In Situ Anabolic Activity of Periodontal Pathogens Porphyromonas gingivalis and Filifactor alocis in Chronic Periodontitis

Opportunistic pathogen Porphyromonas gingivalis targets the LC3B-ceramide complex and mediates lethal mitophagy resistance in oral tumors

Mechanisms by which Porphyromonas gingivalis (P. gingivalis) infection enhances oral tumor growth or resistance to cell death remain elusive. Here, we determined that P. gingivalis infection mediates therapeutic resistance via inhibiting lethal mitophagy in cancer cells and tumors. Mechanistically, P. gingivalis targets the LC3B-ceramide complex by associating with LC3B via bacterial major fimbriae (FimA) protein, preventing ceramide-dependent mitophagy in response to various therapeutic agents. Moreover, ceramide-mediated mitophagy is induced by Annexin A2 (ANXA2)-ceramide association involving the E142 residue of ANXA2. Inhibition of ANXA2-ceramide-LC3B complex formation by wild-type P. gingivalis prevented ceramide-dependent mitophagy. Moreover, a FimA-deletion mutant P. gingivalis variant had no inhibitory effects on ceramide-dependent mitophagy. Further, 16S rRNA sequencing of oral tumors indicated that P. gingivalis infection altered the microbiome of the tumor macroenvironment in response to ceramide analog treatment in mice. Thus, these data provide a mechanism describing the pro-survival roles of P. gingivalis in oral tumors.

NOD2 contributes to Parvimonas micra-induced bone resorption in diabetic rats with experimental periodontitis

BACKGROUND

Type 2 diabetes mellitus (T2DM) may affect the oral microbial community, exacerbating periodontal inflammation; however, its pathogenic mechanisms remain unclear. As nucleotide-binding oligomerization domain 2 (NOD2) plays a crucial role in the activation during periodontitis (PD), it is hypothesized that changes in the oral microbial community due to diabetes enhance periodontal inflammation through the activation of NOD2.

METHODS

We collected subgingival plaque from 180 subjects who were categorized into two groups based on the presence or absence of T2DM. The composition of oral microbiota was detected by 16S rRNA high-throughput sequencing. In animal models of PD with or without T2DM, we assessed alveolar bone resorption by micro-computerized tomography and used immunohistochemistry to detect NOD2 expression in alveolar bone. Primary osteoblasts were cultured in osteogenic induction medium with high or normal glucose and treated with inactivated bacteria. After 24 h of inactivated bacteria intervention, the osteogenic differentiation ability was detected by alkaline phosphatase (ALP) staining, and the expressions of NOD2 and interleukin-12 (IL-6) were detected by western blot.

RESULTS

The relative abundance of Parvimonas and Filifactor in the T2DM group was increased compared to the group without T2DM. In animal models, alveolar bone mass was decreased in PD, particularly in T2DM with PD (DMPD) group, compared to controls. Immunohistochemistry revealed NOD2 in osteoblasts from the alveolar bone in both the PD group and DMPD group, especially in the DMPD group. In vitro, intervention with inactivated Parvimonas significantly reduced ALP secretion of primary osteoblasts in high glucose medium, accompanied by increased expression of NOD2 and IL-6.

CONCLUSIONS

The results suggest that T2DM leading to PD may be associated with the activation of NOD2 by Parvimonas.

Statins Modulate Microenvironmental Cues Driving Macrophage Polarization in Simulated Periodontal Inflammation

Periodontal disease (PD) is a chronic inflammatory disorder characterized by the destruction of connective tissue, tooth loss, and systemic infections. Clinically, treatment of PD includes control of the etiologic factors via several modalities: initial therapy including scaling and root planing (SRP), corrective phase of surgical treatment, both with and without adjunct antimicrobial/pharmacological agents, followed by a maintenance/supportive periodontal therapy phase. Each treatment phase aims to control oral biofilm by addressing risk factors and etiology. Monotherapy of systemic antibiotics is insufficient compared to their use as an adjunct to SRP. The critical issue of systemic antimicrobial usage includes adverse patient outcomes and increased bacterial resistance. Therefore, alternative adjuncts to periodontal therapy have been sought. Statins are widely prescribed for the treatment of hypercholesterolemia and cardiovascular disease. Statins have demonstrated anti-inflammatory properties and immunomodulatory effects, and a few retrospective studies showed that statin patients exhibit fewer signs of periodontal inflammation than subjects without the medication. Despite the available clinical studies on the local administration of statins for PD, no studies have reported the macrophage polarization response. We have developed a gingival fibroblast-macrophage co-culture model to track macrophage response when exposed to a battery of microenvironmental cues mimicking macrophage polarization/depolarization observed in vivo. Using our model, we demonstrate that simvastatin suppresses macrophage inflammatory response and upregulates tissue homeostasis and M2 macrophage markers. Our findings support the usage of statins to mitigate periodontal inflammation as a valid strategy.

Characteristics of the Salivary Microbiota in Periodontal Diseases and Potential Roles of Individual Bacterial Species To Predict the Severity of Periodontal Disease

The purposes of this study were to examine the compositional changes in the salivary microbiota according to the severity of periodontal disease and to verify whether the distribution of specific bacterial species in saliva can distinguish the severity of disease. Saliva samples were collected from 8 periodontally healthy controls, 16 patients with gingivitis, 19 patients with moderate periodontitis, and 29 patients with severe periodontitis. The V3 and V4 regions of the 16S rRNA gene in the samples were sequenced, and the levels of 9 bacterial species showing significant differences among the groups by sequencing analysis were identified using quantitative real-time PCR (qPCR). The predictive performance of each bacterial species in distinguishing the severity of disease was evaluated using a receiver operating characteristic curve. Twenty-nine species, including Porphyromonas gingivalis, increased as the severity of disease increased, whereas 6 species, including Rothia denticola, decreased. The relative abundances of P. gingivalis, Tannerella forsythia, Filifactor alocis, and Prevotella intermedia determined by qPCR were significantly different among the groups. The three bacterial species P. gingivalis, T. forsythia, and F. alocis were positively correlated with the sum of the full-mouth probing depth and were moderately accurate at distinguishing the severity of periodontal disease. In conclusion, the salivary microbiota showed gradual compositional changes according to the severity of periodontitis, and the levels of P. gingivalis, T. forsythia, and F. alocis in mouth rinse saliva had the ability to distinguish the severity of periodontal disease. IMPORTANCE Periodontal disease is one of the most widespread medical conditions and the leading cause of tooth loss, imposing high economic costs and an increasing burden worldwide as life expectancy increases. Changes in the subgingival bacterial community during the progression of periodontal disease can affect the entire oral ecosystem, and bacteria in saliva can reflect the degree of bacterial imbalance in the oral cavity. This study explored whether the specific bacterial species in saliva can distinguish the severity of periodontal disease by analyzing the salivary microbiota and suggested P. gingivalis, T. forsythia, and F. alocis as biomarkers for distinguishing the severity of periodontal disease in saliva.

Clinical and microbiological outcomes of subgingival instrumentation supplemented with high-dose omega-3 polyunsaturated fatty acids in periodontal treatment - a randomized clinical trial

PURPOSE

This study aimed to evaluate the impact of dietary supplementation with omega-3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) combined with scaling and root planing (SRP) in untreated periodontitis stage III and IV.

METHODS

Forty patients were randomly assigned to the test group receiving SRP plus omega-3 PUFAs (n = 20) or control group receiving SRP alone (n = 20). Clinical changes of pocket probing depths (PD), clinical attachment level (CAL), bleeding on probing (BOP) and rates of closed pockets (PPD ≤ 4 mm without BOP) were evaluated at baseline and after 3 and 6 months. Phorphyromonas gingivalis, Tanarella forsythia, Treponema denticola and Aggregatibacter actinomycetemcomitans counts were analysed at baseline and at 6 months. Serum was subjected to lipid gas chromatography/mass spectrometry analysis at baseline and at 6 months.

RESULTS

Significant improvement of all clinical parameters at 3 and 6 months was observed in both groups. For the primary outcome "change of mean PD," no significant difference was detected between the groups. Patients treated with omega-3 PUFAs demonstrated significantly lower rates of BOP, higher gain of CAL and higher number of closed pockets at 3 months in comparison to the control group. After 6 months, no clinical differences between the groups were found, with the exception of lower BOP rates. Moreover, in the test group, the number of key periodontal bacteria was significantly lower than in the control group at 6 months. Increased proportions of serum n-3 PUFAs and decreased proportions of n-6 PUFAs were detected at 6 months in the patients from the test group.

CONCLUSION

High-dose omega-3 PUFA intake during non-surgical treatment of periodontitis results in short-term clinical and microbiological benefits. The study protocol was approved by the ethical committee of Medical University of Lodz (reference number RNN/251/17/KE) and registered at clinicaltrials.gov (NCT04477395) on 20/07/2020.

Impact of Three Nonsurgical, Full-Mouth Periodontal Treatments on Total Bacterial Load and Selected Pathobionts

For the treatment of periodontitis stage III/IV, a quadrant/week-wise debridement (Q-SRP) was compared with three full-mouth approaches: full-mouth scaling (FMS, accelerated Q-SRP within 24 h), full-mouth scaling with chlorhexidine-based disinfection (FMD), and FMD with adjuvant erythritol air polishing (FMDAP). The objective of this prospective, randomized study (a substudy of ClinicalTrials.gov, identifier: NCT03509233) was to compare the clinical and microbiological effects of the treatments. In total, 105 patients were randomized to one of the four aforementioned treatment groups, with n = 25, 28, 27, and 25 patients allocated to each group, respectively. At baseline and 3 and 6 months after treatment, the clinical parameters, including the pocket probing depths, clinical attachment level, and bleeding on probing, were recorded, and the prevalence of the total bacteria and four periodontal pathobionts (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, and Tannerella forsythia) was determined using real-time quantitative PCR. Concerning the clinical outcomes, all the treatment modalities were effective, but the full-mouth approaches, especially FMDAP, were slightly superior to Q-SRP. Using the FMD approach, the reduction in the bacterial load and the number of pathobionts was significantly greater than for FMS, followed by Q-SRP. FMDAP was the least effective protocol for microbial reduction. However, after a temporary increase 3 months after therapy using FMDAP, a significant decrease in the key pathogen, P. gingivalis, was observed. These findings were not consistent with the clinical results from the FMDAP group. In conclusion, the dynamics of bacterial colonization do not necessarily correlate with clinical outcomes after full-mouth treatments for periodontitis stage III/IV.

Electronic cigarette use enriches periodontal pathogens

The effect of electronic cigarette (e-cigarette) smoking, especially its long-term impact on oral health, is poorly understood. Here, we conducted a longitudinal clinical study with two study visits, 6 months apart, to investigate the effect of e-cigarette use on the bacterial community structure in the saliva of 101 periodontitis patients. Our data demonstrated that e-cigarette use altered the oral microbiome in periodontitis patients, enriching members of the Filifactor, Treponema, and Fusobacterium taxa. For patients at the same periodontal disease stage, cigarette smokers and e-cigarette smokers shared more similarities in their oral bacterial composition. E-cigarette smoking may have a similar potential as cigarette smoking at altering the bacterial composition of saliva over time, leading to an increase in the relative abundance of periodontal disease-associated pathogens such as Porphyromonas gingivalis and Fusobacterium nucleatum. The correlation analysis showed that certain genera, such as Dialister, Selenomonas, and Leptotrichia in the e-cigarette smoking group, were positively correlated with the levels of proinflammatory cytokines, including IFN-γ, IL-1β, and TNF-α. E-cigarette use was also associated with elevated levels of proinflammatory cytokines such as IFN-γ and TNF-α, which contribute to oral microbiome dysbiosis and advanced disease state. This article is protected by copyright. All rights reserved.

The Varied Proportion of Filifactor alocis in Periodontal Health and Disease in the South Indian Subpopulation

BACKGROUND AND AIM

The periodontal microbiome being complex, this study was aimed to detect and quantify the prevalence of Filifactor alocis in various stages of periodontitis and to evaluate its prospect as a diagnostic marker for periodontal disease.

SETTINGS AND DESIGN

Sixty subjects were selected (20 healthy controls, 20 with chronic periodontitis, and 20 with aggressive periodontitis) for the study.

MATERIALS AND METHODS

Clinical parameters probing depth and the level of clinical attachment was recorded, subgingival plaque samples were collected. The F. alocis 16srDNA was cloned, sequenced, and used as the standard for real-time quantification of bacterial load using SYBR green chemistry.

STATISTICAL ANALYSIS

Clinical, microbiological, and quantitative polymerase chain reaction (PCR) data were analyzed using ANOVA and Pearson's coefficient correlation.

RESULTS

(a) Real-time PCR analysis showed the highest average F. alocis count in chronic periodontitis subjects (32,409.85), which was followed by count in healthy controls (3046.15) and the least count in aggressive periodontitis subjects (939.84). The bacterial count was statistically significant at P = 0.005. (b) An intra-group comparison reveals that there was a statistically significant increase in the bacterial count with age and mean probing pocket depth at P = 0.0005.

CONCLUSION

F. alocis population in aggressive periodontitis was lower compared to chronic periodontitis and healthy controls. The F. alocis population surge in healthy controls may be due to geographical variations and the ethnicity of the subjects. A higher population of F. alocis in chronic periodontitis proves its high pathogenic potential to invade the host tissues to aid in further periodontal destruction.

Steady-State Pre-rRNA Analysis to Investigate the Functional Microbiome

The gut microbiome is recognized as a critical regulator of human diseases. Constituents of the microbiota and their individual activities can affect a broad range of disease states related to autoimmunity, cancer, infection, metabolism, mental health, and toxicant exposure. A substantial number of microbiome species are not culturable, limiting their study in vitro. Sequencing methods have allowed quantification of the composition of the microbiome, but methods to characterize the physiological status of bacterial species remain limited. Ribosomal RNA precursors (pre-rRNAs) are species-specific intermediates in bacterial ribosomal synthesis, and their levels are highly responsive to environmental changes. Immediately before and during active growth, pre-rRNA levels are high, whereas in non-dividing cells, copy numbers are orders of magnitude lower. These dynamics are conserved in all bacterial species and occur exclusively in viable cells, allowing the specific characterization of living and functional bacteria in their native states. Pre-rRNA analysis has been shown to yield valuable real-time information on the physiology of individual bacterial species within complex samples, beyond what traditional qPCR and sequencing methods can offer. Herein, we describe a PCR-based protocol to interrogate and quantify the in situ growth status of bacterial species of interest within a complex microbiome. We also describe an in vitro protocol to characterize the pre-rRNA/growth relationship for a given bacterial species to provide greater context for values obtained from natural samples. Improved understanding of microbial physiological responses to exposures could reveal novel toxicological mechanisms, biomarkers, and potential treatments. © 2021 Wiley Periodicals LLC. Basic Protocol: Targeted steady-state pre-rRNA analysis Support Protocol: Characterization of pre-rRNA/growth relationship © 2021 by John Wiley & Sons, Inc.

Children with Autism and Their Typically Developing Siblings Differ in Amplicon Sequence Variants and Predicted Functions of Stool-Associated Microbes

The existence of a link between the gut microbiome and autism spectrum disorder (ASD) is well established in mice, but in human populations, efforts to identify microbial biomarkers have been limited due to a lack of appropriately matched controls, stratification of participants within the autism spectrum, and sample size. To overcome these limitations, we crowdsourced the recruitment of families with age-matched sibling pairs between 2 and 7 years old (within 2 years of each other), where one child had a diagnosis of ASD and the other did not. Parents collected stool samples, provided a home video of their ASD child's natural social behavior, and responded online to diet and behavioral questionnaires. 16S rRNA V4 amplicon sequencing of 117 samples (60 ASD and 57 controls) identified 21 amplicon sequence variants (ASVs) that differed significantly between the two cohorts: 11 were found to be enriched in neurotypical children (six ASVs belonging to the Lachnospiraceae family), while 10 were enriched in children with ASD (including Ruminococcaceae and Bacteroidaceae families). Summarizing the expected KEGG orthologs of each predicted genome, the taxonomic biomarkers associated with children with ASD can use amino acids as precursors for butyragenic pathways, potentially altering the availability of neurotransmitters like glutamate and gamma aminobutyric acid (GABA).IMPORTANCE Autism spectrum disorder (ASD), which now affects 1 in 54 children in the United States, is known to have comorbidity with gut disorders of a variety of types; however, the link to the microbiome remains poorly characterized. Recent work has provided compelling evidence to link the gut microbiome to the autism phenotype in mouse models, but identification of specific taxa associated with autism has suffered replicability issues in humans. This has been due in part to sample size that sufficiently covers the spectrum of phenotypes known to autism (which range from subtle to severe) and a lack of appropriately matched controls. Our original study proposes to overcome these limitations by collecting stool-associated microbiome on 60 sibling pairs of children, one with autism and one neurotypically developing, both 2 to 7 years old and no more than 2 years apart in age. We use exact sequence variant analysis and both permutation and differential abundance procedures to identify 21 taxa with significant enrichment or depletion in the autism cohort compared to their matched sibling controls. Several of these 21 biomarkers have been identified in previous smaller studies; however, some are new to autism and known to be important in gut-brain interactions and/or are associated with specific fatty acid biosynthesis pathways.

Host surface ectonucleotidase-CD73 and the opportunistic pathogen, Porphyromonas gingivalis, cross-modulation underlies a new homeostatic mechanism for chronic bacterial survival in human epithelial cells

Cell surface nucleotide-metabolizing enzyme, ectonucleotidase-CD73, has emerged as a central component of the cellular homeostatic-machinery that counterbalances the danger-molecule (extracellular-ATP)-driven proinflammatory response in immune cells. While the importance of CD73 in microbial host fitness and symbiosis is gradually being unraveled, there remains a significant gap in knowledge of CD73 and its putative role in epithelial cells. Here, we depict a novel host-pathogen adaptation mechanism where CD73 takes a center role in the intracellular persistence of Porphyromonas gingivalis, a major colonizer of oral mucosa, using human primary gingival epithelial cell (GEC) system. Temporal analyses revealed, upon invasion into the GECs, P. gingivalis can significantly elevate the host-surface CD73 activity and expression. The enhanced and active CD73 significantly increases P. gingivalis intracellular growth in the presence of substrate-AMP and simultaneously acts as a negative regulator of reactive oxygen species (ROS) generation upon eATP treatment. The inhibition of CD73 by siRNA or by a specific inhibitor markedly increases ROS production. Moreover, CD73 and P. gingivalis cross-signaling significantly modulates pro-inflammatory interleukin-6 (IL-6) in the GECs. Conversely, exogenous treatment of the infected GECs with IL-6 suppresses the intracellular bacteria via amplified ROS generation. However, the decreased bacterial levels can be restored by overexpressing functionally active CD73. Together, these findings illuminate how the local extracellular-purine-metabolism, in which CD73 serves as a core molecular switch, can alter intracellular microbial colonization resistance. Further, host-adaptive pathogens such as P. gingivalis can target host ectonucleotidases to disarm specific innate defenses for successful intracellular persistence in mucosal epithelia.

In Situ Intraepithelial Localizations of Opportunistic Pathogens, Porphyromonas gingivalis and Filifactor alocis, in Human Gingiva

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The gingival epithelium serves as a growth reservoir for opportunistic bacteria.

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Intraepithelial P. gingivalis and F. alocis colonies are detected together in dysbiotic mucosa.

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Increased metabolically active dual species can lead to higher microvasculature.

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Invasion of intraepithelial microvessels leads to systemic pathogen dissemination.

Porphyromonas gingivalis and Filifactor alocis are fastidious oral pathogens and etiological agents associated with chronic periodontitis. Although previous studies showed increased levels of the two obligate anaerobic species in periodontitis patients, methodologies for this knowledge were primarily limited to sampling subgingival plaque, saliva, or gingival crevicular fluid. To evaluate the extent to which P. gingivalis and F. alocis may invade the periodontal tissues, an in situ cross-sectional study was comparatively conducted on the gingival biopsy specimens of patients diagnosed with periodontal health or chronic periodontitis. Immunostained tissue sections for each organism were imaged by Super-Resolution Confocal Scanning Microscopy to determine the relative presence and localization of target bacterial species. Fluorescence-in-situ-hybridization (FISH) coupled with species specific 16S rRNA method was utilized to confirm whether detected bacteria were live within the tissue. In periodontitis, P. gingivalis and F. alocis revealed similarly concentrated localization near the basement membrane or external basal lamina of the gingival epithelium. The presence of both bacteria was significantly increased in periodontitis vs. healthy tissue. However, P. gingivalis was still detected to an extent in health tissue, while only minimal levels of F. alocis were spotted in health. Additionally, the micrographic analyses displayed heightened formation of epithelial microvasculature containing significantly co-localized and metabolically active dual species within periodontitis tissue. Thus, this study demonstrates, for the first-time, spatial arrangements of P. gingivalis and F. alocis in both single and co-localized forms within the complex fabric of human gingiva during health and disease. It also exhibits critical visualizations of co-invaded microvascularized epithelial layer of the tissue by metabolically active P. gingivalis and F. alocis from patients with severe periodontitis. These findings collectively uncover novel visual evidence of a potential starting point for systemic spread of opportunistic bacteria during their chronic colonization in gingival epithelium.

Whole Transcriptome Analysis Reveals That Filifactor alocis Modulates TNFα-Stimulated MAPK Activation in Human Neutrophils

Periodontitis is an irreversible, bacteria-induced, chronic inflammatory disease that compromises the integrity of tooth-supporting tissues and adversely affects systemic health. As the immune system's first line of defense against bacteria, neutrophils use their microbicidal functions in the oral cavity to protect the host against periodontal disease. However, periodontal pathogens have adapted to resist neutrophil microbicidal mechanisms while still propagating inflammation, which provides essential nutrients for the bacteria to proliferate and cause disease. Advances in sequencing technologies have recognized several newly appreciated bacteria associated with periodontal lesions such as the Gram-positive anaerobic rod, Filifactor alocis. With the discovery of these oral bacterial species, there is also a growing need to assess their pathogenic potential and determine their contribution to disease progression. Currently, few studies have addressed the pathogenic mechanisms used by oral bacteria to manipulate the neutrophil functional responses at the level of the transcriptome. Thus, this study aims to characterize the global changes at the gene expression level in human neutrophils during infection with F. alocis. Our results indicate that the challenge of human neutrophils with F. alocis results in the differential expression of genes involved in multiple neutrophil effector functions such as chemotaxis, cytokine and chemokine signaling pathways, and apoptosis. Moreover, F. alocis challenges affected the expression of components from the TNF and MAPK kinase signaling pathways. This resulted in transient, dampened p38 MAPK activation by secondary stimuli TNFα but not by fMLF. Functionally, the F. alocis-mediated inhibition of p38 activation by TNFα resulted in decreased cytokine production but had no effect on the priming of the respiratory burst response or the delay of apoptosis by TNFα. Since the modulatory effect was characteristic of viable F. alocis only, we propose this as one of F. alocis' mechanisms to control neutrophils and their functional responses.

Hydrogel containing minocycline and zinc oxide-loaded serum albumin nanopartical for periodontitis application: preparation, characterization and evaluation

Periodontal disease is a complex problem which often interrelates with several serious systemic diseases. However, the satisfactory clinical therapy has yet to be achieved. Herein, serum albumin microspheres containing minocycline and zinc oxide nanoparticals (ZnO NPs) were prepared and incorporated in a Carbopol 940^® hydrogel. Compared with 2% minocycline ointment (Perio^®), the hydrogel has shown obvious therapy effects and the ability of gingival tissue self-repairing. The serum albumin microspheres containing 0.06% of minocycline and 0.025% of ZnO NPs presented an average size of 139 ± 0.42 nm using electrophoretic light scattering (n = 3). Photomicrographs obtained by TEM showed homogeneous and spherical-shaped particles. The encapsulation efficiency was 99.99% for minocycline and the slow-release time was more than 72 h with pH-sensitive property. The in vitro skin adhesion experiment showed that the largest bioadhesive force is 0.35 N. Moreover, the hydrogel showed broad-spectrum antimicrobial and effective antibacterial ability when concentration of the ZnO NPs was over 0.2 µg/mL. The cell survival rates were more than 85% below 0.8 mg/L of ZnO NPs, which proved its low toxicity and high security.

Periodontal ligament fibroblasts regulate osteoblasts by exosome secretion induced by inflammatory stimuli

OBJECTIVES

This study evaluated the role of human periodontal ligament fibroblasts (hPDLFs)-derived exosomes in periodontitis progression and discovered whether hPDLFs influence bone remodeling activity via exosome secretion.

MATERIALS AND METHODS

Exosomes were isolated and quantified from Porphyromonas gingivalis lipopolysaccharide (LPS)-treated primary hPDLFs and evaluated by western blotting, dynamic light scattering, and transmission electron microscopy. GW4869 was used to block exosome secretion in conditioned medium (CM). hPDLFs-derived CM, CM containing GW4869 (CM + GW4869) and exosomes were used to stimulate MG-63 cell lines. The expression levels of proinflammatory mediators, osteogenic genes, and osteoclastogenesis-related genes were measured by quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, western blotting, and alkaline phosphatase staining.

RESULTS

Exosome-enriched protein and total exosomal protein levels were higher in the LPS-treated group than in the vehicle controls. hPDLFs-derived exosomes were incorporated into MG-63 osteoblasts and slightly upregulated the expression of Interleukin-6 and tumor necrosis factor-alpha. CM and exosomes inhibited alkaline phosphatase, Collagen-I, Runt-related transcription factor 2, and Osteoprotegerin expression as well as ALP activity, and blocking exosome secretion by GW4869 eliminated the inhibitory effects.

CONCLUSION

These results indicate that LPS-pretreated hPDLFs induce inflammation and inhibit osteogenic activity of osteoblasts through secreting exosomes. This study provides a potential mechanism by which localized periodontal inflammation may influence bone remodeling by release exosomes.

Molecular viability testing of viable but non-culturable bacteria induced by antibiotic exposure

Nucleic acid amplification-based methods are limited by their inability to discriminate between viable and dead cells. To overcome this drawback, propidium monoazide (PMA) combined with qPCR has been used to differentiate viable from nonviable cells in environmental samples. However, assessing bacterial physiology using PMA-qPCR remains a challenge due to its incapability of detecting metabolic activities, leading to overestimation of the viable bacteria population under an inactivation condition (e.g. antibiotic treatments). A recent advanced technique to amplify ribosomal RNA precursors (pre-rRNA) has been shown to detect viable cells because pre-rRNAs are intermediates in rRNA synthesis. This study investigated the effect of different types of antibiotics on the bacterial viability or viable but non-culturable (VBNC) state using both PMA-qPCR and pre-rRNA analyses with Pseudomonas aeruginosa. This study demonstrated that P. aeruginosa was more sensitive to colistin than it was to carbenicillin, gentamicin and levofloxacin. We could discriminate VBNCP. aeruginosa cells using PMA-qPCR when antibiotic pressure induced the VBNC state. Also, pre-rRNA was able to distinguish viable cells from colistin-inactivated bacteria cells, and it could detect the presence of VBNC and persister cells. Our results showed that these two molecular methods could successfully eliminate false-positive signals derived from antibiotics-inactivated cells.

Porphyromonas gingivalis traffics into endoplasmic reticulum-rich-autophagosomes for successful survival in human gingival epithelial cells

Porphyromonas gingivalis, an opportunistic pathogen usurps gingival epithelial cells (GECs) as primary intracellular niche for its colonization in the oral mucosa. However, the precise characterization of the intracellular trafficking and fate of P. gingivalis in GECs remains incomplete. Therefore, we employed high-resolution three-dimensional-transmission-electron-microscopy to determine the subcellular location of P. gingivalis in human primary GECs upon invasion. Serial sections of infected-GECs and their tomographic reconstruction depicted ER-rich-double-membrane autophagosomal-vacuoles harboring P. gingivalis. Western-blotting and fluorescence confocal microscopy showed that P. gingivalis significantly induces LC3-lipidation in a time-dependent-manner and co-localizes with LC3, ER-lumen-protein Bip, or ER-tracker, which are major components of the phagophore membrane. Furthermore, GECs that were infected with FMN-green-fluorescent transformant-strain (PgFbFP) and selectively permeabilized by digitonin showed rapidly increasing large numbers of double-membrane-vacuolar-P. gingivalis over 24 hours of infection with a low-ratio of cytosolically free-bacteria. Moreover, inhibition of autophagy using 3-methyladenine or ATG5 siRNA significantly reduced the viability of intracellular P. gingivalis in GECs as determined by an antibiotic-protection-assay. Lysosomal marker, LAMP-1, showed a low-degree colocalization with P. gingivalis (∼20%). PgFbFP was used to investigate the fate of vacuolar- versus cytosolic-P. gingivalis by their association with ubiquitin-binding-adaptor-proteins, NDP52 and p62. Only cytosolic-P. gingivalis had a significant association with both markers, which suggests cytosolically-free bacteria are likely destined to the lysosomal-degradation pathway whereas the vacuolar-P. gingivalis survives. Therefore, the results reveal a novel mechanism for P. gingivalis survival in GECs by harnessing host autophagy machinery to establish a successful replicative niche and persistence in the oral mucosa.

Human Primary Epithelial Cells Acquire an Epithelial-Mesenchymal-Transition Phenotype during Long-Term Infection by the Oral Opportunistic Pathogen, Porphyromonas gingivalis

Porphyromonas gingivalis is a host-adapted oral pathogen associated with chronic periodontitis that successfully survives and persists in the oral epithelium. Recent studies have positively correlated periodontitis with increased risk and severity of oral squamous cell carcinoma (OSCC). Intriguingly, the presence of P. gingivalis enhances tumorigenic properties independently of periodontitis and has therefore been proposed as a potential etiological agent for OSCC. However, the initial host molecular changes induced by P. gingivalis infection which promote predisposition to cancerous transformation through EMT (epithelial-mesenchymal-transition), has never been studied in human primary cells which more closely mimic the physiological state of cells in vivo. In this study, we examine for the first time in primary oral epithelial cells (OECs) the expression and activation of key EMT mediators during long-term P. gingivalis infection in vitro. We examined the inactive phosphorylated state of glycogen synthase kinase-3 beta (p-GSK3β) over 120 h P. gingivalis infection and found p-GSK3β, an important EMT regulator, significantly increases over the course of infection (p < 0.01). Furthermore, we examined the expression of EMT-associated transcription factors, Slug, Snail, and Zeb1 and found significant increases (p < 0.01) over long-term P. gingivalis infection in protein and mRNA expression. Additionally, the protein expression of mesenchymal intermediate filament, Vimentin, was substantially increased over 120 h of P. gingivalis infection. Analysis of adhesion molecule E-cadherin showed a significant decrease (p < 0.05) in expression and a loss of membrane localization along with β-catenin in OECs. Matrix metalloproteinases (MMPs) 2, 7, and 9 are all markedly increased with long-term P. gingivalis infection. Finally, migration of P. gingivalis infected cells was evaluated using scratch assay in which primary OEC monolayers were wounded and treated with proliferation inhibitor, Mitomycin C. The cellular movement was determined by microscopy. Results displayed P. gingivalis infection promoted cell migration which was slightly enhanced by co-infection with Fusobacterium nucleatum, another oral opportunistic pathogen. Therefore, this study demonstrates human primary OECs acquire initial molecular/cellular changes that are consistent with EMT induction during long-term infection by P. gingivalis and provides a critically novel framework for future mechanistic studies.

Microbial profile comparisons of saliva, pooled and site-specific subgingival samples in periodontitis patients

Objectives

The purpose of this study was to compare microbial profiles of saliva, pooled and site-specific subgingival samples in patients with periodontitis. We tested the hypotheses that saliva can be an alternative to pooled subgingival samples, when screening for presence of periopathogens.

Design

Site specific subgingival plaque samples (n = 54), pooled subgingival plaque samples (n = 18) and stimulated saliva samples (n = 18) were collected from 18 patients with generalized chronic periodontitis. Subgingival and salivary microbiotas were characterized by means of HOMINGS (Human Oral Microbe Identification using Next Generation Sequencing) and microbial community profiles were compared using Spearman rank correlation coefficient.

Results

Pronounced intraindividual differences were recorded in site-specific microbial profiles, and site-specific information was in general not reflected by pooled subgingival samples. Presence of Porphyromonas gingivalis, Treponema denticola, Prevotella intermedia, Filifactor alocis, Tannerella forsythia and Parvimona micra in site-specific subgingival samples were detected in saliva with an AUC of 0.79 (sensitivity: 0.61, specificity: 0.94), compared to an AUC of 0.76 (sensitivity: 0.56, specificity: 0.94) in pooled subgingival samples.

Conclusions

Site-specific presence of periodontal pathogens was detected with comparable accuracy in stimulated saliva samples and pooled subgingival plaque samples. Consequently, saliva may be a reasonable surrogate for pooled subgingival samples when screening for presence of periopathogens. Future large-scale studies are needed to confirm findings from this study.

Opportunistic Pathogen Porphyromonas gingivalis Modulates Danger Signal ATP-Mediated Antibacterial NOX2 Pathways in Primary Epithelial Cells

Porphyromonas gingivalis, a major opportunistic pathogen in the etiology of chronic periodontitis, successfully survives in human gingival epithelial cells (GECs). P. gingivalis abrogates the effects of a host danger molecule, extracellular ATP (eATP)/P2X₇ signaling, such as the generation of reactive oxygen species (ROS) via the mitochondria and NADPH oxidases (NOX) from primary GECs. However, antimicrobial functions of ROS production are thoroughly investigated in myeloid-lineage immune cells and have not been well-understood in epithelial cells. Therefore, this study characterizes antibacterial NOX2 generated ROS and host downstream effects in P. gingivalis infected human primary GECs. We examined the expression of NOX isoforms in the GECs and demonstrate eATP stimulation increased the mRNA expression of NOX2 (p < 0.05). Specific peptide inhibition of NOX2 significantly reduced eATP-mediated ROS as detected by DCFDA probe. The results also showed P. gingivalis infection can temporally modulate NOX2 pathway by reorganizing the localization and activation of cytosolic molecules (p47phox, p67phox, and Rac1) during 24 h of infection. Investigation into downstream biocidal factors of NOX2 revealed an eATP-induced increase in hypochlorous acid (HOCl) in GECs detected by R19-S fluorescent probe, which is significantly reduced by a myeloperoxidase (MPO) inhibitor. MPO activity of the host cells was assayed and found to be positively affected by eATP treatment and/or infection. However, P. gingivalis significantly reduced the MPO product, bactericidal HOCl, in early times of infection upon eATP stimulation. Analysis of the intracellular levels of a major host-antioxidant, glutathione during early infection revealed a substantial decrease (p < 0.05) in reduced glutathione indicative of scavenging of HOCl by P. gingivalis infection and eATP treatment. Examination of the mRNA expression of key enzymes in the glutathione synthesis pathway displayed a marked increase (p < 0.05) in glutamate cysteine ligase (GCL) subunits GCLc and GCLm, glutathione synthetase, and glutathione reductase during the infection. These suggest P. gingivalis modulates the danger signal eATP-induced NOX2 signaling and also induces host glutathione synthesis to likely avoid HOCl mediated clearance. Thus, we characterize for the first time in epithelial cells, an eATP/NOX2-ROS-antibacterial pathway and demonstrate P. gingivalis can circumvent this important antimicrobial defense system potentially for successful persistence in human epithelial tissues.

Salivary inflammatory markers and microbiome in normoglycemic lean and obese children compared to obese children with type 2 diabetes

BACKGROUND

There is emerging evidence linking diabetes with periodontal disease. Diabetes is a well-recognized risk factor for periodontal disease. Conversely, pro-inflammatory molecules released by periodontally-diseased tissues may enter the circulation to induce insulin resistance. While this association has been demonstrated in adults, there is little information regarding periodontal status in obese children with and without type 2 diabetes (T2D). We hypothesized that children with T2D have higher rates of gingivitis, elevated salivary inflammatory markers, and an altered salivary microbiome compared to children without T2D.

METHODS

Three pediatric cohorts ages 10-19 years were studied: lean (normal weight-C), obese (Ob), and obese with T2D (T2D). Each subject completed an oral health survey, received a clinical oral examination, and provided unstimulated saliva for measurement of inflammatory markers and microbiome analysis.

RESULTS

The diabetes group was less likely to have had a dental visit within the last six months. Body mass index (BMI) Z-scores and waist circumference/height ratios were similar between Ob and T2D cohorts. The number of carious lesions and fillings were similar for all three groups. The gingival index was greater in the T2D group compared to the Ob and C groups. Although salivary microbial diversity was minimal between groups, a few differences in bacterial genus composition were noted.

CONCLUSIONS

Obese children with T2D show a trend toward poorer oral health compared to normal weight and obese children without T2D. This study characterizes the salivary microbiome of children with and without obesity and T2D. This study supports a modest link between T2D and periodontal inflammation in the pediatric population.