Phosphoinositide 3-kinase, Src, and Akt modulate acute ventilation-induced vascular permeability increases in mouse lungs

Abstract

To determine the role of phosphoinositide 3-OH kinase (PI3K) pathways in the acute vascular permeability increase associated with ventilator-induced lung injury, we ventilated isolated perfused lungs and intact C57BL/6 mice with low and high peak inflation pressures (PIP). In isolated lungs, filtration coefficients ( Kf) increased significantly after ventilation at 30 cmH2O (high PIP) for successive periods of 15, 30 (4.1-fold), and 50 (5.4-fold) min. Pretreatment with 50 μM of the PI3K inhibitor, LY-294002, or 20 μM PP2, a Src kinase inhibitor, significantly attenuated the increase in Kf, whereas 10 μM Akt inhibitor IV significantly augmented the increased Kf. There were no significant differences in Kf or lung wet-to-dry weight (W/D) ratios between groups ventilated with 9 cmH2O PIP (low PIP), with or without inhibitor treatment. Total lung β-catenin was unchanged in any low PIP isolated lung group, but Akt inhibition during high PIP ventilation significantly decreased total β-catenin by 86%. Ventilation of intact mice with 55 cmH2O PIP for up to 60 min also increased lung vascular permeability, indicated by increases in lung lavage albumin concentration and lung W/D ratios. In these lungs, tyrosine phosphorylation of β-catenin and serine/threonine phosphorylation of Akt, glycogen synthase kinase 3β (GSK3β), and ERK1/2 increased significantly with peak effects at 60 min. Thus mechanical stress activation of PI3K and Src may increase lung vascular permeability through tyrosine phosphorylation, but simultaneous activation of the PI3K-Akt-GSK3β pathway tends to limit this permeability response, possibly by preserving cellular β-catenin.

Role of Growth Arrest and DNA Damage–inducible α in Akt Phosphorylation and Ubiquitination after Mechanical Stress-induced Vascular Injury

“…(9). Of note, various reports have now identified augmented injury in animal models of both VILI and lipopolysaccharide-induced ALI associated with Akt inhibition (10,11) and we previously reported increased agonist-induced barrier disruption in Akt1-silenced EC monolayers (9). These findings suggest that Akt depletion contributes directly to the elaboration of acute inflammatory lung injury via increased lung vascular permeability.…”

Mechanical ventilation augments bleomycin-induced epithelial–mesenchymal transition through the Src pathway

“…13 Mechanical ventilation can increase Src phosphorylation by activating adherens junctions, Ca 2 þ entry through stretch-activated cation channels, deformation of cytoskeleton and integrins, focal adhesion kinases, G protein-coupled receptors, and growth factor receptors. 13 In the presence of active TGF-b1 and disrupted cell contacts of the bleomycin mouse model, integrin mediated Src activation after TGF-b1 signaling and Src inhibition blocked EMT and fibrogenesis.…”

“…13 Mechanical ventilation can increase Src phosphorylation by activating adherens junctions, Ca 2 þ entry through stretch-activated cation channels, deformation of cytoskeleton and integrins, focal adhesion kinases, G protein-coupled receptors, and growth factor receptors. 13 In the presence of active TGF-b1 and disrupted cell contacts of the bleomycin mouse model, integrin mediated Src activation after TGF-b1 signaling and Src inhibition blocked EMT and fibrogenesis. 34 Our results revealed that mechanical ventilation induced the phosphorylation of Src both in lung tissue and isolated myofibroblasts, which can be suppressed by Src knockout or pharmacologic inhibition with PP2, a selective Src kinase inhibitor remaining effective up to 6 h after ALI.…”

“…Despite its extensive use as a Srcselective inhibitor, recent studies have demonstrated that PP2 also reduced the activation of serine/threonine kinase/protein kinase B, beta-catenin, Jak kinase and phosphoinositide 3-OH kinase. 13,22 Further experiments are necessary to explore potential regulators of VILI.…”

“…18 Mechanical stretchinduced activation of Src has recently been demonstrated to increase lung vascular permeability in mice. 13 Src protein tyrosine kinase family is categorized into nonreceptor tyrosine kinases and is one of the most crucial families for intracellular signal transduction related to cell proliferation, migration, differentiation and apoptotic cell death. 14,19,20 Src inhibitors that are used in vivo may suppress inflammatory responses, involving neutrophils, monocytes, macrophages, endothelial and epithelial cells.…”