人参皂苷Rb1和Rg1对海马神经元的影响

目的探讨人参皂苷（ginsenoside）Rb1和Rg1（GRb1，GRg1）对海马神经元突起生长及神经保护作用及其机制。方法培养SD新生大鼠海马神经元，分为：正常组、Rb1组、Rg1组、Rb1＋API-2（Akt抑制剂）、Rg1＋API-2、Rb1＋PD98059（MEK抑制剂）和Rg1＋PD98059组，培养1d，用免疫染色观察神经突起的生长。加入Aβ25—35制备海马神经元损伤模型，分为正常组、损伤组（AB组）、Rb1组、Rg1组、Rb1＋API-2、Rg1-I-API-2、Rb1＋PD98059和Rg1＋PD98059，培养48h，用Hoechst33258染色观察活细胞与凋亡细胞。用Elisa观察培养上清液里神经营养因子的浓度（nerve growth factor，NGF；brain—derived neurotrophic factor，BDNF；neurotrophin-3，NT-3）。结果Rb1和Rg1组神经突起生长高于对照组（P〈0．05）；API-2和PD98059显著抑制了Rb1和Rg1诱导的神经突起生长（P〈0．01），API-2的抑制效果强于PD98059；Rg1＋API-2组BDNF高于对照组和Rg1组（P〈0．05），其余各组间差异无统计学意义（P〉0．05）；Rg1组NT-3的浓度高于对照组（P〈0．05）；Rb1＋PD98059组的NGF高于Rb1组。Rb1和Rg1组海马神经元的凋亡率显著低于损伤组（P〈0．01）；PD98059和API-2阻断了Rb1和Rg1对神经元的保护作用（P〈0．01）；神经营养因子水平各组间差异无统计学意义。结论Rb1和Rg1促进海马神经元突起生长及抵抗A1325—35损伤，促进神经元的存活。其机制与Akt和ERK1／2的信号通路激活有关，与增加神经营养因子的分泌无关。

Effects of ginsenoside Rb1 and Rg1 on hippocampal neurons

Objective To investigate the effects of ginsenoside Rb1 and Rg1(Rb1,Rg1) on neurite outgrowth of hippocampal neurons and protection hippocampal neurons against injury caused by Aβ25- 35.Methods Cultured hippocampal neurons from newborn SD rats were divided into groups; normal,Rb1,Rg1,Rb1+API-2(Akt inhibitor),Rg1+API-2,Rb1+PD98059(MEK inhibitor), and Rg1+PD98059.After 24 h of culture the neurite outgrowth was evaluated by immunostaining of neuronal growth associated protein-43(GAP-43).Hippocampal neurons were treated with Aβ25-35 and divided into groups;injured Aβgroup,Rb1,Rg1,Rb1+API-2,Rg1+API-2,Rb1+PD98059 and Rg1+PD98059.After 48 h of cultured the Hoechst33258 staining was performed to evaluate the rate of apoptosis.In addition,the nerve growth factor(NGF),brain-derived neurotrophic factor (BDNF) and neurotrophin-3(NT-3) were analyzed by ELISA method.Results The neurites were significantly longer and the number increased in Rb1 and Rg1 groups compared with normal group(P<0.05).API-2 and PD98059 blocked neurite outgrowth significantly(P<0.01),and API-2 was more efficient than PD98059.No significant difference of BDNF from supernatant was observed between groups except that BDNF in Rg1+API-2 group was higher compared with Rg1 group;NT-3 in Rg1 group was significantly higher than that in normal group;NGF in Rb1 + PD98059 was significantly higher than that in Rb1 group(P<0.05).Apoptotic rates of hippocampal neurons in Rb1 and Rg1 groups decreased significantly(P<0.01) compared with Aβgroup.Moreover,API-2 and PD98059 significantly inhibited neuroprotection of Rb1 and Rg1 against Aβ25-35 injury(P<0.05).No differences of NGF,NT-3 and BDNF were observed among groups(P > 0.05).Conclusion Ginsenosides Rb1 and Rg1 can induce neurite outgrowth of hippocampal neurons and protect neurons against Aβ25 - 35 injury.Their mechanisms are related to Akt and ERK1/2 signal transduction pathways but not to the increase of neurotrophins secretion.