ABSTRACT
Objective To establish an model of fluorosis with human primary osteoblasts in vitro and to detect the influences of different doses of sodium fluoride (NaF) on histone acetylation of CyclinD1,cyclindependent kinases 4 (CDK4) gene in human osteoblasts,then to explore the molecular mechanism of skeletal fluorosis from epigenetic perspective of the cell cycle regulation related genes.Methods Human primary osteoblasts from bone tissues of trauma surgery healthy people (car accident) were isolated by enzyme digestion and identified.The osteoblasts were treated with 0,125,250,500 and 1 000 μmol/L NaF for 72 h.The level of histone acetylation (H3K9,H3K14,H4K12,H4K16) in the transcription regulatory region (ChIP1 region) and in the coding region (ChIP2 region) of CyclinD1 and CDK4 genes were detected by quantitative chmmatin immuno-precipitation (Q-ChIP).Results ①After human osteoblasts were treated with 0,125,250,500 and 1 000 μmol/L NaF,respectively,the levels of histone acetylation of H3K9 in ChIP1 transcription regulatory region of CyclinD1 gene were 1.152 ± 0.104,1.174 ± 0.187,1.090 ± 0.176,1.170 ± 0.197 and 1.147 ± 0.097,respectively,the differences were not statistically significant (F =0.524,P ＞ 0.05);the average levels of histone acetylation of H3K14 were 1.495 ± 0.117,1.465 ± 0.069,1.470 ± 0.187,1.760 ± 1.089 and 1.341 ± 0.443,the differences were not statistically significant (F =0.841,P ＞ 0.05);the levels of histone acetylation of H4K12 were 1.239 ± 0.286,0.702 ± 0.063,0.765 ± 0.370,1.011 ± 0.321 and 1.319 ± 0.026,the differences were not statistically significant (F =2.329,P ＞ 0.05);the levels of histone acetylation of H4K16 were 1.452 ± 0.217,1.621 ± 0.165,1.462 ±0.090,1.510 ± 0.146 and 1.564 ± 0.154,the differences were not statistically significant (F =0.123,P ＞ 0.05).②The levels of histone acetylation of H3K9 in ChIP1 transcription regulatory region of CDK4 were 1.472 ± 0.163,1.580 ± 0.161,1.585 ± 0.132,1.451 ± 0.136 and 1.560 ± 0.039,the differences were not statistically significant (F =0.461,P ＞ 0.05);the levels of histone acetylation of H3K14 were 0.919 ± 0.149,0.900 ± 0.059,0.911 ±0.162,0.663 ± 0.049 and 0.841 ± 0.122,the differences were not statistically significant (F =0.974,P ＞ 0.05);the levels of histone acetylation of H4K12 were 0.456 ± 0.142,0.911 ± 0.126,0.969 ± 0.185,1.110 ± 0.146 and 0.931 ± 0.141,the differences were not statistically significant (F=5.459,P ＞ 0.05);the levels of histone acetylation of H4K16 were 1.315 ± 0.083,1.374 ± 0.153,1.423 ± 0.055,1.300 ± 0.132 and 1.385 ± 0.696,the differences were not statistically significant (F =1.663,P ＞ 0.05).③The differences of histone acetylation levels of H3K9,H3K14,H4K12 and H4K16 in ChIP2 coding region of CyclinD1 and CDK4 genes were not statistically significant between NaF treatment groups (F =0.392,0.823,0.999,0.397,0.705,0.049,1.065,0.196,P ＞ 0.05).Conclusion The histone acetylation of CyclinD1 and CDK4 may not be involved in the transcriptional regulation in human primary osteoblasts treated with fluoride.
ABSTRACT
Background and purpose:B cell-specific MLV integration site 1 (BMI-1) gene plays an important role in DNA damage after exposure to irradiation. The present study aimed to investigate the effect ofBMI-1 on radio-sensitivity of esophageal carcinoma cell after down-regulation of BMI-1 expression by silencing siRNA.Methods:Three pairs of siRNA based on the sequences of the BMI-1 mRNA were synthesized (siRNA1, siRNA2 and siRNA3) by compa-ny, and transfected into cultured TE13 cells as the BMI-1 siRNA groups, and a negative one was synthesized to be used as the negative control (NC) group. The untransfected group was named as the control group. BMI-1 mRNA and protein expression in esophageal cancer TE13 cells were detected by reverse transcription polymerase chain reaction (RT-PCR) and Western blot in different groups. This study used flow cytometry assay to analyze cell cycle of transfected cells, and examined cellular growth and radiosensitivityin vitro by MTT and clone formation assay. mRNA and protein expression of p16 and CDK4 in esophageal cancer TE13 cells were detected by RT-PCR and Western blot.Results:The results of RT-PCR and Western blot showed that the expressions of BMI-1 at gene and protein levels were inhibited after silencing the BMI-1 gene. The mRNA and protein expression of BMI-1 in BMI-1 siRNA3 group were both significantly lower than that in BMI-1 siRNA1 and 2 groups. There was no significant difference in the cell proliferation among control, NC and BMI-1 siRNA3 groups. The values ofD0,Dq, and SF2 in BMI-1 siRNA3 group were 1.761, 2.122 and 0.6255, respectively, obvi-ously lower than those in control group (2.514, 2.694 and 0.8268) and those in NC group (2.506, 2.664 and 0.8231), while the value of N in BMI-1 siRNA3 group (3.336) was higher than that in control group (2.92) and that in NC group (2.895), which showed higher radiosensitivity in BMI-1 siRNA3 group. In addition, the cell cycle was arrested at G2/M phase after irradiation in control and NC groups. The percentage of G0/G1 phase in BMI-1 siRNA3 group was higher than that of control group and NC group, while the percentage of G2/M phase was lower than those in the latter. The up-regulation of p16 and down-regulation of CDK4 at gene and protein levels were detected after knockdown of BMI-1 expression by siRNA (P<0.01).Conclusion:siRNA could inhibitBMI-1 gene expression in esophageal cancer TE13 cells and enhance radiosensitivity, followed by eliminating the cell cycle arrest at G2/M stage after irradiationin vitro, which is related to the regulation of the protein expression ofp16 andCDK4.