Nitrosyl Comlexes of Hemoglobin in Various Model Systems

—Complexes of nitric oxide (NO) with the iron in the heme group of hemoglobin (Hb(II)NO) and dinitrosyl iron complexes with thiols, including the cysteine residues of hemoglobin (Hb–DNIC), can play an important role in the processes of oxidative, halogenative and nitrosative stress in the cardiovascular system. The interaction of hemoglobin complexes of these two types with active forms of halogens, oxygen, and nitrogen, as well as alkoxyl and alkylperoxyl radicals, was studied in various model systems using electron paramagnetic resonance spectroscopy of paramagnetic complexes of NO and DEPMPO spin adducts. It was shown that hypochlorous acid (hypochlorite) and peroxynitrite quantitatively destroyed Hb–DNIC. In the presence of dithionite, S-nitrosoglutathione can participate in the nitrosylation of deoxyhemoglobin to form Hb(II)NO, whereas the addition of peroxynitrite to this system led to the formation of dinitrosyl iron complexes. At the same time, Hb(II)NO and Hb–DNIC reduced the level of organic free radicals produced in the reaction of hemoglobin with tert -butyl hydroperoxide. The data we obtained indicate the ability of the studied hemoglobin nitrosyl complexes to scavenge reactive species of oxygen, nitrogen and halogens and thereby affect the processes of free radical oxidation.