Serum Antibodies to Porphyromonas gingivalis Chaperone HtpG Predict Health in Periodontitis Susceptible Patients

Chaperones are ubiquitous conserved proteins critical in stabilization of new proteins, repair/removal of defective proteins and immunodominant antigens in innate and adaptive immunity. Periodontal disease is a chronic inflammatory infection associated with infection by Porphyromonas gingivalis that culminates in the destruction of the supporting structures of the teeth. We previously reported studies of serum antibodies reactive with the human chaperone Hsp90 in gingivitis, a reversible form of gingival disease confined to the oral soft tissues. In those studies, antibodies were at their highest levels in subjects with the best oral health. We hypothesized that antibodies to the HSP90 homologue of P. gingivalis (HtpG) might be associated with protection/resistance against destructive periodontitis.

Impaired Immune Tolerance to Porphyromonas gingivalis Lipopolysaccharide Promotes Neutrophil Migration and Decreased Apoptosis.

Periodontitis, a chronic inflammatory disease of the tissues supporting the teeth, is characterized by an exaggerated host immune and inflammatory response to periopathogenic bacteria. Toll-like receptor activation, cytokine network induction, and accumulation of neutrophils at the site of inflammation are important in the host defense against infection. At the same time, induction of immune tolerance and the clearance of neutrophils from the site of infection are essential in the control of the immune response, resolution of inflammation, and prevention of tissue destruction. Using a human monocytic cell line, we demonstrate that Porphyromonas gingivalis lipopolysaccharide (LPS), which is a major etiological factor in periodontal disease, induces only partial immune tolerance, with continued high production of interleukin-8 (IL-8) but diminished secretion of tumor necrosis factor alpha (TNF-) after repeated challenge. This cytokine response has functional consequences for other immune cells involved in the response to infection. Primary human neutrophils incubated with P. gingivalis LPS-treated naïve monocyte supernatant displayed a high migration index and increased apoptosis. In contrast, neutrophils treated with P. gingivalis LPS-tolerized monocyte supernatant showed a high migration index but significantly decreased apoptosis. Overall, these findings suggest that induction of an imbalanced immune tolerance in monocytes by P. gingivalis LPS, which favors continued secretion of IL-8 but decreased TNF- production, may be associated with enhanced migration of neutrophils to the site of infection but also with decreased apoptosis and may play a role in the chronic inflammatory state seen in periodontal disease.

Possible potentiation of toxins from Prevotella intermedia, Prevotella nigrescens, and Porphyromonas gingivalis by cotinine

BACKGROUND: Smoking is a recognized risk factor for the initiation and progression of periodontitis. However, the mechanism by which smoking induces its negative effects on the periodontium is not clear. This study aimed to test the hypothesis that synergy may occur between cotinine and bacterial products isolated from 3 putative periodontopathogens.

METHODS: A chick embryo toxin assay was used to investigate bacterial toxins (cell-free extracellular toxins and cell-free cell lysates) from 5 species with and without cotinine. A total of 9 putative periodontopathogens (3 species) and 2 non-oral controls (2 species) were studied. The periodontal species were: Prevotella intermedia (n = 4), Prevotella nigrescens (n = 4), and Porphyromonas gingivalis (n = 1). The control species tested were: Staphylococcus aureus (n = 1) and Escherichia coli (n = 1).

RESULTS: The toxicity kill was significantly greater than expected by simple addition alone (P <0.05, Fisher's exact test) between cotinine (800 ng/ml) and 1) the cell-free extracellular toxins of P. nigrescens MH1 and 2) the cell-free cell lysates of P. intermedia MH2. Synergy occurred with cotinine plus the cell-free extracellular toxins in all but 3 periodontal isolates, and the cell-free cell lysates in all but 2 periodontal isolates. Cotinine significantly (P <0.05, Fisher's exact test) enhanced the effects of cell-free extracellular toxins and cell lysates from one control species (E. coli), but not the other (S. aureus).

CONCLUSIONS: These findings indicate that synergy in an in vitro assay can occur between cotinine and toxins from putative periodontopathogens. This may be one important mechanism by which smoking increases the severity of periodontitis.

LL-37 Degradation by GCF: A Role for Porphyromonas gingivalis Proteinases?

Background: LL-37, composed of 37 amino acid residues, is an innate host defence peptide of the cathelicidin family. It is expressed by neutrophils, monocytes and epithelial cells and exhibits both anti-bacterial and immunomodulatory properties. LL-37 is however prone to proteolytic degradation by proteinases, thus potentially limiting its inherent host defence properties in the inflammatory milieu. Objectives: The present study was designed to determine whether LL-37 was degraded by components of gingival crevicular fluid (GCF) from healthy subjects or those with periodontitis. In addition, we aimed to deduce whether degradation of the peptide was accelerated in GCF samples which were determined to be positive for the periodontopathic bacterium Porphyromonas gingivalis. Methods: GCF and bacterial plaque samples, pre- and post non-surgical periodontal treatment, were collected from 4 individual sites in patients presenting with advanced periodontitis. In healthy subjects, GCF samples only were collected. Plaque samples were analysed by QPCR for the presence or absence of P. gingivalis. Pooled GCF samples from healthy sites; periodontitis sites which were P. gingivalis negative (Pg-); or periodontitis sites which were P. gingivalis positive (Pg+), were incubated with synthetic LL-37 for 0 – 180 min. The degradation products were then analysed by matrix-assisted laser desorption/ionisation time of flight mass spectrometry (MALDI-TOF MS). Results: LL-37 was not degraded when incubated with GCF from healthy subjects. In contrast, LL-37 was degraded after 30 min when incubated with Pg- GCF. However degradation of LL-37 was apparent after only 2 min incubation with Pg+ GCF and the parent molecule was almost completely degraded after 30 min. Conclusions: The rapid degradation of LL-37, particularly in Pg+ sites, highlights the limited role which this host defence peptide may play in the presence of biologically active proteinases. It also underscores a potent virulence mechanism of P. gingivalis used to circumvent innate host responses.

Synthesis, Kinetic Evaluation and Utilization of a Biotinylated Dipeptide Proline Diphenyl Phosphonate for the Disclosure of Dipeptidyl Peptidase IV-like Serine Proteases

In this study, we report on the synthesis, kinetic characterisation, and application of a novel biotinylated and active site-directed inactivator of dipeptidyl peptidase IV (DPP-IV). Thus, the dipeptide-derived proline diphenyl phosphonate NH(2)-Glu(biotinyl-PEG)-Pro(P)(OPh)(2) has been prepared by a combination of classical solution- and solid-phase methodologies and has been shown to be an irreversible inhibitor of porcine DPP-IV, exhibiting an over all second-order rate constant (k(i)/K(i)) for inhibition of 1.57 x 10(3) M(-1) min(-1). This value compares favourably with previously reported rates of inactivation of DPP-IV by dipeptides containing a P(1) proline diphenyl phosphonate grouping [B. Boduszek, J. Oleksyszyn, C.M. Kam, J. Selzler, R.E. Smith, J.C. Powers, Dipeptide phophonates as inhibitors of dipeptidyl peptidase IV, J. Med. Chem. 37 (1994) 3969-3976; B.F. Gilmore, J.F. Lynas, C.J. Scott, C. McGoohan, L. Martin, B. Walker, Dipeptide proline diphenyl phosphonates are potent, irreversible inhibitors of seprase (FAPalpha), Biochem, Biophys. Res. Commun. 346 (2006) 436-446.], thus demonstrating that the incorporation of the side-chain modified (N-biotinyl-3-(2-(2-(3-aminopropyloxy)-ethoxy)-ethoxy)-propyl) glutamic acid residue at the P(2) position is compatible with inhibitor efficacy. The utilisation of this probe for the detection of both purified dipeptidyl peptidase IV and the disclosure of a dipeptidyl peptidase IV-like activity from a clinical isolate of Porphyromonas gingivalis, using established electrophoretic and Western blotting techniques previously developed by our group, is also demonstrated.

Altered Toll-like Receptor 2-mediated Endotoxin Tolerance Is Related to Diminished Interferon β Production

Induction of endotoxin tolerance leads to a reduced inflammatory response after repeated challenge by LPS and is important for resolution of inflammation and prevention of tissue damage. Enterobacterial LPS is recognized by the TLR4 signaling complex, whereas LPS of some non-enterobacterial organisms is capable of signaling independently of TLR4 utilizing TLR2-mediated signal transduction instead. In this study we report that Porphyromonas gingivalis LPS, a TLR2 agonist, fails to induce a fully endotoxin tolerant state in a human monocytic cell line (THP-1) and mouse bone marrow-derived macrophages. In contrast to significantly decreased production of human IL-8 and TNF-alpha and, in mice, keratinocyte-derived cytokine (KC), macrophage inflammatory protein-2 (MIP-2), and TNF-alpha after repeated challenge with Escherichia coli LPS, cells repeatedly exposed to P. gingivalis LPS responded by producing less TNF-alpha but sustained elevated secretion of IL-8, KC, and MIP-2. Furthermore, in endotoxin-tolerant cells, production of IL-8 is controlled at the signaling level and correlates well with NF-kappa B activation, whereas TNF-alpha expression is blocked at the gene transcription level. Interferon beta plays an important role in attenuation of chemokine expression in endotoxin-tolerized cells as shown in interferon regulatory factor-3 knock-out mice. In addition, human gingival fibroblasts, commonly known not to display LPS tolerance, were found to be tolerant to repeated challenge by LPS if pretreated with interferon beta. The data suggest that the inability of the LPS-TLR2 complex to induce full endotoxin tolerance in monocytes/macrophages is related to diminished production of interferon beta and may partly explain the involvement of these LPS isoforms in the pathogenesis of chronic inflammatory diseases.

Antimicrobial and immunomodulatory properties of PGLa-AM1, CPF-AM1, and magainin-AM1: Potent activity against oral pathogens

Cationic amphipathic α-helical peptides are intensively studied classes of host defence peptides (HDPs). Three peptides, peptide glycine-leucine-amide (PGLa-AM1), caerulein-precursor fragment (CPF-AM1) and magainin-AM1, originally isolated from norepinephrine-stimulated skin secretions of the African volcano frog Xenopus amieti (Pipidae), were studied for their antimicrobial and immunomodulatory activities against oral and respiratory pathogens. Minimal effective concentrations (MECs), determined by radial diffusion assay, were generally lower than minimal inhibitory concentrations (MICs) determined by microbroth dilution. PGLa-AM1 and CPF-AM1 were particularly active against Streptococcus mutans and all three peptides were effective against Fusobacterium nucleatum, whereas Enterococcus faecalis and Candida albicans proved to be relatively resistant micro-organisms. A type strain of Pseudomonas aeruginosa was shown to be more susceptible than the clinical isolate studied. PGLa-AM1 displayed the greatest propensity to bind lipopolysaccharide (LPS) from Escherichia coli, P. aeruginosa and Porphyromonas gingivalis. All three peptides showed less binding to P. gingivalis LPS than to LPS from the other species studied. Oral fibroblast viability was unaffected by 50. μM peptide treatments. Production of the pro-inflammatory cytokine IL-8 by oral fibroblasts was significantly increased following treatment with 1 or 10. μM magainin-AM1 but not following treatment with PGLa-AM1 or CPF-AM1. In conclusion, as well as possessing potent antimicrobial actions, the X. amieti peptides bound to LPS from three human pathogens and had no effect on oral fibroblast viability. CPF-AM1 and PGLa-AM1 show promise as templates for the design of novel analogues for the treatment of oral and dental diseases associated with bacteria or fungi.

The association between subgingival periodontal pathogens and systemic inflammation

Aim To investigate associations between periodontal disease pathogens and levels of systemic inflammation measured by C-reactive protein (CRP). Methods A representative sample of dentate 60-70-year-old men in Northern Ireland had a comprehensive periodontal examination. Men taking statins were excluded. Subgingival plaque samples were analysed by quantitative real time PCR to identify the presence of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia. High-sensitivity CRP (mg/l) was measured from fasting blood samples. Multiple linear regression analysis was performed using log-transformed CRP concentration as the dependent variable, with the presence of each periodontal pathogen as predictor variables, with adjustment for various potential confounders. Results A total of 518 men (mean age 63.6 SD 3.0 years) were included in the analysis. Multiple regression analysis showed that body mass index (p < 0.001), current smoking (p < 0.01), the detectable presence of P. gingivalis (p < 0.01) and hypertension (p = 0.01), were independently associated with an increased CRP. The detectable presence of P. gingivalis was associated with a 20% (95% confidence interval 4-35%) increase in CRP (mg/l) after adjustment for all other predictor variables. Conclusion In these 60-70-year-old dentate men, the presence of P. gingivalis in subgingival plaque was significantly associated with a raised level of C-reactive protein.

Interferon-γ stimulates CD14, TLR2 and TLR4 mRNA expression in gingival fibroblasts increasing responsiveness to bacterial challenge

Objective: To investigate the potential effects of IFN-y on the responsiveness of human gingival fibroblasts to bacterial challenge.
Design :mRNA and protein expression of CD14, TLR2 and TLR4 in human gingival fibroblasts was detected by quantitative polymerase chain reaction (Q-PCR) and flow cytometry. The effect of preincubation with IFN-y on subsequent bacterial LPS-induced expression of IL-6 and IL-8 by gingival fibroblasts was determined by ELISA. Bacterial LPS-induced IκBα degradation in human gingival fibroblasts was investigated by western blot.
Results: Human gingival fibroblasts express CD14, TLR2 and TLR4 mRNAs. IFN-y, but not IL-1B, induced mRNA expression of all three receptors and the expression of membrane bound CD14 protein. Pre-incubation of fibroblasts with IFN-y and subsequent stimulation with Escherichia coli LPS or Porphyromonas gingivalis LPS led to increased production of IL-6 and IL-8. LPS-induced pro-inflammatory cytokine production was abrogated by a blocking antibody to CD14. Both E. coli LPS and P. gingivalis LPS induced IκBα degradation in human gingival fibroblasts.
Conclusion: Our data indicate that IFN-y primes human gingival fibroblasts, through the upregulation of CD14 expression, which results in increased responsiveness to bacterial LPS challenge, as determined by pro-inflammatory cytokine production.

A microbiological study of Papillon-Lefévre syndrome in two patients

AIM: To analyse the microflora of subgingival plaque from patients with Papillon-Lefévre syndrome (PLS), which is a very rare disease characterised by palmar-plantar hyperkeratosis with precocious periodontal destruction.

METHODS: Bacterial isolates were identified using a combination of commercial identification kits, traditional laboratory tests, and gas liquid chromatography. Some isolates were also subjected to partial 16S rDNA sequencing. Plaque samples were also assayed for the presence of Porphyromonas gingivalis, Prevotella intermedia, and Actinobacillus actinomycetemcomitans in a quantitative enzyme linked immunosorbent assay (ELISA) using monoclonal antibodies.

RESULTS: The culture results showed that most isolates were capnophilic and facultatively anaerobic species-mainly Capnocytophaga spp and Streptococcus spp. The latter included S. constellatus, S. oralis, and S. sanguis. Other facultative bacteria belonged to the genera gemella, kingella, leuconostoc, and stomatococcus. The aerobic bacteria isolated were species of neisseria and bacillus. Anaerobic species included Prevotella intermedia, P. melaninogenica, and P. nigrescens, as well as Peptostreptococcus spp. ELISA detected P gingivalis in one patient in all sites sampled, whereas A. actinomycetemcomitans was detected in only one site from the other patient. Prevotella intermedia was present in low numbers.

CONCLUSIONS: Patients with PLS have a very complex subgingival flora including recognised periodontal pathogens. However, no particular periodontopathogen is invariably associated with PLS.

LL-37 quantification in gingival crevicular fluid (GCF) from periodontitis patients

Background: LL-37, an anti-microbial peptide belonging to the cathelicidin family, derives its name from two N-terminal leucine residues and the 37 amino acids comprising the peptide. LL-37 is the only known cathelicidin to exist in humans. It exhibits both anti-bacterial and immunomodulatory properties. Objectives: In the current study, LL-37 was quantified in GCF from periodontitis patients. Previous studies have relied on qualitative results from Western blotting to detect LL-37 in GCF. This study aims to quantitatively determine LL-37 levels in GCF. Methods: GCF and bacterial plaque samples, pre- and post non-surgical periodontal treatment, were collected from 4 sites in 12 patients presenting with advanced periodontitis. Plaque samples were analysed by QPCR for the presence or absence of the periodontopathic bacterium Porphyromonas gingivalis (P. gingivalis). The concentrations of LL-37 in patient samples pre- and post-treatment were deduced by indirect enzyme linked immunosorbent assay (ELISA). Results: Concentrations of LL-37 in samples varied between a minimum and maximum of 1 and 40 ng/ml. LL-37 levels were shown, pre-treatment, to be higher in deep pockets (6-9 mm) compared with shallower pockets (3-5 mm) and highest in those sites which were positive for P. gingivalis. Non-surgical therapy resulted in a significant improvement in clinical indices while expression levels of P. gingivalis were reduced. Following treatment, LL-37 levels in GCF decreased from an average of 6.5 ± 1 - 5.8 ± 1.2 ng/ml. The most interesting observation however was the reduction in LL-37 levels, from an average of 7 ± 1.3 – 2.5 ± 1.1 ng/ml in those sites where P. gingivalis infection was eradicated post-treatment. Conclusions: LL-37 levels are increased at sites showing advanced periodontal disease, reduce following treatment and appear to be linked to the presence of P. gingivalis. This study will further our knowledge of host defence in chronic diseases such as periodontitis.