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Formation and maintenance of Alzheimer's disease beta-amyloid plaques in the absence of microglia.

ABSTRACT: In Alzheimer's disease, microglia cluster around beta-amyloid deposits, suggesting that these cells are important for amyloid plaque formation, maintenance and/or clearance. We crossed two distinct APP transgenic mouse strains with CD11b-HSVTK mice, in which nearly complete ablation of microglia was achieved for up to 4 weeks after ganciclovir application. Neither amyloid plaque formation and maintenance nor amyloid-associated neuritic dystrophy depended on the presence of microglia.

SUBMITTER: Grathwohl SA

PROVIDER: S-EPMC4721582 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature

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Formation and maintenance of Alzheimer's disease beta-amyloid plaques in the absence of microglia.

Grathwohl Stefan A SA Kälin Roland E RE Bolmont Tristan T Prokop Stefan S Winkelmann Georg G Kaeser Stephan A SA Odenthal Jörg J Radde Rebecca R Eldh Therese T Gandy Sam S Aguzzi Adriano A Staufenbiel Matthias M Mathews Paul M PM Wolburg Hartwig H Heppner Frank L FL Jucker Mathias M

Nature neuroscience 20091018 11

In Alzheimer's disease, microglia cluster around beta-amyloid deposits, suggesting that these cells are important for amyloid plaque formation, maintenance and/or clearance. We crossed two distinct APP transgenic mouse strains with CD11b-HSVTK mice, in which nearly complete ablation of microglia was achieved for up to 4 weeks after ganciclovir application. Neither amyloid plaque formation and maintenance nor amyloid-associated neuritic dystrophy depended on the presence of microglia. ...[more]

PMID: 19838177

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Nanoscale structure of amyloid-β plaques in Alzheimer's disease.

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Modulation of β-Amyloid Fibril Formation in Alzheimer's Disease by Microglia and Infection.

Project description:Amyloid plaques are a pathological hallmark of Alzheimer's disease. The major component of these plaques are highly ordered amyloid fibrils formed by amyloid-β (Aβ) peptides. However, whilst Aβ amyloid fibril assembly has been subjected to detailed and extensive analysis in vitro, these studies may not reproduce how Aβ fibrils assemble in the brain. This is because the brain represents a highly complex and dynamic environment, and in Alzheimer's disease multiple cofactors may affect the assembly of Aβ fibrils. Moreover, in vivo amyloid plaque formation will reflect the balance between the assembly of Aβ fibrils and their degradation. This review explores the roles of microglia as cofactors in Aβ aggregation and in the clearance of amyloid deposits. In addition, we discuss how infection may be an additional cofactor in Aβ fibril assembly by virtue of the antimicrobial properties of Aβ peptides. Crucially, by understanding the roles of microglia and infection in Aβ amyloid fibril assembly it may be possible to identify new therapeutic targets for Alzheimer's disease.

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?-Amyloid peptides and amyloid plaques in Alzheimer's disease.

Project description:Many lines of evidence support that ?-amyloid (A?) peptides play an important role in Alzheimer's disease (AD), the most common cause of dementia. But despite much effort the molecular mechanisms of how A? contributes to AD remain unclear. While A? is generated from its precursor protein throughout life, the peptide is best known as the main component of amyloid plaques, the neuropathological hallmark of AD. Reduction in A? has been the major target of recent experimental therapies against AD. Unfortunately, human clinical trials targeting A? have not shown the hoped-for benefits. Thus, doubts have been growing about the role of A? as a therapeutic target. Here we review evidence supporting the involvement of A? in AD, highlight the importance of differentiating between various forms of A?, and suggest that a better understanding of A?'s precise pathophysiological role in the disease is important for correctly targeting it for potential future therapy.

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Distinct amyloid-β and tau-associated microglia profiles in Alzheimer's disease.

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2021-11-24 | PXD025620 | Pride

Plasma Exosomes Spread and Cluster Around β-Amyloid Plaques in an Animal Model of Alzheimer's Disease.

Project description:Exosomes, a type of extracellular vesicle, have been shown to be involved in many disorders, including Alzheimer's disease (AD). Exosomes may contribute to the spread of misfolded proteins such as amyloid-β (Aβ) and α-synuclein. However, the specific diffusion process of exosomes and their final destination in brain are still unclear. In the present study, we isolated exosomes from peripheral plasma and injected them into the hippocampus of an AD mouse model, and investigated exosome diffusion. We found that injected exosomes can spread from the dentate gyrus (DG) to other regions of hippocampus and to the cortex. Exosomes targeted microglia preferentially; this phenomenon is stable and is not affected by age. In AD mice, microglia take up lower levels of exosomes. More interestingly, plasma exosomes cluster around the Aβ plaques and are engulfed by activated microglia nearby. Our data indicate that exosomes can diffuse throughout the brain and may play a role in the dynamics of amyloid deposition in AD through microglia.

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Microglia use TAM receptors to detect and engulf amyloid beta plaques

Project description:Two microglial TAM receptor tyrosine kinases - Axl and Mer - have been linked to Alzheimer’s disease, but their roles in disease have not been tested experimentally. We find that in Alzheimer’s disease and its mouse models, induced expression of Axl and Mer in amyloid plaque-associated microglia is coupled to induced plaque decoration by the TAM ligand Gas6 and its co-ligand phosphatidylserine. In the APP/PS1 mouse model of Alzheimer’s disease, sIngle cell RNAseq analysis comparing wild type microglia with those with Axl and Mer deficiency reveals a similar disease state transitional program of microglia but a dampened differential expression of numerous AD siganture genes in microglia lacking TAM receptors. In line with the transcriptomic data, using two-photon microscopy, we show that genetic ablation of Axl and Mer results in microglia that are unable to normally detect, respond to, organize, or phagocytose amyloid beta plaques. These major deficits notwithstanding, and contrary to expectation, TAM-deficient APP/PS1 mice develop fewer dense-core plaques than APP/PS1 mice with normal microglia. Our findings reveal that the TAM system is an essential mediator of microglial recognition and engulfment of amyloid plaques, and that TAM-driven microglial phagocytosis does not constrain, but rather promotes, plaque development.

2021-02-25 | GSE160523 | GEO

Microglia prevent beta-amyloid plaque formation in the early stage of an Alzheimer's disease mouse model with suppression of glymphatic clearance.

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Project description:Senile plaques accumulate over the course of decades in the brains of patients with Alzheimer's disease. A fundamental tenet of the amyloid hypothesis of Alzheimer's disease is that the deposition of amyloid-beta precedes and induces the neuronal abnormalities that underlie dementia. This idea has been challenged, however, by the suggestion that alterations in axonal trafficking and morphological abnormalities precede and lead to senile plaques. The role of microglia in accelerating or retarding these processes has been uncertain. To investigate the temporal relation between plaque formation and the changes in local neuritic architecture, we used longitudinal in vivo multiphoton microscopy to sequentially image young APPswe/PS1d9xYFP (B6C3-YFP) transgenic mice. Here we show that plaques form extraordinarily quickly, over 24 h. Within 1-2 days of a new plaque's appearance, microglia are activated and recruited to the site. Progressive neuritic changes ensue, leading to increasingly dysmorphic neurites over the next days to weeks. These data establish plaques as a critical mediator of neuritic pathology.

| S-EPMC3264491 | biostudies-other

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