Perinatal brain injury

Organelle-level toxicity of nanometals relevant to titanium implants. Original research and comprehensive literature overview

OBJECTIVE

This study analyzed organelle toxicities of nanometals applied as free formulations or titanium rod-coating materials in rats.

METHODS

All materials were injected intraperitoneally, including the physiological saline applied to the control group. The first experimental group was implanted with nanosilver-coated titanium rods, and the second, third, and fourth groups received free nanosilver at rising levels. The fifth group was implanted with nanosilver, nanocopper, and nanozinc-coated titanium rods, and the sixth group received the same nanometals as free formulations. Light and electron microscopy and ICP-Mass Spectrometry were utilized to determine the neural, hepatic, and renal toxicities and tissue metal levels.

RESULTS

In brains, neuropil, myelin, and cellular damages occurred, especially in groups receiving high-dose nanosilver or nanometal combinations. Histiocyte accumulation and dark mitochondria within hepatocytes were discernible in the liver. Kidneys were the organs that were most severely affected by nanometal toxicity. The nephrotoxicity was apparent with the perturbations of the membrane infoldings and mitochondrial damage in the proximal and distal convoluted epithelia. Large angular peroxisomes developed inside the mesangial cells, and Golgi bodies increased in epithelial cells. Systemic metal levels increased on the thirtieth and prominently dropped on the sixtieth day.

CONCLUSION

These results provide insights into the extent of injury and organelle targets of nanometals and will guide optimizing the nanomaterials and implants used in the surgical practice.

Mechanisms of Mitochondrial Oxidative Stress in Brain Injury: From Pathophysiology to Therapeutics

Mitochondrial oxidative stress has been implicated in various forms of brain injury, both traumatic and non-traumatic. Due to its oxidative demand, the brain is intimately dependent on its mitochondrial functioning. However, there remains appreciable heterogeneity in the development of these injuries regarding ROS and their effect on the sequelae. These include traumatic insults such as TBIs and intracranial hemorrhaging secondary to this. In a different vein, such injuries may be attributed to other etiologies such as infection, neoplasm, or spontaneous hemorrhage (strokes, aneurysms). Clinically, the manner of treatment may also be adjusted in relation to each injury and its unique progression in the context of ROS. In the current review, then, the authors highlight the role of mitochondrial ROS in various forms of brain injury, emphasizing both the collective and unique elements of each form. Lastly, these narratives are met with the current therapeutic landscape and the role of emerging therapies in treating reactive oxygen species in brain injuries.

Role of integrating cannabinoids and the endocannabinoid system in neonatal hypoxic-ischaemic encephalopathy

Neonatal hypoxic-ischaemic events, which can result in long-term neurological impairments or even cell death, are among the most significant causes of brain injury during neurodevelopment. The complexity of neonatal hypoxic-ischaemic pathophysiology and cellular pathways make it difficult to treat brain damage; hence, the development of new neuroprotective medicines is of great interest. Recently, numerous neuroprotective medicines have been developed to treat brain injuries and improve long-term outcomes based on comprehensive knowledge of the mechanisms that underlie neuronal plasticity following hypoxic-ischaemic brain injury. In this context, understanding of the medicinal potential of cannabinoids and the endocannabinoid system has recently increased. The endocannabinoid system plays a vital neuromodulatory role in numerous brain regions, ensuring appropriate control of neuronal activity. Its natural neuroprotection against adult brain injury or acute brain injury also clearly demonstrate the role of endocannabinoid signalling in modulating neuronal activity in the adult brain. The goal of this review is to examine how cannabinoid-derived compounds can be used to treat neonatal hypoxic-ischaemic brain injury and to assess the critical function of the endocannabinoid system and its potential for use as a new neuroprotective treatment for neonatal hypoxic-ischaemic brain injury.

Sensorimotor development of male and female rats subjected to neonatal anoxia

Neonatal hypoxic-ischemic encephalopathy (HIE) is one of the most important reasons for morbidity and mortality in term-born infants. HIE impacts early somatic, neurological, and motor development including social. To illustrate the damages in the sensorimotor system, an adapted and validated model of neonatal anoxia is used. This study evaluated the sex differences in Wistar rats, neurological reflex, and motor development at the suckling period. Short- and long-term impairments associated with sex differences were observed. In general, anoxic males were more affected in comparison to their control group and to anoxic females. Long-lasting effects of the injury in adolescent rats predominately affected males. Similar to previous studies, we also found a decrease in the number of the substantia nigra cells in both sexes, compared to their control. So far, the results indicate that HIE caused neurobehavioral alterations and asymmetrical motor behavior with brain damage, possibly related to cognitive impairments previously observed at adolescence. These alterations may represent a useful endpoint for studying the efficacy of potential strategies that may improve the developmental consequences of a perinatal asphyxia insult in humans.

Amniotic LPS-Induced Apoptosis in the Fetal Brain Is Suppressed by Vaginal LPS Preconditioning but Is Promoted by Continuous Ischemic Reperfusion

Chorioamnionitis (CAM) is an increasingly common disease affecting pregnant women which derives from bacterial vaginosis. In different clinical cases, it has been shown that CAM can cause multiple risk factors for fetal brain damage, such as infection, and intra-uterine asphyxia. However, the molecular mechanism remains unknown. In this study, we established a novel CAM mouse model by exposing pregnant mice to a combination of three risk factors: vaginal lipopolysaccharides (LPS), amniotic LPS, and ischemic reperfusion. We found amniotic LPS caused Parkinson's disease-like fetal brain damage, in a dose and time-dependent manner. Moreover, the mechanism of this fetal brain damage is apoptosis induced by amniotic LPS but it was inhibited by being pretreated with a vaginal LPS challenge before amniotic LPS injection. In contrast, amniotic LPS with continuous ischemic reperfusion caused a higher level of apoptotic cell death than amniotic LPS alone. In particular, a potential neuroprotective biomarker phosphorylation (p)-CREB (ser133) appeared in only vaginal LPS preconditioned before amniotic LPS, whereas ischemic reperfusion triggered IKK phosphorylation after amniotic LPS. Despite the need for many future investigations, this study also discussed a developed understanding of the molecular mechanism of how these phenotypes occurred.

The effects of short time hyperoxia on glutamate concentration and glutamate transporters expressions in brain of neonatal rats

Preterm infants often suffer from impaired postnatal brain development, and glutamate excitotoxicity is identified as a pivotal mechanism of hyperoxia-induced neurological abnormality. We aimed to investigate the effect of short time hyperoxia on glutamate homeostasis and glutamate transporters expressions in immature brain. Six-day-old (P6) rat pups were exposed to 80% oxygen for 24 h (the hyperoxia group) or placed in atmospheric air (the control group). The concentrations of glutamate and γ-aminobutyric acid (GABA) in immature cerebrum and cerebellum at P7, P14 and P21 were determined by ELISA. The mRNA levels of glutamate transporters including excitatory amino acid transporter 1 (EAAT1), EAAT2, EAAT3, vesicular glutamate transporter 1 (VGLUT1) and VGLUT2 in brain were determined by qPCR. Glutamate accumulation was induced by hyperoxia both in immature cerebrum and cerebellum at P7 but got gradually attenuated at P14 and P21, as evidenced by the changes of glutamate and GABA concentrations. Hyperoxia also induced sustained glutamatic oxidative stress in both cerebrum and cerebellum, as GSH (reduced glutathione) levels in the hyperoxia group were constantly higher than the control group at three examined time-points. Furthermore, at P7, the expressions of all glutamate transporters decreased in both cerebrum and cerebellum except that of EAAT1. At P21, VGLUT2 in cerebrum and EAAT1, EAAT3 and VGLUT2 in cerebellum still displayed significant decrease in expression levels upon hyperoxia stimulation. Taken together, our results indicate that hyperoxia induces glutamate accumulation in brain of rat pups, which is associated with increased oxidative stress and decreased expressions of glutamate transporters.

Effects of hypoxia ischemia on caspase-3 expression and neuronal apoptosis in the brain of neonatal mice

Effects of hypoxia ischemia on caspase-3 expression and neuronal apoptosis in the brain of neonatal mice were investigated. Twenty-five neonatal CD1 mice aged 1 week were selected and randomly divided into sham-operation group (n=8) and newborn hypoxia ischemia encephalopathy (NHIE) model group (n=17). The messenger ribonucleic acid (mRNA) expression levels of caspase-3 and Fas ligand (FasL) in brain tissues of mice in both groups were detected via reverse transcription-polymerase chain reaction (RT-PCR). The protein expression levels of caspase-3 and FasL in mice in both groups were detected via western blotting. Moreover, apoptosis of brain tissues was detected using the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), and caspase-3 protein expression level in brain tissues was detected using immunohistochemical methods. Results of RT-PCR and western blotting revealed that compared with those in sham-operation group, caspase-3 and FasL expression levels in model group were significantly increased. Results of TUNEL showed that the number of apoptotic neurons in model group was significantly increased. Besides, results of immunohistochemical detection manifested that the caspase-3 protein expression level in model group was obviously increased. Hypoxia ischemia can lead to significant increase of caspase-3 expression and increase of neuronal apoptosis in the brain of neonatal mice.

The first case of neonatal priapism during hypothermia for hypoxic-ischemic encephalopathy and a literature review

Neonatal priapism is a rare condition with only 26 described cases in literature since 1879. It is defined as a persistent penile erection occurring in the first 28 days of life, lasting at least 4 h that usually happens in the first days (from 2 to 12 days). It is a very different condition compared to the adult one because in newborns it is a relatively benign phenomenon. As a result of this paucity of described cases, classification and management are not well known by most of neonatologists and currently there are no established guidelines for its management. Most cases are idiopathic but other aetiologies are possible (polycythemia, blood transfusion and drugs). We describe our only case, which occurred during hypothermia therapy and review the literature to clarify the best choice in management of this rare entity.

Advanced Pediatric Neurosonography Techniques: Contrast-Enhanced Ultrasonography, Elastography, and Beyond

Recent technical advances in neurosonography continue broadening the diagnostic utility, sensitivity, and specificity of ultrasound for detecting intracranial abnormalities bed side. The clinical and functional applications of neurosonography have significantly expanded since the 1980s when transcranial Doppler sonography first allowed anatomic and hemodynamic delineation of the intracranial vessels through the thin temporal skull. In the past few years, contrast-enhanced ultrasonography, elastography, 3D/4D reconstruction tools, and high-resolution microvessel imaging techniques have further enhanced the diagnostic significance of neurosonography. Given these advances, a thorough familiarity with these new techniques and devices is crucial for a successful clinical application allowing improved patient care. It is essential that future neurosonography studies compare these advanced techniques against the current "gold standard" computed tomography and magnetic resonance imaging to assure the accuracy of their diagnostic potential. This review will provide a comprehensive update on currently available advanced neurosonography techniques.

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.

Neuronal Damage Induced by Perinatal Asphyxia Is Attenuated by Postinjury Glutaredoxin-2 Administration

The general disruption of redox signaling following an ischemia-reperfusion episode has been proposed as a crucial component in neuronal death and consequently brain damage. Thioredoxin (Trx) family proteins control redox reactions and ensure protein regulation via specific, oxidative posttranslational modifications as part of cellular signaling processes. Trx proteins function in the manifestation, progression, and recovery following hypoxic/ischemic damage. Here, we analyzed the neuroprotective effects of postinjury, exogenous administration of Grx2 and Trx1 in a neonatal hypoxia/ischemia model. P7 Sprague-Dawley rats were subjected to right common carotid ligation or sham surgery, followed by an exposure to nitrogen. 1 h later, animals were injected i.p. with saline solution, 10 mg/kg recombinant Grx2 or Trx1, and euthanized 72 h postinjury. Results showed that Grx2 administration, and to some extent Trx1, attenuated part of the neuronal damage associated with a perinatal hypoxic/ischemic damage, such as glutamate excitotoxicity, axonal integrity, and astrogliosis. Moreover, these treatments also prevented some of the consequences of the induced neural injury, such as the delay of neurobehavioral development. To our knowledge, this is the first study demonstrating neuroprotective effects of recombinant Trx proteins on the outcome of neonatal hypoxia/ischemia, implying clinical potential as neuroprotective agents that might counteract neonatal hypoxia/ischemia injury.

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.

Effect of Marine Collagen Peptides on Physiological and Neurobehavioral Development of Male Rats with Perinatal Asphyxia

Asphyxia during delivery produces long-term deficits in brain development. We investigated the neuroprotective effects of marine collagen peptides (MCPs), isolated from Chum Salmon skin by enzymatic hydrolysis, on male rats with perinatal asphyxia (PA). PA was performed by immersing rat fetuses with uterine horns removed from ready-to-deliver rats into a water bath for 15 min. Caesarean-delivered pups were used as controls. PA rats were intragastrically administered with 0.33 g/kg, 1.0 g/kg and 3.0 g/kg body weight MCPs from postnatal day 0 (PND 0) till the age of 90-days. Behavioral tests were carried out at PND21, PND 28 and PND 90. The results indicated that MCPs facilitated early body weight gain of the PA pups, however had little effects on early physiological development. Behavioral tests revealed that MCPs facilitated long-term learning and memory of the pups with PA through reducing oxidative damage and acetylcholinesterase (AChE) activity in the brain, and increasing hippocampus phosphorylated cAMP-response element binding protein (p-CREB) and brain derived neurotrophic factor (BDNF) expression.

Combination treatment with ethyl pyruvate and IGF-I exerts neuroprotective effects against brain injury in a rat model of neonatal hypoxic-ischemic encephalopathy

Neonatal hypoxic-ischemic (HI) brain injury causes severe brain damage in newborns. Following HI injury, rapidly accumulating oxidants injure neurons and interrupt ongoing developmental processes. The antioxidant, sodium pyruvate, has been shown to reduce neuronal injury in neonatal rats under conditions of oxygen glucose deprivation (OGD) and HI injury. In this study, we evaluated the effects of ethyl pyruvate (EP) and insulin-like growth factor-I (IGF-I) alone or in combination in a similar setting. For this purpose, we used an in vitro model involving primary neonatal rat cortical neurons subjected to OGD for 2.5 h and an in vivo model involving unilateral carotid ligation in rats on post-natal day 7 with exposure to 8% hypoxia for 2.5 h. The cultured neurons were examined by lactate dehydrogenase (LDH) and cell viability assays. For the in vivo experiments, behavioral development was evaluated by the foot fault test at 4 weeks of recovery. 2,3,5-Triphenyltetrazolium chloride monohydrate and cresyl violet staining were used to evaluate HI injury. The injured neurons were Fluoro-Jade B-labeled, new neuroprecursors were double labeled with bromodeoxyuridine (BrdU) and doublecortin, new mature neurons were BrdU-labeled and neuronal nuclei were labeled by immunofluorescence. Under conditions of OGD, the LDH levels increased and neuronal viability decreased. Treatment with 0.5 mM EP or 25 ng/ml IGF-I protected the neurons (P<0.05), exerting additive effects. Similarly, either the early administration of EP or delayed treatment with IGF-I protected the neonatal rat brains against HI injury and improved neurological performance and these effects were also additive. This effect may be the result of reduced neuronal injury, and enhanced neurogenesis and maturation. On the whole, our findings demonstrate that the combination of the early administration of EP with delayed treatment with IGF-I exerts neuroprotective effects against HI injury in neonatal rat brains.

Perinatal asphyxia leads to PARP-1 overactivity, p65 translocation, IL-1β and TNF-α overexpression, and apoptotic-like cell death in mesencephalon of neonatal rats: prevention by systemic neonatal nicotinamide administration

Perinatal asphyxia (PA) is a leading cause of neuronal damage in newborns, resulting in long-term neurological and cognitive deficits, in part due to impairment of mesostriatal and mesolimbic neurocircuitries. The insult can be as severe as to menace the integrity of the genome, triggering the overactivation of sentinel proteins, including poly (ADP-ribose) polymerase-1 (PARP-1). PARP-1 overactivation implies increased energy demands, worsening the metabolic failure and depleting further NAD⁺ availability. Using a global PA rat model, we report here evidence that hypoxia increases PARP-1 activity, triggering a signalling cascade leading to nuclear translocation of the NF-κB subunit p65, modulating the expression of IL-1β and TNF-α, pro-inflammatory molecules, increasing apoptotic-like cell death in mesencephalon of neonate rats, monitored with Western blots, qPCR, TUNEL and ELISA. PARP-1 activity increased immediately after PA, reaching a maximum 1–8 h after the insult, while activation of the NF-κB signalling pathway was observed 8 h after the insult, with a >twofold increase of p65 nuclear translocation. IL-1β and TNF-α mRNA levels were increased 24 h after the insult, together with a >twofold increase in apoptotic-like cell death. A single dose of the PARP-1 inhibitor nicotinamide (0.8 mmol/kg, i.p.), 1 h post delivery, prevented the effect of PA on PARP-1 activity, p65 translocation, pro-inflammatory cytokine expression and apoptotic-like cell death. The present study demonstrates that PA leads to PARP-1 overactivation, increasing the expression of pro-inflammatory cytokines and cell death in mesencephalon, effects prevented by systemic neonatal nicotinamide administration, supporting the idea that PARP-1 inhibition represents a therapeutic target against the effects of PA.

Intrauterine ischemic reperfusion switches the fetal transcriptional pattern from HIF-1α- to P53-dependent regulation in the murine brain

Ischemic reperfusion (IR) during the perinatal period is a known causative factor of fetal brain damage. So far, both morphologic and histologic evidence has shown that fetal brain damage can be observed only several hours to days after an IR insult has occurred. Therefore, to prevent fetal brain damage under these circumstances, a more detailed understanding of the underlying molecular mechanisms involved during an acute response to IR is necessary. In the present work, pregnant mice were exposed to IR on day 18 of gestation by clipping one side of the maternal uterine horn. Simultaneous fetal electrocardiography was performed during the procedure to verify that conditions resulting in fetal brain damage were met. Fetal brain sampling within 30 minutes after IR insult revealed molecular evidence that a fetal response was indeed triggered in the form of inhibition of the Akt-mTOR-S6 synthesis pathway. Interestingly, significant changes in mRNA levels for both HIF-1α and p53 were apparent and gene regulation patterns were observed to switch from a HIF-1α-dependent to a p53-dependent process. Moreover, pre-treatment with pifithrin-α, a p53 inhibitor, inhibited protein synthesis almost completely, revealing the possibility of preventing fetal brain damage by prophylactic pifithrin-α treatment.

Correlation of EEG, CT, and MRI Brain with Neurological Outcome at 12 Months in Term Newborns with Hypoxic Ischemic Encephalopathy

Objective:

To correlate electroencephalogram (EEG), computed tomography (CT), and magnetic resonance imaging (MRI) brain with neurological outcome at 12 months in term neonates with hypoxic ischemic encephalopathy.

Design:

Prospective observational study.

Setting:

Neonatal intensive care unit (NICU) in a tertiary care teaching hospital.

Materials and Methods:

The study was conducted between June 2010 and November 2011. Consecutive term neonates with perinatal asphyxia and hypoxic ischemic encephalopathy were the subjects. All babies were managed as per standard protocol. EEG was done as soon as the baby was stable and CT brain within 7 days. MRI was done at 3 months. Neurodevelpmental assessment was done at 12 months.

Results:

Of the 31 babies, four died and one was lost to follow-up. Neurodevelopmental at 12 months of age was normal in 15 babies. EEG was normal in six babies and all of them had a normal neurodevelopment. Thirteen of the 14 babies with burst suppression pattern were abnormal (P<0.001). CT brain was normal in 14 and all of them had normal neurodevelopment (P<0.001), while 11 of the 12 with cerebral edema had abnormal outcome (P<0.001). Of the 16 babies with normal MRI, 14 were normal, while all six babies with abnormal signals in the cortex and thalamus had abnormal outcome (P=0.002).

Conclusions:

A normal EEG and CT brain in a term newborn with hypoxic ischemic encephalopathy (HIE) is associated with good neurological outcome. Burst suppression pattern in EEG, bleeds, or hypodensities in the CT and involvement of basal ganglia/thalamus in the MRI are predictors of abnormal outcome.

Stem cell therapy to protect and repair the developing brain: a review of mechanisms of action of cord blood and amnion epithelial derived cells

In the research, clinical, and wider community there is great interest in the use of stem cells to reduce the progression, or indeed repair brain injury. Perinatal brain injury may result from acute or chronic insults sustained during fetal development, during the process of birth, or in the newborn period. The most readily identifiable outcome of perinatal brain injury is cerebral palsy, however, this is just one consequence in a spectrum of mild to severe neurological deficits. As we review, there are now clinical trials taking place worldwide targeting cerebral palsy with stem cell therapies. It will likely be many years before strong evidence-based results emerge from these trials. With such trials underway, it is both appropriate and timely to address the physiological basis for the efficacy of stem-like cells in preventing damage to, or regenerating, the newborn brain. Appropriate experimental animal models are best placed to deliver this information. Cell availability, the potential for immunological rejection, ethical, and logistical considerations, together with the propensity for native cells to form teratomas, make it unlikely that embryonic or fetal stem cells will be practical. Fortunately, these issues do not pertain to the use of human amnion epithelial cells (hAECs), or umbilical cord blood (UCB) stem cells that are readily and economically obtained from the placenta and umbilical cord discarded at birth. These cells have the potential for transplantation to the newborn where brain injury is diagnosed or even suspected. We will explore the novel characteristics of hAECs and undifferentiated UCB cells, as well as UCB-derived endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs), and how immunomodulation and anti-inflammatory properties are principal mechanisms of action that are common to these cells, and which in turn may ameliorate the cerebral hypoxia and inflammation that are final pathways in the pathogenesis of perinatal brain injury.

Oxidative stress in neonatology: a review

Free radicals are highly reactive oxidizing agents containing one or more unpaired electrons. Both in human and veterinary neonathology, it is generally accepted that oxidative stress functions as an important catalysator of neonatal disease. Soon after birth, many sudden physiological and environmental conditions make the newborn vulnerable for the negative effects of oxidative stress, which potentially can impair neonatal vitality. As a clinician, it is important to have in depth knowledge about factors affecting maternal/neonatal oxidative status and the cascades of events that enrol when the neonate is subjected to oxidative stress. This report aims at providing clinicians with an up-to-date review about oxidative stress in neonates across animal species. It will be emphasized which handlings and treatments that are applied during neonatal care or resuscitation can actually impose oxidative stress upon the neonate. Views and opinions about maternal and/or neonatal antioxydative therapy will be shared.

Environmental Enrichment Synergistically Improves Functional Recovery by Transplanted Adipose Stem Cells in Chronic Hypoxic-Ischemic Brain Injury

We investigated the effects of environmental enrichment (EE) on the function of transplanted adipose stem cells (ASCs) and the combined effect of EE and ASC transplantation on neurobehavioral function in an animal model of chronic hypoxic-ischemic (HI) brain injury. HI brain damage was induced in 7-day-old mice by unilateral carotid artery ligation and exposure to hypoxia (8% O2 for 90 min). At 6 weeks of age, the mice were randomly injected with either ASCs or PBS into the striatum and were randomly assigned to either EE or standard cages (SC), comprising ASC-EE ( n = 18), ASC-SC ( n = 19), PBS-EE ( n = 12), PBS-SC ( n = 17), and untreated controls ( n = 23). Rotarod, forelimb-use asymmetry, and grip strength tests were performed to evaluate neurobehavioral function. The fate of transplanted cells and the levels of endogenous neurogenesis, astrocyte activation, and paracrine factors were also measured. As a result, EE and ASC transplantation synergistically improved rotarod latency, forelimb-use asymmetry, and grip strength compared to those of the other groups. The number of engrafted ASCs and βIII-tubulin+ neurons derived from the transplanted ASCs was significantly higher in mice in EE than those in SC. EE and ASC transplantation also synergistically increased BrdU+βIII-tubulin+ neurons, GFAP+ astrocytic density, and fibroblast growth factor 2 (FGF2) level but not the level of CS-56+ glial scarring in the striatum. In conclusion, EE and ASC transplantation synergistically improved neurobehavioral functions. The underlying mechanisms of this synergism included enhanced repair processes such as higher engraftment of the transplanted ASCs, increased endogenous neurogenesis and astrocytic activation coupled with upregulation of FGF2.

Using the endocannabinoid system as a neuroprotective strategy in perinatal hypoxic-ischemic brain injury

One of the most important causes of brain injury in the neonatal period is a perinatal hypoxic-ischemic event. This devastating condition can lead to long-term neurological deficits or even death. After hypoxic-ischemic brain injury, a variety of specific cellular mechanisms are set in motion, triggering cell damage and finally producing cell death. Effective therapeutic treatments against this phenomenon are still unavailable because of complex molecular mechanisms underlying hypoxic-ischemic brain injury. After a thorough understanding of the mechanism underlying neural plasticity following hypoxic-ischemic brain injury, various neuroprotective therapies have been developed for alleviating brain injury and improving long-term outcomes. Among them, the endocannabinoid system emerges as a natural system of neuroprotection. The endocannabinoid system modulates a wide range of physiological processes in mammals and has demonstrated neuroprotective effects in different paradigms of acute brain injury, acting as a natural neuroprotectant. The aim of this review is to study the use of different therapies to induce long-term therapeutic effects after hypoxic-ischemic brain injury, and analyze the important role of the endocannabinoid system as a new neuroprotective strategy against perinatal hypoxic-ischemic brain injury.

Transplantation of human umbilical cord blood cells mediated beneficial effects on apoptosis, angiogenesis and neuronal survival after hypoxic-ischemic brain injury in rats

Transplantation of human umbilical cord blood (hucb) cells in a model of hypoxic-ischemic brain injury led to the amelioration of lesion-impaired neurological and motor functions. However, the mechanisms by which transplanted cells mediate functional recovery after brain injury are largely unknown. In this study, the effects of hucb cell transplantation were investigated in this experimental paradigm at the cellular and molecular level. As the pathological cascade in hypoxic-ischemic brain injury includes inflammation, reduced blood flow, and neuronal cell death, we analyzed the effects of peripherally administered hucb cells on these detrimental processes, investigating the expression of characteristic marker proteins. Application of hucb cells after perinatal hypoxic-ischemic brain injury correlated with an increased expression of the proteins Tie-2 and occludin, which are associated with angiogenesis. Lesion-induced apoptosis, determined by expression of cleaved caspase-3, decreased, whereas the number of vital neurons, identified by counting of NeuN-positive cells, increased. In addition, we observed an increase in the expression of neurotrophic and pro-angiogenic growth factors, namely BDNF and VEGF, in the lesioned brain upon hucb cell transplantation. The release of neurotrophic factors mediated by transplanted hucb cells might cause a lower number of neurons to undergo apoptosis and result in a higher number of living neurons. In parallel, the increase of VEGF might cause growth of blood vessels. Thus, hucb transplantation might contribute to functional recovery after brain injury mediated by systemic or local effects.

Quercetin in hypoxia-induced oxidative stress: novel target for neuroprotection

Oxidative stress in the central nervous system is one of the key players for neurodegeneration. Thus, antioxidants could play important roles in treating several neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and aging-related brain disorders. This review is focused on the new developments in oxidative stress-induced neurodegeneration. Further, based on our own investigations, new roles of quercetin, an antioxidant compound in hypoxia and ischemia induced neuroprotection in relation to suppression of oxidative stress, improvement in behavioral function, reduction in infarct volume, brain swelling, and cellular injury in both in vivo and in vitro models are discussed. Our new findings clearly suggest that antioxidant compounds have potential role in therapeutic strategies to treat neurodegenerative diseases in clinical settings.

Cannabinoid as a neuroprotective strategy in perinatal hypoxic-ischemic injury

Perinatal hypoxia-ischemia remains the single most important cause of brain injury in the newborn, leading to death or lifelong sequelae. Because of the fact that there is still no specific treatment for perinatal brain lesions due to the complexity of neonatal hypoxic-ischemic pathophysiology, the search of new neuroprotective therapies is of great interest. In this regard, therapeutic possibilities of the endocannabinoid system have grown lately. The endocannabinoid system modulates a wide range of physiological processes in mammals and has demonstrated neuroprotective effects in different paradigms of acute brain injury, acting as a natural neuroprotectant. Concerning perinatal asphyxia, the neuroprotective role of this endogenous system is emerging these years. The present review mainly focused on the current knowledge of the cannabinoids as a new neuroprotective strategy against perinatal hypoxic-ischemic brain injury.

Head Ultrasound and MR imaging in the evaluation of neonatal encephalopathy: competitive or complementary imaging studies?

Magnetic resonance (MR) imaging is superior to ultrasonography (US) for the evaluation and prognostication of neonates with neonatal encephalopathy (NE). Nonetheless, US may provide important information early in the course of NE and can be used to document the evolution of lesions. This article provides an overview of useful findings in the US evaluation of infants with NE. Although many of the findings do not appear as conspicuous or as extensively as they do on MR imaging, recognition and familiarity with subtle head US abnormalities may allow head US to play an important complementary role to MR imaging in the evaluation of infants with NE.

Melatonin promotes proliferation and differentiation of neural stem cells subjected to hypoxia in vitro

Melatonin, an endogenously produced neurohormone secreted by the pineal gland, has a variety of physiological functions and neuroprotective effects. It can modulate the functions of neural stem cells (NSCs) including proliferation and differentiation in embryonic brain tissue but its effect and mechanism on the stem cells in hypoxia remains to be explored. Here, we show that melatonin stimulates proliferation of NSCs during hypoxia. Additionally, it also promoted the differentiation of NSCs into neurons. However, it did not appear to exert an obvious effect on the differentiation of astrocytes. The present results have further shown that the promotional effect of NSCs proliferation by melatonin involved the MT1 receptor and increased phosphorylation of ERK1/2. The effect of melatonin on differentiation of NSCs is linked to altered expression of differentiation-related genes. In the light of these findings, it is suggested that melatonin may be beneficial as a supplement for treatment of neonatal hypoxic-ischemic brain injury for promoting the proliferation and differentiation of NSCs.

Pathophysiology of perinatal asphyxia: can we predict and improve individual outcomes?

Perinatal asphyxia occurs still with great incidence whenever delivery is prolonged, despite improvements in perinatal care. After asphyxia, infants can suffer from short- to long-term neurological sequelae, their severity depend upon the extent of the insult, the metabolic imbalance during the re-oxygenation period and the developmental state of the affected regions. Significant progresses in understanding of perinatal asphyxia pathophysiology have achieved. However, predictive diagnostics and personalised therapeutic interventions are still under initial development. Now the emphasis is on early non-invasive diagnosis approach, as well as, in identifying new therapeutic targets to improve individual outcomes. In this review we discuss (i) specific biomarkers for early prediction of perinatal asphyxia outcome; (ii) short and long term sequelae; (iii) neurocircuitries involved; (iv) molecular pathways; (v) neuroinflammation systems; (vi) endogenous brain rescue systems, including activation of sentinel proteins and neurogenesis; and (vii) therapeutic targets for preventing or mitigating the effects produced by asphyxia.

Birth asphyxia as the major complication in newborns: moving towards improved individual outcomes by prediction, targeted prevention and tailored medical care

Perinatal Asphyxia—oxygen deficit at delivery—can lead to severe hypoxic ischaemic organ damage in newborns followed by a fatal outcome or severe life-long pathologies. The severe insults often cause neurodegenerative diseases, mental retardation and epilepsies. The mild insults lead to so-called “minimal brain-damage disorders” such as attention deficits and hyperactivity, but can also be associated with the development of schizophrenia and life-long functional psychotic syndromes. Asphyxia followed by re-oxygenation can potentially lead to development of several neurodegenerative pathologies, diabetes type 2 and cancer. The task of individual prediction, targeted prevention and personalised treatments before a manifestation of the life-long chronic pathologies usually developed by newborns with asphyxic deficits, should be given the extraordinary priority in neonatology and paediatrics. Socio-economical impacts of educational measures and advanced strategies in development of robust diagnostic approaches targeted at effected molecular pathways, biomarker-candidates and potential drug-targets for tailored treatments are reviewed in the paper.

Potential utility of melatonin as an antioxidant during pregnancy and in the perinatal period

Reactive oxygen species (ROS) play a critical role in the pathogenesis of various diseases during pregnancy and the perinatal period. Newborns are more prone to oxidative stress than individuals later in life. During pregnancy, increased oxygen demand augments the rate of production of ROS and women, even during normal pregnancies, experience elevated oxidative stress compared with non-pregnant women. ROS generation is also increased in the placenta during preeclampsia. Melatonin is a highly effective direct free-radical scavenger, indirect antioxidant, and cytoprotective agent in human pregnancy and it appears to be essential for successful pregnancy. This suggests a role for melatonin in human reproduction and in neonatal pathologies (asphyxia, respiratory distress syndrome, sepsis, etc.). This review summarizes current knowledge concerning the role for melatonin in human pregnancy and in the newborn. Numerous studies agree that short-term melatonin therapy is highly effective in reducing complications during pregnancy and in the neonatal period. No significant toxicity or treatment-related side effects with long-term melatonin therapy in children and adults have been reported. Treatment with melatonin might result in a wide range of health benefits, including improved quality of life and reduced healthcare costs.

Umbilical cord blood cell transplantation after brain ischemia--from recovery of function to cellular mechanisms

Cell transplantation has been proposed as a potential approach to the treatment of neurological disorders. One cell population of interest consists of human umbilical cord blood (hUCB) cells, which have previously been shown to be useful for reparative medicine in haematological diseases. However, hUCB cells are also capable of differentiating into various non-haematopoietic cells, including those of the neural lineage. Moreover, hUCB cells can secrete numerous neurotrophic factors and modulate immune function and inflammatory reaction. Several studies on animal models of ischemic brain injury have demonstrated the potential of hUCB cells to minimize damage and promote recovery after ischemic brain injury.This review focuses on the treatment of both stroke and perinatal hypoxic-ischemic brain injury using hUCB cells. We discuss the therapeutic effects demonstrated after hUCB cell transplantation and emphasize possible mechanisms counteracting pathophysiological events of ischemia, thus leading to the generation of a regenerative environment that allows neural plasticity and functional recovery. The therapeutic functional effects of hUCB cells observed in animal models make the transplantation of hUCB cells a promising experimental approach in the treatment of ischemic brain injury. Together with its availability, low risk of transplantation, immaturity of cells, and simple route of application, hUCB transplantation may stand a good chance of being translated into a clinical setting for the therapy of ischemic brain injury.

Perinatal asphyxia: current status and approaches towards neuroprotective strategies, with focus on sentinel proteins

Delivery is a stressful and risky event menacing the newborn. The mother-dependent respiration has to be replaced by autonomous pulmonary breathing immediately after delivery. If delayed, it may lead to deficient oxygen supply compromising survival and development of the central nervous system. Lack of oxygen availability gives rise to depletion of NAD⁺ tissue stores, decrease of ATP formation, weakening of the electron transport pump and anaerobic metabolism and acidosis, leading necessarily to death if oxygenation is not promptly re-established. Re-oxygenation triggers a cascade of compensatory biochemical events to restore function, which may be accompanied by improper homeostasis and oxidative stress. Consequences may be incomplete recovery, or excess reactions that worsen the biological outcome by disturbed metabolism and/or imbalance produced by over-expression of alternative metabolic pathways. Perinatal asphyxia has been associated with severe neurological and psychiatric sequelae with delayed clinical onset. No specific treatments have yet been established. In the clinical setting, after resuscitation of an infant with birth asphyxia, the emphasis is on supportive therapy. Several interventions have been proposed to attenuate secondary neuronal injuries elicited by asphyxia, including hypothermia. Although promising, the clinical efficacy of hypothermia has not been fully demonstrated. It is evident that new approaches are warranted. The purpose of this review is to discuss the concept of sentinel proteins as targets for neuroprotection. Several sentinel proteins have been described to protect the integrity of the genome (e.g. PARP-1; XRCC1; DNA ligase IIIα; DNA polymerase β, ERCC2, DNA-dependent protein kinases). They act by eliciting metabolic cascades leading to (i) activation of cell survival and neurotrophic pathways; (ii) early and delayed programmed cell death, and (iii) promotion of cell proliferation, differentiation, neuritogenesis and synaptogenesis. It is proposed that sentinel proteins can be used as markers for characterising long-term effects of perinatal asphyxia, and as targets for novel therapeutic development and innovative strategies for neonatal care.

IFATS collection: The conditioned media of adipose stromal cells protect against hypoxia-ischemia-induced brain damage in neonatal rats

Adipose tissue stroma contains a population of mesenchymal stem cells, which support repair when administered to damaged tissues, in large part through secreted trophic factors. We directly tested the ability of media collected from cultured adipose-derived stem cells (ASCs) to protect neurons in a rat model of brain hypoxic-ischemic (HI) injury. Concentrated conditioned medium from cultured rat ASCs (ASC-CM) or control medium was infused through the jugular vein of neonatal Sprague-Dawley rats subjected to HI injury. The ASC-CM was administered either 1 hour before or 24 hours after induction of injury. Analysis at 1 week indicated that administration at both time points significantly protected against hippocampal and cortical volume loss. Analysis of parallel groups for behavioral and learning changes at 2 months postischemia demonstrated that both treated groups performed significantly better than the controls in Morris water maze functional tests. Subsequent post-mortem evaluation of brain damage at the 2-month time point confirmed neuronal loss to be similar to that observed at 1 week for all groups. We have identified several neurotrophic factors in ASC-CM, particularly insulin-like growth factor-1 and brain-derived neurotrophic factor, which are important factors that could contribute to the protective effects of ASCs observed in studies with both in vitro and in vivo neuronal injury models. These data suggest that delivery of the milieu of factors secreted by ASCs may be a viable therapeutic option for treatment of HI, as well as other brain injuries.

Adenosine deaminase activity, lipid peroxidation and astrocyte responses in the cerebral cortex of rats after neonatal hypoxia ischemia

Hypoxia ischemia (HI) is a common cause of damage in the fetal and neonatal brain. Lifelong disabilities such as cerebral palsy, epilepsy, behavioral and learning disorders are some of the consequences of brain injury acquired in the perinatal periods. Inflammation and formation of free radicals appear to play key roles in neonatal HI. The aim of this study was to describe the chronological sequence of adenosine deaminase (ADA) activity, the oxidative damage changes and astrocyte response using the classic model of neonatal HI. We observed an increase in the activity of ADA and lipid peroxidation in the cerebral cortex 8 days after neonatal HI. This was accompanied by a GFAP-positive, and the degree of brain damage was determined histochemically by hematoxylin-eosin (HE). Taking into account the important anti-inflammatory role of adenosine, ADA may provide an efficient means for scavenging cell-surrounding adenosine and play an important part in subsequent events of neonatal HI in association with GFAP reactive gliosis. The present investigation showed that neonatal HI causes the increase of free radicals and significant damage in the cerebral cortex. The increase in ADA activity may reflect the activation of the immune system caused by HI because the morphological analysis exhibited a lymphocytic infiltration.

Oxidative stress of the newborn in the pre- and postnatal period and the clinical utility of melatonin

Newborns, and especially those delivered preterm, are probably more prone to oxidative stress than individuals later in life. Also during pregnancy, increased oxygen demand augments the rate of production of reactive oxygen species (ROS) and women, even with normal pregnancies, experience elevated oxidative stress and lipid peroxidation compared with nonpregnant women. Also, there appears to be an increase in ROS generation in the placenta of pre-eclamptic women. In comparison with healthy adults, newborn infants have lower levels of plasma antioxidants such as vitamin E, beta-carotene, and sulphydryl groups, lower levels of plasma metal binding proteins including ceruloplasmin and transferrin, and reduced activity of erythrocyte superoxide dismutase. This review summarizes conditions of newborns where there is elevated oxidative stress. Included in this group of conditions is asphyxia, respiratory distress syndrome and sepsis and the review also summarizes the literature related to clinical trials of antioxidant therapies and of melatonin, a highly effective antioxidant and free radical scavenger. The authors document there is general agreement that short-term melatonin therapy may be highly effective and that it has a remarkably benign safety profile, even when neonates are treated with pharmacological doses. Significant complications with long-term melatonin therapy in children and adults also have not been reported. None of the animal studies of maternal melatonin treatment or in postnatal life have shown any treatment-related side effects. The authors conclude that treatment with melatonin might result in a wide range of health benefits, improved quality of life and reduced healthcare costs and may help reduce complications in the neonatal period.

Proteomics- and metabolomics-based neonatal diagnostics in assessing and managing the critically ill neonate

The use of proteomic-based neonatal screening has been relatively limited until the present era and has focused primarily on the evaluation of newborns for inborn errors of metabolism. The future of proteomic-based screening seems to be much more encompassing, however. Tandem mass spectrometry and other related technologies are highly likely to be used in the evaluation of acute disease processes. Proteomics has the advantage over genomics of permitting a more direct look at an evolving disease process, because genomics primarily relates only the potential for a disease or abnormality to express itself. This article reviews the current uses of proteomics-based newborn evaluation and evaluates how this rapidly evolving area of medicine may be used to assess the fetus and the neonate in the near future.

Brain-regulated metabolic suppression during hibernation: a neuroprotective mechanism for perinatal hypoxia-ischemia

Hypoxic-ischemic brain injury in the perinatal period is a major cause of chronic disability and acute mortality in newborns. Despite numerous therapeutic strategies that reduce hypoxia-ischemia-induced damage in different experimental animal models, most of them have failed to translate to clinical therapies. This challenge calls for an urgent need to explore novel approaches to develop effective therapies for the clinical management of perinatal hypoxia-ischemia brain injury. This review focuses on studies that investigate neuroprotective related events during mammalian hibernation, characterized by dramatic reductions in several parameters including body temperature, oxygen consumption and heart rate, such that it is difficult to tell if the hibernating animal is dead or alive. The first part of this article reviews the mechanisms of metabolic suppression related events during hibernation. In the second part, hypoxic-ischemic events in the perinatal brain are discussed, and in turn, contrasted with brains experiencing metabolic suppression during mammalian hibernation. In the last part of this article, the diverse neuroprotective adaptations of hibernators and the mechanisms that might be involved in mammalian hibernation, and how they could in turn, contribute to neurprotection during perinatal hypoxia-ischemia related injuries are discussed. This article appraises the novel idea that knowledge of the central mechanisms involved in the regulatory metabolic suppression, during which; hibernators switch themselves off without dissolving their brains could represent brain neuroprotective strategy for the clinical management of perinatal hypoxia-ischemia brain injuries in newborns.

Doppler changes in the main fetal brain arteries at different stages of hemodynamic adaptation in severe intrauterine growth restriction

OBJECTIVE

To evaluate changes in the temporal evolution and regional distribution of arterial brain Doppler parameters in relation to different stages of hemodynamic adaptation in fetuses with severe intrauterine growth restriction (IUGR).

METHODS

Thirty-six fetuses with severe IUGR (<or= 32 weeks of gestation) and abnormal umbilical artery (UA) pulsatility index (PI) (mean > 2 SD) were evaluated longitudinally with pulsed Doppler ultrasound at four different hemodynamic stages: Stage 1 (n = 36), mean UA-PI > 2 SD or absent UA end-diastolic flow; Stage 2 (n = 34), abnormal middle cerebral artery (MCA) PI (mean < 2 SD); Stage 3 (n = 30), reversed UA end-diastolic flow; Stage 4 (n = 12), absent or reversed atrial flow in the ductus venosus. In addition, 36 normally grown fetuses were studied for comparison. PI and time-averaged maximum velocity (TAMXV) in the MCA and the anterior cerebral (ACA), pericallosal (PER) and posterior cerebral (PCA) arteries were measured.

RESULTS

In IUGR fetuses, PI values from all arteries were significantly reduced at Stage 2. At Stages 3 and 4, ACA-PI and PCA-PI did not change further, whereas MCA-PI and PER-PI showed a slight increase. In the ACA, MCA and PER, TAMXV in Stage 2 increased significantly. In Stages 3 and 4, ACA and PER-TAMXV remained unchanged, whereas MCA-TAMXV showed a slight decrease, mirroring the PI values. PCA-TAMXV values were similar to controls at all stages.

CONCLUSION

In IUGR fetuses, the brain arteries differ in the magnitude and time sequence of Doppler parameters in relation to systemic hemodynamic adaptation, suggesting the existence of regional brain redistribution processes.

Pituitary adenylate cyclase-activating polypeptide induces pial arteriolar vasodilation through cyclooxygenase-dependent and independent mechanisms in newborn pigs

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a cerebrovascular dilator and was found neuroprotective in numerous in vitro and in vivo models of cerebral ischemia. However, the mechanism of its cerebrovascular action is poorly known, especially in newborns. Therefore, we tested pial arteriolar responses to the two naturally occurring forms PACAP27 and 38 as well as to shorter sequences (PACAP6-27, 6-38, 1-15, 6-15, 20-31). We also investigated the involvement of nitric oxide synthase (NOS), cyclooxygenase-1 and -2 (COX-1 and -2) activity in PACAP-induced pial arteriolar responses using the NOS inhibitor N-omega-nitro-l-arginine methyl ester (L-NAME 15 mg/kg iv), the non-selective COX inhibitor indomethacin (5 mg/kg iv), and the selective COX-1 and COX-2 inhibitors SC-560 (1 mg/kg iv) and NS-398 (1 mg/kg iv), respectively. Anesthetized, ventilated piglets (n=127) were equipped with closed cranial windows, and pial arteriolar diameters were determined via intravital microscopy. Topical application of both natural PACAPs, but none of the PACAP segments, resulted in prominent, repeatable, dose-dependent vasodilation. Percentage changes ranged 5+/-1-29+/-6 (n=7) and 4+/-1-36+/-7 (n=9) to 10(-)(8) to 10(-)(6) M PACAP27 and 38 (mean+/-SEM), respectively. Vasodilation to both natural PACAPs was significantly reduced by co-application with PACAP6-27 or 6-38, but not by L-NAME. Indomethacin abolished PACAP38 but not PACAP27-induced vasodilation. Arteriolar responses to PACAP38 were also sensitive to SC-560 but not to NS-398 suggesting the unique involvement of COX-1 activity in this response. In summary, PACAP27 and 38 are potent vasodilators in the neonatal cerebral circulation with at least two distinct mechanisms of action: a COX-dependent and a COX-independent pathway.

Nicotinamide prevents the effect of perinatal asphyxia on dopamine release evaluated with in vivo microdialysis 3 months after birth

The present study shows that nicotinamide prevents the long-term effect of perinatal asphyxia on dopamine release monitored with in vivo microdialysis in the neostriatum of 3-month-old rats. Perinatal asphyxia was induced by immersing foetuses-containing uterine horns removed from ready-to-deliver rats into a water bath for 16 or 20 min. Sibling, spontaneous, and caesarean-delivered pups were used as controls. Saline or nicotinamide (0.8 mmol/kg, i.p.) was administered to control and asphyxia-exposed animals 24, 48, and 72 h after birth. After weaning, the rats were randomly distributed in laboratory cages for animal care under standard ad libitum laboratory conditions. Approximately 3 months after birth, control and asphyxia-exposed animals were implanted with microdialysis probes into the lateral neostriatum for measuring extracellular monoamine and metabolite levels with HPLC-coupled to an electrochemical detection system under basal, D-amphetamine, and K(+)-depolarising conditions. There was an asphyxia-dependent decrease of extracellular dopamine levels, mainly observed during the periods when D-amphetamine (100 microM) or KCl (100 mM) was added into the perfusion medium. Compared to that observed in caesarean-delivered controls, the effect of D-amphetamine on dopamine levels was decreased by approximately 30 and 70% in animals exposed to 16 and 20 min of perinatal asphyxia, respectively. The effect of K(+)-depolarisation was decreased by 45 and 83% in animals exposed to the same periods of asphyxia, respectively. Both effects were prevented by nicotinamide, even if the treatment started 24 h after the insult. The present results support the idea of nicotinamide as an interesting molecule, useful for protecting against anoxia/ischemia occurring at neonatal stages. Nicotinamide can help to restore NADH/NAD+ depletion, but also to inhibit PARP-1 overactivation, a mechanism of action that has attracted attention, representing a novel target for neuroprotection following insults involving energy failure.

Mass spectrometry in neonatal medicine and clinical diagnosis--the [corrected] potential use of mass spectrometry in neonatal brain [corrected] monitoring

This article discusses the application of mass spectroscopy, a technology that may have great potential for screening neonatal brain injury. This approach is anticipated to become increasingly important in neonatal and perinatal research and newborn care during the next few years.

Immature rat brain slices exposed to oxygen-glucose deprivation as an in vitro model of neonatal hypoxic-ischemic encephalopathy

To analyze whether exposure to oxygen-glucose deprivation (OGD) of immature rat brain slices might reproduce the main pathophysiologic events leading to neuronal death in neonatal hypoxic-ischemic encephalopathy (NHIE), 500 microm-thick brain slices were obtained from 7-day-old Wistar rats, and incubated in oxygenated physiological solution. In OGD group, oxygen and glucose were removed from the medium for 10-30 min (n = 25); then, slices were re-incubated in normal medium. In control group the medium composition remained unchanged (CG, n = 30). Medium samples were obtained every 30 min for 3 h. To analyze neuronal damage, slices were stained with Nissl and CA1 area of hippocampus and cortex were observed under microscopy. In addition, neuronal death was quantified as LDH released to the medium determined by spectrophotometry. Additionally, medium glutamate (Glu) levels were determined by HPLC and those of TNFalpha by ELISA, whereas inducible nitric oxide synthase expression was determined by Western blot performed on slices homogenate. Optimal OGD time was established in 20 min. After OGD, a significant decrease in the number of neurones in hippocampus and cortex was observed. LDH release was maximal at 30 min, when it was five-fold greater than in CG. Furthermore, medium Glu concentrations were 200 times greater than CG levels at the end of OGD period. A linear relationship between Glu and LDH release was demonstrated. Finally, 3 h after OGD a significant induction of iNOS as well as an increase in TNFalpha release were observed. In conclusion, OGD appears as a feasible and reproducible in vitro model, leading to a neuronal damage, which is physiopathologically similar to that found in NHIE.

Diazoxide preserves hypercapnia-induced arteriolar vasodilation after global cerebral ischemia in piglets

Diazoxide (Diaz), an activator of mitochondrial ATP-sensitive K+(mitoKATP) channels, is neuroprotective, but the mechanism of action is unclear. We tested whether Diaz preserves endothelium-dependent (hypercapnia) or -independent [iloprost (Ilo)] cerebrovascular dilator responses after ischemia-reperfusion (I/R) in newborn pigs and whether the effect of Diaz is sensitive to 5-hydroxydecanoate (5-HD), an inhibitor of mitoKATPchannels. Anesthetized, ventilated piglets ( n = 48) were equipped with closed cranial windows. Changes in diameter of pial arterioles were determined with intravital microscopy in response to graded hypercapnia (5–10% CO2-21% O2-balance N2, n = 25) or Ilo (0.1–1 μg/ml, n = 18) before and 1 h after 10 min of global I/R. Experimental groups were pretreated with vehicle, NS-398 (a selective cyclooxygenase-2 inhibitor, 1 mg/kg), Diaz (3 mg/kg), or 5-HD (20 mg/kg) + Diaz. Potential direct effects of Diaz and 5-HD on hypercapnic vasodilation were also tested in the absence of I/R ( n = 5). To confirm the direct effect of Diaz on mitochondria, mitochondrial membrane potential in cultured piglet cerebrovascular endothelial cells was monitored using Mito Tracker Red. Hypercapnia resulted in dose-dependent pial arteriolar vasodilation, which was attenuated by ∼70% after I/R in vehicle- and NS-398-treated animals. Diaz and 5-HD did not affect the CO2response. Diaz significantly preserved the postischemic vasodilation response to hypercapnia, but not to Ilo. Diaz depolarized mitochondria in cultured piglet cerebrovascular endothelial cells, and 5-HD completely abolished the protective effect of Diaz, both findings indicate a role for mitoKATPchannels. In summary, preservation of arteriolar dilator responsiveness by Diaz may contribute to neuroprotection.

Mechanisms of hyperbaric oxygen and neuroprotection in stroke

Cerebral vascular diseases, such as neonatal encephalopathy and focal or global cerebral ischemia, all result in reduction of blood flow to the affected regions, and cause hypoxia-ischemia, disorder of energy metabolism, activation of pathogenic cascades, and eventual cell death. Due to a narrow therapeutic window for neuroprotection, few effective therapies are available, and prognosis for patients with these neurological injuries remains poor. Hyperbaric oxygen (HBO) has been used as a primary or adjunctive therapy over the last 50 years with controversial results, both in experimental and clinical studies. In addition, the mechanisms of HBO on neuroprotection remain elusive. Early applications of HBO within a therapeutic window of 3-6h or delayed but repeated administration of HBO can either salvage injured neuronal tissues or promote neurobehavioral functional recovery. This review explores the discrepancies between experimental and clinical observations of HBO, focusing on its therapeutic window in brain injuries, and discusses the potential mechanisms of HBO neuroprotection.

Absence of cellular stress in brain after hypoxia induced by arousal from hibernation in Arctic ground squirrels

Although hypoxia tolerance in heterothermic mammals is well established, it is unclear whether the adaptive significance stems from hypoxia or other cellular challenge associated with euthermy, hibernation, or arousal. In the present study, blood gases, hemoglobin O2 saturation (S(O2), and indexes of cellular and physiological stress were measured during hibernation and euthermy and after arousal thermogenesis. Results show that arterial O2 tension (Pa(O2)) and S(O2) are severely diminished during arousal and that hypoxia-inducible factor (HIF)-1alpha accumulates in brain. Despite evidence of hypoxia, neither cellular nor oxidative stress, as indicated by inducible nitric oxide synthase (iNOS) levels and oxidative modification of biomolecules, was observed during late arousal from hibernation. Compared with rats, hibernating Arctic ground squirrels (Spermophilus parryii) are well oxygenated with no evidence of cellular stress, inflammatory response, neuronal pathology, or oxidative modification following the period of high metabolic demand necessary for arousal. In contrast, euthermic Arctic ground squirrels experience mild, chronic hypoxia with low S(O2) and accumulation of HIF-1alpha and iNOS and demonstrate the greatest degree of cellular stress in brain. These results suggest that Arctic ground squirrels experience and tolerate endogenous hypoxia during euthermy and arousal.