| Objective:To explore the protective effects and the mechanisms of asiatic acid(AA)on myocardial ischemia injury in mice.Methods:Male C57BL/6 mice were intraperitoneally anesthetized by chloral hydrate at the dose of 30 mg/kg.The model of myocardial infarction(MI)was established by ligation of left anterior descending(LAD)artery after thoracotomy.The mice were randomly divided into five groups:?group A:the sham group;?group B:the MI group;?group C:low-dose group[25 mg/(kg·d)];?group D:middle-dose group[50 mg/(kg·d)];?group E:high-dose group[100 mg/(kg d)].The LADs of the mice of the sham group were only threaded rather than ligated.Each group was administered intragastrically with relevant medicines for two weeks after the operations(Sham group and MI group were given equal volume of saline).Two weeks after surgery,echocardiography was used to detect left ventricular structure and function changes;Evans blue and 2,3,5-Triphenyl-2H-tetrazolium chloride(TTC)staining was used to detect myocardial infarct size;terminal deoxynucleotidy transferate mediated dUTP fluorescein nick end labeling(TUNEL)was used respectively to detect the cardiomyocyte apoptosis;the cardiac muscle tissue was stained by hematoxylin eosin staining(HE)to observe its pathological changes;colorimetry were used to examine Lactate Dehydrogenase(LDH),Creatine kinase-MB(CK-MB),Superoxide Dismutase(SOD)and malondialdehyde(MDA)in serum.and the p-p38 and p38 proteins expression were determined by Western blot.Results:1.AA improved cardiac function after myocardial ischemia in mice2 weeks after MI surgery,LVESD and LVEDD in the model group were significantly increased than the sham operation group(4.78 ± 0.67 vs 2.57 ± 0.31 mm;5.77 ± 0.59 vs 3.93 ±0.24 mm,P<0.05);LVEF and LVFS were significantly lower than the sham operation group(32.8 ± 2.97 vs 63.5 ± 3.11%;24.1 ± 2.77 vs 43.1 ± 2.94%,P<0.05).Compared with the model group,LVESD(4.42 ±0.58 vs 4.78±0.67 mm)and LVEDD(5.55±0.41 vs 5.77± 0.59 mm)in the group of AA 25 mg/(kg· d)had tendency to reduce but no statistical significance(P>0.05).LVESD of the group AA 50mg/(kg·d)and 100 mg/(kg·d)were(4.06 ±0.45)mm and(3.38±0.69)mm respectively,which was significantly less than that of the model group(4.78 ± 0.67mm,5.77 ± 0.59mm).LVEF and LVFS of the group AA 50mg/(kg·d)and 100 mg/(kg·d)were both greater than that of the model group,the differences were statistically significant(P<0.05).2.AA reduced MI area of mice after myocardial ischemiaThe results of Ivins blue/TTC double staining showed that the MI area of the model group was significantly higher than that of the sham operation group,which was up to(34.3 ± 3.22)%,which proved that the myocardium was damaged after ischemia.Compared with model group,MI area of low,medium and high dose groups were lower,among which the effect of medium and high dose group were obvious.The differences were statistically significant(P<0.05).There was a decrease in MI area of the low-dose group,which was(30.1 ± 3.53)%;however,compared with the model group,there was no significant difference(P>0.05).3.AA reduced myocardial apoptosis of myocardial ischemic in miceThe results of TUNEL showed that the apoptosis cells of the sham operation group were very few,and the apoptosis rate was only(5 ± 0.80)%.While the model group brought out more apoptotic cells and the apoptosis rate was as high as(42.8 ± 5.54)%(P<0.05).Compared with the model group,the apoptosis cells in AA medium and high dose group were significantly decreased(P<0.05),and the apoptosis rate were(35.1 ± 5.15)%,(28.6 ± 3.98)%respectively.Compared with the model group,the apoptosis rate decreased in low dose group,which,however,showed no significant difference(39.2 ± 4.64%,P>0.05).4.AA reduced the structural damage of cardiac myocardial tissue in mice after myocardial ischemiaHE staining results showed that myocardial cell necrosis and fibrosis were more in the model group than that in the sham operation group.The myocardial cells in the model group which were hypertrophic arranged disorder.Myocardial cells in the medium and high dose groups were orderly,and the area of cell necrosis and fibrosis decreased than that of the model group.5.The protective effect of AA on myocardial injury after myocardial ischemiaResults showed that the LDH and CK-MB levels were significantly higher in the model group than that in the sham operation group(5874 ± 110.7 vs 1634 ± 123.3 U/L;1497 ± 176.6 vs 322.1 ± 127.1 U/L,P<0.05).Compared with the model group,LDH and CK-MB levels were significantly reduced in low,medium and high dose groups(P<0.05).6.AA improved SOD level and MDA content in mice after myocardial ischemiaCompared with the sham operation group,SOD level of the model group decreased(215 ± 59.1 vs 324 ± 62.2 kU/L),and the MDA content of the model group increased(6.72 ± 0.48 vs 4.41 ± 0.31 ?mol/L).Such differences were statistically significant(P<0.05).Compared with the model group,the SOD level of each treatment group was increased;but SOD level of high dose group was statistically significant.The MDA content of medium and high dose groups decreased significantly than that of the model group(P<0.05).The results mentioned above illustrated that AA had obvious protective effect on myocardial injury of myocardial ischemic mice.7.AA reduced the expression level of p-p38Western blot results showed that the expression level of p-p38 protein in the model group was significantly higher than that in the sham operation group(P<0.05).The expression level of p-p38 protein in each treatment group which compared with the model group was lower accordingly.Meanwhile the results showed that pharmacological effect of AA that reduced protein expression level was dose dependent.Conclusions:AA has a protective effect on cardiac function after MI in mice,which is achieved by reducing the area of MI after ischemia,alleviating the level of myocardial apoptosis,and improving myocardial tissue damage after ischemia.Its specific mechanism may be related to the decrease of oxidative stress and the overexpression of p-p38 in the signal transduction pathway in mice with MI. |
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