Tumor necrosis factor-α stimulates human amelotin gene transcription in gingival epithelial cells.

OBJECTIVE: Amelotin (AMTN) is an enamel protein that is localized in the basal lamina of ameloblasts in their maturation stage and the internal basal lamina of junctional epithelium (JE) and it is suggested that AMTN could be involved in the dentogingival attachment. To elucidate the transcriptional regulation of human AMTN gene in inflamed gingiva, we have analyzed the effect of tumor necrosis factor-α (TNF-α) on the expression of AMTN gene in Ca9-22 and Sa3 human gingival epithelial cells. MATERIALS AND METHODS: Total RNAs were extracted from Ca9-22 and Sa3 cells after stimulation by TNF-α (10 ng/ml). AMTN mRNA and protein levels were measured by real-time PCR and Western blotting. Transient transfection analyses were completed using the various lengths of human AMTN gene promoter constructs with or without TNF-α. Gel mobility shift and chromatin immunoprecipitation assays were performed to investigate the transcription factors bindings to the human AMTN gene promoter by TNF-α. RESULTS: TNF-α (10 ng/ml) increased AMTN mRNA and protein levels after 12 h. TNF-α induced luciferase activities of human AMTN gene promoter constructs (- 211AMTN, - 353AMTN, and - 501AMTN). TNF-α-induced luciferase activities were partially inhibited in the mutation - 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 TNF-α were inhibited by protein kinase A, Src-tyrosine kinase, MEK1/2, p38 kinase, NF-κB, and PI3-kinase inhibitors. Gel shift assays showed that TNF-α increased nuclear proteins binding to two types of C/EBP elements (C/EBP1 and C/EBP2) and YY1 element. The results of the chromatin immunoprecipitation assays showed that C/EBPß binding to C/EBP1 and C/EBP2, and YY1 binding to YY1 were increased by TNF-α. CONCLUSIONS: These findings demonstrated that TNF-α stimulates AMTN gene transcription in human gingival epithelial cells via C/EBP1, C/EBP2, and YY1 elements in the human AMTN gene promoter.

MiR-200b attenuates IL-6 production through IKKß and ZEB1 in human gingival fibroblasts.

OBJECTIVE: MicroRNAs (miRNAs) play important roles in biological processes such as cell differentiation, development, infection, immune response, inflammation and tumorigenesis. We previously reported that the expression of miR-200b was significantly increased in inflamed gingiva compared with non-inflamed gingiva. To elucidate the roles of miR-200b in the inflamed gingiva, we have analyzed the effects of miR-200b on the expression of IL-6 in human gingival fibroblasts (HGF). MATERIALS AND METHODS: Total RNA and protein were extracted from HGF after stimulation by interleukin-1ß (IL-1ß; 1 ng/ml) or tumor necrosis factor-α (TNF-α; 10 ng/ml) and transfected with miR-200b expression plasmid or miR-200b inhibitor. IL-6, IL-1ß, inhibitor of nuclear factor kappa-B kinaseß (IKKß), Zinc-finger E-box-binding homeobox 1 (ZEB1) and E-cadherin mRNA and protein levels were analyzed by real-time PCR and Western blot. RESULTS: IL-1ß and TNF-α increased IL-6 mRNA and protein levels, and they were significantly suppressed by miR-200b overexpression, whereas they were further increased by miR-200b inhibitor in HGF. IKKß and ZEB1 which are target genes of miR-200b negatively regulate E-cadherin. MiR-200b suppressed the expression of IKKß and ZEB1 and increased E-cadherin mRNA and protein levels in HGF. CONCLUSIONS: These results suggest that miR-200b attenuates inflammatory response via IKKß and ZEB1 in periodontal tissue.

Localization and expression pattern of amelotin, odontogenic ameloblast-associated protein and follicular dendritic cell-secreted protein in the junctional epithelium of inflamed gingiva.

The purpose of this study is to elucidate the localization of amelotin (AMTN), odontogenic ameloblast-associated protein (ODAM) and follicular dendritic cell-secreted protein (FDC-SP) at the junctional epithelium (JE) in Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans infected mice and inflamed and non-inflamed human gingiva. We performed immunostaining to determine the localization and expression pattern of AMTN, ODAM and FDC-SP. AMTN, ODAM and FDC-SP in A. actinomycetemcomitans infected mice did not change dramatically compared with non-infected mice. AMTN and FDC-SP expressions were observed stronger in P. gingivalis infected mice at early stage. However, at the following stage, the coronal part of the AMTN expression disappeared from the JE, and FDC-SP expression decreased due to severe inflammation by P. gingivalis. ODAM expressed internal and external basal lamina, and the expression increased not only at early stage but also at the following stage in the inflammatory JE induced by P. gingivalis. In the human gingival tissues, AMTN was detected at the surface of the sulcular epithelium and JE in the non-inflamed and inflamed gingiva, and the localization did not change the process of inflammation. ODAM and FDC-SP were more widely detected at the sulcular epithelium and JE in the non-inflamed gingiva. In the inflamed gingiva, localization of ODAM and FDC-SP was spread into the gingival epithelium, compared to AMTN. These studies demonstrated that the expression pattern of AMTN, ODAM and FDC-SP at the JE were changed during inflammation process and these three proteins might play an important role in the resistance to inflammation.

Amelotin gene expression is temporarily being upregulated at the initiation of apoptosis induced by TGFß1 in mouse gingival epithelial cells.

Amelotin (AMTN) is expressed and secreted by ameloblasts in the maturation stage of amelogenesis and persist with low levels in the junctional epithelium (JE) of erupted teeth. The purpose of this study is to investigate the transcriptional regulation of the AMTN gene by transforming growth factor beta1 (TGFß1) in gingival epithelial (GE1) cells in the apoptosis phase. Apoptosis was evaluated by the fragmentation of chromosomal DNA and TUNEL staining. A real-time PCR was carried out to examine the AMTN mRNA levels induced by TGFß1 and Smad3 overexpression. Transient transfection analyses were completed using the various lengths of mouse AMTN gene promoter constructs with or without TGFß1. Chromatin immunoprecipitation (ChIP) assays were performed to investigate the Smad3 bindings to the AMTN gene promoter by TGFß1. TGFß1-induced apoptosis in GE1 cells were detected at 24 and 48 h by DNA fragmentation and TUNEL staining. AMTN mRNA levels increased at 6 h and reached maximum at 24 h in GE1 cells. Luciferase activities of the mouse AMTN gene promoter constructs were induced by TGFß1. The results of the ChIP assays showed that there was an increase in Smad3 binding to Smad-binding element (SBE)#1 and SBE#2 after stimulation by TGFß1. Immunohistochemical localization of AMTN was detected in the JE, and the AMTN protein levels in Smad3-deficient mice were decreased compared with wild-type mice. AMTN mRNA levels were induced at the initiation of apoptosis by TGFß1, which mediated through the Smad3 bindings to SBEs in the mouse AMTN gene promoter.

Transcriptional regulation of amelotin gene by proinflammatory cytokines in gingival fibroblasts.

Amelotin (AMTN) is a secreted protein expressed during the late stages of enamel formation and in the junctional epithelium. Among many differentially expressed genes, we found significantly increased AMTN mRNA level in inflamed gingiva by DNA microarray. The inductions of AMTN mRNA expressions in inflamed gingiva and human gingival fibroblasts (HGF) were confirmed by real-time polymerase chain reaction. To determine the molecular basis of the expression of AMTN and its regulation by proinflammatory cytokines, we have isolated and characterized the promoter region of mouse AMTN gene. Transient transfection assays were performed using luciferase constructs including mouse AMTN gene promoter. Interleukin-1ß, Interleukin-6 and tumor necrosis factor-α induced AMTN mRNA levels in HGF. These cytokines increased the luciferase activities of the AMTN promoter constructs in HGF. The results suggest that proinflammatory cytokines induce AMTN gene transcription and a role for AMTN in gingival inflammation.

IL-1ß and TNF-α regulate mouse amelotin gene transcription in gingival epithelial cells.

Amelotin (AMTN) is an enamel protein expressed in maturation-stage ameloblasts and junctional epithelium. To clarify the transcriptional regulation of the AMTN gene by interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α), we conducted real-time PCR, Western blotting, transient transfection analyses with luciferase constructs including various lengths of the mouse AMTN gene promoter, and gel shift and chromatin immunoprecipitation assays using mouse gingival epithelial GE1 cells. The levels of AMTN mRNA and protein in GE1 cells were increased after 6 h of stimulation with IL-1ß (1 ng/mL) and TNF-α (10 ng/mL). IL-1ß and TNF-α induced luciferase activities of the constructs between -116AMTN and -705AMTN including the mouse AMTN gene promoter. Transcriptional activation by IL-1ß and TNF-α was partially inhibited in -460AMTN including 3-bp mutations in the CCAAT-enhancer-binding protein 1 (C/EBP1), C/EBP2 and Yin Yang 1 (YY1) elements. Transcriptional activities induced by IL-1ß and TNF-α were inhibited by tyrosine kinase, MEK1/2 and PI3-kinase inhibitors. Results of ChIP assays showed that IL-1ß and TNF-α increased C/EBPß and YY1 binding to the C/EBP1, C/EBP2 and YY1 elements. These results demonstrate that IL-1ß and TNF-α increase AMTN gene transcription via the C/EBP1, C/EBP2 and YY1 elements in the mouse AMTN gene promoter.

Transcriptional regulation of human amelotin gene by interleukin-1ß.

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-1ß (IL-1ß) on AMTN gene transcription in human gingival epithelial Ca9-22 cells. IL-1ß increased AMTN mRNA and protein levels at 3 h, and the levels reached maximum at 6 and 12 h. IL-1ß 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-1ß 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-1ß increased C/EBPß 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-1ß increases AMTN gene transcription in human gingival epithelial cells mediated through C/EBP1, C/EBP2, and YY1 elements in the human AMTN gene promoter.

TGFß1-induced Amelotin gene expression is downregulated by Bax expression in mouse gingival epithelial cells.

Amelotin (AMTN) is induced upon initiation of apoptosis by transforming growth factor beta1 (TGFß1) and is mediated by Smad3 in gingival epithelial cells (GE1 cells). This upregulation of AMTN gene expression is temporary, and the mechanism responsible is still unclear. The present study investigated the transcriptional downregulation of TGFß1-induced AMTN gene expression in GE1 cells during the progression of apoptosis. To examine time-dependent changes in the levels of AMTN, Smad3 and Bax mRNA induced by TGFß1, real-time PCR analyses were performed. Immunocytochemistry was carried out to detect the expression of Smad3 and Bax. Transient transfection analyses were performed using mouse AMTN gene promoter constructs of various lengths including Smad response elements (SBEs), in the presence or absence of TGFß1. Changes in Smad3 binding to SBEs resulting from overexpression of Bax were examined using ChIP assays. Overexpression of Bax dramatically downregulated the levels of TGFß1-induced AMTN mRNA and transcription of the AMTN gene. Smad3 binding to SBEs in the mouse AMTN gene promoter was induced by overexpression of Smad3 or TGFß1, and this was inhibited by Bax overexpression. These results show that the levels of AMTN mRNA induced by TGFß1 and Smad3 are decreased by robust expression of Bax in gingival epithelial cells.

Effects of miR-223 on expression of IL-1ß and IL-6 in human gingival fibroblasts.

MicroRNAs (miRNAs) are small non-coding RNAs that regulate post-transcriptional expression by translational inhibition or mRNA degradation. miRNAs bind to target mRNAs through partial complementarity, and can regulate many genes. In the present study, we investigated the effects of miR-223 on the expression of inflammatory cytokines in human gingival fibroblasts (HGF). To determine the effects of miR-223 on the expressions of interleukin-1ß (IL-1ß) and IL-6, HGF were stimulated by IL-1ß (1 ng/mL) or tumor necrosis factor-α (TNF-α; 10 ng/mL) and transfected with a miR-223 expression plasmid. Levels of mRNA for IL-1ß, IL-6, inhibitor of kappa-B kinase α (IKKα) and mitogen-activated protein kinase phosphatase-5 (MKP-5) were measured by real-time PCR, and levels IL-1ß, IL-6 and IKKα protein were determined by enzyme-linked immunosorbent assay and Western blotting. Expression of IL-1ß and IL-6 mRNAs was induced by IL-1ß and TNF-α and further increased by miR-223 overexpression. IL-1ß and TNF-α induced the expression of IL-1ß and IL-6 mRNAs, and this was reduced by miR-223 inhibitor. Overexpression of miR-223 decreased the levels of IKKα protein and MKP-5 mRNA in HGF. These findings indicate that miR-223 might control the inflammatory response via IKKα and MKP-5 in periodontal tissue. (J Oral Sci 58, 101-108, 2016).

MicroRNA expression in inflamed and noninflamed gingival tissues from Japanese patients.

Periodontitis is a chronic inflammatory disease caused by specific bacteria and viruses. Local, systemic, and environmental factors affect the rate of disease progression. Immune responses to bacterial products, and the subsequent production of inflammatory cytokines, are crucial in the destruction of periodontal tissue. MicroRNAs (miRNAs) are a class of small RNAs that control various cell processes by negatively regulating protein-coding genes. In this study, we compared miRNA expression in inflamed and noninflamed gingival tissues from Japanese dental patients. Total RNAs were isolated from inflamed and noninflamed gingival tissues. miRNA expression profiles were examined by an miRNA microarray, and the data were analyzed by GeneSpring GX, Ingenuity Pathways Analysis, and the TargetScan databases. Observed miRNA expression levels in inflamed gingiva were confirmed by real-time PCR. The three most overexpressed (by >2.72-fold) miRNAs were hsa-miR-150, hsa-miR-223, and hsa-miR-200b, and the three most underexpressed (by <0.39-fold) miRNAs were hsa-miR-379, hsa-miR-199a-5p, and hsa-miR-214. In IPA analysis, hsa-miR-150, hsa-miR-223, and hsa-miR-200b were associated with inflammatory disease, organismal injury, abnormalities, urological disease, and cancer. The present findings suggest that miRNAs are associated with chronic periodontitis lesions in Japanese.

Proinflammatory cytokines induce amelotin transcription in human gingival fibroblasts.

Amelotin (AMTN) is a secreted protein transcribed predominantly during the maturation stage of enamel formation and localized in the junctional epithelium. We investigated differences in the levels of AMTN gene expression between non-inflamed gingiva and inflamed gingiva from patients with chronic periodontitis. Total RNAs were isolated from these tissues and their gene expression profiles were monitored by DNA microarray. The observed induction of AMTN mRNA in inflamed gingiva and cultured human gingival fibroblasts (HGF) was confirmed by real-time PCR. Transient transfection assays were performed using chimeric constructs of mouse AMTN gene promoter fragments linked to a luciferase reporter gene. Immunohistochemical localization of AMTN in inflamed and non-inflamed gingiva was assessed by immunohistochemistry. Among many differentially expressed genes, the level of AMTN mRNA was significantly increased in inflamed gingiva. Treatment of HGF with interleukin-1ß (IL-1ß), IL-6 and tumor necrosis factor-α (TNF-α) induced the expression of AMTN mRNA, and increased the luciferase activities of the AMTN promoter constructs. AMTN protein was detected in inflamed gingival connective tissue and junctional epithelium. These findings demonstrate that proinflammatory cytokines induce AMTN gene expression in human gingival fibroblasts and suggest a role for AMTN in gingival inflammation.

Unliganded estrogen receptor α stimulates bone sialoprotein gene expression.

Estrogen is one of the steroid hormones essential for skeletal development. The estrogen receptor (ER) is a transcription factor and a member of the steroid receptor superfamily. There are two different forms of the ER, usually referred to as α and ß, each encoded by a separate gene. Hormone-activated ERs form dimers, since the two forms are coexpressed in many cell types. Bone sialoprotein (BSP) is a tissue-specific acidic glycoprotein that is expressed by differentiated osteoblasts, odontoblasts and cementoblasts during the initial formation of mineralized tissue. To determine the molecular basis of the tissue-specific expression of BSP and its regulation by estrogen and the ER, we have analyzed the effects of ß-estradiol and ERα on BSP gene transcription. ERα protein levels were increased after ERα overexpression in ROS17/2.8 cells. While BSP mRNA levels were increased by ERα overexpression, the endogenous and overexpressed BSP mRNA levels were not changed by ß-estradiol (10(-8)M, 24 h). Luciferase activities of different sized BSP promoter constructs (pLUC3~6) were increased by ERα overexpression, whereas basal and induced luciferase activities by ERα overexpression were not influenced by ß-estradiol. Effects of ERα overexpression were abrogated by 2 bp mutations in either the cAMP response element (CRE) or activator protein 1 (AP1)/glucocorticoid response element (GRE). Gel shift analyses showed that ERα overexpression increased binding to the CRE and AP1/GRE elements. Notably, the CRE-protein complexes were disrupted by ERα, CREB and phospho-CREB antibodies. The AP1/GRE-protein complexes were supershifted by the c-Fos antibody. These studies demonstrate that ERα stimulates BSP gene transcription in a ligand-independent manner by targeting the CRE and AP1/GRE elements in the rat BSP gene promoter.