Dose-dependent effects of berberine on cell cycle pause and apoptosis in Balb/c 3T3 cells

In determining the morphological appearance of Balb/c 3T3 cells from berberine-treated (100 and 200 mu g/ mi) cultures by light microscopy demonstrated that the high berberine concentration (200 mu g/ml) treatment was associated with the accumulation of numerous apoptotic cells, as identified by condensed nuclei and decrease in cell size. On the other hand, accumulation of cells in G(2)/M phase instead of induction of apoptosis was observed after 48-72 h of 100 mu g/ml berberine treatment. Berberine was found mainly in cytoplasm during berberine-induced (100 mu g/ml) cell cycle G(2)/M arrest, while it was highly concentrated in nuclei in the induction of apoptosis under high dose of berberine (200 mu g/ml) treatment. Further addition of berberine (100-200 mu g/ml) had little effect on the induction of apoptosis in the cells that had already been exposed to 100 mu g/ml of berberine for 48 h. Our results suggest that there may exist in Balb/c 3T3 cells an important threshold for regulation of cell cycle pause and induction of apoptosis, that is dose-dependent.