p16 promoter methylation in premature rats with chronic lung disease induced by hyperoxia / 中华围产医学杂志

ABSTRACT

Objective To investigate p16 promoter methylation in premature rats with chronic lung disease induced by hyperoxia. Methods Eighty premature Wistar rats were randomly divided into two groups hyperoxia group (fraction of inspiratory oxygen) 0. 90 and control group (fraction of inspiratory oxygen 0. 21), 40 rats for each group. Semi-nested methylation specific polymerase chain reaction and methylation specific polymerase chain reaction were applied respectively to detect p16 promoter methylation in lung tissues. Additionally, p16 mRNA and protein expressions in lung tissue were detected by reverse transcription- polymerase chain reaction, Western blot and immunohistochemistry method. Results The methylation was not found in control group by seminested methylation specific polymerase chain reaction and methylation specific polymerase chain reaction, while was found in different aged rats of the hyperoxia group. The methylation detection rate was higher by using the semi-nested methylation-specific polymerase chain reaction (52.5%, 21/40) than that by methylation specific polymerase chain reaction (42.5%, 17/40) in the hyperoxia group,but there was no statistically significant difference between the two methods. The p16 mRNA in the hyperoxia group were significantly lower than in the control group at day 7, 14 and 21(1.73 ± 0.40 vs 2.11±0. 37,1.29±0. 19 vs 1.60±0. 27,0. 95±0.25 vs 1.72±0. 34, t=2.19, 2.95 and 10. 43,P＜0. 05). The p16 protein expressions by western blot in the hyperoxia group were significantly lower than in the control group at day 7, 14 and 21 also (88. 1±8. 7 vs 95.0±4.1,65.7±4.5 vs 83. 5±13.6 and 50.4±4.9 vs 86.7±11.9, t=2.27,3.95 and 13.40,P＜0.05). The expression of p16 mRNA (1.06±0.61) and protein (62.32±25.65) in lung tissues of rats with methylation was lower than that without methylation (1.63±0.62 and 94.93±22.21, respectively) (t=2.95, OR=0. 86;t=4.28, OR=0. 85,P＜0.01, respectively). Conclusions Exposure to hyperoxia might induce p16 promoter methylation in lung tissues in premature rats. Methylation risk increases as exposure time extends. p16 promoter methylation induced by hyperoxia might participate in the mechanism of lowering p16 mRNA and protein expression, but might not result in p16 gene silence.