Protection Effects And Its Underlying Mechanism Of Alpha-lipoic Acid On Myocardial Ischemia/Reperfusion Injury

ObjectiveIn recent years, cardiovascular diseases, especially coronary heart disease, increasedwhich serious harm to human health. When the coronary arteries blocked, the primarytreatment shall be restore its blood supply, to improve myocardial blood perfusion. Thereperfusion could make the ischemia/reperfusion injury happen, which could increase theinfarct size, cause the malignant arrhythmias and reduce the heart function. Now, weconsidered that the ischemia/reperfusion injury likely associated with oxygen free radicalsincreases, apoptosis of myocardial cells, calcium overload, infiltration of inflammatorymediators and other relevant factors. Alpha-lipoic acid(LA) is a kind of universalantioxidant which found in vegetables and meat. It can reduce the free radicals, chelatingmetal ions. There are some studies shown that LA plays an obvious role in the treatment ofsome oxidative stress-related disease. And the studies of LA’s protective effects onmyocardial ischemia/reperfusion injury are in progress. The present study attempted toinvestigate the protection effects and its underlying mechanism of LA on myocardialischemia/reperfusion injury. Methods1. Adult male Sprague-Dawley (SD) rats, weight220to250g were randomly dividedinto the following groups (n=10):(1) sham operation group (sham I/R);(2)I/R+vehicle group (I/R+V);(3)I/R+a-Lipoic acid group (I/R+LA); and (4) a-Lipoicacid+I/R+wortmannin group (I/R+LA+W). LA (99%, Sigma, USA,15mg/kg) wasgiven by tail vein injection30min before ischemia. Wortmannin (Sigma, USA,15mg/kg) was injected via tail vein5min before LA injection. The MI/R animal modelwas constructed by left anterior descending coronary artery (LAD) ligation.2. After3h of reperfusion, myocardial cellular damage was evaluated by measuringlactate dehydrogenase (LDH) and creatinine kinase (CK) activity in plasma.Myocardial apoptosis was determined by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling(TUNEL) staining and caspase-3activity. And after3h of reperfusion, myocardial samples were taken from the AARzones for MPO activity analysis and TNF-a level measurement.3. After24h of reperfusion, myocardial infarct size was evaluated by Evans Blue andTTC staining.4. After72h of reperfusion, left ventricular end-systolic volume (LVESV), leftventricular end-diastolic volume (LVEDV) and left ventricular ejection fraction(LVEF) were calculated by M-mode echocardiography.5. The expression and activation of HO-1, Nrf2, iNOS, Akt, phospho-Akt (Ser-473),p38-MAPK, phospho-p38-MAPK, eNOS, phosphoeNOS, were extracted from themyocardium after3h or24h of reperfusion by western blot.ResultsOur results reveal that LA administration significantly reduced LDH and CK release(P<0.01), attenuated myocardial infarct size(P<0.01), decreased cardiomyocytesapoptosis(P<0.01), and partially preserved heart function(P<0.05). Western blot analysisshowed that LA pretreatment up-regulated Akt phosphorylation and Nrf2nucleartranslocation while producing no impact on p38MAPK activation or nitric oxide (NO)production. LA pretreatment also increased expression of HO-1, a major target of Nrf2. LA treatment inhibited neutrophil accumulation and release of TNF-a. Moreover, PI3Kinhibition abolished the beneficial effects of LA.ConclusionsThis study indicates that LA attenuates cardiac dysfunction by reducingcardiomyoctyes necrosis, apoptosis and inflammation after MI/R. LA exerts its action byactivating the PI3K/Akt pathway as well as subsequent Nrf2nuclear translocation andinduction of cytoprotective genes such as HO-1.