Astragalin and dihydromyricetin as adjuncts to histidine­tryptophan­ketoglutarate cardioplegia enhances protection during cardioplegic arrest.

The present study used an in vitro model of cold cardioplegia in isolated working rat hearts to evaluate the possible effects of two flavonoids, astragalin and dihydromyricetin, as adjuncts to histidine­tryptophan­ketoglutarate (HTK) cardioplegia. The following three groups of male Sprague Dawley rats were evaluated: The HTK group, treated with HTK alone; the HTK­A group, treated with 10 µmol/l astragalin; and the HTK­D group, treated with 10 µmol/l dihydromyricetin. Isolated rat hearts were perfused with Krebs­Henseleit buffer for 30 min and incubated with the respective cardioplegic solution for 6 h at 4˚C. Subsequently, astragalin or dihydromyricetin was added to the cardioplegic solutions. Following 30 min of reperfusion, the left ventricular developed pressure (LVDP), maximum up/down rate of left ventricular pressure (±dp/dtmax) and heart rate were documented as indices of myocardial function using a physiological recorder. Myocardial infarct size (IS) was estimated using 2,3,5­triphenyltetrazolium chloride staining. Lactate dehydrogenase (LDH) and creatine kinase (CK) levels were also determined to assess the degree of cardiac injury. Cardiomyocyte apoptosis analysis was performed using an in situ cell death detection kit. In addition, malondialdehyde (MDA), superoxide dismutase (SOD), interleukin­6 (IL­6), tumor necrosis factor­α (TNF­α), C­reactive protein (CRP) levels, as well as the glutathione/glutathione disulfide (GSH/GSSG) ratio were determined and analyzed using ELISA kits. The protein levels of caspase­9 and B­cell lymphoma­2 (Bcl­2) were determined using western blot analysis. The results demonstrated that exposure to astragalin or dihydromyricetin significantly improved the recovery of LVDP (P<0.05 and P<0.01, respectively), the +dP/dtmax (P<0.05 for dihydromyricetin only) and the ­dP/dtmax (P<0.05 and P<0.01, respectively), increased SOD levels (P<0.05 and P<0.01, respectively) and GSH/GSSG ratios (P<0.05), reduced myocardial IS (P<0.05 and P<0.01, respectively), decreased CK, LDH, IL­6 (all P<0.05 and P<0.01, respectively), MDA (P<0.05), CRP (P<0.05) and TNF­α levels (P<0.05 and P<0.01, respectively), increased Bcl­2 levels (P<0.01) and decreased caspase­9 levels (P<0.01). The results indicated that the addition of either flavonoid (particularly dihydromyricetin) to HTK enhances protection during ischemia, decreases myocardial dysfunction by enhancing anti­inflammatory activities, attenuates myocardial oxidative injury and prevents apoptosis during ischemia/reperfusion.

Cardioprotective Effects of Astragalin against Myocardial Ischemia/Reperfusion Injury in Isolated Rat Heart.

This study aims to evaluate the cardioprotective effects of astragalin against myocardial ischemia/reperfusion (I/R) injury in isolated rat heart. The cardioprotective effects of astragalin on myocardial I/R injury were investigated on Langendorff apparatus. Adult male Sprague-Dawley rats were randomly divided into five groups. The results showed that astragalin pretreatment improved myocardial function. Compared with I/R group, lactate dehydrogenase (LDH) and creatine kinase (CK) activities in coronary flow decreased in astragalin pretreatment groups, whereas superoxide dismutase (SOD) activity and glutathione/glutathione disulfide (GSH/GSSG) ratio significantly increased. The levels of malondialdehyde (MDA), intracellular reactive oxygen species (ROS), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) decreased in astragalin-treated groups. The infarct size (IS) and apoptosis rate in hearts from astragalin-treated groups were lower than those in hearts from the I/R group. Western blot analysis also revealed that astragalin preconditioning significantly reduced Bax level, whereas Bcl-2 was increased in the myocardium. Therefore, astragalin exhibited cardioprotective effects via its antioxidative, antiapoptotic, and anti-inflammatory activities.