Total Glycosides of Ranunculus Japonius Prevent Hypertrophy in Cardiomyocytes via Alleviating Chronic Ca2+ Overload

OBJECTIVE: To evaluate the in vitro anti-hypertrophic effect of total Glycosides of Ranunculus Japonius (TGRJ). METHODS: Neonatal rat cardiomyocytes were cultured and hypertrophy was induced by administrating isoproterenol (ISO, 10 µmol/L) or angiotensin 2 (Ang 2, 1 µmol/L) for 48 hours. In the treatment groups, cells were pretreated with TGRJ (0.3 g/L) for 30 minutes prior to hypertrophic stimuli. The anti-hypertrophic effects of TGRJ were examined by measuring cell size, total protein content, and protein synthesis. Intracellular free Ca(2+) concentration ([Ca(2+)]i) was evaluated using fluorescence dye Fura-2/AM. Sacroplasmic/endoplasmic reticulum Ca(2+) ATPase 2a (SERCA2a), atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP), and beta-myosin heavy chain (β-MHC) protein expression levels were measured by Western blotting . SERCA2a activity was assayed by p-nitrophenal phosphate disodium salt hexahydrate method. RESULTS: Increased cell size, total protein content, and protein synthesis following ISO or Ang 2 stimulation were significantly inhibited by pretreatment with TGRJ (all P<0.05). This anti-hypertrophic effect of TGRJ was confirmed by its suppressing effect on elevated expression of the three hypertrophic related genetic markers, ANP, BNP, and β-MHC. In addition, TGRJ inhibited ISO or Ang 2 induced up-regulation of [Ca(2+)]i under chronic but not acute conditions. And ISO or Ang 2 induced down-regulation of SERCA2a expression and activity was also effectively rectified by TGRJ pretreatment. CONCLUSIONS: The results of present study suggested that TGRJ could prevent ISO or Ang 2 induced cardiac hypertrophy through improving chronic [Ca(2+)]i disorder, might via normalizing SERCA2a expression and activity.