Expression, polymorphism and methylation pattern of interleukin-6 in periodontal tissues

The Role of Interleukin 6 in Periodontitis and Its Complications

Interleukin 6 (IL-6) is a pleomorphic pro-inflammatory cytokine that is strongly associated with local as well as systemic inflammatory processes. Its role in physiological and pathogenic processes throughout the human body has been the subject of numerous studies in recent years. Measurements of the IL-6 levels in gingival crevicular fluid (GFC), as well as in serum, can be important diagnostic and prognostic factors in periodontal diseases (PD) and in assessing their impact on a range of related inflammatory diseases. This narrative review explores the significant role of IL-6 in patients with periodontitis and its association with other widespread inflammatory pathologies.

METTL3 and METTL14 regulate IL-6 expression via RNA m6A modification of zinc transporter SLC39A9 and DNA methylation of IL-6 in periodontal ligament cells

The inflammatory response is a key process in periodontitis. The N6-methyladenosine (m6A) modification has been proven to be involved in various physiological and pathological processes. This study aims to investigate the role and downstream mechanism of N6-adenosine-enzyme subunits methyltransferase (METTL) 3 and 14 in the inflammatory response of periodontal ligament cells (PDLCs). The total m6A content and the expression of METTL3 and METTL14 were upregulated in lipopolysaccharide (LPS)-stimulated PDLCs. Knockdown of METTL3 or METTL14 suppressed the LPS-induced interleukin (IL)-6 expression, as shown by quantitative polymerase chain reaction (qPCR) and enzyme linked immunosorbent assay (ELISA). Mechanistically, conjoint analysis of m6A sequencing of METTL3-knockdown and METTL14-knockdown PDLCs revealed that the expression of solute carrier family 39 member 9 (SLC39A9) was mediated in a m6A-dependent manner. The suppression of LPS-induced IL-6 by METTL3 or METTL14 knockdown was partially counteracted by SLC39A9 knockdown, which induced downregulation of intracellular zinc via immunofluorescence staining. Amplicon bisulfite sequencing (AmpBS) demonstrated that METTL3/14 knockdown increased the methylation at one position of the IL-6 promoter, while SLC39A9 knockdown decreased it, which was basically consistent with the intracellular zinc concentration and negatively associated with IL-6 expression. Moreover, METTL3 or METTL14 knockdown attenuated the LPS-induced phosphorylation of p38 and JNK mitogen-activated protein kinase (MAPK), which was partially counteracted by SLC39A9 knockdown. These results revealed the "LPS-METTL3/14-SLC39A9-zinc-IL-6" axis and involvement of p38 and JNK MAPK signaling pathway in the inflammatory responses of PDLCs.

The Correlation Between IFNG Gene Methylation and Th1|Th2 Cell Balance in ROU and the Interventional Study of Jiaweidaochi Powder

The pathogenesis of recurrent oral ulcers (ROU) is complex, with a long duration of illness and challenging to cure. According to traditional Chinese medicine (TCM),"heat accumulation in the heart-spleen" is one of the main causative factors. Jiaweidaochi powder (JWDCP) is based on the ancient Chinese medicine formula JWDCS, with the addition of Tongcao and gypsum and the removal of Mu Tong. It is generally used to treat "heat accumulation in the heart-spleen." Previous studies have demonstrated that it effectively reduces recurrence rates and is anti-inflammatory in modulating immunity. The ROU rats' model for JWDCP intervention treatment had been established, and histological tests revealed that JWDCP has a therapeutic effect on the pathological changes in the oral mucosa. In addition, the methylation levels of peripheral blood IFNG gene were detected by bisulfite sequencing PCR (BSP), and the methylation levels of the IFNG promoter region in the model group and each dose group were lower than those in the control group. However, no significant methylation differences were observed. Furthermore, the results of enzyme-linked immunosorbent assay (ELISA) and RNA quantitative polymerase chain reaction showed that JWDCP could reduce IFN-γ and IL-4 protein concentrations, with high GATA-3 mRNA production, T-bet mRNAproduction was upgraded, elevated IL-4 mRNA levels, and reduced IFN-γ mRNA levels after treatment (P < 0.001). The expression of transcription factor T-betmRNA and GATA-3 gene mRNA was accompanied by changes in IFN-γmRNA and IL-4mRNA, demonstrating that Th2 type differentiation in RAS suppresses the body's immunity and that the imbalance of transcription factor expression further leads to Th1/Th2 drift. JWDCP is likely to reduce the protein concentration by regulating the imbalance of transcription factors and enhancing antioxidant capacity, thus achieving therapeutic effects. Treatment of recurrent oral ulcer models is not sufficient to reset IFNG methylation levels, correlating with the refractoriness of ROU, further confirming the complexity of epigenetic mechanisms and that epigenetic alterations in specific mediators may persist locally.

Epigenetics in susceptibility, progression, and diagnosis of periodontitis

Periodontitis is characterized by irreversible destruction of periodontal tissue. At present, the accepted etiology of periodontitis is based on a three-factor theory including pathogenic bacteria, host factors, and acquired factors. Periodontitis development usually takes a decade or longer and is therefore called chronic periodontitis (CP). To search for genetic factors associated with CP, several genome-wide association study (GWAS) analyses were conducted; however, polymorphisms associated with CP have not been identified. Epigenetics, on the other hand, involves acquired transcriptional regulatory mechanisms due to reversibly altered chromatin accessibility. Epigenetic status is a condition specific to each tissue and cell, mostly determined by the responses of host cells to stimulations by local factors, like bacterial inflammation, and systemic factors such as nutrition status, metabolic diseases, and health conditions. Significantly, epigenetic status has been linked with the onset and progression of several acquired diseases. Thus, epigenetic factors in periodontal tissues are attractive targets for periodontitis diagnosis and treatments. In this review, we introduce accumulating evidence to reveal the epigenetic background effects related to periodontitis caused by genetic factors, systemic diseases, and local environmental factors, such as smoking, and clarify the underlying mechanisms by which epigenetic alteration influences the susceptibility of periodontitis.

Biomarkers of Periodontitis and Its Differential DNA Methylation and Gene Expression in Immune Cells: A Systematic Review

The characteristic epigenetic profile of periodontitis found in peripheral leukocytes denotes its impact on systemic immunity. In fact, this profile not only stands for periodontitis as a low-grade inflammatory disease with systemic effects but also as an important source of potentially valuable clinical biomarkers of its systemic effects and susceptibility to other inflammatory conditions. Thus, we aimed to identify relevant genes tested as epigenetic systemic biomarkers in patients with periodontitis, based on the DNA methylation patterns and RNA expression profiles in peripheral immune cells. A detailed protocol was designed following the Preferred Reporting Items for Systematic Review and Meta-analysis -PRISMA guideline. Only cross-sectional and case-control studies that reported potential systemic biomarkers of periodontitis in peripheral immune cell types were included. DNA methylation was analyzed in leukocytes, and gene expression was in polymorphonuclear and mononuclear cells. Hypermethylation was found in TLR regulators genes: MAP3K7, MYD88, IL6R, RIPK2, FADD, IRAK1BP1, and PPARA in early stages of periodontitis, while advanced stages presented hypomethylation of these genes. TGFB1I1, VNN1, HLADRB4, and CXCL8 genes were differentially expressed in lymphocytes and monocytes of subjects with poorly controlled diabetes mellitus, dyslipidemia, and periodontitis in comparison with controls. The DAB2 gene was differentially overexpressed in periodontitis and dyslipidemia. Peripheral blood neutrophils in periodontitis showed differential expression in 163 genes. Periodontitis showed an increase in ceruloplasmin gene expression in polymorphonuclears in comparison with controls. Several genes highlight the role of the epigenetics of peripheral inflammatory cells in periodontitis that could be explored in blood as a source of biomarkers for routine testing.

Influence of epigenetics on periodontitis and peri-implantitis pathogenesis

Periodontitis is a disease characterized by tooth-associated microbial biofilms that drive chronic inflammation and destruction of periodontal-supporting tissues. In some individuals, disease progression can lead to tooth loss. A similar condition can occur around dental implants in the form of peri-implantitis. The immune response to bacterial challenges is not only influenced by genetic factors, but also by environmental factors. Epigenetics involves the study of gene function independent of changes to the DNA sequence and its associated proteins, and represents a critical link between genetic and environmental factors. Epigenetic modifications have been shown to contribute to the progression of several diseases, including chronic inflammatory diseases like periodontitis and peri-implantitis. This review aims to present the latest findings on epigenetic influences on periodontitis and to discuss potential mechanisms that may influence peri-implantitis, given the paucity of information currently available.

Resveratrol decreases local inflammatory markers and systemic endotoxin in patients with aggressive periodontitis

BACKGROUND

Inflammation is hypothesized to contribute to the pathogenesis of periodontitis. Resveratrol (RV) is known for its anti-inflammatory properties. The purpose of this study was to investigate the inhibitory effect of RV on local inflammatory markers and systemic endotoxin in patients with periodontitis.

METHODS

A total of 160 patients with periodontitis were enrolled in this study. The selected patients were randomly divided into four groups and received placebo, high-dose (500 mg/d) of RV (HRV, n = 40), middle-dose (250 mg/d) of RV (middle dose RV (MRV), n = 40) and low-dose (125 mg/d) of RV (low dose RV (LRV), n = 40) with orally administration. All patients received an 8-week treatment. The periodontal status of patients with periodontitis was recorded by using clinical attachment level (CAL), bleeding index (BI), oral hygiene index-simplified (OHI-S), and probing pocket depth (PPD). The levels of inflammatory markers in serum and gingival crevicular fluid (GCF), and systemic levels of endotoxin were evaluated using high sensitivity enzyme-linked immuno sorbent assay.

RESULTS

Outcomes showed that symptoms of periodontitis determined by CAL, BI OHI-S and PPD were improved by RV compared to placebo. RV treatment decreased inflammatory markers in serum and GCF compared to placebo in patient with periodontitis. Systemic endotoxin declined more in the RV group than the placebo-treated group.

CONCLUSION

In conclusion, data in the current study indicate that RV is an efficient drug for the treatment of patients with periodontitis. The findings of the present study find that RV inhibits systemic local inflammatory markers and systemic endotoxin and suggest that 500 mg/d RV is the ideal dose for patients with periodontitis.

A Systematic Review and Meta-Analysis on Multiple Cytokine Gene Polymorphisms in the Pathogenesis of Periodontitis

Aim

Periodontitis is an inflammatory disease that destroys both soft and hard periodontal tissues. However, a complex periodontal cytokine network remains unclear. This systematic review explored multiple cytokine gene polymorphisms in the pathogenesis of periodontitis.

Material and Methods

A systematic search was performed using the databases from previous publications, which indicated the association between cytokine polymorphisms and periodontitis pathogenesis. Meta-analysis was conducted using fixed or randomized models to calculate the significance of multiple cytokine polymorphisms. A total of 147 articles were analyzed with polymorphisms in 12 interleukins [Th1 (IL-2, IFN-γ, and TNF-α), Th2 (IL-4 and IL-13), Th17 (IL-1α, IL-1β, IL-6, and IL-17), and Treg cytokines (IL-10 and TGF-β)]. Doi plot was used to probe the occurrence of publication bias.

Results

The polymorphisms of IL-2 and TNF-α of Th1 cytokine family may be associated with the pathogenesis or the prevention of periodontitis risk, while the polymorphism of IFN-γ is not related to periodontitis risk. The polymorphisms for IL-4 and IL-13 of Th2 cytokine family are not found to be associated with the pathogenesis of periodontitis. For the polymorphisms of the members of Th17 cytokine family, different IL-1α polymorphisms may have inverse actions in the pathogenesis of periodontitis. IL-1β is a noteworthy cytokine biomarker in periodontitis development and progression. IL-6 may have a protective function in the inflammatory responses of periodontitis, and IL-17 has a weak relationship the inflammatory responses. The polymorphisms for the members of Treg cell cytokines may have a protective function against periodontitis risk. LFK indexes show the major asymmetry due to publication bias.

Conclusion

IL-1β is a notable cytokine biomarker in periodontitis risk. Treg cytokines favor an anti-inflammatory and protective environment. Further data are needed to confirm the present conclusion due to publication bias.

Interleukin-6 gene -174G>C promoter polymorphism reduces the risk of periodontitis in Brazilian populations: A meta-analysis

INTRODUCTION

Periodontitis is a multifactorial host-mediated oral disease caused by microbes. Previous studies suggested that interleukin-6 (IL-6) gene promoter polymorphism (-174G > C) are associated with the risk of periodontitis, although the results were inconclusive. This study investigated the association between IL-6 -174G > C polymorphism and susceptibility to periodontitis.

METHOD

A comprehensive search was conducted in PubMed, EMBASE, Web of Science, and Google Scholar databases to retrieve relevant studies. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the strength of the association between 174G > C polymorphism and the risk of periodontitis. Cochrane Q and I² statistics were used to measure heterogeneity between studies. Publication bias was estimated using Begg's funnel plots and Egger's test.

RESULTS

Our results showed significant differences in the allelic (C vs. G: OR = 0.82, CI = 0.65-1.03), recessive (CC vs. GC + GG: OR = 0.69, CI = 0.42-1.13), and dominant (GC + CC vs. GG: OR = 0.85, CI = 0.63-1.13) genetic models of the IL6 -174G > C polymorphism and risk of periodontitis. Further, subgroup analysis showed decreased susceptibility to periodontitis associated with IL6 -174 G > C in a Brazilian population (C vs. G: OR = 0.60, CI = 0.41-0.88; GC + CC vs. GG: OR = 0.57, CI = 0.42-0.78) but not in Asian or Caucasian populations.

CONCLUSION

The findings of this study revealed that the IL6 -174 "C" allele is protective against periodontitis in the Brazilian population.

RISK OF AGE-RELATED MACULAR DEGENERATION IN PATIENTS WITH PERIODONTITIS: A Nationwide Population-Based Cohort Study

PURPOSE

Periodontitis is an inflammatory disease that results in loss of connective tissue and bone support. Evidence shows a possible relationship between periodontitis and age-related macular degeneration (AMD).

METHODS

This population-based cohort study was conducted using data from the National Health Insurance Research Database in Taiwan, with a 13-year follow-up, to investigate the risk of AMD in patients with periodontitis. The periodontitis cohort included patients with newly diagnosed periodontitis between 2000 and 2012. The nonperiodontitis cohort was frequency-matched with the periodontitis cohort by age and sex, with a sample size of 41,661 in each cohort.

RESULTS

Patients with periodontitis had an increased risk of developing AMD compared with individuals without periodontitis (5.95 vs. 3.41 per 1,000 person-years, adjusted hazard ratio = 1.58 [95% confidence interval, 1.46-1.70]). The risk of developing AMD remained significant after stratification by age (adjusted hazard ratio = 1.48 [1.34-1.64] for age <65 years and 1.76 [1.57-1.97] for age ≥65 years), sex (adjusted hazard ratio = 1.40 [1.26-1.55] for women and 1.82 [1.63-2.04] for men), and presence of comorbidity (adjusted hazard ratio = 1.52 [1.40-1.66] for with comorbidity and 1.92 [1.63-2.26] for without comorbidity). In addition, patients with periodontitis showed an increased incidence for both nonexudative type AMD (5.43 vs. 3.13 per 1,000 person-years) and exudative type AMD (0.52 vs. 0.28 per 1,000 person-years).

CONCLUSION

People with periodontitis could be at a greater risk of developing AMD than those without periodontitis. However, we need more evidence to support this association.

Evaluation of the Genetic Association and Methylation of Immune Response Pathway Genes with the Risk of Chronic Periodontitis in the Uighur Population

Aim: The aim of this study was to explore the possible associations between single nucleotide polymorphisms (SNPs) and DNA methylation levels of seven genes in the inflammatory response pathway with susceptibility to chronic periodontitis (CP) among the Uighur population of the Xinjiang Autonomous Region of China. Methods: A total of 444 eligible subjects (279 CP patients and 165 healthy controls) were enrolled in the study. Genomic DNA was obtained from gingival tissue for genotyping eight SNPs and performing methylation measurements of seven genes. Results: SNP rs2070745 in the formyl peptide receptor 1 (FPR1) gene achieved statistical significance in a standard allelic association analysis for CP (p = 0.02). The frequency of the rs2070745 minor allele G was higher in the cases than in controls (0.367 vs. 0.291). Additionally, rs2070745 was significantly associated with CP under the dominant genetic model (p = 0.03). Using logistic regression analysis, rs2070745 was found to be consistently associated with CP under the additive dominant model, and this association remained significant after covariates were taken into account [odds ratio (OR) = 1.49 (1.09-2.05), p = 0.014; OR = 1.58 (1.04-2.40), p = 0.031, respectively]. No significant gene-gene interactions were identified. Although we did not find a polymorphism in interleukin 6 (IL6) associated with CP in our study, the methylation level of a CpG island region located within the promoter region of IL6 was significantly less in CP patients compared with controls (p < 0.05). Conclusions: The genetic polymorphism rs2070745 in FPR1 and the methylation level of the promoter region of IL6 might be associated with CP in the Uighur population of China.

Current advances of epigenetics in periodontology from ENCODE project: a review and future perspectives

BACKGROUND

The Encyclopedia of DNA Elements (ENCODE) project has advanced our knowledge of the functional elements in the genome and epigenome. The aim of this article was to provide the comprehension about current research trends from ENCODE project and establish the link between epigenetics and periodontal diseases based on epigenome studies and seek the future direction.

MAIN BODY

Global epigenome research projects have emphasized the importance of epigenetic research for understanding human health and disease, and current international consortia show an improved interest in the importance of oral health with systemic health. The epigenetic studies in dental field have been mainly conducted in periodontology and have focused on DNA methylation analysis. Advances in sequencing technology have broadened the target for epigenetic studies from specific genes to genome-wide analyses.

CONCLUSIONS

In line with global research trends, further extended and advanced epigenetic studies would provide crucial information for the realization of comprehensive dental medicine and expand the scope of ongoing large-scale research projects.

Cytokines and Their Genetic Polymorphisms Related to Periodontal Disease

Periodontal disease (PD) is a chronic inflammatory disease caused by the accumulation of bacterial plaque biofilm on the teeth and the host immune responses. PD pathogenesis is complex and includes genetic, environmental, and autoimmune factors. Numerous studies have suggested that the connection of genetic and environmental factors induces the disease process leading to a response by both T cells and B cells and the increased synthesis of pro-inflammatory mediators such as cytokines. Many studies have shown that pro-inflammatory cytokines play a significant role in the pathogenesis of PD. The studies have also indicated that single nucleotide polymorphisms (SNPs) in cytokine genes may be associated with risk and severity of PD. In this narrative review, we discuss the role of selected cytokines and their gene polymorphisms in the pathogenesis of periodontal disease.

Epigenetic regulation of inflammation in periodontitis: cellular mechanisms and therapeutic potential

Epigenetic mechanisms, namely DNA and histone modifications, are critical regulators of immunity and inflammation which have emerged as potential targets for immunomodulating therapies. The prevalence and significant morbidity of periodontitis, in combination with accumulating evidence that genetic, environmental and lifestyle factors cannot fully explain the susceptibility of individuals to disease development, have driven interest in epigenetic regulation as an important factor in periodontitis pathogenesis. Aberrant promoter methylation profiles of genes involved in inflammatory activation, including TLR2, PTGS2, IFNG, IL6, IL8, and TNF, have been observed in the gingival tissue, peripheral blood or buccal mucosa from patients with periodontitis, correlating with changes in expression and disease severity. The expression of enzymes that regulate histone acetylation, in particular histone deacetylases (HDACs), is also dysregulated in periodontitis-affected gingival tissue. Infection of gingival epithelial cells, gingival fibroblasts and periodontal ligament cells with the oral pathogens Porphyromonas gingivalis or Treponema denticola induces alterations in expression and activity of chromatin-modifying enzymes, as well as site-specific and global changes in DNA methylation profiles and in histone acetylation and methylation marks. These epigenetic changes are associated with excessive production of inflammatory cytokines, chemokines, and matrix-degrading enzymes that can be suppressed by small molecule inhibitors of HDACs (HDACi) or DNA methyltransferases. HDACi and inhibitors of bromodomain-containing BET proteins ameliorate inflammation, osteoclastogenesis, and alveolar bone resorption in animal models of periodontitis, suggesting their clinical potential as host modulation therapeutic agents. However, broader application of epigenomic methods will be required to create a comprehensive map of epigenetic changes in periodontitis. The integration of functional studies with global analyses of the epigenetic landscape will provide critical information on the therapeutic and diagnostic potential of epigenetics in periodontal disease.

Interaction between and impact of IL-6 genotype and alpha-tocopherol levels on periodontal condition in aging individuals

BACKGROUND AND OBJECTIVES

Few studies have assessed the possible interaction between and impact of IL-6 variants and serum α-tocopherol levels on periodontal condition in older individuals. Here, we assessed the relationship between IL-6 variants and serum α-tocopherol levels on periodontal condition by considering effect modification.

MATERIAL AND METHODS

Among the study participants, 359 who were 71 years of age underwent a dental examination, biochemical analysis, and interview. After dividing the participants into tertiles based on serum α-tocopherol levels, we conducted Poisson regression analysis to compare the prevalence rate ratio (PRR) for periodontal disease markers with the IL-6 genotype (rs1800796) based on each tertile adjusted by the number of teeth present (offset).

RESULTS

The PRRs of the IL-6 genotype for periodontal condition (probing pocket depth [PPD], clinical attachment level [CAL], and bleeding on probing [BOP]) which were adjusted by the number of teeth present (offset) were 1.17 (P < .001), 1.37 (P < .001), and 1.08 (P = .048), respectively. In addition, a significant association was found between the reciprocal number of PRRs of the IL-6 genotype and three serum α-tocopherol levels. The adjusted PRRs (± standard error) of the IL-6 genotypes for PPD were 0.48 (0.12) for the first group (P < .001), 1.54 (0.04) for the second group (P < .001), and 2.11 (0.03) for the third group (P < .001); similar tendencies were seen for CAL and BOP.

CONCLUSION

The results of this study suggest a potential association between the IL-6 genotype and periodontal condition in relation to serum antioxidant concentrations.

The Role of DNA Methylation and Histone Modification in Periodontal Disease: A Systematic Review

Despite a number of reports in the literature on the role of epigenetic mechanisms in periodontal disease, a thorough assessment of the published studies is warranted to better comprehend the evidence on the relationship between epigenetic changes and periodontal disease and its treatment. Therefore, the aim of this systematic review is to identify and synthesize the evidence for an association between DNA methylation/histone modification and periodontal disease and its treatment in human adults. A systematic search was independently conducted to identify articles meeting the inclusion criteria. DNA methylation and histone modifications associated with periodontal diseases, gene expression, epigenetic changes after periodontal therapy, and the association between epigenetics and clinical parameters were evaluated. Sixteen studies were identified. All included studies examined DNA modifications in relation to periodontitis, and none of the studies examined histone modifications. Substantial variation regarding the reporting of sample sizes and patient characteristics, statistical analyses, and methodology, was found. There was some evidence, albeit inconsistent, for an association between DNA methylation and periodontal disease. IL6, IL6R, IFNG, PTGS2, SOCS1, and TNF were identified as candidate genes that have been assessed for DNA methylation in periodontitis. While several included studies found associations between methylation levels and periodontal disease risk, there is insufficient evidence to support or refute an association between DNA methylation and periodontal disease/therapy in human adults. Further research must be conducted to identify reproducible epigenetic markers and determine the extent to which DNA methylation can be applied as a clinical biomarker.

DNA methylation profile of genes related to immune response in generalized periodontitis

BACKGROUND AND OBJECTIVE

Epigenetic events, as the DNA methylation, may be related to development of inflammatory diseases. Due to the important role of host's response in the pathogenesis of periodontitis, the purpose of the present study was to investigate the methylation profile of genes related to immune response in gingival tissues from patients with generalized periodontitis (GP) compared to healthy individuals.

METHODS

Gingival tissues were collected from 20 individuals with GP and 20 healthy individuals. Genomic DNA was extracted and submitted to enzymatic digestions. An initial screening using a panel of genes involved with the response immune was performed in pools containing six samples of each group. Genes that presented different levels of methylation between the groups were selected for individual assays for validation.

RESULTS

The array results showed an unmethylated profile in the majority of genes evaluated in both groups. MALT1, LTB, and STAT5 genes presented a profile of partial methylation in the control compared with GP group. Validation individual assays using a larger number of samples (n = 20, each group) confirmed the hypomethylation of STAT5 in the GP group compared with control group (P < .001).

CONCLUSION

Generalized periodontitis is associated with hypomethylation of the STAT5 gene. Further studies are necessary to evaluate the functional impact these findings.

Effect of Saliva Collection Methods on the Detection of Periodontium-Related Genetic and Epigenetic Biomarkers-A Pilot Study

Different collection methods may influence the ability to detect and quantify biomarker levels in saliva, particularly in the expression of DNA/RNA methylation regulators of several inflammations and tissue turnover markers. This pilot study recruited five participants and unstimulated saliva were collected by either spitting or drooling, and the relative preference for each method was evaluated using a visual analogue scale. Subsequently, total RNA, gDNA and proteins were isolated using the Trizol method. Thereafter, a systematic evaluation was carried out on the potential effects of different saliva collection methods on periodontium-associated genes, DNA/RNA epigenetic factors and periodontium-related DNA methylation levels. The quantity and quality of DNA and RNA were comparable from different collection methods. Periodontium-related genes, DNA/RNA methylation epigenetic factors and periodontium-associated DNA methylation could be detected in the saliva sample, with a similar expression for both methods. The methylation of tumour necrosis factor-alpha gene promoter from drooling method showed a significant positive correlation (TNF α, r = 0.9) with clinical parameter (bleeding on probing-BOP). In conclusion, the method of saliva collection has a minimal impact on detecting periodontium-related genetic and epigenetic regulators in saliva. The pilot data shows that TNF α methylation may be correlated with clinical parameters.

Epigenetics and periodontics: A systematic review

Background

Despite decades of research, our knowledge of several important aspects of periodontal pathogenesis remains incomplete. Epigenetics allows to perform dynamic analysis of different variations in gene expression, providing this great advantage to the static measurement provided by genetic markers. The aim of this systematic review is to analyze the possible relationships between different epigenetic mechanisms and periodontal diseases, and to assess their potential use as biomarkers of periodontitis.

Material and Methods

A systematic search was conducted in six databases using MeSH and non-MeSH terms. The review fulfilled PRISMA criteria (Preferred Reporting Items for Systematic reviews and Meta-analysis).

Results

36 studies met the inclusion criteria. Due to the heterogeneity of the articles, it was not possible to conduct quantitative analysis. Regarding qualitative synthesis, however, it was found that epigenetic mechanisms may be used as biological markers of periodontal disease, as their dynamism and molecular stability makes them a valuable diagnostic tool.

Conclusions

Epigenetic markers alter gene expression, producing either silencing or over-expression of molecular transcription that respond to the demands of the cellular surroundings. Gingival crevicular fluid collection is a non-invasive and simple procedure, which makes it an ideal diagnostic medium for detection of both oral and systemic issues. Although further research is needed, this seems to be a promising field of research in the years to come.

Key words:Epigenetics, periodontitis, DNA methylation, miRNA, epigenetic biomarker, periodontal diseases.

Targeting epigenetic mechanisms in periodontal diseases

Epigenetic factors are heritable genome modifications that potentially impact gene transcription, contributing to disease states. Epigenetic marks play an important role in chronic inflammatory conditions, as observed in periodontal diseases, by allowing microbial persistence or by permitting microbial insult to play a role in the so-called 'hit-and-run' infectious mechanism, leading to lasting pathogen interference with the host genome. Epigenetics also affects the health sciences by providing a dynamic mechanistic framework to explain the way in which environmental and behavioral factors interact with the genome to alter disease risk. In this article we review current knowledge of epigenome regulation in light of the multifactorial nature of periodontal diseases. We discuss epigenetic tagging in identified genes, and consider the potential implications of epigenetic changes on host-microbiome dynamics in chronic inflammatory states and in response to environmental stressors. The most recent advances in genomic technologies have placed us in a position to analyze interaction effects (eg, between periodontal disease and type 2 diabetes mellitus), which can be investigated through epigenome-wide association analysis. Finally, because of the individualized traits of epigenetic biomarkers, pharmacoepigenomic perspectives are also considered as potentially novel therapeutic approaches for improving periodontal disease status.

Association of a placental Interleukin-6 genetic variant (rs1800796) with DNA methylation, gene expression and risk of acute chorioamnionitis

BACKGROUND

Acute chorioamnionitis (aCA), inflammation of the placenta and fetal membranes, is a frequently reported lesion in preterm deliveries. Genetic variants in innate immune system genes such as Interleukin-6 (IL6) may contribute to the placenta's inflammatory response, thus predisposing some pregnancies to aCA. These genetic variants may modulate molecular processes such as DNA methylation and gene expression, and in turn might affect susceptibility to aCA. Currently, there is remarkably little research on the role of fetal (placental) genetic variation in aCA. We aimed to explore the associations between genetic variants in candidate immune-system genes and susceptibility towards inflammatory responses in the placenta, which is linked to a strong inflammatory response in the newborn.

METHODS

DNA samples from 269 placentas (72 aCA cases, 197 non-aCA cases) were collected for this study. Samples were genotyped at 55 ancestry informative markers (AIMs) and 16 additional single nucleotide polymorphisms (SNPs) in 12 candidate innate immune system genes using the Sequenom iPLEX Gold Assay. Publicly available datasets were used to obtain DNA methylation (GSE100197, GSE74738, GSE115508, GSE44667, GSE98224) and gene expression data (GSE44711, GSE98224).

RESULTS

Differences in IL6 placental allele frequencies were associated with aCA (rs1800796, p = 0.04) with the CC genotype specifically implicated (OR = 3.1; p = 0.02). In a subset of the placental samples (n = 67; chorionic villi), we showed that the IL6 SNP (rs1800796) was associated with differential DNA methylation in five IL6-related CpG sites (cg01770232, cg02335517, cg07998387, cg13104385, and cg0526589), where individuals with a CC genotype showed higher DNA methylation levels than individuals carrying the GG genotype. Using two publicly available datasets, we observed that the DNA methylation levels at cg01770232 negatively correlated with IL6 gene expression in the placenta (r = - 0.67, p < 0.004; r = - 0.56, p < 2.937e-05).

CONCLUSIONS

We demonstrated that the minor C allele at the IL6 SNP (rs1800796), which is largely limited to East Asian populations, is associated with the presence of aCA. This SNP was associated with increased DNA methylation at a nearby MEPC2 binding site, which was also associated with decreased expression of IL6 in the placenta. Decreased expression of IL6 may increase vulnerability to microbial infection. Additional studies are required to confirm this association in Asian populations with larger sample sizes.

Impact of antipsychotic treatment on methylation status of Interleukin-6 [IL-6] gene in Schizophrenia

Immunopathogenesis of schizophrenia has emerged as one of the predominant research paradigms in recent times. Based on the altered serum levels as well as gene expression, IL-6 has been considered as a peripheral biomarker of schizophrenia. However, the precise mechanism underlying the altered expression of IL6 in schizophrenia is inadequately known. Given the profound influence of environmental factors on schizophrenia risk, it is important to understand the effect of epigenetic changes on schizophrenia risk. Further, it is not known whether epigenetic changes modulate the expression of IL6 and its subsequent effects on the risk and progression of schizophrenia. In this study, we analysed and compared the methylation status of IL6 promoter sequence from -1200bp to +27bp in antipsychotic-naïve/free schizophrenia patients (N = 47) and matched healthy controls (N = 47) using bisulfite sequencing method. In addition, we also examined the methylation status in these patients at least after 3-months of treatment with antipsychotics (N = 40). At baseline, a state of hypomethylation was observed in the IL6 promoter of schizophrenia subjects in comparison to healthy controls. This state of hypomethylation was shown to be reversed by the administration of antipsychotics. In summary, our observations emphasize a significant role for IL-6 promoter methylation in schizophrenia pathogenesis as well as treatment with antipsychotic medications.

Current Concepts of Epigenetics and Its Role in Periodontitis

Purpose

The focus of this review is to provide an overview of the recent findings on the role of epigenetic mechanisms in periodontal disease, including disease susceptibility, progression, and as potential treatment options.

Recent Findings

The findings on the influence of oral pathogens on epigenetic regulation of pathogen recognition receptors, such as Toll-like receptors, as well as pro-inflammatory cytokines suggest an important role for epigenetics in the regulation of the host immune response. Recent studies also show that the epigenetic pattern in periodontitis lesions differ from that of healthy and gingivitis tissue. In addition, these patterns differ between tissues in the same individual. Research is also indicating a role for both DNA methylation and histone acetylation on cells osteogenic differentiation and bone regeneration.

Summary

Knowledge of epigenetic pattern in periodontal diseases may add not only to the knowledge of susceptibility of the disease but may also be a diagnostic tool to identify patients at risk to develop the severe form of periodontitis. In addition, recent research within gene therapy and tissue engineering indicate a role for epigenetics also to improve regeneration of periodontal tissues.

Epigenetic regulation of inflammation in localized aggressive periodontitis

Background

We have previously demonstrated a Toll-like receptor (TLR)-mediated hyper-responsive phenotype in our cohort of localized aggressive periodontitis (LAP) individuals. However, mechanisms related to this phenotype are still not clear in the literature. The objective of this cross-sectional study is to examine the role of epigenetic regulation, specifically DNA methylation status of genes in the TLR pathway in this cohort. Peripheral blood was collected from 20 LAP patients and 20 healthy unrelated controls. Whole blood was stimulated with 1 μl (100 ng/μl) of purified Escherichia coli lipopolysaccharide (LPS) for 24 h and cyto/chemokines in the supernatants analyzed by Luminex multiplex assays. Genomic DNA extracted from buffy coats prepared from a second tube of whole blood was used for DNA methylation analysis by pyrosequencing of seven TLR signaling genes (FADD, MAP3K7, MYD88, IL6R, PPARA, IRAK1BP1, RIPK2).

Results

Significant differences in the methylation status were observed at specific CpG positions in LAP patients compared to healthy controls and interestingly also between severe and moderate LAP. Specifically, subjects with moderate LAP presented hypermethylation of both the upregulating (MAP3K7, MYD88, IL6R, and RIPK2) and downregulating (FADD, IRAK, and PPARA) genes, while severe LAP presented hypomethylation of these genes. Further analysis on CpG sites with significant differences in methylation status correlates with an increased pro-inflammatory cytokine profile for LAP patients.

Conclusions

Our findings suggest that epigenetic modifications of genes in the TLR pathway may orchestrate the thresholds for balancing induction and prevention of tissue destruction during the course of disease, and thus differ significantly at different stages of the disease, where moderate LAP shows hypermethylation and severe LAP shows hypomethylation of several genes.

Trial registration

https://clinicaltrials.gov, NCT01330719

Subgingival microbiota dysbiosis in systemic lupus erythematosus: association with periodontal status

BACKGROUND

Periodontitis results from the interaction between a subgingival biofilm and host immune response. Changes in biofilm composition are thought to disrupt homeostasis between the host and subgingival bacteria resulting in periodontal damage. Chronic systemic inflammatory disorders have been shown to affect the subgingival microbiota and clinical periodontal status. However, this relationship has not been examined in subjects with systemic lupus erythematosus (SLE). The objective of our study was to investigate the influence of SLE on the subgingival microbiota and its connection with periodontal disease and SLE activity.

METHODS

We evaluated 52 patients with SLE compared to 52 subjects without SLE (control group). Subjects were classified as without periodontitis and with periodontitis. Oral microbiota composition was assessed by amplifying the V4 region of 16S rRNA gene from subgingival dental plaque DNA extracts. These amplicons were examined by Illumina MiSeq sequencing.

RESULTS

SLE patients exhibited higher prevalence of periodontitis which occurred at a younger age compared to subjects of the control group. More severe forms of periodontitis were found in SLE subjects that had higher bacterial loads and decreased microbial diversity. Bacterial species frequently detected in periodontal disease were observed in higher proportions in SLE patients, even in periodontal healthy sites such as Fretibacterium, Prevotella nigrescens, and Selenomonas. Changes in the oral microbiota were linked to increased local inflammation, as demonstrated by higher concentrations of IL-6, IL-17, and IL-33 in SLE patients with periodontitis.

CONCLUSIONS

SLE is associated with differences in the composition of the microbiota, independently of periodontal status.

The integration of epigenetics and genetics in nutrition research for CVD risk factors

There is increasing evidence documenting gene-by-environment (G × E) interactions for CVD related traits. However, the underlying mechanisms are still unclear. DNA methylation may represent one of such potential mechanisms. The objective of this review paper is to summarise the current evidence supporting the interplay among DNA methylation, genetic variants, and environmental factors, specifically (1) the association between SNP and DNA methylation; (2) the role that DNA methylation plays in G × E interactions. The current evidence supports the notion that genotype-dependent methylation may account, in part, for the mechanisms underlying observed G × E interactions in loci such asAPOE, IL6and ATP-binding cassette A1. However, these findings should be validated using intervention studies with high level of scientific evidence. The ultimate goal is to apply the knowledge and the technology generated by this research towards genetically based strategies for the development of personalised nutrition and medicine.

Interleukin-6-174G/C Polymorphism Contributes to Periodontitis Susceptibility: An Updated Meta-Analysis of 21 Case-Control Studies

Introduction. Chronic Periodontitis (CP) is suggested to be related to gene variations. Present study aims to quantitatively estimate the association between interleukin-6- (IL-6-) 174G/C polymorphism and CP susceptibility. Materials and Methods. Pubmed, Embase, and Web of Science were searched up to May 2016. The meta-analyses were performed using STATA 12.0. Results. 21 studies were yielded. Significant associations were found under heterozygote comparison and dominant model in studies fulfilling HWE (GC versus GG: OR = 0.690, 95% CI = 0.560–0.849, P = 0.000; CC + GC versus GG: OR = 0.690, 95% CI = 0.568–0.838, P < 0.001); significant associations were found under heterozygote comparison and dominant model in Caucasian studies fulfilling HWE (GC versus GG: OR = 0.752, 95% CI = 0.577–0.980, P = 0.035; CC + GC versus GG: OR = 0.737, 95% CI = 0.576–0.944, P = 0.016); significant associations were found under allele comparison, heterozygote comparison, and dominant model in Brazilian population (C versus G: OR = 0.648, 95% CI = 0.497–0.845, P = 0.001; GC versus GG: OR = 0.621, 95% CI = 0.441–0.876, P = 0.007; CC + GC versus GG: OR = 0.649, 95% CI = 0.470–0.896, P = 0.009). Conclusion. IL-6 174 polymorphism is associated with CP susceptibility. In Brazilian and Caucasian population, IL-6 174 GG genotype plays as a risk factor to CP.

Preliminary indications of the effect of a brief yoga intervention on markers of inflammation and DNA methylation in chronically stressed women

Yoga is associated with reduced stress and increased well-being, although the molecular basis for these benefits is not clear. Mounting evidence implicates the immune response, with current studies focused on protein immune markers (such as cytokines) in clinical populations. To explore the molecular impact, this pilot study uses a subsample (n=28) from a randomised waitlist control trial investigating the impact of an 8-week yoga intervention in a community population of women reporting psychological distress (N=116). We measured interleukin-6 (IL-6), tumour necrosis factor (TNF) and C-reactive protein (CRP) protein levels, and the DNA methylation of these genes and the global indicator, LINE-1. Correlations between these and psychological variables were explored, identifying moderate correlations with CRP protein levels, and methylation of IL-6, CRP and LINE-1. Many cytokine samples were below detection, however a Mann-Whitney U demonstrated a trend of moderate between-group effect for elevated IL-6 in the yoga group. Methylation analyses applied cross-sectional and non-controlled longitudinal analyses. Waist-to-height ratio and age were covaried. We demonstrated reduced methylation of the TNF region in the yoga group relative to the waitlist control group. No other genes demonstrated a significant difference. Longitudinal analysis further supported these results. This study is one of the first to explore yoga and immunological markers in a non-clinical population, and is the first study to explore DNA methylation. These findings indicate that further research into molecular impact of yoga on markers of immune function is warranted, with larger studies required.

Epigenetics and Periodontitis: A Contemporary Review

Periodontitis is characterized by infection and inflammation of the tooth supporting structures. Few signs of susceptibility and recurrence after treatment are seen due to the outgrowth of various pathogenic microorganisms. Many studies have been done to understand the genetic basis of periodontal disease. An increased risk for periodontitis has been shown with the variations in genes related to the inflammatory response. Interestingly, some of the genes regulated by epigenetic modifications are modified in response to environmental stimuli. Conditions such as cancer, autoimmune or inflammatory diseases have been dispensed by epigenetic mechanisms. The understanding of these molecular mechanisms and the early detection of susceptibility may guide in future periodontal disease treatment and prevention.

Association among interleukin-6 gene polymorphisms, type 2 diabetes mellitus, and chronic periodontitis: a pilot study

AIM

The purpose of this pilot study was to determine the association between single nucleotide polymorphisms (-174 G>C) in the interleukin-6 (IL-6) gene with chronic periodontitis (CP) and type 2 diabetes mellitus (T2DM) in south Indian population.

METHODS

Genomic DNA was obtained from the white blood cells of 30 patients with T2DM, 30 patients with CP, 30 patients with T2DM with CP, and 30 controls. DNA was amplified using polymerase chain reaction with specific primers flanking the locus -174 of the IL-6 gene and further genotyped using the restriction fragment length polymorphism method. The genotype distribution and allele frequencies between the study groups were determined using χ² -test. The relative risk was estimated with a 95% confidence interval.

RESULTS

The CP group (26.7%) displayed a greater percentage of GC genotype (P = 0.026) when compared to the control group (3.3%). A statistically-significant difference in the allele frequencies was found between the control and CP group with the C-allele frequency being greater (0.13) in the CP group than normal controls (0.02).

CONCLUSION

The GC genotype was found to be the risk genotype and the C allele was found to be the risk allele for the development of CP.

Increased expression of interleukin-6 (IL-6) gene transcript in relation to IL-6 promoter hypomethylation in gingival tissue from patients with chronic periodontitis

OBJECTIVE

DNA methylation of the cytokine genes may play a role in the pathogenesis of periodontitis. The aim of this study is to evaluate whether the alteration of interleukin-6 (IL-6) gene promoter methylation in the gingival tissue (GT) and peripheral blood (PB) is unique to chronic periodontitis (CP).

DESIGN

DNA isolated from the GT and PB of 25 patients with (CP) and 20 healthy controls (H) was modified with sodium bisulfite and analyzed for IL-6 promoter methylation with direct sequencing. The levels of IL-6 mRNA and serum IL-6 protein were evaluated by a quantitative reverse transcription polymerase chain reaction and an enzyme-linked immunosorbent assay.

RESULTS

The CP group showed that the overall methylation rates of IL-6 promoter that contained 19 cytosine-guanine dinucleotide (CpG) motifs were significantly decreased in GT in comparison to PB (p<0.001), which was significantly negatively correlated with the probing depth (p=0.003). The GT and PB of the H group displayed similar overall methylation rates. No significant difference was observed in the methylation rates at each CpG in GT in comparison to the PB in both groups. The levels of IL-6 mRNA in the GT and PB and serum IL-6 of the two groups were comparable. The ratio of IL-6 mRNA in the GT relative to the PB was significantly higher in the CP group than in the H group (p=0.03).

CONCLUSION

The increased expression of IL-6 gene transcription may be related to IL-6 promoter hypomethylation in the GT from CP patients.

The effects of omega-3 polyunsaturated fatty acids and genetic variants on methylation levels of the interleukin-6 gene promoter

SCOPE

Omega-3 PUFAs (n-3 PUFAs) reduce IL-6 gene expression, but their effects on transcription regulatory mechanisms are unknown. We aimed to conduct an integrated analysis with both population and in vitro studies to systematically explore the relationships among n-3 PUFA, DNA methylation, single nucleotide polymorphisms (SNPs), gene expression, and protein concentration of IL6.

METHODS AND RESULTS

Using data in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study and the Encyclopedia of DNA Elements (ENCODE) consortium, we found that higher methylation of IL6 promoter cg01770232 was associated with higher IL-6 plasma concentration (p = 0.03) and greater IL6 gene expression (p = 0.0005). Higher circulating total n-3 PUFA was associated with lower cg01770232 methylation (p = 0.007) and lower IL-6 concentration (p = 0.02). Moreover, an allele of IL6 rs2961298 was associated with higher cg01770232 methylation (p = 2.55 × 10(-7) ). The association between n-3 PUFA and cg01770232 methylation was dependent on rs2961298 genotype (p = 0.02), but higher total n-3 PUFA was associated with lower cg01770232 methylation in the heterozygotes (p = 0.04) not in the homozygotes.

CONCLUSION

Higher n-3 PUFA is associated with lower methylation at IL6 promoter, which may be modified by IL6 SNPs.

Age dependent changes in the LPS induced transcriptome of bovine dermal fibroblasts occurs without major changes in the methylome

Background

By comparing fibroblasts collected from animals at 5-months or 16-months of age we have previously found that the cultures from older animals produce much more IL-8 in response to lipopolysaccharide (LPS) stimulation. We now expand this finding by examining whole transcriptome differences in the LPS response between cultures from the same animals at different ages, and also investigate the contribution of DNA methylation to the epigenetic basis for the age-dependent increases in responsiveness.

Results

Age-dependent differences in IL-8 production by fibroblasts in response to LPS exposure for 24 h were abolished by pretreatment of cultures with a DNA demethylation agent, 5-aza-2′deoxycytidine (AZA). RNA-Seq analysis of fibroblasts collected from the same individuals at either 5 or 16 months of age and exposed in parallel to LPS for 0, 2, and 8 h revealed a robust response to LPS that was much greater in the cultures from older animals. Pro-inflammatory genes including IL-8, IL-6, TNF-α, and CCL20 (among many other immune associated genes), were more highly expressed (FDR < 0.05) in the 16-month old cultures following LPS exposure. Methylated CpG island recovery assay sequencing (MIRA-Seq) revealed numerous methylation peaks spread across the genome, combined with an overall hypomethylation of gene promoter regions, and a remarkable similarity, except for 20 regions along the genome, between the fibroblasts collected at the two ages from the same animals.

Conclusions

The fibroblast pro-inflammatory response to LPS increases dramatically from 5 to 16 months of age within individual animals. A better understanding of the mechanisms underlying this process could illuminate the physiological processes by which the innate immune response develops and possibly individual variation in innate immune response arises. In addition, although relatively unchanged by age, our data presents a general overview of the bovine fibroblast methylome as a guide for future studies in cattle epigenetics utilizing this cell type.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1223-z) contains supplementary material, which is available to authorized users.

Adhesion of monocytes to periodontal fibroblasts requires activation of NOD1/2- and TLR4-mediated LFA-1 and VLA-4

OBJECTIVE

The aim of this study was to investigate the roles of nucleotide-binding oligomerization domain-containing protein 1/2 (NOD1/2) and Toll-like receptor 4 (TLR4) in mediating the adhesion of monocytes to periodontal fibroblasts through leucocyte function-associated antigen-1 (LFA-1) and very late antigen-4 (VLA-4).

DESIGN

The expression of NOD1, NOD2, and TLR4 was detected in the gingival tissue of patients with chronic periodontitis by immunohistochemistry. Then the adhesion of cells of human monocytic cell line U937 to human gingival fibroblasts (hGFs) and human periodontal ligament cells (hPDLCs) was investigated after U937 cells were treated with the agonists of NOD1, NOD2, and TLR4 for 24 h, or transfected with small interfering RNAs (siRNAs) targeting NOD1, NOD2, and TLR4 for 48 h. Meanwhile, the expression of LFA-1 and VLA-4 was examined in U937 cells through real-time polymerase chain reaction (PCR), Western blot, and flow cytometry. To confirm the roles of LFA-1 and VLA-4 involved in the process of adhesion, the adhesion blockade assay was performed using the corresponding blocking antibodies against these adhesion molecules.

RESULTS

The immunostaining results showed that NOD1, NOD2, and TLR4 were highly expressed in the gingival tissue of patients with periodontitis, especially in the monocyte-infiltrated area. The activation of these receptors by agonists upregulated the expression of LFA-1 and VLA-4 in U937 cells, and it increased the affinity of U937 cells to hGFs or hPDLCs. On the other hand, knockdown of these receptors by specific siRNAs resulted in the opposite results. In addition, blocking either LFA-1 or VLA-4 in U937 cells significantly attenuated the agonist-triggered adhesion of U937 to periodontal fibroblasts (P<0.001).

CONCLUSIONS

These results suggested that NOD1/2 and TLR4 mediated monocyte-periodontal fibroblast adhesion via the modulation of LFA-1 and VLA-4.

Epigenetics and its role in periodontal diseases: a state-of-the-art review

The immune response to oral bacteria and the subsequent activation of inflammatory signaling is not only dependent on genetic factors. The importance of so-called epigenetic mechanisms presents additional regulatory pathways of genes involved in maintaining chronic inflammation, including gingivitis and periodontitis. The term epigenetics relates to changes in gene expression that are not encoded in the DNA sequence itself and include chemical alterations of DNA and its associated proteins. These changes lead to remodeling of the chromatin and subsequent activation or inactivation of a gene. Epigenetic mechanisms have been found to contribute to disease, including cancer and autoimmune or inflammatory diseases. In this state-of-the art review, the authors provide the latest findings on the involvement of epigenetic modifications in the development of periodontal disease and present emerging therapeutic strategies aimed at epigenetic targets (epidrugs) associated with the disruption of tissue homeostasis and the development of periodontitis.

Origin of galactose-deficient immunoglobulin g in gingival crevicular fluid in periodontitis

BACKGROUND

Periodontitis is a chronic inflammatory disease initiated by a synergistic and dysbiotic microbial community that elicits a gingival inflammatory response leading to tissue breakdown. Periodontitis shares many characteristics with other chronic inflammatory diseases, including abnormal glycosylation of immunoglobulin (Ig)G. The current authors have previously demonstrated that IgG from gingival crevicular fluid (GCF) of patients with chronic periodontitis contains galactose (Gal)-deficient IgG.

METHODS

The origin of the aberrantly glycosylated IgG was determined by measuring levels of Gal-deficient IgG in GCF and serum from patients with periodontitis and non-periodontitis controls using lectin enzyme-linked immunosorbent assay. The Ig-producing cells and the proportion of cells producing Gal-deficient IgG were immunohistochemically determined in gingival tissues from patients with periodontitis by fluorescence microscopy. The results were statistically evaluated and correlated with clinical data.

RESULTS

The results indicate that GCF of patients with periodontitis had higher levels of Gal-deficient IgG compared with controls (P = 0.002). In gingival tissues, IgG was the dominant isotype among Ig-producing cells, and 60% of IgG-positive cells produced Gal-deficient IgG. Moreover, the proportion of Gal-deficient IgG-producing cells directly correlated with clinical parameters of probing depth and clinical attachment loss (AL).

CONCLUSION

These results suggest that the presence of Gal-deficient IgG is associated with gingival inflammation and may play a role in the worsening of clinical parameters of periodontitis, such as AL.

Oral neutrophil transcriptome changes result in a pro-survival phenotype in periodontal diseases

Background

Periodontal diseases are inflammatory processes that occur following the influx of neutrophils into the periodontal tissues in response to the subgingival bacterial biofilm. Current literature suggests that while neutrophils are protective and prevent bacterial infections, they also appear to contribute to damage of the periodontal tissues. In the present study we compare the gene expression profile changes in neutrophils as they migrate from the circulation into the oral tissues in patients with chronic periodontits and matched healthy subjects. We hypothesized that oral neutrophils in periodontal disease patients will display a disease specific transcriptome that differs from the oral neutrophil of healthy subjects.

Methods

Venous blood and oral rinse samples were obtained from healthy subjects and chronic periodontitis patients for neutrophil isolation. mRNA was isolated from the neutrophils, and gene expression microarray analysis was completed. Results were confirmed for specific genes of interest by qRT-PCR and Western Blot analysis.

Results and Discussion

Chronic periodontitis patients presented with increased recruitment of neutrophils to the oral cavity. Gene expression analysis revealed differences in the expression levels of genes from several biological pathways. Using hierarchical clustering analysis, we found that the apoptosis network was significantly altered in patients with chronic inflammation in the oral cavity, with up-regulation of pro-survival members of the Bcl-2 family and down-regulation of pro-apoptosis members in the same compartment. Additional functional analysis confirmed that the percentages of viable neutrophils are significantly increased in the oral cavity of chronic periodontitis patients.

Conclusions

Oral neutrophils from patients with periodontal disease displayed an altered transcriptome following migration into the oral tissues. This resulted in a pro-survival neutrophil phenotype in chronic periodontitis patients when compared with healthy subjects, resulting in a longer-lived neutrophil. This is likely to impact the severity and length of the inflammatory response in this oral disease.

Epigenetic biomarkers: a step forward for understanding periodontitis

Periodontitis is a common oral disease that is characterized by infection and inflammation of the tooth supporting tissues. While its incidence is highly associated with outgrowth of the pathogenic microbiome, some patients show signs of predisposition and quickly fall into recurrence after treatment. Recent research using genetic associations of candidates as well as genome-wide analysis highlights that variations in genes related to the inflammatory response are associated with an increased risk of periodontitis. Intriguingly, some of the genes are regulated by epigenetic modifications, supposedly established and reprogrammed in response to environmental stimuli. In addition, the treatment with epigenetic drugs improves treatment of periodontitis in a mouse model. In this review, we highlight some of the recent progress identifying genetic factors associated with periodontitis and point to promising approaches in epigenetic research that may contribute to the understanding of molecular mechanisms involving different responses in individuals and the early detection of predispositions that may guide in future oral treatment and disease prevention.