Mechanism On Acute Lung Injury Induced By Exudation From Intestinal Sepsis In Rats

Objective: Observing the mechanism of acute lung injury by injecting the peritoneal exudate of intestinal sepsis to the portal vein and caval vein.Methods: Cleaning healthy adult SD rats 108 were used in the research, 12 rats were randomly selected for cecal ligation and perforation(CLP) model and collecting intestinal sepsis peritoneal exudate; the remanent 96 rats were randomly divided into two groups :exudate group(E group, n =48) and control group,(S group, n=48); Each group was randomly divided into two subgroups of the portal vein(PV group, n =24), subgroup vena cava(VC group, n=24), each subgroup divided into four sub-sub-groups by 1h, 2h,4h, 6h time point, each sub-sub-group had 6 rats, there were 16 sub-sub-group totaly. The portal vein and caval vein.of E group rats were injected by peritoneal exudate(1ml/each),the portal vein and caval vein.of S group rats were injected with saline(both 1ml/each).Extracting abdominal aortic blood,lungs and collecting BALF after 1h, 2h, 4h and 6h,then observing the morphous of lungs, measuring lung wet / dry ratio(W/D),ELISA assay was used to observe the levels of TNF-α and IL-6 in peritoneal exudate, serum and BALF;LPS was measured in peritoneal exudate, serum and BALF by MB-80 rapid microbial dynamic monitoring system; Observing the microscopic changes and pathology score with light microscope after the lung tissues were fixed sectioned and stained.SPSS17.0 was used for analysising all the date, P<0.05 was considered statistically significant, P<0.01 was considered significant difference.Result:1). The peritoneal exudate of each rat could be collected about 5-10 ml, the samples of rait were slightly turbid liquid which was pale yellow or pale pink. Gram-negative bacilli was detected by microscopy, eight bacteria was isolated from bacterial cultures, which mainly was Escherichia coli; the expression of LPS, TNF-α and IL-6 was detected in peritoneal exudate.2). The gross morphology of lung,pathology score, W/D, the levels of LPS, TNF-α and IL-6 were no significant difference in PV-S and VC-S group at each time. Compared withcontrol group(PV-S、VC-S), the gross morphology of lung,pathology score, W/D, the levels of LPS, TNF-α and IL-6 in the exudate group(PV-E, VC-E group) were statistically significant(aP <0.01, bP <0.01). The levels of LPS, TNF-α and IL-6 in the exudate group(PV-E, VC-E group) were more higher than control group(PV-S、VC-S).3).Lung gross morphology and light microscopy findings: compared with the VC-E groups at each time point, the lung edema and bleeding was more serious than that in the PV-E groups; light microscopy findings: the edema of pulmonary alveolar and pulmonary interstitium was more serious than that in the VC-E groups, and inflammatory cell infiltration with morrhage in alveolar was also more serious in the PV-E groups than the VC-E groups.4).Pathology score: the pathology score in PV-E group was higher than VC-E group at each time point, there was statistically significant(aP < 0.05).The time of lung injury in PV-E group was earlier than VC-E group.5).Lung wet/dry weight ratio(W/D) measurement: The measurement of lung wet / dry weight ratio(W/D) was statistically significance(aP <0.05) in group PV-E and VC-E.6).The levels of LPS in serum and bronchoalveolar lavage fluid: The levels of LPS in serum and bronchoalveolar lavage fluid in both PV-E group and VC-E group were gradually decreasing at each time point,but the of LPS in serum and bronchoalveolar lavage in PV-E group decreased more significantly, compared with the VC-E group, the levels of LPS was statistically significant(aP <0.05) at 1h, 2h, 4h. But there was no significant difference at 6h(P>0.05).7).The levels of TNF-α and IL-6 in serum and bronchoalveolar lavage fluid: the levels of TNF-α and IL-6 in serum and bronchoalveolar lavage fluid gradually increased at all time points in both PV-E and VC-E group, the levels of TNF-α in serum and bronchoalveolar lavage fluid reached the highest value at 4h, decreased after 6h. The levels of IL-6 in serum and bronchoalveolar lavage fluid reached the highest value at 6h.The levels of TNF-α and IL-6 levels in PV-E group and VC-E group at each time point were statistically significant differences(aP <0.05).conclusion:⑴ Intestinal sepsis model can be successfully prepared by CLP, acute lung injury of rats were caused by peritoneal exudate which was injected in the portal vein and vena cava;⑵ Gut-derived sepsis peritoneal exudate include a variety of pathogens which mainly was Escherichia coli endotoxin and TNF-α, IL-6 and other substances;⑶ The levels of TNF-α and IL-6 in PV-E serum and bronchoalveolar lavage fluid were significantly higher than VC-E group, the levels of LPS were significantly lower than VC-E group, the level of lung injury was more serious than VC-E group,which indicated that LPS was the initiation factor in releasing of inflammatory mediators, TNF-α and IL-6 were important factor in acute lung injury which were induced by gut-derived sepsis.The peritoneal exudate acting on the liver or not, the level of lung injury was different,indicating liver maybe played an important role in the acute lung injury which was induced by gut-derived sepsis.