Influence of human haptoglobin polymorphism on oxidative stress induced by free hemoglobin on red blood cells

Background: An in vitro study was conducted to determine whether haptoglobin phenotypes differed in their protective effect against oxidative stress induced by extracellular hemoglobin on red blood cells. Methods: Conjugated dienes and thiobarbituric acid-reactive substances (TBARS) were determined in human red blood cell membranes in the presence of hemoglobin and various concentrations of each type of purified haptoglobin. In addition, the release of K+ and lactate dehydrogenase from red blood cells was measured. Results: A protective effect of haptoglobin was observed in terms of results obtained for the four parameters examined, with significant differences (p < 0.001) between the three haptoglobin types; type 1-1 was the most active and type 2-2 the least active. A proportion of oxidative damage was not sensitive to haptoglobin, but to desferrioxamine (an iron chelator), indicating the participation of two actors, hemoglobin and free iron, in the oxidative stress of membrane lipids. Conclusions: The antioxidant role of haptoglobin and the phenotype dependence were confirmed for preventing possible oxidative damage induced by free hemoglobin and iron release during its catabolism.