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Microglial Dysfunction and Defective β-Amyloid Clearance Pathways in Aging Alzheimer's Disease Mice
Open accessAbstract
Early microglial accumulation in Alzheimer's disease (AD) delays disease progression by promoting clearance of β-amyloid (Aβ) before formation of senile plaques. However, persistent Aβ accumulation despite increasing microglial numbers suggests that the ability of microglia to clear Aβ may decrease with age and progression of AD pathology. To determine the effects of aging and Aβ deposition on microglial ability to clear Aβ, we used quantitative PCR to analyze gene expression in freshly isolated adult microglia from 1.5-, 3-, 8-, and 14-month-old transgenic PS1-APP mice, an established mouse model of AD, and from their nontransgenic littermates. We found that microglia from old PS1-APP mice, but not from younger mice, have a twofold to fivefold decrease in expression of the Aβ-binding scavenger receptors scavenger receptor A (SRA), CD36, and RAGE (receptor for advanced-glycosylation endproducts), and the Aβ-degrading enzymes insulysin, neprilysin, and MMP9, compared with their littermate controls. In contrast, PS1-APP microglia had a 2.5-fold increase in the proinflammatory cytokines IL-1β (interleukin-1β) and tumor necrosis factor α (TNFα), suggesting that there is an inverse correlation between cytokine production and Aβ clearance. In support of this possibility, we found that incubation of cultured N9 mouse microglia with TNFα decreased the expression of SRA and CD36 and reduced Aβ uptake. Our data indicate that, although early microglial recruitment promotes Aβ clearance and is neuroprotective in AD, as disease progresses, proinflammatory cytokines produced in response to Aβ deposition downregulate genes involved in Aβ clearance and promote Aβ accumulation, therefore contributing to neurodegeneration. Antiinflammatory therapy for AD should take this dichotomous microglial role into consideration.
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“their phagocytic capacity declines with aging, chronic exposure to Αβ, and during sustained inflammation in the AD brain76,16,17.”
From Amyloid-β induces lipid droplet-mediated microglial dysfunction via the enzyme DGAT2 in Alzheimer’s disease (2025) · cites this paper as [16]
Experimental — accuracy not yet measuredThe source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“However, as AD progresses, microglia acquire a chronically activated phenotype through unremitting stimulation by cytokines and A itself, which compromises their clearance function (Bamberger et al., 2003;Hickman et al., 2008;Heneka et al., 2010a) .”
From PPARγ/RXRα-Induced and CD36-Mediated Microglial Amyloid-β Phagocytosis Results in Cognitive Improvement in Amyloid Precursor Protein/Presenilin 1 Mice (2012) · cites this paper as Hickman et al., 2008
Experimental — accuracy not yet measuredThe source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“Progression of Alzheimer's disease is associated with reduced Aβ-clearing pathways resulting in Aβ accumulation (4–6).”
From Heterozygous CX3CR1 Deficiency in Microglia Restores Neuronal β-Amyloid Clearance Pathways and Slows Progression of Alzheimer's Like-Disease in PS1-APP Mice (2019) · cites this paper as [5]
Experimental — accuracy not yet measuredThe source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“Progression of Alzheimer's disease in humans and mouse models of the disease is associated with reduced expression of these Aβ-clearing enzymes resulting in decreased Aβ clearance and increased Aβ accumulation (5, 24).”
From Heterozygous CX3CR1 Deficiency in Microglia Restores Neuronal β-Amyloid Clearance Pathways and Slows Progression of Alzheimer's Like-Disease in PS1-APP Mice (2019) · cites this paper as [5]
Experimental — accuracy not yet measuredThe source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“This impairment has been shown to correlate with increased production of proinflammatory cytokines and overwhelming accumulation of Aβ plaques in the AD brain [20–22].”
From IL-1β-driven amyloid plaque clearance is associated with an expansion of transcriptionally reprogrammed microglia (2019) · cites this paper as [22]
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In the citing paper
“Notably, previous studies have shown that microglial function may be adversely affected by Aβ, particularly as a result of chronic exposure to pro-inflammatory cytokines, resulting in increased Aβ accumulation and potentially underpinning the contradiction between our in vitro and in vivo results.39,40”
From Microglial INPP5D limits plaque formation and glial reactivity in the PSAPP mouse model of Alzheimer's disease (2023) · cites this paper as [40]
The cited source says what the claim attributes to it.
In the citing paper
“Thus, endothelial expression of LRP1 promotes the clearance of Aβ across the BBB in vivo, a process directly modulated by PCSK9 inhibitor treatment (93, 94), and the expression of CD36 parallels the ability of microglia to perform Aβ clearance (95).”
From PCSK9 and the nervous system: a no-brainer? (2023) · cites this paper as [95]
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In the citing paper
“Increased pro-inflammatory gene expression in response to accumulating Αβ in older AD mice leads to decreased microglial Αβ clearance receptors or Αβ-degrading enzymes, thereby promoting further Αβ accumulation16.”
From Amyloid-β induces lipid droplet-mediated microglial dysfunction via the enzyme DGAT2 in Alzheimer’s disease (2025) · cites this paper as [16]
The cited source says what the claim attributes to it.
In the citing paper
“the ability of microglia to remove Αβ declines over time”
From Amyloid-β induces lipid droplet-mediated microglial dysfunction via the enzyme DGAT2 in Alzheimer’s disease (2025) · cites this paper as [16]
The cited source says what the claim attributes to it.
In the citing paper
“supporting that the progression of amyloid pathology correlates with impaired capacity of microglia to phagocytose Αβ17,16.”
From Amyloid-β induces lipid droplet-mediated microglial dysfunction via the enzyme DGAT2 in Alzheimer’s disease (2025) · cites this paper as [16]
The cited source says what the claim attributes to it.
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“As one of the most relevant consequences, the loss of microglial phagocytic capacity leads to further Aβ accumulation and aggregation, accelerating the progression of AD [17].”
From Emerging Role of miR-21-5p in Neuron–Glia Dysregulation and Exosome Transfer Using Multiple Models of Alzheimer’s Disease (2022) · cites this paper as [17]
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In the citing paper
“We have previously shown that expression of IDE in microglia from PS1-APP mice decreases with age and progression of AD-like pathology (5).”
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In the citing paper
“Finally, Inpp5d was identified as a target of miR155, and constitutive deletion of miR155, which should increase SHIP1, led to an increase in amyloid plaques.40,41”
From Microglial INPP5D limits plaque formation and glial reactivity in the PSAPP mouse model of Alzheimer's disease (2023) · cites this paper as [40]
Experimental — accuracy not yet measuredThe check wasn’t confident either way, so it gives no verdict — never disputed.
In the citing paper
“Finally, Inpp5d was identified as a target of miR155, and constitutive deletion of miR155, which should increase SHIP1, led to an increase in amyloid plaques.40,41”
From Microglial INPP5D limits plaque formation and glial reactivity in the PSAPP mouse model of Alzheimer's disease (2023) · cites this paper as [40]
Experimental — accuracy not yet measuredIn the citing paper
“Aged glial cells respond less efficiently to antigens, including amyloid-β (Aβ) and α-synuclein, and have reduced phagocytic and antiinflammatory capacity (161–163).”
From Connecting aging biology and inflammation in the omics era (2022) · cites this paper as [161]
In the citing paper
“AD is accompanied by activation of microglia and astrocytes1,2 that affects the clearance and production of Aβ42,3,4 development and propagation of tau pathology,5 exacerbates neurodegeneration, and influences disease progression and severity.6,7”
From CSF biomarkers of neuroinflammation and cerebrovascular dysfunction in early Alzheimer disease (2018) · cites this paper as [3]
In the citing paper
“microglia from a mouse model of Aβ deposition (Aβ-mice) have reduced expression of Aβ-phagocytic receptors and Aβ-degrading enzymes, but their ability to produce proinflammatory cytokines was maintained6.”
From Microglia in neurodegeneration (2018) · cites this paper as [6]
In the citing paper
“In response to such stimuli, microglia can initiate a neuroinflammatory response which, like peripheral inflammation, includes production of cytokines such as TNF and IL-16,27, and possibly chemokines such as Ccl228, to recruit additional cells and induce them to clear injurious agents and maintain brain homeostasis.”
From Microglia in neurodegeneration (2018) · cites this paper as [6]
In the citing paper
“Aβ clearance involves, in part36, phagocytosis and endocytosis via microglial scavenger receptors (SRs)37,38 and extracellular degradation by Aβ-degrading enzymes6,36.”
From Microglia in neurodegeneration (2018) · cites this paper as [6]
In the citing paper
“Despite effective uptake, Aβ clearance by microglia in AD may be ineffective despite phagocytic uptake [55].”
From Identification and therapeutic modulation of a pro-inflammatory subset of disease-associated-microglia in Alzheimer’s disease (2018) · cites this paper as [55]
In the citing paper
“In AD, microglia cluster around beta-amyloid plaques highlighting their inability to clear beta-amyloid (Hickman et al., 2008; Liu et al., 2010).”
From iPSC-derived human microglia-like cells to study neurological diseases (2017) · cites this paper as Hickman et al., 2008
In the citing paper
“Immune involvement in neurodegenerative disease centres on findings that pro-inflammatory microglia are closely associated with protein aggregate pathologies characteristic of most dementias.”
From ROS Generation in Microglia: Understanding Oxidative Stress and Inflammation in Neurodegenerative Disease (2020) · cites this paper as [13]
In the citing paper
“In Alzheimer’s disease (AD), the most common form of dementia, microglia surround amyloid plaques and respond to amyloid-β with a pro-inflammatory phenotype characterised by cytokine expression (e.g., interleukins (IL) 1β and 6 and tumour necrosis factor α (TNFα)) that may initially limit amyloidosis but likely becomes overzealous and neurotoxic [12,13,14].”
From ROS Generation in Microglia: Understanding Oxidative Stress and Inflammation in Neurodegenerative Disease (2020) · cites this paper as [13]
In the citing paper
“For example, PS1-APP mice (a model of Alzheimer's Disease) showed an age-dependent reduction in receptors and enzymes involved in beta amyloid degradation, although still maintaining elevated levels of cytokine (Hickman et al, 2008).”
From Microglia Priming with Aging and Stress (2017) · cites this paper as Hickman et al, 2008
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Citations
Cites
RAGE and amyloid-β peptide neurotoxicity in Alzheimer's disease
Yan, S. D., Chen, X., Fu, J., Chen, M., Zhu, H., Roher, A., Slattery, T., Zhao, L., Nagashima, M., Morser, J., et al. (1996) · Nature · doi:10.1038/382685a0 · Cited by 2,012 · cited 5×
“A, B, D, At 8 and 14 months of age, PS1-APP transgenic mice show significantly reduced expression of SRA (A), CD36 (B), and RAGE (D) compared with their WT littermates.”
BackgroundInfluentialJankowsky, J. L., Fadale, D. J., Anderson, J., Xu, G. M., Gonzales, V., Jenkins, N. A., Copeland, N. G., Lee, M. K., Younkin, L. H., Wagner, S. L., et al. (2004) · Human Molecular Genetics · doi:10.1093/hmg/ddh019 · Cited by 1,575 · cited 1×
“This process is observed at the age of 8 months and appears to precede or parallel the increase in A levels observed in PS1-APP mice at that age (Jankowsky et al., 2001, 2004).”
BackgroundActivation of microglial cells by β-amyloid protein and interferon-γ
Meda, L., Cassatella, M. A., Szendrei, G. I., Otvos, L., Baron, P., Villalba, M., Ferrari, D., & Rossi, F. (1995) · Nature · doi:10.1038/374647a0 · Cited by 1,314
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“…receptors that promote the clearance and phagocytosis of A , such as class A scavenger receptor, CD36, and receptor for advanced-glycosylation endproducts (RAGE) (Yan et al., 1996; El Khoury et al., 1998), and microglia can restrict senile plaque formation by phagocytosing A (Simard et al., 2006).”
BackgroundBorchelt, D. R., Ratovitski, T., van Lare, J., Lee, M. K., Gonzales, V., Jenkins, N. A., Copeland, N. G., Price, D. L., & Sisodia, S. S. (1997) · Neuron · doi:10.1016/s0896-6273(00)80974-5 · Cited by 1,023 · cited 2×
“To investigate this hypothesis, we developed a method to isolate fresh adult mouse microglia from the bigenic APPswe/PSEN1dE9 (PS1-APP) mice (Borchelt et al., 1997; Jankowsky et al., 2001), a robust mouse model of AD, and from their nontransgenic littermates at various ages and stages of AD-like…”
El Khoury, J., Toft, M., Hickman, S. E., Means, T. K., Terada, K., Geula, C., & Luster, A. D. (2007) · Nature Medicine · doi:10.1038/nm1555 · Cited by 915 · cited 5×
“Indeed, early microglial accumulation appears to delay progression of AD-like pathology, and bone marrow-derived microglia may restrict plaque formation in transgenic mice (Simard et al., 2006; El Khoury et al., 2007).”
InfluentialSelf-citationMcGeer, P. L., Itagaki, S., Tago, H., & McGeer, E. G. (1987) · Neuroscience Letters · doi:10.1016/0304-3940(87)90696-3 · Cited by 836 · cited 1×
“Microglia, the mononuclear phagocytes of the brain (Perry and Gordon, 1988), accumulate in senile plaques in AD patients and in animal models of AD (McGeer et al., 1987; Perlmutter et al., 1990; Frautschy et al., 1998; Dickson, 1999; Stalder et al., 1999).”
Macrophages and microglia in the nervous system
Perry, V. H., & Gordon, S. (1988) · Trends in Neurosciences · doi:10.1016/0166-2236(88)90110-5 · Cited by 747 · cited 2×
“Microglia, the mononuclear phagocytes of the brain (Perry and Gordon, 1988), accumulate in senile plaques in AD patients and in animal models of AD (McGeer et al.”
Co-expression of multiple transgenes in mouse CNS: a comparison of strategies
Jankowsky, J. L., Slunt, H. H., Ratovitski, T., Jenkins, N. A., Copeland, N. G., & Borchelt, D. R. (2001) · Biomolecular Engineering · doi:10.1016/s1389-0344(01)00067-3 · Cited by 746 · cited 3×
“…hypothesis, we developed a method to isolate fresh adult mouse microglia from the bigenic APPswe/PSEN1dE9 (PS1-APP) mice (Borchelt et al., 1997; Jankowsky et al., 2001), a robust mouse model of AD, and from their nontransgenic littermates at various ages and stages of AD-like pathology, and…”
Scavenger receptor-mediated adhesion of microglia to β-amyloid fibrils
Khoury, J. E., Hickman, S. E., Thomas, C. A., Cao, L., Silverstein, S. C., & Loike, J. D. (1996) · Nature · doi:10.1038/382716a0 · Cited by 727 · cited 2×
“N9 mouse microglia (a gift from Dr. P. Riciarrdi-Castagnoli, University of Milan, Bicocca, Italy) (El Khoury et al., 1996) were plated on 24-well plates coated with 1 g of fibronectin/ cm 2 (Sigma-Aldrich), and grown overnight in RPMI 1640 supplemented with10% FBS, L-glutamine (2 mM), penicillin…”
BackgroundMethodSelf-citation
Cited by
Sorted by citations
Neuroinflammation in Alzheimer's disease
Heneka, M. T., Carson, M. J., Khoury, J. E., Landreth, G. E., Brosseron, F., Feinstein, D. L., Jacobs, A. H., Wyss-Coray, T., Vitorica, J., Ransohoff, R. M., et al. (2015) · The Lancet Neurology · doi:10.1016/s1474-4422(15)70016-5 · Cited by 6,226
“It has been suggested, that increased cytokine levels are responsible for the insufficient microglial phagocytic capacity by downregulating A β phagocytosis receptors 18 .”
Self-citationNeurovascular pathways to neurodegeneration in Alzheimer’s disease and other disorders
Zlokovic, B. V. (2011) · Nature Reviews Neuroscience · doi:10.1038/nrn3114 · Cited by 2,969
NLRP3 is activated in Alzheimer’s disease and contributes to pathology in APP/PS1 mice
Heneka, M. T., Kummer, M. P., Stutz, A., Delekate, A., Schwartz, S., Vieira-Saecker, A., Griep, A., Axt, D., Remus, A., Tzeng, T.-C., et al. (2013) · Nature · doi:10.1038/nature11729 · Cited by 2,898
“Cytokines, including IL-1 β , were found to impair microglial clearance functions 16,17 .”
Inflammation as a central mechanism in Alzheimer's disease
Kinney, J. W., Bemiller, S. M., Murtishaw, A. S., Leisgang, A. M., Salazar, A. M., & Lamb, B. T. (2018) · Alzheimer's & Dementia: Translational Research & Clinical Interventions · doi:10.1016/j.trci.2018.06.014 · Cited by 2,253
Immune attack: the role of inflammation in Alzheimer disease
Heppner, F. L., Ransohoff, R. M., & Becher, B. (2015) · Nature Reviews Neuroscience · doi:10.1038/nrn3880 · Cited by 2,134
Metadata
- Authors
- Hickman, S. E., Allison, E. K., & El Khoury, J.
- Affiliations
- Harvard University (US)
- ORCID
- Hickman, Suzanne E.
- Venue
- The Journal of Neuroscience
- Publisher
- Society for Neuroscience
- Published
- 2008-08-13
- Volume
- 28
- Issue
- 33
- Pages
- 8354-8360
- ISSN
- 0270-6474 (ISSN-L)
- 1529-2401
- PMC
- PMC2597474
- OpenAlex
- W2018708829
- Cited by
- 1,329
- References
- 28
- Citations by year
- 2026: 49 · 2025: 85 · 2024: 85 · 2023: 96 · 2022: 125 · 2021: 98 · 2020: 113 · 2019: 91 · 2018: 78 · 2017: 63 · 2016: 67 · 2015: 73 · 2014: 64 · 2013: 49 · 2012: 65
- FWCI
- 27.71
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- Locations
- Journal of Neuroscience (publishedVersion, cc-by-nc-sa)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- Funders
- Dana Foundation
- National Institute of Neurological Disorders and Stroke (R01NS059005)
- Topics
- Life Sciences › Neuroscience › Neurology › Neuroinflammation and Neurodegeneration Mechanisms
- Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Alzheimer's disease research and treatments
- Life Sciences › Immunology and Microbiology › Immunology › Phagocytosis and Immune Regulation
- Keywords
- Alzheimer's disease, microglia, amyloid-beta clearance, aging, scavenger receptor A, CD36, RAGE, neprilysin, MMP-9, inflammatory cytokines, TNF-α, IL-1β, neuroinflammation, anti-inflammatory therapy, neurodegeneration
- MeSH terms
- Aging, Alzheimer Disease, Animals, Mice, Transgenic, Signal Transduction, Amyloid beta-Peptides, Microglia, Mice
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