Nitrite-derived nitric oxide formation following ischemia-reperfusion injury in kidney

Abstract

Nitric oxide (NO) is synthesized from l-arginine by nitric oxide synthase (NOS), and nitrite and nitrate are believed to be waste forms of NO. We previously reported an enzyme-independent pathway of NO generation from nitrite in acidic conditions. In this study, we show nitrite-derived NO formation in renal ischemia-reperfusion injury using electron paramagnetic resonance (EPR) spectroscopy. In this experiment, we utilized a stable isotope of [(15)N]nitrite as a source of nitrite to distinguish l-arginine-derived NO from [(15)N]nitrite-derived (15)NO. Intravenous infusion of a stable isotope of [(15)N]nitrite ((15)NO(2)(-)) facilitated the formation of Hb(15)NO during renal ischemia, which demonstrated that the origin of NO was nitrite. The EPR signal of Hb(15)NO in kidney appeared after 40 min of renal ischemia, and renal reperfusion decreased the Hb(15)NO level in the kidney and increased it in blood by contrast. In addition, the amount of HbNO was nitrite concentration dependent, and this formation was NOS independent. Our findings suggest that nitrite can be an alternative source of NO in ischemic kidney and that it binds with hemoglobin and then is spread by the circulation after reperfusion.

Nitrite-Derived Nitric Oxide Protects the Rat Kidney against Ischemia/Reperfusion Injury In Vivo

“…We demonstrate here that the NO scavenger C-PTIO abolished the beneficial effects of nitrite, whereas C-PTIO alone (i.e., in the absence of nitrite) did not aggravate the renal injury and dysfunction that were caused by I/R injury, indicating that, as in the heart (2), NO mediates the beneficial effects of nitrite. This is in accordance with the study of Okamato et al (15), who, using [(15)N]nitrite, demonstrated nitrite-derived NO generation as evidenced by formation of [(15)N]NO adducts after renal ischemia.…”

“…In terms of absolute nitrite reductase activity, it is worth noting that the in vitro experiments were conducted at standard laboratory conditions (25°C) and the activity of XOR is approximately 2.5-fold lower at this temperature compared with 37°C, at least with respect to xanthine oxidation (38). This demonstration of renal nitrite reductase activity confirms the findings of Okamoto et al (15), who used electron paramagnetic resonance spectroscopy. The use of ozone chemiluminescence in our study permits direct measurement of NO in parts per billion and avoids the problem of nitrite itself forming the (MGD) 2 Fe 2ϩ -NO complex detected by electron paramegnetic resonance spectroscopy, especially if GSH or l-cysteine is present (39).…”

“…It is likely that both this pathway and the XOR pathway have a role to play and that their contribution depends largely on the prevailing environmental conditions (O 2 levels and pH). Indeed, Okamoto et al (15) showed important nitrite reductase roles for both Hb and XOR in vivo in the kidney after the intravenous administration of nitrite.…”

“…During ischemia, eNOS activity is compromised as a result of its essential dependence on oxygen and the increasing acidosis (14). However, in ischemic conditions, the endogenous nitrite pool may serve as an important alternative source of NO in the heart, liver, and kidney by providing NOS-independent NO generation (2,3,15,16). Indeed, this nitrite-derived NO generation increases with increasing hypoxemia and acidosis.…”

Taking up the cudgels for the traditional reactive oxygen and nitrogen species detection assays and their use in the cardiovascular system

“…nitric oxide formation in tissues and cells by nitrosyl-Fe(DETC) 2 spin trapping or in whole blood by nitrosyl-iron hemoglobin, Hb-NO) is the gold standard for nitric oxide detection in biological samples [46,62,63]. In addition, whole blood Hb-NO and aortic NO-Fe(DETC) 2 [147,148]. However, the use of fluorescent probes for the time-dependent and location-specific formation of nitric oxide might be straight forward, although these dyes need proper characterization in various biological systems to be sure about their specificity.…”