Abstract:

Objective To investigate the effects of aldosterone on apoptosis of murine pancreatic islets B cell line MIN6, and explore its possible mechanism. Methods Murine pancreatic islets B cell line MIN6 cultured in vitro was divided into control group (treated with serum-free DMEM culture medium), aldosterone group (treated with 10, 100 or 1 000 nmol/L aldosterone) and aldosterone+aldosterone antagonist group (treated with 100 nmol/L aldosterone and 100 nmol/L aldactone). Cell viability was determined by MTT assay, glucose-stimulated insulin secretion (GSIS) was measured by radioimmunoassay, cell apoptosis was detected by flow cytometry in combination with FITC-Annexin V/PI fluorescein staining, Caspase-3 activity in supernatant of culture fluid was determined by ELISA, and the expression of apoptosisrelated proteins of cytochrome C(Cyt-C), Bcl-2, Bax and phosphorylated protein kinase C (p-Akt) was detected by Western blotting. Results The viability of MIN6 cells decreased with the increase of concentrations of aldosterone, with a concentration-dependent manner. Under physical glucose concentration (5.6 mmol/L) and high glucose concentration (28 mmol/L) environment, GSIS of aldosterone group was significantly lower than that of control group (P<0.01), and GSIS of aldosterone+aldosterone antagonist group was significantly higher than that of aldosterone group (P<0.01). The cell apoptosis ratio of aldosterone group was significantly higher than that of control group (P<0.01), and the cell apoptosis ratio of aldosterone+aldosterone antagonist group was significantly lower than that of aldosterone group (P<0.01). Compared with control group, the Caspase-3 activity and expression of Cyt-C were significantly higher, and Bcl-2/Bax and the expression of p-Akt were significantly lower (P<0.01 for all), while aldosterone antagonist significantly inhibited aldosterone-mediated Caspase-3 activity increase and abnormal expression of related proteins. Conclusion Aldosterone enhances apoptosis of MIN6 cells, which may be associated with Cyt-C, Bcl-2, Bax and Akt-mediated mitochondria signaling pathway.

Key words: aldosterone, pancreatic islet B cells, apoptosis, protein kinase C