Molecular mechanisms of ginsenoside Rp1-mediated growth arrest and apoptosis

Abstract

Abstract. Ginsenoside Rp1, a semi-synthesized ginseng saponin, was shown to have chemopreventive action and antimetastatic potential. However, the molecular mechanisms of Rp1 on cell growth and death are not fully understood. In this study, the antiproliferative effect of Rp1 on HeLa cells in vitro was investigated. Treatment with Rp1 at 40 μM inhibited the proliferation and partial accumulation of cells at the G1 phase. Rp1-mediated G1 arrest was accompanied by decreased expression of cyclin D1, E, and A and increased expression of p21 without any significant change in p53 or phospho-p53 (Ser15). On the other hand, prolonged incubation with Rp1 at 40 μM caused apoptosis and activation of caspase-3, -8, and -9. The participation of these three caspases in apoptosis was more clearly shown in experiments using inhibitors, which markedly prevented Rp1-induced apoptosis in the case of each caspase. Cleavage of the polyADP-ribose polymerase, often used as an apoptotic marker, was also found in Rp1-induced apoptosis. Among Bcl-2 family proteins (Bad, Bax, Bid, Bcl-2), Bax and Bid were activated by Rp1 treatment, which resulted in the release of cytochrome c from mitochondria, following activation of caspase-9. These observations indicate that multiple cell cycle regulatory proteins and apoptosis-inducing proteins are regulated by Rp1 and contribute to Rp1-induced growth arrest and apoptosis. IntroductionA number of plant glycosides were reported to have biological activities (1-4). The chronic intake of Panax ginseng C.A.Meyer has been associated with a decreased incidence of cancers that lack organ specificity, as well as cancers of the lung, stomach, liver, colorectum, and pancreas (5,6). Panax ginseng ingredients with anticarcinogenic and antimutagenic activities were identified as minor components in red ginseng (steamed and air-dried Panax ginseng) including ginsenosides Rg3, Rg5 and Rh2 (7,8). The molecular mechanisms of active ingredients were also studied (9-13). Among ginsenosides, Rg3 was developed as an anticancer drug for treating lung and liver cancers in China (14). Ginsenoside Rg5 showed more potent chemopreventive and antitumor action than ginsenoside Rg3 (7,15), but was somewhat unstable in a pure form (16). Therefore, we need to synthesize ginsenosides Rp1 [3-O-ß-D-Glucopyranosyl (1→2)-ß-D-glucopyranosyl dammarane-3ß, 12ß-diol] with chemopreventive activity and stability, to improve the anti-tumor activity of Rg3 and its congeners by chemical modifications.Various types of ginsenosides consist of totally different molecules on the basis of their chemical structure, such as the number of sugars attached to the backbone and part of the side chain of the molecules. Furthermore, Rp1 has C 20 -dehydroxy and saturated side chains whereas Rg3, Rg5 and Rh2 have unsaturated double bonds (17). Rp1 has been shown to have chemopreventive effects on mouse skin papilloma (18). Rp1 is proved to be 10x more active and is more stable than Rg3 and Rh2. Ginsenoside Rp1 was prepared on a large scale and high yield as a ...

Ginsenoside‐Rp1 inhibits platelet activation and thrombus formation via impaired glycoprotein VI signalling pathway, tyrosine phosphorylation and MAPK activation

“…Recently, our group developed a novel semi‐synthetic derivative known as ginsenoside‐Rp1 (3‐O‐β‐ d ‐glucopyranosyl‐(1→2)‐β‐ d ‐glucopyranosyl dammarane‐3β,12β‐diol) by means of a reduction with hydrogenation. We previously reported that ginsenoside‐Rp1, derived from gingenoside‐Rg3 or its derivatives (2H‐Rg3, Rg5 and Rk1), exhibited improved stability and potency with strong anti‐metastatic and anti‐inflammatory activities (Kumar et al ., 2006; 2009; Park et al ., 2008; Kim and Cho, 2009); however, the anti‐platelet effect of G‐Rp1 was not then investigated.…”

“…Rg3, 2H‐Rg3, G‐Rg5 and Rk1) by means of a reduction with hydrogenation and was verified to be chemically stable (Park and Park, 2005). In addition, G‐Rp1 displayed 10‐fold more potent anti‐cancer activity compared with G‐Rg3 and G‐Rg5 (Park et al ., 2008; Kumar et al ., 2009).…”