Ginsenosides may reverse the dexamethasone-induced down-regulation of glucocorticoid receptor

The effects of glucocorticoid (GC) hormones are mediated via an intracellular receptor, the glucocorticoid receptor (GR). It has been established that glucocorticoid down-regulate GR. Ginsenosides (GSS) from extract of Panax ginseng have demonstrated glucocorticoid-like activities in homeostasis and regulation of immunity, etc. We hypothesize that ginsenosides might mediate some of their actions by binding to the GR. The present study is aimed to determine whether GSS can act like a GC analog in the activation of glucocorticoid response element-luciferase activity in HL7702 cells. We found that GSS alone had no effect on the expression of reporter gene, but it enhanced dexamethasone (Dex)-induced transcription of reporter gene. To further explore the effects of GSS, we examined the influence of GSS on the gene and protein expression as well as hormone binding activity of GR by semi-quantitative RT-PCR, Western blot, and radioligand-binding assay, respectively. GSS partially reversed the Dex-induced decrease in GR expression and hormone binding activity with an optimal dose of 25 μg/ml, implicating a positive regulatory effect of GSS on GR expression and binding activity. Therefore, our result suggests that GSS may reverse partially the dexamethasone-induced down-regulation of glucocorticoid receptor.