The host response to the microbial challenge in periodontitis: assembling the players

Levels of interleukin-37 in gingival crevicular fluid, saliva, or plasma in periodontal disease

BACKGROUND AND OBJECTIVE

The aim of this study was to compare the levels of levels of interleukin-37 (IL-37) in gingival crevicular fluid, saliva and plasma in patients with periodontal disease and patients with healthy periodontium and to correlate these levels with clinical parameters.

MATERIAL AND METHODS

Samples of gingival crevicular fluid, whole saliva and plasma were collected from systemically healthy, nonsmoker periodontally healthy controls (group 1, n = 20), gingivitis patients (group 2, n = 20) and chronic periodontitis patients (group 3, n = 20). Full-mouth clinical periodontal parameters, including probing depth, plaque index, gingival index and bleeding on probing, were also recorded. IL-37 levels in the biofluid samples were determined by ELISA. Data were tested statistically using the Kruskal-Wallis test followed by the Mann-Whitney U-test.

RESULTS

The concentration of IL-37 in gingival crevicular fluid was significantly lower in group 3 than in groups 1 and 2 (p = 0.001), whereas the total amounts in gingival crevicular fluid samples were similar (p > 0.05). The salivary and plasma concentrations of IL-37 were similar in the study groups (p > 0.05). There were negative correlations between gingival crevicular fluid IL-37 concentrations and gingival crevicular fluid volume in all groups (p < 0.05). There was also a negative correlation between the gingival crevicular fluid IL-37 concentration and gingival index in group 3 (p < 0.05).

CONCLUSIONS

IL-37 was expressed in all biofluids. According to our findings, the total amount of IL-37 in gingival crevicular fluid, or salivary or plasma concentrations of IL-37, may not be useful diagnostic markers to differentiate periodontal disease and the periodontally healthy condition. The difference in gingival crevicular fluid IL-37 concentration between the study groups may be a result of the variation in gingival crevicular fluid volume, as suggested by the negative correlation between gingival crevicular fluid volume and gingival crevicular fluid IL-37 concentration. In the light of our findings, it seems that IL-37 is not involved in periodontal disease. Further comprehensive studies may clarify this issue more clearly.

The effect of IL-4 gene polymorphisms on cytokine production in patients with chronic periodontitis and in healthy controls

Chronic periodontitis (CP) is an inflammatory disease of the teeth-supporting tissues in which genetic predisposition, dental plaque bacteria, and immune mechanisms all play important roles. The aim of this study was to evaluate the occurrence of IL-4 gene polymorphisms in chronic periodontitis and to investigate the association between polymorphisms and cytokines production after bacterial stimulation. Sixty-two subjects (47 CP patients and 15 healthy controls) with detected two polymorphisms in the IL-4 gene (-590C/T and intron 3 VNTR) were examined. Production of cytokines (IL-1α, IL-1β, IL-4, IL-5, IL-6, IL-10, IL-17, TNFα, INFγ, and VEGF) was studied after in vitro stimulation of isolated peripheral blood by mitogens (Pokeweed mitogen, Concanavalin A), dental plaque bacteria (Aggregatibacter actinomycetemcomitans, Tannerella forsythia, Porphyromonas gingivalis, and Prevotella intermedia), and Heat Shock Protein (HSP) 70 by the Luminex multiplex cytokine analysis system. The results were correlated with IL-4 genotypes in patients with CP and healthy controls. The mononuclear cells isolated from peripheral blood of CP patients with selected IL-4 polymorphisms significantly altered the production of IFNγ, IL-10, IL-1β, IL-1α, TNFα, and IL-6 after stimulation by HSP 70 or selected bacteria (from P < 0.001 to P < 0.05). IL-4 gene polymorphisms may influence the function of mononuclear cells to produce not only interleukin-4 but also other cytokines, especially in patients with CP.

Effect of periodontal therapy on salivary interleukin-12 levels in chronic periodontitis

BACKGROUND

Interleukin-12 (IL-12) is considered a central regulator of host resistance against a variety of pathogens. The influence of scaling and root planing was evaluated on amount of IL-12 in salivary fluid of patients with chronic generalized severe periodontitis, in relation to clinical parameters.

MATERIALS AND METHODS

A total of 50 subjects were enrolled, of which 25 had chronic generalized severe periodontitis, and 25 periodontally healthy as control. The clinical parameters included plaque index (PI), gingival index (GI), pocket probing depth (PPD) bleeding on probing (BOP) and clinical attachment loss (CAL). The level of IL-12 in salivary fluid was measured by ELISA kit at baseline and at four week following scaling and root planing.

RESULTS

Mean IL-12 levels in patients with periodontitis at baseline (9.79 ± 5.70 pg/ml) were higher than in controls (9.18±4.94 pg/ml; p=0.54.) Scaling and root planing resulted in significant increase in IL-12 levels (mean: 15.93±12.09 pg/ml; p =0.001) (control vs postoperative p <0.001). No significant correlations were found between IL-12 levels and any of the above clinical parameters.

CONCLUSION

Short-term nonsurgical therapy resulted in a significant improvement in periodontal indices and a marked increase in IL-12 levels.

Porphyromonas gingivalis gingipains selectively reduce CD14 expression, leading to macrophage hyporesponsiveness to bacterial infection

Cysteine proteases (gingipains) from Porphyromonas gingivalis are key virulence factors in chronic periodontitis. Innate immune receptors CD14, Toll-like receptor (TLR) 2 and TLR4 are important in P. gingivalis recognition. We examined the ability of gingipains to cleave CD14, TLR2 and TLR4, and the consequences for the cellular response to bacterial challenge. Macrophages were exposed to Arg (RgpA and RgpB)- and Lys (Kgp)-gingipains, and residual expression of TLR2, TLR4 and CD14 was determined by flow cytometry. The cellular response to live bacteria following exposure to purified gingipains was evaluated by TNFα production and bacterial phagocytosis. RgpA and Kgp decreased CD14 detection in a concentration (p = 0.0000002)- and time (p = 0.03)-dependent manner, whereas RgpB had no significant effect. TLR2 and TLR4 expression were unaffected. Reduction in CD14 expression was more efficient with Lys-gingipain than with Arg-gingipain. A reduced CD14 surface level correlated with decreased TNFα secretion and bacterial phagocytosis following challenge with live P. gingivalis, but the response to heat-killed bacteria was unaffected. Therefore, gingipains reduce CD14 expression without affecting expression of the bacterial-sensing TLRs. Reduced CD14 expression depends on the gingipain hemagglutinin/adhesion site and results in macrophage hyporesponsiveness to bacterial challenge. Further studies are needed to determine if reduced CD14 expression is linked to periodontitis induced by P. gingivalis.

Differential expression of transglutaminase genes in patients with chronic periodontitis

OBJECTIVE

Gingival epithelium plays a key role in the protection of oral tissues from microbial challenge, especially during the periodontal disease. This study was aimed to evaluate levels of mRNA transcripts of different forms of transglutaminase in the human gingival tissues from patients with chronic periodontitis and relative controls.

SUBJECTS AND METHODS

This study included 22 patients with chronic periodontitis (CP) and 22 healthy controls. For each patient, the values of probing depth (PD), clinical attachment level (CAL), and bleeding on probing (BOP) were recorded. Gene expression of transglutaminase 1, transglutaminase 2, transglutaminase 3, and metalloprotease 2 was evaluated by real-time PCR, while that of Factor XIIIA and metalloprotease 9 by RT-PCR.

RESULTS

The values of all the clinical parameters were significantly higher in the CP group than in the healthy control group (P < 0.05). In the CP group, the mRNA expression of transglutaminase 1 and transglutaminase 3 was significantly decreased in comparison with healthy control group. A slight nonsignificant changes of transglutaminase 2 gene expression were observed in samples from CP patients in comparison with controls.

CONCLUSIONS

These observations suggest that transglutaminase gene expression may be modified in response to chronic injury in the damaged gingival and emphasizes the key role of these enzymes in gingival remodelling/healing and adaptive processes.

Origin of galactose-deficient immunoglobulin g in gingival crevicular fluid in periodontitis

BACKGROUND

Periodontitis is a chronic inflammatory disease initiated by a synergistic and dysbiotic microbial community that elicits a gingival inflammatory response leading to tissue breakdown. Periodontitis shares many characteristics with other chronic inflammatory diseases, including abnormal glycosylation of immunoglobulin (Ig)G. The current authors have previously demonstrated that IgG from gingival crevicular fluid (GCF) of patients with chronic periodontitis contains galactose (Gal)-deficient IgG.

METHODS

The origin of the aberrantly glycosylated IgG was determined by measuring levels of Gal-deficient IgG in GCF and serum from patients with periodontitis and non-periodontitis controls using lectin enzyme-linked immunosorbent assay. The Ig-producing cells and the proportion of cells producing Gal-deficient IgG were immunohistochemically determined in gingival tissues from patients with periodontitis by fluorescence microscopy. The results were statistically evaluated and correlated with clinical data.

RESULTS

The results indicate that GCF of patients with periodontitis had higher levels of Gal-deficient IgG compared with controls (P = 0.002). In gingival tissues, IgG was the dominant isotype among Ig-producing cells, and 60% of IgG-positive cells produced Gal-deficient IgG. Moreover, the proportion of Gal-deficient IgG-producing cells directly correlated with clinical parameters of probing depth and clinical attachment loss (AL).

CONCLUSION

These results suggest that the presence of Gal-deficient IgG is associated with gingival inflammation and may play a role in the worsening of clinical parameters of periodontitis, such as AL.

Salivary biomarkers associated with gingivitis and response to therapy

BACKGROUND

Salivary biomarkers are potentially important for determining the presence, risk, and progression of periodontal disease. However, clinical translation of biomarker technology from lab to chairside requires studies that identify biomarkers associated with the transitional phase between health and periodontal disease (i.e., gingivitis).

METHODS

Eighty participants (40 with gingivitis, 40 healthy) provided saliva at baseline and 7 to 30 days later. An additional sample was collected from gingivitis participants 10 to 30 days after dental prophylaxis. Clinical parameters of gingival disease were recorded at baseline and the final visit. Salivary concentrations of interleukin (IL)-1β, IL-6, matrix metalloproteinase (MMP)-8, macrophage inflammatory protein (MIP)-1α, and prostaglandin E2 (PGE2) were measured.

RESULTS

Clinical features of health and gingivitis were stable at both baseline visits. Participants with gingivitis demonstrated significantly higher bleeding on probing (BOP), plaque index (PI), and gingival index (GI) (P ≤0.002) and a significant drop in BOP, PI, and GI post-treatment (P ≤0.001). Concentrations of MIP-1α and PGE2 were significantly higher (2.8 times) in the gingivitis group than the healthy group (P ≤0.02). After dental prophylaxis, mean biomarker concentrations did not decrease significantly from baseline in the gingivitis group, although concentrations of IL-1β, IL-6, and MMP-8 approached healthy levels, whereas MIP-1α and PGE2 concentrations remained significantly higher than in the healthy group (P ≤0.04). Odds ratio analyses showed that PGE2 concentrations, alone and in combination with MIP-1α, readily discriminated gingivitis from health.

CONCLUSIONS

Salivary PGE2 and MIP-1α discriminate gingivitis from health, and patients with gingivitis who return to clinical health continue to produce inflammatory mediators for weeks after dental prophylaxis.

Impact of the Oral Commensal Flora on Alveolar Bone Homeostasis

Homeostasis of healthy periodontal tissues is affected by innate and adaptive immunosurveillance mechanisms in response to the normal oral flora. Recent comparisons of germ-free (GF) and normal specific-pathogen-free (SPF) mice have revealed the impact of host immunosurveillance mechanisms in response to the normal oral flora on alveolar bone height. Prior reports that alveolar bone height is significantly less in normal SPF mice compared with their age- and strain-matched GF counterparts suggest that naturally occurring alveolar bone loss is a normal component of healthy periodontal tissue homeostasis. In this report, histomorphometric analyses confirmed increased alveolar bone loss and revealed increased numbers of TRAP+ osteoclastic cells lining the alveolar bone surface in SPF compared with GF mice. Increased numbers of RANKL+ cells and IL17+ cells in the periodontium of SPF mice demonstrate possible molecular mechanisms mediating the up-regulated osteoclastogenesis and alveolar bone loss in SPF mice compared with GF mice. Increased numbers of T-lymphocytic cells and T-helper cells in the junctional epithelium of SPF mice compared with GF mice suggest that the adaptive immune response contributes to physiologic alveolar bone loss in the healthy periodontium. This GF animal model study notably begins to elucidate the impact of host immunosurveillance mechanisms in response to the normal oral flora, mediating catabolic alveolar bone homeostasis in the healthy periodontium.

Protein biomarkers of periodontitis in saliva

Periodontitis is a chronic inflammatory condition of the tissues that surround and support the teeth and is initiated by inappropriate and excessive immune responses to bacteria in subgingival dental plaque leading to loss of the integrity of the periodontium, compromised tooth function, and eventually tooth loss. Periodontitis is an economically important disease as it is time-consuming and expensive to treat. Periodontitis has a worldwide prevalence of 5-15% and the prevalence of severe disease in western populations has increased in recent decades. Furthermore, periodontitis is more common in smokers, in obesity, in people with diabetes, and in heart disease patients although the pathogenic processes underpinning these links are, as yet, poorly understood. Diagnosis and monitoring of periodontitis rely on traditional clinical examinations which are inadequate to predict patient susceptibility, disease activity, and response to treatment. Studies of the immunopathogenesis of periodontitis and analysis of mediators in saliva have allowed the identification of many potentially useful biomarkers. Convenient measurement of these biomarkers using chairside analytical devices could form the basis for diagnostic tests which will aid the clinician and the patient in periodontitis management; this review will summarise this field and will identify the experimental, technical, and clinical issues that remain to be addressed before such tests can be implemented.

Association between hypertension and periodontitis: possible mechanisms

This review is to examine the current literatures on the relationship between periodontitis and hypertension as well as to explore the possible biological pathways underlying the linkage between these health conditions. Hypertension is one of the major risk factors for cardiovascular diseases. Oxidative stress and endothelial dysfunction are among the critical components in the development of hypertension. Inflammation has received much attention recently and may contribute to a pivotal role in hypertension. Periodontitis, a chronic low-grade inflammation of gingival tissue, has been linked to endothelial dysfunction, with blood pressure elevation and increased mortality risk in hypertensive patients. Inflammatory biomarkers are increased in hypertensive patients with periodontitis. Over the years, various researches have been performed to evaluate the involvement of periodontitis in the initiation and progression of hypertension. Many cross-sectional studies documented an association between hypertension and periodontitis. However, more well-designed prospective population trials need to be carried out to ascertain the role of periodontitis in hypertension.

Higher expression of galectin-3 and galectin-9 in periapical granulomas than in radicular cysts and an increased toll-like receptor-2 and toll-like receptor-4 expression are associated with reactivation of periapical inflammation

INTRODUCTION

Cysts and periapical granulomas are inflammatory reactions that develop in response to periapical infection by microbial species in dental root canal. It is known that toll-like receptors (TLRs) are pathogen recognition molecules and that galectins are lectins that can be associated with the inflammatory process, stimulating or inhibiting the immune system. The objective of this study was to evaluate the in situ expression of TLRs and galectins in radicular cysts and periapical granulomas.

METHODS

We analyzed 62 cases (30 radicular cysts, 27 periapical granulomas, and 5 control cases). Indirect immunohistochemistry was used to evaluate the expression of TLRs (TRL-2 and TLR-4) and galectins (Gal-3 and Gal-9).

RESULTS

The expression of Gal-3 and Gal-9 was significantly higher in periapical granulomas and radicular cysts than in the control group. Similarly, both Gal-3 and Gal-9 were expressed significantly more in periapical granulomas than in radicular cysts. The expression of TLR-2 was significantly higher in periapical granulomas and radicular cysts than in the control group, and it was also significantly higher in radicular cysts with sinus tract than in the cases without sinus tract. Furthermore, the expression of TLR-4 was significantly higher in the cases of periapical granulomas with sinus tract than in the cases without sinus tract.

CONCLUSIONS

Gal-3/Gal-9 and TLR-2/TLR-4 expression in the periapical granulomas and radicular cysts is associated with reactive periapical inflammation. Pathobiology of periapical disease is a very complex interplay of many bioactive molecules involved in immunoinflammatory responses. Up-regulation of these bioactive molecules might be an important modulator of inflammatory periapical lesions.

Oral health education and therapy reduces gingivitis during pregnancy

BACKGROUND

Pregnant women demonstrate increases in gingivitis despite similar plaque levels to non-pregnant counterparts.

AIM

To evaluate an intensive protocol aimed at reducing gingivitis in pregnant women and provide pilot data for large-scale randomized controlled trials investigating oral hygiene measures to reduce pregnancy gingivitis and alter maternity outcomes.

MATERIALS AND METHODS

One hundred and twenty participants between 16 and 24 weeks gestation with Gingival Index (GI) scores ≥2 at ≥50% of tooth sites were enrolled. Plaque index (PI), gingival inflammation (GI), probing depth (PD), and clinical attachment levels (CAL) were recorded at baseline and 8 weeks. Dental prophylaxis was performed at baseline and oral hygiene instructions at baseline, 4 and 8 weeks. Pregnancy outcomes were recorded at parturition. Mixed-model analysis of variance was used to compare clinical measurements at baseline and 8 weeks.

RESULTS

Statistically significant reductions in PI, GI, PD, and CAL occurred over the study period. Mean whole mouth PI and GI scores decreased approximately 50% and the percentage of sites with PI and GI ≥2 decreased from 40% to 17% and 53% to 21.8%, respectively. Mean decreases in whole mouth PD and CAL of 0.45 and 0.24 mm, respectively, were seen.

CONCLUSIONS

Intensive oral hygiene regimen decreased gingivitis in pregnant patients.

DHA suppresses Prevotella intermedia lipopolysaccharide-induced production of proinflammatory mediators in murine macrophages

Several reports have indicated that dietary intake of DHA is associated with lower prevalence of periodontitis. In the present study, we investigated the effect of DHA on the production of proinflammatory mediators in murine macrophage-like RAW264.7 cells stimulated with lipopolysaccharide (LPS) isolated from Prevotella intermedia, a pathogen implicated in inflammatory periodontal disease, and its mechanisms of action. LPS was isolated from lyophilised P. intermedia ATCC 25,611 cells using the standard hot-phenol-water protocol. Culture supernatants were collected and assayed for NO, IL-1β and IL-6. Real-time PCR analysis was carried out to detect the expression of inducible NO synthase (iNOS), IL-1β, IL-6 and haeme oxygenase-1 (HO-1) mRNA. Immunoblot analysis was carried out to quantify the expression of iNOS and HO-1 protein and concentrations of signalling proteins. DNA-binding activities of NF-κB subunits were determined using an ELISA-based assay kit. DHA significantly attenuated the production of NO, IL-1β and IL-6 at both gene transcription and translation levels in P. intermedia LPS-activated RAW264.7 cells. DHA induced the expression of HO-1 in cells treated with P. intermedia LPS. Selective inhibition of HO-1 activity by tin protoporphyrin IX significantly mitigated the inhibitory effects of DHA on LPS-induced NO production. DHA significantly attenuated the phosphorylation of c-Jun N-terminal kinase induced by LPS. In addition, DHA suppressed the transcriptional activity of NF-κB by regulating the nuclear translocation and DNA-binding activity of NF-κB p50 subunit and inhibited the phosphorylation of signal transducer and activator of transcription 1. Further in vivo studies are needed to better evaluate the potential of DHA in humans as a therapeutic agent to treat periodontal disease.

Body mass index as a predictive factor of periodontal therapy outcomes

Body mass index (BMI) and obesity are associated with the prevalence, extent, and severity of periodontitis. This study investigated the predictive role of overweight/obesity on clinical response following non-surgical periodontal therapy in patients with severe periodontitis. Two hundred sixty adults received an intensive course of non-surgical periodontal therapy. Periodontal status at baseline and 2 months was based upon probing pocket depths (PPD), clinical attachment levels (CAL), and whole-mouth gingival bleeding (FMBS) as assessed by two calibrated examiners. Generalized estimating equations (GEE) were used to estimate the impact of BMI and overweight/obesity on periodontal treatment response while controlling for baseline status, age, smoking status (smoker or non-smoker), and full-mouth dental plaque score. BMI (continuous variable) and obesity (vs. normal weight) were associated with worse mean PPD (p < .005), percentage of PPD > 4 mm (p = .01), but not with FMBS (p > .05) or CAL (p > .05) at 2 months, independent of age, smoking status, or dental plaque levels. The magnitude of this association was similar to that of smoking, which was also linked to a worse clinical periodontal outcome (p < .01). BMI and obesity appear to be independent predictors of poor response following non-surgical periodontal therapy.

Secondary lymphoid organ homing phenotype of human myeloid dendritic cells disrupted by an intracellular oral pathogen

Several intracellular pathogens, including a key etiological agent of chronic periodontitis, Porphyromonas gingivalis, infect blood myeloid dendritic cells (mDCs). This infection results in pathogen dissemination to distant inflammatory sites (i.e., pathogen trafficking). The alteration in chemokine-chemokine receptor expression that contributes to this pathogen trafficking function, particularly toward sites of neovascularization in humans, is unclear. To investigate this, we utilized human monocyte-derived DCs (MoDCs) and primary endothelial cells in vitro, combined with ex vivo-isolated blood mDCs and serum from chronic periodontitis subjects and healthy controls. Our results, using conditional fimbria mutants of P. gingivalis, show that P. gingivalis infection of MoDCs induces an angiogenic migratory profile. This profile is enhanced by expression of DC-SIGN on MoDCs and minor mfa-1 fimbriae on P. gingivalis and is evidenced by robust upregulation of CXCR4, but not secondary lymphoid organ (SLO)-homing CCR7. This disruption of SLO-homing capacity in response to respective chemokines closely matches surface expression of CXCR4 and CCR7 and is consistent with directed MoDC migration through an endothelial monolayer. Ex vivo-isolated mDCs from the blood of chronic periodontitis subjects, but not healthy controls, expressed a similar migratory profile; moreover, sera from chronic periodontitis subjects expressed elevated levels of CXCL12. Overall, we conclude that P. gingivalis actively "commandeers" DCs by reprogramming the chemokine receptor profile, thus disrupting SLO homing, while driving migration toward inflammatory vascular sites.

Pathogen levels and clinical response to periodontal treatment in patients with Interleukin 8 haplotypes

The aim of this study was to investigate the effect of non-surgical treatment of periodontitis on the levels of periodontopathogens and clinical parameters in patients with different genetic backgrounds produced by polymorphisms in the Interleukin ( IL8) gene. Thirty patients grouped according to IL8 ATC/TTC or AGT/TTC haplotypes were submitted to non-surgical periodontal treatment. Levels of Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola were determined in 240 subgingival plaque samples by qPCR. The association between IL8 haplotypes and the levels of periodontopathogens and clinical parameters was investigated by multilevel analysis accounting for the clustering of diseased sites analyzed within patients. It was observed that neither levels of periodontopathogens nor non-surgical treatment was associated with the IL8 haplotype. The clinical parameters after periodontal treatment were similar in diseased and healthy sites, independently of the IL8 haplotype. Nonetheless, in the same period, diseased sites of AGT/TTC patients harbored higher levels of P. gingivalis, T. denticola, T. forsythia, and red complex than those of ATC/TTC patients. However, the non-surgical periodontal therapy decreased the levels of these periodontopathogens and of the tested clinical parameters of diseased sites in both groups. Non-surgical therapy is equally effective in improving clinical parameters and decreasing the levels of periodontopathogens, independent of the genotype groups produced by the IL8 haplotype.

Defensins and LL-37: a review of function in the gingival epithelium

Antimicrobial peptides represent an important aspect of the innate defense system that contributes to the control of bacterial colonization and infection. As studies have progressed it has become clear that antimicrobial peptides manifest other functions in addition to their antimicrobial effects. These functions include chemotaxis of numerous types of host cells involved in both the innate and adaptive immune responses. In this review, the antimicrobial activity, the regulation and the contribution to host homeostasis of alpha-defensins and LL-37, as well as of beta-defensins, are discussed in the context of their specific tissue locations in the junctional epithelium and oral epithelium, respectively.

The role of osteoimmunology in periodontal disease

Periodontal disease is a pathological condition that involves inflammation of the tooth supporting structures. It occurs in response to the presence of bacterial plaque on the tooth structure. The host defense system, including innate and adaptive immunity, is responsible for combating the pathologic bacteria invading the periodontal tissue. Failure to eradicate the invading pathogens will result in a continuous state of inflammation where inflammatory cells such as lymphocytes, PMNs, and macrophages will continue to produce inflammatory mediators in an effort to destroy the invaders. Unfortunately, these inflammatory mediators have a deleterious effect on the host tissue as well as foreign microbes. One of the effects of these mediators on the host is the induction of matrix degradation and bone resorption through activation of proteases and other inflammatory mediators that activate osteoclasts.

Inflammatory mediators in the pathogenesis of periodontitis

Periodontitis is a chronic inflammatory condition of the periodontium involving interactions between bacterial products, numerous cell populations and inflammatory mediators. It is generally accepted that periodontitis is initiated by complex and diverse microbial biofilms which form on the teeth, i.e. dental plaque. Substances released from this biofilm such as lipopolysaccharides, antigens and other virulence factors, gain access to the gingival tissue and initiate an inflammatory and immune response, leading to the activation of host defence cells. As a result of cellular activation, inflammatory mediators, including cytokines, chemokines, arachidonic acid metabolites and proteolytic enzymes collectively contribute to tissue destruction and bone resorption. This review summarises recent studies on the pathogenesis of periodontitis, with the main focus on inflammatory mediators and their role in periodontal disease.

Locally delivered antioxidant gel as an adjunct to nonsurgical therapy improves measures of oxidative stress and periodontal disease

Purpose

The present study has two aims; firstly, it attempts to verify the presence of oxidative stress by estimating the reactive oxygen species (ROS) levels in periodontal pockets ≥5 mm as compared to controls. The second aim is to evaluate the effect of lycopene as a locally delivered antioxidant gel on periodontal health and on the gingival crevicular fluid (GCF) levels of 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative injury.

Methods

Thirty-one subjects participated in this study. In the pretreatment phase, the ROS levels in pockets ≥5 mm were measured by flow cytometry. Three sites in each subject were randomly assigned into each of the following experimental groups: sham group, only scaling and root planing (SRP) was done; placebo group, local delivery of placebo gel after SRP; and lycopene group, local delivery of lycopene gel after SRP. Clinical parameters included recording site-specific measures of GCF 8-OHdG, plaque, gingivitis, probing depth, and clinical attachment level.

Results

The gel, when delivered to the sites with oxidative stress, was effective in increasing clinical attachment and in reducing gingival inflammation, probing depth, and 8-OHdG levels as compared to the placebo and sham sites.

Conclusions

From this trial conducted over a period of 6 months, it was found that locally delivered lycopene seems to be effective in reducing the measures of oxidative stress and periodontal disease.

Periodontal disease immunology: 'double indemnity' in protecting the host

During the last two to three decades our understanding of the immunobiology of periodontal disease has increased exponentially, both with respect to the microbial agents triggering the disease process and the molecular mechanisms of the host engagement maintaining homeostasis or leading to collateral tissue damage. These foundational scientific findings have laid the groundwork for translating cell phenotype, receptor engagement, intracellular signaling pathways and effector functions into a 'picture' of the periodontium as the host responds to the 'danger signals' of the microbial ecology to maintain homeostasis or succumb to a disease process. These findings implicate the chronicity of the local response in attempting to manage the microbial challenge, creating a 'Double Indemnity' in some patients that does not 'insure' health for the periodontium. As importantly, in reflecting the title of this volume of Periodontology 2000, this review attempts to inform the community of how the science of periodontal immunology gestated, how continual probing of the biology of the disease has led to an evolution in our knowledge base and how more recent studies in the postgenomic era are revolutionizing our understanding of disease initiation, progression and resolution. Thus, there has been substantial progress in our understanding of the molecular mechanisms of host-bacteria interactions that result in the clinical presentation and outcomes of destructive periodontitis. The science has embarked from observations of variations in responses related to disease expression with a focus for utilization of the responses in diagnosis and therapeutic outcomes, to current investigations using cutting-edge fundamental biological processes to attempt to model the initiation and progression of soft- and hard-tissue destruction of the periodontium. As importantly, the next era in the immunobiology of periodontal disease will need to engage more sophisticated experimental designs for clinical studies to enable robust translation of basic biologic processes that are in action early in the transition from health to disease, those which stimulate microenvironmental changes that select for a more pathogenic microbial ecology and those that represent a rebalancing of the complex host responses and a resolution of inflammatory tissue destruction.

Effect of nonsurgical periodontal therapy during gestation period on adverse pregnancy outcome: a systematic review

OBJECTIVE

To confirm effectiveness of nonsurgical periodontal treatment during pregnancy on pregnancy outcome in terms of preterm birth and low birth weight (LBW).

METHOD

We searched for Randomized controlled trials in MEDLINE, CINAHL and EMBASE. from January 2000 to October 2012. References of included studies were hand searched. Studies which measured incidence of either preterm labor (PTL), LBW or both were included. Information on study design, population, risk of bias, periodontal parameters, time and type of periodontal treatment given and pregnancy outcome were abstracted independently by three reviewers.

RESULTS

Total thirteen studies were included. Five studies had low risk of bias. Conclusive results could not be obtained for incidence of PTL or LBW because of heterogeneity in results due to various reasons, but all studies which assessed PTL and LBW combined showed significant difference in incidence of same in group which received non surgical periodontal treatment.

CONCLUSION

Our study suggests that treatment of periodontitis during gestation improves pregnancy outcome in terms of PTLBW, a fact which may be used for health and economical benefits but better RCTs with adequate sample size are required for conclusive evidence.

Predicted vitamin D status and incidence of tooth loss and periodontitis

OBJECTIVE

Vitamin D insufficiency is highly prevalent, with particular subgroups at greater risk (e.g. the elderly and those with darker skin). Vitamin D insufficiency may partly explain US racial/ethnic disparities in the prevalence of periodontitis and tooth loss. We evaluated the association between a predictor score of plasma 25-hydroxyvitamin D (25(OH)D) and incidence of periodontitis and tooth loss.

DESIGN

Detailed biennial questionnaires were collected on medical history, lifestyle practices and incident periodontitis and tooth loss. The predictor score was derived from variables known to influence circulating concentrations of plasma 25(OH)D and validated against plasma concentrations among a sub-sample. Multivariable Cox proportional-hazards models with time-varying covariates estimated the association between the predicted 25(OH)D score and time until first tooth loss.

SUBJECTS

A total of 42,730 participants of the Health Professionals Follow-Up Study aged 40-75 years at baseline were followed from 1986 to 2006.

SETTING

USA, representing all fifty states and the District of Columbia.

RESULTS

We observed 13,581 incident tooth loss events from 539,335 person-years. There was a dose-dependent significant inverse association across quintiles of the predicted 25(OH)D score and incidence of tooth loss. In multivariable analyses, the highest quintile of the updated predicted 25(OH)D score compared with the lowest was associated with a 20% lower incidence of tooth loss (hazard ratio = 0.80, 95 % CI 0.76, 0.85; P value for trend <0.001); UV-B was also independently associated. Results for the predicted 25(OH)D score and periodontitis were similar.

CONCLUSIONS

These results are suggestive of an association between predictors of vitamin D and lower incidence of tooth loss and periodontitis.

Chromogranin A: Novel biomarker between periodontal disease and psychosocial stress

CONTEXT

The psychosocial stress has long been regarded as a significant pre-disposing factor for periodontal disease. The association between the periodontal disease and the neuroendocrine hormones has been observed. Chromogranin A (CgA) is supposed to link the activity of the neuroendocrine system to local and systemic immune functions and to be related to periodontitis.

AIMS

The aim of this study was to determine the CgA levels in saliva and plasma in periodontal health and disease and to assess their potential relationship to periodontitis.

SETTINGS AND DESIGNS

In this case-control study, the association between periodontal disease and stress marker has been assessed.

MATERIALS AND METHODS

SIXTY SUBJECTS WERE CHOSEN FOR THIS STUDY: With case group comprising of 30 subjects with chronic periodontitis and control group comprising of 30 healthy subjects. Salivary and plasma CgA levels were determined by ELISA technique. Clinical parameters included were plaque index, papillary bleeding index and clinical attachment loss and probing depth. Correlation analysis was calculated by independent sample t-test.

RESULTS

Significantly higher CgA levels were found in saliva and plasma of patients with chronic periodontitis compared with healthy individuals (P < 0.05). No significant difference were observed between salivary and plasma CgA levels.

CONCLUSIONS

The elevated level CgA in the plasma and saliva of subjects with stress induced chronic periodontitis has yielded insights into biological plausible association between the psychosocial stress and chronic periodontitis. Thus, our results suggest that CgA is a useful biomarker for evaluating at least in part the etiopathogenesis of periodontitis.

Role of MyD88-dependent and MyD88-independent signaling in Porphyromonas gingivalis-elicited macrophage foam cell formation

Clinical studies and experimental modeling identify a potential link between periodontal disease and periodontal pathogens such as Porphyromonas gingivalis and atherosclerosis and formation of macrophage foam cells. Toll-like receptors and molecules governing their intracellular signaling pathways such as MyD88 play roles in atherosclerosis, as well as host response to P. gingivalis. The aim of this study was to define roles of MyD88 and TRIF during macrophage foam cell formation in response to P. gingivalis. In the presence of human low-density lipoprotein (LDL) mouse bone-marrow-derived macrophages (BMφ) cultured with P. gingivalis responded with significant reduction in tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). The BMφ stained strongly with oil red O, regardless of whether bacterial challenge occurred concurrent with or before LDL treatment. Heat-killed P. gingivalis stimulated foam cell formation in a similar way to live bacteria. The BMφ from MyD88-knockout and Lps2 mice revealed a significant role for MyD88, and a minor role for TRIF in P. gingivalis-elicited foam cell formation. Porphyromonas gingivalis-elicited TNF-α and IL-6 were affected by MyD88 ablation and to a lesser extent by TRIF status. These data indicate that LDL affects the TNF-α and IL-6 response of macrophages to P. gingivalis challenge and that MyD88 and TRIF play important roles in P. gingivalis-elicited foam cell formation.

Activation of invariant NK T cells in periodontitis lesions

Periodontitis is one of the most prevalent human inflammatory diseases. The major clinical phenotypes of this polymicrobial, biofilm-mediated disease are chronic and aggressive periodontitis, the latter being characterized by a rapid course of destruction that is generally attributed to an altered immune-inflammatory response against periodontal pathogens. Still, the biological basis for the pathophysiological distinction of the two disease categories has not been well documented yet. Type I NKT cells are a lymphocyte subset with important roles in regulating immune responses to either tolerance or immunity, including immune responses against bacterial pathogens. In this study, we delineate the mechanisms of NKT cell activation in periodontal infections. We show an infiltration of type I NKT cells in aggressive, but not chronic, periodontitis lesions in vivo. Murine dendritic cells infected with aggressive periodontitis-associated Aggregatibacter actinomycetemcomitans triggered a type I IFN response followed by type I NKT cell activation. In contrast, infection with Porphyromonas gingivalis, a principal pathogen in chronic periodontitis, did not induce NKT cell activation. This difference could be explained by the absence of a type I IFN response to P. gingivalis infection. We found these IFNs to be critical for NKT cell activation. Our study provides a conceivable biological distinction between the two periodontitis subforms and identifies factors required for the activation of the immune system in response to periodontal bacteria.

Role of monocyte chemoattractant protein-1 (MCP-1) as an immune-diagnostic biomarker in the pathogenesis of chronic periodontal disease

OBJECTIVE

Monocyte chemoattractant protein-1 (MCP-1) is an important chemokine responsible for the initiation, regulation and mobilization of monocytes to the active sites of severe periodontal inflammation. The present study aims at evaluating the levels of MCP-1 in GCF, saliva and serum and to analyze the changes following phase I periodontal therapy. Assessment of possible correlations between levels of MCP-1 in the three biological fluids was also done.

METHODS

Fifteen healthy and 30 patients of severe chronic periodontitis (diseased) participated in the study. Patients of the diseased group underwent scaling/root planing. Evaluation of PI, GI, PD, CAL and collection of samples of GCF, serum and saliva was done at baseline and 6 weeks following periodontal therapy. MCP-1 levels were quantified in all samples using ELISA.

RESULTS

Compared to healthy controls, MCP-1 levels were statistically significantly higher in GCF (p<0.001), saliva (p=0.002) and serum (p<0.001) in subjects with chronic periodontitis. Levels of MCP-1 in all the three fluids decreased significantly in patients after periodontal therapy (p<0.001). There was a significant positive correlation between MCP-1 levels in GCF, saliva and serum in patients of chronic periodontitis both pre (r>0.9) and post-treatment (r>0.6).

CONCLUSIONS

The results suggest that levels of MCP-1 in GCF and saliva can be reliable indicators of severity of periodontal destruction and their serum levels reflect the systemic impact of this local inflammatory disease thereby strengthening the reciprocal oro-systemic association.

Periodontal disease and diabetes mellitus

Periodontal disease (PD) is one of the most commonly known human chronic disorders. The relationship between PD and several systemic diseases such as diabetes mellitus (DM) has been increasingly recognized over the past decades.

OBJECTIVE

The purpose of this review is to provide the reader with knowledge concerning the relationship between PD and DM. Many articles have been published in the English and Portuguese literature over the last 50 years examining the relationship between these two chronic diseases. Data interpretation is often confounded by varying definitions of DM, PD and different clinical criteria were applied to determine the prevalence, extent and severity of PD, levels of glycemic control and diabetes-related complications.

METHODS

This paper provides a broad overview of the predominant findings from research conducted using the BBO (Bibliografia Brasileira de Odontologia), MEDLINE, LILACS and PubMed for Controlled Trials databases, in English and Portuguese languages published from 1960 to October 2012. Primary research reports on investigations of relationships between DM/DM control, PD/periodontal treatment and PD/DM/diabetes-related complications identified relevant papers and meta-analyses published in this period.

RESULTS

This paper describes the relationship between PD and DM and answers the following questions: 1- The effect of DM on PD, 2- The effects of glycemic control on PD and 3- The effects of PD on glycemic control and on diabetes-related complications.

CONCLUSIONS

The scientific evidence reviewed supports diabetes having an adverse effect on periodontal health and PD having an adverse effect on glycemic control and on diabetes-related complications. Further research is needed to clarify these relationships and larger, prospective, controlled trials with ethnically diverse populations are warranted to establish that treating PD can positively influence glycemic control and possibly reduce the burden of diabetes-related complications.

Prospective potency of TGF-β1 on maintenance and regeneration of periodontal tissue

Periodontal ligament (PDL) tissue, central in the periodontium, plays crucial roles in sustaining tooth in the bone socket. Irreparable damages of this tissue provoke tooth loss, causing a decreased quality of life. The question arises as to how PDL tissue is maintained or how the lost PDL tissue can be regenerated. Stem cells included in PDL tissue (PDLSCs) are widely accepted to have the potential to maintain or regenerate the periodontium, but PDLSCs are very few in number. In recent studies, undifferentiated clonal human PDL cell lines were developed to elucidate the applicable potentials of PDLSCs for the periodontal regenerative medicine based on cell-based tissue engineering. In addition, it has been suggested that transforming growth factor-beta 1 is an eligible factor for the maintenance and regeneration of PDL tissue.

Expression, polymorphism and methylation pattern of interleukin-6 in periodontal tissues

Periodontitis is considered an inflammatory disorder of bacterial etiology that results in periodontal tissue destruction, as a result of complex interactions between periodontal pathogens, host and immune response. Genetic and epigenetic mechanisms may modulate the individual response since it is able to influence the gene expression. The aim of this study was to evaluate the impact of -174 G/C polymorphism and the methylation status of the promoter region of IL-6 gene on the expression of IL-6 in gingival samples from individuals with chronic periodontitis. Gingival biopsies were collected from 21 patients with chronic periodontitis and 21 controls. Histologic sections stained by hematoxylin-eosin were used for histopathological evaluation. The IL-6 gene expression was assessed by quantitative real-time PCR. The polymorphism IL-6 -174 C/G was studied by polymerase chain reaction (PCR) amplification and restriction endonuclease digestion (HspII). Methylation-specific polymerase chain reaction was used to verify the DNA methylation pattern. The number of inflammatory cells in tissue fragments from individuals with chronic periodontitis was higher than in the control group and the inflammatory infiltrate was predominantly mononuclear. The expression of IL-6 was higher in the group with periodontitis. In polymorphism assay, no statistical difference in the distribution of genotypes and alleles in both groups were observed. The most of samples were partially methylated. No difference was observed in methylation pattern from two different regions of the IL-6 gene among groups. The high expression of IL-6 is an important factor related to chronic periodontitis, but was not associated with methylation status or the -174 (G/C) genetic polymorphism, suggesting that other mechanisms are involved in this gene transcription regulation.

Blocking proinflammatory cytokine release modulates peripheral blood mononuclear cell response to Porphyromonas gingivalis

BACKGROUND

Chronic periodontitis (CP) is an inflammatory disease in which cytokines play a major role in the progression of disease. Anti-inflammatory cytokines (interleukin 4 [IL-4] and IL-10) were reported to be absent or reduced in diseased periodontal tissues, suggesting an imbalance between the proinflammatory and anti-inflammatory mediators. This study tests the hypothesis that there is cellular crosstalk mediated by proinflammatory and anti-inflammatory cytokines and that blocking proinflammatory cytokine (tumor necrosis factor-α [TNF-α] and IL-1) production will enhance anti-inflammatory cytokine (IL-4 and IL-10) production from peripheral blood mononuclear cells (PBMCs) in response to Porphyromonas gingivalis.

METHODS

PBMCs were isolated from individuals diagnosed with CP or healthy individuals and cultured for 24 hours. Concanavalin A (ConA) was used as an activator of lymphocyte function. Live and heat-killed P. gingivalis or lipopolysaccharide from P. gingivalis were used as the bacterial stimulants. TNF-α and IL-1 production was neutralized by specific antibodies against TNF-α and IL-1α or IL-β. Culture supernatants were evaluated by enzyme-linked immunosorbent assay for TNF-α, IL-1β, IL-4, and IL-10 production.

RESULTS

Live P. gingivalis did not result in any significant IL-10 or IL-4 release, whereas heat-killed P. gingivalis led to a significant increase in IL-10 levels compared with unstimulated or live P. gingivalis-stimulated cells from both healthy individuals or those with CP. Overall, PBMCs from patients with CP produced significantly lower IL-10 in response to ConA and P. gingivalis, suggesting chronic suppression of the anti-inflammatory cytokine production. Blocking the proinflammatory cytokine response did not result in any substantial change in IL-10 or IL-4 response to live P. gingivalis. Blocking the proinflammatory cytokine response restored IL-10 production by cells from CP in response to P. gingivalis lipopolysaccharide.

CONCLUSIONS

These findings suggest that PBMCs from patients with CP have suppressed anti-inflammatory cytokine production that can, in part, be restored by neutralizing proinflammatory cytokines. Monocytes are an important source of IL-10 production, and monocyte-derived IL-10 might play a regulatory role in the pathogenesis of CP.

Gram-positive bacteria as an antigen topically applied into gingival sulcus of immunized rat accelerates periodontal destruction

BACKGROUND AND OBJECTIVE

Periodontitis is generally accepted to relate to gram-negative bacteria, and the host defense system influences its onset and progression. However, little is known about the relation between gram-positive bacteria and periodontitis. In this study, we topically applied gram-positive and gram-negative bacterial suspensions to the gingival sulcus in rats after immunization, and then histopathologically examined their influence on periodontal destruction.

MATERIALS AND METHODS

Rats previously immunized with heat-treated and sonicated Staphylococcus aureus or Aggregatibacter actinomycetemcomitans were used as immunized groups. The non-immunized group received only sterile phosphate-buffered saline. In each animal, S. aureus or A. actinomycetemcomitans suspension was applied topically to the palatal gingival sulcus of first molars every 24 h for 10 d. Blood samples were collected and the serum level of anti-S. aureus or anti-A. actinomycetemcomitans immunoglobulin G (IgG) antibodies was determined by enzyme-linked immunosorbent assay. The first molar regions were resected and observed histopathologically. Osteoclasts were stained with tartrate-resistant acid phosphatase (TRAP). The formation of immune complexes was confirmed by immunohistological staining of C1qB.

RESULTS

Serum levels of anti-S. aureus and anti-A. actinomycetemcomitans IgG antibodies in the immunized groups were significantly higher than those in the non-immunized groups were. The loss of attachment, increase in apical migration of the junctional epithelium, and decreases in alveolar bone level and number of TRAP-positive multinuclear cells in each immunized group were significantly greater than in each non-immunized group. The presence of C1qB was observed in the junctional epithelium and adjacent connective tissue in the immunized groups.

CONCLUSIONS

Heat-treated and sonicated S. aureus and A. actinomycetemcomitans induced attachment loss in rats immunized with their suspensions. Our results suggest that not only gram-negative but also gram-positive bacteria are able to induce periodontal destruction.

Possible translocation of periodontal pathogens into the lymph nodes draining the oral cavity

Numerous publications have reported the presence of periodontopathogenic bacteria in peripheral and central vascular lesions. However, it is unclear how this bacterial translocation occurs. The objective of this study was to investigate whether periodontopathic bacteria are translocated to lymph nodes proximal to the oral cavity. Obtaining lymph node samples is not ethically feasible unless they are excised as part of the surgical management of patients with cancer. This study analyzed formalin-fixed and paraffin-embedded lymph nodes, histologically negative for cancer cell invasion, that were excised from 66 patients with histories of head and neck cancer. Real-time PCR was performed to amplify the 16S ribosomal DNA fragments from Porphyromonas gingivalis, Treponema denticola, Aggregatibacter actinomycetemcomitans, Tannerella forsythia, and Prevotella intermedia. The relationship between bacterial detection and cancer severity, gender, and the use of anti-cancer therapy was examined by Fisher's exact test. P. gingivalis, T. forsythia, and P. intermedia were present in 17%, 8%, and 8% of the samples of submandibular and submental lymph nodes, respectively. There were no significant relationships between bacterial detection and the cancer disease status, patient gender or use of anticancer therapy. According to these data, it appears that the translocation of periodontopathic bacteria may occur via lymphatic drainage, irrespective of the cancer disease status, gender or anticancer therapy.

Changes in periodontium after extraction of a periodontally-involved tooth in rats

Purpose

Recent interest has focused on intentional replantation to restore an original tooth. Some studies have shown successful results with intentional replantation for periodontally involved teeth. For long-term success of replantation, a healthy periodontal status of the recipient site is required so that delayed replantation is more suitable for periodontally involved teeth. To reveal the ideal timing for delayed replantation of periodontally involved teeth, the healing process of extraction sockets after extraction of periodontitis-induced teeth in rats was evaluated.

Methods

Twenty-eight rats were randomly divided into two groups: a control group (n=8) and test group (n=20). In the test group, periodontitis was induced by a ligature around the cervix of the mandibular first molar of all of the rats. Two weeks later, the mandibular first molars were extracted in all of the animals. The animals were sacrificed on days 0, 3, 7, and 10 after extraction and histological and immunohistochemical analysis was performed.

Results

In histological analysis of the test group, inflammatory cell infiltrate was found abundantly in the remaining periodontium 3 days after tooth extraction and decreased gradually at later time points. In immunohistochemical analysis of the test group, both interleukin-6 (IL-6) and, tumor necrosis factor-α (TNF-α) were numerous in the furcation area at each postextraction day. IL-6 was stained more heavily between 3 and 7 days after extraction; at day 10 after extraction, little staining was observed. TNF-α staining was more intense at 3 days after extraction and gradually weakened at later points in time.

Conclusions

Within the limits of this study, it takes at least 10 days to resolve periodontal inflammation in rat extraction sockets.