Objective To investigate the effects of vitamin E on the methylation of p15 in lung of rats exposed to nickel chloride.
Methods The rats were fed by gavage with the designed concentrations of NiCl2& #183; 6H2O (0.1, 0.2, 0.4 and 0.8 mg/mL) for four different exposed groups and 0.9% NaCl solution for the solvent control group. The antagonism group was supplied with vitamin E (5 mg/mL) along with 0.8 mg/mL NiCl2. After treating the rats for six weeks, we detected the levels of malondialdehyde (MDA)and glutathione (GSH)to assess oxidative stress in the lung tissues. In addition, we also evaluated the methylation status and expressions of tumor suppressor gene p15 using methylation specific PCR and quantitative real time PCR. DNA methyltransferase (DNMT1)and methionine adenosyltransferase 2A (MAT2A)that play key role in methylation process were detected by western blot.
Results Compared with the control group, the levels of MDA in lung of the rats exposed to nickel chloride increased significantly, while the levels of GSH decreased significantly (P < 0.01). As compared with the high-dose group (0.8 mg/mL NiCl2), a significant in crease in GSH contents was observed in the antagonism group (NiCl2+VE), while the levels of MDA decreased significantly (P < 0.05). The tumor suppressor gene of p15 was found to be non-methylated in the control group. The methylation and non-methylation of p15 were both observed in NiCl2 exposure groups and VE antagonism group. Compared with the control group, the levels of p15 were down-regulated significantly in the NiCl2 exposure groups (P<0.01). As compared with the high-dose group (0.8mg/mL NiCl2), a significant increase in p15 levels was observed in the antagonism group (NiCl2+VE) (P<0.05). The levels of DNMT1 and MAT2A significantly increased as the concentrations of NiCl2 increased, and the ratios increased 1.52-and 1.49-folds in the high-dose group respectively compared with the control group. Compared with the high-dose group, the relative ratios of DNMT1 and MAT2A in the antagonism (NiCl2+VE) group decreased 18% and 29% respectively. We found that the levels of GSH were correlated negatively with the relative expressions of DNMT1 (r=-0.889, P=0.018)and MAT2A (r=-0.821, P=0.044).
Conclusion Our findings suggest that glutathione influenced by vitamin E may play important role in DNA methylation.
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