Liposomes containing alpha-tocopherol and ascorbate are protected from an external oxidant stress.
The interaction between alpha-tocopherol and ascorbate in protecting membrane lipids from peroxidation was studied in unilamellar liposomes in which alpha-tocopherol was incorporated into the liposomal membrane, and ascorbate was trapped within the vesicles. Extravesicular ferricyanide was reduced by ascorbate-derived electrons, and this was enhanced by the presence of alpha-tocopherol in the lipid bilayer. When a water-soluble free radical initiator was added to the outside of liposomes, intravesicular ascorbate prevented oxidation of alpha-tocopherol, and this effect was associated with complete protection against peroxidation of membrane lipids. These results suggest that ascorbate-dependent recycling of alpha-tocopherol can protect biological membranes from peroxidation by oxidants originating across the membrane bilayer from ascorbate.
Waters
R E
RE
Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
White
L L
LL
May
J M
JM
D000975:Antioxidants / Q000032:analysis / Q000494:pharmacology; D001205:Ascorbic Acid / Q000032:analysis / Q000494:pharmacology; D002250:Carbon Radioisotopes; D005292:Ferricyanides / Q000737:chemistry; D015227:Lipid Peroxidation / Q000187:drug effects; D008081:Liposomes / Q000032:analysis / Q000737:chemistry*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D014810:Vitamin E / Q000032:analysis / Q000494:pharmacology
D000975:Antioxidants; D002250:Carbon Radioisotopes; D005292:Ferricyanides; D008081:Liposomes; C007931:hexacyanoferrate III; D014810:Vitamin E; D001205:Ascorbic Acid