Ginsenoside Rb1 inhibits tube-like structure formation of endothelial cells by regulating pigment epithelium-derived factor through the oestrogen beta receptor.

BACKGROUND AND PURPOSE: Angiogenesis is a crucial step in tumour growth and metastasis. Ginsenoside-Rb1 (Rb1), the major active constituent of ginseng, potently inhibits angiogenesis in vivo and in vitro. However, the underlying mechanism remains unknown. We hypothesized that the potent anti-angiogenic protein, pigment epithelium-derived factor (PEDF), is involved in regulating the anti-angiogenic effects of Rb1. EXPERIMENTAL APPROACHES: Rb1-induced PEDF was determined by real-time PCR and western blot analysis. The anti-angiogenic effects of Rb1 were demonstrated using endothelial cell tube formation assay. Competitive ligand-binding and reporter gene assays were employed to indicate the interaction between Rb1 and the oestrogen receptor (ER). KEY RESULTS: Rb1 significantly increased the transcription, protein expression and secretion of PEDF. Targeted inhibition of PEDF completely prevented Rb1-induced inhibition of endothelial tube formation, suggesting that the anti-angiogenic effect of Rb1 was PEDF specific. Interestingly, the activation of PEDF occurred via a genomic pathway of ERbeta. Competitive ligand-binding assays indicated that Rb1 is a specific agonist of ERbeta, but not ERalpha. Rb1 effectively recruited transcriptional activators and activated an oestrogen-responsive reporter gene. Furthermore, Rb1-mediated PEDF activation and the subsequent inhibition of tube formation were blocked by the ER antagonist ICI 182,780 or transfection of ERbeta siRNA, indicating ERbeta dependence. CONCLUSIONS AND IMPLICATIONS: Here we show for the first time that the Rb1 suppressed the formation of endothelial tube-like structures through modulation of PEDF via ERbeta. These findings demonstrate a novel mechanism of the action of this ginsenoside that may have value in anti-cancer and anti-angiogenesis therapy.

Angiomodulatory and neurological effects of ginsenosides.

Panax ginseng C.A. Meyer, one of the most popular and valued herbs, has been used extensively in traditional Chinese medicine for thousands of years. More than thirty ginsenosides, the pharmacologically active ingredients in ginseng, have been identified with various sugar moieties attached at the C-3, C-6 and C-20 positions of the steroidal skeleton. We herein review the current literature on the pharmacological effects of ginsenosides on the modulation of angiogenesis, dysregulations of which contribute towards many pathological conditions. Regarding the adaptogenic property of ginseng, the effects of ginsenosides on central nervous system are also discussed. Recent researches have pointed to the steroid hormone receptors as the target molecules to elicit the diverse cellular and physiological activities of ginseng. We believe that understanding the interaction between ginsenosides and various steroid hormone receptors may provide clues to unravel the secret of ginseng.

The angiosuppressive effects of 20(R)- ginsenoside Rg3.

Aberrant angiogenesis is an essential step for the progression of solid tumors. Thus anti-angiogenic therapy is one of the most promising approaches to control tumor growth. In this study, we examined the ability of 20(R)-ginsenoside Rg3 (Rg3), one of the active compounds present in ginseng root, to interfere with the various steps of angiogenesis. Rg3 was found to inhibit the proliferation of human umbilical vein endothelial cells (HUVEC) with an IC50 of 10 nM in Trypan blue exclusion assay. Rg3 (1-10(3) nM) also dose dependently suppressed the capillary tube formation of HUVEC on the Matrigel in the presence or absence of 20 ng/ml vascular endothelial growth factor (VEGF). The VEGF-induced chemoinvasion of HUVEC and ex vivo microvascular sprouting in rat aortic ring assay were both significantly attenuated by Rg3. In addition, Rg3 (150 and 600 nM) remarkably abolished the basic fibroblast growth factor (bFGF)-induced angiogenesis in an in vivo Matrigel plug assay. The Matrix metalloproteinases (MMPs), such as MMP-2 and MMP-9, which play an important role in the degradation of basement membrane in angiogenesis and tumor metastasis present in the culture supernatant of Rg3-treated aortic ring culture were found to decrease in their gelatinolytic activities. Taken together, these data underpin the anti-tumor property of Rg3 through its angiosuppressive activity.

Elucidation of the mechanisms underlying the angiogenic effects of ginsenoside Rg(1) in vivo and in vitro.

The major active constituents of ginseng are ginsenosides, and Rg(1) is a predominant compound of the total extract. Recent studies have demonstrated that Rg(1) can promote angiogenesis in vivo and in vitro. In this study, we used a DNA microarray technology to elucidate the mechanisms of action of Rg(1). We report that Rg(1) induces the proliferation of HUVECs, monitored using [(3)H]-thymidine incorporation and Trypan blue exclusion assays. Furthermore, Rg(1) (150-600 nM) also showed an enhanced tube forming inducing effect on the HUVEC. Rg(1) was also demonstrated to promote angiogenesis in an in vivo Matrigel plug assay, and increase endothelial sprouting in the ex vivo rat aorta ring assay. Differential gene expression profile of HUVEC following treatment with Rg(1) revealed the expression of genes related to cell adhesion, migration and cytoskeleton, including RhoA, RhoB, IQGAP1, CALM2, Vav2 and LAMA4. Our results suggest that Rg(1) can promote angiogenesis in multiple models, and this effect is partly due to the modulation of genes that are involved in the cytoskeletal dynamics, cell-cell adhesion and migration.

The anti-angiogenic effect of sinomenine.

Sinomenine is an alkaloid extracted from the Chinese medicinal plant, Sinomenium acutum, which has been utilized to treat rheumatoid arthritis (RA) in China for over 2000 years. Sinomenine has been shown to mediate a wide range of pharmacological actions which includes anti-inflammatory and anti-rheumatic effects. RA has been classified as a chronic immune-mediated disease that exhibits overlapping manifestation of inflammatory, abnormal cellular and hormonal immune responses with synovial hyperplasia. Since, angiogenesis is recognized to play a critical role in the development of RA and anti-angiogenic therapy has been proposed as a new therapeutic strategy for treatment of RA, we would like to see if sinomenine possesses anti-angiogenic property. In this study, sinomenine inhibited bFGF-induced proliferation of human umbilical vein endothelial cells (HUVEC) and arrested its cell cycle in G1 phase. Sinomenine disrupted tube formation of HUVEC on Matrigel and suppressed the chemotaxis of HUVEC. In addition, sinomenine reduced neovascularization in Matrigel plug assay as well as microvascular outgrowth in rat aorta ring sprouting assay. These results suggest that sinomenine inhibited bFGF-induced angiogenesis in vitro and in vivo. As the leukocytes-endothelial adhesive interactions also play an important role in inflammation, we found that sinomenine reduced the transmigration of granulocytic differentiated HL60 cells across IL-1beta activated HUVEC monolayer. Therefore, the inhibition of leukocytes migration across blood vessel walls and the anti-angiogenic effect of sinomenine may contribute towards its therapeutic mechanisms in alleviating the pathogenesis of RA.