Pathophysiological Responses and Roles of Astrocytes in Traumatic Brain Injury

'Comprehensive review of emerging drug targets in traumatic brain injury (TBI): challenges and future scope

Traumatic brain injury (TBI) is a complex brain problem that causes significant morbidity and mortality among people of all age groups. The complex pathophysiology, varied symptoms, and inadequate treatment further precipitate the problem. Further, TBI produces several psychiatric problems and other related complications in post-TBI survival patients, which are often treated symptomatically or inadequately. Several approaches, including neuroprotective agents targeting several pathways of oxidative stress, neuroinflammation, cytokines, immune system GABA, glutamatergic, microglia, and astrocytes, are being tried by researchers to develop effective treatments or magic bullets to manage the condition effectively. The problem of TBI is therefore treated as a challenge among pharmaceutical scientists or researchers to develop drugs for the effective management of this problem. The goal of the present comprehensive review is to provide an overview of the several pharmacological targets, processes, and cellular pathways that researchers are focusing on, along with an update on their current state.

Ginsenoside Rg1 regulates astrocytes to promote angiogenesis in spinal cord injury via the JAK2/STAT3 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Ginseng (Panax ginseng C. A. Mey) is a common traditional Chinese medicine used for anti-inflammation, anti-apoptosis, anti-oxidative stress, and neuroprotection. Ginsenosides Rg1, the main active components isolated from ginseng, may be a feasible therapy for spinal cord injury (SCI).

AIMS OF THE STUDY

SCI causes endothelial cell death and blood vessel rupture, ultimately resulting in long-term neurological impairment. As a result, encouraging spinal angiogenesis may be a feasible therapy for SCI. This investigation aimed to validate the capacity of ginsenoside Rg1 in stimulating angiogenesis within the spinal cord.

MATERIALS AND METHODS

Rats with SCI were injected intraperitoneally with ginsenoside Rg1. The effectiveness of ginsenoside Rg1 was assessed using the motor function score and the motor-evoked potential (MEP). Immunofluorescence techniques were applied to identify the spinal cord's angiogenesis. Angiogenic factors were examined through Western Blot (WB) and Immunohistochemistry. Oxygen-glucose deprivation (OGD) was employed to establish the hypoxia-ischemia model in vitro, and astrocytes (As) were given ginsenoside Rg1 and co-cultured with spinal cord microvascular endothelial cells (SCMECs). Immunofluorescence, wound healing test, and tube formation assay were used to identify the co-cultured SCMECs' activity. Finally, network pharmacology analysis and siRNA transfection were applied to verify the mechanism of ginsenoside Rg1 promoting angiogenesis.

RESULTS

The rats with SCI treated with ginsenoside Rg1 indicated more significant functional recovery, more pronounced angiogenesis, and higher levels of angiogenic factor expression. In vitro, the co-culture system with ginsenoside Rg1 intervention improved SCMECs' capacity for proliferating, migrating, and forming tubes, possibly by promoting the expression of vascular endothelial growth factor (VEGF) in As via the janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway.

CONCLUSION

Ginsenoside Rg1 can regulate As to promote angiogenesis, which may help to understand the mechanism of promoting SCI recovery.

[Exogenous leptin improves cerebral ischemia-reperfusion-induced glutamate excitotoxic injury in mice by up-regulating GLT-1 and GLAST expression in astrocytes]

OBJECTIVE

To investigate the protective effect of exogenous leptin against focal cerebral ischemia-reperfusion (I/R) injury in mice and explore the underlying mechanism.

METHODS

A total of 100 C57BL/6 mice were randomly divided into 5 groups, including a sham-operated group, cerebral I/R model group, and 3 leptin treatment groups with intraperitoneal injections of 0.5, 1.0 or 2.0 leptin immediately after occlusion of the internal carotid artery. At 24 h after reperfusion, neurological function scores of the mice were assessed, and TTC staining was used to determine the area of cerebral infarction. The pathological changes in the cortical brain tissue of the mice were observed using HE staining, and degenerative damage of the cortical neurons were assessed with Fluoro-Jade C staining. The expression of glial fibrillary acidic protein in cortical brain tissues was detected using immunohistochemistry and Western blotting. In another 45 C57BL/6 mice with sham operation, I/R modeling, or leptin (1 mg/kg) treatment, glutamic acid in the cortical brain tissue was detected using glutamate assay, and cortical glutamate-aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) protein expressions were detected using immunohistochemistry.

RESULTS

Compared with the I/R model mice, the leptin-treated mice had significantly lower neurological deficit scores, smaller cerebral infarct area, milder pathologies in the cortical brain tissue, and lessened cortical neuronal damage with normal morphology and less excessive proliferation of the astrocytes. Leptin treatment significantly up-regulated the expressions of GLT-1 and GLAST and lowered the content of glutamic acid in the brain tissue of the I/R mice.

CONCLUSION

Exogenous leptin has obvious neuroprotective effect against cerebral I/R injury in mice, mediated probably by controlling excessive astrocyte proliferation and up-regulating cortical GLT-1 and GLAST expressions to reduce glutamate-mediated excitotoxic injury of the astrocytes.

Profiling the neuroimmune cascade in 3xTg-AD mice exposed to successive mild traumatic brain injuries

Repetitive mild traumatic brain injuries (rmTBI) sustained within a window of vulnerability can result in long term cognitive deficits, depression, and eventual neurodegeneration associated with tau pathology, amyloid beta (Aβ) plaques, gliosis, and neuronal and functional loss. However, a comprehensive study relating acute changes in immune signaling and glial reactivity to neuronal changes and pathological markers after single and repetitive mTBIs is currently lacking. In the current study, we addressed the question of how repeated injuries affect the brain neuroimmune response in the acute phase of injury (< 24 h) by exposing the 3xTg-AD mouse model of tau and Aβ pathology to successive (1x-5x) once-daily weight drop closed-head injuries and quantifying immune markers, pathological markers, and transcriptional profiles at 30 min, 4 h, and 24 h after each injury. We used young adult 2-4 month old 3xTg-AD mice to model the effects of rmTBI in the absence of significant tau and Aβ pathology. We identified pronounced sexual dimorphism in this model, with females eliciting more diverse changes after injury compared to males. Specifically, females showed: (1) a single injury caused a decrease in neuron-enriched genes inversely correlated with inflammatory protein expression and an increase in AD-related genes within 24 h, (2) each injury significantly increased a group of cortical cytokines (IL-1α, IL-1β, IL-2, IL-9, IL-13, IL-17, KC) and MAPK phospho-proteins (phospho-Atf2, phospho-Mek1), several of which co-labeled with neurons and correlated with phospho-tau, and (3) repetitive injury caused increased expression of genes associated with astrocyte reactivity and macrophage-associated immune function. Collectively our data suggest that neurons respond to a single injury within 24 h, while other cell types, including astrocytes, transition to inflammatory phenotypes within days of repetitive injury.

Inflammatory response in traumatic brain and spinal cord injury: The role of XCL1-XCR1 axis and T cells

BACKGROUND

Traumatic brain injury (TBI) and spinal cord injury (SCI) are acquired injuries to the central nervous system (CNS) caused by external forces that cause temporary or permanent sensory and motor impairments and the potential for long-term disability or even death. These conditions currently lack effective treatments and impose substantial physical, social, and economic burdens on millions of people and families worldwide. TBI and SCI involve intricate pathological mechanisms, and the inflammatory response contributes significantly to secondary injury in TBI and SCI. It plays a crucial role in prolonging the post-CNS trauma period and becomes a focal point for a potential therapeutic intervention. Previous research on the inflammatory response has traditionally concentrated on glial cells, such as astrocytes and microglia. However, increasing evidence highlights the crucial involvement of lymphocytes in the inflammatory response to CNS injury, particularly CD8+ T cells and NK cells, along with their downstream XCL1-XCR1 axis.

OBJECTIVE

This review aims to provide an overview of the role of the XCL1-XCR1 axis and the T-cell response in inflammation caused by TBI and SCI and identify potential targets for therapy.

METHODS

We conducted a comprehensive search of PubMed and Web of Science using relevant keywords related to the XCL1-XCR1 axis, T-cell response, TBI, and SCI.

RESULTS

This study examines the upstream and downstream pathways involved in inflammation caused by TBI and SCI, including interleukin-15 (IL-15), interleukin-12 (IL-12), CD8+ T cells, CD4+ T cells, NK cells, XCL1, XCR1+ dendritic cells, interferon-gamma (IFN-γ), helper T0 cells (Th0 cells), helper T1 cells (Th1 cells), and helper T17 cells (Th17 cells). We describe their proinflammatory effect in TBI and SCI.

CONCLUSIONS

The findings suggest that the XCL1-XCR1 axis and the T-cell response have great potential for preclinical investigations and treatments for TBI and SCI.

Ameliorative properties of quercetin in the treatment of traumatic brain injury: a mechanistic review based on underlying mechanisms

Traumatic brain injury (TBI) is a leading cause of disability worldwide, with an estimated annual incidence of 27-69 million. TBI is a severe condition that can lead to high mortality rates and long-term cognitive, behavioral, and physical impairments in young adults. It is a significant public health concern due to the lack of effective treatments available. Quercetin, a natural flavonoid found in various fruits and vegetables, has demonstrated therapeutic potential with anti-inflammatory, antioxidant, and neuroprotective properties. Recently, some evidence has accentuated the ameliorating effects of quercetin on TBI. This review discusses quercetin's ability to reduce TBI-related damage by regulating many cellular and molecular pathways. Quercetin in vitro and in vivo studies exhibit promise in reducing inflammation, oxidative stress, apoptosis, and enhancing cognitive function post-TBI. Further clinical investigation into quercetin's therapeutic potential as a readily available adjuvant in the treatment of TBI is warranted in light of these findings. This review adds to our knowledge of quercetin's potential in treating TBI by clarifying its mechanisms of action.

Dysregulated brain-gut axis in the setting of traumatic brain injury: review of mechanisms and anti-inflammatory pharmacotherapies

Traumatic brain injury (TBI) is a chronic and debilitating disease, associated with a high risk of psychiatric and neurodegenerative diseases. Despite significant advancements in improving outcomes, the lack of effective treatments underscore the urgent need for innovative therapeutic strategies. The brain-gut axis has emerged as a crucial bidirectional pathway connecting the brain and the gastrointestinal (GI) system through an intricate network of neuronal, hormonal, and immunological pathways. Four main pathways are primarily implicated in this crosstalk, including the systemic immune system, autonomic and enteric nervous systems, neuroendocrine system, and microbiome. TBI induces profound changes in the gut, initiating an unrestrained vicious cycle that exacerbates brain injury through the brain-gut axis. Alterations in the gut include mucosal damage associated with the malabsorption of nutrients/electrolytes, disintegration of the intestinal barrier, increased infiltration of systemic immune cells, dysmotility, dysbiosis, enteroendocrine cell (EEC) dysfunction and disruption in the enteric nervous system (ENS) and autonomic nervous system (ANS). Collectively, these changes further contribute to brain neuroinflammation and neurodegeneration via the gut-brain axis. In this review article, we elucidate the roles of various anti-inflammatory pharmacotherapies capable of attenuating the dysregulated inflammatory response along the brain-gut axis in TBI. These agents include hormones such as serotonin, ghrelin, and progesterone, ANS regulators such as beta-blockers, lipid-lowering drugs like statins, and intestinal flora modulators such as probiotics and antibiotics. They attenuate neuroinflammation by targeting distinct inflammatory pathways in both the brain and the gut post-TBI. These therapeutic agents exhibit promising potential in mitigating inflammation along the brain-gut axis and enhancing neurocognitive outcomes for TBI patients.

Underlying Mechanisms and Treatment of Cellular Senescence-Induced Biological Barrier Interruption and Related Diseases

Given its increasing prevalence, aging is of great concern to researchers worldwide. Cellular senescence is a physiological or pathological cellular state caused by aging and a prominent risk factor for the interruption of the integrity and functionality of human biological barriers. Health barriers play an important role in maintaining microenvironmental homeostasis within the body. The senescence of barrier cells leads to barrier dysfunction and age-related diseases. Cellular senescence has been reported to be a key target for the prevention of age-related barrier diseases, including Alzheimer's disease, Parkinson's disease, age-related macular degeneration, diabetic retinopathy, and preeclampsia. Drugs such as metformin, dasatinib, quercetin, BCL-2 inhibitors, and rapamycin have been shown to intervene in cellular senescence and age-related diseases. In this review, we conclude that cellular senescence is involved in age-related biological barrier impairment. We further outline the cellular pathways and mechanisms underlying barrier impairment caused by cellular senescence and describe age-related barrier diseases associated with senescent cells. Finally, we summarize the currently used anti-senescence pharmacological interventions and discuss their therapeutic potential for preventing age-related barrier diseases.

Fabrication and Characterization of Quad-Component Bioinspired Hydrogels to Model Elevated Fibrin Levels in Central Nervous Tissue Scaffolds

Multicomponent interpenetrating polymer network (mIPN) hydrogels are promising tissue-engineering scaffolds that could closely resemble key characteristics of native tissues. The mechanical and biochemical properties of mIPNs can be finely controlled to mimic key features of target cellular microenvironments, regulating cell-matrix interactions. In this work, we fabricated hydrogels made of collagen type I (Col I), fibrin, hyaluronic acid (HA), and poly (ethylene glycol) diacrylate (PEGDA) using a network-by-network fabrication approach. With these mIPNs, we aimed to develop a biomaterial platform that supports the in vitro culture of human astrocytes and potentially serves to assess the effects of the abnormal deposition of fibrin in cortex tissue and simulate key aspects in the progression of neuroinflammation typically found in human pathologies such as Alzheimer's disease (AD), Parkinson's disease (PD), and tissue trauma. Our resulting hydrogels closely resembled the complex modulus of AD human brain cortex tissue (~7.35 kPa), promoting cell spreading while allowing for the modulation of fibrin and hyaluronic acid levels. The individual networks and their microarchitecture were evaluated using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Human astrocytes were encapsulated in mIPNs, and negligible cytotoxicity was observed 24 h after the cell encapsulation.

The role of astrocyte in neuroinflammation in traumatic brain injury

Traumatic brain injury (TBI), a significant contributor to mortality and morbidity worldwide, is a devastating condition characterized by initial mechanical damage followed by subsequent biochemical processes, including neuroinflammation. Astrocytes, the predominant glial cells in the central nervous system, play a vital role in maintaining brain homeostasis and supporting neuronal function. Nevertheless, in response to TBI, astrocytes undergo substantial phenotypic alternations and actively contribute to the neuroinflammatory response. This article explores the multifaceted involvement of astrocytes in neuroinflammation subsequent to TBI, with a particular emphasis on their activation, release of inflammatory mediators, modulation of the blood-brain barrier, and interactions with other immune cells. A comprehensive understanding the dynamic interplay between astrocytes and neuroinflammation in the condition of TBI can provide valuable insights into the development of innovative therapeutic approaches aimed at mitigating secondary damage and fostering neuroregeneration.

Inhibition of NFAT5-Dependent Astrocyte Swelling Alleviates Neuropathic Pain

Astrocyte swelling is implicated in various neurological disorders. However, whether astrocyte swelling contributes to neuropathic pain remains elusive. This study elucidates the pivotal role of the nuclear factor of activated T-cells 5 (NFAT5) emerges as a master regulator of astrocyte swelling in the spinal dorsal horn (SDH) during neuropathic pain. Despite the ubiquitous expression of NFAT5 protein in SDH cell types, it selectively induces swelling specifically in astrocytes, not in microglia. Mechanistically, NFAT5 directly controls the expression of the water channel aquaporin-4 (AQP4), a key regulator exclusive to astrocytes. Additionally, aurora kinase B (AURKB) orchestrates NFAT5 phosphorylation, enhancing its protein stability and nuclear translocation, thereby regulating AQP4 expression. The findings establish NFAT5 as a crucial regulator for neuropathic pain through the modulation of astrocyte swelling. The AURKB-NFAT5-AQP4 pathway in astrocytes emerges as a potential therapeutic target to combat neuropathic pain.

Astrocyte response to melatonin treatment in rats under high-carbohydrate high-fat diet

The involvement of consumption of high-carbohydrate high-fat (HCHF) diet in cognitive impairment is attributed, at least in part, to the activation of astrocytes, which contributes to the development of neuroinflammation, oxidative stress, and subsequent cognitive deficits. This study aimed to assess the influence of melatonin on cognitive impairment and astrogliosis induced by the HCHF diet in rats. Male Wistar rats were fed an HCHF diet for eight weeks to induce obesity and metabolic syndrome. Subsequently, they received oral melatonin treatment for four weeks at doses of 5 mg/kg, 10 mg/kg, and 30 mg/kg, alongside the HCHF diet. Cognitive function was evaluated using the Y-maze test, while the levels of proinflammatory cytokines, oxidative stress, and the number glial fibrillary acidic protein (GFAP) positive cells were assessed in the hippocampi and hypothalamus. The consumption of the HCHF diet resulted in weight gain, hyperlipidemia, impaired glucose tolerance, cognitive decline, neuroinflammation, oxidative stress damage, and astrogliosis in rats. Although melatonin treatment did not demonstrate beneficial effects on blood glucose and lipid metabolism, it improved the impaired working memory caused by the HCHF diet. Melatonin exhibited a dose-dependent reduction of astrogliosis, neuroinflammation, and lipid peroxidation while restored superoxide dismutase in the hippocampus and hypothalamus of HCHF diet-treated rats. These findings provide evidence that melatonin inhibits astrocyte activation, thereby attenuating inflammation and minimizing oxidative stress damage induced by the HCHF diet.

Neuroinflammation and acquired traumatic CNS injury: a mini review

Acquired traumatic central nervous system (CNS) injuries, including traumatic brain injury (TBI) and spinal cord injury (SCI), are devastating conditions with limited treatment options. Neuroinflammation plays a pivotal role in secondary damage, making it a prime target for therapeutic intervention. Emerging therapeutic strategies are designed to modulate the inflammatory response, ultimately promoting neuroprotection and neuroregeneration. The use of anti-inflammatory agents has yielded limited support in improving outcomes in patients, creating a critical need to re-envision novel approaches to both quell deleterious inflammatory processes and upend the progressive cycle of neurotoxic inflammation. This demands a comprehensive exploration of individual, age, and sex differences, including the use of advanced imaging techniques, multi-omic profiling, and the expansion of translational studies from rodents to humans. Moreover, a holistic approach that combines pharmacological intervention with multidisciplinary neurorehabilitation is crucial and must include both acute and long-term care for the physical, cognitive, and emotional aspects of recovery. Ongoing research into neuroinflammatory biomarkers could revolutionize our ability to predict, diagnose, and monitor the inflammatory response in real time, allowing for timely adjustments in treatment regimens and facilitating a more precise evaluation of therapeutic efficacy. The management of neuroinflammation in acquired traumatic CNS injuries necessitates a paradigm shift in our approach that includes combining multiple therapeutic modalities and fostering a more comprehensive understanding of the intricate neuroinflammatory processes at play.

Deplete and repeat: microglial CSF1R inhibition and traumatic brain injury

Traumatic brain injury (TBI) is a public health burden affecting millions of people. Sustained neuroinflammation after TBI is often associated with poor outcome. As a result, increased attention has been placed on the role of immune cells in post-injury recovery. Microglia are highly dynamic after TBI and play a key role in the post-injury neuroinflammatory response. Therefore, microglia represent a malleable post-injury target that could substantially influence long-term outcome after TBI. This review highlights the cell specific role of microglia in TBI pathophysiology. Microglia have been manipulated via genetic deletion, drug inhibition, and pharmacological depletion in various pre-clinical TBI models. Notably, colony stimulating factor 1 (CSF1) and its receptor (CSF1R) have gained much traction in recent years as a pharmacological target on microglia. CSF1R is a transmembrane tyrosine kinase receptor that is essential for microglia proliferation, differentiation, and survival. Small molecule inhibitors targeting CSF1R result in a swift and effective depletion of microglia in rodents. Moreover, discontinuation of the inhibitors is sufficient for microglia repopulation. Attention is placed on summarizing studies that incorporate CSF1R inhibition of microglia. Indeed, microglia depletion affects multiple aspects of TBI pathophysiology, including neuroinflammation, oxidative stress, and functional recovery with measurable influence on astrocytes, peripheral immune cells, and neurons. Taken together, the data highlight an important role for microglia in sustaining neuroinflammation and increasing risk of oxidative stress, which lends to neuronal damage and behavioral deficits chronically after TBI. Ultimately, the insights gained from CSF1R depletion of microglia are critical for understanding the temporospatial role that microglia develop in mediating TBI pathophysiology and recovery.

Contribution of ApoB-100/SORT1-Mediated Immune Microenvironment in Regulating Oxidative Stress, Inflammation, and Ferroptosis After Spinal Cord Injury

This study aims to explore the impacts of ApoB-100/SORT1-mediated immune microenvironment during acute spinal cord injury (SCI), and to investigate the potential mechanism. CB57BL/6 mice underwent moderate thoracic contusion injury to establish the SCI animal model, and received ApoB-100 lentivirus injection to interfere ApoB-100 level. Functional recovery was assessed using the Basso, Beattie, and Bresnahan (BBB) score and footprint analysis. Transmission electron microscopy was applied to observe the ultrastructure of the injured spinal cord tissue. Hematoxylin-eosin (HE) staining and Perls staining were conducted to assess histological changes and iron deposition. Biochemical factor and cytokines were detected using their commercial kits. M1/M2 macrophage markers were detected by immunofluorescence assay in vivo and by flow cytometry in vitro. HT22 neurons were simulated by lipopolysaccharide (LPS), followed by incubation with polarized macrophage medium to simulate the immune microenvironment of injured spinal cord in vitro. The local immune microenvironment is changed in SCI mice, accompanied with the occurrence of oxidative stress and the elevation of both M1 and M2 macrophages. Knockdown of ApoB-100 ameliorates oxidative stress and lipid disorder, and inhibits inflammation and ferroptosis in SCI mice. Importantly, knockdown of ApoB-100 can partly restrict M1 macrophages but does not change M2 macrophage proportion in SCI mice. Further, M1 macrophages are observed to attenuate the inflammatory response, oxidative stress, and ferroptosis levels of LPS-induced HT22 cells, which is further strengthened by SORT1 knockdown. Blockage of ApoB-100/SORT1-mediated immune microenvironment plays a protective role against SCI via inhibiting oxidative stress, inflammation, lipid disorders, and ferroptosis, providing novel insights of the targeted therapy of SCI.

Norepinephrine-Activated p38 MAPK Pathway Mediates Stress-Induced Cytotoxic Edema of Basolateral Amygdala Astrocytes

The amygdala is a core region in the limbic system that is highly sensitive to stress. Astrocytes are key players in stress disorders such as anxiety and depression. However, the effects of stress on the morphology and function of amygdala astrocytes and its potential mechanisms remain largely unknown. Hence, we performed in vivo and in vitro experiments using a restraint stress (RS) rat model and stress-induced astrocyte culture, respectively. Our data show that norepinephrine (NE) content increased, cytotoxic edema occurred, and aquaporin-4 (AQP4) expression was up-regulated in the basolateral amygdala (BLA) obtained from RS rats. Additionally, the p38 mitogen-activated protein kinase (MAPK) pathway was also observed to be significantly activated in the BLA of rats subjected to RS. The administration of NE to in vitro astrocytes increased the AQP4 level and induced cell edema. Furthermore, p38 MAPK signaling was activated. The NE inhibitor alpha-methyl-p-tyrosine (AMPT) alleviated cytotoxic edema in astrocytes, inhibited AQP4 expression, and inactivated the p38 MAPK pathway in RS rats. Meanwhile, in the in vitro experiment, the p38 MAPK signaling inhibitor SB203580 reversed NE-induced cytotoxic edema and down-regulated the expression of AQP4 in astrocytes. Briefly, NE-induced activation of the p38 MAPK pathway mediated cytotoxic edema in BLA astrocytes from RS rats. Thus, our data provide novel evidence that NE-induced p38 MAPK pathway activation may be one of the mechanisms leading to cytotoxic edema in BLA under stress conditions, which also could enable the development of an effective therapeutic strategy against cytotoxic edema in BLA under stress and provide new ideas for the treatment of neuropsychiatric diseases.

Involvement of Astrocytes in the Formation, Maintenance, and Function of the Blood-Brain Barrier

The blood-brain barrier (BBB) is a fundamental structure that protects the composition of the brain by determining which ions, metabolites, and nutrients are allowed to enter the brain from the blood or to leave it towards the circulation. The BBB is structurally composed of a layer of brain capillary endothelial cells (BCECs) bound to each other through tight junctions (TJs). However, its development as well as maintenance and properties are controlled by the other brain cells that contact the BCECs: pericytes, glial cells, and even neurons themselves. Astrocytes seem, in particular, to have a very important role in determining and controlling most properties of the BBB. Here, we will focus on these latter cells, since the comprehension of their roles in brain physiology has been continuously expanding, even including the ability to participate in neurotransmission and in complex functions such as learning and memory. Accordingly, pathological conditions that alter astrocytic functions can alter the BBB's integrity, thus compromising many brain activities. In this review, we will also refer to different kinds of in vitro BBB models used to study the BBB's properties, evidencing its modifications under pathological conditions.

Transcription Factor EB: A Promising Therapeutic Target for Ischemic Stroke

Transcription factor EB (TFEB) is an important endogenous defensive protein that responds to ischemic stimuli. Acute ischemic stroke is a growing concern due to its high morbidity and mortality. Most survivors suffer from disabilities such as numbness or weakness in an arm or leg, facial droop, difficulty speaking or understanding speech, confusion, impaired balance or coordination, or loss of vision. Although TFEB plays a neuroprotective role, its potential effect on ischemic stroke remains unclear. This article describes the basic structure, regulation of transcriptional activity, and biological roles of TFEB relevant to ischemic stroke. Additionally, we explore the effects of TFEB on the various pathological processes underlying ischemic stroke and current therapeutic approaches. The information compiled here may inform clinical and basic studies on TFEB, which may be an effective therapeutic drug target for ischemic stroke.

[The use of transcranial micropolarization in the acute period of severe traumatic brain injury in children]

Traumatic brain injury, which is often considered as a silent epidemic, is a public health problem. The duration of acute recovery period remains a commonly used criterion for injury severity and clinical management. In this connection, the first stage of medical rehabilitation is carried out in the conditions of resuscitation and neurosurgery department in the hospital providing specialized care. Rehabilitation techniques such as postural training, phase verticalization, individual kinesiotherapy, transcranial micropolarization and etc. are used.

OBJECTIVE

To assess the effectiveness of using transcranial micropolarization in acute period of severe traumatic brain injury in children.

MATERIAL AND METHODS

The study on the effectiveness of using transcranial micropolarization in acute period of severe traumatic brain injury in 85 children, divided into 2 groups, was carried out. The study group (42 patients) received the transcranial micropolarization on the 2nd day after severe traumatic brain injury. The control group (43 patients) received only rehabilitation in neurosurgery department. The neurological status in the patients of both groups was assessed on the 2nd day after severe traumatic brain injury in resuscitation department, and after 1, 3 and 6 months.

RESULTS AND CONCLUSION

The inclusion of transcranial micropolarization in the early medical rehabilitation of children with severe traumatic brain injury increases consciousness level in a shorter period of time, that predicts early patient's socialization.

Stress-induced Neuroinflammation of the Spinal Cord is Restrained by Cort113176 (Dazucorilant), A Specific Glucocorticoid Receptor Modulator

Glucocorticoids exert antiinflammatory, antiproliferative and immunosupressive effects. Paradoxically they may also enhance inflammation particularly in the nervous system, as shown in Cushing´ syndrome and neurodegenerative disorders of humans and models of human diseases. ."The Wobbler mouse model of amyotrophic lateral sclerosis shows hypercorticoidism and neuroinflammation which subsided by treatment with the glucocorticoid receptor (GR) modulator Dazucorilant (CORT113176). This effect suggests that GR mediates the chronic glucocorticoid unwanted effects. We now tested this hypothesis using a chronic stress model resembling the condition of the Wobbler mouse Male NFR/NFR mice remained as controls or were subjected to a restraining / rotation stress protocol for 3 weeks, with a group of stressed mice receiving CORT113176 also for 3 weeks. We determined the mRNAS or reactive protein for the proinflamatory factors HMGB1, TLR4, NFkB, TNFα, markers of astrogliosis (GFAP, SOX9 and acquaporin 4), of microgliosis (Iba, CD11b, P2RY12 purinergic receptor) as well as serum IL1β and corticosterone. We showed that chronic stress produced high levels of serum corticosterone and IL1β, decreased body and spleen weight, produced microgliosis and astrogliosis and increased proinflammatory mediators. In stressed mice, modulation of the GR with CORT113176 reduced Iba + microgliosis, CD11b and P2RY12 mRNAs, immunoreactive HMGB1 + cells, GFAP + astrogliosis, SOX9 and acquaporin expression and TLR4 and NFkB mRNAs vs. stress-only mice. The effects of CORT113176 indicate that glucocorticoids are probably involved in neuroinflammation. Thus, modulation of the GR would become useful to dampen the inflammatory component of neurodegenerative disorders.

Astrocyte-targeted siRNA delivery by adenosine-functionalized LNP in mouse TBI model

Traumatic brain injury (TBI) induces pro-inflammatory polarization of astrocytes and causes secondary disruption of the blood-brain barrier (BBB) and brain damage. Herein, we report a successful astrocyte-targeted delivery of small interfering RNA (siRNA) by ligand functionalized lipid nanoparticles (LNPs) formulated from adenosine-conjugated lipids and a novel ionizable lipid (denoted by Ad4 LNPs). Systemic administration of Ad4 LNPs carrying siRNA against TLR4 to the mice TBI model resulted in the specific internalization of the LNPs by astrocytes in the vicinity of damaged brain tissue. A substantial knockdown of TLR4 at both mRNA and protein levels in the brain was observed, which led to a significant decrease of key pro-inflammatory cytokines and an increase of key anti-inflammatory cytokines in serum. Dye leakage measurement suggested that the Ad4-LNP-mediated knockdown of TLR4 attenuated the TBI-induced BBB disruption. Together, our data suggest that Ad4 LNP is a promising vehicle for astrocyte-specific delivery of nucleic acid therapeutics.

Effect of Hyperbaric Oxygen Intervention on Oxidative Stress and Expression of Nerve Growth Factor in Patients with Craniocerebral Injury

Objective

To examine the impact of hyperbaric oxygen intervention on oxidative stress and nerve growth factor in patients with craniocerebral injury.

Methods

Using the random number table method, 40 patients with craniocerebral injury who were treated at the First People's Hospital of Nantong were randomly assigned to either the control group or the hyperbaric oxygen group, with 20 patients in each group. The control group received routine intervention for clinical traumatic brain injury, while the hyperbaric oxygen group received additional hyperbaric oxygen intervention during the 7 to 30 days of routine intervention. Indicators of oxidative stress and nerve growth factor levels were compared between the two groups at the time of admission and 30 days after therapy.

Results

The serum levels of superoxide dismutase, endothelium-derived relaxing factor-nitric oxide, and nerve growth factor in the hyperbaric oxygen group increased more significantly than in the control group. The serum malondialdehyde concentration was also significantly reduced in the hyperbaric oxygen group.

Conclusion

Hyperbaric oxygen intervention can successfully lower systemic oxidative stress response and increase the expression level of nerve growth factor in patients with craniocerebral injury.

The Rehabilitation Potential of Neurostimulation for Mild Traumatic Brain Injury in Animal and Human Studies

Neurostimulation carries high therapeutic potential, accompanied by an excellent safety profile. In this review, we argue that an arena in which these tools could provide breakthrough benefits is traumatic brain injury (TBI). TBI is a major health problem worldwide, with the majority of cases identified as mild TBI (mTBI). MTBI is of concern because it is a modifiable risk factor for dementia. A major challenge in studying mTBI is its inherent heterogeneity across a large feature space (e.g., etiology, age of injury, sex, treatment, initial health status, etc.). Parallel lines of research in human and rodent mTBI can be collated to take advantage of the full suite of neuroscience tools, from neuroimaging (electroencephalography: EEG; functional magnetic resonance imaging: fMRI; diffusion tensor imaging: DTI) to biochemical assays. Despite these attractive components and the need for effective treatments, there are at least two major challenges to implementation. First, there is insufficient understanding of how neurostimulation alters neural mechanisms. Second, there is insufficient understanding of how mTBI alters neural function. The goal of this review is to assemble interrelated but disparate areas of research to identify important gaps in knowledge impeding the implementation of neurostimulation.

Divergent Spatial Learning, Enhanced Neuronal Transcription, and Blood-Brain Barrier Disruption Develop During Recovery from Post-Injury Sleep Fragmentation

Traumatic brain injury (TBI) causes pathophysiology that may significantly decrease quality of life over time. A major propagator of this response is chronic, maladaptive neuroinflammation, which can be exacerbated by stressors such as sleep fragmentation (SF). This study determined whether post-TBI SF had lasting behavioral and inflammatory effects even with a period of recovery. To test this, male and female mice received a moderate lateral fluid percussion TBI or sham surgery. Half the mice were left undisturbed, and half were exposed to daily SF for 30 days. All mice were then undisturbed between 30 and 60 days post-injury (DPI), allowing mice to recover from SF (SF-R). SF-R did not impair global Barnes maze performance. Nonetheless, TBI SF-R mice displayed retrogression in latency to reach the goal box within testing days. These nuanced behavioral changes in TBI SF-R mice were associated with enhanced expression of neuronal processing/signaling genes and indicators of blood-brain barrier (BBB) dysfunction. Aquaporin-4 (AQP4) expression, a marker of BBB integrity, was differentially altered by TBI and TBI SF-R. For example, TBI enhanced cortical AQP4 whereas TBI SF-R mice had the lowest cortical expression of perivascular AQP4, dysregulated AQP4 polarization, and the highest number of CD45+ cells in the ipsilateral cortex. Altogether, post-TBI SF caused lasting, divergent behavioral responses associated with enhanced expression of neuronal transcription and BBB disruption even after a period of recovery from SF. Understanding lasting impacts from post-TBI stressors can better inform both acute and chronic post-injury care to improve long-term outcome post-TBI.

Single-nucleus transcriptomic mapping of blast-induced traumatic brain injury in mice hippocampus

As a significant type of traumatic brain injury (TBI), blast-induced traumatic brain injury (bTBI) frequently results in severe neurological and psychological impairments. Due to its unique mechanistic and clinical features, bTBI presents diagnostic and therapeutic challenges compared to other TBI forms. The hippocampus, an important site for secondary injury of bTBI, serves as a key niche for neural regeneration and repair post-injury, and is closely associated with the neurological outcomes of bTBI patients. Nonetheless, the pathophysiological alterations of hippocampus underpinning bTBI remain enigmatic, and a corresponding transcriptomic dataset for research reference is yet to be established. In this investigation, the single-nucleus RNA sequencing (snRNA-seq) technique was employed to sequence individual hippocampal nuclei of mice from bTBI and sham group. Upon stringent quality control, gene expression data from 17,278 nuclei were obtained, with the dataset's reliability substantiated through various analytical methods. This dataset holds considerable potential for exploring secondary hippocampal injury and neurogenesis mechanisms following bTBI, with important reference value for the identification of specific diagnostic and therapeutic targets for bTBI.

Exploring Astrocyte-Mediated Mechanisms in Sleep Disorders and Comorbidity

Astrocytes, the most abundant cells in the brain, are integral to sleep regulation. In the context of a healthy neural environment, these glial cells exert a profound influence on the sleep-wake cycle, modulating both rapid eye movement (REM) and non-REM sleep phases. However, emerging literature underscores perturbations in astrocytic function as potential etiological factors in sleep disorders, either as protopathy or comorbidity. As known, sleep disorders significantly increase the risk of neurodegenerative, cardiovascular, metabolic, or psychiatric diseases. Meanwhile, sleep disorders are commonly screened as comorbidities in various neurodegenerative diseases, epilepsy, and others. Building on existing research that examines the role of astrocytes in sleep disorders, this review aims to elucidate the potential mechanisms by which astrocytes influence sleep regulation and contribute to sleep disorders in the varied settings of brain diseases. The review emphasizes the significance of astrocyte-mediated mechanisms in sleep disorders and their associated comorbidities, highlighting the need for further research.

Curcumin, inflammation, and neurological disorders: How are they linked?

Background

Despite the extensive research in recent years, the current treatment modalities for neurological disorders are suboptimal. Curcumin, a polyphenol found in Curcuma genus, has been shown to mitigate the pathophysiology and clinical sequalae involved in neuroinflammation and neurodegenerative diseases.

Methods

We searched PubMed database for relevant publications on curcumin and its uses in treating neurological diseases. We also reviewed relevant clinical trials which appeared on searching PubMed database using 'Curcumin and clinical trials'.

Results

This review details the pleiotropic immunomodulatory functions and neuroprotective properties of curcumin, its derivatives and formulations in various preclinical and clinical investigations. The effects of curcumin on neurodegenerative diseases such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), brain tumors, epilepsy, Huntington's disorder (HD), ischemia, Parkinson's disease (PD), multiple sclerosis (MS), and traumatic brain injury (TBI) with a major focus on associated signalling pathways have been thoroughly discussed.

Conclusion

This review demonstrates curcumin can suppress spinal neuroinflammation by modulating diverse astroglia mediated cascades, ensuring the treatment of neurological disorders.

The role and potential therapeutic targets of astrocytes in central nervous system demyelinating diseases

Astrocytes play vital roles in the central nervous system, contributing significantly to both its normal functioning and pathological conditions. While their involvement in various diseases is increasingly recognized, their exact role in demyelinating lesions remains uncertain. Astrocytes have the potential to influence demyelination positively or negatively. They can produce and release inflammatory molecules that modulate the activation and movement of other immune cells. Moreover, they can aid in the clearance of myelin debris through phagocytosis and facilitate the recruitment and differentiation of oligodendrocyte precursor cells, thereby promoting axonal remyelination. However, excessive or prolonged astrocyte phagocytosis can exacerbate demyelination and lead to neurological impairments. This review provides an overview of the involvement of astrocytes in various demyelinating diseases, emphasizing the underlying mechanisms that contribute to demyelination. Additionally, we discuss the interactions between oligodendrocytes, oligodendrocyte precursor cells and astrocytes as therapeutic options to support myelin regeneration. Furthermore, we explore the role of astrocytes in repairing synaptic dysfunction, which is also a crucial pathological process in these disorders.

A2AR and traumatic brain injury

Accumulating evidence has revealed the adenosine 2A receptor is a key tuner for neuropathological and neurobehavioral changes following traumatic brain injury by experimental animal models and a few clinical trials. Here, we highlight recent data involving acute/sub-acute and chronic alterations of adenosine and adenosine 2A receptor-associated signaling in pathological conditions after trauma, with an emphasis of traumatic brain injury, including neuroinflammation, cognitive and psychiatric disorders, and other severe consequences. We expect this would lead to the development of therapeutic strategies for trauma-related disorders with novel mechanisms of action.

A novel organotypic cortical slice culture model for traumatic brain injury: molecular changes induced by injury and mesenchymal stromal cell secretome treatment

Traumatic brain injury (TBI) is a major worldwide neurological disorder with no neuroprotective treatment available. Three-dimensional (3D) in vitro models of brain contusion serving as a screening platform for drug testing are lacking. Here we developed a new in vitro model of brain contusion on organotypic cortical brain slices and tested its responsiveness to mesenchymal stromal cell (MSC) derived secretome. A focal TBI was induced on organotypic slices by an electromagnetic impactor. Compared to control condition, a temporal increase in cell death was observed after TBI by propidium iodide incorporation and lactate dehydrogenase release assays up to 48 h post-injury. TBI induced gross neuronal loss in the lesion core, with disruption of neuronal arborizations measured by microtubule-associated protein-2 (MAP-2) immunostaining and associated with MAP-2 gene down-regulation. Neuronal damage was confirmed by increased levels of neurofilament light chain (NfL), microtubule associated protein (Tau) and ubiquitin C-terminal hydrolase L1 (UCH-L1) released into the culture medium 48 h after TBI. We detected glial activation with microglia cells acquiring an amoeboid shape with less ramified morphology in the contusion core. MSC-secretome treatment, delivered 1 h post-injury, reduced cell death in the contusion core, decreased NfL release in the culture media, promoted neuronal reorganization and improved microglia survival/activation. Our 3D in vitro model of brain contusion recapitulates key features of TBI pathology. We showed protective effects of MSC-secretome, suggesting the model stands as a tractable medium/high throughput, ethically viable, and pathomimetic biological asset for testing new cell-based therapies.

Traumatic brain injury and immunological outcomes: the double-edged killer

Traumatic brain injury (TBI) is a significant cause of mortality and morbidity worldwide resulting from falls, car accidents, sports, and blast injuries. TBI is characterized by severe, life-threatening consequences due to neuroinflammation in the brain. Contact and collision sports lead to higher disability and death rates among young adults. Unfortunately, no therapy or drug protocol currently addresses the complex pathophysiology of TBI, leading to the long-term chronic neuroinflammatory assaults. However, the immune response plays a crucial role in tissue-level injury repair. This review aims to provide a better understanding of TBI's immunobiology and management protocols from an immunopathological perspective. It further elaborates on the risk factors, disease outcomes, and preclinical studies to design precisely targeted interventions for enhancing TBI outcomes.

Role of astrocytes in sleep deprivation: accomplices, resisters, or bystanders?

Sleep plays an essential role in all studied animals with a nervous system. However, sleep deprivation leads to various pathological changes and neurobehavioral problems. Astrocytes are the most abundant cells in the brain and are involved in various important functions, including neurotransmitter and ion homeostasis, synaptic and neuronal modulation, and blood-brain barrier maintenance; furthermore, they are associated with numerous neurodegenerative diseases, pain, and mood disorders. Moreover, astrocytes are increasingly being recognized as vital contributors to the regulation of sleep-wake cycles, both locally and in specific neural circuits. In this review, we begin by describing the role of astrocytes in regulating sleep and circadian rhythms, focusing on: (i) neuronal activity; (ii) metabolism; (iii) the glymphatic system; (iv) neuroinflammation; and (v) astrocyte-microglia cross-talk. Moreover, we review the role of astrocytes in sleep deprivation comorbidities and sleep deprivation-related brain disorders. Finally, we discuss potential interventions targeting astrocytes to prevent or treat sleep deprivation-related brain disorders. Pursuing these questions would pave the way for a deeper understanding of the cellular and neural mechanisms underlying sleep deprivation-comorbid brain disorders.

Research progress of neuroinflammation-related cells in traumatic brain injury: A review

Neuroinflammation after traumatic brain injury (TBI) is related to chronic neurodegenerative diseases and is one of the causes of acute secondary injury after TBI. Therefore, it is particularly important to clarify the role of cellular mechanisms in the neuroinflammatory response after TBI. The objective of this article is to understand the involvement of cells during the TBI inflammatory response (for instance, astrocytes, microglia, and oligodendrocytes) and shed light on the recent progress in the stimulation and interaction of granulocytes and lymphocytes, to provide a novel approach for clinical research. We searched articles in PubMed published between 1950 and 2023, using the following keywords: TBI, neuroinflammation, inflammatory cells, neuroprotection, clinical. Articles for inclusion in this paper were finalized based on their novelty, representativeness, and relevance to the main arguments of this review. We found that the neuroinflammatory response after TBI includes the activation of glial cells, the release of inflammatory mediators in the brain, and the recruitment of peripheral immune cells. These inflammatory responses not only induce secondary brain damage, but also have a role in repairing the nervous system to some extent. However, not all of the mechanisms of cell-to-cell interactions have been well studied. After TBI, clinical treatment cannot simply suppress the inflammatory response, and the inflammatory phenotype of patients' needs to be defined according to their specific conditions after injury. Clinical trials of personalized inflammation regulation therapy for specific patients should be carried out in order to improve the prognosis of patients.

Profiling the neuroimmune cascade in 3xTg mice exposed to successive mild traumatic brain injuries

Repetitive mild traumatic brain injuries (rmTBI) sustained within a window of vulnerability can result in long term cognitive deficits, depression, and eventual neurodegeneration associated with tau pathology, amyloid beta (Aβ) plaques, gliosis, and neuronal and functional loss. However, we have limited understanding of how successive injuries acutely affect the brain to result in these devastating long-term consequences. In the current study, we addressed the question of how repeated injuries affect the brain in the acute phase of injury (<24hr) by exposing the 3xTg-AD mouse model of tau and Aβ pathology to successive (1x, 3x, 5x) once-daily weight drop closed-head injuries and quantifying immune markers, pathological markers, and transcriptional profiles at 30min, 4hr, and 24hr after each injury. We used young adult mice (2-4 months old) to model the effects of rmTBI relevant to young adult athletes, and in the absence of significant tau and Aβ pathology. Importantly, we identified pronounced sexual dimorphism, with females eliciting more differentially expressed proteins after injury compared to males. Specifically, females showed: 1) a single injury caused a decrease in neuron-enriched genes inversely correlated with inflammatory protein expression as well as an increase in AD-related genes within 24hr, 2) each injury significantly increased expression of a group of cortical cytokines (IL-1α, IL-1β, IL-2, IL-9, IL-13, IL-17, KC) and MAPK phospho-proteins (phospho-Atf2, phospho-Mek1), several of which were co-labeled with neurons and correlated with phospho-tau, and 3) repetitive injury caused increased expression of genes associated with astrocyte reactivity and immune function. Collectively our data suggest that neurons respond to a single injury within 24h, while other cell types including astrocytes transition to inflammatory phenotypes within days of repetitive injury.

Stress and traumatic brain injury: An inherent bi-directional relationship with temporal and synergistic complexities

Traumatic brain injury (TBI) and stress are prevalent worldwide and can both result in life-altering health problems. While stress often occurs in the absence of TBI, TBI inherently involves some element of stress. Furthermore, because there is pathophysiological overlap between stress and TBI, it is likely that stress influences TBI outcomes. However, there are temporal complexities in this relationship (e.g., when the stress occurs) that have been understudied despite their potential importance. This paper begins by introducing TBI and stress and highlighting some of their possible synergistic mechanisms including inflammation, excitotoxicity, oxidative stress, hypothalamic-pituitary-adrenal axis dysregulation, and autonomic nervous system dysfunction. We next describe different temporal scenarios involving TBI and stress and review the available literature on this topic. In doing so we find initial evidence that in some contexts stress is a highly influential factor in TBI pathophysiology and recovery, and vice versa. We also identify important knowledge gaps and suggest future research avenues that will increase our understanding of this inherent bidirectional relationship and could one day result in improved patient care.

Narrative review of roles of astrocytes in subarachnoid hemorrhage

Background and Objective

Astrocytes play an important role in healthy brain function, including the development and maintenance of blood-brain barrier (BBB), structural support, brain homeostasis, neurovascular coupling and secretion of neuroprotective factors. Reactive astrocytes participate in various pathophysiology after subarachnoid hemorrhage (SAH) including neuroinflammation, glutamate toxicity, brain edema, vasospasm, BBB disruption, cortical spreading depolarization (SD).

Methods

We searched PubMed up to 31 May, 2022 and evaluated the articles for screening and inclusion for subsequent systemic review. We found 198 articles with the searched terms. After exclusion based on the selection criteria, we selected 30 articles to start the systemic review.

Key Content and Findings

We summarized the response of astrocytes induced by SAH. Astrocytes are critical for brain edema formation, BBB reconstruction and neuroprotection in the acute stage of SAH. Astrocytes clear extracellular glutamate by increasing the uptake of glutamate and Na+/K+ ATPase activity after SAH. Neurotrophic factors released by astrocytes contribute to neurological recovery after SAH. Meanwhile, Astrocytes also form glial scars which hinder axon regeneration, produce proinflammatory cytokines, free radicals, and neurotoxic molecules.

Conclusions

Preclinical studies showed that therapeutic targeting the astrocytes response could have a beneficial effect in ameliorating neuronal injury and cognitive impairment after SAH. Clinical trials and preclinical animal studies are still urgently needed in order to determine where astrocytes stand in various pathway of brain damage and repair after SAH and, above all, to develop therapeutic approaches which benefit patient outcomes.

Exosomes; multifaceted nanoplatform for targeting brain cancers

At the moment, anaplastic changes within the brain are challenging due to the complexity of neural tissue, leading to the inefficiency of therapeutic protocols. The existence of a cellular interface, namely the blood-brain barrier (BBB), restricts the entry of several macromolecules and therapeutic agents into the brain. To date, several nano-based platforms have been used in laboratory settings and in vivo conditions to overcome the barrier properties of BBB. Exosomes (Exos) are one-of-a-kind of extracellular vesicles with specific cargo to modulate cell bioactivities in a paracrine manner. Regarding unique physicochemical properties and easy access to various biofluids, Exos provide a favorable platform for drug delivery and therapeutic purposes. Emerging data have indicated that Exos enable brain penetration of selective cargos such as bioactive factors and chemotherapeutic compounds. Along with these statements, the application of smart delivery approaches can increase delivery efficiency and thus therapeutic outcomes. Here, we highlighted the recent advances in the application of Exos in the context of brain tumors.

Partial Ablation of Astrocytes Exacerbates Cerebral Infiltration of Monocytes and Neuronal Loss After Brain Stab Injury in Mice

In traumatic brain injury (TBI), mechanical injury results in instantaneous tissue damages accompanied by subsequent pro-inflammatory cascades composed of microgliosis and astrogliosis. However, the interactive roles between microglia and astrocytes during the pathogenesis of TBI remain unclear and sometimes debatable. In this study, we used a forebrain stab injury mouse model to investigate the pathological role of reactive astrocytes in cellular and molecular changes of inflammatory response following TBI. In the ipsilateral hemisphere of stab-injured brain, monocyte infiltration and neuronal loss, as well as increased elevated astrogliosis, microglia activation and inflammatory cytokines were observed. To verify the role of reactive astrocytes in TBI, local and partial ablation of astrocytes was achieved by stereotactic injection of diphtheria toxin in the forebrain of Aldh1l1-CreER^T2::Ai9::iDTR transgenic mice which expressed diphtheria toxin receptor (DTR) in astrocytes after tamoxifen induction. This strategy achieved about 20% of astrocytes reduction at the stab site as validated by immunofluorescence co-staining of GFAP with tdTomato-positive astrocytes. Interestingly, reduction of astrocytes showed increased microglia activation and monocyte infiltration, accompanied with increased severity in stab injury-induced neuronal loss when compared with DTR^-/- mice, together with elevation of inflammatory chemokines such as CCL2, CCL5 and CXCL10 in astrogliosis-reduced mice. Collectively, our data verified the interactive role of astrocytes as an immune modulator in suppressing inflammatory responses in the injured brain. Schematic diagram shows monocyte infiltration and neuronal loss, as well as increased elevated astrogliosis, microglia activation and chemokines were observed in the injured site after stab injury. Local and partial ablation of astrocytes led to increased microglia activation and monocyte infiltration, accompanied with increased severity in neuronal loss together with elevation of inflammatory chemokines as compared with control mice subjected stab injury.

Roles of Astrocytic Endothelin ETB Receptor in Traumatic Brain Injury

Traumatic brain injury (TBI) is an intracranial injury caused by accidents, falls, or sports. The production of endothelins (ETs) is increased in the injured brain. ET receptors are classified into distinct types, including ET_A receptor (ET_A-R) and ET_B receptor (ET_B-R). ET_B-R is highly expressed in reactive astrocytes and upregulated by TBI. Activation of astrocytic ET_B-R promotes conversion to reactive astrocytes and the production of astrocyte-derived bioactive factors, including vascular permeability regulators and cytokines, which cause blood-brain barrier (BBB) disruption, brain edema, and neuroinflammation in the acute phase of TBI. ET_B-R antagonists alleviate BBB disruption and brain edema in animal models of TBI. The activation of astrocytic ET_B receptors also enhances the production of various neurotrophic factors. These astrocyte-derived neurotrophic factors promote the repair of the damaged nervous system in the recovery phase of patients with TBI. Thus, astrocytic ET_B-R is expected to be a promising drug target for TBI in both the acute and recovery phases. This article reviews recent observations on the role of astrocytic ET_B receptors in TBI.

Therapeutic Hypothermia Attenuates Cortical Interneuron Loss after Cerebral Ischemia in Near-Term Fetal Sheep

Therapeutic hypothermia significantly improves outcomes after neonatal hypoxic-ischemic (HI) encephalopathy but is only partially protective. There is evidence that cortical inhibitory interneuron circuits are particularly vulnerable to HI and that loss of interneurons may be an important contributor to long-term neurological dysfunction in these infants. In the present study, we examined the hypothesis that the duration of hypothermia has differential effects on interneuron survival after HI. Near-term fetal sheep received sham ischemia or cerebral ischemia for 30 min, followed by cerebral hypothermia from 3 h after ischemia end and continued up to 48 h, 72 h, or 120 h recovery. Sheep were euthanized after 7 days for histology. Hypothermia up to 48 h recovery resulted in moderate neuroprotection of glutamate decarboxylase (GAD)⁺ and parvalbumin⁺ interneurons but did not improve survival of calbindin⁺ cells. Hypothermia up to 72 h recovery was associated with significantly increased survival of all three interneuron phenotypes compared with sham controls. By contrast, while hypothermia up to 120 h recovery did not further improve (or impair) GAD⁺ or parvalbumin⁺ neuronal survival compared with hypothermia up to 72 h, it was associated with decreased survival of calbindin⁺ interneurons. Finally, protection of parvalbumin⁺ and GAD⁺ interneurons, but not calbindin⁺ interneurons, with hypothermia was associated with improved recovery of electroencephalographic (EEG) power and frequency by day 7 after HI. The present study demonstrates differential effects of increasing the duration of hypothermia on interneuron survival after HI in near-term fetal sheep. These findings may contribute to the apparent preclinical and clinical lack of benefit of very prolonged hypothermia.

The Imbalance of Astrocytic Mitochondrial Dynamics Following Blast-Induced Traumatic Brain Injury

Mild blast-induced traumatic brain injury (bTBI) is a modality of injury that has been of major concern considering a large number of military personnel exposed to explosive blast waves. bTBI results from the propagation of high-pressure static blast forces and their subsequent energy transmission within brain tissue. Exposure to this overpressure energy causes a diffuse injury that leads to acute cell damage and, if chronic, leads to detrimental long-term cognitive deficits. The literature presents a neuro-centric approach to the role of mitochondria dynamics dysfunction in bTBI, and changes in astrocyte-specific mitochondrial dynamics have not been characterized. The balance between fission and fusion events is known as mitochondrial dynamics. As a result of fission and fusion, the mitochondrial structure is constantly altering its shape to respond to physiological stimuli or stress, which in turn affects mitochondrial function. Astrocytic mitochondria are recognized to play an essential role in overall brain metabolism, synaptic transmission, and neuron protection. Mitochondria are vulnerable to injury insults, leading to the increase in mitochondrial fission, a mechanism controlled by the GTPase dynamin-related protein (Drp1) and the phosphorylation of Drp1 at serine 616 (p-Drp1^s616). This site is critical to mediate the Drp1 translocation to mitochondria to promote fission events and consequently leads to fragmentation. An increase in mitochondrial fragmentation could have negative consequences, such as promoting an excessive generation of reactive oxygen species or triggering cytochrome c release. The aim of the present study was to characterize the unique pattern of astrocytic mitochondrial dynamics by exploring the role of DRP1 with a combination of in vitro and in vivo bTBI models. Differential remodeling of the astrocytic mitochondrial network was observed, corresponding with increases in p-Drp1^S616 four hours and seven days post-injury. Further, results showed a time-dependent reactive astrocyte phenotype transition in the rat hippocampus. This discovery can lead to innovative therapeutics targets to help prevent the secondary injury cascade after blast injury that involves mitochondria dysfunction.

Overexpressed cold inducible RNA-binding protein improves cell viability and EGF expression in glial cells

BACKGROUND

Cold inducible RNA-binding protein (CIRP) is a key protein in the hypothermic therapy. Highly expressed CIRP exerts a neuroprotective effect on neurons. The aim of this study is to provide the evidence of the protective effects of CIRP on the glial cells and explore the downstream pathway of CIRP.

RESULTS

The results of this study demonstrated that the cell viability of the glial cells with CIRP overexpression was increased significantly compared to the control. With CIRP overexpression, the epidermal growth factor (EGF) mRNA expression was found increasing significantly and the mRNA expressions of derived neurotrophic factor (BDNF), bcl-2, vascular endothelial growth factor (VEGF) and nerve growth factor (NGF) were not upregulated compared to the control. EGF and CIRP co-expression was demonstrated on the glial cells. With CIRP expression, EGF expression on the glial cells was increased statistically compared to the control.

CONCLUSION

CIRP overexpression increases the cell viability of the glial cells, exerting a neuroprotective effect. EGF expression is activated on the glial cells with CIRP overexpression, implying a pathway of CIRP neuroprotection via EGF activation.

Active immunotherapy against pathogenic Cis pT231-tau suppresses neurodegeneration in traumatic brain injury mouse models

Traumatic brain injury (TBI), characterized by acute neurological impairment, is associated with a higher incidence of neurodegenerative diseases, particularly chronic traumatic encephalopathy (CTE), Alzheimer's disease (AD), and Parkinson's disease (PD), whose hallmarks include hyperphosphorylated tau protein. Recently, phosphorylated tau at Thr231 has been shown to exist in two distinct cis and trans conformations. Moreover, targeted elimination of cis P-tau by passive immunotherapy with an appropriate mAb that efficiently suppresses tau-mediated neurodegeneration in severe TBI mouse models has proven to be a useful tool to characterize the neurotoxic role of cis P-tau as an early driver of the tauopathy process after TBI. Here, we investigated whether active immunotherapy can develop sufficient neutralizing antibodies to specifically target and eliminate cis P-tau in the brain of TBI mouse models. First, we explored the therapeutic efficacy of two different vaccines. C57BL/6 J mice were immunized with either cis or trans P-tau conformational peptides plus adjuvant. After rmTBI in mice, we found that cis peptide administration developed a specific Ab that precisely targeted and neutralized cis P-tau, inhibited the development of neuropathology and brain dysfunction, and restored various structural and functional sequelae associated with TBI in chronic phases. In contrast, trans P-tau peptide application not only lacked neuroprotective properties, but also contributed to a number of neuropathological features, including progressive TBI-induced neuroinflammation, widespread tau-mediated neurodegeneration, worsening functional deficits, and brain atrophy. Taken together, our results suggest that active immunotherapy strategies against pathogenic cis P-tau can halt the process of tauopathy and would have profound clinical implications.

Preclinical findings reveal the pharmacological targets of ferulic acid in the treatment of traumatic brain injury

Traumatic brain injury (TBI) is characterized by cellular damage and inflammation in lesioned brain tissue. Ferulic acid has been shown to have a melioration effect on neurological functions. However, the active pharmacological effects and the underlying mechanisms of ferulic acid against TBI remain unclear. On the basis of network pharmacology and molecular docking methodology, this study aimed to investigate the beneficial effects of ferulic acid in treating TBI, and characterized the detailed biotargets and mechanisms of these actions. The identified core targets were validated via in silico simulation. We identified 91 overlapping targets associated with ferulic acid and TBI. In-silico simulation analysis validated the putative core targets of tumor protein p53, mitogen-activated protein kinase (MAPK) 1, and estrogen receptor 1. The Gene Ontology-enriched annotations and findings were largely associated with cell proliferation, apoptosis, and inflammation in nerve cells. Additional Kyoto Encyclopedia of Genes and Genomes enrichment analysis unmasked the pharmacological pathways of ferulic acid in treating TBI, including the MAPK signaling pathway and hypoxia-inducible factor-1 signaling pathway. Bioinformatic analyses and findings provide a new preclinical strategy for revealing the core targets and network pathways of ferulic acid in treating TBI. Moreover, some bioinformatic findings were computationally validated in silico for exhibiting the neuroprotective action of ferulic acid against TBI.

Potential neurotoxic activity of diverse molecules released by astrocytes

Astrocytes are the main support cells of the central nervous system. They also participate in neuroimmune reactions. In response to pathological and immune stimuli, astrocytes transform to reactive states characterized by increased release of inflammatory mediators. Some of these molecules are neuroprotective and inflammation resolving while others, including reactive oxygen species (ROS), nitric oxide (NO), matrix metalloproteinase (MMP)- 9, L-glutamate, and tumor necrosis factor α (TNF), are well-established toxins known to cause damage to surrounding cells and tissues. We hypothesized that similar to microglia, the brain immune cells, reactive astrocytes can release a broader set of diverse molecules that are potentially neurotoxic. A literature search was conducted to identify such molecules using the following two criteria: 1) evidence of their expression and secretion by astrocytes and 2) direct neurotoxic action. This review describes 14 structurally diverse molecules as less-established astrocyte neurotoxins, including C-X-C motif chemokine ligand (CXCL)10, CXCL12/CXCL12(5-67), FS-7-associated surface antigen ligand (FasL), macrophage inflammatory protein (MIP)- 2α, TNF-related apoptosis inducing ligand (TRAIL), pro-nerve growth factor (proNGF), pro-brain-derived neurotrophic factor (proBDNF), chondroitin sulfate proteoglycans (CSPGs), cathepsin (Cat)B, group IIA secretory phospholipase A₂ (sPLA₂-IIA), amyloid beta peptides (Aβ), high mobility group box (HMGB)1, ceramides, and lipocalin (LCN)2. For some of these molecules, further studies are required to establish either their direct neurotoxic effects or the full spectrum of stimuli that induce their release by astrocytes. Only limited studies with human-derived astrocytes and neurons are available for most of these potential neurotoxins, which is a knowledge gap that should be addressed in the future. We also summarize available evidence of the role these molecules play in select neuropathologies where reactive astrocytes are a key feature. A comprehensive understanding of the full spectrum of neurotoxins released by reactive astrocytes is key to understanding neuroinflammatory diseases characterized by the adverse activation of these cells and may guide the development of novel treatment strategies.

Exosome Derived from Human Neural Stem Cells Improves Motor Activity and Neurogenesis in a Traumatic Brain Injury Model

Traumatic brain injury (TBI) is a leading cause of mortality and long-lasting disability globally. Although novel treatment options have been investigated, no effective therapeutic opportunities for TBI exist. Accumulating studies demonstrated that the paracrine mechanisms of stem cells may allow them to orchestrate regenerative processes after TBI. So far, very little attention has been paid to the beneficial effects of human neural stem cells (hNSCs) in comparison to their exosomes as a paracrine mechanism. This study is aimed at comparing the effect of hNSCs with their exosomes in a TBI model. For in vitro assessments, we cultured hNSCs using the neurosphere method and isolated hNSC-derived exosomes from culture supernatants. For in vivo experiments, male rats were divided into three groups (n = 8/group): TBI group: rats were subjected to a unilateral mild cortical impact; hNSC group: rats received a single intralesional injection of 2 × 10⁶ hNSCs after TBI; and exosome group: rats received a single intralesional injection of 63 μg protein of hNSC-derived exosomes after TBI. Neurological assessments, neuroinflammation, and neurogenesis were performed at the predetermined time points after TBI. Our results indicated that the administration of exosomes improved the neurobehavioral performance measured by the modified neurological severity score (mNSS) on day 28 after TBI. Furthermore, exosomes inhibited the expression of reactive astrocytes as a key regulator of neuroinflammation marked by GFAP at the protein level, while enhancing the expression of Doublecortin (DCX) as a neurogenesis marker at the mRNA level. On the other hand, we observed that the expression of stemness markers (SOX2 and Nestin) was elevated in the hNSC group compared to the exosome and TBI groups. To sum up, our results demonstrated that the superior effects of exosomes versus parent hNSCs could be mediated by improving mNSS score and increasing DCX in TBI. Considerably, more work will need to be done to determine the beneficial effects of exosomes versus parent cells in the context of TBI.

Evaluation of decompressive craniectomy in mice after severe traumatic brain injury

Decompressive craniectomy (DC) is of great significance for relieving acute intracranial hypertension and saving lives after traumatic brain injury (TBI). In this study, a severe TBI mouse model was created using controlled cortical impact (CCI), and a surgical model of DC was established. Furthermore, a series of neurological function assessments were performed to better understand the pathophysiological changes after DC. In this study, mice were randomly allocated into three groups, namely, CCI group, CCI+DC group, and Sham group. The mice in the CCI and CCI+DC groups received CCI after opening a bone window, and after brain injury, immediately returned the bone window to simulate skull condition after a TBI. The CCI+DC group underwent DC and contused tissue removal 6 h after CCI. The mice in the CCI group underwent the same anesthesia process; however, no further treatment of the bone window and trauma was performed. The mice in the Sham group underwent anesthesia and the process of opening the skin and bone window, but not in the CCI group. Changes in Modified Neurological Severity Score, rotarod performance, Morris water maze, intracranial pressure (ICP), cerebral blood flow (CBF), brain edema, blood–brain barrier (BBB), inflammatory factors, neuronal apoptosis, and glial cell expression were evaluated. Compared with the CCI group, the CCI+DC group had significantly lower ICP, superior neurological and motor function at 24 h after injury, and less severe BBB damage after injury. Most inflammatory cytokine expressions and the number of apoptotic cells in the brain tissue of mice in the CCI+DC group were lower than in the CCI group at 3 days after injury, with markedly reduced astrocyte and microglia expression. However, the degree of brain edema in the CCI+DC group was greater than in the CCI group, and neurological and motor functions, as well as spatial cognitive and learning ability, were significantly poorer at 14 days after injury.