Taxifolin prevents fibrillogenesis of HEWL by formation of very large globular, chain-like aggregates

Among therapeutic approaches for amyloid related diseases attention has recently turned to the use of natural products as effective anti-aggregation compounds. Although a wealth of in vitro and in vivo evidence indicates inhibitory activity of these compounds against protein aggregation, but their mechanism of action are largely different. Here, we show that taxifolin, as a ubiquitous bioactive constituent of foods and herbs, is a potent inhibitor of hen egg white lysozyme (HEWL) fibrillogenesis. A range of amyloid specific techniques were employed to explore the mechanism by which taxifolin exert its inhibitory effects. Obtained results demonstrate that taxifolin can inhibit HEWL amyloid formation in vitro, by causing the formation of very large globular, chain-like aggregates. Rather than interfering with HEWL amyloid formation by stabilizing the molecule in its native-like state, we found that taxifolin exerts its effect by binding to HEWL prefibrillar species, produced in the course of fibrillation process. Their binding results in diverting the amyloid pathway toward very large aggregates with globular morphology, arranged in a chain-like structure. Interestingly, ThT fluorescence measurements show that, along with generation of large protofibrillar aggregates at the end of growth phase, the binding capacity of taxifolin was significantly reduced. Finally, the possible binding site(s) and the type of interaction between HEWL and taxifolin were also determined using fluorescence quenching and molecular docking. Although taxifolin appears to be a potent inhibitor of amyloid fibril formation, whether its anti-fibrillation activity is specific to the HEWL model protein or is more generic remains to be established