Advances and Pitfalls in the Capillary Electrophoresis Analysis of Aggregates of Beta Amyloid Peptides

Luc Denoroy,Sandrine Parrot

doi:10.3390/separations5010002

Abstract

Alzheimer’s disease is characterized by the accumulation of brain amyloid plaques composed of aggregates of amyloid β (Aβ) peptides. The present paper describes a novel and easy-to-run capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) method for the specific analysis of fibrillar forms of Aβ aggregates obtained after in vitro incubation of Aβ 1-40 monomer. For that purpose, an affinity CE-LIF approach in which the ligand thioflavine T was added to the running buffer has been used, leading to the separation and detection of various fibrillar aggregates which migrated as spikes. The procedure has been optimized to get spikes only corresponding to Aβ aggregates, through the careful elimination of interfering factors and the electrophoretic validation of the link between spikes and particulate material. This method exhibited semi-quantification capabilities, led to the separation of Aβ fibrillar aggregates of different sizes and showed that highly concentrated solutions of Aβ peptides led to the formation of aggregates of larger size than lower-concentrated solution did. Advances brought by this method as well as future development needed to overcome its present limitations are discussed.

Highlights

The neurodegenerative Alzheimer’s disease (AD) is characterized by the accumulation of brain amyloid plaques that are mainly composed of fibrillar aggregates of the amyloid β peptides 1-40 and
The pathway leading to the formation of amyloid fibrils from the monomer forms of amyloid β (Aβ) 1-40 and Aβ 1-42 starts by the formation of small oligomers of Aβ peptides, leading to larger oligomers, to protofibrils and to fibrils [2,3,4]
Immunoassays have revealed a lowering in the concentrations of monomers of Aβ 1-40 and Aβ 1-42 in the cerebrospinal fluid (CSF) of AD patients, a result that was interpreted as reflecting a sequestration of such peptides in the plaques, leading to their reduced leakage from brain to CSF [8,9,10,11]

Summary

Introduction

The neurodegenerative Alzheimer’s disease (AD) is characterized by the accumulation of brain amyloid plaques that are mainly composed of fibrillar aggregates of the amyloid β peptides 1-40 and1-42 (Aβ 1-40 and Aβ 1-42) [1]. The neurodegenerative Alzheimer’s disease (AD) is characterized by the accumulation of brain amyloid plaques that are mainly composed of fibrillar aggregates of the amyloid β peptides 1-40 and. The involvement of amyloid plaques in the pathophysiological process of AD makes these various forms of Aβ peptides potential biomarkers for AD. Among these forms, the small soluble neurotoxic Aβ oligomers [5] could be candidate biomarkers for AD, especially for the early stage of the disease when plaques start to build up well before the apparition of any cognitive symptoms. Immunoassays have revealed a lowering in the concentrations of monomers of Aβ 1-40 and Aβ 1-42 in the cerebrospinal fluid (CSF) of AD patients, a result that was interpreted as reflecting a sequestration of such peptides in the plaques, leading to their reduced leakage from brain to CSF [8,9,10,11]

Methods

Results

Conclusion