Suppression of inflammatory responses of human gingival fibroblasts by gingipains fromPorphyromonas gingivalis

1,25 dihydroxyvitamin D3-mediated effects on bovine innate immunity and on biofilm-forming Staphylococcus spp. isolated from cattle with mastitis

Mastitis is one the most widespread and serious diseases in dairy cattle. Recurrent and chronic infections are often attributable to certain pathogenicity mechanisms in mastitis-causing pathogens such as Staphylococcus spp. These include growing in biofilm and invading cells, both of which make it possible to resist or evade antimicrobial therapies and the host's immune system. This study tested the effects of active vitamin D3 (i.e., calcitriol or 1,25-dihydroxyvitamin D3) on the internalization and phagocytosis of biofilm-forming Staphylococcus spp. isolated from animals with mastitis. Two established bovine cell lines were used: MAC-T (mammary epithelial cells) and BoMac (macrophages). Calcitriol (0-200 nM) did not affect the viability of MAC-T cells nor that of BoMac cells after 24 and 72 h. Concentrations of 0-100 mM for 24 h upregulated the expression of 24-hydroxylase in MAC-T cells, but did not alter that of VDR. Pre-treatment of the cells with calcitriol for 24 h decreased the internalization of S. aureus V329 into MAC-T cells (0-100 nM), and stimulated the phagocytosis of the same strain and of S. xylosus 4913 (0-10 nM). Calcitriol and two conditioned media, obtained by treating the cells with 25-200 nM of the metabolite for 24 h, were also assessed in terms of their antimicrobial and antibiofilm activity. Neither calcitriol by itself nor the conditioned media affected staphylococcal growth or biofilm formation (0-200 nM for 12 and 24 h, respectively). In contrast, the conditioned media (0-100 nM for 24 h) decreased the biomass of preformed non-aureus staphylococcal biofilms and killed the bacteria within them, without affecting metabolic activity. These effects may be mediated by reactive oxygen species and proteins with antimicrobial and/or antibiofilm activity. In short, calcitriol could make pathogens more accessible to antimicrobial therapies and enhance bacterial clearance by professional phagocytes. Moreover, it may modulate the host's endogenous defenses in the bovine udder and help combat preformed non-aureus staphylococcal biofilms (S. chromogenes 40, S. xylosus 4913, and/or S. haemolyticus 6). The findings confirm calcitriol's potential as an adjuvant to prevent and/or treat intramammary infections caused by Staphylococcus spp., which would in turn contribute to reducing antibiotic use on dairy farms.

Cystatin C: immunoregulation role in macrophages infected with Porphyromonas gingivalis

Background

Periodontitis is a chronic infectious disease, characterized by an exacerbated inflammatory response and a progressive loss of the supporting tissues of the teeth. Porphyromonas gingivalis is a key etiologic agent in periodontitis. Cystatin C is an antimicrobial salivary peptide that inhibits the growth of P. gingivalis. This study aimed to evaluate the antimicrobial activity of this peptide and its effect on cytokine production, nitric oxide (NO) release, reactive oxygen species (ROS) production, and programmed cell death in human macrophages infected with P. gingivalis.

Methods

Monocyte-derived macrophages generated from peripheral blood were infected with P. gingivalis (MOI 1:10) and stimulated with cystatin C (2.75 µg/ml) for 24 h. The intracellular localization of P. gingivalis and cystatin C was determined by immunofluorescence and transmission electron microscopy (TEM). The intracellular antimicrobial activity of cystatin C in macrophages was assessed by counting Colony Forming Units (CFU). ELISA assay was performed to assess inflammatory (TNFα, IL-1β) and anti-inflammatory (IL-10) cytokines. The production of nitrites and ROS was analyzed by Griess reaction and incubation with 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA), respectively. Programmed cell death was assessed with the TUNEL assay, Annexin-V, and caspase activity was also determined.

Results

Our results showed that cystatin C inhibits the extracellular growth of P. gingivalis. In addition, this peptide is internalized in the infected macrophage, decreases the intracellular bacterial load, and reduces the production of inflammatory cytokines and NO. Interestingly, peptide treatment increased ROS production and substantially decreased bacterial-induced macrophage apoptosis.

Conclusions

Cystatin C has antimicrobial and immuno-regulatory activity in macrophages infected with P. gingivalis. These findings highlight the importance of understanding the properties of cystatin C for its possible therapeutic use against oral infections such as periodontitis.

Inhibition of PKM2 suppresses osteoclastogenesis and alleviates bone loss in mouse periodontitis

BACKGROUND

Chronic periodontitis triggers an increase in osteoclastogenesis, with glycolysis playing a crucial role in this process. Pyruvate kinase M2 (PKM2) is a critical enzyme involved in glycolysis and pyruvate metabolism. Yet, the precise function of PKM2 in osteoclasts and their formation remains unclear and requires further investigation.

METHODS

Bioinformatics was used to investigate critical biological processes in osteoclastogenesis. In vitro, osteoclastogenesis was analyzed using tartrate-resistant acid phosphatase (TRAP) staining, phalloidin staining, quantitative real‑time PCR (RT-qPCR), and Western blotting. Small interfering RNA (siRNA) of PKM2 and Shikonin, a specific inhibitor of PKM2, were used to verify the role of PKM2 in osteoclastogenesis. The mouse model of periodontitis was used to assess the effect of shikonin on bone loss. Analyses included micro computed tomography, immunohistochemistry, flow cytometry, TRAP staining and HE staining.

RESULTS

Bioinformatic analysis revealed a significant impact of glycolysis and pyruvate metabolism on osteoclastogenesis. Inhibition of PKM2 leads to a significant reduction in osteoclastogenesis. In vitro, co-culture of the heat-killed Porphyromonas gingivalis significantly promoted osteoclastogenesis, concomitant with an increased PKM2 expression in osteoclasts. Shikonin weakened the promoting effect of porphyromonas gingivalis on osteoclastogenesis. In vivo experiments demonstrated that inhibition of PKM2 by shikonin alleviated bone loss induced by periodontitis, suppressed excessive osteoclastogenesis in alveolar bone, and reduced tissue inflammation to some extent.

CONCLUSION

PKM2 inhibition by shikonin, a specific inhibitor of this enzyme, attenuated osteoclastogenesis and bone resorption in periodontitis. Shikonin appears to be a promising therapeutic agent for treating periodontitis.

Secretory leukocyte protease inhibitor (SLPI) in cancer pathophysiology: Mechanisms of action and clinical implications

Cancer is a multifaceted disorder frequently linked to the dysregulation of several biological processes. The SLPI is a multifunctional protein involved in the modulation of immunological response and the inhibition of protease activities. SLPI acts as an inhibitor of proteases, exerts antibacterial properties, and suppresses the transcription of proinflammatory genes through the nuclear factor-kappa B (NF-κB) pathway. The role of this protein as a regulatory agent has been implicated in various types of cancer. Recent research has revealed that SLPI upregulation in cancer cells enhances the metastatic capacity of epithelial malignancies, indicating the deleterious effects of this protein. Furthermore, SLPI interacts intricately with other cancer-promoting factors, including matrix metalloproteinase-2 (MMP-2), MMP-9, the NF-κB and Akt pathways, and the p53-upregulated modulator of apoptosis (PUMA). This review provides an overview of the role of SLPI in cancer pathophysiology, emphasizing its expression in cancer cells and tissues, its potential as a prognostic biomarker, and its therapeutic promise as a target in cancer treatment. The mechanisms of SLPI action in cancer, including its anti-inflammatory effects, regulation of cell proliferation and angiogenesis, and modulation of the tumor microenvironment, have been investigated. The clinical implications of SLPI in cancer have been discussed, including its potential as a diagnostic and prognostic biomarker, its role in chemoresistance, and its therapeutic potential in several types of cancer, such as hepatocellular carcinoma (HCC), colorectal cancer (CRC), pancreatic cancer, head and neck squamous cell carcinoma (HNSCC), ovarian cancer (OvCa), prostate cancer (PC), gastric cancer (GC), breast cancer, and other cancers. In addition, we emphasized the significance of SLPI in cancer, which offers fresh perspectives on potential targets for cancer therapy.

Local and Systemic Effects of Porphyromonas gingivalis Infection

Porphyromonas gingivalis, a gram-negative anaerobe, is a leading etiological agent in periodontitis. This infectious pathogen can induce a dysbiotic, proinflammatory state within the oral cavity by disrupting commensal interactions between the host and oral microbiota. It is advantageous for P. gingivalis to avoid complete host immunosuppression, as inflammation-induced tissue damage provides essential nutrients necessary for robust bacterial proliferation. In this context, P. gingivalis can gain access to the systemic circulation, where it can promote a prothrombotic state. P. gingivalis expresses a number of virulence factors, which aid this pathogen toward infection of a variety of host cells, evasion of detection by the host immune system, subversion of the host immune responses, and activation of several humoral and cellular hemostatic factors.

Endogenous secretory leukocyte protease inhibitor inhibits microbial-induced monocyte activation

In the intestine, epithelial factors condition incoming immune cells including monocytes to adapt their threshold of activation and prevent undesired inflammation. Colonic epithelial cells express Secretory Leukocyte Protease Inhibitor (SLPI), an inhibitor of NF kappa light chain enhancer of activated B cells (NF-κB) that mediates epithelial hyporesponsiveness to microbial stimuli. Uptake of extracellular SLPI by monocytes has been proposed to inhibit monocyte activation. We questioned whether monocytes can produce SLPI and whether endogenous SLPI can inhibit monocyte activation. We demonstrate that human THP-1 monocytic cells produce SLPI and that CD68⁺ SLPI-producing cells can be detected in human intestinal lamina propria. Knockdown of SLPI in human THP-1 cells significantly increased NF-κB activation and subsequent C-X-C motif chemokine ligand 8 (CXCL8) and TNF-α production in response to microbial stimulation. Reconstitution of SLPI-deficient cells with either full-length SLPI or SLPI lacking its signal peptide rescued inhibition of NF-κB activation and cytokine production, demonstrating that endogenous SLPI inhibits monocytic cell activation. Unexpectedly, exogenous SLPI did not inhibit CXCL8 or TNF-α production, despite efficient uptake. Our data argue that endogenous SLPI can regulate the threshold of activation in monocytes, thereby preventing activation by commensal bacteria in mucosal tissues.

Porphyromonas gingivalis infection promotes inflammation via inhibition of the AhR signalling pathway in periodontitis

Porphyromonas gingivalis (P. gingivalis) is a key pathogen of chronic periodontitis. Aryl hydrocarbon receptor (AhR) is essential in immune homeostasis via modulation of pro-inflammatory cytokines production and indoleamine 2,3-dioxygenase (IDO). In this study, it is demonstrated that P. gingivalis may regulate AhR signalling in periodontitis, which provides a potential target for further immune regulation studies in periodontitis. Experimental periodontitis was induced in C57BL/6 mice by silk ligature and P. gingivalis oral inoculation. The alveolar bone resorption was examined using Micro-CT. Histological structures were observed and related cytokines involved in AhR signalling pathway were analysed. RAW264.7 cells were pretreated with AhR agonist (FICZ) and antagonist (CH223191) and infected with P. gingivalis subsequently. The levels of IDO, AhR and other related cytokines were measured. To demonstrate IDO activity, the concentrations of tryptophan (Trp) and kynurenine (Kyn) were assessed by HPLC. Histological analysis of periodontitis mice showed distinct alveolar bone resorption and inflammatory cell infiltration. The level of AhR and its downstream target factors were significantly decreased in inflamed gingival tissue. Furthermore, RAW 264.7 cells incubated by P. gingivalis exhibited increased pro-inflammatory cytokines production and decreased AhR, CYP1A1, CYP1B1, and IDO expression. Decreased IDO activity was observed as decreased Kyn/Trp ratio in the supernatant. Moreover, FICZ decreased the pro-inflammatory cytokines levels in P. gingivalis infected cells. It is concluded that P. gingivalis may promote inflammatory responses via inhibiting the AhR signalling pathway in periodontitis.

Antimicrobial and anti-inflammatory activity of Cystatin C on human gingival fibroblast incubated with Porphyromonas gingivalis

Background

Periodontal disease is considered one of the most prevalent chronic infectious diseases, often leading to the disruption of tooth-supporting tissues, including alveolar bone, causing tooth mobility and loss. Porphyromonas gingivalis is considered the major etiological agent of this disease, having a plethora of virulence factors, including, lipopolysaccharides (LPS), hemolysins, and proteinases. Antimicrobial peptides are one of the main components of the innate immune response that inhibit the growth of P. gingivalis. The aim of this study was to analyze the antimicrobial activity of cystatin C and to assess the effect on the inflammatory and anti-inflammatory cytokines, the production of reactive oxygen species, and in the release of nitric oxide by human gingival fibroblasts incubated with P. gingivalis in the presence and absence of cystatin C.

Methods

P. gingivalis ATCC 33277 was exposed to cystatin C for 24h and co-cultured with human gingival fibroblasts (HGFs) ATCC CRL-2014. The effect of cystatin on growth of P. gingivalis and HGFs was evaluated. Pro-inflammatory (TNFα, IL-1β) and anti-inflammatory (IL-10) cytokines were determined by ELISA in the supernatants of HGFs incubated with P. gingivalis exposed to cystatin C. Additionally, nitrites and reactive oxygen species (ROS) production were evaluated.

Results

Cystatin Cinhibited the growth of P. gingivalis without affecting HGFs. Incubation of HGFs with P. gingivalis led to a significant increase of TNF-α and IL-1β. In contrast, HGFs incubated with P. gingivalis exposed to cystatin C showed a decreased production of both cytokines, whereas IL-10 was enhanced. Incubation of HGFs with P. gingivalis led to an increase of nitric oxide (NO) and ROS production, which was reduced in the presence of the peptide.

Conclusions

Cystatin C inhibits the growth of P. gingivalis and decreases the inflammatory cytokines, ROS, and NO production during infection of HGFs with P. gingivalis. Knowledge on the antimicrobial and immunomodulatory properties of cystatin C could aid in the design of new therapeutic approaches to facilitate the elimination of this bacterium to improve the treatment of periodontal disease.

Th17/Treg balance and indoleamine 2,3 dioxygenase activity in periodontitis-associated atherosclerotic patients

Objective

This study investigated the peripheral Th17/Treg balance and its potential controlling factor indoleamine 2,3 dioxygenase (IDO) in patients with periodontitis and atherosclerosis (AS), as well as its correlation with Porphyromonas gingivalis infection.

Methods

In this retrospective study, P. gingivalis-infected atherosclerotic patients (Pg-AS), atherosclerotic patients (AS), P. gingivalis-infected periodontitis patients (Pg), and healthy controls (HCs) were selected after clinical examination, subgingival plaque examination, and plasma anti-P. gingivalis antibody analysis. Treg and Th17 cell percentages, related transcription factors, and functional cytokines in peripheral blood were analysed. Plasma tryptophan (Trp) and kynurenine (Kyn) were measured to determine IDO activity.

Results

Atherosclerotic patients (Pg-AS and AS groups) had significantly lower IDO activity and higher Th17/Treg ratio than those in the Pg and HC groups. The Th17/Treg ratio was higher and IDO activity was lower in the Pg-AS group compared with the AS group. Transcription factors and cytokines exhibited the same trend as the Th17 and Treg cells. Additionally, IDO activity was negatively correlated with the plasma anti-P. gingivalis antibody titre and the Th17/Treg ratio in the atherosclerotic group.

Conclusions

P. gingivalis may reduce IDO activity and further promote Th17/Treg imbalance to facilitate AS development. IDO may be a novel molecular marker to predict periodontitis-associated AS.

The Role of Bacterial Proteases in Microbe and Host-microbe Interactions

BACKGROUND

Secreted proteases are an important class of factors used by bacterial to modulate their extracellular environment through the cleavage of peptides and proteins. These proteases can range from broad, general proteolytic activity to high degrees of substrate specificity. They are often involved in interactions between bacteria and other species, even across kingdoms, allowing bacteria to survive and compete within their niche. As a result, many bacterial proteases are of clinical importance. The immune system is a common target for these enzymes, and bacteria have evolved ways to use these proteases to alter immune responses for their benefit. In addition to the wide variety of human proteins that can be targeted by bacterial proteases, bacteria also use these secreted factors to disrupt competing microbes, ranging from outright antimicrobial activity to disrupting processes like biofilm formation.

OBJECTIVE

In this review, we address how bacterial proteases modulate host mechanisms of protection from infection and injury, including immune factors and cell barriers. We also discuss the contributions of bacterial proteases to microbe-microbe interactions, including antimicrobial and anti-biofilm dynamics.

CONCLUSION

Bacterial secreted proteases represent an incredibly diverse group of factors that bacteria use to shape and thrive in their microenvironment. Due to the range of activities and targets of these proteases, some have been noted for having potential as therapeutics. The vast array of bacterial proteases and their targets remains an expanding field of research, and this field has many important implications for human health.

Secretory Leukocyte Protease Inhibitor (SLPI) in mucosal tissues: Protects against inflammation, but promotes cancer

The immune system is continuously challenged with large quantities of exogenous antigens at the barriers between the external environment and internal human tissues. Antimicrobial activity is essential at these sites, though the immune responses must be tightly regulated to prevent tissue destruction by inflammation. Secretory Leukocyte Protease Inhibitor (SLPI) is an evolutionarily conserved, pleiotropic protein expressed at mucosal surfaces, mainly by epithelial cells. SLPI inhibits proteases, exerts antimicrobial activity and inhibits nuclear factor-kappa B (NF-κB)-mediated inflammatory gene transcription. SLPI maintains homeostasis at barrier tissues by preventing tissue destruction and regulating the threshold of inflammatory immune responses, while protecting the host from infection. However, excessive expression of SLPI in cancer cells may have detrimental consequences, as recent studies demonstrate that overexpression of SLPI increases the metastatic potential of epithelial tumors. Here, we review the varied functions of SLPI in the respiratory tract, skin, gastrointestinal tract and genitourinary tract, and then discuss the mechanisms by which SLPI may contribute to cancer.

Synergistic effects of D-arginine, D-methionine and D-histidine against Porphyromonas gingivalis biofilms

Porphyromonas gingivalis biofilms are implicated in the pathology of peri-implantitis and periodontitis. In this study, D-arginine (R), D-methionine (M), D-histidine (H), and a mixture of these D-amino acids (D-AAs) were investigated as an effective therapeutic strategy against P. gingivalis biofilms. The bacterial growth activity and minimum inhibitory concentrations were determined for each D-AA, along with the effects of the D-AAs mixture on biofilm development, morphology, structure, extracellular polysaccharides (EPS), cytotoxicity towards commensals, and bacterial structure. The D-AA mixture delayed the proliferation of P. gingivalis, changed its membrane structure, and decreased biofilm thickness and integrity, as compared with individual D-AAs. The EPS content increased with the concentration of D-AAs. The present study shows that a 4 mM RMH, triple D-AA mixture, enhanced deleterious effects on P. gingivalis biofilms without any cytotoxicity compared with individual D-AAs, thus providing a new strategy for the treatment of peri-implantitis and periodontitis.

Proanthocyanidins and Flavan-3-Ols in the Prevention and Treatment of Periodontitis-Antibacterial Effects

Flavan-3-ols and their oligomeric forms called proanthocyanidins are polyphenolic compounds occurring in several foodstuffs and in many medicinal herbs. Their consumption is associated with numerous health benefits. They exhibit antioxidant, anti-inflammatory, cytoprotective, as well as antimicrobial activity. The latter property is important in the prevention and treatment of periodontal diseases. Periodontitis is a multifactorial polymicrobial infection characterized by a destructive inflammatory process affecting the periodontium. Using non-toxic and efficient natural products such as flavanol derivatives can significantly contribute to alleviating periodontitis symptoms and preventing the disease’s progress. Therefore, a comprehensive systematic review of proanthocyanidins and flavan-3-ols in the prevention and treatment of periodontitis was performed. The present paper reviews the direct antibacterial effects of these compounds against periodontic pathogens. The immunomodulatory effects, including animal and clinical studies, are included in a separate, parallel article. There is significant evidence supporting the importance of the antibacterial action exerted by proanthocyanidins from edible fruits, tea, and medicinal herbs in the inhibition of periodontitis-causing pathogens.

The phenotype of gingival fibroblasts and their potential use in advanced therapies

Advanced therapies in medicine use stem cells, gene editing, and tissues to treat a wide range of conditions. One of their goals is to stimulate endogenous repair of tissues and organs by manipulating stem cells and their niche, as well as to optimize the intrinsic characteristics and plasticity of differentiated cells in adult tissues. In this context, fibroblasts emerge as an alternative source to stem cells because they share phenotypic and regenerative characteristics. Specifically, fibroblasts of the oral mucosae have been shown to have improved regenerative capacity compared to other fibroblast populations. Additionally, their easy access by means of minimally invasive procedures without generating aesthetic problems, with easy and rapid in vitro expansion and with great capacity to respond to extrinsic factors, make oral fibroblasts an attractive and interesting resource for regenerative medicine. This review summarizes current concepts regarding the phenotypic and functional aspects of human Gingival Fibroblasts and their niche, differentiating them from other fibroblast populations of oral-lining mucosa and skin fibroblasts. Furthermore, some applications are presented in regenerative medicine, emphasizing on the biological potential of human Gingival Fibroblasts.

Novel synthetic peptide derived from Porphyromonas gingivalis Lys-gingipain detects IgG-mediated host response in periodontitis

Porphyromonas gingivalis is a keystone pathogen in periodontitis. Analysis of the immunogenicity of its virulence factors may provide insight into the host response to this infection. The Kgp12 (IEDB Epitope ID 763561), an epitope of Lys-gingipain (Kgp) virulence factor from P. gingivalis ATCC 33277, elicits an immunoglobulin G (IgG) immunoreactivity with low cross-reactivity and, therefore, more specificity. The aim of the present study was to determine in silico the localization of Kgp12 within the protein and to evaluate the IgG host response to this novel Kgp peptide through its capacity to differentiate individuals with different periodontal status. Sera of 71 volunteers were tested by indirect ELISA to detect the IgG immunoreactivity specific to Kgp12, as well as to the protein HmuY and to the sonicated total extract of P. gingivalis ATCC33277, both used as gold standard. The participants had no systemic disease and were classified according to periodontal clinical parameters to comparison, firstly, into periodontitis (P) and without periodontitis (WP) groups and, secondly, into periodontitis (P), gingivitis (G) and clinically health (CH) ones. All the antigens tested, Kgp12 (p = 0.02), HmuY (p = 0.00) and P. gingivalis extract (p = 0.03), could differentiate P from WP groups considering IgG serum levels. P group also had higher IgG levels specific to Kgp12 (p = 0.03), HmuY (p < 0.01) and P. gingivalis extract (p = 0.01) when compared to G group. We conclude that the Kgp12 synthetic peptide was useful to detect the IgG-mediated host response signaling that it is a promising epitope to analyze the immunogenicity of P. gingivalis.

Polyphenols in the prevention and treatment of periodontal disease: A systematic review of in vivo, ex vivo and in vitro studies

Plant-derived polyphenols with antimicrobial and immunomodulatory characteristics appear to provide a variety of oral health benefits. Thus, the aim of the present study was to review the scientific literature to identify these effects of polyphenols on periodontal pathogens and inflammation. A MEDLINE search from 1st January 2013 to 18th January 2018 was performed to identify studies reporting polyphenol-containing plant extracts. Reports regarding pure compounds and essential oils, as well as effects on bacteria that are not defined as periodontal pathogens, were excluded. Thirty-eight studies matched the selection criteria. Studies on immunomodulatory effects included in vitro, ex vivo, and in vivo studies (n = 23), whereas studies reporting antibacterial effects against periodontal pathogens included only in vitro studies (n = 18). Three studies were included in both groups. The antibacterial effects were characterised by inhibition of bacterial growth, adhesion to oral cells, and enzymatic activity. Decreased secretion of pro-inflammatory and increased secretion of anti-inflammatory cytokines were demonstrated. Higher attachment levels, lower inflammation, and bone loss were reported by in vivo studies. Due to the high heterogeneity, it is difficult to draw clear conclusions for applicability; nevertheless, polyphenols have great potential as antimicrobial and immunomodulatory substances in the treatment and prevention of periodontal disease.

The role of toll-like and protease-activated receptors and associated intracellular signaling in Porphyromonas gingivalis-infected gingival fibroblasts

Porphyromonas gingivalis, which is considered a keystone agent in periodontitis, has evolved elaborate mechanisms to grow and survive in a hostile milieu. The gingival fibroblast is the major cell type in the gingiva and is considered to be important in the periodontitis-associated inflammation. As a part of the innate immune response, they produce cytokines such as CXCL8 and interleukin (IL)-6 which are believed to contribute to the destruction of the tooth-supporting tissues. This study investigates how the expression of protease-activated receptors (PAR1, PAR2) and toll-like receptors (TLR2, TLR4) changes with P. gingivalis exposure and how silencing of one receptor affects the expression of the other receptors. The importance of protein kinase C (PKC) and p38 in the regulation of CXCL8 and IL-6 was also examined. Receptors were knockdown with small-interfering RNA. PKC or p38 was blocked prior to stimulation with P. gingivalis. Fibroblasts were able to compensate for PAR1 knockdown with increased expression of PAR2. PKC and p38 were involved in the regulation of P. gingivalis-induced CXCL8 and IL-6. Our results indicate that PAR1 and PAR2 could be implicated in periodontitis and that PKC and P38 play a role in the inflammatory response in P. gingivalis-infected gingival fibroblasts.

TLR4-mediated immunomodulatory properties of the bacterial metalloprotease arazyme in preclinical tumor models

Despite the recent approval of new agents for metastatic melanoma, its treatment remains challenging. Moreover, few available immunotherapies induce a strong cellular immune response, and selection of the correct immunoadjuvant is crucial for overcoming this obstacle. Here, we studied the immunomodulatory properties of arazyme, a bacterial metalloprotease, which was previously shown to control metastasis in a murine melanoma B16F10-Nex2 model. The antitumor activity of arazyme was independent of its proteolytic activity, since heat-inactivated protease showed comparable properties to the active enzyme; however, the effect was dependent on an intact immune system, as antitumor properties were lost in immunodeficient mice. The protective response was IFNγ-dependent, and CD8(+) T lymphocytes were the main effector antitumor population, although B and CD4(+) T lymphocytes were also induced. Macrophages and dendritic cells were involved in the induction of the antitumor response, as arazyme activation of these cells increased both the expression of surface activation markers and proinflammatory cytokine secretion through TLR4-MyD88-TRIF-dependent, but also MAPK-dependent pathways. Arazyme was also effective in the murine breast adenocarcinoma 4T1 model, reducing primary and metastatic tumor development, and prolonging survival. To our knowledge, this is the first report of a bacterial metalloprotease interaction with TLR4 and subsequent receptor activation that promotes a proinflammatory and tumor protective response. Our results show that arazyme has immunomodulatory properties, and could be a promising novel alternative for metastatic melanoma treatment.

Transcriptional profiling of human smooth muscle cells infected with gingipain and fimbriae mutants of Porphyromonas gingivalis

Porphyromonas gingivalis (P. gingivalis) is considered to be involved in the development of atherosclerosis. However, the role of different virulence factors produced by P. gingivalis in this process is still uncertain. The aim of this study was to investigate the transcriptional profiling of human aortic smooth muscle cells (AoSMCs) infected with wild type, gingipain mutants or fimbriae mutants of P. gingivalis. AoSMCs were exposed to wild type (W50 and 381), gingipain mutants (E8 and K1A), or fimbriae mutants (DPG-3 and KRX-178) of P. gingivalis. We observed that wild type P. gingivalis changes the expression of a considerable larger number of genes in AoSMCs compare to gingipain and fimbriae mutants, respectively. The results from pathway analysis revealed that the common differentially expressed genes for AoSMCs infected by 3 different wild type P. gingivalis strains were enriched in pathways of cancer, cytokine-cytokine receptor interaction, regulation of the actin cytoskeleton, focal adhesion, and MAPK signaling pathway. Disease ontology analysis showed that various strains of P. gingivalis were associated with different disease profilings. Our results suggest that gingipains and fimbriae, especially arginine-specific gingipain, produced by P. gingivalis play important roles in the association between periodontitis and other inflammatory diseases, including atherosclerosis.

[The relationship of molecular genetic markers with clinical signs and risk factors of periodontitis]

The study revealed positive correlation between bleeding on probing and teeth loss risk with periodontal hypercolonization by Porphyromonas gingivalis, Prevotella intermedia and Treponema denticola. Pathological tooth mobility was associated with hypercolonization by P. intermedia and Tannerella forsythensis. Expression of IL8, TNF-α, MMP8 and MMP9 genes was also assessed in patient groups divided according to the depth of periodontal pockets and-the severity of chronic periodontitis revealing IL8 as positive diagnostic marker.

Mirolase, a novel subtilisin-like serine protease from the periodontopathogen Tannerella forsythia

The genome of Tannerella forsythia, an etiological factor of chronic periodontitis, contains several genes encoding putative proteases. Here, we characterized a subtilisin-like serine protease of T. forsythia referred to as mirolase. Recombinant full-length latent promirolase [85 kDa, without its signal peptide (SP)] processed itself through sequential autoproteolytic cleavages into a mature enzyme of 40 kDa. Mirolase latency was driven by the N-terminal prodomain (NTP). In stark contrast to almost all known subtilases, the cleaved NTP remained non-covalently associated with mirolase, inhibiting its proteolytic, but not amidolytic, activity. Full activity was observed only after the NTP was gradually, and fully, degraded. Both activity and processing was absolutely dependent on calcium ions, which were also essential for enzyme stability. As a consequence, both serine protease inhibitors and calcium ions chelators inhibited mirolase activity. Activity assays using an array of chromogenic substrates revealed that mirolase specificity is driven not only by the substrate-binding subsite S1, but also by other subsites. Taken together, mirolase is a calcium-dependent serine protease of the S8 family with the unique mechanism of activation that may contribute to T. forsythia pathogenicity by degradation of fibrinogen, hemoglobin, and the antimicrobial peptide LL-37.

The role of toll-like and protease-activated receptors in the expression of cytokines by gingival fibroblasts stimulated with the periodontal pathogen Porphyromonas gingivalis

Porphyromonas gingivalis is a periodontitis-associated pathogen and interactions between the bacterium and gingival fibroblasts play an important role in development and progression of periodontitis, an inflammatory disease leading to degeneration of tooth-supporting structures. Gingival fibroblasts, which expresses protease activated receptors (PARs) as well as toll-like receptors (TLRs), produces inflammatory mediators upon bacterial challenges. In this study, we elucidated the importance of PAR1, PAR2, TLR2 and TLR4 for the expression and secretion of CXCL8, interleukin-6 (IL-6), transforming growth factor-β1 (TGF-β1) and secretory leukocyte inhibitor (SLPI). Human gingival fibroblasts were transfected with small-interfering RNA against the target genes, and then stimulated with P. gingivalis wild-type W50 and W50-derived double rgp mutant E8 and kgp mutant K1A. TLR2-silencing reduced P. gingivalis-induced CXCL8 and IL-6. IL-6 was also reduced after PAR1-silencing. No effects were observed for TGF-β1. SLPI was suppressed by P. gingivalis and silencing of PAR1 as well as TLR2, gave additional suppression at the mRNA level. TLR4 was not involved in the regulation of the investigated mediators. CXCL8 and IL-6 are important for progression and development of periodontitis, leading to a chronic inflammation that may contribute to the tissue destruction that follows an exacerbated host response. Therefore, regulating the expression of TLR2 and subsequent release of CXCL8 and IL-6 in periodontitis could attenuate the tissue destruction seen in periodontitis.

Gingipains from the Periodontal Pathogen Porphyromonas gingivalis Play a Significant Role in Regulation of Angiopoietin 1 and Angiopoietin 2 in Human Aortic Smooth Muscle Cells

Angiopoietin 1 (Angpt1) and angiopoietin 2 (Angpt2) are the ligands of tyrosine kinase (Tie) receptors, and they play important roles in vessel formation and the development of inflammatory diseases, such as atherosclerosis. Porphyromonas gingivalis is a Gram-negative periodontal bacterium that is thought to contribute to the progression of cardiovascular disease. The aim of this study was to investigate the role of P. gingivalis infection in the modulation of Angpt1 and Angpt2 in human aortic smooth muscle cells (AoSMCs). We exposed AoSMCs to wild-type (W50 and 381), gingipain mutant (E8 and K1A), and fimbrial mutant (DPG-3 and KRX-178) P. gingivalis strains and to different concentrations of tumor necrosis factor (TNF). The atherosclerosis risk factor TNF was used as a positive control in this study. We found that P. gingivalis (wild type, K1A, DPG3, and KRX178) and TNF upregulated the expression of Angpt2 and its transcription factor ETS1, respectively, in AoSMCs. In contrast, Angpt1 was inhibited by P. gingivalis and TNF. However, the RgpAB mutant E8 had no effect on the expression of Angpt1, Angpt2, or ETS1 in AoSMCs. The results also showed that ETS1 is critical for P. gingivalis induction of Angpt2. Exposure to Angpt2 protein enhanced the migration of AoSMCs but had no effect on proliferation. This study demonstrates that gingipains are crucial to the ability of P. gingivalis to markedly increase the expressed Angpt2/Angpt1 ratio in AoSMCs, which determines the regulatory role of angiopoietins in angiogenesis and their involvement in the development of atherosclerosis. These findings further support the association between periodontitis and cardiovascular disease.

Secreted gingipains from Porphyromonas gingivalis colonies exert potent immunomodulatory effects on human gingival fibroblasts

Periodontal pathogens, including Porphyromonas gingivalis, can form biofilms in dental pockets and cause inflammation, which is one of the underlying mechanisms involved in the development of periodontal disease, ultimately leading to tooth loss. Although P. gingivalis is protected in the biofilm, it can still cause damage and modulate inflammatory responses from the host, through secretion of microvesicles containing proteinases. The aim of this study was to evaluate the role of cysteine proteinases in P. gingivalis colony growth and development, and subsequent immunomodulatory effects on human gingival fibroblast. By comparing the wild type W50 with its gingipain deficient strains we show that cysteine proteinases are required by P. gingivalis to form morphologically normal colonies. The lysine-specific proteinase (Kgp), but not arginine-specific proteinases (Rgps), was associated with immunomodulation. P. gingivalis with Kgp affected the viability of gingival fibroblasts and modulated host inflammatory responses, including induction of TGF-β1 and suppression of CXCL8 and IL-6 accumulation. These results suggest that secreted products from P. gingivalis, including proteinases, are able to cause damage and significantly modulate the levels of inflammatory mediators, independent of a physical host-bacterial interaction. This study provides new insight of the pathogenesis of P. gingivalis and suggests gingipains as targets for diagnosis and treatment of periodontitis.

Noncanonical activation of β-catenin by Porphyromonas gingivalis

Porphyromonas gingivalis is an established pathogen in periodontal disease and an emerging pathogen in serious systemic conditions, including some forms of cancer. We investigated the effect of P. gingivalis on β-catenin signaling, a major pathway in the control of cell proliferation and tumorigenesis. Infection of gingival epithelial cells with P. gingivalis did not influence the phosphorylation status of β-catenin but resulted in proteolytic processing. The use of mutants deficient in gingipain production, along with gingipain-specific inhibitors, revealed that gingipain proteolytic activity was required for β-catenin processing. The β-catenin destruction complex components Axin1, adenomatous polyposis coli (APC), and GSK3β were also proteolytically processed by P. gingivalis gingipains. Cell fractionation and Western blotting demonstrated that β-catenin fragments were translocated to the nucleus. The accumulation of β-catenin in the nucleus following P. gingivalis infection was confirmed by immunofluorescence microscopy. A luciferase reporter assay showed that P. gingivalis increased the activity of the β-catenin-dependent TCF/LEF promoter. P. gingivalis did not increase Wnt3a mRNA levels, a finding consistent with P. gingivalis-induced proteolytic processing causing the increase in TCF/LEF promoter activity. Thus, our data indicate that P. gingivalis can induce the noncanonical activation of β-catenin and disassociation of the β-catenin destruction complex by gingipain-dependent proteolytic processing. β-Catenin activation in epithelial cells by P. gingivalis may contribute to a proliferative phenotype.