The Pathogenic Role Of Phospholipase Cε1 In Mechanical Ventilation Induced Increasing Of Plumonary Endothelial Cells Permeability

Objective To elucidate the pathogenic role of phospholipase C epsilon-1（PLCE l）in mechanical ventilation（MV）induced hyper-permeability of pulmonary microvascular endothelial cells.Methods Twenty-four 8-week-old SPF rats（weighing 180g）with equal ratio of male and female were randomly divided into wild-type rats+’lung protective’or’injurious’MV group（WPM group or WIM group）and PLCE1knock-down（PLCE1-KD）rats+’lung protective’or’injurious’MV group（PPM group or PIM group）.Rats were subjected to 2h’lung protective’（VT=7m L/kg,PEEP=5cm H₂O）or’injurious’（VT=20m L/kg,PEEP=0cm H₂O）mechanical ventilation.The expressions of PLCEl and C-PLA2 were examined by western-blotting and quantitative PCR.Enzyme-linked immunosorbent assay（ELISA）was used to detect the contents of arachidonic acid metabolites such as prostacyclin（PGI2）,thromboxane A2（TXA2）and leukotriene B4（LTB4）in the lung tissue.The wet/dry（W/D）weight ratio of the lung and lung permeability index were determined to evaluate the permeability of the pulmonary microvascular endothelial cells（PMVECs）.The severities of lung injury were evaluated by lung histomorphological scores.Results 1.Pulmonary expressions of PLCE1 and C-PLA2In’injurious’MV groups,PLCE1 and C-PLA2 expressions（at both the protein and m RNA levels if not indicated otherwise）were significantly increased as compared with those in’lung protective’MV groups（P<0.05）.Under the same MV mode,PLCE1 and C-PLA2 expressions were significantly lower in PLCE1-KD rats than those in wild-type rats（P<0.05）.2.Pulmonary contents of LTB4,6-K-PGF1α（PGI2）and TXB2（TXA2）Compared with’lung protective’MV groups,the pulmonary contents of LTB4,6-K-PGF1α（PGI2）and TXB2（TXA2）increased significantly in’injurious’MV groups（P<0.05）.Under the same MV mode,the contents of LTB4,6-K-PGF1α（PGI2）and TXB2（TXA2）were lower in PLCE1-KD rats than those in wild-type rats（P<0.05）.3.Lung W/D weight ratio,lung permeability index and histological scoresCompared with’lung protective’MV groups,lung W/D ratio,lung permeability index and histological scores increased significantly in’injurious’MV groups（P<0.05）.In the’lung protective’MV groups,the lung permeability index was significantly lower in PLCE1-KD rats than that of wild-type rats（P<0.05）,but there was no significant difference in lung W/D weight ratio and lung histological scores.In’injurious’MV groups,the above three indicators were significantly lower in PLCE1-KD rats than those in wild-type rats（P<0.05）.4.Lung histology under light microscopy（HE staining）In WPM group and PPM group,no significant pathological changes were observed except for mild inflammations and capillary dilatation in some areas of the lung tissues.In the WIM group,serious hyperemia and hemonrhage in the lung tissues,thickening and exudation of the alveolar wall,marked red blood cell and inflammatory cell infiltration in the alveolar space were found.In the PIM group,there were scattered congestion and hemorrhage in the lung tissue,more red blood cells and inflammatory cells infiltrated in the alveolar cavity,and the alveolar wall was slightly thickened.Conclusions1.’Lung protective ventilation strategies’could not completely block the increase of PMVEC permeability induced by mechanical ventilation.2.Down-regulation of PLCE1 plays a protective role in MV-induced hpper-permeability of PMVECs by inhibiting the activity of C-PLA2 to reduce inflammatory AA metabolites.