Expression of Na~+/H~+ exchanger 1 in lipopolysaccharide-induced acute lung injury rats

OBJECTIVE To establish the model of the acute lung injury(ALI) induced by lipopolysaccharide(LPS) in rats in vivo and to observe the changes of Na+/H+ exchanger 1(NHE1) mRNA and protein expressions in the injurious lungs.METHODS Forty Sprague-Dawley rats were randomly divided into four groups: control group;LPS-2 h group;LPS-4 h group;LPS-6 h group.The samples of pulmonary tissue and lung lavage fluid were collected.The basic vital signs of rats were monitored and recorded;the pathological changes in lung tissue were examined with optical microscopy;the acute lung injury score and lung tissue wet/dry weight ratio were calculated;the total protein,tumor necrosis factor-α and macrophage inflammatory protein concentration in bronchoalveolar lavage fluid were detected;The myeloperoxidase(MPO) activity of lung tissue were measured;The NHE1 mRNA and protein expressions in lung tissue were detected by immuno-histochemistry,RT-PCR and Western blot.RESULTS The lung tissue in control group rats showed normal alveolar septum and alveolar spaces without exudation;the lung tissue of rats in LPS-2 h,LPS-4 h group and LPS-6 h group showed high levels of intra-alveolar exudates,hyaline membrane formation,inflammatory cell infiltration,intra-alveolar hemorrhage,and interstitial edema.Compared with the control group,the total protein(TP),tumor necrosis factor-α(TNF-α) and macrophage inflammatory protein(MIP-2) concentration in bronchoalveolar lavage fluid and the lung tissue ALI scores,wet / dry weight ratio,the MPO activity,NHE1 protein immuno-histochemistry,NHE1 mRNA and protein expressions of rats in LPS-2 h,LPS-4 h group and LPS-6 h group were significantly elevated in turn(all P0.05).The overall differences between groups were statistically significant.CONCLUSION Rats produced significant acute lung injury after intravenous injection of LPS 4h with 6 mg·kg-1,which includes endotoxin shock symptoms,histological inflammation patho-histological changes in rats' gross specimens,lung tissue water content increased,inflammatory cytokines in lung tissue and bronchoalveolar lavage fluid increased.At the same time,the NHE1 mRNA and protein expressions of lung tissue in each LPS group were significantly elevated and remarkably increased with the duration of acute lung inflammatory response.