Hirsutine inhibits Aβ_1-42 fibrillogenesis and disintegrates preformed fibrils

AimTo explore the inhibitory effect of hirsutine (HS) against amyloid β-protein (Aβ) fibrillogenesis, as well as its disintegrating effect on mature fibrils.MethodsAn in vitro model of amyloid fibrillation was established through constant-temperature incubation of Aβ1-42. Thioflavin-T (ThT) staining was applied to detect the kinetic characteristic of Aβ1-42 aggregation. Transmission electron microscopy (TEM) was applied to observe the morphology of Aβ1-42 fibrils. Congo red(CR)staining and circular dichroism (CD) spectroscopy were used to analyse the transformation of secondary structure. 8-anilino-1-naphthene sulfonic acid (ANS) staining was applied to monitor the change of hydrophobicity. MTT, hemolysis and DCFH-DA staining experiments were used to investigate the neuronal cytotoxicity and intracellular ROS. Molecular docking was performed to analyse the reciprocal action between HS and Aβ1-42.ResultsThe addition of HS before incubation reduced the ThT fluorescence intensity (P P 1–42 amyloid fibrils. Moreover, adding HS at different time points yielded multiple notable effects, and the effects were stronger when HS was added at earlier incubation time point. As shown below, HS not only prevented Aβ1-42 fibrillization, but also transformed mature fibrils into amorphous aggregates, thereby reducing ThT fluorescence intensity (P P 1-42-treated SH-SY5Y cells (P P P P 1-42 through hydrogen bonds and hydrophobic interactions, which exhibited a strong binding affinity.ConclusionsHS can inhibit Aβ1-42 amyloid fibrillation, and may also disassemble preformed fibrils into unstructured smaller amorphous aggregates. Furthermore, these protective effects are likely attributable to its antioxidant activity as well as hydrogen bonding and hydrophobic interactions with protein molecules, thereby competitively inhibiting Aβ1-42 self-interaction and disrupting amyloid fibrillogenesis.