Lung injury after simulated cardiopulmonary bypass in an isolated perfused rat lung preparation: Role of mitogen-activated protein kinase/Akt signaling and the effects of theophylline.
OBJECTIVE
Lung deflation and inflation during cardiac surgery with cardiopulmonary bypass contributes to pulmonary dysfunction postoperatively. Theophylline treatment for lung diseases has traditionally been thought to act by phosphodiesterase inhibition; however, increasing evidence has suggested other plausible mechanisms. We investigated the effects of deflation and reinflation on signaling pathways (p38-mitogen-activated protein kinase [MAPK], extracellular signal-regulated kinase 1 and 2 [ERK1/2], and Akt) and whether theophylline influences the deflation-induced lung injury and associated signaling.


METHODS
Isolated rat lungs were perfused (15 mL/min) with deoxygenated rat blood in bicarbonate buffer and ventilated. After 20 minutes' equilibration, the lungs were deflated (60 minutes, aerobic perfusion 1.5 mL/min), followed by reinflation (60 minutes, anaerobic reperfusion 15 mL/min). Compliance, vascular resistance, and kinase phosphorylation were assessed during deflation and reinflation. The effects of SB203580 (50 μM), a p38-MAPK inhibitor, and theophylline (0.083 mM [therapeutic] or 3 mM [supratherapeutic]) on physiology and signaling were studied.


RESULTS
Deflation reduced compliance by 44% compared with continuously ventilated lungs. p38-MAPK and Akt phosphorylation increased (three to fivefold) during deflation and reinflation, and ERK1/2 phosphorylation increased (approximately twofold) during reinflation. SB203580 had no effect on lung physiology or ERK1/2 and Akt activation. Both theophylline doses increased cyclic adenosine monophosphate, but only 3 mM theophylline improved compliance. p38-MAPK phosphorylation was not affected by theophylline; 0.083 mM theophylline inhibited reinflation-induced ERK1/2 phosphorylation (72%±3%); and 3 mM theophylline inhibited Akt phosphorylation during deflation (75%±5%) and reinflation (87%±4%).


CONCLUSIONS
Lung deflation and reinflation stimulates differential p38-MAPK, ERK1/2, and Akt activation, suggesting a role in lung injury during cardiopulmonary bypass. However, p38-MAPK was not involved in the compromised compliance. A supratherapeutic theophylline dose protected lungs against deflation-induced injury and was associated with inhibition of phosphoinositide 3-kinase/Akt rather than phosphodiesterase.
Cardiac Surgical Research, Rayne Institute, King's College London, St Thomas' Hospital Campus, London, United Kingdom. Electronic address: thomais.markou@kcl.ac.uk.
Thomais
T
Markou
Cardiac Surgical Research, Rayne Institute, King's College London, Guy's and St Thomas' National Health Service Foundation Trust, St Thomas' Hospital, London, United Kingdom.
David J
DJ
Chambers
D000818:Animals; D002315:Cardiopulmonary Bypass / Q000009:adverse effects*; D019610:Cytoprotection; D004789:Enzyme Activation; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology / Q000503:physiopathology; D008170:Lung Compliance; D055370:Lung Injury / Q000201:enzymology / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010477:Perfusion / Q000379:methods*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D013806:Theophylline / Q000494:pharmacology; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D010726:Phosphodiesterase Inhibitors; D047428:Protein Kinase Inhibitors; D013806:Theophylline; D051057:Proto-Oncogene Proteins c-akt; C535149:Mapk1 protein, rat; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases