The Aβ42:Aβ40 ratio modulates aggregation in beta-amyloid oligomers and drives metabolic changes and cellular dysfunction
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Updated: May 8, 2025
Visualization of Amyloid β Deposits in the Human Brain with Matrix-assisted Laser Desorption/Ionization Imaging Mass Spectrometry
Published on: March 7, 2019
Annika Haessler1, Stefanie Gier1, Nathalie Jung1
1Institute of Pharmaceutical Technology, Goethe University Frankfurt, Frankfurt am Main, Germany.
Abstract:
The pathophysiological role of Aβ42 oligomers in the onset of Alzheimer's disease (AD) is heavily disputed, pivoting research toward investigating mixed oligomers composed of Aβ42 and Aβ40, which is more abundant but less aggregation-prone. This study investigates Aβ42:Aβ40 oligomers in different ratios, examining their adverse effects on endothelial cells, neurons, astroglia, and microglia, as well as in a human blood-brain barrier (BBB) model. Combining label-free Raman microscopy with complementary imaging techniques and biochemical assays, we show the prominent impact of Aβ40 on Aβ42 fibrillation, suggesting an inhibitory effect on aggregation. Mixed oligomers, especially with low proportions of Aβ42, were equally detrimental as pure Aβ42 oligomers regarding cell viability, functionality, and metabolism. They also differentially affected lipid droplet metabolism in BBB-associated microglia, indicating distinct pathophysiological responses. Our findings demonstrate the overarching significance of the Aβ42:Aβ40 ratio in Aβ oligomers, challenging the traditional focus on Aβ42 in AD research.
Insights
Alzheimer's research shows that mixtures of amyloid-beta 42 (Aβ42) and Aβ40 oligomers, not just Aβ42 alone, significantly harm brain cells and the blood-brain barrier, regardless of the ratio.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- The role of amyloid-beta 42 (Aβ42) oligomers in Alzheimer's disease (AD) pathogenesis is debated.
- Research is shifting towards investigating mixed Aβ42:Aβ40 oligomers due to Aβ40's abundance and differing aggregation properties.
Purpose of the Study:
- To investigate the impact of Aβ42:Aβ40 oligomers at various ratios on cellular components of the brain and the blood-brain barrier (BBB).
- To understand the differential effects of these mixed oligomers on neuronal and glial cell function and metabolism.
Main Methods:
- Utilized label-free Raman microscopy combined with other imaging techniques.
- Employed biochemical assays to analyze Aβ oligomer composition and cellular responses.
- Assessed effects on endothelial cells, neurons, astroglia, microglia, and a human BBB model.
Main Results:
- Aβ40 significantly influences Aβ42 fibrillation, potentially inhibiting aggregation.
- Mixed Aβ42:Aβ40 oligomers, even with low Aβ42 content, were as detrimental to cell viability, function, and metabolism as pure Aβ42 oligomers.
- Differential effects on lipid droplet metabolism were observed in BBB-associated microglia, suggesting distinct pathophysiological mechanisms.
Conclusions:
- The ratio of Aβ42 to Aβ40 in oligomers is critically important in Alzheimer's disease pathophysiology.
- Findings challenge the exclusive focus on Aβ42, highlighting the broader significance of mixed oligomer composition in AD.
- Mixed oligomers exhibit complex detrimental effects across different brain cell types and the BBB model.
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