کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1909396 | 1046722 | 2010 | 11 صفحه PDF | دانلود رایگان |
Reaction of radicals and singlet oxygen (1O2) with proteins results in both direct damage and the formation of long-lived reactive hydroperoxides. Elevated levels of protein hydroperoxide-derived products have been detected in multiple human pathologies, suggesting that these secondary oxidants contribute to tissue damage. Previous studies have provided evidence for protein hydroperoxide-mediated inhibition of thiol-dependent enzymes and modulation of signaling processes in isolated systems. In this study 1O2 and hydroperoxides have been generated in J774A.1 macrophage-like cells using visible light and the photosensitizer rose bengal, with the consequences of oxidant formation examined both immediately and after subsequent (dark-phase) incubation. Significant losses of GSH (≤ 50%), total thiols (≤ 20%), and activity of thiol-dependent proteins (GAPDH, thioredoxin, protein tyrosine phosphatases, creatine kinase, and cathepsins B and L; 10–50% inhibition) were detected after 1 or 2 min photo-oxidation. Non-thiol-dependent enzymes were not affected. In contrast, NADPH levels increased, together with the activity of glutathione reductase, glutathione peroxidase, and thioredoxin reductase; these increases may be components of a rapid global cytoprotective cellular response to stress. Neither oxidized thioredoxin nor radical-mediated protein oxidation products were detected at significant levels. Further decreases in thiol levels and enzyme activity occurred during dark-phase incubation, with this accompanied by decreased cell viability. These secondary events are ascribed to the reactions of long-lived hydroperoxides, generated by 1O2-mediated reactions. Overall, this study provides novel insights into early cellular responses to photo-oxidative damage and indicates that long-lived hydroperoxides can play a significant role in cellular damage.
Journal: Free Radical Biology and Medicine - Volume 49, Issue 10, 30 November 2010, Pages 1505–1515