Detection of DNA strand breaks by fluroscence assisted DNA unwinding (FADU) assay in Hela cells treated with berbrine chloride before exposure to various doses of γ – radition

Abstract

The DNA damage plays an important role in the cell death and DNA double strand breaks in particular have been implicated in cell mortality. Therefore, the ability of berberine chloride to modulate radiation-induced DNA damage in HeLa cells exposed to different doses of γ-rays was studied by fluorescence assisted DNA unwinding assay. The spontaneous frequency of undamaged DNA remained unaltered in HeLa cells treated with 0, 1, 2, 4, 6 or 8µg/ml of BCL at 0, 0.25, 0.5, 1, 2 or 4h postirradiation. Immediate exposure of HeLa cells to 3 Gy γ-radiation (0h post-irradiation group) caused a drastic rise in the DNA strand breaks as evident by an abrupt reduction in the undamaged double stranded DNA (dsDNA). An elevation in the undamaged ds DNA was observed with time up to 12h post-irradiation in cells exposed to 3Gy irradiation without BCL treatment, indicating repair of radiation-induced DNA damage. However, incubation of HeLa cells with different concentrations of BCL before 3Gy irradiation caused a dose-dependent increase in the DNA strand breaks at all post-irradiation times. The highest DNA strand breaks were observed for 8µg/ml BCL after exposure to 3 Gy. The DNA strand breaks did not show repair up to 12h in cells exposed 3 Gy. The exposure of HeLa cells to 0.25 to 4 Gy γ-radiation resulted in a dose dependent decline in dsDNA at all post-irradiation times and treatment of HeLa cells with 8 µg/ml berberine before irradiation led to a further attrition in the dsDNA. Our study demonstrates that irradiation of HeLa cells resulted in a dose dependent increase in DNA strand breaks and berberine treatment further increased the DNA strand breaks which may be one of the mechanisms of cell death.