Contents lists available at ScienceDirect Nitric Oxide journal homepage: www.elsevier.com/locate/yniox Influence of hemoglobin and albumin on the NO donation effect of tetranitrosyl iron complex with thiosulfate Olesya Pokidova a,* , Tatiana Rudneva a , Bogdan Tretyakov b , Raisa Kotelnikova a , Alexander Kotelnikov a,b , Sergey Aldoshin a,b a Institute of Problems of Chemical Physics of the RAS, Chernogolovka, Moscow Region, 142432, Russian Federation b Lomonosov Moscow State University, Moscow, 119991, Russian Federation ARTICLE INFO Keywords: Deoxyhemoglobin Bovine serum albumin Nitrosyl iron complexes Nitric monoxide ABSTRACT The effects of deoxyhemoglobin (Hb) and albumin on the NO-donor activity of the anionic tetranitrosyl iron complex with thiosulfate ligands (1) were studied for the first time. It was shown that Hb significantly stabilizes complex 1; in its presence, NO generation from the complex proceeds at a noticeably slower rate. A similar effect is observed when complex 1 is bound to albumin, in which case complex 1 decomposes 27 times slower than in the absence of albumin in the solution. The observed effects provide a prolonged action of complex 1 as NO- donor, which may enhance its potential pharmacological efficacy. 1. Introduction Structural synthetic analogs of the active center of non-heme iron- sulfur proteins, nitrosyl iron complexes (DNICs) with functional sulfur- containing ligands, are of great interest as new generation drugs for the treatment of cardiovascular, oncological and other socially significant diseases [1,2]. Anionic binuclear DNIC with thiosulfate ligands (complex 1) Na 2 [Fe 2 (S 2 O 3 ) 2 (NO) 4 ]∙4H 2 O(Fig. 1) is one of the most promising re- presentatives of this compounds class [3]. It has been shown that complex 1 is a more effective NO donor compared with the NONOate, 2,2′-(hydroxynitrosohydrazono)bis-ethanimine [4], it exhibits anti- metastatic activity and induces the expression of the genes of the pro- tective DNA repair pathways in the cell, including the SOS and SoxRS systems of E. Coli [5], and also completely inhibits the catalytic activity of Ca 2+ -ATPase and phosphodiesterase at a concentration of 0.01 mM [6]. To understand the chemical and biological mechanisms of complex 1 action as a prodrug, a comprehensive study of its metabolic processes is necessary to conduct. It is assumed that the targets of DNICs as NO donors in vivo can be Fe- and thiol-containing proteins, as well as low molecular weight thiols [7,8]. In this work, the biotransformation of complex 1 was analyzed by the effects of its interaction with deox- yhemoglobin (Hb) and bovine serum albumin (BSA). According to the literature [9], erythrocyte hemoglobin is one of the most important elements of the biological transformation of NO donors and the NO transport inside the body. It was found that besides the formation of protein-bound complexes with the oxygenated form of the protein (HbO 2 )[10], DNICs are also able to bind with deoxygenated Hb [11], becoming more prolonged NO donors. As a result of the analysis carried out in Ref. [11], it was concluded that the observed effect of cationic complexes stabilization can occur due to the binding of their positively charged groups with negatively charged amino acid residues on the Hb surface. It was interesting to determine whether a similar effect would be observed in the case of anionic complex 1. Another no less important objective of this work was to study the effect of BSA on the decay process of complex 1. BSA is a blood transport protein the main function of which is a transfer of various biologically active substances [12]. It has been established [7] that BSA is one of the main targets of the DNICs action, and the binding of DNICs occurs with cysteine (Cys 34) or histidine residues in the hydrophobic pocket of the molecule to form protein-bound nitrosyl complexes [13]. According to experimental data obtained in animals [14], high- molecular complexes formed by the interaction of DNICs with various proteins are more stable than low-molecular complexes, and as a result, most of the DNICs in cells and tissues have a protein form. 2. Material and methods 2.1. Materials In the work, tris(hydroxymethyl)aminomethane (“Serva”, https://doi.org/10.1016/j.niox.2019.10.010 Received 9 September 2019; Received in revised form 15 October 2019; Accepted 29 October 2019 * Corresponding author. E-mail address: pov@icp.ac.ru (O. Pokidova). Nitric Oxide 94 (2020) 69–72 Available online 31 October 2019 1089-8603/ © 2019 Elsevier Inc. All rights reserved. T