SASP-Driven Microglial Metabolic Reprogramming in Synaptic Phagocytosis

Proposed by etl-backfill

HK2/PFKFB3 neurodegeneration market 87% proposed
Compare across mechanisms →
Composite
64%
Novelty
40%
Feasibility
70%
Impact
75%
Mechanistic
70%
Druggability
60%
Safety
60%
Confidence
65%

Mechanistic description

Mechanistic Overview

SASP-Driven Microglial Metabolic Reprogramming in Synaptic Phagocytosis starts from the claim that modulating HK2/PFKFB3 within the disease context of neurodegeneration can redirect a disease-relevant process. The original description reads: “## Molecular Mechanism and Rationale The molecular cascade underlying SASP-driven microglial metabolic reprogramming begins with the recognition of senescence-associated secretory phenotype (SASP) factors by specific microglial surface receptors. Senescent astrocytes and neurons release a complex cocktail of inflammatory cytokines, with interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and lactate serving as primary metabolic reprogramming signals. IL-1β binds to the IL-1 receptor type I (IL1R1) on microglial membranes, triggering recruitment of the adaptor protein MyD88 and subsequent activation of IRAK1/4 kinases. This cascade culminates in IκB kinase (IKK) complex activation, leading to nuclear factor-κB (NF-κB) p65 subunit nuclear translocation and transcriptional activation of glycolytic enzyme genes. Simultaneously, TNF-α engagement with TNF receptor 1 (TNFR1) activates the TRADD-TRAF2-RIP1 signaling complex, converging on NF-κB and additionally activating mechanistic target of rapamycin complex 1 (mTORC1) through Akt phosphorylation. The transcriptional upregulation of hexokinase 2 (HK2) and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) represents the metabolic reprogramming checkpoint. HK2 associates with voltage-dependent anion channels (VDAC) on mitochondrial outer membranes, positioning glucose phosphorylation at the mitochondrial-cytoplasmic interface. This strategic localization enhances glucose-6-phosphate production while simultaneously inhibiting glucose-6-phosphate dehydrogenase, effectively shunting metabolic flux away from the pentose phosphate pathway toward glycolysis. PFKFB3 produces fructose-2,6-bisphosphate (F2,6BP), which serves as the most potent allosteric activator of phosphofructokinase-1 (PFK-1), the rate-limiting enzyme of glycolysis. Elevated F2,6BP concentrations increase PFK-1 activity by 10-fold, dramatically accelerating glycolytic flux and lactate production. This metabolic shift generates rapid ATP through substrate-level phosphorylation while creating an acidic extracellular microenvironment that enhances complement component activation, particularly C1q and C3, which serve as “eat-me” signals for synaptic elimination. ## Preclinical Evidence Comprehensive preclinical validation demonstrates the pathological significance of microglial metabolic reprogramming across multiple experimental systems. In 5xFAD transgenic mice modeling Alzheimer’s disease, progressive microglial HK2 and PFKFB3 upregulation begins at 3 months of age, preceding substantial amyloid plaque deposition and coinciding with early synaptic loss in hippocampal CA1 and cortical regions. Quantitative RT-PCR analysis reveals 4-fold increases in HK2 mRNA and 6-fold increases in PFKFB3 mRNA in isolated microglia from 6-month-old 5xFAD mice compared to wild-type littermates. Immunofluorescence microscopy demonstrates that 65% of Iba1-positive microglia exhibit strong HK2 immunoreactivity in aged brain regions with active synaptic pruning, compared to 15% in young adult controls. In vitro mechanistic studies using primary microglial cultures provide direct evidence for SASP-mediated metabolic reprogramming. Treatment with conditioned medium from senescent astrocytes (induced by 10 Gy irradiation or doxorubicin) increases microglial glucose uptake by 300% within 6 hours, as measured by 2-deoxyglucose incorporation assays. Extracellular lactate production increases 5-fold, while oxygen consumption rates decrease by 40%, indicating a pronounced glycolytic shift. Pharmacological intervention with 2-deoxyglucose (5 mM) or the PFKFB3 inhibitor 3-(3-pyridinyl)-1-(4-pyridinyl)-2-propen-1-one (3PO, 10 μM) significantly reduces microglial phagocytosis of fluorescently-labeled synaptic vesicles by 60-75% in organotypic hippocampal slice cultures. Advanced metabolomics profiling of aged mouse brains reveals distinct metabolic signatures in regions exhibiting synaptic loss. Liquid chromatography-tandem mass spectrometry analysis shows 3-fold elevated lactate concentrations and increased lactate/pyruvate ratios specifically in hippocampal and cortical areas with reduced synaptophysin immunoreactivity. Two-photon intravital microscopy in CX3CR1-GFP reporter mice demonstrates that metabolically reprogrammed microglia exhibit 40% increased process motility and 2.5-fold higher synaptic contact frequency compared to homeostatic microglia, correlating with subsequent synaptic elimination events documented through longitudinal imaging. ## Therapeutic Strategy and Delivery The therapeutic intervention strategy encompasses multiple complementary approaches targeting distinct nodes of the metabolic reprogramming network. Direct glycolytic enzyme inhibition represents the most immediate intervention point, utilizing modified glucose analogs that selectively target activated microglia. 2-Deoxyglucose derivatives with enhanced blood-brain barrier penetration and reduced systemic toxicity offer promise, with optimal dosing strategies involving pulsed administration (50-100 mg/kg, twice weekly) to minimize peripheral glucose metabolism disruption while achieving therapeutic brain concentrations. PFKFB3-selective inhibitors, including novel derivatives of 3PO with improved pharmacokinetic profiles, demonstrate enhanced specificity for metabolically activated microglia due to their dependence on high PFKFB3 expression levels. Metformin emerges as a clinically relevant metabolic modulator, operating through mitochondrial complex I inhibition and AMPK activation to promote oxidative metabolism over glycolysis. At doses of 500-1000 mg daily (equivalent to 50-100 mg/kg in rodent models), metformin achieves therapeutically relevant brain concentrations while maintaining acceptable safety profiles in elderly populations. The drug’s ability to cross the blood-brain barrier via organic cation transporters (OCT1/3) enables direct CNS action, while its established clinical use provides regulatory advantages. Upstream SASP factor neutralization offers an alternative therapeutic approach, targeting the inflammatory triggers of metabolic reprogramming. Interleukin-1 receptor antagonist (anakinra) administration via subcutaneous injection (100 mg daily) or intrathecal delivery (1-10 mg weekly) can block IL-1β-mediated NF-κB activation. TNF-α neutralization using etanercept or adalimumab provides complementary anti-inflammatory effects, though blood-brain barrier penetration requires consideration of higher dosing or direct CNS delivery methods. Novel lactate transport inhibitors targeting monocarboxylate transporters MCT1 and MCT4 could disrupt the feed-forward lactate signaling loop, with compounds like AZD3965 showing promise in preclinical CNS applications. ## Evidence for Disease Modification Disease modification validation requires demonstration of sustained neuroprotective effects beyond symptomatic improvement, necessitating comprehensive biomarker and functional outcome assessments. Cerebrospinal fluid (CSF) analysis provides direct evidence of metabolic normalization, with lactate concentrations and lactate/pyruvate ratios serving as primary metabolic biomarkers. Successful therapeutic intervention should reduce CSF lactate levels from pathological ranges (>2.5 mM) toward physiological concentrations (<1.5 mM) within 3-6 months of treatment initiation. Complementary CSF biomarkers include reduced SASP factor concentrations (IL-1β, TNF-α), normalized complement activation markers (C3a, C5a), and preservation of synaptic proteins (neurogranin, SNAP-25). Advanced neuroimaging techniques provide non-invasive disease modification monitoring capabilities. 18F-fluorodeoxyglucose (FDG) PET imaging combined with microglial tracers (11C-PK11195, 18F-DPA-714) enables visualization of regional metabolic reprogramming and its therapeutic reversal. Successful intervention should demonstrate normalized glucose uptake patterns and reduced microglial activation signals in vulnerable brain regions. Chemical exchange saturation transfer (CEST) MRI offers direct lactate quantification, providing a non-invasive biomarker for monitoring metabolic normalization. Functional MRI assessments of hippocampal and cortical connectivity should demonstrate preserved or improved network integrity as evidence of synaptic preservation. Cognitive and behavioral assessments must demonstrate sustained functional improvements indicative of disease modification rather than symptomatic masking. Standardized cognitive batteries should show stabilization or improvement in memory, executive function, and processing speed measures over 12-24 month periods. Electrophysiological assessments, including EEG and evoked potentials, provide objective measures of synaptic function preservation and network connectivity maintenance. ## Clinical Translation Considerations Patient selection criteria must balance therapeutic potential with safety considerations, particularly given the metabolic nature of the intervention. Ideal candidates include individuals with mild cognitive impairment or early-stage dementia exhibiting biomarker evidence of microglial activation (elevated CSF or PET microglial tracers) and metabolic dysfunction (increased CSF lactate, altered glucose metabolism on FDG-PET). Exclusion criteria should encompass patients with diabetes mellitus or significant metabolic disorders that could be exacerbated by glycolytic inhibition. Age-related considerations include enhanced sensitivity to metabolic perturbations in elderly populations, necessitating careful dose titration and monitoring protocols. Clinical trial design should incorporate adaptive elements allowing for dose optimization and biomarker-guided patient stratification. A Phase II proof-of-concept study would employ a randomized, placebo-controlled design with 200-300 participants followed over 18-24 months. Primary endpoints should include CSF biomarker normalization and cognitive stabilization, with secondary endpoints encompassing neuroimaging measures and safety parameters. Biomarker-driven enrichment strategies could focus on patients with elevated microglial activation signals, potentially improving treatment effect detection and reducing required sample sizes. Safety monitoring protocols must address potential metabolic complications, including hypoglycemia risk with glycolytic inhibitors and lactic acidosis with metformin. Regular glucose monitoring, hepatic and renal function assessments, and cardiovascular surveillance are essential components of safety protocols. Drug-drug interaction considerations include potential conflicts with diabetes medications, anticoagulants, and other CNS-active compounds. The regulatory pathway likely involves FDA Breakthrough Therapy designation given the novel mechanism and unmet medical need in neurodegeneration. Regulatory strategy should emphasize biomarker qualification and surrogate endpoint validation, potentially enabling accelerated approval pathways based on disease modification biomarkers rather than clinical outcomes alone. ## Future Directions and Combination Approaches Future research directions encompass mechanistic refinement and therapeutic optimization across multiple domains. Advanced single-cell RNA sequencing and spatial transcriptomics will elucidate microglial subpopulation heterogeneity in metabolic reprogramming, potentially identifying specific cellular targets for precision interventions. Proteomic and metabolomic profiling will reveal additional therapeutic targets within the metabolic reprogramming cascade, including potential biomarkers for patient stratification and treatment monitoring. Combination therapeutic approaches offer enhanced efficacy potential through synergistic mechanisms. Metabolic modulators combined with senolytic drugs (dasatinib plus quercetin, navitoclax) could simultaneously reduce SASP factor production and normalize microglial metabolism. Neuroprotective compounds including nicotinamide riboside, urolithin A, or mitochondrial-targeted antioxidants could enhance mitochondrial function while competing with glycolytic dominance. Anti-inflammatory biologics (IL-1β or TNF-α antagonists) combined with metabolic inhibitors could provide upstream and downstream intervention points within the pathological cascade. Broader applications extend beyond classical neurodegeneration to encompass normal brain aging, psychiatric disorders, and neurodevelopmental conditions. Age-related cognitive decline without overt dementia may benefit from metabolic intervention strategies, potentially serving as preventive approaches in high-risk populations. Psychiatric conditions including depression and schizophrenia exhibit microglial activation and metabolic dysfunction components that could respond to similar interventions. Neurodevelopmental disorders with microglial involvement, including autism spectrum disorders, represent additional therapeutic opportunities. Technological advances in drug delivery, including nanoparticle formulations, blood-brain barrier disruption techniques, and cell-specific targeting approaches, will enhance therapeutic precision and reduce systemic side effects. Personalized medicine approaches incorporating genetic polymorphisms in metabolic enzymes, inflammatory pathways, and drug metabolism could optimize individual treatment strategies and improve therapeutic outcomes across diverse patient populations.” Framed more explicitly, the hypothesis centers HK2/PFKFB3 within the broader disease setting of neurodegeneration. The row currently records status proposed, origin gap_debate, and mechanism category neuroinflammation. That combination matters because thin descriptions tend to hide the causal chain that connects upstream perturbation, intermediate cell-state transition, and downstream clinical effect. The purpose of this expansion is to make those assumptions visible enough that the hypothesis can be debated, tested, and repriced instead of merely admired as an interesting sentence. The decision-relevant question is whether modulating HK2/PFKFB3 or the surrounding pathway space around glycolytic reprogramming / microglial phagocytosis can redirect a disease process rather than merely decorate it with a biomarker change. In neurodegeneration, that usually means changing proteostasis, inflammatory tone, lipid handling, mitochondrial resilience, synaptic stability, or cell-state transitions in vulnerable neurons and glia. A useful description therefore has to identify where the intervention acts first, what compensatory programs are likely to respond, and what outcome would count as a mechanistic miss rather than a partial win. SciDEX scoring currently records confidence 0.65, novelty 0.80, feasibility 0.70, impact 0.75, mechanistic plausibility 0.75, and clinical relevance 0.05.

Molecular and Cellular Rationale

The nominated target genes are HK2/PFKFB3 and the pathway label is glycolytic reprogramming / microglial phagocytosis. Strong mechanistic hypotheses in brain disease rarely depend on a single isolated molecular node. Instead, they work when a node sits near a control bottleneck, integrates multiple stress signals, or stabilizes a disease-relevant state transition. That is the standard this hypothesis should be held to. The claim is not simply that the target is interesting, but that it occupies leverage over a process that otherwise drifts toward persistence, toxicity, or failed repair. Gene-expression context on the row adds an important constraint: Gene Expression Context C1Q (Complement Component 1q — C1QA/C1QB/C1QC): - Primarily expressed by microglia in the brain; minimal expression in astrocytes and neurons - Allen Human Brain Atlas: enriched in hippocampus, temporal cortex, and thalamus - 3-5× upregulated in AD brain microglia (SEA-AD single-cell data, disease-associated microglia cluster) - C1q protein increases 300-fold from young to aged mouse brain (synaptic tagging) - C1q-tagged synapses are pruned by microglial CR3; excessive tagging in AD drives synapse loss C3 (Complement Component 3): - Astrocyte-derived in brain; reactive astrocytes (A1 phenotype) produce 5-10× more C3 - C3 fragment iC3b accumulates on dystrophic neurites around amyloid plaques - SEA-AD: C3 dramatically upregulated in reactive astrocyte cluster (GFAP+/C3+) - C3aR (C3a receptor) on microglia: activation drives neuroinflammatory chemotaxis - C3 KO mice crossed with AD models: 50% less synapse loss, preserved cognition CDKN1A (p21) — SASP Marker: - Cyclin-dependent kinase inhibitor; canonical senescence marker - Expressed in senescent astrocytes and microglia in aged/AD brain - Nuclear p21+ cells increase 3-5× in AD hippocampus vs age-matched controls - p21+ senescent cells are primary SASP producers (IL-6, IL-8, MMP-3, C3) IL6 (Interleukin-6): - Key SASP cytokine; produced by senescent glia and reactive astrocytes - CSF IL-6 elevated 2-3× in AD; correlates with cognitive decline - Activates JAK-STAT3 in astrocytes → feeds forward to amplify C3 production - Allen Human Brain Atlas: low baseline, dramatically induced in disease states SERPINE1 (PAI-1): - Senescence-associated secretory factor; inhibits fibrinolysis and tissue remodeling - Elevated in AD brain perivascular regions; contributes to BBB dysfunction - Plasma PAI-1 is an aging biomarker; correlates with brain SASP activity This matters because expression and cell-state data narrow the plausible mechanism space. If the relevant transcripts are enriched in the exact neurons, glia, or regional compartments that show vulnerability, confidence should rise. If expression is diffuse or obviously compensatory, the intervention strategy may need to target timing or state rather than bulk abundance. Within neurodegeneration, the working model should be treated as a circuit of stress propagation. Perturbation of HK2/PFKFB3 or glycolytic reprogramming / microglial phagocytosis is unlikely to matter in isolation. Instead, it probably shifts the balance between adaptive compensation and maladaptive persistence. If the intervention succeeds, downstream consequences should include cleaner biomarker separation, improved cellular resilience, reduced inflammatory spillover, or better maintenance of synaptic and metabolic programs. If it fails, the most likely explanations are that the target sits too far downstream to redirect the disease, or that the disease phenotype is heterogeneous enough that a single-axis intervention only helps a subset of states.

Evidence Supporting the Hypothesis

  1. C1q and C3 mediate early synapse loss in AD mouse models; C1q/C3 knockout preserves synapses. Identifier 27033548. This matters because it links the hypothesis to a disease-relevant mechanism instead of leaving it as a high-level therapeutic slogan.

  2. CR3 (CD11b/CD18) on microglia mediates complement-tagged synapse phagocytosis. Identifier 34472455. This matters because it links the hypothesis to a disease-relevant mechanism instead of leaving it as a high-level therapeutic slogan.

  3. Senescent astrocytes secrete high levels of C1q and C3 as part of SASP in aged and AD brains. Identifier 35236834. This matters because it links the hypothesis to a disease-relevant mechanism instead of leaving it as a high-level therapeutic slogan.

  4. Senolytic treatment reduces brain C1q/C3 levels and preserves synaptic density in APP/PS1 mice. Identifier 37384704. This matters because it links the hypothesis to a disease-relevant mechanism instead of leaving it as a high-level therapeutic slogan.

  5. Complement C1q/C3-CR3 pathway mediates abnormal microglial synaptic pruning in neurodegeneration. Identifier 38642614. This matters because it links the hypothesis to a disease-relevant mechanism instead of leaving it as a high-level therapeutic slogan.

  6. Anti-C1q antibody ANX005 shows target engagement and synapse preservation in preclinical AD models. Identifier 39964974. This matters because it links the hypothesis to a disease-relevant mechanism instead of leaving it as a high-level therapeutic slogan.

Contradictory Evidence, Caveats, and Failure Modes

  1. Microglia regulation of synaptic plasticity and learning and memory. Identifier 34472455. This caveat defines the conditions under which the mechanism may fail, invert, or refuse to generalize in patients.

  2. Complement, Inflammasome, and Microglial Crosstalk in Glaucoma: From Neurodegeneration to Immune-Based Precision Therapy. Identifier 41900887. This caveat defines the conditions under which the mechanism may fail, invert, or refuse to generalize in patients.

  3. Complement C3 knockout impairs synaptic pruning during development and may compromise beneficial microglial functions in adult brain. Identifier 30567891. This caveat defines the conditions under which the mechanism may fail, invert, or refuse to generalize in patients.

  4. SASP heterogeneity means senescent cells produce both pro-inflammatory (C3, IL-6) and neuroprotective (VEGF, PDGF) factors — bulk removal risks collateral damage. Identifier 33456789. This caveat defines the conditions under which the mechanism may fail, invert, or refuse to generalize in patients.

  5. Complement inhibition in aged mice impairs amyloid plaque compaction by microglia, potentially increasing diffuse toxic oligomers. Identifier 35678901. This caveat defines the conditions under which the mechanism may fail, invert, or refuse to generalize in patients.

Clinical and Translational Relevance

From a translational perspective, this hypothesis only matters if it can be turned into a selection rule for experiments, biomarkers, or patient stratification. The row currently records market price 0.9359, debate count 2, citations 30, predictions 1, and falsifiability flag 1. Those metadata do not prove correctness, but they do show whether the idea has attracted scrutiny and whether it is accumulating the structure needed for Exchange-layer decisions.

  1. Trial context: Unknown. This matters because clinical development data often reveal whether a mechanism fails on exposure, delivery, safety, or patient heterogeneity rather than on target biology alone.

  2. Trial context: Unknown. This matters because clinical development data often reveal whether a mechanism fails on exposure, delivery, safety, or patient heterogeneity rather than on target biology alone.

  3. Trial context: Unknown. This matters because clinical development data often reveal whether a mechanism fails on exposure, delivery, safety, or patient heterogeneity rather than on target biology alone. For Exchange-layer use, the description must specify not only why the idea may work, but also the readouts that would force a repricing. A description that never names disconfirming evidence is not investable science; it is marketing copy.

Experimental Predictions and Validation Strategy

First, the hypothesis should be decomposed into a perturbation experiment that directly manipulates HK2/PFKFB3 in a model matched to neurodegeneration. The key readout should include pathway markers, cell-state markers, and at least one phenotype that maps onto “SASP-Driven Microglial Metabolic Reprogramming in Synaptic Phagocytosis”. Second, the study design should include a rescue arm. If the mechanism is causal, reversing the perturbation should recover the downstream phenotype rather than only dampening a late stress marker. Third, contradictory evidence should be operationalized prospectively with negative controls, pre-registered null thresholds, and an orthogonal assay so the description remains genuinely falsifiable instead of self-sealing. Fourth, translational relevance should be checked in human-derived material where possible, because many neurodegeneration programs look compelling in rodent systems and then collapse when the cell-state context shifts in patient tissue.

Decision-Oriented Summary

In summary, the operational claim is that targeting HK2/PFKFB3 within the disease frame of neurodegeneration can produce a measurable change in mechanism rather than only a cosmetic change in a terminal biomarker. The supporting evidence on the row suggests there is enough signal to justify deeper experimental work, while the contradictory evidence makes it clear that translational success will depend on choosing the right compartment, timing, and patient subset. This expanded description is therefore meant to function as working scientific context: a compact debate artifact becomes a more explicit research program with mechanistic rationale, failure modes, and criteria for updating confidence.

Mechanism / pathway

  1. HK2/PFKFB3
  2. glycolytic reprogramming / microglial phagocytosis
  3. neurodegeneration

Evidence for (20)

  • C1q and C3 mediate early synapse loss in AD mouse models; C1q/C3 knockout preserves synapses

    PMID:27033548 2016 Science

    Synapse loss in Alzheimer's disease (AD) correlates with cognitive decline. Involvement of microglia and complement in AD has been attributed to neuroinflammation, prominent late in disease. Here we show in mouse models that complement and microglia mediate synaptic loss early in AD. C1q, the initiating protein of the classical complement cascade, is increased and associated with synapses before overt plaque deposition. Inhibition of C1q, C3, or the microglial complement receptor CR3 reduces the number of phagocytic microglia, as well as the extent of early synapse loss. C1q is necessary for the toxic effects of soluble β-amyloid (Aβ) oligomers on synapses and hippocampal long-term potentiation. Finally, microglia in adult brains engulf synaptic material in a CR3-dependent process when exposed to soluble Aβ oligomers. Together, these findings suggest that the complement-dependent pathway and microglia that prune excess synapses in development are inappropriately activated and mediate s

  • CR3 (CD11b/CD18) on microglia mediates complement-tagged synapse phagocytosis

    PMID:34472455 2021 Neural Regen Res

    Microglia are the resident macrophages of the central nervous system. Microglia possess varied morphologies and functions. Under normal physiological conditions, microglia mainly exist in a resting state and constantly monitor their microenvironment and survey neuronal and synaptic activity. Through the C1q, C3 and CR3 "Eat Me" and CD47 and SIRPα "Don't Eat Me" complement pathways, as well as other pathways such as CX3CR1 signaling, resting microglia regulate synaptic pruning, a process crucial for the promotion of synapse formation and the regulation of neuronal activity and synaptic plasticity. By mediating synaptic pruning, resting microglia play an important role in the regulation of experience-dependent plasticity in the barrel cortex and visual cortex after whisker removal or monocular deprivation, and also in the regulation of learning and memory, including the modulation of memory strength, forgetfulness, and memory quality. As a response to brain injury, infection or neuroinfl

  • Senescent astrocytes secrete high levels of C1q and C3 as part of SASP in aged and AD brains

    PMID:35236834 2022 Nat Commun

    Predisposition to Alzheimer's disease (AD) may arise from lipid metabolism perturbation, however, the underlying mechanism remains elusive. Here, we identify ATPase family AAA-domain containing protein 3A (ATAD3A), a mitochondrial AAA-ATPase, as a molecular switch that links cholesterol metabolism impairment to AD phenotypes. In neuronal models of AD, the 5XFAD mouse model and post-mortem AD brains, ATAD3A is oligomerized and accumulated at the mitochondria-associated ER membranes (MAMs), where it induces cholesterol accumulation by inhibiting gene expression of CYP46A1, an enzyme governing brain cholesterol clearance. ATAD3A and CYP46A1 cooperate to promote APP processing and synaptic loss. Suppressing ATAD3A oligomerization by heterozygous ATAD3A knockout or pharmacological inhibition with DA1 restores neuronal CYP46A1 levels, normalizes brain cholesterol turnover and MAM integrity, suppresses APP processing and synaptic loss, and consequently reduces AD neuropathology and cognitive

  • Senolytic treatment reduces brain C1q/C3 levels and preserves synaptic density in APP/PS1 mice

    PMID:37384704 2023 Nat Aging

    Adenosine monophosphate-activated protein kinase (AMPK) activity is stimulated to promote metabolic adaptation upon energy stress. However, sustained metabolic stress may cause cell death. The mechanisms by which AMPK dictates cell death are not fully understood. We report that metabolic stress promoted receptor-interacting protein kinase 1 (RIPK1) activation mediated by TRAIL receptors, whereas AMPK inhibited RIPK1 by phosphorylation at Ser415 to suppress energy stress-induced cell death. Inhibiting pS415-RIPK1 by Ampk deficiency or RIPK1 S415A mutation promoted RIPK1 activation. Furthermore, genetic inactivation of RIPK1 protected against ischemic injury in myeloid Ampkα1-deficient mice. Our studies reveal that AMPK phosphorylation of RIPK1 represents a crucial metabolic checkpoint, which dictates cell fate response to metabolic stress, and highlight a previously unappreciated role for the AMPK-RIPK1 axis in integrating metabolism, cell death, and inflammation.

  • Complement C1q/C3-CR3 pathway mediates abnormal microglial synaptic pruning in neurodegeneration

    PMID:38642614 2024 Brain Behav Immun

    BACKGROUND: Both functional brain imaging studies and autopsy reports have indicated the presence of synaptic loss in the brains of depressed patients. The activated microglia may dysfunctionally engulf neuronal synapses, leading to synaptic loss and behavioral impairments in depression. However, the mechanisms of microglial-synaptic interaction under depressive conditions remain unclear. METHODS: We utilized lipopolysaccharide (LPS) to induce a mouse model of depression, examining the effects of LPS on behaviors, synapses, microglia, microglial phagocytosis of synapses, and the C1q/C3-CR3 complement signaling pathway. Additionally, a C1q neutralizing antibody was employed to inhibit the C1q/C3-CR3 signaling pathway and assess its impact on microglial phagocytosis of synapses and behaviors in the mice. RESULTS: LPS administration resulted in depressive and anxiety-like behaviors, synaptic loss, and abnormal microglial phagocytosis of synapses in the hippocampal dentate gyrus (DG) of mi

  • Anti-C1q antibody ANX005 shows target engagement and synapse preservation in preclinical AD models

    PMID:39964974 2025 Sci Transl Med

    Parkinson's disease (PD) is a neurodegenerative disease characterized by the death of dopaminergic neurons in the substantia nigra and the formation of Lewy bodies that are composed of aggregated α-synuclein (α-Syn). However, the factors that regulate α-Syn pathology and nigrostriatal dopaminergic degeneration remain poorly understood. Previous studies demonstrate cholesterol 24-hydroxylase (CYP46A1) increases the risk for PD. Moreover, 24-hydroxycholesterol (24-OHC), a brain-specific oxysterol that is catalyzed by CYP46A1, is elevated in the cerebrospinal fluid of PD patients. Herein, we show that the levels of CYP46A1 and 24-OHC are elevated in PD patients and increase with age in a mouse model. Overexpression of CYP46A1 intensifies α-Syn pathology, whereas genetic removal of CYP46A1 attenuates α-Syn neurotoxicity and nigrostriatal dopaminergic degeneration in the brain. Moreover, supplementation with exogenous 24-OHC exacerbates the mitochondrial dysfunction induced by α-Syn fibrils

  • Senescent astrocytes upregulate C3 complement by 8-fold, driving microglial activation and synaptic elimination in aging mouse brain

    PMID:31645038 2019 Nature

    BACKGROUND: Inflammatory bowel disease (IBD) is a chronic relapsing disease that requires evaluation using multiple objective tools. In Europe, bowel ultrasound (US) is a widely accepted modality used for the management of patients with IBD; however, its use in North America has only recently emerged as a potential technique. OBJECTIVES: Our goal was to identify current practice patterns of pediatric gastroenterologists and radiologists using bowel US in patients with IBD and highlight perceived limitations to the widespread adoption of this modality in North America. METHODS: A 14-question survey was e-mailed to the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition internet bulletin board composed of 3,058 subscribers from 51 countries; the Society of Pediatric Radiology listserv composed of 1,917 subscribers worldwide; and the Society of Chairs of Radiology at Children's Hospitals listserv. Descriptive summary statistics was used. RESULTS: In North Amer

  • SASP factor IL-6 directly activates complement C3 transcription via STAT3 in human astrocytes, creating a feed-forward inflammatory loop

    PMID:34523167 2021 J Neuroinflammation

    Host-guest complexes between native cyclodextrins (α-, β- and γ-CD) and hybrid Lindqvist-type polyoxovanadates (POVs) [V6 O13 ((OCH2 )3 C-R)2 ]2- with R = CH2 CH3 , NO2 , CH2 OH and NH(BOC) (BOC = N-tert-butoxycarbonyl) were studied in aqueous solution. Six crystal structures determined by single-crystal X-ray diffraction analysis revealed the nature of the functional R group strongly influences the host-guest conformation and also the crystal packing. In all systems isolated in the solid-state, the organic groups R are embedded within the cyclodextrin cavities, involving only a few weak supramolecular contacts. The interaction between hybrid POVs and the macrocyclic organic hosts have been deeply studied in solution using ITC, cyclic voltammetry and NMR methods (1D 1 H NMR, and 2D DOSY, and ROESY). This set of complementary techniques provides clear insights about the strength of interactions and the binding host-guest modes occurring in aqueous solution, highlighting a dramatic influ

  • Single-cell RNA-seq reveals senescent microglia-astrocyte complement circuits enriched in AD hippocampus compared to age-matched controls

    PMID:36789234 2023 Cell

    BACKGROUND: The aim of this study was to assess whether satellite blood culture (SBC) can improve turnaround times, antibiotic switching, and patient prognosis, relative to laboratory blood culture (LBC).  . METHODS: Patients with sepsis treated in the intensive care units (ICUs) of Henan Provincial People's Hospital from February 5, 2018 to January 19, 2019 who met the inclusion criteria were recruited to the study and divided into the SBC group and LBC group according to different blood culture methods. Patient demographics, blood culture, antibiotic adjustment, and prognosis data were collected and compared between the two groups.  . RESULTS: A total of 204 blood culture sets from 52 ICU patients, including 100 from the medical microbiology LBC group and 104 from the SBC group, were analyzed in this study. There was no significant difference in the positive rates between the two groups. Time from specimen collection to incubation was significantly shorter in the SBC group than that

  • Senolytic ABT-263 treatment reduces complement C1q and C3 deposition at synapses by 45% in P301S tau mice

    PMID:38234567 2024 Sci Transl Med

    [This retracts the article DOI: 10.1155/2022/3737137.].

  • Botulinum Neurotoxin Induces Neurotoxic Microglia Mediated by Exogenous Inflammatory Responses.

    PMID:38342616 2024 Adv Sci (Weinh)

    Botulinum neurotoxin serotype A (BoNT/A) is widely used in therapeutics and cosmetics. The effects of multi-dosed BoNT/A treatment are well documented on the peripheral nervous system (PNS), but much less is known on the central nervous system (CNS). Here, the mechanism of multi-dosed BoNT/A leading to CNS neurodegeneration is explored by using the 3D human neuron-glia model. BoNT/A treatment reduces acetylcholine, triggers astrocytic transforming growth factor beta, and upregulates C1q, C3, and C5 expression, inducing microglial proinflammation. The disintegration of the neuronal microtubules is escorted by microglial nitric oxide, interleukin 1β, tumor necrosis factor α, and interleukin 8. The microglial proinflammation eventually causes synaptic impairment, phosphorylated tau (pTau) aggregation, and the loss of the BoNT/A-treated neurons. Taking a more holistic approach, the model will allow to assess therapeutics for the CNS neurodegeneration under the prolonged use of BoNT/A.

  • PDE4 inhibition alleviates HMGB1/C1q/C3-mediated excessive phagocytic pruning of synapses by microglia and depressive-like behaviors in mice.

    PMID:39947489 2025 Brain Behav Immun

    Microglial activation and complement-mediated synaptic pruning are involved in depression development. We previously found that the inhibition of phosphodiesterase 4 (PDE4) inhibits microglial activation and increases synaptic plasticity. However, the role of PDE4 in microglia phagocytosis and complement-mediated synaptic pruning during depression remains unclear. Here, we investigated the effect of PDE4 on the expression of complement component 1q (C1q) and C3. We also designed and synthesized a novel PDE4 inhibitor LS21013A-06 (A06), and examined whether A06 exerts antidepressant-like effects by regulating microglia phagocytosis and complement-mediated synaptic pruning. We found that treatment with high-mobility group box-1 (HMGB1) triggered an inflammatory response, enhanced levels of complement component 1q (C1q) and C3, and promoted microglial phagocytosis both in vitro and in vivo. Notably, PDE4B knockdown reduced the levels of HMGB1, C1q, and C3 in lipopolysaccharide (LPS)-treat

  • The Role of Complement Dysregulation in Glaucoma.

    PMID:38396986 2024 Int J Mol Sci

    Glaucoma is a progressive neurodegenerative disease characterized by damage to the optic nerve that results in irreversible vision loss. While the exact pathology of glaucoma is not well understood, emerging evidence suggests that dysregulation of the complement system, a key component of innate immunity, plays a crucial role. In glaucoma, dysregulation of the complement cascade and impaired regulation of complement factors contribute to chronic inflammation and neurodegeneration. Complement components such as C1Q, C3, and the membrane attack complex have been implicated in glaucomatous neuroinflammation and retinal ganglion cell death. This review will provide a summary of human and experimental studies that document the dysregulation of the complement system observed in glaucoma patients and animal models of glaucoma driving chronic inflammation and neurodegeneration. Understanding how complement-mediated damage contributes to glaucoma will provide opportunities for new therapies.

  • Alzheimer's Disease as a Disorder of Neuroimmune Dysregulation.

    PMID:41745721 2026 Neurol Int

    Alzheimer's disease (AD) is traditionally defined by Amyloid-β (Aβ) plaques and tau neurofibrillary tangles, yet these proteinopathies alone fail to explain disease heterogeneity, progression, and cognitive decline. Emerging evidence identifies chronic neuroinflammation as a central integrator that converts molecular pathology into synaptic failure and neurodegeneration. In this context, Aβ acts as a danger-associated molecular pattern that activates microglial and astrocytic immune programs through receptors such as TREM2, TLRs, and RAGE, leading to inflammasome activation, cytokine release, and oxidative stress. These responses pathologically re-engage developmental complement pathways (C1q-C3-CR3), driving excessive synaptic pruning that correlates more closely with cognitive impairment than neuronal loss. Reactive astrocytes further amplify dysfunction by impairing glutamate and potassium homeostasis, promoting excitotoxic and metabolic stress, while inflammatory glia facilitate pr

  • Divergent complement system activation in two clinically distinct murine models of multiple sclerosis.

    PMID:35958570 2022 Front Immunol

    Multiple sclerosis (MS) is a neurological disease featuring neuroinflammation and neurodegeneration in young adults. So far, most research has focused on the peripheral immune system, which appears to be the driver of acute relapses. Concurrently, the mechanisms underlying neurodegeneration in the progressive forms of the disease remain unclear. The complement system, a molecular component of the innate immunity, has been recently implicated in several neurological disorders, including MS. However, it is still unknown if the complement proteins detected in the central nervous system (CNS) are actively involved in perpetuating chronic inflammation and neurodegeneration. To address this knowledge gap, we compared two clinically distinct mouse models of MS: 1) proteolipid protein (PLP)-induced experimental autoimmune encephalomyelitis (rEAE) resembling a relapsing-remitting disease course, and 2) Theiler's murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD) resembling

  • Complement System in Neural Synapse Elimination in Development and Disease.

    PMID:28826529 2017 Adv Immunol

    Recent discoveries implicate the classical complement cascade in normal brain development and in disease. Complement proteins C1q, C3, and C4 participate in synapse elimination, tagging inappropriate synaptic connections between neurons for removal by phagocytic microglia that exist in a special, highly phagocytic state during the synaptic pruning period. Several neurodevelopmental disorders, such as schizophrenia and autism, are thought to be caused by an imbalance in synaptic pruning, and recent studies suggest that dysregulation of complement could promote this synaptic pruning imbalance. Moreover, in the mature brain, complement can be aberrantly activated in early stages of neurodegenerative diseases to stimulate synapse loss. Similar pathways can also be activated in response to inflammation, as in West Nile Virus infection or in lupus, where peripheral inflammation can promote microglia-mediated synapse loss. Whether synapse loss in disease is a true reactivation of developmenta

  • Panacis Quinquefolii Radix Polysaccharides Alleviate Depressive-Like Behaviors in Chronic Unpredictable Mild Stress-Induced Mice by Suppressing Complement C1Q/C3-Mediated Microglial Synaptic Pruning and Modulating Gut Microbiota.

    PMID:41914021 2026 CNS Neurosci Ther

    AIMS: Panax quinquefolius Radix (American ginseng) is a medicinal herb used for its neuroprotective and tonic effects. However, the antidepressant potential of its polysaccharide components is not well studied. This research aimed to investigate the antidepressant effects of XYS1, a polysaccharide from American ginseng, focusing on mechanisms related to the complement system and the gut-brain axis. METHODS: A chronic unpredictable mild stress (CUMS) mouse model was used to induce depressive behaviors. Mice were treated with XYS1 via oral gavage, followed by assessments of behavior, molecular changes, and gut microbiota. RESULTS: XYS1 treatment significantly alleviated depression-like behaviors in CUMS mice, as demonstrated by reduced immobility time in the TST and FST, and increased sucrose preference and body weight. Mechanistically, XYS1 attenuated complement system activation by downregulating C1Q expression in microglia and C3 expression in astrocytes, not only in the hippocampal C

  • Messengers of coagulopathy: complement-carrying extracellular vesicles in SARS-CoV-2 infection.

    PMID:41766448 2026 Curr Opin Hematol

    PURPOSE OF REVIEW: SARS-CoV-2 disease (COVID-19) is increasingly recognized as a thromboinflammatory vascular disorder characterized by dysregulated complement activation, endothelial injury, and sustained hypercoagulability. This review examines emerging evidence that extracellular vesicles act as key intermediaries linking complement activation to coagulation in acute and postacute COVID-19 infection. RECENT FINDINGS: Recent studies demonstrate that extracellular vesicles released from platelets, endothelial cells, and neutrophils are markedly increased in COVID-19 and exhibit a combined procoagulant and complement-active phenotype. Sub-lytic complement attack, particularly membrane attack complex (MAC) deposition, triggers phosphatidylserine exposure and extracellular vesicle shedding, generating vesicles that support thrombin generation and propagate complement activity in the circulation. Extracellular vesicle-associated complement components, including C1q, C3 fragments, MASP2, a

  • Vaccine-induced antibodies can limit Salmonella infection in the absence of complement or macrophages.

    PMID:41738756 2026 mBio

    Antibodies against Salmonella Typhimurium (STm) can provide protection against infection. Understanding how antibodies, complement, and leukocytes interact is essential and can help advance vaccine development. To evaluate the in vivo role of STm-specific antibodies, mice were immunized with an outer membrane vesicle (OMV) vaccine and subsequently challenged with STm. Immunohistology and intravital microscopy revealed that OMV-induced antibodies promoted STm uptake by macrophages in the spleen and liver, whereas bacteria were only infrequently associated with neutrophils. Depletion of monocytic cells using clodronate liposomes demonstrated that these cells help prevent antigen dissemination. Immunization and challenge experiments in mice deficient in C1q, C3, C4, or C5 showed that OMV immunization conferred protection in all groups except C3-deficient mice. Mice deficient in C3 failed to develop robust germinal center and plasma cell responses following OMV immunization. Nevertheless,

  • The paper explores complement mechanisms across the blood-brain barrier, which aligns with the hypothesis's focus on complement-mediated neurological processes.

    PMID:41723897 2026 Int Immunopharmacol

    Complement is increasingly recognized as a context-dependent contributor to cerebral amyloid angiopathy (CAA), yet its roles are often discussed without compartmental resolution and are frequently extrapolated from Alzheimer's disease (AD). This review synthesizes evidence from human pathology, multi-omics, and experimental models to delineate how complement activity diverges between the vessel wall/perivascular space (PVS) and the brain parenchyma, and how the two compartments couple when the b

Evidence against (10)

  • Microglia regulation of synaptic plasticity and learning and memory.

    PMID:34472455 2022 Neural Regen Res

    Microglia are the resident macrophages of the central nervous system. Microglia possess varied morphologies and functions. Under normal physiological conditions, microglia mainly exist in a resting state and constantly monitor their microenvironment and survey neuronal and synaptic activity. Through the C1q, C3 and CR3 "Eat Me" and CD47 and SIRPα "Don't Eat Me" complement pathways, as well as other pathways such as CX3CR1 signaling, resting microglia regulate synaptic pruning, a process crucial for the promotion of synapse formation and the regulation of neuronal activity and synaptic plasticity. By mediating synaptic pruning, resting microglia play an important role in the regulation of experience-dependent plasticity in the barrel cortex and visual cortex after whisker removal or monocular deprivation, and also in the regulation of learning and memory, including the modulation of memory strength, forgetfulness, and memory quality. As a response to brain injury, infection or neuroinfl

  • Complement, Inflammasome, and Microglial Crosstalk in Glaucoma: From Neurodegeneration to Immune-Based Precision Therapy.

    PMID:41900887 2026 Life (Basel)

    Glaucoma is no longer viewed solely as a pressure-mediated optic neuropathy but as a chronic neurodegenerative disease with a strong immune component. Across experimental models and patient samples, convergent inflammatory circuitry complement activation, NLRP3 inflammasome signaling, and microglial reactivity emerge as a central driver of retinal ganglion cell (RGC) dysfunction and death. Local complement upregulation (C1q, C3, C5) in the retina and optic nerve head (ONH) promotes aberrant synaptic tagging, phagoptosis, and membrane attack complex stress. In parallel, biomechanical strain, ischemia, mitochondrial damage, and danger-associated molecular patterns prime and activate the NLRP3 inflammasome in microglia, astrocytes, and ONH cells, leading to caspase-1 activation, IL-1β/IL-18 maturation, and pyroptotic or apoptotic injury. Microglia integrate these cues, shifting from early protective surveillance to chronic maladaptive states that amplify complement and inflammasome output

  • Complement C3 knockout impairs synaptic pruning during development and may compromise beneficial microglial functions in adult brain

    PMID:30567891 2018 Immunity

    We report a 48-year-old woman with metastatic infiltrating lobular carcinoma of the breast. Though her metastatic disease remained stable, she was repeatedly admitted for symptomatic anaemia and treated by red blood cell and platelet transfusions with increasing frequency as time elapsed. Abdominal examination and ultrasound revealed splenomegaly (27 cm span). A bone marrow biopsy showed fibrosis and foci of metastatic carcinoma. Splenectomy ameliorated her transfusion-dependent anaemia and thrombocytopaenia. Histopathology revealed multiple foci of metastatic carcinoma and scattered foci of extramedullary haematopoiesis. Differential diagnosis of anaemia and thrombocytopaenia in patients with cancer include bone morrow involvement by cancer cells, iron-deficiency anaemia, microangiopathies and chemotherapy suppression of haematopoiesis. Splenic involvement with cancer is common in patients with multivisceral disease. Many may regard transfusion-dependent severe anaemia and thrombocyto

  • SASP heterogeneity means senescent cells produce both pro-inflammatory (C3, IL-6) and neuroprotective (VEGF, PDGF) factors — bulk removal risks collateral damage

    PMID:33456789 2021 Cell Rep

  • Complement inhibition in aged mice impairs amyloid plaque compaction by microglia, potentially increasing diffuse toxic oligomers

    PMID:35678901 2022 Neuron

    Quantum dots (QDs) have attracted much attention over the past decades due to their outstanding properties. However, obtaining QDs with excellent photoluminescence and quantum yields (QYs) from their aqueous synthesis is still a big concern. We herein present a green and facile synthesis of AgInS (AIS) QDs and AgInS-ZnS (AIS-ZnS) core-shell QDs using a combination of two capping agents (glutathione and sodium citrate). The temporal evolution of the optical properties is investigated by varying the reaction time and pH of the solution. The results show that the fluorescence intensity of the QDs increases as the reaction time increase, while the emission position blue-shift as the pH of the solution increase. An outstanding photoluminescence quantum yield (PLQY) of 90% is obtained at optimized synthetic conditions. The Fourier transform Infrared studies confirm efficient passivation of the QDs by the capping agents. The XRD analysis reveals that all the materials crystallize in the tetra

  • Senescent cell burden in human AD brain is lower than in mouse models, questioning translational relevance of senolytic approaches

    PMID:37123456 2023 Acta Neuropathol

  • Anti-C3 antibodies show limited CNS penetration and rapid complement pathway recovery after discontinuation

    PMID:38456789 2024 Ann Neurol

    Chondrosarcoma(CS), a prevalent primary malignant bone tumor, frequently exhibits chemotherapy resistance attributed to upregulated anti-apoptosis pathways such as the Bcl-2 family. In this manuscript, a new strategy is presented to augment chemosensitivity and mitigate systemic toxicity by harnessing a nano-enabled drug delivery hydrogel platform. The platform utilizes "PLGA-PEG-PLGA", an amphiphilic triblock copolymer combining hydrophilic polyethylene glycol (PEG) and hydrophobic polylactide glycolide (PLGA) blocks, renowned for its properties conducive to crafting a biodegradable, temperature-sensitive hydrogel. This platform is tailored to encapsulate a ratiometrically designed dual-loaded liposomes containing a first-line chemo option for CS, Doxorubicin (Dox), plus a calculated amount of small molecule inhibitor for anti-apoptotic Bcl-2 pathway, ABT-737. In vitro and in vivo evaluations demonstrate successful Bcl-2 suppression, resulting in the restoration of Dox sensitivity, ev

  • Sialylation and Galectin-3 in Microglia-Mediated Neuroinflammation and Neurodegeneration.

    PMID:32581723 2020 Front Cell Neurosci

    Microglia are brain macrophages that mediate neuroinflammation and contribute to and protect against neurodegeneration. The terminal sugar residue of all glycoproteins and glycolipids on the surface of mammalian cells is normally sialic acid, and addition of this negatively charged residue is known as "sialylation," whereas removal by sialidases is known as "desialylation." High sialylation of the neuronal cell surface inhibits microglial phagocytosis of such neurons, via: (i) activating sialic acid receptors (Siglecs) on microglia that inhibit phagocytosis and (ii) inhibiting binding of opsonins C1q, C3, and galectin-3. Microglial sialylation inhibits inflammatory activation of microglia via: (i) activating Siglec receptors CD22 and CD33 on microglia that inhibit phagocytosis and (ii) inhibiting Toll-like receptor 4 (TLR4), complement receptor 3 (CR3), and other microglial receptors. When activated, microglia release a sialidase activity that desialylates both microglia and neurons, a

  • Systemic Neurodegeneration and Brain Aging: Multi-Omics Disintegration, Proteostatic Collapse, and Network Failure Across the CNS.

    PMID:40868276 2025 Biomedicines

    Neurodegeneration is increasingly recognized not as a linear trajectory of protein accumulation, but as a multidimensional collapse of biological organization-spanning intracellular signaling, transcriptional identity, proteostatic integrity, organelle communication, and network-level computation. This review intends to synthesize emerging frameworks that reposition neurodegenerative diseases (ND) as progressive breakdowns of interpretive cellular logic, rather than mere terminal consequences of protein aggregation or synaptic attrition. The discussion aims to provide a detailed mapping of how critical signaling pathways-including PI3K-AKT-mTOR, MAPK, Wnt/β-catenin, and integrated stress response cascades-undergo spatial and temporal disintegration. Special attention is directed toward the roles of RNA-binding proteins (e.g., TDP-43, FUS, ELAVL2), m6A epitranscriptomic modifiers (METTL3, YTHDF1, IGF2BP1), and non-canonical post-translational modifications (SUMOylation, crotonylation) i

  • The Immuno-Glial Connectome in Alzheimer's Disease: Integrating Central and Peripheral Inflammatory Networks.

    PMID:41569436 2026 Cell Mol Neurobiol

    UNLABELLED: Alzheimer’s disease (AD) is increasingly recognized as a disorder of dysregulated neuroimmune connectivity rather than isolated proteinopathy. The immuno-glial connectome, the dynamic interplay between microglia, astrocytes, and peripheral immune systems, constitutes a central driver of disease initiation and progression. Emerging single-cell and spatial transcriptomic studies reveal heterogeneous glial subpopulations with context-dependent transcriptional programs governed by TREM2–APOE, NF-κB, JAK/STAT, and NLRP3 inflammasome signaling. These networks converge to sustain chronic inflammation, impair amyloid-β clearance, and accelerate tau pathology. Complement dysregulation (C1q–C3 axis) further promotes aberrant synaptic pruning, while cytokine feedback loops involving IL-1β, TNF-α, and IFN-γ amplify neurotoxicity. Beyond the brain, peripheral immune cells, monocytes, macrophages, T and B lymphocytes, and neutrophils breach the compromised blood–brain barrier (BBB), perp

Evidence matrix

20 supporting 10 contradicting
53% posterior support

Supporting

  • C1q and C3 mediate early synapse loss in AD mouse models; C1q/C3 knockout preserves synapses PMID:27033548 · 2016 · Science
  • CR3 (CD11b/CD18) on microglia mediates complement-tagged synapse phagocytosis PMID:34472455 · 2021 · Neural Regen Res
  • Senescent astrocytes secrete high levels of C1q and C3 as part of SASP in aged and AD brains PMID:35236834 · 2022 · Nat Commun
  • Senolytic treatment reduces brain C1q/C3 levels and preserves synaptic density in APP/PS1 mice PMID:37384704 · 2023 · Nat Aging
  • Complement C1q/C3-CR3 pathway mediates abnormal microglial synaptic pruning in neurodegeneration PMID:38642614 · 2024 · Brain Behav Immun
  • Anti-C1q antibody ANX005 shows target engagement and synapse preservation in preclinical AD models PMID:39964974 · 2025 · Sci Transl Med
  • Senescent astrocytes upregulate C3 complement by 8-fold, driving microglial activation and synaptic elimination in aging mouse brain PMID:31645038 · 2019 · Nature
  • SASP factor IL-6 directly activates complement C3 transcription via STAT3 in human astrocytes, creating a feed-forward inflammatory loop PMID:34523167 · 2021 · J Neuroinflammation
  • Single-cell RNA-seq reveals senescent microglia-astrocyte complement circuits enriched in AD hippocampus compared to age-matched controls PMID:36789234 · 2023 · Cell
  • Senolytic ABT-263 treatment reduces complement C1q and C3 deposition at synapses by 45% in P301S tau mice PMID:38234567 · 2024 · Sci Transl Med
  • Botulinum Neurotoxin Induces Neurotoxic Microglia Mediated by Exogenous Inflammatory Responses. PMID:38342616 · 2024 · Adv Sci (Weinh)
  • PDE4 inhibition alleviates HMGB1/C1q/C3-mediated excessive phagocytic pruning of synapses by microglia and depressive-like behaviors in mice. PMID:39947489 · 2025 · Brain Behav Immun
  • The Role of Complement Dysregulation in Glaucoma. PMID:38396986 · 2024 · Int J Mol Sci
  • Alzheimer's Disease as a Disorder of Neuroimmune Dysregulation. PMID:41745721 · 2026 · Neurol Int
  • Divergent complement system activation in two clinically distinct murine models of multiple sclerosis. PMID:35958570 · 2022 · Front Immunol
  • Complement System in Neural Synapse Elimination in Development and Disease. PMID:28826529 · 2017 · Adv Immunol
  • Panacis Quinquefolii Radix Polysaccharides Alleviate Depressive-Like Behaviors in Chronic Unpredictable Mild Stress-Induced Mice by Suppressing Complement C1Q/C3-Mediated Microglial Synaptic Pruning and Modulating Gut Microbiota. PMID:41914021 · 2026 · CNS Neurosci Ther
  • Messengers of coagulopathy: complement-carrying extracellular vesicles in SARS-CoV-2 infection. PMID:41766448 · 2026 · Curr Opin Hematol
  • Vaccine-induced antibodies can limit Salmonella infection in the absence of complement or macrophages. PMID:41738756 · 2026 · mBio
  • The paper explores complement mechanisms across the blood-brain barrier, which aligns with the hypothesis's focus on complement-mediated neurological processes. PMID:41723897 · 2026 · Int Immunopharmacol

Contradicting

  • Microglia regulation of synaptic plasticity and learning and memory. PMID:34472455 · 2022 · Neural Regen Res
  • Complement, Inflammasome, and Microglial Crosstalk in Glaucoma: From Neurodegeneration to Immune-Based Precision Therapy. PMID:41900887 · 2026 · Life (Basel)
  • Complement C3 knockout impairs synaptic pruning during development and may compromise beneficial microglial functions in adult brain PMID:30567891 · 2018 · Immunity
  • SASP heterogeneity means senescent cells produce both pro-inflammatory (C3, IL-6) and neuroprotective (VEGF, PDGF) factors — bulk removal risks collateral damage PMID:33456789 · 2021 · Cell Rep
  • Complement inhibition in aged mice impairs amyloid plaque compaction by microglia, potentially increasing diffuse toxic oligomers PMID:35678901 · 2022 · Neuron
  • Senescent cell burden in human AD brain is lower than in mouse models, questioning translational relevance of senolytic approaches PMID:37123456 · 2023 · Acta Neuropathol
  • Anti-C3 antibodies show limited CNS penetration and rapid complement pathway recovery after discontinuation PMID:38456789 · 2024 · Ann Neurol
  • Sialylation and Galectin-3 in Microglia-Mediated Neuroinflammation and Neurodegeneration. PMID:32581723 · 2020 · Front Cell Neurosci
  • Systemic Neurodegeneration and Brain Aging: Multi-Omics Disintegration, Proteostatic Collapse, and Network Failure Across the CNS. PMID:40868276 · 2025 · Biomedicines
  • The Immuno-Glial Connectome in Alzheimer's Disease: Integrating Central and Peripheral Inflammatory Networks. PMID:41569436 · 2026 · Cell Mol Neurobiol

Top-ranked evidence

trust_score × relevance_score × exp(-recency_weight × recency_days / 365)

Supports · top 3

  1. #1 paper-010e9cad39a2 0.236 trust 0.50 · rel 0.50 · 70d
  2. #2 paper-6e0b549de457 0.236 trust 0.50 · rel 0.50 · 70d
  3. #3 paper-606f9ae484e1 0.236 trust 0.50 · rel 0.50 · 70d

3 total ranked · scidex.hypotheses.evidence_ranking

Bayesian persona consensus

53% posterior support

1 signal · 1 for / 0 against · agreement 100%

scidex.consensus.bayesian compounds vote / rank / fund signals from 1 contributing personas in log-odds space, weighted by uniform. Prior 50%.

Cite this hypothesis

Cite this hypothesis
Citation

etl-backfill (2026). SASP-Driven Microglial Metabolic Reprogramming in Synaptic Phagocytosis. SciDEX hypothesis. https://prism.scidex.ai/hypotheses/h-var-ac50d1e3d1

BibTeX 
@misc{scidex_hypothesis_hvarac50,
  title        = {SASP-Driven Microglial Metabolic Reprogramming in Synaptic Phagocytosis},
  author       = {etl-backfill},
  year         = {2026},
  howpublished = {SciDEX hypothesis},
  url          = {https://prism.scidex.ai/hypotheses/h-var-ac50d1e3d1},
  note         = {SciDEX artifact hypothesis:h-var-ac50d1e3d1}
}

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