Affiliations: [a]
Department of Pharmacology, 1009C Stellar Chance Laboratories, University of Pennsylvania, Philadelphia, PA, USA
| [b] Present address: Division of Foods, National Institute of Health Sciences, Kawasaki City, Kanagawa, Japan
| [c]
Present address: College of Pharmaceutical Sciences, Ritsumeikan University, Kusatsu, Shiga, Japan
Correspondence:
[*]
Correspondence to: Paul H. Axelsen, Department of Pharmacology, 1009C Stellar Chance Laboratories, University of Pennsylvania, Philadelphia, PA, 19104-6084, USA. Tel.: +1 2158985000; E-mail: axe@pharm.med.upenn.edu.
Abstract: Background:The extraction and quantification of amyloid-β (Aβ) peptides in brain tissue commonly uses formic acid (FA) to disaggregate Aβ fibrils. However, it is not clear whether FA can disaggregate post-translationally modified Aβ peptides, or whether it induces artifact by covalent modification during disaggregation. Of particular interest are Aβ peptides that have been covalently modified by 4-hydroxy-2-nonenal (HNE), an oxidative lipid degradation product produced in the vicinity of amyloid plaques that dramatically accelerates the aggregation of Aβ peptides. Objective:Test the ability of FA to disaggregate Aβ peptides modified by HNE and to induce covalent artifacts. Methods:Quantitative liquid-chromatography-tandem-mass spectrometry of monomeric Aβ peptides and identify covalently modified forms. Results:FA disaggregated ordinary Aβ fibrils but also induced the time-dependent formylation of at least 2 residue side chains in Aβ peptides, as well as oxidation of its methionine side chain. FA was unable to disaggregate Aβ peptides that had been covalently modified by HNE. Conclusion:The inability of FA to disaggregate Aβ peptides modified by HNE prevents FA-based approaches from quantifying a pool of HNE-modified Aβ peptides in brain tissue that may have pathological significance.
