Application of an Electrochemical Method to Evaluation of Amyloid-beta Aggregation Inhibitors: Testing the RGKLVFFGR-NH2 Peptide Antiaggregant

摘要

The aggregation of amyloid- peptide (A) is believed to play a crucial role in the Alzheimer's disease (AD) pathogenesis and is considered as a therapeutic target for treating AD. The A electrooxidation via a Tyr-10 residue, sensitive to a depletion of a pool of A monomers and oligomers in the course of A aggregation, may be employed for testing natural and synthetic organic compounds (including short peptides) potentially able to inhibit the pathological A aggregation (antiaggregants). In the present work, using the known peptide antiaggregant RGKLVFFGR-NH2 (OR2) and its scrambled variant KGLRVGFRF-NH2 as a control, we demonstrate that the electrochemical method based on electrooxidation of an A42 Tyr-10 residue, when combined with methods allowing for the evaluation of the A42 aggregate structure and size, can provide essential information regarding the antiaggregant impact on A42 aggregation. Electrochemical measurements were performed using square wave voltammetry on carbon screen printed electrodes whereas the A42 aggregate structure and size were analyzed by means of the conventional thioflavin T (ThT) based fluorescence assay and dynamic light scattering. While inhibiting A42 fibrillation as manifested by the unchanged level of ThT fluorescence, the OR2 peptide antiaggregant had no effect on the decrease of A42 electrooxidation current in the course of A42 aggregation. These observations suggest that OR2 does not stop the aggregation but redirects it into a pathway where amorphous rather than fibrillar aggregates are formed. Hence, the direct electrochemistry appears to offer a simple and cost-effective approach for probing potential peptide antiaggregants, which is complementary to methods based on detecting A aggregates.