Effect of alpha-tocopherol on cytotoxicity induced by UV irradiation and antioxidants.
The addition of DL-alpha-tocopherol (vitamin E) at the time of UV irradiation only marginally protects cells from UV-induced cytotoxicity. However, a protective effect of alpha-tocopherol emerged when it was added to the cells before UV irradiation, alpha-Tocopherol was progressively and dose-dependently incorporated into the cells. Washout experiments showed that the intracellular concentration of alpha-tocopherol decreased with an approximate half-life of 14-20 hours, due to the release from the cells and dilution by cell proliferation. Pretreatment of the cells with alpha-tocopherol significantly increased the resistancy against the cytotoxic action of UV irradiation and antioxidants such as sodium ascorbate, gallic acid, n-propyl gallate and caffeic acid. ESR spectroscopy showed that alpha-tocopherol enhanced the ascorbyl radical intensity, whereas it reduced caffeic acid radical intensity, without affecting the radical intensity of gallic acid and n-propyl gallate. Both control and treated cell lysates scavenged superoxide anion (generated by xanthine-xanthine oxidase reaction) and hydroxyl radical (generated by Fenton reaction) to a comparable extent. The present study suggests that the protective effect of alpha-tocopherol might be derived from its incorporation into the cell membranes rather than its scavenging activity.
Sakagami
H
H
Department of Biochemistry, School of Medicine, Showa University, Tokyo, Japan.
Satoh
K
K
Makino
Y
Y
Kojima
T
T
Takeda
M
M
D000975:Antioxidants / Q000633:toxicity*; D001205:Ascorbic Acid / Q000633:toxicity; D002109:Caffeic Acids / Q000633:toxicity; D002470:Cell Survival / Q000187:drug effects* / Q000528:radiation effects*; D003683:Dehydroascorbic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000378:metabolism; D005707:Gallic Acid / Q000633:toxicity; D018922:HL-60 Cells / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D007700:Kinetics; D011435:Propyl Gallate / Q000633:toxicity; D013997:Time Factors; D014466:Ultraviolet Rays; D014810:Vitamin E / Q000378:metabolism* / Q000494:pharmacology*
D000975:Antioxidants; D002109:Caffeic Acids; D005609:Free Radicals; D014810:Vitamin E; D005707:Gallic Acid; C000820:semidehydroascorbic acid; D011435:Propyl Gallate; D001205:Ascorbic Acid; C040048:caffeic acid; D003683:Dehydroascorbic Acid