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Amyloid-β oligomers are inefficiently measured by enzyme-linked immunosorbent assay
Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Public Health and Caring Sciences.
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2005 In: Annals of Neurology, ISSN 0364-5134, Vol. 58, no 1, 147-150 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2005. Vol. 58, no 1, 147-150 p.
Identifiers
URN: urn:nbn:se:uu:diva-95486OAI: oai:DiVA.org:uu-95486DiVA: diva2:169719
Available from: 2007-03-02 Created: 2007-03-02Bibliographically approved
In thesis
1. Pathogenic Mechanisms of the Arctic Alzheimer Mutation
Open this publication in new window or tab >>Pathogenic Mechanisms of the Arctic Alzheimer Mutation
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder, neuropathologically characterized by neurofibrillay tangles and deposition of amyloid-β (Aβ) peptides. Several mutations in the gene for amyloid precursor protein (APP) cause familial AD and affect APP processing leading to increased levels of Aβ42. However, the Arctic Alzheimer mutation (APP E693G) reduces Aβ levels. Instead, the increased tendency of Arctic Aβ peptides to form Aβ protofibrils is thought to contribute to the pathogenesis.

In this thesis, the pathogenic mechanisms of the Arctic mutation were further investigated, specifically addressing if and how the mutation affects APP processing. Evidence of a shift towards β-secretase cleavage of Arctic APP was demonstrated. Arctic APP did not appear to be an inferior substrate for α-secretase, but the availability of Arctic APP for α-secretase cleavage was reduced, with diminished levels of cell surface APP in Arctic cells. Interestingly, administration of the fatty acid docosahexaenoic acid (DHA) stimulated α-secretase cleavage and partly reversed the effects of the Arctic mutation on APP processing.

In contrast to previous findings, the Arctic mutation generated enhanced total Aβ levels suggesting increased Aβ production. Importantly, this thesis illustrates and explains why measures of both Arctic and wild type Aβ levels are highly dependent upon the Aβ assay used, with enzyme-linked immunosorbent assay (ELISA) and Western blot generating different results. It was shown that these differences were due to inefficient detection of Aβ oligomers by ELISA leading to an underestimation of total Aβ levels.

In conclusion, the Arctic APP mutation leads to AD by multiple mechanisms. It facilitates protofibril formation, but it also alters trafficking and processing of APP which leads to increased steady state levels of total Aβ, in particular at intracellular locations. Importantly, these studies highlight mechanisms, other than enhanced production of Aβ peptide monomers, which could be implicated in sporadic AD.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 59 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 229
Keyword
Neurosciences, Alzheimer's disease, Arctic mutation, Amyloid precursor protein, Amyloid-β, APP processing, Aβ oligomers, Docosahexaenoic acid, Neurovetenskap
Identifiers
urn:nbn:se:uu:diva-7582 (URN)978-91-554-6806-4 (ISBN)
Public defence
2007-03-23, Rudbecksalen, Rudbecklaboratoriet, Dag Hammarskjölds väg 20, Uppsala, 09:15
Opponent
Supervisors
Available from: 2007-03-02 Created: 2007-03-02 Last updated: 2013-06-18Bibliographically approved
2. Soluble amyloid-β aggregates in Alzheimer’s disease
Open this publication in new window or tab >>Soluble amyloid-β aggregates in Alzheimer’s disease
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Soluble oligomeric aggregates of the amyloid-β (Aβ) peptide are suggested to initiate Alzheimer's disease (AD), leading to impaired synapse signalling, widespread neuronal death and loss of cognitive functions. These aggregates seem tightly linked to disease progression, and have therefore gained much attention as potential novel disease markers. In this thesis soluble oligomeric Aβ aggregates in general, and the Aβ protofibril species in particular, have been investigated with the aim to quantify and determine their role in AD pathogenesis.

Sandwich-ELISAs specifically measuring Aβ42 peptides are widely used both in AD research and as complements for clinical diagnosis. Here it was demonstrated that presence of soluble Aβ aggregates disturbs such analyses, making it difficult to interpret the results. This discovery was made through analyses of samples from cell- and mouse models carrying the AD causing 'Arctic' APP mutation. When analyzed by ELISA, Aβ42 levels were reduced in Arctic samples, in contrast to levels measured by denaturing SDS-PAGE Western blot. The same divergence in Aβ42-levels between analyses was observed in CSF samples from Down syndrome infants. The discrepancy between methods was hypothesized to be due to presence of soluble Aβ aggregates leading to impaired ELISA detection caused by epitope masking. This was confirmed by developing a protofibril specific ELISA, by which samples from Arctic cell- and mouse models were demonstrated to have enhanced Aβ protofibril levels.

AD patients have reduced ELISA-measured Aβ42-levels in CSF compared to healthy controls. To test if this reduction was due to oligomeric Aβ species present in AD CSF, Aβ42-levels were analyzed under both denaturing and non-denaturing conditions. These two measures were combined and an Aβ42 oligomer ratio established. Higher ratios were found in AD patients than healthy controls, implying that Aβ oligomers are present in CSF during Alzheimer pathogenesis. The observations from AD patients and young Down syndrome individuals suggest that Aβ42 oligomer formation is an early mechanism of AD pathogenesis, which potentially could be used as a biomarker to monitor disease development.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 69 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 430
National Category
Geriatrics
Research subject
Geriatrics
Identifiers
urn:nbn:se:uu:diva-98512 (URN)978-91-554-7441-6 (ISBN)
Public defence
2009-04-17, Rudbecksalen, Rudbecklaboratoriet, Dag Hammarskjölds väg 20, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2009-03-25 Created: 2009-02-24 Last updated: 2009-03-27Bibliographically approved

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