| Asperosaponin VI (ASAVI) is a saponin of the medicinal herb Dipsacus asper(Xuduan), and no pharmacological activity has been reported yet. The present study was designed to investigate the therapeutic effect of ASAVI on myocardial ischemia and to clarify the underlying biochemical mechanism through setting up the models in vivo and in vitro.To investigate the therapeutic effect of ASAVI on acute myocardial infarction (AMI)in rats, AMI in rats was induced by ligating the descending anterior branch of the left coronary artery. The results in rats showed that ASAVI reduced the levels of creatine kinase(CK), lactate dehydrogenase(LDH), glutamic oxalacetic transaminase(GOT) and cardiac troponin T(cTnT) in serum to near normal levels, decreased the elevation in ST-segment level and infarction area, and increased the survival rate. ASAVI also increased the levels of glutathione peroxidase(GSH-Px) and superoxide dismutase(SOD) levels in heart, and decreased that of malondialdehyde(MDA) level in AMI rats. Under the same dose of ASAVI, the activities of mitochondrial enzymes(succinate dehydrogenase(SDH), isocitrate dehydrogenase(ICDH), malate dehydrogenase(MDH) and a-ketoglutarate dehydrogenase(a-KGDH)) and those of ATP content were raised, whereas Ca2+ level, was lowered. At the same time, ASAVI enhanced the activities of mitochondrial SOD and the activity of myocardium mitochondria, ameliorated the mitochondria swelling and decreased the MDA contents, respectively. In addition, histopathological observations demonstrated the same protective effects. ASAVI reduced the number of apoptosis cadiocytes in accordance with the upregulation of Bcl-2/Bax ratio.To investigate the therapeutic effect of ASAVI on AMI in dogs, AMI in dogs was induced by ligating the descending anterior branch of the left coronary artery. The results in dogs demonstraed that ASAVI reduced the levels of CK, LDH and GOT in serum to near normal levels, prevented the elevation of the degree of myocardial infarction(∑-ST), the range of myocardial infarction(N-ST)and the infarction area. In addition, ASAVI signifacently improve the parameters of hemodynamics in AMI dogs, such as increasing the left ventricular systolic pressure (LVSP), ventricular pressure maximal change rate(±dp/dtmax), coronary blood flow(CBF), cardiac blood flow(MBF), cardiac output(CO), stroke volume(SV)and cardiac index(CI), and decreasing the left ventricular end diastolic pressure (LVEDP), total peripheral vascular resistance(TPVR), coronary vascular resistance(CVR) and cardiac oxygen intake ratio(MOUR)。In order to investigate the underlying mechanisms of the cardioprotective role of ASA VI, the H9C2 myocytes damaged by H2O2 simulated the oxidative stress. The results in vitro experiments demonstrated that ASAVI increased the survival rate of cardiac myocytes, reduced the release of LDH and CK from the myocytes and the generation of MDA, increased the activity of SOD in myocytes, ameliorated histochemical characterization of H2O2-induced apoptotic myocytes, reduced apoptosis percentage, stablized the mitochondrial membrane potential, reduced the intracellular calcium overload. Meanwhile, ASA VI treatment inhibited apoptosis in H2O2-induced cardiomyocyte by increasing Bcl-2/bax ratio, inhibiting the release of cytochrome C (Cyt C) in mitochondria and decreasing active Caspase-3 expression, as well as enhancing the expression of p-Akt and p-CREB. Moreover, the protective effects of ASA VI in vitro were prevented by phosphatidylinositol-3-kinase (PI3K) inhibitor LY294002 treatment.In consequence, ASA VI could provide significant cardioprotective effects against AMI in rats or dogs, and oxidative stress in H9C2 cells damaged by H2O2. Based on the above experiments in vivo and in vitro, it was proved that ASA VI protected the cardiac myocyte from apoptosis probably owing to reducing free radical damnification, decreasing intracellular calcium overload, and protecting the mitochondria. The molecular mechanism of ASAVI against cardiomyocytes apoptosis was probably by activating the PI3K/Akt and CREB pathways. Key Words:ASAⅥ; Myocardial ischemia; Apoptosis; Akt; CREB... |
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