Wojciech Michno (Presenter)
Sahlgrenka Academy at University of Gothenburg
Bio: Wojciech Michno has studied in Poland, Sweden, Norway, and the United States. He is a United World College (Norway) scholar and a Macalester College (USA) alumnus. At the university he completed two degrees in parallel, one in Chemistry and one in Neuroscience, with a focus on molecular neurobiology. Wojciech did his master’s thesis in pharmacology, and is now completing his PhD in analytical neurochemistry working with Alzheimer’s disease at Sahlgrenska Academy, University of Gothenburg, Sweden.
Authorship: Wojciech Michno (1), Dimitri Brinet (1) and Stina Syvänen (2) and Jörg Hanrieder* (1,3,4)
(1) University of Gothenburg, Mölndal, Sweden; (2) Uppsala University, Uppsala, Sweden; (3) University College London, UK; (4) Chalmers University of Technology, Gothenburg, Sweden;
| Short Abstract Alzheimer's disease (AD) is a chronic, neurodegenerative disease, of which the underlying pathological mechanism is still not understood. The disease is characterized by accumulation of amyloid-beta (Abeta) peptides into different extracellular plaques. Plaques have also been found in non-demented pathological ageing patients. Therefore, discrimination between structural and molecular plaque architecture are of essential interest to resolve Abeta plaque pathology in AD. Here, hyperspectral imaging paradigm employing the Abeta aggregate binding luminescent conjugated oligothiophenes (LCO) in combination with an in-house software was used to differentiate between different types of plaques. The approach was further shown to be applicable for laser microdissection and offline mass spectrometric analysis, which validated the presence of various C- and N-terminal Aβ in the plaques. |
Long Abstract
Alzheimer's disease is a chronic, neurodegenerative disease that affects more than 44 million people worldwide and accounts for about 60% of all dementia cases (1,2). It is characterized by cognitive decline and memory loss as a result of neuronal degeneration and loss of synapses (3). The exact mechanisms underlying AD pathogenesis are still not fully understood, significantly hampering the development of therapeutic treatment strategies. These have however been linked to progressive accumulation of hyperphosphorylated tau protein into intraneuronal tangles and amyloid beta (A) peptides into intra- and extracellular deposits or plaques (2).
While this amyloid pathology has been suggested to be a critical inducer of AD pathogenesis, the correlation of plaque burden and AD progression has been questioned. For instance, amyloid plaques have been found in pathological ageing (PA) patients that were cognitively normal (4). However, Abeta plaques present in PA brains are mostly diffuse in nature, while plaques in AD brain tissue are mostly mature/compact. Diffuse plaques can be a consequence of an alternative, neuroprotective aggregation mechanism. Alternatively, diffuse plaques can represent an immature non-toxic state of mature compact amyloid plaques. The factors that promote neurotoxic plaque formation are still unknown. Chemical imaging that allows the efficient discrimination of structural and molecular plaque architecture is of essential interest to resolve Abeta plaque pathology in AD. Further, changes in amyloid peptide truncation and plaque associated neuronal lipid species have been implicated with proteopathic mechanisms in AD (5,6). Current biochemical methods, however, lack the necessary molecular specificity to study plaque chemistry, highlighting the need to develop new and to employ new bioanalytical techniques, such as mass spectrometry.
The aim of this study was therefore to employ chemical and immuno-labeling strategies for hyperspectral imaging of individual Abeta plaques in AD and PA brain. These were later to be isolated using laser microdissection for subsequent offline analysis using various mass spectrometric techniques.
Therefore, Luminescent conjugated oligothiophenes (LCO), in combination with fluorescence immunolabelling, were optimized and applied to detect and discriminate Abeta plaque heterogeneity based on chemical and structural features. LCOs have been suggested to exhibit differential binding to the various amyloid aggregation states (7). In particular, q-FTAA (quattro-formylthiophene, green) has been suggested to respond only to mature Aβ amyloid fibrils, whereas h-FTAA (hepta-FTAA, red) binds to mature amyloid fibrils and early pre-fibrillar states (diffuse plaques). Here these two LCO’s probes were used and complemented with immunohistochemistry to verify the Aβ identity of these plaques in general and validate MS results (e.g. ratio of Aβ1-42/Aβ1-40).
Preliminary studies in human AD brain tissue revealed that the attributed characteristics of the LCO were not directly transferable to the human brain tissue, due to the possible mixed nature of Abeta conformation states being present in the Abeta deposits. However, the use of a hyperspectral imaging paradigm, in combination with an in-house developed software, showed that the LCOs can still be use for characterization of Abeta aggregates by using multiplexed image acquisition with two wavelength excitation and linear unmixing. The approach was further shown to be applicable for laser microdissection and offline mass spectrometric analysis, which validated the presence of various C- and N-terminal Aβ in the plaques. Further, different extraction procedures were shown to yield differential peptide population, highlighting the significance of understanding of the chemical structures underlying the plaque formation.
References & Acknowledgements:
(1) Alzheimer’s Disease International. Alzheimers Disease International. World Alzheimer Report 2014. (2014).
(2) Blennow, K., de Leon, M. J. & Zetterberg, H. Alzheimer’s disease. Lancet 368, 387–403 (2006).
(3) Burns, A. & Iliffe, S. Alzheimer’s disease. BMJ 338, b158 (2009).
(4) Moore, B. D. et al. Overlapping profiles of Abeta peptides in the Alzheimer’s disease and pathological aging brains. Alzheimers. Res. Ther. 4, 18 (2012).
(5) Di Paolo G. and Kim TW, Nat Rev Neurosci, 2011, 12(5): p.284-296
(6) Selkoe, D.J. and Schenk D., Annu Rev Pharmacol Toxicol, 2003.43: p. 545-84
(7) K. P. Nilsson, A. Aslund, I. Berg, et al., ACS Chem Biol
2007, 2. 553-60
| Description | Y/N | Source |
| Grants | no | |
| Salary | no | |
| Board Member | no | |
| Stock | no | |
| Expenses | no |
IP Royalty: no
| Planning to mention or discuss specific products or technology of the company(ies) listed above: | no |