title: Structural characterization and immunochemical detection of a fluorophore derived from 4-hydroxy-2-nonenal and lysine.
abstract: Aging and the progression of certain degenerative diseases are accompanied by increases in intracellular fluorescent material, termed "lipofuscin" and ceroid, respectively. These pigments are observed within granules composed, in part, of damaged protein and lipid. Modification of various biomolecules by aldehyde products of lipid peroxidation is believed to contribute to lipofuscin and ceroid formation. However, little direct evidence currently exists because the structures responsible for the fluorescent, cross-linked nature of this material are not well characterized. In this study, we have identified a fluorescent product formed in the reaction of Nalpha-acetyllysine and 4-hydroxy-2-nonenal (HNE), a major product of lipid peroxidation and the most reactive of these compounds under physiological conditions [Esterbauer, H., Shaur, R. J. & Zollner, H. (1991) Free Radical Biol. Med. 11, 81-128]. This fluorescent compound, characterized as a 2-hydroxy-3-imino-1,2-dihydropyrrol derivative, appears to form upon oxidative cyclization of the nonfluorescent 2:1 lysine-HNE Michael adduct-Schiff base cross-link. Polyclonal antibody was raised to the Nalpha-acetyllysine-HNE fluorophore and found to be highly specific to the chromophore structure of the compound. This antibody has been used to conclusively demonstrate that the lysine-HNE derivative of this fluorophore forms on protein upon exposure to HNE. The results of this study therefore provide the basis for future investigations on the contribution(s) of HNE-derived fluorophore formation to lipofuscin and ceroid accumulation.
authors.affiliation: Laboratory of Biochemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: L
authors.initials: L
authors.lastname: Tsai
authors.forename: P A
authors.initials: PA
authors.lastname: Szweda
authors.forename: O
authors.initials: O
authors.lastname: Vinogradova
authors.forename: L I
authors.initials: LI
authors.lastname: Szweda
mesh_terms: D000447:Aldehydes / Q000737:chemistry* / Q000276:immunology; D000818:Animals; D003432:Cross-Linking Reagents; D005260:Female; D005456:Fluorescent Dyes / Q000737:chemistry*; D007114:Immunization; D007118:Immunoassay / Q000379:methods; D008239:Lysine / Q000737:chemistry* / Q000276:immunology; D011817:Rabbits
chemical_list: D000447:Aldehydes; D003432:Cross-Linking Reagents; D005456:Fluorescent Dyes; C027576:4-hydroxy-2-nonenal; D008239:Lysine