The hemoglobin 293cys residue is conserved and received much attention recently as a potential modulator of how red cells affect vascular nitric oxide (NO) metabolism and function. However, the precise function and mechanisms involved remain unclear. Understanding how this residue controls vascular nitric oxide function is critical since dysfunction in these mechanisms may contribute to a number of vascular pathological states. In this proposal we build upon preliminary data generated from novel mouse models that express exclusively either wild-type human hemoglobin or human hemoglobin in which the 293cys residue has been replaced with an Ala in their red cells. Specifically, we present data indicating that under physiological conditions, deoxygenation of red cells and hemoglobin activates a nitrite reductase activity that results in the one-electron reduction of the anion nitrite to NO. This process is regulated allosterically by controlling hemoglobin oxygen affinity and interestingly modulated by the 293cys residue. In this context we propose that the 293cys residue is critical in coupling hemoglobin oxygen sensing with nitrite derived NO-bioactivity. In contrast, during the acute inflammatory disease Sepsis, we propose that the 293cys is a target for nitrosative stress forming S-nitrosohemoglobin (SNOHb), which in turn contributes to the vascular and pulmonary dysfunction associated with this disease. The latter is indicated by data showing SNO-containing red cells can stimulate neutrophil adhesion to pulmonary endothelial cells and elicit vasodilation in a manner that is independent on allosteric regulation. Both pulmonary inflammation and lung injury are features of sepsis. These novel concepts will be investigated in this proposal by pursuit of the hypothesis that during acute inflammation, the role of the 293cys residue as a modulator of vascular NO-signaling changes from a nitrite-reductase dependent to SNOHb dependent mechanism which will be tested via the following specific aims 1) Determine the mechanism by which 293cys regulates RBC dependent NO vascular cell signaling., 2) Determine the role of 293cys residue in controlling nitrite reduction and NO- dependent vascular cell signaling in vivo, 3) Determine the role of the 293cys residue in affecting RBC effects during Sepsis induced hypotension and pulmonary inflammation. Accomplishment of these aims will yield insights into the mechanisms novel therapeutic targets focusing on how RBCs modulate NO-metabolism.

Public Health Relevance

Red blood cells play important roles in controlling vascular homeostasis mechanisms. We propose herein that a specific amino acid residue of the hemoglobin protein (the 293cys residue) is critical in this regard by modulating how red cells control nitric oxide function. In this proposal we aim to elucidate the specific mechanisms by which the 293cys residue controls nitric oxide function both during normal physiological conditions and during inflammation associated with the disease Sepsis and in doing so, hope to identify novel therapeutic targets and strategies.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
Project #
Application #
Study Section
Erythrocyte and Leukocyte Biology Study Section (ELB)
Program Officer
Luksenburg, Harvey
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Alabama Birmingham
Schools of Medicine
United States
Zip Code
Harper, Victoria M; Oh, Joo Yeun; Stapley, Ryan et al. (2015) Peroxiredoxin-2 recycling is inhibited during erythrocyte storage. Antioxid Redox Signal 22:294-307
Hahn, Cornelia S; Scott, David W; Xu, Xin et al. (2015) The matrikine N-?-PGP couples extracellular matrix fragmentation to endothelial permeability. Sci Adv 1:
Dhall, Sandeep; Do, Danh; Garcia, Monika et al. (2014) A novel model of chronic wounds: importance of redox imbalance and biofilm-forming bacteria for establishment of chronicity. PLoS One 9:e109848
Scott, David W; Vallejo, Matthew O; Patel, Rakesh P (2013) Heterogenic endothelial responses to inflammation: role for differential N-glycosylation and vascular bed of origin. J Am Heart Assoc 2:e000263
Espey, Michael Graham (2013) Role of oxygen gradients in shaping redox relationships between the human intestine and its microbiota. Free Radic Biol Med 55:130-40
Vitturi, Dario A; Sun, Chiao-Wang; Harper, Victoria M et al. (2013) Antioxidant functions for the hemoglobin ?93 cysteine residue in erythrocytes and in the vascular compartment in vivo. Free Radic Biol Med 55:119-29
Owusu, Benjamin Y; Stapley, Ryan; Patel, Rakesh P (2012) Nitric oxide formation versus scavenging: the red blood cell balancing act. J Physiol 590:4993-5000
Rameez, Shahid; Guzman, Nicole; Banerjee, Uddyalok et al. (2012) Encapsulation of hemoglobin inside liposomes surface conjugated with poly(ethylene glycol) attenuates their reactions with gaseous ligands and regulates nitric oxide dependent vasodilation. Biotechnol Prog 28:636-45
Kelpke, Stacey S; Chen, Bo; Bradley, Kelley M et al. (2012) Sodium nitrite protects against kidney injury induced by brain death and improves post-transplant function. Kidney Int 82:304-13
Patel, Rakesh P (2011) Losing control over adenosine 5'-triphosphate release: implications for the red blood cell storage lesion. Crit Care Med 39:2573-4

Showing the most recent 10 out of 15 publications