The Autoxidation Of αα Cross-Linked Hemoglobin: A Possible Role In The Oxidative Stress To Endothelium

The aim of the present study was to investigate the role of hemoglobin autoxidation in the induction of endothelial heme oxygenase (HO), an inducible “stress” protein which is responsible for heme catabolism. Porcine aortic endothelial cells were incubated for six hours in the presence of 60 μM unmodified hemoglobin (HbA0), hemoglobin cross-linked between the a chains with bis-(3,5-dibromosalicyl) fumarate (ααHb) or cyanomet-αα-hemoglobin (CNmetααHb). Microsomal HO content increased 4.1-fold in the presence of ααHb, 2.7-fold with HbA0 and 1.8-fold with CNmetααHb over the control value. The rates of methemoglobin formation exhibited a linear relationship over the time of incubation (r = 0.94) and the apparent rate constant was 1.8-fold higher for ααHb (0.023 h-1) than HbA0 (0.013 h-1). In addition, a linear relationship was obtained by plotting the rates of autoxidation of hemoglobins versus the HO activity (r = 0.99). When cells were incubated with 100% methemoglobin, HO activity increased 5.0-fold and 4....