Levels of interleukin 1 beta in tissue from sites of active periodontal disease

Effect of non-surgical periodontal therapy on C-telopeptide pyridinoline cross-links (ICTP) and interleukin-1 levels

BACKGROUND

Biochemical markers harvested from gingival crevicular fluid (GCF) may be useful to identify and predict periodontal disease progression and to monitor the response to treatment. C-telopeptide pyridinoline cross-links (ICTP), a host-derived breakdown product specific for bone, and interleukin-1beta (IL-1), a potent bone-resorptive cytokine, have been associated with periodontal tissue destruction. The aim of this study was to examine the effect of non-surgical periodontal therapy on GCF levels of ICTP and IL-1.

METHODS

Twenty-five chronic periodontitis subjects were monitored at 8 sites per subject at baseline prior to scaling and root planing and 1, 3, and 6 months after therapy. Four shallow (probing depths < 4 mm) and 4 deep (probing depths > or = 5 mm) sites were monitored for both marker levels and clinical parameters. GCF was collected for 30 seconds on paper strips, and levels of ICTP and IL-1 were determined using radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) techniques, respectively. Clinical measurements included probing depth (PD), clinical attachment level (CAL), and bleeding on probing (BOP).

RESULTS

Deep sites exhibited significantly (P<0.001) higher ICTP and IL-1 levels compared to shallow sites at all time intervals. ICTP demonstrated a stronger association to clinical parameters than IL-1 including a modest correlation (r = 0.40, P<0.001) between ICTP and attachment loss. Significant improvements in PD, CAL, and BOP were observed at 1, 3, and 6 months in all sites (P<0.01). However, non-surgical mechanical therapy did not significantly reduce ICTP and IL-1 levels over the 6-month period. Further examination of subjects based on smoking status revealed that ICTP levels were significantly reduced at 3 and 6 months and IL-1 levels reduced at 3 months among non-smokers only.

CONCLUSIONS

A single episode of non-surgical mechanical therapy did not significantly reduce biochemical markers associated with bone resorption in patients exhibiting chronic periodontitis. Future longitudinal studies are warranted to specifically evaluate the relationship between C-telopeptide pyridinoline cross-links and periodontal disease progression.

Expression of cytokines and inducible nitric oxide synthase in inflamed gingival tissue

BACKGROUND

Periodontopathic bacteria induce inflammation of periodontal tissues. The cytokines and nitric oxide released in periodontal lesions have been reported to play a protective role in bacterial infection and to relate to the process of inflammation. To clarify the relationship between colonization of periodontopathic bacteria and cytokines, we evaluated profiles of inflammatory cytokines, chemokine, anti-inflammatory cytokines, and inducible nitric oxide synthase (iNOS) and colonization by Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans, which are major pathogens of periodontitis.

METHODS

mRNA expression of cytokines and iNOS in inflamed and healthy gingival tissue was determined using reverse transcription-polymerase chain reaction (RT-PCR), and the relationship between their profiles and the detection of specific bacteria was analyzed.

RESULTS

The relative expression of interleukin (IL)-6 and iNOS mRNAs in periodontal lesions was significantly higher than those in healthy individuals. IL-6 mRNA expression was also significantly higher at bleeding on probing (BOP)-positive sites than at BOP-negative sites. The expressions of IL-1alpha and IL-8 increased, but IL-10 expression decreased at sites where A. actinomycetemcomitans was detected. We found no correlation between the expression of cytokine and iNOS mRNA and infection by P. gingivalis.

CONCLUSIONS

The expression of IL-6 may reflect inflammation in gingival tissue, and iNOS may be involved in the inflammatory process in periodontitis. The presence of A. actinomycetemcomitans or P. gingivalis might relate to the different cytokine profiles of IL-1alpha, IL-8, and IL-10.

Cyclosporin A upregulates phospholipase C beta1 in fibroblasts from gingival overgrowth

BACKGROUND

In an attempt to evaluate the influence of cyclosporin A (CsA) on fibroblast metabolism, the phospholipase C beta1, (PLC beta1) nuclear expression was evaluated in fibroblasts from heart transplantation patients treated with CsA who exhibited gingival overgrowth (GO) and from controls.

METHODS

PLC beta1 was assessed by immunoblotting and immunocytochemistry means.

RESULTS

Findings did not show any difference in terms of PLC beta1 expression between the 2 groups when fibroblasts were incubated in media without CsA, while the addition of CsA highly stimulated the fibroblasts from CsA-treated patients compared to controls. The abnormal fibroblastic response in CsA-treated patients was detected both in cells from enlarged gingival sites and in cells from clinically healthy gingival sites.

CONCLUSIONS

These results do not explain whether the exaggerated reactivity to in vitro CsA is the consequence of a genetically transmitted susceptibility to CsA that identifies those subjects at risk for developing GO, or whether it is a secondary effect of the long-term in vivo exposure to CsA. However, the present data underline the lack of any close relationship between enhanced fibroblast activity and clinical signs of GO and support the hypothesis that some other factors, together with CsA, are involved in the pathogenesis of CsA-induced GO.

Levels of interleukin-1 beta, -8, and -10 and RANTES in gingival crevicular fluid and cell populations in adult periodontitis patients and the effect of periodontal treatment

BACKGROUND

Various cytokines have been identified at sites of chronic inflammation such as periodontitis. Cytokines are synthesized in response to bacteria and their products, inducing and maintaining an inflammatory response in the periodontium. The purpose of the present study was to investigate the involvement of interleukin-1 beta (IL-1 beta), IL-8, and IL-10 and RANTES (regulated on activation, normally T cell expressed and secreted) and the cell populations associated with the immune response in destructive periodontitis, as well as the effect of periodontal therapy on cytokine levels in gingival crevicular fluid (GCF).

METHODS

Data were obtained from 12 patients with moderate to advanced periodontitis and 6 healthy controls. Patients presenting at least 2 sites with > or =2 mm clinical attachment loss were included in the destructive periodontitis group. After monitoring for 4 months, only 6 patients showed destructive periodontitis and GCF samples and soft tissues biopsies were collected from these patients. GCF samples and biopsies were collected both from active (12 CGF samples and 6 biopsies) and inactive (12 CGF samples and 6 biopsies) sites. The comparison with healthy controls was carried out by collecting GCF samples from 6 healthy volunteers (12 samples) and biopsies during the surgical removal of wisdom teeth. In periodontal patients, clinical data and GCF samples were obtained prior to periodontal treatment (72 samples) and 2 months after periodontal therapy (72 samples). GCF was collected using a paper strip; eluted and enzyme-linked immunoabsorbent assays (ELISA) were performed to determine cytokine levels. The inflammatory infiltrate was analyzed by immunohistochemistry of gingival biopsy samples with monoclonal antibodies against CD3, CD8, CD4, CD11c, and CD19 antigens.

RESULTS

Cellular components of the inflammatory infiltrate include B and T lymphocytes and monocyte/macrophages. Active sites contained a higher number of B lymphocytes and macrophages. IL-8 and IL-1 beta and RANTES in GCF were detected in the majority of sites from periodontal patients (100%, 94% and 87%, respectively); IL-10 was found in only 43%. IL-8 was the only cytokine detected in the GCF (75%) of the control group. Moreover, IL-1 beta levels were significantly higher in active sites versus inactive sites (P <0.05). IL-8 and IL-10 and RANTES were increased in active sites; however, differences were not significant (P>0.05). A positive correlation between the IL-8 and RANTES (r = 0.677, P<0.05) was observed in periodontitis patients. Periodontal therapy reduced the total amount of IL-1 beta, IL-8, and IL-10 and RANTES. Data showed a weak correlation between the clinical parameters and the total amount of cytokines in periodontitis.

CONCLUSIONS

These data suggest that the amount of crevicular IL-1 beta, IL-8, and IL-10 and RANTES is associated with periodontal status. Removal of the bacterial plaque reduces the antigenic stimuli and consequently could modulate the chemokines present in GCF. We propose that the dynamic interactions between cytokines, their production rates, and their quantity could represent factors controlling the induction, perpetuation, and collapse of the cytokine network present in the periodontal disease.

Cytokine responses of oral epithelial cells to Porphyromonas gingivalis infection

Accumulating evidence indicates that epithelia are not merely mechanical barriers but also important elements of the innate immune system. The present study was performed to examine cytokine responses of oral epithelial cells after infection with the periodontal pathogen Porphyromonas gingivalis. The KB-cell line and primary cultures of periodontal pocket epithelium were infected with P. gingivalis for assessment of bacterial invasion by an antibiotic protection assay, and examination of expression of interleukin-1 beta, interleukin-6, interleukin-8, and tumor necrosis factor-alpha by in situ hybridization and immunohistochemistry. We observed that P. gingivalis induces a strong cytokine response, positively correlated with the adhesive/invasive potential of the infecting strain, in both KB cells and primary cultures. These findings indicate that the epithelial cells of the periodontal pocket are an integral part of the immune system, eliciting cytokine responses to a bacterial challenge. In this context, the adhesive/invasive phenotype of P. gingivalis appears to contribute to pathogenicity.

Effects of smoking on periodontal health: a review

Cigarette smoking is a risk factor for several diseases, and recent evidence strongly suggests an adverse effect on periodontal health. Nevertheless, the nature of the relationship between smoking and periodontal disease is not clear. Smoking causes defects in neutrophil function, impairs inflammatory and immune responses to periodontal pathogens, and exerts both systemic and local effects. Smoking is associated with an increased rate of periodontal disease in terms of alveolar bone loss and attachment loss, as well as pocket formation. Nicotine, the major component of cigarette smoke, may weaken host defenses to the bacterial invasion induced by plaque.

The role of immune responses in bone loss during periodontal disease

A network of cytokines and other soluble mediators unites the immune system and bone; bacterial infections induce immune responses which may perturb this network. Periodontal diseases are Gram-negative infections resulting in bone loss in the jaw. Evidence is presented that immune responses to these infections produces net resorption of bone.

Pathophysiological relationships between periodontitis and systemic disease: recent concepts involving serum lipids

Periodontitis has been traditionally regarded as a chronic inflammatory oral infection. However, recent studies indicate that this oral disease may have profound effects on systemic health. The search for cellular/molecular mechanisms linking periodontitis to changes in systemic health and systemic physiology has resulted in the evolution of a new area of lipid research establishing linkages between existing multidisciplinary biomedical literature, recent observations concerning the effects of serum lipids on immune cell phenotype/function, and a heightened interest in systemic responses to chronic localized infections. There appears to be more than a casual relationship between serum lipid levels and systemic health (particularly cardiovascular disease, diabetes, tissue repair capacity, and immune cell function), susceptibility to periodontitis, and serum levels of pro-inflammatory cytokines. In terms of the potential relationship between periodontitis and systemic disease, it is possible that periodontitis-induced changes in immune cell function cause metabolic dysregulation of lipid metabolism through mechanisms involving proinflammatory cytokines. Sustained elevations of serum lipids and/or pro-inflammatory cytokines may have a serious negative impact on systemic health. The purpose of this paper is to present the background, supporting data, and hypotheses related to this concept. As active participants in this emerging and exciting area of investigation, we hope to stimulate interest and awareness among biomedical scientists and practitioners.

The mouthwash: a non-invasive sampling method to study cytokine gene polymorphisms

BACKGROUND

We describe a simple, non-invasive mouthwash sampling method for rapid DNA isolation to detect cytokine gene polymorphisms. In the present paper, interleukin- 1beta(IL-1B) and interleukin-1 receptor antagonist (IL-1RN) gene polymorphisms were studied.

METHODS

Two mouthwash samples and blood samples were collected from 11 healthy individuals. The second mouthwash sample was stored for 7 days at room temperature. Polymerase chain reaction amplification was used to identify a bi-allelic polymorphism at position +3953 in the IL-1B gene and a variable number of tandem repeats (VNTR) polymorphism in the IL-1RN gene.

RESULTS

Our results show that the typing of these cytokine gene polymorphisms using DNA isolated from mouthwash samples did not differ from those obtained by a phenol/chloroform isolation method from EDTA anti-coagulated blood. Moreover, reliable results from mouthwash samples were obtained after storage for at least 7 days at room temperature.

CONCLUSIONS

Mouthwash can be the method of choice to study gene polymorphisms in periodontitis and other chronic inflammatory diseases.

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

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

The impact of molecular genetics on oral health paradigms

As a result of our increased understanding of the human genome, and the functional interrelationships of gene products with each other and with the environment, it is becoming increasingly evident that many human diseases are influenced by heritable alterations in the structure or function of genes. Significant advances in research methods and newly emerging partnerships between private and public sector interests are creating new possibilities for utilization of genetic information for the diagnosis and treatment of human diseases. The availability and application of genetic information to the understanding of normal and abnormal human growth and development are fundamentally changing the way we approach the study of human diseases. As a result, the issues and principles of medical genetics are coming to bear across all disciplines of health care. In this review, we discuss some of the potential applications of human molecular genetics for the diagnosis and treatment of oral diseases. This discussion is presented in the context of the ongoing technological advances and conceptual changes that are occurring in the field of medical genetics. To realize the promise of this new molecular genetics, we must be prepared to foresee the possibilities and to incorporate these newly emergent technologies into the evolving discipline of dentistry. By using examples of human conditions, we illustrate the broad application of this emerging technology to the study of simple as well as complex genetic diseases. Throughout this paper, we will use the following terminology: Penetrance--In a population, defined as the proportion of individuals possessing a disease-causing genotype who express the disease phenotype. When this proportion is less than 100%, the disease is said to have reduced or incomplete penetrance. Polymerase chain reaction (PCR)--A technique for amplifying a large number of copies of a specific DNA sequence flanked by two oligonucleotide primers. The DNA is alternately heated and cooled in the presence of DNA polymerase and free nucleotides, so that the specified DNA segment is denatured, hybridized with primers, and extended by DNA polymerase. MIM--Mendelian Inheritance in Man catalogue number from V. McKusick's Mendelian Inheritance in man (OMIM, 1998).

Herpesviruses and periodontopathic bacteria in Trisomy 21 periodontitis

BACKGROUND

Little is known about the etiology and pathogenesis of periodontal disease in Trisomy 21 patients. This study determined the occurrence of herpesviruses and putative periodontopathic bacteria in Trisomy 21 periodontitis.

METHODS

Nineteen Trisomy 21 patients (17 to 37 years of age) contributed subgingival samples from molar and bicuspid teeth presenting interproximal periodontitis lesions (probing depths, 5 to 8 mm) and from shallow periodontal sites (probing depths, 1 to 3 mm). Samples were obtained at baseline, and at 1 and 4 weeks after subgingival debridement by means of hand instruments and ultrasonic scalers. Epstein-Barr virus type 1 and 2 (EBV-1 and EBV-2), human cytomegalovirus (HCMV), and herpes simplex virus (HSV) were identified by sensitive and specific nested polymerase chain reaction. Putative periodontopathic bacteria were identified by means of non-selective and selective culture.

RESULTS

Of 19 Trisomy 21 periodontitis lesions, 6 (32%) were positive for EBV-1, 5 (26%) were positive for HCMV, 3 (16%) were positive for HSV, and 2 (11%) showed viral co-infection. Of 19 shallow periodontal sites, only one revealed HCMV. Prevotella intermedia, Bacteroides forsythus, and Capnocytophaga species were detected in higher proportions in deep than in shallow periodontal pockets (P = 0.02). Subgingival debridement did not reduce genomic herpesvirus presence but caused a decrease in proportions of Porphyromonas gingivalis and Capnocytophaga species.

CONCLUSIONS

Periodontal herpesvirus-bacteria coinfections may play important roles in the pathogenesis of destructive periodontal disease in Trisomy 21 patients. Herpesviruses may reduce the periodontal defense and promote growth of subgingival bacteria capable of causing periodontal breakdown.

The association of calprotectin level in gingival crevicular fluid with gingival index and the activities of collagenase and aspartate aminotransferase in adult periodontitis patients

BACKGROUND

Calprotectin, a major cytosol protein of leukocytes, exists in plasma and other body fluids of healthy human subjects. Since the calprotectin concentration rises markedly in some inflammatory diseases including rheumatoid arthritis, this protein has been thought to be a marker of inflammatory disease. Recently, we identified calprotectin in human dental calculus and gingival crevicular fluid (GCF), and found that the calprotectin concentration in GCF from patients with periodontitis was significantly higher than that in GCF from healthy subjects. In the present study, the association of GCF calprotectin level with GCF volume, gingival index (GI), and levels of biochemical markers including collagenase and aspartate aminotransferase (AST) in GCF was investigated to clarify the relationship between GCF calprotectin level and periodontal inflammation.

METHODS

Ninety GCF samples collected from periodontal pockets with a probing depth of more than 4 mm in 54 patients with adult periodontitis were used for these assays. The GCF volume was measured, and GI in each site was recorded. The calprotectin content in GCF samples was determined by ELISA using a specific antibody. The activity of collagenase or AST was measured by a respective assay kit.

RESULTS

The total amount of calprotectin and GCF volume showed a highly significant correlation (r = 0.64, P <0.0001), whereas the calprotectin concentration had no correlation with the GCF volume (r = 0.01, P= 0.924). The mean calprotectin concentration in GCF increased with the degree of GI, and the concentration in individual samples was significantly correlated with the GI score (r = 0.56, P<0.0001). Significant positive correlations were observed in GCF calprotectin versus collagenase (r = 0.57, P <0.0001) and GCF calprotectin versus AST levels (r = 0.40, P <0.005).

CONCLUSIONS

From the present results and our previous findings, it is shown that the GCF calprotectin level significantly correlates not only with clinical indicators but also with current biochemical marker levels and that calprotectin may be a useful marker for periodontal inflammation.

Use of defined mutants to assess the role of the Campylobacter rectus S-layer in bacterium-epithelial cell interactions

Campylobacter rectus is a periodontal pathogen with a 150-kDa protein on its cell surface. This protein forms a paracrystalline lattice, called the S-layer, surrounding the outer membrane of this gram-negative bacterium. To initiate a genetic analysis of the possible role of the S-layer in the initial interaction of C. rectus with host epithelial cells, C. rectus strains lacking the S-layer protein gene (crsA) were constructed by allelic exchange mutagenesis. Surprisingly, the lack of the S-layer had only a minor effect on the interaction of C. rectus with HEp-2 epithelial cells; CrsA(+) cells were 30 to 50% more adherent than were CrsA(-) bacteria. Since the host cell expression of cytokines appears to play an important role in the pathogenesis of periodontal diseases, the effect of the S-layer on the epithelial cell cytokine response was also examined by quantitative reverse transcriptase PCR and enzyme-linked immunosorbent assay. Although there were no changes in the mRNA levels for the anti-inflammatory cytokines interleukin-1 receptor agonist (IL-1ra), IL-13, and transforming growth factor beta, the expression and secretion of the proinflammatory cytokines IL-6, IL-8, and tumor necrosis factor alpha (TNF-alpha) were significantly induced by both wild-type C. rectus and CrsA(-) bacteria. Interestingly, the kinetics of cytokine induction differed for the CrsA(+) and CrsA(-) bacteria. At early time points, the HEp-2 cells challenged with CrsA(-) bacteria produced higher levels of IL-6, IL-8, and TNF-alpha mRNA and protein than did cells challenged with CrsA(+) bacteria. We conclude that C. rectus may help initiate periodontitis by increasing the expression of proinflammatory cytokines and that the S-layer may temper this response to facilitate the survival of C. rectus at the site of infection.

Interleukin-1 genetic association with periodontitis in clinical practice

BACKGROUND

Periodontitis is a bacterial disease modified by multiple risk factors. The pro-inflammatory cytokine interleukin- (IL-1) is a key regulator of the host responses to microbial infection and a major modulator of extracellular matrix catabolism and bone resorption. It has been reported that variations in the IL-1 gene cluster on chromosome 2 are associated with increased susceptibility to severe adult periodontitis.

METHODS

The present study evaluated the association between a composite IL-1 genotype, including allele 2 at each of two loci (IL-1A +4845 plus IL- B +3954), and a broad spectrum of periodontally healthy to diseased patients in a population that is typically encountered in a dental practice setting. Ninety patients, non-smokers or former smokers with less than 10 pack-year (pk/yr) history, were recruited from a private dental practice. The major outcome variable was bone loss determined by computerized linear measurements of radiographs. Genotypes were analyzed from finger-stick blood samples using previously reported methods.

RESULTS

Multivariate logistic regression models demonstrated that patient age, former smoking history, and the IL-1 genotype were significantly associated with severity of adult periodontitis. For non-smokers or former light smokers (<5 pk/yr), IL-1 genotype positives were at increased odds ratio of having moderate to severe periodontal disease of 3.75 (95% CI: 1.04-13.50) to 5.27 (95% CI: 1.23-22.70), depending on ethnicity, compared to IL-1 genotype negatives. Former moderate smokers (>5 pk/yr and <10 pk/yr) who were IL-1 genotype negative were at increased odds ratio of having moderate to severe periodontal disease of 7.43 (95% CI: 1.20-46.20) compared to non-smokers or former light smokers who were IL-1 genotype negative. In addition, past smoking history was also a significant effect modifier as demonstrated by the statistically significant interaction between past smoking history status and IL-1 genotype status.

CONCLUSIONS

This study demonstrates that the composite IL-1 genotype is significantly associated with the severity of adult periodontitis. It also confirmed that both IL-1 genotyping and smoking history provide objective risk factors for periodontal disease in a private practice environment.

Herpesviruses in periodontal pocket and gingival tissue specimens

Human cytomegalovirus (HCMV) and Epstein-Barr virus type 1 (EBV-1) are frequently detected in crevicular fluid of deep periodontal pockets, but little or no information is available on occurrence of herpesviruses in gingival tissue. This investigation studied the presence of herpesviruses in periodontal pockets and the corresponding gingival tissues from 11 periodontally healthy and 14 periodontitis sites. A nested-polymerase chain reaction was employed to identify the presence of HCMV, EBV-1, EBV-2, herpes simplex virus, human herpesvirus (HHV)-6, HHV-7 and HHV-8 in each test sample. In healthy periodontal sites, HCMV was detected in 1 (9%) and EBV-1 in 2 (18%) pocket samples, and HCMV was detected in 2 (18%) and EBV-1 in 3 (27%) gingival tissue samples. In periodontitis lesions, HCMV was detected in 9 (64%) pocket samples and in 12 (86%) gingival tissue samples, and EBV-1 was detected in 6 (43%) pocket samples and in 11 (79%) gingival tissue samples. HHV-6 and HHV-8 were detected exclusively in gingival tissue samples. The present findings confirm the frequent presence of HCMV and EBV-1 in periodontitis lesions and suggest using gingival tissue specimens for detecting periodontal HHV-6, HHV-7 and HHV-8.

Increased interleukin-1beta concentration in gingival crevicular fluid as a characteristic of periodontitis

BACKGROUND

The levels of interleukin-1beta (IL-1beta) have been reported to be higher in sites with periodontitis than in healthy controls. This may be the result of a more severe inflammation and/or constitutional differences in IL-1beta production. Our aim was to test the hypothesis that the level of IL-1beta in gingival crevicular fluid (GCF) is a characteristic trait of periodontitis, regardless of the degree of tissue destruction. As a secondary aim, we investigated the correlation between IL-1beta and neutrophil elastase. An untreated population was used.

METHODS

GCF samples from inflamed sites in 13 patients with gingivitis (GG), and from inflamed sites with shallow (GP) and deep (PP) pockets in 18 patients with periodontitis were collected. Interleukin-1beta, elastase-alpha-1-antitrypsin complex (E-A1AT), alpha-1-antitrypsin (A1AT), and alpha-2-macroglobulin (A2MG) were measured with ELISA. Elastase activity was measured with a specific substrate.

RESULTS

The concentration of IL-1beta was significantly higher in PP than in GG, but no significant differences were detected between PP and GP. A weak positive correlation between the elastase activity and IL-1beta was also observed. The elastase activity had a tendency to be higher in PP, although no significant difference was found among the 3 groups. The concentrations of E-A1AT, A1AT, and A2MG were similar in the 3 types of sites.

CONCLUSIONS

The levels of IL-1beta in GCF were increased in samples from periodontitis patients, regardless of the severity of disease at the sampled site, suggesting that the levels of IL-1beta are typical of a given patient.

Association between periodontitis and hyperlipidemia: cause or effect?

BACKGROUND

Epidemiological studies suggest a relationship between periodontitis and coronary artery disease, but the mechanism has not been established. Recent studies in animals indicate that low dose endotoxin, as in a gram-negative infection, can induce hyperlipidemia and myeloid cell hyperactivity. The association between periodontitis, systemic exposure to Porphyromonas gingivalis, lipopolysaccharides (LPS), and hyperlipidemia has not been examined in humans.

METHODS

Sera were obtained from 26 adult periodontitis patients and 25 healthy control (C) subjects selected from patients and staff. Serum antibodies against Porphyromonas gingivalis and its LPS were analyzed by enzyme-linked immunosorbent assay (ELISA) and Western blotting, respectively. Serum triglycerides (TG) and cholesterol (CHOL) were assayed by a commercial laboratory. The associations between AP and blood levels of TG, CHOL, and anti-P. gingivalis whole cells and LPS were examined by logistic regression analysis. Peripheral blood polymorphonuclear leukocytes (PMNs) from 6 healthy fasted donors were incubated with purified TG (0.1 mg/ml) for 2 hours at 37 degrees C, stimulated with 100 ng/ml P. gingivalis LPS, and the release of IL-1beta measured by ELISA.

RESULTS

The presence of periodontitis was significantly associated with age (odds ratio = 3.5, P = 0.04), elevated TG levels (odds ratio = 8.6, P = 0.0009), elevated CHOL levels (odds ratio = 7, P = 0.004), elevated ELISA titer (odds ratio = 35, P = 0.003) and reactivity with P. gingivalis LPS (odds ratio = 41, P = 0.001). PMNs from all 6 healthy patients released modest levels of IL-1beta (10 to 60 pg/ml) when stimulated with 100 ng/ml P. gingivalis LPS. Addition of TG resulted in a significant increase (P <0.05) in IL- 1beta secreted that ranged from 7 to 150% over LPS alone. No IL-1beta was elicited by TG or vehicle alone.

CONCLUSIONS

The results of this study indicate the presence of a significant relationship between periodontitis, hyperlipidemia, and serum antibodies against P. gingivalis LPS that warrants further examination in a larger patient population. Furthermore, these studies indicate that elevated triglycerides are able to modulate IL-1beta production by PMNs stimulated with P. gingivalis LPS.

Heightened gingival inflammation and attachment loss in type 2 diabetics with hyperlipidemia

BACKGROUND

Our previous studies in diabetic (DB) rats suggest that hyperlipidemia may cause a dysregulation of the cellular and local cytokine response to periodontitis (AP). The objective of the present study was to determine if diabetes has a similar dysregulatory effect on the gingival response to AP in humans.

METHODS

Peripheral blood, as well as gingival tissue (GT) and gingival crevicular fluid (GCF), was obtained from a total of 35 patients who were categorized into the following groups based on level of diabetic (type 2) control and presence or absence of adult periodontitis (AP): group 1, systemically and periodontally healthy (n = 6); group 2, systemically healthy with adult periodontitis (n = 7); group 3, well-controlled diabetes and periodontally healthy (n = 6); group 4, well-controlled diabetes with adult periodontitis (n = 5); group 5, poorly controlled diabetes and periodontally healthy (n = 5); group 6, poorly controlled diabetes and adult periodontitis (n = 6). All subjects were given a thorough periodontal examination, including probing depths (PD), clinical attachment levels (CAL), gingival index (GI), plaque index (PI), and vertical bitewing radiographs. Blood studies included levels of glycated hemoglobin (HbA1c), triglycerides (TG), cholesterol (CHL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL). The levels of interleukin-1 beta (IL-1beta) in GCF and GT, interleukin-6 (IL-6), and platelet-derived growth factor AB (PDGF-AB) in GT from patients in each experimental group were analyzed by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Our results indicate that all clinical indices except PI were significantly elevated in the poorly controlled and well-controlled diabetics, compared to systemically healthy patients, but only in the subjects without preexisiting AP (Tukey's multiple comparisons, P <0.05). Pairwise linear regression analysis revealed significant (P <0.01) positive associations between periodontal inflammation (PD, CAL, PI, GI) and levels of GCF IL-1beta, GT IL- 1beta GT IL-6, but not GT PDGF; moreover, GT IL-6 levels were significantly associated (P<0.05) with GT IL-1beta. As TG levels increased in the non-AP patients (group 1 < group 3 < group 5), there was a trend, not significant, for increased GCF IL-1beta levels and increased gingival inflammation. Interestingly, periodontitis resulted in increased PDGF-AB levels in the gingiva of systemically healthy and well-controlled diabetes patients, but this increase was obtunded in poorly controlled diabetes patients.

CONCLUSIONS

This confirms our earlier work in the diabetic rat model. These studies indicate that decreased metabolic control in type 2 diabetics results in increased serum triglycerides and has a negative influence on all clinical measures of periodontal health, particularly in patients without preexisting periodontitis. Levels of the cytokine IL- 1beta showed a trend for increasing as diabetic control diminished. In contrast, levels of the growth factor PDGF, which normally increase in periodontitis, decreased in poorly controlled diabetics with periodontitis. These studies suggest a possible dysregulation of the normal cytokine/growth factor signaling axis in poorly controlled type 2 diabetics that may contribute to periodontal breakdown/diminished repair.

Interleukin 1beta-secreting cells in inflamed gingival tissue of adult periodontitis patients

Interleukin 1beta (IL-1beta) is a cytokine with a wide range of biological activities. It is produced by various cell types including macrophages, fibroblasts, and neutrophils. The inflammatory responses mediated by IL-1beta play an important role in periodontal tissue destruction. The purposes of this study were: (1) to determine the location of IL-1beta in inflamed human gingival tissues by the immunofluorescence method; and (2) to correlate this location to the concomitant presence of macrophage or neutrophils by immunohistochemistry. Five patients with moderate to advanced adult periodontitis receiving periodontal phase I therapy were included in this study. One month after phase I therapy, 15 sites with a probing pocket depth >/=5 mm and gingivitis index >/=1 were arranged for modified Widman flap operation. Another three sites with a probing pocket depth </=3 mm and gingivitis index=0 from two gingival healthy subjects who received crown-lengthening operation were also chosen as a control group. After clinical parameter recording, a biopsy of gingival tissues from all sites was obtained during the operation. The gingival specimens were frozen immediately for further immunofluorescent examination of IL-1beta and immunocytochemical localization of macrophages and neutrophils. The macrophages were found to be widely distributed in inflamed gingival connective tissue and near-by pocket wall tissue. The neutrophils were aggregated in pocket wall and were sparsely seen in connective tissue. IL-1beta immunofluorescent reaction was detected with high intensity in gingival connective tissue especially at the subepithelial region. IL-1beta immunofluorescence with low intensity was only occasionally seen in pocket wall tissue. There was a strong association between the presence of macrophages and IL-1beta expression. Similarly, there was a positive association between neutrophils and IL-1beta immunofluorecence. These results suggested that large amounts of IL-1beta are present in inflamed gingival tissues, and that both macrophages and neutrophils are predominate in IL-1beta production in inflamed gingival tissues.

Herpesvirus infection of inflammatory cells in human periodontitis

Human cytomegalovirus (HCMV) and Epstein-Barr virus type 1 (EBV-1) are frequently detected in human periodontitis lesions. However, no information is available on the types of gingival cells infected by herpesviruses. The present study determined the presence of herpesviruses in polymorphonuclear neutrophils, monocytes, macrophages and T and B lymphocytes in biopsies of periodontitis lesions from 20 adults. A nested polymerase chain reaction method was employed to detect HCMV, EBV-1, EBV-2, human herpes virus-6 and herpes simplex virus (HSV) in periodontal tissue biopsy and in gingival cell fractions separated by immunomagnetic cell sorting. Tissue specimens from 18 (90%) and cell fractions from 14 (70%) patients demonstrated herpesviruses. Periodontitis-derived monocytes and macrophages revealed HCMV in cell fractions from 11 (55%) patients and HSV in cells from 1 (5%) patient. T lymphocytes harbored HCMV in cell fractions from 4 (20%) patients and HSV in cell fractions from 4 (20%) patients. B lymphocytes showed EBV-1 in cell fractions from 9 (45%) patients. Periodontal polymorphonuclear neutrophils demonstrated no herpesviruses. This study suggests that HCMV mainly infects periodontal monocytes, macrophages and less frequently T lymphocytes and that EBV-1 infects periodontal B lymphocytes. The possible etio-pathologic significance of periodontal herpesvirus infection is discussed.

Vascular endothelial growth factors and progression of periodontal diseases

BACKGROUND

Tissues become hemorrhagic and edematous coincident to periodontal diseases; however, there is little information concerning the biologic mechanisms which may produce these changes. Vascular endothelial growth factor (VEGF) is a macromolecule which enhances blood vessel growth and permeability. However, there is no information concerning gingival VEGF concentrations within normal or diseased gingiva. The purpose of this study was to assess changes in gingival concentrations of VEGF during initiation and progression of periodontal diseases and compare them to changes in the number of blood vessel profiles and concentration of recognized markers of periodontal disease severity (interleukin-6[IL-6]).

METHODS

Normal (non-hemorrhagic gingiva adjacent to a < or =3 mm gingival sulcus) and inflamed gingiva (hemorrhagic gingiva adjacent to a < or =3 mm, 4 to 6 mm, or >6 mm periodontal pocket) were studied. VEGF and IL-6 concentrations were assessed by ELISA and the number of blood vessels determined by histomorphometric techniques. Data were placed into one of the following groups: < or =3 mm, normal; < or =3 mm, diseased; 4 to 6 mm, diseased; and >6 mm, diseased. These groups were compared by factorial ANOVA and Scheffe comparisons. In addition, groups were compared by simple and multiple regression and regression ANOVA to determine possible correlations between them.

RESULTS

VEGF and IL-6 concentrations were significantly lower within normal than within diseased gingiva. The number of blood vessel profiles and mean IL-6 concentrations were highest in diseased tissues adjacent to >6 mm sulci and were significantly correlated with sulcular depth (P <0.001). In contrast, VEGF concentrations were highest within diseased gingiva adjacent to 4 to 6 mm periodontal pockets (P <0.001) and were not correlated with sulcular depth.

CONCLUSIONS

VEGF may be a factor in initiation and progression of gingivitis to periodontitis, possibly by promoting expansion of the vascular network coincident to progression of the inflammation.

The pathogenesis of periodontal diseases

This informational paper was prepared by the Research, Science, and Therapy Committee of The American Academy of Periodontology, and is intended for the information of the dental profession. The purpose of the paper is to provide an overview of current knowledge relating to the pathogenesis of periodontal diseases. The paper will review biological processes thought to provide protection against periodontal infections. It will further discuss the mechanisms thought to be responsible for both overcoming and subverting such protective mechanisms and those that lead to destruction of periodontal tissues. Since an understanding of pathogenic mechanisms of disease is one foundation upon which new diagnostic and therapeutic modalities are based, the practitioner can use this information to help make decisions regarding the appropriate application of such new modalities in patient care settings.

Intracellular interleukin-1 alpha production in human gingival fibroblasts is differentially regulated by various cytokines

Interleukin-1 (IL-1) may play a critical role in immune and inflammatory responses in inflamed gingiva, and it is synthesized by a wide variety of host cells. In this study, we examined the regulatory effects of various cytokines on bioactive membrane IL-1 and intracellular IL-1 alpha production in cultured human gingival fibroblasts (HGF). Recombinant human (rh) IL-1 beta stimulated membrane IL-1 activity, which was mainly attributed to IL-1 alpha. rhIL-1 beta and rh tumor necrosis factor (TNF)-alpha stimulated HGF to produce intracellular IL-1 alpha, whereas rh interleukin-6 (IL-6), rh interleukin-4 (IL-4), and rh interferon (IFN)-gamma did not do so. Intracellular IL-1 alpha production induced by rhIL-1 beta or rhTNF-alpha may be partially related to protein kinase C (PKC) activation, because rhIL-1 beta or rhTNF-alpha-induced intracellular IL-1 alpha production was stimulated by pre-treatment with 12-o-tetradecanoylphorbol 13-acetate (TPA), a PKC activator, but was suppressed by the pre-treatment with 1-(5-isoquinoline-sulfonyl) -2-methylpiperazine dihydrochloride (H-7), which is a PKC inhibitor. rhIL-4 inhibited rhIL-1 beta- or rhTNF-alpha-induced intracellular IL-1 alpha production, but rhIL-6 had no effect on this production. Pre-treatment with rh IFN-gamma remarkably enhanced intracellular IL-1 alpha production induced by subsequent treatment with rhIL-1 beta or rhTNF-alpha. Simultaneous treatment with rhIFN-gamma and rhIL-1 beta inhibited rhIL-1 beta-induced intracellular IL-1 alpha production, but co-treatment with rhIFN-gamma and rhTNF-alpha enhanced rhTNF-alpha-induced intracellular IL-1 alpha production. These results suggest that in inflamed gingiva, pro-inflammatory cytokines such as IL-1 beta and TNF-alpha may induce bioactive intracellular IL-1 alpha production in human gingival fibroblasts and that this production can be differentially modulated by T-cell-derived cytokines such as IFN-gamma or IL4.

Linkage disequilibrium of interleukin-1 genetic polymorphisms with early-onset periodontitis

BACKGROUND

Genetic polymorphisms at interleukin (IL)-1alpha and IL-1beta were recently suggested to be associated with severity of adult periodontitis. We evaluated whether these polymorphisms might also be associated with early-onset periodontitis (EOP) in 28 African American families and 7 Caucasian American families with 2 or more affected members.

METHODS

Genomic DNA from peripheral blood was amplified, followed by restriction endonuclease digestion and acrylamide gel electrophoresis to distinguish alleles of different fragment sizes. Genetic epidemiological methods suitable for family data were used that are robust to false-positive findings due to mismatching of cases and controls or mixed subpopulations of different ethnic or geographic origin. The 2 major EOP subtypes, localized juvenile periodontitis (LJP), and generalized early-onset periodontitis (G-EOP, encompassing rapidly progressive periodontitis and generalized juvenile periodontitis), were analyzed both separately and together.

RESULTS

We obtained highly significant evidence of linkage disequilibrium for both African American and Caucasian G-EOP subjects. A similar trend was noted for LJP. The IL- alleles associated with high risk of EOP had been suggested previously to be correlated with low risk for severe adult periodontitis. Disequilibrium with G-EOP was equally strong for smoking and non-smoking subjects. IL-1alpha and IL-1beta polymorphisms were in strong disequilibrium with each other in Caucasians, but not in African Americans. Haplotype analyses evaluating both polymorphisms simultaneously indicated that the IL-1beta variant is likely to be most important for EOP risk. Sibpair linkage analyses, by contrast, provided only marginal support for a gene of very major effect on EOP risk attributable to these IL-1 polymorphisms.

CONCLUSIONS

Recent theoretical analyses indicate that our findings are most consistent with an interpretation of EOP as a complex, oligogenic disorder, with IL-1 genetic variation contributing an important but not exclusive influence on disease risk.

Activation of murine macrophages by lipoprotein and lipooligosaccharide of Treponema denticola

We have recently demonstrated that the periodontopathogenic oral spirochete Treponema denticola possesses membrane-associated lipoproteins in addition to lipooligosaccharide (LOS). The aim of the present study was to test the potential of these oral spirochetal components to induce the production of inflammatory mediators by human macrophages, which in turn may stimulate tissue breakdown as observed in periodontal diseases. An enriched lipoprotein fraction (dLPP) from T. denticola ATCC 35404 obtained upon extraction of the treponemes with Triton X-114 was found to stimulate the production of nitric oxide (NO), tumor necrosis factor alpha (TNF-alpha), and interleukin-1 (IL-1) by mouse macrophages in a dose-dependent manner. Induction of NO by dLPP was at 25% of the levels obtained by Salmonella typhosa lipopolysaccharide (LPS) at similar concentrations, while IL-1 was produced at similar levels by both inducers. dLPP-mediated macrophage activation was unaffected by amounts of polymyxin B that neutralized the induction produced by S. typhosa LPS. dLPP also induced NO and TNF-alpha secretion from macrophages isolated from endotoxin-unresponsive C3H/HeJ mice to an extent similar to the stimulation produced in endotoxin-responsive mice. Purified T. denticola LOS also produced a concentration-dependent activation of NO and TNF-alpha in LPS-responsive and -nonresponsive mouse macrophages. However, macrophage activation by LOS was inhibited by polymyxin B. These results suggest that T. denticola lipoproteins and LOS may play a role in the inflammatory processes that characterize periodontal diseases.

Gingival fluid IL-1beta in postmenopausal females on supportive periodontal therapy. A longitudinal 2-year study

Posterior interproximal alveolar bone in 59 women, within 5 years after menopause, was assessed at baseline and after 2 years of supportive periodontal therapy (history of moderate/advanced periodontitis) using digitized image analysis. Baseline lumbar spine bone mineral density, smoking status, and yearly serum estradiol (E2) levels also were obtained to group subjects. An additional 16 non-periodontitis postmenopausal women were followed 2 years for clinical and estrogen status. 2-min GCF IL-1beta levels averaged from 2 baseline periodontal pockets (in periodontitis subjects) and 2 non-periodontitis sites (in non-periodontitis and periodontitis subjects) were determined with an enzyme immunoassay. A progressive and stable site were also monitored every 6 months for GCF IL-1beta in 15 patients. Results after 2 years indicated that 17 subjects had no posterior interproximal sites losing > or =0.4 mm of alveolar crest bone height, while 13 subjects had > or =3 such sites. Using analysis of variance, none of the above clinical groupings resulted in a significant difference in mean baseline or longitudinal GCF IL-1beta levels. However, when subjects who lost alveolar crest bone height were considered, E2-sufficient subjects had significantly depressed baseline GCF IL-1beta (in past-periodontitis sites) compared to E2-deficient patients (9.1+/-2.1 versus 31.7+/-10.2 pg/2-min sample, p<0.05), suggesting E2 influences gingival IL-1beta production in progressive periodontitis patients.

Interleukin-1beta+3953 allele 2: association with disease status in adult periodontitis

Adult periodontitis is a complex multifactorial disease whose etiology is not well defined. The pro-inflammatory and bone resorptive properties of interleukin-1 beta (IL-1beta) strongly suggest a role for this cytokine in the pathogenesis of periodontal disease. In the study reported here, the frequency of IL-1beta genotypes including allele 2 of the IL-1beta+3953 restriction fragment length bi-allelic polymorphism was significantly increased in patients with advanced adult periodontitis compared to those with early and moderate disease. Furthermore, allele 2 was associated with increased production of IL-1beta by activated peripheral blood polymorphonuclear cells of patients with advanced disease, although this increase failed to reach statistical significance. Finally, the data obtained revealed significant linkage disequilibrium between allele 2 of the IL-1beta+3953 polymorphism and allele 2 of the bi-allelic IL-1alpha-889 polymorphism in both patients and orally healthy controls. These findings provide new insight into the possible role of IL-1alpha and beta gene polymorphisms in the susceptibility to adult periodontitis.

PDGF-alpha receptor subunit expression down-regulated by IL-1beta in human periodontal ligament cells

The responses of cells to the distinct PDGF isoforms have been correlated directly to the relative numbers of specific PDGF receptor subunits on the cell surface. The modulation of PDGF-alpha receptor subunits, the major subunit expressed in human periodontal ligament (PDL) cells, by cytokines present in the periodontal wound site, such as interleukin-1 (IL-1), may be an important factor influencing regenerative outcomes. The purpose of the present study was to examine the effects of IL-1 beta on PDGF-alpha receptor subunit expression in human PDL cells. Primary cultures of human PDL cells were treated with IL-1 beta over a range of concentrations. We assessed PDGF-alpha receptor subunits by examining the mitogenic responses of cells to PDGF-AA, specific binding of 125I-labeled PDGF-AA, immunofluorescent analysis of PDGF-alpha receptor subunits, and PDGF-alpha receptor subunit mRNA levels using Northern blot analysis. The results demonstrate a significant concentration-dependent decrease in 3H-thymidine incorporation in response to PDGF-AA following IL-1 beta treatment (p < 0.001). This decreased response correlated directly with IL-1-induced decreases in 125I-labeled PDGF-AA binding (p < 0.01), the numbers of immunolabeled PDGF-alpha receptor subunits, and in PDGF-alpha receptor subunit mRNA levels. However, when combined with TGF-beta, IL-1 beta did not show additional down-regulation in proliferative response to PDGF-AA or PDGF-alpha receptor subunits beyond that achieved with these factors individually. These experiments identify IL-1 beta, along with TGF-beta, as significant inhibitors of PDGF stimulation in human PDL cells, acting through the down-regulation of PDGF-alpha receptor subunit expression.

Cytokine expression in periodontal health and disease

Soluble proteins that serve as mediators of cell function and are produced by various cell types, such as structural and inflammatory cells, are collectively called cytokines. Several lines of evidence have revealed that cytokines play important roles not only in tissue homeostasis but also in the pathogenesis of many infectious diseases. Recent research on biological activities in normal periodontium and the pathogenesis of periodontal diseases has clarified the involvement of various cytokines in the biological activities observed in the sites. Cytokines play crucial roles in the maintenance of tissue homeostasis, a process which requires a delicate balance between anabolic and catabolic activities. In particular, growth factors--such as fibroblast growth factor (FGF), platelet-derived growth factor (PDGF), insulin-like growth factor (IGF), transforming growth factor-beta (TGF-beta)--are thought to play important roles in modulating the proliferation and/or migration of structural cells in the periodontium and the production of various extracellular matrices by these cells. On the other hand, there is little doubt that excessive and/or continuous production of cytokines in inflamed periodontal tissues is responsible for the progress of periodontitis and periodontal tissue destruction. Particularly, inflammatory cytokines--such as IL-1 alpha, IL-1 beta, IL-6, and IL-8--are present in the diseased periodontal tissues, and their unrestricted production seems to play a role in chronic leukocyte recruitment and tissue destruction. It is possible that monitoring cytokine production or its profile may allow us to diagnose an individual's periodontal disease status and/or susceptibility to the disease. In addition, although the hypothesis is still controversial, it has been suggested that discrete T-cell subsets (Th1 and Th2) with different cytokine profiles play specific roles in the immunopathogenesis of periodontal diseases.

Active cytomegalovirus infection in human periodontitis

This study used the reverse transcription polymerase chain reaction method to determine mRNA transcription of subgingival human cytomegalovirus (HCMV) in six adult and three localized juvenile periodontitis patients. The oligonucleotide primers targeted the major capsid protein gene to determine active HCMV infection. HCMV major capsid protein transcript was detected in deep periodontal pockets of two adult and two localized juvenile periodontitis patients but not in any shallow periodontal sites. The findings suggest that active HCMV replication can occur in periodontal sites. Further studies are necessary to establish whether periodontal reactivation of HCMV correlates with the initiation or progression of destructive periodontal disease.

Genetic variations in cytokine expression: a risk factor for severity of adult periodontitis

Periodontitis is a collection of chronic inflammatory diseases that are caused by specific bacteria. The bacteria activate inflammatory mechanisms in the periodontal tissues that destroy collagen and bone that support the teeth. Although bacteria are essential for the initiation of periodontitis, the quantity and types of bacteria have not been sufficient to explain the differences in disease severity. In recent years, it has become evident that for many common chronic diseases, there are modifying factors that do not cause the disease but rather amplify some disease mechanisms to make the clinical condition more severe. There are now data to suggest that a few factors which amplify the inflammatory process make people susceptible to an increased severity of periodontitis. Studies of untreated disease in Sri Lanka identified 3 patterns of disease progression. Studies in twins suggested that part of the clinical characteristics of periodontitis may be explained by genetic factors, but previous attempts to identify genetic markers for periodontitis have been unsuccessful Some genetic variations (polymorphisms) are commonly found in our population and represent a mechanism by which individuals may exhibit variations within the range of what is considered biologically normal. Since certain cytokines are key regulators of the inflammatory response and are important in periodontitis, we investigated the relationship between genetic variations associated with cytokine production and periodontitis severity. There are several polymorphisms in the cluster of genes that influence IL-1 biological activity. In recent clinical trials, two of these polymorphisms, when found together, have been associated with a significant increase in the risk for severe generalized periodontitis. Genetic association with periodontitis was evident only when smokers were excluded from the analysis, confirming the importance of smoking, and suggesting that both smoking and the IL- I genotype are independent factors in severe periodontitis. It is notable that 1 polymorphism associated with severe periodontitis in our study is also known to correlate with a 2- to 4-fold increase in IL-1 beta production. These findings are consistent with the current model of how genetic factors influence common chronic diseases. If we apply this model to periodontitis, it would involve the following: 1) a disease-initiating factor that would undoubtedly be specific bacteria such as Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans. and Bacteroides forsythus: and 2) modifiers of disease mechanisms that account for the clinical severity, including smoking, the IL-I genotype, certain systemic diseases, and psychosocial stress. The association of the IL-I genotype with severe periodontitis is consistent with several lines of periodontal research. Several studies have suggested there is a substantial genetic influence in periodontal disease. Although specific genetic markers have been identified in the uncommon juvenile forms of periodontitis, previous studies of specific genetic markers in adults with periodontitis have not been encouraging. Many investigators have, however, demonstrated a role for IL-1 in the initiation and progression of periodontitis. For example, IL-1 activates the degradation of the extracellular matrix and bone of the periodontal tissues, and elevated tissue or gingival fluid levels of IL-1 beta have been repeatedly associated with periodontitis. In addition, IL-1 is a strong enhancer of tissue levels of PGE2 and TNF-alpha. The association of severe periodontitis with smoking and the IL-1 genotype suggest a role for these factors in the pathogenesis of periodontitis. The finding that host modifying factors are associated with severe periodontitis suggest a biological mechanism by which some individuals, if challenged by bacterial accumulations, may have a more vigorous immunoinflammatory response, leading to more severe clinical disease. (ABSTRACT

Estrogen inhibits interleukin-1beta-induced interleukin-6 production by human osteoblast-like cells

Estrogen supplements are the primary pharmacologic intervention therapy to prevent and treat loss of bone mass (osteoporosis) in postmenopausal women. Furthermore, at sites of local inflammation near bone, estrogen-deficient women are significantly more susceptible to bone loss than are estrogen-sufficient women. In the present study, we investigate whether estrogen modulates osteoblast (MG-63) production of interleukin-6 (IL-6), an osteoclast recruitment and differentiation of cytokine, in the presence of the proinflammatory cytokine, IL-1beta. Using enzyme-linked immunosorbent assay (ELISA), we demonstrate that IL-1beta significantly enhances IL-6 secretion into culture supernatants in a dose-dependent and time-dependent manner. Using reverse-transcriptase polymerase chain reaction (RT-PCR) and ELISA respectively, we demonstrate further that levels of 17beta-estradiol (active metabolite of estrogen) > or = those found in serum of estrogen-sufficient women inhibit steady-state IL-6 mRNA levels as well as inhibit secretion of IL-6 into culture supernatants. One mechanism by which estrogen therapy preserves bone mass in areas of inflammation may be via inhibition of IL-1beta-stimulated obsteoblast-derived IL-6.

Strain-dependent activation of monocytes and inflammatory macrophages by lipopolysaccharide of Porphyromonas gingivalis

Porphyromonas gingivalis is one of the pathogens associated with periodontal diseases, and its lipopolysaccharide (LPS) has been suggested as a possible virulence factor, acting by stimulation of host cells to secrete proinflammatory mediators. However, recent studies have shown that P. gingivalis LPS inhibited some components of the inflammatory response. The present study was designed to test the hypothesis that there are strain-dependent variations in the ability of P. gingivalis LPS to elicit the host inflammatory response. By using LPS preparations from two strains of P. gingivalis, W50 and A7346, the responses of mouse macrophages and human monocytes were evaluated by measuring the secretion of nitric oxide (NO) and tumor necrosis factor alpha (TNF-alpha). Both direct and indirect (priming) effects were investigated. LPS from Salmonella typhosa was used as a reference LPS. P. gingivalis A7436 LPS induced lower secreted levels of NO from the tested cells than S. typhosa LPS but induced similar levels of TNF-alpha. In contrast, LPS from P. gingivalis W50 did not induce NO or TNF-alpha secretion. Preincubation of macrophages with LPS from S. typhosa or P. gingivalis A7436 prior to stimulation with S. typhosa LPS upregulated NO secretion and downregulated TNF-alpha secretion, while preincubation with P. gingivalis W50 LPS enhanced both TNF-alpha and NO secretory responses. These results demonstrate that LPSs derived from different strains of P. gingivalis vary in their biological activities in vitro. The findings may have an impact on our understanding of the range of P. gingivalis virulence in vivo.

Rapid progression of bone loss in HIV-associated necrotizing ulcerative stomatitis

This report describes a case of rapidly progressive periodontal tissue breakdown and bone loss in an HIV-infected markedly immunosuppressed homosexual male. Within 6 months of initial presentation with a necrotizing ulcerative gingivitis, the lesion extended to a necrotizing ulcerative stomatitis involving the surrounding periodontium and palatal mucosa. With only partial compliance to local debridement, chlorhexidine oral rinses, and systemic metronidazole therapy, alveolar bone loss resulted in tooth mobility necessitating extraction of 2 involved teeth. This case illustrates the continuum of necrotizing ulcerative infections of the periodontium in the severely immunosuppressed patient. The implications of these oral manifestations of HIV infection are discussed.

Tumor necrosis factor alpha production by oral leukocytes: influence of tumor necrosis factor genotype

Tumor necrosis factor alpha (TNF-alpha) is a proinflammatory cytokine that is thought to play a role in the pathogenesis of periodontal disease. TNF-alpha production is regulated by many factors, including certain alleles of TNF gene polymorphisms. In the present study, TNF genotypes of 3 bi-allelic polymorphisms were determined in 32 Caucasian patients with adult periodontitis and 32 orally-healthy matched controls, and correlated with TNF-alpha production by oral polymorphonuclear leukocytes (PMN). No differences in distribution of TNF alleles of the -238, -308, or +252 gene polymorphisms were observed between patients and controls or between patients with different disease severity. However, the level of TNF-alpha production by oral PMN correlated with the TNF-alpha 308 genotype in patients with adult periodontitis, with increased production found in patients with the T1,2 genotype (t-test; P=0.037). When cytokine production was examined in patients according to disease severity, an association between the T1,2 genotype and increased production was observed only in patients with advanced disease (t-test; P=0.05). These findings suggest that further studies are warranted to determine if the TNF genotype is a risk factor for severity of disease in adult periodontitis.

Nicotine and smokeless tobacco effects on gingival and peripheral blood mononuclear cells

The pathogenesis of tobacco-related periodontal diseases is not well understood. The purpose of this study was therefore to investigate smokeless tobacco extract (ST) and nicotine effects on prostaglandin E2 (PGE2) and interleukin-1beta (IL-1beta) secretion by peripheral blood mononuclear cells (PBMC, consisting of monocytes and lymphocytes) and gingival mononuclear cells (GMC). Both peripheral blood and gingival tissue adjacent to the alveolar crest were taken from non-smoking adult periodontitis patients. Gingival tissue was treated with collagenase and deoxyribonuclease and GMC and PBMC were isolated by Ficoll-Hypaque centrifugation. GMC and PBMC (100,000 cells/200 microl) were cultured for 24 hours in supplemented RPMI 1640 alone (control), or in supplemented RPMI 1640 containing 1% ST, 100 microg/ml nicotine, 1 microg/ml Porphyromonas gingivalis LPS, or 1 microg/ml P. gingivalis LPS and either 100 microg/ml nicotine or 1% ST. Enzyme immunoassays were used to quantify PGE2 and IL-1beta. Treatments were compared by repeated measures ANOVA. 100 microg/ml nicotine (7-fold, p<0.02) and 1% ST (3.5-fold, p<0.004) significantly increased secretion of PGE2 by PBMC relative to control cultures. 100 microg/ml nicotine and 1% ST, however, had no effect on IL-1beta secretion by PBMC. Enhanced PGE2 secretion also was seen when PBMC were treated with P. gingivalis LPS+ 100 microg/ml nicotine relative to P. gingivalis LPS alone (p<0.007). In contrast, 100 microg/ml nicotine significantly downregulated IL-1beta secretion by GMC relative to medium alone (p<0.008) and had no effect on PGE2 secretion by GMC. These data indicate that while nicotine and ST can stimulate PBMC to secrete PGE2, they cannot activate further mononuclear cells extracted from gingiva, possibly due to maximal previous stimulation in the periodontitis lesion.

Coordinate production of PGE2 and IL-1 beta in the gingival crevicular fluid of adults with periodontitis: its relationship to alveolar bone loss and disruption by twice daily treatment with ketorolac tromethamine oral rinse

The inflammatory mediators prostaglandin E2 (PGE2) and interleukin-1 beta (IL-1 beta) play critical roles in the inflammatory process leading to alveolar bone and connective tissue loss in periodontal disease. Data from a previously published 6-month clinical study demonstrated that twice daily use of 0.1% ketorolac tromethamine oral rinse prevented alveolar bone loss in adults with periodontitis. We further analyzed data from this study to examine the relationship between PGE2. IL-1 beta and bone loss. Patient mean PGE2 and IL-1 beta levels in gingival crevicular fluid (M-GCF) measured throughout the course of the study were directly compared to the maximum amount of alveolar bone height loss observed at a single study site in each patient. The maximum amount of bone loss measured was chosen for the analysis since the pattern of bone loss was clearly episodic in nature. A statistically significant correlation (r = 0.73, p = 0.001) exists between M-GCF PGE2 concentration and the maximum amount of bone height lost at individual patient study sites. The correlation between M-GCF IL-1 beta concentration and maximum bone height lost is also statistically significant (r = 0.66, p = 0.005). Over the 6-month duration of the study, both PGE2 and IL-1 beta were coordinately expressed in the placebo treatment group as reflected in the significant correlation between M-GCF concentrations of the 2 mediators (r = 0.81, p < 0.001). Treatment of patients with 0.1% ketorolac tromethamine twice daily for 6 months resulted in reductions of PGE2 in GCF and a negligible correlation between M-GCF PGE2 and M-GCF IL-1 beta (r = 0.42, p = 0.088). This lack of a strong association between the 2 mediators in the ketorolac treatment group provides a direct biochemical readout of the anti-inflammatory efficacy of ketorolac tromethamine oral rinse in patients with periodontitis. Further studies are warranted to determine the full diagnostic potential of M-GCF levels of PGE2 and IL-1 beta for predicting risk of alveolar bone loss in patients with periodontitis and monitoring periodontal therapy effectiveness.

CD11b mRNA expression in neutrophils isolated from peripheral blood and gingival crevicular fluid

Adhesion molecule CD11b/CD18 expressed by neutrophils (PMNs) participates in cell migration and phagocytosis of C3bi derivatized bacteria. It is this phagocytic function that eliminates some of the known periodontal pathogens in periodontal pockets. In patients with advanced periodontitis, homotypic aggregation of crevicular fluid PMNs (CF-PMNs) may occur due to overexpression of CD11b/CD18 and this may lead to ineffective elimination of periodontal pathogens. We have previously shown that CF-PMNs isolated from the periodontal pockets overexpress CD11b compared to PB-PMNs. This study tested the hypotheses that (1) overexpression of surface CD11b correlates with expression of CD11b mRNA in CF-PMNs isolated from advanced periodontitis subjects, and (2) the intrinsic capacity of CD11b mRNA upregulation by PB-PMNs from periodontitis patients differs from that of control subjects. CF-PMNs and peripheral blood PMNs (PB-PMNs) were isolated from 13 subjects with healthy gingiva (control group) and 13 subjects with advanced periodontitis (patient group). The surface expression of CD11b was determined by flow cytometry and CD11b mRNA was determined by extraction of mRNA and reverse transcription to cDNA followed by DNA amplification using primers to detect a segment of the cDNA which encodes CD11b. The results of this study confirm that the surface expression of CD11b on CF-PMNs is significantly higher in periodontitis subjects vs control subjects (p = 0.03), whereas surface CD11b expression on PB-PMNs does not differ significantly between groups (p = 0.06). The level of surface CD11b expression on CF-PMNs did not correlate with the amount of mRNA present in CF-PMNs in either group (p = 0.056, 0.07 for control and periodontitis patients, respectively). Most (9 of 13) individuals in the patient group expressed CD11b mRNA whereas very few control subjects (2 of 11) had CD11b mRNA in their CF-PMNs. This difference between groups was statistically significant (p = 0.004). The capacity to upregulate CD11b mRNA upon stimulation with fMLP and/or GM-CSF was highly variable and there was no statistical difference between the 2 groups.

Alveolar bone loss one year following ovariectomy in sheep

There is little information concerning the incidence of alveolar bone loss in estrogen-deficient women. Ovariectomized sheep are valid models for study of the effects of estrogen deficiency on bone metabolism. The objective of this study was to compare alveolar bone loss in control (C) and ovariectomized sheep (OVX) at 3 and 12 months following surgery. OVX animals had decreased serum levels of 17-beta-estradiol and increased serum levels of osteocalcin, IL-6, and urinary levels of deoxypyridinoline which, taken together, suggest development of osteoporosis. The mean probing depths and percentage of sites with pocket depths 4 to 6 mm and > 6 mm were significantly greater in OVX than C at each time period and in OVX were significantly greater at 12 months that at 3 months. Gingival tissue interleukin-6 (IL-6) levels (but not the number of IL-6(+) cells) were elevated adjacent to deep periodontal pockets; however, there was no significant elevation of levels of the proinflammatory cytokines IL-1 beta and IL-8 within gingiva. Taken together, the data suggest a systemic contribution for progression of periodontal disease associated with estrogen deficiency. This may involve upregulation of systemic IL-6 synthesis and transfer to gingiva in serum, resulting in enhanced IL-6 accumulation within the gingival tissues or reduced bone density allowing for a greater amount of alveolar bone loss.

Cytokine production by oral and peripheral blood neutrophils in adult periodontitis

Proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) and interleukin 1 beta (IL-1 beta) also possess bone-resorptive properties, and are generally considered to play a role in the pathogenesis of periodontal disease. In the present study, TNF-alpha and IL-1 beta production by oral and peripheral blood polymorphonuclear leukocytes (PMN) was examined in 40 patients with adult periodontitis and 40 orally healthy matched controls. Oral PMN released considerable amounts of both cytokines in unstimulated culture, and there was no difference between patients and controls when the cytokine levels were corrected for cell number. However, when the effect of disease activity was examined, cytokine release by oral PMN was found to be greatest in patients with advanced periodontitis. Within the healthy control group, IL-1 beta production by oral PMN was significantly higher in males (Mann-Whitney test, P = 0.0008). Examination of IL-1 beta production by peripheral blood PMN exposed to recombinant human granulocyte-macrophage colony stimulating factor revealed no difference between the patient and control groups. In contrast, IL-1 beta production by peripheral blood PMN was significantly reduced in patients with advanced disease (Mann-Whitney test, P = 0.02), and peripheral PMN IL-1 beta synthesis was greater in female controls (Mann-Whitney test, P = 0.054). No effect of race on cytokine production could be discerned in patients or controls. These results indicate that several factors influence cytokine production in oral health and disease, and that a dichotomy in cytokine gene expression exists between oral and peripheral blood PMN in adult periodontitis.

Effects of interleukin-1 beta on matrix metalloproteinase-3 levels in human periodontal ligament cells

MATRIX METALLOPROTEINASE-3 (MMP-3), or stromelysin-1, is an enzyme responsible for the degradation of a wide range of extracellular matrix proteins. Increases in MMP-3 activity have been found in several chronic inflammatory diseases, and this increased activity is thought to be mediated by interleukin-1 beta (IL-1 beta). Because IL-1 beta has been strongly associated with inflammatory periodontal disease, the purpose of this in vitro study was to investigate the role of IL-1 beta on the regulation of MMP-3 levels in cells derived from the human periodontal ligament (PDL). Human PDL cell cultures were treated with IL-1 beta at varying concentrations (0.01-1.0 ng/ml) for 24 hour prior to analysis at either transcript or protein levels. Following the isolation of total RNA, the relative levels of MMP-3 mRNA were determined using reverse transcription-polymerase chain reaction (RT-PCR) with 32P-end-labeled primers. Immunocytochemical detection of MMP-3 protein was performed using polyclonal antibodies to human MMP-3. The results of RT-PCR analysis demonstrated a concentration-dependent increase in MMP-3 mRNA expression, with IL-1 beta treatments of 0.1 and 1.0 ng/ml significantly (P < 0.01) increased over those cells not treated with IL-1 beta. This increase in mRNA expression was paralleled by significant (P < 0.001) changes at the protein level, with an average of 27.6% of the cells stained positive for MMP-3 following IL-1 beta treatment (1.0 ng/ml), compared with control cells showing no positive staining for MMP-3. In conclusion, the results of this study demonstrate that IL-1 beta upregulates MMP-3 in human PDL cells on both an mRNA and a protein level. These findings suggest possibly important roles for IL-1 beta and MMP-3 in both normal turnover and maintenance of the PDL and in the connective tissue degradation associated with periodontal disease.

Epidemiology and diagnosis of HIV-associated periodontal diseases

A review of periodontal disease as a manifestation of HIV infection suggests a shift in emphasis over the past 5 years. Initially the focus was on newly described forms of periodontal disease (i.e., HIV-associated gingivitis or linear gingival erythema (LGE); HIV-associated periodontitis or necrotizing ulcerative periodontitis (NUP). While the clinical definition of LGE varies from study to study, an association between LGE and Candida infection has been described. Furthermore, the prevalence of NUP is quite low and this disorder is associated with severe immunosuppression. In contrast, the focus today is on the accelerated rate of chronic adult periodontitis occurring in seropositive patients. While the organisms that characterize adult periodontitis in seronegative individuals are present in subgingival plaque from seropositive individuals, reports suggest that atypical pathogens are also present (i.e., Mycoplasma salivarium, Enterobacter cloacae). Recent studies from our laboratory have identified a novel strain of Clostridium isolated from the subgingival plaque of injecting drug users that has pathologic potential. This organism, however, was found in both seropositive and seronegative individuals in this cohort, suggesting an association with lifestyle rather than serostatus. In addition, data has been published examining the local host response in periodontitis in seropositive individuals. Distinctly elevated levels of IgG in gingival crevicular fluid (GCF) have been observed in seropositive patients. Furthermore, data from our laboratory examining inflammatory mediators in GCF (polymorphonuclear leukocyte lysosomal enzyme beta-glucuronidase and the pro-inflammatory cytokine interleukin-1 beta) suggests an altered response in patients with HIV infection. The alteration manifests as the absence of the expected strong correlation between polymorphonuclear leukocyte activity in the gingival crevice and clinical measures of existing periodontal disease, as well as elevated levels of interleukin-1 beta in sites with deeper probing depths. Therefore, it can be concluded that the progression of periodontal disease in the presence of HIV infection is dependent upon the immunologic competency of the host as well as the local inflammatory response to typical and atypical subgingival microorganisms.

Bone-resorptive cytokine gene expression in periapical lesions in the rat

Periapical bone destruction is an important pathogenic sequela of pulpal infection. Recent findings from this laboratory have demonstrated that most bone-resorbing activity in extracts of rat periapical lesions can be neutralized by an anti-interleukin (IL)-1 alpha antiserum. To further clarify pathogenic mechanisms, bone-resorptive cytokine messenger RNA (mRNA) expression was analyzed in developing rat periapical lesions. The molar teeth of 20 Sprague-Dawley rats were surgically exposed and left open to permit infection from the oral environment. Total cell RNA was isolated from periapical granuloma tissue obtained on days 3, 7, 15 and 30 after exposure. mRNA for IL-1 alpha, IL-1 beta and tumor necrosis factor alpha (TNF-alpha) was amplified by reverse transcription polymerase chain reaction, and levels were approximated by comparison to the parallel amplification of the housekeeping gene glyceraldehyde phosphate dehydrogenase. IL-1 alpha and TNF-alpha mRNA were both highly expressed beginning on day 7, increased on day 15, and declined somewhat on day 30. In contrast, IL-1 beta mRNA was expressed at much lower levels, but with similar kinetics. The kinetics of steady state IL-1 alpha and TNF-alpha mRNA levels were confirmed using the quantitative RNase protection assay, whereas IL-1 beta mRNA could not be detected by this technique. IL-1 alpha mRNA-expressing cells were identified using in situ hybridization and included infiltrating macrophages, as well as resident fibroblasts, endothelial cells and osteoclasts. These results demonstrate that the IL-1 alpha and TNF-alpha genes are highly expressed in developing periapical lesions in the rat and confirm previous studies at the protein level in this model.