Fibroblasts, mononuclear phagocytes, and endothelial cells express monocyte chemoattractant protein-1 (MCP-1) in inflamed human gingiva

Inflammation and mechanical force-induced bone remodeling

Periodontitis arises from imbalanced host-microbe interactions, leading to dysbiosis and destructive inflammation. The host's innate and adaptive immune responses produce pro-inflammatory mediators that stimulate destructive events, which cause loss of alveolar bone and connective tissue attachment. There is no consensus on the factors that lead to a conversion from gingivitis to periodontitis, but one possibility is the proximity of the inflammation to the bone, which promotes bone resorption and inhibits subsequent bone formation during coupled bone formation. Conversely, orthodontic tooth movement is triggered by the mechanical force applied to the tooth, resulting in bone resorption on the compression side and new bone formation on the tension side. However, the environment around orthodontic brackets readily retains dental plaque and may contribute to inflammation and bone remodeling. The immune, epithelial, stromal, endothelial and bone cells of the host play an important role in setting the stage for bone remodeling that occurs in both periodontitis and orthodontic tooth movement. Recent advancements in single-cell RNA sequencing have provided new insights into the roles and interactions of different cell types in response to challenges. In this review, we meticulously examine the functions of key cell types such as keratinocytes, leukocytes, stromal cells, osteocytes, osteoblasts, and osteoclasts involved in inflammation- and mechanical force-driven bone remodeling. Moreover, we explore the combined effects of these two conditions: mechanical force-induced bone remodeling combined with periodontal disease (chronic inflammation) and periodontally accelerated osteogenic orthodontics (acute transient inflammation). This comprehensive review enhances our understanding of inflammation- and mechanical force-induced bone remodeling.

Possible immunomodulatory role of Filifactor alocis through beta-defensin 2 in gingival keratinocytes

OBJECTIVES

The present study aimed to investigate a possible immunomodulatory role of the periodontopathogen Filifactor alocis through the antimicrobial peptide hBD-2 on the expression of chemokines in human gingival keratinocytes.

MATERIALS AND METHODS

Cells were cultured in the presence or absence of periodontopathogenic bacteria, such as F. alocis, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Treponema denticola, to evaluate the regulation of hBD-2, CXCL8 and CCL20. Furthermore, the cells were exposed or not to hBD-2 and the expression of CXCL8 and CCL20 and their receptors was evaluated.

RESULTS

All bacteria induced a significant upregulation of hBD-2, CXCL8, and CCL20 gene expressions. In addition, F. alocis significantly increased their protein levels, as detected by ELISA. Pre-incubation of the cells with the TLR2 inhibitor resulted in a significant downregulation of hBD-2 expression in F. alocis-treated cells. Gingival keratinocytes exposed to hBD-2 resulted in a significant and dose-dependent increase of all chemokines and their receptors.

CONCLUSIONS

F. alocis increased the production of chemotactic cytokines, suggesting an increase in the recruitment of immunoinflammatory cells in periodontal diseases. The chemotaxis-promoting effect is partly direct, but is also mediated via hBD-2. F. alocis stimulates the synthesis of hBD-2, which in turn could promote the expression and synthesis of these chemokines and their receptors. In addition, hBD-2 has an autostimulatory effect and stimulates the synthesis of these chemokines, so that the chemotaxis triggered by F. alocis is further fueled.

CLINICAL RELEVANCE

F. alocis and hBD-2 have a significant role in periodontitis, showing their importance for diagnostic and treatment approaches.

An update on periodontal inflammation and bone loss

Periodontal disease is a chronic inflammatory condition that affects the supporting structures of the teeth, including the periodontal ligament and alveolar bone. Periodontal disease is due to an immune response that stimulates gingivitis and periodontitis, and its systemic consequences. This immune response is triggered by bacteria and may be modulated by environmental conditions such as smoking or systemic disease. Recent advances in single cell RNA-seq (scRNA-seq) and in vivo animal studies have provided new insight into the immune response triggered by bacteria that causes periodontitis and gingivitis. Dysbiosis, which constitutes a change in the bacterial composition of the microbiome, is a key factor in the initiation and progression of periodontitis. The host immune response to dysbiosis involves the activation of various cell types, including keratinocytes, stromal cells, neutrophils, monocytes/macrophages, dendritic cells and several lymphocyte subsets, which release pro-inflammatory cytokines and chemokines. Periodontal disease has been implicated in contributing to the pathogenesis of several systemic conditions, including diabetes, rheumatoid arthritis, cardiovascular disease and Alzheimer's disease. Understanding the complex interplay between the oral microbiome and the host immune response is critical for the development of new therapeutic strategies for the prevention and treatment of periodontitis and its systemic consequences.

Primed inflammatory response by fibroblast subset is necessary for proper oral and cutaneous wound healing

Fibroblasts are ubiquitous mesenchymal cells that exhibit considerable molecular and functional heterogeneity. Besides maintaining stromal integrity, oral fibroblast subsets are thought to play an important role in host-microbe interaction during injury repair, which is not well explored in vivo. Here, we characterize a subset of fibroblast lineage labeled by paired-related homeobox-1 promoter activity (Prx1Cre+) in oral mucosa and skin and demonstrate these fibroblasts readily respond to microbial products to facilitate the normal wound healing process. Using a reporter mouse model, we determined that Prx1Cre+ fibroblasts had significantly higher expression of toll-like receptors 2 and 4 compared to other fibroblast populations. In addition, Prx1 immunopositive cells exhibited heightened activation of inflammatory transcription factor NF-κB during the early wound healing process. At the cytokine level, CXCL1 and CCL2 were significantly upregulated by Prx1Cre+ fibroblasts at baseline and upon LPS stimulation. Importantly, lineage-specific knockout to prevent NF-κB activation in Prx1Cre+ fibroblasts drastically impaired both oral and skin wound healing processes, which was linked to reduced macrophage infiltration, failure to resolve inflammation, and clearance of bacteria. Together, our data implicate a pro-healing role of Prx1-lineage fibroblasts by facilitating early macrophage recruitment and bacterial clearance.

The adiponectin receptor agonist AdipoAI attenuates periodontitis in diabetic rats by inhibiting gingival fibroblast-induced macrophage migration

BACKGROUND AND PURPOSE

Low-grade inflammation, a common feature of both diabetes and periodontitis, partly accounts for the complexity and refractoriness of diabetes-associated periodontitis. Adiponectin (APN), the most abundant adipokine in human blood, has been widely reported to have anti-inflammatory functions. Herein, we investigated the ability of an APN receptor agonist, AdipoAI, to alleviate diabetes-associated periodontitis. Furthermore, we revealed the possible mechanism underlying its anti-inflammatory effects.

EXPERIMENTAL APPROACH

The maxillary first molar of Zucker diabetic fatty (ZDF) rats was ligated to construct a diabetes-associated periodontitis model, and rats were administered AdipoAI by gavage. We examined diabetes-related indexes, pathological changes in insulin target organs, alveolar bone resorption and systemic and local inflammation. In vitro, transwell assays were used to evaluate monocyte/macrophage migration induced by human gingival fibroblasts (hGFs) with/without AdipoAI treatment. Additionally, we examined chemokine expression levels in hGFs and hGF-induced monocyte/macrophage migration upon siRNA knockdown of Adiponectin receptor expression. Expression of Adipo1/Adipo2 receptors and inflammation-related signalling pathways were examined by IHC and WB, followed by confirmation with an NF-κB P65 inhibitor (BAY 11-7082).

KEY RESULTS

AdipoAI lowered fasting blood glucose and serum insulin in ZDF rats and alleviated inflammation in insulin target tissues. Locally, AdipoAI reduced alveolar bone absorption and gingival inflammation. Mechanistically, AdipoAI inhibited hGF-induced monocyte/macrophage migration by reducing CCL2 secretion. In hGFs, AdipoAI attenuated LPS-induced activation of NF-κB P65 and CCL2 expression, which was dependent on the Adipo receptor 1.

CONCLUSION AND IMPLICATIONS

AdipoAI, with its ability to alleviate inflammatory damage in tissues, is a candidate for diabetes-associated periodontitis treatment.

The Role of Gingival Fibroblasts in the Pathogenesis of Periodontitis

Gingival fibroblasts (GFs) are essential components of the periodontium, which are responsible for the maintenance of tissue structure and integrity. However, the physiological role of GFs is not restricted to the production and remodeling of the extracellular matrix. GFs also act as sentinel cells that modulate the immune response to oral pathogens invading the gingival tissue. As an important "nonclassical" component of the innate immune system, GFs respond to bacteria and damage-related signals by producing cytokines, chemokines, and other inflammatory mediators. Although the activation of GFs supports the elimination of invading bacteria and the resolution of inflammation, their uncontrolled or excessive activation may promote inflammation and bone destruction. This occurs in periodontitis, a chronic inflammatory disease of the periodontium initiated and sustained by dysbiosis. In the inflamed gingival tissue, GFs acquire imprinted proinflammatory phenotypes that promote the growth of inflammophilic pathogens, stimulate osteoclastogenesis, and contribute to the chronicity of inflammation. In this review, we discuss the biological functions of GFs in healthy and inflamed gingival tissue, highlighting recent studies that provide insight into their role in the pathogenesis of periodontal diseases. We also draw parallels with the recently discovered fibroblast populations identified in other tissues and their roles in health and disease. This knowledge should be used in future studies to discover more about the role of GFs in periodontal diseases, especially chronic periodontitis, and to identify therapeutic strategies targeting their pathological interactions with oral pathogens and the immune system.

M2 macrophages with inflammation tropism facilitate cementoblast mineralization

BACKGROUND

Cementum regeneration was regarded as the critical goal for periodontal regeneration, and M2 macrophage-based therapy was expected to be a promising strategy. However, little is known about the effects of M2 macrophages on cementoblast mineralization and tropism, especially under inflammation. Here we investigated for the first time the crosstalk between M2 macrophages and Porphyromonas gingivalis (Pg)-stimulated cementoblasts.

METHODS

M2 macrophages were induced with interleukin (IL)-4, and identified. CC-chemokine ligand 2 (CCL2) expression and secretion of inflammatory cementoblasts were detected by reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR), western blotting (WB), immunohistochemistry for apical periodontitis (AP) mice, and by enzyme-linked immunosorbent assay. Crystal violet staining was used to observe macrophage migration. Conditional medium (CM) and transwell coculture methods were applied to evaluate the effects of M2 macrophages on cementum mineralization with or without Pg, and to explore the mechanism. Mineralization-related markers and pathway-related proteins were measured by RT-qPCR and WB.

RESULTS

M2 macrophages were identified successfully. We found an increase of CCL2 in cementoblasts and their supernatant. Also, higher CCL2 in cementoblasts was observed in the AP model. Superior recruitment of M2 macrophages to supernatant from Pg-stimulated cementoblasts or CCL2-containing medium was verified. Moreover, CM2 and Trans-M2 showed better mineralization-accelerating and rescuing effects when compared to their controls, and application of p38 inhibitor partially blocked the promotion.

CONCLUSIONS

Our study demonstrated the inflammation-targeting and mineralization-promoting effects of M2 macrophages on cementoblasts, which may provide evidence for M2 macrophage-based cementum regeneration.

Distinct fibroblast progenitor subpopulation expedites regenerative mucosal healing by immunomodulation

Injuries that heal by fibrosis can compromise organ function and increase patient morbidity. The oral mucosal barrier has a high regenerative capacity with minimal scarring, but the cellular mechanisms remain elusive. Here, we identify distinct postnatal paired-related homeobox-1+ (Prx1+) cells as a critical fibroblast subpopulation that expedites mucosal healing by facilitating early immune response. Using transplantation and genetic ablation model in mice, we show that oral mucosa enriched with Prx1+ cells heals faster than those that lack Prx1+ cells. Lineage tracing and scRNA-seq reveal that Prx1+ fibroblasts exhibit progenitor signatures in physiologic and injured conditions. Mechanistically, Prx1+ progenitors accelerate wound healing by differentiating into immunomodulatory SCA1+ fibroblasts, which prime macrophage recruitment through CCL2 as a key part of pro-wound healing response. Furthermore, human Prx1+ fibroblasts share similar gene and spatial profiles compared to their murine counterpart. Thus, our data suggest that Prx1+ fibroblasts may provide a valuable source in regenerative procedures for the treatment of corneal wounds and enteropathic fibrosis.

Critical roles for CCR2 and the therapeutic potential of cenicriviroc in periodontitis: a pre-clinical study

AIM

CCR2 plays important roles in many inflammatory and bone metabolic diseases, but its specific role in periodontitis is unknown. In the present study, we aimed to explore the role of CCR2 in the progression of periodontitis and evaluate the effect of cenicriviroc (CVC) on periodontitis.

METHODS

The expression of CCR2 was studied in patients with periodontitis and in ligation-induced murine model of periodontitis. The role of CCR2 in promoting inflammation and bone resorption in periodontitis was evaluated in Ccr2^-/- mice and wild-type mice. The effect of CVC in the prevention and treatment of periodontitis was evaluated by systemic and local medication. Micro-CT, Hematoxylin and eosin staining, tartrate-resistant acid phosphatase staining, real-time qPCR, ELISA, and flow cytometric were used for histomorphology, molecular biology and cytology analysis respectively.

RESULTS

In this study, we demonstrated that CCR2 was highly expressed in human and murine periodontitis and that CCR2 deficiency was associated with decreased inflammation, alveolar bone resorption, osteoclast number, monocyte and macrophage infiltration. Prevention and treatment with CVC significantly reduced the severity of periodontitis, regardless of whether it was administered systemically or locally.

CONCLUSION

CCR2 plays an important role in the development and progression of periodontitis and CVC is a potential drug for the prevention and treatment of periodontitis.

Aseptic and septic prosthetic joint loosening: Impact of biomaterial wear on immune cell function, inflammation, and infection

The success of total joint replacements has led to consistent growth in the use of arthroplasty in progressively younger patients. However, more than 10 percent of patients require revision surgeries due to implant failure caused by osteolytic loosening. These failures are classified as either aseptic or septic and are associated with the presence of particulate wear debris generated by mechanical action between implant components. Aseptic loosening results from chronic inflammation caused by activation of resident immune cells in contact with implant wear debris. In contrast, septic loosening is defined by the presence of chronic infection at the implant site. However, recent findings suggest that subclinical biofilms may be overlooked when evaluating the cause of implant failure, leading to a misdiagnosis of aseptic loosening. Many of the inflammatory pathways contributing to periprosthetic joint infections are also involved in bone remodeling and resorption. In particular, wear debris is increasingly implicated in the inhibition of the innate and adaptive immune response to resolve an infection or prevent hematogenous spread. This review examines the interconnectivity of wear particle- and infection-associated mechanisms of implant loosening, as well as biomaterials-based strategies to combat infection-related osteolysis.

Inhibition of CCL2 by bindarit alleviates diabetes-associated periodontitis by suppressing inflammatory monocyte infiltration and altering macrophage properties

Diabetes-associated periodontitis (DP) aggravates diabetic complications and increases mortality from diabetes. DP is caused by diabetes-enhanced host immune-inflammatory responses to bacterial insult. In this study, we found that persistently elevated CCL2 levels in combination with proinflammatory monocyte infiltration of periodontal tissues were closely related to DP. Moreover, inhibition of CCL2 by oral administration of bindarit reduced alveolar bone loss and increased periodontal epithelial thickness by suppressing periodontal inflammation. Furthermore, bindarit suppressed the infiltration of proinflammatory monocytes and altered the inflammatory properties of macrophages in the diabetic periodontium. This finding provides a basis for the development of an effective therapeutic approach for treating DP.

Cannabinoid type-2 receptor agonist, inverse agonist, and anandamide regulation of inflammatory responses in IL-1β stimulated primary human periodontal ligament fibroblasts

OBJECTIVE

The aim of this study is to understand the role of cannabinoid type 2 receptor (CB2R) during periodontal inflammation and to identify anti-inflammatory agents for the development of drugs to treat periodontitis (PD).

BACKGROUND

Cannabinoid type 2 receptor is found in periodontal tissue at sites of inflammation/infection. Our previous study demonstrated anti-inflammatory responses in human periodontal ligament fibroblasts (hPDLFs) via CB2R ligands.

METHODS

Anandamide (AEA), HU-308 (agonist), and SMM-189 (inverse agonist) were tested for effects on IL-1β-stimulated cytokines, chemokines, and angiogenic and vascular markers expressed by hPDLFs using Mesoscale Discovery V-Plex Kits. Signal transduction pathways (p-c-Jun, p-ERK, p-p-38, p-JNK, p-CREB, and p-NF-kB) were investigated using Cisbio HTRF kits. ACTOne and Tango™ -BLA functional assays were used to measure cyclic AMP (cAMP) and β-arrestin activity.

RESULTS

IL-1β stimulated hPDLF production of 18/39 analytes, which were downregulated by the CB2R agonist and the inverse agonist. AEA exhibited pro-inflammatory and anti-inflammatory effects. IL-1β increased phosphoproteins within the first hour except p-JNK. CB2R ligands attenuated p-p38 and p-NFĸB, but a late rise in p-38 was seen with HU-308. As p-ERK levels declined, a significant increase in p-ERK was observed later in the time course by synthetic CB2R ligands. P-JNK was significantly affected by SMM-189 only, while p-CREB was elevated significantly by CB2R ligands at 180 minutes. HU-308 affected both cAMP and β-arrestin pathway. SMM-189 only stimulated cAMP.

CONCLUSION

The findings that CB2R agonist and inverse agonist may potentially regulate inflammation suggest that development of CB2R therapeutics could improve on current treatments for PD and other oral inflammatory pathologies.

Association between Monocyte Chemoattractant Protein-1 -2518 (A/G) Single Nucleotide Polymorphism and Chronic Periodontitis in End-stage Renal Disease Patients - A Case-control Study

Monocyte chemoattractant protein 1 (MCP-1) plays an important role in the development of periodontitis. The purpose of this investigation was to evaluate association of the  MCP-1 gene polymorphism with chronic periodontitis in patients with end-stage renal disease (ESRD). One hundred fifty ESRD patients with chronic periodontitis (CP), 100 without CP and 190 healthy controls were included in this study. Genomic DNA from all participants was genotyped for the -2518 (A/G) polymorphism by a polymerase chain reaction - restriction fragment length polymorphism (PCR--RFLP) assay. Significant differences were observed in the genotype and allele frequencies between patients with ESRD and CP and controls.  The G allele frequency was significantly higher in patients than in control subjects, with odds ratio 1.77 (95 % CI 1.2-2.5), p = 0.0014. For the GG genotype the OR was 3.63 (95 % CI 1.5-8.76), p = 0.041.  No significant differences in the polymorphism distribution were observed between ESRD patients  without CP and control subjects. Comparison of the MCP-1 gene polymorphism distribution in ESRD patients with various primary diseases leading to ESRD did not show any significant differences. The mean MCP-1 serum levels were compared between subgroups. They were significantly higher in ESRD patients with CP (582 ± 112 pg/ml) than in patients without CP (309 ± 103 pg/ml) and controls (265 ± 85 pg/ml). Our results suggest that the MCP-1-2518 A/G  polymorphism might be a novel risk factor for developing chronic periodontitis in patients with ESRD.

Evaluation of chemokine CXCL10 in human gingival crevicular fluid, saliva, and serum as periodontitis biomarker

Purpose

The aim of this study was to evaluate CXCL10 as a biomarker for periodontitis by determining the CXCL10 levels in saliva, serum, and gingival crevicular fluid (GCF) samples from periodontally healthy control subjects and adult subjects with chronic periodontitis.

Patients and methods

Adult patients seeking dental treatment at Umm Al-Qura University dental clinic underwent a complete periodontal examination, and saliva, serum, and GCF samples were collected. Subjects were classified as chronic periodontitis patients (n=31) if they have a periodontal probing depth (PD) of ≥4 mm and/or clinical attachment level (CAL) of ≥3 mm in >30% of the teeth. The control group (n=25) had PD ≤3 mm and/or CAL ≤2 mm. ELISA was performed to determine the concentration of CXCL10 in saliva, serum, and GCF samples. Student’s t-test was carried out to evaluate the significant difference between different groups. Spearman’s correlation test was used to analyze the relationship between the levels of CXCL10 and the clinical periodontal parameters. P-value of ≤0.05 was considered significant.

Results

Significantly higher concentrations of CXCL10 were found in saliva and serum in chronic periodontitis patients as compared with the controls (272±60.4 pg/mL and 72±13.4 pg/mL vs 130±22.2 pg/mL and 44.08±4.5 pg/mL, P≤0.05). The CXCL10 levels in GCF were higher in the periodontitis group as compared with the control group (66.36±32.0 pg/mL and 44.56±17.5 pg/mL, respectively); the difference did not reach statistical significance (P≥0.05). Moreover, serum CXCL10 level was significantly higher in periodontitis patients with moderate to severe bone loss as compared with those with mild bone loss (71.05±4.7 pg/mL vs 54.8±7.7 pg/mL, P≤0.05). The serum CXCL10 levels were found to be related to CAL measurements (r=0.3, P=0.026), while the saliva CXCL10 levels were related to PD measurements (r=0.8, P=0.0007).

Conclusion

CXCL10 is significantly increased in periodontitis subjects as compared with controls and could be used as a marker for periodontal disease.

Gingival crevicular fluid levels of monocyte chemoattractant protein-1 in patients with aggressive periodontitis

OBJECTIVES

The purpose of this study was to investigate the gingival crevicular fluid (GCF) levels of monocyte chemoattractant protein (MCP)-1 in aggressive periodontitis (AgP) and whether GCF MCP-1 levels differ among localized (L) AgP and generalized (G) AgP.

MATERIAL AND METHODS

A total of 160 subjects including 80 AgP and 80 age- and gender-matched periodontally healthy (H) controls were recruited in this cross-sectional study (NCT02927704). GCF samples were collected from 160 patients including 50 LAgP, 30 GAgP, and 80 H. Volume of GCF was measured by Periotron 8000^® , and enzyme-linked immunosorbent assay was used to assess MCP-1 levels.

RESULTS

Compared to H controls, all clinical parameters and total amounts (pg 30 s^-1 ) of MCP-1 were significantly higher in subjects with LAgP and GAgP (P < 0.05). Although concentrations of GCF MCP-1 did not differ between LAgP and GAgP (P > 0.05), total amounts of MCP-1 were higher in GAgP than LAgP (P < 0.05).

CONCLUSION

It can be concluded that the total amount of MCP-1 level in GCF may be a potential determinant in AgP subjects. Increased MCP-1 levels in line with the degree of periodontal destruction in GAgP patients reveal that MCP-1 can be used to understand the disease pathogenesis of LAgP and GAgP.

Role of tumor microenvironment in tumorigenesis

Tumorigenesis is a complex and dynamic process, consisting of three stages: initiation, progression, and metastasis. Tumors are encircled by extracellular matrix (ECM) and stromal cells, and the physiological state of the tumor microenvironment (TME) is closely connected to every step of tumorigenesis. Evidence suggests that the vital components of the TME are fibroblasts and myofibroblasts, neuroendocrine cells, adipose cells, immune and inflammatory cells, the blood and lymphatic vascular networks, and ECM. This manuscript, based on the current studies of the TME, offers a more comprehensive overview of the primary functions of each component of the TME in cancer initiation, progression, and invasion. The manuscript also includes primary therapeutic targeting markers for each player, which may be helpful in treating tumors.

Chemokines in Oral Inflammatory Diseases: Apical Periodontitis and Periodontal Disease

The inflammatory oral diseases are characterized by the persistent migration of polymorphonuclear leukocytes, monocytes, lymphocytes, plasma and mast cells, and osteoblasts and osteoclasts. In the last decade, there has been a great interest in the mediators responsible for the selective recruitment and activation of these cell types at inflammatory sites. Of these mediators, the chemokines have received particular attention in recent years. Chemokine messages are decoded by specific receptors that initiate signal transduction events, leading to a multitude of cellular responses, including chemotaxis and activation of inflammatory and bone cells. However, little is known about their role in the pathogenesis of inflammatory oral diseases. The purpose of this review is to summarize the findings regarding the role of chemokines in periapical and periodontal tissue inflammation, and the integration, into experimental models, of the information about the role of chemokines in human diseases.

Increased Eotaxin and MCP-1 Levels in Serum from Individuals with Periodontitis and in Human Gingival Fibroblasts Exposed to Pro-Inflammatory Cytokines

Periodontitis is a chronic inflammatory disease of tooth supporting tissues resulting in periodontal tissue destruction, which may ultimately lead to tooth loss. The disease is characterized by continuous leukocyte infiltration, likely mediated by local chemokine production but the pathogenic mechanisms are not fully elucidated. There are no reliable serologic biomarkers for the diagnosis of periodontitis, which is today based solely on the degree of local tissue destruction, and there is no available biological treatment tool. Prompted by the increasing interest in periodontitis and systemic inflammatory mediators we mapped serum cytokine and chemokine levels from periodontitis subjects and healthy controls. We used multivariate partial least squares (PLS) modeling and identified monocyte chemoattractant protein-1 (MCP-1) and eotaxin as clearly associated with periodontitis along with C-reactive protein (CRP), years of smoking and age, whereas the number of remaining teeth was associated with being healthy. Moreover, body mass index correlated significantly with serum MCP-1 and CRP, but not with eotaxin. We detected higher MCP-1 protein levels in inflamed gingival connective tissue compared to healthy but the eotaxin levels were undetectable. Primary human gingival fibroblasts displayed strongly increased expression of MCP-1 and eotaxin mRNA and protein when challenged with tumor necrosis factor-α (TNF-α and interleukin-1β (IL-1β), key mediators of periodontal inflammation. We also demonstrated that the upregulated chemokine expression was dependent on the NF-κΒ pathway. In summary, we identify higher levels of CRP, eotaxin and MCP-1 in serum of periodontitis patients. This, together with our finding that both CRP and MCP-1 correlates with BMI points towards an increased systemic inflammatory load in patients with periodontitis and high BMI. Targeting eotaxin and MCP-1 in periodontitis may result in reduced leukocyte infiltration and inflammation in periodontitis and maybe prevent tooth loss.

Fundamental study of osteoclast chemotaxis toward chemoattractants expressed in periodontitis

BACKGROUND AND OBJECTIVE

Periodontitis is a chronic inflammatory disease that leads to bone resorption by osteoclasts (OCs). Several factors contribute to the differentiation of OCs from hematopoietic precursors. Cellular chemotactic factors are expressed in periodontitis tissue, but the effects of these chemoattractants on OCs are not well understood. Here we examined the effects of chemoattractants produced in inflamed periodontal tissue on OC chemotaxis.

MATERIAL AND METHODS

Rat bone-marrow OCs were cultured in OC culture medium for 3 or 6 d. Using EZ-TAXIScan™, the chemotactic response of these OCs to several chemoattractants [monocyte chemotactic protein-1; macrophage inflammatory protein 1α; regulated on activation, normal T-cell expressed and secreted; stromal cell-derived factor-1α; and complement activation product 5a (C5a)] was measured. In addition, we measured the effect of C5a-specific inhibitors on chemotactic responses toward C5a. The recorded chemotactic responses were quantitatively analysed using ImageJ software.

RESULTS

Chemoattractants associated with periodontal disease significantly increased the chemotactic activity of differentiated rat OCs in a concentration-dependent manner, with C5a inducing the highest chemotactic activity of OCs cultured for 3 or 6 d. The C5a-specific inhibitor significantly inhibited chemotaxis toward C5a in a concentration-dependent manner.

CONCLUSION

We suggest that C5a plays an important role in pathologic bone resorption in periodontal disease by stimulating the chemotaxis of OCs. Therefore, C5a is a potential target for the treatment of periodontal disease.

Effects of resolvin D1 on cell survival and cytokine expression of human gingival fibroblasts

BACKGROUND

Tissue breakdown in periodontitis is initiated by bacteria, such as Porphyromonas gingivalis, and is caused largely by host responses. Resolvins protect the host against acute inflammation by blocking the migration of polymorphonuclear neutrophils to initiate resolution. The effects of resolvins on human gingival fibroblasts (HGFs) are unknown. This study examines the effects of resolvin D1 on HGF survival and cytokine expression when treated with or without P. gingivalis supernatant.

METHODS

Cytotoxicity of resolvin D1 on HGFs with or without a toxic level of P. gingivalis supernatant was measured with lactate dehydrogenase assays. Cytokine arrays were performed on HGF-conditioned media treated with or without resolvin D1 and with or without P. gingivalis supernatant.

RESULTS

Resolvin D1 had no cytotoxic effects on HGFs at concentrations between 1 and 1,000 nM (all P > 0.05). Resolvin D1 (1,000 nM) significantly inhibited the toxic effects of 13.5% (v/v) P. gingivalis supernatant on HGFs (P = 0.002). Resolvin D1 significantly reduced the expression of interleukin (IL)-6 (P = 0.010) and monocyte chemoattractant protein (MCP)-1 (P = 0.04) in untreated fibroblasts. P. gingivalis (10%) supernatant significantly increased the expression levels of granulocyte-macrophage colony-stimulating factor (CSF), granulocyte CSF, growth-regulated oncogene (GRO), IL-5, IL-6, IL-7, IL-8, IL-10, MCP-1, MCP-2, MCP-3, and monokine induced by γ-interferon. Resolvin D1 significantly reduced the expression of GRO (P = 0.04), marginally reduced the levels of MCP-1 (P = 0.10), and marginally increased the levels of transforming growth factor (TGF)-β1 (P = 0.07) from HGFs treated with P. gingivalis supernatant.

CONCLUSIONS

Resolvin D1 altered the cytotoxicity of P. gingivalis supernatant on HGFs. Resolvin D1 significantly reduced GRO, marginally reduced MCP-1, and marginally increased TGF-β1 from P. gingivalis-treated HGFs, which could alter the ability of P. gingivalis to induce inflammation.

Role of monocyte chemoattractant protein-1 (MCP-1) as an immune-diagnostic biomarker in the pathogenesis of chronic periodontal disease

OBJECTIVE

Monocyte chemoattractant protein-1 (MCP-1) is an important chemokine responsible for the initiation, regulation and mobilization of monocytes to the active sites of severe periodontal inflammation. The present study aims at evaluating the levels of MCP-1 in GCF, saliva and serum and to analyze the changes following phase I periodontal therapy. Assessment of possible correlations between levels of MCP-1 in the three biological fluids was also done.

METHODS

Fifteen healthy and 30 patients of severe chronic periodontitis (diseased) participated in the study. Patients of the diseased group underwent scaling/root planing. Evaluation of PI, GI, PD, CAL and collection of samples of GCF, serum and saliva was done at baseline and 6 weeks following periodontal therapy. MCP-1 levels were quantified in all samples using ELISA.

RESULTS

Compared to healthy controls, MCP-1 levels were statistically significantly higher in GCF (p<0.001), saliva (p=0.002) and serum (p<0.001) in subjects with chronic periodontitis. Levels of MCP-1 in all the three fluids decreased significantly in patients after periodontal therapy (p<0.001). There was a significant positive correlation between MCP-1 levels in GCF, saliva and serum in patients of chronic periodontitis both pre (r>0.9) and post-treatment (r>0.6).

CONCLUSIONS

The results suggest that levels of MCP-1 in GCF and saliva can be reliable indicators of severity of periodontal destruction and their serum levels reflect the systemic impact of this local inflammatory disease thereby strengthening the reciprocal oro-systemic association.

Association analysis between the -2518MCP-1(A/G) polymorphism and generalized aggressive periodontitis in a Chinese population

BACKGROUND AND OBJECTIVE

It has been suggested that aggressive periodontitis has a genetic basis. Monocyte chemoattractant protein 1 (MCP-1) plays a critical role in the recruitment of monocytes and the development of periodontitis. The -2518MCP-1(A/G) polymorphism has been implicated as a risk or susceptibility factor for a variety of autoimmune conditions and inflammatory diseases. The intent of this investigation was to study whether the -2518MCP-1(A/G) polymorphism is associated with generalized aggressive periodontitis in the Chinese population.

MATERIAL AND METHODS

One hundred and twenty-four patients with generalized aggressive periodontitis and 94 healthy subjects were included in this case-control study. Genomic DNA was isolated from a peripheral blood sample obtained from each subject. Gene polymorphisms of -2518MCP-1(A/G) were analyzed by a standard polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. A logistic regression analysis was performed to test the association between the -2518MCP-1(A/G) genotype (alleles) and generalized aggressive periodontitis with adjustment of the major covariates (gender, age and smoking status).

RESULTS

There was no significant association of the -2518MCP-1(A/G) polymorphism with generalized aggressive periodontitis in the unstratified subjects. However, when patients were stratified by gender, the frequency of the G(+) genotype was significantly lower in female patients with generalized aggressive periodontitis compared with female controls (p = 0.036, adjusted odds ratio = 0.3, 95% CI: 0.1-0.9). In female patients with generalized aggressive periodontitis, the probing pocket depth was larger in subjects with the AA genotype than in subjects with the G(+) genotype (5.07 mm vs. 4.30 mm; Z = -2.470, p = 0.014).

CONCLUSION

The polymorphisms of -2518MCP-1 may play an important role in determining generalized aggressive periodontitis susceptibility in this cohort of Chinese women.

MCP-1 and CCR2 gene variants and the risk for osteoporosis and osteopenia

AIM

In this study, we investigated whether monocyte chemotactic protein 1 (MCP-1) and CC chemokine receptor 2 (CCR2) gene polymorphisms account for an increased risk of osteoporosis or osteopenia.

METHODS

Three hundred three postmenopausal women, 80 osteoporotic, 123 osteopenic, and 100 unrelated age-matched healthy controls, were included in the study. Genotyping of MCP-1 A2518G and CCR2 V64I gene polymorphisms were detected by PCR-RFLP.

RESULTS

We, for the first time, demonstrated the positive association of MCP-1 GG, CCR2 Val/Ile, and CCR2 Val+ genotype with osteoporosis risk. However, CCR2 Ile/Ile genotype frequencies were high in the control group compared with those of the patients with osteoporosis and osteopenia. Haplotype analysis confirmed the association of MCP-1/CCR2 gene variants with osteopenia and revealed that the frequency of MCP-1 A:CCR2 Val haplotype was significantly higher in patients when compared with controls.

CONCLUSIONS

In conclusion, our findings have suggested that MCP-1 and CCR2 gene variants were risk factors for osteoporosis and osteopenia.

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

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

Inflammation and uncoupling as mechanisms of periodontal bone loss

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

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

OBJECTIVES

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

DESIGN

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

RESULTS

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

CONCLUSIONS

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

Mechanisms of tooth eruption and orthodontic tooth movement

Teeth move through alveolar bone, whether through the normal process of tooth eruption or by strains generated by orthodontic appliances. Both eruption and orthodontics accomplish this feat through similar fundamental biological processes, osteoclastogenesis and osteogenesis, but there are differences that make their mechanisms unique. A better appreciation of the molecular and cellular events that regulate osteoclastogenesis and osteogenesis in eruption and orthodontics is not only central to our understanding of how these processes occur, but also is needed for ultimate development of the means to control them. Possible future studies in these areas are also discussed, with particular emphasis on translation of fundamental knowledge to improve dental treatments.

Substance P regulates macrophage inflammatory protein 3alpha/chemokine C-C ligand 20 (CCL20) with heme oxygenase-1 in human periodontal ligament cells

Although substance P (SP), a potent proinflammatory peptide, is involved in inflammation and immune responses, the effect of SP on the expression of macrophage inflammatory protein 3alpha[MIP-3alpha, chemokine C-C ligand 20 (CCL20)] in periodontal ligament (PDL) cells is unknown. Equally enigmatic is the link between SP, the stress protein heme oxygenase-1 (HO-1), and CCL20 production. We investigated whether SP induces the release of chemokine CCL20 from immortalized PDL (IPDL) cells, and further clarify SP-mediated pathways. We also examined the relationship between HO-1 and CCL20 by treating PDL cells with SP. Incubating IPDL cells with SP increased expression of CCL20 mRNA and CCL20 protein in a dose-time-dependent manner. Highly selective p38 and extracellular-regulated kinase 1/2 (ERK1/2) inhibitors abrogated SP-induced expression of CCL20 in IPDL cells. SP is also responsible for initiating phosphorylation of IkappaB, degradation of IkappaB and activation of nuclear factor (NF)-kappaB. SP induced expression of HO-1 in both a concentration- and time-dependent manner, and CCL20 reflected similar patterns. The inductive effects of SP on HO-1 and CCL20 were enhanced by HO-1 inducer hemin and the membrane-permeable guanosine 3',5'-monophosphate (cGMP) analogue 8-bromo-cGMP. Conversely, this pathway was inhibited by the HO-1 inhibitor zinc protoporphyrin IX (ZnPP IX) and the selective inhibitor of guanylate cyclase, 1H-(1,2,4)oxadiazole(4,3-a)quinoxalin-1-one (ODQ). We report herein the pathway that connects SP along with other modulators of neuroimmunoregulation to the induction of HO-1 and the inflammatory mediator macrophage inflammatory protein (MIP)-3alpha/CCL20 in IPDL cells, which play an important role in the development of periodontitis or inflammation during orthodontic tooth movement.

Gingival levels of monocyte chemoattractant protein-1 (MCP-1) in diabetes mellitus and periodontitis: an experimental study in rats

The objectives of this study were to investigate and compare the monocyte chemoattractant protein-1 (MCP-1) levels of gingival tissues in diabetes mellitus (DM) and periodontitis and to reveal the effects of MCP-1 on periodontal inflammation and destruction in these diseases. DM was created in 15 rats (group 1) by streptozotocin injection, and periodontitis was obtained by ligature induction in 15 rats (group 2). Fifteen systemically and periodontally healthy rats were used as control (group 3). Gingival MCP-1 levels were measured by enzyme-linked immunosorbent assay (ELISA). Periodontal inflammation was quantified by the inflammatory cell infiltration in the gingival samples, whereas periodontal destruction was assessed by the alveolar bone loss in the experimental regions. MCP-1 concentrations were higher in groups 1 and 2 than in group 3 (p < 0.001). Increased gingival inflammatory cell infiltration and alveolar bone loss were observed in groups 1 and 2 compared to group 3 (p < 0.001). There were positive correlations among the MCP-1 level, gingival inflammatory cell infiltration, and alveolar bone loss in groups 1 and 2 (p < 0.001). Our results suggest that (1) DM may lead to enhanced MCP-1 production in periodontal tissues likewise for periodontitis and (2) there may be a positive correlation between the MCP-1 concentration and diseased nature of periodontium in both diseases.

Gingival crevicular fluid levels of monocyte chemoattractant protein-1 and tumor necrosis factor-alpha in patients with chronic and aggressive periodontitis

BACKGROUND

Monocyte chemoattractant protein-1 (MCP-1) is a well-known chemotactic cytokine that regulates mononuclear inflammatory cell recruitment. This recruitment has particular importance in the oral cavity because inflammatory cells will be challenged with periodontopathogenic bacteria during infections. Tumor necrosis factor-alpha (TNF-alpha) is a cytokine that induces bone resorption by stimulating proliferation and differentiation of osteoclasts' progenitors and also stimulates MCP-1 expression. The aims of this study were to investigate the presence of MCP-1 in gingival crevicular fluid (GCF) samples from patients with chronic periodontitis (CP) and aggressive periodontitis (AgP) and to examine the possible correlations between the GCF levels of MCP-1 and TNF-alpha.

METHODS

Twenty-five CP, 20 AgP, and 20 healthy control (C) patients were selected for the study. Plaque index (PI), gingival index (GI), probing depth (PD), and clinical attachment level (CAL) measurements were recorded from each sampling area. Assays for GCF MCP-1 and TNF-alpha were carried out by an enzyme-linked immunosorbent assay (ELISA) method.

RESULTS

The concentration (nanograms per microliters) and total MCP-1 and TNF-alpha (nanograms per site) were not statistically significant between CP and AgP groups, but total MCP-1 and TNF-alpha was statistically different between CP and C and between AgP and C groups (P <0.001). All clinical parameters were statistically different between CP and C and between AgP and C groups (P <0.001). A positive statistical correlation was detected between the levels of MCP-1 and TNF-alpha, and there was also a positive correlation between all clinical parameters and total MCP-1 and TNF-alpha levels.

CONCLUSIONS

These results suggest that MCP-1 could have an important role in the activation and recruitment of inflammatory and immune cells in periodontal diseases, and both AgP and CP patients may have the same pattern of MCP-1 expression. A strong positive correlation between the GCF levels of MCP-1 and TNF-alpha may account for the mechanism of amplification of inflammatory events in gingival inflammation.

Increase of CCL20 expression by human gingival fibroblasts upon stimulation with cytokines and bacterial endotoxin

We have demonstrated recently that CCL20 was expressed in periodontal diseased tissues and abundant CCR6 positive T cells infiltrated in periodontally diseased tissue. However, it is uncertain which cells can elicit CCL20 production. In the present study, we examined the properties of CCL20 production by human gingival fibroblasts (HGF) culture. Here, we report that interleukin-1 beta (IL-1beta), tumour necrosis factor-alpha (TNF-alpha) and Escherichia coli lipopolysaccharide (LPS) can significantly induce the production of CCL20 by HGF. We found that TNF-alpha and E. coli LPS enhanced the production of CCL20 by HGF treated with IL-1beta. In contrast, interferon-gamma (IFN-gamma) dramatically diminished CCL20 production induced by IL-1beta. Moreover, we demonstrated that nuclear factor-kappaB (NF-kappaB), p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinases (ERK) play an important role in mediating the production of CCL20 induced by IL-1beta and TNF-alpha. On the other hand, we found that not only NF-kappaB, p38 MAPK and ERK but also c-Jun NH2-terminal kinase (JNK) are involved in CCL20 production induced by E. coli LPS. Finally, we found that HGF express CCR6, CCL20 receptor, and CCL20 induced vascular endothelial growth factor (VEGF) by HGF. Taken together, these findings that HGF will be a source of CCL20 in periodontal tissue, and the CCL20 production will be controlled by proinflammatory cytokine and bacterial LPS in periodontally diseased tissue. Thus, CCL20 by HGF might be involved in inflammatory cells infiltration, and promote the progression of periodontal disease.

Cytokine profiling of macrophages exposed to Porphyromonas gingivalis, its lipopolysaccharide, or its FimA protein

To characterize the roles of Porphyromonas gingivalis and its components in the disease processes, we investigated the cytokine profile induced by live P. gingivalis, its lipopolysaccharides (LPS), and its major fimbrial protein, fimbrillin (FimA). Using cytokine antibody arrays, we found that P. gingivalis LPS and FimA induced a similar profile of cytokine expression when exposed to mouse peritoneal macrophages but that this profile differed significantly in response to live P. gingivalis. In vitro, mouse peritoneal macrophages were stimulated to produce interleukin-6 (IL-6), granulocyte colony-stimulating factor, and lymphotactin by live P. gingivalis, but not by P. gingivalis LPS or FimA, while RANTES, gamma interferon, IL-17, vascular cell adhesion molecule 1 (VCAM-1), and vascular endothelial growth factor were induced by P. gingivalis LPS or FimA, but not by live P. gingivalis. In vivo, IL-6 mRNA was strongly induced only by live P. gingivalis while monocyte chemoattractant protein 1 mRNA was strongly induced only by P. gingivalis LPS and FimA in mouse calvarial scalp, further confirming the differences of cytokine profile induced in vitro. Cytokine antibody arrays using toll-like receptor 2 (TLR2)- and TLR4-deficient macrophages revealed that most of the cytokines induced by P. gingivalis LPS or FimA signal through TLR2, while most of cytokines induced by live P. gingivalis signal through both TLR2 and TLR4. Interestingly, the activation of TLR2 by live P. gingivalis inhibited the release of RANTES, VCAM-1, and IL-1alpha from mouse peritoneal macrophages. A tumor necrosis factor alpha enzyme-linked immunosorbent assay further confirmed that P. gingivalis LPS and FimA activate mouse peritoneal macrophages via TLR2. These results indicate that host immune cells sense live P. gingivalis and its components differently, which translates into the expression of different inflammatory cytokine profiles.

Gingival crevicular fluid monocyte chemoattractant protein-1 and RANTES levels in patients with generalized aggressive periodontitis

BACKGROUND

Local and systemic inflammatory and immune mechanisms may be implicated in the pathogenesis of the aggressive forms of periodontal disease. Chemokines, monocyte chemoattractant protein-1 (MCP-1) and regulated on activation, normal T cells expressed and secreted RANTES (regulated on activation, normal T cells expressed and secreted), are involved in the activation and recruitment of inflammatory and immune cells to the infected sites and thereby mediating a variety of pathophysiological conditions. The aim of the present study was to examine the gingival crevicular fluid (GCF) levels of MCP-1 and RANTES in patients with generalized agressive periodontitis (G-AgP).

METHODS

MCP-1 and RANTES levels were investigated in GCF samples of 10 patients with G-AgP and 10 periodontally healthy subjects. Periodontal status was evaluated by measuring probing depth, clinical attachment loss, presence of bleeding on probing and plaque. In the G-AgP group, GCF samples were collected from the two approximal sites; from one single-rooted tooth and from one first molar tooth with > or =6 mm probing depth. In the healthy group, GCF samples were collected from one of the single-rooted teeth. GCF MCP-1 and RANTES levels were quantified by enzyme immunoassay.

RESULTS

The G-AgP patients had significantly higher GCF MCP-1 and RANTES levels compared to the healthy group (p<0.05). GCF MCP-1 and RANTES levels were positively correlated with both probing depth and clinical attachment loss (p<0.05). There was no correlation between GCF MCP-1 and RANTES levels and the percentage of sites with bleeding (p>0.05).

CONCLUSIONS

The results of the present study suggest that MCP-1 and RANTES could play key roles in both activation and recruitment of inflammatory and immune cells in periodontal environment of G-AgP patients. In conclusion, these CC chemokines may be considered in the biological mechanism underlying the pathogenesis and progression of G-AgP.

Potential role of vascular endothelial growth factor, interleukin-8 and monocyte chemoattractant protein-1 in periodontal diseases

Host-mediated immunoinflammatory pathways activated by bacteria lead to destruction of the periodontal connective tissues and alveolar bone. The objective of this study was to elucidate the activation of the inflammatory processes in periodontal disease by quantitative assessment of cytokines and periodontopathogens. Gingival crevicular fluids (GCF) and subgingival plaque samples were collected from patients with chronic periodontitis and gingivitis and from periodontally healthy sites. Vascular endothelial growth factor (VEGF), monocyte chemoattractant protein-1 (MCP-1), and interleukin 8 (IL-8) in GCF were analyzed by enzyme-linked immunosorbent assay. Periodontopathogens, including Bacteroides forsythus, Campylobacter rectus, Porphyromonas gingivalis and Prevotella intermedia, were analyzed by immunofluorescence and dark-field microscopy. There was significantly more VEGF and IL-8 in chronic periodontitis and gingivitis sites than in periodontally healthy sites. There were significant positive correlations between the concentrations and total amounts of VEGF and IL-8 in chronic periodontitis and gingivitis sites, and between the levels of periodontopathogens and the total amounts of VEGF, MCP-1 and IL-8. These data indicate that inflammatory processes induced by periodontopathogens and the activation of certain cytokines (VEGF, MCP-1, IL-8) in periodontal diseases may be relevant to host-mediated destruction in chronic periodontitis.

Cellular, molecular, and genetic determinants of tooth eruption

Tooth eruption is a complex and tightly regulated process that involves cells of the tooth organ and the surrounding alveolus. Mononuclear cells (osteoclast precursors) must be recruited into the dental follicle prior to the onset of eruption. These cells, in turn, fuse to form osteoclasts that resorb alveolar bone, forming an eruption pathway for the tooth to exit its bony crypt. Some of the molecules possibly involved in the signaling cascades of eruption have been proposed in studies from null mice, osteopetrotic rodents, injections of putative eruption molecules, and cultured dental follicle cells. In particular, recruitment of the mononuclear cells to the follicle may require colony-stimulating factor-one (CSF-1) and/or monocyte chemotactic protein-1 (MCP-1). Osteoclastogenesis is needed for the bone resorption and may involve inhibition of osteoprotegerin transcription and synthesis in the follicle, as well as enhancement of receptor activator of NF kappa B ligand (RANKL), in the adjacent alveolar bone and/or in the follicle. Paracrine signaling by parathyroid-hormone-related protein and interleukin -1 alpha, produced in the stellate reticulum adjacent to the follicle, may also play a role in regulating eruption. Osteoblasts might also influence the process of eruption, the most important physiologic role likely being at the eruptive site, in the formation of osteoclasts through signaling via the RANKL/OPG pathway. Evidence thus far supports a role for an osteoblast-specific transcription factor, Cbfa1 (Runx2), in molecular events that regulate tooth eruption. Cbfa1 is also expressed at high levels by the dental follicle cells. This review concludes with a discussion of the several human conditions that result in a failure of or delay in tooth eruption.

CD14-mediated induction of interleukin-8 and monocyte chemoattractant protein-1 by a heat-resistant constituent of Porphyromonas gingivalis in endothelial cells

Viable and inactivated Porphyromonas gingivalis dose-dependently induced interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) secretion in human umbilical vein endothelial cells (HUVECs). The inactivated P. gingivalis, in comparison with viable bacteria, tended to enhance the production of both chemokines more strongly. The production of MCP-1 protein began increasing immediately after stimulation by P. gingivalis, and there was a nearly linear increase from 0 to 8 h of incubation, whereas IL-8 production showed a linear increase between 4 and 12 h of incubation. The IL-8 and MCP-1 mRNA expressions in HUVECs as determined by reverse transcriptase-polymerase chain reaction (RT-PCR) or Quantikine mRNA colorimetric quantification kits were found to be enhanced by P. gingivalis. Furthermore, the time courses of IL-8 and MCP-1 mRNA expressions were in accordance with those of protein production. Addition of polymyxin B or boiling did not weaken the stimulatory effect of P. gingivalis, which inhibited the effect of Escherichia coli lipopolysaccharide (E. coli LPS) and tumour necrosis factor-alpha (TNF-alpha), respectively. In contrast, the induction of IL-8 and MCP-1 by P. gingivalis was significantly reduced by anti-CD14 antibody. Our results suggest that some heat-stable component of P. gingivalis, including LPS, may be responsible for the induction of IL-8 and MCP-1 in HUVECs by a CD14-dependent mechanism. These effects might be involved in the accumulation and activation of neutrophils and monocytes at an early stage of the periodontal pathogenesis.

Macrophage inflammatory protein 3alpha-CC chemokine receptor 6 interactions play an important role in CD4+ T-cell accumulation in periodontal diseased tissue

The regulatory role of chemokines and chemokine receptors on specific lymphocyte recruitment into periodontal diseased tissue is poorly characterized. We observed that lymphocytes infiltrating inflamed gingival tissue expressed marked levels of CCR6. In periodontal diseased tissue, the expression of MIP-3alpha mRNA was detected by RT-PCR and further, MIP-3alpha was distributed in the basal layer of gingival epithelial cells, microvascular endothelial cells and the areas of inflammatory cells as shown by immunohistochemistry. Moreover, CCR6-expressing cells infiltrated into periodontal diseased tissue, and the proportion of CCR6-positive CD4+ T cells was significantly elevated in periodontal diseased tissue compared with peripheral blood in the same patients. Furthermore, gingival lymphocytes isolated from patients showed migration toward MIP-3alpha in an in vitro chemotaxis assay in which migration was abrogated by specific antibody to CCR6. Thus, these findings suggested that CCR6 and the corresponding chemokine, MIP-3alpha may have an important regulatory role in specific lymphocyte migration into inflamed periodontal tissue.

Biological characterization of lipopolysaccharide from Treponema pectinovorum

This study investigated the endotoxic and biological properties of purified lipopolysaccharide (LPS) isolated from an oral spirochete, Treponema pectinovorum. Endotoxicity, measured by Limulus amoebocyte lysate kinetic assay, showed that the LPS contained 1.28 endotoxin units per microg of purified LPS, which was approximately 4,000 times less than Escherichia coli O55:B5 LPS. To determine in vivo endotoxicity, LPS responder mice were administered LPS following galactosamine (GalN) sensitization. The LPS induced neither endotoxic symptoms nor lethality for 96 h, suggesting negligible or very low endotoxicity. In contrast, infection with live T. pectinovorum induced 100% lethality within 12 h in GalN-sensitized LPS responder mice, indicating an endotoxin-like property of this treponeme. Heat-killed microorganisms exhibited no lethality in GalN-sensitized mice, suggesting that the endotoxicity was associated with heat-labile components. To determine cytokine and chemokine induction by LPS, human gingival fibroblasts were stimulated and secretion of interleukin 1beta (IL-1beta), granulocyte-macrophage colony-stimulating factor, gamma interferon, IL-6, IL-8, and monocyte chemoattractant protein 1 (MCP-1) was assessed. The purified LPS induced significant amounts of only IL-6, IL-8, and MCP-1, although they were substantially lower than levels after challenge with live T. pectinovorum. After injection of LPS or live or heat-killed T. pectinovorum, serum was collected from mice and analyzed for proinflammatory cytokines IL-1beta, tumor necrosis factor alpha (TNF-alpha), and IL-6. LPS induced only IL-6 consistently. Both live and heat-killed T. pectinovorum induced serum IL-6, which was higher than the level detected following LPS administration. Importantly, live bacteria elicited systemic TNF-alpha and IL-1beta levels similar to those induced by a lethal dose of live E. coli O111. The results indicated that T. pectinovorum LPS has very low or no endotoxicity, although it can elicit low levels of cytokines from host cells. In contrast to the LPS, live T. pectinovorum demonstrated in vivo toxicity, which was associated with serum IL-1beta, TNF-alpha, and IL-6, suggesting an endotoxin-like property of a heat-labile molecule(s) of the spirochete.

Overexpression of monocyte chemoattractant protein 1 in systemic sclerosis: role of platelet-derived growth factor and effects on monocyte chemotaxis and collagen synthesis

OBJECTIVE

In addition to its chemotactic properties, recent evidence suggests that monocyte chemoattractant protein 1 (MCP-1) might participate in the fibrotic process by inducing the secretion of extracellular matrix (ECM) components. Since the factors that initiate the accumulation of inflammatory infiltrates and ECM deposits in systemic sclerosis (SSc) skin lesions are still unknown, this study was undertaken to examine the role of MCP-1 in SSc.

METHODS

In situ hybridization and immunohistochemistry studies for MCP-1 were performed on skin biopsy specimens from patients with SSc and healthy controls. To identify possible stimulators of MCP-1 overexpression in SSc lesions, cultured dermal fibroblasts were incubated with recombinant platelet-derived growth factor (PDGF) and analyzed by real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay. The chemotactic effects of SSc fibroblasts were examined using a modified Boyden chamber assay. To analyze the fibrotic potential of MCP-1, cultured dermal fibroblasts were incubated with recombinant MCP-1, and type I procollagen was measured by radioimmunoassay and real-time PCR.

RESULTS

MCP-1 was expressed by fibroblasts, keratinocytes, and perivascular infiltrates throughout the skin, in involved as well as uninvolved skin areas, from 10 of 11 SSc patients, whereas no expression of MCP-1 was found in healthy controls. Stimulation with PDGF resulted in a significant increase in MCP-1 messenger RNA and protein, with differences between healthy control fibroblasts and fibroblasts from SSc patients. The chemotactic activity for peripheral blood mononuclear cells of SSc fibroblast supernatants increased in a time-dependent manner. Antibodies blocking MCP-1 decreased the chemotactic activity of SSc fibroblasts by a mean +/- SD of 37 +/- 12%. Despite an increase in type I collagen levels over time, no effect of recombinant MCP-1 on the synthesis of type I collagen was observed.

CONCLUSION

These data indicate that MCP-1 might contribute to the initiation of inflammatory infiltrates in SSc. Possible stimuli of MCP-1 in dermal SSc lesions include PDGF, which is known to be expressed in SSc. In contrast to previous findings in fibrotic lung diseases, no effect of MCP-1 on collagen synthesis was observed in SSc dermal fibroblasts in vitro.

Involvement of T-lymphocytes in periodontal disease and in direct and indirect induction of bone resorption

Periodontal disease is a peripheral infection involving species of gram-negative organisms. T-lymphocytes can be found in the dense inflammatory infiltrate in this disease. CD4+ and CD8+ T-cells are present in periodontal lesions, as are memory/activated T-lymphocytes. In addition, Th1- and Th2-type T-lymphocytes and their associated cytokines with a subtle polarization to Th1 may be present. Th1-type T-cells up-regulate the production of pro-inflammatory cytokines IL-1 and TNF-alpha, which can induce bone resorption indirectly by promoting differentiation of osteoclast precursors and subsequently by activating osteoclasts. Such osteoclast differentiation is dependent on stimulation of osteoprotegerin ligand (OPG-L) production by osteoblastic cells. By contrast, activated T-cells, by virtue of direct production and expression of OPG-L, can directly promote osteoclast differentiation. OPG-L appears to be predominantly expressed on Th1-type cells. The direct and indirect T-cell involvement in periodontal bone resorption appears to be dependent on the degree of Th1-type T-cell recruitment into inflamed gingival tissues. This T-cell recruitment is regulated by adhesion molecules and chemokines/chemokine receptors. The adhesion molecules involved include alpha4 and alpha6 integrins, LFA-1, and ICAM-1. The Th1-type T-cells preferentially express CCR5 and CXCR3, which are found prominently in diseased gingivae. By contrast, little CCR4, expressed by Th2-type T-cells, can be detected. Also, the chemokine ligands RANTES, MIP1-alpha (both CCR5), and IP-10 (CXCR3 ligand) were elevated in inflamed periodontal tissues. The T-cell features in diseased periodontal tissues can be compared with those in rheumatoid arthritis, wherein bone resorption often attributed to Th1-type T-cell involvement has also been demonstrated.

Connective tissue growth factor in drug-induced gingival overgrowth

BACKGROUND

Drug-induced gingival overgrowth is a known side effect of certain chemotherapeutic agents used for the treatment of systemic disorders. The pathogenesis and mechanisms responsible for this condition are not fully understood. This study assesses for the presence and localization of connective tissue growth factor (CTGF) in drug-induced gingival overgrowth tissues. CTGF immunostaining was compared with sections stained with transforming growth factor (TGF)-beta1 and CD31 antibodies in order to investigate possible pathogenic mechanisms.

METHODS

Gingival overgrowth samples were obtained from patients undergoing therapy with phenytoin (n = 9), nifedipine (n = 4), cyclosporin A (n = 5), and control tissues from systemically healthy donors (n = 9). Tissue sections were subjected to peroxidase immunohistochemistry and were stained with CTGF and TGF-beta1 polyclonal primary antibodies. Possible relationships between CTGF staining and angiogenesis were also studied using an anti-CD31 antibody as a marker for endothelial cells. Staining was analyzed by computer-assisted quantitative and semiquantitative methodology at 5 defined sites in all samples based on the location of specific landmarks including epithelium and underlying connective tissues.

RESULTS

Cellular and extracellular CTGF content in phenytoin gingival overgrowth tissues was significantly (P<0.05) higher compared to the other gingival overgrowth tissues and the controls. Higher CTGF staining in phenytoin gingival overgrowth tissues was accompanied by an increased abundance of fibroblasts and connective tissue fibers. No strong association of CTGF staining with TGF-beta1 or CD31 staining was found.

CONCLUSIONS

The data from the present study show significantly higher CTGF staining in phenytoin-induced gingival overgrowth tissues compared to controls, cyclosporin A-, or nifedipine-induced gingival overgrowth. Moreover, semiquantitative analyses of histologic samples support the concept that the phenytoin overgrowth tissues are fibrotic. These associations suggest a possible role for CTGF in promoting development of fibrotic lesions in phenytoin-induced gingival overgrowth.

Production of Rantes/CCL5 in human gingival fibroblasts challenged with tumor necrosis factor alpha

Chemokines are small-secreted proteins that stimulate the directional migration of leukocytes and thereby mediate the inflammatory process. The present study investigates the capacity of human gingival fibroblasts to produce the beta chemokine Rantes/CCL5. In situ hybridization, immunohistochemistry and ELISA were used to measure the induction of Rantes/CCL5 at the mRNA and protein levels, both in unstimulated gingival fibroblasts as well as in fibroblasts treated with the proinflammatory cytokines tumor necrosis factor (TNF)alpha or interleukin (IL)-1beta. TNFalpha in different concentrations (0.1-10 ng/ml) induced Rantes/CCL5 mRNA expression and protein production in 24-h cultures of human gingival fibroblasts. The expression of Rantes/CCL5-mRNA and protein production, induced by TNFalpha, was evident at 6 h and thereafter increased continuously during the study period (24 h). IL-1beta (3-300 pg/ml) also enhanced the production of Rantes/CCL5 in gingival fibroblasts. The amount of Rantes/CCL5 induced by IL-1beta (300 pg/ml), however, was less than that induced by TNFalpha (10 ng/ml). The study suggests that human gingival fibroblasts, by producing the chemokine Rantes/CCL5, participate in the regulation of the host response during the inflammatory process in the periodontal tissue.

Cytokine responses to treponema pectinovorum and treponema denticola in human gingival fibroblasts

Human gingival fibroblasts were challenged with Treponema pectinovorum and Treponema denticola to test three specific hypotheses: (i) these treponemes induce different cytokine profiles from the fibroblasts, (ii) differences in cytokine profiles are observed after challenge with live versus killed treponemes, and (iii) differences in cytokine profiles are noted from different gingival fibroblast cell lines when challenged with these treponemes. Three normal gingival fibroblast cell cultures were challenged with T. pectinovorum and T. denticola strains, and the supernatants were analyzed for cytokine production (i.e., interleukin-1alpha [IL-1alpha], IL-1beta, IL-6, IL-8, IL-10, gamma interferon, macrophage chemotactic protein 1 [MCP-1], platelet-derived growth factor, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor). Unstimulated fibroblast cell lines produced IL-6, IL-8, and MCP-1. T. pectinovorum routinely elicited the greatest production of these cytokines from the fibroblast cell lines, increasing 10- to 50-fold over basal production. While T. denticola also induced IL-6 and IL-8 production, these levels were generally lower than those elicited by challenge with T. pectinovorum. MCP-1 levels were significantly lower after T. denticola challenge, and the kinetics suggested that this microorganism actually inhibited basal production by the fibroblasts. No basal or stimulated production of the other cytokines was observed. Significant differences were noted in the responsiveness of the various cell lines with respect to the two species of treponemes and the individual cytokines produced. Finally, dead T. pectinovorum generally induced a twofold-greater level of IL-6 and IL-8 than the live bacteria. These results supported the idea that different species of oral treponemes can elicit proinflammatory cytokine production by gingival cells and that this stimulation did not require live microorganisms. Importantly, a unique difference was noted in the ability of T. pectinovorum to induce a robust MCP-1 production, while T. denticola appeared to inhibit this activity of the fibroblasts. While the general cytokine profiles of the fibroblast cell cultures were similar, significant differences were noted in the quantity of individual cytokines produced, which could relate to individual patient variation in local inflammatory responses in the periodontium.

Periodontal disease: bacterial virulence factors, host response and impact on systemic health

Teeth are coated with a biofilm that contains periodontal pathogens. Pathogens express virulence factors which enable them to invade and replicate within epithelial cells and to invade the underlying connective tissue. This stimulates production of prostaglandins and cytokines that induce tissue loss. In addition, these bacteria have the potential to modulate the course of systemic diseases such as atherosclerosis and to contribute to low birthweight and preterm labor.

Inducible expression of human beta-defensin 2 by Fusobacterium nucleatum in oral epithelial cells: multiple signaling pathways and role of commensal bacteria in innate immunity and the epithelial barrier

Human gingival epithelial cells (HGE) express two antimicrobial peptides of the beta-defensin family, human beta-defensin 1 (hBD-1) and hBD-2, as well as cytokines and chemokines that contribute to innate immunity. In the present study, the expression and transcriptional regulation of hBD-2 was examined. HBD-2 mRNA was induced by cell wall extract of Fusobacterium nucleatum, an oral commensal microorganism, but not by that of Porphyromonas gingivalis, a periodontal pathogen. HBD-2 mRNA was also induced by the proinflammatory cytokine tumor necrosis factor alpha (TNF-alpha) and phorbol myristate acetate (PMA), an epithelial cell activator. HBD-2 mRNA was also expressed in 14 of 15 noninflamed gingival tissue samples. HBD-2 peptide was detected by immunofluorescence in HGE stimulated with F. nucleatum cell wall, consistent with induction of the mRNA by this stimulant. Kinetic analysis indicates involvement of multiple distinct signaling pathways in the regulation of hBD-2 mRNA; TNF-alpha and F. nucleatum cell wall induced hBD-2 mRNA rapidly (2 to 4 h), while PMA stimulation was slower ( approximately 10 h). In contrast, each stimulant induced interleukin 8 (IL-8) within 1 h. The role of TNF-alpha as an intermediary in F. nucleatum signaling was ruled out by addition of anti-TNF-alpha that did not inhibit hBD-2 induction. However, inhibitor studies show that F. nucleatum stimulation of hBD-2 mRNA requires both new gene transcription and new protein synthesis. Bacterial lipopolysaccharides isolated from Escherichia coli and F. nucleatum were poor stimulants of hBD-2, although they up-regulated IL-8 mRNA. Collectively, our findings show inducible expression of hBD-2 mRNA via multiple pathways in HGE in a pattern that is distinct from that of IL-8 expression. We suggest that different aspects of innate immune responses are differentially regulated and that commensal organisms have a role in stimulating mucosal epithelial cells in maintaining the barrier that contributes to homeostasis and host defense.

Monocyte chemotactic protein-1 (MCP-1) accelerates the organization and resolution of venous thrombi

PURPOSE

Organization, recanalization, and contraction are common to wound healing and thrombus resolution. Monocytes are essential to wound healing and are also found in venous thrombi. We measured endogenous levels of the monocyte chemotactic protein-1 (MCP-1) in naturally resolving venous thrombi and determined the effect of injecting MCP-1 into newly formed thrombus.

METHODS

Endogenous MCP-1 levels were estimated in rat blood, thrombi, and the adjacent vessel wall after thrombus formation, in cohorts of eight animals at 1, 7, and 14 days. In another group (n = 10), 1 microgram of MCP-1 was injected into newly formed thrombi. Carrier was injected into the thrombi of control animals (n = 10). Thrombi and adjacent vein walls were obtained for histology at 7 days. Thrombi were given an arbitrary organization score based on erythrocyte and extracellular matrix content, which was assessed by means of computerized and observer analysis. Specimen weight, thrombus area, and cellular and monocyte content were measured.

RESULTS

Endogenous MCP-1 increased between days 1 and 7 in the thrombus (1-day median, 1.1 ng/g wet wt; 1-day range, 0.8 to 1.4 ng/g wet wt; 7-day median, 5.4 ng/g wet wt; 7-day range, 1.5 to 7.4 ng/g wet wt; P <.0001) and vein wall (1-day median, 1.5 ng/g wet wt; 1-day range, 0.8 to 4.3 ng/g wet wt; 7-day median, 3.3 ng/g wet wt; 7-day range, 2.7 to 8.3 ng/g wet wt; P <. 05). At 14 days, thrombus was incorporated in the vein wall, and total MCP-1 levels remained high (median, 3.9 ng/g wet wt; range, 1.1 to 7.4 ng/g wet wt). Less MCP-1 was found in the thrombus than the adjacent vessel wall at day 1 (P <.05), but there was no difference at day 7. MCP-1 could not be detected in the blood. MCP-1 injection into thrombus increased the computer (P =.016) and observer (P =.004) organization scores, reduced the thrombus area (from median, 3. 4 mm(2), and range, 1.5 to 5.7 mm(2), to median, 0.2 mm(2), and range, 0.02 to 2.6 mm(2); P =.048), and increased the surrounding vessel wall monocyte content (P =.008). Specimen weights of treated animals were lower than those of control animals (P <.02).

CONCLUSION

Venous thrombus MCP-1 levels increase during natural resolution. MCP-1 treatment increased the organization and resolution of thrombi. MCP-1 may therefore be of therapeutic use.