Salivary Cathelicidin (LL-37) in Children and Adolescents Living with HIV.

Introduction: Human cathelicidin LL-37 is a salivary antimicrobial peptide (AMP) with broad-spectrum activity against oral diseases, but few studies have assessed its role in children and adolescents living with HIV (CALHIV). We assessed salivary LL-37 levels and correlates in a long-term cohort of Kenyan CALHIV followed since antiretroviral therapy (ART) initiation. Methods: Saliva was collected from 76 CALHIV who were recruited from two ongoing pediatric HIV studies in Nairobi, Kenya. Oral examinations documenting oral manifestations of HIV, dental caries, and gingivitis were completed. Additional variables included age, sex, HIV treatment (initial ART regimen) and disease parameters, caregivers' demographics, and oral pathologies were conducted. Data were statistically analyzed using the independent T test on the log-transformed LL-37. Results: At the oral exam visit, the mean age of participants was 13.3 years (±SD = 3.4), and the median CD4 count was 954 cells/mm3. Mean salivary cathelicidin values of the cohort were 23.7 ± 21.1 ng/mL. Children with permanent dentition at time of oral examination, and children who initiated ART at ≥2 years old had higher mean LL-37 concentrations compared to those with mixed dentition and those who initiated ART <2 years old (p = 0.0042, 0.0373, respectively). LL-37 levels were not found to differ by initial type of ART regimen, CD4 count, or oral disease. Conclusion: Further research and longitudinal studies are necessary to evaluate and improve the innate immunity of CALHIV in Kenya.

Immunomodulatory Effects of N-Acetyl Cysteine Treated SCAP.

INTRODUCTION: Stem cells of the apical papilla (SCAP) play an important role in regenerative endodontic procedures (REPs). Previous studies have shown that during REPs, bacteria can activate the innate immune system and cause indirect stem cell toxicity, leading to the lysis of SCAP. N-acetylcysteine (NAC)-treated cells are resistant to apoptosis and have increased differentiation capabilities. The immunomodulatory properties of NAC-treated SCAP are still unknown. Hence, the aim of this study is to evaluate the interactions of SCAP pretreated with and without NAC with the immune system. METHODS: Flow cytometric analysis was performed to assess the effects of NAC on SCAP viability. Human SCAP were then cultured and were either pretreated with NAC or non-treated and co-cultured with human peripheral blood mononuclear cells. A lactate dehydrogenase assay was performed to evaluate the levels of immune cell mediated apoptosis, followed by an enzyme-linked immunosorbent assay (ELISA) to measure levels of proinflammatory cytokines for these co-cultures. Data were analyzed using analysis of variance with post hoc Tukey test. RESULTS: Cells treated with NAC had similar levels of viability as the controls. SCAP pretreated with NAC had significantly lower immune cell-mediated cytotoxicity to nonactivated and activated peripheral blood mononuclear cells. The ELISA results showed that SCAP pretreated with NAC induced lower levels of proinflammatory cytokines. CONCLUSIONS: SCAP pretreated with NAC have a higher chance of surviving the activated immune system. This information may provide a better insight into the properties of these stem cells and may be the key to making REPs more predictable.

Age-related heterogeneity in dental caries and associated risk factors in individuals with cystic fibrosis ages 6-20 years: A pilot study.

BACKGROUND: The literature conflicts regarding dental caries risk in cystic fibrosis (CF) relative to controls. METHODS: Prospective, observational study of age-related heterogeneity in caries rates and potential risk factors in individuals with CF ages 6-20 at a single clinic in Washington state (N=85). Caries rates for enrolled CF participants and historical controls from NHANES were compared using cubic spline regression models. Generalized linear regression models identified correlates of age and caries in CF. RESULTS: Children ages 6-9 with CF had significantly lower caries than controls (Holm's P<0.05). There was no difference for ages 10-20 by CF status (Holm's P>0.05). Various biological/intraoral, medical, and behavioral factors were associated with caries and age in CF. CONCLUSIONS: Younger children with CF may be protected from caries, but there is apparent loss of protection in early adolescence associated with multiple risk factors. Additional studies are needed to confirm these findings.

Characterization of the Cellular Responses of Dental Mesenchymal Stem Cells to the Immune System.

INTRODUCTION: Dental stem cells have gained importance recently and are being used for various purposes in regenerative medicine and dentistry. Although much research has been done to show the various properties of these dental stem cells, the immunomodulatory properties of some of these stem cells are still unknown. This is important considering these cells are being used routinely. Therefore, the aim of this study was to investigate the interactions between the activated immune cells and 3 types of dental-derived mesenchymal stem cells: dental pulp stem cells, stem cells from human exfoliated deciduous teeth, and stem cells of the apical papilla (SCAP). METHODS: SCAP, dental pulp stem cells, stem cells from human exfoliated deciduous teeth, and periodontal ligament fibroblasts were cultured, and various assays were performed including a proliferation assay, flow cytometric analysis, lactate dehydrogenase and chromium-51 cytotoxicity assays, and an enzyme-linked immunosorbent assay to evaluate the interactions of these dental stem cells when cocultured with either peripheral blood mononuclear cells or natural killer cells. RESULTS: SCAP were less resistant to immune cell-mediated cytotoxicity as seen from the results obtained from the LDH and chromium-51 cytotoxicity assays. The flow cytometric analysis showed a lower resilience of SCAP to cytotoxic compounds. The enzyme-linked immunosorbent assay results demonstrated that the SCAP induced high levels of proinflammatory cytokine secretion compared with the other dental stem cells. CONCLUSIONS: SCAP did not perform as well as the other dental stem cells. This could in turn affect their survival and differentiation abilities as well as their functionality. This may be an important aspect to consider when selecting dental stem cells for various regenerative procedures.

Increased Levels of Dissolved Titanium Are Associated With Peri-Implantitis - A Cross-Sectional Study.

BACKGROUND: Peri-implantitis represents a disruption of the biocompatible interface between the titanium dioxide layer of the implant surface and the peri-implant tissues. Increasing preclinical data suggest that peri-implantitis microbiota not only triggers an inflammatory immune response but also causes electrochemical alterations of the titanium surfaces, i.e., corrosion, that aggravate this inflammatory response. Thus, it was hypothesized that there is an association between dissolution of titanium from dental implants, which suggests corrosion, and peri-implantitis in humans. The objective of this study is to compare levels of dissolved titanium in submucosal plaque collected from healthy implants and implants with peri-implantitis. METHODS: Submucosal plaque from 20 implants with peri-implantitis and 20 healthy implants was collected with sterile curets from 30 participants. Levels of titanium were quantified using inductively coupled plasma mass spectrometry and normalized for mass of bacterial DNA per sample to exclude confounding by varying amounts of plaque per site. Statistical analysis was performed using generalized estimated equations to adjust for clustering of implants per participant. RESULTS: Implants with peri-implantitis harbored significantly higher mean levels of titanium (0.85 ± 2.47) versus healthy implants (0.07 ± 0.19) after adjusting for amount of plaque collected per site (P = 0.033). CONCLUSIONS: Greater levels of dissolved titanium were detected in submucosal plaque around implants with peri-implantitis compared with healthy implants, indicating an association between titanium dissolution and peri-implantitis. Factors triggering titanium dissolution, as well as the role of titanium corrosion in the peri-implant inflammatory process, warrant further investigation.

Genotype-specific regulation of oral innate immunity by T2R38 taste receptor.

The bitter taste receptor T2R38 has been shown to regulate mucosal innate immune responses in the upper airway epithelium. Furthermore, SNPs in T2R38 influence the sensitivity to 6-n-propylthiouracil (PROP) and are associated with caries risk/protection. However, no study has been reported on the role of T2R38 in the innate immune responses to oral bacteria. We hypothesize that T2R38 regulates oral innate immunity and that this regulation is genotype-specific. Primary gingival epithelial cells carrying three common genotypes, PAV/PAV (PROP super-taster), AVI/PAV (intermediate) and AVI/AVI (non-taster) were stimulated with cariogenic bacteria Streptococcus mutans, periodontal pathogen Porphyromonas gingivalis or non-pathogen Fusobacterium nucleatum. QRT-PCR analyzed T2R38 mRNA, and T2R38-specific siRNA and ELISA were utilized to evaluate induction of hBD-2 (antimicrobial peptide), IL-1α and IL-8 in various donor-lines. Experiments were set up in duplicate and repeated three times. T2R38 mRNA induction in response to S. mutans was highest in PAV/PAV (4.3-fold above the unstimulated controls; p<0.05), while lowest in AVI/AVI (1.2-fold). In PAV/PAV, hBD-2 secretion in response to S. mutans was decreased by 77% when T2R38 was silenced. IL-1α secretion was higher in PAV/PAV compared to AVI/PAV or AVI/AVI with S. mutans stimulation, but it was reduced by half when T2R38 was silenced (p<0.05). In response to P. gingivalis, AVI/AVI showed 4.4-fold increase (p<0.05) in T2R38 expression, whereas the levels in PAV/PAV and AVI/PAV remained close to that of the controls. Secretion levels of IL-1α and IL-8 decreased in AVI/AVI in response to P. gingivalis when T2R38 was silenced (p<0.05), while the changes were not significant in PAV/PAV. Our data suggest that the regulation of gingival innate immunity by T2R38 is genotype-dependent and that the ability to induce a high level of hBD-2 by PAV/PAV carriers may be a reason for protection against caries in this group.

Titanates and Titanate-Metal Compounds in Biological Contexts.

Metal ions are notorious environmental contaminants, some causing toxicity at exquisitely low (ppm-level) concentrations. Yet, the redox properties of metal ions make them attractive candidates for bio-therapeutics. Titanates are insoluble particulate compounds of titanium and oxygen with crystalline surfaces that bind metal ions; these compounds offer a means to scavenge metal ions in environmental contexts or deliver them in therapeutic contexts while limiting systemic exposure and toxicity. In either application, the toxicological properties of titanates are crucial. To date, the accurate measurement of the in vitro toxicity of titanates has been complicated by their particulate nature, which interferes with many assays that are optical density (OD)-dependent, and at present, little to no in vivo titanate toxicity data exist. Compatibility data garnered thus far for native titanates in vitro are inconsistent and lacking in mechanistic understanding. These data suggest that native titanates have little toxicity toward several oral and skin bacteria species, but do suppress mammalian cell metabolism in a cells-pecific manner. Titanate compounds bind several types of metal ions, including some common environmental toxins, and enhance delivery to bacteria or cells. Substantial work remains to address the practical applicability of titanates. Nevertheless, titanates have promise to serve as novel vehicles for metal-based therapeutics or as a new class of metal scavengers for environmental applications.

DNA methylation differentially regulates cytokine secretion in gingival epithelia in response to bacterial challenges.

Epigenetic modifications are changes in gene expression without altering DNA sequence. We previously reported that bacteria-specific innate immune responses are regulated by epigenetic modifications. Our hypothesis is that DNA methylation affects gingival cytokine secretion in response to bacterial stimulation. Gingival epithelial cells (GECs) were treated with DNMT-1 inhibitors prior to Porphyromonas gingivalis (Pg) or Fusobacterium nucleatum (Fn) exposure. Protein secretion was assessed using ELISA. Gene expression was quantified using qRT-PCR. The ability of bacteria to invade inhibitor pretreated GECs was assessed utilizing flow cytometry. Changes were compared to unstimulated GECs. GEC upregulation of IL-6 and CXCL1 by Pg or Fn stimulation was significantly diminished by inhibitor pretreatment. Pg stimulated IL-1α secretion and inhibitor pretreatment significantly enhanced this upregulation, while Fn alone or with inhibitor pretreatment had no effect on IL-1α expression. GEC upregulation of human beta-definsin-2 in response to Pg and Fn exposure was enhanced following the inhibitor pretreatment. GEC susceptibility to bacterial invasion was unaltered. These results suggest that DNA methylation differentially affects gingival cytokine secretion in response to Pg or Fn. Our data provide basis for better understanding of how epigenetic modifications, brought on by exposure to oral bacteria, will subsequently affect host susceptibility to oral diseases.

Antibacterial activity of gold-titanates on Gram-positive cariogenic bacteria.

Objective: Gram-positive cariogenic bacteria are etiological agents in dental caries; therefore, strategies to inhibit these bacteria to reduce the incident of this disease have intensified. In this study, we investigated antibacterial activities of titanates and gold-titanates against Lactobacillus casei (Lc) and Streptococcus mutans (Sm). Materials and methods: Monosodium titanate (MST), nanomonosodium titanate (nMST) and amorphous peroxo-titanate (APT), which are inorganic compounds with high-binding affinity for specific metal ions, were used. Total bacterial proteins were measured to represent bacterial cell mass after 24 h incubation with gold-titanates. We further examined the effect of nMST-Au(III) concentrations (10,200,400 mg/L) on Lc and Sm cell viability over time via Live/Dead fluorescent staining and colony forming units (CFUs). Transmission electron microscopy (TEM) was used to determine specific locations on the bacterial cells affected by the nMST-Au(III). Results: We found all gold-titanates and APT alone reduced bacterial protein for Lc (p value <0.001) while only MST-Au(III) and nMST-Au(III) affected Sm growth (p value <0.001). Overall, nMST-Au(III) showed the most effectiveness against both Lc and Sm at 400 mg/L. The Live/Dead staining showed all concentrations of nMST-Au(III) affected Lc growth but only 200 and 400 mg/L nMST-Au(III) interrupted Sm growth. The growth curves based on CFUs/mL showed all nMST-Au(III) concentrations affected growth of both Lc and Sm. TEM images showed nMST-Au(III) attached to Lc and Sm cell wall and were internalized into both cells.Conclusions: nMST-Au(III) demonstrated potential antimicrobial activity against Gram-positive cariogenic bacteria. These results support further development of nMST-Au(III) as a potential novel material to prevent dental caries.

Ellagic acid modulates the expression of oral innate immune mediators: potential role in mucosal protection.

BACKGROUND: Ellagic acid (EA) found in various fruits such as pomegranates, blackberries, raspberries, strawberries, and walnuts has different pharmacological functions including antioxidant, antitumor, antiallergic, anti-inflammatory, antibacterial, and antiviral activities. It is not known, however, if EA could enhance mucosal innate immunity. Our goal was to determine the effects of EA on the expression of innate immune mediators produced by oral epithelial cells. METHODS: Culture of primary human gingival epithelial cells (HGEs) was performed in duplicate, and after the primary HGEs had been treated with EA at a concentration ranging from 12.5 to 100 µM for 18 h the cells and supernatants were harvested. The expression of innate immune mediators including human ß-defensin 2 (hBD2), secretory leukocyte protease inhibitor (SLPI), and various cytokines and chemokines was measured at both transcriptional and translational levels by using quantitative real-time PCR, ELISA, and Luminex assay. RESULTS: In the presence of EA, the expression of hBD2-and SLPI mRNA was 3.7-folds and 2.6-folds greater than untreated controls, respectively, and consistent with their secreted protein levels. For cytokines and chemokines, increased expression of RANTES, IL-2, and IL-1ß was found in response to EA. In contrast, EA decreased the expression of IL-6, IL-8, and TNF-α. CONCLUSIONS: This study demonstrated that oral innate immunity is affected by EA found in fruits. Thus, it may play some roles in mucosal innate immunity. The potential of EA for modulating the innate immune mediators may lead to developing a new topical agent to treat and/or prevent immune-mediated oral diseases.

Nickel alloys in the oral environment.

The use of nickel casting alloys for long-term restorations in dentistry has long been controversial. A 'tug-of-war' between economic, engineering and biological considerations is central to this controversy; nickel-casting alloys have low costs and favorable physical properties, but are corrosion-prone in the oral environment. Clinicians and researchers have questioned the safety of nickel-containing dental alloys because several nickel compounds are known to cause adverse biological effects in vivo and in vitro in contexts outside of dentistry. The debate revolves around the extent to which corrosion products from oral restorations cause intraoral or systemic biological problems. Current evidence suggests that nickel alloys may be used successfully and safely in dentistry if clinical risks are taken into account. However, these alloys may cause significant clinical problems, primarily allergenic and inflammatory, if the risks are ignored.

Effect of Ni(II) on inflammatory gene expression in THP1 monocytic cells.

Nickel-containing alloys are in common use for dental restorations, but tend to corrode and release Ni(II) in service. Ni(II) increases secretion of several inflammatory cytokines from activated monocytic cells, suggesting that nickel alloys may exaggerate inflammatory responses in adjacent periodontal tissues. In this work, the effects of Ni(II) on expression of inflammatory cytokine and receptor genes as well as nuclear factor-kappa B (NFκB)-related genes were assessed using quantitative real-time polymerase chain reaction (PCR) and PCR-based arrays in the human THP1 monocytic cell line pre-exposed to Ni(II) for 72 h, then activated by lipopolysaccharide. The expression of 10 inflammatory genes was down-regulated ≥50% by Ni(II) versus non-Ni(II) controls, whereas some genes like IL8 were up-regulated significantly by Ni(II). Expression of seven NFκB-related genes was up-regulated by Ni(II) by ≥50%, and HMOX1 expression, a redox protein regulated by NRF2, was increased by >500%. The current results suggest that Ni(II) has diverse effects on inflammatory gene expression, which may partly account for previous reports of Ni(II)-induced changes in inflammatory cytokine secretion from monocytes and alterations in NFκB regulation. Further work is needed to verify these effects in primary cells and to ascertain how Ni(II) alters gene expression.

Antimicrobial responses of primary gingival cells to Porphyromonas gingivalis.

BACKGROUND: Human beta-defensins (hBDs) and the C-C chemokine ligand 20 (CCL20) produced by gingival epithelial cells (GECs) and fibroblasts (HGFs) are antimicrobial peptides (AMPs) that play an important role in innate immunity. The aim of this study was to determine the differential immune response of GECs and HGFs to the oral commensal Streptococcus gordonii (SG) and the pathogen Porphyromonas gingivalis (PG). MATERIAL AND METHODS: In addition to the analysis of gingival biopsies, primary GECs and HGFs were exposed to SG and/or PG, and expression of various AMPs and pro-inflammatory mediators was studied by real-time PCR and ELISA. RESULTS: Gene expression of AMPs was detected in gingival connective tissue. Both SG and PG induced the mRNA-expression of hBD-2 and hBD-3 in GECs as well as HGFs after 24 h (p < 0.05). In HGFs, the commensal bacterium SG stimulated the mRNAs of hBD-3 and CCL20 after 24 h (p < 0.05), while not in GECs. In GECs, the inductive effect of PG on the mRNA-expression of hBD-2 was amplified when cells were first exposed to commensal SG (for 1 h) prior to stimulation with PG (SG-PG; p < 0.05). CONCLUSION: Our data indicate that cell-bacteria interactions and/or bacteria-bacteria cross-talk may have an impact on AMP-regulation in gingiva.

Ni(II) alters the NFκB signaling pathway in monocytic cells.

Nickel-based alloys are used for dental restorations because of their strength, high moduli, and relatively low cost. However, these alloys corrode significantly in use, particularly in lower pH environments that are common under oral biofilms. Ni(II) corrosion products increase inflammatory cytokine secretion from activated monocytes, suggesting that nickel alloys may exacerbate inflammatory responses in adjacent periodontal tissues caused by dental plaque. Because inflammatory cytokine secretion is regulated in part by the NFκB signaling pathway, our goal in the current work was to determine whether Ni(II) altered cellular levels or nuclear localization of NFκB-family subtypes. THP1 monocytes were exposed to Ni(II) for 72 h, and activated with lipopolysaccharide for the last 30 min to 6 h. Secretion of IL6 and TNFα were measured using ELISA, and NFκB levels and localization was measured using SDS-PAGE with immunoblots and digital analysis. We observed that Ni(II) did not alter the levels of secreted TNFα from activated monocytes, but increased secreted IL6 levels about 30% over controls. Ni(II) did not alter whole-cell levels of any NFκB subtype, but increased nuclear persistance of p65 and c-Rel. Our results suggest that Ni(II) may increase inflammatory cytokine secretion by increasing nuclear localization of some NFκB subtypes. Further studies should be done to determine the prominence of this mechanism in clinical environments.

Peroxotitanate- and monosodium metal-titanate compounds as inhibitors of bacterial growth.

Sodium titanates are ion-exchange materials that effectively bind a variety of metal ions over a wide pH range. Sodium titanates alone have no known adverse biological effects but metal-exchanged titanates (or metal titanates) can deliver metal ions to mammalian cells to alter cell processes in vitro. In this work, we test a hypothesis that metal-titanate compounds inhibit bacterial growth; demonstration of this principle is one prerequisite to developing metal-based, titanate-delivered antibacterial agents. Focusing initially on oral diseases, we exposed five species of oral bacteria to titanates for 24 h, with or without loading of Au(III), Pd(II), Pt(II), and Pt(IV), and measuring bacterial growth in planktonic assays through increases in optical density. In each experiment, bacterial growth was compared with control cultures of titanates or bacteria alone. We observed no suppression of bacterial growth by the sodium titanates alone, but significant (p < 0.05, two-sided t-tests) suppression was observed with metal-titanate compounds, particularly Au(III)-titanates, but with other metal titanates as well. Growth inhibition ranged from 15 to 100% depending on the metal ion and bacterial species involved. Furthermore, in specific cases, the titanates inhibited bacterial growth 5- to 375-fold versus metal ions alone, suggesting that titanates enhanced metal-bacteria interactions. This work supports further development of metal titanates as a novel class of antibacterials.

PAR1- and PAR2-induced innate immune markers are negatively regulated by PI3K/Akt signaling pathway in oral keratinocytes.

BACKGROUND: Protease-Activated Receptors (PARs), members of G-protein-coupled receptors, are activated by proteolytic activity of various proteases. Activation of PAR1 and PAR2 triggers innate immune responses in human oral keratinocytes (HOKs), but the signaling pathways downstream of PAR activation in HOKs have not been clearly defined. In this study, we aimed to determine if PAR1- and PAR2-mediated signaling differs in the induction of innate immune markers CXCL3, CXCL5 and CCL20 via ERK, p38 and PI3K/Akt. RESULTS: Our data show the induction of innate immunity by PAR1 requires both p38 and ERK MAP kinases, while PAR2 prominently signals via p38. However, inhibition of PI3K enhances expression of innate immune markers predominantly via suppressing p38 phosphorylation signaled by PAR activation. CONCLUSION: Our data indicate that proteases mediating PAR1 and PAR2 activation differentially signal via MAP kinase cascades. In addition, the production of chemokines induced by PAR1 and PAR2 is suppressed by PI3K/Akt, thus keeping the innate immune responses of HOK in balance. The results of our study provide a novel insight into signaling pathways involved in PAR activation.

Differential and coordinated expression of defensins and cytokines by gingival epithelial cells and dendritic cells in response to oral bacteria.

BACKGROUND: Epithelial cells and dendritic cells (DCs) both initiate and contribute to innate immune responses to bacteria. However, much less is known about the coordinated regulation of innate immune responses between GECs and immune cells, particularly DCs in the oral cavity. The present study was conducted to investigate whether their responses are coordinated and are bacteria-specific in the oral cavity. RESULTS: The beta-defensin antimicrobial peptides hBD1, hBD2 and hBD3 were expressed by immature DCs as well as gingival epithelial cells (GECs). HBD1, hBD2 and hBD3 are upregulated in DCs while hBD2 and hBD3 are upregulated in GECs in response to bacterial stimulation. Responses of both cell types were bacteria-specific, as demonstrated by distinctive profiles of hBDs mRNA expression and secreted cytokines and chemokines in response to cell wall preparations of various bacteria of different pathogenicity: Fusobacterium nucleatum, Actinomyces naeslundii and Porphyromonas gingivalis. The regulation of expression of hBD2, IL-8, CXCL2/GRObeta and CCL-20/MIP3alpha by GECs was greatly enhanced by conditioned medium from bacterially activated DCs. This enhancement was primarily mediated via IL-1beta, since induction was largely attenuated by IL-1 receptor antagonist. In addition, the defensins influence DCs by eliciting differential cytokine and chemokine secretion. HBD2 significantly induced IL-6, while hBD3 induced MCP-1 to approximately the same extent as LPS, suggesting a unique role in immune responses. CONCLUSIONS: The results suggest that cytokines, chemokines and beta-defensins are involved in interaction of these two cell types, and the responses are bacteria-specific. Differential and coordinated regulation between GECs and DCs may be important in regulation of innate immune homeostasis and response to pathogens in the oral cavity.

Interplay of protease-activated receptors and NOD pattern recognition receptors in epithelial innate immune responses to bacteria.

Protease-activated receptors (PARs), nucleotide-binding oligomerization domain (NOD) receptors and Toll-like receptors (TLRs) play a role in innate immunity, but little is known about interaction between these receptors. The goal of this study was to investigate how silencing one receptor affects the expression of other receptors and downstream innate immune markers in response to bacteria. Human gingival epithelial cells (GECs) were transfected with siRNA specific for PAR1 or PAR2, then stimulated with periopathogen Porphyromonas gingivalis, bridging organism between pathogens and non-pathogens Fusobacterium nucleatum, or non-pathogen Streptococcus gordonii. PAR1 or PAR2 knock-down resulted in up-regulated NOD1 and NOD2 expression with P. gingivalis or F. nucleatum stimulation (p<0.01), as well as enhanced TLR2 and TLR4 expression when cells were stimulated by bacteria that utilize TLR2 or TLR4, respectively. Involvement of PARs for induction of CC chemokine ligand 20 (CCL20), a cytokine with antimicrobial properties, was observed following stimulation of the three bacterial species. Furthermore, results from multiple cytokine ELISA array showed receptors utilized in the induction of various innate immune markers are tailored to individual bacterium tested. Our data suggest complex interplay of several receptors is required for appropriate innate immune responses to the different types of bacteria present within the oral cavity and that receptor expression itself is altered depending on which organism the cell encounters.

Differential effects of periopathogens on host protease inhibitors SLPI, elafin, SCCA1, and SCCA2.

OBJECTIVE: Secretory leukocyte peptidase inhibitors (SLPI), elafin, squamous cell carcinoma antigen 1 and 2 (SCCA1 and SCCA2) are specific endogenous serine protease inhibitors expressed by epithelial cells that prevent tissue damage from excessive proteolytic enzyme activity due to inflammation. To determine the effects of various periopathogens on these protease inhibitors, we utilized human gingival epithelial cells (GECs) challenged with cell-free bacteria supernatants of various periopathogens Porphyromonas gingivalis, Tannerella forsythia, Aggregatibacter actinomycetemcomitans, and Fusobacterium nucleatum. DESIGN: The gene expression and secretion of SLPI, elafin, SCCA1, and SCCA2 were determined using real-time PCR and ELISA, respectively. The direct effects of periopathogens and P. gingivalis gingipain mutants on these inhibitors were examined in vitro by Western Blot. The effect on the innate immune response of GECs was measured by expression of antimicrobial peptides: human beta-defenisin-2 (hBD2) and chemokine (C-C motif) ligand 20 (CCL20). RESULTS: We found that SLPI, SCCA2, elafin, hBD2, and CCL20 gene expression levels were significantly induced (p<0.001) in response to P. gingivalis, whose virulence factors include cysteine proteases, but not in response to stimulation by other bacteria. P. gingivalis reduced the secretion of SLPI and elafin significantly in GECs, and degraded recombinant SLPI, elafin, SCCA1, and SCCA2. Differential degradation patterns of SLPI, elafin, SCCA1, and SCCA2 were observed with different bacteria as well as P. gingivalis mutants associated with the loss of specific gingipains secreted by P. gingivalis. In addition, pretreatment of GECs with SLPI, SCCA1, or SCCA2 partially blocked hBD2 and CCL20 mRNA expression in response to P. gingivalis, suggesting a protective effect. CONCLUSION: Our results suggest that different periopathogens affect the host protease inhibitors in a different manner, suggesting host susceptibility may differ in the presence of these pathogens. The balance between cellular protease inhibitors and their degradation may be an important factor in susceptibility to periodontal infection.