Study On The Early Biological Effect Index Of Fluoride Exposure

Fluorine is one of the necessary trace elements of human beings, which is regarded as a classic example of double-edged. Fluoride is beneficial to promote the growth of tooth and bone, keep the balance of calcium and phosphate, and prevent dental caries in trace amount, whereas could accumulate in fluids and tissues, and then have more toxic effects on the body in excessive amount, even result in dental and skeletal fluorosis. Now, endemic fluorosis is one of the most severe problems of public health, which is popular in almost all the provinces, municipalities, and autonomous regions of China in different degree, except Shanghai and Hainan province, especially in the rural and remote mountainous areas.For a long time, many early researches have been conducted to explore the bone injury from fluoride exposure. In this process, dental and skeletal fluorosis was always selected as the biomarker of fluoride exposure. However, they were found to have certain limits. Because both of them belong to quantal data, the accuracy of exposure-effect fitting result would be directly influenced when using them as the biomarkers. So in order to explore the relationship of exposure-effect and search for the early and sensitive biomarker of fluoride exposure, we conducted the cell and animal toxicity test experiments from fluoride exposure, which consists of two main parts:(1) Human myeloma cell RPMI8226 were selected as the research object and treated with NaF to build the cell model. The cells were treated with 0、 10、20、40、80、160、320 μM respectively. After 48h, their RNA were extracted and the change of their expression (up-regulate or down-regulate) were determined by RT-QPCR. The results revealed that the expression of genes relating to transcription, protein biosynthesis and cell proliferation, apoptosis, and cycle were influenced in varying degrees. Among them, the mRNA expression genes relating to transcription, including ANKRD1, KLF2, SBNO2 and ZNF649, were found increased significantly (P<0.01) in the high concentration group (320μM) when compared to the control group. Also, the expression of the gene FANCM relating to protein biosynthesis in two groups (80,320μM) were show higher than the control group. And as for the genes relating to cell proliferation, apoptosis, and cycle, including PDGFAR, NF152, CDK10 and CETN2, their mRNA expression elevated significantly compared to the control group when the exposure concentration was more than 160 uM.(2) SD rats were selected as the research object and treated by gavage with NaF to build the animal model. The rats had been treated with 0、2、4、 8、16、320 mg/kg. b. w respectively for 3 months. In the process, the rats were weighted once every other day and their teeth were examined. After 3 months, the regular indicators, clinical indicators and key protein were detected. The result showed that the growth rate of rats’ weight gradually decreased with the increasing of fluoride exposure concentration. The organ coefficient of heart and thymus exhibited decreasing trends, while that of liver increased gradually with the increasing of fluoride exposure concentration. Compared to the control group, the organ coefficient of liver in rats treated with 16、32mg/kg. b. w showed increased significantly (P＜0.05), which indicated that the liver was injured in high concentration exposure. What’s more, the activity of AST, as the indicator of liver function, displayed decreasing trend. When the concentration was more than 4 mg/kg. b. w, its activity decreased significantly. Finally, the content of key protein, GLRa2 and RYR1, had no significant change, but the ATF4 showed decreasing trend with the increasing of exposure concentration. In addition, a strong inverse relationship was observed between exposure levels and ATF4 (R=-0.586; P<0.01). So, it is suggested that ATF4 may be act as one of the early and sensitive indicators to evaluate fluoride exposure in epidemiology.This study has determined the changes of various indicators based on the cell and animal models from fluoride exposure and also have explored the relationship of exposure-effect. Our findings not only give experimental data to further study on the early and sensitive biomarker of fluoride exposure, but also provide scientific basis for fluorosis prevention and treatment.