知母皂苷对淀粉样β蛋白片段25~35引起的神经细胞凋亡的保护作用(英文)

目的研究知母皂苷(SAaB)对淀粉样β蛋白片段25~35(Aβ25~35)激活巨噬细胞引起神经细胞凋亡的保护作用及有关的机制。方法体外培养小鼠腹腔巨噬细胞24 h,加入Aβ25~35(20μmol.L-1),分别在加入Aβ25~350.5,1,2和6 h取巨噬细胞,应用Western印迹方法检测不同时间点的胞外信号调节激酶1/2(ERK1/2)和丝裂原活化蛋白激酶p38(p38MAPK)的蛋白表达改变,确定ERK1/2和p38 MAPK蛋白表达达峰时间。然后,在加入Aβ25~35前10 min,加入SAaB(10,30和100μmol.L-1)或在加入Aβ25~35前30 min,分别加入p38MAPK的特异性阻断剂SB203580和ERK上游激酶MEK的特异性阻断剂PD98059,分别在Aβ25~35作用0.5和2 h后,取细胞进行Western印迹实验。Aβ25~35作用48 h后,取培养的巨噬细胞上清液测定肿瘤坏死因子-α(TNF-α)及一氧化氮(NO)生成量的改变,应用免疫细胞化学染色观察巨噬细胞诱导型一氧化氮合酶(iNOS)的表达。为了观察SAaB对Aβ25~35激活巨噬细胞所介导的神经细胞凋亡的保护作用,在巨噬细胞培养液内加入SAaB(10,30和100μmol.L-1)作用10 min,然后加入Aβ25~35(20μmo.lL-1)作用48 h后,将培养的上清液转移到体外培养8 d的小脑颗粒细胞内作用72 h,对照组将未被Aβ25~35刺激的巨噬细胞上清液加入到神经细胞内。应用Hoechst 33258染色观察小脑颗粒细胞凋亡改变。结果Aβ25~35(20μmol.L-1)可使巨噬细胞磷酸化ERK1/2和磷酸化p38 MAPK表达明显增加,分别在加入Aβ25~35后0.5 h和2 h作用达高峰。另外,Aβ25~35也可使巨噬细胞的TNF-α和NO产生增加以及iNOS表达增加,Aβ25~35引起的巨噬细胞TNF-α产生增加是通过ERK1/2信号通路激活介导的,因为MEK的特异性阻断剂PD98059可明显抑制Aβ25~35引起的巨噬细胞TNF-α产生增加。将Aβ25~35刺激48 h的巨噬细胞上清液加入到培养的小脑颗粒细胞内,可使神经细胞凋亡百分比较对照组明显增加。SAaB(30和100μmol.L-1)能明显抑制Aβ25~35引起的巨噬细胞磷酸化ERK1/2、磷酸化p38 MAPK和iNOS表达增加,SAaB(10,30和100μmol.L-1)也能对抗Aβ25~35引起的TNF-α和NO的生成增加及明显降低由Aβ25~35激活巨噬细胞所介导的神经细胞凋亡。结论SAaB对Aβ25~35激活巨噬细胞引起神经细胞凋亡具有对抗作用,该作用与其抑制巨噬细胞的ERK1/2信号转导通路,进而抑制巨噬细胞TNF-α和NO的产生有关。

Saponins from Anemarrhena asphodeloides Bge. protect neurons from amyloid β-protein fragment 25-35-induced apoptosis

AIM To investigate the neuroprotective effects and possible mechanisms of saponins from Anemarrhena asphodeloides Bge. (SAaB) on neuronal damage induced by amyloid β-protein fragments 25-35 (Aβ25-35). METHODS Cultured mouse peritoneal macrophages were stimulated with Aβ25-35 (20 μmol·L-1) for 0.5, 1, 2 and 6 h or preincubated with SAaB (10, 30 and 100 μmol·L-1)for 10 min or mitogen-activated protein kinase (MAPK) specific inhibitors (p38 MAPK inhibitor SB 203580 and MEK specific inhibitor PD98059) for 30 min prior to the addition of Aβ25-35(20 μmol·L-1). After stimulation with Aβ25-35 for the indicated times, total cellular extracts were prepared for Western blotting of extracellular signal-regulated kinase (ERK) and p38 MAPK. After stimulation with Aβ25-35 for 48 h, the supernatants of cultured macrophages were collected for quantification of tumor necrosis factor-α (TNF-α) and nitric oxide (NO) and protein expression of inducible nitric oxide synthase (iNOS) in macrophages was determined by immunocytochemical staining. To determine whether SAaB has protective effect against neuronal apoptosis mediated by Aβ25-35-induced macrophages activation, macrophages were stimulated with Aβ25-35 in the presence or absence of SAaB (10, 30 and 100 μmol·L-1) for 48 h and then the cell-free supernatant of Aβ25-35-stimulated macrophages was transferred to the culture of cerebellar granule neurons for 72 h. Neuronal apoptosis was quantitated by scoring the percentage of cells with apoptotic nuclear morphology after Hoechst 33258 staining. RESULTS Aβ25-35(20 μmol·L-1) significantly induced increase in phospho-ERK1/2 and phospho-p38 MAPK protein expression without affecting total protein levels and in the production of TNF-α and NO in cultured macrophages. Aβ25-35-induced increase of TNF-α production in macrophages involved activation of ERK1/2 signal pathway. Importantly, TNF-α and NO generated by cultured macrophages after Aβ25-35 stimulation may be responsible for the majority of the neuronal apoptosis. SAaB (30 and 100 μmol·L-1) significantly suppressed Aβ25-35-induced increase in phospho-ERK1/2 and phospho-p38 MAPK protein. In addition, SAaB (10, 30 and 100 μmol·L-1) also decreased the level of TNF-α and NO in supernatants of cultured macrophage and inhibited Aβ25-35-induced increase in iNOS protein expression of macrophages. Neuronal apoptosis mediated by Aβ25-35-induced macrophage activation was also significantly attenuated by treatment with SAaB (10, 30 and 100 μmol·L-1). CONCLUSION SAaB protects neurons against the neuronal cell death induced by Aβ25-35. The beneficial effects of SAaB may be related to the reduction of TNF-α and NO from activated macrophage induced by Aβ25-35.