| Přispěvatelé: |
Smit, AB, Rozemuller, J.M., Hoozemans, Jeroen Joseph Maria, Molecular and Cellular Neurobiology, Amsterdam Neuroscience - Neurodegeneration |
| Popis: |
AD pathology is characterized by the presence of amyloid beta (Aβ) aggregates, as plaques in the brain parenchyma and around the brain vasculature as Cerebral Amyloid Angiopathy (CAA). In addition, AD pathology is hallmarked by the presence of intraneuronal aggregates of tau protein as neurofibrillary tangles (NFTs). Another feature in AD is the increased presence of granulovacuolar degeneration (GVD) bodies which are considered to be associated with a pre-tangle stage in neuronal tau pathology. There is a positive correlation between the increase and distribution of these features and the clinical symptoms. However, there is a long pre-symptomatic phase of AD, in which brain pathology builds up and neurodegeneration starts to occur. Hence, earlier diagnosis is probably essential for a better chance of success in treating AD. In addition, AD can be clinically and pathologically divers. Disease heterogeneity, and possible differences in disease mechanisms, could also explain why past clinical trials have not yielded satisfying results, as different patients or patient groups might require different therapies. Increased insight in early disease mechanisms is highly needed and there is a clinical need to identify novel biomarkers for early, pre-symptomatic diagnosis and patient stratification. A useful approach is to identify changes in the proteome in brain tissue from AD patients. We analyzed the proteome of the CA1 and subiculum regions from the hippocampus of 40 cases derived from all stages of AD as defined by the Braak stages for tau pathology (Chapter 2). This allowed differentiation between early and late changes in protein abundance during the development of AD pathology. The abundance of 372 proteins was altered, including several proteins not linked to AD previously. Protein groups that displayed similar expression profiles over the disease course were identified and linked to specific cell-types and functional cellular processes. Next we successfully established a single cell type proteomics workflow, which allowed us to obtain insight in the molecular mechanisms associated with GVD and tau pathology in neurons (Chapter 3). A change in abundance was found for 115 proteins in GVD- and 197 in tangle-bearing neurons. Affected processes in GVD-bearing neurons included protein folding, endolysosomal function glycolysis and RNA processing. In tangle-bearing neurons similar processes are affected, yet often more extensively, and in addition, ribosomal proteins and protein folding in the ER become dysregulated. CAA type-1 is characterized by the deposition of Aβ in the brain vasculature including brain capillaries and contributes to the clinical manifestation of AD. In Chapter 4 the proteome of the occipital lobe was analyzed in cases with severe CAA type-1, AD cases with severe plaque pathology but without vascular Aβ and cognitively heathy control subjects. 29 proteins were found selectively expressed/increased in CAA type-1. IHC analysis of selected proteins in brain tissue from AD, CAA type-1 and several other types of small vessel disease cases, indicated that especially Norrin (NDP) is a highly specific marker for CAA. Guidelines for performing a successful proteomics analysis on human post-mortem tissue with the aid of (immuno-) histochemistry and LMD are provided in Chapter 5. Overall the results in this thesis improve insight in the molecular events that are involved at various stages in AD, both at a tissue level in different Braak stages for pathology, as well as at the cellular level during tangle formation. In addition, our data shows the heterogeneity in AD with respect to protein changes associated with Aβ plaque pathology compared to CAA. As such, the results presented in this thesis provide a stepping stone to new research directions, aimed to implement new biomarkers and further investigating early disease mechanisms in human brain tissue and available disease models. |
