Study On The Mechanism Of Lipopolysaccharide Pretreatment To Reduce Myocardial Ischemia-reperfusion Injury

Objective:The objective of the present study is to explore the protective effect of lipopolysaccharide(LPS)pretreatment on myocardial ischemia reperfusion injury in mice,and explore its possible related mechanism.Methods:Thirty male C57BL/6 mice(initial 8 weeks of age,weight about20g)were selected and randomly divided into control(NC)group and LPS pretreatment(NL)group(n=15).Both the NC group and the NL group were cultured under constant oxygen for 7 days(the laboratory altitude was about600 meters).Mice in the NL group were intraperitoneally injected with lipopolipaccharide(LPS)1.5mg/kg/d from the first day of culture for 7consecutive days,and other cultures were the same as those in the NL group.All mice were free to drink and feed,the temperature was controlled at 22-26℃,and the day-night ratio was 12 hours :12 hours.7 days later,the left anterior descending coronary artery(LAD)was ligated for 30 minutes,and blood perfusion was restored for 24 hours to establish myocardial ischemia reperfusion(I/R)injury model.The state of mice was observed by monitoring the changes of general conditions,body weight and fasting blood glucose.Pathological staining was used to observe the histopathological changes of myocardium in each group.Western blot was used to detect the expression of inflammatory factors and glycosylated modified proteins in myocardial tissue.EVANS BLUE-Triphenyltetrazolium chloride(TTC),a double-staining method was used to determine the concentration of mi in mice.Results: 1 Effect of lipopolysaccharide pretreatment on basic signs of miceThrough close observation and monitoring of mice every day,obviously we found that the weight of mice in the NL group decreased from the 1st day after LPS injection,and gradually increased from the 5th day after LPS injection,comparing with the NC group.General conditions,such as body hair flexibility and activity,were relatively poor.There was no significant difference in fasting blood glucose between the two groups on day 1 or day 7(P>0.05).2 Effect of lipopolysaccharide pretreatment on inflammatory expression in myocardium of miceHE staining was used to pathologically detect the myocardial tissue of mice in the two groups,and it was found that compared with the NC group,the myocardial cells in the NL group were closely arranged and the infiltration of inflammatory cells was increased.The expressions of tumor necrosis factor(TNF-α)protein in the myocardium of the NL group increased significantly,comparing with mice in the NC group,and the difference was statistically significant(P < 0.05).3 Effect of lipopolysaccharide pretreatment on myocardial infarction area after I/R in miceUsing EVANS BLUE-TTC staining method,by means of two groups of mice after I/R surgery myocardial infarction size analysis found that compared with NC group,myocardial infarction area in NL mice(infarct size,IS)relative to the dangerous area(area at risk,AAR)significantly reduced,and the difference IS statistically significant(P < 0.05),and dangerous area relative to the area of the left ventricle,left ventricle,LV)has no obvious difference(P>0.05).4 Effects of lipopolysaccharide pretreatment on glycosylation level of mouse myocardial tissueAfter 7 days of culture,Western blot assay was used to detect the total glycosylated levels of O-glc NAc protein,OGT protein,O-Glcnacase(OGA)protein and UDP galactose-4-heterozygous isomerase(GALE)protein in the myocardial tissues of mice in the two groups.In the NL group,the expression levels of glyco-modified proteins such as O-GLCNAC,OGT,OGA and GALE in the myocardial tissue of mice were all increased,and their respective differences were all significant statistically(P < 0.05).Conclusion: After pretreatment of lipopolysaccharide,myocardial presents a state of chronic inflammation in mice.In this kind of lipopolysaccharide preprocessing myocardial tissue in mice caused by chronic inflammation state glycosylation modification levels rise,and lipopolysaccharide preconditioning on myocardial ischemia reperfusion in mice after myocardial infarction area decreases.As a result,we found that the lipopolysaccharide preconditioning can alleviate myocardial ischemia-reperfusion injury in mice,and its mechanism might be elevated by glycosylation modification level to play a role.