Porphyromonas gingivalis induction of mediator and cytokine secretion by human gingival fibroblasts

Effect of a Novel Food Rich in Miraculin on the Oral Microbiome of Malnourished Oncologic Patients with Dysgeusia

BACKGROUND/OBJECTIVES

Dysgeusia contributes to the derangement of nutritional status in patients with cancer as well as worsening the quality of life. There has been a lack of effective treatments for taste disorders provided by the pharmaceutical industry.

METHODS

This was a pilot randomized, parallel, triple-blind, and placebo-controlled intervention clinical trial in which 31 malnourished patients with cancer and dysgeusia receiving antineoplastic treatment were randomized into three arms [standard dose of DMB (150 mg DMB/tablet), high dose of DMB (300 mg DMB/tablet) or placebo (300 mg freeze-dried strawberry)] for three months. Patients consumed a DMB or placebo tablet before each main meal. Using the nanopore methodology, we analyzed the oral microbiome of patients with cancer using saliva samples.

RESULTS

All patients with cancer and dysgeusia had dysbiosis in terms of lower bacterial diversity and richness. DMB consumption was associated with changes in oral microbiome composition. Neither selected bacteria nor taste perception, type of diet, and cytokine levels were associated with mucositis. Likewise, alcohol and tobacco consumption as well as general and digestive toxicity due to systemic therapy were not associated with specific changes of the oral microbiome, according to logistic binary regression. The standard dose of DMB resulted in a lower abundance of Veillonella compared with the high DMB dose and placebo at 3 months after intervention with DMB. In particular, some species such as Streptococcus parasanguinis, Veillonella parvula, and Streptococcus mutans were less abundant in the DMB standard-dose group. Additionally, the consumption of a standard dose of DMB revealed a negative association between the concentrations of TNF-α and the abundance of species such as Streptococcus thermophilus, Streptococcus pneumoniae, Streptococcus dysgalactiae and Streptococcus agalactiae.

CONCLUSIONS

Accordingly, regular DMB consumption could modify the oral microbiome in patients with cancer and dysgeusia, which may contribute to maintaining an appropriate immune response. However, as the present pilot study involved a small number of participants, further studies are necessary to draw robust conclusions from the data.

The role of oral microbiota in cancer

Cancer remains a significant global challenge, with an estimated 47% increase in cancer patients from 2020 to 2040. Increasing research has identified microorganism as a risk factor for cancer development. The oral cavity, second only to the colon, harbors more than 700 bacterial species and serves as a crucial microbial habitat. Although numerous epidemiological studies have reported associations between oral microorganisms and major systemic tumors, the relationship between oral microorganisms and cancers remains largely unclear. Current research primarily focuses on respiratory and digestive system tumors due to their anatomical proximity to the oral cavity. The relevant mechanism research mainly involves 47% dominant oral microbial population that can be cultured in vitro. However, further exploration is necessary to elucidate the mechanisms underlying the association between oral microbiota and tumors. This review systematically summarizes the reported correlations between oral microbiota and common cancers while also outlining potential mechanisms that may guide biological tumor treatment.

IL-1β and TNF-α play an important role in modulating the risk of periodontitis and Alzheimer's disease

BACKGROUND

Systemic activation of the immune system can exert detrimental effects on the central nervous system. Periodontitis, a chronic disease of the oral cavity, is a common source of systemic inflammation. Neuroinflammation might be a result of this to accelerate progressive deterioration of neuronal functions during aging or exacerbate pre-existing neurodegenerative diseases, such as Alzheimer's disease. With advancing age, the progressive increase in the body's pro-inflammatory status favors the state of vulnerability to both periodontitis and Alzheimer's disease. In the present study, we sought to delineate the roles of cytokines in the pathogenesis of both diseases.

METHODS

To examine the impacts of periodontitis on the onset and progression of Alzheimer's disease, 6-month-old female 3 × Tg-AD mice and their age-matched non-transgenic mice were employed. Periodontitis was induced using two different experimental models: heat-killed bacterial-induced periodontitis and ligature-induced periodontitis. To delineate the roles of pro-inflammatory cytokines in the pathogenesis of periodontitis and Alzheimer's disease, interleukin 1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) were also injected into the buccal mandibular vestibule of mice.

RESULTS

Here, we show that IL-1β and TNF-α were two of the most important and earliest cytokines upregulated upon periodontal infection. The systemic upregulation of these two cytokines promoted a pro-inflammatory environment in the brain contributing to the development of Alzheimer's disease-like pathology and cognitive dysfunctions. Periodontitis-induced systemic inflammation also enhanced brain inflammatory responses and subsequently exacerbated Alzheimer's disease pathology and cognitive impairment in 3 × Tg-AD mice. The role of inflammation in connecting periodontitis to Alzheimer's disease was further affirmed in the conventional magnetization transfer experiment in which increased glial responses resulting from periodontitis led to decreased magnetization transfer ratios in the brain of 3 × Tg-AD mice.

CONCLUSIONS

Systemic inflammation resulting from periodontitis contributed to the development of Alzheimer's disease tau pathology and subsequently led to cognitive decline in non-transgenic mice. It also potentiated Alzheimer's disease pathological features and exacerbated impairment of cognitive function in 3 × Tg-AD mice. Taken together, this study provides convincing evidence that systemic inflammation serves as a connecting link between periodontitis and Alzheimer's disease.

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.

Atypical cyclic di-AMP signaling is essential for Porphyromonas gingivalis growth and regulation of cell envelope homeostasis and virulence

Microbial pathogens employ signaling systems through cyclic (di-) nucleotide monophosphates serving as second messengers to increase fitness during pathogenesis. However, signaling schemes via second messengers in Porphyromonas gingivalis, a key Gram-negative anaerobic oral pathogen, remain unknown. Here, we report that among various ubiquitous second messengers, P. gingivalis strains predominantly synthesize bis-(3',5')-cyclic di-adenosine monophosphate (c-di-AMP), which is essential for their growth and survival. Our findings demonstrate an unusual regulation of c-di-AMP synthesis in P. gingivalis. P. gingivalis c-di-AMP phosphodiesterase (PDE) gene (pdepg) positively regulates c-di-AMP synthesis and impedes a decrease in c-di-AMP concentration despite encoding conserved amino acid motifs for phosphodiesterase activity. Instead, the predicted regulator gene cdaR, unrelated to the c-di-AMP PDE genes, serves as a potent negative regulator of c-di-AMP synthesis in this anaerobe. Further, our findings reveal that pdepg and cdaR are required to regulate the incorporation of ATP into c-di-AMP upon pyruvate utilization, leading to enhanced biofilm formation. We show that shifts in c-di-AMP signaling change the integrity and homeostasis of cell envelope, importantly, the structure and immunoreactivity of the lipopolysaccharide layer. Additionally, microbe-microbe interactions and the virulence potential of P. gingivalis were modulated by c-di-AMP. These studies provide the first glimpse into the scheme of second messenger signaling in P. gingivalis and perhaps other Bacteroidetes. Further, our findings indicate that c-di-AMP signaling promotes the fitness of the residents of the oral cavity and the development of a pathogenic community.

Porphyromonas gingivalis Gingipains Induce Cyclooxygenase-2 Expression and Prostaglandin E2 Production via ERK1/2-Activated AP-1 (c-Jun/c-Fos) and IKK/NF-κB p65 Cascades

Porphyromonas gingivalis is commonly known as one of the major pathogens contributing to periodontitis, and its persistent infection may increase the risk for the disease. The proinflammatory mediators, including IL-6, TNF-α, and cyclooxygenase-2 (COX-2)/PGE₂, are closely associated with progression of periodontitis. In this study, we focused on the cysteine protease "gingipains," lysine-specific gingipain, arginine-specific gingipain (Rgp) A, and RgpB, produced by P. gingivalis, and used the wild-type strain and several gene-deletion mutants (rgpA, rgpB, kgp, and fimA) to elucidate the involvement of gingipains in COX-2 expression and PGE₂ production. We infected human monocytes, which are THP-1 cells and primary monocytes, with these bacterial strains and found that gingipains were involved in induction of COX-2 expression and PGE₂ production. We have shown that the protease activity of gingipains was crucial for these events by using gingipain inhibitors. Furthermore, activation of ERK1/2 and IκB kinase was required for gingipain-induced COX-2 expression/PGE₂ production, and these kinases activated two transcription factors, c-Jun/c-Fos (AP-1) and NF-κB p65, respectively. In particular, these data suggest that gingipain-induced c-Fos expression via ERK is essential for AP-1 formation with c-Jun, and activation of AP-1 and NF-κB p65 plays a central role in COX-2 expression/PGE₂ production. Thus, we show the (to our knowledge) novel finding that gingipains with the protease activity from P. gingivalis induce COX-2 expression and PGE₂ production via activation of MEK/ERK/AP-1 and IκB kinase/NF-κB p65 in human monocytes. Hence it is likely that gingipains closely contribute to the inflammation of periodontal tissues.

Characterization of the foreign body response of titanium implants modified with polyphenolic coatings

The foreign body response is dictating the outcome of wound healing around any implanted materials. Patients who suffer from chronic inflammatory diseases and impaired wound healing often face a higher risk for implant failure. Therefore, functional surfaces need to be developed to improve tissue integration. For this purpose, we evaluated the impact of surface coatings made of antioxidant polyphenolic molecules tannic acid (TA) and pyrogallol (PG) on the host response in human blood. Our results showed that although the polyphenolic surface modifications impact the initial blood protein adsorption compared to Ti, the complement and coagulation systems are triggered. Despite complement activation, monocytes and granulocytes remained inactivated, which was manifested in a low pro-inflammatory cytokine expression. Under oxidative stress, both coatings were able to reduce intracellular reactive oxygen species in human gingival fibroblasts (hGFs). However, no anti-inflammatory effects of polyphenolic coatings could be verified in hGFs stimulated with lipopolysaccharide and IL-1β. Although polyphenols reportedly inhibit the NF-κB signaling pathway, phosphorylation of NF-κB p65 was observed. In conclusion, our results indicated that TA and PG coatings improved the hemocompatibility of titanium surfaces and have the potential to reduce oxidative stress during wound healing.

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.

Oral microbiota and Helicobacter pylori in gastric carcinogenesis: what do we know and where next?

Gastric cancer (GC) is one of the most common malignancies causing death worldwide, and Helicobacter pylori is a powerful inducer of precancerous lesions and GC. The oral microbiota is a complex ecosystem and is responsible for maintaining homeostasis, modulating the immune system, and resisting pathogens. It has been proposed that the gastric microbiota of oral origin is involved in the development and progression of GC. Nevertheless, the causal relationship between oral microbiota and GC and the role of H. pylori in this relationship is still controversial. This study was set to review the investigations done on oral microbiota and analyze various lines of evidence regarding the role of oral microbiota in GC, to date. Also, we discussed the interaction and relationship between H. pylori and oral microbiota in GC and the current understanding with regard to the underlying mechanisms of oral microbiota in carcinogenesis. More importantly, detecting the patterns of interaction between the oral cavity microbiota and H. pylori may render new clues for the diagnosis or screening of cancer. Integration of oral microbiota and H. pylori might manifest a potential method for the assessment of GC risk. Hence it needs to be specified the patterns of bacterial transmission from the oral cavity to the stomach and their interaction. Further evidence on the mechanisms underlying the oral microbiota communities and how they trigger GC may contribute to the identification of new prevention methods for GC. We may then modulate the oral microbiota by intervening with oral-gastric bacterial transmission or controlling certain bacteria in the oral cavity.

Litsea japonica Leaf Extract Suppresses Proinflammatory Cytokine Production in Periodontal Ligament Fibroblasts Stimulated with Oral Pathogenic Bacteria or Interleukin-1β

Periodontal disease, a chronic disease caused by bacterial infection, eventually progresses to severe inflammation and bone loss. Regulating excessive inflammation of inflamed periodontal tissues is critical in treating periodontal diseases. The periodontal ligament (PDL) is primarily a connective tissue attachment between the root and alveolar bone. PDL fibroblasts (PDLFs) produce pro-inflammatory cytokines in response to bacterial infection, which could further adversely affect the tissue and cause bone loss. In this study, we determined the ability of Litsea japonica leaf extract (LJLE) to inhibit pro-inflammatory cytokine production in PDLFs in response to various stimulants. First, we found that LJLE treatment reduced lipopolysaccharide (LPS)-induced pro-inflammatory cytokine (interleukin-6 and interleukin-8) mRNA and protein expression in PDLFs without cytotoxicity. Next, we observed the anti-inflammatory effect of LJLE in PDLFs after infection with various oral bacteria, including Fusobacterium nucleatum, Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia. These anti-inflammatory effects of LJLE were dose-dependent, and the extract was effective following both pretreatment and posttreatment. Moreover, we found that LJLE suppressed the effect of interleukin-1 beta-induced pro-inflammatory cytokine production in PDLFs. Taken together, these results indicate that LJLE has anti-inflammatory activity that could be exploited to prevent and treat human periodontitis by controlling inflammation.

Infection of microglia with Porphyromonas gingivalis promotes cell migration and an inflammatory response through the gingipain-mediated activation of protease-activated receptor-2 in mice

Despite a clear correlation between periodontitis and cognitive decline in Alzheimer's disease, the precise mechanism underlying the relationship remains unclear. The periodontal pathogen Porphyromonas gingivalis produces a unique class of cysteine proteinases termed gingipains that comprises Arg-gingipain (Rgp) and Lys-gingipain (Kgp). Rgp and Kgp are important in the bacterial mediated host cell responses and the subsequent intracellular signaling in infected cells. In the present study, we attempted to clarify the potential effects of Rgp and Kgp on the cellular activation of brain-resident microglia. We provide the first evidence that Rgp and Kgp cooperatively contribute to the P. gingivalis-induced cell migration and expression of proinflammatory mediators through the activation of protease-activated receptor 2. The subsequent activation of phosphoinositide 3-kinase/Akt and mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase/ERK pathways contributes to cell migration and inflammatory response of microglia.

The oral cavity microbiota: between health, oral disease, and cancers of the aerodigestive tract

Many studies show that the human microbiome plays a critical role in the chronic pathologies of obesity, inflammatory bowel diseases, and diabetes. More recently, the interaction between cancer and the microbiome has been highlighted. Most studies have focused on the gut microbiota because it represents the most extensive bacterial community, and the body of evidence correlating it with gut syndromes is increasing. However, in the strict sense, the gastrointestinal (GI) tract begins in the oral cavity, and special attention should be paid to the specific flora of this cavity. This study reviewed the current knowledge about the various microbial ecosystems of the upper part of the GI tract and discussed their potential link to carcinogenesis. The overall composition of the microbial communities, as well as the presence or absence of "key species", in relation to carcinogenesis is addressed. Alterations in the oral microbiota can potentially be used to predict the risk of cancer. Molecular advances and the further monitoring of the microbiota will increase our understanding of the role of the microbiota in carcinogenesis and open new perspectives for future therapeutic and prophylactic modalities.

Pro-inflammatory Cytokines Up-regulate MUC1 Gene Expression in Oral Epithelial Cells

The membrane-bound mucin MUC1 is expressed ubiquitously on epithelial surfaces and is thought to provide protection from bacterial and chemical injury. The present study was undertaken to determine whether MUC1 was expressed in cultured oral epithelial cells and whether expression is modulated by pro-inflammatory mediators released as part of the host response to infection by oral pathogens. Northern and Western blotting experiments showed that KB cells express MUC1 mRNA and protein. When cells were treated with interleukins (IL-1β, IL-6), tumor necrosis factor-alpha (TNF-α), or interferon-gamma (IFN-γ), or combinations of these, real-time PCR demonstrated that MUC1 mRNA increased 1.4- to 3.2-fold. Interestingly, a significant increase in levels of MUC1 protein was also observed. While no effect was observed when KB cells were incubated with LPS from Porphyromonas gingivalis, infection of KB monolayers with this oral pathogen caused a 2.85-fold increase in MUC1 transcript levels. These results suggest that increased MUC1 synthesis may be a key element in the host response to infection with oral pathogens.

Peptidylarginine deiminase from Porphyromonas gingivalis contributes to infection of gingival fibroblasts and induction of prostaglandin E2 -signaling pathway

Porphyromonas gingivalis (P. gingivalis) expres-ses the enzyme peptidylarginine deiminase (PPAD), which has a strong preference for C-terminal arginines. Due to the combined activity of PPAD and Arg-specific gingipains, P. gingivalis on the cell surface is highly citrullinated. To investigate the contribution of PPAD to the interaction of P. gingivalis with primary human gingival fibroblasts (PHGF) and P. gingivalis-induced synthesis of prostaglandin E2 (PGE2 ), PHGF were infected with wild-type P. gingivalis ATCC 33277, an isogenic PPAD-knockout strain (∆ppad) or a mutated strain (C351A) expressing an inactive enzyme in which the catalytic cysteine has been mutated to alanine (PPAD(C351A) ). Cells were infected in medium containing the mutants alone or in medium supplemented with purified, active PPAD. PHGF infection was assessed by colony-forming assay, microscopic analysis and flow cytometry. Expression of cyclo-oxygenase 2 (COX-2) and microsomal PGE synthase-1 (mPGES-1), key factors in the prostaglandin synthesis pathway, was examined by quantitative reverse transcription polymerase chain reaction (qRT-PCR), while PGE2 synthesis was evaluated by enzyme immunoassay. PHGF were infected more efficiently by wild-type P. gingivalis than by the ∆ppad strain, which correlated with strong induction of COX-2 and mPGES-1 expression by wild-type P. gingivalis, but not by the PPAD activity-null mutant strains (Δppad and C351A). The impaired ability of the Δppad strain to adhere to and/or invade PHGF and both Δppad and C351A to stimulate the PGE2 -synthesis pathway was fully restored by the addition of purified PPAD. The latter effect was strongly inhibited by aspirin. Collectively, our results implicate PPAD activity, but not PPAD itself, as an important factor for gingival fibroblast infection and activation of PGE2 synthesis, the latter of which may strongly contribute to bone resorption and eventual tooth loss.

miR-584 expressed in human gingival epithelial cells is induced by Porphyromonas gingivalis stimulation and regulates interleukin-8 production via lactoferrin receptor

BACKGROUND

MicroRNAs (miRNAs) are short, non-coding RNAs that are involved in post-transcriptional regulation of gene expression. Differential miRNA expression in innate and acquired immunity has been shown to regulate immune cell development and function. miRNA expression has been demonstrated to affect pathophysiology of inflammatory diseases, such as rheumatoid arthritis and lupus. As such, this study explores the role of miRNA in the context of pathophysiology of destructive periodontitis. Specifically, this investigation profiles the differentially expressed miRNA of Porphyromonas gingivalis (Pg)-stimulated human gingival epithelial cells (HGECs).

METHODS

The specific miRNAs differentially expressed in Pg-stimulated OBA-9, immortalized HGECs, were analyzed using microarray. Real-time polymerase chain reaction (PCR) and Western blotting were performed to confirm the level of miRNA expression and determine target production of miRNA in OBA-9. The production of interleukin (IL)-8 was measured to determine the bioactivity of target protein regulated by miRNA.

RESULTS

miR-584, which targets lactoferrin receptor (LfR), was 3.39-fold upregulated by Pg stimulation. This upregulation of miR-584 was confirmed by real-time PCR. Pg stimulation resulted in the suppression of LfR at mRNA and protein levels. The transfection of the miR inhibitor for miR-584 in OBA-9 recovered Pg-induced suppression of LfR. The addition of human lactoferrin (hLf) had a suppressive effect on IL-8 production in Pg-stimulated OBA-9. However, hLf also decreased IL-8 production strongly in Pg-stimulated OBA-9 in the presence of the miR inhibitor for miR-584.

CONCLUSION

These findings suggest that the upregulation of miR-584 by Pg in OBA-9 inhibits the anti-inflammatory effects of hLf via the suppression of LfR.

Porphyromonas gingivalis downregulates the immune response of fibroblasts

Background

Porphyromonas gingivalis is a key pathogen in periodontitis, an inflammatory disease leading to destruction of bone and tooth-supporting tissue. P. gingivalis possesses a number of pathogenic properties to enhance growth and survival, including proteolytic gingipains. Accumulating data shows that gingipains are involved in the regulation of host inflammatory responses. The aim of this study was to determine if P. gingivalis infection modulates the inflammatory response of fibroblasts, including the release of chemokines and cytokines. Human gingival fibroblasts or primary dermal fibroblasts were pre-stimulated with tumor-necrosis factor-α (TNF- α) and cocultured with P. gingivalis. Gingipain inhibitors were used to explore the effect of gingipains. CXCL8 levels were determined with ELISA and the relative levels of various inflammatory mediators were determined by a cytokine assay.

Results

TNF-α-triggered CXCL8 levels were completely abolished by viable P. gingivalis, whereas heat-killed P. gingivalis did not suppress CXCL8. Accumulation of CXCL8 was partially restored by an arginine-gingipain inhibitor. Furthermore, fibroblasts produced several inflammatory mediators, notably chemokines, all of which were suppressed by viable P. gingivalis.

Conclusion

These findings provide evidence that fibroblast-derived inflammatory signals are modulated by heat-instable gingipains, whereby the bacteria can escape killing by the host immune system and promote its own growth and establishment. In addition, we show that fibroblasts are important mediators of inflammation in response to infection and thereby play a crucial role in determining the nature and magnitude of the invasion of immune cells.

The role of chromogranin B in an animal model of multiple sclerosis

Chromogranin B (CGB) is a high capacity, low affinity calcium binding protein in the endoplasmic reticulum (ER) that binds to the inositol 1,4,5 trisphosphate receptor (InsP3R) and amplifies calcium release from ER stores. Recently, it was discovered that levels of CGB-derived peptides are decreased in the cerebrospinal fluid of multiple sclerosis (MS) patients. One of the mechanisms by which neurodegeneration in MS is thought to occur is through increased levels of intra-axonal calcium. The combination of excess intracellular calcium and dysregulated levels of CGB in MS led us to hypothesize that CGB may be involved in MS pathophysiology. Here, we show in a mouse model of MS that CGB levels are elevated in neurons prior to onset of symptoms. Once symptoms develop, CGB protein levels increase with disease severity. Additionally, we show that elevated levels of CGB may have a role in the pathophysiology of MS and suggest that the initial elevation of CGB, prior to symptom onset, is due to inflammatory processes. Upon development of symptoms, CGB accumulation in neurons results from decreased ubiquitination and decreased secretion. Furthermore, we show that calpain activity is increased and levels of InsP3R are decreased. From these results, we suggest that the elevated levels of CGB and altered InsP3R levels may contribute to the axonal/neuronal damage and dysregulated calcium homeostasis observed in MS. Additionally, we propose that CGB can be a biomarker that predicts the onset and severity of disease in patients with MS.

Cytokine and matrix metalloproteinase expression in fibroblasts from peri-implantitis lesions in response to viable Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

To assess inflammatory reactions of fibroblasts in the pathophysiology of peri-implantitis, we compared the pro-inflammatory and matrix-degrading responses of gingival and granulation tissue fibroblasts from periodontally healthy controls, peri-implantitis, and periodontitis lesions to an in vitro challenge with Porphyromonas gingivalis.

METHODS

Fibroblasts from periodontally healthy, peri-implantitis and periodontitis donors were challenged with viable P. gingivalis. The inflammatory reactions of fibroblasts were analyzed before and after 6 h P. gingivalis challenge, and 2.5 and 18 h after removal of the challenge. Gene expression and induction of pro-inflammatory mediators, and matrix metalloproteinases (MMPs) were assessed by real-time polymerase chain reaction. Protein expression was measured by enzyme-linked immunosorbent assay.

RESULTS

Non-challenged fibroblasts from peri-implantitis and periodontitis lesions expressed higher levels of interleukin (IL)-1β, IL-8, and monocyte chemotactic protein (MCP)-1 than fibroblasts from periodontally healthy individuals. The P. gingivalis challenge induced expression of IL-1β, IL-8, IL-6, MCP-1, and MMP-1 in periodontitis and peri-implantitis fibroblasts, but not in fibroblasts from periodontally healthy individuals. MMP-8 expression was higher in non-challenged peri-implantitis fibroblasts than in fibroblasts from periodontally healthy individuals. However, the P. gingivalis challenge downregulated MMP-8 gene expression in peri-implantitis fibroblasts. After removal of the P. gingivalis challenge, peri-implantitis fibroblasts sustained higher induction of IL-1β, MCP-1, and MMP-1 compared to periodontitis fibroblasts.

CONCLUSIONS

Fibroblasts from peri-implantitis and periodontitis lesions gave a more pronounced inflammatory response to the P. gingivalis challenge than fibroblasts from healthy donors. They may therefore be involved in the development of inflammation in peri-implantitis and periodontitis. Moreover, the sustained upregulation of inflammatory mediators and MMP-1 in peri-implantitis fibroblasts may play a role in the pathogenesis of peri-implantitis.

Expression levels of novel cytokine IL-32 in periodontitis and its role in the suppression of IL-8 production by human gingival fibroblasts stimulated with Porphyromonas gingivalis

Background

IL-32 was recently found to be elevated in the tissue of rheumatoid arthritis and inflammatory bowel disease. Periodontitis is a chronic inflammatory disease caused by polymicrobial infections that result in soft tissue destruction and alveolar bone loss. Although IL-32 is also thought to be associated with periodontal disease, its expression and possible role in periodontal tissue remain unclear. Therefore, this study investigated the expression patterns of IL-32 in healthy and periodontally diseased gingival tissue. The expression of IL-32 in cultured human gingival fibroblasts (HGF) as well as effects of autocrine IL-32 on IL-8 production from HGF were also examined.

Methods

Periodontal tissue was collected from both healthy volunteers and periodontitis patients, and immunofluorescent staining was performed in order to determine the production of IL-32. Using real-time PCR and ELISA, mRNA expression and protein production of IL-32 in HGF, stimulated by Porphyromonas gingivalis (Pg), were also investigated.

Results

Contrary to our expectation, the production of IL-32 in the periodontitis patients was significantly lower than in the healthy volunteers. According to immunofluorescent microscopy, positive staining for IL-32 was detected in prickle and basal cell layers in the epithelium as well as fibroblastic cells in connective tissue. Addition of fixed Pgin vitro was found to suppress the otherwise constitutive expression of IL-32 mRNA and protein in HGF. However, recombinant IL-32 in vitro inhibited the expression of IL-8 mRNA by HGF stimulated with Pg. Interestingly, anti-IL-32 neutralizing antibody upregulated the IL-8 mRNA expression in non-stimulated HGF, indicating that constitutive expression of IL-32 in HGF suppressed IL-8 mRNA expression in the absence of bacterial stimulation.

Conclusion

These results indicate that IL-32 is constitutively produced by HGF which can be suppressed by Pg and may play a role in the downregulation of inflammatory responses, such as IL-8 production, in periodontal tissue.

Diverse effects of Porphyromonas gingivalis on human osteoclast formation

Porphyromonas gingivalis is associated with periodontitis, a chronic inflammatory disease of the tooth-supporting tissues. A major clinical symptom is alveolar bone loss due to excessive resorption by osteoclasts. P. gingivalis may influence osteoclast formation in diverse ways; by interacting directly with osteoclast precursors that likely originate from peripheral blood, or indirectly by activating gingival fibroblasts, cells that can support osteoclast formation. In the present study we investigated these possibilities. Conditioned medium from viable or dead P. gingivalis, or from gingival fibroblasts challenged with viable or dead P. gingivalis were added to human mononuclear osteoclast precursors. After 21 days of culture the number of multinucleated (≥3 nuclei) tartrate resistant acid phosphatase (TRACP)-positive cells was determined as a measure for osteoclast formation. Conditioned medium from viable P. gingivalis, and from fibroblasts with viable P. gingivalis stimulated osteoclast formation (1.6-fold increase p < 0.05). Conditioned medium from dead bacteria had no effect on osteoclast formation, whereas conditioned medium from fibroblasts with dead bacteria stimulated formation (1.4-fold increase, p < 0.05). Inhibition of P. gingivalis LPS activity by Polymyxin B reduced the stimulatory effect of conditioned medium. Interestingly, when RANKL and M-CSF were added to cultures, conditioned media inhibited osteoclast formation (0.6-0.7-fold decrease, p < 0.05). Our results indicate that P. gingivalis influences osteoclast formation in vitro in different ways. Directly, by bacterial factors, likely LPS, or indirectly, by cytokines produced by gingival fibroblasts in response to P. gingivalis. Depending on the presence of RANKL and M-CSF, the effect of P. gingivalis is either stimulatory or inhibitory.

Supernatants from oral epithelial cells and gingival fibroblasts modulate human immunodeficiency virus type 1 promoter activation induced by periodontopathogens in monocytes/macrophages

Bacterial and host cell products during coinfections of Human Immunodeficiency Virus type 1-positive (HIV-1(+)) patients regulate HIV-1 recrudescence in latently infected cells (e.g. T cells, monocytes/macrophages), impacting highly active antiretroviral therapy (HAART) failure and progression of acquired immunodeficiency syndrome. A high frequency of oral opportunistic infections (e.g. periodontitis) in HIV-1(+) patients has been demonstrated; however, their potential to impact HIV-1 exacerbation is unclear. We sought to determine the ability of supernatants derived from oral epithelial cells (OKF4) and human gingival fibroblasts (Gin-4) challenged with periodontal pathogens, to modulate the HIV-1 promoter activation in monocytes/macrophages. BF24 monocytes/macrophages transfected with the HIV-1 promoter driving the expression of chloramphenicol acetyltransferase (CAT) were stimulated with Porphyromonas gingivalis, Fusobacterium nucleatum, or Treponema denticola in the presence of supernatants from OKF4 or Gin4 cells either unstimulated or previously pulsed with bacteria. CAT levels were determined by enzyme-linked immunosorbent assay and cytokine production was evaluated by Luminex beadlyte assays. OKF4 and Gin4 supernatants enhanced HIV-1 promoter activation particularly related to F. nucleatum challenge. An additive effect was observed in HIV-1 promoter activation when monocytes/macrophages were simultaneously stimulated with gingival cell supernatants and bacterial extracts. OKF4 cells produced higher levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukins -6 and -8 in response to F. nucleatum and P. gingivalis. Preincubation of OKF4 supernatants with anti-GM-CSF reduced the additive effect in periodontopathogen-induced HIV-1 promoter activation. These results suggest that soluble mediators produced by gingival resident cells in response to periodontopathogens could contribute to HIV-1 promoter activation in monocytes/macrophages, albeit this effect is most notable following direct stimulation of the cells with oral gram-negative bacteria.

In vitro modeling of host-parasite interactions: the 'subgingival' biofilm challenge of primary human epithelial cells

Background

Microbial biofilms are known to cause an increasing number of chronic inflammatory and infectious conditions. A classical example is chronic periodontal disease, a condition initiated by the subgingival dental plaque biofilm on gingival epithelial tissues. We describe here a new model that permits the examination of interactions between the bacterial biofilm and host cells in general. We use primary human gingival epithelial cells (HGEC) and an in vitro grown biofilm, comprising nine frequently studied and representative subgingival plaque bacteria.

Results

We describe the growth of a mature 'subgingival' in vitro biofilm, its composition during development, its ability to adapt to aerobic conditions and how we expose in vitro a HGEC monolayer to this biofilm. Challenging the host derived HGEC with the biofilm invoked apoptosis in the epithelial cells, triggered release of pro-inflammatory cytokines and in parallel induced rapid degradation of the cytokines by biofilm-generated enzymes.

Conclusion

We developed an experimental in vitro model to study processes taking place in the gingival crevice during the initiation of inflammation. The new model takes into account that the microbial challenge derives from a biofilm community and not from planktonically cultured bacterial strains. It will facilitate easily the introduction of additional host cells such as neutrophils for future biofilm:host cell challenge studies. Our methodology may generate particular interest, as it should be widely applicable to other biofilm-related chronic inflammatory diseases.

Gingival and periodontal ligament fibroblasts differ in their inflammatory response to viable Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

Porphyromonas gingivalis is an oral pathogen strongly associated with destruction of the tooth-supporting tissues in human periodontitis. Gingival fibroblasts (GF) and periodontal ligament fibroblasts (PDLF) are functionally different cell types in the periodontium that can participate in the host immune response in periodontitis. This study aimed to investigate the effects of viable P. gingivalis on the expression of genes associated with inflammation and bone degradation by these fibroblast subsets.

MATERIAL AND METHODS

Primary human GF and PDLF from six healthy donors were challenged in vitro with viable P. gingivalis W83 for 6 h. Gene expression of inflammatory cytokines in GF and PDLF was analyzed using real-time PCR, and protein expression was analyzed using ELISA.

RESULTS

Viable P. gingivalis induced a strong in vitro inflammatory response in both GF and PDLF. We found increased gene expression of interleukin (IL)-1beta, IL-6, IL-8, tumor necrosis factor-alpha, monocyte chemotactic protein-1 and regulated upon activation, normal T-cell expressed and secreted (RANTES). Macrophage colony-stimulating factor was induced and the expression of osteoprotegerin was decreased in GF, but not in PDLF. In nonchallenged cells, a higher level of expression of IL-6 was observed in GF than in PDLF. Between individual donors there was large heterogeneity in responsiveness to P. gingivalis. Also, in each individual, either GF or PDLF was more responsive to P. gingivalis.

CONCLUSION

Considerable heterogeneity in responsiveness to P. gingivalis exists both between GF and PDLF and between individuals, which may be crucial determinants for the susceptibility to develop periodontitis.

The host cytokine response to Porphyromonas gingivalis is modified by gingipains

BACKGROUND/AIMS

Clinical studies indicate that primary proinflammatory cytokines, such as interleukin-1beta (IL-1beta) are elevated in the gingival crevice around teeth with periodontitis but the secondary cytokines and chemokines, IL-6 and IL-8, are not. The human gingival epithelial cells (HGECs) lining the gingival sulcus respond to perturbation by microbes of dental plaque by releasing a wide range of cytokines. Porphyromonas gingivalis, a putative periodontal pathogen, possesses numerous virulence factors some of which directly impact on the host response. In the present study, we sought to determine how P. gingivalis influences the inflammatory cytokine responses.

METHODS

HGECs were challenged with P. gingivalis and other putative periodontal pathogens, and the resultant production of IL-1beta, IL-6, and IL-8 was assayed by enzyme-linked immunosorbent assay (ELISA). Culture supernatants and recombinant human cytokines were challenged with live P. gingivalis wild-type and gingipain-deficient strains and the resultant cytokine profile was assessed by ELISA and Western blot.

RESULTS

We show here that primary HGECs challenged with live P. gingivalis result in high levels of IL-1beta but not the related secondary cytokines IL-6 and IL-8. We further demonstrate that cytokine response differences are the result of the action of P. gingivalis proteases, with lysine gingipain being the most effective.

CONCLUSION

We conclude that P. gingivalis, through lysine gingipain, can subvert the protective host proinflammatory response by direct cytokine degradation. Changes in the crevicular cytokine profile have consequences in periodontal disease pathogenesis that should be considered in the development of diagnostic and therapeutic modalities.

Porphyromonas gingivalis RgpA-Kgp proteinase-adhesin complexes penetrate gingival tissue and induce proinflammatory cytokines or apoptosis in a concentration-dependent manner

The RgpA-Kgp proteinase-adhesin complexes of Porphyromonas gingivalis were observed, using immunostaining, in human gingival tissue associated with periodontitis but not in healthy tissue. The staining pattern suggested a concentration gradient from the subgingival plaque into the subjacent gingival connective tissue. Intense immunostaining was observed in areas displaying gross disturbance of tissue architecture. P. gingivalis cells and the RgpA-Kgp complexes at low concentrations were shown to stimulate secretory intercellular adhesion molecule 1, interleukin-8 (IL-8), IL-6, and macrophage chemoattractant protein secretion from cultured human epithelial (KB) and fibroblast (MRC-5) cells. However, at high concentrations a reduction in the level of these mediators was observed. In contrast, macrophage inflammatory protein 1alpha and IL-1alpha were stimulated only at high P. gingivalis cell concentrations. P. gingivalis cells and the RgpA-Kgp complexes were shown to induce apoptosis in KB and MRC-5 cells in a time- and dose-dependent manner. These data suggest that the RgpA-Kgp complexes penetrate the gingival connective tissue; at low concentrations distal from the plaque the complexes stimulate the secretion of proinflammatory mediators, while at high concentrations proximal to the plaque they induce apoptosis and attenuate the secretion of proinflammatory mediators.

Free radicals and antioxidants in inflammatory processes and ischemia-reperfusion injury

This article discusses the current understanding of the role of free radicals and antioxidants in inflammatory processes and in ischemia reperfusion injury. It begins by describing the manifestations of acute inflammation and outlining the cellular events that occur during inflammation. It then describes the biochemical mediators of inflammation with special attention to nitric oxide. It details the process of hypoxia reperfusion injury, the enzymes involved, its treatment, and studies involving specific hypoxia reperfusion injuries in various animal species.

Gingipains from Porphyromonas gingivalis synergistically induce the production of proinflammatory cytokines through protease-activated receptors with Toll-like receptor and NOD1/2 ligands in human monocytic cells

Gingipains (HRgpA, RgpB and Kgp) are cysteine proteinases and virulence factors of Porphyromonas gingivalis, the major causative bacterium of periodontal disease. To study synergistic effects of gingipains and signalling via Toll-like receptors (TLRs) and NOD1/2, we investigated effects of a gingipain on the secretion of proinflammatory cytokines from monocytic THP-1 cells in the presence of pathogen-associated molecular patterns (PAMPs). Gingipains stimulated interleukin (IL)-8's secretion from THP-1 cells, which was completely inhibited by proteinase inhibitors of gingipain and increased in the presence of PAMPs. Synergistic effects of gingipains and PAMPs were also seen in the secretion of IL-6 and MCP-1 and reduced to about 50% the secretion of IL-8 from THP-1 cells treated with siRNA targeting either protease-activated receptor (PAR)-1, -2 or -3. PAR agonist peptides mimicked the synergistic effects of gingipains with PAMPs. These results indicate that gingipains stimulate the secretion of cytokines from monocytic cells through the activation of PARs with synergistic effects by PAMPs. This is the first report of synergism of signalling via PARs, and TLRs or NOD1/2. The host defence system against P. gingivalis may be triggered through the activation of PARs by gingipains and augmented by PAMPs from this pathogen via TLRs or NOD1/2.

Cranberry components inhibit interleukin-6, interleukin-8, and prostaglandin E production by lipopolysaccharide-activated gingival fibroblasts

Periodontitis is a chronic inflammatory disease that affects the tooth supporting tissues. Gingival fibroblasts are the most abundant cells in periodontal tissues and participate actively in the host inflammatory response to periodontopathogens, which is known to mediate local tissue destruction in periodontitis. The aim of this study was to investigate the effect of a proanthocyanidin-enriched cranberry fraction, prepared from cranberry juice concentrate, on inflammatory mediator production by gingival fibroblasts stimulated by the lipopolysaccharide (LPS) of Aggregatibacter actinomycetemcomitans. Interleukin (IL)-6, IL-8, and prostaglandin E(2) (PGE(2)) production by fibroblasts treated with the cranberry fraction and stimulated by A. actinomycetemcomitans LPS was evaluated by enzyme-linked immunosorbent assay. Changes induced by A. actinomycetemcomitans LPS and the cranberry fraction in the expression and phosphorylation state of fibroblast intracellular signaling proteins were characterized by antibody microarrays. The LPS-induced IL-6, IL-8, and PGE(2) responses of gingival fibroblasts were inhibited by treatment with the cranberry fraction. This fraction was found to inhibit fibroblast intracellular signaling proteins, a phenomenon that may lead to a down-regulation of activating protein-1 activity. Cranberry components also reduced cyclooxygenase 2 expression. This study suggests that cranberry juice contains molecules with interesting properties for the development of new host-modulating therapeutic strategies in the adjunctive treatment of periodontitis.

Proinflammatory gene expression in mouse ST2 cell line in response to infection by Porphyromonas gingivalis

Porphyromonas gingivalis is a predominant periodontal pathogen, whose infection causes inflammatory responses in periodontal tissue and alveolar bone resorption. Various virulence factors of this pathogen modulate host innate immune responses. It has been reported that gingipains degrade a wide variety of host cell proteins, and fimbriae are involved in bacterial adhesion to and invasion of host cells. In the present study, we profiled ST2 stromal cell gene expression following infection with the viable P. gingivalis strain ATCC33277 as well as with its gingipain- and fimbriae-deficient mutants, using microarray technology and quantitative real-time polymerase chain reaction. Using a mouse array of about 20,000 genes, we found that infection with the wild strain elicited a significant upregulation (greater than 2-fold) of expression of about 360 genes in ST2 cells, which included the chemokines CCL2, CCL5, and CXCL10, and other proinflammatory proteins such as interleukin-6 (IL-6) and matrix metalloproteinase-13 (MMP-13). Further, infection with the gingipain-deficient mutant elicited a reduced expression of the CXCL10, IL-6 and MMP-13 genes, suggesting that gingipains play an important role in inducing the expression of those genes following P. gingivalis infection. On the other hand, the pattern of global gene expression induced by the fimbriae-deficient mutant was similar to that by the wild strain. These results suggest that P. gingivalis infection induces gene expression of a wide variety of proinflammatory proteins in stromal cells/osteoblasts, and gingipains may be involved in inducing several of the proinflammatory factors.

Porphyromonas gingivalis lipopolysaccharide signaling in gingival fibroblasts-CD14 and Toll-like receptors

Periodontal disease is the major cause of adult tooth loss and is commonly characterized by a chronic inflammation caused by infection of oral bacteria. Porphyromonas gingivalis (P. gingivalis) is one of the suspected periodontopathic bacteria and is frequently isolated from the periodontal pockets of patients with chronic periodontal disease. The lipopolysaccharide (LPS) of P. gingivalis is a key factor in the development of periodontitis. Gingival fibroblasts, which are the major constituents of gingival connective tissue, may directly interact with bacteria and bacterial products, including LPS, in periodontitis lesions. It is suggested that gingival fibroblasts play an important role in the host responses to LPS in periodontal disease. P. gingivalis LPS enhances the production of inflammatory cytokines such as interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor alpha (TNF-alpha) in gingival fibroblasts. However, the receptor that binds with P. gingivalis LPS on gingival fibroblasts remained unknown for many years. Recently, it was demonstrated that P. gingivalis LPS binds to gingival fibroblasts. It was also found that gingival fibroblasts express CD14, Toll-like receptor 4 (TLR4), and myeloid differentiation primary response gene 88 (MyD88). P. gingivalis LPS treatment of gingival fibroblasts activates several intracellular proteins, including protein tyrosine kinases, and up-regulates the expression of monocyte chemoattractant protein-1 (MCP-1), extracellular signal-regulated kinase 1 (ERK1), and signal-regulated kinase 2 (ERK2), IL-1 receptor-associated kinase (IRAK), nuclear factor-kappaB (NF-kappaB), and activating protein-1 (AP-1). These results suggest that the binding of P. gingivalis LPS to CD14 and TLR4 on gingival fibroblasts activates various second-messenger systems. In this article, we review recent findings on the signaling pathways induced by the binding of P. gingivalis LPS to CD14 and Toll-like receptors (TLRs) in gingival fibroblasts.

CD14-mediated induction of interleukin-8 and monocyte chemoattractant protein-1 by a heat-resistant constituent of Porphyromonas gingivalis in endothelial cells

Viable and inactivated Porphyromonas gingivalis dose-dependently induced interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) secretion in human umbilical vein endothelial cells (HUVECs). The inactivated P. gingivalis, in comparison with viable bacteria, tended to enhance the production of both chemokines more strongly. The production of MCP-1 protein began increasing immediately after stimulation by P. gingivalis, and there was a nearly linear increase from 0 to 8 h of incubation, whereas IL-8 production showed a linear increase between 4 and 12 h of incubation. The IL-8 and MCP-1 mRNA expressions in HUVECs as determined by reverse transcriptase-polymerase chain reaction (RT-PCR) or Quantikine mRNA colorimetric quantification kits were found to be enhanced by P. gingivalis. Furthermore, the time courses of IL-8 and MCP-1 mRNA expressions were in accordance with those of protein production. Addition of polymyxin B or boiling did not weaken the stimulatory effect of P. gingivalis, which inhibited the effect of Escherichia coli lipopolysaccharide (E. coli LPS) and tumour necrosis factor-alpha (TNF-alpha), respectively. In contrast, the induction of IL-8 and MCP-1 by P. gingivalis was significantly reduced by anti-CD14 antibody. Our results suggest that some heat-stable component of P. gingivalis, including LPS, may be responsible for the induction of IL-8 and MCP-1 in HUVECs by a CD14-dependent mechanism. These effects might be involved in the accumulation and activation of neutrophils and monocytes at an early stage of the periodontal pathogenesis.

The effect of recombinant human bone morphogenetic protein-4 on the osteoblastic differentiation of mouse calvarial cells affected by Porphyromonas gingivalis

BACKGROUND

A number of studies have shown effective bone regeneration induced by bone morphogenetic proteins (BMPs), but it is not clear whether the presence of periodontopathic bacteria has any significant modulation effect on the bone regeneration ability of BMPs. The present study examined whether pretreatment of mouse calvarial cells with Porphyromonas gingivalis extracts can make a difference in their osteoblastic differentiation exerted by recombinant human bone morphogenetic protein-4 (rhBMP-4).

METHODS

Primary mouse calvarial osteoblastic (MCO) cells were cultured until they reached confluence. At confluence, cells were untreated or pretreated with 1 microgram/ml of sonicated P gingivalis extracts (SPEs) for 2 days. After washing, the cells were further incubated in the presence of rhBMP-4 (0 to 100 ng/ml) for 3 days. At the end of the treatment, the cells were harvested and lysed for measurement of the alkaline phosphatase (ALP) activity. Total RNA was extracted, and reverse transcription-polymerase chain reaction (RT-PCR) analysis for expression of ALP mRNA was conducted. The amount of prostaglandin E2 (PGE2) secreted into the culture supernatant was determined using an enzyme immunoassay.

RESULTS

The stimulatory effect of rhBMP-4 on ALP activity was observed in both untreated MCO cells and in cells pretreated with 1 microgram/ml of SPEs in a dose-dependent manner. The ALP activities were significantly reduced in the cells pretreated with SPEs at all concentrations of rhBMP-4 used in the study when compared to untreated cells. Similar results were obtained in the RT-PCR analysis for ALP mRNA. Cells pretreated with SPEs released significantly larger amounts of PGE2 than untreated cells, but the treatment with 100 ng/ml of rhBMP-4 had no significant effect on the amount of PGE2 released. These results suggest that the stimulatory effect of rhBMP-4 on osteoblastic differentiation might be significantly reduced by P gingivalis, possibly through the endogenous PGE2 pathway, but rhBMP-4 still has a stimulatory effect on osteoblastic differentiation of mouse calvarial cells affected by P gingivalis.

CONCLUSION

Our results suggest that supplemental BMPs would be beneficial for improved treatment of osseous defects, although their biologic effect might be significantly reduced by periodontopathic bacteria.

Biological characterization of lipopolysaccharide from Treponema pectinovorum

This study investigated the endotoxic and biological properties of purified lipopolysaccharide (LPS) isolated from an oral spirochete, Treponema pectinovorum. Endotoxicity, measured by Limulus amoebocyte lysate kinetic assay, showed that the LPS contained 1.28 endotoxin units per microg of purified LPS, which was approximately 4,000 times less than Escherichia coli O55:B5 LPS. To determine in vivo endotoxicity, LPS responder mice were administered LPS following galactosamine (GalN) sensitization. The LPS induced neither endotoxic symptoms nor lethality for 96 h, suggesting negligible or very low endotoxicity. In contrast, infection with live T. pectinovorum induced 100% lethality within 12 h in GalN-sensitized LPS responder mice, indicating an endotoxin-like property of this treponeme. Heat-killed microorganisms exhibited no lethality in GalN-sensitized mice, suggesting that the endotoxicity was associated with heat-labile components. To determine cytokine and chemokine induction by LPS, human gingival fibroblasts were stimulated and secretion of interleukin 1beta (IL-1beta), granulocyte-macrophage colony-stimulating factor, gamma interferon, IL-6, IL-8, and monocyte chemoattractant protein 1 (MCP-1) was assessed. The purified LPS induced significant amounts of only IL-6, IL-8, and MCP-1, although they were substantially lower than levels after challenge with live T. pectinovorum. After injection of LPS or live or heat-killed T. pectinovorum, serum was collected from mice and analyzed for proinflammatory cytokines IL-1beta, tumor necrosis factor alpha (TNF-alpha), and IL-6. LPS induced only IL-6 consistently. Both live and heat-killed T. pectinovorum induced serum IL-6, which was higher than the level detected following LPS administration. Importantly, live bacteria elicited systemic TNF-alpha and IL-1beta levels similar to those induced by a lethal dose of live E. coli O111. The results indicated that T. pectinovorum LPS has very low or no endotoxicity, although it can elicit low levels of cytokines from host cells. In contrast to the LPS, live T. pectinovorum demonstrated in vivo toxicity, which was associated with serum IL-1beta, TNF-alpha, and IL-6, suggesting an endotoxin-like property of a heat-labile molecule(s) of the spirochete.

A 4.1-kilodalton polypeptide in the cultural supernatant of Mycoplasma fermentans is one of the substances responsible for induction of interleukin-6 production by human gingival fibroblasts

The cultural supernatant of Mycoplasma fermentans induced interleukin-6 production by human gingival fibroblasts. The active entities were divided into hydrophilic and hydrophobic substances. In this study, we purified a 4.1-kilodalton polypeptide from the hydrophilic substances. It reacted with polyclonal antibodies to M. fermentans and activated human macrophages.

Cytokine responses to treponema pectinovorum and treponema denticola in human gingival fibroblasts

Human gingival fibroblasts were challenged with Treponema pectinovorum and Treponema denticola to test three specific hypotheses: (i) these treponemes induce different cytokine profiles from the fibroblasts, (ii) differences in cytokine profiles are observed after challenge with live versus killed treponemes, and (iii) differences in cytokine profiles are noted from different gingival fibroblast cell lines when challenged with these treponemes. Three normal gingival fibroblast cell cultures were challenged with T. pectinovorum and T. denticola strains, and the supernatants were analyzed for cytokine production (i.e., interleukin-1alpha [IL-1alpha], IL-1beta, IL-6, IL-8, IL-10, gamma interferon, macrophage chemotactic protein 1 [MCP-1], platelet-derived growth factor, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor). Unstimulated fibroblast cell lines produced IL-6, IL-8, and MCP-1. T. pectinovorum routinely elicited the greatest production of these cytokines from the fibroblast cell lines, increasing 10- to 50-fold over basal production. While T. denticola also induced IL-6 and IL-8 production, these levels were generally lower than those elicited by challenge with T. pectinovorum. MCP-1 levels were significantly lower after T. denticola challenge, and the kinetics suggested that this microorganism actually inhibited basal production by the fibroblasts. No basal or stimulated production of the other cytokines was observed. Significant differences were noted in the responsiveness of the various cell lines with respect to the two species of treponemes and the individual cytokines produced. Finally, dead T. pectinovorum generally induced a twofold-greater level of IL-6 and IL-8 than the live bacteria. These results supported the idea that different species of oral treponemes can elicit proinflammatory cytokine production by gingival cells and that this stimulation did not require live microorganisms. Importantly, a unique difference was noted in the ability of T. pectinovorum to induce a robust MCP-1 production, while T. denticola appeared to inhibit this activity of the fibroblasts. While the general cytokine profiles of the fibroblast cell cultures were similar, significant differences were noted in the quantity of individual cytokines produced, which could relate to individual patient variation in local inflammatory responses in the periodontium.