Actinobacillus actinomycetemcomitans outer membrane protein 100 triggers innate immunity and production of beta-defensin and the 18-kilodalton cationic antimicrobial protein through the fibronectin-integrin pathway in human gingival epithelial cells

Human β-Defensin 2 and Its Postulated Role in Modulation of the Immune Response

Studies described so far suggest that human β-defensin 2 is an important protein of innate immune response which provides protection for the human organism against invading pathogens of bacterial, viral, fungal, as well as parasitical origin. Its pivotal role in enhancing immunity was proved in infants. It may also be considered a marker of inflammation. Its therapeutic administration has been suggested for maintenance of the balance of systemic homeostasis based on the appropriate composition of the microbiota. It has been suggested that it may be an important therapeutic tool for modulating the response of the immune system in many inflammatory diseases, offering new treatment modalities. For this reason, its properties and role in the human body discussed in this review should be studied in more detail.

The induced RNA-binding protein, HuR, targets 3'-UTR region of IL-6 mRNA and enhances its stabilization in periodontitis

RNA-binding proteins (RBPs) regulate mRNA stability by binding to the 3'-untranslated region (UTR) region of mRNA. Human antigen-R (HuR), one of the RBPs, is involved in the progression of diseases, such as rheumatoid arthritis, diabetes mellitus and some inflammatory diseases. Interleukin (IL)-6 is a major inflammatory cytokine regulated by HuR binding to mRNA. Periodontal disease (PD) is also an inflammatory disease caused by elevations in IL-6 following an infection by periodontopathogenic bacteria. The involvement of HuR in the progression of PD was assessed using in-vitro and in-vivo experiments. Immunohistochemistry of inflamed periodontal tissue showed strong staining of HuR in the epithelium and connective tissue. HuR mRNA and protein level was increased following stimulation with Porphyromonas gingivalis (Pg), one of the periodontopathogenic bacteria, lipopolysacchride (LPS)-derived from Pg (PgLPS) and tumour necrosis factor (TNF)-α in OBA-9, an immortalized human gingival epithelial cell. The luciferase activity of 3'-UTR of IL-6 mRNA was increased by TNF-α, Pg and PgLPS in OBA-9. Luciferase activity was also increased in HuR-over-expressing OBA-9 following a bacterial stimulation. Down-regulation of HuR by siRNA resulted in a decrease in mRNA expression and production of IL-6. In contrast, the over-expression of HuR increased IL-6 mRNA expression and production in OBA-9. The HuR inhibitor, quercetin, suppressed Pg-induced HuR mRNA expression and IL-6 production in OBA-9. An oral inoculation with quercetin also inhibited bone resorption in ligature-induced periodontitis model mice as a result of down-regulation of IL-6. These results show that HuR modulates inflammatory responses by regulating IL-6.

Sensitivity of caries pathogens to antimicrobial peptides related to caries risk

OBJECTIVES

Antimicrobial peptides (AMPs) represent important facets of the immune system controlling infectious diseases. However, pathogens show varying susceptibilities to AMPs. This study investigates the susceptibilities of strains of Streptococcus mutans (SM), Actinomyces naeslundii (AN), and Lactobacillus spp. (LB) towards AMPs and if there are correlations between the appearance of such high-risk strains and clinical caries status.

MATERIAL AND METHODS

Plaque samples were collected from patients along with clinical examinations. Bacterial strains were identified via selective media, matrix-assisted laser desorption/ionization analysis-time of flight (MALDI-TOF), and arbitrary-primed-PCR (AP-PCR). Each strain was tested for susceptibility to LL-37, HBD-2, HNP-1, and HNP-3 or phosphate-buffered saline as negative control in a biofilm model on hydroxylapatite discs. Survival rates and resulting risk classification for each strain were determined. Correlations were calculated between the number of high-risk strains (all/S. mutans) appearing in patients and their clinical caries status.

RESULTS

Forty-seven patients were included with mean DMFT values of 11.4 ± 8.7. A total of 8 different SM, 30 LB, and 47 AN strains were detected. One-way ANOVA indicated that type/concentration of AMPs had major influence on reductions of Lactobacilli and Actinomyces. Seventeen strains of AN, 2 of SM, and 6 of LB had low susceptibilities to AMPs. The number of such strains in patients showed significant positive correlations to the DMFT values (all p = 0.001; r = 0.452; S. mutans p < 0.0001, r = 0.558).

CONCLUSION

The occurrence of low susceptible strains to AMPs seems to correlate with the individual caries status.

CLINICAL RELEVANCE

The results may lead to new ways to identify individuals with increased caries risk.

Outer membrane protein 100 of Aggregatibacter actinomycetemcomitans act as a biopharmaceutical target for photodynamic therapy: An in silico analysis

BACKGROUND

Periodontitis is a polymicrobial, chronic, and degenerative disease that can lead to destruction of the teeth-supporting tissues and eventually to loss of teeth. Aggregatibacter actinomycetemcomitans is predominantly associated with periodontal diseases. Outer membrane protein (Omp) 100 is a more important virulence factor of A. actinomycetemcomitans due to the effect of adhesion and invasion into human gingival epithelial cells. Attachment of A. actinomycetemcomitans inhibition is significant in the treatment process.

METHODS

We evaluated the capacity of Omp100 in A. actinomycetemcomitans as a novel target for photodynamic therapy (PDT) using a range of bioinformatic tools. In silico analysis was used to predict molecular modeling, the hierarchical nature of protein structure and backbone, and sub-cellular localization.

RESULTS

The results showed that Omp100 is most similar to thiamine-phosphate pyrophosphorylase [Haemophilus influenzae PittGG], with a 74% similarity. The predicted structure of Omp100 displayed that it is a protein with positive charge (10.4) in pH 7 and alpha helix dominates other secondary structures located outside the cell. Protein-protein interaction network showed that Omp100 interacted with extracellular matrix protein adhesion, glycoside hydrolase, Omp 64, phospholipase D/Transphosphatidylase, Flp pilus assembly protein, and heme acquisition system receptor.

CONCLUSION

According to the results, anionic indocyanine green tends to interact with Omp100 during PDT as a major target.

Laser-activated transforming growth factor-β1 induces human β-defensin 2: implications for laser therapies for periodontitis and peri-implantitis

BACKGROUND

There is increasing popularity of high-power lasers for surgical debridement and antimicrobial therapy in the management of peri-implantitis and periodontal therapy. Removal of the noxious foci would naturally promote tissue healing directly. However, there are also anecdotal reports of better healing around routine high-power laser procedures. The precise mechanisms mediating these effects remain to be fully elucidated. This work examines these low-dose laser bystander effects on oral human epithelial and fibroblasts, particularly focusing on the role of human β-defensin 2 (HBD-2 or DEFB4A), a potent factor capable of antimicrobial effects and promoting wound healing.

MATERIAL AND METHODS

Laser treatments were performed using a near-infrared laser (810 nm diode) at low doses. Normal human oral keratinocytes and fibroblast cells were used and HBD-2 mRNA and protein expression was assessed with real time polymerase chain reaction, western blotting and immunostaining. Role of transforming growth factor (TGF)-β1 signaling in this process was dissected using pathway-specific small molecule inhibitors.

RESULTS

We observed laser treatments robustly induced HBD-2 expression in an oral fibroblast cell line compared to a keratinocyte cell line. Low-dose laser treatments results in activation of the TGF-β1 pathway that mediated HBD-2 expression. The two arms of TGF-β1 signaling, Smad and non-Smad are involved in laser-mediated HBD-2 expression.

CONCLUSIONS

Laser-activated TGF-β1 signaling and induced expression of HBD-2, both of which are individually capable of promoting healing in tissues adjacent to high-power surgical laser applications. Moreover, the use of low-dose laser therapy itself can provide additional therapeutic benefits for effective clinical management of periodontal or peri-implant disease.

Gut microbiota-derived lipopolysaccharide uptake and trafficking to adipose tissue: implications for inflammation and obesity

The composition of the gut microbiota and excessive ingestion of high-fat diets (HFD) are considered to be important factors for development of obesity. In this review we describe a coherent mechanism of action for the development of obesity, which involves the composition of gut microbiota, HFD, low-grade inflammation, expression of fat translocase and scavenger receptor CD36, and the scavenger receptor class B type 1 (SR-BI). SR-BI binds to both lipids and lipopolysaccharide (LPS) from Gram-negative bacteria, which may promote incorporation of LPS in chylomicrons (CMs). These CMs are transported via lymph to the circulation, where LPS is transferred to other lipoproteins by translocases, preferentially to HDL. LPS increases the SR-BI binding, transcytosis of lipoproteins over the endothelial barrier,and endocytosis in adipocytes. Especially large size adipocytes with high metabolic activity absorb LPS-rich lipoproteins. In addition, macrophages in adipose tissue internalize LPS-lipoproteins. This may contribute to the polarization from M2 to M1 phenotype, which is a consequence of increased LPS delivery into the tissue during hypertrophy. In conclusion, evidence suggests that LPS is involved in the development of obesity as a direct targeting molecule for lipid delivery and storage in adipose tissue.

Smad2 is involved in Aggregatibacter actinomycetemcomitans-induced apoptosis

Apoptosis is thought to contribute to the progression of periodontitis. It has been suggested that the apoptosis of epithelial cells may contribute to the loss of epithelial barrier function. Smad2, a downstream signaling molecule of TGF-β receptors (TGF-βRs), is critically involved in apoptosis in several cell types. However, the relationship between smad2 and bacteria-induced apoptosis has not yet been elucidated. It is possible that the regulation of apoptosis induced by periodontopathic bacteria may lead to novel preventive therapies for periodontitis. Therefore, in the present study, we investigated the involvement of smad2 phosphorylation in apoptosis of human gingival epithelial cells induced by Aggregatibacter actinomycetemcomitans (Aa). Aa apparently induced the phosphorylation of smad2 in primary human gingival epithelial cells (HGECs) or the human gingival epithelial cell line, OBA9 cells. In addition, Aa induced phosphorylation of the serine residue of the TGF-β type I receptor (TGF-βRI) in OBA9 cells. SB431542 (a TGF-βRI inhibitor) and siRNA transfection for TGF-βRI, which reduced both TGF-βRI mRNA and protein levels, markedly attenuated the Aa-induced phosphorylation of smad2. Furthermore, the disruption of TGF-βRI signaling cascade by SB431542 and siRNA transfection for TGF-βRI abrogated the activation of cleaved caspase-3 expression and repressed apoptosis in OBA9 cells treated with Aa. Thus, Aa induced apoptosis in gingival epithelial cells by activating the TGF-βRI-smad2-caspase-3 signaling pathway. The results of the present study may suggest that the periodontopathic bacteria, Aa, activates the TGF-βR/smad2 signaling pathway in human gingival epithelial cells and induces apoptosis in epithelial cells, which may lead to new therapeutic strategies that modulate the initiation of periodontitis.

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.

The extracellular matrix regulates MaeuCath1a gene expression

We have previously shown that the gene for MaeuCath1, a cathelicidin secreted in wallaby milk is alternately spliced into two variants, MaeuCath1a and MaeuCath1b which are temporally regulated in order to provide antimicrobial protection to the newborn and stimulate mammary growth, respectively. The current study investigated the extracellular matrix (ECM) for its regulatory role in MaeuCath1 gene expression. Reverse transcription qPCR using RNA isolated from mammary epithelial cells (WallMEC) cultured on ECM showed that ECM regulates MaeuCath1a gene expression in a lactation phase-dependent manner. Luciferase reporter-based assays and in silico analysis of deletion fragments of the 2245bp sequence upstream of the translation start site identified ECM-dependent positive regulatory activity in the -709 to -15 region and repressor activity in the -919 to -710 region. Electrophoretic Gel Mobility Shift Assays (EMSA) using nuclear extract from ECM-treated WallMEC showed differential band shift in the -839 to -710 region.

Irsogladine maleate regulates the inflammatory related genes in human gingival epithelial cells stimulated by Aggregatibacter actinomycetemcomitans

Periodontitis is an infectious inflammatory disease. Our previous studies have revealed that irsogladine maleate (IM) regulates intercellular junctional function and chemokine secretion in gingival epithelium, resulting in the suppression of the onset of periodontal disease in a rat model. Therefore, it is plausible that IM is a promising preventive remedy for periodontal disease. In this study, to gain a better understanding of IM in gingival epithelial cells, we employed a DNA microarray analysis. More specifically, human gingival epithelial cells (HGEC) were exposed to Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) in the presence or absence of IM. Then, a human genome focus array was used. A. actinomycetemcomitans facilitated the expression of several inflammatory-related genes, including these for matrix metalloproteinase (MMP)-3, interleukin (IL)-6, and intercellular adhesion molecule-1 (ICAM-1) in HGEC, while these mRNA levels were attenuated by IM treatment. Importantly, consistent with mRNA levels, immunoblotting, immunofluorescence staining and ELISA analysis indicated that IM also abrogated the A. actinomycetemcomitans-induced increase in MMP-3, IL-6, and ICAM-1 at the protein level. In addition, inhibition of the ERK or p38 MAP kinase signaling cascade, previously reported to be disturbed by IM treatment in HGEC, clearly blocked A. actinomycetemcomitans-induced MMP-3, IL-6, or ICAM-1 protein expression. Moreover, animal study revealed that IM-pretreatment inhibited the A. actinomycetemcomitans-induced increase of ICAM-1 in gingival junctional epithelium. Taken together, these results suggested that IM can regulate inflammatory responses in HGEC by inhibiting the ERK or p38 MAP kinase signaling cascade, which may result in suppression of inflammation in gingival tissue, thereby contributing to the prevention of periodontitis.

O-polysaccharide glycosylation is required for stability and function of the collagen adhesin EmaA of Aggregatibacter actinomycetemcomitans

Aggregatibacter actinomycetemcomitans is hypothesized to colonize through the interaction with collagen and establish a reservoir for further dissemination. The trimeric adhesin EmaA of A. actinomycetemcomitans binds to collagen and is modified with sugars mediated by an O-antigen polysaccharide ligase (WaaL) that is associated with lipopolysaccharide (LPS) biosynthesis (G. Tang and K. Mintz, J. Bacteriol. 192:1395-1404, 2010). This investigation characterized the function and cellular localization of EmaA glycosylation. The interruption of LPS biogenesis by using genetic and pharmacological methods changed the amount and biophysical properties of EmaA molecules in the outer membrane. In rmlC and waaL mutant strains, the membrane-associated EmaA was reduced by 50% compared with the wild-type strain, without changes in mRNA levels. The membrane-associated EmaA protein levels were recovered by complementation with the corresponding O-polysaccharide (O-PS) biosynthetic genes. In contrast, another trimeric autotransporter, epithelial adhesin ApiA, was not affected in the same mutant background. The inhibition of undecaprenyl pyrophosphate recycling by bacitracin resulted in a similar decrease in the membrane-associated EmaA protein. This effect was reversed by removal of the compound. A significant decrease in collagen binding activity was observed in strains expressing the nonglycosylated form of EmaA. Furthermore, the electrophoretic mobility shifts of the EmaA monomers found in the O-PS mutant strains were associated only with the membrane-associated protein and not with the cytoplasmic pre-EmaA protein, suggesting that this modification does not occur in the cytoplasm. The glycan modification of EmaA appears to be required for collagen binding activity and protection of the protein against degradation by proteolytic enzymes.

Understanding the roles of gingival beta-defensins

Gingival epithelium produces β-defensins, small cationic peptides, as part of its contribution to the innate host defense against the bacterial challenge that is constantly present in the oral cavity. Besides their functions in healthy gingival tissues, β-defensins are involved in the initiation and progression, as well as restriction of periodontal tissue destruction, by acting as antimicrobial, chemotactic, and anti-inflammatory agents. In this article, we review the common knowledge about β-defensins, coming from in vivo and in vitro monolayer studies, and present new aspects, based on the experience on three-dimensional organotypic culture models, to the important role of gingival β-defensins in homeostasis of the periodontium.

Host-microbial interactions and regulation of intestinal epithelial barrier function: From physiology to pathology

The gastrointestinal tract is the largest reservoir of commensal bacteria in the human body, providing nutrients and space for the survival of microbes while concurrently operating mucosal barriers to confine the microbial population. The epithelial cells linked by tight junctions not only physically separate the microbiota from the lamina propria, but also secrete proinflammatory cytokines and reactive oxygen species in response to pathogen invasion and metabolic stress and serve as a sentinel to the underlying immune cells. Accumulating evidence indicates that commensal bacteria are involved in various physiological functions in the gut and microbial imbalances (dysbiosis) may cause pathology. Commensal bacteria are involved in the regulation of intestinal epithelial cell turnover, promotion of epithelial restitution and reorganization of tight junctions, all of which are pivotal for fortifying barrier function. Recent studies indicate that aberrant bacterial lipopolysaccharide-mediated signaling in gut mucosa may be involved in the pathogenesis of chronic inflammation and carcinogenesis. Our perception of enteric commensals has now changed from one of opportunistic pathogens to active participants in maintaining intestinal homeostasis. This review attempts to explain the dynamic interaction between the intestinal epithelium and commensal bacteria in disease and health status.

Effects of fruit and vegetable low molecular mass fractions on gene expression in gingival cells challenged with Prevotella intermedia and Actinomyces naeslundii

Low molecular mass (LMM) fractions obtained from extracts of raspberry, red chicory, and Shiitake mushrooms have been shown to be an useful source of specific antibacterial, antiadhesion/coaggregation, and antibiofilm agent(s) that might be used for protection towards caries and gingivitis. In this paper, the effects of such LMM fractions on human gingival KB cells exposed to the periodontal pathogens Prevotella intermedia and Actinomyces naeslundii were evaluated. Expression of cytokeratin 18 (CK18) and β4 integrin (β4INT) genes, that are involved in cell proliferation/differentiation and adhesion, and of the antimicrobial peptide β2 defensin (HβD2) in KB cells was increased upon exposure to either live or heat-killed bacteria. All LMM fractions tested prevented or reduced the induction of gene expression by P. intermedia and A. naeslundii depending on the experimental conditions. Overall, the results suggested that LMM fractions could modulate the effects of bacteria associated with periodontal disease in gingival cells.

Mechanotransduction activates α₅β₁ integrin and PI3K/Akt signaling pathways in mandibular osteoblasts

It is unclear how bone cells at different sites detect mechanical loading and how site-specific mechanotransduction affects bone homeostasis. To differentiate the anabolic mechanical responses of mandibular cells from those of calvarial and long bone cells, we isolated osteoblasts from C57B6J mouse bones, cultured them for 1week, and subjected them to therapeutic low intensity pulsed ultrasound (LIPUS). While the expression of the marker proteins of osteoblasts and osteocytes such as alkaline phosphatase and FGF23, as well as Wnt1 and β-catenin, was equally upregulated, the expression of mandibular osteoblast messages related to bone remodeling and apoptosis differed from that of messages of other osteoblasts, in that the messages encoding the pro-remodeling protein RANKL and the anti-apoptotic protein Bcl-2 were markedly upregulated from the very low baseline levels. Blockage of the PI3K and α(5)β(1) integrin pathways showed that the mandibular osteoblast required mechanotransduction downstream of α(5)β(1) integrin to upregulate expression of the proteins β-catenin, p-Akt, Bcl-2, and RANKL. Mandibular osteoblasts thus must be mechanically loaded to preserve their capability to promote remodeling and to insure osteoblast survival, both of which maintain intact mandibular bone tissue. In contrast, calvarial Bcl-2 is fully expressed, together with ILK and phosphorylated mTOR, in the absence of LIPUS. The antibody blocking α(5)β(1) integrin suppressed both the baseline expression of all calvarial proteins examined and the LIPUS-induced expression of all mandibular proteins examined. These findings indicate that the cellular environment, in addition to the tridermic origin, determines site-specific bone homeostasis through the remodeling and survival of osteoblastic cells. Differentiated cells of the osteoblastic lineage at different sites transmit signals through transmembrane integrins such as α(5)β(1) integrin in mandibular osteoblasts, whose signaling may play a major role in controlling bone homeostasis.

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.

Probing local innate immune responses after mucosal immunisation

Background

Intranasal immunisation is potentially a very effective route for inducing both mucosal and systemic immunity to an infectious agent.

Methods

Balb/c mice were intranasally immunised with the mucosal adjuvant heat labile toxin and the Mycobacterium tuberculosis fusion protein Ag85B-ESAT6 and early changes in innate immune responses within local mucosal tissues were examined using flow cytometry and confocal microscopy. Antigen-specific humoral and cellular immune responses were also evaluated.

Results

Intranasal immunisation induced significant changes in both number and distribution of dendritic cells, macrophages and neutrophils within the nasal-associated lymphoid tissue and cervical lymph nodes in comparison to controls as early as 5 h post immunisation. Immunisation also resulted in a rapid and transient increase in activation marker expression first in the nasal-associated lymphoid tissue, and then in the cervical lymph nodes. This heightened activation status was also apparent from the pro-inflammatory cytokine profiles of these innate populations. In addition we also showed increased expression and distribution of a number of different cell adhesion molecules early after intranasal immunisation within these lymphoid tissues. These observed early changes correlated with the induction of a T_H1 type immune response.

Conclusions

These data provide insights into the complex nature of innate immune responses induced following intranasal immunisation within the upper respiratory tract, and may help clarify the concepts and provide the tools that are needed to exploit the full potential of mucosal vaccines.

Psychological stress has no association with salivary levels of β-defensin 2 and β-defensin 3

BACKGROUND

Recent studies suggest that stress can predispose an individual to the development of periodontal disease, but the exact biological mechanism is unknown. Considering that psychological stress can down-regulate the production of β-defensins (antimicrobial peptides produced in the oral cavity), the aim of the present study was to evaluate the association between stress and salivary levels of β-defensin 2 (HBD-2) and β-defensin 3 (HBD-3).

METHODS

For this purpose, seventy five volunteers, classified as periodontally healthy, were submitted to a psychological evaluation using a validated questionnaire (Questionnaire of Lipp-ISS). Following analysis of the questionnaires, the subjects were divided in two groups (Group A: Absence of stress and Group B: Presence of stress). Unstimulated saliva samples were collected and the concentration of total protein was determined using the BCA method, and the concentrations of HBD-2 and HBD-3 were determined by ELISA.

RESULTS

The levels of total protein did not show a statistically significant difference between the groups. Analyses of HBD-2 and HBD-3 concentrations indicate that the stress condition was not associated with the levels of either peptide in saliva (P=0.3664 for HBD-2 and P=0.3608 for HBD-3).

CONCLUSION

In periodontally healthy subjects, HBD-2 and HBD-3 levels are not influenced by stress.

Host defense peptides in the oral cavity and the lung: similarities and differences

Peptides with broad-spectrum antimicrobial activity are found in the mucosal surfaces at many sites in the body, including the airway, the oral cavity, and the digestive tract. Based on their in vitro antimicrobial and other immunomodulatory activities, these host defense peptides have been proposed to play an important role in the innate defense against pathogenic microbial colonization. The genes that encode these peptides are up-regulated by pathogens, further supporting their role in innate immune defense. However, the differences in the local microbial environments between the generally sterile airway and the highly colonized oral cavity suggest a more complex role for these peptides in innate immunity. For example, beta-defensin genes are induced in the airway by all bacteria and Toll-like receptor (TLR) agonists primarily through an NF-kappaB-mediated pathway. In contrast, the same genes are induced in the gingival epithelium by only a subset of bacteria and TLR ligands, via different pathways. Furthermore, the environments into which the peptides are secreted--specifically saliva, gingival crevicular fluid, and airway surface fluid--differ greatly and can effect their respective activities in host defense. In this review, we examine the differences and similarities between host defense peptides in the oral cavity and the airway, to gain a better understanding of their contributions to immunity.

Highly conserved surface proteins of oral spirochetes as adhesins and potent inducers of proinflammatory and osteoclastogenic factors

Oral spirochetes include enormously heterogeneous Treponema species, and some have been implicated in the etiology of periodontitis. In this study, we characterized highly conserved surface proteins in four representative oral spirochetes (Treponema denticola, T. lecithinolyticum, T. maltophilum, and T. socranskii subsp. socranskii) that are homologs of T. pallidum Tp92, with opsonophagocytic potential and protective capacity against syphilis. Tp92 homologs of oral spirochetes had predicted signal peptides (20 to 31 amino acids) and molecular masses of 88 to 92 kDa for mature proteins. They showed amino acid sequence identities of 37.9 to 49.3% and similarities of 54.5 to 66.9% to Tp92. The sequence identities and similarities of Tp92 homologs of oral treponemes to one another were 41.6 to 71.6% and 59.9 to 85.6%, respectively. The tp92 gene homologs were successfully expressed in Escherichia coli, and the recombinant proteins were capable of binding to KB cells, an epithelial cell line, and inhibited the binding of the whole bacteria to the cells. Antiserum (the immunoglobulin G fraction) raised against a recombinant form of the T. denticola Tp92 homolog cross-reacted with homologs from three other species of treponemes. The Tp92 homologs stimulated various factors involved in inflammation and osteoclastogenesis, like interleukin-1beta (IL-1beta), tumor necrosis factor alpha, IL-6, prostaglandin E(2), and matrix metalloproteinase 9, in host cells like monocytes and fibroblasts. Our results demonstrate that Tp92 homologs of oral spirochetes are highly conserved and may play an important role in cell attachment, inflammation, and tissue destruction. The coexistence of various Treponema species in a single periodontal pocket and, therefore, the accumulation of multiple Tp92 homologs may amplify the pathological effect in periodontitis.

Role of beta-defensins in oral epithelial health and disease

The oral epithelium functions as a mechanical and protective barrier to resist bacterial infection. beta-Defensins are a group of antimicrobial peptides mainly produced by epithelial cells of many organs including skin, lung, kidney, pancreas, uterus, eye, and nasal and oral mucosa. This review focuses on beta-defensins (BDs) in oral epithelia and discusses their importance in oral epithelial health and disease. BDs exhibit antimicrobial activity against oral microbes including periodontitis-related bacteria, Candida, and papilloma virus. Alterative expression of BDs was observed in oral epithelial diseases, including oral inflammatory lesions with and without microbial infection and oral cancer. BDs may be useful in the treatment of oral infectious diseases, ulcerative lesions, and cancer. BDs play an important role in protection against oral microbes and may be used in clinical applications.

Differential regulation of innate immune response genes in gingival epithelial cells stimulated with Aggregatibacter actinomycetemcomitans

BACKGROUND AND OBJECTIVE

The gingival epithelium provides the first line of defense against colonization by periodontal pathogens, both as a physical barrier and by the production of inducible innate immune mediators such as beta-defensins and pro-inflammatory cytokines. The gram-negative bacterium Aggregatibacter actinomycetemcomitans is implicated in the pathogenesis of localized aggressive periodontitis, although the bacterium is found widely in the healthy population. We hypothesized that gingival epithelial cell-derived innate immune mediators triggered in response to A. actinomycetemcomitans infection may play an important role in increased susceptibility to infection.

MATERIAL AND METHODS

Primary cultures of human gingival epithelial cells were cultured in the presence of A. actinomycetemcomitans. Total mRNA was examined for the presence of innate immune markers using RT-PCR.

RESULTS

We show here that the mRNA levels of human beta-defensin 2 and interleukin-8 are elevated by live cultures of a clinical isolate of A. actinomycetemcomitans in cultured gingival epithelial cells from healthy individuals, but not by A. actinomycetemcomitans lipopolysaccharide. Cells from a patient with localized aggressive periodontitis, however, did not respond to this bacterial stimulation. In contrast, the pro-inflammatory cytokine interleukin-19 was induced in cells from both localized aggressive periodontitis and healthy subjects. Examination of Toll-like receptors and associated adapter molecules indicated lower levels of Toll-like receptor 2 mRNA in the localized aggressive periodontitis patient-derived cells compared with cells from healthy subjects.

CONCLUSION

These results suggest that a differential expression of innate immune response genes to A. actinomycetemcomitans in the gingival epithelium could be an underlying factor of susceptibility to localized aggressive periodontitis.

Defensins in the immunology of bacterial infections

Defensins are a component of the host response against bacterial infections. Multiple studies suggest a linked upregulation of beta-defensins and pro-inflammatory cytokines expression in various tissues, as well as the possibility of mutual induction. Recent data demonstrate the importance of nucleotide-binding oligomerization proteins for the expression of defensins, and associate low levels of alpha-defensins expression by intestinal Paneth cells with susceptibility to Crohn's disease of the ileum. A novel anti-toxin activity has been identified for several alpha- and theta-defensins, expanding the repertoire of the antimicrobial functions of defensins. It has been shown that bacterial proteins can inactivate the action of defensins, and that pathogen type III secretion systems (T3SS) manipulate defensins expression via T3SS-mediated inhibition of the NF-kappaB pathway.

Cross-reactive adaptive immune response to oral commensal bacteria results in an induction of receptor activator of nuclear factor-?B ligand (RANKL)-dependent periodontal bone resorption in a mouse model

INTRODUCTION

The present study examined whether induction of an adaptive immune response to orally colonizing non-pathogenic Pasteurella pneumotropica by immunization with the phylogenetically closely related bacterium, Actinobacillus actinomycetemcomitans, can result in periodontal bone loss in mice.

METHODS

BALB/c mice harboring P. pneumotropica (P. pneumotropica(+) mice) in the oral cavity or control P. pneumotropica-free mice were immunized with fixed A. actinomycetemcomitans. The animals were sacrificed on day 30, and the following measurements were carried out: (i) serum immunoglobulin G and gingival T-cell responses to A. actinomycetemcomitans and P. pneumotropica; (ii) periodontal bone loss; and (iii) identification of receptor activator of nuclear factor-kappaB ligand (RANKL) -positive T cells in gingival tissue.

RESULTS

Immunization with A. actinomycetemcomitans induced a significantly elevated serum immunoglobulin G response to the 29-kDa A. actinomycetemcomitans outer membrane protein (Omp29), which showed strong cross-reactivity with P. pneumotropica OmpA compared to results in the control non-immunized mice. The A. actinomycetemcomitans-immunized P. pneumotropica(+) mice developed remarkable periodontal bone loss in a RANKL-dependent manner, as determined by the abrogation of bone loss by treatment with osteoprotegerin-Fc. The T cells isolated from the gingival tissue of A. actinomycetemcomitans-immunized P. pneumotropica(+) mice showed an in vitro proliferative response to both A. actinomycetemcomitans and P. pneumotropica antigen presentation, as well as production of soluble(s)RANKL in the culture supernatant. Double-color confocal microscopy demonstrated that the frequency of RANKL(+) T cells in the gingival tissue of A. actinomycetemcomitans-immunized P. pneumotropica(+) mice was remarkably elevated compared to control mice.

CONCLUSION

The induction of an adaptive immune response to orally colonizing non-pathogenic P. pneumotropica results in RANKL-dependent periodontal bone loss in mice.

Innate immune peptide LL-37 displays distinct expression pattern from beta-defensins in inflamed gingival tissue

Anti-microbial peptides produced from mucosal epithelium appear to play pivotal roles in the host innate immune defence system in the oral cavity. In particular, human beta-defensins (hBDs) and the cathelicidin-type anti-microbial peptide, LL-37, were reported to kill periodontal disease-associated bacteria. In contrast to well-studied hBDs, little is known about the expression profiles of LL-37 in gingival tissue. In this study, the anti-microbial peptides expressed in gingival tissue were analysed using immunohistochemistry and enxyme-linked immunosorbent assay (ELISA). Immunohistochemistry revealed that neutrophils expressed only LL-37, but not hBD-2 or hBD-3, and that such expression was prominent in the inflammatory lesions when compared to healthy gingivae which showed very few or no LL-37 expressing neutrophils. Gingival epithelial cells (GEC), however, expressed all three examined anti-microbial peptides, irrespective of the presence or absence of inflammation. Moreover, as determined by ELISA, the concentration of LL-37 in the gingival tissue homogenates determined was correlated positively with the depth of the gingival crevice. Stimulation with periodontal bacteria in vitro induced both hBD-2 and LL-37 expressions by GEC, whereas peripheral blood neutrophils produced only LL-37 production, but not hBD-2, in response to the bacterial stimulation. These findings suggest that LL-37 displays distinct expression patterns from those of hBDs in gingival tissue.