Ginsenoside Rb1 preconditioning protects against myocardial infarction after regional ischemia and reperfusion by activation of phosphatidylinositol-3- kinase signal transduction

Background: Ginsenoside Rb1, a major bioactive component of Panax ginseng, bears various beneficial effects on the cardiovascular system. This study investigated whether ginsenoside Rb1 preconditioning has protective effects on myocardial ischemia-reperfusion injury and its potential mechanism. Methods: Rats subjected to 45 min of myocardial ischemia followed by 120 min of reperfusion were assigned to the following groups: sham-operated, ischemia-reperfusion (I/R), ginsenoside Rb1+I/R, wortmannin(a specific PI3K inhibitor)+I/R, wortmannin drug vehicle (dimethyl sulfoxide, DMSO), wortmannin+sham, ginsenoside Rb1+ wortmannin +I/R. Infarct size was assessed by triphenyltetrazolium chloride staining. Plasma creatine kinase (CK), creatine kinase isoenzyme MB (CK-MB), lactate dehydrogenase (LDH), and troponin T levels were also measured. Akt phosphorylation expression was assessed by immunoblotting. Results: Ginsenoside Rb1 preconditioning reduced infarct size compared with that in the I/R group: 30±2.6% versus 51±2.7% (p<0.01). Ginsenoside Rb1 preconditioning also markedly reduced the plasma CK, CK-MB, LDH and troponin T levels in blood. Akt phosphorylation expression increased after ginsenoside Rb1 preconditioning. These effects of ginsenoside Rb1 preconditoning were significantly inhibited by wortmannin. Conclusion: This is the first study to demonstrate that ginsenoside Rb1 preconditioning has protective effects on myocardial ischemia and reperfusion injury, partly by mediating the activation of the PI3K pathway and phosphorylation of Akt.