Effects of albumin-bound nitrosyl iron complex with thiosulfate ligands on lipid peroxidation and activities of mitochondrial enzymes in vitro

Cardioprotective Effect of 2-Ethyl-3-Hydroxy-6-Methylpyridinium 2-Nitroxysuccinate Against Adrenaline/Hydrocortisone-Induced Myocardial Ischemia in Mice: Modulation of Free-Radical Processes in Biomembranes and Monoamine Oxidase A Activity

Oxidative stress (OS) plays a key role in the development of cardiovascular diseases (CVD) in three major ways: reactive oxygen species (ROS)-induced reduction of nitric oxide (NO) bioavailability, ROS-induced inflammation and ROS-induced mitochondrial dysfunction. Oxidation of lipid molecules under the action of ROS leads to damage to membrane structures, changes the functioning of membrane-bound enzymes, and impairs membrane permeability and stability. An increase in OS results in the occurrence of endothelial dysfunction and drug tolerance, side effects, requiring discontinuation of drugs. All of these are significant problems of cardiotherapy. Therefore, the search for new alternative NO donors continues. The present research was aimed at studying the protective effect of 2-ethyl-3-hydroxy-6-methylpyridinium 2-nitroxysuccinate (NS) on the cardiovascular system on mouse myocardial ischemia (MI) model. The NS hybrid molecule includes a synthetic vitamin B6 analog 2-ethyl-3-hydroxy-6-methylpyridine (an antioxidant) and 2-nitroxysuccinic acid (a source of nitric oxide). Using the electron paramagnetic resonance (EPR) method and biochemical methods, we showed that the pronounced ability of NS to release NO is favorably combines with the capacity to prevent OS due to mechanisms such as suppression of the lipid peroxidation (LPO) process, antiradical activity and inhibition of the mitochondrial membrane-bound monoamine oxidase A (MAO-A). Using histological methods, we established that the administration of NS (10 mg/kg, i.p.) reduces the number of ischemic fibers and protects cardiomyocytes against ischemia injury. Thus, the complex protective effect allows us to consider NS as an alternative NO donor and a candidate for the development of a new pharmaceutical agent for the treatment of CVD.

Histidine-Bound Dinitrosyl Iron Complexes: Antioxidant and Antiradical Properties

Dinitrosyl iron complexes (DNICs) are important physiological derivatives of nitric oxide. These complexes have a wide range of biological activities, with antioxidant and antiradical ones being of particular interest and importance. We studied the interaction between DNICs associated with the dipeptide L-carnosine or serum albumin and prooxidants under conditions mimicking oxidative stress. The ligands of these DNICs were histidine residues of carnosine or His39 and Cys34 in bovine serum albumin. Carnosine-bound DNICs reduced the level of piperazine free radicals in the reaction system containing tert-butyl hydroperoxide (t-BOOH), bivalent iron ions, a nitroxyl anion donor (Angeli's salt), and HEPES buffer. The ability of carnosine DNICs to intercept organic free radicals produced from t-BOOH decay could lead to this effect. In addition, carnosine DNICs reacted with the superoxide anion radical (O2•-) formed in the xanthine/xanthine oxidase enzymatic system. They also reduced the oxoferryl form of the heme group formed in the reaction of myoglobin with t-BOOH. DNICs associated with serum albumin were found to be rapidly destroyed in a model system containing metmyoglobin and t-BOOH. At the same time, these protein DNICs inhibited the t-BOOH-induced oxidative degradation of coenzymes Q9 and Q10 in rat myocardial homogenate. The possible mechanisms of the antioxidant and antiradical action of the DNICs studied and their role in the metabolism of reactive oxygen and nitrogen species are discussed.

Influence of Nitrosyl Iron Complex with Thiosulfate Ligands on Therapeutically Important Targets Related to Type 2 Diabetes Mellitus

The high prevalence of type 2 diabetes mellitus (T2DM), and the lack of effective therapy, determine the need for new treatment options. The present study is focused on the NO-donors drug class as effective antidiabetic agents. Since numerous biological systems are involved in the pathogenesis and progression of T2DM, the most promising approach to the development of effective drugs for the treatment of T2DM is the search for pharmacologically active compounds that are selective for a number of therapeutic targets for T2DM and its complications: oxidative stress, non-enzymatic protein glycation, polyol pathway. The nitrosyl iron complex with thiosulfate ligands was studied in this work. Binuclear iron nitrosyl complexes are synthetic analogues of [2Fe-2S] centers in the regulatory protein natural reservoirs of NO. Due to their ability to release NO without additional activation under physiological conditions, these compounds are of considerable interest for the development of potential drugs. The present study explores the effects of tetranitrosyl iron complex with thiosulfate ligands (TNIC-ThS) on T2DM and its complications regarding therapeutic targets in vitro, as well as its ability to bind liposomal membrane, inhibit lipid peroxidation (LPO), and non-enzymatic glycation of bovine serum albumin (BSA), as well as aldose reductase, the enzyme that catalyzes the reduction in glucose to sorbitol in the polyol pathway. Using the fluorescent probe method, it has been shown that TNIC-ThS molecules interact with both hydrophilic and hydrophobic regions of model membranes. TNIC-ThS inhibits lipid peroxidation, exhibiting antiradical activity due to releasing NO (IC50 = 21.5 ± 3.7 µM). TNIC-ThS was found to show non-competitive inhibition of aldose reductase with Ki value of 5.25 × 10^-4 M. In addition, TNIC-ThS was shown to be an effective inhibitor of the process of non-enzymatic protein glycation in vitro (IC50 = 47.4 ± 7.6 µM). Thus, TNIC-ThS may be considered to contribute significantly to the treatment of T2DM and diabetic complications.

A nitrosyl iron complex with 3.4-dichlorothiophenolyl ligands: synthesis, structures and its reactions with targets - carriers of nitrogen oxide (NO) in vivo

In this work, a new binuclear nitrosyl complex with 3.4-dichlorothiophenolyl ligands [Fe₂(SC₆H₃Cl₂)₂(NO)₄] has been synthesized. Nitrosyl iron complexes (NICs) are systems for the storage and delivery of NO in the body. There is a dynamic equilibrium between dinitrosyl iron units bound to low molecular weight ligands and high molecular weight (protein) ligands in vivo. From this point of view, the transformation of the studied complex in DMSO and buffer, as well as in biological systems, has been analyzed. In DMSO, it decomposes into mononuclear NICs, which quickly decay in buffer solutions with NO release. The high molecular weight product is formed as a result of the binding of the complex to bovine serum albumin (the Stern-Volmer constant is 2.1 × 10⁵ M^-1). In this case, the complex becomes a prolonged NO-donor. Such a long-term effect has been observed for the first time. Similarly, in a system with oxyhemoglobin, NO generation is slower; the UV-vis spectra show a gradual formation of methemoglobin. On the other hand, reduced glutathione has little effect on the NO-donor properties of the complex despite the fact that ligand substitution is observed in the system and a binuclear product is formed. Mucin binds the complex, and the decomposition mechanism is different from that for buffer solutions. Thus, these proteins and glutathione are able to participate in the transformation of the complex and modulate its properties as a potential drug.

Antiglycation and Antioxidant Effect of Nitroxyl towards Hemoglobin

Donors of nitroxyl and nitroxyl anion (HNO/NO⁻) are considered to be promising pharmacological treatments with a wide range of applications. Remarkable chemical properties allow nitroxyl to function as a classic antioxidant. We assume that HNO/NO⁻ can level down the non-enzymatic glycation of biomolecules. Since erythrocyte hemoglobin (Hb) is highly susceptible to non-enzymatic glycation, we studied the effect of a nitroxyl donor, Angeli’s salt, on Hb modification with methylglyoxal (MG) and organic peroxide―tert-butyl hydroperoxide (t-BOOH). Nitroxyl dose-dependently decreased the amount of protein carbonyls and advanced glycation end products (AGEs) that were formed in the case of Hb incubation with MG. Likewise, nitroxyl effectively protected Hb against oxidative modification with t-BOOH. It slowed down the destruction of heme, formation of carbonyl derivatives and inter-subunit cross-linking. The protective effect of nitroxyl on Hb in this system is primarily associated with nitrosylation of oxidized Hb and reduction of its ferryl form, which lowers the yield of free radical products. We suppose that the dual (antioxidant and antiglycation) effect of nitroxyl makes its application possible as part of an additional treatment strategy for oxidative and carbonyl stress-associated diseases.

Albumin as a prospective carrier of the nitrosyl iron complex with thiourea and thiosulfate ligands under aerobic conditions

High-molecular-weight dinitrosyl iron complexes (DNICs) are formed in living systems and are a stable depot of nitrogen monoxide (NO). In this work, using experimental and theoretical methods, we investigated the interaction of their synthetic analog, a promising cardiotropic complex of the composition [Fe(SC(NH₂)₂)₂(NO)₂]₂[Fe₂(S₂O₃)₂(NO)₄], with bovine serum albumin (BSA) in aqueous aerobic solutions. We suggested that, under these conditions, the decomposition product of the initial complex with oxygen, the [Fe(NO)(NO₂)]⁺ fragment, can bind in the hydrophobic pocket of the protein. As a result of this interaction, high-molecular-weight Fe(Cys34)(His39)(NO)(NO₂) is formed. The binding constant of the complex with protein measured by the quenching of intrinsic fluorescence of BSA is 7.2 × 10⁵ M^-1. According to EPR and UV-spectroscopy data, the interaction of the complex with the protein leads to its significant stabilization. In addition to coordination binding, the studied complex can be adsorbed onto the protein surface due to weak intermolecular interactions, resulting in the prolonged generation of NO.