Synergistic effects of negatively charged hydrophobic nanoparticles and (-)-epigallocatechin-3-gallate on inhibiting amyloid beta-protein aggregation

摘要

Fibrillogenesis of amyloid beta-protein (A beta) in human brain has been implicated as the main cause of Alzheimer's disease. A few small molecules from natural sources have been discovered for their inhibition effects on A beta fibrillation, of which (-)-epigallocatechin-3-gallate (EGCG) is one of the most broadly investigated compounds for its potent inhibitory activity. However, in vivo applicability of the inhibitors is largely limited by their low transmembrane efficiency. Hence, it is of great significance to develop inhibition systems that function at low concentrations. In this work, a dual-inhibitor system containing EGCG and negatively charged polymeric nanoparticles (NP10), which was also demonstrated effective on the inhibition of A beta aggregation, was developed and comprehensively studied by extensive biophysical and biological assays. It was found that the dual-inhibitor system at low concentrations was more effective on the inhibition and detoxification of A beta (A beta(42) and A beta(40)) fibrillation than the additive effects of these two agents working individually. Namely, there was a synergistic effect of the two inhibitors. The synergism factor reached 1.25 with 5 mu M EGCG and 5 mu g/mL NP10. Kinetic studies with A beta(40) revealed that the two inhibitors functioned in different A beta assembling stages: NP10 mainly inhibited primary nucleation, while EGCG suppressed fibril elongation and changed the fibril structure to make it show less seeding activities in the secondary nucleation. NP10 might also help EGCG binding to All, leading to its enhanced inhibitory effects on fibril elongation and secondary nucleation. The synergistic effect observed in the dual-inhibitor system offered new insight into the development of potent inhibitor systems against amyloid neurotoxicity. (C) 2016 Elsevier Inc. All rights reserved.