Olga V. Kosmachevskaya

Dinitrosyl iron complexes bind with hemoglobin as markers of oxidative stress.

Prooxidant and antioxidant properties of nitric oxide (NO) during oxidative stress are mostly dependent on its interaction with reactive oxygen species, Fe ions, and hemoproteins. One form of NO storage and transportation in cells and tissues is dinitrosyl iron complexes (DNIC), which can bind with both low-molecular-weight thiols and proteins, including hemoglobin. It was shown that dinitrosyl iron complexes bound with hemoglobin (Hb-DNIC) were formed in rabbit erythrocytes after bringing low-molecular-weight DNIC with thiosulfate into blood. It was ascertained that Hb-DNIC intercepted free radicals reacting with hemoglobin SH-groups and prevented oxidative modification of this protein caused by hydrogen peroxide. Destruction of Hb-DNIC can take place in the presence of both hydrogen peroxide and tert-butyl hydroperoxide. Hb-DNIC can also be destroyed at the enzymatic generation of superoxide-anion radical in the xanthine-xanthine oxidase system. If aeration in this system was absent, formation of the nitrosyl R-form of hemoglobin could be seen during the process of Hb-DNIC destruction. Study of Hb-DNIC interaction with reactive oxygen metabolites is important for understanding NO and Hb roles in pathological processes that could result from oxidative stress.

Carbonyl Stress in Bacteria: Causes and Consequences.

Pathways of synthesis of the α-reactive carbonyl compound methylglyoxal (MG) in prokaryotes are described in this review. Accumulation of MG leads to development of carbonyl stress. Some pathways of MG formation are similar for both pro- and eukaryotes, but there are reactions specific for prokaryotes, e.g. the methylglyoxal synthase reaction. This reaction and the glyoxalase system constitute an alternative pathway of glucose catabolism–the MG shunt not associated with the synthesis of ATP. In violation of the regulation of metabolism, the cell uses MG shunt as well as other glycolysis shunting pathways and futile cycles enabling stabilization of its energetic status. MG was first examined as a biologically active metabolic factor participating in the formation of phenotypic polymorphism and hyperpersistent potential of bacterial populations. The study of carbonyl stress is interesting for evolutionary biology and can be useful for constructing highly effective producer strains.

Formation of nitri- and nitrosylhemoglobin in systems modeling the Maillard reaction.

Abstract Background: Nitric oxide (NO) and its metabolites can nitrosylate hemoglobin (Hb) through the heme iron. Nitrihemoglobin (nitriHb) can be formed as result of porphyrin vinyl group modification with nitrite. However, in those with diabetes the non-enzymatic glycation of Hb amino acids residues (the Maillard reaction) can take place. The objectives of this study were to investigate effects of the Maillard reaction on the interaction of methemoglobin (metHb) with S-nitrosoglutathione (GSNO) and nitrite. Methods: Nitrosylhemoglobin production was registered using increasing optical density at 572 nm and compared with 592 nm, and with EPR spectroscopy. Formation of nitriHb was determined using an absorbance band of reduced hemochromogen (582 nm) in the alkaline pyridine solution. Accumulation of fluorescent advanced glycation end-products of Hb was measured through increasing of fluorescence at 385–395 nm (excitation λ=320 nm). Results: We determined that NO metabolites such as GSNO and nitrite at physiological pH values and aerobic conditions caused modification of metHb porphyrin vinyl groups with nitriHb formation. It was ascertained that this formation was inhibited by superoxide dismutase. In microaerobic conditions metHb was nitrosylated under the action of GSNO or GSNO with methylglyoxal. Nitrite nitrosylated metHb only in the presence of methylglyoxal. It was shown that GSNO inhibited accumulation of fluorescent products which formed during Hb glycation with methylglyoxal. Conclusions: The assumption was made that intermediates of the Hb glycation reaction play an important role both in vinyl group nitration and in heme iron nitrosylation. Oxygen content in reaction medium is an important factor influencing these processes. These effects can play an important role in pathogenesis of the diseases connected with carbonyl, oxidative and nitrosative stresses.

Interaction of S-nitrosoglutathione with methemoglobin under conditions of modeling carbonyl stress

The Maillard reaction is the key process in protein modification during pathologies connected with carbonyl stress. It was shown in system modeling that Maillard reaction interaction of L-lysine (L-lys) with methylglyoxal (MG) led to the formation of compounds reducing methemoglobin (metHb). Under the above conditions and in the presence of S-nitrosoglutathione (GSNO), metHb nitrosylation took place. Processes of metHb reduction and nitrosylation had the lag phase that was dependent on the presence of oxygen (O2) in the reaction mixture. Oxygen interacting with organic free radicals of the Maillard reaction inhibited hemoglobin (Hb) reduction and hence Hb nitrosylation during the first minutes of the reaction. It was also shown that the yield of organic free-radical intermediates of the L-lys with MG was increased in the presence of GSNO and metHb. All effects described could be a result of the formation of active red-ox GSNO derivates in the Maillard reaction. These derivates are probably mediators of one-electron oxidation of dialkylimine by MG. Anion radicals of S-nitrosothiols can function as such mediators.

New dinitrosyl iron complexes bound with physiologically active dipeptide carnosine

Dinitrosyl iron complexes (DNICs) are physiological NO derivatives and account for many NO functions in biology. Polyfunctional dipeptide carnosine (beta-alanyl-l-histidine) is considered to be a very promising pharmacological agent. It was shown that in the system containing carnosine, iron ions and Angeli’s salt, a new type of DNICs bound with carnosine as ligand {(carnosine)2-Fe-(NO)2}, was formed. We studied how the carbonyl compound methylglyoxal influenced this process. Carnosine-bound DNICs appear to be one of the cell’s adaptation mechanisms when the amount of reactive carbonyl compounds increases at hyperglycemia. These complexes can also participate in signal and regulatory ways of NO and can act as protectors at oxidative and carbonyl stress conditions.

Methemoglobin Reductase of Bacteria and Bacteroids Bradyrhizobium lupini: Purification and Properties

Reductase capable of reducing hemoglobin-like proteins was isolated from nodule bacteria Bradyrhizobium lupini and bacteroids of lupine root nodules. It is similar in some properties to many known methemoglobin reductases reducing animal and plant hemoglobins. It is a NADH-dependent FAD-containing flavoprotein with molecular weight of 87 kDa without metals. The presence of such enzymes in prokaryotes could be an explanation for the physiological activity of both bacterial and eukaryotic hemoglobins expressed in bacterial cells.

Signal and regulatory effects of methylglyoxal in eukaryotic cells (review)

Methylglyoxal (MG) is one of the physiological glucose metabolites formed in living organisms. The data on the influence of MG on different internal systems of eukaryotic cells, including the central signaling pathways, are been discussed in the review. The central signaling pathways are stress-activated and sensitive to the action of reactive oxygen species. Integration of the literary data and authors’ results has allowed the conclusion that MG action on cells is multidirectional and is determined by its concentration and the physiological state of the cell. The cellular reaction upon increasing MG concentrations has a phase pattern and can be described by the hormesis concept. It has been hypothesized that MG participates in the formation of the braking regulatory circuit, which modulates the sensitivity of hypothalamus neurons to glucose. It is concluded that MG has a possible role in the functioning of the great biological clock. We propose that the data discussed in this review allow methylglyoxal to be considered a molecule with signal and regulatory functions.