| Background and ObjectiveSmoke inhalation injury refers to the inhalation of toxic smoke or chemical substances into the respiratory tract caused by injury,which is a common complication in thermally injured patients,particularly in patients with flame burns.Sometime maybe combine with severe pulmonary substance injury.Symptoms of mild symptoms such as irritating cough,chest tightness and other discomfort,severe cases may have airway obstruction,pulmonary emergencies,and even lifethreatening acute respiratory distress syndrome(ARDS)and multiple organ dysfunction syndrome(MODS).However,the current research shows that in addition to the direct respiratory tract damage caused by heat,the particles and chemicals contained in the smoke also play an important role in the occurrence and development of smoke inhalation injury.When all kinds of particles and chemicals in the smoke enter the respiratory tract,it will cause a large number of inflammatory cells and the inflammatory mediators released in the respiratory tract,which will cause the body to produce a series of stress reactions.At the same time iNOS through various cell signaling pathways lead to apoptosis,exacerbating the occurrence of lung tissue damage.Many components of the smoke are strong oxidants,and a large number of inflammatory response cells accumulate in the lung when the inflammatory response is out of control.Overproduction of reactive oxygen species(ROS)can also induce oxidative stress injury.Several studies have shown that inhalation injury after neutrophil activation,arachidonic acid metabolism and other lead to increased oxygen free radicals.Oxygen free radicals can cause lipid peroxidation of polyunsaturated fatty acids on cell biofilms,producing lipid peroxides,leading to cell damage.Simvastatin as a hydroxymethyl glutaryl-A(HMG-COA)reductase inhibitor,once used as a classic lipid-lowering drugs in clinical treatment is widely used.Simvastatin not only can significantly reduce the incidence of cardiovascular events in patients with hyperlipidemia,and with the deepening of clinical research,it was found that simvastatin also has anti-inflammatory and anti-oxidant effects,independent of lipid-lowering effect.The purpose of this experiment was to observe the protective effect of simvastatin on lung injury induced by smoke inhalation in rats.MethodsAccording to the principle of randomization,75 S-D male rats were divided into 5 groups: normal group,saline group,low dose group,medium dose group and high dose group,with 15 rats in each group.The rats in saline group,low dose group,middle dose group and high dose group were inhaled by smoke for 6 minutes respectively.The rats in low dose group,medium dose group and high dose group were given simvastatin according to body weight 25 mg / kg,50 mg / kg,100 mg / kg were given.The rats in saline group were administrated with the same amount of saline,and all rats were given gavage with interval of 12 hours.Rats were sacrificed at 24 h,48h,72 h after smoke injury.10% chloral hydrate solution 350 mg / kg were given intraperitoneal injection.Take 2ml blood from aorta after the success of the anesthesia,and then take the left lung to do the pathology examination and the pathology scoring.At the same time,the expression of iNOS and Caspase-3 mRNA was detected by real-time quantitative polymerase chain reaction(RT-qPCR)in the right upper lobes,the expression of i NOS and Caspase-3 was detected by Western Blot in the right middle lobes,the activities of superoxide dismutase(SOD),malondialdehyde(MDA)in serum and lung tissues were measured in the lower lobes.Results 1.Pathological examination and scoresBy light microscopy,the normal lung tissue alveolar structure was complete,with uniform alveolar intervals and an alveolar cavity with no exudate or leukocyte infiltration.The lung tissues exposed to smoke in the saline group,low-dose,middle-dose and high-dose groups showed hemorrhage,alveolar septal edema,and extensive neutrophil infiltration to varying degrees.The alveolar cavity contained a visibly large number of inflammatory cells and high erythrocyte exudation.In the simvastatin group,the inflammatory response was significantly reduced.The pathological scores of the saline,low-dose,middle-dose and high-dose groups were higher than that of the control group(P<0.05).Compared with the saline group,the pathological scores of the low-dose,middle-dose and high-dose groups were decreased(P<0.05).Compared with the low-dose group,the pathological scores of middle-dose group and high-dose group were decreased(P<0.05),and the difference between the middle-dose group and high-dose group showed no statistical significance(P>0.05).2.ImmunohistochemistryCompared with the control group,iNOS and Caspase-3 expression in the saline group,low-dose group,medium-dose group and high-dose group was increased(P<0.05).Compared with the saline group,iNOS and Caspase-3 expression in the low-dose,middle-dose and high-dose group was decreased(P<0.05).Compared with the low-dose group,iNOS and Caspase-3 expression in the middle-dose and high-dose groups were decreased(P<0.05),but no significant difference was evident between the middle-dose and high-dose groups(P>0.05).3.RT-qPCRCompared with the saline group,iNOS and Caspase-3 mRNA expression was lower in the low-dose group,middle-dose group and high-dose group(P<0.05).Compared with the low-dose group,iNOS and Caspase-3 mRNA expression in the middle-dose group and high-dose group were decreased(P<0.05).Compared with the middle-dose group,iNOS and Caspase-3 mRNA expression in the high-dose group showed no significant difference(P>0.05).4.Western BlotCompared with the control group,iNOS and Caspase-3 expression in the saline group,low-dose group,middle-dose group and high-dose group increased(P<0.05).iNOS and Caspase-3 expression was lower in the low-dose group,middle-dose group and high-dose group than in the saline group(P<0.05).iNOS and Caspase-3 expression was lower in the middle-dose group and high-dose group than in the low-dose group(P<0.05).However,no significant difference in iNOS and Caspase-3 expression was evident between the middle-dose group and the high-dose group(P>0.05)5.SODCompared with the control group,the SOD activities in the lung tissues and serum of the saline group,low-dose group,middle-dose group and high-dose group were decreased(P<0.05).Compared with the saline group,the SOD activities in the lung tissues and serum of the low-dose group,medium-dose group and high-dose group were significantly increased(P<0.05).Compared with the low-dose group,the SOD activities in the lung tissue and sera of the middle-dose and high-dose group were increased(P<0.05),while the SOD activities have in serum no significant difference between high dose group and medium dose group(P> 0.05),The activity of SOD in lung tissue was higher than that in middle dose group except 48H(P <0.05).6.MDAThe levels of MDA in serum and lung tissue of saline group,low-dose group,medium-dose group and high-dose group were significantly higher than those of control group at three time points(P<0.05).Compared with saline group,the content of MDA in serum and lung tissue of low dose group,medium dose group and high dose group were decreased(P <0.05).Compared with the low dose group,the content of MDA in serum and lung tissue of medium-dose group and high-dose group decreased(P <0.05).Compared with the medium-dose group,content of MDA serum and lung in high-dose group was no significantly statistical different except for 48 H serum(P> 0.05).Conclusion 1.Through this experiment,we can demonstrates that simvastatin can inhibit the expression of iNOS and Caspase-3,down regulate the synthesis of NO and the apoptosis of lung cells.2.Simvastatin also has some anti-oxidative effects and inhibits excessive oxidative stress in smoke inhalation injury,thus having a protective effect on smoke inhalation injury.3.The therapeutic effect of simvastatin on smoke inhalation lung injury was positively correlated with dose within a certain range. |
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