Heterogeneity of microglial activation in the innate immune response in the brain

Long-term nucleus basalis cholinergic lesions alter the structure of cortical vasculature, astrocytic density and microglial activity in Wistar rats

Basal forebrain cholinergic neurons (BFCNs) are the sole source of cholinergic innervation to the cerebral cortex and hippocampus in humans and the primary source in rodents. This system undergoes early degeneration in Alzheimer's disease. BFCNs terminal synapses are involved in the regulation of the cerebral blood flow by making classical synaptic contacts with other neurons. Additionally, they are located in proximity to cortical cerebral blood vessels, forming connections with various cell types of the neurovascular unit (NVU), including vascular smooth muscle cells, endothelial cells, and astrocytic end-feet. However, the effects of the BFCNs input on NVU components remain unresolved. To address this issue, we immunolesioned the nucleus basalis by administering bilateral stereotaxic injections of the cholinergic immunotoxin 192-IgG-Saporin in 2.5-month-old Wistar rats. Seven months post-lesion, we observed a significant reduction in cortical vesicular acetylcholine transporter-immunoreactive synapses. This was accompanied by changes in the diameter of cortical capillaries and precapillary arterioles, as well as lower levels of vascular endothelial growth factor A (VEGF-A). Additionally, the cholinergic immunolesion increased the density of cortical astrocytes and microglia in the cortex. At these post-BFCN-lesion stages, astrocytic end-feet exhibited an increased co-localization with arterioles. The number of microglia in the parietal cortex correlated with cholinergic loss and exhibited morphological changes indicative of an intermediate activation state. This was supported by decreased levels of proinflammatory mediators IFN-γ, IL-1β, and KC/GRO (CXCL1), and by increased expression of M2 markers SOCS3, IL4Rα, YM1, ARG1, and Fizz1. Our findings offer a novel insight: that the loss of nucleus basalis cholinergic input negatively impacts cortical blood vessels, NVU components, and microglia phenotype.

Crosstalk Between Mitochondrial DNA and Immune Response: Focus on Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by multiple dysfunctions in behavior, the nervous system, and the immune system. Increasing evidence suggests that mitochondrial DNA (mtDNA) plays a crucial role in the pathology of ASD. In clinical practice, altered mtDNA levels have been observed in various tissues of individuals with ASD. Mutation or oxidation of mtDNA is also closely related to the immune response associated with the pathology of autism. With mtDNA identified as a causal factor, much interest has focused on how its production affects neurodevelopment and neurophysiology. Here, we review how mtDNA leads to dysfunction of cellular mitochondria and immune response. We also illustrate the relationship between mtDNA alterations and the pathology of autism. Finally, we discuss the existing evidence on cell-free mtDNA associated with ASD and look forward to its application in clinical diagnosis and treatment.

Cytokine Profile Analysis During Sialodacryoadenitis Virus and Mouse Hepatitis Virus JHM Strain Infection in Primary Mixed Microglia and Astrocyte Culture-Preliminary Research

The Coronaviridae family has again demonstrated the potential for significant neurological complications in humans during the recent pandemic. In patients, these symptoms persist throughout the infection, often lasting for months. The consequences of most of these post-infection symptoms might be linked with abnormal cytokine production and reactive oxygen species (ROS) expression, resulting in neuron damage. We investigated the effect of infection with the Mouse Hepatitis Virus (MHV) JHM strain and Sialodacryoadenitis Virus (SDAV) on a primary microglia and astrocyte culture by analysing ROS production, cytokine and chemokine expression, and cell death during one month post infection. For this purpose, confocal microscopy, flow cytometry, and a high-throughput Luminex ProcartaPlex immunopanel for 48 cytokines and chemokines were utilised. The replication of MHV-JHM and SDAV in microglia and astrocytes has increased the production of pro-inflammatory cytokines and inhibited the production of anti-inflammatory cytokines. The cytokine expression induced by the two viruses differed, as did their detection after infection. SDAV infection resulted in a much broader cytokine response compared to that of MHV-JHM. Both viruses significantly increased ROS levels and induced apoptosis in a small percentage of the cells, but without necrosis.

The role of Ergothioneine in cognition and age-related neurodegenerative disease: a systematic review

Ergothioneine (ET) is an under recognised diet-derived compound which has the potential to be a "longevity vitamin". It was found to be beneficial for cognitive function and age-related neurodegenerative disorder (ARND). Thus, this study was conducted to synthesise the existing evidence of ET's effects on cognition and ARND, emphasizing its potential as a micronutrient for healthy aging. This study also highlights the future prospects of the research regarding ET's effects on cognition and ARND that are suggested in existing literature. Three databases (Pubmed, Scopus, and Web of Science) were used to search for the studies that meet the inclusion and exclusion criteria. A total of 19 studies were included after screening in this review. The risk of bias of each study was assessed using the Office of Health Assessment and Translation (OHAT) risk of bias rating tool. All studies' characteristics and main findings were tabulated according to their type of study. Mechanisms of ET in improving cognitive function and preventing ARND were found to be through its antioxidative, anti-inflammatory and antisenescence properties. Its role in neurotransmission and neuroprotection also contributed to improving cognition and preventing ARND. In conclusion, ET is a potential compound to be explored as its role in cognition and ARND have been discovered through several studies.

Oxygen metabolism abnormalities and high-altitude cerebral edema

Hypobaric hypoxia is widely recognized as a prominent risk factor for high-altitude cerebral edema (HACE), which contributes to the exacerbation of multiple pathological mechanisms, including oxidative stress, mitochondrial dysfunction, disruption of blood-;brain barrier integrity, neuroinflammation, and neuronal apoptosis. Among these mechanisms, abnormalities in oxygen metabolism, including hypoxia, oxidative stress, and mitochondrial dysfunction, play pivotal roles in the pathophysiology of HACE. In this review, our objective is to enhance our comprehension of the underlying molecular mechanisms implicated in HACE by investigating the potential involvement of oxygen metabolism. Addressing aberrations in oxygen metabolism holds promise for providing innovative therapeutic strategies for managing HACE.

Lactylation and Central Nervous System Diseases

As the final product of glycolysis, lactate serves as an energy substrate, metabolite, and signaling molecule in various diseases and mediates lactylation, an epigenetic modification that occurs under both physiological and pathological conditions. Lactylation is a crucial mechanism by which lactate exerts its functions, participating in vital biological activities such as glycolysis-related cellular functions, macrophage polarization, and nervous system regulation. Lactylation links metabolic regulation to central nervous system (CNS) diseases, such as traumatic brain injury, Alzheimer's disease, acute ischemic stroke, and schizophrenia, revealing the diverse functions of lactylation in the CNS. In the future, further exploration of lactylation-associated enzymes and proteins is needed to develop specific lactylation inhibitors or activators, which could provide new tools and strategies for the treatment of CNS diseases.

Impact of neuroinflammation on brain glutamate and dopamine signalling in schizophrenia: an update

Schizophrenia is one of the most severe and chronic psychiatric disorders. Over the years, numerous treatment options have been introduced for schizophrenia. Although they are relatively successful in managing the positive symptoms of schizophrenia, most of the current treatments have a negligible effect on the negative and cognitive symptoms. Thus, none of them could prevent the relapse of psychotic episodes. Among the numerous hypotheses explaining the development and progression of schizophrenia, the cytokine hypothesis explains the role of inflammatory markers as a significant culprit in the development of schizophrenia. Elevated cytokines are reported in animal models and schizophrenic patients. The cytokine hypothesis is based on how increased inflammatory markers can cause changes in the dopaminergic, glutamate, and tryptophan metabolism pathways, like that observed in schizophrenic patients. Reasons, such as autoimmune disease, maternal immune activation, infection, etc., can pave the way for the development of schizophrenia and are associated with the negative, positive and cognitive symptoms of schizophrenia. Thus, there is a need to focus on the significance of anti-inflammatory drugs against these symptoms. The development of new treatment strategies in the management of schizophrenia can provide better therapeutic outcomes in terms of the severity of symptoms and treatment of drug-resistant schizophrenia. This review attempts to explain the association between elevated inflammatory markers and various neurotransmitters, and the possible use of medications like nonsteroidal anti-inflammatory drugs, monoclonal antibodies, statins, and estrogens as adjuvant therapy. Over the years, these hypotheses have been the basis for drug discovery for the treatment of schizophrenia.

Role of NLRP3 Inflammasome in Chronic Pain and Alzheimer's Disease-A Review

The coexistence of Alzheimer's disease (AD) and chronic pain (CP) in the elderly population has been extensively documented, and a growing body of evidence supports the potential interconnections between these two conditions. This comprehensive review explores the mechanisms by which CP may contribute to the development and progression of AD, with a particular focus on neuroinflammatory pathways and the role of microglia, as well as the activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome. The review proposes that prolonged pain processing in critical brain regions can dysregulate the activity of the NLRP3 inflammasome within microglia, leading to the overproduction of pro-inflammatory cytokines and excessive oxidative stress in these regions. This aberrant microglial response also results in localized neuroinflammation in brain areas crucial for cognitive function. Additionally, CP as a persistent physiological and psychological stressor may be associated with hypothalamic-pituitary-adrenal (HPA) axis dysfunction, systemic inflammation, disruption of the blood-brain barrier (BBB), and neuroinflammation. These pathophysiological changes can cause morphological and functional impairments in brain regions responsible for cognition, memory, and neurotransmitter production, potentially contributing to the development and progression of CP-associated AD. Resultant neuroinflammation can further promote amyloid-beta (Aβ) plaque deposition, a hallmark of AD pathology. Potential therapeutic interventions targeting these neuroinflammatory pathways, particularly through the regulation of microglial NLRP3 activation, hold promise for improving outcomes in individuals with comorbid CP and AD. However, further research is required to fully elucidate the complex interplay between these conditions and develop effective treatment strategies.

From acute lung injury to cerebral ischemia: a unified concept involving intercellular communication through extracellular vesicle-associated miRNAs released by macrophages/microglia

Ischemic stroke and acute lung injury are prevalent life-threatening conditions marked by intricate molecular mechanisms and elevated mortality rates. Despite evident pathophysiological distinctions, a notable similarity exists in the gene responses to tissue injury observed in both pathologies. This similarity extends to both protein-encoding RNAs and non-coding RNAs. Extracellular vesicles (EVs) are nano-scale vesicles derived through cell secretion, possessing unique advantages such as high biocompatibility, low immunogenicity, intrinsic cell targeting, and facile chemical and genetic manipulation. Importantly, miRNAs, the most prevalent non-coding RNAs, are selectively concentrated within EVs. Macrophages/microglia serve as immune defense and homeostatic cells, deriving from progenitor cells in the bone marrow. They can be classified into two contrasting types: classical proinflammatory M1 phenotype or alternative anti-inflammatory M2 phenotype. However, there exists a continuum of various intermediate phenotypes between M1 and M2, and macrophages/microglia can transition from one phenotype to another. This review will investigate recent discoveries concerning the impact of EVs derived from macrophages/microglia under various states on the progression of ischemic stroke and acute lung injury. The focus will be on the involvement of miRNAs within these vesicles. The concluding remarks of this review will underscore the clinical possibilities linked to EV-miRNAs, accentuating their potential as both biomarkers and therapeutic targets.

Astrocytes and microglia in multiple sclerosis and neuromyelitis optica

Multiple sclerosis and neuromyelitis optica are autoimmune neurodegenerative diseases primarily targeting myelin sheath and neuroglia. In multiple sclerosis, autoantibodies destroy oligodendrocytes and myelin, which underlies primary neurologic symptoms. Focal damage to myelin triggers reactive astrogliosis and microgliosis, which contribute to and to a large extent define the disease progression. In neuromyelitis optica, autoantibodies against water channel aquaporin 4 (AQP4), which are localized at astrocytic endfeet mediate damage of the glia limitans thus facilitating infiltration of blood-borne molecules and cells that propagate the damage to nerves and neurons. This primary astrocytopathy recruits microglia, which contribute to the neuroinflammatory response. Neuroglial cells therefore are potential targets for cell-specific therapies.

Therapeutic targeting of neuroinflammation in methamphetamine use disorder

Methamphetamine (METH) is a highly addictive illicit psychostimulant with a significant annual fatality rate. Emerging studies highlight its role in neuroinflammation and a range of neurological disorders. This review examines the current landscape of potential drug targets for managing neuroinflammation in METH use disorders (MUDs), with a particular focus on the rationale behind targeting Toll-like receptor 4 (TLR4), the NLR family pyrin domain containing 3 (NLRP3) inflammasome, and other promising targets. Given the multifactorial neurological effects of METH, including cognitive impairment and neurodegeneration, addressing METH-induced neuroinflammation has shown considerable promise in partially mitigating the damaging effects on the central nervous system and improving behavioral outcomes. This article provides an overview of the existing understanding while charting a promising path forward for developing innovative MUD treatments, focusing on neuroinflammation as a therapeutic target. Targeting neuroinflammation in METH-induced neurological disorders shows significant promise in mitigating cognitive impairment and neurodegeneration, offering a potential therapeutic strategy for improving outcomes in MUD. While challenges remain in optimizing treatments, ongoing research into combination therapies, novel drug delivery systems, and neuroprotective agents suggests a positive outlook for more effective interventions.

Therapeutic implications for the PD-1 axis in cerebrovascular injury

Since the discovery and characterization of the PD-1/PD-L pathway, mounting evidence has emerged regarding its role in regulating neuroinflammation following cerebrovascular injury. Classically, PD-L1 on antigen-presenting cells or tissues binds PD-1 on T cell surfaces resulting in T cell inhibition. In myeloid cells, PD-1 stimulation induces polarization of microglia and macrophages into an anti-inflammatory, restorative phenotype. The therapeutic potential of PD-1 agonism in ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage-related vasospasm, and traumatic brain injury rests on the notion of harnessing the immunomodulatory function of immune checkpoint pathways to temper the harmful effects of immune overactivation and secondary injury while promoting repair and recovery. Immune checkpoint agonism has greater specificity than the wider and non-specific anti-inflammatory effects of other agents, such as steroids. PD-1 agonism has already demonstrated success in clinical trials for rheumatoid arthritis and is being tested in other chronic inflammatory diseases. Further investigation of PD-1 agonism as a therapeutic strategy in cerebrovascular injury can help clarify the mechanisms underlying clinical benefit, develop drugs with optimal pharmacodynamic and pharmacokinetic properties, and mitigate unwanted side effects.

Macrophages at Low-Inflammatory Status Improved Osteogenesis via Autophagy Regulation

Accumulating evidence indicates that the interaction between immune and skeletal systems is vital in bone homeostasis. However, the detailed mechanisms between macrophage polarization and osteogenic differentiation of mesenchymal stromal cells (bone marrow-derived stromal cells [BMSCs]) remain largely unknown. We observed enhanced macrophage infiltration along with bone formation in vivo, which showed a transition from early-stage M1 phenotype to later stage M2 phenotype, cells at the transitional stage expressed both M1 and M2 markers that actively participated in osteogenesis, which was mimicked by stimulating macrophages with lower inflammatory stimulus (compared with typical M1). Using conditioned medium (CM) from M0, typical M1, low-inflammatory M1 (M1semi), and M2 macrophages, it was found that BMSCs treated with M1semi CM showed significantly induced migration, osteogenic differentiation, and mineralization, compared with others. Along with the induced osteogenesis, the autophagy level was the highest in M1semi CM-treated BMSCs, which was responsible for BMSC migration and osteogenic differentiation, as autophagy interruption significantly abolished this effect. This study indicated that low-inflammatory macrophages could activate autophagy in BMSCs to improve osteogenesis.

Role of Noncoding RNAs in Modulating Microglial Phenotype

Microglia are immunocompetent cells that are present in the retina and central nervous system, and are involved in the development maintenance and immune functions in these systems. Developing from yolk sac-primitive macrophages, they proliferate in the local tissues during the embryonic period without resorting to the production from the hematopoietic stem cells, and are critical in sustaining homeostasis and performing in disease and injury; they have morphological characteristics and distinct phenotypes according to the microenvironment. Microglia are also present in close association with resident cells in the retina where they engage in synapse formation, support normal functions, as well as immune defense. They are involved in the development of numerous neurodegenerative and ophthalmic diseases and act as diversity shields and triggers. Noncoding ribonucleic acids (ncRNAs) refer to RNA molecules synthesized from the mammalian genome, and these do not have protein-coding capacity. These ncRNAs play a role in the regulation of gene expression patterns. ncRNAs have only been recently identified as vastly significant molecules that are involved in the posttranscriptional regulation. Microglia are crucial for brain health and functions and current studies have focused on the effects caused by ncRNA on microglial types. Thus, the aim of the review was to provide an overview of the current knowledge about the regulation of microglial phenotypes by ncRNAs.

Microglia-Impaired Phagocytosis Contributes to the Epileptogenesis in a Mouse Model of Dravet Syndrome

Dravet syndrome (DS) is a genetic disorder caused by a deficit in the Nav1.1 channel, leading to drug-resistant epilepsy. The Nav1.1 channel plays a crucial role in microglial cell activation, and microglia are recognized as key mediators of seizures. In this study, we explored the role of microglia in DS-related epileptogenesis using a knock-in mouse model (Scn1aE1099X/+) that mimics a subset of DS patients. In these DS mice, we observed a significant downregulation of the Nav1.1 channel in microglia. This channel deficit led microglia to adopt a pro-inflammatory state in their quiescent phase. In the LPS-activated state, microglia predominantly exhibited an intermediate morphology rather than the expected fully activated form. The reduced expression of pro-inflammatory cytokines was detected in microglia following treatment with LPS. Notably, we found a significant decrease in the phagocytic ability of microglia in DS mice. Electrophysiological studies revealed an increased immature synaptic activity in the dentate gyrus in DS mice. The impaired microglial phagocytosis of damaged cells, combined with reduced cytokine secretion, may result in an excess of immature synaptic connections, neuronal hyperexcitation, and the formation of abnormal neural circuits in the hippocampus of Scn1aE1099X/+ mice. These changes could potentially contribute to mechanisms relevant to epileptogenesis in DS.

Research on the innate immune response in transgenic mice following ischemic stroke

The high incidence, death, disability, and recurrence of ischemic stroke (CIS) place a significant cost on families and society. According to recent research on the condition, immune-related damage is a major contributor to the development and occurrence of CIS. Innate immunity and adaptive immunity are the two primary categories of the immune system in the body. The body's first line of defense is innate immunity, and immune cells play a role in every stage of the immune system. At the same time, protein molecules play a vital function in regulating and differentiating immune cells. It can be said that protein molecules are the foundation of immune regulation. Model mice are necessary for us to examine fixed compounds in our studies. Conditional deletion and overexpression mouse models are the two primary categories of model mice. Numerous model mice have been documented in CIS research. The study of innate immune responses following ischemic stroke will benefit more from the use of these transgenic mice that target innate immunity. This paper analyzes the literature on transgenic mice related to innate immune responses following ischemic stroke because of the significance of these responses. It is anticipated to produce novel medications, improve clinical treatment guidance, and undergo a metamorphosis and application in the clinic in the future.

Panaroma of microglia in traumatic brain injury: a bibliometric analysis and visualization study during 2000-2023

Background

Traumatic brain injury (TBI) is a critical global health concern characterized by elevated rates of both morbidity and mortality. The pathological and physiological changes after TBI are closely related to microglia. Microglia, the primary immune cells in the brain, are closely linked to the mechanisms and treatment of TBI. With increasing research in this area, this study employs bibliometric analysis to identify current research hotspots and predict future trends.

Objective

We decided to perform a bibliometric analysis to provide a comprehensive overview of the advancements in microglia research related to traumatic brain injury. We aim to offer researchers insights into current trends and future research directions.

Method

We collected all articles and reviews related to microglia and traumatic brain injury published between 2000 and 2023 from the Web of Science Core Collection. These records were analyzed using VOSviewer, CiteSpace, and the R package "bibliometrix".

Results

We retrieved 665 publications from 25 countries, with the majority contributed by the United States and China. The number of publications on traumatic brain injury and microglia has been steadily increasing each year. Our analysis highlighted the Journal of Neurotrauma and the Journal of Neuroinflammation as the most influential journals in this field. Alan I. Faden and David J. Loane are recognized as leading contributors. Keyword analysis indicates that neuroinflammation, microglial polarization, and neurodegenerative diseases are pivotal areas for future research.

Conclusion

In recent years, research on TBI-related microglia has proliferated, with current studies primarily focusing on microglial involvement in neuroinflammation, neurodegenerative changes, and microglial polarization following TBI. Since neuroinflammation and neurodegeneration are two hallmark features of TBI, targeting microglia in TBI treatment may become a central focus for future research.

CD200-CD200R Pathway: A Regulator of Microglial Polarization in Postoperative Cognitive Dysfunction

Microglial polarization refers to the ability of microglia to exhibit different functional states under various conditions. As the resident immune cells of the brain, changes in the functional state of microglia play a crucial role in the progression of postoperative cognitive dysfunction. Recent studies have indicated that CD200-CD200R signaling is associated with microglial polarization. This review focuses on the latest advancements regarding whether CD200-CD200R signaling can regulate microglial polarization and thereby influence postoperative cognitive dysfunction.

The emerging role of disease-associated microglia in Parkinson's disease

Disease-associated microglia (DAM) are a subset of microglia that appear at various stages of central nervous system neurodegenerative diseases. DAM were identified using single-cell RNA sequencing within Alzheimer's Disease (AD) where they were characterized by their unique localization near amyloid-β plaques and their phagocytic and lipid-metabolizing features. Unfortunately, activation and etiology of DAM are only understood within the context of AD where Triggering Receptor Expressed On Myeloid Cells 2 (TREM2), a receptor for amyloid-β, appears to be the key regulator in microglial transition to a DAM state. Despite this reliance on TREM2 in AD, DAM appear across other neurodegenerative diseases in which TREM2 may not be a critical player. This begs the question of if DAM are truly the same across all neurodegenerative diseases or if there exists a heterogeneity to DAM across neurodegenerative pathologies. Investigation into this critical gap in the field regarding DAM etiology and activation, as well as DAM function, could be delineated utilizing models of Parkinson's disease (PD) to complement studies in models of AD. Though highly underexplored regarding DAM, PD with its pattern of protein aggregation-associated pathology like AD could serve as the spatiotemporal comparison against AD findings to ascertain the nature of DAM. The experimental vehicle that could guide the future of such investigation is the multi-omics model. With a compound approach focusing on exploring triggers for DAM at the chromatin or mRNA level and related protein output, it becomes possible to strongly characterize and firmly answer the question of what is a DAM.

Exosomes Derived from DPA-treated UCMSCs Attenuated Depression-like Behaviors and Neuroinflammation in a Model of Depression Induced by Chronic Stress

Depression is characterized by both neuroinflammation and neurodegeneration. Exosomes (Exo) have been shown to function as inhibitors of inflammation and promoters of neurogenesis. Omega-3 polyunsaturated fatty acids, such as eicosapentaenoic acid, can combat depression by increasing levels of docosapentaenoic acid (DPA). This study explored the effects of DPA on the therapeutic potential of Exo derived from human umbilical cord mesenchymal stem cells (hUCMSCs) in glia-induced neuroinflammation associated with depression. Exposure to chronic unpredictable mild stress (CUMS) over six weeks induced depression- and anxiety-like behaviors, while decreasing the levels of serotonin and dopamine. Molecularly, CUMS increased the concentrations of the microglial M1 markers Iba1, iNOS, and IL-1β, while reducing the M2 markers Arg1, CD206, and IL-10 in the prefrontal cortex and hippocampus. However, Exo therapy reversed these effects. Moreover, DPA treatment of Exo demonstrated superior efficacy in alleviating depressive behaviors, neurotransmitter deficiencies, and M1 microglial activation. In vitro, Exo suppressed LPS-stimulated BV2 cell viability and M1 microglial activation, while mitigating the SH-SY5Y cell apoptosis triggered by treatment with the conditioned medium from LPS-activated BV2 cells. Furthermore, administration of DPA enhanced this effect. Mechanically, DPA enhanced Exo function by upregulating miR125b-5p expression, thereby targeting the MyD88/TRAF6/NF-κB signaling pathway. In summary, Exo exhibited antidepressant effects by suppressing M1 microglial neuroinflammation, while DPA treatment provided a more potent therapeutic effect on depression-like changes through the upregulation of miR125b-5p targeting the MyD88/TRAF6/NF-κB pathway.

Predicting Vasospasm and Early Mortality in Severe Traumatic Brain Injury: A Model Using Serum Cytokines, Neuronal Proteins, and Clinical Data

BACKGROUND AND OBJECTIVES

Prediction of patient outcomes after severe traumatic brain injury (sTBI) is limited with current clinical tools. This study aimed to improve such prognostication by combining clinical data and serum inflammatory and neuronal proteins in patients with sTBI to develop predictive models for post-traumatic vasospasm (PTV) and mortality.

METHODS

Fifty-three adult civilian patients were prospectively enrolled in the sTBI arm of the Surgical Critical Care Initiative (SC2i). Clinical, serum inflammatory, and neuronal protein data were combined using the parsimonious machine learning methods of least absolute shrinkage and selection operator (LASSO) and classification and regression trees (CART) to construct parsimonious models for predicting development of PTV and mortality.

RESULTS

Thirty-six (67.9%) patients developed vasospasm and 10 (18.9%) died. The mean age was 39.2 years; 22.6% were women. CART identified lower IL9, lower presentation pulse rate, and higher eotaxin as predictors of vasospasm development (full data area under curve (AUC) = 0.89, mean cross-validated AUC = 0.47). LASSO identified higher Rotterdam computed tomography score and lower age as risk factors for vasospasm development (full data AUC 0.94, sensitivity 0.86, and specificity 0.94; cross-validation AUC 0.87, sensitivity 0.79, and specificity 0.93). CART identified high levels of eotaxin as most predictive of mortality (AUC 0.74, cross-validation AUC 0.57). LASSO identified higher serum IL6, lower IL12, and higher glucose as predictive of mortality (full data AUC 0.9, sensitivity 1.0, and specificity 0.72; cross-validation AUC 0.8, sensitivity 0.85, and specificity 0.79).

CONCLUSION

Inflammatory cytokine levels after sTBI may have predictive value that exceeds conventional clinical variables for certain outcomes. IL-9, pulse rate, and eotaxin as well as Rotterdam score and age predict development of PTV. Eotaxin, IL-6, IL-12, and glucose were predictive of mortality. These results warrant validation in a prospective cohort.

Observations on the efficacy of edaravone dexborneol in preventing post-stroke depression and its inflammatory mechanism: a prospective, randomized, control trial

Objective

This study aimed to observe the effect of edaravone dexborneol (EDB) on the incidence of early post-stroke depression (PSD) and explore its inflammatory mechanisms.

Methods

A prospective, randomized controlled study was conducted from January 2022 to June 2023, involving patients with acute ischemic stroke (AIS) at the Neurology Department of the Third Affiliated Hospital of Beijing University of Traditional Chinese Medicine. The control group received routine treatment, while the experimental group received routine combined EDB treatment. The main outcome measures included PSD incidence, Patient Health Questionnaire (PHQ-9) and Hamilton Depression Scale (HAMD) scores on days 14 and 30, and inflammatory factor levels on day 14.

Results

A total of 93 patients were included in the study, 51 in the experimental group and 42 in the control group. On day 14, the PSD incidence was 13.7% in the experimental group, lower than 31.0% in the control group (95%CI 0.127-0.996; p = 0.044). Compared to the control group, the experimental group showed significantly lower concentrations of pro-inflammatory cytokines IL-1β (95%CI 3.353-5.184), IL-6 (95%CI 2.694-3.426), TNF-α (95%CI 4.985-12.196), IFN-γ (95%CI 0.163-0.451), MCP-1 (95%CI 0.335-0.787), IL-17A (95%CI 0.543-1.024), and IL-23p19 (95%CI 1.677-1.959) (all p < 0.001), and higher levels of anti-inflammatory cytokines IL-4 (95%CI -1.087 to -0.941), IL-10 (95%CI -6.125 to -1.662), and IL-13 (95%CI -6.078 to -2.953) (all p ≤ 0.001). On day 30, the PSD incidence in the experimental group was 15.7%, lower than 40.5% in the control group (95%CI 0.103-0.725; p = 0.007). Compared with the control group, the experimental group had lower PHQ-9 scores on day 14 (95%CI 0.034-1.577; p = 0.041) and day 30 (95%CI 0.018-1.573; p = 0.045), and also had lower HAMD scores on day 14 (95% CI 0.281-2.856; p = 0.018) and day 30 (95% CI 0.647-3.482; p = 0.005).

Conclusion

EDB could reduce the incidence of early PSD, reduce pro-inflammatory cytokine levels, and elevate anti-inflammatory cytokine levels, which was possibly related to the anti-inflammatory mechanism of EDB.

Clinical trial registration

http://www.chictr.org.cn/, identifier [ChiCTR2300067750].

Microglia contribute to methamphetamine reinforcement and reflect persistent transcriptional and morphological adaptations to the drug

Methamphetamine use disorder (MUD) is a chronic, relapsing disease that is characterized by repeated drug use despite negative consequences and for which there are currently no FDA-approved cessation therapeutics. Repeated methamphetamine (METH) use induces long-term gene expression changes in brain regions associated with reward processing and drug-seeking behavior, and recent evidence suggests that methamphetamine-induced neuroinflammation may also shape behavioral and molecular responses to the drug. Microglia, the resident immune cells in the brain, are principal drivers of neuroinflammatory responses and contribute to the pathophysiology of substance use disorders. Here, we investigated transcriptional and morphological changes in dorsal striatal microglia in response to methamphetamine-taking and during methamphetamine abstinence, as well as their functional contribution to drug-taking behavior. We show that methamphetamine self-administration induces transcriptional changes associated with protein folding, mRNA processing, immune signaling, and neurotransmission in dorsal striatal microglia. Importantly, many of these transcriptional changes persist through abstinence, a finding supported by morphological analyses. Functionally, we report that microglial ablation increases methamphetamine-taking, possibly involving neuroimmune and neurotransmitter regulation. In contrast, microglial depletion during abstinence does not alter methamphetamine-seeking. Taken together, these results suggest that methamphetamine induces both short and long-term changes in dorsal striatal microglia that contribute to altered drug-taking behavior and may provide valuable insights into the pathophysiology of MUD.

A Comparative Study of the Stability, Transport, and Structure-Activity Relationship of Round Scad Derived Peptides with Antineuroinflammatory Ability

Our previous study identified round scad neuroprotective peptides with different characteristics. However, the intrinsic relationship between their structure and bioactivity, as well as their bioavailability, remains unclear. The aim of this study is to elucidate the bioavailability of these peptides and their structure-activity relationship against neuroinflammation. Results showed that the SR and WCP peptides were resistant to gastrointestinal digestion. Additionally, peptides SR, WCP, and WCPF could transport Caco-2 monolayers as intact peptides. The permeability coefficients (Papp) of SR, WCP, and WCPF in Caco-2 monolayer were (1.53 ± 0.01) × 10-5, (2.12 ± 0.01) × 10-5, and (8.86 ± 0.03) × 10-7 cm/s, respectively. Peptides SR, WCP, and WCPF, as promising inhibitors of JAK2 and STAT3, could attenuate the levels of pro-inflammatory cytokines and regulate the NFκB and JAK2/STAT3 signaling pathway in LPS-treated BV-2 cells. WCPF exerted the highest anti-inflammatory activity. Moreover, bioinformatics, molecular docking, and quantum chemistry studies indicated that the bioactivity of SR was attributed to Arg, whereas those of WCP and WCPF were attributed to Trp. This study supports the application of round-scad peptides and deepens the understanding of the structure-activity relationship of neuroprotective peptides.

Molecular mechanisms and therapeutic potential of lithium in Alzheimer's disease: repurposing an old class of drugs

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline and memory loss. Despite advances in understanding the pathophysiological mechanisms of AD, effective treatments remain scarce. Lithium salts, recognized as mood stabilizers in bipolar disorder, have been extensively studied for their neuroprotective effects. Several studies indicate that lithium may be a disease-modifying agent in the treatment of AD. Lithium's neuroprotective properties in AD by acting on multiple neuropathological targets, such as reducing amyloid deposition and tau phosphorylation, enhancing autophagy, neurogenesis, and synaptic plasticity, regulating cholinergic and glucose metabolism, inhibiting neuroinflammation, oxidative stress, and apoptosis, while preserving mitochondrial function. Clinical trials have demonstrated that lithium therapy can improve cognitive function in patients with AD. In particular, meta-analyses have shown that lithium may be a more effective and safer treatment than the recently FDA-approved aducanumab for improving cognitive function in patients with AD. The affordability and therapeutic efficacy of lithium have prompted a reassessment of its use. However, the use of lithium may lead to potential side effects and safety issues, which may limit its clinical application. Currently, several new lithium formulations are undergoing clinical trials to improve safety and efficacy. This review focuses on lithium's mechanism of action in treating AD, highlighting the latest advances in preclinical studies and clinical trials. It also explores the side effects of lithium therapy and coping strategies, offering a potential therapeutic strategy for patients with AD.

Anatomical location of injected microglia in different activation states and time course of injury determines survival of retinal ganglion cells after optic nerve crush

Background: Activated microglia release harmful substances to retinal ganglion cells (RGCs), but may also benefit by removing cellular debris and secreting neurotrophic factors. These paradoxical roles remain controversial because the nature and time-course of the injury that defines their role is unknown. The aim of this study was to determine if pharmacological manipulation of microglia to acquire a pro-inflammatory or pro-survival phenotype will exacerbate or enhance neuronal survival after injury.Material and methods: Treated HAP I (highly aggressively proliferating immortalized) microglia were injected into the vitreous or tail vein (T V) of female Sprague-Dawley rats. Retinas were examined at 4-14 days following optic nerve crush (ONC) and the number of surviving RGCs was determined.Results: Injection of untreated HAP I cells resulted in the greater loss of RGCs early after ONC when injected into the vitreous and later after ONC when injected into the T V. LP S activated HAP I cells injected into the vitreous resulted in greater RGC loss with and without injury. When injected into the T V with ONC there was no loss of RGCs 4 days after ONC but greater loss afterwards. Minocycline treated HAP I cells injected into the vitreous resulted in greater RGC survival than untreated HAP I cells. However, when injected into the T V with ONC there was greater loss of RGCs. These results suggest that optic nerve signals attract extrinsic microglia to the retina, resulting in a proinflammatory response.Conclusion: Neuroprotection or cytotoxicity of microglia depends on the type of activation, time course of the injury, and if they act on the axon or cell body.

Mild and deep hypothermia differentially affect cerebral neuroinflammatory and cold shock response following cardiopulmonary bypass in rat

INTRODUCTION

Targeted temperature management (TTM) is considered to be a neuroprotective strategy during cardiopulmonary bypass (CPB) assisted procedures, possibly through the activation of cold shock proteins. We therefore investigated the effects of mild compared with deep hypothermia on the neuroinflammatory response and cold shock protein expression after CPB in rats.

METHODS

Wistar rats were subjected to 1 hr of mild (33 °C) or deep (18 °C) hypothermia during CPB or sham procedure. PET scan analyses using TSPO ligand [11C]PBR28 were performed on day 1 (short-term) or day 3 and 7 post-procedure (long-term) to assess neuroinflammation. Hippocampal and cortical samples were obtained at day 1 in the short-term group and at day 7 in the long-term group. mRNA expression of M1 and M2 microglia associated cytokines was analysed with RT-PCR. Cold shock protein RNA-binding motive 3 (RBM3) and tyrosine receptor kinase B (TrkB) receptor protein expression were determined with Western Blot and quantified.

RESULTS

In both groups target temperature was reached within an hour. Standard uptake values (SUV) of [11C]PBR28 in CPB rats at 1 day and 3 days were similar to that of sham animals. At 7 days after CPB the SUV was significantly higher in amygdala and hippocampal regions of the CPB 18 °C group as compared to the CPB 33 °C group. No differences were observed in the expression of M1 and M2 microglia-related cytokines between TTM 18 °C and 33 °C. RBM3 protein levels in cortex and hippocampus were significantly higher in CPB 33 °C compared to CPB 18 °C and sham 33 °C, at day 1 and day 7, respectively.

CONCLUSIONS

TTM at 18 °C increased the neuroinflammatory response in amygdala and hippocampus compared to TTM at 33 °C in rats undergoing a CPB procedure. Additionally, TTM at 33 °C induced increased expression of TrkB and RBM3 in cortex and hippocampus of rats on CPB compared to TTM at 18 °C. Together, these data indicate that neuroinflammation is alleviated by TTM at 33 °C, possibly by recruiting protective mechanisms through cold shock protein induction.

Aspartame-induced cognitive dysfunction: Unveiling role of microglia-mediated neuroinflammation and molecular remediation

Aspartame, an artificial sweetener, is consumed by millions of people globally. There are multiple reports of aspartame and its metabolites affecting cognitive functions in animal models and humans, which include learning problems, headaches, seizures, migraines, irritable moods, anxiety, depression, and insomnia. These cognitive deficits and associated symptoms are partly attributed to dysregulated excitatory and inhibitory neurotransmitter balance due to aspartate released from aspartame, resulting in an excitotoxic effect in neurons, leading to neuronal damage. However, microglia, a central immunocompetent cell type in brain tissue and a significant player in inflammation can contribute to the impact. Microglia rapidly respond to changes in CNS homeostasis. Aspartame consumption might affect the microglia phenotype directly via methanol-induced toxic effects and indirectly via aspartic acid-mediated excitotoxicity, exacerbating symptoms of cognitive decline. Long-term oral consumption of aspartame thus might change microglia's phenotype from ramified to activated, resulting in chronic or sustained activation, releasing excess pro-inflammatory molecules. This pro-inflammatory surge might lead to the degeneration of healthy neurons and other glial cells, impairing cognition. This review will deliberate on possible links and research gaps that need to be explored concerning aspartame consumption, ecotoxicity and microglia-mediated inflammatory cognitive impairment. The study covers a comprehensive analysis of the impact of aspartame consumption on cognitive function, considering both direct and indirect effects, including the involvement of microglia-mediated neuroinflammation. We also propose a novel intervention strategy involving tryptophan supplementation to mitigate cognitive decline symptoms in individuals with prolonged aspartame consumption, providing a potential solution to address the adverse effects of aspartame on cognitive function.

cGAS/STING signaling pathway-mediated microglial activation in the PFC underlies chronic ethanol exposure-induced anxiety-like behaviors in mice

Chronic ethanol consumption is a prevalent condition in contemporary society and exacerbates anxiety symptoms in healthy individuals. The activation of microglia, leading to neuroinflammatory responses, may serve as a significant precipitating factor; however, the precise molecular mechanisms underlying this phenomenon remain elusive. In this study, we initially confirmed that chronic ethanol exposure (CEE) induces anxiety-like behaviors in mice through open field test and elevated plus maze test. The cGAS/STING signaling pathway has been confirmed to exhibits a significant association with inflammatory signaling responses in both peripheral and central systems. Western blot analysis confirmed alterations in the cGAS/STING signaling pathway during CEE, including the upregulation of p-TBK1 and p-IRF3 proteins. Moreover, we observed microglial activation in the prefrontal cortex (PFC) of CEE mice, characterized by significant alterations in branching morphology and an increase in cell body size. Additionally, we observed that administration of CEE resulted in mitochondrial dysfunction within the PFC of mice, accompanied by a significant elevation in cytosolic mitochondrial DNA (mtDNA) levels. Furthermore, our findings revealed that the inhibition of STING by H-151 effectively alleviated anxiety-like behavior and suppressed microglial activation induced by CEE. Our study unveiled a significant association between anxiety-like behavior, microglial activation, inflammation, and mitochondria dysfunction during CEE.

CD36 deletion prevents white matter injury by modulating microglia polarization through the Traf5-MAPK signal pathway

BACKGROUND

White matter injury (WMI) represents a significant etiological factor contributing to neurological impairment subsequent to Traumatic Brain Injury (TBI). CD36 receptors are recognized as pivotal participants in the pathogenesis of neurological disorders, including stroke and spinal cord injury. Furthermore, dynamic fluctuations in the phenotypic polarization of microglial cells have been intimately associated with the regenerative processes within the injured tissue following TBI. Nevertheless, there is a paucity of research addressing the impact of CD36 receptors on WMI and microglial polarization. This investigation aims to elucidate the functional role and mechanistic underpinnings of CD36 in modulating microglial polarization and WMI following TBI.

METHODS

TBI models were induced in murine subjects via controlled cortical impact (CCI). The spatiotemporal patterns of CD36 expression were examined through quantitative polymerase chain reaction (qPCR), Western blot analysis, and immunofluorescence staining. The extent of white matter injury was assessed via transmission electron microscopy, Luxol Fast Blue (LFB) staining, and immunofluorescence staining. Transcriptome sequencing was employed to dissect the molecular mechanisms underlying CD36 down-regulation and its influence on white matter damage. Microglial polarization status was ascertained using qPCR, Western blot analysis, and immunofluorescence staining. In vitro, a Transwell co-culture system was employed to investigate the impact of CD36-dependent microglial polarization on oligodendrocytes subjected to oxygen-glucose deprivation (OGD).

RESULTS

Western blot and qPCR analyses revealed that CD36 expression reached its zenith at 7 days post-TBI and remained sustained at this level thereafter. Immunofluorescence staining exhibited robust CD36 expression in astrocytes and microglia following TBI. Genetic deletion of CD36 ameliorated TBI-induced white matter injury, as evidenced by a reduced SMI-32/MBP ratio and G-ratio. Transcriptome sequencing unveiled differentially expressed genes enriched in processes linked to microglial activation, regulation of neuroinflammation, and the TNF signaling pathway. Additionally, bioinformatics analysis pinpointed the Traf5-p38 axis as a critical signaling pathway. In vivo and in vitro experiments indicated that inhibition of the CD36-Traf5-MAPK axis curtailed microglial polarization toward the pro-inflammatory phenotype. In a Transwell co-culture system, BV2 cells treated with LPS + IFN-γ exacerbated the damage of post-OGD oligodendrocytes, which could be rectified through CD36 knockdown in BV2 cells.

CONCLUSIONS

This study illuminates that the suppression of CD36 mitigates WMI by constraining microglial polarization towards the pro-inflammatory phenotype through the down-regulation of the Traf5-MAPK signaling pathway. Our findings present a potential therapeutic strategy for averting neuroinflammatory responses and ensuing WMI damage resulting from TBI.

Neuronal deletion of Gtf2i results in developmental microglial alterations in a mouse model related to Williams syndrome

Williams syndrome (WS) is a genetic neurodevelopmental disorder caused by a heterozygous microdeletion, characterized by hypersociability and unique neurocognitive abnormalities. Of the deleted genes, GTF2I has been linked to hypersociability in WS. We have recently shown that Gtf2i deletion from forebrain excitatory neurons, referred to as Gtf2i conditional knockout (cKO) mice leads to multi-faceted myelination deficits associated with the social behaviors affected in WS. These deficits were potentially mediated also by microglia, as they present a close relationship with oligodendrocytes. To study the impact of altered myelination, we characterized these mice in terms of microglia over the course of development. In postnatal day 30 (P30) Gtf2i cKO mice, cortical microglia displayed a more ramified state, as compared with wild type (controls). However, postnatal day 4 (P4) microglia exhibited high proliferation rates and an elevated activation state, demonstrating altered properties related to activation and inflammation in Gtf2i cKO mice compared with control. Intriguingly, P4 Gtf2i cKO-derived microglial cells exhibited significantly elevated myelin phagocytosis in vitro compared to control mice. Lastly, systemic injection of clemastine to P4 Gtf2i cKO and control mice until P30, led to a significant interaction between genotypes and treatments on the expression levels of the phagocytic marker CD68, and a significant reduction of the macrophage/microglial marker Iba1 transcript levels in the cortex of the Gtf2i cKO treated mice. Our data thus implicate microglia as important players in WS, and that early postnatal manipulation of microglia might be beneficial in treating inflammatory and myelin-related pathologies.

The Ang-(1-7)/MasR axis ameliorates neuroinflammation in hypothermic traumatic brain injury in mice by modulating phenotypic transformation of microglia

The Ang-(1-7)/MasR axis is critically involved in treating several diseases; For example, Ang-(1-7) improves inflammatory response and neurological function after traumatic brain injury and inhibits post-inflammatory hypothermia. However, its function in traumatic brain injury (TBI) combined with seawater immersion hypothermia remains unclear. Here, we used a mice model of hypothermic TBI and a BV2 cell model of hypothermic inflammation to investigate whether the Ang-(1-7)/MasR axis is involved in ameliorating hypothermic TBI. Quantitative reverse transcription PCR, western blotting assay, and immunofluorescence assay were performed to confirm microglia polarization and cytokine regulation. Hematoxylin-eosin staining, Nissl staining, and immunohistochemical assay were conducted to assess the extent of hypothermic TBI-induced damage and the ameliorative effect of Ang-(1-7) in mice. An open field experiment and neurological function scoring with two approaches were used to assess the degree of recovery and prognosis in mice. After hypothermic TBI establishment in BV2 cells, the Ang-(1-7)/MasR axis induced phenotypic transformation of microglia from M1 to M2, inhibited IL-6 and IL-1β release, and upregulated IL-4 and IL-10 levels. After hypothermic TBI development in mice, intraperitoneally administered Ang-(1-7) attenuated histological damage and promoted neurological recovery. These findings suggest that hypothermia exacerbates TBI-induced damage and that the Ang-(1-7)/MasR axis can ameliorate hypothermic TBI and directly affect prognosis.

Exploring the Role of Apigenin in Neuroinflammation: Insights and Implications

Neuroinflammation, a hallmark of various central nervous system disorders, is often associated with oxidative stress and neuronal or oligodendrocyte cell death. It is therefore very interesting to target neuroinflammation pharmacologically. One therapeutic option is the use of nutraceuticals, particularly apigenin. Apigenin is present in plants: vegetables (parsley, celery, onions), fruits (oranges), herbs (chamomile, thyme, oregano, basil), and some beverages (tea, beer, and wine). This review explores the potential of apigenin as an anti-inflammatory agent across diverse neurological conditions (multiple sclerosis, Parkinson's disease, Alzheimer's disease), cancer, cardiovascular diseases, cognitive and memory disorders, and toxicity related to trace metals and other chemicals. Drawing upon major studies, we summarize apigenin's multifaceted effects and underlying mechanisms in neuroinflammation. Our review underscores apigenin's therapeutic promise and calls for further investigation into its clinical applications.

Circulating cytokines and vascular dementia: A bi-directional Mendelian randomization study

Inflammatory responses are associated with the development of vascular dementia (VaD). Circulating cytokines modulate the inflammatory response and are important for the immune system. To further elucidate the role of the immune system in VaD, we used Mendelian randomization (MR) to comprehensively and bi-directionally assess the role of circulating cytokines in VaD. Using state-of-the-art genome-wide association studies, we primarily assessed whether different genetic levels of 41 circulating cytokines affect the risk of developing VaD and, in turn, whether the genetic risk of VaD affects these circulating cytokines. We used inverse variance weighting (IVW) and several other MR methods to assess the bidirectional causality between circulating cytokines and VaD, and performed sensitivity analyses. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) was inversely associated with VaD risk [odds ratio (OR): 0.74, 95 % confidence interval (CI): 0.60-0.92, P = 0.007, 0.007]. VaD was associated with seven circulating cytokines: macrophage inflammatory protein 1b (MIP-1 beta) [OR: 1.05, 95 % CI: 1.01-1.08, P = 0.009], Interleukin-12p70 (IL-12) [OR: 1.04, 95 % CI: 1.00-1.08, P = 0.047], Interleukin-17 (IL-17) [OR: 1.04, 95 % CI: 1.00-1.07, P = 0.038], Interleukin-7 (IL-7) [OR: 1.07, 95 % CI: 1.02-1.12, P = 0.009], Interferon gamma (IFN-γ) [OR: 1.03, 95 % CI: 1.00-1.07, P = 0.046], Granulocyte-colony stimulating factor (GCSF) [OR: 1.06, 95 % CI: 1.02-1.09, P = 0.001], Fibroblast growth factor (FGF) [P = 0.001], and Fibroblast growth factor (FGF) [P = 0.001]. Fibroblast growth factor basic (FGF-Basic) [OR: 1.04, 95 % CI: 1.01-1.08, P = 0.02] were positively correlated. Circulating cytokines are associated with VaD, and further studies are needed to determine whether they are effective targets for intervention to prevent or treat VaD.

P2X7 Receptor: an Emerging Target in Alzheimer's Disease

Alzheimer's disease (AD) is a major cause of age-related dementia, which is becoming a global health crisis. However, the pathogenesis and etiology of AD are still not fully understood. And there are no valid treatment methods or precise diagnostic tools for AD. There is increasing evidence that P2X7R expression is upregulated in AD and is involved in multiple related pathological processes such as Aβ plaques, neurogenic fiber tangles, oxidative stress, and chronic neuroinflammation. This suggests that P2X7R may be a key player in the development of AD. P2X7R is a member of the ligand-gated purinergic receptor (P2X) family. It has received attention in neuroscience due to its role in a wide range of aging and age-related neurological disorders. In this review, we summarize current information on the roles of P2X7R in AD and suggest potential pharmacological interventions to slow down AD progression.

Nicotinic regulation of microglia: potential contributions to addiction

Clinical and preclinical studies have identified immunosuppressive effects of nicotine, with potential implications for treating nicotine addiction. Here we review how nicotine can regulate microglia, the resident macrophages in the brain, and corresponding effects of nicotine on neuroimmune signaling. There is significant evidence that activation of α7 nicotinic acetylcholine receptors (nAChRs) on microglia can trigger an anti-inflammatory cascade that alters microglial polarization and activity, cytokine release, and intracellular calcium concentrations, leading to neuroprotection. These anti-inflammatory effects of nicotine-dependent α7 nAChR signaling are lost during withdrawal, suggesting that neuroimmune signaling is potentiated during abstinence, and thus, heightened microglial activity may drive circuit disruption that contributes to withdrawal symptoms and hyperkatifeia. In sum, the clinical literature has highlighted immunomodulatory effects of nicotine and the potential for anti-inflammatory compounds to treat addiction. The preclinical literature investigating the underlying mechanisms points to a role of microglial engagement in the circuit dysregulation and behavioral changes that occur during nicotine addiction and withdrawal, driven, at least in part, by activation of α7 nAChRs on microglia. Specifically targeting microglial signaling may help alleviate withdrawal symptoms in people with nicotine dependence and help to promote abstinence.

The emerging importance of skull-brain interactions in traumatic brain injury

The recent identification of skull bone marrow as a reactive hematopoietic niche that can contribute to and direct leukocyte trafficking into the meninges and brain has transformed our view of this bone structure from a solid, protective casing to a living, dynamic tissue poised to modulate brain homeostasis and neuroinflammation. This emerging concept may be highly relevant to injuries that directly impact the skull such as in traumatic brain injury (TBI). From mild concussion to severe contusion with skull fracturing, the bone marrow response of this local myeloid cell reservoir has the potential to impact not just the acute inflammatory response in the brain, but also the remodeling of the calvarium itself, influencing its response to future head impacts. If we borrow understanding from recent discoveries in other CNS immunological niches and extend them to this nascent, but growing, subfield of neuroimmunology, it is not unreasonable to consider the hematopoietic compartment in the skull may similarly play an important role in health, aging, and neurodegenerative disease following TBI. This literature review briefly summarizes the traditional role of the skull in TBI and offers some additional insights into skull-brain interactions and their potential role in affecting secondary neuroinflammation and injury outcomes.

Review on anti-alzheimer drug development: approaches, challenges and perspectives

Alzheimer is an irreversible progressive neurodegenerative disease that causes failure of cerebral neurons and disability of the affected person to practice normal daily life activities. There is no concrete evidence to identify the exact reason behind the disease, so several relevant hypotheses emerged, highlighting many possible therapeutic targets, such as acetylcholinesterase, cholinergic receptors, N-methyl d-aspartate receptors, phosphodiesterase, amyloid β protein, protein phosphatase 2A, glycogen synthase kinase-3 beta, β-secretase, γ-secretase, α-secretase, serotonergic receptors, glutaminyl cyclase, tumor necrosis factor-α, γ-aminobutyric acid receptors, and mitochondria. All of these targets have been involved in the design of new potential drugs. An extensive number of these drugs have been studied in clinical trials. However, only galantamine, donepezil, and rivastigmine (ChEIs), memantine (NMDA antagonist), and aducanumab and lecanemab (selective anti-Aβ monoclonal antibodies) have been approved for AD treatment. Many drugs failed in the clinical trials to such an extent that questions have been posed about the significance of some of the aforementioned targets. On the contrary, the data of other drugs were promising and shed light on the significance of their targets for the development of new potent anti-alzheimer drugs.

Microglia orchestrate synaptic and neuronal stripping: Implication in neuropsychiatric lupus

Systemic lupus erythematosus (SLE), a multifactorial autoimmune disease, can affect the brain and cause neuropsychiatric dysfunction, also named neuropsychiatric lupus (NPSLE). Microglial activation is observed in NPSLE patients. However, the mechanisms regulating microglia-mediated neurotoxicity in NPSLE remain elusive. Here, we showed that M1-like proinflammatory cytokine levels were increased in the cerebrospinal fluid (CSF) of SLE patients, especially those with neuropsychiatric symptoms. We also demonstrated that MRL/lpr lupus mice developed anxiety-like behaviours and cognitive deficits in the early and active phases of lupus, respectively. An increase in microglial number was associated with upregulation of proinflammatory cytokines in the MRL/lpr mouse brain. RNA sequencing revealed that genes associated with phagocytosis and M1 polarization were upregulated in microglia from lupus mice. Functionally, activated microglia induced synaptic stripping in vivo and promoted neuronal death in vitro. Finally, tofacitinib ameliorated neuropsychiatric disorders in MRL/lpr mice, as evidenced by reductions in microglial number and synaptic/neuronal loss and alleviation of behavioural abnormalities. Thus, our results indicated that classically activated (M1) microglia play a crucial role in NPSLE pathogenesis. Minocycline and tofacitinib were found to alleviate NPSLE by inhibiting micrglial activation, providing a promising therapeutic strategy.

Neuroinflammation of Microglial Regulation in Alzheimer's Disease: Therapeutic Approaches

Alzheimer's disease (AD) is a complex degenerative disease of the central nervous system that is clinically characterized by a progressive decline in memory and cognitive function. The pathogenesis of AD is intricate and not yet fully understood. Neuroinflammation, particularly microglial activation-mediated neuroinflammation, is believed to play a crucial role in increasing the risk, triggering the onset, and hastening the progression of AD. Modulating microglial activation and regulating microglial energy metabolic disorder are seen as promising strategies to intervene in AD. The application of anti-inflammatory drugs and the targeting of microglia for the prevention and treatment of AD has emerged as a new area of research interest. This article provides a comprehensive review of the role of neuroinflammation of microglial regulation in the development of AD, exploring the connection between microglial energy metabolic disorder, neuroinflammation, and AD development. Additionally, the advancements in anti-inflammatory and microglia-regulating therapies for AD are discussed.

The role of SIRT3 in mediating the cognitive deficits and neuroinflammatory changes associated with a developmental animal model of schizophrenia

The neuroinflammatory state may contribute to the pathogenesis of many mental disorders including schizophrenia. Nicotinamide adenine dinucleotide (NAD+) is an essential cofactor for activation of proteins involved in mitochondria quality control, such as Sirtuin3 (SIRT3). Our previous study has found that NAD+ supplement could rescue early life stress (ELS)-induced neuroinflammation and down-regulation of SIRT3 in adult offspring. However, it is unclear whether SIRT3 is the key to the neuroprotective effects of NAD+ supplement in this animal model of schizophrenia. The present study used 24 h maternal separation (MS) as ELS to Wistar rat pups on the postnatal day (PND) 9. Schizophrenia-like behaviors and memory impairments were detected by behavioral tests. Microglial activation, pro-inflammatory cytokine expression, and NAD+/SIRT3 expression were detected in the prefrontal cortex and hippocampus. Meanwhile, NAM (a precursor of NAD+), and the SIRT3 activator Honokiol (HNK), and the SIRT3 inhibitor 3-TYP were used as an intervention in vivo. Our results showed that ELS could induce schizophrenia-like behaviors and M1 microglial activation, NAD+ decline, lower expression of SIRT3, and increased acetylated superoxide dismutase 2 expression at the adult stage. NAD+ supplement or HNK administration could block this process and normalize the behavioral alterations of the MS animals. 3-TYP administration in the control group and the NAM-treated MS rats caused M1 microglial activation and cognitive deficits. Our results demonstrated that SIRT3 mediated the stabilizing effect of NAD+ on normalizing M1 microglial activation and behavioral phenotypes in MS rats.

Role of pyroptosis in the pathogenesis of various neurological diseases

Pyroptosis, an inflammatory programmed cell death process, has recently garnered significant attention due to its pivotal role in various neurological diseases. This review delves into the intricate molecular signaling pathways governing pyroptosis, encompassing both caspase-1 dependent and caspase-1 independent routes, while emphasizing the critical role played by the inflammasome machinery in initiating cell death. Notably, we explore the Nucleotide-binding domain leucine-rich repeat (NLR) containing protein family, the Absent in melanoma 2-like receptor family, and the Pyrin receptor family as essential activators of pyroptosis. Additionally, we comprehensively examine the Gasdermin family, renowned for their role as executioner proteins in pyroptosis. Central to our review is the interplay between pyroptosis and various central nervous system (CNS) cell types, including astrocytes, microglia, neurons, and the blood-brain barrier (BBB). Pyroptosis emerges as a significant factor in the pathophysiology of each cell type, highlighting its far-reaching impact on neurological diseases. This review also thoroughly addresses the involvement of pyroptosis in specific neurological conditions, such as HIV infection, drug abuse-mediated pathologies, Alzheimer's disease, and Parkinson's disease. These discussions illuminate the intricate connections between pyroptosis, chronic inflammation, and cell death in the development of these disorders. We also conducted a comparative analysis, contrasting pyroptosis with other cell death mechanisms, thereby shedding light on their unique aspects. This approach helps clarify the distinct contributions of pyroptosis to neuroinflammatory processes. In conclusion, this review offers a comprehensive exploration of the role of pyroptosis in various neurological diseases, emphasizing its multifaceted molecular mechanisms within various CNS cell types. By elucidating the link between pyroptosis and chronic inflammation in the context of neurodegenerative disorders and infections, it provides valuable insights into potential therapeutic targets for mitigating these conditions.

The role of microglia heterogeneity in synaptic plasticity and brain disorders: Will sequencing shed light on the discovery of new therapeutic targets?

Microglia play a crucial role in interacting with neuronal synapses and modulating synaptic plasticity. This function is particularly significant during postnatal development, as microglia are responsible for removing excessive synapses to prevent neurodevelopmental deficits. Dysregulation of microglial synaptic function has been well-documented in various pathological conditions, notably Alzheimer's disease and multiple sclerosis. The recent application of RNA sequencing has provided a powerful and unbiased means to decipher spatial and temporal microglial heterogeneity. By identifying microglia with varying gene expression profiles, researchers have defined multiple subgroups of microglia associated with specific pathological states, including disease-associated microglia, interferon-responsive microglia, proliferating microglia, and inflamed microglia in multiple sclerosis, among others. However, the functional roles of these distinct subgroups remain inadequately characterized. This review aims to refine our current understanding of the potential roles of heterogeneous microglia in regulating synaptic plasticity and their implications for various brain disorders, drawing from recent sequencing research and functional studies. This knowledge may aid in the identification of pathogenetic biomarkers and potential factors contributing to pathogenesis, shedding new light on the discovery of novel drug targets. The field of sequencing-based data mining is evolving toward a multi-omics approach. With advances in viral tools for precise microglial regulation and the development of brain organoid models, we are poised to elucidate the functional roles of microglial subgroups detected through sequencing analysis, ultimately identifying valuable therapeutic targets.

Libertellenone C attenuates oxidative stress and neuroinflammation with the capacity of NLRP3 inhibition

Neurodegenerative diseases (NDs) are common chronic diseases arising from progressive damage to the nervous system. Here, in-house natural product database screening revealed that libertellenone C (LC) obtained from the fermentation products of Arthrinium arundinis separated from the gut of a centipede collected in our Tongji campus, showed a remarkable neuroprotective effect. Further investigation was conducted to clarify the specific mechanism. LC dose-dependently reversed glutamate-induced decreased viability, accumulated reactive oxygen species, mitochondrial membrane potential loss, and apoptosis in SH-SY5Y cells. Network pharmacology analysis predicted that the targets of LC were most likely directly related to oxidative stress and the regulation of inflammatory factor-associated signaling pathways. Further study demonstrated that LC attenuated nitrite, TNF-α, and IL-1β production and decreased inducible nitric oxide synthase and cyclooxygenase expression in lipopolysaccharide-induced BV-2 cells. LC could directly inhibit NLRP3 inflammasome activation by decreasing the expression levels of NLRP3, ASC, cleaved Caspase-1, and NF-κB p65. Our results provide a new understanding of how LC inhibits the NLRP3 inflammasome in microglia, providing neuroprotection. These findings might guide the development of effective LC-based therapeutic strategies for NDs.

Microglia contribute to methamphetamine reinforcement and reflect persistent transcriptional and morphological adaptations to the drug

Methamphetamine use disorder (MUD) is a chronic, relapsing disease that is characterized by repeated drug use despite negative consequences and for which there are currently no FDA-approved cessation therapeutics. Repeated methamphetamine (METH) use induces long-term gene expression changes in brain regions associated with reward processing and drug-seeking behavior, and recent evidence suggests that methamphetamine-induced neuroinflammation may also shape behavioral and molecular responses to the drug. Microglia, the resident immune cells in the brain, are principal drivers of neuroinflammatory responses and contribute to the pathophysiology of substance use disorders. Here, we investigated transcriptional and morphological changes in dorsal striatal microglia in response to methamphetamine-taking and during methamphetamine abstinence, as well as their functional contribution to drug-taking behavior. We show that methamphetamine self-administration induces transcriptional changes associated with protein folding, mRNA processing, immune signaling, and neurotransmission in dorsal striatal microglia. Importantly, many of these transcriptional changes persist through abstinence, a finding supported by morphological analyses. Functionally, we report that microglial ablation increases methamphetamine-taking, possibly involving neuroimmune and neurotransmitter regulation, and that post-methamphetamine microglial repopulation attenuates drug-seeking following a 21-day period of abstinence. In contrast, microglial depletion during abstinence did not alter methamphetamine-seeking. Taken together, these results suggest that methamphetamine induces both short and long-term changes in dorsal striatal microglia that contribute to altered drug-taking behavior and may provide valuable insights into the pathophysiology of MUD.

Oxidative stress and inflammation cause auditory system damage via glial cell activation and dysregulated expression of gap junction proteins in an experimental model of styrene-induced oto/neurotoxicity

BACKGROUND

Redox imbalance and inflammation have been proposed as the principal mechanisms of damage in the auditory system, resulting in functional alterations and hearing loss. Microglia and astrocytes play a crucial role in mediating oxidative/inflammatory injury in the central nervous system; however, the role of glial cells in the auditory damage is still elusive.

OBJECTIVES

Here we investigated glial-mediated responses to toxic injury in peripheral and central structures of the auditory pathway, i.e., the cochlea and the auditory cortex (ACx), in rats exposed to styrene, a volatile compound with well-known oto/neurotoxic properties.

METHODS

Male adult Wistar rats were treated with styrene (400 mg/kg daily for 3 weeks, 5/days a week). Electrophysiological, morphological, immunofluorescence and molecular analyses were performed in both the cochlea and the ACx to evaluate the mechanisms underlying styrene-induced oto/neurotoxicity in the auditory system.

RESULTS

We showed that the oto/neurotoxic insult induced by styrene increases oxidative stress in both cochlea and ACx. This was associated with macrophages and glial cell activation, increased expression of inflammatory markers (i.e., pro-inflammatory cytokines and chemokine receptors) and alterations in connexin (Cxs) and pannexin (Panx) expression, likely responsible for dysregulation of the microglia/astrocyte network. Specifically, we found downregulation of Cx26 and Cx30 in the cochlea, and high level of Cx43 and Panx1 in the ACx.

CONCLUSIONS

Collectively, our results provide novel evidence on the role of immune and glial cell activation in the oxidative/inflammatory damage induced by styrene in the auditory system at both peripheral and central levels, also involving alterations of gap junction networks. Our data suggest that targeting glial cells and connexin/pannexin expression might be useful to attenuate oxidative/inflammatory damage in the auditory system.

Relation between Apolipoprotein E in Alzheimer's Disease and SARS-CoV-2 and their Treatment Strategy: A Review

COVID-19, which primarily affects the pulmonary system, turned out to be a global pandemic, whereas the effects on other systems are still unknown. SARS-CoV-2, binds to angiotensinconverting enzyme 2 (ACE2) receptors in the lungs, causing pneumonia-like symptoms. The same ACE receptors are also present in organs other than the lungs. Therefore, there is a need to study the impact of coronavirus on other human body organs. Recently, UK Biobank reports on the genetic risk factor of the virus attack. A double mutation in the apolipoprotein E (APOE4) allele has shown a significant role in COVID-19. The same APOE4 mutation has already been proven to hold a key role in developing early-onset Alzheimer's disease (EOAD). Despite this data, Alzheimer's disease is believed to be a comorbidity of COVID-19. Previous virus attacks on the same viral family, Coronaviridae, produced neurological effects like neurodegeneration, neuronal inflammation, and other central nervous system-related dysfunctions. Since the long-term implications of COVID-19 are unknown, more research into the impact of the virus on the central nervous system is needed. Both COVID-19 and AD share a common genetic factor, so that AD patients may have a greater risk of SARS-CoV-2. Here, in this review, we have briefly discussed the role of APOE4 in the pathogenesis of AD and SARS-CoV-2, along with their treatment strategy, current scenario, and possible future directions.

Severity of Peripheral Infection Differentially Affects Brain Functions in Mice via Microglia-Dependent and -Independent Mechanisms

Peripheral infection induces inflammation in peripheral tissues and the brain, impacting brain function. Glial cells are key players in this process. However, the effects of peripheral infection on glial activation and brain function remain unknown. Here, we showed that varying degrees of peripheral infection had different effects on the regulation of brain functions by microglia-dependent and -independent mechanisms. Acute mild infection (one-day LPS challenge: 1LPS) exacerbated middle cerebral artery occlusion (MCAO) injury, and severe infection (four-day LPS challenge: 4LPS) for one week suppressed it. MCAO injury was assessed by triphenyltetrazolium chloride staining. We observed early activation of microglia in the 1LPS and 4LPS groups. Depleting microglia with a colony-stimulating factor-1 receptor (CSF1R) antagonist had no effect on 1LPS-induced brain injury exacerbation but abolished 4LPS-induced protection, indicating microglial independence and dependence, respectively. Microglia-independent exacerbation caused by 1LPS involved peripheral immune cells including macrophages. RNA sequencing analysis of 4LPS-treated microglia revealed increased factors related to anti-inflammatory and neuronal tissue repair, suggesting their association with the protective effect. In conclusion, varying degrees of peripheral inflammation had contradictory effects (exacerbation vs. protection) on MCAO, which may be attributed to microglial dependence. Our findings highlight the significant impact of peripheral infection on brain function, particularly in relation to glial cells.

Deep analysis of CD4 T cells in the rhesus CNS during SIV infection

Virologic suppression with antiretroviral therapy (ART) has significantly improved health outcomes for people living with HIV, yet challenges related to chronic inflammation in the central nervous system (CNS)-known as Neuro-HIV- persist. As primary targets for HIV-1 with the ability to survey and populate the CNS and interact with myeloid cells to co-ordinate neuroinflammation, CD4 T cells are pivotal in Neuro-HIV. Despite their importance, our understanding of CD4 T cell distribution in virus-targeted CNS tissues, their response to infection, and potential recovery following initiation of ART remain limited. To address these gaps, we studied ten SIVmac251-infected rhesus macaques using an ART regimen simulating suboptimal adherence. We evaluated four macaques during the acute phase pre-ART and six during the chronic phase. Our data revealed that HIV target CCR5+ CD4 T cells inhabit both the brain parenchyma and adjacent CNS tissues, encompassing choroid plexus stroma, dura mater, and the skull bone marrow. Aligning with the known susceptibility of CCR5+ CD4 T cells to viral infection and their presence within the CNS, high levels of viral RNA were detected in the brain parenchyma and its border tissues during acute SIV infection. Single-cell RNA sequencing of CD45+ cells from the brain revealed colocalization of viral transcripts within CD4 clusters and significant activation of antiviral molecules and specific effector programs within T cells, indicating CNS CD4 T cell engagement during infection. Acute infection led to marked imbalance in the CNS CD4/CD8 ratio which persisted into the chronic phase. These observations underscore the functional involvement of CD4 T cells within the CNS during SIV infection, enhancing our understanding of their role in establishing CNS viral presence. Our findings offer insights for potential T cell-focused interventions while underscoring the challenges in eradicating HIV from the CNS, particularly in the context of sub-optimal ART.

CD137L Inhibition Ameliorates Hippocampal Neuroinflammation and Behavioral Deficits in a Mouse Model of Sepsis-Associated Encephalopathy

Anxiety manifestations and cognitive dysfunction are common sequelae in patients with sepsis-associated encephalopathy (SAE). Microglia-mediated inflammatory signaling is involved in anxiety, depression, and cognitive dysfunction during acute infection with bacterial lipopolysaccharide (LPS). However, the molecular mechanisms underlying microglia activation and behavioral and cognitive deficits in sepsis have not been in fully elucidated. Based on previous research, we speculated that the CD137 receptor/ligand system modulates microglia function during sepsis to mediate classical neurological SAE symptoms. A murine model of SAE was established by injecting male C57BL/6 mice with LPS, and cultured mouse BV2 microglia were used for in vitro assays. RT-qPCR, immunofluorescence staining, flow cytometry, and ELISA were used to assess microglial activation and the expression of CD137L and inflammation-related cytokines in the mouse hippocampus and in cultured BV2 cells. In addition, behavioral tests were conducted in assess cognitive performance and behavioral distress. Immunofluorescence and RT-qPCR analyses showed that hippocampal expression of CD137L was upregulated in activated microglia following LPS treatment. Pre-treatment with the CD137L neutralizing antibody TKS-1 significantly reduced CD137L levels, attenuated the expression of M1 polarization markers in microglia, and inhibited the production of TNF-α, IL-1β, and IL-6 in both LPS-treated mice and BV2 cells. Conversely, stimulation of CD137L signaling by recombinant CD137-Fc fusion protein activated the synthesis and release of pro-inflammatory cytokines in cultures BV2 microglia. Importantly, open field, elevated plus maze, and Y-maze spontaneous alternation test results indicated that TKS-1 administration alleviated anxiety-like behavior and spatial memory decline in mice with LPS-induced SAE. These findings suggest that CD137L upregulation in activated microglia critically contributes to neuroinflammation, anxiety-like behavior, and cognitive dysfunction in the mouse model of LPS-induced sepsis. Therefore, therapeutic modulation of the CD137L/CD137 signaling pathway may represent an effective way to minimize brain damage and prevent cognitive and emotional deficits associated with SAE.