[Effects of DNA polymerase beta on the genotoxicity and genetic instability induced by benzo(a)pyrene].

OBJECTIVE

To explore the effects of DNA polymerase β expression level on the genotoxicity and genetic instability induced by benzo(a)pyrene (BaP),and provide experimental the basis for further study on the carcinogenic molecular mechanism of BaP.

METHODS

Three kinds of cell lines with the identical genetic background, polβ wild-type cells (polβ+/+), polβ null cells (polβ-/-) and polβ overexpression cells (polβ oe) were applied as cellular models. The oxidative damage, genotoxicity and genetic instability induced by BaP were analyzed by using different methods respectively.

RESULTS

Cell viability and colony forming ability of 3 kinds of cell lines exposed to BaP decreased with BaP. After treated with 5 and 20 µmol/L concentration of BaP, fluorescence intensity of polβ-/- cell line was significantly higher than that of other two cell lines (P < 0.05). When treated with 5.00 µmol/L and 20.00 µmol/L concentration of BaP, the SOD activities (76.56 ± 2.84 and 62.78 ± 4.28 U/mg pro) of polβ-/- cell line were significantly lower than that (84.85 ± 3.59) of control group and those (85.21 ± 3.20 and 76.90 ± 3.38 U/mg pro) of polβ+/+ cell line. In 20.00 µmol/L BaP group. SOD activity (82.59 ± 4.64 U/mg pro) of polβ oe cell line was lower than that (88.58 ± 6.77 U/mg pro) of control but higher than that of polβ+/+ cell line (P < 0.05). In 1.25, 5.00 and 20.00 µmol/L concentration BaP groups, the micronucleus rates of polβ-/- cell line were much higher than those of polβ+/+ cell line (P < 0.05). In 5.00 and 20.00 µmol/L concentration BaP groups, the micronucleus rates of polβ oe cell line were significantly lower than those of polβ+/+ line (P < 0.05). In 5.00 and 20.00 µmol/L concentration BaP groups, HPRT gene mutation frequencies (26.16 × 10(-6) and 37.51 × 10(-6); 27.68 × 10(-6) and 38.63 × 10(-6)) in polβ-/- cells and polβ oe cells were significantly higher than those (19.76 × 10(-6) and 24.78 × 10(-6)) of polβ+/+ cells (P < 0.05).

CONCLUSION

Polβ could play a role in protecting the cells from the genotoxicity and genetic instability induced by BaP, and the normal expression level of polβ was indispensable for maintaining genome stability.