Effects of Sodium Fluoride on Histone Acetylation and Expression of p21 Gene in Human Primary Osteoblasts

Objective To observe the effects of sodium fluoride on the levels of histone acetylation, mRNA transcription, and protein expression of p21 gene in human primary osteoblasts and provide evidence for a potential molecular mechanism of sk eletal fluorosis.

Methods Primary osteoblasts were treated with 0, 125, 250, 500, and 1 000 μmol/L sodium fluoride for 72 h. The levels of histone acetylation in transcription regulatory region (ChIP1 region) and coding region (ChIP2 region) of p21 gene were detected by quantitative chromatin immuno precipitation. The levels of p21 mRNA transcription were detected by real-time quantitative PCR. The expression levels of P21 protein were detected by Western blot.

Results After human osteoblasts were tre ated with 0, 125, 250, 500, and 1 000 μmol/L sodium fluoride, in ChIP1 transcription regulatory region of p21 gene, the levels of histone acetylation of H3K9 were 1.998±0.085, 1.644±0.162, 1.381±0.069, 1.280±0.129, and 1.040±0.270, respectively (F=15.757, P < 0.05); the levels of histone acetylation of H3K14 were 1.344±0.068, 1.248±0.070, 1.140±0.090, 1.040±0.116, and 0.770±0.059, respectively (F=21.284, P < 0.05); the levels of histone acetylation of H4K16 were 1.330±0.084, 1.251±0.085, 1.087±0.044, 0.854±0.070, and 0.788±0.051, respectively (F=36.429, P < 0.05). Among the groups treated with different concentrations of fluoride, the levels of histone acetylation of H3K9, H3K14, and H4K16 in ChIP2 coding region were not statistically different (F=0.084, 0.206, and 0.500, all Ps>0.05). The levels of p21 mRNA transcription were 2.65±0.35, 1.93±0.48, 0.88±0.17, 0.82±0.09, and 0.67±0.16, respectively (F=3.90, P < 0.05). The levels of P21 protein expression were 1.62±0.06, 1.02±0.08, 0.84±0.07, 0.26±0.05, and 0.07±0.03, respectively (F=281.58, P < 0.05).

Conclusion Fluoride could reduce the levels of histone acetylation of p21 gene transcription regulatory region in human primary osteoblasts, then suppress the expression of p21 mRNA transcription and the protein, which might be one of the important molecular mechanisms of active cell proliferation in skeletal fluorosis.