380553 The Natural Stilbenoid Resveratrol and Its Derivatives' Inhibitory Capability Toward Alzheimer's Disease Associated Amyloid-β Protein Aggregation
Non-toxic, Aβ monomers are natural and non-harmful proteins that exist in human brain; however, after their self-assembly into aggregated species like oligomers, protofibrils and eventually fibrils, they become toxic and lead to neurodegeneration associated with Alzheimer’s disease (AD). AD is a top 10 cause of death in the United States and it is the only one that presently has no cure. Numerous studies on treatment of AD along with epidemiological evidence indicate that moderate consumption of red wine, which is abundant in the polyphenol resveratrol, might reduce the incidence of AD. Therefore, resveratrol becomes a potential drug target for AD. This study elucidates the ability of derivatives of the small molecule resveratrol, including piceatannol, oxyresveratrol and piceid, to inhibit the AD-associated Ab aggregation process.
First, the ability of resveratrol derivatives to inhibit the overall process of Aβ monomer aggregation into mature fibrils is evaluated using dot blotting with an antibody that binds to amyloid aggregate fibril structure. TEM images are also used to confirm inhibition as well as to identify morphological changes caused by the presence of compounds. Inhibition of the early stages of aggregation is examined using an oligomerization assay that employs SDS-PAGE with Western blot to determine the size of oligomers formed. Inhibition of later stages of aggregation is examined by evaluating the effect of compounds on soluble aggregate growth by elongation via monomer addition or lateral association of soluble aggregates. Here, dynamic light scattering is used to measure increases in aggregate hydrodynamic radius. Finally, these compounds’ ability to dissociate already formed Aβ fibrils into smaller species is tested by dot blot as described above.
Aggregation assays reveal that piceatannol exhibits the most promising inhibition of Aβ aggregation, with a 90% inhibition of fibril formation. In contrast, only oxyresveratrol has a slight effect on decreasing the amount of small oligomers (molecular weight 25-100kDa) and none of the compounds are capable of decreasing the amount of larger oligomers (molecular weight 100-250kDa). Interestingly, all of the compounds are effective inhibitors of soluble aggregate elongation; however, only piceatannol can effectively inhibit soluble aggregate association. Piceatannol also stimulates dissociation of Aβ fibrils, while other compounds have a limited effect.
The inhibitory capability of piceatannol and, to a lesser extent, other resveratrol derivatives on Aβ aggregation could in part explain the correlation between red wine consumption and a reduced incidence of AD. Piceatannol shows superior inhibitory ability in Aβ monomer aggregation, soluble aggregate elongation and association, and Aβ fibril dissociation. Therefore, this resveratrol derivative is the most promising compound for further study toward a therapeutic role in the treatment of AD.