Mechanistic aspects of the relationship between low‐level chemiluminescence and lipid peroxides in oxidation of low‐density lipoprotein

Abstract

In this study oxidation of low-density lipoprotein (LDL) induced by different Cu 2+ concentrations was investigated. Lipid peroxidation was assessed by monitoring low-level chemiluminescence (LL-CL), conjugated diene hydroperoxide (CD) and K K-tocopherol (TocOH), the major lipophilic antioxidant in LDL. At high Cu 2+ concentration, LDL oxidation was characterised by CD formation, LL-CL emission and TocOH consumption. At low Cu 2+ concentration, CD formation was independent of LL-CL and occurred in the presence of TocOH. Thus, two different mechanisms lead to lipid peroxide formation in LDL. The combination of CD assay and LL-CL monitoring makes it possible to distinguish the autocatalytic mechanism of CD formation and that associated with TocOH, found at a high and a low rate of initiation, respectively. z 1999 Federation of European Biochemical Societies.

Chemiluminescence Associated with Singlet Oxygen Reactions with Amino Acids, Peptides and Proteins†

“…In particular, the oxidation of amino acids and proteins by peroxyl radicals (7,8), hypochlorite (9–11) or peroxynitrite (12,13) leads to CL emission in the visible region. Similar emissions are observed in the Cu(II), Fe(II) and peroxyl radical‐promoted oxidation of lipoproteins (14,15). From the time profile of the emission, as well as the response of the emitted intensity to the addition of free radical scavengers and compounds with peroxidase‐like activity, it has been concluded that this emission is due to the decomposition of peroxides and/or endoperoxides formed during the oxidation process (7–9,15,16).…”

“…Similar emissions are observed in the Cu(II), Fe(II) and peroxyl radical‐promoted oxidation of lipoproteins (14,15). From the time profile of the emission, as well as the response of the emitted intensity to the addition of free radical scavengers and compounds with peroxidase‐like activity, it has been concluded that this emission is due to the decomposition of peroxides and/or endoperoxides formed during the oxidation process (7–9,15,16). The thermal decomposition of these intermediates would lead to the formation of the excited carbonyls responsible of the emitted CL (7,9).…”

A New Chemiluminescence Method for Detecting Lipid Peroxides in Vegetable Oils

“…As a consequence of unsaturated lipids doublebonds oxidation, peroxide radicals are generated (LOO * ). Reactions between peroxide radicals leads to the formation of products in the electronic excitation state (L = O * ), which are able to emit light [3][4][5]. The reaction is as follows:…”

Bovine rod rhodopsin. 1. Bleaching by luminescence in vitro by recombination of radicals from polyunsaturated fatty acids

“…The xanthine/xanthine oxidase system (Sigma) was added several times to the same sample, which was spectrophotometrically monitored to check its absorbance at 500 nm [19][20][21].…”

“…This cascade of radical reactions results in a final partial recombination of lipid peroxyl radicals to form a nonradical product; this reaction is accompanied by a photoemission that can activate rhodopsin and may lead to the perception of light [18][19][20][21] in humans and other vertebrates. It has been reported that this emission has a spectrum with a maximum between 420 and 500 nm, which is coincident with that of retinal [22].…”