论文部分内容阅读
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。
Objective To investigate the protective effect of timosaponin (SAaB) on apoptosis of neurons induced by amyloid β-protein fragment 25~35 (Aβ25~35) and its related mechanisms. METHODS: Mouse peritoneal macrophages were cultured in vitro for 24 h and Aβ25-35 (20 μmol.L-1) was added. Macrophages were harvested by adding Aβ25-350.5, 1, 2, and 6 h, and Western blotting was used to detect different time points. The protein expression of extracellular signal-regulated kinase 1/2 (ERK1/2) and mitogen-activated protein kinase p38 (p38MAPK) was altered to determine the peak time of ERK1/2 and p38 MAPK protein expression. Then, 10 minutes before adding Aβ25~35, adding SAaB (10, 30 and 100 μmol.L-1) or adding Aβ25~35 for 30 min before adding the specific blocker of p38MAPK SB203580 and ERK upstream kinase MEK PD98059, a specific blocker, was treated with Aβ25~35 for 0.5 and 2 h, and cells were taken for Western blotting. 48 h after the administration of Aβ25~35, the supernatants of cultured macrophages were used to measure the changes of tumor necrosis factor-α (TNF-α) and nitric oxide (NO) production. Immunocytochemical staining was used to observe macrophage induction. Nitric oxide synthase (iNOS) expression. In order to observe the protective effect of SAaB on Apoptosis induced by Aβ25~35 activated macrophages, SAaB (10, 30 and 100 μmol·L-1) was added to macrophage culture medium for 10 min, then Aβ25 was added. At 48 h after ~35(20 μmol·lL-1) treatment, the cultured supernatants were transferred to cultured cerebellar granule cells in vitro for 72 h. In the control group, supernatants of macrophages not stimulated by Aβ25~35 were treated with supernatants. The fluid is added to nerve cells. Hoechst 33258 staining was used to observe the apoptosis of cerebellar granule cells. Results Aβ25~35(20μmol.L-1) increased the expression of phosphorylated ERK1/2 and phosphorylated p38 MAPK in macrophages, and peaked at 0.5 h and 2 h after addition of Aβ25~35, respectively. In addition, Aβ25-35 also increased macrophage TNF-α and NO production and increased iNOS expression. The increase in macrophage TNF-α production by Aβ25-35 was mediated through activation of the ERK1/2 signaling pathway. PD98059, a specific blocker of MEK, significantly inhibited the production of TNF-α by macrophages induced by Aβ25-35. Adding macrophages supernatants stimulated by Aβ25~35 for 48 h into cultured cerebellar granule cells resulted in a significant increase in the percentage of apoptotic neurons compared with the control group. SAaB (30 and 100 μmol.L-1) significantly inhibited the expression of phosphorylated ERK1/2, phosphorylated p38 MAPK, and iNOS in macrophages induced by Aβ25-35, and SAaB (10, 30, and 100 μmol.L-1) also Increased production of TNF-α and NO induced by Aβ25-35 and significantly decreased apoptosis of neurons mediated by Aβ25-35 activated macrophages. Conclusion SAaB has an antagonistic effect on Apoptosis induced by Aβ25~35 activated macrophages. This effect is related to its inhibition of ERK1/2 signal transduction pathway in macrophages and the inhibition of macrophage TNF-α and NO production.