in group A (dosed on bodyweight) was three times higher than targeted (median AUC_0-24h 2,398 ng*h/mL). Renal function was an important covariate; therefore, in cohort B, dosing was performed on eGFR on admission. In cohort B and C, the targeted exposure was met (median AUC_0-24h 2,917 and 7,323 ng*h/mL, respectively).

Conclusion

The administration of 2-IB to adults after OHCA is feasible and safe. PK can be well predicted with correction for renal function on admission. Efficacy studies with 2-IB after OHCA are needed.

Iron promotes neurological function recovery in mice with ischemic stroke through endogenous repair mechanisms

The endogenous repair mechanisms play an important role in the recovery of nerve function after stroke, such as gliosis, synaptic plasticity, remyelination and nerve regeneration. Iron is the most abundant trace metal element in the brain and plays a crucial role in the maintenance of normal cerebral function. It is an important coenzyme factor in the process of cell metabolism, DNA synthesis, purine catabolism and neurotransmitter synthesis and decomposition. However, it is unclear what role iron plays in the long-term recovery of neurological function after stroke. In this study, we first observed that changes in iron metabolism occurred during neurological function recovery in the mice with distal middle cerebral artery occlusion (dMCAO). Our data showed that plasticity changes due to endogenous repair mechanisms resulted in improvements in cerebral cortex function. These changes involved gliosis, synaptic function reconstruction, remyelination, and activation of neural stem cells. In order to examine the potential role of iron, we synthesized liposomal-encapsulated deferoxamine (DFO) nanoparticles to further explore the effect and the mechanism of iron on the recovery of neurological function in dMCAO mice. Our results showed that liposome-DFO decreased iron deposition and reversed plasticity changes in cerebral cortex function after stroke, which delayed neurological function recovery. This experiment shows that the increasing iron level promotes endogenous repair in ischemic stroke. Our finding reveals the change regularity of iron and emphasizes the beneficial role of iron in the recovery process of neurological function, which provides an important basis for the prevention and/or treatment of ischemia-reperfusion and recovery after stroke.

Therapeutic potential of nitric oxide synthase inhibitor from natural sources for the treatment of ischemic stroke

Nitric oxide (NO) is one of the major signalling molecules in the mammalian body playing critical role in regulation of blood pressure, cardiovascular disease including stroke, immune activation, neuronal and cell communication. Moreover, hyper production of NO by the activity of nitric oxide synthase (NOS) involved in neuropathic pain, neurodegenerative disorders and stroke. Hence, the search on small molecules from the natural sources for the inhibition of NOS is desirable in therapeutic point of view. The elevated level of NO caused by NOS enzyme become a novel target in finding new inhibitors from natural sources as antistroke agents. The present study focuses on the molecular docking of quercetin and its analogues against NOS. The active site of the enzyme was docked with the ligand and pharmacological properties were analysed. From this result, we suggest the therapeutic property of quercetin and its analogues against NOS.

Therapies for neonatal encephalopathy: Targeting the latent, secondary and tertiary phases of evolving brain injury

In term and near-term neonates with neonatal encephalopathy, therapeutic hypothermia protocols are well established. The current focus is on how to improve outcomes further and the challenge is to find safe and complementary therapies that confer additional protection, regeneration or repair in addition to cooling. Following hypoxia-ischemia, brain injury evolves over three main phases (latent, secondary and tertiary), each with a different brain energy, perfusion, neurochemical and inflammatory milieu. While therapeutic hypothermia has targeted the latent and secondary phase, we now need therapies that cover the continuum of brain injury that spans hours, days, weeks and months after the initial event. Most agents have several therapeutic actions but can be broadly classified under a predominant action (e.g., free radical scavenging, anti-apoptotic, anti-inflammatory, neuroregeneration, and vascular effects). Promising early/secondary phase therapies include Allopurinol, Azithromycin, Exendin-4, Magnesium, Melatonin, Noble gases and Sildenafil. Tertiary phase agents include Erythropoietin, Stem cells and others. We review a selection of promising therapeutic agents on the translational pipeline and suggest a framework for neuroprotection and neurorestoration that targets the evolving injury.

Nitric oxide homeostasis is maintained during acute in vitro hypoxia and following reoxygenation in naked mole-rat but not mouse cortical neurons

Reactive nitrogen species (RNS), including nitric oxide (NO), are important cellular messengers when tightly regulated, but unregulated production of RNS during hypoxia or ischemia and reoxygenation is deleterious to hypoxia-intolerant brain. Therefore, maintaining NO homeostasis during hypoxia/ischemia and reoxygenation may be a hallmark of hypoxia-tolerant brain. Unlike most mammals, naked mole-rats (NMRs; Heterocephalus glaber) are tolerant of repeated bouts of hypoxia in vivo. Although there is some evidence that NMR brain is tolerant of hypoxia/ischemia, little is known about the underlying neuroprotective mechanism(s), and their tolerance to reoxygenation injury has not been examined. We hypothesized that NMR brain would maintain NO homeostasis better than hypoxia-intolerant mouse brain during hypoxic/ischemic stresses and following reoxygenation. To test this, we exposed adult NMR and mouse cortical slices to transitions from normoxia (21% O₂) to hypoxia (< 1% O₂) or ischemia (oxygen glucose deprivation, OGD), followed by reoxygenation, while measuring neuronal NO production. We report that NMR cortical neurons maintain NO homeostasis during hypoxia/OGD and avoid bursts of NO upon reoxygenation. Conversely, mouse cortical neurons maintain NO homeostasis in OGD but not hypoxia and exhibit a burst of NO upon reperfusion. This suggests that maintenance of NO homeostasis during fluctuating O₂ availability may be a contributing neuroprotective mechanism against hypoxia/ischemia and reoxygenation injury in hypoxia-tolerant NMR brain.

Free radicals and neonatal encephalopathy: mechanisms of injury, biomarkers, and antioxidant treatment perspectives

Neonatal encephalopathy (NE), most commonly a result of the disruption of cerebral oxygen delivery, is the leading cause of neurologic disability in term neonates. Given the key role of free radicals in brain injury development following hypoxia-ischemia-reperfusion, several oxidative biomarkers have been explored in preclinical and clinical models of NE. Among these, antioxidant enzyme activity, uric acid excretion, nitric oxide, malondialdehyde, and non-protein-bound iron have shown promising results as possible predictors of NE severity and outcome. Owing to high costs and technical complexity, however, their routine use in clinical practice is still limited. Several strategies aimed at reducing free radical production or upregulating physiological scavengers have been proposed for NE. Room-air resuscitation has proved to reduce oxidative stress following perinatal asphyxia and is now universally adopted. A number of medications endowed with antioxidant properties, such as melatonin, erythropoietin, allopurinol, or N-acetylcysteine, have also shown potential neuroprotective effects in perinatal asphyxia; nevertheless, further evidence is needed before these antioxidant approaches could be implemented as standard care.

Pharmacokinetics and short-term safety of the selective NOS inhibitor 2-iminobiotin in asphyxiated neonates treated with therapeutic hypothermia

BACKGROUND

Neonatal encephalopathy following perinatal asphyxia is a leading cause for neonatal death and disability, despite treatment with therapeutic hypothermia. 2-Iminobiotin is a promising neuroprotective agent additional to therapeutic hypothermia to improve the outcome of these neonates.

METHODS

In an open-label study, pharmacokinetics and short-term safety of 2-iminobiotin were investigated in neonates treated with therapeutic hypothermia. Group A (n = 6) received four doses of 0.16 mg/kg intravenously q6h. Blood sampling for pharmacokinetic analysis and monitoring of vital signs for short-term safety analysis were performed. Data from group A was used to determine the dose for group B, aiming at an AUC_0-48 h of 4800 ng*h/mL.

RESULTS

Exposure in group A was higher than targeted (median AUC_0-48 h 9522 ng*h/mL); subsequently, group B (n = 6) received eight doses of 0.08 mg/kg q6h (median AUC_0-48 h 4465 ng*h/mL). No changes in vital signs were observed and no adverse events related to 2-iminobiotin occurred.

CONCLUSION

This study indicates that 2-iminobiotin is well tolerated and not associated with any adverse events in neonates treated with therapeutic hypothermia after perinatal asphyxia. Target exposure was achieved with eight doses of 0.08 mg/kg q6h. Optimal duration of therapy for clinical efficacy needs to be determined in future clinical trials.

A Phase IIa Clinical Trial of 2-Iminobiotin for the Treatment of Birth Asphyxia in DR Congo, a Low-Income Country

AIM

The main burden of hypoxic-ischemic encephalopathy falls in low-income countries. 2-Iminobiotin, a selective inhibitor of neuronal and inducible nitric oxide synthase, has been shown to be safe and effective in preclinical studies of birth asphyxia. Recently, safety and pharmacokinetics of 2-iminobiotin treatment on top of hypothermia has been described. Since logistics and the standard of medical care are very different in low-resource settings, the aim of this study was to investigate safety and pharmacokinetics of Two-IminoBiotin in the Democratic Republic of Congo (TIBC).

METHODS

Near-term neonates, born in Kinshasa, Democratic Republic of Congo, with a Thompson score ≥ 7 were eligible for inclusion. Excluded were patients with (1) inability to insert an umbilical venous catheter for administration of the study drug; (2) major congenital or chromosomal abnormalities; (3) birth weight < 1800 g; (4) clear signs of infection; and (5) moribund patients. Neonates received six infusions of 2-iminobiotin 0.16 mg/kg started within 6 h after birth, with 4-h intervals, targeting an AUC_0-4h of 365 ng*h/mL. Safety, defined as vital signs, the need for clinical intervention after administration of study drug, occurrence of (serious) adverse events, and pharmacokinetics were assessed.

RESULTS

After parental consent, seven patients were included with a median Thompson score of 10 (range 8-16). No relevant changes in vital signs were observed over time. There was no need for clinical intervention due to administration of study drug. Three patients died, two after completing the study protocol, one was moribund at inclusion and should not have been included. Pharmacokinetic data of 2-iminobiotin were best described using a two-compartment model. Median AUC_0-4h was 664 ng*h/mL (range 414-917). No safety issues attributed to the administration of 2-iminobiotin were found.

CONCLUSION

The present dosing regimen resulted in higher AUCs than targeted, necessitating a change in the dose regimen in future efficacy trials. No adverse effects that could be attributed to the use of 2-iminobiotin were observed. EudraCT number 2015-003063-12.

Combined network pharmacology and virtual reverse pharmacology approaches for identification of potential targets to treat vascular dementia

Dementia is a major cause of disability and dependency among older people. If the lives of people with dementia are to be improved, research and its translation into druggable target are crucial. Ancient systems of healthcare (Ayurveda, Siddha, Unani and Sowa-Rigpa) have been used from centuries for the treatment vascular diseases and dementia. This traditional knowledge can be transformed into novel targets through robust interplay of network pharmacology (NetP) with reverse pharmacology (RevP), without ignoring cutting edge biomedical data. This work demonstrates interaction between recent and traditional data, and aimed at selection of most promising targets for guiding wet lab validations. PROTEOME, DisGeNE, DISEASES and DrugBank databases were used for selection of genes associated with pathogenesis and treatment of vascular dementia (VaD). The selection of new potential drug targets was made by methods of NetP (DIAMOnD algorithm, enrichment analysis of KEGG pathways and biological processes of Gene Ontology) and manual expert analysis. The structures of 1976 phytomolecules from the 573 Indian medicinal plants traditionally used for the treatment of dementia and vascular diseases were used for computational estimation of their interactions with new predicted VaD-related drug targets by RevP approach based on PASS (Prediction of Activity Spectra for Substances) software. We found 147 known genes associated with vascular dementia based on the analysis of the databases with gene-disease associations. Six hundred novel targets were selected by NetP methods based on 147 gene associations. The analysis of the predicted interactions between 1976 phytomolecules and 600 NetP predicted targets leaded to the selection of 10 potential drug targets for the treatment of VaD. The translational value of these targets is discussed herewith. Twenty four drugs interacting with 10 selected targets were identified from DrugBank. These drugs have not been yet studied for the treatment of VaD and may be investigated in this field for their repositioning. The relation between inhibition of two selected targets (GSK-3, PTP1B) and the treatment of VaD was confirmed by the experimental studies on animals and reported separately in our recent publications.

Oxygen radical disease in the newborn, revisited: Oxidative stress and disease in the newborn period

Thirty years ago, there was an emerging appreciation for the significance of oxidative stress in newborn disease. This prompted a renewed interest in the impact of oxygen therapy for the newborn in the delivery room and beyond, especially in premature infants. Today, the complexity of oxidative stress both in normal regulation and pathology is better understood, especially as it relates to neonatal mitochondrial oxidative stress responses to hyperoxia. Mitochondria are recipients of oxidative damage and have a propensity for oxidative self-injury that has been implicated in the pathogenesis of neonatal lung diseases. Similarly, both intrauterine growth restriction (IUGR) and macrosomia are associated with mitochondrial dysfunction and oxidative stress. Additionally, reoxygenation with 100% O₂ in a hypoxic-ischemic newborn lamb model increased the production of pro-inflammatory cytokines in the brain. Moreover, the interplay between inflammation and oxidative stress in the newborn is better understood because of animal studies. Transcriptomic analyses have found a number of genes to be differentially expressed in murine models of bronchopulmonary dysplasia (BPD). Epigenetic changes have also been detected both in animal models of BPD and premature infants exposed to oxygen. Antioxidant therapy to prevent newborn disease has not been very successful; however, new therapeutic principles, like melatonin, are under investigation.

Neuroprotective strategies following perinatal hypoxia-ischemia: Taking aim at NOS

Perinatal asphyxia is characterized by oxygen deprivation and lack of perfusion in the perinatal period, leading to hypoxic-ischemic encephalopathy and sequelae such as cerebral palsy, mental retardation, cerebral visual impairment, epilepsy and learning disabilities. On cellular level PA is associated with a decrease in oxygen and glucose leading to ATP depletion and a compromised mitochondrial function. Upon reoxygenation and reperfusion, the renewed availability of oxygen gives rise to not only restoration of cell function, but also to the activation of multiple detrimental biochemical pathways, leading to secondary energy failure and ultimately, cell death. The formation of reactive oxygen species, nitric oxide and peroxynitrite plays a central role in the development of subsequent neurological damage. In this review we give insight into the pathophysiology of perinatal asphyxia, discuss its clinical relevance and summarize current neuroprotective strategies related to therapeutic hypothermia, ischemic postconditioning and pharmacological interventions. The review will also focus on the possible neuroprotective actions and molecular mechanisms of the selective neuronal and inducible nitric oxide synthase inhibitor 2-iminobiotin that may represent a novel therapeutic agent for the treatment of hypoxic-ischemic encephalopathy, both in combination with therapeutic hypothermia in middle- and high-income countries, as well as stand-alone treatment in low-income countries.

Perinatal hypoxic-ischemic brain injury in large animal models: Relevance to human neonatal encephalopathy

Perinatal hypoxia-ischemia resulting in death or lifelong disabilities remains a major clinical disorder. Neonatal models of hypoxia-ischemia in rodents have enhanced our understanding of cellular mechanisms of neural injury in developing brain, but have limitations in simulating the range, accuracy, and physiology of clinical hypoxia-ischemia and the relevant systems neuropathology that contribute to the human brain injury pattern. Large animal models of perinatal hypoxia-ischemia, such as partial or complete asphyxia at the time of delivery of fetal monkeys, umbilical cord occlusion and cerebral hypoperfusion at different stages of gestation in fetal sheep, and severe hypoxia and hypoperfusion in newborn piglets, have largely overcome these limitations. In monkey, complete asphyxia produces preferential injury to cerebellum and primary sensory nuclei in brainstem and thalamus, whereas partial asphyxia produces preferential injury to somatosensory and motor cortex, basal ganglia, and thalamus. Mid-gestational fetal sheep provide a valuable model for studying vulnerability of progenitor oligodendrocytes. Hypoxia followed by asphyxia in newborn piglets replicates the systems injury seen in term newborns. Efficacy of post-insult hypothermia in animal models led to the success of clinical trials in term human neonates. Large animal models are now being used to explore adjunct therapy to augment hypothermic neuroprotection.

Biochemical Characterization of the Brain Hippocampal Areas after Cerebral Ischemia-Reperfusion Using Raman Spectroscopy

Cerebral ischemic stroke is one of the most common neurodegenerative conditions characterized by cerebral infarction, death of the brain tissue, and loss of brain function. Cerebral ischemia-reperfusion injury is the tissue damage caused when blood supply begins to the tissue after a period of ischemia or poor oxygen supply. In this study, we preliminarily investigated the biochemical changes in the brain hippocampal area, CA1, resulting from ischemia reperfusion and neuronal nitric oxide synthase (nNOS) inhibitor treatment in rats using Raman spectroscopy. A drastic spectral change was observed in the ischemia-reperfusion brain tissue; a strong dependency between the intensity of certain Raman bands was observed at the amide positions of 1276 and 1658 cm^-1 and at the lipid positions of 1300 and 1438 cm^-1. The spectrum of nNOS inhibitor-treated brain tissue was similar to that of the normal brain tissue, indicating that the nNOS inhibitor could protect the brain against excessive production of NO and biochemical processes dependent on it. Principal component analysis (PCA) precisely identified three classes of tissues: normal; ischemic; and nNOS inhibitor-treated. Therefore, we suggest that quantitative analysis of the changes in the brain tissue by using Raman spectroscopy with multivariate statistical technique could be effective for evaluating neuronal injury and drug effects.

Nitric Oxide Synthase Inhibition as a Neuroprotective Strategy Following Hypoxic-Ischemic Encephalopathy: Evidence From Animal Studies

BACKGROUND

Hypoxic-ischemic encephalopathy following perinatal asphyxia is a leading cause of neonatal death and disability worldwide. Treatment with therapeutic hypothermia reduced adverse outcomes from 60 to 45%. Additional strategies are urgently needed to further improve the outcome for these neonates. Inhibition of nitric oxide synthase (NOS) is a potential neuroprotective target. This article reviews the evidence of neuroprotection by nitric oxide (NO) synthesis inhibition in animal models.

METHODS

Literature search using the EMBASE, Medline, Cochrane, and PubMed databases. Studies comparing NOS inhibition to placebo, with neuroprotective outcome measures, in relevant animal models were included. Methodologic quality of the included studies was assessed.

RESULTS

26 studies were included using non-selective or selective NOS inhibition in rat, piglet, sheep, or rabbit animal models. A large variety in outcome measures was reported. Outcome measures were grouped as histological, biological, or neurobehavioral. Both non-selective and selective inhibitors show neuroprotective properties in one or more outcome measures. Methodologic quality was either low or moderate for all studies.

CONCLUSION

Inhibition of NO synthesis is a promising strategy for additional neuroprotection. In humans, intervention can only take place after the onset of the hypoxic-ischemic event. Therefore, combined inhibition of neuronal and inducible NOS seems the most likely candidate for human clinical trials. Future studies should determine its safety and effectiveness in neonates, as well as a potential sex-specific neuroprotective effect. Researchers should strive to improve methodologic quality of animal intervention studies by using a systematic approach in conducting and reporting of these studies.

2-Iminobiotin Superimposed on Hypothermia Protects Human Neuronal Cells from Hypoxia-Induced Cell Damage: An in Vitro Study

Perinatal asphyxia represents one of the major causes of neonatal morbidity and mortality. Hypothermia is currently the only established treatment for hypoxic-ischemic encephalopathy (HIE), but additional pharmacological strategies are being explored to further reduce the damage after perinatal asphyxia. The aim of this study was to evaluate whether 2-iminobiotin (2-IB) superimposed on hypothermia has the potential to attenuate hypoxia-induced injury of neuronal cells. In vitro hypoxia was induced for 7 h in neuronal IMR-32 cell cultures. Afterwards, all cultures were subjected to 25 h of hypothermia (33.5°C), and incubated with vehicle or 2-IB (10, 30, 50, 100, and 300 ng/ml). Cell morphology was evaluated by brightfield microscopy. Cell damage was analyzed by LDH assays. Production of reactive oxygen species (ROS) was measured using fluorometric assays. Western blotting for PARP, Caspase-3, and the phosphorylated forms of akt and erk1/2 was conducted. To evaluate early apoptotic events and signaling, cell protein was isolated 4 h post-hypoxia and human apoptosis proteome profiler arrays were performed. Twenty-five hour after the hypoxic insult, clear morphological signs of cell damage were visible and significant LDH release as well as ROS production were observed even under hypothermic conditions. Post-hypoxic application of 2-IB (10 and 30 ng/ml) reduced the hypoxia-induced LDH release but not ROS production. Phosphorylation of erk1/2 was significantly increased after hypoxia, while phosphorylation of akt, protein expression of Caspase-3 and cleavage of PARP were only slightly increased. Addition of 2-IB did not affect any of the investigated proteins. Apoptosis proteome profiler arrays performed with cellular protein obtained 4 h after hypoxia revealed that post-hypoxic application of 2-IB resulted in a ≥ 25% down regulation of 10/35 apoptosis-related proteins: Bad, Bax, Bcl-2, cleaved Caspase-3, TRAILR1, TRAILR2, PON2, p21, p27, and phospho Rad17. In summary, addition of 2-IB during hypothermia is able to attenuate hypoxia-induced neuronal cell damage in vitro. Combination treatment of hypothermia with 2-IB could be a promising strategy to reduce hypoxia-induced neuronal cell damage and should be considered in further animal and clinical studies.

Insights into the neuroprotective mechanisms of 2-iminobiotin employing an in-vitro model of hypoxic-ischemic cell injury

Several animal models have been used to simulate cerebral hypoxia-ischemia and suggested neuroprotective effects of the biotin analogue 2-iminobiotin (2-IB). The aims of this study were to employ a human in-vitro hypoxia model to confirm protective effects of 2-IB on neuronal cells, determine the optimal neuroprotective concentrations of 2-IB and scrutinize underlying cellular effects of 2-IB. Neuronal IMR-32 cells were exposed to hypoxia employing an enzymatic hypoxia system and were thereafter incubated with various concentrations of 2-IB (10 to 300ng/ml). Cell damage, metabolic activity and generation of reactive oxygen species were quantified using colorimetric/fluorometric lactate dehydrogenase (LDH), tetrazolium-based (MTS) and reactive oxygen species assays. Proteome profiling arrays were performed to evaluate the regulation of cell stress protein expression by hypoxia and 2-IB. Seven hours of hypoxia led to morphological changes in IMR-32 cultures, increased neuronal cell damage (P<0.001), reduction of metabolic activity (P<0.01) and enhanced reactive oxygen species production (P<0.05). Post-hypoxic application of 2-IB (30ng/ml) attenuated hypoxia-induced LDH release (P<0.05) and increased metabolic activity of IMR-32 cells (P<0.05), while reactive oxygen species production was only by trend decreased. Array-based protein expression profiling revealed that 2-IB attenuated the expression of several hypoxia-induced cell stress-associated proteins by more than 25% (pp38α, HIF2α, ADAMTS1, pHSP27, PON2, PON3 and p27). Hypoxia-induced neuronal cell damage can be simulated using the described in-vitro model. 2-IB inhibits hypoxia-mediated neurotoxicity most efficiently at 30ng/ml and the underlying mechanisms involve a downregulation of stress-associated protein expression. Our results suggest 2-IB as a potential drug for the treatment of perinatal hypoxia-ischemia.

Neonatal Encephalopathy: Update on Therapeutic Hypothermia and Other Novel Therapeutics

Neonatal encephalopathy (NE) is a major cause of neonatal mortality and morbidity. Therapeutic hypothermia (TH) is standard treatment for newborns at 36 weeks of gestation or greater with intrapartum hypoxia-related NE. Term and late preterm infants with moderate to severe encephalopathy show improved survival and neurodevelopmental outcomes at 18 months of age after TH. TH can increase survival without increasing major disability, rates of an IQ less than 70, or cerebral palsy. Neonates with severe NE remain at risk of death or severe neurodevelopmental impairment. This review discusses the evidence supporting TH for term or near term neonates with NE.

Drugs for neuroprotection after birth asphyxia: Pharmacologic adjuncts to hypothermia

An adverse outcome is still encountered in 45% of full-term neonates with perinatal asphyxia who are treated with moderate hypothermia. At present pharmacologic therapies are developed to be added to hypothermia. In the present article, these potential neuroprotective interventions are described based on the molecular pathways set in motion during fetal hypoxia and following reoxygenation and reperfusion after birth. These pathways include excessive production of excitotoxins with subsequent over-stimulation of NMDA receptors and calcium influx in neuronal cells, excessive production of reactive oxygen and nitrogen species, activation of inflammation leading to inappropriate apoptosis, and loss of neurotrophic factors. Possibilities for pharmacologic combination therapy, where each drug will be administered based on the optimal point of time in the cascade of destructive molecular reactions, may further reduce brain damage due to perinatal asphyxia.

Plasma Biomarkers of Oxidative Stress in Neonatal Brain Injury

Perinatal encephalopathy is a leading cause of lifelong disability. Increasing evidence indicates that the pathogenesis of perinatal brain damage is much more complex than originally thought, with multiple pathways involved. An important role of oxidative stress (OS) in the pathogenesis of brain injury is recognized for preterm and term infants. This article examines potential reliable and specific OS biomarkers that can be used in premature and term infants for the early detection and follow-up of the most common neonatal brain injuries, such as hypoxic-ischemic encephalopathy, intraventricular hemorrhage, and periventricular leukomalacia. The next step will be to explore the correlation between brain-specific OS biomarkers and functional brain outcomes.

Motor and cognitive deficits due to permanent cerebral hypoperfusion/ischemia improve by pomegranate seed extract in rats

This study aimed to evaluate the effect of two weeks oral administration of Pomegranate Seed Extract (PGSE) on active avoidance memory and motor coordination activities after permanent bilateral common carotid arteries occlusion (2CCAO) in male adult rats. Adult male albino rats of Wistar strain (250 ± 20 g, 3-4 months) were used. Animals were divided into eight groups with 10 in each: (1) Sham operated (Sh); (2) Ischemic (I); (3) Ischemic received 100 mg kg(-1) PGSE, orally (I+E100); (4) Ischemic received 200 mg kg(-1) PGSE, orally (I+E200); (5) Ischemic received 400 mg kg(-1) PGSE, orally (I+E400); (6) Ischemic received 800 mg kg(-1) PGSE, orally (I+ E800); (7) Ischemic received 2 mL kg(-1) normal saline, orally (I+Veh); (8) Sham operated received 400 mg kg(-1) PGSE, orally (Sh+E400). In order to make 2CCAO an animal Cerebral Hypoperfusion Ischemia (CHI) model, carotid arteries were ligatured and then bilaterally cut. To evaluate active avoidance task, Correct Response Percentages (CRP) was measured by Y-maze apparatus and motor coordination activity was evaluated using standard behavioral tests by rotarod apparatus in all the rats. It was found that memory. Memory and motor coordination activities were significantly impaired in the rats after CHI (p < 0.01). PGSE treatment significantly improved impairment of memory and motor coordination in the rats with 2CCAO (p < 0.001). PGSE exhibited therapeutic potential for memory and muscular coordination, which was most likely related at least in some part to its antioxidative and free radical scavenging actions.

Pathophysiology and neuroprotection of global and focal perinatal brain injury: lessons from animal models

BACKGROUND

Arterial ischemic stroke occurs more frequently in term newborns than in the elderly, and brain immaturity affects mechanisms of ischemic injury and recovery. The susceptibility to injury of the brain was assumed to be lower in the perinatal period as compared with childhood. This concept was recently challenged by clinical studies showing marked motor disabilities after stroke in neonates, with the severity of motor and cortical sensory deficits similar in both perinatal and childhood ischemic stroke. Our understanding of the triggers and the pathophysiological mechanisms of perinatal stroke has greatly improved in recent years, but many factors remain incompletely understood.

METHODS

In this review, we focus on the pathophysiology of perinatal stroke and on therapeutic strategies that can protect the immature brain from the consequences of stroke by targeting inflammation and brain microenvironment.

RESULTS

Studies in neonatal rodent models of cerebral ischemia have suggested a potential role for soluble inflammatory molecules as important modulators of injury and recovery. A great effort is underway to investigate neuroprotective molecules based on our increasing understanding of the pathophysiology.

CONCLUSION

In this review, we provide a comprehensive summary of new insights concerning pathophysiology of focal and global perinatal brain injury and their implications for new therapeutic approaches.

Mitochondria: hub of injury responses in the developing brain

Progress in the field of mitochondrial biology in the past few years has shown that mitochondrial activities go beyond bioenergetics. These new aspects of mitochondrial physiology and pathophysiology have important implications for the immature brain. A picture emerges in which mitochondrial biogenesis, mitophagy, migration, and morphogenesis are crucial for brain development and synaptic pruning, and play a part in recovery after acute insults. Mitochondria also affect brain susceptibility to injury, and mitochondria-directed interventions can make the immature brain highly resistant to acute injury. Finally, the mitochondrion is a platform for innate immunity, contributes to inflammation in response to infection and acute damage, and participates in antiviral and antibacterial defence. Understanding of these new aspects of mitochondrial function will provide insights into brain development and neurological disease, and enable discovery and development of new strategies for treatment.

Capacity of HSYA to inhibit nitrotyrosine formation induced by focal ischemic brain injury

Peroxynitrite-mediated protein tyrosine nitration represents a crucial pathogenic mechanism of stroke. Hydroxysafflor yellow A (HSYA) is the most important active component of the safflower plant. Here we assess the neuroprotective efficacy of HSYA and investigate the mechanism through anti-nitrative pathway. Rats were subjected to 60-min ischemia followed by reperfusion. HSYA (2.5-10mg/kg) was injected at 1h after ischemia onset. Other groups received HSYA (10mg/kg) treatment at 3-9h after onset. Infarct volume, brain edema, and neurological score were evaluated at 24h after ischemia. Nitrotyrosine and inducible NO synthase (iNOS) expression, as well as NO level (nitrate/nitrite) in ischemic cortex was examined within 24h after ischemia. The ability of HSYA to scavenge peroxynitrite was evaluated in vitro. Infarct volume was significantly decreased by HSYA (P<0.05), with a therapeutic window of 3h after ischemia at dose of 10mg/kg. HSYA treatment also reduced brain edema and improved neurological score (P<0.05). Nitrotyrosine formation was dose- and time-dependently inhibited by HSYA. The time window of HSYA in decreasing protein tyrosine nitration paralleled its action in infarct volume. HSYA also greatly reduced iNOS expression and NO content at 24h after ischemia, suggesting prevention of peroxynitrite generation from iNOS. In vitro, HSYA blocked authentic peroxynitrite-induced tyrosine nitration in bovine serum albumin and primary cortical neurons. Collectively, our results indicated that post-ischemic HSYA treatment attenuates brain ischemic injury which is at least partially due to reducing nitrotyrosine formation, possibly by the combined mechanism of its peroxynitrite scavenging ability and its reduction in iNOS production.

Partial neuroprotection by nNOS inhibition during profound asphyxia in preterm fetal sheep

Preterm brain injury is partly associated with hypoxia-ischemia starting before birth. Excessive nitric oxide production during HI may cause nitrosative stress, leading to cell membrane and mitochondrial damage. We therefore tested the hypothesis that therapy with a new, selective neuronal nitric oxide synthase (nNOS) inhibitor, JI-10 (0.022mg/kg bolus, n=8), given 30min before 25min of complete umbilical cord occlusion was protective in preterm fetal sheep at 101-104day gestation (term is 147days), compared to saline (n=8). JI-10 had no effect on fetal blood pressure, heart rate, carotid and femoral blood flow, total EEG power, nuchal activity, temperature or intracerebral oxygenation on near-infrared spectroscopy during or after occlusion. JI-10 was associated with later onset of post-asphyxial seizures compared with saline (p<0.05), and attenuation of the subsequent progressive loss of cytochrome oxidase (p<0.05). After 7days recovery, JI-10 was associated with improved neuronal survival in the caudate nucleus (p<0.05), but not the putamen or hippocampus, and more CNPase positive oligodendrocytes in the periventricular white matter (p<0.05). In conclusion, prophylactic nNOS inhibition before profound asphyxia was associated with delayed onset of seizures, slower decline of cytochrome oxidase and partial white and gray matter protection, consistent with protection of mitochondrial function.

Inflammatory responses in hypoxic ischemic encephalopathy

Inflammation plays a critical role in mediating brain injury induced by neonatal hypoxic ischemic encephalopathy (HIE). The mechanisms underlying inflammatory responses to ischemia may be shared by neonatal and adult brains; however, HIE exhibits a unique inflammation phenotype that results from the immaturity of the neonatal immune system. This review will discuss the current knowledge concerning systemic and local inflammatory responses in the acute and subacute stages of HIE. The key components of inflammation, including immune cells, adhesion molecules, cytokines, chemokines and oxidative stress, will be reviewed, and the differences between neonatal and adult inflammatory responses to cerebral ischemic injury will also be discussed.

Brain susceptibility to oxidative stress in the perinatal period

Oxidative stress (OS) occurs at birth in all newborns as a consequence of the hyperoxic challenge due to the transition from the hypoxic intrauterine environment to extrauterine life. Free radical (FRs) sources such as inflammation, hyperoxia, hypoxia, ischaemia-reperfusion, neutrophil and macrophage activation, glutamate and free iron release, all increases the OS during the perinatal period. Newborns, and particularly preterm infants, have reduced antioxidant defences and are not able to counteract the harmful effects of FRs. Energy metabolism is central to life because cells cannot exist without an adequate supply of ATP. Due to its growth, the mammalian brain can be considered as a steady-state system in which ATP production matches ATP utilisation. The developing brain is particularly sensitive to any disturbances in energy generation, and even a short-term interruption can lead to long-lasting and irreversible damage. Whenever energy failure develops, brain damage can occur. Accumulating evidence indicates that OS is implicated in the pathogenesis of many neurological diseases, such as intraventricular haemorrhage, hypoxic-ischaemic encephalopathy and epilepsy.

Pathophysiology of an hypoxic–ischemic insult during the perinatal period

Hypoxia-ischemia is a leading cause of morbidity and mortality in the perinatal period with an incidence of 1/4000 live births. Biochemical events such as energy failure, membrane depolarization, brain edema, an increase of neurotransmitter release and inhibition of uptake, an increase of intracellular Ca(2+), production of oxygen-free radicals, lipid peroxidation, and a decrease of blood flow are triggered by hypoxia-ischemia and may lead to brain dysfunction and neuronal death. These abnormalities can result in mental impairments, seizures, and permanent motor deficits, such as cerebral palsy. The physical and emotional strain that is placed on the children affected and their families is enormous. The care that these individuals need is not only confined to childhood, but rather extends throughout their entire life span, so it is very important to understand the pathophysiology that follows a hypoxic-ischemic insult. This review will highlight many of the mechanisms that lead to neuronal death and include the emerging area of white matter injury as well as the role of inflammation and will provide a summary of therapeutic strategies. Hypothermia and oxygen will also be discussed as treatments that currently lack a specific target in the hypoxic/ischemic cascade.

Prenatal hypoxia, habituation memory and oxidative stress

Hypoxia-ischemia (HI) is characterized by a reduced supply of oxygen during pregnancy, which leads to both central nervous system and peripheral injuries in the foetus, resulting in impairment in its development. The purpose of this study was to investigate behavioural changes and systemic oxidative stress in adult animals that have been affected by HI during pregnancy. HI was induced by the occlusion of the maternal uterine artery with aneurysm clamps for a period of 45 min on the 18th gestational day. Animals from the sham group were submitted to same surgical procedure as the HI animals, without occlusion of the maternal uterine artery. The control group consisted of non-manipulated healthy animals. At postnatal day 90, the pups were submitted to behavioural tests followed by blood collection. HI adult animals presented an increase in anxiety behaviour and a lack of habituation compared to both sham and control groups. Oxidative damage, assessed by protein and lipid oxidation in serum, did not differ between HI and sham-operated animals. However, HI animals presented reduced activity of the glutathione peroxidase enzyme and increased formation of nitrite, indicating alterations in the systemic antioxidant repair system. Our results suggest an association among HI, systemic oxidative stress and behavioural alterations.

Pathophysiological role of inflammatory molecules in paediatric ischaemic brain injury

Ischaemic stroke is one of the major causes of death and lifelong disability also in the paediatric population. Strong scientific effort has been put to clarify the pathophysiology of this disease in adults. However, only few studies have been performed in children. Preliminary results indicate that pathophysiological processes might differently affect the poststroke neuronal injury in neonates as compared to children. During the neural development, selective molecular mechanisms might be differently triggered by an ischaemic insult, thus potentially resulting in defined postischaemic clinical outcomes. Basic research studies in neonatal animal models of cerebral ischaemia have recently shown a potential role of soluble inflammatory molecules (such as cytokines, chemokines and oxidants) as pivotal players of neuronal injury in both perinatal and childhood ischaemic stroke. Although larger clinical trials are still needed to confirm these preliminary results, the potential benefits of selective treatments targeting inflammation in perinatal asphyxia encephalopathy might represent a promising investigation field in the near future. In this review, we will update evidence on the pathophysiological role of soluble inflammatory mediators in neonatal and childhood ischaemic stroke. Recent evidence on potential anti-inflammatory treatments to improve paediatric stroke prognosis will be discussed.

Differential effect of intrauterine hypoxia on caspase 3 and DNA fragmentation in fetal guinea pig hearts and brains

The aim of this study is to quantify the effect of intrauterine hypoxia (HPX) and the role of nitric oxide (NO) on the apoptotic enzyme, caspase 3, and DNA fragmentation in fetal heart and brain. Hypoxia and NO are important regulators of apoptosis, although this has been little studied in the fetal organs. We investigated the effect of intrauterine HPX on apoptosis and the role of NO in both fetal hearts and brains. Pregnant guinea pigs were exposed to room temperature (N = 14) or 10.5% O₂ (N = 12) for 14 days prior to term (term = 65 days) and administered water or L-N6-(1-iminoethyl)-lysine (LNIL), an inducible nitric oxide synthase (iNOS) inhibitor, for 10 days. Fetal hearts and brains were excised from anesthetized near-term fetuses for study. Chronic HPX decreased pro- and active caspase 3, caspase 3 activity, and DNA fragmentation levels in fetal hearts compared with normoxic controls. L-N6-(1-iminoethyl)-lysine prevented the HPX-induced decrease in caspase 3 activity but did not alter DNA fragmentation levels. In contrast, chronic HPX increased both apoptotic indices in fetal brains, which were inhibited by LNIL. Thus, the effect of HPX on apoptosis differs between fetal organs, and NO may play an important role in modulating these effects.

Increased concentrations of both NMDA receptor co-agonists D-serine and glycine in global ischemia: a potential novel treatment target for perinatal asphyxia

Worldwide, perinatal asphyxia is an important cause of morbidity and mortality among term-born children. Overactivation of the N-methyl-d-aspartate receptor (NMDAr) plays a central role in the pathogenesis of cerebral hypoxia–ischemia, but the role of both endogenous NMDAr co-agonists d-serine and glycine remains largely elusive. We investigated d-serine and glycine concentration changes in rat glioma cells, subjected to oxygen and glucose deprivation (OGD) and CSF from piglets exposed to hypoxia–ischemia by occlusion of both carotid arteries and hypoxia. We illustrated these findings with analyses of cerebrospinal fluid (CSF) from human newborns affected by perinatal asphyxia. Extracellular concentrations of glycine and d-serine were markedly increased in rat glioma cells exposed to OGD, presumably through increased synthesis from l-serine. Upon reperfusion glycine concentrations normalized and d-serine concentrations were significantly lowered. The in vivo studies corroborated the finding of initially elevated and then normalizing concentrations of glycine and decreased d-serine concentrations upon reperfusion These significant increases of both endogenous NMDAr co-agonists in combination with elevated glutamate concentrations, as induced by global cerebral ischemia, are bound to lead to massive NMDAr activation, excitotoxicity and neuronal damage. Influencing these NMDAr co-agonist concentrations provides an interesting treatment target for this common, devastating and currently poorly treatable condition.

Hepcidin is involved in iron regulation in the ischemic brain

Oxidative stress plays an important role in neuronal injuries caused by cerebral ischemia. It is well established that free iron increases significantly during ischemia and is responsible for oxidative damage in the brain. However, the mechanism of this ischemia-induced increase in iron is not completely understood. In this report, the middle cerebral artery occlusion (MCAO) rat model was performed and the mechanism of iron accumulation in cerebral ischemia-reperfusion was studied. The expression of L-ferritin was significantly increased in the cerebral cortex, hippocampus, and striatum on the ischemic side, whereas H-ferritin was reduced in the striatum and increased in the cerebral cortex and hippocampus. The expression level of the iron-export protein ferroportin1 (FPN1) significantly decreased, while the expression of transferrin receptor 1 (TfR1) was increased. In order to elucidate the mechanisms of FPN1 regulation, we studied the expression of the key regulator of FPN1, hepcidin. We observed that the hepcidin level was significantly elevated in the ischemic side of the brain. Knockdown hepcidin repressed the increasing of L-ferritin and decreasing of FPN1 invoked by ischemia-reperfusion. The results indicate that hepcidin is an important contributor to iron overload in cerebral ischemia. Furthermore, our results demonstrated that the levels of hypoxia-inducible factor-1α (HIF-1α) were significantly higher in the cerebral cortex, hippocampus and striatum on the ischemic side; therefore, the HIF-1α-mediated TfR1 expression may be another contributor to the iron overload in the ischemia-reperfusion brain.

Reprint of "The developing oligodendrocyte: key cellular target in brain injury in the premature infant"

Brain injury in the premature infant, a problem of enormous importance, is associated with a high risk of neurodevelopmental disability. The major type of injury involves cerebral white matter and the principal cellular target is the developing oligodendrocyte. The specific phase of the oligodendroglial lineage affected has been defined from study of both human brain and experimental models. This premyelinating cell (pre-OL) is vulnerable because of a series of maturation-dependent events. The pathogenesis of pre-OL injury relates to operation of two upstream mechanisms, hypoxia-ischemia and systemic infection/inflammation, both of which are common occurrences in premature infants. The focus of this review and of our research over the past 15-20 years has been the cellular and molecular bases for the maturation-dependent vulnerability of the pre-OL to the action of the two upstream mechanisms. Three downstream mechanisms have been identified, i.e., microglial activation, excitotoxicity and free radical attack. The work in both experimental models and human brain has identified a remarkable confluence of maturation-dependent factors that render the pre-OL so exquisitely vulnerable to these downstream mechanisms. Most importantly, elucidation of these factors has led to delineation of a series of potential therapeutic interventions, which in experimental models show marked protective properties. The critical next step, i.e., clinical trials in the living infant, is now on the horizon.

Selective vulnerability of rat brain regions to unconjugated bilirubin

Hippocampus is one of the brain regions most vulnerable to unconjugated bilirubin (UCB) encephalopathy, although cerebellum also shows selective yellow staining in kernicterus. We previously demonstrated that UCB induces oxidative stress in cortical neurons, disruption of neuronal network dynamics, either in developing cortical or hippocampal neurons, and that immature cortical neurons are more prone to UCB-induced injury. Here, we studied if immature rat neurons isolated from cortex, cerebellum and hippocampus present distinct features of oxidative stress and cell dysfunction upon UCB exposure. We also explored whether oxidative damage and its regulation contribute to neuronal dysfunction induced by hyperbilirubinemia, considering neurite extension and ramification, as well as cell death. Our results show that UCB induces nitric oxide synthase expression, as well as production of nitrites and cyclic guanosine monophosphate in immature neurons, mainly in those from hippocampus. After exposure to UCB, hippocampal neurons presented the highest content of reactive oxygen species, disruption of glutathione redox status and cell death, when compared to neurons from cortex or cerebellum. In particular, the results indicate that cells exposed to UCB undertake an adaptive response that involves DJ-1, a multifunctional neuroprotective protein implicated in the maintenance of cellular oxidation status. However, longer neuronal exposure to UCB caused down-regulation of DJ-1 expression, especially in hippocampal neurons. In addition, a greater impairment in neurite outgrowth and branching following UCB treatment was also noticed in immature neurons from hippocampus. Interestingly, pre-incubation with N-acetylcysteine, a precursor of glutathione synthesis, protected neurons from UCB-induced oxidative stress and necrotic cell death, preventing DJ-1 down-regulation and neuritic impairment. Taken together, these data point to oxidative injury and disruption of neuritic network as hallmarks in hippocampal susceptibility to UCB. Most importantly, they also suggest that local differences in glutathione content may account to the different susceptibility between brain regions exposed to UCB.

The developing oligodendrocyte: key cellular target in brain injury in the premature infant

Brain injury in the premature infant, a problem of enormous importance, is associated with a high risk of neurodevelopmental disability. The major type of injury involves cerebral white matter and the principal cellular target is the developing oligodendrocyte. The specific phase of the oligodendroglial lineage affected has been defined from study of both human brain and experimental models. This premyelinating cell (pre-OL) is vulnerable because of a series of maturation-dependent events. The pathogenesis of pre-OL injury relates to operation of two upstream mechanisms, hypoxia-ischemia and systemic infection/inflammation, both of which are common occurrences in premature infants. The focus of this review and of our research over the past 15-20 years has been the cellular and molecular bases for the maturation-dependent vulnerability of the pre-OL to the action of the two upstream mechanisms. Three downstream mechanisms have been identified, i.e., microglial activation, excitotoxicity and free radical attack. The work in both experimental models and human brain has identified a remarkable confluence of maturation-dependent factors that render the pre-OL so exquisitely vulnerable to these downstream mechanisms. Most importantly, elucidation of these factors has led to delineation of a series of potential therapeutic interventions, which in experimental models show marked protective properties. The critical next step, i.e., clinical trials in the living infant, is now on the horizon.

The pig as a model animal for studying cognition and neurobehavioral disorders

In experimental animal research, a short phylogenetic distance, i.e., high resemblance between the model species and the species to be modeled is expected to increase the relevance and generalizability of results obtained in the model species. The (mini)pig shows multiple advantageous characteristics that have led to an increase in the use of this species in studies modeling human medical issues, including neurobehavioral (dys)functions. For example, the cerebral cortex of pigs, unlike that of mice or rats, has cerebral convolutions (gyri and sulci) similar to the human neocortex. We expect that appropriately chosen pig models will yield results of high translational value. However, this claim still needs to be substantiated by research, and the area of pig research is still in its infancy. This chapter provides an overview of the pig as a model species for studying cognitive dysfunctions and neurobehavioral disorders and their treatment, along with a discussion of the pros and cons of various tests, as an aid to researchers considering the use of pigs as model animal species in biomedical research.

Patterns of neonatal hypoxic-ischaemic brain injury

Enormous progress has been made in assessing the neonatal brain, using magnetic resonance imaging (MRI). In this review, we will describe the use of MRI and proton magnetic resonance spectroscopy in detecting different patterns of brain injury in (full-term) human neonates following hypoxic–ischaemic brain injury and indicate the relevance of these findings in predicting neurodevelopmental outcome.

Patterns of neonatal hypoxic-ischaemic brain injury

Enormous progress has been made in assessing the neonatal brain, using magnetic resonance imaging (MRI). In this review, we will describe the use of MRI and proton magnetic resonance spectroscopy in detecting different patterns of brain injury in (full-term) human neonates following hypoxic-ischaemic brain injury and indicate the relevance of these findings in predicting neurodevelopmental outcome.

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.

Does inflammation after stroke affect the developing brain differently than adult brain?

The immature brain is prone to hypoxic-ischemic encephalopathy and stroke. The incidence of arterial stroke in newborns is similar to that in the elderly. However, the pathogenesis of ischemic brain injury is profoundly affected by age at the time of the insult. Necrosis is a dominant type of neuronal cell death in adult brain, whereas widespread neuronal apoptosis is unique for the early postnatal synaptogenesis period. The inflammatory response, in conjunction with excitotoxic and oxidative responses, is the major contributor to ischemic injury in both the immature and adult brain, but there are several areas where these responses diverge. We discuss the contribution of various inflammatory mechanisms to injury and repair after cerebral ischemia in the context of CNS immaturity. In particular, we discuss the role of lower expression of selectins, a more limited leukocyte transmigration, undeveloped complement pathways, a more rapid microglial activation, differences in cytokine and chemokine interplay, and a different threshold to oxidative stress in the immature brain. We also discuss differences in activation of intracellular pathways, especially nuclear factor kappaB and mitogen-activated protein kinases. Finally, we discuss emerging data on both the supportive and adverse roles of inflammation in plasticity and repair after stroke.

Perinatal neuroprotection by muscle relaxants against hypoxic-ischemic lesions: Is it a possible hypothesis?

The incidence of neurological disabilities ascribable to hypoxia-ischemia in the perinatal period (HIPP) is rising. Glutamate plays a key role in the development of cerebral damage related to HIPP: it triggers the excitotoxic cascade by overactivating N-methyl-D-aspartate receptors (NMDA), implicated as important mediators of both learning and neuronal development. Laudanosine is the metabolite of the neuromuscular blocking drugs, atracurium and cisatracurium, administered as part of obstetric general anesthesia. In elective cesarean section, laudanosine may be found in the fetus with a mean umbilical vein concentration of 26 (range 6-60) ng ml(-1). At nM concentrations, laudanosine can activate alpha4beta2 nACh subtype receptors. Activation of alpha4beta2 nAChRs provided neuroprotection against NMDA excitotoxic cascade in a neonatal model. Taken together, experimental and clinical data widely indicate a potential neuroprotective role for laudanosine against perinatal brain lesions of hypoxic-ischemic origin. The clinical relevance is that administration of the neuromuscular blocking drugs atracurium and cisatracurium, administered as part of general anesthesia for cesarean section, could be potentially therapeutic in obstetric anesthesia. Therefore, we find laudanosine to be an attractive proposal for further studies in the prevention of neurological disabilities ascribable to perinatal injury related to hypoxia and ischemia.

Antioxidant therapy and neuroprotection in the newborn

Injury to the perinatal brain is a leading cause of childhood mortality and lifelong disability. Despite recent improvements in neonatal care, no effective treatment for perinatal brain lesions is available. The newborn, especially if preterm, is highly prone to oxidative stress (OS) and to the toxic effect of free radicals (FRs). At birth, the newborn is exposed to a relatively hyperoxic environment caused by an increased oxygen bioavailability with greatly enhanced generation of FRs. Additional sources (e.g., inflammation, hypoxia, ischemia, glutamate and free iron release) occur, magnifying OS. In the preterm baby, the perinatal transition is accompanied by the immaturity of the antioxidant systems and the reduced ability to induce efficient homeostatic mechanisms designed to control overproduction of cell-damaging FRs. Improved understanding of the pathophysiological mechanism involved in perinatal brain lesions helps to identify potential targets for neuroprotective interventions, and the knowledge of these mechanisms has enabled scientists to develop new therapeutic strategies that have confirmed their neuroprotective effects in animal studies. Considering the growing role of OS in preterm newborn morbidity in respect to the higher risk of FR damage in these babies, erythropoietin, allopurinol, melatonin and hypothermia demonstrate great promise as potential neuroprotectans. This article provides an overview of the pathogenesis of FR-mediated diseases of the newborn and the antioxidant strategies now tested in order to reduce OS and its damaging effects.