Production of inflammatory mediators and cytokines by human gingival fibroblasts following bacterial challenge

In Vitro Anti-Inflammatory Activity of Essential Oil and β-Bisabolol Derived from Cotton Gin Trash

Natural α-bisabolol has been widely used in cosmetics and is sourced mainly from the stems of Candeia trees that have become endangered due to over exploitation. The in vitro anti-inflammatory activity of cotton gin trash (CGT) essential oil and the major terpenoid (β-bisabolol) purified from the oil were investigated against lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages as well as the 3t3 and HS27 fibroblast cell lines. Nitric oxide (NO), prostaglandin E₂ (PGE₂), tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), and interleukin 8 (IL-8) were measured using Greiss reagent, enzyme-linked immunosorbent assay (ELISA), and cytokine bead array (CBA)-flow cytometry. Non-toxic concentrations of CGT oil and β-bisabolol (1.6–50.0 µg/mL) significantly inhibited the production of the inflammatory mediators in a dose-dependent manner. Maximal inhibition by β-bisabolol was 55.5% for NO, 62.3% for PGE₂, and 45.3% for TNF-α production in RAW cells. β-Bisabolol induced a level of inhibition similar to an equal concentration of α-bisabolol (50.0 µg/mL), a known anti-inflammatory agent. These results suggest β-bisabolol exerts similar in vitro effects to known topical anti-inflammatory agents and could therefore be exploited for cosmetic and therapeutic uses. This is the first study to report the in vitro anti-inflammatory activity of β-bisabolol in CGT essential oil.

Correlation of Periodontal Bacteria with Chronic Inflammation Present in Patients with Metabolic Syndrome

Metabolic syndrome (MS) is correlated with many chronic diseases, and so far is moderately followed and treated. The present study follows a correlation of the presence of pathogens (Fusobacterium nucleatum, Bacteroides forsythus, and others) in the gingival crevicular fluid and MS. (1) An important role in the fight against MS is to reduce fat mass, inflammatory mediators, and prevent cytokine-associated diseases. (2) A group of 111 people with MS was studied, divided into 3 groups. The control group (CG) received no treatment for either periodontitis or MS. The diet therapy group (DG) followed a clinical diet therapy specific to MS, and the diet therapy and sports group (DSG) in addition to diet therapy introduced regular physical activity; (3) A statistically significant worsening of periodontopathogens was observed correlated with the advancement of MS (increase in fat mass, visceral fat, and ECW/TBW ratio) in the CG group. In the case of DG and DSG groups, an improvement of the parameters was observed, including periodontal diseases. Therefore, anti-inflammatory diet therapy contributes to the reduction of gingival inflammation and thus contributes to the reduction of the development of pathogenic bacteria in the gingival, responsible for the development of periodontal disease and directly by other chronic diseases.

Effect of Low-Level Laser Therapy on Peri-Miniscrew Fluid Prostaglandin E2 and Substance P Levels: A Controlled Clinical Trial

Objective

This study aims to evaluate the effect of low-level laser therapy on peri-miniscrew fluid prostaglandin E2 (PGE2) and substance P (SP) levels during orthodontic treatment.

Methods

A total of 15 individuals were included in this study. Miniscrews were inserted to the inter-radicular region of the maxillary right and left second premolar and the first molar teeth, and diode lasers were randomly applied to the right or left side. Irradiation was performed at 940 nm wavelength using a gallium-aluminum-arsenide diode laser with 100 mW power output, 0.125 cm2 spectral area, 8 J/cm2 energy density, and 10 seconds of exposure time. Peri-miniscrew fluid samples were collected on the 1st, 3rd, and 7th days, and PGE2 and SP levels were assessed. For statistical comparison, two-way (factors) analysis of variance with repeated measurements on one-factor levels was used at statistical significance (p) of <0.05.

Results

PGE2 levels on the 1st, 3rd, and 7th days were 160.64±10.05, 135.17±37.18, and 98.57±22.94, respectively, in the control group and 150.75±9.08, 87.17±40.67, and 78.10±16.50, respectively, in the laser group. SP levels on the 1st, 3rd, and 7th days were 79.90±12.05, 64.61±10.05, and 70.05±9.10, respectively, in the control group and 76.32±11.39, 60.25±9.08, and 65.71±5.59, respectively, in the laser group. The differences in PGE2 and SP levels between the laser and control groups were not statistically significant at all time intervals.

Conclusion

Low-level laser therapy cannot be recommended as a clinical adjunct therapy to reduce inflammation and pain around the miniscrews.

Prolyl hydroxylase inhibitor DMOG suppressed inflammatory cytokine production in human gingival fibroblasts stimulated with Fusobacterium nucleatum

OBJECTIVE

Fusobacterium nucleatum (F. nucleatum) is one of the most common bacteria involved in the initiation and progression of periodontal diseases. Pharmacological inhibitor of prolyl hydroxylases (PHDs), dimethyloxallyl glycine (DMOG), has been reported to exert anti-inflammatory effects. The aim of this investigation was to evaluate the role of DMOG in inflammatory cytokine production of human gingival fibroblasts (HGFs) stimulated with F. nucleatum.

MATERIAL AND METHODS

HGFs were pretreated with 10, 50, and 100 μM DMOG for 24 h before infected with F. nucleatum (MOI = 100). Cell morphology and survival after infection with F. nucleatum were determined by crystal violet staining assay. The mRNA levels of interleukin (IL)-6, IL-8, tumor necrosis factor (TNF)-α, and IL-1β were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). The production of IL-6, IL-8, TNF-α, and IL-1β was assessed by enzyme-linked immunosorbent assay (ELISA).

RESULTS

F. nucleatum did not affect the morphology and survival of HGFs by the concentrations of MOI (multiplicity of infection) = 10, 50, and 100. The mRNA levels of IL-6, IL-8, TNF-α, and IL-1β were significantly enhanced with the stimulation of F. nucleatum, and the maximal effect reached at 6 h. The secretion of IL-6, IL-8, and TNF-α was significantly upregulated by the infection of F. nucleatum while the production of IL-1β was nearly unchanged. Above all, DMOG suppressed F. nucleatum-stimulated IL-6, IL-8, TNF-α, and IL-1β expressions.

CONCLUSIONS

These data indicate that prolyl hydroxylase inhibitor DMOG partly downregulates inflammatory cytokine expression in F. nucleatum-infected HGFs.

CLINICAL RELEVANCE

DMOG may provide a novel strategy for the therapy of periodontitis.

The Clinical Importance of Campylobacter concisus and Other Human Hosted Campylobacter Species

Historically, Campylobacteriosis has been considered to be zoonotic; the Campylobacter species that cause human acute intestinal disease such as Campylobacter jejuni and Campylobacter coli originate from animals. Over the past decade, studies on human hosted Campylobacter species strongly suggest that Campylobacter concisus plays a role in the development of inflammatory bowel disease (IBD). C. concisus primarily colonizes the human oral cavity and some strains can be translocated to the intestinal tract. Genome analysis of C. concisus strains isolated from saliva samples has identified a bacterial marker that is associated with active Crohn's disease (one major form of IBD). In addition to C. concisus, humans are also colonized by a number of other Campylobacter species, most of which are in the oral cavity. Here we review the most recent advancements on C. concisus and other human hosted Campylobacter species including their clinical relevance, transmission, virulence factors, disease associated genes, interactions with the human immune system and pathogenic mechanisms.

Cytotoxic and biological effects of bulk fill composites on rat cortical neuron cells

The aim of this study was to investigate potential cellular responses and biological effects of new generation dental composites on cortical neuron cells in two different exposure times. The study group included five different bulk-fill flow able composites; Surefil SDR Flow, X-tra Base Flow, Venus Bulk Flow, Filtek Bulk Flow and Tetric-Evo Flow. They were filled in Teflon molds (Height: 4 mm, Width: 6 mm) and irradiated for 20 s. Cortical neuron cells were inoculated into 24-well plates. After 80% of the wells were coated, the 3 µm membrane was inserted and dental filling materials were added. The experiment was continued for 24 and 72 h. Cell viability measured by MTT assay test, total antioxidant and total oxidant status were examined using real assay diagnostic kits. The patterns of cell death (apoptosis) were analyzed using annexin V-FITC staining with flow cytometry. Β-defensins were quantitatively assessed by RT-PCR. IL-6, IL-8 and IL-10 cytokines were measured from the supernatants. All composites significantly affected analyses parameters during the exposure durations. Our data provide evidence that all dental materials tested are cytotoxic in acute phase and these effects are induced cellular death after different exposure periods. Significant cytotoxicity was detected in TE, XB, SS, FBF and VBF groups at 24 and 72 h, respectively.

Innate Immune Response of Human Embryonic Stem Cell-Derived Fibroblasts and Mesenchymal Stem Cells to Periodontopathogens

Periodontitis involves complex interplay of bacteria and host immune response resulting in destruction of supporting tissues of the tooth. Toll-like receptors (TLRs) play a role in recognizing microbial pathogens and eliciting an innate immune response. Recently, the potential application of multipotent stem cells and pluripotent stem cells including human embryonic stem cells (hESCs) in periodontal regenerative therapy has been proposed. However, little is known about the impact of periodontopathogens on hESC-derived progenies. This study investigates the effects of heat-killed periodontopathogens, namely, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, on TLR and cytokine expression profile of hESC-derived progenies, namely, fibroblasts (hESC-Fib) and mesenchymal stem cells (hESC-MSCs). Additionally, the serotype-dependent effect of A. actinomycetemcomitans on hESC-derived progenies was explored. Both hESC-Fib and hESC-MSCs constitutively expressed TLR-2 and TLR-4. hESC-Fib upon exposure to periodontopathogens displayed upregulation of TLRs and release of cytokines (IL-1β, IL-6, and IL-8). In contrast, hESC-MSCs were largely nonresponsive to bacterial challenge, especially in terms of cytokine production. Further, exposure of hESC-Fib to A. actinomycetemcomitans serotype c was associated with higher IL-8 production than serotype b. In contrast, the hESC-MSCs displayed no serotype-dependent response. Differential response of the two hESC progenies implies a phenotype-dependent response to periodontopathogens and supports the concept of immunomodulatory properties of MSCs.

Synergistic anti-inflammatory activity of the antimicrobial peptides human beta-defensin-3 (hBD-3) and cathelicidin (LL-37) in a three-dimensional co-culture model of gingival epithelial cells and fibroblasts

Given the spread of antibiotic resistance in bacterial pathogens, antimicrobial peptides that can also modulate the immune response may be a novel approach for effectively controlling periodontal infections. In the present study, we used a three-dimensional (3D) co-culture model of gingival epithelial cells and fibroblasts stimulated with Aggregatibacter actinomycetemcomitans lipopolysaccharide (LPS) to investigate the anti-inflammatory properties of human beta-defensin-3 (hBD-3) and cathelicidin (LL-37) and to determine whether these antimicrobial peptides can act in synergy. The 3D co-culture model composed of gingival fibroblasts embedded in a collagen matrix overlaid with gingival epithelial cells had a synergistic effect with respect to the secretion of IL-6 and IL-8 in response to LPS stimulation compared to fibroblasts and epithelial cells alone. The 3D co-culture model was stimulated with non-cytotoxic concentrations of hBD-3 (10 and 20 µM) and LL-37 (0.1 and 0.2 µM) individually and in combination in the presence of A. actinomycetemcomitans LPS. A multiplex ELISA assay was used to quantify the secretion of 41 different cytokines. hBD-3 and LL-37 acted in synergy to reduce the secretion of GRO-alpha, G-CSF, IP-10, IL-6, and MCP-1, but only had an additive effect on reducing the secretion of IL-8 in response to A. actinomycetemcomitans LPS stimulation. The present study showed that hBD-3 acted in synergy with LL-37 to reduce the secretion of cytokines by an LPS-stimulated 3D model of gingival mucosa. This combination of antimicrobial peptides thus shows promising potential as an adjunctive therapy for treating inflammatory periodontitis.

Serum cyclophilin A concentrations in renal transplant recipients receiving cyclosporine A: clinical implications for gingival overgrowth

OBJECTIVE

The aim of this study was to investigate the clinical factors in relation to the cyclosporine A (CsA) induced gingival overgrowth (GO).

STUDY DESIGN

Seventy-three participants were assigned as GO+ and GO-. Factors including demographic, pharmacological, gingival variables and the serum cyclophilin A (CyPA) concentration were analyzed.

RESULTS

The occurrence of GO was 39.72%. Papillary bleeding index (PBI) had a significantly higher risk of GO than plaque index (PI), the ratio of CsA to CyPA, and serum CyPA concentration (odds ratio = 364.323, 25.791, 1.002, 0.096, respectively). The severity of GO correlated with PI, the ratio of CsA to CyPA, PBI, serum concentrations of CsA and CyPA (r = 0.366, 0.355, 0.344, 0.305, and -0.232, respectively).

CONCLUSIONS

Since a cross-sectional study is not able to explain whether plaque and inflammation are the cause or consequence of GO, the ratio of CsA to CyPA may be a valuable marker for predicting GO.

Identification of 1,8-cineole, borneol, camphor, and thujone as anti-inflammatory compounds in a Salvia officinalis L. infusion using human gingival fibroblasts

Drinking or gargling Salvia officinalis L. infusion (sage infusion) is thought to soothe a sore throat, tonsillitis, and inflamed, red gums, although structure-based scientific evidence for the key anti-inflammatory compounds in sage infusion is scarce. Human gingival fibroblasts (HGF-1) were treated with sage infusion (SI) or SI fractions containing either its volatile components and water (aqueous distillate, AD) or its dry matter (DM) for six hours. SI, AD, and DM reduced a mean phorbol-12-myristate-13-acetate/ionomycin (PMA/I)-stimulated release of the pro-inflammatory interleukins IL-6 and IL-8 by more than 50% (p < 0.05). Cellular uptake experiments and subsequent GC-MS analysis using stable-isotope-labeled internal standards revealed the presence of 1,8-cineole, borneol, camphor, and α-/β-thujone in SI-treated cells; LC-MS analysis demonstrated the presence of rosmarinic acid. A significant, more than 50% mean inhibition of PMA/I-induced IL-6 and IL-8 release was demonstrated for the volatile compounds 1,8-cineole, borneol, camphor, and thujone, but not for the nonvolatile rosmarinic acid when applied in concentrations representative of sage infusion. Therefore, the volatile compounds were found to be more effective than rosmarinic acid. 1,8-Cineole, borneol, camphor, and α-/β-thujone chiefly contribute to the anti-inflammatory activity of sage infusion in human gingival fibroblasts.

The polysaccharide capsule of Campylobacter jejuni modulates the host immune response

Campylobacter jejuni is a major cause of bacterial diarrheal disease worldwide. The organism is characterized by a diversity of polysaccharide structures, including a polysaccharide capsule. Most C. jejuni capsules are known to be decorated nonstoichiometrically with methyl phosphoramidate (MeOPN). The capsule of C. jejuni 81-176 has been shown to be required for serum resistance, but here we show that an encapsulated mutant lacking the MeOPN modification, an mpnC mutant, was equally as sensitive to serum killing as the nonencapsulated mutant. A nonencapsulated mutant, a kpsM mutant, exhibited significantly reduced colonization compared to that of wild-type 81-176 in a mouse intestinal colonization model, and the mpnC mutant showed an intermediate level of colonization. Both mutants were associated with higher levels of interleukin 17 (IL-17) expression from lamina propria CD4(+) cells than from cells from animals infected with 81-176. In addition, reduced levels of Toll-like receptor 4 (TLR4) and TLR2 activation were observed following in vitro stimulation of human reporter cell lines with the kpsM and mpnC mutants compared to those with wild-type 81-176. The data suggest that the capsule polysaccharide of C. jejuni and the MeOPN modification modulate the host immune response.

Effects of resolvin D1 on cell survival and cytokine expression of human gingival fibroblasts

BACKGROUND

Tissue breakdown in periodontitis is initiated by bacteria, such as Porphyromonas gingivalis, and is caused largely by host responses. Resolvins protect the host against acute inflammation by blocking the migration of polymorphonuclear neutrophils to initiate resolution. The effects of resolvins on human gingival fibroblasts (HGFs) are unknown. This study examines the effects of resolvin D1 on HGF survival and cytokine expression when treated with or without P. gingivalis supernatant.

METHODS

Cytotoxicity of resolvin D1 on HGFs with or without a toxic level of P. gingivalis supernatant was measured with lactate dehydrogenase assays. Cytokine arrays were performed on HGF-conditioned media treated with or without resolvin D1 and with or without P. gingivalis supernatant.

RESULTS

Resolvin D1 had no cytotoxic effects on HGFs at concentrations between 1 and 1,000 nM (all P > 0.05). Resolvin D1 (1,000 nM) significantly inhibited the toxic effects of 13.5% (v/v) P. gingivalis supernatant on HGFs (P = 0.002). Resolvin D1 significantly reduced the expression of interleukin (IL)-6 (P = 0.010) and monocyte chemoattractant protein (MCP)-1 (P = 0.04) in untreated fibroblasts. P. gingivalis (10%) supernatant significantly increased the expression levels of granulocyte-macrophage colony-stimulating factor (CSF), granulocyte CSF, growth-regulated oncogene (GRO), IL-5, IL-6, IL-7, IL-8, IL-10, MCP-1, MCP-2, MCP-3, and monokine induced by γ-interferon. Resolvin D1 significantly reduced the expression of GRO (P = 0.04), marginally reduced the levels of MCP-1 (P = 0.10), and marginally increased the levels of transforming growth factor (TGF)-β1 (P = 0.07) from HGFs treated with P. gingivalis supernatant.

CONCLUSIONS

Resolvin D1 altered the cytotoxicity of P. gingivalis supernatant on HGFs. Resolvin D1 significantly reduced GRO, marginally reduced MCP-1, and marginally increased TGF-β1 from P. gingivalis-treated HGFs, which could alter the ability of P. gingivalis to induce inflammation.

Luteolin and fisetin inhibit the effects of lipopolysaccharide obtained from Porphyromonas gingivalis in human gingival fibroblasts

Periodontitis is an inflammatory process of infectious origin that affects the gums and, in severe cases, destroys connective tissue, leading to loss of the dental organ. Gram-negative Porphyromonas gingivalis bacteria are recovered from patients with chronic periodontitis. The polysaccharide obtained from these bacteria induces the expression of interleukin (IL)-1 beta, tumor necrosis factor, and IL-6. Flavonoids are molecules that participate in the control of inflammatory processes. We studied the role of the flavonoids fisetin, luteolin, myricetin, and morin in inhibiting the activation of mitogen-activated protein kinase (MAPK) and AKT as well as their role in lipopolysaccharide (LPS)-induced cyclooxygenase-2 (COX-2) transcription. All four of these flavonoids were found to inhibit MAPK and AKT. Fisetin and luteolin blocked the activation of MAPK and AKT to levels below basal levels. All of these flavonoids also blocked LPS-mediated COX-2 expression.

Interleukin-1β is internalised by viable Aggregatibacter actinomycetemcomitans biofilm and locates to the outer edges of nucleoids

The opportunistic pathogen Aggregatibacter actinomycetemcomitans causes periodontitis, which is a biofilm infection that destroys tooth-supportive tissues. Interleukin (IL)-1β, a central proinflammatory cytokine of periodontitis, is an essential first line cytokine for local inflammation that modulates the cell proliferation and anti-pathogen response of human gingival keratinocytes. Previously, we demonstrated that A. actinomycetemcomitans biofilms bind IL-1β; however, whether this binding is an active process is not known. In this study, we showed for the first time with immuno-electron microscopy that viable bacterial biofilm cells internalised IL-1β when co-cultured with an organotypic mucosa. Decreased biofilm viability hindered the ability of biofilm to sequester IL-1β and caused IL-1β leakage into the culture medium. In some A. actinomycetemcomitans cells, intracellular IL-1β localized to the outer edges of the nucleoids. We identified the DNA-binding protein HU as an IL-1β interacting protein with mass spectroscopy and showed the interaction of recombinant HU and IL-1βin vitro using enzyme-linked immunosorbent assay (ELISA). Close contact with a viable A. actinomycetemcomitans biofilm decreased the proliferation and apoptosis of human gingival keratinocytes as demonstrated using Ki-67 and the terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) staining, respectively. Our results suggest that viable A. actinomycetemcomitans biofilms may disturb the critical first steps of local inflammation in periodontitis by binding and internalising IL-1β. The interaction of IL-1β with conserved HU provides a potential mechanism for shaping bacterial gene expression.

Cranberry proanthocyanidins: natural weapons against periodontal diseases

Cranberry ( Vaccinium macrocarpon ) is known to have a beneficial effect on several aspects of human health. Proanthocyanidins (PACs), the most abundant flavonoids extracted from red cranberry fruits, have been reported to possess antimicrobial, antiadhesion, antioxidant, and anti-inflammatory properties. Recent in vitro studies have shown that cranberry PACs may be potential therapeutic agents for the prevention and management of periodontitis, an inflammatory disease of bacterial origin affecting tooth-supporting tissues. After presenting an overview of cranberry phytochemicals and their potential for human health benefits, this review will focus on the effects of cranberry PACs on connective tissue breakdown and alveolar bone destruction, as well as their potential for controlling periodontal diseases. Possible mechanisms of action of cranberry PACs include the inhibition of (i) bacterial and host-derived proteolytic enzymes, (ii) host inflammatory response, and (iii) osteoclast differentiation and activity. Given that cranberry PACs have shown interesting properties in in vitro studies, clinical trials are warranted to better evaluate the potential of these molecules for controlling periodontal diseases.

Base-metal dental casting alloy biocompatibility assessment using a human-derived three-dimensional oral mucosal model

Nickel-chromium (Ni-Cr) alloys used in fixed prosthodontics have been associated with type IV Ni-induced hypersensitivity. We hypothesised that the full-thickness human-derived oral mucosa model employed for biocompatibility testing of base-metal dental alloys would provide insights into the mechanisms of Ni-induced toxicity. Primary oral keratinocytes and gingival fibroblasts were seeded onto Alloderm™ and maintained until full thickness was achieved prior to Ni-Cr and cobalt-chromium (Co-Cr) alloy disc exposure (2-72 h). Biocompatibility assessment involved histological analyses with cell viability measurements, oxidative stress responses, inflammatory cytokine expression and cellular toxicity analyses. Inductively coupled plasma mass spectrometry analysis determined elemental ion release levels. We detected adverse morphology with significant reductions in cell viability, significant increases in oxidative stress, inflammatory cytokine expression and cellular toxicity for the Ni-Cr alloy-treated oral mucosal models compared with untreated oral mucosal models, and adverse effects were increased for the Ni-Cr alloy that leached the most Ni. Co-Cr demonstrated significantly enhanced biocompatibility compared with Ni-Cr alloy-treated oral mucosal models. The human-derived full-thickness oral mucosal model discriminated between dental alloys and provided insights into the mechanisms of Ni-induced toxicity, highlighting potential clinical relevance.

Paradigm shift in the pharmacological management of periodontal diseases

It is becoming clear that variations in inflammatory response are a major determinant in susceptibility to periodontitis. However, our understanding of the relationship of the causal agents in periodontitis to the pathogenesis is not as clear as we once thought, and thus therapies based on etiopathogenesis are similarly in question. We are entering a new era of therapeutic discovery that may have a major impact on our management of the periodontal diseases. Fundamentally, periodontitis is an irreversible condition and once both soft and hard tissues are lost, the healthy periodontal architecture cannot be completely or predictably rebuilt. The discovery of new families of lipid mediators of resolution of inflammation (the lipoxins) and eicosapentaenoic-acid- and docosahexaenoic-acid-derived chemical mediators (the resolvins and protectins) opens new avenues to designing resolution-targeted therapies to control the unwanted side effects of excessive inflammation. The novel protective and therapeutic actions of pro-resolution lipid mediators following microbial challenge are mediated by regulation of the local and systemic inflammatory response that has a direct impact on the organization of the biofilm (plaque) and suggests a new paradigm in clinical periodontal therapeutics.

The role of Desulfovibrio desulfuricans lipopolysaccharides in modulation of periodontal inflammation through stimulation of human gingival fibroblasts

OBJECTIVE

Periodontitis is a destructive disease which is likely to be the result of the activities of different microbial complexes. Recently, sulphate-reducing bacteria (SRB) have been detected in the oral cavity, and they have been found to be common inhabitants of sites showing periodontal destruction. The aim of study was to evaluate the influence of endotoxins of Desulfovibrio desulfuricans bacteria on human gingival fibroblast HGF-1 line.

METHODS

The immunological response of gingival fibroblasts was evaluated by determination of their IL-6 and IL-8 secretion upon treatment with D. desulfuricans intestinal and type strain LPS, sodium butyrate (NaB) and IL-1beta. The amounts of cytokines were estimated by ELISA immunoassay. The influence of LPS and NaB on fibroblast proliferation was determined using the CyQUANT Cell Proliferation Assay Kit.

RESULTS

No significant growth inhibition of cells exposed to LPS was observed, except for the culture growing in the presence of intestinal strain endotoxin at the highest concentration (100 microg/ml). The secretion of IL-6 and IL-8 by fibroblasts was increased by D. desulfuricans endotoxins. Cells stimulated with proinflammatory cytokine 1L-1beta showed very high levels of both cytokines secretion. The release of IL-6 and IL-8 by cells in response to LPS and 1L-1beta was modulated by butyric acid.

CONCLUSIONS

The observed response of gingival fibroblasts to stimulation by endotoxin suggests that D. desulfuricans can be involved in the pathogenesis of periodontitis. Moreover, butyrate present in the oral cavity seems to have immunoregulatory effect on cytokine production by gingival fibroblasts under physiological conditions and during microbe-induced inflammation.

Relationships between subgingival microbiota and GCF biomarkers in generalized aggressive periodontitis

AIM

To examine relationships between subgingival biofilm composition and levels of gingival crevicular fluid (GCF) cytokines in periodontal health and generalized aggressive periodontitis (GAP).

MATERIALS AND METHODS

Periodontal parameters were measured in 25 periodontally healthy and 31 GAP subjects. Subgingival plaque and GCF samples were obtained from 14 sites from each subject. Forty subgingival taxa were quantified using checkerboard DNA-DNA hybridization and the concentrations of eight GCF cytokines were measured using Luminex. Cluster analysis was used to define sites with similar subgingival microbiotas in each clinical group. Significance of differences in clinical, microbiological and immunological parameters among clusters was determined using the Kruskal-Wallis test.

RESULTS

GAP subjects had statistically significantly higher GCF levels of interleukin-1beta (IL-1beta) (p<0.001), granulocyte-macrophage colony-stimulating factor (GM-CSF) (p<0.01) and IL-1beta/IL-10 ratio (p<0.001) and higher proportions of Red and Orange complex species than periodontally healthy subjects. There were no statistically significant differences in the mean proportion of cytokines among clusters in the periodontally healthy subjects, while the ratio IL-1beta/IL-10 (p<0.05) differed significantly among clusters in the aggressive periodontitis group.

CONCLUSIONS

Different subgingival biofilm profiles are associated with distinct patterns of GCF cytokine expression. Aggressive periodontitis subjects were characterized by a higher IL-1beta/IL-10 ratio than periodontally healthy subjects, suggesting an imbalance between pro- and anti-inflammatory cytokines in aggressive periodontitis.

Involvement of Cot/Tp12 in Bone Loss during Periodontitis

Periodontitis causes resorption of alveolar bone, in which RANKL induces osteoclastogenesis. The binding of lipopolysaccharide to Toll-like receptors causes phosphorylation of Cot/Tp12 to activate the MAPK cascade. Previous in vitro studies showed that Cot/Tp12 was essential for the induction of RANKL expression by lipopolysaccharide. In this study, we examined whether Cot/Tp12 deficiency reduced the progression of alveolar bone loss and osteoclastogenesis during experimental periodontitis. We found that the extent of alveolar bone loss and osteoclastogenesis induced by ligature-induced periodontitis was decreased in Cot/Tp12-deficient mice. In addition, reduction of RANKL expression was observed in periodontal tissues of Cot/Tp12-deficient mice with experimental periodontitis. Furthermore, we found that Cot/Tp12 was involved in the induction of TNF-α mRNA expression in gingiva of mice with experimental periodontitis. Our observations suggested that Cot/Tp12 is essential for the progression of alveolar bone loss and osteoclastogenesis in periodontal tissue during experimental periodontitis mediated through increased RANKL expression.

Chlamydia pneumoniae induces interleukin-6 and interleukin-10 in human gingival fibroblasts

Chlamydia pneumoniae is an obligate intracellular Gram-negative bacterium with a unique biphasic developmental cycle that can cause persistent infections. In humans, Chlamydia causes airway infection and has been implicated in chronic inflammatory diseases, such as asthma and atherosclerosis. In addition, recent studies demonstrated that patients with severe periodontitis can harbor C. pneumoniae, which can increase the risk for a host inflammatory response with weighty clinical sequelae. Previous studies have established that periodontal pathogenic bacteria (i.e. Gram-negative bacteria) can induce the synthesis and release of cytokines and other inflammatory mediators in human gingival fibroblasts. HGF are resident cells of the periodontium that respond to receptor stimulation by producing a variety of substances including cytokines and growth factors. Our results demonstrate that after 48 hr of incubation with viable C. pneumoniae HGF showed a proliferative response, as seen by both colorimetric MTT assay and direct cell count (30% and 35%, respectively). In addition, HGF incubated with viable or UV light-inactivated C. pneumoniae organisms showed an increase in the levels of IL-6 and IL-10, but not IL-4; on the contrary, HGF infected with heat-killed bacteria did not show a significant production of any of the cytokines considered. In conclusion, the present study suggests that C. pneumoniae may modulate the expression of IL-6 and IL-10 by human gingival fibroblasts. Further studies are warranted to clarify the molecular mechanisms of C. pneumoniae in the regulation of cytokine expression by host cells and to elaborate the relevant clinical implications.

Thymosin beta4 is cytoprotective in human gingival fibroblasts

Thymosin beta4 (Tbeta(4)) is a naturally occurring, ubiquitous, non-toxic protein with documented wound-healing, anti-inflammatory, anti-apoptotic, and tissue-repair properties in skin, the ocular surface, and the heart. The ability of Tbeta(4) to demonstrate similar protective properties in cells of the oral cavity was analyzed using an in vitro model of cultured human gingival fibroblasts. Thymosin beta 4 significantly suppressed the secretion of interleukin-8 (IL-8) following stimulation with tumor necrosis factoralpha (TNF-alpha), suggesting that it may suppress the inflammatory response initiated by pro-inflammatory cytokines. By contrast, Tbeta(4) was not effective in protecting fibroblasts from challenge with lipopolysaccharide purified from Porphyromonas gingivalis or Escherichia coli. Thymosin beta 4 was able to protect gingival fibroblasts against the known cytotoxic effects of chlorhexidine digluconate, a mouthrinse containing chlorhexidine digluconate, and carbamide peroxide. Additionally, Tbeta(4) was able to protect gingival fibroblasts from the apoptosis that is induced by stimulation with TNF-alpha or by exposure to chlorhexidine. Because of its multifunctional roles in protecting cells against damage, Tbeta(4) may have significant potential for use as an oral heathcare aid with combined antimicrobial, anti-inflammatory, anti-apoptotic, and cytoprotective properties.

Differential regulation of innate immune response genes in gingival epithelial cells stimulated with Aggregatibacter actinomycetemcomitans

BACKGROUND AND OBJECTIVE

The gingival epithelium provides the first line of defense against colonization by periodontal pathogens, both as a physical barrier and by the production of inducible innate immune mediators such as beta-defensins and pro-inflammatory cytokines. The gram-negative bacterium Aggregatibacter actinomycetemcomitans is implicated in the pathogenesis of localized aggressive periodontitis, although the bacterium is found widely in the healthy population. We hypothesized that gingival epithelial cell-derived innate immune mediators triggered in response to A. actinomycetemcomitans infection may play an important role in increased susceptibility to infection.

MATERIAL AND METHODS

Primary cultures of human gingival epithelial cells were cultured in the presence of A. actinomycetemcomitans. Total mRNA was examined for the presence of innate immune markers using RT-PCR.

RESULTS

We show here that the mRNA levels of human beta-defensin 2 and interleukin-8 are elevated by live cultures of a clinical isolate of A. actinomycetemcomitans in cultured gingival epithelial cells from healthy individuals, but not by A. actinomycetemcomitans lipopolysaccharide. Cells from a patient with localized aggressive periodontitis, however, did not respond to this bacterial stimulation. In contrast, the pro-inflammatory cytokine interleukin-19 was induced in cells from both localized aggressive periodontitis and healthy subjects. Examination of Toll-like receptors and associated adapter molecules indicated lower levels of Toll-like receptor 2 mRNA in the localized aggressive periodontitis patient-derived cells compared with cells from healthy subjects.

CONCLUSION

These results suggest that a differential expression of innate immune response genes to A. actinomycetemcomitans in the gingival epithelium could be an underlying factor of susceptibility to localized aggressive periodontitis.

Neisseria meningitidis type C capsular polysaccharide inhibits lipooligosaccharide-induced cell activation by binding to CD14

Encapsulated Neisseria meningitidis can invade mucosal barriers and cause systemic diseases. Activation of the innate immune system by conserved meningococcal molecules such as lipooligosaccharides (LOS) is essential for the generation of an effective host immune response. Here we show that the type C capsular polysaccharide of N. meningitidis (MCPS) inhibited LOS-induced interleukin-6 and TNF-alpha secretion from monocytes, and blocked the maturation of dendritic cells induced by LOS, while the capsular polysaccharide from group B streptococcus type III and t(4-hydroxy-3-nitrophenyl) acetyl (NP)-Ficoll had no such effect. MCPS also inhibited the LOS-induced NF-kappaB activation and phosphorylation of signalling molecules such as ERK1/2, p38 and Jun N-terminal kinase. In a direct binding assay, MCPS manifested a concentration-dependent binding to recombinant lipoprotein binding protein and CD14, the two members of the LOS receptor complex. In addition, the binding of LOS to CD14 and lipopolysaccharide binding protein was inhibited by MCPS. We established that MCPS binding to CD14 is responsible for the inhibition of LOS-mediated cell activation because MCPS inhibition of LOS was reversed when access amounts of CD14 were added to culture media of HEK293 cells expressing TLR4 and MD-2, and the magnitude of recovery in LOS stimulation correlated with the increase in CD14 concentration. These results suggest a new virulence property of meningococcal capsular polysaccharides.

Nicotine and Lipopolysaccharide Affect Cytokine Expression From Gingival Fibroblasts

BACKGROUND

This in vitro study investigated the influence of nicotine, lipopolysaccharide (LPS), and a combination of both agents on cytokine expression from human gingival fibroblasts (HGFs).

METHODS

HGFs were exposed for 48 hours to 250 microg/ml nicotine, 1 microg/ml Porphyromonas gingivalis LPS, or both. The expression of multiple cytokines was detected in the HGFs conditioned media using cytokine protein arrays.

RESULTS

The untreated HGFs expressed several cytokines, which included relatively high levels of interleukin (IL)-6, IL-8, and monocyte chemoattractant protein-1 (MCP-1). They also expressed low levels of growth-regulated oncogene (GRO), IL-3, and IL-10. Nicotine had the greatest effect on the expression of GRO-alpha, IL-7, IL-10, and IL-15 compared to the untreated control. P. gingivalis LPS had the greatest effect on the expression of GRO-alpha; IL-7; IL-10; and RANTES (regulated on activation, normal T-cell expressed, and presumably secreted) compared to the untreated control. The combination of both agents had the biggest impact on the expression of GRO-alpha, IL-7, IL-10, IL-15, RANTES, and interferon-gamma (IFN-gamma) compared to the untreated control.

CONCLUSION

HGFs exposed to nicotine, P. gingivalis LPS, or a combination of both agents increased the expression of multiple cytokines.

Muscarinic cholinoceptor activation modulates DNA synthesis and CD40 expression in fibroblast cells

1 The aim of the present work was to examine the role of muscarinic acetylcholine receptors (mAChR) on DNA synthesis and CD40 expression in human fibroblast cells. Neonatal human skin fibroblast cultures were stimulated with carbachol in presence or absence of specific antagonists and the following parameters were measured: identification of mAChR subtypes, DNA synthesis, inositol phosphates (InsP) production and CD40 expression. 2 Human fibroblasts express mAChR with Kd 0.47 +/- 0.11 nm and Bmax 236 +/- 22 fmol mg protein(-1). Carbachol stimulates DNA synthesis, InsP and the expression of CD40. All these effects were inhibited by atropine, mustard hydrochloride (4-DAMP) and pirenzepine but not by AF-DX 116 and tropicamide, indicating that M3 and M1 mAChR are implicated in carbachol action. The relative Ki of the antagonists obtained by competition binding assay was in parallel to the relative potency for blocking both carbachol-stimulated InsP accumulation and DNA synthesis. 3 The intracellular pathway leading to carbachol-induced biological effects involved phospholipase C and calcium/calmodulin, as U-73122 and trifluoroperazine blocked carbachol effects, respectively. Calphostin C, a protein kinase C inhibitor, had no effect, indicating that this enzyme does not participate in the system. 4 These results may contribute to a better understanding of the modulatory role of the parasympathetic muscarinic system on normal human fibroblast function.

Increased transglutaminase activity was associated with IL-6 release in cultured human gingival fibroblasts exposed to dental cast alloys

Molecular mechanisms underlying gingival and periodontal inflammation caused by dental alloys are still poorly understood. Recently, it has been demonstrated that tissue transglutaminase can be involved in inflammatory cell response. The aim of this study was to evaluate effects of exposure to orthodontic materials on transglutaminase in cultured human gingival fibroblasts. The incubation with Ni-Ti heat-activated (T3) or Ni-Ti super-elastic (T4), and with Ni-Cr-Co (T2) alloys produced respectively 2.5-fold and 8-fold increases in IL-6 release compared with control cultures. Transglutaminase activity was significantly increased in cells exposed to T3 and T4 alloys (about 170% of control; p < 0.05), where it was mainly localized close to inner part of cell membrane. The exposure to T3 and T4 specimens significantly up-regulated also tTG expression compared with control cultures. These data first show an association between IL-6 release and tissue transglutaminase increases, suggesting that TGase-mediated reactions may play a major role in periodontal inflammation.

Toxic effect of nickel in an in vitro model of human oral epithelium

Nickel is a metal widely employed in dental alloys, and due to peculiar properties of certain nickel-based materials, it cannot be substituted with other metals in some applications. The release of nickel ions from dental alloys placed into long-term contact with mouth soft tissues is alarming because of the toxic, immunological and carcinogenic effects which have been well documented for some nickel compounds. Our study was focussed on the toxic effects induced "in vitro" on human oral epithelium by the exposure to low concentrations of nickel chloride. In view of this, we adopted a three-dimensional model of epithelial cultures, reconstituted from TR 146 cells, resembling the physiological environment of the oral cavity and useful for biocompatibility testing. The effects on cell viability, apoptosis, cellular content of reduced and oxidized glutathione (GSH and GSSG) and release of prostaglandin E(2) (PGE(2)), interleukin-8 (IL-8) and interleukin-6 (IL-6) were investigated following topical application of a NiCl(2) solution ranging from 7.6mM to 0.05 mM for 72 h. Our findings show that nickel concentrations, which do not significantly modify cell viability and inflammation mediator release, can affect the redox equilibrium and stimulate apoptosis in oral epithelium cells. Further studies are needed to demonstrate the hypothesis that the oxidative imbalance induced by nickel might be implicated in the induction of apoptosis.

Cytokine responses of human gingival fibroblasts to Actinobacillus actinomycetemcomitans cytolethal distending toxin

Actinobacillus actinomycetemcomitans is implicated in the pathogenesis of localized aggressive periodontitis, and has the capacity to express a cytolethal distending toxin (Cdt). Gingival fibroblasts (GF) are resident cells of the periodontium, which can express several osteolytic cytokines. The aims of this study were a) to investigate the role of Cdt in A. actinomycetemcomitans-induced expression of osteolytic cytokines and their cognate receptors in GF and b) to determine if the previously demonstrated induction of receptor activator of NFkappaB ligand (RANKL) by A. actinomycetemcomitans is mediated by these pro-inflammatory cytokines or by prostaglandin E(2) (PGE(2)). A. actinomycetemcomitans clearly induced interleukin (IL)-6, IL-1beta, and to a minimal extent, tumor necrosis factor (TNF)-alpha mRNA expression. At the protein level, IL-6 but not IL-1beta or TNF-alpha expression was stimulated. The mRNA expression of the different receptor subtypes recognizing IL-6, IL-1beta and TNF-alpha was not affected. A cdt-knockout strain of A. actinomycetemcomitans had similar effects on cytokine and cytokine receptor mRNA expression, compared to its parental wild-type strain. Purified Cdt stimulated IL-6, but not IL-1beta or TNF-alpha protein biosynthesis. Antibodies neutralizing IL-6, IL-1 or TNF-alpha, and the PGE(2) synthesis inhibitor indomethacin, did not affect A. actinomycetemcomitans-induced RANKL expression. In conclusion, a) A. actinomycetemcomitans induces IL-6 production in GF by a mechanism largely independent of its Cdt and b) A. actinomycetemcomitans-induced RANKL expression in GF occurs independently of IL-1, IL-6, TNF-alpha, or PGE(2).

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.

Interleukin-1beta induces matrix metalloproteinase-1 expression in cultured human gingival fibroblasts: role of cyclooxygenase-2 and prostaglandin E2

OBJECTIVE

Matrix metalloproteinases (MMPs) degrade extracellular matrices and are responsible for excessive connective tissue breakdown in inflammatory disorders. We investigated the mechanism of MMP-1 expression in human gingival fibroblasts in response to the stimulation with interleukin-1beta (IL-1beta), and the role of inducible-type cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2) in the regulation of MMP-1 expression.

MATERIALS AND METHODS

We stimulated cultured human gingival fibroblasts with r(h)IL-1beta, and examined the expression of MMP-1 mRNA and protein by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. The effect of indomethacin, dexamethasone, or cycloheximide (CHX) on the IL-1beta-induced expression of MMP-1 was examined. The expression of MMP-1 in gingival fibroblasts stimulated with PGE2 was also examined.

RESULTS

IL-1beta stimulated the expressions of mRNA and protein for MMP-1, in cultured fibroblasts, in time- and concentration-dependent manners. Pretreatment of the cells with indomethacin or dexamethasone inhibited the IL-1beta-induced MMP-1 expression. CHX, a protein synthesis inhibitor, also suppressed the MMP-1 expression. IL-1beta also induced COX-2 expression in gingival fibroblasts, and PGE2, a major COX-2 product, was found to enhance MMP-1 expression.

CONCLUSION

The IL-1beta-induced MMP-1 expression in gingival fibroblasts may be mediated, at least in part, by COX-2 and its product PGE2.

Outer membrane protein 100, a versatile virulence factor of Actinobacillus actinomycetemcomitans

Actinobacillus actinomycetemcomitans (Aa) is one of the pathogenic bacteria involved in periodontal diseases. We have previously identified six major outer membrane proteins (Omps) of Aa Y4. Among them is an Omp with high molecular mass, designated Omp100, which has homology to a variety of virulence factors. Electron microscopic observation indicated that Omp100 is randomly localized on the cell surface of Aa. Aa Y4 has been shown to adhere and invade KB or normal human gingival keratinocytes. Anti-Omp100 antibody inhibited 50% of adhesion and 70% of invasion of Aa Y4 to KB cells. An Omp100 knock-out mutant had a decreased adhesion and invasion efficiency of 60%, compared with that of the wild type. Escherichia coli HB101 expressing Omp100 adhered twofold and invaded 10-fold more than the wild-type E. coli HB101. HB101 expressing Omp100 showed resistance to serum by trapping factor H, an inhibitor for C3b, with Omp100. Omp100 induced inflammatory cytokine responses of interleukin (IL)-8, IL-6 and tumour necrosis factor (TNF)alpha in epithelial cells, and induced IL-1beta and TNFalpha production in mouse macrophages. These results indicate that Omp100 is a versatile virulence factor that may demonstrate potential significance in the onset of periodontal diseases related to Aa.

Capsular polysaccharide from Actinobacillus actinomycetemcomitans inhibits IL-6 and IL-8 production in human gingival fibroblast

We previously reported that a capsular polysaccharide (CP) from Actinobacillus actinomycetemcomitans Y4 induces bone resorption in a mouse organ culture system and osteoclast formation in mouse bone marrow cultures. However, the effects of A. actinomycetemcomitans Y4 CP on human gingival fibroblasts (HGF) are still unclear. The present study was undertaken to test the hypothesis that A. actinomycetemcomitans Y4 CP alters the production of inflammatory cytokines, such as interleukin-6 (IL-6) and IL-8 by HGF. When HGF were cultured with various concentrations of Y4 CP for 24 h, IL-6 and IL-8 production decreased in a concentration-dependent manner. Y4 CP (100 microg/ml) suppressed the release of IL-6 from 9.09 +/- 0.08 ng/ml to 0.34 +/- 0.21 ng/ml (P < 0.01) and IL-8 production decreased from 3.76 +/- 0.03 ng/ml to 0.09 +/- 0.01 ng/ml (P < 0.01). Y4 CP suppressed 70-80% of the release of IL-6 and IL-8 from HGF stimulated with Y4 lipopolysaccharide (LPS), too. Interestingly, anti-A. actinomycetemcomitans Y4 CP completely inhibited the effect of A. actinomycetemcomitans Y4 CP on IL-6 and IL-8 production from HGF. These results indicate that Y4 CP inhibits the release of IL-6 and IL-8 from HGF, suggesting that A. actinomycetemcomitans Y4 modulates the inflammatory response in periodontitis. Remarkably, this inhibitory effect was reversed by specific anti-A. actinomycetemcomitans Y4 CP suggesting an important relationship between the organism and the humoral host response.

Campylobacter surface-layers (S-layers) and immune evasion

Many pathogenic bacteria have evolved mechanisms for evading host immune systems. One evasion mechanism is manifest by the surface layer (S-layer), a paracrystalline protein structure composed of S-layer proteins (SLPs). The S-layer, possessed by 2 Campylobacter species (C. fetus and C. rectus), is external to the bacterial outer membrane and can have multiple functions in immune avoidance. C. fetus is a pathogen of ungulates and immunocompromised humans, in whom it causes disseminated bloodstream disease. In C. fetus, the S-layer is required for dissemination and is involved in 2 mechanisms of evasion. First, the S-layer confers resistance to complement-mediated killing in non-immune serum by preventing the binding of complement factor C3b to the C. fetus cell surface. S-layer expressing C. fetus strains remain susceptible to complement-independent killing, utilizing opsonic antibodies directed against the S-layer. However, C. fetus has also evolved a mechanism for avoiding antibody-mediated killing by high-frequency antigenic variation of SLPs. Antigenic variation is accomplished by complex DNA inversion events involving a family of multiple SLP-encoding genes and a single SLP promoter. Inversion events result in the expression of antigenically variant S-layers, which require distinct antibody responses for killing. C. rectus is implicated in the pathogenesis of periodontal disease and also possesses an S-layer that appears to be involved in evading the human system. Although studied less extensively than its C. fetus counterpart, the C. rectus S-layer appears to confer resistance to complement-mediated killing and to cause the down-regulation of proinflammatory cytokines.

LPS-stimulated human gingival fibroblasts inhibit the differentiation of monocytes into osteoclasts through the production of osteoprotegerin

Periodontitis is an inflammatory bone disease caused by Gram-negative anaerobic bacteria, but the precise mechanism of bone destruction remains unknown. Activated T lymphocytes secrete receptor activator of NF-kappaB ligand (RANKL) and support the differentiation of monocytes into mature osteoclasts. The purpose of this study was to examine the expression of RANKL and its inhibitor, osteoprotegerin (OPG), in inflamed gingival tissue and to clarify the role of human gingival fibroblasts (HGFs) in osteoclastogenesis regulated by RANKL. HGFs and gingival mononuclear cells (GMCs) were obtained from chronic periodontitis patients during routine periodontal surgery. Expression of OPG and RANKL mRNA in gingival tissue and HGFs was examined with RT-PCR. OPG production was measured using ELISA. Expression of RANKL, CD4, CD8 and CD69 on GMCs was determined by flow-cytometry using RANK-Fc fusion protein and the respective monoclonal antibodies. Osteoclastogenesis by RANKL was assayed by counting the number of tartarate-resistant acid phosphatase (TRAP)-positive cells after culturing human peripheral blood monocytes with recombinant human RANKL and macrophage-colony stimulating factor (M-CSF) for 10 days. OPG and RANKL mRNA were expressed in 80% (16/20) and 25% (5/20) of periodontitis lesions, respectively. OPG, but not RANKL, mRNA was expressed within HGFs. OPG mRNA expression and production by HGFs was augmented by LPS stimulation. All GMC samples expressed CD69, and two of five GMC samples expressed RANKL. The culture supernatant of LPS-stimulated gingival fibroblasts significantly reduced the number of TRAP positive cells generated by culturing monocytes with RANKL and M-CSF. The present study suggests that LPS-stimulated HGFs inhibit monocyte differentiation into osteoclasts through the production of OPG.

Inhibited proliferation of human periodontal ligament cells and gingival fibroblasts by Actinobacillus actinomycetemcomitans: involvement of the cytolethal distending toxin

Actinobacillus actinomycetemcomitans can inhibit fibroblast proliferation. The objective of this study was to characterize the early proliferative responses of human periodontal ligament cells (PDLC) and gingival fibroblasts (GF) to A. actinomycetemcomitans components and to investigate the possible involvement of the cytolethal distending toxin (cdt) produced by this bacterium. The PDLC and GF were challenged with surface components of A. actinomycetemcomitans. Both DNA and protein synthesis as well as cell lysis or apoptosis were assayed for a 6-h period after addition of the bacterial extract. Unlike the controls, inhibition of DNA synthesis had already occurred in the challenged cells at the end of the initial 3- to 6-h period. No lysis or apoptosis was detected, and the total protein synthesis remained unaffected. The persistence of the effect on cell growth was confirmed after a 72-h period of challenge, during which the cells remained viable but exhibited an elongated and distended cell body. No significant differences were observed between PDLC and GF. When a cdt-knockout strain of A. actinomycetemcomitans was used almost no inhibitory effect on cell proliferation was observed. It was concluded that A. actinomycetemcomitans causes a non-lethal inhibition of proliferation in PDLC and GF as a result of an early arrest of DNA synthesis. Cytolethal distending toxin is responsible for most of this effect. This bacterial property may compromise tissue homeostasis in the periodontium.

Interaction of blood components with heparin-immobilized polyurethanes prepared by plasma glow discharge

The blood compatibility of poly(ethylene oxide) (PEO)-grafted and heparin (Hep) immobilized polyurethanes was investigated using in vitro plasma recalcification time (PRT), activated partial thromboplastin time (APTT), platelet adhesion and activation, and peripheral blood mononuclear cell (PBMC) adhesion and activation. In the experiment with plasma proteins, the PRT of the polyurethane (PU) surface was prolonged by PEO grafting and further prolonged by heparin immobilization. The APTT was prolonged on PU-Hep, suggesting the binding of immobilized heparin to antithrombin III. The percentage of platelet adhesion on PU was not much different from that on acrylic acid- and PEO-grafted PUs (PU-C, PU-6, PU-33), yet was substantially decreased by heparin immobilization (PU-6-Hep, PU-33-Hep). The release of serotonin from adhering platelets was slightly suppressed on PEO-grafted PUs yet significantly suppressed on heparin-immobilized PUs. In the PBMC experiments, the adhesion and activation of the cells were significantly suppressed on heparin-immobilized PUs, and the amount of interleukin-6 (IL-6) released from PBMCs stimulated with surface-modified PUs decreased with a decrease in PBMC adhesion.

Biological characterization of lipopolysaccharide from Treponema pectinovorum

This study investigated the endotoxic and biological properties of purified lipopolysaccharide (LPS) isolated from an oral spirochete, Treponema pectinovorum. Endotoxicity, measured by Limulus amoebocyte lysate kinetic assay, showed that the LPS contained 1.28 endotoxin units per microg of purified LPS, which was approximately 4,000 times less than Escherichia coli O55:B5 LPS. To determine in vivo endotoxicity, LPS responder mice were administered LPS following galactosamine (GalN) sensitization. The LPS induced neither endotoxic symptoms nor lethality for 96 h, suggesting negligible or very low endotoxicity. In contrast, infection with live T. pectinovorum induced 100% lethality within 12 h in GalN-sensitized LPS responder mice, indicating an endotoxin-like property of this treponeme. Heat-killed microorganisms exhibited no lethality in GalN-sensitized mice, suggesting that the endotoxicity was associated with heat-labile components. To determine cytokine and chemokine induction by LPS, human gingival fibroblasts were stimulated and secretion of interleukin 1beta (IL-1beta), granulocyte-macrophage colony-stimulating factor, gamma interferon, IL-6, IL-8, and monocyte chemoattractant protein 1 (MCP-1) was assessed. The purified LPS induced significant amounts of only IL-6, IL-8, and MCP-1, although they were substantially lower than levels after challenge with live T. pectinovorum. After injection of LPS or live or heat-killed T. pectinovorum, serum was collected from mice and analyzed for proinflammatory cytokines IL-1beta, tumor necrosis factor alpha (TNF-alpha), and IL-6. LPS induced only IL-6 consistently. Both live and heat-killed T. pectinovorum induced serum IL-6, which was higher than the level detected following LPS administration. Importantly, live bacteria elicited systemic TNF-alpha and IL-1beta levels similar to those induced by a lethal dose of live E. coli O111. The results indicated that T. pectinovorum LPS has very low or no endotoxicity, although it can elicit low levels of cytokines from host cells. In contrast to the LPS, live T. pectinovorum demonstrated in vivo toxicity, which was associated with serum IL-1beta, TNF-alpha, and IL-6, suggesting an endotoxin-like property of a heat-labile molecule(s) of the spirochete.