THE EFFECT OF HEMOGLOBIN, HEMATIN, AND IRON ON NEUTROPHIL INACTIVATION IN SUPEROXIDE GENERATING SYSTEMS

When Escherichia coli was incubated with xanthine oxidase and acetalde hyde, the killing of E. coli was accelerated by iron-EDTA but inhibite d by hematin or hemoglobin. On the other hand, when E. coli was incuba ted with human neutrophils in the presence of phorbol myristate acetat e (PMA), all of these iron species at concentrations of a few micromol ar accelerated the inactivation of neutrophils and in so doing protect ed the E. coli from being killed by the neutrophils. The inactivation of the neutrophils was accompanied by an increase in lipid peroxidatio n and by a decrease in viability measured with trypan blue. This inact ivation was inhibited by scavengers such as deoxyribose, mannitol, or thiourea. Desferrioxamine B and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO ) both inhibited the inactivation mediated by iron-EDTA, but had no ef fect on the hematin- or hemoglobin-mediated inactivation. Vanadium (va nadyl ion), an effective Fenton reagent, behaved in the same way as ir on-EDTA relative to the effects of DMPO on neutrophil inactivation. Th ese results led us to conclude that neutrophils were inactivated durin g PMA stimulation by OH radicals in the presence of iron-EDTA and by s ome other oxidizing species when hematin or Hb is present. Ascorbate e nhanced the inactivation of neutrophils mediated by these iron species . Catalase was very effective in inhibiting neutrophil inactivation. S uperoxide dismutase was not as effective but the combination with cata lase was most effective. (C) 1994 Academic Press, Inc.