The roles of cyclooxygenase-2 and prostaglandin E2in periodontal disease

Quercitrin for periodontal regeneration: effects on human gingival fibroblasts and mesenchymal stem cells

Periodontal disease (PD) is the result of an infection and chronic inflammation of the gingiva that may lead to its destruction and, in severe cases, alveolar bone and tooth loss. The ultimate goal of periodontal treatment is to achieve periodontal soft and hard tissues regeneration. We previously selected quercitrin, a catechol-containing flavonoid, as a potential agent for periodontal applications. In this study, we tested the ability of quercitrin to alter biomarker production involved in periodontal regeneration on primary human gingival fibroblasts (hGF) and primary human mesenchymal stem cells (hMSC) cultured under basal and inflammatory conditions. To mimic PD inflammatory status, interleukin-1 beta (IL-1β) was used. The expression of different genes related to inflammation and extracellular matrix were evaluated and prostaglandin E2 (PGE2) production was quantified in hGFs; alkaline phosphatase (ALP) activity and calcium content were analysed in hMSCs. Quercitrin decreased the release of the inflammatory mediator PGE2 and partially re-established the impaired collagen metabolism induced by IL-1β treatment in hGFs. Quercitrin also increased ALP activity and mineralization in hMSCs, thus, it increased hMSCs differentiation towards the osteoblastic lineage. These findings suggest quercitrin as a novel bioactive molecule with application to enhance both soft and hard tissue regeneration of the periodontium.

Cigarette smoke condensate inhibits collagen gel contraction and prostaglandin E2 production in human gingival fibroblasts

BACKGROUND

Granulation tissue remodeling and myofibroblastic differentiation are critically important events during wound healing. Tobacco smoking has a detrimental effect in gingival tissue repair. However, studies evaluating the effects of cigarette smoke on these events are lacking.

MATERIAL AND METHODS

We used gingival fibroblasts cultured within free-floating and restrained collagen gels to simulate the initial and final steps of the granulation tissue phase during tissue repair. Collagen gel contraction was stimulated with serum or transforming growth factor-β1. Cigarette smoke condensate (CSC) was used to evaluate the effects of tobacco smoke on gel contraction. Protein levels of alpha-smooth muscle actin, β1 integrin, matrix metalloproteinase-3 and connective tissue growth factor were evaluated through Western blot. Prostaglandin E(2) (PGE(2)) levels were determined through ELISA. Actin organization was evaluated through confocal microscopy.

RESULTS

CSC reduced collagen gel contraction induced by serum and transforming growth factor-β1 in restrained collagen gels. CSC also altered the development of actin stress fibers in fibroblasts cultured within restrained collagen gels. PGE(2) levels were strongly diminished by CSC in three-dimensional cell cultures. However, other proteins involved in granulation tissue remodeling and myofibroblastic differentiation such as alpha-smooth muscle actin, β1 integrin, matrix metalloproteinase-3 and connective tissue growth factor, were unmodified by CSC.

CONCLUSIONS

CSC may alter the capacity of gingival fibroblasts to remodel and contract a collagen matrix. Inhibition of PGE(2) production and alterations of actin stress fibers in these cells may impair proper tissue maturation during wound healing in smokers.

Peptidylarginine deiminase from Porphyromonas gingivalis contributes to infection of gingival fibroblasts and induction of prostaglandin E2 -signaling pathway

Porphyromonas gingivalis (P. gingivalis) expres-ses the enzyme peptidylarginine deiminase (PPAD), which has a strong preference for C-terminal arginines. Due to the combined activity of PPAD and Arg-specific gingipains, P. gingivalis on the cell surface is highly citrullinated. To investigate the contribution of PPAD to the interaction of P. gingivalis with primary human gingival fibroblasts (PHGF) and P. gingivalis-induced synthesis of prostaglandin E2 (PGE2 ), PHGF were infected with wild-type P. gingivalis ATCC 33277, an isogenic PPAD-knockout strain (∆ppad) or a mutated strain (C351A) expressing an inactive enzyme in which the catalytic cysteine has been mutated to alanine (PPAD(C351A) ). Cells were infected in medium containing the mutants alone or in medium supplemented with purified, active PPAD. PHGF infection was assessed by colony-forming assay, microscopic analysis and flow cytometry. Expression of cyclo-oxygenase 2 (COX-2) and microsomal PGE synthase-1 (mPGES-1), key factors in the prostaglandin synthesis pathway, was examined by quantitative reverse transcription polymerase chain reaction (qRT-PCR), while PGE2 synthesis was evaluated by enzyme immunoassay. PHGF were infected more efficiently by wild-type P. gingivalis than by the ∆ppad strain, which correlated with strong induction of COX-2 and mPGES-1 expression by wild-type P. gingivalis, but not by the PPAD activity-null mutant strains (Δppad and C351A). The impaired ability of the Δppad strain to adhere to and/or invade PHGF and both Δppad and C351A to stimulate the PGE2 -synthesis pathway was fully restored by the addition of purified PPAD. The latter effect was strongly inhibited by aspirin. Collectively, our results implicate PPAD activity, but not PPAD itself, as an important factor for gingival fibroblast infection and activation of PGE2 synthesis, the latter of which may strongly contribute to bone resorption and eventual tooth loss.

Amphotericin B down-regulates Aggregatibacter actinomycetemcomitans-induced production of IL-8 and IL-6 in human gingival epithelial cells

Gingival epithelium is the primary barrier against microorganism invasion and produces inflammatory cytokines. Amphotericin B, a major antifungal drug, binds to cholesterol in the mammalian cell membrane in addition to fungal ergosterol. Amphotericin B has been shown to regulate inflammatory cytokines in host cells. To investigate the suppressive effect of amphotericin B on the gingival epithelium, we examined the expression of interleukin (IL)-8 and IL-6 and involvement of MAP kinase in human gingival epithelial cells (HGEC) stimulated by Aggregatibacter actinomycetemcomitans. Amphotericin B and the p38 MAP kinase inhibitor down-regulated the A. actinomycetemcomitans-induced increase in the expression of IL-8 and IL-6 at the mRNA. The ERK inhibitor suppressed the A. actinomycetemcomitans-induced IL-8 mRNA expression. Amphotericin B inhibited the A. actinomycetemcomitans-induced phosphorylation of ERK and p38 MAP kinase. Furthermore, amphotericin B inhibited the A. actinomycetemcomitans-induced production of prostaglandin E2. These results suggest that amphotericin B regulate inflammatory responses in HGEC.

Anti-inflammatory Actions of Adjunctive Tetracyclines and Other Agents in Periodontitis and Associated Comorbidities

The non-antimicrobial properties of tetracyclines such as anti-inflammatory, proanabolic and anti-catabolic actions make them effective pharmaceuticals for the adjunctive management of chronic inflammatory diseases. An over-exuberant inflammatory response to an antigenic trigger in periodontitis and other chronic inflammatory diseases could contribute to an autoimmune element in disease progression. Their adjunctive use in managing periodontitis could have beneficial effects in curbing excessive inflammatory loading from commonly associated comorbidities such as CHD, DM and arthritis. Actions of tetracyclines and their derivatives include interactions with MMPs, tissue inhibitors of MMPs, growth factors and cytokines. They affect the sequence of inflammation with implications on immunomodulation, cell proliferation and angiogenesis; these actions enhance their scope, in treating a range of disease entities. Non-antimicrobial chemically modified tetracyclines (CMTs) sustain their diverse actions in organ systems which include anti-inflammatory, anti-apoptotic, anti-proteolytic actions, inhibition of angiogenesis and tumor metastasis. A spectrum of biological actions in dermatitis, periodontitis, atherosclerosis, diabetes, arthritis, inflammatory bowel disease, malignancy and prevention of bone resorption is particularly relevant to minocycline. Experimental models of ischemia indicate their specific beneficial effects. Parallel molecules with similar functions, improved Zn binding and solubility have been developed for reducing excessive MMP activity. Curbing excessive MMP activity is particularly relevant to periodontitis, and comorbidities addressed here, where specificity is paramount. Unique actions of tetracyclines in a milieu of excessive inflammatory stimuli make them effective therapeutic adjuncts in the management of chronic inflammatory disorders. These beneficial actions of tetracyclines are relevant to the adjunctive management of periodontitis subjects presenting with commonly prevalent comorbidities addressed here.

Preventive Effects of a Kampo Medicine, Kakkonto, on Inflammatory Responses via the Suppression of Extracellular Signal-Regulated Kinase Phosphorylation in Lipopolysaccharide-Treated Human Gingival Fibroblasts

Periodontal disease is accompanied by inflammation of the gingiva and destruction of periodontal tissues, leading to alveolar bone loss in severe clinical cases. The chemical mediator prostaglandin E₂ (PGE₂) and cytokines such as interleukin- (IL-)6 and IL-8 have been known to play important roles in inflammatory responses and tissue degradation. In the present study, we investigated the effects of a kampo medicine, kakkonto (TJ-1), on the production of prostaglandin E₂ (PGE₂), IL-6, and IL-8 by human gingival fibroblasts (HGFs) treated with lipopolysaccharide (LPS) from Porphyromonas gingivalis. Kakkonto concentration dependently suppressed LPS-induced PGE₂ production but did not alter basal PGE₂ levels. In contrast, kakkonto significantly increased LPS-induced IL-6 and IL-8 production. Kakkonto decreased cyclooxygenase- (COX-)1 activity to approximately 70% at 1 mg/mL but did not affect COX-2 activity. Kakkonto did not affect cytoplasmic phospholipase A₂ (cPLA₂), annexin1, or LPS-induced COX-2 expression. Kakkonto suppressed LPS-induced extracellular signal-regulated kinase (ERK) phosphorylation, which is known to lead to ERK activation and cPLA₂ phosphorylation. These results suggest that kakkonto decreased PGE₂ production by inhibition of ERK phosphorylation which leads to inhibition of cPLA₂ phosphorylation and its activation. Therefore, kakkonto may be useful to improve gingival inflammation in periodontal disease.

Nothing to smile about

BACKGROUND

Several studies have demonstrated the high incidence of periodontal disorders among patients suffering from mental illnesses, probably because of self-care impairment, the difficult financial conditions, and the lack of motivation. The primary aim of this study was to evaluate the impact of depression and alexithymia on periodontal status. Due to the influence of personality traits on behavior in general, the secondary aim of our study was to investigate the possible impact of personality disorders on dental status.

METHODS

Patients with major depression (DP) referred to our psychiatry unit and healthy individuals (controls) were consecutively enrolled during the period April 2012-September 2012. All the participants to the study underwent a psychiatric evaluation (through questionnaires investigating the presence of depression, anxiety, personality disorders, and alexithymia) and a dental examination through the following indexes: plaque index, gingival index, simplified oral hygiene index, periodontal index.

RESULTS

Fifty DP (aged 56.7±15.2 years) and 40 controls (aged 56.1±15.9 years) were enrolled in the study. DP showed a worse oral hygiene status. In particular, statistically significant differences were found when comparing DP and controls in terms of plaque index, simplified oral hygiene index, gingival index, periodontal index, and oral health impact profile. In addition, periodontal health was found to be negatively related to the severity of depression and the presence of alexithymia. The strength of association between depression and dental indexes was reduced after adjusting for the other psychiatric variables (alexithymia and personality disorders) and was confirmed only for oral health impact profile.

CONCLUSION

Psychiatric variables seem to affect the patients' periodontal status; due to the high frequency of dental problems, patients suffering from mental illnesses should be referred to the oral health services for evaluation.

COX-2 gene polymorphisms and risk of chronic periodontitis: a case-control study and meta-analysis

OBJECTIVE

Cyclooxygenase-2 (COX-2) enzyme is a major mediator of inflammation in periodontitis, leading to loss of gingival tissues and alveolar bone supporting the teeth. Previous studies have explored the role of COX-2 polymorphisms with the risk of periodontitis in different ethnic groups; however, findings are inconsistent. So, we aimed to investigate the association of COX-2 polymorphisms (rs20417, rs689466, and rs5275) in susceptibility to chronic periodontitis (CP) in northern Indian population. Meta-analysis was also carried out to precisely estimate the effect of COX-2 polymorphisms in CP.

MATERIALS AND METHODS

Genotyping of COX-2 polymorphisms was carried out through PCR-RFLP in 200 CP cases and 200 controls. For risk estimation, binary logistic regression was applied using SPSS, version 15.0, while meta-analysis was carried using MIX 2.0 software.

RESULTS

None of the COX-2 polymorphisms independently were associated with the risk of CP. Meta-analysis suggested a significant reduced risk of CP with rs5275+8473 C allele and rs20417 in Chinese population.

CONCLUSIONS

No association was observed in any of the studied COX-2 polymorphisms with CP in North India. But, the study should be replicated in larger sample size to arrive at a definitive conclusion. Meta-analysis suggested a role of rs5275 COX-2 polymorphisms in susceptibility to overall CP, and on ethnic basis, rs20417 showed reduced risk of CP in Chinese population.

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.

Effects of chitosan particles in periodontal pathogens and gingival fibroblasts

Chitosan is a naturally derived polymer with antimicrobial and anti-inflammatory properties. However, studies evaluating the role of chitosan in the control of periodontal pathogens and the responses of fibroblasts to inflammatory stimuli are lacking. In the present study, we analyzed whether chitosan particles may inhibit the growth of periodontal pathogens and modulate the inflammatory response in human gingival fibroblasts. Chitosan particles were generated through ionic gelation. They inhibited the growth of Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans at 5 mg/mL. Conversely, IL-1β strongly stimulated PGE2 protein levels in gingival fibroblasts, and chitosan inhibited this response at 50 µg/mL. IL-1β-stimulated PGE2 production was dependent on the JNK pathway, and chitosan strongly inhibited this response. IL-1β stimulated NF-κB activation, another signaling pathway involved in PGE2 production. However, chitosan particles were unable to modify NF-κB signaling. The present study shows that chitosan exerts a predominantly anti-inflammatory activity by modulating PGE2 levels through the JNK pathway, which may be useful in the prevention or treatment of periodontal inflammation.

Endotoxins potentiate COX-2 and RANKL expression in compressed PDL cells

OBJECTIVE

This study aims to demonstrate in vitro the synergistic effect of orthodontic forces and periodontal pathogens on cyclooxygenase-2 regulation and the subsequent receptor activator of nuclear factor kappa-B ligand (RANKL) production from periodontal ligament (PDL) cells.

MATERIALS AND METHODS

In comparison to a control group, three experimental groups were formed from human primary PDL cells stressed with compressive forces, bacterial endotoxins, or a combination of both. Gene expression of cyclooxygenase-2 and RANKL was analysed with RT real-time PCR. The prostaglandin E2 production was determined with ELISA. A co-culture of PDL cells and an osteoclast-progenitor cell line was used in order to demonstrate the osteoclast formation effect caused by the simultaneous combined stress.

RESULTS

The simultaneous combined stress resulted in a 56-fold up-regulation of cyclooxygenase-2 gene expression with a subsequent noticeable rise in the prostaglandin E2 in the culture medium. The RANKL/osteoprotegerin gene expression ratio was 50-fold up-regulated and the osteoclast formation assay revealed 153.5 ± 15.7 tartrate-resistant acid phosphatase (TRAP)-positive cells per well compared with 42.3 ± 3.8 TRAP-positive cells per well of the control group.

CONCLUSION

The synergistic action of periodontal pathogens and orthodontic forces leads to an increased expression of cyclooxygenase-2 from PDL cells that intensify the RANKL production which in turn induces osteoclast differentiation and subsequent osteoclastogenesis.

CLINICAL RELEVANCE

The present study puts an emphasis on the detrimental effect of orthodontic forces on patients with an active periodontal disease by underlining the significance of cyclooxygenase-2 activity and RANKL binding on the osteoclastogenesis process.

Cyclooxygenase 2 gene polymorphisms and chronic periodontitis in a North Indian population: a pilot study

PURPOSE

Cyclooxygenase (COX) enzyme catalyzes the production of prostaglandins, which are important mediators of tissue destruction in periodontitis. Single nucleotide polymorphisms of COX2 enzyme have been associated with increasing susceptibility to inflammatory diseases. The present study evaluates the association of two single nucleotide polymorphisms in COX2 gene (-1195G>A and 8473C>T) with chronic periodontitis in North Indians.

METHODS

Both SNPs and their haplotypes were used to explore the associations between COX2 polymorphisms and chronic periodontitis in 56 patients and 60 controls. Genotyping was done by polymerase chain reaction followed by restriction fragment length polymorphism. Chi-square test and logistic regression analysis were performed for association analysis.

RESULTS

By the individual genotype analysis, mutant genotypes (GA and AA) of COX2 -1195 showed more than a two fold risk (odds ratio [OR]>2) and COX2 8473 (TC and CC) showed a reduced risk for the disease, but the findings were not statistically significant. Haplotype analysis showed that the frequency of the haplotype AT was higher in the case group and a significant association was found for haplotype AT (OR, 1.79; 95% confidence interval, 1.03 to 3.11; P=0.0370) indicating an association between the AT haplotype of COX2 gene SNPs and chronic periodontitis.

CONCLUSIONS

Individual genotypes of both the SNPs were not associated while haplotype AT was found to be associated with chronic periodontitis in North Indians.

Transcriptional profiling of bone marrow stromal cells in response to Porphyromonas gingivalis secreted products

Periodontitis is an infectious inflammatory disease that destroys the tooth-supporting (periodontal) tissues. Porphyromonas gingivalis is an oral pathogen highly implicated in the pathogenesis of this disease. It can exert its effects to a number of cells, including osteogenic bone marrow stromal cells which are important for homeostastic capacity of the tissues. By employing gene microarray technology, this study aimed to describe the overall transcriptional events (>2-fold regulation) elicited by P. gingivalis secreted products in bone marrow stromal cells, and to dissect further the categories of genes involved in bone metabolism, inflammatory and immune responses. After 6 h of challenge with P. gingivalis, 271 genes were up-regulated whereas 209 genes were down-regulated, whereas after 24 h, these numbers were 259 and 109, respectively. The early (6 h) response was characterised by regulation of genes associated with inhibition of cell cycle, induction of apoptosis and loss of structural integrity, whereas the late (24 h) response was characterised by induction of chemokines, cytokines and their associated intracellular pathways (such as NF-κB), mediators of connective tissue and bone destruction, and suppression of regulators of osteogenic differentiation. The most strongly up-regulated genes were lipocalin 2 (LCN2) and serum amyloid A3 (SAA3), both encoding for proteins of the acute phase inflammatory response. Collectively, these transcriptional changes elicited by P. gingivalis denote that the fundamental cellular functions are hindered, and that the cells acquire a phenotype commensurate with propagated innate immune response and inflammatory-mediated tissue destruction. In conclusion, the global transcriptional profile of bone marrow stromal cells in response to P. gingivalis is marked by deregulated homeostatic functions, with implications in the pathogenesis of periodontitis.

ASC-dependent RIP2 kinase regulates reduced PGE2 production in chronic periodontitis

Levels of prostaglandin E(2) (PGE(2)) and its processing enzyme, prostaglandin-endoperoxide-synthase-2/ cyclooxygenase-2 (PTGS2/COX-2), are elevated in actively progressing periodontal lesions, but suppressed in chronic disease. COX-2 expression is regulated through inflammatory signaling that converges on the mitogen-activated protein kinase (MAPK) pathway. Emerging evidence suggests a role for the inflammatory adaptor protein, ASC/Pycard, in MAPK activation. We postulated that ASC may represent a mediator of the MAPK-mediated regulatory network of PGE(2) production. Using RNAi-mediated gene slicing, we demonstrated that ASC regulates COX-2 expression and PGE(2) production in THP1 monocytic cells following infection with Porphyromonas gingivalis (Pg). Production of PGE(2) did not require the inflammasome adaptor function of ASC, but was dependent on MAPK activation. Furthermore, the MAP kinase kinase kinase CARD domain-containing protein RIPK2 was induced by Pg in an ASC-dependent manner. Reduced ASC and RIPK2 levels were revealed by orthogonal comparison of the expression of the RIPK family in ASC-deficient THP1 cells with that in chronic periodontitis patients. We show that pharmacological inhibition of RIPK2 represses PGE(2) secretion, and RNAi-mediated silencing of RIPK2 leads to diminished MAPK activation and PGE(2) secretion. These findings identify a novel ASC-RIPK2 axis in the generation of PGE(2) that is repressed in patients diagnosed with chronic adult periodontitis.

Porphyromonas gingivalis infection at different gestation periods on fetus development and cytokines profile

AIM

Infective agents may affect pregnancy outcomes by deregulating homeostasis.

OBJECTIVES

The effects of Porphyromonas gingivalis infection before and at different gestation periods were evaluated.

MATERIALS AND METHODS

Wistar rats infected via subcutaneous with P. gingivalis W83, one week before mating (BM), days 1 (PR1) and 11 of gestation (PR11), and controls were evaluated, and samples were obtained at the end of gestation. P. gingivalis was detected by PCR. Cytokine was determined by ELISA.

RESULTS

Infected rats had lower maternal gain of weight. Implantation was not observed in 2/12 BM rats. PR11 presented more fetal-placental resorptions and lower placenta/fetus weight than controls. P. gingivalis was detected in placenta and fetus. IL-6 and TNF-α levels were higher in placenta and serum of infected groups, except for TNF-α in placenta of PR1. IL-1β levels were higher in placenta of PR11, but lower in serum and placenta of PR1. There were no differences in IL-10 and PGE2 concentrations among the groups (P < 0.05).

CONCLUSIONS

The experimental infection by P. gingivalis resulted in alterations in the gestational pattern and in fetal development. The consequences of infection at mid-gestation were more severe than at the beginning, possibly due to the induction of pro-inflammatory cytokines in the fetal compartment.

Protein kinase A enhances lipopolysaccharide-induced IL-6, IL-8, and PGE₂ production by human gingival fibroblasts

OBJECTIVE

Periodontal disease is accompanied by inflammation of the gingiva and destruction of periodontal tissues, leading to alveolar bone loss in severe clinical cases. Interleukin (IL)-6, IL-8, and the chemical mediator prostaglandin E₂ (PGE₂) are known to play important roles in inflammatory responses and tissue degradation. Recently, we reported that the protein kinase A (PKA) inhibitor H-89 suppresses lipopolysaccharide (LPS)-induced IL-8 production by human gingival fibroblasts (HGFs). In the present study, the relevance of the PKA activity and two PKA-activating drugs, aminophylline and adrenaline, to LPS-induced inflammatory cytokines (IL-6 and IL-8) and PGE₂ by HGFs were examined.

METHODS

HGFs were treated with LPS from Porphyromonas gingivalis and H-89, the cAMP analog dibutyryl cyclic AMP (dbcAMP), aminophylline, or adrenaline. After 24 h, IL-6, IL-8, and PGE₂ levels were evaluated by ELISA.

RESULTS

H-89 did not affect LPS-induced IL-6 production, but suppressed IL-8 and PGE₂ production. In contrast, dbcAMP significantly increased LPS-induced IL-6, IL-8, and PGE₂ production. Up to 10 μg/ml of aminophylline did not affect LPS-induced IL-6, IL-8, or PGE₂ production, but they were significantly increased at 100 μg/ml. Similarly, 0.01 μg/ml of adrenaline did not affect LPS-induced IL-6, IL-8, or PGE₂ production, but they were significantly increased at concentrations of 0.1 and 1 μg/ml. In the absence of LPS, H-89, dbcAMP, aminophylline, and adrenaline had no relevance to IL-6, IL-8, or PGE₂ production.

CONCLUSION

These results suggest that the PKA pathway, and also PKA-activating drugs, enhance LPS-induced IL-6, IL-8, and PGE₂ production by HGFs. However, aminophylline may not have an effect on the production of these molecules at concentrations used in clinical settings (8 to 20 μg/ml in serum). These results suggest that aminophylline does not affect inflammatory responses in periodontal disease.

Interleukin-17F affects cartilage matrix turnover by increasing the expression of collagenases and stromelysin-1 and by decreasing the expression of their inhibitors and extracellular matrix components in chondrocytes

Interleukin (IL)-17, a proinflammatory cytokine, is produced primarily by activated Th17 cells. IL-17 consists of six ligands that signal through five receptors (IL-17Rs); IL-17A and IL-17F share the highest homology in the family. Matrix metalloproteinases (MMPs) degrade the extracellular matrix during cartilage remodeling whereas tissue inhibitor of metalloproteinases (TIMPs) inhibit the action of MMPs. In the present study, we examined the effect of IL-17F on the degradation and synthesis of the extracellular matrix in cartilage using human articular chondrocytes. We examined the effect of IL-17F on the expression of IL-17Rs, MMPs, TIMPs, type II collagen, aggrecan, link protein, and cyclooxygenases (COXs), as well as on prostaglandin E2 (PGE2) production. We also examined the indirect effect of PGE2 on the above IL-17F-induced/reduced components using NS-398, a specific inhibitor of COX-2. Cells were cultured with or without IL-17F in the presence or absence of either an IL-17R antibody or NS-398 for up to 28 days. Expression of IL-17Rs, MMPs, TIMPs, type II collagen, aggrecan, link protein, and COXs at mRNA and protein levels was determined using real-time polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA), respectively. PGE2 production was determined by ELISA. The expression of all types of IL-17Rs was detected in chondrocytes. However, IL-17RE expression was extremely low, compared with other IL-17Rs. The expression of MMP-1, MMP-3, MMP-13, and COX-2 as well as PGE2 production were increased by addition of IL-17F, whereas the expression of IL-17RD, TIMP-2, TIMP-4, type II collagen, aggrecan, link protein, and COX-1 was decreased. The expression of IL-17RA, IL-17RB, IL-17RC, MMP-2, MMP-14, TIMP-1, and TIMP-3 was unaffected by addition of IL-17F. The IL-17R antibody blocked the stimulating/reducing effect of IL-17F on the expression of MMP-1, MMP-3, MMP-13, TIMP-2, TIMP-4, type II collagen, aggrecan, and link protein. NS-398 blocked the reducing effect of IL-17F on aggrecan expression, whereas it did not completely block the stimulating/reducing effects of IL-17F on the expression of MMP-1, MMP-3, MMP-13, TIMP-2, TIMP-4, type II collagen, and link protein. Our results suggest that IL-17F stimulates cartilage degradation by increasing the expression of collagenases (MMP-1 and -13) and stromelysin-1 (MMP-3) and by decreasing expression of their inhibitors (TIMP-2 and -4), type II collagen, aggrecan, and link protein in chondrocytes. Furthermore, our results suggest that the expression of aggrecan, link protein, and TIMP-4 decrease through the autocrine action of PGE2 in chondrocytes.

Differential effects of prostaglandin E(2) and enamel matrix derivative on the proliferation of human gingival and dermal fibroblasts and gingival keratinocytes

BACKGROUND AND OBJECTIVE

Elevated levels of prostaglandins contribute to periodontal destruction but can impair gingival healing by affecting local fibroblasts. Enamel matrix derivative (EMD) has beneficial effects on supporting and gingival tissues. We showed that prostaglandin E(2) (PGE(2) ) inhibits the proliferation of human gingival fibroblasts (hGFs) and that EMD stimulates it. Prostaglandins and EMD may also affect skin healing by targeting dermal fibroblasts (DFs). Thus, we compared the effects of these two agents on the proliferation of hGFs, human gingival keratinocytes (hGKs) and hDFs.

MATERIAL AND METHODS

Cells from healthy human gingiva or skin were treated with PGE(2) and/or EMD, and proliferation was assessed by measuring cell number and DNA synthesis.

RESULTS

In hGFs, PGE(2) (1 μm) inhibited proliferation while EMD stimulated it. When present together, EMD abolished the PGE(2) -induced inhibition. Serum increased (by a factor of 10) the amount of phosphorylated extracellular signal-regulated kinase (p-ERK), PGE(2) reduced it (by 70-80%) and EMD restored it when present with PGE(2). Prostaglandin E(2) stimulated cAMP production in hGFs while serum or EMD did not. Enamel matrix derivative stimulated hDF proliferation, but the inhibitory effect of PGE(2) was milder than with hGFs. When present together, EMD abolished the PGE(2) -induced inhibition. Enamel matrix derivative inhibited the proliferation of primary hGKs, but PGE(2) had no effect. Finally, we found that hDFs contained about five times less prostaglandin EP(2) receptor mRNA than hGFs, while hGKs contained none.

CONCLUSION

Prostaglandin E(2) inhibits and EMD stimulates hGF proliferation via distinct pathways. The different sensitivities of hDFs and hGKs to PGE(2) can be explained by the levels of EP(2) expression.

Review of osteoimmunology and the host response in endodontic and periodontal lesions

Both lesions of endodontic origin and periodontal diseases involve the host response to bacteria and the formation of osteolytic lesions. Important for both is the upregulation of inflammatory cytokines that initiate and sustain the inflammatory response. Also important are chemokines that induce recruitment of leukocyte subsets and bone-resorptive factors that are largely produced by recruited inflammatory cells. However, there are differences also. Lesions of endodontic origin pose a particular challenge since that bacteria persist in a protected reservoir that is not readily accessible to the immune defenses. Thus, experiments in which the host response is inhibited in endodontic lesions tend to aggravate the formation of osteolytic lesions. In contrast, bacteria that invade the periodontium appear to be less problematic so that blocking arms of the host response tend to reduce the disease process. Interestingly, both lesions of endodontic origin and periodontitis exhibit inflammation that appears to inhibit bone formation. In periodontitis, the spatial location of the inflammation is likely to be important so that a host response that is restricted to a subepithelial space is associated with gingivitis, while a host response closer to bone is linked to bone resorption and periodontitis. However, the persistence of inflammation is also thought to be important in periodontitis since inflammation present during coupled bone formation may limit the capacity to repair the resorbed bone.

Anti-inflammatory effects of EMD in the presence of biomechanical loading and interleukin-1β in vitro

Enamel matrix derivative (EMD) used to promote periodontal regeneration has been shown to exert anti-inflammatory effects. This in vitro study was performed to investigate if the anti-inflammatory actions of EMD are modulated by the local cellular environment, such as inflammation or occlusal, i.e., biomechanical, loading. Human periodontal ligament cells were seeded on BioFlex plates and incubated with EMD under normal, inflammatory, and biomechanical loading conditions for 1 and 6 days. In order to mimic inflammatory and biomechanical loading conditions in vitro, cells were stimulated with interleukin (IL)-1β and exposed to dynamic tensile strain, respectively. The gene expression of IL-1β, IL-1 receptor antagonist (IL-1RN), IL-6, IL-8, IL-10, and cyclooxygenase (COX)-2 was analyzed by real-time RT-PCR and the IL-6 protein synthesis by enzyme-linked immunoassay. For statistical analysis, Student's t test, ANOVA, and post-hoc comparison tests were applied (p < 0.05). EMD downregulated significantly the expression of IL-1β and COX-2 at 1 day and of IL-6, IL-8, and COX-2 at 6 days in normal condition. In an inflammatory environment, the anti-inflammatory actions of EMD were significantly enhanced at 6 days. In the presence of low biomechanical loading, EMD caused a downregulation of IL-1β and IL-8, whereas high biomechanical loading significantly abrogated the anti-inflammatory effects of EMD at both days. Neither IL-1RN nor IL-10 was upregulated by EMD. These data suggest that high occlusal forces may abrogate anti-inflammatory effects of EMD and should, therefore, be avoided immediately after the application of EMD to achieve best healing results.

Inflammation and uncoupling as mechanisms of periodontal bone loss

Periodontal disease is characterized by both inflammation and bone loss. Advances in research in both these areas have led to a new appreciation of not only each field but also the intimate relationship between inflammation and bone loss. This relationship has resulted in a new field of science called osteoimmunology and provides a context for better understanding the pathogenesis of periodontal disease. In this review, we discuss several aspects of the immuno-inflammatory host response that ultimately results in loss of alveolar bone. A proposal is made that periodontal inflammation not only stimulates osteoclastogenesis but also interferes with the uncoupling of bone formation and bone resorption, consistent with a pathologic process. Furthermore, arguments based on experimental animal models suggest a critical role of the spatial and temporal aspects of inflammation in the periodontium. A review of these findings leads to a new paradigm to help explain more fully the impact of inflammation on alveolar bone in periodontal disease so that it includes the effects of inflammation on uncoupling of bone formation from resorption.

Prevotella intermedia induces prostaglandin E2 via multiple signaling pathways

Prostaglandin E(2) (PGE(2)) plays important roles in the bone resorption of inflammatory diseases such as rheumatoid arthritis and periodontitis via specific prostaglandin receptors (i.e., EP1-EP4). In this study, the authors examined whether Prevotella intermedia regulates PGE(2) production and EP expression in human periodontal ligament fibroblasts (hPDLs); they also explored the potential signaling pathways involved in PGE(2) production. P. intermedia induced PGE(2) production and cyclooxygenase-2 (COX-2) expression in a dose- and time-dependent manner. Indomethacin and NS-398 completely abrogated the P. intermedia-induced PGE(2) production without modulating COX-2 expression. Specific inhibitors of extracellular signal-regulated kinase, c-Jun N-terminal kinase, p38, phosphatidylinositol 3-kinase, and protein kinase C--but not c-AMP and protein kinase A--significantly attenuated the P. intermedia-induced COX-2 and PGE(2) expression. P. intermedia reduced EP1 expression in a concentration- and time-dependent manner. The results indicate that the COX-2-dependent induction of PGE(2) by P. intermedia in hPDLs is mediated by multiple signaling pathways.

A ceramide analog inhibits cPLA(2) activity and consequent PGE(2) formation in LPS-stimulated macrophages

Prostaglandin E(2) (PGE(2)) is an important mediator of the inflammatory response. Phospho-ceramide analogue-1 (PCERA-1), a synthetic phospholipid-like molecule, was previously reported to modulate pro- and anti-inflammatory cytokine production. We show here that PCERA-1 inhibited LPS-stimulated PGE(2) production in RAW264.7 macrophages, without affecting COX-2 expression. Furthermore, PCERA-1 efficiently suppressed arachidonic acid (AA) release in response to LPS. The dephosphorylated derivative of PCERA-1, ceramide analogue-1 (CERA-1), mimicked the inhibitory effect of PCERA-1 on AA release and PGE(2) production in macrophages. Inhibition of PGE(2) production by CERA-1 was completely rescued by addition of exogenous AA. Importantly, PCERA-1 and ceramide-1-phosphate (C1P) stimulated the enzymatic activity of cPLA(2)α in an in vitro assay, whereas CERA-1 and ceramide inhibited both basal and C1P-stimulated cPLA(2)α activity. Collectively, these results indicate that CERA-1 suppresses AA release and subsequent PGE(2) production in LPS-stimulated macrophages by direct interaction with cPLA(2), and suggest that ceramide may similarly counteract C1P effect on cPLA(2) activity in cells. The suppression of PGE(2) production is suggested to contribute to the anti-inflammatory action of PCERA-1.

Destructive and protective roles of cytokines in periodontitis: a re-appraisal from host defense and tissue destruction viewpoints

Periodontal diseases (PD) are chronic infectious inflammatory diseases characterized by the destruction of tooth-supporting structures, being the presence of periodontopathogens required, but not sufficient, for disease development. As a general rule, host inflammatory mediators have been associated with tissue destruction, while anti-inflammatory mediators counteract and attenuate disease progression. With the discovery of several T-cell subsets bearing distinct immunoregulatory properties, this pro- vs. anti-inflammatory scenario became more complex, and a series of studies has hypothesized protective or destructive roles for Th1, Th2, Th17, and Treg subpopulations of polarized lymphocytes. Interestingly, the "protective vs. destructive" archetype is usually considered in a framework related to tissue destruction and disease progression. However, it is important to remember that periodontal diseases are infectious inflammatory conditions, and recent studies have demonstrated that cytokines (TNF-α and IFN-γ) considered harmful in the context of tissue destruction play important roles in the control of periodontal infection. Therefore, in this review, the state-of-the-art knowledge concerning the protective and destructive roles of host inflammatory immune response will be critically evaluated and discussed from the tissue destruction and control-of-infection viewpoints.

Heme oxygenase-1 mediates nicotine- and lipopolysaccharide-induced expression of cyclooxygenase-2 and inducible nitric oxide synthase in human periodontal ligament cells

BACKGROUND AND OBJECTIVE

Although heme oxygenase-1 (HO-1) plays a key role in inflammation, its anti-inflammatory effects and mechanism of action in periodontitis are still unknown. This study aimed to identify the effects of HO-1 on the proinflammatory mediators activated by nicotine and lipopolysaccharide (LPS) stimulation in human periodontal ligament (PDL) cells.

MATERIAL AND METHODS

The production of nitric oxide (NO) and prostaglandin E(2) (PGE(2)) was evaluated using Griess reagent and an enzyme immunoassay, respectively. The expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and HO-1 proteins was evaluated by Western blot analysis.

RESULTS

Lipopolysaccharide and nicotine synergistically induced the production of NO and PGE(2) and increased the protein expression of iNOS, COX-2 and HO-1. Treatment with an HO-1 inhibitor and HO-1 small interfering RNAs blocked the LPS- and nicotine-stimulated NO and PGE(2) release as well as the expression of iNOS and COX-2.

CONCLUSION

Our data suggest that the nicotine- and LPS-induced inflammatory effects on PDL cells may act through a novel mechanism involving the action of HO-1. Thus, HO-1 may provide a potential therapeutic target for the treatment of periodontal disease associated with smoking and dental plaque.

Too old to fight? Aging and its toll on innate immunity

Elderly individuals display increased susceptibility to chronic inflammatory diseases and microbial infections, such as periodontitis and oral aspiration pneumonia. The resurgent interest in innate immunity in the 2000s has been accompanied by parallel studies to understand the impact of aging on the function of the innate immune system, which not only provides first-line defense but is essential for the development of adaptive immunity. This review summarizes and discusses our current understanding of age-associated molecular alterations in neutrophils and macrophages, key inflammatory phagocytes implicated in both protective and destructive host responses. The analysis of recent literature suggests that, in advanced age, phagocytes undergo significant changes in signal transduction pathways that may affect their ability to perform antimicrobial functions or regulate the inflammatory response. These abnormalities are expected to contribute to the pathology of oral infection-driven inflammatory diseases in the elderly. Moreover, the elucidation of age-associated defects in the innate immune system will facilitate the development of intervention therapeutic strategies to promote or restore innate immune function and improve the quality of health in old age.

Signal pathways JNK and NF-kappaB, identified by global gene expression profiling, are involved in regulation of TNFalpha-induced mPGES-1 and COX-2 expression in gingival fibroblasts

Background

Prostaglandin E₂ (PGE₂) is involved in several chronic inflammatory diseases including periodontitis, which causes loss of the gingival tissue and alveolar bone supporting the teeth. We have previously shown that tumor necrosis factor α (TNFα) induces PGE₂ synthesis in gingival fibroblasts. In this study we aimed to investigate the global gene expression profile of TNFα-stimulated primary human gingival fibroblasts, focusing on signal pathways related to the PGE₂-synthesizing enzymes prostaglandin E synthases (PGES), as well as the upstream enzyme cyclooxygenase-2 (COX-2) and PGE₂ production.

Results

Microarray and western blot analyses showed that the mRNA and protein expression of the inflammatory induced microsomal prostaglandin E synthase-1 (mPGES-1) was up-regulated by the cytokine TNFα, accompanied by enhanced expression of COX-2 and increased production of PGE₂. In contrast, the expression of the isoenzymes microsomal prostaglandin E synthase-2 (mPGES-2) and cytosolic prostaglandin E synthase (cPGES) was unaffected by TNFα treatment. Using oligonucleotide microarray analysis in a time-course factorial design including time points 1, 3 and 6 h, differentially expressed genes in response to TNFα treatment were identified. Enrichment analysis of microarray data indicated two positively regulated signal transduction pathways: c-Jun N-terminal kinase (JNK) and Nuclear Factor-κB (NF-κB). To evaluate their involvement in the regulation of mPGES-1 and COX-2 expression, we used specific inhibitors as well as phosphorylation analysis. Phosphorylation analysis of JNK (T183/Y185) and NF-κB p65 (S536) showed increased phosphorylation in response to TNFα treatment, which was decreased by specific inhibitors of JNK (SP600125) and NF-κB (Bay 11-7082, Ro 106-9920). Inhibitors of JNK and NF-κB also decreased the TNFα-stimulated up-regulation of mPGES-1 and COX-2 as well as PGE₂ production.

Conclusion

In the global gene expression profile, the enrichment analysis of microarray data identified the two signal transduction pathways JNK and NF-κB as positively regulated by the cytokine TNFα. Inhibition of these TNFα-activated signal pathways reduced the expression of mPGES-1 and COX-2 as well as their end product PGE₂ in gingival fibroblasts. The involvement of the signal pathways JNK and NF-κB in the regulation of PGE₂ induced by TNFα may suggest these two pathways as possible attractive targets in the chronic inflammatory disease periodontitis.

Too old to fight? Aging and its toll on innate immunity

Elderly individuals display increased susceptibility to chronic inflammatory diseases and microbial infections, such as periodontitis and oral aspiration pneumonia. The resurgent interest in innate immunity in the 2000s has been accompanied by parallel studies to understand the impact of aging on the function of the innate immune system, which not only provides first-line defense but is essential for the development of adaptive immunity. This review summarizes and discusses our current understanding of age-associated molecular alterations in neutrophils and macrophages, key inflammatory phagocytes implicated in both protective and destructive host responses. The analysis of recent literature suggests that, in advanced age, phagocytes undergo significant changes in signal transduction pathways that may affect their ability to perform antimicrobial functions or regulate the inflammatory response. These abnormalities are expected to contribute to the pathology of oral infection-driven inflammatory diseases in the elderly. Moreover, the elucidation of age-associated defects in the innate immune system will facilitate the development of intervention therapeutic strategies to promote or restore innate immune function and improve the quality of health in old age.

Prostaglandin E2 inhibits the proliferation of human gingival fibroblasts via the EP2 receptor and Epac

Elevated levels of prostaglandins such as PGE(2) in inflamed gingiva play a significant role in the tissue destruction caused by periodontitis, partly by targeting local fibroblasts. Only very few studies have shown that PGE(2) inhibits the proliferation of a gingival fibroblast (GF) cell line, and we expanded this research by using primary human GFs (hGFs) and looking into the mechanisms of the PGE(2) effect. GFs derived from healthy human gingiva were treated with PGE(2) and proliferation was assessed by measuring cell number and DNA synthesis and potential signaling pathways were investigated using selective activators or inhibitors. PGE(2) inhibited the proliferation of hGFs dose-dependently. The effect was mimicked by forskolin (adenylate cyclase stimulator) and augmented by IBMX (a cAMP-breakdown inhibitor), pointing to involvement of cAMP. Indeed, PGE(2) and forskolin induced cAMP generation in these cells. Using selective EP receptor agonists we found that the anti-proliferative effect of PGE(2) is mediated via the EP(2) receptor (which is coupled to adenylate cyclase activation). We also found that the effect of PGE(2) involved activation of Epac (exchange protein directly activated by cAMP), an intracellular cAMP sensor, and not PKA. While serum increased the amount of phospho-ERK in hGFs by approximately 300%, PGE(2) decreased it by approximately 50%. Finally, the PGE(2) effect does not require endogenous production of prostaglandins since it was not abrogated by two COX-inhibitors. In conclusion, in human gingival fibroblasts PGE(2) activates the EP(2)-cAMP-Epac pathway, reducing ERK phosphorylation and inhibiting proliferation. This effect could hamper periodontal healing and provide further insights into the pathogenesis of inflammatory periodontal disease.

Alteration of PTGS2 promoter methylation in chronic periodontitis

Levels of prostaglandin E(2) and the prostaglandin-endoperoxide synthase-2 (PTGS2, or COX-2) increase in actively progressing periodontal lesions, but decrease in chronic disease. We hypothesized that chronic inflammation is associated with altered DNA methylation levels within the PTGS2 promoter, with effects on COX-2 mRNA expression. PTGS2 promoter methylation levels from periodontally inflamed gingival biopsies showed a 5.06-fold increase as compared with non-inflamed samples (p = 0.03), and the odds of methylation in a CpG site in the inflamed gingival group is 4.46 times higher than in the same site in the non-inflamed group (p = 0.016). The level of methylation at -458 bp was inversely associated with transcriptional levels of PTGS2 (RT-PCR) (p = 0.01). Analysis of the data suggests that, in chronically inflamed tissues, there is a hypermethylation pattern of the PTGS2 promoter in association with a lower level of PTGS2 transcription, consistent with a dampening of COX-2 expression in chronic periodontitis. These findings suggest that the chronic persistence of the biofilm and inflammation may be associated with epigenetic changes in local tissues at the biofilm-gingival interface.

Preventive effects of a cocoa-enriched diet on gingival oxidative stress in experimental periodontitis

BACKGROUND

Oxidative stress affects the progression of periodontitis. Cocoa is a rich source of flavonoids with antioxidant properties, which could suppress gingival oxidative stress in periodontal lesions. The purpose of the present study was to investigate the effects of a cocoa-enriched diet on gingival oxidative stress in a rat-periodontitis model.

METHODS

In this 4-week study, rats were divided into three groups (n = 8/group): a control group (fed a regular diet) and two periodontitis groups (fed a regular diet or cocoa-enriched diet [10% of food intake]). Periodontitis was induced by ligature placement around the mandibular first molars. Serum levels for reactive oxygen metabolites were measured at baseline and 2 and 4 weeks. At 4 weeks, the levels of 8-hydroxydeoxyguanosine and reduced/oxidized glutathione ratio were determined to evaluate gingival oxidative damage and antioxidant status, respectively.

RESULTS

Rats with experimental periodontitis that were fed a regular diet showed an increase in the level of serum reactive oxygen metabolites in a time-dependent manner. These rats also had an increased 8-hydroxydeoxyguanosine level and decreased reduced/oxidized glutathione ratio in the gingival tissue, inducing alveolar bone loss and polymorphonuclear leukocyte infiltration. Although experimental periodontitis was induced in the rats fed a cocoa-enriched diet, they did not show impairments in serum reactive oxygen metabolite level and gingival levels for 8-hydroxydeoxyguanosine and reduced/oxidized glutathione ratio. Alveolar bone loss and polymorphonuclear leukocyte infiltration after ligature placement were also inhibited by cocoa intake.

CONCLUSION

Consuming a cocoa-enriched diet could diminish periodontitis-induced oxidative stress, which, in turn, might suppress the progression of periodontitis.

Macrolide antibiotics like azithromycin increase lipopolysaccharide-induced IL-8 production by human gingival fibroblasts

Objective

Macrolide antibiotics are reported to modulate the production of cytokines in various type of cells. We examined the effect of macrolide antibiotics on inflammatory cytokines (IL-6 and IL-8) and chemical mediator (PGE₂) and also matrix metalloproteinases (MMPs) productions by human gingival fibroblasts (HGFs) treated with lipopolysaccharide (LPS).

Methods

The effect of macrolide antibiotics [erythromycin (EM), azithromycin (AZM) and josamycin (JOM)] on HGFs proliferation were examined by MTT assay. HGFs were treated with LPS from Porphyromonas gingivalis (PgLPS) and macrolide antibiotics, and IL-6, IL-8 and PGE₂ levels were evaluated by ELISA. MMPs were detected by gelatin zymography.

Results

AZM slightly but significantly decreased HGFs proliferation, while EM and JOM did not affected. AZM increased PgLPS-induced IL-8 production dose-dependently, while AZM did not alter IL-6 and PGE₂ productions. EM and JOM did not altered PgLPS-induced IL-6, IL-8 and PGE₂ productions. All macrolide antibiotics did not alter MMPs production. These results indicate that macrolide antibiotics have no direct anti-inflammatory effect. However, the use of the inhibitors of cell signaling pathway failed to reveal the mechanism that AZM enhanced PgLPS-induced IL-8 production.

Conclusion

These results suggest macrolide antibiotics have an indirect anti-inflammatory effect as a result of their antimicrobial properties. Because AZM increased LPS-induced IL-8 production by HGFs, the possibility is considered that neutrophils may be migrated to periodontal tissue and phagocytize the periodontopathic bacteria more efficiently.

Changes in inflammatory mediators in peri-implant fluid after implant insertion

BACKGROUND

Endosseous dental titanium implants have revolutionized restorative dentistry and have made a significant impact on improved patient care. The aim of this study was to compare and evaluate the influence of the placement technique on periodontal health.

METHODS

A baseline examination was performed in patients with submerged and non-submerged titanium implants, including an evaluation of plaque index (PI), gingival index (GI), periodontal probing depth (PD), clinical attachment level (CAL), and bone level, as well as histamine and arachidonic acid metabolite concentrations, in the peri-implant crevicular fluid. Examinations were repeated after 12, 24, and 36 months.

RESULTS

Bone loss was significantly higher in the submerged group relative to the non-submerged group at 3 years (P <0.01), with a slight increase at 24 months. All clinical parameters were significantly higher in the submerged group relative to the non-submerged group at 24 and 36 months (P <0.05 for PI; P <0.01 for GI, PD, and CAL). The mean levels of histamine and other inflammatory mediators were significantly higher, whereas 15(S)-hydroxy-5,8,11,13-eicosatetraenoic acid concentrations were significantly reduced in the submerged group, with a high correlation with periodontal indices at 24 and 36 months (P <0.001).

CONCLUSION

This longitudinal study suggested that submerged implants present a number of risks for periodontal complications compared to non-submerged implants, which can be evidenced by inflammatory mediator variations in the peri-implant crevicular fluid.