Interleukin 18 and periodontal disease

Comparison of smoking traditional, heat not burn and electronic cigarettes on salivary cytokine, chemokine and growth factor profile in healthy young adults-pilot study

Objective: Smoking is the cause of numerous oral pathologies. The aim of the study was to evaluate the effect of smoking traditional cigarettes, e-cigarettes, and heat-not-burn products on the content of salivary cytokines, chemokines, and growth factors in healthy young adults. Design: Three groups of twenty-five smokers each as well as a control group matched in terms of age, gender, and oral status were enrolled in the study. In unstimulated saliva collected from study groups and participants from the control group, the concentrations of cytokines, chemokines, and growth factors were assessed by Bio-Plex® Multiplex System. Results: We demonstrated that smoking traditional cigarettes is responsible for increasing the level of IFN-γ compared to non-smokers and new smoking devices users in unstimulated saliva in the initial period of addiction. Furthermore, e-cigarettes and heat-not-burn products appear to have a similar mechanism of affecting the immune response system of unstimulated saliva, leading to inhibition of the local inflammatory response in the oral cavity. Conclusion: Smoking traditional cigarettes as well as e-cigarettes and heat-not-burn products is responsible for changes of the local immune response in saliva. Further research is necessary to fill the gap in knowledge on the effect of new smoking devices on the oral cavity immune system.

IL-18 Gene rs187238 and rs1946518 Polymorphisms and Expression in Gingival Tissue in Patients with Periodontitis

Periodontitis is a chronic disease with disturbed balance between the immune and inflammatory response of the host to bacteria. Many studies have shown that proinflammatory cytokines play a significant role in the pathogenesis of periodontal disease. In this study, we examined the association between the IL-18 gene rs187238 and rs1946518 polymorphisms and periodontitis in non-smoking and smoking patients. This study enrolled 200 patients with periodontitis (130 non-smokers and 70 smokers) and 156 control subjects (124 non-smokers and 32 smokers). There were no statistically significant differences in the distribution of the rs187238 and rs1946518 IL-18 genotypes and alleles between patients with periodontitis and control subjects, between smoking patients with periodontitis and smoking control subjects, and between non-smoking patients with periodontitis and non-smoking control subjects. There were no statistically significant differences in clinical parameters in relation to the IL18 rs187238 genotypes. In patients with the IL18 rs1946518 GG genotype, we observed increased values of bleeding on probing (BoP) and periodontal probing depth (PPD), compared to subjects with the TT genotype. In patients with periodontitis, we observed statistically significant decreased expression of the IL-18 gene in comparison with healthy subjects (0.231 ± 0.163 vs. 0.663 ± 0.197, p = 0.0008). In addition, the IL-18 gene expression in gingival tissue in patients with periodontitis correlated positively with the number of remaining teeth. The results of our study suggest that the IL-18 rs187238 and rs1946518 polymorphisms are not significant risk indicators of periodontitis in our population. However, in patients with the IL18 rs1946518 GG genotype, we observed increased values of BoP and PPD, compared to subjects with the TT genotype. In addition, in gingival tissue of patients with periodontitis, we have detected decreased expression of IL-18. The gingival expression of IL-18 in patients with periodontitis correlated positively with number of remaining teeth. The above results suggest that IL-18, in addition to its pro-inflammatory effects in periodontal disease, may also exhibit protective properties.

Activation and Function of NLRP3 Inflammasome in Bone and Joint-Related Diseases

Inflammation is a pivotal response to a variety of stimuli, and inflammatory molecules such as cytokines have central roles in the pathogenesis of various diseases, including bone and joint diseases. Proinflammatory cytokines are mainly produced by immune cells and mediate inflammatory and innate immune responses. Additionally, proinflammatory cytokines accelerate bone resorption and cartilage destruction, resulting in the destruction of bone and joint tissues. Thus, proinflammatory cytokines are involved in regulating the pathogenesis of bone and joint diseases. Interleukin (IL)-1 is a representative inflammatory cytokine that strongly promotes bone and cartilage destruction, and elucidating the regulation of IL-1 will advance our understanding of the onset and progression of bone and joint diseases. IL-1 has two isoforms, IL-1α and IL-1β. Both isoforms signal through the same IL-1 receptor type 1, but the activation mechanisms are completely different. In particular, IL-1β is tightly regulated by protein complexes termed inflammasomes. Recent research using innovative technologies has led to a series of discoveries about inflammasomes. This review highlights the current understanding of the activation and function of the NLRP3 (NOD-like receptor family, pyrin domain-containing 3) inflammasome in bone and joint diseases.

Oral biosciences: The annual review 2020

BACKGROUND

The Journal of Oral Biosciences is devoted to the advancement and dissemination of fundamental knowledge concerning every aspect of oral biosciences.

HIGHLIGHT

This review featured the review articles in the fields of "Microbiology," "Palate," "Stem Cells," "Mucosal Diseases," "Bone Cell Biology," "MicroRNAs," "TRPV1 Cation Channels," and "Interleukins" in addition to the review article by prize-winners of the "Rising Members Award" ("DKK3 expression and function in head and neck squamous cell carcinoma and other cancers"), presented by the Japanese Association for Oral Biology.

CONCLUSION

These reviews in the Journal of Oral Biosciences have inspired the readers of the journal to broaden their knowledge regarding the various aspects of oral biosciences. The current editorial review introduces these exciting review articles.

Development of an miRNA-Array-Based Diagnostic Signature for Periodontitis

Periodontitis progression is accompanied by irreversible alveolar bone absorption and leads to tooth loss. Early diagnosis is important for tooth stability and periodontal tissue preservation. However, there is no recognized miRNA diagnostic signature with convincing sensitivity and specificity for periodontitis. In this study, we obtained miRNA array expression profiles of periodontitis from the Gene Expression Omnibus (GEO) database. After screening for differentially expressed miRNAs, the least absolute shrinkage and selection operator (LASSO) method was performed to identify and construct a 17-miRNA-based diagnostic signature (hsa-miR-3917, hsa-mir-4271, hsa-miR-3156, hsa-miR-3141, hsa-miR-1246, hsa-miR-125a-5p, hsa-miR-671-5p, hcmv-mir-UL70, hsa-miR-650, hsa-miR-497-3p, hsa-miR-145-3p, hsa-miR-141-3p, hsa-miR-210-3p, hsa-miR-204-3p, hsa-miR-203a-5p, hsa-miR-99a-3p, and hsa-miR-30a-3p). Periodontal tissue samples with higher risk scores were more likely to show symptoms of periodontitis. Then, the receiver operating characteristic (ROC) curves were used to assess the diagnostic value of the miRNA signature, which indicated that the optimum cutoff value in periodontitis diagnosis was 0.5056 with an area under the ROC curve (AUC) of 0.996, a sensitivity of 97.3%, a specificity of 100.0% in the training cohort; in the testing cohort, the corresponding values were as follows: an AUC of 0.998, a sensitivity of 97.9%, and a specificity of 91.7%. We next evaluated the efficacy of the signature in differentiating disease subtype and affected range. Furthermore, we conducted functional enrichment analysis of the 17 miRNA-targeted mRNAs, including the regulation of mTOR activity and cell autophagy, Th1/Th2 cell balance and immunoregulation, cell apoptosis, and so on. In summary, our study identified and validated a 17-miRNA diagnostic signature with convincing AUC, sensitivity, and specificity for periodontitis.

Role of interleukin-1 and inflammasomes in oral disease

BACKGROUND

Inflammation promotes immune cell infiltration into tissues and induces production of pro-inflammatory cytokines that mediate innate immune responses. Acute or temporary inflammation results in the required repair of the inflamed tissues. However, chronic inflammation leads to pathogenesis of inflammatory conditions such as periodontal disease. In periodontal tissues, pro-inflammatory cytokines mediate inflammatory responses and accelerate the bone-resorbing activity of osteoclasts, resulting in destruction of alveolar bone. Levels of interleukin-1 (IL-1), a major pro-inflammatory cytokine that strongly promotes osteoclastic activity, are elevated in oral tissues of patients with periodontitis. Therefore, elucidation of the mechanisms underlying IL-1 production will enhance our understanding of the pathogenesis of periodontal disease.

HIGHLIGHT

IL-1 has two isoforms: IL-1α and IL-1β. Both isoforms bind to the same IL-1 receptor and have identical biological activity. Unlike that of IL-1α, the IL-1β precursor is not bioactive. To induce its bioactivity, the IL-1β precursor is cleaved by caspase-1, whose activation is mediated by multiprotein complexes termed inflammasomes. Thus, IL-1β maturation and activity are strictly regulated by inflammasomes. This review highlights the current understanding of the molecular mechanisms underlying IL-1 production and the related inflammasome activity.

CONCLUSION

Inhibition of IL-1 production or the inflammasomes via their regulatory mechanisms may facilitate prevention or treatment of periodontal disease and other inflammatory diseases.

Cytokines and Bone: Osteoimmunology

Cytokines and hematopoietic growth factors have traditionally been thought of as regulators of the development and function of immune and blood cells. However, an ever-expanding number of these factors have been discovered to have major effects on bone cells and the development of the skeleton in health and disease (Table 1). In addition, several cytokines have been directly linked to the development of osteoporosis in both animal models and in patients. In order to understand the mechanisms regulating bone cells and how this may be dysregulated in disease states, it is necessary to appreciate the diverse effects that cytokines and inflammation have on osteoblasts, osteoclasts, and bone mass. This chapter provides a broad overview of this topic with extensive references so that, if desired, readers can access specific references to delve into individual topics in greater detail.

Macrophage roles in the clearance of apoptotic cells and control of inflammation in the prostate gland after castration

BACKGROUND

Androgen deprivation results in massive apoptosis in the prostate gland. Macrophages are actively engaged in phagocytosing epithelial cell corpses. However, it is unknown whether microtubule-associated protein 1 light chain 3 alpha (LC3)-associated phagocytosis (LAP) is involved and contribute to prevent inflammation.

METHODS

Flow cytometry, RT-PCR and immunohistochemistry were used to characterize the macrophage subpopulation residing in the epithelial layer of the rat ventral prostate (VP) after castration. Stereology was employed to determine variations in the number of ED1 and ED2. Mice were treated with either chloroquine or L-asparagine to block autophagy.

RESULTS

M1 (iNOS-positive) and M2 macrophages (MRC1+ and ARG1+) were not found in the epithelium at day 5 after castration. The percentage of CD68⁺ (ED1) and CD163⁺ (ED2) phenotypes increased after castration but only CD68⁺ cells were present in the epithelium. RT-PCR showed increased content of the autophagy markers Bcl1 and LC3 after castration. In addition, immunohistochemistry showed the presence of LC3⁺ and ATG5⁺ cells in the epithelium. Double immunohistochemistry showed these cells to be CD68⁺ /LC3⁺ , compatible with the LAP phenotype. LC3⁺ cells accumulate significantly after castration. Chloroquine and L-asparagine administration caused inflammation of the glands at day 5 after castration.

CONCLUSIONS

CD68⁺ macrophages phagocytose apoptotic cell corpses and activate the LAP pathway, thereby contributing to the preservation of a non-inflammed microenvironment. Marked inflammation was detected when autophagy blockers were administered to castrated animals.

The Effects of Smoking on Expression of IL-12 and IL-1β in Gingival Tissues of Patients with Chronic Periodontitis

Aim:

The purpose of this study was to compare IL-1β and IL-12 gene expression in the gingival tissue of smokers and non-smokers either with healthy periodontium or with chronic periodontitis.

Materials and Methods:

41 individuals consisting of 21 healthy controls (11 non-smokers and 10 smokers) and 20 chronic periodontitis patients (10 non-smokers and 10 smokers) participated in this study. Samples were collected from papillary regions of targeted areas and cytokines were analyzed using Real Time PCR. Shapiro-Wilk, Mann-Witney and Independent T tests were employed for statistical analysis.

Results:

IL-1β gene expression in gingival tissue of non-smoker group with chronic periodontitis was significantly higher than non-smoker-healthy group (p=0.011). Smoker-chronic periodontitis group showed lower IL-1β gene expression than non-smoker-chronic periodontitis group (p=0.003). IL-12 gene expression was not significantly different between analyzed groups.

Conclusion:

IL-1β gene expression increases in gingival tissue of non-smoker-chronic periodontitis patients due to inflammatory processes but smoking reduces the expression of this cytokine in diseased periodontal tissues. On the other hand periodontal condition and smoking habits do not seem to affect IL-12 gene expressions in gingival tissues. Authors concluded that reduced levels of IL1 and in some extent IL12 in smoking patients are responsible for higher tissue and bone degenerations and less treatment responses in smokers.

Immune cellular profile of bisphosphonate-related osteonecrosis of the jaw

OBJECTIVES

Characterize the cell profile and immunostaining of proinflammatory markers in an experimental model of bisphosphonate-related osteonecrosis of the jaw (BRONJ).

MATERIALS AND METHODS

Male Wistar rats (n = 6-7) were treated chronically with saline solution or zoledronic acid (ZA) at 0.04, 0.20, and 1.00 mg kg(-1) (1.4 × 10(-7) , 6.9 × 10(-6) , and 3.4 × 10(-5)  mol kg(-1) ), and subsequently, the first left inferior molar was extracted. Were performed counting of viable and empty osteocyte lacunae, viable and apoptotic osteoclasts, polymorphonuclear neutrophil, mast cells (toluidine blue), and the positive presence cells for CD68, tumor necrosis factor-alpha (TNF-α), IL (interleukin)-1β, inducible nitric oxide synthase (iNOS), nuclear factor-kappa B (NF-kB) and IL-18 binding protein (IL-18 bp).

RESULTS

BRONJ was showed in ZA treated with 0.20 and 1.00 mg kg(-1) . There is a dose dependent increase in percentage of empty osteocyte lacunae (P < 0.001) and apoptotic osteoclasts (P < 0.001), counting of total osteoclasts (P = 0.003), polymorphonuclear neutrophil cells (P = 0.009), cytoplasmic-positive cells of CD68 (P < 0.001), TNF-α (P = 0.001), IL-1β (P = 0.001), iNOS (P < 0.001), NF-kB (P = 0.006), and nuclear-positive cells of NF-kB (P = 0.011). Consequently, there is no difference in mast cells (P = 0.957), and IL-18 bp immunostaining decreases dose dependently (P = 0.005).

CONCLUSIONS

BRONJ is characterized by increases in immunostaining for proinflammatory markers and NF-kB and inversely associated with cells exhibiting IL-18 bp.

Effects of aging in the expression of NOD-like receptors and inflammasome-related genes in oral mucosa

The molecular changes underlying the higher risk of chronic inflammatory disorders during aging remain incompletely understood. Molecular variations in the innate immune response related to recognition and interaction with microbes at mucosal surfaces could be involved in aging-related inflammation. We developed an ontology analysis of 20 nucleotide-binding and oligomerization domain (NOD)-like receptors (NLRs) and seven inflammasome-related genes (IRGs) in healthy and inflamed/periodontitis oral mucosal tissues from young, adolescent, adult, and aged non-human primates (Macaca mulatta) using the GeneChip(®) Rhesus Macaque Genome array. Validation of some of the significant changes was done by quantitative reverse transcription-polymerase chain reaction. The expression of NLRB/NAIP, NLRP12, and AIM2 increased with aging in healthy mucosa whereas NLRC2/NOD2 expression decreased. Although higher expression levels of some NLRs were generally observed with periodontitis in adult mucosal tissues (e.g. NLRB/NAIP, NLRP5, and NLRX1), various receptors (e.g. NLRC2/NOD2 and NLRP2) and the inflammasome adaptor protein ASC, exhibited a significant reduction in expression in aged periodontitis tissues. Accordingly, the expression of NLR-activated innate immune genes, such as HBD3 and IFNB1, was impaired in aged but not adult periodontitis tissues. Both adult and aged tissues showed significant increase in interleukin-1β expression. These findings suggest that the expression of a subset of NLRs appears to change with aging in healthy oral mucosa, and that aging-related oral mucosal inflammation could involve an impaired regulation of the inflammatory and antimicrobial response associated with downregulation of specific NLRs and IRGs.

Interleukin-17 and interleukin-18 levels in different stages of inflammatory periodontal disease

Context:

Chronic periodontitis is an inflammatory condition of the tooth supporting structures. There is increasing evidence that the cytokines interleukin-17 (IL-17) and interleukin-18 (IL-18) play a role in progression of chronic periodontitis.

Aim:

The objective of this study was to compare the levels of the cytokines IL-17 and IL-18 in gingival tissue extracts from individuals with healthy gingiva, chronic gingivitis, and mild chronic periodontitis.

Settings and Design:

The study was performed in a hospital-based population with an experimental design.

Materials and Methods:

A total of 69 individuals (n = 23 per group) were recruited for the study. Group 1 included 23 individuals with healthy gingiva and Group 2 included 23 chronic gingivitis patients and Group 3 included 23 patients with mild chronic periodontitis. Gingival tissues were collected during surgical procedures and levels of IL-17 and IL-18 were determined using enzyme-linked immunosorbent assay.

Statistical Analysis:

Intergroup comparison was done by posthoc Tukey's test.

Results:

The gingival tissue concentration of IL-17 was found to be highest in Group 2 (415.19 ± 76.84 pg/mg) followed by Group 3 (193.77 ± 37.32 pg/mg) and Group 1 (20.49 ± 6.05 pg/mg). Concentrations of IL-18 were significantly higher (P < 0.01) in Group 2 (1479.42 ± 330.33 pg/mg) when compared with Group 1 (385.18 ± 71.26 pg/mg) and Group 3 (330.24 ± 48.56 pg/mg).

Conclusion:

There appears to be considerable variation of IL-17 and IL-18 levels in gingival tissue during periodontal health and disease.

Correlation of Toll-like receptor 4, interleukin-18, transaminases, and uric acid in patients with chronic periodontitis and healthy adults

BACKGROUND

Because of the potential association between periodontal disease and inflammation, the purpose of the present study is to examine the level of Toll-like receptor 4 (TLR-4), interleukin-18 (IL-18), and uric acid as markers of the inflammatory host response in the plasma and saliva of healthy individuals and patients with periodontitis. In addition, routine biochemical parameters such as fasting glucose, insulin, total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, triglycerides, alanine transaminase (ALT), and aspartate transaminase (AST) were measured. The authors also wanted to check whether patients with chronic periodontitis (CP) exhibit different modulations in salivary and/or plasma concentrations of these parameters compared with clinically healthy individuals.

METHODS

Saliva and plasma samples were collected from 40 patients with CP and 20 healthy individuals. TLR-4 and IL-18 measurements were done using commercially available enzyme-linked immunosorbent assay kits. Total, HDL, and LDL cholesterol; triglycerides; fasting glucose; AST; and ALT levels were analyzed on a biochemistry analysis system using specific kits. Non-parametric tests were used for certain parameters in the statistical analyses because the data did not follow Gaussian distribution.

RESULTS

Significant differences were observed in plasma and salivary TLR-4 and IL-18 levels, along with clinical measurements such as plaque index and probing depth, in patients with CP (P < 0.001). The plasma level of TLR-4 was found to be increased from 0.99 to 3.28 ng/mL in patients with CP. Salivary TLR-4 levels also showed a slightly higher increase in the diseased state (12.44 to 29.97 ng/mL). A significant increase of ≈ 46% was recorded in the plasma IL-18 level. However, salivary IL-18 levels rose up to > 5-fold in the patients with CP compared with healthy individuals. The level of plasma uric acid was found to be highly significantly increased compared with control individuals. HDL cholesterol and triglyceride also showed significant differences (P < 0.02 and P < 0.03, respectively). Plasma glucose, total cholesterol, LDL cholesterol, and insulin levels did not show any significant difference. There was only a slight increase in plasma AST and ALT levels between diseased and healthy states (22.55 versus 25.50 IU/L and 12.35 versus 15.95 IU/L, respectively). However, salivary AST and ALT levels showed a ≈ 6-fold rise in the patients with CP compared with the healthy individuals. Cross-correlation analysis in the periodontitis disease group showed a significant association of plasma AST, salivary AST, and salivary ALT with uric acid level.

CONCLUSIONS

Based on this study, the authors believe that TLR-4, IL-18, and uric acid could have a role in the inflammatory pathology of periodontitis. These parameters are suggested to be useful in the prognosis and diagnosis of CP. However, the mechanistic association of these parameters with inflammatory pathology of patients with periodontitis needs to be further elucidated in a higher number of samples.

Cytokine gene expression profiles during initiation, progression and resolution of periodontitis

AIM

Variations in the expression of cytokines during the progression of periodontitis remain ill-defined. We evaluated the expression of 19 cytokine genes related to T-cell phenotype/function during initiation, progression and resolution of periodontitis, and related these to the expression of soft and bone tissue destruction genes (TDGs).

MATERIALS AND METHODS

A ligature-induced periodontitis model was used in rhesus monkeys (M. mulatta) (n = 18). Gingival tissues were taken at baseline pre-ligation, 2 weeks and 1 month (Initiation) and 3 months (progression) post ligation. Ligatures were removed and samples taken 2 months later (resolution). Total RNA was isolated and the Rhesus Gene 1.0 ST (Affymetrix) used for gene expression analysis. Significant expression changes were validated by qRT-PCR.

RESULTS

Disease initiation/progression was characterized by overexpression of Th17/Treg cytokine genes (IL-1β, IL-6, TGFβ and IL-21) and down-regulation of Th1/Th2 cytokine genes (IL-18 and IL-25). Increased IL-2 and decreased IL-10 levels were seen during disease resolution. Several Th17/Treg cytokine genes positively correlated with TDGs, whereas most Th1/Th2 genes exhibited a negative correlation.

CONCLUSION

Initiation, progression and resolution of periodontitis involve over- and underexpression of cytokine genes related to various T-helper subsets. In addition, variations in individual T-helper response subset/genes during disease progression correlated with protective/destructive outcomes.

Inflammation-related cytokines in oral lichen planus: an overview

Cytokines are powerful mediators which play a central role in both innate and adapted immune responses. Aberrant productions of cytokines may lead to the onset of immune deficiency, allergy or autoimmunity, which are involved in the mechanisms of various immune-mediated inflammatory diseases. Oral lichen planus (OLP) is a chronic inflammation disease affecting the oral mucosa with unknown aetiology. Previous studies have described the abnormal expression patterns of various inflammation-related cytokines, such as IL-1, 2, 4, 5, 6, 8, 10, 12, 17, 18, TGF-β, IFN-γ and TNF-α, in lesions, saliva, serum and peripheral blood mononuclear cells from patients with OLP, which may reflect the immune dysregulation status and emerge as central players in the immunopathogenesis of OLP. Besides, the gene polymorphisms of several cytokines such as IFN-γ, TNF-α, IL-4, IL-10 have been found to be involved in the susceptibility of OLP. In this review, we gave a brief introduction of the characteristics and biological functions of these inflammation-related cytokines and summarized for the first time the current knowledge on the involvement of inflammation-related cytokines in OLP. Further research on the exact roles of these cytokines will aid the understanding of the pathogenesis and the identification of novel therapeutic approaches of OLP.

Capsaicin inhibits Porphyromonas gingivalis growth, biofilm formation, gingivomucosal inflammatory cytokine secretion, and in vitro osteoclastogenesis

The prevention and treatment of periodontitis requires not only the control of causative pathogens, especially Porphyromonas gingivalis, but also the regulation of inflammatory immune response. Investigating auxiliary drugs for periodontitis during conventional treatments is, thus, quite important. Capsaicin, an agonist for the vanilloid receptor subtype 1 (TRPV1), due to its bacteriostatic activity against Gram-negative bacteria and anti-inflammatory effects, appears to be a promising drug. In this work, the antimicrobial activity of capsaicin against P. gingivalis and biofilm formation, inflammatory cytokine levels in experimental periodontitis, osteoclast precursor proliferation, and osteoclastogenesis in vitro were fully investigated. The results showed that capsaicin inhibited P. gingivalis growth with a minimum inhibitory concentration (MIC) and a minimum bactericidal concentration (MBC) of 16 and 64 mg/l, respectively. Capsaicin also inhibited P. gingivalis biofilm formation, with minimum biofilm inhibition concentrations MBIC50 and MBIC90 of 16 and 32 mg/l, respectively, and reduced pre-formed biofilms' viability with a minimum biofilm reduction concentration MBRC50 of 64 mg/l, as demonstrated by confocal laser scanning microscopy. In experimental periodontitis, except for IL-10, TNF-α, IL-1β, IL-6, IL-12, and iNOS were depressed after capsaicin treatment. Moreover, capsaicin also suppressed osteoclast precursor proliferation and osteoclastogenesis, as demonstrated by NF-ĸB p65. However, this favorable effect was attenuated by the TRPV1 antagonist, camphor. It, thus, suggests that capsaicin is a potential drug for the auxiliary treatment of periodontitis. TRPV1 activation may involve in beneficial roles of capsaicin on periodontitis.

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

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

Relationship between single nucleotide polymorphism of interleukin-18 and susceptibility to pulmonary tuberculosis in the Chinese Han population

Interleukin-18 (IL-18) is a multi-functional cytokine capable of inducing either Th1 or Th2 polarization depending on the immunologic milieu. IL-18 may influence the host response to Mycobacterium tuberculosis (M.tb) infection. To investigate the relationship between single nucleotide polymorphisms of the IL-18 and susceptibility to pulmonary tuberculosis in the Chinese Han population, the IL-18 gene was sequenced to detect polymorphisms and to examine the genotype frequencies in 300 patients and 702 healthy controls. DNA sequencing revealed three IL-18 variants: rs1946518, rs5744247, and rs549908. It also revealed that allele A of rs1946518 confers a 1.47-fold increased risk of developing tuberculosis (TB) (P = 0.0001, OR [95%CI] = 1.47 [1.21-1.78]), and that the C allele of rs5744247 confers a 0.77-fold decreased risk of disease (P = 0.01, R [95%CI] = 0.77 [0.632-0.937]). The genotypes rs1946518, rs5744247 and rs549908 were found to be significantly associated with TB. Estimation of the frequencies of haplotypes revealed a potential risk haplotype AGA (P = 0.01, OR [95%CI] = 1.41 [1.15-1.72]) and a protective haplotype CCA (P = 0.01, OR [95%CI] = 0.70 [0.57-0.85]) for TB. The present findings suggest that polymorphisms in the IL-18 gene may affect susceptibility to TB and increase the risk of developing the disease in the Chinese Han population.

Interleukin-17 and interleukin-18 levels in saliva and plasma of patients with chronic periodontitis

BACKGROUND AND OBJECTIVE

This study was planned to investigate whether patients with chronic periodontitis exhibit different salivary and/or plasma concentrations of interleukin (IL)-17 and IL-18 compared with clinically healthy subjects.

MATERIAL AND METHODS

Whole saliva and blood samples, together with full-mouth clinical periodontal recordings, were obtained from 22 otherwise healthy untreated nonsmokers with chronic periodontitis and from 21 systemically and periodontally healthy control subjects. The concentrations of IL-17 and IL-18 in saliva and plasma were determined using ELISAs.

RESULTS

The healthy control group exhibited significantly lower values in all clinical periodontal measurements (p < 0.001). The salivary concentration of IL-17 was significantly lower, and that of IL-18 significantly higher, in patients from the chronic periodontitis group compared with healthy control subjects (p = 0.025 and p = 0.009, respectively). Plasma IL-17 and IL-18 concentrations were similar in the two study groups (p > 0.05).

CONCLUSION

Within the limits of the present study, it may be suggested that an elevated salivary IL-18 level in untreated nonsmoker chronic periodontitis patients has the potential to be a biomarker for periodontal tissue destruction.

Correlations among inflammatory markers in plasma, saliva and oral mucosal transudate in post-menopausal women with past intimate partner violence

The relationship between psychosocial factors and an increased risk for disease has been related to a heightened pro-inflammatory status reflected in increased circulating levels of pro-inflammatory cytokines and/or C-reactive protein (CRP). Routinely, epidemiological studies rely on measurements of inflammatory markers in serum or plasma, but the use of biological fluids such as saliva or oral mucosal transudate (OMT) may offer potential advantages. This study investigated correlations among plasma CRP and levels of IL-6 and soluble IL-6 receptor (sIL-6R) in plasma, saliva and OMT in a population of middle aged women with histories of past intimate partner violence (IPV). A total of 67 women without existing chronic diseases participated in the study, which included two visits each in which psychological tests were administered, and blood, saliva and OMT samples were collected. Although significantly higher plasma CRP levels were found in past IPV sufferers compared to controls, there were no significant differences in IL-6 or sIL-6R levels in plasma, saliva or OMT between the two groups. There were only relatively modest correlations between IL-6 levels in plasma and those in saliva or OMT and between plasma IL-6 and CRP levels. A significant correlation between IL-6 and sIL-6R levels in both saliva and OMT, but not in plasma, was also detected. No significant correlations were found between levels of IL-6 in saliva or OMT and periodontal health measures. Results indicate that IL-6 and sIL-6R levels in saliva or OMT do not closely reflect those in plasma, and therefore are not a good surrogate for systemic levels.

Autoimmune responses in periodontal diseases

Periodontal diseases are characterized by localized infections and inflammatory conditions and directly affect teeth supporting structures which are the major cause of tooth loss. Several studies have demonstrated the involvement of autoimmune responses in periodontal disease. Evidences of involvement of immunopathology have been reported in periodontal disease. Bacteria in the dental plaque induce antibody formation. Lymphocytes, cytokines and complement system are reported to have an important role in the progression of periodontal disease. The present review describes the involvement of autoimmune responses in periodontal diseases. The mechanisms underlying these responses are also discussed.

Serum cytokine and periodontal profiles in relation to disease activity of rheumatoid arthritis in Japanese adults

BACKGROUND

Rheumatoid arthritis (RA) and periodontitis are common chronic inflammatory conditions and share many pathologic features. A similar profile of cytokines is involved in the pathogenesis of the two diseases. The relationship between the disease activity of RA and the periodontal condition remains unclear. This study examines whether the disease activity of RA affects serum cytokine and periodontal profiles.

METHODS

The study subjects consisted of 84 Japanese adults with RA and 22 race-matched control individuals. After periodontal and rheumatologic examination, the disease activity of RA was determined with the Disease Activity Score including 28 joints using C-reactive protein (DAS28-CRP). Serum levels of cytokines including interleukin (IL)-1beta, IL-6, IL-12, IL-12 p40, IL-18, and tumor necrosis factor-alpha (TNF-alpha) were determined by an enzyme-linked immunosorbent assay. High-sensitive CRP was also measured with a latex particle-enhanced nephelometric method.

RESULTS

Of 84 patients with RA, 28 and 56 patients exhibited low and moderate to high disease activity, respectively. Serum levels of IL-6, TNF-alpha, and CRP were significantly different between the two groups (P <0.05). Additionally, a significant correlation was observed between DAS28-CRP and percentage of sites with bleeding on probing (BOP) (P = 0.008) and between serum TNF-alpha levels and percentage of sites with BOP (P = 0.01) in 56 patients with RA with moderate to high activity.

CONCLUSION

These results suggest that the disease activity of RA correlated with serum levels of IL-6, TNF-alpha, and CRP, and it might influence BOP in the patients with moderate to high disease activity.

Porphyromonas gingivalis infection-induced tissue and bone transcriptional profiles

Porphyromonas gingivalis has been associated with subgingival biofilms in adult periodontitis. However, the molecular mechanisms of its contribution to chronic gingival inflammation and loss of periodontal structural integrity remain unclear. This investigation aimed to examine changes in the host transcriptional profiles during a P. gingivalis infection using a murine calvarial model of inflammation and bone resorption. P. gingivalis FDC 381 was injected into the subcutaneous soft tissue over the calvaria of BALB/c mice for 3 days, after which the soft tissues and calvarial bones were excised. RNA was isolated from infected soft tissues and calvarial bones and was analysed for transcript profiles using Murine GeneChip((R)) arrays to provide a molecular profile of the events that occur following infection of these tissues. After P. gingivalis infection, 6452 and 2341 probe sets in the infected soft tissues and calvarial bone, respectively, were differentially expressed (P </= 0.05). Biological pathways significantly impacted by P. gingivalis infection in tissues and calvarial bone included cell adhesion (immune system) molecules, Toll-like receptors, B-cell receptor signaling, transforming growth factor-beta cytokine family receptor signaling, and major histocompatibility complex class II antigen processing pathways resulting in proinflammatory, chemotactic effects, T-cell stimulation, and downregulation of antiviral and T-cell chemotactic effects. P. gingivalis-induced inflammation activated osteoclasts, leading to local bone resorption. This is the first in vivo evidence that localized P. gingivalis infection differentially induces transcription of a broad array of host genes, the profiles of which differed between inflamed soft tissues and calvarial bone.

TLR4 and IL-18 gene variants in chronic periodontitis: impact on disease susceptibility and severity

The aim of the study was to assess whether genotypes in the Toll-like receptor 4 gene and in the promoter of the interleukin-18 gene are associated with the susceptibility to chronic periodontitis. 108 chronic periodontitis patients and 76 controls were genotyped for c.896A>G/1196C>T (TLR4 gene) and for c.-368G>C/ c.-838C>A (IL-18 promoter). There were no significant differences in genotype and allele distributions between the study groups. Periodontitis severity in patients with TLR4 c.896AG/1196CT genotype was significantly higher than wildtype carriers. The percentage of teeth with clinical attachment loss > or = 5 mm was 77.3% and 58.8%, respectively (p < or = 0.006, t-test). All subjects were further classified into carriers and non-carriers of at least one variant of each gene. A logistic regression analysis adjusted for gender, smoking, and age showed no association between gene variant carrier status and periodontitis (OR = 1.98, 95% CI 0.61-6.39). The results did not show that IL-18 and TLR4 variants have an effect on the susceptibility to chronic periodontitis. Considering the low number of periodontitis patients carrying TLR4 variants (11%), a comparison of the periodontitis severity depending on the genotype has to be interpreted cautiously.

Activation of the acquired immune response reduces coupled bone formation in response to a periodontal pathogen

Osteoimmunolgy involves the interaction of the immune system with skeletal elements. This interaction can lead to the formation of osseous lesions. To investigate how the acquired immune response could contribute to osteolytic lesions, we injected the periodontal pathogen Porphyromonas gingivalis adjacent to calvarial bone with or without prior immunization against the bacterium. Activation of the acquired immune response increased osteoclastogenesis and decreased coupled bone formation. The latter was accompanied by an increase in nuclear translocation of the transcription factor FOXO1 in vivo, increased apoptosis of bone-lining cells measured by the TUNEL assay and number of activated caspase-3 positive cells and a decrease in bone lining cell density. Further studies were conducted with MC3T3 osteoblastic cells. Apoptosis and increased FOXO1 DNA binding activity were induced when a combination of cytokines was tested, IL-beta, TNF-alpha, and IFN-gamma. Knockdown of FOXO1 by small interfering RNA significantly reduced cytokine stimulated apoptosis, cleaved caspase-3/7 activity and decreased mRNA levels of the proapoptotic genes, TNF-alpha, FADD, and caspase-3, -8, and -9. These results indicate that activation of the acquired immunity by a periodontal pathogen reduces the coupling of bone formation and resorption. This may occur by enhancing bone lining cell apoptosis through a mechanism that involves increased FOXO1 activation. These studies give insight into inflammatory bone diseases such as periodontal disease and arthritis were the formation of lytic lesions occurs in conjunction with deficient bone formation and activation of an acquired immune response.

TLR4 and IL-18 gene variants in aggressive periodontitis

AIM

We aimed to assess the association of different genotypes with increased aggressive periodontitis susceptibility by studying functional relevant variants in the pathogen-recognition receptor Toll-like receptor 4 (TLR4) and variants in the promoter region of the pro-inflammatory cytokine interleukin-18 (IL-18).

MATERIAL AND METHODS

One hundred and eleven patients with aggressive periodontitis and 80 periodontally healthy controls were genotyped for four functional variants in the TLR4 gene (c.896A>G and c.1196C>T) and in the IL-18 promoter (c.-368G>C and c.-838C>A). The genotype and allele frequencies, as well as the frequency of combined genotypes were compared between study groups.

RESULTS

There were no statistical differences in genotype and allele frequencies within the four variants between the groups. All study subjects were further classified into carriers and non-carriers of at least one variant of both genes. The logistic regression analysis adjusted for gender and smoking showed no association between carrier status of at least one variant of both genes and periodontal status (OR=1.41, 95% CI: 0.43-4.70).

CONCLUSIONS

Our results reject the hypothesis that functionally relevant IL-18 and TLR4 gene mutations have a major effect on aggressive periodontitis susceptibility alone or in combination.

Osteoimmunology: interactions of the bone and immune system

Bone and the immune system are both complex tissues that respectively regulate the skeleton and the body's response to invading pathogens. It has now become clear that these organ systems often interact in their function. This is particularly true for the development of immune cells in the bone marrow and for the function of bone cells in health and disease. Because these two disciplines developed independently, investigators in each don't always fully appreciate the significance that the other system has on the function of the tissue they are studying. This review is meant to provide a broad overview of the many ways that bone and immune cells interact so that a better understanding of the role that each plays in the development and function of the other can develop. It is hoped that an appreciation of the interactions of these two organ systems will lead to better therapeutics for diseases that affect either or both.