Resting Microglial Cells Are Highly Dynamic Surveillants of Brain Parenchyma in Vivo

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.

The STAT1-SLC31A1 axis: Potential regulation of cuproptosis in diabetic retinopathy

BACKGROUND

By identifying molecular biological markers linked to cuproptosis in diabetic retinopathy (DR), new pathobiological pathways and more accessible diagnostic markers can be developed.

METHODS

The datasets related to DR were acquired from the Gene Expression Omnibus database, while genes associated with cuproptosis were sourced from previously published compilations. Consensus clustering was conducted to delineate distinct DR subclasses. Feature genes were identified utilizing weighted correlation network analysis (WGCNA). Additionally, two machine-learning algorithms were employed to refine the selection of feature genes. Finally, we conducted preliminary validation experiments to ascertain the involvement of cuproptosis in DR development and the transcriptional regulation of critical genes using both the streptozotocin-induced diabetic mouse model and the high glucose-induced BV2 model.

RESULTS

In the STZ-induced diabetic mouse retinas, a decrease in the expression of cuproptosis signature proteins (FDX1, DLAT, and NDUFS8) suggested the occurrence of cuproptosis in DR. Subsequently, the expression of eight cuproptosis differential genes was validated through the STZ-induced diabetes and oxygen-induced retinopathy (OIR) models, with the key gene SLC31A1 showing upregulation in both models and dataset species. Further analyses, including weighted gene co-expression network analysis, GSVA, and immune infiltration analysis, indicated a close correlation between cuproptosis and microglia function. Additionally, validation in an in vitro model of microglia indicated the occurrence of cuproptosis in microglia under high glucose conditions, alongside abnormal expression of STAT1 with SLC31A1.

CONCLUSION

Our findings suggest that STAT1/SLC31A1 may pave the way for a deeper comprehension of the mechanistic basis of DR and offer potential therapeutic avenues.

Rotating magnetic field improved cognitive and memory impairments in a sporadic ad model of mice by regulating microglial polarization

Neuroinflammation, triggered by aberrantly activated microglia, is widely recognized as a key contributor to the initiation and progression of Alzheimer's disease (AD). Microglial activation in the central nervous system (CNS) can be classified into two distinct phenotypes: the pro-inflammatory M1 phenotype and the anti-inflammatory M2 phenotype. In this study, we investigated the effects of a non-invasive rotating magnetic field (RMF) (0.2T, 4Hz) on cognitive and memory impairments in a sporadic AD model of female Kunming mice induced by AlCl3 and D-gal. Our findings revealed significant improvements in cognitive and memory impairments following RMF treatment. Furthermore, RMF treatment led to reduced amyloid-beta (Aβ) deposition, mitigated damage to hippocampal morphology, prevented synaptic and neuronal loss, and alleviated cell apoptosis in the hippocampus and cortex of AD mice. Notably, RMF treatment ameliorated neuroinflammation, facilitated the transition of microglial polarization from M1 to M2, and inhibited the NF-кB/MAPK pathway. Additionally, RMF treatment resulted in reduced aluminum deposition in the brains of AD mice. In cellular experiments, RMF promoted the M1-M2 polarization transition and enhanced amyloid phagocytosis in cultured BV2 cells while inhibiting the TLR4/NF-кB/MAPK pathway. Collectively, these results demonstrate that RMF improves memory and cognitive impairments in a sporadic AD model, potentially by promoting the M1 to M2 transition of microglial polarization through inhibition of the NF-кB/MAPK signaling pathway. These findings suggest the promising therapeutic applications of RMF in the clinical treatment of AD.

Phloretin alleviates sleep deprivation-induced cognitive impairment by reducing inflammation through PPARγ/NF-κB signaling pathway

Sleep loss leads to significant pathophysiological consequences, including cognitive impairment. The neuroinflammation are pivotal factors in the pathogenesis of cognitive impairment induced by sleep loss. The phloretin (PHL), derived from peel of juicy fruits, has demonstrated potent anti-inflammatory properties. However, the precise influence of PHL on the cognitive impairment triggered by sleep loss and its underlying mechanism remain uncertain. In the present study, mice were subjected to sleep deprivation (SD) paradigm. Cognitive impairment induced by SD were significantly relieved by administration of PHL in a dose-dependent manner. Furthermore, PHL not only mitigated the synaptic losses but also enhanced dendritic spine density and neuronal activity within mice hippocampus following exposure to SD. Moreover, PHL treatment decreased the microglial numbers and altered microglial morphology in the hippocampus to restore the M1/M2 balances; these effects were accompanied by regulation of pro-/anti-inflammatory cytokine production and secretion in SD-exposed mice. Additionally, in vivo and in vitro studies showed PHL might attenuate the inflammation through the PPARγ/NF-κB pathway. Our findings suggest that PHL exerts inhibitory effects on microglia-mediated neuroinflammation, thereby providing protection against cognitive impairment induced by SD through a PPAR-γ dependent mechanism. The results indicate PHL is expected to provide a valuable candidate for new drug development for SD-induced cognitive impairment in the future.

Role of Noncoding RNAs in Modulating Microglial Phenotype

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

Phosphoproteomic analysis reveals CDK5-Mediated phosphorylation of MTDH inhibits protein synthesis in microglia

CDK5 plays a crucial role in maintaining normal central nervous system (CNS) development and synaptic function, while microglia are the primary immune cells present in the CNS and play vital physiological roles in CNS development, immune surveillance, and regulation of synaptic plasticity. Despite this, our understanding of both the substrate proteins and functional mechanisms of CDK5 in microglia remains limited. To address this, we utilized CRISPR-Cas9 knockout of Cdk5 in BV2 cells and conducted quantitative phosphoproteomics analysis to systematically screen potential CDK5 substrates in microglia. Our findings identified 335 phosphorylation sites on 234 proteins as potential CDK5 substrates in microglia based on the reported sequence motif. Through in vitro kinase assay and intracellular inhibition and knockout of CDK5 experiments, we confirmed that ER proteins MTDH (protein LYRIC) and Calnexin are novel substrate proteins of CDK5. Moreover, we demonstrated for the first time a critical mechanism for regulating protein synthesis in microglia, that the phosphorylation of S565 site on MTDH, a key protein mediating cell growth, by CDK5 inhibits protein synthesis. Our data provide valuable insights for the discovery of new substrate proteins of CDK5 and the in-depth investigation of the function and mechanism of CDK5 in microglia.

A bottom-up approach identifies the antipsychotic and antineoplastic trifluoperazine and the ribose derivative deoxytubercidin as novel microglial phagocytosis inhibitors

Phagocytosis is an indispensable function of microglia, the brain professional phagocytes. Microglia is particularly efficient phagocytosing cells that undergo programmed cell death (apoptosis) in physiological conditions. However, mounting evidence suggests microglial phagocytosis dysfunction in multiple brain disorders. These observations prompted us to search for phagocytosis modulators (enhancers or inhibitors) with therapeutic potential. We used a bottom-up strategy that consisted on the identification of phagocytosis modulators using phenotypic high throughput screenings (HTSs) in cell culture and validation in organotypic cultures and in vivo. We performed two complementary HTS campagnes: at Achucarro, we used primary cultures of mouse microglia and compounds of the Prestwick Chemical Library; at Roche, we used human iPSC derived macrophage-like cells and a proprietary chemo-genomic library with 2200 compounds with known mechanism-of-action. Next, we validated the more robust compounds using hippocampal organotypic cultures and identified two phagocytosis inhibitors: trifluoperazine, a dopaminergic and adrenergic antagonist used as an antipsychotic and antineoplastic; and deoxytubercidin, a ribose derivative. Finally, we tested whether these compounds were able to modulate phagocytosis of apoptotic newborn cells in the adult hippocampal neurogenic niche in vivo by administering them into the mouse hippocampus using osmotic minipumps. We confirmed that both trifluoperazine and deoxytubercidin have anti-phagocytic activity in vivo, and validated our bottom-up strategy to identify novel phagocytosis modulators. These results show that chemical libraries with annotated mechanism of action are an starting point for the pharmacological modulation of microglia in drug discovery projects aiming at the therapeutic manipulation of phagocytosis in brain diseases.

Insulin Mediates Lipopolysaccharide-Induced Inflammatory Responses and Oxidative Stress in BV2 Microglia

Introduction

Insulin, the key hormone for glucose regulation, has garnered attention for its role as an immune modulator. Impaired insulin signaling in the central nervous system is linked to neuroinflammation and neurodegenerative diseases. Microglia, the resident macrophage-like immune cells in the brain, are key regulators of neuroinflammation. However, the mechanisms by which insulin influences microglial immune responses remain relatively unknown.

Methods

This study aimed to assess the effects of post-treatment with insulin [30 minutes after lipopolysaccharide (LPS) exposure] on LPS-induced inflammatory responses in BV2 microglial cells.

Results

Post-treatment with insulin potentiated LPS-induced production of nitric oxide and pro-inflammatory cytokines, such as TNF and IL-6, through activation of the Akt/NF-κB pathway. Insulin also enhanced the ability of BV2 cells to phagocytose bacteria particles and β-amyloid fibrils. Conversely, insulin inhibited activation of NADPH oxidase and reduced intracellular levels of reactive oxygen species in LPS-treated BV2 cells.

Conclusion

Insulin enhances microglial immune competence when challenged by endotoxins but mitigates oxidative stress in these cells.

Peripheral and central neuroplasticity in a mouse model of endometriosis

Chronic pelvic pain (CPP) is the most debilitating symptom of gynaecological disorders such as endometriosis. However, it remains unclear how sensory neurons from pelvic organs affected by endometriosis, such as the female reproductive tract, detect and transmit nociceptive events and how these signals are processed within the central nervous system (CNS). Using a previously characterized mouse model of endometriosis, we investigated whether the increased pain sensitivity occurring in endometriosis could be attributed to (i) changes in mechanosensory properties of sensory afferents innervating the reproductive tract, (ii) alterations in sensory input from reproductive organs to the spinal cord or (iii) neuroinflammation and sensitization of spinal neural circuits. Mechanosensitivity of vagina-innervating primary afferents was examined using an ex vivo single-unit extracellular recording preparation. Nociceptive signalling from the vagina to the spinal cord was quantified by phosphorylated MAP kinase ERK1/2 immunoreactivity. Immunohistochemistry was used to determine glial and neuronal circuit alterations within the spinal cord. We found that sensory afferents innervating the rostral, but not caudal portions of the mouse vagina, developed mechanical hypersensitivity in endometriosis. Nociceptive signalling from the vagina to the spinal cord was significantly enhanced in mice with endometriosis. Moreover, mice with endometriosis developed microgliosis, astrogliosis and enhanced substance P neurokinin-1 receptor immunoreactivity within the spinal cord, suggesting the development of neuroinflammation and sensitization of spinal circuitry in endometriosis. These results demonstrate endometriosis-induced neuroplasticity occurring at both peripheral and central sites of sensory afferent pathways. These findings may help to explain the altered sensitivity to pain in endometriosis and provide a novel platform for targeted pain relief treatments for this debilitating disorder.

Border-Associated Macrophages: From Embryogenesis to Immune Regulation

Border-associated macrophages (BAMs) play a pivotal role in maintaining brain homeostasis and responding to pathological conditions. Understanding their origins, characteristics, and roles in both healthy and diseased brains is crucial for advancing our knowledge of neuroinflammatory and neurodegenerative diseases. This review addresses the ontogeny, replenishment, microenvironmental regulation, and transcriptomic heterogeneity of BAMs, highlighting recent advancements in lineage tracing and fate-mapping studies. Furthermore, we examine the roles of BAMs in maintaining brain homeostasis, immune surveillance, and responses to injury and neurodegenerative diseases. Further research is crucial to clarify the dynamic interplay between BAMs and the brain's microenvironment in health and disease. This effort will not only resolve existing controversies but also reveal new therapeutic targets for neuroinflammatory and neurodegenerative disorders, pushing the boundaries of neuroscience.

Effects of social dominance and acute social stress on morphology of microglia and structural integrity of the medial prefrontal cortex

Chronic stress increases activity of the brain's innate immune system and impairs function of the medial prefrontal cortex (mPFC). However, whether acute stress triggers similar neuroimmune mechanisms is poorly understood. Across four studies, we used a Syrian hamster model to investigate whether acute stress drives changes in mPFC microglia in a time-, subregion-, and social status-dependent manner. We found that acute social defeat increased expression of ionized calcium binding adapter molecule 1 (Iba1) in the infralimbic (IL) and prelimbic (PL) and altered the morphology Iba1+ cells 1, 2, and 7 days after social defeat. We also investigated whether acute defeat induced tissue degeneration and reductions of synaptic plasticity 2 days post-defeat. We found that while social defeat increased deposition of cellular debris and reduced synaptophysin immunoreactivity in the PL and IL, treatment with minocycline protected against these cellular changes. Finally, we tested whether a reduced conditioned defeat response in dominant compared to subordinate hamsters was associated with changes in microglia reactivity in the IL and PL. We found that while subordinate hamsters and those without an established dominance relationships showed defeat-induced changes in morphology of Iba1+ cells and cellular degeneration, dominant hamsters showed resistance to these effects of social defeat. Taken together, these findings indicate that acute social defeat alters microglial morphology, increases markers of tissue degradation, and impairs structural integrity in the IL and PL, and that experience winning competitive interactions can specifically protect the IL and reduce stress vulnerability.

Nanotherapeutic Approaches of Interleukin-3 to Clear the α-Synuclein Pathology in Mouse Models of Parkinson's Disease

Astrocyte-microglia crosstalk is vital for neuronal survival and clearing aggregate accumulation in neurodegenerative diseases. While interleukin-3 (IL-3) has been reported to exert both protective and detrimental effects in neurodegenerative diseases, however, its role in α-synuclein pathology remains unclear. In this study, it is found that astrocytic IL-3 and microglial IL-3R are positively responsive to α-synuclein pathology in the brains of transgenic A53T Parkinson's disease (PD) mice and in an adeno-associated virus (AAV)-human α-synuclein (AAV-hα-Syn)-injected PD mouse model. Exogenous IL-3 infusion reduces behavioral abnormities and nigrostriatal α-synuclein pathology. Mechanistically, IL-3 induces microglial phagocytosis of pathological α-synuclein while simultaneously stimulating dopaminergic (DA) neurons to clear pathological α-synuclein via induction of autophagy through the IFN-β/Irgm1 pathway. Due to its limited efficiency in crossing the blood-brain barrier, a precise IL-3 delivery strategy is developed by cross-linking IL-3 and RVG29 with PEG-Linker (RVG-modified IL-3 nanogels-RVG-IL3 NGs). Intravenous administration of RVG-IL3 NGs shows efficient uptake by microglia and DA neurons within the brain. RVG-IL3 NGs ameliorate motor deficits and pathological α-synuclein by improving microglial and neuronal function in the AAV-hα-Syn mouse model of PD. Collectively, IL-3 may represent a feasible therapeutic strategy for PD.

Constitutive expression of the deubiquitinating enzyme CYLD does not affect microglia phenotype or function in homeostasis and neuroinflammation

The deubiquitinating enzyme CYLD negatively regulates NF-κB signaling by removing activating ubiquitin chains from several members of the NF-κB pathway. Thereby, CYLD is critical for the maintenance and differentiation of various immune cells. Despite the importance of the NF-κB pathway in microglia regulation, the role of CYLD in microglia has not been investigated so far. In this study, we investigated whether CYLD in microglia can protect against neuroinflammation using a newly generated conditional mouse strain (Rosa26-Cyld-tdTomato) that allows cell type-specific CYLD overexpression. Here, we show that overexpression of CYLD in microglia did not alter microglia numbers or microglia morphology in different brain regions. Additionally, CYLD overexpression did not modify the microglial response to LPS-induced neuroinflammation or the disease severity in experimental autoimmune encephalomyelitis (EAE). Finally, also immune cell infiltration into the CNS during EAE and under steady state conditions remained unaffected by microglial CYLD overexpression. Our findings suggest that CYLD overexpression does not alter microglial function, and thus does not represent a viable therapeutic strategy in neuroinflammatory conditions. This study highlights the complexity of ubiquitin-mediated signaling in neuroinflammation and the need for cell-type-specific investigations. The Rosa26-Cyld-tdTomato mouse model offers a valuable tool for studying CYLD's role across various tissues and cell types. KEY MESSAGES: Novel mouse strain for cell type-specific overexpression of the deubiquitinating enzyme CYLD. CYLD overexpression in microglia did not alter microglia numbers or morphology in the steady state. CYLD overexpression in microglia did not protect mice from LPS-induced neuroinflammation or EAE. CYLD overexpression in microglia did not influence their gene expression during neuroinflammation.

The role of the neuronal microenvironment in sensory function and pain pathophysiology

The high prevalence of pain and the at times low efficacy of current treatments represent a significant challenge to healthcare systems worldwide. Effective treatment strategies require consideration of the diverse pathophysiologies that underlie various pain conditions. Indeed, our understanding of the mechanisms contributing to aberrant sensory neuron function has advanced considerably. However, sensory neurons operate in a complex dynamic microenvironment that is controlled by multidirectional interactions of neurons with non-neuronal cells, including immune cells, neuronal accessory cells, fibroblasts, adipocytes, and keratinocytes. Each of these cells constitute and control the microenvironment in which neurons operate, inevitably influencing sensory function and the pathology of pain. This review highlights the importance of the neuronal microenvironment for sensory function and pain, focusing on cellular interactions in the skin, nerves, dorsal root ganglia, and spinal cord. We discuss the current understanding of the mechanisms by which neurons and non-neuronal cells communicate to promote or resolve pain, and how this knowledge could be used for the development of mechanism-based treatments.

Constitutive DAMPs in CNS injury: From preclinical insights to clinical perspectives

Damage-associated molecular patterns (DAMPs) are endogenous molecules released in tissues upon cellular damage and necrosis, acting to initiate sterile inflammation. Constitutive DAMPs (cDAMPs) have the particularity to be present within the intracellular compartments of healthy cells, where they exert diverse functions such as regulation of gene expression and cellular homeostasis. However, after injury to the central nervous system (CNS), cDAMPs are rapidly released by stressed, damaged or dying neuronal, glial and endothelial cells, and can trigger inflammation without undergoing structural modifications. Several cDAMPs have been described in the injured CNS, such as interleukin (IL)-1α, IL-33, nucleotides (e.g. ATP), and high-mobility group box protein 1. Once in the extracellular milieu, these molecules are recognized by the remaining surviving cells through specific DAMP-sensing receptors, thereby inducing a cascade of molecular events leading to the production and release of proinflammatory cytokines and chemokines, as well as cell adhesion molecules. The ensuing immune response is necessary to eliminate cellular debris caused by the injury, allowing for damage containment. However, seeing as some molecules associated with the inflammatory response are toxic to surviving resident CNS cells, secondary damage occurs, aggravating injury and exacerbating neurological and behavioral deficits. Thus, a better understanding of these cDAMPs, as well as their receptors and downstream signaling pathways, could lead to identification of novel therapeutic targets for treating CNS injuries such as SCI, TBI, and stroke. In this review, we summarize the recent literature on cDAMPs, their specific functions, and the therapeutic potential of interfering with cDAMPs or their signaling pathways.

Polymer nanotherapeutics: A promising approach toward microglial inhibition in neurodegenerative diseases

Nanoparticles (NPs) that target multiple transport mechanisms facilitate targeted delivery of active therapeutic agents to the central nervous system (CNS) and improve therapeutic transport and efficacy across the blood-brain barrier (BBB). CNS nanotherapeutics mostly target neurons and endothelial cells, however, microglial immune cells are the first line of defense against neuronal damage and brain infections. Through triggering release of inflammatory cytokines, chemokines and proteases, microglia can however precipitate neurological damage-a significant factor in neurodegenerative diseases. Thus, microglial inhibitory agents are attracting much attention among those researching and developing novel treatments for neurodegenerative disorders. The most established inhibitors of microglia investigated to date are resveratrol, curcumin, quercetin, and minocycline. Thus, there is great interest in developing novel agents that can bypass or easily cross the BBB. One such approach is the use of modified-nanocarriers as, or for, delivery of, therapeutic agents to the brain and wider CNS. For microglial inhibition, polymeric NPs are the preferred vehicles for choice. Here, we summarize the immunologic and neuroinflammatory role of microglia, established microglia inhibitor agents, challenges of CNS drug delivery, and the nanotherapeutics explored for microglia inhibition to date. We also discuss applications of the currently considered "most useful" polymeric NPs for microglial-inhibitor drug delivery in CNS-related diseases.

The evolving pathophysiology of TBI and the advantages of temporally-guided combination therapies

Several clinical and experimental studies have demonstrated that traumatic brain injury (TBI) activates cascades of biochemical, molecular, structural, and pathological changes in the brain. These changes combine to contribute to the various outcomes observed after TBI. Given the breadth and complexity of changes, combination treatments may be an effective approach for targeting multiple detrimental pathways to yield meaningful improvements. In order to identify targets for therapy development, the temporally evolving pathophysiology of TBI needs to be elucidated in detail at both the cellular and molecular levels, as it has been shown that the mechanisms contributing to cognitive dysfunction change over time. Thus, a combination of individual mechanism-based therapies is likely to be effective when maintained based on the time courses of the cellular and molecular changes being targeted. In this review, we will discuss the temporal changes of some of the key clinical pathologies of human TBI, the underlying cellular and molecular mechanisms, and the results from preclinical and clinical studies aimed at mitigating their consequences. As most of the pathological events that occur after TBI are likely to have subsided in the chronic stage of the disease, combination treatments aimed at attenuating chronic conditions such as cognitive dysfunction may not require the initiation of individual treatments at a specific time. We propose that a combination of acute, subacute, and chronic interventions may be necessary to maximally improve health-related quality of life (HRQoL) for persons who have sustained a TBI.

Histamine stimulates human microglia to alter cellular prion protein expression via the HRH2 histamine receptor

Although the cellular prion protein (PrPC) has been evolutionarily conserved, the role of this protein remains elusive. Recent evidence indicates that PrPC may be involved in neuroinflammation and the immune response in the brain, and its expression may be modified via various mechanisms. Histamine is a proinflammatory mediator and neurotransmitter that stimulates numerous cells via interactions with histamine receptors 1-4 (HRH1-4). Since microglia are the innate immune cells of the central nervous system, we hypothesized that histamine-induced stimulation regulates the expression of PrPC in human-derived microglia. The human microglial clone 3 (HMC3) cell line was treated with histamine, and intracellular calcium levels were measured via a calcium flux assay. Cytokine production was monitored by enzyme-linked immunosorbent assay (ELISA). Western blotting and quantitative reverse transcription-polymerase chain reaction were used to determine protein and gene expression of HRH1-4. Flow cytometry and western blotting were used to measure PrPC expression levels. Fluorescence microscopy was used to examine Iba-1 and PrPC localization. HMC3 cells stimulated by histamine exhibited increased intracellular calcium levels and increased release of IL-6 and IL-8, while also modifying PrPC localization. HMC3 stimulated with histamine for 6 and 24 hours exhibited increased surface PrPC expression. Specifically, we found that stimulation of the HRH2 receptor was responsible for changes in surface PrPC. Histamine-induced increases in surface PrPC were attenuated following inhibition of the HRH2 receptor via the HRH2 antagonist ranitidine. These changes were unique to HRH2 activation, as stimulation of HRH1, HRH3, or HRH4 did not alter surface PrPC. Prolonged stimulation of HMC3 decreased PrPC expression following 48 and 72 hours of histamine stimulation. HMC3 cells can be stimulated by histamine to undergo intracellular calcium influx. Surface expression levels of PrPC on HMC3 cells are altered by histamine exposure, primarily mediated by HRH2. While histamine exposure also increases release of IL-6 and IL-8 in these cells, this cytokine release is not fully dependent on PrPC levels, as IL-6 release is only partially reduced and IL-8 release is unchanged under the conditions of HRH2 blockade that prevent PrPC changes. Overall, this suggests that PrPC may play a role in modulating microglial responses.

L-PGDS-PGD2-DP1 Axis Regulates Phagocytosis by CD36+ MGs/MΦs That Are Exclusively Present Within Ischemic Areas After Stroke

Brain injuries, such as ischemic stroke, cause cell death. Although phagocytosis of cellular debris is mainly performed by microglia/macrophages (MGs/MΦs), excessive accumulation beyond their phagocytic capacities results in waste product buildup, delaying brain cell regeneration. Therefore, it is essential to increase the potential for waste product removal from damaged brains. Lipocalin-type prostaglandin D synthase (L-PGDS) is the primary synthase for prostaglandin D2 (PGD2) and has been reported as a scavenger of waste products. However, the mechanism by which the L-PGDS-PGD2 axis exerts such an effect remains unelucidated. In this study, using a mouse model of ischemic stroke, we found that L-PGDS and its downstream signaling pathway components, including PGD2 and PGD2 receptor DP1 (but not DP2), were significantly upregulated in ischemic areas. Immunohistochemistry revealed the predominant expression of L-PGDS in the leptomeninges of ischemic areas and high expression levels of DP1 in CD36+ MGs/MΦs that were specifically present within ischemic areas. Furthermore, PGD2 treatment promoted the conversion of MGs/MΦs into CD36+ scavenger types and increased phagocytic activities of CD36+ MGs/MΦs. Because CD36+ MGs/MΦs specifically appeared within ischemic areas after stroke, our findings suggest that the L-PGDS-PGD2-DP1 axis plays an important role in brain tissue repair by regulating phagocytic activities of CD36+ MGs/MΦs.

Anti-CD49d Ab treatment ameliorates age-associated inflammatory response and mitigates CD8+ T-cell cytotoxicity after traumatic brain injury

Patients aged 65 years and older account for an increasing proportion of patients with traumatic brain injury (TBI). Older TBI patients experience increased morbidity and mortality compared to their younger counterparts. Our prior data demonstrated that by blocking α4 integrin, anti-CD49d antibody (aCD49d Ab) abrogates CD8+ T-cell infiltration into the injured brain, improves survival, and attenuates neurocognitive deficits. Here, we aimed to uncover how aCD49d Ab treatment alters local cellular responses in the aged mouse brain. Consequently, mice incur age-associated toxic cytokine and chemokine responses long-term post-TBI. aCD49d Ab attenuates this response along with a T helper (Th)1/Th17 immunological shift and remediation of overall CD8+ T cell cytotoxicity. Furthermore, aCD49d Ab reduces CD8+ T cells exhibiting higher effector status, leading to reduced clonal expansion in aged, but not young, mouse brains with chronic TBI. Together, aCD49d Ab is a promising therapeutic strategy for treating TBI in the older people.

Mitochondria are absent from microglial processes performing surveillance, chemotaxis, and phagocytic engulfment

Microglia continually surveil the brain allowing for rapid detection of tissue damage or infection. Microglial metabolism is linked to tissue homeostasis, yet how mitochondria are subcellularly partitioned in microglia and dynamically reorganize during surveillance, injury responses, and phagocytic engulfment in the intact brain are not known. Here, we performed intravital imaging of microglia mitochondria, revealing that microglial processes diverge, with some containing multiple mitochondria while others are completely void. Microglial processes that engage in minute-to-minute surveillance typically do not have mitochondria. Moreover, unlike process surveillance, mitochondrial motility does not change with animal anesthesia. Likewise, the processes that acutely chemoattract to a lesion site or initially engage with a neuron undergoing programmed cell death do not contain mitochondria. Rather, microglia mitochondria have a delayed arrival into the responding cell processes. Thus, there is subcellular heterogeneity of mitochondrial partitioning and asymmetry between mitochondrial localization and cell process motility or acute damage responses.

MAVS signaling shapes microglia responses to neurotropic virus infection

Viral encephalitis is characterized by a series of immunological reactions that can control virus infection in the brain, but dysregulated responses may cause excessive inflammation and brain damage. Microglia are brain-resident myeloid cells that are specialized in surveilling the local CNS environment and in case of viral brain infection they contribute to the control of the infection and to restriction of viral dissemination. Here, we report that after exposure to neurotropic vesicular stomatitis virus (VSV), murine in vitro microglia cultures showed rapid upregulation of a broad range of pro-inflammatory and antiviral genes, which were stably expressed over the entire 8 h infection period. Additionally, a set of immunomodulatory genes was upregulated between 6 and 8 h post infection. In microglia cultures, the induction of several immune response pathways including cytokine responses was dependent on mitochondrial antiviral-signaling protein (MAVS). Consequently, in Mavs-deficient microglia the control of virus propagation failed as indicated by augmented virus titers and the accumulation of viral transcripts. Thus, in the analyzed in vitro system, MAVS signaling is critically required to achieve full microglia activation and to mediate profound antiviral effects. In Mavs-deficient mice, intranasal VSV instillation caused higher disease severity than in WT mice and virus dissemination was noticed beyond the olfactory bulb. Virus spread to inner regions of the olfactory bulb, i.e., the granular cell layer, correlated with the recruitment of highly inflammatory non-microglia myeloid cells into the olfactory bulb in Mavs-/- mice. Furthermore, increased cytokine levels were detected in the nasal cavity, the olfactory bulb and in other brain regions. Thus, microglial MAVS signaling is critically needed for virus sensing, full microglia activation, and for orchestration of protective immunity in the virus-infected CNS.

Metabolic dysregulation in Huntington's disease: Neuronal and glial perspectives

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by a mutant huntingtin protein with an abnormal CAG/polyQ expansion in the N-terminus of HTT exon 1. HD is characterized by progressive neurodegeneration and metabolic abnormalities, particularly in the brain, which accounts for approximately 20 % of the body's resting metabolic rate. Dysregulation of energy homeostasis in HD includes impaired glucose transporters, abnormal functions of glycolytic enzymes, changes in tricarboxylic acid (TCA) cycle activity and enzyme expression in the basal ganglia and cortical regions of both HD mouse models and HD patients. However, current understanding of brain cell behavior during energy dysregulation and its impact on neuron-glia crosstalk in HD remains limited. This review provides a comprehensive summary of the current understanding of the differences in glucose metabolism between neurons and glial cells in HD and how these differences contribute to disease development compared with normal conditions. We also discuss the potential impact of metabolic shifts on neuron-glia communication in HD. A deeper understanding of these metabolic alterations may reveal potential therapeutic targets for future drug development.

Neuroimmune and neuroinflammation response for traumatic brain injury

Traumatic brain injury (TBI) is one of the major diseases leading to mortality and disability, causing a serious disease burden on individuals' ordinary lives as well as socioeconomics. In primary injury, neuroimmune and neuroinflammation are both responsible for the TBI. Besides, extensive and sustained injury induced by neuroimmune and neuroinflammation also prolongs the course and worsens prognosis of TBI. Therefore, this review aims to explore the role of neuroimmune, neuroinflammation and factors associated them in TBI as well as the therapies for TBI. Thus, we conducted by searching PubMed, Scopus, and Web of Science databases for articles published between 2010 and 2023. Keywords included "traumatic brain injury," "neuroimmune response," "neuroinflammation," "astrocytes," "microglia," and "NLRP3." Articles were selected based on relevance and quality of evidence. On this basis, we provide the cellular and molecular mechanisms of TBI-induced both neuroimmune and neuroinflammation response, as well as the different factors affecting them, are introduced based on physiology of TBI, which supply a clear overview in TBI-induced chain-reacting, for a better understanding of TBI and to offer more thoughts on the future therapies for TBI.

In vivo imaging in mouse spinal cord reveals that microglia prevent degeneration of injured axons

Microglia, the primary immune cells in the central nervous system, play a critical role in regulating neuronal function and fate through their interaction with neurons. Despite extensive research, the specific functions and mechanisms of microglia-neuron interactions remain incompletely understood. In this study, we demonstrate that microglia establish direct contact with myelinated axons at Nodes of Ranvier in the spinal cord of mice. The contact associated with neuronal activity occurs in a random scanning pattern. In response to axonal injury, microglia rapidly transform their contact into a robust wrapping form, preventing acute axonal degeneration from extending beyond the nodes. This wrapping behavior is dependent on the function of microglial P2Y12 receptors, which may be activated by ATP released through axonal volume-activated anion channels at the nodes. Additionally, voltage-gated sodium channels (NaV) and two-pore-domain potassium (K2P) channels contribute to the interaction between nodes and glial cells following injury, and inhibition of NaV delays axonal degeneration. Through in vivo imaging, our findings reveal a neuroprotective role of microglia during the acute phase of single spinal cord axon injury, achieved through neuron-glia interaction.

Glial cells undergo rapid changes following acute chemogenetic manipulation of cortical layer 5 projection neurons

Bidirectional communication between neurons and glial cells is crucial to establishing and maintaining normal brain function. Some of these interactions are activity-dependent, yet it remains largely unexplored how acute changes in neuronal activity affect glial-to-neuron and neuron-to-glial dynamics. Here, we use excitatory and inhibitory designer receptors exclusively activated by designer drugs (DREADD) to study the effects of acute chemogenetic manipulations of a subpopulation of layer 5 cortical projection and dentate gyrus neurons in adult (Rbp4Cre) mouse brains. We show that acute chemogenetic neuronal activation reduces synaptic density, and increases microglia and astrocyte reactivity, but does not affect parvalbumin (PV+) neurons, only perineuronal nets (PNN). Conversely, acute silencing increases synaptic density and decreases glial reactivity. We show fast glial response upon clozapine-N-oxide (CNO) administration in cortical and subcortical regions. Together, our work provides evidence of fast, activity-dependent, bidirectional interactions between neurons and glial cells.

A Morphological Study of HLA-DR-Immunopositive Cells in Multiple Sclerosis Lesions and Their Implications for Pathogenesis

BACKGROUND

Multiple sclerosis (MS) is characterized by white matter demyelinating plaques, which can be classified as active, chronic active, or chronic inactive based on the extent of demyelination, cellularity, and inflammation. Microglia and macrophages play a central role in these processes. This study aimed to investigate the morphological characteristics of HLA-DR-immunopositive cells in these plaques to improve our understanding of the roles of these cells in MS plaques.

METHODS

This study is a retrospective post-mortem histopathological study. We analyzed 90 plaques from 6 MS cases. Of the plaques studied, 77 were grouped into three categories: 28 active, 34 chronic active, and 15 chronic inactive. Additionally, five vacuolated white matter lesions, two axonal degeneration lesions, and six lesions with mixed histological features were included. Six control cases were also examined to assess HLA-DR-immunopositive cell expression across various age groups. The cells were classified based on their morphology into two types: round cells without processes (macrophages) and cells with varying processes and shapes (ramified microglia).

RESULTS

Both macrophages and ramified microglia were present in all lesion types, with a focus on identifying the predominant cell type. Of the 28 active plaques, macrophages were the primary cell type in 25 plaques, while ramified microglia predominated in 3. In the center of 49 chronic plaques, scattered ramified microglia were observed in 46, with three plaques showing a predominance of macrophages. Among the 34 chronic active lesions, ramified microglia were the main cell type in the periphery of 32 plaques, with the remaining two predominantly exhibiting macrophages.

CONCLUSIONS

The predominance of macrophages in active lesions and the presence of scattered ramified microglia in the center of chronic plaques are consistent with the phagocytic role of macrophages. Meanwhile, the prevalence of ramified microglia at the periphery of chronic active lesions suggests a potential protective function in maintaining lesion stability.

Tracking changes in functionality and morphology of repopulated microglia in young and old mice

BACKGROUND

Microglia (MG) are myeloid cells of the central nervous system that support homeostasis and instigate neuroinflammation in pathologies. Single-cell RNA sequencing (scRNA-seq) revealed the functional heterogeneity of MG in mouse brains. Microglia are self-renewing cells and inhibition of colony-stimulating factor 1 receptor (CSF1R) signaling depletes microglia which rapidly repopulate. The functions of repopulated microglia are poorly known.

METHODS

We combined scRNA-seq, bulk RNA-seq, immunofluorescence, and confocal imaging to study the functionalities and morphology of repopulated microglia.

RESULTS

A CSRF1R inhibitor (BLZ-945) depleted microglia within 21 days and a number of microglia was fully restored within 7 days, as confirmed by TMEM119 staining and flow cytometry. ScRNA-seq and computational analyses demonstrate that repopulated microglia originated from preexisting progenitors and reconstituted functional clusters but upregulated inflammatory genes. Percentages of proliferating, immature microglia displaying inflammatory gene expression increased in aging mice. Morphometric analysis of MG cell body and branching revealed a distinct morphology of repopulated MG, particularly in brains of old mice. We demonstrate that with aging some repopulated MG fail to reach the homeostatic phenotype. These differences may contribute to the deterioration of MG protective functions with age.

Boosting peripheral immunity to fight neurodegeneration in the brain

Reciprocal communication between the brain and the immune system is essential for maintaining lifelong brain function. This interaction is mediated, at least in part, by immune cells recruited from both the circulation and niches at the borders of the brain. Here, we describe how immune exhaustion and senescence, even if not primary causative factors, can accelerate neurodegenerative diseases. We emphasize the role of a compromised peripheral immune system in driving neurodegeneration and discuss strategies for harnessing peripheral immunity to effectively treat neurodegenerative diseases, including the underlying mechanisms and opportunities for clinical translation. Specifically, we highlight the potential of boosting the immune system by blocking inhibitory checkpoint molecules to harness reparative immune cells in helping the brain to fight against neurodegeneration.

Proteomic analysis of P. gingivalis-Lipopolysaccharide induced neuroinflammation in SH-SY5Y and HMC3 cells

Chronic periodontitis and its keystone pathogen, Porphyromonas gingivalis, have increasingly been linked with Alzheimer's disease (AD). However, P.gingivalis-lipopolysaccharide (LPS) mediated release of neuroinflammatory proteins contributes to AD remains underexplored. In this study, we utilized data-independent acquisition mass spectrometry to characterize P.gingivalis-LPS induced profile of differentially expressed proteins associated with the neuroinflammatory response in human neuroblastoma (SH-SY5Y) and human microglial (HMC3) cells. We reported a set of 124 proteins in SH-SY5Y cells and 96 proteins in HMC3 cells whose levels were significantly upregulated or downregulated by exposure to P. gingivalis-LPS. Our findings demonstrate that P. gingivalis-LPS contributed to the elevated expressions of dementia biomarkers and pro-inflammatory cytokines that include APP, Aβ1-42, Aβ1-40, T-Tau, p-Tau, VEGF, TGF-β, IL-1β, IL-6 and TNF-α through 2 distinct pathways of extracellular sensing by cell surface receptors and intracellular cytosolic receptors. Interestingly, intracellular signaling proteins activated with P. gingivalis-LPS transfection using Lipofectamine™ 2000 had significantly higher fold change protein expression compared to the extracellular signaling with P. gingivalis-LPS treatment. Additionally, we also explored P. gingivalis-LPS mediated activation of caspase-4 dependent non canonical inflammasome pathway in both SH-SY5Y and HMC3 cells. In summary, P. gingivalis-LPS induced neuroinflammatory protein expression in SH-SY5Y and HMC3 cells, provided insights into the specific inflammatory pathways underlying the potential link between P. gingivalis-LPS infection and the pathogenesis of Alzheimer's disease and related dementias.

Neuroimmune interactions in the development and chronification of migraine headache

Migraine is highly prevalent and debilitating. The persistent headaches in this condition are thought to arise from the activation and sensitization of the trigeminovascular pathway. Both clinical and animal model studies have suggested that neuroimmune interactions contribute to the pathophysiology of migraine headache. In this review, we first summarize the findings from human studies implicating the dysregulation of the immune system in migraine, including genetic analyses, measurement of circulatory factors, and neuroimaging data. We next discuss recent advances from rodent studies aimed at elucidating the neuroimmune interactions that manifest at various levels of the trigeminovascular pathway and lead to the recruitment of innate and adaptive immune cells as well as immunocompetent glial cells. These cells reciprocally modulate neuronal activity via multiple pro- and anti-inflammatory mediators, thereby regulating peripheral and central sensitization. Throughout the discussions, we highlight the potential clinical and translational implications of the findings.

Development and validation of a nomogram for predicting mortality in patients with acute severe traumatic brain injury: A retrospective analysis

BACKGROUND

Recent evidence links the prognosis of traumatic brain injury (TBI) to various factors, including baseline clinical characteristics, TBI specifics, and neuroimaging outcomes. This study focuses on identifying risk factors for short-term survival in severe traumatic brain injury (sTBI) cases and developing a prognostic model.

METHODS

Analyzing 430 acute sTBI patients from January 2018 to December 2023 at the 904th Hospital's Neurosurgery Department, this retrospective case-control study separated patients into survival outcomes: 288 deceased and 142 survivors. It evaluated baseline, clinical, hematological, and radiological data to identify risk and protective factors through univariate and Lasso regression. A multivariate model was then formulated to pinpoint independent prognostic factors, assessing their relationships via Spearman's correlation. The model's accuracy was gauged using the Receiver Operating Characteristic (ROC) curve, with additional statistical analyses for quantitative factors and model effectiveness. Internal validation employed ROC, calibration curves, Decision Curve Analysis (DCA), and Clinical Impact Curves (CIC) to assess model discrimination, utility, and accuracy. The International Mission for Prognosis and Analysis of Clinical Trials in TBI (IMPACT) and Corticosteroid Randomization After Significant Head injury (CRASH) models were also compared through multivariate regression.

RESULTS

Factors like unilateral and bilateral pupillary non-reactivity at admission, the derived neutrophil to lymphocyte ratio (dNLR), platelet to lymphocyte ratio (PLR), D-dimer to fibrinogen ratio (DFR), infratentorial hematoma, and Helsinki CT score were identified as independent risk factors (OR > 1), whereas serum albumin emerged as a protective factor (OR < 1). The model showed superior predictive performance with an AUC of 0.955 and surpassed both IMPACT and CRASH models in predictive accuracy. Internal validation confirmed the model's high discriminative capability, clinical relevance, and effectiveness.

CONCLUSIONS

Short-term survival in sTBI is significantly influenced by factors such as pupillary response, dNLR, PLR, DFR, serum albumin levels, infratentorial hematoma occurrence, and Helsinki CT scores at admission. The developed nomogram accurately predicts sTBI outcomes, offering significant clinical utility.

DAMPs Drive Fibroinflammatory Changes in the Glaucomatous ONH

Purpose

The optic nerve head (ONH) is well known to be the initial site of glaucomatous damage; however, the molecular mechanisms initiating this pathology are not fully understood. To further understand the initiating factors in glaucomatous damage we utilized a novel mouse model of glaucoma, B6.EDA+/+ mice, which constitutively express fibronectin containing the extra domain A (FN+EDA). FN+EDA is a known damage-associated molecular pattern (DAMP) that activates Toll-like receptor 4 and elicits a fibro-inflammatory response.

Methods

Eyes from B6.EDA+/+ and C57BL/6J mice were evaluated for retinal ganglion cell (RGC) death, retinal nerve fiber layer (RNFL) thickness, and optic nerve (ON) damage at 12 months and 22 months of age. ONH sections were isolated using laser capture microdissection for subsequent RNA-sequencing and Gene Set Enrichment Analysis (GSEA). GSEA results were confirmed using immunohistochemical (IHC) staining.

Results

B6.EDA+/+ mice exhibit significantly higher intraocular pressure, loss of RGCs, thinning of the RNFL, and progressive levels of ON damage at 12 months and 22 months of age compared to C57BL/6J controls. Protein expression of DAMPs FN+EDA and biglycan was significantly increased in B6.EDA+/+ mice compared to C57BL/6J controls. GSEA analysis identified significantly up- and downregulated gene groupings at both 12 months and 22 months of age, and IHC staining at 12 and 18 months of age demonstrated significant increases of IFNα, IFNβ, and pSTAT1 expression in B6.EDA+/+ mice compared to C57BL/6J controls.

Conclusions

Our study characterizes glaucomatous changes to the retina, ON, and ONH over the course of 2 years and identifies novel molecular pathways associated with these pathophysiological changes. These data illustrate the effects of FN+EDA on the fibro-inflammatory response in the aging ONH in a novel mouse model of glaucoma.

Microglial priming by IFN-γ involves STAT1-mediated activation of the NLRP3 inflammasome

BACKGROUND

Inflammatory and immune responses in the brain that contribute to various neuropsychiatric disorders may begin as microglial "priming". Interferon (IFN)-γ is known to cause microglial priming, but the mechanism is unclear.

METHODS

We examined the effects of IFN-γ on gene expression, microglial activation, inflammatory and immune responses and activity of the NLRP3 inflammasome in primary microglia and in the brains of mice.

RESULTS

Our results showed that treating microglial cultures with IFN-γ induced a hedgehog-like morphology and upregulated markers of microglial activation (CD86, CD11b) and pro-inflammatory molecules (IL-1β, IL-6, TNF-α, iNOS), while downregulating markers of microglial homeostasis (CX3CR1, CD200R1), anti-inflammatory molecules (MCR1, Arg-1) and neurotrophic factors (IGF-1, BDNF). IFN-γ also upregulated markers of NLRP3 inflammasome activation (NLRP3, caspase-1, gasdermin D, IL-18). This particular transcriptional profiling makes IFN-γ-primed microglia with exaggerated responses upon lipopolysaccharide (LPS) stimulation. The level of NLRP3, caspase-1, gasdermin D, IL-1β, IL-18, TNF-α and iNOS in microglia cultures treated with both IFN-γ and LPS were highest than with either one alone. Injecting IFN-γ into the lateral ventricle of mice induced similar morphological and functional changes in hippocampal microglia as in primary microglial cultures. The effects of IFN-γ on NLRP3 inflammasome and microglia from cultures or hippocampus were abolished when STAT1 was inhibited using fludarabin. Injecting mice with IFN-γ alone or together with LPS induced anxiety- and depression-like behaviors and impaired hippocampus-dependent spatial memory; these effects were mitigated by fludarabin.

CONCLUSIONS

IFN-γ primes microglia by activating STAT1, which upregulates genes that activate the NLRP3 inflammasome. Inhibiting the IFN-γ/STAT1 axis may be a way to treat neurodegenerative diseases and psychiatric disorders that involve microglial priming.

The effect of intra spinal administration of cerium oxide nanoparticles on central pain mechanism: An experimental study

This study investigated Cerium oxide nanoparticles (CeONPs) effect on central neuropathic pain (CNP). The compressive method of spinal cord injury (SCI) model was used for pain induction. Three groups were formed by a random allocation of 24 rats. In the treatment group, CeONPs were injected above and below the lesion site immediately after inducing SCI. pain symptoms were evaluated using acetone, Radian Heat, and Von Frey tests weekly for six weeks. Finally, we counted fibroblasts using H&E staining. We evaluated the expression of Cx43, GAD65 and HDAC2 proteins using the western blot method. The analysis of results was done by PRISM software. At the end of the study, we found that CeONPs reduced pain symptoms to levels similar to those observed in normal animals. CeONPs also increased the expression of GAD65 and Cx43 proteins but did not affect HDAC2 inhibition. CeONPs probably have a pain-relieving effect on chronic pain by potentially preserving GAD65 and Cx43 protein expression and hindering fibroblast infiltration.

Melanoma Brain Metastasis: Biology and Therapeutic Advances

Metastasis to the brain is a frequent complication of advanced melanoma. Historically, patients with melanoma brain metastasis (MBM) have had dismal outcomes, but outcomes have improved with the development of more effective treatments, including stereotactic radiosurgery and effective immune and targeted therapies. Despite these advances, MBM remains a leading cause of death from this disease, and many therapies show decreased efficacy against these tumors compared with extracranial metastases. This differential efficacy may be because of recently revealed unique molecular and immune features of MBMs-which may also provide rational new therapeutic strategies.

IRF8 defines the epigenetic landscape in postnatal microglia, thereby directing their transcriptome programs

Microglia are innate immune cells in the brain. Transcription factor IRF8 (interferon regulatory factor 8) is highly expressed in microglia. However, its role in postnatal microglia development is unknown. We demonstrate that IRF8 binds stepwise to enhancer regions of postnatal microglia along with Sall1 and PU.1, reaching a maximum after day 14. IRF8 binding correlated with a stepwise increase in chromatin accessibility, which preceded the initiation of microglia-specific transcriptome. Constitutive and postnatal Irf8 deletion led to a loss of microglia identity and gain of disease-associated microglia (DAM)-like genes. Combined analysis of single-cell (sc)RNA sequencing and single-cell transposase-accessible chromatin with sequencing (scATAC-seq) revealed a correlation between chromatin accessibility and transcriptome at a single-cell level. IRF8 was also required for microglia-specific DNA methylation patterns. Last, in the 5xFAD model, constitutive and postnatal Irf8 deletion reduced the interaction of microglia with amyloidβ plaques and the size of plaques, lessening neuronal loss. Together, IRF8 sets the epigenetic landscape, which is required for postnatal microglia gene expression.

Microglia signaling in health and disease - Implications in sex-specific brain development and plasticity

Microglia, the intrinsic neuroimmune cells residing in the central nervous system (CNS), exert a pivotal influence on brain development, homeostasis, and functionality, encompassing critical roles during both aging and pathological states. Recent advancements in comprehending brain plasticity and functions have spotlighted conspicuous variances between male and female brains, notably in neurogenesis, neuronal myelination, axon fasciculation, and synaptogenesis. Nevertheless, the precise impact of microglia on sex-specific brain cell plasticity, sculpting diverse neural network architectures and circuits, remains largely unexplored. This article seeks to unravel the present understanding of microglial involvement in brain development, plasticity, and function, with a specific emphasis on microglial signaling in brain sex polymorphism. Commencing with an overview of microglia in the CNS and their associated signaling cascades, we subsequently probe recent revelations regarding molecular signaling by microglia in sex-dependent brain developmental plasticity, functions, and diseases. Notably, C-X3-C motif chemokine receptor 1 (CX3CR1), triggering receptors expressed on myeloid cells 2 (TREM2), calcium (Ca2+), and apolipoprotein E (APOE) emerge as molecular candidates significantly contributing to sex-dependent brain development and plasticity. In conclusion, we address burgeoning inquiries surrounding microglia's pivotal role in the functional diversity of developing and aging brains, contemplating their potential implications for gender-tailored therapeutic strategies in neurodegenerative diseases.

Integrity of neural extracellular matrix is required for microglia-mediated synaptic remodeling

Microglia continuously remodel synapses, which are embedded in the extracellular matrix (ECM). However, the mechanisms, which govern this process remain elusive. To investigate the influence of the neural ECM in synaptic remodeling by microglia, we disrupted ECM integrity by injection of chondroitinase ABC (ChABC) into the retrosplenial cortex of healthy adult mice. Using in vivo two-photon microscopy we found that ChABC treatment increased microglial branching complexity and ECM phagocytic capacity and decreased spine elimination rate under basal conditions. Moreover, ECM attenuation largely prevented synaptic remodeling following synaptic stress induced by photodamage of single synaptic elements. These changes were associated with less stable and smaller microglial contacts at the synaptic damage sites, diminished deposition of calreticulin and complement proteins C1q and C3 at synapses and impaired expression of microglial CR3 receptor. Thus, our findings provide novel insights into the function of the neural ECM in deposition of complement proteins and synaptic remodeling by microglia.

Prolonged extracellular low sodium concentrations and subsequent their rapid correction modulate nitric oxide production dependent on NFAT5 in microglia

Hyponatremia is the most common clinical electrolyte disorder. Chronic hyponatremia has been recently reported to be associated with falls, fracture, osteoporosis, neurocognitive impairment, and mental manifestations. In the treatment of chronic hyponatremia, overly rapid correction of hyponatremia can cause osmotic demyelination syndrome (ODS), a central demyelinating disease that is also associated with neurological morbidity and mortality. Using a rat model, we have previously shown that microglia play a critical role in the pathogenesis of ODS. However, the direct effect of rapid correction of hyponatremia on microglia is unknown. Furthermore, the effect of chronic hyponatremia on microglia remains elusive. Using microglial cell lines BV-2 and 6-3, we show here that low extracellular sodium concentrations (36 mmol/L decrease; LS) suppress Nos2 mRNA expression and nitric oxide (NO) production of microglia. On rapid correction of low sodium concentrations, NO production was significantly increased in both cells, suggesting that acute correction of hyponatremia partly directly contributes to increased Nos2 mRNA expression and NO release in ODS pathophysiology. LS also suppressed expression and nuclear translocation of nuclear factor of activated T cells-5 (NFAT5), a transcription factor that regulates the expression of genes involved in osmotic stress. Furthermore, overexpression of NFAT5 significantly increased Nos2 mRNA expression and NO production in BV-2 cells. Expressions of Nos2 and Nfat5 mRNA were also modulated in microglia isolated from cerebral cortex in chronic hyponatremia model mice. These data indicate that LS modulates microglial NO production dependent on NFAT5 and suggest that microglia contribute to hyponatremia-induced neuronal dysfunctions.

COVID-19 and the impact on Alzheimer's disease pathology

Coronavirus disease 2019 (COVID-19) has rapidly escalated into a global pandemic that primarily affects older and immunocompromised individuals due to underlying clinical conditions and suppressed immune responses. Furthermore, COVID-19 patients exhibit a spectrum of neurological symptoms, indicating that COVID-19 can affect the brain in a variety of manners. Many studies, past and recent, suggest a connection between viral infections and an increased risk of neurodegeneration, raising concerns about the neurological effects of COVID-19 and the possibility that it may contribute to Alzheimer's disease (AD) onset or worsen already existing AD pathology through inflammatory processes given that both COVID-19 and AD share pathological features and risk factors. This leads us to question whether COVID-19 is a risk factor for AD and how these two conditions might influence each other. Considering the extensive reach of the COVID-19 pandemic and the devastating impact of the ongoing AD pandemic, their combined effects could have significant public health consequences worldwide.

Inflammaging and Brain Aging

Progress made by the medical community in increasing lifespans comes with the costs of increasing the incidence and prevalence of age-related diseases, neurodegenerative ones included. Aging is associated with a series of morphological changes at the tissue and cellular levels in the brain, as well as impairments in signaling pathways and gene transcription, which lead to synaptic dysfunction and cognitive decline. Although we are not able to pinpoint the exact differences between healthy aging and neurodegeneration, research increasingly highlights the involvement of neuroinflammation and chronic systemic inflammation (inflammaging) in the development of age-associated impairments via a series of pathogenic cascades, triggered by dysfunctions of the circadian clock, gut dysbiosis, immunosenescence, or impaired cholinergic signaling. In addition, gender differences in the susceptibility and course of neurodegeneration that appear to be mediated by glial cells emphasize the need for future research in this area and an individualized therapeutic approach. Although rejuvenation research is still in its very early infancy, accumulated knowledge on the various signaling pathways involved in promoting cellular senescence opens the perspective of interfering with these pathways and preventing or delaying senescence.

Convergence of endothelial dysfunction, inflammation and glucocorticoid resistance in depression-related cardiovascular diseases

Major Depressive Disorder, or depression, has been extensively linked to dysregulated HPA axis function, chronic inflammation and cardiovascular diseases. While the former two have been studied in depth, the mechanistic connection between depression and cardiovascular disease is unclear. As major mediators of vascular homeostasis, vascular pathology and immune activity, endothelial cells represent an important player connecting the diseases. Exaggerated inflammation and glucocorticoid function are important topics to explore in the endothelial response to MDD. Glucocorticoid resistance in several cell types strongly promotes inflammatory signaling and results in worsened severity in many diseases. However, endothelial health and inflammation in chronic stress and depression are rarely considered from the perspective of glucocorticoid signaling and resistance. In this review, we aim to discuss (1) endothelial dysfunction in depression, (2) inflammation in depression, (3) general glucocorticoid resistance in depression and (4) endothelial glucocorticoid resistance in depression co-morbid inflammatory diseases. We will first describe vascular pathology, inflammation and glucocorticoid resistance separately in depression and then describe their potential interactions with one another in depression-relevant diseases. Lastly, we will hypothesize potential mechanisms by which glucocorticoid resistance in endothelial cells may contribute to vascular disease states in depressed people. Overall, endothelial-glucocorticoid signaling may play an important role in connecting depression and vascular pathology and warrants further study.

The effects of P2Y12 loss on microglial gene expression, dynamics, and injury response in the cerebellum and cerebral cortex

Despite the emerging consensus that microglia are critical to physiological and pathological brain function, it is unclear how microglial roles and their underlying mechanisms differ between brain regions. Microglia throughout the brain express common markers, such as the purinergic receptor P2Y12, that delineate them from peripheral macrophages. P2Y12 is a critical sensor of injury but also contributes to the sensing of neuronal activity and remodeling of synapses, with microglial loss of P2Y12 resulting in behavioral deficits. P2Y12 has largely been studied in cortical microglia, despite the fact that a growing body of evidence suggests that microglia exhibit a high degree of regional specialization. Cerebellar microglia, in particular, exhibit transcriptional, epigenetic, and functional profiles that set them apart from their better studied cortical and hippocampal counterparts. Here, we demonstrate that P2Y12 deficiency does not alter the morphology, distribution, or dynamics of microglia in the cerebellum. In fact, loss of P2Y12 does little to disturb the distinct transcriptomic profiles of cortical and cerebellar microglia. However, unlike in cortex, P2Y12 is not required for a full microglial response to focal injury, suggesting that cerebellar and cortical microglia use different cues to respond to injury. Finally, we show that P2Y12 deficiency impairs cerebellar learning in a delay eyeblink conditioning task, a common test of cerebellar plasticity and circuit function. Our findings suggest not only region-specific roles of microglial P2Y12 signaling in the focal injury response, but also indicate a conserved role for P2Y12 in microglial modulation of plasticity across regions.

Pre-metastatic niche: formation, characteristics and therapeutic implication

Distant metastasis is a primary cause of mortality and contributes to poor surgical outcomes in cancer patients. Before the development of organ-specific metastasis, the formation of a pre-metastatic niche is pivotal in promoting the spread of cancer cells. This review delves into the intricate landscape of the pre-metastatic niche, focusing on the roles of tumor-derived secreted factors, extracellular vesicles, and circulating tumor cells in shaping the metastatic niche. The discussion encompasses cellular elements such as macrophages, neutrophils, bone marrow-derived suppressive cells, and T/B cells, in addition to molecular factors like secreted substances from tumors and extracellular vesicles, within the framework of pre-metastatic niche formation. Insights into the temporal mechanisms of pre-metastatic niche formation such as epithelial-mesenchymal transition, immunosuppression, extracellular matrix remodeling, metabolic reprogramming, vascular permeability and angiogenesis are provided. Furthermore, the landscape of pre-metastatic niche in different metastatic organs like lymph nodes, lungs, liver, brain, and bones is elucidated. Therapeutic approaches targeting the cellular and molecular components of pre-metastatic niche, as well as interventions targeting signaling pathways such as the TGF-β, VEGF, and MET pathways, are highlighted. This review aims to enhance our understanding of pre-metastatic niche dynamics and provide insights for developing effective therapeutic strategies to combat tumor metastasis.

Limitations and potential strategies of immune checkpoint blockade in age-related neurodegenerative disorders

Neurological disorders such as Alzheimer's disease (AD), and Parkinson's disease (PD) have no disease-modifying treatments, resulting in a global dementia crisis that affects more than 50 million people. Amyloid-beta (Aβ), tau, and alpha-synuclein (α-Syn) are three crucial proteins that are involved in the pathogenesis of these age-related neurodegenerative diseases. Only a few approved AD medications have been used in the clinic up to this point, and their results are only partial symptomatic alleviation for AD patients and cannot stop the progression of AD. Immunotherapies have attracted considerable interest as they target certain protein strains and conformations as well as promote clearance. Immunotherapies also have the potential to be neuroprotective: as they limit synaptic damage and spread of neuroinflammation by neutralizing extracellular protein aggregates. Lately, disease-modifying therapies (DMTs) that can alter the pathophysiology that underlies AD with anti-Aβ monoclonal antibodies (MAbs) (e.g., aducanumab, lecanemab, gantenerumab, donanemab, solanezumab, crenezumab, tilavonemab). Similarly, in Parkinson's disease (PD), DMTs utilizing anti-αSyn (MAbs) (e.g., prasinezumab, cinpanemab,) are progressively being developed and evaluated in clinical trials. These therapies are based on the hypothesis that both AD and PD may involve systemic impairments in cell-dependent clearance mechanisms of amyloid-beta (Aβ) and alpha-synuclein (αSyn), respectively, meaning the body's overall inability to effectively remove Aβ and αSyn due to malfunctioning cellular mechanisms. In this review we will provide possible evidence behind the use of immunotherapy with MAbs in AD and PD and highlight the recent clinical development landscape of anti-Aβ (MAbs) and anti-αSyn (MAbs) from these clinical trials in order to better investigate the therapeutic possibilities and adverse effects of these anti-Aβ and anti-αSyn MAbs on AD and PD.

The intricate interplay between microglia and adult neurogenesis in Alzheimer's disease

Microglia, the resident immune cells of the central nervous system, play a crucial role in regulating adult neurogenesis and contribute significantly to the pathogenesis of Alzheimer's disease (AD). Under physiological conditions, microglia support and modulate neurogenesis through the secretion of neurotrophic factors, phagocytosis of apoptotic cells, and synaptic pruning, thereby promoting the proliferation, differentiation, and survival of neural progenitor cells (NPCs). However, in AD, microglial function becomes dysregulated, leading to chronic neuroinflammation and impaired neurogenesis. This review explores the intricate interplay between microglia and adult neurogenesis in health and AD, synthesizing recent findings to provide a comprehensive overview of the current understanding of microglia-mediated regulation of adult neurogenesis. Furthermore, it highlights the potential of microglia-targeted therapies to modulate neurogenesis and offers insights into potential avenues for developing novel therapeutic interventions.

The role of the gut microbiome in neuroinflammation and chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the most debilitating adverse effects caused by chemotherapy drugs such as paclitaxel, oxaliplatin and vincristine. It is untreatable and often leads to the discontinuation of cancer therapy and a decrease in the quality of life of cancer patients. It is well-established that neuroinflammation and the activation of immune and glial cells are among the major drivers of CIPN. However, these processes are still poorly understood, and while many chemotherapy drugs alone can drive the activation of these cells and consequent neuroinflammation, it remains elusive to what extent the gut microbiome influences these processes. In this review, we focus on the peripheral mechanisms driving CIPN, and we address the bidirectional pathways by which the gut microbiome communicates with the immune and nervous systems. Additionally, we critically evaluate literature addressing how chemotherapy-induced dysbiosis and the consequent imbalance in bacterial products may contribute to the activation of immune and glial cells, both of which drive neuroinflammation and possibly CIPN development, and how we could use this knowledge for the development of effective treatment strategies.

Microglia contact cerebral vasculature through gaps between astrocyte endfeet

The close spatial relationship between microglia and cerebral blood vessels implicates microglia in vascular development, homeostasis and disease. In this study we used the publicly available Cortical MM^3 electron microscopy dataset to systematically investigate microglial interactions with the vasculature. Our analysis revealed that approximately 20% of microglia formed direct contacts with blood vessels through gaps between adjacent astrocyte endfeet. We termed these contact points "plugs". Plug-forming microglia exhibited closer proximity to blood vessels than non-plug forming microglia and formed multiple plugs, predominantly near the soma, ranging in surface area from ∼0.01 μm2 to ∼15 μm2. Plugs were enriched at the venule end of the vascular tree and displayed a preference for contacting endothelial cells over pericytes at a ratio of 3:1. In summary, we provide novel insights into the ultrastructural relationship between microglia and the vasculature, laying a foundation for understanding how these contacts contribute to the functional cross-talk between microglia and cells of the vasculature in health and disease.