Dynamic Change Of Inflammation In Endogenous And Exogenous ALI Models Caused By Different Causes

Objective: Acute lung injury ( ALI ) is a kind of common and frequently encountered diseases in clinic. People pay much attention on it because of the high fatality rate. Its pathogenesis is still not clear so far. The inflammatory reaction is different between different ALI courses which are induced by different causes. In experiment, we duplicated two models: instill Escherichia coli( E.coli ) suspension in rats trachea to simulate endogenous ALI model; inject LPS( 8 mg/kg ) in rats caudal vein to simulate exogenous ALI model. Observe the inflammatory reaction and of the two models, and observe the therapeutic efficacy after glucocorticosteriod( GC ) therapy at the same time, in order to make a better guidance for therapeutic methods of ALI.Methods: One hundred and twelve male clean degree Sprague-Dawley rats were randomly divided into fourteen groups. By intravenous injection of physiological saline 1 ml as control group; The experiment by intravenous injection of lipopolysaccharide ( LPS 8 mg/kg ) for two hours, four hours, six hours and tracheal instillation of Escherichia coli( E. coli, 5.0×10~9 cfu/ml, 3 ml/kg) for twelve hours, twenty-four hours, thirty-six hours as ALI models were duplicated; NS+Dex group, LPS+Dex for two hours, four hours, six hours group, E.coli+Dex for twelve hours, twenty-four hours, thirty-six hours group as intervention groups. With eight animals for each group: The Glucocorticoid intervention groups were intraperitoneal injection Dex ( 2 mg/kg ) immediately after replicating models.Anaesthetize the rats by intraperitoneal injection with 10% chloral hydrate ( 3 ml/kg ) and hold them on the operating table after making models successfully. Fiat venaesection from femoral artery to kill the rats, collect the blood and centrifuge it ( 3000 rpm, 4℃, 10 min ), store the supernatant at -80℃for measuring TNF-α. Take middle lobe of right lung for the test of wet/dry( W/D ). Take the inferior lobe of right lung fix it with 10 % neutrophilia formalin fluid for pathology. Separate the trachea and operate trachea intubation. Use 4 ml sterile normal saline ( NS ) for bronchoalveolar lavage. Collect the Bronchoalveloar lavag fluid (BALF) and centrifuge it ( 1200 rpm, 4℃, 10 min), store the supernatant at -80℃for the test of TNF-αand protein concentration in BALF. Dissolve the cell deposite by 200μl NS for counting the total leukocytes.Results:1 The lung organization pathology: By Light microscope, In LPS two hours group, it had pulmonary vascular congestion, inflammatory cell infiltration, interstitial pulmonary edema; At four hours it had typical performance of acute lung injury, hyaline membrane formation, six hours and four hours pathological semi-quantitative score was no statistically difference; Instillation E.coli into the trachea for twelve hours, it found a large number of inflammatory cells Infiltration, shedding of airway epithelial cells, alveolar edema; At twenty-four hours, it found that alveolar epithelial cells appeared vacuolization, necrosis, cell proliferation, a large number of fibrin exudation, hyaline membrane formation, part of the lung tissue consolidation. Twenty-four hours and Thirty-six hours pathological semi-quantitative score were no statistically difference; After given dexamethasone, lps group in two hours, four hours, six hours appeared the infiltration of inflammatory cells, protein leakage, pathological semi-quantitative score less than corresponding non-steroid group; E.coli group in twenty-four hours, thirty-six hours alveolar edema, inflammatory cell infiltration, hyaline membrane less than corresponding non-steroid group. But pathological semi-quantitative score was no statistically difference.2 The change of BALF total cells, protein levels and the lung W/D: In the LPS model with time increased, the cell count in BALF was significantly increased. After glucocorticoid given, the cell count in BALF was significantly decreased; at four hours the protein in BALF was peaked, at six hours began to decrease. After glucocorticoid given, it has a corresponding decline; The lung W/D in LPS two hours group was significantly higher than the control group. But as time goes on, it did not appear statistically significant further increase. It has a corresponding decline in glucocorticoid intervention group; In the E.coli model the cell count, protein in BALF, the lung W/D were increased, with time increased. But it did not appear statistically significant further increase. After given glucocorticoid twenty-four hours and thirty-six hours, the date of the three indicators were significantly less than corresponding non-steroid group.3 The level of TNF-αin serum: In LPS model 2h,4h,6h group, the level of TNF-αwas much higher than NS group. With the development of ALI, an obvious tendency would arise: the level of TNF-αwould step up at the beginning of ALI, and the peak would appear at the middle time point, and then it would decline after the peak. It would decline obviously after hormonal therapy ( P<0.01 ). In E.coli model, the level of the three groups was much higher than NS group. With the development of ALI, there was also an obvious tendency in E.coli model: step up at the beginning, reach the top, and then decline. But there was a difference between E.coli and LPS group: the level of TNF-αwould not decline after hormonal therapy.4 The level of TNF-αin BALF: In LPS model 2h,4h,6h group, the level of TNF-αwas much higher than NS group. With the development ALI, there were a same tendency like the level in serum, which was that it would step up at the beginning of ALI, and the peak would appear at the middle time point, and then the level would decline after the peak. It would decline obviously after hormonal therapy ( P<0.01 ). With the development of ALI, there was also an obvious tendency in E.coli model: step up at the beginning, reach the top, and then decline. But there was a difference between E.coli and LPS groups: the level of TNF-αwould not decline after hormonal therapy.Conclusions:1 We duplicated the two model groups successfully.2 LPS model manifest classic pathologic change at 4-hour time point. Ecoli model manifest classic pathologic change at 24-hour time point. It is different between the two models in the development of ALI time window.3 The therapeutic effect of GC and the cause of ALI are related closely. After hormonal therapy, LPS model mainly manifests induction of fibrin dxsudation and remission of pulmonary edema. E.coli model mainly manifests induction of inflammatory cells infiltration, but the pathologic grade is same to LPS group. The result tells us we should use GC carefully when we treat ALI in clinic as it is different in pathologic details.4 The change tendencies of TNF-αof the two models in serum and BALF are same. After GC therapy, the level of TNF-αof LPS group declines obviously in serum and BALF; On the contrary, E.coli group has no obvious change. In conclusion, the glucocorticoids effect is better for pulmonary acute lung injury by endotoxin, but is worse for extrapulmonary acute lung injury by infection.