Background/aims: Shenxian-shengmai (SXSM) oral liquid, a Chinese patent compound medicine, has been used to treat sinus bradyarrhythmias induced by mild sick sinus syndrome in clinical practice. Myocardial ischemia, in particular in serious or right coronary-related heart diseases, can cause bradyarrhythmias and cardiac dysfunction. Moreover, reperfusion of ischemic myocardium is associated with additional myocardial damage known as myocardial ischemia-reperfusion (I/R) injury. This study was designed to evaluate the effects of SXSM on bradyarrhythmias and cardiac dysfunction induced by myocardial I/R injury, and to explore the underlying mechanisms.
Methods: Administration of SXSM to adult male Sprague Dawley (SD) rats was achieved orally by gavage and control rats were given equivalent deionized water every day for 14 days. After the last administration, the heart was connected with the Langendorff perfusion apparatus and both groups were subjected to ischemia for 20 min followed by reperfusion for 40 min to induce myocardial I/R injury. Heart rate (HR), left ventricular developed pressure (LVDP), the maximal increase rate of left ventricular pressure (+dp/dtmax) and the maximal decrease rate of left ventricular pressure (-dp/dtmax) were recorded by a physiological signal acquisition system. The heart treated with ischemic preconditioning (IPC) for 3 times at a range of 5 min/time before ischemia served as a positive control group. The hearts without I/R injury served as control group. After reperfusion, superoxide dismutase (SOD), glutathione (GSH) and glutathione peroxidase (GSH-Px) activities in the myocardium were determined by appropriate assay kits. Myocardial SOD1 and glutamate cysteine ligase catalytic subunit (GCLC) expression were assessed by western blot analysis. For the in vitro study, SXSM serum was prepared according to the serum pharmacological method and neonatal rat cardiomyocytes were isolated from the heart of new born SD rats. Neonatal rat cardiomyocytes were pretreated with SXSM serum and subjected to H2O2 or anoxia/ reoxygenation (A/R) treatment to induce oxidative damage. Cell viability was evaluated using a Cell Counting Kit-8 (CCK8) assay. Levels of reactive oxygen species (ROS), SOD, GSH and GSH-Px in cardiomyocytes were determined by appropriate assay kits. SOD1 and GCLC expression were assessed by western blot analysis. Buthionine-[S, R]-sulfoximine (BSO), a GCLC inhibitor, and SOD1 siRNA were also used for identifying the cardiac protective targets of SXSM.
Results: SXSM and ischemic preconditioning (IPC) significantly increased heart rate during myocardial reperfusion and protected cardiac function against myocardial I/R injury, including an increase in left ventricular diastolic pressure (LVDP), the maximal increase rate of left ventricular pressure (+dp/dtmax) and the maximal decrease rate of left ventricular pressure (-dp/dtmax). We also found that SXSM and IPC improved the expansion of myocardial interstitium, the structural abnormality and morphological changes of cardiomyocytes induced by I/R injury. Meanwhile, SXSM protected cardiomyocytes against the oxidative damage induced by H2O2 and A/R injury through reducing intracellular ROS levels. Moreover, SXSM increased SOD activity through enhancing SOD1 expression and increased GSH content through promoting GCLC expression as well as GSH-Px activity. BSO and SOD1 siRNA counteracted anti-arrhythmic and cardiac protective effect of SXSM, suggesting that the therapeutic targets of SXSM might be SOD1 and GCLC.
Conclusion: SXSM is effective in protecting the myocardium from I/R injury, with myocardial SOD1 and GCLC being the potential therapeutic targets.
Keywords: Antioxidant; Bradyarrhythmia; Cardiomyocytes; Oxidative stress; Traditional Chinese medicine.
© 2018 The Author(s). Published by S. Karger AG, Basel.