Pro-inflammatory cytokine production from normal human fibroblasts is induced by Tannerella forsythia detaching factor

Mitochondrial Dysfunction in Periodontitis and Associated Systemic Diseases: Implications for Pathomechanisms and Therapeutic Strategies

Periodontitis is a chronic infectious disorder damaging periodontal tissues, including the gingiva, periodontal ligament, cementum, and alveolar bone. It arises from the complex interplay between pathogenic oral bacteria and host immune response. Contrary to the previous view of "energy factories", mitochondria have recently been recognized as semi-autonomous organelles that fine-tune cell survival, death, metabolism, and other functions. Under physiological conditions, periodontal tissue cells participate in dynamic processes, including differentiation, mineralization, and regeneration. These fundamental activities depend on properly functioning mitochondria, which play a crucial role through bioenergetics, dynamics, mitophagy, and quality control. However, during the initiation and progression of periodontitis, mitochondrial quality control is compromised due to a range of challenges, such as bacterial-host interactions, inflammation, and oxidative stress. Currently, mounting evidence suggests that mitochondria dysfunction serves as a common pathological mechanism linking periodontitis with systemic conditions like type II diabetes, obesity, and cardiovascular diseases. Therefore, targeting mitochondria to intervene in periodontitis and multiple associated systemic diseases holds great therapeutic potential. This review provides advanced insights into the interplay between mitochondria, periodontitis, and associated systemic diseases. Moreover, we emphasize the significance of diverse therapeutic modulators and signaling pathways that regulate mitochondrial function in periodontal and systemic cells.

Periodontal Pathogens and Their Links to Neuroinflammation and Neurodegeneration

Pathogens that play a role in the development and progression of periodontitis have gained significant attention due to their implications in the onset of various systemic diseases. Periodontitis is characterized as an inflammatory disease of the gingival tissue that is mainly caused by bacterial pathogens. Among them, Porphyromonas gingivalis, Treponema denticola, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, and Tannerella forsythia are regarded as the main periodontal pathogens. These pathogens elicit the release of cytokines, which in combination with their virulence factors induce chronic systemic inflammation and subsequently impact neural function while also altering the permeability of the blood-brain barrier. The primary objective of this review is to summarize the existing information regarding periodontal pathogens, their virulence factors, and their potential association with neuroinflammation and neurodegenerative diseases. We systematically reviewed longitudinal studies that investigated the association between periodontal disease and the onset of neurodegenerative disorders. Out of the 24 studies examined, 20 showed some degree of positive correlation between periodontal disease and neurodegenerative disorders, with studies focusing on cognitive function demonstrating the most robust effects. Therefore, periodontal pathogens might represent an exciting new approach to develop novel preventive treatments for neurodegenerative diseases.

Changes in the oral and nasal microbiota in pediatric obstructive sleep apnea

Background

Several clinical studies have demonstrated that pediatric obstructive sleep apnea (OSA) is associated with dysbiosis of airway mucosal microbiota. However, how oral and nasal microbial diversity, composition, and structure are altered in pediatric OSA has not been systemically explored.

Methods

30 polysomnography-confirmed OSA patients with adenoid hypertrophy, and 30 controls who did not have adenoid hypertrophy, were enrolled. Swabs from four surface oral tissue sites (tongue base, soft palate, both palatine tonsils, and adenoid) and one nasal swab from both anterior nares were collected. The 16S ribosomal RNA (rRNA) V3-V4 region was sequenced to identify the microbial communities.

Results

The beta diversity and microbial profiles were significantly different between pediatric OSA patients and controls at the five upper airway sites. The abundances of Haemophilus, Fusobacterium, and Porphyromonas were higher at adenoid and tonsils sites of pediatric patients with OSA. Functional analysis revealed that the differential pathway between the pediatric OSA patients and controls involved glycerophospholipids and amino acid metabolism.

Conclusions

In this study, the oral and nasal microbiome of pediatric OSA patients exhibited certain differences in composition compared with the controls. However, the microbiota data could be useful as a reference for studies on the upper airway microbiome.

The oral microbiota and its role in carcinogenesis

Despite decades of research, cancer continues to be a major global health concern. In recent years, the role played by microorganisms in the development and progression of cancer has come under increased scrutiny. The aim of the present review is to highlight the main associations between members of the human oral microbiota and various cancers. The PubMed database was searched for available literature to outline the current state of understanding regarding the role of the oral microbiota and a variety of human cancers. Oral squamous cell carcinoma (OSCC) is associated with carriage of a number of oral bacteria (e.g., Porphyromonas gingivalis, Fusobacterium nucleatum, Streptococcus sp.), certain viruses (e.g., human papilloma virus, human herpes virus 8, herpes simplex virus 1 and Epstein-Barr virus) and yeast (Candida albicans). Moreover, members of the oral microbiota are associated with cancers of the esophagus, stomach, pancreas, colon/rectum and lung. Furthermore, the present review outlines a number of the carcinogenic mechanisms underlying the presented microbial associations with cancer. Such information may one day help clinicians to diagnose neoplastic diseases at earlier stages and prescribe treatments that take into account the possible microbial nature of carcinogenesis.

Lysine-specific proteolytic activity responsible for forsythia detaching factor modification

OBJECTIVES

The objective of the present study was to clarify the lysine-specific proteolytic activity derived from periodontal pathogens responsible for Forsythia detaching factor (FDF) modification.

DESIGN

The activity responsible for FDF modification in Tannerella forsythia and Porphyromonas gingivalis were evaluated by colorimetric assay using Ac-Arg-Ala-Lys-p-nitroaniline as a substrate. FDF modification in T. forsythia and P. gingivalis were evaluated by Western blotting using recombinant FDF (rFDF) as a substrate. Furthermore, the activity in GCF of 20 patients with periodontitis and 10 healthy subjects was also evaluated by colorimetric assay. Bacteria in subgingival plaque were detected using polymerase chain reaction.

RESULTS

The activity of both bacteria in colorimetric assay were 21.35 unit (P. gingivalis) and 3.61 unit (T. forsythia), respectively. Western blot analysis revealed that P. gingivalis was found to efficiently degrade rFDF and T. forsythia partially cleaved rFDF. The activity in GCF from patients with periodontitis (clinically healthy sites: CH, deep bleeding sites: DB and deep non-bleeding sites: DNB) was significantly higher than those from healthy subjects (healthy sites: H). Among the patients with periodontitis, the activity from CH was significantly lower than those from DB and DNB. T. forsythia was detected in 68.4% of DNB, in 78.4% of DB and in none of CH. P. gingivalis was detected in 63.2% of DNB, in 84.0% of DB and in 10.5% of CH. No bacterium was detected in healthy subjects.

CONCLUSION

The lysine-specific proteolytic activity responsible for FDF modification correlates with the presence of major periodontal pathogens.

Mirolase, a novel subtilisin-like serine protease from the periodontopathogen Tannerella forsythia

The genome of Tannerella forsythia, an etiological factor of chronic periodontitis, contains several genes encoding putative proteases. Here, we characterized a subtilisin-like serine protease of T. forsythia referred to as mirolase. Recombinant full-length latent promirolase [85 kDa, without its signal peptide (SP)] processed itself through sequential autoproteolytic cleavages into a mature enzyme of 40 kDa. Mirolase latency was driven by the N-terminal prodomain (NTP). In stark contrast to almost all known subtilases, the cleaved NTP remained non-covalently associated with mirolase, inhibiting its proteolytic, but not amidolytic, activity. Full activity was observed only after the NTP was gradually, and fully, degraded. Both activity and processing was absolutely dependent on calcium ions, which were also essential for enzyme stability. As a consequence, both serine protease inhibitors and calcium ions chelators inhibited mirolase activity. Activity assays using an array of chromogenic substrates revealed that mirolase specificity is driven not only by the substrate-binding subsite S1, but also by other subsites. Taken together, mirolase is a calcium-dependent serine protease of the S8 family with the unique mechanism of activation that may contribute to T. forsythia pathogenicity by degradation of fibrinogen, hemoglobin, and the antimicrobial peptide LL-37.

KLIKK proteases of Tannerella forsythia: putative virulence factors with a unique domain structure

Comparative genomics of virulent Tannerella forsythia ATCC 43037 and a close health-associated relative, Tannerella BU063, revealed, in the latter, the absence of an entire array of genes encoding putative secretory proteases that possess a nearly identical C-terminal domain (CTD) that ends with a -Lys-Leu-Ile-Lys-Lys motif. This observation suggests that these proteins, referred to as KLIKK proteases, may function as virulence factors. Re-sequencing of the loci of the KLIKK proteases found only six genes grouped in two clusters. All six genes were expressed by T. forsythia in routine culture conditions, although at different levels. More importantly, a transcript of each gene was detected in gingival crevicular fluid (GCF) from periodontitis sites infected with T. forsythia indicating that the proteases are expressed in vivo. In each protein, a protease domain was flanked by a unique N-terminal profragment and a C-terminal extension ending with the CTD. Partially purified recombinant proteases showed variable levels of proteolytic activity in zymography gels and toward protein substrates, including collagen, gelatin, elastin, and casein. Taken together, these results indicate that the pathogenic strain of T. forsythia secretes active proteases capable of degrading an array of host proteins, which likely represents an important pathogenic feature of this bacterium.

Single cell genomics of uncultured, health-associated Tannerella BU063 (Oral Taxon 286) and comparison to the closely related pathogen Tannerella forsythia

The uncultivated bacterium Tannerella BU063 (oral taxon 286) is the closest relative to the periodontal pathogen Tannerella forsythia, but is not disease-associated itself. Using a single cell genomics approach, we isolated 12 individual BU063 cells by flow cytometry, and we amplified and sequenced their genomes. Comparative analyses of the assembled genomic scaffolds and their gene contents allowed us to study the diversity of this taxon within the oral community of a single human donor that provided the sample. Eight different BU063 genotypes were represented, all about 5% divergent at the nucleotide level. There were 2 pairs of cells and one group of three that were more highly identical, and may represent clonal populations. We did pooled assemblies on the nearly identical genomes to increase the assembled genomic coverage. The presence of a set of 66 “core” housekeeping genes showed that two of the single cell assemblies and the assembly derived from the three putatively identical cells were essentially complete. As expected, the genome of BU063 is more similar to Tannerella forsythia than any other known genome, although there are significant differences, including a 44% difference in gene content, changes in metabolic pathways, loss of synteny, and an 8–9% difference in GC content. Several identified virulence genes of T. forsythia are not found in BU063 including karilysin, prtH, and bspA. The absence of these genes may explain the lack of periodontal pathogenesis by this species and provides a new foundation to further understand the genome evolution and mechanisms of bacterial-host interaction in closely related oral microbes with different pathogenicity potential.

Modification of forsythia detaching factor by gingival crevicular fluid in periodontitis

OBJECTIVES

Forsythia detaching factor (FDF) is a virulence factor of Tannerella forsythia detected as a mixture of the 60-kDa form of FDF and the 28-kDa C-terminal fragment (FDFc). The objective of the present study was to clarify the proteolytic activity of gingival crevicular fluid (GCF) from patients with periodontitis and healthy subjects using recombinant FDF (rFDF) as substrate.

DESIGN

Eleven patients with periodontitis and 6 healthy subjects were recruited. Modification of rFDF and subsequent production of rFDFc by proteolytic activity of GCF was determined by Western blotting. Proteolytic activity of GCF was evaluated using an Ac-Arg-Ala-Lys-p-nitroaniline substrate. Correlation analysis between two different sets of variables was performed. Variables used in this analysis were proteolytic activity, clinical parameters, relative band density of rFDFc and those of rFDF.

RESULTS

Proteolytic activity in GCF was significantly higher in patients with periodontitis than in healthy subjects. Production of rFDFc was determined by treatment of rFDF with GCF from patients with periodontitis and with GCF from healthy subjects. Correlations between clinical parameters and proteolytic activity in GCF were significantly positive. On the other hand, correlations between relative band density of rFDFc or rFDF on Western blot and cleaving activity or clinical parameters were significantly negative.

CONCLUSION

The detected extend of GCF-activity generating rFDFc from rFDF and/or even further degrading rFDF correlates with severity of periodontitis.

Levels of specific immunoglobulin G to the forsythia detaching factor of Tannerella forsythia in gingival crevicular fluid are related to the periodontal status

BACKGROUND AND OBJECTIVE

Forsythia detaching factor (FDF) is a putative virulence factor of Tannerella forsythia that induces detachment of adherent cells and interleukin-8 production in human fibroblasts. The objective of the present study was to clarify the relationship between anti-FDF IgG levels in gingival crevicular fluid and the clinical status in patients with periodontitis and in healthy subjects.

MATERIAL AND METHODS

Gingival crevicular fluid and subgingival plaque samples were obtained from both the diseased and healthy sites of 37 patients with periodontitis and from 30 healthy subjects. Anti-FDF IgG levels were evaluated, and both the fdf gene and T. forsythia 16S ribosomal RNA (rRNA) were detected using the PCR.

RESULTS

Anti-FDF IgG levels (of both diseased and healthy sites) of patients with periodontitis were significantly higher than those of healthy subjects. Among the patients with periodontitis, anti-FDF IgG levels of healthy sites were significantly higher than those of diseased sites and the levels showed negative correlations with probing pocket depth and clinical attachment level. Among the patients with periodontitis, T. forsythia 16S rRNA was detected in 18 of 37 diseased sites and in 5 of 29 healthy sites, and the fdf gene was detected in 19 of 37 diseased sites and in 7 of 29 healthy sites. By contrast, no healthy subjects were positive for T. forsythia 16S rRNA or the fdf gene.

CONCLUSION

These data suggest that anti-FDF IgG levels in gingival crevicular fluid are related to the periodontal status.

DNA methylation status of the IL8 gene promoter in oral cells of smokers and non-smokers with chronic periodontitis

AIM

This study analysed the status of DNA methylation in the promoter region of the IL8 gene in oral mucosa cells from healthy, smoker and non-smoker subjects with chronic periodontitis and compared these findings among groups with mRNA levels.

MATERIAL AND METHODS

Genomic DNA from epithelial oral cells of 41 healthy subjects, 30 smokers with chronic periodontitis and 40 non-smokers with chronic periodontitis were purified and modified by sodium bisulphite. Genomic DNA from blood leucocytes and gingival cells from biopsies of 13 subjects of each group were also purified and modified by sodium bisulphite. Modified DNA was submitted by methylation-specific polymerase chain reaction (PCR) (MSP), electrophoresed on 10% polyacrylamide gels and stained with SYBR Gold. Total RNA from gingival cells was also isolated using the TRIzol reagent, and real-time PCR performance was used to detect the levels of interleukin-8 mRNA.

RESULTS

Our results indicate that individuals with chronic periodontitis, independent of smoking habit, have a higher percentage of hipomethylation of the IL8 gene than those controls in epithelial oral cells (p<0.0001), and expression of higher levels of interleukin-8 (IL-8) mRNA than controls in gingival cells (p=0.007). No significant differences among groups were observed in gingival cells and blood cells.

CONCLUSION

We conclude that inflammation in the oral mucosa might lead to changes in the DNA methylation status of the IL8 gene in epithelial oral cells.