Dynamic Changes Of Inflammatory Response In Early Stage Of Acute Lung Injury Induced By LPS

Objective To study the dynamic changes of proinflammatory factors [interleukin-1β (IL-1β)、 interleukin-6] and anti-inflammatory factors [interleukin-10、soluble triggering receptor expressed on myeloid cell-1(sTREM-1)] in the early stage of acute lung injury(ALI) induced by escherichia coli lipopolysaccharide(LPS),and to discuss the relationship between their ratios as well as inflammatory reaction and lung injury.Method52male kunming mice,(23±2)g,were randomly divided into7groups,control group,1hr group,4hr group,8hr group,12hr group,24hr group and32hr group with10mice for each of the front4groups and4mice for each of the back3groups.Mice of the back6groups received intravenous injection of LPS at a dose of5mg·kg-1in5ml normal saline to reproduce mouse ALI model.Mice were taken blood samples and anesthetized respectively1hr,4hr,8hr,12hr,24hr,32hr after LPS injection and chest was opened.Then lungs were removed and stored at-80℃before being used for cytokins measurement,protein measurement,W/D measurement and pathological obsevation.Blood samples were centrifuged at3000rpm(4℃)for15min.Then the supernate was taken and stored at-80℃before being used for cytokins measurement.The mice of the back3groups were only taken lungs without blood samples. Mice of the control group were taken blood samples and lung samples1hr after intravenous injection of normal saline at the same dose. IL-1β、 IL-6IL-10and sTREM-1in the lung tissue and plasma were quantifyed using enzyme-linked immunosorbent assay(ELISA)，according to the instruction.Total protein of lung homogenate was detected by Coomassie brilliant blue method.The pathology of lung tissue was examined by HE.Proliferating cell nuclear antigen(PCNA) in the lung tissue was examined with immunohistochemical method.Result (1) Dynamic changes of proinflammatory factors in plasma:Compared with control group,IL-1β and IL-6levels in plasma increased significantly1hr after LPS injection,4hr later, IL-6sustain rising(P<0.05), IL-1β drop, though exceed control group(P<0.05).(2) Dynamic changes of antiinflammatory factors in plasma:Compared with control group.sTREM-1and IL-10levels in plasma increased significantly1hr after LPS injection(P<0.05), but decrease obviously4hr after LPS injection compared with1hr group(P<0.05).though exceed control group(P<0.05).(3)Dynamic changes of proinflammatory factors in lung homogenate:1hr after LPS injection.IL-1 β and IL-6levels in lung homogenate increase compared with control group(P<0.05),4hr later,IL-6levels in lung homogenate keep rising (P<0.05), IL-1β level also increase compared with the level of1hr group(P<0.05),but8hr later, IL-1β in lung homogenate express decreasing tendency, though does not have statistical significance compared with the4hr group(P=0.05).(4) Dynamic changes of proinflammatory factors in lung homogenate:1hr after LPS injection,sTREM-1levels in lung homogenate increase obviously compared with control group(P<0.05),4hr later, sTREM-1levels decrease obviously compared with the levels of1hr group(P<0.05),but more slowly than that in the plasma at the same time.IL-10in lung homogenate has not been detected.(5) Dynamic changes of the ratios of proinflammatory factors and antiinflammatory factors in plasma:1hr after LPS injection,IL-1β/sTREM-1,IL-6/sTREM-1,IL-1β/IL-10and IL-6/IL-10levels in plasma decrease obviously(P<0.05).4hr later,these ratios in plasma increase compared with1hr group(P<0.05),and sustain increasing.(6)Dynamic changes of the ratios of proinflammatory factors and antiinflammatory factors in lung homogenate:1hr after LPS injection,IL-1β/sTREM-1and IL-6/sTREM-1levels in lung homogenate also decrease obviously compared with control group(P<0.05),4hr later, these ratios in lung homogenate keep increasing (P<0.05);(7)Correlation analysis:IL-1β/sTREM-1,IL-6/sTREM-1,IL-1β/IL-10and IL-6/IL-10in plasma and IL-1β/sTREM-1and IL-6/sTREM-1in lung homogenate present possitive correlation(r>0.8, P<0.05).(8)Wet/Dry weight ratio(W/D) of the lung tissue and the total protain(TP) of lung tissue homogenate increased gradually.The pathological changes of lung tissue was parallel to them.(9)Immunohistochemical staining for PCNA show a large number of epithelial cells and interstitial cells proliferate at32hr after LPS injection. In contrast, no proliferous cells were found at24hr after LPS injection.(10) Significant correlation between sTREM-1and IL-10in plasma were obtained(r>0.8, P<0.05). sTREM-1in plasma have notable correlation with sTREM-1in lung homogenate(r>0.8, P<0.05).Conclution (1)In the early stage of ALI induced by LPS, antiinflammatory factors arise obviously1hr after LPS injection,and more distinctly than proinflammatory factors.4hr and later after LPS injection,antiinflammatory factors drop more markedly than proinflammatory factors.(2) The relationship between the ratios of proinflammatory factors and antiinflammatory factors in the plasma and in the lung homogenate is positive correlation and we hypothesize that the ratios in the plasma can be used to conjecture the inflammatory response in the lung tissue.(3) The inflammatory response in lung tissue are more serious than in the system.(4)In the process of ALI/ARDS,the proliferative stage of lung tissue may occur after24hr after LPS injection.(5) sTREM-1and IL-10have the same changes.sTREM-1act as an antiinflammatory factor,may play a more crucial protective role during lung injury.