There is an emerging appreciation that heme proteins such as myoglobin and hemoglobin catalyze the metabolism of nitric oxide (NO) and nitrite, and thereby modulate cell and tissue responses to hypoxia. Over the last five years our group has published biochemical and physiological studies that suggest a novel function for hemoglobin as a nitrite reductase that generates NO under physiological and pathological hypoxia, suggesting that myoglobin, the other major heme globin, may also possess a capability to mediate the metabolism of oxides of nitrogen in a manner influenced by oxygen tension. Analogous to the bacterial nitrite reductases, a concerted proton and electron transfer reaction to nitrite reduces the anion to NO. We have also discovered a novel nitrite anhydrase activity that converts two nitrite molecules into the highly diffusible, nitrosating molecule N2O3, allowing efficient NO signaling in a heme rich environment. In the current research proposal, the NO/ N2O3 signaling pathways will be explored in myoglobin, with special focus on an ability to regulate cellular responses to hypoxic and ischemic stress by a) modulating cellular metabolism via the regulation of mitochondrial electron transfer reactions and b) activating net cytoprotective cell signaling reactions after ischemia-reperfusion injury. These concepts will be addressed by testing the hypothesis that myoglobin-mediated nitrite metabolism regulates hypoxic NO signaling and promotes NO bioavailability in the heart. More specifically, using mutant myoglobin proteins in in vitro biochemical and cell culture systems as well as an in vivo model of myocardial infarction, we aim 1) to determine the molecular and enzymatic mechanisms underlying the nitrite reductase activity of myoglobin in hypoxia, 2) define critical molecular targets of myoglobin-derived NO and N2O3, and 3) to determine the role of myoglobin in regulating downstream cytoprotective signaling (apoptosis and mitochondrial biogenesis) after ischemia/reperfusion. Successful completion of the proposed research plan will advance our understanding of the biological function of myoglobin and the physiological and pharmacological potential of nitrite in the cardiovascular system.

Public Health Relevance

After a heart attack, part of the tissue in the heart dies. A heart protein called myoglobin can convert nitrite, a chemical found in the diet, to nitric oxide, a chemical that protects heart cells from death. This project will investigate how nitrite and myoglobin work together so that nitrite can be used to protect the heart during a heart attack.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Myocardial Ischemia and Metabolism Study Section (MIM)
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Schwartz, Lisa
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University of Pittsburgh
Internal Medicine/Medicine
Schools of Medicine
United States
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Simon, Marc A; Vanderpool, Rebecca R; Nouraie, Mehdi et al. (2016) Acute hemodynamic effects of inhaled sodium nitrite in pulmonary hypertension associated with heart failure with preserved ejection fraction. JCI Insight 1:e89620
Lai, Yen-Chun; Tabima, Diana M; Dube, John J et al. (2016) SIRT3-AMP-Activated Protein Kinase Activation by Nitrite and Metformin Improves Hyperglycemia and Normalizes Pulmonary Hypertension Associated With Heart Failure With Preserved Ejection Fraction. Circulation 133:717-31
Corti, Paola; Xue, Jianmin; Tejero, Jesús et al. (2016) Globin X is a six-coordinate globin that reduces nitrite to nitric oxide in fish red blood cells. Proc Natl Acad Sci U S A 113:8538-43
Tejero, Jesús; Sparacino-Watkins, Courtney E; Ragireddy, Venkata et al. (2015) Exploring the mechanisms of the reductase activity of neuroglobin by site-directed mutagenesis of the heme distal pocket. Biochemistry 54:722-33
Saraf, Santosh L; Zhang, Xu; Shah, Binal et al. (2015) Genetic variants and cell-free hemoglobin processing in sickle cell nephropathy. Haematologica 100:1275-84
Wang, Jun; Krizowski, Sabina; Fischer-Schrader, Katrin et al. (2015) Sulfite Oxidase Catalyzes Single-Electron Transfer at Molybdenum Domain to Reduce Nitrite to Nitric Oxide. Antioxid Redox Signal 23:283-94
Kamga Pride, Christelle; Mo, Li; Quesnelle, Kelly et al. (2014) Nitrite activates protein kinase A in normoxia to mediate mitochondrial fusion and tolerance to ischaemia/reperfusion. Cardiovasc Res 101:57-68
Corti, Paola; Gladwin, Mark T (2014) Is nitrite the circulating endocrine effector of remote ischemic preconditioning? Circ Res 114:1554-7
Griffin, Paula J; Sebastiani, Paola; Edward, Heather et al. (2014) The genetics of hemoglobin A2 regulation in sickle cell anemia. Am J Hematol 89:1019-23
Tejero, Jesús; Gladwin, Mark T (2014) The globin superfamily: functions in nitric oxide formation and decay. Biol Chem 395:631-9

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