15N CIDNP investigations of the peroxynitric acid nitration of l-tyrosine and of related compounds

Oxidative risk for atherothrombotic cardiovascular disease

In the vasculature, reactive oxidant species, including reactive oxygen, nitrogen, or halogenating species, and thiyl, tyrosyl, or protein radicals may oxidatively modify lipids and proteins with deleterious consequences for vascular function. These biologically active free radical and nonradical species may be produced by increased activation of oxidant-generating sources and/or decreased cellular antioxidant capacity. Once formed, these species may engage in reactions to yield more potent oxidants that promote transition of the homeostatic vascular phenotype to a pathobiological state that is permissive for atherothrombogenesis. This dysfunctional vasculature is characterized by lipid peroxidation and aberrant lipid deposition, inflammation, immune cell activation, platelet activation, thrombus formation, and disturbed hemodynamic flow. Each of these pathobiological states is associated with an increase in the vascular burden of free radical species-derived oxidation products and, thereby, implicates increased oxidant stress in the pathogenesis of atherothrombotic vascular disease.

15N-CIDNP investigations during tryptophan, N-acetyl-L-tryptophan, and melatonin nitration with reactive nitrogen species

Tryptophan and melatonin are nitrated by peroxynitrite; tryptophan residues in proteins are susceptible to attack by reactive nitrogen species. Nitrated tryptophan might therefore be used as a biomarker for the involvement of reactive species derived from nitrogen oxide in a variety of pathophysiological conditions. The radical character of the tryptophan (Trp) and N-acetyl-L-tryptophan (N-AcTrp) nitration with peroxynitrite is shown using (15)N-CIDNP. During the decay of peroxynitrite-(15)N in the presence of Trp at pH 5 in the probe of a (15)N-NMR spectrometer, the (15)N-NMR signals of various nitrated tryptophans ((15)NO(2)-Trp) show emission (E). The effects are built up in radical pairs [Trp( radical), 15NO2 ](F) formed by diffusive encounters of radicals 15NO2 and Trp( radical) generated during decay of peroxynitrite-(15)N in the presence of Trp. Similar (15)N-CIDNP effects are observed during reaction of Trp and/or N-AcTrp using the nitrating systems H(15)NO(3), H(15)NO(4) and H(2)O(2)/15NO2 /HRP, which are also built up in radical pairs [Trp, 15NO2 ](F). During nitration of melatonin (Mel) with peroxynitrite-(15)N and H(15)NO(4), the (15)N-NMR signal of 4-nitromelatonin (4-(15)NO(2)-Mel) shows emission arising from radical pairs [Mel, 15NO2 ](F) which are formed in an analogous manner.