Microglial-derived microparticles mediate neuroinflammation after traumatic brain injury

Brain incoming call from glia during neuroinflammation: Roles of extracellular vesicles

The functionality of the central nervous system (CNS) relies on the connection, integration, and the exchange of information among neural cells. The crosstalk among glial cells and neurons is pivotal for a series of neural functions, such as development of the nervous system, electric conduction, synaptic transmission, neural circuit establishment, and brain homeostasis. Glial cells are crucial players in the maintenance of brain functionality in physiological and disease conditions. Neuroinflammation is a common pathological process in various brain disorders, such as neurodegenerative diseases, and infections. Glial cells, including astrocytes, microglia, and oligodendrocytes, are the main mediators of neuroinflammation, as they can sense and respond to brain insults by releasing pro-inflammatory or anti-inflammatory factors. Recent evidence indicates that extracellular vesicles (EVs) are pivotal players in the intercellular communication that underlies physiological and pathological processes. In particular, glia-derived EVs play relevant roles in modulating neuroinflammation, either by promoting or inhibiting the activation of glial cells and neurons, or by facilitating the clearance or propagation of pathogenic proteins. The involvement of EVs in neurodegenerative diseases such as Alzheimer's Disease (AD), Parkinson's Disease (PD), Huntington's Disease (HD), and Multiple Sclerosis (MS)- which share hallmarks such as neuroinflammation and oxidative stress to DNA damage, alterations in neurotrophin levels, mitochondrial impairment, and altered protein dynamics- will be dissected, showing how EVs act as pivotal cell-cell mediators of toxic stimuli, thereby propagating degeneration and cell death signaling. Thus, this review focuses on the EVs secreted by microglia, astrocytes, oligodendrocytes and in neuroinflammatory conditions, emphasizing on their effects on neurons and on central nervous system functions, considering both their beneficial and detrimental effects.

Traumatic brain injury: Symptoms to systems in the 21st century

Severe traumatic brain injury (TBI) is a devastating injury with a mortality of ∼ 25-30 %. Despite decades of high-quality research, no drug therapy has reduced mortality. Why is this so? We argue two contributing factors for the lack of effective drug therapies include the use of specific-pathogen free (SPF) animals for translational research and the flawed practice of single-nodal targeting for drug design. A revolution is required to better understand how the whole body responds to TBI, identify new markers of its progression, and discover new system-acting drugs to treat it. In this review, we present a brief history of TBI, discuss its system's pathophysiology and propose a new research strategy for the 21st century. TBI progression develops from injury signals radiating from the primary impact, which can cause local ischemia, hemorrhage, excitotoxicity, cellular depolarization, immune dysfunction, sympathetic hyperactivity, blood-brain barrier breach, coagulopathy and whole-body dysfunction. Metabolic reprograming of immune cells drives neuroinflammation and secondary injury processes. We propose if sympathetic hyperactivity and immune cell activation can be corrected early, cardiovascular function and endothelial-glycocalyx-mitochondrial coupling can be restored, and secondary injury minimized with improved patient outcomes. The therapeutic goal is to switch the injury phenotype to a healing phenotype by restoring homeostasis and maintaining sufficient tissue O2 delivery. We have been developing a small-volume fluid therapy comprising adenosine, lidocaine and magnesium (ALM) to treat TBI and have shown that it blunts the CNS-stress response, supports cardiovascular function and reduces secondary injury. Future research will investigate its suitability for human translation.

Connecting cellular mechanisms and extracellular vesicle cargo in traumatic brain injury

Traumatic brain injury is followed by a cascade of dynamic and complex events occurring at the cellular level. These events include: diffuse axonal injury, neuronal cell death, blood-brain barrier break down, glial activation and neuroinflammation, edema, ischemia, vascular injury, energy failure, and peripheral immune cell infiltration. The timing of these events post injury has been linked to injury severity and functional outcome. Extracellular vesicles are membrane bound secretory vesicles that contain markers and cargo pertaining to their cell of origin and can cross the blood-brain barrier. These qualities make extracellular vesicles intriguing candidates for a liquid biopsy into the pathophysiologic changes occurring at the cellular level post traumatic brain injury. Herein, we review the most commonly reported cargo changes in extracellular vesicles from clinical traumatic brain injury samples. We then use knowledge from animal and in vitro models to help infer what these changes may indicate regrading cellular responses post traumatic brain injury. Future research should prioritize labeling extracellular vesicles with markers for distinct cell types across a range of timepoints post traumatic brain injury.

Microglia in retinal diseases: From pathogenesis towards therapeutic strategies

Microglia, a widely dispersed cohort of immune cells in the retina, are intricately involved in a diverse range of pivotal biological processes, including inflammation, vascular development, complement activation, antigen presentation, and phagocytosis. Within the retinal milieu, microglia are crucial for the clearance of dead cells and cellular debris, release of anti-inflammatory agents, and orchestration of vascular network remodeling to maintain homeostasis. In addition, microglia are key mediators of neuroinflammation. Triggered by oxidative stress, elevated intraocular pressure, genetic anomalies, and immune dysregulation, microglia release numerous inflammatory cytokines, contributing to the pathogenesis of various retinal disorders. Recent studies on the ontogeny and broad functions of microglia in the retina have elucidated their characteristics during retinal development, homeostasis, and disease. Furthermore, therapeutic strategies that target microglia and their effector cytokines have been developed and shown positive results for some retinal diseases. Therefore, we systematically review the microglial ontogeny in the retina, elucidate their dual roles in retinal homeostasis and disease pathogenesis, and demonstrate microglia-based targeted therapeutic strategies for retinal diseases.

Analysis of miRNA Expression Profiles in Traumatic Brain Injury (TBI) and Their Correlation with Survival and Severity of Injury

Traumatic brain injury (TBI) is the leading cause of traumatic death worldwide and is a public health problem associated with high mortality and morbidity rates, with a significant socioeconomic burden. The diagnosis of brain injury may be difficult in some cases or may leave diagnostic doubts, especially in mild trauma with insignificant pathological brain changes or in cases where instrumental tests are negative. Therefore, in recent years, an important area of research has been directed towards the study of new biomarkers, such as micro-RNAs (miRNAs), which can assist clinicians in the diagnosis, staging, and prognostic evaluation of TBI, as well as forensic pathologists in the assessment of TBI and in the estimation of additional relevant data, such as survival time. The aim of this study is to investigate the expression profiles (down- and upregulation) of a panel of miRNAs in subjects deceased with TBI in order to assess, verify, and define the role played by non-coding RNA molecules in the different pathophysiological mechanisms of brain damage. This study also aims to correlate the detected expression profiles with survival time, defined as the time elapsed between the traumatic event and death, and with the severity of the trauma. This study was conducted on 40 cases of subjects deceased with TBI (study group) and 10 cases of subjects deceased suddenly from non-traumatic causes (control group). The study group was stratified according to the survival time and the severity of the trauma. The selection of miRNAs to be examined was based on a thorough literature review. Analyses were performed on formalin-fixed, paraffin-embedded (FFPE) brain tissue samples, with a first step of total RNA extraction and a second step of quantification of the selected miRNAs of interest. This study showed higher expression levels in cases compared to controls for miR-16, miR-21, miR-130a, and miR-155. In contrast, lower expression levels were found in cases compared to controls for miR-23a-3p. There were no statistically significant differences in the expression levels between cases and controls for miR-19a. In cases with short survival, the expression levels of miR-16-5p and miR-21-5p were significantly higher. In cases with long survival, miR-21-5p was significantly lower. The expression levels of miR-130a were significantly higher in TBI cases with short and middle survival. In relation to TBI severity, miR-16-5p and miR-21-5p expression levels were significantly higher in the critical-fatal TBI subgroup. Conclusions: This study provides evidence for the potential of the investigated miRNAs as predictive biomarkers to discriminate between TBI cases and controls. These miRNAs could improve the postmortem diagnosis of TBI and also offer the possibility to define the survival time and the severity of the trauma. The analysis of miRNAs could become a key tool in forensic investigations, providing more precise and detailed information on the nature and extent of TBI and helping to define the circumstances of death.

Progress in extracellular vesicle homeostasis as it relates to cardiovascular diseases

Extracellular vesicles (EVs) are involved in both physiological and pathological processes in many organ systems and are essential in mediating intercellular communication and maintaining organismal homeostasis. It is helpful to propose new strategies for disease treatment by elucidating the mechanisms of EV release and sorting. An increasing number of studies have shown that there is specific homeostasis in EVs, which is helpful for the human body to carry out physiological activities. In contrast, an EV homeostasis im-balance promotes or accelerates disease onset and development. Alternatively, regulating the quality of EVs can maintain homeostasis and even achieve the purpose of treating conditions. An analysis of the role of EV homeostasis in the onset and development of cardiovascular disease is presented in this review. This article also summarizes the methods that regulate EV homeostasis and their application in cardiovascular diseases. In particular, this study focuses on the connection between EV steady states and the cardiovascular system and the potential value of EVs in treating cardiovascular diseases.

Therapeutic potential of microglia-derived extracellular vesicles in ischemic stroke

Ischemic stroke (IS) is a debilitating neurological disorder with limited treatment options. Extracellular vesicles (EVs) have emerged as crucial lipid bilayer particles derived from various cell types that facilitate intercellular communication and enable the exchange of proteins, lipids, and genetic material. Microglia are resident brain cells that play a crucial role in brain development, maintenance of neuronal networks, and injury repair. They secrete numerous extracellular vesicles in different states. Recent evidence indicates that microglia-derived extracellular vesicles (M-EVs) actively participate in mediating various biological processes, such as neuroprotection and neurorepair, in stroke, making them an excellent therapeutic approach for treating this condition. This review comprehensively summarizes the latest research on M-EVs in stroke and explores their potential as novel therapeutic targets for this disorder. Additionally, it provides an overview of the effects and functions of M-EVs on stroke recovery to facilitate the development of clinically relevant therapies for IS.

Persistent neuroinflammation and functional deficits in a murine model of decompression sickness

We hypothesized that early intra-central nervous system (CNS) responses in a murine model of decompression sickness (DCS) would be reflected by changes in the microparticles (MPs) that exit the brain via the glymphatic system, and due to systemic responses the MPs would cause inflammatory changes lasting for many days leading to functional neurological deficits. Elevations on the order of threefold of blood-borne inflammatory MPs, neutrophil activation, glymphatic flow, and neuroinflammation in cerebral cortex and hippocampus were found in mice at 12 days after exposure to 760 kPa of air for 2 h. Mice also exhibited a significant decline in memory and locomotor activity, as assessed by novel object recognition and rotarod testing. Similar inflammatory changes in blood, neuroinflammation, and functional impairments were initiated in naïve mice by injection of filamentous (F-) actin-positive MPs, but not F-actin-negative MPs, obtained from decompressed mice. We conclude that high pressure/decompression stress establishes a systemic inflammatory process that results in prolonged neuroinflammation and functional impairments in the mouse decompression model.NEW & NOTEWORTHY Elevated glymphatic flow due to astrocyte and microglial activation from high-pressure exposure triggers release of microparticles (MPs) to the circulation where neutrophil activation and production of filamentous (F)-actin expressing MPs result in a persistent feed-forward neuroinflammatory cycle and functional deficits lasting for at least 12 days.

Deferoxamine Induces Autophagy Following Traumatic Brain Injury via TREM2 on Microglia

Previous studies have indicated that iron disorder, inflammation, and autophagy play an important role in traumatic brain injury (TBI). The triggering receptor expressed on myeloid cells 2 (TREM2), an immunoglobulin superfamily transmembrane receptor, is involved in inflammation. However, the role of TREM2 in modulating the microglia response in TBI has been rarely investigated. The present study aimed to investigate if the iron chelator deferoxamine (DFO) could ameliorate TBI through autophagy mediated by the TREM2. TBI was developed by the controlled cortical impact (CCI) mouse model and stretching of individual primary cortical microglia taken from the tissue of the rat brain. DFO was intraperitoneally used for intervention. Western blotting assay, qRT-PCR, TUNEL staining, immunofluorescence staining, confocal microscopy analysis, transmission electron microscopy, H&E staining, brain water content measurement, and the neurobehavioral assessments were performed. TREM2 expression was up-regulated in cortex of TBI mice model and in microglia stretching model, which was attenuated by DFO. After the mice were subjected to CCI, DFO treatment significantly up-regulated the protein levels of autophagy compared with the TBI group at 3 days and caused an increase of autophagic vacuoles. Treatment with DFO reduced TBI-induced cell apoptosis, cerebral edema, neuroinflammation, and motor function impairment in mice, at least partly via the mTOR signaling pathway that facilitates the TREM2 activity. The results indicated that the maintenance of iron homeostasis by DFO plays neuroprotection by modulating the inflammatory response to TBI through TREM2-mediated autophagy. This study suggested that TREM2-mediated autophagy might be a potential target for therapeutic intervention in TBI.

Microparticles in Human Perspiration as an Inflammatory Response Index

A blood component analysis is an early step for evaluating inflammatory disorders, but it can be unfeasible in some settings. This pilot study assessed whether extracellular vesicle (EV) changes in perspiration are parallel to those occurring in blood as an alternative or complementary option to diagnose an inflammatory response. In parallel studies, EVs were analyzed in perspiration and blood obtained before and after five self-contained underwater breathing apparatus (SCUBA) divers at the National Aquarium in Baltimore performed a dive to 3.98 m of sea water for 40 min, and five non-divers performed an exercise routine at ambient atmospheric pressure. The results demonstrated that microparticles (MPs) are present in perspiration, their numbers increase in the blood in response to SCUBA diving, and the interleukin (IL)-1β content increases. In contrast, while blood-borne MPs became elevated in response to terrestrial exercise, no statistically significant increases occurred in perspiration, and there were no changes in IL-1β. There were no statistically significant elevations in the exosomes in perspiration or blood in response to SCUBA diving and few changes following terrestrial exercise. These findings suggest that an MP perspiration analysis could be a non-invasive method for detecting inflammatory responses that can occur due to the oxidative stress associated with SCUBA diving.

Elevated extracellular particle concentration in plasma predicts in-hospital mortality after severe trauma

Background

Extracellular particles (EPs), particularly extracellular vesicles, play a crucial role in regulating various pathological mechanisms, including immune dysregulations post-trauma. Their distinctive expression of cell-specific markers and regulatory cargo such as cytokines or micro-ribonucleic acid suggests their potential as early biomarkers for organ-specific damage and for identifying patients at risk for complications and mortality. Given the critical need for reliable and easily assessable makers to identify at-risk patients and guide therapeutic decisions, we evaluated the early diagnostic value of circulating EPs regarding outcomes in severely injured multiple-trauma patients.

Methods

Plasma samples were collected from 133 severely injured trauma patients (Injury Severity Score (ISS) ≥16) immediately upon arrival at the emergency department (ED). Patients were categorized into survivors and non-survivors. Injury characteristics and outcomes related to sepsis, pneumonia, or early (<1 day after admission) and late mortality were assessed. Circulating EPs, cytokine profiles, and blood counts of platelets and leukocytes were determined. Receiver operating characteristic analyses were conducted.

Results

Despite no significant differences in injury pattern or severity, non-survivors exhibited significantly elevated counts of circulating EPs compared to survivors. The optimal cut-off for EPs <200 nm indicating non-survivors was 17380/µl plasma, with a sensitivity of 77% and a specificity of 61% in predicting in-hospital mortality. Later non-survivors received significantly higher numbers of units of packed red blood cells [8.54 ± 5.45 vs. 1.29 ± 0.36 units], had higher serum lactate [38.00 ± 7.51 vs. 26.98 ± 1.58 mg/dL], significantly lower platelet counts [181.30 ± 18.06 vs. 213.60 ± 5.85 *10³/µL] and lower heart rates [74.50 ± 4.93 vs. 90.18 ± 2.06 beats/minute] upon arrival at the ED compared to survivors.

Conclusion

Our results demonstrate the high diagnostic potential of elevated concentrations of circulating EPs <200 nm for identifying patients at risk of mortality after severe trauma. This parameter shows comparable sensitivity to established clinical predictors. Early evaluation of EPs concentration could complement assessment markers in guiding early therapeutic decisions.

Hypochlorous acid derived from microglial myeloperoxidase could mediate high-mobility group box 1 release from neurons to amplify brain damage in cerebral ischemia-reperfusion injury

Myeloperoxidase (MPO) plays critical role in the pathology of cerebral ischemia-reperfusion (I/R) injury via producing hypochlorous acid (HOCl) and inducing oxidative modification of proteins. High-mobility group box 1 (HMGB1) oxidation, particularly disulfide HMGB1 formation, facilitates the secretion and release of HMGB1 and activates neuroinflammation, aggravating cerebral I/R injury. However, the cellular sources of MPO/HOCl in ischemic brain injury are unclear yet. Whether HOCl could promote HMGB1 secretion and release remains unknown. In the present study, we investigated the roles of microglia-derived MPO/HOCl in mediating HMGB1 translocation and secretion, and aggravating the brain damage and blood-brain barrier (BBB) disruption in cerebral I/R injury. In vitro, under the co-culture conditions with microglia BV cells but not the single culture conditions, oxygen-glucose deprivation/reoxygenation (OGD/R) significantly increased MPO/HOCl expression in PC12 cells. After the cells were exposed to OGD/R, MPO-containing exosomes derived from BV2 cells were released and transferred to PC12 cells, increasing MPO/HOCl in the PC12 cells. The HOCl promoted disulfide HMGB1 translocation and secretion and aggravated OGD/R-induced apoptosis. In vivo, SD rats were subjected to 2 h of middle cerebral artery occlusion (MCAO) plus different periods of reperfusion. Increased MPO/HOCl production was observed at the reperfusion stage, accomplished with enlarged infarct volume, aggravated BBB disruption and neurological dysfunctions. Treatment of MPO inhibitor 4-aminobenzoic acid hydrazide (4-ABAH) and HOCl scavenger taurine reversed those changes. HOCl was colocalized with cytoplasm transferred HMGB1, which was blocked by taurine in rat I/R-injured brain. We finally performed a clinical investigation and found that plasma HOCl concentration was positively correlated with infarct volume and neurological deficit scores in ischemic stroke patients. Taken together, we conclude that ischemia/hypoxia could activate microglia to release MPO-containing exosomes that transfer MPO to adjacent cells for HOCl production; Subsequently, the production of HOCl could mediate the translocation and secretion of disulfide HMGB1 that aggravates cerebral I/R injury. Furthermore, plasma HOCl level could be a novel biomarker for indexing brain damage in ischemic stroke patients.

Identification of novel blood-based extracellular vesicles biomarker candidates with potential specificity for traumatic brain injury in polytrauma patients

Objective

The goal of this study was to identify changes in extracellular vesicles (EV) surface proteins specific to traumatic brain injury (TBI), which could be used as a diagnostic and prognostic tool in polytrauma patients.

Summary Background Data

Known serum TBI-specific biomarkers (S100B, NSE, and GFAP), which can predict the severity and outcome of isolated TBI, lose their predictive value in the presence of additional extracranial injuries. Extracellular vesicles (EVs) are released from cells in response to various stimuli and carry specific cargo/surface molecules that could be used for tracking injury-responding cells.

Methods

EVs were isolated using size exclusion chromatography (SEC) from the plasma of two groups of patients (with isolated TBI, ISS≥16, AIShead≥4, n=10; and polytraumatized patients without TBI ISS≥16, AIShead=0, n=10) collected in the emergency room and 48 h after trauma. EVs' surface epitope expression was investigated using a neurospecific multiplex flow cytometry assay and compared with healthy controls (n=10). Three enrichments of EV epitopes found to be specific to TBI were validated by western blot.

Results

The expression of 10 EV epitopes differed significantly among the patient and control groups, and five of these epitopes (CD13, CD196, MOG, CD133, and MBP) were TBI-specific. The increased expression of CD196, CD13, and MOG-positive EVs was validated by western blot.

Conclusion

Our data showed that TBI is characterized by a significant increase of CD13, CD196, MOG, CD133, and MBP-positive EVs in patients' plasma. A high level of MOG-positive EVs negatively correlated with the Glasgow Coma Scale score at admission and could be an indicator of poor neurological status.

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.

Serum amyloid A and mitochondrial DNA in extracellular vesicles are novel markers for detecting traumatic brain injury in a mouse model

This study investigates the potential use of circulating extracellular vesicles' (EVs) DNA and protein content as biomarkers for traumatic brain injury (TBI) in a mouse model. Despite an overall decrease in EVs count during the acute phase, there was an increased presence of exosomes (CD63+ EVs) during acute and an increase in microvesicles derived from microglia/macrophages (CD11b+ EVs) and astrocytes (ACSA-2+ EVs) in post-acute TBI phases, respectively. Notably, mtDNA exhibited an immediate elevation post-injury. Neuronal (NFL) and microglial (Iba1) markers increased in the acute, while the astrocyte marker (GFAP) increased in post-acute TBI phases. Novel protein biomarkers (SAA, Hp, VWF, CFD, CBG) specific to different TBI phases were also identified. Biostatistical modeling and machine learning identified mtDNA and SAA as decisive markers for TBI detection. These findings emphasize the importance of profiling EVs' content and their dynamic release as an innovative diagnostic approach for TBI in liquid biopsies.

Traumatic brain injury disrupts state-dependent functional cortical connectivity in a mouse model

Traumatic brain injury (TBI) is the leading cause of death in young people and can cause cognitive and motor dysfunction and disruptions in functional connectivity between brain regions. In human TBI patients and rodent models of TBI, functional connectivity is decreased after injury. Recovery of connectivity after TBI is associated with improved cognition and memory, suggesting an important link between connectivity and functional outcome. We examined widespread alterations in functional connectivity following TBI using simultaneous widefield mesoscale GCaMP7c calcium imaging and electrocorticography (ECoG) in mice injured using the controlled cortical impact (CCI) model of TBI. Combining CCI with widefield cortical imaging provides us with unprecedented access to characterize network connectivity changes throughout the entire injured cortex over time. Our data demonstrate that CCI profoundly disrupts functional connectivity immediately after injury, followed by partial recovery over 3 weeks. Examining discrete periods of locomotion and stillness reveals that CCI alters functional connectivity and reduces theta power only during periods of behavioral stillness. Together, these findings demonstrate that TBI causes dynamic, behavioral state-dependent changes in functional connectivity and ECoG activity across the cortex.

Extracellular Vesicles in the Central Nervous System: A Novel Mechanism of Neuronal Cell Communication

Cell-to-cell communication is essential for the appropriate development and maintenance of homeostatic conditions in the central nervous system. Extracellular vesicles have recently come to the forefront of neuroscience as novel vehicles for the transfer of complex signals between neuronal cells. Extracellular vesicles are membrane-bound carriers packed with proteins, metabolites, and nucleic acids (including DNA, mRNA, and microRNAs) that contain the elements present in the cell they originate from. Since their discovery, extracellular vesicles have been studied extensively and have opened up new understanding of cell-cell communication; they may cross the blood-brain barrier in a bidirectional way from the bloodstream to the brain parenchyma and vice versa, and play a key role in brain-periphery communication in physiology as well as pathology. Neurons and glial cells in the central nervous system release extracellular vesicles to the interstitial fluid of the brain and spinal cord parenchyma. Extracellular vesicles contain proteins, nucleic acids, lipids, carbohydrates, and primary and secondary metabolites. that can be taken up by and modulate the behaviour of neighbouring recipient cells. The functions of extracellular vesicles have been extensively studied in the context of neurodegenerative diseases. The purpose of this review is to analyse the role extracellular vesicles extracellular vesicles in central nervous system cell communication, with particular emphasis on the contribution of extracellular vesicles from different central nervous system cell types in maintaining or altering central nervous system homeostasis.

A New Paradigm in Spinal Cord Injury Therapy: from Cell-free Treatment to Engineering Modifications

Spinal cord injury (SCI) is an intractable and poorly prognostic neurological disease, and current treatments are still unable to cure it completely and avoid sequelae. Extracellular vesicles (EVs), as important carriers of intercellular communication and pharmacological effects, are considered to be the most promising candidates for SCI therapy because of their low toxicity and immunogenicity, their ability to encapsulate endogenous bioactive molecules (e.g., proteins, lipids, and nucleic acids), and their ability to cross the blood-brain/cerebrospinal barriers. However, poor targeting, low retention rate, and limited therapeutic efficacy of natural EVs have bottlenecked EVs-based SCI therapy. A new paradigm for SCI treatment will be provided by engineering modified EVs. Furthermore, our limited understanding of the role of EVs in SCI pathology hinders the rational design of novel EVbased therapeutic approaches. In this study, we review the pathophysiology after SCI, especially the multicellular EVs-mediated crosstalk; briefly describe the shift from cellular to cell-free therapies for SCI treatment; discuss and analyze the issues related to the route and dose of EVs administration; summarize and present the common strategies for EVs drug loading in the treatment of SCI and point out the shortcomings of these drug loading methods; finally, we analyze and highlight the feasibility and advantages of bio-scaffold-encapsulated EVs for SCI treatment, providing scalable insights into cell-free therapy for SCI.

Microglia-derived extracellular vesicles in homeostasis and demyelination/remyelination processes

Microglia (MG) play a crucial role as the predominant myeloid cells in the central nervous system and are commonly activated in multiple sclerosis. They perform essential functions under normal conditions, such as actively surveying the surrounding parenchyma, facilitating synaptic remodeling, engulfing dead cells and debris, and protecting the brain against infectious pathogens and harmful self-proteins. Extracellular vesicles (EVs) are diverse structures enclosed by a lipid bilayer that originate from intracellular endocytic trafficking or the plasma membrane. They are released by cells into the extracellular space and can be found in various bodily fluids. EVs have recently emerged as a communication mechanism between cells, enabling the transfer of functional proteins, lipids, different RNA species, and even fragments of DNA from donor cells. MG act as both source and recipient of EVs. Consequently, MG-derived EVs are involved in regulating synapse development and maintaining homeostasis. These EVs also directly influence astrocytes, significantly increasing the release of inflammatory cytokines like IL-1β, IL-6, and TNF-α, resulting in a robust inflammatory response. Furthermore, EVs derived from inflammatory MG have been found to inhibit remyelination, whereas Evs produced by pro-regenerative MG effectively promote myelin repair. This review aims to provide an overview of the current understanding of MG-derived Evs, their impact on neighboring cells, and the cellular microenvironment in normal conditions and pathological states, specifically focusing on demyelination and remyelination processes.

The Impact of Juvenile Microglia Transcriptomics on the Adult Brain Regeneration after Cerebral Ischemia

Microglial cells play a pivotal role in the brain's health and operation through all stages of life and in the face of illness. The contributions of microglia during the developmental phase of the brain markedly contrast with their contributions in the brain of adults after injury. Enhancing our understanding of the pathological mechanisms that involve microglial activity in brains as they age and in cerebrovascular conditions is crucial for informing the creation of novel therapeutic approaches. In this work we provide results on microglia transcriptomics in the juvenile vs injured adult brain and its impact on adult brain regeneration after cerebral ischemia. During fetal brain development, microglia cells are involved in gliogenesis, angiogenesis, axonal outgrowth, synaptogenesis, neurogenesis and synaptic reorganization by engulfing neuronal extensions. Within the mature, intact brain, microglial cells exhibit reduced movement of their processes in response to minimal neuronal activity, while they continuously monitor their surroundings and clear away cellular debris. Following a stroke in the adult brain, inflammation, neurodegeneration, or disruptions in neural equilibrium trigger alterations in both the genetic blueprint and the structure and roles of microglia, a state often described as "activated" microglia. Such genetic shifts include a notable increase in the pathways related to phagosomes, lysosomes, and the presentation of antigens, coupled with a rise in the expression of genes linked to cell surface receptors. We conclude that a comparison of microglia transcriptomic activity during brain development and post-stroke adult brain might provide us with new clues about how neurodegeneration occurs in the adult brain. This information could very useful to develop drugs to slow down or limit the post-stroke pathology and improve clinical outcome.

Extracellular vesicles derived from monomeric α-synuclein-treated microglia ameliorate neuroinflammation by delivery of miRNAs targeting PRAK

Parkinson's disease (PD) is characterized by the formation of Lewy body, which mainly contains misfolded α-synuclein. Microglial activation plays a role in neurodegeneration. The pathologically oligomeric α-synuclein promotes inflammatory microglia, while physiologically monomeric α-synuclein induces anti-inflammatory microglia, the relationship between these two forms in activating microglia and the molecular mechanism is essentially unknown. In this study, using in vivo and in vitro models, we challenged primary or BV2 microglia with exogenous stimuli including α-synuclein. We examined microglial activation and the underlying mechanism by Western blot, RT-PCR, ELISA, IF, FCM, miRNA sequencing and bioinformatic analysis. Oligomeric α-synuclein activatedmicroglia via theinvolvement of the PRAK/MK5 pathway. The specific PRAK inhibitor GLPG0259 could mitigate microglial activation insulted by oligomeric α-synuclein. Monomeric α-synuclein regulated theanti-inflammatory microglia by delivering microglia-derived extracellular vesicles (EVs) in vitro and in vivo. Furthersequencingand bioinformatic analysis of microglial EVs-associated miRNAs indicatedthatmost of these miRNAs targeted PRAK. These results suggest that PRAK serves as an intersection in microglial activation when challenged with conformationally different α-synuclein. EVs derived from microglia treated with monomeric α-synuclein promote anti-inflammatory microglia by delivering miRNAs that target PRAK into recipient microglia.

Ilexchinene, a new seco-ursane triterpenoid from the leaves of Ilex chinensis with therapeutic effect on neuroinflammation by attenuating the MAPK/NF-κB signaling pathway

BACKGROUND

Neuroinflammation is a vital factor participating in the whole pathogenetic process of diverse neurodegenerative disorders, but accessible clinical drugs are still insufficient due to their inefficacy and side effects. Triterpenoids are reported to possess potential anti-neuroinflammatory activities, and the leaves of Ilex chinensis are a commonly used herbal medicine containing many ursane-type and oleanane-type triterpenoids. However, the novel triterpenoids from I. chinensis and their underlying mechanisms are still elusive.

PURPOSE

To isolate novel seco-ursane triterpenoids with anti-neuroinflammatory effects from the leaves of I. chinensis and reveal their underlying mechanisms.

STUDY DESIGN AND METHODS

The novel compound was purified by column chromatography and identified by comprehensive spectroscopic experiments. The LPS-induced BV-2 cell model and LPS-induced acute murine brain inflammation model were used to assess the anti-neuroinflammatory effect of the structure and further understand its underlying mechanisms by cell viability, ELISA, Western blot analysis, qRT‒PCR analysis, behavior analysis, H&E staining, and immunofluorescence staining experiments.

RESULTS

Ilexchinene is a novel ursane-type triterpenoid with a rare 18,19-seco-ring skeleton that was first isolated and identified from I. chinensis. Ilexchinene evidently reduced the overexpression of inflammatory substances in vitro. A mechanistic study suggested that ilexchinene could decrease NF-κB activation to prevent the formation of the NLRP3 inflammasome in the early neuroinflammatory response; in addition, it could prevent the phosphorylation of ERK and JNK. In vivo, ilexchinene remarkably improved LPS-induced mouse behavioral deficits and diminished the number of overactivated microglial cells. Furthermore, ilexchinene evidently diminished the overexpression of inflammatory substances in mouse brains. A mechanistic study confirmed that ilexchinene markedly suppressed the MAPK/NF-κB pathway to relieve the neuroinflammatory response.

CONCLUSION

We identified a novel 18,19-seco-ursane triterpenoid from the leaves of I. chinensis and revealed its underlying mechanism of neuroinflammation for the first time. These findings suggest that ilexchinene might possess promising therapeutic effects in neuroinflammation.

Multiomic integration reveals neuronal-extracellular vesicle coordination of gliotic responses in degeneration

In the central nervous system (CNS), including in the retina, neuronal-to-glial communication is critical for maintaining tissue homeostasis including signal transmission, transfer of trophic factors, and in the modulation of inflammation. Extracellular vesicle (EV)-mediated transport of molecular messages to regulate these processes has been suggested as a mechanism by which bidirectional communication between neuronal and glial cells can occur. In this work we employed multiomics integration to investigate the role of EV communication pathways from neurons to glial cells within the CNS, using the mouse retina as a readily accessible representative CNS tissue. Further, using a well-established model of degeneration, we aimed to uncover how dysregulation of homeostatic messaging between neurons and glia via EV can result in retinal and neurodegenerative diseases. EV proteomics, glia microRNA (miRNA) Open Array and small RNA sequencing, and retinal single cell sequencing were performed, with datasets integrated and analysed computationally. Results demonstrated that exogenous transfer of neuronal miRNA to glial cells was mediated by EV and occurred as a targeted response during degeneration to modulate gliotic inflammation. Taken together, our results support a model of neuronal-to-glial communication via EV, which could be harnessed for therapeutic targeting to slow the progression of retinal-, and neuro-degenerations of the CNS.

Extracellular Vesicles: Therapeutic Potential in Central Nervous System Trauma by Regulating Cell Death

CNS (central nervous system) trauma, which is classified as SCI (spinal cord injury) and TBI (traumatic brain injury), is gradually becoming a major cause of accidental death and disability worldwide. Many previous studies have verified that the pathophysiological mechanism underlying cell death and the subsequent neuroinflammation caused by cell death are pivotal factors in the progression of CNS trauma. Simultaneously, EVs (extracellular vesicles), membrane-enclosed particles produced by almost all cell types, have been proven to mediate cell-to-cell communication, and cell death involves complex interactions among molecules. EVs have also been proven to be effective carriers of loaded bioactive components to areas of CNS trauma. Therefore, EVs are promising therapeutic targets to cure CNS trauma. However, the link between EVs and various types of cell death in the context of CNS trauma remains unknown. Therefore, in this review, we summarize the mechanism underlying EV effects, the relationship between EVs and cell death and the pathophysiology underlying EV effects on the CNS trauma based on information in published papers. In addition, we discuss the prospects of applying EVs to the CNS as feasible therapeutic strategies for CNS trauma in the future.

Neuroglial components of brain lesions may provide new therapeutic strategies for multiple sclerosis

Multiple sclerosis (MS) is a chronic autoimmune and demyelinating disease of the central nervous system (CNS) which leads to focal demyelinated lesions in the brain and spinal cord. Failure of remyelination contributes to chronic disability in young adults. Characterization of events occurring during the demyelination and remyelination processes and those of which subsequently limit remyelination or contribute to demyelination can provide the possibility of new therapies development for MS. Most of the currently available therapies and investigations modulate immune responses and mediators. Since most therapeutic strategies have unsatisfied outcomes, developing new therapies that enhance brain lesion repair is a priority. A close look at cellular and chemical components of MS lesions will pave the way to a better understanding of lesions pathology and will provide possible opportunities for repair strategies and targeted pharmacotherapy. This review summarizes the lesion components and features, particularly the detrimental elements, and discusses the possibility of suggesting new potential targets as therapies for demyelinating diseases like MS.

Apolipoprotein D as a Potential Biomarker in Neuropsychiatric Disorders

Neuropsychiatric disorders (NDs) are a diverse group of pathologies, including schizophrenia or bipolar disorders, that directly affect the mental and physical health of those who suffer from them, with an incidence that is increasing worldwide. Most NDs result from a complex interaction of multiple genes and environmental factors such as stress or traumatic events, including the recent Coronavirus Disease (COVID-19) pandemic. In addition to diverse clinical presentations, these diseases are heterogeneous in their pathogenesis, brain regions affected, and clinical symptoms, making diagnosis difficult. Therefore, finding new biomarkers is essential for the detection, prognosis, response prediction, and development of new treatments for NDs. Among the most promising candidates is the apolipoprotein D (Apo D), a component of lipoproteins implicated in lipid metabolism. Evidence suggests an increase in Apo D expression in association with aging and in the presence of neuropathological processes. As a part of the cellular neuroprotective defense machinery against oxidative stress and inflammation, changes in Apo D levels have been demonstrated in neuropsychiatric conditions like schizophrenia (SZ) or bipolar disorders (BPD), not only in some brain areas but in corporal fluids, i.e., blood or serum of patients. What is not clear is whether variation in Apo D quantity could be used as an indicator to detect NDs and their progression. This review aims to provide an updated view of the clinical potential of Apo D as a possible biomarker for NDs.

Sirtuins as Potential Targets for Neuroprotection: Mechanisms of Early Brain Injury Induced by Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a prevalent cerebrovascular disease with significant global mortality and morbidity rates. Despite advancements in pharmacological and surgical approaches, the quality of life for SAH survivors has not shown substantial improvement. Traditionally, vasospasm has been considered a primary contributor to death and disability following SAH, but anti-vasospastic therapies have not demonstrated significant benefits for SAH patients' prognosis. Emerging studies suggest that early brain injury (EBI) may play a crucial role in influencing SAH prognosis. Sirtuins (SIRTs), a group of NAD + -dependent deacylases comprising seven mammalian family members (SIRT1 to SIRT7), have been found to be involved in neural tissue development, plasticity, and aging. They also exhibit vital functions in various central nervous system (CNS) processes, including cognition, pain perception, mood, behavior, sleep, and circadian rhythms. Extensive research has uncovered the multifaceted roles of SIRTs in CNS disorders, offering insights into potential markers for pathological processes and promising therapeutic targets (such as SIRT1 activators and SIRT2 inhibitors). In this article, we provide an overview of recent research progress on the application of SIRTs in subarachnoid hemorrhage and explore their underlying mechanisms of action.

Clinical Theragnostic Signature of Extracellular Vesicles in Traumatic Brain Injury (TBI)

Traumatic brain injury (TBI) is a common cause of disability and fatality worldwide. Depending on the clinical presentation, it is a type of acquired brain damage that can be mild, moderate, or severe. The degree of patient's discomfort, prognosis, therapeutic approach, survival rates, and recurrence can all be strongly impacted by an accurate diagnosis made early on. The Glasgow Coma Scale (GCS), along with neuroimaging (MRI (Magnetic Resonance Imaging) and CT scan), is a neurological assessment tools used to evaluate and categorize the severity of TBI based on the patient's level of consciousness, eye opening, and motor response. Extracellular vesicles (EVs) are a growing domain, explaining neurological complications in a more detailed manner. EVs, in general, play a role in cellular communication. Its molecular signature such as DNA, RNA, protein, etc. contributes to the status (health or pathological stage) of the parental cell. Brain-derived EVs support more specific screening (diagnostic and prognostic) in TBI research. Therapeutic impact of EVs are more promising for aiding in TBI healing. It is nontoxic, biocompatible, and capable of crossing the blood-brain barrier (BBB) to transport therapeutic molecules. This review has highlighted the relationships between EVs and TBI theranostics, EVs and TBI-related clinical trials, and related research domain-associated challenges and solutions. This review motivates further exploration of associations between EVs and TBI and develops a better approach to TBI management.

Leveraging the ATP-P2X7 receptor signalling axis to alleviate traumatic CNS damage and related complications

The P2X7 receptor is an exceptional member of the P2X purinergic receptor family, with its activation requiring high concentrations of extracellular adenosine 5'-triphosphate (ATP) that are often associated with tissue damage and inflammation. In the central nervous system (CNS), it is highly expressed in glial cells, particularly in microglia. In this review, we discuss the role and mechanisms of the P2X7 receptor in mediating neuroinflammation and other pathogenic events in a variety of traumatic CNS damage conditions, which lead to loss of neurological and cognitive functions. We raise the perspective on the steady progress in developing CNS-penetrant P2X7 receptor-specific antagonists that leverage the ATP-P2X7 receptor signaling axis as a potential therapeutic strategy to alleviate traumatic CNS damage and related complications.

Roles and therapeutic potential of different extracellular vesicle subtypes on traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of injury-related disability and death around the world, but the clinical stratification, diagnosis, and treatment of complex TBI are limited. Due to their unique properties, extracellular vesicles (EVs) are emerging candidates for being biomarkers of traumatic brain injury as well as serving as potential therapeutic targets. However, the effects of different extracellular vesicle subtypes on the pathophysiology of traumatic brain injury are very different, or potentially even opposite. Before extracellular vesicles can be used as targets for TBI therapy, it is necessary to classify different extracellular vesicle subtypes according to their functions to clarify different strategies for EV-based TBI therapy. The purpose of this review is to discuss contradictory effects of different EV subtypes on TBI, and to propose treatment ideas based on different EV subtypes to maximize their benefits for the recovery of TBI patients. Video Abstract.

Current aspects of small extracellular vesicles in pain process and relief

Small extracellular vesicles (sEVs) have been identified as a noteworthy paracrine mechanism of intercellular communication in diagnosing and managing neurological disorders. Current research suggests that sEVs play a pivotal role in the pathological progression of pain, emphasizing their critical function in the pathological progression of pain in acute and chronic pain models. By facilitating the transfer of diverse molecules, such as proteins, nucleic acids, and metabolites, sEVs can modulate pain signaling transmission in both the central and peripheral nervous systems. Furthermore, the unique molecules conveyed by sEVs in pain disorders indicate their potential as diagnostic biomarkers. The application of sEVs derived from mesenchymal stem cells (MSCs) in regenerative pain medicine has emerged as a promising strategy for pain management. Moreover, modified sEVs have garnered considerable attention in the investigation of pathological processes and therapeutic interventions. This review presents a comprehensive overview of the current knowledge regarding the involvement of sEVs in pain pathogenesis and treatment. Nevertheless, additional research is imperative to facilitate their clinical implementation. Schematic diagram of sEVs in the biogenesis, signal transmission, diagnosis, and treatment of pain disorders. Small extracellular vesicles (sEVs) are secreted by multiple cells, loading with various biomolecules, such as miRNAs, transmembrane proteins, and amino acids. They selectively target other cells and regulating pain signal transmission. The composition of sEVs can serve as valuable biomarkers for pain diagnosis. In particular, mesenchymal stem cell-derived sEVs have shown promise as regenerative medicine for managing multiple pain disorders. Furthermore, by modifying the structure or contents of sEVs, they could potentially be used as a potent analgesic method.

Emerging role of non-coding RNAs in neuroinflammation mediated by microglia and astrocytes

Neuroinflammation has been implicated in the initiation and progression of several central nervous system (CNS) disorders, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, ischemic stroke, traumatic brain injury, spinal cord injury, viral encephalitis, and bacterial encephalitis. Microglia and astrocytes are essential in neural development, maintenance of synaptic connections, and homeostasis in a healthy brain. The activation of astrocytes and microglia is a defense mechanism of the brain against damaged tissues and harmful pathogens. However, their activation triggers neuroinflammation, which can exacerbate or induce CNS injury. Non-coding RNAs (ncRNAs) are functional RNA molecules that lack coding capabilities but can actively regulate mRNA expression and function through various mechanisms. ncRNAs are highly expressed in astrocytes and microglia and are potential mediators of neuroinflammation. We reviewed the recent research progress on the role of miRNAs, lncRNAs, and circRNAs in regulating neuroinflammation in various CNS diseases. Understanding how these ncRNAs affect neuroinflammation will provide important therapeutic insights for preventing and managing CNS dysfunction.

Liquid Biopsy in Neurological Diseases

The most recent and non-invasive approach for studying early-stage biomarkers is liquid biopsy. This implies the extraction and analysis of non-solid biological tissues (serum, plasma, saliva, urine, and cerebrospinal fluid) without undergoing invasive procedures to determine disease prognosis. Liquid biopsy can be used for the screening of several components, such as extracellular vesicles, microRNAs, cell-free DNA, cell-free mitochondrial and nuclear DNA, circulating tumour cells, circulating tumour DNA, transfer RNA, and circular DNA or RNA derived from body fluids. Its application includes early disease diagnosis, the surveillance of disease activity, and treatment response monitoring, with growing evidence for validating this methodology in cancer, liver disease, and central nervous system (CNS) disorders. This review will provide an overview of mentioned liquid biopsy components, which could serve as valuable biomarkers for the evaluation of complex neurological conditions, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, epilepsy, stroke, traumatic brain injury, CNS tumours, and neuroinfectious diseases. Furthermore, this review highlights the future directions and potential limitations associated with liquid biopsy.

Progress in research on the role of clinical nutrition in treating traumatic brain injury affecting the neurovascular unit

The neurovascular unit (NVU) is composed of neurons, glial cells, and blood vessels. NVU dysfunction involves the processes of neuroinflammation, and microcirculatory disturbances, as well as neuronal injury after traumatic brain injury (TBI). Traditional anti-inflammatory drugs have limited efficacy in improving the prognosis of TBI. Thus, treatments that target NVU dysfunction may provide a breakthrough. A large number of clinical studies have shown that the nutritional status of patients with TBI was closely related to their conditions and prognoses. Nutrient complexes and complementary therapies for the treatment of TBI are therefore being implemented in many preclinical studies. Importantly, the mechanism of action for this treatment may be related to repair of NVU dysfunction by ensuring adequate omega-3 fatty acids, curcumin, resveratrol, apigenin, vitamins, and minerals. These nutritional supplements hold promise for translation to clinical therapy. In addition, dietary habits also play an important role in the rehabilitation of TBI. Poor dietary habits may worsen the pathology and prognosis of TBI. Adjusting dietary habits, especially with a ketogenic diet, may improve outcomes in patients with TBI. This article discusses the impact of clinical nutrition on NVU dysfunction after TBI, focusing on nutritional complexes and dietary habits.

Extracellular vesicles as personalized medicine

Extracellular vesicles (EVs) are released from all cells in the body, forming an important intercellular communication network that contributes to health and disease. The contents of EVs are cell source-specific, inducing distinct signaling responses in recipient cells. The specificity of EVs and their accumulation in fluid spaces that are accessible for liquid biopsies make them highly attractive as potential biomarkers and therapies for disease. The duality of EVs as favorable (therapeutic) or unfavorable (pathological) messengers is context dependent and remains to be fully determined in homeostasis and various disease states. This review describes the use of EVs as biomarkers, drug delivery vehicles, and regenerative therapeutics, highlighting examples involving viral infections, cancer, and neurological diseases. There is growing interest to provide personalized therapy based on individual patient and disease characteristics. Increasing evidence suggests that EV biomarkers and therapeutic approaches are ideal for personalized medicine due to the diversity and multifunctionality of EVs.

Non-coding RNAs and Exosomal Non-coding RNAs in Traumatic Brain Injury: the Small Player with Big Actions

Nowadays, there is an increasing concern regarding traumatic brain injury (TBI) worldwide since substantial morbidity is observed after it, and the long-term consequences that are not yet fully recognized. A number of cellular pathways related to the secondary injury in brain have been identified, including free radical production (owing to mitochondrial dysfunction), excitotoxicity (regulated by excitatory neurotransmitters), apoptosis, and neuroinflammatory responses (as a result of activation of the immune system and central nervous system). In this context, non-coding RNAs (ncRNAs) maintain a fundamental contribution to post-transcriptional regulation. It has been shown that mammalian brains express high levels of ncRNAs that are involved in several brain physiological processes. Furthermore, altered levels of ncRNA expression have been found in those with traumatic as well non-traumatic brain injuries. The current review highlights the primary molecular mechanisms participated in TBI that describes the latest and novel results about changes and role of ncRNAs in TBI in both clinical and experimental research.

Unpacking the Role of Extracellular Vesicles in Ischemic and Hemorrhagic Stroke: Pathophysiology and Therapeutic Implications

Stroke is a leading cause of death and disability worldwide. Inflammation and microvascular dysfunction have been associated with brain injury and long-term disability after both ischemic and hemorrhagic stroke. Recent studies have suggested a potential role of extracellular vesicles (EVs) as a link underlying these pathogenic processes. EVs are cell-derived particles enveloped by a lipid bilayer, containing proteins, lipids, and nucleic acids. From a functional standpoint, EVs can facilitate intercellular communication, including across the blood-brain barrier (BBB). Recent advances in EV research have shown a preferential release of EVs from specific cell types in the context of stroke, some of which were associated with increased neuroinflammation, microvascular dysfunction, and neuronal cytotoxicity while others offered a degree of neuroprotection. However, one historic challenge in the studies of EVs in stroke is the lack of consistent definitions and methods to analyze EVs, only recently updated in the MISEV2018 guidelines. Given limitations and complexity in the treatment of stroke, particularly delivery of therapeutics across the BBB, increasing attention has been paid towards manipulating EVs as one vehicle that can permit targeted therapeutic delivery to the central nervous system. These discoveries point towards a future where a better understanding of EVs will advance our knowledge of stroke-associated mechanisms of cerebral and systemic injury and contribute to the development of novel treatments. Here, we review the role that EVs play in ischemic and hemorrhagic stroke.

Lipocalin-2 Is a Key Regulator of Neuroinflammation in Secondary Traumatic and Ischemic Brain Injury

Reactive glial cells are hallmarks of brain injury. However, whether these cells contribute to secondary inflammatory pathology and neurological deficits remains poorly understood. Lipocalin-2 (LCN2) has inflammatory and neurotoxic effects in various disease models; however, its pathogenic role in traumatic brain injury remains unknown. The aim of the present study was to investigate the expression of LCN2 and its role in neuroinflammation following brain injury. LCN2 expression was high in the mouse brain after controlled cortical impact (CCI) and photothrombotic stroke (PTS) injury. Brain levels of LCN2 mRNA and protein were also significantly higher in patients with chronic traumatic encephalopathy (CTE) than in normal subjects. RT-PCR and immunofluorescence analyses revealed that astrocytes were the major cellular source of LCN2 in the injured brain. Lcn2 deficiency or intracisternal injection of an LCN2 neutralizing antibody reduced CCI- and PTS-induced brain lesions, behavioral deficits, and neuroinflammation. Mechanistically, in cultured glial cells, recombinant LCN2 protein enhanced scratch injury-induced proinflammatory cytokine gene expression and inhibited Gdnf gene expression, whereas Lcn2 deficiency exerted opposite effects. Together, our results from CTE patients, rodent brain injury models, and cultured glial cells suggest that LCN2 mediates secondary damage response to traumatic and ischemic brain injury by promoting neuroinflammation and suppressing the expression of neurotropic factors.

Immune regulation in neurovascular units after traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. Survivors may experience movement disorders, memory loss, and cognitive deficits. However, there is a lack of understanding of the pathophysiology of TBI-mediated neuroinflammation and neurodegeneration. The immune regulation process of TBI involves changes in the peripheral and central nervous system (CNS) immunity, and intracranial blood vessels are essential communication centers. The neurovascular unit (NVU) is responsible for coupling blood flow with brain activity, and comprises endothelial cells, pericytes, astrocyte end-feet, and vast regulatory nerve terminals. A stable NVU is the basis for normal brain function. The concept of the NVU emphasizes that cell-cell interactions between different types of cells are essential for maintaining brain homeostasis. Previous studies have explored the effects of immune system changes after TBI. The NVU can help us further understand the immune regulation process. Herein, we enumerate the paradoxes of primary immune activation and chronic immunosuppression. We describe the changes in immune cells, cytokines/chemokines, and neuroinflammation after TBI. The post-immunomodulatory changes in NVU components are discussed, and research exploring immune changes in the NVU pattern is also described. Finally, we summarize immune regulation therapies and drugs after TBI. Therapies and drugs that focus on immune regulation have shown great potential for neuroprotection. These findings will help us further understand the pathological processes after TBI.

Antidiabetic Drugs Can Reduce the Harmful Impact of Chronic Smoking on Post-Traumatic Brain Injuries

Traumatic Brain Injury (TBI) is a primary cause of cerebrovascular and neurological disorders worldwide. The current scientific researchers believe that premorbid conditions such as tobacco smoking (TS) can exacerbate post-TBI brain injury and negatively affect recovery. This is related to vascular endothelial dysfunction resulting from the exposure to TS-released reactive oxygen species (ROS), nicotine, and oxidative stress (OS) stimuli impacting the blood-brain barrier (BBB) endothelium. Interestingly, these pathogenic modulators of BBB impairment are similar to those associated with hyperglycemia. Antidiabetic drugs such as metformin (MF) and rosiglitazone (RSG) were shown to prevent/reduce BBB damage promoted by chronic TS exposure. Thus, using in vivo approaches, we evaluated the effectiveness of post-TBI treatment with MF or RSG to reduce the TS-enhancement of BBB damage and brain injury after TBI. For this purpose, we employed an in vivo weight-drop TBI model using male C57BL/6J mice chronically exposed to TS with and without post-traumatic treatment with MF or RSG. Our results revealed that these antidiabetic drugs counteracted TS-promoted downregulation of nuclear factor erythroid 2-related factor 2 (NRF2) expression and concomitantly dampened TS-enhanced OS, inflammation, and loss of BBB integrity following TBI. In conclusion, our findings suggest that MF and RSG could reduce the harmful impact of chronic smoking on post-traumatic brain injuries.

Neuroinflammation with increased glymphatic flow in a murine model of decompression sickness

This project investigated glial-based lymphatic (glymphatic) function and its role in a murine model of decompression sickness (DCS). DCS pathophysiology is traditionally viewed as being related to gas bubble formation from insoluble gas on decompression. However, a body of work implicates a role for a subset of inflammatory extracellular vesicles, 0.1 to 1 µm microparticles (MPs) that are elevated in human and rodent models in response to high gas pressure and rise further after decompression. Herein, we describe immunohistochemical and Western blot evidence showing that following high air pressure exposure, there are elevations of astrocyte NF-κB and microglial-ionized calcium-binding adaptor protein-1 (IBA-1) along with fluorescence contrast and MRI findings of an increase in glymphatic flow. Concomitant elevations of central nervous system-derived MPs coexpressing thrombospondin-1 (TSP) drain to deep cervical nodes and then to blood where they cause neutrophil activation. A new set of blood-borne MPs are generated that express filamentous actin at the surface that exacerbate neutrophil activation. Blood-brain barrier integrity is disrupted due to activated neutrophil sequestration that causes further astrocyte and microglial perturbation. When postdecompression node or blood MPs are injected into naïve mice, the same spectrum of abnormalities occur and they are blocked with coadministration of antibody to TSP. We conclude that high pressure/decompression causes neuroinflammation with an increased glymphatic flow. The resulting systemic liberation of TSP-expressing MPs sustains the neuroinflammatory cycle lasting for days.NEW & NOTEWORTHY A murine model of central nervous system (CNS) decompression sickness demonstrates that high gas pressure activates astrocytes and microglia triggering inflammatory microparticle (MP) production. Thrombospondin-expressing MPs are released from the CNS via enhanced glymphatic flow to the systemic circulation where they activate neutrophils. Secondary production of neutrophil-derived MPs causes further cell activation and neutrophil adherence to the brain microvasculature establishing a feed-forward neuroinflammatory cycle.

Myokines may target accelerated cognitive aging in people with spinal cord injury: A systematic and topical review

Persons with spinal cord injury (SCI) can suffer accelerated cognitive aging, even when correcting for mood and concomitant traumatic brain injury. Studies in healthy older adults have shown that myokines (i.e. factors released from muscle tissue during exercise) may improve brain health and cognitive function. Myokines may target chronic neuroinflammation, which is considered part of the mechanism of cognitive decline both in healthy older adults and SCI. An empty systematic review, registered in PROSPERO (CRD42022335873), was conducted as proof of the lack of current research on this topic in people with SCI. Pubmed, Embase, Cochrane and Web of Science were searched, resulting in 387 articles. None were considered eligible for full text screening. Hence, the effect of myokines on cognitive function following SCI warrants further investigation. An in-depth narrative review on the mechanism of SCI-related cognitive aging and the myokine-cognition link was added to substantiate our hypothetical framework. Readers are fully updated on the potential role of exercise as a treatment strategy against cognitive aging in persons with SCI.

Extracellular vesicles as contributors in the pathogenesis of multiple sclerosis

Extracellular vesicles (EVs) are a heterogeneous family of extracellular structures bounded by a phospholipid bilayer, released by all cell types in various biological fluids, such as blood and cerebrospinal fluid (CSF), playing important roles in intercellular communication, both locally and systemically. EVs carry and deliver a variety of bioactive molecules (proteins, nucleic acids, lipids and metabolites), conferring epigenetic and phenotypic changes to the recipient cells and thus resulting as important mediators of both homeostasis and pathogenesis. In neurological diseases, such as multiple sclerosis (MS), the EV ability to cross Blood-Brain Barrier (BBB), moving from central nervous system (CNS) to the peripheral circulation and vice versa, has increased the interest in EV study in the neurological field. In the present review, we will provide an overview of the recent advances made in understanding the pathogenic role of EVs regarding the immune response, the BBB dysfunction and the CNS inflammatory processes.

The link between neuroinflammation and the neurovascular unit in synucleinopathies

The neurovascular unit (NVU) is composed of vascular cells, glial cells, and neurons. As a fundamental functional module in the central nervous system, the NVU maintains homeostasis in the microenvironment and the integrity of the blood-brain barrier. Disruption of the NVU and interactions among its components are involved in the pathophysiology of synucleinopathies, which are characterized by the pathological accumulation of α-synuclein. Neuroinflammation contributes to the pathophysiology of synucleinopathies, including Parkinson's disease, multiple system atrophy, and dementia with Lewy bodies. This review aims to summarize the neuroinflammatory response of glial cells and vascular cells in the NVU. We also review neuroinflammation in the context of the cross-talk between glial cells and vascular cells, between glial cells and pericytes, and between microglia and astroglia. Last, we discuss how α-synuclein affects neuroinflammation and how neuroinflammation influences the aggregation and spread of α-synuclein and analyze different properties of α-synuclein in synucleinopathies.

Traumatic Brain Injury-Mediated Neuroinflammation and Neurological Deficits are Improved by 8-Methoxypsoralen Through Modulating PPARγ/NF-κB Pathway

8-Methoxypsoralen (8-MOP) has anti-inflammatory, antioxidant and tissue-repairing abilities. Here, we probed the function and mechanism of 8-MOP in traumatic brain injury (TBI). The in-vivo TBI model was constructed in Sprague-Dawley (SD) rats using controlled cortical impact (CCI) surgery. In parallel, BV2 microglia and HT22 neurons were activated by lipopolysaccharide (LPS) to establish an in-vitro model. The modified neurological score (mNSS) and the Morris water maze experiment were employed to evaluate the rats' neurological functions. The rats' brain edema was assessed by the dry and wet method, and neuronal apoptosis in damaged brain tissues was monitored by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) and Nissl's staining. Immunohistochemistry (IHC) was applied to verify Iba1-microglial activation in brain lesions of rats. The expression of inflammatory cytokines in BV2 microglia and HT22 neurons in the injured lesion of TBI rats was examined by the enzyme-linked immunosorbent assay (ELISA). The levels of iNOS, COX2, TLR4, PPARγ, STAT3, and NF-κB in brain lesions, BV2 microglia and HT22 neurons were compared by Western blot. As a result, 8-MOP administration reduced inflammation and LPS-induced neuronal damage in BV2 microglia. In vivo, 8-MOP treatment relieved neurological deficits in TBI rats, improved cognitive, learning and motor functions and mitigated brain edema and neuroinflammation induced by TBI. Furthermore, LPS or TBI activated the NF-κB and STAT3 pathways and repressed the PPARγ expression. However, 8-MOP treatment attenuated NF-κB and STAT3 phosphorylation and elevated PPARγ levels. Hence, 8-MOP exerts neuroprotective and anti-inflammatory effects in TBI rats by modulating the PPARγ/NF-κB pathway.

Neuroglia Cells Transcriptomic in Brain Development, Aging and Neurodegenerative Diseases

Glia cells are essential for brain functioning during development, aging and disease. However, the role of astroglia plays during brain development is quite different from the role played in the adult lesioned brain. Therefore, a deeper understanding of pathomechanisms underlying astroglia activity in the aging brain and cerebrovascular diseases is essential to guide the development of new therapeutic strategies. To this end, this review provides a comparison between the transcriptomic activity of astroglia cells during development, aging and neurodegenerative diseases, including cerebral ischemia. During fetal brain development, astrocytes and microglia often affect the same developmental processes such as neuro-/gliogenesis, angiogenesis, axonal outgrowth, synaptogenesis, and synaptic pruning. In the adult brain astrocytes are a critical player in the synapse remodeling by mediating synapse elimination while microglia activity has been associated with changes in synaptic plasticity and remove cell debris by constantly sensing the environment. However, in the lesioned brain astrocytes proliferate and play essential functions with regard to energy supply to the neurons, neurotransmission and buildup of a protective scar isolating the lesion site from the surroundings. Inflammation, neurodegeneration, or loss of brain homeostasis induce changes in microglia gene expression, morphology, and function, generally referred to as "primed" microglia. These changes in gene expression are characterized by an enrichment of phagosome, lysosome, and antigen presentation signaling pathways and is associated with an up-regulation of genes encoding cell surface receptors. In addition, primed microglia are characterized by upregulation of a network of genes in response to interferon gamma. Conclusion. A comparison of astroglia cells transcriptomic activity during brain development, aging and neurodegenerative disorders might provide us with new therapeutic strategies with which to protect the aging brain and improve clinical outcome.

Neuroinflammation of traumatic brain injury: Roles of extracellular vesicles

Traumatic brain injury (TBI) is a major cause of neurological disorder or death, with a heavy burden on individuals and families. While sustained primary insult leads to damage, subsequent secondary events are considered key pathophysiological characteristics post-TBI, and the inflammatory response is a prominent contributor to the secondary cascade. Neuroinflammation is a multifaceted physiological response and exerts both positive and negative effects on TBI. Extracellular vesicles (EVs), as messengers for intercellular communication, are involved in biological and pathological processes in central nervous system (CNS) diseases and injuries. The number and characteristics of EVs and their cargo in the CNS and peripheral circulation undergo tremendous changes in response to TBI, and these EVs regulate neuroinflammatory reactions by activating prominent receptors on receptor cells or delivering pro- or anti-inflammatory cargo to receptor cells. The purpose of this review is to discuss the possible neuroinflammatory mechanisms of EVs and loading in the context of TBI. Furthermore, we summarize the potential role of diverse types of cell-derived EVs in inflammation following TBI.

Immune response following traumatic spinal cord injury: Pathophysiology and therapies

Traumatic spinal cord injury (SCI) is a devastating condition that is often associated with significant loss of function and/or permanent disability. The pathophysiology of SCI is complex and occurs in two phases. First, the mechanical damage from the trauma causes immediate acute cell dysfunction and cell death. Then, secondary mechanisms of injury further propagate the cell dysfunction and cell death over the course of days, weeks, or even months. Among the secondary injury mechanisms, inflammation has been shown to be a key determinant of the secondary injury severity and significantly worsens cell death and functional outcomes. Thus, in addition to surgical management of SCI, selectively targeting the immune response following SCI could substantially decrease the progression of secondary injury and improve patient outcomes. In order to develop such therapies, a detailed molecular understanding of the timing of the immune response following SCI is necessary. Recently, several studies have mapped the cytokine/chemokine and cell proliferation patterns following SCI. In this review, we examine the immune response underlying the pathophysiology of SCI and assess both current and future therapies including pharmaceutical therapies, stem cell therapy, and the exciting potential of extracellular vesicle therapy.

An emerging role of astrocytes in aging/neuroinflammation and gut-brain axis with consequences on sleep and sleep disorders

Understanding the role of astrocytes in the central nervous system has changed dramatically over the last decade. The accumulating findings indicate that glial cells are involved not only in the maintenance of metabolic and ionic homeostasis and in the implementation of trophic functions but also in cognitive functions and information processing in the brain. Currently, there are some controversies regarding the role of astrocytes in complex processes such as aging of the nervous system and the pathogenesis of age-related neurodegenerative diseases. Many findings confirm the important functional role of astrocytes in age-related brain changes, including sleep disturbance and the development of neurodegenerative diseases and particularly Alzheimer's disease. Until recent years, neurobiological research has focused mainly on neuron-glial interactions, in which individual astrocytes locally modulate neuronal activity and communication between neurons. The review considers the role of astrocytes in the physiology of sleep and as an important "player" in the development of neurodegenerative diseases. In addition, the features of the astrocytic network reorganization during aging are discussed.

Mesenchymal "stem" cells, or facilitators for the development of regenerative macrophages? Pericytes at the interface of wound healing

Cultured mesenchymal stromal cells are among the most used cells in clinical trials. Currently, their potential benefits include provision of mature cell types through differentiation, and secretion of various types of paracrine signaling molecules. Even though research on these cells has spanned some decades now, surprisingly, their therapeutic potential has not been fully translated into clinical practice yet, which calls for further understanding of their intrinsic nature and modes of action. In this review, after discussing pieces of evidence that suggest that some perivascular cells may exhibit mesenchymal stem cell characteristics in vivo, we examine the possibility that subpopulations of perivascular and/or adventitial cells activated after tissue injury behave as MSCs and contribute to the resolution of tissue injury by providing cues for the development of regenerative macrophages at injured sites. Under this perspective, an important contribution of cultured MSCs (or their acellular products, such as extracellular vesicles) used in cell therapies would be to instigate the development of M2-like macrophages that support the tissue repair process.