Search

Junctional epithelium (JE) develops from reduced enamel epithelium during tooth formation and is critical for the maintenance of healthy periodontal tissue through ensuring appropriate immune responses and the rapid turnover of gingival epithelial cells. We have previously shown a relationship between inflammatory cytokines and expression of JE‐specific genes, such as amelotin (AMTN), in gingival epithelial cells. Here, we elucidated the effects of Porphyromonas gingivalis‐derived lipopolysaccharide (PgLPS) on Amtn gene transcription and the interaction of transcription factors. To determine the molecular basis of transcriptional regulation of the Amtn gene by PgLPS, we performed real‐time PCR and carried out luciferase assays using a mouse Amtn gene promoter linked to a luciferase reporter gene in mouse gingival epithelial GE1 cells. Gel mobility shift and chromatin immunoprecipitation assays were performed to identify response elements bound to LPS‐induced transcription factors. Next, we analyzed protein levels of the LPS‐induced transcription factors and the interaction of transcription factors by western blotting and immunoprecipitation. LPS increased Amtn mRNA levels and elevated luciferase activities of constructs containing regions between −116 and −238 of the mouse Amtn gene promoter. CCAAT/enhancer‐binding protein (C/EBP) 1–, C/EBP2– and Ying Yang 1 (YY1)–nuclear protein complexes were increased by LPS treatment. Furthermore, we identified LPS‐modulated interactions with C/EBPβ, YY1 and Smad3. These results demonstrate that PgLPS regulates Amtn gene transcription via binding of C/EBPβ–Smad3 and YY1–Smad3 complexes to C/EBP1, C/EBP2 and YY1 response elements in the mouse Amtn gene promoter. Porphyromonas gingivalis lipopolysaccharide (LPS)‐induced physical interactions between CCAAT/enhancer‐binding protein β (C/EBPβ), Ying Yang 1 (YY1) and Smad3 upregulate amelotin (Amtn) gene transcription via mitogen‐activated protein kinase kinase 1/2 (MEK1/2), phosphatidylinositol 3‐kinase (PI3‐K) and Smad2/3 pathways in gingival epithelial cells. These findings raise the possibility of an association between induced C/EBPβ and YY1 in inflammation and a constitutive interaction with Smad3 in gingival epithelial cells. [ABSTRACT FROM AUTHOR]

One of the major causes of tooth loss is chronic inflammation of the periodontium, the tissues surrounding the tooth. Amelotin (AMTN) is a tooth enamel protein which is expressed in maturation‐stage ameloblasts and also in the internal basal lamina of junctional epithelium, a unique epithelial structure attached to the tooth surface which protects against the constant microbiological challenge to the periodontium. Localization of AMTN suggests that its function could be involved in the dentogingival attachment. The purpose of this study was to investigate the effect of interleukin‐1β (IL‐1β) on AMTN gene transcription in human gingival epithelial Ca9‐22 cells. IL‐1β increased AMTN mRNA and protein levels at 3 h, and the levels reached maximum at 6 and 12 h. IL‐1β induced luciferase activities of human AMTN gene promoter constructs (−211, −353, −501, −769, and −950AMTN), but these activities were partially inhibited in −353AMTN constructs that included 3‐bp mutations in CCAAT/enhancer binding protein 1 (C/EBP1), C/EBP2, and Ying Yang 1 (YY1) elements. Transcriptional activities induced by IL‐1β were abrogated by protein kinase A (PKA), tyrosine kinase, mitogen‐activated protein kinase kinase (MEK1/2), and phosphatidylinositol 3‐kinase (PI3K) inhibitors. Gel shift and ChIP assays showed that IL‐1β increased C/EBPβ binding to C/EBP1 and C/EBP2, and YY1 binding to YY1 elements after 3 h, and that these DNA–protein interactions were inhibited by PKA, tyrosine kinase, MEK1/2, and PI3K inhibitors. These results demonstrated that IL‐1β increases AMTN gene transcription in human gingival epithelial cells mediated through C/EBP1, C/EBP2, and YY1 elements in the human AMTN gene promoter. [ABSTRACT FROM AUTHOR]

Follicular dendritic cell‐secreted protein (FDC‐SP) is a secreted protein expressed in follicular dendritic cells, periodontal ligament and junctional epithelium. To elucidate the transcriptional regulation of the human FDC‐SP gene by tumor necrosis factor‐α (TNF‐α), we conducted real‐time PCR, Western blotting, transient transfection analyses with chimeric constructs of the FDC‐SP gene promoter linked to a luciferase reporter gene, gel mobility shift and chromatin immunoprecipitation assays using Ca9‐22 gingival epithelial cells. TNF‐α (10 ng/ml) induced FDC‐SP mRNA and protein levels at 3 hr and reached maximum at 12 hr. In transient transfection assays, TNF‐α (12 hr) increased the LUC activities of constructs between −116FDCSP and −948FDCSP including the human FDC‐SP gene promoter. Transcriptional stimulations by TNF‐α were partially inhibited in the −345FDCSP constructs that included 3‐bp mutations in the YY1, GATA, CCAAT enhancer‐binding protein 2 (C/EBP2) and C/EBP3. Transcriptional activities induced by TNF‐α were inhibited by tyrosine kinase, MEK1/2 and phosphoinositide 3‐kinase inhibitors. The results of ChIP assays showed that YY1, GATA and C/EBPβ transcription factors interacted with the YY1, GATA, C/EBP2 and C/EBP3 elements that were increased by TNF‐α. These studies show that TNF‐α stimulates human FDC‐SP gene transcription by targeting YY1, GATA, C/EBP2 and C/EBP3 in the FDC‐SP gene promoter. [ABSTRACT FROM AUTHOR]