Effects Of Atorvastatin On Myocardiocyte Apoptosis And ROS After Acute Myocardial Infarction In Rats

Backgrounds and ObjectiveAcute myocardial infarction (AMI) is a serious menace to human health. After AMI, left ventricular remodeling occurs and results in heart failure in the end. Left ventricular remodeling is the alleosis of myocardial structure, function and phaenotype caused by a series of molecular and corpuscular mechanisms. Recently, people attach more and more attendence on the early and late left ventricular remodeling caused by myocardiocyte apoptosis. Apoptosis is an initiative process of cell death involved many signal molecules and regulatory factors. It is confirmed that oxidative stress could induce apoptosis in different cultivated cells, and the oxidative stress is the common mediator of cell apoptosis. In addition, it is reported that ROS(production of oxidatve stress) could work as a signal molecule. But how ROS induce the apoptosis signal cunduction pathway on earth is still unknown. Many studies indicated that the expression of P53mRNA increased obviously in the process of apoptosis induced by ROS, and P53 could then activate the downstreamed signal molecules. Recent studies attach more and more attention on the non-lipid-lowering effects of statins, especially the effects of anti-inflammation and antioxygen, and both of them were demonstrated clearly. But the effect of statins on apoptosis is still under disputing, different studies yield to different results. Whether statins could inhibit myocardiocyte apoptosis after acute myocardial infarction because of its antioxygen effect is uncertain. Further researching the mechanism of myocardiocyte apoptosis and the effect of atorvstatin, we chose atorvastatin, observed its effect on the content of ROS, the expression of P53mRNA and the apoptosis index in myocardium after myocardial infarction. And then analyzed the correlation of this three indexes.Materials and Methods1.Model and groups Sixty-five healthy male Wistar rats were randomly divided into sham operation group(n=15) and AMI group (n=50). Rats in the AMI group were induced by left anterior descending branch ligation. Thirty six rats survived 24 hours later, and were then randomly divided into AMI control subgroup (n=18) and atorvastatin administered subgroup(n=18). Rats in atorvastatin administered subgroup were treated with atorvastatin (gastric gavage, 40mg/kg/d) for 4 weeks, and rats in AMI control subgroup and sham operation group were treated with only physiological saline.2.Echocardiography analysis After the rats were anesthetized, two-dimensional echocardiography was performed with a 10-MHz (short focus) transducer. Left ventricular end-diastolic diameter (LVEDd), left ventricular ejection fraction (LVEF) and fractional shortening (FS) were obtained from long-axis, short-axis views.3.Detection of ROS Tissue homogenate was made with myocardium from non-infarcted area. And then we detected the content of O^2-·and OH·with colorimetric method respectively.4. Detection of P53 mRNA Sample was collected from non-infarcted myocardium of each rat in the condition of asepsis and free of RNase. Using SYBR Green I Real Time PCR to detect the expresion of P53mRNA. Considering the house-keeping gene GAPDH as contrast, we standarded the expression of P53 mRNA with GAPDH mRNA. And then analyzed the difference in the expression of P53mRNA among the three groups with comparative quantitation. 5.Mensuration of myocardiocyte apoptosis (AI) Tissue from non-infarcted myocardium, we detected the myocardiocyte apoptosis with TUNEL(TdT-mediated dUTP nick end labeling),and then computed the apoptosis index.Reasult1.Generic parameters After four weeks, there were fourteen, thirteen and fourteen rats in the sham operation group,AMI control subgroup and atorvastatin administered subgroup espectively. There were no significant differences in body weight among the three groups (all P >0.05). But the heart weight,the left ventricular weight,the heart weight index and the left ventricular weight index were significantly higher in atorvastatin administered subgroup and AMI control subgroup then in sham operation group (all P<0.05), and those data in atorvastatin administered subgroup markedly decreased(all P<0.05) comparing with AMI control group.2.Echocardiography analysis Compared with sham operation group, there were significant increase of LVEDd (all P<0.05) and reduction of LVEF and FS (all P<0.05) in atorvastatin administered subgroup and AMI control subgroup. Compared with AMI control subgroup, LVEDd significantly decreased in atorvastatin administered subgroup (P<0.05), while the LVEF and FS markedly increased (all P<0.05).3 The content of ROS,expression of P53mRNA and AI In atorvastatin administered subgroup and AMI control subgroup, the content of superoxide anion (O^2-·) and hydroxy radical (OH·), the expression of P53mRNA and the myocardiocyte apoptosis index in non-infarcted myocardium were all significantly higher than these in sham operation group (all P<0.05). Compared with AMI control subgroup, rats in atorvastatin administered subgroup displayed significant reductions of these data in non-infarcted area (all P<0.05).4.Pearson linear regression analysis It indicated that the content of superoxide anion (O^2-·) and the expression of P53 mRNA in non-infarcted myocardium were all correlated positively with the myocadiocyte apoptosis index between atorvastatin administered subgroup and AMI control subgroup (all P<0.05); Moreover, the content of superoxide anion (O^2-·) in non-infarcted myocardium was correlated positively with the expression of P53 mRNA in that two groups as well.Conclusions1.The myocardiocyte apoptosis index in the non-infarcted area increased significantly company with the left ventricular function decreased severely after AMI in rats. Atorvastatin could reduce the myocardiocyte apoptosis index and improve the left ventricular function.2. The content of superoxide anion (O^2-·) and hydroxy radical (OH·), the expression of P53 mRNA in non-infarcted myocardium increased significantly after AMI in rats. Atorvastatin can partly reverse these changes.3. Reactive oxygen species and P53 gene take part in the process of myocardiocyte apoptosis after acute myocardial infarction in rats.4. Inhibition of the content of superoxide anion (O^2-·) and hydroxy radical (OH·), the expression of P53 mRNA in non-infarcted area may be one of atorvastatin's mechanisms to reduce the myocardiocyte apoptosis and to improve left ventricualr function after acute myocardial infarction in rats.