Ginsenosides Rb1 and Rg1 promote proliferation and expression of neurotrophic factors in primary Schwann cell cultures.

Ginsenoside Rb1 (GRb1) and ginsenoside Rg1 (GRg1), two major ingredients in ginseng root, have gained extensive attention because of its neuroprotective properties. Thus far, most of the studies on GRb1 and GRg1 have been focused on their neuroprotective effects on neurons. The potential beneficial effects of GRb1 and GRg1 on Schwann cells have not been investigated comprehensively. The present study was designed to examine the possible beneficial effect of GRb1 and GRg1 on proliferation and expression of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) in Schwann cells. Schwann cells were incubated without or with GRb1 and GRg1 at different doses. The proliferation of Schwann cells was examined by cell counting. The expression and secretion of NGF and BDNF were examined by western blotting and ELISA. We found that both GRb1 and GRg1 were capable of increasing the proliferation of, and the expression and secretion of NGF and BDNF in Schwann cells. Further studies showed that both GRb1 and GRg1 were able to increase intracellular cyclic AMP (cAMP) level and protein kinase A (PKA) activity. Preincubation with 10 μM H89 (a PKA inhibitor) significantly inhibited the beneficial effects of GRb1 and GRg1 on Schwann cells. These findings indicate that the beneficial effects of GRb1 and GRg1 on proliferation and expression of NGF and BDNF occurs mainly through the PKA pathway in cultured Schwann cells.