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

IL-18 Gene rs187238 and rs1946518 Polymorphisms and Expression in Gingival Tissue in Patients with Periodontitis

Periodontitis is a chronic disease with disturbed balance between the immune and inflammatory response of the host to bacteria. Many studies have shown that proinflammatory cytokines play a significant role in the pathogenesis of periodontal disease. In this study, we examined the association between the IL-18 gene rs187238 and rs1946518 polymorphisms and periodontitis in non-smoking and smoking patients. This study enrolled 200 patients with periodontitis (130 non-smokers and 70 smokers) and 156 control subjects (124 non-smokers and 32 smokers). There were no statistically significant differences in the distribution of the rs187238 and rs1946518 IL-18 genotypes and alleles between patients with periodontitis and control subjects, between smoking patients with periodontitis and smoking control subjects, and between non-smoking patients with periodontitis and non-smoking control subjects. There were no statistically significant differences in clinical parameters in relation to the IL18 rs187238 genotypes. In patients with the IL18 rs1946518 GG genotype, we observed increased values of bleeding on probing (BoP) and periodontal probing depth (PPD), compared to subjects with the TT genotype. In patients with periodontitis, we observed statistically significant decreased expression of the IL-18 gene in comparison with healthy subjects (0.231 ± 0.163 vs. 0.663 ± 0.197, p = 0.0008). In addition, the IL-18 gene expression in gingival tissue in patients with periodontitis correlated positively with the number of remaining teeth. The results of our study suggest that the IL-18 rs187238 and rs1946518 polymorphisms are not significant risk indicators of periodontitis in our population. However, in patients with the IL18 rs1946518 GG genotype, we observed increased values of BoP and PPD, compared to subjects with the TT genotype. In addition, in gingival tissue of patients with periodontitis, we have detected decreased expression of IL-18. The gingival expression of IL-18 in patients with periodontitis correlated positively with number of remaining teeth. The above results suggest that IL-18, in addition to its pro-inflammatory effects in periodontal disease, may also exhibit protective properties.

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

AIM

The aim of the study was to evaluate the association of IL-18 137 G > C, 607 C > A gene polymorphism in Uyghur population with chronic periodontitis (CP) and combine the results with the meta-analysis.

METHODS

In a case-control study, 200 cases with CP and 100 healthy controls were recruited; IL-18 137 G > C, 607 C > A genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). In the meta-analysis, we used electronic databases, including CNKI, Wan Fang, PubMed, EMBASE databases etc.to obtain relevant research published through June 2020. Studies were considered eligible if odds ratios (ORs) and 95% confidence intervals (95% CI) were provided or calculated from the given data. The size of the combined effect was calculated using STATA 15.0.

RESULTS

Our study revealed significant association between CP and IL-18 137 G > C (P = .045, OR = 1.67), 607 C > A (P = .045, OR = 1.67). The overall meta-analysis revealed significant associations between IL-18 137 G > C polymorphism and CP risk in Allele, dominant, co-dominant and recessive genetic models. The subgroup analysis also showed a significant association between the IL-18 137 G > C and risk for periodontitis and aggressive periodontitis in the Asian (GC+ CC VS. GG: P = .047, OR = 1.64,95%CI = 1.01-2.68).

CONCLUSIONS

IL-18 137 G > C, 607 C > A could be associated with susceptibility to periodontitis in Uyghur population. Further case-control of candidate genes studies targeting larger sample sizes and different ethnic groups are needed to arrive more accurate conclusions.

The Influence of TLR4, CD14, OPG, and RANKL Polymorphisms in Periodontitis: A Case-Control Study

The pathogenesis of periodontitis involves a complex interaction between the microbial challenge and the host immune response. The individual immunoinflammatory response has a great contribution in the pathogenesis of the disease and becomes a trigger in the process of bone remodeling which is a characteristic of the disease. Thus, the aim of this study was to evaluate the influence of the TLR4 A896G (rs4986790), TLR4 C1196T (rs4986791), CD14 C-260T (rs2569190), RANKL (TNFSF11, rs2277438), and OPG (TNFSF11B C163T, rs3102735) polymorphisms in periodontitis. A case-control study was conducted on patients with periodontitis (N = 203) and controls (N = 213) over 30 years of age, without diabetes mellitus, acute infections, and osteoarthritis, and patients without aggressive periodontitis, i.e., stage IV and C degree of periodontitis, and any periodontal treatment performed in the last 6 months. Genotypes were determined by the PCR-RFLP and sequencing method. The frequency comparisons between case and controls were performed using the chi-square test and logistic regression (OpenEpi and SNPStats software). The risk (OR) was evaluated for values of P < 0.05. Differences in TLR4, CD14, RANKL, and OPG genotype and allele frequency distributions were not observed between patients and controls. However, some variants were a risk factor for the development of periodontitis when considering gender and smoking habits. The TLR4 896 A/G genotype was a risk factor for periodontitis in males (OR = 2.86), and the TLR4 1196C/C genotype was a risk factor for nonsmoking males (OR = 1.85) when compared to women. The RANKL A/A and the OPG T/C genotype was associated with the risk of the disease in nonsmoking men compared to nonsmoking women with the same genotype (OR = 1.96 and OR = 2.9, respectively). In conclusion, TLR4, CD14, RANKL, and OPG variants were not associated with periodontitis. However, TLR4, RANKL, and OPG polymorphisms could be a risk for periodontitis in males regardless of smoking habits.

TLR4 polymorphism and periodontitis susceptibility: A meta-analysis

BACKGROUND

Many primary and secondary studies reported the association between Toll-like receptor 4 (TLR4) polymorphism and periodontitis susceptibility, which mainly focused on TLR4-299A>G or TLR4-399C>T of Caucasian, however, these studies had different conclusions. The aim of this study was to reassess relative studies about TLR4 polymorphism and periodontitis susceptibility, and update meta-analysis.

METHODS

We searched the electronic database including CNKI (Chinese National Knowledge Infrastructure), PubMed, Embase, and hand searched relative studies until January 4, 2016. Two authors selected studies according to inclusion and exclusion criteria, assessed studies using Newcastle-Ottawa Scale case control study (NOS), and calculated the combined effect size using STATA software, version 12.0.

RESULTS

This meta-analysis included 18 studies, containing 2453 healthy participants and 2987 patients with chronic periodontitis (CP) and 462 patients with aggressive periodontitis (AP). There was a significance between TLR4C>G (rs7873784) allele and CP in Asian, and its recessive model was also significant (for C vs G: odds ratio [OR] = 0.72, 95% confidence interval [CI] = 0.54-0.95, I = 0%; for CC + CG vs GG: OR = 0.66, 95% CI = 0.49-0.89, I = 0%). However, we did not detect any significant relevance between other TLR4 polymorphism and periodontitis susceptibility in overall and subgroup analyses. The sensitive analysis showed that dropping any single studies did not affect the pooled-analysis results. Publication bias was not detected.

CONCLUSIONS

The meta-analysis found association between TLR4C>G (rs7873784) allele and CP in Asian and it may passed on to offsprings in the form of recessiveness. However, further studies about the association between TLR4C>G (rs7873784) and CP is warranted to confirm.

Genetic polymorphisms in pattern recognition receptors and risk of periodontitis: Evidence based on 12,793 subjects

Pattern recognition receptors (PRRs) constitute a pivotal arm of innate immunity. Many studies investigated the association between PRRs polymorphisms and periodontitis risk, which showed inconclusive results. The aim of the meta-analysis was to evaluate the precise association between five widely-evaluated polymorphisms (CD14 -260C/T (rs2569190), Toll-like receptor (TLR) 2 2408G/A (rs5743708), TLR4 896A/G (rs4986790), TLR4 1196C/T (rs4986791), mannose-binding lectin (MBL) codon 54 (rs1800450)) within the PRRs and susceptibility to either chronic (CP) or aggressive periodontitis (AgP). Overall, no significant association was found for the PRRs polymorphisms with either CP or AgP. In the subgroup analyses, TLR4 896G and 1196T alleles yielded a 32% (OR=1.32, 95% CI: 1.04-1.68) and a 37% increased CP risk (OR=1.37, 95% CI: 1.05-1.80) in Caucasians, respectively. Further stratified analyses revealed links between CD14, MBL2 polymorphisms and the severity of CP. This meta-analysis suggested that the periodontitis susceptibility was partly controlled by PRRs polymorphisms involved in the innate immunity.

The role of TLR4 896 A>G and 1196 C>T in susceptibility to infections: a review and meta-analysis of genetic association studies

Background

Toll-like receptor 4 plays a role in pathogen recognition, and common polymorphisms may alter host susceptibility to infectious diseases.

Purpose

To review the association of two common polymorphisms (TLR4 896A>G and TLR4 1196C>T) with infectious diseases.

Data Sources

We searched PubMed and EMBASE up to March 2013 for pertinent literature in English, and complemented search with references lists of eligible studies.

Study Selection

We included all studies that: reported an infectious outcome; had a case-control design and reported the TLR4 896A>G and/or TLR4 1196C>T genotype frequencies; 59 studies fulfilled these criteria and were analyzed.

Data Extraction

Two authors independently extracted study data.

Data Synthesis

The generalized odds ratio metric (OR_G) was used to quantify the impact of TLR4 variants on disease susceptibility. A meta-analysis was undertaken for outcomes reported in >1 study. Eleven of 37 distinct outcomes were significant. TLR4 896 A>G increased risk for all parasitic infections (OR_G 1.59; 95%CI 1.05-2.42), malaria (1.31; 95%CI 1.04-1.66), brucellosis (2.66; 95%CI 1.66-4.27), cutaneous leishmaniasis (7.22; 95%CI 1.91-27.29), neurocysticercosis (4.39; 95%CI 2.53-7.61), Streptococcus pyogenes tonsillar disease (2.93; 95%CI 1.24-6.93) , typhoid fever (2.51; 95%CI 1.18-5.34) and adult urinary tract infections (1.98; 95%CI 1.04-3.98), but was protective for leprosy (0.36; 95%CI 0.22-0.60). TLR4 1196 C>T effects were similar to TLR4 896 A>G for brucellosis, cutaneous leishmaniasis, leprosy, typhoid fever and S. pyogenes tonsillar disease, and was protective for bacterial vaginosis in pregnancy (0.55; 95%CI 0.31-0.98) and Haemophilus influenzae tonsillar disease (0.42; 95%CI 0.17-1.00). The majority of significant associations were among predominantly Asian populations and significant associations were rare among European populations.

Conclusions

Depending on the type of infection and population, TLR4 polymorphisms are associated with increased, decreased or no difference in infectious disease. This may be due to differential functional expression of TLR4, the co-segregation of TLR4 variants or a favorable inflammatory response.

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.

Epigenetic regulation of human β-defensin 2 and CC chemokine ligand 20 expression in gingival epithelial cells in response to oral bacteria

Gingival epithelia utilize multiple signaling pathways to regulate innate immune responses to various oral bacteria, but little is understood about how these bacteria alter epithelial epigenetic status. In this study we report that DNA methyltransferase (DNMT1) and histone deacetylase expression were decreased in gingival epithelial cells treated with oral pathogen Porphyromonas gingivalis and nonpathogen Fusobacterium nucleatum. Pretreatment with trichostatin A and sodium butyrate, which increase acetylation of chromatin histones, significantly enhanced the gene expression of antimicrobial proteins human β-defensin 2 (hBD2) and CC chemokine ligand 20 (CCL20) in response to both bacterial challenges. Pretreatment with DNMT inhibitor 5'-azacytidine increased hBD2 and CCL20 expression in response to F. nucleatum, but not to P. gingivalis. Furthermore, we observed a differential pattern of protein levels of H3K4me3, which has been associated with chromatin remodeling and activation of gene transcription, in response to P. gingivalis vs. F. nucleatum. This study provides a new insight into the bacteria-specific innate immune responses via epigenetic regulation.

What do 'omic technologies have to offer periodontal clinical practice in the future?

BACKGROUND AND OBJECTIVE

Periodontal diseases are the most common chronic inflammatory diseases of humans and a major cause of tooth loss. Inflammatory periodontitis is also a complex multifactorial disease involving many cell types, cell products and interactions. It is associated with a dysregulated inflammatory response, which fails to resolve, and which also fails to re-establish a beneficial periodontal microbiota. There is a rich history of biomarker research within the field of periodontology, but exemplary improvements in analytical platform technologies offer exciting opportunities for discovery. These include the 'omic technologies, such as genomics, transcriptomics, proteomics and metabolomics, which provide information on global scales that can match the complexity of the disease. This narrative review focuses on the recent advances made in in vivo human periodontal research by use of 'omic technologies.

MATERIAL AND METHODS

The Medline database was searched to identify articles currently available on 'omic technologies with regard to periodontal research.

RESULTS

One hundred and sixty-one articles focusing on biomarkers of and 'omic advances in periodontal research were analysed for their contributions to the understanding of periodontal diseases.

CONCLUSION

The data generated by the use of 'omic technologies have huge potential to inform paradigm shifts in our understanding of periodontal diseases, but data management, analysis and interpretation require a thoughtful and systematic bioinformatics approach, to ensure meaningful conclusions can be made.

Genetic factors responsible for long bone fractures non-union

INTRODUCTION

Approximately 10-15% of all fractures of long bones heal with delay, prolonged immobilization and repetitive operative interventions. Despite intense investigations, the pathomechanism of impaired healing of skeletal tissue remains unclear. An important role in the pathomechanism of mal-union of close fractures plays subclinically proceeding infections.

AIM

The question arises whether colonization and proliferation of bacteria in the fracture gap could be related to the mutation of genes for factors regulating local antimicrobial response, such as pathogen recognizing receptors (PRR), cytokines and chemokines.

METHODS

We carried out studies in patients with delayed long bone fractures estimating the frequency of mutation of genes crucial for pathogen recognition (TLR2, TLR4 and CD14), and elimination (CRP, IL-6, IL-1ra), as well as wound healing (TGF-β). The molecular milieu regulating healing process (IGF-1, COLL1a, TGF-β, BMP-2, and PDGF) was validated by Western blot analysis of the gap tissue.

RESULTS

Microbiological investigations showed the presence of viable bacterial strains in 34 out of 108 gaps in patients with non-healing fractures (31.5%) and in 20 out of 122 patients with uneventful healing (16.4%) (P < 0.05). The occurrence of mutated TLR4 1/W but not 2/W gene was significantly higher (P < 0.05) in the non-healing infected than sterile group. In the non-healing infected group 1/W mutated gene frequency was also higher than in healing infected. In the TGF-β codon 10 a significantly higher frequency of mutated homozygote T and heterozygote C/T in the non-healing infected versus non-healing sterile subgroup was observed (P < 0.05). Similar difference was observed in the non-healing infected versus healing infected subgroup (P < 0.05). The CRP (G1059C), IL1ra (genotype 2/2), IL-6 (G176C), CD14 (G-159T), TLR2 (G2259A) and TLR4/2 (Thr399Ile) polymorphisms did not play evident role in the delay of fracture healing.

CONCLUSIONS

Individuals bearing the mutant TLR 4 gene 1/W (Asp299Gly) and TGF-β gene codon 10 mutant T and T/C allele may predispose to impaired pathogen recognition and elimination, leading to prolonged pathogen existence in the fracture gaps and healing delays.