Effects of an organic hydroperoxide on the activity of antioxidant enzymes in cultured mammalian cells.
As a basis for an evaluation of the role of the cellular antioxidant defense system against oxidative stress, the effects of an organic hydroperoxide, tertiary-butyl hydroperoxide (t-BuOOH), on the activity of antioxidant enzymes were investigated in cultured Chinese hamster V79 cells. Incubation of cells with t-BuOOH for 1 h significantly increased the activity of Cu-Zn superoxide dismutase (SOD) up to a level 1.4 times that of control cells. In contrast, the activities of catalase and glutathione reductase (GSSG-Rx) were not affected, while the activity of glutathione peroxidase (GSH-Px) was inhibited to a significant extent by t-BuOOH. Hydrogen peroxide also inhibited GSH-Px activity but its potency in this regard was somewhat lower than that of equimolar amount of t-BuOOH. Earlier studies demonstrated that t-BuOOH-induced cytotoxicity, single strand breaks (ssb) in DNA and structural aberrations in the chromosomes of V79 cells can be suppressed almost completely by an iron chelator o-phenanthroline. However, the iron chelator did not suppress the t-BuOOH-induced inhibition of GSH-Px activity. Likewise, a diffusible scavenger of free radicals, butylated hydroxytoluene (BHT) did not affect the hydroperoxide-induced inhibition of the enzymatic activity. These results suggest that a mechanism other than iron-mediated radical reaction is involved in the inhibition of GSH-Px activity by t-BuOOH. Modulation of the activity of antioxidant enzymes by the oxidative agent diamide was very similar to that by t-BuOOH. Inhibition of GSH-Px activity by t-BuOOH was reversible and the reduced activity returned to pre-inhibition levels within 1-2 h of post-treatment incubation. A mechanism for the inhibition of GSH-Px by t-BuOOH is discussed with reference to the oxidation of selenocysteine residues which results in perturbation of the normal catalytic cycle.
Ochi
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Department of Environmental Toxicology, Faculty of Pharmaceutical Sciences, Teikyo University, Kanagawa, Japan.
D000818:Animals; D002084:Butylated Hydroxytoluene / Q000494:pharmacology; D002457:Cell Extracts / Q000494:pharmacology; D002478:Cells, Cultured; D006224:Cricetinae; D003958:Diamide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005609:Free Radicals; D005979:Glutathione Peroxidase / Q000037:antagonists & inhibitors*; D005980:Glutathione Reductase / Q000378:metabolism; D007501:Iron / Q000494:pharmacology; D008297:Male; D010545:Peroxides / Q000494:pharmacology*; D010618:Phenanthrolines / Q000494:pharmacology; D013482:Superoxide Dismutase / Q000378:metabolism; D020122:tert-Butylhydroperoxide
D002457:Cell Extracts; D005609:Free Radicals; D010545:Peroxides; D010618:Phenanthrolines; D003958:Diamide; D002084:Butylated Hydroxytoluene; D020122:tert-Butylhydroperoxide; D007501:Iron; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D005980:Glutathione Reductase; C025205:1,10-phenanthroline