| Objective:To explore the dynamic changes of VEGF in acute lung injury and significance of dexamethasone treatment, For clinical treatment of glucocorticoid provide a theoretical basis induced by different incentives ALI / ARDS.Methods:One hundred and twelve male clean degree Sprague-Dawley rats were randomly divided into fourteen groups. By intravenous injection of physiological saline 1ml as control group; The experiment by intravenous injection of lipopolysaccharide (LPS 8mg/kg) for two hours, four hours, six hours and tracheal instillation of Escherichia coli (E. coli 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(2mg/kg) immediately after replicating models. After being duplicated at different time points, the animals were anaesthetized by intraperitoneal injection 10% chloral hydrate(3ml/kg) and then set them on the operating table. Drawn and collected blood by puncturing the femoral artery, centrifuged(3000rpm,4℃, 10min) and draw serum. Then stored them separately under -80℃for future cytokine VEGF determination. The animal were sacrificed by thoracotomy exposed lung tissue, after the clamp off the right main bronchus, the complete removal of the right lung, right upper lobe lung tissue taken for wet/dry weight ratio testing, taken right middle lobe lung tissue in 10% neutral formalin fixed for future chemical examination of pathology and immunohistochemistry. Isolated trachea, A trachea catheter was used for bronchoalveloar lavage in left lung. BALF were collected and centrifuged (1200rpm, 4℃, 10min). Supernatant -packing was stored in -80℃and was used to measure the concentration of VEGF and protein. Cellular sediment was suspended in 0.9% saline 200ul to be counted the total leukocytes. Moreover, observed dexamethasone effecting on the index.Results:(1)The lung organization pathology Pathomorphology: 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 significant 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 significant 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 decreased than corresponding non-steroid group; E.coli group appeared in twenty-four hours, thirty-six hours alveolar edema, inflammatory cell infiltration hyaline membrane and pathological semi-quantitative score decreased than corresponding non-steroid group.(2)BALF total cells, protein levels and the lung W/D changes: In the LPS model with time, 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 peaked, at six hours began to decrease, a corresponding decline in glucocorticoid intervention group; The lung W/D in the LPS two hours group was significantly higher than the control group, But as time goes on, It did not appear statistically significant further increase. Corresponding decline in glucocorticoid intervention group; In the E.coli model cell count, protein in BALF, the lung W/D increased with time, But it did not appear statistically significant further increase. After given glucocorticoid intervention twenty-four hours and thirty-six hours, The three indicators were significantly decreased than corresponding non-steroid group.(3)VEGF levels in serum and BALF: In the LPS model, The serum VEGF was significantly higher than control group at two hours, peaked at six hours; In the E.coli model the serum VEGF was significantly higher than the control group at twelve hours. As time prolonging no statistically significant increase furthermore. After given glucocorticoid intervention the serum VEGF in two models had no significant difference than non-steroid; In the LPS model, The BALF VEGF was significantly higher than control group at two hours,with time increased; in the E.coli model the BALF VEGF was significantly higher than control group at twelve hours, As time increased, After given glucocorticoid intervention the BALF VEGF in two models were decreased than corresponding non-steroid group.(4)The VEGF expression changes in lung tissue: The positive rate of VEGF at two hours in the LPS model was significantly lower than the control group, increased at four hours and it was higher than the control group, At six hours it was significantly higher than at four hours; The glucocorticoid intervention group were decreased at all time points than corresponding non-steroid group; In the E.coli model the positive rate of VEGF was significantly higher than control group at twelve hours, As time increased. After glucocorticoid intervention it was decreased than corresponding non-steroid group; Integral optical density of positive target value in the LPS two hours model was significantly lower than the control group, with time increased. But at six hours reached to the control level, After given glucocorticoid they were significantly decreased; In the E.coli model the integral optical density of positive target value was significantly higher than control group at twelve hours, as time increased, After glucocorticoid intervention they were decreased than corresponding non-steroid group.(5)Linear correlation analysis showed: The relationship Between the positive rate of VEGF, cell count in BALF and the integral optical density in E.coli group, the linear correlation analysis showed a significant positive correlation and serum VEGF was negatively correlated; The relationship Between BALF VEGF, cell count in BALF, pathological score, the positive rate of VEGF and positive target integrated optical density in LPS group, the linear correlation analysis showed a significant positive correlation and serum VEGF was negatively correlated.Conclusitions:1 Suspension Escherichia coli into the trachea successfully duplicated ARDSp resulting from pneumonia and intravenous injection of exogenous LPS successfully duplicated ARDSexp.2 LPS induced acute lung injury decreased expression of VEGF in lung tissue, increased with time, The serum and BALF VEGF expression were increased; E.coli induced acute lung injury in the lung tissue and BALF VEGF expression was increased with time.3 The overexpression of VEGF in acute lung injury, participated in the development of acute lung injury, Glucocorticoid by reducing the expression of VEGF, reduced pulmonary edema in the early; In the late inhibition of epithelial cells in culture.
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