Dual modulators of aggregation and dissociation of amyloid beta and tau: In vitro, in vivo, and in silico studies of Uncaria rhynchophylla and its bioactive components

Abstract

A prominent characteristic of Alzheimer's disease (AD) is the deposition of both amyloid-β (Aβ) peptide and tau protein in the brain. Aβ and tau not only induce toxicity through self-aggregation but also induce more potent toxicity through the synergistic action of Aβ and tau. In particular, neurotoxic aggregates of Aβ and tau directly affect several AD pathologies including neuroinflammation and cognitive decline. Therefore, there is increasing interest in strategies to modulate the aggregation and dissociation of Aβ and tau for treatment of AD. Our recent study found that Uncaria rhynchophylla (UR) has a therapeutic effect on AD via the inhibition of Aβ aggregation and attenuating Aβ-mediated pathogenesis of AD. However, no studies have investigated whether UR has anti- and disaggregation effects on both Aβ and tau. In this study, we showed the significant effects of UR on aggregation and dissociation of Aβ₄₂ and tau K18 using a thioflavin T (ThT) assay. In addition, histological study revealed an inhibitory effect of UR on the accumulation of Aβ and tau and AD-related pathologies in 3xTg mice with both Aβ and tau pathology. Furthermore, we found that rhynchophylline and corynoxeine, bioactive components of UR, could modulate the aggregation and dissociation of both Aβ and tau using molecular docking simulation, isothermal titration calorimetry, and ThT assays. In conclusion, our results demonstrate that UR can inhibit the aggregation of Aβ and tau and promote the degradation of their aggregates in AD.

Keywords: Alzheimer’s disease; Amyloid-β; Corynoxeine; Rhynchophylline; Tau; Uncaria rhynchophylla.