Amodiaquine Modulates Aggregation and Disassembly of Amyloid-β and Tau and Attenuates Neuroinflammatory Responses and Aβ Production.

Background: Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the accumulation of amyloid-β (Aβ) plaques and hyperphosphorylated tau tangles, which synergistically accelerate disease progression. Since Aβ plaques and tau tangles are key factors in the development of AD, dual-targeting of Aβ and tau aggregation represents a promising therapeutic strategy. Amodiaquine (AQ), a quinoline-based antimalarial, has recently attracted attention for its ability to suppress protein aggregation. However, direct effects of AQ on both Aβ and tau aggregation remain unclear. Methods: The effects of AQ on the aggregation and dissociation of Aβ and tau were examined using a thioflavin T (ThT) assays. Molecular docking and molecular dynamics (MD) simulations were performed to examine binding characteristics and structural interactions. The effects of AQ on the expression of pro-inflammatory cytokines induced by Aβ and tau aggregation in BV2 microglial cells were analyzed by qRT-PCR. Results: ThT assay demonstrated a dose-dependent dual effect of AQ on Aβ, where 25 μM inhibited aggregation after 36 h, while 250 μM markedly accelerated it, reaching a plateau within 12 h. All concentrations of AQ promoted the disassembly of mature Aβ fibrils within 12 h. Molecular docking revealed stronger binding of AQ to aggregated Aβ (-45.17 and -23.32 kcal/mol for pentameric 2BEG and hexameric 2NAO) than to monomeric Aβ (-4.81 and -7.29 kcal/mol for 1Z0Q and 2BEG). MD simulation suggested that AQ disrupted the cross-β-sheet interactions of Aβ aggregates. In the case of tau, ThT assay showed that all concentrations of AQ inhibited tau aggregation from 6 h, and 350 μM AQ promoted the disassembly of mature fibrils from 6 h. Molecular docking indicated stronger binding of AQ to aggregated tau (-27.95 and -12.13 kcal/mol for the pentameric and decameric 5O3L) than to monomeric tau (-3.05 kcal/mol for 8Q96). MD simulations revealed no major structural changes in the aggregates. In BV2 cells, 1 and 10 μM AQ significantly reduced Aβ and tau-induced TNF-α and IL-6 mRNA expressions. In APP-H4 cells, 10 μM AQ decreased the level of Aβ compared to the control. Conclusions: AQ modulates both Aβ and tau aggregation and attenuates neuroinflammation and reduces Aβ pathology, supporting its potential as a dual-target therapeutic candidate for AD.