Rapamycin up-regulates NIX for protecting exertional heat stroke rats against acute lung injury

Wang Jiaxing; Zhang Yuxiang; Gu Yan; Sun Zhengzhong; Meng Ran; Chi Ruxue

doi:10.3969/j.issn.1002-1949.2024.06.008

Abstract：Objective To investigate the mechanism of rapamycin(Rapa)on alleviating acute lung injury of rats with exertional heat stroke(EHS).Methods Sixty heathy male SD rates were randomly divided into four groups:control group(Ctrl group),Rapa group,EHS group,and EHS+Rapa group,with 15 rats in each group.After establishing the EHS models,the core temperature and the arterial blood gas analysis were measured.The pulmonary vascular permeability was measured by Evans blue(EB)staining.The pulmonary histopathological changes were analyzed by hematoxylin eosin(HE)staining.The apoptosis in rat lung tissue was observed by terminal-deoxynucleoitidyl transferase mediated nick end labeling(TUNEL).Mitochondrial morphology in type Ⅱ epithelial cells of rat lung was observed by transmission electron microscopy.Western blot was used to detect the expressions of NIX and LC3,and the ratio of LC3-Ⅱ to LC3-Ⅰ was calculated.Immunofluorescence was used to detect the co-localization of LC3 and Tom20 in lung tissue.Results The core temperature of EHS group and EHS+Rapa group increased sharply to 42 ℃.Rapamycin alleviated the pathological injury,decreased the apoptosis of lung tissues,reduced pulmonary vascular permeability,and improved the oxygenation of arterial blood.Under transmission electron microscopy,the mitochondrial morphology in type Ⅱ epithelial cells of rat lung was maintained in EHS+Rapa group.Western blot and immunofluorescence results showed that rapamycin up-regulated the expressions of NIX proteins,increased the ratio of LC3-Ⅱ/LC3-Ⅰ in lung tissues of EHS rats,and enhanced the co-localization of LC3 and Tom20 in EHS rat's lung tissue.Conclusions Rapamycin up-regulates NIX expression and activates mitochondrial autophagy,thereby alleviating EHS-induced lung injury and protecting lung function.