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This article comprehensively reviews how cerebral hypoxia impacts the physiological state of neurons and dendritic spines through a series of molecular changes, and explores the causal relationship between these changes and neuronal functional impairment. As a severe pathological condition, cerebral hypoxia can significantly alter the morphology and function of neurons and dendritic spines. Specifically, dendritic spines, being the critical structures for neurons to receive information, undergo changes such as a reduction in number and morphological abnormalities under hypoxic conditions. These alterations further affect synaptic function, leading to neurotransmission disorders. This article delves into the roles of molecular pathways like MAPK, AMPA receptors, NMDA receptors, and BDNF in the hypoxia-induced changes in neurons and dendritic spines, and outlines current treatment strategies. Neurons are particularly sensitive to cerebral hypoxia, with their apical dendrites being vulnerable to damage, thereby affecting cognitive function. Additionally, astrocytes and microglia play an indispensable role in protecting neuronal and synaptic structures, regulating their normal functions, and contributing to the repair process following injury. These studies not only contribute to understanding the pathogenesis of related neurological diseases but also provide important insights for developing novel therapeutic strategies. Future research should further focus on the dynamic changes in neurons and dendritic spines under hypoxic conditions and their intrinsic connections with cognitive function., (© 2024. The Author(s).)

Background/aim: Chronic cerebral hypoxia often leads to brain damage and inflammation. Propofol is suggested to have neuroprotective effects under anaesthesia., Materials and Methods: This study used rat models with carotid artery coarctation or closure. Four groups of rats were compared: a control group, a propofol-treated group, a group with bilateral common carotid artery blockage (BCAO), and a BCAO group treated with propofol post-surgery., Results: The Morris water maze test indicated cognitive impairment in BCAO rats, which also showed hippocampal structure changes, oxidative stress markers alteration, and reduced Klotho expression. Propofol treatment post-BCAO surgery improved these outcomes, suggesting its potential in mitigating chronic cerebral hypoxia effects., Conclusion: Propofol may increase klotho levels and reduce apoptosis and inflammation linked to oxidative stress in cognitively impaired mice., (Copyright © 2024, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

The progression of human degenerative and hypoxic/ischemic diseases is accompanied by widespread cell death. One death process linking iron-catalyzed reactive species with lipid peroxidation is ferroptosis, which shows hallmarks of both programmed and necrotic death in vitro. While evidence of ferroptosis in neurodegenerative disease is indicated by iron accumulation and involvement of lipids, a stable marker for ferroptosis has not been identified. Its prevalence is thus undetermined in human pathophysiology, impeding recognition of disease areas and clinical investigations with candidate drugs. Here, we identified ferroptosis marker antigens by analyzing surface protein dynamics and discovered a single protein, Fatty Acid-Binding Protein 5 (FABP5), which was stabilized at the cell surface and specifically elevated in ferroptotic cell death. Ectopic expression and lipidomics assays demonstrated that FABP5 drives redistribution of redox-sensitive lipids and ferroptosis sensitivity in a positive-feedback loop, indicating a role as a functional biomarker. Notably, immunodetection of FABP5 in mouse stroke penumbra and in hypoxic postmortem patients was distinctly associated with hypoxically damaged neurons. Retrospective cell death characterized here by the novel ferroptosis biomarker FABP5 thus provides first evidence for a long-hypothesized intrinsic ferroptosis in hypoxia and inaugurates a means for pathological detection of ferroptosis in tissue., (© 2024. The Author(s).)

Diffuse cortical diffusion changes on magnetic resonance imaging (MRI) are characteristically ascribed to global cerebral anoxia, typically after cardiac arrest. Far from being pathognomonic, however, this neuroimaging finding is relatively nonspecific, and can manifest in a myriad of disease states including hypoxia, metabolic derangements, infections, seizure, toxic exposures, and neuroinflammation. While these various conditions can all produce a neuroimaging pattern of widespread cortical diffusion restriction, many of these underlying causes do have subtly unique imaging features that are appreciable on MRI and can be of clinical and diagnostic utility. Specific populations of neurons are variably sensitive to certain types of injury, whether due to differences in perfusion, receptor type density, or the unique tropisms of infectious organisms. In this narrative review, we discuss a number of distinct etiologies of diffuse cortical diffusion restriction on MRI, the unique pathophysiologies responsible for tissue injury, and the resulting neuroimaging characteristics that can be of assistance in differentiating them. As widespread cortical injury from any cause often presents with altered mental status or coma, the differential diagnosis can be enhanced with rapid acquisition of MRI when clinical history or detailed physical examination is limited. In such settings, the distinct imaging features discussed in this article are of interest to both the clinician and the radiologist., (© 2023 The Authors. Journal of Neuroimaging published by Wiley Periodicals LLC on behalf of American Society of Neuroimaging.)

Neonatal hypoxic encephalopathy is a type of central nervous system dysfunction manifested by high mortality and morbidity. Exosomes play a crucial role in neuroprotection by enhancing angiogenesis. The objective of this study was to investigate the effect of human amniotic fluid-derived exosomes (hAFEXOs) on functional recovery in neonatal hypoxic encephalopathy. The transwell assay, scratch wound healing assay, and tube formation assay were used to evaluate the effect of hAFEXOs on the angiogenesis of human umbilical vein endothelial cells (HUVECs) after oxygen and glucose deprivation (OGD). The angiogenesis of microvascular endothelial cells (MECs) in the cortex was tested in neonatal mice treated with hAFEXOs or phosphate-buffered saline (PBS) after hypoxia. Expressions of hypoxia-inducible factor 1 α (HIF-1α) and vascular endothelial growth factor (VEGF) in the cerebral cortex were also tested by western blot. The Morris Water Maze Test (MWM) was carried out to detect the performance of spatial memory after processing with hAFEXOs or PBS. The results indicated that hAFEXOs favored tubing formation and migration of HUVECs after in vitro OGD. The hAFEXOs also favored the expression of CD31 in neonatal mice following hypoxia. The expressions of both HIF-1α and VEGF were significantly augmented in the cerebral cortex of neonatal mice which were treated with hAFEXOs. Moreover, the MWM test results showed that the performance of the spatial memory was better in the hAFEXO-treated group than in the PBS-treated group. Our study indicates that hAFEXOs alleviated hypoxic encephalopathy and enhanced angiogenesis in neonatal mice after hypoxia. In addition, hAFEXOs  promoted migration and tube formation of HUVECs after OGD in vitro. These findings confirm that hAFEXOs show great potential for further studies aimed at developing therapeutic agents for hypoxic encephalopathy., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Hypobaric Hypoxia (HH) is known to cause oxidative stress in the brain that leads to spatial memory deficit and neurodegeneration. For decades therapeutic hypothermia is used to treat global and focal ischemia in preserving brain functions that proved to be beneficial in humans and rodents. Considering these previous reports, the present study was designed to establish the therapeutic potential of hypothermia preconditioning on HH induced spatial memory, biochemical and morphological changes in adult rats. Male Sprague Dawley rats were exposed to HH (7620 m, ~ 282 mmHg) for 1, 3 and 7 days with and without hypothermic preconditioning. Spatial learning memory was assessed by Morris water maze (MWM) test along with evaluation of hippocampal pyramidal neuron damage by histological study. Oxidative stress was measured by studying the levels of nitric oxide (NO), reactive oxygen species (ROS), lipid peroxidation (LPO), oxidized and reduced glutathione (GSSG and GSH). Results of MWM test indicated prolonged path length and latency to reach the platform in HH groups that regained to normal in cold pre-treated groups. A likely neurodegeneration was evident in HH groups that lessen in the cold pre-treated groups. Hypothermic preconditioning prevented spatial memory impairment and neurodegeneration in animals subjected to HH via decreasing the NO, ROS and LPO compared to control animals. The GSH level and GSH/GSSG ratio was found to be higher in preconditioned animals as compared to respective HH exposed animals, indicative of redox scavenging and restoration of hippocampal neuronal structure as well as spatial memory. Therefore, hypothermic preconditioning improves spatial memory deficit by reducing HH induced oxidative stress and hippocampal neurodegeneration, hence can be used as a multi-target prophylactic measure to combat HH induced neurodegeneration., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Aims: Sevoflurane preconditioning (SPC) results in cerebral ischemic tolerance; however, the mechanism remains unclear. Promoting microglia/macrophages polarization from pro-inflammatory state to anti-inflammatory phenotype has been indicated as a potential treatment target against ischemic stroke. In this study, we aimed to assess the effect of SPC on microglia polarization after stroke and which signaling pathway was involved in this transition., Methods: Mouse primary microglia with SPC were challenged by oxygen-glucose deprivation (OGD) or lipopolysaccharide (LPS), and mice with SPC were subjected to middle cerebral artery occlusion (MCAO). Then, the mRNA and protein levels of pro-inflammatory/anti-inflammatory factors were analyzed. GSK-3β phosphorylation and Nrf2 nuclear translocation were measured. The mRNA and protein expression of pro-inflammatory/anti-inflammatory factors, neurological scores, infarct volume, cellular apoptosis, the proportion of pro-inflammatory/anti-inflammatory microglia/macrophages, and the generation of super-oxidants were examined after SPC or GSK-3β inhibitor TDZD treatment with or without Nrf2 deficiency., Results: Sevoflurane preconditioning promoted anti-inflammatory and inhibited pro-inflammatory microglia/macrophages phenotype both in vitro and in vivo. GSK-3β phosphorylation at Ser9 was increased after SPC. Both SPC and TDZD administration enhanced Nrf2 nuclear translocation, reduced pro-inflammatory microglia/macrophages markers expression, promoted anti-inflammatory markers level, and elicited a neuroprotective effect. Nrf2 deficiency abolished the promoted anti-inflammatory microglia/macrophages polarization and ischemic tolerance induced by TDZD treatment. The reduced percentage of pro-inflammatory positive cells and super-oxidants generation induced by SFC or TDZD was also reversed by Nrf2 knockdown., Conclusions: Our results indicated that SPC exerts brain ischemic tolerance and promotes anti-inflammatory microglia/macrophages polarization by GSK-3β-dependent Nrf2 activation, which provides a novel mechanism for SPC-induced neuroprotection., (© 2021 The Authors. CNS Neuroscience & Therapeutics published by John Wiley & Sons Ltd.)

Brain hypoxia can occur after non-traumatic subarachnoid hemorrhage (SAH), even when levels of intracranial pressure (ICP) remain normal. Brain tissue oxygenation (PbtO 2 ) can be measured as a part of a neurological multimodal neuromonitoring. Low PbtO 2 has been associated with poor neurologic recovery. There is scarce data on the impact of PbtO 2 guided-therapy on patients' outcome. This single-center cohort study (June 2014-March 2020) included all patients admitted to the ICU after SAH who required multimodal monitoring. Patients with imminent brain death were excluded. Our primary goal was to assess the impact of PbtO 2 -guided therapy on neurological outcome. Secondary outcome included the association of brain hypoxia with outcome. Of the 163 patients that underwent ICP monitoring, 62 were monitored with PbtO 2 and 54 (87%) had at least one episode of brain hypoxia. In patients that required treatment based on neuromonitoring strategies, PbtO 2 -guided therapy (OR 0.33 [CI 95% 0.12-0.89]) compared to ICP-guided therapy had a protective effect on neurological outcome at 6 months. In this cohort of SAH patients, PbtO 2 -guided therapy might be associated with improved long-term neurological outcome, only when compared to ICP-guided therapy., (© 2021. The Author(s).)

Preterm infants experience frequent arterial oxygen desaturations during oxygen therapy, or intermittent hypoxia (IH). Neonatal IH increases oxidative distress which contributes to neuroinflammation and brain injury. We tested the hypotheses that exposure to neonatal IH is detrimental to the immature brain and that early supplementation with antioxidants and/or omega 3 polyunsaturated fatty acids (n-3 PUFAs) combined with non-steroidal anti-inflammatory drugs (NSAIDs) is protective. Newborn rats were exposed to brief hypoxia (12% O 2 ) during hyperoxia (50% O 2 ) from the first day of life (P0) until P14 during which they received daily oral supplementation with antioxidants, namely coenzyme Q10 (CoQ10) or glutathione nanoparticles (nGSH), n-3 PUFAs and/or topical ocular ketorolac. Placebo controls received daily oral olive oil and topical ocular saline. Room air (RA) littermates remained in 21% O 2 from birth to P21 with all treatments identical. At P14 animals were allowed to recover in RA until P21 with no further treatment. Whole brains were harvested for histopathology and morphometric analyses, and assessed for biomarkers of oxidative stress and inflammation, as well as myelin injury. Neonatal IH resulted in higher brain/body weight ratios, an effect that was reversed with n-3 PUFAs and n-3 PUFAs+CoQ10 with or without ketorolac. Neonatal IH was also associated with hemorrhage, oxidative stress, and elevations in inflammatory prostanoids. Supplementation with n-3 PUFAs and nGSH with and without ketorolac were most beneficial for myelin growth and integrity when administered in RA. However, the benefit of n-3 PUFAs was significantly curtailed in neonatal IH. Neonatal IH during a critical time of brain development causes inflammation and oxidative injury. Loss of therapeutic benefits of n-3 PUFAs suggest its susceptibility to oxidation in neonatal IH and therefore indicate that co-administration with antioxidants may be necessary to sustain its efficacy., (© 2021 International Society for Developmental Neuroscience.)

Brain ischemia is one of the leading causes of disability and mortality worldwide. Nitric oxide (NO • ), a molecule that is involved in the regulation of proper blood flow, vasodilation, neuronal and glial activity constitutes the crucial factor that contributes to the development of pathological changes after stroke. One of the early consequences of a sudden interruption in the cerebral blood flow is the massive production of reactive oxygen and nitrogen species (ROS/RNS) in neurons due to NO • synthase uncoupling, which leads to neurotoxicity. Progression of apoptotic or necrotic neuronal damage activates reactive astrocytes and attracts microglia or lymphocytes to migrate to place of inflammation. Those inflammatory cells start to produce large amounts of inflammatory proteins, including pathological, inducible form of NOS (iNOS), which generates nitrosative stress that further contributes to brain tissue damage, forming vicious circle of detrimental processes in the late stage of ischemia. S-nitrosylation, hypoxia-inducible factor 1α (HIF-1α) and HIF-1α-dependent genes activated in reactive astrocytes play essential roles in this process. The review summarizes the roles of NO • -dependent pathways in the early and late aftermath of stroke and treatments based on the stimulation or inhibition of particular NO • synthases and the stabilization of HIF-1α activity.

Objectives: Endovascular treatment (EVT) has become the standard of care for acute ischemic stroke. Despite successful recanalization, a limited subset of patients benefits from the new treatment. Human MRI studies have shown that during removal of the thrombus, a shower of microclots is released from the initial thrombus, possibly causing new ischemic lesions. The aim of the current study is to quantify tissue damage following microembolism., Materials and Methods: In a rat model, microembolism was generated by injection of a mixture of polystyrene fluorescent microspheres (15, 25 and 50 µm in diameter). The animals were killed at three time-points: day 1, 3 or 7. AMIRA and IMARIS software was used for 3D reconstruction of brain structure and damage, respectively., Conclusions: Microembolism induces ischemia, hypoxia and infarction. Infarcted areas persist, but hypoxic regions recover over time suggesting that repair processes in the brain rescue the regions at risk., Competing Interests: Declaration of Competing Interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Perinatal hypoxia severely disrupts cerebral metabolic and maturational programs beyond apoptotic cell death. Antiapoptotic treatments such as erythropoietin are suggested to improve outcomes in hypoxic brain injury; however, the results are controversial. We analyzed the neuroprotective effects of recombinant human growth hormone (rhGH) on regenerative mechanisms in the hypoxic developing mouse brain in comparison to controls. Using an established model of neonatal acute hypoxia (8% O2, 6 hours), P7 mice were treated intraperitoneally with rhGH (4000 µg/kg) 0, 12, and 24 hours after hypoxic exposure. After a regeneration period of 48 hours, expression of hypoxia-inducible neurotrophic factors (erythropoietin [EPO], vascular endothelial growth factor A [VEGF-A], insulin-like growth factors 1 and 2 [IGF-1/-2], IGF binding proteins) and proinflammatory markers was analyzed. In vitro experiments were performed using primary mouse cortical neurons (E14, DIV6). rhGH increased neuronal gene expression of EPO, IGF-1, and VEGF (P < .05) in vitro and diminished apoptosis of hypoxic neurons in a dose-dependent manner. In the developing brain, rhGH treatment led to a notable reduction of apoptosis in the subventricular zone and hippocampus (P < .05), abolished hypoxia-induced downregulation of IGF-1/IGF-2 expression (P < .05), and led to a significant accumulation of endogenous EPO protein and anti-inflammatory effects through modulation of interleukin-1β and tumor necrosis factor α signaling as well as upregulation of cerebral phosphorylated extracellularly regulated kinase 1/2 levels (ERK1/2). Indicating stabilizing effects on the blood-brain barrier (BBB), rhGH significantly modified cerebrovascular occludin expression. Thus, we conclude that rhGH mediates neuroprotective effects by the activation of endogenous neurotrophic growth factors and BBB stabilization. In addition, the modification of ERK1/2 pathways is involved in neuroprotective actions of rhGH. The present study adds further evidence that pharmacologic activation of neurotrophic growth factors may be a promising target for neonatal neuroprotection., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Endocrine Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

To elucidate the mechanisms of memory impairment after chronic neonatal intermittent hypoxia (IH), we employed a mice model of severe IH administered at postnatal days 3 to 7. Since prior studies in this model did not demonstrate increased cell death, our primary hypothesis was that IH causes a functional disruption of synaptic plasticity in hippocampal neurons. In vivo recordings of Schaffer collateral stimulation-induced synaptic responses during and after IH in the CA1 region of the hippocampus revealed pathological late phase hypoxic long term potentiation (hLTP) (154%) that lasted more than four hours and could be reversed by depotentiation with low frequency stimulation (LFS), or abolished by NMDA and PKA inhibitors (MK-801 and CMIQ). Furthermore, late phase hLTP partially occluded normal physiological LTP (pLTP) four hours after IH. Early and late hLTP phases were induced by neuronal depolarization and Ca 2+ influx, determined with manganese enhanced fMRI, and had increased both AMPA and NMDA - mediated currents. This was consistent with mechanisms of pLTP in neonates and also consistent with mechanisms of ischemic LTP described in vitro with OGD in adults. A decrease of pLTP was also recorded on hippocampal slices obtained 2 days after IH. This decrease was ameliorated by MK-801 injections prior to each IH session and restored by LFS depotentiation. Occlusion of pLTP and the observed decreased proportion of NMDA-only silent synapses after neonatal hLTP may explain long term memory, behavioral deficits and abnormal synaptogenesis and pruning following neonatal IH., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Brain organoids have emerged as a novel model system for neural development, neurodegenerative diseases, and human-based drug screening. However, the heterogeneous nature and immature neuronal development of brain organoids generated from pluripotent stem cells pose challenges. Moreover, there are no previous reports of a three-dimensional (3D) hypoxic brain injury model generated from neural stem cells. Here, we generated self-organized 3D human neural organoids from adult dermal fibroblast-derived neural stem cells. Radial glial cells in these human neural organoids exhibited characteristics of the human cerebral cortex trend, including an inner (ventricular zone) and an outer layer (early and late cortical plate zones). These data suggest that neural organoids reflect the distinctive radial organization of the human cerebral cortex and allow for the study of neuronal proliferation and maturation. To utilize this 3D model, we subjected our neural organoids to hypoxic injury. We investigated neuronal damage and regeneration after hypoxic injury and reoxygenation. Interestingly, after hypoxic injury, reoxygenation restored neuronal cell proliferation but not neuronal maturation. This study suggests that human neural organoids generated from neural stem cells provide new opportunities for the development of drug screening platforms and personalized modeling of neurodegenerative diseases, including hypoxic brain injury.

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., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background/aims: Obstructive sleep apnea (OSA) is characterized by repeated episodes of complete or partial obstruction of the upper airways, leading to chronic intermittent hypoxia (IH). OSA patients are considered at high cerebrovascular risk and may also present cognitive impairment. One hypothesis explored is that disturbances may be linked to blood-brain barrier (BBB) dysfunction. The BBB is a protective barrier separating the brain from blood flow. The BBB limits the paracellular pathway through tight and adherens junctions, and the transcellular passage by efflux pumps (ABC transporters). The aims of this study were to evaluate the impact of IH and sustained hypoxia (SH) on a validated in vitro BBB model and to investigate the factors expressed under both conditions., Methods: Exposure of endothelial cells (HBEC-5i) in our in vitro model of BBB to hypoxia was performed using IH cycles: 1% O2-35 min/18% O2-25 min for 6 cycles or 6 h of SH at 1% O2. After exposure, we studied the cytotoxicity and the level of ROS in our cells. We measured the apparent BBB permeability using sodium fluorescein, FITC-dextran and TEER measurement. Whole cell ELISA were performed to evaluate the expression of tight junctions, ABC transporters, HIF-1α and Nrf2. The functionality of ABC transporters was evaluated with accumulation studies. Immunofluorescence assays were also conducted to illustrate the whole cell ELISAs., Results: Our study showed that 6 h of IH or SH induced a BBB disruption marked by a significant decrease in junction protein expressions (claudin-5, VE-cadherin, ZO-1) and an increase in permeability. We also observed an upregulation in P-gp protein expression and functionality and a downregulation in BCRP. Hypoxia induced production of ROS, Nrf2 and HIF-1α. They were expressed in both sustained and intermittent conditions, but the expression and the activity of P-gp and BCRP were different., Conclusion: Understanding these mechanisms seems essential in order to propose new therapeutic strategies for patients with OSA., Competing Interests: The authors have no conflicts of interest to declare., (© Copyright by the Author(s). Published by Cell Physiol Biochem Press.)

Hypoxia, the major cause of ischemic injury, leads to debilitating disease in infants via birth asphyxia and cerebral palsy, whereas in adults via heart attack and stroke. A widespread, natural protective phenomenon termed 'hypoxic preconditioning' (PH) occurs when prior exposures to hypoxia eventually result in robust hypoxia resistance. Accordingly, we have developed and optimized a novel model of hypoxic preconditioning in adult zebrafish to mimic the tolerance of mini stroke(s) in human, which appears to protect against the severe damage inflicted by a major stroke event. Here, we observed a remarkable difference in the progression pattern of neuroprotection between preconditioning hypoxia followed by acute hypoxia (PH) group, and acute hypoxia (AH) only group, with noticeable sex difference when compared with normoxia behaviour upon recovery. Since gender difference has been reported in stroke risk factors and disease history, it was pertinent to investigate whether any such sex difference also exists in PH's protective mechanism against acute ischemic stroke. In order to elucidate the neural molecular mechanisms behind sex difference in neuroprotection induced by PH, a high throughput proteomics approach utilizing iTRAQ was performed, followed by protein enrichment analysis using ingenuity pathway analysis (IPA) tool. Out of thousands of significantly altered proteins in zebrafish brain, the ones having critical role either in neuroglial proliferation/differentiation or neurotrophic functions were validated by analyzing their expression levels in preconditioned (PH), acute hypoxia (AH), and normoxia groups. The data indicate that female zebrafish brains are more protected against the severity of AH when exposed to the hypoxic preconditioning. The study also sheds light on the involvement of many signalling pathways underlying sex difference in preconditioning-induced neuroprotective mechanism, which can be further validated for the therapeutic approach.

Exosomes secreted by microglia have been found to play a role in neurovascular unit injury under the ischemic/hypoxic state. However, the modulatory effect of exosomes shuttled miRNAs produced by microglia in endothelial cells remains undefined. Here, an oxygen-glucose deprivation (OGD) model was constructed both in microglia and brain microvascular endothelial cells (BMEC). The exosomes secreted by microglia were isolated, and the exosomal miRNA profile was detected. Next, gain- and loss- functions of miR-424-5p, one of the most differentially expressed miRNAs in microglia derived exosomes, were conducted in BMEC. The results demonstrated that exosomes from OGD-activated microglia aggravated OGD induced BMEC viability and integrity damage as well as the loss of vascular formation. While the damaging effects were markedly attenuated by inhibiting miR-424-5p. In addition, miR-424-5p overexpression significantly aggravated OGD induced BMEC damage and permeability. Mechanistically, bioinformatics analysis indicated that miR-424-5p targeted the FGF2 mediated STAT3 signaling pathway, which was verified via dual luciferase activity assay and RIP experiment. Furthermore, in vivo experiments in the middle cerebral artery occlusion (MCAO) model mice were conducted. The results revealed that inhibition of miR-424-5p markedly reduced neurological dysfunctions and endothelial cell injury induced by MCAO. The above results confirmed that exosomes from OGD activated microglia induced significant cell damage and permeability of BMEC, in which the upregulated miR-424-5p in the exosomes functioned by regulating FGF2/STAT3 pathway., Competing Interests: Declaration of Competing Interest The authors declare that they have no competing interests., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Pial collaterals provide protection in stroke. Evidence suggests their formation late during gestation (collaterogenesis) is driven by reduced oxygen levels in the cerebral watersheds. The purpose of this study was to determine if collaterogenesis can be re-activated in the adult to induce formation of additional collaterals ("neo-collateral formation", NCF). Mice were gradually acclimated to reduced inspired oxygen (FIO 2 ) and maintained at 12, 10, 8.5 or 7% for two-to-eight weeks. Hypoxemia induced "dose"-dependent NCF and remodeling of native collaterals, and decreased infarct volume after permanent MCA occlusion. In contrast, no formation occurred of addition collateral-like intra-tree anastomoses, PComs, or branches within the MCA tree. Hypoxic NCF, remodeling and infarct protection were durable, i.e. retained for at least six weeks after return to normoxia. Hypoxia increased expression of Hif2α, Vegfa, Rabep2, Angpt2, Tie2 and Cxcr4 . Neo-collateral formation was abolished in mice lacking Rabep2, a novel gene involved in VEGFA→Flk1 signaling and required for formation of collaterals during development, and inhibited by knockdown of Vegfa , Flk1 and Cxcr4 . Rabep2 -dependent NCF was also induced by permanent MCA occlusion. This is the first report that hypoxia induces new pial collaterals to form. Hypoxia- and occlusion-induced neo-collateral formation provide models to study collaterogenesis in the adult.

White matter hyperintensities (WMH) occur in association with dementia but the aetiology is unclear. Here we test the hypothesis that there is a combination of impaired elimination of interstitial fluid from the white matter together with a degree of hypoxia in WMH. One of the mechanisms for the elimination of amyloid-β (Aβ) from the brain is along the basement membranes in the walls of capillaries and arteries (Intramural Peri-Arterial Drainage - IPAD). We compared the dynamics of IPAD in the grey matter of the hippocampus and in the white matter of the corpus callosum in 10 week old C57/B16 mice by injecting soluble Aβ as a tracer. The dynamics of IPAD in the white matter were significantly slower compared with the grey matter and this was associated with a lower density of capillaries in the white matter. Exposing cultures of smooth muscle cells to hypercapnia as a model of cerebral hypoperfusion resulted in a reduction in fibronectin and an increase in laminin in the extracellular matrix. Similar changes were detected in the white matter in human WMH suggesting that hypercapnia/hypoxia may play a role in WMH. Employing therapies to enhance both IPAD and blood flow in the white matter may reduce WMH in patients with dementia.

Multimodal continuous bedside monitoring is increasingly recognized as a promising option for early treatment stratification in patients at risk for ischemia during neurocritical care. Modalities used at present are, for example, oxygen availability and subdural electrocorticography. The assessment of mitochondrial function could be an interesting complement to these modalities. For instance, flavin adenine dinucleotide (FAD) fluorescence permits direct insight into the mitochondrial redox state. Therefore, we explored the possibility of using FAD fluorometry to monitor consequences of hypoxia in brain tissue in vitro and in vivo. By combining experimental results with computational modeling, we identified the potential source responsible for the fluorescence signal and gained insight into the hypoxia-associated metabolic changes in neuronal energy metabolism. In vitro, hypoxia was characterized by a reductive shift of FAD, impairment of synaptic transmission and increasing interstitial potassium [K + ] o . Computer simulations predicted FAD changes to originate from the citric acid cycle enzyme α-ketoglutarate dehydrogenase and pyruvate dehydrogenase. In vivo, the FAD signal during early hypoxia displayed a reductive shift followed by a short oxidation associated with terminal spreading depolarization. In silico, initial tissue hypoxia followed by a transient re-oxygenation phase due to glucose depletion might explain FAD dynamics in vivo. Our work suggests that FAD fluorescence could be readily used to monitor mitochondrial function during hypoxia and represents a potential diagnostic tool to differentiate underlying metabolic processes for complementation of multimodal brain monitoring.

Objective: White matter lesions (WMLs) are more common in migraine patients than in the normal population. Ischemia/hypoxia and oxidative stress are considered to play a role in WMLs formation. This study aimed to investigate ischemia-modified albumin (IMA), ferroxidase and thiol/disulfide homeostasis in migraineurs with and without WMLs., Patients and Methods: Sixty-two migraineurs with WML, 59 migraineurs without WML and 61 controls were included in the study. All participants underwent brain MRI. WMLs was evaluated according to the Fazekas scale. IMA, ferroxidase, total thiol, native thiol and disulfide measurements were carried out in all participants., Results: The IMA levels were higher in the migraine groups compared to the control group (p < 0.001) and in the WML group compared to non-WML (p < 0.001). The total and native thiol levels were higher in the non-WML group compared to the control and WML groups (p < 0.001 for both). The disulfide levels were similar between the control and non-WML groups, but they were significantly lower in the WML group compared to the control and non-WML groups. There was no significant difference between the groups in terms of the ferroxidase levels (p = 0.092). The thiol/disulfide, IMA and ferroxidase levels were not significantly correlated with the frequency and duration of attacks, severity of pain and disability due to migraine., Conclusion: Increased serum IMA levels in migraineurs point to the role of ischemia/hypoxia, and increased total thiol and decreased disulfide levels indicate an oxidant/antioxidant imbalance in migraine. Ischemia/hypoxia may play a role in WMLs formation in migraine., Competing Interests: Declaration of competing Interest None., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Tripartite motif 16 (TRIM16) has emerged as a novel oxidative stress-responsive protein that confers cytoprotective effects by reinforcing the cellular antioxidant system. However, whether TRIM16 is involved in regulating oxidative stress during cerebral ischemia/reperfusion injury remains unclear. In the present study, we aimed to explore the potential function and molecular mechanism of TRIM16 in regulating oxidative stress in neurons induced by oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro. Here, we found that OGD/R exposure resulted in a significant induction of TRIM16 expression in neurons. Depletion of TRIM16 by siRNA-mediated gene knockdown markedly upregulated the sensitivity of neurons to OGD/R-induced apoptosis and reactive oxygen species (ROS) generation. Notably, upregulation of TRIM16 expression significantly alleviated OGD/R-induced apoptosis and ROS generation in neurons. Moreover, TRIM16 overexpression markedly increased nuclear factor erythroid 2-related factor 2 (Nrf2) expression and enhanced Nrf2/antioxidant response element (ARE) activation associated with downregulation of kelch-like ECH-associated protein 1 (Keap1) expression. Restoration of Keap1 significantly reversed the TRIM16-mediated promotion effect on Nrf2/ARE activation. In addition, knockdown of Nrf2 also markedly abrogated the TRIM16-conferred neuroprotective effect in OGD/R-exposed neurons. Taken together, our results of our study demonstrate that induction of TRIM16 confers a cytoprotective effect in OGD/R-exposed neurons through enhancement of Nrf2/ARE antioxidant signaling via downregulation of Keap1. These findings suggest that TRIM16 may play a critical role in cerebral ischemia/reperfusion injury and serve as a promising target for neuroprotection., Competing Interests: Declaration of competing interest All authors declare that they have no conflict of interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Neonatal hypoxic-ischemic brain damage (HIBD) is prone to cognitive and memory impairments, and there is no effective clinical treatment until now. Ferulic acid (FA) is found within members of the genus Angelica, reportedly shows protective effects on neuronal damage. However, the protective effects of FA on HIBD remains unclear. In this study, using the Morris water maze task, we herein found that the impairment of spatial memory formation in adult rats exposed to HIBD was significantly reversed by FA treatment and the administration of LNA-miR-9. The expression of miRNA-9 was detected by RT-PCR analyses, and the results shown that miRNA-9 was significantly increased in the hippocampus of neonatal rats following HIBD and in the PC12 cells following hypoxic-ischemic injury, while FA and LNA-miR-9 both inhibited the expression of miRNA-9, suggesting that the therapeutic effect of FA was mainly attributed to the inhibition of miRNA-9 expression. Indeed, the silencing of miR-9 by LNA-miR-9 or FA similarly attenuated neuronal damage and cerebral atrophy in the rat hippocampus after HIBD, which was consistent with the restored expression levels of brain-derived neurotrophic factor (BDNF). Therefore, our findings indicate that FA treatment may protect against neuronal death through the inhibition of miRNA-9 induction in the rat hippocampus following hypoxic-ischemic damage., Competing Interests: The authors have declared that no competing interests exist.

Perinatal hypoxia is still one of the greatest threats to the newborn child, even in developed countries. However, there is a lack of works which summarize up-to-date information about that huge topic. Our review covers a broader spectrum of recent results from studies on mechanisms leading to hypoxia-induced injury. It also resumes possible primary causes and observed behavioral outcomes of perinatal hypoxia. In this review, we recognize two types of hypoxia, according to the localization of its primary cause: environmental and placental. Later we analyze possible pathways of prenatal hypoxia-induced injury including gene expression changes, glutaminergic excitatory damage (and a role of NMDA receptors in it), oxidative stress with ROS and RNS production, inflammation and apoptosis. Moreover, we focus on the impact of these pathophysiological changes on the structure and development of the brain, especially on its regions: corpus striatum and hippocampus. These brain changes of the offspring lead to impairments in their postnatal growth and sensorimotor development, and in their motor functions, activity, emotionality and learning ability in adulthood. Later we compare various animal models used to investigate the impact of prenatal and postnatal injury (hypoxic, ischemic or combinatory) on living organisms, and show their advantages and limitations.

Hypoxia (HYPX) induced-overload Ca 2+ entry results in increase of mitochondrial oxidative stress, inflammation and apoptosis in several neurons. Ca 2+ permeable TRPM2 channel was gated by ADP-ribose (ADPR) and reactive oxygen species (ROS), although its activity was modulated in HYPX-exposed neurons by resveratrol (RSV). The aim of this study was to evaluate if a therapy of RSV can modulate the effect of HYPX in the TRPM2 expressing SH-SY5Y neuronal and HEK293 (no expression of TRPM2) cell lines. The SH-SY5Y and HEK293 cells were divided into four groups as control, RSV (50 μM and 24 hours), and HYPX and RSV + HYPX. For induction of HYPX in the cells, CoCl 2 (200 μM and 24 hours) incubation was used. HYPX-induced intracellular Ca 2+ responses to TRPM2 activation were increased in the SH-SY5Y cells but not in the HEK293 cells from coming H 2 O 2 and ADPR. RSV treatment improved intracellular Ca 2+ responses, mitochondrial function, suppressed the generation of cytokine (IL-1β and TNF-α), cytosolic and mitochondrial ROS in the SH-SY5Y cells. Intracellular free Zn 2+ , apoptosis, cell death, PARP-1, TRPM2 expression, caspase -3 and -9 levels are increased through activating TRPM2 in the SH-SY5Y cells exposed to the HYPX. However, the values were decreased in the cells by RSV and TRPM2 blockers (ACA and 2-APB). In SH-SY5Y neuronal cells exposed to HYPX conditions, the neuroprotective effects of RSV were shown to be exerted via modulation of oxidative stress, inflammation, apoptosis and death through modulation of TRPM2 channel. RSV could be used as an effective agent in the treatment of neurodegeneration exposure to HYPX.

Background and Purpose: Anoxic brain injury is a result of prolonged hypoxia. We sought to describe the nonquantitative arterial spin-labeling perfusion imaging patterns of anoxic brain injury, characterize the relationship of arterial spin-labeling and DWI, and evaluate the normalized diffusion-to-perfusion ratio to differentiate patients with anoxic brain injury from healthy controls., Materials and Methods: We identified all patients diagnosed with anoxic brain injuries from 2002 to 2019. Twelve ROIs were drawn on arterial spin-labeling with coordinate-matched ROIs identified on DWI. Linear regression analysis was performed to examine the relationship between arterial spin-labeling perfusion and diffusion signal. Normalized diffusion-to-perfusion maps were generated using a custom-built algorithm., Results: Thirty-five patients with anoxic brain injuries and 34 healthy controls were identified. Linear regression analysis demonstrated a significant positive correlation between arterial spin-labeling and DWI signal. By means of a combinatory cutoff of slope of >0 and R 2 of > 0.78, linear regression using arterial spin-labeling and DWI showed a sensitivity of 0.86 (95% CI, 0.71-0.94) and specificity of 0.82 (95% CI, 0.66-0.92) for anoxic brain injuries. A normalized diffusion-to-perfusion color map demonstrated heterogeneous ratios throughout the brain in healthy controls and homogeneous ratios in patients with anoxic brain injuries., Conclusions: In anoxic brain injuries, a homogeneously positive correlation between qualitative perfusion and DWI signal was identified so that areas of increased diffusion signal showed increased ASL signal. By exploiting this relationship, the normalized diffusion-to-perfusion ratio color map may be a valuable imaging biomarker for diagnosing anoxic brain injury and potentially assessing BBB integrity., (© 2020 by American Journal of Neuroradiology.)

Inflammatory pathways involved in blood-brain barrier (BBB) vulnerability and hypoxic brain oedema in models of perinatal brain injury seem to provide putative therapeutic targets. To investigate impacts of C1-esterase inhibitor (C1-INH; 7.5-30 IU/kg, i.p.) on functional BBB properties in the hypoxic developing mouse brain (P7; 8% O 2 for 6 h), expression of pro-apoptotic genes (BNIP3, DUSP1), inflammatory markers (IL-1ß, TNF-alpha, IL-6, MMP), and tight junction proteins (ZO-1, occludin, claudin-1, -5), and S100b protein concentrations were analysed after a regeneration period of 24 h. Apoptotic cell death was quantified by CC3 immunohistochemistry and TUNEL staining. In addition to increased apoptosis in the parietal cortex, hippocampus, and subventricular zone, hypoxia significantly enhanced the brain-to-plasma albumin ratio, the cerebral S100b protein levels, BNIP3 and DUSP1 mRNA concentrations as well as mRNA expression of pro-inflammatory cytokines (IL-1ß, TNF-alpha). In response to C1-INH, albumin ratio and S100b concentrations were similar to those of controls. However, the mRNA expression of BNIP3 and DUSP1 and pro-inflammatory cytokines as well as the degree of apoptosis were significantly decreased compared to non-treated controls. In addition, occludin mRNA levels were elevated in response to C1-INH (p < 0.01). Here, we demonstrate for the first time that C1-INH significantly decreased hypoxia-induced BBB leakage and apoptosis in the developing mouse brain, indicating its significance as a promising target for neuroprotective therapy.

Obstructive sleep apnea (OSA), a chronic sleep disorder characterized by repetitive reduction or cessation of airflow during sleep, is widely prevalent and is associated with adverse neurocognitive sequelae including increased risk of Alzheimer's disease (AD). In humans, OSA is more common in elderly males. OSA is characterized by sleep fragmentation and chronic intermittent hypoxia (CIH), and recent epidemiological studies point to CIH as the best predictor of neurocognitive sequelae associated with OSA. The sex- and age- specific effects of OSA-associated CIH on specific cell populations such as γ-aminobutyric acid (GABA)-ergic neurons in the hippocampus and the medial prefrontal cortex (mPFC), regions important for cognitive function, remain largely unknown. The present study examined the effect of 35 days of either moderate (10% oxygen) or severe (5% oxygen) CIH on GABAergic neurons in the mPFC and hippocampus of young and aged male and female mice as well as post-accelerated ovarian failure (AOF) female mice. In the mPFC and hippocampus, the number of GABA-labeled neurons increased in aged and young severe CIH males compared to controls but not in young moderate CIH males. This change was not representative of the individual GABAergic cell subpopulations, as the number of parvalbumin-labeled neurons decreased while the number of somatostatin-labeled neurons increased in the hippocampus of severe CIH young males only. In all female groups, the number of GABA-labeled cells was not different between CIH and controls. However, in the mPFC, CIH increased the number of parvalbumin-labeled neurons in young females and the number of somatostatin-labeled cells in AOF females but decreased the number of somatostatin-labeled cells in aged females. In the hippocampus, CIH decreased the number of somatostatin-labeled neurons in young females. CIH decreased the density of vesicular GABA transporter in the mPFC of AOF females only. These findings suggest sex-specific changes in GABAergic neurons in the hippocampus and mPFC with males showing an increase of this cell population as compared to their female counterparts following CIH. Age at exposure and severity of CIH also differentially affect the GABAergic cell population in mice., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interest., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Remote ischemic postconditioning (RIPost) has been shown to reduce the ischemia-reperfusion injury of the heart and brain. However, the protection mechanisms have not yet been fully elucidated. We have observed that RIPost could alleviate the brain injury after cardiac arrest (CA). The aim of this study was to explore whether α7 nicotinic acetylcholine receptor (α7nAChR) mediates the neuroprotection of RIPost in a rat model of asphyxial CA., Materials and Methods: Asphyxial CA model was induced by occlusion of the tracheal tube for 8 min and resuscitated later. RIPost produced by three cycles of 15-min occlusion and 15-min release of the right hind limb by a tourniquet was performed respectively at the moment and the third hour after restoration of spontaneous circulation. The α7nAChR agonist PHA-543613 and the antagonist methyllycaconitine (MLA) were used to investigate the role of α7nAChR in mediating neuroprotective effects., Results: Results showed that α7nAChR was decreased in hippocampus and cortex after resuscitation, whereas RIPost could attenuate the reduction. The use of PHA-543613 provided neuroprotective effects against cerebral injury after CA. Furthermore, RIPost decreased the levels of neuron-specific enolase, inflammatory mediators, the number of apoptotic cells, and phosphorylation of nuclear factor-κB while increased the phosphorylation of signal transducer and activator of transcription-3. However, the above effects of RIPost were attenuated by α7nAChR antagonist methyllycaconitine., Conclusions: Neuroprotection of RIPost was related with the activation of α7nAChR, which could suppress nuclear factor-κB and activate signal transducer and activator of transcription-3 in a rat asphyxial CA model., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objectives: To study the effects of total flavones of Rhododendra simsii Planch flower (TFR) on hypoxia/reoxygenation (H/R) injury in rat hippocampal neurons and its underlying mechanism., Method: Model of H/R was established in newborn rat primary cultured hippocampal neuron. Lactate dehydrogenase (LDH) and neuron-specific enolase (NSE) activity as well as malondialdehyde (MDA) content in cultured supernatants of the neurons were examined. Methyl thiazolyl tetrazolium assay and Hoechst33258 staining were, respectively, used to detect cell viability and apoptosis of neurons. Protein expression and current of BK Ca channel were assessed by using Western blotting and whole-cell patch-clamp methods, respectively., Key Findings: In the ranges of 3.7-300 mg/l, TFR significantly inhibited H/R-induced decrease of neuronal viability and increases of LDH, NSE and MDA in the supernatants as well as apoptosis; TFR 33.3, 100 and 300 mg/l markedly increased current of BK Ca channel rather than the BK Ca channel protein expression in the neurons., Conclusions: Total flavones of R. simsii Planch flower had a protective effect against H/R injury in rat hippocampal neuron, and activation of BK Ca channel may contribute to the neuroprotection., (© 2019 Royal Pharmaceutical Society.)

Xenon is an inhalation anesthetic with a favorable safety profile, and previous studies have demonstrated its neuroprotective efficacy. However, whether xenon plays a role in the treatment of epilepsy or seizure remains unclear. This study aimed to investigate the role of xenon inhalation and explore the role of different xenon ratio gradients and different delayed treatment times in seizure models. Kainic acid (KA)-induced status epilepticus and neonatal hypoxia-induced seizure models were used in our study. Animals were subject to inhalation of xenon mixture for 60 min after the stimulation used to induce seizures. The control group was treated with 70% nitrogen/30% oxygen, as in previous reports. Behavioral changes, electroencephalography, neuronal injury, and learning and memory function were investigated in each group. The results indicate that xenon mixture significantly reduced the severity of seizures and neurodegeneration in both KA-induced status epilepticus and in neonatal mice with hypoxia-induced seizure. Moreover, treatment with different percentages of xenon (35%, 50%, or 70%), as well as at different intervention time points (immediately, delayed for 15 min, delayed for 30 min) after hypoxia induction significantly attenuated the severity of seizure and neuronal injury. Additionally, 50% or 70% xenon treatment, as well as immediate xenon treatment or with a delay of 15 min attenuated the learning and memory impairments induced by hypoxia. This study confirmed that xenon mixture exerts strong inhibitive effects in seizure and seizure-induced neuronal injury and defects of cognitive function. Moreover, the results suggest that intervention time window and percentage of xenon influence the efficacy of the xenon treatment. Our study supports that xenon inhalation represents a safe means to inhibit seizures and neuronal injury., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Our previous study found that 5-Aza-2'-deoxycytidine (5-Aza-CdR) can repress the expression and activity of protein serine/threonine phosphatase-1γ (PP1γ) in mouse hippocampus. It is well known that PP1γ regulates cell metabolism, which is related to hypoxia/ischaemia tolerance. It has been reported that it can also induce autophagy in cancer cells. Autophagy is important for maintaining cellular homeostasis associated with metabolism. In this study, we examined whether 5-Aza-CdR increases hypoxia tolerance-dependent autophagy by initiating the TSC1/mTOR/autophagy signalling pathway in neuronal cells., Methods: 5-Aza-CdR was either administered to mice via intracerebroventricular injection (i.c.v) or added to cultured hippocampal-derived neuronal cell line (HT22 cell) in the medium for cell culture. The hypoxia tolerance of mice was measured by hypoxia tolerance time and Perl's iron stain. The mRNA and protein expression levels of tuberous sclerosis complex 1 (TSC1), mammalian target of rapamycin (mTOR) and autophagy marker light chain 3 (LC3) were measured by real-time PCR and western blot. The p-mTOR and p-p70S6k proteins were used as markers for mTOR activity. In addition, the role of autophagy was determined by correlating its intensity with hypoxia tolerance in a time-dependent manner. At the same time, the involvement of the TSC1/mTOR pathway in autophagy was also examined through transfection with TSC1 (hamartin) plasmid., Results: 5-Aza-CdR was revealed to increase hypoxia tolerance and induce autophagy, accompanied by an increase in mRNA and protein expression levels of TSC1, reduction in p-mTOR (Ser2448) and p-p70S6k (Thr389) protein levels, and an increase in the ratio of LC3-II/LC3-I in both mouse hippocampus and hippocampal-derived neuronal cell line (HT22). The fluorescence intensity of hamartin was enhanced in the hippocampus of mice exposed to 5-Aza-CdR. Moreover, HT22 cells that over-expressed TSC1 showed more autophagy., Conclusions: 5-Aza-CdR can increase hypoxia tolerance by inducing autophagy by initiating the TSC1/mTOR pathway., (Copyright © 2019 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

OCT4 is a key regulator in maintaining the pluripotency and self-renewal of embryonic stem cells (ESCs). Human OCT4 gene has three mRNA isoforms, termed OCT4A, OCT4B and OCT4B1. The 190-amino-acid protein isoform (OCT4B-190) is one of the major products of OCT4B mRNA, the biological function of which is still not well defined. Recent evidence suggests that OCT4B-190 may function in the cellular stress response. The glycogen synthase kinase-3β (GSK-3β) and histone deacetylase 6 (HDAC6) are also key stress modulators that play critical roles in the ischemic cascades of stroke. Hence, we here further investigated the effects of OCT4B-190 in the experimental stroke, and explored the underlying roles of GSK-3β and HDAC6. We found that OCT4B-190 overexpression enhanced neuronal viability at 24 h after oxygen-glucose deprivation (OGD) treatment. Moreover, in male C57BL/6 mice subjected to transit middle cerebral artery occlusion (MCAO), OCT4B-190 overexpression reduced infarct volume and improved neurological function after stroke. Notably, we found spatio-temporal alterations of GSK-3β and HDAC6 in the ischemic cortex and striatum, which were affected by adenovirus-mediated OCT4B-190 overexpression. OCT4B-190 demonstrated similar impacts on neuronal cultures in vitro, downregulating OGD-induced GSK-3β activity and HDAC6 expression. In addition, we found that GSK-3β and HDAC6 were co-expressed in the cytoplasm of neurons, and OCT4B-190 had an effect on interactions between GSK-3β and HDAC6 in neuronal cultures subjected to OGD treatment. These findings suggest that OCT4B-190 exerts neuroprotection in the experimental stroke potentially by regulating actions of GSK-3β and HDAC6 simultaneously, which may be an attractive therapeutic strategy for ischemic stroke., (Copyright © 2019. Published by Elsevier Inc.)

Post-conditioning is exposure of an injured organism to the same harmful factors but of milder intensity which mobilizes endogenous protective mechanisms. Recently, we have developed a novel noninvasive post-conditioning (PostC) protocol involving three sequential episodes of mild hypobaric hypoxia which exerts pronounced neuroprotective action. In particular, it prevents development of pathological cascades caused by severe hypobaric hypoxia (SH) such as cellular loss, lipid peroxidation, abnormal neuroendocrine responses and behavioural deficit in experimental animals. Development of these post-hypoxic pathological effects has been associated with the delayed reduction of hypoxia-inducible factor 1 (HIF1) regulatory α-subunit levels in rat hippocampus, whereas PostC up-regulated it. The present study has been aimed at experimental examination of the hypothesis that intrinsic mechanisms underlying the neuroprotective and antioxidant effects of PostC involves HIF1-dependent stimulation of the pentose phosphate pathway (PPP). We have observed that SH leads to a decrease of glucose-6-phosphate dehydrogenase (G6PD) activity in the hippocampus and neocortex of rats as well as to a reduction in NADPH and total glutathione levels. This depletion of the antioxidant defense system together with excessive lipid peroxidation during the reoxygenation phase resulted in increased oxidative stress and massive cellular death observed after SH. In contrast, PostC led to normalization of G6PD activity, stabilization of the NADPH and total glutathione levels and thereby resulted in recovery of the cellular redox state and prevention of neuronal death. Our data suggest that stabilization of the antioxidant system via HIF1-associated PPP regulation represents an important neuroprotective mechanism enabled by PostC.

Microglial cells are now recognized as the "gate-keepers" of healthy brain microenvironment with their disrupted functions adversely affecting neurovascular integrity, neuronal homeostasis, and network connectivity. The perception that these cells are purely toxic under neurodegenerative conditions has been challenged by a continuously increasing understanding of their complexity, the existence of a broad array of microglial phenotypes, and their ability to rapidly change in a context-dependent manner to attenuate or exacerbate injuries of different nature. Recent studies have demonstrated that microglial cells exert crucial physiological functions during embryonic and postnatal brain development, some of these functions being unique to particular stages of development, and extending far beyond sensing dangerous signals and serving as antigen presenting cells. In this focused review we cover the roles of microglial cells in regulating embryonic vasculogenesis, neurogenesis, and establishing network connectivity during postnatal brain development. We further discuss context-dependent microglial contribution to neonatal brain injuries associated with prenatal and postnatal infection and inflammation, in relation to neurodevelopmental disorders, as well as perinatal hypoxia-ischemia and arterial focal stroke. We also emphasize microglial phenotypic diversity, notably at the ultrastructural level, and their sex-dependent influence on the pathophysiology of neurodevelopmental disorders., (Copyright © 2018 IBRO. Published by Elsevier Ltd. All rights reserved.)

Owing to recent medical and technological advances in neonatal care, infants born extremely premature have increased survival rates 1,2 . After birth, these infants are at high risk of hypoxic episodes because of lung immaturity, hypotension and lack of cerebral-flow regulation, and can develop a severe condition called encephalopathy of prematurity 3 . Over 80% of infants born before post-conception week 25 have moderate-to-severe long-term neurodevelopmental impairments 4 . The susceptible cell types in the cerebral cortex and the molecular mechanisms underlying associated gray-matter defects in premature infants remain unknown. Here we used human three-dimensional brain-region-specific organoids to study the effect of oxygen deprivation on corticogenesis. We identified specific defects in intermediate progenitors, a cortical cell type associated with the expansion of the human cerebral cortex, and showed that these are related to the unfolded protein response and changes. Moreover, we verified these findings in human primary cortical tissue and demonstrated that a small-molecule modulator of the unfolded protein response pathway can prevent the reduction in intermediate progenitors following hypoxia. We anticipate that this human cellular platform will be valuable for studying the environmental and genetic factors underlying injury in the developing human brain.

The assessment of the wellbeing of the cardiovascular status in premature infants has come to the forefront in recent years. There is an increasing realisation that myocardial performance, systemic blood flow and end-organ perfusion (particularly during the transitional period) play an important role in determining short and long-term outcomes in this population. The recent open access series on Neonatologist Performed Echocardiography (NPE) published in this journal outline the necessary techniques for image acquisition and analysis and provide a framework for the potential clinical applications of NPE in neonatal, and specifically preterm care. In this "Future Perspectives" review, we describe the important determinants of adequate cellular metabolism and myocardial performance (e.g. loading conditions, intrinsic contractility and morphological change), we discuss the maladaptive state of the preterm cardiovascular system, and highlight the emerging role that non-invasive echocardiography techniques, such as deformation analysis, serve in identifying the underlying physiological basis for cardiovascular instability.

Neonatal anoxia induces long-term brain injury that may underlie neurobehavioral deficits at adolescence. Neonatal anoxia, induced by exposure of 30-hour old pups to 100% nitrogen, represents a non-invasive and global stimulus, which simulates clinical conditions of human pre-term babies (around 6 gestational months). Previous studies showed that neonatal anoxia induced impairments of spatial memory and altered anxiety-like behaviors in male rats tested at adult age. This study evaluated if neonatal anoxia induces similar behavioral effects in female rats, as compared to males, by testing the animals at adolescence, and also searched for possible cell losses in hippocampal subfields. Results in the Elevated Plus Maze test showed that anoxic females spent proportionally more time within the open arms as compared to anoxic males, suggesting a less anxious-like behavior. In the Morris Water Maze Test, latencies and path lengths of the anoxic subjects were longer as compared to control subjects, thus indicating that anoxia disrupted the cognitive functions required for spatial mapping. In addition, results showed that anoxia-induced disruption was greater in male rats as compared to female rats. Stereological analysis revealed that anoxic male rats exhibited significant cell losses in the dorsal hippocampus dentate gyrus and CA1 subfields, but not in CA3-2 subfield. Similar results were observed in the ventral hippocampus, but now with cell loss in the male CA3-2 subfield. There were also significant cell loss differences of anoxic male rats as compared to anoxic female rats. In conclusion, neonatal anoxia induces deleterious and long lasting behavioral and cognitive disruptions, and these effects were stronger in male rats as compared to female rats. These changes are congruent with the pattern of cell losses observed in hippocampal subfields. Together, these results emphasize the relevance of scientific research, aiming at clinical strategies and treatments, consider the sex differential patterns of response to neonatal injury., (Copyright © 2018 ISDN. Published by Elsevier Ltd. All rights reserved.)

Emerging evidence has suggested a significant role of long non-coding RNAs (lncRNAs) in ischemic stroke by acting as competing endogenous RNAs (ceRNAs) for microRNAs (miRNAs) to regulate certain RNA transcripts. AK038897 is an lncRNA that was reported to be upregulated in rat brains in response to transient focal ischemia. We aimed to investigate the possible regulatory role of AK038897 in ischemic stroke. We detected increased AK038897 and decreased miR-26a-5p levels in mouse brains following middle cerebral artery occlusion/reperfusion (MCAO/R) and in neuro-2A (N2a) neuroblastoma cells following oxygen-glucose deprivation and reoxygenation (OGD/R). With bioinformatics, we identified shared putative miR-26a-5p binding sites in AK038897 as well as in the 3'-UTR of death-associated protein kinase 1 (DAPK1), which is a central mediator of ischemic neuronal death. MiR-26a-5p overexpression attenuated OGD/R-induced N2a cell apoptosis. The luciferase reporter assay results confirmed that miR-26a-5p directly targets DAPK1. Further studies showed that AK038897 directly binds to miR-26a-5p and functions as a ceRNA for miR-26a-5p to regulate DAPK1. As a result, AK038897 overexpression antagonized while AK038897 knockdown enhanced the inhibitory effects of miR-26a-5p on DAPK1 expression and OGD/R-induced N2a cell apoptosis. Further, AK038897 knockdown protected against MCAO/R-induced brain injury and neurological deficits in vivo. In summary, we identified a AK038897/miR-26a-5p/DAPK1 signaling cascade as a key mechanism controlling cerebral ischemia/reperfusion injury. Pharmaceutical intervention of this cascade may provide novel therapy for ischemic insults., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The brains of humans and other mammals are highly vulnerable to interruptions in blood flow and decreases in oxygen levels. Here we describe the restoration and maintenance of microcirculation and molecular and cellular functions of the intact pig brain under ex vivo normothermic conditions up to four hours post-mortem. We have developed an extracorporeal pulsatile-perfusion system and a haemoglobin-based, acellular, non-coagulative, echogenic, and cytoprotective perfusate that promotes recovery from anoxia, reduces reperfusion injury, prevents oedema, and metabolically supports the energy requirements of the brain. With this system, we observed preservation of cytoarchitecture; attenuation of cell death; and restoration of vascular dilatory and glial inflammatory responses, spontaneous synaptic activity, and active cerebral metabolism in the absence of global electrocorticographic activity. These findings demonstrate that under appropriate conditions the isolated, intact large mammalian brain possesses an underappreciated capacity for restoration of microcirculation and molecular and cellular activity after a prolonged post-mortem interval.

Background: Survival following cardiac arrest (CA) and subsequent cardiopulmonary resuscitation (CPR), to a great extent, depends on brain damage. Adipose-derived stem cells (ADSCs), as a source of paracrine growth factors and the capacity of neural differentiation may reduce this brain damage., Objective: The purpose of this study is to evaluate the protection of ADSCs to brain damage following CPR., Methods: Rats were divided into 3 groups, sham, CA, and ADSCs group. Rats in sham group went through sham surgery. Rats in CA group went through CA, CPR, and injection PBS (phosphate buffer saline). Rats in ADSCs group went through CA, CPR, and intravenous injection of ADSCs. Rats in sham group were sacrificed immediately after operation. At 24, 72, and 168 hours after return of spontaneous circulation operation, rats in CA and ADSCs group were randomly selected and sacrificed. Brain damage was evaluated by using Neurological Deficit Scale (NDS) score, hippocampal pathology, serum level of S100β, and apoptosis ratio of hippocampal neurons. Protein of brain derived neurotrophic factor (BDNF) and IL-6 (interleukin-6) in the hippocampus were detected., Results: Compared with sham group, CA and ADSCs group showed a decrease in NDS score, an increased apoptosis ratio of hippocampal nerve cells, increased serum level of S100-β, and a significant increase in neuroprotective IL-6 and BDNF. In comparison to CA group, ADSCs group had a mild degree of brain damage and higher expression of IL-6 and BDNF., Conclusions: In the acute stage of cerebral injury following CA, ADSCs might improve the prognosis of brain damage by stimulating the expression of neuroprotective IL-6 and BDNF., (Copyright © 2018 National Stroke Association. Published by Elsevier Inc. All rights reserved.)

Individuals with sleep apnea often exhibit changes in cognitive behaviors consistent with alterations in the hippocampus. It is hypothesized that adult neurogenesis in the dentate gyrus is an ongoing process that maintains normal hippocampal function in many mammalian species, including humans. However, the impact of chronic intermittent hypoxia (IH), a principal consequence of sleep apnea, on hippocampal adult neurogenesis remains unclear. Using a murine model, we examined the impact of 30 d of IH (IH 30 ) on adult neurogenesis and synaptic plasticity in the dentate gyrus. Although IH 30 did not affect paired-pulse facilitation, IH 30 suppressed long-term potentiation (LTP). Immunohistochemical experiments also indicate that IH perturbs multiple aspects of adult neurogenesis. IH 30 increased the number of proliferating Sox2 + neural progenitor cells in the subgranular zone yet reduced the number of doublecortin-positive neurons. Consistent with these findings, cell lineage tracing revealed that IH 30 increased the proportion of radial glial cells in the subgranular zone, yet decreased the proportion of adult-born neurons in the dentate gyrus. While administration of a superoxide anion scavenger during IH did not prevent neural progenitor cell proliferation, it mitigated the IH-dependent suppression of LTP and prevented adult-born neuron loss. These data demonstrate that IH causes both reactive oxygen species-dependent and reactive oxygen species-independent effects on adult neurogenesis and synaptic plasticity in the dentate gyrus. Our findings identify cellular and neurophysiological changes in the hippocampus that may contribute to cognitive and behavioral deficits occurring in sleep apnea. SIGNIFICANCE STATEMENT Individuals with sleep apnea experience periods of intermittent hypoxia (IH) that can negatively impact many aspects of brain function. Neurons are continually generated throughout adulthood to support hippocampal physiology and behavior. This study demonstrates that IH exposure attenuates hippocampal long-term potentiation and reduces adult neurogenesis. Antioxidant treatment mitigates these effects indicating that oxidative signaling caused by IH is a significant factor that impairs synaptic plasticity and reduces adult neurogenesis in the hippocampus., (Copyright © 2019 the authors 0270-6474/19/391320-12$15.00/0.)

Background and Aims: Inhibition of the mechanistic target of rapamycin (mTOR) is a promising approach to halt atherogenesis in different animal models. This study evaluated whether the mTOR inhibitor everolimus can stabilize pre-existing plaques, prevent cardiovascular complications and improve survival in a mouse model of advanced atherosclerosis., Methods: ApoE -/- Fbn1 C1039G+/- mice (n = 24) were fed a Western diet (WD) for 12 weeks. Subsequently, mice were treated with everolimus (1.5 mg/kg daily) or vehicle for another 12 weeks while the WD continued., Results: Despite hypercholesterolemia, everolimus treatment was associated with a reduction in circulating Ly6C high monocytes (15 vs. 28% of total leukocytes, p = 0.046), a depletion of plaque macrophages (2.1 vs. 4.1%, p = 0.040) and an abolishment of intraplaque neovascularization, which are all indicative of a more stable plaque phenotype. Moreover, everolimus reduced hypoxic brain damage and improved cardiac function, which led to increased survival (100 vs. 67% of animals, p = 0.038)., Conclusions: Everolimus enhances features of plaque stability and counters cardiovascular complications in ApoE -/- Fbn1 C1039G+/- mice, even when administered at a later stage of the disease., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Primary blast traumatic brain injury (bTBI) accounts for a significant proportion of wartime trauma. Previous studies have demonstrated direct brain injury by blast waves, but the effect of the location of the blast epicenter on the skull with regard to brain injury remains poorly characterized. In order to investigate the role of the blast epicenter location, we modified a previously established rodent model of cranium-only bTBI to evaluate two specific blast foci: a rostrally focused blast centered on bregma (B-bTBI), which excluded the foramen magnum region, and a caudally focused blast centered on the occipital crest, which included the foramen magnum region (FM-bTBI). At all blast overpressures studied (668-1880 kPa), rats subjected to FM-bTBI demonstrated strikingly higher mortality, increased durations of both apnea and hypoxia, and increased severity of convexity subdural hematomas, than rats subjected to B-bTBI. Together, these data suggest a unique role for the foramen magnum region in mortality and brain injury following blast exposure, and emphasize the importance of the choice of blast focus location in experimental models of bTBI.

Chronic hypoxic stress results in deposition of lipofuscin granules in the CA3 region of hippocampal neurons which contributes to neurodegeneration and accelerated neuronal aging. Oxidative stress and mitophagy during hypoxia are crucial to cause aggregation of these lipofuscin granules in hypoxic neurons. Salidroside, a glucoside derivative of β-Tyrosol, has been reported to protect hypoxic neurons through maintenance of mitochondrial activity. The present study is aimed at investigating the potential of Salidroside in preventing mitophagy during chronic hypoxia and identification of the molecular targets and underlying signaling mechanisms. In-silico analysis for interaction of salidroside with Bcl-x L was carried out using VLife MDS software. The prophylactic efficacy of Salidroside for amelioration of global hypoxia induced neuronal aging was studied in adult male Sprague-Dawley rats exposed to hypobaric hypoxia simulating an altitude of 7600 m for 21 days. Salidroside was supplemented at a daily dose of 25 mg kg -1 b.w. p.o. during hypoxic exposure. Ultra-structural and immune-histological studies were conducted to study lipofuscin aggregation and mitophagy. In-silico findings on salidroside mediated stabilization of Bcl-x L were validated by investigating its effect on downstream signaling molecules involved in mitophagy. Administration of Salidroside reduced deposition of lipofuscin in hypoxic CA3 hippocampal neurons and prevented mitophagy. Salidroside stabilizes Bcl-x L in hypoxic neurons resulting in inhibition of PGAM5 phosphatase activity and maintenance of FUNDC1 in phosphorylated state. Salidroside mediated inhibition of pFUNDC1 dephosphorylation prevents FUNDC1-LC3 II interaction which is crucial for mitophagy. The present study demonstrates potential of Salidroside in preventing lipofuscin deposition during chronic hypoxic stress., (Copyright © 2018. Published by Elsevier Inc.)

Objective: According to our previous studies, ghrelin protects blood brain barrier (BBB) integrity and it attenuates hypoxia-induced brain edema in the hypoxic conditions. However, the underlying mechanisms remain poorly understood. Several studies suggest a role for matrix metal-loproteinase-9 (MMP9) in the BBB disruption and cerebral edema formation. The present study was conducted to determine the effect of ghrelin on MMP9 protein expression in the model of acute and chronic systemic hypoxia., Methods: Adult male Wistar rats were divided into acute or chronic controls, acute or chronic hypoxia and ghrelin-treated acute or chronic hypoxia groups. The hypoxic groups were kept in the hypoxic chamber (10-11% O2) for two (acute) or ten days (chronic). Effect of ghrelin on MMP9 protein expression was assessed using immunoblotting., Results: Our results showed that acute and chronic systemic hypoxia increased the MMP9 protein expression in the brain (p<0.001). Treatment with ghrelin significantly attenuated this expression in the cerebral hypoxia (p<0.05)., Conclusion: Our results demonstrate that the neuroprotective effects of ghrelin may be mediated, in part, by decreasing in MMP9 production in the hypoxic brain.

A significant proportion of children that survive hypoxic-ischemic encephalopathy (HIE) develop visual impairment. These visual deficits are generally attributed to injuries that occur in the primary visual cortex and other visual processing systems. Recent studies suggested that neuronal damage might also occur in the retina. An important structure affecting the viability of retinal neurons is the vasculature. However, the effects of HIE on the retinal neurovasculature have not been systemically evaluated. Here we investigated whether exposure of postnatal day 9 (P9) neonatal mice to HIE is sufficient to induce neurovascular damage in the retina. We demonstrate that the blood vessels on the surface of the retina, from mice subjected to HIE, were abnormally enlarged with signs of degeneration. The intermediate and deep vascular layers in these retinas failed to form normally, particularly in the periphery. All the vascular damages observed here were irreversible in nature up to 100 days post HIE. We also observed loss of retinal neurons, together with changes in both astrocytes and Müller cells mainly in the inner retina at the periphery. Collectively, our findings suggest that HIE results in profound alterations in the retinal vasculature, indicating the importance of developing therapeutic strategies to protect neurovascular dysfunction not only in the brain but also in the retina for infants exposed to HIE.

Hypoxia-ischaemia (HI) remains a major cause of foetal brain damage presented a scarcity of effective therapeutic approaches. Dexmedetomidine (DEX) and microRNA-140-5p (miR-140-5p) have been highlighted due to its potentially significant role in the treatment of cerebral ischaemia. This study was to investigate the role by which miR-140-5p provides cerebral protection using DEX to treat hypoxic-ischaemic brain damage (HIBD) in neonatal rats via the Wnt/β-catenin signalling pathway. The HIBD rat models were established and allocated into various groups with different treatment plans, and eight SD rats into sham group. The learning and memory ability of the rats was assessed. Apoptosis and pathological changes in the hippocampus CA1 region and expressions of the related genes of the Wnt/β-catenin signalling pathway as well as the genes responsible of apoptosis were detected. Compared with the sham group, the parameters of weight, length growth, weight ratio between hemispheres, the rate of reaching standard, as well as Bcl-2 expressions, were all increased. Furthermore, observations of increased levels of cerebral infarction volume, total mortality rate, response times, total response duration, expressions of Wnt1, β-catenin, TCF-4, E-cadherin, apoptosis rate of neurons, and Bax expression were elevated. Following DEX treatment, the symptoms exhibited by HIBD rats were ameliorated. miR-140-5p and si-Wnt1 were noted to attenuate the progression of HIBD. Our study demonstrates that miR-140-5p promotes the cerebral protective effects of DEX against HIBD in neonatal rats by targeting the Wnt1 gene through via the negative regulation of the Wnt/β-catenin signalling pathway., (© 2018 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.)