地塞米松诱导小鼠MIN6胰岛β细胞凋亡及其对AKT磷酸化的影响

Dexamethasone-induced apoptosis of murine MIN6 pancreatic β-cells and its effect on AKT phosphorylation

为观察地塞米松对小鼠MIN6胰岛β细胞凋亡及其对凋亡相关蛋白表达和AKT磷酸化的影响,选用小鼠MIN6胰岛β细胞为研究对象,用不同浓度地塞米松(50、100、200、400及800nmol·L?1)诱导刺激不同时间,观察细胞凋亡的变化。通过Hochest/PI、AnnexinV-FITC细胞凋亡检测试剂盒观测细胞凋亡率;caspase-3检测试剂盒测定caspase-3含量;Westernblotting测定细胞色素c(Cyt-c)、Bcl-2、Bax、T-AKT及p-AKT的蛋白含量。结果显示:地塞米松(50～800nmol·L?1)作用48h后,可诱导β细胞凋亡;100nmol·L?1地塞米松处理72h后,caspase-3含量明显增多;不同浓度地塞米松处理48h,随着浓度的增加Cyt-c表达增多,Bax蛋白含量无明显变化,而Bcl-2蛋白含量有所降低。T-AKT表达无明显变化,p-AKT随地塞米松浓度增加表达减少。因此,地塞米松能够引起小鼠MIN6胰岛β细胞凋亡,其机制可能与抑制AKT磷酸化、下调Bcl-2表达有关。

This study is to investigate the effect of dexamethasone on cell apoptosis of murine MIN6 pancreatic β-cells, and to investigate the mechanism of dexamethasone-dependent cell apoptosis. The cell apoptosis model was established by choosing the murine MIN6 pancreatic β-cells, which was cultured in vitro and induced by dexamethasone. The morphology of the cell apoptosis was observed through fluorescence microscopic analysis after Hochest/PI staining and flow cytometric assay after Annexin-V/PI staining. The expression of caspase-3 was detected with caspase-3 activity assay kit. The expressions of Cyt-c, Bcl-2, Bax, AKT and p-AKT were observed with Western blotting. The results indicated that after exposure to dexamethasone at a concentration ranging from 50-800 nmol·L^-1 for 48 h, the percentage of cell apoptosis was significantly increased with the concentration over 100 nmol·L？1 of dexamethasone; after exposure to dexamethasone （100 nmol·L^-1） for 72 h, the activity of caspase-3 increased significantly; after exposure to dexamethasone at a concentration ranging from 50？800 nmol·L^-1 for 48 h, the expression of Cyt-c increased, Bcl-2 and AKT phosphorylation decreased while Bax and T-AKT remained unchanged. It could be concluded that the effect of dexamethasone on murine MIN6 pancreatic β-cells apoptosis is significant. The mechanism of dexamethasone-dependent cell apoptosis is probably related to down regulation of the Bcl-2 expression and reduction of AKT phosphorylation.