32 ENDOTHELIN 1 DECREASES LUNG EDEMA CLEARANCE IN ALVEOLAR EPITHELIAL CELLS VIA ENDOTHELIAL ET-B RECEPTOR ACTIVATION AND NITRIC OXIDE GENERATION

RationaleIn models of acute lung injury, high levels of endothelin 1 (ET-1) are linked with a rapid increase in edema formation. It has been shown that decreased alveolar fluid clearance is associated with increase hospital mortality in patients with acute lung injury. We hypothesized that ET-1 via...

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Published in:Journal of investigative medicine 2007-03, Vol.55 (2), p.S353-S353
Main Authors: Comellas, A., Briva, A., Butti, M., Chen, J., Litvan, J., Azzam, Z., Lecuona, E., Pesce, L., Yanagisawa, M., Sznajder, J. I.
Format: Article
Language:English
Subjects:
Edema
Nitric oxide
Rodents
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Summary:RationaleIn models of acute lung injury, high levels of endothelin 1 (ET-1) are linked with a rapid increase in edema formation. It has been shown that decreased alveolar fluid clearance is associated with increase hospital mortality in patients with acute lung injury. We hypothesized that ET-1 via ET-B receptor activation and nitric oxide (NO) generation impairs the ability of the lung to reabsorb fluid from the alveolar space by inhibiting the alveolar epithelial Na,K-ATPase.Methods(A) Isolated-perfused rat lung model: Alveolar fluid clearance was measured using an isolated-perfused rat lung model by determining the changes in concentration of Evans blue-tagged albumin in the instillate as a function of time. (B) Alveolar epithelial cells (AECs) were isolated from pathogen-free male Sprague-Dawley rats, treated with ET-1 to assess Na,K-ATPase activity by an ouabain-sensitive 86Rb+ uptake and protein analysis by Western blotting. (C) Human microvascular endothelial cells cocultured in six-well plates with AECs in the presence and absence of endothelin. (D) Immunocytochemistry performed in AECs and rat lung tissue.ResultsIsolated rat lungs perfused for 60 minutes with different concentrations of ET-1 (10-10 M to 10-6 M) had a decrease in alveolar fluid reabsorption in a dose-dependent fashion. A nonselective ET-A/B receptor antagonist blocked the endothelin decrease in lung edema clearance. An ET-B receptor agonist decreased alveolar fluid clearance to a similar degree compared with ET-1 (≈50%). When ET-1 was perfused in vascular endothelin B receptor-deficient rats, the decrease in alveolar fluid clearance was prevented. ET-1 decrease in alveolar fluid clearance was also blocked by a nitric oxide antagonist (L-NAME) and cGMP antagonist (ODQ). Neither the Na,K-ATPase activity nor its plasma membrane expression was affected in vitro when AECs were directly incubated with endothelin. However, coculture with endothelial cells in the presence of endothelin caused a decrease in Na,K-ATPase activity in AECs.SummaryWe provide for the first time evidence that the endothelium regulates alveolar fluid clearance; specifically, ET-1 impairs the ability of the lung to clear edema via the endothelial ET-B receptor activation, nitric oxide generation, and cGMP signaling in AECs.Funding: HL-48129 and HL080966.
ISSN:1081-5589
1708-8267
DOI:10.1136/jim-55-02-32