Molecular Neurodegeneration

Tauopathies, including Alzheimers disease, involve progressive neurodegeneration and sustained neuroinflammation. We present a multi-compartment transcriptomic atlas of 9.6-month-old PS19 tauopathy mice compared with wild-type (WT) controls (n=8/group), profiling cortical mRNA, cortical non-coding RNA (ncRNA), and plasma small extracellular vesicle (pEV) ncRNA. In the PS19 cortex, mRNA sequencing identified 917 differentially expressed genes (DEGs), with microglial deconvolution revealing a robust transition toward disease-associated microglia (DAM) gene signature and downregulation of genes involved in oxidative phosphorylation and cholesterol biosynthesis relative to WT. Cortical ncRNA profiling identified 466 differentially expressed ncRNAs, primarily circular RNAs (circRNAs; n=331). In pEVs, 822 ncRNAs were differentially abundant, of which 657 circRNAs were identified in PS19 compared to WT mice. Cross-compartment integration demonstrated that pEV miRNA gene targets functionally mirrored genes involved in the brains inflammatory and metabolic failure. We identified a core shared signature of 33 ncRNAs, including miR-5114 (up in brain, down in pEV), circ_0008242 and circ_0002153 (up in brain and pEV), and circ_0007688 (down in brain and pEV) differentially enriched across both brain and periphery in PS19 compared to WT mice. These results demonstrate that the pEV non-coding landscape effectively tracks central tau-mediated changes in the brain transcriptional response. This study identifies circRNAs as the most numerically perturbed ncRNA class and provides a foundation for non-invasive biomarker development in tauopathy.

Astrocytes are key regulators of lipid metabolism, and dysregulated astrocytic lipid processing is implicated in Parkinsons disease (PD) pathogenesis. Our prior genome-wide screens identified ACSBG1, an astrocyte-enriched acyl-CoA synthetase, as a candidate regulator of -synuclein (-Syn) levels. However, how ACSBG1 links lipid reprogramming to inflammatory astrocyte activation and -Syn pathology remains unknown. We compared the transcriptomic, cytokine, and lipid secretomes of TNF- and IL-1 stimulated primary astrocytes from wild-type (WT) and Acsbg1 knockout (KO) mice. In vivo, we crossed Acsbg1 KO mice with a Thy1--Syn PD model to assess behavior, neuroinflammation, synaptic integrity, and -Syn levels. Following cytokine exposure, Acsbg1 KO astrocytes mounted an attenuated inflammatory transcriptional response, secreting significantly fewer inflammatory mediators (e.g., IL-6, RANTES, MIP-3) and less long-chain Sphingosine 20:1 than WT astrocytes. Importantly, exogenous Sphingosine 20:1 or cytokines from WT reactive astrocytes induced neuronal -Syn phosphorylation (pS129). In vivo, Acsbg1 deletion in Thy1--Syn mice reduced astrogliosis, rescued synaptic and behavioral deficits, and decreased total and pS129--Syn. These findings establish ACSBG1 as a key regulator of inflammatory astrocyte signaling that contributes to -Syn phosphorylation via specific cytokine and lipid mediators, identifying ACSBG1 as a novel therapeutic target for modulating astrocyte-neuron communication in PD.

Microglial activation has been closely associated with accelerated ALS disease progression. However, specific microglial pathways that regulate microglial activation and ALS disease progression remain limitedly understood. Here, we determined the role of Clec7a (or Dectin-1), a core signature gene of disease-associated microglia (DAM) in ALS, in regulating microglial activation and ALS disease progression. Our spinal cord scRNA-Seq results found that Clec7a deficiency specifically attenuated microglial neuroimmune gene expression in SOD1G93A mice and human ALS. In addition, in vivo two-photon imaging of human (h) TDP43 phagocytosis by microglia in the cortex showed that Clec7a deficiency promotes microglial phagocytosis of pathological hTDP43 by enhancing microglial process dynamics. Subsequent survival analysis further showed that selective deletion of Clec7a in microglia mitigates motor neuron degeneration and delays disease progression in SOD1G93A ALS mice. Together, our results establish that Clec7a is a key regulator in shaping disease microglial functions and promotes disease progression in ALS.

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.

Astrocytes directly influence neuronal survival and increasingly are understood to contribute to the progression of neurodegenerative diseases including Parkinsons disease (PD). Mitochondrial damage is a hallmark of PD pathology in both neurons and astrocytes. Damaged mitochondria are cleared by PINK1/Parkin-mediated mitophagy; loss-of-function mutations in either PINK1 or Parkin are sufficient to cause PD. Neuronal mitophagy is well-studied, but far less is known about how mitochondrial dysfunction in astrocytes affects neural health. While microglial release of pro-inflammatory cytokines has been shown to induce astrocytes to mount their own inflammatory response, we hypothesize that a more direct pathway is involved, and that mitochondrial damage to astrocytes directly triggers release of proinflammatory cytokines. To address these questions, we treated primary murine cortical astrocytes with oxidative phosphorylation (OXPHOS) inhibitors antimycin A (AA) and oligomycin A (OA) and observed the PINK1-dependent accumulation of Parkin on damaged mitochondria, leading to phospho-ubiquitination of proteins in the outer mitochondrial membrane and the recruitment of the autophagy receptor SQSTM1/p62. To identify transcriptional changes caused by mitochondrial damage and the resulting activation of mitophagic machinery, we performed bulk RNA-sequencing on astrocytes isolated from WT, PINK1-/-, or Parkin-/- mice treated with AA/OA or a vehicle control. In WT astrocytes, TNF- signaling via NF-{kappa}B was the most significantly upregulated pathway following OXPHOS inhibition. OXPHOS inhibitor treatment also stimulated p62 expression, while NF-{kappa}B inhibition prevented this upregulation. Astrocytic secretion of cytokines, including TNF-, was increased following mitochondrial damage; this secretion was dependent on NF-{kappa}B activation and occurred at levels sufficient to induce mitochondrial depolarization in hippocampal neurons. Compared to WT astrocytes, PINK1-/- astrocytes showed a significant reduction in transcriptional signatures associated with TNF- signaling following mitochondrial damage, while Parkin-/- astrocytes exhibited upregulation of both IFN-{gamma} and IFN- signaling. These findings indicate altered inflammatory responses to mitochondrial damage in the absence of functional PINK1 or Parkin. Finally, we analyzed scRNA-sequencing data from substantia nigra astrocytes harvested from human brain tissue from PD-positive or control samples. Distinct clusters comprised predominantly of PD-positive or control astrocytes emerged. Astrocytes in the PD-positive cluster were enriched for NF-{kappa}B, IFN- and IFN-{gamma} responses, consistent with the signaling observed in vitro post-OXPHOS inhibition. Together, these findings identify inflammatory signatures activated by mitochondrial damage in astrocytes, and establish this pathway as a potential contributor to neuroinflammation in PD.

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.

Retrospective studies in patients with non-muscle invasive bladder cancer (NMIBC) have reported a significant reduction in Alzheimers disease (AD) incidence (12-78%) among Bacillus Calmette-Guerin (BCG) recipients versus controls. To investigate the underlying mechanisms, we evaluated BCG in the PS19 mouse model of tauopathy. We found that BCG administration reduced hippocampal phospho-tau and microgliosis while preserving neuronal markers. In vivo volumetric T2-MRI demonstrated attenuation of brain atrophy accompanied by increased glutamate-weighted CEST-MRI signals. Functionally, BCG-treated mice showed improved performance in the novel object recognition test (NORT), as well as improved body-weight maintenance and survival. Transcriptomic profiling of the hippocampus revealed near complete normalization of the PS19 disease-associated gene expression signature towards that of healthy controls. Flow cytometric profiling of brain myeloid populations demonstrated a reduction in activated resident microglia, but total microglia cells remain elevated. Moreover, an increase of the co-stimulatory marker CD80 on the recruited peripheral myeloid cells ensues following BCG treatment. Consistent with this shift in myeloid state, primary brain myeloid cells from BCG-treated mice also exhibited enhanced phagocytosis of FITC-labeled tau fibrils and increased lactate production. Together, these findings indicate that BCG induces systemic and CNS myeloid cell reprogramming that limits neuroinflammation, enhances tau clearance, and rescues cognitive and neurodegenerative phenotypes in a tauopathy model. BCG is a safe, readily available therapy that merits consideration as a preventive agent against dementia. One sentence summaryBCG therapy prevents tauopathy in PS19 mouse model.

TDP-43 dysfunction is a defining feature of amyotrophic lateral sclerosis (ALS), yet no biofluid biomarker directly measures its functional activity. We developed a serum-based homogeneous time-resolved FRET (hTR-FRET) assay that quantifies TDP-43 RNA-binding activity using synthetic UU rich RNA probes. We analyzed 1,080 serum samples from controls, sporadic ALS, and genetic subgroups (C9orf72, SOD1) across multiple biorepositories. Cross-sectionally, TDP-43 ligation activity was elevated in ALS (mean 390 a.u.) versus controls (304 a.u.), yielding AUC = 0.79. Genotype means were 392 a.u. (sporadic), 382 a.u. (C9orf72), and 323 a.u. (SOD1); with a 366 a.u threshold achieved 95% specificity against controls. Longitudinally, Target ALS showed a modest but significant inverse correlation between TDP-43 activity and ALSFRS-R, while other cohorts exhibited similar non-significant trends. Elevated signal likely reflects increased extracellular, probe-competent TDP-43 species. This assay provides direct functional measurement of disease-relevant TDP-43 biology, supporting applications in diagnostic discrimination, genotype stratification, and progression monitoring in prospective studies.

Alzheimers disease (AD) is a relentlessly progressive, fatal neurodegenerative disorder that results in widespread protein dysfunctions. However, the full extent of aberrant proteomic changes in AD and their impact remains unknown, in part, because of the challenges of comprehensively measuring the proteome. Here, we used plexDIA, an approach that provides deep proteomic coverage and high throughput by parallelizing the acquisition of peptides and samples, to characterize proteomic changes in AD. Using human dorsolateral prefrontal cortex tissue, we identified 281 differentially abundant proteins in AD. By systematically analyzing compartment and protein complex-specific shifts in protein abundance, we identified an AD-specific decrease in levels of the 20S proteasome, the catalytic core of the cells primary protein degradation pathway. This alteration was accompanied by widespread decreases in proteasome subunit stoichiometries. Many proteasome substrate proteins were negatively correlated with 20S levels and increased in AD, suggesting that reduced 20S levels leads to abnormal protein accumulation. By analyzing proteins increased in AD, we identify key properties of such proteins: They have fast degradation rates, they contain signal sequences that allow them to be targeted for proteasomal degradation, and they are targeted by quality control pathways that recognize mislocalized proteins. Changes in these gene products at the protein and mRNA levels were highly discordant, providing additional evidence for increased protein abundance driven by impaired clearance. We also identified coherent sets of ubiquitin system enzymes, proteins that target substrates for proteasomal degradation, whose levels robustly discriminate AD from non-AD samples. One subset exhibited consistent increases in AD, while another, which contained the tau E3 ligase Cul5, exhibited consistent decreases, revealing complex changes in the ubiquitin system in AD. Taken together, our results suggest that decreased ubiquitin-proteasome system capacity and impaired clearance of short-lived and mislocalized proteins contribute substantially to proteopathic burden in AD.

Presenilin 2 (PS2) mutations cause familial Alzheimers disease, yet their effects beyond amyloid processing remain poorly understood. Here, we investigated how PS2 deletion and the N141I mutation affect neuronal lipid homeostasis and mitochondrial dynamics in mouse primary neurons. Both PS2 deletion and N141I mutation reduced neuronal lipid content. However, exogenous lipid supplementation rescued this deficit only in N141I-expressing neurons, indicating a partial loss-of-function effect. N141I neurons also displayed reduced OPA1, a mitochondrial fusion regulator, restored by lipid supplementation. RNA-sequencing identified Gbf1, a Golgi-specific guanine nucleotide exchange factor, as selectively downregulated in N141I but not knockout tissue, which was confirmed at the protein level in mouse brain and primary neurons. Gbf1 knockdown in mouse embryonic fibroblasts (MEFs) recapitulated the N141I lipid profile. Together, these findings reveal a PS2-GBF1-lipid-mitochondria axis disrupted specifically by the N141I mutation, suggesting an amyloid-independent pathway contributing to neurodegeneration and identifying potential therapeutic targets for familial Alzheimers disease.

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.

Apolipoprotein E (ApoE) is the principal lipid transport protein in the central nervous system and the strongest genetic modifier of late-onset Alzheimers disease (AD) risk. The three common isoforms, ApoE2, ApoE3, and ApoE4, differ in their propensity to self-associate, with ApoE4 forming oligomers more readily than ApoE3 or ApoE2. This enhanced self-association is proposed to reduce the pool of lipid-competent monomeric ApoE4 available for cholesterol transport and amyloid-{beta} clearance, contributing to AD pathogenesis. Here we describe a quantitative, cell-based split-luciferase complementation assay for ApoE self-association using the NanoBiT system, in which SmBiT- and LgBiT-tagged ApoE produced by HEK293 cells are combined and luminescence is measured. ApoE4 shows significantly enhanced self-association relative to ApoE3, while ApoE2 is no different from ApoE3. Testing a panel of naturally occurring and engineered variants demonstrates that the C-terminal self-association interface is the primary determinant of isoform-specific differences: two APOE {varepsilon}3-backbone C-terminal variants, Jacksonville (V236E) and W276C, both reduce self-association below ApoE3 levels, while the APOE {varepsilon}4-backbone protective variant R251G and the engineered domain-interaction probe R61T both reduce ApoE4 self-association to the level of ApoE3. In contrast, the Christchurch variant (R136S), the African-ancestry risk variant R145C, and the Admixed American risk variant R189C do not alter self-association. These findings establish a sensitive cell-based assay for ApoE self-association and highlight the C-terminal domain as a potential therapeutic target for normalizing ApoE4 function.

T cells modulate disease associated neuroinflammation in Parkinsons disease (PD). We report that circulating CD4+ T cells from people with PD have a dysregulated transcriptional and cytokine response to fasting and refeeding and an altered metabolic profile. The CD4+ T cell secretome mediates a metabolic program in neurons that is impaired in PD, revealing dysfunctional neuro-immune signalling that may contribute to disease pathology.

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

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.

Alzheimers disease (AD), the leading cause of dementia, is characterized by early synaptic dysfunction that precedes overt cognitive decline. While amyloid-{beta} and Tau remain central to AD pathogenesis, molecular triggers of synapse weakening remain unclear. Here, we investigated AETA, a novel brain-secreted peptide derived from amyloid precursor protein (APP), as a potential mediator of synapse dysfunction in AD. We previously identified AETA as a unique modulator of NMDA receptor activity in the healthy brain; however, its role in AD etiology was yet to be explored. Post-mortem analyses of human hippocampal and prefrontal cortex tissues revealed significantly elevated AETA levels in AD patients, particularly in females. To further explore the contribution of AETA to AD synaptic pathology, we analyzed a new mouse model, the AETA-m mouse, exhibiting chronically increased brain AETA expression. Hippocampi of female AETA-m mice display an increase in the number of astrocyte and microglia, but no overt neuroinflammation. RNA sequencing of female AETA-m hippocampi revealed alterations in synaptic gene expression that closely paralleled those observed in vulnerable human AD brain regions, most notably in the hippocampus. These two phenotypes were absent in males. Functionally, hippocampal neurons from AETA-m mice displayed impaired NMDA receptor signaling, dendritic spine loss, and memory deficits especially in females, mirroring early AD-associated synaptic dysfunction. Together, these findings identify AETA as a novel key contributor of synaptic vulnerability in AD and associated memory processing, especially in females. Targeting AETA signaling may therefore offer new therapeutic avenues for preventing or mitigating synaptic and cognitive decline in AD.

Mislocalization and aggregation of transactive response DNA-binding protein 43 kDa (TDP-43) represent a neuropathological hallmark of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) and are increasingly recognized in Alzheimers disease (AD) and limbic-predominant age-related TDP-43 encephalopathy (LATE). However, the in vivo value of CSF TDP-43 as a biomarker and its relation to established markers remains unclear. We quantified CSF concentrations of TDP-43 using ELISA in 25 controls, 32 ALS, 9 probable LATE, and 24 AD patients. CSF TDP-43 levels differed significantly between groups, with the highest concentrations in LATE, exceeding both ALS and AD. ALS and AD showed intermediate, comparable increases versus controls. In parallel, conventional AD biomarkers (t-tau, p-tau, and amyloid-b) showed the expected AD-typical profile but remained largely unaltered in probable LATE, indicating a dissociation between TDP-43 an AD-type pathology. These findings identify CSF TDP-43 as a promising candidate biomarker for LATE, characterized by disproportionate elevation in the absence of AD-type biomarker changes, and neurodegeneration in aging populations.

APOE gene variants encoding the apolipoprotein E (ApoE) protein are strong genetic modifiers of risk of Alzheimers disease (AD) with the APOE {varepsilon}4 allele (APOE4) associated with substantially increased disease risk, APOE {varepsilon}2 allele (APOE2) associated with decreased risk and APOE {varepsilon}3 allele (APOE3) considered neutral. Recently the Christchurch variant of APOE3 (APOE3Ch) has been shown to protect people from familial AD. Despite this strong evidence for APOE mediating AD risk, the exact biological mechanisms through which APOE influences pathogenesis remain unknown. Our previous work implicates APOE in synapse degeneration in AD with exacerbated plaque-associated synapse loss, increased accumulation of amyloid beta in synapses, and increased ingestion of synapses by glia around plaques observed in APOE4 carriers. Here we used a cell culture system to test the hypothesis that APOE isoforms would differentially regulate phagocytosis of synapses isolated from human post-mortem AD brain tissue. Humanized APOE knock-in astrocyte cell lines exhibited isoform-dependent differences in phagocytic activity with APOE2 < APOE3 < APOE4 as would be expected if APOE genotype mediated risk at least in part through synapse phagocytosis. Interestingly, astrocytes with the protective APOE3Ch allele phagocytosed synapses similarly to APOE4 astrocytes indicating this variant does not likely protect from AD by reducing astrocyte phagocytosis of synapses. These findings indicate that APOE isoforms differentially regulate astrocytic engulfment of AD-associated synaptic material. These isoform-specific effects are not explained by differences in phosphatidylserine recognition, suggesting the involvement of additional mechanisms underlying ApoE-dependent modulation of astrocyte function. Significance StatementSekizar and colleagues tested whether APOE, the most important genetic risk factor for Alzheimers disease, could affect risk by influencing the ability of astrocytes to phagocytose synapses. Using astrocyte cell lines exposed to synapses isolated from Alzheimers disease brain tissue, they demonstrate that different APOE isoforms differentially modulate astrocyte-mediated synapse phagocytosis. These results will inform future work to develop therapies that aim to preserve synapses in Alzheimers disease.

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.

Importance: Alzheimer disease (AD) pathogenesis begins decades before clinical symptoms, yet environmental determinants of early disease risk, particularly during fetal development, remain largely uncharacterized. Prenatal exposure to dichlorodiphenyldichloroethylene (DDE), the primary persistent metabolite of DDT, is a biologically plausible early-life contributor to AD risk given long half-life in human tissue and higher levels observed in AD patients. However, prospective human evidence linking prenatal DDE to midlife AD-relevant outcomes is absent. Objective: To determine whether prenatal DDE exposure is associated with plasma AD biomarkers and cognitive performance in early midlife offspring, and whether APOE {epsilon}4 genotype modifies these associations. Design: Observational cohort analysis nested within the Child Health and Development Studies (CHDS), a population-based birth cohort. Setting: CHDS enrolled pregnant women between 1959-1967 in the San Francisco Bay Area. Participants: Among 367 eligible adult offspring who participated in a follow-up study (2010-2013) at mean age 49.3 years, 179 with available prenatal DDE measurements were included. Main Outcomes and Measures: Prenatal DDE levels from maternal serum. Primary outcomes were plasma A{beta}42/40 ratio and Digit Symbol Substitution Test (DSST) performance. Secondary outcomes included plasma pTau217, GFAP, NfL and APOE genotype. Results: Among 179 participants (56% female; 26% APOE {epsilon}4 carriers), mean prenatal DDE was 47.4 (25.4) ng/mL. Higher prenatal DDE was associated with lower DSST scores ({beta}=-0.021, 95% CI, -0.041 to -0.001, P=0.039) and lower plasma A{beta}42/40 ratio ({beta}=-0.079, 95% CI, -0.133 to -0.024, P=0.005) per ng/mL DDE, adjusting for sex, race, education, and APOE {epsilon}4 status. Associations were strongest among APOE {epsilon}4 non-carriers for DSST ({beta}=-0.033, 95% CI, -0.050 to -0.016, P=0.001) and A{beta}42/40 ratio ({beta}=-0.101, 95% CI, -0.161 to -0.040, P=0.001). No significant associations were observed for pTau217, GFAP, or NfL. Conclusions and Relevance: In this prospective birth cohort study, prenatal exposure to a persistent environmental toxicant was associated with lower plasma A{beta}42/40 ratio and worse cognitive performance in early midlife, consistent with DDE accelerating the preclinical trajectory of AD-related biological changes decades before symptom onset. These findings support a life-course framework for AD risk and identify prenatal DDE as a potentially modifiable determinant of early AD-related pathology amenable to prevention.