Differential Responses of Amyloid-β 42 Aggregates to Resveratrol.

Amyloid-β (Aβ) aggregation is targeted with small molecules as a pathway toward developing potential Alzheimer's disease (AD) therapies. Resveratrol, a natural polyphenol, has been proposed as an inhibitor of Aβ aggregation, but its mechanistic effects across distinct Aβ42 aggregates remain unresolved. To better evaluate resveratrol's potential to treat AD, here we focus on molecular-level insights into the mechanisms that underlie its interaction with several distinct classes of Aβ42 aggregates. In contrast to published approaches that are based on monitoring the evolution of the total fibrillar mass, we employ time-resolved in situ atomic force microscopy to explore the effects of resveratrol on Aβ42 amyloid and non-amyloid assemblies. While data suggest a weak interaction between resveratrol and low-molecular-weight Aβ42 species, we also observe a concentration-dependent reduction in fibrillization. In the presence of resveratrol, we observe a decrease in fibril thickness and end-dependent slowing of elongation; furthermore, the fibrils exhibit reduced mechanical integrity and fragment under minimal scanning stress. Importantly, resveratrol does not affect the formation or morphology of oligomers and amorphous aggregates. These findings suggest that resveratrol selectively targets the fibril pathway while leaving oligomeric assemblies unaltered. The results provide mechanistic insights into the differential effects of small molecules on Aβ42 assemblies and establish a framework for evaluating inhibitors of aggregation with single-aggregate resolution.