Antioxidant and prooxidant action of nitric oxide donors and metabolites

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.     

Formation of a new type of dinitrosyl iron complexes bound to cysteine modified with methylglyoxal

It has been shown that interaction of cysteine dinitrosyl iron complexes with methylglyoxal leads to the formation of a new type of dinitrosyl iron complexes, EPR spectrum of these complexes essentially differs from spectra of dinitrosyl iron complexes containing unmodified thiol. The products of the cysteine reaction with methylglyoxal are hemithioacetals, Schiff bases and thiazolidines, which most likely serve as ligands for the new type of dinitrosyl iron complexes. It has been shown that the new type of dinitrosyl iron complexes as cysteine dinitrosyl iron complexes, which are physiological donors of nitric oxide, exert a vasodilator effect. It has also been found that the oxidative destruction of the new type of dinitrosyl iron complexes occurs at normal oxygen partial pressure, but these dinitrosyl iron complexes remain rather stable under hypoxia modeling. An assumption that the destruction of the new type of dinitrosyl iron complexes is caused by the formation of a bound peroxynitrite-containing intermediate is made.     

The interaction between dinitrosy iron complexes and intermediates of oxidative stress

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.     

Interaction between albumin-bound dinitrosyl iron complexes and reactive oxygen species

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.     

Autowave mode of the functioning of the nitric oxide + free iron + thiols system as a basis for control of the biological action of nitric oxide and its endogenous compounds

The NO + Fe²⁺ + thiols system in an aqueous solution has been found earlier to exhibit temporal oscillatory changes in the concentration of paramagnetic dinitrosyl iron complexes with thiol-containing ligands and S-nitrosothiols, as well as in the concentration of free iron (not included in the complexes). It is proposed that autowaves can appear in this system characterized by periodic changes in the concentrations of its components in time and space. Such changes may form a basis for the control of the physiological effects of nitric oxide, dinitrosyl iron complexes, and S-nitrosothiols as agents affecting various cellular and tissue targets.     

Repair of nitric oxide-modified ferredoxin [2Fe-2S] cluster by cysteine desulfurase (IscS)

Iron-sulfur proteins are among the sensitive targets of the nitric oxide cytotoxicity. When Escherichia coli cells are exposed to nitric oxide, iron-sulfur clusters are modified forming protein-bound dinitrosyl iron complexes. Such modified protein dinitrosyl iron complexes are stable in vitro but are efficiently repaired in aerobically growing E. coli cells even without any new protein synthesis. Here we show that cysteine desulfurase encoded by the gene iscS of E. coli can directly convert the ferredoxin dinitrosyl iron complex to the ferredoxin [2Fe-2S] cluster in the presence of L-cysteine in vitro. A reassembly of the [2Fe-2S] cluster in the ferredoxin dinitrosyl iron complex does not require any addition of iron or other protein components. Furthermore, a complete removal of the dinitrosyl iron complex from ferredoxin prevents reassembly of the [2Fe-2S] cluster in the protein. The results suggest that cysteine desulfurase (IscS) together with L-cysteine can efficiently repair the nitric oxide-modified ferredoxin [2Fe-2S] cluster and that the iron center in the dinitrosyl iron complex may be recycled for the reassembly of iron-sulfur clusters in proteins.     

Effect of dinitrosyl iron complex with glutathione as a nitric oxide donor on blood circulation in healthy animals

It has been shown that the hypotensive action of the nitric oxide donor, the dinitrosyl complex of iron with glutathione, on the organism of healthy rats, which is caused by a decrease in the general peripherical immunity, does not impair the microcirculation and is accompanied by an enhancement of the contractile activity of the myocardium. In hypotension caused by the dinitrosyl iron complex, neither the tension of oxygen and nitrogen in the blood nor its basic-acidic status changes. Thus, the possible inhibitory action of this complex on some enzymes and proteins in the animal organism does not affect the functioning of the heart, vessels, and blood. The dinitrosyl iron complex with glutathione only causes a decrease in arterial pressure. It is assumed that these complexes as well as dinitrosyl complexes of iron with other thiol ligands may be considered as the basis for designing a novel type of drugs for the treatment of cardiovascular diseases.     

L-cysteine-mediated destabilization of dinitrosyl iron complexes in proteins.

Nitric oxide is a signaling molecule in intercellular communication as well as a powerful weapon used by macrophages to kill tumor cells and pathogenic bacteria. Here, we show that when Escherichia coli cells are exposed to nitric oxide, its ferredoxin [2Fe-2S] cluster is nitrosylated, forming the dinitrosyl iron complex with a characteristic EPR signal at g(av) = 2.04. Such formed ferredoxin dinitrosyl iron complex is efficiently repaired in E. coli cells even in the absence of new protein synthesis. However, the repair activity is completely inactivated once E. coli cells are disrupted, indicating that repairing the ferredoxin dinitrosyl iron complex requires cellular reducing equivalents. In search of such cellular factors, we find that l-cysteine can effectively eliminate the EPR signal of the ferredoxin dinitrosyl iron complex and release the ferrous iron from the complex. In contrast, N-acetyl-l-cysteine and reduced glutathione are much less effective. l-Cysteine seems to have a general function, since it can also remove the otherwise stable dinitrosyl iron complexes from proteins in the cell extracts prepared from the E. coli cells treated with nitric oxide. We propose that l-cysteine is responsible for removing the dinitrosyl iron complexes from the nitric oxide-modified proteins into which a new iron-sulfur cluster will be reassembled.     

Autowave mode of functioning of the system nitric oxide + free iron + thiols may ensure the regulation of biological action of nitric oxide and its endogenic compounds

It has been shown earlier that, in a system NO + Fe2+ + thiols in aqueous solution, an oscillatory mode of changes with time in the concentration of paramagnetic dinitrosyl iron complexes with thiol-containing legends and S-nitrosothiols formed in this system and in the concentration of free iron (not included into dinitrosyl iron complexes) can be realized. It is assumed that, in this system, autowaves can arise, which ensure periodic changes with time and space in the concentration of the system constituents. These changes may underlie the regulation of the physiologic effect of nitric oxide, dinitrosyl iron complexes, and S-nitrosothiols as agents affecting various intracellular and tissue targets.     

Effects of the donor of nitric oxide,dinitrosyl iron complex with glutathione,on blood circulation in healthy animals

We have found that the hypotensive effect of the nitric oxide donor dinitrosyl iron complex with glutathione was caused by a decrease in general peripheral resistance in healthy rats. This effect did not impair microcirculation and was accompanied by an increase in the myocardial contractile activity. Under the hypotension condition induced by dinitrosyl iron complex with glutathione, we did not find any changes in the oxygen or carbon dioxide tensions in the blood as compared to the control or any change in the acidic-basic blood state. Thus, the possible inhibitory influence of this complex on some enzymes and proteins in the animal body was not accompanied by effects on the heart, vessels, or blood. The dinitrosyl iron complex with glutathione induced a decrease in the arterial pressure only. We hypothesize that a new type of drugs for the treatment of cardiovascular diseases can be developed on the basis of such complexes and complexes with other thiol-containing ligands.     

Dinitrosyl iron complexes with thiol-containing ligands in plant tissues

The formation of dinitrosyl iron complexes with thiol-containing ligands in plant tissues (parsley and apple leaves) in the presence of nitric monoxide was demonstrated using electron paramagnetic resonance. In two types of tissues dinitrosyl iron complexes are predominantly represented by the binuclear diamagnetic form. This diamagnetic form can be transformed in EPR-detectable mononitrosyl iron complexes with diethyldithiocarbamate due to the ability of diethyldithiocarbamate to accept the iron-mononitrosyl groups from iron-dinitrosyl fragments of binuclear complexes. A similar transformation was observed under the effect of diethyldithiocarbamate on a mononuclear paramagnetic form of dinitrosyl iron complexes. The significant amount of binuclear dinitrosyl iron complexes found in plant tissues suggests that these complexes can be considered as a “working form” of nitric monoxide, which is recognized now as a universal regulator of metabolic processes in plants as well as in other organisms.     

Effect of dinitrosyl iron complexes with thiol-containing ligands on the penile cavernosum bodies in rats

A beneficial effect of dinitrosyl iron complexes (DNIC) with thiol-containing ligands on penile cavernus tissue was shown in rats subjected to penile denervation. Histological and histochemical investigations demonstrated that intracavernous injections of dinitrosyl iron complexes (2 times per one week during 6 months) blocked the reinforcement of endothelial cell proliferation in the tissue characteristic of the cavernous tissue when the penile nerve was removed. On the other hand, treatment with dinitrosyl iron complexes led to the preservation of mitotic activity of smooth myocytes and protected against the appearance in these cells of collagenase, an indicator of muscle transformation into fibrous tissue. It was shown that the process of fibrous transformation of myocytes correlates with a decrease in the mitotic activity of fibroblasts in the adventive part of cavernosa. The mitotic activity increased in cavernous tissue in the absence of dinitrosyl iron complexes. The efficiency of long-term action of dinitrosyl iron complexes on the erection in both intact animals and animals subjected to neuroectomy of cavernous tissue nerve was shown. The injection of low-molecular dinitrosyl iron complexes to the cavernous tissue resulted in the formation of protein-bound dinitrosyl iron complexes in the tissue, which were detected by the EPR technique. It is assumed that these dinitrosyl iron complexes function as a depot of nitric oxide, providing long-lasting penis erection.     

The relation between sphingomyelinase activity, lipid peroxide oxidation and NO-releasing in mice liver and brain

We used animal models to study connection between oxidating system and sphingomyelin signaling cascade, because this models are more close related to people disease. Activation of n-sphingomyelinase (n-SMase) in mice liver and brain is coincided in time with increased level of peroxide products (conjugated dienes) after injection of tumor necrosis factor alpha (TNF-alpha). We found that ceramide can induce peroxide oxidation and lead to accumulation of TNF-alpha in animal organs. Nitric oxide (NO) donors (S-nitrosoglutathione and dinitrosyl iron complex) reversibly inhibited activity of n-SMase and decreased level of lipid peroxidation products. This data proposed that both SMase and messengers of oxidative systems could be targets for NO-derived oxidants.     

The interaction of ferritin and myoglobin as inductors of lipid peroxidation. The role of reactive oxygen and nitrogen species

The effect of iron dinitrosyl complexes, S-nitrosoglutathione, and glutathione on free radical oxidation of rat heart mitochondria induced by tert-butyl hydroperoxide and metmyoglobin or their combination with ferritin was studied. It was shown that iron dinitrosyl complexes or the combination of S-nitrosoglutathione and glutathione inhibited most effectively the peroxidation of mitochondrial membranes. It was found that ferritin stimulated the prooxidant action of metmyoglobin. Using EPR spectroscopy, it was established that, in conditions of O2*- generation, the destruction of iron dinitrosyl complexes took place. Iron dinitrosyl complexes also inhibited the formation of thiyl radicals, which appeared during O2*- generation in the system containing glutathione and S-nitrosoglutathione. It is essential that the formation of iron dinitrosyl complexes in this reaction system took place with the involvement of ferritin. It was proposed that the prooxidant action of ferritin and myoglobin could be inverted to the antioxidant one.     

EPR Characterization of Dinitrosyl Iron Complexes with Thiol-Containing Ligands as an Approach to Their Identification in Biological Objects: An Overview

The overview demonstrates how the use of only one physico-chemical approach, viz., the electron paramagnetic resonance method, allowed detection and identification of dinitrosyl iron complexes with thiol-containing ligands in various animal and bacterial cells. These complexes are formed in biological objects in the paramagnetic (electron paramagnetic resonance-active) mononuclear and diamagnetic (electron paramagnetic resonance-silent) binuclear forms and control the activity of nitrogen monoxide, one of the most universal regulators of metabolic processes in the organism. The analysis of electronic and spatial structures of dinitrosyl iron complex sheds additional light on the mechanism whereby dinitrosyl iron complex with thiol-containing ligands function in human and animal cells as donors of nitrogen monoxide and its ionized form, viz., nitrosonium ions (NO⁺).     

Antidiabetes drug metformin is a donor of nitric oxide: EPR measurement of efficiency

It is shown that metformin, which is a drug used for treatment of type 2 diabetes mellitus, is metabolized in vivo in the intestine and liver of mice with the release of nitric oxide. Subsequently the released nitric oxide forms paramagnetic mono- and dinitrosyl iron complexes which can be registered by EPR. It is suggested that nitric oxide is responsible for the multifarious therapeutic action of metformin such as lowering of blood glucose level, reduction of arterial hypertension, and other biological effects.     

Antidiabetes drug metformin is a donor of nitric oxide: ESR measurement of efficiency

It is shown that metformin, which is a drug used for treatment of type 2 diabetes mellitus, metabolizes itself in vivo in the intestine and liver of mice with the release of nitric oxide. Subsequently the released nitric oxide forms paramagnetic mono- and dinitrosyl iron complexes which can be registered by EPR method. It is suggested that nitric oxide is just responsible for multifarious therapeutic action of metformin such as lowering of blood glucose level, reduction of arterial hypertension and other biological effects.     

Role of the Nitrosonium Cation in the Mechanism Underlying the Antitumor Effects of Drugs in Combination with Dinitrosyl Iron Complexes

Biophysics - This work is dedicated to the mechanism of the antitumor action of dinitrosyl iron complexes, which generate nitric oxide NO and nitrosonium cations, NO+. The effect of...     

Nitric oxide modulation of the crystallogenic properties of a biological fluid

A comparative analysis of the influence of different nitric oxide forms on the character of the dehydration structuring of human serum samples was carried out. The effects of an NO-containing gas flow that was generated by a Plazon device (800 and 80 ppm), an experimental NO generator (20, 50, 75, and 100 ppm), as well as by glutathione-containing dinitrosyl iron complexes (3 mM/L) were investigated using 15 healthy donors. The influence of endogenous sodium on serum crystallization of intact and NO treated blood samples was evaluated. It was found that the effect of NO on the crystallogenic properties of blood serum is directly determined by its concentration and form (free or bound), as well as by the presence of reactive oxygen species in a gas flow. The most pronounced stimulatory effect was observed for the bound NO form, dinitrosyl iron complexes with glutathione ligands. Low NO concentrations modulated the crystallogenic properties of blood serum, while the best stimulatory effect was demonstrated by the gas flow that contained 20 ppm nitric oxide. In contrast, high NO concentrations (800 ppm) inhibited the crystallogenic activity of the biological medium due to an increase in the destruction of structural elements by many times, which lead to the formation of an additional band in the marginal zone of the microscope specimen.