Objective      To explore the role and mechanism of mTORC2/SGK1 signaling pathway in alveolar fluid clearance (AFC) of acute lung injury (ALI) by regulating alveolar epithelial alpha sodium channel (ENaC-α) upstream signaling pathway.       Methods      Fifty male BALB/c mice were randomly divided into blank group

lipopolysaccharide (LPS) group

insulin group

LPS+rapamycin (mTORC1 inhibitor) group

and LPS+PP242 (mTORC1 and mTORC2 double inhibitor) group (n=10). ALI animal models were constructed by intranasal administration of 5 mg/kg LPS. After 2 h

the models were treated by intraperitoneal injection of 0.8 U/kg insulin

4 mg/kg rapamycin

and 60 mg/kg PP242

respectively

and the mice were put to death after 8 h. A549 cells were divided into control group

insulin group

rapamycin group and PP242 group

which were treated with culture medium

10 mmol/L insulin

5 mmol/L rapamycin

and 5 mmol/L PP242

respectively. The bronchoalveolar lavage fluid (BALF) IL-6 and TNF-α were measured by ELISA

and wet/dry (W/D) weight ratio was determined to evaluate AFC. HE staining was adopted to observe the lung tissue pathological changes. Real-time PCR

Western blotting and immunofluorescence assay were used to detect the expressions of rictor

SGK1

Nedd4-2 and ENaC-α in A549 cells.       Results      In vivo experiment showed that

compared with the LPS group

BALF IL-6 (77.48±6.04 vs 49.17±8.49)

TNF-α (116.2±13.5 vs 92.4±8.37) and W/D weight ratio were significantly decreased

AFC was increased

and lung injury was alleviated in the insulin group （all P0.05）. Compared with the LPS group

BALF IL-6 (77.48±6.04 vs 100.6±14.69)

TNF-α (116.2±13.5 vs 192.5±16.01) and W/D weight ratio were significantly increased

AFC was decreased

and lung injury was significantly worse in the LPS+PP242 group（all P0.05）. The inflammation indexes and pathological change had no significantly statistical differences between the LPS group and LPS+rapamycin group（all P0.05）. In vitro experiment showed that

compared with the control group

the expression of rictor

SGK1

Nedd4-2 and ENaC-α in A549 cells were obviously increased in the insulin group

and obviously decreased in the PP242 group

but no obvious changes were found between the rapamycin group and LPS group（all P0.05）.       Conclusion      Activated mTORC2/SGK1 pathway signaling can increase the expression of ENaC-α

and improve the AFC

thereby playing a protective role in lung tissue.