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Alzheimer's disease. Beta-amyloid precursor protein expression in the nucleus basalis of Meynert
G M Murphy1, B D Greenberg, W G Ellis
1Department of Psychiatry, Stanford University School of Medicine, California.
Abstract:
The nucleus basalis of Meynert (nbM) was examined using immunocytochemistry for beta-amyloid precursor protein (beta APP) expression in Alzheimer's disease (AD). In mild AD cases, light labeling of the cell body and proximal processes was observed, and small intracellular structures were labeled rarely. In the more severe cases, intense cytoplasmic beta APP labeling was seen, often along with small beta APP-positive structures. Double-labeling experiments demonstrated that in the more severe cases these small structures were also decorated by a neurofibrillary tangle (NFT) antiserum. Other neurons in the severe cases showed incorporation of beta APP into large inclusions, which were also labeled with the NFT antiserum. However, some large inclusions in the severe cases were labeled by the NFT antiserum but contained no beta APP. Extraneuronal NFTs did not show beta APP labeling and did not react with an antibody to the beta-amyloid peptide. These results suggest that increased expression of beta APP coincides with intracellular NFT formation in the nbM, but that the formation of extraneuronal NFTs results in a loss of beta APP immunoreactivity.
Insights
Beta-amyloid precursor protein (beta APP) expression increases with neurofibrillary tangle (NFT) formation in Alzheimer
Area of Science:
- Neuroscience
- Neuropathology
- Molecular Biology
Background:
- Alzheimer's disease (AD) is characterized by the accumulation of beta-amyloid plaques and neurofibrillary tangles (NFTs).
- The nucleus basalis of Meynert (nbM) is significantly affected in AD, showing neuronal loss and neurofibrillary pathology.
- Beta-amyloid precursor protein (beta APP) is central to AD pathogenesis, but its precise role in NFT formation within specific brain regions remains under investigation.
Purpose of the Study:
- To investigate the expression and localization of beta-amyloid precursor protein (beta APP) in the nucleus basalis of Meynert (nbM) in relation to neurofibrillary tangle (NFT) formation in Alzheimer's disease (AD).
- To determine the correlation between beta APP accumulation and the development of intracellular and extraneuronal NFTs in the nbM.
Main Methods:
- Immunocytochemistry was employed to detect beta APP expression in the nbM of AD brains.
- Double-labeling techniques were used to co-localize beta APP with neurofibrillary tangle (NFT) markers.
Main Results:
- Mild AD cases showed light beta APP labeling in nbM neurons, with rare labeling of small intracellular structures.
- Severe AD cases exhibited intense cytoplasmic beta APP labeling and small beta APP-positive structures that were also decorated by NFT antiserum.
- Large inclusions in severe AD cases contained beta APP and NFT markers, while some NFT-positive inclusions lacked beta APP. Extraneuronal NFTs did not show beta APP or beta-amyloid peptide immunoreactivity.
Conclusions:
- Increased beta APP expression correlates with intracellular neurofibrillary tangle (NFT) formation in the nucleus basalis of Meynert (nbM) in Alzheimer's disease (AD).
- The formation of extraneuronal NFTs in the nbM appears to be associated with a loss of beta APP immunoreactivity, suggesting distinct pathological pathways.