Evaluation of insulin and ascorbic acid effects on expression of Bcl-2 family proteins and caspase-3 activity in hippocampus of STZ-induced diabetic rats.

Abstract

Effects of insulin and ascorbic acid on expression of Bcl-2 family proteins and caspase-3 activity in hippocampus of diabetic rats were evaluated in this study. Diabetes was induced in Wistar male rats by streptozotocin (STZ). Six weeks after verification of diabetes, the animals were treated for 2 weeks with insulin or/and ascorbic acid in separate groups. Hippocampi of rats were removed and evaluation of Bcl-2, Bcl-x(L), and Bax proteins expression in frozen hippocampi tissues were done by SDS-PAGE electrophoresis and blotting. The Bcl-2, Bcl-x(L), and Bax proteins bands were visualized after incubation with specific antibodies using enhanced chemiluminescences method. Caspase-3 activity was determined using the caspase-3/CPP32 Fluorometric Assay Kit. Diabetic rats showed increase in Bax protein expression and decrease in Bcl-2 and Bcl-x(L) proteins expression. The Bax/Bcl-2 and Bax/Bcl-x(L) ratios were found higher compared with non-diabetic control group. Treatments with insulin and/or ascorbic acid were resulted in decrease in Bax protein expression and increase in Bcl-2 and Bcl-x(L) proteins expression. The Bcl-2/Bax and Bcl-x(L)/Bax ratios were found higher in treated groups than untreated diabetic group. Caspase-3 activity level was found higher in diabetic group compared with non-diabetic group. Treatment with insulin and ascorbic acid did downregulated caspase-3 activity. Our data provide supportive evidence to demonstrate the antiapoptotic effects of insulin and ascorbic acid on hippocampus of STZ-induced diabetic rats.