Tetrandrine reduces infarct size and preserves cardiac function in rat myocardial ischemia/reperfusion injury through activation of Akt/GSK-3b signaling

Objective: This study aims to determine the effect of TTD on myocardial ischemia/reperfusion (MI/R) injury (a pathological condition where ROS production is significantly increased) and to investigate the underlying mechanisms. Methods: This study utilized an in vivo rat model of MI/R injury and an in vitro neonatal rat cardiomyocyte (NRC) model of simulated ischemia/reperfusion (SI/R) injury. Infarct size was measured by Evans blue/TTC double staining. NRC injury was determined by MTT and lactate dehydrogenase (LDH) leakage assay. ROS accumulation and apoptosis were assessed by flow cytometry. Mitochondrial membrane potential (MMP) was determined by 5, 59, 6, 69-tetrachloro-1, 19, 3, 39-tetrathylbenzimidazol carbocyanine iodide (JC-1). Cytosolic translocation of mitochondrial cytochrome c and expression of caspase-9, caspase-3, Bcl-2 family proteins, and phosphorylated Akt and GSK-3b were determined by western blot. Results: Pretreatment with TTD (50 mg/kg) significantly augmented rat cardiac function, as evidenced by increased left ventricular end-diastolic pressure (LVEDP), left ventricular systolic pressure (LVSP) and LV dP/dt. TTD reduced myocardial infarct size, apoptotic cell death, and blood creatine kinase/lactate dehydrogenase levels after MI/R. In NRCs, TTD (10 mM) inhibited SI/R-induced ROS generation (P < 0.01), decreased cellular apoptosis, stabilized the mitochondrial membrane potential (MMP), and attenuated cytosolic translocation of mitochondrial cytochrome c. TTD inhibited activation of caspase-9 and caspase-3, increased the phosphorylated Akt and GSK-3b, and increased the Bcl-2/Bax ratio. Conclusions: These data demonstrate that TTD mediated cardioprotective effect against MI/R-induced apoptosis via a mitochondrial-dependent apoptotic pathway.