Basha_2021_Int.J.Biol.Macromol__

Investigating the drug-AChE binding mechanism is vital in understanding its cogent use in medical practice against Alzheimer's disease (AD). The production and accumulation of oligomers of beta-amyloid is a central event in the neuropathology of AD. Beside the inhibition of assembly process, modulation of the aggregation process of these proteins towards minimally toxic pathways may be a possible therapeutic strategy for AD. Hence, the present study aims to examine the effect of multifunctional fused tricyclic 7-hydroxy 4-methy coumarin analogs (HMC(1-5)) on the self-induced aggregation of beta-amyloid using Thioflavin T (ThT) assay, scanning electron microscopic study, AlamarBlue and immune blotting assays and also the binding mechanism with AChE by fluorescence emission, conformational, molecular docking and molecular dynamic simulation studies under physiological pH 7.4. The ThT assay, FE-SEM study, cell line and western blots establish that the HMC(1-5) molecules could irreversibly disrupt preformed Abeta(42) fibrils, accelerate the aggregates into micro size co-assembled structures, and effectively eliminate the cytotoxicity of Abeta(1-42). Fluorescence emission studies indicating a strong binding affinity between HMC(1-5) and AChE with the binding constants of 1.04 x 10(5), 3.57 x 10(4), 1.97 x 10(4), 3.07 x 10(4) and 2.95 x 10(4) M(-1), respectively and binding sites number found to be 1. CD studies disclosed a partial unfolding in the secondary structure of AChE upon binding with HMC(1-5). Docking analysis inferred that the HMC(1-5) were bound through hydrophobic and hydrophilic interactions to the AChE active site. Molecular dynamics simulations emphasized the stability of AChE-HMC(1-5) complexes throughout the 100 ns simulations, and the local conformational changes of the residues of AChE validate the stability of complexes. These results provide new and unique complementary approach for modulating the biological effects of the Abeta aggregates by coumarin analogs and new insights for further in vivo investigations as novel anti AD agents.