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Tanshinone IIA extracted from danshen, a popular medicinal herb used in traditional Chinese medicine, exhibits cardio-protective effects. However, the mechanism of its cardioprotective effect is not well established. The aims of this study were to examine whether tanshinone IIA may alter angiotensin II (Ang II)-induced cell proliferation and to identify the putative underlying signaling pathways in rat cardiac fibroblasts. Cultured rat cardiac fibroblasts were pre-treated with tanshinone IIA and stimulated with Ang II, cell proliferation and endothelin-1 (ET-1) expression were examined. The effect of tanshinone IIA on Ang II-induced reactive oxygen species (ROS) formation, and extracellular signal-regulated kinase (ERK) phosphorylation were also examined. In addition, the effect of tanshinone IIA on nitric oxide (NO) production, and endothelial nitric oxide synthase (eNOS) phosphorylation were tested to elucidate the intracellular mechanism. The increased cell proliferation and ET-1 expression by Ang II (100 nM) were partially inhibited by tanshinone IIA. Tanshinone IIA also inhibited Ang II-increased ROS formation, and ERK phosphorylation. In addition, tanshinone IIA was found to increase the NO generation, and eNOS phosphorylation. N(G)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NOS, and the short interfering RNA transfection for eNOS markedly attenuated the inhibitory effect of tanshinone IIA on Ang II-induced cell proliferation. The results suggest that tanshinone IIA prevents cardiac fibroblast proliferation by interfering with the generation of ROS and involves the activation of the eNOS-NO pathway.

Background/aims: Nicorandil, an ATP-sensitive potassium (K(ATP)) channel opener, nitric oxide (NO) donor and antioxidant, was shown to exert a variety of pharmacological effects including cardioprotective properties. However, its mechanisms of action are not completely understood. The aims of this study were to examine whether nicorandil may alter angiotensin-II (Ang II)-induced cell proliferation and to identify the putative underlying signaling pathways in rat cardiac fibroblasts., Methods: Cultured rat cardiac fibroblasts were pretreated with nicorandil, then stimulated with Ang II, and cell proliferation and endothelin-1 (ET-1) expression were examined. The effects of nicorandil on Ang-II-induced reactive oxygen species (ROS) formation and extracellular signal-regulated kinase (ERK) phosphorylation were also examined. In addition, the effects of nicorandil on NO production and endothelial nitric oxide synthase (eNOS) phosphorylation were tested to elucidate the intracellular mechanism., Results: Nicorandil (0.1-10 μmol/l) caused a concentration-dependent inhibition of Ang-II-increased cell proliferation and ET-1 expression which were prevented by the K(ATP) channel blocker glibenclamide (1 μmol/l). Nicorandil also inhibited Ang-II-increased ROS and ERK phosphorylation. In addition, nicorandil was found to increase the NO and eNOS phosphorylation. N-nitro-L-arginine methyl ester, an inhibitor of NOS, and the short interfering RNA transfection for eNOS markedly attenuated the inhibitory effect of nicorandil on Ang-II-induced cell proliferation., Conclusion: Our results suggest that nicorandil prevents cardiac fibroblast proliferation, and the inhibitory effect might be associated with the opening K(ATP) channels, by interfering with the generation of ROS, and the activation of the eNOS-NO pathway., (Copyright © 2011 S. Karger AG, Basel.)