Rapamycin reverse lipopolysaccharide-induced acute lung injury through activating autophagy flux

This study was designed to examine the effects of autophagy on the lipopolysaccharide(LPS)-induced acute lung injury(ALI)and to analyze the possible mechanism. Kunming mice of clean grade were randomly divided into 6 groups: control group(saline, ip), model group(LPS 10 mg/kg, ip), RAP group(rapamycin 6 mg/kg, ip), RAP+LPS group(RAP 6 mg/kg and LPS 10 mg/kg, ip), 3-MA group(3-methyladenine 300 μg/kg, ip), and 3-MA+LPS group(3-MA 300 μg/kg and LPS 10 mg/kg, ip). 6 h after LPS injection, mortality was checked. Neutrophil aggregation, and the expressions of TNF-α, LC3 and P62 in lung tissue were checked by fluorescence microscopy and Western blot. The results revealed a higher mortality, neutrophil infiltration and TNF-α expression and significantly increased levels of autophagy marker LC3-II and P62 in LPS group; in RAP+LPS group, pretreatment with RAP notably reversed LPS-induced neutrophil infiltration and TNF-α expression, LC3-II were further slightly increased, while P62 was significantly decreased; in 3-MA+LPS group, pretreatment of 3-MA slightly decreased LC3-II expression, P62, neutrophil infiltration and TNF-α remained almost the same to those in LPS group. These data suggesed that, in sepsis, autophagy flux in the lung tissue is partially blocked, and RAP help to alleviate LPS-induced lung injury, which might through promoting autophagosome maturation, smoothing autophagy flux, and eventually to mitigate pulmonary inflammation.