Antioxidant Action of Dinitrosyl Iron Complexes in Model Systems Containing Cytochrome c and Organic Hydroperoxides

The antioxidant/prooxidant effects of dinitrosyl iron complexes (DNICs), physiological donors of nitric oxide (NO^•), are studied in reaction systems modeling processes with cytochrome <i>c</i> occurring in mitochondria under oxidative stress and leading to apoptosis. Using luminol-dependent chemiluminescence, DNICs with glutathione and phosphate ligands were shown to decrease the level of prooxidants in a reaction system containing ferricytochrome <i>c</i> and cumene hydroperoxide. Electron paramagnetic resonance (EPR) spectroscopy revealed that glutathione DNICs (DNICs-GS) intercepted the free radicals formed during the interaction between cytochrome <i>c</i> and <i>tert</i>-butyl hydroperoxide. DNICs-GS were also shown to prevent the formation of oligomeric forms of cytochrome <i>c</i>, which were induced by organic hydroperoxides. Reduced glutathione was less effective as an antioxidant than DNICs-GS or could even occasionally exhibit the prooxidant properties. Ferricytochrome <i>c</i> also catalyzed the formation of DNICs-GS with nitroxyl anion (NO^-) taking part.