P. gingivalis regulates the expression of Cathepsin B and Cystatin C

Cathepsins in oral diseases: mechanisms and therapeutic implications

Cathepsins are a type of lysosomal globulin hydrolase and are crucial for many physiological processes, including the resorption of bone matrix, innate immunity, apoptosis, proliferation, metastasis, autophagy, and angiogenesis. Findings regarding their functions in human physiological processes and disorders have drawn extensive attention. In this review, we will focus on the relationship between cathepsins and oral diseases. We highlight the structural and functional properties of cathepsins related to oral diseases, as well as the regulatory mechanisms in tissue and cells and their therapeutic uses. Elucidating the associated mechanism between cathepsins and oral diseases is thought to be a promising strategy for the treatment of oral diseases and may be a starting point for further studies at the molecular level.

Effect of Lactobacillus reuteri on Gingival Inflammation and Composition of the Oral Microbiota in Patients Undergoing Treatment with Fixed Orthodontic Appliances: Study Protocol of a Randomized Control Trial

The effect of probiotics in improving or maintaining oral health in orthodontic patients is understudied. The aim of this study is to evaluate the effect of probiotic administration in addition to tooth brushing on clinical gingival inflammation, plaque formation, subgingival microbiota composition, and salivary biomarkers of inflammation in adolescents with fixed orthodontic appliances. The present study is a 6-month, double-blind, two-arm, placebo-controlled, single-center trial, in which 116 adolescent volunteers aged 12-16 years will be recruited from the patients of the orthodontics clinic of the University Hospital of Lille, France. Subjects who meet the eligibility criteria will be allocated to one of the following groups: (i) control: two placebo lozenges per day for 90 days together with regular oral hygiene, (ii) test: two probiotic lozenges per day for 90 days together with regular oral hygiene. Clinical assessment and biological sample collection will be performed at baseline, 3 and 6 months. In addition, compliance outcomes and adverse events will be monitored.

Implication of Toll/IL-1 receptor domain containing adapters in Porphyromonas gingivalis-induced inflammation

Periodontitis is induced by periodontal dysbiosis characterized by the predominance of anaerobic species. TLRs constitute the classical pathway for cell activation by infection. Interestingly, the Toll/IL-1 receptor homology domain adapters initiate signaling events, leading to the activation of the expression of the genes involved in the host immune response. The aim of this study was to evaluate the effects of Porphyromonas gingivalis on the expression and protein-protein interactions among five TIR adapters (MAL, MyD88, TRIF, TRAM and SARM) in gingival epithelial cells and endothelial cells. It was observed that P. gingivalis is able to modulate the signaling cascades activated through its recognition by TLR4/2 in gingival epithelial cells and endothelial cells. Indeed, MAL-MyD88 protein-protein interactions associated with TLR4 was the main pathway activated by P. gingivalis infection. When transient siRNA inhibition was performed, cell viability, inflammation, and cell death induced by infection decreased and such deleterious effects were almost absent when MAL or TRAM were targeted. This study emphasizes the role of such TIR adapter proteins in P. gingivalis elicited inflammation and the precise evaluation of TIR adapter protein interactions may pave the way for future therapeutics in both periodontitis and systemic disease with a P. gingivalis involvement, such as atherothrombosis.

Involvement of Cathepsins in Innate and Adaptive Immune Responses in Periodontitis

Periodontitis is an infectious disease whereby the chronic inflammatory process of the periodontium stimulated by bacterial products induces specific host cell responses. The activation of the host cell immune system upregulates the production of inflammatory mediators, comprising cytokines and proteolytic enzymes, which contribute to inflammation and bone destruction. It has been well known that periodontitis is related to systemic inflammation which links to numerous systemic diseases, including diabetes and arteriosclerosis. Furthermore, periodontitis has been reported in association with neurodegenerative diseases such as Alzheimer's disease (AD) in the brain. Regarding immune responses and inflammation, cathepsin B (CatB) plays pivotal role for the induction of IL-1β, cathepsin K- (CatK-) dependent active toll-like receptor 9 (TLR9) signaling, and cathepsin S (CatS) which involves in regulating both TLR signaling and maturation of the MHC class II complex. Notably, both the production and proteolytic activities of cathepsins are upregulated in chronic inflammatory diseases, including periodontitis. In the present review, we focus on the roles of cathepsins in the innate and adaptive immune responses within periodontitis. We believe that understanding the roles of cathepsins in the immune responses in periodontitis would help to elucidate the therapeutic strategies of periodontitis, thus benefit for reduction of systemic diseases as well as neurodegenerative diseases in the global aging society.

Porphyromonas gingivalis bypasses epithelial barrier and modulates fibroblastic inflammatory response in an in vitro 3D spheroid model

Porphyromonas gingivalis-induced inflammatory effects are mostly investigated in monolayer cultured cells. The aim of this study was to develop a 3D spheroid model of gingiva to take into account epithelio-fibroblastic interactions. Human gingival epithelial cells (ECs) and human oral fibroblasts (FBs) were cultured by hanging drop method to generate 3D microtissue (MT) whose structure was analyzed on histological sections and the cell-to-cell interactions were observed by scanning and transmission electron microscopy (SEM and TEM). MTs were infected by P. gingivalis and the impact on cell death (Apaf-1, caspase-3), inflammatory markers (TNF-α, IL-6, IL-8) and extracellular matrix components (Col-IV, E-cadherin, integrin β1) was evaluated by immunohistochemistry and RT-qPCR. Results were compared to those observed in situ in experimental periodontitis and in human gingival biopsies. MTs exhibited a well-defined spatial organization where ECs were organized in an external cellular multilayer, while, FBs constituted the core. The infection of MT demonstrated the ability of P. gingivalis to bypass the epithelial barrier in order to reach the fibroblastic core and induce disorganization of the spheroid structure. An increased cell death was observed in fibroblastic core. The development of such 3D model may be useful to define the role of EC–FB interactions on periodontal host-immune response and to assess the efficacy of new therapeutics.

Porphyromonas gingivalis Differentially Modulates Apoptosome Apoptotic Peptidase Activating Factor 1 in Epithelial Cells and Fibroblasts

Porphyromonas gingivalis is able to invade and modulate host-immune response to promote its survival. This bacterium modulates the cell cycle and programed cell death, contributing to periodontal lesion worsening. Several molecular pathways have been identified as key triggers of apoptosis, including apoptosome apoptotic peptidase activating factor 1 (APAF-1). Apaf-1 and X-linked inhibitor of apoptosis protein (Xiap) mRNA were differentially expressed between gingival samples harvested from human healthy and chronic periodontitis tissues (Apaf-1, 19.2-fold; caspase-9, 14.5-fold; caspase-3, 6.8-fold; Xiap: 2.5-fold in chronic periodontitis) (P < 0.05), highlighting their potential role in periodontitis. An increased proteic expression of APAF-1 was also observed in a murine experimental periodontitis model induced by P. gingivalis-soaked ligatures. In vitro, it was observed that P. gingivalis targets APAF-1, XIAP, caspase-3, and caspase-9, to inhibit epithelial cell death at both mRNA and protein levels. Opposite effect was observed in fibroblasts in which P. gingivalis increased cell death and apoptosis. To assess if the observed effects were associated to APAF-1, epithelial cells and fibroblasts were transfected with siRNA targeting Apaf-1. Herein, we confirmed that APAF-1 is targeted by P. gingivalis in both cell types. This study identified APAF-1 apoptosome and XIAP as intracellular targets of P. gingivalis, contributing to the deterioration of periodontal lesion through an increased persistence of the bacteria within tissues and the subversion of host-immune response.

Heterogeneous Porphyromonas gingivalis LPS modulates immuno-inflammatory response, antioxidant defense and cytoskeletal dynamics in human gingival fibroblasts

Periodontal (gum) disease is a highly prevalent infection and inflammation accounting for the majority of tooth loss in adult population worldwide. Porphyromonas gingivalis is a keystone periodontal pathogen and its lipopolysaccharide (PgLPS) acts as a major virulence attribute to the disease. Herein, we deciphered the overall host response of human gingival fibroblasts (HGFs) to two featured isoforms of tetra-acylated PgLPS_1435/1449 and penta-acylated PgLPS₁₆₉₀ with reference to E. coli LPS through quantitative proteomics. This study unraveled differentially expressed novel biomarkers of immuno-inflammatory response, antioxidant defense and cytoskeletal dynamics in HGFs. PgLPS₁₆₉₀ greatly upregulated inflammatory proteins (e.g. cyclophilin, inducible nitric oxide synthase, annexins, galectin, cathepsins and heat shock proteins), whereas the anti-inflammatory proteins (e.g. Annexin A2 and Annexin A6) were significantly upregulated by PgLPS_1435/1449. Interestingly, the antioxidants proteins such as mitochondrial manganese-containing superoxide dismutase and peroxiredoxin 5 were only upregulated by PgLPS_1690. The cytoskeletal rearrangement-related proteins like myosin were differentially regulated by these PgLPS isoforms. The present study gives new insight into the biological properties of P. gingivalis LPS lipid A moiety that could critically modulate immuno-inflammatory response, antioxidant defense and cytoskeletal dynamics in HGFs, and thereby enhances our understanding of periodontal pathogenesis.

Porphyromonas gingivalis Differentially Modulates Cell Death Profile in Ox-LDL and TNF-α Pre-Treated Endothelial Cells

Objective

Clinical studies demonstrated a potential link between atherosclerosis and periodontitis. Porphyromonas gingivalis (Pg), one of the main periodontal pathogen, has been associated to atheromatous plaque worsening. However, synergism between infection and other endothelial stressors such as oxidized-LDL or TNF-α especially on endothelial cell (EC) death has not been investigated. This study aims to assess the role of Pg on EC death in an inflammatory context and to determine potential molecular pathways involved.

Methods

Human umbilical vein ECs (HUVECs) were infected with Pg (MOI 100) or stimulated by its lipopolysaccharide (Pg-LPS) (1μg/ml) for 24 to 48 hours. Cell viability was measured with AlamarBlue test, type of cell death induced was assessed using Annexin V/propidium iodide staining. mRNA expression regarding caspase-1, -3, -9, Bcl-2, Bax-1 and Apaf-1 has been evaluated with RT-qPCR. Caspases enzymatic activity and concentration of APAF-1 protein were evaluated to confirm mRNA results.

Results

Pg infection and Pg-LPS stimulation induced EC death. A cumulative effect has been observed in Ox-LDL pre-treated ECs infected or stimulated. This effect was not observed in TNF-α pre-treated cells. Pg infection promotes EC necrosis, however, in infected Ox-LDL pre-treated ECs, apoptosis was promoted. This effect was not observed in TNF-α pre-treated cells highlighting specificity of molecular pathways activated. Regarding mRNA expression, Pg increased expression of pro-apoptotic genes including caspases-1,-3,-9, Bax-1 and decreased expression of anti-apoptotic Bcl-2. In Ox-LDL pre-treated ECs, Pg increased significantly the expression of Apaf-1. These results were confirmed at the protein level.

Conclusion

This study contributes to demonstrate that Pg and its Pg-LPS could exacerbate Ox-LDL and TNF-α induced endothelial injury through increase of EC death. Interestingly, molecular pathways are differentially modulated by the infection in function of the pre-stimulation.

Gingival crevicular fluid proteomes in health, gingivitis and chronic periodontitis

OBJECTIVE

The aim of this study was to compare the proteome composition of gingival crevicular fluid obtained from healthy periodontium, gingivitis and chronic periodontitis affected sites.

BACKGROUND

Owing to its site-specific nature, gingival crevicular fluid is ideal for studying biological processes that occur during periodontal health and disease progression. However, few studies have been conducted into the gingival crevicular fluid proteome due to the small volumes obtained.

METHODS

Fifteen males were chosen for each of three different groups, healthy periodontium, gingivitis and chronic periodontitis. They were categorized based on clinical measurements including probing depth, bleeding on probing, plaque index, radiographic bone level, modified gingival index and smoking status. Gingival crevicular fluid was collected from each patient, pooled into healthy, gingivitis and chronic periodontitis groups and their proteome analyzed by gel electrophoresis and liquid chromatography electrospray ionization ion trap tandem mass spectrometry.

RESULTS

One hundred and twenty-one proteins in total were identified, and two-thirds of these were identified in all three conditions. Forty-two proteins were considered to have changed in abundance. Of note, cystatin B and cystatin S decreased in abundance from health to gingivitis and further in chronic periodontitis. Complement proteins demonstrated an increase from health to gingivitis followed by a decrease in chronic periodontitis. Immunoglobulins, keratin proteins, fibronectin, lactotransferrin precursor, 14-3-3 protein zeta/delta, neutrophil defensin 3 and alpha-actinin exhibited fluctuations in levels.

CONCLUSION

The gingival crevicular fluid proteome in each clinical condition was different and its analysis may assist us in understanding periodontal pathogenesis.

Porphyromonas gingivalis-impaired innate immune response via NLRP3 proteolysis in endothelial cells

Porphyromonas gingivalis (Pg) is involved in the link between periodontal diseases and atherosclerosis worsening. In periodontal cells, Pg modifies IL-1β expression via the NLRP3 inflammasome pathway activation. Our aim was to investigate NLRP3 inflammasome activation in endothelial cells (ECs) after Pg infection and Pg-LPS stimulation. In both situations, RT-PCR experiments demonstrated an increase of the NLRP3 mRNA level that can be potentiated by pre-treatment of ECs with 5 mM ATP. However, Western blotting analysis revealed that Pg infection induced a proteolysis of NLRP3 protein and a major decrease of the native protein. After ATP pre-treatment and/or Pg-LPS stimulation, this proteolysis was not observed, while NLRP3 protein levels were increased. Proteolysis of the NLRP3 protein was not observed with heat-killed Pg and inhibition of ECs protein synthesis with cycloheximide did not abolish the NLRP3 protein degradation induced by Pg infection in ATP pre-treated cells. Additionally, significant increases of secreted IL-1β were measured after ATP pre-treatment and/or Pg-LPS stimulation, but not after Pg infection. These data showed that Pg and Pg-LPS differentially controlled the NLRP3 inflammasome pathway in ECs, and suggested a novel potential mechanism developed by Pg to reduce IL-1β secretion and to escape host immune response.

Periodontal and systemic responses in various mice models of experimental periodontitis: respective roles of inflammation duration and Porphyromonas gingivalis infection

BACKGROUND

The great variability of periodontal and systemic responses to experimental periodontitis reflects the inherent pathogenic complexity of mice models and could limit the resulting interpretations and their extension to human diseases. This study compared the effect of Porphyromonas gingivalis (Pg) infection and experimental periodontitis duration at local and systemic levels in various models.

METHODS

Periodontitis was induced in C57BL/6J mice by ligatures previously incubated with Pg (LIGPG group) or not (LIG group) or by oral gavage (GAV) with Pg ATCC 33277. Blood samples were taken, and mice were euthanized at different times. Periodontal tissue destruction, osteoclast number, and inflammation were assessed by histomorphometry, tartrate-resistant acid phosphatase histoenzymology, and cathepsin B (CATB) and matrix metalloproteinase 9 (MMP9) immunochemistry. Serum levels of interleukin-6 (IL-6) and IL-1β were measured using enzyme-linked immunosorbent assay bioplex methods.

RESULTS

Periodontal tissue destruction and osteoclast numbers were significantly elevated in LIGPG models compared to LIG and GAV models. They increased with time with the exception of osteoclast numbers in the LIG model. CATB and MMP9 expression was related to bone destruction processes and Pg infection. The highest serum levels of IL-6 and IL-1β were observed in the LIGPG group. A decrease of IL-6 and an increase of IL-1β serum level were observed with time in LIGPG group contrary to LIG group.

CONCLUSIONS

These data indicate that Pg infection worsened periodontal tissue destruction through specific pathogenic pathways and modified systemic response to periodontal inflammation. Furthermore, the blood cytokine response to ligature models showed their relevance for evaluating the systemic impact of periodontal disease.

Antimicrobial peptides and periodontal disease

AIMS

The goal of this review is to identify the antimicrobial proteins in the oral fluids, saliva and gingival crevicular fluid and identify functional families and candidates for antibacterial treatment.

RESULTS

Periodontal biofilms initiate a cascade of inflammatory and immune processes that lead to the destruction of gingival tissues and ultimately alveolar bone loss and tooth loss. Treatment of periodontal disease with conventional antibiotics does not appear to be effective in the absence of mechanical debridement. An alternative treatment may be found in antimicrobial peptides and proteins, which can be bactericidal and anti-inflammatory and block the inflammatory effects of bacterial toxins. The peptides have co-evolved with oral bacteria, which have not developed significant peptide resistance. Over 45 antibacterial proteins are found in human saliva and gingival crevicular fluid. The proteins and peptides belong to several different functional families and offer broad protection from invading microbes. Several antimicrobial peptides and proteins (AMPs) serve as templates for the development of therapeutic peptides and peptide mimetics, although to date none have demonstrated efficacy in human trials.

CONCLUSIONS

Existing and newly identified AMPs may be developed for therapeutic use in periodontal disease or can serve as templates for peptide and peptide mimetics with improved therapeutic indices.

Evaluating periodontal risk for patients at risk of or suffering from atherosclerosis: recent biological hypotheses and therapeutic consequences

Cardiovascular disease, such as atherosclerosis, is the main cause of mortality in developed countries. Most atherosclerosis risk factors have been identified and are treated, improving patient cardiovascular status and reducing mortality, but some remain unknown. Periodontal disease is generally defined as inflammatory disease initiated by accumulation of dental bacterial plaque, leading to the destruction of tissues that support the teeth. Severe forms have a high prevalence (15% of the population) and are associated with the presence of virulent pathogens such as Porphyromonas gingivalis. Epidemiological studies have shown that severe periodontal disease negatively influences cardiovascular status. The aim of this paper was to present a synthesis of the most recent biological data related to the link between periodontal and cardiovascular disease. The potential biological mechanisms involved in these two inflammatory diseases (bacteriological theory, inflammatory theory, immune theory) were developed. According to the observed positive effects of periodontal treatment on systemic conditions, the benefit of a reinforced collaboration between dentists and cardiologists was discussed, especially for patients at risk for cardiovascular disease.