Cytokines and prostaglandins in immune homeostasis and tissue destruction in periodontal disease

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.

Diabetes, periodontitis, and the subgingival microbiota

Both type 1 and type 2 diabetes have been associated with increased severity of periodontal disease for many years. More recently, the impact of periodontal disease on glycaemic control has been investigated. The role of the oral microbiota in this two-way relationship is at this stage unknown. Further studies, of a longitudinal nature and investigating a wider array of bacterial species, are required in order to conclusively determine if there is a difference in the oral microbiota of diabetics and non-diabetics and whether this difference accounts, on the one hand, for the increased severity of periodontal disease and on the other for the poorer glycaemic control seen in diabetics.

Antibiotic-induced Porphyromonas gingivalis LPS release and inhibition of LPS-stimulated cytokines by antimicrobial peptides

Bacterial lipopolysaccharide (LPS) release during periodontal infection is a significant component of periodontal disease. We hypothesized that some bacterial LPS release results from bacterial exposure to antibiotics. Therefore, we examined the ability of various classes of antibiotics to induce LPS release from Porphyromonas gingivalis as well as the ability of antimicrobial peptides (AMPs) to inhibit purified LPS. All antibiotics tested against P. gingivalis were able to liberate 1.9-12.9 times more LPS as compared to untreated bacteria. Among the three AMPs tested, LL-37 was found to be the most potent inhibitor of cytokine (tumor necrosis factor-alpha, interleukin-1beta, interleukin-6) production and completely neutralized purified P. ginigivalis LPS activity in the chromogenic limulus amebocyte lysate (LAL) and whole blood cytokine stimulation assays. These observations suggest that therapeutic approaches utilizing AMPs as adjuncts to neutralize released LPS should be considered.

Evidence that metyrapone in the presence of inflammation modulates cytokine mRNA expression

OBJECTIVE

Metyrapone (MT) has been used clinically to decrease glucocorticoid levels in human and animal studies. However, the potential effects of MT in the presence of inflammation are poorly understood. Thus, the aim of this study was to evaluate the effects of the administration of MT on the mRNA levels of pro-inflammatory cytokines in the presence of inflammation induced by the well-established model of ligature-induced periodontitis in rats.

MATERIAL AND METHODS

Sixty animals were randomly assigned into three experimental groups of 20 rats each: G1-control; G2-periodontal disease (PD) induced by cotton ligature; G3-PD associated with 3 daily doses of MT (50mg/kg/3×3h). After 30 days, all animals were killed by decapitation. Blood samples were taken and the concentrations of corticosterone and catecholamines measured. Marginal tissues around ligated and non-ligated teeth were harvested and gene expression was assessed by quantitative polymerase chain reaction technique (qPCR). Moreover, the area of interradicular bone loss (ABL) was histometrically determined.

RESULTS

Data analysis showed that: (i) ligature placement resulted in a significant ABL, as compared to non-ligated sites of G1 group; (ii) mRNA levels of all the pro-inflammatory factors assessed (INF-γ, TNF-α, IL-1β and IL-6) were increased in the PD group (G2) (p<0.05) when compared to G1; (iii) there were no significant differences in corticosterone and catecholamine plasmatic levels between the three groups; (iv) MT administration, in the presence of inflammation, induces an increased ABL and significantly increased mRNA levels of all pro-inflammatory cytokines analyzed (p<0.05).

CONCLUSION

Within the limits of this study, it can be concluded that MT in the presence of inflammation may modulate expression of pro-inflammatory cytokines, regardless of its effect on plasma corticosterone levels.

Impaired immune tolerance to Porphyromonas gingivalis lipopolysaccharide promotes neutrophil migration and decreased apoptosis

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

Expression of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor, fibroblast growth factor-inducible 14 protein (Fn14), in healthy tissues and in tissues affected by periodontitis

BACKGROUND AND OBJECTIVE

Host-derived enzymes, cytokines and other proinflammatory mediators play an integral role in periodontal destruction. The levels of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor, fibroblast growth factor-inducible 14 protein (Fn14), are elevated in tissues from a number of chronic inflammatory diseases. The aim of the present study was to investigate the expression of TWEAK and Fn14 at the protein and mRNA levels in gingival biopsies from periodontitis patients and from clinically healthy patients.

MATERIALS AND METHODS

Gingival biopsies were obtained from healthy sites (n = 7) and from sites affected by periodontitis (n = 27). The expression of TWEAK and Fn14 was investigated by immunohistochemistry in formalin-fixed, paraffin-embedded tissues. The levels of mRNA for TWEAK and Fn14 were also investigated by RT-PCR.

RESULTS

The expression of TWEAK and Fn14 proteins was significantly higher in periodontitis tissue than in healthy tissue. In periodontitis tissues, TWEAK and Fn14 proteins were mainly expressed by mononuclear leukocytes (morphologically resembling lymphocytes and plasma cells), by cells lining blood vessels, by spindle-shaped cells resembling fibroblasts and by multinucleated cells. The Fn14 mRNA level in periodontitis tissue was significantly higher than that in healthy tissue. A moderate correlation between TWEAK/Fn14 expression and inflammation and bone loss, but not pocket depth, was noted.

CONCLUSION

This study demonstrates higher expression of TWEAK protein and of Fn14 mRNA and protein in periodontitis tissues than in clinically healthy controls. Our data support the concept that TWEAK/Fn14 signaling is an additional player in the pathogenesis of periodontitis and adds to the increasing number of cytokine networks involved in periodontal inflammation.

[Pathogenesis of parodontitis in rheumatic diseases]

Inflammatory periodontal disease (PD) is a common disease worldwide that has a primarily bacterial aetiology and is characterized by dysregulation of the host inflammatory response. The degree of inflammation varies among individuals with PD independently of the degree of bacterial infection, suggesting that alteration of the immune function may substantially contribute to its extent. Factors such as smoking, education, and body mass index (BMI) are discussed as potential risk factors for PD. Most PD patients respond to bacterial invaders by mobilizing their defensive cells and releasing cytokines such as interleukin (IL)-1beta, tumour necrosis factor (TNF)-alpha, and IL-6, which ultimately causes tissue destruction by stimulating the production of collagenolytic enzymes, such matrix metalloproteinases. Recently, there has been growing evidence suggesting an association between PD and the increased risk of systemic diseases, such ateriosclerosis, diabetes mellitus, stroke, and rheumatoid arthritis (RA). PD and rheumatologic diseases such as RA share many pathological aspects and immunological findings.

Association of single nucleotide gene polymorphism at interleukin-1beta +3954, -511, and -31 in chronic periodontitis and aggressive periodontitis in Dravidian ethnicity

BACKGROUND

Interleukin (IL)-1beta gene polymorphisms are considered a potential risk factor for periodontal disease. The aim of this study is to identify the association of IL-1beta gene polymorphisms with chronic periodontitis and aggressive periodontitis in a Malayalam-speaking Dravidian population from South India.

METHODS

The case-control study consisted of 43 patients with chronic periodontitis and 54 patients with aggressive periodontitis as cases, and the control group consisted of 101 healthy subjects. All subjects were genotyped for IL-1beta +3954, -511, and -31 loci by polymerase chain reaction amplification followed by restriction enzyme digestion and gel electrophoresis. Genotype, allele, and haplotype analyses were done.

RESULTS

Analyses for allele and genotypes showed a high frequency of the C allele and CC genotype for single nucleotide polymorphism IL-1beta +3954 in the group with chronic periodontitis and no difference for patients with aggressive periodontitis compared to controls (P <0.05). Haplotype analysis showed that IL-1beta -31 and -511 were in strong linkage disequilibrium in all groups. The IL-1beta -31 allele T was in linkage with allele T of IL-1beta +3954 in the control group.

CONCLUSIONS

In the Malayalam-speaking Dravidian population, allele C of IL-1beta +3954 appeared to be an important risk factor for chronic periodontitis. The IL-1beta -31 allele T was in linkage with allele T of IL-1beta +3954 in the control group. No gene polymorphisms were found in patients with aggressive periodontitis. More studies with a larger sample size involving the entire cluster of the IL-1beta gene are necessary to determine the exact role of IL-1beta gene polymorphisms in periodontal disease.

Stem cell factor in gingival crevicular fluid in periodontal health and disease

Background: Stem cell factor is a pleiotropic cytokine produced by several cell types including fibroblasts, bone marrow stromal cells, mast cells, and endothelial cells. In addition, stem cell factor is an important hematopoietic growth factor, which binds to and activates the ligand for the tyrosine kinase-type receptor c-kit. Objectives: Analyze concentration of stem cell factor within gingival crevicular fluid (GCF) in both periodontal health and disease and to determine the correlation of stem cell factor in GCF and inflammatory status of periodontal tissues. Materials and methods: Forty-five subjects (aged 24 to 75 years) were classified into the following three groups according to their periodontal tissue status as group I (clinically healthy gingiva with no loss of attachment), group II (gingivitis with no attachment loss), and group III (periodontitis). GCF samples collected from each patient were examined for stem cell factor level using enzyme-linked immunosorbant assay. Results: The maximum level of stem cell factor in GCF was obtained for group III (71.8±7.8 pg/g protein), and the lowest mean stem cell factor concentration in GCF was observed for group I (22.1±7.3 pg/g protein). The GCF stem cell factor level of patients in group III was statistically higher than that in group II (p <0.04) and group I (p <0.001). In addition, the mean GCF levels of stem cell factor in group II (48.1±7.5 pg/g protein) were significantly higher than those in group I (p <0.02). There was a positive correlation between stem cell factor in GCF and gingival inflammation index (r=0.59, p <0.001) Conclusion: GCF levels of stem cell factor increased in parallel with the severity of periodontal disease. Its levels in GCF could be potentially useful as a biochemical marker of periodontal inflammation and the host response.

Flutamide inhibits nifedipine- and interleukin-1 beta-induced collagen overproduction in gingival fibroblasts

BACKGROUND AND OBJECTIVE

To understand the role of the androgen receptor in gingival overgrowth, the effects of flutamide on interleukin-1 beta- and nifedipine-induced gene expression of connective tissue growth factor (CTGF/CCN2) and collagen production in gingival fibroblasts were examined.

MATERIAL AND METHODS

Gingival fibroblasts from healthy subjects and patients with dihydropyridine-induced gingival overgrowth (DIGO) were used. Confluent cells were treated with nifedipine, interleukin-1 beta or both. The mRNA expression was examined using real-time polymerase chain reaction, and the concentration of total soluble collagen in conditioned media was analysed by Sircol Collagen Assay. In addition, the protein expressions of androgen receptor, CTGF/CCN2 and type I collagen in gingival tissue were determined by western blot.

RESULTS

Interleukin-1 beta was more potent than nifedipine in stimulating CTGF/CCN2 and procollagen alpha1(I) mRNA expression, and there was an additive effect of the two drugs. Healthy cells exhibited an equal or stronger response of procollagen alpha1(I) than those with DIGO, but DIGO cells displayed a stronger response in the secretion of soluble collagen in the same conditions. Flutamide, an androgen receptor antagonist, inhibited stimulation by nifedipine or interleukin-1 beta. Additionally, the protein expressions of androgen receptor and type I collagen were higher in DIGO gingival tissue than those in healthy gingival tissue.

CONCLUSION

The data suggest that both nifedipine and interleukin-1 beta play an important role in DIGO via androgen receptor upregulation and that gingival overgrowth is mainly due to collagen accumulation. Flutamide decreases the gene expression and protein production of collagen from dihydropyridine-induced overgrowth cells.

Interleukin-6 polymorphisms modify the risk of periodontitis: a systematic review and meta-analysis

OBJECTIVE

To clarify the association of IL-6 polymorphisms and periodontitis, a meta-analysis of case-control studies and a systemic review were conducted.

MATERIAL AND METHODS

We performed a literature search using PubMed and Medline database to May 2009, with no restrictions. We also reviewed references from all retrieved articles. Six case-control studies involving 1 093 periodontitis cases and 574 controls were selected for meta-analysis to assess the purported associations between IL-6 polymorphisms and the risk of periodontitis. IL-6 -174 G/C and -572 C/G polymorphisms were included in the present meta-analysis, and the association between IL-6 -6331 T/C polymorphism and the risk of periodontitis was adequately reviewed as well.

RESULTS AND CONCLUSION

The present meta-analysis indicates that the IL-6 -174 G allele could not modify the risk of chronic periodontitis, but increased the risk of aggressive periodontitis. And -572 C/G polymorphism is associated with the pathogenesis of periodontitis, including chronic periodontitis or aggressive periodontitis.

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.

Relationship between periodontitis and hepatic abnormalities in young adults

OBJECTIVE

Obesity has been implicated as a risk factor for periodontitis and non-alcoholic fatty liver disease (NAFLD). In NAFLD, elevated alanine aminotransferase (ALT) is associated with obesity. Although a possible interrelationship between liver function and periodontitis has been reported among the middle-aged population, the correlation in young adults is little known. This study was designed to investigate the relationship between ALT and the presence of periodontitis in university students in Japan.

MATERIAL AND METHODS

Medical and oral health data were collected in a cross-sectional examination conducted by the Health Service Center of Okayama University. Systemically healthy, non-smoking students aged 18 and 19 years old (n = 2225) were included. The protocol of the United States National Health and Nutrition Examination Survey was applied. Subjects with probing pocket depth >or= 4 mm were defined as having periodontitis. Logistic regression analysis was used to estimate the association between ALT, body mass index and periodontitis.

RESULTS

The number of subjects with periodontitis was 104 (4.7%). In males, having periodontitis was significantly associated with an increased level of ALT (>or= 41 IU/l) in logistic regression analysis (adjusted odds ratio 2.3; 95% confidence interval 1.0-5.2; p < 0.05). However, there was no significant association between periodontitis and ALT in female students.

CONCLUSIONS

Elevated ALT could be a potential risk indicator for periodontitis among young males. Monitoring hepatic abnormalities to prevent periodontitis must be better understood, even in the young adult population.

Expression and regulation of the NALP3 inflammasome complex in periodontal diseases

Periodontitis is an infectious process characterized by inflammation affecting the supporting structures of the teeth. Porphyromonas gingivalis is a major oral bacterial species implicated in the pathogenesis of periodontitis. Processing of interleukin (IL)-1 family cytokines is regulated by an intracellular innate immune response system, known as the NALP3 [nacht domain-, leucine-rich repeat-, and pyrin domain (PYD)-containing protein 3] inflammasome complex. The aim of the present study was to investigate by quantitative real-time polymerase chain reaction (PCR) the mRNA expression of NALP3, its effector molecule apoptosis associated speck-like protein (ASC), its putative antagonist NLRP2 (NLR family, PYD-containing protein 2), IL-1beta and IL-18 (i) in gingival tissues from patients with gingivitis (n = 10), chronic periodontitis (n = 18), generalized aggressive periodontitis (n = 20), as well as in healthy subjects (n = 20), (ii) in vitro in a human monocytic cell line (Mono-Mac-6), in response to P. gingivalis challenge for 6 h. The clinical data indicate that NALP3 and NLRP2, but not ASC, are expressed at significantly higher levels in the three forms of inflammatory periodontal disease compared to health. Furthermore, a positive correlation was revealed between NALP3 and IL-1beta or IL-18 expression levels in these tissues. The in vitro data demonstrate that P. gingivalis deregulates the NALP3 inflammasome complex in Mono-Mac-6 cells by enhancing NALP3 and down-regulating NLRP2 and ASC expression. In conclusion, this study reveals a role for the NALP3 inflammasome complex in inflammatory periodontal disease, and provides a mechanistic insight to the host immune responses involved in the pathogenesis of the disease by demonstrating the modulation of this cytokine-signalling pathway by bacterial challenge.

The 15-deoxy-Delta12,14-prostaglandin J2 inhibits LPS-stimulated AKT and NF-kappaB activation and suppresses interleukin-6 in osteoblast-like cells MC3T3E-1

AIMS

Periodontitis is a chronic inflammatory disease that results in gingival inflammation and periodontal tissue destruction and is accompanied by alveolar bone resorption and eventual tooth loss. We examined the effect of 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) on periodontitis by inhibiting the production of interleukin-6 (IL-6).

MAIN METHODS

Osteoblast-like cells MC3T3E-1 were pretreated with 15d-PGJ(2) before being incubated with lipopolysaccharide (LPS), the effect of 15d-PGJ(2) on IL-6 production, expression and its regulatory mechanisms were studied by reverse transcription-polymerase chain reaction (RT-PCR), Western blot, electrophoretic mobility shift assay (EMSA), and confocal laser scanning microscopy study.

KEY FINDINGS

15d-PGJ(2) inhibits LPS-stimulated IL-6 production in a concentration-dependent manner in osteoblast-like cells MC3T3E-1, without appreciable cytotoxicity. To further examine the mechanism responsible for the inhibition of IL-6 production by 15d-PGJ(2), we examined the effect of 15d-PGJ(2) on nuclear factor-kappaB (NF-kappaB) activation and the phosphorylation of protein kinase B (Akt). 15d-PGJ(2) treatment clearly reduced the DNA binding activity of NF-kappaB in LPS-stimulated osteoblast-like cells MC3T3E-1, an effect that was mediated by inhibiting the degradation of inhibitor kappaB (IkappaB) and nuclear translocation of NF-kappaB p65 subunit. In addition, 15d-PGJ(2) attenuated the LPS-mediated Akt pathway. These effects of 15d-PGJ(2) were not abrogated by the PPARgamma antagonist, GW9662, indicating that they are PPARgamma-independent actions.

SIGNIFICANCE

These results suggest that 15d-PGJ(2) possess a potent suppressive effect on inflammatory responses of osteoblast-like cells MC3T3E-1 via the Akt and NF-kappaB pathways independent of PPARgamma and suggest that this compound may offer some insight into the development of a new therapeutic approach to the prevention and treatment of periodontal diseases.

Gingival crevicular fluid levels of monocyte chemoattractant protein-1 in periodontal health and disease

OBJECTIVES

Monocyte chemoattractant protein-1 (MCP-1) stimulates the chemotaxis of monocytes and also several cellular events associated with chemotaxis thus causes recruitment of inflammatory cells. Its increased gingival crevicular fluid (GCF) levels in periodontal disease have been reported in previous studies. The present study has been carried out to assess the role of MCP-1 in periodontal disease progression and also to determine the effect of periodontal treatment on MCP-1 concentration in GCF.

DESIGN

A total of 60 subjects were divided into three groups (n=20) based on gingival index (GI), probing pocket depth (PPD) and clinical attachment loss (CAL): healthy (group I), gingivitis (group II) and chronic periodontitis (group III). A fourth group (group IV) consisted of 20 subjects from group III, 6-8 weeks after treatment (i.e. scaling and root planing). GCF samples collected from each patient were quantified for MCP-1 using ELISA.

RESULTS

The mean MCP-1 concentration in GCF was found to be the highest in group III, i.e. 72.60 pg/microl. The mean MCP-1 concentration in group I was 19.70 pg/microl and in group IV was 8.50 pg/microl. The mean MCP-1 concentration (37.00 pg/microl) in group II was found to lie in between the concentrations obtained in groups I and III.

CONCLUSIONS

GCF MCP-1 levels increased progressively with the progression of disease and decreased after treatment. Levels of MCP-1 correlated positively with clinical parameters like GI, PPD and CAL thus it can be considered as an inflammatory biomarker in periodontal disease and also deserves further consideration as a therapeutic target.

Effect of periodontal treatment on IL-1beta, IL-1ra, and IL-10 levels in gingival crevicular fluid in patients with aggressive periodontitis

AIM

The aim of this study was to examine the effect of phase I periodontal treatment on the levels of interleukin (IL)-1beta, IL-1ra, and IL-10 in gingival crevicular fluid (GCF) in patients with generalized aggressive periodontitis (G-AgP).

MATERIAL AND METHODS

Data were obtained from 15 patients with aggressive periodontitis and 15 healthy controls. GCF was collected from at least four pre-selected sites (one shallow, at least two moderate, or at least one deep pockets) in patients with G-AgP. In the healthy group, GCF samples were collected from one site. The cytokine levels were determined by an enzyme-linked immunosorbent assay. Probing depth, clinical attachment level (CAL), gingival and plaque indices, and bleeding on probing were measured. The GCF sampling and clinical measurements were recorded at baseline and 6 weeks later after periodontal treatment.

RESULTS

IL-1beta levels were significantly higher at the moderate and deep pocket sites compared with the shallow sites (p<0.05). After periodontal therapy, IL-1beta levels were significantly reduced in the moderate and deep pocket sites (p<0.05). IL-1ra levels at baseline of the moderate and deep pocket sites were significantly lower than the control sites (p<0.05). IL-10 levels were similar in all pockets and did not change after periodontal therapy.

CONCLUSIONS

The periodontal treatment improves the clinical parameters in G-AgP, and this improvement is evident in deep pocket sites for pocket depth and CAL values. These results confirm that IL-1beta is effective for evaluating the periodontal inflammation and can thus be used as a laboratory tool for assessing the activity of periodontal disease.

Microarray analysis of nicotine-induced changes in gene expression in a macrophage-like human cell line

BACKGROUND AND OBJECTIVE

Cigarette smoking has been suggested as a risk factor for periodontitis. Thousands of components are present in cigarette smoke, including nicotine, which may play an important role in the observed effects of smoking on cell metabolism. However, the mechanisms underlying these effects are unclear. Using DNA microarrays, we monitored differentially expressed genes, responsive to nicotine, in a macrophage-like human cell line.

MATERIAL AND METHODS

Human U937 cells were treated for 1 h, with or without 1.0 microg/ml of nicotine. For differentiation, cultures were incubated with 10 nm phorbol myristate acetate for 48 h. Analysis of gene expression was performed using a DNA microarray of 8500 genes.

RESULTS

The expression of 4914 genes was detected. Screening was carried out on those genes whose expression in three separate experiments showed an average change of twofold or greater, and 118 up-regulated genes and 97 down-regulated genes were identified. Among these were genes related to inflammation and other immune responses, such as phospholipase A2 and interferon. Consistent with the array findings, we found similar changes in mRNA expression after analysis using the real-time polymerase chain reaction.

CONCLUSION

The results suggest that nicotine causes excess inflammation and disturbs host defense mechanisms against pathogens.

Porphyromonas gingivalis antagonises Campylobacter rectus induced cytokine production by human monocytes

Porphyromonas gingivalis and Campylobacter rectus are two major bacterial species implicated in the pathogenesis of periodontitis. P. gingivalis can antagonise the inflammatory response to other periodontal pathogens, a property commonly attributed to its lipopolysaccharide (LPS). The aim of this study was to investigate the capacity of P. gingivalis to antagonise C. rectus induced cytokine stimulation from human monocytes, and to investigate the involvement of its LPS. Primary human monocytes and Monomac-6 cells were challenged with culture supernatants from P. gingivalis and C. rectus, and levels of IL-1beta, IL-6 and IL-8 produced were measured by ELISA after 6h incubation. Purified P. gingivalis LPS was also added alone or in combination with C. rectus culture supernatant. Both species significantly stimulated the production of all three cytokines from the two cell lines, but P. gingivalis was considerably weaker inducer. Co-stimulation of the cells with P. gingivalis and C. rectus suppressed the cytokine-stimulatory capacity of the latter. P. gingivalis LPS alone was sufficient to antagonise IL-6 and IL-8, but not IL-1beta stimulation by C. rectus. In conclusion, mixed infections may impair host immune responses by reducing pro-inflammatory cytokine levels, which may be of relevance to the pathogenesis of periodontitis.

Gingival Epithelial Cell Expression of Macrophage Inflammatory Protein-1α Induced by Interleukin-1β and Lipopolysaccharide

BACKGROUND

Elevated levels of the macrophage inflammatory protein-1alpha (MIP-1alpha) are reported in inflammatory bone diseases including periodontitis. We evaluated the ability of interleukin-1beta (IL-1beta) and bacterial lipopolysaccharides (LPSs) to modulate MIP-1alpha expression in epithelial cells, fibroblasts, and polymorphonuclear leukocytes (PMNs). We also evaluated the effect of MIP-1alpha as an osteoclast activating factor.

METHODS

Human gingival epithelial cells and fibroblasts were obtained by primary cell culture. PMNs were isolated from healthy controls. Human MG63 osteosarcoma cells were used as osteoblastic cells. After incubation of each cell type with IL-1beta, Porphyromonas gingivalis LPS, and Actinobacillus actinomycetemcomitans LPS, MIP-1alpha mRNA and secreted protein levels were quantified by reverse transcription-polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemistry. The ability of recombinant MIP-1alpha to induce osteoclast formation was determined by tartrate resistant acid phosphatase assay.

RESULTS

MIP-1alpha expression in PMNs and gingival epithelial cells was induced by IL-1beta and LPS, but neither induced MIP-1alpha expression in gingival fibroblasts or osteoblastic cells. MIP-1alpha was highly expressed in the basal epithelial layer of inflamed gingiva but not in healthy gingiva. MIP-1alpha induced osteoclast formation at an optimal concentration of 0.05 to 2 ng/ml.

CONCLUSIONS

MIP-1alpha expression by gingival epithelial cells may be important in initiating inflammation by facilitating accumulation and activation of leukocytes. The ability of MIP-1alpha to facilitate formation of multinuclear bone cells indicates a possible role in periodontitis-associated bone destruction. These findings indicate MIP-1alpha may play an important role in early and later stages of inflammatory-related periodontitis.

Interleukin-6 expression and gene polymorphism are associated with severity of periodontal disease in a sample of Brazilian individuals

Interleukin (IL)-6 is an inflammatory mediator involved in bone resorption. G/C polymorphism at position -174 of the IL-6 gene has been reported to influence IL-6 expression, with the G allele associated with higher expression levels. The aims of this study were to investigate the expression of IL-6 as well as the incidence of IL-6 (-174) gene polymorphism and their correlation to the severity of periodontitis in Brazilians. Peripheral blood mononuclear cells were collected from 12 non-smoker individuals with periodontitis for evaluation of IL-6 expression using flow cytometry. We observed a positive correlation between the mean clinical attachment loss and intensity of expression of IL-6, in which the greater the attachment loss, the higher the expression of IL-6 (P=0 x 007, R2=0 x 52). Also, patients with severe periodontitis displayed a higher intensity of IL-6 expression compared to moderate periodontitis (P=0 x 04). To determine the occurrence of IL-6 gene polymorphism, DNA was obtained from oral swabs of 209 Brazilian individuals with and without periodontitis. Polymerase chain reaction, restriction endonuclease digestion and electrophoresis were performed, allowing for detection of the IL-6 (-174) polymorphism. We observed that non-smokers with moderate periodontitis (P=0 x 05) and control (P=0 x 04) groups displayed a higher incidence of the G genotype when compared to severe periodontitis. This suggests that the G genotype may represent a protective role in severity of periodontitis. Thus, the increased expression of IL-6 and IL-6 (-174) polymorphism are associated with periodontal disease severity in Brazilian individuals.

Polymorphisms in the CD14 and IL-6 genes associated with periodontal disease

AIM

To compare the frequencies of cytokine and receptor molecule genotypes in patients with chronic periodontitis with the corresponding frequencies in a reference population and to study the relationship between periodontal disease severity and polymorphisms in the studied genes.

SUBJECTS AND METHODS

CD14, IL-6, TNF-alpha, IL-10, IL-1alpha, IL-1beta, and TLR-4 polymorphisms of 51 periodontitis patients were studied using polymerase chain reaction. The genotype frequencies in the periodontitis patients and a reference population (n=178) were compared. Probing pocket depth (PD), periodontal attachment level (AL), and alveolar bone level (BL) were related to the genotypes.

RESULTS

No statistically significant differences could be found between the frequencies of the cytokine genotypes in the periodontitis patients and in the reference group. The extent of periodontal disease was higher in subjects with the T-containing genotype of CD14(-260) and the GG genotype of IL-6(-174) when compared with the extent in the rest of the group. Subjects carrying the composite genotype of the above two were most severely affected by periodontal disease.

CONCLUSION

According to the present results, an evident association exists between the carriage of the T-containing genotype of CD14(-260) and the GG genotype of IL-6(-174) and the extent periodontal disease.

Associations between peri-implant crevicular fluid volume, concentrations of crevicular inflammatory mediators, and composite IL-1A ?889 and IL-1B +3954 genotype: A cross-sectional study on implant recall patients with and without clinical signs of peri-implantitis

OBJECTIVES

To assess possible relationships between peri-implant crevicular fluid (PICF) volumes, biochemical markers of the peri-implant immune response, and periodontitis-associated genotype.

MATERIAL AND METHODS

PICF samples from 29 implant maintenance patients, 24 wearing overdentures, five having single crowns and bridgework (11 patients with peri-implantitis and 18 individuals with healthy peri-implant conditions), were analyzed for per site and per crevicular-fluid-volume concentrations of interleukin-1beta, plasminogen activator inhibitor type 2, and prostaglandin E2 by ELISA. Associations between the three substance concentrations and to crevicular fluid flow rate were analyzed by linear regression analysis. The possible differentiating influence of the composite interleukin-1A and -1B genotype on the patients' peri-implant health and biochemical inflammatory status was checked formally with t-test statistics and the Wilcoxon' test. One implant per patient was chosen for analysis.

RESULTS

In patients with healthy peri-implant conditions, genotype-positive individuals showed elevated crevicular fluid flow rates and at the same time reduced mediator concentrations. In patients with an implant affected from peri-implantitis, no statistically significant influence of the periodontitis-associated genotype around the fixture can be stated. There was no statistical difference between per site and per crevicular-fluid-volume concentration analyses. All three mediator concentrations were positively related to each other, while there was a strong negative correlation between crevicular fluid volume and plasminogen activator inhibitor 2 or prostaglandin E2.

CONCLUSIONS

The Interleukin-1 polymorphism investigated exerted only little influence on the peri-implant crevicular immune response, and this influence appeared to be of limited impact in sites with established peri-implantitis lesions.

Protective effects of Tacrolimus, a calcineurin inhibitor, in experimental periodontitis in rats

OBJECTIVE

Periodontitis is a well-appreciated example of leukocyte-mediated bone loss and inflammation with pathogenic features similar to those observed in other inflammatory diseases, such as arthritis. Since Tacrolimus, is an immunomodulatory drug used for the treatment of some cases of arthritis, we hypothesized that it may modulate periodontal disease.

DESIGN

Using a murine model of ligature-induced periodontal disease, we assessed the effects of daily administrations of Tacrolimus (1mg/kg body weight) on bone loss, enzymatic (myeloperoxidase) analysis, differential white blood cells counts, airpouch exudate and cytokine expression for 5-30 days.

RESULTS

Radiographic, enzymatic (myeloperoxidase) and histological analysis revealed that Tacrolimus reduced the severity of periodontitis. More specifically, Tacrolimus suppressed the expression of serum interleukin (IL-1beta), tumour necrosis factor (TNF-alpha), IL-6, airpouch exudate PGE(2) and leukocytosis usually observed after the induction of periodontitis. Tacrolimus treatment in periodontitis-induced rats conferred protection against the inflammation-induced tissue and bone loss associated with periodontitis, through a mechanism involving IL-1beta, TNF-alpha and IL-6.

CONCLUSIONS

The effects of Tacrolimus on periodontal disease pathogenesis may provide clues to a novel approach to host modulation therapy in destructive periodontal disease.

Differential chemokine response of fibroblast subtypes to complement C1q

BACKGROUND AND OBJECTIVE

The pathogenesis of periodontitis includes an inappropriate activation of the classical complement cascade (C') with accumulation of inflammatory C' products in fluids and tissues. Our hypothesis is that in vivo the C' product, C1q, may act as a regulatory component of the innate immune response of distinct matrix fibroblasts to the inflammatory environment. This study analyzed the C1q induction of pro-inflammatory cytokine secretion in fibroblast subtypes derived from distinct periodontal tissues, and identified a mechanism of the cell response.

MATERIAL AND METHODS

Primary human gingival fibroblast, periodontal ligament fibroblast, and granulation tissue fibroblast cultures were treated for 24 h with C1q. Protein arrays assessed the secretory profile of constitutive and C1q-inducible pro-inflammatory cytokines, and enzyme-linked immunosorbent assays were used to quantify the kinetics of each inducible cytokine.

RESULTS

Granulation tissue fibroblast cultures were unresponsive to C1q challenge. In contrast, periodontal ligament fibroblasts responded with a release of monocyte chemoattractant protein (MCP)-1, interleukin-6, interleukin-8, and macrophage inflammatory protein (MIP)-1beta higher than the basal level by 8.2-, 7.0-, 3.8-, and 7.2-fold, respectively. Human gingival fibroblast cultures increased secretion of these chemokines by 5.2-, 4.5-, 3.0-, and 9.8-fold, respectively. Inhibitor studies revealed that C1q-inducible release of chemokines by the human gingival fibroblast and periodontal ligament cultures was contingent upon p38 mitogen-activated protein kinase activity.

CONCLUSION

The ability of C1q to stimulate secretion of pro-inflammatory chemokines depends upon which specific fibroblast subtype is involved. Targeting C1q-activated intracellular signaling pathways may be an effective means to inhibit the production of chemokines that promote inflammatory cell infiltration into gingival and periodontal ligament tissues.