Cyclooxygenase-2-dependent prostaglandin E(2) upregulates interleukin (IL)-1alpha-induced IL-6 generation in mouse cementoblasts

Necrotizing Gingivitis: Microbial Diversity and Quantification of Protein Secretion in Necrotizing Gingivitis

Necrotizing gingivitis (NG) is a necrotizing periodontal disease that differs from chronic gingivitis (CG). To date, both the microbiological causes and the involved host cytokine response of NG still remain unclear. Here, we investigated corresponding interdental plaque and serum samples from two groups of Chinese patients with CG (n = 21) or NG (n = 21). The microbiota were studied by 16S rRNA Illumina MiSeq sequencing of the microbial metagenome and by assessing quantitatively the abundance of the phylum Bacteroidetes, the genus Prevotella and the species T. forsythia, P. endodontalis, and P. gingivalis using fluorescence in situ hybridization (FISH). With respect to the associated host response, the levels of 30 inflammatory mediators were quantified by multiplex immunoassay analysis. Differential microbial abundance analysis of the two disease groups revealed at the phylum level that Proteobacteria accounted for 67% of the differentially abundant organisms, followed by organisms of Firmicutes (21%) and Actinobacteria (9%). At the species level, significant differences in abundance were seen for 75 species of which 58 species were significantly more abundant in CG patients. Notably, the FISH analysis revealed that Bacteroidetes was the most prevalent phylum in NG. The multiplex cytokine assay showed significant quantitative differences between the disease groups for eight analytes (GM–CSF, G–CSF, IFN–α, IL–4, IL–13, TNF–α, MIG, and HGF). The G–CSF was found to be the most significantly increased inflammatory protein marker in NG. The next-generation sequencing (NGS) data supported the understanding of NG as a multi-microbial infection with distinct differences to CG in regard to the microbial composition.

Vibration enhances PGE2 , IL-6, and IL-8 expression in compressed hPDL cells via cyclooxygenase pathway

BACKGROUND

Although vibration combined with orthodontic force may accelerate orthodontic tooth movement, little is known about the mechanisms that regulate the associated cellular responses. The goal of this study was to investigate whether mechanical vibration combined with compressive force regulates cyclooxygenase (COX)-2/prostaglandin E2 (PGE₂ ) and interleukin (IL)-6 and IL-8 messenger RNA (mRNA) and protein expression in human periodontal ligament (hPDL) cells via the COX pathway.

METHODS

The primary cultured hPDL cells were exposed to mechanical vibration, compressive force or a combination of both mechanical vibration and compressive force at 24, 48, and 72 hours. The COX-2, IL-6, IL-8, receptor activator of nuclear factor kappa-Β ligand (RANKL), and osteoprotegrin (OPG) mRNA expressions were determined using quantitative real-time polymerase chain reaction (qPCR). The PGE₂ , IL-6, and IL-8 protein expressions were quantified by enzyme-linked immunosorbent assay (ELISA). To demonstrate whether the expression of PGE₂ , IL-6, and IL-8 was in the COX-dependent pathway, the hPDL cells were treated with indomethacin. To determine whether PGE₂ stimulated the hPDL cells to express IL-6 and IL-8, exogenous PGE₂ was added to the culture media.

RESULTS

The combination of mechanical vibration and compressive force synergistically upregulated RANKL/OPG, COX-2/PGE₂ , IL-6 and IL-8 mRNA, and protein expression. The indomethacin significantly attenuated the increases of PGE₂ , IL-6, and IL-8 expression in cells stimulated with compressive force or mechanical vibration combined with compressive force. In addition, exogenous PGE₂ increased IL-6 and IL-8 mRNA and protein expressions in hPDL cells.

CONCLUSION

Mechanical vibration may enhance alveolar bone resorption at the compression side during orthodontic tooth movement via a mechanism involving the cyclooxygenase pathway.

Regulation of inflammation by lipid mediators in oral diseases

Lipid mediators (LM) of inflammation are a class of compounds derived from ω-3 and ω-6 fatty acids that play a wide role in modulating inflammatory responses. Some LM possess pro-inflammatory properties, while others possess proresolving characteristics, and the class switch from pro-inflammatory to proresolving is crucial for tissue homeostasis. In this article, we review the major classes of LM, focusing on their biosynthesis and signaling pathways, and their role in systemic and, especially, oral health and disease. We discuss the detection of these LM in various body fluids, focusing on diagnostic and therapeutic applications. We also present data showing gender-related differences in salivary LM levels in healthy controls, leading to a hypothesis on the etiology of inflammatory diseases, particularly Sjögren's syndrome. We conclude by enumerating open areas of research where further investigation of LM is likely to result in therapeutic and diagnostic advances.

TNF-α stimulates MMP-3 production via PGE2 signalling through the NF-kB and p38 MAPK pathway in a murine cementoblast cell line

BACKGROUND

Cementoblasts are considered to play an important role in the homeostasis of periodontal tissues under both physiologic and pathologic conditions. Matrix metalloproteinases (MMPs) is the key family of enzymes participating in extracellular matrix remodelling. In the present study, the effects and regulatory mechanisms of tumour necrosis factor (TNF)-α on the expression of MMPs and their inhibitors (tissue inhibitor of metalloproteinases; TIMPs) were investigated.

MATERIALS AND METHODS

OCCM-30, an immortalised murine cementoblast cell line, was stimulated with TNF-α at 1 and 10ng/ml for 24h. The expression of Mmp-2, Mmp-3, Mmp-13, Mmp-14, Timp-1, and Timp-2 as well as PGE2 was determined. Inhibitors of MAPKs, PI3K/Akt, NF-kB and Cox-2 were employed to reveal possible TNF-α induced regulatory signalling pathway(s). The mRNA and protein expression were analysed by (semi)quantitative real-time PCR and enzyme-linked immunosorbent assay (ELISA), respectively.

RESULTS

TNF-α dose-dependently stimulated MMP-3 expression by cementoblasts. This was found for mRNA as well as protein expression. No significant differences were found in the mRNA expression of Mmp-2, Mmp-13, Mmp-14, Timp-1, and Timp-2 upon TNF-α stimulation. The level of PGE2, however, was significantly increased along with MMP-3. Treatment with a selective Cox-2 inhibitor resulted in partial suppression of TNF-α-induced Mmp-3 mRNA expression. Addition of PGE2 enhanced Mmp-3 mRNA in a dose dependent manner, suggesting an inductive effect of TNF-α partly via PGE2. The up-regulation of Mmp-3 by TNF-α was completely suppressed by a combination of NF-kB and p38 MAPK inhibitors, while partial suppression was found with each inhibitor. The effect of PGE2 on Mmp-3 expression was abolished by treating cells with an NF-kB inhibitor; a p38 MAPK inhibitor had only a small effect.

CONCLUSIONS

The present study indicates that cementoblasts respond to TNF-α by increasing MMP-3 production partially via PGE2 and signalling through the NF-kB and p38 MAPK pathway. MMP-3 may participate in periodontal tissue degradation/remodelling.

Endotoxins potentiate COX-2 and RANKL expression in compressed PDL cells

OBJECTIVE

This study aims to demonstrate in vitro the synergistic effect of orthodontic forces and periodontal pathogens on cyclooxygenase-2 regulation and the subsequent receptor activator of nuclear factor kappa-B ligand (RANKL) production from periodontal ligament (PDL) cells.

MATERIALS AND METHODS

In comparison to a control group, three experimental groups were formed from human primary PDL cells stressed with compressive forces, bacterial endotoxins, or a combination of both. Gene expression of cyclooxygenase-2 and RANKL was analysed with RT real-time PCR. The prostaglandin E2 production was determined with ELISA. A co-culture of PDL cells and an osteoclast-progenitor cell line was used in order to demonstrate the osteoclast formation effect caused by the simultaneous combined stress.

RESULTS

The simultaneous combined stress resulted in a 56-fold up-regulation of cyclooxygenase-2 gene expression with a subsequent noticeable rise in the prostaglandin E2 in the culture medium. The RANKL/osteoprotegerin gene expression ratio was 50-fold up-regulated and the osteoclast formation assay revealed 153.5 ± 15.7 tartrate-resistant acid phosphatase (TRAP)-positive cells per well compared with 42.3 ± 3.8 TRAP-positive cells per well of the control group.

CONCLUSION

The synergistic action of periodontal pathogens and orthodontic forces leads to an increased expression of cyclooxygenase-2 from PDL cells that intensify the RANKL production which in turn induces osteoclast differentiation and subsequent osteoclastogenesis.

CLINICAL RELEVANCE

The present study puts an emphasis on the detrimental effect of orthodontic forces on patients with an active periodontal disease by underlining the significance of cyclooxygenase-2 activity and RANKL binding on the osteoclastogenesis process.

Prevotella intermedia induces prostaglandin E2 via multiple signaling pathways

Prostaglandin E(2) (PGE(2)) plays important roles in the bone resorption of inflammatory diseases such as rheumatoid arthritis and periodontitis via specific prostaglandin receptors (i.e., EP1-EP4). In this study, the authors examined whether Prevotella intermedia regulates PGE(2) production and EP expression in human periodontal ligament fibroblasts (hPDLs); they also explored the potential signaling pathways involved in PGE(2) production. P. intermedia induced PGE(2) production and cyclooxygenase-2 (COX-2) expression in a dose- and time-dependent manner. Indomethacin and NS-398 completely abrogated the P. intermedia-induced PGE(2) production without modulating COX-2 expression. Specific inhibitors of extracellular signal-regulated kinase, c-Jun N-terminal kinase, p38, phosphatidylinositol 3-kinase, and protein kinase C--but not c-AMP and protein kinase A--significantly attenuated the P. intermedia-induced COX-2 and PGE(2) expression. P. intermedia reduced EP1 expression in a concentration- and time-dependent manner. The results indicate that the COX-2-dependent induction of PGE(2) by P. intermedia in hPDLs is mediated by multiple signaling pathways.