Excessive fluoride inducing calcium overload and apoptosis of ameloblasts.

Objective To study the effect of excessive fluoride on calcium overload and apoptosis in cultured rat amelo-blasts in vitro. Methods Logarithmic-phase ameloblasts (HAT-7) were treated with 0, 0.4, 0.8, 1.6, 3.2, and 6.4 mmol-L^-1 sodium fluoride (NaF) solution. Cell activities were detected by using a Cell Counting Kit 8 (CCK-8) assay after 48 h of treatment. The effect of fluoride on cell apoptosis was analyzed by using flow cytometry. Excessive fluoride-induced calcium concentration and calreticulin expression changes in ameloblasts were detected by using laser scanning confocal microscopy, Western blot analysis, and real-time quantitative polymerase chain reaction. Results NaF inhibited ameloblast activity at 1.6, 3.2, and 6.4 mmol-L^-1 (dose-dependent) after 48 h of induction. The Ca²⁺ fluorescence intensity of HAT-7 cells incubated with 1.6 and 3.2 mmol*L^-1 NaF was higher than that in the control group. The fluoride-induced early-stage apoptosis of ameloblasts after 48 h of induction and the early-stage apoptosis rate was positively correlated with fluoride concentration. Calreticulin mRNA expression in HAT-7 cells was higher than that in the control group after 48 h of incubation with 0.8, 1.2, and 1.6 mmol-L^-1 NaF. Conclusion Excessive fluoride-induced calcium overload in ameloblasts and further caused endoplasmic reticulum stress-mediated apoptosis. [ABSTRACT FROM AUTHOR]