Objective:

2

To investigate apoptotic effects of berberine

a significant alkaloids component existing in

Rhizoma coptidis

and its possible acting mechanism in insulinoma cells.

Methods:

2

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:

2

The half-maximal inhibitory concentration (IC

50

) of berberine was 5.7 μmol/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 μmol/L) for 8 and 16 h

while 3- and 8.7-fold after 10 μmol/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:

2

High concentration (5 and 10 μmol/L) of berberine could induce the apoptosis of MIN6 cells through cytochrome C/Apaf-1/caspase-3 and apoptosis inducing factor (AIF) pathway.