Cytoprotective effects of nitrite during in vivo ischemia-reperfusion of the heart and liver
Mark R. Duranski, … , Mark T. Gladwin, David J. Lefer
Mark R. Duranski, … , Mark T. Gladwin, David J. Lefer
Published May 2, 2005
Citation Information: J Clin Invest. 2005;115(5):1232-1240. https://doi.org/10.1172/JCI22493.
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Article Cardiology

Cytoprotective effects of nitrite during in vivo ischemia-reperfusion of the heart and liver

Abstract

Nitrite represents a circulating and tissue storage form of NO whose bioactivation is mediated by the enzymatic action of xanthine oxidoreductase, nonenzymatic disproportionation, and reduction by deoxyhemoglobin, myoglobin, and tissue heme proteins. Because the rate of NO generation from nitrite is linearly dependent on reductions in oxygen and pH levels, we hypothesized that nitrite would be reduced to NO in ischemic tissue and exert NO-dependent protective effects. Solutions of sodium nitrite were administered in the setting of hepatic and cardiac ischemia-reperfusion (I/R) injury in mice. In hepatic I/R, nitrite exerted profound dose-dependent protective effects on cellular necrosis and apoptosis, with highly significant protective effects observed at near-physiological nitrite concentrations. In myocardial I/R injury, nitrite reduced cardiac infarct size by 67%. Consistent with hypoxia-dependent nitrite bioactivation, nitrite was reduced to NO, S-nitrosothiols, N-nitros-amines, and iron-nitrosylated heme proteins within 1–30 minutes of reperfusion. Nitrite-mediated protection of both the liver and the heart was dependent on NO generation and independent of eNOS and heme oxygenase-1 enzyme activities. These results suggest that nitrite is a biological storage reserve of NO subserving a critical function in tissue protection from ischemic injury. These studies reveal an unexpected and novel therapy for diseases such as myocardial infarction, organ preservation and transplantation, and shock states.

Authors

Mark R. Duranski, James J.M. Greer, Andre Dejam, Sathya Jaganmohan, Neil Hogg, William Langston, Rakesh P. Patel, Shaw-Fang Yet, Xunde Wang, Christopher G. Kevil, Mark T. Gladwin, David J. Lefer

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Nitrite therapy in myocardial I/R injury. (A) Experimental protocol for ...
Nitrite therapy in myocardial I/R injury. (A) Experimental protocol for myocardial I/R studies in mice. Asterisk indicates in vivo AAR as shown by Evans blue injection, with infarct size 1.0% of 2,3,5-triphenyltetrazolium chloride (TTC). (B) Representative photomicrographs of murine hearts after 30 minutes of myocardial ischemia (MI) and 24 hours of reperfusion. Areas of the myocardium that appear blue (i.e., Evans blue dye) represent the areas of myocardium not at risk for infarction. In contrast, the areas of myocardium that stain red (i.e., TTC-positive) represent viable myocardium that was at risk for infarction. Myocardium that appears pale (i.e., TTC-negative) indicates areas of myocardium at risk that are necrotic (i.e., infarcted). Nitrite treatment significantly reduced myocardial infarction after 30 minutes of myocardial ischemia and 24 hours of reperfusion. (C) Myocardial AAR per LV for mouse hearts receiving nitrate (48 nmol) or doses of nitrite ranging from 2.4 to 1,920 nmol. The myocardial AAR per LV was similar for all of the study groups (P = NS between groups). (D) Myocardial infarct size per AAR for mouse hearts receiving nitrate (48 nmol) or doses of nitrite ranging from 2.4 to 1,920 nmol. Nitrite therapy (2.4–960 nmol) significantly reduced myocardial infarct size compared with nitrate therapy (**P < 0.001). (E) Blood levels of iron-nitrosylated hemoglobin after intraventricular injection of 48 nmol nitrite. (F) Myocardial AAR per LV and infarct size (INF) per AAR and per LV in mice treated with the NO scavenger PTIO prior to nitrite therapy (48 nmol). Nitrite-mediated cardioprotection was not observed in the presence of PTIO (P = NS, PTIO versus PTIO + nitrite). (G) Myocardial AAR per LV and INF per AAR and per LV in mice treated with the HO-1 inhibitor ZnDPGG prior to nitrite therapy (48 nmol). Treatment with ZnDPGG did not attenuate the protective effects of nitrite therapy. Numbers inside bars indicate the number of animals that were investigated in each group.