title: Excessive fluoride induces endoplasmic reticulum stress and interferes enamel proteinases secretion.
abstract: Protein retention in the enamel layer during tooth formation is well known to be associated with dental fluorosis but the underlying mechanism is unclear. The functions of the endoplasmic reticulum (ER) correlate directly with secreted protein metabolism. We used an ameloblast-derived cell line to determine whether excessive amounts of fluoride cause ER stress, and whether this interferes with the secretion of enamel matrix proteinases. ER stress activates a signaling network called the unfolded protein response (UPR). Here, we used real-time RT-PCR and immunofluorescence to study the effect of fluoride on the expression, translation, and secretion of UPR transcription factors in ameloblast-like cells. Measurement of both the gene and protein expression of UPR transcription factors indicated that high-dose fluoride increases the expression of UPR transcription factors in a dose-dependent manner. We also used ELISA to detect and quantify the enamel proteinases secreted by ameloblasts. We found a corresponding decrease in extracellular secretion of the enamel proteinases matrix metalloproteinase-20 and kallikrein-4, after exposure to fluoride. Furthermore, correlation analysis indicated that the expression of UPR transcription factors showed a strong inverse correlation with that of enamel proteinases. The results suggest that high-dose fluoride initiates an ER stress response in ameloblasts and induces the UPR, which interferes with the synthesis and secretion of enamel proteinases. Taken together, these results suggest that excessive ingestion of fluoride during tooth formation can decrease the secretion of proteinases, thus causing protein retention in the enamel layer, indicating that the ER stress response may be responsible for dental fluorosis.
authors.affiliation: Center for Endemic Disease Control, Chinese Center for Disease Control and Prevention, Harbin Medical University, Harbin 150081, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.forename: Yanhui
authors.initials: Y
authors.lastname: Gao
authors.forename: Cheng
authors.initials: C
authors.lastname: Wang
authors.forename: Lijun
authors.initials: L
authors.lastname: Zhao
authors.forename: Dianjun
authors.initials: D
authors.lastname: Sun
mesh_terms: D000565:Ameloblasts / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D003746:Dental Enamel Proteins / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress; D009050:Fluorosis, Dental / Q000209:etiology / Q000378:metabolism; D007610:Kallikreins / Q000378:metabolism*; D053519:Matrix Metalloproteinase 20 / Q000378:metabolism*; D051379:Mice; D012969:Sodium Fluoride / Q000633:toxicity*; D014157:Transcription Factors / Q000378:metabolism; D056811:Unfolded Protein Response
chemical_list: D003746:Dental Enamel Proteins; D014157:Transcription Factors; D012969:Sodium Fluoride; D007610:Kallikreins; C120801:kallikrein 4; D053519:Matrix Metalloproteinase 20