Expression of toll-like receptors 2, 4 and 9 is increased in gingival tissue from patients with type 2 diabetes and chronic periodontitis

Diabetes mellitus: Classification, mediators, and complications; A gate to identify potential targets for the development of new effective treatments

Nowadays, diabetes mellitus has emerged as a significant global public health concern with a remarkable increase in its prevalence. This review article focuses on the definition of diabetes mellitus and its classification into different types, including type 1 diabetes (idiopathic and fulminant), type 2 diabetes, gestational diabetes, hybrid forms, slowly evolving immune-mediated diabetes, ketosis-prone type 2 diabetes, and other special types. Diagnostic criteria for diabetes mellitus are also discussed. The role of inflammation in both type 1 and type 2 diabetes is explored, along with the mediators and potential anti-inflammatory treatments. Furthermore, the involvement of various organs in diabetes mellitus is highlighted, such as the role of adipose tissue and obesity, gut microbiota, and pancreatic β-cells. The manifestation of pancreatic Langerhans β-cell islet inflammation, oxidative stress, and impaired insulin production and secretion are addressed. Additionally, the impact of diabetes mellitus on liver cirrhosis, acute kidney injury, immune system complications, and other diabetic complications like retinopathy and neuropathy is examined. Therefore, further research is required to enhance diagnosis, prevent chronic complications, and identify potential therapeutic targets for the management of diabetes mellitus and its associated dysfunctions.

Circ_0099630 knockdown alleviates lipopolysaccharide-induced injuries of human periodontal ligament cells through the inhibition of TLR4 by releasing miR-409-3p

BACKGROUND

Periodontitis triggers tooth loss and affects the health of population worldwide. Emerging evidence hints that circular RNAs (circRNAs) are involved in various diseases, including periodontitis. This study aimed to investigate the role of circ_0099630 in the progression of periodontitis.

METHODS

Periodontitis cell model was constructed by treating human periodontal ligament cells (HPDLCs) with lipopolysaccharide (LPS). Quantitative real-time PCR was used to analyze the expression of circ_0099630, microRNA-409-3p (miR-409-3p) and toll-like receptor 4 (TLR4) mRNA. Western blot was used for detecting protein levels of TLR4, cleaved-caspase 3, Bcl-2, CyclinD1 and NF-κB signaling markers. For function analyses, cell proliferation was assessed by CCK-8 assay and EdU assay. The releases of pro-inflammation factors were monitored by ELISA kits. The potential relationship between miR-409-3p and circ_0099630 or TLR4 was verified by dual-luciferase reporter assay, RIP assay and pull-down assay.

RESULTS

The expression of circ_0099630 and TLR4 was elevated in periodontitis patients and LPS-treated HPDLCs. LPS induced HPDLC proliferation inhibition, apoptosis and inflammatory responses, while circ_0099630 knockdown or TLR4 knockdown alleviated these injuries. Besides, TLR4 overexpression reversed the inhibitory effect of circ_0099630 knockdown on LPS-induced HPDLC injuries. Mechanism analysis showed that circ_0099630 positively regulated TLR4 expression by acting as miR-409-3p sponge. MiR-409-3p restoration largely ameliorated LPS-induced HPDLC injuries by depleting TLR4. Moreover, LPS activated the NF-κB signaling pathway, while circ_0099630 knockdown inhibited the activity of NF-κB signaling via the miR-409-3p/TLR4 axis.

CONCLUSION

Circ_0099630 knockdown relieved LPS-induced HPDLC injury by miR-409-3p/TLR4 axis, suggesting that circ_0099630 might be a potential target for periodontitis treatment.

Host insulin resistance caused by Porphyromonas gingivalis-review of recent progresses

Porphyromonas gingivalis (P. gingivalis) is a Gram-negative oral anaerobic bacterium that plays a key role in the pathogenesis of periodontitis. P. gingivalis expresses a variety of virulence factors that disrupt innate and adaptive immunity, allowing P. gingivalis to survive and multiply in the host and destroy periodontal tissue. In addition to periodontal disease, P.gingivalis is also associated with systemic diseases, of which insulin resistance is an important pathological basis. P. gingivalis causes a systemic inflammatory response, disrupts insulin signaling pathways, induces pancreatic β-cell hypofunction and reduced numbers, and causes decreased insulin sensitivity leading to insulin resistance (IR). In this paper, we systematically review the studies on the mechanism of insulin resistance induced by P. gingivalis, discuss the association between P. gingivalis and systemic diseases based on insulin resistance, and finally propose relevant therapeutic approaches. Overall, through a systematic review of the mechanisms related to systemic diseases caused by P. gingivalis through insulin resistance, we hope to provide new insights for future basic research and clinical interventions for related systemic diseases.

CpG Single-Site Methylation Regulates TLR2 Expression in Proinflammatory PBMCs From Apical Periodontitis Individuals

Introduction

Apical periodontitis (AP) is a common oral disease caused by the inflammatory destruction of the periapical tissues due to the infection of the root canal system of the tooth. It also contributes to systemic bacterial translocation, where peripheric mononuclear blood cells (PBMCs) can act as carriers. Toll-like receptor (TLR) 2 mediates the response to infection and activates inflammatory responses. DNA methylation can be induced by bacteria and contributes to the modulation of this response. Despite the evidence that supports the participation of PBMCs in immune-inflammatory disorders, the inflammatory profile and epigenetic regulatory mechanisms of PBMCs in AP individuals are unknown.

Aim

To determine TLR2 gene methylation and inflammatory profiles of PBMCs in AP.

Methods

Cross-sectional exploratory study. Otherwise, healthy individuals with AP (n=27) and controls (n=30) were included. PMBCs were isolated by a Ficoll gradient, cultured for 24 hours, and both RNA and DNA were extracted. DNA was bisulfite-treated, and specific sites at the promoter region of the TLR2 gene were amplified by qPCR using validated primers. To verify its amplification, agarose gels were performed. Then, the PCR product was sequenced. mRNA expression of TLR2 was determined by qPCR. The soluble levels of 105 inflammatory mediators were first explored with Proteome Profiler Human Cytokine Array Kit. Consequently, tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-10, IL-6Rα, IL-1β, and IL-12p70 levels were measured by Multiplex assay.

Results

PBMCs from individuals with AP demonstrated a proinflammatory profile showing higher soluble levels of TNF-α, IL-6, and IL-1β compared to controls (p<0.05). Higher TLR2 expression and higher global methylation pattern of the promoter region of the gene were found in AP compared to controls (p<0.05). The CpGs single-sites at positions -166 and -146 were completely methylated, while the site -102 was totally unmethylated, independently of the presence of AP. DNA methylation of CpG single-sites in positions -77 and +24 was positively associated with TLR2 expression.

Conclusions

PBMCs from AP subjects show a hyperinflammatory phenotype and TLR2 upregulation in association with single CpG-sites’ methylation from the TLR2 gene promoter, thereby contributing to a sustained systemic inflammatory load in individuals with periapical endodontic diseases.

Effect of TLR9 methylation on its transcription in apical inflammation

AIM

to explore the methylation pattern, its role on transcriptional regulation and potential modifiers of methylation of theTLR9 gene in chronic periapical inflammation.

METHODOLOGY

In this cross-sectional study, apical lesions of endodontic origin (ALEO, n=61) and healthy periodontal ligaments (HPL, n=15) were included. Products from bisulfited and PCR-amplified DNA were analyzed for their methylation profiles in the promoter region and at each CpG island. Additionally, TLR9 mRNA levels were quantified by qPCR and bivariate and multiple modelling were performed to better understand the influence of methylations on gene transcription.

RESULTS

TLR9 mRNA levels were upregulated in ALEO compared to HPL (p<0.001). TLR9 promoter CpG sites and CpG +2086 in the intragenic island 1 were demethylated in ALEO compared to HPL (p<0.05). Multivariate analysis, adjusted by smoking and gender, revealed that demethylation of TLR9 promoter sites enhanced transcriptional activity, specifically demethylated CpGs at positions -736 and -683, (p=0.02), which are close to CRE binding. Whereas ALEO reduced the global methylation of the gene-promoter and intragenic-island 2 (p<0.05) by -42.5 and -9.5 percentage points, respectively, age reduced the global methylation of intragenic-island 3 within the exon 2.

CONCLUSIONS

Demethylations of TLR9 promoter CpG sites, along with the intragenic DNA methylation status, were involved in higher transcription in ALEO. Hence, chronic periapical inflammation and aging modify the methylation status both in the gene promoter and in intragenic CpG islands.

State of Evidence on Oral Health Problems in Diabetic Patients: A Critical Review of the Literature

Diabetes mellitus (DM) is a global health problem, having recognized that in the next 20 years the number of diabetic patients in the world will increase to 642 million. DM exerts enormous repercussions on general health diabetic (especially derived from vascular, cardiac, renal, ocular, or neurological affectation). It entails in addition a high number of deaths directly related to the disease, as well as a high health care cost, estimated at $673 billion annually. Oral cavity is found among all the organs and systems affected in the course of DM. Important pathologies are developed with higher prevalence, such as periodontitis (PD), alterations in salivary flow, fungal infections, oral cancer, and oral potentially malignant disorders (OPMD). It has been proven that PD hinders the metabolic control of DM and that the presence of PD increases the possibility for developing diabetes. Despite the relevance of these oral pathologies, the knowledge of primary care physicians and diabetes specialists about the importance of oral health in diabetics, as well as the knowledge of dentists about the importance of DM for oral health of patients is scarce or non-existent. It is accepted that the correct management of diabetic patients requires interdisciplinary teams, including dentists. In this critical review, the existing knowledge and evidence-degree on the preventive, clinical, diagnosis, prognosis, and therapeutic aspects of oral diseases that occur with a significant frequency in the diabetic population are developed in extension.

State of Evidence on Oral Health Problems in Diabetic Patients: A Critical Review of the Literature

Diabetes mellitus (DM) is a global health problem, having recognized that in the next 20 years the number of diabetic patients in the world will increase to 642 million. DM exerts enormous repercussions on general health diabetic (especially derived from vascular, cardiac, renal, ocular, or neurological affectation). It entails in addition a high number of deaths directly related to the disease, as well as a high health care cost, estimated at $673 billion annually. Oral cavity is found among all the organs and systems affected in the course of DM. Important pathologies are developed with higher prevalence, such as periodontitis (PD), alterations in salivary flow, fungal infections, oral cancer, and oral potentially malignant disorders (OPMD). It has been proven that PD hinders the metabolic control of DM and that the presence of PD increases the possibility for developing diabetes. Despite the relevance of these oral pathologies, the knowledge of primary care physicians and diabetes specialists about the importance of oral health in diabetics, as well as the knowledge of dentists about the importance of DM for oral health of patients is scarce or non-existent. It is accepted that the correct management of diabetic patients requires interdisciplinary teams, including dentists. In this critical review, the existing knowledge and evidence-degree on the preventive, clinical, diagnosis, prognosis, and therapeutic aspects of oral diseases that occur with a significant frequency in the diabetic population are developed in extension.

State of Evidence on Oral Health Problems in Diabetic Patients: A Critical Review of the Literature

Diabetes mellitus (DM) is a global health problem, having recognized that in the next 20 years the number of diabetic patients in the world will increase to 642 million. DM exerts enormous repercussions on general health diabetic (especially derived from vascular, cardiac, renal, ocular, or neurological affectation). It entails in addition a high number of deaths directly related to the disease, as well as a high health care cost, estimated at $673 billion annually. Oral cavity is found among all the organs and systems affected in the course of DM. Important pathologies are developed with higher prevalence, such as periodontitis (PD), alterations in salivary flow, fungal infections, oral cancer, and oral potentially malignant disorders (OPMD). It has been proven that PD hinders the metabolic control of DM and that the presence of PD increases the possibility for developing diabetes. Despite the relevance of these oral pathologies, the knowledge of primary care physicians and diabetes specialists about the importance of oral health in diabetics, as well as the knowledge of dentists about the importance of DM for oral health of patients is scarce or non-existent. It is accepted that the correct management of diabetic patients requires interdisciplinary teams, including dentists. In this critical review, the existing knowledge and evidence-degree on the preventive, clinical, diagnosis, prognosis, and therapeutic aspects of oral diseases that occur with a significant frequency in the diabetic population are developed in extension.

Dysregulation of metallothionein and zinc aggravates periodontal diseases

BACKGROUND

Periodontitis (PD) is a multifaceted inflammatory disease connected to bacterial infection that results in the destruction of tooth supporting structures and eventually tooth loss. Given their involvement in infection and inflammation, both metallothionein (MT) and zinc (Zn) might play vital roles in the development and progression of PD. More specifically, both MT and Zn are heavily involved in regulating immune functions, controlling bacterial infection, balancing inflammatory responses, and reducing oxidative stress, all of which are associated with the pathogenesis of PD.

OBJECTIVE

This review paper will explore the physiological functions of MT and Zn and hypothesise how dysregulation could negatively affect periodontal health, leading to PD.

FINDINGS

Bacterial lipopolysaccharide (LPS) derived from periodontal pathogens, namely P. gingivalis initiates the acute phase response, thus upregulating the expression of MT which leads to the subsequent deficiency of Zn, a hallmark of periodontal disease. This deficiency leads to ineffective NETosis, increases the permeability of the gingival epithelium, and disrupts the humoral immune response, collectively contributing to PD. In addition, the presence of LPS in Zn deficient conditions favours M1 macrophage polarisation and maturation of dendritic cells, and also inhibits the anti-inflammatory activity of regulatory T cells. Collectively, these observations could theoretically give rise to the chronic inflammation seen in PD.

CONCLUSION

A disrupted MT and Zn homeostasis is expected to exert an adverse impact on periodontal health and contribute to the development and progression of PD.

Bacterial Cyclic Dinucleotides and the cGAS-cGAMP-STING Pathway: A Role in Periodontitis?

Host cells can recognize cytosolic double-stranded DNAs and endogenous second messengers as cyclic dinucleotides-including c-di-GMP, c-di-AMP, and cGAMP-of invading microbes via the critical and essential innate immune signaling adaptor molecule known as STING. This recognition activates the innate immune system and leads to the production of Type I interferons and proinflammatory cytokines. In this review, we (1) focus on the possible role of bacterial cyclic dinucleotides and the STING/TBK1/IRF3 pathway in the pathogenesis of periodontal disease and the regulation of periodontal immune response, and (2) review and discuss activators and inhibitors of the STING pathway as immune response regulators and their potential utility in the treatment of periodontitis. PubMed/Medline, Scopus, and Web of Science were searched with the terms "STING", "TBK 1", "IRF3", and "cGAS"-alone, or together with "periodontitis". Current studies produced evidence for using STING-pathway-targeting molecules as part of anticancer therapy, and as vaccine adjuvants against microbial infections; however, the role of the STING/TBK1/IRF3 pathway in periodontal disease pathogenesis is still undiscovered. Understanding the stimulation of the innate immune response by cyclic dinucleotides opens a new approach to host modulation therapies in periodontology.

Comparative Analysis of Cytokine Expression in Oral Keratinocytes and THP-1 Macrophages in Response to the Most Prevalent Serotypes of Aggregatibacter actinomycetemcomitans

BACKGROUND

Periodontitis is a chronic inflammatory disease associated with a dysbiotic biofilm. Many pathogens have been related with its progression and severity, one of which is Aggregatibacter actinomycetemcomitans, a Gram-negative bacteria with seven serotypes (a-g) according with the structure of its LPS, with serotype b defined as the most virulent compared with the other serotypes. The aim of this study was to evaluate the response of oral keratinocytes and macrophages to A. actinomycetemcomitans.

METHODS

Oral keratinocytes (OKF6/TERT2) and macrophages (THP-1) were infected with A. actinomycetemcomitans serotypes a, b and c. The expression of IL-1β, IL-6, IL-8, IL-18, TNF-α, MMP-9, RANKL, TLR-2, TLR-4, TLR-6, thymic stromal lymphopoietin (TSLP), and ICAM-1 was evaluated by qPCR at 2 and 24 h after infection.

RESULTS

An increase in the expression of these molecules was induced by all serotypes at both times of infection, with macrophages showing higher levels of expression at 24 h compared to epithelial cells in which the highest levels were observed in the first hours after infection.

CONCLUSIONS

Keratinocytes and macrophages contribute to the inflammation in periodontitis from the early stages of infection, producing the first waves of cytokines, acting as the first signal for professional immune cell recruitment and modulation of more specific immune responses.

Autophagy and its significance in periodontal disease

Autophagy is an evolutionarily conserved process essential for cellular homeostasis and human health. As a lysosome-dependent degradation pathway, autophagy acts as a modulator of the pathogenesis of diverse diseases. The relationship between autophagy and oral diseases has been explored in recent years, and there is increasing interest in the role of autophagy in periodontal disease. Periodontal disease is a prevalent chronic inflammatory disorder characterized by the destruction of periodontal tissues. It is initiated through pathogenic bacterial infection and interacts with the host immune defense, leading to inflammation and alveolar bone resorption. In this review, we outline the machinery of autophagy and present an overview of work on the significance of autophagy in regulating pathogen invasion, the immune response, inflammation, and alveolar bone homeostasis of periodontal disease. Existing data provide support for the importance of autophagy as a multi-dimensional regulator in the pathogenesis of periodontal disease and demonstrate the importance of future research on the potential roles of autophagy in periodontal disease.

Diabetes as a risk factor for periodontal disease-plausible mechanisms

The present narrative review examines the scientific evidence of the biological mechanisms that may link periodontitis and diabetes, as a source of comorbidity. Publications regarding periodontitis and diabetes, in human, animals, and in vitro were screened for their relevance. Periodontal microbiome studies indicate a possible association between altered glucose metabolism in prediabetes and diabetes and changes in the periodontal microbiome. Coinciding with this, hyperglycemia enhances expression of pathogen receptors, which enhance host response to the dysbiotic microbiome. Hyperglycemia also promotes pro-inflammatory response independently or via the advanced glycation end product/receptor for advanced glycation end product pathway. These processes excite cellular tissue destruction functions, which further enhance pro-inflammatory cytokines expression and alteration in the RANKL/osteoprotegerin ratio, promoting formation and activation of osteoclasts. The evidence supports the role of several pathogenic mechanisms in the path of true causal comorbidity between poorly controlled diabetes and periodontitis. However, further research is needed to better understand these mechanisms and to explore other mechanisms.

Response of Human Mesenchymal Stromal Cells from Periodontal Tissue to LPS Depends on the Purity but Not on the LPS Source

Human periodontal ligament stromal cells (hPDLSCs) and gingival mesenchymal stromal cells (hGMSCs) are resident mesenchymal stromal cells (MSCs) of the periodontal tissue. The lipopolysaccharide (LPS) from Porphyromonas gingivalis is structurally distinct from that of other Gram-negative bacteria, and earlier studies linked this structural difference to a distinct virulence activity and the ability to activate toll-like receptor 2 (TLR-2), besides TLR-4 as commonly occurring upon LPS challenge. Later studies, in contrast, argue that TLR-2 activation by P. gingivalis LPS is due to lipoprotein contamination. In the present study, we aimed to define the influence of structure versus purity of P. gingivalis LPS on the immune response of hPDLSCs and hGMSCs. Cells were stimulated with commercially available "standard" P. gingivalis LPS, "ultrapure" P. gingivalis LPS, or "ultrapure" Escherichia coli LPS, and the expression of interleukin- (IL-) 8, IL-6, monocyte chemoattractant protein- (MCP-) 1, TLR-2, and TLR-4 was evaluated. The contribution of TLR-4 to the LPS-induced response was assessed using the specific TLR-4 inhibitor TAK-242. "Standard" P. gingivalis LPS induced significantly higher IL-8, IL-6, and MCP-1 production compared to the "ultrapure" LPS preparations, with no significant difference detectable for "ultrapure" LPS from P. gingivalis and E. coli. By using TAK-242, the response of hPDLSCs and hGMSCs to "ultrapure" LPS preparations was effectively inhibited to the levels comparable to those of nonstimulated controls. In contrast, high levels of response to "standard" LPS were observed, even in the presence of TAK-242. Our data show that the response of MSCs from periodontal tissue to LPS depends more on the purity of the LPS preparation than on the LPS source. Even a small amount of contaminating lipoproteins can drastically enhance the hPDLSCs' and hGMSCs; responsiveness to P. gingivalis LPS, which might also contribute to the progression of periodontal disease.

Functional assessment of peptide-modified PLGA nanoparticles against oral biofilms in a murine model of periodontitis

The interaction of the periodontal pathogen Porphyromonas gingivalis (Pg) with commensal streptococci promotes Pg colonization of the oral cavity. Previously, we demonstrated that a peptide (BAR) derived from Streptococcus gordonii (Sg) potently inhibited adherence of Pg to streptococci and reduced Pg virulence in a mouse model of periodontitis. Thus, BAR may represent a novel therapeutic to control periodontitis by preventing Pg colonization of the oral cavity. However, while BAR inhibited the initial formation of Pg/Sg biofilms, much higher concentrations of peptide were required to disrupt an established Pg/Sg biofilm. To improve the activity of the peptide, poly(lactic-co-glycolic acid) (PLGA) nanoparticles were surface-modified with BAR and shown to more potently disrupt Pg/Sg biofilms relative to an equimolar amount of free peptide. The goal of this work was to determine the in vivo efficacy of BAR-modified NPs (BNPs) and to assess the toxicity of BNPs against human gingival epithelial cells. In vivo efficacy of BNPs was assessed using a murine model of periodontitis by measuring alveolar bone resorption and gingival IL-17 expression as outcomes of Pg-induced inflammation. Infection of mice with Pg and Sg resulted in a significant increase in alveolar bone loss and gingival IL-17 expression over sham-infected animals. Treatment of Pg/Sg infected mice with BNPs reduced bone loss and IL-17 expression almost to the levels of sham-infected mice and to a greater extent than treatment with an equimolar amount of free BAR. The cytotoxicity of the maximum concentration of BNPs and free BAR used in in vitro and in vivo studies (1.3 and 3.4 μM), was evaluated in telomerase immortalized gingival keratinocytes (TIGKs) by measuring cell viability, cell lysis and apoptosis. BNPs were also tested for hemolytic activity against sheep erythrocytes. TIGKs treated with BNPs or free BAR demonstrated >90% viability and no significant lysis or apoptosis relative to untreated cells. In addition, neither BNPs nor free BAR exhibited hemolytic activity. In summary, BNPs were non-toxic within the evaluated concentration range of 1.3-3.4 μM and provided more efficacious protection against Pg-induced inflammation in vivo, highlighting the potential of BNPs as a biocompatible platform for translatable oral biofilm applications.

Differential profiles of soluble and cellular toll like receptor (TLR)-2 and 4 in chronic periodontitis

Chronic periodontitis is a common inflammatory disease initiated by a complex microbial biofilm and mediated by the host response causing destruction of the supporting tissues of the teeth. Host recognition of pathogens is mediated by toll-like receptors (TLRs) that bind conserved molecular patterns shared by large groups of microorganisms. The oral epithelial cells respond to most periodontopathic bacteria via TLR-2 and TLR-4. In addition to the membrane-associated receptors, soluble forms of TLR-2 (sTLR-2) and TLR-4 (sTLR-4) have been identified and are thought to play a regulatory role by binding microbial ligands. sTLR-2 has been shown to arise from ectodomain shedding of the extracellular domain of the membrane receptor and sTLR-4 is thought to be an alternate spliced form. Many studies have previously reported the presence of elevated numbers of viable exfoliated epithelial cells in the saliva of patients with chronic periodontitis. The objective of this study was to investigate the potential value of salivary sTLR-2 and sTLR-4 together with the paired epithelial cell-associated TLR-2/4 mRNA as diagnostic markers for chronic periodontitis. Unstimulated whole saliva was collected after obtaining informed consent from 40 individuals with either periodontitis or gingivitis. The sTLR-2 and sTLR4 in saliva was measured by enzyme-linked immunosorbent assay. The TLR-2 and TLR-4 transcript in the epithelial cells in saliva was measured by real time polymerase chain reaction. While levels of sTLR-2 exhibited an inverse correlation, sTLR-4 positively correlated with clinical parameters in the gingivitis cohort. Interestingly, both correlations were lost in the periodontitis cohort indicating a dysregulated host response. On the other hand, while the sTLR-2 and the paired epithelial cell associated TLR-2 mRNA exhibited a direct correlation (r2 = 0.62), that of sTLR4 and TLR-4 mRNA exhibited an inverse correlation (r2 = 0.53) in the periodontitis cohort. Collectively, assessments of salivary sTLR2 and sTLR4 together with the respective transcripts in the epithelial cells could provide clinically relevant markers of disease progression from gingivitis to periodontitis.

Effects of Diabetes and Hypertension on Oral Mucosa and TGFβ1 Salivary Levels

The aim of this study was to investigate salivary levels of TGFβ1 and proliferation/ maturation of epithelial mucosa cells in diabetic and hypertensive patients.

DESIGN

in this cross-sectional study, whole stimulated saliva and oral mucosa exfoliative cytology specimens were collected from 39 patients that were healthy (control, n=10) or presented history of arterial hypertension (HAS, n=9), diabetes mellitus (DM, n=10) or both (DM+HAS, n=10). Salivary flow rate (SFR), TGFβ1 level in saliva, AgNORs and the epithelial maturation were evaluated. Non-parametric Kruskal-Wallis test, followed by Dunn's multiple comparison post-test and the Spearman test correlation analysis were used. SFR showed a significant decreased in DM and DM+HAS (0.47±0.11 and 0.64±0.43 mL/min) when compared to control (1.4±0.38 mL/min). DM+HAS presented the highest value of TGFβ1 concentration (24.72±5.89 pg/mL). It was observed a positive correlation between TGFβ1 and glycaemia (R=0.6371; p<0.001) and a negative correlation between TGFβ1 and saliva (R=-0.6162; p<0.001) and glycaemia and SFR (R=-0.5654; P=0.001). AgNORs number and status of maturation of mucosa cells were similar for all conditions. DM and DM+HAS presented the lowest SFR, which correlated with increased TGFβ1 levels. Despite the higher TGFβ1 secretion it was not observed changes in the morphology or proliferation of epithelial cells when diabetes or hypertension was present.

Estimation of Toll-like receptor 9 in gingival tissues of patients with chronic periodontitis with or without hyperlipidemia and its association with the presence of Porphyromonas gingivalis

Background:

Recent evidence suggests the interactions between bacterial DNA and nucleic acid receptors to play a role in inflammatory tissue destruction. The current study aims to evaluate the expression of Toll-like receptor 9 (TLR9) in periodontal disease associated with or without hyperlipidemia and to associate it with the presence of Porphyromonas gingivalis.

Materials and Methods:

Thirty participants in the age range of 25–50 years were randomly recruited and divided into three groups, i.e., healthy (Group I), chronic periodontitis without hyperlipidemia (Group II), and chronic periodontitis with hyperlipidemia (Group III). The gingival tissue samples were analyzed for TLR9 using immunohistochemistry, and plaque samples were analyzed for P. gingivalis using polymerase chain reaction.

Results:

The TLR9-positive cell ratio in gingival connective tissue for Group II and Group III was 0.95 ± 0.03 and 0.94 ± 0.03, respectively, which was significantly higher than that of Group I, with P < 0.001 (0.88 ± 0.04). These groups also demonstrated significantly higher presence of P. gingivalis as compared to Group I with P < 0.001. There was a positive association between TLR9 in gingival connective tissue and presence of P. gingivalis.

Conclusion:

The results of this study reveal a potential role of TLR9 in chronic periodontitis, in association with P. gingivalis. Furthermore, these variables do not show an appreciable change in hyperlipidemics suggesting a weak relation between TLR9 and lipid levels.

Immunohistochemical localization of TLR2 and CD14 in gingival tissue of healthy individuals and patients with chronic periodontitis

We used immunohistochemistry to quantify and compare the expression of Toll-like receptor 2 (TLR2) and cluster of differentiation 14 (CD14) in gingival tissues of both healthy individuals and patients with chronic periodontitis. We also correlated the expression of TLR2 and CD14 with the histological grades of chronic periodontitis. We examined 30 gingival specimens from chronic periodontitis patients and 10 from healthy individuals. Tissues from both groups were immunostained with antibodies against TLR2 and CD14. TLR2 and CD14 were expressed by endothelial cells, fibroblasts, lymphocytes and plasma cells. The immunohistochemical expression of TLR2 and CD14 was significantly greater in inflammatory cells of the chronic periodontitis group than in healthy individuals. Expression of these molecules was greater in the inflammatory cells of connective tissue adjacent to pocket epithelium in both groups. The expression of TLR2 and CD14 was greatest in the periodontitis group that was classified as severe grade, followed by moderate and mild grades, which suggests a role of TLR2 and CD14 in the pathogenesis of chronic periodontitis. The positive correlation of TLR2 and CD14 expression levels with the severity grades of chronic periodontitis suggests that they are correlated also with disease severity; therefore, they may be useful for predicting disease progression. Our findings are consistent with the possibility that CD14 acts as a co-receptor for TLR2.

Necroptosis in the periodontal homeostasis: Signals emanating from dying cells

Periodontal tissues are constantly exposed to microbial stimuli. The equilibrium between microbes and host defense system helps maintain the homeostasis in the periodontal microenvironment. Growth of pathogenic bacteria in dental biofilms may induce proinflammatory cytokine production to recruit sentinel cells, mainly neutrophils and monocytes into the gingival sulcus or the periodontal pocket. Moreover, dysbiosis with overgrowth of anaerobic pathogens, such as Porphyromonas gingivalis and Tannerella forsythia, may induce death of both immune cells and host resident cells. Necroptosis is one newly characterized programmed cell death mediated by receptor-interacting protein kinase (RIPK)-1, RIPK3, and mixed lineage kinase like (MLKL). With its release of death-associated molecular patterns (DAMPs) into extracellular environment, necroptosis may help transmit the danger signal and amplify the inflammatory responses. In this review, we present recent advances on how necroptosis influences bacterial infection progression and what a role necroptosis plays in maintaining the homeostasis in the periodontal niche. Until we fully decipher the signals emanated from dying cells, we cannot completely understand the mechanism of disease progression.

Ginkgolide B Suppresses TLR4-Mediated Inflammatory Response by Inhibiting the Phosphorylation of JAK2/STAT3 and p38 MAPK in High Glucose-Treated HUVECs

Aim

Ginkgolide B is a Ginkgo biloba leaf extract that has been identified as a natural platelet-activating factor receptor (PAFR) antagonist. We investigated the effect of ginkgolide B on high glucose-induced TLR4 activation in human umbilical vein endothelial cells (HUVECs).

Methods

Protein expression was analyzed by immunoblotting. Small-interfering RNA (siRNA) was used to knock down PAFR and TLR4 expression.

Results

Ginkgolide B suppressed the expression of TLR4 and MyD88 that was induced by high glucose. Ginkgolide B also reduced the levels of platelet endothelial cell adhesion molecule-1, interleukin-6, and monocyte chemotactic protein 1. Further, we examined the association between PAFR and TLR4 by coimmunoprecipitation. The result showed that high glucose treatment caused the binding of PAFR and TLR4, whereas ginkgolide B abolished this binding. The functional analysis indicated that PAFR siRNA treatment reduced TLR4 expression, and TLR4 siRNA treatment decreased PAFR expression in high glucose-treated HUVECs, further supporting the coimmunoprecipitation data. Ginkgolide B inhibited the phosphorylation of Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) and p38 mitogen-activated protein kinase (MAPK).

Conclusion

Ginkgolide B exerted protective effects by inhibiting the TLR4-mediated inflammatory response in high glucose-treated endothelial cells. The mechanism of action of ginkgolide B might be associated with inhibition of the JAK2/STAT3 and p38 MAPK phosphorylation.

MicroRNA-126 Regulates Inflammatory Cytokine Secretion in Human Gingival Fibroblasts Under High Glucose via Targeting Tumor Necrosis Factor Receptor Associated Factor 6

BACKGROUND

MicroRNAs (miRs) play a crucial role in inflammatory diseases, including periodontitis. Meanwhile, miRs act as biomarkers for predicting diabetes mellitus (DM). However, the regulatory mechanism of miR-126 on development of periodontitis in patients with DM still remains unclear.

METHODS

Human gingival fibroblasts were cultured with low (5.5 mmol/L), medium (15 mmol/L), and high (25 mmol/L) glucose, respectively. Expressions of miR-126, tumor necrosis factor (TNF) receptor associated factor (TRAF) 6, and related cytokines were analyzed by real-time polymerase chain reaction (PCR). After transfection with miR-126 mimic, PCR and western blot were performed to detect level of TRAF6, and luciferase reporter assay confirmed if TRAF6 is the direct target of miR-126. Production of cytokines was measured using enzyme-linked immunosorbent assay.

RESULTS

Increased glucose significantly suppressed miR-126 expression in human gingival fibroblasts (P <0.05). Also, high glucose increased TRAF6, interleukin (IL)-6, TNF-α, and chemical chemokine ligand (CCL) 2 levels, whereas it decreased IL-10 level. MiR-126 mimic significantly decreased TRAF6 mRNA and protein levels under high glucose (P <0.05). Also, miR-126 directly targeted TRAF6 through binding to its 3' untranslated region in human gingival fibroblasts. Overexpression of miR-126 significantly abrogated high glucose-induced secretion of proinflammatory cytokines such as IL-6, TNF-α, and CCL2 and promoted production of IL-10.

CONCLUSION

These data suggest that miR-126 inhibits inflammation of human gingival fibroblasts under high glucose through targeting TRAF6, which may be a potential therapeutic target for periodontitis concomitant with DM.

Toll-like receptor 2 and type 2 diabetes

Innate immunity plays a crucial role in the pathogenesis of type 2 diabetes and related complications. Since the toll-like receptors (TLRs) are central to innate immunity, it appears that they are important participants in the development and pathogenesis of the disease. Previous investigations demonstrated that TLR2 homodimers and TLR2 heterodimers with TLR1 or TLR6 activate innate immunity upon recognition of damage-associated molecular patterns (DAMPs). Several DAMPs are released during type 2 diabetes, so it may be hypothesized that TLR2 is significantly involved in its progression. Here, we review recent data on the important roles and status of TLR2 in type 2 diabetes and related complications.

High glucose-induced oxidative stress increases IL-8 production in human gingival epithelial cells

OBJECTIVE

Diabetes is often associated with increased prevalence and severity of periodontal disease. We hypothesized that gingival epithelial cells modify periodontal disease progression and predicted that hyperglycemia would activate an inflammatory response in human gingival epithelial cells (HGECs).

MATERIALS AND METHODS

We tested our hypothesis in immortalized HGECs (epi 4 cells) isolated from periodontal tissue and transfected with the simian virus 40 T antigen. The epi 4 cells were cultured in high (25 mM, HG) and normal (6 mM, NG) glucose conditions.

RESULTS

The epi 4 cells showed increased interleukin-8 (IL-8) protein secretion and mRNA expression when cultured in HG, compared with in NG. These effects were not associated with increased cell proliferation and were not observed in a hyperosmolar control group (normal glucose with 19 mM mannitol). Increased IL-8 secretion in HG was inhibited by pretreatment with an antioxidant, N-acetylcysteine, or a protein kinase C inhibitor, Ro31-8220. Hyperglycemia did not affect IL-8 secretion by gingival fibroblasts or periodontal ligament cells. In epi 4 cells, hyperglycemia also induced expression of toll-like receptor 2 (TLR2) but not TLR4.

CONCLUSION

These findings suggest a potential participation of epithelial cells in periodontal disease during diabetes by evoking an excessive host inflammatory response.

Macrophages Play a Key Role in the Obesity-Induced Periodontal Innate Immune Dysfunction via Nucleotide-Binding Oligomerization Domain-Like Receptor Protein 3 Pathway

BACKGROUND

Obesity is associated with infiltration of macrophages into adipose tissue. However, effects of obesity on macrophage infiltration and activation in periodontal tissues with periodontitis are still to be elucidated.

METHODS

A diet-induced obesity 16-week mouse model was constructed, and periodontitis was induced by periodontal ligation for 10 days. The model consisted of periodontitis (P) and control (C) groups, with high fat (HF) and normal (N) diet conditions. Bone loss (BL) was analyzed by microcomputed tomography. In periodontal tissues, immunohistochemical staining and quantitative polymerase chain reaction (qPCR) detected expressions of: 1) nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) pathway; 2) macrophage-specific marker (F4/80); and 3) macrophage chemotactic protein 1 (MCP1). Bone marrow-derived macrophages (BMDMs) from the mouse model were stimulated by Porphyromonas gingivalis lipopolysaccharide (LPS) in vitro (NC/NC + LPS: BMDMs from NC group without/with LPS stimulation; HFC/HFC + LPS: BMDMs from HFC group without/with LPS stimulation). Expressions of NLRP3 pathway in BMDMs were detected by immunocytochemical staining and qPCR.

RESULTS

BL increased significantly with periodontitis (NC versus NP; HFC versus HFP) and obesity (NP versus HFP). Expressions of NLRP3 pathway were significantly elevated in gingival tissues with periodontitis (NC versus NP; HFC versus HFP), but not with obesity (NC versus HFC; NP versus HFP). F4/80 and MCP1 expressions were significantly upregulated in gingival tissues with periodontitis (NC versus NP; HFC versus HFP) but significantly downregulated in the context of obesity (NP versus HFP). In vitro, NLRP3 pathway expressions were significantly upregulated in BMDMs after LPS stimulation (NC + LPS versus NC; HFC + LPS versus HFC), but significantly downregulated in HFC groups (HFC versus NC; HFC + LPS versus NC + LPS).

CONCLUSION

Obesity may paralyze innate immune response of periodontium via attenuating infiltration and activation of macrophages and further aggravate periodontal disease.

A review of the evidence for pathogenic mechanisms that may link periodontitis and diabetes

AIMS

To review the evidence for the molecular and cellular processes that may potentially link periodontal disease and diabetes. The pathogenic roles of cytokines and metabolic molecules (e.g. glucose, lipids) are explored and the role of periodontal bacteria is also addressed. Paradigms for bidirectional relationships between periodontitis and diabetes are discussed and opportunities for elaborating these models are considered.

METHODS

Database searches were performed using MeSH terms, keywords, and title words. Studies were evaluated and summarized in a narrative review.

RESULTS

Periodontal microbiota appears unaltered by diabetes and there is little evidence that it may influence glycaemic control. Small-scale clinical studies and experiments in animal models suggest that IL-1β, TNF-α, IL-6, OPG and RANKL may mediate periodontitis in diabetes. The AGE-RAGE axis is likely an important pathway of tissue destruction and impaired repair in diabetes-associated periodontitis. A role for locally activated pro-inflammatory factors in the periodontium, which subsequently impact on diabetes, remains speculative.

CONCLUSION

There is substantial information on potential mechanistic pathways which support a close association between diabetes and periodontitis, but there is a real need for longitudinal clinical studies using larger patient groups, integrated with studies of animal models and cells/tissues in vitro.

The role of Toll-like receptors in periodontitis

Periodontitis is a common infectious disease. Recent studies have indicated that the progression of periodontitis may be regulated by interactions between host immunity and periodontopathic bacteria. Although periodontopathic bacteria can destroy periodontal tissue, a dysfunctional host immune response triggered by the bacteria can lead to more severe and persistent destruction. Toll-like receptors (TLRs), a type of pattern recognition receptor (PRR) that recognizes pathogens, have been implicated in host innate immune responses to periodontopathic bacteria and in the activation of adaptive immunity. TLR-targeted drugs may hold promise to treat periodontal disease. This review summarizes recent studies on the role of TLRs in periodontitis and discusses areas needing further research. We believe TLRs may be an effective biomarker for the prevention, diagnosis, and treatment of periodontitis in the near future.

Prediabetes Enhances Periodontal Inflammation Consistent With Activation of Toll-Like Receptor-Mediated Nuclear Factor-κB Pathway in Rats

BACKGROUND

Clinical studies have showed that prediabetes (preDM) is a predisposing factor for periodontitis. However, the pathogenic mechanism involved is unclear. Because it is known that the activation of Toll-like receptor (TLR)-mediated nuclear factor-kappa B (NF-κB) signaling pathway plays a crucial role in periodontitis, it is hypothesized that preDM enhances periodontal inflammation by activation of the TLR-mediated NF-κB pathway.

METHODS

In this study, a preDM rat model is established by feeding a high-fat diet (HFD). HFD-induced rats with preDM (n = 7) and normal chow-fed rats (n = 7) were studied. The animal model was characterized in terms of body weight and the glycemic and insulinemic profiles. The following parameters were assessed to evaluate possible early periodontal alterations and underlying mechanisms: 1) histology analysis of periodontal tissue; and 2) serum and mRNA levels and/or the tissue protein expression of TLRs, myeloid differentiation factor 88 (MyD88), tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6), NF-κB, cytokines, advanced glucose ends (AGEs), and free fatty acids (FFAs).

RESULTS

Rats with preDM presented higher expression of TLR2 and TLR4 in periodontal tissue in the HFD group compared with the control group. The TLR2 and TLR4 was mostly expressed in gingiva, and TLR4 was expressed in periodontal ligament in rats. Furthermore, the MyD88 and TRAF6 protein levels were significantly increased in gingiva in rats with preDM compared with normal rats. The activity of NF-κB signals was higher in rats with preDM than in normal rats. Regarding cytokines expression, the TNF-α protein levels and interleukin-1β mRNA levels were significantly increased in the HFD group compared with the control group. In the serum, AGEs levels were significantly increased in the rats with preDM. Mean FFAs concentrations were increased in rats with preDM compared with normal rats, but it did not reach statistical significance.

CONCLUSION

In rats with preDM, TLR2 and TLR4 gene and protein levels were higher in periodontal tissue, and the activation of NF-κB may, through TLRs/MyD88, cause more cytokine secretion, which is associated with the onset or development of periodontal disease.

Host response mechanisms in periodontal diseases

Periodontal diseases usually refer to common inflammatory disorders known as gingivitis and periodontitis, which are caused by a pathogenic microbiota in the subgingival biofilm, including Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Tannerella forsythia and Treponema denticola that trigger innate, inflammatory, and adaptive immune responses. These processes result in the destruction of the tissues surrounding and supporting the teeth, and eventually in tissue, bone and finally, tooth loss. The innate immune response constitutes a homeostatic system, which is the first line of defense, and is able to recognize invading microorganisms as non-self, triggering immune responses to eliminate them. In addition to the innate immunity, adaptive immunity cells and characteristic cytokines have been described as important players in the periodontal disease pathogenesis scenario, with a special attention to CD4⁺ T-cells (T-helper cells). Interestingly, the T cell-mediated adaptive immunity development is highly dependent on innate immunity-associated antigen presenting cells, which after antigen capture undergo into a maturation process and migrate towards the lymph nodes, where they produce distinct patterns of cytokines that will contribute to the subsequent polarization and activation of specific T CD4+ lymphocytes. Skeletal homeostasis depends on a dynamic balance between the activities of the bone-forming osteoblasts (OBLs) and bone-resorbing osteoclasts (OCLs). This balance is tightly controlled by various regulatory systems, such as the endocrine system, and is influenced by the immune system, an osteoimmunological regulation depending on lymphocyte- and macrophage-derived cytokines. All these cytokines and inflammatory mediators are capable of acting alone or in concert, to stimulate periodontal breakdown and collagen destruction via tissue-derived matrix metalloproteinases, a characterization of the progression of periodontitis as a stage that presents a significantly host immune and inflammatory response to the microbial challenge that determine of susceptibility to develop the destructive/progressive periodontitis under the influence of multiple behavioral, environmental and genetic factors.

Periodontal CD14 mRNA expression is downregulated in patients with chronic periodontitis and type 2 diabetes

Background

Patients with type 2 diabetes mellitus (T2DM) have increased severity of periodontitis. Toll-like receptor (TLR)4, its co-receptors CD14 and MD-2, and adaptor MyD88 play pivotal roles in lipopolysaccharide (LPS)-triggered tissue inflammation and periodontitis. This study investigated the effects of T2DM and periodontitis on TLR4, CD14, MD-2 and MyD88 mRNA expression in surgically removed periodontal tissues.

Methods

Periodontal tissue specimens were collected from 14 patients without periodontitis and T2DM (Group 1), 15 patients with periodontitis alone (Group 2), and 7 patients with both periodontitis and T2DM (Group 3). The mRNA of TLR4, CD14, MD-2 and MyD88 was quantified using real-time PCR and compared between the groups.

Results

Statistical analysis showed that periodontal expression of CD14 mRNA was significantly reduced across Groups 1, 2 and 3 (p = 0.02) whereas the mRNA expression of TLR4, MD-2 and MyD88 was not significantly different among the groups. Furthermore, when patients in Groups 1 and 2 were combined (n = 22), the CD14 mRNA expression was significantly lower than that in patients of Group 1 (p = 0.04).

Conclusions

CD14 mRNA expression was downregulated across patients with neither periodontitis nor T2DM, patients with periodontitis alone and patients with both diseases, suggesting that CD14 mRNA expression is associated with a favorable host response or subjected to a negative feedback regulation.

Microbial Nucleic Acid Sensing in Oral and Systemic Diseases

One challenge in studying chronic infectious and inflammatory disorders is understanding how host pattern recognition receptors (PRRs), specifically toll-like receptors (TLRs), sense and respond to pathogen- or damage-associated molecular patterns, their communication with each other and different components of the immune system, and their role in propagating inflammatory stages of disease. The discovery of innate immune activation through nucleic acid recognition by intracellular PRRs such as endosomal TLRs (TLR3, TLR7, TLR8, and TLR9) and cytoplasmic proteins (absent in melanoma 2 and DNA-dependent activator of interferon regulatory factor) opened a new paradigm: Nucleic acid sensing is now implicated in multiple immune and inflammatory conditions (e.g., atherosclerosis, cancer), viral (e.g., human papillomavirus, herpes virus) and bacterial (e.g., Helicobacter pylori, pneumonia) diseases, and autoimmune disorders (e.g., systemic lupus erythematosus, rheumatoid arthritis). Clinical investigations reveal the overexpression of specific nucleic acid sensors in diseased tissues. In vivo animal models show enhanced disease progression associated with receptor activation. The involvement of nucleic acid sensors in various systemic conditions is further supported by studies reporting receptor knockout mice being either protected from or prone to disease. TLR9-mediated inflammation is also implicated in periodontal diseases. Considering that persistent inflammation in the oral cavity is associated with systemic diseases and that oral microbial DNA is isolated at distal sites, nucleic acid sensing may potentially be a link between oral and systemic diseases. In this review, we discuss recent advances in how intracellular PRRs respond to microbial nucleic acids and emerging views on the role of nucleic acid sensors in various systemic diseases. We also highlight new information on the role of intracellular PRRs in the pathogenesis of oral diseases including periodontitis and oral cavity cancer, which might offer future possibilities for disease prevention and therapy.

Circulating cell-free mitochondrial DNA as the probable inducer of early endothelial dysfunction in the prediabetic patient

Recent evidence has shown that 346million people in the world have diabetes mellitus (DM); this number will increase to 439million by 2030. In addition, current data indicate an increase in DM cases in the population between 40 and 59years of age. Diabetes is associated with the development of micro- and macro-vascular complications, derived from chronic hyperglycemia on the endothelium. Some reports demonstrate that people in a prediabetic state have a major risk of developing early endothelial dysfunction (ED). Today, it is accepted that individuals considered as prediabetic patients are in a pro-inflammatory state associated with endothelial and mitochondrial dysfunction. It is important to mention that impaired mitochondrial functionality has been linked to endothelial apoptosis and release of mitochondrial DNA (mtDNA) in patients with sepsis, cardiac disease, or atherosclerosis. This free mtDNA could promote ED, as well as other side effects on the vascular system through the activation of the toll-like receptor 9 (TLR9). TLR9 is expressed in different cell types (e.g., T or B lymphocytes, mastocytes, and epithelial and endothelial cells). It is localized intracellularly and recognizes non-methylated dinucleotides of viral, bacterial, and mitochondrial DNA. Recently, it has been reported that TLR9 is associated with the pathogenesis of lupus erythematosus, rheumatoid arthritis, and autoimmune diabetes. In this work, it is hypothesized that the increase in the levels of circulating mtDNA is the trigger of early ED in the prediabetic patient, and later on in the older patient with diabetes, through activation of the TLR9 present in the endothelium.

Toll-Like Receptor 9-Mediated Inflammation Triggers Alveolar Bone Loss in Experimental Murine Periodontitis

Chronic periodontitis is a local inflammatory disease induced by a dysbiotic microbiota and leading to destruction of the tooth-supporting structures. Microbial nucleic acids are abundantly present in the periodontium, derived through release after phagocytic uptake of microbes and/or from biofilm-associated extracellular DNA. Binding of microbial DNA to its cognate receptors, such as Toll-like receptor 9 (TLR9), can trigger inflammation. In this study, we utilized TLR9 knockout (TLR9(-/-)) mice and wild-type (WT) controls in a murine model of Porphyromonas gingivalis-induced periodontitis and report the first in vivo evidence that TLR9 signaling mediates the induction of periodontal bone loss. P. gingivalis-infected WT mice exhibited significantly increased bone loss compared to that in sham-infected WT mice or P. gingivalis-infected TLR9(-/-) mice, which were resistant to bone loss. Consistent with this, the expression levels of interleukin 6 (IL-6), tumor necrosis factor (TNF), and receptor-activator of nuclear factor kappa B ligand (RANKL) were significantly elevated in the gingival tissues of the infected WT mice but not in infected TLR9(-/-) mice compared to their levels in controls. Ex vivo studies using splenocytes and bone marrow-derived macrophages revealed significantly diminished cytokine production in TLR9(-/-) cells relative to the cytokine production in WT cells in response to P. gingivalis, thereby implicating TLR9 in inflammatory responses to this organism. Intriguingly, compared to the cytokine production in WT cells, TLR9(-/-) cells exhibited significantly decreased proinflammatory cytokine production upon challenge with lipopolysaccharide (LPS) (TLR4 agonist) or Pam3Cys (TLR2 agonist), suggesting possible cross talk between TLR9, TLR4, and TLR2. Collectively, our results provide the first proof-of-concept evidence implicating TLR9-triggered inflammation in periodontal disease pathogenesis, thereby identifying a new potential therapeutic target to control periodontal inflammation.

Chemokine function in periodontal disease and oral cavity cancer

The chemotactic cytokines, or chemokines, comprise a superfamily of polypeptides with a wide range of activities that include recruitment of immune cells to sites of infection and inflammation, as well as stimulation of cell proliferation. As such, they function as antimicrobial molecules and play a central role in host defenses against pathogen challenge. However, their ability to recruit leukocytes and potentiate or prolong the inflammatory response may have profound implications for the progression of oral diseases such as chronic periodontitis, where tissue destruction may be widespread. Moreover, it is increasingly recognized that chronic inflammation is a key component of tumor progression. Interaction between cancer cells and their microenvironment is mediated in large part by secreted factors such as chemokines, and serves to enhance the malignant phenotype in oral and other cancers. In this article, we will outline the biological and biochemical mechanisms of chemokine action in host–microbiome interactions in periodontal disease and in oral cancer, and how these may overlap and contribute to pathogenesis.

High acid phosphatase level in the gingival tissues of periodontitis subjects

Aim:

Periodontitis is one of the major problems slowly progressing and could affect 70% of the global population. The prevalence of periodontitis differs from mild to moderate forms of race and geographic region. The aim of this study is to determine the acid phosphatase (ACP) activity in the gingival tissues of periodontitis subjects. In this study, the activity of ACP in the gingival tissue of subjects with periodontitis was examined.

Materials and Methods:

A total of 30 subjects were selected for the study and are divided into group I (n = 15, healthy subjects in control) and in group II (n = 15, periodontitis subjects). The gingival tissue from group I and group II subjects were collected after the surgery and the ACP enzyme level was analyzed using ultraviolet spectrophotometer. Assessment of periodontitis was done based on periodontal probing depth (PPD) and clinical attachment level (CAL). The statistical analysis applied was independent sample t-test, P < 0.05 was considered as significant.

Results:

The results of group II periodontitis subjects showed statistically significant increased gingival tissues ACP level when compared with the control group I subject. The mean levels of CAL and PPD were significantly >4 mm in periodontitis subjects when compared to control.

Conclusions:

The elevated level of ACP in the gingival tissue and Gram-negative microorganisms found in sub-gingival plaque was greater in periodontitis. Based on these results, gingival tissue ACP level can be considered as an independent risk factor for evaluating the microbial status and periodontal tissue damage.

Resveratrol ameliorates experimental periodontitis in diabetic mice through negative regulation of TLR4 signaling

AIM

To investigate the therapeutic effects of resveratrol (RSV) on periodontitis in diabetic mice and to explore the underlying mechanisms in vitro.

METHODS

Experimental periodontitis was induced in db/db mice by ligature application of porphyromonas gingivalis. The mice were treated with RSV (20 mg/kg, p.o.) daily for 4 weeks. Alveolar bone loss, proinflammatory cytokines and TLR4 expression in the gingival tissue were measured. Cultured gingival epithelial cells (GECs) were used for in vitro studies. The transcriptional activity of TLR4 downstream signaling was analyzed using Western blotting.

RESULTS

RSV administration significantly decreased the blood glucose levels, and ameliorated alveolar bone loss in db/db mice with experimental periodontitis. RSV administration also suppressed the high levels of IL-1β, IL-6, IL-8, TNF-α, and TLR4 in gingival tissue of the mice. In the GECs incubated in high glucose medium, TLR4 expression was substantially upregulated, which was partly blocked in the presence of RSV. Lipopolysaccharides markedly increased the expression and secretion of IL-1β, IL-6, IL-8, and TNF-α in the GECs cultured in high glucose medium, which was also partly blocked in the presence of RSV. Furthermore, RSV significantly suppressed the phosphorylation of TLR4 downstream factors NF-κB p65, p38MAPK, and STAT3.

CONCLUSION

RSV exerts protective effects against experimental periodontitis in db/db mice via negative regulation of TLR4 signaling.

mRNA expression of pattern recognition receptors and their signaling mediators in healthy and diseased gingival tissues

Background:

Gingivitis and periodontitis are initiated by inflammation caused by microorganisms. Pathogen-associated molecular patterns (PAMPs) from these microorganisms are recognized through various toll-like receptors (TLRs) and NOD-like receptors (NLRs). In this study, we have chosen five TLRs and two NLRs as representatives taking part in the recognition and inflammation process, along with a few of their signaling mediators including CD14, MYD88, and TRIF to compare their mRNA expression levels between healthy and diseased gingival tissues. This will provide deeper insight into the mechanisms underlying gingivitis and periodontitis. Understanding the mechanisms involved in the onset and progression of the periodontal diseases could greatly help in establishing effective ways for prevention and treatment of these diseases besides decreasing the risk factor for relevant systemic disorders.

Materials and Methods:

Gingival tissue samples for mRNA extraction and cDNA synthesis were taken from patients with gingivitis and periodontitis and from healthy control subjects. Messenger RNA expression of all genes was assessed using real-time polymerase chain reaction (PCR).

Results:

Among the genes studied in different groups, only MYD88 mRNA expression was significantly higher in the periodontitis group compared to that of the controls. The expression level of this molecule was also significantly higher in patients with severe periodontitis compared to other patients and also compared to healthy individuals. In different tissues, positive significant correlations were observed between the mRNA expression levels of some genes.

Conclusions:

Elevated mRNA levels of MYD88 in periodontitis might have a key role in the pathogenesis of this disease. Therefore, MYD88 may be a useful target for the therapy of this disease.

Lipopolysaccharide differentially affects the osteogenic differentiation of periodontal ligament stem cells and bone marrow mesenchymal stem cells through Toll-like receptor 4 mediated nuclear factor κB pathway

Introduction

Periodontitis is initiated and sustained by bacteria. However, the mechanism of bacteria induced periodontitis is still unknown. We hypothesized that bacterial components can affect the functions of stem cells in the periodontium. In this study, we comparatively investigated the influence of Lipopolysaccharide (LPS) on the osteogenesis potential of human periodontal ligament stem cells (PDLSCs) and bone marrow mesenchymal stem cells (BMMSCs).

Methods

Human PDLSCs and BMMSCs were harvested and mineralized nodule formation was assessed by alizarin red S staining. Expression level of osteogenic related gene was detected by quantitative RT-PCR (qRT-PCR). The expression of Toll-like receptor 4 (TLR4) and its downstream signaling pathway were examined by western blot. The role of TLR4 and related signaling pathway in LPS impairing the osteogenic potential of human PDLSCs and BMMSCs were also studied by alizarin red S staining and qRT-PCR. Experimental periodontitis was induced in adult Sprague–Dawley rats and the alveolar bone loss was measured by micro computed tomography analysis. The expression of alkaline phosphatase (ALP) was assessed by immunohistochemistry and the number of osteoclasts was shown by Tartrate-resistant acid phosphatase (TRAP) staining.

Results

LPS decreased the osteogenic differentiation of human PDLSCs through TLR4 regulated nuclear factor (NF)-κB pathway, but not for BMMSCs. Blocking TLR4 or NF-κB signaling partially reversed the decreased osteogenic potential of PDLSCs and prevented the alveolar bone loss caused by LPS experimental periodontitis in rats. The ALP expression in the periodontal ligament was elevated after treatment with anti-TLR4 antibody or pyrrolidinedithiocarbamate, whereas there was no statistical significance among groups for the number of osteoclasts.

Conclusions

These data suggest that LPS can activate TLR4 regulated NF-κB pathway of human PDLSCs, thus decreasing their osteogenic potential. Blockage of TLR4 or NF-κB pathway might provide a new approach for periodontitis treatment.

Prioritization of candidate genes for periodontitis using multiple computational tools

BACKGROUND

Both genetic and environmental factors contribute to the development of periodontitis. Genetic studies identified a variety of candidate genes for periodontitis. The aim of the present study is to identify the most promising candidate genes for periodontitis using an integrative gene ranking method.

METHODS

Seed genes that were confirmed to be associated with periodontitis were identified using text mining. Three types of candidate genes were then extracted from different resources (expression profiles, genome-wide association studies). Combining the seed genes, four freely available bioinformatics tools (ToppGene, DIR, Endeavour, and GPEC) were integrated for prioritization of candidate genes. Candidate genes that identified with at least three programs and ranked in the top 20 by each program were considered the most promising.

RESULTS

Prioritization analysis resulted in 21 promising genes involved or potentially involved in periodontitis. Among them, IL18 (interleukin 18), CD44 (CD44 molecule), CXCL1 (chemokine [CXC motif] ligand 1), IL6ST (interleukin 6 signal transducer), MMP3 (matrix metallopeptidase 3), MMP7, CCR1 (chemokine [C-C motif] receptor 1), MMP13, and TLR9 (Toll-like receptor 9) had been associated with periodontitis. However, the roles of other genes, such as CSF3 (colony stimulating factor 3 receptor), CD40, TNFSF14 (tumor necrosis factor receptor superfamily, member 14), IFNB1 (interferon-β1), TIRAP (toll-interleukin 1 receptor domain containing adaptor protein), IL2RA (interleukin 2 receptor α), ETS1 (v-ets avian erythroblastosis virus E26 oncogene homolog 1), GADD45B (growth arrest and DNA-damage-inducible 45 β), BIRC3 (baculoviral IAP repeat containing 3), VAV1 (vav 1 guanine nucleotide exchange factor), COL5A1 (collagen, type V, α1), and C3 (complement component 3), have not been investigated thoroughly in the process of periodontitis. These genes are mainly involved in bacterial infection, immune response, and inflammatory reaction, suggesting that further characterizing their roles in periodontitis will be important.

CONCLUSIONS

A combination of computational tools will be useful in mining candidate genes for periodontitis. These theoretical results provide new clues for experimental biologists to plan targeted experiments.

Analysis of Expression and Localization of TLR-2 by Immunofluorescent Technique in Healthy and Inflammed Oral Tissues

INTRODUCTION

Toll-like receptors (TLRs) are an important component of immune system. Among them, TLR-2 plays a dominant role in the oral tissues in initiating inflammation in chronic periodontitis. Not many studies have been done on quantitative expression of TLR-2 by using immunofluorescent techniques (IFT) in oral tissues. In this study, the expression and localisation of TLR-2 were detected in gingival tissues of chronic periodontitis patients and healthy individuals.

MATERIAL AND METHODS

Immuno Fluorescent Technique (IFT) was used for the expression and localization of TLR-2 in gingival tissue samples from 25 chronic periodontitis patients and from 25 healthy controls. Haematoxylin and Eosin staining was also done for all the samples to determine the histological characteristics of the gingival tissue samples.

RESULT

Both healthy and periodontitis gingival tissues expressed TLR-2. We found that the expression level of TLR-2 was higher in all the periodontitis patients than in healthy individuals. We also found out that the expression of TLR-2 was higher in the epithelial cells than in the connective tissue cells.

CONCLUSION

These data suggest a definite involvement of TLR-2 in initiating an inflammatory response in periodontal tissues. More studies are required to define the mechanisms and expression levels of TLR-2 in oral health and diseases.

Periodontitis: oral complication of diabetes

Periodontitis is a common, chronic, inflammatory disease in which the supporting apparatus of the teeth is gradually destroyed, resulting in tooth mobility and tooth loss. Susceptibility to periodontitis is increased approximately three-fold in people with diabetes. Hyperglycemia leads to exacerbated tissue destruction and the clinical signs of periodontitis. There is evidence to support a two-way relationship between periodontitis and diabetes; not only does diabetes increase the risk for periodontitis, but periodontitis is associated with compromised glycemic control. Cooperation between health care teams would benefit the treatment of patients with diabetes and periodontitis.

The role of Toll-like receptor 2 and 4 in gingival tissues of chronic periodontitis subjects with type 2 diabetes

BACKGROUND AND OBJECTIVE

Diabetes is one important risk factor of chronic periodontitis. However, the roles of toll-like receptor (TLR) 2 and TLR4, which are implicated in the inflammatory process in both chronic periodontitis and diabetes, have not been studied. This study aimed to determine whether TLR2 and TLR4 might be involved in the relationship between chronic periodontitis and diabetes by examining TLR2 and TLR4 expression in gingival tissues from subjects with chronic periodontitis without diabetes (CP) and with diabetes (CP+DM) and from periodontally healthy subjects without diabetes (PH) and with diabetes (PH+DM).

MATERIAL AND METHODS

Gingival tissues were collected from 23 CP subjects, 21 CP+DM subjects, 22 PH subjects and 20 PH+DM subjects. The expression of TLR2 and TLR4 in gingival tissues was determined using an immunohistochemical method. In gingival epithelium, staining patterns and intensity levels of TLR2 and TLR4 expression were studied. In connective tissues, the percentages of TLR2- and TLR4-positive cells were calculated. The intensity levels and the percentages of positive cells were statistically analyzed.

RESULTS

Chronic periodontitis or diabetes showed no significant effect on TLR2 expression in the oral epithelium. However, diabetes increased the expression of TLR2 in sulcular epithelium and changed the pattern of TLR2 expression in gingival epithelium. Chronic periodontitis decreased the expression of TLR4 in gingival epithelium. In connective tissue under sulcular epithelium, CP+DM subjects showed statistically significant higher percentages of TLR2- and TLR4-positive cells compared with PH and PH+DM subjects.

CONCLUSION

Our results suggest that hyperglycemia and chronic periodontitis had effects on TLR2 and TLR4 expression in gingival tissue. The differences in TLR2 and TLR4 expression could contribute to a greater inflammatory response, leading to periodontal disease initiation and progression.

Increased nucleic Acid receptor expression in chronic periodontitis

BACKGROUND

Nucleic acid sensing has emerged as one of the important components of the immune system triggering inflammation. The aim of this study is to determine the expression of bacterial DNA sensors, including Toll-like receptor 9 (TLR-9), DNA-dependent activator of interferon-regulatory factors (DAI), and absent in melanoma 2 (AIM2) in chronic periodontitis (CP versus healthy) (H) tissues.

METHODS

Thirty-five CP and 27 H gingival biopsies were included. Real-time quantitative polymerase chain reaction was performed to determine mRNA levels of AIM2, DAI, and TLRs (TLR-1 through TLR-9). The difference in gene expression for each sensor between CP and H tissues was calculated using analysis of covariance. The Spearman test was used to determine correlations among innate receptors. The expression of TLR-9, AIM2, and DAI in gingival tissues was further confirmed using immunohistochemistry.

RESULTS

The present results reveal statistically significant upregulation of TLR-9 (P <0.006), DAI (P <0.001), and TLR-8 (P <0.01) in CP tissues compared to H sites. Although mRNA expression was not changed significantly between groups for other receptors, the present results reveal significant correlations between receptors (P <0.05), suggesting that cooperation between multiple components of the host immune system may influence the overall response. Immunohistochemistry further confirmed expression of TLR-9, AIM2, and DAI in gingival tissues.

CONCLUSIONS

This study highlights a possible role for nucleic acid receptors in periodontal inflammation. Future investigations will determine whether cytoplasmic receptors and their ligands can be targeted to improve clinical outcomes in periodontitis.

25-Hydroxyvitamin D3 attenuates experimental periodontitis through downregulation of TLR4 and JAK1/STAT3 signaling in diabetic mice

Vitamin D has been known to be closely associated with diabetes and periodontitis while the underlying mechanism has yet to be clarified. The present study aimed to discover the effect of 25-hydroxyvitamin D3 (25-OHD3) on glycemic control and periodontal health in mice with periodontitis superimposed on experimental diabetes (known as diabetic periodontitis). We showed that 25-OHD3 intraperitoneal injection attenuated diabetic periodontitis by reducing serum fasting blood glucose, glycosylated hemoglobin and TNF-α levels, which led to decreased alveolar bone loss. Immunohistochemical staining and western blot analysis of gingival epithelia revealed that vitamin D receptor (VDR) expression was enhanced upon 25-OHD3 treatment, while toll-like receptor 4 (TLR4) expression was reduced. The expressions of Janus family kinase (JAK) 1 and signal transducer and activator of transcription (STAT) 3 as well as their phosphorylation were inhibited in gingival epithelia of diabetic periodontitis mice, whereas the expression and phosphorylation of STAT1 remained unchanged. These results suggest that 25-OHD3 could improve diabetic periodontitis through downregulation of TLR4 and JAK1/STAT3 signaling in the gingival epithelium. Our study extends the previous findings on the regulation of diabetes with periodontitis, and may also provide a potential therapy for the patients with this disease.