Relationship of NIX expression with pulmonary alveolus apoptosis after severe thoracic collision injury

Abstract

Objective To explore the relationship between the mRNA and protein expressions of NIX and the pulmonary alveolus apoptosis following severe acute lung injury (ALI). Methods Rat models of severe collision injury on the chest were built.The mRNA and protein expressions of NIX in the alveolar cells at 6,12,24,48,72 and 96 hours after injury were detected using immunohistochemistry,immunoblotting and RT-PCR.Meanwhile,apoptosis of the alveolar cells was checked at different time points with Tunel assay. Results The protein expression of NIX in the alveolar cells was observed both in experimental and control groups,which increased at 6 h post injury,peaked at 48 h and then declined till approaching the pre-injury level at 96 h.In the meantime,NIX showed a high expression both in the vascular endothelial cells (VECs) and the renal interstitial fibroblasts.The apoptosis of alveolar cells mainly presented in bronchi,blood vessel endothelium (BVE) and alveolar epithelium at 24 h post injury.The post-injury apoptosis rate of the alveolar cells was significantly higher than the pre-injury rate ( P ＜ 0.01 ),which reached the peak at 72 h and then decreased gradually.The changes of NIX protein in lung tissue showed a positive correlation with the apoptosis rate of alveolar cells after injury (r =0.303,P ＜ 0.01 ). Conclusions The up-regulated expression of NIX takes part in the pathophysiological process of apoptosis of the alveolar cells and shows consistency with the apoptosis rate change of the alveolar cells,as may be the molecular basis for apoptosis of the alveolar cells after ALI. Key words: Thoracic injuries; Pulmonary alveoli; Gene expression; Apoptosis