NO-redox paradox: direct oxidation of alpha-tocopherol and alpha-tocopherol-mediated oxidation of ascorbate.
Biochem Biophys Res Commun
; 219(3): 835-41, 1996 Feb 27.
Article
em En
| MEDLINE
| ID: mdl-8645266
ABSTRACT
Nitric-oxide (NO) can act as both a pro- or an antioxidant, yielding either cytotoxic or protective effects, respectively. The previously unrecognized redox interactions of NO with antioxidants, and not solely its well-known reactions with oxygen radicals, peroxyl radicals and transition metal centers, may be essential for its dual mechanisms in cells. Since the alpha-tocopherol/ascorbate redox cycle is central to antioxidant protection, we studied the direct effects of NO on alpha-tocopherol, ascorbate and combinations thereof in aqueous, micellar environments using ESR spectral and HPLC quantitative techniques. We found that NO does not directly oxidize ascorbate under anaerobic conditions. alpha-Tocopherol, however, in the presence of NO and under anaerobic conditions, was oxidized to the alpha-tocopheroxyl radical. Under conditions where NO oxidized alpha-tocopherol, the subsequent production of the alpha-tocopheroxyl radical depleted ascorbate, yielding the semidehydroascorbyl radical and regenerating alpha-tocopherol. Thus, NO interacts with the redox cycle involving alpha-tocopherol and ascorbate in a pro-oxidant manner.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Ácido Ascórbico
/
Vitamina E
/
Espécies Reativas de Oxigênio
/
Óxido Nítrico
/
Antioxidantes
Idioma:
En
Revista:
Biochem Biophys Res Commun
Ano de publicação:
1996
Tipo de documento:
Article
País de afiliação:
Estados Unidos