Tannerella forsythia GroEL induces inflammatory bone resorption and synergizes with interleukin-17

Effect of cold atmospheric plasma on common oral pathogenic microorganisms: a narrative review

BACKGROUND

The oral microbiota is a diverse and complex community that maintains a delicate balance. When this balance is disturbed, it can lead to acute and chronic infectious diseases such as dental caries and periodontitis, significantly affecting people's quality of life. Developing a new antimicrobial strategy to deal with the increasing microbial variability and resistance is important. Cold atmospheric plasma (CAP), as the fourth state of matter, has gradually become a hot topic in the field of biomedicine due to its good antibacterial, anti-inflammatory, and anti-tumor capabilities. It is expected to become a major asset in the regulation of oral microbiota.

METHODS

We conducted a search in PubMed, Medline, and Wiley databases, focusing on studies related to CAP and oral pathogenic microorganisms. We explored the biological effects of CAP and summarized the antimicrobial mechanisms behind it.

RESULTS

Numerous articles have shown that CAP has a potent antimicrobial effect against common oral pathogens, including bacteria, fungi, and viruses, primarily due to the synergy of various factors, especially reactive oxygen and nitrogen species.

CONCLUSIONS

CAP is effective against various oral pathogenic microorganisms, and it is anticipated to offer a new approach to treating oral infectious diseases. The future objective is to precisely adjust the parameters of CAP to ensure safety and efficacy, and subsequently develop a comprehensive CAP treatment protocol. Achieving this objective is crucial for the clinical application of CAP, and further research is necessary.

GroEL triggers NLRP3 inflammasome activation through the TLR/NF-κB p-p65 axis in human periodontal ligament stem cells

The interaction between bacteria and the host plays a vital role in the initiation and progression of systemic diseases, including gastrointestinal and oral diseases, due to the secretion of various virulence factors from these pathogens. GroEL, a potent virulence factor secreted by multiple oral pathogenic bacteria, is implicated in the damage of gingival epithelium, periodontal ligament, alveolar bone and other peripheral tissues. However, the underlying biomechanism is still largely unknown. In the present study, we verify that GroEL can trigger the activation of NLRP3 inflammasome and its downstream effector molecules, IL-1β and IL-18, in human periodontal ligament stem cells (hPDLSCs) and resultantly induce high activation of gelatinases (MMP-2 and MMP-9) to promote the degradation of extracellular matrix (ECM). GroEL-mediated activation of the NLRP3 inflammasome requires the participation of Toll-like receptors (TLR2 and TLR4). High upregulation of TLR2 and TLR4 induces the enhancement of NF-κB (p-p65) signaling and promotes its nuclear accumulation, thus activating the NLRP3 inflammasome. These results are verified in a rat model with direct injection of GroEL. Collectively, this study provides insight into the role of virulence factors in bacteria-induced host immune response and may also provide a new clue for the prevention of periodontitis.

Proteome and immune responses of extracellular vesicles derived from macrophages infected with the periodontal pathogen Tannerella forsythia

Periodontitis is a chronic inflammatory disease caused by periodontal pathogens in subgingival plaque and is associated with systemic inflammatory diseases. Extracellular vesicles (EVs) released from host cells and pathogens carry a variety of biological molecules and are of interest for their role in disease progression and as diagnostic markers. In the present study, we analysed the proteome and inflammatory response of EVs derived from macrophages infected with Tannerella forsythia, a periodontal pathogen. The EVs isolated from the cell conditioned medium of T. forsythia-infected macrophages were divided into two distinct vesicles, macrophage-derived EVs and T. forsythia-derived OMVs, by size exclusion chromatography combined with density gradient ultracentrifugation. Proteome analysis showed that in T. forsythia infection, macrophage-derived EVs were enriched with pro-inflammatory cytokines and inflammatory mediators associated with periodontitis progression. T. forsythia-derived OMVs harboured several known virulence factors, including BspA, sialidase, GroEL and various bacterial lipoproteins. T. forsythia-derived OMVs induced pro-inflammatory responses via TLR2 activation. In addition, we demonstrated that T. forsythia actively released OMVs when T. forsythia encountered macrophage-derived soluble molecules. Taken together, our results provide insight into the characterisation of EVs derived from cells infected with a periodontal pathogen.

Antimicrobial Activity of Zinc against Periodontal Pathogens: A Systematic Review of In Vitro Studies

Background and Objectives: More than a billion people worldwide suffer from chronic periodontitis. The primary etiological factor of periodontal diseases is dental plaque and the bacteria it contains, particularly Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Prevotella intermedia, and Aggregatibacter actinomycetemcomitans. Zinc, owing to its antibacterial properties, can be employed in periodontology. The objective of this review was to analyze scientific literature that examines the effects of zinc on periopathogens. Materials and methods: A systematic review protocol of scientific literature was designed following PRISMA recommendations. Data search was conducted in PubMed, Web of Science, and ScienceDirect databases. Full-text articles in English that examine the effects of zinc on periopathogens and were published between 2011 and 2021 were included. Results: Fifteen articles were included in the analysis based on inclusion criteria. ZnO exhibited antibacterial activity against P. gingivalis and P. intermedia (p < 0.001). The minimum inhibitory concentration against P. gingivalis was 10 μg/mL. ZnO demonstrated a significant antibacterial effect, as evidenced by inhibition zones of 15.10 mm for S. oralis, 13.36 mm for P. gingivalis, 12.98 mm for S. sanguis, and 14.01 mm for P. intermedia. Zn (II)-based polymers inhibited the ragA and ragB genes of P. gingivalis. Titanium dental implants coated with ZnO effectively disrupted the cell walls of P. gingivalis and A. actinomycetemcomitans. ZnO inhibited the growth of P. gingivalis within 2 h and the growth of F. nucleatum and P. intermedia within 3 h. ZnO exhibited nontoxic effects, and concentrations up to 0.8 mg/L increased cell survival rates by up to 90%. Conclusions: The analysis of the literature confirms the antibacterial action of zinc against periodontal pathogenic bacteria. At low concentrations, these substances do not exhibit cytotoxic effects on fibroblasts.

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.

The virulence factor GroEL directs the osteogenic and adipogenic differentiation of human periodontal ligament stem cells through the involvement of JNK/MAPK and NF-κB signaling

OBJECTIVE

GroEL, a bacterial metabolite, is an important stimulator of inflammation. The aim of this study is to confirm the effect of the virulence factor GroEL on differentiation potential of periodontal ligament (PDL) stem cells (PDLSCs) and the potential mechanisms.

METHODS

PDLSCs were obtained from extracted human premolars. GroEL was administered to osteogenic- and adipogenic-induced hPDLSCs. Alkaline phosphatase (ALP) staining, Alizarin Red staining and Oil Red staining were performed. Gene and protein expression were separately measured by qPCR and Western blotting. The expression and localization of activated signaling factors were confirmed by immunofluorescence staining. The inhibitors of myeloid differentiation factor 88 (MyD88, an adaptor protein of TLRs), JNK/MAPK and NF-κB signaling were used to verify their specific effects.

RESULTS

First, we found that GroEL inhibited the osteogenic differentiation and enhanced the adipogenic differentiation of hPDLSCs. Next, we found that GroEL increased the expression of TLR2 and TLR4 and GroEL activated JNK/MAPK and NF-κB signaling, which can be blocked by inhibition of MyD88. Finally, we found that inhibition of MyD88 restored GroEL-induced osteogenic and adipogenic differentiation and blocking JNK/MAPK or NF-κB signaling partly restored GroEL effects.

CONCLUSION

In the current study, we revealed a potential interaction between bacteria and host cells by showing that GroEL directs the osteogenic and adipogenic differentiation of hPDLSCs by the involvement of JNK/MAPK and NF-κB signaling. This study provides evidence that bacterial products can influence the differentiation of stem cells and reveals potential effect of GroEL on the context of tissue regeneration.

The virulence factor GroEL promotes gelatinase secretion from cells in the osteoblast lineage: Implication for direct crosstalk between bacteria and adult cells

OBJECTIVE

The aim of this study was to demonstrate the influence of the virulence factor GroEL on osteoblast behavior by characterizing the changes of secreted gelatinases.

DESIGN

ELISA was performed to detect GroEL from samples from patients with or without apical periodontitis. An apical periodontitis model was established in rats and the expression of MMP-2, MMP-9 and NF-κB was evaluated by immunofluorescence staining. The primary osteoblasts and osteoblast-like MC3T3 cells were stimulated with recombinant GroEL, and gelatin zymography was used to determine the activity and expression of MMP-2 and MMP-9. Western blot was used to screen signaling pathways, and immunofluorescence staining was performed to confirm the activated signaling.

RESULTS

First, we found expression of GroEL to be higher in oral saliva, gingival crevicular fluid and periradicular granulation tissue of patients with apical periodontitis than it was in healthy control patients. We next found that recombinant GroEL could increase the activity of the gelatinases, MMP-2 and MMP-9, which were secreted by both primary osteoblasts and MC3T3 cells. In a rat apical periodontitis model, strong expression of gelatinases was confirmed. Then, we found that GroEL-enhanced gelatinase activity was mediated through activation of NF-κB signaling. Acetylated NF-κB accumulated in the cell nucleus and bound to the promoter of MMP-2 and MMP-9 genes, thus initiating their high expression.

CONCLUSION

This study reveals a direct interaction between oral bacteria and adult cells by demonstrating that gelatinase secretion is induced by GroEL, which partially explains bone resorption through gelatinase activation.

Cytokines and Chemokines in Periodontitis

Periodontitis is a common inflammatory periodontal disease affecting a wide range of population all over the world. The causing bacteria releases chemicals which activate the innate immune system to release proinflammatory cytokines contributing to more progression. This activates the acquired immune system leading to more progression of periodontitis. As the immune response goes on, released cytokines and chemokines can damage the periodontal ligaments, gingiva, and alveolar bone. There are many types of cytokines and chemokines in periodontitis. Cytokines are peptide mediators who are responsible for cell signaling and communication. Chemokines are a large subfamily of cytokines having the ability to coordinate leukocyte recruitment and activation. This paper is a narrative review of the literature.This review ensures that inflammatory mediators in the case of periodontitis can cause a noticeable damage in the whole apparatus of the periodontium. It causes soft tissue inflammation and bone damage affected by the mediators of both innate and acquired immune system.The inflammatory process is accompanied by large network of cytokines and chemokines. There is high expression of proinflammatory cytokines such as interleukin (IL)-1α, IL-1β, IL-6, IL-12, tumor necrosis factor (TNF)-α, and regulatory cytokines such as IL-4, IL-1(RA) receptor antagonist, IL-10, and induced protein (IP)-10. There is also increased production of cytokines IL-10, IL-12, interferon-γ, IP-10, IL-1RA, and IL-4. Cytokines IL-17, IL-6, IL-1β, TNF-α, macrophage colony-stimulating factor, and prostaglandin E ₂ trigger the osteoclast activity causing bone resorption.

Meta-Analysis of Risk Association between Interleukin-17A Gene Polymorphism and Chronic Periodontitis

The association of genetic polymorphisms with periodontitis has been studied extensively. The interleukin-7 (IL-17) is a group of cytokines, which comprises six different molecules (IL-17A, B, C, D, E, and F). Among this, IL-17A is the most commonly understood cytokine, and its polymorphism plays a critical role in inflammatory diseases and periodontal inflammation. The present study was aimed at pooling the data available for meta-analysis and to evaluate whether IL-17A (rs2275913) polymorphism is associated with the susceptibility of chronic periodontitis.

Interleukin (IL)-35 Suppresses IL-6 and IL-8 Production in IL-17A-Stimulated Human Periodontal Ligament Cells

Interleukin (IL)-35 is a novel anti-inflammatory cytokine that is produced by regulatory T cells. IL-35 is reported to suppress IL-17A-producing helper T (Th17) cell activation. IL-17A is related to progression of periodontitis. Furthermore, IL-35 and IL-17A are detected in human gingival crevicular fluid. However, the effect of IL-35 and interaction between IL-35 and IL-17A on pro-inflammatory cytokine production in human periodontal resident cells are still unclear. The aim of this study was to clarify the effect of IL-35 on IL-6 and IL-8 production in human periodontal ligament cells (HPDLCs) stimulated with IL-17A. IL-35 inhibited IL-6 and IL-8 production in IL-17A-stimulated HPDLCs. Moreover, western blot analysis showed that IL-35 suppressed extracellular signal-regulated kinase (ERK) and nuclear factor (NF)-κB p65 phosphorylation in IL-17A-stimulated HPDLCs. Our findings suggested that IL-35 produced from regulatory T cells might inhibit progression of periodontitis by decreasing IL-17A-induced levels of IL-6 and IL-8.

Gingival crevicular fluid levels of SLIT3 are increased in periodontal disease

This study aims to investigate the levels of SLIT3 in gingival crevicular fluid (GCF) of healthy and periodontal disease subjects, and their correlations to periodontal disease. A total of 45 periodontal patients and 45 periodontally healthy volunteers were enrolled. The clinical parameters, radiographic bone loss and the levels of SLIT3, receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG) in GCF were measured. The prevalences of Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia in subgingival plaque were also analyzed. The expression of SLIT3 and RANKL was detected in the periodontium of experimental periodontitis in rats and lipopolysaccharide (LPS)-induced mouse macrophage. The total amounts and concentrations of SLIT3 and RANKL were significantly higher in periodontitis than those in healthy, while the level of OPG was significantly lower (p < .05). Significant positive correlations were observed between the level of GCF SLIT3 and clinical attachment level and radiographic bone loss (p < .05). There existed a significant positive correlation between SLIT3 and RANKL (p < .05). Increased expression of SLIT3 and RANKL was observed in the periodontium of periodontal rats. SLIT3 expression was induced by LPS stimulation in macrophages. These results suggest that SLIT3 may act as a diagnostic indicator of periodontal disease and should be further investigated.

Regulation of IL-24 in human oral keratinocytes stimulated with Tannerella forsythia

Interleukin-24 is a pleiotropic immunoregulatory cytokine and a member of the IL-20R subfamily of the IL-10 family. The aim of this study was to investigate the regulation of IL-24 in the human oral keratinocyte cell line HOK-16B following infection with Tannerella forsythia, a major periodontal pathogen. T. forsythia induced the expression of IL-24 mRNA and the secretion of glycosylated IL-24 in HOK-16B cells. Glycosylation of IL-24 is linked to its solubility and bioavailability. T. forsythia-stimulated reactive oxygen species (ROS) induced the expression of IL-24, which was regulated by IL-6. The ROS inhibitor N-acetylcysteine and MAPK inhibitors significantly reduced the expression of IL-6 and IL-24 induced by T. forsythia. Recombinant human IL-24 significantly enhanced the expression of IL-1α, IL-8, CXCL10, and MCP-1 in HOK-16B cells. Together, these results indicate that ROS, MAPKs, and IL-6 comprise the axis of IL-24 expression in HOK-16B cells stimulated with T. forsythia. Thus, IL-24 may be involved in inflammation in oral keratinocytes.

The innate host response in caries and periodontitis

INTRODUCTION

Innate immunity rapidly defends the host against infectious insults. These reactions are of limited specificity and exhaust without providing long-term protection. Functional fluids and effector molecules contribute to the defence against infectious agents, drive the immune response, and direct the cellular players.

AIM

To review the literature and present a summary of current knowledge about the function of tissues, cellular players and soluble mediators of innate immunity relevant to caries and periodontitis.

METHODS

Historical and recent literature was critically reviewed based on publications in peer-reviewed scientific journals.

RESULTS

The innate immune response is vital to resistance against caries and periodontitis and rapidly attempts to protect against infectious agents in the dental hard and soft tissues. Soluble mediators include specialized proteins and lipids. They function to signal to immune and inflammatory cells, provide antimicrobial resistance, and also induce mechanisms for potential repair of damaged tissues.

CONCLUSIONS

Far less investigated than adaptive immunity, innate immune responses are an emerging scientific and therapeutic frontier. Soluble mediators of the innate response provide a network of signals to organize the near immediate molecular and cellular response to infection, including direct and immediate antimicrobial activity. Further studies in human disease and animal models are generally needed.

The Immune Response in Periodontal Tissues

The uniqueness of periodontal diseases is caused by several factors. This group of diseases is caused by numerous bacterial species formed in the dental biofilm, and one cannot distinguish the specific pathogen that is responsible for the disease initiation or progress (though Gram-negative anaerobic rods are associated with the advanced form of the disease). The disease is both infectious and inflammatory in its nature, and in the state of health there is always a subclinical level of inflammatory response, caused by the so-called harmless bacteria. Negligence in oral hygiene may result in maturation of the biofilm and trigger host response, manifesting clinically as gingivitis or-later and in susceptible subjects-as periodontitis. The article presents the contemporary knowledge of the inflammatory reaction occurring in tissues surrounding the tooth during periodontal inflammation. The most important mechanisms are described, together with implications for clinicists.