ASTRAGALOSIDE IV ATTENUATES HYPOXIA-INDUCEDCARDIOMYOCYTE DAMAGE IN RATS BY UPREGULATINGSUPEROXIDE DISMUTASE-1 LEVELS

摘要

1. Astragaloside IV (AST-IV) is purified from a natural plant product. Previous studies have shown that AST-IV has antioxidant activity. In the present study, we investigated the effect and mechanism of action AST-IV on rat cardiomyocytes subjected to hypoxic conditions (up to 12 h).2. Cardiomyocytes were prepared from neonatal rats and cultured under normoxic or hypoxic conditions in the absence or presence of AST-IV (12.5, 25 or 50 (mu)g/mL,). Cell viability, malondialdehyde (MDA) levels, activity and expression of superoxide dismutase (SOD)-l (mRNA and protein levels determined by reverse transcription-polymerase chain reaction and western blotting, respectively) and reactive oxygen species (ROS; determined by 2',7'-dichlorodihydrofluorescein diacetate) were investigated under these culture conditions. Intracellular localization of AST-IV was tested using fluorescein isothiocyanate-labelled AST-IV.3. Hypoxic culture reduced the viability of cardiomyocytes, which was improved following treatment with 25 or 50 (mu)g/mL AST-IV. Under hypoxic conditions, MDA levels were double those under control conditions. Astragaloside IV (25 and 50 (mu)G/mL) dose-dependently reduced the increase in MDA seen in hypoxic cardiomyocytes.4. Fluorescein isothiocyanate-labelled AST-IV entered cardiomyocytes and was localized mainly within the cytoplasm.5. Under hypoxic conditions, SOD-1 activity was decreased, but mRNA and protein expression increased, compared with normoxia. Following treatment with 25 (mu)g/mL AST-IV, SOD-1 activity and expression were increased under both normoxic and hypoxic conditions. The ROS scavenging effect of AST-IV was abolished in the presence of the SOD inhibitor sodium diethyl dithiocarbamate (25 (mu)mol/L).6. These in vitro results show that AST-IV protects cardiomyocytes from oxidative stress-mediated injury under hypoxicconditions. A major part of this action is achieved by upregulation of SOD-1 content and activity within the cell cytoplasm.