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

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.