Berberine Induces Cell Apoptosis through Cytochrome C/Apoptotic Protease-Activating Factor 1/Caspase-3 and Apoptosis Inducing Factor Pathway in Mouse Insulinoma Cells

Objective: To investigate apoptotic effects of berberine, a significant alkaloids component existing in Rhizoma coptidis, and its possible acting mechanism in insulinoma cells. Methods: Different concentrations of berberine were used to treat mouse insulinoma (MIN6) cells for various period of time. The viability and apoptosis of the cells were analyzed using methylthiazolyldiphenvl-tetrazolium bromide assay, flow cytometry and enzyme-linked immuno sorbent assay. Changes in the relating pro- and anti-apoptosis proteins were detected by western-blotting. Results: The half-maximal inhibitory concentration (IC50) of berberine was 5.7 mu mol/L on MIN6 cells viability for 16 h. Berberine caused a 20% reduction (P<0.05) in cell number after only 4-h incubation; which reached 50% after 24 h (P<0.01). Berberine treatment for 16 h significantly increased the level of DNA fragmentation. The flow cytometry showed the apoptotic rate increased 2.9- and 4.6- fold after treating with berberine (5 mu mol/L) for 8 and 16 h, while 3- and 8.7-fold after 10 mu mol/L treatment for 8 and 16 h (P<0.01). Berberine treatment dramatically elevated the expression ratio of Bax to Bcl-2. Meanwhile, berberine notably increased the apoptosis-inducing factors and cytochrome C transforming from the mitochondria to the cytoplasm. Apoptotic protease-activating factor 1 (Apaf-1) was subsequently activated after cytochrome C release. Furthermore, caspase-3 and poly adenosine diphosphate-ribose polymerase were also activated to trigger apoptosis cascade. Conclusion: High concentration (5 and 10 mu mol/L) of berberine could induce the apoptosis of MIN6 cells through cytochrome C/Apaf-1/caspase-3 and apoptosis inducing factor (AIF) pathway.