title: Fluoride affects enamel protein content via TGF-β1-mediated KLK4 inhibition.
abstract: Dental fluorosis is caused by chronic high-level fluoride (F(-)) exposure during enamel development, and fluorosed enamel has a higher than normal protein content. Matrix metalloproteinase 20 cleaves enamel matrix proteins during the secretory stage, and KLK4 further cleaves these proteins during the maturation stage so that the proteins can be reabsorbed from the hardening enamel. We show that transforming growth factor β1 (TGF-β1) can induce Klk4 expression, and we examine the effect of F(-) on TGF-β1 and KLK4 expression. We found that in vivo F(-) inhibits Klk4 but not Mmp20 transcript levels. LacZ-C57BL/6-Klk4 (+/LacZ) mice have LacZ inserted in frame at the Klk4 translation initiation site so that the endogenous Klk4 promoter drives LacZ expression in the same temporal/spatial way as it does for Klk4. KLK4 protein levels in rat enamel and β-galactosidase staining in LacZ-C57BL/6-Klk4 (+/LacZ) mouse enamel were both significantly reduced by F(-) treatment. Since TGF-β1 induces KLK4 expression, we tested and found that F(-) significantly reduced Tgf-β1 transcript levels in rat enamel organ. These data suggest that F(-)-mediated downregulation of TGF-β1 expression contributes to reduced KLK4 protein levels in fluorosed enamel and provides an explanation for why fluorosed enamel has a higher than normal protein content.
authors: Department of Mineralized Tissue Biology, The Forsyth Institute, Cambridge, MA, USA, and Harvard School of Dental Medicine, Boston, MA, USA.
authors: M
authors: M
authors: Suzuki
authors: Department of Mineralized Tissue Biology, The Forsyth Institute, Cambridge, MA, USA, and Harvard School of Dental Medicine, Boston, MA, USA.
authors: M
authors: M
authors: Shin
authors: Department of Biological and Material Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA.
authors: J P
authors: JP
authors: Simmer
authors: Department of Mineralized Tissue Biology, The Forsyth Institute, Cambridge, MA, USA, and Harvard School of Dental Medicine, Boston, MA, USA jbartlett@forsyth.org.
authors: J D
authors: JD
authors: Bartlett
mesh_terms: D000565:Ameloblasts / Q000187:drug effects / Q000473:pathology; D053523:Amelogenin / Q000032:analysis / Q000187:drug effects; D000818:Animals; D002327:Cariostatic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003746:Dental Enamel Proteins / Q000187:drug effects*; D015536:Down-Regulation; D004658:Enamel Organ / Q000187:drug effects; D005459:Fluorides / Q000494:pharmacology*; D055879:Gene Knock-In Techniques; D007610:Kallikreins / Q000032:analysis / Q000037:antagonists & inhibitors*; D007763:Lac Operon / Q000187:drug effects; D053519:Matrix Metalloproteinase 20 / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D051381:Rats; D017207:Rats, Sprague-Dawley; D053773:Transforming Growth Factor beta1 / Q000187:drug effects*; D001616:beta-Galactosidase / Q000032:analysis
chemical_list: D053523:Amelogenin; D002327:Cariostatic Agents; D003746:Dental Enamel Proteins; D053773:Transforming Growth Factor beta1; C109069:enamel matrix proteins; D001616:beta-Galactosidase; D007610:Kallikreins; C120801:kallikrein 4; D053519:Matrix Metalloproteinase 20; D005459:Fluorides
keywords: amelogenin; cell stress; gene expression; matrix metalloproteinases; proteases/proteinases; signal transduction