Yeast red pigment modifies Amyloid beta growth in Alzheimer disease models in both Saccharomyces cerevisiae and Drosophila melanogaster

The effect of yeast red pigment on amyloid-beta (A beta) aggregation and fibril growth was studied in yeasts, fruit flies and in vitro. Yeast strains accumulating red pigment (red strains) contained less amyloid and had better survival rates compared to isogenic strains without red pigment accumulation (white strains). Confocal and fluorescent microscopy was used to visualise fluorescent A beta-GFP aggregates. Yeast cells containing less red pigment had more A beta-GFP aggregates despite the lower level of overall GFP fluorescence. Western blot analysis with anti-GFP, anti-A beta and A11 antibodies also revealed that red cells contained a considerably lower amount of A beta GFP aggregates as compared to white cells. Similar results were obtained with exogenous red pigment that was able to penetrate yeast cells. In vitro experiments with thioflavine and TEM showed that red pigment effectively decreased A beta fibril growth. Transgenic flies expressing A beta were cultivated on medium containing red and white isogenic yeast strains. Flies cultivated on red strains had a significant decrease in A beta accumulation levels and brain neurodegeneration. They also demonstrated better memory and learning indexes and higher locomotor ability.