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The amyloid beta-protein of Alzheimer's disease is chemotactic for mononuclear phagocytes
J B Davis1, H F McMurray, D Schubert
1Salk Institute for Biological Studies, San Diego, CA 92186-5800.
Abstract:
The cellular pathology of Alzheimer's disease includes an accumulation of microglia surrounding the amyloid plaques. We report that human amyloid beta-protein is chemotactic for murine resident peritoneal macrophages and rat microglia, which may account for the increased density of microglia in plaques. A maximal chemotactic response was observed at 1-10nM, with a 2.5 fold increase in activity over controls for both classes of mononuclear phagocytes. The neurotoxic peptide fragment (25-35) of amyloid beta-protein is similarly chemotactic, while a control scrambled version and the precursor protein are not chemotactic. These results indicate that beta-protein may influence plaque formation via the recruitment of phagocytes, with consequent implications for the future development of treatments for Alzheimer's disease.
Insights
Alzheimer's disease pathology involves microglia clustering around amyloid plaques. Amyloid beta-protein attracts these immune cells, potentially driving plaque formation and offering new treatment targets.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Alzheimer's disease (AD) is characterized by amyloid plaques.
- Microglia, the brain's immune cells, accumulate around these plaques in AD pathology.
- The mechanism driving microglial recruitment to plaques is not fully understood.
Purpose of the Study:
- To investigate the chemotactic properties of amyloid beta-protein for phagocytic cells.
- To determine if amyloid beta-protein directly influences the migration of microglia and macrophages.
Main Methods:
- Chemotaxis assays were performed using murine peritoneal macrophages and rat microglia.
- Tested the chemotactic activity of human amyloid beta-protein, its neurotoxic fragment (25-35), a scrambled control, and the precursor protein.
- Quantified the migration of mononuclear phagocytes in response to varying concentrations of amyloid beta-protein.
Main Results:
- Human amyloid beta-protein demonstrated significant chemotactic activity for both macrophages and microglia.
- Maximal chemotaxis was observed at nanomolar concentrations (1-10nM), with a 2.5-fold increase in cell activity.
- The neurotoxic fragment (25-35) was chemotactic, while the scrambled control and precursor protein were not.
Conclusions:
- Amyloid beta-protein acts as a chemoattractant for microglia and macrophages.
- This recruitment of phagocytes by beta-protein may contribute to the increased density of microglia observed in amyloid plaques.
- These findings suggest a potential therapeutic strategy targeting beta-protein-mediated immune cell recruitment in Alzheimer's disease.