Neutrophil Extracellular Traps Aggravate Apical Periodontitis by Stimulating Osteoclast Formation

Neutrophil Extracellular Traps in Oral Diseases

OBJECTIVE

To summarize the current knowledge of the neutrophil extracellular traps (NETs) and its critical role in various oral diseases.

METHODS

We reviewed the recent research on NETs through PubMed and Web of Science. An analysis of recent research results was summarized from three aspects: NETs induction and formation, functions of NETs, and NETs in oral diseases.

RESULTS

The relationship between neutrophils and NETs is critical to the body's defense against microbial invasion. NETs can effectively combat pathogens with an anti-inflammatory effect and meanwhile it can contribute to inflammation. Moreover, it can synergize with other immune cells to respond to stimuli, such as pathogens, host-derived mediators, and drugs. It was revealed that NETs play different roles to influence various oral diseases like periodontitis, endodontic infection, oral mucosal diseases, maxillofacial tumors, and many other oral diseases.

CONCLUSION

The balance between the protective and potentially harmful effects of NETs is a key factor in determining the outcome of infections and inflammatory responses. The role of NETs in oral diseases needs to be further studied to enable better understanding of its role in the different oral diseases.

The immune landscape in apical periodontitis: From mechanism to therapy

Apical periodontitis (AP) is featured by a persistent inflammatory response and alveolar bone resorption initiated by microorganisms, posing risks to both dental and systemic health. Nonsurgical endodontic treatment is the recommended treatment plan for AP with a high success rate, but in some cases, periapical lesions may persist despite standard endodontic treatment. Better comprehension of the AP inflammatory microenvironment can help develop adjunct therapies to improve the outcome of endodontic treatment. This review presents an overview of the immune landscape in AP, elucidating how microbial invasion triggers host immune activation and shapes the inflammatory microenvironment, ultimately impacting bone homeostasis. The destructive effect of excessive immune activation on periapical tissues is emphasized. This review aimed to systematically discuss the immunological basis of AP, the inflammatory bone resorption and the immune cell network in AP, thereby providing insights into potential immunotherapeutic strategies such as targeted therapy, antioxidant therapy, adoptive cell therapy and cytokine therapy to mitigate AP-associated tissue destruction.

Roles of Toll-like Receptor Signaling in Inflammatory Bone Resorption

Toll-like receptors (TLRs) are pattern recognition receptors expressed in immune cells, including neutrophils, macrophages, and dendritic cells. Microbe-associated molecular patterns, including bacterial components, membranes, nucleic acids, and flagella are recognized by TLRs in inflammatory immune responses. Periodontal disease is an inflammatory disease known to cause local infections associated with gingival inflammation, subsequently leading to alveolar bone resorption. Prostaglandin E2 (PGE2) is a key mediator of TLR-induced inflammatory bone resorption. We previously reported that membrane-bound PGE synthase (mPGES-1)-deficient mice failed to induce bone resorption by lipopolysaccharide (LPS), a major pathogenic factor involved in periodontal bone resorption. Further experiments exploring specific pathogen-promoting osteoclast differentiation revealed that various TLR ligands induced osteoclast differentiation in a co-culture model. The ligands for TLR2/1, TLR2/6, TLR3, and TLR5, as well as TLR4, induce osteoclast differentiation associated with the production of PGE2 and the receptor activator of nuclear factor-kappa B ligand (RANKL), an inevitable inducer of osteoclast differentiation in osteoblasts. In vivo, local injection of TLR ligands, including TLR2/1, TLR2/6, and TLR3, resulted in severe alveolar bone resorption. This review summarizes the latest findings on TLR-mediated osteoclast differentiation and bone resorption in inflammatory diseases, such as periodontal diseases.

The associations of two novel inflammation indexes, systemic immune-inflammation index (SII) and system inflammation response index (SIRI), with periodontitis: evidence from NHANES 2009-2014

OBJECTIVES

The research's goal is to look for any potential relationships between the systemic immune-inflammation index (SII) and the system inflammation response index (SIRI), along with inflammation indicators and the likelihood of periodontitis.

METHODS

Ten thousand two hundred eighty-two individuals in sum were determined to be eligible for this cross-sectional study from the National Health and Nutrition Examination Survey (NHANES) between 2009 and 2014. Multiple logistic regression, generalized additive model, smooth curve fitting, subgroup analysis, and interaction tests were done for analyzing the association between periodontitis and SII, SIRI, and other inflammatory indicators.

RESULTS

The analysis, adjusted for population weighting, revealed that individuals with moderate/severe periodontitis had SII levels of 545.46 (95% CI (529.10, 561.82), P = 0.0044) and SIRI levels of 1.33 (95% CI (1.29, 1.37), P < 0.0001). In a fully adjusted multivariate logistic regression model, SII was not sensibly associated with moderate/severe periodontitis among the continuous and quartile Q1-Q4 groups (OR = 0.97, 95% CI (0.91, 1.02)). The continuous variable of SIRI (OR = 1.11, 95% CI (1.06, 1.17)) and the quartile Q4 group (OR = 1.58, 95% CI (1.28, 1.94)) had a deemed significant positive association with moderate to severe periodontitis. In addition, other inflammatory indicators, especially NLR, PPN, PLR, MLR, PC, NC, and MC were observed to be notably involved moderate/severe periodontist in this research.

CONCLUSION

We explored the association between periodontitis and two novel comprehensive markers of inflammation (SII and SIRI).

CLINICAL RELEVANCE

These inflammatory markers are expected to serve as tools to assist clinicians in diagnosing periodontitis.

Extracellular DNA and Markers of Neutrophil Extracellular Traps in Saliva from Patients with Periodontitis-A Case-Control Study

Periodontitis is a chronic inflammatory disease. We have previously shown that salivary DNA is higher in patients with periodontitis. Neutrophil extracellular traps (NETs) are involved in the pathogenesis of chronic inflammatory diseases. The objective of this case-control study was to compare patients with periodontitis and healthy controls regarding the salivary concentrations of extracellular DNA and NET components. Unstimulated saliva samples were collected from 49 patients with periodontitis and 71 controls before an oral examination. Salivary extracellular DNA was isolated and quantified fluorometrically and using PCR. NET-associated markers were assessed using ELISA. We have found significantly higher concentrations of salivary extracellular DNA in samples from periodontitis patients (five-times higher for supernatant and three times for pellet). Our results show that patients also have three-times-higher salivary nucleosomes and NET-associated enzymes-myeloperoxidase and neutrophil elastase (both two-times higher). Neutrophil elastase and salivary DNA in the pellet correlated positively with the pocket depth/clinical attachment level in periodontitis patients (r = 0.31-weak correlation; p = 0.03 and r = 0.41-moderate correlation, p = 0.004). Correlations between salivary extracellular DNA and NET enzymes were positive and significant. Based on our results, the higher salivary extracellular DNA in periodontitis seems to be related to components of NETs, albeit with weak to moderate correlations indicating that NETs are produced in periodontitis and can play a role in its pathogenesis similarly to other inflammatory diseases. Further studies should prove this assumption with potential diagnostic and therapeutic consequences.