Abstract: Objective To investigate the level of autophagy and apoptosis of ameloblasts in rats with different degrees of fluorosis, and to explore the effect of autophagy on the ameloblast apoptosis in rats with chronic fluorosis. Methods Forty-eight Wistar rats of 4-week-olds were randomly divided into 6 groups to establish a fluorosis rat model by adding 75 mg/L or 150 mg/L fluoride to the drinking water, and an autophagy inhibition model treated with an intraperitoneal injection of 10 mg/kg 3-methyladenine (3-MA). The morphology and expression of Beclin1, p62, LC3, and Cleaved Caspase-3 in rat incisor ameloblasts were observed, and statistical analysis of quantitative results of immunohistochemistry was performed using SPSS 22.0 software package. Results With the increase of fluoride in drinki ng water, features of dental fluorosis became more obvious and found disorders in morphological and structural of ameloblasts. Results of immunohistochemistry showed that the expression of Beclin1 and LC3 increased while p62 expression decreased in rat ameloblasts drinking 150 mg/L fluoride, and the expression of Cleaved Caspase-3 increased. these changes are more obvious than rats drinking 75 mg/L fluoride-containing water. After administration 3-MA to inhibit autophagy, and they, in turn, decreased the expression of Beclin1 and LC3 and increased the p62 expression. Meanwhile, the expression level of Cleaved Caspase-3 in ameloblast increased significantly. Conclusions There is autophagy in rat ameloblast with chronic fluorosis, the induction of it is enhanced by the high concentration of fluoride and may play a protective role in reducing the level of apoptosis in ameloblasts during the fluorosis.

Key words: Fluoride, Ameloblast, Autophagy, Apoptosis