[The effect of fluoride on the expression of GRP-78 and caspase-12 in rat ameloblast].

PURPOSE: To study the effect of GRP-78 and caspase-12 on fluoride-induced endoplasmic reticulum stress and apoptosis in rat ameloblast, and explore whether fluoride-induced endoplasmic reticulum stress results in the occurrence of apoptosis. METHODS: The cell activity of ameloblast cultured in various concentrations of fluoride was measured by CCK8 and flow cytometry; Real-time RT-PCR and Western blot were used to analyze the endoplasmic reticulum chaperone GRP-78 and caspase-12 genes and the expression of related proteins. The data was analyzed with SPSS13.0 software package. RESULTS: With the increasing concentration of fluoride, the cell activity of rat ameloblasts decreased gradually, and flow cytometry also showed that the number of apoptosis gradually increased; Real-time RT-PCR and Western blot showed the expression of GRP-78 and caspase-12 increased while the fluoride concentration increased. CONCLUSIONS: Excessive fluoride induces endoplasmic reticulum stress of rat ameloblast, and leads to cell apoptosis.

[Effect of fluoride on the viability and apoptosis of ameloblasts in vitro].

PURPOSE: To evaluate the effect of fluoride on viability of rat ameloblasts in vitro. METHODS: The ameloblasts of rat was exposed to different concentrations of NaF (0, 0.4, 0.8, 1.6, 3.2, 6.4 mmol/L) for 24, 48 and 72 hours. CCK-8 assays were performed to measure the cells proliferation; The morphology of apoptosis was observed by Hoechst 33258 staining and the rate of apoptosis was determined by flow cytometry. The data was analyzed using SPSS 13.0 software package. RESULTS: (1)The proliferation of ameloblasts was increased when concentrations of NaF between 0.4 mmol/L and 0.8 mmol/L, whereas inhibited at 1.6 mmol/L NaF and above. The effects were in time-dependent manner.(2)Cells in the 1.6 mmol/L NaF groups showed unclear karyorrhexis and apoptotic cell morphology. The effects were in concentration-dependent manner. CONCLUSIONS: (1)Fluoride has two-phase effects to ameloblasts: At low doses, it promoted cell proliferation while at high doses it had negative effects. (2)1.6 mmol/L NaF could induce apoptosis of ameloblasts.

[The effect of fluoride on the metabolism of teeth and bone in rats].

PURPOSE: To investigate the effect of fluoride on the metabolism of teeth and bone in rats, and to probe the mechanism of pathogenesis of dental fluorosis. METHODS: A total of 48 Wistar rats were randomly and equally divided into 4 groups including control group (distilled water), low-dose group(NaF,50 mg/L), medium-dose group (NaF,100 mg/L) and high-dose group (NaF, 150 mg/L). After 8 weeks, the rats were sacrificed under anesthesia, and serums were collected. The biochemical technique was used to test serum calcium. Changes in the fluorine content in serums and teeth of each group were analyzed with fluoride ion selective electrode method. Radioimmunoassay was employed to detect the levels of osteocalcin (OC), parathormone (PTH) and calcitonin (CT), respectively. SPSS13.0 software package was used for statistical analysis. RESULTS: The fluorine content in serum and teeth in the fluoride group were significantly higher than that of the control group (P<0.05), and increased with the increasing concentrations (F value was 11.234 and 275.148 respectively, P<0.01). The level of calcium in serum (F=3.906, P<0.05) in the fluoride group was significantly lower than in the control group. The level of PTH and OC in serum in medium and high-dose group were significantly higher than in the control group (P<0.01), with the level of CT in high-dose group decreased significantly (P<0.01). The differences of the level of OC, PTH, CT between groups were significant (F value was 8.548, 3.801 and 5.121 respectively, P<0.05). CONCLUSIONS: Fluoride affects the metabolism of teeth and bone in rats and OC, PTH, CT plays a key role in the pathogenesis of dental fluorosis.

[Effect of fluoride on the expression of endoplasmic reticulum chaperone in ameloblast of rat incisor].

PURPOSE: To investigate the effect of different concentrations of fluoride on the expression of endoplasmic reticulum chaperone, and to explore the mechanism of dental fluorosis in rat. METHODS: Thirty Wistar rats were randomly divided into 3 groups. Immunohistochemistry was used to detect the expression of CRT, GRP78, XBP-1 and caspase-12 in rat incisors. Metamorph microscope images analysis system and SPSS 13.0 software package was used to analyze the data. RESULTS: Typical features of dental fluorosis were found in the fluoride group. Results of immunohistochemistry showed that CRT (F=238.6, P<0.05), GRP78 (F=27.42, P<0.05), XBP-1 (F=139.7, P<0.05) and caspase-12 (F=43.91, P<0.05) were significantly different among the 3 groups. CONCLUSIONS: Excessive fluoride can increase the secretion of CRT, GRP78, XBP-1 and caspase-12 suggest the ameloblasts and in status of endoplasmic reticulum stress and caspase-12 plays an important role during ameloblast apoptosis. Supported by National Natural Science Foundation of China (81072245) and Natural Science Foundation of Liaoning Province (20102278).