Neuroinflammation: An astrocyte perspective

Activation of chaperone-mediated autophagy exerting neuroprotection effect on intracerebral hemorrhage-induced neuronal injury by targeting Lamp2a

Intracerebral hemorrhage (ICH) is a common and devastating type of stroke, marked by significant morbidity and a grim prognosis. The inflammation cascade triggered by astrocytes plays a critical role in secondary brain injury (SBI) following ICH, leading to detrimental effects such as cell death. However, effective intervention strategies are currently lacking. This study aims to investigate the role of the astrocyte cascade reaction following ICH and identify potential intervention targets. Utilizing the GSE216607 and GSE206971 databases for analysis, we established a mouse autologous blood model. Firstly, our research revealed a significant activation of the autophagy pathway following intracerebral hemorrhage (ICH), with a notable upregulation of Lamp2a, a key factor in chaperone-mediated autophagy (CMA), primarily localized in astrocytes. Additionally, the downregulation of Lamp2a resulted in a significant augmentation of A1 reactive astrocytes, concomitant with a reduction in myelin coverage area, heightened neuronal injury, exacerbated motor and sensory deficits, and diminished neurological scores after ICH in mice. Conversely, CA77.1, an activator of CMA, could reverse ICH-induced augmentation of A1 reactive astrocytes, myelin damage, neuronal death, and neurobehavioral disorders. In conclusion, the activation of astrocyte CMA following ICH can exert neuroprotective effects. Lamp2a represents a promising therapeutic target for post-ICH treatment.

Vitamin D: The crucial neuroprotective factor for nerve cells

Vitamin D is well known for its role in regulating the absorption and utilization of calcium and phosphorus as well as bone formation, and a growing number of studies have shown that vitamin D also has important roles in the nervous system, such as maintaining neurological homeostasis and protecting normal brain function, and that neurons and glial cells may be the targets of these effects. Most reviews of vitamin D's effects on the nervous system have focused on its overall effects, without distinguishing the contributors to these effects. In this review, we mainly focus on the cells of the central nervous system, summarizing the effects of vitamin D on them and the related pathways. With this review, we hope to elucidate the role of vitamin D in the nervous system at the cellular level and provide new insights into the prevention and treatment of neurodegenerative diseases in the direction of neuroprotection, myelin regeneration, and so on.

Role of astrocytes in Alzheimer's disease pathogenesis and the impact of exercise-induced remodeling

Alzheimer's disease (AD) is a prevalent and debilitating brain disorder that worsens progressively with age, characterized by cognitive decline and memory impairment. The accumulation of amyloid-beta (Aβ) leading to amyloid plaques and hyperphosphorylation of Tau, resulting in intracellular neurofibrillary tangles (NFTs), are primary pathological features of AD. Despite significant research investment and effort, therapies targeting Aβ and NFTs have proven limited in efficacy for treating or slowing AD progression. Consequently, there is a growing interest in non-invasive therapeutic strategies for AD prevention. Exercise, a low-cost and non-invasive intervention, has demonstrated promising neuroprotective potential in AD prevention. Astrocytes, among the most abundant glial cells in the brain, play essential roles in various physiological processes and are implicated in AD initiation and progression. Exercise delays pathological progression and mitigates cognitive dysfunction in AD by modulating astrocyte morphological and phenotypic changes and fostering crosstalk with other glial cells. This review aims to consolidate the current understanding of how exercise influences astrocyte dynamics in AD, with a focus on elucidating the molecular and cellular mechanisms underlying astrocyte remodeling. The review begins with an overview of the neuropathological changes observed in AD, followed by an examination of astrocyte dysfunction as a feature of the disease. Lastly, the review explores the potential therapeutic implications of exercise-induced astrocyte remodeling in the context of AD.

Brain Metabolism in Health and Neurodegeneration: The Interplay Among Neurons and Astrocytes

The regulation of energy in the brain has garnered substantial attention in recent years due to its significant implications in various disorders and aging. The brain's energy metabolism is a dynamic and tightly regulated network that balances energy demand and supply by engaging complementary molecular pathways. The crosstalk among these pathways enables the system to switch its preferred fuel source based on substrate availability, activity levels, and cell state-related factors such as redox balance. Brain energy production relies on multi-cellular cooperation and is continuously supplied by fuel from the blood due to limited internal energy stores. Astrocytes, which interface with neurons and blood vessels, play a crucial role in coordinating the brain's metabolic activity, and their dysfunction can have detrimental effects on brain health. This review characterizes the major energy substrates (glucose, lactate, glycogen, ketones and lipids) in astrocyte metabolism and their role in brain health, focusing on recent developments in the field.

Human Astrocytes Synchronize Neural Organoid Networks

Biological neural networks exhibit synchronized activity within and across interconnected regions of the central nervous system. Understanding how these coordinated networks are established and maintained may reveal therapeutic targets for neurodegeneration and neuromodulation. Here, we tested the influence of astrocytes upon synchronous network activity using human pluripotent stem cell-derived bioengineered neural organoids. This study revealed that astrocytes significantly increase activity within individual organoids and across long distances among numerous rapidly merged organoids via influencing synapses and bioenergetics. Treatment of amyloid protein inhibited synchronous activity during neurodegeneration, yet this can be rescued by propagating activity from neighboring networks. Altogether, this study identifies critical contributions of human astrocytes to biological neural networks and delivers a rapid, reproducible, and scalable model to investigate long-range functional communication of the nervous system in healthy and disease states.

Cedrol attenuates acute ischemic injury through inhibition of microglia-associated neuroinflammation via ERβ-NF-κB signaling pathways

Microglia-associated neuroinflammation plays essential roles in pathology of acute stroke. Cedrol, a natural compound extracted from ginger, has been shown to confer inhibitory effects on inflammation in various diseases. However, whether Cedrol suppresses neuroinflammation and protects brains from acute ischemic injury still remains unclear. In this study, we found that Cedrol inhibited microglia activation and the production of inflammatory factors in LPS-challenged microglia and the penumbra region of middle cerebral artery occlusion (MCAO) mice. We also found that Cedrol reduced the infarct size and mNSS scores and improved acute cerebral ischemia-induced behavioral outcomes, suggesting remarked neuroprotection of Cedrol. Molecular docking analysis showed that Cedrol bound to estrogen receptor β (ERβ) with moderate-strong affinity. Intriguingly, treatment with fulvestrant, an ER blocker, abolished the anti-inflammatory effects of Cedrol. Cedrol significantly reversed the LPS- and MCAO-induced increases in phosphorylation levels of IκB and NF-κB P65 in primary microglia and MCAO mice, respectively. Additionally, Cedrol was observed to rescue LPS-induced shuttling of NF-κB P65 from cytoplasm to nuclei in primary microglia, indicating inhibitory effects of Cedrol on NF-κB signaling. These results suggest microglia associated neuroinflammation may be mediated by ERβ-NF-κB signaling pathway. Together, our study reveals that Cedrol protected brain function from acute cerebral ischemia through inhibition of microglia-associated neuroinflammation via ERβ-NF-κB signaling pathways, and Cedrol may serve as an alternative option for treatment of acute stroke injury.

Prevention and Treatment Strategies for Alzheimer's Disease: Focusing on Microglia and Astrocytes in Neuroinflammation

Alzheimer's disease (AD) is a fatal neurodegenerative disease characterized by its insidious onset and progressive development, making it the most common form of dementia. Despite its prevalence, the exact causes and mechanisms responsible for AD remain unclear. Recent studies have highlighted that inflammation in the central nervous system (CNS) plays a crucial role in both the initiation and progression of AD. Neuroinflammation, an immune response within the CNS triggered by glial cells in response to various stimuli, such as nerve injury, infection, toxins, or autoimmune reactions, has emerged as a significant factor alongside amyloid deposition and neurofibrillary tangles (NFTs) commonly associated with AD. This article aims to provide an overview of the most recent research regarding the involvement of neuroinflammation in AD, with a particular focus on elucidating the specific mechanisms involving microglia and astrocytes. By exploring these intricate processes, a new theoretical framework can be established to further probe the impact of neuroinflammation on the development and progression of AD. Through a deeper understanding of these underlying mechanisms, potential targets for therapeutic interventions and novel treatment strategies can be identified in the ongoing battle against AD.

RiboTag RNA Sequencing Identifies Local Translation of HSP70 In Astrocyte Endfeet After Cerebral Ischemia

Brain ischemia causes disruption in cerebral blood flow and blood-brain barrier (BBB) integrity which are normally maintained by the astrocyte endfeet. Emerging evidence points to dysregulation of the astrocyte translatome during ischemia, but its effects on the endfoot translatome are unknown. In this study, we aimed to investigate the early effects of ischemia on the astrocyte endfoot translatome in a rodent model of cerebral ischemia-reperfusion. To do so, we immunoprecipitated astrocyte-specific tagged ribosomes (RiboTag IP) from mechanically isolated brain microvessels. In mice subjected to middle cerebral artery occlusion and reperfusion and contralateral controls, we sequenced ribosome-bound RNAs from perivascular astrocyte endfeet and identified 205 genes that were differentially expressed in the translatome after ischemia. Pathways associated with the differential expressions included proteostasis, inflammation, cell cycle, and metabolism. Transcription factors whose targets were enriched amongst upregulated translating genes included HSF1, the master regulator of the heat shock response. The most highly upregulated genes in the translatome were HSF1-dependent Hspa1a and Hspa1b , which encode the inducible HSP70. We found that HSP70 is upregulated in astrocyte endfeet after ischemia, coinciding with an increase in ubiquitination across the proteome. These findings suggest a robust proteostasis response to proteotoxic stress in the endfoot translatome after ischemia. Modulating proteostasis in endfeet may be a strategy to preserve endfeet function and BBB integrity after ischemic stroke.

Inhibiting endoplasmic reticulum stress alleviates perioperative neurocognitive disorders by reducing neuroinflammation mediated by NLRP3 inflammasome activation

AIM

The aim of this study is to explore the key mechanisms of perioperative neurocognitive dysfunction (PND) after anesthesia/surgery (A/S) by screening hub genes.

METHODS

Transcriptome sequencing was conducted on hippocampal samples obtained from 18-month-old C57BL/6 mice assigned to control (Ctrl) and A/S groups. The functionality of differentially expressed genes (DEGs) was investigated using Metascape. Hub genes associated with changes between the two groups were screened by combining weighted gene coexpression network analysis within CytoHubba. Reverse transcription PCR and western blotting were used to validate changes in mRNA and protein expression, respectively. NLRP3 inflammasome activation was detected by western blotting and ELISA. Tauroursodeoxycholic acid (TUDCA), an inhibitor of endoplasmic reticulum (ER) stress, was administrated preoperatively to explore its effects on the occurrence of PND. Immunofluorescence analysis was performed to evaluate the activation of astrocytes and microglia in the hippocampus, and hippocampus-dependent learning and memory were assessed using behavioral experiments.

RESULTS

In total, 521 DEGs were detected between the control and A/S groups. These DEGs were significantly enriched in biological processes related to metabolic processes and their regulation. Four hub genes (Hspa5, Igf1r, Sfpq, and Xbp1) were identified. Animal experiments have shown that mice in the A/S group exhibited cognitive impairments accompanied by increased Hspa5 and Xbp1 expression, ER stress, and activation of NLRP3 inflammasome.

CONCLUSIONS

Inhibiting ER stress alleviated cognitive impairment in A/S mice; particularly, ER stress induced by A/S results in NLRP3 inflammasome activation and neuroinflammation. Moreover, the preoperative administration of TUDCA inhibited ER stress, NLRP3 inflammasome activation, and neuroinflammation.

Droplet-based functional CRISPR screening of cell-cell interactions by SPEAC-seq

Cell-cell interactions are essential for the function and contextual regulation of biological tissues. We present a platform for high-throughput microfluidics-supported genetic screening of functional regulators of cell-cell interactions. Systematic perturbation of encapsulated associated cells followed by sequencing (SPEAC-seq) combines genome-wide CRISPR libraries, cell coculture in droplets and microfluidic droplet sorting based on functional read-outs determined by fluorescent reporter circuits to enable the unbiased discovery of interaction regulators. This technique overcomes limitations of traditional methods for characterization of cell-cell communication, which require a priori knowledge of cellular interactions, are highly engineered and lack functional read-outs. As an example of this technique, we describe the investigation of neuroinflammatory intercellular communication between microglia and astrocytes, using genome-wide CRISPR-Cas9 inactivation libraries and fluorescent reporters of NF-κB activation. This approach enabled the discovery of thousands of microglial regulators of astrocyte NF-κB activation important for the control of central nervous system inflammation. Importantly, SPEAC-seq can be adapted to different cell types, screening modalities, cell functions and physiological contexts, only limited by the ability to fluorescently report cell functions and by droplet cultivation conditions. Performing genome-wide screening takes less than 2 weeks and requires microfluidics capabilities. Thus, SPEAC-seq enables the large-scale investigation of cell-cell interactions.

Upregulated expression of ubiquitin ligase TRIM21 promotes PKM2 nuclear translocation and astrocyte activation in experimental autoimmune encephalomyelitis

Reactive astrocytes play critical roles in the occurrence of various neurological diseases such as multiple sclerosis. Activation of astrocytes is often accompanied by a glycolysis-dominant metabolic switch. However, the role and molecular mechanism of metabolic reprogramming in activation of astrocytes have not been clarified. Here, we found that PKM2, a rate-limiting enzyme of glycolysis, displayed nuclear translocation in astrocytes of EAE (experimental autoimmune encephalomyelitis) mice, an animal model of multiple sclerosis. Prevention of PKM2 nuclear import by DASA-58 significantly reduced the activation of mice primary astrocytes, which was observed by decreased proliferation, glycolysis and secretion of inflammatory cytokines. Most importantly, we identified the ubiquitination-mediated regulation of PKM2 nuclear import by ubiquitin ligase TRIM21. TRIM21 interacted with PKM2, promoted its nuclear translocation and stimulated its nuclear activity to phosphorylate STAT3, NF-κB and interact with c-myc. Further single-cell RNA sequencing and immunofluorescence staining demonstrated that TRIM21 expression was upregulated in astrocytes of EAE. TRIM21 overexpressing in mice primary astrocytes enhanced PKM2-dependent glycolysis and proliferation, which could be reversed by DASA-58. Moreover, intracerebroventricular injection of a lentiviral vector to knockdown TRIM21 in astrocytes or intraperitoneal injection of TEPP-46, which inhibit the nuclear translocation of PKM2, effectively decreased disease severity, CNS inflammation and demyelination in EAE. Collectively, our study provides novel insights into the pathological function of nuclear glycolytic enzyme PKM2 and ubiquitination-mediated regulatory mechanism that are involved in astrocyte activation. Targeting this axis may be a potential therapeutic strategy for the treatment of astrocyte-involved neurological disease.

Jiawei Xionggui Decoction promotes meningeal lymphatic vessels clearance of β-amyloid by inhibiting arachidonic acid pathway

BACKGROUND

Alzheimer's disease (AD) is an aging-associated form of dementia characterized by the pathological deposition of toxic misfolded proteins in the central nervous system (CNS), which is closely related to the clearance impairment of meningeal lymphatic vessels (mLVs). Thus, enhancement dural meningeal lymphatic drainage to remove amyloid-β (Aβ) is usually considered as a potential therapeutic target for AD.

PURPOSE

This study aimed to investigate the mechanisms of Jiawei Xionggui Decoction (JWXG) to attenuate cognitive dificits in APP/PS1 mice with impaired meningeal lymphatic drainage.

METHODS

Ligation of deep cervical lymph nodes (dcLNs) was performed to establish the mice model of the impaired meningeal lymphatic drainage in APP/PS1 mice. Cognitve behaviors and pathological morphology of mice were assessed. Cerebral blood flow (CBF) of mice was determined using Laser speckle contrast imaging analysis. Serum non-targeted metabolomics analysis was applied to decipher the mechanisms of JWXG in rescuing the impairment of mLVs, and C8-D1A cells were employed to validate in vitro.

RESULTS

Disruption of mLVs in APP/PS1 mice deteriorated cognitive dysfunction, accelerated Aβ burden and glia activation, accompanied by more severe neuropathological damage, CBF reduction and neuroinflammation exacerbation. Serum non-targeted metabolomics analysis indicates the increase of arachidonic acid (AA) metabolic pathway was the key contributor to the neuropathological exacerbation of dcLNs ligation APP/PS1 mice. Interestingly, clinically equivalent dose of JWXG was sufficient to restore mLVs drainage and rescue cognitive performance by inhibiting neuroinflammation depended by AA metabolic pathway in dcLNs ligation APP/PS1 mice.

CONCLUSION

Our findings establish a novel mechanism that rescue mLVs by inhibiting AA metabolic pathway to clear brain Aβ, and support JWXG as a feasible treatment strategy for AD by suppressing AA metabolic pathway to improve mLVs drainage efficiency.

The mechanisms, hallmarks, and therapies for brain aging and age-related dementia

Age-related cognitive decline and dementia are significant manifestations of brain aging. As the elderly population grows rapidly, the health and socio-economic impacts of cognitive dysfunction have become increasingly significant. Although clinical treatment of dementia has faced considerable challenges over the past few decades, with limited breakthroughs in slowing its progression, there has been substantial progress in understanding the molecular mechanisms and hallmarks of age-related dementia (ARD). This progress brings new hope for the intervention and treatment of this disease. In this review, we categorize the latest findings in ARD biomarkers into four stages based on disease progression: healthy brain, pre-clinical, mild cognitive impairment, and dementia. We then systematically summarize the most promising therapeutic approaches to prevent or slow ARD at four levels: genome and epigenome, organelle, cell, and organ and organism. We emphasize the importance of early prevention and detection, along with the implementation of combined treatments as multimodal intervention strategies, to address brain aging and ARD in the future.

Intranasal Delivery of circATF7IP siRNA via Lipid Nanoparticles Alleviates LPS-induced Depressive-Like Behaviors

Major depressive disorder (MDD) is a prevalent mental disorder that significantly impacts social and psychological function, but no effective medication is currently available. Circular RNAs (circRNAs) have been reported to participate in the pathogenesis of MDD which are envisioned as promising therapeutic targets. However, nonviral-based delivery strategies targeting circRNA against MDD are not thoroughly investigated. Here, it is identified that circATF7IP is significantly upregulated in plasma samples and positively correlated with 24-Hamilton Depression Scale (HAMD-24) scores of MDD patients. Synergistic amine lipid nanoparticles (SALNPs) are designed to deliver siRNA targeting circATF7IP (si-circATF7IP) into the hippocampus brain region by intranasal administration. Intranasal delivery of SALNP-si-circATF7IP successfully alleviated the depressive-like behaviors in the LPS-induced mouse depression model via decreasing CD11b+CD45dim microglia population and pro-inflammatory cytokine productions (TNF-α and IL-6). These results indicate that the level of circATF7IP positively correlates with MDD pathogenesis, and SALNP delivery of si-circATF7IP via intranasal administration is an effective strategy to ameliorate LPS-induced depressive-like behaviors.

Integrating large-scale single-cell RNA sequencing in central nervous system disease using self-supervised contrastive learning

The central nervous system (CNS) comprises a diverse range of brain cell types with distinct functions and gene expression profiles. Although single-cell RNA sequencing (scRNA-seq) provides new insights into the brain cell atlases, integrating large-scale CNS scRNA-seq data still encounters challenges due to the complexity and heterogeneity among CNS cell types/subtypes. In this study, we introduce a self-supervised contrastive learning method, called scCM, for integrating large-scale CNS scRNA-seq data. scCM brings functionally related cells close together while simultaneously pushing apart dissimilar cells by comparing the variations of gene expression, effectively revealing the heterogeneous relationships within the CNS cell types/subtypes. The effectiveness of scCM is evaluated on 20 CNS datasets covering 4 species and 10 CNS diseases. Leveraging these strengths, we successfully integrate the collected human CNS datasets into a large-scale reference to annotate cell types and subtypes in neural tissues. Results demonstrate that scCM provides an accurate annotation, along with rich spatial information of cell state. In summary, scCM is a robust and promising method for integrating large-scale CNS scRNA-seq data, enabling researchers to gain insights into the cellular and molecular mechanisms underlying CNS functions and diseases.

Empagliflozin alleviates neuroinflammation by inhibiting astrocyte activation in the brain and regulating gut microbiota of high-fat diet mice

A high-fat diet can modify the composition of gut microbiota, resulting in dysbiosis. Changes in gut microbiota composition can lead to increased permeability of the gut barrier, allowing bacterial products like lipopolysaccharides (LPS) to enter circulation. This process can initiate systemic inflammation and contribute to neuroinflammation. Empagliflozin (EF), an SGLT2 inhibitor-type hypoglycemic drug, has been reported to treat neuroinflammation. However, there is a lack of evidence showing that EF regulates the gut microbiota axis to control neuroinflammation in HFD models. In this study, we explored whether EF could improve neuroinflammation caused by an HFD via regulation of the gut microbiota and the mechanism underlying this phenomenon. Our data revealed that EF alleviates pathological brain injury, reduces the reactive proliferation of astrocytes, and increases the expression of synaptophysin. In addition, the levels of inflammatory factors in hippocampal tissue were significantly decreased after EF intervention. Subsequently, the results of 16S rRNA gene sequencing showed that EF could change the microbial community structure of mice, indicating that the abundance of Lactococcus, Ligilactobacillus and other microbial populations decreased dramatically. Therefore, EF alleviates neuroinflammation by inhibiting gut microbiota-mediated astrocyte activation in the brains of high-fat diet-fed mice. Our study focused on the gut-brain axis, and broader research on neuroinflammation can provide a more holistic understanding of the mechanisms driving neurodegenerative diseases and inform the development of effective strategies to mitigate their impact on brain health. The results provide strong evidence supporting the larger clinical application of EF.

Isoliquiritigenin alleviates experimental autoimmune encephalomyelitis by modulating inflammatory and neuroprotective reactive astrocytes

Multiple sclerosis (MS) is an autoimmune-mediated chronic inflammatory demyelinating disease of the central nervous system (CNS) that poses significant treatment challenges. Currently, it is believed that inflammatory and neuroprotective reactive astrocytes, along with other resident CNS cells and immune cells, contribute to the pathophysiology of MS. In our study, we found that isoliquiritigenin (ILG), a bioactive chalcone compound, significantly reduces the clinical scores of experimental autoimmune encephalomyelitis (EAE) by 44 % (P < 0.05). Additionally, ILG significantly decreases the pathological scores of spinal cord inflammation and demyelination by 61 % and 65 %, respectively (both P < 0.0001). Furthermore, ILG affects the populations of CD4, Th1, Th17, and Treg cells in vivo. More importantly, ILG significantly promotes the activation of astrocytes in EAE (P < 0.0001). Additionally, ILG treatment indirectly inhibits inflammatory reactive astrocytes and promotes neuroprotective reactive astrocytes. It reduces spleen levels of TNFα, IL1α, C1qa, IL1β, and IL17A by 95 % (P < 0.001), 98 % (P < 0.01), 46 % (P < 0.05), 97 % (P < 0.001), and 60 % (P < 0.001), respectively. It also decreases CNS levels of TNFα, IL1α, C1qa, IL1β, and IL17A by 53 % (P < 0.05), 88 % (P < 0.05), 64 % (P < 0.01), 57 % (P < 0.05), and 60 % (P < 0.001), respectively. These results indicate that ILG exerts an immunoregulatory effect by inhibiting the secretion of pro-inflammatory cytokines. Consequently, ILG inhibits inflammatory reactive astrocytes, promotes neuroprotective reactive astrocytes, alleviates inflammation and improves EAE. These findings provide a theoretical basis and support for the application of ILG in the prevention and treatment of MS.

Curcumin as a potential therapeutic agent for treating neurodegenerative diseases

Neurodegenerative diseases are characterized by the progressive loss of neuronal structure and function, posing a tremendous burden on health systems worldwide. Although the underlying pathological mechanisms for various neurodegenerative diseases are still unclear, a common pathological hallmark is the abundance of neuroinflammatory processes, which affect both disease onset and progression. In this review, we explore the pathways and role of neuroinflammation in various neurodegenerative diseases and further assess the potential use of curcumin, a natural spice with antioxidant and anti-inflammatory properties that has been extensively used worldwide as a traditional medicine and potential therapeutic agent. Following the examination of preclinical and clinical studies that assessed curcumin as a potential therapeutic agent, we highlight the bioavailability of curcumin in the body and discuss both the challenges and benefits of using curcumin as a therapeutic compound for treating neurodegeneration. Although elucidating the involvement of curcumin in aging and neurodegeneration has great potential for developing future CNS-related therapeutic targets, further research is required to elucidate the mechanisms by which Curcumin affects brain physiology, especially BBB integrity, under both physiological and disease conditions.

Astrocyte-derived MFG-E8 facilitates microglial synapse elimination in Alzheimer's disease mouse models

Region-specific synapse loss is an early pathological hallmark in Alzheimer's disease (AD). Emerging data in mice and humans highlight microglia, the brain-resident macrophages, as cellular mediators of synapse loss; however, the upstream modulators of microglia-synapse engulfment remain elusive. Here, we report a distinct subset of astrocytes, which are glial cells essential for maintaining synapse homeostasis, appearing in a region-specific manner with age and amyloidosis at onset of synapse loss. These astrocytes are distinguished by their peri-synaptic processes which are 'bulbous' in morphology, contain accumulated p62-immunoreactive bodies, and have reduced territorial domains, resulting in a decrease of astrocyte-synapse coverage. Using integrated in vitro and in vivo approaches, we show that astrocytes upregulate and secrete phagocytic modulator, milk fat globule-EGF factor 8 (MFG-E8), which is sufficient and necessary for promoting microglia-synapse engulfment in their local milieu. Finally, we show that knocking down Mfge8 specifically from astrocytes using a viral CRISPR-saCas9 system prevents microglia-synapse engulfment and ameliorates synapse loss in two independent amyloidosis mouse models of AD. Altogether, our findings highlight astrocyte-microglia crosstalk in determining synapse fate in amyloid models and nominate astrocytic MFGE8 as a potential target to ameliorate synapse loss during the earliest stages of AD.

Discovery of 23,24-diols containing ergosterols with anti-neuroinflammatory activity from Penicillium citrinum TJ507

Citristerones A-E (1-5), five new 23,24-diols containing ergosterols, along with three known analogues, were isolated from the endophytic fungus Penicillium citrinum TJ507 obtained from Hypericum wilsonii N. Robson. Their structures and absolute configurations were determined by NMR, HRESIMS, Snatzke's method, X-ray diffraction analyses and ECD calculation. Subsequently, the anti-neuroinflammatory effects of these isolates were screened using lipopolysaccharide (LPS)-induced BV-2 microglial cells, and citristerone B (2) showed outstanding anti-neuroinflammatory activity, with IC50 value of 0.60 ± 0.04 μM. Moreover, immunofluorescence and western blot analysis suggested that citristerone B not only reduced the release of nitric oxide (NO) and proinflammatory cytokines in LPS-induced BV-2 microglial cells, but also significantly inhibited the expression of TNF-α, iNOS and NF-κB, along with the production of cellular ROS.

The impact of physical exercise on neuroinflammation mechanism in Alzheimer's disease

Introduction

Alzheimer's disease (AD), a major cause of dementia globally, imposes significant societal and personal costs. This review explores the efficacy of physical exercise as a non-pharmacological intervention to mitigate the impacts of AD.

Methods

This review draws on recent studies that investigate the effects of physical exercise on neuroinflammation and neuronal enhancement in individuals with AD.

Results

Consistent physical exercise alters neuroinflammatory pathways, enhances cognitive functions, and bolsters brain health among AD patients. It favorably influences the activation states of microglia and astrocytes, fortifies the integrity of the blood-brain barrier, and attenuates gut inflammation associated with AD. These changes are associated with substantial improvements in cognitive performance and brain health indicators.

Discussion

The findings underscore the potential of integrating physical exercise into comprehensive AD management strategies. Emphasizing the necessity for further research, this review advocates for the refinement of exercise regimens to maximize their enduring benefits in decelerating the progression of AD.

Mitochondrial complex III-derived ROS amplify immunometabolic changes in astrocytes and promote dementia pathology

Neurodegenerative disorders alter mitochondrial functions, including the production of reactive oxygen species (ROS). Mitochondrial complex III (CIII) generates ROS implicated in redox signaling, but its triggers, targets, and disease relevance are not clear. Using site-selective suppressors and genetic manipulations together with mitochondrial ROS imaging and multiomic profiling, we found that CIII is the dominant source of ROS production in astrocytes exposed to neuropathology-related stimuli. Astrocytic CIII-ROS production was dependent on nuclear factor-κB (NF-κB) and the mitochondrial sodium-calcium exchanger (NCLX) and caused oxidation of select cysteines within immune and metabolism-associated proteins linked to neurological disease. CIII-ROS amplified metabolomic and pathology-associated transcriptional changes in astrocytes, with STAT3 activity as a major mediator, and facilitated neuronal toxicity in a non-cell-autonomous manner. As proof-of-concept, suppression of CIII-ROS in mice decreased dementia-linked tauopathy and neuroimmune cascades and extended lifespan. Our findings establish CIII-ROS as an important immunometabolic signal transducer and tractable therapeutic target in neurodegenerative disease.

mTOR activation induces endolysosomal remodeling and nonclassical secretion of IL-32 via exosomes in inflammatory reactive astrocytes

Astrocytes respond and contribute to neuroinflammation by adopting inflammatory reactive states. Although recent efforts have characterized the gene expression signatures associated with these reactive states, the cell biology underlying inflammatory reactive astrocyte phenotypes remains under-explored. Here, we used CRISPR-based screening in human iPSC-derived astrocytes to identify mTOR activation a driver of cytokine-induced endolysosomal system remodeling, manifesting as alkalinization of endolysosomal compartments, decreased autophagic flux, and increased exocytosis of certain endolysosomal cargos. Through endolysosomal proteomics, we identified and focused on one such cargo-IL-32, a disease-associated pro-inflammatory cytokine not present in rodents, whose secretion mechanism is not well understood. We found that IL-32 was partially secreted in extracellular vesicles likely to be exosomes. Furthermore, we found that IL-32 was involved in the polarization of inflammatory reactive astrocyte states and was upregulated in astrocytes in multiple sclerosis lesions. We believe that our results advance our understanding of cell biological pathways underlying inflammatory reactive astrocyte phenotypes and identify potential therapeutic targets.

3-Methyladenine attenuates neuroinflammation and improves cognitive function in sepsis-associated encephalopathy by inhibiting autophagy

OBJECTIVE

Sepsis-associated encephalopathy (SAE) can lead to severe cerebral dysfunction as well as cognitive dysfunction, resulting in a significant disease burden. 3-Methyladenine (3-MA) has been confirmed to have anti-inflammatory effects on diseases characterized by enhanced autophagy. However, its role in SAE has not been clarified.

METHODS

An SAE mouse model was generated by intraperitoneal injection of lipopolysaccharide (LPS). Mice were given 5, 20, or 80 mg/kg 3-MA to determine the therapeutic dose. The mice in the different groups were given 20 mg/kg 3-MA or saline, and survival, body temperature, body weight and neurobehavioral scores were measured at different time points. The expression of autophagy-related proteins and inflammatory factors was detected by Western blotting, enzyme linked immunosorbent assay (ELISA) and real-time quantitative polymerase chain reaction (RT-qPCR) 12 h after LPS induction. Glial activation and neuronal injury in the hippocampus were detected by immunofluorescence staining and HE staining. The open Field test, novel object recognition (NOR) test, Y-maze test, and Morris water maze (MWM) test were performed to assess cognitive function.

RESULTS

Treatment with 20 or 80 mg/kg 3-MA reduced the increase in hippocampal TNF-α, IL-6, and IL-1β expression in SAE model mice, with 20 mg/kg 3-MA having the greatest therapeutic effect. Treatment with 20 mg/kg 3-MA effectively reduced the expression of hippocampal autophagy-related proteins and mortality, ameliorated hypothermia, decreased body weight and electroencephalography (EEG) performance, and attenuated the activation of neuroglia and neuronal damage. Moreover, it alleviated the cognitive dysfunction 2 weeks after LPS induction.

CONCLUSIONS

3-MA reduced neuroglial activation and neuronal damage, attenuated neuroinflammation, and improved cognitive deficits during recovery period by inhibiting autophagy in SAE.

Dysfunctional astrocyte glutamate uptake in the hypothalamic paraventricular nucleus contributes to visceral pain and anxiety-like behavior in mice with chronic pancreatitis

Abdominal visceral pain is a predominant symptom in patients with chronic pancreatitis (CP); however, the underlying mechanism of pain in CP remains elusive. We hypothesized that astrocytes in the hypothalamic paraventricular nucleus (PVH) contribute to CP pain pathogenesis. A mouse model of CP was established by repeated intraperitoneal administration of caerulein to induce abdominal visceral pain. Abdominal mechanical stimulation, open field and elevated plus maze tests were performed to assess visceral pain and anxiety-like behavior. Fiber photometry, brain slice Ca2+ imaging, electrophysiology, and immunohistochemistry were used to investigate the underlying mechanisms. Mice with CP displayed long-term abdominal mechanical allodynia and comorbid anxiety, which was accompanied by astrocyte glial fibrillary acidic protein reactivity, elevated Ca2+ signaling, and astroglial glutamate transporter-1 (GLT-1) deficits in the PVH. Specifically, reducing astrocyte Ca2+ signaling in the PVH via chemogenetics significantly rescued GLT-1 deficits and alleviated mechanical allodynia and anxiety in mice with CP. Furthermore, we found that GLT-1 deficits directly contributed to the hyperexcitability of VGLUT2PVH neurons in mice with CP, and that pharmacological activation of GLT-1 alleviated the hyperexcitability of VGLUT2PVH neurons, abdominal visceral pain, and anxiety in these mice. Taken together, our data suggest that dysfunctional astrocyte glutamate uptake in the PVH contributes to visceral pain and anxiety in mice with CP, highlighting GLT-1 as a potential therapeutic target for chronic pain in patients experiencing CP.

Potential value and research frontiers of virus in neuroinflammation: a bibliometric and visualized analysis

Background

Neuroinflammation represents the immune response of the central nervous system to nerve injury, infection, toxin stimulation, or autoimmunity and is implicated in a wide range of neurological disorders. Viruses play a pivotal role as extrinsic biological drivers in neuroinflammation; however, numerous aspects remain unexplored. In this study, we employed bibliometric analysis to assess the current status of viral research in neuroinflammation and anticipate future research directions and emerging trends.

Methods

Conduct a comprehensive search for scholarly publications within the Web of Science Core Collection database, with search terms on neuroinflammation and virus. Apply Microsoft Excel Office, Hiplot, R (version 4.3.1), VOSviewer (version 1.6.20) and CiteSpace (6.2.R6, advanced) software for the bibliometric analysis and visualization.

Results

A total of 4230 articles and reviews on virus and neuroinflammation were identified, demonstrating a consistent upward trend over time. The United States was the country that contributed the most publications. Approximately 22274 authors from 4474 institutions contributed to the research. Johns Hopkins University leads with the highest number of publications and citations. The top three authors with the most published articles on this field are Power, C., Lane, T. E., and Buch, S. The Journal of Neuroinflammation is the most authoritative choice for researchers. The main research focuses in this field include multiple sclerosis, Parkinson's disease, blood-brain barrier, COVID-19, Alzheimer's disease, gene therapy. In recent years, stress have emerged as hot keywords, particularly depression, human immunodeficiency virus-associated neurocognitive disorders, blood-brain barrier, gut microbiota related directions, indicating a potential shift in research focus.

Conclusion

Research on the virus and neuroinflammation has attracted increasing attention in the past decade. European and American countries have been pivotal in conducting research on virus and neuroinflammation, while China has produced a significant number of publications, its impact is still limited. Stress is likely to emerge as the next area of focus in this field. The association and regulation between viral infection and psychiatric disorders are not fully understood, and further research is needed to explore the role of neuroinflammation caused by different types of viral infection and psychiatric disorders.

Synergism Between Hypothalamic Astrocytes and Neurons in Metabolic Control

Astrocytes are no longer considered as passive support cells. In the hypothalamus, these glial cells actively participate in the control of appetite, energy expenditure, and the processes leading to obesity and its secondary complications. Here we briefly review studies supporting this conclusion and the advances made in understanding the underlying mechanisms.

Myelin oligodendrocyte glycoprotein reactive Th17 cells drive Janus Kinase 1 dependent transcriptional reprogramming in astrocytes and alter cell surface cytokine receptor profiles during experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an autoimmune demyelinating disease affecting the central nervous system (CNS). T helper (Th) 17 cells are involved in the pathogenesis of MS and its animal model of experimental autoimmune encephalomyelitis (EAE) by infiltrating the CNS and producing effector molecules that engage resident glial cells. Among these glial cells, astrocytes have a central role in coordinating inflammatory processes by responding to cytokines and chemokines released by Th17 cells. In this study, we examined the impact of pathogenic Th17 cells on astrocytes in vitro and in vivo. We identified that Th17 cells reprogram astrocytes by driving transcriptomic changes partly through a Janus Kinase (JAK)1-dependent mechanism, which included increased chemokines, interferon-inducible genes, and cytokine receptors. In vivo, we observed a region-specific heterogeneity in the expression of cell surface cytokine receptors on astrocytes, including those for IFN-γ, IL-1, TNF-α, IL-17, TGFβ, and IL-10. Additionally, these receptors were dynamically regulated during EAE induced by adoptive transfer of myelin-reactive Th17 cells. This study overall provides evidence of Th17 cell reprogramming of astrocytes, which may drive changes in the astrocytic responsiveness to cytokines during autoimmune neuroinflammation.

A novel PSMB8 isoform associated with multiple sclerosis lesions induces P-body formation

Introduction

Multiple sclerosis (MS) is an inflammatory and demyelinating disease of the central nervous system (CNS). Current therapies primarily target the inflammatory component of the disease and are highly effective in early stages of MS while limited therapies have an effect in the more chronic progressive stages of MS where resident glia have a larger role. MS lesions tend to be inflammatory even after the initial peripheral immune cell invasion has subsided and this inflammation is known to cause alternative splicing events.

Methods

We used qPCR of normal-appearing white matter and white matter lesions from postmortem MS tissue, in vitro studies, and immunostaining in MS tissue to investigate the alternative splicing of one gene known to be important during recovery in an animal model of MS, PSMB8.

Results

We found a novel, intron-retained isoform which has not been annotated, upregulated specifically in MS patient white matter lesions. We found that this novel isoform activates the nonsense-mediated decay pathway in primary human astrocytes, the most populous glial cell in the CNS, and is then degraded. Overexpression of this isoform in astrocytes leads to an increased number of processing bodies in vitro, the primary site of mRNA decay. Finally, we demonstrated that MS white matter lesions have a higher burden of processing bodies compared to normal-appearing white matter, predominantly in GFAP-positive astrocytes.

Discussion

The increase in alternative splicing of the PSMB8 gene, the stress that this alternative splicing causes, and the observation that processing bodies are increased in white matter lesions suggests that the lesion microenvironment may lead to increased alternative splicing of many genes. This alternative splicing may blunt the protective or reparative responses of resident glia in and around white matter lesions in MS patients.

Biomaterials targeting the microenvironment for spinal cord injury repair: progression and perspectives

Spinal cord injury (SCI) disrupts nerve pathways and affects sensory, motor, and autonomic function. There is currently no effective treatment for SCI. SCI occurs within three temporal periods: acute, subacute, and chronic. In each period there are different alterations in the cells, inflammatory factors, and signaling pathways within the spinal cord. Many biomaterials have been investigated in the treatment of SCI, including hydrogels and fiber scaffolds, and some progress has been made in the treatment of SCI using multiple materials. However, there are limitations when using individual biomaterials in SCI treatment, and these limitations can be significantly improved by combining treatments with stem cells. In order to better understand SCI and to investigate new strategies for its treatment, several combination therapies that include materials combined with cells, drugs, cytokines, etc. are summarized in the current review.

mTOR and neuroinflammation in epilepsy: implications for disease progression and treatment

Epilepsy remains a major health concern as anti-seizure medications frequently fail, and there is currently no treatment to stop or prevent epileptogenesis, the process underlying the onset and progression of epilepsy. The identification of the pathological processes underlying epileptogenesis is instrumental to the development of drugs that may prevent the generation of seizures or control pharmaco-resistant seizures, which affect about 30% of patients. mTOR signalling and neuroinflammation have been recognized as critical pathways that are activated in brain cells in epilepsy. They represent a potential node of biological convergence in structural epilepsies with either a genetic or an acquired aetiology. Interventional studies in animal models and clinical studies give strong support to the involvement of each pathway in epilepsy. In this Review, we focus on available knowledge about the pathophysiological features of mTOR signalling and the neuroinflammatory brain response, and their interactions, in epilepsy. We discuss mitigation strategies for each pathway that display therapeutic effects in experimental and clinical epilepsy. A deeper understanding of these interconnected molecular cascades could enhance our strategies for managing epilepsy. This could pave the way for new treatments to fill the gaps in the development of preventative or disease-modifying drugs, thus overcoming the limitations of current symptomatic medications.

AhR Agonistic Components in Urban Particulate Matter Regulate Astrocytic Activation and Function

Exposure to atmospheric particulate matter (PM) has been found to accelerate the onset of neurological disorders via the induction of detrimental neuroinflammatory responses. To reveal how astrocytes respond to urban atmospheric PM stimulation, a commercially available standard reference material (SRM1648a) was tested in this study on the activation of rat cortical astrocytes. The results showed that SRM1648a stimulation induced both A1 and A2 phenotypes in astrocytes, as characterized by the exposure concentration-dependent increases in Fkbp5, Sphk1, S100a10, and Il6 mRNA levels. Studying the functional alterations of astrocytes indicated that the neurotrophic factors of Gdnf and Ngf were transcriptionally upregulated due to astrocytic A2-type activation. SRM1648a also promoted autonomous motility of astrocytes and elevated the expressions of chemokines. The aryl hydrocarbon receptor (AhR) agonistic components, such as polycyclic aromatic hydrocarbons (PAHs), were recognized to greatly contribute to SRM1648a-induced effects on astrocytes, which was confirmed by the attenuation of PM-disturbed astrocytic effects via AhR blockage. This study, for the first time, uncovered the direct regulation of urban atmospheric PM on astrocytic activation and function and traced the containing bioactive components (e.g., PAHs) with AhR agonistic activity. The findings provided new knowledge on understanding the ambiguous neurological disturbance from ambient fine PM pollution.

Disease-associated astrocyte epigenetic memory promotes CNS pathology

Disease-associated astrocyte subsets contribute to the pathology of neurologic diseases, including multiple sclerosis and experimental autoimmune encephalomyelitis1-8 (EAE), an experimental model for multiple sclerosis. However, little is known about the stability of these astrocyte subsets and their ability to integrate past stimulation events. Here we report the identification of an epigenetically controlled memory astrocyte subset that exhibits exacerbated pro-inflammatory responses upon rechallenge. Specifically, using a combination of single-cell RNA sequencing, assay for transposase-accessible chromatin with sequencing, chromatin immunoprecipitation with sequencing, focused interrogation of cells by nucleic acid detection and sequencing, and cell-specific in vivo CRISPR-Cas9-based genetic perturbation studies we established that astrocyte memory is controlled by the metabolic enzyme ATP-citrate lyase (ACLY), which produces acetyl coenzyme A (acetyl-CoA) that is used by histone acetyltransferase p300 to control chromatin accessibility. The number of ACLY+p300+ memory astrocytes is increased in acute and chronic EAE models, and their genetic inactivation ameliorated EAE. We also detected the pro-inflammatory memory phenotype in human astrocytes in vitro; single-cell RNA sequencing and immunohistochemistry studies detected increased numbers of ACLY+p300+ astrocytes in chronic multiple sclerosis lesions. In summary, these studies define an epigenetically controlled memory astrocyte subset that promotes CNS pathology in EAE and, potentially, multiple sclerosis. These findings may guide novel therapeutic approaches for multiple sclerosis and other neurologic diseases.

A novel PSMB8 isoform associated with multiple sclerosis lesions induces P-body formation

Multiple sclerosis (MS) is an inflammatory and demyelinating disease of the central nervous system (CNS). Current therapies primarily target the inflammatory component of the disease and are highly effective in early stages of MS while limited therapies have an effect in the more chronic progressive stages of MS where resident glia have a larger role. MS lesions tend to be inflammatory even after the initial peripheral immune cell invasion has subsided and this inflammation is known to cause alternative splicing events. We used qPCR of normal-appearing white matter and white matter lesions from postmortem MS tissue, in vitro studies, and immunostaining in MS tissue to investigate the alternative splicing of one gene known to be important during recovery in an animal model of MS, PSMB8. We found a novel, intron-retained isoform which has not been annotated, upregulated specifically in MS patient white matter lesions. We found that this novel isoform activates the nonsense-mediated decay pathway in primary human astrocytes, the most populous glial cell in the CNS, and is then degraded. Overexpression of this isoform in astrocytes leads to an increased number of processing bodies in vitro, the primary site of mRNA decay. Finally, we demonstrated that MS white matter lesions have a higher burden of processing bodies compared to normal-appearing white matter, predominantly in GFAP-positive astrocytes. The increase in alternative splicing of the PSMB8 gene, the stress that this alternative splicing causes, and the observation that processing bodies are increased in white matter lesions suggests that the lesion microenvironment may lead to increased alternative splicing of many genes. This alternative splicing may blunt the protective or reparative responses of resident glia in and around white matter lesions in MS patients.

Disease-associated astrocyte epigenetic memory promotes CNS pathology

Astrocytes play important roles in the central nervous system (CNS) physiology and pathology. Indeed, astrocyte subsets defined by specific transcriptional activation states contribute to the pathology of neurologic diseases, including multiple sclerosis (MS) and its pre-clinical model experimental autoimmune encephalomyelitis (EAE) 1-8 . However, little is known about the stability of these disease-associated astrocyte subsets, their regulation, and whether they integrate past stimulation events to respond to subsequent challenges. Here, we describe the identification of an epigenetically controlled memory astrocyte subset which exhibits exacerbated pro-inflammatory responses upon re-challenge. Specifically, using a combination of single-cell RNA sequencing (scRNA-seq), assay for transposase-accessible chromatin with sequencing (ATAC-seq), chromatin immunoprecipitation with sequencing (ChIP-seq), focused interrogation of cells by nucleic acid detection and sequencing (FIND-seq), and cell-specific in vivo CRISPR/Cas9-based genetic perturbation studies we established that astrocyte memory is controlled by the metabolic enzyme ATP citrate lyase (ACLY), which produces acetyl coenzyme A (acetyl-CoA) used by the histone acetyltransferase p300 to control chromatin accessibility. ACLY + p300 + memory astrocytes are increased in acute and chronic EAE models; the genetic targeting of ACLY + p300 + astrocytes using CRISPR/Cas9 ameliorated EAE. We also detected responses consistent with a pro-inflammatory memory phenotype in human astrocytes in vitro ; scRNA-seq and immunohistochemistry studies detected increased ACLY + p300 + astrocytes in chronic MS lesions. In summary, these studies define an epigenetically controlled memory astrocyte subset that promotes CNS pathology in EAE and, potentially, MS. These findings may guide novel therapeutic approaches for MS and other neurologic diseases.