Toward the Optimization of Dinitrosyl Iron Complexes as Therapeutics for Smooth Muscle Cells

Abstract

In this study, dinitrosyl iron complexes (DNICs) are shown to deliver nitric oxide (NO) into the cytosol of vascular smooth muscle cells (SMCs), which play a major role in vascular relaxation and contraction. Malfunction of SMCs can lead to hypertension, asthma, and erectile dysfunction, among other disorders. For comparison of the five DNIC derivatives, the following protocols were examined: (a) the Griess assay to detect nitrite (derived from NO conversion) in the absence and presence of SMCs; (b) the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4sulfophenyl)-2H-tetrazolium (MTS) assay for cell viability; (c) an immunotoxicity assay to establish if DNICs stimulate immune response; and (d) a fluorometric assay to detect intracellular NO from treatment with DNICs. Dimeric Roussin's red ester (RRE)-type {Fe(NO) 2 } 9 complexes containing phenylthiolate bridges, [(μ-SPh)Fe(NO) 2 ] 2 or SPhRRE, were found to deliver NO with the lowest effect on cell toxicity (i.e., highest IC 50 ). In contrast, the RRE-DNIC with the biocompatible thioglucose moiety, [(μ-SGlu)Fe(NO) 2 ] 2 (SGlu = 1-thio-β-D-glucose tetraacetate) or SGluRRE, delivered a higher concentration of NO to the cytosol of SMCs with a 10-fold decrease in IC 50 . Additionally, monomeric DNICs stabilized by a bulky N-heterocyclic carbene (NHC), namely, 1,3-bis(2,4,6-trimethylphenyl)imidazolidene (IMes), were synthesized and yielded the DNIC complexes SGluNHC, [IMes(SGlu)Fe(NO) 2 ], and SPhNHC, [IMes(SPh)Fe(NO) 2 ]. These oxidized {Fe(NO) 2 } 9 NHC DNICs have an IC 50 of ∼7 μM; however, the NHC-based complexes did not transfer NO into the SMC. Per contra, the reduced, mononuclear {Fe(NO) 2 } 10 neocuproine-based DNIC, neoDNIC, depressed the viability of the SMCs, as well as generated an increase of intracellular NO. Regardless of the coordination environment or oxidation state, all DNICs showed a dinitrosyl iron unit (DNIU)-dependent increase in viability. This study demonstrates a structure−function relationship between the DNIU coordination environment and the efficacy of the DNIC treatments.

Nitrosonium Cation as a Cytotoxic Component of Dinitrosyl Iron Complexes with Thiol-containing Ligands (based on the Experimental Work on MCF7 Human Breast Cancer Cell Culture)

“…Upon a subsequent elevation of DNIC concentration in a cell culture medium, S-nitrosylation of the surface proteins caused by these complexes became crucial for DNIC proapoptotic activity. Thus, the results obtained in this work and elsewhere [ 14 , 15 , 30 , 31 , 33 – 35 ] as well as the data from [ 9 ] enrich rather than contradict each other.…”

“…Our study confirms the findings obtained by other researchers concerning the ability of M-DNIC and B-DNIC with thiol-containing ligands to exert cytotoxic activity toward transformed cells [ 14 , 33 – 35 ]. It should be noted here that these complexes could well exert this activity toward the normal cells [ 15 , 30 , 31 ]. Therefore, there is also no evidence of the specific activity of these complexes toward the transformed cells.…”

How is Nitric Oxide (NO) Converted into Nitrosonium Cations (NO+) in Living Organisms? (Based on the Results of Optical and EPR Analyses of Dinitrosyl Iron Complexes with Thiol-Containing Ligands)

“…The material presented above, demonstrating the ability of DNICs with thiol-containing ligands to be donors of nitrosonium cations, is opposed to the opinion of many DNIC researchers who consider that a d 9 electronic configuration of iron in these complexes corresponds to their electronic and spatial structure most closely [ 43 – 47 ]. This opinion stems from the results of crystallographic studies of M- and B-DNICs with thiol-containing ligands.…”

“…As it follows from the above, our group considers the d 7 configuration of an iron dinitrosyl group of DNICs to be valid. The validity of another viewpoint of our opponents [ 43 – 47 ] will be described below.…”

Efficacy and safety of Shugan Jieyu capsule in the treatment of essential hypertension with insomnia, anxiety or depression

“…[ 8 ] In addition, SJC can also increase the secretion of dopamine and 5-HT to improve nerve excitability and play the role of anti-anxiety and depression. [ 9 ] The SJC made by the combination of Hypericum perforatum and Acanthopanax senticosus can effectively relieve the liver and relieve depression, calm the mind, replenish qi and invigorate the spleen,. In other words, it can reduce the patient's blood pressure, improve the patient's anxiety, depression and other bad emotions.…”