Attenuating effects of dihydromyricetin on angiotensin II-induced rat cardiomyocyte hypertrophy related to antioxidative activity in a NO-dependent manner

Abstract

CONTEXT: Dihydromyricetin (DMY) displays a range of biological properties. However, whether DMY attenuates cardiomyocyte hypertrophy is unknown. OBJECTIVE: To investigate whether DMY had potential therapeutic value to protect against angiotensin II (Ang II)-induced cardiomyocyte hypertrophy. MATERIALS AND METHODS: Neonatal rat cardiomyocytes were pretreated with DMY (0-320 μM) followed with Ang II (100 nM) stimulation for 24 h, and then degree of hypertrophy was evaluated by cell surface analysis. Levels of reactive oxygen species (ROS) were measured with 2',7'-dichlorfluorescein-diacetate (DCFH-DA) fluorescent staining. Antioxidative activity was evaluated by malondialdehyde (MDA) level, superoxide dismutase (SOD) activity, and total antioxidant capacity (T-AOC). Cyclic guanosine monophosphate (cGMP) was determined with a radioimmunoassay. RESULTS: Pre-incubation with DMY (20, 40, 80, and 160 μM) for 8 h, 12 h, 24 h, or 48 h decreased cell surface areas. It down-regulated mRNA expression of atrial natriuretic factor (1.95- to 1.24-fold) and β-myosin heavy chains (3.51- to 2.32-fold), reduced levels of MDA as well as increased SOD activity and T-AOC. Expression of SOD and thioredoxin were enhanced by DMY, whereas p22(phox) and phosphorylation of mitogen-activated protein kinases were inhibited. Content of cGMP (0.54- to 0.80-fold) and phosphorylation of endothelial nitric oxide synthase at serine 1177 (0.70- to 1.05-fold) were augmented by DMY. Moreover, attenuating effect of DMY on hypertrophy was abolished when NO production was inhibited by l-NAME. CONCLUSION: Attenuating effects of DMY on Ang II-induced cardiomyocyte hypertrophy related to antioxidative activity in a NO-dependent manner.