Sickle cell disease is a progressive vasculopathy stemming from decreased red blood cell (RBC) deformability. Vascular disease is at the heart of both acute and chronic sickle disease, including pain crisis, acute chest syndrome, stroke, skin ulcers, and pulmonary hypertension. However, the mechanisms linking decreased RBC deformability to chronic vasculopathy are multifactorial and poorly characterized. Nitric oxide (NO) is the key mediator linking blood mechanics to vessel tone and vascular remodeling. As bloodflow shears the endothelium, NO is released, causing vasodilation and inhibiting platelet aggregation. NO bioavailability is diminished in SCD because decellularized hemoglobin and arginase, released during hemolysis, scavenge NO and lower endothelial NO production. Recent evidence suggests that 50% of bioavailable NO is synthesized within RBC, themselves, though a shear-activated eNOS enzyme. RBC NO is primarily converted to nitrite and nitrosylated hemoglobins when tissue oxygenation is high, but deoxygenated hemoglobin converts these species to nitric oxide under hypoxic conductions. Thus, RBC generated NO appears to be a vital mediator of oxygen supply and demand and its role in sickle cell vasculopathy is completely unexplored. Our fundamental hypothesis is that decreased red cell deformability reduces shear-mediated nitric oxide production by the red cell itself, crippling vita storage forms of nitric oxide, causing vascular dysfunction at several levels of the vascular system. This research proposal merges novel laboratory methods in RBC nitric oxide production with clinical investigation of vascular dysfunction in patients with sickle cell disease Multimodal characterization of the different vascular beds will lead to improved phenotypic categorization and pathophysiological links to the underlying RBC biophysical/biochemical derangements. We will also explore whether RBC-generated NO has the ability to directly affect the vasculature using aortic ring preps and whether RBC-generated NO decreases platelet aggregation. Support from this grant benefits SCD patients in three ways: 1) it improves cross- specialization (i.e. hematology and cardiology), 2) it translates novel lab based methods in RBC generation of NO to patients using vascular preps and measurement of platelet aggregation, and 3) it will set the ground work for larger clinical translational studies linking RBC-generated NO and rheology with sophisticated measures of vascular function in patients with SCD. The K23 mechanism represents the natural extension my career development to date, combining my previous laboratory and patient-oriented research expertise with the specific clinical research training necessary to conduct large translational studies of novel targets in vascular dysfunction.

Public Health Relevance

Sickle cell disease (SCD) is a significant cause of morbidity and mortality throughout the world and there are more than 80,000 individuals suffering from SCD in the United States, with the annual cost of care for these patients greater than 1.1 billion dollars. Decreased red blood cell (RBC) deformability and vascular disease underlie the majority of suffering in these patients and despite improvements in overall survival, treatment is limited. Linking RBC nitric oxide production in SCD with RBC deformability and vascular disease will expose new therapeutic targets in this complex disease process.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Mentored Patient-Oriented Research Career Development Award (K23)
Project #
5K23HL119627-03
Application #
9023586
Study Section
Special Emphasis Panel (ZHL1)
Program Officer
Werner, Ellen
Project Start
2014-08-15
Project End
2017-03-31
Budget Start
2016-04-01
Budget End
2017-03-31
Support Year
3
Fiscal Year
2016
Total Cost
Indirect Cost
Name
Children's Hospital of Los Angeles
Department
Type
DUNS #
052277936
City
Los Angeles
State
CA
Country
United States
Zip Code
90027
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Detterich, Jon A; Kato, Roberta M; Rabai, Miklos et al. (2015) Chronic transfusion therapy improves but does not normalize systemic and pulmonary vasculopathy in sickle cell disease. Blood 126:703-10

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