Cellular effects of photogenerated oxidants and long-lived, reactive, hydroperoxide photoproducts
Research output: Contribution to journal › Journal article
Reaction of radicals and singlet oxygen ((1)O(2)) 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 (1)O(2) 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 (1)O(2)-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 & Medicine|
|Number of pages||11|
|Publication status||Published - 30 Nov 2010|
- Animals, Antioxidants, Cell Survival, Cells, Cultured, Glutathione, Glutathione Peroxidase, Glutathione Reductase, Humans, Hydrogen Peroxide, Macrophages, Mice, Oxidants, Photochemical Processes, Proteins, Rose Bengal, Singlet Oxygen, Sulfhydryl Compounds, Thioredoxins