ARDS is a major cause of morbidity and mortality in the United States. There are no specific therapies for ARDS other than protective mechanical ventilation and conservative fluid management and mortality remains high at 30-50%. Thus, there is a critical need for specific therapies that target fundamental mechanisms of ARDS. Increased lung epithelial permeability is a pathophysiologic hallmark of ARDS and is manifest clinically by pulmonary edema, impaired gas exchange and acute respiratory failure. We have identified cell free hemoglobin as a novel mediator of increased epithelial permeability in ARDS. Our preliminary data show that airspace levels of cell-free hemoglobin are high in ARDS and are associated with increased lung permeability and poor clinical outcomes. Furthermore, it is the Ferryl oxidized form of hemoglobin that is elevated in the airspaces in ARDS. In a clinical trial in severe sepsis, the leading cause of ARDS, treatment with an inhibitor of Ferryl hemoglobin, acetaminophen, decreased lipid peroxidation and attenuated acute kidney injury. In cultured lung epithelial cells, hemoglobin treatment induces epithelial barrier permeability through cellular and mitochondrial reactive oxygen species generation. Furthermore, intratracheal administration of cell-free hemoglobin to the lungs of mice leads to generation of oxidized Ferryl hemoglobin and increased lung alveolar capillary barrier permeability. These findings support the overall hypothesis for the proposed studies, that formation of Ferryl-Hgb in the airspace in ARDS causes alveolar epithelial cell oxidative stress and increased epithelial permeability, contributing to the pathophysiology of ARDS. To test this hypothesis I have assembled a cross-disciplinary team of co-Investigators and consultants with expertise in clinical ARDS (Ware), Hgb redox chemistry (Roberts), primary alveolar epithelial cell isolation and culture (Guttentag), mitochondrial oxidative stress (Dikalov), human models of ARDS (Matthay) and advanced in vivo imaging techniques (West) whose expertise complements my own in cellular models of epithelial permeability and animal models of ARDS. We will utilize clinical samples of pulmonary edema fluid already collected from patients with ARDS and hydrostatic pulmonary edema along with mouse and epithelial cell culture studies to show that levels of Ferryl hemoglobin in the airspace are increased in human ARDS and cause increased lung epithelial permeability in mice and cultured epithelial cells (Aim 1). We will define the cellular and molecular mechanism of hemoglobin induced increases in epithelial permeability and cellular and mitochondrial oxidative stress in the epithelium (Aim 2). Finally we will test a therapy targeted at Ferryl hemoglobin (acetaminophen) in cell culture, in a clinically relevant model of ventilator induced lung injury in mice and in an isolated perfused human lung model (Aim 3). This proposal is highly innovative and addresses a clinically significant problem. Results from these studies will greatly advance our understanding of the mechanisms of lung epithelial permeability in acute lung injury and will pave the way for future novel targeted therapeutics in ARDS.

Public Health Relevance

ARDS is a common and life-threatening condition affecting over 190,000 Americans per year, 30-50% of whom will die. There are no disease-specific therapies other than supportive care highlighting the urgent need to identify novel mediators that will lead to new therapies. Our group has identified cell-free hemoglobin (Hgb) (Hgb that has escaped from red blood cells) as a potential driver of lung epithelial injury and increased lung permeability in ARDS and have shown that a therapy targeted at the harmful effects of Hgb (acetaminophen) may be beneficial in patients with ARDS; the studies in this proposal could drastically change how we think about and treat patients with ARDS.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL126671-01
Application #
8857982
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Harabin, Andrea L
Project Start
2015-04-01
Project End
2020-03-31
Budget Start
2015-04-01
Budget End
2016-03-31
Support Year
1
Fiscal Year
2015
Total Cost
Indirect Cost
Name
Vanderbilt University Medical Center
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
004413456
City
Nashville
State
TN
Country
United States
Zip Code
37240
McNeil, J Brennan; Shaver, Ciara M; Kerchberger, V Eric et al. (2018) Novel Method for Noninvasive Sampling of the Distal Airspace in Acute Respiratory Distress Syndrome. Am J Respir Crit Care Med 197:1027-1035
Shaver, Ciara M; Wickersham, Nancy; McNeil, J Brennan et al. (2018) Cell-free hemoglobin promotes primary graft dysfunction through oxidative lung endothelial injury. JCI Insight 3:
Kuck, Jamie L; Bastarache, Julie A; Shaver, Ciara M et al. (2018) Ascorbic acid attenuates endothelial permeability triggered by cell-free hemoglobin. Biochem Biophys Res Commun 495:433-437
DesPrez, Katherine; McNeil, J Brennan; Wang, Chunxue et al. (2017) Oxygenation Saturation Index Predicts Clinical Outcomes in ARDS. Chest 152:1151-1158
Zheng, Neil S; Bastarache, Lisa A; Bastarache, Julie A et al. (2017) A common deletion in the haptoglobin gene associated with blood cholesterol levels among Chinese women. J Hum Genet 62:911-914
Luo, Liang; Shaver, Ciara M; Zhao, Zhiguo et al. (2017) Clinical Predictors of Hospital Mortality Differ Between Direct and Indirect ARDS. Chest 151:755-763
Murphy, Laura S; Wickersham, Nancy; McNeil, J Brennan et al. (2017) Endothelial glycocalyx degradation is more severe in patients with non-pulmonary sepsis compared to pulmonary sepsis and associates with risk of ARDS and other organ dysfunction. Ann Intensive Care 7:102
Casey, Jonathan D; Semler, Matthew W; Bastarache, Julie A (2017) Aspirin for Sepsis Prophylaxis: An Ounce of Prevention? Crit Care Med 45:1959-1960
Shaver, Ciara M; Wickersham, Nancy; McNeil, J Brennan et al. (2017) Cell-Free Hemoglobin-mediated Increases in Vascular Permeability. A Novel Mechanism of Primary Graft Dysfunction and a New Therapeutic Target. Ann Am Thorac Soc 14:S251-S252
Shaver, Ciara M; Woods, Justin; Clune, Jennifer K et al. (2017) Circulating microparticle levels are reduced in patients with ARDS. Crit Care 21:120

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