Mannose-binding lectin gene polymorphism in relation to periodontal infection

DAMPs and alarmin gene expression patterns in aging healthy and diseased mucosal tissues

Introduction

Periodontitis is delineated by a dysbiotic microbiome at sites of lesions accompanied by a dysregulated persistent inflammatory response that undermines the integrity of the periodontium. The interplay of the altered microbial ecology and warning signals from host cells would be a critical feature for maintaining or re-establishing homeostasis in these tissues.

Methods

This study used a nonhuman primate model (Macaca mulatta) with naturally-occurring periodontitis (n = 34) and experimental ligature-induced periodontitis (n = 36) to describe the features of gene expression for an array of damage-associate molecular patterns (DAMPs) or alarmins within the gingival tissues. The animals were age stratified into: ≤3 years (Young), 7-12 years (Adolescent), 12-15 years (Adult) and 17-23 years (Aged). Gingival tissue biopsies were examined via microarray. The analysis focused on 51 genes representative of the DAMPs/alarmins family of host cell warning factors and 18 genes associated with tissue destructive processed in the gingival tissues. Bacterial plaque samples were collected by curette sampling and 16S rRNA gene sequences used to describe the oral microbiome.

Results

A subset of DAMPs/alarmins were expressed in healthy and naturally-occurring periodontitis tissues in the animals and suggested local effects on gingival tissues leading to altered levels of DAMPs/alarmins related to age and disease. Significant differences from adult healthy levels were most frequently observed in the young and adolescent animals with few representatives in this gene array altered in the healthy aged gingival tissues. Of the 51 target genes, only approximately ⅓ were altered by ≥1.5-fold in any of the age groups of animals during disease, with those increases observed during disease initiation. Distinctive positive and negative correlations were noted with the DAMP/alarmin gene levels and comparative expression changes of tissue destructive molecules during disease across the age groups. Finally, specific correlations of DAMP/alarmin genes and relative abundance of particular microbes were observed in health and resolution samples in younger animals, while increased correlations during disease in the older groups were noted.

Conclusions

Thus, using this human-like preclinical model of induced periodontitis, we demonstrated the dynamics of the activation of the DAMP/alarmin warning system in the gingival tissues that showed some specific differences based on age.

Toll-like receptor-1, -2, and -6 genotypes in relation to salivary human beta-defensin-1, -2, -3 and human neutrophilic peptide-1

AIM

To examine whether functional gene polymorphisms of toll-like receptor (TLR)1, TLR2, and TLR6 are related to the salivary concentrations of human beta-defensins (hBDs)-1, -2, -3, and human neutrophilic peptide (HNP)-1.

MATERIALS AND METHODS

Polymorphisms of TLR1 (rs5743618), TLR2 (rs5743708), and TLR6 (rs5743810) were genotyped by PCR-based pyrosequencing from the salivary samples of 230 adults. Salivary hBD-1, -2, -3, and HNP-1 concentrations were measured using enzyme-linked immunosorbent assay. General and periodontal health examinations, including panoramic radiography, were available for all participants.

RESULTS

The genotype frequencies for wild types and variant types were as follows: 66.5% and 33.5% for TLR1, 95.5% and 4.5% for TLR2, and 25.1% and 74.9% for TLR6, respectively. The TLR2 heterozygote variant group exhibited higher salivary hBD-2 concentrations than the TLR2 wild-type group (p = .038). On the contrary, elevated hBD-2 concentrations were detected in the TLR6 wild-type group compared with the TLR6 heterozygote and homozygote variant group (p = .028). The associations between TLR6 genotypes and salivary hBD-2 concentrations remained significant after adjusting them for periodontal status, age, and smoking.

CONCLUSION

hBD-2 concentrations in saliva are related to TLR2 and TLR6 polymorphisms, but only the TLR6 genotype seems to exhibit an independent association with the salivary hBD-2 concentrations.

Influence of the treatment of periodontal disease in serum concentration of sirtuin 1 and mannose-binding lectin

BACKGROUND

Increased levels of periodontal pathogens disrupt the homeostasis between the host and its microbiota and increase susceptibility to periodontal diseases. Periodontitis increases the serum concentration of mannose-binding lectin (MBL), which exacerbates local inflammatory processes. In animal studies, sirtuin 1 (SIRT1) was associated with protection against inflammation. This study analyzed the influence of non-surgical periodontal treatment on serum levels of MBL and SIRT1.

METHODS

Forty patients with periodontitis and 38 periodontally healthy individuals (aged 45 to 79 years) were included. Periodontitis patients received scaling and root planing using machine driven and hand instruments. Clinical parameters, inflammatory biomarkers, MBL, and SIRT1 levels were measured at baseline and at post-treatment.

RESULTS

For all patients, an inverse correlation was observed between serum concentrations of MBL and SIRT1 (r = -0.30; P = 0.006). Periodontal treatment reduced serum concentrations of MBL (1,099.35 ± 916.59 to 861.42 ± 724.82 ng/mL; P < 0.001) and C-reactive protein (6.05 ± 8.99 to 2.49 ± 2.89 mg/L; P = 0.009). By contrast, SIRT1 serum levels increased (1.06 ± 1.03 to 1.66 ± 1.64 ng/mL; P < 0.001) following periodontal treatment.

CONCLUSIONS

Periodontal treatment was associated with decreased serum concentrations of MBL and CRP and increased serum levels of SIRT1. Prospective studies are needed to assess the impact of these biomarkers on pathophysiology of periodontitis.

Periodontal Infectogenomics

Periodontal diseases are chronic infectious disease in which the pathogenic bacteria initiate the host immune response leading to the destruction of tooth supporting tissue and eventually result in the tooth loss. It has multifactorial etiological factors including local, systemic, environmental and genetic factors. The effect of genetic factors on periodontal disease is already under extensive research and has explained the role of polymorphisms of immune mediators affecting disease response. The role genetic factors in pathogens colonisation is emerged as a new field of research as "infectogenomics". It is a rapidly evolving and high-priority research area now days. It further elaborates the role of genetic factors in disease pathogenesis and help in the treatment, control and early prevention of infection. The aim of this review is to summarise the contemporary evidence available in the field of periodontal infectogenomics to draw some valuable conclusions to further elaborate its role in disease pathogenesis and its application in the clinical practice. This will open up opportunity for more extensive research in this field.

Spontaneous preterm birth: advances toward the discovery of genetic predisposition

Evidence from family and twin-based studies provide strong support for a significant contribution of maternal and fetal genetics to the timing of parturition and spontaneous preterm birth. However, there has been only modest success in the discovery of genes predisposing to preterm birth, despite increasing sophistication of genetic and genomic technology. In contrast, DNA variants associated with other traits/diseases have been identified. For example, there is overwhelming evidence that suggests that the nature and intensity of an inflammatory response in adults and children are under genetic control. Because inflammation is often invoked as an etiologic factor in spontaneous preterm birth, the question of whether spontaneous preterm birth has a genetic predisposition in the case of pathologic inflammation has been of long-standing interest to investigators. Here, we review various genetic approaches used for the discovery of preterm birth genetic variants in the context of inflammation-associated spontaneous preterm birth. Candidate gene studies have sought genetic variants that regulate inflammation in the mother and fetus; however, the promising findings have often not been replicated. Genome-wide association studies, an approach to the identification of chromosomal loci responsible for complex traits, have also not yielded compelling evidence for DNA variants predisposing to preterm birth. A recent genome-wide association study that included a large number of White women (>40,000) revealed that maternal loci contribute to preterm birth. Although none of these loci harbored genes directly related to innate immunity, the results were replicated. Another approach to identify DNA variants predisposing to preterm birth is whole exome sequencing, which examines the DNA sequence of protein-coding regions of the genome. A recent whole exome sequencing study identified rare mutations in genes encoding for proteins involved in the negative regulation (dampening) of the innate immune response (eg, CARD6, CARD8, NLRP10, NLRP12, NOD2, TLR10) and antimicrobial peptide/proteins (eg, DEFB1, MBL2). These findings support the concept that preterm labor, at least in part, has an inflammatory etiology, which can be induced by pathogens (ie, intraamniotic infection) or "danger signals" (alarmins) released during cellular stress or necrosis (ie, sterile intraamniotic inflammation). These findings support the notion that preterm birth has a polygenic basis that involves rare mutations or damaging variants in multiple genes involved in innate immunity and host defense mechanisms against microbes and their noxious products. An overlap among the whole exome sequencing-identified genes and other inflammatory conditions associated with preterm birth, such as periodontal disease and inflammatory bowel disease, was observed, which suggests a shared genetic substrate for these conditions. We propose that whole exome sequencing, as well as whole genome sequencing, is the most promising approach for the identification of functionally significant genetic variants responsible for spontaneous preterm birth, at least in the context of pathologic inflammation. The identification of genes that contribute to preterm birth by whole exome sequencing, or whole genome sequencing, promises to yield valuable population-specific biomarkers to identify the risk for spontaneous preterm birth and potential strategies to mitigate such a risk.