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

Activatable Photoacoustic Probe for Imaging Infection: Gold Nanorod Dissociation In Vivo Reports Bacterial Protease Activity

We present a strategy for constructing activatable photoacoustic imaging (PAI) probes for in vivo enzyme activity measurements, based on a dissociation strategy previously applied to in vitro sensing. Unlike conventional nanoparticle aggregation strategies, dissociation minimizes false positives and functions effectively in complex biological environments. Overcoming the challenge of dissociating nanostructure aggregates, which arises from the strong van der Waals forces at short distances, we demonstrate the controlled assembly and dissociation of citrate-capped gold nanorods (AuNRs-citrate) using a diarginine peptide additive and a thiolated polyethylene glycol (HS-PEG-OMe), respectively. This assembly dissociation mechanism enables precise control of the optical and photoacoustic (PA) properties of AuNRs in both in vitro and in vivo settings. Building on these findings, we engineered an enzyme-sensitive PAI probe (AuNRs@RgpB) composed of AuNR assemblies and a PEG-peptide conjugate with a protease-specific cleavage sequence. The probe detects Arg-specific gingipain (RgpB), a protease expressed by Porphyromonas gingivalis associated with periodontal disease and Alzheimer's disease. Proteolytic cleavage of the peptide sequence triggers AuNR dissociation, resulting in enhanced PA signal output. The probe was designed to be injected intrathecally for preclinical trials to image gingipains and investigate the value of gingipain inhibitors developed for Alzheimer's disease. The probe's performance was characterized in vitro using UV-vis spectroscopy and PAI, achieving detection limits of 5 and 20 nM, respectively. In vivo studies involved intracranial injection of AuNRs@RgpB into RgpB-containing murine models, with PA monitoring over time. RgpB activity produced a four-fold PA signal increase within 2 h, while P. gingivalis-infected mice showed similar signal enhancement. Specificity was confirmed by negligible responses to Fusobacterium nucleatum, a non-RgpB-producing bacterium. Additionally, the system demonstrated utility in drug development by successfully monitoring the inhibition of RgpB activity using RgpB inhibitors (leupeptin and KYT-1) in vivo models. Beyond its immediate application to RgpB detection, this modular approach to plasmonic-based sensing holds significant potential for detecting other proteases, advancing both nanotechnology and protease-targeted diagnostics.

In Silico Docking of Medicinal Herbs Against P. gingivalis for Chronic Periodontitis Intervention

OBJECTIVE

This study aimed to explore the therapeutic potential of medicinal herbs for chronic periodontitis by examining the molecular interactions between specific herbal compounds and the heme-binding protein of Porphyromonas gingivalis, a key pathogen involved in the disease.

METHODS

The crystal structure of heme-binding protein was obtained from the Protein Data Bank. Herbal compounds were identified through an extensive literature review. Molecular docking simulations were performed to predict binding affinities, followed by Absorption, Distribution, Metabolism, and Excretion (ADME) parameter prediction. Drug-likeness was assessed based on Lipinski's Rule of Five, and pharmacophore modeling was conducted to identify key molecular interactions.

RESULTS

The molecular docking simulations revealed that chelidonine, rotenone, and myricetin exhibited significant binding affinities to the heme-binding protein, with docking scores of -6.5 kcal/mol, -6.4 kcal/mol, and -6.1 kcal/mol, respectively. These compounds formed stable interactions with key amino acid residues within the binding pocket. ADME analysis indicated that all 3 compounds had favourable pharmacokinetic properties, with no violations of Lipinski's rules and minimal predicted toxicity. Pharmacophore modeling further elucidated the interaction profiles, highlighting specific hydrogen bonds and hydrophobic interactions critical for binding efficacy.

CONCLUSIONS

Chelidonine, rotenone, and myricetin emerged as promising therapeutic candidates for chronic periodontitis due to their strong binding affinities, favorable ADME profiles, and lack of significant toxicity. The detailed pharmacophore modeling provided insights into the molecular mechanisms underpinning their inhibitory effects on the heme-binding protein of P. gingivalis. These findings suggest that these compounds have the potential for further development as effective treatments for chronic periodontitis. Future research should focus on in vitro and in vivo validation of these findings to confirm the efficacy and safety of these compounds in biological systems.

Insights into the complexities of Citrullination: From immune regulation to autoimmune disease

Citrullination, a post-translational modification that changes arginine to citrulline in proteins, is vital for immune response modulation and cell signaling. Catalyzed by peptidyl arginine deiminases (PADs), citrullination is linked to various diseases, particularly autoimmune disorders like rheumatoid arthritis (RA). Citrullinated proteins can trigger the production of anti-citrullinated protein antibodies (ACPAs), included in RA classification criteria. The immune response to citrullination involves both innate and adaptive immunity, affecting monocytes/macrophages, neutrophils, dendritic cells, natural killer cells, B cells, and T cells. Citrullination contributes to disease development in RA and other conditions such as multiple sclerosis, sepsis, and cancer. Therapeutic strategies targeting citrullination and its effects are being explored, including B cell depletion therapies, T cell-directed approaches, PAD inhibitors, and citrullinated peptide-based vaccines. Understanding the interplay between citrullination and the immune system may lead to novel diagnostic tools and targeted therapies for autoimmune diseases and beyond.

Unveiling the Molecular Crosstalk Between Periodontal and Cardiovascular Diseases: A Systematic Review

Background/Objectives: Periodontal disease (PD) is a chronic inflammatory condition caused by dysbiosis of the oral microbiome. PD is linked to systemic inflammation and endothelial dysfunction, which associate it with cardiovascular disease (CVD). This systematic review explores the molecular and microbial mechanisms through which periodontal pathogens, including "Red Complex" bacteria (Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola) and Fusobacterium nucleatum, influence cardiovascular health via inflammatory pathways, immune modulation, and microbial dissemination. Methods: A systematic review was conducted following PRISMA guidelines. A literature search was conducted in the PubMed and ScienceDirect databases using relevant keywords, with strict inclusion and exclusion criteria, from the first week of September 2024 to the first week of October 2024. Studies addressing the relationship between PD and CVD were assessed for methodological rigor, relevance, and data availability. The outcomes were synthesized using a descriptive narrative approach. Out of 591 records screened, 421 full-text articles were sought for retrieval. The final review included 58 articles providing supplementary aggregated data after eligibility assessment. Results: The pathogenesis of PD involves the activation of immune cells and the release of pro-inflammatory cytokines (such as IL-1, IL-6, TNF-α, and PGE2) and chemokines (including IL-8 and MCP-1) along with oxidative stress driven by reactive oxygen species (ROS). Periodontal pathogens trigger endothelial oxidative stress and systemic inflammation via Toll-like receptors (TLRs), NF-κB signaling, and nitric oxide (NO) dysregulation, contributing to endothelial dysfunction and atherogenesis. Biomarkers, such as C-reactive protein, interleukins, and matrix metalloproteinases (MMPs), further highlight the systemic inflammatory response. Conclusions: This review underscores the significant role of periodontal pathogens and inflammatory mediators in systemic health, particularly in the progression of CVD. Although existing evidence illustrates these associations, the underlying molecular mechanisms remain inadequately understood, indicating a need for further research to advance precision medicine and therapeutic strategies.

In vitro modulation of proinflammatory and proteolytic activities of Porphyromonas gingivalis by selected lactobacilli

Objective

The aim of the present study was to characterize the antimicrobial and anti-inflammatory activities of postbiotics from lactic acid bacteria against Porphyromonas gingivalis.

Material and methods

The anti-P. gingivalis activity of postbiotics from the CERELA culture collection was assessed by measuring changes in the expression of key host proteins by ELISA and qPCR, the proteolytic activity by a fluorescence and a spectrophotometric method and virulence factors from P. gingivalis by qPCR.

Results

Even though Lacticaseibacillus (L.) rhamnosus CRL1522 and Lactiplantibacillus (L.) plantarum CRL1363 exhibit only a discrete antibacterial activity against P. gingivalis, the cell-free supernatants of these strains significantly reduced P. gingivalis-induced secretion of interleukins IL-6 and IL-8 by keratinocytes and TNF-α and IL-6 by U937 macrophage-like cells. More importantly, P. gingivalis arginine-gingipain (Rgp) protease activity was markedly reduced by both lactic acid bacteria (LAB) strains. This finding is particularly interesting because it means that both LAB might prevent the ulterior citrullination of peptides and the consequent generation of autoantibodies. The expression of COX2 and TLR2 was also significantly downregulated in macrophages.

Conclusion

Postbiotics from L. rhamnosus CRL1522 and L. plantarum CRL1363 rise as suitable candidates for antagonizing the periodontopathogen P. gingivalis, since they were able to reduce the expression of proinflammatory cytokines and the protein degradation induced by this pathogen. We propose that postbiotics from these LAB could potentially halt the progression of periodontitis based on this in vitro study.

Smoking Impacts Alzheimer's Disease Progression Through Oral Microbiota Modulation

Alzheimer's disease (AD) is an important public health challenge with a limited understanding of its pathogenesis. Smoking is a significant modifiable risk factor for AD progression, and its specific mechanism is often interpreted from a toxicological perspective. However, microbial infections also contribute to AD, with oral microbiota playing a crucial role in its progression. Notably, smoking alters the ecological structure and pathogenicity of the oral microbiota. Currently, there is no systematic review or summary of the relationship between these three factors; thus, understanding this association can help in the development of new treatments. This review summarizes the connections between smoking, AD, and oral microbiota from existing research. It also explores how smoking affects the occurrence and development of AD through oral microbiota, and examines treatments for oral microbiota that delay the progression of AD. Furthermore, this review emphasizes the potential of the oral microbiota to act as a biomarker for AD. Finally, it considers the feasibility of probiotics and oral antibacterial therapy to expand treatment methods for AD.

Exosome applications for the diagnosis and treatment of pancreatic ductal adenocarcinoma: An update (Review)

Pancreatic ductal adenocarcinoma (PDAC) is a malignant neoplasm that typically manifests with subtle clinical manifestations in its early stages and frequently eludes diagnosis until the advanced phases of the disease. The limited therapeutic options available for PDAC significantly contribute to its high mortality rate, highlighting the urgent need for novel biomarkers capable of effectively identifying early clinical manifestations and facilitating precise diagnosis. The pivotal role of cellular exosomes in both the pathogenesis and therapeutic interventions for PDAC has been underscored. Furthermore, researchers have acknowledged the potential of exosomes as targeted drug carriers against regulatory cells in treating PDAC. The present article aims to provide a comprehensive review encompassing recent advancements in utilizing exosomes for elucidating mechanisms underlying disease development, patterns of metastasis, diagnostic techniques and treatment strategies associated with PDAC.

Pathogenic mechanisms and potential applications of extracellular vesicles from periodontal pathogens in periodontitis

Periodontitis is a multifactorial disease characterized by chronic destruction of the periodontal supporting tissues and is closely associated with the dysbiosis of the plaque biofilm. It is the leading cause of tooth loss in adults. Bacterial extracellular vesicles (BEVs) are released from bacteria, which range in size from 20 to 400 nm. These vesicles contain various components derived from their parent bacteria, including nucleic acids, proteins, lipids, and other molecules, which facilitate functions such as molecular transfer, metabolic regulation, bacterial interactions, biofilm formation, and immune modulation. BEVs participated in the pathophysiological process of periodontitis. Recently emerging evidence also showed that the contents of EVs in saliva and gingival crevicular fluid (miRNAs, mRNAs, and proteins) could be used as potential biomarkers for periodontitis. While most current research focuses on human-derived components, much less is known about BEVs. Therefore, this review introduces the formation mechanisms and components of BEVs related to periodontitis. Then, this review summarizes the current information about the mechanism, the diagnostic and theraputic value of periodontal pathogen-derived extracellular vesicles in the development of periodontitis. Furthermore, the future challenges of exploring the role of BEVs in periodontitis are also discussed.

Local Drug Delivery Systems as Novel Approach for Controlling NETosis in Periodontitis

Periodontitis is a chronic inflammation caused by periodontopathogenic bacteria in the dental biofilm, and also involves the inflammatory-immune response of the host. Polymorphonuclear neutrophils (PMNs) play essential roles in bacterial clearance by multiple mechanisms, including the formation of neutrophil extracellular traps (NETs) that retain and destroy pathogens. During PD progression, the interaction between PMNs, NETs, and bacteria leads to an exaggerated immune response and a prolonged inflammatory state. As a lesion matures, PMNs accumulate in the periodontal tissues and die via NETosis, ultimately resulting in tissue injury. A better understanding of the role of NETs, the associated molecules, and the pathogenic pathways of NET formation in periodontitis, could provide markers of NETosis as reliable diagnostic and prognostic tools. Moreover, an assessment of NET biomarker levels in biofluids, particularly in saliva or gingival crevicular fluid, could be useful for monitoring periodontitis progression and treatment efficacy. Preventing excessive NET accumulation in periodontal tissues, by both controlling NETs' formation and their appropriate removal, could be a key for further development of more efficient therapeutic approaches. In periodontal therapy, local drug delivery (LDD) systems are more targeted, enhancing the bioavailability of active pharmacological agents in the periodontal pocket and surrounding tissues for prolonged time to ensure an optimal therapeutic outcome.

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.

Arginine-specific gingipains (RgpA/RgpB) knockdown modulates neutrophil machinery

Background

Gingipains are important virulence factors present in Porphyromonas gingivalis. Arginine-specific gingipains (RgpA and RgpB) are critically associated with increased proteolytic activity and immune system dysfunction, including neutrophilic activity. In this study, we assessed the impact of gingipains (RgpA and RgpB) on neutrophil function.

Methods

Peripheral blood samples were obtained; neutrophils were isolated and incubated with P. gingivalis A7436, W50, and the double RgpA/RgpB double knockout mutant E8 at MOI 20 for 2 hours. Neutrophil viability was assessed by Sytox staining. Phagocytic capacity and apoptosis were measured by flow cytometry. Superoxide release was measured by superoxide dismutase and cytochrome c reduction assay. Gene expression of TLR2, p47-phox, p67-phox, and P2 × 7was measured by qPCR. Inflammatory cytokine and chemokine production was measured by IL-1β, IL-8, RANTES, and TNF-α in cell supernatants.

Results

Neutrophil TLR2 gene expression was reduced in the absence of RgpA/RgpB (p < 0.05), while superoxide production was not significantly impacted. RgpA/RgpB-/- significantly impaired neutrophil phagocytic function (p < 0.05) and increased TNF-α production when compared with the wild-type control (p < 0.05). Neutrophil apoptosis was not altered when exposed to RgpA/RgpB-/- E8 (p > 0.05).

Conclusion

These data suggest that arginine-specific gingipains (RgpA/RgpB) can modulate neutrophil responses against P. gingivalis infection.

Porphyromonas gingivalis Vaccine: Antigens and Mucosal Adjuvants

Porphyromonas gingivalis (Pg), a Gram-negative anaerobic bacterium found in dental plaque biofilm within periodontal pockets, is the primary pathogenic microorganism responsible for chronic periodontitis. Infection by Pg significantly impacts the development and progression of various diseases, underscoring the importance of eliminating this bacterium for effective clinical treatment. While antibiotics are commonly used to combat Pg, the rise of antibiotic resistance poses a challenge to complete eradication. Thus, the prevention of Pg infection is paramount. Research suggests that surface antigens of Pg, such as fimbriae, outer membrane proteins, and gingipains, can potentially be utilized as vaccine antigens to trigger protective immune responses. This article overviews these antigens, discusses advancements in mucosal adjuvants (including immunostimulant adjuvants and vaccine-delivery adjuvants), and their application in Pg vaccine development. Furthermore, the review examines the advantages and disadvantages of different immune pathways and common routes of Pg vaccine immunization. By summarizing the current landscape of Pg vaccines, addressing existing challenges, and highlighting the potential of mucosal vaccines, this review offers new insights for the advancement and clinical implementation of Pg vaccines.

Porphyromonas gingivalis, a bridge between oral health and immune evasion in gastric cancer

Porphyromonas gingivalis (P. gingivalis) is a gram-negative oral pathogen associated with chronic periodontitis. Previous studies have linked poor oral health and periodontitis with oral cancer. Severe cases of periodontal disease can result in advanced periodontitis, leading to tissue degradation, tooth loss, and may also correlate with higher gastric cancer (GC) risk. In fact, tooth loss is associated with an elevated risk of cancer. However, the clinical evidence for this association remains inconclusive. Periodontitis is also characterized by chronic inflammation and upregulation of members of the Programmed Death 1/PD1 Ligand 1 (PD1/PDL1) axis that leads to an immunosuppressive state. Given that chronic inflammation and immunosuppression are conditions that facilitate cancer progression and carcinogenesis, we hypothesize that oral P. gingivalis and/or its virulence factors serve as a mechanistic link between oral health and gastric carcinogenesis/GC progression. We also discuss the potential impact of P. gingivalis' virulence factors (gingipains, lipopolysaccharide (LPS), and fimbriae) on inflammation and the response to immune checkpoint inhibitors in GC which are part of the current standard of care for advanced stage patients.

Antioxidant Effects and Probiotic Properties of Latilactobacillus sakei MS103 Isolated from Sweet Pickled Garlic

Fermented vegetable-based foods, renowned for their unique flavors and human health benefits, contain probiotic organisms with reported in vitro antioxidative effects. This study investigates the probiotic properties of Latilactobacillus sakei MS103 (L. sakei MS103) and its antioxidant activities using an in vitro oxidative stress model based on the hydrogen peroxide (H2O2)-induced oxidative damage of RAW 264.7 cells. L. sakei MS103 exhibited tolerance to extreme conditions (bile salts, low pH, lysozyme, H2O2), antibiotic sensitivity, and auto-aggregation ability. Moreover, L. sakei MS103 co-aggregated with pathogenic Porphyromonas gingivalis cells, inhibited P. gingivalis-induced biofilm formation, and exhibited robust hydrophobic and electrostatic properties that enabled it to strongly bind to gingival epithelial cells and HT-29 cells for enhanced antioxidant effects. Additionally, L. sakei MS103 exhibited other antioxidant properties, including ion-chelating capability and the ability to effectively scavenge superoxide anion free radicals, hydroxyl, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid, and 2,2-diphenyl-1-picrylhydrazyl. Furthermore, the addition of live or heat-killed L. sakei MS103 cells to H2O2-exposed RAW 264.7 cells alleviated oxidative stress, as reflected by reduced malondialdehyde levels, increased glutathione levels, and the up-regulated expression of four antioxidant-related genes (gshR2, gshR4, Gpx, and npx). These findings highlight L. sakei MS103 as a potential probiotic capable of inhibiting activities of P. gingivalis pathogenic bacteria and mitigating oxidative stress.

Association of chronic periodontitis with multiple sclerosis: A systematic review and meta-analysis

BACKGROUND

Chronic periodontitis (CP) is a multifactorial, chronic inflammatory disease of microbial etiology that manifests as a result of the dysfunction of the immune mechanism, culminating in the destruction of the alveolar bone of the jaws. Multiple sclerosis (MS) is an autoimmune disorder that affects the central nervous system (CNS), leads to demyelination and degeneration of nerve axons and often causes severe physical and/or cognitive impairment. As CP and MS involve inflammatory mechanisms and immune dysfunction, researchers have attempted to study the association between them.

AIM

To systematically review the literature on the epidemiological association between CP and MS in adults.

METHODS

PRISMA 2020 statement was used in the study protocol. The design was done according to the Cochrane methodology. A comprehensive literature search was performed in PubMed, Scopus and Cochrane databases; a manual search and evaluation of the gray literature was also performed. The meta-analysis was performed by Review Manager (RevMan) 5.4. Odds ratio (OR) with 95% confidence interval (CI) was defined as the effect size of the outcome. Heterogeneity was assessed by Chi-square and I2. The articles evaluated were written in English, without a time limit, concern observational studies (patient-controls) and report the diagnostic criteria of the diseases. Duplicate entries were excluded. To evaluate the reliability of the results of each study, Newcastle-Ottawa Scale (NOS) and GRADE tools were used. Two independent reviewers did all evaluations with a resolution of discrepancies by a third.

RESULTS

Meta-analysis included three observation studies examined 3376 people. MS patients are significantly more likely to be diagnosed with CP than healthy controls (OR 1.93, 95% CI 1.54-2.42, p<0.0001).

CONCLUSION

A high prevalence of CP was found among MS patients compared with healthy controls. Healthcare professionals should be aware of the association between these pathological entities to provide patients with high-quality care through an effective and holistic diagnostic and therapeutic approach.

Who is in the driver's seat? Parvimonas micra: An understudied pathobiont at the crossroads of dysbiotic disease and cancer

Recent advances in our understanding of microbiome composition at sites of inflammatory dysbiosis have triggered a substantial interest in a variety of historically understudied bacteria, especially among fastidious obligate anaerobes. A plethora of new evidence suggests that these microbes play outsized roles in establishing synergistic polymicrobial infections at many different sites in the human body. Parvimonas micra is a prime example of such an organism. Despite being almost completely uncharacterized at the genetic level, it is one of the few species commonly detected in abundance at multiple mucosal sites experiencing either chronic or acute inflammatory diseases, and more recently, it has been proposed as a discriminating biomarker for multiple types of malignancies. In the absence of disease, P. micra is commonly found in low abundance, typically residing within the oral cavity and gastrointestinal tract. P. micra exhibits the typical features of an inflammophilic organism, meaning its growth actually benefits from active inflammation and inflammatory tissue destruction. In this mini-review, we will describe our current understanding of this underappreciated but ubiquitous pathobiont, specifically focusing upon the role of P. micra in polymicrobial inflammatory dysbiosis and cancer as well as the key emerging questions regarding its pathobiology. Through this timely work, we highlight Parvimonas micra as a significant driver of disease and discuss its unique position at the crossroads of dysbiosis and cancer.