Dihydrophthalazinediones accelerate amyloid β peptide aggregation to nontoxic species

Abstract

The production and accumulation of toxic amyloid plaques is one of the hallmarks of Alzheimer’s disease (AD). Amyloid beta (Aβ) peptides undergo self-aggregation to form soluble oligomers, protofibrils and insoluble fibrils. This process is termed as amyloidogenesis and is a major contributor to the observed neuronal damage and memory impairment in the AD brain. Therefore, modulation of Aβ aggregation process is considered to be an effective target to prevent neuronal damage under AD conditions. Modulation of amyloidogenesis involves inhibition of aggregation to form a toxic species or acceleration to drive the aggregation process to form species that are nontoxic by employing well-designed external ligands. In this context, we report a set of 2,3-dihydrophthalazine-1,4-dione (dihydrophthalazinedione, Phz) based small molecules (Phz 1–4) to modulate the Aβ42 aggregation and in cellular toxicity. Our detailed study (thioflavin T fluorescence assay, dot blot and transmission electron microscopy analysis) revealed fluorine containing Phz 4 as the potent modulator of Aβ42 aggregation by accelerating the process to form nontoxic aggregated species through hydrophobic and halogen interactions. Aβ42 aggregates formed in the presence of Phz 4 are mostly nontoxic when compared to the normal amyloid aggregates in the cellular milieu (PC12 cells). This study established that the hydrophobic and halogen interactions can be employed to develop anti-AD drug candidates. The excellent cell viability, effective modulation of Aβ42 aggregation to form nontoxic species and cellular (neuronal) rescue by Phz 4 offer a novel platform to develop therapeutic strategies for AD.