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Increased Release of Apolipoprotein E in Extracellular Vesicles Following Amyloid-β Protofibril Exposure of Neuroglial Co-Cultures
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Chemistry. (Clinical Chemistry)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.ORCID iD: 0000-0001-5466-8370
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2017 (English)In: Journal of Alzheimer's Disease, ISSN 1387-2877, E-ISSN 1875-8908, Vol. 60, no 1, p. 305-321Article in journal (Refereed) Published
Abstract [en]

Extracellular vesicles (EVs), including exosomes and larger microvesicles, have been implicated to play a role in several conditions, including Alzheimer's disease (AD). Since the EV content mirrors the intracellular environment, it could contribute with important information about ongoing pathological processes and may be a useful source for biomarkers, reflecting the disease progression. The aim of the present study was to analyze the protein content of EVs specifically released from a mixed co-culture of primary astrocytes, neurons, and oligodendrocytes treated with synthetic amyloid-beta (A beta(42)) protofibrils. The EV isolation was performed by ultracentrifugation and validated by transmission electron microscopy. Mass spectrometry analysis of the EV content revealed a total of 807 unique proteins, of which five displayed altered levels in A beta(42) protofibril exposed cultures. The most prominent protein was apolipoprotein E (apoE), and by western blot analysis we could confirm a threefold increase of apoE in EVs from A beta(42) protofibril exposed cells, compared to unexposed cells. Moreover, immunoprecipitation studies demonstrated that apoE was primarily situated inside the EVs, whereas immunocytochemistry indicated that the EVs most likely derived from the astrocytes and the neurons in the culture. The identified A beta-induced sorting of apoE into EVs from cultured neuroglial cells suggests a possible role for intercellular transfer of apoE in AD pathology and encourage future studies to fully elucidate the clinical relevance of this event.

Place, publisher, year, edition, pages
2017. Vol. 60, no 1, p. 305-321
Keyword [en]
Alzheimer’s disease, amyloid-beta, apolipoprotein E, astrocytes, exosomes, extracellular vesicles, mass spectrometry, neurons, shedding microvesicles
National Category
Medical and Health Sciences Neurosciences
Identifiers
URN: urn:nbn:se:uu:diva-331137DOI: 10.3233/JAD-170278ISI: 000408582800025OAI: oai:DiVA.org:uu-331137DiVA, id: diva2:1148449
Funder
Swedish Research CouncilStiftelsen Gamla TjänarinnorÅke Wiberg Foundation
Available from: 2017-10-11 Created: 2017-10-11 Last updated: 2018-01-13Bibliographically approved
In thesis
1. Cellular responses to amyloid-beta protofibrils: Focus on astrocytes, extracellular vesicles and antibody treatment
Open this publication in new window or tab >>Cellular responses to amyloid-beta protofibrils: Focus on astrocytes, extracellular vesicles and antibody treatment
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Knowledge about the cellular mechanisms behind the initiation and propagation of Alzheimer’s disease (AD) is limited. Decades of research have focused on neuronal abnormalities in AD, but recently more attention has been given to the glial cells. Being the most numerous glial cell type in the brain, astrocytes are important for many functions, but their role in AD is poorly understood. The aim with this thesis was to clarify the involvement of astrocytes in AD by using a co-culture system of primary neurons and glia. The co-cultures were exposed to soluble amyloid-beta (Aβ) aggregates, i.e. protofibrils that are known to be particularly harmful.

In Paper I, the capacity of astrocytes to ingest and degrade Aβ protofibrils was investigated. We found that astrocytes effectively ingested Aβ, but were ineffective in degrading the material. The intracellular accumulation of Aβ in astrocytes resulted in lysosomal dysfunction, high intracellular load of partly N-terminally truncated Aβ and extracellular vesicle (EV) mediated neuronal cell death.

Cells can communicate by releasing cargo into EVs, but the role of EVs in the spreading of Aβ pathology is unclear. In Paper II, the protein content of EVs released specifically following Aβ protofibril exposure was analyzed. We found markedly increased levels of apolipoprotein E (apoE) in EVs from Aβ protofibril exposed co-cultures, suggesting a role for intercellular transfer of apoE in Aβ pathology.

Passive immunotherapy has been suggested as a promising therapeutic strategy for AD. In Paper III, we investigated if the Aβ protofibril-selective antibody mAb158 could affect Aβ clearance in the co-culture. The mAb158 treatment reduced Aβ accumulation in astrocytes and rescued neurons from Aβ-induced cell death.

In Paper IV, we explored the effect of EVs, isolated from Aβ protofibril exposed co-cultures on cultured neurons. In addition to increased cell death, we found that such EVs had a strong negative impact on the synapses, dendrites and mitochondria of the neurons.

Taken together, this thesis contributes with important knowledge about the role of astrocytes in Aβ pathology, the vesicle-mediated spreading of Aβ and the effects of anti-Aβ antibody treatment.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 70
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1405
Keyword
Alzheimer’s disease, Amyloid-beta, Protofibrils, Astrocytes, Extracellular vesicles, Antibody, Neurons, Degradation
National Category
Medical and Health Sciences
Research subject
Medical Science
Identifiers
urn:nbn:se:uu:diva-334358 (URN)978-91-513-0173-0 (ISBN)
Public defence
2018-02-09, Rudbecksalen, Rudbecklaboratoriet, Dag Hammarskjölds väg 20, Uppsala, 09:15 (English)
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Available from: 2018-01-17 Created: 2017-11-28 Last updated: 2018-03-07

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