| ObjectiveTraumatic acute lung injury accounts for 25% of trauma deaths, more effective treatment methods are needed. We hypothesize Schisandrin B can exert the effect of lung protection. We aim to establish a rat model of bilateral isolated pulmonary contusion leading to the event of Acute Lung Injury(ALI) using a cylindrical weigh free falling method. After stable replication of traumatic ALI model, we set observe the histopathological changes of acute lung injury in response to oxidative stress pathways, and the protective effect of schisandrin B in traumatic acute lung injury by the change of lipid peroxide malondialdehyde (MDA) content and antioxidant enzyme activity superoxide dismutase (SOD) activity as well as iNOS protein expression. In order to provide more content and theoretical support for the clinical application of Schisandrin B in the event of of blunt chest trauma.Materials and Methods50 healthy Spargue-Dawley rats were selected and equally devided using random number method, and randomly assigned to control group (control group) (n= 10), model group (model group, n= 10), Low dose Schisandrin B group (SchB-LD group, n= 10), High dose Schisandrin B group group (SchB-HD group, n= 10) and dexamethasone positive control group (Dex-Group, n= 10),. After intraperitoneal anesthesia, the rat traumatic ALI model was established using a self-made experimental blunt chest trauma set, and a 500g of steel impact weight was dropped from the 40.8cm, reaching 2.0 Joules impact energy. After the hit, rats in SchB-LD group and SchB-HD was immediately injected with Schisandrin B injection solution, the drug is given every 2h, for the total of 3 times. Dexamethasone solution was injected intraperitoneally at the same time. Control group was not manipulated and resumed normal feeding. The rats in each group were fed with free diet and observed closely. In 0-48h, the survival rate of rats in each group was recorded from the aspects of the activity status, respiratory status, the color of the fur, the frequency of foraging, and the number of deaths every 4h. Kaplan-Meier method was used to calculate the survival curve of each group of rats and control and treatment group, and the Rank Log analysis was performed. All rats were sacrificed after 48h. After fixation of lung tissue and conventional dehydration, the tissues were paraffin embedded and 2milimiter sections was obtained. HE staining was used to observe histopathological changes in each group and the extent of injury is determined using semi-quantitative method; MDA content and superoxide dismutase enzyme activity (SOD) is analyzed using ELISA assay; immunohistochemistry staining was used to detect the expression of inducible nitric oxide synthase(iNOS) expression, the expression level is determined using a semi-quantitative method.ResultsCompared to the control group, the lung water content (wet/dry weight ratio) the rats in the model group was significantly increased; pathological score of lung tissue changes in acute lung injury (ALI) increased significantly; lung tissue MDA levels were significantly increased, SOD activity decreased, iNOS protein expression rate increased significantly. The results showed that the oxygen free radical increased, the antioxidant capacity decreased, all the indexes showed significant changes. The results showed that the a successful and reliable rat traumatic ALI model was obtained. The 48h survival curve was significantly different between the treatment group (high and low dose of the Schisandrin B group) and model group, and the survival rate was significantly increased. (X2= 7.16,p<0.01, HR (Mantel-Haenszel)=5.33). The 48h survival curve of high dose Schisandrin B group survival is significantly different compared with the model group, (x2= 6.03, p< 0.01, HR (Mantel Haenszel)=5.03); Between high and low dose of Schisandrin B group and dexamethasone group, the survival rate had no significant difference (x2=0.79,p=0.67).Compare to control group the lung water content increase significantly in model group, (p< 0.01), the lung water content decreased significantly in high and low dose of SCH B treatment group compared with the model group (p< 0.01);Between the high dose and low dose of SCH B treatment groups the lung water content difference have no statistical significance (p= 0.07). The ALI pathological score of high and low dose SCH B treatment group. There was no significant difference between the positive control group and the pathological score of between Schisandrin B group. The levels of MDA in the tissue of the model group was significantly higher than those in the control group, (p<0.01). The level of MDA in the tissue of the high and low dose of the B group was significantly lower than that of the model group, the difference was statistically significant (p<0.05). The activity of SOD in model group was significantly lower than that of control group (p<0.01); the SOD activity in the the high and low dose of the Schisandrin B group was significantly lower than that of the model group, the difference was statistically significant. By One-Way ANOVA analysis, there are no significant difference in the activity of SOD between Schisandrin B groups (F=2.549, p=0.09). iNOS protein expression score:the score of model group was significantly higher than that of the control group, the score of high and low dose of the treatment group was significantly lower than that of model group (p<0.01), the difference was statistically significant. By One-Way ANOVA analysis, high and low dose of the iNOS protein expression in the Schisandrin B group and dexamethasone group was no significant difference between the two groups (F=2.35,p=0.11). Compared with model group, the comparative indicators in Schisandrin B groups have remarkably improved, this includes lung water content (wet/dry ratio), indicating that the decreased permeability of alveolar epithelial cell; pathological score of lung tissue in acute lung injury (ALI) decreased significantly, the level of MDA significantly decreased, activity of SOD significantly increased. iNOS protein expression was significantly decreased, suggesting that schisandrin B exerts the function of lung protection.ConclusionThe current cylindrical weigh free falling method can produce a stable rat traumatic acute lung injury model, the oxidative stress response pathway in lung injury and is one of the targets pathways of potential therapeutic intervention; Schisandrin B can effectively alleviate the traumatic injury of lung pathological changes, pulmonary edema, reduce inflammatory cell infiltration, therefore exerts the lung protection function after trauma, increase the survival rate; For traumatic acute lung injury, the Schisandrin B’s protective role may be associated with reduce content of oxygen free radical therefore reducing the oxidative stress. |
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