PAI-2/SerpinB2 inhibits proteolytic activity in a P. gingivalis-dominated multispecies bacterial consortium

Antimicrobial Potential of Strontium-Functionalized Titanium Against Bacteria Associated With Peri-Implantitis

OBJECTIVES

To explore the antimicrobial potential of strontium (Sr)-functionalized wafers against multiple bacteria associated with per-implant infections, in both mono- and multispecies biofilms.

MATERIALS AND METHODS

The bactericidal and bacteriostatic effect of silicon wafers functionalized with a strontium titanium oxygen coating (Sr-Ti-O) or covered only with Ti (controls) against several bacteria, either grown as a mono-species or multispecies biofilms, was assessed using a bacterial viability assay and a plate counting method. Mono-species biofilms were assessed after 2 and 24 h, while the antimicrobial effect on multispecies biofilms was assessed at Days 1, 3, and 6. The impact of Sr functionalization on the total percentage of Porphyromonas gingivalis in the multispecies biofilm, using qPCR, and gingipain activity was also assessed.

RESULTS

Sr-functionalized wafers, compared to controls, were associated with statistically significant less viable cells in both mono- and multispecies tests. The number of colony forming units (CFUs) within the biofilm was significantly less in Sr-functionalized wafers, compared to control wafers, for Staphylococcus aureus at all time points of evaluation and for Escherichia coli at Day 1. Gingipain activity was less in Sr-functionalized wafers, compared to control wafers, and the qPCR showed that P. gingivalis remained below detection levels at Sr-functionalized wafers, while it consisted of 15% of the total biofilm on control wafers at Day 6.

CONCLUSION

Sr functionalization displayed promising antimicrobial potential, possessing bactericidal and bacteriostatic ability against bacteria associated with peri-implantitis grown either as mono-species or mixed in a multispecies consortium with several common oral microorganisms.

A Novel Role for Plasminogen Activator Inhibitor Type-2 as a Hypochlorite-Resistant Serine Protease Inhibitor and Holdase Chaperone

Plasminogen activator inhibitor type-2 (PAI-2), a member of the serpin family, is dramatically upregulated during pregnancy and in response to inflammation. Although PAI-2 exists in glycosylated and non-glycosylated forms in vivo, the majority of in vitro studies of PAI-2 have exclusively involved the intracellular non-glycosylated form. This study shows that exposure to inflammation-associated hypochlorite induces the oligomerisation of PAI-2 via a mechanism involving dityrosine formation. Compared to plasminogen activator inhibitor type-1 (PAI-1), both forms of PAI-2 are more resistant to hypochlorite-induced inactivation of its protease inhibitory activity. Holdase-type extracellular chaperone activity plays a putative non-canonical role for PAI-2. Our data demonstrate that glycosylated PAI-2 more efficiently inhibits the aggregation of Alzheimer’s disease and preeclampsia-associated amyloid beta peptide (Aβ), compared to non-glycosylated PAI-2 in vitro. However, hypochlorite-induced modification of non-glycosylated PAI-2 dramatically enhances its holdase activity by promoting the formation of very high-molecular-mass chaperone-active PAI-2 oligomers. Both PAI-2 forms protect against Aβ-induced cytotoxicity in the SH-SY5Y neuroblastoma cell line in vitro. In the villous placenta, PAI-2 is localised primarily to syncytiotrophoblast with wide interpersonal variation in women with preeclampsia and in gestational-age-matched controls. Although intracellular PAI-2 and Aβ staining localised to different placental cell types, some PAI-2 co-localised with Aβ in the extracellular plaque-like aggregated deposits abundant in preeclamptic placenta. Thus, PAI-2 potentially contributes to controlling aberrant fibrinolysis and the accumulation of misfolded proteins in states characterised by oxidative and proteostasis stress, such as in Alzheimer’s disease and preeclampsia.

Global proteomics of fibroblast cells treated with bacterial cyclic dinucleotides, c-di-GMP and c-di-AMP

BACKGROUND

Constant exposure of human gingival fibroblasts (HGFs) to oral pathogens trigger selective immune responses. Recently, the activation of immune response to cyclic dinucleotides (CDNs) via STING has come to the forefront. Reports show that other proteins outside the STING-TBK1-IRF3 axis respond to CDNs but a global view of impacted proteome in diverse cells is lacking. HGFs are constantly exposed to bacterial-derived cyclic-di-adenosine monophosphate (c-di-AMP) and cyclic-di-guanosine monophosphate (c-di-GMP).

AIM

To understand the response of HGFs to bacterial-derived CDNs, we carried out a global proteomics analysis of HGFs treated with c-di-AMP or c-di-GMP.

METHODS

The expression levels of several proteins modulated by CDNs were examined.

RESULTS

Interferon signaling proteins such as Ubiquitin-like protein ISG15 (ISG15), Interferon-induced GTP-binding protein Mx1 (MX1), Interferon-induced protein with tetratricopeptide repeats (IFIT) 1 (IFIT1), and (IFIT3) were significantly upregulated. Interestingly, other pathways not fully characterized to be regulated by CDNs, such as necroptosis signaling, iron homeostasis signaling, protein ubiquitination, EIF2 signaling, sumoylation and nucleotide excision repair pathways were also modulated by the bacterial-derived CDNs.

CONCLUSION

This study has added to the increasing appreciation that beyond the regulation of cytokine production via STING, cyclic dinucleotides also broadly affect many critical processes in human cells.

Differential gene expression profiles of periodontal soft tissue from rat teeth after immediate and delayed replantation: a pilot study

Purpose

In dental avulsion, delayed replantation usually has an uncertain prognosis. After tooth replantation, complex inflammatory responses promote a return to periodontal tissue homeostasis. Various types of cytokines are produced in the inflammatory microenvironment, and these cytokines determine the periodontal tissue response. This study aimed to identify the gene expression profiles of replanted teeth and evaluate the functional differences between immediate and delayed replantation.

Methods

Maxillary molars from Sprague-Dawley rats were extracted, exposed to a dry environment, and then replanted. The animals were divided into 2 groups according to the extra-oral time: immediate replantation (dry for 5 minutes) and delayed replantation (dry for 60 minutes). Either 3 or 7 days after replantation, the animals were sacrificed. Periodontal soft tissues were harvested for mRNA sequencing. Hallmark gene set enrichment analysis was performed to predict the function of gene-gene interactions. The normalized enrichment score (NES) was calculated to determine functional differences.

Results

The hallmark gene sets enriched in delayed replantation at 3 days were oxidative phosphorylation (NES=2.82, Q<0.001) and tumor necrosis factor-alpha (TNF-α) signaling via the nuclear factor kappa light chain enhancer of activated B cells (NF-κB) pathway (NES=1.52, Q=0.034). At 7 days after delayed replantation, TNF-α signaling via the NF-κB pathway (NES=–1.82, Q=0.002), angiogenesis (NES=–1.66, Q=0.01), and the transforming growth factor-beta signaling pathway (NES=–1.46, Q=0.051) were negatively highlighted.

Conclusions

Differentially expressed gene profiles were significantly different between immediate and delayed replantation. TNF-α signaling via the NF-κB pathway was marked during the healing process. However, the enrichment score of this pathway changed in a time-dependent manner between immediate and delayed replantation.

Porphyromonas gingivalis initiates coagulation and secretes polyphosphates - A mechanism for sustaining chronic inflammation?

BACKGROUND

Periodontitis is a chronic inflammation resulting in destruction of tooth-supporting bone. Chronic inflammation is characterized by extravascular fibrin deposition. Fibrin is central to destruction of bone; monocytes bind to fibrin and form osteoclasts, thus providing a link between coagulation and the tissue destructive processes in periodontitis. The oral microbiome is essential to oral health. However, local ecological changes, such as increased biofilm formation, result in a dysbiotic microbiome characterized by an increase of protease-producing species e.g. Porphyromonas gingivalis. Proteases initiate inflammation and may cleave coagulation factors. Polyphosphates (polyP) may also provide bacteria with procoagulant properties similar to platelet-released polyP. P. gingivalis has also been found in remote locations related to vascular pathology and Alzheimer's disease.

OBJECTIVES

The aim of this study was to investigate procoagulant activity of ten different species of oral bacteria present in oral health and disease as well as presence of polyP and fibrin formation in planktonic and biofilm bacteria.

METHODS

Oral bacteria were studied for protease production and procoagulant activity. The presence of polyP and formation of fibrin was observed using confocal microscopy.

RESULTS

P. gingivalis showed strong protease activity and was the only species exerting procoagulant activity. Confocal microscopy showed polyP intracellularly in planktonic bacteria and extracellularly after biofilm formation. Fibrin formation emanated from planktonic bacteria and from both bacteria and polyP in biofilm cultures.

CONCLUSIONS

The procoagulant activity of P. gingivalis could explain its role in chronic inflammation, locally in oral tissues as well as in remote locations.

Plasmin inhibition by bacterial serpin: Implications in gum disease

Tannerella forsythia is a periodontopathogen that expresses miropin, a protease inhibitor in the serpin superfamily. In this study, we show that miropin is also a specific and efficient inhibitor of plasmin; thus, it represents the first proteinaceous plasmin inhibitor of prokaryotic origin described to date. Miropin inhibits plasmin through the formation of a stable covalent complex triggered by cleavage of the Lys³⁶⁸-Thr³⁶⁹ (P2-P1) reactive site bond with a stoichiometry of inhibition of 3.8 and an association rate constant (k_ass) of 3.3 × 10⁵ M^-1s^-1. The inhibition of the fibrinolytic activity of plasmin was nearly as effective as that exerted by α₂-antiplasmin. Miropin also acted in vivo by reducing blood loss in a mice tail bleeding assay. Importantly, intact T. forsythia cells or outer membrane vesicles, both of which carry surface-associated miropin, strongly inhibited plasmin. In intact bacterial cells, the antiplasmin activity of miropin protects envelope proteins from plasmin-mediated degradation. In summary, in the environment of periodontal pockets, which are bathed in gingival crevicular fluid consisting of 70% of blood plasma, an abundance of T. forsythia in the bacterial biofilm can cause local inhibition of fibrinolysis, which could have possible deleterious effects on the tooth-supporting structures of the periodontium.

Triggering NETosis via protease-activated receptor (PAR)-2 signaling as a mechanism of hijacking neutrophils function for pathogen benefits

Neutrophil-derived networks of DNA-composed extracellular fibers covered with antimicrobial molecules, referred to as neutrophil extracellular traps (NETs), are recognized as a physiological microbicidal mechanism of innate immunity. The formation of NETs is also classified as a model of a cell death called NETosis. Despite intensive research on the NETs formation in response to pathogens, the role of specific bacteria-derived virulence factors in this process, although postulated, is still poorly understood. The aim of our study was to determine the role of gingipains, cysteine proteases responsible for the virulence of P. gingivalis, on the NETosis process induced by this major periodontopathogen. We showed that NETosis triggered by P. gingivalis is gingipain dependent since in the stark contrast to the wild-type strain (W83) the gingipain-null mutant strain only slightly induced the NETs formation. Furthermore, the direct effect of proteases on NETosis was documented using purified gingipains. Notably, the induction of NETosis was dependent on the catalytic activity of gingipains, since proteolytically inactive forms of enzymes showed reduced ability to trigger the NETs formation. Mechanistically, gingipain-induced NETosis was dependent on proteolytic activation of protease-activated receptor-2 (PAR-2). Intriguingly, both P. gingivalis and purified Arg-specific gingipains (Rgp) induced NETs that not only lacked bactericidal activity but instead stimulated the growth of bacteria species otherwise susceptible to killing in NETs. This protection was executed by proteolysis of bactericidal components of NETs. Taken together, gingipains play a dual role in NETosis: they are the potent direct inducers of NETs formation but in the same time, their activity prevents P. gingivalis entrapment and subsequent killing. This may explain a paradox that despite the massive accumulation of neutrophils and NETs formation in periodontal pockets periodontal pathogens and associated pathobionts thrive in this environment.

Periodontitis, or gum disease, is characterized by chronic inflammation and erosion of the tooth-supporting tissues. The condition is fuelled by bacterial accumulation on the tooth surface below the gum line that resists the host innate immune response, including massive accumulation of neutrophils. Despite possessing a formidable array of bactericidal machineries, including neutrophil extracellular traps (NETs) formation whereby neutrophils release DNA-composed fibers decorated with bactericidal proteins and peptides to efficiently trap and kill bacteria. Nevertheless, neutrophils in periodontitis are unable to clear the infection due to the presence of key periodontal pathogens, including Porphyromonas gingivalis. This bacterium secretes a variety of virulence factors, including proteases (gingipains) that allow the organism to manipulate the host immune response to benefit the entire dysbiotic microbial community. Here, we describe a unique strategy whereby P. gingivalis trigger NET formation through gingipain-dependent cleavage of Protease Activated Receptor (PAR)-2 on the neutrophil surface. Importantly, NETs formed in this way are deficient in antibacterial activity but instead, supports bacterial growth due to degradation of bactericidal components by gingipains. This finding may explain a paradox that dysbiotic bacteria flourished in periodontal pockets in spite of massive accumulation of neutrophils and abundant NETs formation.

Phytosphingosine Prevents the Formation of Young Salivary Biofilms in vitro

Dental biofilms are formed in a multistep process that is initiated by the adhesion of oral bacteria to the dental hard surface. As dental biofilms are associated with oral diseases their control is necessary in order to maintain oral health. Recently, it was revealed that phytosphingosine (PHS)-treated hydroxyapatite discs showed anti-adhesive activity in a static in vitro biofilm model against Streptococcus mutans. The goal of the present study was to further unravel the anti-adhesive and anti-biofilm properties of PHS in both static and dynamic in vitro biofilm models against a full salivary inoculum. After 3 h under static conditions, bacterial adherence on PHS-treated cover glass slides was reduced by 60% compared to the untreated surface. After 6 and 24 h under static conditions, no significant differences in bacterial adherence were observed between PHS-treated and untreated cover glass slides. However, under dynamic conditions, i.e., the presence of shear forces, virtually no bacterial adherence was observed for up to 16 h on PHS-coated surfaces. Besides, PHS showed a strong bactericidal activity on salivary biofilms. Treatment of a 3- and 6-h statically grown biofilm resulted in a 99 and 94% reduction of viable cells, respectively, which was effectuated within minutes. In principle, these anti-adherence and anti-biofilm properties make PHS a promising candidate ingredient for use in oral care products aimed at oral microbial control.

Relevance of the plasminogen system in physiology, pathology, and regeneration of oral tissues - From the perspective of dental specialties

Plasmin is a proteolytic enzyme that is crucial in fibrinolysis. In oral tissues, the plasminogen system plays an essential role in physiological and pathological processes, which in addition to fibrinolysis include degradation of extracellular matrix, inflammation, immune response, angiogenesis, tissue remodeling, cell migration, and wound healing. Oral tissues reveal a change in the plasminogen system during pathological processes such as periodontitis, peri-implantitis, or pulpitis, as well as in response to mechanical load. The plasminogen system is also a key element in tissue regeneration. The number of studies investigating the plasminogen system in dentistry have grown continuously in recent years, highlighting its increasing relevance in dental medicine. In this review, we present the diverse functions of the plasminogen system in physiology and its importance for dental specialists in pathology and regeneration. We thus provide an overview of the current knowledge on the role of the plasminogen system in the different fields of dentistry, including endodontics, orthodontics, periodontics, and oral surgery.