Protective Effect Of MiR-155 On Acute Lung Injury Induced By Sepsis And Its Mechanism In Mice

ObjectiveTo observation of sepsis in the lung tissue of mice miR-155 expression changes and the effect and mechanism of the inflammatory response in the lungs in acute lung injury(ALI) mice induced by sepsis.MethodsSepsis ALI model was established by cecum ligation perforation(CLP).Mice were randomly assigned to two groups:Sham group,CLP group; Alveolar lavage fluid(BALF) and lung tissue specimens were obtainedrespectively at 0 h, 6 h, 12 h, 24 h, 48 h post operation.Transfection complex compromising miR-155 agomir was transfected into trachea of SPF BALB/c mice,while PBS or Negtive Control(NC) Control group was drip into trachea.After transfection 6 h, 12 h, 24 h, 36 h, 72 h,lung tissue specimen collection, miR-155 expression changes in the lung tissue of mice was detected by RT-q PCR, optimize the optimal transfection time; After in vivo transfection miR-155 1 h then CLP operation.Respectively in light mirror pathological change in mice lung tissue was observed, wet dry weight ratio was calculated, protein TAB2, Caspase 1, LC3 ?/? expression changes in lung tissue homogenate were detected by western blot, TNF alpha and beta IL-1 levels of BALF were detected by ELISA, autophagosomes were observed under electron microscope.ResultsSeptic lung injury model was successfully copied afte cell infiltration and alveolar hemorrhage,;lung wet to dry weight ratio,TNF-? and IL-1? of BALF increased with CLP time gradually increasing and at 24 h achieved peak(5.59± 0.54vs4.03±0.18,2367.35±624.35pg/ml vs 131.89±40.84pg/ml and 152.97± 52.27pg/ ml vs 64.33 ± 20.54pg/ml); miR-155 increased after CLP 6h and achieved peak at 24h(15.66 ±2.06 than 1.00 ± 0.00); The expression of Caspase-1, LC3?/? increased and autophagosome under electron microscope increased and similarly achieved at 24h(2.15 ± 0.30vs0.93±0.13, 2.6±0.20 vs 0. 95±0.12, 4.8±0.84 vs 1.00±0.70); There were significant differences between each groups at CLP 24 h. The ALI group showed that the whole lung was red and swollen,pathological alveolar structural disorder, alveolar septal thickening, rupture, inflammatorytatistically(P <0.05).We confirmed that septic acute lung injury model was established after CLP 24 h.miR-155 expression was elevated in lung tissue after transfection 24 h to a multiple of(49.51 ± 8.92) times,and was stably expressing for 36h;After transfection of miR-155, compared with the NC group, CLP group showed alveolar septal thickening reduced alveolar inflammatory cell infiltration decreased under light microscopy,lung wet and dry ratio decreased, TNF-?, IL-1? levels in BALF decreased(5.03±0.15vs5.62±0.52,783.53±229.11pg/mlvs2029.95± 766.80pg/ml, 109.13±13.10pg/mlvs209.85±50.06pg/ml); caspase-1 expression was downregulated(1.03 ± 0.06vs0.48 ± 0.26); There were significant differences statistically(P <0.05).It suggested that miR-155 could reduce septic ALI.The expression of LC3?/?was increased and the number of autophagosomeswas under electron microscope increased and similarly both achieved at 24h(2.6±0.20 vs 0. 95±0.12, 4.8±0.84 vs 1.00±0.70);After transfection of miR-155, compared with the NC group,the transfection group showed TAB2 expression was downregulated(1.11±0.13vs0.51±0.07), LC3?/? expression was increased(1.00±0.07vs1.89±0.15), the number of autophagic bodies increased under electron microscopy(8.50±0.76vs3.33±0.42); There were significant differences statistically(P <0.05).It suggested that miR-155 may downregulate TAB2 to upregulate autophagy.ConclusionMiR-155 expression in septic lung injury mouse lung tissues increases. miR-155 may inhibit the expression of TAB2, increased autophagy,then inhibits caspase-1 expression, reducing IL-1?, TNF-? release and other inflammatory factors so as to reduce septic acute lung injury.