Mechanisms of hypoxic-ischemic injury in the term infant

Early Neuroprotective Effects of Bovine Lactoferrin Associated with Hypothermia after Neonatal Brain Hypoxia-Ischemia in Rats

Neonatal hypoxic-ischemic (HI) encephalopathy (HIE) in term newborns is a leading cause of mortality and chronic disability. Hypothermia (HT) is the only clinically available therapeutic intervention; however, its neuroprotective effects are limited. Lactoferrin (LF) is the major whey protein in milk presenting iron-binding, anti-inflammatory and anti-apoptotic properties and has been shown to protect very immature brains against HI damage. We hypothesized that combining early oral administration of LF with whole body hypothermia could enhance neuroprotection in a HIE rat model. Pregnant Wistar rats were fed an LF-supplemented diet (1 mg/kg) or a control diet from (P6). At P7, the male and female pups had the right common carotid artery occluded followed by hypoxia (8% O2 for 60') (HI). Immediately after hypoxia, hypothermia (target temperature of 32.5-33.5 °C) was performed (5 h duration) using Criticool®. The animals were divided according to diet, injury and thermal condition. At P8 (24 h after HI), the brain neurochemical profile was assessed using magnetic resonance spectroscopy (1H-MRS) and a hyperintense T2W signal was used to measure the brain lesions. The mRNA levels of the genes related to glutamatergic excitotoxicity, energy metabolism and inflammation were assessed in the right hippocampus. The cell markers and apoptosis expression were assessed using immunofluorescence in the right hippocampus. HI decreased the energy metabolites and increased lactate. The neuronal-astrocytic coupling impairments observed in the HI groups were reversed mainly by HT. LF had an important effect on astrocyte function, decreasing the levels of the genes related to glutamatergic excitotoxicity and restoring the mRNA levels of the genes related to metabolic support. When combined, LF and HT presented a synergistic effect and prevented lactate accumulation, decreased inflammation and reduced brain damage, pointing out the benefits of combining these therapies. Overall, we showed that through distinct mechanisms lactoferrin can enhance neuroprotection induced by HT following neonatal brain hypoxia-ischemia.

Perfusion system for studying dynamic metabolomics in rat brain slices exposed to oxygen-glucose deprivation using proton and phosphorus nuclear magnetic resonance

The aim of the current study was to establish a controlled and reproducible model to study metabolic changes during oxygen-glucose deprivation (OGD) in rat brain using a nuclear magnetic resonance (NMR)-compatible perfusion system. Rat brains were cut into 400-μm thick slices and perfused with artificial cerebrospinal fluid (aCSF) in a 10-mm NMR tube inside a 600-MHz NMR spectrometer. Four experimental conditions were tested: (1) continuous perfusion with aCSF with glucose and normoxia, and (2) 30-, (3) 60-, or (4) 120-min periods of OGD followed by reperfusion of aCSF containing glucose and normoxia. The energetic state of perfused brain slices was measured using phosphorus (³¹ P) NMR and metabolite changes were measured using proton (¹ H) NMR. aCSF samples were collected every 30 min and analyzed using ¹ H NMR. The sample temperature was maintained at 36.7 ± 0.1°C and was checked periodically throughout the experiments. Brain slice histology was compared before and after OGD in the perfusion system using hematoxylin-eosin-saffron staining. NMR data clearly distinguished three severity groups (mild, moderate, and severe) after 30, 60, and 120 min of OGD, respectively, compared with the control group. ³¹ P NMR spectra obtained from controls showed that phosphocreatine levels were stable for 5 h inside the perfusion system. Control ¹ H NMR spectra showed that lactate, N-acetylaspartic acid, glutamate, γ-aminobutyric acid, and creatine metabolite levels were stable over time, with lactate levels having a tendency to gradually increase due to the recirculation of the aCSF in the perfusion system. A controlled and reproducible perfusion system was established to study the energetic and metabolic changes in rat brain slices during and after OGD of varying severity.

The Role of Melatonin in Pregnancy and the Health Benefits for the Newborn

In the last few years, there have been significant evolutions in the understanding of the hormone melatonin in terms of its physiology, regulatory role, and potential utility in various domains of clinical medicine. Melatonin's properties include, among others, the regulation of mitochondrial function, anti-inflammatory, anti-oxidative and neuro-protective effects, sleep promotion and immune enhancement. As it is also bioavailable and has little or no toxicity, it has been proposed as safe and effective for the treatment of numerous diseases and to preserve human health. In this manuscript, we tried to evaluate the role of melatonin at the beginning of human life, in pregnancy, in the fetus and in newborns through newly published literature studies.

Metabolomics analysis identifies glutamic acid and cystine imbalances in COVID-19 patients without comorbid conditions. Implications on redox homeostasis and COVID-19 pathophysiology

It is well known that the presence of comorbidities and age-related health issues may hide biochemical and metabolic features triggered by SARS-CoV-2 infection and other diseases associated to hypoxia, as they are by themselves chronic inflammatory conditions that may potentially disturb metabolic homeostasis and thereby negatively impact on COVID-19 progression. To unveil the metabolic abnormalities inherent to hypoxemia caused by COVID-19, we here applied gas chromatography coupled to mass spectrometry to analyze the main metabolic changes exhibited by a population of male patients less than 50 years of age with mild/moderate and severe COVID-19 without pre-existing comorbidities known to predispose to life-threatening complications from this infection. Several differences in serum levels of particular metabolites between normal controls and patients with COVID-19 as well as between mild/moderate and severe COVID-19 were identified. These included increased glutamic acid and reduced glutamine, cystine, threonic acid, and proline levels. In particular, using the entire metabolomic fingerprint obtained, we observed that glutamine/glutamate metabolism was associated with disease severity as patients in the severe COVID-19 group presented the lowest and higher serum levels of these amino acids, respectively. These data highlight the hypoxia-derived metabolic alterations provoked by SARS-CoV-2 infection in the absence of pre-existing co-morbidities as well as the value of amino acid metabolism in determining reactive oxygen species recycling pathways, which when impaired may lead to increased oxidation of proteins and cell damage. They also provide insights on new supportive therapies for COVID-19 and other disorders that involve altered redox homeostasis and lower oxygen levels that may lead to better outcomes of disease severity.

Current Therapies for Neonatal Hypoxic-Ischaemic and Infection-Sensitised Hypoxic-Ischaemic Brain Damage

Neonatal hypoxic-ischaemic brain damage is a leading cause of child mortality and morbidity, including cerebral palsy, epilepsy, and cognitive disabilities. The majority of neonatal hypoxic-ischaemic cases arise as a result of impaired cerebral perfusion to the foetus attributed to uterine, placental, or umbilical cord compromise prior to or during delivery. Bacterial infection is a factor contributing to the damage and is recorded in more than half of preterm births. Exposure to infection exacerbates neuronal hypoxic-ischaemic damage thus leading to a phenomenon called infection-sensitised hypoxic-ischaemic brain injury. Models of neonatal hypoxia-ischaemia (HI) have been developed in different animals. Both human and animal studies show that the developmental stage and the severity of the HI insult affect the selective regional vulnerability of the brain to damage, as well as the subsequent clinical manifestations. Therapeutic hypothermia (TH) is the only clinically approved treatment for neonatal HI. However, the number of HI infants needed to treat with TH for one to be saved from death or disability at age of 18-22 months, is approximately 6-7, which highlights the need for additional or alternative treatments to replace TH or increase its efficiency. In this review we discuss the mechanisms of HI injury to the immature brain and the new experimental treatments studied for neonatal HI and infection-sensitised neonatal HI.

Paeoniflorin treatment regulates TLR4/NF-κB signaling, reduces cerebral oxidative stress and improves white matter integrity in neonatal hypoxic brain injury

Neonatal hypoxia/ischemia (H/I), injures white matter, results in neuronal loss, disturbs myelin formation, and neural network development. Neuroinflammation and oxidative stress have been reported in neonatal hypoxic brain injuries. We investigated whether Paeoniflorin treatment reduced H/I-induced inflammation and oxidative stress and improved white matter integrity in a neonatal rodent model. Seven-day old Sprague–Dawley pups were exposed to H/I. Paeoniflorin (6.25, 12.5, or 25 mg/kg body weight) was administered every day via oral gavage from postpartum day 3 (P3) to P14, and an hour before induction of H/I. Pups were sacrificed 24 h (P8) and 72 h (P10) following H/I. Paeoniflorin reduced the apoptosis of neurons and attenuated cerebral infarct volume. Elevated expression of cleaved caspase-3 and Bad were regulated. Paeoniflorin decreased oxidative stress by lowering levels of malondialdehyde and reactive oxygen species generation and while, and it enhanced glutathione content. Microglial activation and the TLR4/NF-κB signaling were significantly down-regulated. The degree of inflammatory mediators (interleukin 1β and tumor necrosis factor-α) were reduced. Paeoniflorin markedly prevented white matter injury via improving expression of myelin binding protein and increasing O1-positive olidgodendrocyte and O4-positive oligodendrocyte counts. The present investigation demonstrates the potent protective efficiency of paeoniflorin supplementation against H/I-induced brain injury by effectually preventing neuronal loss, microglial activation, and white matter injury via reducing oxidative stress and inflammatory pathways.

Neuroprotective effects of a dendrimer-based glutamate carboxypeptidase inhibitor on superoxide dismutase transgenic mice after neonatal hypoxic-ischemic brain injury

The result of a deprivation of oxygen and glucose to the brain, hypoxic-ischemic encephalopathy (HIE), remains the most common cause of death and disability in human neonates globally and is mediated by glutamate toxicity and inflammation. We have previously shown that the enzyme glutamate carboxypeptidase (GCPII) is overexpressed in activated microglia in the presence of inflammation in fetal/newborn rabbit brain. We assessed the therapeutic utility of a GCPII enzyme inhibitor called 2-(3-Mercaptopropyl) pentanedioic acid (2MPPA) attached to a dendrimer (D-2MPPA), in order to target activated microglia in an experimental neonatal hypoxia-ischemia (HI) model using superoxide dismutase transgenic (SOD) mice that are often more injured after hypoxia-ischemia than wildtype animals. SOD overexpressing and wild type (WT) mice underwent permanent ligation of the left common carotid artery followed by 50 min of asphyxiation (10% O₂) to induce HI injury on postnatal day 9 (P9). Cy5-labeled dendrimers were administered to the mice at 6 h, 24 h or 72 h after HI and brains were evaluated by immunofluorescence analysis 24 h after the injection to visualize microglial localization and uptake over time. Expression of GCPII enzyme was analyzed in microglia 24 h after the HI injury. The expression of pro- and anti-inflammatory cytokines were analyzed 24 h and 72 h post-HI. Brain damage was analyzed histologically 7 days post-HI in the three randomly assigned groups: control (C); hypoxic-ischemic (HI); and HI mice who received a single dose of D-2MPPA 6 h post-HI (HI+D-2MPPA). First, we found that GCPII was overexpressed in activated microglia 24 h after HI in the SOD overexpressing mice. Also, there was an increase in microglial activation 24 h after HI in the ipsilateral hippocampus which was most visible in the SOD+HI group. Dendrimers were mostly taken up by microglia by 24 h post-HI; uptake was more prominent in the SOD+HI mice than in the WT+HI. The inflammatory profile showed significant increase in expression of KC/GRO following injury in SOD mice compared to WT at 24 and 72 h. A greater and significant decrease in KC/GRO was seen in the SOD mice following treatment with D-2MPPA. Seven days after HI, D-2MPPA treatment decreased brain injury in the SOD+HI group, but not in WT+HI. This reduced damage was mainly seen in hippocampus and cortex. Our data indicate that the best time point to administer D-2MPPA is 6 h post-HI in order to suppress the expression of GCPII by 24 h after the damage since dendrimer localization in microglia is seen as early as 6 h with the peak of GCPII upregulation in activated microglia seen at 24 h post-HI. Ultimately, treatment with D-2MPPA at 6 h post-HI leads to a decrease in inflammatory profiles by 24 h and reduction in brain injury in the SOD overexpressing mice.

A Metabolomics Study of Hypoxia Ischemia during Mouse Brain Development Using Hyperpolarized 13C

BACKGROUND

Hyperpolarized 13C spectroscopic magnetic resonance spectroscopy (MRS) is an advanced imaging tool that may provide important real-time information about brain metabolism.

METHODS

Mice underwent unilateral hypoxia-ischemia (HI) on postnatal day (P)10. Injured and sham mice were scanned at P10, P17, and P31. We used hyperpolarized 13C MRS to investigate the metabolic exchange of pyruvate to lactate in real time during brain development following HI. 13C-1-labeled pyruvate was hyperpolarized and injected into the tail vein through a tail-vein catheter. Chemical-shift imaging was performed to acquire spectral-spatial information of the metabolites in the brain. A voxel placed on each of the injured and contralateral hemispheres was chosen for comparison. The difference in pyruvate delivery and lactate to pyruvate ratio was calculated for each of the voxels at each time point. The normalized lactate level of the injured hemisphere was also calculated for each mouse at each of the scanning time points.

RESULTS

There was a significant reduction in pyruvate delivery and a higher lactate to pyruvate ratio in the ipsilateral (HI) hemisphere at P10. The differences decreased at P17 and disappeared at P31. The normalized lactate level in the injured hemisphere increased from P10 to P31 in both sham and HI mice without brain injury.

CONCLUSION

We describe a method for detecting and monitoring the evolution of HI injury during brain maturation which could prove to be an excellent biomarker of injury.

Synthesis, pharmacological evaluation and mechanistic study of scutellarin methyl ester -4'-dipeptide conjugates for the treatment of hypoxic-ischemic encephalopathy (HIE) in rat pups

A series of novel scutellarin methyl ester-4'-dipeptide conjugates exhibiting active transport characteristics and protection against pathological damage caused by hypoxic-ischemic encephalopathy (HIE) were successfully designed and synthesized. The physiochemical properties of the obtained compounds, as well as the Caco-2 cell-based permeability and uptake into hPepT1-MDCK cells were evaluated using various analytical methods. Scutellarin methyl ester-4'-Val-homo-Leu dipeptide (5k) was determined as the optimal candidate with a high apparent permeability coefficient (P_{app A to B}) of 1.95 ± 0.24 × 10^-6 cm/s, low ER (P_{app BL to AP}/P_{app AP to BL}) of 0.52 in Caco-2 cells, and high uptake of 25.47 μmol/mg/min in hPepT1-MDCK cells. Comprehensive mechanistic studies demonstrated that pre-treatment of PC12 cells with 5k resulted in more potent anti-oxidative activity, which was manifested by a significant decrease in the malondialdehyde (MDA) and reactive oxygen species (ROS) levels, attenuation of the H₂O₂-induced apoptotic cell accumulation in the sub-G1 peak, and improvement in the expression of the relevant apoptotic proteins (Bcl-2, Bax, and cleave-caspase-3). Moreover, evaluation of in vivo neuroprotective characteristics in hypoxic-ischemic rat pups revealed that 5k significantly reduced infarction and alleviated the related pathomorphological damage. The compound was also shown to ameliorate the neurological deficit at 48 h as well as to decrease the brain tissue loss at 4 weeks. Conjugate 5k was demonstrated to reduce the amyloid precursor protein (APP) and β-site APP-converting enzyme-1 (BACE-1) expression. Pharmacokinetic characterization of 5k indicated favorable druggability and pharmacokinetic properties. The conducted docking studies revealed optimal binding of 5k to PepT1. Hydrogen bonding as well as cation-π interactions with the corresponding amino acid residues in the target active site were clearly observed. The obtained results suggest 5k as a potential candidate for anti-HIE therapy, which merits further investigation.

The physiology of intrapartum fetal compromise at term

Uterine contractions in labor result in a 60% reduction in uteroplacental perfusion, causing transient fetal and placental hypoxia. A healthy term fetus with a normally developed placenta is able to accommodate this transient hypoxia by activation of the peripheral chemoreflex, resulting in a reduction in oxygen consumption and a centralization of oxygenated blood to critical organs, namely the heart, brain, and adrenals. Providing there is adequate time for placental and fetal reperfusion between contractions, these fetuses will be able to withstand prolonged periods of intermittent hypoxia and avoid severe hypoxic injury. However, there exists a cohort of fetuses in whom abnormal placental development in the first half of pregnancy results in failure of endovascular invasion of the spiral arteries by the cytotrophoblastic cells and inadequate placental angiogenesis. This produces a high-resistance, low-flow circulation predisposing to hypoperfusion, hypoxia, reperfusion injury, and oxidative stress within the placenta. Furthermore, this renders the placenta susceptible to fluctuations and reduction in uteroplacental perfusion in response to external compression and stimuli (as occurs in labor), further reducing fetal capillary perfusion, placing the fetus at risk of inadequate gas/nutrient exchange. This placental dysfunction predisposes the fetus to intrapartum fetal compromise. In the absence of a rare catastrophic event, intrapartum fetal compromise occurs as a gradual process when there is an inability of the fetal heart to respond to the peripheral chemoreflex to maintain cardiac output. This may arise as a consequence of placental dysfunction reducing pre-labor myocardial glycogen stores necessary for anaerobic metabolism or due to an inadequate placental perfusion between contractions to restore fetal oxygen and nutrient exchange. If the hypoxic insult is severe enough and long enough, profound multiorgan injury and even death may occur. This review provides a detailed synopsis of the events that can result in placental dysfunction, how this may predispose to intrapartum fetal hypoxia, and what protective mechanisms are in place to avoid hypoxic injury.

Tissue Injury and Astrocytic Reaction, But Not Cognitive Deficits, Are Dependent on Hypoxia Duration in Very Immature Rats Undergoing Neonatal Hypoxia-Ischemia

Preterm birth and hypoxia-ischemia (HI) are major causes of neonatal death and neurological disabilities in newborns. The widely used preclinical HI model combines carotid occlusion with hypoxia exposure; however, the relationship between different hypoxia exposure periods with brain tissue loss, astrocyte reactivity and behavioral impairments following HI is lacking. Present study evaluated HI-induced behavioral and morphological consequences in rats exposed to different periods of hypoxia at postnatal day 3. Wistar rats of both sexes were assigned into four groups: control group, HI-120 min, HI-180 min and HI-210 min. Neurodevelopmental reflexes, exploratory abilities and cognitive function were assessed. At adulthood, tissue damage and reactive astrogliosis were measured. Animals exposed to HI-180 and HI-210 min had delayed neurodevelopmental reflexes compared to control group. Histological assessment showed tissue loss that was restricted to the ipsilateral hemisphere in lower periods of hypoxia exposure (120 and 180 min) but affected both hemispheres when 210 min was used. Reactive astrogliosis was increased only after 210 min of hypoxia. Interestingly, cognitive deficits were induced regardless the duration of hypoxia and there were correlations between behavioral parameters and cortex, hippocampus and corpus callosum volumes. These results show the duration of hypoxia has a close relationship with astrocytic response and tissue damage progression. Furthermore, the long-lasting cognitive memory deficit and its association with brain structures beyond the hippocampus suggests that complex anatomical changes should be involved in functional alterations taking place as hypoxia duration is increased, even when the cognitive impairment limit is achieved.

hUC-MSCs Exert a Neuroprotective Effect via Anti-apoptotic Mechanisms in a Neonatal HIE Rat Model

In this study, we investigated how human umbilical cord mesenchymal stem cells exerted a neuroprotective effect via antiapoptotic mechanisms in a neonatal hypoxic-ischemic encephalopathy rat model. A total of 78 10-day old (P10) rats were used. After human umbilical cord mesenchymal stem cells were collected from human umbilical cords and amplified in culture, they were administered to rat subjects 1 h after induced hypoxic-ischemic encephalopathy treatment. The short-term (48 h) and long-term (28 day) outcomes were evaluated after human umbilical cord mesenchymal stem cells treatment using neurobehavioral function assessment. Triphenyltetrazolium chloride monohydrate staining was performed at 48 h. Beclin-2 and caspase-3 levels were evaluated with Western blot and real time polymerase chain reaction at 48 h. Human umbilical cord mesenchymal stem cells were collected and administrated to hypoxic-ischemic encephalopathy pups by intracerebroventricular injection. Hypoxic-ischemic encephalopathy typically induced significant delay in development and caused impairment in both cognitive and motor functions in rat subjects. Human umbilical cord mesenchymal stem cells were shown to ameliorate hypoxic-ischemic encephalopathy-induced damage and improve both cognitive and motor functions. Although hypoxic-ischemic encephalopathy induced significant expression of caspase-3 and Beclin-2, human umbilical cord mesenchymal stem cells decreased the expression of both of them. Human umbilical cord mesenchymal stem cells may serve as a potential treatment to ameliorate brain injury in hypoxic-ischemic encephalopathy patients.

Maternal pomegranate juice intake and brain structure and function in infants with intrauterine growth restriction: A randomized controlled pilot study

Polyphenol-rich pomegranate juice has been shown to have benefit as a neuroprotectant in animal models of neonatal hypoxic-ischemia. No published studies have investigated maternal polyphenol administration as a potential neuroprotectant in at-risk newborns, such as those with intrauterine growth restriction (IUGR). This was a randomized, placebo-controlled, double-blind pilot study to investigate the impact of maternal pomegranate juice intake in pregnancies with IUGR, on newborn brain structure and function at term-equivalent age (TEA). Mothers with IUGR at 24-34 weeks' gestation were recruited from Barnes-Jewish Hospital obstetrical clinic. Consented mothers were randomized to treatment (8 oz. pomegranate juice) or placebo (8 oz. polyphenol-free juice) and continued to take juice daily from enrollment until delivery (mean 20.1 and 27.1 days, respectively). Infants underwent brain MRI at TEA (36-41 weeks' gestation). Brain measures were compared between groups including: brain injury score, brain metrics, brain volumes, diffusion tensor imaging and resting state functional connectivity. Statistical analyses were undertaken as modified intention-to-treat (including randomized participants who received their allocated intervention and whose infants received brain MRI) and per-protocol (including participants who strictly adhered to the protocol, based on metabolite status). Seventy-seven mothers were randomized to treatment (n = 40) or placebo (n = 37). Of these, 28 and 27 infants, respectively, underwent term-equivalent MRI. There were no group differences in brain injury, metrics or volumes. However, treatment subjects displayed reduced diffusivity within the anterior and posterior limbs of the internal capsule compared with placebo. Resting state functional connectivity demonstrated increased correlation and covariance within several networks in treatment subjects, with alterations most apparent in the visual network in per-protocol analyses. Direct effects on health were not found. In conclusion, maternal pomegranate juice intake in pregnancies with known IUGR was associated with altered white matter organization and functional connectivity in the infant brain, suggesting differences in brain structure and function following in utero pomegranate juice exposure, warranting continued investigation. Clinical trial registration. NCT00788866, registered November 11, 2008, initial participant enrollment August 21, 2012.

Advanced nanotherapies to promote neuroregeneration in the injured newborn brain

Neonatal brain injury affects thousands of babies each year and may lead to long-term and permanent physical and neurological problems. Currently, therapeutic hypothermia is standard clinical care for term newborns with moderate to severe neonatal encephalopathy. Nevertheless, it is not completely protective, and additional strategies to restore and promote regeneration are urgently needed. One way to ensure recovery following injury to the immature brain is to augment endogenous regenerative pathways. However, novel strategies such as stem cell therapy, gene therapies and nanotechnology have not been adequately explored in this unique age group. In this perspective review, we describe current efforts that promote neuroprotection and potential targets that are unique to the developing brain, which can be leveraged to facilitate neuroregeneration.

Gestational folic acid supplementation does not affects the maternal behavior and the early development of rats submitted to neonatal hypoxia-ischemia but the high supplementation impairs the dam's memory and the Na+, K+ - ATPase activity in the pup's hippocampus

Folic acid (FA) is a B-complex vitamin important to the development of the fetus, being supplemented during pregnancy. Our recent findings showed that gestation supplementation (normal and excess doses) prevented the cognitive deficits and BDNF imbalance in adult rats that were submitted to neonatal hypoxia-ischemia (HI). To better understand this protective effect, the present study aimed to evaluate whether FA supplementation could be related to (1) maternal behavior, memory and Na⁺, K⁺ - ATPase activity in the hippocampus of the dams; (2) on somatic growth, early neurobehavioral development and Na⁺, K⁺ - ATPase activity in the hippocampus of the offspring; and (3) the effects of this supplementation in pups submitted to neonatal HI. Pregnant Wistar rats were divided into three groups, according to the diet they received during gestation: standard diet (SD), supplemented with 2 mg/kg of FA (FA2 - normal dose) and supplemented with 20 mg/kg of FA (FA20 -excessive dose). At the 7^th PND pups were submitted to the Levine-Vannucci model of HI. During weaning the maternal behavior, the somatic growth and the neurobehavior development of pups were assessed. After weaning, the memory of the dams (by the Ox-maze task) and the Na⁺, K⁺ - ATPase activity in the hippocampus of both dams and offspring were evaluated. Considering the dams (1), both doses of FA did not alter the maternal behavior or the Na⁺, K⁺ - ATPase activity in the hippocampus, but a memory deficit was observed in the high FA-supplemented mothers. Considering the offspring (2), both FA doses did not affect the somatic growth or the neurobehavior development, but the FA20 pups had a decreased Na⁺, K⁺ - ATPase activity in the hippocampus. The FA supplementation did not change the parameters evaluated in the HI rats (3) and did not prevent the decreased Na⁺, K⁺ - ATPase activity in the hippocampus of the HI pups. These results indicate that normal FA supplementation dose does not influence the maternal behavior and memory and does not impact on the offspring early development in rats. Further studies are needed to confirm the effects of the high FA supplementation dose in the dams' memory and in the Na⁺, K⁺ - ATPase activity in the hippocampus of the offspring.

Prefrontal cortex dysfunction in hypoxic-ischaemic encephalopathy contributes to executive function impairments in rats: Potential contribution for attention-deficit/hyperactivity disorder

OBJECTIVES

The attention-deficit/hyperactivity disorder (ADHD) compromises the quality of life of individuals including adaptation to the social environment. ADHD aetiology includes perinatal conditions such as hypoxic-ischaemic events; preclinical studies have demonstrated attentional deficits and impulsive-hyperactive outcomes after neonatal hypoxic and/or ischaemic intervention, but data are missing to understand this relationship. Thus, the aim of this study was to evaluate executive function (EF) and impulsivity, and tissue integrity and dopaminergic function in the prefrontal cortex (PFC) of rats submitted to hypoxia-ischaemia (HI).

METHODS

At postnatal day (PND) 7, male Wistar rats were divided into control (n = 10) and HI groups (n = 11) and the HI procedure was conducted. At PND60, the animals were tested in the attentional set-shifting (ASS) task to EF and in the tolerance to delay of reward for assessment of impulsivity. After, morphological analysis and the dopaminergic system were evaluated in the PFC.

RESULTS

Animals subjected to HI had impairments in EF evidenced by a behavioural inflexibility that was correlated to PFC atrophy. Moreover, HI animals presented reduced D2 receptors in the ipsilateral side of ischaemia in the PFC.

CONCLUSIONS

Animals submitted to HI presented impaired EF associated with tissue atrophy and dopaminergic disturbance in the PFC.

Intracardiac Injection of Dental Pulp Stem Cells After Neonatal Hypoxia-Ischemia Prevents Cognitive Deficits in Rats

Neonatal hypoxia-ischemia (HI) is associated to cognitive and motor impairments and until the moment there is no proven treatment. The underlying neuroprotective mechanisms of stem cells are partially understood and include decrease in excitotoxicity, apoptosis and inflammation suppression. This study was conducted in order to test the effects of intracardiac transplantation of human dental pulp stem cells (hDPSCs) for treating HI damage. Seven-day-old Wistar rats were divided into four groups: sham-saline, sham-hDPSCs, HI-saline, and HI-hDPSCs. Motor and cognitive tasks were performed from postnatal day 30. HI-induced cognitive deficits in the novel-object recognition test and in spatial reference memory impairment which were prevented by hDPSCs. No motor impairments were observed in HI animals. Immunofluorescence analysis showed human-positive nuclei in hDPSC-treated animals closely associated with anti-GFAP staining in the lesion scar tissue, suggesting that these cells were able to migrate to the injury site and could be providing support to CNS cells. Our study evidence novel evidence that hDPSC can contribute to the recovery following hypoxia-ischemia and highlight the need of further investigation in order to better understand the exact mechanisms underlying its neuroprotective effects.

Astrocyte-produced carbon monoxide and the carbon monoxide donor CORM-A1 protect against cerebrovascular dysfunction caused by prolonged neonatal asphyxia

Neonatal asphyxia leads to cerebrovascular disease and neurological complications via a mechanism that may involve oxidative stress. Carbon monoxide (CO) is an antioxidant messenger produced via a heme oxygenase (HO)-catalyzed reaction. Cortical astrocytes are the major cells in the brain that express constitutive HO-2 isoform. We tested the hypothesis that CO, produced by astrocytes, has cerebroprotective properties during neonatal asphyxia. We developed a survival model of prolonged asphyxia in newborn pigs that combines insults of severe hypoxia, hypercapnia, and acidosis while avoiding extreme hypotension and cerebral blood flow reduction. During the 60-min asphyxia, CO production by brain and astrocytes was continuously elevated. Excessive formation of reactive oxygen species during asphyxia/reventilation was potentiated by the HO inhibitor tin protoporphyrin, suggesting that endogenous CO has antioxidant effects. Cerebral vascular outcomes tested 24 and 48 h after asphyxia demonstrated the sustained impairment of cerebral vascular responses to astrocyte- and endothelium-specific vasodilators. Postasphyxia cerebral vascular dysfunction was aggravated in newborn pigs pretreated with tin protoporphyrin to inhibit brain HO/CO. The CO donor CO-releasing molecule-A1 (CORM-A1) reduced brain oxidative stress during asphyxia/reventilation and prevented postasphyxia cerebrovascular dysfunction. The antioxidant and antiapoptotic effects of HO/CO and CORM-A1 were confirmed in primary cultures of astrocytes from the neonatal pig brain exposed to glutamate excitotoxicity. Overall, prolonged neonatal asphyxia leads to neurovascular injury via an oxidative stress-mediated mechanism that is counteracted by an astrocyte-based constitutive antioxidant HO/CO system. We propose that gaseous CO or CO donors can be used as novel approaches for prevention of neonatal brain injury caused by prolonged asphyxia. NEW & NOTEWORTHY Asphyxia in newborn infants may lead to lifelong neurological disabilities. Using the model of prolonged asphyxia in newborn piglets, we propose novel antioxidant therapy based on systemic administration of low doses of a carbon monoxide donor that prevent loss of cerebral blood flow regulation and may improve the neurological outcome of asphyxia.

Seizure Severity Is Correlated With Severity of Hypoxic-Ischemic Injury in Abusive Head Trauma

BACKGROUND

The objective of this study was to characterize hypoxic-ischemic injury and seizures in abusive head trauma.

METHODS

We studied 58 children with moderate or severe traumatic brain injury due to abusive head trauma. Continuous electroencephalograms and magnetic resonance images were scored.

RESULTS

Electrographic seizures (51.2%) and hypoxic-ischemic injury (77.4%) were common in our cohort. Younger age was associated with electrographic seizures (no seizures: median age 13.5 months, interquartile range five to 25 months, versus seizures: 4.5 months, interquartile range 3 to 9.5 months; P = 0.001). Severity of hypoxic-ischemic injury was also associated with seizures (no seizures: median injury score 1.0, interquartile range 0 to 3, versus seizures: 4.5, interquartile range 3 to 8; P = 0.01), but traumatic injury severity was not associated with seizures (no seizures: mean injury score 3.78 ± 1.68 versus seizures: mean injury score 3.83 ± 0.95, P = 0.89). There was a correlation between hypoxic-ischemic injury severity and seizure burden when controlling for patient age (r_s=0.61, P < 0.001). The ratio of restricted diffusion volume to total brain volume (restricted diffusion ratio) was smaller on magnetic resonance imaging done early (median restricted diffusion ratio 0.03, interquartile range 0 to 0.23 on magnetic resonance imaging done within two days versus median restricted diffusion ratio 0.13, interquartile range 0.01 to 0.43 on magnetic resonance imaging done after two days, P = 0.03).

CONCLUSIONS

Electrographic seizures are common in children with moderate to severe traumatic brain injury from abusive head trauma, and therefore children with suspected abusive head trauma should be monitored with continuous electroencephalogram. Severity of hypoxic-ischemic brain injury is correlated with severity of seizures, and evidence of hypoxic-ischemic injury on magnetic resonance imaging may evolve over time. Therefore children with a high seizure burden should be reimaged to evaluate for evolving hypoxic-ischemic injury.

Atomoxetine, a selective norepinephrine reuptake inhibitor, improves short-term histological outcomes after hypoxic-ischemic brain injury in the neonatal male rat

BACKGROUND

Despite the recent progress of perinatal medicine, perinatal hypoxic-ischemic (HI) insult remains an important cause of brain injury in neonates, and is pathologically characterized by neuronal loss and the presence of microglia. Neurotransmitters, such as norepinephrine (NE) and glutamate, are involved in the pathogenesis of hypoxic-ischemic encephalopathy via the interaction between neurons and microglia. Although it is well known that the monoamine neurotransmitter NE acts as an anti-inflammatory agent in the brain under pathological conditions, its effects on perinatal HI insult remains elusive. Atomoxetine, a selective NE reuptake inhibitor, has been used clinically for the treatment of attention-deficit hyperactivity disorder in children. Here, we investigated whether the enhancement of endogenous NE by administration of atomoxetine could protect neonates against HI insult by using the neonatal male rat model. We also examined the involvement of microglia in this process.

METHODS

Unilateral HI brain injury was induced by the combination of left carotid artery dissection followed by ligation and hypoxia (8% O₂, 2 h) in postnatal day 7 (P7) male rat pups. The pups were randomized into three groups: the atomoxetine treatment immediately after HI insult, the atomoxetine treatment at 3 h after HI insult, or the vehicle treatment group. The pups were euthanized on P8 and P14, and the brain regions including the cortex, striatum, hippocampus, and thalamus were evaluated by immunohistochemistry.

RESULTS

HI insult resulted in severe brain damage in the ipsilateral hemisphere at P14. Atomoxetine treatment immediately after HI insult significantly increased NE levels in the ipsilateral hemisphere at 1 h after HI insult and reduced the neuronal damage via the increased phosphorylation of cAMP response element-binding protein (pCREB) in all brain regions examined. In addition, the number of microglia was maintained under atomoxetine treatment compared with that of the vehicle treatment group. To determine the involvement of microglia in the process of neuronal loss by HI insult, we further examined the influence of hypoxia on rat primary cultured microglia by the quantitative real-time polymerase chain reaction. Hypoxia did not cause the upregulation of interleukin-1beta (IL-1β) mRNA expression, but decreased the microglial intrinsic nitric oxide synthase (iNOS)/arginase1 mRNA expression ratio. NE treatment further decreased the microglial iNOS/arginase1 mRNA expression ratio. In contrast, no significant neuroprotective effect was observed at P14 when atomoxetine was administered at 3 h after HI insult.

CONCLUSIONS

These findings suggested that the enhancement of intrinsic neurotransmitter NE signaling by a selective NE reuptake inhibitor, atomoxetine, reduced the perinatal HI insult brain injury. In addition, atomoxetine treatment was associated with changes of TUNEL, pCREB, and BDNF expression levels, and microglial numbers, morphology, and responses.

Pretreatment with Group II Metabotropic Glutamate Receptor Agonist LY379268 Protects Neonatal Rat Brains from Oxidative Stress in an Experimental Model of Birth Asphyxia

Hypoxia-ischemia (H-I) at the time of birth may cause neonatal death or lead to persistent brain damage. The search for an effective treatment of asphyxiated infants has not resulted in an effective therapy, and hypothermia remains the only available therapeutic strategy. Among possible experimental therapies, the induction of ischemic tolerance is promising. Recent investigations have shown that activation of group II metabotropic glutamate receptors (mGluR2/3) can provide neuroprotection against H-I, but the mechanism of this effect is not clear. The aim of this study was to investigate whether an mGluR2/3 agonist applied before H-I reduces brain damage in an experimental model of birth asphyxia and whether a decrease in oxidative stress plays a role in neuroprotection. Neonatal H-I on seven-day-old rats was used as an experimental model of birth asphyxia. Rats were injected intraperitoneally with the mGluR2/3 agonist LY379268 24 or 1 h before H-I (5 mg/kg). LY379268 reduced the infarct area in the ischemic hemisphere. Application of the agonist at both times also reduced the elevated levels of reactive oxygen species (ROS) in the ipsilateral hemisphere observed after H-I and prevented the increase in antioxidant enzyme activity in the injured hemisphere. The decrease in glutathione (GSH) level was also restored after agonist application. The results suggest that the neuroprotective mechanisms triggered by the activation of mGluR2/3 before H-I act through the decrease of glutamate release and its extracellular concentration resulting in the inhibition of ROS production and reduction of oxidative stress. This, rather than induction of ischemic tolerance, is probably the main mechanism involved in the observed neuroprotection.

Protection of melatonin in experimental models of newborn hypoxic-ischemic brain injury through MT1 receptor

The function of melatonin as a protective agent against newborn hypoxic-ischemic (H-I) brain injury is not yet well studied, and the mechanisms by which melatonin causes neuroprotection in neurological diseases are still evolving. This study was designed to investigate whether expression of MT1 receptors is reduced in newborn H-I brain injury and whether the protective action of melatonin is by alterations of the MT1 receptors. We demonstrated that there was significant reduction in MT1 receptors in ischemic brain of mouse pups in vivo following H-I brain injury and that melatonin offers neuroprotection through upregulation of MT1 receptors. The role of MT1 receptors was further supported by observation of increased mortality in MT1 knockout mice following H-I brain injury and the reversal of the inhibitory role of melatonin on mitochondrial cell death pathways by the melatonin receptor antagonist, luzindole. These data demonstrate that melatonin mediates its neuroprotective effect in mouse models of newborn H-I brain injury, at least in part, by the restoration of MT1 receptors, the inhibition of mitochondrial cell death pathways and the suppression of astrocytic and microglial activation.

CpG-ODN exerts a neuroprotective effect via the TLR9/pAMPK signaling pathway by activation of autophagy in a neonatal HIE rat model

Hypoxic Ischemic Encephalopathy (HIE) is an injury caused to the brain due to prolonged lack of oxygen and blood supply which results in death or long-term disabilities. The main aim of this study was to investigate the role of Cytosine-phospho-guanine oligodeoxynucleotide (CpG-ODN) in autophagy after HIE. Ten-day old (P10) rat pups underwent right common carotid artery ligation followed by 2.5h of hypoxia as previously described by Rice-Vannucci. At 1h post HIE, rats were intranasally administered with recombinant CpG-ODN. Time-course expression levels of endogenous key proteins, TLR9, pAMPK/AMPK, LC3II/I, and LAMP1 involved in CpG-ODN's protective effects were measured using western blot. Short (48h) and long (4w) term neurobehavior studies were performed using righting reflex, negative geotaxis, water maze, foot fault and Rota rod tests. Brain samples were collected after long term for histological analysis. Furthermore, to elucidate the pathway via which CpG-ODN confers protection, TLR9 and AMPK inhibitors were used. Time course results showed that the expression of TLR9, pAMPK/AMPK, LC3II/I, LAMP1 increased after HIE. Neurobehavioral studies showed that HIE induced a significant delay in development and resulted in cognitive and motor function deficits. However, CpG-ODN ameliorated HIE-induced outcomes and improved long term neurological deficits. In addition, CpG-ODN increased expression of pAMPK/AMPK, p-ULK1/ULK1, P-AMBRA1/AMBRA1, LC3II/I and LAMP1 while inhibition of TLR9 and AMPK reversed those effects. In summary, CpG-ODN increased HIE-induced autophagy and improved short and long term neurobehavioral outcomes which may be mediated by the TLR9/pAMPK signaling pathway after HIE.

Early metabolite changes after melatonin treatment in neonatal rats with hypoxic-ischemic brain injury studied by in-vivo1H MR spectroscopy

Melatonin is a promising neuroprotective agent after perinatal hypoxic-ischemic (HI) brain injury. We used in-vivo¹H magnetic resonance spectroscopy to investigate effects of melatonin treatment on brain metabolism after HI. Postnatal day 7 Sprague-Dawley rats with unilateral HI brain injury were treated with either melatonin 10 mg/kg dissolved in phosphate-buffered saline (PBS) with 5% dimethyl sulfoxide (DMSO) or vehicle (5% DMSO and/or PBS) directly and at 6 hours after HI. ¹H MR spectra from the thalamus in the ipsilateral and contralateral hemisphere were acquired 1 day after HI. Our results showed that injured animals had a distinct metabolic profile in the ipsilateral thalamus compared to sham with low concentrations of total creatine, choline, N-acetyl aspartate (NAA), and high concentrations of lipids. A majority of the melatonin-treated animals had a metabolic profile characterized by higher total creatine, choline, NAA and lower lipid levels than other HI animals. When comparing absolute concentrations, melatonin treatment resulted in higher glutamine levels and lower lipid concentrations compared to DMSO treatment as well as higher macromolecule levels compared to PBS treatment day 1 after HI. DMSO treated animals had lower concentrations of glucose, creatine, phosphocholine and macromolecules compared to sham animals. In conclusion, the neuroprotective effects of melatonin were reflected in a more favorable metabolic profile including reduced lipid levels that likely represents reduced cell injury. Neuroprotective effects may also be related to the influence of melatonin on glutamate/glutamine metabolism. The modulatory effects of the solvent DMSO on cerebral energy metabolism might have masked additional beneficial effects of melatonin.

Neonatal Hypoxia Ischaemia: Mechanisms, Models, and Therapeutic Challenges

Neonatal hypoxia-ischaemia (HI) is the most common cause of death and disability in human neonates, and is often associated with persistent motor, sensory, and cognitive impairment. Improved intensive care technology has increased survival without preventing neurological disorder, increasing morbidity throughout the adult population. Early preventative or neuroprotective interventions have the potential to rescue brain development in neonates, yet only one therapeutic intervention is currently licensed for use in developed countries. Recent investigations of the transient cortical layer known as subplate, especially regarding subplate's secretory role, opens up a novel set of potential molecular modulators of neonatal HI injury. This review examines the biological mechanisms of human neonatal HI, discusses evidence for the relevance of subplate-secreted molecules to this condition, and evaluates available animal models. Neuroserpin, a neuronally released neuroprotective factor, is discussed as a case study for developing new potential pharmacological interventions for use post-ischaemic injury.

Role of Antioxidants in Neonatal Hypoxic-Ischemic Brain Injury: New Therapeutic Approaches

Hypoxic-ischemic brain damage is an alarming health and economic problem in spite of the advances in neonatal care. It can cause mortality or detrimental neurological disorders such as cerebral palsy, motor impairment and cognitive deficits in neonates. When hypoxia-ischemia occurs, a multi-faceted cascade of events starts out, which can eventually cause cell death. Lower levels of oxygen due to reduced blood supply increase the production of reactive oxygen species, which leads to oxidative stress, a higher concentration of free cytosolic calcium and impaired mitochondrial function, triggering the activation of apoptotic pathways, DNA fragmentation and cell death. The high incidence of this type of lesion in newborns can be partly attributed to the fact that the developing brain is particularly vulnerable to oxidative stress. Since antioxidants can safely interact with free radicals and terminate that chain reaction before vital molecules are damaged, exogenous antioxidant therapy may have the potential to diminish cellular damage caused by hypoxia-ischemia. In this review, we focus on the neuroprotective effects of antioxidant treatments against perinatal hypoxic-ischemic brain injury, in the light of the most recent advances.

Decreasing intrapartum malpractice: Targeting the most injurious neonatal adverse events

Medical malpractice expenditures are mainly due to the occurrence of preventable harm with some of the highest liability rates in obstetrics. Establishing delivery system models which decrease preventable harm and malpractice risk have had varied results over the last decade. We conducted a case study of a risk reduction labor and delivery model at 5 demonstration sites. The model included standardized protocols for the most injurious events, training teams in labor and delivery emergencies, rapid reporting with cause analysis for all unplanned events, and disclosing unexpected occurrences to patients using coordinated communication and documentation. Each of the model's components required buy in from the hospital's clinical and administrative leadership, and it also required collaboration, training, and continual feedback to labor and delivery nurses, doctors, midwives, and risk managers. The case study examined the key elements in the development of the model based on interviews of all team members and document review. We also completed data analysis pre and post implementation of the new model to assess the impact on event reporting and high liability occurrence rates. After 27 months post implementation, reporting of unintended events increased significantly (43 vs 84 per 1000 births, p < .01) while high-risk malpractice events decreased significantly (14 vs 7 per 1000 births, p < .01). This decrease enabled money allotted for malpractice claims to be reallocated for the implementation of the new model at 42 additional labor and delivery sites. Due to these results, this multilevel integrated model showed promise.

Dexmedetomidine alleviates cerebral ischemia-induced short-term memory impairment by inhibiting the expression of apoptosis-related molecules in the hippocampus of gerbils

Cerebral ischemia results from cerebrovascular occlusion, which leads to neuronal cell death and eventually causes neurological impairments. Dexmedetomidine is a potent and highly selective α₂-adrenoreceptor agonist with actions such as sedation, anxiolysis, analgesia and anesthetic-sparing effects. We investigated the effect of dexmedetomidine on apoptosis in the hippocampus after transient global ischemia in gerbils. Transient global ischemia was induced by ligation of both common carotid arteries. Dexmedetomidine was administrated intraperitoneally at three respective doses (0.1, 1 and 10 µg/kg) once per day for 14 consecutive days beginning a day after surgery. Short-term memory was assessed by use of a step-down avoidance task. Apoptosis was evaluated by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling assay, immunohistochemistry for caspase-3, and western blot analysis of Bcl-2-associated X protein, B-cell lymphoma 2, Bid, cytochrome c, apoptotic protease activating factor-1 and caspase-9 in the hippocampus. Induction of global ischemia deteriorated short-term memory by enhancing the expression of apoptosis-related molecules in the hippocampus. Treatment with dexmedetomidine suppressed the expression of apoptosis-related molecules under ischemic conditions, resulting in short-term memory improvement. Under normal conditions, dexmedetomidine exerted no significant effect on apoptosis in the hippocampus. The present results suggest that the α₂-adrenoceptor agonist dexmedetomidine may be a useful therapeutic agent for the treatment of ischemic brain diseases.

Docosahexaenoic Acid Reduces Cerebral Damage and Ameliorates Long-Term Cognitive Impairments Caused by Neonatal Hypoxia-Ischemia in Rats

As the interest in the neuroprotective possibilities of docosahexaenoic acid (DHA) for brain injury has grown in the recent years, we aimed to investigate the long-term effects of this fatty acid in an experimental model of perinatal hypoxia-ischemia in rats. To this end, motor activity, aspects of learning, and memory function and anxiety, as well as corticofugal connections visualized by using tracer injections, were evaluated at adulthood. We found that in the hours immediately following the insult, DHA maintained mitochondrial inner membrane integrity and transmembrane potential, as well as the integrity of synaptic processes. Seven days later, morphological damage at the level of the middle hippocampus was reduced, since neurons and myelin were preserved and the astroglial reactive response and microglial activation were seen to be diminished. At adulthood, the behavioral tests revealed that treated animals presented better long-term working memory and less anxiety than non-treated hypoxic-ischemic animals, while no difference was found in the spontaneous locomotor activity. Interestingly, hypoxic-ischemic injury caused alterations in the anterograde corticofugal neuronal connections which were not so evident in rats treated with DHA. Thus, our results indicate that DHA treatment can lead to long-lasting neuroprotective effects in this experimental model of neonatal hypoxia-ischemic brain injury, not only by mitigating axonal changes but also by enhancing cognitive performance at adulthood.

No improvement of neuronal metabolism in the reperfusion phase with melatonin treatment after hypoxic-ischemic brain injury in the neonatal rat

Mitochondrial impairment is a key feature underlying neonatal hypoxic-ischemic (HI) brain injury and melatonin is potentially neuroprotective through its effects on mitochondria. In this study, we have used (1) H and (13) C NMR spectroscopy after injection of [1-(13) C]glucose and [1,2-(13) C]acetate to examine neuronal and astrocytic metabolism in the early reperfusion phase after unilateral HI brain injury in 7-day-old rat pups, exploring the effects of HI on mitochondrial function and the potential protective effects of melatonin on brain metabolism. One hour after hypoxia-ischemia, astrocytic metabolism was recovered and glycolysis was normalized, whereas mitochondrial metabolism in neurons was clearly impaired. Pyruvate carboxylation was also lower in both hemispheres after HI. The transfer of glutamate from neurons to astrocytes was higher whereas the transfer of glutamine from astrocytes to neurons was lower 1 h after HI in the contralateral hemisphere. Neuronal metabolism was equally affected in pups treated with melatonin (10 mg/kg) immediately after HI as in vehicle treated pups indicating that the given dose of melatonin was not capable of protecting the neuronal mitochondria in this early phase after HI brain injury. However, any beneficial effects of melatonin might have been masked by modulatory effects of the solvent dimethyl sulfoxide on cerebral metabolism. Neuronal and astrocytic metabolism was examined by (13) C and (1) H NMR spectroscopy in the early reperfusion phase after unilateral hypoxic-ischemic brain injury and melatonin treatment in neonatal rats. One hour after hypoxia-ischemia astrocytic mitochondrial metabolism had recovered and glycolysis was normalized, whereas mitochondrial metabolism in neurons was impaired. Melatonin treatment did not show a protective effect on neuronal metabolism.

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.

Cognitive Dysfunction and Hippocampal Damage Induced by Hypoxic-Ischemic Brain Injury and Prolonged Febrile Convulsions in Immature Rats

Objective

Perinatal hypoxic-ischemic encephalopathy (HIE) and prolonged febrile seizures (pFS) are common neurologic problems that occur during childhood. However, there is insufficient evidence from experimental studies to conclude that pFS directly induces hippocampal injury. We studied cognitive function and histological changes in a rat model and investigated which among pFS, HIE, or a dual pathologic effect is most detrimental to the health of children.

Methods

A rat model of HIE at postnatal day (PD) 7 and a pFS model at PD10 were used. Behavioral and cognitive functions were investigated by means of weekly open field tests from postnatal week (PW) 3 to PW7, and by daily testing with the Morris water maze test at PW8. Pathological changes in the hippocampus were observed in the control, pFS, HIE, and HIE+pFS groups at PW9.

Results

The HIE priming group showed a seizure-prone state. The Morris water maze test revealed a decline in cognitive function in the HIE and HIE+pFS groups compared with the pFS and control groups. Additionally, the HIE and HIE+pFS groups showed significant hippocampal neuronal damage, astrogliosis, and volume loss, after maturation. The pFS alone induced minimal hippocampal neuronal damage without astrogliosis or volume loss.

Conclusion

Our findings suggest that pFS alone causes no considerable memory or behavioral impairment, or cellular change. In contrast, HIE results in lasting memory impairment and neuronal damage, gliosis, and tissue loss. These findings may contribute to the understanding of the developing brain concerning conditions caused by HIE or pFS.

Blood-brain barrier dysfunction in disorders of the developing brain

Disorders of the developing brain represent a major health problem. The neurological manifestations of brain lesions can range from severe clinical deficits to more subtle neurological signs or behavioral problems and learning disabilities, which often become evident many years after the initial damage. These long-term sequelae are due at least in part to central nervous system immaturity at the time of the insult. The blood-brain barrier (BBB) protects the brain and maintains homeostasis. BBB alterations are observed during both acute and chronic brain insults. After an insult, excitatory amino acid neurotransmitters are released, causing reactive oxygen species (ROS)-dependent changes in BBB permeability that allow immune cells to enter and stimulate an inflammatory response. The cytokines, chemokines and other molecules released as well as peripheral and local immune cells can activate an inflammatory cascade in the brain, leading to secondary neurodegeneration that can continue for months or even years and finally contribute to post-insult neuronal deficits. The role of the BBB in perinatal disorders is poorly understood. The inflammatory response, which can be either acute (e.g., perinatal stroke, traumatic brain injury) or chronic (e.g., perinatal infectious diseases) actively modulates the pathophysiological processes underlying brain injury. We present an overview of current knowledge about BBB dysfunction in the developing brain during acute and chronic insults, along with clinical and experimental data.

Increased expression of inflammatory genes in the neonatal mouse brain after hyperoxic reoxygenation

BACKGROUND

Hyperoxic reoxygenation following hypoxia increases the expression of inflammatory genes in the neonatal mouse brain. We have therefore compared the temporal profile of 44 a priori selected genes after hypoxia and hyperoxic or normoxic reoxygenation.

METHODS

Postnatal day 7 mice were subjected to 2 h of hypoxia (8% O2) and 30 min reoxygenation with 60% or 21% O2. After 0 to 72 h observation, mRNA and protein were examined in the hippocampus and striatum.

RESULTS

There were significantly higher gene expression changes in six genes after hyperoxic compared to normoxic reoxygenation. Three genes had a generally higher expression throughout the observation period: the inflammatory genes Hmox1 (mean difference: 0.52, 95% confidence interval (CI): 0.15-1.01) and Tgfb1 (mean difference: 0.099, CI: 0.003-0.194), and the transcription factor Nfkb1 (mean difference: 0.049, CI: 0.011-0.087). The inflammatory genes Cxcl10 and Il1b, and the DNA repair gene Neil3, had a higher gene expression change after hyperoxic reoxygenation at one time point only. Nineteen genes involved in inflammation, transcription regulation, apoptosis, angiogenesis, and glucose transport had significantly different gene expression changes with time in all intervention animals.

CONCLUSION

We confirm that hyperoxic reoxygenation induces a stronger inflammatory gene response than reoxygenation with air.

Mechanisms of perinatal arterial ischemic stroke

The incidence of perinatal stroke is high, similar to that in the elderly, and produces a significant morbidity and severe long-term neurologic and cognitive deficits, including cerebral palsy, epilepsy, neuropsychological impairments, and behavioral disorders. Emerging clinical data and data from experimental models of cerebral ischemia in neonatal rodents have shown that the pathophysiology of perinatal brain damage is multifactorial. These studies have revealed that, far from just being a smaller version of the adult brain, the neonatal brain is unique with a very particular and age-dependent responsiveness to hypoxia-ischemia and focal arterial stroke. In this review, we discuss fundamental clinical aspects of perinatal stroke as well as some of the most recent and relevant findings regarding the susceptibility of specific brain cell populations to injury, the dynamics and the mechanisms of neuronal cell death in injured neonates, the responses of neonatal blood-brain barrier to stroke in relation to systemic and local inflammation, and the long-term effects of stroke on angiogenesis and neurogenesis. Finally, we address translational strategies currently being considered for neonatal stroke as well as treatments that might effectively enhance repair later after injury.

Hypoxic ischemic brain injury: Potential therapeutic interventions for the future

Perinatal hypoxic-ischemic brain injury is a common problem with potentially devastating impact on neurodevelopmental outcomes. While therapeutic hypothermia, the first available treatment for this disease, reduces the risk of death or major neurodevelopmental disability, the risk of major neurologic morbidity following HI remains significant. Basic research has identified cellular mechanisms that mediate neuronal death. This article reviews the cellular processes induced that lead to brain injury following HI, and identify treatments currently under investigation for potential translation to clinical trials.

Spatial working memory deficits in male rats following neonatal hypoxic ischemic brain injury can be attenuated by task modifications

Hypoxia-ischemia (HI; reduction in blood/oxygen supply) is common in infants with serious birth complications, such as prolonged labor and cord prolapse, as well as in infants born prematurely (<37 weeks gestational age; GA). Most often, HI can lead to brain injury in the form of cortical and subcortical damage, as well as later cognitive/behavioral deficits. A common domain of impairment is working memory, which can be associated with heightened incidence of developmental disorders. To further characterize these clinical issues, the current investigation describes data from a rodent model of HI induced on postnatal (P)7, an age comparable to a term (GA 36–38) human. Specifically, we sought to assess working memory using an eight-arm radial water maze paradigm. Study 1 used a modified version of the paradigm, which requires a step-wise change in spatial memory via progressively more difficult tasks, as well as multiple daily trials for extra learning opportunity. Results were surprising and revealed a small HI deficit only for the final and most difficult condition, when a delay before test trial was introduced. Study 2 again used the modified radial arm maze, but presented the most difficult condition from the start, and only one daily test trial. Here, results were expected and revealed a robust and consistent HI deficit across all weeks. Combined results indicate that male HI rats can learn a difficult spatial working memory task if it is presented in a graded multi-trial format, but performance is poor and does not appear to remediate if the task is presented with high initial memory demand. Male HI rats in both studies displayed impulsive characteristics throughout testing evidenced as reduced choice latencies despite more errors. This aspect of behavioral results is consistent with impulsiveness as a core symptom of ADHD—a diagnosis common in children with HI insult. Overall findings suggest that task specific behavioral modifications are crucial to accommodating memory deficits in children suffering from cognitive impairments following neonatal HI.

MicroRNA-23a/b and microRNA-27a/b suppress Apaf-1 protein and alleviate hypoxia-induced neuronal apoptosis

Expression of apoptotic protease activating factor-1 (Apaf-1) gradually decreases during brain development, and this decrease is likely responsible for the decreased sensitivity of brain tissue to apoptosis. However, the mechanism by which Apaf-1 expression is decreased remains elusive. In the present study, we found that four microRNAs (miR-23a/b and miR-27a/b) of miR-23a-27a-24 and miR-23b-27b-24 clusters play key roles in modulating the expression of Apaf-1. First, we found that miR-23a/b and miR-27a/b suppressed the expression of Apaf-1 in vitro. Interestingly, the expression of the miR-23-27-24 clusters in the mouse cortex gradually increased in a manner that was inversely correlated with the pattern of Apaf-1 expression. Second, hypoxic injuries during fetal distress caused reduced expression of the miR-23b and miR-27b that was inversely correlated with an elevation of Apaf-1 expression during neuronal apoptosis. Third, we made neuronal-specific transgenic mice and found that overexpressing the miR-23b and miR-27b in mouse neurons inhibited the neuronal apoptosis induced by intrauterine hypoxia. In conclusion, our results demonstrate, in central neural system, that miR-23a/b and miR-27a/b are endogenous inhibitory factors of Apaf-1 expression and regulate the sensitivity of neurons to apoptosis. Our findings may also have implications for the potential target role of microRNAs in the treatment of neuronal apoptosis-related diseases.

Protection by vascular prostaglandin E2 signaling in hypoxic-ischemic encephalopathy

Hypoxic-ischemic encephalopathy (HIE) in neonates is a leading cause of neurological impairment. Significant progress has been achieved investigating the pathologic contributions of excitotoxicity, oxidative stress, and neuroinflammation to cerebral injury in HIE. Less extensively investigated has been the contribution of vascular dysfunction, and whether modulation of cerebral perfusion may improve HIE outcome. Here, we investigated the function of the prostaglandin E2 (PGE2) EP4 receptor, a vasoactive Gαs-protein coupled receptor (GPCR), in rodent models of neonatal HIE. The function of PGE2 signaling through the EP4 receptor was investigated using pharmacological and conditional knockout genetic strategies in vivo in rodent models of HIE. Pharmacologic activation of the EP4 receptor with a selective agonist was significantly cerebroprotective both acutely and after 7days. Measurement of cerebral perfusion during and after hypoxia-ischemia demonstrated that EP4 receptor activation improved cerebral perfusion in both the contralateral and ipsilateral hypoxic-ischemic hemispheres. To test whether vascular EP4 signaling exerted a critical function in HIE injury, cell specific conditional knockout mouse pups were generated in which endothelial EP4 receptor was selectively deleted postnatally. VE-Cadherin Cre-ER(T2);EP4(lox/lox) pups demonstrated significant increases in cerebral injury as compared to VE-Cadherin Cre-ER(T2);EP4(+/+) control littermates, indicating that endothelial EP4 signaling is protective in HIE. Our findings identify vascular PGE2 signaling through its EP4 receptor as protective in HIE. Given the pharmacologic accessibility of endothelial EP4 GPCRs, these data support further investigation into novel approaches to target cerebral perfusion in neonatal HIE.

Sex differences in behavioral outcome following neonatal hypoxia ischemia: insights from a clinical meta-analysis and a rodent model of induced hypoxic ischemic brain injury

Hypoxia ischemia (HI; reduced oxygen and/or blood flow to the brain) is one of the most common injuries among preterm infants and term infants with birth complications. Both populations show cognitive/behavioral deficits, including impairments in sensory, learning/memory, and attention domains. Clinical data suggests a sex difference in HI outcomes, with males exhibiting more severe cognitive/behavioral deficits relative to matched females. Our laboratory has also reported more severe behavioral deficits among male rats with induced HI relative to females with comparable injury (Hill et al., 2011a,b). The current study initially examined published clinical studies from the past 20years where long-term IQ outcome scores for matched groups of male and female premature infants were reported separately (IQ being the most common outcome measure). A meta-analysis revealed a female "advantage," as indicated by significantly better scores on performance and full scale IQ (but not verbal IQ) for premature females. We then utilized a rodent model of neonatal HI injury to assess sham and postnatal day 7 (P7) HI male and female rats on a battery of behavioral tasks. Results showed expected deficits in HI male rats, but also showed task-dependent sex differences, with HI males having significantly larger deficits than HI females on some tasks but equivalent deficits on other tasks. In contrast to behavioral results, post mortem neuropathology associated with HI was comparable across sex. These findings suggest: 1) neonatal female "protection" in some behavioral domains, as indexed by superior outcome following early injury relative to males; and 2) female protection may entail sex-specific plasticity or compensation, rather than a reduction in gross neuropathology. Further exploration of the mechanisms underlying this sex effect could aid in neuroprotection efforts for at-risk neonates in general, and males in particular. Moreover, our current report of comparable anatomical damage coupled with differences in cognitive outcomes (by sex) provides a framework for future studies to examine neural mechanisms underlying sex differences in cognition and behavior in general.

Interleukin-1 receptor blockade in perinatal brain injury

Interleukin-1 (IL-1) is a potent inflammatory cytokine that can be produced by a variety of cell types throughout the body. While IL-1 is a central mediator of inflammation and response to infection, the role of IL-1 signaling in adult and pediatric brain injury is becoming increasingly clear. Although the mechanisms of IL-1 expression are largely understood, the downstream effects and contributions to excitotoxicity and oxidative stress are poorly defined. Here, we present a review of mechanisms of IL-1 signaling with a focus on the role of IL-1 in perinatal brain injury. We highlight research models of perinatal brain injury and the use of interleukin-1 receptor antagonist (IL-1RA) as an agent of therapeutic potential in preventing perinatal brain injury due to exposure to inflammation.

Aprotinin, but not ε-aminocaproic acid and tranexamic acid, exerts neuroprotection against excitotoxic injury in an in vitro neuronal cell culture model

OBJECTIVE

Lack of availability of aprotinin has resulted in increased clinical use of the alternative antifibrinolytic agents, ε-aminocaproic acid (EACA) and tranexamic acid (TXA), which are known to be associated with an increased risk of seizures. In contrast, aprotinin has previously been demonstrated to be neuroprotective through suppression of excitotoxicity-mediated neuronal degeneration via the extracellular plasminogen/plasmin system. This study compares the effect of antifibrinolytic agents on neuronal and mixed glial/neuronal cell cultures.

METHODS

Mixed cortical cultures containing neuronal and glial cells were prepared from fetal mice and plated on a layer of confluent astrocytes from postnatal pups. A primary neuronal culture was obtained from the same gestational stage and plated in multiwall vessels. Slowly triggered excitotoxicity was induced by 24-hour exposure to 12.5 mM N-methyl-D-aspartate (NMDA). Apoptotic neuronal cell death was induced by exposure of primary neural cultures to 24 hours of serum deprivation.

RESULTS

Compared with NMDA alone, no significant changes in cell death were observed for any dose of TXA or EACA in mixed cultures. Conversely, a clinical dose of aprotinin significantly reduced cell death by -31% on average. Aprotinin reduced apoptotic neuronal cell death from 75% to 37.3%, and to 34.1% at concentrations of 100 and 200 kIU/mL, respectively, and significantly decreased neuronal nuclear damage. These concentrations of aprotinin significantly inhibited caspase 9 and 3/7 activations; 250 kIU/mL aprotinin exerted maximal protection on primary cortical neurons.

CONCLUSIONS

In contrast to aprotinin, EACA and TXA exert no protective effect against excitotoxic neuronal injury that can occur during cardiac surgery.

Detection of hypoxic-ischemic brain injury with 3D-enhanced T2* weighted angiography (ESWAN) imaging

OBJECTIVE

To demonstrate the use of 3D-enhanced T2* weighted angiography (ESWAN) imaging for the observation and quantification of the evolution of brain injury induced by a recently developed model of hypoxic-ischemic brain injury (HI/R) in neonatal piglets.

METHODS

For these experiments, newborn piglets were subjected to HI/R injury, during which ESWAN scanning was performed, followed by H&E staining and immunohistochemistry of AQP-4 expression.

RESULTS

In the striatum, values from T2* weighted magnetic resonance imaging (MRI) increased and reached their highest level at 3 days post injury, whereas T2* values increased and peaked at 24h in the subcortical region. The change in T2* values was concordant with brain edema. Phase values in the subcortical border region were not dependent on time post-injury. Magnitude values were significantly different from the control group, and increased gradually over time in the subcortical border region. Susceptibility-weighted images (SWI) indicated small petechial hemorrhages in the striatum and thalamus, as well as dilated intramedullary veins.

CONCLUSION

SWI images can be used to detect white and gray matter microhemorrhages and dilated intramedullary veins. The T2*, phase, and magnitude map can also reflect the development of brain injury. Our data illustrate that ESWAN imaging can increase the diagnostic sensitivity and specificity of MRI in neonatal hypoxic-ischemic encephalopathy.

Neuroprotective effect of melatonin: a novel therapy against perinatal hypoxia-ischemia

One of the most common causes of mortality and morbidity in children is perinatal hypoxia-ischemia (HI). In spite of the advances in neonatology, its incidence is not diminishing, generating a pediatric population that will require an extended amount of chronic care throughout their lifetime. For this reason, new and more effective neuroprotective strategies are urgently required, in order to minimize as much as possible the neurological consequences of this encephalopathy. In this sense, interest has grown in the neuroprotective possibilities of melatonin, as this hormone may help to maintain cell survival through the modulation of a wide range of physiological functions. Although some of the mechanisms by which melatonin is neuroprotective after neonatal asphyxia remain a subject of investigation, this review tries to summarize some of the most recent advances related with its use as a therapeutic drug against perinatal hypoxic-ischemic brain injury, supporting the high interest in this indoleamine as a future feasible strategy for cerebral asphyctic events.

VEGF expression and microvascular responses to severe transient hypoxia in the fetal sheep brain

BACKGROUND

Fetal hypoxia contributes significantly to the pathogenesis of permanent perinatal brain injury. We hypothesized that hypoxia-induced cerebral angiogenesis and microvascular changes would occur in fetal sheep subjected to a severe hypoxic insult produced by umbilical cord occlusion (UCO) for 10 min.

METHODS

At 124-126 d of gestation, singleton fetal sheep underwent surgery for implantation of catheters and placement of an inflatable cuff around the umbilical cord. A 10-min UCO or sham UCO (n = 5) was induced at 130 d gestation. The fetal brain was collected at 24 h (n = 5) or 48 h (n = 4) after UCO for immunohistochemical analysis of vascular endothelial growth factor (VEGF), Ki67, and serum albumin.

RESULTS

By 48 h after UCO, the percentage of blood vessels expressing VEGF had increased in the subventricular zone, periventricular and subcortical white matter, corpus callosum, and cortex. Alterations in vascular permeability (albumin extravasation) were observed only in the periventricular and subcortical white matter and the subventricular zone following UCO.

CONCLUSION

The upregulation of VEGF expression and increased leakage of plasma protein in the fetal sheep brain show that the microvasculature in white matter is sensitive to hypoxia in the near-term brain.