IL-18 Gene Promoter Polymorphisms are Involved in Periodontal Disease: A Meta-Analysis.

Microbial plaque that builds up in the gingival crevice area causes inflammation and leads to periodontal disease. Previous research has shown an association between interleukins with periodontitis. The association between interleukin-18 (IL-18) gene polymorphism and periodontitis risk was studied extensively, but the results are contradictory. The aim of this study is to find the association of two IL-18 promoter variants namely -607 C > A (rs1946518) and -137 G > C (rs187238), and the risk of chronic and aggressive periodontal disease by meta-analysis. The databases of PubMed, Medline, Web of Science, and Google Scholar were all explored to find the appropriate studies. The MetaGenyo software was used to calculate each analysis. Outcomes of the pooled analyses revealed significantly elevated risk for periodontitis for both polymorphisms. There is no significant heterogeneity between studies. No significant publication bias was observed. This meta-analysis provided the evidence of a link between IL-18 gene polymorphism in periodontitis.

Association of Polymorphism in IL-18 Gene with Periodontitis in Uyghur Adults in Xinjiang and Evidence from Six Case-Control Studies with a Comprehensive Analysis.

AIM: The aim of the study was to evaluate the association of IL-18 137 G > C, 607 C > A gene polymorphism in Uyghur population with chronic periodontitis (CP) and combine the results with the meta-analysis. METHODS: In a case-control study, 200 cases with CP and 100 healthy controls were recruited; IL-18 137 G > C, 607 C > A genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). In the meta-analysis, we used electronic databases, including CNKI, Wan Fang, PubMed, EMBASE databases etc.to obtain relevant research published through June 2020. Studies were considered eligible if odds ratios (ORs) and 95% confidence intervals (95% CI) were provided or calculated from the given data. The size of the combined effect was calculated using STATA 15.0. RESULTS: Our study revealed significant association between CP and IL-18 137 G > C (P = .045, OR = 1.67), 607 C > A (P = .045, OR = 1.67). The overall meta-analysis revealed significant associations between IL-18 137 G > C polymorphism and CP risk in Allele, dominant, co-dominant and recessive genetic models. The subgroup analysis also showed a significant association between the IL-18 137 G > C and risk for periodontitis and aggressive periodontitis in the Asian (GC+ CC VS. GG: P = .047, OR = 1.64,95%CI = 1.01-2.68). CONCLUSIONS: IL-18 137 G > C, 607 C > A could be associated with susceptibility to periodontitis in Uyghur population. Further case-control of candidate genes studies targeting larger sample sizes and different ethnic groups are needed to arrive more accurate conclusions.

MicroRNA-22 suppresses NLRP3/CASP1 inflammasome pathway-mediated proinflammatory cytokine production by targeting the HIF-1α and NLRP3 in human dental pulp fibroblasts.

AIM: To investigate the synergetic regulatory effect of miR-22 on HIF-1α and NLRP3, subsequently regulating the production of the NLRP3/CASP1 inflammasome pathway-mediated proinflammatory cytokines IL-1ß and IL-18 in human dental pulp fibroblasts (HDPFs) during the progression of pulpitis. METHODOLOGY: Fluorescence in situ hybridization (FISH) and immunofluorescence (IF) were performed to determine the localization of miR-22-3p, NLRP3 and HIF-1α in human dental pulp tissues (HDPTs). The miR-22 mimics and inhibitor or plasmid of NLRP3 or HIF-1α were used to upregulate or downregulate miR-22 or NLRP3 or HIF-1α in HDPFs, respectively. Computational prediction via TargetScan 5.1 and a luciferase reporter assay were conducted to confirm target association. The mRNA and protein expression of HIF-1α, NLRP3, caspase-1, IL-1ß and IL-18 were determined by qRT-PCR and western blotting, respectively. The release of IL-1ß and IL-18 was analysed by ELISA. The significance of the differences between the experimental and control groups was determined by one-way analysis of variance, p < .05 indicated statistical significance. RESULTS: A decrease in miR-22 and an increase in HIF-1α and NLRP3 in HDPTs occurred during the transformation of reversible pulpitis into irreversible pulpitis compared with that in the healthy pulp tissues (p < .05). In the normal HDPTs, miR-22-3p was extensively expressed in dental pulp cells. HIF-1α and NLRP3 were mainly expressed in the odontoblasts and vascular endothelial cells. Whereas in the inflamed HDPTs, the odontoblast layers were disrupted. HDPFs were positive for miR-22-3p, HIF-1α and NLRP3. Computational prediction via TargetScan 5.1 and luciferase reporter assays confirmed that both NLRP3 and HIF-1α were direct targets of miR-22 in HDPFs. The miR-22 inhibitor further promoted the activation of NLRP3/CASP1 inflammasome pathway induced by ATP plus LPS and hypoxia (p < .05). In contrast, the miR-22 mimic significantly inhibited the NLRP3/CASP1 inflammasome pathway activation induced by ATP plus LPS and hypoxia (p < .05). CONCLUSION: MiR-22, as a synergetic negative regulator, is involved in controlling the secretion of proinflammatory cytokines mediated by the NLRP3/CASP1 inflammasome pathway by targeting NLRP3 and HIF-1α. These results provide a novel function and mechanism of miR-22-HIF-1α-NLRP3 signalling in the control of proinflammatory cytokine secretion, thus indicating a potential therapeutic strategy for future endodontic treatment.

The Role of Cytokines Produced via the NLRP3 Inflammasome in Mouse Macrophages Stimulated with Dental Calculus in Osteoclastogenesis.

Dental calculus (DC) is a common deposit in periodontitis patients. We have previously shown that DC contains both microbial components and calcium phosphate crystals that induce an osteoclastogenic cytokine IL-1ß via the NLRP3 inflammasome in macrophages. In this study, we examined the effects of cytokines produced by mouse macrophages stimulated with DC on osteoclastogenesis. The culture supernatants from wild-type (WT) mouse macrophages stimulated with DC accelerated osteoclastogenesis in RANKL-primed mouse bone marrow macrophages (BMMs), but inhibited osteoclastogenesis in RANKL-primed RAW-D cells. WT, but not NLRP3-deficient, mouse macrophages stimulated with DC produced IL-1ß and IL-18 in a dose-dependent manner, indicating the NLRP3 inflammasome-dependent production of IL-1ß and IL-18. Both WT and NLRP3-deficient mouse macrophages stimulated with DC produced IL-10, indicating the NLRP3 inflammasome-independent production of IL-10. Recombinant IL-1ß accelerated osteoclastogenesis in both RANKL-primed BMMs and RAW-D cells, whereas recombinant IL-18 and IL-10 inhibited osteoclastogenesis. These results indicate that DC induces osteoclastogenic IL-1ß in an NLRP3 inflammasome-dependent manner and anti-osteogenic IL-18 and IL-10 dependently and independently of the NLRP3 inflammasome, respectively. DC may promote alveolar bone resorption via IL-1ß induction in periodontitis patients, but suppress resorption via IL-18 and IL-10 induction in some circumstances.

Interleukin Gene Variability and Periodontal Bacteria in Patients with Generalized Aggressive Form of Periodontitis.

Host genetic predispositions to dysregulated immune response can influence the development of the aggressive form of periodontitis (AgP) through susceptibility to oral dysbiosis and subsequent host-microbe interaction. This case-control study aimed to perform a multilocus analysis of functional variants in selected interleukin (IL) genes in patients with the generalized form of AgP in a homogenous population. Twelve polymorphisms in IL-1 gene cluster, IL-6 and its receptor, IL-10, IL-17A, and IL-18 were determined in 91 AgP patients and 210 controls. Analysis of seven selected periodontal bacteria in subgingival sulci/pockets was performed with a commercial DNA-microarray kit in a subgroup of 76 individuals. The pilot in vitro study included stimulation of peripheral blood monocytes (PBMC) from 20 individuals with periodontal bacteria and measurement of IL-10 levels using the Luminex method. Only the unctional polymorphism IL­10-1087 A/G (rs1800896) and specific IL-10 haplotypes were associated with the development of the disease (P < 0.05, Pcorr > 0.05). Four bacterial species occurred more frequently in AgP than in controls (P < 0.01, Pcorr < 0.05). Elevated IL-10 levels were found in AgP patients, carriers of IL­10-1087GG genotype, and PBMCs stimulated by periodontal bacteria (P < 0.05, Pcorr > 0.05). We therefore conclude that a combination of genetic predisposition to the altered expression of IL-10 and the presence of specific periodontal bacteria may contribute to Th1/Th2 balance disruption and AgP development.

IL18 Polymorphism and Periodontitis Susceptibility, Regardless of IL12B, MMP9, and Smoking Habits.

Genetic variations contribute to the susceptibility in the development of periodontitis. The aim of this study was to investigate the influence of IL18, IL12, and MMP9 polymorphisms in the chronic periodontitis. This case-control study involved 381 individuals matched by gender and age. Genotyping of IL18 (rs187238 and rs1946518) and IL12B (rs3212227) was performed by PCR-SSP and PCR-RFLP was used for MMP9 (rs3918242). IL-18 and MMP-9 were quantified in the serum by ELISA. SNPStats and OpenEpi software were used for statistical analysis and, in order to eliminate smoking as a confounding factor, the analyses were also performed in nonsmoking subjects. The IL18-137G/C genotype was associated with the risk of chronic periodontitis in nonsmokers (P c = 0.03; OR = 1.99; overdominant inherence model). In the multivariate analyses, homozygous IL18-137G/G and IL18-607C/C were more frequent in males compared to women with these same genotypes (OR = 2.51 and OR = 3.30, respectively). The serum levels of the IL-18 in patients were higher than those in healthy controls (P = 0.005). IL12B and MMP9 polymorphisms and MMP-9 serum concentration were similar in patients and controls. In this study, IL18 was associated with chronic periodontitis susceptibility. Men had greater risk than women for developing the disease when IL18 polymorphism was considered and the susceptibility was independent of the smoking status.

Oral microbe-host interactions: influence of ß-glucans on gene expression of inflammatory cytokines and metabolome profile.

BACKGROUND: The aim of this study was to evaluate the effects of ß-glucan on the expression of inflammatory mediators and metabolomic profile of oral cells [keratinocytes (OBA-9) and fibroblasts (HGF-1) in a dual-chamber model] infected by Aggregatibacter actinomycetemcomitans. The periodontopathogen was applied and allowed to cross the top layer of cells (OBA-9) to reach the bottom layer of cells (HGF-1) and induce the synthesis of immune factors and cytokines in the host cells. ß-glucan (10 µg/mL or 20 µg/mL) were added, and the transcriptional factors and metabolites produced were quantified in the remaining cell layers and supernatant. RESULTS: The relative expression of interleukin (IL)-1-α and IL-18 genes in HGF-1 decreased with 10 µg/mL or 20 µg/mL of ß-glucan, where as the expression of PTGS-2 decreased only with 10 µg/mL. The expression of IL-1-α increased with 20 µg/mL and that of IL-18 increased with 10 µg/mL in OBA-9; the expression of BCL 2, EP 300, and PTGS-2 decreased with the higher dose of ß-glucan. The production of the metabolite 4-aminobutyric acid presented lower concentrations under 20 µg/mL, whereas the concentrations of 2-deoxytetronic acid NIST and oxalic acid decreased at both concentrations used. Acetophenone, benzoic acid, and pinitol presented reduced concentrations only when treated with 10 µg/mL of ß-glucan. CONCLUSIONS: Treatment with ß-glucans positively modulated the immune response and production of metabolites.

Interleukin-18 protects mice from Enterovirus 71 infection.

Previous study has demonstrated that the NLRP3 inflammasome is essential for protecting murine host against Enterovirus 71 (EV71) infection. However, the underlying mechanism remained unknown. Here we discovered that the pleiotropic cytokine interleukin-18 (IL-18), an NLRP3 inflammasome-dependent effector protein, exhibits a protective capability against EV71 challenge. Deficiency of IL-18 in mice exacerbated EV71 infection, which was reflected by increased viral replication, elevated production of interferons (IFN-ß, IFN-γ), proinflammatory cytokines (TNF-α, IL-6) and chemokine CCL2,as well as decreased survival of experimental animals. Conversely, administration of recombinant IL-18 considerably restrained EV71 infection in IL-18 deficient mice. Thus, our results revealed a protective role for IL-18 against EV71 challenge, and indicated a novel therapeutic application for IL-18 in EV71 associated hand, foot, and mouth disease (HFMD).

The IL18 Promoter Polymorphism, rs1946518, Is Associated with the Risk of Periodontitis in Japanese Women: The Kyushu Okinawa Maternal and Child Health Study.

Interleukin-18 (IL-18) is a proinflammatory cytokine that plays an important role in periodontitis and its polymorphisms might modulate the individual susceptibility to periodontitis. Only a limited number of studies on the association between IL18 single-nucleotide polymorphisms (SNPs) and the risk of periodontitis have been realized, however. The aim of this case-control study among young post-partum Japanese women (18 to 45 years) was to determine the impact of SNPs, rs1946518 (-607 C/A) and rs187238 (-137G/C), on periodontitis. The two SNPs may be located within a transcription factor-binding element, thereby influencing transcription from the IL18 promoter. Subjects were 131 cases who had at least one tooth with a probing pocket depth of ≥ 4.0 mm and 1,017 periodontally healthy controls. Probing pocket depth measurements were performed between 1 and 12 months post-partum. In this population, the A allele of rs1946518 and the C allele of rs187238 are more common. After adjustment for age, education, smoking, and use of an interdental brush, compared with subjects with the AA or AC genotype of SNP rs1946518, those with the CC genotype had a significantly reduced risk of periodontitis (adjusted odds ratio = 0.54, 95% confidence interval = 0.29-0.97). No significant association was observed between rs187238 and the risk of periodontitis. Our study did not reveal any evidence of interaction between the IL18 polymorphisms and smoking. Our findings indicate that the IL18 promoter SNP, rs1946518, is a potential risk factor of periodontitis among young Japanese women.

Interleukin-10.rs1800896 and Interleukin-18.rs1946518 gene polymorphisms could not predict the outcome of hepatitis C virus infection in Egyptian patients treated with pegylated interferon plus ribavirin.

A single-nucleotide polymorphism (SNP) in the interleukin (IL)-28B gene was used as a major predictor of the response to treatment in patients with hepatitis C virus (HCV) infection. Data examining the role of IL-10 and IL-18 gene polymorphisms among HCV genotype 4 (G4)-infected Egyptians in response to pegylated interferon (PEG-IFN) plus ribavirin (RBV) therapy are limited. This study investigated the impact of SNP at IL-10.rs1800896 (at position -1082) and IL-18.rs1946518 genes (at position -607) on the response to PEG-IFN/RBV therapy in HCV-infected Egyptians. This study was carried out on 100 HCV patients treated with PEG-IFN plus RBV and 100 healthy controls. The HCV patients included 50 treatment non-responders (NR) and 50 subjects with sustained virologic response (SVR). Genomic DNA from venous blood of subjects was extracted and IL-10.rs1800896 and IL-18.rs1946518 genotypes were determined using allele-specific amplification and SYBR Green real-time PCR. Linkage disequilibrium between the two SNPs was estimated using Haploview software. The frequency of the IL-10.rs1800896 AA, AG and GG genotypes among non-responders were 16 %, 70 % and 14 % while among SVR subjects, the frequency was 34 %, 60 % and 6 %, respectively (p=0.073). On the other hand, the frequency of the IL-18.rs1946518 AA, AC and CC genotypes among non-responders was 14 %, 50 % and 36 %, respectively, while among responders, these frequencies were 28 %, 44 % and 28 %, (p = 0.220). Both markers were in linkage equilibrium (D' = 0.23; r (2) = 0.052). SNPs in the IL-10.rs1800896 and IL-18.rs1946518 genes could not predict the outcome of HCV infection in Egyptians treated with PEG-IFN/RBV.

Altered transcription of inflammation-related genes in dental pulp of coeliac children.

BACKGROUND: Coeliac disease is a chronic small intestinal immune-mediated enteropathy precipitated by exposure to dietary gluten, and possible relationships between coeliac disease and dental pathogenic conditions during childhood have been poorly investigated. AIM: The dental pulp plays a pivotal role in the immune defence against possible entry of pathogens from teeth, and the aim of this work was to investigate quantitative transcription levels of selected genes (IL-9, IL-11, IL-15, IL-18, IL-21, IL-27, MICA, IFN-γ) coding for pro-inflammatory immune innate activities in the pulp of primary teeth from healthy children and children with coeliac disease. DESIGN: The pulp from primary teeth of 10 healthy children and 10 children with coeliac disease was used to extract RNA and prepare cDNA for quantitative PCR transcription analysis employing commercial nucleotide probes for selected genes. RESULTS: In children with coeliac disease, the genes coding for pro-inflammatory cytokines IFN-γ, IL-11, IL-18, and IL-21 were significantly overexpressed, suggesting the possible importance of these cytokines in the relationships between coeliac disease and dental disorders. CONCLUSION: For the first time, we reported in dental pulp of children possible relationships between coeliac disease and modulation in transcription of cytokine-dependent inflammatory activities.

Interleukin-18 promoter polymorphisms and plasma levels are associated with increased risk of periodontitis: a meta-analysis.

OBJECTIVE: Emerging evidence has showed that interleukin-18 (IL-8) promoter polymorphisms and plasma IL-18 levels may be associated with increased risk of periodontitis, but individually published results are inconclusive. The aim of this meta-analysis was to derive a more precise estimation of these associations. METHODS: A literature search of PubMed, Cochrane Library, Embase, Web of Science, SpringerLink, China BioMedicine and China National Knowledge Infrastructure databases was conducted on articles published before April 1st, 2013. Crude odds ratio (OR) or standardized mean difference (SMD) with 95 % confidence intervals (CI) were calculated. RESULTS: Nine case-control studies were included with a total of 576 periodontitis patients and 458 healthy controls. Two common polymorphisms (-607A > C and -137G>C) in the IL-18 gene were addressed. Our meta-analysis results indicated that the C variant of IL-18 -607A>C polymorphism was associated with increased periodontitis risk (C allele vs. A allele: OR = 1.86, 95 % CI: 1.30-2.65, P = 0.001; AC+CC vs. AA: OR = 2.64, 95 % CI: 1.34-5.21, P = 0.005). There was also a significant association between the C variant of IL-18 -137G>C polymorphism and an increased periodontitis risk (C allele vs. G allele: OR = 1.47, 95 % CI: 1.13-1.91, P = 0.004; GC+CC vs. GG: OR = 1.66, 95 % CI: 1.21-2.29, P = 0.002). Furthermore, the mean levels of plasma IL-18 of periodontitis patients were also higher than those of healthy controls (SMD = 1.18, 95 % CI: 0.51-1.85, P = 0.001). CONCLUSION: The current meta-analysis suggests that IL-18 promoter polymorphisms and plasma IL-18 levels are associated with increased risk of periodontitis. IL-18 promoter polymorphisms and elevated plasma IL-18 levels may be useful biomarkers for predicting the development of periodontitis.

Cytokine gene expression profiles during initiation, progression and resolution of periodontitis.

AIM: Variations in the expression of cytokines during the progression of periodontitis remain ill-defined. We evaluated the expression of 19 cytokine genes related to T-cell phenotype/function during initiation, progression and resolution of periodontitis, and related these to the expression of soft and bone tissue destruction genes (TDGs). MATERIALS AND METHODS: A ligature-induced periodontitis model was used in rhesus monkeys (M. mulatta) (n = 18). Gingival tissues were taken at baseline pre-ligation, 2 weeks and 1 month (Initiation) and 3 months (progression) post ligation. Ligatures were removed and samples taken 2 months later (resolution). Total RNA was isolated and the Rhesus Gene 1.0 ST (Affymetrix) used for gene expression analysis. Significant expression changes were validated by qRT-PCR. RESULTS: Disease initiation/progression was characterized by overexpression of Th17/Treg cytokine genes (IL-1ß, IL-6, TGFß and IL-21) and down-regulation of Th1/Th2 cytokine genes (IL-18 and IL-25). Increased IL-2 and decreased IL-10 levels were seen during disease resolution. Several Th17/Treg cytokine genes positively correlated with TDGs, whereas most Th1/Th2 genes exhibited a negative correlation. CONCLUSION: Initiation, progression and resolution of periodontitis involve over- and underexpression of cytokine genes related to various T-helper subsets. In addition, variations in individual T-helper response subset/genes during disease progression correlated with protective/destructive outcomes.

NLRP3 inflammasome plays a critical role in the pathogenesis of hydroxyapatite-associated arthropathy.

The proinflammatory and catabolic cytokine IL-1ß has been implicated in the pathogenesis of osteoarthritis (OA) by mediating synovial inflammation and cartilage degeneration. Although synovial macrophages are suggested to be the source of IL-1ß, the mechanism remains unclear. Ectopic deposition of hydroxyapatite (HA) crystals in joints is closely associated with OA and other arthropathies, but the precise role of HA in arthritis pathogenesis has not been clearly demonstrated. Here we show that HA crystals of a particular size and shape can stimulate robust secretion of proinflammatory cytokines IL-1ß and IL-18 from murine macrophages in a NLRP3 inflammasome-dependent manner. HA-induced inflammasome activation is dependent on potassium efflux, generation of reactive oxygen species (ROS), and lysosomal damage, but independent of cell death. Mice lacking the inflammasome components are protected against HA-induced neutrophilic inflammation in the air-pouch model of synovitis, and they show decreased joint pathology accompanying spontaneous HA deposition in the ank-deficient mouse model of arthritis. Moreover, calcium crystal positive synovial fluids from some OA patients exhibited inflammasome-stimulatory activity in vitro. These results demonstrate that the NLRP3 inflammasome mediates the pathological effect of HA crystals in vitro and in vivo and suggest a critical role for the inflammasome in the pathogenesis of OA.

Role of Th1/Th2 cytokines in serum on the pathogenesis of chronic hepatitis C and the outcome of interferon therapy.

The aim of this study was to investigate the role of T-helper cell (Th)1/Th2 cytokines in the chronicity of hepatitis C virus (HCV) infection and the outcome of interferon (IFN) alpha therapy. A total of 30 patients with chronic hepatitis C were enrolled in the study. The levels of Th1/Th2 cytokines were determined. The differentiation of HCV genotypes was determined by direct sequencing. HCV RNA loads were detected by fluorescence quantitative polymerase chain reaction (qPCR). In chronic hepatitis C, the levels of interleukin (IL)-2 and transforming growth factor (TGF)-ß significantly decreased, and IL-5 and IL-18 levels increased compared with normal controls. The IL-6 serum levels were directly proportional to the serum levels of alanine aminotransferase, and were inversely proportional to the HCV RNA loading levels. Patients with severe hepatitis C had higher levels of IL-4, IL-6, and IL-1ß compared to milder cases. Patients with genotype 1 showed higher serum levels of IL-6 than those with genotype 2. The levels of IL-2 and IL-18 showed a decreasing tendency, whereas TGF-ß, IL-6, and IL-1ß showed an increasing tendency over time. There was no difference in any cytokines detected between the response and nonresponse groups before IFN therapy. However, the IFN-y level increased after IFN therapy in the response group. There was no correlation between the Th1/Th2 cytokine levels in the serum before IFN treatment and in the outcome of IFN therapy. Increasing IFN-y levels in the serum induced by IFN treatment is associated with systemic vascular resistance.

Effects of Lipopolysaccharide from Porphyromonas gingivalis and Escherichia coli on Gene Expression Levels of Toll-like Receptors and Inflammatory Cytokines in Human Dental Pulp Stem Cells.

BACKGROUND: Periodontal diseases originate from a group of oral inflammatory infections initiated by oral pathogens. Among these pathogens, Gram-negative bacteria such as p. gingivalis play a major role in chronic periodontitis. P. gingivalis harbours lipopolysaccharide (LPS) which enables it to attach to TLR2. OBJECTIVES: Evaluating the effects of P. gingivalis and E. coli LPS on the gene expression of TLRs and inflammatory cytokines in human dental pulp stem cells (hDPSCs). METHODS: We evaluated the expression level of TLR2, TLR4, IL-6, IL-10, and 1L-18 in hDPSCs treated with 1µg/mL of P. gingivalis lipopolysaccharide and E. coli LPS at three different exposure times using Real-time RT-PCR. RESULT: The test group treated with P. gingivalis LPS showed a high level of TLR4 expression in 24 hours exposure period and the lowest expression in 48 hours of exposure time. In the case of IL-10, the lowest expression was in the 24 hours exposure period. Although in the E.coli LPS treated group, IL-10 showed the highest expression in 24 and lowest in 48 hours exposure period. Moreover, IL-18 in P. gingivalis LPS treated group showed a significant difference between 6, 24, and 48-time periods of exposure, but not in the E. coli LPS treated group. CONCLUSION: Both types of LPS stimulate inflammation through TLR4 expression. P. gingivalis LPS performs more potentially than E. coli in terms of stimulating inflammation at the first 24 hours of exposure. Nevertheless, our study confirmed that increasing P. gingivalis and/or the E.coli LPS exposure time, despite acting as an inflammatory stimulator, apparently showed anti-inflammatory properties.

Expression and regulation of the NALP3 inflammasome complex in periodontal diseases.

Periodontitis is an infectious process characterized by inflammation affecting the supporting structures of the teeth. Porphyromonas gingivalis is a major oral bacterial species implicated in the pathogenesis of periodontitis. Processing of interleukin (IL)-1 family cytokines is regulated by an intracellular innate immune response system, known as the NALP3 [nacht domain-, leucine-rich repeat-, and pyrin domain (PYD)-containing protein 3] inflammasome complex. The aim of the present study was to investigate by quantitative real-time polymerase chain reaction (PCR) the mRNA expression of NALP3, its effector molecule apoptosis associated speck-like protein (ASC), its putative antagonist NLRP2 (NLR family, PYD-containing protein 2), IL-1beta and IL-18 (i) in gingival tissues from patients with gingivitis (n = 10), chronic periodontitis (n = 18), generalized aggressive periodontitis (n = 20), as well as in healthy subjects (n = 20), (ii) in vitro in a human monocytic cell line (Mono-Mac-6), in response to P. gingivalis challenge for 6 h. The clinical data indicate that NALP3 and NLRP2, but not ASC, are expressed at significantly higher levels in the three forms of inflammatory periodontal disease compared to health. Furthermore, a positive correlation was revealed between NALP3 and IL-1beta or IL-18 expression levels in these tissues. The in vitro data demonstrate that P. gingivalis deregulates the NALP3 inflammasome complex in Mono-Mac-6 cells by enhancing NALP3 and down-regulating NLRP2 and ASC expression. In conclusion, this study reveals a role for the NALP3 inflammasome complex in inflammatory periodontal disease, and provides a mechanistic insight to the host immune responses involved in the pathogenesis of the disease by demonstrating the modulation of this cytokine-signalling pathway by bacterial challenge.

Porphyromonas gingivalis culture supernatants differentially regulate interleukin-1beta and interleukin-18 in human monocytic cells.

Porphyromonas gingivalis is a major bacterial species implicated in chornic periodontitis, a disease characterized by inflammatory destruction of the tooth supporting tissues. Its main virulence factors are lipopolysaccharide (LPS) and gingipains, a group of cysteine proteinases. Interleukin (IL)-18 is a potent pro-inflammatory cytokine with structural similarities to IL-1beta. This study aimed to investigate if P .gingivalis regulates IL-1beta and IL-18 in monocytic cells. Monomac-6 cells were challenged with P. gingivalis culture supernatants. Quantitative real-time PCR and ELISA were used to investigate IL-1beta and IL-18 mRNA expression and protein secretion, respectively. P. gingivalis enhanced IL-1beta and IL-18 mRNA expression, the former being induced earlier, but transiently. IL-18 up-regulation was not affected by P. gingivalis heat-inactivation or chemical inhibition of its gingipains, whereas both treatments resulted in 50% reduction of IL-1beta expression. Purified P. gingivalis LPS enhanced both IL-1beta and IL-18 expression. However, only IL-1beta, but not IL-18, secretion was detected, and was up-regulated by P. gingivalis. In conclusion, although IL-1beta and IL-18 belong to the same cytokine family, their gene expression and secretion are differentially regulated in human monocytic cells in response to P. gingivalis. Therefore, cytokines of the IL-1 family may participate via different pathways in the complex pathogenesis of periodontitis.

TLR4 and IL-18 gene variants in chronic periodontitis: impact on disease susceptibility and severity.

The aim of the study was to assess whether genotypes in the Toll-like receptor 4 gene and in the promoter of the interleukin-18 gene are associated with the susceptibility to chronic periodontitis. 108 chronic periodontitis patients and 76 controls were genotyped for c.896A>G/1196C>T (TLR4 gene) and for c.-368G>C/ c.-838C>A (IL-18 promoter). There were no significant differences in genotype and allele distributions between the study groups. Periodontitis severity in patients with TLR4 c.896AG/1196CT genotype was significantly higher than wildtype carriers. The percentage of teeth with clinical attachment loss > or = 5 mm was 77.3% and 58.8%, respectively (p < or = 0.006, t-test). All subjects were further classified into carriers and non-carriers of at least one variant of each gene. A logistic regression analysis adjusted for gender, smoking, and age showed no association between gene variant carrier status and periodontitis (OR = 1.98, 95% CI 0.61-6.39). The results did not show that IL-18 and TLR4 variants have an effect on the susceptibility to chronic periodontitis. Considering the low number of periodontitis patients carrying TLR4 variants (11%), a comparison of the periodontitis severity depending on the genotype has to be interpreted cautiously.