Cyanidin-3-O-glucoside inhibits Aβ40 fibrillogenesis, disintegrates preformed fibrils, and reduces amyloid cytotoxicity
Alzheimer's disease (AD) is mainly caused by the fibrillogenesis of amyloid-β protein (Aβ). Therefore, development of effective inhibitors against Aβ fibrillogenesis offers great hope for the treatment of AD. Cyanidin-3-O-glucoside (Cy-3G) is a commonly found anthocyanin that is mainly present in fruits, with established neuroprotective effects in situ. However, it remains unknown if Cy-3G can prevent Aβ fibrillogenesis and alleviate the corresponding cytotoxicity. In this study, extensive biochemical, biophysical, biological and computational experiments were combined to address the issue. It was found that Cy-3G significantly inhibits Aβ40 fibrillogenesis and disintegrates mature Aβ fibrils, and its inhibitory capacity is dependent on Cy-3G concentration. The circular dichroism results showed that Cy-3G prevents the structural transformation of Aβ40 from its initial random coil to the β-sheet-rich structure. Co-incubation of Aβ40 with Cy-3G significantly reduced the production of intracellular reactive oxygen species induced by Aβ40 fibrillogenesis and deviated Aβ40-induced cytotoxicity. Molecular dynamics simulations revealed that Cy-3G disrupted the β-sheet structure of the Aβ40 trimer. Cy-3G was found to mainly interact the N-terminal region, the central hydrophobic cluster and the β-sheet region II via hydrophobic and electrostatic interactions. The ten hot spot residues D7, Y10, E11, F19, F20, E22, I31, I32, M35 and V40 were also identified. These findings not only enable a comprehensive understanding of the inhibitory effect of Cy-3G on Aβ40 fibrillogenesis, but also identify a valuable dietary ingredient that possesses great potential to be developed into functional foods to alleviate AD.