Destructive and protective roles of cytokines in periodontitis: a re-appraisal from host defense and tissue destruction viewpoints

Curcumin inhibits inflammatory response and bone loss during experimental periodontitis in rats

OBJECTIVE

Curcumin, an active ingredient of turmeric, is proved to be a potential candidate of controlling inflammation and bone resorption, but few reports are on the periodontitis. The purpose of this study was to evaluate whether the intra-gastric administration of curcumin could inhibit the inflammation and alveolar bone resorption in rats following ligature-induced experimental periodontitis.

MATERIALS AND METHOD

Male Wistar rats were randomly divided into three groups: no ligature placement and administration of vehicle, ligature placement and administration of vehicle, ligature placement and administration of curcumin. After the animals were sacrificed, their mandibles were collected for morphological, histological and immunohistochemical analysis; their gingival tissues were collected for cytokine measurements.

RESULTS

Bone resorption was significantly higher in the experimental periodontitis animals treated with vehicle compared with the curcumin-treated group or the control group. Furthermore, receptor activator of nuclear factor-κB ligand (RANKL), receptor activator of nuclear factor-κB (RANK), osteoprotegerin (OPG), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) expression levels were higher in the experimental periodontitis animals treated with vehicle compared with the curcumin treated group or the control group. CONCLUSIONS. Curcumin may decrease alveolar bone loss in the experimental periodontitis rats via suppressing the expression of RANKL/RANK/OPG and its anti-inflammatory properties.

Epigenetic regulation of TNFA expression in periodontal disease

BACKGROUND

Tumor necrosis factor-α (TNF-α) plays a central role in the molecular pathogenesis of periodontal disease. However, the epigenetic regulation attributable to microbial and inflammatory signals at the biofilm-gingival interface are poorly understood. In this study, the DNA methylation alteration within the TNFA promoter in human gingival biopsies from different stages of periodontal disease is investigated and the regulatory mechanism of TNFA transcription by DNA methylation is explored.

METHODS

Gingival biopsies were obtained from 17 patients with chronic periodontitis (CP) and 18 periodontally healthy individuals. Another 11 individuals participated in an experimentally induced gingivitis study, and gingival biopsies were collected at the baseline, induction, and resolution phase. To confirm that TNFA promoter methylation modulated TNFA transcription, THP.1 cells were treated with a DNA methyltransferase inhibitor, 5-Aza-2-deoxycytidine (5-Aza-2dC), and an RAW294.7 cell line transfected with a TNFA promoter-specific luciferase reporter system with or without methylation was used.

RESULTS

In gingival biopsies from individuals with severe CP, two individual cytosine-guanine dinucleotides (CpG sites) within the TNFA promoter (at -163 and -161 bp) displayed increased methylation in CP samples compared to those with gingival health (16.1% ± 5.1% versus 11.0% ± 4.6%, P = 0.02 and 19.8% ± 4.1% versus 15.4% ± 3.6%, P = 0.04, respectively). The methylation level at -163 bp was inversely associated with the transcription level of TNFA (P = 0.018). However, no significant difference in the TNFA promoter methylation pattern was observed in samples biopsied during the induction or resolution phase of experimentally induced gingivitis, which represented a reversible periodontal lesion. THP.1 cells treated with 5-Aza-2dC demonstrated a time-dependent increase in TNFA messenger level. It was also found that the luciferase activity decreased 2.6-fold in a construct containing an in vitro methylated TNFA promoter when compared to the unmethylated insert (P = 0.03).

CONCLUSION

Although the biopsy samples represented a mixed cell population, the change in promoter methylation status in chronic periodontal disease suggested that DNA methylation may be an important regulatory mechanism in controlling TNFA transcriptional expression in periodontal disease.

Activation of invariant NK T cells in periodontitis lesions

Periodontitis is one of the most prevalent human inflammatory diseases. The major clinical phenotypes of this polymicrobial, biofilm-mediated disease are chronic and aggressive periodontitis, the latter being characterized by a rapid course of destruction that is generally attributed to an altered immune-inflammatory response against periodontal pathogens. Still, the biological basis for the pathophysiological distinction of the two disease categories has not been well documented yet. Type I NKT cells are a lymphocyte subset with important roles in regulating immune responses to either tolerance or immunity, including immune responses against bacterial pathogens. In this study, we delineate the mechanisms of NKT cell activation in periodontal infections. We show an infiltration of type I NKT cells in aggressive, but not chronic, periodontitis lesions in vivo. Murine dendritic cells infected with aggressive periodontitis-associated Aggregatibacter actinomycetemcomitans triggered a type I IFN response followed by type I NKT cell activation. In contrast, infection with Porphyromonas gingivalis, a principal pathogen in chronic periodontitis, did not induce NKT cell activation. This difference could be explained by the absence of a type I IFN response to P. gingivalis infection. We found these IFNs to be critical for NKT cell activation. Our study provides a conceivable biological distinction between the two periodontitis subforms and identifies factors required for the activation of the immune system in response to periodontal bacteria.

Periodontal disease and gene-expression levels of metalloendopeptidases in human buccal mucosal epithelium

BACKGROUND AND OBJECTIVE

Endopeptidases, such as neutral endopeptidase (NEP), endothelin-converting enzyme-1 (ECE-1) and a disintegrin and metalloprotease 17 (ADAM17), are believed to have various important roles in oral mucosal and epidermal tissue for the regulation of defensive biological responses in the oral cavity, and their expression and activity are influenced by various factors, including oral diseases. However, knowledge concerning these endopeptidases in the oral cavity has been minimal until now. This study focused on three metalloendopeptidases - NEP, ECE-1 and ADAM17 - in the oral buccal mucosal epithelium of patients with periodontal diseases and investigated the relationship between their gene-expression levels and periodontal disease.

MATERIAL AND METHODS

The levels of expression of NEP, ECE-1 and ADAM17 mRNAs in tissue samples collected from the oral buccal mucosal epithelium of 61 patients were investigated by relative quantification using real-time RT-PCR analysis. information on oral and systemic health was obtained from the clinical record of each patient.

RESULTS

Among the three groups, classified based on the diagnosis of periodontal diseases (healthy/gingivitis, early periodontitis and moderate/advanced periodontitis), the relative expression level of NEP mRNA was significantly increased in the early periodontitis group and in the moderate/advanced periodontitis group compared with that in the healthy/gingivitis group. Moreover, the relative expression levels of ECE1 and ADAM17 mRNAs were significantly increased in the moderate/advanced periodontitis group compared with those in the healthy/gingivitis group. The correlation coefficients between the mean relative expression levels of NEP and ECE1 mRNAs, NEP and ADAM17 mRNAs, and ECE1 and ADAM17 mRNAs were r = 0.758, r = 0.707 and r = 0.934, respectively (p < 0.001). Furthermore, among the oral-related factors, there was a significant correlation between the number of sites with probing pocket depths of more than 4 mm and of more than 6 mm and the relative expression levels of NEP, ECE1 and ADAM17 mRNAs. In stepwise logistic regression models, high relative expression levels of ECE1 and ADAM17 mRNAs were significantly associated with moderate/advanced periodontitis.

CONCLUSION

The present study suggests that the severity of periodontal disease may be associated with the expression of metalloendopeptidase genes, including NEP, ECE1 and ADAM17, in the buccal mucosal epithelium.

Involvement of toll-like receptor 2 and 4 in association between dyslipidemia and osteoclast differentiation in apolipoprotein E deficient rat periodontium

Background

Dyslipidemia increases circulating levels of oxidized low-density lipoprotein (OxLDL) and this may induce alveolar bone loss through toll-like receptor (TLR) 2 and 4. The purpose of this study was to investigate the effects of dyslipidemia on osteoclast differentiation associated with TLR2 and TLR4 in periodontal tissues using a rat dyslipidemia (apolipoprotein E deficient) model.

Methods

Levels of plasma OxLDL, and the cholesterol and phospholipid profiles in plasma lipoproteins were compared between apolipoprotein E-deficient rats (16-week-old males) and wild-type (control) rats. In the periodontal tissue, we evaluated the changes in TLR2, TLR4, receptor activator of nuclear factor kappa B ligand (RANKL) and tartrate resistant acid phosphatase (TRAP) expression.

Results

Apolipoprotein E-deficient rats showed higher plasma levels of OxLDL than control rats (p<0.05), with higher plasma levels of total cholesterol (p<0.05) and LDL-cholesterol (p<0.05) and lower plasma levels of high-density lipoprotein cholesterol (p<0.05). Their periodontal tissue also exhibited a higher ratio of RANKL-positive cells and a higher number of TRAP-positive osteoclasts than control rats (p<0.05). Furthermore, periodontal gene expression of TLR2, TLR4 and RANKL was higher in apolipoprotein E-deficient rats than in control rats (p<0.05).

Conclusion

These findings underscore the important role for TLR2 and TLR4 in mediating the osteoclast differentiation on alveolar bone response to dyslipidemia.

Evidence supporting a protective role for th9 and th22 cytokines in human and experimental periapical lesions

INTRODUCTION

The development of periapical granulomas is dependent on the host response and involves Th1, Th2, Th17, and Treg-related cytokines. The discovery of new Th9 and Th22 subsets, with important immunomodulatory roles mediated by interleukin (IL)-9 and IL-22, respectively, emphasizes the need for reevaluation of current cytokine paradigms in context of periapical lesions. We investigated the expression of IL-9 and IL-22 in active and stable human granulomas and throughout experimental lesion development in mice.

METHODS

Periapical granulomas (N = 83) and control specimens (N = 24) were evaluated regarding the expression of IL-9 and IL-22 via real-time polymerase chain reaction. Experimental periapical lesions were induced in mice (pulp exposure and bacterial inoculation) and the lesions evolution correlation with IL-9 and IL-22 expression kinetics was evaluated.

RESULTS

IL-9 and IL-22 mRNA expression was higher in periapical lesions than in control samples; higher levels of IL-9 and IL-22 were observed in inactive than in active lesions. In the experimental lesions model, increasing levels of IL-9 and IL-22 mRNA were detected in the lesions, and inverse correlations were found between IL-9 and IL-22 and the increase of lesion area in the different time point intervals.

CONCLUSIONS

Our results suggest that Th9 and Th22 pathways may contribute to human and experimental periapical lesion stability.

Baicalin downregulates Porphyromonas gingivalis lipopolysaccharide-upregulated IL-6 and IL-8 expression in human oral keratinocytes by negative regulation of TLR signaling

Periodontal (gum) disease is one of the main global oral health burdens and severe periodontal disease (periodontitis) is a leading cause of tooth loss in adults globally. It also increases the risk of cardiovascular disease and diabetes mellitus. Porphyromonas gingivalis lipopolysaccharide (LPS) is a key virulent attribute that significantly contributes to periodontal pathogenesis. Baicalin is a flavonoid from Scutellaria radix, an herb commonly used in traditional Chinese medicine for treating inflammatory diseases. The present study examined the modulatory effect of baicalin on P. gingivalis LPS-induced expression of IL-6 and IL-8 in human oral keratinocytes (HOKs). Cells were pre-treated with baicalin (0–80 µM) for 24 h, and subsequently treated with P. gingivalis LPS at 10 µg/ml with or without baicalin for 3 h. IL-6 and IL-8 transcripts and proteins were detected by real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. The expression of nuclear factor-κB (NF-κB), p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) proteins was analyzed by western blot. A panel of genes related to toll-like receptor (TLR) signaling was examined by PCR array. We found that baicalin significantly downregulated P. gingivalis LPS-stimulated expression of IL-6 and IL-8, and inhibited P. gingivalis LPS-activated NF-κB, p38 MAPK and JNK. Furthermore, baicalin markedly downregulated P. gingivalis LPS-induced expression of genes associated with TLR signaling. In conclusion, the present study shows that baicalin may significantly downregulate P. gingivalis LPS-upregulated expression of IL-6 and IL-8 in HOKs via negative regulation of TLR signaling.

Association between polymorphisms in interleukin-17A and -17F genes and chronic periodontal disease

OBJECTIVE

Interleukin-17 (IL-17) is a cytokine that induces neutrophil recruitment and the release of inflammatory mediators in several inflammatory conditions; nevertheless, the involvement of IL-17 gene polymorphisms in chronic periodontitis (CP) has not been addressed yet. Our aim was to evaluate the association between periodontal status and the polymorphisms IL-17A G197A and IL-17F C7488T in subjects with CP along with their impact on levels of inflammatory mediators.

MATERIAL AND METHODS

Genomic DNA was obtained from 30 CP patients and 30 healthy controls (HCs). IL-17A G197A and IL-17F C7488T polymorphisms were determined using PCR-RFLP. Serum and periodontal tissues were collected and processed for ELISA, myeloperoxidase (MPO), and/or microscopic analysis.

RESULTS

The frequencies of genotypes in the CP group were significantly different from those of HC. Odds ratio indicated that increased risks for CP were associated with the -197A allele, not with the -7488T allele. In addition, the -197A allele was correlated with worse clinical parameters, higher MPO activity, and increased expression of inflammatory mediators (IL-17A and IL-8) than the other genotypes.

CONCLUSIONS

These results indicate that the IL-17A -197A allele is associated with increased risk for CP, likely because this genotype relates to the enhanced inflammation in periodontal tissues.

Increased gingival crevicular fluid levels of soluble triggering receptor expressed on myeloid cells (sTREM) -1 in severe periodontitis

AIM

This study was designed to evaluate the presence of a new regulator of innate immunity in periodontitis: the soluble form of triggering receptor on myeloid cells-1 (sTREM-1) in gingival crevicular fluid (GCF).

MATERIAL AND METHODS

GCF was collected at four sites, three pathological and one healthy from 17 patients with periodontitis, and at one healthy site from 23 control patients. An enzyme-linked immunosorbent assay (ELISA) kit was used to quantify sTREM-1 levels in collected crevicular fluid. Recorded clinical parameters were probing pocket depth (PPD), bleeding upon probing, tooth mobility, plaque index (PlI), and gingival index (GI).

RESULTS

The mean sTREM-1 level in collected fluid was significantly higher in pathological sites than in healthy sites from either periodontal or control patients: 353.9 pg/ml, 50.2 pg/ml and 25.4 pg/ml respectively. Soluble TREM-1 concentration was significantly correlated with PPD. The sTREM-1 levels increased with the augmentation of the PlI and GI scores and levelled off at score 2 for both indexes. In multivariate analysis, periodontal pocket depth and smoking status were statistically associated with highest sTREM-1 concentrations.

CONCLUSION

sTREM-1 was detected in crevicular fluid and its concentration was higher in pathological sites. It could be a marker of periodontal tissue destruction.

Lymphotoxin-Alpha Gene Polymorphism +252A/G (rs909253, A/G) Is Associated with Susceptibility to Chronic Periodontitis: A Pilot Study

Background. Periodontal disease leading to clinical findings such as increased periodontal probing depth involves a complex interaction between invading pathogenic microorganisms and the patient's immune system. Lymphotoxin alpha (LT-α) is a potent multifunctional immune modulator that contributes toward susceptibility to immune regulation disorders, including periodontal disease. Objective. In this study, we tested the hypothesis that chronic periodontitis (CP) is associated with polymorphisms of the LT-α gene. Materials and Methods. A total of 126 subjects, 44 healthy subjects, and 82 subjects with CP, were evaluated for periodontal disease by measuring clinical attachment loss and separation. Samples of epithelial cells were obtained for DNA analysis by scraping of the buccal mucosa. The LT-α gene was analyzed by polymerase chain reaction followed by endonuclease digestion with NcoI to analyze restriction fragment length polymorphisms. Results. The LT-α gene (+252A/G) polymorphism was associated with CP. LT-α allele frequencies were significantly different (P = 0.0019) between patients with CP and healthy individuals, with an odds ratio of 2.67 for patients with CP with the G allele. Conclusions. These findings suggest the LT-α gene genotype is a risk indicator for susceptibility to chronic periodontal disease in the Brazilian population studied.

Aggressive periodontitis defined by recursive partitioning analysis of immunologic factors

BACKGROUND

The present study aims to extend recent findings of a non-linear model of the progression of periodontitis supporting the notion that aggressive periodontitis (AgP) and chronic periodontitis (CP) are distinct clinical entities. This approach is based on the implementation of recursive partitioning analysis (RPA) to evaluate a series of immunologic parameters acting as predictors of AgP and CP.

METHODS

RPA was applied to three population samples, that were retrieved from previous studies, using 17 immunologic parameters. The mean values of the parameters in control subjects were used as the cut-off points. Leave-one-out cross-validation (LOOCV) prediction errors were estimated in the proposed models, as well as the Kullback-Leibler divergence (DKL) of the distribution of positive results in AgP compared to CP and negative results in CP compared to AgP.

RESULTS

Seven classification trees were derived showing that the relationship of interleukin (IL)-4, IL-1, IL-2 has the highest potential to rule out or rule in AgP. On the other hand, immunoglobulin (Ig)A, IgM used to rule out AgP and cluster of differentiation 4 (CD4)/CD8, CD20 used to rule in AgP showed the least LOOCV cost. Penalizing DKL with LOOCV cost promotes the IL-4, IL-1, IL-2 model for ruling out AgP, whereas the single CD4/CD8 ratio with a lowered discrimination cut-off point was used to rule in AgP.

CONCLUSIONS

Although a test is unlikely to have both high sensitivity and high specificity, the use of immunologic parameters in the right model can efficiently complement a clinical examination for ruling out or ruling in AgP.

Divergence of the systemic immune response following oral infection with distinct strains of Porphyromonas gingivalis

Periodontitis is a polymicrobial oral infection characterized by the destruction of tooth-supporting structures that can be linked to systemic diseases such as cardiovascular disease, diabetes or rheumatoid arthritis. Porphyromonas gingivalis, a bacterium implicated in the etiology of periodontitis, has shown variation in inducing T-cell responses among different strains. Therefore, in this study we investigated the strain-specific immune response using a murine experimental model of periodontitis. Periodontitis was induced by P. gingivalis strains A7A1-28, W83 and W50, and later confirmed by the presence of P. gingivalis in the oral microflora and by alveolar bone resorption. Splenocytes were evaluated for gene expression, cellular proteins and cytokine expression. Dendritic cells were stimulated in vitro for T helper cell-cytokine profiling. Results showed that P. gingivalis had the ability to alter the systemic immune response after bacterial exposure. Strains W50 and W83 were shown to induce alveolar bone loss, whereas the A7A1-28 strain did not significantly promote bone resorption in mice. Splenocytes derived from mice infected with strains W50 and W83 induced expression of high levels of interleukin-4 (IL-4) but A7A1-28 stimulated increased IL-10. Stimulation of dendritic cells in vitro showed a similar pattern of cytokine expression of IL-12p40, IL-6 and transforming growth factor-β among strains. A distinct systemic response in vivo was observed among different strains of P. gingivalis, with IL-10 associated with the least amount of alveolar bone loss. Evaluation of pathogen-driven systemic immune responses associated with periodontal disease pathogenesis may assist in defining how periodontitis may impact other diseases.

Human oral mucosa and gingiva: a unique reservoir for mesenchymal stem cells

Mesenchymal stem cells (MSCs) represent a heterogeneous population of progenitor cells with self-renewal and multipotent differentiation potential. Aside from their regenerative role, extensive in vitro and in vivo studies have demonstrated that MSCs are capable of potent immunomodulatory effects on a variety of innate and adaptive immune cells. In this article, we will review recent experimental studies on the characterization of a unique population of MSCs derived from human oral mucosa and gingiva, especially their immunomodulatory and anti-inflammatory functions and their application in the treatment of several in vivo models of inflammatory diseases. The ease of isolation, accessible tissue source, and rapid ex vivo expansion, with maintenance of stable stem-cell-like phenotypes, render oral mucosa- and gingiva-derived MSCs a promising alternative cell source for MSC-based therapies.

Signs of the presence of Th17 cells in chronic periodontal disease

BACKGROUND AND OBJECTIVE

The aim of this study was to identify the specific markers of T helper 17 (Th17) cells and their variations in people suffering from chronic periodontal disease in comparison with normal control subjects.

MATERIAL AND METHODS

In 30 patients with periodontitis and 30 normal control subjects, the mRNA expressions of interleukin (IL)-17A and retinoic orphan receptor C2 (RORC2) were measured by quantitative RT-PCR. The protein levels of IL-17A and RORC2 were also evaluated by immunohistochemistry. The levels of these markers were compared between healthy and diseased periodontal tissues by the Mann-Whitney U-test.

RESULTS

In periodontal lesions, IL-17A and RORC2 were significantly overexpressed compared with normal tissues. According to our immunohistochemical analysis, the number of IL-17A-positive cells and RORC2-positive cells was significantly greater in periodontal lesions compared with control sites. Moreover, there was a positive correlation between the presence of IL-17A and RORC2 transcript and protein content levels in the gingiva of diseased patients.

CONCLUSION

The results demonstrated a significant increase in the number of some specific markers of Th17 cells in patients suffering from periodontal disease in comparison with normal control subjects.

Analysis of IL1 gene polymorphisms and transcript levels in periodontal and chronic kidney disease

Chronic kidney disease (CKD) and periodontitis (PD) are complex inflammatory disturbances, influenced by genetic factors. Interleukin (IL)-1 genes code for inflammatory mediators involved in the physiopathogenesis of both diseases. Functional polymorphisms in IL1 genes modulate cytokine levels and have been associated with susceptibility to immune-inflammatory conditions.

OBJECTIVES

The aim of this study was investigate the association of functional IL1 gene polymorphisms and transcript levels with susceptibility to CKD and PD.

DESIGN

The sample consisted of 246 individuals, mean age 44.8 years, divided into: group 1 (64 patients without CKD and without PD), group 2 (58 without CKD and with PD), group 3 (52 with CKD and without PD) and group 4 (72 with CKD and with PD). DNA was obtained from cells of oral mucosa and polymorphisms IL1AC-889T, IL1BC-511T, IL1BC+3954T and IL1RN (intron 2) were analyzed by PCR-RFLP. Transcript levels from gingival tissues were analyzed by real-time PCR.

RESULTS

IL1RN(*)1 allele was associated with almost 4-fold increased risk for CKD (OR 3.92 95% CI=1.6-9.4, p=0.002). IL1RN(*)2 allele was associated with 3-fold increased risk for PD in CKD patients (OR 3.08 95% CI=1.2-7.9, p=0.019). Allele T for polymorphism IL1B+3954 was associated with CKD in PD patients (OR 2.28 95% CI=1.1-4.7, p=0.019). Significantly increased levels of transcripts of IL1A, IL1B and IL1RN genes were found in PD patients.

CONCLUSIONS

It was observed an evidence for association of IL1B and IL1RN alleles with susceptibility to CKD and PD. Higher levels of IL1 gene transcripts were found in PD patients.

The plant coumarins auraptene and lacinartin as potential multifunctional therapeutic agents for treating periodontal disease

BACKGROUND

Periodontal diseases are bacterial infections leading to chronic inflammation disorders that are frequently observed in adults. In the present study, we evaluated the effect of auraptene and lacinartin, two natural oxyprenylated coumarins, on the growth, adherence properties, and collagenase activity of Porphyromonas gingivalis. We also investigated the capacity of these compounds to reduce cytokine and matrix metalloproteinase (MMP) secretion by lipopolysaccharide (LPS)-stimulated macrophages and to inhibit MMP-9 activity.

METHODS

Microplate dilution assays were performed to determine the effect of auraptene and lacinartin on P. gingivalis growth as well as biofilm formation stained with crystal violet. Adhesion of FITC-labeled P. gingivalis to oral epithelial cells was monitored by fluorometry. The effects of auraptene and lacinartin on LPS-induced cytokine and MMP secretion by macrophages were determined by immunological assays. Fluorogenic assays were used to evaluate the capacity of the two coumarins to inhibit the activity of P. gingivalis collagenase and MMP-9.

RESULTS

Only lacinartin completely inhibited P. gingivalis growth in a complex culture medium. However, under iron-limiting conditions, auraptene and lacinartin both inhibited the growth of P. gingivalis. Lacinartin also inhibited biofilm formation by P. gingivalis and promoted biofilm desorption. Both compounds prevented the adherence of P. gingivalis to oral epithelial cells, dose-dependently reduced the secretion of cytokines (IL-8 and TNF-α) and MMP-8 and MMP-9 by LPS-stimulated macrophages, and inhibited MMP-9 activity. Lacinartin also inhibited P. gingivalis collagenase activity.

CONCLUSIONS

By acting on multiple targets, including pathogenic bacteria, tissue-destructive enzymes, and the host inflammatory response, auraptene and lacinartin may be promising natural compounds for preventing and treating periodontal diseases.

Effects of aging on endotoxin tolerance induced by lipopolysaccharides derived from Porphyromonas gingivalis and Escherichia coli

BACKGROUND

Periodontitis is a bacterially induced chronic inflammatory disease. Exposure of the host to periodontal pathogens and their virulence factors induces a state of hyporesponsiveness to subsequent stimulations, termed endotoxin tolerance. Aging has a profound effect on immune response to bacteria challenge. The aim of this study was to explore the effects of aging on endotoxin tolerance induced by Porphyromonas gingivalis (P. gingivalis) lipopolysaccharide (LPS) and Escherichia coli (E. coli) LPS in murine peritoneal macrophages.

METHODOLOGY/PRINCIPAL FINDINGS

We studied the cytokine production (TNF-α and IL-10) and Toll-like receptor 2, 4 (TLR2, 4) gene and protein expressions in peritoneal macrophages from young (2-month-old) and middle-aged (12-month-old) ICR mice following single or repeated P. gingivalis LPS or E. coli LPS stimulation. Pretreatment of peritoneal macrophages with P. gingivalis LPS or E. coli LPS resulted in a reduction in TNF-α production and an increase in IL-10 production upon secondary stimulation (p<0.05), and the markedly lower levels of TNF-α and higher levels of IL-10 were observed in macrophages from young mice compared with those from middle-aged mice (p<0.05). In addition, LPS restimulations also led to the significantly lower expression levels of TLR2, 4 mRNA and protein in macrophages from young mice (p<0.05).

CONCLUSIONS/SIGNIFICANCE

Repeated LPS stimulations triggered endotoxin tolerance in peritoneal macrophages and the ability to develop tolerance in young mice was more excellent. The impaired ability to develop endotoxin tolerance resulted from aging might be related to TLR2, 4 and might lead to the incontrollable periodontal inflammation in older adults.

Oral inflammatory diseases and systemic inflammation: role of the macrophage

Inflammation is a complex reaction to injurious agents and includes vascular responses, migration, and activation of leukocytes. Inflammation starts with an acute reaction, which evolves into a chronic phase if allowed to persist unresolved. Acute inflammation is a rapid process characterized by fluid exudation and emigration of leukocytes, primarily neutrophils, whereas chronic inflammation extends over a longer time and is associated with lymphocyte and macrophage infiltration, blood vessel proliferation, and fibrosis. Inflammation is terminated when the invader is eliminated, and the secreted mediators are removed; however, many factors modify the course and morphologic appearance as well as the termination pattern and duration of inflammation. Chronic inflammatory illnesses such as diabetes, arthritis, and heart disease are now seen as problems that might have an impact on the periodontium. Reciprocal effects of periodontal diseases are potential factors modifying severity in the progression of systemic inflammatory diseases. Macrophages are key cells for the inflammatory processes as regulators directing inflammation to chronic pathological changes or resolution with no damage or scar tissue formation. As such, macrophages are involved in a remarkably diverse array of homeostatic processes of vital importance to the host. In addition to their critical role in immunity, macrophages are also widely recognized as ubiquitous mediators of cellular turnover and maintenance of extracellular matrix homeostasis. In this review, our objective is to identify macrophage-mediated events central to the inflammatory basis of chronic diseases, with an emphasis on how control of macrophage function can be used to prevent or treat harmful outcomes linked to uncontrolled inflammation.

The use of chronic gingivitis as reference status increases the power and odds of periodontitis genetic studies: a proposal based in the exposure concept and clearer resistance and susceptibility phenotypes definition

AIM

Current literature on chronic periodontitis genetics encompasses numerous single nucleotide polymorphisms-focused case-control studies with inconsistent and controversial results, which typically disregards the exposure concept embraced by case-control definition. Herein, we propose a case-control design reappraisal by clear phenotype selection, where chronic gingivitis represents a genetically resistant phenotype/genotype opposing the susceptible cohort.

MATERIAL AND METHODS

The hypothesis was tested in healthy, chronic periodontitis and gingivitis groups through Real-time PCR-based allelic discrimination of classic variants IL1B-3954, IL6-174, TNFA-308, IL10-592 and TLR4-299.

RESULTS

Observed allele/genotype frequencies characterize the healthy group with an intermediate genetic profile between periodontitis and gingivitis cohorts. When comparing genotype/allele frequencies in periodontitis versus healthy and periodontitis versus gingivitis scenarios, the number of positive associations (2-4) and the degree of association (p and odds ratio values) were significantly increased by the new approach proposed (periodontitis versus gingivitis), suggesting the association of IL1B-3954, TNFA-308, IL10-592 and TLR4-299 with periodontitis risk. Power study was also significantly improved by the new study design proposed when compared to the traditional approach.

CONCLUSIONS

The data presented herein support the use of new case-control study design based on the case-control definition and clear resistance/susceptibility phenotypes selection, which can significantly impact the study power and odds of identification of genetic factors involved in PD.

Interactions of adiponectin and lipopolysaccharide from Porphyromonas gingivalis on human oral epithelial cells

BACKGROUND

Periodontitis is an inflammatory disease caused by pathogenic microorganisms, such as Porphyromonas gingivalis, and characterized by the destruction of the periodontium. Obese individuals have an increased risk for periodontitis and show decreased serum levels of adiponectin. This in-vitro study was established to examine whether adiponectin modulates critical effects of lipopolysaccharide (LPS) from P. gingivalis on oral epithelial cells (OECs).

METHODOLOGY/PRINCIPAL FINDINGS

The presence of adiponectin and its receptors in human gingival tissue samples and OECs was analyzed by immunohistochemistry and PCR. Furthermore, OECs were treated with LPS and/or adiponectin for up to 72 h, and the gene expression and protein synthesis of pro- and anti-inflammatory mediators, matrix metalloproteinases (MMPs) and growth factors were analyzed by real-time PCR and ELISA. Additionally, cell proliferation, differentiation and in-vitro wound healing were studied. The nuclear translocation of NFκB was investigated by immunofluorescence. Gingival tissue sections showed a strong synthesis of adiponectin and its receptors in the epithelial layer. In cell cultures, LPS induced a significant up-regulation of interleukin (IL) 1β, IL6, IL8, MMP1 and MMP3. Adiponectin abrogated significantly the stimulatory effects of LPS on these molecules. Similarly, adiponectin inhibited significantly the LPS-induced decrease in cell viability and increase in cell proliferation and differentiation. Adiponectin led to a time-dependent induction of the anti-inflammatory mediators IL10 and heme oxygenase 1, and blocked the LPS-stimulated NFκB nuclear translocation.

CONCLUSIONS/SIGNIFICANCE

Adiponectin may counteract critical actions of P. gingivalis on oral epithelial cells. Low levels of adiponectin, as observed in obese individuals, may increase the risk for periodontal inflammation and destruction.

Periodontal disease-associated compensatory expression of osteoprotegerin is lost in type 1 diabetes mellitus and correlates with alveolar bone destruction by regulating osteoclastogenesis

Alveolar bone resorption results from the inflammatory response to periodontal pathogens. Systemic diseases that affect the host response, such as type 1 diabetes mellitus (DM1), can potentiate the severity of periodontal disease (PD) and accelerate bone resorption. However, the biological mechanisms by which DM1 modulates PD are not fully understood. The aim of this study was to determine the influence of DM1 on alveolar bone resorption and to evaluate the role of receptor activator of nuclear factor-kappaB ligand (RANKL)/osteoprotegerin (OPG) in osteoclastogenesis in rats. PD was induced by means of ligature in nondiabetic and in streptozotocyn-induced DM1 rats. Morphological and morphometric analyses, stereology and osteoclast counting were performed. RANKL and OPG mRNA levels, protein content, and location were determined. PD caused alveolar bone resorption, increased the number of osteoclasts in the alveolar bone crest and also promoted changes in RANKL/OPG mRNA expression. DM1 alone showed alveolar bone destruction and an increased number of osteoclasts at the periapical and furcal regions. DM1 exacerbated these characteristics, with a greater impact on bone structure, resulting in a low OPG content and a higher RANKL/OPG ratio, which correlated with prominent osteoclastogenesis. This work demonstrates that the effects of PD and DM1 enhance bone destruction, confirms the importance of the RANKL signaling pathway in bone destruction in DM1 in animal models and suggests the existence of alternative mechanisms potentiating bone degradation in PD.

Translational and clinical applications of salivary diagnostics

There have been significant advances in techniques for the detection of biomarker signals in the oral cavity (e.g., ELISAs for proteins, PCR for RNA and DNA) as well as the engineering and development of microfluidic approaches to make oral-based point-of-care (POC) methods for the diagnosis for both local and systemic conditions a reality. In this section, we focus on three such approaches, namely, periodontal disease management, early markers for systemic diseases, and salivary markers useful for pharmacogenomic studies. Novel approaches using non-invasive, salivary samples and user-friendly devices offer results that are as sensitive and specific as laboratory-based analyses using blood or urine.

Influence of oral conditions on colonization by highly toxigenic Staphylococcus aureus strains

OBJECTIVES

As the oral cavity is regarded as a relevant site for Staphylococcus aureus colonization and interhuman transmission, this study aimed to investigate whether different oral conditions influence the rates of S. aureus oral carriage and genetic characters of S. aureus isolates.

SUBJECTS AND METHODS

Staphylococcus aureus was searched in samples collected from cheek, gingival margin, and anterior nares of 45 healthy subjects, 27 periodontitis affected subjects, and 29 subjects with fixed prosthetic restorations. Isolates were screened for 17 genetic determinants, and Partial Least Square Discriminant Analysis was performed to evaluate whether specific characters correlated with oral condition or site of isolation.

RESULTS

The three subject groups showed comparable nasal carriage rates but, both the periodontitis and prosthetic restoration groups showed significantly higher oral carriage rates, as compared to healthy subjects (P = 0.01 and 0.02, respectively). Moreover, periodontitis affected subjects hosted strains possessing a distinct genotypic and phenotypic background, characterized by the presence of a larger number of exotoxins encoding genes.

CONCLUSIONS

These data confirm that the oral cavity is an important site of S. aureus colonization and demonstrate that conditions modifying the oral environment, as the presence of periodontitis and of fixed prosthetic restorations, promote S. aureus carriage and may favor the spread of more pathogenic strains.

Diabetes aggravates periodontitis by limiting repair through enhanced inflammation

Periodontitis is the most common lytic bone disease and one of the first clinical manifestations of diabetes. Diabetes increases the risk of periodontitis. The aim of the present study was to examine mechanisms by which diabetes aggravates periodontitis. Ligature-induced periodontitis was examined in Goto-Kakizaki rats with type 2 diabetes. A tumor necrosis factor (TNF)-specific-inhibitor, pegsunercept, was applied to diabetic rats after the onset of periodontal disease. Interferon-γ (IFN-γ), TNF-α, interleukin-1 β (IL-1β), fibroblast growth factor-2 (FGF-2), transforming growth factor beta-1 (TGFβ-1), bone morphogenetic protein-2 (BMP-2), and BMP-6 were measured by real-time RT-PCR, and histological sections were examined for leukocyte infiltration and several parameters related to bone resorption and formation. Inflammation was prolonged in diabetic rats and was reversed by the TNF inhibitor, which reduced cytokine mRNA levels, leukocyte infiltration, and osteoclasts. In contrast, new bone and osteoid formation and osteoblast numbers were increased significantly vs. untreated diabetic animals. TNF inhibition in diabetic animals also reduced apoptosis, increased proliferation of bone-lining cells, and increased mRNA levels of FGF-2, TGFβ-1, BMP-2, and BMP-6. Thus, diabetes prolongs inflammation and osteoclastogenesis in periodontitis and through TNF limits the normal reparative process by negatively modulating factors that regulate bone.

Effects of periodontal therapy on GCF cytokines in generalized aggressive periodontitis subjects

AIM

To examine changes in levels of gingival crevicular fluid (GCF) cytokines, after periodontal therapy of generalized aggressive periodontitis (GAgP).

MATERIALS AND METHODS

Twenty-five periodontally healthy and 24 GAgP subjects had periodontal clinical parameters measured and gingival crevicular fluid (GCF) samples collected from up to 14 sites/subject. GCF samples were analysed using multiplex bead immunoassay for: GM-CSF, IFN-γ, IL-10, IL-1β, IL-2, IL-6 and TNF-α. Aggressive periodontitis subjects were randomly assigned to either scaling and root planing (SRP) alone or SRP plus systemic amoxicillin (500 mg) and metronidazole (400 mg) 3 times a day for 14 days. Clinical parameters and GCF cytokines were re-measured 6 months after treatment. Differences over time were analysed using the Wilcoxon test and between groups using the Mann-Whitney test.

RESULTS

Significant reductions in GCF GM-CSF, IL-1β and the ratio IL-1β/IL-10 and increases in GCF IL-6 were detected after therapy. The mean change in GCF cytokines did not differ significantly between groups.

CONCLUSIONS

Periodontal therapy improved GCF cytokine profiles by lowering IL-1β and increasing IL-10 levels. The reduction in GCF GM-CSF after therapy implicates this cytokine in the pathogenesis of GAgP. There was no difference between therapies in changes of GCF cytokines.

MIF induces osteoclast differentiation and contributes to progression of periodontal disease in mice

Periodontal disease (PD) is a chronic inflammatory and alveolar bone destructive disease triggered by microorganisms from the oral biofilm. Oral inoculation of mice with the periodontopathogen Aggregatibacter actinomycetemcomitans (Aa) induces marked alveolar bone loss and local production of inflammatory mediators, including Macrophage Migration Inhibitory Factor (MIF). The role of MIF for alveolar bone resorption during PD is not known. In the present study, experimental PD was induced in BALB/c wild-type mice (WT) and MIF knockout mice (MIF⁻/⁻) through oral inoculation of Aa. Despite enhanced number of bacteria, MIF⁻/⁻ mice had reduced infiltration of TRAP-positive cells and reduced alveolar bone loss. This was associated with decreased neutrophil accumulation and increased levels of IL-10 in periodontal tissues. TNF-α production was similar in both groups. In vitro, LPS from Aa enhanced osteoclastic activity in a MIF-dependent manner. In conclusion, MIF has role in controlling bacterial growth in the context of PD but contributes more significantly to the progression of bone loss during PD by directly affecting differentiation and activity of osteoclasts.

Experimental arthritis triggers periodontal disease in mice: involvement of TNF-α and the oral Microbiota

Rheumatoid arthritis (RA) and periodontal disease (PD) are prevalent chronic inflammatory disorders that affect bone structures. Individuals with RA are more likely to experience PD, but how disease in joints could induce PD remains unknown. This study aimed to experimentally mimic clinical parameters of RA-induced PD and to provide mechanistic findings to explain this association. Chronic Ag-induced arthritis (AIA) was triggered by injection of methylated BSA in the knee joint of immunized mice. Anti-TNF-α was used to assess the role of this cytokine. Intra-articular challenge induced infiltration of cells, synovial hyperplasia, bone resorption, proteoglycan loss, and increased expression of cytokines exclusively in challenged joints. Simultaneously, AIA resulted in severe alveolar bone loss, migration of osteoclasts, and release of proinflammatory cytokines in maxillae. Anti-TNF-α therapy prevented the development of both AIA and PD. AIA did not modify bacterial counts in the oral cavity. PD, but not AIA, induced by injection of Ag in immunized mice was decreased by local treatment with antiseptic, which decreased the oral microbiota. AIA was associated with an increase in serum C-reactive protein levels and the expression of the transcription factors RORγ and Foxp3 in cervical lymph nodes. There were higher titers of anti-collagen I IgG, and splenocytes were more responsive to collagen I in AIA mice. In conclusion, AIA-induced PD was dependent on TNF-α and the oral microbiota. Moreover, PD was associated with changes in expression of lymphocyte transcription factors, presence of anti-collagen Abs, and increased reactivity to autoantigens.

Licorice and its potential beneficial effects in common oro-dental diseases

Licorice, the name given to the roots and stolons of Glycyrrhiza species, has been used since ancient times as a traditional herbal remedy. Licorice contains several classes of secondary metabolites with which numerous human health benefits have been associated. Recent research suggests that licorice and its bioactive ingredients such as glycyrrhizin, glabridin, licochalcone A, licoricidin, and licorisoflavan A possess potential beneficial effects in oral diseases. This paper reviews the effects of licorice and licorice constituents on both the oral microbial pathogens and the host immune response involved in common ora-dental diseases (dental caries, periodontitis, candidiasis, and recurrent aphthous ulcers). It also summarizes results of clinical trials that investigated the potential beneficial effects of licorice and its constituents for preventing/treating oro-dental diseases.

Benzyl isothiocyanate, a major component from the roots of Salvadora persica is highly active against Gram-negative bacteria

Plants produce a number of antimicrobial substances and the roots of the shrub Salvadora persica have been demonstrated to possess antimicrobial activity. Sticks from the roots of S. persica, Miswak sticks, have been used for centuries as a traditional method of cleaning teeth. Diverging reports on the chemical nature and antimicrobial repertoire of the chewing sticks from S. persica led us to explore its antibacterial properties against a panel of pathogenic or commensal bacteria and to identify the antibacterial component/s by methodical chemical characterization. S. persica root essential oil was prepared by steam distillation and solid-phase microextraction was used to sample volatiles released from fresh root. The active compound was identified by gas chromatography-mass spectrometry and antibacterial assays. The antibacterial compound was isolated using medium-pressure liquid chromatography. Transmission electron microscopy was used to visualize the effect on bacterial cells. The main antibacterial component of both S. persica root extracts and volatiles was benzyl isothiocyanate. Root extracts as well as commercial synthetic benzyl isothiocyanate exhibited rapid and strong bactericidal effect against oral pathogens involved in periodontal disease as well as against other Gram-negative bacteria, while Gram-positive bacteria mainly displayed growth inhibition or remained unaffected. The short exposure needed to obtain bactericidal effect implies that the chewing sticks and the essential oil may have a specific role in treatment of periodontal disease in reducing Gram-negative periodontal pathogens. Our results indicate the need for further investigation into the mechanism of the specific killing of Gram-negative bacteria by S. persica root stick extracts and its active component benzyl isothiocyanate.

Dose-response met-RANTES treatment of experimental periodontitis: a narrow edge between the disease severity attenuation and infection control

Chemokines and chemokine receptors have been implicated in the selective migration of leukocyte subsets to periodontal tissues, which consequently influences the disease outcome. Among these chemoattractants, the chemokines CCL3, CCL4 and CCL5 and its receptors, CCR1 and CCR5, have been associated with increased disease severity in mice and humans. Therefore, in this study we investigated the modulation of experimental periodontitis outcome by the treatment with a specific antagonist of CCR1 and 5 receptors, called met-RANTES. C57Bl/6 mice was orally infected with Aggregatibacter actinomycetemcomitans and treated with 0.05, 0.1, 0.5, 1.5 and 5 mg doses of met-RANTES on alternate days, and evaluated by morphometric, cellular, enzymatic and molecular methods. At 0.5 mg up to 5 mg doses, a strong reduction in the alveolar bone loss and inflammatory cell migration were observed. Interestingly, 5 mg dose treatment resulted in the maximum inhibition of inflammatory cell migration, but resulted in a similar inhibition of bone loss when compared with the lower doses, and also resulted in increased bacterial load and CRP response. When 0.5 and 5 mg therapy regimens were compared it was observed that both therapeutic protocols were able to downregulate the levels of pro-inflammatory, Th1-type and osteoclastogenic cytokines, and CD3+ and F4/80+ cells migration to periodontal tissues, but the high dose modulates host response in a more pronounced and unspecific and excessive way, interfering also with the production of antimicrobial mediators such as MPO, iNOS and IgG, and with GR1+ and CD19+ cells migration. Our results demonstrate a thin line between beneficial immunoregulation and impaired host defense during experimental periodontitis, and the determination of the exact equilibrium point is mandatory for the improvement of immune-targeted therapy of periodontitis.

Increased plasma levels epithelial cell-derived neutrophil-activating peptide 78/CXCL5 in periodontitis patients undergoing supportive therapy

AIM

To investigate the influence of cigarette smoking on plasma epithelial cell-derived neutrophil-activating peptide-78 (CXCL5/ENA-78) and interleukin-6 (IL-6) in supportive therapy periodontitis patients.

MATERIALS AND METHODS

Plasma concentrations of CXCL5/ENA-78 and IL-6 were evaluated in 167 systemically healthy subjects (54 smokers and 113 non-smokers) divided into four groups: non-smokers with periodontitis (n=90), smokers with periodontitis (n=49), healthy non smokers (n=23) and healthy smokers (n=5).

RESULTS

Clinical probing depth (CPD) of smokers with periodontitis were significantly greater than those of non-smoking patients (p<0.05). Although clinical attachment loss (CAL) and the number of deep sites affected were greater in the smokers with periodontitis, these differences were not significant. Periodontitis patients had significantly higher plasma IL-6 and ENA-78 than healthy subjects (p<0.05). There was no significant difference in IL-6 between smokers and non-smokers with periodontitis but CXCL5/ENA-78 concentrations were significantly greater in smokers with periodontitis (p=0.006). Plasma CXCL5/ENA-78 correlated with CPD, CAL and tobacco consumption (all p<0.05).

CONCLUSION

Plasma CXCL5/ENA-78 concentrations are a good systemic indicator of the inflammatory process and disease severity in subjects with periodontitis and in addition are potential indicator of inflammatory effects of cigarette smoking. Further studies are required to elucidate the biological mechanisms underlining this increase in CXCL5/ENA-78.

Microbiological and host factors are involved in promoting the periodontal failure of metaloceramic crowns

This study was aimed at looking into the microbiological/inflammatory parameters predicting the periodontal success/failure of fixed prostheses. Microbiological and inflammatory patterns were studied at 102 sites having metaloceramic crowns in place from 3 to 6 years and divided in healthy sites (HS), gingivitis affected (MG), and periodontitis affected (PB). Total bacterial flora and selected indicator species in subgingival plaque were quantified by quantitative real-time PCR. The concentrations of IL-1β, IL-6, and TNF-α were determined in gingival crevicular fluid (GCF) by enzyme-linked immunosorbent assays. The experimental sites showed no significant difference with respect to the age and gender of the patients and to the position of the crown margins. Poor marginal adaptation was significantly higher in MG and PB. The total amounts of bacteria per probing depth showed no significant differences among the three groups and their controls, while both MG and PB sites showed altered patterns in the distribution of specific bacteria. Both MG and PB sites showed significantly higher levels of inflammatory cytokines in GCF. The control teeth of PB subjects showed significantly higher levels of IL-1β as compared to other control sites. Data confirm that the application of metaloceramic crowns is a factor of risk for the development of gingival/periodontal inflammation. This risk is possibly associated with microbiological and host factors that predispose to the onset of periodontal alterations at sites reconstructed with metaloceramic crowns. These factors, once their role is confirmed by longitudinal studies, could be used to set up rapid tests to early predict the onset of periodontal disease at reconstructed sites.

Single nucleotide polymorphisms in interleukin-1gene cluster and subgingival colonization with Aggregatibacter actinomycetemcomitans in patients with aggressive periodontitis

Periodontitis is initiated by the subgingival occurrence of periodontopathogens. It is triggered by a specific host-dependent immune response that is influenced by genetic predisposition. Polymorphisms in the interleukin-1 (IL-1) gene cluster have been suggested to influence the pathogenesis of periodontitis. A total of 159 periodontitis patients (chronic disease: n = 73, aggressive disease: n = 86) and 89 periodontitis-free controls were included in the study. Polymorphisms IL-1α (rs1800587), IL-1β (rs16944, rs1143634), IL-1 receptor (rs2234650), and IL-1 receptor antagonist (rs315952) were determined by polymerase chain reaction with sequence-specific primers (PCR-SSP). Subgingival bacterial colonization was assessed using a polymerase chain reaction/DNA probe test (micro-Ident). Haplotype block structure was determined using Haploview 4.2. Statistical analyses were performed applying SPSS 17.0 considering dominant, recessive, and codominant genetic models. In this case-control study, no association between genomic variants of the IL-1 gene cluster and the incidence of severe periodontitis could be shown. Carriers of the rare genotypes of rs1800587 (p(corr) = 0.009), rs1143634 (p(corr) = 0.009) and composite genotype (rs1800587+rs1143634) (p(corr) = 0.031) had a twofold higher risk for subgingival occurrence of Aggregatibacter actinomycetemcomitans. In forward stepwise binary logistic regression analyses considering age, gender, smoking, and approximal plaque index as potential confounders these significant associations were demonstrated. Despite the genetic background of IL-1 gene cluster could be shown to be associated with subgingival colonization of A actinomycetemcomitans, there is no evidence that it is an independent risk indicator for periodontitis.

Aggregatibacter actinomycetemcomitans leukotoxin: a powerful tool with capacity to cause imbalance in the host inflammatory response

Aggregatibacter actinomycetemcomitans has been described as a member of the indigenous oral microbiota of humans, and is involved in the pathology of periodontitis and various non-oral infections. This bacterium selectively kills human leukocytes through expression of leukotoxin, a large pore-forming protein that belongs to the Repeat in Toxin (RTX) family. The specificity of the toxin is related to its prerequisite for a specific target cell receptor, LFA-1, which is solely expressed on leukocytes. The leukotoxin causes death of different leukocyte populations in a variety of ways. It activates a rapid release of lysosomal enzymes and MMPs from neutrophils and causes apoptosis in lymphocytes. In the monocytes/macrophages, the toxin activates caspase-1, a cysteine proteinase, which causes a proinflammatory response by the activation and secretion of IL-1β and IL-18. A specific clone (JP2) of A. actinomycetemcomitans with enhanced leukotoxin expression significantly correlates to disease onset in infected individuals. Taken together, the mechanisms by which this toxin kills leukocytes are closely related to the pathogenic mechanisms of inflammatory disorders, such as periodontitis. Therapeutic strategies targeting the cellular and molecular inflammatory host response in periodontal diseases might be a future treatment alternative.

Cytokine production by leukocytes of Papillon-Lefèvre syndrome patients in whole blood cultures

Papillon-Lefèvre syndrome (PLS) is characterised by aggressively progressive periodontitis combined with palmo-plantar hyperkeratosis. It is caused by "loss of function" mutations in the cathepsin C gene. The hypothesis behind this study is that PLS patients' polymorphonuclear leukocytes (PMNs) produce more proinflammatory cytokines to compensate for their reduced capacity to neutralize leukotoxin and to eliminate Aggregatibacter actinomycetemcomitans. Production of more interleukin (IL)-8 would result in the attraction of more PMNs. The aim of this study was to evaluate the cytokine profile in PLS patients' blood cultures. Blood was sampled from eight PLS patients (one female) from six families (antiinfective therapy completed: six; edentulous: two) with confirmed cathepsin C mutations and deficient enzyme activity. Nine healthy males served as controls. Whole blood cultures were stimulated with highly pure lipopolysaccharide (LPS) from Escherichia coli R515 and IL-1β plus tumor necrosis factor (TNF)-α. Thereafter, release of IL-1β (stimulation: LPS and LPS plus adenosine triphosphate), IL-6, IL-8, interferon-inducible protein (IP)-10, and interferon (IFN)-γ (stimulation: LPS, IL-1β/TNFα) were detected by ELISA. Medians of cytokine release were, with the exception of IP-10, slightly higher for PLS than for controls' cultures. None of these differences reached statistical significance. Increased production of IL-1β, IL-6, IL-8, IP-10, or IFNγ as a significant means to compensate for diminished activity and stability of polymorphonuclear leukocyte-derived proteases could not be confirmed in this study. Cytokine profiles in blood cultures may not be used to identify PLS patients.