All living systems are characterized by fundamental properties such as the ability to adaptation and self-regulation. Mammalian nonnuclear erythrocytes also have the ability to adapt to external effects, but their regulatory capabilities are limited by cytoplasmic mechanisms, including phase transitions of proteins and membranes. This is one of the most ancient mechanisms of adaptation of living systems to external and internal conditions. Erythrocytes under changes in plasma composition, aging, and energy depletion, undergo a reversible morpho-functional transformation, the transition from a discocyte to an echinocyte. The metabolic shifts occurring in this case correspond to a complex of universal changes that take place during erythrocyte transition to metabolic depression. As a rule, echinocytosis is considered as a pathological process preceding eryptosis and hemolysis. However, it can be also considered as the first stage of the implementation of a universal program of passive cell adaptation, the ultimate goal of which is to transfer the system to a state of suspended animation. The energy status of an erythrocyte is determined by the equilibrium of soluble and membrane-bound hemoglobin (Hb) forms. Compounds with pronounced electrophilic properties—nitric oxide and methylglyoxal—affecting this equilibrium can induce cell’s transition from one metabolic state to another. The mechanism of their action is largely related to the modification of thiol groups of membrane and cytoskeleton proteins, including reactive SH-groups of Hb. It seems relevant to consider their effect on the state of Hb and erythrocytes.

The view on the reductase systems supporting hemoglobin in physiologically active reduced state is providing. The existence of such reductase systems is essential for functioning of all hemoglobins. They can be special reductases, reductase domains, connected with globin molecule, and reductas-es of wide spectrum of activitie for which reduction of hemoglobin is one of possible functions.

The antioxidant activity of carnosine and of carnosine dinitrosyl iron complexes (DNICs) was studied. A system with metmyoglobin (metMb) or hemin in combination with tert-butyl hydroperoxide (t-BOOH) was used as an experimental model. Using the luminol-dependent chemiluminescence method, it was shown that carnosine and carnosine DNICs effectively diminished the level of prooxidants formed by the interaction of heme groups with t-BOOH. In addition, carnosine and carnosine DNICs inhibited the formation of diene conjugates arising during the oxidation of arachidonic acid in the metMb–t-BOOH system. In the reaction systems used, the antioxidant effect of carnosine DNICs was higher than that of carnosine. The antioxidant effect of carnosine also depended on the presence of bivalent iron ions added at a concentration equivalent to their content in DNICs. These results show that the insertion of carnosine as a ligand to nitrosyl iron complexes enhances its antioxidant properties.

Carnosine and carnosine dinitrosyl iron complexes (DNICs) effectively inhibit the formation of free radical intermediates formed during myoglobin oxidation, and also reduced the formation of diene conjugates arising during peroxidation of arachidonic acid. At the same time, antioxidant effect of carnosine DNICs was higher than that of carnosine.

Nitrosyl iron complexes with glutathione, phosphate and thiosulfate ligands inhibited the produc-tion of free radical intermediates in the oxidation of hemoglobin with tert-butyl hydroperoxide, and also prevented the oxidative modification of hemoglobin. Tetranitrosyl iron complex (TNIC) was a more effective antioxidant compared to other studied complexes.

Angeli’s salt is regarded as a nitroxyl donor, so it can counteract hemolysis-driven adverse effects such as the vasoconstrictive effects of free hemoglobin in blood plasma. However, the molecular mechanisms of interaction of nitroxyl with various heme proteins are not fully understood. Oxoferryl forms of hemoproteins emerged under oxidative stress are known to be strong pro-oxidants. This study has been carried out to investigate reductive nitrosylation of metand oxoferryl forms of hemoglobin and myoglobin upon interaction with nitroxyl. Experiments were performed in vitro using electron paramagnetic resonance spectroscopy for detection of nitrosyl forms. The results obtained indicate the antioxidant effect of Angeli’s salt in model systems of hemoglobin or myoglobin oxidation with hydrogen peroxide. Moreover, the addition of hydrogen peroxide to methemoglobin and metmyoglobin led to the appearance of an EPR signal of free radicals with g = 2.005, associated with the protein part of hemoproteins. Thus, nitroxyl acts both as a reducing agent and a nitrosylating agent, thereby preventing the formation of oxoferryl forms of hemoproteides. The therapeutic properties of Angeli’s salt may be largely related to the antioxidant effect it has on blood components.

Glutathione dinitrosyl iron complexes (GS-DNICs) effectively protected hemoglobin from ox-idative modification. They prevented the formation of carbonyl derivatives, oxidation of tryp-tophan and tyrosine residues, degradation of heme group, as well as the formation of protein crosslinking. GS-DNICs inhibited erythrocyte lysis induced by HOCl.

Low-molecular-weight dinitrosyl iron complexes (DNICs) with thiol-containing ligands are a physiological form for deposit and transport of nitric oxide (NO) in the organism; DNICs can exhibit antioxidant and antiradical properties. It has been found that DNICs containing cysteine, glutathione and lipoic acid as ligands, decreased the rate of dihydrodamine oxidation by peroxynitrite formed during 3-morpholinonymine decomposition. Thiol (sulfhydryl) ligands are present in DNICs in the form of thiolate anions (RS−), which protects these groups from oxidation by peroxynitrite. When tert-butyl hydroperoxide was used as an oxidizer at low concentration, the protective effect of DNICs on their SH-groups was observed for complexes with lipoic acid (LA-DNIC) and with glutathione (GS-DNIC). LA-DNICs were more resistant to oxidizing agents and were a more effective peroxynitrite trap than other DNICs. DNICs associated with bovine serum albumin had a negligible protective effect on cysteine residues during oxidation by peroxynitrite and tert-butyl hydroperoxide. These results allow us to consider low-molecular-weight DNICs with thiol ligands as peroxynitrite traps and thiol residues protectors in proteins.

Carbonyl stress is an increase in the amount of monosaccharides and active dicarbonyl compounds (glyoxal and methylglyoxal (MG)), which leads to raising the rate of formation of advanced glycation end-products (AGEs). MG added to an Escherichia coli culture inhibited the growth of bacteria, while the number of fluorescent proteins-associated AGEs increased. The effect of nitroxyl (HNO) on cells depended on the level of aeration of the bacterial culture. Nitroxyl decreased the toxic effect of MG on the bacterial culture, which was expressed in an increase of cell viability, assessed by the MTT test, and in the decrease of the autofluorescence of nonenzymatic glycation products associated with proteins. Under lowered aeration conditions, the cytoprotective effect of a nitroxyl donor, Piloty’s acid, was more obvious. The cytoprotective effect of HNO at carbonyl stress conditions may be associated with its antioxidant and antiglycemic effects. The results of the study are important for understanding the mechanisms of the protective and regulatory action of HNO in cells.

Nitroxyl in biological systems can work as a classic antioxidant. It has been shown that ni-troxyl reduces the yield of free radical products in the reaction of hemoglobin with tert-butyl peroxide. Due to this, nitroxyl slows down the formation of non-enzymatic glycation products in the reaction of hemoglobin with methylglyoxal.

The article discusses the evolutionary aspects of the functioning of nitric oxide (NO) in various organisms. As a signaling molecule, NO is widely distributed in both prokaryotes and eukar-yotes. The diverse action of NO is due to the formation of its biologically active metabolites. The formation of these NO derivatives was associated with the evolution of energy homeosta-sis and protection of living systems from oxidative stress.

Hemoglobin-bound dinitrosyl iron complexes (Hb-DNICs) are dose-dependently degraded by peroxynitrite. At the same time, they protect Hb from oxidative modification: they prevent the formation of carbonyl derivatives, the oxidation of tryptophan residues, the degradation of the heme group, and the formation of crosslinks between subunits.

Bacteria suffer carbonyl stress at sudden transition to high-level carbohydrate substrates or in a stationary phase. Methylglyoxal (MG) inhibited bacterial growth and increased advanced glycation end products. Nitroxyl prevented the toxic effect of MG in a low-aerated cell culture.

Escherichia coli cells with an embedded soybean leghemoglobin (Lb) gene produce this protein in a reduced oxygenated state. The cells synthesizing Lb turned out to be more sensitive to the action of oxidative and nitrosative stress inducers, than cells without Lb.

Like many other hemoglobins, leghemoglobin (Lb), the hemoglobin of legume nodules, demonstrates peroxidase activity and can oxidize various substances with the participation of H 2 O 2 or organic peroxides. The peroxidase activity of Lb isolated from bean nodules ( Vicia faba L.) was studied in reaction with tert -butyl hydroperoxide, an analog of organic hydroperoxides, and o -dianisidine as a reducing substrate. The reaction catalyzed by Lb had classical Michaelis kinetics ( V max = 1.3 M/min ⋅ mM of heme, K m = 0.8 mmol/L). The substrate concentrations that do not limit the peroxidase reaction rate were determined: 0.8 mmol/L for o -dianisidine and 1 mmol/L for tert -butyl hydroperoxide. With a pH decrease from 9 to 6, the Lb peroxidase activity increased by almost two times. This may be important for nodules in vivo, for example, during their aging, when the pH decreases and the oxidized Lb content increases. Although Lb is inferior in peroxidase activity to the true peroxidases, it can provide additional antioxidant protection under oxidative stress due to its high concentration in nodules.

We have demonstrated that dinitrosyl iron complexes (DNICs) eliminate free radicals formed during the interaction of hemoproteins with tert-butyl hydroperoxide, as well as during the co-oxidation of lipids and glucose. Thus, DNICs act as antioxidants under conditions simulating different types of oxidative stress.

The antioxidant effect of dinitrosyl iron complexes (DNICs) was studied in various model systems. DNICs with glutathione ligand (DNIC-GS) effectively inhibited Cu2+-induced peroxidation of low density lipoproteins (LDL). The antioxidant effect of DNICs with phosphate ligands and free reduced glutathione (GSH) was less pronounced. In addition, DNIC-GS suppressed reactive oxygen species (ROS) formation during co-oxidation of lecithin liposomes and glucose. Free radical oxidation in this system was induced with a lipophilic azo initiator (AIBN) and evaluated by luminol-dependent chemiluminescence. NO sharply stimulated chemiluminescence during co-oxidation of glucose and liposomes, thus suggesting the formation of potent oxidants under these conditions. DNIC-GS scavenged the superoxide radical anion generated in the xanthine-xanthine oxidase system. Superoxide production was assessed by lucigenin-dependent chemiluminescence and electron paramagnetic resonance (EPR) spectroscopy. Chemiluminescence revealed the dose-dependent mode of the antiradical effect DNIC-GS; moreover, these complexes were more efficient than GSH. EPR spectra of adducts of the DEPMPO spin trap with free radicals suggest that the interaction of DNIC-GS and superoxide does not result in the formation of the thiyl radical of glutathione. Here we propose a mechanism of the antioxidant action of DNIC-GS, suggesting that unstable intermediate complexes are formed upon their interaction with superoxide or lipid radicals. After subsequent intramolecular rearrangement, these intermediates decompose without the free radical formation as the by-products.

Abstract—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.

Plants experience a variety of biotic and abiotic stresses that cause crop losses worldwide. Preventing crop losses due to these factors is of particular importance. For this, it is important to understand the mechanisms of both suppressing and stimulating seed germination and to develop technologies for controlling seed dormancy and development in order to avoid unwanted germination in the ears. Gene switching technologies can be used to address this and similar problems in seed development. Recent studies have shown that classical phytohormones - auxins, cytokinins, abscisic acid, ethylene, gibberellins - control all stages of plant ontogenesis. In addition to the classic phytohormones, there are relatively new ones - brassinosteroids, jasmonates, strigolactones, salicylates, which deserve consideration in a separate review. Together, these compounds are important metabolic engineering targets for the production of stress-resistant crops. In this review, we have summarized the role of phytohormones in plant development and resistance to abiotic stresses. Experimental data were presented on the transport of phytohormones, the interaction between them, as a result of which the activity of a certain hormone can be either enhanced or suppressed. We have identified the main links of phytohormones with an emphasis on the response of plants to abiotic stresses and have shown that the effect of an individual hormone depends on the ratio with other phytohormones and metabolites. Additional research along these lines will help explain different stress responses and provide tools to improve plant stress tolerance.