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Phagocytosis of full-length Tau oligomers by Actin-remodeling of activated microglia

BACKGROUND: Alzheimer’s disease is associated with the accumulation of intracellular Tau tangles within neurons and extracellular amyloid-β plaques in the brain parenchyma, which altogether results in synaptic loss and neurodegeneration. Extracellular concentrations of oligomers and aggregated prote...

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Autores principales: Das, Rashmi, Balmik, Abhishek Ankur, Chinnathambi, Subashchandrabose
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6950897/
https://www.ncbi.nlm.nih.gov/pubmed/31915009
http://dx.doi.org/10.1186/s12974-019-1694-y
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author Das, Rashmi
Balmik, Abhishek Ankur
Chinnathambi, Subashchandrabose
author_facet Das, Rashmi
Balmik, Abhishek Ankur
Chinnathambi, Subashchandrabose
author_sort Das, Rashmi
collection PubMed
description BACKGROUND: Alzheimer’s disease is associated with the accumulation of intracellular Tau tangles within neurons and extracellular amyloid-β plaques in the brain parenchyma, which altogether results in synaptic loss and neurodegeneration. Extracellular concentrations of oligomers and aggregated proteins initiate microglial activation and convert their state of synaptic surveillance into a destructive inflammatory state. Although Tau oligomers have fleeting nature, they were shown to mediate neurotoxicity and microglial pro-inflammation. Due to the instability of oligomers, in vitro experiments become challenging, and hence, the stability of the full-length Tau oligomers is a major concern. METHODS: In this study, we have prepared and stabilized hTau40(WT) oligomers, which were purified by size-exclusion chromatography. The formation of the oligomers was confirmed by western blot, thioflavin-S, 8-anilinonaphthaalene-1-sulfonic acid fluorescence, and circular dichroism spectroscopy, which determine the intermolecular cross-β sheet structure and hydrophobicity. The efficiency of N9 microglial cells to phagocytose hTau40(WT) oligomer and subsequent microglial activation was studied by immunofluorescence microscopy with apotome. The one-way ANOVA was performed for the statistical analysis of fluorometric assay and microscopic analysis. RESULTS: Full-length Tau oligomers were detected in heterogeneous globular structures ranging from 5 to 50 nm as observed by high-resolution transmission electron microscopy, which was further characterized by oligomer-specific A11 antibody. Immunocytochemistry studies for oligomer treatment were evidenced with A11(+) Iba1(high) microglia, suggesting that the phagocytosis of extracellular Tau oligomers leads to microglial activation. Also, the microglia were observed with remodeled filopodia-like actin structures upon the exposure of oligomers and aggregated Tau. CONCLUSION: The peri-membrane polymerization of actin filament and co-localization of Iba1 relate to the microglial movements for phagocytosis. Here, these findings suggest that microglia modified actin cytoskeleton for phagocytosis and rapid clearance of Tau oligomers in Alzheimer’s disease condition.
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spelling pubmed-69508972020-01-09 Phagocytosis of full-length Tau oligomers by Actin-remodeling of activated microglia Das, Rashmi Balmik, Abhishek Ankur Chinnathambi, Subashchandrabose J Neuroinflammation Research BACKGROUND: Alzheimer’s disease is associated with the accumulation of intracellular Tau tangles within neurons and extracellular amyloid-β plaques in the brain parenchyma, which altogether results in synaptic loss and neurodegeneration. Extracellular concentrations of oligomers and aggregated proteins initiate microglial activation and convert their state of synaptic surveillance into a destructive inflammatory state. Although Tau oligomers have fleeting nature, they were shown to mediate neurotoxicity and microglial pro-inflammation. Due to the instability of oligomers, in vitro experiments become challenging, and hence, the stability of the full-length Tau oligomers is a major concern. METHODS: In this study, we have prepared and stabilized hTau40(WT) oligomers, which were purified by size-exclusion chromatography. The formation of the oligomers was confirmed by western blot, thioflavin-S, 8-anilinonaphthaalene-1-sulfonic acid fluorescence, and circular dichroism spectroscopy, which determine the intermolecular cross-β sheet structure and hydrophobicity. The efficiency of N9 microglial cells to phagocytose hTau40(WT) oligomer and subsequent microglial activation was studied by immunofluorescence microscopy with apotome. The one-way ANOVA was performed for the statistical analysis of fluorometric assay and microscopic analysis. RESULTS: Full-length Tau oligomers were detected in heterogeneous globular structures ranging from 5 to 50 nm as observed by high-resolution transmission electron microscopy, which was further characterized by oligomer-specific A11 antibody. Immunocytochemistry studies for oligomer treatment were evidenced with A11(+) Iba1(high) microglia, suggesting that the phagocytosis of extracellular Tau oligomers leads to microglial activation. Also, the microglia were observed with remodeled filopodia-like actin structures upon the exposure of oligomers and aggregated Tau. CONCLUSION: The peri-membrane polymerization of actin filament and co-localization of Iba1 relate to the microglial movements for phagocytosis. Here, these findings suggest that microglia modified actin cytoskeleton for phagocytosis and rapid clearance of Tau oligomers in Alzheimer’s disease condition. BioMed Central 2020-01-08 /pmc/articles/PMC6950897/ /pubmed/31915009 http://dx.doi.org/10.1186/s12974-019-1694-y Text en © The Author(s). 2020 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research
Das, Rashmi
Balmik, Abhishek Ankur
Chinnathambi, Subashchandrabose
Phagocytosis of full-length Tau oligomers by Actin-remodeling of activated microglia
title Phagocytosis of full-length Tau oligomers by Actin-remodeling of activated microglia
title_full Phagocytosis of full-length Tau oligomers by Actin-remodeling of activated microglia
title_fullStr Phagocytosis of full-length Tau oligomers by Actin-remodeling of activated microglia
title_full_unstemmed Phagocytosis of full-length Tau oligomers by Actin-remodeling of activated microglia
title_short Phagocytosis of full-length Tau oligomers by Actin-remodeling of activated microglia
title_sort phagocytosis of full-length tau oligomers by actin-remodeling of activated microglia
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6950897/
https://www.ncbi.nlm.nih.gov/pubmed/31915009
http://dx.doi.org/10.1186/s12974-019-1694-y
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