Effects of glutathione, Trolox and desferrioxamine on hemoglobin-induced protein oxidative damage: anti-oxidant or pro-oxidant?

Evidence to support the role of heme proteins as major inducers of oxidative damage is increasingly present. Antioxidants have been widely used to ameliorate oxidative damage in vivo and in vitro, where the mechanism of this therapeutic action was usually dependent on their anti-oxidant effects. In this study, we chose three classic antioxidants, i.e. glutathione (GSH, an important intracellular antioxidant), 6-hydroxy-2, 5, 7, 8-tetramethylchroman-2-carboxylic acid (Trolox, a phenolic antioxidant without chelating effect) and desferrioxamine (DFO, a good iron chelator), to study their efficiencies on hemoglobin-induced protein oxidative damage. It was found that all of these antioxidants had the capacities to act as free radical scavengers and reducing agents to remove cytotoxic ferryl hemoglobin, demonstrating apparent anti-oxidant activities. However, the effects on hemoglobin-H(2)O(2)-induced protein oxidation depended on the categories and concentrations of antioxidants. GSH efficiently inhibited protein (bovine serum albumin or rat heart homogenate) carbonyl formation in a dose-dependent manner. In contrast to their protective effects at high concentrations, both Trolox and DFO could significantly aggravate protein oxidation at low concentrations. The pro-oxidant effects of Trolox and DFO on hemoglobin-mediated oxidative damage were probably related to their abilities in producing additional free radicals, such as superoxide (O·(2)(-)) and hydroxyl radical (·OH). The dual effects on hemoglobin redox reactions may provide new insights into the physiological implications of Trolox and DFO with cellular heme proteins.