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Background: The noble gases argon and xenon are potential novel neuroprotective treatments for acquired brain injuries. Xenon has already undergone early-stage clinical trials in the treatment of ischaemic brain injuries, with mixed results. Argon has yet to progress to clinical trials as a treatment for brain injury. Here, we aim to synthesise the results of preclinical studies evaluating argon and xenon as neuroprotective therapies for brain injuries.Methods: After a systematic review of the MEDLINE and Embase databases, we carried out a pairwise and stratified meta-analysis. Heterogeneity was examined by subgroup analysis, funnel plot asymmetry, and Egger's regression.Results: A total of 32 studies were identified, 14 for argon and 18 for xenon, involving measurements from 1384 animals, including murine, rat, and porcine models. Brain injury models included ischaemic brain injury after cardiac arrest (CA), neurological injury after cardiopulmonary bypass (CPB), traumatic brain injury (TBI), and ischaemic stroke. Both argon and xenon had significant (P<0.001), positive neuroprotective effect sizes. The overall effect size for argon (CA, TBI, stroke) was 18.1% (95% confidence interval [CI], 8.1-28.1%), and for xenon (CA, TBI, stroke) was 34.1% (95% CI, 24.7-43.6%). Including the CPB model, only present for xenon, the xenon effect size (CPB, CA, TBI, stroke) was 27.4% (95% CI, 11.5-43.3%). Xenon, both with and without the CPB model, was significantly (P<0.001) more protective than argon.Conclusions: These findings provide evidence to support the use of xenon and argon as neuroprotective treatments for acquired brain injuries. Current evidence suggests that xenon is more efficacious than argon overall. [ABSTRACT FROM AUTHOR]

Abstract There is an ongoing discussion whether hyperoxia, i.e. ventilation with high inspiratory O2 concentrations (FIO2), and the consecutive hyperoxaemia, i.e. supraphysiological arterial O2 tensions (PaO2), have a place during the acute management of circulatory shock. This concept is based on experimental evidence that hyperoxaemia may contribute to the compensation of the imbalance between O2 supply and requirements. However, despite still being common practice, its use is limited due to possible oxygen toxicity resulting from the increased formation of reactive oxygen species (ROS) limits, especially under conditions of ischaemia/reperfusion. Several studies have reported that there is a U-shaped relation between PaO2 and mortality/morbidity in ICU patients. Interestingly, these mostly retrospective studies found that the lowest mortality coincided with PaO2 ~ 150 mmHg during the first 24 h of ICU stay, i.e. supraphysiological PaO2 levels. Most of the recent large-scale retrospective analyses studied general ICU populations, but there are major differences according to the underlying pathology studied as well as whether medical or surgical patients are concerned. Therefore, as far as possible from the data reported, we focus on the need of mechanical ventilation as well as the distinction between the absence or presence of circulatory shock. There seems to be no ideal target PaO2 except for avoiding prolonged exposure (> 24 h) to either hypoxaemia (PaO2 100 mmHg). Moreover, the need for mechanical ventilation, absence or presence of circulatory shock and/or the aetiology of tissue dysoxia, i.e. whether it is mainly due to impaired macro- and/or microcirculatory O2 transport and/or disturbed cellular O2 utilization, may determine whether any degree of hyperoxaemia causes deleterious side effects.

Context Selenium-containing protein from selenium-enriched Spirulina platensis (Se-SP) (syn. Arthrospira platensis [Microcoleaceae]) showed novel antioxidant activity. However, the protective effect of Se-SP against oxygen glucose deprivation (OGD)-induced neural apoptosis has not been reported yet. Objective To verify whether Se-SP can inhibit OGD-induced neural apoptosis and explore the underlying mechanism. Materials and methods Primary hippocampal neurons were separated from Sprague–Dawley (SD) rats. 95% N2 + 5% CO2 were employed to establish OGD model. Neurons were treated with 5 and 10 µg/mL Se-SP under OGD condition for 6 h. Neurons without treatment were the control group. Neural viability and apoptosis were detected by MTT, immunofluorescence and western blotting methods. Results Se-SP significantly improved neuronal viability (from 57.2% to 94.5%) and inhibited apoptosis in OGD-treated primary neurons (from 45.6% to 6.3%), followed by improved neuronal morphology and caspases activation. Se-SP co-treatment also effectively suppressed OGD-induced DNA damage by inhibiting ROS accumulation in neurons (from 225.6% to 106.3%). Additionally, mitochondrial dysfunction was also markedly improved by Se-SP co-treatment via balancing Bcl-2 family expression. Moreover, inhibition of mitochondrial permeability transition pore (MPTP) by CsA (an MPTP inhibitor) dramatically attenuated OGD-induced ROS generation (from 100% to 56.2%), oxidative damage, mitochondrial membrane potential (MPP) loss (from 7.5% to 44.3%), and eventually reversed the neuronal toxicity and apoptosis (from 57.4% to 79.6%). Discussion and conclusions Se-SP showed enhanced potential to inhibit OGD-induced neurotoxicity and apoptosis by inhibiting ROS-mediated oxidative damage through regulating MPTP opening, indicating that selenium-containing protein showed broad application in the chemoprevention and chemotherapy against human ischaemic brain injury.

Abstract The PI3 K/AKT/mTOR signalling pathway plays an important role in the regulation of signal transduction and biological processes such as cell proliferation, apoptosis, metabolism and angiogenesis. Compared with those of other signalling pathways, the components of the PI3K/AKT/mTOR signalling pathway are complicated. The regulatory mechanisms and biological functions of the PI3K/AKT/mTOR signalling pathway are important in many human diseases, including ischaemic brain injury, neurodegenerative diseases, and tumours. PI3K/AKT/mTOR signalling pathway inhibitors include single-component and dual inhibitors. Numerous PI3K inhibitors have exhibited good results in preclinical studies, and some have been clinically tested in haematologic malignancies and solid tumours. In this review, we briefly summarize the results of research on the PI3K/AKT/mTOR pathway and discuss the structural composition, activation, communication processes, regulatory mechanisms and biological functions of the PI3K/AKT/mTOR signalling pathway in the pathogenesis of neurodegenerative diseases and tumours.

Selenium-containing protein from selenium-enriched Spirulina platensis (Se-SP) (syn. Arthrospira platensis [Microcoleaceae]) showed novel antioxidant activity. However, the protective effect of Se-SP against oxygen glucose deprivation (OGD)-induced neural apoptosis has not been reported yet. To verify whether Se-SP can inhibit OGD-induced neural apoptosis and explore the underlying mechanism. Primary hippocampal neurons were separated from Sprague–Dawley (SD) rats. 95% N2 + 5% CO2 were employed to establish OGD model. Neurons were treated with 5 and 10 µg/mL Se-SP under OGD condition for 6 h. Neurons without treatment were the control group. Neural viability and apoptosis were detected by MTT, immunofluorescence and western blotting methods. Se-SP significantly improved neuronal viability (from 57.2% to 94.5%) and inhibited apoptosis in OGD-treated primary neurons (from 45.6% to 6.3%), followed by improved neuronal morphology and caspases activation. Se-SP co-treatment also effectively suppressed OGD-induced DNA damage by inhibiting ROS accumulation in neurons (from 225.6% to 106.3%). Additionally, mitochondrial dysfunction was also markedly improved by Se-SP co-treatment via balancing Bcl-2 family expression. Moreover, inhibition of mitochondrial permeability transition pore (MPTP) by CsA (an MPTP inhibitor) dramatically attenuated OGD-induced ROS generation (from 100% to 56.2%), oxidative damage, mitochondrial membrane potential (MPP) loss (from 7.5% to 44.3%), and eventually reversed the neuronal toxicity and apoptosis (from 57.4% to 79.6%). Se-SP showed enhanced potential to inhibit OGD-induced neurotoxicity and apoptosis by inhibiting ROS-mediated oxidative damage through regulating MPTP opening, indicating that selenium-containing protein showed broad application in the chemoprevention and chemotherapy against human ischaemic brain injury. [ABSTRACT FROM AUTHOR]

There is an ongoing discussion whether hyperoxia, i.e. ventilation with high inspiratory O2 concentrations (FIO2), and the consecutive hyperoxaemia, i.e. supraphysiological arterial O2 tensions (PaO2), have a place during the acute management of circulatory shock. This concept is based on experimental evidence that hyperoxaemia may contribute to the compensation of the imbalance between O2 supply and requirements. However, despite still being common practice, its use is limited due to possible oxygen toxicity resulting from the increased formation of reactive oxygen species (ROS) limits, especially under conditions of ischaemia/reperfusion. Several studies have reported that there is a U-shaped relation between PaO2 and mortality/morbidity in ICU patients. Interestingly, these mostly retrospective studies found that the lowest mortality coincided with PaO2 ~ 150 mmHg during the first 24 h of ICU stay, i.e. supraphysiological PaO2 levels. Most of the recent large-scale retrospective analyses studied general ICU populations, but there are major differences according to the underlying pathology studied as well as whether medical or surgical patients are concerned. Therefore, as far as possible from the data reported, we focus on the need of mechanical ventilation as well as the distinction between the absence or presence of circulatory shock. There seems to be no ideal target PaO2 except for avoiding prolonged exposure (> 24 h) to either hypoxaemia (PaO2 < 55–60 mmHg) or supraphysiological (PaO2 > 100 mmHg). Moreover, the need for mechanical ventilation, absence or presence of circulatory shock and/or the aetiology of tissue dysoxia, i.e. whether it is mainly due to impaired macro- and/or microcirculatory O2 transport and/or disturbed cellular O2 utilization, may determine whether any degree of hyperoxaemia causes deleterious side effects. [ABSTRACT FROM AUTHOR]

• EA treatment reduces infarct damage and cell apoptosis following MCAO. • MiR-34 mediates the Wnt pathway involved in the effect of EA on improving cerebral ischaemia injury by targeting Wnt1. • EA improves ischaemic brain injury by regulating the miRNA-34/Wnt/autophagy axis. Electroacupuncture (EA), a modern form of acupuncture therapy, has been widely used for the treatment of ischaemic brain injury. However, the molecular mechanism by which EA improves ischaemic brain injury remains unclear. In the current study, middle cerebral artery occlusion (MCAO) rats were treated with EA. The infarct volumes and apoptosis of neurocytes were assessed to determine the therapeutic effect of EA. The differentially expressed miRNAs between the control, MCAO and MCAO treated with EA groups were detected by high-throughput sequencing. The results indicated that EA treatment decreased neurocyte apoptosis and ischaemic infarct volume. Between the three groups, miR-34, miR-235 and miR-275 were found to be significantly different. Furthermore, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway data suggest that the Wnt pathway may play an important role in ischaemic brain injury and in the treatment of EA. Our data documented that miR-34 was obviously increased in the MCAO group, while EA treatment decreased miR-34 expression. WNT1 was the target of miR-34 and was confirmed by a luciferase reporter assay. A previous study suggested that the Wnt pathway mediates autophagy in EA-pretreated MCAO mice. Our data further confirmed that EA treatment after MCAO also alleviated autophagy in the MCAO group. Our results suggest that EA treatment alleviates ischaemic brain injury by inhibiting autophagy through the miR-34/Wnt pathway. [ABSTRACT FROM AUTHOR]

• LncRNA Gas5 is highly expressed during ischemic brain injury, but miR-21 is reciprocal. • LncRNA Gas5 upregulates PTEN by competitively binding to miR-21. • Downregulation of lncRNA Gas5 inhibits neuronal apoptosis. • Down-regulated lncRNA Gas5 activates the PI3K/Akt signaling pathway. • LncRNA Gas5 could be a potential target for ischemic brain injury. Brain ischaemia, which can cause severe nerve injury, is a global health challenge. Long non-coding RNA (lncRNA) growth-arrest specific 5 (Gas5) has been documented to exert tumour suppressive effects in several cancers. However, its role in cerebrovascular disease still requires further investigation. Therefore, in this study, we focused on the role of lncRNA regulatory signalling related to lncRNA Gas5 in ischaemic brain injury. Middle cerebral artery occlusion (MCAO) was employed as a model of ischaemic brain injury in rats. The expression of lncRNA Gas5 and microRNA-21 (miR-21) was altered in neurons to elucidate their effects in ischaemic brain injury and to identify the interactions among lncRNA Gas5, miR-21 and Pten. The neuronal survival rate, apoptosis and the expression of phosphatidyl inositol 3-kinase (PI3K)/Akt signalling pathway-related genes were also evaluated in vitro to determine the effects of lncRNA Gas5. In the brains of rats subjected to MCAO, the expression of lncRNA Gas5 and Pten was upregulated, while miR-21 was downregulated. LncRNA Gas5 inhibited miR-21 expression, leading to elevated levels of Pten. In vitro experiments revealed that lncRNA Gas5 depletion and miR-21 elevation resulted in the suppression of neuronal apoptosis, thus promoting neuronal survival via the PI3K/Akt signalling pathway. These findings demonstrate that lncRNA Gas5 increases miR-21 and activates Pten, contributing to the development of ischaemic brain injury, supporting the silencing of lncRNA Gas5 as a possible therapeutic target for the treatment of ischaemic brain injury. [ABSTRACT FROM AUTHOR]

The PI3 K/AKT/mTOR signalling pathway plays an important role in the regulation of signal transduction and biological processes such as cell proliferation, apoptosis, metabolism and angiogenesis. Compared with those of other signalling pathways, the components of the PI3K/AKT/mTOR signalling pathway are complicated. The regulatory mechanisms and biological functions of the PI3K/AKT/mTOR signalling pathway are important in many human diseases, including ischaemic brain injury, neurodegenerative diseases, and tumours. PI3K/AKT/mTOR signalling pathway inhibitors include single-component and dual inhibitors. Numerous PI3K inhibitors have exhibited good results in preclinical studies, and some have been clinically tested in haematologic malignancies and solid tumours. In this review, we briefly summarize the results of research on the PI3K/AKT/mTOR pathway and discuss the structural composition, activation, communication processes, regulatory mechanisms and biological functions of the PI3K/AKT/mTOR signalling pathway in the pathogenesis of neurodegenerative diseases and tumours. [ABSTRACT FROM AUTHOR]

It is generally accepted that the cerebellum is particularly vulnerable to ischaemic injury, and this may contribute to the high mortality arising from posterior circulation strokes. However, this has not been systematically examined in an animal model. This study compared the development and resolution of matched photothrombotic microvascular infarcts in the cerebellar and cerebral cortices in adult 129/SvEv mice of both sexes. The photothrombotic lesions were made using tail vein injection of Rose Bengal with a 532 nm laser projected onto a 2 mm diameter aperture over the target region of the brain (with skull thinning). Infarct size was then imaged histologically following 2 h to 30-day survival using serial reconstruction of haematoxylin and eosin stained cryosections. This was complemented with immunohistochemistry for neuron and glial markers. At 2 h post-injury, the cerebellar infarct volume averaged ~ 2.7 times that of the cerebral cortex infarcts. Infarct volume reached maximum in the cerebellum in a quarter of the time (24 h) taken in the cerebral cortex (4 days). Remodelling resolved the infarcts within a month, leaving significantly larger residual injury volume in the cerebellum. The death of neurons in the core lesion at 2 h was confirmed by NeuN and Calbindin immunofluorescence, alongside activation of astrocytes and microglia. The latter persisted in the region within and surrounding the residual infarct at 30 days. This comparison of acute focal ischaemic injuries in cerebellar and cerebral cortices provides direct confirmation of exacerbation of neuropathology and faster kinetics in the cerebellum. [ABSTRACT FROM AUTHOR]

Spreading depolarizations occur spontaneously and frequently in injured human brain. They propagate slowly through injured tissue often cycling around a local area of damage. Tissue recovery after an spreading depolarization requires greatly augmented energy utilisation to normalise ionic gradients from a virtually complete loss of membrane potential. In the injured brain, this is difficult because local blood flow is often low and unreactive. In this study, we use a new variant of microdialysis, continuous on-line microdialysis, to observe the effects of spreading depolarizations on brain metabolism. The neurochemical changes are dynamic and take place on the timescale of the passage of an spreading depolarization past the microdialysis probe. Dialysate potassium levels provide an ionic correlate of cellular depolarization and show a clear transient increase. Dialysate glucose levels reflect a balance between local tissue glucose supply and utilisation. These show a clear transient decrease of variable magnitude and duration. Dialysate lactate levels indicate non-oxidative metabolism of glucose and show a transient increase. Preliminary data suggest that the transient changes recover more slowly after the passage of a sequence of multiple spreading depolarizations giving rise to a decrease in basal dialysate glucose and an increase in basal dialysate potassium and lactate levels. [ABSTRACT FROM AUTHOR]

Backgrounds: Increase in SP release as a function of hypoxia of the rat carotid body is a tissue response to ischemia that leads to neurogenic inflammation and cognitive deficits. Substance P-mediated inflammation is reported to attenuate the neuroprotective PPAR-γ. This study was undertaken to investigate the effect of aprepitant, a substance P-NK1 receptor antagonist in bilateral carotid artery occlusion (BCCAO)-induced ischaemic brain injury and vascular dementia. Methods: Bilateral carotid artery occlusion was performed in Wistar rats to produce hypoperfusion and ischaemic injury. Dementia was noted by an increase in brain acetylcholinesterase (AChE) activity, and attenuation of learning ability (escape latency time) and memory retention (time spent in target quadrant) using Morris water maze. Oxidative stress was estimated by an increase in thiobarbituric acid reactive substances (TBARS) level and a decrease in reduced glutathione level. Vascular dysfunction was measured by attenuation of acetylcholine-induced endothelium-dependent relaxation (isolated carotid ring preparation), and increased in carotid artery TBARS level. Neurodegeneration was assessed in the hippocampus by H&E staining. Aprepitant and donepezil (positive control) were administered to rats from day 28 to day 42 after BCCAO. Results: Aprepitant (20 and 40 mg/kg) and donepezil (2 mg/kg) significantly improved vascular function, learning and memory ability, and decreases the neuronal cell death, oxidative stress, and ache in BCCAO rats. Donepezil effect was more significant than the low dose of aprepitant on disease markers. However, BADGE (30 mg/kg a, PPAR-γ antagonist) prevented the ameliorative effect of aprepitant. Conclusion: Thus, it may be concluded that aprepitant attenuates vascular dysfunction and dementia in BCCAO rats by activating downstream PPAR-γ. [ABSTRACT FROM AUTHOR]

Much of our knowledge of functional brain anatomy is based on lesion-deficit studies. Mah et al. show that the established methodology for conducting these — voxel-wise mass univariate inference — mislocalises function owing to complex correlations in natural patterns of damage across the brain; a problem soluble only by high-dimensional multivariate inference.Our knowledge of the anatomical organization of the human brain in health and disease draws heavily on the study of patients with focal brain lesions. Historically the first method of mapping brain function, it is still potentially the most powerful, establishing the necessity of any putative neural substrate for a given function or deficit. Great inferential power, however, carries a crucial vulnerability: without stronger alternatives any consistent error cannot be easily detected. A hitherto unexamined source of such error is the structure of the high-dimensional distribution of patterns of focal damage, especially in ischaemic injury—the commonest aetiology in lesion-deficit studies—where the anatomy is naturally shaped by the architecture of the vascular tree. This distribution is so complex that analysis of lesion data sets of conventional size cannot illuminate its structure, leaving us in the dark about the presence or absence of such error. To examine this crucial question we assembled the largest known set of focal brain lesions (n = 581), derived from unselected patients with acute ischaemic injury (mean age = 62.3 years, standard deviation = 17.8, male:female ratio = 0.547), visualized with diffusion-weighted magnetic resonance imaging, and processed with validated automated lesion segmentation routines. High-dimensional analysis of this data revealed a hidden bias within the multivariate patterns of damage that will consistently distort lesion-deficit maps, displacing inferred critical regions from their true locations, in a manner opaque to replication. Quantifying the size of this mislocalization demonstrates that past lesion-deficit relationships estimated with conventional inferential methodology are likely to be significantly displaced, by a magnitude dependent on the unknown underlying lesion-deficit relationship itself. Past studies therefore cannot be retrospectively corrected, except by new knowledge that would render them redundant. Positively, we show that novel machine learning techniques employing high-dimensional inference can nonetheless accurately converge on the true locus. We conclude that current inferences about human brain function and deficits based on lesion mapping must be re-evaluated with methodology that adequately captures the high-dimensional structure of lesion data. [ABSTRACT FROM PUBLISHER]

Summary. Objectives: To look for evidence of early ischaemic neurochemical changes in patients suffering severe traumatic brain injury (TBI) and severe subarachnoid haemorrhage (SAH). Proton metabolite concentrations were measured in normal and abnormal areas of brain on T2 MR imaging, in regions considered particularly vulnerable to ischaemic injury. Methods: Intensive care patients underwent T2 weighted imaging in a 1.5 Tesla MR scanner and proton magnetic resonance spectroscopy (single voxel or chemical shift imaging). Metabolite values in areas that appeared `normal' and `abnormal' on T2 MR imaging were compared with those obtained from normal controls. Results: 18 TBI and 6 SAH patients were imaged at 1 to 26 days. N-acetyl aspartate (NAA) was lower in TBI and SAH patients compared to controls in both T2 normal and T2 abnormal areas (p<0.0005). SAH, but not TBI patients also had increased choline and creatine compared to controls in the T2 normal (p<0.02, p<0.02 respectively) and T2 abnormal (p=0.0003, p=0.003) areas. No lactate was found in TBI or SAH patients. Conclusions: Significant loss of normal functioning neurones was present in TBI and SAH, but no evidence of anaerobic metabolism using lactate as a surrogate marker, questioning the role of `ischemia' as a major mechanism of damage. Increased choline and creatine were found in SAH patients suggestive of increased cell-wall turnover. Current theories of brain injury after TBI or SAH do not explain these observed neurochemical changes and further research is required. [ABSTRACT FROM AUTHOR]