Hydrogen Peroxide Is Generated during the Very Early Stages of Aggregation of the Amyloid Peptides Implicated in Alzheimer Disease and Familial British Dementia

Brian J Tabner,Omar M.A El-Agnaf,Stuart Turnbull,Matthew J German,Katerina E Paleologou,Yoshihito Hayashi,Leanne J Cooper,Nigel J Fullwood,David Allsop

doi:10.1074/jbc.c500238200

Brian J Tabner, Omar M.A El-Agnaf + Show 7 more

Open Access

https://doi.org/10.1074/jbc.c500238200

Copy DOI

Abstract

Alzheimer disease and familial British dementia are neurodegenerative diseases that are characterized by the presence of numerous amyloid plaques in the brain. These lesions contain fibrillar deposits of the beta-amyloid peptide (Abeta) and the British dementia peptide (ABri), respectively. Both peptides are toxic to cells in culture, and there is increasing evidence that early "soluble oligomers" are the toxic entity rather than mature amyloid fibrils. The molecular mechanisms responsible for this toxicity are not clear, but in the case of Abeta, one prominent hypothesis is that the peptide can induce oxidative damage via the formation of hydrogen peroxide. We have developed a reliable method, employing electron spin resonance spectroscopy in conjunction with the spin-trapping technique, to detect any hydrogen peroxide generated during the incubation of Abeta and other amyloidogenic peptides. Here, we monitored levels of hydrogen peroxide accumulation during different stages of aggregation of Abeta-(1-40) and ABri and found that in both cases it was generated as a short "burst" early on in the aggregation process. Ultrastructural studies with both peptides revealed that structures resembling "soluble oligomers" or "protofibrils" were present during this early phase of hydrogen peroxide formation. Mature amyloid fibrils derived from Abeta-(1-40) did not generate hydrogen peroxide. We conclude that hydrogen peroxide formation during the early stages of protein aggregation may be a common mechanism of cell death in these (and possibly other) neurodegenerative diseases.

Highlights

Alzheimer disease and familial British dementia are neurodegenerative diseases that are characterized by the presence of numerous amyloid plaques in the brain
We focused most of our ESR measurements on the first few hours of incubation because preliminary experiments, together with our own previously published results [13, 17, 18], indicated that the dimethyl-1-pyrroline N-oxide (DMPO)-OH spectrum was usually observable after ϳ1 h
The time course for hydrogen peroxide formation was monitored by ESR spectroscopy (Fig. 1, A and B, curve b) and, again, showed three characteristic phases in DMPO-OH spectral intensity, i.e. a brief time lag before a spectrum was observed, followed by a rapid growth in spectral intensity and a subsequent decay

Summary

Introduction

Alzheimer disease and familial British dementia are neurodegenerative diseases that are characterized by the presence of numerous amyloid plaques in the brain. The full methodology has been published elsewhere [13,14,15], but, briefly, any hydrogen peroxide formed during peptide incubation can be converted to hydroxyl radicals via the Fenton reaction upon addition of Fe(II) These radicals are trapped by 5,5-dimethyl-1-pyrroline N-oxide (DMPO) to form the DMPO hydroxyl radical adduct (DMPO-OH), which has a uniquely characteristic 4-line ESR spectrum. Using this technique, we have shown that various amyloidogenic peptides, including A␤-(1– 40), A␤-(1– 42), A␤-(25–35), as well as ␣-synuclein (implicated in Parkinson disease and related disorders) and certain toxic fragments of the prion protein (implicated in the transmissible spongiform encephalopathies) can all generate hydrogen peroxide [13,14,15,16,17,18]. Similar experiments were carried out with the ABri and WT peptides

Methods

Results

Conclusion