1. Albumin-bound quercetin repairs vitamin E oxidized by apolipoprotein radicals in native HDL3 and LDL.
- Author
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Filipe P, Patterson LK, Bartels DM, Hug GL, Freitas JP, Mazière JC, Santus R, and Morlière P
- Subjects
- Free Radicals chemistry, Free Radicals pharmacology, Humans, Kinetics, Oxidation-Reduction, Protein Binding, Tryptophan chemistry, Tyrosine chemistry, Apolipoprotein A-I pharmacology, Apolipoprotein A-II pharmacology, Lipoproteins, HDL3 pharmacology, Lipoproteins, LDL pharmacology, Quercetin pharmacology, Serum Albumin chemistry, Vitamin E metabolism
- Abstract
In the minor fraction of HDL3 containing alpha-tocopherol (alphaTocOH), selective one-electron oxidation of Trp and Tyr residues of apolipoproteins A-I and A-II by *Br2- radical-anions produces the corresponding semioxidized species, TyrO* and *Trp. Repair of TyrO* by endogenous alphaTocOH generates the alpha-tocopheroxyl radical (alphaTocO*). Fast spectroscopic studies show that two populations representing 80% of alphaTocO* initially formed are repaired over several seconds with rate constants of 3.0 x 10(6) and 1.5 x 10(5) M-1 s-1 by quercetin bound to human serum albumin (HSA) at physiologically relevant concentration. Formation of HSA-bound quercetin radicals (*Qb) is observed. In the major fraction of HDL3 particles lacking alphaTocOH, TyrO* and *Trp are repaired by free and HSA-bound quercetin. In LDL particles which all contain alphaTocOH, alphaTocO* radicals are formed in the millisecond time scale by repair of TyrO* radicals produced in apolipoprotein B. Then, 75% of initial alphaTocO* are repaired over seconds by HSA-bound quercetin (rate constant: 2.0 x 10(6) M-1 s-1). HSA-bound quercetin can also repair *Trp radicals. In O2-saturated solutions, the fraction of alphaTocO* radicals (more than 50%) not repaired by superoxide radical-anions can be repaired by HSA-bound quercetin with formation of *Qb but to a much lesser extent in LDL than in HDL.
- Published
- 2007
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