Document Type

Journal Article

Department/Unit

Department of Biology

Title

Ginsenoside-Rg1 mediates a hypoxia-independent upregulation of hypoxia-inducible factor-1α to promote angiogenesis

Language

English

Abstract

Hypoxia-inducible factor (HIF-1) is the key transcription regulator for multiple angiogenic factors and is an appealing target. Ginsenoside-Rg1, a nontoxic saponin isolated from the rhizome of Panax ginseng, exhibits potent proangiogenic activity and has the potential to be developed as a new angiotherapeutic agent. However, the mechanisms by which Rg1 promotes angiogenesis are not fully understood. Here, we show that Rg1 is an effective stimulator of HIF-1α under normal cellular oxygen conditions in human umbilical vein endothelial cells. HIF-1α steady-state mRNA was not affected by Rg1. Rather, HIF-1α protein synthesis was stimulated by Rg1. This effect was associated with constitutive activation of phosphatidylinositol 3-kinase (PI3K)/Akt and its effector p70 S6 kinase (p70 S6K), but not extracellular-signal regulated kinase 1/2. We further revealed that HIF-1α induction triggered the expression of target genes, including vascular endothelial growth factor (VEGF). The use of small molecule inhibitors LY294002 or rapamycin to inhibit PI3K/Akt and p70 S6K activities, respectively, resulted in diminished HIF-1α activation and subsequent VEGF expression. RNA interference-mediated knockdown of HIF-1α suppressed Rg1-induced VEGF synthesis and angiogenic tube formation, confirming that the effect was HIF-1α specific. Similarly, the angiogenic phenotype could be reversed by inhibition of PI3K/Akt and p70 S6K. These results define a hypoxia-independent activation of HIF-1α, uncovering a novel mechanism for Rg1 that could play a major role in angiogenesis and vascular remodeling. © 2011 The Author(s).

Keywords

Angiogenesis, Ginsenoside, HIF-1α, PI3K/Akt, Signaling

Publication Date

2011

Source Publication Title

Angiogenesis

Volume

14

Issue

4

Start Page

515

End Page

522

Publisher

Springer Verlag

DOI

10.1007/s10456-011-9235-z

Link to Publisher's Edition

http://dx.doi.org/10.1007/s10456-011-9235-z

ISSN (print)

09696970

ISSN (electronic)

15737209

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