The saponin of red ginseng protects the cardiac myocytes against ischemic injury in vitro and in vivo

Steamed root of Panax ginseng C.A. Mayer, known as "red ginseng", differs from other ginseng preparations in terms of its saponin components and content, as some partly deglycosylated saponins are produced as artifacts during the steaming process. However, whether saponins derived from red ginseng (SRG) can have a protective effect on cardiomyocytes remains unknown. The present study aimed to explore the effect of SRG on myocardial ischemia in vitro and in vivo. MTT assays revealed that SRG pretreatment significantly increased the viability of cardiomyocytes injured by Na(2)S(2)O(4) hypoxia in vitro. This effect was almost completely abolished by glibenclamide, a blocker of the ATP-sensitive potassium channel, but the cardioprotective activity of SRG was not influenced by the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002. SRG also significantly reduced the Na(2)S(2)O(4)-induced increase in intracellular calcium, as shown by Fluo-3/AM probes with flow cytometry. Adult rat heart ischemia, which was induced by ligation of the left anterior descending coronary artery, was employed for the in vivo analysis. SRG pretreatment reduced infarct size and resulted in a higher left ventricle (LV) developed pressure, LV (+)dP/dt(max) and LV systolic pressure and lower LV (-)dP/dt(max) and LV end diastolic pressure after 24h of ischemia. Moreover, SRG significantly reduced the level of cardiac Troponin I (cTnI) in the serum, which suggests that cTnI, a protein component of the troponin regulatory complex involved in cardiac contractility, contributes to the SRG-mediated recovery of cardiac systolic function. In conclusion, this study is the first to provide evidence and a mechanistic analysis of the cardioprotective effects of SRG. SRG significantly attenuated myocardial ischemic injury by improving cardiac systole function, partly by reducing cTnI secretion and improving cardiac diastolic function. Also, SRG attenuated the Ca(2+) overload in cardiomyocytes and modulated the K(ATP), but not PI3K, signaling pathway; taken together, these mechanisms synergistically reduced infarct size.