Microglia Function in the Central Nervous System During Health and Neurodegeneration

Spatial transcriptomics combined with single-nucleus RNA sequencing reveals glial cell heterogeneity in the human spinal cord

JOURNAL/nrgr/04.03/01300535-202511000-00032/figure1/v/2024-12-20T164640Z/r/image-tiff Glial cells play crucial roles in regulating physiological and pathological functions, including sensation, the response to infection and acute injury, and chronic neurodegenerative disorders. Glial cells include astrocytes, microglia, and oligodendrocytes in the central nervous system, and satellite glial cells and Schwann cells in the peripheral nervous system. Despite the greater understanding of glial cell types and functional heterogeneity achieved through single-cell and single-nucleus RNA sequencing in animal models, few studies have investigated the transcriptomic profiles of glial cells in the human spinal cord. Here, we used high-throughput single-nucleus RNA sequencing and spatial transcriptomics to map the cellular and molecular heterogeneity of astrocytes, microglia, and oligodendrocytes in the human spinal cord. To explore the conservation and divergence across species, we compared these findings with those from mice. In the human spinal cord, astrocytes, microglia, and oligodendrocytes were each divided into six distinct transcriptomic subclusters. In the mouse spinal cord, astrocytes, microglia, and oligodendrocytes were divided into five, four, and five distinct transcriptomic subclusters, respectively. The comparative results revealed substantial heterogeneity in all glial cell types between humans and mice. Additionally, we detected sex differences in gene expression in human spinal cord glial cells. Specifically, in all astrocyte subtypes, the levels of NEAT1 and CHI3L1 were higher in males than in females, whereas the levels of CST3 were lower in males than in females. In all microglial subtypes, all differentially expressed genes were located on the sex chromosomes. In addition to sex-specific gene differences, the levels of MT-ND4 , MT2A , MT-ATP6 , MT-CO3 , MT-ND2 , MT-ND3 , and MT-CO2 in all spinal cord oligodendrocyte subtypes were higher in females than in males. Collectively, the present dataset extensively characterizes glial cell heterogeneity and offers a valuable resource for exploring the cellular basis of spinal cord-related illnesses, including chronic pain, amyotrophic lateral sclerosis, and multiple sclerosis.

The pivotal role of microglia in injury and the prognosis of subarachnoid hemorrhage

Subarachnoid hemorrhage leads to a series of pathological changes, including vascular spasm, cellular apoptosis, blood-brain barrier damage, cerebral edema, and white matter injury. Microglia, which are the key immune cells in the central nervous system, maintain homeostasis in the neural environment, support neurons, mediate apoptosis, participate in immune regulation, and have neuroprotective effects. Increasing evidence has shown that microglia play a pivotal role in the pathogenesis of subarachnoid hemorrhage and affect the process of injury and the prognosis of subarachnoid hemorrhage. Moreover, microglia play certain neuroprotective roles in the recovery phase of subarachnoid hemorrhage. Several approaches aimed at modulating microglia function are believed to attenuate subarachnoid hemorrhage injury. This provides new targets and ideas for the treatment of subarachnoid hemorrhage. However, an in-depth and comprehensive summary of the role of microglia after subarachnoid hemorrhage is still lacking. This review describes the activation of microglia after subarachnoid hemorrhage and their roles in the pathological processes of vasospasm, neuroinflammation, neuronal apoptosis, blood-brain barrier disruption, cerebral edema, and cerebral white matter lesions. It also discusses the neuroprotective roles of microglia during recovery from subarachnoid hemorrhage and therapeutic advances aimed at modulating microglial function after subarachnoid hemorrhage. Currently, microglia in subarachnoid hemorrhage are targeted with TLR inhibitors, nuclear factor-κB and STAT3 pathway inhibitors, glycine/tyrosine kinases, NLRP3 signaling pathway inhibitors, Gasdermin D inhibitors, vincristine receptor α receptor agonists, ferroptosis inhibitors, genetic modification techniques, stem cell therapies, and traditional Chinese medicine. However, most of these are still being evaluated at the laboratory stage. More clinical studies and data on subarachnoid hemorrhage are required to improve the treatment of subarachnoid hemorrhage.

Advances in nanomedicine for retinal drug delivery: overcoming barriers and enhancing therapeutic outcomes

Nanomedicine offers a promising avenue for improving retinal drug delivery, effectively addressing challenges associated with ocular diseases like age-related macular degeneration and diabetic retinopathy. Nanoparticles, with their submicron size and customisable surface properties, enable enhanced permeability and retention within retinal tissues, supporting sustained drug release and minimising systemic side effects. Nanostructured scaffolds further provide a supportive environment for retinal cell growth and tissue regeneration, crucial for treating degenerative conditions. Additionally, advanced nanodevices facilitate real-time monitoring and controlled drug release, marking significant progress in retinal therapy. This study reviews recent advancements in nanomedicine for retinal drug delivery, critically analysing design innovations, therapeutic benefits, and limitations of these systems. By advancing nanotechnology integration in ocular therapies, this field holds strong potential for overcoming current barriers, ultimately improving patient outcomes and quality of life.

A review on the lncRNA-miRNA-mRNA regulatory networks involved in inflammatory processes in Alzheimer's disease

Alzheimer's disease is a progressive neurodegenerative condition that is the most frequent reason for dementia. Due to the increasing trend of aging in societies, it will place a large social and financial burden on society. Although beta amyloid plaques and the formation of neurofibrillary tangles are mentioned as the main events in this disorder, the exact molecular pathology and inflammatory regulatory networks involved in neuroinflammatory events, as a fundamental pathogenic mechanism remain unknown. Understanding these molecular network pathways in addition to helping to understand the pathogenesis of Alzheimer's disease, can also help in the early diagnosis as well as the control of inflammatory processes that are involved in its progression. So, in this study, we intend to have an overview on the regulatory lncRNAs of Alzheimer's disease and their related miRNA and mRNAs, as well as the relationship of these regulatory pathways with inflammatory processes, so that we can provide a perspective for future studies in the field of diagnosis and possibly treatment of this disorder.

The potential mechanism and clinical application value of remote ischemic conditioning in stroke

Some studies have confirmed the neuroprotective effect of remote ischemic conditioning against stroke. Although numerous animal researches have shown that the neuroprotective effect of remote ischemic conditioning may be related to neuroinflammation, cellular immunity, apoptosis, and autophagy, the exact underlying molecular mechanisms are unclear. This review summarizes the current status of different types of remote ischemic conditioning methods in animal and clinical studies and analyzes their commonalities and differences in neuroprotective mechanisms and signaling pathways. Remote ischemic conditioning has emerged as a potential therapeutic approach for improving stroke-induced brain injury owing to its simplicity, non-invasiveness, safety, and patient tolerability. Different forms of remote ischemic conditioning exhibit distinct intervention patterns, timing, and application range. Mechanistically, remote ischemic conditioning can exert neuroprotective effects by activating the Notch1/phosphatidylinositol 3-kinase/Akt signaling pathway, improving cerebral perfusion, suppressing neuroinflammation, inhibiting cell apoptosis, activating autophagy, and promoting neural regeneration. While remote ischemic conditioning has shown potential in improving stroke outcomes, its full clinical translation has not yet been achieved.

Electroacupuncture mitigates cognitive impairments in chronic hypoxia-induced mice by modulating neuroinflammation

This study investigates the therapeutic effects and mechanisms of electroacupuncture (EA) on cognitive impairment induced by chronic hypoxia (CH) in mice. Chronic hypoxia was simulated by exposing mice to a 10 % oxygen environment for 8 hours daily over 3 months. The cognitive functions of the mice were assessed through behavioral tests, including the open field test (OFT), Y-maze, and Morris water maze (MWM). Results showed that CH induced significant anxiety-like behaviors and memory impairments in mice. EA treatment, targeting the Baihui (GV20), Shenting (GV24), and Zusanli (ST36) acupoints, significantly ameliorated these behavioral deficits. Histological analyses using HE staining, Nissl staining, and TUNEL assays demonstrated that EA reduced neuronal damage, apoptosis, and myelin loss in the cerebral cortex and hippocampus. Additionally, EA treatment significantly lowered the expression of the pro-inflammatory cytokine TNF-α in brain tissues, suggesting its anti-inflammatory effects. Immunofluorescence and Western blot analyses revealed that EA inhibited the overactivation of microglia and astrocytes in the CH model. Specifically, EA suppressed the expression of Iba1 and GFAP, markers of microglial and astrocytic activation, respectively. Furthermore, EA promoted the polarization of microglia towards the M2 anti-inflammatory phenotype by downregulating iNOS and upregulating Arg1. Similarly, EA reduced the expression of C3, a marker of A1 astrocytes, thereby preventing astrocytic polarization towards the pro-inflammatory state. Organotypic brain slice cultures subjected to oxygen-glucose deprivation (OGD) confirmed that electrical stimulation, akin to EA, inhibited the activation of microglia and astrocytes under hypoxic conditions. In conclusion, EA improves cognitive function in CH-induced mice by reducing neuroinflammation, inhibiting glial cell overactivation, and promoting anti-inflammatory phenotypes. These findings highlight EA's potential as a therapeutic intervention for cognitive impairments related to chronic hypoxia.

Microglial cannabinoid receptor 2 and epigenetic regulation: Implications for the treatment of depression

Depression, often stress-induced, is closely related to neuroinflammation, in which microglia, the brain's immune cells, are the leading players. Microglia shift between a quiescent and an active state, promoting both pro- and anti-inflammatory responses. Cannabinoid type 2 (CB2) receptor encoded by the CNR2 gene is a key player to modulate inflammatory activity. CB2 receptor is highly controlled at the epigenetic level, especially in response to stressful stimuli, positioning it between stress, neuroinflammation, and depression. The following review addresses how epigenetic regulation of CNR2 expression affects depression and the dissection, further, of molecular pathways driving neuroinflammation-related depressive states. The present study emphasizes the therapeutic potential of CB2 receptor agonists that selectively interact with activated microglia and opens a new avenue for the treatment of depression associated with neuroinflammation. The review, therefore, provides a framework of underlying mechanisms for developing novel therapeutic strategies that focus on relieving symptoms by modulating the neuroinflammatory response. Finally, this review underlines the possibilities of therapeutic interventions taking into account CB2 receptors in combating depression.

Characterizing Microglial Signaling Dynamics During Inflammation Using Single-Cell Mass Cytometry

Microglia play a critical role in maintaining central nervous system (CNS) homeostasis and display remarkable plasticity in their response to inflammatory stimuli. However, the specific signaling profiles that microglia adopt during such challenges remain incompletely understood. Traditional transcriptomic approaches provide valuable insights, but fail to capture dynamic post-translational changes. In this study, we utilized time-resolved single-cell mass cytometry (CyTOF) to measure distinct signaling pathways activated in microglia upon exposure to bacterial and viral mimetics-lipopolysaccharide (LPS) and polyinosinic-polycytidylic acid (Poly(I:C)), respectively. Furthermore, we evaluated the immunomodulatory role of astrocytes on microglial signaling in mixed cultures. Microglia or mixed cultures derived from neonatal mice were treated with LPS or Poly(I:C) for 48 h. Cultures were stained with a panel of 33 metal-conjugated antibodies targeting signaling and identity markers. High-dimensional clustering analysis was used to identify emergent signaling modules. We found that LPS treatment led to more robust early activation of pp38, pERK, pRSK, and pCREB compared to Poly(I:C). Despite these differences, both LPS and Poly(I:C) upregulated the classical reactivity markers CD40 and CD86 at later time points. Strikingly, the presence of astrocytes significantly blunted microglial responses to both stimuli, particularly dampening CD40 upregulation. Our studies demonstrate that single-cell mass cytometry effectively captures the dynamic signaling landscape of microglia under pro-inflammatory conditions. This approach may pave the way for targeted therapeutic investigations of various neuroinflammatory disorders. Moreover, our findings underscore the necessity of considering cellular context, such as astrocyte presence, in interpreting microglial behavior during inflammation.

Intestinal 8 gingerol attenuates TBI-induced neuroinflammation by inhibiting microglia NLRP3 inflammasome activation in a PINK1/Parkin-dependent manner

BACKGROUND

traumatic brain injury (TBI) is irreversible brain damage, leading to inflammation and cognitive dysfunction. Microglia involved in the inflammatory response after TBI. The gut microbiota, known as the body's "second brain," regulates neurogenesis and immune responses, but its precise role in regulating TBI remains unclear.

PURPOSE

to investigate the effect of gut microbiota and metabolites disorder on TBI injury.

STUDY DESIGN

16SrRNA and metabolomics compared gut microbiota and metabolites in sham group and TBI group, then proved that the differential metabolite 8-gingerol (8G) alleviated the microglia neuroinflammatory response after TBI.

METHODS

fecal microbiota transplantation explored the role of dysbiosis in TBI. LC/MS detected the content of 8-gingerol in cecum, blood, and brain. HE, Nissl, Tunel staining and mNSS score evaluated brain injury. Western blot and immunofluorescence detected the expression of inflammasome-related proteins and mitophagy-related proteins in brain tissue and BV2 cells. RNA sequencing analyzed the molecular mechanism of 8-gingerol.

RESULT

rats transplanted with TBI feces had worse brain injury and neurological deficits than those with normal feces. 16SrRNA and metabolomics found that TBI caused dysbiosis and decreased 8-gingerol level, leading to severe neuroinflammation. Mechanistically, 8-gingerol inhibited NLRP3 inflammasome by promoting PINK1-Parkin mediated mitophagy in microglia. Inhibition of Parkin, through either small interfering RNA or the inhibitor 3MA reversed the inhibitory effect of 8-gingerol on NLRP3 by blocking mitophagy. BV2 cells transcriptome showed that 8-gingerol significantly increased the expression of autophagy factor Wipi1, and small interfering RNA of Wipi1 abolished the effect of 8-gingerol on promoting mitophagy and the inhibitory effect on NLRP3.

CONCLUSION

our findings shed light on the pivotal role of gut microbes in TBI, and identify 8 gingerol as an important anti-inflammatory compound during TBI.

Dectin-1 participates in neuroinflammation and dopaminergic neurodegeneration through synergistic signaling crosstalk with TLR4

Neuroinflammation mediated by microglial activation plays a prominent role in the pathogenesis of Parkinson's disease (PD). Dendritic cell-associated C-type lectin-1 (Dectin-1) is a pattern recognition receptor that is involved in innate immunity. However, the role of Dectin-1 on dopaminergic neuronal damage remains unclear. Our results demonstrated that the expression of Dectin-1 was significantly increased in the microglia of the LPS-induced PD mouse model. Inhibition of Dectin-1 by laminarin (LAM) attenuated LPS-induced dopaminergic neuronal damage in substantia nigra (SN) and behavioral deficits and promoted the phenotypic transformation of microglia from M1 to M2. Moreover, inhibition or knockdown of Dectin-1 significantly decreased LPS-induced phosphorylation of Syk and P65 as well as the production of COX-2 and iNOS in BV2 cells. Knockdown of Syk also significantly decreased LPS-induced protein expressions of COX-2 and iNOS. Mechanistically, both TLR4 inhibitor and NF-κB inhibitor could antagonize LPS-induced Dectin-1 expression. Chromatin immunoprecipitation (ChIP) assays showed a physical binding of NF-κB/P65 to Dectin-1 promoter, which further indicated the regulatory effect of toll-like receptor 4 (TLR4)/NF-κB signaling pathway on Dectin-1 expression. Furthermore, the present study provided the first evidence that Dectin-1 activation by hot-alkali treated depleted zymosan (d-Zymosan) could induce dopaminergic neurotoxicity and motor dysfunction, and promote up-regulation of TLR4, iNOS and Iba-1 in C57BL/6J mice. In conclusion, Dectin-1-Syk synergistic signaling crosstalk with TLR4/NF-κB promotes and maintains inflammatory phenotypes of M1 microglia which induces dopaminergic neuronal damage in SN. These findings provide novel insights into the pivotal role of Dectin-1 in neuroinflammation, suggesting its potential as a novel therapeutic target for PD.

Microglial pyroptosis induced by SENP7 via the cGAS/STING/IRF3 pathway contributes to neuronal apoptosis

BACKGROUND

Maternal anesthetic exposure may exacerbate significant neurocognitive risks in the immature brains of fetuses. However, the mechanisms through which sevoflurane exposure during pregnancy results in cognitive impairments in offspring remain unclear.

METHODS

Pregnant C57BL/6 mice (gestational day 14) were intervented with 2.5 % sevoflurane for 6 h. Morris water maze test and context fear conditioning test were utilized to evaluate the cognitive function of the offspring. BV2 cells were stimulated with LPS-ATP to evaluate the impacts of SENP7 on microglial pyroptosis. A co-culture experiment was conducted to investigate the apoptosis of mouse hippocampal neuronal cells induced by BV2 cells. The regulatory roles of SENP7 in the cGAS/STING/IRF3 pathway were assessed using an immunoprecipitation SUMOylation assay, along with Western blot analysis.

RESULTS

Sevoflurane exposure during pregnancy resulted in cognitive impairments in offspring mice, which were associated with the upregulation of SENP7, Iba1, Caspase1, and GSDMD-N proteins, as well as the downregulation of NeuN and TH proteins in the brains of the offspring. The knockdown of SENP7 inhibited the elevation of GSDMD-N, Caspase1, and NLRP3 protein levels, subsequently reducing the concentrations of IL-1β and IL-18 in BV2 cells induced by LPS-ATP. Furthermore, SENP7 facilitated the activation of the cGAS/STING/IRF3 axis by regulating the deSUMOylation of cGAS, which triggered microglial pyroptosis and subsequently led to neuronal apoptosis.

CONCLUSION

Maternal exposure to sevoflurane increased the expression of SENP7 in the brains of offspring and resulted in detrimental effects on cognitive function. This phenomenon was associated with neuronal apoptosis triggered by microglial pyroptosis, which was regulated by SENP7 through the cGAS/STING/IRF3 pathway.

Senkyunolide I Improves Septicemia-Induced Brain Dysfunction via Regulating Nrf2 and Astrocyte Activity

Senkyunolide I (Sen I) has a protective effect on the blood-brain barrier (BBB) in rats with sepsis-associated encephalopathy (SAE). This study investigated whether Sen I regulates Nrf2 to ameliorate sepsis-induced brain dysfunction (SIBD). Sixty rats were randomly assigned into Sham group, SAE group (Model group), SAE + Sen I group (72 mg/kg, Sen I group), and SAE+ positive control group (RTA 402, Nrf2 receptor agonist, RTA 402 group), with 15 rats in each group. The cecal ligation and puncture (CLP) method was applied to induce sepsis in rats. SAE modeling was verified 6 h after operation. The drug was administered 24 h after surgery. Six rats in each group were sacrificed 24 h after administration, with brains extracted. The remaining rats would continue to be observed for their survival status until 72 h post-surgery. Brain cell apoptosis was measured using TUNEL. We detected the expression of glial fibrillary acidic protein (GFAP) by immunofluorescence, Nrf2 gene expression by RT-qPCR, and the protein expression of Nrf2, MMP-9, AQP-4, and occludin by Western blot. TNF-α and IL-1β levels were tested by ELISA, and malondialdehyde (MDA) and glutathione peroxidase (GSH-Px) by biochemical tests. Survival rate at 72 h post-surgery, Sham group was 100%. The survival rate of the Sen I group (44.4%) and the RTA 402 group (55.6%) is significantly higher than that of the Model group (11.1%). Both Sen I and RTA 402 can improve the brain tissue damage in rats caused by sepsis, specifically by reducing apoptosis and GFAP expression, reducing TNF-α, IL-1β, and MDA levels, increasing the activity of GSH-Px, downregulating the protein expression of MMP-9 and AQP-4, and upregulating the protein expression of Nrf2 and occludin. Moreover, Sen I significantly increased the expression of Nrf2 in rat brain tissues. Sen I ameliorates SIBD in rats by regulating the expression of Nrf2 and astrocyte activation.

Myeloid lineage C3 induces reactive gliosis and neuronal stress during CNS inflammation

Complement component C3 mediates pathology in CNS neurodegenerative diseases. Here we use scRNAseq of sorted C3-reporter positive cells from mouse brain and optic nerve to characterize C3 producing glia in experimental autoimmune encephalomyelitis (EAE), a model in which peripheral immune cells infiltrate the CNS, causing reactive gliosis and neuro-axonal pathology. We find that C3 expression in the early inflammatory stage of EAE defines disease-associated glial subtypes characterized by increased expression of genes associated with mTOR activation and cell metabolism. This pro-inflammatory subtype is abrogated with genetic C3 depletion, a finding confirmed with proteomic analyses. In addition, early optic nerve axonal injury and retinal ganglion cell oxidative stress, but not loss of post-synaptic density protein 95, are ameliorated by selective deletion of C3 in myeloid cells. These data suggest that in addition to C3b opsonization of post synaptic proteins leading to neuronal demise, C3 activation is a contributor to reactive glia in the optic nerve.

Tanycytes in the Nexus of Hypothalamic Inflammation, Appetite Control, and Obesity

Hypothalamic inflammation has been identified as a critical factor driving the development of obesity and associated metabolic disorders. This inflammation-related disruption of energy balance relies on alterations in metabolic cues sensing and hypothalamic cellular functions, together leading to overeating and weight gain. Within the hypothalamic cellular networks controlling energy balance, recent studies have highlighted the significance of glial dysfunction in these processes, suggesting that these cells could provide new avenues for weight loss therapies. Glia rapidly activates following the consumption of a high-fat diet, even after a very short exposure, and contributes to the disruption of the entire system through inflammatory crosstalk. This review explores recent progress in understanding the molecular interactions between glial cells and neurons in hypothalamic inflammation related to obesity, diabetes, and associated complications. Notably, it highlights specialized ependymal cells called tanycytes, whose role is still underestimated in hypothalamic inflammation, and examines the potential for targeting this cell type as a treatment strategy for metabolic disorders.

Immune checkpoint TIM-3 regulates microglia and Alzheimer's disease

Microglia are the resident immune cells in the brain and have pivotal roles in neurodevelopment and neuroinflammation1,2. This study investigates the function of the immune-checkpoint molecule TIM-3 (encoded by HAVCR2) in microglia. TIM-3 was recently identified as a genetic risk factor for late-onset Alzheimer's disease3, and it can induce T cell exhaustion4. However, its specific function in brain microglia remains unclear. We demonstrate in mouse models that TGFβ signalling induces TIM-3 expression in microglia. In turn, TIM-3 interacts with SMAD2 and TGFBR2 through its carboxy-terminal tail, which enhances TGFβ signalling by promoting TGFBR-mediated SMAD2 phosphorylation, and this process maintains microglial homeostasis. Genetic deletion of Havcr2 in microglia leads to increased phagocytic activity and a gene-expression profile consistent with the neurodegenerative microglial phenotype (MGnD), also referred to as disease-associated microglia (DAM). Furthermore, microglia-targeted deletion of Havcr2 ameliorates cognitive impairment and reduces amyloid-β pathology in 5×FAD mice (a transgenic model of Alzheimer's disease). Single-nucleus RNA sequencing revealed a subpopulation of MGnD microglia in Havcr2-deficient 5×FAD mice characterized by increased pro-phagocytic and anti-inflammatory gene expression alongside reduced pro-inflammatory gene expression. These transcriptomic changes were corroborated by single-cell RNA sequencing data across most microglial clusters in Havcr2-deficient 5×FAD mice. Our findings reveal that TIM-3 mediates microglia homeostasis through TGFβ signalling and highlight the therapeutic potential of targeting microglial TIM-3 in Alzheimer's disease.

Effect of microglial Pd1 on glial scar formation after spinal cord injury in mice

The crosstalk between microglia and astrocytes following spinal cord injury (SCI) greatly decides the prognosis. However, a comprehensive understanding of the molecular mechanisms by which microglia regulate astrocytic activity post-SCI is lacking. Programmed cell death protein 1 (Pdcd1, Pd1) plays a crucial role in modulating immune responses by exerting suppressive effects on microglia and peripheral immune cells within the central nervous system (CNS). Previous studies have shown the involvement of Pd1 in the pathogenesis of SCI; however, the role of microglial Pd1 in astrocytic activation and the following glial scar formation remains elusive. Here, we demonstrated that the pharmacological depletion of microglia using minocycline decreased the expression of TNF-α and IL-6 while concurrently increasing the expression of IL-10 following SCI, thereby facilitating motor function recovery in mice. We observed an increase in Pd1 expression in the injured spinal cord after SCI, with precise localization of Pd1 within microglia. Based on Pd1 knockout (KO) mice, we further revealed that Pd1 deficiency disrupted glial scar formation, leading to increased inflammation, impeded nerve regeneration, enlarged tissue damage, and compromised functional recovery following SCI. In vitro study showed that siRNA-mediated inhibition of Pd1 in microglia followed by lipopolysaccharide (LPS) treatment significantly inhibited astrocyte migration and upregulated the secretion of TNF-α and CXCL9 from microglia, indicating that microglial Pd1 regulates glial scar formation through modulating the inflammatory microenvironment. Our study gains a new mechanistic insight into how microglial Pd1 decides the fate of SCI and promotes microglial Pd1 as a promising therapeutic target for SCI.

Neuroinvasive and neurovirulent potential of SARS-CoV-2 in the acute and post-acute phase of intranasally inoculated ferrets

Severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) can cause systemic disease, including neurological complications, even after mild respiratory disease. Previous studies have shown that SARS-CoV-2 infection can induce neurovirulence through microglial activation in the brains of patients and experimentally inoculated animals, which are models representative for moderate to severe respiratory disease. Here, we aimed to investigate the neuroinvasive and neurovirulent potential of SARS-CoV-2 in intranasally inoculated ferrets, a model for subclinical to mild respiratory disease. The presence of viral RNA, histological lesions, virus-infected cells, and the number and surface area of microglia and astrocytes were investigated. Viral RNA was detected in various respiratory tissue samples by qPCR at 7 days post inoculation (dpi). Virus antigen was detected in the nasal turbinates of ferrets sacrificed at 7 dpi and was associated with inflammation. Viral RNA was detected in the brains of ferrets sacrificed 7 dpi, but in situ hybridization nor immunohistochemistry did confirm evidence for viral RNA or antigen in the brain. Histopathological analysis of the brains showed no evidence for an influx of inflammatory cells. Despite this, we observed an increased number of Alzheimer type II astrocytes in the hindbrains of SARS-CoV-2 inoculated ferrets. Additionally, we detected increased microglial activation in the olfactory bulb and hippocampus, and a decrease in the astrocytic activation status in the white matter and hippocampus of SARS-CoV-2 inoculated ferrets. In conclusion, although SARS-CoV-2 has limited neuroinvasive potential in this model for subclinical to mild respiratory disease, there is evidence for neurovirulent potential. This study highlights the value of this ferret model to study the neuropathogenecity of SARS-CoV-2 and reveals that a mild SARS-CoV-2 infection can affect both microglia and astrocytes in different parts of the brain.

Silybin attenuates microglia-mediated neuroinflammation via inhibition of STING in experimental subarachnoid hemorrhage

BACKGROUND

The primary cause of subarachnoid hemorrhage (SAH) is the rupture of intracranial aneurysms. Over-activation of microglia following SAH is a primary driving force in early brain injury (EBI), which is a leading cause of poor outcomes. Silybin is a flavonoid compound extracted from Silybum marianum, a plant belonging to the Asteraceae family. Its anti-inflammatory and antioxidant properties could provide neuroprotective effects. The mechanism of silybin on EBI after SAH is unclear.

PURPOSE

To determine the therapeutic effect of silybin on SAH and its underlying mechanisms.

METHODS

We used a prechiasmatic autologous arterial blood injection in vivo and hemoglobin in vitro to establish experimental SAH model. Dexamethasone was used as a positive control drug. We evaluated the neuroprotective effect of silybin on the in vivo SAH model by neurological function scores, rotarod test, and open field test, and explored the protective effect of silybin on neuroinflammation and apoptosis after SAH by quantitative polymerase chain reaction (qPCR), western blot (WB), Immunofluorescence (IF) and TUNEL staining. IF staining of CD86 and CD206 was used to assess microglial phenotype polarization. Then we used WB and IF labeling of STING to explore the effect of silybin on the STING pathway after SAH, and used a combination of transcriptomics and non-targeted metabolomics to study the potential mechanism of silybin in detail, and verified the essential genes by qPCR. We also extracted cerebrospinal fluid from SAH patients and detected the expression level of STING in cerebrospinal fluid by enzyme-linked immunosorbent assay (ELISA) to clarify the association between STING and neural function.

RESULTS

Results showed that silybin ameliorated neuronal damage and improved short-term neurological function, and reduced inflammatory damage and neuronal apoptosis in SAH mice. Silybin inhibited the expression levels of TNF-α, IL-1β and NLRP3, and promoted the expression levels of CD206, Arg1 and IL-10. Notably, Silybin promoted M2 microglia polarization. Further studies found that silybin reduced the mRNA and protein levels of the stimulator of interferon genes (STING) in microglia. And the use of a specific activator of STING (CMA) disrupted the protective effect of silybin. A total of 358 differential expression genes were identified using transcriptomics, and 150 different metabolites abundance were identified using metabolomic screening. Analysis of the effects of STING on transcriptomics and metabolomics revealed that STING might impact metabolic pathways, including linoleic acid metabolism. The qPCR results confirmed the decreased expression of essential proteins involved in the pathway. Finally, we found that increased STING expression in the cerebrospinal fluid of SAH patients was associated with decreased neurological function scores and poor prognosis.

CONCLUSION

Silybin had a therapeutic effect on SAH. The underlying mechanism involves linoleic acid metabolism, which is associated with the differential genes and metabolites detected in the study. This study presented a pharmacological rationale for using silybin to treat SAH.

Unraveling the cGAS-STING pathway in Alzheimer's disease: A new Frontier in neuroinflammation and therapeutic strategies

Alzheimer's disease (AD) is the most prevalent type of neurological disorder characterized by cognitive decline and memory loss, marked by the accumulation of amyloid beta (Aβ) plaques and hyperphosphorylated tau protein, causing extensive neuronal death and neuroinflammation. There is growing evidence that AD development extends beyond the neuronal compartment and has a major impact on the immunological functions of the brain. The cyclic GMP-AMP synthase (cGAS) detects cytosolic DNA, including pathogenic foreign DNA and self-DNA from cellular injury, triggering a type I interferon (IFN-I) response through activation of the stimulator of interferon genes (STING). The activation of the cGAS-STING pathway in response to mitochondrial dysfunction drives neuroinflammation in AD, which is mediated by the release of IFN-I cytokines. Furthermore, the release of oxidized mtDNA is necessary for the stimulation of the nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome, which is a family of protein complexes that macrophages can produce to induce inflammation. AD becomes severe by the stimulation of the cGAS-STING pathway, which results in sterile inflammation and microglial dysfunction. This review aims to explore the potential impact of the cGAS-STING signaling pathway in the pathogenesis and progression of AD. Additionally; after overviewing recent findings, this article highlights the molecular mechanism involved in the onset of disease and its modulation regarding the therapeutic approach of AD. Finally, deliberated a deep insight, the cGAS-STING axis could provide novel therapeutic avenues for slowing or halting the progression of AD, thereby offering new prospects for treatment development.

Perfluoropentane-based oxygen-loaded nanodroplets reduce microglial activation through metabolic reprogramming

JOURNAL/nrgr/04.03/01300535-202504000-00032/figure1/v/2024-07-06T104127Z/r/image-tiff Microglia, the primary immune cells within the brain, have gained recognition as a promising therapeutic target for managing neurodegenerative diseases within the central nervous system, including Parkinson's disease. Nanoscale perfluorocarbon droplets have been reported to not only possess a high oxygen-carrying capacity, but also exhibit remarkable anti-inflammatory properties. However, the role of perfluoropentane in microglia-mediated central inflammatory reactions remains poorly understood. In this study, we developed perfluoropentane-based oxygen-loaded nanodroplets (PFP-OLNDs) and found that pretreatment with these droplets suppressed the lipopolysaccharide-induced activation of M1-type microglia in vitro and in vivo, and suppressed microglial activation in a mouse model of Parkinson's disease. Microglial suppression led to a reduction in the inflammatory response, oxidative stress, and cell migration capacity in vitro. Consequently, the neurotoxic effects were mitigated, which alleviated neuronal degeneration. Additionally, ultrahigh-performance liquid chromatography-tandem mass spectrometry showed that the anti-inflammatory effects of PFP-OLNDs mainly resulted from the modulation of microglial metabolic reprogramming. We further showed that PFP-OLNDs regulated microglial metabolic reprogramming through the AKT-mTOR-HIF-1α pathway. Collectively, our findings suggest that the novel PFP-OLNDs constructed in this study alleviate microglia-mediated central inflammatory reactions through metabolic reprogramming.

Targeting chaperone-mediated autophagy in neurodegenerative diseases: mechanisms and therapeutic potential

The pathological hallmarks of various neurodegenerative diseases including Parkinson's disease and Alzheimer's disease prominently feature the accumulation of misfolded proteins and neuroinflammation. Chaperone-mediated autophagy (CMA) has emerged as a distinct autophagic process that coordinates the lysosomal degradation of specific proteins bearing the pentapeptide motif Lys-Phe-Glu-Arg-Gln (KFERQ), a recognition target for the cytosolic chaperone HSC70. Beyond its role in protein quality control, recent research underscores the intimate interplay between CMA and immune regulation in neurodegeneration. In this review, we illuminate the molecular mechanisms and regulatory pathways governing CMA. We further discuss the potential roles of CMA in maintaining neuronal proteostasis and modulating neuroinflammation mediated by glial cells. Finally, we summarize the recent advancements in CMA modulators, emphasizing the significance of activating CMA for the therapeutic intervention in neurodegenerative diseases.

NLRP3 inflammasome in neuroinflammation and central nervous system diseases

Neuroinflammation plays an important role in the pathogenesis of various central nervous system (CNS) diseases. The NLRP3 inflammasome is an important intracellular multiprotein complex composed of the innate immune receptor NLRP3, the adaptor protein ASC, and the protease caspase-1. The activation of the NLRP3 inflammasome can induce pyroptosis and the release of the proinflammatory cytokines IL-1β and IL-18, thus playing a central role in immune and inflammatory responses. Recent studies have revealed that the NLRP3 inflammasome is activated in the brain to induce neuroinflammation, leading to further neuronal damage and functional impairment, and contributes to the pathological process of various neurological diseases, such as multiple sclerosis, Parkinson's disease, Alzheimer's disease, and stroke. In this review, we summarize the important role of the NLRP3 inflammasome in the pathogenesis of neuroinflammation and the pathological course of CNS diseases and discuss potential approaches to target the NLRP3 inflammasome for the treatment of CNS diseases.

The microglial state transition as a novel mechanism by which fresh Baihe Dihuang decoction prevents depression by regulating SIRT1/HMGB1 signaling

BACKGROUND

Fresh Baihe Dihuang decoction (FBD) is a classic Traditional Chinese Medicine (TCM) formula used to treat depression. However, its underlying molecular mechanisms in treating depression still need further exploration.

PURPOSE

In this study, we investigated whether FBD could prevent depressive-like behaviors by remodeling the microglial state transition via the inhibition of SIRT1/HMGB1 signaling in vivo and in vitro.

STUDY DESIGN AND METHODS

In vivo, adult male C57BL/6 J mice were subjected to chronic unpredictable mild stress (CUMS) for 6 weeks to investigate whether FBD could produce antidepressant-like behavioral effects. At 9 weeks of age, EX527, a SIRT1 inhibitor, was injected intraperitoneally 30 min before the intragastric administration of FBD, Flx or vehicle daily until 12 weeks of age, and the effects of alterations in SIRT1/HMGB1 signaling on CUMS-mediated depression were investigated. In vitro, the anti-depressive mechanism of FBD was further investigated using BV-2 cells (a microglial cell line) and primary PFC neurons. We examined depression-like behaviors using behavioral tests. Serum and supernatants samples were collected and interleukin-1β (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α) levels were measured using enzyme-linked immunosorbent assays (ELISAs). Prefrontal cortical (PFC) tissues, BV-2 cells and PFC neurons were collected to detect neuronal apoptosis, the microglial state or proteins in the silent information regulator 2 homolog 1 (SIRT1)/high mobility group box 1 (HMGB1) signaling pathway via flow cytometry, immunohistochemical staining, immunofluorescence staining,TUNEL staining or western blot analysis.

RESULTS

The administration of FBD ameliorated the depressive-like behaviors induced by CUMS. In addition, FBD supplementation promoted the transition from a proinflammatory microglial phenotype to an anti-inflammatory microglial phenotype. The FBD-mediated inhibition of HMGB1 expression and its nucleocytoplasmic translocation were identified as likely due to increased SIRT1 activity, effectively inhibiting the subsequent inflammatory response. Furthermore, our findings revealed that FBD notably attenuated neuronal apoptosis in the PFC. In contrast, the SIRT1 inhibitor EX527 counteracted the antidepressant effect of FBD while also reversing the expression of brain-derived neurotrophic factor (BDNF), NeuN, cleaved caspase-3, bax, and bcl-2 proteins.

CONCLUSIONS

This study showed that FBD prevents depression by mediating a microglial state transition via the SIRT1/HMGB1 signaling pathway, providing a promising and novel antidepressant therapeutic strategy.

Alleviation of Microglia Mediating Hippocampal Neuron Impairments and Depression-Related Behaviors by Urolithin B via the SIRT1-FOXO1 Pathway

AIMS

Conventional antidepressants exhibit limited efficacy and delayed onset. This study aimed to elucidate the antidepressant effects of urolithin B (UB) and its regulatory role in microglia-mediated hippocampal neuronal dysfunction.

METHODS

The mouse model of depression was established using both chronic unpredicted stress (CUS) and lipopolysaccharide (LPS) injection. The therapeutic efficacy of UB was assessed through behavioral paradigms. The microglia activation, cellular cytotoxicity and apoptosis levels, and underlying molecular mechanisms were delineated utilizing proteomics analysis, immunofluorescence staining, real-time PCR and Western blotting.

RESULTS

UB efficiently alleviated depression-related behaviors, accompanied by suppressed microglia activation, neuroinflammation, changes of classic activation (M1)/alternative activation (M2) polarization and recovered sirtuin-1 (SIRT1) and forkhead box protein O1 (FOXO1) expression in the hippocampus. Additionally, UB reduced the cytotoxicity and apoptosis of HT22 cells and depression-related phenotypes treated by the cellular supernatant from LPS-incubated BV2 cells, which was mediated by the SIRT1-FOXO1 pathway. The proteomics analysis of the cellular supernatant content revealed abundant secreting proteins among the LPS/UB application.

CONCLUSION

This study confirmed that microglial SIRT1 mediates UB's antidepressant effects, positioning UB as a promising therapeutic candidate for depression by targeting neuroinflammatory pathways.

Autotaxin regulates the expression and the activity of P-glycoprotein in lipopolysaccharide -activated microglial cells

Neurodegenerative diseases (NDs), such as Alzheimer's and Parkinson's, are characterized by chronic inflammation and oxidative stress, often mediated by activated microglial cells. Microglia-induced neuroinflammation is essential to neuronal damage, driven by the overproduction of pro-inflammatory cytokines and reactive oxygen species. Autotaxin (ATX), a lysophospholipase D enzyme, can modulate inflammation through its enzymatic product lysophosphatidic acid (LPA). While previous studies highlighted ATX's anti-inflammatory properties, its impact on P-glycoprotein (P-gp), a key efflux transporter involved in drug resistance and neuroinflammation, remains not fully understood. The objective of this study was to explore how ATX modulates the expression and activity of P-gp in lipopolysaccharide (LPS)-activated and H2O2-stressed BV-2 microglial cells. Microglial cells were transfected with either an empty vector (EV) or an ATX cDNA vector (A +) and exposed to LPS (1 µg/mL) or H2O2 (100 µM). The mRNA expression levels of P-gp and pro-inflammatory cytokines were analyzed using qRT-PCR, and P-gp activity was assessed using the NBD-CSA fluorescence efflux assay. Our findings revealed that while LPS- and H2O2-treated microglial cells were characterized by an abnormal cellular morphology with long ramified processes, ATX overexpression restored the round shape morphology normally observed in the control untreated cells. Interestingly, ATX overexpression significantly reduced the mRNA levels of pro-inflammatory cytokines, such as TNF-α, in LPS- and H2O2-treated microglial cells. Moreover, ATX overexpression reduced both the mRNA levels and efflux activity of P-gp under inflammatory and oxidative stress conditions. These results suggest that ATX mitigates microglial activation and its downstream effects, highlighting its therapeutic potential in reducing neuroinflammation.

Mechanisms and Therapeutic Prospects of Microglia-Astrocyte Interactions in Neuropathic Pain Following Spinal Cord Injury

Neuropathic pain is a prevalent and debilitating condition experienced by the majority of individuals with spinal cord injury (SCI). The complex pathophysiology of neuropathic pain, involving continuous activation of microglia and astrocytes, reactive gliosis, and altered neuronal plasticity, poses significant challenges for effective treatment. This review focuses on the pivotal roles of microglia and astrocytes, the two major glial cell types in the central nervous system, in the development and maintenance of neuropathic pain after SCI. We highlight the extensive bidirectional interactions between these cells, mediated by the release of inflammatory mediators, neurotransmitters, and neurotrophic factors, which contribute to the amplification of pain signaling. Understanding the microglia-astrocyte crosstalk and its impact on neuronal function is crucial for developing novel therapeutic strategies targeting neuropathic pain. In addition, this review discusses the fundamental biology, post-injury pain roles, and therapeutic prospects of microglia and astrocytes in neuropathic pain after SCI and elucidates the specific signaling pathways involved. We also speculated that the extracellular matrix (ECM) can affect the glial cells as well. Furthermore, we also mentioned potential targeted therapies, challenges, and progress in clinical trials, as well as new biomarkers and therapeutic targets. Finally, other relevant cell interactions in neuropathic pain and the role of glial cells in other neuropathic pain conditions have been discussed. This review serves as a comprehensive resource for further investigations into the microglia-astrocyte interaction and the detailed mechanisms of neuropathic pain after SCI, with the aim of improving therapeutic efficacy.

Microglia, Trem2, and Neurodegeneration

Microglia are a specialized type of neuroimmune cells that undergo morphological and molecular changes through multiple signaling pathways in response to pathological protein aggregates, neuronal death, tissue injury, or infections. Microglia express Trem2, which serves as a receptor for a multitude of ligands enhancing their phagocytic activity. Trem2 has emerged as a critical modulator of microglial activity, especially in many neurodegenerative disorders. Human TREM2 mutations are associated with an increased risk of developing Alzheimer disease (AD) and other neurodegenerative diseases. Trem2 plays dual roles in neuroinflammation and more specifically in disease-associated microglia. Most recent developments on the molecular mechanisms of Trem2, emphasizing its role in uptake and clearance of amyloid β (Aβ) aggregates and other tissue debris to help protect and preserve the brain, are encouraging. Although Trem2 normally stimulates defense mechanisms, its dysregulation can intensify inflammation, which poses major therapeutic challenges. Recent therapeutic approaches targeting Trem2 via agonistic antibodies and gene therapy methodologies present possible avenues for reducing the burden of neurodegenerative diseases. This review highlights the promise of Trem2 as a therapeutic target, especially for Aβ-associated AD, and calls for more mechanistic investigations to understand the context-specific role of microglial Trem2 in developing effective therapies against neurodegenerative diseases.

Modification of Neural Circuit Functions by Microglial P2Y6 Receptors in Health and Neurodegeneration

Neural circuits consisting of neurons and glial cells help to establish all functions of the CNS. Microglia, the resident immunocytes of the CNS, are endowed with UDP-sensitive P2Y6 receptors (P2Y6Rs) which regulate phagocytosis/pruning of excessive synapses during individual development and refine synapses in an activity-dependent manner during adulthood. In addition, this type of receptor plays a decisive role in primary (Alzheimer's disease, Parkinson's disease, neuropathic pain) and secondary (epilepsy, ischemic-, mechanical-, or irradiation-induced) neurodegeneration. A whole range of microglial cytokines controlled by P2Y6Rs, such as the interleukins IL-1β, IL-6, IL-8, and tumor necrosis factor-α (TNF-α), leads to neuroinflammation, resulting in neurodegeneration. Hence, small molecular antagonists of P2Y6Rs and genetic knockdown of this receptor provide feasible ways to alleviate inflammation-induced neurological disorders but might also interfere with the regulation of the synaptic circuitry. The present review aims at investigating this dual role of P2Y6Rs in microglia, both in shaping neural circuits by targeted phagocytosis and promoting neurodegenerative illnesses by fostering neuroinflammation through multiple transduction mechanisms.

IL-2/anti-IL-2 complexes attenuates neuroinflammation and neurodegeneration in mice of experimental Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease, with motor and non-motor symptoms being its main clinical manifestations. Neuroinflammation has been shown to involve in pathogenesis of PD. Regulatory T cells (Tregs) in PD exhibited reduction in number and suppressive activity. Existing methods to increase the Tregs remains challenging for clinical application because of the difficulty in Tregs expanding or serious side-effects. Therefore, new approaches still need to be explored to balance the amount and activity of Tregs. In this study, we assessed the protective effects of IL-2/anti-IL-2 complexes (IL-2C) on mouse models of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). And the results showed that IL-2C significantly increased the number of Tregs both in spleen and brain, accompanied by reduced nigral dopaminergic neuron loss and behavioral defects. Besides, IL-2C also attenuated neuroinflammation as observed by diminished glial activation, fewer infiltration of CD4+ and CD8+ T cells and reduced pro-inflammatory cytokines releasing in the nigral region. Moreover, the protective effects of IL-2C were abolished by pre-treatment of anti-CD25 antibody (PC61), which was used to delete the Tregs. In summary, our results demonstrate that IL-2C-induced Tregs expansion attenuates the dopaminergic neurons loss and the neuroinflammatory response in vivo, suggesting that IL-2C maybe a promising therapeutic target for PD.

Characterization of [3H]AZ12464237 as a high affinity, non-nucleotide antagonist radioligand for the P2Y12 receptor

The purinergic receptor P2Y12 (P2Y12R) is a well-recognized target for anti-thrombotic agents. This receptor is also expressed in microglia, the main immune cells of the brain, where it modulates microglial activation states and inflammatory responses. To investigate P2Y12R-mediated actions in the central nervous system (CNS), developing novel brain-penetrant ligands and further in vitro studies on brain tissues are essential. A radiolabeled, easily accessible tool compound would significantly advance such drug discovery efforts. Herein, we describe the 3H-labeling of a non-nucleotide P2Y12R antagonist AZ12464237, and its in vitro binding properties to the receptor in membrane preparations from transfected cells, as well as on mouse brain tissues. The radioligand shows high affinity toward both the human and rat P2Y12R, with Kd values of 3.12 ± 0.70 nM (human) and 16.6 ± 3.40 nM (rat), as determined by saturation binding studies. The binding kinetics of [3H]AZ12464237 are rapid with a short target residence time (∼1 min). We further confirmed the selectivity of the radioligand by performing competitive displacement studies, in which reported P2Y12R ligands and other P2Y receptors ligands were tested for binding against [3H]AZ12464237. Additionally, the radioligand proved valuable for in vitro autoradiography studies on mouse brain tissues, although limited off-target binding was observed in P2Y12R knock-out mouse brain. This could be traced to glycogen synthase kinase 3 α. Considering the growing interest in P2Y12R as a biomarker for anti-inflammatory microglia, [3H]AZ12464237 represents a promising tool for in vitro studies, including screening assays aimed at identifying novel P2Y12R ligands for CNS applications.

Minocycline treatment attenuates neurobehavioural abnormalities and neurostructural aberrations in the medial prefrontal cortex in mice fed a high-fat diet during adolescence

A preference for and overconsumption of a high-fat diet (HFD) are common among adolescents and are recognized as risk factors for multiple mental disorders. The protracted maturation of the medial prefrontal cortex (mPFC), a key brain structure that plays a critical role in mental functions that are essential for both developing and mature individuals (including emotional processing, decision making, risk assessment, and creative thinking), during adolescence renders it more vulnerable to the environmental insults experienced during this critical developmental window. However, the effects of HFD consumption during adolescence on mPFC-related behaviours and the underlying mechanisms need to be further investigated. In this study, we observed that mice fed a HFD throughout adolescence developed depressive- and anxiety-like behaviours and distinctively increased risk-avoidance behaviour, accompanied by morphological aberrations of both pyramidal neuron and microglia in the mPFC. The systemic administration of minocycline, a well-known broad-spectrum antibiotic, effectively attenuated the adverse effects of HFD consumption during adolescence on neurobehaviours and the morphology of pyramidal neurons in the mPFC. This study provides new insights into the psychological effects of long-term HFD consumption during adolescence and indicates the existence of a window during which microglial stabilization may be a promising strategy to protect against the HFD consumption-induced increase in the risk of psychiatric disorders.

The Role of α7-Nicotinic Acetylcholine Receptors in the Pathophysiology and Treatment of Parkinson's Disease

The α7 nicotinic acetylcholine receptor (α7-nAChR) is a pivotal regulator of neurotransmission, neuroprotection, and immune modulation in the central nervous system. This review explores its structural and functional attributes, highlighting its therapeutic potential in neurodegenerative disorders, particularly Parkinson's disease (PD). α7-nAChRs mediate synaptic plasticity, modulate inflammatory responses, and influence dopamine release, positioning them as a promising pharmacological target. Positive allosteric modulators (PAMs) enhance α7-nAChR activity mainly by reducing desensitization, offering a superior therapeutic approach compared with direct agonists. Emerging preclinical studies suggest that α7-nAChR activation mitigates dopaminergic neurodegeneration, improves L-dopa-induced dyskinesia, and reduces neuroinflammation. Despite promising findings, clinical trials have yielded mixed results, necessitating further research into optimizing α7-targeted therapies. This review underscores the significance of α7-nAChRs in PD pathophysiology and highlights future directions for their translational potential in neuroprotection and symptomatic relief.

Spermidine attenuates microglial activation, neuroinflammation, and neuronal injury in rat model of vascular dementia

Spermidine has been implicated to provide beneficial effects on cognitive function in several model organisms as well as older adults with mild and moderate dementia. Nevertheless, the potential impact of spermidine on learning and memory deficits in vascular dementia (VaD) remains largely unknown. Here, bilateral common carotid artery occlusion (BCCAo) was applied to induce chronic cerebral hypoperfusion in rats. We demonstrated that spermidine therapy improved the spatial learning performance in model animals, accompanied with decreased cerebral histopathologic injury and increased restored myelin basic protein (MBP) expression. Moreover, spermidine suppressed abnormal microglia activation, inhibited the excessive generation of proinflammatory mediators, such as tumor necrosis factor (TNF)α and inducible nitric oxide synthase (iNOS), and increased the anti-inflammatory cytokine transforming growth factor (TGF)β expression in rodent brain following hypoperfusion. Our findings indicated that spermidine alleviated cognitive impairments of rats after VaD-like injury possibly via suppressing microglia-modulated neuroinflammation and neuronal injury. These data may shed light on understanding the pathogenesis of VaD and point to the promising value of spermidine supplementation for cognition improvement.

A Chloroform Fraction Derived from Vitis vinifera Root Ethanol Extract Attenuates Lipopolysaccharide-Induced Inflammatory Responses and Cognitive Dysfunction in BV-2 Microglia Cells and C57BL/6J Mouse Model

This study aimed to investigate the inhibitory effect of the chloroform fraction (CF) from Vitis vinifera root extract on LPS-induced neuroinflammation in BV-2 microglia cells and a C57/BL6J mouse model. CF significantly suppressed LPS-induced proinflammatory cytokines, including nitric oxide (NO), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in BV-2 microglia cells. Mechanistically, CF inhibited LPS-induced activation of nuclear factor-κB (NF-κB) by blocking the p65 subunit and preventing the phosphorylation of NF-kappa-B inhibitor α (IκBα), while its effect was independent of the mitogen-activated protein kinase (MAPK) pathway. Furthermore, CF modulated the TRIF signaling pathway by regulating TANK-binding kinase 1 (TBK1) and interferon regulatory factor 3 (IRF3), which contributed to the suppression of inflammatory mediators in BV-2 microglia cells. In vivo, we evaluated the neuroprotective effects of CF against cognitive dysfunction and inflammatory responses in an LPS-induced mouse model. Our behavioral assessments, including the Morris water maze and Y-maze tests, demonstrated that CF alleviated LPS-induced spatial learning impairment and cognitive decline. Additionally, CF significantly reduced the levels of inflammatory cytokines in serum and inflammatory mediators proteins expression in whole brain in LPS-injected mice, suggesting a direct link between reduced inflammatory responses and improved cognitive function. These findings suggest that CF from V. vinifera root extract may serve as a potential therapeutic strategy for neurodegenerative diseases mediated by microglial activation, such as Alzheimer's disease.

Choroidal Neovascularization Is Suppressed With Activation of TREM2 in Mononuclear Phagocytes

BACKGROUND

Mononuclear phagocytes contribute to pathological angiogenesis in age-related macular degeneration, a leading worldwide cause of visual impairment. However, the mechanisms that orchestrate the functions of mononuclear phagocytes remain poorly understood. TREM2 (triggering receptor on myeloid cells 2) has been shown to be crucial for the activation of mononuclear phagocytes in atherosclerosis, fatty liver disease, and Alzheimer disease. The objective of this study was to investigate the role of TREM2 in pathological angiogenesis in age-related macular degeneration.

METHODS

C57BL/6J and Trem2 knockout mice were subjected to laser-induced choroidal neovascularization, a model of choroidal neovascular age-related macular degeneration. Purified bovine sulfatide and agonist anti-TREM2 antibody was used to activate TREM2 signaling. The expression of TREM2 or downstream signals were assessed with immunohistochemistry or qPCR. In vitro murine macrophage RAW264.7 cells were used to investigate the direct impact of sulfatide on inflammatory and phagocytic responses.

RESULTS

We found that pharmacological activation of TREM2 suppressed laser-induced choroidal neovessel formation. The activation of TREM2 in mononuclear phagocytes suppressed TNF (tumor necrosis factor) and subsequently promoted phagocytosis.

CONCLUSIONS

These findings demonstrate that activation of TREM2 in mononuclear phagocytes suppresses the proinflammatory response, promotes phagocytosis, and impedes choroidal neovessel formation. Our study provides insight into the critical role of TREM2 in pathological angiogenesis.

Neuronal CD47 induces behavioral alterations and ameliorates microglial synaptic pruning in wild-type and Alzheimer's mouse models

BACKGROUND

Microglia are brain-resident macrophages that play a crucial role in synapse pruning during the development and progression of various neuropsychiatric disorders, including autism spectrum disorder (ASD) and Alzheimer's disease (AD). Mechanistically, CD47 protein acts as a potent 'do not eat me' signal, protecting synapses from phagocytosis by microglia. However, the functional role of the upregulated neuronal CD47 signal under both physiological and pathological conditions remains unclear.

RESULTS

We utilized an adeno-associated virus gene expression system to induce neuron-specific overexpression of CD47 in wild-type and 5xFAD mice, assessing its effects on microglial synaptic phagocytosis and mouse behaviors. Our results indicate that neuronal CD47 induces ASD-like behaviors and synaptic pruning defects, while promoting behavioral disinhibition and improving memory in wild-type mice. Single-nucleus RNA sequencing was employed to profile gene expression patterns in subpopulations of neurons and microglia. Notably, neuronal CD47 enhances synaptic pathways in neurons and particularly shifts microglial subpopulations from a disease-associated state to a homeostatic state. Additionally, neuronal CD47 reduces excessive microglial synaptic phagocytosis induced by Aβ pathology in 5xFAD mice.

CONCLUSION

Our study provides evidence that neuronal CD47 overexpression results in synaptic pruning defects and is involved in the pathogenesis of ASD, while also playing a beneficial role in mitigating excessive synaptic loss in Alzheimer's disease.

Ginsenoside 1 mitigates postoperative cognitive dysfunction by enhancing microglial Aβ clearance through the endo-lysosomal pathway

BACKGROUND

Postoperative cognitive dysfunction (POCD) is a common complication in patients after surgery, especially in the elderly. The incidence of POCD not only impaired learning and memory, but also increased morbidity and mortality in patients. However, the exploration of therapeutic agents is limited. Ginsenoside 1 (Rg1) is one of the main compounds of ginseng, which exhibits bioactive and neuroprotective efficiency. In the present study, we aimed to investigate the effects of Rg1 on POCD.

METHODS

The POCD model was established by performing aseptic laparotomy surgery under anesthesia in 18-month mice. The cognition and anxiety of mice were assessed with MWM, OFT, and NOR tests. An in vitro model was performed on BV2 microglial cells. RNA sequencing, Western blotting, electrophysiology, Golgi staining, engulfment, and immunofluorescence analysis were performed.

RESULTS

Our results showed that Rg1 effectively alleviated the cognitive dysfuncion and anxiety of POCD mice. Transcriptomic sequencing data in microglia indicated that Rg1 mainly affects endosomes and lysosomes. By upregulating Rab7 and TFEB expression, Rg1 promoted microglial engulfment of Aβ through the endo-lysosomal pathway. Additionally, Rg1 reduced inflammatory levels, increased synaptic plasticity, and mitigated neuronal damage caused by Aβ. Moreover, the effects of Rg1 on TFEB depended on MEK/ERK signaling, while activation of MEK reversed Rg1's protective effects.

CONCLUSIONS

In conclusion, our study demonstrates that Rg1 can effectively ameliorate cognitive and synaptic deficit by enhancing microglial Aβ clearance through the endo-lysosomal pathway in aged POCD mice, which provides a potential strategy for the prevention of POCD.

Role of triggering receptor expressed on myeloid cells 1/2 in secondary injury after cerebral hemorrhage

Intracerebral hemorrhage (ICH) is a common severe emergency in neurosurgery, causing tremendous economic pressure on families and society and devastating effects on patients both physically and psychologically, especially among patients with poor functional outcomes. ICH is often accompanied by decreased consciousness and limb dysfunction. This seriously affects patients' ability to live independently. Although rapid advances in neurosurgery have greatly improved patient survival, there remains insufficient evidence that surgical treatment significantly improves long-term outcomes. With in-depth pathophysiological studies after ICH, increasing evidence has shown that secondary injury after ICH is related to long-term prognosis and that the key to secondary injury is various immune-mediated neuroinflammatory reactions after ICH. In basic and clinical studies of various systemic inflammatory diseases, triggering receptor expressed on myeloid cells 1/2 (TREM-1/2), and the TREM receptor family is closely related to the inflammatory response. Various inflammatory diseases can be upregulated and downregulated through receptor intervention. How the TREM receptor functions after ICH, the types of results from intervention, and whether the outcomes can improve secondary brain injury and the long-term prognosis of patients are unknown. An analysis of relevant research results from basic and clinical trials revealed that the inhibition of TREM-1 and the activation of TREM-2 can alleviate the neuroinflammatory immune response, significantly improve the long-term prognosis of neurological function in patients with cerebral hemorrhage, and thus improve the ability of patients to live independently.

Harnessing microglia-based cell therapies for the treatment of neurodegenerative diseases

Given the growing evidence linking microglia to the onset and progression of various neurodegenerative diseases, these brain-resident macrophages have emerged as a promising cell type for targeted therapeutic interventions. This review highlights recent studies that utilized innovative, microglia-focused strategies for the treatment of diverse neurodegenerative disorders including lysosomal storage disorders, granulin frontotemporal dementia, and Alzheimer's disease. Cutting-edge therapeutic strategies range from replacing faulty microglia with peripheral macrophage precursors or induced human pluripotent stem cell-derived microglia to engineering microglia that target toxic aggregates or deliver remediating payloads. We also examine the potential limitations as well as the clinical benefits of these strategies.

Tabersonine ameliorates depressive-like behavior by inhibiting NLRP3 inflammasome activation in a mouse model

Depression, a common mental disorder, is intimately linked to neuroinflammation. In the central nervous system, microglia, the principal cells involved in immunity, are crucial in neuroinflammation and closely associated with the pathogenesis of depression. Several studies have demonstrated that depressive-like behaviors could be ameliorated by improving brain inflammation. Notably, natural products occupy a critical position in the study of antidepressants. Herein, we explored the antidepressant effects of tabersonine (Tab), a natural inhibitor of NLRP3. Tab significantly improved depressive-like behaviors and anxiety in lipopolysaccharide (LPS)-treated mice. To further elucidate mechanisms underlying the antidepressant actions of Tab, BV2 microglial cells were exposed to LPS and ATP in vitro. Tab effectively inhibited NLRP3 inflammasome activation, subsequent Caspase-1 cleavage, and interleukin-1β secretion both in the hippocampi of mice in vivo and BV2 cells in vitro. Additionally, Tab strongly decreased the concentrations of the proinflammatory cytokines interleukin-1β, tumor necrosis factor, and interleukin-6 in BV2 cell culture supernatants and sera of mice. Further studies indicated that Tab improved LPS-induced neuronal loss, as indicated by a significant rise in the quantity of Nissl-positive cells within the hippocampal regions CA1, CA3, and dentate gyrus. Importantly, Tab counteracted the LPS-induced microglial activation in the hippocampus. Our results indicate that Tab significantly improves LPS-triggered depressive-like behaviors and reverses injuries to hippocampal microglia and neurons, implying its potential as a therapeutic agent for depression.

Peripheral nervous system microglia-like cells regulate neuronal soma size throughout evolution

Microglia, essential in the central nervous system (CNS), were historically considered absent from the peripheral nervous system (PNS). Here, we show a PNS-resident macrophage population that shares transcriptomic and epigenetic profiles as well as an ontogenetic trajectory with CNS microglia. This population (termed PNS microglia-like cells) enwraps the neuronal soma inside the satellite glial cell envelope, preferentially associates with larger neurons during PNS development, and is required for neuronal functions by regulating soma enlargement and axon growth. A phylogenetic survey of 24 vertebrates revealed an early origin of PNS microglia-like cells, whose presence is correlated with neuronal soma size (and body size) rather than evolutionary distance. Consistent with their requirement for soma enlargement, PNS microglia-like cells are maintained in vertebrates with large peripheral neuronal soma but absent when neurons evolve to have smaller soma. Our study thus reveals a PNS counterpart of CNS microglia that regulates neuronal soma size during both evolution and ontogeny.

BDNF Signaling and Pain Modulation

Brain-derived neurotrophic factor (BDNF) is an important neuromodulator of nervous system functions and plays a key role in neuronal growth and survival, neurotransmission, and synaptic plasticity. The effects of BDNF are mainly mediated by the activation of tropomyosin receptor kinase B (TrkB), expressed in both the peripheral and central nervous system. BDNF has been implicated in several neuropsychiatric conditions such as schizophrenia and anxio-depressive disorders, as well as in pain states. This review summarizes the evidence for a critical role of BDNF throughout the pain system and describes contrasting findings of its pro- and anti-nociceptive effects. Different cellular sources of BDNF, its influence on neuroimmune signaling in pain conditions, and its effects in different cell types and regions are described. These and endogenous BDNF levels, downstream signaling mechanisms, route of administration, and approaches to manipulate BDNF functions could explain the bidirectional effects in pain plasticity and pain modulation. Finally, current knowledge gaps concerning BDNF signaling in pain are discussed, including sex- and pathway-specific differences.

Cognitive frailty: A comprehensive clinical paradigm beyond cognitive decline

Cognitive frailty is an emerging concept in research and clinical practice that incorporates both physical frailty and mild cognitive impairment (MCI) or subjective cognitive decline (SCD). Unlike traditional approaches that separate physical frailty and dementia, cognitive frailty treats these domains as interrelated and coexisting, with significant implications for clinical outcomes and predicting cognitive decline. Despite growing recognition of this interrelationship, a dualistic view of physical and cognitive processes persists. The paradigm of cognitive frailty holds promise as a biomarker- like amyloid plaques or neurofibrillary tangles- but with the advantage of identifying risk at a prefrail stage, before clinical signs of MCI or dementia emerge. This review examines the pathophysiological and clinical dimensions of cognitive frailty and promotes for its integration into routine assessments in memory clinics.

Identification of Cytochrome P450 2E1 as a Novel Target in Neuroinflammation and Development of Its Inhibitor Q11 as a Treatment Strategy

Neuroinflammation is implicated in nearly all pathological processes of central nervous system (CNS) diseases. However, no medications specifically targeting neuroinflammation are clinically available, and conventional anti-inflammatory drugs exhibit limited efficacy. Here, we identified cytochrome P450 2E1 (CYP2E1) as a novel therapeutic target in neuroinflammation. Elevated CYP2E1 levels were observed in hippocampal tissues of mouse and rat neuroinflammation models, as well as in LPS-stimulated primary microglia. Genetic ablation of Cyp2e1 improved spatial learning and memory in neuroinflammatory rats and reduced pro-inflammatory cytokine levels in Cyp2e1-deficient microglia. Furthermore, Q11 (1-(4-methyl-5-thiazolyl) ethenone), a novel CYP2E1 inhibitor developed and synthesized in our laboratory, effectively ameliorated Alzheimer's disease-related spatial learning and memory functions and depression-related anxiety-like behaviors in mice/rats. Mechanistically, Q11 attenuated microglial activation, neuronal damage, oxidative stress, and neuroinflammation by suppressing the PI3K/Akt, STAT1/3, and NF-κB signaling pathways. These findings establish CYP2E1 as a druggable target for neuroinflammation and propose Q11 as a promising candidate for treating neuroinflammation-related diseases.

Targeting Neuroinflammation in Central Nervous System Diseases by Oral Delivery of Lipid Nanoparticles

Neuroinflammation within the central nervous system (CNS) is a primary characteristic of CNS diseases, such as Parkinson's disease, Alzheimer's disease (AD), amyotrophic lateral sclerosis, and mental disorders. The excessive activation of immune cells results in the massive release of pro-inflammatory cytokines, which subsequently induce neuronal death and accelerate the progression of neurodegeneration. Therefore, mitigating excessive neuroinflammation has emerged as a promising strategy for the treatment of CNS diseases. Despite advancements in drug discovery and the development of novel therapeutics, the effective delivery of these agents to the CNS remains a serious challenge due to the restrictive nature of the blood-brain barrier (BBB). This underscores the need to develop a novel drug delivery system. Recent studies have identified oral lipid nanoparticles (LNPs) as a promising approach to efficiently deliver drugs across the BBB and treat neurological diseases. This review aims to comprehensively summarize the recent advancements in the development of LNPs designed for the controlled delivery and therapeutic modulation of CNS diseases through oral administration. Furthermore, this review addresses the mechanisms by which these LNPs overcome biological barriers and evaluate their clinical implications and therapeutic efficacy in the context of oral drug delivery systems. Specifically, it focuses on LNP formulations that facilitate oral administration, exploring their potential to enhance bioavailability, improve targeting precision, and alleviate or manage the symptoms associated with a range of CNS diseases.

Single-cell multiomics reveals disrupted glial gene regulatory programs in Alzheimer's disease via interpretable machine learning

Recent development of single-cell technology across multiple omics platforms has provided new ways to obtain holistic views of cells to study disease pathobiology. Alzheimer's disease (AD) is the most common form of dementia worldwide, yet the detailed understanding of its cellular and molecular mechanisms remains limited. In this study, we analyzed paired single-cell transcriptomic (scRNA-seq) and chromatin accessibility (scATAC-seq) data from the Seattle Alzheimer's Disease Brain Cell Atlas (SEA-AD) Consortium to investigate the molecular mechanisms of AD at a cell-subpopulation-specific resolution focusing on glial cells. We benchmarked various multi-omics integration methods using diverse metrics and built an analytic workflow that enabled effective batch correction and cross-modality alignment, creating a unified cell state space. Through integrative analysis of 26 human brain samples, we uncovered AD-associated gene expression and pathway changes in glial subpopulations and highlighted important transcriptomic and epigenomic signatures via functional inference and interpretable machine learning paradigms, discovering the profound involvement of the Solute Carrier proteins (SLC) family genes in multiple glial cell types. We also identified glial cell-specific regulatory programs mediated by key transcription factors such as JUN and FOSL2 in astrocytes, the Zinc Finger (ZNF) family genes in microglia, and the SOX family of transcription factors in oligodendrocytes. Our study provides a comprehensive workflow and a high-resolution view of how glial regulatory programs are disrupted in AD. Our findings offer novel insights into disease-related changes in gene regulation and suggest potential targets for further research and therapy.

Inflammaging and Immunosenescence in the Post-COVID Era: Small Molecules, Big Challenges

Aging naturally involves a decline in biological functions, often triggering a disequilibrium of physiological processes. A common outcome is the altered response exerted by the immune system to counteract infections, known as immunosenescence, which has been recognized as a primary cause, among others, of the so-called long-COVID syndrome. Moreover, the uncontrolled immunoreaction leads to a state of subacute, chronic inflammatory state known as inflammaging, responsible in turn for the chronicization of concomitant pathologies in a self-sustaining process. Anti-inflammatory and immunosuppressant drugs are the current choice for the therapy of inflammaging in post-COVID complications, with contrasting results. The increasing knowledge of the biochemical pathways of inflammaging led to disclose new small molecules-based therapies directed toward different biological targets involved in inflammation, immunological response, and oxidative stress. Herein, paying particular attention to recent clinical data and preclinical literature, we focus on the role of endocannabinoid system in inflammaging, and the promising therapeutic option represented by the CB2R agonists, the role of novel ligands of the formyl peptide receptor 2 and ultimately the potential of newly discovered monoamine oxidase (MAO) inhibitors with neuroprotective activity in the treatment of immunosenescence.

Exploring human brain development and disease using assembloids

How the human brain develops and what goes awry in neurological disorders represent two long-lasting questions in neuroscience. Owing to the limited access to primary human brain tissue, insights into these questions have been largely gained through animal models. However, there are fundamental differences between developing mouse and human brain, and neural organoids derived from human pluripotent stem cells (hPSCs) have recently emerged as a robust experimental system that mimics self-organizing and multicellular features of early human brain development. Controlled integration of multiple organoids into assembloids has begun to unravel principles of cell-cell interactions. Moreover, patient-derived or genetically engineered hPSCs provide opportunities to investigate phenotypic correlates of neurodevelopmental disorders and to develop therapeutic hypotheses. Here, we outline the advances in technologies that facilitate studies by using assembloids and summarize their applications in brain development and disease modeling. Lastly, we discuss the major roadblocks of the current system and potential solutions.

The Role of IL-17A in Mediating Inflammatory Responses and Progression of Neurodegenerative Diseases

IL-17A has been implicated as a critical pro-inflammatory cytokine in the pathogenesis of autoimmune and neurodegenerative disorders. Emerging evidence indicates its capacity to activate microglial cells and astrocytes, subsequently inducing the production of inflammatory mediators that exacerbate neuronal injury and functional impairment. Clinical observations have revealed a demonstrated association between IL-17A concentrations and blood-brain barrier (BBB) dysfunction, creating a pathological feedback loop that amplifies neuro-inflammatory responses. Recent advances highlight the cytokine's critical involvement in neurodegenerative disorders through multiple molecular pathways. Therapeutic interventions utilizing monoclonal antibodies (mAbs) against IL-17A or its cognate receptor (IL-17R) have shown promising clinical potential. This review systematically examines the IL-17A-mediated neuro-inflammatory cascades; the mechanistic contributions to neurodegenerative pathology in the established disease models including multiple sclerosis, Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis; and current therapeutic strategies targeting the IL-17A signaling pathways. The analysis provides novel perspectives on optimizing cytokine-directed therapies while identifying the key challenges and research priorities for translational applications in neurodegeneration.

A Novel Glia-immune humanized mouse model for investigation of HIV CNS infection and neuroinflammation

Although combined antiretroviral therapy (ART) is successful in suppressing viral replication, HIV persists in anatomic reservoirs, including the central nervous system (CNS). Current models, such as HSC-reconstituted humanized mice, lack matched human glia in the brain, limiting insights into HIV CNS infection and pathogenesis. We developed a novel glia-immune humanized mouse model integrating human glial cells in the brain with donor-matched human immune reconstitution in peripheral blood and lymphoid tissues. Neonatal NSG mice were injected intrahepatically with Hematopoietic Stem Cells (HSCs) and intracranially with donor-matched glia. We observed extensive engraftment of all three types of human glial cells (astrocytes, oligodendroglia, and microglia-like cells) in key CNS regions, including the cerebral cortex and hippocampus. These glia-immune mice supported robust HIV-1 replication in the peripheral blood, lymphoid tissues and CNS. HIV-infected mice exhibited heightened inflammation and elevated expression of type I interferon-stimulated genes (ISGs) in peripheral and brain tissues. Bulk RNAseq revealed significant transcriptional changes in human glia, such as upregulation of ISGs, inflammasome-associated genes, and downregulation of transcriptional regulators implicated in metabolic regulations and epigenetic controls. Overall, this model allows interrogation of glial transcriptomic changes and neuron-immune interactions, offering insights into HIV CNS infection, pathology, and therapeutic strategies targeting CNS HIV reservoirs and neuroinflammatory pathways.