Preparation of Glycosylated Nitrosohemoglobin by Maillard Reaction and its Stability under Fluorescent Light at 20°C

One of the roles nitrite played in meat curing is to produce the characteristic pink color, but the use is limited due to its potential carcinogenicity. In this study, porcine blood was used for synthesizing glycosylated nitrosyl-hemoglobin (G-NO-Hb) through maillard reaction and the preparation conditions were optimized. Also, the stability of G-NO-Hb was assessed by UV-Vis spectra. The results showed that: the optimum ratio of blood cells to water was 1: 2, nitrite of 2 mg/kg reaction mixture was chosen. The synthesized G-NO-Hb solution was rather stable under light radiation at 20°C for 20d. It revealed that G-NO-Hb was a potential stable pigment used for meat curing as a nitrite substitute.

Dietary doses of nitrite restore circulating nitric oxide level and improve renal injury in l-NAME-induced hypertensive rats

We have reported that pharmacological doses of oral nitrite increase circulating nitric oxide (NO) and exert hypotensive effects in Nω-nitro-l-arginine methyl ester (l-NAME)-induced hypertensive rats. In this study, we examined the effect of a chronic dietary dose of nitrite on the hypertension and renal damage induced by chronic l-NAME administration in rats. The animals were administered tap water containing l-NAME (1 g/l) or l-NAME + nitrite (low dose: 0.1 mg/l, medium dose: 1 mg/l, high dose: 10 mg/l) for 8 wk. We evaluated blood NO levels as hemoglobin-NO adducts (iron-nitrosyl-hemoglobin), using an electron paramagnetic resonance method. Chronic administration of l-NAME for 8 wk induced hypertension and renal injury and reduced the blood iron-nitrosyl-hemoglobin level (control 38.8 ± 8.9 vs. l-NAME 6.0 ± 3.1 arbitrary units). Coadministration of a low dose of nitrite with l-NAME did not change the reduced iron-nitrosyl-hemoglobin signal and did not improve the l-NAME-induced renal injury. The blood iron-nitrosyl-hemoglobin signals of the medium dose and high dose of nitrite were significantly higher than that of l-NAME alone. Chronic administration of a medium dose of nitrite attenuated l-NAME-induced renal histological changes and proteinuria. A high dose of nitrite also attenuated l-NAME-induced renal injury. These findings suggest that dietary doses of nitrite that protect the kidney are associated with significant increase in iron-nitrosyl-hemoglobin levels. We conclude that dietary nitrite-derived NO generation may serve as a backup system when the nitric oxide synthase/l-arginine-dependent NO generation system is compromised.

Potential of Angeli’s Salt To Reduce Nitric Oxide Scavenging in Hemolysis.

Since cell-free hemoglobin (Hb) scavenges nitric oxide (NO) more effectively than that encapsulated in the red blood cell (RBC), hemolysis reduces NO bioavailability with pathological consequences in sickle cell disease and other hemolytic anemias, paroxysmal nocturnal hemoglobinuria, thalassemia intermedia, malaria, and cardiopulomonary bypass. The ability of the cell-free Hb to scavenge NO is reduced when the Hb is converted from its oxygenated form (HbO2) to its oxidized form, methemoglobin (MetHb). We show that Angeli’s salt (AS) can convert two OxyHb to two MetHb molecules through its release of nitroxyl (HNO). AS also further converts the MetHb to less potentially oxidative forms: nitrite bound MetHb and iron-nitrosyl hemoglobin. We also show that, due to the fast reactivity of HNO with Hb (like NO), AS preferentially reacts with cell-free rather than RBC encapsulated Hb. In conditions simulating sickle cell crisis, within six minutes, AS converted 45 ± 12% of cell-free Hb to non-NO scavenging forms (MetHb and iron-nitrosyl Hb) and only converted 0.4 ± 0.3% of RBC encapsulated Hb (n=3). Similar preferential reactivity was observed under other physiologically relevant conditions. We conclude that, as AS preferentially reacts with cell-free Hb compared to RBC encapsulated Hb, converting it to species that do not effectively scavenge NO, it is has promise as a treatment for increasing NO biavailability in conditions associated with hemolysis.