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Title of article :
Mechanism of the antioxidant to pro-oxidant switch in the behavior of dehydroascorbate during LDL oxidation by copper(II) ions
Author/Authors :
Horsley، نويسنده , , Elizabeth T.M. and Burkitt، نويسنده , , Mark J. and Jones، نويسنده , , Clare M. and Patterson، نويسنده , , Rebecca A. and Harris، نويسنده , , Lynda K. and Moss، نويسنده , , Nicola J. and del Rio، نويسنده , , Jessica D. and Leake، نويسنده , , David S.، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2007
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Abstract :
Oxidised low density lipoprotein (LDL) may be involved in the pathogenesis of atherosclerosis. We have therefore investigated the mechanisms underlying the antioxidant/pro-oxidant behavior of dehydroascorbate, the oxidation product of ascorbic acid, toward LDL incubated with Cu2+ ions. By monitoring lipid peroxidation through the formation of conjugated dienes and lipid hydroperoxides, we show that the pro-oxidant activity of dehydroascorbate is critically dependent on the presence of lipid hydroperoxides, which accumulate during the early stages of oxidation. Using electron paramagnetic resonance spectroscopy, we show that dehydroascorbate amplifies the generation of alkoxyl radicals during the interaction of copper ions with the model alkyl hydroperoxide, tert-butylhydroperoxide. Under continuous-flow conditions, a prominent doublet signal was detected, which we attribute to both the erythroascorbate and ascorbate free radicals. On this basis, we propose that the pro-oxidant activity of dehydroascorbate toward LDL is due to its known spontaneous interconversion to erythroascorbate and ascorbate, which reduce Cu2+ to Cu+ and thereby promote the decomposition of lipid hydroperoxides. Various mechanisms, including copper chelation and Cu+ oxidation, are suggested to underlie the antioxidant behavior of dehydroascorbate in LDL that is essentially free of lipid hydroperoxides.
Keywords :
atherosclerosis , Copper , dehydroascorbate , Lipid hydroperoxide , Lipid peroxidation , Lipoprotein , low density lipoprotein , ascorbic acid , Low density lipoprotein oxidation , EPR spectroscopy
Journal title :
Archives of Biochemistry and Biophysics
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