Acta Pharmacologica Sinica (2010) 31: 175–183; doi: 10.1038/aps.2009.190

¹Division of Analytical Toxicology, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, USA; ²Division of Pulmonary & Critical Care Medicine, ³Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA; ⁴Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, University of Colorado Denver School of Medicine, Denver, CO, USA; ⁵Oregon Health & Science University, Division of Pulmonary and Critical Care Medicine, Portland, OR, USA; ⁶Department of Medicine, University of Chicago Pritzker School of Medicine, Chicago, IL, USA; ⁷Department of Pharmacology, Institute of Materia Medica, Chinese Academy of Medical Sciences, Beijing 100050, China

Aim: To test the hypothesis that PI3K/Akt/eNOS signaling has a protective role in a murine model of ventilation associated lung injury (VALI) through down-regulation of p38 MAPK signaling.

Methods: Male C57BL/J6 (wild-type, WT) or eNOS knockout mice (eNOS^–/–) were exposed to mechanical ventilation (MV) with low (LV_T, 7 mL/kg) and high tidal volume (HV_T, 20 mL/kg) for 0−4 h.  A subset of WT mice was administered the specific inhibitors of PI3K (100 nmol/L Wortmannin [Wort], ip) or of p38 MAPK (SB203580, 2 mg/kg, ip) 1 h before MV.  Cultured type II alveolar epithelial cells C10 were exposed to 18% cyclic stretch for 2 h with or without 20 nmol/L Wort pretreatment.  At the end of the experiment, the capillary leakage in vivo was assessed by extravasation of Evans blue dye (EBD), wet/dry weight ratio and lung lavage protein concentration.  The lung tissue and cell lysate were also collected for protein and histological review.  

Results: MV decreased PI3K/Akt phosphorylation and eNOS expression but increased phospho-p38 MAPK expression along with a lung leakage of EBD.  Inhibitions of phospho-Akt by Wort worsen the lung edema, whereas inhibition of p38 MAPK kinase restored activation of Akt together with alleviated capillary leakage.  eNOS^–/– mice showed an exacerbated lung edema and injury.  The stretched C10 cells demonstrated that Wort diminished the activation of Akt, but potentiated phosphorylation of MAPK p38. 

Conclusion: Our results indicate that PI-3K/Akt/eNOS pathway has significant protective effects in VALI by preventing capillary leakage, and that there is a cross-talk between PI3K/Akt and p38 MAPK pathways in vascular barrier dysfunction resulting from VALI.

Keywords: mechanical stress; ventilator-associated lung injury; pulmonary capillary leakage; PI3K/Akt/eNOS; p38 MAPK signalings; signals cross-talk; pulmonary edema; wortmannin