Abstract
OBJECTIVES: To investigate the molecular mechanism by which salvianolic acid B (Sal-B) modulates mitochondrial functional homeostasis and alleviates myocardial ischemia-reperfusion (I/R) injury in mice. METHODS: Mouse cardiomyocyte HL-1 cells were pretreated with 5 μmol/L Sal-B with or without sh-Sirt1 transfection before exposure to hypoxia-reoxygenation (HR), and the changes in ATP production, mitochondrial superoxide activity, substrate oxidation level were evaluated. In the animal experiment, 36 C57BL/6J mice were randomized into 3 groups (n=12) for sham operation or ligation of the left anterior coronary artery to induce myocardial I/R injury with or without intravenous injection of Sal-B+I/R (50 mg/kg). In the rescue experiment, 60 adult C57BL/6J mice were randomized into 5 groups (n=12): sham-operated group, myocardial I/R group, Sal-B+I/R group, I/R+Sal-B+Sirt1fl/fl group, and I/R+Sal-B+cKO-Sirt1 group. Myocardial injury was evaluated with HE staining, and cardiac function was assessed by measurement of the ejection fraction and fractional shortening using echocardiography. RESULTS: In HL-1 cells with HR injury, Sal-B pretreatment significantly increased cellular ATP production, reduced mitochondrial superoxide anion levels, and enhanced oxygen consumption level. In the mouse models of myocardial I/R injury, Sal-B pretreatment markedly ameliorated I/R-induced structural disarray of the cardiac myocytes and improved cardiac ejection. Cycloheximide chase with Western blotting and ubiquitination assays after Sirt1-IP showed that Sal-B significantly inhibited Sirt1 degradation in HL-1 cells. Sirt1 knock-down reversed Sal-B-induced increases in ATP production, reduction in superoxide, and elevation of OCR in HL-1 cells. Cardiomyocyte-specific Sirt1 knockout obviously reversed Sal-B-mediated improvement in cardiac ejection function and myocardial structure damage in mice with myocardial I/R injury. CONCLUSIONS: Sal-B promotes mitochondrial functional homeostasis in cardiomyocytes with HR injury and improves cardiac function in mice after myocardial I/R by inhibiting Sirt1 protein degradation.