Credit: NHLBI
Results of preclinical research could aid the development of new treatments for hemolysis, which may have implications for patients with sickle cell anemia and those who receive blood transfusions.
The researchers were investigating the possibility of using haptoglobin to prevent the chemical reactions triggered by hemoglobin after hemolysis.
Haptoglobin is known to bind acellular adult hemoglobin dimers and facilitate their clearance after hemolysis.
But haptoglobin exists in different forms. The 3 main phenotypes—Hp1-1, Hp2-1, and Hp2-2—have diverse structural configurations, and previous research suggested they have different biological activities.
With the current study, however, the researchers showed the different forms of haptoglobin actually exhibit similar activity.
Todd L. Mollan, PhD, of the Center for Biologics Evaluation and Research at the Food and Drug Administration in Bethesda, Maryland, and his colleagues presented these findings in Free Radical Biology and Medicine.
The researchers studied hemoglobin dimers in complex with unfractionated haptoglobin (a mixture of Hp1-1, Hp2-1, and Hp2-2); fractionated, dimeric haptoglobin (Hp1-1); and fractionated, polymeric haptoglobin (predominantly Hp2-2, with minor amounts of Hp2-1).
The team also complexed ferrous and ferric hemoglobins with unfractionated haptoglobin and its fractionated forms.
Experiments revealed no significant differences among the different complexes with regard to hemoglobin-haptoglobin binding kinetics, hydrogen-peroxide-driven oxidative transitions of the heme iron, radical formation, heme loss, or intrinsic redox potential.
The researchers said these results should be taken into account when designing phenotype-specific haptoglobin therapies.
