Effect of DNA polymerase beta on apoptosis and mitochondrial membrane potential induced by hydroquinone, a metabolite of benzene

Abstract

To explore the effect and mechanism of DNA polymerase β expression level on cell apoptosis and mitochondrial membrane potential induced by hydroquinone. Polβ wild-type cells (polβ+/+), polβ overexpressed cells (polβ oe) and polβ null cells (polβ-/-) were applied as a model cell system, The effect of cell apoptosis and mitochondrial membrane potential induced by different doses of hydroquinone were analyzed by flow cytometry. The ROS and ·OH assay kit were used to examine the cellular ROS and ·OH level. The activity of cellular SOD and GSH-Px were tested by Chemiluminescence method after exposed to different concentrations of hydroquinone. With the dose of hydroquinone increased, the rate of apoptosis and falling of mitochondrial membrane potential (ΔΨm) in cells were increased compared with the control. When compared with polβ+/+ cells, the rate of apoptosis in polβ-/- cells exposed to 20.00, 40.00, 80.00 µmol/L hydroquinone increased and the rate of apoptosis in polβ oe cells exposed to 10.00, 20.00, 40.00, 80.00 µmol/L hydroquinone decreased (P < 0.05). Compared with polβ+/+ cells (20.60% ± 0.57%, 37.95% ± 0.64%, 44.50% ± 1.27%, 57.55% ± 1.06%), the rate of cell which undergone mitochondrial depolarization in polβ-/- cells treated with 10.00, 20.00, 40.00, 80.00 µmol/L hydroquinone (33.60% ± 1.55%, 46.05% ± 1.77%, 52.75% ± 2.05%, 75.20% ± 0.56%) increased. The rate of cell which undergone mitochondrial depolarization in polβ oe cells exposed to 10.00, 20.00, 40.00, 80.00 µmol/L hydroquinone (16.05% ± 1.20%, 29.80% ± 1.21%, 35.15% ± 1.06%, 53.80% ± 0.85%) decreased (P < 0.05). When compared with polβ+/+ cells, fluorescent intensity of polβ-/- cells treated with different dosages of hydroquinone increased, while which of polβ oe cells decreased (P < 0.05). Compared with polβ+/+ cells, ·OH level of polβ-/- cells treated with 20.00, 40.00 µmol/L hydroquinone significantly enhanced, while which of polβ oe cells decreased sharply (P < 0.05). Under the same concentrations of hydroquinone, the activity of SOD and GSH-Px were decreased most rapidly in polβ-/- cells. The activity of SOD and GSH-Px in polβ oe cells decreased slower than in the polβ-/- cells. Hydroquinone could induced apoptosis by the generation of ROS and decrease of ΔΨm; polβ could protect cells from apoptosis induced by hydroquinone through decrease of ROS level and depolarization of mitochondria.