The long term goal of this project is to determine the mechanisms by which ischemia and reperfusion injure the isolated lung and whether these mechanisms are relevant to ischemia-reperfusion lung injury in intact animals. We hypothesize that unlike other organs the lung is injureed by toxic oxygen metabolites generated during ischemia, when oxygen tension is high and glucose depleted. The endothelium is a primary target of injury, which, therefore, results in increased vascular permeability and edema formation upon reperfusion. To test this hypothesis, experiments will be performed in isolated sheep lungs to quantitate the effects of ischemic duration and oxygen tension, confirm that the O2- dependence of the injury is related to production of toxic O2 metabolites, and determine the source of these metabolites. Parallel experiments using cultured sheep pulmonary endothelial cells in an in vitro model of lung ischemia-reperfusion will evaluate endothelium both as a target and as a source of injury. Isolated lungs and pulmonary endothelial cells from dogs will be studied to confirm that ischemia-reperfusion lung injury is less severe in this species and to determine the mechanisms of the difference. The response and role of the bronchial circulation will be evaluated in vivo and in isolated lungs from sheep, a species anatomically suited to this purpose. Hemodynamics, fluid balance, antioxidant activity and energy state will be measured in isolated lungs. Viability, biochemical function, and barrier function will be measured in endothelial cells. In addition, free radical concentrations will be measured in both preparations by eletron paramagnetic resonance spectroscopy to assess directly the role and identify of these substances. Electron microscopic evaluation of endothelium in lung and monolayer will be performed to establish structure-function correlations. Therapeutic interventions suggested by the above studies will be tested in intact animals acutely after transient left lung ischemia and chroncially after left lung autotransplantation. Preliminary experiments confirm the feasibility and usefulness of these approaches. The results could have significant implications with respect to human conditions in which lung ischemia-reperfusion is thought to play a pathogenetic role, such as cardiopulmonary bypass, pulmonary thromboendarectomy and thrombolysis after pulmonary embolism, and lung transplantation.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL041970-01
Application #
3359870
Study Section
(SRC)
Project Start
Project End
1993-07-31
Budget Start
1988-09-30
Budget End
1989-07-31
Support Year
1
Fiscal Year
1988
Total Cost
Indirect Cost
Name
Johns Hopkins University
Department
Type
Schools of Medicine
DUNS #
045911138
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Pearse, D B; Sylvester, J T (1996) Vascular injury in isolated sheep lungs. Role of ischemia, extracorporeal perfusion, and oxygen. Am J Respir Crit Care Med 153:196-202
Sanders, S P; Harrison, S J; Kuppusamy, P et al. (1994) A comparative study of EPR spin trapping and cytochrome c reduction techniques for the measurement of superoxide anions. Free Radic Biol Med 16:753-61
Pearse, D B; Wagner, E M (1994) Role of the bronchial circulation in ischemia-reperfusion lung injury. J Appl Physiol 76:259-65
Sanders, S P; Zweier, J L; Kuppusamy, P et al. (1993) Hyperoxic sheep pulmonary microvascular endothelial cells generate free radicals via mitochondrial electron transport. J Clin Invest 91:46-52
Becker, P M; Pearse, D B; Permutt, S et al. (1992) Separate effects of ischemia and reperfusion on vascular permeability in ventilated ferret lungs. J Appl Physiol 73:2616-22
Zweier, J L; Duke, S S; Kuppusamy, P et al. (1989) Electron paramagnetic resonance evidence that cellular oxygen toxicity is caused by the generation of superoxide and hydroxyl free radicals. FEBS Lett 252:12-6