Triclosan reduces microsomal prostaglandin E synthase-1 expression in human gingival fibroblasts

Current material engineering strategies to prevent catheter encrustation in urinary tracts

Catheters and ureteric stents have played a vital role in relieving urinary obstruction in many urological conditions. With the increasing use of urinary catheters/stents, catheter/stent-related complications such as infection and encrustation are also increasing because of their design defects. Long-term use of antibiotics and frequent replacement of catheters not only increase the economic burden on patients but also bring the pain of catheter replacement. This is unfavorable for patients with long indwelling catheters or stents but inconvenient to replace. In recent years, some promising technologies and mechanisms have been used to prevent infection and encrustation, mainly drug loading coatings, functional coatings, biodegradable polymers and metallic materials for urinary devices. Obvious effects in anti-encrustation and anti-infection experiments of the above strategies in vivo or in vitro have been conducted, which is very helpful for further clinical trials. This review mainly introduces catheter/stent technology and mechanisms in the past ten years to address the potential impact of anti-encrustation coating of catheter/stent materials for the prevention of encrustation and to analyze the progress made in this field.

Triclosan: An Update on Biochemical and Molecular Mechanisms

Triclosan (TCS) is a synthetic, chlorinated phenolic antimicrobial agent commonly used in commercial and healthcare products. Items made with TCS include soaps, deodorants, shampoos, cosmetics, textiles, plastics, surgical sutures, and prosthetics. A wealth of information obtained from in vitro and in vivo studies has demonstrated the therapeutic effects of TCS, particularly against inflammatory skin conditions. Nevertheless, extensive investigations on the molecular aspects of TCS action have identified numerous adversaries associated with the disinfectant including oxidative injury and influence of physiological lifespan and longevity. This review presents a summary of the biochemical alterations pertaining to TCS exposure, with special emphasis on the diverse molecular pathways responsive to TCS that have been elucidated during the present decade.

Morphine, but not methadone, inhibits microsomal prostaglandin E synthase-1 and prostaglandin-endoperoxide synthase 2 in lipopolysaccharide-stimulated horse synoviocytes

Osteoarthritis (OA) is one of the main locomotor disorders in horses. Although nonsteroidal anti-inflammatory drugs are the first-line treatment for OA, opioids could also be used. In previous studies, opioids showed promising anti-inflammatory and analgesic effects. In this study, we aimed to investigate the effects of two opioids (morphine and methadone) against inflammation in lipopolysaccharide (LPS)-stimulated synoviocytes by analyzing microsomal prostaglandin E synthase-1 (mPGES-1) and prostaglandin-endoperoxide synthase 2 (PTGS2) expression. Synoviocytes were obtained from the joints at the distal limbs of dead animals. The cytotoxic effects of LPS, morphine, and methadone were investigated by using a cell viability assay with crystal violet dye. Synoviocytes were treated with LPS, LPS plus morphine, or LPS plus methadone for 3, 6, and 12 h, and mPGES-1 and PTGS2 expression was measured using real-time polymerase chain reaction. LPS, and morphine did not affect the viability of synoviocytes, even at high concentrations. LPS treatment increased mPGES-1 and PTGS2 expression, whereas morphine inhibited the increase in mPGES-1 and PTGS2 expression in LPS-stimulated synoviocytes. Methadone did not inhibit mPGES-1 or PTGS2 expression. These results suggest that morphine may exhibit anti-inflammatory effect; therefore, it might be beneficial for the treatment of OA.

Targeting inflammation: multiple innovative ways to reduce prostaglandin E₂

The PGE2 pathway is important in inflammation-driven diseases and specific targeting of the inducible mPGES-1 is warranted due to the cardiovascular problems associated with the long-term use of COX-2 inhibitors. This review focuses on patents issued on methods of measuring mPGES-1 activity, on drugs targeting mPGES-1 and on other modulators of free extracellular PGE2 concentration. Perspectives and conclusions regarding the status of these drugs are also presented. Importantly, no selective inhibitors targeting mPGES-1 have been identified and, despite the high number of published patents, none of these drugs have yet made it to clinical trials.

Community-level assessment of dental plaque bacteria susceptibility to triclosan over 19 years

Background

Triclosan is a broad-spectrum antimicrobial agent used in toothpaste to reduce dental plaque, gingivitis and oral malodor. This community-level assessment evaluated the susceptibility of dental plaque bacteria to triclosan in samples collected over 19 years.

Methods

A total of 155 dental plaque samples were collected at eleven different times over 19 years from 58 adults using 0.3% triclosan, 2% copolymer, 0.243% sodium fluoride toothpaste and from 97 adults using toothpaste without triclosan. These included samples from 21 subjects who used triclosan toothpaste for at least five years and samples from 20 control subjects. The samples were cultured on media containing 0, 7.5 or 25 μg/ml triclosan. Descriptive statistics and p values were computed and a linear regression model and the runs test were used to examine susceptibility over time.

Results

Growth inhibition averaged 99.451% (91.209 - 99.830%) on media containing 7.5 μg/ml triclosan and 99.989% (99.670 - 100%) on media containing 25 μg/ml triclosan. There was no change in microbial susceptibility to triclosan over time discernible by regression analysis or the runs test in plaque samples taken over 19 years including samples from subjects using a triclosan-containing dentifrice for at least five years.

Conclusions

This community-level assessment of microbial susceptibility to triclosan among supragingival plaque bacteria is consistent with the long-term safety of a 0.3% triclosan, 2% copolymer, 0.243% sodium fluoride dentifrice.

PGE2 signaling and its biosynthesis-related enzymes in cholangiocarcinoma progression

Prostaglandin E2 (PGE2) involves in progression of various chronic inflammation-related cancers including cholangiocarcinoma (CCA). This study aimed to determine the role of PGE2 signaling, its biosynthesis-related enzymes in a clinical prognosis, and their targeted inhibition in CCA progression. The immunohistochemical staining of cyclooxygenase (COX)-1, COX-2, mPGES-1, EP1, and EP4 was examined in CCA tissues, and their expressions were compared with clinicopathological parameters. The effect of PGE2 on levels of its signaling molecules was examined in CCA cell lines using proteome profiler array. The suppression of mPGES-1 using a small-molecule inhibitor (CAY10526) and small interfering RNA (siRNA) was determined for growth and migration ability in CCA cells. The results indicated that strong expressions of COX-1, COX-2, mPGES-1, EP1, and EP4 were found in CCA tissues as 87.5, 47.5, 52.5, 55, and 80 % of frequencies, respectively. High mPGES-1 expression was significantly correlated with tumor stages III-IV (p = 0.001), lymph node metastasis (p = 0.004), shorter survival (p = 0.009), and prognostic indicator of CCA patients (HR = 2.512, p = 0.041). Expressions of COX-1, COX-2, and EP receptors did not correlate with data tested from patients. PGE2 markedly enhanced protein levels of integrinα6, VE-cadherin, Jagged1, and Notch3, and CAY10526 suppressed those protein levels as well as PGE2 production in CCA cells. CAY10526 and siRNA mPGES-1 markedly suppressed mPGES-1 protein levels, growth, and migration abilities of CCA cell lines. In conclusion, PGE2 signaling strongly promotes CCA progression. Therefore, inhibition of PGE2 synthesis by suppression of its biosynthesis-related enzymes could be useful for prevention and treatment of CCA.

Triclosan/copolymer containing toothpastes for oral health

BACKGROUND

Periodontal disease and dental caries are highly prevalent oral diseases that can lead to pain and discomfort, oral hygiene and aesthetic problems, and eventually tooth loss, all of which can be costly to treat and are a burden to healthcare systems. Triclosan is an antibacterial agent with low toxicity, which, along with a copolymer for aiding retention, can be added to toothpastes to reduce plaque and gingivitis (inflammation of the gums). It is important that these additional ingredients do not interfere with the anticaries effect of the fluoride present in toothpastes, and that they are safe.

OBJECTIVES

To assess the effects of triclosan/copolymer containing fluoride toothpastes, compared with fluoride toothpastes, for the long-term control of caries, plaque and gingivitis in children and adults.

SEARCH METHODS

We searched the Cochrane Oral Health Group's Trials Register (to 19 August 2013), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 7), MEDLINE via OVID (1946 to 19 August 2013), EMBASE via OVID (1980 to 19 August 2013), and the US National Institutes of Health Trials Register (clinicaltrials.gov) (to 19 August 2013). We applied no restrictions regarding language or date of publication in the searches of the electronic databases.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) assessing the effects triclosan/copolymer containing toothpastes on oral health.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the search results against the inclusion criteria for this review, extracted data and carried out risk of bias assessments. We attempted to contact study authors for missing information or clarification when feasible. We combined sufficiently similar studies in meta-analyses using random-effects models when there were at least four studies (fixed-effect models when fewer than four studies), reporting mean differences (MD) for continuous data and risk ratios (RR) for dichotomous data.

MAIN RESULTS

We included 30 studies, analysing 14,835 participants, in this review. We assessed 10 studies (33%) as at low risk of bias, nine (30%) as at high risk of bias and 11 (37%) as unclear. Plaque Compared with control, after six to seven months of use, triclosan/copolymer toothpaste reduced plaque by 0.47 on a 0 to 5 scale (MD -0.47, 95% confidence interval (CI) -0.60 to -0.34, 20 studies, 2675 participants, moderate-quality evidence). The control group mean was 2.17, representing a 22% reduction in plaque. After six to seven months of use, it also reduced the proportion of sites scoring 3 to 5 on a 0 to 5 scale by 0.15 (MD -0.15, 95% CI -0.20 to -0.10, 13 studies, 1850 participants, moderate-quality evidence). The control group mean was 0.37, representing a 41% reduction in plaque severity. Gingivitis After six to nine months of use, triclosan/copolymer toothpaste reduced inflammation by 0.27 on a 0 to 3 scale (MD -0.27, 95% CI -0.33 to -0.21, 20 studies, 2743 participants, moderate-quality evidence). The control group mean was 1.22, representing a 22% reduction in inflammation. After six to seven months of use, it reduced the proportion of bleeding sites (i.e. scoring 2 or 3 on the 0 to 3 scale) by 0.13 (MD -0.13, 95% CI -0.17 to -0.08, 15 studies, 1998 participants, moderate-quality evidence). The control group mean was 0.27, representing a 48% reduction in bleeding. Periodontitis After 36 months of use, there was no evidence of a difference between triclosan/copolymer toothpaste and control in the development of periodontitis (attachment loss) (RR 0.92, 95% CI 0.67 to 1.27, one study, 480 participants, low-quality evidence). Caries After 24 to 36 months of use, triclosan/copolymer toothpaste slightly reduced coronal caries when using the decayed and filled surfaces (DFS) index (MD -0.16, 95% CI -0.31 to -0.02, four studies, 9692 participants, high-quality evidence). The control group mean was 3.44, representing a 5% reduction in coronal caries. After 36 months of use, triclosan/copolymer toothpaste probably reduced root caries (MD -0.31, 95% CI -0.39 to -0.23, one study, 1357 participants, moderate-quality evidence). Calculus After six months of use, triclosan/copolymer toothpaste may have reduced the mean total calculus per participant by 2.12 mm (MD -2.12 mm, 95% CI -3.39 to -0.84, two studies, 415 participants, low-quality evidence). The control group mean was 14.61 mm, representing a 15% reduction in calculus. Adverse effects There were no data available for meta-analysis regarding adverse effects, but 22 studies (73%) reported that there were no adverse effects caused by either the experimental or control toothpaste.There was considerable heterogeneity present in the meta-analyses for plaque, gingivitis and calculus. Plaque and gingivitis showed such consistent results that it did not affect our conclusions, but the reader may wish to interpret the results with more caution.

AUTHORS' CONCLUSIONS

There was moderate-quality evidence showing that toothpastes containing triclosan/copolymer, in addition to fluoride, reduced plaque, gingival inflammation and gingival bleeding when compared with fluoride toothpastes without triclosan/copolymer. These reductions may or may not be clinically important, and are evident regardless of initial plaque and gingivitis levels, or whether a baseline oral prophylaxis had taken place or not. High-quality evidence showed that triclosan/copolymer toothpastes lead to a small reduction in coronal caries. There was weaker evidence to show that triclosan/copolymer toothpastes may have reduced root caries and calculus, but insufficient evidence to show whether or not they prevented periodontitis. There do not appear to be any serious safety concerns regarding the use of triclosan/copolymer toothpastes in studies up to three years in duration.

The effect of a dentifrice containing Magnolia extract on established plaque and gingivitis in man: a six-month clinical study

AIM

The aim was to evaluate the clinical effect of a dentifrice containing 0.3% Magnolia extract on dental plaque and gingivitis.

MATERIAL AND METHODS

The trial was a 6-month double-blind, stratified, randomized and 2-armed parallel group study. Forty-six subjects in the test group brushed their teeth with a dentifrice containing 0.3% Magnolia extract and 48 subjects in the control group brushed with a placebo dentifrice. Plaque and gingivitis were assessed at baseline, 3 and 6 months.

RESULTS

There was a significantly larger gingivitis reduction in the Magnolia group than in the control group (0.26 ± 0.11 versus 0.11 ± 0.12) (P < 0.001). There was a greater increase in the total number of healthy gingival units Gingival Index (GI score 0) in the Magnolia group than in the control group (149% versus 31%) and a larger reduction in inflamed gingival units (GI score 2/3) (60% versus 30%). Furthermore, at sites with similar amounts of plaque, less clinical signs of gingival inflammation were observed in the Magnolia group than in the control group.

CONCLUSION

Six months' unsupervised use of a dentifrice containing 0.3% Magnolia extract resulted in significantly greater gingivitis reduction than a corresponding control dentifrice.

Inhibition of microsomal prostaglandin E synthase-1 by aminothiazoles decreases prostaglandin E2 synthesis in vitro and ameliorates experimental periodontitis in vivo

The potent inflammatory mediator prostaglandin E2 (PGE2) is implicated in the pathogenesis of several chronic inflammatory conditions, including periodontitis. The inducible enzyme microsomal prostaglandin E synthase-1 (mPGES-1), catalyzing the terminal step of PGE2 biosynthesis, is an attractive target for selective PGE2 inhibition. To identify mPGES-1 inhibitors, we investigated the effect of aminothiazoles on inflammation-induced PGE2 synthesis in vitro, using human gingival fibroblasts stimulated with the cytokine IL-1β and a cell-free mPGES-1 activity assay, as well as on inflammation-induced bone resorption in vivo, using ligature-induced experimental periodontitis in Sprague-Dawley rats. Aminothiazoles 4-([4-(2-naphthyl)-1,3-thiazol-2-yl]amino)phenol (TH-848) and 4-(3-fluoro-4-methoxyphenyl)-N-(4-phenoxyphenyl)-1,3-thiazol-2-amine (TH-644) reduced IL-1β-induced PGE2 production in fibroblasts (IC50 1.1 and 1.5 μM, respectively) as well as recombinant mPGES-1 activity, without affecting activity or expression of the upstream enzyme cyclooxygenase-2. In ligature-induced experimental periodontitis, alveolar bone loss, assessed by X-ray imaging, was reduced by 46% by local treatment with TH-848, compared to vehicle, without any systemic effects on PGE2, 6-keto PGF1α, LTB4 or cytokine levels. In summary, these results demonstrate that the aminothiazoles represent novel mPGES-1 inhibitors for inhibition of PGE2 production and reduction of bone resorption in experimental periodontitis, and may be used as potential anti-inflammatory drugs for treatment of chronic inflammatory diseases, including periodontitis.

Identification and development of mPGES-1 inhibitors: where we are at?

Microsomal prostaglandin E synthase-1 (mPGES-1) is the terminal synthase responsible for the synthesis of the pro-tumorigenic prostaglandin E(2) (PGE(2)). mPGES-1 is overexpressed in a wide variety of cancers. Since its discovery in 1997 by Bengt Samuelsson and collaborators, the enzyme has been the object of over 200 peer-reviewed articles. Although today mPGES-1 is considered a validated and promising therapeutic target for anticancer drug discovery, challenges in inhibitor design and selectivity are such that up to this date there are only a few published records of small-molecule inhibitors targeting the enzyme and exhibiting some in vivo anticancer activity. This review summarizes the structures, and the in vitro and in vivo activities of these novel mPGES-1 inhibitors. Challenges that have been encountered are also discussed.

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.

Triclosan inhibits tumor necrosis factor-alpha-stimulated urokinase production in human gingival fibroblasts

BACKGROUND AND OBJECTIVES

Destruction of the supporting periodontal tissues is mediated by the action of several proteolytic enzymes. Urokinase is a serine protease that plays a key role in connective tissue destruction through conversion of plasminogen into plasmin. The present study was conducted to evaluate the effect of triclosan on the production and activity of urokinase in cultured gingival fibroblasts.

MATERIAL AND METHODS

Urokinase production was studied in primary cultures of human gingival fibroblasts stimulated with tumor necrosis factor-alpha. Urokinase activity and production were evaluated using casein zymography and western blotting, respectively. Urokinase mRNA expression was evaluated using the reverse transcription-polymerase chain reaction. Triclosan was used to interfere with this stimulatory effect. The roles of different cell-signaling cascades involved in urokinase production were assessed through western blotting and immunofluorescence using several cell-signaling inhibitors.

RESULTS

Tumor necrosis factor-alpha was found to be a strong stimulus for urokinase production and triclosan was able to inhibit this response at the protein and mRNA levels. Triclosan was also able to inhibit conversion of plasminogen into plasmin. Tumor necrosis factor-alpha-stimulated urokinase production was shown to be dependent on the nuclear factor-kappaB and c-Jun N-terminal kinase signaling pathways. Triclosan inhibited c-Jun N-terminal kinase phosphorylation and c-Jun production.

CONCLUSIONS

Within the limits of this study, these results show that triclosan may inhibit urokinase production and plasminogen activation in gingival fibroblasts through modulation of the c-Jun N-terminal kinase signaling pathway.

Novel in vitro model for studying ureteric stent-induced cell injury

OBJECTIVE

To develop a novel in vitro model for the study of bladder and kidney epithelial cell injury akin to stent movement, as ureteric stents are associated with urinary tract complications that can significantly add to patient morbidity. These sequelae may be linked to inflammation triggered by stent-mediated mechanical injury to the urinary tract.

MATERIALS AND METHODS

T24 bladder and A498 kidney cell line monolayers were damaged mechanically by segments of either Percuflex Plus (PP) or Triumph (triclosan-eluting) stents (both from Boston Scientific Corporation Inc. Natick, MA, USA) and the resulting expression profiles of several pro-inflammatory cytokines and growth factors were analysed.

RESULTS

After control injury using the PP stent, supernatants of both cell lines had significantly increased levels of interleukin (IL)-6, IL-8, basic fibroblast growth factor and platelet-derived growth factor BB, and A498 cells also had increased tumour necrosis factor alpha. In almost all cases, the presence of triclosan within the media abrogated the pro-inflammatory cytokine increases, while its effects on growth factors varied.

CONCLUSION

This study suggests that stent-related symptoms in the bladder and kidney may be partially due to a local inflammatory response to epithelial damage caused by the presence and movement of the stent. Future stent design should take these inflammatory responses, with respect to physical injury, into consideration, using either more biocompatible materials or anti-inflammatory compounds such as triclosan.

The clinical efficacy of triclosan/copolymer and other common therapeutic approaches to periodontal health

The maintenance of an effective level of oral hygiene is the cornerstone of all attempts to prevent and control periodontal disease, and yet the widespread prevalence of the disease indicates the inability of most people to maintain a level of plaque control commensurate with periodontal health. The inclusion of antibacterial agents, such as chlorhexidine and triclosan, in oral care products has provided a means to improve oral health. Randomised, controlled clinical trials have demonstrated that the unsupervised use of a dentifrice (toothpaste) containing triclosan/copolymer significantly improves gingival health, prevents the onset of periodontitis and reduces further progression of tissue destruction. The delivery of such benefits has positive implications for the oral health of individuals and populations.

Antibacterials as anti-inflammatory agents: dual action agents for oral health

BACKGROUND

Inflammatory processes with a range of specialized cells and biochemical mediators form a complex network of inter-related signal transducing pathways that relay information to preserve normal functions. Advances in molecular analyses of the information relay pathways for their constituents and principal ligands along with mechanisms utilized by the host for microbial recognition have stimulated interest in therapeutic agents with dual functionalities i.e. antibacterial and anti-inflammatory effects.

AIM

This review examines clinically tested agents for oral health applications with both antimicrobial and anti-inflammatory effects to include antibiotics, antimicrobials and phenolics.

RESULTS

Bis-phenols such as triclosan, representing a unique dual functional therapeutic for routine oral hygiene, with its demonstrated clinical effects on inhibiting the dental plaque biofilm, reducing inflammation (gingivitis) and subsequent periodontitis is described. Cyclines, comprising another class of approved anti-inflammatory agents used at the patient level for oral health is discussed. Dual active agents in current clinical practice for systemic conditions are highlighted to summarize the clinical validity of dual function agents as an emerging therapeutic strategy.

CONCLUSIONS

Clinical studies demonstrate therapeutic benefits of agents with dual functionality with their effects on microorganisms and the concomitant host inflammatory response. Advances in microbial pathogenesis and resultant inflammation will facilitate progress in this emerging area poised to be a significant milestone for dental therapeutics.

The effect of age on prostaglandin-synthesizing enzymes in the development of gingivitis

BACKGROUND AND OBJECTIVE

The aim of this study was to identify the expression of cyclooxygenase-1, cyclooxygenase-2, cyclooxygenase-3, and microsomal prostaglandin E synthase-1 in young and elderly subjects.

MATERIAL AND METHODS

Periodontally healthy subjects were divided into young (18-30 years, n = 7) and elderly (46-77 years, n = 7). A gingival biopsy was taken at baseline. After experimental gingivitis, clinical examination was repeated and a second biopsy was taken. The expression of cyclooxygenase-1, cyclooxygenase-2, cyclooxygenase-3, and microsomal prostaglandin E synthase-1 was analyzed by means of immunohistochemistry.

RESULTS

In both healthy age groups, cyclooxygenase-1 and microsomal prostaglandin E synthase-1 were expressed in epithelial cells, endothelial cells and fibroblast-like connective tissue cells. Cyclooxygenase-1 was found in Langerhans' cells of the epithelium. Cyclooxygenase-2 expression was observed in cells exhibiting the morphology of epithelial mitosis cells, and the expression of cyclooxygenase-2 in periodontally healthy elderly subjects was significantly lower (p < or = 0.05). Following experimental gingivitis, cyclooxygenase-1 and microsomal prostaglandin E synthase-1 expression did not change. However, the expression of cyclooxygenase-2 was significantly increased in both age groups (p < or = 0.05). Cyclooxygenase-3 was not detected in any group investigated.

CONCLUSION

Cyclooxygenase-1 and microsomal prostaglandin E synthase-1 were expressed constitutively in gingival tissue, and expression was unaffected by age or inflammation states. In contrast, the expression of cyclooxygenase-2 was weaker in elderly subjects. In the course of experimental gingivitis, cyclooxygenase-2 was induced in both age groups.

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.