Objective To investigate the effects of sodium arsenite (NaAsO2) on DNA double-strand break and the expression of histone H4 lysine 20 monomethylation and dimethylation (H4K20me1 and H4K20me2) in immortalized human keratinocytes (HaCaT cells), and to study the roles of H4K20me1 and H4K20me2 in DNA double-strand break induced by arsenic.
Methods HaCaT cells were conventionally cultured in vitro and treated continuously with different concentrations of NaAsO2 (0.00, 1.25, 2.50, 5.00, and 10.00 μmol/L) for 24 h, or treated with 10.00 μmol/L NaAsO2 for 0, 6, 12, and 24 h, respectively. The 0.00 μmol/L and 0 h treatments were used as blank control group. The damage degree of DNA double-strand break (DSB) (tail DNA% and Olive tail moment) in HaCaT cells were measured by neutral single cell gel electrophoresis. Western blot was used to observe the protein expression levels of H4K20me1 and H4K20me2.
Results After exposure to NaAsO2 for 24 h, the degrees of DSB in HaCaT cells of the 5.00 and 10.00 μmol/L groups were higher than that of the blank control group (P＜0.05), and the protein expression levels of H4K20me1 and H4K20me2 in HaCaT cells of the 2.50, 5.00, and 10.00 μmol/L groups were lower than that of the blank control group (P＜0.05). Regarding treatment with 10.00 μmol/L NaAsO2 for different time periods, compared with the blank control group, the degrees of DSB in HaCaT cells at 12 and 24 h were significantly increased (P＜0.05), and the H4K20me1 and H4K20me2 protein expression levels in HaCaT cells at 6, 12, and 24 h were reduced (P＜0.05). Tail DNA% was negatively associated with the protein expression level of H4K20me1 and H4K20me2 (r=-0.955, -0.855, both Ps＜0.05). Olive tail moment was also negatively associated (r=-0.940, -0.841, both Ps＜0.05).
Conclusion Arsenic can cause DNA double-strand break damage and changes in the expression of H4K20me1 and H4K20me2 in HaCaT cells, suggesting that DNA damage induced by arsenic may be related to histone H4K20 methylation.
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