Sex-specific effects of N-acetylcysteine in neonatal rats treated with hypothermia after severe hypoxia-ischemia

Bumetanide Attenuates Cognitive Deficits and Brain Damage in Rats Subjected to Hypoxia-Ischemia at Two Time Points of the Early Postnatal Period

Neonatal hypoxia-ischemia (HI) is one of the main causes of tissue damage, cell death, and imbalance between neuronal excitation and inhibition and synaptic loss in newborns. GABA, the major inhibitory neurotransmitter of the central nervous system (CNS) in adults, is excitatory at the onset of neurodevelopment and its action depends on the chloride (Cl-) cotransporters NKCC1 (imports Cl-) and KCC2 (exports Cl-) expression. Under basal conditions, the NKCC1/KCC2 ratio decreases over neurodevelopment. Thus, changes in this ratio caused by HI may be related to neurological disorders. The present study evaluated the effects of bumetanide (NKCC cotransporters inhibitor) on HI impairments in two neurodevelopmental periods. Male Wistar rat pups, 3 (PND3) and 11 (PND11) days old, were submitted to the Rice-Vannucci model. Animals were divided into 3 groups: SHAM, HI-SAL, and HI-BUM, considering each age. Bumetanide was administered intraperitoneally at 1, 24, 48, and 72 h after HI. NKCC1, KCC2, PSD-95, and synaptophysin proteins were analyzed after the last injection by western blot. Negative geotaxis, righting reflex, open field, object recognition test, and Morris water maze task were performed to assess neurological reflexes, locomotion, and memory function. Tissue atrophy and cell death were evaluated by histology. Bumetanide prevented neurodevelopmental delay, hyperactivity, and declarative and spatial memory deficits. Furthermore, bumetanide reversed HI-induced brain tissue damage, reduced neuronal death and controlled GABAergic tone, maintained the NKCC1/KCC2 ratio, and synaptogenesis close to normality. Thereby, bumetanide appears to play an important therapeutic role in the CNS, protecting the animals against HI damage and improving functional performance.

Hypothermia combined with extracellular vesicles from clonally expanded immortalized mesenchymal stromal cells improves neurodevelopmental impairment in neonatal hypoxic-ischemic brain injury

BACKGROUND

Neonatal encephalopathy following hypoxia-ischemia (HI) is a leading cause of childhood death and morbidity. Hypothermia (HT), the only available but obligatory therapy is limited due to a short therapeutic window and limited efficacy. An adjuvant therapy overcoming limitations of HT is still missing. Mesenchymal stromal cell (MSC)-derived extracellular vesicles (EVs) have shown promising therapeutic effects in various brain injury models. Challenges associated with MSCs' heterogeneity and senescence can be mitigated by the use of EVs from clonally expanded immortalized MSCs (ciMSCs). In the present study, we hypothesized that intranasal ciMSC-EV delivery overcomes limitations of HT.

METHODS

Nine-day-old C57BL/6 mice were exposed to HI by occlusion of the right common carotid artery followed by 1 h hypoxia (10% oxygen). HT was initiated immediately after insult for 4 h. Control animals were kept at physiological body core temperatures. ciMSC-EVs or vehicle were administered intranasally 1, 3 and 5 days post HI/HT. Neuronal cell loss, inflammatory and regenerative responses were assessed via immunohistochemistry, western blot and real-time PCR 7 days after insult. Long-term neurodevelopmental outcome was evaluated by analyses of cognitive function, activity and anxiety-related behavior 5 weeks after HI/HT.

RESULTS

In contrast to HT monotherapy, the additional intranasal therapy with ciMSC-EVs prevented HI-induced cognitive deficits, hyperactivity and alterations of anxiety-related behavior at adolescence. This was preceded by reduction of striatal neuronal loss, decreased endothelial, microglia and astrocyte activation; reduced expression of pro-inflammatory and increased expression of anti-inflammatory cytokines. Furthermore, the combination of HT with intranasal ciMSC-EV delivery promoted regenerative and neurodevelopmental processes, including endothelial proliferation, neurotrophic growth factor expression and oligodendrocyte maturation, which were not altered by HT monotherapy.

CONCLUSION

Intranasal delivery of ciMSC-EVs represents a novel adjunct therapy, overcoming limitations of acute HT thereby offering new possibilities for improving long-term outcomes in neonates with HI-induced brain injury.

Neuroserpin As an Adjuvant Therapy for Hypothermia on Brain Injury in Neonatal Hypoxic-Ischemic Rats

OBJECTIVE

 We aimed to assess the effects of neuroserpin and its combination with hypothermia on hypoxic-ischemic (HI) brain injury in neonatal rats. Neuroserpin is an axon-secreted serine protease inhibitor and is important for brain development, neuronal survival, and synaptic plasticity.

STUDY DESIGN

 Male Wistar-Albino rats on postnatal day 7 (P7) were randomly divided into five groups: sham group (n = 10), (HI; n = 10), hypoxic-ischemic hypothermia (HIH; n = 10), hypoxic-ischemic neuroserpin (HIN; n = 10), and hypoxic-ischemic neuroserpin-hypothermia (HINH; n = 10). The P7 rat brain's maturation is similar to a late preterm human brain at 34 to 36 weeks of gestation. HI was induced in rats on P7 as previously described. A single dose of 0.2 µM neuroserpin (HINH and HIN) or an equivalent volume of phosphate-buffered saline (sham, HIH, and HI) was administered intraventricularly by a Hamilton syringe immediately after hypoxia. In the follow-up, pups were subjected to systemic hypothermia or normothermia for 2 hours. Euthanasia was performed for histopathological evaluation on P10. Apoptosis was detected by caspase-3 activity and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining and was counted in the hippocampus.

RESULTS

 In comparison to the HI group, the TUNEL-positive and caspase-3-positive neurons in the sham, HIN, HIH, and HINH groups were considerably lower (13.4 ± 1.0 vs. 1.9 ± 0.9, 6.0 ± 0.9, 5.3 ± 1.6, and 4.0 ± 1.1; p < 0.001) and (13.5 ± 1.7 vs. 1.2 ± 0.7, 9.1 ± 2.7, 4.8 ± 1.0, and 3.9 ± 1.6; p < 0.001). HIN, HIH, and HINH, compared to the sham group, showed more TUNEL-positive and caspase-3-positive neurons (6.0 ± 0.9, 5.3 ± 1.6, 4.0 ± 1.1 vs. 1.9 ± 0.9 and 9.1 ± 2.7, 4.8 ± 1.0, 3.9 ± 1.6 vs. 1.2 ± 0.7; p < 0.001). The HINH group (synergistic effect) had significantly fewer TUNEL-positive neurons and caspase-3-positive neurons than the HIN group (4.0 ± 1.1vs. 6.0 ± 0.9 and 3.9 ± 1.6 vs. 9.1 ± 2.7; p < 0.001).

CONCLUSION

 Our study showed that both neuroserpin alone and as an adjuvant treatment for hypothermia may have a neuroprotective effect on brain injury.

KEY POINTS

· Neuroserpin decreased brain injury.. · Neuroserpin showed a synergistic effect when used as an adjuvant treatment for hypothermia.. · The neuroprotective effect of neuroserpine was related to its antiapoptotic properties..

N-Acetylcysteine Administration Attenuates Sensorimotor Impairments Following Neonatal Hypoxic-Ischemic Brain Injury in Rats

Hypoxic ischemic (HI) brain injury that occurs during neonatal period has been correlated with severe neuronal damage, behavioral deficits and infant mortality. Previous evidence indicates that N-acetylcysteine (NAC), a compound with antioxidant action, exerts a potential neuroprotective effect in various neurological disorders including injury induced by brain ischemia. The aim of the present study was to investigate the role of NAC as a potential therapeutic agent in a rat model of neonatal HI brain injury and explore its long-term behavioral effects. To this end, NAC (50 mg/kg/dose, i.p.) was administered prior to and instantly after HI, in order to evaluate hippocampal and cerebral cortex damage as well as long-term functional outcome. Immunohistochemistry was used to detect inducible nitric oxide synthase (iNOS) expression. The results revealed that NAC significantly alleviated sensorimotor deficits and this effect was maintained up to adulthood. These improvements in functional outcome were associated with a significant decrease in the severity of brain damage. Moreover, NAC decreased the short-term expression of iNOS, a finding implying that iNOS activity may be suppressed and that through this action NAC may exert its therapeutic action against neonatal HI brain injury.

Therapeutic hypothermia for the treatment of neonatal hypoxia-ischemia: sex-dependent modulation of reactive astrogliosis

Therapeutic hypothermia (TH) is the standard treatment for neonatal hypoxia-ischemia (HI) with a time window limited up to 6 h post injury. However, influence of sexual dimorphism in the therapeutic window for TH has not yet been elucidated in animal models of HI. Therefore, the aim of this study was to investigate the most effective time window to start TH in male and female rats submitted to neonatal HI. Wistar rats (P7) were divided into the following groups: NAÏVE and SHAM (control groups), HI (submitted to HI) and TH (submitted to HI and TH; 32ºC for 5 h). TH was started at 2 h (TH-2 h group), 4 h (TH-4 h group), or 6 h (TH-6 h group) after HI. At P14, animals were subjected to behavioural tests, volume of lesion and reactive astrogliosis assessments. Male and female rats from the TH-2 h group showed reduction in the latency of behavioral tests, and decrease in volume of lesion and intensity of GFAP immunofluorescence. TH-2 h females also showed reduction of degenerative cells and morphological changes in astrocytes. Interestingly, females from the TH-6 h group showed an increase in volume of lesion and in number of degenerative hippocampal cells, associated with worse behavioral performance. Together, these results indicate that TH neuroprotection is time- and sex-dependent. Moreover, TH started later (6 h) can worsen volume of brain lesion in females. These data indicate the need to develop specific therapeutic protocols for each sex and reinforce the importance of early onset of the hypothermic treatment.

Cerebral Oxygenation and Metabolism After Hypoxia-Ischemia

Perinatal hypoxia-ischemia (HI) is still a significant contributor to mortality and adverse neurodevelopmental outcomes in term and preterm infants. HI brain injury evolves over hours to days, and involves complex interactions between the endogenous protective and pathological processes. Understanding the timing of evolution of injury is vital to guide treatment. Post-HI recovery is associated with a typical neurophysiological profile, with stereotypic changes in cerebral perfusion and oxygenation. After the initial recovery, there is a delayed, prolonged reduction in cerebral perfusion related to metabolic suppression, followed by secondary deterioration with hyperperfusion and increased cerebral oxygenation, associated with altered neurovascular coupling and impaired cerebral autoregulation. These changes in cerebral perfusion are associated with the stages of evolution of injury and injury severity. Further, iatrogenic factors can also affect cerebral oxygenation during the early period of deranged metabolism, and improving clinical management may improve neuroprotection. We will review recent evidence that changes in cerebral oxygenation and metabolism after HI may be useful biomarkers of prognosis.

Mitochondrial dysfunction in perinatal asphyxia: role in pathogenesis and potential therapeutic interventions

Perinatal asphyxia (PA)-induced brain injury may present as hypoxic-ischemic encephalopathy in the neonatal period, and long-term sequelae such as spastic motor deficits, intellectual disability, seizure disorders and learning disabilities. The brain injury is secondary to both the hypoxic-ischemic event and oxygenation-reperfusion following resuscitation. Following PA, a time-dependent progression of neuronal insult takes place in terms of transition of cell death from necrosis to apoptosis. This transition is the result of time-dependent progression of pathomechanisms which involve excitotoxicity, oxidative stress, and ultimately mitochondrial dysfunction in developing brain. More precisely mitochondrial respiration is suppressed and calcium signalling is dysregulated. Consequently, Bax-dependent mitochondrial permeabilization occurs leading to release of cytochrome c and activation of caspases leading to transition of cell death in developing brain. The therapeutic window lies within this transition process. At present, therapeutic hypothermia (TH) is the only clinical treatment available for treating moderate as well as severe asphyxia in new-born as it attenuates secondary loss of high-energy phosphates (ATP) (Solevåg et al. in Free Radic Biol Med 142:113-122, 2019; Gunn et al. in Pediatr Res 81:202-209, 2017), improving both short- and long-term outcomes. Mitoprotective therapies can offer a new avenue of intervention alone or in combination with therapeutic hypothermia for babies with birth asphyxia. This review will explore these mitochondrial pathways, and finally will summarize past and current efforts in targeting these pathways after PA, as a means of identifying new avenues of therapeutic intervention.

NAC and Vitamin D Improve CNS and Plasma Oxidative Stress in Neonatal HIE and Are Associated with Favorable Long-Term Outcomes

N-acetylcysteine (NAC) and vitamin D provide effective neuroprotection in animal models of severe or inflammation-sensitized hypoxic ischemic encephalopathy (HIE). To translate these FDA-approved drugs to HIE neonates, we conducted an early phase, open-label trial of 10 days of NAC (25, 40 mg/kg q12h) + 1,25(OH)₂D (calcitriol 0.05 mg/kg q12h, 0.03 mg/kg q24h), (NVD), for pharmacokinetic (PK) estimates during therapeutic hypothermia and normothermia. We paired PK samples with pharmacodynamic (PD) targets of plasma isoprostanoids, CNS glutathione (GSH) and total creatine (tCr) by serial MRS in basal ganglia (BG) before and after NVD infusion at five days. Infants had moderate (n = 14) or severe HIE (n = 16), funisitis (32%), and vitamin D deficiency (75%). NVD resulted in rapid, dose-responsive increases in CNS GSH and tCr that correlated positively with plasma [NAC], inversely with plasma isofurans, and was greater in infants with lower baseline [GSH] and [tCr], suggesting increases in these PD markers were titrated by neural demand. Hypothermia and normothermia altered NAC PK estimates. NVD was well tolerated. Excluding genetic syndromes (2), prolonged ECMO (2), lost-to-follow-up (1) and SIDS death (1), 24 NVD treated HIE infants have no evidence of cerebral palsy, autism or cognitive delay at 24–48 months. These data confirm that low, safe doses of NVD in HIE neonates decreased oxidative stress in plasma and CNS, improved CNS energetics, and are associated with favorable developmental outcomes at two to four years.

Umbilical cord blood therapy modulates neonatal hypoxic ischemic brain injury in both females and males

Preclinical and clinical studies have shown that sex is a significant risk factor for perinatal morbidity and mortality, with males being more susceptible to neonatal hypoxic ischemic (HI) brain injury. No study has investigated sexual dimorphism in the efficacy of umbilical cord blood (UCB) cell therapy. HI injury was induced in postnatal day 10 (PND10) rat pups using the Rice-Vannucci method of carotid artery ligation. Pups received 3 doses of UCB cells (PND11, 13, 20) and underwent behavioural testing. On PND50, brains were collected for immunohistochemical analysis. Behavioural and neuropathological outcomes were assessed for sex differences. HI brain injury resulted in a significant decrease in brain weight and increase in tissue loss in females and males. Females and males also exhibited significant cell death, region-specific neuron loss and long-term behavioural deficits. Females had significantly smaller brains overall compared to males and males had significantly reduced neuron numbers in the cortex compared to females. UCB administration improved multiple aspects of neuropathology and functional outcomes in males and females. Females and males both exhibited injury following HI. This is the first preclinical evidence that UCB is an appropriate treatment for neonatal brain injury in both female and male neonates.

NAC and Vitamin D Restore CNS Glutathione in Endotoxin-Sensitized Neonatal Hypoxic-Ischemic Rats

Therapeutic hypothermia does not improve outcomes in neonatal hypoxia ischemia (HI) complicated by perinatal infection, due to well-described, pre-existing oxidative stress and neuroinflammation that shorten the therapeutic window. For effective neuroprotection post-injury, we must first define and then target CNS metabolomic changes immediately after endotoxin-sensitized HI (LPS-HI). We hypothesized that LPS-HI would acutely deplete reduced glutathione (GSH), indicating overwhelming oxidative stress in spite of hypothermia treatment in neonatal rats. Post-natal day 7 rats were randomized to sham ligation, or severe LPS-HI (0.5 mg/kg 4 h before right carotid artery ligation, 90 min 8% O2), followed by hypothermia alone or with N-acetylcysteine (25 mg/kg) and vitamin D (1,25(OH)2D3, 0.05 μg/kg) (NVD). We quantified in vivo CNS metabolites by serial 7T MR Spectroscopy before, immediately after LPS-HI, and after treatment, along with terminal plasma drug concentrations. GSH was significantly decreased in all LPS-HI rats compared with baseline and sham controls. Two hours of hypothermia alone did not improve GSH and allowed glutamate + glutamine (GLX) to increase. Within 1 h of administration, NVD increased GSH close to baseline and suppressed GLX. The combination of NVD with hypothermia rapidly improved cellular redox status after LPS-HI, potentially inhibiting important secondary injury cascades and allowing more time for hypothermic neuroprotection.

Drug delivery platforms for neonatal brain injury

Hypoxic-ischemic encephalopathy (HIE), initiated by the interruption of oxygenated blood supply to the brain, is a leading cause of death and lifelong disability in newborns. The pathogenesis of HIE involves a complex interplay of excitotoxicity, inflammation, and oxidative stress that results in acute to long term brain damage and functional impairments. Therapeutic hypothermia is the only approved treatment for HIE but has limited effectiveness for moderate to severe brain damage; thus, pharmacological intervention is explored as an adjunct therapy to hypothermia to further promote recovery. However, the limited bioavailability and the side-effects of systemic administration are factors that hinder the use of the candidate pharmacological agents. To overcome these barriers, therapeutic molecules may be packaged into nanoscale constructs to enable their delivery. Yet, the application of nanotechnology in infants is not well examined, and the neonatal brain presents unique challenges. Novel drug delivery platforms have the potential to magnify therapeutic effects in the damaged brain, mitigate side-effects associated with high systemic doses, and evade mechanisms that remove the drugs from circulation. Encouraging pre-clinical data demonstrates an attenuation of brain damage and increased structural and functional recovery. This review surveys the current progress in drug delivery for treating neonatal brain injury.

Perinatal hypoxic-ischemic damage: review of the current treatment possibilities

Neonatal hypoxic-ischemic encephalopathy is a disorder with heterogeneous manifestation due to asphyxia during perinatal period. It affects approximately 3-12 children per 1000 live births and cause death of 1 million neonates worldwide per year. Besides, motor disabilities, seizures, impaired muscle tone and epilepsy are few of the consequences of hypoxic-ischemic encephalopathy. Despite an extensive research effort regarding various treatment strategies, therapeutic hypothermia with intensive care unit supportive treatment remains the only approved method for neonates who have suffered from moderate to severe hypoxic-ischemic encephalopathy. However, these protocols are only partially effective given that many infants still suffer from severe brain damage. Thus, further research to systematically test promising neuroprotective treatments in combination with hypothermia is essential. In this review, we discussed the pathophysiology of hypoxic-ischemic encephalopathy and delved into different promising treatment modalities, such as melatonin and erythropoietin. However, preclinical studies and clinical trials are still needed to further elucidate the mechanisms of action of these modalities.

N-acetylcysteine reduces brain injury after delayed hypoxemia following traumatic brain injury

Preclinical investigations into neuroprotective agents for traumatic brain injury (TBI) have shown promise when administered before or very early after experimental TBI. However clinical trials of therapeutics demonstrating preclinical efficacy for TBI have failed to replicate these results in humans, a lost in translation phenomenon. N-acetylcysteine (NAC) is a potent anti-oxidant with demonstrated efficacy in pre-clinical TBI when administered early after primary injury. Utilizing our clinically relevant mouse model, we hypothesized that NAC administration in a clinically relevant timeframe could improve the brain's resilience to the secondary insult of hypoxemia. NAC or vehicle administered daily starting 2 h prior to hypoxemia (24 h after controlled cortical impact) for 3 doses in male mice reduced short-term axonal injury and hippocampal neuronal loss. Six month behavioral assessments including novel object recognition, socialization, Barnes maze, and fear conditioning did not reveal performance differences between sham controls and injured mice receiving NAC or saline vehicle. At 7 months after injury, NAC administered mice had reduced hippocampal neuronal loss but no reduction in lesion volume. In summary, our preclinical trial to test the neuroprotective efficacy of NAC against a secondary hypoxic insult after TBI demonstrated short and long-term neuropathological evidence of neuroprotection but a lack of detectable differences in long-term behavioral assessments between sham controls and injured mice limits conclusions on its impact on long-term neurobehavioral outcomes.

How to Improve the Antioxidant Defense in Asphyxiated Newborns-Lessons from Animal Models

Oxygen free radicals have been implicated in brain damage after neonatal asphyxia. In the early phase of asphyxia/reoxygenation, changes in antioxidant enzyme activity play a pivotal role in switching on and off the cascade of events that can kill the neurons. Hypoxia/ischemia (H/I) forces the brain to activate endogenous mechanisms (e.g., antioxidant enzymes) to compensate for the lost or broken neural circuits. It is important to evaluate therapies to enhance the self-protective capacity of the brain. In animal models, decreased body temperature during neonatal asphyxia has been shown to increase cerebral antioxidant capacity. However, in preterm or severely asphyxiated newborns this therapy, rather than beneficial seems to be harmful. Thus, seeking new therapeutic approaches to prevent anoxia-induced complications is crucial. Pharmacotherapy with deferoxamine (DFO) is commonly recognized as a beneficial regimen for H/I insult. DFO, via iron chelation, reduces oxidative stress. It also assures an optimal antioxidant protection minimizing depletion of the antioxidant enzymes as well as low molecular antioxidants. In the present review, some aspects of recently acquired insight into the therapeutic effects of hypothermia and DFO in promoting neuronal survival after H/I are discussed.

Variability and sex-dependence of hypothermic neuroprotection in a rat model of neonatal hypoxic-ischaemic brain injury: a single laboratory meta-analysis

Therapeutic hypothermia (HT) is standard care for term infants with hypoxic–ischaemic (HI) encephalopathy. However, the efficacy of HT in preclinical models, such as the Vannucci model of unilateral HI in the newborn rat, is often greater than that reported from clinical trials. Here, we report a meta-analysis of data from every experiment in a single laboratory, including pilot data, examining the effect of HT in the Vannucci model. Across 21 experiments using 106 litters, median (95% CI) hemispheric area loss was 50.1% (46.0–51.9%; n = 305) in the normothermia group, and 41.3% (35.1–44.9%; n = 317) in the HT group, with a bimodal injury distribution. Median neuroprotection by HT was 17.6% (6.8–28.3%), including in severe injury, but was highly-variable across experiments. Neuroprotection was significant in females (p < 0.001), with a non-significant benefit in males (p = 0.07). Animals representing the median injury in each group within each litter (n = 277, 44.5%) were also analysed using formal neuropathology, which showed neuroprotection by HT throughout the brain, particularly in females. Our results suggest an inherent variability and sex-dependence of the neuroprotective response to HT, with the majority of studies in the Vannucci model vastly underpowered to detect true treatment effects due to the distribution of injury.

Exogenous Ketone Bodies as Promising Neuroprotective Agents for Developmental Brain Injury

Ketone bodies are a promising area of neuroprotection research that may be ideally suited to the injured newborn. During normal development, the human infant is in significant ketosis for at least the first week of life. Ketone uptake and metabolism is upregulated in the both the fetus and neonate, with ketone bodies providing at least 10% of cerebral metabolic energy requirements, as well as being the preferred precursors for the synthesis of fatty acids and cholesterol. At the same time, ketone bodies have been shown to have multiple neuroprotective effects, including being anticonvulsant, decreasing oxidative stress and inflammation, and epigenetically upregulating the production of neurotrophic factors. While ketogenic diets and exogenous ketosis are largely being investigated in the setting of adult brain injury, the adaptation of the neonate to ketosis suggests that developmental brain injury may be the area most suited to the use of ketones for neuroprotection. Here, we describe the mechanisms by which ketone bodies exert their neuroprotective effects, and how these may translate to benefits within each of the phases of neonatal asphyxial brain injury.

Mechanism and Treatment Related to Oxidative Stress in Neonatal Hypoxic-Ischemic Encephalopathy

Hypoxic ischemic encephalopathy (HIE) is a type of neonatal brain injury, which occurs due to lack of supply and oxygen deprivation to the brain. It is associated with a high morbidity and mortality rate. There are several therapeutic strategies that can be used to improve outcomes in patients with HIE. These include cell therapies such as marrow mesenchymal stem cells (MSCs) and umbilical cord blood stem cells (UCBCs), which are being incorporated into the new protocols for the prevention of ischemic brain damage. The focus of this review is to discuss the mechanism of oxidative stress in HIE and summarize the current available treatments for HIE. We hope that a better understanding of the relationship between oxidative stress and HIE will provide new insights on the potential therapy of this devastating condition.

Severe Perinatal Hypoxic-Ischemic Brain Injury Induces Long-Term Sensorimotor Deficits, Anxiety-Like Behaviors and Cognitive Impairment in a Sex-, Age- and Task-Selective Manner in C57BL/6 Mice but Can Be Modulated by Neonatal Handling

Perinatal brain injury (PBI) leads to neurological disabilities throughout life, from motor deficits, cognitive limitations to severe cerebral palsy. Yet, perinatal brain damage has limited therapeutic outcomes. Besides, the immature brain of premature children is at increased risk of hypoxic/ischemic (HI) injury, with males being more susceptible to it and less responsive to protective/therapeutical interventions. Here, we model in male and female C57BL/6 mice, the impact of neonatal HI and the protective effects of neonatal handling (NH), an early life tactile and proprioceptive sensory stimulation. From postnatal day 1 (PND1, modeling pre-term) to PND21 randomized litters received either NH or left undisturbed. HI brain damage occurred by permanent left carotid occlusion followed by hypoxia at PND7 (modeling full-term) in half of the animals. The behavioral and functional screening of the pups at weaning (PND23) and their long-term outcomes (adulthood, PND70) were evaluated in a longitudinal study, as follows: somatic development (weight), sensorimotor functions (reflexes, rods and hanger tests), exploration [activity (ACT) and open-field (OF) test], emotional and anxiety-like behaviors [corner, open-field and dark-light box (DLB) tests], learning and memory [T-maze (TM) and Morris Water-Maze (MWM)]. HI induced similar brain damage in both sexes but affected motor development, sensorimotor functions, induced hyperactivity at weaning, and anxiety-like behaviors and cognitive deficits at adulthood, in a sex- and age-dependent manner. Thus, during ontogeny, HI affected equilibrium especially in females and prehensility in males, but only reflexes at adulthood. Hyperactivity of HI males was normalized at adulthood. HI increased neophobia and other anxiety-like behaviors in males but emotionality in females. Both sexes showed worse short/long-term learning, but memory was more affected in males. Striking neuroprotective effects of NH were found, with significantly lower injury scores, mostly in HI males. At the functional level, NH reversed the impaired reflex responses and improved memory performances in hippocampal-dependent spatial-learning tasks, especially in males. Finally, neuropathological correlates referred to atrophy, neuronal densities and cellularity in the affected areas [hippocampal-CA, caudate/putamen, thalamus, neocortex and corpus callosum (CC)] point out distinct neuronal substrates underlying the sex- and age- functional impacts of these risk/protection interventions on sensorimotor, behavioral and cognitive outcomes from ontogeny to adulthood.

Protective effects of zinc and N-acetyl-L-cysteine supplementation against cadmium induced erythrocyte cytotoxicity in Arbor Acres broiler chickens (Gallus gallus domesticus)

Cadmium (Cd) is one of the most toxic metals released into the environment. Here, we investigated the protective role of Zn²⁺ and/or N-acetyl-L-cysteine (NAC) against Cd cytotoxicity in the erythrocytes of Arbor Acres (AA) broiler chickens. Four hundred one-day-old AA chickens were divided into 12 groups for in vitro and in vivo studies. Zn²⁺ and/or NAC was given to the Cd exposed AA chickens to assess their protective roles. This was accomplished by investigating nuclear morphological abnormalities, oxidative stress (SOD, CAT, GPx, GSH and T-AOC), cell apoptosis, ROS accumulation and mitochondrial membrane potential (MMP). Results showed that Cd led to dose- and time-dependent cytotoxicity in the erythrocytes of AA chickens characterized by morphological abnormalities, nucleus damage, increased apoptosis rate and antioxidants depletion. Zn²⁺ or NAC significantly decreased the erythrocyte apoptosis, ROS production and mitochondrial membrane depolarization caused by Cd. SOD, CAT, GPx, GSH and T-AOC activities significantly decreased both in serum and erythrocytes of Cd exposed AA chickens. The supplementation with Zn²⁺ or NAC alleviated Cd induced oxidative stress through promoting SOD or GPx/GSH activities respectively. NAC presented a better role in reducing apoptosis, improving antioxidant activities more than Zn²⁺ in vitro. The combined use of Zn²⁺ and NAC enhanced cytoprotection in Cd exposed erythrocytes of AA chickens compared to Zn²⁺ or NAC alone. In conclusion, Zn²⁺ and NAC exerted remarkable protective roles in Cd exposed erythrocytes of AA chickens by inhibiting cell apoptosis and oxidative stress, and this provides a promising approach to antagonize Cd poisoning in poultry.

Peripheral myeloid cells contribute to brain injury in male neonatal mice

Background

Neonatal brain injury is increasingly understood to be linked to inflammatory processes that involve specialised CNS and peripheral immune interactions. However, the role of peripheral myeloid cells in neonatal hypoxic-ischemic (HI) brain injury remains to be fully investigated.

Methods

We employed the Lys-EGFP-ki mouse that allows enhanced green fluorescent protein (EGFP)-positive mature myeloid cells of peripheral origin to be easily identified in the CNS. Using both flow cytometry and confocal microscopy, we investigated the accumulation of total EGFP⁺ myeloid cells and myeloid cell subtypes: inflammatory monocytes, resident monocytes and granulocytes, in the CNS for several weeks following induction of cerebral HI in postnatal day 9 mice. We used antibody treatment to curb brain infiltration of myeloid cells and subsequently evaluated HI-induced brain injury.

Results

We demonstrate a temporally biphasic pattern of inflammatory monocyte and granulocyte infiltration, characterised by peak infiltration at 1 day and 7 days after hypoxia-ischemia. This occurs against a backdrop of continuous low-level resident monocyte infiltration. Antibody-mediated depletion of circulating myeloid cells reduced immune cell accumulation in the brain and reduced neuronal loss in male but not female mice.

Conclusion

This study offers new insight into sex-dependent central-peripheral immune communication following neonatal brain injury and merits renewed interest in the roles of granulocytes and monocytes in lesion development.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1344-9) contains supplementary material, which is available to authorized users.

Nesting Environment Provides Sex-Specific Neuroprotection in a Rat Model of Neonatal Hypoxic-Ischemic Injury

Hypoxic-ischemic (HI) encephalopathy is a devastating injury that occurs when the fetal brain is deprived of oxygen and blood to a degree that may lead to neurological damage, seizing and cerebral palsy. In rodents, early environmental enrichment that promotes maternal care-taking behavior (mCTB) can improve neurobehavioral outcomes and protect against neurological decline. We hypothesized that an enhanced nesting environment would improve mCTB as measured by pup weight gain, and support greater HI recovery in developing rats. Pregnant dams (E15-16) were introduced to either control Standard Facility (SF) housing or closed nestbox (CN) conditions and maintained in larger cages through pup weaning. On postnatal day (PND) 7, male and female Long-Evans rat pups (N = 73) were randomly sorted into one of two surgical conditions: control and HI. HI pups received isoflurane anesthesia and right carotid artery ligation, a 2-h rest followed by 90 min exposure to a moist hypoxic (92% N, 8% O2) chamber. Pups (PND 8) were weighed daily, and tested on the Morris Water Maze (MWM) task (PND 35-50). Results demonstrate significant differences afforded to male and female pups based on weight measure, where CN-rearing modifies pre-weaning adolescent weights in females and increases post-weaning weights in males and females by an average of 10 g. Following successful MWM training and acquisition (PND 35-37), both male and female CN-raised animals demonstrated faster latency to find the hidden platform (HP) during HP trials (PND 38-42) and appeared to freely explore the MWM pool during an additional probe trial (PND 43). Moreover, after sacrifice (PND 60), CN rearing created sex-specific alterations in brain-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GDNF) immunopositive cell staining of the dorsomedial striatum and CA1 of the hippocampus. CN-rearing afforded HI males higher BDNF levels in the striatum and produced greater GDNF levels in the hippocampus of HI-injured females. These results suggest that early life environmental enrichment positively modifies nesting environment, increases weight gain, as well as spatial learning and memory in a sex-specific directionality. Our findings also implicate correlative changes in corticolimbic neurotrophin protein levels in the CN-reared animals that may contribute to these benefits.

N-Acetylcysteine rapidly replenishes central nervous system glutathione measured via magnetic resonance spectroscopy in human neonates with hypoxic-ischemic encephalopathy

Persistent oxidative stress depletes reduced glutathione (GSH), an intracellular antioxidant and an important determinant of CNS injury after hypoxia ischemia. We used standard, short echo time Stimulated Echo Acquisition Mode (STEAM) to detect GSH by magnetic resonance spectroscopy (MRS) in 24 term neonates with hypoxic-ischemic encephalopathy (HIE), on day of life 5-6, after rewarming from therapeutic hypothermia. MRS demonstrated reliable, consistent GSH of 1·64 ± 0·20 mM in the basal ganglia immediately before intravenous infusion of N-acetylcysteine. N-acetylcysteine resulted in a rapid and significant GSH increase to 1·93 ± 0.23 mM within 12-30 min after completion of infusion ( n = 21, p < 0.0001, paired t-test), compared with those who did not receive N-acetylcysteine ( n = 3, GSH = 1.66 ± 0.06 mM and 1.64 ± 0.09 mM). In one perinatal stroke patient, GSH in the diffusion-restricted stroke area was 1.0 mM, indicating significant compromise of intracellular redox potential, which also improved after N-acetylcysteine. For comparison, GSH in healthy term neonates has been reported at 2.5 ± 0.9 mM in the thalamus. This is the first report to show persistent oxidative stress reflected in GSH during the subacute phase in neonates with HIE and rapid response to N-acetylcysteine, using a short echo MRS sequence that is available on all clinical scanners without spectral editing.

Sexually Dimorphic Outcomes after Neonatal Stroke and Hypoxia-Ischemia

Cohort studies have demonstrated a higher vulnerability in males towards ischemic and/or hypoxic-ischemic injury in infants born near- or full-term. Male sex was also associated with limited brain repair following neonatal stroke and hypoxia-ischemia, leading to increased incidence of long-term cognitive deficits compared to females with similar brain injury. As a result, the design of pre-clinical experiments considering sex as an important variable was supported and investigated because neuroprotective strategies to reduce brain injury demonstrated sexual dimorphism. While the mechanisms underlining these differences between boys and girls remain unclear, several biological processes are recognized to play a key role in long-term neurodevelopmental outcomes: gonadal hormones across developmental stages, vulnerability to oxidative stress, modulation of cell death, and regulation of microglial activation. This review summarizes the current evidence for sex differences in neonatal hypoxic-ischemic and/or ischemic brain injury, considering the major pathways known to be involved in cognitive and behavioral deficits associated with damages of the developing brain.

Oxidative stress and endoplasmic reticulum (ER) stress in the development of neonatal hypoxic-ischaemic brain injury

Birth asphyxia in term neonates affects 1–2/1000 live births and results in the development of hypoxic–ischaemic encephalopathy with devastating life-long consequences. The majority of neuronal cell death occurs with a delay, providing the potential of a treatment window within which to act. Currently, treatment options are limited to therapeutic hypothermia which is not universally successful. To identify new interventions, we need to understand the molecular mechanisms underlying the injury. Here, we provide an overview of the contribution of both oxidative stress and endoplasmic reticulum stress in the development of neonatal brain injury and identify current preclinical therapeutic strategies.

Neuroprotection with hypothermia and allopurinol in an animal model of hypoxic-ischemic injury: Is it a gender question?

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) is one of the most important causes of neonatal brain injury. Therapeutic hypothermia (TH) is the standard treatment for term newborns after perinatal hypoxic ischemic injury (HI). Despite this, TH does not provide complete neuroprotection. Allopurinol seems to be a good neuroprotector in several animal studies, but it has never been tested in combination with hypothermia. Clinical findings show that male infants with (HI) fare more poorly than matched females in cognitive outcomes. However, there are few studies about neuroprotection taking gender into account in the results. The aim of the present study was to evaluate the potential additive neuroprotective effect of allopurinol when administrated in association with TH in a rodent model of moderate HI. Gender differences in neuroprotection were also evaluated.

METHODS

P10 male and female rat pups were subjected to HI (Vannucci model) and randomized into five groups: sham intervention (Control), no treatment (HI), hypothermia (HIH), allopurinol (HIA), and dual therapy (hypothermia and allopurinol) (HIHA). To evaluate a treatment's neuroprotective efficiency, 24 hours after the HI event caspase3 activation was measured. Damaged area and hippocampal volume were also measured 72 hours after the HI event. Negative geotaxis test was performed to evaluate early neurobehavioral reflexes. Learning and spatial memory were assessed via Morris Water Maze (MWM) test at 25 days of life.

RESULTS

Damaged area and hippocampal volume were different among treatment groups (p = 0.001). The largest tissue lesion was observed in the HI group, followed by HIA. There were no differences between control, HIH, and HIHA. When learning process was analyzed, no differences were found. Females from the HIA group had similar results to the HIH and HIHA groups. Cleaved caspase 3 expression was increased in both HI and HIA. Despite this, in females cleaved caspase-3 was only differently increased in the HI group. All treated animals present an improvement in short-term (Negative geotaxis) and long-term (WMT) functional tests. Despite this, treated females present better long-term outcome. In short-term outcome no sex differences were observed.

CONCLUSIONS

Our results suggest that dual therapy confers great neuroprotection after an HI event. There were functional, histological, and molecular improvements in all treated groups. These differences were more important in females than in males. No statistically significant differences were found between HIHA and HIH; both of them present a great improvement. Our results support the idea of different regulation mechanisms and pathways of cell death, depending on gender.

Vitamin D improves functional outcomes in neonatal hypoxic ischemic male rats treated with N-acetylcysteine and hypothermia

Hypothermia treatment neuroprotects approximately 50% of neonates who present with moderate to severe hypoxic ischemic encephalopathy (HIE). N-acetylcysteine (NAC), a potent antioxidant, is neuroprotective in combination with hypothermia in neonatal hypoxia-ischemia (HI) female rats, but less protective in males. Vitamin D is a neurosteroid, which may provide immunomodulation and improve outcomes for both sexes. We investigated the efficacy of this combination of drugs with hypothermia after severe HI, as well as potential mechanisms of vitamin D effects in the transition to chronic inflammation. DOL 7 rats were randomized to sham, or HI and hypothermia treated with either saline (HYPO), NAC (50 mg/kg/d, HNAC), or HNAC plus 1,25-dihydroxy-vitamin D₃ (0.1 μg/kg/d, HNAC + VitD) daily for 2 weeks. A second set of animals were randomized and treated for 11 days to investigate vitamin D metabolism and inflammatory mediators. Rats treated with HNAC + VitD performed significantly better on tests of strength and use of affected limb, adaptive sensorimotor skills, motor sequence learning, and working memory than either HYPO or HNAC, particularly benefiting male rats. Significantly fewer rats in the HNAC + VitD group had severe hemispheric volume loss. HI injury decreased serum vitamin D at 11 days and induced the enzyme that deactivates vitamin D in the hippocampus, particularly in males. Persistent vitamin D dysregulation was seen in both hippocampi in males, which was not reversed by hypothermia. Vitamin D in combination with hypothermia and NAC supports functional recovery in both sexes of neonatal rats significantly better than hypothermia alone or hypothermia and NAC in this severe HI model.

Sex Bias in Pathogenesis of Autoimmune Neuroinflammation: Relevance for Dimethyl Fumarate Immunomodulatory/Anti-oxidant Action

In the present study, upon showing sexual dimorphism in dimethyl fumarate (DMF) efficacy to moderate the clinical severity of experimental autoimmune encephalomyelitis (EAE) in Dark Agouti rats, cellular and molecular substrate of this dimorphism was explored. In rats of both sexes, DMF administration from the day of immunization attenuated EAE severity, but this effect was more prominent in males leading to loss of the sexual dimorphism observed in vehicle-administered controls. Consistently, in male rats, DMF was more efficient in diminishing the number of CD4+ T lymphocytes infiltrating spinal cord (SC) and their reactivation, the number of IL-17+ T lymphocytes and particularly cellularity of their highly pathogenic IFN-γ+GM-CSF+IL-17+ subset. This was linked with changes in SC CD11b+CD45+TCRαβ- microglia/proinflammatory monocyte progeny, substantiated in a more prominent increase in the frequency of anti-inflammatory phygocyting CD163+ cells and the cells expressing high surface levels of immunoregulatory CD83 molecule (associated with apoptotic cells phagocytosis and implicated in downregulation of CD4+ T lymphocyte reactivation) among CD11b+CD45+TCRαβ- cells in male rat SC. These changes were associated with greater increase in the nuclear factor (erythroid-derived 2)-like 2 expression in male rats administered with DMF. In accordance with the previous findings, DMF diminished reactive nitrogen and oxygen species generation and consistently, SC level of advanced oxidation protein products, to the greater extent in male rats. Overall, our study indicates sex-specificity in the sensitivity of DMF cellular and molecular targets and encourages sex-based clinical research to define significance of sex for action of therapeutic agents moderating autoimmune neuroinflammation-/oxidative stress-related nervous tissue damage.

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.