Caracterização farmacológica da atividade vasodilatadora de novos complexos de rutênio contendo derivados imidazólicos

Abstract

The ruthenium is a metal that allows high affinity to the NO due to its chemical structure, forming nitrosyl-ruthenium complexes (RuNO). Complexes based on ruthenium may be metallopharmaceuticals with potential medical applications, especially for the treatment of cardiovascular diseases. The objective of this study was to perform a pharmacological screening to evaluate the vasodilator potential in conductance vessels of ruthenium complexes cis-[Ru(bpy)2(2-MIM)Cl]+ (FOR011A), cis-[Ru(bpy)2(2-MIM)2]2+ (FOR011AA), cis-[Ru(bpy)2(2-MIM)(NO2)]+ (FOR711A) and cis-[Ru(bpy)2(2-MIM)(NO)]3+ (FOR811A) in an attempt to characterize the mechanism of action of those with greater pharmacological potency. The project was approved by the Ethics Committee on Use of Animals / UFC under protocol number 03/2016. Aortic rings of Wistar rats with intact or denuded endothelium were precontracted with phenylephrine (PHE) (1 μmol/L) or KCl (60 mmol/L) for subsequent creation of a concentration-effect curve (0.01 to 30 μmol/L) with the compounds and registration in a data system. Their effects were compared to the precursor molecules cis-[Ru(bpy)2(Cl)2] (FOR000) and 2-methylimidazole (L11A), sodium nitroprusside (SNP) and BAY 41-2272. The interference of pharmacological inhibitors in the vasodilator effect of the two most potent molecules, FOR011A and FOR811A, was evaluated, as well as protocols to verify their actions on the Ca2+ influx and the time-course for maximum relaxation. In addition, protocols were used to evaluate the expression of tissue cyclic GMP (cGMP) and molecular docking with soluble guanylate cyclase (sGC). The compounds produced a vasodilator effect with variable potencies and were able to revert 100% of the pre-contractions by PHE (FOR011A: CE50 = 0.190 [0.1379-0.2607] µmol/L and EMAX = 101.317 ± 1.839%; FOR011AA: CE50 = 0.624 [0.4456-0.8709] µmol/L and EMAX = 105.273 ± 2.450%; FOR711A: CE50 = 0.474 [0.3926-0.5725] µmol/L and EMAX = 112.057 ± 1.903%; FOR811A: CE50 = 0.204 [0.1618-0.2573] µmol/L and EMAX = 113.406 ± 1.780%). Their potencies were lower than that of the SNP, higher than that of FOR000 and L11A; and similar to those of BAY in FOR011A and FOR811A and lower in FOR011AA and FOR711A. The FOR011A and FOR011AA presented reduced potency to the increase of the extracellular concentration of K+. The absence of the endothelium reduced the potency of the FOR011A and FOR011AA, but had no influence on FOR711A and FOR811A. In the preparations with different inhibitors and FOR011A, the compound presented a reduction in potency when incubated with L-NAME, wortmannin, ODQ, tetraethylammonium, 4-aminopyridine and glibenclamide. In the preparations with different inhibitors and FOR811A, the compound presented reduction in potency when incubated with hydroxocobalamin, L-cysteine, ODQ, MDL-12,330A and increase in potency when incubated with tetraethylammonium and propranolol. Tissue cGMP levels were modified by FOR811A, but not by FOR011A. The presence of ODQ did not influence the expression of cGMP levels in both preparations. Both ruthenium complexes were able to bind to sites in the reduced and oxidized sGC, maintaining low binding distances to various residues and negative Gibbs free energy. These findings indicate that FOR011A is a possible NO-independent sGC stimulator/activator agent and FOR811A a possible direct NO donor and/or NO-dependent sGC stimulator/activator.