On site visual detection of Porphyromonas gingivalis related periodontitis by using a magnetic-nanobead based assay for gingipains protease biomarkers

Unravelling the intricacies of Porphyromonas gingivalis: virulence factors, lifecycle dynamics and phytochemical interventions for periodontal disease management

Porphyromonas gingivalis is a gram-negative anaerobic bacterium recognized for its pivotal role in the pathogenesis of periodontal diseases. This review covers an overview of the virulence factors and lifecycle stages of P. gingivalis, with a specific focus on attachment and colonization, biofilm formation, growth and multiplication, dormancy survival and dissemination. Additionally, we explore the significance of inter-bacterial cross-feeding within biofilms. Furthermore, we discuss potential phytochemical-based strategies to target P. gingivalis, including the use of curcumin, apigenin, quercetin and resveratrol. Understanding the virulence factors and lifecycle stages of P. gingivalis, along with the promising phytochemical-based interventions, holds promise for advancing strategies in periodontal disease management and oral health promotion.

Point-of-care diagnostic devices for periodontitis - current trends and urgent need

Point of care (POC) diagnostic devices provide a method for rapid accurate identification of disease through analysis of biologically relevant substances. This review focuses on the utility of POC testing for early detection of periodontitis, a critical factor in treating the disease. Accessing the oral cavity for biological sampling is less invasive when compared to other internal test sites, and oral fluids contain biomarkers indicative of periodontitis. The ease of access makes the mouth an excellent target location for the development of POC devices. In this review, accepted standards in industry by which these devices must adhere, provided by the World Health Organization such as REASSURED and CLIA, are discussed. An overview is provided for many periodontal biomarkers currently being investigated as a means of predicting periodontal disease and its progression. POC devices currently being investigated for the identification and monitoring of periodontal disease such as paper-based and lab-on-a-chip based devices are outlined. Limitations of current POC devices on the market are provided and future directions in leveraging biomarkers as an adjunctive method for oral diagnosis along with AI-based analysis systems are discussed. Here, we present the ESSENCE sensor platform, which combines a porous non-planar electrode with enhanced shear flow to achieve unprecedented sensitivity and selectivity. The combination of the ESENCE chip with an automated platform allows us to meet the WHO's ASSURED criteria. This platform promises to be an exciting POC candidate for early detection of periodontitis.

Rapid Colorimetric Quantita2tive Portable Platform for Detection of Brucella melitensis Based on a Fluorescence Resonance Energy Transfer Assay and Nanomagnetic Particles

Brucellosis is a bacterial zoonotic disease that requires major attention for both health and financial facilities in many parts of the world including the Mediterranean and the Middle East. The existing gold standard diagnosis relies on the culturing technique, which is costly and time-consuming with a duration of up to 45 days. The Brucella protease biosensor represents a new detection approach that will lead to low-cost point-of-care devices for sensitive Brucella detection. In addition, the described diagnostic device is portable and simple to operate by a nurse or non-skilled clinician making it appropriate for the low-resource setting. In this study, we rely on the total extracellular protease proteolytic activity on specific peptide sequences identified using the FRET assay by high-throughput screening from the library of peptide (96 short peptides such as dipeptides and tripeptides) substrates for Brucella melitensis (B. melitensis). The B. melitensis-specific protease substrate was utilized in the development of the paper-based colorimetric assay. Two specific and highly active dipeptide substrates were identified (FITC-Ahx-K-r-K-Ahx-DABCYL and FITC-Ahx-R-r-K-Ahx-DABCYL). The peptide-magnetic bead nanoprobe sensors developed based on these substrates were able to detect the Brucella with LOD as low as 1.5 × 102 and 1.5 × 103 CFU/mL using K-r dipeptide and R-r dipeptide substrates, respectively, as the recognition element. The samples were tested using this sensor in few minutes. Cross-reactivity studies confirmed that the other proteases extracted from closely related pathogens have no significant effect on the sensor. To the best of our knowledge, this assay is the first assay that can be used with low-cost, rapid, direct, and visual detection of B. melitensis.

Nanochemistry of gold: from surface engineering to dental healthcare applications

Advancements in nanochemistry have led to the development of engineered gold nanostructures (GNSs) with remarkable potential for a variety of dental healthcare applications. These innovative nanomaterials offer unique properties and functionalities that can significantly improve dental diagnostics, treatment, and overall oral healthcare applications. This review provides an overview of the latest advancements in the design, synthesis, and application of GNSs for dental healthcare applications. Engineered GNSs have emerged as versatile tools, demonstrating immense potential across different aspects of dentistry, including enhanced imaging and diagnosis, prevention, bioactive coatings, and targeted treatment of oral diseases. Key highlights encompass the precise control over GNSs' size, crystal structure, shape, and surface functionalization, enabling their integration into sensing, imaging diagnostics, drug delivery systems, and regenerative therapies. GNSs, with their exceptional biocompatibility and antimicrobial properties, have demonstrated efficacy in combating dental caries, periodontitis, peri-implantitis, and oral mucosal diseases. Additionally, they show great promise in the development of advanced sensing techniques for early diagnosis, such as nanobiosensor technology, while their role in targeted drug delivery, photothermal therapy, and immunomodulatory approaches has opened new avenues for oral cancer therapy. Challenges including long-term toxicity, biosafety, immune recognition, and personalized treatment are under rigorous investigation. As research at the intersection of nanotechnology and dentistry continues to thrive, this review highlights the transformative potential of engineered GNSs in revolutionizing dental healthcare, offering accurate, personalized, and minimally invasive solutions to address the oral health challenges of the modern era.

Recent advances in nanomaterial-based biosensor for periodontitis detection

Periodontitis, a chronic inflammatory condition caused by bacteria, often causes gradual destruction of the components that support teeth, such as the alveolar bone, cementum, periodontal ligament, and gingiva. This ultimately results in teeth becoming loose and eventually falling out. Timely identification has a crucial role in preventing and controlling its progression. Clinical measures are used to diagnose periodontitis. However, now, there is a hunt for alternative diagnostic and monitoring methods due to the progress of technology. Various biomarkers have been assessed using multiple bodily fluids as sample sources. Furthermore, conventional periodontal categorization factors do not provide significant insights into the present disease activity, severity and amount of tissue damage, future development, and responsiveness to treatment. In recent times, there has been a growing utilization of nanoparticle (NP)-based detection strategies to create quick and efficient detection assays. Every single one of these platforms leverages the distinct characteristics of NPs to identify periodontitis. Plasmonic NPs include metal NPs, quantum dots (QDs), carbon base NPs, and nanozymes, exceptionally potent light absorbers and scatterers. These find application in labeling, surface-enhanced spectroscopy, and color-changing sensors. Fluorescent NPs function as photostable and sensitive instruments capable of labeling various biological targets. This article presents a comprehensive summary of the latest developments in the effective utilization of various NPs to detect periodontitis.

Microstructured Polymer System Containing Proanthocyanidin-Enriched Extract from Limonium brasiliense as a Prophylaxis Strategy to Prevent Recurrence of Porphyromonas gingivalis

Periodontal diseases are a global oral health problem affecting almost 10% of the global population. Porphyromonas gingivalis is one of the main bacteria involved in the initiation and progression of inflammatory processes as a result of the action of the cysteine proteases lysin- and arginine-gingipain. Surelease/polycarbophil microparticles containing a lyophilized proanthocyanidin-enriched fraction from the rhizomes of Limonium brasiliense, traditionally named "baicuru" (ethyl acetate fraction), were manufactured. The ethyl acetate fraction was characterized by UHPLC by the presence of samarangenins A and B (12.10 ± 0.07 and 21.05 ± 0.44%, respectively) and epigallocatechin-3-O-gallate (13.44 ± 0.27%). Physiochemical aspects of Surelease/polycarbophil microparticles were characterized concerning particle size, zeta potential, entrapment efficiency, ethyl acetate fraction release, and mucoadhesion. Additionally, the presence of the ethyl acetate fraction-loaded microparticles was performed concerning potential influence on viability of human buccal KB cells, P. gingivalis adhesion to KB cells, gingipain activity, and P. gingivalis biofilm formation. In general, all Surelease/polycarbophil microparticles tested showed strong adhesion to porcine cheek mucosa (93.1 ± 4.2% in a 30-min test), associated with a prolonged release of the ethyl acetate fraction (up to 16.5 ± 0.8% in 24 h). Preincubation of KB cells with Surelease/polycarbophil microparticles (25 µg/mL) resulted in an up to 93 ± 2% reduced infection rate by P. gingivalis. Decreased activity of the P. gingivalis-specific virulence factors lysin- and arginine-gingipain proteases by Surelease/polycarbophil microparticles was confirmed. Surelease/polycarbophil microparticles decreased biofilm formation of P. gingivalis (97 ± 2% at 60 µg/mL). Results from this study prove the promising activity of Surelease/polycarbophil microparticles containing ethyl acetate fraction microparticles as a prophylaxis strategy to prevent the recurrence of P. gingivalis.

Accuracy of aMMP-8 point-of-care test in indicating periodontal treatment outcomes in stage III/IV periodontitis: A 24-week follow-up study

OBJECTIVE

To analyse the correspondence between aMMP-8 PoC test results and the clinical endpoints of non-surgical periodontal treatment in stage III/IV periodontitis.

BACKGROUND

The diagnostic success of the active-matrix metalloproteinase-8 (aMMP-8) point-of-care (PoC) test has been demonstrated in various studies, but the evidence of its accuracy following periodontal treatment is limited.

MATERIALS AND METHODS

Altogether 42 stage III/IV grade C periodontitis patients were included in this prospective diagnostic study. Clinical periodontal indices were recorded, aMMP-8 PoC test was applied and mouthrinse was collected before and at 6, 12 and 24 weeks after non-surgical periodontal treatment. Quantitative aMMP-8 levels were determined with immunofluorometric assay (IFMA) for the verification of the PoC test results. The accuracy of the aMMP-8 PoC test was assessed using previously established clinical endpoints as references.

RESULTS

Sensitivity and specificity of aMMP-8 PoC test to indicate clinical endpoints were ranged as follows: Sensitivity 71.4% at baseline, 39.3%-42.4% at week 6, 28.6%-32.4% at week 12 and 35.3%-42.9% at week 24; specificity 64.3%-80% at week 6, 40%-57.1% at week 12 and 56%-64.3% at week 24.

CONCLUSIONS

The accuracy of aMMP-8 PoC test in identifying clinical endpoints after non-surgical periodontal treatment is reduced in relation to baseline. Individual healing patterns of each diseased pocket eventually limit the accuracy of the dichotomous aMMP-8 oral rinse test during the post-treatment period.

Implications of Porphyromonas gingivalis peptidyl arginine deiminase and gingipain R in human health and diseases

Porphyromonas gingivalis is a major pathogenic bacterium involved in the pathogenesis of periodontitis. Citrullination has been reported as the underlying mechanism of the pathogenesis, which relies on the interplay between two virulence factors of the bacterium, namely gingipain R and the bacterial peptidyl arginine deiminase. Gingipain R cleaves host proteins to expose the C-terminal arginines for peptidyl arginine deiminase to citrullinate and generate citrullinated proteins. Apart from carrying out citrullination in the periodontium, the bacterium is found capable of citrullinating proteins present in the host synovial tissues, atherosclerotic plaques and neurons. Studies have suggested that both virulence factors are the key factors that trigger distal effects mediated by citrullination, leading to the development of some non-communicable diseases, such as rheumatoid arthritis, atherosclerosis, and Alzheimer’s disease. Thus, inhibition of these virulence factors not only can mitigate periodontitis, but also can provide new therapeutic solutions for systematic diseases involving bacterial citrullination. Herein, we described both these proteins in terms of their unique structural conformations and biological relevance to different human diseases. Moreover, investigations of inhibitory actions on the enzymes are also enumerated. New approaches for identifying inhibitors for peptidyl arginine deiminase through drug repurposing and virtual screening are also discussed.

A Photoacoustic-Fluorescent Imaging Probe for Proteolytic Gingipains Expressed by Porphyromonas gingivalis

Porphyromonas gingivalis is a keystone pathogen in periodontal disease. We herein report a dual-modal fluorescent and photoacoustic imaging probe for the detection of gingipain proteases secreted by P. gingivalis. Upon proteolytic cleavage by Arg-specific gingipain (RgpB), five-fold photoacoustic enhancement and >100-fold fluorescence activation was measured with detection limits of 1.1 nM RgpB and 5.0E4 CFU mL-1 bacteria in vitro. RgpB activity was imaged in porcine jaws with low-nanomolar sensitivity. Diagnostic efficacy was evaluated in gingival crevicular fluid samples from subjects with and without periodontal disease, wherein activation was correlated to qPCR-based detection of P. gingivalis (Pearson's r=0.71). Finally, photoacoustic imaging of RgpB-cleaved probe was achieved in murine brains ex vivo, with relevance and potential utility for disease models of general infection by P. gingivalis, motivated by the recent biological link between gingipain and Alzheimer's disease.

Fast, Simple, and Highly Specific Molecular Detection of Porphyromonas gingivalis Using Isothermal Amplification and Lateral Flow Strip Methods

Porphyromonas gingivalis is an important oral pathogen that causes periodontal disease and is difficult to culture under conventional conditions. Therefore, a reliable technique for detecting this pathogenic bacterium is required. Here, isothermal recombinase polymerase amplification (RPA), a new nucleic acid amplification method, was combined with a visualization method based on nanoparticle-based lateral flow strips (LFS) for the rapid detection of P. gingivalis. The species-specific 16S rRNA sequence of P. gingivalis was used as the target for RPA, and a set of specific primer–probe combinations were designed and screened to amplify the target sequences. As a thermostatic amplification method, the RPA reaction, under optimized conditions, takes only 30 min to complete at a constant temperature (37°C). The amplification reaction products can be detected visually by LFS without any need for special equipment. The RPA-LFS method established for the detection of P. gingivalis was shown to be highly specific in distinguishing P. gingivalis from other pathogenic organisms by using 20 clinical isolates of P. gingivalis and 23 common pathogenic microorganisms. Susceptibility measurements and probit regression analysis were performed with gradient dilutions of P. gingivalis genomic DNA. The method was obtained to be highly sensitive, with a detection limit of 9.27 CFU per reaction at 95% probability. By analyzing the gingival sulcus fluid specimens from 130 patients with chronic periodontitis, the results showed that the RPA-LFS method detected 118 positive cases and 12 negative cases of P. gingivalis, and the results obtained were consistent with those of a conventional PCR assay. The RPA–LFS method is an efficient, rapid, and convenient diagnostic method that simplifies the tedious process of detecting P. gingivalis.

Nanomaterial application in bio/sensors for the detection of infectious diseases

Infectious diseases are a potential risk for public health and the global economy. Fast and accurate detection of the pathogens that cause these infections is important to avoid the transmission of the diseases. Conventional methods for the detection of these microorganisms are time-consuming, costly, and not applicable for on-site monitoring. Biosensors can provide a fast, reliable, and point of care diagnostic. Nanomaterials, due to their outstanding electrical, chemical, and optical features, have become key players in the area of biosensors. This review will cover different nanomaterials that employed in electrochemical, optical, and instrumental biosensors for infectious disease diagnosis and how these contributed to enhancing the sensitivity and rapidity of the various sensing platforms. Examples of nanomaterial synthesis methods as well as a comprehensive description of their properties are explained. Moreover, when available, comparative data, in the presence and absence of the nanomaterials, have been reported to further highlight how the usage of nanomaterials enhances the performances of the sensor.

Research on Autophagy of Gingiva Epithelial Cell Induced by Porphyromonas Gingivalis Regulated by Long Non-Coding RNA Transforming Growth Factor Beta-2 Overlapping Transcript 1 (LncRNA TGFB2-OT1)

Our study analyzes lncRNA TGFB2-OT1’s effect on autophagy and migration of gingiva epithelial cells and porphyromonas gingivalis. The expression of TGFB2-OT1 and TIMP2 in GEC cells was detected by QRT-PCR. Cell proliferation and colon formation was assessed by MTT method and colony forming assay. The relation between TGFB2-OT1 and TIMP2 was confirmed luciferase assay. The autophagy, apoptosis rate and period distribution was detected by flow cytometry along with analysis of porphyromonas gingivalis of GEC cells. TGFB2-OT1 was upregulated significantly as shown by IncRNA array. TGFB2-OT1 overexpression in GEC cells improved cell proliferation and migration, enhanced the sensibility of gingiva epithelial cell on the porphyromonas gingivalis and increased autophagy. The GEC cells were blocked at G2/M period. The TIMP2 was a direct target of TGFB2-OT1. In conclusion, TIMP2 participates in the up-regulation of MMP10 induced by TGFB2-OT1. The lncRNA TGFB2-OT1 maybe be a potential biomarker to assess the autophagy of gingiva epithelial cell.

Washing- and Separation-Free Electrochemical Detection of Porphyromonas gingivalis in Saliva for Initial Diagnosis of Periodontitis

Indirect detection of Porphyromonas gingivalis in saliva, based on proteolytic cleavage by an Arg-specific gingipain (Arg-gingipain), has traditionally been used for simple, initial diagnosis of periodontitis. To accurately detect P. gingivalis using a point-of-care format, development of a simple biosensor that can measure the exact concentration of P. gingivalis is required. However, electrochemical detection in saliva is challenging due to the presence of various interfering electroactive species in different concentrations. Here, we report a washing- and separation-free electrochemical biosensor for sensitive detection of P. gingivalis in saliva. Glycine-proline-arginine conjugated with 4-aminophenol (AP) was used as an electrochemical substrate for a trypsin-like Arg-gingipain, and glycylglycine was used to increase the Arg-gingipain activity. The electrochemical signal of AP was increased using electrochemical-chemical (EC) redox cycling involving an electrode, AP, and tris(2-carboxyethyl)phosphine, and the electrochemical charge signal was corrected using the initial charge obtained before a 15 min incubation period. The EC redox cycling combined with the matrix-corrected signal facilitated a high and reproducible signal without requiring washing and separation steps. The proteolytic cleavage of the electrochemical substrate was specific to P. gingivalis. The calculated detection limit for P. gingivalis in artificial saliva was 5 × 10⁵ colony-forming units/mL, and the concentration of P. gingivalis in human saliva could be measured. The developed biosensor can be used as an initial diagnosis method to distinguish between healthy people and patients with periodontal diseases.

In situ gel drug delivery system for periodontitis: an insight review

Background

Periodontitis is a microbial disease that leads to inflammation in the tooth-supporting tissues of the oral cavity that is common among the elderly. It is initiated by oral inflammation induced by bacterial dysbiosis. Choosing an appropriate antimicrobial agent with the right course of drug administration is the key to successful periodontal therapy. In recent times, with more biomarkers and the development of new technologies, several point-of-care testing (POCT) platforms have been developed for the diagnosis and monitoring of periodontitis. This review focuses on oral microbiology and the pathogenesis of periodontitis as well as recent insights into the in situ gel system for periodontitis.

Design

An exhaustive search was conducted in the following scientific databases Science Direct, Springer, Pub Med, and Google Scholar to review all relevant literatures. This is a comprehensive narrative review of the literature, summarizing the perspectives of the authors.

Results

Novel in situ forming gel is introduced at the site that shows a promising potential to overcome one of the main practical obstacles associated with the treatment of local periodontitis: partial adhesion to the surrounding tissue, causing in the accidental expulsion of at least parts of the implants from patient’s pockets. This results in a large residence time of the system at the site of action and uncertainty of the final exposure to the drug.

Conclusion

From the reviewed literature, it is concluded that experimental evidence suggests that the in situ gel-forming systems can be useful in treating several common diseases of the oral cavity. Future research should focus on clinical studies to be performed for the in situ gel to make a significant contribution to periodontitis.

Graphical abstract

Salivary Total Protease Activity Based on a Broad-Spectrum Fluorescence Resonance Energy Transfer Approach to Monitor Induction and Resolution of Gingival Inflammation

OBJECTIVE

Salivary total protease and chitinase activities were measured by a broad-spectrum fluorescence resonance energy transfer approach as predictors of induction and resolution of gingival inflammation in healthy individuals by applying an experimental human gingivitis model.

METHODS

Dental biofilm accumulated (21 days, Induction Phase) by omitting oral hygiene practices followed by a 2-week Resolution Phase to restore gingival health in an experimental gingivitis study. Plaque accumulation, as assessed by the Turesky Modification of the Quigley-Hein Plaque Index (TQHPI), and gingival inflammation, assessed using the Modified Gingival Index (MGI), scores were recorded and unstimulated saliva was collected weekly. Saliva was analysed for total protein, albumin, total protease activity and chitinase activity (n = 18).

RESULTS

The TQHPI and MGI scores, as well as total protease activity, increased until day 21. After re-establishment of oral hygiene, gingival inflammation levels returned to values similar to baseline (day 0). Levels of protease activity decreased significantly, but not to baseline values. Furthermore, 'fast' responders, who responded immediately to plaque, exhibited significantly higher proteolytic activity throughout the experimental course than 'slow' responders, who showed a lagged inflammatory response.

CONCLUSION

The results indicate that differential inflammatory responses encompass inherent variations in total salivary proteolytic activities, which could be further utilised in contemporary diagnostic, prognostic and treatment modalities for periodontal diseases.

Rapid Colorimetric Detection of Pseudomonas aeruginosa in Clinical Isolates Using a Magnetic Nanoparticle Biosensor

A rapid, sensitive, and specific colorimetric biosensor based on the use of magnetic nanoparticles (MNPs) was designed for the detection of Pseudomonas aeruginosa in clinical samples. The biosensing platform was based on the measurement of P. aeruginosa proteolytic activity using a specific protease substrate. At the N-terminus, this substrate was covalently bound to MNPs and was linked to a gold sensor surface via cystine at the C-terminus of the substrates. The golden sensor appears black to naked eyes because of the coverage of the MNPs. However, upon proteolysis, the cleaved peptide-MNP moieties will be attracted by an external magnet, revealing the golden color of the sensor surface, which can be observed by the naked eye. In vitro, the biosensor was able to detect specifically and quantitatively the presence of P. aeruginosa with a detection limit of 10² cfu/mL in less than 1 min. The colorimetric biosensor was used to test its ability to detect in situ P. aeruginosa in clinical isolates from patients. This biochip is anticipated to be useful as a rapid point-of-care device for the diagnosis of P. aeruginosa-related infections.

Quercetin Inhibits Inflammatory Response Induced by LPS from Porphyromonas gingivalis in Human Gingival Fibroblasts via Suppressing NF-κB Signaling Pathway

Quercetin, a natural flavonol existing in many food resources, has been reported to be an effective antimicrobial and anti-inflammatory agent for restricting the inflammation in periodontitis. In this study, we aimed to investigate the anti-inflammatory effects of quercetin on Porphyromonas gingivalis (P. gingivalis) lipopolysaccharide- (LPS-) stimulated human gingival fibroblasts (HGFs). HGFs were pretreated with quercetin prior to LPS stimulation. Cell viability was evaluated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. The levels of inflammatory cytokines, including interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), along with chemokine interleukin-8 (IL-8), were determined by enzyme-linked immunosorbent assay (ELISA). The mRNA levels of IL-1β, IL-6, IL-8, TNF-α, IκBα, p65 subunit of nuclear factor-kappa B (NF-κB), peroxisome proliferator-activated receptor-γ (PPAR-γ), liver X receptor α (LXRα), and Toll-like receptor 4 (TLR4) were measured by real-time quantitative PCR (RT-qPCR). The protein levels of IκBα, p-IκBα, p65, p-p65, PPAR-γ, LXRα, and TLR4 were characterized by Western blotting. Our results demonstrated that quercetin inhibited the LPS-induced production of IL-1β, IL-6, IL-8, and TNF-α in a dose-dependent manner. It also suppressed LPS-induced NF-κB activation mediated by TLR4. Moreover, the anti-inflammatory effects of quercetin were reversed by the PPAR-γ antagonist of GW9662. In conclusion, these results suggested that quercetin attenuated the production of IL-1β, IL-6, IL-8, and TNF-α in P. gingivalis LPS-treated HGFs by activating PPAR-γ which subsequently suppressed the activation of NF-κB.

Tolerance induced by Porphyromonas gingivalis may occur independently of TLR2 and TLR4

OBJECTIVE

Periodontitis is a microbe-induced chronic inflammatory disease. Previous exposure of the host to bacteria or their virulence factors leads to refractory responses to further stimuli, which is called tolerance. Porphyromonas gingivalis (P. gingivalis) is one of the most important pathogenic microorganisms associated with periodontitis, and is a potent inducer of pro- and anti-inflammatory cytokines. The aim of this study was to explore the roles and possible mechanisms of tolerance induced by P. gingivalis.

METHODS

THP-1-derived macrophages were pretreated with 1x108 colony-forming units/ml P. gingivalis ATCC 33277 or 21 clinical isolates from moderate to severe chronic periodontitis patients (24 h), washed (2 h) and treated with P. gingivalis ATCC 33277 or the same clinical isolates again (24 h). Levels of pro-inflammatory cytokines TNF-α and IL-1β and anti-inflammatory cytokine IL-10 in supernatants were detected by ELISA. Moreover, to identify the possible mechanisms for the changes in cytokine secretion, Toll-like receptor 2 (TLR2) and TLR4 protein expressions were explored in these cells by flow cytometry.

RESULTS

After repeated challenge with P. gingivalis ATCC 33277 or clinical isolates, production of TNF-α and IL-1β in macrophages was decreased significantly compared with that following a single stimulation (p<0.05), while only comparable levels of IL-10 were detected in P. gingivalis ATCC 33277 or clinical isolate-tolerized cells (p>0.05). In addition, there was interstrain variability in the ability to induce IL-1β and IL-10 production after repeated P. gingivalis stimulation. However, no significant changes in TLR2 or TLR4 were detected in macrophages that were repeatedly treated with P. gingivalis ATCC 33277 or clinical isolates compared with those stimulated with P. gingivalis only once (p>0.05).

CONCLUSIONS

Repeated P. gingivalis stimulation triggered tolerance, which might contribute to limiting periodontal inflammation. However, tolerance induced by P. gingivalis might develop independently of TLR2 and TLR4 and be related to molecules in signaling pathways downstream of TLR2 and TLR4.