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 μ 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 μ mol/L) for 8 and 16 h,while 3-and 8.7-fold after 10 μ 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 μ mol/L) of berberine could induce the apoptosis of MIN6 cells through cytochrome C/Apaf-1/caspase-3 and apoptosis inducing factor (AIF) pathway.