Endothelium-derived relaxing factor, identified as nitric oxide (NO), is a key mediator regulating vascular tone and blood pressure. NO mediates vascular relaxation through activation of soluble guanylate cyclase (sGC) in the smooth muscle. While NO is synthesized by a specific well characterized NO synthase in the endothelium (eNOS), the process of vascular NO degradation and metabolism is poorly understood. It is hypothesized that NO degradation in the vessel wall is mediated by an O2-dependent NO dioxygenase (NOD) that oxidizes NO to nitrate. However, the identity of the specific NO dioxygenase that serves as the main in vivo regulator of O2- dependent NO degradation in vascular smooth muscle has remained elusive. Cytoglobin (Cgb) is a recently discovered globin expressed in smooth muscle with unknown function. Based on our preliminary data where we observe that: 1) Cgb is the major globin expressed in smooth muscle; and 2) knockout of Cgb greatly prolongs NO decay, increases vascular relaxation, lowers blood pressure and systemic vascular resistance, we hypothesize that Cgb is the major heme protein regulating the rate of O2-dependent NO metabolism in the vessel wall, in turn profoundly modulating vascular tone. In this grant, there are 3 aims in which we sequentially test this hypothesis, first in vascular smooth muscle cells, then in isolated vessels and finally in the in vivo cardiovascular system with experimental measurements and computational modeling. The latter will enable us to determine how well the process of Cgb-mediated O2-dependent NO metabolism accounts for the measured vascular NO metabolism along with enabling prediction of the effects of modulating Cgb expression and NOD function. Since the O2-dependent NOD function of Cgb is controlled by its rate of reduction, studies will be performed to elucidate the process and mechanisms of Cgb reduction in smooth muscle cells, vessels and in vivo in mice utilizing molecular knockdown, pharmacological inhibition, or other manipulation of these reducing pathways. We will determine how modulation of the NOD function of Cgb modulates vascular tone in normal physiology and vascular disease with studies in vessels and mice with varying Cgb expression levels and inhibition of each of the major pathways of its reduction or specific inhibition of its NOD function. These studies will be performed in normal mice and mice with angiotensin-induced hypertension. In these settings, studies will be performed to measure and scavenge superoxide (O2-.) to determine how the O2-dependent reaction of NO with Cgb compares to that of O2-. and specific attention paid to the role of the endothelium and the coupling state of eNOS in NO metabolism. Accomplishment of this research plan will elucidate the molecular mechanism underlying the important role of Cgb in vascular NO metabolism and provide important insights into the regulation of vascular tone in normal physiology and cardiovascular disease. This work will illuminate the path leading to development of novel therapeutic approaches to reverse vascular dysfunction and ameliorate secondary disease through modulation of the process of NO degradation.

Public Health Relevance

Nitric oxide (NO) regulates vascular tone and blood pressure; however, the process of vascular NO degradation and metabolism is not well understood. Cytoglobin (Cgb) is a recently discovered globin expressed in smooth muscle. We hypothesize that Cgb is the major heme protein regulating the rate of O2- dependent NO metabolism in the vessel wall, in turn, profoundly modulating vascular tone. We will test this hypothesis in smooth muscle cells, isolated vessels and in vivo to determine how Cgb functions to modulate vascular tone in normal physiology and disease. This work will elucidate the mechanism of vascular NO metabolism and the regulation of vascular tone in normal physiology and cardiovascular disease, leading to development of novel therapeutics to reverse vascular dysfunction and disease.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
Project #
Application #
Study Section
Vascular Cell and Molecular Biology Study Section (VCMB)
Program Officer
Charette, Marc F
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Ohio State University
Internal Medicine/Medicine
Schools of Medicine
United States
Zip Code
Boslett, James; Hemann, Craig; Christofi, Fedias L et al. (2018) Characterization of CD38 in the major cell types of the heart: endothelial cells highly express CD38 with activation by hypoxia-reoxygenation triggering NAD(P)H depletion. Am J Physiol Cell Physiol 314:C297-C309
Khayat, Rami N; Varadharaj, Saradhadevi; Porter, Kyle et al. (2018) Angiotensin Receptor Expression and Vascular Endothelial Dysfunction in Obstructive Sleep Apnea. Am J Hypertens 31:355-361
Kang, Patrick T; Chen, Chwen-Lih; Lin, Paul et al. (2018) Mitochondrial complex I in the post-ischemic heart: reperfusion-mediated oxidative injury and protein cysteine sulfonation. J Mol Cell Cardiol 121:190-204
Tarragó, Mariana G; Chini, Claudia C S; Kanamori, Karina S et al. (2018) A Potent and Specific CD38 Inhibitor Ameliorates Age-Related Metabolic Dysfunction by Reversing Tissue NAD+ Decline. Cell Metab 27:1081-1095.e10
Liu, Xiaoping; El-Mahdy, Mohamed A; Boslett, James et al. (2017) Cytoglobin regulates blood pressure and vascular tone through nitric oxide metabolism in the vascular wall. Nat Commun 8:14807
Zhang, Bo; Novitskaya, Tatiana; Wheeler, Debra G et al. (2017) Kcnj11 Ablation Is Associated With Increased Nitro-Oxidative Stress During Ischemia-Reperfusion Injury: Implications for Human Ischemic Cardiomyopathy. Circ Heart Fail 10:
Zhou, Danlei; Hemann, Craig; Boslett, James et al. (2017) Oxygen binding and nitric oxide dioxygenase activity of cytoglobin are altered to different extents by cysteine modification. FEBS Open Bio 7:845-853
Boslett, James; Hemann, Craig; Zhao, Yong Juan et al. (2017) Luteolinidin Protects the Postischemic Heart through CD38 Inhibition with Preservation of NAD(P)(H). J Pharmacol Exp Ther 361:99-108
Varadharaj, Saradhadevi; Kelly, Owen J; Khayat, Rami N et al. (2017) Role of Dietary Antioxidants in the Preservation of Vascular Function and the Modulation of Health and Disease. Front Cardiovasc Med 4:64