Journal of Neuroinflammation

HIV-associated neurocognitive disorders (HAND) have become a major clinical concern, particularly among the aging HIV-1-seropositive population, which is generally characterized by persistent viral reservoirs and a lower level of chronic inflammation. NLRP3 inflammasome activation exhibits its unique role in the progression of many chronic inflammatory diseases. Furthermore, pyroptosis, an inflammatory form of programmed cell death, has been implicated in numerous neurological diseases. However, the mechanisms linking EcoHIV infection, microglial pyroptosis, and NLRP3 inflammasome activation remain incompletely understood. In this study, EcoHIV was retro-orbitally injected into C57BL/6J wild-type mice and analyzed at 14-, 30-, 60-, and 90-days post-infection to establish a NeuroHIV model. Additionally, in vitro, BV2 microglial cell line was infected with EcoHIV and treated with MCC950, an inhibitor of the NLRP3 inflammasome, for three days. Pyroptosis marker GSDMD, NLRP3 inflammasome components, Caspase-1 (a marker of inflammasome activation), HLA-DR (an immune activation marker), Programmed-death 1 (PD-1, an immune checkpoint molecule), and Ki67 (a cellular proliferation marker) were assessed by immunofluorescence staining. Results showed that EcoHIV-infected mice showed a peak in NLRP3 expression at 14 days post-infection, compared with controls, followed by a modest decline at 30 days, while GSDMD expression increased progressively across 14 and 30 days. These findings demonstrate dynamic changes in microglial pyroptosis and NLRP3 inflammasome activation over the course of EcoHIV infection. In vitro, EcoHIV-infected BV2 cells exhibited significantly increased EcoHIV-eGFP fluorescence compared with controls, confirming the utility of BV2 cells as an in vitro model of microglial EcoHIV infection. Expression levels of GSDMD and NLRP3 were elevated following infection, indicating enhanced pyroptosis and neuroinflammation. Treatment with MCC950 significantly reduced the expression of GSDMD, NLRP3, HLA-DR, PD-1, and Ki67, suggesting that inhibition of NLRP3 inflammasome activity suppresses both pyroptosis and microglial activation and proliferation. Together, elucidating the interplay between microglial pyroptosis and NLRP3 inflammasome activation may provide new insights into the pathogenesis and potential therapeutic strategies for NeuroHIV in the aging HIV-1-seropositive population.

Growing evidence supports a strong association between periodontitis and Alzheimers disease (AD), yet the mechanisms linking these conditions remain poorly defined. In neurodegenerative disorders, including AD, microglia are often characterized by increased lipid droplet (LD) accumulation, heightened activation, and impaired function. In this study, we examined whether Porphyromonas gingivalis (Pg), a keystone periodontal pathogen, promotes LD accumulation in microglia and disrupts their function. We found that Pg infection induces robust LD accumulation in BV2 microglial cells and in microglia from Pg-infected App KI mice. This Pg-driven LD buildup was closely associated with elevated reactive oxygen species (ROS) production, impaired phagocytic ability, and altered activation. Notably, pharmacological inhibition of LD with a triglyceride synthesis inhibitor effectively reversed Pg-induced LD accumulation, mitigated ROS production, and restored phagocytic function, thus underscoring the critical role of lipid metabolism in regulating microglial function. These findings support a model in which, in the context of periodontitis, systemic dissemination of periodontal pathogens promotes LD accumulation in microglia, and this metabolic alteration exacerbates microglia dysfunction via a self-reinforcing cycle of excessive oxidative stress and impaired phagocytosis, potentially accelerating AD progression.

HIV-1 infection of the brain occurs early in acute infection and results in neuroinflammation and - when untreated - in cognitive impairment, yet the mechanisms by which microglia become infected remain poorly defined. Evidence from simian immunodeficiency virus (SIV) studies supports a model in which infected CD4+ T cells disseminate HIV-1 to tissue macrophages, but this has not yet been confirmed for human microglia. Here, we used human monocyte-derived microglia (MDMi) and autologous HIV-1-infected primary CD4+ T cells to investigate viral transmission and immune cell interactions. Transcriptional profiling of MDMi confirmed microglia signature genes such as CX3CR1, P2RY12 and C1QB, and surface staining showed expression of CD4 and the HIV-1 coreceptor CCR5. Compared to cell-free infection, direct cell-to-cell contact between MDMi and HIV-1-infected CD4+ T cells markedly enhanced productive infection of MDMi. HIV-1 infection downmodulated the "dont-eat-me" signal CD47 and increased phosphatidylserine on the surface of primary CD4+ T cells. Consequently, HIV-1 infection of primary CD4+ T cells increased microglia-CD4+ T cell interactions and resulted in enhanced phagocytosis by MDMi. Together, this supports a mechanism where HIV-1 facilitates cell-to-cell spread from primary CD4+ T cells to microglia, which has important implications for therapeutic targeting of HIV-1 brain reservoir seeding.

The impact of microglia antigen presentation on CNS infiltrating CD8 T cells responses during neurotropic virus infection has been difficult to define. Using Theilers murine encephalomyelitis virus (TMEV) infection of neurons as a model system, our laboratory has previously determined that H-2Db restricted, but not H-2Kb restricted CD8 T cells are required for viral clearance, demonstrating the role of discrete MHC class I alleles. To determine the extent microglia antigen presentation impacts brain-infiltrating CD8 T cells, our laboratory generated novel single MHC class I conditional knockout mice in which H-2Kb or H-2Db can be specifically deactivated in TMEM119+ microglia with tamoxifen administration. During TMEV infection, conditional knockout of H-2Kb in microglia reduced antigen-specific CD8 T cell proliferation in the brain. Meanwhile, mice with deletion of Db in microglia had reduced levels of perforin in antigen-specific CD8 T cells. Furthermore, microglia specific deletion of H-2Db reduced CD8 T cell numbers in the brain and preserved blood-brain barrier (BBB) integrity. Microglial Db restricted antigen presentation was also essential for the reactivation of CD8 tissue resident memory (TRM) cells and BBB integrity during memory recall responses. These findings further our understanding of how brain infiltrating antiviral CD8 T cell responses are impacted by microglia, as well as define how this cellular interaction contributes to BBB disruption during neuroinflammation. These findings also have high significance to our understanding of how microglia impact CD8 TRM cell populations that reside in the brain long after virus infection is cleared. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=111 SRC="FIGDIR/small/722741v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@9302a9org.highwire.dtl.DTLVardef@193b5f4org.highwire.dtl.DTLVardef@8eb036org.highwire.dtl.DTLVardef@1d2cd6a_HPS_FORMAT_FIGEXP M_FIG C_FIG

BackgroundMicroglial heterogeneity is a fundamental feature of brain homeostasis and pathology. The purpose of this study was to investigate the complexity of microglial plasticity by characterizing specialized oligodendrocyte-like microglial subsets. MethodsThe study was performed utilizing single-cell transcriptomics analyses and immunofluorescence staining to identify and profile microglial subpopulations. Additionally, spatial transferring and morphological analyses were conducted to determine the anatomical distribution and structural features of these specific cells. ResultsWe identified a distinct microglial subset termed dual-phenotype microglia (DPM), which co-expresses microglial and oligodendrocyte markers. DPM consisted of two subtypes with distinct functions: myelin-associated DPM (mDPM) and neuron-associated DPM (nDPM). Spatial and morphological evaluations revealed that mDPMs were sparsely distributed across the whole brain and exhibited a highly ramified architecture, whereas nDPMs were enriched in the hippocampal dentate gyrus. Mechanistically, we found that mDPM function was driven by the Sox10 regulon to modulate myelin maintenance and axonal ensheathment, while nDPM was orchestrated by Glis2, facilitating essential neuron-glia crosstalk and synaptic regulation. Furthermore, we demonstrated that nDPM and mDPM were predicted to undergo significant alterations in multiple sclerosis and Alzheimers disease. Notably, mDPMs were selectively enriched in active multiple sclerosis lesions, revealing that DPM were closely related to neuropsychiatric disorders. ConclusionsBy comprehensively characterizing the morphology, molecular signatures, and spatial logic of these oligodendrocyte-like microglial subsets, our study elucidated the complexity of microglial plasticity. These findings provided new insights into their diverse roles in central nervous system health and disease. Graphical abstractIdentification, Molecular Profiling, and Functional Modeling of Dual-Phenotype Microglia (DPM). (1) Discovery: Identification of the dual-phenotype microglia (DPM) population through single-cell transcriptomics. (2) Molecular Signatures: The transcriptomic identity of DPM subtypes is governed by specific regulatory networks. (3) Distribution & Pathology: Spatial mapping reveals divergent anatomical logic and disease relations for DPM subtypes. (4) Mechanism/Theory: A proposed functional model of mDPMs as "metabolic relay" and support units. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/724239v2_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@b7db1dorg.highwire.dtl.DTLVardef@9265e7org.highwire.dtl.DTLVardef@1605d82org.highwire.dtl.DTLVardef@19b048f_HPS_FORMAT_FIGEXP M_FIG C_FIG

Microglia are the brains resident immune cells that exhibit complex signaling behavior, including phagocytic activity in response to threats and prolonged neuronal activity. Adenosine triphosphate (ATP) is a chemoattractant for microglia. In the nucleus accumbens (NAc), ATP is co-packaged and released with DA, and microglia express dopamine (DA) receptors and ATP receptors. The present work examines microglia chemotactic motility for these transmitters using iontophoresis and multiphoton microscopy approaches in NAc brain slices from GFP-monocyte labeled transgenic mice. ATP chemoattraction was more regularly observed than DA chemoattraction, and DA chemoattraction occurred in only a small subset of microglia. The DA chemoattraction of this subset was blocked by DA D1 antagonism. Microglia are reactive oxygen species (ROS) scavengers. Application of glucose oxidase produces mild but consistent increases in ROS and induced inflammatory-related changes in microglial morphology and motility. Glucose oxidase application decreased DA release but had variable effects on ATP release. The toll-like receptor 4 (TLR4) agonist lipopolysaccharide (LPS) transitioned microglia from ramified to amoeboid morphology over a period of 4 hours, and increased DA and ATP release across this same period. These studies highlight the complex relationship between local immune activation and DA terminal functionality.

The effect of sortilin inhibition on acute inner retinal neurodegeneration induced by optic nerve crush was investigated. Pharmacological sortilin inhibition using intravitreal delivery of a polyclonal antibody or a small-molecule inhibitor was evaluated in C57BL/6JRj male mice subjected to unilateral crush. Inner retinal thickness was evaluated by optical coherence tomography, and retinal ganglion cell density was determined in retinal flat mounts. Furthermore, the effect of constitutive sortilin deficiency was examined using Sort1-/- mice. Changes in protein and mRNA levels of sortilin, p75NTR, and associated injury markers were analyzed. Neither pharmacological inhibition or constitutive loss of sortilin protected against inner retinal thinning or retinal ganglion cell loss following optic nerve crush. A transient 1.4-fold increase in p75NTR mRNA was observed early after injury, accompanied by a two-fold increase in protein levels. While sortilin expression remained largely unchanged, sortilin deficiency was associated with an altered baseline retinal state, including increased GFAP, p75NTR, and proBDNF levels. Following optic nerve crush, the induction of p75NTR was significantly attenuated in sortilin-deficient retinas compared with wild type, without affecting the extent of RGC degeneration. In summary, sortilin inhibition does not preserve inner retinal structure following optic nerve crush, but modulates glial activation, inflammatory signaling, and proneurotrophin dynamics. These findings indicate that sortilin-dependent pathways are not key drivers of optic nerve crush-induced neurodegeneration but may be more relevant in disease contexts characterized by chronic stress and neuroinflammation.

Progressive neurodegeneration in the central nervous system (CNS) in multiple sclerosis (MS) is driven by chronic inflammatory demyelination. Neutrophils are increasingly recognized as versatile innate immune cells with potentially underappreciated roles in CNS inflammation, but their contribution to MS pathology remains poorly understood. Interestingly, we observed foamy neutrophils in active CNS lesions of MS patients. Therefore, we investigated the ability of human neutrophils to internalize myelin debris and assessed how this impacts their functional phenotype. Neutrophils exhibited efficient myelin uptake, peaking between 3 and 6 hours, predominantly through complement opsonization and internalization via complement receptor 3. Prolonged exposure to high concentrations of myelin induced a pro-inflammatory phenotype, marked by increased production of reactive oxygen species, neutrophil extracellular traps, and inflammatory mediators such as CXCL8 and CCL3. Gene expression analysis revealed a dose-dependent inflammatory signature after myelin uptake, characterized by gradual upregulation of CXCL8 and decreased ARG1 expression, suggesting a shift toward a pro-inflammatory neutrophil phenotype. These findings provide novel insights into the role of neutrophils in myelin clearance and inflammation in the CNS, highlighting complement receptor 3-mediated uptake and downstream pro-inflammatory activation as key mechanisms.

While Apolipoprotein E4 (APOE4) is the greatest known genetic risk factor for late-onset Alzheimers disease, its mechanistic role in the brain-resident macrophage, microglia, remains elusive. Microglia are important in the clearance of pathology in disease, heavily relying on lysosome functionality; therefore, we sought to understand the impact of APOE4 on microglial function. APOE44 microglia have been shown to have lipid accumulation, yet the mechanisms leading to this accumulation are unknown. Using induced pluripotent stem cell-derived microglia, we found that the APOE4 haplotype resulted in transcriptional state shifts in microglia, suppressing activated-response microglia (ARMs) and promoting a G2 senescent-like state. We found that APOE44 microglia accumulate cholesterol esters and provide less lipid support to fibroblast-induced neurons, decreasing their synaptic connections. APOE44 microglia secrete significantly less lipoproteins, leading to the accumulation of lipoproteins within the cells including the lysosomes. APOE44 microglia exhibit impaired lysosomal acidification and degradation capacity. Further, our results elucidated that APOE44 microglia are proinflammatory and shift away from fatty acid oxidation towards glycolysis, due to dysfunctional mitochondria. Taken together, our findings indicate that a loss-of-function in lipoprotein secretion drives intracellular lipid accumulation, including within lysosomes, ultimately disrupting the lysosome-endoplasmic reticulum-mitochondrial axis. This drives a proinflammatory and metabolically compromised microglial phenotype with impaired neuro-supportive functions. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=138 SRC="FIGDIR/small/724612v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@18d6a2org.highwire.dtl.DTLVardef@b3644dorg.highwire.dtl.DTLVardef@17e3716org.highwire.dtl.DTLVardef@1529caf_HPS_FORMAT_FIGEXP M_FIG C_FIG

Background/ObjectivesNeuroinflammation-driven iron dysregulation and neurotoxic astrocyte polarization are increasingly recognized as interconnected pathological mechanisms in neurodegenerative diseases. Systemic inflammation triggered by strenuous exercise or infection can engage the central nervous system and astrocytic inflammatory responses and perturb iron homeostasis; however, targeted nutritional strategies to counteract these processes remain limited. Inflamate(R) is a multi-component botanical supplement comprising boswellic acids, astilbin, xanthohumol, and cinnamaldehyde, each with documented anti-inflammatory properties. However, whether this combined formulation can modulate the inflammatory-iron metabolic axis and astrocyte phenotypic polarization remains unexplored. This study aimed to investigate the effects of Inflamate(R) on LPS-induced pro-inflammatory gene expression, iron metabolism-related gene regulation, and A1/A2 astrocyte phenotypic polarization in mouse astrocytes. MethodsMouse astrocytes (AWT) were pre-treated with Inflamate(R) (0.0375 g/mL) or DMSO vehicle for 24 h, followed by lipopolysaccharide (LPS; 1 g/mL) stimulation for an additional 24 h. The non-cytotoxic working concentration was determined by morphological assessment, CCK-8 cell viability, and LDH cytotoxicity assays. Expression of 14 target genes spanning pro-inflammatory mediators (NOS2, IL6, C3, COX2, PLA2g15, SOCS3), iron metabolism regulators (FTH1, Hepcidin, TFRC, SLC40A1, RGMa, RGMb), and astrocyte polarization markers (S100A10, GFAP) was quantified by qRT-PCR. ResultsUnder normal culture conditions, Inflamate(R) did not significantly alter the expression of any target gene except S100A10, confirming the absence of baseline cytotoxicity or transcriptional homeostatic perturbation. Upon LPS stimulation, Inflamate(R) selectively suppressed NOS2 (approximately 64% reduction, p < 0.0001), IL6 (approximately 37% reduction, p < 0.0001), and C3 (approximately 47% reduction, p < 0.0001), while COX2, PLA2g15, and SOCS3 remained unaffected. Concurrently, Inflamate(R) significantly reduced LPS-induced Hepcidin expression to approximately 17% of the control level (p < 0.05) and attenuated FTH1 upregulation (p < 0.01), without altering the expression of iron transporters (TFRC, SLC40A1) or BMP-SMAD pathway components (RGMa, RGMb). Furthermore, Inflamate(R) upregulated the neuroprotective A2 marker S100A10 under both basal (p < 0.05) and LPS-stimulated conditions (p < 0.01), while the general reactivity marker GFAP remained unchanged. ConclusionsInflamate(R) exerts a selective, multi-target modulatory effect at the transcriptional level in LPS-stimulated astrocytes, encompassing suppression of the iNOS-NO and IL-6 signaling axes, attenuation of inflammation-driven hepcidin-ferritin iron dysregulation via the IL-6-STAT3 pathway, and promotion of a phenotypic shift from neurotoxic A1 toward neuroprotective A2 astrocyte polarization. Given that the IL-6-JAK-STAT3-hepcidin axis is also activated during exercise-induced systemic inflammation, these findings suggest that Inflamate(R) may represent a targeted nutritional strategy for preserving CNS iron homeostasis and supporting neuroprotective astrocyte function in both neurodegenerative and exercise-related neuroinflammatory contexts. Further validation in in vivo neurodegenerative and exercise models, including protein-level analyses, is warranted to confirm these transcriptional findings.

Microglia represent the immune component of the central nervous system (CNS) that displays dynamic responses to injury and disease. Across the developing and mature CNS, microglia emerge as immunocompetent cells that continuously survey their surroundings to maintain tissue homeostasis and respond to threats. There remains a gap in 3D in vitro models that contain microglia and can provide both developmental and mature functional hallmarks. Using a 3D neural multicellular model, cortical microtissues, derived from primary rat cortical cells, we conducted live imaging to monitor microglia dynamics from early, middle, and late stage microtissue maturation. We optimized a within-micromold imaging approach that allows for live microglia imaging without removing microtissues from their culturing environment. We confirm that microglia exhibit baseline surveillance characterized by relatively stationary somas and highly dynamic cell processes that continuously extend and retract. Following proinflammatory challenges, microglia engulf lipopolysaccharide particles, accompanied by dynamic shifts in motility patterns; and rapidly respond to laser-induced tissue damage through process extension, whole-cell displacement, and local recruitment. Lastly, we show that microtissue age in culture strongly influences both baseline and directed motility profiles. Collectively, these studies demonstrate that within a 3D microenvironment, microglia exhibit pronounced changes in morphology, surveillance area, motility, and injury response across microtissue maturation. Microtissues can serve as a valuable in vitro platform for both microglia developmental studies and investigations of brain inflammation related to CNS injuries, infections, and diseases.

IntroductionApoE4 is the strongest genetic risk factor for Alzheimers disease (AD). Emerging evidence suggests that ApoE4 increases AD risk by disrupting microglial metabolism and function. However, whether ApoE lipidation state contributes to microglial dysfunction remains poorly understood. MethodsHuman microglia were treated with lipid-free or lipid-bound ApoE3 or ApoE4. Label-free live-cell holotomography and global proteomics were used to assess isoform- and lipidation-specific effects on lipid droplet dynamics, mitochondrial morphology, and microglial phenotype. ResultsApoE4 treatment resulted in fewer but enlarged lipid droplets and increased mitochondrial fragmentation compared to ApoE3, effects that were enhanced by lipid-bound ApoE4. Proteomic analyses revealed a strong type I interferon response in cells exposed to lipid-free ApoE, which was exacerbated by lipid-free ApoE4. DiscussionThese findings indicate that lipid-bound ApoE4 drives metabolic reprogramming, whereas lipid-free ApoE4 promotes inflammatory signaling, identifying ApoE lipidation as a critical modifier of ApoE4-associated AD risk.

Aggregates of misfolded -synuclein (Syn) and neuroinflammation are pathological features of Parkinsons disease (PD). These, misfolded conformations of Syn promote cytokine and chemokine signaling in the surrounding microenvironment by triggering activation of glial cells through pattern recognition receptors. Microglia and astrocytes act as innate mediators of the neuroimmune response in the brain by regulating inflammatory signaling via paracrine and autocrine forms of cell communication. Extracellular vesicles (EVs) represent a form of glial cell to cell communication that can regulate the glial neuroimmune responses depending on the phenotype of the donor cell. Research has shown that the contents of EVs can be altered via pharmacologically altering the donor cell which offers a potential avenue for the regulation of inflammation. As such, we analyzed enriched mouse cortical primary astrocytes and characterized their response to Syn exposure in the absence and presence of microglia-derived EVs. Using trans-resveratrol, a naturally occurring polyphenol implicated for its anti-inflammatory properties, as our pharmacological agent to generate an anti-inflammatory microglial-derived EV phenotype we found that EVs derived from resveratrol-treated microglia decreased the production of proinflammatory molecules in enriched astrocytes exposed to Syn. Sequencing of EV miRNAs revealed two miRNAs (miR-5099 and miR-115) with significant up-regulation in resveratrol EVs compared to control EVs. Astrocytes transfected with corresponding miRNA mimics prior to Syn exposure showed a dramatic decrease in inflammatory biomarker production. These findings show that microglia-derived EVs and their specific miRNA cargo can attenuate Syn-directed inflammation in astrocytes and may serve as a novel therapeutic for proteinopathies like PD.

STRUCTURED ABSTRACTO_ST_ABSINTRODUCTIONC_ST_ABSA higher incidence of dementia, including Alzheimer s-like pathology, is observed in aged people living with HIV-1. However, mechanisms linking HIV-1 to Alzheimers disease (AD) pathology remain unclear, due to the lack of animal models that allow for concurrent study. METHODSWe created a novel APP knock-in (KI) AD mouse, NOG/APPKM670,671NL/IL-34 (hNAIL) that permits study of progressive brain HIV-1 replication. The mice harbor human microglia-like cells. Four-month-old CD34+ human cell reconstituted mice infected with the HIV-1ADA strain facilitated studies of HIV-1 replication on AD pathologies. RESULTSHIV-1 replication increased A{beta} levels and reduced synaptic and neuronal integrity. Spatial transcriptomics demonstrated distinct A{beta} and HIV-1 transcriptional patterns, whereas dual diseased combinations amplified AD pathology. Neurons showed highest transcriptional change, with genes linked to neuroinflammation, protein trafficking, and synaptic dysfunction. DISCUSSIONThe hNAIL mice enable interrogation of HIV-AD comorbidities, with a future potential for the development of novel therapeutic interventions.

Alzheimers disease (AD) is influenced by both genetic risk and environmental exposures, but how these factors interact in human microglia remains unclear. Here, we investigate whether the late-onset AD risk allele APOE4 impacts microglial vulnerability to arsenite exposure. To that end, we used CRISPR/Cas9 to generate an isogenic APOE4+/+ iPSC-derived transcription factor-induced microglia-like cells (iTFM). We demonstrate that APOE4+/+ iTFM exhibit decreased survival following arsenite exposure, as evidenced by a lower LC50 compared to APOE3+/+ controls. Transcriptomic profiling identified arsenite concentration as the primary driver of gene expression changes, while genotype contributed a secondary, distinct component of the response. Weighted gene co-expression network analysis revealed genotype-dependent modules enriched for phagocytic and oxidative stress pathways, including KEAP1-NFE2L2 signaling. These transcriptomic changes were further supported by functional assays. APOE4+/+ iTFM had a high proportion of phagocytic cells and altered mitochondrial phenotypes including increased mitochondrial mass, reduced membrane potential, and reduced superoxide production, all of which were further perturbed by low dose arsenite exposure. These results support a gene-environment interaction-dependent increase in microglial vulnerability via reshaping of transcriptional and functional stress responses, and provide a human cell-based framework for studying environmentally mediated microglial contributions to AD.

Traumatic brain injury (TBI) triggers secondary neurovascular damage characterized by oxidative stress, blood-brain barrier (BBB) disruption, and neuroinflammation, leading to long-term cognitive deficits. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator of cellular antioxidant defense, but its role in maintaining neurovascular integrity after TBI remains unclear. Here, using in vivo fluid percussion injury in wild-type, Nrf2-/-, and ICAM-1-/- mice, and in vitro stretch injury in human brain microvascular endothelial cells (hBMVECs), we demonstrate that TBI suppresses Nrf2 signaling, reducing antioxidant gene expression, and increasing oxidative and nitrosative stress. Nrf2 impairment enhances BBB permeability, ICAM-1-mediated leukocyte transmigration and promotes neutrophil extracellular trap (NET) formation. ICAM-1 deletion rescues these effects, confirming the mechanistic link between Nrf2, ICAM-1, and immune-mediated vascular damage. Preservation of Nrf2 signaling maintains antioxidant defenses, limits immune cell infiltration, and restricts NET-mediated injury. Importantly, Nrf2 deficiency impairs functional recovery, whereas its presence correlates with improved neurological outcomes. Targeting the Nrf2-ICAM-1 axis may reduce immune-mediated neurovascular injury, limit NET formation, and improve functional recovery after traumatic brain injury.

Alzheimers disease (AD) is characterized not only by tau and amyloid-{beta} aggregation but also by systemic disruptions in circadian rhythms, metabolism, and gut-brain communication that exacerbate neuroinflammation and neurodegeneration. While glial cells play central roles in inflammatory signaling and proteostasis, the contribution of the gut microbiome to glia-driven AD pathology remains poorly understood. Here, we used Drosophila models with glial-specific expressions of human tau and amyloid-associated transgenes to investigate how microbiome integrity influences disease progression. AD models exhibited significant shifts in gut microbial composition, particularly in Lactobacillus and Acetobacter species, suggesting an adaptive microbial response to pathological stress. Strikingly, microbiome depletion (axenic condition) markedly worsened behavioral and physiological outcomes, including disrupted sleep-circadian rhythms, impaired memory, and reduced locomotor function. These deficits were accompanied by amplified neuroinflammatory signaling (Upd-Dome-Hop-Stat92e axis), increased apoptotic gene expression, lipid dysregulation, and altered synaptic markers. Moreover, microbiome loss induced energy stress marked by elevated phospho-AMPK (p-AMPK), yet failed to restore proteostasis, as evidenced by accumulation of ubiquitinated proteins and the autophagy adaptor Ref2p, indicating impaired autophagic flux. This dysfunction correlated with increased tau, phospho-tau, and A{beta}42 accumulation. Together, our findings demonstrate that microbiome depletion exacerbates glial-mediated inflammation, disrupts circadian and metabolic homeostasis, impairs, and accelerates cognitive and motor decline. This work highlights a previously underappreciated role of the gut microbiome in restraining glial dysfunction and mitigating AD-like pathology, positioning microbial homeostasis as a critical modulator of neurodegenerative disease progression.

Zika virus (ZIKV) encephalitis induces cytokine-mediated cognitive deficits which persist long-term. Here, we determined if NOD2-mediated conversion of monocytes from Ly6CHi inflammatory to Ly6CLo anti-inflammatory phenotypes during ZIKV encephalitis preserves neural correlates of learning and memory within the hippocampus. Short-term administration of the NOD2 agonist, muramyl dipeptide (MDP), during peak ZIKV infection prevents synapse elimination and loss of adult hippocampal neurogenesis, without impacting CNS virologic control. Transcriptomic analyses of forebrain immune cells in MDP-treated mice revealed functional modulation of infiltrated monocytes and T cells, reducing their expression of pro-inflammatory cytokines, with limited effects on microglia, compared to controls. Notably, NOD2 activation in peripheral immune cells alone balances innate immune signals, preserving synapses, and increasing macrophage phagocytic capacities that do not target synapses. Our findings identify infiltrating Ly6CHi monocytes as key drivers of long-term cognitive dysfunction following ZIKV encephalitis and as potential therapeutic targets for limiting synapse loss. HighlightsO_LINOD2 activation via MDP phenotypically shifts monocyte subsets from inflammatory to anti-inflammatory during the acute phase of ZIKV encephalitis. C_LIO_LIShort-term MDP administration increases phagocytic machinery and reduces inflammatory cytokine/chemokine production within macrophage populations. C_LIO_LISynapse elimination is attenuated within the hippocampus of ZIKV-infected animals treated with MDP. C_LIO_LIMDP derived effects are mediated through peripherally derived immune cells. C_LI

Herpes Simplex virus type 1 (HSV-1) is a highly prevalent neurotropic virus from the alphaherpesviruses family. In recent years, a growing body of research has focused on the potential role of HSV-1 infections and recurrent reactivations in the pathophysiology of Alzheimers disease (AD). In particular, it has been hypothesized that HSV-1 could initiate or amplify the formation of neuropathological lesions characteristic of AD. To explore further this hypothesis, we adopted an integrated approach aiming at deciphering the impact of HSV-1 infection on AD molecular markers (A{beta} and Tau pathologies) and combining experimental animal models of in vivo infection, postmortem neuropathological analysis of AD brains, as well as in-vivo clinical analysis in AD patients. In animal models of peripheral (labial) infection with HSV-1 virus, we analyzed viral dissemination from peripheral tissues to the CNS, and the associated neuropathological consequences. Histological and molecular analyses revealed the occurrence of viral material (RNA, proteins) in the brainstem, the primary site of viral neuroinvasion, and in more anterior regions of the brain. Viral signatures were accompanied by early abnormal deposits of A{beta} peptides and accumulation of phosphoTau (pTau) proteins in various brain areas. Neuropathological examination of AD/control participants also underlined the presence of HSV-1 DNA in the human brainstem (pons) that was always associated with local A{beta}/Tau aggregates. Finally, in AD patients, associations were found between HSV-1 seropositivity and neuropathological lesion burden (region-specific Tau and A{beta} deposition detected by neuroimaging). Taken together, these data provide new evidence in favor of the involvement of HSV-1 in the pathophysiology of AD, stressing a possible causal link between HSV-1 infection, neuroinvasion and AD neuropathological hallmarks (A{beta} lesions and tauopathy).

Although remyelination, a central nervous system (CNS) regenerative process mediated by oligodendrocyte progenitor cells (OPCs), takes place in an inflammatory environment the long-term impact of inflammation on OPC remyelination capacity remains unclear. Here, we studied the short- and long-term impact of systemic inflammation on adult OPCs to assess whether transient inflammation triggers enduring chromatin remodelling indicative of inflammatory memory in OPCs. We observed long-lasting epigenetic modifications in response to both lipopolyssaccharide (LPS) and polyinosinic:polycytidylic acid (Poly(I:C)), but only LPS induced a tolerance-like memory. LPS-mediated tolerance-like memory enhanced OPC differentiation after demyelination in aged mice, reducing axonal damage. Our findings reveal OPC epigenetic memory of inflammation as a mechanism by which adult OPCs adapt to inflammatory challenges, which could be harnessed to reduce neuroinflammation and enhance remyelination efficiency in ageing and neurodegenerative diseases.