Ginsenoside Re, a Main Phytosterol of Panax ginseng, Activates Cardiac Potassium Channels via a Nongenomic Pathway of Sex Hormones Tetsushi Furukawa, Chang-Xi Bai, Asami Kaihara, Eri Ozaki, Takashi Kawano, Yutaka Nakaya, Muhammad Awais, Moritoshi Sato, Yoshio Umezawa, and Junko Kurokawa Department of Bio-informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University (T.F., C.-X.B., A.K., E.O., J.K.); Departments of Anesthesiology (T.K.) and Nutrition (Y.N.), Tokushima University School of Medicine; and Department of Chemistry, School of Science, the University of Tokyo, Tokyo, Japan (M.A., M.S., Y.U.) Received June 20, 2006; accepted September 19, 2006 ABSTRACT Ginseng root is one of the most popular herbs throughout the world and is believed to be a panacea and to promote longev- ity. It has been used as a medicine to protect against cardiac ischemia, a major cause of death in the West. We have previ- ously demonstrated that ginsenoside Re, a main phytosterol of Panax ginseng, inhibits Ca 2+ accumulation in mitochondria during cardiac ischemia/reperfusion, which is attributable to nitric oxide (NO)-induced Ca 2+ channel inhibition and K + chan- nel activation in cardiac myocytes. In this study, we provide compelling evidence that ginsenoside Re activates endothelial NO synthase (eNOS) to release NO, resulting in activation of the slowly activating delayed rectifier K + current. The eNOS acti- vation occurs via a nongenomic pathway of each of androgen receptor, estrogen receptor-, and progesterone receptor, in which c-Src, phosphoinositide 3-kinase, Akt, and eNOS are sequentially activated. However, ginsenoside Re does not stim- ulate proliferation of androgen-responsive LNCaP cells and estrogen-responsive MCF-7 cells, implying that ginsenoside Re does not activate a genomic pathway of sex hormone recep- tors. Fluorescence resonance energy transfer experiments with a probe, SCCoR (single cell coactivator recruitment), indicate that the lack of genomic action is attributable to failure of coactivator recruitment. Thus, ginsenoside Re acts as a spe- cific agonist for the nongenomic pathway of sex steroid recep- tors, and NO released from activated eNOS underlies cardiac K + channel activation and protection against ischemia-reper- fusion injury. The earliest evidence of humans’ use of herbs for healing dates back to the Neanderthal period (Winslow and Kroll, 1998; Goldman, 2001). In the late 20th century, concerns over the iatrogenic effects of conventional medicine and de- sire for more self-reliance led to increased interest in natural health, and use of herbal medicines again became popular (Winslow and Kroll, 1998; Goldman, 2001). Among the 20,000 herbal products that are currently on the market, ginseng root is one of the most popular herbs (Attele et al., 1999). Ginseng is known as a panacea (cure-all), and it ex- hibits a variety of actions, including modulation of immune responses and antineoplastic effects (Attele et al., 1999). Although estrogenic activities (Kim et al., 2004) and nitric oxide (NO) action (Gillis, 1997) have been suggested as a mechanism of ginseng’s actions, the precise mechanism re- mains unknown, which is major hindrance for use of ginseng in modern medicine. Ginseng root exhibits protection against cardiac ischemia- This work was supported, in part, by grant-in-aid 17081007 for Scientific Research on Priority Areas, grant 18659066 from the Ministry of Education, Culture, Sports, Science, and Technology of Japan, and Research Grant from Takeda Science Foundation, and the Cosmetology Foundation. Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org. doi:10.1124/mol.106.028134. ABBREVIATIONS: NO, nitric oxide; NOS, NO synthase; eNOS, endothelial NOS; nNOS, neuronal NOS; E 2 , 17-estradiol; DHT, 5-dihydrotes- tosterone; AR, androgen receptor; ER, estrogen receptor-; PR, progesterone receptor; FRET, fluorescence resonance energy transfer; SCCoR, single cell coactivator recruitment; LBD, ligand binding domain; CFP, cyan fluorescent protein; YFP, yellow fluorescent protein; P 4 , progesterone; SMTC, S-methyl-L-thiocitrulline; L-NIO, L-N 5 -(l-iminoethyl)ornithine; SH-6, D-2,3-dideoxy-myo-inositol 1-[(R)-2-methoxy-3-(octadecyloxy)propyl hydrogen phosphate]; PP2, 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine; ICI182,780, fulvestrant; DMSO, dimethyl sulfoxide; PI3, phosphoinositide 3; pyrazole, 1,2,5-tris(4-hydroxyphenyl)-4-propylpyrazole; estren, 4-estren-3,17-diol; DMEM, Dulbecco’s modified Eagle medium; I Ca,L , L-type Ca 2+ current; I Ks , the slowly activating delayed rectifier K + current. 0026-895X/06/7006-1916 –1924$20.00 MOLECULAR PHARMACOLOGY Vol. 70, No. 6 Copyright © 2006 The American Society for Pharmacology and Experimental Therapeutics 28134/3156556 Mol Pharmacol 70:1916–1924, 2006 Printed in U.S.A. 1916 at ASPET Journals on August 16, 2017 molpharm.aspetjournals.org Downloaded from