Abstract

Fluorine compounds are widely used for the prevention of caries, and recently sodium fluorosilicate has been used in water fluorination. The cytotoxic effects of sodium fluorosilicate in several osteosarcoma and oral cancer cells were evaluated in this study by measurement of inhibition of cell proliferation. Human osteogenic sarcoma (HOS) cells were the most sensitive to sodium fluorosilicate treatment. Induction of apoptosis, such as nucleosomal DNA fragmentation and the appearance of apoptotic bodies, were observed in HOS cells by agarose gel electrophoresis and by flow cytometric analysis, respectively. The molecular mechanism of apoptosis induction in HOS was investigated by Western blot analysis. The level of Bcl-2 was decreased and consequent release of cytochrome c was increased. Caspase-3 was activated and the cleavage of poly (ADP-ribosyl) polymerase was increased. In conclusion, sodium fluorosilicate induces apoptosis in HOS cells through decrease in Bcl-2, the release of cytochrome c to the cytosol and activation of caspase-3.

Excerpt:

Materials and Methods
Fluorine compounds and cell culture. The fluorine compounds used in this study were sodium fluorosilicate (F6Na2Si, Fluka, Switzerland) and sodium fluoride (NaF, Sigma, USA)…

Results
Cytotoxicity of sodium fluorosilicate. To determine a concentration which leads to 50% growth inhibition (IC50 values), we performed cytotoxicity analysis by MTT assay. HOS, MG-63, KB and A-253 cells were treated with 0-250 ppm of sodium fluorosilicate or sodium fluoride. The cells were treated with the fluorine compound for 48 h, and relative cell survivals were observed. The cell survivals decreased with increasing dose of fluorine compounds (Figure 1). The relative cell survival of each cell line was plotted against the fluorine content of sodium fluorosilicate (60.6%) and sodium fluoride (45.3%). IC50 values of sodium fluorosilicate were 20 ppmF for HOS, 22 ppmF for A253, 64 ppmF for KB and 82 ppmF for MG63. Similar
IC50 values were obtained with sodium fluoride; 21 ppmF, 14 ppmF, 73 ppmF and 80 ppmF for HOS, A253, KB and MG63, respectively. MG63 cells were most resistant to both sodium fluorosilicate and sodium fluoride treatment. A253 cells were a little more sensitive to sodium fluoride. Among the cell lines used in this study, HOS cells were the most sensitive to sodium fluorosilicate treatment. Therefore, HOS cells were used to examine the effect of sodium fluorosilicate in the following experiments…

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