Astrocyte activation and reactive gliosis-A new target in stroke?

Beta-Secretase 1 Underlies Reactive Astrocytes and Endothelial Disruption in Neurodegeneration

Dysfunction in the neurovascular unit (NVU) is a key component in the progressive deterioration of Alzheimer's disease (AD) and is critical in vascular dementia. Recent studies have shown that inflammation plays early and perhaps causal roles in the pathogenesis of AD related to NVU damage, possibly in part by overactivating the aspartic acid protease activity of β-site amyloid precursor protein-cleaving enzyme 1 (BACE1), which until now has almost solely been studied in the context of the β-amyloid cascade. In this study, we analyzed the relationship of BACE1 with astrocytes and blood vessels in human brains with sporadic and familial dementia [Autosomal dominant cerebral arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), sporadic Alzheimer's disease (SAD), and familial Alzheimer's disease (FAD)] and how BACE1 inhibition affects astrocytes and endothelial cells under conditions of glutamate toxicity. Our results show increased BACE1, PHF (Paired helical filaments)-tau and GFAP (Glial Fibrillary Acid Protein) immunoreactivity (IR) in the CA1 hippocampal regions of FAD and SAD brains. Furthermore, BACE1 immunoprecipitated with GFAP in tissue samples from all study cases, but their immunofluorescence close to (10 μm³) or overlapping blood vessels was only increased in FAD and SAD brains, and PHF-tau was present around the vessels mainly in FAD brains. Interestingly, the increased BACE1 levels were associated with reactive astrocytes, characterized by morphological changes and upregulation of GFAP under pathological and stressful conditions, and endothelial disruption by glutamate excitotoxicity, and these effects were reversed by BACE1 inhibition; further, BACE1-inhibited astrocytes protected endothelial cell integrity by preserving zonula occludens-1 (ZO-1) distribution and decreasing the expression of inflammatory markers. Taken together, these findings suggest that BACE1 dysregulation in astrocytes may have a role in the alterations in NVU integrity implicated in neurodegeneration.

Neuroprotective Effect of a New Free Radical Scavenger HL-008 in an Ischemia-Reperfusion Injury Rat Model

Oxidative stress plays a critical role in cerebral ischemia-reperfusion injury. We have previously developed a powerful antioxidant, HL-008. This study aimed to investigate the neuroprotective function of HL-008. HL-008 efficacy in vitro and in vivo was evaluated using a PC-12 cell oxidative stress model induced by hydrogen peroxide and a rat model of middle cerebral artery occlusion, respectively. The MTT assay was used to analyze cell viability. 2,3,5-Triphenyltetrazolium chloride and Hematoxylin and Eosin staining, immunofluorescence, western blot, and proteomics were used to evaluate the infarction volume, brain tissue morphology, apoptosis, inflammation, and related pathways. Indicators related to oxidative levels were also detected. HL-008 significantly reduced the cerebral infarction volume induced by ischemia-reperfusion, improved the neurological score, alleviated oxidative stress and inflammation in the brain tissue, reduced glial cell activation, inhibited brain tissue apoptosis by influencing multiple signaling pathways, and had a neuroprotective effect. If HL-008 is successfully developed, it could significantly improve stroke patients' quality of life.

Endothelin ETB Receptor-Mediated Astrocytic Activation: Pathological Roles in Brain Disorders

In brain disorders, reactive astrocytes, which are characterized by hypertrophy of the cell body and proliferative properties, are commonly observed. As reactive astrocytes are involved in the pathogenesis of several brain disorders, the control of astrocytic function has been proposed as a therapeutic strategy, and target molecules to effectively control astrocytic functions have been investigated. The production of brain endothelin-1 (ET-1), which increases in brain disorders, is involved in the pathophysiological response of the nervous system. Endothelin B (ET_B) receptors are highly expressed in reactive astrocytes and are upregulated by brain injury. Activation of astrocyte ET_B receptors promotes the induction of reactive astrocytes. In addition, the production of various astrocyte-derived factors, including neurotrophic factors and vascular permeability regulators, is regulated by ET_B receptors. In animal models of Alzheimer’s disease, brain ischemia, neuropathic pain, and traumatic brain injury, ET_B-receptor-mediated regulation of astrocytic activation has been reported to improve brain disorders. Therefore, the astrocytic ET_B receptor is expected to be a promising drug target to improve several brain disorders. This article reviews the roles of ET_B receptors in astrocytic activation and discusses its possible applications in the treatment of brain disorders.

Prospects of Therapeutic Target and Directions for Ischemic Stroke

Stroke is a serious, adverse neurological event and the third leading cause of death and disability worldwide. Most strokes are caused by a block in cerebral blood flow, resulting in neurological deficits through the death of brain tissue. Recombinant tissue plasminogen activator (rt-PA) is currently the only immediate treatment medication for stroke. The goal of rt-PA administration is to reduce the thrombus and/or embolism via thrombolysis; however, the administration of rt-PA must occur within a very short therapeutic timeframe (3 h to 6 h) after symptom onset. Components of the pathological mechanisms involved in ischemic stroke can be used as potential biomarkers in current treatment. However, none are currently under investigation in clinical trials; thus, further studies investigating biomarkers are needed. After ischemic stroke, microglial cells can be activated and release inflammatory cytokines. These cytokines lead to severe neurotoxicity via the overactivation of microglia in prolonged and lasting insults such as stroke. Thus, the balanced regulation of microglial activation may be necessary for therapy. Stem cell therapy is a promising clinical treatment strategy for ischemic stroke. Stem cells can increase the functional recovery of damaged tissue after post-ischemic stroke through various mechanisms including the secretion of neurotrophic factors, immunomodulation, the stimulation of endogenous neurogenesis, and neovascularization. To investigate the use of stem cell therapy for neurological diseases in preclinical studies, however, it is important to develop imaging technologies that are able to evaluate disease progression and to “chase” (i.e., track or monitor) transplanted stem cells in recipients. Imaging technology development is rapidly advancing, and more sensitive techniques, such as the invasive and non-invasive multimodal techniques, are under development. Here, we summarize the potential risk factors and biomarker treatment strategies, stem cell-based therapy and emerging multimodal imaging techniques in the context of stroke. This current review provides a conceptual framework for considering the therapeutic targets and directions for the treatment of brain dysfunctions, with a particular focus on ischemic stroke.

Long Non-coding RNAs as Promising Therapeutic Approach in Ischemic Stroke: a Comprehensive Review

In recent years, ischemic stroke (IS) has been one of the major causes of disability and mortality worldwide. The general mechanism of IS is based on reduced blood supply to neuronal tissue, resulting in neuronal cell damage by various pathological reactions. One of the main techniques for acute IS treatment entails advanced surgical approaches for restoration of cerebral blood supply but this is often associated with secondary brain injury, also known as ischemic reperfusion injury (I/R injury). Many researches have come to emphasize the significant role of long non-coding RNAs (lncRNAs) in IS, especially in I/R injury and their potential as therapeutic approaches. LncRNAs are non-protein transcripts that are able to regulate cellular processes and gene expression. Further, lncRNAs have been shown to be involved in neuronal signaling pathways. Several lncRNAs are recognized as key factors in the physiological and pathological processes of IS. In this review, we discuss the role of lncRNAs in neuronal injury mechanisms and their association with brain neuroprotection. Moreover, we identify the lncRNAs that show the greatest potential as novel therapeutic approaches in IS, which therefore merit further investigation in preclinical research. Graphical Abstract.

Repair of brain damage size and recovery of neurological dysfunction after ischemic stroke are different between strains in mice: evaluation using a novel ischemic stroke model

In the current study, we established a novel murine ischemic brain damage model using a photochemical reaction to evaluate the recovery of neurological dysfunction and brain repair reactions. In this model, reproducible damage was induced in the frontal lobe of the cortex, which was accompanied by neurological dysfunction. Sequential changes in damage size, microglial accumulation, astrocyte activation, and neurological dysfunction were studied in C57BL/6J and BALB/c mouse strains. Although the initial size of damage was comparable in both strains, the extent of damage was later reduced to a greater extent in C57BL/6J mice than that in BALB/c mice. In addition, C57BL/6J mice showed later edema clearance until day 7, less microglial accumulation, and relatively more astrocyte activation on day 7. Neurologic dysfunction was evaluated by three behavioral tests: the von Frey test, the balance beam test, and the tail suspension test. The behavioral abnormalities evaluated by these tests were remarkable following the induction of damage and recovered by day 21 in both strains. However, the abnormalities were more prominent and the recovery was later in C57BL/6J mice. These findings demonstrate that our novel ischemic stroke model is useful for evaluating brain repair reactions and the recovery of neurological dysfunction in mice with different genetic backgrounds. In addition, we found that both the brain repair reactions and the recovery of neurological dysfunction after comparable ischemic brain damage varied between strains; in that, they both occurred later in C57BL/6J mice.

Changes in Smad1/5/9 expression and phosphorylation in astrocytes of the rat hippocampus after transient global cerebral ischemia

Smad proteins are known to transduce the actions of the transforming growth factor-β (TGF-β) family including TGF-βs, activins, and bone morphogenetic proteins (BMPs). We previously reported that Smad1/5/9 immunoreactivity was observed in astrocytes of various rat brain regions including the hippocampus, suggesting that Smad1/5/9 may be associated with the physiology of astrocytes. However, the Smad1/5/9 expression and activation in the hippocampal astrocytes after global cerebral ischemia has not been yet elucidated. In this study, we examined temporal changes in the expression and phosphorylation of Smad1/5/9 in the hippocampus using a rat model of global cerebral ischemia. Furthermore, we examined the candidate ligand involved in the phosphorylation of Smad1/5/9 in the hippocampus after ischemia. Pyramidal neuronal cell death in the CA1 regions was visible at 3 days, and maximum death occurred within 7 days after ischemia. At 7 days after ischemia, astrocytes that showed strong immunoreactivity for Smad1/5/9 were frequently observed in the CA1 region. Additionally, there was an increase in phosphorylated Smad1/5/9 (phospho-Smad1/5/9) -immunopositive astrocytes in the CA1 region 7 days after ischemia. Real-time PCR analysis showed an increase in the expression level of TGF-β1 mRNA in the hippocampus after ischemia. Intracerebroventricular injection of SB525334, an inhibitor of TGF-β/Smad signaling, reduced immunoreactivity for phospho-Smad1/5/9 in astrocytes. These results suggest that TGF-β1 may be a key molecule for ischemia-induced Smad1/5/9 phosphorylation in astrocytes, and TGF-β1-Smad1/5/9 signaling may play a role in post-ischemic events, including brain inflammation or tissue repair rather than neuroprotection of the hippocampus.

Hyperactive Behavior and Altered Brain Morphology in Adult Complement C3a Receptor Deficient Mice

The C3a receptor (C3aR) is a seven trans-membrane domain G-protein coupled receptor with a range of immune modulatory functions. C3aR is activated by the third complement component (C3) activation derived peptide C3a and a neuropeptide TLQP-21. In the central nervous system (CNS), C3aR is expressed by neural progenitors, neurons as well as glial cells. The non-immune functions of C3aR in the adult CNS include regulation of basal neurogenesis, injury-induced neural plasticity, and modulation of glial cell activation. In the developing brain, C3aR and C3 have been shown to play a role in neural progenitor cell proliferation and neuronal migration with potential implications for autism spectrum disorder, and adult C3aR deficient (C3aR^−/−) mice were reported to exhibit subtle deficit in recall memory. Here, we subjected 3 months old male C3aR^−/− mice to a battery of behavioral tests and examined their brain morphology. We found that the C3aR^−/− mice exhibit a short-term memory deficit and increased locomotor activity, but do not show any signs of autistic behavior as assessed by self-grooming behavior. We also found regional differences between the C3aR^−/− and wild-type (WT) mice in the morphology of motor and somatosensory cortex, as well as amygdala and hippocampus. In summary, constitutive absence of C3aR signaling in mice leads to neurodevelopmental abnormalities that persist into adulthood and are associated with locomotive hyperactivity and altered cognitive functions.

Astrocyte-induced synapse formation and ischemic stroke

Astrocytes are closely associated with the regulation of synapse formation and function. In addition, astrocytes have been shown to block certain brain impairments, including synaptic damage from stroke and other diseases of the central nervous system (CNS). Although astrocytes do not completely prevent synaptic damage, they appear to be protective and to restore synaptic function following damage. The purpose of this study is to discuss the role of astrocytes in synaptogenesis and synaptic damage in ischemic stroke. I detail the mechanism of action of the multiple factors secreted by astrocytes that are involved in synapse formation. In particular, I describe the characteristics and role in synapse formation of each secreted molecule related to synaptic structure and function. Furthermore, I discuss the effect of astrocytes on synaptogenesis and repair in ischemic stroke and in other CNS diseases. Astrocytes release molecules such as thrombospondin, hevin, secreted protein acidic rich in cysteine, etc., due to activation by ischemia to induce synaptic structure and function, an effect associated with protection of the brain from synaptic damage in ischemic stroke. In conclusion, I show that astrocytes may regulate synaptic transmission while having the potential to block and repair synaptic dysfunction in stroke-associated brain damage.

Heterogeneity of cellular inflammatory responses in ageing white matter and relationship to Alzheimer's and small vessel disease pathologies

White matter lesions (WML) are common in the ageing brain, often arising in a field effect of diffuse white matter abnormality. Although WML are associated with cerebral small vessel disease (SVD) and Alzheimer’s disease (AD), their cause and pathogenesis remain unclear. The current study tested the hypothesis that different patterns of neuroinflammation are associated with SVD compared to AD neuropathology by assessing the immunoreactive profile of the microglial (CD68, IBA1 and MHC‐II) and astrocyte (GFAP) markers in ageing parietal white matter (PARWM) obtained from the Cognitive Function and Ageing Study (CFAS), an ageing population‐representative neuropathology cohort. Glial responses varied extensively across the PARWM with microglial markers significantly higher in the subventricular region compared to either the middle‐zone (CD68 p = 0.028, IBA1 p < 0.001, MHC‐II p < 0.001) or subcortical region (CD68 p = 0.002, IBA1 p < 0.001, MHC‐II p < 0.001). Clasmatodendritic (CD) GFAP⁺ astrocytes significantly increased from the subcortical to the subventricular region (p < 0.001), whilst GFAP⁺ stellate astrocytes significantly decreased (p < 0.001). Cellular reactions could be grouped into two distinct patterns: an immune response associated with MHC‐II/IBA1 expression and CD astrocytes; and a more innate response characterised by CD68 expression associated with WML. White matter neuroinflammation showed weak relationships to the measures of SVD, but not to the measures of AD neuropathology. In conclusion, glial responses vary extensively across the PARWM with diverse patterns of white matter neuroinflammation. Although these findings support a role for vascular factors in the pathogenesis of age‐related white matter neuroinflammation, additional factors other than SVD and AD pathology may drive this. Understanding the heterogeneity in white matter neuroinflammation will be important for the therapeutic targeting of age‐associated white matter damage.

An Overview on the Differential Interplay Among Neurons-Astrocytes-Microglia in CA1 and CA3 Hippocampus in Hypoxia/Ischemia

Neurons have been long regarded as the basic functional cells of the brain, whereas astrocytes and microglia have been regarded only as elements of support. However, proper intercommunication among neurons-astrocytes-microglia is of fundamental importance for the functional organization of the brain. Perturbation in the regulation of brain energy metabolism not only in neurons but also in astrocytes and microglia may be one of the pathophysiological mechanisms of neurodegeneration, especially in hypoxia/ischemia. Glial activation has long been considered detrimental for survival of neurons, but recently it appears that glial responses to an insult are not equal but vary in different brain areas. In this review, we first take into consideration the modifications of the vascular unit of the glymphatic system and glial metabolism in hypoxic conditions. Using the method of triple-labeling fluorescent immunohistochemistry coupled with confocal microscopy (TIC), we recently studied the interplay among neurons, astrocytes, and microglia in chronic brain hypoperfusion. We evaluated the quantitative and morpho-functional alterations of the neuron-astrocyte-microglia triads comparing the hippocampal CA1 area, more vulnerable to ischemia, to the CA3 area, less vulnerable. In these contiguous and interconnected areas, in the same experimental hypoxic conditions, astrocytes and microglia show differential, finely regulated, region-specific reactivities. In both areas, astrocytes and microglia form triad clusters with apoptotic, degenerating neurons. In the neuron-astrocyte-microglia triads, the cell body of a damaged neuron is infiltrated and bisected by branches of astrocyte that create a microscar around it while a microglial cell phagocytoses the damaged neuron. These coordinated actions are consistent with the scavenging and protective activities of microglia. In hypoxia, the neuron-astrocyte-microglia triads are more numerous in CA3 than in CA1, further indicating their protective effects. These data, taken from contiguous and interconnected hippocampal areas, demonstrate that glial response to the same hypoxic insult is not equal but varies significantly. Understanding the differences of glial reactivity is of great interest to explain the differential susceptibility of hippocampal areas to hypoxia/ischemia. Further studies may evidence the differential reactivity of glia in different brain areas, explaining the higher or lower sensitivity of these areas to different insults and whether glia may represent a target for future therapeutic interventions.

The Function of Astrocyte Mediated Extracellular Vesicles in Central Nervous System Diseases

Astrocyte activation plays an important role during disease-induced inflammatory response in the brain. Exosomes in the brain could be released from bone marrow (BM)-derived stem cells, neuro stem cells (NSC), mesenchymal stem cells (MSC), etc. We summarized that exosomes release and transport signaling to the target cells, and then produce function. Furthermore, we discussed the pathological interactions between astrocytes and other brain cells, which are related to brain diseases such as stroke, Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS) disease, multiple sclerosis (MS), psychiatric, traumatic brain injury (TBI), etc. We provide up-to-date, comprehensive and valuable information on the involvement of exosomes in brain diseases, which is beneficial for basic researchers and clinical physicians.

Astrocytes in the regulation of cerebrovascular functions

Astrocytes are the most numerous type of neuroglia in the brain and have a predominant influence on the cerebrovascular system; they control perivascular homeostasis, the integrity of the blood-brain barrier, the dialogue with the peripheral immune system, the transfer of metabolites from the blood, and blood vessel contractility in response to neuronal activity. These regulatory processes occur in a specialized interface composed of perivascular astrocyte extensions that almost completely cover the cerebral blood vessels. Scientists have only recently started to study how this interface is formed and how it influences cerebrovascular functions. Here, we review the literature on the astrocytes' role in the regulation of the cerebrovascular system. We cover the anatomy and development of the gliovascular interface, the known gliovascular functions, and molecular factors, the latter's implication in certain pathophysiological situations, and recent cutting-edge experimental tools developed to examine the astrocytes' role at the vascular interface. Finally, we highlight some open questions in this field of research.

Exosome-Shuttled circSHOC2 from IPASs Regulates Neuronal Autophagy and Ameliorates Ischemic Brain Injury via the miR-7670-3p/SIRT1 Axis

The aim of the present study was to investigate the neuroprotective roles and mechanisms of the circular RNA circSHOC2 in ischemic-preconditioned astrocyte-derived exosomes (IPAS-EXOs) against ischemic stroke. We established an ischemia model based on oxygen glucose deprivation (OGD) in vitro and isolated resultant exosomes from astrocytes. Neuronal viability and apoptosis were determined by Cell Counting Kit-8 (CCK-8) assays and TUNEL (terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate nick end labeling) staining, respectively. Autophagy-related proteins were analyzed by western blotting. We found that exosomes derived from IPAS-preconditioned medium (IPAS-CM) exerted neuroprotection. Furthermore, circSHOC2 expression was significantly upregulated in exosomes released from IPAS-CM. Overexpression of circSHOC2 in neurons yielded the same protective effects as those from IPAS-EXOs in vitro, and similar results were also observed in the middle cerebral artery occlusion (MCAO) mouse model. Mechanistically, circSHOC2 reduced neuronal apoptosis via regulating autophagy. Furthermore, circSHOC2 was found to sponge miR-7670-3p, which regulated SIRT1 expression. Transfection with an miR-7670-3p small interfering RNA (siRNA) (siRNA-7670-3p) and incubation with circSHOC2 extracellular vesicles attenuated ischemia-induced neuronal apoptosis in vivo and in vitro, while silencing of SIRT1 reversed the protective effects of exosomal circSHOC2 on hypoxic cerebral neurons. Taken together, our findings indicate that circSHOC2 in IPAS-EXOs suppressed neuronal apoptosis and ameliorated neuronal damage by regulating autophagy and acting on the miR-7670-3p/SIRT1 axis, which might contribute to a therapeutic strategy for ischemic stroke treatment.

Common aspects between glaucoma and brain neurodegeneration

Neurodegeneration can be defined as progressive cell damage to nervous system cells, and more specifically to neurons, which involves morphologic alterations and progressive loss of function until cell death. Glaucoma exhibits many aspects of neurodegenerative disease. This review examines the pathogenesis of glaucoma, comparing it with that of Alzheimer's disease (AD) and Parkinson's disease (PD), highlighting their common features. Indeed, in all three diseases there are not only the same types of pathogenic events, but also similarities of temporal cadences that determine neuronal damage. All three age-related illnesses have oxidative damage and mitochondrial dysfunction as the first pathogenic steps. The consequence of these alterations is the death of visual neurons in glaucoma, cognitive neurons in AD and regulatory motor neurons (substantia nigra) in PD. The study of these common pathogenic events (oxidative stress, mitochondrial dysfunction, protein degradation, apoptosis and autophagy) leads us to consider common therapeutic strategies for the treatment and prevention of these diseases. Also, examination of the genetic aspects of the pathways involved in neurodegenerative processes plays a key role in shedding light on the details of pathogenesis and can suggest new treatments. This review discusses the common molecular aspects involved in these three oxidative-stress and age-related diseases.

Repetitive injury and absence of monocytes promote astrocyte self-renewal and neurological recovery

Unlike microglia and NG2 glia, astrocytes are incapable of migrating to sites of injury in the posttraumatic cerebral cortex, instead relying on proliferation to replenish their numbers and distribution in the affected region. However, neither the spectrum of their proliferative repertoire nor their postinjury distribution has been examined in vivo. Using a combination of different thymidine analogs and clonal analysis in a model of repetitive traumatic brain injury, we show for the first time that astrocytes that are quiescent following an initial injury can be coerced to proliferate after a repeated insult in the cerebral cortex grey matter. Interestingly, this process is promoted by invasion of monocytes to the injury site, as their genetic ablation (using CCR2^-/- mice) increased the number of repetitively dividing astrocytes at the expense of newly proliferating astrocytes in repeatedly injured parenchyma. These differences profoundly affected both the distribution of astrocytes and recovery period for posttraumatic behavior deficits suggesting key roles of astrocyte self-renewal in brain repair after injury.

Amburana cearensis: Pharmacological and Neuroprotective Effects of Its Compounds

Amburana cearensis A.C. Smith is an endemic tree from Northeastern Brazil used in folk medicine as teas, decocts and syrups for the treatment of various respiratory and inflammatory diseases, since therapeutic properties have been attributed to compounds from its stem bark and seeds. Numerous pharmacological properties of semi-purified extracts and isolated compounds from A. cearensis have been described in several biological systems, ranging from antimicrobial to anti-inflammatory effects. Some of these activities are attributed to coumarins and phenolic compounds, the major compounds present in A. cearensis seed extracts. Multiple lines of research demonstrate these compounds reduce oxidative stress, inflammation and neuronal death induced by glutamate excitotoxicity, events central to most neuropathologies, including Alzheimer’s disease (AD) and Parkinson’s Disease (PD). This review focuses on the botanical aspects, folk medicine use, biological effects and pharmacological activities of A. cearensis compounds and their potential as novel non-toxic drugs for the treatment of neurodegenerative diseases.

Inflammation in Neurological Disorders: The Thin Boundary Between Brain and Periphery

Significance: Accumulating evidence suggests that inflammation is a major contributor in the pathogenesis of several highly prevalent, but also rare, neurological diseases. In particular, the neurodegenerative processes of Alzheimer's disease (AD), vascular dementia (VAD), Parkinson's disease (PD), and multiple sclerosis (MS) are fueled by neuroinflammation, which, in turn, is accompanied by a parallel systemic immune dysregulation. This cross-talk between periphery and the brain becomes substantial when the blood-brain barrier loses its integrity, as often occurs in the course of these diseases. It has been hypothesized that the perpetual bidirectional flux of inflammatory mediators is not a mere "static" collateral effect of the neurodegeneration, but represents a proactive phenomenon sparking and driving the neuropathological processes. However, the upstream/downstream relationship between inflammatory events and neurological pathology is still unclear. Recent Advances: Solid recent evidence clearly suggests that metabolic factors, systemic infections, Microbiota dysbiosis, and oxidative stress are implicated, although to a different extent, in the development in brain diseases. Critical Issues: Here, we reviewed the most solid published evidence supporting the implication of the axis systemic inflammation-neuroinflammation-neurodegeneration in the pathogenesis of AD, VAD, PD, and MS, highlighting the possible cause of the putative downstream component of the axis. Future Directions: Reaching a definitive clinical/epidemiological appreciation of the etiopathogenic significance of the connection between peripheral and brain inflammation in neurologic disorders is pivotal since it could open novel therapeutic avenues for these diseases.

Reactive Glia Inflammatory Signaling Pathways and Epilepsy

Neuroinflammation and epilepsy are interconnected. Brain inflammation promotes neuronal hyper-excitability and seizures, and dysregulation in the glia immune-inflammatory function is a common factor that predisposes or contributes to the generation of seizures. At the same time, acute seizures upregulate the production of pro-inflammatory cytokines in microglia and astrocytes, triggering a downstream cascade of inflammatory mediators. Therefore, epileptic seizures and inflammatory mediators form a vicious positive feedback loop, reinforcing each other. In this work, we have reviewed the main glial signaling pathways involved in neuroinflammation, how they are affected in epileptic conditions, and the therapeutic opportunities they offer to prevent these disorders.

The Expression and Localization of Histone Acetyltransferases HAT1 and PCAF in Neurons and Astrocytes of the Photothrombotic Stroke-Induced Penumbra in the Rat Brain Cortex

Stroke is one of the leading reasons of human death. Ischemic penumbra that surrounds the stroke-induced infarction core is potentially salvageable, but molecular mechanisms of its formation are poorly known. Histone acetylation induces chromatin decondensation and stimulates gene expression. We studied the changes in the levels and localization of histone acetyltransferases HAT1 and PCAF in penumbra after photothrombotic stroke (PTS, a stroke model). In PTS, laser irradiation induces local occlusion of cerebral vessels after photosensitization by Rose Bengal. HAT1 and PCAF are poorly expressed in normal cortical neurons and astrocytes, but they are overexpressed 4-24 h after PTS. Their predominant localization in neuronal nuclei did not change after PTS, but their levels in the astrocyte nuclei significantly increased. Western blotting showed the increase of HAT1 and PCAF levels in the cytoplasmic fraction of the PTS-induced penumbra. In the nuclear fraction, PCAF level did not change, and HAT1 was overexpressed only at 24 h post-PTS. PTS-induced upregulation of HAT1 and PCAF in the penumbra was mainly associated with overexpression in the cytoplasm of neurons and especially astrocytes. HAT1 and PCAF did not co-localize with TUNEL-positive cells that indicated their nonparticipation in PTS-induced apoptosis.

Cathodal tDCS exerts neuroprotective effect in rat brain after acute ischemic stroke

BACKGROUND

Transcranial direct current stimulation (tDCS) is a non-invasive brain modulation technique that has been proved to exert beneficial effects in the acute phase of stroke. To explore the underlying mechanism, we investigated the neuroprotective effects of cathodal tDCS on brain injury caused by middle cerebral artery occlusion (MCAO).

RESULTS

We established the MCAO model and sham MCAO model with an epicranial electrode implanted adult male Sprague-Dawley rats, and then they were randomly divided into four groups (MCAO + tDCS, MCAO + sham tDCS (Sham), Control + tDCS and Control + Sham group). In this study, the severity degree of neurological deficit, the morphology of brain damage, the apoptosis, the level of neuron-specific enolase and inflammatory factors, the activation of glial cells was detected. The results showed that cathodal tDCS significantly improved the level of neurological deficit and the brain morphology, reduced the brain damage area and apoptotic index, and increased the number of Nissl body in MCAO rats, compared with MCAO + Sham group. Meanwhile, the high level of NSE, inflammatory factors, Caspase 3 and Bax/Bcl2 ratio in MCAO rats was reduced by cathodal tDCS. Additionally, cathodal tDCS inhibited the activation of astrocyte and microglia induced by MCAO. No difference was found in two Control groups.

CONCLUSION

Our results suggested that cathodal tDCS could accelerate the recovery of neurologic deficit and brain damage caused by MCAO. The inhibition of neuroinflammation and apoptosis resulted from cathodal tDCS may be involved in the neuroprotective process.

Toll-Like Receptor 4 Signaling in Focal Cerebral Ischemia: a Focus on the Neurovascular Unit

A robust innate immune activation leads to downstream expression of inflammatory mediators that amplify tissue damage and consequently increase the morbidity after stroke. The Toll-like receptor 4 (TLR4) pathway is a major innate immune pathway activated acutely and chronically after stroke. Hence, understanding the intricacies of the temporal profile, specific control points, and cellular specificity of TLR4 activation is crucial for the development of any novel therapeutics targeting the endogenous innate immune response after focal cerebral ischemia. The goal of this review is to summarize the current findings related to TLR4 signaling after stroke with a specific focus on the components of the neurovascular unit such as astrocytes, neurons, endothelial cells, and pericytes. In addition, this review will examine the effects of focal cerebral ischemia on interaction of these neurovascular unit components.

Inflammatory Responses in the Secondary Thalamic Injury After Cortical Ischemic Stroke

Stroke is one of the major causes of chronic disability worldwide and increasing efforts have focused on studying brain repair and recovery after stroke. Following stroke, the primary injury site can disrupt functional connections in nearby and remotely connected brain regions, resulting in the development of secondary injuries that may impede long-term functional recovery. In particular, secondary degenerative injury occurs in the connected ipsilesional thalamus following a cortical stroke. Although secondary thalamic injury was first described decades ago, the underlying mechanisms still remain unclear. We performed a systematic literature review using the NCBI PubMed database for studies that focused on the secondary thalamic degeneration after cortical ischemic stroke. In this review, we discussed emerging studies that characterized the pathological changes in the secondary degenerative thalamus after stroke; these included excitotoxicity, apoptosis, amyloid beta protein accumulation, blood-brain-barrier breakdown, and inflammatory responses. In particular, we highlighted key findings of the dynamic inflammatory responses in the secondary thalamic injury and discussed the involvement of several cell types in this process. We also discussed studies that investigated the effects of blocking secondary thalamic injury on inflammatory responses and stroke outcome. Targeting secondary injuries after stroke may alleviate network-wide deficits, and ultimately promote stroke recovery.

A mouse model of complete-crush transection spinal cord injury made by two operations

Background

More and more studies have focused on the treatment of spinal cord injury (SCI) by tissue engineering, but there is still no ideal animal model that can genuinely and objectively simulate the real pathological process in clinical practice. Also, given the increasing availability and use of genetically modified animals in basic science research, it has become essential to develop clinically related models for SCI for use in mice.

Methods

Forty-eight C57BL/6 mice were divided into three groups (injured/sham/uninjured). We determined the scar range made by the first crush injury by specimen observation, hematoxylin and eosin (HE) staining, and immunofluorescence staining. Transection to completely remove a 2-mm spinal cord segment centered on the lesion core was completed 6 weeks after the first injury in injured groups, whereas the sham group only underwent re-exposure of the spinal cord without transection injury. The characteristics of this SCI model were fully ascertained by specimen observation, HE staining, immunofluorescence staining, and quantitative real-time polymerase chain reaction (qRT-PCR).

Results

No mice died after the first injury. Histopathological findings suggested a scar range of 2 mm. After the second operation, 2 mice of the injured group and 1 mouse of the sham group died. The Basso Mouse Scale (BMS) score and motor evoked potential (MEP) results showed that the neurological function of mice did not recover. Immunostaining showed that there were no neurons or neurofilament residues in the lesion core 4 weeks after the second injury. Astrocytes encapsulated immune cells to form dense glial scars. Most immune cells were confined to the core of the lesion and formed fibrous scars with the fibroblasts. At the same time, there was considerable angiogenesis in the lesion core and around the injury. The results of qRT-PCR showed that Ptprc was highly expressed in the lesion core, while Gfap, nestin, Cnp, and Sv2b were highly expressed in the adjacent region. This suggests that the lesion core is a highly inflammatory zone, but there may be spontaneous neurogenesis adjacent to the lesion core.

Conclusions

The mouse crash-complete transection SCI model made by the two operations has good simulation, high feasibility, and high reproducibility; it will be a useful tool for pre-clinical testing of SCI treatment.

Glial Cells: Role of the Immune Response in Ischemic Stroke

Ischemic stroke, which accounts for 75-80% of all strokes, is the predominant cause of morbidity and mortality worldwide. The post-stroke immune response has recently emerged as a new breakthrough target in the treatment strategy for ischemic stroke. Glial cells, including microglia, astrocytes, and oligodendrocytes, are the primary components of the peri-infarct environment in the central nervous system (CNS) and have been implicated in post-stroke immune regulation. However, increasing evidence suggests that glial cells exert beneficial and detrimental effects during ischemic stroke. Microglia, which survey CNS homeostasis and regulate innate immune responses, are rapidly activated after ischemic stroke. Activated microglia release inflammatory cytokines that induce neuronal tissue injury. By contrast, anti-inflammatory cytokines and neurotrophic factors secreted by alternatively activated microglia are beneficial for recovery after ischemic stroke. Astrocyte activation and reactive gliosis in ischemic stroke contribute to limiting brain injury and re-establishing CNS homeostasis. However, glial scarring hinders neuronal reconnection and extension. Neuroinflammation affects the demyelination and remyelination of oligodendrocytes. Myelin-associated antigens released from oligodendrocytes activate peripheral T cells, thereby resulting in the autoimmune response. Oligodendrocyte precursor cells, which can differentiate into oligodendrocytes, follow an ischemic stroke and may result in functional recovery. Herein, we discuss the mechanisms of post-stroke immune regulation mediated by glial cells and the interaction between glial cells and neurons. In addition, we describe the potential roles of various glial cells at different stages of ischemic stroke and discuss future intervention targets.

In Vivo Analysis of Glial Immune Responses to Axon Degeneration in Drosophila melanogaster

Axon degeneration elicits a range of immune responses from local glial cells, including striking changes in glial gene expression, morphology, and phagocytic activity. Here, we describe a detailed set of protocols to assess discrete components of the glial reaction to axotomy in the adult nervous system of Drosophila melanogaster. These methods allow one to visualize and quantify transcriptional, morphological, and functional responses of glia to degenerating axons in a model system that is highly amenable to genetic manipulation.

Role of vinpocetine in ischemic stroke and poststroke outcomes: A critical review

Vinpocetine (VPN) is a synthetic ethyl-ester derivative of the alkaloid apovincamine from Vinca minor leaves. VPN is a selective inhibitor of phosphodiesterase type 1 (PDE1) that has potential neurological effects through inhibition of voltage-gated sodium channel and reduction of neuronal calcium influx. VPN has noteworthy antioxidant, anti-inflammatory, and anti-apoptotic effects with inhibitory effect on glial and astrocyte cells during and following ischemic stroke (IS). VPN is effective as adjuvant therapy in the management of epilepsy; it reduces seizure frequency by 50% in a dose of 2 mg/kg/day. VPN improves psychomotor performances through modulation of brain monoamine pathway mainly on dopamine and serotonin, which play an integral role in attenuation of depressive symptoms. VPN recover cognitive functions and spatial memory through inhibition of hippocampal and cortical PDE1 with augmentation of cyclic adenosin monophosphate and cyclic guanosin monophosphate ratio, enhancement of cholinergic neurotransmission, and inhibition of neuronal inflammatory mediators. Therefore, VPN is an effective agent in the management of IS and plays an integral role in the prevention and attenuation of poststroke epilepsy, depression, and cognitive deficit through direct cAMP/cGMP-dependent pathway or indirectly through anti-inflammatory and antioxidant effects.

Resveratrol Downregulates STAT3 Expression and Astrocyte Activation in Primary Astrocyte Cultures of Rat

Astrocytes respond to all forms of central nervous system (CNS) insults by a process referred to as reactive astrogliosis. Inhibition of astrocyte growth and activation is an important strategy for promoting injured CNS repair. STAT3 (signal transducer and activator of transcription 3) is reported to be a critical regulator of astrogliosis, and resveratrol (RES, a dietary polyphenol) is considered to be a natural inhibitor of STAT3 expression and phosphorylation. In this study, we investigated the effects of RES on STAT3 expression and phosphorylation, and then on the proliferation and activation of astrocytes, a critical process in reactive astrogliosis, in rat primary cultured astrocytes and an in vitro scratch-wound model. RES downregulated the expression levels of STAT3, P-STAT3 and GFAP (glial fibrillary acidic protein) in cultured astrocytes. The positive index of Ki67 was apparently reduced in cultured astrocytes after RES treatment. Meanwhile, cultured astrocyte proliferation and activation were attenuated by RES. Moreover, in the established in vitro scratch-wound model the increased expression levels of STAT3, P-STAT3 and GFAP induced by scratching injury were also clearly inhibited by RES. In addition, the inhibitory effect of RES on cell proliferation was similar to that of AG490 (a selective inhibitor of STAT3 phosphorylation) and abrogated by Colivelin (a STAT3 activator) stimuli. Taken together, our data suggest that RES is able to inhibit reactive astrocyte proliferation and activation mainly via deactivating STAT3 pathway. So RES may have a therapeutic benefit for the treatment of the injured CNS.

High potassium exposure reveals the altered ability of astrocytes to regulate their volume in the aged hippocampus of GFAP/EGFP mice

In this study, we focused on age-related changes in astrocyte functioning, predominantly on the ability of astrocytes to regulate their volume in response to a pathological stimulus, namely extracellular 50 mM K⁺ concentration. The aim of our project was to identify changes in the expression and function of transport proteins in the astrocytic membrane and properties of the extracellular space, triggered by aging. We used three-dimensional confocal morphometry, gene expression profiling, immunohistochemical analysis, and diffusion measurement in the hippocampal slices from 3-, 9-, 12-, and 18-month-old mice, in which astrocytes are visualized by enhanced green fluorescent protein under the control of the promoter for human glial fibrillary acidic protein. Combining a pharmacological approach and the quantification of astrocyte volume changes evoked by hyperkalemia, we found that marked diversity in the extent of astrocyte swelling in the hippocampus during aging is due to the gradually declining participation of Na⁺-K⁺-Cl^- transporters, glutamate transporters (glutamate aspartate transporter and glutamate transporter 1), and volume-regulated anion channels. Interestingly, there was a redistribution of Na⁺-K⁺-Cl^- cotransporter and glutamate transporters from astrocytic soma to processes. In addition, immunohistochemical analysis confirmed an age-dependent decrease in the content of Na⁺-K⁺-Cl^- cotransporter in astrocytes. The overall extracellular volume changes revealed a similar age-dependent diversity during hyperkalemia as observed in astrocytes. In addition, the recovery of the extracellular space was markedly impaired in aged animals.

Co-stimulation with IL-1β and TNF-α induces an inflammatory reactive astrocyte phenotype with neurosupportive characteristics in a human pluripotent stem cell model system

Astrocyte reactivation has been discovered to be an important contributor to several neurological diseases. In vitro models involving human astrocytes have the potential to reveal disease-specific mechanisms of these cells and to advance research on neuropathological conditions. Here, we induced a reactive phenotype in human induced pluripotent stem cell (hiPSC)-derived astrocytes and studied the inflammatory natures and effects of these cells on human neurons. Astrocytes responded to interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) treatment with a typical transition to polygonal morphology and a shift to an inflammatory phenotype characterized by altered gene and protein expression profiles. Astrocyte-secreted factors did not exert neurotoxic effects, whereas they transiently promoted the functional activity of neurons. Importantly, we engineered a novel microfluidic platform designed for investigating interactions between neuronal axons and reactive astrocytes that also enables the implementation of a controlled inflammatory environment. In this platform, selective stimulation of astrocytes resulted in an inflammatory niche that sustained axonal growth, further suggesting that treatment induces a reactive astrocyte phenotype with neurosupportive characteristics. Our findings show that hiPSC-derived astrocytes are suitable for modeling astrogliosis, and the developed in vitro platform provides promising novel tools for studying neuron-astrocyte crosstalk and human brain disease in a dish.

Longitudinal Functional Assessment of Brain Injury Induced by High-Intensity Ultrasound Pulse Sequences

Exposure of the brain to high-intensity stress waves creates the potential for long-term functional deficits not related to thermal or cavitational damage. Possible sources of such exposure include overpressure from blast explosions or high-intensity focused ultrasound (HIFU). While current ultrasound clinical protocols do not normally produce long-term neurological deficits, the rapid expansion of potential therapeutic applications and ultrasound pulse-train protocols highlights the importance of establishing a safety envelope beyond which therapeutic ultrasound can cause neurological deficits not detectable by standard histological assessment for thermal and cavitational damage. In this study, we assessed the neuroinflammatory response, behavioral effects, and brain micro-electrocorticographic (µECoG) signals in mice following exposure to a train of transcranial pulses above normal clinical parameters. We found that the HIFU exposure induced a mild regional neuroinflammation not localized to the primary focal site, and impaired locomotor and exploratory behavior for up to 1 month post-exposure. In addition, low frequency (δ) and high frequency (β, γ) oscillations recorded by ECoG were altered at acute and chronic time points following HIFU application. ECoG signal changes on the hemisphere ipsilateral to HIFU exposure are of greater magnitude than the contralateral hemisphere, and persist for up to three months. These results are useful for describing the upper limit of transcranial ultrasound protocols, and the neurological sequelae of injury induced by high-intensity stress waves.

Hypertension and Its Impact on Stroke Recovery: From a Vascular to a Parenchymal Overview

Hypertension is the first modifiable vascular risk factor accounting for 10.4 million deaths worldwide; it is strongly and independently associated with the risk of stroke and is related to worse prognosis. In addition, hypertension seems to be a key player in the implementation of vascular cognitive impairment. Long-term hypertension, complicated or not by the occurrence of ischemic stroke, is often reviewed on its vascular side, and parenchymal consequences are put aside. Here, we sought to review the impact of isolated hypertension or hypertension associated to stroke on brain atrophy, neuron connectivity and neurogenesis, and phenotype modification of microglia and astrocytes. Finally, we discuss the impact of antihypertensive therapies on cell responses to hypertension and functional recovery. This attractive topic remains a focus of continued investigation and stresses the relevance of including this vascular risk factor in preclinical investigations of stroke outcome.

Nestin Null Mice Show Improved Reversal Place Learning

The intermediate filament protein nestin is expressed by neural stem cells, but also by some astrocytes in the neurogenic niche of the hippocampus in the adult rodent brain. We recently reported that nestin-deficient (Nes^−/−) mice showed increased adult hippocampal neurogenesis, reduced Notch signaling from Nes^−/− astrocytes to the neural stem cells, and impaired long-term memory. Here we assessed learning and memory of Nes^−/− mice in a home cage set up using the IntelliCage system, in which the mice learn in which cage corner a nose poke earns access to drinking water. Nes^−/− and wildtype mice showed comparable place learning assessed as the incorrect corner visit ratio and the incorrect nose poke ratio. However, during reversal place learning, a more challenging task, Nes^−/− mice, compared to wildtype mice, showed improved learning over time demonstrated by the incorrect visit ratio and improved memory extinction over time assessed as nose pokes per visit to the previous drinking corner. In addition, Nes^−/− mice showed increased explorative activity as judged by the increased total numbers of corner visits and nose pokes. We conclude that Nes^−/− mice exhibit improved reversal place learning and memory extinction, a finding which together with the previous results supports the concept of the dual role of hippocampal neurogenesis in cognitive functions.

Beneficial Effects of Theta-Burst Transcranial Magnetic Stimulation on Stroke Injury via Improving Neuronal Microenvironment and Mitochondrial Integrity

Recent work suggests that repetitive transcranial magnetic stimulation (rTMS) may beneficially alter the pathological status of several neurological disorders, although the mechanism remains unclear. The current study was designed to investigate the effects of rTMS on behavioral deficits and potential underlying mechanisms in a rat photothrombotic (PT) stroke model. From day 0 (3 h) to day 5 after the establishment of PT stroke, 5-min daily continuous theta-burst rTMS (3 pulses of 50 Hz repeated every 200 ms, intensity at 200 G) was applied on the infarct hemisphere. We report that rTMS significantly attenuated behavioral deficits and infarct volume after PT stroke. Further investigation demonstrated that rTMS remarkably reduced synaptic loss and neuronal degeneration in the peri-infarct cortical region. Mechanistic studies displayed that beneficial effects of rTMS were associated with robust suppression of reactive micro/astrogliosis and the overproduction of pro-inflammatory cytokines, as well as oxidative stress and oxidative neuronal damage especially at the late stage following PT stroke. Intriguingly, rTMS could effectively induce a shift in microglial M1/M2 phenotype activation and an A1 to A2 switch in astrocytic phenotypes. In addition, the release of anti-inflammatory cytokines and mitochondrial MnSOD in peri-infarct regions were elevated following rTMS treatment. Finally, rTMS treatment efficaciously preserved mitochondrial membrane integrity and suppressed the intrinsic mitochondrial caspase-9/3 apoptotic pathway within the peri-infarct cortex. Our novel findings indicate that rTMS treatment exerted robust neuroprotection when applied at least 3 h after ischemic stroke. The underlying mechanisms are partially associated with improvement of the local neuronal microenvironment by altering inflammatory and oxidative status and preserving mitochondrial integrity in the peri-infarct zone. These findings provide strong support for the promising therapeutic effect of rTMS against ischemic neuronal injury and functional deficits following stroke.

Vimentin Phosphorylation Is Required for Normal Cell Division of Immature Astrocytes

Vimentin (VIM) is an intermediate filament (nanofilament) protein expressed in multiple cell types, including astrocytes. Mice with VIM mutations of serine sites phosphorylated during mitosis (VIM^SA/SA) show cytokinetic failure in fibroblasts and lens epithelial cells, chromosomal instability, facilitated cell senescence, and increased neuronal differentiation of neural progenitor cells. Here we report that in vitro immature VIM^SA/SA astrocytes exhibit cytokinetic failure and contain vimentin accumulations that co-localize with mitochondria. This phenotype is transient and disappears with VIM^SA/SA astrocyte maturation and expression of glial fibrillary acidic protein (GFAP); it is also alleviated by the inhibition of cell proliferation. To test the hypothesis that GFAP compensates for the effect of VIM^SA/SA in astrocytes, we crossed the VIM^SA/SA and GFAP^−/− mice. Surprisingly, the fraction of VIM^SA/SA immature astrocytes with abundant vimentin accumulations was reduced when on GFAP^−/− background. This indicates that the disappearance of vimentin accumulations and cytokinetic failure in mature astrocyte cultures are independent of GFAP expression. Both VIM^SA/SA and VIM^SA/SAGFAP^−/− astrocytes showed normal mitochondrial membrane potential and vulnerability to H₂O₂, oxygen/glucose deprivation, and chemical ischemia. Thus, mutation of mitotic phosphorylation sites in vimentin triggers formation of vimentin accumulations and cytokinetic failure in immature astrocytes without altering their vulnerability to oxidative stress.

Questions and (some) answers on reactive astrocytes

Astrocytes are key cellular partners for neurons in the central nervous system. Astrocytes react to virtually all types of pathological alterations in brain homeostasis by significant morphological and molecular changes. This response was classically viewed as stereotypical and is called astrogliosis or astrocyte reactivity. It was long considered as a nonspecific, secondary reaction to pathological conditions, offering no clues on disease-causing mechanisms and with little therapeutic value. However, many studies over the last 30 years have underlined the crucial and active roles played by astrocytes in physiology, ranging from metabolic support, synapse maturation, and pruning to fine regulation of synaptic transmission. This prompted researchers to explore how these new astrocyte functions were changed in disease, and they reported alterations in many of them (sometimes beneficial, mostly deleterious). More recently, cell-specific transcriptomics revealed that astrocytes undergo massive changes in gene expression when they become reactive. This observation further stressed that reactive astrocytes may be very different from normal, nonreactive astrocytes and could influence disease outcomes. To make the picture even more complex, both normal and reactive astrocytes were shown to be molecularly and functionally heterogeneous. Very little is known about the specific roles that each subtype of reactive astrocytes may play in different disease contexts. In this review, we have interrogated researchers in the field to identify and discuss points of consensus and controversies about reactive astrocytes, starting with their very name. We then present the emerging knowledge on these cells and future challenges in this field.

Epigenetic Alterations Induced by Photothrombotic Stroke in the Rat Cerebral Cortex: Deacetylation of Histone h3, Upregulation of Histone Deacetylases and Histone Acetyltransferases

Ischemic penumbra that surrounds a stroke-induced infarction core is potentially salvageable; however, mechanisms of its formation are not well known. Covalent modifications of histones control chromatin conformation, gene expression and protein synthesis. To study epigenetic processes in ischemic penumbra, we used photothrombotic stroke (PTS), a stroke model in which laser irradiation of the rat brain cortex photosensitized by Rose Bengal induces local vessel occlusion. Immunoblotting and immunofluorescence microscopy showed decrease in acetylation of lysine 9 in histone H3 in penumbra at 1, 4 or 24 h after PTS. This was associated with upregulation of histone deacetylases HDAC1 and HDAC2, but not HDAC4, which did not localize in the nuclei. HDAC2 was found in cell nuclei, HDAC4 in the cytoplasm and HDAC1 both in nuclei and cytoplasm. Histone acetyltransferases HAT1 and PCAF (p300/CBP associated factor) that acetylated histone H3 synthesis were also upregulated, but lesser and later. PTS increased localization of HDAC2 and HAT1 in astroglia. Thus, the cell fate in PTS-induced penumbra is determined by the balance between opposite tendencies leading either to histone acetylation and stimulation of gene expression, or to deacetylation and suppression of transcriptional processes and protein biosynthesis. These epigenetic proteins may be the potential targets for anti-stroke therapy.

Inhibition of miR-19a protects neurons against ischemic stroke through modulating glucose metabolism and neuronal apoptosis

Background

Accumulating evidence has shown that altered microRNA (miR) modulation is implicated in the pathologies of ischemic stroke. However, it is unclear whether and how hsa-miR-19a-3p mediates cerebral ischemic injury. Herein, we investigated the functional role of miR-19a-3p in cerebral ischemic injury and explored its underlying regulatory mechanism.

Methods

In vivo ischemic/reperfusion (I/R) neuronal injury and in vitro oxygen-glucose deprivation (OGD) were established. Expression of miR-19a-3p was determined by quantitative real-time polymerase chain reaction (qRT-PCR). Glucose uptake, lactate production, and apoptosis were determined. ADIPOR2 was predicted as a target of miR-19a-3p in silico and experimentally validated by qRT-PCR, Western blot analysis and luciferase assay assays.

Results

MiR-19a expression was significantly downregulated and upregulated in rat neurons and astrocytes, respectively (P < 0.01). A significantly elevated level of miR-19a-3p was found in I/R and OGD models in comparison to sham/control groups (P < 0.01). Expression of the glycolysis enzyme markers LDHA, PKM2, HK2, Glut1 and PDK1, apoptosis-related factors levels, apoptosis, glucose uptake, and lactate production were significantly repressed by both I/R and OGD (P < 0.01 in each case). Moreover, miR-19a-3p mimic aggravated, while miR-19a-3p inhibitor alleviated, the above observations. Adipor2 was predicted and confirmed to be a direct target of miR-19a. Furthermore, restoration of Adipor2 reversed miR-19a-3p-induced effects.

Conclusions

Collectively, our results indicate that elevated miR-19a-3p mediates cerebral ischemic injury by targeting ADIPOR2. MiR-19a-3p attenuation thus might offer hope of a novel therapeutic target for ischemic stroke injury treatment.

Dual Roles of Astrocyte-Derived Factors in Regulation of Blood-Brain Barrier Function after Brain Damage

The blood-brain barrier (BBB) is a major functional barrier in the central nervous system (CNS), and inhibits the extravasation of intravascular contents and transports various essential nutrients between the blood and the brain. After brain damage by traumatic brain injury, cerebral ischemia and several other CNS disorders, the functions of the BBB are disrupted, resulting in severe secondary damage including brain edema and inflammatory injury. Therefore, BBB protection and recovery are considered novel therapeutic strategies for reducing brain damage. Emerging evidence suggests key roles of astrocyte-derived factors in BBB disruption and recovery after brain damage. The astrocyte-derived vascular permeability factors include vascular endothelial growth factors, matrix metalloproteinases, nitric oxide, glutamate and endothelin-1, which enhance BBB permeability leading to BBB disruption. By contrast, the astrocyte-derived protective factors include angiopoietin-1, sonic hedgehog, glial-derived neurotrophic factor, retinoic acid and insulin-like growth factor-1 and apolipoprotein E which attenuate BBB permeability resulting in recovery of BBB function. In this review, the roles of these astrocyte-derived factors in BBB function are summarized, and their significance as therapeutic targets for BBB protection and recovery after brain damage are discussed.

Bursting at the Seams: Molecular Mechanisms Mediating Astrocyte Swelling

Brain swelling is one of the most robust predictors of outcome following brain injury, including ischemic, traumatic, hemorrhagic, metabolic or other injury. Depending on the specific type of insult, brain swelling can arise from the combined space-occupying effects of extravasated blood, extracellular edema fluid, cellular swelling, vascular engorgement and hydrocephalus. Of these, arguably the least well appreciated is cellular swelling. Here, we explore current knowledge regarding swelling of astrocytes, the most abundant cell type in the brain, and the one most likely to contribute to pathological brain swelling. We review the major molecular mechanisms identified to date that contribute to or mitigate astrocyte swelling via ion transport, and we touch upon the implications of astrocyte swelling in health and disease.

Progress in research into spinal cord injury repair: Tissue engineering scaffolds and cell transdifferentiation

As with all tissues of the central nervous system, the low regeneration ability of spinal cord tissue after injury decreases the potential for repair and recovery. Initially, in spinal cord injuries (SCI), often the surgeon can only limit further damage by early surgical decompression. However, with the development of basic science, especially the development of genetic engineering, molecular biology, tissue engineering, and materials science, some promising progress has been made in promoting the repair of central nervous system injuries. For example, transplantation of neural stem cells (NSCs), olfactory ensheathing cells (OECs), and gene- mediated transdifferentiation to repair central nervous system injury. This paper summarizes the progress and prospects of SCI repair with tissue engineering scaffold and cell transdifferentiation from an extensive literatures.