Tanshinone IIA Inhibits Angiotensin II-Induced Cell Proliferation in Rat Cardiac Fibroblasts Paul Chan, * ,a Ju-Chi Liu, * Li-Jen Lin, y Po-Yuan Chen, z,a Tzu-Hurng Cheng, z Jaung-Geng Lin y and Hong-Jye Hong y * Department of Medicine Taipei Medical University-Wan Fang Hospital, Taipei, Taiwan y School of Chinese Medicine, College of Chinese Medicine Medical University, Taichung, Taiwan z Department of Biological Science and Technology College of Life Sciences, China Medical University, Taichung, Taiwan Abstract: Tanshinone IIA extracted from Danshen, a popular medicinal herb used in traditional Chinese medicine, exhibits cardio-protective effects. However, the mechanism of its cardio- protective 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 fibro- blasts 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 mark- edly 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. Keywords: Tanshinone IIA; Traditional Chinese Medicine; Angiotensin II; Cardiac Fibroblast Proliferation; Nitric Oxide. Correspondence to: Dr. Hong-Jye Hong, School of Chinese Medicine, China Medical University, Taichung, Taiwan. Tel: (þ886) 4-2205-3366, Fax: (þ886) 4-2201-3703, E-mail: hongjh@mail.cmu.edu.tw a Both Paul Chan and Po-Yuan Chen contributed equally to this work. The American Journal of Chinese Medicine, Vol. 39, No. 2, 381–394 © 2011 World Scientific Publishing Company Institute for Advanced Research in Asian Science and Medicine DOI: 10.1142/S0192415X11008890 381