| Reexpansion pulmonary edema(RPE) is an acute pulmonary edema which happens after any atelectasis when the lung is rapidly reexpansing or in after reexpansion. It is a rare but potentially fatal pulmonary complication, which mainly go with pulmonary capillary permeability increase. Although glucocorticoid has been drawing everybody's attention because of its powerful anti-inflammatory role in the treatment of various lung injuries, whether it is effective in its pre-treatment for acute lung injury is rarely reported in the literature. So, this study is to examine the effects of methylprednisolone pretreatment on reexpansion pulmonary edema in rabbit lung permeability and on lung surfactant dipalmitoylphosphatidylcholine(DPPC).The most fundamental changes of early RPE is cause by the alveolar fluid transport and external imbalances right after the increase in liquid and protein permeability by the path physiology of pulmonary vascular endothelial cells and alveolar epithelial cell barrier. It has been found that protein percentage is significantly higher in the RPE edema fluid than in hydrostatic pulmonary edema when pulmonary capillary wedge pressure (PCWP) is normal. As for the mechanism, how to rise to increased alveolar capillary permeability and leakage of blood components is unknown. Recent studies including: mechanical damage, pulmonary surfactant Substances (PS) reduced, lung reperfusion injury and inflammatory-mediated response.The reduction of pulmonary surfactant has been demonstrated in clinical tests when RPE happens:PS, a kind of complex phospholipids, containing DPPC which plays a main role when RPE. In the pathophysiological process of RPE, the ischemia and hypoxia of the lung tissue lead to a reduction of pulmonary surfactant's formation and secretion. While after reexpantion, PS inactivated by plasma proteins such as albumin, fibrinogen, C-reactive protein. And there would be a loss of its binding hemoglobin; inflammation can promote phospholipase A2 (PLA2) release, speed up the PS, especially DPPC decomposition, so that the PS content decreases.RPE model was established in this study. Based on the model, we do bronchoalveolar by BALF. In some extent, the total protein proportion of BALF reflects that the endothelial cells and alveolar epithelial cell have barrier function. BALF's total protein and plasma's total protein ratio is the lung permeability index, and lung permeability index reflects the protein permeability of lung tissue. Research indicated that the damage of pulmonary vascular endothelial cell and plasma matrix metalloproteinase -9 (MMP-9) are most closely related. The increase of MMP-9 expression and activity are closed related to lung tissue damage and alveolar capillary permeability increase. Also, other studies shows that the using of methylprednisolone reduce the activation of neutrophils and inhibit the release of MMP-9 and may therefore reduce the reexpansion pulmonary edema in lung permeability. In addition, in BALF, we chose the determination of DPPC. Research has shown the large doses of methylprednisolone on the PS activity in maintaining a good influence. Methylprednisolone can significantly reduce lung injury, and reduce the leakage of plasma protein into the alveolar space of the inactivation of PS. In conclusion, methylprednisolone can reduce the reexpansion pulmonary edema in rabbit lung protein leakage and reduce the lung permeability index, and can improve the pulmonary surfactant DPPC content of the active ingredients.Materials and methods:1. Experimental animal preparation and grouping:21 New Zealand male white rabbits which weighted 2.5-3.0kg were randomly divided into three groups:group C, group R and group R+M. Group C was the control group, group R was the reexpansion pulmonary edema group, group R + M was the reexpansion pulmonary edema + methylprednisolone pretreatment group. The experimental animals in the model are fasted the night before.Group R: with 7 days'feeding after the establishment of reexpansion pulmonary edema, inject the rabbits'ear vein with 2.0ml/kg 0.9% saline in the first 20 minutes of its lung reexpansion.Group R + M:with 7 days' feeding after the establishment of reexpansion pulmonary edema, inject the rabbits'ear vein with 3mg/kg methylprednisolone in the first 20 minutes of lung reexpansion.Group C:the ear vein was inject with 2.0ml/kg 0.9% saline.2. Animal modelSlowly inject the Rabbit's ear vein with 3% sodium pentobarbital until corneal reflex disappears. Then fix the rabbit on the autopsy table. Modify the reexpansion pulmonary edema model by Sakao modeling: In the right side of the thorax, incision the fourth and fifth intercostal of the skin, place a sterile rubber cuff into the chest, inject gas (10ml/kg), and sterile silk ligature cuff mouth, then closed the chest. Place the rabbit in the cage for 7 days, then anesthetized again, tracheotomy. After that, measure the pressure of the right carotid artery catheter and connect the polygraph.20 minutes before removing the air bag, inject the rabbit's ear vein by 2.0ml/kg 0.9% group R and 3mg/kg of methylprednisolone of group R + M. Observe for 20 minutes, if vital signs are stable, remove the right side of the chest air bags. In the mean while insertl2F catheter and fix it on the chest wall. In order to completely promote lung recruitment, do vacuum suction through the catheter with a pressure of 20cmH2O, exhaust the chest's air. In the mean while open the tracheotomy tube and ventilator with a simple drum, pulmonary the airway 5 times with a pressure that does not exceed 20 cmH2O. Finally, clamp the chest tube. Take the blood samples correspond. Kill the rabbit by air embolism, open the chest, take the right lung tissue and fix with formalin. It is proved in the light microscopy that the lung tissue has lung biopsy pulmonary interstitial and alveolar edema. The exudate evidently happens, and the neutrophils and monocytes and a series of reexpansion pulmonary edema pathology appears. Finally, clamp the left bronchus, take 20ml/kg 0.9% NaCl solution, do bronchoalveolar lavage in the opening of the airway.3. Specimen collectionAfter 4 hours of reexpansion, in preparing for serum total protein, collect 3ml arterial blood. Bronchial lavage over the same period for the determination of total protein and fluid in the DPPC4. Specimen handling(1) The blood were saved in refrigerator at 4℃for 3 hours, and then the supernatant was centrifuged at 4℃centrifuge (2500r/min,8 min), supernatant after centrifugation home Refrigerator at-80℃.(2) Prepare bronchoalveolar lavage fluid after the success with filtered of impurities by dialysis and sputum, centrifugate centrifuge at 4℃(3000 r/min,10 min), was then place supernatant in-80℃refrigerator.5. Sample testingThe study use Bicinchoninic acid(BCA). And serum and BALF total protein content determination method BALF dppc detected by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).6. Statistics AnalysisSPSS 13.0 statistical software is used for statistical analysis, measurement data as mean±standard deviation (x±s), P<0.05 was considered statistically significantResults1. The differential of the weight among the three groups of male New Zealand white rabbits, and of the recovery lavage fluid showed no statistical significant.2. This experimental model produced by a balloon inserted in the right side of the chest, keeping seven days before the reexpansion. When placing in the first day and seventh day under the X light it can be seen: in the first day,80% compression in the right middle and lower lobe, the seventh day 60% -70%. After the animals were sacrificed, the lung biopsy tissue was produced. Under the light microscope, there was pulmonary interstitial and alveolar edema, exudate clear neutrophils and monocytes and a series of reexpansion pulmonary edema pathology3. The lung permeability index in group R+M (0.007±0.002) was significantly lower than that in group R (0.177±0.004) (p <0.05) with respective DPPC concentration of 101.955±24.544μg/ml and 61.815±28.307μg/ml (p<0.05).Conclusion Methylprednisolone pretreatment may increase the density of pulmonary surfactant and improve lung permeability in rabbit model of reexpansion pulmonary edema. |
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