A Sensitive Aβ Oligomerization Assay for Identification of Small Molecule Inhibitors

Abstract

Amyloid deposits found in Alzheimer’s disease result from aggregation of Aβ peptide which leads to loss of synaptic function, chronic microglial activation and cognitive impairment. Because of this, identification of small molecule inhibitors of Aβ aggregation as potential therapeutics is a topic of current interest. The majority of inhibitor screening approaches rely on in vitro assays that lack the necessary sensitivity to distinguish low-molecular weight Aβ oligomers from larger, more advanced-stage fibrillar structures. Differentiating between these two structures is of vital concern since recent studies indicate that small, early-stage Aβ oligomers are the most neurotoxic form of peptide aggregate. To address this limitation, we have explored the adaptability of a recently described ELISA-based assay for discovery of small molecule inhibitors of Aβ oligomerization. Results show that this assay is highly sensitive as it is able to quantify Aβ oligomers with as little as 80 nM input peptide. In addition, data were obtained re-confirming the function of curcumin as a potent inhibitor of Aβ aggregation (IC 50 = 2 μM) and defining its inhibitor:peptide functional stoichiometry. Further examination of other known anti-aggregation compounds showed that this assay is able to discriminate between inhibitors of early-stage, low-molecular weight oligomers and later-stage, high-molecular weight fibrillar structures. These findings indicate that this new ELISA-based assay is capable of identifying novel small molecule inhibitors that function during the initial stages of Aβ peptide assembly.