A2B adenosine receptor signaling attenuates acute lung injury by enhancing alveolar fluid clearance in mice
Tobias Eckle, … , Stefanie Laucher, Holger K. Eltzschig
Tobias Eckle, … , Stefanie Laucher, Holger K. Eltzschig
Published September 11, 2008
Citation Information: J Clin Invest. 2008;118(10):3301-3315. https://doi.org/10.1172/JCI34203.
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Research Article Pulmonology

A2B adenosine receptor signaling attenuates acute lung injury by enhancing alveolar fluid clearance in mice

Abstract

Although acute lung injury contributes significantly to critical illness, resolution often occurs spontaneously via activation of incompletely understood pathways. We recently found that mechanical ventilation of mice increases the level of pulmonary adenosine, and that mice deficient for extracellular adenosine generation show increased pulmonary edema and inflammation after ventilator-induced lung injury (VILI). Here, we profiled the response to VILI in mice with genetic deletions of each of the 4 adenosine receptors (ARs) and found that deletion of the A2BAR gene was specifically associated with reduced survival time and increased pulmonary albumin leakage after injury. In WT mice, treatment with an A2BAR-selective antagonist resulted in enhanced pulmonary inflammation, edema, and attenuated gas exchange, while an A2BAR agonist attenuated VILI. In bone marrow–chimeric A2BAR mice, although the pulmonary inflammatory response involved A2BAR signaling from bone marrow–derived cells, A2BARs located on the lung tissue attenuated VILI-induced albumin leakage and pulmonary edema. Furthermore, measurement of alveolar fluid clearance (AFC) demonstrated that A2BAR signaling enhanced amiloride-sensitive fluid transport and elevation of pulmonary cAMP levels following VILI, suggesting that A2BAR agonist treatment protects by drying out the lungs. Similar enhancement of pulmonary cAMP and AFC were also observed after β-adrenergic stimulation, a pathway known to promote AFC. Taken together, these studies reveal a role for A2BAR signaling in attenuating VILI and implicate this receptor as a potential therapeutic target during acute lung injury.

Authors

Tobias Eckle, Almut Grenz, Stefanie Laucher, Holger K. Eltzschig

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Figure 3

Transcriptional consequences of mechanical ventilation on AR expression.

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Transcriptional consequences of mechanical ventilation on AR expression....
(A) C57BL/6 mice were mechanically ventilated (inspiratory pressure of 35 mbar, 100% oxygen). After the indicated time periods, lungs were harvested, total RNA was isolated, and A1AR, A2AAR, A2BAR, and A3AR mRNA levels were determined by real-time RT-PCR. Data were calculated relative to the internal housekeeping gene (β-actin) and are expressed as mean fold change compared with control (0 min ventilation) ± SD at each indicated time (n = 4). Note selective induction of the A2BAR gene during high-pressure ventilation (10-fold, P < 0.01; n = 4). (B) Comparative gene expression of pulmonary ARs using real-time PCR. Relative expression levels in untreated controls or in mice after 180 min mechanical ventilation (inspiratory pressure of 35 mbar, 100% oxygen) are shown. Values are expressed as mean ± SEM (n = 4). *P < 0.05 compared with A2AAR. (C) Mice were mechanically ventilated (35 mbar inspiratory pressure, 100% oxygen), and lungs were harvested at the indicated time points, shock frozen, and lysed, and proteins were resolved by SDS-PAGE. Resultant western blots were probed with anti-A2BAR antibodies. To control for loading conditions, blots were stripped and reprobed for actin expression. One representative experiment of 3 is shown. (D) To examine the influence of mechanical ventilation on pulmonary A2BAR expression patterns, C57BL/6 mice were ventilated in a pressure-controlled setting over 0 h or 3 h (35 mbar inspiratory pressure, 100% inspired oxygen concentration). Lungs were stained with antibodies for A2BAR. IgG controls were used at identical concentrations and staining conditions as the target primary antibodies (original magnification, ×400; n = 4).