The Myocardial Protective Effcts And Its Mechanism Of Clopidogrel Preconditioning On Septic Rats

Objective:To explore the role of platelet aggregation and the effects of clopidogrelinhibiting platelet P2Y12receptor in endotoxin-induced myocardial injury.Methods:Seventy-two Wistar rats were randomly divided into threegroups: normal control group (NC,n=24), endotoxin group (ET,n=24),clopidogrel pretreatment and endotoxin group (CL+ET，n=24). Then each groupwas divided into3subgroups:0h,6h,12h. Rats in NC group were injectedintraperitineally with NS2ml/kg. Rats in ET group and CL+ET group wereinjected intraperitineally with LPS(10mg·kg-1) to establish an acute cardiacinjury model,then continuous intragastric administration of clopidogrel wereadministrated for three days. Each group was observed at three timepoint(0,6,12h,n=8).Platelet aggregation was tested with impedance plateletaggregometry; serum cTnI in blood was determined with che+luminescenttechnique; serum CK-MB was assayed by enzymology; the expressions ofTNF-α in blood and cardiac myocytes were measured with enzyme-linked immunoadsorbent assay(ELISA) kits; myocardial tissues were determined withdry-wet weight ratios;myocardial pathological damage was observed under thelight at certain time(0h,6h,12h).Results:1. The rats behavioral expressionThere were no significantly changes in the NC group at all time points.Rats in ET group had mental fatigue, insensitive, less dynamic, gregarious, dullcoat, shaggy hair,unhairing and convulsion, and the symptoms became worseas time goes by. Compared with the NC group at all time points, the changes ofbehavioral expression of rats in the CL+ET group were started after injectedintraperitineally with LPS, but somewhat less severe than those in the ETgroup.2. The pathomorphological changes of rats myocardial tissue under lightmicroscopeThe results showed that the cardiac structure was normal in the NC group.The myocardial damage could be observed in ET-6h group: the inflammatorycells were infiltrated,the fibrilla of myocardial cell were swelled,their cristaewere disrupted,and the most severe myocardial damage could be observed withtime go by. Compared with the ET group at all time points, the changes ofrats in the CL+ET group were less severe.3. The comparison of serum cTnI in each groupThere were no statistic differences in the expression of cTnI between threegroups at0h. The expression of cTnI at ET-6h group and ET-12h group wasdramatically higher than in the NC group and the CL+NC group at the sametime point，the statistic differences were significant (P＜0.05).However,compared the NC group with the CL+ET group，the expressions of cTnI had no statistic differences (P＞0.05).4. The comparison of serum CK-MB activity in each groupThere were no statistic differences in CK-MB activity between threegroups at0h. CK-MB activity at ET-6h group and ET-12h group wasdramatically higher than in the NC group and the CL+NC group at the sametime point，the statistic differences were significant (P＜0.05).However,compared the NC group with the CL+ET group，the expressions of CK-MBactivity had no statistic differences (P＞0.05).5. The comparison of dry-wet weight ratios of myocardial tissues in eachgroupThere were no statistic differences in dry-wet weight ratios between threegroups at0h and6h(P＞0.05). Compared with the NC-12h group and theCL+ET-12h group，dry-wet weight ratios of myocardial tissues in the ET-12hgroup was decresased markedly, the statistic differences were significant (P＜0.05); but there were no statistic differences in dry-wet weight ratios betweenthe NC-12h group and the CL+ET-12h group.6. The comparison of platelet aggregation in each groupPlatelet aggregation in the CL+ET-0h group was much lower than that inthe NC-0h group and the CL+ET-0h group, and the statistic differences weresignificant (P＜0.05). There were no statistic differences when compared withthose in the NC-0h group and the CL+ET-0h group(P＞0.05). There werestatistic differences in platelet aggregation between three groups at6h and12h(P＜0.05)，and pairwise comparison are statistically significant(P＜0.05).7. The comparison of TNF-α of serum and myocardium tissue in each groupThe results showed no statistic differences in TNF-α of serum andmyocardium tissue between three groups at0h (P＞0.05). There were statistic differences in TNF-α of serum and myocardium tissue between three groupsat6h and12h (P＜0.05)，and pairwise comparison are statistically significant(P＜0.05).Conclusions:1. Myocardium tissue pathological changes could be observed, while thelevel of platelet aggregation and myocardial injury biochemical markers ofcTNI, CK-MB increased. Meanwhile, the expression TNF-α in serum andmyocardium tissue rised dramatically.2. By administration of clopidogrel preconditioning, we can observe thedecreasing of TNF-α level and myocardial damage degree.The mechanism ofclopidogrel for preventing myocardial injury in sepsis is inhibiting plateletADP-P2Y12-GPIIb/IIIa signal transduction pathways and platelet activition,then reducing inflammatory reaction.