Activation of c-Src tyrosine kinase mediated the degradation of occludin in ventilator-induced lung injury.

Tao Zhao,Changping Gu,Yuelan Wang,Mengjie Liu,Xin Wang

doi:10.1186/s12931-014-0158-2

Abstract

BackgroundVentilator-induced lung injury (VILI) is characterized by increased alveolar permeability, pulmonary edema. The tyrosine kinase, c-Src, is involved in VILI but its role has not been fully elucidated. This study examined the relationship between c-Src activation and occludin levels in VILI both in vitro and in vivo.MethodsFor the in vivo study, Wistar rats were randomly divided into five groups: control (group C); normal tidal volume (group M); normal tidal volume + c-Src inhibitor (PP2) (group M + P); high tidal volume (group H); and high tidal volume + c-Src inhibitor (PP2) (group H + P). Rats in all groups but group C underwent mechanical ventilation for 4 h. For the in vitro study, MLE-12 cells pretreated with PP2 and siRNA underwent cyclic stretching at 8% or 20% for 0, 1, 2 and 4 h. The expressions of occludin, c-Src, and p-c-Src were analyzed by western blotting, hematoxylin and eosin (HE) staining, and immunofluorescence.ResultsFor the in vivo study, rats in group H showed decreased occludin expression and activated c-Src compared with group C. HE staining and lung injury score showed more severe lung injury and alveolar edema in group H compared with group M and group C. Group H + P had less pulmonary edema induced by the high tidal volume ventilation. For the in vitro study, occludin expression decreased and c-Src activation increased as indicated by the phosphorylation of c-Src over time. Consistently, PP2 could restore occludin levels.ConclusionsMechanical ventilation can activate c-Src by phosphorylation and increase the degradation of occludin. c-Src inhibitor can ameliorate barrier function and lung injury by up-regulating occludin.

Highlights

Ventilator-induced lung injury (VILI) is characterized by increased alveolar permeability, pulmonary edema
The barrier function of pulmonary epithelial cells plays an important role in maintaining alveolar membrane permeability and preventing the destruction of alveolar epithelial cell junctions, which could lead to acute lung injury and acute respiratory distress syndrome [5,6,7]
A recent study demonstrated that the expression of the transmembrane protein occludin and the tight junction protein ZO-1 decreased during cyclic mechanical stretching in primary rat cells [8]

Summary

Introduction

Ventilator-induced lung injury (VILI) is characterized by increased alveolar permeability, pulmonary edema. VILI can, both in vivo and in vitro, decrease oxygenation capacity, increase alveolar membrane permeability, and induce secondary pulmonary function damage and acute respiratory distress syndrome [2,3]. Maintaining normal permeability and the integrity of the alveolar membrane could prevent pulmonary edema, and may play a key role in inhibiting or reducing the subsequent development of lung injury [4]. The barrier function of pulmonary epithelial cells plays an important role in maintaining alveolar membrane permeability and preventing the destruction of alveolar epithelial cell junctions, which could lead to acute lung injury and acute respiratory distress syndrome [5,6,7]. The underlying mechanism for how occludin regulates barrier function is not fully understood

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