Effects of tanshinone VI on the hypertrophy of cardiac myocytes and fibrosis of cardiac fibroblasts of neonatal rats

The possible effects of tanshinone VI (tsh), a diterpene from the root of Tan-Shen (Salvia miltiorrhiza, Bunge (Labiatae)) on hypertrophy and Fibrosis in cultured neonatal rat cardiac myocytes and fibroblasts were examined. Tsh had no significant effect on protein synthesis, which was evaluated by [H-3]-leucine incorporation into the acid insoluble fraction in the cells, in the absence of stimulatory factors in cardiac myocytes. The amount of protein produced in cardiac myocytes was increased by 10(-8) M endothelin-1 (ET-1), 10(-6) M phenylephrine (PE), or 10(-8) M insulin-like growth factor-1 (IGF-1), suggesting that hypertrophy of cardiac myocytes in vitro was induced by these factors. The ET-1-, PE-, or IGF-1-induced increase in protein synthesis was attenuated by treatment with 10(-5) M tsh. Treatment with 10(-5) M tsh significantly decreased the synthesis of collagen by cardiac fibroblasts, which was evaluated by [H-3]-proline incorporation into acid-insoluble fraction of the fiblobrasts, in the absence of stimulatory factors for the production. Fetal bovine serum (FBS) or IGF-1 increased collagen synthesis in a concentration-dependent manner. The increase at 5% FBS or 10(-8) M IGF-1 was inhibited by 10(-5) M tsh. Fibroblast-conditioned medium (FB-CM) increased protein synthesis in cardiac myocytes in a concentration-dependent manner (10 - 100 %). Tsh attenuated the FB-CM-induced increase in protein-synthesis by cardiac myocytes. These results show that tsh may attenuate the humoral factor-induced hypertrophy of cardiac myocytes and Fibrosis of cardiac fibroblasts. The findings suggest that tsh may improve the development of cardiac remodeling under pathophysiological conditions.