Production of inflammatory cytokines by human gingival fibroblasts stimulated by cell-surface preparations of Porphyromonas gingivalis

Photobiomodulation of oral fibroblasts stimulated with periodontal pathogens

Photobiomodulation (PBM) utilises light energy to treat oral disease, periodontitis. However, there remains inconsistency in the reporting of treatment parameters and a lack of knowledge as to how PBM elicits its molecular effects in vitro. Therefore, this study aimed to establish the potential immunomodulatory effects of blue and near infra-red light irradiation on gingival fibroblasts (GFs), a key cell involved in the pathogenesis of periodontitis. GFs were seeded in 96-well plates in media + / - Escherichia coli lipopolysaccharide (LPS 1 μg/ml), or heat-killed Fusobacterium nucleatum (F. nucleatum, 100:1MOI) or Porphyromonas gingivalis (P. gingivalis, 500:1MOI). Cultures were incubated overnight and subsequently irradiated using a bespoke radiometrically calibrated LED array (400-830 nm, irradiance: 24 mW/cm² dose: 5.76 J/cm²). Effects of PBM on mitochondrial activity (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and adenosine triphosphate (ATP) assays, total reactive oxygen species production (ROS assay) and pro-inflammatory/cytokine response (interleukin-8 (IL-8) and tumour growth factor-β1 (TGFβ1)) were assessed 24 h post-irradiation. Data were analysed using one-way ANOVA followed by the Tukey test. Irradiation of untreated (no inflammatory stimulus) cultures at 400 nm induced 15%, 27% and 13% increases in MTT, ROS and IL-8 levels, respectively (p < 0.05). Exposure with 450 nm light following application of P. gingivalis, F. nucleatum or LPS induced significant decreases in TGFβ1 secretion relative to their bacterially stimulated controls (p < 0.001). Following stimulation with P. gingivalis, 400 nm irradiation induced 14% increases in MTT, respectively, relative to bacteria-stimulated controls (p < 0.05). These findings could identify important irradiation parameters to enable management of the hyper-inflammatory response characteristic of periodontitis.

Effect of epigallocatechin-3-gallate on tumor necrosis factor-alpha production by human gingival fibroblasts stimulated with bacterial lipopolysaccharide: An in vitro study

Background:

Evidence shows that epigallocatechin-3-gallate (EGCG) in green tea has anti-inflammatory effects.

Aim:

This study assessed the effect of EGCG on the production of tumor necrosis factor-alpha (TNF-α) as an inflammatory cytokine in periodontitis, which produced by human gingival fibroblasts (HGFs) stimulated with lipopolysaccharide (LPS) of Porphyromonas gingivalis.

Materials and Methods:

In this study, HGFs were cultured and subjected to LPS and EGCG. Cell viability of different concentrations of EGCG (10, 25, 50, 75, and 100 μM) and LPS (1, 10, 20, and 50 μg/mL) was assessed using methyl-thiazole-tetrazolium (MTT) assay. Then, the best concentrations of EGCG and P. gingivalis LPS were used simultaneously and separately to assess the production of TNF-α by HGFs using the enzyme-linked immunosorbent assay (ELISA). Assessments were done at 1, 3, and 5 days. Data were read using the ELISA reader and analyzed by the SPSS through two-way ANOVA.

Results:

LPS at 1, 10, and 20 and EGCG at 10.25 and 50 μM showed the least cytotoxicity in MTT assay. ELISA showed EGCG alone decreased the production of TNF-α in all days, except 10 μM on day 1. 1, 10, and 20 μg/mL LPS increased the output of TNF-α on days 1 and 3 while reducing it on day 5. The combination of EGCG and LPS showed a decrease of TNF-α in all days except on day 5 that revealed an increase in the production of TNF-α at 25 and 50 μM EGCG.

Conclusion:

In the combination use of EGCG and LPS, EGCG shows anti-inflammatory effects by decreasing the production of TNF-α by HGFs stimulated with P. gingivalis.

Hyperresponsiveness of human gingival fibroblasts from patients with aggressive periodontitis against bacterial lipopolysaccharide

The present study aimed to investigate whether gingival fibroblasts (GFs) of patients with aggressive periodontitis (AgP) are more sensitive to lipopolysaccharide (LPS) stimulation than GFs of control subjects. AgP causes rapid periodontal destruction, including the production of cytokines [i.e. interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α] and matrix metalloproteinases (MMP)-1, -3 and -9 in AgP GFs. LPS upregulates IL-1β, IL-6, TNF-α, MMP-1, MMP-3, MMP-9 and mitochondrial reactive oxygen species (mtROS). Fibroblasts are known to be associated with immune responses to bacterial virulence factors, but the precise mechanisms underlying this severe periodontal disease are unclear. In the present study, primary human GFs of four patients with AgP and four healthy subjects were challenged in vitro with LPS from Porphyromonas gingivalis (P. gingivalis). The generation of mtROS in GFs was assessed using MitoSOX Red. The expression of genes encoding inflammatory cytokines and MMPs in GFs was analyzed using reverse transcription-quantitative polymerase chain reaction, and the expression of proteins was analyzed using ELISA and Western blotting. Human GFs of patients with AgP exhibited higher levels of mtROS, and higher mRNA and protein expression levels of proinflammatory cytokines, including IL-1β, IL-6, MMP-1, MMP-3 and MMP-9 compared with healthy human GFs following stimulation with LPS from P. gingivalis. In the present study, it was demonstrated that GFs of patients with AgP display hyperreactivity when challenged with LPS.

Activation of Gingival Fibroblasts by Bacterial Cyclic Dinucleotides and Lipopolysaccharide

Human gingival fibroblasts (HGFs) recognize microbe-associated molecular patterns (MAMPs) and respond with inflammatory proteins. Simultaneous impacts of bacterial cyclic di-guanosine monophosphate (c-di-GMP), cyclic di-adenosine monophosphate (c-di-AMP), and lipopolysaccharide (LPS) on gingival keratinocytes have been previously demonstrated, but the effects of these MAMPs on other periodontal cell types, such as gingival fibroblasts, remain to be clarified. The present aim was to examine the independent and combined effects of these cyclic dinucleotides and LPS on interleukin (IL) and matrix metalloproteinase (MMP) response of HGFs. The cells were incubated with c-di-GMP and c-di-AMP, either in the presence or absence of Porphyromonas gingivalis LPS, for 2 h and 24 h. The levels of IL-8, -10, and -34, and MMP-1, -2, and -3 secreted were measured by the Luminex technique. LPS alone or together with cyclic dinucleotides elevated IL-8 levels. IL-10 levels were significantly increased in the presence of c-di-GMP and LPS after 2 h but disappeared after 24 h of incubation. Concurrent treatment of c-di-AMP and LPS elevated MMP-1 levels, whereas c-di-GMP with LPS suppressed MMP-2 levels but increased MMP-3 levels. To conclude, we produce evidence that cyclic dinucleotides interact with LPS-mediated early response of gingival fibroblasts, while late cellular response is mainly regulated by LPS.

Adipokines and periodontal markers as risk indicators of early rheumatoid arthritis: a cross-sectional study

OBJECTIVE

To establish the association between adipokine levels and markers of periodontal involvement as risk indicators of early stages of RA (eRA) and the interaction between the presence of markers of periodontal disease with adipokine in eRA individuals.

MATERIALS AND METHODS

Fifty-one patients with a diagnosis of eRA and 51 healthy controls matched for age and sex were studied. Clinical joint condition, clinical and serological markers of disease activity, serum adipokine levels (leptin, adiponectin, resistin, adipsin, vaspin, and IL-6), periodontal diagnosis, presence of Porphyromonas gingivalis, and related IgG1 and IgG2 antibodies were evaluated. Comparisons were made between eRA and healthy controls for periodontal indicators and adipokines. A subgroup analysis was realized with a non-conditional logistic regression to establish the association between the levels of leptin in individuals with eRA and controls according to the periodontal condition, presence of P. gingivalis, or high titers of IgG antibodies against P. gingivalis.

RESULTS

The condition of overweight or obesity is associated with the diagnosis of eRA (p = 0.05), and these individuals also have higher levels of leptin (p = 0.001) and vaspin (p = 0.007). Higher frequency of P. gingivalis (p = 0.001) was found in the eRa group. Individuals with eRA with higher IgG2 titers against P. gingivalis had higher levels of leptin (OR: 1.66 (CI 95% 1.01-2.73)); however, individuals with periodontitis or P. gingivalis with eRA were associated with highest levels of leptin (OR: 1.86, CI 95% 1.19-24.3; and OR: 2.04, CI 95% 1.37-3 respectively).

CONCLUSIONS

eRA individuals have high levels of leptin and vaspin. However, the presence of periodontitis and related-periodontal disease markers showed an effect only in leptin levels in eRA individuals.

CLINICAL RELEVANCE

Emphasizing in personalized medicine, monitoring serum leptin levels and periodontitis markers can improve the early diagnosis of RA.

Antioxidant Activity of Compounds Isolated from Elaeagnus umbellata Promotes Human Gingival Fibroblast Well-Being

Four new triterpenoid bidesmosidic saponins (1-4) and a sesquiterpenoid glucoside (5), together with nine known phenolic compounds (6-14), were isolated from the fruits of Elaeagnus umbellata. Their structures were elucidated using 1D and 2D NMR spectroscopy and mass spectrometry data. The antioxidant capability of the isolated compounds was evaluated in human gingival fibroblasts. Compound 6 decreased ROS production and promoted cell proliferation. It also counteracted the cell cycle blockade induced by a low concentration of H2O2 decreasing the expression of p21 and CDKN2A (p16INK4A). Compound 6 decreased the expression of inflammatory cytokines (IL-6 and IL-8) in response to inflammatory stimuli, supporting its possible use in periodontitis lesions.

Cigarette Smoking Aggravates the Activity of Periodontal Disease by Disrupting Redox Homeostasis- An Observational Study

The aim of this study was to evaluate the associations between cigarette use and five salivary oxidative stress biomarkers, copper-zinc superoxide dismutase (Cu/Zn SOD), manganese superoxide dismutase (MnSOD), catalase, thioredoxin-1 (TRX1), and peroxiredoxin-2 (PRX2), to assess the effectiveness of non-surgical periodontal therapy.

MATERIALS AND METHODS

This is an observational study,167 patients diagnosed with periodontitis were recruited. Both saliva samples and clinical measurements (plaque index (PI), bleeding on probing (BOP), and pocket depth (PD)) were taken at baseline and after completing non-surgical periodontal therapy. The Levels of salivary biomarkers were determined using a MILLIPLEX® MAP Human Oxidative Stress Magnetic Bead Panel kit. The overall reductions in PI and BOP were 31.56% and 42.16%, respectively. BOP reduction after treatment in female or male non-smokers was significantly higher than in male former smokers (p < 0.05). After completing non-surgical periodontal therapy, Cu/ZnSOD, MnSOD, catalase, and Prx2 significantly decreased. There was a significant interaction between smoking status and ΔCu/ZnSOD on PI and a significant interaction between smoking status and ΔCatalase on BOP.

CONCLUSIONS

Cigarette smoking interferes with redox homeostasis in the body, alters antioxidants levels, and influences the periodontal disease activity.

Antibacterial and Anti-inflammatory Potential of Morus alba Stem Extract

Background:

Periodontitis, a chronic inflammatory disease, is the leading cause of tooth loss in adults. Evidence for the anti inflammatory activity of M. alba Stem Extract (MSE) in periodontal disease is limited.

Objective:

The study aimed to investigate the inhibitory effect of MSE on the growth of periodontopathic bacteria and expression of interleukin (IL)-6 and IL-8 in Porphyromonas gingivalis Lipopolysaccharide (LPS)-stimulated human Periodontal Ligament (hPDL) fibroblasts.

Methods:

The antimicrobial activities of MSE were tested against P. gingivalis and Aggregatibacter actinomycetemcomitans by the disk diffusion, the minimum inhibitory concentration and the minimal bactericidal concentration methods. Cytotoxicity of P. gingivalis LPS and MSE on hPDL fibroblasts was determined by MTS assay. The expression of cytokines (IL-6 and IL-8) mRNA and proteins in hPDL fibroblasts was measured using the reverse transcription-qPCR and enzyme-linked immunosorbent assay, respectively.

Results:

MSE exhibited antibacterial activities against P. gingivalis and A. actinomycetemcomitans with the zones of inhibition of 10.00 ± 0.33 mm and 17.33 ± 0.58 mm, respectively. MIC and MBC values for MSE against P. gingivalis were 62.5 μg/ml. The MIC and MBC values against A. actinomycetemcomitans were 250 μg/mL and 500 μg/ml, respectively. P. gingivalis LPS was shown to mediate the expression of pro-inflammatory cytokines in hPDL fibroblasts. However, treatment with MSE concentrations of 2.5 and 5.0 μg/ml significantly suppressed P. gingivalis LPS-induced IL-6 and IL-8 mRNA and protein expression (p< 0.05).

Conclusion:

The present study demonstrates that MSE has antibacterial activity against two putative periodontal pathogens. MSE suppressed IL-6 and IL-8 expression in P. gingivalis LPS-stimulated hPDL fibroblasts, indicating a possible anti-inflammatory effect. Thus, it is a potential adjunctive agent for the treatment of periodontitis.

Pro-inflammatory Cytokines Up-regulate MUC1 Gene Expression in Oral Epithelial Cells

The membrane-bound mucin MUC1 is expressed ubiquitously on epithelial surfaces and is thought to provide protection from bacterial and chemical injury. The present study was undertaken to determine whether MUC1 was expressed in cultured oral epithelial cells and whether expression is modulated by pro-inflammatory mediators released as part of the host response to infection by oral pathogens. Northern and Western blotting experiments showed that KB cells express MUC1 mRNA and protein. When cells were treated with interleukins (IL-1β, IL-6), tumor necrosis factor-alpha (TNF-α), or interferon-gamma (IFN-γ), or combinations of these, real-time PCR demonstrated that MUC1 mRNA increased 1.4- to 3.2-fold. Interestingly, a significant increase in levels of MUC1 protein was also observed. While no effect was observed when KB cells were incubated with LPS from Porphyromonas gingivalis, infection of KB monolayers with this oral pathogen caused a 2.85-fold increase in MUC1 transcript levels. These results suggest that increased MUC1 synthesis may be a key element in the host response to infection with oral pathogens.

Pro-atherogenic properties of lipopolysaccharide from the periodontal pathogen Actinobacillus actinomycetemcomitans

An association between cardiovascular and periodontal disease may be due to lipopolysaccharide (LPS)-promoted release of inflammatory mediators, adverse alterations of the lipoprotein profile, and an imbalance in cholesterol homeostasis. Since periodontopathogenic potential differs between serotypes of a major periodontal pathogen, Actinobacillus actinomycetemcomitans, we studied the pro-atherogenic properties of LPS preparations from serotypes b and d strains on macrophages (RAW 264.7). A. actinomycetemcomitans LPS preparations induced a time-dependent release of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). LPS induced foam cell formation and cholesteryl ester accumulation from native low density lipoprotein in the following order: A. actinomycetemcomitans strains JP2 (serotype b) > Y4 (serotype b) > IDH781 (serotype d). mRNA expression levels of scavenger receptor class B, type-I, and ATP-binding cassette transporter-1, receptors mediating cholesterol efflux from macrophages, were decreased by LPS preparations. The results suggest that the pro-atherogenic potential of A. actinomycetemcomitans LPS may depend on the infecting strain and correlate with the periodontopathogenic potential of the pathogen.

Wild Bitter Melon Leaf Extract Inhibits Porphyromonas gingivalis-Induced Inflammation: Identification of Active Compounds through Bioassay-Guided Isolation

Porphyromonas gingivalis has been identified as one of the major periodontal pathogens. Activity-directed fractionation and purification processes were employed to identify the anti-inflammatory active compounds using heat-killed P. gingivalis-stimulated human monocytic THP-1 cells in vitro. Five major fractions were collected from the ethanol/ethyl acetate extract of wild bitter melon (Momordica charantia Linn. var. abbreviata Ser.) leaves and evaluated for their anti-inflammatory activity against P. gingivalis. Among the test fractions, Fraction 5 effectively decreased heat-killed P. gingivalis-induced interleukin (IL)-8 and was subjected to separation and purification by using chromatographic techniques. Two cucurbitane triterpenoids were isolated from the active fraction and identified as 5β,19-epoxycucurbita-6,23-diene-3β,19,25-triol (1) and 3β,7β,25-trihydroxycucurbita-5,23-dien-19-al (2) by comparing spectral data. Treatments of both compounds in vitro potently suppressed P. gingivalis-induced IL-8, IL-6, and IL-1β levels and the activation of mitogen-activated protein kinase (MAPK) in THP-1 cells. Both compounds effectively inhibited the mRNA levels of IL-6, tumor necrosis factor (TNF)-α, and cyclooxygenase (COX)-2 in P. gingivalis-stimulated gingival tissue of mice. These findings imply that 5β,19-epoxycucurbita-6,23-diene-3β,19,25-triol and 3β,7β,25-trihydroxycucurbita-5,23-dien-19-al could be used for the development of novel therapeutic approaches against P. gingivalis infections.

Periodontal Disease-Induced Atherosclerosis and Oxidative Stress

Periodontal disease is a highly prevalent disorder affecting up to 80% of the global population. Recent epidemiological studies have shown an association between periodontal disease and cardiovascular disease, as oxidative stress plays an important role in chronic inflammatory diseases such as periodontal disease and cardiovascular disease. In this review, we focus on the mechanisms by which periodontopathic bacteria cause chronic inflammation through the enhancement of oxidative stress and accelerate cardiovascular disease. Furthermore, we comment on the antioxidative activity of catechin in atherosclerosis accelerated by periodontitis.

Leukocyte inclusion within a platelet rich plasma-derived fibrin scaffold stimulates a more pro-inflammatory environment and alters fibrin properties

One of the main differences among platelet-rich plasma (PRP) products is the inclusion of leukocytes that may affect the biological efficacy of these autologous preparations. The purpose of this study was to evaluate whether the addition of leukocytes modified the morphological, biomechanical and biological properties of PRP under normal and inflammatory conditions. The release of pro-inflammatory cytokines from plasma rich in growth factors (PRGF) and leukocyte-platelet rich plasma (L-PRP) scaffolds was determined by enzyme-linked immunosorbent assay (ELISA) and was significantly increased under an inflammatory condition when leukocytes were included in the PRP. Fibroblasts and osteoblasts treated with L-PRP, under an inflammatory situation, underwent a greater activation of NFĸB pathway, proliferated significantly less and secreted a higher concentration of pro-inflammatory cytokines. These cellular events were assessed through Western blot and fluorimetric and ELISA methods, respectively. Therefore, the inclusion of leukocytes induced significantly higher pro-inflammatory conditions.

Change of scaling-induced proinflammatory cytokine on the clinical efficacy of periodontitis treatment

Proinflammatory cytokines are key inflammatory mediators in periodontitis. This study aimed to investigate the relationship between proinflammatory cytokines in saliva and periodontal status. To investigate the usefulness of cytokines in the therapeutic approach for periodontal disease, the relationship between stimulated cytokine changes and the periodontitis treatment outcome was investigated in this study. Saliva was obtained from 22 patients diagnosed by dentists as having chronic periodontitis. The proinflammatory cytokine (interleukin-1α (IL-1α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor α (TNF-α), and tumor necrosis factor β (TNF-β)) levels were determined using a commercially available kit. The IL-1β and IL-6 levels increased, whereas the TNF-β levels decreased with the severity of periodontitis (4 mm pocket percentage). Poststimulation IL-1α, IL-6, and IL-8 levels were higher in patients who had an improved treatment outcome. The differences of IL-6 levels (cut point: 0.05 μg/g) yielded a sensitivity and specificity of 90.0% and 81.82%, respectively, for predicting the periodontitis treatment outcome. Among the proinflammatory cytokines, stimulated IL-6 was an excellent marker for predicting the periodontitis treatment outcome.

miR-584 expressed in human gingival epithelial cells is induced by Porphyromonas gingivalis stimulation and regulates interleukin-8 production via lactoferrin receptor

BACKGROUND

MicroRNAs (miRNAs) are short, non-coding RNAs that are involved in post-transcriptional regulation of gene expression. Differential miRNA expression in innate and acquired immunity has been shown to regulate immune cell development and function. miRNA expression has been demonstrated to affect pathophysiology of inflammatory diseases, such as rheumatoid arthritis and lupus. As such, this study explores the role of miRNA in the context of pathophysiology of destructive periodontitis. Specifically, this investigation profiles the differentially expressed miRNA of Porphyromonas gingivalis (Pg)-stimulated human gingival epithelial cells (HGECs).

METHODS

The specific miRNAs differentially expressed in Pg-stimulated OBA-9, immortalized HGECs, were analyzed using microarray. Real-time polymerase chain reaction (PCR) and Western blotting were performed to confirm the level of miRNA expression and determine target production of miRNA in OBA-9. The production of interleukin (IL)-8 was measured to determine the bioactivity of target protein regulated by miRNA.

RESULTS

miR-584, which targets lactoferrin receptor (LfR), was 3.39-fold upregulated by Pg stimulation. This upregulation of miR-584 was confirmed by real-time PCR. Pg stimulation resulted in the suppression of LfR at mRNA and protein levels. The transfection of the miR inhibitor for miR-584 in OBA-9 recovered Pg-induced suppression of LfR. The addition of human lactoferrin (hLf) had a suppressive effect on IL-8 production in Pg-stimulated OBA-9. However, hLf also decreased IL-8 production strongly in Pg-stimulated OBA-9 in the presence of the miR inhibitor for miR-584.

CONCLUSION

These findings suggest that the upregulation of miR-584 by Pg in OBA-9 inhibits the anti-inflammatory effects of hLf via the suppression of LfR.

MicroRNA-146 inhibits pro-inflammatory cytokine secretion through IL-1 receptor-associated kinase 1 in human gingival fibroblasts

Background

Although various microRNAs (miRNAs) regulate immune and inflammatory responses, the function of miRNAs in periodontitis has not been clearly illuminated. In this study, we measured miRNA-146 (miRNA-146a and miRNA-146b-5p) expression and explored its regulatory function in the inflammatory response in human gingival fibroblasts (HGFs).

Methods

miRNA-146a and miRNA-146b-5p expression was measured by performing real-time polymerase chain reaction in HGFs after Porphyromonas gingivalis (p.g) lipopolysaccharide (LPS) stimulation. After the HGFs were transfected with miRNA-146a and miRNA-146b-5p inhibitor, the expression levels of interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were measured by enzyme-linked immunosorbent assay (ELISA). Meanwhile, IL-1 receptor-associated kinase 1 (IRAK1) and TNF receptor-associated factor 6 (TRAF6) were detected by western blot and quantitative PCR. A luciferase assay was used to detect whether miRNA-146 could directly bind to the 3’-UTR of IRAK1.

Results

The expression levels of miRNA-146a and miRNA-146b-5p significantly increased in the P.g LPS-stimulated HGFs compared to the non-stimulated HGFs. The inhibition of miRNA-146a and miRNA-146b-5p resulted in increased IL-1β, IL-6 and TNF-α secretion. The mRNA and protein levels of IRAK1, but not TRAF6, also increased. We further found that miRNA-146a and miRNA-146b-5p directly bound to the IRAK1 3’-UTR.

Conclusion

Our data suggest that miRNA-146 inhibits pro-inflammatory cytokine secretion through IRAK1 in HGFs, which indicates that miRNA-146 functions as a negative regulator of periodontal inflammation.

Anti-inflammatory effect of (-)-epigallocatechin-3-gallate on Porphyromonas gingivalis lipopolysaccharide-stimulated fibroblasts and stem cells derived from human periodontal ligament

PURPOSE

(-)-epigallocatechin-3-gallate (EGCG) has been reported to exert anti-inflammatory and antibacterial effects in periodontitis. However, its exact mechanism of action has yet to be determined. The present in vitro study evaluated the anti-inflammatory effects of EGCG on human periodontal ligament fibroblasts (hPDLFs) and human periodontal ligament stem cells (hPDLSCs) affected by bacterial lipopolysaccharide (LPS) extracted from Porphyromonas gingivalis.

METHODS

hPDLFs and hPDLSCs were extracted from healthy young adults and were treated with EGCG and/or P. gingivalis LPS. After 1, 3, 5, and 7 days from treatment, cytotoxic and proliferative effects were evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and bromodeoxyuridine assay, respectively. And then, the gene expressions of hPDLFs and hPDLSCs were observed for interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, osteoprotegerin (OPG), receptor activator of nuclear factor kappa-B ligand (RANKL), and RANKL/OPG using real-time polymerase chain reaction (PCR) at 0, 6, 24, and 48 hours after treatment. The experiments were performed with the following groups for hPDLFs and hPDLSCs; 1) No treat, 2) EGCG alone, 3) P. gingivalis LPS alone, 4) EGCG+P. gingivalis LPS.

RESULTS

The 20 µM of EGCG and 20 µg/mL of P. gingivalis LPS had the lowest cytotoxic effects, so those concentrations were used for further experiments. The proliferations of hPDLFs and hPDLSCs increased in all groups, though the 'EGCG alone' showed less increase. In real-time PCR, the hPDLFs and hPDLSCs of 'EGCG alone' showed similar gene expressions to those cells of 'no treat'. The gene expressions of 'P. gingivalis LPS alone' in both hPDLFs and hPDLSCs were highly increased at 6 hours for IL-1β, IL-6, TNF-α, RANKL, and RANKL/OPG, except the RANKL/OPG in hPDLSCs. However, those increased gene expressions were down-regulated in 'EGCG+P. gingivalis LPS' by the additional treatment of EGCG.

CONCLUSIONS

Our results demonstrate that EGCG could exert an anti-inflammatory effect in hPDLFs and hPDLSCs against a major pathogen of periodontitis, P. gingivalis LPS.

Bradykinin promotes Toll like receptor-4 expression in human gingival fibroblasts

Bacterial infections are a potent mechanism for enzymatic generation of kinins such as bradykinin (BK), a universal mediator for inducing inflammatory reaction by associating with the B2 receptor and stimulating liberation of arachidonic acid and synthesis of prostaglandin E2 (PGE2). In this study we evaluate the role of bradykinin in regulating the expression of TLR4 receptor in human gingival fibroblasts. We examine the ability of bradykinin to modulate inflammatory response of human gingival fibroblasts to Gram-negative components and evaluated the role of Toll-like receptors (TLR)-4 in the co-operation between bradykinin and bacterial pathogens. We show that treatment with bradykinin promotes TLR4 receptor expression in human gingival fibroblasts (HGF) and amplifies inflammatory responses to the bacterial components of Gram-negative bacteria. The TLR4 expression induced by bradykinin was blocked with Hoe 140, a B2R antagonist. When HGF cells were incubated with BK resulted of an increased in cyclooxygenase-2 (COX-2) expression and prostaglandin E2 synthesis. Bradykinin and lipopolysaccharide, a specific TLR4 ligand stimulated COX-2 expression. In other series of experiments we found that ERK, phosphatidylinositol-3 kinase, protein kinase C and NFkB are involved in BK promoted-increased in TLR4 expression. The results demonstrate that bradykinin up-regulates the expression of TLR4 and promotes an additive increase in inflammatory responses to lipopolysaccharides.

Expression levels of novel cytokine IL-32 in periodontitis and its role in the suppression of IL-8 production by human gingival fibroblasts stimulated with Porphyromonas gingivalis

Background

IL-32 was recently found to be elevated in the tissue of rheumatoid arthritis and inflammatory bowel disease. Periodontitis is a chronic inflammatory disease caused by polymicrobial infections that result in soft tissue destruction and alveolar bone loss. Although IL-32 is also thought to be associated with periodontal disease, its expression and possible role in periodontal tissue remain unclear. Therefore, this study investigated the expression patterns of IL-32 in healthy and periodontally diseased gingival tissue. The expression of IL-32 in cultured human gingival fibroblasts (HGF) as well as effects of autocrine IL-32 on IL-8 production from HGF were also examined.

Methods

Periodontal tissue was collected from both healthy volunteers and periodontitis patients, and immunofluorescent staining was performed in order to determine the production of IL-32. Using real-time PCR and ELISA, mRNA expression and protein production of IL-32 in HGF, stimulated by Porphyromonas gingivalis (Pg), were also investigated.

Results

Contrary to our expectation, the production of IL-32 in the periodontitis patients was significantly lower than in the healthy volunteers. According to immunofluorescent microscopy, positive staining for IL-32 was detected in prickle and basal cell layers in the epithelium as well as fibroblastic cells in connective tissue. Addition of fixed Pgin vitro was found to suppress the otherwise constitutive expression of IL-32 mRNA and protein in HGF. However, recombinant IL-32 in vitro inhibited the expression of IL-8 mRNA by HGF stimulated with Pg. Interestingly, anti-IL-32 neutralizing antibody upregulated the IL-8 mRNA expression in non-stimulated HGF, indicating that constitutive expression of IL-32 in HGF suppressed IL-8 mRNA expression in the absence of bacterial stimulation.

Conclusion

These results indicate that IL-32 is constitutively produced by HGF which can be suppressed by Pg and may play a role in the downregulation of inflammatory responses, such as IL-8 production, in periodontal tissue.

Inhibitory effect of galectin-3 on the cytokine-inducing activity of periodontopathic Aggregatibacter actinomycetemcomitans endotoxin in splenocytes derived from mice

Galectins, a family of animal lectins, are involved not only in development and differentiation but also in immunoregulation and host-pathogen interactions. Galectin-3 interacts with lipopolysaccharides in gram-negative bacteria such as Escherichia coli, Salmonella minnesota and Pseudomonas aeruginosa. The present study investigated whether galectin-3 inhibited the cytokine-inducing activity of periodontopathic bacterial lipopolysaccharides using splenocytes derived from mice of different ages. Lipopolysaccharides were extracted from Aggregatibacter actinomycetemcomitans Y4 and Porphyromonas gingivalis ATCC 33277, and then purified. Enzyme-linked immunosorbent assay (ELISA) analysis revealed that galectin-3 adhered to A. actinomycetemcomitans lipopolysaccharides, but not to the lipopolysaccharides of P. gingivalis. Splenocytes were prepared from 1- or 7-month-old C57BL/6 mice. Either A. actinomycetemcomitans lipopolysaccharides (200 ng mL(-1)) alone or lipopolysaccharides and murine galectin-3 (10 microg mL(-1)) were added to culture solutions, and the release of interleukin-6 (IL-6) and interferon-gamma (IFNgamma) from splenocytes was measured by ELISA after a 17-h incubation. In all mice tested, A. actinomycetemcomitans lipopolysaccharide stimulation significantly increased the production of IL-6 and IFNgamma (P<0.01). Murine galectin-3 suppressed lipopolysaccharide-induced cytokine production in the splenocytes of the 1-month-old mice (P<0.02 for IL-6; P<0.05 for IFNgamma), but not in the splenocytes of the 7-month-old mice. This suggests that responses change with age.

Effect of eel galectin AJL-1 on periodontopathic bacterial biofilm formation and their lipopolysaccharide-mediated inflammatory cytokine induction

Porphyromonas gingivalis, Prevotella intermedia and Aggregatibacter actinomycetemcomitans, infectious pathogenic bacteria found in oral biofilm, cause periodontal disease. The inhibitory effect of AJL-1, a galectin present in the skin mucus of the Japanese eel Anguilla japonica, on biofilm formation by each of these strains was investigated by staining adherent bacteria on culture plates with crystal violet. An ATP bioluminescence assay was used to determine whether inhibition of biofilm formation was due to the bactericidal activity of AJL-1. The effect of AJL-1 on cytokine induction in human umbilical vascular endothelial cells (HUVECs) by lipopolysaccharide (LPS) isolated from A. actinomycetemcomitans was also investigated by enzyme-linked immunosorbent assay (ELISA). AJL-1 significantly inhibited biofilm formation by A. actinomycetemcomitans strains Y4, ATCC 29523 and ATCC 29524 but not by any strain of P. gingivalis or P. intermedia, and showed no bactericidal activity against A. actinomycetemcomitans strains. AJL-1 markedly suppressed interleukin (IL)-6 and IL-8 induction in HUVECs by LPS from A. actinomycetemcomitans strains Y4 and ATCC 29523. These observations indicate that AJL-1 is an effective inhibitor of biofilm formation by A. actinomycetemcomitans as well as of inflammatory cytokine induction in HUVECs by LPS. These finding indicate that AJL-1 may be of therapeutic value in A. actinomycetemcomitans-associated periodontal diseases.

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.

The effect of flavonoids on transduction mechanisms in lipopolysaccharide-treated human gingival fibroblasts

Periodontal disease comprises a group of infections that lead to inflammation of the gingival and destruction of periodontal tissues and is accompanied by the loss of the alveolar bone with eventual exfoliation of the teeth. Porphyromonas gingivalis is a Gram-negative bacteria obtained from the periodontal pocket of patients with aggressive and chronic periodontitis. This bacteria presents in the external membrane lipopolysaccharide (LPS). Flavonoids are molecules obtained from plants and possess anti-inflammatory properties. Herein we characterize the effect of the flavonoids quercetin, genistein, luteolin, and quercetagetin on LPS-activated transduction mechanism regulation in human gingival fibroblasts (HGF). In this study, we investigated the role of the previously mentioned flavonoids on mitogen-activated protein kinase (MAPK) activation induced by LPS obtained from P. gingivalis. Our results showed that LPS treatment induces activation of extracellular signal related kinase 1/2 (ERK1/2), p38, and c-jun-NH(2)-terminal kinase (JNK). All flavonoids demonstrated an inhibitory effect on MAPK activation, interleukin, 1beta, and cyclooxygenase-2 (COX-2) expression, IL-1beta and prostaglandin E2 (PGE2) synthesis. The most active flavonoid was quercetagetin. Finally we found that the treatment with quercetagetin had no effect on cellular viability or in genetic material integrity.

Changes of immunoresponse in BALB/c mice neonatally treated with periodontopathic bacterial endotoxin

The aim of this investigation was to analyze the effects of early life exposure to periodontopathic bacterial lipopolysaccharides on immunoresponse. Newborn BALB/c mice were subcutaneously injected with 20 ng lipopolysaccharide of Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans or Escherichia coli daily for 2 days, starting within 24 h after birth. The treated mice were given intraperitoneal injections of bovine serum albumin at 180 and 187 days of age. Seventeen hours after each injection, the mice were bled and sera were separated. Their sera were tested in an enzyme-linked immunosorbent assay system. The mean interleukin-4, interleukin-5, interleukin-6 and immunoglobulin E levels in the sera of mice treated neonatally with P. gingivalis lipopolysaccharide were significantly higher than those of the controls. However, in all cases, no significant difference was noted between mice treated neonatally with A. actinomycetemcomitans- or E. coli lipopolysaccharide and control mice. These data suggest that neonatal exposure to P. gingivalis lipopolysaccharide induces changes in immunological responses when the mice reach maturity.

Periodontopathic bacterial endotoxin-induced tumor necrosis factor alpha production was inhibited by exercise in mice

The effects of exercise on serum interleukin-6 and tumor necrosis factor alpha levels were investigated using mice. Five-week-old female BALB/c mice (Th2-biased) and C57BL/6 mice (Th1-biased) were divided into exercise and control groups. The exercise group was exercised in a rotating basket type treadmill for 1 h (5 r.p.m.). Blood was collected and the serum was separated immediately after exercise. The serum interleukin-6 and tumor necrosis factor alpha levels were measured using an Endogen ELISA kit. Exercise significantly increased the serum interleukin-6 level in the two strains of mice (P<0.05 and P<0.01). The tumor necrosis factor alpha level was decreased in the exercise group. Next, periodontopathic bacterial endotoxin (lipopolysaccharide) was administered after exercise, and the effects of exercise on the lipopolysaccharide-induced serum interleukin-6 and tumor necrosis factor alpha levels were investigated. Exercise inhibited lipopolysaccharide-induced tumor necrosis factor alpha production, suggesting it has a defensive action against endotoxin shock.

The K1 serotype capsular polysaccharide of Porphyromonas gingivalis elicits chemokine production from murine macrophages that facilitates cell migration

Porphyromonas gingivalis is the principal organism associated with aggressive forms of generalized periodontal disease. Previous reports have suggested that encapsulated P. gingivalis strains are more virulent than unencapsulated strains; however, the contribution of capsular polysaccharide (CPS) to the virulence of this organism is poorly understood. Since periodontal disease presents with a complex inflammatory cell lesion comprised of neutrophils and monocytes, we cultured murine peritoneal macrophages with heat-killed P. gingivalis W83, CPS purified from P. gingivalis strain W83, and the seven known serotype-specific P. gingivalis CPS and assessed the ability of supernatant fluids produced by challenged macrophages to attract naïve inflammatory cells. We also defined JE/MCP-1, KC, MIP-2, and RANTES production in response to the P. gingivalis CPS antigens. We observed that supernatant fluids collected from macrophages incubated with P. gingivalis W83 and serotype K1 CPS stimulated the migration of naïve murine bone marrow-derived polymorphonuclear leukocytes in an in vitro cell migration chamber. CPS from W83 and the K1 serotype elicited potent chemokine secretion patterns for macrophages, while those specific to serotypes K2 to K7 were significantly less stimulatory. Reverse transcription-PCR and enzyme-linked immunosorbent assay revealed JE/MCP-1, KC, MIP-2, and RANTES expression from murine macrophages which had been challenged with purified P. gingivalis W83 CPS. Chemokine production appeared to be dependent on both the dose of and time of exposure to P. gingivalis W83 CPS. These data demonstrate that the P. gingivalis serotype K1 CPS elicits chemokine production from phagocytic cells. Furthermore, these data suggest that the host response to this antigen may contribute to the formation of the inflammatory cell lesion observed during P. gingivalis-elicited periodontal disease.

Human periodontal ligament cells secrete macrophage colony-stimulating factor in response to tumor necrosis factor-alpha in vitro

BACKGROUND

Human periodontal ligament (HPDL) cells may support osteoclastogenesis by expressing receptor activator of nuclear factor-kappa B ligand (RANKL) in response to periopathogenic factors and inflammatory cytokines. Because osteoclastogenesis requires the presence of macrophage colony-stimulating factor (M-CSF), we examined whether HPDL cells secrete M-CSF in response to tumor necrosis factor-alpha (TNF-alpha).

METHODS

Cultured HPDL cells were treated with TNF-alpha in serum-free condition. The expression of M-CSF and RANKL was determined by reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. Inhibitors and anti-TNF receptor (TNFR) neutralizing antibodies were used for the inhibitory experiments. A migration assay was performed.

RESULTS

TNF-alpha upregulated M-CSF and RANKL in HPDL cells. The effect on M-CSF expression could be partially blocked by pyrrolidine-dithiocarbamate ammonium salt and LY294002 but not by NS398. Neutralizing antibody to TNFR1 could diminish the effect of TNF-alpha. In addition, TNF-treated culture medium exhibited chemotactic effect for RAW264.7.

CONCLUSIONS

HPDL cells are capable of secreting M-CSF and expressing RANKL in response to TNF-alpha. The upregulation of M-CSF is possibly one of the mechanisms essential for periodontal tissue destruction in response to inflammatory cytokines. The upregulation is partly through nuclear factor-kappa B (NF-kappaB) and phosphatidylinositol 3'-kinase and possibly involves TNFR1.

Surface-associated material from Porphyromonas gingivalis stimulates the release of nitric oxide by inducing expression of inducible nitric oxide synthase

The purpose of this study was to examine the effects of surface-associated material (SAM) from Porphyromonas gingivalis, a major cause of inflammatory periodontal disease, on the production of nitric oxide (NO) and expression of inducible nitric oxide synthase (iNOS) in the murine macrophage cell line RAW264.7. We also attempted to throw light on the signaling mechanisms involved in P. gingivalis SAM-induced NO production. SAM from P. gingivalis 381 was obtained by saline extraction. NO production was assayed by measuring the accumulation of nitrite in culture supernatants. Western blot analysis of iNOS and analysis of reverse transcription-polymerase chain reaction (RT-PCR) products were carried out. We found that P. gingivalis SAM can induce iNOS expression and stimulate the release of NO without additional stimuli and demonstrated an important role of the transcription factor NF-kappaB and microtubule polymerization in NO production. The production of NO required L-arginine, protein tyrosine kinase, and protein kinase C. The ability of P. gingivalis SAM to promote the production of NO may be important in the pathogenesis of inflammatory periodontal disease.

ANTI-PHAGOCYTIC ROLE OF SURFACE FIBROUS STRUCTURE OF AN INVASIVE PORPHYROMONAS GINGIVALIS STRAIN

Recent studies have shown that invasive and non-invasive strains of Porphyromonas gingivalis can both be isolated from patients with periodontitis. We examined the interaction between an invasive 16-1 P. gingivalis strain and phagocytes obtained from human peripheral blood and guinea pig peritoneal cavity. Phagocytes from human peripheral blood, mainly polymorphonuclear leukocytes (PMNs) isolated by centrifugation in Ficoll Hypaque, and macrophages collected from the peritoneal cavity of guinea pigs, were exposed to P. gingivalis cells. After this exposure, greater numbers of the non-invasive P. gingivalis ATCC 33277 were observed in human PMNs and guinea pig macrophages compared with the invasive P. gingivalis 16-1. Electron microscopic observations showed that invasive 16-1 within phagosomes in human PMNs and guinea pig macrophages retained their surface fibrous structures as well as their outer membranes. Electron microscopic examination showed that destruction and damage to the cell membranes and inner structures were clear in human PMNs and guinea pig macrophages after exposure to invasive 16-1 for 6 and 24 hours; this was a clear difference from exposure to the non-invasive ATCC 33277. Release of lactate dehydrogenase (LDH) activities into the culture supernatant of PMNs after exposure to the invasive 16-1 for 4 and 6 hours was significantly greater than that after exposure to the non-invasive ATCC 33277 (p<0.05). On the other hand, the LDH activity after exposure for 21 hours to the invasive 16-1 was significantly lower than that of untreated cells and cells after exposure to the non-invasive ATCC 33277 strain (p<0.05). The PMN viabilities after exposure to cells of the invasive 16-1 for 3, 4, and 6 hours as evaluated by trypan blue staining were similar to those after exposure to cells of the non-invasive ATCC 33277, but that after exposure to the invasive 16-1 strain for 21 hours was significantly lower than that after exposure to cells of the non-invasive ATCC 33277 strain.

Involvement of periodontopathic biofilm in vascular diseases

Oral bacteria inhabit biofilms, which are firm clusters adhering in layers to surfaces and are not easily eliminated by immune responses and are resistant to antimicrobial agents. Dental plaque is one such biofilm. In the past 10 years, subgingival plaque bacteria forming biofilms have been increasingly reported to be involved in systemic diseases. A close relationship between microbial infections and vascular disease has also been reported in the past two decades. The present review discusses the significance of the ecologic characteristics of biofilms formed by periodontopathic bacteria in order to further clarify the associations between periodontal disease and systemic disease. We focus on the relationships between periodontal disease-associated bacteria forming biofilms and vascular diseases including atherosclerosis and carotid coronary stenotic artery disease, and we discuss the direct and indirect effects on vascular diseases of lipopolysaccharides as well as heat shock proteins produced by periodontopathic bacteria.

Gingival and dermal fibroblasts produce interleukin-1? converting enzyme and interleukin-1? but not interleukin-18 even after stimulation with lipopolysaccharide

Epithelial cells play a critical role in periodontal disease through the secretion of pro-inflammatory cytokines such as interleukin-1 beta (IL-1 beta) and interleukin-18 (IL-18). However, the role played by fibroblasts is still unclear. The rationale of this study was to throw light on the role of gingival fibroblasts in periodontal disease. We thus investigated the expression of IL-1 beta, IL-18, and ICE mRNA and the secretion of the corresponding proteins by human normal gingival fibroblasts before and after stimulation with lipopolysaccharide (LPS) from Porphyromonas gingivalis and Escherichia coli. IL-1 beta, IL-18, and ICE mRNA expression was evaluated by RT-PCR. Proteins were analyzed by Western blot and ELISA. We demonstrated that gingival fibroblasts expressed ICE mRNA. Basal expression of ICE was modulated following cell stimulation with lipopolysaccharide (5 mug/ml). However, gingival fibroblasts expressed low levels of IL-1 beta mRNA. The expression was potentiated by LPS. The expression of IL-1 beta mRNA was followed by the secretion of IL-1 beta but not IL-18 protein. Our study suggests that fibroblasts may be involved in the defense against infections via an IL-1 beta-mediated but not an IL-18-mediated mechanism.

Salivary cystatins induce interleukin-6 expression via cell surface molecules in human gingival fibroblasts

Recently, family 2 cystatins have been demonstrated to upregulate interleukin-6 (IL-6) production by human gingival fibroblasts [Biol. Chem. 381 (2000) 1143]. To elucidate the mechanism of the IL-6 inducing activity of cystatins, we tested NF-kappa B activation with salivary cystatins SA1 and SA2-stimulated human gingival fibroblast whole cell lysates. The IL-6 production by human fibroblasts in response to these cystatins was inhibited by tyrosine kinase inhibitors and an inhibitor of NF-kappa B activation. The IL-6 inducing activity of the cystatins was depressed by the anti-CD58 monoclonal antibody. These findings supply evidence that cystatins SA1 and SA2 adhere to human fibroblasts and that the event results in tyrosine phosphorylation and upregulation of the release of IL-6 mediated enhancement of NF-kappa B activity.

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.

Human gingival fibroblasts rescue butyric acid-induced T-cell apoptosis

We previously demonstrated that butyric acid, an extracellular metabolite from periodontopathic bacteria, induces cytotoxicity and apoptosis in murine thymocytes, splenic T cells, and human Jurkat T cells. In this study, we used a cell-to-cell interaction system to examine the contribution of gingival fibroblasts to the regulation of T-cell death induced by butyric acid. Butyric acid slightly suppressed fibroblast viability in a concentration-dependent fashion. However, DNA fragmentation assays indicated that butyric acid did not induce apoptosis for up to 21 h in human gingival fibroblasts (Gin 1, F41-G, and H. pulp cells). The culture supernatants were assayed for interleukin 1alpha (IL-1alpha), IL-1beta, IL-6, IL-8, IL-11, tumor necrosis factor alpha, and transforming growth factor beta, but only the IL-6, IL-8, and IL-11 levels were significantly increased by addition of butyric acid. Butyric acid- or Fas-induced Jurkat-cell apoptosis was attenuated when Jurkat cells were cocultured with either F41-G or Gin 1 cells that had been preincubated for 6 h with butyric acid. IL-8 slightly stimulated butyric acid- or Fas-induced Jurkat-cell apoptosis in a dose-dependent manner, although a low dose of IL-8 had a mildly inhibitory effect on apoptosis. In contrast, IL-6 and IL-11 significantly suppressed butyric acid- or Fas-induced apoptosis in a dose-dependent fashion. Furthermore, the addition of monoclonal antibodies against human IL-6 and IL-11 to cocultures of gingival fibroblasts and Jurkat cells partially eliminated T-cell recovery. These results suggest that the proinflammatory cytokines such as IL-6 and IL-11, produced in fibroblasts stimulated with butyric acid, are involved in the attenuation of T-cell apoptosis by gingival fibroblasts.