Protection by Neuroglobin Expression in Brain Pathologies

Cellular iron deposition patterns predict clinical subtypes of multiple system atrophy

BACKGROUND

Multiple system atrophy (MSA) is a primary oligodendroglial synucleinopathy, characterized by elevated iron burden in early-affected subcortical nuclei. Although neurotoxic effects of brain iron deposition and its relationship with α-synuclein pathology have been demonstrated, the exact role of iron dysregulation in MSA pathogenesis is unknown. Therefore, advancing the understanding of iron dysregulation at the cellular level is critical, especially in relation to α-synuclein cytopathology.

METHODS

Iron burden in subcortical and brainstem regions were histologically mapped in human post-mortem brains of 4 MSA-parkinsonian (MSA-P), 4 MSA-cerebellar (MSA-C), and 1 MSA case with both parkinsonian and cerebellar features. We then performed the first cell type-specific evaluation of pathological iron deposition in α-synuclein-affected and -unaffected cells of the globus pallidus, putamen, and the substantia nigra, regions of highest iron concentration, using a combination of iron staining with immunolabelling. Selective regional and cellular vulnerability patterns of iron deposition were compared between disease subtypes. In 7 MSA cases, expression of key iron- and closely related oxygen-homeostatic genes were examined.

RESULTS

MSA-P and MSA-C showed different patterns of regional iron burden across the pathology-related systems. We identified subcortical microglia to predominantly accumulate iron, which was more distinct in MSA-P. MSA-C showed relatively heterogenous iron accumulation, with greater or similar deposition in astroglia. Iron deposition was also found outside cellular bodies. Cellular iron burden associated with oligodendrocytic, and not neuronal, α-synuclein cytopathology. Gene expression analysis revealed dysregulation of oxygen homeostatic genes, rather than of cellular iron. Importantly, hierarchal cluster analysis revealed the pattern of cellular vulnerability to iron accumulation, distinctly to α-synuclein pathology load in the subtype-related systems, to distinguish MSA subtypes.

CONCLUSIONS

Our comprehensive evaluation of iron deposition in MSA brains identified distinct regional, and for the first time, cellular distribution of iron deposition in MSA-P and MSA-C and revealed cellular vulnerability patterns to iron deposition as a novel neuropathological characteristic that predicts MSA clinical subtypes. Our findings suggest distinct iron-related pathomechanisms in MSA clinical subtypes that are therefore not a consequence of a uniform down-stream pathway to α-synuclein pathology, and inform current efforts in iron chelation therapies at the disease and cellular-specific levels.

Post-stroke cognitive impairment: exploring molecular mechanisms and omics biomarkers for early identification and intervention

Post-stroke cognitive impairment (PSCI) is a major stroke consequence that has a severe impact on patients' quality of life and survival rate. For this reason, it is especially crucial to identify and intervene early in high-risk groups during the acute phase of stroke. Currently, there are no reliable and efficient techniques for the early diagnosis, appropriate evaluation, or prognostication of PSCI. Instead, plenty of biomarkers in stroke patients have progressively been linked to cognitive impairment in recent years. High-throughput omics techniques that generate large amounts of data and process it to a high quality have been used to screen and identify biomarkers of PSCI in order to investigate the molecular mechanisms of the disease. These techniques include metabolomics, which explores dynamic changes in the organism, gut microbiomics, which studies host-microbe interactions, genomics, which elucidates deeper disease mechanisms, transcriptomics and proteomics, which describe gene expression and regulation. We looked through electronic databases like PubMed, the Cochrane Library, Embase, Web of Science, and common databases for each omics to find biomarkers that might be connected to the pathophysiology of PSCI. As all, we found 34 studies: 14 in the field of metabolomics, 5 in the field of gut microbiomics, 5 in the field of genomics, 4 in the field of transcriptomics, and 7 in the field of proteomics. We discovered that neuroinflammation, oxidative stress, and atherosclerosis may be the primary causes of PSCI development, and that metabolomics may play a role in the molecular mechanisms of PSCI. In this study, we summarized the existing issues across omics technologies and discuss the latest discoveries of PSCI biomarkers in the context of omics, with the goal of investigating the molecular causes of post-stroke cognitive impairment. We also discuss the potential therapeutic utility of omics platforms for PSCI mechanisms, diagnosis, and intervention in order to promote the area's advancement towards precision PSCI treatment.

Repurposing of Tibolone in Alzheimer's Disease

Alzheimer's disease (AD) is a debilitating neurodegenerative disease characterised by the accumulation of amyloid-beta and tau in the brain, leading to the progressive loss of memory and cognition. The causes of its pathogenesis are still not fully understood, but some risk factors, such as age, genetics, and hormones, may play a crucial role. Studies show that postmenopausal women have a higher risk of developing AD, possibly due to the decrease in hormone levels, especially oestrogen, which may be directly related to a reduction in the activity of oestrogen receptors, especially beta (ERβ), which favours a more hostile cellular environment, leading to mitochondrial dysfunction, mainly affecting key processes related to transport, metabolism, and oxidative phosphorylation. Given the influence of hormones on biological processes at the mitochondrial level, hormone therapies are of clinical interest to reduce the risk or delay the onset of symptoms associated with AD. One drug with such potential is tibolone, which is used in clinics to treat menopause-related symptoms. It can reduce amyloid burden and have benefits on mitochondrial integrity and dynamics. Many of its protective effects are mediated through steroid receptors and may also be related to neuroglobin, whose elevated levels have been shown to protect against neurological diseases. Its importance has increased exponentially due to its implication in the pathogenesis of AD. In this review, we discuss recent advances in tibolone, focusing on its mitochondrial-protective effects, and highlight how valuable this compound could be as a therapeutic alternative to mitigate the molecular pathways characteristic of AD.

Intravitreal Neuroglobin Mitigates Primate Experimental Glaucomatous Structural Damage in Association with Reduced Optic Nerve Microglial and Complement 3-Astrocyte Activation

Current management of glaucomatous optic neuropathy is limited to intraocular pressure control. Neuroglobin (Ngb) is an endogenous neuroprotectant expressed in neurons and astrocytes. We recently showed that exogenous intravitreal Ngb reduced inflammatory cytokines and microglial activation in a rodent model of hypoxia. We thus hypothesised that IVT-Ngb may also be neuroprotective in experimental glaucoma (EG) by mitigating optic nerve (ON) astrogliosis and microgliosis as well as structural damage. In this study using a microbead-induced model of EG in six Cynomolgus primates, optical coherence imaging showed that Ngb-treated EG eyes had significantly less thinning of the peripapillary minimum rim width, retinal nerve fibre layer thickness, and ON head cupping than untreated EG eyes. Immunohistochemistry confirmed that ON astrocytes overexpressed Ngb following Ngb treatment. A reduction in complement 3 and cleaved-caspase 3 activated microglia and astrocytes was also noted. Our findings in higher-order primates recapitulate the effects of neuroprotection by Ngb treatment in rodent EG studies and suggest that Ngb may be a potential candidate for glaucoma neuroprotection in humans.

Cell-Specific Dysregulation of Iron and Oxygen Homeostasis as a Novel Pathophysiology in PSP

OBJECTIVE

Progressive supranuclear palsy (PSP) is a 4R-tauopathy showing heterogeneous tau cytopathology commencing in the globus pallidus (GP) and the substantia nigra (SN), regions also associated with age-related iron accumulation. Abnormal iron levels have been extensively associated with tau pathology in neurodegenerative brains, however, its role in PSP pathogenesis remains yet unknown. We perform the first cell type-specific evaluation of PSP iron homeostasis and the closely related oxygen homeostasis, in relation to tau pathology in human postmortem PSP brains.

METHODS

In brain regions vulnerable to PSP pathology (GP, SN, and putamen), we visualized iron deposition in tau-affected and unaffected neurons, astroglia, oligodendrocytes, and microglia, using a combination of iron staining with immunolabelling. To further explore molecular pathways underlying our observations, we examined the expression of key iron and oxygen homeostasis mRNA transcripts and proteins.

RESULTS

We found astrocytes as the major cell type accumulating iron in the early affected regions of PSP, highly associated with cellular tau pathology. The same regions are affected by dysregulated expression of alpha and beta hemoglobin and neuroglobin showing contrasting patterns. We discovered changes in iron and oxygen homeostasis-related gene expression associated with aging of the brain, and identified dysregulated expression of rare neurodegeneration with brain iron accumulation (NBIA) genes associated with tau pathology to distinguish PSP from the healthy aging brain.

INTERPRETATION

We present novel aspects of PSP pathophysiology highlighting an overlap with NBIA pathways. Our findings reveal potential novel targets for therapy development and have implications beyond PSP for other iron-associated neurodegenerative diseases. ANN NEUROL 2023;93:431-445.

The prognostic value of neutrophil-to-lymphocyte ratio in patients with traumatic brain injury: A systematic review

Traumatic brain injury (TBI) places a heavy load on healthcare systems worldwide. Despite significant advancements in care, the TBI-related mortality is 30–50% and in most cases involves adolescents or young adults. Previous literature has suggested that neutrophil-to-lymphocyte ratio (NLR) may serve as a sensitive biomarker in predicting clinical outcomes following TBI. With conclusive evidence in this regard lacking, this study aimed to systematically review all original studies reporting the effectiveness of NLR as a predictor of TBI outcomes. A systematic search of eight databases was conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analyses statement (PRISMA) recommendations. The risk of bias was assessed using the Quality in Prognostic Studies (QUIPS) tool. Eight studies were ultimately included in the study. In most of the studies interrogated, severity outcomes were successfully predicted by NLR in both univariate and multivariate prediction models, in different follow-up durations up to 6 months. A high NLR at 24 and 48 h after TBI in pediatric patients was associated with worse clinical outcomes. On pooling the NLR values within studies assessing its association with the outcome severity (favorable or not), patients with favorable outcomes had 37% lower NLR values than those with unfavorable ones (RoM= 0.63; 95% CI = 0.44–0.88; p = 0.007). However, there were considerable heterogeneity in effect estimates (I² = 99%; p < 0.001). Moreover, NLR was a useful indicator of mortality at both 6-month and 1-year intervals. In conjunction with clinical and radiographic parameters, NLR might be a useful, inexpensive marker in predicting clinical outcomes in patients with TBI. However, the considerable heterogeneity in current literature keeps it under investigation with further studies are warranted to confirm the reliability of NLR in predicting TBI outcomes.

New Strategies for Stroke Therapy: Nanoencapsulated Neuroglobin

Stroke is a global health and socio-economic problem. However, no efficient preventive and/or palliative treatments have yet been found. Neuroglobin (Ngb) is an endogen neuroprotective protein, but it only exerts its beneficial action against stroke after increasing its basal levels. Therefore, its systemic administration appears to be an efficient therapy applicable to stroke and other neurodegenerative pathologies. Unfortunately, Ngb cannot cross the blood-brain barrier (BBB), making its direct pharmacological use unfeasible. Thus, the association of Ngb with a drug delivery system (DDS), such as nanoparticles (NPs), appears to be a good strategy for overcoming this handicap. NPs are a type of DDS which efficiently transport Ngb and increase its bioavailability in the infarcted area. Hence, we previously built hyaluronate NPS linked to Ngb (Ngb-NPs) as a therapeutic tool against stroke. This nanoformulation induced an improvement of the cerebral infarct prognosis. However, this innovative therapy is still in development, and a more in-depth study focusing on its long-lasting neuroprotectant and neuroregenerative capabilities is needed. In short, this review aims to update the state-of-the-art of stroke therapies based on Ngb, paying special attention to the use of nanotechnological drug-delivering tools.

Probing the Role of Murine Neuroglobin CDloop-D-Helix Unit in CO Ligand Binding and Structural Dynamics

We produced a neuroglobin variant, namely, Ngb CDless, with the excised CDloop- and D-helix, directly joining the C- and E-helices. The CDless variant retained bis-His hexacoordination, and we investigated the role of the CDloop–D-helix unit in controlling the CO binding and structural dynamics by an integrative approach based on X-ray crystallography, rapid mixing, laser flash photolysis, resonance Raman spectroscopy, and molecular dynamics simulations. Rapid mixing and laser flash photolysis showed that ligand affinity was unchanged with respect to the wild-type protein, albeit with increased on and off constants for rate-limiting heme iron hexacoordination by the distal His64. Accordingly, resonance Raman spectroscopy highlighted a more open distal pocket in the CO complex that, in agreement with MD simulations, likely involves His64 swinging inward and outward of the distal heme pocket. Ngb CDless displays a more rigid overall structure with respect to the wild type, abolishing the structural dynamics of the CDloop–D-helix hypothesized to mediate its signaling role, and it retains ligand binding control by distal His64. In conclusion, this mutant may represent a tool to investigate the involvement of CDloop–D-helix in neuroprotective signaling in a cellular or animal model.

Serum Neuroglobin as a Potential Prognostic Biomarker for Cognitive Impairment After Intracerebral Hemorrhage

Objective

Stroke is closely related to dementia, but there are few prospective studies on cognitive decline after stroke in patients with cerebral hemorrhage. Neuroglobin is an oxygen-binding protein mainly expressed in brain neurons. The aim of our current study was to determine whether neuroglobin could serve as a biomarker for cognitive prognosis in patients with intracerebral hemorrhage (ICH).

Methods

Three hundred and sixteen patients with ICH were consecutively enrolled in a prospective study. Baseline data such as age and gender of ICH patients on admission were recorded. Serum neuroglobin concentrations were determined by enzyme-linked immunosorbent assay (ELISA). All ICH patients 3 months after onset were divided into post-stroke cognitive impairment group (PSCI) and non-PSCI group according to MoCA assessment results.

Results

The PSCI and Non-PSCI groups had serum neuroglobin concentrations of (4.7 ± 0.9) and (7.5 ± 1.1) ng/ml, respectively, with a statistically significant difference between the two groups (p &lt; 0.05). Age, gender, LDL, FBG, SBP, DBP, NHISS, and Hematoma volume were found to be adversely connected with MoCA (p &lt; 0.05), while education, HDL, and serum neuroglobin were found to be positively correlated with MoCA (p &lt; 0.05). After controlling for baseline data, regression analysis revealed that serum neuroglobin was remained an efficient biomarker for predicting cognitive performance in individuals with ICH (p &lt; 0.05). The diagnostic accuracy of blood neuroglobin concentration for PSCI in ICH patients was 72.6%, the sensitivity was 67.4%, and the specificity was 75.5%, according to receiver operating characteristic (ROC) curve analysis.

Conclusions

Serum neuroglobin may serve as a potential biomarker to predict cognitive decline after ICH.

Identification of HMGCR, PPGARG and prohibitin as potential druggable targets of dihydrotestosterone for treatment against traumatic brain injury using system pharmacology

BACKGROUND

Traumatic Brain Injury (TBI) has long-term devastating effects for which there is no accurate and effective treatment for inflammation and chronic oxidative stress. As a disease that affects multiple signalling pathways, the search for a drug with a broader spectrum of pharmacological action is of clinical interest. The fact that endocrine disruption (e.g hypogonadism) has been observed in TBI patients suggests that endogenous therapy with testosterone, or its more androgenic derivative, dihydrotestosterone (DHT), may attenuate, at least in part, the TBI-induced inflammation, but the underlying molecular mechanisms by which this occurs are still not completely clear.

AIMS AND METHODS

In this study, the main aim was to investigate proteins that may be related to the pathophysiological mechanism of TBI and also be pharmacological targets of DHT in order to explore a possible therapy with this androgen using network pharmacology.

RESULTS AND CONCLUSIONS

We identified 2.700 proteins related to TBI and 1.567 that are potentially molecular targets of DHT. Functional enrichment analysis showed that steroid (p-value: 2.1-22), lipid metabolism (p-value: 2.8-21) and apoptotic processes (p-value: 5.2-21) are mainly altered in TBI. Furthermore, being mitochondrion an organelle involved on these molecular processes we next identified that out of 32 mitochondrial-related proteins 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR), peroxisome proliferator activated receptor gamma (PPGARG) and prohibitin are those found highly regulated in the network and potential targets of DHT in TBI. In conclusion, the identification of these cellular nodes may prove to be essential as targets of DHT for therapy against post-TBI inflammation.

Skeletal muscle transcriptomics identifies common pathways in nerve crush injury and ageing

Motor unit remodelling involving repeated denervation and re-innervation occurs throughout life. The efficiency of this process declines with age contributing to neuromuscular deficits. This study investigated differentially expressed genes (DEG) in muscle following peroneal nerve crush to model motor unit remodelling in C57BL/6 J mice. Muscle RNA was isolated at 3 days post-crush, RNA libraries were generated using poly-A selection, sequenced and analysed using gene ontology and pathway tools. Three hundred thirty-four DEG were found in quiescent muscle from (26mnth) old compared with (4-6mnth) adult mice and these same DEG were present in muscle from adult mice following nerve crush. Peroneal crush induced 7133 DEG in muscles of adult and 699 DEG in muscles from old mice, although only one DEG (ZCCHC17) was found when directly comparing nerve-crushed muscles from old and adult mice. This analysis revealed key differences in muscle responses which may underlie the diminished ability of old mice to repair following nerve injury.

Hormonal Regulation of Oxidative Phosphorylation in the Brain in Health and Disease

The developing and adult brain is a target organ for the vast majority of hormones produced by the body, which are able to cross the blood–brain barrier and bind to their specific receptors on neurons and glial cells. Hormones ensure proper communication between the brain and the body by activating adaptive mechanisms necessary to withstand and react to changes in internal and external conditions by regulating neuronal and synaptic plasticity, neurogenesis and metabolic activity of the brain. The influence of hormones on energy metabolism and mitochondrial function in the brain has gained much attention since mitochondrial dysfunctions are observed in many different pathological conditions of the central nervous system. Moreover, excess or deficiency of hormones is associated with cell damage and loss of function in mitochondria. This review aims to expound on the impact of hormones (GLP-1, insulin, thyroid hormones, glucocorticoids) on metabolic processes in the brain with special emphasis on oxidative phosphorylation dysregulation, which may contribute to the formation of pathological changes. Since the brain concentrations of sex hormones and neurosteroids decrease with age as well as in neurodegenerative diseases, in parallel with the occurrence of mitochondrial dysfunction and the weakening of cognitive functions, their beneficial effects on oxidative phosphorylation and expression of antioxidant enzymes are also discussed.

An immune response characterizes early Alzheimer's disease pathology and subjective cognitive impairment in hydrocephalus biopsies

Early Alzheimer's disease (AD) pathology can be found in cortical biopsies taken during shunt placement for Normal Pressure Hydrocephalus. This represents an opportunity to study early AD pathology in living patients. Here we report RNA-seq data on 106 cortical biopsies from this patient population. A restricted set of genes correlate with AD pathology in these biopsies, and co-expression network analysis demonstrates an evolution from microglial homeostasis to a disease-associated microglial phenotype in conjunction with increasing AD pathologic burden, along with a subset of additional astrocytic and neuronal genes that accompany these changes. Further analysis demonstrates that these correlations are driven by patients that report mild cognitive symptoms, despite similar levels of biopsy β-amyloid and tau pathology in comparison to patients who report no cognitive symptoms. Taken together, these findings highlight a restricted set of microglial and non-microglial genes that correlate with early AD pathology in the setting of subjective cognitive decline.

Astrocyte-derived extracellular vesicles enhance the survival and electrophysiological function of human cortical neurons in vitro

Neurons derived from human induced pluripotent stem cells (hiPSCs) are powerful tools for modeling neural pathophysiology and preclinical efficacy/toxicity screening of novel therapeutic compounds. However, human neurons cultured in vitro typically do not fully recapitulate the physiology of the human nervous system, especially in terms of exhibiting morphological maturation, longevity, and electrochemical signaling ability comparable to that of adult human neurons. In this study, we investigated the potential for astrocyte-derived extracellular vesicles (EVs) to modulate survival and electrophysiological function of human neurons in vitro. Specifically, we demonstrate that EVs obtained from human astrocytes promote enhanced single cell electrophysiological function and anti-apoptotic behavior in a homogeneous population of human iPSC-derived cortical neurons. Furthermore, EV-proteomic analysis was performed to identify cargo proteins with the potential to promote the physiological enhancement observed. EV cargos were found to include neuroprotective proteins such as heat shock proteins, alpha-synuclein, and lipoprotein receptor-related protein 1 (LRP1), as well as apolipoprotein E (APOE), which negatively regulates neuronal apoptosis, and a peroxidasin homolog that supports neuronal oxidative stress management. Proteins that positively regulate neuronal excitability and synaptic development were also detected, such as potassium channel tetramerization domain containing 12 (KCTD12), glucose-6- phosphate dehydrogenase (G6PD), kinesin family member 5B (KIF5B), spectrin-alpha non-erythrocytic1 (SPTAN1). The remarkable improvements in electrophysiological function and evident inhibition of apoptotic signaling in cultured neurons exposed to these cargos may hold significance for improving preclinical in vitro screening modalities. In addition, our collected data highlight the potential for EV-based therapeutics as a potential class of future clinical treatment for tackling inveterate central and peripheral neuropathies.

Dissecting Sex-Related Cognition between Alzheimer's Disease and Diabetes: From Molecular Mechanisms to Potential Therapeutic Strategies

The brain is a sexually dimorphic organ that implies different functions and structures depending on sex. Current pharmacological approaches against different neurological diseases act distinctly in male and female brains. In all neurodegenerative diseases, including Alzheimer's disease (AD), sex-related outcomes regarding pathogenesis, prevalence, and response to treatments indicate that sex differences are important for precise diagnosis and therapeutic strategy. Pathogenesis of AD includes vascular dementia, and in most cases, this is accompanied by metabolic complications with similar features as those assembled in diabetes. This review discusses how AD-associated dementia and diabetes affect cognition in relation to sex difference, as both diseases share similar pathological mechanisms. We highlight potential protective strategies to mitigate amyloid-beta (Aβ) pathogenesis, emphasizing how these drugs act in the male and female brains.

The potential of mitochondrial modulation by neuroglobin in treatment of neurological disorders

Neuroglobin is the third member of the globin family to be identified in 2000 in neurons of both human and mouse nervous systems. Neuroglobin is an oxygen-binding globin found in neurons within the central nervous system as well as in peripheral neurons, that produces a protective effect against hypoxic/ischemic damage induced by promoting oxygen availability within the mitochondria. Numerous investigations have demonstrated that impaired neuroglobin functioning is implicated in the pathogenesis of multiple neurodegenerative disorders. Several in vitro and animal studies have reported the potential of neuroglobin upregulation in improving the neuroprotection through modulation of mitochondrial functions, such as ATP production, clearing reactive oxygen species (ROS), promoting the dynamics of mitochondria, and controlling apoptosis. Neuroglobin acts as a stress-inducible globin, which has been associated hypoxic/ischemic insults where it acts to protect the heart and brain, providing a wide range of applicability in the treatment of human disorders. This review article discusses normal physiological functions of neuroglobin in mitochondria-associated pathways, as well as outlining how dysregulation of neuroglobin is associated with the pathogenesis of neurodegenerative disorders.

Tibolone as Hormonal Therapy and Neuroprotective Agent

Tibolone (TIB), a selective tissue estrogenic activity regulator (STEAR) in clinical use by postmenopausal women, activates hormonal receptors in a tissue-specific manner. Estrogenic activity is present mostly in the brain, vagina, and bone, while the inactive forms predominate in the endometrium and breast. Conflicting literature on TIB's actions has been observed. While it has benefits for vasomotor symptoms, bone demineralization, and sexual health, a higher relative risk of hormone-sensitive cancer has been reported. In the brain, TIB can improve mood and cognition, neuroinflammation, and reactive gliosis. This review aims to discuss the systemic effects of TIB on peri- and post-menopausal women and its role in the brain. We suggest that TIB is a hormonal therapy with promising neuroprotective properties.

Neuroglobin and Prolactin As Potential Biomarkers for Differentiating Epileptic versus Nonepileptic Paroxysmal Disorders in Children

At least 20% of patients referred to pediatric epilepsy centers with the suspicion of epileptic seizures actually have other conditions. Neuroglobin is a new globin member which is highly expressed in the central and peripheral nervous systems. In this article, we aimed to evaluate usefulness of neuroglobin to differentiate between epilepsy and other conditions that mimic epilepsy. Our study was conducted on 90 children divided into three groups: 30 patients with epileptic seizures, 35 children with nonepileptic paroxysmal disorder, and 25 apparently healthy, age and sex-matched children as a normal control. Complete blood count, blood chemistries including random blood glucose, calcium, sodium, in addition to serum prolactin, and neuroglobin were performed for all children. This study showed a significant increase of both serum neuroglobin and prolactin levels in epileptic group compared with nonepileptic paroxysmal disorder and control groups (p < 0.01). Serum neuroglobin showed 95% sensitivity and 95.7% specificity in the diagnosis of generalized seizures. Serum neuroglobin may be a promising novel marker to differentiate epileptic versus nonepileptic disorders in children in the emergency setting, when history and clinical presentation are equivocal.

Insight into the molecular sex dimorphism of ischaemic stroke in rat cerebral cortex: Focus on neuroglobin, sex steroids and autophagy

Including sex is of paramount importance in preclinical and clinical stroke researches, and molecular studies dealing in depth with sex differences in stroke pathophysiology are needed. To gain insight into the molecular sex dimorphism of ischaemic stroke in rat cerebral cortex, male and female adult rats were subjected to transient middle cerebral artery occlusion. The expression of neuroglobin (Ngb) and other functionally related molecules involved in sex steroid signalling (oestrogen and androgen receptors), steroidogenesis (StAR, TSPO and aromatase) and autophagic activity (LC3B-II/LC3B-I ratio, UCP2 and HIF-1α) was assessed in the ipsilateral ischaemic and contralateral non-ischaemic hemispheres. An increased expression of Ngb was detected in the injured female cerebral cortex. In contrast, increased expression of oestrogen receptor α, GPER, StAR, TSPO and UCP2, and decreased androgen receptor expression were detected in the injured male cortex. In both sexes, the ischaemic insult induced an upregulation of LC3B-II/-I ratio, indicative of increased autophagy. Therefore, the cerebral cortex activates both sex-specific and common molecular responses with neuroprotective potential after ischaemia-reperfusion, which globally results in similar stroke outcome in both sexes. Nonetheless, these different potential molecular targets should be taken into account when neuroprotective drugs aiming to reduce brain damage in ischaemic stroke are investigated.

Lack of orientation selectivity of the heme insertion in murine neuroglobin revealed by resonance Raman spectroscopy

Different murine neuroglobin variants showing structural and dynamic alterations that are associated with perturbation of ligand binding have been studied: the CD loop mutants characterized by an enhanced flexibility (Gly-loop^40-48 and Gly-loop^44-47 ), the F106A mutant, and the double Gly-loop^44-47 /F106A mutant. Their ferric resonance Raman spectra in solution and in crystals are almost identical. In the high-frequency region, the identification of a double set of core size marker bands indicates the presence of two 6-coordinate low spin species. The resonance Raman data, together with the corresponding crystal structures, indicate the presence of two neuroglobin conformers with a reversed (A conformer) or a canonical (B conformer) heme insertion orientation. With the identification of the marker bands corresponding to each conformer, the data indicate that the B conformer increases at the expense of the A form, predominantly in the Gly-loop^44-47 /F106A double mutant, as confirmed by X-ray crystallography. This is the first time that a reversed heme insertion has been identified by resonance Raman in a native 6-coordinate low-spin heme protein. This diagnostic tool could be extended to other heme proteins in order to detect heme orientational disorder, which are likely to be correlated to functionally relevant heme dynamics. DATABASE: Crystallographic structure: structural data are deposited in the Protein Data Bank under the 6RA6 PDB entry.

New Insights into Oxidative Damage and Iron Associated Impairment in Traumatic Brain Injury

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Traumatic Brain Injury is considered one of the most prevalent causes of death around the world; more than seventy millions of individuals sustain the condition per year. The consequences of traumatic brain injury on brain tissue are complex and multifactorial, hence, the current palliative treatments are limited to improve patients’ quality of life. The subsequent hemorrhage caused by trauma and the ongoing oxidative process generated by biochemical disturbances in the in the brain tissue may increase iron levels and reactive oxygen species. The relationship between oxidative damage and the traumatic brain injury is well known, for that reason, diminishing factors that potentiate the production of reactive oxygen species have a promissory therapeutic use. Iron chelators are molecules capable of scavenging the oxidative damage from the brain tissue and are currently in use for ironoverload- derived diseases.

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Here, we show an updated overview of the underlying mechanisms of the oxidative damage after traumatic brain injury. Later, we introduced the potential use of iron chelators as neuroprotective compounds for traumatic brain injury, highlighting the action mechanisms of iron chelators and their current clinical applications.

Lipotoxicity, neuroinflammation, glial cells and oestrogenic compounds

The high concentrations of free fatty acids as a consequence of obesity and being overweight have become risk factors for the development of different diseases, including neurodegenerative ailments. Free fatty acids are strongly related to inflammatory events, causing cellular and tissue alterations in the brain, including cell death, deficits in neurogenesis and gliogenesis, and cognitive decline. It has been reported that people with a high body mass index have a higher risk of suffering from Alzheimer's disease. Hormones such as oestradiol not only have beneficial effects on brain tissue, but also exert some adverse effects on peripheral tissues, including the ovary and breast. For this reason, some studies have evaluated the protective effect of oestrogen receptor (ER) agonists with more specific tissue activities, such as the neuroactive steroid tibolone. Activation of ERs positively affects the expression of pro-survival factors and cell signalling pathways, thus promoting cell survival. This review aims to discuss the relationship between lipotoxicity and the development of neurodegenerative diseases. We also elaborate on the cellular and molecular mechanisms involved in neuroprotection induced by oestrogens.

Mn-TAT PTD-Ngb attenuates oxidative injury by an enhanced ROS scavenging ability and the regulation of redox signaling pathway

Neurological diseases have a close relationship to excessive reactive oxygen species (ROS). Neuroglobin (Ngb), an intrinsic protective factor, protected cells from hypoxic/ischemic injury. In the present, we reported a novel neuroprotective manganese porphyrin reconstituted metal protein, Mn-TAT PTD-Ngb, consisting of a HIV Tat protein transduction domain sequence (TAT PTD) attached to the N-terminal of apo-Ngb. Mn-TAT PTD-Ngb had a stronger ROS scavenging ability than that of TAT PTD-Ngb, and reduced intracellular ROS production and restored the function of the mitochondria and inhibited the mitochondria-dependent apoptosis. Besides, Mn-TAT PTD-Ngb activated the phosphoinositide-3 kinase (PI3K)/Akt signaling pathway, which up-regulated the expression of nuclear factor E2-related factor 2 (Nrf2), Heme oxygenase-1 (HO-1), superoxide dismutase (SOD), catalase (CAT). The results showed that the redox chemistry of Mn-TAT PTD-Ngb and redox regulation of multiple signaling pathways attenuated the oxidative injury.

Brain oxidative damage in murine models of neonatal hypoxia/ischemia and reoxygenation

The brain is one of the main organs affected by hypoxia and reoxygenation in the neonatal period and one of the most vulnerable to oxidative stress. Hypoxia/ischemia and reoxygenation leads to impairment of neurogenesis, disruption of cortical migration, mitochondrial damage and neuroinflammation. The extent of the injury depends on the clinical manifestation in the affected regions. Preterm newborns are highly vulnerable, and they exhibit severe clinical manifestations such as intraventricular hemorrhage (IVH), retinopathy of prematurity (ROP) and diffuse white matter injury (DWMI) among others. In the neonatal period, the accumulation of high levels of reactive oxygen species exacerbated by the immature antioxidant defense systems in represents cellular threats that, if they exceed or bypass physiological counteracting mechanisms, are responsible of significant neuronal damage. Several experimental models in mice mimic the consequences of perinatal asphyxia and the use of oxygen in the reanimation process that produce brain injury. The aim of this review is to highlight brain damage associated with oxidative stress in different murine models of hypoxia/ischemia and reoxygenation.

Molecular mechanisms and cellular events involved in the neuroprotective actions of estradiol. Analysis of sex differences

Estradiol, either from peripheral or central origin, activates multiple molecular neuroprotective and neuroreparative responses that, being mediated by estrogen receptors or by estrogen receptor independent mechanisms, are initiated at the membrane, the cytoplasm or the cell nucleus of neural cells. Estrogen-dependent signaling regulates a variety of cellular events, such as intracellular Ca²⁺ levels, mitochondrial respiratory capacity, ATP production, mitochondrial membrane potential, autophagy and apoptosis. In turn, these molecular and cellular actions of estradiol are integrated by neurons and non-neuronal cells to generate different tissue protective responses, decreasing blood-brain barrier permeability, oxidative stress, neuroinflammation and excitotoxicity and promoting synaptic plasticity, axonal growth, neurogenesis, remyelination and neuroregeneration. Recent findings indicate that the neuroprotective and neuroreparative actions of estradiol are different in males and females and further research is necessary to fully elucidate the causes for this sex difference.

Elevated Neuroglobin Lessens Neuroinflammation and Alleviates Neurobehavioral Deficits Induced by Acute Inhalation of Combustion Smoke in the Mouse

Acute inhalation of combustion smoke produces long-term neurologic deficits in survivors. To study the mechanisms that contribute to the development of neurologic deficits and identify targets for prevention, we developed a mouse model of acute inhalation of combustion smoke, which supports longitudinal investigation of mechanisms that underlie the smoke induced inimical sequelae in the brain. Using a transgenic mouse engineered to overexpress neuroglobin, a neuroprotective oxygen-binding globin protein, we previously demonstrated that elevated neuroglobin preserves mitochondrial respiration and attenuates formation of oxidative DNA damage in the mouse brain after smoke exposure. In the current study, we show that elevated neuronal neuroglobin attenuates the persistent inflammatory changes induced by smoke exposure in the mouse brain and mitigates concordant smoke-induced long-term neurobehavioral deficits. Specifically, we found that increases in hippocampal density of GFAP and Iba-1 positive cells that are detected post-smoke in wild-type mice are absent in the neuroglobin overexpressing transgenic (Ngb-tg) mice. Similarly, the smoke induced hippocampal myelin depletion is not observed in the Ngb-tg mice. Importantly, elevated neuroglobin alleviates behavioral and memory deficits that develop after acute smoke inhalation in the wild-type mice. Taken together, our findings suggest that the protective effects exerted by neuroglobin in the brains of smoke exposed mice afford protection from long-term neurologic sequelae of acute inhalation of combustion smoke. Our transgenic mouse provides a tool for assessing the potential of elevated neuroglobin as possible strategy for management of smoke inhalation injury.

Connecting the Dots in the Neuroglobin-Protein Interaction Network of an Unstressed and Ferroptotic Cell Death Neuroblastoma Model

Neuroglobin is a heme protein of which increased levels provide neuroprotection against amyloid proteinopathy and hemorrhagic damage. These cellular stressors involve the promotion of ferroptosis—an iron-dependent, lipid peroxide-accreting form of cell death. Hence, we questioned whether neuroglobin could oppose ferroptosis initiation. We detected human neuroglobin (hNgb)-EGFP-expressing SH-SY5Y cells to be significantly more resistant to ferroptosis induction, identifying 0.68-fold less cell death. To elucidate the underlying pathways, this study investigated hNgb-protein interactions with a Co-IP-MS/MS approach both under a physiological and a ferroptotic condition. hNgb binds to proteins of the cellular iron metabolism (e.g., RPL15 and PCBP3) in an unstressed condition and shows an elevated binding ratio towards cell death-linked proteins, such as HNRNPA3, FAM120A, and ABRAXAS2, under ferroptotic stress. Our data also reveal a constitutive interaction between hNgb and the longevity-associated heterodimer XRCC5/XRCC6. Disentangling the involvement of hNgb and its binding partners in cellular processes, using Ingenuity Pathway Analysis, resulted in the integration of hNgb in the ubiquitination pathway, mTOR signaling, 14-3-3-mediated signaling, and the glycolysis cascade. We also detected a previously unknown strong link with motor neuropathies. Hence, this study contributes to the elucidation of neuroglobin’s involvement in cellular mechanisms that provide neuroprotection and the upkeep of homeostasis.

The Therapeutic Potential of Mesenchymal Stem Cell-Derived Exosomes in Treatment of Neurodegenerative Diseases

Neurologic complications are commonly regarded as irreversible impairments that stem from limited potential of regeneration of the central nervous system (CNS). On the other side, the regenerative potential of stem cells has been evaluated in basic research, as well as in preclinical studies. Mesenchymal stem cells (MSCs) have been regarded as candidate cell sources for therapeutic purposes of various neurological disorders, because of their self-renewal ability, plasticity in differentiation, neurotrophic characteristics, and immunomodulatory properties. Exosomes are extracellular vesicles which can deliver biological information over long distances and thereby influencing normal and abnormal processes in cells and tissues. The therapeutic capacity of exosomes relies on the type of cell, as well as on the physiological condition of a given cell. Therefore, based on tissue type and physiological condition of CNS, exosomes may function as contributors or suppressors of pathological conditions in this tissue. When it comes to the therapeutic viewpoint, the most promising cellular source of exosomes is considered to be MSCs. The aim of this review article is to discuss the current knowledge around the potential of stem cells and MSC-derived exosomes in the treatment of neurodegenerative diseases.

The Neuroprotective Effect of Hemin and the Related Mechanism in Sevoflurane Exposed Neonatal Rats

Background

Many studies have reported that sevoflurane can increase neuronal apoptosis and result in cognitive deficits in rodents. Although neurotoxicity may be associated with mitochondrial dysfunction and oxidative stress, the exact mechanism remains unclear. In order to evaluate potential treatment therapies, we studied the effects of hemin on neurotoxicity of neonatal rat sevoflurane exposure.

Methods

Postnatal day (P) seven rats were assigned randomly to four groups; (1) group C: non-anesthesia, (2) group H: intraperitoneal hemin (50 mg kg^-1) treatment on days 5 and 6, (3) group S: 3% sevoflurane exposure for 4 h, and (4) group SH: hemin treatment + sevoflurane exposure. The expression of neuroglobin in neonatal hippocampus was determined by western blot and immunohistochemistry. Neuroglobin was localized by immunofluorescence. Western blot for the expression of cleaved caspase-3 and TUNEL were used to detect neonatal hippocampal apoptosis, and cytochrome c was used to evaluate mitochondrial function. Drp-1 and Mfn-2 immunoblotting were used to assess mitochondrial dynamics. The Morris water maze test was performed to detect cognitive function in the rats on P30.

Results

Exposure to sevoflurane increased the expression of cleaved caspase-3, cytochrome c, and Drp1 in the neonatal hippocampus and resulted in cognitive deficiency but decreased expression of Mfn2. Hemin reduced apoptosis, improved mitochondrial dynamics and ameliorated the cognitive impairment caused by sevoflurane exposure.

Conclusion

Hemin reduced neuronal apoptosis, improved mitochondrial dynamics and protected against cognitive deficits induced by sevoflurane in neonatal rats. This neuroprotective effect may be achieved by increasing the expression of neuroglobin.

Proximal and distal control for ligand binding in neuroglobin: role of the CD loop and evidence for His64 gating

Neuroglobin (Ngb) is predominantly expressed in neurons of the central and peripheral nervous systems and it clearly seems to be involved in neuroprotection. Engineering Ngb to observe structural and dynamic alterations associated with perturbation in ligand binding might reveal important structural determinants, and could shed light on key features related to its mechanism of action. Our results highlight the relevance of the CD loop and of Phe106 as distal and proximal controls involved in ligand binding in murine neuroglobin. We observed the effects of individual and combined mutations of the CD loop and Phe106 that conferred to Ngb higher CO binding velocities, which we correlate with the following structural observations: the mutant F106A shows, upon CO binding, a reduced heme sliding hindrance, with the heme present in a peculiar double conformation, whereas in the CD loop mutant “Gly-loop”, the original network of interactions between the loop and the heme was abolished, enhancing binding via facilitated gating out of the distal His64. Finally, the double mutant, combining both mutations, showed a synergistic effect on CO binding rates. Resonance Raman spectroscopy and MD simulations support our findings on structural dynamics and heme interactions in wild type and mutated Ngbs.

Mitochondrial Neuroglobin Is Necessary for Protection Induced by Conditioned Medium from Human Adipose-Derived Mesenchymal Stem Cells in Astrocytic Cells Subjected to Scratch and Metabolic Injury

Astrocytes are specialized cells capable of regulating inflammatory responses in neurodegenerative diseases or traumatic brain injury. In addition to playing an important role in neuroinflammation, these cells regulate essential functions for the preservation of brain tissue. Therefore, the search for therapeutic alternatives to preserve these cells and maintain their functions contributes in some way to counteract the progress of the injury and maintain neuronal survival in various brain pathologies. Among these strategies, the conditioned medium from human adipose-derived mesenchymal stem cells (CM-hMSCA) has been reported with a potential beneficial effect against several neuropathologies. In this study, we evaluated the potential effect of CM-hMSCA in a model of human astrocytes (T98G cells) subjected to scratch injury. Our findings demonstrated that CM-hMSCA regulates the cytokines IL-2, IL-6, IL-8, IL-10, GM-CSF, and TNF-α, downregulates calcium at the cytoplasmic level, and regulates mitochondrial dynamics and the respiratory chain. These actions are accompanied by modulation of the expression of different proteins involved in signaling pathways such as AKT/pAKT and ERK1/2/pERK, and may mediate the localization of neuroglobin (Ngb) at the cellular level. We also confirmed that Ngb mediated the protective effects of CM-hMSCA through regulation of proteins involved in survival pathways and oxidative stress. In conclusion, regulation of brain inflammation combined with the recovery of fundamental cellular aspects in the face of injury makes CM-hMSCA a promising candidate for the protection of astrocytes in brain pathologies.

Role of GTPases in the Regulation of Mitochondrial Dynamics in Alzheimer's Disease and CNS-Related Disorders

Data obtained from several studies have shown that mitochondria are involved and play a central role in the progression of several distinct pathological conditions. Morphological alterations and disruptions on the functionality of mitochondria may be related to metabolic and energy deficiency in neurons in a neurodegenerative disorder. Several recent studies demonstrate the linkage between neurodegeneration and mitochondrial dynamics in the spectrum of a promising era called precision mitochondrial medicine. In this review paper, an analysis of the correlation between mitochondria, Alzheimer's disease, and other central nervous system (CNS)-related disorders like the Parkinson's disease and the autism spectrum disorder is under discussion. The role of GTPases like the mfn1, mfn2, opa1, and dlp1 in mitochondrial fission and fusion is also under investigation, influencing mitochondrial population and leading to oxidative stress and neuronal damage.

Fucosterol exerts protection against amyloid β-induced neurotoxicity, reduces intracellular levels of amyloid β and enhances the mRNA expression of neuroglobin in amyloid β-induced SH-SY5Y cells

Alzheimer's disease (AD) is a neurodegenerative disease that leads to progressive loss of neurons which often results in deterioration of memory and cognitive function. The development of AD is highly associated with the formation of senile plaques and neurofibrillary tangles. Amyloid β (Aβ) induces neurotoxicity and contributes to the development of AD. Recent evidences also highlighted the importance of neuroglobin (Ngb) in ameliorating AD. This study assessed the ability of fucosterol, a phytosterol found in brown alga, in protecting SH-SY5Y cells against Aβ-induced neurotoxicity. Its effects on the mRNA levels of APP and Ngb as well as the intracellular Aβ levels were also determined in Aβ-induced SH-SY5Y cells. SH-SY5Y cells were exposed to fucosterol prior to Aβ treatment. The effect on apoptosis was determined using Annexin V FITC staining and mRNA expression was studied using RT-PCR. Flow cytometry confirmed the protective effects of fucosterol on SH-SY5Y cells against Aβ-induced apoptosis. Pretreatment with fucosterol increased the Ngb mRNA levels but reduced the levels of APP mRNA and intracellular Aβ in Aβ-induced SH-SY5Y cells. These observations demonstrated the protective properties of fucosterol against Aβ-induced neurotoxicity in neuronal cells.

N-acetyl-l-cysteine attenuates oxidative damage and neurodegeneration in rat brain during aging

N-acetyl-l-cysteine (NAC) is a precursor of cysteine, which is known to increase the level of glutathione (GSH) in the brain. Several neurodegenerative changes linked to oxidative stress take place in the aging brain. This study aimed to assess the neuroprotective effect of NAC supplementation on age-dependent neurodegeneration in the rat brain. Young (4 months) and old (24 months) Wistar rats (n = 6 rats/group) were supplemented with NAC (100 mg/kg b.w. orally) for 14 days. Enzymatic and nonenzymatic antioxidants such as superoxide dismutase and catalase, and GSH and total thiol respectively, prooxidants such as protein carbonyl, advanced oxidation protein products, reactive oxygen species, and malondialdehyde were assessed in the brain homogenates. Furthermore, nitric oxide level, acetylcholinesterase activity, and Na⁺/K⁺-ATPase activity were measured and gene expression studies were also performed. The results indicated that NAC augmented the level of enzymatic and nonenzymatic antioxidants with a significant reduction in prooxidant levels in old rats. NAC supplementation also downregulated the expression of inflammatory markers (TNF-α, IL-1β, IL-6) and upregulated the expression of marker genes associated with aging (sirtuin-1) and neurodegeneration (neuron-specific enolase, neuroglobin, synapsin-I, myelin basic protein 2) in old rats. The present findings support a neuroprotective role of NAC which has therapeutic implication in controlling age-related neurological disorders.

Investigating molecular interactions between oxidized neuroglobin and cytochrome c

The formation of a complex between neuroglobin (Ngb) and cytochrome c (Cyt c) has an important biological role in preventing apoptosis. Binding of Ngb to Cyt c alone is sufficient to block the caspase 9 activation by ferric Cyt c that is released during ischemic insults. Therefore, a detailed information on the Ngb-Cyt c interactions is important for understanding apoptosis. However, the exact nature of the interactions between oxidized human neuroglobin (hNgb) and Cyt c is not well understood. In this work, we used a combination of computational modeling and surface plasmon resonance experiments to obtain and characterize the complex formation between oxidized hNgb and Cyt c. We identified important residues involved in the complex formation, including K72 in Cyt c, which is otherwise known to interact with the apoptotic protease-activation factor-1. Our computational results, together with an optimized structure of the hNgb-Cyt c complex, provide unique insights into how the hNgb-Cyt c complex can abate the apoptotic cascade without an hNgb-Cyt c redox reaction.

Growth Factors and Neuroglobin in Astrocyte Protection Against Neurodegeneration and Oxidative Stress

Neurodegenerative diseases, such as Parkinson and Alzheimer, are among the main public health issues in the world due to their effects on life quality and high mortality rates. Although neuronal death is the main cause of disruption in the central nervous system (CNS) elicited by these pathologies, other cells such as astrocytes are also affected. There is no treatment for preventing the cellular death during neurodegenerative processes, and current drug therapy is focused on decreasing the associated motor symptoms. For these reasons, it has been necessary to seek new therapeutical procedures, including the use of growth factors to reduce α-synuclein toxicity and misfolding in order to recover neuronal cells and astrocytes. Additionally, it has been shown that some growth factors are able to reduce the overproduction of reactive oxygen species (ROS), which are associated with neuronal death through activation of antioxidative enzymes such as catalase, superoxide dismutase, glutathione peroxidase, and neuroglobin. In the present review, we discuss the use of growth factors such as PDGF-BB, VEGF, BDNF, and the antioxidative enzyme neuroglobin in the protection of astrocytes and neurons during the development of neurodegenerative diseases.

Neuroactive steroids, neurosteroidogenesis and sex

The nervous system is a target and a source of steroids. Neuroactive steroids are steroids that target neurons and glial cells. They include hormonal steroids originated in the peripheral glands, steroids locally synthesized by the neurons and glial cells (neurosteroids) and synthetic steroids, some of them used in clinical practice. Here we review the mechanisms of synthesis, metabolism and action of neuroactive steroids, including the role of epigenetic modifications and the mitochondria in their sex specific actions. We examine sex differences in neuroactive steroid levels under physiological conditions and their role in the establishment of sex dimorphic structures in the nervous system and sex differences in its function. In addition, particular attention is paid to neuroactive steroids under pathological conditions, analyzing how pathology alters their levels and their role as neuroprotective factors, considering the influence of sex in both cases.

Protective Effects of Curcumin Against Ischemia-Reperfusion Injury in the Nervous System

Ischemia-reperfusion injury (I/R injury) is a common feature of ischemic stroke which occurs when blood supply is restored after a period of ischemia. Although stroke is an important cause of death in the world, effective therapeutic strategies aiming at improving neurological outcomes in this disease are lacking. Various studies have suggested the involvement of different mechanisms in the pathogenesis of I/R injury in the nervous system. These mechanisms include oxidative stress, platelet adhesion and aggregation, leukocyte infiltration, complement activation, blood-brain barrier (BBB) disruption, and mitochondria-mediated mechanisms. Curcumin, an active ingredient of turmeric, can affect all these pathways and exert neuroprotective activity culminating in the amelioration of I/R injury in the nervous system. In this review, we discuss the protective effects of curcumin against I/R injury in the nervous system and highlight the studies that have linked biological functions of curcumin and I/R injury improvement.

Neuroglobin boosts axon regeneration during ischemic reperfusion via p38 binding and activation depending on oxygen signal

Cerebral ischemia causes severe cell death or injury including axon breakdown or retraction in the brain. Axon regeneration is crucial for the functional recovery of injured neurons or brains after ischemia/reperfusion (I/R); however, this process has been proved extremely difficult in adult brains and there is still no effective therapy for it. Here we reported that neuroglobin (Ngb), a novel oxygen-binding or sensor protein existing predominantly in neurons or brains, functions as a driving factor for axon regeneration during I/R. Ngb was upregulated and accumulated in growth cones of ischemic neurons in primary cultures, rat, and human brains, correlating positively to the elevation of axon-regeneration markers GAP43, neurofilament-200, and Tau-1. Ngb overexpression promoted while Ngb knockdown suppressed axon regeneration as well as GAP43 expression in neurons during oxygen-glucose deprivation/reoxygenation (OGD/Re). By using specific pharmacological inhibitors, we identified p38 MAPK as the major downstream player of Ngb-induced axon regeneration during OGD/Re. Mechanistically, Ngb directly bound to and activated p38 in neurons upon OGD/Re. Serial truncation and point mutation of Ngb revealed that the 7-105 aa fragment of Ngb was required and the oxygen-binding site (His⁶⁴) of Ngb was the major regulatory site for its p38 interaction/activation. Finally, administration of exogenous TAT-Ngb peptides significantly enhanced axon regeneration in cultured neurons upon OGD/Re. Taken together, Ngb promotes axon regeneration via O₂-Ngb-p38-GAP43 signaling during I/R. This novel mechanism suggests potential therapeutic applications of Ngb for ischemic stroke and other related axonopathy.

Dissecting Endoplasmic Reticulum Unfolded Protein Response (UPRER) in Managing Clandestine Modus Operandi of Alzheimer's Disease

Alzheimer's disease (AD), a neurodegenerative disorder, is most common cause of dementia witnessed among aged people. The pathophysiology of AD develops as a consequence of neurofibrillary tangle formation which consists of hyperphosphorylated microtubule associated tau protein and senile plaques of amyloid-β (Aβ) peptide in specific brain regions that result in synaptic loss and neuronal death. The feeble buffering capacity of endoplasmic reticulum (ER) proteostasis in AD is evident through alteration in unfolded protein response (UPR), where UPR markers express invariably in AD patient's brain samples. Aging weakens UPR^ER causing neuropathology and memory loss in AD. This review highlights molecular signatures of UPR^ER and its key molecular alliance that are affected in aging leading to the development of intriguing neuropathologies in AD. We present a summary of recent studies reporting usage of small molecules as inhibitors or activators of UPR^ER sensors/effectors in AD that showcase avenues for therapeutic interventions.

Mapping Hydrophobic Tunnels and Cavities in Neuroglobin with Noble Gas under Pressure

Internal cavities are crucial for conformational flexibility of proteins and can be mapped through noble gas diffusion and docking. Here we investigate the hydrophobic cavities and tunnel network in neuroglobin (Ngb), a hexacoordinated heme protein likely to be involved in neuroprotection, using crystallography under noble gas pressure, mostly at room temperature. In murine Ngb, a large internal cavity is involved in the heme sliding mechanism to achieve binding of gaseous ligands through coordination to the heme iron. In this study, we report that noble gases are hosted by two major sites within the internal cavity. We propose that these cavities could store oxygen and allow its relay in the heme proximity, which could correspond to NO location in the nitrite-reductase function of Ngb. Thanks to a recently designed pressurization cell using krypton at high pressure, a new gas binding site has been characterized that reveals an alternate pathway for gaseous ligands. A new gas binding site on the proximal side of the heme has also been characterized, using xenon pressure on a Ngb mutant (V140W) that binds CO with a similar rate and affinity to the wild-type, despite a reshaping of the internal cavity. Moreover, this study, to our knowledge, provides new insights into the determinants of the heme sliding mechanism, suggesting that the shift at the beginning of helix G precedes and drives this process.

Neurotrauma: The Crosstalk between Neurotrophins and Inflammation in the Acutely Injured Brain

Traumatic brain injury (TBI) is a major cause of morbidity and mortality among young individuals worldwide. Understanding the pathophysiology of neurotrauma is crucial for the development of more effective therapeutic strategies. After the trauma occurs, immediate neurologic damage is produced by the traumatic forces; this primary injury triggers a secondary wave of biochemical cascades together with metabolic and cellular changes, called secondary neural injury. In the scenario of the acutely injured brain, the ongoing secondary injury results in ischemia and edema culminating in an uncontrollable increase in intracranial pressure. These areas of secondary injury progression, or areas of “traumatic penumbra”, represent crucial targets for therapeutic interventions. Neurotrophins are a class of signaling molecules that promote survival and/or maintenance of neurons. They also stimulate axonal growth, synaptic plasticity, and neurotransmitter synthesis and release. Therefore, this review focuses on the role of neurotrophins in the acute post-injury response. Here, we discuss possible endogenous neuroprotective mechanisms of neurotrophins in the prevailing environment surrounding the injured areas, and highlight the crosstalk between neurotrophins and inflammation with focus on neurovascular unit cells, particularly pericytes. The perspective is that neurotrophins may represent promising targets for research on neuroprotective and neurorestorative processes in the short-term following TBI.

Blockade of Neuroglobin Reduces Protection of Conditioned Medium from Human Mesenchymal Stem Cells in Human Astrocyte Model (T98G) Under a Scratch Assay

Previous studies have indicated that paracrine factors (conditioned medium) increase wound closure and reduce reactive oxygen species in a traumatic brain injury in vitro model. Although the beneficial effects of conditioned medium from human adipose tissue-derived mesenchymal stem cells (hMSCA-CM) have been previously suggested for various neurological diseases, their actions on astrocytic cells are not well understood. In this study, we have explored the effect of hMSCA-CM on human astrocyte model (T98G cells) subjected to scratch assay. Our results indicated that hMSCA-CM improved cell viability, reduced nuclear fragmentation, attenuated the production of reactive oxygen species, and preserved mitochondrial membrane potential and ultrastructural parameters. In addition, hMSCA-CM upregulated neuroglobin in T98G cells and the genetic silencing of this protein prevented the protective action of hMSCA-CM on damaged cells, suggesting that neuroglobin is mediating, at least in part, the protective effect of hMSCA-CM. Overall, this evidence suggests that the use of hMSCA-CM is a promising therapeutic strategy for the protection of astrocytic cells in central nervous system (CNS) pathologies.