Redox reactions of cationic nitrosyl iron complexes with thiourea and its aliphatic derivatives: The experiment and DFT investigation

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.

A divergent mode of activation of a nitrosyl iron complex with unusual antiangiogenic activity

Nitric oxide (NO) and nitroxyl (HNO) have gained broad attention due to their roles in several physiological and pathophysiological processes. Remarkably, these sibling species can exhibit opposing effects including the promotion of angiogenic activity by NO compared to HNO, which blocks neovascularization. While many NO donors have been developed over the years, interest in HNO has led to the recent emergence of new donors. However, in both cases there is an expressive lack of iron-based compounds. Herein, we explored the novel chemical reactivity and stability of the trans-[Fe(cyclam)(NO)Cl]Cl₂ (cyclam = 1,4,8,11-tetraazacyclotetradecane) complex. Interestingly, the half-life (t_1/2) for NO release was 1.8 min upon light irradiation, vs 5.4 h upon thermal activation at 37 °C. Importantly, spectroscopic evidence supported the generation of HNO rather than NO induced by glutathione. Moreover, we observed significant inhibition of NO donor- or hypoxia-induced HIF-1α (hypoxia-inducible factor 1α) accumulation in breast cancer cells, as well as reduced vascular tube formation by endothelial cells pretreated with the trans-[Fe(cyclam)(NO)Cl]Cl₂ complex. Together, these studies provide the first example of an iron-nitrosyl complex with anti-angiogenic activity as well as the potential dual activity of this compound as a NO/HNO releasing agent, which warrants further pharmacological investigation.

Cytoprotective Effects of Dinitrosyl Iron Complexes on Viability of Human Fibroblasts and Cardiomyocytes

Nitric oxide (NO) is an important signaling molecule that plays a key role in maintaining vascular homeostasis. Dinitrosyl iron complexes (DNICs) generating NO are widely used to treat cardiovascular diseases. However, the involvement of DNICs in the metabolic processes of the cell, their protective properties in doxorubicin-induced toxicity remain to be clarified. Here, we found that novel class of mononuclear DNICs with functional sulfur-containing ligands enhanced the cell viability of human lung fibroblasts and rat cardiomyocytes. Moreover, DNICs demonstrated remarkable protection against doxorubicin-induced toxicity in fibroblasts and in rat cardiomyocytes (H9c2 cells). Data revealed that the DNICs compounds modulate the mitochondria function by decreasing the mitochondrial membrane potential (ΔΨm). Results of flow cytometry showed that DNICs were not affected the proliferation, growth of fibroblasts. In addition, this study showed that DNICs did not affect glutathione levels and the formation of reactive oxygen species in cells. Moreover, results indicated that DNICs maintained the ATP equilibrium in cells. Taken together, these findings show that DNICs have protective properties in vitro. It was further suggested that DNICs may be uncouplers of oxidative phosphorylation in mitochondria and protective mechanism is mainly provided by the leakage of excess charge through the mitochondrial membrane. It is assumed that the DNICs have the therapeutic potential for treating cardiovascular diseases and for decreasing of chemotherapy-induced cardiotoxicity in cancer survivors.