Signal transduction pathways involved in the synergistic stimulation of prostaglandin production by interleukin-1beta and tumor necrosis factor alpha in human gingival fibroblasts

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.

Gallic and vanillic acid suppress inflammation and promote myelination in an in vitro mouse model of neurodegeneration

Neuroinflammation affects millions of people around the world as a result of injury or stress. Neuroinflammation represents almost all types of neurological diseases such as multiple sclerosis and Alzheimer's disease. Neurodegenerative diseases comprise demyelination and synaptic loss. The inflammatory response is further propagated by the activation of glial cells and modulation of constitutively expressed extracellular matrix proteins. The aim of the present study was to identify the anti-inflammatory effects of purified compounds gallic acid (GA, 1.0 µM) and vanillic acid (VA, 0.2 µM) on the lysolecithin (LPC, 0.003%)-induced model of inflammation. Hippocampal neurons were co-cultured with glial cells, and LPC was added to induce inflammation. Neurite outgrowth was measured by morphometry software. The level of myelination and demyelination was identified by immunostaining and sodium dodecyl sulfate polyacrylamide gel electrophoresis and western blotting techniques using different antibodies. Whole-cell patch clamp recordings were used to observe the sustained repetitive firing pattern. The data showed that GA and VA significantly increased the neurite outgrowth after 48 h in culture. Both compounds significantly reduced the expression of cyclooxygenase-2, NFκB, tenascin-C, chondroitin sulfate proteoglycans and glial fibrillary acidic protein in astrocytes in the LPC-induced model of inflammation. The level of myelin protein in neurites and oligodendrocyte cell bodies was significantly upregulated by GA and VA treatment. The reduction in sustained repetitive firing in the LPC-induced model of inflammation was reversed by both GA and VA treatment. This study supports the hypothesis that VA and GA have anti-inflammatory activities and could be regarded as potential treatments for neurodegenerative disease.

Essential Oils from Ugandan Medicinal Plants: In Vitro Cytotoxicity and Effects on IL-1β-Induced Proinflammatory Mediators by Human Gingival Fibroblasts

The study investigated cytotoxicity of essential oils from four medicinal plants (Bidens pilosa, Ocimum gratissimum, Cymbopogon nardus, and Zanthoxylum chalybeum) on human gingival fibroblasts and their effects on proinflammatory mediators' secretion. Cytotoxicity of essential oils was investigated using 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay. Effects of essential oils at subcytotoxicity concentrations on interleukin- (IL-) 6, IL-8, and prostaglandin E₂ (PGE₂) secretions by gingival fibroblasts treated with IL-1β (300 pg/mL) were evaluated by ELISA and EIA. IC₅₀ values of the essential oils ranged from 26 μg/mL to 50 μg/mL. Baseline and IL-1β-induced secretion of PGE₂ was inhibited by treatment with essential oil from O. gratissimum. Essential oils from B. pilosa and C. nardus had synergistic effects with IL-1β on PGE₂ seceretion. In conclusion, the study suggests that essential oil from O. gratissimum decreases gingival fibroblasts secretion of PGE₂, while essential oils from B. pilosa and C. nardus increase PGE₂ secretion. Essential oil from Z. chalybeum was the most cytotoxic, while oil from C. nardus was the least cytotoxic. Although the clinical significance of these findings remains to be determined, it may be suggested that essential oil from O. gratissimum, applied at subcytotoxicity concentrations, could reduce the participation of gingival fibroblasts in the gingival inflammation and tissue destruction associated with periodontitis.

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.

Modulation of heme oxygenase-1 by metalloporphyrins increases anti-viral T cell responses

Heme oxygenase (HO)-1, the inducible isoform of HO, has immunomodulatory functions and is considered a target for therapeutic interventions. In the present study, we investigated whether modulation of HO-1 might have regulatory effects on in-vitro T cell activation. The study examined whether: (i) HO-1 induction by cobalt-protoporphyrin (CoPP) or inhibition by tin-mesoporphyrin (SnMP) can affect expansion and function of virus-specific T cells, (ii) HO-1 modulation might have a functional effect on other cell populations mediating effects on proliferating T cells [e.g. dendritic cells (DCs), regulatory T cells (T(regs)) and natural killer cells] and (iii) HO-1-modulated anti-viral T cells might be suitable for adoptive immunotherapy. Inhibition of HO-1 via SnMP in cytomegalovirus (CMV)pp65-peptide-pulsed peripheral blood mononuclear cells (PBMCs) led to increased anti-viral T cell activation and the generation of a higher proportion of effector memory T cells (CD45RA(-) CD62L(-)) with increased capability to secrete interferon (IFN)-γ and granzyme B. T(reg) depletion and SnMP exposure increased the number of anti-viral T cells 15-fold. To test the possibility that HO-1 modulation might be clinically applicable in conformity with good manufacturing practice (GMP), SnMP was tested in isolated anti-viral T cells using the cytokine secretion assay. Compared to control, SnMP treatment resulted in higher cell counts and purity without negative impact on quality and effector function [CD107a, IFN-γ and tumour necrosis factor (TNF)-α levels were stable]. These results suggest an important role of HO-1 in the modulation of adaptive immune responses. HO-1 inhibition resulted in markedly more effective generation of functionally active T cells suitable for adoptive T cell therapy.

Peptidylarginine deiminase from Porphyromonas gingivalis contributes to infection of gingival fibroblasts and induction of prostaglandin E2 -signaling pathway

Porphyromonas gingivalis (P. gingivalis) expres-ses the enzyme peptidylarginine deiminase (PPAD), which has a strong preference for C-terminal arginines. Due to the combined activity of PPAD and Arg-specific gingipains, P. gingivalis on the cell surface is highly citrullinated. To investigate the contribution of PPAD to the interaction of P. gingivalis with primary human gingival fibroblasts (PHGF) and P. gingivalis-induced synthesis of prostaglandin E2 (PGE2 ), PHGF were infected with wild-type P. gingivalis ATCC 33277, an isogenic PPAD-knockout strain (∆ppad) or a mutated strain (C351A) expressing an inactive enzyme in which the catalytic cysteine has been mutated to alanine (PPAD(C351A) ). Cells were infected in medium containing the mutants alone or in medium supplemented with purified, active PPAD. PHGF infection was assessed by colony-forming assay, microscopic analysis and flow cytometry. Expression of cyclo-oxygenase 2 (COX-2) and microsomal PGE synthase-1 (mPGES-1), key factors in the prostaglandin synthesis pathway, was examined by quantitative reverse transcription polymerase chain reaction (qRT-PCR), while PGE2 synthesis was evaluated by enzyme immunoassay. PHGF were infected more efficiently by wild-type P. gingivalis than by the ∆ppad strain, which correlated with strong induction of COX-2 and mPGES-1 expression by wild-type P. gingivalis, but not by the PPAD activity-null mutant strains (Δppad and C351A). The impaired ability of the Δppad strain to adhere to and/or invade PHGF and both Δppad and C351A to stimulate the PGE2 -synthesis pathway was fully restored by the addition of purified PPAD. The latter effect was strongly inhibited by aspirin. Collectively, our results implicate PPAD activity, but not PPAD itself, as an important factor for gingival fibroblast infection and activation of PGE2 synthesis, the latter of which may strongly contribute to bone resorption and eventual tooth loss.

Inflammatory mediators in the pathogenesis of periodontitis

Periodontitis is a chronic inflammatory condition of the periodontium involving interactions between bacterial products, numerous cell populations and inflammatory mediators. It is generally accepted that periodontitis is initiated by complex and diverse microbial biofilms which form on the teeth, i.e. dental plaque. Substances released from this biofilm such as lipopolysaccharides, antigens and other virulence factors, gain access to the gingival tissue and initiate an inflammatory and immune response, leading to the activation of host defence cells. As a result of cellular activation, inflammatory mediators, including cytokines, chemokines, arachidonic acid metabolites and proteolytic enzymes collectively contribute to tissue destruction and bone resorption. This review summarises recent studies on the pathogenesis of periodontitis, with the main focus on inflammatory mediators and their role in periodontal disease.

Effects of chitosan particles in periodontal pathogens and gingival fibroblasts

Chitosan is a naturally derived polymer with antimicrobial and anti-inflammatory properties. However, studies evaluating the role of chitosan in the control of periodontal pathogens and the responses of fibroblasts to inflammatory stimuli are lacking. In the present study, we analyzed whether chitosan particles may inhibit the growth of periodontal pathogens and modulate the inflammatory response in human gingival fibroblasts. Chitosan particles were generated through ionic gelation. They inhibited the growth of Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans at 5 mg/mL. Conversely, IL-1β strongly stimulated PGE2 protein levels in gingival fibroblasts, and chitosan inhibited this response at 50 µg/mL. IL-1β-stimulated PGE2 production was dependent on the JNK pathway, and chitosan strongly inhibited this response. IL-1β stimulated NF-κB activation, another signaling pathway involved in PGE2 production. However, chitosan particles were unable to modify NF-κB signaling. The present study shows that chitosan exerts a predominantly anti-inflammatory activity by modulating PGE2 levels through the JNK pathway, which may be useful in the prevention or treatment of periodontal inflammation.

Imiquimod: the biochemical mechanisms of immunomodulatory and anti-inflammatory activity

Imidazoquinolins represent a new group of compounds that recently entered into clinical practice as anti-tumor and anti-viral immune modulators. They are low molecular weight synthetic guanosine-like molecules. Although imiquimod, the most widely used imidazoquinolin, is recommended for the treatment of several forms of skin cancer and papillomas, the molecular mechanisms of its action are not fully understood. In particular, imiquimod has been characterized as a specific agonist of Toll-like receptor 7 (TLR7) and is widely used in this capacity in a large number of experimental studies and clinical trials. However, detailed analysis of the published data with the use of imiquimod, suggests that its biological activity can not be explained only by interaction with TLR7. There are indications of a direct interaction of imiquimod with adenosine receptors and other molecules that regulate the synthesis of cyclic adenosine monophosphate. A detailed understanding of the biochemical basis of imiquimod immunomodulating and antitumor effect will increase its clinical effectiveness and accelerate the development of new drugs with similar but improved medical properties. This review summarizes the published data concerning the effects of imiquimod on a variety of intracellular biochemical processes and signaling pathways.

2-Hydroxyethyl methacrylate inflammatory effects in human gingival fibroblasts

AIM

To investigate the inflammatory response in human gingival fibroblasts (HGFs) treated with a relatively low 2-hydroxyethyl methacrylate (HEMA) concentration by studying reactive oxygen species (ROS) production, cyclooxygenase-2 (COX-2) and tumour necrosis factor-alpha (TNF-α) gene expression, and prostaglandin E2 (PGE₂) release.

METHODOLOGY

Cultured HGFs were exposed to 3 mmol L⁻¹ HEMA for 0, 24 or 96 h. ROS production was investigated by flow cytometry; TNF-α and COX-2 gene expression was determined by RT-PCR, and prostaglandin E2 production was detected by an enzyme immunoassay.

RESULTS

After 24- or 96-h HEMA incubation, ROS levels were approximately eightfold and elevenfold higher than controls, whilst COX-2 gene expression was approximately twofold or fourfold higher than controls, respectively. Twenty-four-hour exposure enhanced TNF-α mRNA levels by approximately 66%, whilst after 96-h incubation, TNF-α gene expression was fivefold higher than controls. Ninety-six-hour HEMA treatment increased PGE₂ concentration in the culture medium by around 17% compared with controls.

CONCLUSIONS

2-Hydroxyethyl methacrylate treatment (3 mmol L⁻¹) induced an inflammatory response in HGFs modulated by ROS production, as well as by the increase in TNF-α and COX-2 gene expression and by PGE₂ release.

Genistein regulates the IL-1 beta induced activation of MAPKs in human periodontal ligament cells through G protein-coupled receptor 30

Periodontal ligament (PDL) cells are fibroblasts that play key roles in tissue integrity, periodontal inflammation and tissue regeneration in the periodontium. The periodontal tissue destruction in periodontitis is mediated by host tissue-produced inflammatory cytokines, including interleukin-1β (IL-1β). Here, we report the expression of G protein-coupled receptor 30 (GPR30, also known as G protein-coupled estrogen receptor 1 GPER) in human PDL cells and its regulation by IL-1β. IL-1β-induced GPR30 expression in human PDL cells leads to the activation of multiple signaling pathways, including MAPK, NF-κB and PI3K. In contrast, genistein, an estrogen receptor ligand, postpones the activation of MAPKs induced by IL-1β. Moreover, the inhibition of GPR30 by G15, a GPR30-specific antagonist, eliminates this delay. Thus, genistein plays a role in the regulation of MAPK activation via GPR30, and GPR30 represents a novel target regulated by steroid hormones in PDL cells.

The association between inflammatory bowel disease and periodontitis among Jordanians: a case-control study

BACKGROUND AND OBJECTIVE

Inflammatory bowel disease (IBD) is hypothesized to involve immuno-inflammatory alterations, and the condition has been related to increased susceptibility to oral challenges. The objective of the study was to determine the association between the prevalence, severity and extent of periodontitis and both ulcerative colitis (UC) and Crohn's disease (CD).

MATERIAL AND METHODS

A case-control study was conducted among patients who attended outpatient clinics at King Hussein Medical City in Jordan during the study period. All participants completed the questionnaire and underwent thorough oral and periodontal examinations. Periodontitis was defined as presence of four or more teeth with one or more sites with probing pocket depth ≥ 4 mm and clinical attachment level ≥ 3 mm. The general linear model multivariate procedure and multivariate binary logistic regression were used to analyse the data.

RESULTS

This case-control study included 260 Jordanian adults (101 with UC, 59 with CD and 100 with no IBD) with a mean (SD) age of 39.4 (0.7) years. The prevalence of periodontitis was much higher among patients with CD and those with UC compared with subjects having no IBD in the age groups < 36 and 36-45 years old only. After adjusting for age and number of missing teeth, patients with CD (odds ratio 4.9, 95% confidence interval 1.8-13.2) and patients with UC (odds ratio 7.00, 95% confidence interval 2.8-17.5) had significantly higher odds of periodontitis than subjects with no IBD. In multivariate analysis, the severity of periodontitis was significantly higher among patients with CD and patients with UC when compared with subjects having no IBD. Ulcerative colitis patients but not CD patients had significantly higher prevalence of deep ulcers in oral soft tissues than the non-IBD group (p = 0.004).

CONCLUSION

Patients with IBD have higher prevalence, severity and extent of periodontitis compared with those having no IBD.

Host-derived diagnostic markers related to soft tissue destruction and bone degradation in periodontitis

BACKGROUND

A major challenge in clinical periodontics is to find a reliable molecular marker of periodontal tissue destruction with high sensitivity, specificity and utility.

OBJECTIVES

The aim of this systematic review is to evaluate available literature on 'the utility of molecular markers of soft and hard periodontal tissue destruction'.

MATERIALS AND METHODS

Based on the focused question, 'What is the utility of molecular markers of soft and hard periodontal tissue destruction', an electronic and manual search was conducted for human studies presenting clinical data for the potential of molecular markers of tissue destruction in biofluids; gingival crevicular fluid (GCF), saliva, and serum.

RESULTS

Papers fulfilling the inclusion criteria were selected. All relevant data from the selected papers were extracted and recorded in separate tables for molecules in GCF, saliva, and serum.

CONCLUSION

Within the defined limits of the Problem/Population, Intervention, Comparison, Outcome, the present analysis reveals that (a) no single or combination of markers exists that can disclose periodontal tissue destruction adequately; (b) while the most fruitful source of biomarkers for periodontal destruction appears to be in molecules tightly related to bone and soft tissue destruction, this remains to be objectively demonstrated. Currently, clinical measurements are still the most reliable.

Signal pathways JNK and NF-kappaB, identified by global gene expression profiling, are involved in regulation of TNFalpha-induced mPGES-1 and COX-2 expression in gingival fibroblasts

Background

Prostaglandin E₂ (PGE₂) is involved in several chronic inflammatory diseases including periodontitis, which causes loss of the gingival tissue and alveolar bone supporting the teeth. We have previously shown that tumor necrosis factor α (TNFα) induces PGE₂ synthesis in gingival fibroblasts. In this study we aimed to investigate the global gene expression profile of TNFα-stimulated primary human gingival fibroblasts, focusing on signal pathways related to the PGE₂-synthesizing enzymes prostaglandin E synthases (PGES), as well as the upstream enzyme cyclooxygenase-2 (COX-2) and PGE₂ production.

Results

Microarray and western blot analyses showed that the mRNA and protein expression of the inflammatory induced microsomal prostaglandin E synthase-1 (mPGES-1) was up-regulated by the cytokine TNFα, accompanied by enhanced expression of COX-2 and increased production of PGE₂. In contrast, the expression of the isoenzymes microsomal prostaglandin E synthase-2 (mPGES-2) and cytosolic prostaglandin E synthase (cPGES) was unaffected by TNFα treatment. Using oligonucleotide microarray analysis in a time-course factorial design including time points 1, 3 and 6 h, differentially expressed genes in response to TNFα treatment were identified. Enrichment analysis of microarray data indicated two positively regulated signal transduction pathways: c-Jun N-terminal kinase (JNK) and Nuclear Factor-κB (NF-κB). To evaluate their involvement in the regulation of mPGES-1 and COX-2 expression, we used specific inhibitors as well as phosphorylation analysis. Phosphorylation analysis of JNK (T183/Y185) and NF-κB p65 (S536) showed increased phosphorylation in response to TNFα treatment, which was decreased by specific inhibitors of JNK (SP600125) and NF-κB (Bay 11-7082, Ro 106-9920). Inhibitors of JNK and NF-κB also decreased the TNFα-stimulated up-regulation of mPGES-1 and COX-2 as well as PGE₂ production.

Conclusion

In the global gene expression profile, the enrichment analysis of microarray data identified the two signal transduction pathways JNK and NF-κB as positively regulated by the cytokine TNFα. Inhibition of these TNFα-activated signal pathways reduced the expression of mPGES-1 and COX-2 as well as their end product PGE₂ in gingival fibroblasts. The involvement of the signal pathways JNK and NF-κB in the regulation of PGE₂ induced by TNFα may suggest these two pathways as possible attractive targets in the chronic inflammatory disease periodontitis.

The evaluation of cystatin C, IL-1beta, and TNF-alpha levels in total saliva and gingival crevicular fluid from 11- to 16-year-old children

BACKGROUND

The aim of this study was to evaluate the levels of cystatin C, interleukin-1beta (IL-1beta), and tumor necrosis factor-alpha (TNF-alpha) in the total saliva and gingival crevicular fluid (GCF) of periodontally healthy children (PHC) and children with gingivitis (CG) who were between 11 and 16 years old.

METHODS

The study was carried out with 10 PHC and 25 CG. Unstimulated total saliva and GCF samples were obtained. Clinical parameters, including probing depth (PD), clinical attachment loss (CAL), plaque index (PI), gingival index (GI), and gingival bleeding index (GBI), were assessed. GCF samples were collected from four maxillary upper incisors. After sampling, biochemical analyses were performed using latex particle-enhanced turbidimetric immunoassay for cystatin C and enzyme-linked immunosorbent assay for IL-1beta and TNF-alpha. The multivariate analysis of variance test was used for statistical evaluation.

RESULTS

In total saliva, cystatin C and TNF-alpha levels were higher in PHC, and IL-1beta levels were higher in CG, but the differences were not statistically significant. In GCF, cystatin C levels were higher in PHC (P >0.05), whereas TNF-alpha and IL-1beta levels were higher in CG (P >0.05). In the CG group, there were positive correlations between the GCF cystatin C level and the PI of the sampled site (r = 0.488; P <0.05); also, GCF IL-1beta (r = 0.603; P <0.05) and TNF-alpha (r = 0.456; P <0.05) levels were positively correlated with PD and CAL. For the whole mouth and the sampled sites, PI, GI, GBI, PD, and CAL values were higher in CG (P <0.05), but no significant differences were detected between GCF volumes of the two groups.

CONCLUSIONS

To the best of our knowledge, this study represents the first evaluation of cystatin C in the gingival disease mechanism in children. Our results showed that total saliva and GCF cystatin C levels were higher in PHC (P >0.05), but there was no correlation between cystatin C levels and IL-1beta or TNF-alpha levels in total saliva or GCF.

Highly conserved surface proteins of oral spirochetes as adhesins and potent inducers of proinflammatory and osteoclastogenic factors

Oral spirochetes include enormously heterogeneous Treponema species, and some have been implicated in the etiology of periodontitis. In this study, we characterized highly conserved surface proteins in four representative oral spirochetes (Treponema denticola, T. lecithinolyticum, T. maltophilum, and T. socranskii subsp. socranskii) that are homologs of T. pallidum Tp92, with opsonophagocytic potential and protective capacity against syphilis. Tp92 homologs of oral spirochetes had predicted signal peptides (20 to 31 amino acids) and molecular masses of 88 to 92 kDa for mature proteins. They showed amino acid sequence identities of 37.9 to 49.3% and similarities of 54.5 to 66.9% to Tp92. The sequence identities and similarities of Tp92 homologs of oral treponemes to one another were 41.6 to 71.6% and 59.9 to 85.6%, respectively. The tp92 gene homologs were successfully expressed in Escherichia coli, and the recombinant proteins were capable of binding to KB cells, an epithelial cell line, and inhibited the binding of the whole bacteria to the cells. Antiserum (the immunoglobulin G fraction) raised against a recombinant form of the T. denticola Tp92 homolog cross-reacted with homologs from three other species of treponemes. The Tp92 homologs stimulated various factors involved in inflammation and osteoclastogenesis, like interleukin-1beta (IL-1beta), tumor necrosis factor alpha, IL-6, prostaglandin E(2), and matrix metalloproteinase 9, in host cells like monocytes and fibroblasts. Our results demonstrate that Tp92 homologs of oral spirochetes are highly conserved and may play an important role in cell attachment, inflammation, and tissue destruction. The coexistence of various Treponema species in a single periodontal pocket and, therefore, the accumulation of multiple Tp92 homologs may amplify the pathological effect in periodontitis.

M, O'Connell PA, Nóbrega PBD, Costa PP, Kawata VKDS, Trevisan GL, Novaes Jr. AB, Souza SLSD, Palioto DB, Grisi MFDM. Inflammation markers in healthy and periodontitis patients: a preliminary data screening

Advances in diagnostic research are moving towards methods whereby the periodontal risk can be identified and quantified by objective measures using biomarkers. Patients with periodontitis may have elevated circulating levels of specific inflammatory markers that can be correlated to the severity of the disease. The purpose of this study was to evaluate whether differences in the serum levels of inflammatory biomarkers are differentially expressed in healthy and periodontitis patients. Twenty-five patients (8 healthy patients and 17 chronic periodontitis patients) were enrolled in the study. A 15 mL blood sample was used for identification of the inflammatory markers, with a human inflammatory flow cytometry multiplex assay. Among 24 assessed cytokines, only 3 (RANTES, MIG and Eotaxin) were statistically different between groups (p<0.05). In conclusion, some of the selected markers of inflammation are differentially expressed in healthy and periodontitis patients. Cytokine profile analysis may be further explored to distinguish the periodontitis patients from the ones free of disease and also to be used as a measure of risk. The present data, however, are limited and larger sample size studies are required to validate the findings of the specific biomarkers.

Regulation of prostaglandin E synthases: Effects of siRNA-mediated inhibition of microsomal prostaglandin E synthase-1

Prostaglandin E2 (PGE2) is a key mediator involved in several inflammatory conditions. In this study, we investigated the expression and regulation of the terminal PGE2 synthesizing enzyme prostaglandin E synthases (mPGES-1, mPGES-2 and cPGES) in gingival fibroblasts stimulated with pro-inflammatory cytokines. We used siRNA knockdown of mPGES-1 to elucidate the impact of mPGES-1 inhibition on mPGES-2 and cPGES expression, as well as on PGE2 production. The cytokines TNFalpha and IL-1beta increased protein expression and activity of mPGES-1, accompanied by increased COX-2 expression and PGE2 production. The isoenzymes mPGES-2 and cPGES, constitutively expressed at mRNA and protein levels, were unaffected by the pro-inflammatory cytokines. We show for the first time that treatment with mPGES-1 siRNA down-regulated the cytokine-induced mPGES-1 protein expression and activity. Interestingly, mPGES-1 siRNA did not affect the cytokine-stimulated PGE2 production, whereas PGF(2alpha) levels were enhanced. Neither mPGES-2 nor cPGES expression was affected by siRNA silencing of mPGES-1. Dexamethasone and MK-886 both inhibited the cytokine-induced mPGES-1 expression while mPGES-2 and cPGES expression remained unaffected. In conclusion, mPGES-1 siRNA down-regulates mPGES-1 expression, and neither mPGES-2 nor cPGES substituted for mPGES-1 in a knockdown setting in gingival fibroblasts. Moreover, mPGES-1 siRNA did not affect PGE2 levels, whereas PGF(2alpha) increased, suggesting a compensatory pathway of PGE2 synthesis when mPGES-1 is knocked down.

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

BACKGROUND

Prostaglandin E(2) (PGE(2)), which exerts its biologic actions via EP receptors (EP(1), EP(2), EP(3,) and EP(4)), is a bioactive metabolite of arachidonic acid that is produced by cyclooxygenase (COX)-1 and/or COX-2. In the present study, we investigated whether a mouse cementoblast cell line, OCCM-30 cells, that was stimulated with interleukin (IL)-1alpha produced COX-2-dependent PGE(2) and whether the produced PGE(2) affected IL-1alpha-induced IL-6 production.

METHODS

OCCM-30 cells were stimulated with vehicle or IL-1alpha in the presence or absence of indomethacin (a COX-1/COX-2 inhibitor), NS-398 (a specific COX-2 inhibitor), PGE(2), and EP receptor agonists. PGE(2) and IL-6 levels were assayed by enzyme linked immunosorbent assay.

RESULTS

IL-1alpha induced PGE(2) production in a time-dependent fashion. Indomethacin and NS-398 completely inhibited IL-1alpha-induced PGE(2) production. 17-phenyl-omega-trinor PGE(2) (an EP(1) agonist) and an EP(4) agonist mimicked PGE(2) enhancement of IL-1alpha-induced IL-6 production in OCCM-30 cells.

CONCLUSIONS

From these data, we suggest that IL-1alpha induced PGE(2) production in a COX-2-dependent manner in OCCM-30 cells and that the COX-2-derived PGE(2) upregulates IL-1alpha-elicited IL-6 production via EP(1) and/or EP(4) receptors. PGE(2) and IL-6 produced by cementoblasts may be involved in the pathogenesis of periodontal disease.

Signal pathways involved in the regulation of prostaglandin E synthase-1 in human gingival fibroblasts

Microsomal prostaglandin E synthase-1 (mPGES-1) is the terminal enzyme regulating the synthesis of prostaglandin E2 (PGE2) in inflammatory conditions. In this study we investigated the regulation of mPGES-1 in gingival fibroblasts stimulated with the inflammatory mediators interleukin-1 beta (IL-1beta) and tumour necrosis factor alpha (TNFalpha). The results showed that IL-1beta and TNFalpha induce the expression of mPGES-1 without inducing the expression of early growth response factor-1 (Egr-1). Treatment of the cells with the PLA2 inhibitor 4-bromophenacyl bromide (BPB) decreased the cytokine-induced mPGES-1 expression accompanied by decreased PGE2 production whereas the addition of arachidonic acid (AA) upregulated mPGES-1 expression and PGE2 production. The protein kinase C (PKC) activator PMA did not upregulate the expression of mPGES-1 in contrast to COX-2 expression and PGE2 production. In addition, inhibitors of PKC, tyrosine and p38 MAP kinase markedly decreased the cytokine-induced PGE2 production but not mPGES-1 expression. Moreover, the prostaglandin metabolites PGE2 and PGF2alpha induced mPGES-1 expression as well as upregulated the cytokine-induced mPGES-1 expression indicating positive feedback regulation of mPGES-1 by prostaglandin metabolites. The peroxisome proliferator-activated receptor-gamma (PPARgamma) ligand, 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2), decreased mPGES-1 expression but not COX-2 expression or PGE2 production. The results indicate that the inflammatory-induced mPGES-1 expression is regulated by PLA2 and 15d-PGJ2 but not by PKC, tyrosine kinase or p38 MAP kinase providing new insights into the regulation of mPGES-1.

LPS exacerbates endothelin-1 induced activation of cytosolic phospholipase A2 and thromboxane A2 production from Kupffer cells of the prefibrotic rat liver

BACKGROUND/AIMS

Thromboxane A2 (TXA2) has been suggested to play a significant role in the development of portal hypertension in fibrosis, and Kupffer cell (KC) derived TXA2 has been shown to mediate the hyperresponsiveness of the portal circulation to the vasoconstrictive actions of endothelin-1 (ET-1) during endotoxemia. The aim of this study was to determine whether the double stresses of prefibrotic changes and endotoxemia additively activate KC to increase release of TXA2 in response to ET-1, resulting in elevated portal resistance.

METHODS

One week Bile duct ligation (BDL) rats and sham-operated controls were subjected to isolated liver perfusions following LPS or saline for 6h. In a separate experiment, KC were isolated from BDL or sham rats and incubated with LPS or saline for 6h before the ET-1 treatment.

RESULTS

The double stresses of early fibrosis and LPS resulted in a greater sustained increase in portal pressure in response to ET-1 in BDL rats, and this increase correlated well with the much enhanced release of TXA2 in the perfusate. Media from the cultured KC showed significantly greater TXA2 release in response to ET-1 in BDL group than those in sham group, and LPS exacerbated this effect. Protein levels of cytosolic phospholipase A2 (cPLA2), cyclooxygenase-2, and thromboxane synthase were also significantly elevated in KC from BDL rats. ET-1 produced a marked increase in cPLA2 activation as measured by the phosphorylation of cPLA2 in KC of both BDL and sham groups. LPS greatly exacerbated the activation of cPLA2.

CONCLUSIONS

The data suggest that the double stresses additively activate KC with an upregulation of the key enzymes in the TXA2 biosynthesis and release increased amount of TXA2 via the augmented activation of cPLA2 in response to ET-1, which leads to the increased portal resistance and ultimately hepatic microcirculatory dysfunction.

Epidermal growth factor synergistically enhances interleukin-8 production in human gingival fibroblasts stimulated with interleukin-1beta

The chemokine interleukin-8 (IL-8) has been implicated in inflammatory diseases including periodontitis. In this study the effect of epidermal growth factor (EGF) on the production and regulation of interleukin-8 (IL-8) in human gingival fibroblasts challenged with interleukin-1beta (IL-1beta) was investigated. EGF, in comparison to the effect of IL-1beta, weakly increased the mRNA and protein expression of IL-8 in gingival fibroblasts. When the cells were treated simultaneously with EGF and IL-1beta, however, EGF synergistically enhanced the mRNA expression and production of IL-8. The stimulatory effect of EGF on IL-1beta-induced IL-8 production was completely abolished by the broad range tyrosine kinase inhibitor Herbimycin A, and considerably reduced by the receptor tyrosine kinase specific inhibitor PD 153035. Herbimycin A abolished IL-8 production induced by IL-1beta, whereas PD 153035 had no effect on the cytokine-induced IL-8 production. Furthermore, the p38 mitogen-activated protein (MAP) kinase inhibitor SB 203580 reduced IL-8 production induced by IL-1beta as well as by the combination of EGF and IL-1beta but had no effect on EGF-induced IL-8 production. In conclusion, the study demonstrates that EGF synergistically stimulates IL-8 production in the presence of IL-1beta and that tyrosine kinase(s) seem to be involved in the signalling pathway of IL-1beta and EGF. The synergistic interactions between EGF and IL-1beta on IL-8 production may play an essential role in the pathogenesis of the inflammatory disease periodontitis.

Inhibition of growth of human gingival fibroblasts by chimeric DNA-RNA hammerhead ribozyme targeting transforming growth factor-beta 1

BACKGROUND

Transforming growth factor (TGF)-beta1 is involved in the pathogenesis of both drug-induced gingival overgrowth and hereditary gingival fibromatosis. Ribozymes enzymatically cleave target mRNAs and are expected to be utilized as the basis of novel nucleic acid-based therapies. We designed a chimeric DNA-RNA ribozyme targeting TGF-beta1 mRNA and examined its effect on growth of gingival fibroblasts in culture.

METHODS

Chimeric DNA-RNA hammerhead ribozyme with sequence complementary to the loop structure of human TGF-beta1 mRNA was used. We evaluated transfer of the chimeric ribozyme by hemagglutinating virus of Japan (HVJ)-envelope into cultured human gingival fibroblasts in vitro and rat gingival tissues in vivo. We then examined effects of the chimeric ribozyme to TGF-beta1 on proliferation and DNA synthesis in human gingival fibroblasts. We also examined effects of the chimeric ribozyme to TGF-beta1 on expression of TGF-beta1, type IV collagens, and fibronectin mRNAs and expression of TGF-beta1 protein in human gingival fibroblasts.

RESULTS

Chimeric ribozyme was sufficiently distributed into human fibroblasts in vitro and rat gingivae in vivo. Chimeric ribozyme to TGF-beta1 significantly inhibited expression of TGF-beta1, type IV collagen, and fibronectin mRNAs and TGF-beta1 protein in human gingival fibroblasts. Mismatch ribozyme had no effect on expression of these molecules. Chimeric ribozyme to TGF-beta1 also significantly inhibited proliferation and DNA synthesis in gingival fibroblasts.

CONCLUSION

Chimeric DNA-RNA ribozyme targeting TGF-beta1 may be a useful gene therapy agent for treatment of gingival hyperplasia.

Interleukin-1β–Induced Prostaglandin E2Production by Human Gingival Fibroblasts Is Upregulated by Glycine

BACKGROUND

Human gingival fibroblasts (GFB) may produce prostaglandin E(2) (PGE(2)) in response to proinflammatory cytokines. Elevated concentrations of glycine were previously found in periodontal pockets and saliva of periodontitis patients and, therefore, we aimed to study the influence of glycine on PGE(2) production.

METHODS

Human GFB were cultured in the presence of various concentrations of glycine and/or interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, and IL-10 and their influence on PGE(2) production was measured. The expression of cyclooxygenases (COX) was analyzed by Western blot and immunocytochemistry.

RESULTS

The PGE(2) production by IL-1beta-stimulated GFB was significantly upregulated by glycine. The effect of glycine on IL- 1beta-induced cell proliferation and PGE(2) production was concentration- dependent, reached a peak at 3 mM, and declined slowly at higher doses. The synthesis of PGE(2) by human GFB cultured in the absence of glycine was significantly inhibited by IL-10 and partially induced in cells cultured with glycine. Glycine had no effect on TNF-alpha-induced PGE(2) production. The IL-1beta-driven PGE(2) synthesis was blocked by indomethacin, a COX-1/COX-2 inhibitor, and by COX-2 inhibitor NS-398. The expression of COX-2 protein was slightly induced by glycine, more evidently by IL-1beta, and mostly enhanced by combined IL-1beta with glycine.

CONCLUSION

Since PGE(2) is a potent stimulator of bone resorption, and production of PGE(2) and COX-2 protein is augmented by glycine, our results strongly suggest that glycine may be involved in the pathogenesis of periodontitis.

Small bowel cyclooxygenase 2 (COX-2) expression in patients with IgA nephropathy

BACKGROUND

Clinical manifestation of IgA nephropathy (IgAN) strikingly occurs after respiratory tract infections. An intestinal inflammation has also been described. We hypothesized that the intestinal inflammation should manifest itself as an increase in inflammatory cells and mucosal cyclooxygenase 2 (COX-2) expression.

METHODS

By using immunohistochemistry, we determined the phenotype and quantity of inflammatory cells in duodenal biopsy specimens from 17 IgAN patients. Control material comprised 18 patients undergoing gastroscopy because of dyspepsia.

RESULTS

All the biopsy specimens disclosed normal villous architecture. In IgAN, CD3(+) cells and COX-2-positive cells were significantly increased and J chain-producing plasma cells were significantly decreased. CD3(+) cells coexpressed COX-2 protein and COX-2-positive cells also expressed CD45RO antigen. The number of lymphocytes correlated significantly with serum IgA and COX-2-expression with serum IgA and the degree of hematuria. COX-2-positive subepithelial fibroblasts were a conspicuous finding in IgAN. In CD68(+) and CD15(+) cells, a significant increase was seen. Many of these cells also expressed COX-2 protein. CD15(+) positivity correlated significantly with proteinuria in IgAN.

CONCLUSION

Our results indicate that small bowel inflammation in IgAN shows itself as an increased number of mucosal inflammatory cells. However, polymeric IgA production is significantly decreased. An increased mucosal COX-2 expression suggests activation of the inflammatory cells and the degree of inflammation significantly correlates with serum IgA and the amount of proteinuria and hematuria. Subepithelial fibroblasts seem also to be involved in the inflammatory reaction.

Er:YAG laser irradiation increases prostaglandin E2 production via the induction of cyclooxygenase-2 mRNA in human gingival fibroblasts

BACKGROUND AND OBJECTIVES

It has been reported that both prostaglandin E2 (PGE2) and Er:YAG laser irradiation accelerate wound healing. The stimulatory action of laser seems to occur during the proliferative stage of healing by stimulation of prostaglandin E2 and cyclooxygenase-2 (COX-2), which are crucial early mediators in the natural healing process. We have then investigated the effect of Er:YAG laser irradiation on PGE2 production and COX-2 gene expression in human gingival fibroblast in vitro.

MATERIAL AND METHODS

Cultured fibroblasts were exposed to low-power Er:YAG laser irradiation with an energy density of 3.37 J/cm2. The amount of PGE2 production was measured by enzyme-linked immunosorbent assay (ELISA). COX-2 mRNA level, which is a critical enzyme for PGE2 production, was analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

Er:YAG laser significantly increased PGE2 production by human gingival fibroblasts. COX-2 mRNA, which was hardly detectable in control, increased dramatically after irradiation. COX-2 inhibitor, NS398, completely inhibited the PGE2 synthesis stimulated by Er:YAG laser irradiation.

CONCLUSION

Our results showed that Er:YAG laser irradiation appears to exert its stimulative action on gingival fibroblasts proliferation through the production of PGE2 via the expression of COX-2. This should be considered as one of the important regulatory pathways to accelerate wound healing after Er:YAG laser irradiation.

Platelet-derived growth factor-induced arachidonic acid release for enhancement of prostaglandin E(2) synthesis in human gingival fibroblasts pretreated with interleukin-1beta

Platelet-derived growth factor (PDGF) is a biological mediator for connective tissue cells and plays a critical role in a wide variety of physiological and pathological processes. We here investigated the effect of PDGF on arachidonic acid release and prostaglandin E(2) (PGE(2)) synthesis in human gingival fibroblasts (HGF). PDGF induced arachidonic acid release in a time- and dose-dependent manner, and simultaneously induced a transient increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), but less provoked PGE(2) release and cyclooxygenase-2 (COX-2) mRNA expression. When [Ca(2+)](i) was increased by Ca(2+)-mobilizing reagents, arachidonic acid release was increased. The PDGF-induced arachidonic acid release and increase in [Ca(2+)](i) were prevented by a tyrosine kinase inhibitor. On the other hand, in the HGF pre-stimulated with interleukin-1beta (IL-1beta), PDGF clearly increased PGE(2) release. The PDGF-induced PGE(2) release was inhibited by a tyrosine kinase inhibitor. In the HGF pretreated with IL-1beta, arachidonic acid strongly enhanced PGE(2) release and COX-2 mRNA expression. These results suggest that PDGF stimulates arachidonic acid release by the increase in [Ca(2+)](i) via tyrosine kinase activation, and which contributes to PGE(2) production via COX-2 expression in HGF primed with IL-1beta.

Immuno-localization of COX-1 and COX-2 in the rat molar periodontal tissue after topical application of lipopolysaccharide

Up-regulation of prostaglandin E2 (PGE2) production in the periodontal tissue is considered to be important for periodontal tissue destruction. The purpose of the study was to demonstrate the dynamic changes of immuno-localization of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) in rat periodontal tissue after topical application of lipopolysaccharide (LPS: 5 mg/ml in physiological saline) from Escherichia coli into the rat molar gingival sulcus. In the normal periodontal tissue, small numbers of junctional epithelium (JE) cells and numerous osteocytes embedded in alveolar bone constitutively expressed COX-1. The COX-1 expression was not effected by LPS application. JE cells, especially in the coronal portion of JE also expressed COX-2. LPS application induced the JE cells with consequent transient expression of COX-2 with a peak at day 1. These findings suggest that JE cells may play a critical role in first defense line against LPS challenge and PGE2 from JE cells may be responsible for the initiation of periodontal inflammation. In the deep periodontal tissue, cementoblasts and osteoblasts showed constitutive expression of COX-2, which may be induced by continuous cyclic tension force due to occlusal pressure. LPS application caused a transient up-regulation of COX-2 expression in periodontal ligament fibroblasts, cementoblasts and osteoblasts. It is suggested that the inducible production of PGE2 via COX-2 by these cells may be associated with connective tissue destruction and alveolar bone resorption.

Relationship between clinical parameters and cytokine profiles in inflamed gingival tissue and serum samples from patients with chronic periodontitis

OBJECTIVE

The purpose of the present study was to assess the relation between clinical parameters and concentrations of the key (IL-1beta, TNF-alpha, IL-2, IFN-gamma, IL-4, IL-10) cytokines, important in the initiation and progression of periodontal diseases, within inflamed gingival tissues and serum samples from patients with severe chronic periodontitis.

MATERIAL AND METHODS

Twenty-five patients with severe chronic periodontitis, who had sites with probing depths (PD) > 5 mm, and 25 periodontally healthy persons were included in the study. Clinical examinations including PD, clinical attachment loss, plaque index, and bleeding index were performed before periodontal treatment. Gingival tissue biopsies were collected from one active site of each patient and from healthy individuals, and blood samples were withdrawn on the day of tissue biopsy. The concentrations of cytokines were determined by an enzyme-linked immunosorbent assay, and the relationship between their profiles in situ and in circulation with clinical parameters was analysed.

RESULTS

The concentrations of IL-1beta, TNF-alpha, IL-2, IFN-gamma were, on average, significantly higher in serum samples and gingival tissue biopsies from periodontitis patients than in healthy controls. However, serum samples from both groups showed high individual variability of cytokine profiles, and no association between cytokine concentrations and clinical parameters of periodontitis was found. On the contrary, the levels of IL-4 and IL-10 in both kinds of samples obtained from patients and controls were generally low or even undetectable, and remained, on average, on the same level. However, the frequency of IL-4 (88% positive samples) and IL-10 (72%) was much higher in healthy gingival tissues. High concentrations of TNF-alpha, IFN-gamma and IL-2 and, especially, a high ratio of IL-1beta/IL-10 and TNF-alpha/IL-4 found in tissue biopsies from periodontitis patients, strongly correlated with the severity of periodontitis.

CONCLUSION

These results indicate that high variability of cytokine concentrations and low frequency of their detection in serum samples from periodontitis patients make these determinations useless for the detection of disease presence and/or its severity. In contrast, high absolute levels of IL-1beta, TNF-alpha, IL-2 and IFN-gamma and, especially their high ratios to IL-4 and IL-10 found in inflamed tissue biopsies, were closely associated with periodontal disease severity.

Cyclooxygenase-2 inhibitors decrease interleukin-1beta-stimulated prostaglandin E2 and IL-6 production by human gingival fibroblasts

BACKGROUND

Previous work showed that normal and aggressive periodontitis (AgP) gingival fibroblasts produce the bone-resorbing cytokine IL-6. PGE2 is important in regulating IL-6 production. Non-steroidal anti-inflammatory drugs inhibit PG synthesis via COX-1 and/or COX-2 isoenzymes and may inhibit periodontal destruction. COX-2 is induced after cellular activation (i.e., by inflammatory cytokines such as IL-1beta). Little is known about IL-1beta-stimulated AgP fibroblast IL-6 and PGE2 production and their regulation by COX inhibitors. The objective of this study was to determine the effects of COX-2 inhibitors on amounts of PGE2 and IL-6 made by IL-1beta-stimulated gingival fibroblasts.

METHODS

Gingival fibroblasts (2.5 x 10(4)) from healthy or severe periodontitis patients were cultured in serum-free medium, with or without IL-1beta (10(-11)M) for 24 hours, with or without the COX-1/2 inhibitor indomethacin or the selective COX-2 inhibitors NS-398, celecoxib, or rofecoxib. PGE2 and IL-6 in culture supernatants were determined by specific enzyme-linked immunosorbent assay (ELISA)s.

RESULTS

All of the COX inhibitors caused dose-dependent decreases in IL-1beta-stimulated PGE2, to a maximum of > 90% in all cell lines (P < or = 0.0001). The selective COX-2 inhibitors, but not indomethacin, caused partial (generally up to approximately 60%), dose-dependent decreases in IL-1beta-stimulated IL-6 in all cell lines (P < or = 0.003). When exogenous PGE2 was added concurrently with COX-2 inhibitors before addition of IL-1beta, IL-6 production returned to levels at or approaching that produced by cells exposed only to IL-1beta (P < or = 0.04).

CONCLUSION

The results suggest that COX-2 inhibition may be useful in helping to control fibroblast production of IL-6 in patients with severe periodontitis.

Examination of the signal transduction pathways involved in matrix metalloproteinases-2 in human pulp cells

OBJECTIVES

Matrix metalloproteinases (MMPs) play an important role in pulp tissue destruction. However, the mechanisms and signal transduction pathways involved in the production of MMPs in human pulp cells are not fully understood. The purpose of this study was to investigate the gelatinolytic activity in human pulp cells stimulated with various pharmacological agents.

STUDY DESIGN

Human dental pulp cells were cultured using an explant technique obtained from impacted third molars with informed consent of the patients. The effects of p38 inhibitor SB203580, MEK inhibitor U0126, extracellular signal-regulated kinase (ERK) inhibitor PD098059, phosphatidylinositaol 3-kinase (PI3K) inhibitor LY294002, cyclooxygenase-2 (COX-2) inhibitor NS-398, nuclear factor kappa B (NF-kappaB) inhibitor dexamethasone, and tyrosine kinase inhibitor herbimycin A on the production and secretion of MMPs by human pulp cells were determined by gelatin zymography.

RESULTS

The main gelatinase secreted by human pulp cells migrated at 72 kd and represented MMP-2. Minor gelatinolytic bands were also observed at 92 kd regions that correspond to MMP-9. After a 4-day culture period, NS-398, dexamethasone, and herbimycin A were found to depress MMP-2 production (P<.05). The inhibition decreased in an order of dexamethasone >NS-398>herbimycin A. Human pulp cells, however, treated with various pharmacological agents had no effect on the pattern of MMP-9 produced or secreted in either cell extracts or conditioned medium fractions (P>.05).

CONCLUSION

These observations suggest that NS-398, dexamethasone, and herbimycin A can regulate MMP-2 produced by human pulp cells. The signal transduction pathways COX-2, NF-kappaB, and tyrosine kinase may be involved in the production of MMPs.

Cyclooxygenase-2 inhibits tumor necrosis factor alpha-mediated apoptosis in renal glomerular mesangial cells

Renal mesangial cell apoptosis is a crucial repair mechanism in glomerular nephritis (GN). These cells express receptors to tumor necrosis factor alpha (TNFalpha), a cytokine with proapoptotic properties implicated in the resolution of GN. Progression to proliferative GN is accompanied by cyclooxygenase-mediated formation of prostaglandins and inefficient apoptosis of mesangial cells. The aims of this study were to quantify TNFalpha-mediated apoptosis in renal mesangial cells and to determine whether expression of the inducible form of cyclooxygenase, cylooxygenase-2 (COX-2), inhibits this apoptosis. By 24 h significant levels of apoptosis were induced by TNFalpha (100 ng/ml) or etoposide control (100 microm), as shown by phosphatidylserine externalization, caspase-3 activation, development of a sub-G(0)/G(1) region, and distinct chromatin condensation. Using adenoviral-mediated delivery of the COX-2 gene (AdCOX-2) apoptotic features were prevented from appearing in AdCOX-2 cells treated with TNFalpha, whereas etoposide-treated AdCOX-2 cells were not protected. Furthermore, COX-2 expression, induced by the vasoconstrictor peptide ET-1 or the cytokine interleukin-1beta also inhibited TNFalpha-mediated but not etoposide-mediated apoptosis, to an extent, similar to adenoviral COX-2 infection. Selective COX-2 inhibition by NS-398 restored TNFalpha-mediated apoptosis. Prostaglandin (PG) E(2) and PGI(2) were shown to be the major prostaglandin metabolites in AdCOX-2 cells. The addition of PGE(2) and PGI(2) protected against TNFalpha-mediated apoptosis. These results demonstrate COX-2 anti-apoptotic activity via a death receptor route and suggest that selective COX-2 inhibition may augment TNFalpha apoptosis in chronic inflammatory conditions.

Proinflammatory cytokines induce cyclooxygenase-2 mRNA and protein expression in human pulp cell cultures

The increased release of prostaglandins (PG) within pulpal tissues is considered to play a pathogenic role during pulpal disease progression. The rate-limiting step in the formation of PG from arachidonic acid is catalyzed by cyclooxygenase (COX). COX-2 is an inducible enzyme believed to be responsible for PG synthesis at site of inflammation. The effect of proinflammatory cytokines on human pulp cells with special reference to COX-2 expression has not been reported earlier. The aim of the present study was to investigate the effects of interleukin (IL)-1alpha and tumor necrosis factor-alpha (TNF-alpha) on the expression of COX-2 mRNA gene and protein in cultured human pulp cells. Investigations of the time dependence of COX-2 mRNA expression in proinflammatory cytokines-treated human pulp cells revealed a rapid accumulation of the transcript, a significant signal first detectable 1 h after exposure. In addition, both IL-1alpha and TNF-alpha up-regulated COX-2 protein expression by human pulp cells. The kinetics of this response showed that COX-2 was detectable in cell lysates as early as 2 h post proinflammatory cytokines challenge and remained elevated throughout the 24-h incubation period. This suggests that one of the pathogenic mechanisms of pulpal inflammation in vivo may be the synthesis of COX-2 by resident cells in response to a proinflammatory cytokines challenge. COX-2 may play an important role in the regulation of prostanoid formation in the pathogenesis of pulpal inflammation. Taken together, we propose that the use of selective COX-2 inhibitors might provide a valuable tool in the control of pulpal inflammation.

Tumor necrosis factor alpha (TNF-alpha)-induced prostaglandin E2 release is mediated by the activation of cyclooxygenase-2 (COX-2) transcription via NFkappaB in human gingival fibroblasts

Nuclear factor kappaB (NFkappaB) is a transcription factor and plays a key role in the expression of several genes involved in the inflammatory process. Cyclooxygenase (COX) is the key regulatory enzyme of the prostaglandin/eicosanoid synthetic pathway. COX-2 is a highly inducible enzyme by proinflammatory cytokines, of which gene expression is regulated by NFkappaB. TNF-alpha is a pro-inflammatory cytokine. In this paper, we investigated the involvement of NFkappaB on TNF-alpha-mediated prostaglandin E2 (PGE2) release and COX-2 gene expression in human gingival fibroblasts (HGF). TNF-alpha-induced PGE2 release and COX-2 mRNA accumulation in a time- and concentration-dependent manner in HGF. The results of transient transfection assays using a chimeric construct of the human COX-2 promoter (nts -1432 approximately +59) ligated to a luciferase reporter gene indicated that TNF-a stimulated the transcriptional activity approximately 1.4-fold. Gel mobility shift assays with a radiolabelled COX-2-NFkappaB oligonucleotide (nts -223 to -214) revealed an increase in the binding of nuclear proteins from TNF-alpha-stimulated HGF. The COX-2-NFKB DNA-protein complex disappeared after treatment with pyrrolidine dithiocarbamate (PDTC; an antioxidant) or herbimycin A (a tyrosine kinase inhibitor). PDTC and herbimycin A attenuated TNF-alpha-stimulated PGE2 release. These results suggest that NFkappaB transcription factor is a key regulator of COX-2 expression in TNF-alpha-induced PGE2 production, which is mediated through a tyrosine kinase pathway in HGF.

Signal pathways involved in the production of MMP-1 and MMP-3 in human gingival fibroblasts

Periodontitis is associated with enhanced production of cytokines, prostaglandins and matrix metalloproteinases (MMPs). The aim of this study was to investigate the production and regulation of MMP-1 and MMP-3 in human gingival fibroblasts challenged with the cytokines interleukin-lbeta (IL-1beta), tumor necrosis factor alpha (TNFalpha) or epidermal growth factor (EGF). The results showed that gingival fibroblasts constitutively produce MMP-1 and MMP-3, and that the cytokines IL-1beta, TNFalpha and EGF increase both MMP-1 and MMP-3 production in gingival fibroblasts. The upregulation by the cytokines was apparent at 8 h of incubation and increased thereafter continuously during 48 h of incubation. The upregulation of MMPs, induced by IL-1beta or TNFalpha, was reduced by the cyxlooxygenase-2 (COX-2) inhibitor NS-398, the p38 MAP-kinase inhibitor SB 203580, and the tyrosine kinase inhibitor herbimycin A. In addition, MMP-1 and MMP-3 production, induced by IL-1beta, TNFalpha or EGF, was strongly reduced by the presence of the glucocorticoid dexamethasone. Our findings demonstrate that the cytokines IL-1beta, TNFalpha and EGF, respectively, enhance both MMP-1 and MMP-3 production in human gingival fibroblasts, and that the signal pathways COX-2, MAP-kinases and tyrosine kinases are partly involved in the production of MMPs.

Effects of TNFalpha and prostaglandin E2 on the expression of MMPs in human periodontal ligament fibroblasts

Accumulating evidence indicates that TNFalpha plays an important role in the pathogenesis of periodontitis, but the effect of TNFalpha on the degradation of the periodontal ligament is not well understood. This study used reverse transcriptase-PCR to investigate the effects of TNFalpha on matrix metalloproteinase (MMP) mRNA expression in human periodontal ligament fibroblasts. TNFalpha increased MMP-1, MMP-3 and MMP-13 mRNA levels in both a time-dependent (0-24 h) and a dose-dependent (0.1-10 ng/ml) manner. TNFalpha also increased COX-2 mRNA levels. Because elevation of COX-2 mRNA levels enhances the production of prostaglandins, we therefore investigated whether endogenous prostaglandins are involved in the MMP mRNA expression that is enhanced by TNFalpha. Pretreatment with the selective COX-2 inhibitor, NS-398, increased MMP-13 mRNA levels, while prostaglandin E2 and dibutyryl cyclic AMP decreased MMP-13 mRNA levels. Neither MMP-1 nor MMP-3 mRNA levels were affected by these chemicals. These findings indicate that prostaglandin E2 has a lowering effect on TNFalpha-enhanced MMP-13 mRNA levels, and that this effect is dependent on cAMP. Our results suggest that TNFalpha participates in periodontal ligament destruction by stimulating the production of MMPs (MMP-1, MMP-3 and MMP-13), while endogenous prostaglandin E2 has a negative feedback role in TNFalpha-enhanced MMP-13 production.

The spinal phospholipase-cyclooxygenase-prostanoid cascade in nociceptive processing

Intrathecal phospholipase A2 (PLA2) and cyclooxygenase-2 (COX-2), but not COX-1, inhibitors attenuate facilitated pain states generated by peripheral injury/inflammation and by direct activation of spinal glutamate and substance P receptors. These results are consistent with the constitutive expression of PLA2 and COX-2 in spinal cord, the spinal release of prostaglandins by persistent afferent input, and the effects of prostaglandins on spinal excitability. Whereas the acute actions of COX-2 inhibitors are clearly mediated by constitutively expressed spinal COX-2, studies of spinal COX-2 expression indicate that it is upregulated by neural input and circulating cytokines. Given the intrathecal potency of COX-2 inhibitors, the comparable efficacy of intrathecal versus systemic COX-2 inhibitors in hyperalgesic states not associated with inflammation, and the onset of antihyperalgesic activity prior to COX-2 upregulation, it is argued that a principal antihyperalgesic mechanism of COX-2 inhibitors lies with modulation of constitutive COX-2 present at the spinal level.

Selected contribution: synergism between TNF-alpha and IL-1 beta in airway smooth muscle cells: implications for beta-adrenergic responsiveness

In human cultured airway smooth muscle cells, interleukin (IL)-1 beta increases cyclooxygenase (COX)-2 expression and PGE(2) release, ultimately resulting in decreased beta-adrenergic responsiveness. In this study, we aimed to determine whether tumor necrosis factor-alpha (TNF-alpha) synergizes with IL-1 beta in the induction of these events. TNF-alpha alone, at concentrations up to 10 ng/ml, had no effect on COX-2 protein expression; at concentrations as low as 0.1 ng/ml, it significantly enhanced the ability of IL-1 beta (0.2 ng/ml) to induce COX-2 and to increase PGE(2) release. IL-1 beta and TNF-alpha in combination also significantly enhanced COX-2 promoter activity, indicating that synergism between the cytokines is mediated at the level of gene transcription. Although IL-1 beta and TNF-alpha each increased nuclear factor-kappa B activation and induced extracellular regulated kinase and p38 phosphorylation, combined administration of the cytokines did not enhance either nuclear factor-kappa B or mitogen-activated protein kinase activation. Combined administration of IL-1 beta (0.2 ng/ml) and TNF-alpha (0.1 or 1.0 ng/ml) reduced the ability of isoproterenol to decrease human airway smooth muscle cell stiffness, as measured by magnetic twisting cytometry, even though individually these cytokines, at these concentrations, had no effect on isoproterenol responses. Treatment with the selective COX-2 inhibitor NS-398 abolished the synergistic effects of TNF-alpha and IL-1 beta on beta-adrenergic responsiveness. Our results indicate that low concentrations of IL-1 beta and TNF-alpha synergize to promote beta-adrenergic hyporesponsiveness and that effects on COX-2 expression and PGE(2) are responsible for these events. The data suggest that the simultaneous release in the airway, of even very small amounts of cytokines, can have important functional consequences.

Enhanced cyclooxygenase-2 mRNA expression in human gingival fibroblasts induced by cell contact with human lymphocytes

Prostaglandins, especially prostaglandin E2 (PGE2), play a crucial role in the pathogenesis of periodontal disease. We have previously reported that inflammatory mediators interleukin-1 (IL-1) and tumor necrosis factor alpha (TNFalpha) increase the production of PGE2 in human gingival fibroblasts. In this study, we investigated the effect of cell-to-cell interactions between gingival fibroblasts and lymphocytes on PGE2 production by using co-culture technique. Cell-to-cell contact between gingival fibroblasts and lymphocytes synergistically enhanced the production of PGE2 in co-cultures. In contrast to lymphocytes, the cyclooxygenase-2 (COX-2) mRNA expression in gingival fibroblasts was strongly enhanced following cell contact between gingival fibroblasts and lymphocytes. The level of COX-1 mRNA expression, however, was not affected either in gingival fibroblasts or in lymphocytes by the interactions between fibroblasts and lymphocytes. The study demonstrates that cell contact between gingival fibroblasts and lymphocytes strongly stimulates PGE2 production partly due to enhanced COX-2 mRNA expression in gingival fibroblasts. The cell-to-cell contact between gingival fibroblasts and lymphocytes should be considered as an important regulatory aspect for the enhancement of PGE2 in periodontal disease.

An immunohistological study on cyclooxygenase-2 in human dental pulp

Characteristics of cyclooxygenase-2 (COX-2) expressing cells in human dental pulp were immunohistologically studied. Extirpated pulpal tissues from extracted teeth were examined to elucidate the localization and distribution of COX-2. Pulpal tissues were examined by the labeled streptavidin biotin method using specific mouse monoclonal antibodies for COX-2. Cell types of the COX-2 expressing cells were also investigated by the double stain technique using both monoclonal antibodies for CD68/macrophage and anti-COX-2. COX-2 expressing cells could be found in all of the inflamed pulps, and these cells were mostly distributed close to the area of accumulation of inflammatory cells. COX-2 was mainly expressed in fibroblasts rather than macrophages. In contrast, COX-2 expressing cells were scarcely found in the normal pulps. These findings indicate that pulpal fibroblasts, as well as macrophages, may participate in the production of prostaglandin through COX-2 expression in pulpal inflammation, and might be involved in the pathogenesis of irreversible pulpitis.

Effects of mechanical compression on hypertrophic scars: prostaglandin E2 release

An alteration in the normal process of tissue repair can lead to the formation of hypertrophic scars. The best prevention and control of hypertrophy, especially in burn scars, is achieved using elastocompression, through a mechanism not yet clarified. Various studies have shown that mechanical compression induces the release of prostaglandin E2 (PGE2) and that PGE2 increases the expression of collagenases. In this study, we evaluated the effect of mechanical compression in vitro on PGE2 release in human normotrophic (NS) and hypertrophic (HS) burn scars. PGE2 basal levels in HS were significantly lower than those present in NS, and compression induced a significant increase in the release of PGE2 in HS scar in remission (7.2 times basal level) and active stages (5.88 times basal level). This increase seemed to be only partially IL-1beta-dependent. These data suggest a role for PGE2 in the process of hypertrophy remission induced by pressure therapy.

Cyclooxygenase-2-dependent prostaglandin E2 down-regulates intercellular adhesion molecule-1 expression via EP2/EP4 receptors in interleukin-1beta-stimulated human gingival fibroblasts

Prostaglandin E2 (PGE2), which exerts its actions via EP receptors (EP1, EP2, EP3, and EP4), is a bioactive metabolite of arachidonic acid produced by cyclooxygenase (COX)-1 and/or COX-2. We have previously demonstrated that PGE2 down-regulates intercellular adhesion molecule-1 (ICAM-1) expression in interleukin-1beta (IL-1beta)-stimulated human gingival fibroblasts (HGF). In the present study, we investigated which COX was involved in down-regulation of ICAM-1 expression by PGE2 in IL-1beta-stimulated HGF and which subtypes of EP receptors modulated the ICAM-1 expression. NS-398, a specific COX-2 inhibitor, completely inhibited PGE2 production by IL-1beta-stimulated HGF, as did indomethacin, a COX-1/COX-2 inhibitor. Northern blot analysis and immunocytochemical staining showed that mRNA and protein of COX-2 were expressed in IL-1beta-challenged HGF, but not in unstimulated HGF, and that the expression of mRNA and protein of COX-1 was similar both in unstimulated and in stimulated cells. NS-398 and indomethacin enhanced ICAM-1 expression in IL-1beta-challenged HGF. EP1, EP2, and EP4 receptor mRNA was expressed in HGF according to reverse-transcription/polymerase chain-reaction. PGE2, 11-deoxy-PGE1 (a selective EP2/EP4 agonist), and Butaprost (a selective EP2 agonist) attenuated IL-1beta-elicited ICAM-1 expression, although Butaprost was less potent than PGE2 and 11-deoxy-PGE1. AH-23848B, an EP4 antagonist, antagonized the inhibitory effect of IL-1beta-elicited ICAM-1 expression by PGE2. Sulprostone, an EP1/EP3 agonist, had no effect on IL-1beta-elicited ICAM-1 expression. Analysis of these data suggests that COX-2-derived PGE2 down-regulates ICAM-1 expression via EP2/EP4 receptors in IL-1beta-stimulated HGF.

Tumor necrosis factor-alpha (TNF-alpha)-induced and interleukin-1 beta (IL-1 beta)-induced shedding of TNF receptors from gingival fibroblasts

Tumor necrosis factor-alpha (TNF-alpha) exerts its functions by binding two different receptors (TNFR55 and TNFR75). Both TNFR55 and TNFR75 exist in cell-associated and soluble forms. Soluble TNF receptors (sTNFR), sTNFR55 and sTNFR75, are proteolytically shed upon inflammatory stimuli and then modulate various TNF-alpha bioactivities. As human gingival fibroblasts (HGF) can be potential targets for TNF-alpha in inflamed gingiva, we hypothesized that HGF partially modulate the cellular responses to TNF-alpha by regulating their own TNFR. In this study, the kinetics of expression of cell-associated and soluble forms of both receptors from cultured HGF in response to proinflammatory cytokines TNF-alpha and interleukin-1 beta (IL-1 beta) were investigated in vitro. Both TNF-alpha and IL-1 beta upregulated the gene expression of TNFR75 and did not affect that of TNFR55. TNF-alpha and IL-1 beta decreased binding of [(125)I]TNF-alpha to HGF. Moreover, TNF-alpha and IL-1 beta upregulated the release of sTNFR75 from HGF but not that of sTNFR55. These results suggest that HGF under inflammatory conditions may contribute to the inactivation of circulating TNF-alpha through the preferential induction and shedding of TNFR75.

Tumor necrosis factor has positive and negative self regulatory feed back cycles centered around cAMP

This paper reviews data that allow recognition of, (1) two opposing intracellular chains of events occurring subsequent to an increase in tumor necrosis factor, TNF, and (2) that these two chains have opposing effects on intracellular cyclic adenosine monophosphate, cAMP. The two chains - attenuation cycle, where TNF results in prostaglandin E mediated increased cAMP and, consequent to this, suppression of TNF levels; and an amplification cycle, where increased TNF increases intracellular cyclic adenosine phosphodiesterase, lowering cAMP, thereby raising TNF levels further. TNF is a central mediator in several inflammatory diseases. Understanding TNF control systems will allow better delineation of pathophysiology and clinical care.