Ginsenosides are considered the major constituents that are responsible for most of the pharmacological actions of ginseng. However, some ginsenosides exist as stereoisomeric pairs, detailed and molecular exposition based on the structural differences of ginsenoside stereoisomers has not been emphasized in most studies. Here we explore the functional differences of ginsenoside Rg₃ stereoisomers on angiogenesis. In this study, we demonstrated the distinctive differential angiogenic activities of 20(S)-Rg₃ and 20(R)-Rg₃ stereoisomers. 20(S)-Rg₃ at micromolar concentration promotes human endothelial cells proliferation, migration and tube formation in vitro, as well as ex vivo endothelial sprouting. The effects induced by 20(S)-Rg₃ are significantly more potent than 20(R)-Rg₃. These effects are partially mediated through the activation of AKT/ERK-eNOS signaling pathways. Moreover, knockdown of peroxisome proliferator-activated receptor-gamma (PPARγ) by specific small interference RNA abolished the 20(S)-Rg₃-induced angiogenesis, indicating that PPARγ is responsible for mediating the angiogenic activity of Rg₃. Using reporter gene assay, the PPARγ agonist activity of 20(S)-Rg₃ has been found 10-fold higher than that of 20(R)-Rg₃. Computer modeling also revealed the differential binding is due to the chiral center of 20(S)-Rg₃ can form a critical hydrogen bond with Tyr473 of PPARγ ligand binding domain. The present study elucidated the differential angiogenic effects of Rg₃ stereoisomers by acting as agonist of PPARγ. The results shed light on the structural difference between two ginsenoside stereoisomers that can lead to significant differential physiological outcomes which should be carefully considered in the future development of ginsenoside-based therapeutics.

Ginsenoside-Rb1 (Rb1), one of the bioactive components in ginseng extract, is recently reported to be able to promote adipogenesis and peroxisome proliferator-activated receptor gamma (PPARγ) expression. Meanwhile, microRNA-27b (miR-27b) is also identified to regulate adipogenesis by targeting PPARγ2. In the present study, we attempted to link up the Rb1-promoted adipogenesis with PPARγ binding and miR-27b regulation. First, we demonstrated that GW9662, an antagonist of PPARγ, could block Rb1-induced 3T3-L1 differentiation with little toxicity towards cell proliferation. Then, expression levels for both of miR-27b and its primary transcript, pri-mir-27b, were found to decrease upon Rb1 treatment. Again, GW9662 could attenuate the inhibitory effect of Rb1 on both miR-27 and pri-mir-27b expression. Since Rb1 was demonstrated to have binding activity towards PPARγ, we thus speculate that Rb1 may act though PPARγ to downregulate mir-27b gene transcription and mature miR-27b activity, which in turn promotes PPARγ expression and adipogenesis. Enhancement on adipogenesis of adipose tissues is expected to prevent lipotoxicty in nonadipose tissues. Our data may give a better illustration to explain the antidiabetic effect of Rb1 and provide a hint on treatment of lipid related metabolic diseases in the future.

BackgroundGinsenoside-Rg3, the pharmacologically active component of red ginseng, has been found to inhibit tumor growth, invasion, metastasis, and angiogenesis in various cancer models. Previously, we found that 20(R)-ginsenoside-Rg3 (Rg3) could inhibit angiogenesis. Since microRNAs (miRNAs) have been shown to affect many biological processes, they might play an important role in ginsenoside-mediated angiomodulation.MethodsIn this study, we examined the underlying mechanisms of Rg3-induced angiosuppression through modulating the miRNA expression. In the miRNA-expression profiling analysis, six miRNAs and three miRNAs were found to be up- or down-regulated in vascular-endothelial-growth-factor-induced human-umbilical-vein endothelial cells (HUVECs) after Rg3 treatment, respectively.ResultsA computational prediction suggested that mature hsa-miR-520h (miR-520h) targets ephrin receptor (Eph) B2 and EphB4, and hence, affecting angiogenesis. The up-regulation of miR-520h after Rg3 treatment was validated by quantitative real-time polymerase chain reaction, while the protein expressions of EphB2 and EphB4 were found to decrease, respectively. The mimics and inhibitors of miR-520h were transfected into HUVECs and injected into zebra-fish embryos. The results showed that overexpression of miR-520h could significantly suppress the EphB2 and EphB4 protein expression, proliferation, and tubulogenesis of HUVECs, and the subintestinal-vessel formation of the zebra fish.ConclusionThese results might provide further information on the mechanism of Rg3-induced angiosuppression and the involvement of miRNAs in angiogenesis.