Minocycline Ameliorates Acute Lung Injury Via Inducing Autophagy Through Inactivating Mammalian Target Of Rapamycin

Background : Acute lung injury is a common respiratory critical illness characterized by excessive inflammation,with high mortality.Minocycline,a semisynthetic tetracycline derivative,has been reported to have positive effects on anti-inflammatory and immunomodulatory.However,the effects of Minocycline on LPS-stimulated acute lung injury in mice have not been reported.Objctive : To determine the effect of minocycline on the secretion of inflammatory factors in THP-1 cell line stimulated by lipopolysaccharide.To investigate the inhibitory effects of minocycline on ALI treated by LPS and to elucidate its possible mechanisms.Methods:1.Minocycline is added or pretreated with 3BDO after THP-1 cells are stimulated by lipopolysaccharide.The concentrations of cytokines IL-6 and TNF-α at different time are determined by ELISA.2.Mice are divided into normal saline control group,acute lung injury model group,minocycline therapeutic intervention group,minocycline preventive intervention group and autophagy inhibition group.The cells in bronchoalveolar lavage fluid are counted and classified.The protein concentration and cytokine concentration in bronchoalveolar lavage fluid are determined by ELISA.Pathological damage of lung tissue is observed under microscope,and the wet/dry ratio of lung tissue is calculated.The expression of p-m TOR,LC3,p-p70S6K1 and p70S6K1 in lung tissue is measured by Western blot.In addition,mice with the same grouping scheme are taken to evaluate the mortality.Results:After THP-1 cells are stimulated by lipopolysaccharide,the production of IL-6 and TNF-α increases in a time-dependent manner.Minocycline significantly inhibits the release of cytokines,which may be related to the inhibition of m TOR.In vivo,minocycline significantly reduces neutrophils,total protein content,TNF-α and IL-6 in bronchoalveolar lavage fluid of ALI mice.Histological alterations including pulmonary edema are significantly relieved and the mortality of ALI mice is also reduced.Minocycline up-regulates LC3-II/LC3-I and p-p70S6K1/p70S6K1 levels and induces autophagy.Pretreatment with 3BDO weakens the aforementioned effects of minocycline in ALI mice.Conclusion:Minocycline decreases the production of inflammatory cytokines in ALI mice by modulating the m TOR pathway-related autophagy,which may offer a unique therapeutic perspective in ameliorating ALI.