Astragaloside IV attenuates hypoxia-induced cardiomyocyte damage in rats by upregulating superoxide dismutase-1 levels

Abstract

Astragaloside IV (AST-IV) is purified from a natural plant product. Previous studies have shown that AST-IV has anti-oxidant 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). 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 μg/mL). Cell viability, malondialdehyde (MDA) levels, activity and expression of superoxide dismutase (SOD)-1 (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. Hypoxic culture reduced the viability of cardiomyocytes, which was improved following treatment with 25 or 50 μg/mL AST-IV. Under hypoxic conditions, MDA levels were double those under control conditions. Astragaloside IV (25 and 50 μg/mL) dose-dependently reduced the increase in MDA seen in hypoxic cardiomyocytes. Fluorescein isothiocyanate-labelled AST-IV entered cardiomyocytes and was localized mainly within the cytoplasm. Under hypoxic conditions, SOD-1 activity was decreased, but mRNA and protein expression increased, compared with normoxia. Following treatment with 25 μg/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 μmol/L). These in vitro results show that AST-IV protects cardiomyocytes from oxidative stress-mediated injury under hypoxic conditions. A major part of this action is achieved by upregulation of SOD-1 content and activity within the cell cytoplasm. © 2008 Blackwell Publishing Asia Pty Ltd.