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This study was designed to evaluate the antioxidant effect of probucol on peroxidation of low-density lipoproteins (LDLs) initiated by oxygenated free radicals ( O2· -) and ethanol-derived peroxyl radicals ( ${\rm RO}_{2}{}^{\cdot}$ ) generated by ? radiolysis. Initial radiolytic yields related to the markers of lipid peroxidation [i.e. decrease in endogenous ?-tocopherol, formation of thiobarbituric acid-reactive substances (TBARS) and conjugated dienes] were determined as a function of LDL concentration (1.5 and $3\ {\rm g}\ {\rm l}^{-1}$ , expressed as total LDL) and in the absence or the presence of probucol at different concentrations (2.3× 10-6, $3.5\times 10^{-6}$ , 9× 10-6 and $20.5\times 10^{-6}\ {\rm mol}\ {\rm l}^{-1}$ ). Our results showed that probucol was able to decrease not only the yields of TBARS and conjugated dienes but also the levels of these peroxidation products obtained at high doses (2500 Gy) compared ...

The aim of this work was to specify the mechanisms involved in the radical oxidation of human high-density lipoprotein (HDL) and to compare these mechanisms with those described previously for the oxidation of low-density lipoprotein (LDL) under the same experimental conditions (Bonnefont-Rousselot et al., Radiat, Res. 134, 271-282, 1993). The oxidation of HDL, initiated by .OH or .OH/O(.-)2 free radicals from gamma radiolysis of water, was evaluated as a function of increasing radiation dose by analyzing quantitatively the decrease of endogenous alpha-tocopherol and the formation of oxidation products (thiobarbituric acid-reactive substances and conjugated dienes). All qualitative conclusions were supported by quantitative data (radiation yields and concentrations of the oxidation markers at high radiation doses) and by the mechanisms of the kinetics, .OH free radicals in the absence of oxygen were less efficient in initiating HDL oxidation than in the presence of oxygen (action of .OH/O(.-)2 free radicals), which was in agreement with the enhancement of the action of .OH free radicals by oxygen. The remaining significant level of vitamin E in HDLs at high radiation doses in the absence of oxygen could be explained by a regeneration of vitamin E by an oxidation product that was able to reduce the alpha-tocopheroxyl radical. The yields related to the decrease in the vitamin E content of HDLs after exposure to radiation with .OH or .OH/O(.-)2 free radicals were slightly higher than those obtained previously in LDLs under similar experimental conditions. Moreover, in the presence of oxygen, .OH free radicals led to a lower formation of thiobarbituric acid-reactive substances in HDLs than in LDLs. Such discrepancies in the behavior of these two lipoprotein fractions could be related to the differences in the chemical composition of HDLs and LDLs.

The aim of this study was to analyze quantitatively the oxidative modification of low-density lipoproteins (LDLs) induced by OH· free radicals produced by gamma radiolysis, in the absence or in the presence of oxygen (action of OH· free radicals, or simultaneous action of OH· and ${\rm O}_{2}^{\overline{\cdot}}$ free radicals, respectively). The effects of increasing radiation doses on aqueous LDL solutions have been monitored by several parameters: a decrease in endogenous vitamin E, the formation of thiobarbituric acidreactive substances (TBARS) and conjugated dienes, the appearance of a differential fluorescence (excitation wavelength = 360 nm), and an increase in the relative electrophoretic mobility. Initial radiation yields (decrease in vitamin E, formation of TBARS) have been determined at pH 7 as a function of LDL concentration (from 0.75 to 9 g liter-1). From the comparison of these yields with those of OH· and ${\rm O}_{2}^{\overline{\cdot}}$ free radicals produced by water radiolysis, we have d...

This study aimed to analyze quantitatively the initiation and the consequences of low-density lipoprotein (LDL) peroxidation by O2·−/HO2· free radicals produced by gamma radiolysis. The action of i...