Protective role of PI3-kinase/Akt/eNOS signaling in mechanical stress through inhibition of p38 mitogen-activated protein kinase in mouse lung.
OBJECTIVE
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.


CONCLUSIONS
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.
US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, USA. xinqipeng@gmail.com
Xin-qi
XQ
Peng
Mahendra
M
Damarla
Jarrett
J
Skirball
Stephanie
S
Nonas
Xiao-ying
XY
Wang
Eugenia J
EJ
Han
Emile J
EJ
Hasan
Xuan
X
Cao
Adel
A
Boueiz
Rachel
R
Damico
Rubin M
RM
Tuder
Alfred M
AM
Sciuto
Dana R
DR
Anderson
Joe G N
JG
Garcia
David A
DA
Kass
Paul M
PM
Hassoun
Jun-tian
JT
Zhang
D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008168:Lung / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015398:Signal Transduction; D013314:Stress, Mechanical; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D004791:Enzyme Inhibitors; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases