Complexes of ^.NO with nucleophiles as agents for the controlled biological release of nitric oxide. Vasorelaxant effects

Abstract

Selected nucleophile/nitric oxide adducts [compounds which contain the anionic moiety, XN(O-)N = O] were studied for their ability to release nitric oxide spontaneously in aqueous solution and for possible vasoactivity. The diversity of structures chosen included those in which the nucleophile residue, X, was that of a secondary amine [Et2N, as in [Et2NN(N = O)O]Na, 1], a primary amine [iPrHN, as in [iPrHNN(N = O)O]Na, 2], a polyamine, spermine [as in the zwitterion H2N(CH2)3NH2+(CH2)4N[N(N = O)O-](CH2)3NH2, 3], oxide [as in Na[ON(N = O)O]Na, 4], and sulfite [as in NH4[O3SN(N = O)O]NH4, 5]. The rate constants (k) for decomposition in pH 7.4 phosphate buffer at 37 degrees C, as measured by following loss of chromophore at 230-260 nm, were as follows: 1, 5.4 x 10(-3) s-1; 2, 5.1 x 10(-3) s-1; 3, 0.30 x 10(-3) s-1; 4, 5.0 x 10(-3) s-1; and 5, 1.7 x 10(-3) s-1. The corresponding extents of nitric oxide release (ENO) were 1.5, 0.73, 1.9, 0.54, and 0.001 mol/mol of starting material consumed, respectively, as determined from the integrated chemiluminescence response. Vasodilatory activities expressed as the concentrations required to induce 50% relaxation in norepinephrine-constricted aortic rings bathed in pH 7.4 buffer at 37 degrees C (EC50) were as follows: 1, 0.19 microM; 2, 0.45 microM; 3, 6.2 microM; 4, 0.59 microM; and 5, 62 microM. Vasorelaxant potency (expressed as 1/EC50) was strongly correlated with the quantity of .NO calculated from the physicochemical data to be released in the interval required to achieve maximum relaxation at the EC50 doses (r = 0.995). This suggests that such nucleophile/.NO adducts might generally be useful as vehicles for the nonenzymatic generation of nitric oxide, in predictable amounts and at predictable rates, for biological purposes. The particular significance for possible drug design is underscored in the very favorable potency comparison between several of these agents and the established nitrovasodilators sodium nitroprusside and glyceryl trinitrate (EC50 values of 2.0 and greater than 10 microM, respectively) in parallel aortic ring tests.

Nitric oxide inhibits insulin-degrading enzyme activity and function through S-nitrosylation

“…The control compound, sulfo-NONOate, is chemically similar to PAPANONOate, but it does not release NO; it dissociates in solution to form only sulfate and nitrous oxide (N 2 O) [43]. PAPANONOate showed a significant inhibitory effect on both insulin and Ab degradation, but the control compound sulfo-NONOate did not affect the degradation of either substrate, indicating that the inhibition seen was likely due to NO.…”

A multilevel analytical approach for detection and visualization of intracellular NO production and nitrosation events using diaminofluoresceins

“…Thus, SNOC could directly nitrosate DAFͲFM without intermediacy of free NO [44]. For this reason we additionally employed the NO donor Sper/NO, which spontaneously releases NO [45]. A concentration of 100 μM Sper/NO, which translates into a constant release of 2.1 Ͳ 3.6 μM NO/min within the first 30 min of decomposition, also increased the formation of DAFͲFMͲT in RBCs with an efficacy comparable to that of SNOC.…”

Nitric oxide synthase and NAD(P)H oxidase modulate coronary endothelial cell growth

“…SpNO was prepared in phosphate buffered saline (pH 8.5) to release NO at a predictable rate that does not require bioconversion to NO [24]. The incubation with SpNO almost completely abolished CMEC proliferation in proliferating cells as determined by the levels of total cellular protein (331 ± 21 g vs 357 ± 23 g.…”