Degradation of amyloid beta species by multi-copper oxidases

Abstract

Reduction of the production of amyloid beta (A{beta}) species has been intensively investigated as potential therapeutic approaches for Alzheimers disease (AD). However, the degradation of A{beta} species, another potential beneficial approach, has been far less explored. In this study, we discovered that ceruloplasmin (CP), an important multi-copper oxidase (MCO) in human blood, could degrade A{beta} peptides. We also found that the presence of Vitamin C could enhance the degrading effect in a concentration-dependent manner. We then validated the CP-A{beta} interaction using total internal reflection fluorescence (TIRF) microscopy, fluorescence photometer, and fluorescence polarization measurement. Based on the above discovery, we hypothesized that other MCOs had similar A{beta}-degrading functions. Indeed, we found that other MCOs could induce A{beta} degradation as well. Remarkably, we revealed that ascorbate oxidase (AO) had the strongest degrading effect among the tested MCOs. Using induced pluripotent stem (iPS) neuron cells, we observed that AO could rescue neuron toxicity which induced by A{beta} oligomers. In addition, our electrophysiological analysis with brain slices suggested that AO could prevent an A{beta}-induced deficit in synaptic transmission in the hippocampus. To the best of our knowledge, our report is the first to demonstrate that MCOs have a degrading function for peptides/proteins. Further investigations are warranted to explore the possible benefits of MCOs for future AD treatment.