Abstract:

BACKGROUND: Previous studies have demonstrated that ginsenoside Rb and beta-amyloid peptide 25-35 (Aβ25-35) can regulate the phospholation of Tan protein during the differentiation of neural stem cells (NSCs). Protein phosphatase 2A (PP2A) is closely related to hyperphosphorylation of Tau protein.
OBJECTIVE: To investigate the effects of Aβ_25-35 and ginsenoside Rb1 on phosphorylation level of Tau protein and activity of PP2A during the differentiation of NSCs.
METHODS: NSCs were isolated from newborn rat hippocampus. After culture for 1 week, passage 3 NSCs were divided into three groups. In the control group, NSCs were further cultured for 36 hours without any medium added. In the Aβ group, after 24 hours of culture, Aβ_25-35 was added for another 12 hours of culture. In the ginsenoside Rb1 froup, ginsenoside Rb1 was added for 24 hour pretreatment, and Aβ_25-35 was added for another 12 hours of culture. The expression of Tau[pS396] and Tau[pS262] was tested by the immunofluorescent cytochemical staining and western blot method, and PP2A activity was tested by ELISA.
RESULTS AND CONCLUSION: Cellular expression of Tau[pS396] and Tau[pS262] was detected during the differentiation of NSCs. In the Aβ group, cellular expression of Tau[pS396] and Tau[pS262] was up-regulated, and PP2A activity was not altered obviously. In the ginsenoside Rb1 group, cellular expression of Tau[pS396] and Tau[pS262] was down-regulated and PP2A activity was significantly increased. These findings suggest that during normal differentiation of NSCs, Tau protein was phosphorylated at a certain level, and ginsenoside Rb1 can alleviate Aβ25-35-induced hyperphosphorylation of Tau protein during the differentiation of NSCs by increasing PP2A activity.