Oxidative stress and endoplasmic reticulum (ER) stress in the development of neonatal hypoxic-ischaemic brain injury.Biochem Soc Trans. 2017;45:1067-1076. [PMID: 28939695 DOI: 10.1042/BST20170017]

Inhibition of Endoplasmic Reticulum Stress Improves Chronic Ischemic Hippocampal Damage Associated with Suppression of IRE1α/TRAF2/ASK1/JNK-Dependent Apoptosis

Chronic cerebral ischemia is a complex form of stress, of which the most common hemodynamic characteristic is chronic cerebral hypoperfusion (CCH). Lasting endoplasmic reticulum (ER) stress can drive neurological disorders. Targeting ER stress shows potential neuroprotective effects against stroke. However, the role of ER stress in CCH pathological processes and the effects of targeting ER stress on brain ischemia are unclear. Here, a CCH rat model was established by bilateral common carotid artery occlusion. Rats were treated with 4-PBA, URB597, or both for 4 weeks. Neuronal morphological damage was detected using hematoxylin-eosin staining. The expression levels of the ER stress-ASK1 cascade-related proteins GRP78, IRE1α, TRAF2, CHOP, Caspase-12, ASK1, p-ASK1, JNK, and p-JNK were assessed by Western blot. The mRNA levels of TNF-α, IL-1β, and iNOS were assessed by RT-PCR. For oxygen-glucose deprivation experiments, mouse hippocampal HT22 neurons were used. Apoptosis of the hippocampus and HT22 cells was detected by TUNEL staining and Annexin V-FITC analysis, respectively. CCH evoked ER stress with increased expression of GRP78, IRE1α, TRAF2, CHOP, and Caspase-12. Co-immunoprecipitation experiments confirmed the interaction between TRAF2 and ASK1. ASK1/JNK signaling, inflammatory cytokines, and neuronal apoptosis were enhanced, accompanied by persistent ER stress; these were reversed by 4-PBA and URB597. Furthermore, the ASK1 inhibitor GS4997 and 4-PBA displayed synergistic anti-apoptotic effects in cells with oxygen-glucose deprivation. In summary, ER stress-induced apoptosis in CCH is associated with the IRE1α/TRAF2/ASK1/JNK signaling pathway. Targeting the ER stress-ASK1 cascade could be a novel therapeutic approach for ischemic cerebrovascular diseases.

Endoplasmic Reticulum Stress Promotes Neuronal Damage in Neonatal Hypoxic-Ischemic Brain Damage by Inducing Ferroptosis

Hypoxic-ischemic brain damage (HIBD) poses a significant risk of neurological damage in newborns. This study investigates the impact of endoplasmic reticulum stress (ERS) on neuronal damage in neonatal HIBD and its underlying mechanisms. HIBD neonatal rat model was constructed and pre-treated with 4-phenylbutiric acid (4-PBA). Nissl and TUNEL staining were utilised to assess neuronal damage and apoptosis in rat brains. HIBD cell model was established by inducing oxygen-glucose deprivation (OGD) in rat H19-7 neurons, which were then pre-treated with Thapsigargin (TG), Ferrostatin-1 (Fer-1), or both. Cell viability and apoptosis of H19-7 neurons were analysed using cell counting kit-8 assay and TUNEL staining. GRP78-PERK-CHOP pathway activity and glutathione peroxidase-4 (GPX4) expression in rat brains and H19-7 neurons were assessed using Western blot. Ferroptosis-related indicators, including glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA) and iron content, were measured using commercial kits in both rat brains and H19-7 neurons. GRP78-PERK-CHOP pathway was overactivated in HIBD neonatal rats' brains, which was mitigated by 4-PBA treatment. 4-PBA treatment demonstrated a reduction in neuronal damage and apoptosis in HIBD-affected neonatal rat brains. Furthermore, it attenuated ferroptosis in rats by increasing GPX4, GSH and SOD while decreasing MDA and iron content. In the OGD-induced H19-7 neurons, Fer-1 treatment counteracted the suppressive effects of TG on viability, the exacerbation of apoptosis, the promotion of ferroptosis and the activation of the GRP78-PERK-CHOP pathway. Overall, ERS facilitates neuronal damage in neonatal HIBD by inducing ferroptosis. Consequently, the suppression of ERS may represent a promising therapeutic strategy for treating neonatal HIBD.

MicroRNA-124 negatively regulates STAT3 to alleviate hypoxic-ischemic brain damage by inhibiting oxidative stress

MicroRNA-124 (miR-124) is implicated in various neurological diseases; however, its significance in hypoxic-ischaemic brain damage (HIBD) remains unclear. This study aimed to elucidate the underlying pathophysiological mechanisms of miR-124 in HIBD. In our study performed on oxygen-glucose deprivation followed by reperfusion (OGD)/R-induced primary cortical neurons, a substantial reduction in miR-124 was observed. Furthermore, the upregulation of miR-124 significantly mitigated oxidative stress, apoptosis, and mitochondrial impairment. We demonstrated that miR-124 interacts with the signal transducer and activator of transcription 3 (STAT3) to exert its biological function using the dual-luciferase reporter gene assay. As the duration of OGD increased, miR-124 exhibited a negative correlation with STAT3. STAT3 overexpression notably attenuated the protective effects of miR-124 mimics, while knockdown of STAT3 reversed the adverse effects of the miR-124 inhibitor. Subsequently, we conducted an HIBD model in rats. In vivo experiments, miR-124 overexpression attenuated cerebral infarction volume, cerebral edema, apoptosis, oxidative stress, and improved neurological function recovery in HIBD rats. In summary, the neuroprotective effects of the miR-124/STAT3 axis were confirmed in the HIBD model. MiR-124 may serve as a potential biomarker with significant therapeutic implications for HIBD.

Neuroprotective strategies for neonatal hypoxic-ischemic brain damage: Current status and challenges

Neonatal hypoxic-ischemic brain damage (HIBD) is a prominent contributor to both immediate mortality and long-term impairment in newborns. The elusive nature of the underlying mechanisms responsible for neonatal HIBD presents a significant obstacle in the effective clinical application of numerous pharmaceutical interventions. This comprehensive review aims to concentrate on the potential neuroprotective agents that have demonstrated efficacy in addressing various pathogenic factors associated with neonatal HIBD, encompassing oxidative stress, calcium overload, mitochondrial dysfunction, endoplasmic reticulum stress, inflammatory response, and apoptosis. In this review, we conducted an analysis of the precise molecular pathways by which these drugs elicit neuroprotective effects in animal models of neonatal hypoxic-ischemic brain injury (HIBD). Our objective was to provide a comprehensive overview of potential neuroprotective agents for the treatment of neonatal HIBD in animal experiments, with the ultimate goal of enhancing the feasibility of clinical translation and establishing a solid theoretical foundation for the clinical management of neonatal HIBD.

Irisin prevents hypoxic-ischemic brain damage in rats by inhibiting oxidative stress and protecting the blood-brain barrier

Hypoxic-ischemic encephalopathy (HIE) is associated with excessive inflammation, blood-brain barrier dysfunction, and oxidative stress. Irisin can reduce inflammation and ameliorate oxidative stress; however, its effects on hypoxic-ischemic brain damage in newborns are unknown. Newborn Sprague-Dawley rats were subjected to hypoxic-ischemic injury and irisin treatment. TUNEL staining assays, the albumin-Evans blue dye extravasation method, an antioxidants detection kit, quantitative reverse-transcriptase PCR, enzyme linked immunosorbent assay, Western blot analysis, immunohistochemistry, and electron microscopy were used to investigate the possible mechanisms underlying the prevention of HIE by irisin. We discovered that rats affected by HIE and administered irisin had lower levels of IL-6 (but not TNF-α or IL-1β) less oxidative stress, and enhanced blood-brain barrier integrity. Irisin can effectively attenuate brain damage by reducing oxidative stress and protecting the blood-brain barrier.

Neonatal Hypoxic-Ischemic Encephalopathy: Perspectives of Neuroprotective and Neuroregenerative Treatments

Hypoxic-ischemic encephalopathy (HIE) is a serious condition that could have deleterious neurological outcomes, such as cerebral palsy, neuromotor disability, developmental disability, epilepsy, and sensitive or cognitive problems, and increase the risk of death in severe cases. Once HIE occurs, molecular cascades are triggered favoring the oxidative stress, excitotoxicity, and inflammation damage that promote cell death via apoptosis or necrosis. Currently, the therapeutic hypothermia is the standard of care in HIE; however, it has a small window of action and only can be used in children of more than 36 gestational weeks; for this reason, it is very important to develop new therapies to prevent the progression of the hypoxic-ischemic injury or to develop neuroregenerative therapies in severe HIE cases. The objective of this revision is to describe the emerging treatments for HIE, either preventing cell death for oxidative stress, excitotoxicity, or exacerbated inflammation, as well as describing a new therapeutic approach for neuroregeneration, such as mesenchymal stem cells, brain-derived neurotrophic factor, and gonadotropin realizing hormone agonists.

Nursing Method of Patients with Severe Traumatic Brain Injury and Fracture in the Ambulance

Craniocerebral injury accounts for 9%-21% of the injuries in all parts of the body, and the incidence rate ranks first in all types of trauma or only lower than limb fractures. This study mainly discusses the nursing methods of patients with severe traumatic brain injury and fractures in ambulances. This study is based on risk factors with moderate-to-higher association strength from retrospective studies. According to the regression coefficients of the logistic regression model, the risk factors were assigned, and the early warning score table of craniocerebral injury complicated with hyponatremia was established. The energy efficiency of the early warning score table was evaluated by case diagnostic test and ROC analysis. At the same time, risk grading is carried out, and the chi-square test is used to test the reliability of the grading standard, so as to identify the risk of hyponatremia in patients with craniocerebral injury early and screen out high-risk patients as the key observation objects of nurses. Based on the early warning score table of craniocerebral injury complicated with hyponatremia, different systematic nursing intervention measures were taken for low-risk patients and high-risk patients, and their application effects were evaluated. The clinical application effect of the systematic nursing intervention program was evaluated by the historical control research method, which provided a reference for the nursing in the ambulance to prevent other complications of patients with craniocerebral injury. The positive rate of prehospital operation can reach 64.44%, and the specific rate can reach 84.44%. 60% of the sample sought better metastatic care in terms of the purpose of using an ambulance. The systematic nursing intervention program has a certain effect on reducing the incidence of hyponatremia in patients with craniocerebral injury and shortening the hospitalization time of patients with craniocerebral injury. The early warning score of craniocerebral injury complicated with hyponatremia developed in this study is concise and practical and can provide a basis for clinical assessment of the risk of hyponatremia in patients with craniocerebral injury.

Alpha Tocopherol Loaded Polymeric Nanoparticles: Preparation, Characterizations, and In Vitro Assessments Against Oxidative Stress in Spinal Cord Injury Treatment

Spinal cord injury (SCI) is characterized by mechanical injury or trauma to the spinal cord. Currently, SCI treatment requires extremely high doses of neuroprotective agents, which in turn, causes several adverse effects. To overcome these limitations, the present study focuses on delivery of a low but effective dose of a naturally occurring antioxidant, α-tocopherol (α-TP). Calcium alginate nanoparticles (CA-NP) and poly D,L-lactic-co-glycolic acid nanoparticles (PLGA-NP) prepared by ionotropic gelation and solvent evaporation technique had particle size of 21.9 ± 11.19 and 152.4 ± 10.6 nm, respectively. Surface morphology, surface charge, as well as particle size distribution of both nanoparticles were evaluated. Entrapment of α-TP into CA-NP and PLGA-NP quantified by UPLC showed entrapment efficiency of 4.00 ± 1.63% and 76.6 ± 11.4%, respectively. In vitro cytotoxicity profiles on human astrocyte-spinal cord (HA-sp) showed that blank CA-NP at high concentrations reduced the cell viability whereas blank PLGA-NP showed relatively safer cytotoxic profiles. In addition, PLGA nanoparticles encapsulated with α-TP (α-TP-PLGA-NP) in comparison to α-TP alone at high concentrations were less toxic. Pretreatment of HA-sp cells with α-TP-PLGA-NP showed two-fold higher anti-oxidative protection as compared to α-TP alone, when oxidative stress was induced by H₂O₂. In conclusion, CA-NP were found to be unsuitable for treatment of SCI due to their cytotoxicity. Comparatively, α-TP-PLGA-NP were safer and showed high degree of protection against oxidative stress than α-TP alone.

Dihydroartemisinin attenuates hypoxic-ischemic brain damage in neonatal rats by inhibiting oxidative stress

Neonatal hypoxic-ischemic encephalopathy (HIE) induced by perinatal asphyxia is a major cause of neurological disability among infants. Dihydroartemisinin (DHA), derived from artemisinin, well known as an anti-malarial medicine, was proved to be able to inhibit oxidative stress and inflammation. However, whether those functions of DHA play roles in hypoxic-ischemic brain damage (HIBD), an animal model of HIE in patient which also been observed to have oxidative stress and inflammation, is unknown. In this study, we demonstrated that the DHA treatment on newborn rats significantly relieved the neuron loss and motor and cognitive impairment caused by HIBD. One of the underlying mechanisms is that DHA enhanced the anti-oxidant capacity of HIBD rats by up-regulating the total antioxidant capacity (T-AOC), gluathione reductase (GR) and catalase (CAT) while down regulating the pro-oxidative substances including hydrogen peroxide (H₂O₂), total nitric oxide synthase (T-NOS) and inducible nitric oxide synthase (iNOS). Thus, our study illustrated that DHA could alleviate the damage of brains and improve the cognitive and motor function of HIBD rats by inhibiting oxidative stress, provided an opportunity to interrogate potential therapeutics for affected HIE patients.

Temporal Characterization of Microglia-Associated Pro- and Anti-Inflammatory Genes in a Neonatal Inflammation-Sensitized Hypoxic-Ischemic Brain Injury Model

Hypoxic-ischemic encephalopathy (HIE) mainly affects preterm and term newborns, leading to a high risk of brain damage. Coexisting infection/inflammation and birth asphyxia are key factors associated with intracerebral increase of proinflammatory cytokines linked to HIE. Microglia are key mediators of inflammation during perinatal brain injury, characterized by their phenotypic plasticity, which may facilitate their participation in both the progression and resolution of injury-induced inflammation. The purpose of this study was to investigate the temporal expression of genes associated with pro- and anti-inflammatory cytokines as well as the nucleotide-binding domain, leucine-rich repeat protein (NLRP-3) inflammasome from microglia cells. For this purpose, we used our established neonatal rat model of inflammation-sensitized hypoxic-ischemic (HI) brain injury in seven-day-old rats. We assessed gene expression profiles of 11 cytokines and for NLRP-3 using real-time PCR from sorted CD11b/c microglia of brain samples at different time points (3.5 h after LPS injection and 0, 5, 24, 48, and 72 hours post HI) following different treatments: vehicle, E. coli lipopolysaccharide (LPS), vehicle/HI, and LPS/HI. Our results showed that microglia are early key mediators of the inflammatory response and exacerbate the inflammatory response following HI, polarizing into a predominant proinflammatory M1 phenotype in the early hours post HI. The brains only exposed to HI showed a delay in the expression of proinflammatory cytokines. We also demonstrated that NLRP-3 plays a role in the inflammatory resolution with a high expression after HI insult. The combination of both, a preinfection/inflammation condition and hypoxia-ischemia, resulted in a higher proinflammatory cytokine storm, highlighting the significant contribution of acute inflammation sensitizing prior to a hypoxic insult on the severity of perinatal brain damage.

Is late prevention of cerebral palsy in extremely preterm infants plausible?

Preterm birth continues to be associated with neurodevelopmental problems including cerebral palsy. Cystic white matter injury is still the major neuropathology underlying cerebral palsy, affecting 1-3% of preterm infants. Although rates have gradually fallen over time, the pathogenesis and evolution of cystic white matter injury are still poorly understood. Hypoxia-ischemia (HI) remains an important contributor yet there is no established treatment to prevent injury. Clinically, serial ultrasound and magnetic resonance imaging studies typically show delayed development of cystic lesions 2 to 4 weeks after birth. This raises the important and unresolved question as to whether this represents slow evolution of injury occurring around the time of birth, or repeated injury over many weeks after birth. There is increasing evidence that tertiary injury after HI can contribute to impairment of white and grey matter maturation. In the present review, we discuss preclinical evidence that severe, cystic white matter injury can evolve for many weeks after acute HI and is associated with microglia activity. This suggests the intriguing hypothesis that the tertiary phase of injury is not as subtle as often thought and that there may be a window of therapeutic opportunity for one to two weeks after hypoxic-ischemic injury to prevent delayed cystic lesions and so further reduce the risk of cerebral palsy after preterm birth.

Climate change and neurodegenerative diseases

The climate change induced global warming, and in particular the increased frequency and intensity of heat waves, have been linked to health problems. Among them, scientific works have been reporting an increased incidence of neurological diseases, encompassing also neurodegenerative ones, such as Dementia of Alzheimer's type, Parkinson's Disease, and Motor Neuron Diseases. Although the increase in prevalence of neurodegenerative diseases is well documented by literature reports, the link between global warming and the enhanced prevalence of such diseases remains elusive. This is the main theme of our work, which aims to examine the connection between high temperature exposure and neurodegenerative diseases. Firstly, we evaluate the influence of high temperatures exposure on the pathophysiology of these disorders. Secondly, we discuss its effects on the thermoregulation, already compromised in affected patients, and its interference with processes of excitotoxicity, oxidative stress and neuroinflammation, all of them related with neurodegeneration. Finally, we investigate chronic versus acute stressors on body warming, and put forward a possible interpretation of the beneficial or detrimental effects on the brain, which is responsible for the incidence or progression of neurological disorders.

Neural stem cell therapy for brain disease

Brain diseases, including brain tumors, neurodegenerative disorders, cerebrovascular diseases, and traumatic brain injuries, are among the major disorders influencing human health, currently with no effective therapy. Due to the low regeneration capacity of neurons, insufficient secretion of neurotrophic factors, and the aggravation of ischemia and hypoxia after nerve injury, irreversible loss of functional neurons and nerve tissue damage occurs. This damage is difficult to repair and regenerate the central nervous system after injury. Neural stem cells (NSCs) are pluripotent stem cells that only exist in the central nervous system. They have good self-renewal potential and ability to differentiate into neurons, astrocytes, and oligodendrocytes and improve the cellular microenvironment. NSC transplantation approaches have been made for various neurodegenerative disorders based on their regenerative potential. This review summarizes and discusses the characteristics of NSCs, and the advantages and effects of NSCs in the treatment of brain diseases and limitations of NSC transplantation that need to be addressed for the treatment of brain diseases in the future.

Randomized trial of oxygen weaning strategies following chest compressions during neonatal resuscitation

BACKGROUND

The Neonatal Resuscitation Program (NRP) recommends using 100% O2 during chest compressions and adjusting FiO2 based on SpO2 after return of spontaneous circulation (ROSC). The optimal strategy for adjusting FiO2 is not known.

METHODS

Twenty-five near-term lambs asphyxiated by umbilical cord occlusion to cardiac arrest were resuscitated per NRP. Following ROSC, lambs were randomized to gradual decrease versus abrupt wean to 21% O2 followed by FiO2 titration to achieve NRP SpO2 targets. Carotid blood flow and blood gases were monitored.

RESULTS

Three minutes after ROSC, PaO2 was 229 ± 32 mmHg in gradual wean group compared to 57 ± 13 following abrupt wean to 21% O2 (p < 0.001). PaO2 remained high in the gradual wean group at 10 min after ROSC (110 ± 10 vs. 67 ± 12, p < 0.01) despite similar FiO2 (~0.3) in both groups. Cerebral O2 delivery (C-DO2) was higher above physiological range following ROSC with gradual wean (p < 0.05). Lower blood oxidized/reduced glutathione ratio (suggesting less oxidative stress) was observed with abrupt wean.

CONCLUSION

Weaning FiO2 abruptly to 0.21 with adjustment based on SpO2 prevents surge in PaO2 and C-DO2 and minimizes oxidative stress compared to gradual weaning from 100% O2 following ROSC. Clinical trials with neurodevelopmental outcomes comparing post-ROSC FiO2 weaning strategies are warranted.

IMPACT

In a lamb model of perinatal asphyxial cardiac arrest, abrupt weaning of inspired oxygen to 21% prevents excessive oxygen delivery to the brain and oxidative stress compared to gradual weaning from 100% oxygen following return of spontaneous circulation. Clinical studies assessing neurodevelopmental outcomes comparing abrupt and gradual weaning of inspired oxygen after recovery from neonatal asphyxial arrest are warranted.

Mechanisms of neuronal cell death in ischemic stroke and their therapeutic implications

Ischemic stroke caused by arterial occlusion is the most common type of stroke, which is among the most frequent causes of disability and death worldwide. Current treatment approaches involve achieving rapid reperfusion either pharmacologically or surgically, both of which are time-sensitive; moreover, blood flow recanalization often causes ischemia/reperfusion injury. However, even though neuroprotective intervention is urgently needed in the event of stroke, the exact mechanisms of neuronal death during ischemic stroke are still unclear, and consequently, the capacity for drug development has remained limited. Multiple cell death pathways are implicated in the pathogenesis of ischemic stroke. Here, we have reviewed these potential neuronal death pathways, including intrinsic and extrinsic apoptosis, necroptosis, autophagy, ferroptosis, parthanatos, phagoptosis, and pyroptosis. We have also reviewed the latest results of pharmacological studies on ischemic stroke and summarized emerging drug targets with a focus on clinical trials. These observations may help to further understand the pathological events in ischemic stroke and bridge the gap between basic and translational research to reveal novel neuroprotective interventions.

Emerging therapies and management for neonatal encephalopathy-controversies and current approaches

Neonatal encephalopathy (NE) continues to have a major impact on newborn survival and neurodevelopmental outcomes worldwide. In high-income settings, therapeutic hypothermia is the only established standard treatment for neonates with moderate-to-severe NE, with compelling evidence that cooling reduces mortality and major neurodevelopmental impairment in survivors. Despite therapeutic hypothermia, a significant proportion of cooled infants continue to suffer long-term disability from brain injury. Innovative therapies offer the possibility of further improving neurodevelopmental outcomes by working synergistically with therapeutic hypothermia to decrease hypoxia-ischemia-induced excitotoxicity, prevent progression to secondary energy failure, and in some cases, promote neuroregeneration in the developing neonatal brain. This review discusses emerging NE therapies currently under investigation, offers insight into controversies surrounding various approaches to clinical care during therapeutic hypothermia, and identifies ongoing knowledge deficits that hinder attainment of optimal outcomes for neonates with NE.

Crocin enhances hypothermia therapy in hypoxic ischemia-induced brain injury in mice

Hypoxic-ischemic encephalopathy (HIE) is a serious medical situation at labor which leads to severe brain damage. Hypothermia therapy is the standard treatment for infants with HIE, but the efficacy is limited. Combination treatments are considered to enhance the efficacy of hypothermia. Crocin is an extract from saffron which has anti-inflammatory, anti-oxidant, and neuroprotective properties. The present study sought to investigate whether crocin could act as a combined treatment with hypothermia in a mouse model of HIE. C57BL/6J mice at post-natal day 7 were subjected to left common carotid artery ligation, followed by treatment of crocin (10 mg/kg) and hypothermia, either alone or in combination. Brain edema and tissue infarct were measured to evaluate brain damage. Mediators involved in inflammatory response and oxidative stress were measured. Neurological severity score test was performed to evaluate the functional outcome. Results show that crocin treatment alone could reduce inflammation and brain damage after hypoxia-ischemia. Combined treatment of crocin and hypothermia exerted enhanced therapeutic effect compared with single treatment, resulting in significantly less brain damage, reduced inflammatory and oxidative responses, and improved functional outcome. Together, these data suggest that crocin plays a beneficial effect in the mouse model of HIE. It could also enhance the neuroprotective effect of hypothermia and might be considered as a combination therapeutic treatment with hypothermia in HIE.

Hydrogen and therapeutic gases for neonatal hypoxic-ischemic encephalopathy: potential neuroprotective adjuncts in translational research

Numerous studies have examined the potential use of therapeutic gases for the treatment of various neurological disorders. Hydrogen gas, a promising neuroprotective agent, has been a focus of study due to its potent antioxidative properties. In translational research into adult diseases, hydrogen has been shown to be neuroprotective in disorders such as cerebral ischemia and traumatic brain injury, and in neurodegenerative diseases such as Alzheimer's disease. Animal and human studies have verified the safety and feasibility of molecular hydrogen. However, despite extensive research on its efficacy in adults, only a few studies have investigated its application in pediatric and neonatal medicine. Neonatal hypoxic-ischemic encephalopathy (HIE) is characterized by damage to neurons and other cells of the nervous system. One of the major contributing factors is excessive exposure to oxidative stress. Current research interest in HIE is shifting toward new neuroprotective agents, as single agents or as adjuncts to therapeutic hypothermia. Here, we review therapeutic gases, particularly hydrogen, and their potentials and limitations in the treatment of HIE in newborns. IMPACT: Translational animal models of neonatal HIE are a current focus of research into the therapeutic usefulness of various gases. Hydrogen ventilation as a single agent or in combination with therapeutic hypothermia shows short- and long-term neuroprotection in neonatal translational HIE models. The optimal target severity for therapeutic interventions should be well established to improve outcomes.

Metformin ameliorates brain damage caused by cardiopulmonary resuscitation via targeting endoplasmic reticulum stress-related proteins GRP78 and XBP1

Cerebral damage after cardiac arrest (CA) and cardiopulmonary resuscitation (CPR) is a primary cause of death. Endoplasmic reticulum stress (ERS) is very important during these situations. This study aimed to explore the role of metformin in protecting brain endoplasmic reticulum post CA/CPR. Male SD rats (n = 132) were treated with 6-min CA-posted asphyxia and sham surgery. Before CA/CPR, metformin (200 mg/kg/day) or a vehicle (0.9% saline) were administered randomly for two weeks. The neurological deficit scores were assessed 24 h, 48 h, 72 h, and 7 days after CA/CPR, and the rat brains were analyzed by Western blotting and qRT-PCR. Apoptosis was detected by the TUNEL assay according to the mitochondrial membrane potential (MMP). Oxidative stress and ERS-related protein expression were also investigated. The Western blotting and qRT-PCR results revealed that the resuscitated animals had time-dependent elevated GRP78 and XBP1 levels compared with the sham operative rats. Moreover, our results showed that the rats treated with metformin had increased neurological deficit scores (NDS), an improved seven-day survival rate, decreased cell apoptosis within the hippocampus CA1 area, and less oxidative stress compared with the CA/CPR group. Furthermore, metformin inhibited the mRNA and protein expressions of glucose-regulated protein 78 (GRP78) and X-box binding protein 1 (XBP1) in the CA/CPR rat model. We confirmed that CA/CPR can induce ERS-related apoptosis and oxidative stress in the brain; moreover, inhibiting ERS-related proteins GRP78 and XBP1 with metformin might attenuate cerebral injury post CA/CPR.

Neurotoxicity of Unconjugated Bilirubin in Neonatal Hypoxic-Ischemic Brain Injury in vitro

Background: The pathophysiology of bilirubin neurotoxicity in course of hypoxic-ischemic encephalopathy (HIE) in term and preterm infants is still poorly understood. We hypothesized that oxidative stress may be a common mechanism that link hyperbilirubinemia and HIE. Objectives: The objective of the present study was to evaluate whether unconjugated bilirubin (UCB) may enhance the HI brain injury by increasing oxidative stress and to test pioglitazone and allopurinol as new antioxidant therapeutic drugs in vitro. Methods: The effects of UCB were tested on organotypic hippocampal slices subjected to 30 min oxygen-glucose deprivation (OGD), used as in vitro model of HIE. The experiments were performed on mature (14 days in culture) and immature (7 days in culture) slices, to mimic the brains of term and preterm infants, respectively. Mature and immature slices were exposed to UCB, human serum albumin (HSA), pioglitazone, and/or allopurinol for 24 h, immediately after 30 min OGD. Neuronal injury was assessed using propidium iodide (PI) fluorescence. ROS formation was quantified by using the 2',7'-dichlorodihydrofluorescein diacetate (DCF-DA) method. Results: In mature slices, we found that the neurotoxicity, as well as oxidative stress, induced by OGD were enhanced by UCB. HSA significantly prevented UCB-increased neurotoxicity, but had a slight reduction on ROS production. Allopurinol, but not pioglitazone, significantly reduced UCB-increased neurotoxicity induced by OGD. In immature slices exposed to OGD, no increase of neuronal death was observed, whereas oxidative stress was detected after UCB exposure. HSA, pioglitazone and allopurinol have no protective effects on both OGD-induced neuronal death and on UCB-induced oxidative stress. For this reason, UCB, pioglitazone and allopurinol was also tested on ischemic preconditioning protocol. We found that UCB abolished the neuroprotection induced by preconditioning and increased oxidative stress. These effects were restored by allopurinol but not pioglitazone. Conclusions: UCB characterized a different path of neuronal damage and oxidative stress in mature and immature hippocampal slice model of HIE. Management of hyperbilirubinemia in a complex pathological condition, such as HIE and hyperbilirubinemia, should be very careful. Allopurinol could deserve attention as a novel pharmacological intervention for hyperbilirubinemia and HIE.

Mechanisms of neuroplasticity and brain degeneration: strategies for protection during the aging process

Aging is a dynamic and progressive process that begins at conception and continues until death. This process leads to a decrease in homeostasis and morphological, biochemical and psychological changes, increasing the individual’s vulnerability to various diseases. The growth in the number of aging populations has increased the prevalence of chronic degenerative diseases, impairment of the central nervous system and dementias, such as Alzheimer’s disease, whose main risk factor is age, leading to an increase of the number of individuals who need daily support for life activities. Some theories about aging suggest it is caused by an increase of cellular senescence and reactive oxygen species, which leads to inflammation, oxidation, cell membrane damage and consequently neuronal death. Also, mitochondrial mutations, which are generated throughout the aging process, can lead to changes in energy production, deficiencies in electron transport and apoptosis induction that can result in decreased function. Additionally, increasing cellular senescence and the release of proinflammatory cytokines can cause irreversible damage to neuronal cells. Recent reports point to the importance of changing lifestyle by increasing physical exercise, improving nutrition and environmental enrichment to activate neuroprotective defense mechanisms. Therefore, this review aims to address the latest information about the different mechanisms related to neuroplasticity and neuronal death and to provide strategies that can improve neuroprotection and decrease the neurodegeneration caused by aging and environmental stressors.

Dl-3-n-butylphthalide attenuates hypoxic-ischemic brain injury through inhibiting endoplasmic reticulum stress-induced cell apoptosis and alleviating blood-brain barrier disruption in newborn rats

Dl-3-n-butylphthalide (NBP) has been demonstrated to exert neuroprotective effects in experimental models and human patients. This study was performed to assess the therapeutic effects and the underlying molecular mechanisms of NBP in a neonatal hypoxic-ischemic rat model. The results showed that NBP treatment significantly reduced the infarct volume, improved histological recovery, decreased neuronal cell loss, enhanced neuronal cell rehabilitation, promoted neurite growth and decreased white matter injury. In addition, NBP treatment effectively improved long-term neurobehavioral development and prognosis after HI injury. We further demonstrated an inhibitory effect of NBP on endoplasmic reticulum (ER) stress-induced apoptosis, evidenced by reduction in ER stress-related protein expressions (GRP78, XBP-1, PDI and CHOP), decrease in TUNEL-positive cells, down-regulation in pro-apoptosis protein (Bax and cleaved caspase-3), up-regulation in anti-apoptosis protein (Bcl-2). Moreover, NBP exerted a protective effect in blood-brain barrier disruption, which ameliorated brain edema and reduced the degeneration of the tight junction proteins (Occludin and Claudin-5) and adherens junction proteins (P120-Catenin, VE-Cadherin and β-Catenin). Overall, our findings demonstrated that NBP treatment attenuated HI brain injury through inhibiting ER stress-induced apoptosis and alleviating blood-brain barrier disruption in newborn rats. This work provides an effective therapeutic strategy to reduce brain damage and enhance recovery after neonatal HI brain injury.

Morroniside protects HT-22 cells against oxygen-glucose deprivation/reperfusion through activating the Nrf2/HO-1 signaling pathway

Neonatal hypoxic-ischemic encephalopathy (HIE) is a devastating condition that affects neurodevelopment and results in brain injury in infants. Morroniside (MOR), a natural secoiridoid glycoside, has been found to possess neuroprotective effect. However, the effects of MOR on neonatal HIE are unclear. An in vitro HIE model was established in murine hippocampal neurons HT-22 cells using oxygen-glucose deprivation/reoxygenation (OGD/R) stimulation. Our results showed that MOR improved OGD/R-caused cell viability reduction in HT-22 cells. MOR suppressed the production of reactive oxygen species (ROS) and malondialdehyde (MDA) in OGD/R-induced HT-22 cells in a dose-dependent manner. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GP_X) were significantly elevated by MOR. Moreover, MOR treatment caused a significant increase in bcl-2 expression, and obvious decreases in the expression levels of bax, cleaved caspase-3, and cleaved caspase-9 expression. Furthermore, MOR significantly upregulated the expression levels of nuclear Nrf2 and HO-1 in OGD/R-treated HT-22 cells. Additionally, knockdown of Nrf2 or HO-1 abrogated the effects of MOR on OGD/R-induced oxidative stress and apoptosis in HT-22 cells. In conclusion, these findings suggested that MOR protects HT-22 cells against OGD/R via regulating the Nrf2/HO-1 signaling pathway.

Intranasal Administration of Mesenchymal Stem Cell Secretome Reduces Hippocampal Oxidative Stress, Neuroinflammation and Cell Death, Improving the Behavioral Outcome Following Perinatal Asphyxia

Perinatal Asphyxia (PA) is a leading cause of motor and neuropsychiatric disability associated with sustained oxidative stress, neuroinflammation, and cell death, affecting brain development. Based on a rat model of global PA, we investigated the neuroprotective effect of intranasally administered secretome, derived from human adipose mesenchymal stem cells (MSC-S), preconditioned with either deferoxamine (an hypoxia-mimetic) or TNF-α+IFN-γ (pro-inflammatory cytokines). PA was generated by immersing fetus-containing uterine horns in a water bath at 37 °C for 21 min. Thereafter, 16 μL of MSC-S (containing 6 μg of protein derived from 2 × 10⁵ preconditioned-MSC), or vehicle, were intranasally administered 2 h after birth to asphyxia-exposed and control rats, evaluated at postnatal day (P) 7. Alternatively, pups received a dose of either preconditioned MSC-S or vehicle, both at 2 h and P7, and were evaluated at P14, P30, and P60. The preconditioned MSC-S treatment (i) reversed asphyxia-induced oxidative stress in the hippocampus (oxidized/reduced glutathione); (ii) increased antioxidative Nuclear Erythroid 2-Related Factor 2 (NRF2) translocation; (iii) increased NQO1 antioxidant protein; (iv) reduced neuroinflammation (decreasing nuclearNF-κB/p65 levels and microglial reactivity); (v) decreased cleaved-caspase-3 cell-death; (vi) improved righting reflex, negative geotaxis, cliff aversion, locomotor activity, anxiety, motor coordination, and recognition memory. Overall, the study demonstrates that intranasal administration of preconditioned MSC-S is a novel therapeutic strategy that prevents the long-term effects of perinatal asphyxia.

Quercetin alleviates neonatal hypoxic-ischemic brain injury by inhibiting microglia-derived oxidative stress and TLR4-mediated inflammation

OBJECTIVE AND DESIGN

Microglia stimulated by oxygen glucose deprivation (OGD) were treated with quercetin to investigate the effect on oxidative stress and the inflammatory response and to explore whether toll-like receptor 4 (TLR4) signaling was involved. In addition, the effect of quercetin on the neurological functions of neonatal mice with hypoxic-ischemic brain injury (HIBI) was examined.

MATERIALS AND SUBJECTS

Mouse BV2 microglial cells and postnatal day 7 neonatal mice were used.

TREATMENT

A predetermined concentration of quercetin was used in cell experiments. Quercetin was injected i.p. (50 mg/kg) at three time points after HI insult: 0, 24, and 48 h.

METHODS

Cell viability assay, Western blotting, qRT-RCR, ELISA, HIBI model construction and behavioral tests.

RESULTS

This study first showed that quercetin protected BV2 cells from OGD-induced damage and reversed the changes in microglial oxidative stress-related molecules. Second, quercetin inhibited OGD-induced expression of inflammatory factors in BV2 cells and suppressed TLR4/MyD88/NF-κB signaling. Finally, quercetin was disclosed to be effective in mitigating cerebral infarct volume and cognitive and motor function deficits in HIBI mice.

CONCLUSION

These results suggest that the neuroprotective effect of quercetin in HIBI mice is partially due to the inhibition of oxidative stress and TLR4-mediated inflammatory responses in activated microglia.

Neuroprotective role of Nrf2 on hypoxic-ischemic brain injury in neonatal mice

Inflammation and oxidative stress play a key role in mediating the pathophysiology of hypoxic-ischemic (HI) brain injury. Nrf2 is a transcriptional factor that contributes to the innate defense of the body against oxidative stress and inflammation. The current study investigated the effect of Nrf2 in neonatal HI brain injury using Nrf2^-/- mice. Nrf2^-/- and wild-type Nrf2^+/+ mice on a C57BL/6J background at postnatal day 9 underwent unilateral common carotid artery ligation, followed by hypoxia. Brain damage was determined by infarct size measurement. Apoptosis was evaluated by measuring the expression of Bax and Bcl-2. The levels of inflammatory cytokines and mediators involved in oxidative stress were measured. Nrf2 knockout exacerbated HI injury-induced brain infarct and cell apoptosis in the brain. Nrf2^-/- mice showed increased inflammatory cytokines and MDA, and reduced activities of antioxidant enzymes including CAT, GSH-Px, and SOD. Nrf2^-/- mice showed reduced HO-1 expression after HI injury compared with wild-type mice. This study supported a protective effect of Nrf2 in neonatal HI brain injury.

Circular RNA expression alteration in whole blood of premature infants with periventricular white matter damage

Circular RNAs (circRNAs) are evolutionarily conserved and tissue-specific types of non-coding RNA and can serve as potential diagnostic biomarkers for disease. However, the clinical significance and levels of expression of circRNAs for whole blood samples of prematurely born infants afflicted by diseases such as periventricular white matter damage (PWMD) are largely unknown. Therefore, we sought to identify measures of expression of circRNAs in whole blood samples obtained from prematurely born infants afflicted by PWMD and comparatively in samples from prematurely born infants without PWMD. We found the expression levels of circRNAs which from premature with PWMD has changed. Further analysis suggests that these circRNAs have important roles in PWMD. This study can improve the understanding for the potential of the circRNAs to serve as biomarkers in PWMD. Moreover, these circRNAs may provide evidence for improving diagnosis and treatment for infants afflicted by PWMD, and merits continued research.

Overview of Crosstalk Between Multiple Factor of Transcytosis in Blood Brain Barrier

Blood brain barrier (BBB) conserves unique regulatory system to maintain barrier tightness while allowing adequate transport between neurovascular units. This mechanism possess a challenge for drug delivery, while abnormality may result in pathogenesis. Communication between vascular and neural system is mediated through paracellular and transcellular (transcytosis) pathway. Transcytosis itself showed dependency with various components, focusing on caveolae-mediated. Among several factors, intense communication between endothelial cells, pericytes, and astrocytes is the key for a normal development. Regulatory signaling pathway such as VEGF, Notch, S1P, PDGFβ, Ang/Tie, and TGF-β showed interaction with the transcytosis steps. Recent discoveries showed exploration of various factors which has been proven to interact with one of the process of transcytosis, either endocytosis, endosomal rearrangement, or exocytosis. As well as providing a hypothetical regulatory pathway between each factors, specifically miRNA, mechanical stress, various cytokines, physicochemical, basement membrane and junctions remodeling, and crosstalk between developmental regulatory pathways. Finally, various hypotheses and probable crosstalk between each factors will be expressed, to point out relevant research application (Drug therapy design and BBB-on-a-chip) and unexplored terrain.

Resveratrol protects against cadmium chloride-induced hippocampal neurotoxicity by inhibiting ER stress and GAAD 153 and activating sirtuin 1/AMPK/Akt

This study investigated whether the apoptotic effect induced by cadmium chloride (CdCl₂ ) in rat's hippocampi and neuroprotection afforded by resveratrol (RES) are mediated by modulation of ER stress and involve sirtuin 1 (SIRT1)/AMPK/Akt axis. Adult male Wistar rats were divided into four groups (n = 24/group) as control, control + RES (300 mg/kg), CdCl₂ (5 mg/kg), and CdCl₂  + RES. All treatments were conducted orally for 45 days. Also, cultured hippocampal cells were treated with CdCl₂ in the presence or absence of RES and with or without preincubation with SIRT1, AMPK, or PI3K inhibitors. CdCl₂ impaired retention and spatial memories of rats and reduced levels and activities of SIRT1 and inhibited AMPK/Akt axis in their hippocamapi where SIRT1 was the upstream regulator. It also enahnced hippocampal levels of reactive oxygen species (ROS) and expression of caspase-12 and caspase-3, depleted glutathione (GSH) levels, and activated GRP78, activating transcription factor-6, GAAD 153, X-box binding protein-1 arms of ER stress. On the contrary, RES coadminsitration completley abolished all these events. Interstingly and in control rats, RES not only increased levels of GSH, but also enhenced protein levels of B-cell lymphoma 2 (Bcl-2) and dwonregulated GAAD 153. In both control and CdCl₂ -treated rats, pharmacological inhibtion of SIRT1, AMPK, and Akt compleltely abolished all effects afforded by RES. In conclusion, CdCl₂ -induced hippocampal apopotis is associated with reduction of SIRT1/AMPK/Akt activity levels, ROS generation, downregulation of Bcl-2, and activities, activation of ER stress, and GAAD 153, whereas RES is able to reverse these effects through activation of SIRT1/AMPK/Akt.

Endoplasmic Reticulum Targeting Ratiometric Fluorescent Probe for Carboxylesterase 2 Detection in Drug-Induced Acute Liver Injury

Carboxylesterase 2 (CES2), an endoplasmic reticulum (ER) located phase I enzyme, plays a vital role in the metabolism of various endogenous and exogenous substances, and is regarded as an important target for the design of prodrugs. Unfortunately, superior highly selective ER targeting fluorescent probes for monitoring of CES2 are not currently available. Herein, we report an ER targeting CES2 selective and sensitive ratiometric fluorescent probe ERNB based on the ER localizing group p-toluenesulfonamide. ERNB possessed high specificity, sensitivity, and exhibited excellent subcellular localization when compared to commercial ER tracker, and was used to image CES2 in the ER of living cells. Additionally, using ERNB we evaluated the CES2 regulation under d,l-dithiothreitol and tunicamycin-induced ER stress. Furthermore, we determined the down regulation of CES2 activity and expression in the acetaminophen-induced acute liver injury model. On the basis of these results, we conclude that ERNB is a promising tool for highlighting the role of CES2 in the ER and in exploring the role of CES2 in the development of diseases associated with ER stress.

Brain diseases in changing climate

Climate change is one of the biggest and most urgent challenges for the 21st century. Rising average temperatures and ocean levels, altered precipitation patterns and increased occurrence of extreme weather events affect not only the global landscape and ecosystem, but also human health. Multiple environmental factors influence the onset and severity of human diseases and changing climate may have a great impact on these factors. Climate shifts disrupt the quantity and quality of water, increase environmental pollution, change the distribution of pathogens and severely impacts food production - all of which are important regarding public health. This paper focuses on brain health and provides an overview of climate change impacts on risk factors specific to brain diseases and disorders. We also discuss emerging hazards in brain health due to mitigation and adaptation strategies in response to climate changes.

The Role of Mitochondrial and Endoplasmic Reticulum Reactive Oxygen Species Production in Models of Perinatal Brain Injury

Significance: Perinatal brain injury is caused by hypoxia-ischemia (HI) in term neonates, perinatal arterial stroke, and infection/inflammation leading to devastating long-term neurodevelopmental deficits. Therapeutic hypothermia is the only currently available treatment but is not successful in more than 50% of term neonates suffering from hypoxic-ischemic encephalopathy. Thus, there is an urgent unmet need for alternative or adjunct therapies. Reactive oxygen species (ROS) are important for physiological signaling, however, their overproduction/accumulation from mitochondria and endoplasmic reticulum (ER) during HI aggravate cell death. Recent Advances and Critical Issues: Mechanisms underlying ER stress-associated ROS production have been primarily elucidated using either non-neuronal cells or adult neurodegenerative experimental models. Findings from mature brain cannot be simply transferred to the immature brain. Therefore, age-specific studies investigating ER stress modulators may help investigate ER stress-associated ROS pathways in the immature brain. New therapeutics such as mitochondrial site-specific ROS inhibitors that selectively inhibit superoxide (O2•-)/hydrogen peroxide (H2O2) production are currently being developed. Future Directions: Because ER stress and oxidative stress accentuate each other, a combinatorial therapy utilizing both antioxidants and ER stress inhibitors may prove to be more protective against perinatal brain injury. Moreover, multiple relevant targets need to be identified for targeting ROS before they are formed. The role of organelle-specific ROS in brain repair needs investigation. Antioxid. Redox Signal. 31, 643-663.

Sex differences in neonatal mouse brain injury after hypoxia-ischemia and adaptaquin treatment

Hypoxia-inducible factor prolyl 4-hydroxylases (HIF-PHDs) are important targets against oxidative stress. We hypothesized that inhibition HIF-PHD by adaptaquin reduces hypoxic-ischemic brain injury in a neonatal mouse model. The pups were treated intraperitoneally immediately with adaptaquin after hypoxia-ischemia (HI) and then every 24 h for 3 days. Adaptaquin treatment reduced infarction volume by an average of 26.3% at 72 h after HI compared to vehicle alone, and this reduction was more pronounced in males (34.8%) than in females (11.7%). The protection was also more pronounced in the cortex. The subcortical white matter injury as measured by tissue loss volume was reduced by 24.4% in the adaptaquin treatment group, and this reduction was also more pronounced in males (28.4%) than in females (18.9%). Cell death was decreased in the cortex as indicated by Fluoro-Jade labeling, but not in other brain regions with adaptaquin treatment. Furthermore, in the brain injury area, adaptaquin did not alter the number of cells positive for caspase-3 activation or translocation of apoptosis-inducing factor to the nuclei. Adaptaquin treatment increased glutathione peroxidase 4 mRNA expression in the cortex but had no impact on 3-nitrotyrosine, 8-hydroxy-2 deoxyguanosine, or malondialdehyde production. Hif1α mRNA expression increased after HI, and adaptaquin treatment also stimulated Hif1α mRNA expression, which was also more pronounced in males than in females. However, nuclear translocation of HIF1α protein was decreased after HI, and adaptaquin treatment had no influence on HIF1α expression in the nucleus. These findings demonstrate that adaptaquin treatment is neuroprotective, but the potential mechanisms need further investigation. Read the Editorial Highlight for this article on page 645.

Neuroprotective effect of Vanillin on hypoxic-ischemic brain damage in neonatal rats

Neonatal hypoxic-ischemic brain damage (HIBD) is a leading cause of death and perpetual neurological dysfunction in neonates. Vanillin (Van), a natural phenolic compound with neuroprotective properties, exerts neuroprotection on a gerbil model of global ischemia by inhibiting oxidative damage. This study aimed to explore the potential neuroprotective roles of Van in neonatal rats suffering from hypoxic-ischemic (HI). An HI model of 7-day-old SD rats was induced by left carotid artery ligation followed by exposure to 8% oxygen (balanced with nitrogen) for 2.5 h at 37 °C. At 48 h after intraperitoneal injection with Van (20, 40, and 80 mg/kg) or saline, neurobehavioral function, cerebral infract volume, brain water content, and histomorphological changes were performed to evaluate brain injury. Transmission electron microscopy and immunoglobulin G (IgG) staining were conducted to evaluate the integrity of the blood-brain barrier (BBB). The levels of oxidative stress and tight junction proteins, as well as the activities of matrix metalloproteinases (MMPs), were also determined in the ipsilateral hemisphere. Results showed that Van post-treatment significantly ameliorated early neurobehavioral deficits, decreased infarct volume and brain edema, as well as attenuated histopathologic injury and IgG extravasation. Furthermore, Van markedly increased the activities of endogenous antioxidant enzymes and decreased malondialdehyde content. Meanwhile, the activation of MMP-2 and MMP-9 induced by HI was partially blocked by Van. Finally, Van obviously increased the expression of ZO-1, Occludin, and Claudin-5 compared with the HI group. Collectively, Van can provide neuroprotective effects against neonatal HIBD possibly by attenuating oxidative damage and preserving BBB integrity.

CYP46A1 Activation by Efavirenz Leads to Behavioral Improvement without Significant Changes in Amyloid Plaque Load in the Brain of 5XFAD Mice

Efavirenz, the FDA-approved anti-retroviral medication, is evaluated in the clinical trial in patients with mild cognitive impairment or early dementia due to Alzheimer's disease. Efavirenz is assessed for activation of cytochrome P450 46A1 (CYP46A1), a CNS-specific enzyme that converts cholesterol to 24-hydroxycholesterol. Cholesterol 24-hydroxylation is the major pathway for brain cholesterol removal, and a mechanism that controls brain cholesterol turnover. The present study tested efavirenz on 5XFAD mice (an Alzheimer's model) at a very low daily dose of 0.1 mg/kg body weight. Efavirenz treatment started from three months of age, after amyloid plague appearance, and continued for 6 months. This treatment led to CYP46A1 activation in the brain, enhancement of brain cholesterol turnover, behavioral improvements, reduction in microglia activation but increased astrocyte reactivity. The levels of the soluble and insoluble amyloid 40 and 42 peptides were unchanged while the number and area of the dense core amyloid plaques were slightly decreased. The measurements of the brain levels of several pre- and post-synaptic proteins (Munc13-1, PSD-95, gephyrin, synaptophysin, synapsin-1, and calbindin-D28k) suggested efavirenz effect at the synaptic level. Efavirenz treatment in the present work seems to represent a model of behavioral and other improvements independent of the levels of the amyloid peptides and provides insight into potential outcomes of the future clinical trial.

Peroxiredoxin 4 ameliorates amyloid beta oligomer-mediated apoptosis by inhibiting ER-stress in HT-22 hippocampal neuron cells

Alzheimer's disease (AD) is a neurodegenerative disorder caused by amyloid beta oligomers (AβO), which induce cell death by triggering oxidative stress and endoplasmic reticulum (ER) stress. Oxidative stress is regulated by antioxidant enzymes, including peroxiredoxins. Peroxiredoxins (Prx) are classified into six subtypes, based on their localization and cysteine residues, and protect cells by scavenging hydrogen peroxide (H₂O₂). Peroxiredoxin 4 (Prx4) is unique in being localized to the ER; however, whether Prx4 protects neuronal cells from AβO-induced toxicity remains unclear, although Prx4 expression is upregulated in AβO-induced oxidative stress and ER stress. In this study, we established HT-22 cells in which Prx4 was either overexpressed or silenced to investigate its role in AβO-induced toxicity. AβO-stimulation of HT-22 cells with overexpressed Prx4 caused decreases in both AβO-induced ROS and ER stress (followed by ER expansion). In contrast, AβO stimulation caused increases in both ROS and ER stress that were notably higher in HT-22 cells with silenced Prx4 expression than in HT-22 cells. Consequently, Prx4 overexpression decreased apoptotic cell death and ameliorated the AβO-induced increase in intracellular Ca²⁺. Therefore, we conclude that Prx4 has a protective effect against AβO-mediated oxidative stress, ER stress, and neuronal cell death. Furthermore, these results suggest that Prx4 may be a target for preventing AβO toxicity in AD. Graphical abstract .

Glial Cell AMPA Receptors in Nervous System Health, Injury and Disease

Glia form a central component of the nervous system whose varied activities sustain an environment that is optimised for healthy development and neuronal function. Alpha-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA)-type glutamate receptors (AMPAR) are a central mediator of glutamatergic excitatory synaptic transmission, yet they are also expressed in a wide range of glial cells where they influence a variety of important cellular functions. AMPAR enable glial cells to sense the activity of neighbouring axons and synapses, and as such many aspects of glial cell development and function are influenced by the activity of neural circuits. However, these AMPAR also render glia sensitive to elevations of the extracellular concentration of glutamate, which are associated with a broad range of pathological conditions. Excessive activation of AMPAR under these conditions may induce excitotoxic injury in glial cells, and trigger pathophysiological responses threatening other neural cells and amplifying ongoing disease processes. The aim of this review is to gather information on AMPAR function from across the broad diversity of glial cells, identify their contribution to pathophysiological processes, and highlight new areas of research whose progress may increase our understanding of nervous system dysfunction and disease.

Experimental necrotizing enterocolitis induces neuroinflammation in the neonatal brain

Background

Necrotizing enterocolitis (NEC) is an inflammatory gastrointestinal disease primarily affecting preterm neonates. Neonates with NEC suffer from a degree of neurodevelopmental delay that is not explained by prematurity alone. There is a need to understand the pathogenesis of neurodevelopmental delay in NEC. In this study, we assessed the macroscopic and microscopic changes that occur to brain cell populations in specific brain regions in a neonatal mouse model of NEC. Moreover, we investigated the role of intestinal inflammation as part of the mechanism responsible for the changes observed in the brain of pups with NEC.

Methods

Brains of mice were assessed for gross morphology and cerebral cortex thickness (using histology). Markers for mature neurons, oligodendrocytes, neural progenitor cells, microglia, and astrocytes were used to quantify their cell populations in different regions of the brain. Levels of cell apoptosis in the brain were measured by Western blotting and immunohistochemistry. Endoplasmic reticulum (ER) stress markers and levels of pro-inflammatory cytokines (in the ileum and brain) were measured by RT-qPCR and Western blotting. A Pearson test was used to correlate the levels of cytokines (ELISA) in the brain and ileum and to correlate activated microglia and astrocyte populations to the severity of NEC.

Results

NEC pups had smaller brain weights, higher brain-to-body weight ratios, and thinner cortices compared to control pups. NEC pups had increased levels of apoptosis and ER stress. In addition, NEC was associated with a reduction in the number of neurons, oligodendrocytes, and neural progenitors in specific regions of the brain. Levels of pro-inflammatory cytokines and the density of activated microglia and astrocytes were increased in the brain and positively correlated with the increase in the levels pro-inflammatory cytokines in the gut and the severity of NEC damage respectively.

Conclusions

NEC is associated with severe changes in brain morphology, a pro-inflammatory response in the brain that alters cell homeostasis and density of brain cell populations in specific cerebral regions. We show that the severity of neuroinflammation is associated with the severity of NEC. Our findings suggest that early intervention during NEC may reduce the chance of acute neuroinflammation and cerebral damage.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1481-9) contains supplementary material, which is available to authorized users.

Reduction of Leukocyte Microvascular Adherence and Preservation of Blood-Brain Barrier Function by Superoxide-Lowering Therapies in a Piglet Model of Neonatal Asphyxia

Background: Asphyxia is the most common cause of brain damage in newborns. Substantial evidence indicates that leukocyte recruitment in the cerebral vasculature during asphyxia contributes to this damage. We tested the hypothesis that superoxide radical (O 2 ⋅ _ ) promotes an acute post-asphyxial inflammatory response and blood-brain barrier (BBB) breakdown. We investigated the effects of removingO 2 ⋅ _ by superoxide dismutase (SOD) or C3, the cell-permeable SOD mimetic, in protecting against asphyxia-related leukocyte recruitment. We also tested the hypothesis that xanthine oxidase activity is one source of this radical. Methods: Anesthetized piglets were tracheostomized, ventilated, and equipped with closed cranial windows for the assessment of post-asphyxial rhodamine 6G-labeled leukocyte-endothelial adherence and microvascular permeability to sodium fluorescein in cortical venules. Asphyxia was induced by discontinuing ventilation. SOD and C3 were administered by cortical superfusion. The xanthine oxidase inhibitor oxypurinol was administered intravenously. Results: Leukocyte-venular adherence significantly increased during the initial 2 h of post-asphyxial reperfusion. BBB permeability was also elevated relative to non-asphyxial controls. Inhibition ofO 2 ⋅ _ production by oxypurinol, or elimination ofO 2 ⋅ _ by SOD or C3, significantly reduced rhodamine 6G-labeled leukocyte-endothelial adherence and improved BBB integrity, as measured by sodium fluorescein leak from cerebral microvessels. Conclusion: Using three different strategies to either prevent formation or enhance elimination ofO 2 ⋅ _ during the post-asphyxial period, we saw both reduced leukocyte adherence and preserved BBB function with treatment. These findings suggest that agents which lowerO 2 ⋅ _ in brain may be attractive new therapeutic interventions for the protection of the neonatal brain following asphyxia.

Changes in bilirubin in infants with hypoxic-ischemic encephalopathy

Antioxidant properties of bilirubin have been reported in many studies. We hypothesized that bilirubin might be involved in neuroprotection mechanisms against oxidative stress in infants with hypoxic-ischemic encephalopathy (HIE) and that total serum bilirubin (TSB) might increase in these patients. We retrospectively studied infants with gestational age ≥ 35 weeks and birth weight ≥ 1800 g who were admitted to the neonatal intensive care unit (NICU) with a diagnosis of moderate-to-severe HIE and received or did not receive therapeutic hypothermia. We evaluated peak TSB and changes of mean TSB in these patients in comparison with a control group of infants admitted to the NICU with diagnoses other than HIE. Peak and mean TSB values were lower in the no hypothermia and hypothermia groups in comparison with the control group, while differences were not noted between infants who received hypothermia or did not. Regression analysis showed that HIE and hypothermia significantly reduced the risk of developing TSB values higher than median value (> 8.4 mg/dL) in our population.Conclusion: Peak and mean TSB values were lower in infants with moderate-to-severe HIE than in control infants. HIE and hypothermia independently decreased TSB. These results exclude a TSB increase as a neuroprotective mechanism in infants with HIE. We speculated that low TSB values in infants with HIE could be due to hypoxic repression of HO expression and represent a defensive strategy for limiting brain injuries in these patients. What is Known: • The role of oxidative stress in the pathophysiology of hypoxic-ischemic encephalopathy (HIE) has been elucidated in many studies, and other studies have demonstrated the antioxidant properties of bilirubin. • The potential neuroprotective role of bilirubin as antioxidant agent has never been evaluated in infants with HIE. What is New: • Mean total serum bilirubin (TSB) values are lower in infants with moderate-to-severe HIE than in control infants, since HIE and hypothermia independently decreased TSB. • An increase in bilirubin was not a neuroprotective mechanism in infants with HIE possibly because of hypoxic repression of HO expression as defensive strategy for limiting brain injuries.

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

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

Temporal patterns of circulating cell-free DNA (cfDNA) in a newborn piglet model of perinatal asphyxia

Perinatal asphyxia is a severe medical condition resulting from oxygen deficiency (hypoxia) at the time of birth, causing worldwide approximately 680,000 newborn deaths every year. Better prediction of severity of damages including early biomarkers is highly demanded. Elevated levels of circulating cell-free DNA (cfDNA) in blood have been reported for a range of different diseases and conditions, including cancer and prematurity. The objective of this study was to validate methods for assessing cfDNA in blood and cerebrospinal fluid (CSF) and to explore temporal variations in a piglet model of neonatal hypoxia-reoxygenation. Different cfDNA extraction methods in combination with cfDNA detection systems were tested, including a fluorescent assay using SYBR Gold and a qRT-PCR-based technique. Newborn piglets (n = 55) were exposed to hypoxia-reoxygenation, hypoxia-reoxygenation and hypothermia, or were part of the sham-operated control group. Blood was sampled at baseline and at post-intervention, further at 30, 270, and 570 minutes after the end of hypoxia. Applying the fluorescent method, cfDNA concentration in piglets exposed to hypoxia (n = 32) increased from 36.8±27.6 ng/ml prior to hypoxia to a peak level of 61.5±54.9 ng/ml after the intervention and deceased to 32.3±19.1 ng/ml at 570 minutes of reoxygenation, whereas the group of sham-operated control animals (n = 11) revealed a balanced cfDNA profile. Animals exposed to hypoxia and additionally treated with hypothermia (n = 12) expressed a cfDNA concentration of 54.4±16.9 ng/ml at baseline, 39.2±26.9 ng/ml at the end of hypoxia, and of 41.1±34.2 ng/ml at 570 minutes post-intervention. Concentrations of cfDNA in the CSF of piglets exposed to hypoxia revealed at post-intervention higher levels in comparison to the controls. However, these observations were only tendencies and not significant. In a first methodological proof-of-principle study exploring cfDNA using a piglet model of hypoxia-reoxygenation variations in the temporal patterns suggest that cfDNA might be an early indicator for damages caused by perinatal asphyxia.

Combination of drug and stem cells neurotherapy: Potential interventions in neurotrauma and traumatic brain injury

Traumatic brain injury (TBI) has been recognized as one of the major public health issues that leads to devastating neurological disability. As a consequence of primary and secondary injury phases, neuronal loss following brain trauma leads to pathophysiological alterations on the molecular and cellular levels that severely impact the neuropsycho-behavioral and motor outcomes. Thus, to mitigate the neuropathological sequelae post-TBI such as cerebral edema, inflammation and neural degeneration, several neurotherapeutic options have been investigated including drug intervention, stem cell use and combinational therapies. These treatments aim to ameliorate cellular degeneration, motor decline, cognitive and behavioral deficits. Recently, the use of neural stem cells (NSCs) coupled with selective drug therapy has emerged as an alternative treatment option for neural regeneration and behavioral rehabilitation post-neural injury. Given their neuroprotective abilities, NSC-based neurotherapy has been widely investigated and well-reported in numerous disease models, notably in trauma studies. In this review, we will elaborate on current updates in cell replacement therapy in the area of neurotrauma. In addition, we will discuss novel combination drug therapy treatments that have been investigated in conjunction with stem cells to overcome the limitations associated with stem cell transplantation. Understanding the regenerative capacities of stem cell and drug combination therapy will help improve functional recovery and brain repair post-TBI. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".