Role of instilled air in establishment of lipopolysaccharideinduced mouse model of acute lung injury

Objective To investigate the effect of instilled air on lipopolysaccharide(LPS)-induced mouse model of acute lung injury(ALI)and to provide evidence for establishment of more effective intratracheal instillation.Methods Forty-five male C57BL/6Jmice were randomly divided into control group(n=15),LPS group(n=15),and LPS+air group(n=15).The mice in LPS and LPS+air groups were instilled with LPS to establish ALI models by exposed intratracheal instillation method.LPS was instilled intratracheally into the lungs of the mice in LPS+air group with 1mL syringe prefilled with 100μL air and the mice in control group were not treated.The detection of the biochemical indexes in bronchoalveolar lavage fluid(BALF),cell differential counting in BALF,lung wet/dry weight(W/D)ratio,and the morphological observation of lung tissue were performed 24hafter intratracheal instillation.Results Compared with control group,the activities of alkaline phosphatase(ALP)and lactate dehydrogenase(LDH),the concentrations of total protein in BALF,the amounts of total cells and neutrophils in BALF,and lung W/D ratios of the mice in LPS and LPS+air groups were significantly increased(P0.05).Compared with LPS group,the activities of ALP and LDH,the concentration of total protein in BALF,the amounts of total cells and neutrophils in BALF,and lung W/D ratio in LPS+air group were significantly increased(P0.05).The histological observation results of lung tissue showed that there were different degrees of fluid accumulation,neutrophils infiltration,congestion and hemorrhage of the mice in LPS+air and LPS groups compared with control group;there were more protein-rich fluid,neutrophils and erythrocytes accumulated in alveolar spaces of the mice in LPS+air group compared with LPS group.Conclusion The instilled air can be used to improve the method of intratracheal instillation and establish the more reliable experimental animal model of ALI.