Gingipain-carrying outer membrane vesicles from Porphyromonas gingivalis cause barrier dysfunction of Caco-2 cells by releasing gingipain into the cytosol.

Ingestion of Porphyromonas gingivalis, a periodontal pathogen, disrupts the intestinal barrier in mice. However, the involvement of outer membrane vesicles (OMVs) secreted from P. gingivalis in the destruction of the intestinal barrier remains unclear. In this study, we tested the hypothesis that OMVs carrying gingipains, the major cysteine proteases produced by P. gingivalis, affects the intestinal barrier function. OMVs increased the permeability of the Caco-2 cell monolayer, a human intestinal epithelial cell line, accompanied by degradation of the tight junction protein occludin. In contrast, OMVs prepared from mutant strains devoid of gingipains failed to induce intestinal barrier dysfunction or occludin degradation in Caco-2 cells. A close histological examination revealed the intracellular localization of gingipain-carrying OMVs. Gingipain activity was detected in the cytosolic fraction of Caco-2 cells after incubation with OMVs. These results suggest that gingipains were internalized into intestinal cells through OMVs and transported into the cytosol, where they then directly degraded occludin from the cytosolic side. Thus, P. gingivalis OMVs might destroy the intestinal barrier and induce systemic inflammation via OMV itself or intestinal substances leaked into blood vessels, causing various diseases.

rgpA-Engineered/Functionalized DNA Vaccine as a Novel Prophylactic Vaccination to Prevent Porphyromonas gingivalis-Induced Periodontitis: An in Vivo Study.

BACKGROUND: Arg-gingipain A (rgpA) and Arg-gingipain B (rgpB) are crucial virulence factors associated with Porphyromonas gingivalis (P. gingivalis) and have been recognized as promising targets for antibacterial vaccines. Although vaccines containing rgpA have shown efficacy, the incorporation of rgpB, which lacks the haemagglutinin adhesin (HA) domain, diminishes the vaccine's effectiveness. This study aims to assess the immunogenicity of the functional HA domain of rgpA in mouse periodontitis models. METHODS: A total of 24 mice were randomly divided into four groups, each receiving different immune injections: group A received phosphate-buffered saline (PBS) as an empty control; group B received pVAX1 as a negative control (NC); group C received pVAX1-HA; and group D received pVAX1-rgpA. The mice were subjected to intramuscular injections every two weeks for a total of three administrations. Prior to each immunization, blood samples were collected for antibody detection under isoflurane anesthesia. Following the final immunization, periodontitis was induced two weeks later by using sutures soaked in a P. gingivalis solution. The mice were euthanized after an additional two-week period. To assess the safety of the procedure, major organs were examined through hematoxylin-eosin (HE) staining. Subsequently, the levels of IgG, IgG1, and IgG2a in the serum were quantified via enzyme-linked immunosorbent assay (ELISA). Additionally, the expression of inflammatory factors in the gingiva, including interleukin-6 (IL-6), interleukin-1ß (IL-1ß), and tumor necrosis factor alpha (TNF-α), was determined using quantitative real-time reverse transcript PCR (qRT-PCR). The extent of bone loss in periodontal tissues was evaluated using micro-computed tomography (micro-CT) and HE staining. RESULTS: HE staining of the organs confirmed the absence of vaccine-induced toxicity in vivo. After the second immunization, both the rgpA and HA groups displayed significantly higher specific IgG titers in comparison to the NC and PBS groups (p < 0.05). Furthermore, the rgpA and HA groups exhibited a noteworthy predominance of IgG1 antibodies after three immunization doses, while there was a noticeable reduction in IgG2a levels observed following ligation with P. gingivalis sutures, as opposed to the NC and PBS groups (p < 0.05). Additionally, both the HA and rgpA groups showed a significant decrease in the expression of inflammatory factors such as IL-6, IL-1ß, and TNF-α, as well as a reduction in bone loss around periodontitis-affected teeth, when compared to the NC and PBS groups (p < 0.05). CONCLUSIONS: The results of this study demonstrate that the rgpA-engineered/functionalized HA gene vaccine is capable of eliciting a potent prophylactic immune response against P. gingivalis-induced periodontitis, effectively serving as an immunogenic and protective agent in vivo.

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.

Porphyromonas gingivalis, a periodontal pathogen, impairs post-infarcted myocardium by inhibiting autophagosome-lysosome fusion.

While several previous studies have indicated the link between periodontal disease (PD) and myocardial infarction (MI), the underlying mechanisms remain unclear. Autophagy, a cellular quality control process that is activated in several diseases, including heart failure, can be suppressed by Porphyromonas gingivalis (P.g.). However, it is uncertain whether autophagy impairment by periodontal pathogens stimulates the development of cardiac dysfunction after MI. Thus, this study aimed to investigate the relationship between PD and the development of MI while focusing on the role of autophagy. Neonatal rat cardiomyocytes (NRCMs) and MI model mice were inoculated with wild-type P.g. or gingipain-deficient P.g. to assess the effect of autophagy inhibition by P.g. Wild-type P.g.-inoculated NRCMs had lower cell viability than those inoculated with gingipain-deficient P.g. This study also revealed that gingipains can cleave vesicle-associated membrane protein 8 (VAMP8), a protein involved in lysosomal sensitive factor attachment protein receptors (SNAREs), at the 47th lysine residue, thereby inhibiting autophagy. Wild-type P.g.-inoculated MI model mice were more susceptible to cardiac rupture, with lower survival rates and autophagy activity than gingipain-deficient P.g.-inoculated MI model mice. After inoculating genetically modified MI model mice (VAMP8-K47A) with wild-type P.g., they exhibited significantly increased autophagy activation compared with the MI model mice inoculated with wild-type P.g., which suppressed cardiac rupture and enhanced overall survival rates. These findings suggest that gingipains, which are virulence factors of P.g., impair the infarcted myocardium by cleaving VAMP8 and disrupting autophagy. This study confirms the strong association between PD and MI and provides new insights into the potential role of autophagy in this relationship.

Production and properties of adhesin-free gingipain proteinase RgpA.

The Arg-specific gingipains of Porphyromonas gingivalis RgpA and RgpB have 97% identical sequences in their catalytic domains yet their propeptides are only 76% identical. RgpA isolates as a proteinase-adhesin complex (HRgpA) which hinders direct kinetic comparison of RgpAcat as a monomer with monomeric RgpB. We tested modifications of rgpA identifying a variant that enabled us to isolate histidine-tagged monomeric RgpA (rRgpAH). Kinetic comparisons between rRgpAH and RgpB used benzoyl-L-Arg-4-nitroanilide with and without cysteine and glycylglycine acceptor molecules. With no glycylglycine, values of Km, Vmax, kcat and kcat/Km for each enzyme were similar, but with glycylglycine Km decreased, Vmax increased and kcat increased ~ twofold for RgpB but ~ sixfold for rRgpAH. The kcat/Km for rRgpAH was unchanged whereas that of RgpB more than halved. Recombinant RgpA propeptide inhibited rRgpAH and RgpB with Ki 13 nM and 15 nM Ki respectively slightly more effectively than RgpB propeptide which inhibited rRgpAH and RgpB with Ki 22 nM and 29 nM respectively (p < 0.0001); a result that may be attributable to the divergent propeptide sequences. Overall, the data for rRgpAH reflected observations previously made by others using HRgpA, indicating rRgpAH fidelity and confirming the first production and isolation of functional affinity tagged RgpA.

Antibodies against Porphyromonas gingivalis in serum and saliva and their association with rheumatoid arthritis and periodontitis. Data from two rheumatoid arthritis cohorts in Sweden.

Background: Periodontitis and oral pathogenic bacteria can contribute to the development of rheumatoid arthritis (RA). A connection between serum antibodies to Porphyromonas gingivalis (P. gingivalis) and RA has been established, but data on saliva antibodies to P. gingivalis in RA are lacking. We evaluated antibodies to P. gingivalis in serum and saliva in two Swedish RA studies as well as their association with RA, periodontitis, antibodies to citrullinated proteins (ACPA), and RA disease activity. Methods: The SARA (secretory antibodies in RA) study includes 196 patients with RA and 101 healthy controls. The Karlskrona RA study includes 132 patients with RA ≥ 61 years of age, who underwent dental examination. Serum Immunoglobulin G (IgG) and Immunoglobulin A (IgA) antibodies and saliva IgA antibodies to the P. gingivalis-specific Arg-specific gingipain B (RgpB) were measured in patients with RA and controls. Results: The level of saliva IgA anti-RgpB antibodies was significantly higher among patients with RA than among healthy controls in multivariate analysis adjusted for age, gender, smoking, and IgG ACPA (p = 0.022). Saliva IgA anti-RgpB antibodies were associated with RA disease activity in multivariate analysis (p = 0.036). Anti-RgpB antibodies were not associated with periodontitis or serum IgG ACPA. Conclusion: Patients with RA had higher levels of saliva IgA anti-RgpB antibodies than healthy controls. Saliva IgA anti-RgpB antibodies may be associated with RA disease activity but were not associated with periodontitis or serum IgG ACPA. Our results indicate a local production of IgA anti-RgpB in the salivary glands that is not accompanied by systemic antibody production.

A conditional gene expression system in Porphyromonas gingivalis for study of the secretion mechanisms of lipoproteins and T9SS cargo proteins.

The Gram-negative anaerobe, Porphyromonas gingivalis, is known to be a pathogen associated with chronic periodontitis. P. gingivalis possesses virulence factors such as fimbriae and gingipain proteinases. Fimbrial proteins are secreted to the cell surface as lipoproteins. In contrast, gingipain proteinases are secreted into the bacterial cell surface via the type IX secretion system (T9SS). The transport mechanisms of lipoproteins and T9SS cargo proteins are entirely different and remain unknown. Therefore, using the Tet-on system developed for the genus Bacteroides, we newly created a conditional gene expression system in P. gingivalis. We succeeded in establishing conditional expression of nanoluciferase and its derivatives for lipoprotein export, of FimA for a representative of lipoprotein export, and of T9SS cargo proteins such as Hbp35 and PorA for representatives of type 9 protein export. Using this system, we showed that the lipoprotein export signal, which has recently been found in other species in the phylum Bacteroidota, is also functional in FimA, and that a proton motive force inhibitor can affect type 9 protein export. Collectively, our conditional protein expression method is useful for screening inhibitors of virulence factors, and may be used to investigate the role of proteins essential to bacterial survival in vivo.

Porphyromonas gingivalis Gingipains Destroy the Vascular Barrier and Reduce CD99 and CD99L2 Expression To Regulate Transendothelial Migration.

Porphyromonas gingivalis is an important periodontal pathogen that can cause vascular injury and invade local tissues through the blood circulation, and its ability to evade leukocyte killing is critical to its distal colonization and survival. Transendothelial migration (TEM) is a series of that enable leukocytes to squeeze through endothelial barriers and migrate into local tissues to perform immune functions. Several studies have shown that P. gingivalis-mediated endothelial damage initiates a series of proinflammatory signals that promote leukocyte adhesion. However, whether P. gingivalis is involved in TEM and thus influences immune cell recruitment remains unknown. In our study, we found that P. gingivalis gingipains could increase vascular permeability and promote Escherichia coli penetration by downregulating platelet/endothelial cell adhesion molecule 1 (PECAM-1) expression in vitro. Furthermore, we demonstrated that although P. gingivalis infection promoted monocyte adhesion, the TEM capacity of monocytes was substantially impaired, which might be due to the reduced CD99 and CD99L2 expression on gingipain-stimulated endothelial cells and leukocytes. Mechanistically, gingipains mediate CD99 and CD99L2 downregulation, possibly through the inhibition of the phosphoinositide 3-kinase (PI3K)/Akt pathway. In addition, our in vivo model confirmed the role of P. gingivalis in promoting vascular permeability and bacterial colonization in the liver, kidney, spleen, and lung and in downregulating PECAM-1, CD99, and CD99L2 expression in endothelial cells and leukocytes. IMPORTANCE P. gingivalis is associated with a variety of systemic diseases and colonizes in distal locations in the body. Here, we found that P. gingivalis gingipains degrade PECAM-1 to promote bacterial penetration while simultaneously reducing leukocyte TEM capacity. A similar phenomenon was also observed in a mouse model. These findings established P. gingivalis gingipains as the key virulence factor in modulating the permeability of the vascular barrier and TEM processes, which may provide a new rationale for the distal colonization of P. gingivalis and its associated systemic diseases.

The involvement of CdhR in Porphyromonas gingivalis during nitric oxide stress.

Porphyromonas gingivalis, the causative agent of adult periodontitis, must gain resistance to frequent oxidative and nitric oxide (NO) stress attacks from immune cells in the periodontal pocket to survive. Previously, we found that, in the wild-type and under NO stress, the expression of PG1237 (CdhR), the gene encoding for a putative LuxR transcriptional regulator previously called community development and hemin regulator (CdhR), was upregulated 7.7-fold, and its adjacent gene PG1236 11.9-fold. Isogenic mutants P. gingivalis FLL457 (ΔCdhR::ermF), FLL458 (ΔPG1236::ermF), and FLL459 (ΔPG1236-CdhR::ermF) were made by allelic exchange mutagenesis to determine the involvement of these genes in P. gingivalis W83 NO stress resistance. The mutants were black pigmented and ß hemolytic and their gingipain activities varied with strains. FLL457 and FLL459 mutants were more sensitive to NO compared to the wild type, and complementation restored NO sensitivity to that of the wild type. DNA microarray analysis of FLL457 showed that approximately 2% of the genes were upregulated and over 1% of the genes downregulated under NO stress conditions compared to the wild type. Transcriptome analysis of FLL458 and FLL459 under NO stress showed differences in their modulation patterns. Some similarities were also noticed between all mutants. The PG1236-CdhR gene cluster revealed increased expression under NO stress and may be part of the same transcriptional unit. Recombinant CdhR showed binding activity to the predicted promoter regions of PG1459 and PG0495. Taken together, the data indicate that CdhR may play a role in NO stress resistance and be involved in a regulatory network in P. gingivalis.

Gingipains are the important virulence factors of Porphyromonas gingivalis downregulating B10 cells.

Porphyromonas gingivalis is a keystone pathogen in periodontitis. Our previous study indicated that periodontitis induced by P. gingivalis increased the percentage of CD19+ B cells but decreased the ratio of IL-10-producing regulatory B cells (B10) in collagen-induced arthritis (CIA) mice. It is still unclear which virulence factors of P. gingivalis are involved in these processes. Here, we compared the effects of different components of P. gingivalis on the biogenesis of B10 cells and found that the decreased proportion of B10 cells mainly resulted from the undenatured proteins other than the DNA, RNA, or lipopolysaccharides of P. gingivalis. As gingipains are enzymes and virulence factors that play a vital role in the progression in periodontitis through affecting the innate and adaptive immune system, we then compared the influence of the wild-type (WT) strain of P. gingivalis (ATCC 33277) and its isogenic gingipain-null mutant (∆K∆RAB) on the differentiation of splenic B cells into B10 cells. Interestingly, compared to WT strain, ∆K∆RAB treatment increased the frequency of B10 cells as well as the expression of IL-6 in B cells. Furthermore, the acute peritonitis, an ideal model for the quick evaluation of immune effects of agents, induced by ∆K∆RAB, showed the higher IL-6 production and proportion of B10 cells compared with WT. Finally, we performed transcriptomic analysis to better understand the effects and possible mechanisms of gingipains on B cells. Compared with WT, ∆K∆RAB upregulated the PI3K-Akt pathway of B cells, which is important for IL-10 production and B10 cell biogenesis, and more activated Jak-STAT pathway, which is a classical signaling pathway mediated by IL-6. Cumulatively, this study preliminarily revealed that gingipains of P. gingivalis are vital virulence factors downregulating B10 cells and altering immune responses.

Impacts of Porphyromonas gingivalis periodontitis on rheumatoid arthritis autoimmunity.

In RA patients' synovial sites, citrullinated RA-related antigens such as type II collagens, fibrin (ogen), vimentin, and α-enolase could be targeted by ACCPAs. Since ACCPA production can be initiated a long time before RA sign appearance, primary auto-immunization against these citrullinated proteins can be originated from extra-articular sites. It has been shown that there is a significant association between P. gingivalis periodontitis, anti- P. gingivalis antibodies, and RA. P. gingivalis gingipains (Rgp, Kgp) can degrade proteins such as fibrin and α-enolase into some peptides in the form of Arg in the C-terminal which is converted to citrulline by PPAD. Also, PPAD can citrullinate type II collagen and vimentins (SA antigen). P. gingivalis induces inflammation and chemoattraction of immune cells such as neutrophils and macrophages through the increase of C5a (gingipain C5 convertase-like activity) and SCFA secretion. Besides, this microorganism stimulates anoikis, a special type of apoptosis, and NETosis, an antimicrobial form of neutrophil death, leading to the release of PAD1-4, α-enolase, and vimentin from apoptotic cells into the periodontal site. In addition, gingipains can degrade macrophages CD14 and decrease their ability in apoptotic cell removal. Gingipains also can cleave IgGs in the Fc region and transform them into rheumatoid factor (RF) antigens. In the present study, the effects of P. gingivalis on rheumatoid arthritis autoimmune response have been reviewed, which could attract practical insight both in bench and clinic.

P. gingivalis Infection Upregulates PD-L1 Expression on Dendritic Cells, Suppresses CD8+ T-cell Responses, and Aggravates Oral Cancer.

Accumulating evidence shows that PD-L1 expression on dendritic cells (DC) is critical for cancer immunotherapy and that Porphyromonas gingivalis (Pg) colonization aggravates the progression of upper gastrointestinal cancers. However, the effects of Pg infection on PD-L1 expression on DCs and related immune consequences in the infection milieu of oral cancer remain unexplored. Here, we found that Pg infection robustly enhanced PD-L1 expression on DCs in a gingipain-dependent manner in cultured cell and systemic infection assays. Pg infection suppressed antigen-specific CD8+ T cells through upregulation of PD-L1 expression on ovalbumin (OVA)-pulsed DCs. This suppression was manifested by decreased IFNγ, perforin, granzyme B, and CD107a. Further analysis showed that Pg drastically reduced CD8+ T cells' ability to lyse OVA-pulsed target cells. Additionally, Pg infection increased the phosphorylation of Akt and STAT3, leading to a significant increase in PD-L1 expression. This was substantiated by using siRNA, overexpression plasmids, and pharmacologic inhibitors. Consistent with the in vitro observations, in a syngeneic mouse oral cancer model, Pg infection significantly enhanced PD-L1 expression on DCs from intratumoral tissues and cervical lymph nodes and exacerbated oral cancer progression, whereas a Pg lysine-specific, gingipain-defective mutant failed to do so. These influences of Pg were largely diminished when tumor cells were pretreated with antibiotics or a STAT3 inhibitor. Therefore, we demonstrated that Pg infection upregulates PD-L1 expression on DCs through Akt-STAT3 signaling, suppresses CD8+ T-cell cytotoxicity, and aggravates oral cancer growth, suggesting targeting Pg, and/or its mediated signaling, could be a therapeutic strategy to improve the efficacy of checkpoint blockade immunotherapy.

Computational Study of the Inhibition of RgpB Gingipain, a Promising Target for the Treatment of Alzheimer's Disease.

Alzheimer's disease represents one of the most ambitious challenges for biomedical sciences due to the growing number of cases worldwide in the elderly population and the lack of efficient treatments. One of the recent attempts to develop a treatment points to the cysteine protease RgpB as a promising drug target. In this attempt, several small-molecule covalent inhibitors of this enzyme have been proposed. Here, we report a computational study at the atomic level of the inhibition mechanism of the most promising reported compounds. Molecular dynamics simulations were performed on six of them, and their binding energies in the active site of the protein were computed. Contact maps and interaction energies were decomposed by residues to disclose those key interactions with the enzyme. Finally, quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulations were performed to evaluate the reaction mechanism by which these drug candidates lead to covalently bound complexes, inhibiting the RgpB protease. The results provide a guide for future re-design of prospective and efficient inhibitors for the treatment of Alzheimer's disease.

Porphyromonas gingivalis bacteremia increases the permeability of the blood-brain barrier via the Mfsd2a/Caveolin-1 mediated transcytosis pathway.

Bacteremia induced by periodontal infection is an important factor for periodontitis to threaten general health. P. gingivalis DNA/virulence factors have been found in the brain tissues from patients with Alzheimer's disease (AD). The blood-brain barrier (BBB) is essential for keeping toxic substances from entering brain tissues. However, the effect of P. gingivalis bacteremia on BBB permeability and its underlying mechanism remains unclear. In the present study, rats were injected by tail vein with P. gingivalis three times a week for eight weeks to induce bacteremia. An in vitro BBB model infected with P. gingivalis was also established. We found that the infiltration of Evans blue dye and Albumin protein deposition in the rat brain tissues were increased in the rat brain tissues with P. gingivalis bacteremia and P. gingivalis could pass through the in vitro BBB model. Caveolae were detected after P. gingivalis infection in BMECs both in vivo and in vitro. Caveolin-1 (Cav-1) expression was enhanced after P. gingivalis infection. Downregulation of Cav-1 rescued P. gingivalis-enhanced BMECs permeability. We further found P. gingivalis-gingipain could be colocalized with Cav-1 and the strong hydrogen bonding between Cav-1 and arg-specific-gingipain (RgpA) were detected. Moreover, P. gingivalis significantly inhibited the major facilitator superfamily domain containing 2a (Mfsd2a) expression. Mfsd2a overexpression reversed P. gingivalis-increased BMECs permeability and Cav-1 expression. These results revealed that Mfsd2a/Cav-1 mediated transcytosis is a key pathway governing BBB BMECs permeability induced by P. gingivalis, which may contribute to P. gingivalis/virulence factors entrance and the subsequent neurological impairments.

A GntR family transcription factor in Porphyromonas gingivalis regulates bacterial growth, acylpeptidyl oligopeptidase, and gingipains activity.

Porphyromonas gingivalis is a keystone pathogen for periodontitis. The function of the GntR family transcription factor is poorly studied in P. gingivalis. Numerous processes govern bacterial growth. The survival and pathogenicity of P. gingivalis depend heavily on its capacity to acquire amino acids as nutritional sources. In this investigation, a GntR transcription factor, pg1007, was identified in P. gingivalis, the deletion of which significantly inhibited bacterial growth. The mutant strain also exhibited an increased extracellular activity of gingipains and acylpeptidyl oligopeptidase (AOP). Global gene expression profiling revealed that the expression levels of 59 genes were significantly altered in the Δpg1007 mutant, with an upregulation in gene expression for AOP, ABC transporters, and some membrane proteins. In addition, His-PG1007 protein was purified as a recombinant protein from Escherichia coli, and the conserved DNA sequence bound by it was determined using electrophoretic mobility shift assays and DNase I footprinting assays. Consequently, this study demonstrated that pg1007 is a crucial transcription factor in P. gingivalis and regulates the bacterial growth and activity of gingipains and AOP. These findings may enhance our understanding of the regulation of bacterial proliferation and protease activity in P. gingivalis.

Porphyromonas gingivalis outer membrane vesicles in cerebral ventricles activate microglia in mice.

OBJECTIVE: Porphyromonas gingivalis (Pg) is thought to be involved in the progression of Alzheimer's disease (AD). Whether Pg or its contents can reach the brain and directly affect neuropathology is, however, unknown. Here, we investigated whether outer membrane vesicles (OMVs) of Pg translocate to the brain and induce the pathogenic features of AD. MATERIAL AND METHODS: Pg OMVs were injected into the abdominal cavity of mice for 12 weeks. Pg OMV translocation to the brain was detected by immunohistochemistry using an anti-gingipain antibody. Tau protein and microglial activation in the mouse brain were examined by western blotting and immunohistochemistry. The effect of gingipains on inflammation was assessed by real-time polymerase chain reaction using human microglial HMC3 cells. RESULTS: Gingipains were detected in the region around cerebral ventricles, choroid plexus, and ventricular ependymal cells in Pg OMV-administered mice. Tau and phosphorylated Tau protein increased and microglia were activated. Pg OMVs also increased the gene expression of proinflammatory cytokines in HMC3 cells in a gingipain-dependent manner. CONCLUSION: Pg OMVs, including gingipains, can reach the cerebral ventricle and induce neuroinflammation by activating microglia. Pg OMVs may provide a better understanding of the implications of periodontal diseases in neurodegenerative conditions such as AD.

Dental follicle cells-derived small extracellular vesicles inhibit pathogenicity of Porphyromonas gingivalis.

OBJECTIVE: It aims to explore the effect of dental follicle cells-derived small extracellular vesicles (D-sEVs) with or without lipopolysaccharides (LPS) pretreating on the pathogenicity of Porphyromonas gingivalis (P. gingivalis). METHODS: The antibacterial effects of D-sEV were evaluated by measuring the growth, biofilm formation, gingipains, and type IX secretion system (T9SS) expression of P. gingivalis. And the influence of D-sEV on P. gingivalis adhesion, invasion, cytotoxicity, and host immune response was examined in gingival epithelial cells (GECs). Then P. gingivalis treated with D-sEV was applied to investigate the pathogenicity in experimental periodontitis of mice. RESULTS: It showed that both D-sEV and P. gingivalis LPS-pretreated D-sEV (L-D-sEV) could target P. gingivalis, inhibit their growth and biofilm formation, and hinder the attachment and invasion in GECs, therefore remarkably decreasing P. gingivalis cytotoxicity and the expression of IL-1ß and IL-6 in GECs. In addition, they significantly reduced the expression of P. gingivalis virulence factors (gingipains and T9SS). In vivo, it showed that the bacteria in the gingiva were significantly decreased after sEV treatment. Meanwhile, less bone loss and fewer inflammatory cells infiltration and osteoclast formation in D-sEV and L-D-sEV groups. CONCLUSION: Both D-sEV and L-D-sEV were proven to inhibit the pathogenicity of P. gingivalis and thus prevented the development of periodontitis.

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

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

Porphyromonas gingivalis, a periodontal pathogen, impairs post-infarcted myocardium by inhibiting autophagosome-lysosome fusion / 国际口腔科学杂志·英文版

While several previous studies have indicated the link between periodontal disease (PD) and myocardial infarction (MI), the underlying mechanisms remain unclear. Autophagy, a cellular quality control process that is activated in several diseases, including heart failure, can be suppressed by Porphyromonas gingivalis (P.g.). However, it is uncertain whether autophagy impairment by periodontal pathogens stimulates the development of cardiac dysfunction after MI. Thus, this study aimed to investigate the relationship between PD and the development of MI while focusing on the role of autophagy. Neonatal rat cardiomyocytes (NRCMs) and MI model mice were inoculated with wild-type P.g. or gingipain-deficient P.g. to assess the effect of autophagy inhibition by P.g. Wild-type P.g.-inoculated NRCMs had lower cell viability than those inoculated with gingipain-deficient P.g. This study also revealed that gingipains can cleave vesicle-associated membrane protein 8 (VAMP8), a protein involved in lysosomal sensitive factor attachment protein receptors (SNAREs), at the 47th lysine residue, thereby inhibiting autophagy. Wild-type P.g.-inoculated MI model mice were more susceptible to cardiac rupture, with lower survival rates and autophagy activity than gingipain-deficient P.g.-inoculated MI model mice. After inoculating genetically modified MI model mice (VAMP8-K47A) with wild-type P.g., they exhibited significantly increased autophagy activation compared with the MI model mice inoculated with wild-type P.g., which suppressed cardiac rupture and enhanced overall survival rates. These findings suggest that gingipains, which are virulence factors of P.g., impair the infarcted myocardium by cleaving VAMP8 and disrupting autophagy. This study confirms the strong association between PD and MI and provides new insights into the potential role of autophagy in this relationship.

Porphyromonas gingivalis bacteremia increases the permeability of the blood-brain barrier via the Mfsd2a/Caveolin-1 mediated transcytosis pathway / 国际口腔科学杂志·英文版

Bacteremia induced by periodontal infection is an important factor for periodontitis to threaten general health. P. gingivalis DNA/virulence factors have been found in the brain tissues from patients with Alzheimer's disease (AD). The blood-brain barrier (BBB) is essential for keeping toxic substances from entering brain tissues. However, the effect of P. gingivalis bacteremia on BBB permeability and its underlying mechanism remains unclear. In the present study, rats were injected by tail vein with P. gingivalis three times a week for eight weeks to induce bacteremia. An in vitro BBB model infected with P. gingivalis was also established. We found that the infiltration of Evans blue dye and Albumin protein deposition in the rat brain tissues were increased in the rat brain tissues with P. gingivalis bacteremia and P. gingivalis could pass through the in vitro BBB model. Caveolae were detected after P. gingivalis infection in BMECs both in vivo and in vitro. Caveolin-1 (Cav-1) expression was enhanced after P. gingivalis infection. Downregulation of Cav-1 rescued P. gingivalis-enhanced BMECs permeability. We further found P. gingivalis-gingipain could be colocalized with Cav-1 and the strong hydrogen bonding between Cav-1 and arg-specific-gingipain (RgpA) were detected. Moreover, P. gingivalis significantly inhibited the major facilitator superfamily domain containing 2a (Mfsd2a) expression. Mfsd2a overexpression reversed P. gingivalis-increased BMECs permeability and Cav-1 expression. These results revealed that Mfsd2a/Cav-1 mediated transcytosis is a key pathway governing BBB BMECs permeability induced by P. gingivalis, which may contribute to P. gingivalis/virulence factors entrance and the subsequent neurological impairments.