JNK/c-Jun signaling pathway mediates the fluoride-induced down-regulation of MMP-20 in vitro

Abstract

Delayed removal of amelogenins, which are initially hydrolyzed by matrix metalloproteinase MMP-20, is a characteristic of enamel fluorosis. In this study, we investigated the regulation of MMP-20 and possible effects of fluoride on MMP-20 expression in human ameloblast lineage cells. Protein expression and signaling pathways of human ameloblast lineage cells, exposed to 10 muM fluoride, were compared to control cells without fluoride exposure. The role of activator protein-1 in MMP-20 regulation was analyzed by DNA-protein affinity precipitation and luciferase reporter gene assays. MMP-20 protein levels in human ameloblast lineage cells decreased in the presence of fluoride, while amelogenin and TIMP-2 were not altered. Fluoride also decreased the transcription of a luciferase reporter gene driven by the MMP-20 promoter. Down-regulation of MMP-20 by fluoride was related to suppression of JNK/c-Jun phosphorylation. In contrast, the JNK activator elevated the expression of MMP-20. Three c-Jun binding sites on the MMP-20 promoter were identified for the first time, and were occupied by c-Jun as MMP-20 was induced. Deletion of any one of AP-1 binding sites on the MMP-20 promoter significantly reduced the transcription of downstream luciferase reporter. These in vitro findings suggest that c-Jun is a key regulatory element for MMP-20 expression, and human ameloblast lineage cells can respond to fluoride by down-regulating MMP-20 transcription through the JNK/c-Jun signaling pathway.

Calcium‐mediated differentiation of ameloblast lineage cells in vitro

“…1) (DenBesten et al, 2005;Zhang et al, 2006Zhang et al, , 2007Le et al, 2007). We used these cells to determine whether calcium has a role in ameloblast lineage cell differentiation.…”

Molecular Mechanisms of Cytotoxicity and Apoptosis Induced by Inorganic Fluoride

“…In the human osteoblastlike TE85 osteosarcoma cells fluoride induced a sustained activation of ERK p44 [84]. In ameloblasts exposed to 10 μM NaF, the JNK/c-Jun signaling pathway mediates the downregulation of metalloproteinase 20 (MMP-20), the protein responsible for the initial hydrolysis of amelogenin and regulation of the enamel matrix formation [85]. A direct correlation between the progression of apoptosis induced by 5 mM NaF and MAPKs activation was demonstrated in the MDPC-23 odontoblast-like cells [21] and human epithelial lung A549 cells [25].…”

Pathogenesis Of Dental Fluorosis: Biochemical And Cellular Mechanisms

“…concentrations of 10 to 20 µM of F -produce an increase in apoptosis, and concentrations above 1 mM produce alterations in cell proliferation. 47 In addition, concentrations of 120 µM of F -reduce the expression of messengers of amelogenin, ameloblastin, enamelin, and MMP-20, as well as factors of vascularization, such as the endothelial growth factor (VEGF), monocyte chemoattractant proteins (MCP-1) and the interferon inducible protein (IP-10).…”

“…a concentraciones de entre 10 y 20 µM F -se da un aumento de la apoptosis, y a concentraciones mayores a 1 mM se presenta una alteración de la proliferación celular. 47 Además, concentraciones de 120 µM de F -reducen la expresión de mensajeros de amelogenina, ameloblastina, enamelina y MMP-20, así como factores de vascularización como el factor de crecimiento endotelial (VEGF), las proteínas quimio-atrayentes de monocitos (MCP-1) y la proteína inducible por interferón (IP-10). 48 La regulación del pH es fundamental para el crecimiento cristalino: la precipitación de los iones durante la maduración del esmalte libera gran cantidad de protones (H + ), después de lo cual sigue la reacción [10Ca 2+ + 6 HPO 4 2-+ 2H 2 O Ca 10 (PO 4 ) 6 (OH) 2 + 8H + ], y el pH de la matriz extracelular pasa de neutro a levemente ácido.…”

“…En el desarrollo normal del esmalte se presenta una alternancia de estas morfologías; sin embargo, en estudios in vitro se ha observado que la modulación entre la morfología lisa y rugosa se retarda, con predominio de la rugosa. 47 Por lo tanto, como consecuencia de la presencia de fluoruro, el pH de la matriz extracelular permanece ácido por un tiempo prolongado.…”