Interleukin-6 deficiency increases inflammatory bone destruction

B Cells at the Core: Immune Mechanisms and Therapeutic Potentials in Periapical Lesions

INTRODUCTION

Periapical lesions (PLs) are common inflammatory diseases primarily caused by microbial infections within root canals. These infections trigger complex immune responses in periapical tissues, with B lymphocytes playing dual roles: defending against pathogens while also contributing to tissue damage. This highlights the crucial role of B cells in the immunological processes of PLs.

METHODS

A comprehensive review of the literature on B cells in PLs was conducted using PubMed, Web of Science, Scopus, and ScienceDirect databases.

RESULTS

The review included 120 studies that examined the distribution and subtypes of B cells, their dual functions in PLs, and the potential applications of B-cell-related therapies in treating apical periodontitis.

CONCLUSIONS

This review enhances our understanding of the complex immune mechanisms in PLs and aids in the development of new therapeutic approaches from a B-cell perspective.

Inflammatory mediators' essence in apical periodontitis

Apical periodontitis (AP) represents chronic inflammatory reaction of periradicular tissues of teeth with necrotic pulp. Although AP has been considered as a multifactorial disease, different microorganisms and their virulence factors from infected root canals are considered to be the primary cause of periradicular inflammatory process. The interplay between microbes and host leads to an inflammatory cascade of events that includes activation of innate and adaptive components of immunity. Activation of different immune cells in AP is intermediated by different molecules known as mediators of inflammation. These molecules establish various network interrelationships in the inflamed periapical area and induce alveolar bone resorption. This narrative review aimed to explore and present the current knowledge of selected inflammatory mediators, including cytokines, matrix metalloproteinases, bone resorption regulators and components of oxidative stress involved in the alveolar bone resorption in AP.

Effects of adjacent periodontitis on osseointegrated dental implants

PURPOSE

This study aimed to investigate whether new-onset periodontitis or apical periodontitis in the adjacent teeth affects osseointegrated dental implants in a beagle dog model.

METHODS

One control group and 2 experimental groups (periodontitis and apical periodontitis groups) were defined based on the presence of experimental periodontitis or apical periodontitis, with 1 beagle dog randomly assigned to each group. The mandibular second and fourth premolars on both sides of the 3 beagles were extracted. Eight weeks after extraction, 4 bone-level implant fixtures, 2 on both sides of each mandible, were placed in each beagle. Six weeks after implant surgery, healing abutments were connected. After sufficient osseointegration, plaque control was performed in the control group, while periodontitis and apical periodontitis were induced in the experimental groups. The beagles were euthanized for histological analyses 20 weeks after induction of experimental periodontitis. Statistical analyses were performed using the Kruskal-Wallis test with the Bonferroni correction to compare the 3 groups.

RESULTS

The implants in the control and apical periodontitis groups were well-maintained, while those in the periodontitis group showed clinical signs of inflammation with bone resorption. The bone-to-implant contact (BIC) and bone area values in the periodontitis group were lower than those in the other groups. The distance between the implant shoulder and the first BIC was significantly greater in the periodontitis group than in the control group (P<0.05).

CONCLUSIONS

The presence of periodontitis in adjacent teeth can pose a risk to dental implants, potentially resulting in peri-implantitis. However, this was not observed for apical periodontitis. Within the limitations of this study, periodontal care is necessary to reduce the impact of periodontitis in adjacent teeth on osseointegrated implants.

A novel experimental model to investigate fungal involvement shows expression of Dectin-1 in periapical lesion pathogenesis

BACKGROUND

Candida albicans is linked to persistent endodontic lesions. However, the recognition receptor that identifies it is not explored previously.

OBJECTIVES

The aim of this study was to (1) establish a zymosan-induced model of apical periodontitis in mouse, (2) observe the expression of Dectin-1 and its possible relationship with toll-like receptor (TLR) 2 and (3) observe relationship between Osteopontin (OPN) and inflammatory cytokines.

METHODS

A total of 138 Naval Medical Research Institute (NMRI) mice were randomly divided into; Experimental Group n = 69 and Zymosan Group n = 69. Periapical periodontitis was developed in right maxillary molar. The animals were sacrificed at 7, 21 and 42 days. Bone blocks containing the mesial root (n = 15 for qRT-PCR, n = 45 for enzyme-linked immune sorbent assay (ELISA)) were collected for mRNA expression and ELISA. While whole maxilla (n = 3 from each time interval) were used for histology and immunohistochemical analysis. One way analysis of variance (ANOVA) and Tuckey's posthoc was used for statistical analysis at p ≤ .05.

RESULTS

TLR-2, Dectin-1 and TLR4-positive cells was detected at all time intervals in both groups. A strong positive correlation was observed between TLR-2 and Dectin-1 in both lesions (regular r = .680, p = .015, zymosan (r = .861, p < .001)). A significant correlation was found between OPN and tumour necrosis factor-alpha (TNF-α) in zymosan lesion (r = .827, p = .001).

CONCLUSIONS

Immune cells of inflamed periapical tissue expressed Dectin-1 receptor in response to the microbial challenge from infected root canals and showed positive correlation with TLR-2 and OPN suggesting a possible receptor collaboration mediated by OPN. The expression of OPN and TNF-α showed positive correlation in response to fungal antigen, indicating a possible relationship.

Antimicrobial, Cytotoxic, and Anti-Inflammatory Activities of Tigridia vanhouttei Extracts

In this work, bulb extracts of Tigridia vanhouttei were obtained by maceration with solvents of increasing polarity. The extracts were evaluated against a panel of pathogenic bacterial and fungal strains using the minimal inhibitory concentration (MIC) assay. The cytotoxicity of the extracts was tested against two cell lines (THP-1 and A549) using the MTT assay. The anti-inflammatory activity of the extracts was evaluated in THP-1 cells by measuring the secretion of pro-inflammatory (IL-6 and TNF-α) and anti-inflammatory (IL-10) cytokines by ELISA. The chemical composition of the extracts was recorded by FTIR spectroscopy, and their chemical profiles were evaluated using GC-MS. The results revealed that only hexane extract inhibited the growth of the clinical isolate of Pseudomonas aeruginosa at 200 μg/mL. Against THP-1 cells, hexane and chloroform extracts were moderately cytotoxic, as they exhibited LC50 values of 90.16, and 46.42 μg/mL, respectively. Treatment with methanol extract was weakly cytotoxic at LC50 443.12 μg/mL against the same cell line. Against the A549 cell line, hexane, chloroform, and methanol extracts were weakly cytotoxic because of their LC50 values: 294.77, 1472.37, and 843.12 μg/mL. The FTIR analysis suggested the presence of natural products were confirmed by carboxylic acids, ketones, hydroxyl groups, or esters. The GC-MS profile of extracts revealed the presence of phytosterols, tetracyclic triterpenes, multiple fatty acids, and sugars. This report confirms the antimicrobial, cytotoxic, and anti-inflammatory activities of T. vanhouttei.

Neutralization of Staphylococcus aureus Protein A Prevents Exacerbated Osteoclast Activity and Bone Loss during Osteomyelitis

Osteomyelitis caused by Staphylococcus aureus is an important and current health care problem worldwide. Treatment of this infection frequently fails not only due to the increasing incidence of antimicrobial-resistant isolates but also because of the ability of S. aureus to evade the immune system, adapt to the bone microenvironment, and persist within this tissue for decades. We have previously demonstrated the role of staphylococcal protein A (SpA) in the induction of exacerbated osteoclastogenesis and increased bone matrix degradation during osteomyelitis. The aim of this study was to evaluate the potential of using anti-SpA antibodies as an adjunctive therapy to control inflammation and bone damage. By using an experimental in vivo model of osteomyelitis, we demonstrated that the administration of an anti-SpA antibody by the intraperitoneal route prevented excessive inflammatory responses in the bone upon challenge with S. aureus. Ex vivo assays indicated that blocking SpA reduced the priming of osteoclast precursors and their response to RANKL. Moreover, the neutralization of SpA was able to prevent the differentiation and activation of osteoclasts in vivo, leading to reduced expression levels of cathepsin K, reduced expression of markers associated with abnormal bone formation, and decreased trabecular bone loss during osteomyelitis. Taken together, these results demonstrate the feasibility of using anti-SpA antibodies as an antivirulence adjunctive therapy that may prevent the development of pathological conditions that not only damage the bone but also favor bacterial escape from antimicrobials and the immune system.

Revisiting the role of IL-1 signaling in the development of apical periodontitis

Apical periodontitis (AP) develops as a result of an immune response to pulpal bacterial infection, and various cytokines are involved in the pathogenesis of AP, with Interleukin (IL)-1 being considered a key cytokine. The role of IL-1 in the pathogenesis of AP has been well studied. It is known that IL-1 expression in periapical lesions correlates closely with the development of AP. IL-1 is a potent bone-resorptive cytokine that induces osteoclast formation and activation. Hence, inhibiting its signaling with IL-1 receptor antagonist (IL-1RA) results in a reduction in periapical lesion size. On the other hand, IL-1 is also a central cytokine that combats bacterial infection by activating innate immune responses. Therefore, a complete loss of IL-1 signaling leads to a failure to limit bacterial dissemination and consequently exacerbates AP. In vivo, IL-1 expression is tightly regulated and its signaling is modulated to optimize the immune response. Obesity causes systemic low-grade chronic inflammation and increases the risk of cardiovascular, renal, and other disorders. In experimentally induced AP, obesity significantly increases periapical bone loss, albeit the underlying mechanism remains unclear. Recent technological innovations have enabled more comprehensive and detailed analyses than previously, leading to new insights into the role of IL-1RA in regulating IL-1 signaling, and modulating apical lesion progression in obesity. In this review, we provide a brief overview of the function of IL-1 in AP development, with special emphasis on the latest findings in normal weight and obese states.

A comparative analysis of the efficacy of moxifloxacin and cefixime in the reduction of postoperative inflammatory sequelae after mandibular third molar surgery

Background/Aim. There is no scientific evidence that the prophylactic use of antibiotics as a part of the mandibular third molar surgery is effective in suppressing postoperative pain, edema, trismus, and dry socket. The aim of the study was to investigate the effects of antibiotics from the fluoroquinolone (moxifloxacin) and cephalosporin (cefixime) groups in reducing postoperative inflammatory sequelae (pain, edema, and trismus), as well as in possibly reducing the incidence of dry socket after mandibular third molar surgery. Methods. This double-blind study was completed by 157 subjects, comprising two study groups (who received the aforementioned antibiotics) and a control group, who received placebo tablets. Subjects were assessed on the first, second, and seventh day following surgery. In the postoperative course, patients were monitored for the occurrence, intensity, and duration of postoperative inflammatory sequelae and dry socket. Results. Both antibiotics, especially moxifloxacin, had a pronounced effect on reducing all inflammatory sequelae (pain, edema, and trismus) as the most common postoperative complaints following mandibular third molar surgery, and also contributed to reducing the incidence of dry socket. Conclusion. Antibiotic prophylaxis with cefixime and, especially moxifloxacin, reduced the occurrence of postoperative inflammatory sequelae and alleviated discomfort. It is interesting, that both antibiotics, especially moxifloxacin, also contributed to reducing the incidence of postoperative dry socket, which is not provoked by inflammation. Therefore, further research into the underlying mechanisms behind such an effect is warranted.

The inflammatory signalling mediator TAK1 mediates lymphocyte recruitment to lipopolysaccharide-activated murine mesenchymal stem cells through interleukin-6

As a response to pro-inflammatory signals mesenchymal stem cells (MSCs) secrete agents and factors leading to lymphocyte recruitment, counteracting inflammation, and stimulating immunosuppression. On a molecular level, the signalling mediator TGF-β-activated kinase 1 (TAK1) is activated by many pro-inflammatory signals, plays a critical role in inflammation and regulates innate and adaptive immune responses as well. While the role of TAK1 as a signalling factor promoting inflammation is well documented, we also considered a role for TAK1 in anti-inflammatory actions exerted by activated MSCs. We, therefore, investigated the capacity of lipopolysaccharide (LPS)-treated murine MSCs with lentivirally modulated TAK1 expression levels to recruit lymphocytes. TAK1 downregulated by lentiviral vectors expressing TAK1 shRNA in murine MSCs interfered with the capacity of murine MSCs to chemoattract lymphocytes, indeed. Analysing a pool of 84 secreted factors we found that among 26 secreted cytokines/factors TAK1 regulated expression of one cytokine in LPS-activated murine MSCs in particular: interleukin-6 (IL-6). IL-6 in LPS-treated MSCs was responsible for lymphocyte recruitment as substantiated by neutralizing antibodies. Our studies, therefore, suggest that in LPS-treated murine MSCs the inflammatory signalling mediator TAK1 may exert anti-inflammatory properties via IL-6.

Re-Programming Autoreactive T Cells Into T-Regulatory Type 1 Cells for the Treatment of Autoimmunity

Systemic delivery of peptide-major histocompatibility complex (pMHC) class II-based nanomedicines can re-program cognate autoantigen-experienced CD4+ T cells into disease-suppressing T-regulatory type 1 (TR1)-like cells. In turn, these TR1-like cells trigger the formation of complex regulatory cell networks that can effectively suppress organ-specific autoimmunity without impairing normal immunity. In this review, we summarize our current understanding of the transcriptional, phenotypic and functional make up of TR1-like cells as described in the literature. The true identity and direct precursors of these cells remain unclear, in particular whether TR1-like cells comprise a single terminally-differentiated lymphocyte population with distinct transcriptional and epigenetic features, or a collection of phenotypically different subsets sharing key regulatory properties. We propose that detailed transcriptional and epigenetic characterization of homogeneous pools of TR1-like cells will unravel this conundrum.

Tocilizumab, a Potent Interleukin-6 Receptor Inhibitor, Decreases Bone Resorption and Increases the Rate of Bacterial Infection After Tooth Extraction in Rats

PURPOSE

Our objective was to evaluate the influence of pretreatment with tocilizumab (TCZ) in bone healing after tooth extraction in rats.

METHODS

Wistar male rats were equally divided into sham (ie, nonoperated), saline (both treated with 0.1 ml/kg saline), and six TCZ groups treated with 1, 2, 4, 8, 16, and 32 mg/kg TCZ (TCZ1 to TCZ32, respectively). Twenty-four hours after administration of vehicle or TCZ, exodontia of the first lower left molar was performed, and the animals were euthanized three days later for hematological analysis and organ (liver, spleen, and kidney mass indexes, and histological evaluation), gingiva (myeloperoxidase [MPO] assay), and mandible (radiographic, histomorphometric analysis, and IL-6 immunostaining) evaluation. Analysis of variance/Bonferroni test (statistical significance, P < .05) was performed using GraphPad Prism version 5.0 (GraphPad Inc, San Diego, CA, USA).

RESULTS

There was no difference in radiographic results; however, leukopenia (P = .039) and neutropenia (P < .001) were statistically significant in the TCZ16 and TCZ32 groups. Weight loss (P < .001) and reduced liver index (P = .001) were significantly dose-dependent; however, no histological alterations were observed in the other organs. Osteoclast counts were reduced in groups TCZ4 to TCZ32 (P < .001), and IL-6 immunostaining increased in the TCZ8 to TCZ32 groups (P < .001). Alveolar infection rates increased in groups TCZ4 to TCZ32 (P < .001), and MPO had a biphasic response, exhibiting a reduction in groups TCZ2 and TCZ4, and an increase in group TCZ32 (P = .004).

CONCLUSION

TCZ-induced immunosuppression led to a reduction in osteoclast function, an increase in alveolar infection, and compensatory neutrophil infiltration.

Suppressors of cytokine signaling (SOCS) proteins in inflammatory bone disorders

Suppressor of cytokine signaling (SOCS) proteins are significant regulators of cellular immune responses. Therefore, the role of SOCS in bone-inflammatory disorders, including arthritis and periodontitis, has been investigated in experimental and clinical conditions. Recent evidence shows that SOCS proteins are expressed in major bone-related cells, including osteoblasts, osteoclasts, chondrocytes and synoviocytes, although their direct role in these cells is not fully described. These signaling molecules, especially SOCS1, 2 and 3, were shown to play critical roles in the control of bone resorption associated to inflammation. This review focuses on the involvement of SOCS proteins in inflammatory bone remodeling, including their direct and indirect role in the control of osteoclast hyperactivation, during arthritis and periodontitis. The description of the roles of SOCS proteins in inflammatory bone diseases highlights the pathways involved in the pathophysiology of these conditions and, thus, may contribute to the development and improvement of potential therapeutic interventions.

The inflammatory response to bone infection - a review based on animal models and human patients

Bone infections are difficult to diagnose and treat, especially when a prosthetic joint replacement or implant is involved. Bone loss is a major complication of osteomyelitis, but the mechanism behind has mainly been investigated in cell cultures and has not been confirmed in human settings. Inflammation is important in initiating an appropriate immune response to invading pathogens. However, many of the signaling molecules used by the immune system can also modulate bone remodeling and contribute to bone resorption during osteomyelitis. Our current knowledge of the inflammatory response relies heavily on animal models as research based on human samples is scarce. Staphylococcus aureus is one of the most common causes of bone infections and is the pathogen of choice in animal models. The regulation of inflammatory genes during prosthetic joint infections and implant-associated osteomyelitis has only been studied in rodent models. It is important to consider the validity of an animal model when results are extrapolated to humans, and both bone composition and the immune system of pigs has been shown to be more similar to humans, than to rodents. Here in vivo studies on the inflammatory response to prosthetic joint infections and implant-associated osteomyelitis are reviewed.

Estimation of Sialic Acid and IL10 Levels in Stage 1 and 2 Periodontitis Patients

Objective

The role of biomarkers in staging and grading periodontal disease has become detrimental in relation to the overall treatment plan. This study aimed at evaluating and comparing the role of sialic acid and IL10 in the early and moderate stages of periodontitis.

Materials and Methods

Patients were selected according to the assessment of pocket depth and radiographic bone loss. Bone loss was calculated as <15% for stage 1 and 15–33% for stage 2. Salivary samples were collected using spit technique 2 hrs post consumption of food. The unstimulated saliva was collected in a sterile graduated container every minute for 5–8 minutes. IL10 estimation was done using ELISA, and sialic acid estimation was done using the diphenylamine method. The variables for the three groups were assessed using ANOVA, and intragroup comparisons for quantitative data were evaluated using the post hoc Bonferroni test (P < 0.05).

Results

On comparing sialic acid levels among the three groups, stage 2 showed the highest mean (8.61) compared with the other two groups and was highly significant (P < 0.001). On the contrary, IL10 when compared to stage 1 and 2 periodontitis revealed insignificant change.

Conclusion

The value of IL10 was higher as patients progressed from health to periodontitis.

Determinants of low bone mineral density in people with multiple sclerosis: Role of physical activity

BACKGROUND

People with multiple sclerosis (PwMS) have reduced bone mineral density (BMD), but the causes are unclear. Some factors that may cause reduced BMD in PwMS have been understudied, including physical activity, inflammation, cortisol, symptomatic fatigue, and depression. The aim of this study was to investigate factors that may uniquely contribute to reduced BMD in PwMS as compared to people without MS. We hypothesized that physical activity would be the primary determinant of low BMD in PwMS, with additional contributions from inflammation and sympathetic nervous system activation.

METHODS

We tested 23 PwMS (16 women; median EDSS: 2) and 22 control participants (16 women). BMD was measured from the femoral neck and lumbar spine with dual x-ray absorptiometry. Disability was measured with the Expanded Disability Status Scale, and functional capacity was measured with the Multiple Sclerosis Functional Composite. Questionnaires measured symptomatic fatigue and depression. A blood draw was used to measure calcium, phosphate, vitamin D, N-terminal telopeptide, osteopontin, and cytokine markers of inflammation. Physical activity was measured with accelerometry. Salivary cortisol and cardiac heart rate variability also were obtained. All outcome variables were compared between groups with independent samples t-tests. Variables that were different between groups and significantly correlated (Pearson product-moment) with femoral neck BMD, were included in a theoretical model to explain femoral neck BMD. The expected direction of relations in the theoretical model were developed based upon the results of previous research. A Bayesian path analysis was used to test the relations of predictive variables with femoral neck BMD and interrelations among predictive variables, as detailed in the theoretical model.

RESULTS

PwMS had lower BMD at the femoral neck than controls (p = =0.04; mean difference: -0.09; 95% CI: -0.2, -0.004; Cohen's d = =0.65), and there was a smaller, statistically non-significant difference in BMD at the lumbar spine (p = =0.07; mean difference: -0.08; 95% CI: -0.17, 0.007; Cohen's d = =0.59). PwMS also had lower functional capacity (p ≤ 0.001; Cohen's d = =1.50), greater fatigue (p<0.001; Cohen's d = =1.88), greater depression (p<0.001; d = =1.31), and decreased physical activity (p = =0.03; Cohen's d = =0.62). Using path analysis to test our theoretical model, we found that disability (standardized estimate= -0.17), physical activity (standardized estimate=0.39), symptomatic fatigue (standardized estimate= -0.36), depression (standardized estimate= -0.30), and inflammatory markers (standardized estimate=0.27) explained 51% of the variance in femoral neck BMD. Inflammatory markers were also predictive of disability (standardized estimate=0.44) and physical activity (standardized estimate= -0.40). Symptomatic fatigue and depression were correlated (r = =0.64).

CONCLUSION

Physical activity, symptomatic fatigue, depression, disability, and inflammation all contributed independently to decreased femoral neck BMD in PWMS. Bone metabolism in PwMS is complex. Efforts to increase physical activity and address symptomatic fatigue and depression may improve bone mineral density in PwMS. Future research should investigate the mechanisms through which symptomatic fatigue and depression contribute to reduced BMD in PwMS.

Metabolomic Profiling of the Immune Stimulatory Effect of Eicosenoids on PMA-Differentiated THP-1 Cells

Honey bee venom has been established to have significant effect in immunotherapy. In the present study, (Z)-11-eicosenol-a major constituent of bee venom, along with its derivations methyl cis-11-eicosenoate and cis-11-eicosenoic acid, were synthesised to investigate their immune stimulatory effect and possible use as vaccine adjuvants. Stimuli that prime and activate the immune system have exerted profound effects on immune cells, particularly macrophages; however, the effectiveness of bee venom constituents as immune stimulants has not yet been established. Here, the abilities of these compounds to act as pro-inflammatory stimuli were assessed, either alone or in combination with lipopolysaccharide (LPS), by examining the secretion of tumour necrosis factor-α (TNF-α) and the cytokines interleukin-1β (IL-1β), IL-6 and IL-10 by THP-1 macrophages. The compounds clearly increased the levels of IL-1β and decreased IL-10, whereas a decrease in IL-6 levels suggested a complex mechanism of action. A more in-depth profile of macrophage behaviour was therefore obtained by comprehensive untargeted metabolic profiling of the cells using liquid chromatography mass spectrometry (LC-MS) to confirm the ability of the eicosanoids to trigger the immune system. The level of 358 polar and 315 non-polar metabolites were changed significantly (p < 0.05) by all treatments. The LPS-stimulated production of most of the inflammatory metabolite biomarkers in glycolysis, the tricarboxylic acid (TCA) cycle, the pentose phosphate pathway, purine, pyrimidine and fatty acids metabolism were significantly enhanced by all three compounds, and particularly by methyl cis-11-eicosenoate and cis-11-eicosenoic acid. These findings support the proposed actions of (Z)-11-eicosenol, methyl cis-11-eicosenoate and cis-11-eicosenoic acid as immune system stimulators.

The Role of Interleukin 6 in Osteogenic and Neurogenic Differentiation Potentials of Dental Pulp Stem Cells

INTRODUCTION

Studies have shown that there is a significantly higher concentration of interleukin 6 (IL-6) in inflamed pulp tissues compared with healthy pulp tissues. The aims of this study were to investigate the baseline differences between mesenchymal stem cells (MSCs) isolated from healthy human dental pulp stem cells (H-DPSCs) and inflamed dental pulp stem cells (I-DPSCs) and their correlation to IL-6 and to determine whether IL-6 can affect the differentiation potentials of these cells.

METHODS

MSCs isolated from healthy and inflamed pulp tissues were cultured and characterized in vitro. The levels of secreted IL-6 in the culture supernatants from H-DPSCs and I-DPSCs were measured by enzyme-linked immunosorbent assay. IL-6 and neutralizing IL-6 were added to H-DPSCs and I-DPSCs, respectively. Immunofluorescence staining, alizarin red staining, and Western blotting were performed to assess the differentiation potentials of H-DPSCs and I-DPSCs. The independent unpaired 2-tailed Student's t-test was performed after quantification analysis.

RESULTS

H-DPSCs and I-DPSCs showed a similar expression of MSC-associated markers including CD44, CD73, CD90, and CD105, whereas H-DPSCs showed a lower level of IL-6, lower osteogenic differentiation potentials, and higher neurogenic differentiation potentials compared with I-DPSCs. The addition of IL-6 to H-DPSCs increased osteogenic potentials and decreased neurogenic potentials, whereas the neutralization of IL-6 for I-DPSCs led to decreased osteogenic potentials and increased neurogenic potentials.

CONCLUSIONS

The findings of this study indicated IL-6 has the capacity to enhance osteogenesis while hindering neurogenesis of DPSCs.

MicroRNA-181b-5p modulates tumor necrosis factor-α-induced inflammatory responses by targeting interleukin-6 in cementoblasts

Tooth cementum is a bone-like mineralized tissue and serves as a microbial barrier against invasion and destruction. Cementum is also responsible for tooth stability and defending pulp from outside stimuli, which is formed by cementoblasts. Although it is crucial for periodontal and periapical diseases, the mechanisms underlying the pathophysiological changes of cementoblasts and their inflammatory responses remain unclear. MiR-181b is found to modulate vascular inflammation and endotoxin tolerance. In this study, miR-181b-5p was downregulated in tumor necrosis factor-α (TNF-α)-stimulated cementoblasts, whereas proinflammatory molecules increased. The mouse periapical lesions have similar results, which imitate an inflammatory environment for cementoblasts in vivo. The bioinformatics analysis and dual luciferase reporter assay suggested that miR-181b-5p targeted interleukin-6 (IL-6). Overexpressing miR-181b-5p negatively regulated IL-6 and proinflammatory chemokine. Western blot analysis and luciferase activity reporter assay verified that miR-181b-5p weakened the NF-κB activity. Hence, miR-181b-5p moderated proinflammatory chemokine production by targeting IL-6 in cementoblasts and NF-κB signaling pathway was involved. Furthermore, miR-181b-5p promoted cementoblast apoptosis, which may enhance the resolution of inflammation. Overall, our data revealed that miR-181b-5p was a negative regulator of TNF-α-induced inflammatory responses in cementoblasts.

Influence of static forces on the expression of selected parameters of inflammation in periodontal ligament cells and alveolar bone cells in a co-culture in vitro model

OBJECTIVE

Aim of this study was to investigate the impact of human PDL-derived fibroblasts (HPDF) and human alveolar bone-derived osteoblasts (HABO) co-culture on the expression of cytokines involved in tissue remodeling using an in vitro compressive force (CF) model.

MATERIALS AND METHODS

Static compressive force (CF) of 47.4 g/cm² was applied on mono- and co-cultured HPDFs and HABOs for 1, 2, or 4 h at 30 °C. TNFA, PTGS2, and IL6 gene expressions were determined by quantitative real-time polymerase chain reaction. TNF, PGE₂, and IL6 concentrations were measured using enzyme-linked immunosorbent assay.

RESULTS

In mono-culture, TNFA, PTGS2, and IL6 gene expressions were upregulated under CF as compared to controls for each time period in both cell types. PGE₂ increased at 1 and 2 h in both cell types, and IL6 increased only at 2 and 4 h in HPDFs. Co-culture alleviated the force-induced increase of the expression of TNFA, PTGS2, IL6, PGE2, and IL6 in HPDFs at any time point. In HABOs, co-cultivation decreased the expression of PGE₂ after 1 h and 4 h, and that of IL6 after 1 h compared to mono-culture.

CONCLUSIONS

CF application on co-cultures of HPDFs and HABOs causes significant changes of TNFA, PTGS2, and IL6 gene expressions and PGE₂ and IL6 production in comparison to mono-culture indicating intercellular communication.

CLINICAL RELEVANCE

Mechanical stimulation of HPDFs and HABOs in co-culture induces a different gene expression pattern than stimulation of individual cell types alone. Co-culture might therefore be a relevant method to elucidate periodontal regeneration during orthodontic therapy.

Development and in vitro evaluation of chitosan based system for local delivery of atorvastatin for treatment of periodontitis

In recent years, statin group drugs have been widely investigated in treatment of periodontal diseases due to their anti-inflammatory effect. The efficacy of statins can be enhanced by local administration into the periodontal pocket by appropriate delivery systems. The aim of our study was to develop a bioadhesive delivery system for local delivery of atorvastatin in treatment of periodontal disease. For this purpose, gel formulations were prepared using different types of chitosan (base and water soluble) and viscosity, bioadhesivity and syringeability of the gels as well as in vitro drug release properties were investigated vitro. Furthermore, anti-inflammatory effect of the formulations was studied in vitro using tumor necrosis factor (TNF)-alfa induced human gingival fibroblast (hGF) cells. Release of proinflammatory (IL-1β, IL-6, IL-8) and anti-inflammatory (TGF-β1, TGF-β2, TGF-β3, IL-10) cytokines were measured after incubating the hGF cells with the formulations. The viscosity of the formulations was found to be suitable for a local application into periodontal pocket. In presence of drug, bioadhesive property of the formulations was found to increase, and bioadhesion force was within the range, which would retain the delivery system at the application site, subsequently maintain drug levels at desired amount for longer period of time. The release of atorvastatin from the gels was found to be slower than that of the solution. The cytokine levels were found to decrease following application of the formulations, and anti-inflammatory effect was observed to enhance in presence of chitosan. No significant differences were found between base and water-soluble chitosan.

Pro-inflammatory and anti-inflammatory cytokine expression in post-treatment apical periodontitis

OBJECTIVE

This study evaluated the expression of pro-inflammatory (IL-1β, IL-6, IFN-γ and TNF-α) and anti-inflammatory (IL-4 and TGF-β) cytokines in apical periodontitis lesions. Correlations between these cytokines and clinical and cone-beam computed tomographic (CBCT) data were also assessed.

MATERIAL AND METHODS

Apical periodontitis lesions' data were obtained from 27 patients subjected to periradicular surgery. Specimens were processed for histopathologic and immunohistochemical analysis. Sections were evaluated according to the amount of positive staining for each antibody. Expression levels of the target mediators were compared with clinical and CBCT data.

RESULTS

Twenty lesions were diagnosed as granuloma and 7 as cyst. In granulomas, IL-4 expression was significantly higher than IL-6 (p=0.001) and TNF-α (p=0.001). There was a significant relationship between high levels of TNF-α and lesions <5 mm (p=0.017). In cysts, IL-6 expression was significant lower than IL-4 (p=0.001) and IFN-γ (p=0.004). There was a significant relationship between high levels of TGF-β and endodontic treatment performed ≤4 years before (p=0.045). In general, IL-4 was the most expressed mediator in both cysts and granulomas.

CONCLUSIONS

There was a balance between the expression of pro-inflammatory and anti-inflammatory cytokines associated with the chronic periradicular inflammatory process. TNF-α and TGF-β were related to some clinical and CBCT data.

Activation of hypoxia-inducible factor 1 attenuates periapical inflammation and bone loss

Hypoxia (low oxygen level) is an important feature during infections and affects the host defence mechanisms. The host has evolved specific responses to address hypoxia, which are strongly dependent on the activation of hypoxia-inducible factor 1 (HIF-1). Hypoxia interferes degradation of HIF-1 alpha subunit (HIF-1α), leading to stabilisation of HIF-1α, heterodimerization with HIF-1 beta subunit (HIF-1β) and subsequent activation of HIF-1 pathway. Apical periodontitis (periapical lesion) is a consequence of endodontic infection and ultimately results in destruction of tooth-supporting tissue, including alveolar bone. Thus far, the role of HIF-1 in periapical lesions has not been systematically examined. In the present study, we determined the role of HIF-1 in a well-characterised mouse periapical lesion model using two HIF-1α-activating strategies, dimethyloxalylglycine (DMOG) and adenovirus-induced constitutively active HIF-1α (CA-HIF1A). Both DMOG and CA-HIF1A attenuated periapical inflammation and tissue destruction. The attenuation in vivo was associated with downregulation of nuclear factor-κappa B (NF-κB) and osteoclastic gene expressions. These two agents also suppressed NF-κB activation and subsequent production of proinflammatory cytokines by macrophages. Furthermore, activation of HIF-1α by DMOG specifically suppressed lipopolysaccharide-stimulated macrophage differentiation into M1 cells, increasing the ratio of M2 macrophages against M1 cells. Taken together, our data indicated that activation of HIF-1 plays a protective role in the development of apical periodontitis via downregulation of NF-κB, proinflammatory cytokines, M1 macrophages and osteoclastogenesis.

Concentration-dependent effect of bleaching agents on the immunolabelling of interleukin-6, interleukin-17 and CD5-positive cells in the dental pulp

AIM

To evaluate lymphocyte-like cell activation (CD5-positive cells) and the expression of interleukin (IL)-6 and IL-17 in the pulp after tooth bleaching with two concentrations of hydrogen peroxide (H₂ O₂ ).

METHODOLOGY

The right and left maxillary molars from 40 rats were treated randomly with bleaching gel with 20% H₂ O₂ (BLUE group, 1 application of 50 min), 35% H₂ O₂ (MAXX group, three applications of 15 min), or placebo gel (control). After 2 and 30 days, the rats were killed (n = 10), and the jaws were processed for histological and immunohistochemistry analysis of the pulp tissue. The scores of inflammation and immunolabelling (IL-6/IL-17) were submitted to Mann-Whitney and Kruskal-Wallis followed Dunn tests, respectively; anova tests were used for comparisons of number of CD5-positive cells and pulp chamber area values (P < 0.05).

RESULTS

At 2 days, 60% of specimens of the BLUE group were associated with moderate inflammation in pulp horns, and in the MAXX group with necrosis (P < 0.05). At 30 days, the pulp was organized, and tertiary dentine was formed. The MAXX group had superior immunolabelling of IL-17 at 2 days differing significantly from other groups (P < 0.05). At 2 days, 90% of the specimens of the BLUE group had moderate immunolabelling of IL-6, and 50% of the MAXX group had severe immunolabelling, both significantly different from the control (P < 0.05). There was no significant difference between the groups at 30 days (P > 0.05). CD5-positive cells were present at 2 and 30 days, particularly in the bleached groups (P < 0.05), without significant difference between time periods (P > 0.05).

CONCLUSIONS

IL-6 and IL-17 participated in inflammation in the pulp tissue of rats after tooth bleaching, particularly at 2 days. The immunolabelling was greater with increasing H₂ O₂ concentration. This process was accompanied by the prolonged activation of CD5-positive cells.

The immunopathogenic and immunomodulatory effects of interleukin-12 in periodontal disease

Interleukin 12 (IL-12) is an inflammatory cytokine that promotes the response of the immune system. This cytokine has been implicated as a potent stimulator of several diseases characterized by inflammatory-induced bone destruction, such as rheumatoid arthritis and periodontitis. Yet, the exact role of IL-12 in the development and progress of periodontitis has not been clarified. Several studies have demonstrated a positive correlation between the level of IL-12 and the severity of periodontal destruction. Deletion of IL-12 in mice with periodontitis significantly suppressed the level of bone destruction. Interestingly, next to a role in modulating the pathogenesis, IL-12 also has immunological-regulatory properties. This cytokine induces expression of immunosuppressive molecules, such as indoleamine-pyrrole 2,3-dioxygenase (IDO). Thus, these findings suggest both negative and positive influences of IL-12 in periodontal disease. It is currently proposed that the diversity of action of cytokines is a molecular key which regulates biological development and homeostasis. Accordingly, the actions of IL-12 might be one of the mechanisms that regulate homeostasis of periodontal tissue during and following inflammation. Therefore, this article aims to review both destructive and protective functionalities of IL-12 with an emphasis on periodontal disease.

The effect of dental bleaching on pulpal tissue response in a diabetic animal model: a study of immunoregulatory cytokines

AIM

To evaluate the influence of tooth bleaching on immunoregulatory cytokines production (IL-6, Tumour necrosis factor (TNF)-α and IL-17) in the pulp tissue of normoglycaemic and diabetic rats.

METHODOLOGY

Twenty-eight rats were divided into normoglycaemic and diabetic rats (n = 14). Diabetes mellitus (DM) was induced with a single dose of alloxan diluted in citrate buffer via intramuscular injection. After DM confirmation, all rats were sedated and tooth bleaching was performed using 35% hydrogen peroxide on the right maxillary molars for 30 min. Left molars were used as controls. Bleaching resulted in four hemimaxillae groups: normoglycaemic (N), N-bleached (NBle), diabetic (D) and D-bleached (DBle). After 2 and 30 days, rats were euthanized and hemimaxillae processed for analysis by haematoxylin and eosin and immunohistochemistry. Results within and between animals were submitted to Wilcoxon signed-rank and Mann-Whitney tests (P < 0.05).

RESULTS

At 2 days, the NBle group had mild, and the DBle had severe inflammatory infiltration in the pulpal tissue (P < 0.05). TNF-α and IL-6 cytokines were associated with increased immunolabelling in the bleached groups compared to nonbleached (P < 0.05). However, IL-17 had increased immunolabelling in the NBle compared to the N and DBle group (P < 0.05). At 30 days, reactionary dentine was observed in the coronal pulp of all bleached teeth and no inflammation was present (P > 0.05). TNF-α cytokines had increased immunolabelling in the DBle group compared to the D group (P < 0.05). However, for IL-6 and IL-17, no difference was observed in this period (P > 0.05).

CONCLUSIONS

Tooth bleaching increased IL-6 and TNF-α in the pulp tissue regardless of diabetes mellitus; however, diabetic rats had higher TNF-α levels for longer periods. Tooth bleaching influenced the increase in IL-17 in the early periods in normoglycaemic rats.

Potassium is a key signal in host-microbiome dysbiosis in periodontitis

Dysbiosis, or the imbalance in the structural and/or functional properties of the microbiome, is at the origin of important infectious inflammatory diseases such as inflammatory bowel disease (IBD) and periodontal disease. Periodontitis is a polymicrobial inflammatory disease that affects a large proportion of the world's population and has been associated with a wide variety of systemic health conditions, such as diabetes, cardiovascular and respiratory diseases. Dysbiosis has been identified as a key element in the development of the disease. However, the precise mechanisms and environmental signals that lead to the initiation of dysbiosis in the human microbiome are largely unknown. In a series of previous in vivo studies using metatranscriptomic analysis of periodontitis and its progression we identified several functional signatures that were highly associated with the disease. Among them, potassium ion transport appeared to be key in the process of pathogenesis. To confirm its importance we performed a series of in vitro experiments, in which we demonstrated that potassium levels a increased the virulence of the oral community as a whole and at the same time altering the immune response of gingival epithelium, increasing the production of TNF-α and reducing the expression of IL-6 and the antimicrobial peptide human β-defensin 3 (hBD-3). These results indicate that levels of potassium in the periodontal pocket could be an important element in of dysbiosis in the oral microbiome. They are a starting point for the identification of key environmental signals that modify the behavior of the oral microbiome from a symbiotic community to a dysbiotic one.

Homeostasis of the human microbiome plays a key role in maintaining the healthy status of the human body. Changes in composition and function of the human microbiome (dysbiosis) are at the origin of important infectious inflammatory diseases such as inflammatory bowel disease (IBD) and periodontal disease. However, the environmental elements that trigger the development of dysbiotic diseases are largely unknown. In previous studies, using community-wide transcriptome analysis, we identified ion potassium transport as one of the most important functions in the pathogenesis of periodontitis and its progression. Here, we confirm with a series of in vitro experiments that potassium can act as an important signal in the dysbiotic process inducing pathogenesis in the oral microbiome and altering the host response in front of the microbial challenge that could lead to microbial immune subversion. Our study provides new insights into the important role that ion potassium plays a signal in oral dysbiosis during periodontitis.

Interleukin-12 Induces Receptor Activator of Nuclear Factor-Kappa B Ligand Expression by Human Periodontal Ligament Cells

BACKGROUND

Increased level of proinflammatory cytokine interleukin (IL)-12 correlates with the severity of periodontitis. Yet, a possible role of IL-12 in periodontal disease has not been clarified. The aim of this study is to investigate whether IL-12 affects expression of receptor activator of nuclear factor-kappa B (NF-κB) ligand (RANKL), a potent osteoclast-stimulating factor, by human periodontal ligament (hPDL) cells.

METHODS

To determine the effect of IL-12, hPDL cells were incubated with recombinant human IL-12 (p70) in a dose- (0 to 10 ng/mL) and time-dependent manner. Expression of RANKL was evaluated at mRNA and protein levels. Underlying signaling pathways of IL-12 were determined by using specific inhibitors.

RESULTS

Under the influence of IL-12, hPDL cells expressed significantly higher levels of RANKL. Expression was mediated by signal transducer and activator of transcription 4 and NF-κB signaling pathways. Conditioned medium of IL-12-incubated cells proved to contain molecule(s) that induced RANKL expression. Addition of suramin (G protein-coupled receptor inhibitor) and ethylene glycol tetraacetic acid (calcium chelator) suggested existence of intermediate molecule(s) that could activate heterotrimeric G protein signaling in a calcium-dependent pathway.

CONCLUSIONS

Expression of RANKL by hPDL cells significantly increased after IL-12 treatment. Therefore, this study supports a close interrelationship between immune and skeletal systems and suggests an osteolytic role of IL-12 in pathogenesis of periodontal disease.

Modulation of infection-mediated migration of neutrophils and CXCR2 trafficking by osteopontin

Osteopontin (OPN) is a pro-inflammatory protein that paradoxically protects against inflammation and bone destruction in a mouse model of endodontic infection. Here we have tested the hypothesis that this effect of OPN is mediated by effects on migration of innate immune cells to the site of infection. Using the air pouch as a model of endodontic infection in mice, we showed that neutrophil accumulation at the site of infection with a mixture of endodontic pathogens is significantly reduced in OPN-deficient mice. Reduced neutrophil accumulation in the absence of OPN was accompanied by an increase in bacterial load. OPN-deficiency did not affect neutrophil survival, CXCR2 ligand expression, or the production of inflammatory cytokines in the air pouch. In vitro, OPN enhanced neutrophil migration to CXCL1, whereas in vivo, inhibition of CXCR2 suppressed cellular infiltration in air pouches of infected wild-type mice by > 50%, but had no effect in OPN-deficient mice. OPN increased cell surface expression of CXCR2 on bone marrow neutrophils in an integrin-α_v -dependent manner, and suppressed the internalization of CXCR2 in the absence of ligand. Together, these results support a model where the protective effect of OPN results from enhanced initial neutrophil accumulation at sites of infection resulting in optimal bacterial killing. We describe a novel mechanism for this effect of OPN: integrin-α_v -dependent suppression of CXCR2 internalization in neutrophils, which increases the ability of these cells to migrate to sites of infection in response to CXCR2 ligands.

Epigenetic gene regulation by histone demethylases: emerging role in oncogenesis and inflammation

Histone N-terminal tails of nucleosomes are the sites of complex regulation of gene expression through post-translational modifications. Among these modifications, histone methylation had long been associated with permanent gene inactivation until the discovery of Lys-specific demethylase (LSD1), which is responsible for dynamic gene regulation. There are more than 30 members of the Lys demethylase (KDM) family, and with exception of LSD1 and LSD2, all other KDMs possess the Jumonji C (JmjC) domain exhibiting demethylase activity and require unique cofactors, for example, Fe(II) and α-ketoglutarate. These cofactors have been targeted when devising KDM inhibitors, which may yield therapeutic benefit. KDMs and their counterpart Lys methyltransferases (KMTs) regulate multiple biological processes, including oncogenesis and inflammation. KDMs' functional interactions with retinoblastoma (Rb) and E2 factor (E2F) target promoters illustrate their regulatory role in cell cycle progression and oncogenesis. Recent findings also demonstrate the control of inflammation and immune functions by KDMs, such as KDM6B that regulates the pro-inflammatory gene expression and CD4⁺ T helper (Th) cell lineage determination. This review will highlight the mechanisms by which KDMs and KMTs regulate the target gene expression and how epigenetic mechanisms may be applied to our understanding of oral inflammation.

Osteoclast-Primed Foxp3+ CD8 T Cells Induce T-bet, Eomesodermin, and IFN-γ To Regulate Bone Resorption

Osteoimmunology arose from the recognition that cytokines produced by lymphocytes can affect bone homeostasis. We have previously shown that osteoclasts, cells that resorb bone, act as APCs. Cross-presentation of Ags by osteoclasts leads to expression of CD25 and Foxp3, markers of regulatory T cells in the CD8 T cells. Octeoclast-induced Foxp3(+) CD25(+) regulatory CD8 T cells (OC-iTcREG) suppress priming of CD4 and CD8 T cells by dendritic cells. OC-iTcREG also limit bone resorption by osteoclasts, forming a negative feedback loop. In this study, we show that OC-iTcREG express concurrently T-bet and Eomesodermin (Eomes) and IFN-γ. Pharmacological inhibition of IκK blocked IFN-γ, T-bet, and Eomes production by TcREG Furthermore, we show, using chromatin immunoprecipitation, NF-κB enrichment in the T-bet and Eomes promoters. We demonstrate that IFN-γ produced by TcREG is required for suppression of osteoclastogenesis and for degradation of TNFR-associated factor 6 in osteoclast precursors. The latter prevents signaling by receptor activator of NF-κB ligand needed for osteoclastogenesis. Knockout of IFN-γ rendered TcREG inefficient in preventing actin ring formation in osteoclasts, a process required for bone resorption. TcREG generated in vivo using IFN-γ(-/-) T cells had impaired ability to protect mice from bone resorption and bone loss in response to high-dose receptor activator of NF-κB ligand. The results of this study demonstrate a novel link between NF-κB signaling and induction of IFN-γ in TcREG and establish an important role for IFN-γ in TcREG-mediated protection from bone loss.

Use of micro-computed tomography for the assessment of periapical lesions in small rodents: a systematic review

This systematic review aimed to evaluate the literature on the acquisition-, reconstruction- and analysis parameters of micro-computed tomography (micro-CT) for the assessment of periapical lesions in rats and mice, and to illustrate the effect of variation in these parameters. The PubMed database was searched from 2000 to January 2015 (English-language publications) for reports on the use of micro-CT to evaluate periapical lesions in rats and mice. QUADAS criteria were used to rate the quality of the studies. To illustrate the effect of variations in acquisition-, reconstruction-, and analysis parameters on images of periapical lesions, micro-CT examination of two hemi-mandibles of mice, with periapical lesions around the first molar was undertaken. Twenty-one studies were identified, which analysed periapical lesions in rats or mice using micro-CT. According to the QUADAS, no study was classified as high-, seven were classified as moderate-, and 14 as low quality. The effect of variation in parameters was that voxel size may interfere with image sharpness, reconstruction may interfere with image sharpness and contrast, and inadequate plane orientation may alter the size of the periapical lesion. Nonpersonalized ROIs resulted in areas that were not part of the periapical lesion. Changing the limits of the threshold for bone-tissue visualization increased lesion size. There is no defined protocol for acquiring and analysing micro-CT images of periapical lesions in rats and mice. Furthermore, acquisition-, reconstruction- and analysis parameters are not adequately explained, which may compromise the scientific impact of the studies.

Effects of Topical Emu Oil on Burn Wounds in the Skin of Balb/c Mice

The goal of this study was to determine the effect of topical Emu oil on the healing of burn wounds and hair follicle restoration in superficial II-degree burns in the skin of Balb/c mice. Thirty-two male Balb/c mice with burns on the back of the neck were divided into two groups: The Emu oil group received topical Emu oil twice daily, whereas the control was left untreated. Skin biopsies were obtained on days 4, 7, 10, and 14 of the experiment. Then the specimens were viewed with Olympus SZX research microscope. The Emu oil treated burns were found to heal more slowly and inflammation lasted longer in this group. The number of hair follicles in the margins of the wounds increased through time in the Emu oil group compared to the control group. Also, the hair follicles in the Emu oil group were in several layers and seemed to be more active and mature. Moreover, Emu oil had a positive effect on fibrogenesis and synthesis of collagen. The findings indicate that although Emu oil delays the healing process, it has a positive effect on wound healing and it increases the number of hair follicles in the margins of the wound.

Interrelationship Between Periapical Lesion and Systemic Metabolic Disorders

BACKGROUND

Periapical periodontitis, also known as periapical lesion, is a common dental disease, along with periodontitis (gum disease). Periapical periodontitis is a chronic inflammatory disease, caused by endodontic infection, and its development is regulated by the host immune/inflammatory response. Metabolic disorders, which are largely dependent on life style such as eating habits, have been interpreted as a "metabolically-triggered" low-grade systemic inflammation and may interact with periapical periodontitis by triggering immune modulation. The host immune system is therefore considered the common fundamental mechanism of both disease conditions.

METHOD

We have reviewed >200 articles to discuss the interrelationship between periapical lesions and metabolic disorders including type 2 diabetes mellitus, hypertension, and non-alcoholic fatty liver diseases (NAFLD), and their common pathological background in immunology/osteoimmunology and cytokine biology.

RESULTS

An elevated inflammatory state caused by metabolic disorders can impact the clinical outcome of periapical lesions and interfere with wound healing after endodontic treatment. Although additional well-designed clinical studies are needed, periapical lesions appear to affect insulin sensitivity and exacerbate non-alcoholic steatohepatitis.

CONCLUSION

Immune regulatory cytokines produced by various cell types, including immune cells and adipose tissue, play an important role in this interrelationship.

Interleukin-6 inhibits apoptosis of exocrine gland tissues under inflammatory conditions

Interleukin (IL)-6 is a multi-functional cytokine that can either promote or suppress tissue inflammation depending on the specific disease context. IL-6 is elevated in the exocrine glands and serum of patients with Sjögren's syndrome (SS), but the specific role of IL-6 in the pathogenesis of this disease has not been defined. In this study, we showed that IL-6 expression levels were increased with age in C56BL/6.NOD-Aec1Aec2 mice, a primary SS model, and higher than the control C57BL/6 mice. To assess the role of IL-6 during the immunological phase of SS development, a neutralizing anti-IL-6 antibody was administered into 16 week-old female C56BL/6.NOD-Aec1Aec2 mice, 3 times weekly for a consecutive 8 weeks. Neutralization of endogenous IL-6 throughout the immunological phase of SS development led to increased apoptosis, caspase-3 activation, leukocytic infiltration, and IFN-γ- and TNF-α production in the salivary gland. To further determine the effect of IL-6 on the apoptosis of exocrine gland cells, recombinant human IL-6 or the neutralizing anti-IL-6 antibody was injected into female C57BL/6 mice that received concurrent injection of anti-CD3 antibody to induce the apoptosis of exocrine gland tissues. Neutralization of IL-6 enhanced, whereas administration of IL-6 inhibited apoptosis and caspase-3 activation in salivary and lacrimal glands in this model. The apoptosis-suppressing effect of IL-6 was associated with up-regulation of Bcl-xL and Mcl-1 in both glands. Moreover, IL-6 treatment induced activation of STAT3 and up-regulated Bcl-xL and Mcl-1 gene expression in a human salivary gland epithelial cell line. In conclusion, IL-6 inhibits the apoptosis of exocrine gland tissues and exerts a tissue-protective effect under inflammatory conditions including SS. These findings suggest the possibility of using this property of IL-6 to preserve exocrine gland tissue integrity and function under autoimmune and inflammatory conditions.

Synergy between IL-6 and soluble IL-6 receptor enhances bone morphogenetic protein-2/absorbable collagen sponge-induced bone regeneration via regulation of BMPRIA distribution and degradation

Bone morphogenetic protein-2/absorbable collagen sponge (BMP-2/ACS) implants have been approved for clinical use to induce bone regeneration. We previously showed that exaggerated inflammation characterized by elevated level of inflammatory cytokines including TNF-α, IL-1β, and IL-6 has been shown to inhibit BMP-2/ACS-induced bone regeneration. Furthermore, unlike the negative effects of TNF-α and IL-1β, IL-6 seemed not to affect BMP-2-induced osteoblastic differentiation of bone marrow mesenchymal stem cells (BMSCs). We hypothesized that there may be a regulatory loop between IL-6 and BMP-2 singling to affect BMP-2/ACS-induced bone regeneration. Here, we established a BMP-2/ACS-induced ectopic bone formation model in rats and fund that IL-6 injection significantly increased BMP-2/ACS-induced bone mass. Consistent with this animal model, an in vitro study demonstrated that synergy between IL-6 and soluble IL-6 receptor (IL-6/sIL-6R) promotes BMP-2-induced osteoblastic differentiation of human BMSCs through amplification of BMP/Smad signaling. Strikingly, IL-6 injection did not activate osteoclast-mediated bone resorption in the ectopic bone formation model, and IL-6/sIL-6R treatment did not affect receptor activator of NF-κB ligand (RANKL)-induced osteoclastic differentiation of human peripheral blood mononuclear cells (PBMCs) in vitro. Furthermore, IL-6/sIL-6R treatment did not affect expression of BMP receptors, but enhanced the cell surface translocation of BMP receptor IA (BMPRIA) and inhibited the degradation of BMPRIA. Collectively, these findings indicate that synergy between IL-6 and sIL-6R promotes the cell surface translocation of BMPRIA and maintains the stability of BMPRIA expression, leading to enhanced BMP-2/ACS-induced bone regeneration.

Early Cytokine Response to Infection with Pathogenic vs Non-Pathogenic Organisms in a Mouse Model of Endodontic Infection

Using the subcutaneous chamber model of infection, we showed previously that a mixture of four endodontic pathogens (EP: P. intermedia, F. nucleatum, S. intermedius and P. micra) are able to persist without clearance for up to seven days, while a non-pathogenic oral species, S. mitis, was substantially cleared in this time. Here we have compared the cytokine response inside the chambers against these microorganisms. A majority of cytokines tested (17/24) showed different patterns of expression. Several cytokines had a peak of expression at 2 h after infection in response to the EP, while none showed this pattern in S. mitis infections. Chemokines were uniformly present at similar or higher levels in response to S. mitis, with redundant expression of CXCR2 ligands, while several growth/survival factors were present at higher levels in EP infections. Protease activity expressed by EP may be responsible for the lower levels of some chemokines. T-cell associated cytokines were in general expressed at extremely low levels, and did not differ between the two infections. The inflammatory markers IL-6, IL-1α and IL1-β were expressed at similar levels in both infections at early times, while TNFα was preferentially present in S. mitis infections. In EP infected chambers, reciprocal changes in levels of IL-6 and IL-1α were observed at later times suggesting a switch in the inflammatory response. Analysis of the cytokine response to infection with the individual species from the EP mix suggests that P. intermedia drives this inflammatory switch. Together these results show a surprising level of divergence of the host response to pathogenic and non-pathogenic organisms associated with oral infections, and supports a dominant effect of P. intermedia in polymicrobial endodontic infections.

Contribution of Reduced Interleukin-10 Levels to the Pathogenesis of Osteomyelitis in Children with Sickle Cell Disease

Osteomyelitis is a significant complication of sickle cell disease (SCD), and several factors contribute to its pathogenesis, including altered expression of proinflammatory and anti-inflammatory cytokines. In view of the role of interleukin-10 (IL-10) as an anti-inflammatory cytokine, we tested the notion that SCD osteomyelitis is associated with a reduction in IL-10 secretion and, hence, precipitation of a proinflammatory state. Study subjects comprised 52 SCD patients with confirmed diagnosis of osteomyelitis and 165 age- and gender-matched SCD patients with negative histories of osteomyelitis. Results obtained showed that IL-10 serum levels in SCD osteomyelitis patients were significantly lower than those of control SCD patients. Receiver operating characteristic (ROC) analysis demonstrated that altered IL-10 serum levels predicted the development of osteomyelitis, and the mean area under ROC curves of IL-10 was 0.810 among SCD patients with osteomyelitis. A systematic shift in IL-10 serum levels toward lower values was seen in osteomyelitis cases, with an increased osteomyelitis risk associated with decreased IL-10 levels. Multivariate logistic regression analyses confirmed the independent association of reduced IL-10 with osteomyelitis after controlling for sickle hemoglobin (HbS), fetal hemoglobin (HbF), platelet count, and white blood cell (WBC) count. These data support the strong association of decreased IL-10 levels with osteomyelitis, thereby supporting a role for IL-10 in osteomyelitis follow-up.

Temporal profile of inflammatory response to fracture and hemorrhagic shock: Proposal of a novel long-term survival murine multiple trauma model

Hemorrhagic shock (hS) interacts with the posttraumatic immune response and fracture healing in multiple trauma. Due to the lack of a long-term survival multiple trauma animal models, no standardized analysis of fracture healing referring the impact of multiple trauma on fracture healing was performed. We propose a new long-term survival (21 days) murine multiple trauma model combining hS (microsurgical cannulation of carotid artery, withdrawl of blood and continuously blood pressure measurement), femoral (osteotomy/external fixation) and tibial fracture (3-point bending technique/antegrade nail). The posttraumatic immune response was measured via IL-6, sIL-6R ELISA. The hS was investigated via macrohemodynamics, blood gas analysis, wet-dry lung ration and histologic analysis of the shock organs. We proposed a new murine long-term survival (21 days) multiple trauma model mimicking clinical relevant injury patterns and previously published human posttraumatic immune response. Based on blood gas analysis and histologic analysis of shock organs we characterized and standardized our murine multiple trauma model. Furthermore, we revealed hemorrhagic shock as a causative factor that triggers sIL-6R formation underscoring the fundamental pathophysiologic role of the transsignaling mechanism in multiple trauma.

Effects of electroacupuncture on experimental periodontitis in rats

BACKGROUND

Acupuncture has shown the capability of modulating the immuno-inflammatory response of the host. This study aims to evaluate the effects of electroacupuncture (EA) on ligature-induced periodontitis in rats.

METHODS

Thirty-two animals were divided into four groups: 1) control; 2) experimental periodontitis (EP); 3) sham-treated (EP/EA-sham); and 4) treated with EA (EP/EA). For the EP groups, a ligature was placed around the right mandibular first molars at day 1. Sessions of EA or EA-sham were assigned every other day. For EA treatment, large intestine meridian points LI4 and LI11 and stomach meridian points ST36 and ST44 were used. EA-sham was performed in off-meridian points. Animals were euthanized at day 11. Histomorphometric and microtomographic analyses were performed. Immunolabeling patterns for the receptor activator of nuclear factor κB ligand (RANKL), osteoprotegerin (OPG), and tartrate-resistant acid phosphatase (TRAP) were assessed. Expressions of interleukin (IL)-1β, matrix metalloproteinase (MMP)-8, IL-6, and cyclooxygenase (COX)-2 messenger RNAs (mRNAs) were evaluated by quantitative reverse transcription-polymerase chain reaction. Data were analyzed statistically (P <0.05, analysis of variance).

RESULTS

Histomorphometric and microtomographic analyses demonstrated that group EP/EA presented reduced alveolar bone loss when compared to group EP (P <0.05). Reduced RANKL immunolabeling and fewer TRAP-positive multinucleated cells were observed in the EA-treated group in relation to group EP. No differences were observed in OPG expression among groups. EA treatment decreased the genic expression of IL-1β and MMP-8 (P <0.05), increased the mRNA expression of IL-6 (P <0.05), and did not modify the genic expression of COX-2 in animals with EP (P >0.05).

CONCLUSION

It can be concluded that EA reduced periodontal tissue breakdown and the expression of some proinflammatory mediators and a proresorptive factor in EP in rats.

Pathogenic bacterial species associated with endodontic infection evade innate immune control by disabling neutrophils

Endodontic infections, in which oral bacteria access the tooth pulp chamber, are common and do not resolve once established. To investigate the effects of these infections on the innate immune response, we established a mouse subcutaneous chamber model, where a mixture of four oral pathogens commonly associated with these infections (endodontic pathogens [EP]), i.e., Fusobacterium nucleatum, Streptococcus intermedius, Parvimonas micra, and Prevotella intermedia, was inoculated into subcutaneously implanted titanium chambers. Cells that infiltrated the chamber after these infections were primarily neutrophils; however, these neutrophils were unable to control the infection. Infection with a nonpathogenic oral bacterial species, Streptococcus mitis, resulted in well-controlled infection, with bacterial numbers reduced by 4 to 5 log units after 7 days. Propidium iodide (PI) staining of the chamber neutrophils identified three distinct populations: neutrophils from EP-infected chambers were intermediate in PI staining, while cells in chambers from mice infected with S. mitis were PI positive (apoptotic) or negative (live). Strikingly, neutrophils from EP-infected chambers were severely impaired in their ability to phagocytose and to generate reactive oxygen species in vitro after removal from the chamber compared to cells from S. mitis-infected chambers. The mechanism of neutrophil impairment was necrotic cell death as determined by morphological analyses. P. intermedia alone could induce a similar neutrophil phenotype. We conclude that the endodontic pathogens, particularly P. intermedia, can efficiently disable and kill infiltrating neutrophils, allowing these infections to become established. These results can help explain the persistence of endodontic infections and demonstrate a new virulence mechanism associated with P. intermedia.

Lessons learned and unlearned in periodontal microbiology

Periodontal diseases are initiated by bacterial species living in polymicrobial biofilms at or below the gingival margin and progress largely as a result of the inflammation elicited by specific subgingival species. In the past few decades, efforts to understand the periodontal microbiota have led to an exponential increase in information about biofilms associated with periodontal health and disease. In fact, the oral microbiota is one of the best-characterized microbiomes that colonize the human body. Despite this increased knowledge, one has to ask if our fundamental concepts of the etiology and pathogenesis of periodontal diseases have really changed. In this article we will review how our comprehension of the structure and function of the subgingival microbiota has evolved over the years in search of lessons learned and unlearned in periodontal microbiology. More specifically, this review focuses on: (i) how the data obtained through molecular techniques have impacted our knowledge of the etiology of periodontal infections; (ii) the potential role of viruses in the etiopathogenesis of periodontal diseases; (iii) how concepts of microbial ecology have expanded our understanding of host-microbe interactions that might lead to periodontal diseases; (iv) the role of inflammation in the pathogenesis of periodontal diseases; and (v) the impact of these evolving concepts on therapeutic and preventive strategies to periodontal infections. We will conclude by reviewing how novel systems-biology approaches promise to unravel new details of the pathogenesis of periodontal diseases and hopefully lead to a better understanding of their mechanisms.

IL-6 Alters Osteocyte Signaling toward Osteoblasts but Not Osteoclasts

Mechanosensitive osteocytes regulate bone mass in adults. Interleukin 6 (IL-6), such as present during orthodontic tooth movement, also strongly affects bone mass, but little is known about the effect of IL-6 on osteocyte function. Therefore we aimed to determine in vitro whether IL-6 affects osteocyte mechanosensitivity, and osteocyte regulation of osteoclastogenesis and osteoblast differentiation. MLO-Y4 osteocytes were incubated with/without IL-6 (1 or 10 pg/mL) for 24 hr. Subsequently, osteocytes were subjected to mechanical loading by pulsating fluid flow (PFF) for 1 hr. Mouse osteoclast precursors were cultured for 7 days on top of IL-6-treated osteocytes. Conditioned medium from osteocytes treated with/without IL-6 was added to MC3T3-E1 pre-osteoblasts for 14 days. Exogenous IL-6 (10 pg/mL) did not alter the osteocyte response to PFF. PFF significantly enhanced IL-6 production by osteocytes. IL-6 enhanced Rankl expression but reduced caspase 3/7 activity by osteocytes, and therefore did not affect osteocyte-stimulated osteoclastogenesis. Conditioned medium from IL-6-treated osteocytes reduced alkaline phosphatase (ALP) activity and Runx2 expression in osteoblasts, but increased expression of the proliferation marker Ki67 and osteocalcin. Our results suggest that IL-6 is produced by shear-loaded osteocytes and that IL-6 may affect bone mass by modulating osteocyte communication toward osteoblasts.

Role of regulatory B cells in chronic intestinal inflammation: association with pathogenesis of Crohn's disease

The role of regulatory B cells (Bregs) producing interleukin (IL)-10 in the pathogenesis of inflammatory bowel diseases remains unknown. We investigated IL-10 production in B cells from patients with inflammatory bowel diseases and immunoregulatory functions of Bregs in experimental colitis mouse models. CpG DNA-induced IL-10 production in peripheral blood B cells isolated from patients with inflammatory bowel diseases and control subjects was examined. CD19 and CD1d were used for evaluating possible cell surface markers of Bregs. Colitis models of severe combined immunodeficiency mice were established by adoptive transfer of whole CD4 T cells or regulatory T cell (Treg)-depleted T cells (CD4CD25) isolated from SAMP1/Yit mice and the function of Bregs in intestinal inflammation was elucidated by evaluating the effects of cotransfer of whole or Breg-depleted B cells. CpG DNA-induced IL-10 production was significantly decreased in B cells from patients with Crohn's disease (CD), as compared with those from healthy controls, whereas Bregs were found to be enriched in a population of CD19 and CD1d B cells isolated from both human and mouse samples. The severity of intestinal inflammation was significantly increased in the Breg-depleted mice, with similar results also found in adoptive transfer colitis model mice even after Treg depletion. Our findings show that Bregs, characterized by the cell surface markers CD19 and CD1d, significantly reduced experimental colitis regardless of the presence or absence of Tregs. These results suggest that a deficiency or decrease of Bregs function exacerbates intestinal inflammation, which may be associated with the pathogenesis of CD.

The role of IL-6 on apical periodontitis: a systematic review

The aim of this review was to examine current knowledge of the role of interleukin-6 (IL-6) in apical periodontitis (AP) pathogenesis as an inflammatory or pro-inflammatory cytokine. It also looked at whether IL-6 could serve as a measure for differential diagnosis or as a biomarker that can further predict the progression of bone resorption. A systematic review relating to AP and IL-6 was made via PubMed, BIOSIS, Cochrane, EMBASE and Web of Science databases using keywords and controlled vocabulary. Two independent reviewers first screened titles and abstracts and then the full texts. The reference lists of the identified publications were examined for additional titles. Eighteen papers were studied in total. In vitro studies (n = 6) revealed that IL-6 is present in AP, and its levels are proportional to the size of the periapical lesions. Neutrophils and macrophages resident in these lesions can produce IL-6 in vitro after a bacterial stimulus. Animal studies (n = 5) showed that IL-6 is present in AP and that osteoblasts can produce IL-6 in vivo. On the other hand, two studies using IL-6 knockout mice revealed larger periapical lesions when compared with control groups, demonstrating IL-6's role as an anti-inflammatory cytokine. In human studies (n = 7), IL-6 was identified in AP, and its levels were higher in symptomatic, epithelialized and large lesions than in asymptomatic and small lesions. These data lead to the conclusion that IL-6 may play a pro-inflammatory role, increasing its levels and reabsorbing bone in the presence of infections. When IL-6 is not present, other cytokines such as IL-1 and TNF-α induce bone resorption. Further studies about the relationship between AP development and the cytokine network must be performed to establish the exact role of each cytokine in the inflammatory process.

Differential interactions of Streptococcus gordonii and Staphylococcus aureus with cultured osteoblasts

The impedance of normal osteoblast function by microorganisms is at least in part responsible for the failure of dental or orthopedic implants. Staphylococcus aureus is a major pathogen of bone, and exhibits high levels of adhesion and invasion of osteoblasts. In this article we show that the commensal oral bacterium Streptococcus gordonii also adheres to and is internalized by osteoblasts. Entry of S. gordonii cells had typical features of phagocytosis, similar to S. aureus, with membrane protrusions characterizing initial uptake, and closure of the osteoblast membrane leading to engulfment. The sensitivities of S. gordonii internalization to inhibitors cytochalasin D, colchicine and monensin indicated uptake through endocytosis, with requirement for actin accumulation. Internalization levels of S. gordonii were enhanced by expression of S. aureus fibronectin-binding protein A (FnBPA) on the S. gordonii cell surface. Lysosomal-associated membrane protein-1 phagosomal membrane marker accumulated with intracellular S. aureus and S. gordonii FnBPA, indicating trafficking of bacteria into the late endosomal/lysosomal compartment. Streptococcus gordonii cells did not survive intracellularly for more than 12 h, unless expressing FnBPA, whereas S. aureus showed extended survival times (>48 h). Both S. aureus and S. gordonii DL-1 elicited a rapid interleukin-8 response by osteoblasts, whereas S. gordonii FnBPA was slower. Only S. aureus elicited an interleukin-6 response. Hence, S. gordonii invades osteoblasts by a mechanism similar to that exhibited by S. aureus, and elicits a proinflammatory response that may promote bone resorption.

Distinct cytokine profiles of circulating mononuclear cells stimulated with Staphylococcus aureus enterotoxin A in vitro during early and late episodes of chronic osteomyelitis

We investigated the cytokine profile of peripheral mononuclear cells from chronic osteomyelitis (OST) patients following in vitro stimulation with staphylococcal enterotoxin A (SEA). We demonstrate that stimulation with SEA induced prominent lymphocyte proliferation and high levels of tumour necrosis factor (TNF)-α, interleukin (IL)-4 and IL-10 secretion in both OST and non-infected individuals (NI). Even though stimulation with SEA had no impact on IL-6 production in either patient group, the baseline level of IL-6 production by cells from OST patients was always significantly less than that produced by cells from NI. After classifying the osteomyelitic episodes based on the time after the last reactivation event as "early" (1-4 months) or "late" osteomyelitis (5-12 months), we found that increased levels of TNF-α and IL-4 in combination with decreased levels of IL-6 were observed in the early episodes. By contrast, increased levels of IL-10, IL-2 and IL-6 were hallmarks of late episodes. Our data demonstrate that early osteomyelitic episodes are accompanied by an increased frequency of "high producers" of TNF-α and IL-4, whereas late events are characterised by increased frequencies of "high producers" of IL-10, IL-6 and IL-2. These findings demonstrate the distinct cytokine profiles in chronic osteomyelitis, with a distinct regulation of IL-6 production during early and late episodes.

Accelerated calvarial healing in mice lacking Toll-like receptor 4

The bone and immune systems are closely interconnected. The immediate inflammatory response after fracture is known to trigger a healing cascade which plays an important role in bone repair. Toll-like receptor 4 (TLR4) is a member of a highly conserved receptor family and is a critical activator of the innate immune response after tissue injury. TLR4 signaling has been shown to regulate the systemic inflammatory response induced by exposed bone components during long-bone fracture. Here we tested the hypothesis that TLR4 activation affects the healing of calvarial defects. A 1.8 mm diameter calvarial defect was created in wild-type (WT) and TLR4 knockout (TLR4(-/-)) mice. Bone healing was tested using radiographic, histologic and gene expression analyses. Radiographic and histomorphometric analyses revealed that calvarial healing was accelerated in TLR4(-/-) mice. More bone was observed in TLR4(-/-) mice compared to WT mice at postoperative days 7 and 14, although comparable healing was achieved in both groups by day 21. Bone remodeling was detected in both groups on postoperative day 28. In TLR4(-/-) mice compared to WT mice, gene expression analysis revealed that higher expression levels of IL-1β, IL-6, TNF-α,TGF-β1, TGF-β3, PDGF and RANKL and lower expression level of RANK were detected at earlier time points (≤ postoperative 4 days); while higher expression levels of IL-1β and lower expression levels of VEGF, RANK, RANKL and OPG were detected at late time points (> postoperative 4 days). This study provides evidence of accelerated bone healing in TLR4(-/-) mice with earlier and higher expression of inflammatory cytokines and with increased osteoclastic activity. Further work is required to determine if this is due to inflammation driven by TLR4 activation.

The role of prophylactic ibuprofen and N-acetylcysteine on the level of cytokines in periapical exudates and the post-treatment pain

Background

Periapical lesions are inflammatory diseases that result in periapical bone destruction because of host defensive–microbial disturbances.

Objective

To evaluate the role of prophylactic ibuprofen and N-acetylcysteine (NAC) on the levels of tumor necrosis factor alpha (TNF- α), interleukin- 6(IL-6) and IL-17 and post-treatment pain level in chronic periapical lesions.

Materials and methods

Eighty patients with chronic apical lesions less than 1 cm were randomly assigned to receive NAC tablets (400 mg), ibuprofen tablets (400 mg), NAC (400 mg)/ibuprofen (200 mg) combination and placebo 90 minutes prior to sampling. Periapical exudates were collected from root canals. TNF- α, IL-6 and IL-17 levels were determined by ELISA and post-treatment pain was assessed using a visual analog scale (VAS).

Results

There was a significant difference in IL-6 level between ibuprofen group and placebo (p = 0.019). Significant difference in IL-17 level was observed between NAC/ibuprofen combination group and placebo (p = 0.043). Four hours after treatment, a significant difference was observed in VAS pain score between ibuprofen group and placebo (p = 0.017). Eight hours post-treatment, VAS pain score for NAC group was statistically lower than placebo group (p = 0.033). After 12 hours VAS pain score showed a significant decrease in NAC group compared to placebo (p = 0.049).

Conclusion

The prophylactic ibuprofen and NAC failed to clearly reflect their effect on cytokines levels in exudates of chronic periapical lesions. On the other hand it seems that NAC can be a substitute for ibuprofen in the management of post endodontic pain.