Inhibition of amyloid fibril formation and disassembly of pre-formed fibrils by natural polyphenol rottlerin.

Abstract Natural polyphenols, curcumin, rottlerin and EGCG were selected for initial computational modeling of protein-ligand interaction patterns. The docking calculations demonstrated that these polyphenols can easily adjust their conformational shape to fit well into the binding sites of amyloidogenic proteins. The experimental part of the study focused on the effect of rottlerin on fibrillation of three distinct amyloidogenic proteins, namely insulin, lysozyme and Aβ 1–40 peptide. Different experimental protocols such as fluorescence spectroscopy, circular dichroism and atomic force microscopy, demonstrated that amyloid fibril formation of any of the three proteins is inhibited by low micromolar rottlerin concentrations. Most likely, the inhibition of amyloid formation proceeded via interaction of rottlerin with amyloidogenic regions of the studied proteins. Moreover, rottlerin was also effective in pre-formed fibrils disassembly, suggesting that interactions of rottlerin with fibrils were capable to interrupt the fibril-stabilizing bonds of β-sheets. The apparent IC 50 and DC 50 values were calculated in the range of 1.3–36.4 μM and 15.6–25.8 μM, respectively. The strongest inhibiting/disassembling effect of rottlerin was observed on Aβ 1–40 peptide. The cytotoxicity assay performed on the Neuro 2a cells indicated time-dependent cell morphology changes but rottlerin affected the cell viability only at concentration above 50 μM. The results of this study suggest that chemical modifications on rottlerin could be tested in the future as a promising strategy for the modulation of amyloidogenic proteins aggregation. Graphical abstract Unlabelled Image Highlights • " In silico " studies on ligand-amyloidogenic proteins interactions of selected polyphenols recommended rottlerin for experimental analysis • The computational studies indicate easily adjustment of rottlerin conformational shape to match the binding site of amyloidogenic proteins • Rottlerin is able to inhibit amyloid fibril formation and to disassemble pre-formed amyloid fibrils for all of the amyloidogenic proteins tested • In vivo assays indicated concentration and time-dependent effects on cell viability and morphology [ABSTRACT FROM AUTHOR]