Ginsenoside Rb1 protects hippocampal neurons from high glucose-induced neurotoxicity by inhibiting GSK3β-mediated CHOP induction.

Ginsenoside Rb1 is generally recognized as one of the principal bioactive ingredients in ginseng and shows neuroprotective effects in various neurons. Endoplasmic reticulum (ER) stress is considered to play an important role in numerous neurodegenerative disorders. Recently, glucogen synthase kinase 3 beta (GSK3 beta) was reported to regulate ER stress-induced C/EBP homologous protein (CHOP) in neuronal cells. Therefore, in this study, we investigated the effects of ginsenoside Rb1 on GSK3 beta-mediated ER stress in high glucose-treated hippocampal neurons. Results from the MTT assay showed that treatment with 1 mu M Rb1 for 72 h protected neurons from high glucose-induced cell injury. Using western blot analysis, we found that treatment with Rb1 effectively inhibited the phosphorylation of the high glucose-induced protein kinase RNA-like ER kinase (PERK) and of GSK3 beta, and reduced the level of the CHOP protein. The levels of these proteins were also decreased by treatment with the GSK3 beta inhibitor Licl. Rb1 also significantly decreased the mRNA expression of the gene CHOP, as shown by quantitative RT-PCR analysis. Taken together, the present results suggested that Rb1 may protect neurons from high glucose-induced cell damage by inhibiting GSK3 beta-mediated CHOP induction, providing a potentially new strategy for preventing and treating cognitive impairment caused by diabetes.