Anticancer Activity of Dinitrosyl Iron Complex (NO Donor) on the Multiple Myeloma Cells.

The results of the study of the effect of a mononuclear dinitrosyl iron complex (DNIC7) with functional sulfur-containing ligands (NO donors) on the viability of multiple myeloma cells are presented. It was shown that DNIC7 decreased cell viability and inhibited the proliferation of multiple myeloma cells, i.e., exhibits cytotoxic properties. Fluorescent analysis showed that the DNIC7 compound decreases the level of intracellular glutathione and increases the level of reactive oxygen species in multiple myeloma cells. It is assumed that DNIC7 has a therapeutic potential for the treatment of cancer.

Effect of Dinitrosyl Iron Complexes (NO Donors) on the Metabolic Processes in Human Fibroblasts.

The results of the study of the effect of mononuclear dinitrosyl iron complexes (DNICs) with functional sulfur-containing ligands (NO donors) on the cell viability and metabolism of human lung fibroblasts are presented, and the efficiency of their action is evaluated. It was shown that cationic DNICs increased the cell viability of fibroblasts and demonstrated the cytoprotective properties. Fluorescent analysis revealed that the DNICs compounds decrease the mitochondrial membrane potential but do not have a significant effect on the level of glutathione and reactive oxygen species in fibroblasts. It is assumed that the DNICs have the therapeutic potential for treating cardiovascular diseases.

The inhibitory effect of dinitrosyl iron complexes (NO donors) on myeloperoxidase activity.

The effect of synthetic analogues of dinitrosyl mononuclear iron complexes (DNICs) with functional sulfur-containing ligands (NO donors) on the activity of myeloperoxidase (MPO) was studied, and their efficiency was evaluated. It was shown that the enzyme MPO is the molecular target of DNICs. It was found that six DNICs inhibited the activity of MPO and one compound potentiated it. The evaluation of their efficiency showed that two DNICs effectively inhibited the activity of MPO by 50% at IC50 = 2 × 10-4 M and IC50 = 5 × 10-7 M.

[A rapid method to evaluate potential vasodilatory activity of organic nitrates].

The kinetics of interaction between organic nitrates (3,3-bis(nitroxymethyl)oxetane) and cysteine were evaluated by the rate of nitrite ion formation at various concentrations of reagents and pH. The activities of natural reducing agents, including cysteine, glutathione, and NADH, in generating the nitrite ion from organic nitrates (3,3-bis(nitroxymethyl)oxetane) were compared. Cysteine was shown to be the most potent reducing agent. Studying the effectiveness of nitrates (trinitroglycerol, 3,3-bis(nitroxymethyl)oxetane, and nicorandil) at a concentration of 3 mM showed that the rate of nitrite ion accumulation in the reaction with 10 mM cysteine is 1.66, 0.37, and 0.02 microM/min, respectively.

Reactions of sulfur-nitrosyl iron complexes of "g=2.03" family with hemoglobin (Hb): kinetics of Hb-NO formation in aqueous solutions.

NO-donating ability of nitrosyl [Fe-S] complexes, namely, mononuclear dinitrosyl complexes of anionic type [Fe(S2O3)2(NO)2]-(I) and neutral [Fe2(SL1)2(NO)2] with L1=1H-1,2,4-triazole-3-yl (II); tetranitrosyl binuclear neutral complexes [Fe2(SL2)2(NO)4] with L2=5-amino-1,2,4-triazole-3-yl (III); 1-methyl-1H-tetrazole-5-yl (IV); imidazole-2-yl (V) and 1-methyl-imidazole-2-yl (VI) has been studied. In addition, Roussin's "red salt" Na2[Fe2S2(NO)4] x 8H2O (VII) and Na2[Fe(CN)5NO] x H2O (VIII) have been investigated. The method for research has been based on the formation of Hb-NO adduct upon the interaction of hemoglobin with NO generated by complexes I-VIII in aqueous solutions. Kinetics of NO formation was studied by registration of absorption spectra of the reaction systems containing Hb and the complex under study. For determination of HbNO concentration, the experimental absorption spectra were processed during the reaction using standard program MATHCAD to determine the contribution of individual Hb and HbNO spectra in each spectrum. The reaction rate constants were obtained by analyzing kinetic dependence of Hb interaction with NO donors under study. All kinetic dependences for complexes I-VI were shown to be described well in the frame of formalism of pseudo first-order reactions. The effective first-order rate constants for the studied reactions have been determined. As follows from the values of rate constants, the rate of interaction of sulfur-nitrosyl iron complexes (I-VI) with Hb is limited by the stage of NO release in the solution.

Kinetics of elementary steps of electron transfer in nitrogenase in the presence of a photodonor.

The kinetics of transfer of two electrons from a photodonor (a system containing eosin and NADH or 4;,5;-dibromofluorescein and NADH) to Fe-protein (Av2) and the kinetics of transfer of the first and second electrons from Av2 to Mo-Fe-protein (Av1) were studied by kinetic laser spectroscopy of nitrogenase from Azotobacter vinelandii. The effects of the substrates of nitrogenase (nitrogen, acetylene, and protons) on the intramolecular electron transfer in nitrogenase were studied. Analysis of the effect of photodonor excitation radiation intensity on the rate of electron transfer was used to determine the transfer rate constants for the first (k1) and second (k2) electrons from Av2 to Av1. In the presence of MgATP, two electrons are sequentially transferred from Av2 to Av1, and no delay between these reactions was detected. The first electron transferred from Av2 to Av1 is not targeted to the substrate; k1 = 154 +/- 15 sec-1 at 23 degrees C for the system 4;,5;-dibromofluorescein-NADH; k2 = 53 +/- 5 sec-1, 95 +/- 9 sec-1, and 24 +/- 2 sec-1 at 23 degrees C in the presence of nitrogen, acetylene, and argon, respectively. An unidentified slow step (k3 = 18 +/- 2 sec-1 at 23 degrees C) may be associated with electron transfer within Av1.

Xanthene dyes as photochemical donors for the nitrogenase reaction.

The ability of xanthene dyes to mediate photoinduced reduction of nitrogenase was tested. In addition to eosin, which was studied in the preceding work (Biochemistry (Moscow), 1996, 61, 2165-2172), 4', 5'-dibromofluorescein (DBF), cyanosine, and erythrosin are effective photodonors of an electron in the presence of NADH. Fluorescein, rhodamine B, rhodamine 6G, and porphyrins are unable to mediate photoinduced reduction of nitrogenase. The mechanism underlying different efficiency of xanthene dyes in this reaction was studied. At high concentrations, all xanthene dyes tested were shown to inhibit the intramolecular electron transfer in nitrogenase. The inhibiting concentration of DBF is 1.5.10-4 M, whereas for other dyes, the inhibiting concentrations are less than 1.5.10-4 M. Under otherwise identical conditions, the ATPase activity was inhibited by xanthene dyes to a lesser extent than the nitrogenase activity. DBF, the most effective photodonor, was also studied by differential kinetic pulse laser spectroscopy. Photoinduced reduction of nitrogenase, (Fe-proteinox.Mo-Fe-protein).MgATP or (Av2ox.Av1).MgATP, was studied within the time range from 0 to 100 msec. Two initial stages of the nitrogenase turnover were detected: photoinduced reduction of Av2 and electron transfer from Av2red to Av1. The kinetics of the photoinduced reduction of Av2.MgADP was studied in the presence of DBF (up to 1.3.10-4 M) both in solution and the complex with Av1. The apparent second-order rate constants of the photoinduced reduction of Av2.MgADP in solution and the complex with Av1 were determined as 9.7.107 +/- 106 and 1.2.108 +/- 1.2.107 M-1. sec-1, respectively. The rate constant of the second reaction in the presence of another donor (dithionite) is 2500 times less. In complexes with Av1, the photochemical donor system DBF--NADH reduces Av2 more effectively than in free state in solution. In the presence of the photochemical donor system, neither photoreduction of Av2 in complexes with Av1 nor electron transfer from Av2red to Av1 are the rate-limiting stages of nitrogenase turnover.