Alzheimer's disease, characterized by deposits of amyloid β-peptide (Aβ), is the most common neurodegenerative disease, but it still lacks a specific treatment. We have discovered five chemically unrelated inhibitors of the in vitro aggregation of the Aβ17-40 peptide by screening two commercial chemical libraries. Four of them (1-4) exhibit relatively low MCCs toward HeLa cells (17-184 μM). The usefulness of compounds 1-4 to inhibit the in vivo aggregation of Aβ1-42 has been demonstrated using two fungi models, Saccharomyces cerevisiae and Podospora anserina, previously transformed to express Aβ1-42. Estimated IC(50)s are around 1-2 μM. Interestingly, addition of any of the four compounds to sonicated preformed P. anserina aggregates completely inhibited the appearance of SDS-resistant oligomers. This combination of HTP in vitro screening with validation in fungi models provides an efficient way to identify novel inhibitory compounds of Aβ1-42 aggregation for subsequent testing in animal models.

Human Amylin, or islet amyloid polypeptide (hIAPP), is a small hormone secreted by pancreatic β-cells that forms aggregates under insulin deficiency metabolic conditions, and it constitutes a pathological hallmark of type II diabetes mellitus. In type II diabetes patients, amylin is abnormally increased, self-assembled into amyloid aggregates, and ultimately contributes to the apoptotic death of β-cells by mechanisms that are not completely understood. We have screened a library of approved drugs in order to identify inhibitors of amylin aggregation that could be used as tools to investigate the role of amylin aggregation in type II diabetes or as therapeutics in order to reduce β-cell damage. Interestingly, three of the compounds analyzed—benzbromarone, quercetin, and folic acid—are able to slow down amylin fiber formation according to Thioflavin T binding, turbidimetry, and Transmission Electron Microscopy assays. In addition to the in vitro assays, we have tested the effect of these compounds in an amyloid toxicity cell culture model and we have found that one of them, quercetin, has the ability to partly protect cultured pancreatic insulinoma cells from the cytotoxic effect of amylin. Our data suggests that quercetin can contribute to reduce oxidative damage in pancreatic insulinoma β cells by modulating the aggregation propensity of amylin.

DMSO alters Abeta's conformation and its recognition by inhibitors.