Unique Oxidative Mechanisms for the Reactive Nitrogen Oxide Species, Nitroxyl Anion

Abstract

The nitroxyl anion (NO. ), respectively, can lead to oxidation, hydroxylation, nitration, and nitrosation of biomolecules (1). Although a substantial literature exists on the putative biological effects of other RNOS, few studies have focused on nitroxyl (NO Ϫ ), the one electron reduction product of NO. Several reports suggest that NO Ϫ (or its conjugate acid, HNO) can be generated from chemical reactions that occur in vivo (2, 3) including oxidation of L-arginine by tetrahydrobiopterin-free nitric oxide synthase (NOS) (4 -6) and decomposition of Snitrosothiols (7, 8). Taken together, these studies indicate that the chemistry of NO Ϫ is an essential component of the redox chemistry of NO in biological systems.Angeli's salt (AS) is the most commonly used synthetic donor in the study of NO Ϫ effects under biological conditions (9). At physiological pH and temperature, AS spontaneously decomposes to HNO and nitrite with a half-life of 2.5 min,The cytotoxic effects of AS are several orders of magnitude greater than those of other RNOS and are comparable to alkylhydroperoxides (10), suggesting that NO Ϫ formation in vivo could have deleterious consequences. In a myocardial ischemiareperfusion model, treatment with AS markedly increased infarct area (11). In contrast, NO, either from a donor or from oxidation of NO Ϫ in the presence of an electron acceptor, afforded protection in the same model. In the present report, the chemistry of AS is compared with that of ONOO Ϫ and NO/N 2 O 3 to gain insight into the biological mechanisms in which the chemistry of NO Ϫ could be involved. MATERIALS AND METHODSAngeli's salt (Na 2 N 2 O 3 ) was synthesized as described previously (10). The NONOate, DEA/NO (NaEt 2 NN(O)NO), was a generous gift from Dr. Joseph Saavedra (National Cancer Institute, Frederick, MD). Stock solutions (ϳ10 mM) of AS and DEA/NO were prepared in 10 mM NaOH and stored at Ϫ20°C (12). Peroxynitrite was synthesized by mixing solutions of 0.5 M NO 2 Ϫ in 0.5 M HCl and 0.5 M hydrogen peroxide (H 2 O 2 ) followed by rapid quenching in 1 M NaOH, as described previously (13). The resulting basic solution was exposed to MnO 2 to remove excess H 2 O 2 , which was reduced to Ͻ1% per mol of ONOO Ϫ . After filtering, aliquots were stored at Ϫ20°C for less than 2 weeks. Directly prior to use, the concentrations of these RNOS donors in 10 mM NaOH were

A mosquito 2-Cys peroxiredoxin protects against nitrosative and oxidative stresses associated with malaria parasite infection

“…However, the chemistries of HNO and PN differ, and some studies have noted that toxicities of these compounds derive from different reactive intermediates [53]. For example, HNO has a high affinity for GSH [54]; exposure of cells to millimolar concentrations of AS can dramatically reduce intracellular GSH through the production of GSNHOH [51,53]. As such, Prxs may function to protect cells through direct recycling of oxidized thiols to maintain cellular homeostasis [55] in mosquito cells.…”

“…Thus, the ability of AsPrx-4783 to protect against HNO may be due in part to PN reductase activity of AsPrx-4783. However, the chemistries of HNO and PN differ, and some studies have noted that toxicities of these compounds derive from different reactive intermediates [53]. For example, HNO has a high affinity for GSH [54]; exposure of cells to millimolar concentrations of AS can dramatically reduce intracellular GSH through the production of GSNHOH [51,53].…”

Nitroxyl anion exerts redox-sensitive positive cardiac inotropy in vivo by calcitonin gene-related peptide signaling

“…A direct comparison of the biological effects of these two redox-related species often reveals them to have opposite biochemical and physiological properties. For instance, NO ⅐ reacts with O 2 to form a nitrosating species, whereas NO Ϫ reacts with O 2 to form an oxidizing species (24). At a physiological level, NO ⅐ is protective in myocardial ischemia, whereas high levels of NO Ϫ can aggravate ischemia͞reperfusion injury (21).…”

“…Thiols such as NAC do have a higher affinity for HNO than do oxidants such as ROS or peroxynitrite (ONOO Ϫ ; ref. 24). Quenching of dihydrorhodamine oxidation required less than 10 M GSH, whereas oxidation by equimolar N 2 O 3 or ONOO Ϫ required concentrations of thiol 100ϫ higher.…”

Inflammatory Modulation of Hepatocyte Apoptosis by Nitric Oxide: In Vivo, In Vitro, and In Silico Studies

“…Mechanistically, these reactions were suggested to occur with the intermediate formation of [49][50][51][52][53] or (an isomer of) [54] peroxynitrite; [53,55] direct detection of the corresponding oxidizing species, however, has proven to be difficult. Irrespectively of the exact mechanism of these reaction(s), overproduction of HNO in tissues subjected to acidosis may lead to oxidative stress inasmuch as the ability of HNO to act as a pro-oxidant dramatically increases in acidic solutions (ref.…”