Abstract
Purpose:
Vascular endothelial growth Factor (VEGF) is a protein, which causes an increase in endothelial cell proliferation and capillary neovascularization. In a previous study, ginsenoside Rb1 (a steroid glycoside derived from Panax ginseng) was shown to inhibit the release of VEGF by adult retinal pigment epithelial cells (ARPE-19) in culture. In the present study, we examined the amount of VEGF in conditioned media of ARPE-19 treated with Rb1, hydrogenated Rb1 (Rb1H2) and acylated Rb1 (Rb1Acyl), along with vehicle controls. We hypothesized that chemical modification of Rb1 induces a change in the Rb1 inhibition of VEGF release by ARPE-19 cells.
Methods:
ARPE-19 cells were seeded into 24 well plates at a density of approximately 20,000 cells per well. Cells were treated with 250 nM Rb1, Rb1H2, Rb1Acyl or vehicle controls. Levels of VEGF in the conditioned media after 72 hours treatment were measured by ELISA. Structural modification was confirmed by NMR and MS.
Results:
Normalization to control (treated with un-modified Rb1) showed that hVEGF levels in the conditioned media of ARPE-19 cells treated with Rb1H2 increased by 63%. An increase by 39% was noted in cells treated with Rb1Epoxide and an increase by 65% was measured in conditioned media from cells treated with Rb1Acylated.
Conclusions:
Our results support the hypothesis that chemical modification of Rb1 significantly changes Rb1-induced inhibition of VEGF release by ARPE-19 cells. In contrast to Rb1 inhibition of VEGF release, hydrogenation and acetylation of Rb1 resulted in an increase of VEGF release by ARPE19 cells. Further studies on chemical modifications of this natural compound will be carried out in order to provide data critically needed for anti-VEGF therapy on angiogenic ocular disorders such as diabetic retinopathy and macular degeneration.