Exercise-induced oxidative stress leads hemolysis in sedentary but not trained humans
01/2005; 99:1434-1441. pp.1434-1441
ABSTRACT Times Cited: 14
Article: Haptoglobin Binding Stabilizes Hemoglobin Ferryl Iron and the Globin Radical on Tyrosine β145.[show abstract] [hide abstract]
ABSTRACT: Abstract Aim: Hemoglobin (Hb) becomes toxic when released from the erythrocyte. The acute phase protein haptoglobin (Hp) binds avidly to Hb and decreases oxidative damage to Hb itself and to the surrounding proteins and lipids. However, the molecular mechanism underpinning Hp protection is to date unclear. The aim of this study was to use electron paramagnetic resonance (EPR) spectroscopy, stopped flow optical spectrophotometry, and site-directed mutagenesis to explore the mechanism and specifically the role of specific tyrosine residues in this protection. Results: Following peroxide challenge Hb produces reactive oxidative intermediates in the form of ferryl heme and globin free radicals. Hp binding increases the steady state level of ferryl formation during Hb-catalyzed lipid peroxidation, while at the same time dramatically inhibiting the overall reaction rate. This enhanced ferryl stability is also seen in the absence of lipids and in the presence of external reductants. Hp binding is not accompanied by a decrease in the pK of ferryl protonation; the protonated ferryl species still forms, but is intrinsically less reactive. Ferryl stabilization is accompanied by a significant increase in the concentration of the peroxide-induced tyrosine free radical. EPR spectral parameters and mutagenesis studies suggest that this radical is located on tyrosine 145, the penultimate C-terminal amino acid on the beta Hb subunit. Innovation: Hp binding decreases both the ferryl iron and free radical reactivity of Hb. Conclusion: Hp protects against Hb-induced damage in the vasculature, not by preventing the primary reactivity of heme oxidants, but by rendering the resultant protein products less damaging. Antioxid. Redox Signal. 18, 2264–2273.Antioxidants & Redox Signaling 06/2013; 18(17):2264–2273. · 8.20 Impact Factor
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ABSTRACT: Handball is considered an intermittent sport that places an important stress on a player's aerobic and anaerobic metabolism. However, the oxidative stress responses following a handball game remain unknown. We investigated the responses of plasma and erythrocyte antioxidant system and oxidative stress biomarkers following a single handball game. Fourteen male elite Brazilian handball athletes were recruited in the present study. Blood samples were taken before, immediately, and 24 hours after the game. After the game and during 24 hours of recovery, the concentration of all oxidative stress indices changed significantly in a way indicating increased oxidative stress in the blood (thiol groups and reduced glutathione decreased, whereas TBARS and plasma antioxidant capacity was increased) as well as in erythrocyte (increased levels of TBARS and protein carbonyls). Erythrocyte antioxidant enzyme activities were also significantly changed by handball. Muscle damage indices (creatine kinase and lactate dehydrogenase) increased significantly after exercise. In addition, IL-6 increased after the game, whereas TNF-α decreased during recovery. This study demonstrates that a single handball game in elite athletes induces a marked state of oxidative stress evidenced by the oxidative modification in plasma and erythrocyte macromolecules, as well as by changes in the enzymatic and nonenzymatic antioxidant system.Oxidative Medicine and Cellular Longevity 01/2011; 2011:804873.
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