[show abstract][hide abstract] ABSTRACT: Treatment of catechol, pyrogallol, DOPA, dopamine, norepinephrine, and natural polyhydroxy�
1,4�naphthoquinone echinochrome with solution of potassium superoxide (KO2) in the presence of CaCl2
leads to the formation of water�insoluble dark pigments with stable paramagnetic properties (“calcium mel�
anins”). In control experiments in the same procedure without Ca2+, the pigments were not formed. EPR
spectra of the calcium melanins had little difference from each other and from known melanins in shape, line
width, and the g factor about 2.004. Addition of EDTA water solution to dried paramagnetic pigments leads
to their fast dissolving and disappearing of EPR signal. Formation of similar polymers is also observed during
autoxidation of o�diphenols in Ca2+�containing alkaline buffer solution, however, this process takes a few
days instead of few seconds in the presence of KO2. Thus, calcium (and other divalent cation M2+) can be
considered as a key structural element in formation of M2+�catecholate paramagnetic polymer. We assume
the existence of two types of paramagnetic centers in melanin�like polymer: M2+�stabilized o�semiquinone
radical or bi�radical complex containing o�semiquinone and superoxide anion radicals, stabilized by M2+.
[show abstract][hide abstract] ABSTRACT: The objective of the present research was to study transformations of various physiological NO forms in an isolated rat heart, perfused with the medium containing dinitrosyl iron complexes with glutathione ligand (DNIC-GH). We showed that such aerobic perfusion resulted in accumulation of mostly diamagnetic NO physiological forms (S-nitrosothiols) in myocardial tissue. They were transformed into protein-bound mononuclear dinitrosyl iron complexes during subsequent total ischemia. Meantime, DNIC-GH injection on the onset of ischemia resulted in changes in the state of mitochondrial respiratory chain, characterized by the increase in myocardial concentration of flavosemiquinones.
[show abstract][hide abstract] ABSTRACT: The effect of calcium ions on the rate of pyrocatechol autoxidation at pH 9.0 has been studied by mathematical modeling. The
effect of Ca2+ on the oxygen absorption rate has been studied, and a kinetic model has been suggested, which takes different stages of interaction
of pyrocatechol and its radical form with oxygen into account. It has been shown that the prooxidant action of Ca2+ is related to an abrupt increase (approximately by three orders of magnitude) in the rate constant of comproportionation
(reaction of chain branching and formation of o-semiquinonates) and a marked decrease (by two orders of magnitude, from 1.4 · 107 to 0.6 · 105 M−1 s−1) in the rate constant of disproportionation of o-semiquinones. The system can be used as a model for studying the prooxidant action of calcium ions.
[show abstract][hide abstract] ABSTRACT: The injection of dinitrosyliron iron complexes with glutathione at the onset of 40-min rat regional myocardial ischemia was shown to exert a clear cardioprotective action by decreasing the infarct size and suppressing the cardiac rhythm disturbance. After the introduction of the preparation, its effective accumulation with protein thiol-containing ligands in the myocardial tissue was registered be the EPR method. It was also found that, as a result of postischemic reperfusion, the rate of the decrease in the content of these complexes in the ischemic area increases, which demonstrates the effective scavenging of short-lived reactive oxygen species by molecules of dinitrosyl iron complexes.
[show abstract][hide abstract] ABSTRACT: It has been established that, in the presence of S-nitrosothiols, cysteine, and mitochondria, dinitrosyl iron complexes (DNIC)
coupled to low-molecular-weight ligands and proteins are formed. The concentration of DNIC depended on oxygen partial pressure.
It was shown that, under the conditions of hypoxia, the kinetics of the formation of low-molecular DNIC was biphasic. After
the replacement of anaerobic conditions of incubation with aerobic ones, the level of DNIC came down; in this case, protein
dinitrosyl complexes became more stable. We proposed that iron-and sulfur-containing proteins and low-molecular-weight iron
complexes are the sources of iron for DNIC formation in mitochondrial suspensions. It was shown that a combination of DNIC
and S-nitrosothiols inhibited effectively the respiration of cardiomyocytes.
Key wordsdinitrosyl iron complexes-nitric oxide-superoxide-mitochondria-iron-sulfur proteins-cysteine-S-nitrosothiols
[show abstract][hide abstract] ABSTRACT: The EPR signal recorded in reaction medium containing L-lysine and methylglyoxal is supposed to come from the anion radical (semidione) of methylglyoxal and cation radical of methylglyoxal dialkylimine. These free-radical intermediates might be formed as a result of electron transfer from dialkylimine to methylglyoxal. The EPR signal was observed in a nitrogen atmosphere, whereas only trace amounts of free radicals were registered under aerobic conditions. It has been established that the decay of methylglyoxal anion radical on aeration of the medium is inhibited by superoxide dismutase. Using the methods of EPR spectroscopy and lucigenin-dependent chemiluminescence, it has been shown that nonenzymatic generation of free radicals including superoxide anion radical takes place during the interaction of L-lysine with methylglyoxal--an intermediate of carbonyl stress--at different (including physiological) pH values. In the course of analogous reaction of L-lysine with malondialdehyde (the secondary product of the free radical derived oxidation of lipids), the formation of organic free radicals or superoxide radical was not observed.
[show abstract][hide abstract] ABSTRACT: We studied action of a nitric oxide donor, dinitrosyl complex of iron (DNIC) with glutathione as a ligand on the hemodynamics of normotensive Wistar rats, spontaneously hypertensive rats (SHR), and monkeys. Intravenous DNIC introduction (2-120 mg/kg) rendered fast (1-2 min) hypotensive effect combined with increased heart rate by 10-25%. Second phase of the effect in Wistar rats was characterized by slowed recovery of arterial pressure and heart rate up to initial level. A gradual DNIC breakdown in blood occurred during this period associated with increased NO accumulation in organs with intensive oxidative metabolism (liver, heart, and kidney). Duration of hypotensive effect in all animals depended on dose, this dependence was most expressed in SHR.
[show abstract][hide abstract] ABSTRACT: 110 Many authors consider the unstable compound nitric oxide (NO) as an important regulator of many metabolic and physiological processes in the body . In the cardiovascular system, NO plays the role of an endogenous vasodilator, regulating the vascular tonus [2, 3]. For many years, the preparations of organic nitrates donating NO, such as nitroglycerin, its derivatives, and analogs, have been used in clinical practice. Along with intravenous and sublingual administration of the NO donors, an inhalation administration of NO has been recently used in the laboratory and clinical practice. Despite a comparatively wide use of this delivery route, its effect on the NO level in tissues of various organs is still vague as well as the on the animal or human blood. In many respects, this can be connected with the fact that the NO content in organs is assessed according to the concentration of nitrates and nitrites as NO metabolites . In this case, the corresponding data cannot be considered adequate, because it is impossible under such conditions to discriminate between the nitrates and nitrites that were formed as a result of the NO metabolism or entered the mammalian body with food. In this work, we have studied the effect of a longterm inhalation of the air with increased NO content by narcotized rats on its levels in tissues of the organs corresponding to different circulation circles and on the animal blood. The NO level was detected with special selective spin traps (complexes of iron ions and diethyldithiocarbamate, Fe-DETC) [5‐7] using ESR analysis. EXPERIMENTAL
Doklady Biochemistry and Biophysics 01/2009; 425:110-3. · 0.32 Impact Factor
[show abstract][hide abstract] ABSTRACT: It was found that microdialysis, i.e., passage of aqueous solutions of iron-N-methyl-D-glucamine dithiocarbamate complexes through dialysis fibers implanted into heart, kidney and liver tissues of narcotized rats, was accompanied by effective binding of the complexes to nitric oxide from interstitial fluid. The walls of dialysis fibers used in this study were permeable for compounds with molecular weight not exceeding 5 kDa. The dialyzate samples collected every 20 min and containing diamagnetic nitrosyl Fe3+-MGD adducts were reduced to the paramagnetic state with sodium dithionite; their concentration was measured by the EPR method. The basic level of the adducts, which represented mononitrosyl iron complexes with MGD (MNIC-MGD), in the dialyzate samples of all tested organs were similar (1 microM). Treatment of animals with the water-soluble nitroglycerine analog Isoket or a low-molecular dinitrosyl iron thiosulfate complex as a NO donor increased the concentration of MNIC-MGD with going out into a plateau. The novel approach allows determination of nitric oxide levels in tissue interstitial fluid from concentration of MNIC-MGD formed during microdialysis.
[show abstract][hide abstract] ABSTRACT: EPR studies have shown that water-soluble mononitrosyl iron complexes with N-methyl-d-glucamine dithiocarbamate (MNIC-MGD) (3 micromol) injected to intact mice were decomposed virtually completely within 1h. The total content of MNIC-MGD in animal urine did not exceed 30 nmol/ml. In the liver, a small amount of MNIC-MGD were converted into dinitrosyl iron complexes (30 nmol/g of liver tissue). The same was observed in intact rabbits in which MNIC-MGD formation was induced by endogenous or exogenous NO binding to NO traps, viz., iron complexes with MGD. In mice, the content of MNIC-MGD in urine samples did not change after bacterial lipopolysaccharide-induced expression of iNOS. It was supposed that MNIC-MGD decomposition in intact animals was largely due to the release of NO from the complexes and its further transfer to other specific acceptors. In mice with iNOS expression, the main contribution to MNIC-MGD decomposition was made by superoxide ions whose destructive effect is mediated by an oxidative mechanism. This effect could fully compensate the augmented synthesis of MNIC-MGD involving endogenous NO whose production was supported by iNOS. Water-soluble dinitrosyl iron complexes (DNIC) with various thiol-containing ligands and thiosulfate injected to intact mice were also decomposed; however, in this case the effect was less pronounced than in the case of MNIC-MGD. It was concluded that DNIC decomposition was largely due to the oxidative effect of superoxide ions on these complexes.
[show abstract][hide abstract] ABSTRACT: Destructive effect of superoxide anions O2- derived from KO(2) or xanthine-xanthine oxidase system on dinitrosyl-iron complexes bound with bovine albumin or methemoglobin (DNIC-BSA or DNIC-MetHb) was demonstrated. The sensitivity of DNIC-BSA synthesized by the addition of DNIC with cysteine, thiosulfate or phosphate (DNIC-BSA-1, DNIC-BSA-2 or DNIC-BSA-3, respectively) to destructive action of O2- decreased in row: DNIC-BSA-1>DNIC-BSA-3>DNIC-BSA-2. The estimated rate constant for the reaction between O2- and DNIC-BSA-3 was equal to approximately 10(7)M(-1)s(-1). However, hydrogen peroxide and tert-butyl hydrogenperoxide (t-BOOH) did not induce any noticeable degradation of DNIC-BSA-3 even when used at concentrations exceeding by one order of magnitude those of the complex. As to their action on DNIC-MetHb both hydrogen peroxide and t-BOOH-induced rapid degradation of the complex. Both agents could induce the process due to the effect of alkylperoxyl or protein-derived free radicals formed at the interaction of the agents with ferri-heme groups of MetHb. Peroxynitrite (ONOO(-)) could also initiate protein-bound DNIC degradation more efficiently in the reaction with DNIC-BSA-3. Higher resistance of DNIC-MetHb to peroxynitrite was most probably due to the protective action of heme groups on ONOO(-). However, the analysis allows to suggest that the interaction of protein-bound DNICs with O2- is the only factor responsible for the degradation of the complexes in cells and tissues.
[show abstract][hide abstract] ABSTRACT: Changes in nitric oxide concentration in the rat myocardium in situ during temporary occlusion of the anterior descending
coronary artery and subsequent reperfusion were monitored by microdialysis in the risk zone and a normal zone, using an NO
trap (complex of ferrous ions with N-methyl-D-glucamine dithiocarbamate, Fe3+-MGD). The amplitude of the EPR signal of the reduced adduct NO-Fe2+-MGD in the samples from the risk zone increased during the 40-min occlusion and remained higher than the initial or the current
control values during 60-min postischemic reperfusion, indicating substantial NO production. By the end of reperfusion, the
infarct size was 47 ± 3% of the risk area. The contents of ATP, creatine phosphate, and total creatine in the risk zone decreased
to respectively 44 ± 4, 51 ± 5, and 60 ± 3% of the initial values, whereas the level of lactate was six times the initial.
The normal zone of the left ventricle showed no changes in NO or energy metabolite levels throughout the experiment. Thus,
intense nitric oxide production in acute regional ischemia and reperfusion is associated with disturbance of energy metabolism,
cell membrane damage, and death of cardiomyocytes.
[show abstract][hide abstract] ABSTRACT: The unexpected effects of Ca(2+) on the free-radical chain reactions of dopamine, norepinephrine, isoproterenol, and pyrocatechol oxidation are studied using oxygen consumption measurements, EPR-spectroscopy, UV/VIS spectrophotometry, and by potentiometric titration. It is found that the formation of Ca(2+)-catecholate complexes is accompanied by an increase in the dissociation constants (K(ai) ) of their phenolic hydroxyls. At pH>pK(ai) and in the presence of alkaline-earth metal cations, the rate of catecholate oxidation increases (Ca(2+), Mg(2+)> Sr(2+), Ba(2+)), whereas on addition of Zn ions the rate decreases. The effects of Group II metal cations on catecholate autoxidation are concomitant with a transient increase of the EPR signal for metal-semiquinonate complexes. Therefore, the effects of Ca(2+) and other alkaline-earth metal cations on catecholate autoxidation can be defined as 1) additional deprotonation of catechol OH-groups involved in the formation of M(2+)-catecholate complexes, the latter exceeding catechols in the susceptibility to dioxygen-induced oxidation and 2) formation of relatively stable free-radical intermediates responsible for chain propagation.
[show abstract][hide abstract] ABSTRACT: The formation of protein-bound dinitrosyl-iron complexes (DNIC) in blood plasma and packed red cell fraction has been demonstrated by the EPR method in the experiments on rabbits which were i/v injected with the low-molecular DNIC with thiosulphate. This formation was ensured by transfer of Fe(+)(NO(+))(2) moieties from low-molecular DNIC onto serum albumin or hemoglobin molecules. Protein-bound DNICs appeared immediately after low-molecular DNIC injection followed with gradually decreasing their amounts. The complexes could be detected by EPR technique during more than two days. The addition of water-soluble NO scavenger, the iron complex with N-methyl-d-glucamine dithiocarbamate (MGD) resulted in decomposition of a part of protein-bound DNICs and in effective excretion of secondary products (mainly mononitrosyl-iron complexes with MGD) from the blood flow.
[show abstract][hide abstract] ABSTRACT: It has been established that albumin-bound dinitrosyl iron complexes can be destroyed by superoxide radicals generated in a xanthine-xanthine oxidase system. It was shown that peroxynitrite also effectively destroyed albumin-bound dinitrosyl iron complexes. At the same time, hydrogen peroxide and tert-butyl hydroperoxide did not stimulate the destruction of albumin-bound dinitrosyl iron complexes up to concentrations one order higher than the content of NO. The data have been obtained indicating that dinitrosyl iron complexes possess the vasodilatory activity. It has been proposed that peroxynitrite and superoxide radical, by causing the destruction of albumin-bound dinitrosyl iron complexes, affect the physiological properties of nitric oxide.
[show abstract][hide abstract] ABSTRACT: It has been shown that various nitric oxide donors and metabolites have similar effects on lipid peroxidation in rat myocardium homogenate. The formation of malondialdehyde, a secondary product of lipid peroxidation, was inhibited in a dose-dependent manner by PAPA/NONO (a synthetic nitric oxide donor), S-nitrosoglutathione, nitrite, and nitroxyl anion. The inhibition of lipid peroxidation was provided most efficiently by the administration of dinitrosyl-iron complexes with dextran and PAPA/NONO. S-nitrosoglutathione also inhibited the destruction of coenzymes Q9 and Q10 during free radical oxidation of myocardium homogenate. Low-molecular-weight dinitrosyl iron complexes with cysteine also promoted lipid peroxidation, which is probably due to iron release during the destruction dinitrosyl iron complexes. It is likely that the antioxidant action of nitric oxide derivatives is related to the reduction of ferry forms of hemoproteins and interaction of nitric oxide with lipid radicals.
[show abstract][hide abstract] ABSTRACT: The effect of adriamycin (doxorubicin) on superoxide radical formation in isolated rat heart mitochondria was studied by the spin trapping technique. The samples were placed into the cavity of EPR spectrometer in thin - wall gas - permeable capillary tubes, which allowed keeping the mitochondria of suspension in aerobic conditions. TIRON was used as a spin trap. We demonstrated that the rate of superoxide generation by isolated mitochondria depended radically on the presence of 1-150 microM adriamycin in incubation medium and was considerably higher than in control. The effect of adriamycin could be observed in the presence of both complex I (succinate) or complex II (glutamate and malate) substrates. The results obtained let to conclude that isolated cardiac mitochondria modified by adriamycin have a higher rate of production of superoxide radicals, which can react with spin traps not penetrating through the internal membrane.
[show abstract][hide abstract] ABSTRACT: The interaction between the glutathione-containing dinitrosyl iron complexes and the superoxide radical generated in mitochondria
and in the xanthine-xanthine oxidase system was studied. Both superoxide and hydroxyl radicals proved to be involved in destruction
of dinitrosyl iron complexes. However, the iron within dinitrosyl complexes is unlikely to catalyze decomposition of hydrogen
peroxide yielding hydroxyl radical. It was found that iron dinitrosyl complexes with various anion ligands efficiently inhibited
the formation of probucol phenoxyl radical in the hemin-H2O2 system, different components of these complexes being involved in the antioxidant action.