Interleukin-21 Expression and Its Association With Proinflammatory Cytokines in Untreated Chronic Periodontitis Patients

Association between periodontitis severity and prostate-specific antigen levels using the NHANES data

BACKGROUND

Periodontitis has been linked to various systemic health conditions. This study investigated whether the association between periodontitis and prostate-specific antigen (PSA) is direct or mediated through intermediary systemic diseases.

METHODS

Three data cycles (2001-2002, 2003-2004, and 2009-2010) from the National Health and Nutrition Examination Survey (NHANES) comprising 12,874 subjects were included, and 3020 male participants were analyzed for demographic information, periodontal health indicators, systemic conditions, PSA, and C-reactive protein (CRP) levels. The severity of periodontitis was assessed based on tooth loss, the 2012 Centers for Disease Control and Prevention (CDC)/American Academy of Periodontology (AAP) severity, the 2017 European Federation of Periodontology (EFP)/AAP Workshop stage, and a composite outcome of stage and open pocket percentage. Multilevel stepwise regression analysis examined the association between periodontitis severity (expressed by staging and open pocket percentage) and total PSA levels. Mediation analysis explored potential mediators affecting PSA levels, such as calcium (Ca) levels, osteoporosis, arthritis, and CRP. Logistic regression models were also used to assess the likelihood of elevated PSA levels based on different thresholds (>2 ng/mL, >2.5 ng/mL, >4 ng/mL). Additionally, the data from a complete follow-up survey of 58 patients from the 2003-2004 cycle were included in the analysis.

RESULTS

The study revealed a marginal association between the composite outcome and total PSA levels (p < 0.05). However, logistic regression failed to establish significant associations between periodontitis indicators and elevated PSA levels. Mediation analysis demonstrated that Ca levels, osteoporosis, arthritis, and CRP did not significantly mediate this relationship. The follow-up revealed that edentulous patients were more likely to require additional prostate therapy.

CONCLUSION

There is a marginal association between periodontitis severity and total PSA levels with no significant mediation through factors such as Ca levels, osteoporosis, arthritis, or CRP. Longitudinally, edentulous patients were more likely to require more invasive prostate therapy in the future.

PLAIN LANGUAGE SUMMARY

Periodontitis is an inflammatory condition known to be associated with systemic health. This study aimed to investigate a potential association between periodontitis and prostate cancer, focusing on levels of prostate-specific antigen (PSA), a marker used in prostate cancer screening. Age, race, periodontitis severity, and open pocket percentage were significantly associated with total PSA levels. However, this increase did not significantly correlate with the defined PSA cutoff points of 2, 2.5, and 4. Additionally, calcium levels, osteoporosis, arthritis, and C-reactive protein levels as potential mediators did not significantly impact this relationship. Moreover, edentulous patients were significantly associated with higher odds of needing further treatment for prostate disease. Hence, while considering cases where periodontal disease may contribute to systemic prostate issues, implementing a dual-therapy strategy that addresses both the local inflammation as well as the systemic effects of periodontal disease might be a more effective approach in the management of these conditions.

The role of acquired host immunity in periodontal diseases

The aim of this narrative review is to relate the contribution of European researchers to the complex topic of the host immune system in periodontal disease, focusing on acquired immunity. Other chapters in this volume will address the genetics and autoantibody responses and other forms of immunity to periodontal disease. While the contribution of European authors is the focus, global literature is included in this descriptive narrative for contextual clarity, albeit many with European co-authors. The topic is relatively intense and is thus broken down into sections outlined below, tackled as descriptive narratives to enhance understanding. Any attempt at a systematic or scoping review was quickly abandoned given the descriptive nature and marked variation of approach in almost all publications. Even the most uniform area of this acquired periodontal immunology literature, antibody responses to putative pathogens in periodontal diseases, falls short of common structures and common primary outcome variables one would need and expect in clinical studies, where randomized controlled clinical trials (RCTs) abound. Addressing 'the host's role' in immunity immediately requires a discussion of host susceptibility, which necessitates consideration of genetic studies (covered elsewhere in the volume and superficially covered here).

Comparative evaluation of serum and gingival crevicular fluid levels of interleukin 21 in periodontally diseased and healthy patients

Background

Periodontitis is an inflammatory reaction to subgingival pathogenic microorganisms that causes gradual deterioration of the gingiva, periodontal ligament, and alveolar bone. Interleukin (IL)-21 is the most recently found member of type I cytokine family that is upregulated during inflammation. The current study aims to investigate the biological plausibility of IL-21 as a biomarker for chronic periodontitis.

Materials and methods

This cross-sectional clinico-biochemical investigation included 15 systemically healthy, 15 periodontally healthy, 15 chronic gingivitis, and 15 chronic periodontitis subjects aged 25 to 60 years. Following subject enrollment, gingival crevicular fluid (GCF) and blood samples were then taken from each subject. The concentration of IL-21 in all samples was determined using enzyme-linked immunosorbent assay (ELISA) kit. The data was examined using the Kruskal-Wallis test and the Spearman correlation test.

Results

Serum IL-21 levels in chronic periodontitis patients were substantially greater than in periodontally healthy individuals. GCF IL-21 levels were substantially greater in gingivitis and chronic periodontitis patients compared to periodontally healthy individuals. In terms of clinical indicators, serum IL-21 levels correlated significantly with bleeding index (BI) in the chronic periodontitis group. In chronic periodontitis group, disease severity as evaluated by probing pocket depth (PPD) and clinical attachment loss (CAL) did not correlate with serum or GCF IL-21 levels.

Conclusion

According to the current study's findings, periodontally involved patients had higher IL-21 levels than periodontally healthy patients, suggesting it can be used as biomarker. Further studies with larger sample size can shed more light on the clinical advantage of IL-21 as a possible marker for disease activity and progression.

Transcriptomic analysis reveals shared gene signatures and molecular mechanisms between obesity and periodontitis

Background

Both obesity (OB) and periodontitis (PD) are chronic non-communicable diseases, and numerous epidemiological studies have demonstrated the association between these two diseases. However, the molecular mechanisms that could explain the association between OB and PD are largely unclear. This study aims to investigate the common gene signatures and biological pathways in OB and PD through bioinformatics analysis of publicly available transcriptome datasets.

Methods

The RNA expression profile datasets of OB (GSE104815) and PD (GSE106090) were used as training data, and GSE152991 and GSE16134 as validation data. After screening for differentially expressed genes (DEGs) shared by OB and PD, gene enrichment analysis, protein-protein interaction (PPI) network construction, GeneMANIA analysis, immune infiltration analysis and gene set enrichment analysis (GSEA) were performed. In addition, receiver operating characteristic (ROC) curves were used to assess the predictive accuracy of the hub gene. Finally, we constructed the hub gene-associated TF-miRNA-mRNA regulatory network.

Results

We identified a total of 147 DEGs shared by OB and PD (38 down-regulated and 109 up-regulated). Functional analysis showed that these genes were mainly enriched in immune-related pathways such as B cell receptor signalling, leukocyte migration and cellular defence responses. 14 hub genes (FGR, MNDA, NCF2, FYB1, EVI2B, LY86, IGSF6, CTSS, CXCR4, LCK, FCN1, CXCL2, P2RY13, MMP7) showed high sensitivity and specificity in the ROC curve analysis. The results of immune infiltration analysis showed that immune cells such as macrophages, activated CD4 T cells and immune B cells were present at high infiltration levels in both OB and PD samples.The results of GeneMANIA analysis and GSEA analysis suggested that five key genes (FGR, LCK, FYB1, LY86 and P2RY13) may be strongly associated with macrophages. Finally, we constructed a TF-miRNA-mRNA regulatory network consisting of 233 transcription factors (TFs), 8 miRNAs and 14 mRNAs based on the validated information obtained from the database.

Conclusions

Five key genes (FGR, LCK, FYB1, LY86, P2RY13) may be important biomarkers of OB and PD. These genes may play an important role in the pathogenesis of OB and PD by affecting macrophage activity and participating in immune regulation and inflammatory responses.

Diagnostic potential of salivary interleukin-17, RANKL, and OPG to differentiate between periodontal health and disease and discriminate stable and unstable periodontitis: A case-control study

Background and Aims

Limitations of the conventional diagnostic techniques urged researchers to seek novel methods to predict, diagnose, and monitor periodontal disease. Use of the biomarkers available in oral fluids could be a revolutionary surrogate for the manual probing/diagnostic radiograph. Several salivary biomarkers have the potential to accurately discriminate periodontal health and disease. This study aimed to determine the diagnostic sensitivity and specificity of salivary interleukin (IL)-17, receptor activator of nuclear factor-κB ligand (RANKL), osteoprotegerin (OPG), RANKL/OPG for differentiating (1) periodontal health from disease and (2) stable and unstable periodontitis.

Methods

Participants with periodontitis (n = 50) and gingivitis (n = 25), both diseases represented the cases, and subjects with healthy periodontium (n = 15) as a control were recruited for this study. Periodontitis cases were further equally subdivided into stable and unstable. Whole unstimulated salivary sample were collected from all participants. Periodontal parameters including bleeding on probing, probing pocket depth, clinical attachment loss, and number of missing teeth were recorded. The protein levels of salivary IL-17, RANKL, and OPG were determined by using enzyme-linked immunosorbent assays technique.

Results

Salivary IL-17, OPG, RANKL, and RANKL/OPG showed high sensitivity and specificity to differentiate periodontal health from gingivitis and periodontitis. Similar pattern was observed in discriminating stable and unstable periodontitis. Salivary IL-17 and RANKL showed a good accuracy to differentiate gingivitis from periodontitis. However, OPG and RANKL/OPG did not exhibit enough sensitivity and specificity to differentiate the latter conditions.

Conclusion

Salivary IL-17, RANKL, OPG, and RANKL/OPG system are potential candidates for differentiating periodontal health and disease and discriminate stable and unstable periodontitis.

Association between Porphyromonas Gingivalis and systemic diseases: Focus on T cells-mediated adaptive immunity

The association between periodontal disease and systemic disease has become a research hotspot. Porphyromonas gingivalis (P. gingivalis), a crucial periodontal pathogen, affects the development of systemic diseases. The pathogenicity of P. gingivalis is largely linked to interference with the host's immunity. This review aims to discover the role of P. gingivalis in the modulation of the host's adaptive immune system through a large number of virulence factors and the manipulation of cellular immunological responses (mainly mediated by T cells). These factors may affect the cause of large numbers of systemic diseases, such as atherosclerosis, hypertension, adverse pregnancy outcomes, inflammatory bowel disease, diabetes mellitus, non-alcoholic fatty liver disease, rheumatoid arthritis, and Alzheimer's disease. The point of view of adaptive immunity may provide a new idea for treating periodontitis and related systemic diseases.

Osteoimmunology in periodontitis; a paradigm for Th17/IL-17 inflammatory bone loss

Periodontitis is a prevalent human disease of inflammation-induced bone destruction. Through studies in patient lesions of rare and common forms of periodontitis and animal model experimentation, Th17/IL-17 related immune pathways have emerged as mediators of disease pathology. In this focused review, we examine mechanisms of induction, amplification and pathogenicity of Th17 cells in periodontitis.

Comparative Evaluation of Gingival Crevicular Fluid Interleukin-17, 18 and 21 in Different Stages of Periodontal Health and Disease

Background and Objectives: The elicitation of a host’s immune−inflammatory responses to overcome oral bacterial biofilm challenges is mediated by numerous cytokines. We explored the role of three such cytokines, viz. interleukin (IL)-17, 18 and 21, by measuring their levels in the gingival crevicular fluid (GCF) of Indian individuals with healthy gingiva, chronic gingivitis, or chronic periodontitis. Materials and Method: Ninety systemically healthy individuals were enrolled in the study on the basis of predefined criteria and were categorized into three groups of 30 participants each. Groups A, B and C were composed of a control group with healthy gingiva, subjects with chronic gingivitis and subjects with chronic periodontitis, respectively. The periodontal disease status was assessed on the basis of a subject’s gingival index, probing pocket depth, clinical attachment loss and radiographic evidence of bone loss. After the complete history-taking and identification of gingival sulcus/pocket depth areas for GCF collection, a sample was collected from each subject in all groups for an estimation of the cytokine levels using ELISA. Statistical analysis was performed using SPSS v 21.0. Intergroup comparisons were conducted using a post hoc Tukey’s test. A value of p < 0.05 was considered to be statistically significant. Results: The mean IL-17, 18 and 21 concentrations in pg/mL was the greatest for Group C (99.67 ± 18.85, 144.61 ± 20.83 and 69.67 ± 12.46, respectively), followed by Group B (19.27 ± 2.78, 22.27 ± 2.43 and 22.74 ± 1.43, respectively) and finally by Group A (healthy control; 11.56 ± 0.99, 17.94 ± 1.24 and 12.83 ± 1.21 respectively). A statistically significant difference in the mean concentrations of two interleukins (IL-17 and IL-18) was observed between Groups A and C and also between Groups B and C. A statistically significant difference in the mean concentrations of IL-21 was observed between Groups B and C. Conclusions: Within the limitations of the present study, the findings revealed that the GCF levels of IL-17, IL-18 and IL-21 rose and correlated well with the severity of the disease. Thus, these cytokines present in GCF have the potential to be considered as biomarkers for periodontal tissue destruction. IL-21 in particular appears to be a promising biomarker for differentiating between gingivitis and periodontitis.

Immunopathogenesis and distinct role of Th17 in Periodontitis: A review

BACKGROUND

Periodontitis is a multifactorial inflammatory disease mediated by the host immune response to dental plaque. Periodontitis is characterized by periodontal bone loss and loss of tooth support. Several studies have corroborated the infiltration of T lymphocytes in periodontitis and correlated the infiltration with chronic inflammation in a dysregulated T cell-mediated immune response. The complexity of the disease has prompted multiple studies aiming to understand T cell-mediated pathogenesis.

HIGHLIGHT

Recent findings have demonstrated the pivotal role of helper T cells in many autoimmune diseases, such as rheumatoid arthritis, which has been conventionally correlated with periodontal bone loss. In contrast, the roles of helper T subsets, Th1, Th2, and particularly Th17, have not been explored. Th17-mediated pathogenesis is a significant aspect of the progression and therapy of periodontitis.

CONCLUSION

In this review, we highlight the complex role of Th17 in the underlying pro-inflammatory cascades mediated by a repertoire of Th17-released molecules and their role in aggravated inflammation in periodontitis. We also summarize recent therapeutics targeting Th17 and related molecules, primarily to ameliorate inflammation and maintain periodontal care.

Interleukin-17 is disease promoting in early stages and protective in late stages of experimental periodontitis

Periodontitis is one of the most common infectious diseases in humans. It is characterized by a chronic inflammation of the tooth-supporting tissue that results in bone loss. However, the role and source of the pro-inflammatory cytokine interleukin-17 (IL-17) and of the cells producing it locally in the gingiva is still controversial. Th17 αβ T cells, CD4⁺ exFoxP3⁺ αβ T cells, or IL-17-producing γδ T cells (γδ17 cells) seem to be decisive cellular players in periodontal inflammation. To address these issues in an experimental model for periodontitis, we employed genetic mouse models deficient for either γδ T cells or IL-17 cytokines and assessed the bone loss during experimental periodontal inflammation by stereomicroscopic, histological, and μCT-analysis. Furthermore, we performed flow-cytometric analyses and qPCR-analyses of the gingival tissue. We found no γδ T cell- or IL-17-dependent change in bone loss after four weeks of periodontitis. Apart from that, our data are complementary with earlier studies, which suggested IL-17-dependent aggravation of bone loss in early periodontitis, but a rather bone-protective role for IL-17 in late stages of experimental periodontitis with respect to the osteoclastogenicity defined by the RANKL/OPG ratio.

Do cytokines associate periodontitis with metabolic disorders? An overview of current documents

Periodontitis is an oral chronic inflammatory condition affecting the adult population worldwide. Many microorganisms act as an initiator for induction of inflammatory immune responses, which participate in the destruction of connective tissue surrounding the teeth and thereby result in tooth loss. Cytokines may have indispensable roles in its pathogenesis through enhancing inflammatory and immune responses. Cytokines can affect functions of some cells of different tissues, such as the cells of the pancreas, liver, and adipose tissues. There is evidence that periodontitis is associated with metabolic disorders, like liver cirrhosis, obesity, and diabetes mellitus. Hence, this review was focused on determining how cytokines can participate in the correlation of periodontitis with metabolic disorders.

The Th17/Treg cell balance: crosstalk among the immune system, bone and microbes in periodontitis

Periodontopathic bacteria constantly stimulate the host, which causes an immune response, leading to host-induced periodontal tissue damage. The complex interaction and imbalance between Th17 and Treg cells may be critical in the pathogenesis of periodontitis. Furthermore, the RANKL/RANK/OPG system plays a significant role in periodontitis bone metabolism, and its relationship with the Th17/Treg cell imbalance may be a bridge between periodontal bone metabolism and the immune system. This article reviews the literature related to the Th17/Treg cell imbalance mediated by pathogenic periodontal microbes, and its mechanism involving RANKL/RANK/OPG in periodontitis bone metabolism, in an effort to provide new ideas for the study of the immunopathological mechanism of periodontitis.

Porphyromonas gingivalis exacerbates ulcerative colitis via Porphyromonas gingivalis peptidylarginine deiminase

Ulcerative Colitis (UC) has been reported to be related to Porphyromonas gingivalis (P. gingivalis). Porphyromonas gingivalis peptidylarginine deiminase (PPAD), a virulence factor released by P. gingivalis, is known to induce inflammatory responses. To explore the pathological relationships between PPAD and UC, we used homologous recombination technology to construct a P. gingivalis strain in which the PPAD gene was deleted (Δppad) and a Δppad strain in which the PPAD gene was restored (comΔppad). C57BL/6 mice were orally gavaged with saline, P. gingivalis, Δppad, or comΔppad twice a week for the entire 40 days (days 0-40), and then, UC was induced by dextran sodium sulfate (DSS) solution for 10 days (days 31-40). P. gingivalis and comΔppad exacerbated DDS-induced colitis, which was determined by assessing the parameters of colon length, disease activity index, and histological activity index, but Δppad failed to exacerbate DDS-induced colitis. Flow cytometry and ELISA revealed that compared with Δppad, P. gingivalis, and comΔppad increased T helper 17 (Th17) cell numbers and interleukin (IL)-17 production but decreased regulatory T cells (Tregs) numbers and IL-10 production in the spleens of mice with UC. We also cocultured P. gingivalis, Δppad, or comΔppad with T lymphocytes in vitro and found that P. gingivalis and comΔppad significantly increased Th17 cell numbers and decreased Treg cell numbers. Immunofluorescence staining of colon tissue paraffin sections also confirmed these results. The results suggested that P. gingivalis exacerbated the severity of UC in part via PPAD.

Effect of probiotic Lactobacillus rhamnosus by-products on gingival epithelial cells challenged with Porphyromonas gingivalis

OBJECTIVE

Probiotics are usually given as living cells, but their effects may be also achieved by postbiotics. We hypothesized that probiotics products (spent media and lysate) altered the response induced by P. gingivalis in gingival epithelial cells (GECS).

METHODS

Immortalized human OBA-9 GECs (∼2,5 × 10⁵cells/well) were challenged with P. gingivalis ATCC33277, and co-infected with L. rhamnosus Lr-32 for 4 h. L. rhamnosus Lr-32 spent medium or cells lysate was added to GECs co-infected with P. gingivalis. Another set of OBA-9 GECs were first exposed to P. gingivalis ATCC 33277 and then to the living probiotic or probiotic products. Transcription of genes encoding inflammatory mediators (IL-1β, TNF-α, IL-6, and CXCL-8) and receptors (TLR2 and TLR4) were evaluated by RT-qPCR. P. gingivalis growth under L. rhamnosus Lr-32 postbiotics was also evaluated.

RESULTS

L. rhamnosus Lr-32 spent media decreased cell viability, while living cells and cell lysates did not. L. rhamnosus Lr-32 lysate, but not spent media, upregulated transcription of inflammatory mediators (IL-1β, TNF-α, IL-6, and CXCL-8) in GECs infected with P. gingivalis. Transcription of TRL2 was upregulated in all experimental groups compared to control, whereas TLR4 was upregulated by the probiotic or its postbiotics in P. gingivalis infected cells. Spent media and lysates reduced the growth of P. gingivalis.

CONCLUSION

L. rhamnosus Lr-32 cell components rather than live probiotic enhanced the expression of inflammatory mediators in P. gingivalis infected gingival epithelial cells. The increased potential of Lr-32 cell lysates to promote immune response to the periodontopathogen may favor pathogen elimination but may also lead to additional deleterious effects of the exacerbated inflammation.

Interleukin-17 induces pyroptosis in osteoblasts through the NLRP3 inflammasome pathway in vitro

OBJECTIVE

Interleukin-17 (lL-17), a pro-inflammatory cytokine produced by Th17 cells, is also considered to play an important role in bone metabolism, but the exact mechanism of bone destruction remains unclear. In this study, we explored whether IL-17 could induce osteoblasts pyroptosis in vitro.

METHODS

The murine primary osteoblasts were isolated from the calvarial bones of mice. The proliferation of osteoblasts was evaluated by cell counting kit-8 (CCK-8) assay. The mRNA levels of NOD-like receptor family pyrin domain containing 3 (NLRP3), apoptosis associated speck like protein containing a card (ASC), caspase-1, gasdermin-D (GSDMD), IL-1β and receptor activator of nuclear factor-kappa B ligand (RANKL) were measured by real-time quantitative PCR. Pyroptosis after IL-17 treatment was evaluated by lactate dehydrogenase (LDH) Release Assay Kit and the morphological characteristics of osteoblasts were observed via Scanning Electron Microscopy (SEM). Pyroptosis associated proteins, cleaved IL-1β and RANKL were evaluated through western blot. The release of IL-1β and RANKL was measured by ELISA. In addition, calcium nodule was tested by alizarin red staining.

RESULTS

High concentration IL-17 (100 ng/mL) could affect the proliferation of osteoblasts, promote the gene expression of NLRP3, caspase-1, GSDMD, IL-1β and RANKL. In contrast to control group, osteoblasts treated with IL-17 had the appearance of numerous pores, swelling and rupture. Also, the release of LDH, IL-1β and RANKL increased in the presence of IL-17. However, inhibition of NLRP3 prevented activation of the NLRP3 inflammasome, thereby restoring osteoblasts morphology and function.

CONCLUSION

IL-17 induced osteoblasts pyroptosis, and the pyroptosis of osteoblasts may prompt the release of IL-1β and RANKL,which may further contribute to disruption of bone metabolism. Besides, the NLRP3 inflammasome pathway was involved in the pyroptosis of osteoblasts.

Evaluation of periodontal status and cytokine/chemokine profile of GCF in patients with severe congenital neutropenia

Severe congenital neutropenia (SCN) is a primary immunodeficiency characterized by defect in neutrophil count. Increased risk of infections in addition to periodontal problems, such as ulcerations of oral mucosa, gingival inflammation, and rapid loss of attachment are common in the course of the disease. The aim of the present study is to define the causal relationship between the severity of periodontal inflammation and severe congenital neutropenia through identification of cytokine profile in gingival crevicular fluid (GCF). A case-control study was performed in patients diagnosed with SCN and healthy controls. Demographic data, the molecular defect, laboratory work-up were gathered from the hospital registry. Periodontal indices were recorded and GCF samples were analyzed using multiplex analysis for the simultaneous measurements of the particular cytokines and chemokines. The present study included 14 patients and 22 control subjects. Both groups were comparable in terms of age and sex. Severity of gingival inflammation measured by the criteria of Löe was higher in the SCN cases (p < 0.05). Moreover, GCF levels of IFN-α, TNF-α, IL-10, IL-13, IL-15, IL-17, IL-2, IL-7, IL-33, IP-10, MIG, MIP-1β were significantly higher in the controls. Decreased cytokine secretion seems to correlate with the decrease in neutrophil counts. The severity of gingival inflammation in SCN patients may be due to the bacterial overgrowth and the change in the content of the oral flora due to the decreased neutrophil counts. Therefore, regular periodontal examinations, the motivation of oral hygiene as well as the compliance with therapy in SCN patients contribute to the periodontal health.

A review of T helper 17 cell-related cytokines in serum and saliva in periodontitis

Periodontitis is a chronic inflammatory disease with a complex underlying immunopathology. Cytokines, as molecular mediators of inflammation, play a role in all stages of disease progression. T helper 17 (Th17) cells are thought to play a role in periodontitis. Th17 cell development and maintenance requires a pro-inflammatory cytokine milieu, with many of the cytokines implicated in the pathogenesis of periodontitis. Serum and saliva are easily accessible biofluids which can represent the systemic and local environment to promote the development of Th17 cells. Here we review human clinical studies that investigate IL-1β, IL-4, IL-6, IL-10, IL-17A, IL-17F, IL-21, IL-22, IL-23, IL-25, IL-31, IL-33, IFN-γ, sCD40L and TNF-α in serum and saliva in periodontitis. We highlight their putative role in the pathogenesis of periodontitis and place them within a wider context of animal and other clinical studies.

The Interrelationship Between Diabetes, IL-17 and Bone Loss

PURPOSE OF REVIEW

Diabetes has a detrimental effect on bone, increasing the risk of fracture and formation of osteolytic lesions such as those seen in periodontitis. Several diabetic complications are caused by diabetes-enhanced inflammation. This review examines mechanisms by which IL-17 contributes to diabetes-enhanced periodontitis and other effects of IL-17 on bone.

RECENT FINDINGS

IL-17 upregulates anti-bacterial defenses, yet its expression is also linked to a destructive host response in the periodontium. Periodontal disease is caused by bacteria that stimulate an inflammatory response. Diabetes-enhanced IL-17 increases gingival inflammation, which alters the composition of the oral microbiota to increase its pathogenicity. In addition, IL-17 can induce osteoclastogenesis by upregulation of TNF and RANKL in a number of cell types, and IL-17 has differential effects on osteoblasts and their progenitors. Increased IL-17 production caused by diabetes alters the pathogenicity of the oral microbiota and can promote periodontal bone resorption.

Roles of Porphyromonas gingivalis and its virulence factors in periodontitis

Periodontitis is an infection-driven inflammatory disease, which is characterized by gingival inflammation and bone loss. Periodontitis is associated with various systemic diseases, including cardiovascular, respiratory, musculoskeletal, and reproductive system related abnormalities. Recent theory attributes the pathogenesis of periodontitis to oral microbial dysbiosis, in which Porphyromonas gingivalis acts as a critical agent by disrupting host immune homeostasis. Lipopolysaccharide, proteases, fimbriae, and some other virulence factors are among the strategies exploited by P. gingivalis to promote the bacterial colonization and facilitate the outgrowth of the surrounding microbial community. Virulence factors promote the coaggregation of P. gingivalis with other bacteria and the formation of dental biofilm. These virulence factors also modulate a variety of host immune components and subvert the immune response to evade bacterial clearance or induce an inflammatory environment. In this chapter, our focus is to discuss the virulence factors of periodontal pathogens, especially P. gingivalis, and their roles in regulating immune responses during periodontitis progression.

Association of A-197G polymorphism in interleukin-17 gene with chronic periodontitis: Evidence from six case-control studies with a computational biology approach

AIM

The aim of the present study was to evaluate the association of interleukin-17 (IL-17) A-197G gene polymorphism with chronic periodontitis (CP) in a case-control study, a meta-analysis, and an in silico approach.

METHODS

In the case-control study, 122 cases with CP and 126 healthy controls were recruited; IL-17 A-197G genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism. In the meta-analysis, comprehensive literature retrieval was performed on valid databases to identify relevant studies. Bioinformatics tools were employed to investigate the effects of A-197G transition on the promoter region of IL-17.

RESULTS

Our case-control study revealed a significant association between IL-17 A-197G transition and CP. The overall meta-analysis revealed significant associations between the IL-17 A-197G polymorphism and CP risk in homozygote co-dominant and recessive models. The stratified analysis also showed a statistically significant association between the mentioned transition and CP risk in the Caucasian population. The in silico analysis revealed that the A-197G polymorphism could make changes in protein-binding sites of the IL-17 promoter region.

CONCLUSIONS

Our study supports that IL-17 A-197G transition could be a genetic risk factor for CP. However, further studies with a larger sample size among different ethnicities are required to obtain a more accurate conclusion.

Interleukin-21 and its association with chronic periodontitis

Context:

Interleukin-21 (IL-21) is a pleiotropic cytokine, well documented to contribute to the development of Th17 cells which have been shown to play an important role in the pathogenesis of periodontitis. Periodontal disease is a chronic infection of tooth-supporting tissue.

Aim:

This study evaluates the saliva and serum levels of IL-21 in patients with chronic periodontitis and periodontally healthy individuals.

Settings and Design:

The present study was carried out in the Department of Microbiology in association with Department of Oral Medicine and Radiology, Maratha Mandal's N.G.H Institute of Dental Sciences and Research Centre, Belgavi, Karnataka.

Materials and Methods:

Fifty samples of each group were included in the present study. The levels of IL-21 were assessed using a commercially available enzyme-linked immunosorbent assay (ELISA) kit and the results were expressed as pg/mL.

Statistical Analysis Used:

Statistical analysis was performed using SPSS 17.0 software. Data were expressed as mean ± standard deviation and interquartile ranges and comparison of controls and cases by Mann–Whitney test.

Results:

Serum and salivary levels of IL-21 were significantly higher in chronic periodontitis group than in controls (P < 0.001). Clinical periodontal parameters correlated positively with serum IL-21 levels.

Conclusions:

IL-21 is highly expressed in patients with chronic periodontitis and correlated well with clinical parameters of periodontal destruction. Therefore, IL-21 appears to play a role in tissue destruction and can be used as diagnostic biomarker in chronic periodontitis. Saliva can be considered to be a useful alternative to serum as a diagnostic sample.

Clinical attachment loss and molecular profile of inflamed sites before treatment

Objective:

To monitor early periodontal disease progression and to investigate clinical and molecular profile of inflamed sites by means of crevicular fluid and gingival biopsy analysis.

Methodology:

Eighty-one samples of twenty-seven periodontitis subjects and periodontally healthy individuals were collected for the study. Measurements of clinical parameters were recorded at day −15, baseline and 2 months after basic periodontal treatment aiming at monitoring early variations ofthe clinical attachment level. Saliva, crevicular fluid and gingival biopsies were harvested from clinically inflamed and non-inflamed sites from periodontal patients and from control sites of healthy patients for the assessment of IL-10, MMP-8, VEGF, RANKL, OPG and TGF-β1 protein and gene expression levels.

Results:

Baseline IL-10 protein levels from inflamed sites were higher in comparison to both non-inflamed and control sites (p<0.05). Higher expression of mRNA for IL-10, RANK-L, OPG, e TGF-β1 were also observed in inflamed sites at day −15 prior treatment (p<0.05). After the periodontal treatment and the resolution of inflammation, seventeen percent of evaluated sites still showed clinically detectable attachment loss without significant differences in the molecular profile.

Conclusions:

Clinical attachment loss is a negative event that may occur even after successful basic periodontal therapy, but it is small and limited to a small percentage of sites. Elevated inflammation markers of inflamed sites from disease patients reduced to the mean levels of those observed in healthy subjects after successful basic periodontal therapy. Significantly elevated both gene and protein levels of IL-10 in inflamed sites prior treatment confirms its modulatory role in the disease status.

T Helper 17 Cells as Pathogenic Drivers of Periodontitis

T helper 17 (Th17) cells were first described as a T helper subset involved in the pathogenesis of experimental autoimmune inflammation. Since then, these cells have been described as orchestrators of immunopathology in several human inflammatory conditions including psoriasis, rheumatoid arthritis, and inflammatory bowel disease. More recently, the crucial role of Th17 cells in the regulation of immunity and protection of barrier sites has been unveiled. In the present work, we review the available evidence regarding Th17 cells in health and disease with a focus on the oral mucosa and their role in periodontitis pathogenesis. Recent mechanistic studies in animal models have demonstrated that interleukin-17A (IL-17A) and Th17 cells are critical mediators for alveolar bone destruction during periodontal inflammation. Observations in a cohort of patients with naturally occurring impaired Th17 cell differentiation supported these findings. However, interventional studies are needed to conclusively implicate Th17 cells in the immunopathogenesis of human alveolar bone and tissue destruction that characterize periodontitis.

Assessment of microRNA-144-5p and its putative targets in inflamed gingiva from chronic periodontitis patients

BACKGROUND AND OBJECTIVE

This study aimed to discover the distinctive MicroRNAs (miRNA) functioning in the pathogenesis of periodontal inflammation, which might be potential therapy targets of chronic periodontitis.

MATERIAL AND METHODS

miRNA profiles of human inflamed gingival tissue from three previous microarrays were re-analysed. Gingival tissues were collected for the validation of overlapping miRNAs, and a network was constructed to show regulatory connection between overlapping miRNAs and periodontitis-associated target genes. Potential miRNAs were screened based on their expression levels and predicted target genes. Correlation analysis and binding site prediction were conducted to reveal the relationship between the potential miRNAs and their target genes.

RESULTS

miR-144-5p, found to be upregulated in all three studies, showed the greatest upregulation (P < 0.0001). Another 16 miRNAs (10 upregulated and six downregulated) overlapped between any two of the three studies. All overlapping miRNAs had expected expression levels except for miR-203 during validation. Ten miRNAs (six upregulated and four downregulated) were found to have periodontal inflammation-associated targets. Cyclooxygenase 2 (COX2) and interleukin-17F (IL17F), predicted target genes of upregulated miR-144-5p, showed significant decreases and were negatively correlated with miR-144-5p in the periodontitis group (r = -0.742 for COX2, r = -0.615 for IL17F).

CONCLUSION

This re-analysis of miRNA signatures has implied the potential regulatory mechanism of miR-144-5p and its potential for exploring alternative therapeutic approaches, especially those that use miRNA delivery systems to treat chronic periodontitis. Nevertheless, further study based on larger sample size and homogenous cells is needed to reveal the exact roles of miRNAs in chronic periodontitis.

Revisiting the Page & Schroeder model: the good, the bad and the unknowns in the periodontal host response 40 years later

In their classic 1976 paper, Page & Schroeder described the histopathologic events and the types of myeloid cells and lymphocytes involved in the initiation and progression of inflammatory periodontal disease. The staging of periodontal disease pathogenesis as 'initial', 'early', 'established' and 'advanced' lesions productively guided subsequent research in the field and remains fundamentally valid. However, major advances regarding the cellular and molecular mechanisms underlying the induction, regulation and effector functions of immune and inflammatory responses necessitate a reassessment of their work and its integration with emerging new concepts. We now know that each type of leukocyte is actually represented by functionally distinct subsets with different, or even conflicting, roles in immunity and inflammation. Unexpectedly, neutrophils, traditionally regarded as merely antimicrobial effectors in acute conditions and protagonists of the 'initial' lesion, are currently appreciated for their functional versatility and critical roles in chronic inflammation. Moreover, an entirely new field of study, osteoimmunology, has emerged and sheds light on the impact of immunoinflammatory events on the skeletal system. These developments and the molecular dissection of crosstalk interactions between innate and adaptive leukocytes, as well as between the immune system and local homeostatic mechanisms, offer a more nuanced understanding of the host response in periodontitis, with profound implications for treatment. At the same time, deeper insights have generated new questions, many of which remain unanswered. In this review, 40 years after Page & Schroeder proposed their model, we summarize enduring and emerging advances in periodontal disease pathogenesis.

Sialidase Deficiency in Porphyromonas gingivalis Increases IL-12 Secretion in Stimulated Macrophages Through Regulation of CR3, IncRNA GAS5 and miR-21

Porphyromonas gingivalis (P. gingivalis) is a major periodontal pathogen that can induce an immune response leading to a destructive inflammatory process. During the inflammatory process, interleukin-12 (IL-12) is secreted, correlating with bacterial clearance by macrophages. Bacterial sialidase has recently been shown to influence the synthesis and modification of the macromolecules on its surface, and is associated with the interaction between bacteria and host cells. We have previously constructed a P. gingivalis sialidase gene mutant strain in P. gingivalis W83 (ΔPG0352) and found that ΔPG0352 showed less pathogenicity than the wild-type strain. In this study, U937-differentiated macrophages were stimulated by P. gingivalis W83, ΔPG0352, or PG0352 complemented strain (comΔPG0352). Transmission electron microscopy showed that P. gingivalis caused a loss of membrane integrity in macrophages and the intracellular bacteria were enclosed within endocytic vacuoles. The expression of both IL-12p35 and IL-12p40 genes and the levels of IL-12p70 were significantly higher in U937 stimulated by ΔPG0352 than in those with P. gingivalis W83 and comΔPG0352. In order to explain why ΔPG0352 induced more IL-12 in macrophages, immunofluorescence assays, PCR arrays, and gene silence or overexpression experiments were carried out. Immunofluorescence assays showed that ΔPG0352 induced lower expression of CR3 in macrophages. After CR3 was suppressed, there were no significant differences in the IL-12p70 levels between macrophages stimulated by P. gingivalis W83, ΔPG0352 or comΔPG0352. PCR array experiments showed that miR-21 and lncRNA GAS5 were differentially expressed between macrophages stimulated by P. gingivalis W83 and ΔPG0352, which had been identified by real-time PCR. The results of CR3 blocking and lncRNA GAS5 gene silence or overexpression showed that the difference in IL-12 levels between P. gingivalis W83 and ΔPG0352 groups was associated with CR3, lncRNA GAS5 and miR-21. Thus it can be concluded that the sialidase-deficient strain is more easily cleared by attenuating CR3 activation, reducing the inhibition of lncRNA GAS5, inducing less miR-21 and more IL-12 in macrophages. These results indicate that inhibiting the activity of sialidase in P. gingivalis will cause rapid clearing by macrophages.

The function of dendritic cells in modulating the host response

Dendritic cells (DCs) are antigen-presenting cells that capture, process, and present antigens to lymphocytes to initiate and regulate the adaptive immune response. DCs detect bacteria in skin and mucosa and migrate into regional lymph nodes, where they stimulate antigen-specific T and B lymphocyte activation and proliferation. DCs direct CD4 T cells to differentiate to T-cell subsets such as T helper cells types 1, 2, and 17, and regulatory T cells. The periodontium is chronically exposed to oral bacteria that stimulate an inflammatory response to induce gingivitis or periodontitis. DCs play both protective and destructive roles through activation of the acquired immune response and are also reported to be a source of osteoclast precursors that promote bone resorption. FOXO1, a member of the forkhead box O family of transcription factors, plays a significant role in the activation of DCs. The function of DCs in periodontal inflammation has been investigated in a mouse model by lineage-specific deletion of FOXO1 in these cells. Deletion of FOXO1 reduces DC protective function and enhances susceptibility to periodontitis. The kinase Akt, phosphorylates FOXO1 to inhibit FOXO activity. Hence the Akt-FOXO1 axis may play a key role in regulating DCs to have a significant impact on periodontal disease.

Basic biology and role of interleukin-17 in immunity and inflammation

Interleukin-17 (also known as interleukin-17A) is a key cytokine that links T-cell activation to neutrophil mobilization and activation. As such, interleukin-17 can mediate protective innate immunity to pathogens or contribute to the pathogenesis of inflammatory diseases, such as psoriasis and rheumatoid arthritis. This review summarizes the basic biology of interleukin-17 and discusses its emerging role in periodontal disease. The current burden of evidence from human and animal model studies suggests that the net effect of interleukin-17 signaling promotes disease development. In addition to promoting neutrophilic inflammation, interleukin-17 has potent pro-osteoclastogenic effects that are likely to contribute to the pathogenesis of periodontitis, rheumatoid arthritis and other diseases involving bone immunopathology. Systemic treatments with anti-interleukin-17 biologics have shown promising results in clinical trials for psoriasis and rheumatoid arthritis; however, their impact on the highly prevalent periodontal disease has not been investigated or reported. Future clinical trials, preferably using locally administered interleukin-17 blockers, are required to implicate conclusivelyinterleukin-17 in periodontitis and, more importantly, to establish an effective adjunctive treatment for this oral inflammatory disease.

IL-17: overview and role in oral immunity and microbiome

Interleukin-17 (IL-17) is a multifaceted cytokine with diverse roles in both immune protection and also immunopathology. IL-17 has a well-recognized role in immune surveillance at mucosal and barrier surfaces, but also has been increasingly implicated as a driver of immunopathology in settings of autoimmunity and chronic inflammation. The current review introduces basic aspects of IL-17 biology and examines the protective and pathogenic roles of IL-17 with a focus on oral mucosal immunity and inflammation. Specific emphasis is given to the role of the IL-17 response as a catalyst in 'shaping the microbiome at the oral barrier'.

Dendritic-cell-derived osteoclasts: a new game changer in bone-resorption-associated diseases

Bone-resorbing cells, osteoclasts (OCs), and antigen-presenting cells, dendritic cells (DCs), share several features. They are derived from a common hematopoietic precursor, exhibit phagocytic activities and their functions are dependent upon receptor activator of nuclear factor κB ligand (RANKL). Upon inflammatory conditions, DCs can transdifferentiate toward functional OCs in the presence of RANKL. It has then been assumed that the increase in proinflammatory cytokines could provide a supportive environment for this transdifferentiation. In this review, we emphasize the molecular mechanisms underlying the potential for DCs to give rise to resorbing OCs in the context of bone-destruction-associated diseases upon inflammatory conditions. Whether these mechanisms reveal new strategies for the discovery of therapeutic targets and drugs is discussed extensively.

The Effect of Periodontitis on Expression of Interleukin-21: A Systematic Review

Purpose. Inflammation and tissue breakdown are led by an array of inflammatory destructive mediators associated with initiation and progression of inflammatory diseases like periodontitis. Current evidence shows that these inflammatory mediators have a definitive role in the pathogenesis of various systemic diseases with an inflammatory component. Interleukin-21 (IL-21) has been associated with systemic diseases like rheumatoid arthritis and Crohn's disease that follow a chronic inflammatory cascade. Similarly recent studies have associated Interleukin-21 levels with periodontitis. This systematic review was aimed to assess the levels of IL-21 in subjects with periodontitis. Methods. A complete literature search was done in PubMed, Medline, Science Direct, and Cochrane databases and Google Scholar based on the inclusion/exclusion criteria. Six relevant articles were procured. Full text was read individually by two reviewers and data extraction was done based on STROBE statement. Results. After data extraction five observational and one interventional study were obtained. All the studies showed an increased expression of IL-21 in periodontitis and the interventional study showed reduction in IL-21 levels after nonsurgical periodontal therapy (NSP). Conclusion. Interleukin-21 levels are higher in periodontitis than controls. With this limited evidence further longitudinal studies are required to consider this as a definitive inflammatory marker.

Inflammatory Mediators of Leprosy Reactional Episodes and Dental Infections: A Systematic Review

Reactional episodes in leprosy are a result of complex interactions between the immune system, Mycobacterium leprae, and predisposing factors, including dental infections. To determine the main inflammatory mediators in the immunopathological process of dental infections and leprosy reactions, we conducted a systematic review of primary literature published between 1996 and 2013. A three-stage literature search was performed (Stage I, "leprosy reactions" and "inflammatory mediators"; Stage II, "dental infections" and "inflammatory mediators"; and Stage III, "leprosy reactions," "dental infections," and "inflammatory mediators"). Of the 911 eligible publications, 10 were selected in Stage I, 68 in Stage II, and 1 in Stage III. Of the 27 studied inflammatory mediators, the main proinflammatory mediators were IL-6, IFN-γ, TNF-α, IL-1β, and IL-17; the main anti-inflammatory mediators were IL-10 and IL-4. Serum IL-6 and TNF-α concentrations were significant during periodontal and reactional lesion evolution; IFN-γ and IL-1β were associated with types 1 and 2 reactions and chronic periodontal disease. The proinflammatory mediators in dental infections and leprosy reactions, especially IL-6 and TNF-α, were similar across studies, regardless of the laboratory technique and sample type. IFN-γ and IL-1β were significant for leprosy reactions and periodontal diseases. This pattern was maintained in serum.

Subcutaneous vaccination with Porphyromonas gingivalis ameliorates periodontitis by modulating Th17/Treg imbalance in a murine model

To date, Porphyromonas gingivalis (P. gingivalis) vaccination has been studied only in animals, and no effective prophylactic human periodontal vaccine has been developed, with the reason for the failure of prophylactic human periodontal vaccines unknown. T helper 17 cell (Th17)/regulatory T (Treg) cell responses play an important role in the development of periodontitis, and a Th17/Treg imbalance causes the pathogenesis of periodontitis. However, whether vaccination with P. gingivalis can prevent periodontitis through modulation of the Th17/Treg imbalance remains unknown. In this study, mice were subcutaneously vaccinated with formalin-killed P. gingivalis and then orally challenged with P. gingivalis. The vaccination protected the mice from alveolar bone resorption and inflammation. These protective effects might be ascribed to downregulation of Th17 cells and interleukin (IL)-17A production, upregulation of Treg and receptor activator of nuclear factor-kappa B ligand (RANKL)(+)CD4(+)T cells, and IL-10 and transforming growth factor-β1 production, and inhibition of lymphocyte proliferation. Our findings may provide a direction for the development of a vaccine or therapy against periodontitis by alteration of the Th17/Treg imbalance.

Association study between salivary levels of interferon (IFN)-gamma, interleukin (IL)-17, IL-21, and IL-22 with chronic periodontitis

OBJECTIVE

To investigate if the salivary levels of IL-17, IL-21, IL-22, and its ratio regarding salivary IFN-γ may be linked with the periodontal clinical status.

DESIGN

One hundred and five chronic periodontitis (CP) subjects and 44 healthy controls (HC) were recruited. Periodontal status was assessed based on full-mouth clinical periodontal measurements. Cytokine salivary levels were analyzed by ELISA. The association between the analytes with CP was analyzed using a binary logistic regression model.

RESULTS

A statistically significant increase in salivary levels of IFN-γ and IFN-γ/IL-22 ratio in CP group could be detected, but there was no significant domination of any Th17 cytokine that could be of predictive value for health/disease status. Univariate and binary logistic regression analyses revealed a strong and independent association of IFN-γ salivary levels and IFN-γ/IL-22 ratio with disease status. An interaction effect of ageing on IFN-γ levels also could be noted.

CONCLUSION

While salivary levels of IFN-γ and IFN-γ/IL-22 ratio may act as strong/independent indicators of the amount and extent of periodontal breakdown, the low detection frequency of Th17 cytokines in saliva samples make these determinations useless for the detection of disease presence and/or its severity.

Simultaneous analysis of T helper subsets (Th1, Th2, Th9, Th17, Th22, Tfh, Tr1 and Tregs) markers expression in periapical lesions reveals multiple cytokine clusters accountable for lesions activity and inactivity status

Previous studies demonstrate that the balance between pro- and anti-inflammatory mediators determines the stable or progressive nature of periapical granulomas by modulating the balance of the osteoclastogenic factor RANKL and its antagonist OPG. However, the cytokine networks operating in the development of periapical lesions are quite more complex than what the simple pro- versus anti-inflammatory mediators' paradigm suggests. Here we simultaneously investigated the patterns of Th1, Th2, Th9, Th17, Th22, Thf, Tr1 and Tregs cytokines/markers expression in human periapical granulomas.

METHODS

The expression of TNF-α, IFN-γ, IL-17A, IL23, IL21, IL-33, IL-10, IL-4, IL-9, IL-22, FOXp3 markers (via RealTimePCR array) was accessed in active/progressive (N=40) versus inactive/stable (N=70) periapical granulomas (as determined by RANKL/OPG expression ratio), and also to compare these samples with a panel of control specimens (N=26). A cluster analysis of 13 cytokine levels was performed to examine possible clustering between the cytokines in a total of 110 granulomas.

RESULTS

The expression of all target cytokines was higher in the granulomas than in control samples. TNF-α, IFN-γ, IL-17A and IL-21 mRNA levels were significantly higher in active granulomas, while in inactive lesions the expression levels of IL-4, IL-9, IL-10, IL-22 and FOXp3 were higher than in active granulomas. Five clusters were identified in inactive lesion groups, being the variance in the expression levels of IL-17, IL-10, FOXp3, IFN-γ, IL-9, IL-33 and IL-4 statistically significant (KW p<0.05). Three clusters were identified in active lesions, being the variance in the expression levels of IL-22, IL-10, IFN-γ, IL-17, IL-33, FOXp3, IL-21 and RANKL statistically significant (KW p<0.05).

CONCLUSION

There is a clear dichotomy in the profile of cytokine expression in inactive and active periapical lesions. While the widespread cytokine expression seems to be a feature of chronic lesions, hierarchical cluster analysis demonstrates the association of TNF-α, IL-21, IL-17 and IFN-γ with lesions activity, and the association of FOXP3, IL-10, IL-9, IL-4 and IL-22 with lesions inactivity.

Correlation of Toll-like receptor 4, interleukin-18, transaminases, and uric acid in patients with chronic periodontitis and healthy adults

BACKGROUND

Because of the potential association between periodontal disease and inflammation, the purpose of the present study is to examine the level of Toll-like receptor 4 (TLR-4), interleukin-18 (IL-18), and uric acid as markers of the inflammatory host response in the plasma and saliva of healthy individuals and patients with periodontitis. In addition, routine biochemical parameters such as fasting glucose, insulin, total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, triglycerides, alanine transaminase (ALT), and aspartate transaminase (AST) were measured. The authors also wanted to check whether patients with chronic periodontitis (CP) exhibit different modulations in salivary and/or plasma concentrations of these parameters compared with clinically healthy individuals.

METHODS

Saliva and plasma samples were collected from 40 patients with CP and 20 healthy individuals. TLR-4 and IL-18 measurements were done using commercially available enzyme-linked immunosorbent assay kits. Total, HDL, and LDL cholesterol; triglycerides; fasting glucose; AST; and ALT levels were analyzed on a biochemistry analysis system using specific kits. Non-parametric tests were used for certain parameters in the statistical analyses because the data did not follow Gaussian distribution.

RESULTS

Significant differences were observed in plasma and salivary TLR-4 and IL-18 levels, along with clinical measurements such as plaque index and probing depth, in patients with CP (P < 0.001). The plasma level of TLR-4 was found to be increased from 0.99 to 3.28 ng/mL in patients with CP. Salivary TLR-4 levels also showed a slightly higher increase in the diseased state (12.44 to 29.97 ng/mL). A significant increase of ≈ 46% was recorded in the plasma IL-18 level. However, salivary IL-18 levels rose up to > 5-fold in the patients with CP compared with healthy individuals. The level of plasma uric acid was found to be highly significantly increased compared with control individuals. HDL cholesterol and triglyceride also showed significant differences (P < 0.02 and P < 0.03, respectively). Plasma glucose, total cholesterol, LDL cholesterol, and insulin levels did not show any significant difference. There was only a slight increase in plasma AST and ALT levels between diseased and healthy states (22.55 versus 25.50 IU/L and 12.35 versus 15.95 IU/L, respectively). However, salivary AST and ALT levels showed a ≈ 6-fold rise in the patients with CP compared with the healthy individuals. Cross-correlation analysis in the periodontitis disease group showed a significant association of plasma AST, salivary AST, and salivary ALT with uric acid level.

CONCLUSIONS

Based on this study, the authors believe that TLR-4, IL-18, and uric acid could have a role in the inflammatory pathology of periodontitis. These parameters are suggested to be useful in the prognosis and diagnosis of CP. However, the mechanistic association of these parameters with inflammatory pathology of patients with periodontitis needs to be further elucidated in a higher number of samples.

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-1β, IL-6, TGFβ 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.

Salivary cytokines and the association between obstructive sleep apnea syndrome and periodontal disease

BACKGROUND

A higher prevalence of periodontal disease has been reported in patients with obstructive sleep apnea syndrome (OSAS), and these two chronic conditions may be linked via inflammatory pathways. The aim of the present study is to evaluate the salivary interleukin (IL)-1β, IL-6, IL-21, IL-33, and pentraxin-3 (PTX3) concentrations in patients with and without OSAS.

METHODS

A total of 52 patients were included in the study. Thirteen individuals were in the control (non-OSAS) group, 17 were in the mild/moderate OSAS group, and 22 were in the severe OSAS group. Clinical periodontal measurements were recorded, and saliva samples were obtained before initiation of periodontal intervention. Enzyme-linked immunosorbent assay was used to determine salivary cytokine concentrations. Data were statistically analyzed using D'Agostino-Pearson omnibus normality, Spearman ρ rank, Kruskal-Wallis, and Dunn tests.

RESULTS

Salivary IL-6 and IL-33 concentrations were similar in the two OSAS groups (P >0.05), which were statistically higher than the control group (P <0.05). IL-1β, IL-21, and PTX3 concentrations were similar in the study groups. The only significant correlation between clinical periodontal parameters and salivary cytokines was found between clinical attachment level (CAL) and IL-21 (P = 0.02). Highly significant correlations were found between probing depth, CAL measures, and indicators of OSAS severity (P <0.01).

CONCLUSIONS

The present findings suggest that OSAS may have an increasing effect on salivary IL-6 and IL-33 concentrations regardless of OSAS severity. Additional investigation is required to elucidate a potential bidirectional relationship between OSAS and periodontal disease.

Oral administration of all-trans retinoic acid suppresses experimental periodontitis by modulating the Th17/Treg imbalance

BACKGROUND

A T-helper 17 (Th17)/regulatory T (Treg) imbalance has been suggested recently to play a role in the development of periodontitis. All-trans retinoic acid (ATRA) has been reported to modulate Th17/Treg imbalances in some diseases. However, the effect of ATRA on periodontitis remains unknown. This study observes the effect of ATRA on Th17/Treg imbalance modulation in experimental periodontitis.

METHODS

Experimental periodontitis was induced in mice by oral infection with Porphyromonas gingivalis (P. gingivalis). ATRA was orally administered every other day. Alveolar bone resorption (ABR) was estimated by measuring the distance from the cemento-enamel junction to the alveolar bone crest. CD4(+) T-cell subsets in the cervical lymph nodes (CLNs) and spleen were analyzed by flow cytometry. Th17/Treg cell-related cytokine messenger ribonucleic acid expression was quantified by real-time reverse transcription-polymerase chain reaction.

RESULTS

The present data shows that ATRA suppressed ABR and inhibited inflammatory cell infiltration into periodontal tissues. These effects were closely associated with reduced CD4(+) retinoid-related orphan receptor γτ(+) cells and increased CD4(+) forkhead box P3(+) cells in the CLNs. Furthermore, ATRA downregulated interleukin (IL)-17A expression and upregulated IL-10 and transforming growth factor-β1 expression in both the CLNs and P. gingivalis-infected gingival tissues.

CONCLUSIONS

These results suggest that ATRA modulation of the Th17/Treg imbalance provides protection against periodontitis by enhancing Treg cell activation and inhibiting Th17 cell activation. These results indicate the potential for clinical prevention of periodontitis.

Periodontal disease: the influence of metabolic syndrome

Metabolic syndrome (MetS) is a cluster of cardiovascular risk factors that include obesity, impaired glucose tolerance or diabetes, hyperinsulinemia, hypertension, and dyslipidemia. Recently, more attention has been reserved to the correlation between periodontitis and systemic health. MetS is characterized by oxidative stress, a condition in which the equilibrium between the production and the inactivation of reactive oxygen species (ROS) becomes disrupted. ROS have an essential role in a variety of physiological systems, but under a condition of oxidative stress, they contribute to cellular dysfunction and damage. Oxidative stress may act as a common link to explain the relationship between each component of MetS and periodontitis. All those conditions show increased serum levels of products derived from oxidative damage, promoting a proinflammatory state. Moreover, adipocytokines, produced by the fat cells of fat tissue, might modulate the balance between oxidant and antioxidant activities. An increased caloric intake involves a higher metabolic activity, which results in an increased production of ROS, inducing insulin resistance. At the same time, obese patients require more insulin to maintain blood glucose homeostasis – a state known as hyperinsulinemia, a condition that can evolve into type 2 diabetes. Oxidation products can increase neutrophil adhesion and chemotaxis, thus favoring oxidative damage. Hyperglycemia and an oxidizing state promote the genesis of advanced glycation end-products, which could also be implicated in the degeneration and damage of periodontal tissue. Thus, MetS, the whole of interconnected factors, presents systemic and local manifestations, such as cardiovascular disease and periodontitis, related by a common factor known as oxidative stress.