Levels of Porphyromonas gingivalis Fimbriae and inflammatory cytokines in gingival crevicular fluid from adult human subjects

Cholesterol crystals enhance TLR2- and TLR4-mediated pro-inflammatory cytokine responses of monocytes to the proatherogenic oral bacterium Porphyromonas gingivalis

Cholesterol deposits and pro-inflammatory cytokines play an essential role in the pathogenesis of atherosclerosis, a predominant cause of cardiovascular disease (CVD). Epidemiological evidence has linked periodontal disease (PD) with atherosclerotic CVD. Accordingly, viable periodontal pathogens, including Porphyromonas gingivalis, have been found in atherosclerotic plaques in humans and mice. We aimed to determine whether cholesterol crystals (CHCs) and oral bacteria synergize in the stimulation of human monocytes. Incubation of human monocytes with CHCs induced secretion of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-6, and IL-8. Moreover, CHCs markedly enhanced secretion of IL-1β by monocytes stimulated with the toll-like receptor (TLR) 4 agonist Escherichia coli lipopolysaccharide (LPS), and the TLR2 agonist Staphylococcus aureus lipoteichoic acid. Notably, CHCs also enhanced IL-1β secretion induced by P. gingivalis LPS and IL-1β secretion induced by whole P. gingivalis bacteria. This enhancement was abrogated by the NLRP3 inflammasome inhibitors Z-YVAD-FMK and glibenclamide. CHCs had no effect on cytokine production induced by P. gingivalis gingipains. Taken together, our findings support that CHCs, via stimulation of NLRP3 inflammasomes, act in synergy with the periodontal pathogen P. gingivalis to promote monocyte secretion of pro-atherogenic cytokines.

A pathogenic trace of Tannerella forsythia - shedding of soluble fully active tumor necrosis factor α from the macrophage surface by karilysin

Tannerella forsythia is implicated as a pathogen causing chronic and aggressive periodontitis. However, its virulence factors, including numerous putative proteases, are mostly uncharacterized. Karilysin is a newly described matrix metalloprotease-like enzyme of T. forsythia. Since pathogen-derived proteases may affect the host defense system via modulation of the cytokine network, the aim of this study was to determine the influence of karilysin on tumor necrosis factor-α (TNF-α). The results showed that karilysin cleaved the membrane form of TNF-α on the surface of macrophages, and that this led to an increased concentration of soluble TNF-α in the conditioned medium. Importantly, despite partial degradation of soluble TNF-α by karilysin, the released cytokine retained its biological activity, inducing apoptosis and stimulating autocrine pathway of pro-inflammatory gene expression. Notably, the observed effect required proteolytic activity by karilysin, since a catalytically inactive mutant of the enzyme did not affect TNF-α secretion. The shedding was independent of the activity of ADAM17, a major endogenous TNF-α converting enzyme. Karilysin-dependent TNF-α release from the cell surface is likely to occur in vivo because human plasma, the main constituent of gingival crevicular fluid, only slightly affected the sheddase activity of karilysin. Taken together, these results indicate that karilysin modulates the host immune response through regulation of TNF-α secretion, and should therefore be considered as a new virulence factor of T. forsythia.

MAPK usage in periodontal disease progression

In periodontal disease, host recognition of bacterial constituents, including lipopolysaccharide (LPS), induces p38 MAPK activation and subsequent inflammatory cytokine expression, favoring osteoclastogenesis and increased net bone resorption in the local periodontal environment. In this paper, we discuss evidence that the p38/MAPK-activated protein kinase-2 (MK2) signaling axis is needed for periodontal disease progression: an orally administered p38α inhibitor reduced the progression of experimental periodontal bone loss by reducing inflammation and cytokine expression. Subsequently, the significance of p38 signaling was confirmed with RNA interference to attenuate MK2-reduced cytokine expression and LPS-induced alveolar bone loss. MAPK phosphatase-1 (MKP-1), a negative regulator of MAPK activation, was also critical for periodontal disease progression. In MPK-1-deficient mice, p38-sustained activation increased osteoclast formation and bone loss, whereas MKP-1 overexpression dampened p38 signaling and subsequent cytokine expression. Finally, overexpression of the p38/MK2 target RNA-binding tristetraprolin (TTP) decreased mRNA stability of key inflammatory cytokines at the posttranscriptional level, thereby protecting against periodontal inflammation. Collectively, these studies highlight the importance of p38 MAPK signaling in immune cytokine production and periodontal disease progression.

B cells as under-appreciated mediators of non-auto-immune inflammatory disease

B lymphocytes play roles in many auto-immune diseases characterized by unresolved inflammation, and B cell ablation is proving to be a relatively safe, effective treatment for such diseases. B cells function, in part, as important sources of regulatory cytokines in auto-immune disease, but B cell cytokines also play roles in other non-auto-immune inflammatory diseases. B cell ablation may therefore benefit inflammatory disease patients in addition to its demonstrated efficacy in auto-immune disease. Current ablation drugs clear both pro- and anti-inflammatory B cell subsets, which may unexpectedly exacerbate some pathologies. This possibility argues that a more thorough understanding of B cell function in human inflammatory disease is required to safely harness the clinical promise of B cell ablation. Type 2 diabetes (T2D) and periodontal disease (PD) are two inflammatory diseases characterized by little autoimmunity. These diseases are linked by coincident presentation and alterations in toll-like receptor (TLR)-dependent B cell cytokine production, which may identify B cell ablation as a new therapy for co-affected individuals. Further analysis of the role B cells and B cell cytokines play in T2D, PD and other inflammatory diseases is required to justify testing B cell depletion therapies on a broader range of patients.

Targeting mRNA stability arrests inflammatory bone loss

Many proinflammatory cytokines contain adenylate-uridylate-rich elements (AREs) within the 3'-untranslated region (UTR) that confer rapid mRNA destabilization. During the inflammatory response, cytokine mRNA are stabilized via complex interactions with RNA-binding proteins controlled by phosphorylation via multiple signaling pathways including the mitogen-activated protein kinases (MAPKs). In the absence of inflammation, a key cytokine-regulating RNA-binding protein, tristetraprolin (TTP), shuttles mRNA transcripts to degradation machinery in order to maintain low levels of inflammatory cytokines. Using this general model of mRNA decay, over expression of TTP was evaluated in an experimental model of inflammatory bone loss to determine whether altering cytokine mRNA stability has an impact in pathological bone resorption. Using adenoviral-delivered TTP, significant reductions of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and prostaglandin (PG)E(2) were observed in vitro through a mechanism consistent with targeting mRNA stability. In vivo analysis indicates a significant protective effect from inflammation-induced bone loss and inflammatory infiltrate in animals overexpressing TTP compared with reporter controls. These findings provide experimental evidence that mRNA stability is a valid therapeutic target in inflammatory bone loss.

p38 MAPK signaling in oral-related diseases

Multiple dental diseases are characterized by chronic inflammation, due to the production of cytokines, chemokines, and prostanoids by immune and non-immune cells. Membrane-bound receptors provide a link between the extracellular environment and the initiation of intracellular signaling events that activate common signaling components, including p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and nuclear factor (NF)-kappaB. Although ERK pathways regulate cell survival and are responsive to extracellular mitogens, p38 MAPK, JNK, and NF-kappaB are involved in environmental stress responses, including inflammatory stimuli. Over the past decade, significant advances have been made relative to our understanding of the fundamental intracellular signaling mechanisms that govern inflammatory cytokine expression. The p38 MAPK pathway has been shown to play a pivotal role in inflammatory cytokine and chemokine gene regulation at both the transcriptional and the post-transcriptional levels. In this review, we present evidence for the significance of p38 MAPK signaling in diverse dental diseases, including chronic pain, desquamative disorders, and periodontal diseases. Additional information is presented on the molecular mechanisms whereby p38 signaling controls post-transcriptional gene expression in inflammatory states.

Targeting of Porphyromonas gingivalis with a bispecific antibody directed to FcalphaRI (CD89) improves in vitro clearance by gingival crevicular neutrophils

Phagocytosis and killing of pathogens by polymorphonuclear neutrophils (PMN) from gingival crevicular fluid (GCF) is diminished in chronic periodontitis patients. As an approach to improve targeting of PMN toward a periodontopathogen, Porphyromonas gingivalis, the efficacy of a bispecific antibody (BsAb) directed against both recombinant 130 kDa hemagglutinin domain (r130k-HMGD) of P. gingivalis, and PMN Fc receptor (FcR) was evaluated. GCF PMN exhibited higher IgA FcR (FcalphaRI) levels, and lower IgG FcR (FcgammaRIIa and FcgammaRIIIb) levels than PB PMN. Functional studies revealed that GCF PMN exhibited a higher capacity to phagocytose and kill P. gingivalis opsonized with a BsAb targeting P. gingivalis r130k-HMGD to FcalphaRI as compared to an anti-r130k-HMGD antibody. However, phagocytosis and killing activity of PB PMN that were incubated with the two antibodies proved comparable. These data support targeting of pathogens toward FcalphaRI as an option to improve antibacterial immunity in chronic periodontitis patients.

Inactivation of membrane tumor necrosis factor alpha by gingipains from Porphyromonas gingivalis

Gingipains are cysteine proteinases produced by Porphyromonas gingivalis, a major causative bacterium of adult periodontitis. They consist of arginine-specific (HRgpA and RgpB) and lysine-specific (Kgp) proteinases. Gingipains strongly affect the host defense system by degrading some cytokines, components of the complement system, and several immune cell receptors. In an in vitro model, gingipains were shown to degrade soluble tumor necrosis factor alpha (TNF-alpha). However, since membrane TNF-alpha shows strong biological activity, especially in local inflammatory lesions, it was worth investigating whether gingipains might also destroy membrane TNF-alpha and limit its biological activities. To avoid a possible influence of gingipains on ADAM17, the secretase of TNF-alpha, the majority of experiments were performed using ADAM17-/- fibroblasts stably transfected with cDNA of human pro-TNF-alpha (ADAM17-/- TNF+). Arginine-specific gingipains (Rgp's) strongly diminished the level of TNF-alpha on the cell surface as measured by flow cytometry, and this process was not accompanied by an increased concentration of soluble TNF-alpha in the culture medium. Degradation of membrane TNF-alpha by Rgp's correlated with a strong decrease in TNF-alpha-mediated biological activities of ADAM17-/- TNF+ cells. First, the activation state of transcription factor NF-kappaB was suppressed; second, the cells were no longer able to induce apoptosis in HL-60 cells. Kgp was also able to cleave membrane TNF-alpha, but its effect was much weaker than that of Rgp's. Gingipains also limited the binding of native TNF-alpha to the target cells. Thus, gingipains are able not only to cleave soluble TNF-alpha but also to destroy the membrane form of the cytokine, which may additionally dysregulate the cytokine network.

Localization of Porphyromonas gingivalis-carrying fimbriae in situ in human periodontal pockets

Fimbriae, which are involved in adherence, constitute an important pathogenic factor of Porphyromonas gingivalis. In vivo, however, the distribution of P. gingivalis-carrying fimbriae is unknown. The localization of P. gingivalis-carrying fimbriae was examined in situ. From 19 patients with severe periodontitis and P. gingivalis, we obtained 20 teeth with periodontal tissue attached, with and without immunolocalized fimbriae. Eleven teeth were subjected to light microscopy, 9 to electron microscopy. In 6 of the 11 samples examined, we detected positive reactions with an anti-P. gingivalis-fimbriae serum, located in the cementum-attached plaque area in the deep pocket zones. In the so-called 'plaque-free zones', P. gingivalis-carrying fimbriae were immunocytochemically observed to reside in contact with the dental cuticle in 6 of the 9 samples examined. These findings suggest that P. gingivalis-carrying fimbriae are strongly related to adherence to the root surface at the bottoms of human periodontal pockets.

Cytokine profile in gingival crevicular fluid of aggressive periodontitis: influence of smoking and stress

BACKGROUND

Cigarette smoking and stress are considered risk factors that have been associated with periodontal disease progression. Conflicting results have been reported concerning the direct influence of smoking on the subgingival microbiota of periodontitis patients. Cytokine production may also be influenced by smoking and stress leading to an imbalance that disturbs the host-parasite relationship.

AIM

The objective of the present study was to evaluate the influence of cigarette smoking on the gingival crevicular fluid (GCF) levels of interleukin (IL)-1beta, IL-4, IL-6 and IL-8 in aggressive or early onset periodontitis (EOP) patients and in healthy controls (H), psychosocial stress being considered as modifying factor.

MATERIAL AND METHODS

Sixty-five EOP and 35 periodontally healthy individuals participated in this cross-sectional study. All the participants were interviewed about their smoking habits and their stressful social events. Clinical examination included the assessment of plaque index (PI), bleeding on probing (BOP), clinical attachment level (CAL) and probing pocket depth (PPD). GCF was collected using durapore strips, from four sites per patient, randomly selected in each quadrant. The total amounts of IL-1beta, IL-4, IL-6 and IL-8 were measured in a total of 400 samples using commercially available enzyme-linked immunosorbent assays.

RESULTS

All clinical parameters were significantly higher in the EOP group compared to the H group. There were no significant differences between EOP smokers and EOP non-smokers with regard to plaque accumulation, CAL and PPD of the sampling sites, whereas mean CAL and PPD of the diseased sites were greater in EOP smokers than in EOP non-smokers. In addition, EOP smokers seemed to have significantly less BOP and greater bone loss compared to EOP non-smokers. Significant interactions between "EOP" and "smoking" were present for total amounts of IL-1beta and IL-4. IL-1beta, IL-6 and IL-8 showed significant main effects with healthy smokers and healthy non-smokers, respectively. For IL-8, stress presented a statistically significant interaction with smoking status and EOP (F=4.742, p=0.030). More specifically EOP smokers were statistically affected by stress.

CONCLUSIONS

Smoking influences host-related factors including cytokine network. The relative importance of smoking and stress-related alterations and their precise mode of action in increasing the risk of aggressive periodontitis remains to be elucidated.

Interleukin 1 and receptor antagonist levels in gingival crevicular fluid in heavy smokers versus non-smokers

BACKGROUND/AIMS

This study aimed to investigate the concentration of the cytokine interleukin (IL)-1beta and its receptor antagonist IL-1ra in gingival crevicular fluid (GCF) in patients with adult periodontitis who were heavy smokers compared with non-smokers.

METHOD

GCF samples were collected from two groups of subjects: smokers and non-smokers. Thirty-nine GCF samples were harvested from 13 subjects with moderate to severe adult periodontitis who were heavy smokers. A further 30 GCF samples were harvested from 10 subjects with moderate to severe adult periodontitis who were non-smokers. Subjects were selected from both genders and none had any relevant systemic illness, were pregnant, had recent medication or had received any periodontal therapy in the preceding 3 months. One deep bleeding site, one deep non-bleeding site and one healthy site were investigated in each subject. Clinical measurements were recorded for each site, after obtaining a GCF sample using a Periopaper strip. IL-1beta and IL-1ra were quantified using new commercially available ELISA kits (Quantikine), and could be detected in all samples.

RESULTS

For smokers, the mean concentrations for IL-1beta were 2714.5 (SD 4416.2) pg/ micro L for healthy sites, 37.0 (SD 57.2) pg/ micro L for non-bleeding periodontitis sites and 24.5 (SD 29.2) pg/ micro L for bleeding periodontitis sites. The concentrations of IL-1beta for non-smokers for the same category of sites were 393.8 (SD 867.1), 74.2 (SD 107.0) and 73.1 (SD 61.0) pg/ micro L, respectively. The mean concentrations of IL-1ra for smokers were 5.8 x 10(5) (SD 9.7) pg/ micro L for healthy sites, 2.2 x 10(5) (SD 0.15) pg/ micro L for deep non-bleeding sites and 0.19 x 10(5) (SD 0.07) pg/ micro L for deep bleeding sites. The concentrations for non-smokers were: 4.1 x 10(10) (SD 3.8), 18.1 x 10(5) (SD 20.4) and 3.2 x 10(5) (SD 2.3) pg/ micro L, respectively. Significance levels of P < 0.05 were found for comparisons of healthy vs. deep bleeding and deep non-bleeding sites for IL-1beta and IL-1ra in smokers, before adjustments for multiple testing. However, none of these comparisons reached statistical significance following adjustments for multiple testing. P < 0.05 for the correlation between IL-1beta and IL-1ra at healthy sites in smokers only. Differences in GCF concentrations for IL-1beta in smokers vs. non-smokers were significant for deep bleeding sites only (P < 0.05), the mean concentration of IL-1beta being lower in GCF from smokers vs. non-smokers. All differences in GCF concentrations of IL-1ra reached statistical significance for smokers vs. non-smokers. The mean concentrations of IL-1ra in GCF were lower in smokers compared with non-smokers for all categories of sites.

CONCLUSIONS

A decreased concentration of IL-1beta and also IL-1ra was found in GCF from periodontitis sites compared to healthy sites in smokers and in non-smokers, although this did not reach statistical significance following adjustments for multiple testing. For comparisons between heavy smokers and non-smokers, statistically significant differences were found in the GCF concentrations of IL-1beta from deep bleeding sites only. Statistically significant differences were found in the IL-1ra concentrations for smokers vs. non-smokers for all categories of sites.

Hepatocyte growth factor in gingival crevicular fluid and the distribution of hepatocyte growth factor-activator in gingival tissue from adult periodontitis

Hepatocyte growth factor (HGF), also known as scatter factor, is a broad-spectrum and multifunctional cytokine required for the development, growth and regeneration of various organs and tissues. The expression of HGF in human gingival fibroblasts is induced by inflammatory cytokines such as interleukin 1. Thus, although it is possible that content of HGF in gingival crevicular fluid (GCF) in periodontitis is increased, this has not so far been reported because the volume of GCF is too small to determine HGF by the available enzyme-linked immunosorbent assay (ELISA). A recently developed, highly sensitive ELISA for HGF, with a detection limit of 1 pg/ml sample, has now enabled HGF to be measured in GCF.The mean HGF content in GCF from sites with clinically healthy gingiva, defined by the absence of overt signs of gingival inflammation and a probing depth (PD) <3 mm, was 1.7 ng/ml, and that of periodontitis, defined by obvious alveolar bone loss detected by radiographic examination and a PD> or =3 mm, was 3.23 ng/ml. Although treating the periodontitis did not significantly decrease the HGF concentration despite significantly improved clinical scores such as PD and Gingival Index, the total amount of HGF in GCF did decrease significantly after treatment. HGF was expressed by gingival fibroblasts and inflammatory cells as determined by in situ hybridization. HGF-activator (HGFA), which converts inactive pro-HGF to active mature HGF, was detected in gingival epithelial cells by immunostaining. The expression of HGFA was also confirmed in gingival tissue by reverse transcription-polymerase chain reaction (RT-PCR). These findings indicate that HGF is synthesized and activated in gingiva that is clinically healthy or associated with periodontitis.

Effective in vitro clearance of Porphyromonas gingivalis by Fc alpha receptor I (CD89) on gingival crevicular neutrophils

Porphyromonas gingivalis has been implicated as a causative pathogen in periodontitis. Immunotherapeutic approaches have recently been suggested to aid in the clearance of P. gingivalis from disease sites. Because antibody-Fc receptor (FcR) interactions play a role in the effector functions of polymorphonuclear neutrophils (PMN), we evaluated which FcR on PMN from gingival crevicular fluid (GCF) serves as an optimal target molecule for FcR-directed immunotherapy. GCF PMN and peripheral blood (PB) PMN from adult periodontitis patients were analyzed for their immunoglobulin G (IgG) and IgA FcR (Fc gamma R and Fc alpha R, respectively) expression and function by studying IgG- and IgA-mediated elimination of P. gingivalis. GCF PMN exhibited higher Fc alpha RI and Fc gamma RI levels and lower Fc gamma RIIa and Fc gamma RIIIb levels than PB PMN. Functional studies revealed that GCF PMN exhibited less of a capacity to phagocytose and kill IgG1-opsonized P. gingivalis than PB PMN. IgA1-mediated phagocytosis and killing capacity was, however, comparable between GCF PMN and PB PMN. In summary, these in vitro results document that Fc alpha RI represents a candidate target for FcR-directed immunotherapy for the clearance of P. gingivalis.

Enhanced interleukin-1beta, interleukin-6 and tumor necrosis factor-alpha production by LPS stimulated human monocytes isolated from HIV+ patients

Periodontal disease and tooth loss is a common finding among advanced HIV+ patients. In addition to local oral lipopolysaccharide (LPS) stimulation, systemic up-regulation of monocyte pro-inflammatory cytokine secretion may also be involved in the pathogenesis of HIV disease. A study was undertaken to investigate IL-1beta, IL-6 and TNF-alpha production by resting and LPS stimulated monocytes isolated from HIV+ patients and also to investigate the relationship of the patient's HIV viral load status to the cytokine production. Whole blood samples in EDTA were collected from 39 HIV-1 infected patients and 20 age and sex matched uninfected controls. Plasma was separated by centrifugation. Viral load was determined using a quantitative RT-PCR. Monocytes were isolated by Ficoll-hypaque gradient separation followed by overnight plastic adherence. Cultured monocytes (1x10(6)/ml) were stimulated with LPS (1 microg/ml) of either P. gingivalis or F. nucleatum for 2, 8, 24 and 48 h and supernatant fluids were collected. IL-1beta, IL-6, and TNF-alpha levels in supernatant fluids were estimated by ELISA. Increased overall production of IL-1beta, IL-6 and TNF-alpha by LPS stimulated monocytes isolated from HIV-1 infected patients was observed when compared to HIV-1 uninfected controls. LPS stimulated monocytes from HIV-1 infected patients with high viral load (HVL) produced significant (p<0.05) elevations in these pro-inflammatory cytokines when compared to HIV-1 uninfected controls. Both LPS of P. gingivalis and F. nucleatum produced a comparable cytokine production by monocytes after 8 h of stimulation. These data suggest that enhanced IL-1beta, IL-6 and TNF-alpha is produced by monocytes/macrophages isolated from HVL HIV+ patients and may be involved in the overall pathogenesis of HIV-1 infection.

Enhanced interleukin 1 beta, interleukin 6 and tumor necrosis factor alpha in gingival crevicular fluid from periodontal pockets of patients infected with human immunodeficiency virus 1

Loss of periodontal support and eventually tooth loss is a common finding among acquired immunodeficiency syndrome (AIDS) patients. The cause of this destruction may be an increase in periodontal disease activity at sites within the same individual and also may be related to an increase in the pro-inflammatory cytokines, diffused through the gingival crevicular sulcus in AIDS patients. A study was undertaken to determine the relative levels of the pro-inflammatory cytokines, interleukin 1 beta (IL-1 beta), IL-6, and tumor necrosis factor alpha (TNF-alpha), in gingival crevicular fluid collected from the deep (> 5 mm periodontal pocket depth) and shallow (< or = 3 mm periodontal pocket depth) periodontal pockets of 39 HIV-1-infected patients and 20 age-, race- and sex-matched uninfected controls. Complete medical history including risk factors such as intravenous drug abuse was taken. Gingival crevicular fluid samples were collected on periopaper strips. Cytokines were estimated by solid-phase enzyme-linked immunosorbent assay. To assess the degree of HIV activity, the viral load of these patients was determined by an Amplicor HIV-1 monitor kit using reverse transcriptase polymerase chain reaction. Gingival crevicular fluid from HIV-1-infected patients showed a two-fold increase in both IL-1 beta and TNF-alpha in deep periodontal pockets in comparison to shallow pockets, whereas IL-6 increased 1.8-fold. There was a significant (P < 0.05) increase in IL-1 beta, IL-6 and TNF-alpha in gingival crevicular fluid (both shallow and deep pockets) from HIV-1-infected patients in comparison to uninfected controls and also significantly elevated in deep versus shallow pockets in these patients. Although IL-1 beta, L-6 and TNF-alpha levels among HIV-1-infected patients with a high viral load (> 10,000 copies/ml) were higher than those from patients with a low viral load (< 400 copies/ml), only the increase in IL-1 beta level associated with deep pockets was significant (P < 0.05). There was also a trend of an increase in all the three cytokines among intravenous drug-abusing HIV-1-infected patients in comparison to non-intravenous drug abusers, but only the difference in IL-1 beta levels from deep pockets reached significance (P < 0.05). These enhanced pro-inflammatory cytokine levels in the gingival crevicular fluid of HIV-positive patients may be an important factor in causing the advanced periodontal lesions sometimes observed in HIV-positive patients.

Root-surface caries in rats and humans: inhibition by a non-antimicrobial property of tetracyclines

The incidence of root caries has been found to increase as the population ages and as edentulism becomes less prevalent due to improved dental awareness and care, and as exposure of roots due to gingival recession has also increased in the elderly. The mechanism of root caries is thought to be mediated by both bacterial and mammalian proteases produced by plaque and the periodontal tissues, respectively. In the current study, a rat model of periodontal disease was used in which gnotobiotic rats were infected intra-orally with a periodontal pathogen (P. gingivalis). Infecting the rats with P. gingivalis increased the collagenase activity in the gingival tissue in association with severe alveolar bone loss. Treating P. gingivalis-infected rats with doxycycline or CMT-1 prevented the destruction of the periodontium by MMPs, thus preventing exposure of roots to subgingival bacterial plaque and host tissue collagenases and the subsequent development of root caries. In addition, a low-dose doxycycline (LDD, 20 mg bid, non-antimicrobial dose) for 3 months was used in humans predisposed to increased root caries as the result of heavy use of smokeless (chewing) tobacco, causing gingival recession, subgingival plaque accumulation with Gram-negative bacteria, increased gingival crevicular fluid flow (GCF), and elevated GCF collagenase. Daily administration of LDD in smokeless tobacco patients reduced the GCF collagenase and prevented the further development of root caries.

Relationship between C-telopeptide pyridinoline cross-links (ICTP) and putative periodontal pathogens in periodontitis

Crevicular fluid pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP) is predictive for future alveolar bone loss in experimental periodontitis in dogs. The present study sought to relate ICTP to a panel of subgingival species in subjects exhibiting various clinical presentations such as health (n=7), gingivitis (n=8) and periodontitis (n=21). 28 subgingival plaque and GCF samples were taken from mesiobuccal sites in each of 36 subjects. The presence and levels of 40 subgingival taxa were determined in plaque samples using whole genomic DNA probes and checkerboard DNA-DNA hybridization. GCF ICTP levels were quantified using radioimmunoassay (RIA). Clinical assessments made at the same sites included: BOP, gingival redness, plaque, pocket depth, and attachment level. Differences among ICTP levels in the 3 subject groups were sought using the Kruskal-Wallis test. Relationships between ICTP levels and clinical parameters as well as subgingival species were determined by regression analysis. The results demonstrated significant differences among disease categories for GCF ICTP levels for healthy (1.1+0.6 pg/site (mean+/-SEM)) gingivitis (14.8+/-6.6 pg/site) and periodontitis subjects (30.3+5.7 pg/site) (p= 0.0017). ICTP levels related modestly to several clinical parameters. Regression analysis indicated that ICTP levels correlated strongly with mean subject levels of several periodontal pathogens including B. forsythus, P. gingivalis, P. intermedia, P. nigrescens and T. denticola (p<0.01). The data indicate that there is a positive relationship between the putative bone resorptive marker ICTP and periodontal pathogens.