Divergent Age-Dependent Conformational Rearrangement within Aβ Amyloid Deposits in APP23, APPPS1, and AppNL-F Mice

It is of critical importance to our understanding of Alzheimers disease (AD) pathology to determine how key pathological factors are interconnected and implicated in nerve cell death, clinical symptoms, and disease progression. The formation of extracellular beta-amyloid plaques is the major pathological hallmark of AD and beta-amyloid has been suggested to be a critical inducer of AD, driving disease pathogenesis. Exactly how beta-amyloid plaque formation begins and how ongoing plaque deposition proceeds and initiates subsequent neurotoxic mechanisms is not well understood. The primary aim of our research is to elucidate the biochemical processes underlying early beta-amyloid plaque formation in brain tissue. We recently introduced a chemical imaging paradigm based on mass spectrometry imaging (MSI) and metabolic isotope labelling to follow stable isotope labelling kinetics (iSILK) in vivo to track the in vivo build-up and deposition of beta-amyloid. Herein, knock-in beta-amyloid mouse models (AppNL-F) that develop beta-amyloid pathology gradually are metabolically labeled with stable isotopes. This chemical imaging approach timestamps amyloid plaques during the period of initial deposition allowing the fate of aggregating beta-amyloid species from before and during the earliest events of plaque pathology through plaque maturation to be tracked. To identify the molecular and cellular response to plaque maturation, we integrated iSILK with single plaque transcriptomics performed on adjacent tissue sections. This enabled changes in gene expression to be tracked as a function of plaque age (as encoded in the beta-amyloid peptide isotopologue pattern) distinct from changes due to the chronological age or pathological severity. This approach identified that plaque age correlates negatively with gene expression patterns associated with synaptic function as early as in 10-month-old animals but persists into 18 months. Finally, we integrated hyperspectral confocal microscopy into our multiomic approach to image amyloid structural isomers, revealing a positive correlation between plaque age and amyloid structural maturity. This analysis identified three categories of plaques, each with a distinct impact on the surrounding microenvironment. Here, we identified that older, more compact plaques were associated with the most significant synapse loss and toxicity. These data show how isotope-encoded MS imaging can be used to delineate beta-amyloid toxicity dynamics in vivo. Moreover, we show for the first time a functional integration of dynamic MSI, structural plaque imaging and whole genome-wide spatial transcriptomics at the single plaque level. This multiomic approach offers an unprecedented combination of temporal and spatial resolution enabling a description of the earliest events of precipitating amyloid pathology and how beta-amyloid modulates synaptotoxic mechanisms.

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Amyloid beta 1‐40 and 1‐42 fibril ratios and maturation level cause conformational differences with minimal impact on autophagy and cytotoxicity

Johansson,

Sandberg,

Nyström

et al. 2024

Journal of Neurochemistry

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The amyloid β (Aβ) peptide has a central role in Alzheimer's disease (AD) pathology. The peptide length can vary between 37 and 49 amino acids, with Aβ1‐42 being considered the most disease‐related length. However, Aβ1‐40 is also found in Aβ plaques and has shown to form intertwined fibrils with Aβ1‐42. The peptides have previously also shown to form different fibril conformations, proposed to be related to disease phenotype. To conduct more representative in vitro experiments, it is vital to uncover the impact of different fibril conformations on neurons. Hence, we fibrillized different Aβ1‐40:42 ratios in concentrations of 100:0, 90:10, 75:25, 50:50, 25:75, 10:90 and 0:100 for either 24 h (early fibrils) or 7 days (aged fibrils). These were then characterized based on fibril width, LCO‐staining and antibody‐staining. We further challenged differentiated neuronal‐like SH‐SY5Y human cells with the different fibrils and measured Aβ content, cytotoxicity and autophagy function at three different time‐points: 3, 24, and 72 h. Our results revealed that both Aβ1‐40:42 ratio and fibril maturation affect conformation of fibrils. We further show the impact of these conformation changes on the affinity to commonly used Aβ antibodies, primarily affecting Aβ1‐40 rich aggregates. In addition, we demonstrate uptake of the aggregates by neuronally differentiated human cells, where aggregates with higher Aβ1‐42 ratios generally caused higher cellular levels of Aβ. These differences in Aβ abundance did not cause changes in cytotoxicity nor in autophagy activation. Our results show the importance to consider conformational differences of Aβ fibrils, as this can have fundamental impact on Aβ antibody detection. Overall, these insights underline the need for further exploration of the impact of conformationally different fibrils and the need to reliably produce disease relevant Aβ aggregates.image

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Divergent Age-Dependent Conformational Rearrangement within Aβ Amyloid Deposits in APP23, APPPS1, and App^NL-F Mice

Cited by 3 publications

References 55 publications

Efficient Seeding of Cerebral Vascular Aβ-Amyloidosis by Recombinant AβM1-42 Amyloid Fibrils

Efficient Seeding of Cerebral Vascular Aβ-Amyloidosis by Recombinant AβM1-42 Amyloid Fibrils

Isotope Encoded chemical Imaging Identifies Amyloid Plaque Age Dependent Structural Maturation, Synaptic Loss, and Increased Toxicity

Amyloid beta 1‐40 and 1‐42 fibril ratios and maturation level cause conformational differences with minimal impact on autophagy and cytotoxicity

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