Excessive fluoride reduces Foxoi expression in dental epithelial cells of the rat incisor

摘要

Enamel fluorosis is characterized by hypomineralization, and forkhead box Ol (Foxol) is essential for mouse enamel biomineralization. This study investigated the effect of fluoride on Foxol expression and its implications for enamel fluorosis. Mandibular incisors were extracted from Sprague Dawley rats treated for 3 months with water containing 0, 50, or 100 p.p.m. F~. Immunohistochemistry was used to localize and quantify FOXO1 expression in dental epithelial layer cells of the incisors. The effect of fluoride on expression of Foxol, kallikrein-4 (Klk4), and amelotin (Amtri) mRNAs was analyzed by real-time RT-PCR, and western blotting was used to measure total and nuclear FOXO1 protein levels in mature dental epithelial cells. The results revealed that nuclear FOXO1 was mainly localized in the transition and the mature ameloblasts and exhibited weaker expression in the rats exposed to fluoride. In addition to the reduced levels of Foxol, Klk4, and Amtn mRNAs, the protein levels of total and nuclear FOXO1 were decreased in the mature dental epithelial cells exposed to fluoride. Thus, excessive fluoride may have an effect on the expression levels of Foxol in dental epithelial cells and thereby affect hypomineralization of the enamel during fluorosis.