Molecular Strategies Underlying Porphyromonas gingivalis Virulence

Inhibition of SARS-CoV-2 infection by Porphyromonas gingivalis and the oral microbiome

The COVID-19 pandemic persists despite the availability of vaccines, and it is, therefore, crucial to develop new therapeutic and preventive approaches. In this study, we investigated the potential role of oral microbiome in SARS-CoV-2 infection. Using an in vitro SARS-CoV-2 pseudovirus infection assay, we found a potent inhibitory effect exerted by Porphyromonas gingivalis on SARS-CoV-2 infection mediated by known P. gingivalis compounds such as phosphoglycerol dihydroceramide (PGDHC) and gingipains as well as by unknown bacterial factors. We found that the gingipain-mediated inhibition of infection is likely due to cytotoxicity, whereas PGDHC inhibited virus infection by an unknown mechanism. Unidentified factors present in P. gingivalis supernatant inhibited SARS-CoV-2 likely via the fusion step of the virus life cycle. We addressed the role of other oral bacteria and found certain periodontal pathogens capable of inhibiting SARS-CoV-2 pseudovirus infection by inducing cytotoxicity on target cells. In the human oral cavity, we observed that the modulatory activity of oral microbial communities varied among individuals, in that some saliva-based cultures were capable of inhibiting while others were enhancing infection. These findings contribute to our understanding of the complex relationship between the oral microbiome and viral infections, offering potential avenues for innovative therapeutic strategies in combating COVID-19.

IMPORTANCE

The oral microbiome is important in health and disease, and in this study, we addressed the potential role of the oral microbiome in COVID-19 infection. Our in vitro studies suggest that certain bacteria of the oral microbiome such as P. gingivalis produce compounds that could potentially inhibit SARS-CoV-2 infection. These findings elucidating the interactions between the oral microbiome and SARS-CoV-2 infection will be important in our understanding of COVID-19 pathogenesis and the development of innovative therapeutic and preventive strategies against COVID-19 infection.

Glycolanguage of the oral microbiota

The oral cavity harbors a diverse and dynamic bacterial biofilm community which is pivotal to oral health maintenance and, if turning dysbiotic, can contribute to various diseases. Glycans as unsurpassed carriers of biological information are participating in underlying processes that shape oral health and disease. Bacterial glycoinfrastructure-encompassing compounds as diverse as glycoproteins, lipopolysaccharides (LPSs), cell wall glycopolymers, and exopolysaccharides-is well known to influence bacterial fitness, with direct effects on bacterial physiology, immunogenicity, lifestyle, and interaction and colonization capabilities. Thus, understanding oral bacterias' glycoinfrastructure and encoded glycolanguage is key to elucidating their pathogenicity mechanisms and developing targeted strategies for therapeutic intervention. Driven by their known immunological role, most research in oral glycobiology has been directed onto LPSs, whereas, recently, glycoproteins have been gaining increased interest. This review draws a multifaceted picture of the glycolanguage, with a focus on glycoproteins, manifested in prominent oral bacteria, such as streptococci, Porphyromonas gingivalis, Tannerella forsythia, and Fusobacterium nucleatum. We first define the characteristics of the different glycoconjugate classes and then summarize the current status of knowledge of the structural diversity of glycoconjugates produced by oral bacteria, describe governing biosynthetic pathways, and list biological roles of these energetically costly compounds. Additionally, we highlight emerging research on the unraveling impact of oral glycoinfrastructure on dental caries, periodontitis, and systemic conditions. By integrating current knowledge and identifying knowledge gaps, this review underscores the importance of studying the glycolanguage oral bacteria speak to advance our understanding of oral microbiology and develop novel antimicrobials.

Nicotinamide employs a starvation strategy against Porphyromonas gingivalis virulence by inhibiting the heme uptake system and gingipain activities

Periodontitis is a common oral bacterial infection characterized by inflammatory responses. Its high prevalence lowers the quality of life for individuals and increases the global economic and disease burden. As microorganisms in dental plaque are responsible for this oral disease, antibacterial drug treatments are effective strategies for preventing and treating periodontitis. In this study, we investigated the inhibitory effect of nicotinamide (NAM), a vitamin B3 derivative, on the growth and virulence of Porphyromonas gingivalis, a key member of the red complex. Our findings revealed that NAM inhibited bacterial growth and gingipain activities, which played a dominant role in protein hydrolysis and heme acquisition. NAM decreased hemagglutination and hemolysis abilities and changed hemin and hemoglobin binding capacities, controlling bacterial infection through a starvation strategy by blocking access to growth-essential nutrients from the outside and reducing bacterial virulence. Several experiments in an animal model showed the effectiveness of NAM in preventing alveolar bone loss and reducing inflammatory cell infiltration, shedding light on its potential therapeutic applicability.

Delineation of global, absolutely essential and conditionally essential pangenomes of Porphyromonas gingivalis

Porphyromonas gingivalis is a Gram-negative, anaerobic oral pathobiont, an etiological agent of periodontitis and the most commonly studied periodontal bacterium. Multiple low passage clinical isolates were sequenced, and their genomes compared to several laboratory strains. Phylogenetic distances were mapped, a gene absence-presence matrix generated, and core (present in all genomes) and accessory (absent in one or more genomes) genes delineated. Subsequently, a second pangenome delineating the prevalence of inherently essential genes was generated. The prevalence of genes conditionally essential for surviving tobacco exposure, abscess formation and epithelial invasion was also determined, in addition to genes encoding key proteolytic enzymes containing putative signal peptides. While the absolutely essential pangenome was highly conserved, significant differences in the complete and conditionally essential pangenomes were apparent. Thus, genetic plasticity appears to lie primarily in gene sets facilitating adaptation to variant disease-related environments. Those genes that are highly pervasive in the P. gingivalis absolutely essential pangenome or are highly prevalent and essential for fitness in disease-relevant models, may represent particularly attractive therapeutic targets worthy of further investigation. As mutations in absolutely essential genes are expected to be lethal, the data provided herein should also facilitate improved planning for P. gingivalis gene mutation strategies.

SIRT6 alleviates senescence induced by Porphyromonas gingivalis in human gingival fibroblasts

OBJECTIVE

Bidirectional influences between senescence and inflammation are newly discovered. This study aimed to clarify the roles and mechanism of Porphyromonas gingivalis (P. gingivalis) in exacerbating senescence in human gingival fibroblasts (HGFs).

DESIGN

Subgingival plaque and gingivae were collected from twenty-four periodontitis patients and eighteen periodontally healthy subjects. Quantities of P. gingivalis in subgingival plaque were explored using real-time PCR and the expressions of p53, p21 and SIRT6 in gingivae were detected by IHC. Moreover, senescence in HGFs was induced by P. gingivalis lipopolysaccharide (LPS) and the expressions of senescence-related β-galactosidase (SA-β-gal), p53, p21 and senescence-associated secretory phenotype (IL-6 and IL-8) with or without treatment by SIRT6 activator UBCS039 were explored by IHC, western blot and ELISA, respectively. In addition, the levels of SIRT6, Nrf2, HO-1 and reactive oxygen species (ROS) were examined by western blot and flow cytometry.

RESULTS

Quantities of P. gingivalis in subgingival plaque and semi-quantitative scores of p53 and p21 in gingivae of periodontitis patients were increased compared with healthy controls (p < 0.05), while SIRT6 score in periodontitis patients was decreased (p < 0.001). Quantities of P. gingivalis were positively correlated with p53 and p21 scores (0.6 < r < 0.9, p < 0.01), and negatively correlated with SIRT6 score (-0.9 < r<-0.6, p < 0.01). Moreover, P. gingivalis LPS increased the levels of SA-β-gal, p53, p21, IL-6, IL-8 and ROS and decreased the levels of SIRT6, Nrf2 and HO-1 in HGFs, which was rescued by UBCS039 (p < 0.05).

CONCLUSIONS

P. gingivalis LPS could induce senescence of HGFs, which could be reversed by SIRT6 via Nrf2-HO-1 signaling pathway.

Gingipain and oncostatin M synergistically disrupt kidney tight junctions in periodontitis-associated acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is characterized by rapid renal decline. Periodontitis, a chronic oral inflammatory disease, is increasingly associated with renal dysfunction. Although periodontitis is recognized as a contributor to kidney damage, the mechanisms linking it to AKI remain unclear.

METHODS

This study explored the effects of Porphyromonas gingivalis (P. gingivalis) W83-infected periodontitis on AKI in C57BL/6J mice, using ischemia-reperfusion injury 55 days post-infection. Gingipain inhibitors, KYT-1 and KYT-36, were applied. Detection of P. gingivalis was performed using quantitative real-time polymerase chain reaction (qRT-PCR) and PCR, while transcriptome sequencing, qRT-PCR, immunohistochemistry, and immunofluorescence staining assessed renal damage. In vitro, HK-2 cells were exposed to P. gingivalis at a multiplicity of infection of 10 for 48 h, with inhibition by gingipain or oncostatin M (OSM). Disruption of tight junctions (TJs) was quantified using qRT-PCR, transepithelial electrical resistance, and cell counting kit-8 assays.

RESULTS

Periodontitis worsened AKI, linked to P. gingivalis infection and renal TJ disruption in the kidney. P. gingivalis infection activated OSM expression, which correlated positively with gingipain. Significantly, OSM and gingipain might collaboratively contribute to the damage of renal TJs, with the reduced expression of TJ proteins. Suppressing gingipain activity presented itself as a protective strategy against the destruction of TJs and the attendant worsening of AKI due to periodontitis.

CONCLUSIONS

Our study enhances the understanding of the interplay between periodontitis and AKI, highlighting the harmful impact of P. gingivalis in AKI.

Anaerobic bacteria in chronic wounds: Roles in disease, infection and treatment failure

Infection is among the most common factors that impede wound healing, yet standard treatments routinely fail to resolve chronic wound infections. The chronic wound environment is largely hypoxic/anoxic, and wounds are predominantly colonised by facultative and obligate anaerobic bacteria. Oxygen (O2) limitation is an underappreciated driver of microbiota composition and behaviour in chronic wounds. In this perspective article, we examine how anaerobic bacteria and their distinct physiologies support persistent, antibiotic-recalcitrant infections. We describe the anaerobic energy metabolisms bacteria rely on for long-term survival in the wound environment, and why many antibiotics become less effective under hypoxic conditions. We also discuss obligate anaerobes, which are among the most prevalent taxa to colonise chronic wounds, yet their potential roles in influencing the microbial community and wound healing have been overlooked. All of the most common obligate anaerobes found in chronic wounds are opportunistic pathogens. We consider how these organisms persist in the wound environment and interface with host physiology to hinder wound healing processes or promote chronic inflammation. Finally, we apply our understanding of anaerobic physiologies to evaluate current treatment practices and to propose new strategies for treating chronic wound infections.

CXCR4-mediated neutrophil dynamics in periodontitis

BACKGROUND AND OBJECTIVE

Periodontitis is a common oral disease closely related to immune response and this study is aimed to identify the key immune-related pathogenic genes and analyze the infiltration and function of immune cells in the disease using bioinformatics methods.

METHODS

Transcriptome datasets and single-cell RNA sequencing (scRNA-seq) datasets were downloaded from the GEO database. We utilized weighted correlation network analysis and least absolute selection and shrinkage operator, protein-protein interaction network construction to screen out key pathogenic genes as well as conducted the cell-type identification by estimating relative subsets of RNA transcripts algorithm to analyze and characterize immune cell types in periodontal tissues. In addition to bioinformatics validations, clinical and cell samples were collected and mouse periodontitis models were constructed to validate the important role of key genes in periodontitis.

RESULTS

Bioinformatics analysis pointed out the positive correlation between CXCR4 expression and periodontitis, and revealed the increased infiltration of neutrophils in periodontal inflammatory. Similar results were obtained from clinical samples and animal models. In addition, the clustering and functional enrichment results based on CXCR4 expression levels included activation of immune response and cell migration, implying the possible function of CXCR4 on regulating neutrophil dynamics, which might contribute to periodontitis. Subsequent validation experiments confirmed that the increased expression of CXCR4 in neutrophils under periodontitis, where cell migration-related pathways also were activated.

CONCLUSION

CXCR4 could be the key pathogenic gene of periodontitis and CXCR4/CXCL12 signal axial might contribute to the development of periodontitis by mediating neutrophil dynamics, suggesting that CXCR4 could be a potential target to help identify novel strategies for the clinical diagnosis and treatment of periodontitis.

Evaluation of a Novel Immunochromatographic Device for Detecting Porphyromonas gingivalis in Patients with Periodontal Disease

Porphyromonas gingivalis is the most pathogenic periodontal bacterium in the world. Recently, P. gingivalis has been considered responsible for dysbiosis during the development of periodontitis. This study aimed to evaluate a novel immunochromatographic device using monoclonal antibodies against P. gingivalis in subgingival plaques. A total of 72 patients with chronic periodontitis and 53 periodontally healthy volunteers underwent clinical and microbiological examinations. Subgingival plaque samples were analyzed for the presence of P. gingivalis and compared using real-time polymerase chain reaction (PCR). In the periodontitis group, a significant positive correlation was observed between the test device scores and the real-time PCR results. The specificity, positive predictive value, negative predictive value, and accuracy of the test device for P. gingivalis, as determined by real-time PCR, were 98%, 94%, 89%, and 90%, respectively. There were significant differences in bacterial counts by real-time PCR among the groups with different ranges of device scores. Additionally, there was a significant positive correlation between the device scores for P. gingivalis and periodontal parameters. These results suggest that this novel immunochromatographic device can be effectively used for rapid detection and semi-quantification of P. gingivalis in subgingival plaques.

Toll-like receptors 2 and 4, and bacterial proteins in IgG4-related sialadenitis, other types of chronic sialadenitis and sialolithiasis

Background

The association of chronic sclerosing sialadenitis and IgG4-related disease (IgG4-RD) has resulted in the more frequent identification of IgG4-positivity in submandibular gland inflammations, also uncovering IgG4 overexpression in nonspecific inflammations. These findings lead us to hypothesise that IgG4-positive sialadenitis represents a continuous inflammatory process overlapping histologically with IgG4-RD, possibly differing in aetiology. However, the antigen underlying IgG4 overexpression in IgG4-positive sialadenitis and IgG4-RD remains unknown.

Materials and methods

Here, we investigated toll-like receptor (TLR) - mediated bacterial inflammation in submandibular gland tissues of patients with IgG4-positive and IgG4-negative chronic inflammatory lesions of the submandibular gland (n = 61), with noninflamed submandibular glands serving as controls (n = 4). Utilising immunohistochemistry, we assessed the expression of TLR2 and TLR4, lipopolysaccharide (LPS) and the P. gingivalis-specific antigen gingipain R1.

Results

We observed TLR2- and TLR4-immunopositivity in 64 (98%) samples. However, TLR2 and TLR4 staining intensity was significantly stronger in the IgG4-positive group. LPS- and gingipain R1 immunopositivity were observed in 56 (86%) and 58 (89%) samples, respectively. LPS-positivity localised exclusively in mast cell-like cells, while gingipain R1-positivity remained scarce.

Conclusions

A stronger TLR2 or TLR4 expression in IgG4-positive sialadenitis may indicate a tissue-related factor underlying this form of chronic sialadenitis. LPS- and P. gingivalis immunopositivity remained weak throughout this series. Thus, gram-negative bacteria may not represent pathogens underlying these forms of chronic sialadenitis.

Ethanol extract from Astilbe chinensis inflorescence suppresses inflammation in macrophages and growth of oral pathogenic bacteria

Chronic oral inflammation and biofilm-mediated infections drive diseases such as dental caries and periodontitis. This study investigated the anti-inflammatory and antibacterial potential of an ethanol extract from Astilbe chinensis inflorescence (GA-13-6) as a prominent candidate for natural complex substances (NCS) with therapeutic potential. In LPS-stimulated RAW 264.7 macrophages, GA-13-6 significantly suppressed proinflammatory mediators, including interleukin-6 (IL-6), tumor necrosis factor (TNF), and nitric oxide (NO), surpassing purified astilbin, a known bioactive compound found in A. chinensis. Furthermore, GA-13-6 downregulated the expression of cyclooxygenase-2 (COX2) and inducible nitric oxide synthase (iNOS), indicating an inhibitory effect on the inflammatory cascade. Remarkably, GA-13-6 exhibited selective antibacterial activity against Streptococcus mutans, Streptococcus sanguinis, and Porphyromonas gingivalis, key players in dental caries and periodontitis, respectively. These findings suggest that complex GA-13-6 holds the potential for the treatment or prevention of periodontal and dental diseases, as well as various other inflammation-related conditions, while averting the induction of antibiotic resistance.

Identification of keystone taxa in root canals and periapical lesions of post-treatment endodontic infections: Next generation microbiome research

AIM

The aim of this study was to analyse and compare the microbiome present in root canals and periapical lesions of teeth with post-treatment infections, and to identify the presence of keystone taxa in both habitats using next-generation sequencing analysis.

METHODOLOGY

Apices and periapical lesions of patients with post-treatment apical periodontitis were surgically extracted. Specimens were cryo-pulverized, bacterial DNA was extracted, and the V3-V4 hypervariable regions of the 16S rRNA gene were sequenced using the Illumina Miseq platform. Bioinformatic analysis was carried out with Mothur software, whilst diversity indices were obtained using operational taxonomic units (OTUs). The diversity indices were compared with the Kruskal-Wallis test, and community composition differences were explored with Permutational Multivariate Analysis of Variance (PERMANOVA). A bacterial functional study was performed with the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis. Co-occurrence network analyses were performed using the Sparse Correlations for Compositional data (SparCC). Eigencentrality, clr-based abundance and ubiquitousness were applied to infer keystone taxa. P values <.05 were considered statistically significant.

RESULTS

Thirty-two apices and thirty-nine periapical lesions were sequenced and analysed. A similar alpha-diversity (p < .05) and community composition (p = .91) was observed for apices and lesion samples. The most abundant OTUs identified amongst all samples included Fusobacterium nucleatum, Prevotella loescheii, Streptococcus intermedius, Porphyromonas gingivalis, Parvimonas micra, Synergistetes bacterium, Tannerella forsythia and Peptostreptococcus stomatis. The metabolic pathways with >0.81% abundances included membrane transport, genetic information processing and metabolic pathways. F. nucleatum was identified as a keystone taxon as it showed ubiquitousness, an eigenvector centrality value of 0.83 and a clr-based abundance >4.

CONCLUSIONS

The microbiome in apices and periapical lesions of post-treatment endodontic infections showed a similar diversity and taxonomic composition. Co-occurrence network analyses at OTU level identified F. nucleatum as a keystone taxon candidate in these infections.

Porphyromonas gingivalis LPS-stimulated BMSC-derived exosome promotes osteoclastogenesis via miR-151-3p/PAFAH1B1

OBJECTIVES

Porphyromonas gingivalis-LPS regulated bone metabolism by triggering dysfunction of osteoblasts directly, and affecting activity of osteoclasts through intracellular communication. Exosome, as the mediator of intercellular communication, was important vesicle to regulate osteogenesis and osteoclastogenesis. This research was designed for investigating the mechanism of BMSCs-EXO in modulating osteoclastic activity under the P. gingivalis-LPS.

MATERIALS AND METHODS

The cytotoxicity and osteogenic effects of P. gingivalis-LPS on BMSCs was evaluated, and then osteoclastic activity of RAW264.7 co-cultured with exosomes was detected. Besides, Affymetrix miRNA array and luciferase reporter assay were used to identify the target exosomal miRNA signal pathway.

RESULTS

BMSCs' osteogenic differentiation and proliferation were decreased under 1 and 10 μg/mL P. gingivalis-LPS. Osteoclastic-related genes and proteins levels were promoted by P. gingivalis-LPS-stimulated BMSCs-EXO. Based on the miRNA microarray analysis, exosomal miR-151-3p was lessened in BMExo-LPS group, which facilitated osteoclastic differentiation through miR-151-3p/PAFAH1B1.

CONCLUSIONS

Porphyromonas gingivalis-LPS could regulated bone metabolism by inhibiting proliferation and osteogenesis of BMSCs directly. Also, P. gingivalis-LPS-stimulated BMSCs-EXO promoted osteoclastogenesis via activating miR-151-3p/PAFAH1B1 signal pathway.

Effects of honokiol combined with resveratrol on bacteria responsible for oral malodor and their biofilm

Background

This study aimed to investigate the effect of honokiol combined with resveratrol on bacteria responsible for oral malodor and their biofilm.

Method

This study investigated drug's MIC, FICI and dynamic bactericidal susceptibility activities against Pg and Fn. The effects of drugs on biofilm metabolic activity, biofilm total amount, and biofilm microstructure were determined by CCK-8 experiment, semi-quantitative adhesion experiment and SEM, respectively. The effects of drugs on biofilm genes, extracellular polysaccharides, proteins and DNA content were determined by qRT-PCR, phenol-sulfuric acid method, BCA method and Nano Drop one C, respectively.

Results

The combination had synergistic antibacterial effect on Pg and Fn. 1/2×MIC and 1×MIC combination inhibit the whole process of Pg and Fn growth. The results showed that the combination effectively reduce biofilm metabolic activity and total amount, and destroy biofilm microstructure. The results showed that the combination downregulate the gene expression both Pg and Fn, reduce extracellular polysaccharides and DNA of Pg, and reduce extracellular proteins and DNA of Fn.

Conclusion

This study showed that the combination had a synergistic antibacterial effect on Pg and Fn, reduced the biofilm extracellular matrix, inhibited biofilm formation, and downregulated the expression of genes related to biofilm formation.

Fucoidan-hybrid hydroxyapatite nanoparticles promote the osteogenic differentiation of human periodontal ligament stem cells under inflammatory condition

Inflammation-related bone defects often lead to poor osteogenesis. Therefore, it is crucial to reduce the inflammation response and promote the osteogenic differentiation of stem/progenitor cells to revitalize bone physiology. Here, a kind of hybrid nano-hydroxyapatite was prepared using the confined phosphate ion release method with the participation of fucoidan, a marine-sourced polysaccharide with anti-inflammation property. The physicochemical analyses confirmed that the fucoidan hybrid nano-hydroxyapatite (FC/n-HA) showed fine needle-like architectures. With a higher amount of fucoidan, the crystal size and crystallinity of the FC/n-HA reduced while the liquid dispersibility was improved. Cell experiences showed that FC/n-HA had an optimal cytocompatibility at concentration of 50 μg/mL. Moreover, the lipopolysaccharide-induced cellular inflammatory model with PDLSCs was established and used to evaluate the anti-inflammatory and osteogenic properties. For the 1%FC/n-HA group, the expression levels of TNF-α and IL-1β were significantly reduced at 24 h, while the expression of alkaline phosphatase of PDLSCs was significantly promoted at days 3 and 7, and calcium precipitates was enhanced at 21 days. In this study, the FC/n-HA particles showed effective anti-inflammatory properties and facilitated osteogenic differentiation of PDLSCs, indicating which has potential application in treating bone defects associated with inflammation, such as periodontitis.

Mycobacterium tuberculosis : a new hitchhiker in the etiopathogenesis of periodontitis

Periodontitis, a chronic inflammatory disease of the gums affects both the ligament and alveolar bone. A severe form of periodontal disease affects a strikingly high number of one billion adults globally. The disease permutes both the soft and hard tissues of the oral cavity leading to localized and systemic diseases. Periodontitis has a deleterious impact on systemic health causing diabetes, cardiovascular diseases (CVD), and other disease. The cause of the enhanced inflammatory process is due to dysbiosis and an unregulated immune response. Innate immune response and T cells trigger uninhibited cytokine release causing an unwarranted inflammatory response. The RANK- RANKL interaction between osteoblasts, immune cells, and progenitor osteoclasts results in the maturation of osteoclasts, which promote bone resorption. It is well established that dysbiosis of the oral cavity has been implicated in periodontitis. But emerging reports suggest that the pulmonary pathogen, Mycobacterium tuberculosis (Mtb), causes extrapulmonary diseases such as periodontitis. Many clinical case reports advocate the involvement of Mtb in periodontitis, which poses a threat with the surge of tuberculosis in HIV and other immunocompromised individuals. Fostering a better understanding of the mechanism, causative agents and control on inflammatory response is imperative in the prevention and treatment of periodontitis.

A sono-responsive antibacterial nanosystem co-loaded with metformin and bone morphogenetic protein-2 for mitigation of inflammation and bone loss in experimental peri-implantitis

Background

Dental implants have become an increasingly popular option for replacing missing teeth, and the prevalence of peri-implantitis has also increased, which is expected to become a public health problem worldwide and cause high economic and health burdens. This scenario highlights the need for new therapeutic options to treat peri-implantitis.

Methods

In this study, we proposed a novel sono-responsive antibacterial nanosystem co-loaded with metformin (Met) and bone morphogenetic protein-2 (BMP-2) to promote efficacy in treating peri-implantitis. We introduced the zeolitic imidazolate framework-8 (ZIF-8) as a carrier for hematoporphyrin monomethyl ether (HMME) to enhance the antibacterial effect of sonodynamic antibacterial therapy and tested its reactive oxygen species (ROS) production efficiency and bactericidal effect in vitro. Afterward, HMME-loaded ZIF-8, BMP-2-loaded polylactic acid-glycolic acid (PLGA), and Met were incorporated into gelatin methacryloyl (GelMA) hydrogels to form HMME@ZIF-8/Met/BMP-2@PLGA/GelMA composite hydrogels, and the biocompatibility of which was determined in vitro and in vivo. A bacterial-induced peri-implantitis model in the maxilla of rats was established to detect the effects of the composite hydrogels with adjunctive use of ultrasound on regulating inflammation and promoting bone tissue repair in vivo.

Results

The results indicated that HMME@ZIF-8 with ultrasound stimulation demonstrated more better ROS production efficiency and antimicrobial efficacy. The composite hydrogels had good biocompatibility. Ultrasound-assisted application of the composite hydrogels reduced the release of the inflammatory factors IL-6 and TNF-α and reduced bone loss around the implant in rats with bacterial-induced peri-implantitis.

Conclusion

Our observations suggest that HMME@ZIF-8 may be a new good sonosensitizer material for sonodynamic antibacterial therapy. The use of HMME@ZIF-8/Met/BMP-2@PLGA/GelMA composite hydrogels in combination with ultrasound can provide a novel option for treating peri-implantitis in the future.

Diosgenin prevents periodontitis by inhibiting inflammation and promoting osteogenic differentiation

Diosgenin, an essential dietary steroidal sapogenin, possess multiple pharmacological activities. This study aimed to assess the effects of diosgenin on periodontitis and elucidate the mechanisms. Lipopolysaccharide (LPS)-stimulated human periodontal ligament stem cells (hPDLCs) and a Porphyromonas gingivalis (P.g) plus ligation-induced animal model were used for in vitro and in vivo studies, respectively. Inflammatory responses, nuclear factor κ-B (NF-κB) signaling and osteogenesis-related markers were measured both in LPS-stimulated hPDLSCs and in gingival tissue of periodontitis rats. Treatment with diosgenin significantly inhibited the production of tumor necrosis factor α (TNF-α), interleukin (IL)-1β, and interleukin (IL)-6 and the activation of NF-κB pathway in LPS-stimulated hPDLSCs. Further, treatment with diosgenin enhanced the expression of osteoblast-related genes and increased the osteogenic differentiation capacity. Further, activation NF-κB pathway largely abolished the protective effects of diosgenin. Consistent with the in vitro studies, in vivo studies showed that administering diosgenin to periodontitis rats significantly lowered the levels of the TNF-α, IL-1β, and IL-6 and the inflammatory transcription factor NF-κB in gingival tissue. In addition, osteoblast-related genes were promoted. Diosgenin attenuates periodontitis by adjusting NF-κB signaling to inhibit inflammatory effects and promoting osteogenesis, suggesting diosgenin might be developed as a therapeutic strategy for treating periodontitis in the future.

Differential Response of Human Dendritic Cells upon Stimulation with Encapsulated or Non-Encapsulated Isogenic Strains of Porphyromonas gingivalis

During periodontitis, the extracellular capsule of Porphyromonas gingivalis favors alveolar bone loss by inducing Th1 and Th17 patterns of lymphocyte response in the infected periodontium. Dendritic cells recognize bacterial antigens and present them to T lymphocytes, defining their activation and polarization. Thus, dendritic cells could be involved in the Th1 and Th17 response induced against the P. gingivalis capsule. Herein, monocyte-derived dendritic cells were obtained from healthy individuals and then stimulated with different encapsulated strains of P. gingivalis or two non-encapsulated isogenic mutants. Dendritic cell differentiation and maturation were analyzed by flow cytometry. The mRNA expression levels for distinct Th1-, Th17-, or T-regulatory-related cytokines and transcription factors, as well as TLR2 and TLR4, were assessed by qPCR. In addition, the production of IL-1β, IL-6, IL-23, and TNF-α was analyzed by ELISA. The encapsulated strains and non-encapsulated mutants of P. gingivalis induced dendritic cell maturation to a similar extent; however, the pattern of dendritic cell response was different. In particular, the encapsulated strains of P. gingivalis induced higher expression of IRF4 and NOTCH2 and production of IL-1β, IL-6, IL-23, and TNF-α compared with the non-encapsulated mutants, and thus, they showed an increased capacity to trigger Th1 and Th17-type responses in human dendritic cells.

Single-cell transcriptome analysis reveals periodontal ligament fibroblast heterogeneity with distinct IL-1β and RANKL expression in periodontitis

Periodontitis (PD) is an inflammatory disease with alveolar bone destruction by osteoclasts (OCs). In PD, both inflammation and OC activation are significantly influenced by periodontal ligament fibroblasts (PDL-Fib). Yet, whether PDL-Fib has heterogeneity and whether distinct PDL-Fib subsets have specific functions have not been investigated. In this study, we discovered the complexity of PDL-Fib in PD, utilizing single-cell RNA sequencing data from human PD patients. We identified distinct subpopulations of PDL-Fib: one expressing interleukin-1 beta (IL-1β) and another expressing the receptor activator of nuclear factor-kappa B ligand (RANKL), both crucial in OC differentiation and bone resorption. In periodontal tissues of mice with PD, active IL-1β, cleaved caspase 1, and nucleotide-binding oligomerization domain-like receptor 3 (NLPR3) were significantly elevated, implicating the NLRP3 inflammasome in IL-1β production. Upon stimulation of PDL-Fib with LPS from Porphyromonas gingivalis (pg), the most well-characterized periodontal bacteria, a more rapid increase in IL-1β, followed by RANKL induction, was observed. IL-1β and tumor necrosis factor alpha (TNF-α), another LPS-responsive cytokine, effectively increased RANKL in PDL-Fib, suggesting an indirect effect of pgLPS through IL-1β and TNF-α on RANKL induction. Immunohistological analyses of mouse periodontal tissues also showed markedly elevated levels of IL-1β and RANKL upon PD induction and displayed separate locations of IL-1β-expressing PDL-Fib and RANKL-expressing PDL-Fib in PD. The heterogenic feature of fibroblasts expressing IL-1β and RANKL was also mirrored in our combined cross-tissue single-cell RNA sequencing datasets analysis. In summary, our study elucidates the heterogeneity of PDL-Fib, highlighting distinct functional groups for producing RANKL and IL-1β, which collectively promote OC generation and bone destruction in PD.

Co-Culture of P. gingivalis and F. nucleatum Synergistically Elevates IL-6 Expression via TLR4 Signaling in Oral Keratinocytes

Periodontitis, characterized by persistent inflammation in the periodontium, is intricately connected to systemic diseases, including oral cancer. Bacteria, such as Porphyromonas gingivalis and Fusobacterium nucleatum, play a pivotal role in periodontitis development because they contribute to dysbiosis and tissue destruction. Thus, comprehending the interplay between these bacteria and their impacts on inflammation holds significant relevance in clinical understanding and treatment advancement. In the present work, we explored, for the first time, their impacts on the expressions of pro-inflammatory mediators after infecting oral keratinocytes (OKs) with a co-culture of pre-incubated P. gingivalis and F. nucleatum. Our results show that the co-culture increases IL-1β, IL-8, and TNF-α expressions, synergistically augments IL-6, and translocates NF-kB to the cell nucleus. These changes in pro-inflammatory mediators-associated with chronic inflammation and cancer-correlate with an increase in cell migration following infection with the co-cultured bacteria or P. gingivalis alone. This effect depends on TLR4 because TLR4 knockdown notably impacts IL-6 expression and cell migration. Our study unveils, for the first time, crucial insights into the outcomes of their co-culture on virulence, unraveling the role of bacterial interactions in polymicrobial diseases and potential links to oral cancer.

Structure-function analysis of PorXFj, the PorX homolog from Flavobacterium johnsioniae, suggests a role of the CheY-like domain in type IX secretion motor activity

The type IX secretion system (T9SS) is a large multi-protein transenvelope complex distributed into the Bacteroidetes phylum and responsible for the secretion of proteins involved in pathogenesis, carbohydrate utilization or gliding motility. In Porphyromonas gingivalis, the two-component system PorY sensor and response regulator PorX participate to T9SS gene regulation. Here, we present the crystal structure of PorXFj, the Flavobacterium johnsoniae PorX homolog. As for PorX, the PorXFj structure is comprised of a CheY-like N-terminal domain and an alkaline phosphatase-like C-terminal domain separated by a three-helix bundle central domain. While not activated and monomeric in solution, PorXFj crystallized as a dimer identical to active PorX. The CheY-like domain of PorXFj is in an active-like conformation, and PorXFj possesses phosphodiesterase activity, in agreement with the observation that the active site of its phosphatase-like domain is highly conserved with PorX.

Inhibition of SARS-CoV-2 infection by Porphyromonas gingivalis and the oral microbiome

The COVID-19 pandemic persists despite the availability of vaccines, and it is therefore crucial to develop new therapeutic and preventive approaches. In this study, we investigated the potential role of the oral microbiome in SARS-CoV-2 infection. Using an in vitro SARS-CoV-2 pseudovirus infection assay, we found a potent inhibitory effect exerted by Porphyromonas gingivalis on SARS-CoV-2 infection mediated by known P. gingivalis compounds such as phosphoglycerol dihydroceramide (PGDHC) and gingipains as well as by unknown bacterial factors. We found that the gingipain-mediated inhibition of infection is likely due to cytotoxicity, while PGDHC inhibited virus infection by an unknown mechanism. Unidentified factors present in P. gingivalis supernatant inhibited SARS-CoV-2 likely via the fusion step of the virus life cycle. We addressed the role of other oral bacteria and found certain periodontal pathogens capable of inhibiting SARS-CoV-2 pseudovirus infection by inducing cytotoxicity on target cells. In the human oral cavity, we observed the modulatory activity of oral microbial communities varied among individuals in that some saliva-based cultures were capable of inhibiting while others were enhancing infection. These findings contribute to our understanding of the complex relationship between the oral microbiome and viral infections, offering potential avenues for innovative therapeutic strategies in combating COVID-19.

Evaluation of loop-mediated isothermal amplification method for efficient detection of the periodontopathic bacteria Porphyromonas gingivalis

Background

Periodontitis is a multifactorial, polymicrobial oral inflammatory illness brought on by oral pathogens. Porphyromonas gingivalis is a Gram-negative, obligatory anaerobic, black-pigmented coccobacillus and is regarded as a primary etiological factor in the progression of periodontitis. Rapid, highly senstitive and specific detection methods are emerging. The present study aimed to evaluate the loop-mediated isothermal amplification (LAMP) technique for efficiently detecting P. gingivalis from subgingival plaque samples of chronic periodontitis patients.

Materials and Methods

This study included 50 subgingival plaque samples from patients suffering from chronic periodontitis. The DNA (Deoxyribonucleic acid) was extracted by the "modified proteinase K" method. A set of six primers, targeting the pepO gene of P. gingivalis, was used for conducting LAMP. The amplification was visualized by naked-eye detection and agarose electrophoresis. Conventional polymerase chain reaction (PCR) and real-time qantitative PCR (qPCR) were carried out by targeting the 16SrRNA (16S ribosomal ribonucleic acid) gene of P. gingivalis.

Results

The results showed that LAMP detected P. gingivalis in 40 out of 50 samples (80%). Whereas, qPCR and conventional PCR technique detected P. gingivalis in 38 (76%) and 33 (66%) samples respectively. The sensitivity and specificity of the LAMP method were 94.87% and 90.90%, respectively. With qPCR, the sensitivity and specificity were found to be 92.30% and 81.81%, respectively, whereas, with conventional PCR, it was found to be 76.92% and 72.72%, respectively.

Conclusion

LAMP is an efficient technique for quick, accurate, and reliable identification of P. gingivalis from subgingival plaque samples. The technique needs to be validated analytically, and further studies can be conducted by taking saliva and/or gingival crevicular fluid samples from periodontitis patients.

A telluroviologen-anchored tetraphenylporphyrin as sonosensitizer for periodontitis sonodynamic therapy

Periodontitis is a chronic disease caused by bacteria (e.g. Porphyromonas gingivalis, P.gingivalis) that currently lacks effective non-invasive treatment options. Sonodynamic therapy (SDT) is an emerging non-invasive antimicrobial therapeutic strategy. Since ultrasonic tooth cleaning is widely used in dental treatments, SDT has significant potential for the facile implementation of treat periodontitis. However, hypoxia in periodontitis severely limits the effectiveness of traditional sonosensitizers. To address this issue, we have developed a new sonosensitizer termed as TPP-TeV, which combines the traditional sonosensitizer tetraphenylporphyrin (TPP) with a new photosensitizer telluroviologen (TeV). Under ultrasound radiation, TPP-TeV can produce numerous cationic free radicals (TPP-TeV•), which subsequently generate ROS free radicals (O2•-, •OH) efficiently via electron transfer mechanism, resulting in the effective killing of anaerobic P.gingivalis both in vivo and in vitro. As a result, the dental environment is improved, and the inhibition rate of alveolar bone loss reaches 80 %. The introduction of tellurium into the viologen molecule induces changes in its reduction potential, resulting in increased rigidity of the molecule. This modification systematically reduces the biotoxicity of our novel sonosensitizer by 75 % at 50 μM based on bacterial experiments. These promising findings could potentially establish new options for sonodynamic therapy (SDT) in periodontitis clinical treatments.

Molecular commensalism-how to investigate underappreciated health-associated polymicrobial communities

The study of human commensal bacteria began with the first observation of prokaryotes >340 years ago. Since then, the study of human-associated microbes has been justifiably biased toward the study of infectious pathogens. However, the role of commensal microbes has in recent years begun to be understood with some appreciation of them as potential protectors of host health rather than bystanders. As our understanding of these valuable microbes grows, it highlights how much more remains to be learned about them and their roles in maintaining health. We note here that a thorough framework for the study of commensals, both in vivo and in vitro is overall lacking compared to well-developed methodologies for pathogens. The modification and application of methods for the study of pathogens can work well for the study of commensals but is not alone sufficient to properly characterize their relationships. This is because commensals live in homeostasis with the host and within complex communities. One difficulty is determining which commensals have a quantifiable impact on community structure and stability as well as host health, vs benign microbes that may indeed serve only as bystanders. Human microbiomes are composed of bacteria, archaea, fungi, and viruses. This review focuses particularly on oral bacteria, yet many of the principles of commensal impacts on host health observed in the mouth can translate well to other host sites. Here, we discuss the value of commensals, the shortcomings involved in model systems for their study, and some of the more notable impacts they have upon not only each other but host health.

Oral Pathogenic Bacteria and the Oral-Gut-Liver Axis: A New Understanding of Chronic Liver Diseases

Liver diseases have long been a prevalent cause of morbidity and mortality, and their development and progression involve multiple vital organs throughout the body. Recent studies on the oral-gut-liver axis have revealed that the oral microbiota is associated with the pathophysiology of chronic liver diseases. Since interventions aimed at regulating oral biological disorders may delay the progress of liver disease, it is crucial to better comprehend this process. Oral bacteria with potential pathogenicity have been extensively studied and are closely related to several types of chronic liver diseases. Therefore, this review will systemically describe the emerging role of oral pathogenic bacteria in common liver diseases, including alcoholic liver disease (ALD), non-alcoholic steatohepatitis (NASH), non-alcoholic fatty liver disease (NAFLD), cirrhosis, autoimmune liver diseases (AILD), and liver cancer, and bring in new perspectives for future research.

Isolation, characterization, and fibroblast uptake of bacterial extracellular vesicles from Porphyromonas gingivalis strains

Periodontitis is an inflammatory condition caused by bacteria and represents a serious health problem worldwide as the inflammation damages the supporting tissues of the teeth and may predispose to systemic diseases. Porphyromonas gingivalis is considered a keystone periodontal pathogen that releases bacterial extracellular vesicles (bEVs) containing virulence factors, such as gingipains, that may contribute to the pathogenesis of periodontitis. This study aimed to isolate and characterize bEVs from three strains of P. gingivalis, investigate putative bEV uptake into human oral fibroblasts, and determine the gingipain activity of the bEVs. bEVs from three bacterial strains, ATCC 33277, A7A1-28, and W83, were isolated through ultrafiltration and size-exclusion chromatography. Vesicle size distribution was measured by nano-tracking analysis (NTA). Transmission electron microscopy was used for bEV visualization. Flow cytometry was used to detect bEVs and gingipain activity was measured with an enzyme assay using a substrate specific for arg-gingipain. The uptake of bEVs into oral fibroblasts was visualized using confocal microscopy. NTA showed bEV concentrations from 108 to 1011 particles/mL and bEV diameters from 42 to 356 nm. TEM pictures demonstrated vesicle-like structures. bEV-gingipains were detected both by flow cytometry and enzyme assay. Fibroblasts incubated with bEVs labeled with fluorescent dye displayed intracellular localization consistent with bEV internalization. In conclusion, bEVs from P. gingivalis were successfully isolated and characterized, and their uptake into human oral fibroblasts was documented. The bEVs displayed active gingipains demonstrating their origin from P. gingivalis and the potential role of bEVs in periodontitis.

Systematic analysis of prophages carried by Porphyromonas gingivalis

To systematically investigate the prophages carrying in Porphyromonas gingivalis (P. gingivalis) strains, analyze potential antibiotic resistance genes (ARGs) and virulence genes in these prophages. We collected 90 whole genome sequences of P. gingivalis from NCBI and utilized the Prophage Hunter online software to predict prophages; Comprehensive antibiotic research database (CARD) and virulence factors database (VFDB) were adopted to analyze the ARGs and virulence factors (VFs) carried by the prophages. Sixty-nine prophages were identified among 24/90 P. gingivalis strains, including 17 active prophages (18.9%) and 52 ambiguous prophages (57.8%). The proportion of prophages carried by each P. gingivalis genome ranged from 0.5% to 6.7%. A total of 188 antibiotic resistance genes belonging to 25 phenotypes and 46 different families with six mechanisms of antibiotic resistance were identified in the 17 active prophages. Three active prophages encoded 4 virulence genes belonging to type III and type VI secretion systems. The potential hosts of these virulence genes included Escherichia coli, Shigella sonnei, Salmonella typhi, and Klebsiella pneumoniae. In conclusion, 26.7% P. gingivalis strains carry prophages, while the proportion of prophage genes in the P. gingivalis genome is relatively low. In addition, approximately 39.7% of the P. gingivalis prophage genes have ARGs identified, mainly against streptogramin, peptides, and aminoglycosides. Only a few prophages carry virulence genes. Prophages may play an important role in the acquisition, dissemination of antibiotic resistance genes, and pathogenicity evolution in P. gingivalis.

Porphyromonas gingivalis exacerbates alcoholic liver disease by altering gut microbiota composition and host immune response in mice

AIM

Porphyromonas gingivalis (P. gingivalis), a major periodontal pathogen, increases the risk of systemic diseases. P. gingivalis infection is closely associated with alcoholic liver disease (ALD), but the underlying mechanism remains unclear. We aimed to investigate the role of P. gingivalis in the pathogenesis of ALD.

MATERIALS AND METHODS

An ALD mouse model was established using a Lieber-DeCarli liquid diet, and C57BL/6 mice were treated with P. gingivalis to detect the pathological indicators of ALD.

RESULTS

Oral administration of P. gingivalis exacerbated alcohol-induced alterations in the gut microbiota, leading to gut barrier dysfunction and inflammatory response and disruption of the T-helper 17 cell/T-regulatory cell ratio in the colon of ALD mice. Furthermore, P. gingivalis worsened liver inflammation in ALD mice by increasing the protein expression of toll-like receptor 4 (TLR4) and p65, increasing the mRNA expression of interleukins-6 (IL-6) and tumour necrosis factor-alpha (TNF-α) and up-regulating the transforming growth factor-beta 1 (TGF-β1) and galectin-3 (Gal-3) production.

CONCLUSIONS

These results indicate that P. gingivalis accelerates the pathogenesis of ALD via the oral-gut-liver axis, necessitating a new treatment strategy for patients with ALD complicated by periodontitis.

Hemin availability induces coordinated DNA methylation and gene expression changes in Porphyromonas gingivalis

Periodontal disease is a chronic inflammatory disease in which the oral pathogen Porphyromonas gingivalis plays an important role. Porphyromonas gingivalis expresses virulence determinants in response to higher hemin concentrations, but the underlying regulatory processes remain unclear. Bacterial DNA methylation has the potential to fulfil this mechanistic role. We characterized the methylome of P. gingivalis, and compared its variation to transcriptome changes in response to hemin availability. Porphyromonas gingivalis W50 was grown in chemostat continuous culture with excess or limited hemin, prior to whole-methylome and transcriptome profiling using Nanopore and Illumina RNA-Seq. DNA methylation was quantified for Dam/Dcm motifs and all-context N6-methyladenine (6mA) and 5-methylcytosine (5mC). Of all 1,992 genes analyzed, 161 and 268 were respectively over- and under-expressed with excess hemin. Notably, we detected differential DNA methylation signatures for the Dam "GATC" motif and both all-context 6mA and 5mC in response to hemin availability. Joint analyses identified a subset of coordinated changes in gene expression, 6mA, and 5mC methylation that target genes involved in lactate utilization and ABC transporters. The results identify altered methylation and expression responses to hemin availability in P. gingivalis, with insights into mechanisms regulating its virulence in periodontal disease. IMPORTANCE DNA methylation has important roles in bacteria, including in the regulation of transcription. Porphyromonas gingivalis, an oral pathogen in periodontitis, exhibits well-established gene expression changes in response to hemin availability. However, the regulatory processes underlying these effects remain unknown. We profiled the novel P. gingivalis epigenome, and assessed epigenetic and transcriptome variation under limited and excess hemin conditions. As expected, multiple gene expression changes were detected in response to limited and excess hemin that reflect health and disease, respectively. Notably, we also detected differential DNA methylation signatures for the Dam "GATC" motif and both all-context 6mA and 5mC in response to hemin. Joint analyses identified coordinated changes in gene expression, 6mA, and 5mC methylation that target genes involved in lactate utilization and ABC transporters. The results identify novel regulatory processes underlying the mechanism of hemin regulated gene expression in P. gingivalis, with phenotypic impacts on its virulence in periodontal disease.

Antibacterial performance of a porous Cu-bearing titanium alloy by laser additive manufacturing

Porphyromonas gingivalis (P. gingivalis) is the most common species that causes peri-implantitis. It forms an irreversible dense biofilm and causes inflammation. A novel 3D-printed porous TC4-6Cu alloy was fabricated using selective laser melting (SLM) technology for the dental implant, which is anticipated to inhibit biofilm formation. We attempted to investigate the antibacterial ability and antibacterial mechanism of the 3D-printed porous TC4-6Cu alloy against P. gingivalis. This work used scanning electron microscopy (SEM) and laser confocal microscopy (CLSM) to detect the antimicrobial ability of the alloy against sessile P. gingivalis. The results indicated that the 3D-printed porous TC4-6Cu alloy could cause bacterial fragmentation and deformation. Plate antimicrobial counting experiments showed that the antibacterial rates of the alloy against adherent bacteria and planktonic bacteria after 24 h were 98.05% and 73.92%, respectively. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Cu2+ were tested to appraise the antibacterial property of the alloy against planktonic P. gingivalis. The relationship between the antibacterial mechanism of the alloy with oxidative stress was evaluated through ROS fluorescence intensity and protein leakage concentration. The results revealed that the alloy significantly eliminated adherent bacteria and inhibited biofilm formation. Moreover, 3D-printed porous TC4-6Cu alloy demonstrated significant bactericidal ability by inducing the production of reactive oxygen species (ROS), which could result in protein leakage from the bacterial cell membrane. This research may open a new perspective on the development and biomedical applications for dental implantation.

Phylogenomic analysis of the Porphyromonas gingivalis - Porphyromonas gulae duo: approaches to the origin of periodontitis

Porphyromonas gingivalis is an oral human pathogen associated with the onset and progression of periodontitis, a chronic immune-inflammatory disease characterized by the destruction of the teeth-supporting tissue. P. gingivalis belongs to the genus Porphyromonas, which is characterized by being composed of Gram-negative, asaccharolytic, non-spore-forming, non-motile, obligatory anaerobic species, inhabiting niches such as the oral cavity, urogenital tract, gastrointestinal tract and infected wound from different mammals including humans. Among the Porphyromonas genus, P. gingivalis stands out for its specificity in colonizing the human oral cavity and its keystone pathogen role in periodontitis pathogenesis. To understand the evolutionary process behind P. gingivalis in the context of the Pophyoromonas genus, in this study, we performed a comparative genomics study with publicly available Porphyromonas genomes, focused on four main objectives: (A) to confirm the phylogenetic position of P. gingivalis in the Porphyromonas genus by phylogenomic analysis; (B) the definition and comparison of the pangenomes of P. gingivalis and its relative P. gulae; and (C) the evaluation of the gene family gain/loss events during the divergence of P. gingivalis and P. gulae; (D) the evaluation of the evolutionary pressure (represented by the calculation of Tajima-D values and dN/dS ratios) comparing gene families of P. gingivalis and P. gulae. Our analysis found 84 high-quality assemblies representing P. gingivalis and 14 P. gulae strains (from a total of 233 Porphyromonas genomes). Phylogenomic analysis confirmed that P. gingivalis and P. gulae are highly related lineages, close to P. loveana. Both organisms harbored open pangenomes, with a strong core-to-accessory ratio for housekeeping genes and a negative ratio for unknown function genes. Our analyses also characterized the gene set differentiating P. gulae from P. gingivalis, mainly associated with unknown functions. Relevant virulence factors, such as the FimA, Mfa1, and the hemagglutinins, are conserved in P. gulae, P. gingivalis, and P. loveana, suggesting that the origin of those factors occurred previous to the P. gulae - P. gingivalis divergence. These results suggest an unexpected evolutionary relationship between the P. gulae - P. gingivalis duo and P. loveana, showing more clues about the origin of the role of those organisms in periodontitis.

"Medicine food homology" plants promote periodontal health: antimicrobial, anti-inflammatory, and inhibition of bone resorption

"Medicine food homology" (MFH) is a term with a lengthy history. It refers to the fact that a lot of traditional natural products have both culinary and therapeutic benefits. The antibacterial, anti-inflammatory and anticancer effects of MFH plants and their secondary metabolites have been confirmed by numerous research. A bacterially generated inflammatory illness with a complicated pathophysiology, periodontitis causes the loss of the teeth's supporting tissues. Several MFH plants have recently been shown to have the ability to prevent and treat periodontitis, which is exhibited by blocking the disease's pathogens and the virulence factors that go along with them, lowering the host's inflammatory reactions and halting the loss of alveolar bone. To give a theoretical foundation for the creation of functional foods, oral care products and adjuvant therapies, this review has especially explored the potential medicinal benefit of MFH plants and their secondary metabolites in the prevention and treatment of periodontitis.

Periodontitis as a promoting factor of T2D: current evidence and mechanisms

Periodontitis is an infectious disease caused by an imbalance between the local microbiota and host immune response. Epidemiologically, periodontitis is closely related to the occurrence, development, and poor prognosis of T2D and is recognized as a potential risk factor for T2D. In recent years, increasing attention has been given to the role of the virulence factors produced by disorders of the subgingival microbiota in the pathological mechanism of T2D, including islet β-cell dysfunction and insulin resistance (IR). However, the related mechanisms have not been well summarized. This review highlights periodontitis-derived virulence factors, reviews how these stimuli directly or indirectly regulate islet β-cell dysfunction. The mechanisms by which IR is induced in insulin-targeting tissues (the liver, visceral adipose tissue, and skeletal muscle) are explained, clarifying the influence of periodontitis on the occurrence and development of T2D. In addition, the positive effects of periodontal therapy on T2D are overviewed. Finally, the limitations and prospects of the current research are discussed. In summary, periodontitis is worthy of attention as a promoting factor of T2D. Understanding on the effect of disseminated periodontitis-derived virulence factors on the T2D-related tissues and cells may provide new treatment options for reducing the risk of T2D associated with periodontitis.

Effect of a protease‐activated receptor‐2 antagonist ( GB88 ) on inflammation‐related loss of alveolar bone in periodontal disease

BACKGROUND AND OBJECTIVE

Protease-activated receptor-2 (PAR₂ ), a pro-inflammatory G-protein coupled receptor, has been associated with pathogenesis of periodontitis and the resulting bone loss caused by oral pathogens, including the keystone pathogen Porphyromonas gingivalis (P. gingivalis). We hypothesised that administration of a PAR₂ antagonist, GB88, might prevent inflammation and subsequent alveolar bone resorption in a mouse model of periodontal disease.

METHODS

Periodontitis was induced in mice by oral inoculations with P. gingivalis for a total of eight times over 24 days. The infected mice were treated with either GB88 or vehicle for the duration of the trial. Following euthanasia on day 56, serum was collected and used for the detection of mast cell tryptase. The right maxillae were defleshed and stained with methylene blue to measure the exposed cementum in molar teeth. The left maxillae were prepared for cryosections followed by staining for tartrate-resistant acid phosphatase to identify osteoclasts or with toluidine blue to identify mast cells. Reverse transcription quantitative PCR (RT-qPCR) was used to quantify the expression of inflammatory cytokines in the gingival tissue. Supernatants of T-lymphocyte cultures isolated from the regional lymph nodes were assayed using a cytometric bead array to measure the Th1/Th2/Th17 cytokine levels.

RESULTS

Measurement of the exposed cementum showed that GB88 reduced P. gingivalis-induced alveolar bone loss by up to 69%. GB88 also prevented the increase in osteoclast numbers observed in the infected mice. Serum tryptase levels were significantly elevated in both the infected groups, and not altered by treatment. RT-qPCR showed that GB88 prevented the upregulation of Il1b, Il6, Ifng and Cd11b. In T-lymphocyte supernatants, only IFNγ and IL-17A levels were increased in response to infection, but this was prevented by GB88 treatment.

CONCLUSIONS

GB88 significantly reduced osteoclastic alveolar bone loss in mice infected with P. gingivalis, seemingly by preventing the upregulation of several inflammatory cytokines. PAR₂ antagonism may be an effective treatment strategy for periodontal disease.

Porphyromonas gingivalis regulates atherosclerosis through an immune pathway

Atherosclerosis (AS) is a chronic inflammatory disease, involving a pathological process of endothelial dysfunction, lipid deposition, plaque rupture, and arterial occlusion, and is one of the leading causes of death in the world population. The progression of AS is closely associated with several inflammatory diseases, among which periodontitis has been shown to increase the risk of AS. Porphyromonas gingivalis (P. gingivalis), presenting in large numbers in subgingival plaque biofilms, is the “dominant flora” in periodontitis, and its multiple virulence factors are important in stimulating host immunity. Therefore, it is significant to elucidate the potential mechanism and association between P. gingivalis and AS to prevent and treat AS. By summarizing the existing studies, we found that P. gingivalis promotes the progression of AS through multiple immune pathways. P. gingivalis can escape host immune clearance and, in various forms, circulate with blood and lymph and colonize arterial vessel walls, directly inducing local inflammation in blood vessels. It also induces the production of systemic inflammatory mediators and autoimmune antibodies, disrupts the serum lipid profile, and thus promotes the progression of AS. In this paper, we summarize the recent evidence (including clinical studies and animal studies) on the correlation between P. gingivalis and AS, and describe the specific immune mechanisms by which P. gingivalis promotes AS progression from three aspects (immune escape, blood circulation, and lymphatic circulation), providing new insights into the prevention and treatment of AS by suppressing periodontal pathogenic bacteria.

Relationship between pathogenic microorganisms and the occurrence of esophageal carcinoma based on pathological type: a narrative review

INTRODUCTION

Esophageal cancer (EC) is one of the most common malignant tumors of the upper gastrointestinal tract. The etiology of EC is complicated and increasing evidence has shown that microbial infection is closely related to the occurrence of various malignant tumors. Though many studies have been focused on this subject in recent years, the exact relationship between microbial infection and the occurrence of EC remains unclear.

AREAS COVERED

In this review, we searched all eligible literature reports, summarized the most recent studies in this research field, and analyzed the pathogenic microorganisms associated with EC, providing the latest evidence and references for the prevention of pathogenic microorganism-related EC.

EXPERT OPINION

In recent years, increasing evidence has shown that pathogenic microbial infections are closely associated with the development of EC. Therefore, it is necessary to describe in detail the relationship between microbial infection and EC and clarify its possible pathogenic mechanism, which will shed a light on clinical prevention and treatment of cancer caused by pathogenic microbial infection.

Erythromycin Restores Osteoblast Differentiation and Osteogenesis Suppressed by Porphyromonas gingivalis Lipopolysaccharide

The macrolide erythromycin (ERM) inhibits excessive neutrophil accumulation and bone resorption in inflammatory tissues. We previously reported that the expression of developmental endothelial locus-1 (DEL-1), an endogenous anti-inflammatory factor induced by ERM, is involved in ERM action. Furthermore, DEL-1 is involved in the induction of bone regeneration. Therefore, in this study, we investigated whether ERM exerts an osteoblastogenic effect by upregulating DEL-1 under inflammatory conditions. We performed in vitro cell-based mechanistic analyses and used a model of Porphyromonas gingivalis lipopolysaccharide (LPS)-induced periodontitis to evaluate how ERM restores osteoblast activity. In vitro, P. gingivalis LPS stimulation suppressed osteoblast differentiation and bone formation. However, ERM treatment combined with P. gingivalis LPS stimulation upregulated osteoblast differentiation-related factors and Del1, indicating that osteoblast differentiation was restored. Alveolar bone resorption and gene expression were evaluated in a periodontitis model, and the results confirmed that ERM treatment increased DEL-1 expression and suppressed bone loss by increasing the expression of osteoblast-associated factors. In conclusion, ERM restores bone metabolism homeostasis in inflammatory environments possibly via the induction of DEL-1.

Association Between Oral Bacteria and Alzheimer's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Pre-clinical evidence implicates oral bacteria in the pathogenesis of Alzheimer's disease (AD), while clinical studies show diverse results.

OBJECTIVE

To comprehensively assess the association between oral bacteria and AD with clinical evidence.

METHODS

Studies investigating the association between oral bacteria and AD were identified through a systematic search of six databases PubMed, Embase, Cochrane Central Library, Scopus, ScienceDirect, and Web of Science. Methodological quality ratings of the included studies were performed. A best evidence synthesis was employed to integrate the results. When applicable, a meta-analysis was conducted using a random-effect model.

RESULTS

Of the 16 studies included, ten investigated periodontal pathobionts and six were microbiome-wide association studies. Samples from the brain, serum, and oral cavity were tested. We found over a ten-fold and six-fold increased risk of AD when there were oral bacteria (OR = 10.68 95% CI: 4.48-25.43; p < 0.00001, I2 = 0%) and Porphyromonas gingivalis (OR = 6.84 95% CI: 2.70-17.31; p < 0.0001, I2 = 0%) respectively in the brain. While AD patients exhibited lower alpha diversity of oral microbiota than healthy controls, the findings of bacterial communities were inconsistent among studies. The best evidence synthesis suggested a moderate level of evidence for an overall association between oral bacteria and AD and for oral bacteria being a risk factor for AD.

CONCLUSION

Current evidence moderately supports the association between oral bacteria and AD, while the association was strong when oral bacteria were detectable in the brain. Further evidence is needed to clarify the interrelationship between both individual species and bacterial communities and the development of AD.

Impact of Porphyromonas gingivalis-odontogenic infection on the pathogenesis of non-alcoholic fatty liver disease

Aim: Non-alcoholic fatty liver disease is characterized by diffuse hepatic steatosis and has quickly risen to become the most prevalent chronic liver disease. Its incidence is increasing yearly, but the pathogenesis is still not fully understood. Porphyromonas gingivalis (P. gingivalis) is a major pathogen widely prevalent in periodontitis patients. Its infection has been reported to be a risk factor for developing insulin resistance, non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), and metabolic syndrome. The aim of this review is to evaluate the association between P. gingivalis infection and NAFLD, identify the possible etiopathogenetic mechanisms, and raise public awareness of oral health to prevent and improve NAFLD.Methods: After searching in PubMed and Web of Science databases using 'Porphyromonas gingivalis', 'non-alcoholic fatty liver disease', and 'hepatic steatosis' as keywords, studies related were compiled and examined.Results: P. gingivalis infection is a direct risk factor for NAFLD based on clinical and basic research. Moreover, it induces systematic changes and systemic abnormalities by disrupting metabolic, inflammatory, and immunologic homeostasis.Conclusion: P. gingivalis-odontogenic infection promotes the occurrence and development of NAFLD. Further concerns are needed to emphasize oral health and maintain good oral hygiene for the prevention and treatment of NAFLD.

Contribution of -Omics Technologies in the Study of Porphyromonas gingivalis during Periodontitis Pathogenesis: A Minireview

Periodontitis is a non-communicable chronic inflammatory disease characterized by the progressive and irreversible breakdown of the soft periodontal tissues and resorption of teeth-supporting alveolar bone. The etiology of periodontitis involves dysbiotic shifts in the diversity of microbial communities inhabiting the subgingival crevice, which is dominated by anaerobic Gram-negative bacteria, including Porphyromonas gingivalis. Indeed, P. gingivalis is a keystone pathogen with a repertoire of attributes that allow it to colonize periodontal tissues and influence the metabolism, growth rate, and virulence of other periodontal bacteria. The pathogenic potential of P. gingivalis has been traditionally analyzed using classical biochemical and molecular approaches. However, the arrival of new techniques, such as whole-genome sequencing, metagenomics, metatranscriptomics, proteomics, and metabolomics, allowed the generation of high-throughput data, offering a suitable option for bacterial analysis, allowing a deeper understanding of the pathogenic properties of P. gingivalis and its interaction with the host. In the present review, we revise the use of the different -omics technologies and techniques used to analyze bacteria and discuss their potential in studying the pathogenic potential of P. gingivalis.

Prevotella genus and its related NOD-like receptor signaling pathway in young males with stage III periodontitis

Background

As periodontitis progresses, the oral microbiota community changes dynamically. In this study, we evaluated the dominant bacteria and their roles in the potential pathway in young males with stage III periodontitis.

Methods

16S rRNA sequencing was performed to evaluate variations in the composition of oral bacteria between males with stage I and III periodontitis and identify the dominant bacteria of each group. Function prediction was obtained based on 16S rRNA sequencing data. The inhibitor of the predominant pathway for stage III periodontitis was used to investigate the role of the dominant bacteria in periodontitis in vivo and in vitro.

Results

Chao1 index, Observed Species and Phylogenetic Diversity (PD) whole tree values were significantly higher in the stage III periodontitis group. β-diversity suggested that samples could be divided according to the stages of periodontitis. The dominant bacteria in stage III periodontitis were Prevotella, Prevotella_7, and Dialister, whereas that in stage I periodontitis was Cardiobacterium. KEGG analysis predicted that variations in the oral microbiome may be related to the NOD-like receptor signaling pathway. The inhibitor of this pathway, NOD-IN-1, decreased P. intermedia -induced Tnf-α mRNA expression and increased P. intermedia -induced Il-6 mRNA expression, consistent with the ELISA results. Immunohistochemistry confirmed the down-regulation of TNF-α and IL-6 expressions by NOD-IN-1 in P. intermedia-induced periodontitis.

Conclusion

The composition of the oral bacteria in young males varied according to the stage of periodontitis. The species richness of oral microtia was greater in young males with stage III periodontitis than those with stage I periodontitis. Prevotella was the dominant bacteria in young males with stage III periodontitis, and inhibition of the NOD-like receptor signaling pathway can decrease the periodontal inflammation induced by P. intermedia.

Biological Roles of Fibroblasts in Periodontal Diseases

Periodontal diseases include periodontitis and gingival overgrowth. Periodontitis is a bacterial infectious disease, and its pathological cascade is regulated by many inflammatory cytokines secreted by immune or tissue cells, such as interleukin-6. In contrast, gingival overgrowth develops as a side effect of specific drugs, such as immunosuppressants, anticonvulsants, and calcium channel blockers. Human gingival fibroblasts (HGFs) are the most abundant cells in gingival connective tissue, and human periodontal ligament fibroblasts (HPLFs) are located between the teeth and alveolar bone. HGFs and HPLFs are both crucial for the remodeling and homeostasis of periodontal tissue, and their roles in the pathogenesis of periodontal diseases have been examined for 25 years. Various responses by HGFs or HPLFs contribute to the progression of periodontal diseases. This review summarizes the biological effects of HGFs and HPLFs on the pathogenesis of periodontal diseases.

Microbiota-assisted therapy for systemic inflammatory arthritis: advances and mechanistic insights

Research on the influence of gut microbiota on systemic inflammatory arthritis has exploded in the past decade. Gut microbiota changes may be a crucial regulatory component in systemic inflammatory arthritis. As a result of advancements in the field, microbiota-assisted therapy has evolved, but this discipline is still in its infancy. Consequently, we review the limitations of current systemic inflammatory arthritis treatment, analyze the connection between the microbiota and arthritis, and summarize the research progress of microbiota regulating systemic inflammatory arthritis and the further development aspects of microbiota-assisted therapy. Finally, the partial mechanisms of microbiota-assisted therapy of systemic inflammatory arthritis are being discussed. In general, this review summarizes the current progress, challenges, and prospects of microbiota-assisted therapy for systemic inflammatory arthritis and points out the direction for the development of microbiota-assisted therapy in the future.

High Molecular Weight Hyaluronic Acid Reduces the Expression of Virulence Genes fimA, mfa1, hagA, rgpA, and kgp in the Oral Pathogen Porphyromonas gingivalis

Porphyromonas gingivalis (P. gingivalis) is a cornerstone pathogen in the development and progression of periodontal and peri-implant tissue destruction. It is capable of causing dysbiosis of the microbial biofilm and modulation of the host immune system. Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan found in all living organisms. It is well known and has been used for improving tissue healing. In addition, some studies have suggested that there may be an antimicrobial potential to HA. The aim of this study was to evaluate the effect of hyaluronic acid, azithromycin (AZM), and chlorhexidine (CHX) on the expression of genes (i.e., fimA, mfa1, hagA, rgpA, rgpB, and kgp) related to the virulence and adhesion of P. gingivalis. The study groups were divided into four: (1) HA treated group; (2) AZM treated group; (3) CHX treated group; and (4) untreated group to serve as a negative control. P. gingivalis ATCC 33277 was cultured and then exposed to four different concentrations (100% MIC, 50% MIC, 25% MIC, and 12.5% MIC) of HA, AZM, and CHX for 24 h. The expression levels of the aforementioned genes were measured using quantitative reverse transcription polymerase chain reaction (RT-qPCR). Relative fold-change values were calculated and compared between groups. The fold-change values of all genes combined were 0.46 ± 0.33, 0.31 ± 0.24, and 0.84 ± 0.77 for HA, AZM, and CHX, respectively. HA has downregulated all the genes by mostly a half-fold: 0.35 ± 0.20, 0.47 ± 0.35, 0.44 ± 0.25, 0.67 ± 0.46, 0.48 ± 0.33 and 0.35 ± 0.22 with fimA, mfa1, hagA, rgpA, rgpB and kgp, respectively. The effect of HA was significant on all genes except rgpB compared to the untreated control. Lower concentrations of HA tended to exhibit greater downregulation with 1 mg/mL being the most effective. High molecular weight (1.5 MDa) hyaluronic acid has a potent effect on P. gingivalis by downregulating fimA, mfa1, hagA, rgpA, and kgp. The effect of HA was generally less than that of AZM but greater than that of CHX.

JMJD3 Promotes Porphyromonas gingivalis Lipopolysaccharide-Induced Th17-Cell Differentiation by Modulating the STAT3-RORc Signaling Pathway

The immune response mediated by Th17 cells is essential in the pathogenesis of periodontitis. Emerging evidence has demonstrated that lipopolysaccharide from Porphyromonas gingivalis (Pg-LPS) could promote Th17-cell differentiation directly, while the downstream signaling remains elusive. This study was aimed to explore the role of JMJD3 (a JmjC family histone demethylase) and signal transducers and activators of transcription 3 (STAT3) in Th17-cell differentiation triggered by Pg-LPS and clarify the interaction between them. We found that the expression of JMJD3 and STAT3 was significantly increased under Th17-polarizing conditions. Pg-LPS could promote Th17-cell differentiation from CD4⁺ T cells, with an increased expression of JMJD3 and STAT3 compared to the culture without Pg-LPS. The coimmunoprecipitation results showed that the interactions of JMJD3 and STAT3, STAT3 and retinoid-related orphan nuclear receptor γt (RORγt) were enhanced following Pg-LPS stimulation during Th17-cell differentiation. Further blocking assays were performed and the results showed that inhibition of STAT3 or JMJD3 both suppressed the Th17-cell differentiation, JMJD3 inhibitor could reduce the expression of STAT3 and p-STAT3, while JMJD3 expression was not affected when STAT3 was inhibited. Taken together, this study found that JMJD3 could promote Pg-LPS induced Th17-cell differentiation by modulating the STAT3-RORc signaling pathway.

Effects of a Berry Polyphenolic Fraction on the Pathogenic Properties of Porphyromonas gingivalis

Porphyromonas gingivalis expresses a broad array of virulence factors that enable it to play a central role in the etiopathogenesis of periodontitis. The objective of the present study was to assess the effects of a berry polyphenolic fraction (Orophenol®) composed of extracts from cranberry, wild blueberry, and strawberry on the main pathogenic determinants of P. gingivalis. Orophenol® attenuated the growth of P. gingivalis and decreased its hemolytic activity, its adherence to a basement membrane matrix model, and its proteinase activities. The berry polyphenolic fraction also impaired the production of reactive oxygen species (ROS) by oral keratinocytes stimulated with P. gingivalis. Lastly, using an in vitro model of oral keratinocyte barrier, the fraction exerted a protective effect against the damages mediated by P. gingivalis. In conclusion, the berry polyphenolic fraction investigated in the present study attenuated several pathogenic properties of P. gingivalis. Although future clinical investigations are required, our study provided evidence that the polyphenols contained in this fraction may represent bioactive molecules of high interest for the prevention and/or treatment of periodontal disease.