Total Ginsenoside Extract from Panax ginseng Enhances Neural Stem Cell Proliferation and Neuronal Differentiation by Inactivating GSK-3β

Objective: To study the effects of total ginsenosides (TG) extract from Panax ginseng on neural stem cell (NSC) proliferation and differentiation and their underlying mechanisms. Methods: The migration of NSCs after treatment with various concentrations of TG extract (50, 100, or 200 mu g/mL) were monitored. The proliferation of NSCs was examined by a combination of cell counting kit-8 and neurosphere assays. NSC differentiation mediated by TG extract was evaluated by Western blotting and immunofluorescence staining to monitor the expression of nestin and microtubule associated protein 2 (MAP2). The GSK-3 beta/beta-catenin pathway in TG-treated NSCs was examined by Western blot assay. The NSCs with constitutively active GSK-3 beta mutant were made by adenovirus-mediated gene transfection, then the proliferation and differentiation of NSCs mediated by TG were further verified. Results: TG treatment significantly enhanced NSC migration (P<0.01 or P<0.05) and increased the proliferation of NSCs (P<0.01 or P<0.05). TG mediation also significantly upregulated MAP2 expression but downregulated nestin expression (P<0.01 or P<0.05). TG extract also significantly induced GSK-3 beta phosphorylation at Ser9, leading to GSK-3 beta inactivation and, consequently, the activation of the GSK-3 beta/beta -catenin pathway (P<0.01 or P<0.05). In addition, constitutive activation of GSK-3 beta in NSCs by the transfection of GSK-3 beta S9A mutant was found to significantly suppress TG-mediated NSC proliferation and differentiation (P<0.01 or P<0.05). Conclusion: TG promoted NSC proliferation and neuronal differentiation by inactivating GSK-3 beta.