Quinazolinone Acrylamides as Multifunctional Anti-Alzheimer Agents: Unraveling their Modulating Efficacy on Amyloidogenic Peptide Assembly at the Molecular Level.

Abstract

Amyloid β peptide (Aβ) aggregation in the brain represents an initial detrimental episode in the etiology of Alzheimer's disease (AD). Recently, it has been discovered that inhibiting Aβ neurotoxicity by modulating highly toxic Aβ oligomers (AβOs) is more rewarding than reducing the overall amyloid fibril production. In line with this, here, we discussed the efficiency of multifunctional quinazolinone and vanillin acrylamide hybrids (QVA_1-5) as modulators of aggregation behavior. The thioflavin T (ThT) assay inferred dose-dependent intensification of Aβ_1-42 aggregation by QVA_1-5, which may be due to the coassembly of hybrids with AβOs. Field emission-scanning electron microscopy (FE-SEM) disclosed enormously distinctive differences among the aggregate morphologies of Aβ_1-42 and Aβ_1-42+ QVA_1-5, which intensely reinforced the modulatory action of QVA_1-5 on the molecular assembly of the Aβ_1-42 peptide. Supportingly, the Alamar Blue assay proved QVA_1-5 as an effective neuroprotector in the SH-SY5Y cell line against Aβ_1-42-induced toxicity. Consistent with these findings, western blot data showed an increased number of Aβ_1-42 fibrils in SH-SY5Y cells treated with QVA_1-5. In our molecular docking approach, all ligands had identical binding positions at sites 4-6 of the Aβ fibril structure (PDB ID: 2M4J). In the interaction pattern, ligands spanned across five Aβ monomers that were stacked together and stabilized the fibril formation by hydrophobic interactions with the Aβ monomer residues as well as neighboring ligands. In the molecular dynamics simulations, the lower RMSD and similar rGyr values for the ligands further supported the stability of the ligands inside the binding pocket of the 2M4J Aβ fibril. Overall, the present study provided a mechanistic explanation at the atomic level for the impact of small molecules (QVA_1-5) on Aβ fibril stabilization for the first time. Hence, we strongly believe that these findings will be a resource for the development of imminent drug candidates against AD that can manipulate Aβ aggregate formation.