T-Lymphocyte and Cytokine Expression in Human Inflammatory Periapical Lesions

Cytokine expression of IL-8 before and after root canal treatment in patients with symptomatic apical periodontitis: A clinical trial

This study's objective was to compare the cytokine expression of IL-8 in periapical tissues of single-rooted teeth with symptomatic apical periodontitis (SAP) before and after root canal treatments. As well as, comparing IL-8 levels in peri-apical tissues between vital and necrotic teeth with SAP.

METHODOLOGY

Thirty-six patients were allocated according to their pulp status into two experimental groups (n = 18) receiving the same treatment protocol; group 1: Vital pulps with SAP, and group 2: non-vital pulps with SAP. Conventional endodontic treatment was done on two visits; isolation and disinfection of the operative field were undertaken, and two-stage access cavity preparation was implemented. The first pre-instrumentation peri-apical sample (S1) was collected prior to cleaning and shaping procedures. A 2.5% NaOCl irrigation was used to thoroughly irrigate the canal after performing root canal preparation utilising the ProTaper Next (PTN) rotary system. After 1 week, the second post-instrumentation peri-apical sample (S2) was collected. Using an ELISA kit, the quantity of IL-8 was evaluated following the collection of all samples.

RESULTS

In all pre-instrumentation samples, IL-8 was detected (100%). The level of IL-8 expression was significantly decreased from the S1 to S2 of all samples (p < 0.001). The intra-group comparison showed a statistically significant reduction in the level of IL-8 expression between S1 and S2 in both vital and non-vital groups where p < 0.001* in both groups. The inter-group comparison of levels of IL-8 expression (vital and non-vital) revealed a significant difference between both groups regarding the pretreatment sample with the higher levels of IL-8 shown in the non-vital group (p < 0.001). While in the post-treatment sample, both groups showed a significant reduction in the level of IL-8 expression but the difference between them was not statistically significant (p = 0.226).

CONCLUSION

Root canal instrumentation seems to be efficient in decreasing the levels of anti-inflammatory cytokines, namely IL-8. Further research should clarify how intra-canal medicaments affect inflammatory mediator levels.

Correlation Between Proinflammatory Cytokine Expression and Clinical Data in Apical Granuloma

INTRODUCTION

This study was intended to evaluate the expression of inflammatory cytokines commonly secreted by CD4+ T cells (IL-2, IL-5, IL-17, TGF-β, TNF-α, and IFN-γ) in apical granulomas and correlate with the clinical conditions and time elapsed since root canal treatment.

METHODS

Eighteen biopsy specimens obtained by periradicular surgery of teeth with post-treatment apical periodontitis and diagnosed as apical granuloma were available from the oral pathology laboratory. Silanized slides containing paraffin sections were used for immunohistochemical reactions. Images were analyzed by using an optical microscopy and each slide was subdivided into 5 fields at high magnification.

RESULTS

IFN-γ and TGF-β were the cytokines with the highest expression levels. There were statistically significant differences when comparing IL-2 and IFN-γ (P < .05), and IL-2 and TGF-β (P < .05). Comparison between the detected cytokines and clinical data and time of treatment demonstrated significant correlation (P < .05) between lower expression of IL-2 and the presence of painful symptoms, absence of sinus tract, and treatments performed more than 4 years before. It was also possible to observe a significant correlation between lower expression of IL-5 and treatments performed less than 4 years before (P < .05).

CONCLUSION

IFN-γ and TGF-β were highly expressed in apical granulomas. However, only IL-2 and IL-5 levels were associated with clinical data and time since previous root canal treatment.

Mines of cytokine: A treasure trove in pulpal and periapical diseases

Pulpitis is a special disease of dental pulp. It causes localized inflammation, due to various inflammatory mediators such as cytokines and chemokines. These inflammatory mediators are responsible for various reparative and resorptive processes in the dental pulp. The balance between these processes ultimately determines the viability of the tooth. Due to the important properties of various inflammatory markers, the correlation of cytokinin gene expression in various stages of inflammation becomes necessary to focus on. Several studies in the past have focused on the importance of such correlation to help in diagnostic applications. The nature of these inflammatory mediators can help us in diagnostic evaluation. Several attempts have been made to focus on these associations so that it can assist in making clinical decisions effectively. The data available are vast but are the most neglected topic. This review article briefly outlines and summarizes the importance of various inflammatory mediators such as cytokinin and chemokines in various pathways of pulpal and periapical inflammation in explanatory and diagrammatic forms. Knowledge gained about pulpal inflammatory response may aid in understanding the molecular level of inflammatory pulpal and periapical diseases, which shall modify our future diagnostic modalities. Several medicaments are used in the treatment of minimal to advanced dental caries which leads to periapical infections. Thorough understanding of these medicaments can resolve secondary infection and can improve the prognosis of the treated tooth.

Zoledronic Acid Modulates Cytokine Expression and Mitigates Bone Loss during the Development of Induced Apical Periodontitis in a Mice Model

INTRODUCTION

Bisphosphonates are antiresorptive drugs used worldwide to treat systemic bone pathologies. This study aimed to assess the impact of zoledronic acid on the progression of induced apical periodontitis and the expression of cytokines interleukin (IL)-1β, IL-10, IL-6, and tumor necrosis factor alpha (TNF-α) in a mouse model.

METHODS

Sixteen female isogenic BALB/c mice 6 weeks of age were distributed into 2 groups: mice with induced apical periodontitis (the AP group, n = 8) and mice with induced apical periodontitis treated with zoledronic acid (the AP-ZA group, n = 8). The AP-ZA group received a dose of 125 μg/kg zoledronic acid diluted in sterile saline solution administered intraperitoneally once a week for 4 weeks before pulp exposure, whereas the AP group received only saline solution. Pulp exposures were performed on the maxillary first molars for the induction of apical periodontitis, and mice were euthanized after 7 and 21 days. The jaws were collected; scanned using micro-computed tomographic imaging; and processed for polymerase chain reaction analysis of IL-1β, IL-10, IL-6, and TNF-α. The Student t test was performed for parametric data, and Mann-Whitney U tests were used for nonparametric data. The level of significance was set at 5%.

RESULTS

Micro-computed tomographic imaging revealed higher bone resorption in the AP group compared with the AP-ZA group at both time points (P < .05). Real-time polymerase chain reaction demonstrated higher TNF-α expression in the AP group at both time points and higher IL-6 and IL-1β expression in the AP group at the 7- and 21-day time points, respectively, compared with the AP-ZA group (P < .05). No differences were observed regarding IL-10 expression between the groups.

CONCLUSIONS

Zoledronic acid had significant anti-inflammatory and antiresorptive effects on apical periodontitis in mice.

Effects of direct pulp capping with recombinant human erythropoietin and/or mineral trioxide aggregate on inflamed rat dental pulp

OBJECTIVE

This study aimed to evaluate the dental pulp responses to recombinant human erythropoietin (rhEPO) and/or mineral trioxide aggregate (MTA) in pulp capping of inflamed dental pulp in vivo.

MATERIALS AND METHODS

In accordance with ARRIVE guidelines, pulp inflammation was induced by exposing the maxillary first molars (n = 64) of Wistar rats (n = 32) to the oral environment for two days. The exposed pulps were randomly assigned four groups based on the pulp capping material: rhEPO, MTA, MTA + rhEPO, or an inert membrane. An additional eight rats formed the healthy control group. After four weeks, the animals were euthanized, and histological, qRT-PCR, and spectrophotometric techniques were employed to analyze the left maxillary segments, right first maxillary molars, and blood samples, respectively. Statistical significance was set at p < 0.05 and < 0.001.

RESULTS

Pulp capping with rhEPO, MTA, or MTA + rhEPO resulted in lower inflammation and higher mineralization scores compared to untreated control. MTA + rhEPO group exhibited significantly decreased expression of tumor necrosis factor-alpha, and interleukin 1-beta, while MTA group showed substantially reduced expression of interferon-gamma. Both rhEPO and MTA + rhEPO groups presented elevated dentin matrix protein 1 levels compared to untreated control. Furthermore, pulp capping with rhEPO and/or MTA led to increased transforming growth factor-beta 1 expression and reductions of pro-inflammatory/immunoregulatory cytokine ratios and prooxidative markers. Pulp capping with rhEPO also resulted in increase of systemic antioxidative stress markers.

CONCLUSION

Capping with rhEPO or MTA + rhEPO resulted in a favorable effect that was similar or even superior to that of MTA.

Interleukin 6 and Interleukin 1β hypomethylation and overexpression are common features of apical periodontitis: a case-control study with gingival tissue as control

OBJECTIVES

Apical periodontitis is a periradicular tissue disorder that usually arises from infection by microorganisms in the root canal system resulting in local bone resorption. This usually involves the dysregulation of inflammatory mediators, which can be mediated by epigenetic mechanisms. Thus, the objective of this study was to evaluate Interleukin 6 (IL6) and Interleukin 1β (IL1β) and DNA methylation and gene expression levels in apical periodontitis.

METHODS

Gene expression was analyzed in 60 participants using quantitative polymerase chain reaction, while the methylation levels of IL6 and IL1β promoters were analyzed in 72 patients using pyrosequencing. All statistical analyzes were performed using the GraphPad Prism software version 8.0. The p value was considered statistically significant when < 0.05.

RESULTS

A significantly higher IL6 and IL1β expression levels were observed in cases relative to controls (fold-changes of 27.4 and 11.43, respectively, and p < 0.0001). By comparing the same groups, lower promoter methylation levels were observed for both genes in cases (methylation percentage delta relative to controls of -24.57% and -16.02%, respectively, and p < 0.0001). A significant inverse correlation between gene expression and promoter methylation was observed for both IL6 (p = 0.0002) and IL1β (p = 0.001). Neither IL6 expression nor promoter methylation were significantly associated with cases' age, smoking history, alcohol consumption history or sex. For IL1β, alcoholic cases showed lower methylation level relative to non-alcoholic cases (p = 0.01), while females showed higher methylation levels relative to males (p = 0.03).

CONCLUSIONS

Our data suggest a role for DNA methylation in IL6 and IL1β upregulation in apical periodontitis.

NLRP3 Disturbs Treg/Th17 Cell Balance to Aggravate Apical Periodontitis

Apical periodontitis is an inflammatory condition that is considered an immunological reaction of the periapical tissue to invading bacteria and their pathogenic components. Recent research has revealed that NLR family pyrin domain containing 3 (NLRP3) is crucial to the pathogenesis of apical periodontitis and serves as a link between innate and adaptive immunity. The balance between regulatory T-cell (Treg) and T helper cell 17 (Th17 cell) determines the direction of the inflammatory response. Therefore, this study aimed to investigate whether NLRP3 exacerbated periapical inflammation by disturbing Treg/Th17 balance and the underlying regulatory mechanisms. In the present study, NLRP3 was raised in apical periodontitis tissues as opposed to healthy pulp tissues. Low NLRP3 expression in dendritic cells (DCs) increased transforming growth factor β secretion while decreasing interleukin (IL)-1β and IL-6 production. The Treg ratio and IL-10 secretion rose when CD4⁺ T cells were cocultured with DCs primed with IL-1β neutralizing antibody (anti-IL-1β) and specific small interfering RNA (siRNA) targeting NLRP3 (siRNA NLRP3), but the proportion of Th17 cells and IL-17 release dropped. Furthermore, siRNA NLRP3-mediated suppression of NLRP3 expression aided Treg differentiation and elevated Foxp3 expression as well as IL-10 production in CD4⁺ T cells. Inhibition of NLRP3 activity by MCC950 boosted the percentage of Tregs while decreasing the ratio of Th17 cells, leading to reduced periapical inflammation and bone resorption. Nigericin administration, however, exacerbated periapical inflammation and bone destruction with an unbalanced Treg/Th17 response. These findings demonstrate that NLRP3 is a pivotal regulator by regulating the release of inflammatory cytokines from DCs or directly suppressing Foxp3 expression to disturb Treg/Th17 balance, thus exacerbating apical periodontitis.

0.1% Nano-silver mediates PD-1/PD-L1 pathway and alleviates chronic apical periodontitis in rats

This study was to investigate whether the programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) and T-helper 17 (Th17)/regulatory T (Treg) balance are associated with chronic apical periodontitis (CAP) relived by 0.1% nano-silver. CAP rat models were established by opening the first molars of the right and left mandible and exposing the pulp cavity to the oral cavity. CAP model was verified by cone-beam computed tomography, X-ray digital radiovisiography, and hematoxylin-eosin (H and E) staining. The rats were randomly divided into the sham, Ca(OH)₂, and 0.1% nano-silver groups (n = 12 in each group) 2 weeks after surgery. The pathological changes in the apical area were detected by H and E staining. PD-1, PD-L1, RORγT, IL-17, and Foxp3 in periapical tissues were detected by qRT-PCR and immunohistochemistry. Th17/Treg and PD-1/PD-L1 were analyzed by flow cytometry. After 7, 14, and 21 days of 0.1% nano-silver treatment, inflammatory cells in the apical region were slightly reduced and inflammatory infiltration was relieved compared with the sham group. RORγT, IL-17, PD-1, and PD-L1 decreased and Foxp3 increased after 7, 14, and 21 days of 0.1% nano-silver treatment compared with the sham group (p < 0.05); however, there were no significant differences with Ca(OH)₂ group (p > 0.05). Flow cytometry revealed that 0.1% nano-silver solution decreased Th17/Treg and PD-1/PD-L1 ratio. 0.1% Nano-silver significantly reduced the inflammation of CAP in rats. PD-1/PD-L1 was included in Th17/Treg balance restored by 0.1% nano-silver.

Protective Actions in Apical Periodontitis: The Regenerative Bioactivities Led by Mesenchymal Stem Cells

Resulting from bacterial infection, apical periodontitis (AP) is a common inflammatory disease of the periapical region of the tooth. The regeneration of the destroyed periapical alveolar bone and the surrounding periodontium tissues has long been a difficult task in clinical practice. These lesions are closely related to pathogen invasion and an overreactive immune response. It is worth noting that the protective healing process occurs simultaneously, in which mesenchymal stem cells (MSCs) have a crucial function in mediating the immune system and promoting regeneration. Here, we review the recent studies related to AP, with a focus on the regulatory network of MSCs. We also discuss the potential therapeutic approaches of MSCs in inflammatory diseases to provide a basis for promoting tissue regeneration and modulating inflammation in AP. A deeper understanding of the protective action of MSCs and the regulatory networks will help to delineate the underlying mechanisms of AP and pave the way for stem-cell-based regenerative medicine in the future.

Curcumin reduces inflammation in rat apical periodontitis

AIM

To evaluate the effect of systemic curcumin administration on the severity of apical periodontitis (AP).

METHODOLOGY

Forty male Wistar rats weighing 250-280g each, age 2.5 months, were distributed into four groups (n=10): control untreated rats (C), control rats treated with curcumin (CUR), rats with pulp exposure-induced apical periodontitis (AP), and rats with pulp exposure-induced apical periodontitis treated with curcumin (AP-CUR). Curcumin treatment was administered orally once daily for 15 days before pulp exposure and continued for 30 days after pulp exposure. The rats were sacrificed at 30 days, and the jaws were collected and reconstructed in a program specific for micro-CT. The jaws were processed for analysis of the inflammatory process using Haemotoxylin and Eosin staining and immunohistochemical assays for interleukin tumour necrosis factor alpha (TNF-α), interleukin (Il)-6, and Il-1β. Tartrate-resistant acid phosphatase (TRAP) and osteocalcin (OCN) staining were used to analyze the resorptive process on the bone surface of periapical area. Kruskal-Wallis with Dunn's test was performed for nonparametric data, and ANOVA with Tukey's test for parametric data, p < .05.

RESULTS

Micro-CT revealed no statistically significant differences in bone resorption between the AP and AP-CUR groups (p > .05). The levels of inflammatory cell infiltration and immunoreactivity for the proinflammatory cytokines TNF-α, Il-6, and Il-1β were significantly higher in the periapical lesions of the AP group than in the AP-CUR group (p < .05). The number of TRAP-positive multinucleated cells was higher in the AP group than in the AP-CUR group (p < .05). In OCN-positive cells, no differences were observed between the AP and AP-CUR groups (p > .05).

CONCLUSIONS

Oral supplementation with curcumin had a significant effect on the AP severity in rats, suggesting an anti-inflammatory effect of curcumin on AP development.

Effects of calcium hydroxide intracanal medications on T helper (Th1, Th2, Th9, Th17, and Tfh) and regulatory T (Treg) cell cytokines in apical periodontitis: a CONSORT RCT

INTRODUCTION

This CONSORT RCT investigated T helper (Th1, Th2, Th9, Th17, and Tfh), regulatory T (Treg) cell-type cytokines, and their networks in apical periodontitis (AP). We also assessed the effects of calcium hydroxide [Ca(OH)2] intracanal medications (ICMs) on helper T and Treg cell-type cytokines.

METHODS

Twenty teeth with primary endodontic infection and apical periodontitis (PEIAP) were randomly divided into two groups: Ca(OH)2 + saline solution (SSL; n = 10) and Ca (OH)2 + 2% Chlorhexidine-gel (2% CHX-gel; n = 10). Samples were collected from the periradicular tissue fluid (PTF) before (PTFs1) and after 14 days of ICMs (PTFs2). The Human High Sensitivity T Cell Panel was used to quantify target T-helper (Th)1: IL-2, 12, and IFN-γ; Th2: IL-4, -5, -13; Th9: IL-9; Th17: IL-17; T follicular helper cells (Tfh): IL-21; and Treg-cell-type cytokine: IL-10.

RESULTS

Th1-type cytokines were higher, compared to Th2-type, at PTFs1. Positive (+) associations were found among all Th1-type cytokines and all Th2-type cytokines. There were negative (-) correlations between all Th1- and Th2-type cytokines. Size of radiolucent lesions (SRL) and symptoms (TTP and/or POP) were positively correlated with Th1-type cytokines, IL-17, and IL-21 but negatively correlated with Th2-type cytokines and IL-10 (all, p < 0.001). Both ICMs increased Th2-type cytokines and IL-10 (P < 0.05) and decreased Th1- type cytokines, IL-17, and IL-21 (P < 0.05), with no differences among them (P > 0.05).

CONCLUSIONS

Complex T-cell cytokine networks are involved in AP. Both Ca(OH)2 ICMs effectively increased IL-4, IL-5, IL-10, and IL-13 and lowered IL-2, IL-12, IL-17, IL-21, and IFN-γ.

Local immunomodulatory effects of intracanal medications in apical periodontitis

The immune system is an extremely complex biological network that plays a crucial role in the hemostasis of periapical tissue, pathogenesis of apical periodontitis (AP) as well as periapical tissue healing. The successful elimination of microbial infections remains a significant challenge, mostly due to the ever-growing development of antimicrobial-resistant pathogens. The bacterial endurance in the root canal system contributes to features ranging from altered post-treatment healing to exacerbation of chronic periradicular immune response, that compromise the outcome of endodontic treatment. A highly effective strategy for combating infectious diseases and the associated inflammation-mediated tissue damage is to modulate the host immune response in conjunction with antimicrobial therapy. There are several medications currently used in endodontic treatment, however, they suffer various levels of microbial resistance and do not deliver all the required characteristics to simultaneously address both intracanal bacteria and periapical inflammation. Interaction of antimicrobial agents with the immune system can impact its function, leading to immune-suppressive or immune-stimulatory effects. The group of non-conventional antimicrobial medications, such as antimicrobial peptides, propolis, and nanomaterials, are agents that provide strong antimicrobial effectiveness and concomitant immunomodulatory and/or reparative effect, without any host tissue damages. Herein, we provide an overview of local immune modulation in AP and a comprehensive review of the immunomodulatory effect of antimicrobials intracanal medications applied in endodontics with specific emphasis on the antimicrobial nanomaterial-based approaches that provide immunomodulatory potential for successful clinical deployment in endodontics.

The Potential Roles of T Cells in Periapical Lesions

INTRODUCTION

Periapical lesions are inflammatory diseases mainly caused by microbial infection from the root canal system, affecting the integrity of alveolar bone, periapical cementum, and periodontal ligament. The invasion of pathogenic microorganisms activates local inflammation and host immune response, especially the recruitment and differentiation of T cells. Many studies have discussed the fundamental roles of T cell-related immunological regulation and the possible clinical significance of cytokine disorders in periapical lesions. However, oral pathogen-mediated T cell immune response is far more clarified. Therefore, the aim of this study was to discuss the research status of T cell-related immunology involved in the progression of periapical lesions and potential future directions.

METHODS

We conducted a literature review focusing on T cell-related immunology in periapical lesions by searching PubMed, Web of Science, Scopus and ScienceDirect online databases.

RESULTS

In total 108 articles were involved in this narrative review. During the development of periapical lesions, the infiltrated number of different types of T cells and the secretion of T cell-related cytokines in root apex region reflected the inflammatory status of periapical lesions. In addition, it was also highly correlated with the periapical bone destruction. Future study could attempt to provide a wider and deeper study on the expression profile and regulatory function of T cells in the development of periapical lesions.

CONCLUSION

This review would help us understand the essence of the T cell-related pathology of periapical lesions and raise the potential therapeutic targets for the treatment of apical periodontitis.

Periapical lesions in two inbred strains of rats differing in immunological reactivity

AIM

To investigate the influence of strain differences in immune responses on the pathogenesis of experimental periapical lesions in Dark Agouti (DA) and Albino Oxford (AO) inbred strains of rats.

METHODOLOGY

Periapical lesions were induced in male DA and AO rats by pulp exposure of the first mandibular right molars to the oral environment. Animals were killed 21 days after pulp exposure. The mandibular jaws were retrieved and prepared for radiographic, pathohistological, immunohistochemical analysis, real-time PCR and flow cytometry. Blood samples and the supernatant of periapical lesions were collected for measurement of cytokines and oxidative stress marker levels. Statistical analysis was performed using the Kruskal-Wallis H and Mann-Whitney U non-parametric tests or parametric One-Way anova and Independent Samples T-test to determine the differences between groups depending on the normality of the data. A significant difference was considered when p values were <.05.

RESULTS

DA rats developed significantly larger (p < .05) periapical lesions compared to AO rats as confirmed by radiographic and pathohistological analysis. The immunohistochemical staining intensity for CD3 was significantly greater in periapical lesions of DA rats compared to AO rats (p < .05). In DA rats, periapical lesions had a significantly higher (p < .05) percentage of CD3+ cells compared to AO rats. Also, the percentage of INF-γ, IL-17 and IL-10 CD3+CD4+ cells was significantly higher in DA rats (p < .05). DA rats had a significantly higher Th17/Th10 ratio. RT-PCR expression of IL-1β, INF-γ and IL-17 genes was significantly higher in periapical lesions of DA compared to AO rats (p < .05). The receptor activator of nuclear factor kappa-Β ligand/osteoprotegerin ratio was higher in DA compared to AO rats with periapical lesions (p < .05). Systemic levels of TNF-α and IL-6 were significantly higher in DA compared to AO rats (p < .05). Levels of lipid peroxidation measured as thiobarbituric acid reactive substances and reduced glutathione were significantly higher (p < .05) in the supernatant in the periapical lesions of DA rats.

CONCLUSION

After pulp exposure, DA rats developed much larger periapical lesions compared to AO rats. Genetically determined differences in immunopathology have been demonstrated to be a significant element defining the severity of periapical lesions.

Immunoexpression of Interleukin 17, 6, and 1 Beta in Primary Chronic Apical Periodontitis in Smokers and Nonsmokers

INTRODUCTION

The purpose of this study was to compare the immunoexpression of biomarkers interleukin (IL)-17, IL-6, and IL-1β in primary chronic apical periodontitis in smokers and nonsmokers.

METHODS

Teeth with primary chronic apical periodontitis indicated for extraction in 16 cigarette smokers and 16 nonsmokers were selected. Silanized sections of tissue were used for immunohistochemical analysis after being stained with hematoxylin-eosin for histopathologic categorization. Subsequently, the images were analyzed with an optical microscope, and each slide was subdivided into 5 high-magnification fields, with scores (0-2) being assigned according to the amount of staining for each antibody.

RESULTS

The qualitative analysis of IL-17 cytokine expression showed no focal expression in 5.8%, weak to moderate expression in 17.6%, and strong expression in 76.4% of the smokers and no focal expression in 78.5% and weak to moderate expression in 21.4% of the nonsmokers. IL-6 expression was negative to focal in 13.3%, weak to moderate in 53.3%, and strong in 33.3% of the smokers and negative to focal in 33.3%, weak to moderate in 25%, and strong in 41.6% of the nonsmokers. IL-1β expression was weak to moderate in 87.5% and negative to focal expression in 12.5% of the smokers and negative to focal expression in 100% of the nonsmokers. Quantitative evaluation of the data using the Mann-Whitney U test showed a significant difference in the immunoexpression of IL-17 (P < .0001) and IL-1β (P < .0001) and no significant difference in the immunoexpression of IL-6 (P = .46) between the 2 groups (P < .05).

CONCLUSIONS

The cytokines IL-17 and IL-1β were more highly expressed in smokers than nonsmokers, whereas IL-6 expression was similar in the 2 groups.

Selenium intracanal dressing: effects on the periapical immune response

OBJECTIVES

To evaluate the selenium (Se) behavior when used as an endodontic dressing in teeth with pulp necrosis. Additionally, its effects was also compared with the calcium hydroxide (C.H.), which is used globally as a root canal dressing, and the combination of the C.H. with Se (C.H. + Se).

MATERIALS AND METHODS

The sample consisted of 60 patients requiring endodontic treatment who were divided into groups, i.e., without intracanal medication (empty) and with medications as follows: selenium (Se), calcium hydroxide (C.H.), and calcium hydroxide + selenium (C.H. + Se) (n = 15). After the coronary opening, three absorbent paper points were placed in the RCS and maintained for 2 min for microbial evaluation. Following the cleaning and shaping procedures, new paper points were introduced into the root canal system, passing passively through the root apex (2 mm) into the periapical tissues for 2 min, for immune evaluation. The collections were performed again 15 days later. Real-time PCR quantified the expression of the prokaryotic 16S ribosomal RNA. The 16S mRNA was evaluated before the cleaning and shaping procedures and 15 days later in the groups treated with or without medication.

RESULTS

A significant reduction in the microbial load was observed only in the groups that received endodontic dressing (p < 0.05). The cytokines IFN-γ, TNF-α, IL-1α, IL-17A, IL-10, IL-6 and MCP-1, were also quantified by real-time PCR. There was an increase in the gene expression level of the cytokines (T15) TNF-α and IL-10 in the C.H. group compared to the other groups (p < 0.05). The IFN-γ mRNA expression was reduced in the groups treated with the medications (Se, C.H., and C.H. + Se).

CONCLUSIONS

The findings of the present study indicate that in the case of treatment over multiple sessions, the use of root canal dressing is essential to avoid the root canal system (RCS) microbial recolonization. Selenium potentiated the effects of calcium hydroxide inducing an anti-inflammatory response in periapical tissues.

CLINICAL RELEVANCE

Se is a mineral essential for the formation of the amino acid selenocysteine, which is directly involved in the maintenance of the immune response. Selenium has been widely used in the medical field in the treatment of cancer, as an activator of bone metabolism, and as a stimulator of the immune system. In this study, it was shown that the incorporation of Se, whether as intracanal medication alone or in conjunction with other medications, may potentiate periapical tissue repair after RCS cleaning and shaping procedures.

Immunological profile of periapical endodontic infection in patients undergoing haematopoietic transplantation

OBJECTIVES

To evaluate the mRNA expression levels of cytokines interferon-γ, tumour necrosis factor-α, interleukin IL-1β, IL-10, and the chemokine CCL2/MCP-1, CCL4, and CXCR4 in the periapical interstitial fluid from root canal infections before and after bacterial load reduction in patients undergoing haematopoietic stem cell transplantation (HSCT).

MATERIALS AND METHODS

The case group was composed of 10 patients undergoing HSCT, and our control group included 10 healthy patients. Clinical samples were taken from teeth with pulp necrosis. Three paper points were placed in the RCS and maintained for 2 min for microbial evaluation before cleaning and shaping procedures. After cleaning and drying the canal, three paper points were introduced into the root canal, passing passively through the root apex (2 mm) into the periapical tissues for 1 min. Samples were collected immediately after root canal cleaning and 7 days later (restrained root canal bacterial load) to characterize gene expression using real-time PCR.

RESULTS

The results showed significantly reduction in the microbial load on day 7. An increased expression level of TNF-α and IFN-γ on day 7 in control and case groups was observed (p < 0.05). The mRNA levels of IL-1β and IL-10 in the pre-HSCT group increased in the samples from day 7 (p < 0.05). The chemokine CCL-2/MCP-1 was not detected in pre-HSCT group. Chemokine receptor CXCR4 levels increased in samples obtained from the day 7 in the control group (p < 0.05).

CONCLUSIONS

Individuals undergoing HSTC presented similar cytokine and chemokine mRNA expression compared with healthy individuals. However, it was observed the total absence of mRNA MCP-1/CCL2 expression in those individuals undergoing HSCT.

CLINICAL RELEVANCE

Patients undergoing HSCT are at higher risk of infection. No study has analysed the periapical immune responses to root canal infections in HSCT individuals.

An update of knowledge on the regulatory role of Treg cells in apical periodontitis

Apical periodontitis (AP) is a prevalent infectious and inflammatory disorder that involves inflammation of periapical tissues and the disintegration of alveolar bone. AP may eventually lead to tooth loss if not timely treated. This disease is caused by pathogenic bacteria in the necrotic pulps and root canals, thereby triggering responses from the innate and adaptive immune system of the periapical tissues. Regulatory T (Treg) cells play a major role in maintaining immune homoeostasis and immunological self-tolerance; however, these only account for roughly 5%-10% of human peripheral CD4⁺ T cells. Several studies have examined the possible role and underlying mechanism of Treg cells in different inflammatory and autoimmune disorders to facilitate the development of novel treatments for these diseases. Recent studies have indicated that Treg cells may gather at the sites of infection, thus limiting the generation of immune responses and bone resorption in the periapical area. This review will summarize studies regarding the presence and regulatory role of Treg cells in AP.

Effect of ethylenediaminetetraacetic acid irrigation on immune-inflammatory response in teeth submitted to regenerative endodontic therapy

AIM

To analyse longitudinally the immune-inflammatory response in teeth of mice that underwent a regenerative protocol with or without the use of ethylenediaminetetraacetic acid (EDTA) to irrigate the root canal system.

METHODOLOGY

First maxillary molars of mice were devitalized using size 10 and 15 files. Teeth were divided into the following groups: Empty - the canals were left empty; Blood Clot (BC) - the canals were filled with a blood clot; and EDTA + Blood - the canals were irrigated with 0.06 mL of 17% EDTA for 1 min and filled with a blood clot. Access cavities were restored with Coltosol^® . Animals were sacrificed at 7, 14 or 21 days after the operative procedures, and teeth were collected. RNA was extracted, mRNA expression of the cytokines IGF, NGF, IL-1α, IL-10, TGF and VEGF was assessed using real-time PCR, and the anova Kruskal-Wallis test was used.

RESULTS

IL-1 mRNA expression was significantly higher in the EDTA + BC group than in the Empty and BC groups at the 7th and 14th days of evaluation (P < 0.05). IL-10 mRNA expression was similar across the three groups at all time periods. TGF-β mRNA expression in the EDTA + BC group was significantly higher on the 7th and 21st days than on the 14th (P < 0.05); at day 21, TGF-β mRNA expression was similar between the BC and EDTA + BC groups but significantly higher than in the Empty group (P < 0.05). IGF mRNA expression was significantly higher in the EDTA + BC group than in the other groups at all time periods. VEGF mRNA expression remained unchanged throughout the experimental period in all groups (P > 0.05). NGF mRNA expression was similar amongst all groups at the 7th and 21st days (P > 0.05). At the 14th day, however, there was a significant increase in NGF mRNA expression in the EDTA + Blood group (P < 0.05) when compared with the expression in the other groups.

CONCLUSION

EDTA promoted increased expression of factors that have the potential to improve the outcome of regenerative endodontic treatment.

The Presence and involvement of interleukin-17 in apical periodontitis

Apical periodontitis (AP) is a chronic inflammatory disease characterized by periapical tissue inflammation and destruction of the associated alveolar bone. It is caused by microbial infections within the root canal and the resultant host immune responses in the periapical tissues. The proinflammatory cytokine interleukin (IL)-17 has been shown to play an important role in many inflammatory diseases. There is increasing evidence of the presence of IL-17 in AP, which might be associated with disease pathogenesis. Moreover, several animal studies indicate the potential role of IL-17 in periapical inflammation and the resultant bone resorption in AP. This article reviews recent studies regarding the collective in vitro, in vivo and clinical evidence of the presence and involvement of IL-17 in AP. A search related to IL-17 in apical periodontitis was conducted on PubMed, EMBASE and Web of Science databases using keywords and controlled vocabulary. Two independent reviewers first screened titles and abstracts and then the full texts that were included. A total of 25 papers were identified, of the 25 included articles, 7 involved laboratory studies on cell cultures, 11 involved animal experimentations, and 7 were observational studies using human clinical samples. In conclusion, evidence for the presence of IL-17 in AP from human and animal models is clear. However, there is relatively little information currently available that would highlight the specific role of IL-17 in AP.

Notch signaling pathway mediates alveolar bone resorption in apical periodontitis

Apical periodontitis represents a chronic inflammatory process within periapical tissues, mostly caused by etiological agents of endodontic origin. Progressive bone resorption in the periapical region represents the hallmark of apical periodontitis and occurs as the consequence of interplay between polymicrobial infections and host response. The Notch signaling pathway is an evolutionary conserved cell-signaling system that plays an important role in a variety of cell functions including proliferation, differentiation and apoptosis. In recent years its involvement in bone homeostasis has attracted a significant consideration. We hypothesized that Notch signaling pathway, which has a complex interplay with proinflammatory cytokines and bone resorption regulators, contributes to alveolar bone resorption via increased Notch receptors on immune cell surface and stimulates Notch receptor intracellular domain (NICD) translocation into the nucleus. The potential benefit of medications aimed to down-regulate these pathways in apical periodontitis treatment remains to be assessed.

TBX21-1993T/C polymorphism association with Th1 and Th17 response at periapex and with periapical lesions development risk

TBX21-1993T/C (rs4794067) polymorphism increases the transcriptional activity of the Tbx21, essential for interferon gamma (IFNg) transcription, but its functional impact on development Th1- response in vivo remains unclear, as well its potential influence over inflammatory osteolytic conditions, such as periapical lesions. Therefore, this study comprises a case-control and functional investigation of Tbx21 genetic variations impact on Th1 response in vivo and in vitro, and its impact on periapical lesions risk and outcome, performed with a population of healthy controls (H; N = 283) and patients presenting periapical lesions (L; N = 188) or deep caries (DC; N = 152). TBX21-1993T/C genotyping demonstrated that the polymorphic allele C, as well TC/TC+CC genotypes, was significantly less frequent in the L patients compared to H and DC groups. Additionally, gene expression analysis demonstrates that T-cell-specific T-box transcription factor (Tbet) and IFNg transcripts levels were downregulated whereas IL-17 levels were upregulated in the TBX21-1993 C carriers (TC/TC+CC) in comparison with the TT group. Also, while TT and TC+CC genotypes are equally prevalent in the lesions presenting low IFN/IL17 ratio, a significant decrease in polymorphic TC+CC genotypes was observed in lesions presenting intermediate and high IFN/IL17 ratio. In vitro experiments confirmed the predisposition to Th1 polarization associated with TBX21-1993, since PBMC CD4 T cells from T allele carriers produce higher IFNg levels upon CD3/CD28 stimulation than the C group, in both standard/neutral and Th1-polarizing culture conditions. In conclusion, the TBX21-1993 T allele and TC/CC genotypes predispose to Th1-type immune response development in vitro, influence immune response polarization in vivo, and consequently account for the risk for apical periodontitis development.

Evaluation of apoptosis/necrosis and cytokine release provoked by three root canal sealers in human polymorphonuclears and monocytes

AIM

To evaluate the in vitro cytotoxicity and cytokine release of three fresh root canal sealers and to determine the type of cell death they induce.

METHODOLOGY

The sealers tested were Sealer 26 (S26), AH Plus (AHP), and Endosequence BC Sealer (END). Fresh sealers were cultivated in contact with monocytes and polymorphonuclears (PMNs) obtained from the peripheral blood of humans. Cell viability, apoptosis and necrosis were analysed at 4 h (PMNs) or 24 h (monocytes) using Annexin-V and propidium iodide in a cytometer. The supernatants were used to quantify Interleukin (IL)-4, IL-6, IL-10, IL-12 and tumour necrosis factor-α (TNF-α) in monocytes and IL-8 in PMNs by ELISA. One-way ANOVA and the Tukey post-test were used to compare data for cytotoxicity, and the multiple T-test was used to determine the differences between sealers in the release of cytokines that were statistically significant.

RESULTS

After 4 h of treatment, S26 was associated with greater cell viability than the other sealers (P < 0.05) in the PMN culture and had similar values of necrosis as END (P > 0.05). After 24 h of treatment, AHP and END had greater monocyte cell viability than S26 (P < 0.05), which had more necrosis (P < 0.05). END had the lowest levels of IL-12 compared to the other sealers (P < 0.05) and higher levels of IL-6 compared to S26 (P < 0.05). The tested sealers did not differ in the release of IL-8, IL-10, TNF-α and IL-4 (P > 0.05).

CONCLUSIONS

The effect of toxic agents released varied depending on the cell type studied. The composition of the sealers appeared to alter the form of self-regulation in the production of these cytokines by cells.

Evaluation of chemokines and receptors in gnotobiotic root canal infection by F. nucleatum and E. faecalis

The present study aims to evaluate the longitudinal effects of induced experimental infections in gnotoxenic animals on the expression of inflammatory chemokines and their receptors in periradicular tissues. The null hypothesis tested was that Enterococcus faecalis and Fusobacterium nucleatum had no effect on CCR5, CCL5, CXCL10, CCL2/MCP-1, CXCR2 and CCR1 expression. Two groups of five animals (n = 5) aged between 8 and 12 weeks were used in this study. The animals were anaesthetized, and coronary access was performed in the first molar on the right and left sides. Microorganisms were inoculated into the left molar, and the right molar was sealed without contamination to function as a control. Animals were sacrificed 7 and 14 days after infection, and periapical tissues were collected. The cytokine mRNA expression levels were assessed using real-time PCR. The chemokine mRNA expression levels demonstrated that the experimental infection was capable of inducing increased chemokine expression on day 7 compared to that on day 14, except for CCR5 and CCL5, which showed no changes. The gnotoxenic animal model proved to be effective and allowed evaluation of the immune response against a known infection. Additionally, this study demonstrates that gene expression of chemokines and their receptors against the experimental infection preferentially prevailed during the initial phase of induction of the periradicular alteration (i.e., on day 7 post-infection).

Etiologic role of root canal infection in apical periodontitis and its relationship with clinical symptomatology

Evidence shows the polymicrobial etiology of endodontic infections, in which bacteria and their products are the main agents for the development, progression, and dissemination of apical periodontitis. Microbial factors in necrotic root canals (e.g., endotoxin) may spread into apical tissue, evoking and supporting a chronic inflammatory load. Thus, apical periodontitis is the result of the complex interplay between microbial factors and host defense against invasion of periradicular tissues. This review of the literature aims to discuss the complex network between endodontic infectious content and host immune response in apical periodontitis. A better understanding of the relationship of microbial factors with clinical symptomatology is important to establish appropriate therapeutic procedures for a more predictable outcome of endodontic treatment.

Effect of root canal debridement on inflammatory cytokine levels

In endodontic infections, inflammatory mediators such as cytokines are released, recruited and retained until the infection is eradicated. Root canal therapy is performed to prevent the spread of infection. The aim of this study was to investigate the effects of root canal debridement (cleaning and shaping) on periapical inflammation by measuring the levels of inflammatory cytokines, Interleukin-8 (IL-8) and Interleukin-10 (IL-10). The study includes twenty patients with pulp necrosis and asymptomatic apical periodontitis. Periradicular sample was collected using paper points before and after root canal debridement. Cytokine levels were determined by Sandwich Enzyme-Linked Immunosorbent Assay (ELISA). Data were analysed using paired t-test (PASW Statistics 18) (P = 0.05). All samples showed the presence of IL-8 and IL-10 prior to root canal debridement. Significantly reduced levels (P < 0.05) of IL-8 and IL-10 were detected after root canal debridement. In conclusion, root canal debridement significantly decreased the levels of the tested pro- and anti-inflammatory cytokine in the periradicular interstitial fluid.

Immunological profile of teeth with inflammatory periapical disease from chronic liver disease patients

AIM

To evaluate the mRNA expression levels of the cytokines interferon-γ, tumour necrosis factor-α, interleukin (IL)-1β, IL-10, IL-6, VEGF, and AGT and the chemokine CCL2/MCP-1 in periapical interstitial fluid associated with root canal infections before and after the reduction of the bacterial load using a cleaning procedure.

METHODOLOGY

The case group included 11 patients with chronic liver disease, and the control group included 11 healthy patients. Clinical samples were taken from teeth with pulp necrosis. After cleaning and drying the canal, three paper points were introduced into the root canal and passed through the root apex (2 mm) into the periapical tissues for 1 min. The samples were collected immediately after root canal cleaning and 7 days later to characterize those gene expression levels using real-time PCR. The data were subjected to the Shapiro-Wilk and the Wilcoxon tests.

RESULTS

In the control group, significantly increased expression of the pro-inflammatory cytokines IFN-γ and TNF-α was observed in teeth with restrained bacterial loads (day 7) (P < 0.05). Similarly, increased TNF-α expression was found on day 7 in the liver group (P < 0.05). No differences were observed in the expression levels of the IL-1β, IL-10 and, IL-6, MCP-1/CCL-2 and VEGF between the first collection (day 0) and second collection (day 7), over time in either group.

CONCLUSION

Chronic liver disease patients exhibited sufficient immunologic ability showing relatively similar expression levels of cytokines, chemokines and angiogenic factors in periapical samples compared with the responses from no-chronic liver disease patients. The outcomes of this study suggest that liver impairment did not compromise the periapical immune response.

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

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

Cytokine expression in response to root repair agents

AIM

To evaluate the expression of TNF-α, IL-6, IFN-γ, TGF-β, IL-4, IL-10, RANKL, RANK and OPG on mouse calvarial bone treated with MTA, Geristore^® and Emdogain^® .

METHODOLOGY

Bone wounds were made on the heads of C57BL/6 mice, breaking the periosteum and the cortical surface of the calvaria. Each repair agent was inserted into sectioned Eppendorf microtubes and placed on the bone wound, and soft tissues were sutured. At 14 and 21 days, animals were sacrificed and the treated region was dissected. The calvaria bone was removed, and RNA was extracted. mRNA expression of the aforementioned cytokines was assessed using real-time PCR. Data were analysed by nonparametric methods, including the Mann-Whitney and Kruskal-Wallis tests (P < 0.05).

RESULTS

Following treatment with Emdogain^® and MTA, mRNA expression of RANKL, RANK and OPG increased significantly (P < 0.05) between days 14 to 21. Geristore^® did not alter the basal expression of these mediators during the same period of evaluation. Whilst treatment with Emdogain^® did cause a significant increase in TNF-α mRNA expression between days 14 and 21 (P < 0.05), treatment with MTA did not alter the basal expression of this cytokine at either experimental time point. However, TNF-α mRNA expression was down-regulated significantly at day 21 (P < 0.05) when Geristore^® was applied. A significant increase in the mRNA expression of IL-6, TGF-β, IL-10, IL-4 and IFN-γ was observed with Emdogain^® and MTA treatment between days 14 to 21, whereas Geristore^® reduced significantly the expression of IL-6, TGF-β and IL-4 (P < 0.05).

CONCLUSION

The clinical indication of these repair agents depends on the root resorption diagnosis. Whilst MTA and Emdogain^® induce a pro- and anti-inflammatory response early and late, respectively, Geristore^® was not associated with an inflammatory reaction when compared with both repair agents.

Analysis of CD57+ natural killer cells and CD8+ T lymphocytes in periapical granulomas and radicular cysts

The aim of this study was to compare the number of CD57+ natural killer (NK) cells and CD8+ T lymphocytes between periapical granulomas (PGs) and radicular cysts (RCs). Twenty-fives cases of PGs and 25 of RCs were submitted to histological analysis and immunohistochemistry using anti-CD57 and anti-CD8 biomarkers. Positive cells were counted in 10 fields (400× magnification) and the median value was calculated for each case. Statistical tests were used to evaluate differences in the number of CD57+ NK cells and CD8+ T lymphocytes according to type of lesion, intensity of the infiltrate and thickness of the lining epithelium. The number of CD57+ NK cells and CD8+ T lymphocytes was higher in PGs than in RCs (p = 0.129 and p = 0.541, respectively). Comparison of the number of CD57+ NK cells in atrophic and hyperplastic epithelium revealed a larger number of cells in the atrophic epithelium (p = 0.042). A larger number of CD57+ NK cells and CD8+ T lymphocytes were observed in grade III infiltrates compared to grade I/II (p = 0.145 and p = 0.725, respectively). CD8+ T lymphocytes were more prevalent than CD57+ NK cells in most cases when PGs and RCs were analyzed separately or in combination (p < 0.0001). CD57+ NK cells and CD8+ T lymphocytes play a key role in antiviral defense and the presence of these cells supports evidence suggesting the participation of these microorganisms in the pathogenesis of PGs and RCs. The response mediated by CD8+ T lymphocytes was more frequent, indicating greater participation of the adaptive immunity in these chronic lesions.

Antimicrobial and immunomodulatory activity of host defense peptides, clavanins and LL-37, in vitro: An endodontic perspective

Endodontic treatment is mainly based on root canal disinfection and its failure may be motivated by microbial resistance. Endodontic therapy can be benefitted by host defense peptides (HDPs), which are multifunctional molecules that act against persistent infection and inflammation. This study aimed to evaluate the antimicrobial, cytotoxic and immunomodulatory activity of several HDPs, namely clavanin A, clavanin A modified (MO) and LL-37, compared to intracanal medication Ca(OH)₂. HDPs and Ca(OH)₂ were evaluated by: (1) antimicrobial assays against Candida albicans and Enterococcus faecalis, (2) cytotoxicity assays and (3) cytokine tumor necrosis factor (TNF)-α, monocyte chemoattractant protein (MCP)-1, interleukin (IL)-1α, IL-6, IL-10 and IL-12 and nitric oxide (NO) production by RAW 264.7 cells incubated with or without heat-killed (HK) C. albicans or E. faecalis combined or not with interferon-γ. The minimum inhibitory concentration (MIC) was established only for E. faecalis (LL-37, 57μM). Considering cytotoxicity, clavanin MO was able to reduce cell viability in many groups and demonstrated lowest LC₅₀. The Ca(OH)₂ up-regulated the production of MCP-1, TNF-α, IL-12 and IL-6 and down-regulated IL-1α, IL-10 and NO. Clavanins up-regulated the TNF-α and NO and down-regulated IL-10 production. LL-37 demonstrated up-regulation of IL-6 and TNF-α production and down-regulation in IL-10 and NO production. In conclusion, LL-37 demonstrated better antibacterial potential. In addition, Ca(OH)₂ demonstrated a proinflammatory response, while the HDPs modulated the inflammatory response from non-interference with the active cytokines in the osteoclastogenesis process, probably promoting the health of periradicular tissues.

Modulation of stromal cell-derived factor 1 alpha (SDF-1α) and its receptor CXCR4 in Porphyromonas gingivalis-induced periodontal inflammation

Background

The production of chemokines by tissue resident cells during inflammation is considered one of the main mechanisms involved in the formation of inflammatory infiltrates. Fibroblasts are the main resident cell type in gingival and periodontal ligament tissues, and their ability to produce chemokine stromal cell-derived factor 1 alpha (SDF-1α) and its receptor CXCR4 under stimulation by gram negative bacteria, Porphyromonas gingivalis, commonly found in periodontal infections was investigated.

Methods

Western blots were used to assess SDF-1α and CXCR4 protein expression levels in human gingival fibroblast cells (HGF-1) induced by Lipopolysaccharide (LPS) from P. gingivalis in the presence or absence of LY294002, a highly selective inhibitor of PI-3K/Akt. RT-PCR and quantitative Real-time PCR was performed using gingival mRNAs from periodontitis patients. Immunohistochemistry was performed to analyze the expression and subcellular localization of SDF-1α and CXCR4, together with NF-kβ phosphorylation, in specimens from patients with periodontitis and in an experimental rat periodontitis model.

Results

We found that P. gingivalis LPS up-regulated SDF-1α and CXCR4 protein levels and elevated phosphorylation of the SDF-1α-responsive NF-kβ and Akt at 24 h in HGF-1 cells. SDF-1α and CXCR4 mRNA and protein expression levels were high in all patients with periodontitis. In the P. gingivalis-induced rat experimental periodontitis model, SDF-1α and CXCR4 immunoreactivity was higher in gingival and periodontal ligament tissues compared to the control.

Conclusion

Our data showed that PI-3K/Akt is an upstream participant in the P. gingivalis LPS-mediated induction of SDF-1α. Taken together, these results suggest that the chemokine SDF-1α and its receptor CXCR4 contribute to P. gingivalis-induced periodontal inflammation.

Expression of programmed death 1 ligand 1 on periodontal tissue cells as a possible protective feedback mechanism against periodontal tissue destruction

Programmed death 1 ligand 1 (PD-L1) is a negative co-stimulatory molecule in immune responses. Previous reports have indicated that inflammatory cytokines can upregulate the expression of PD-L1 in tumor cells, which in turn suppresses host immune responses. Periodontitis is characterized by persistent inflammation of the periodontium, which is initiated by infection with oral bacteria and results in damage to cells and the matrices of the periodontal connective tissues. In the present study, the expression and function of PD-L1 in periodontal tissue destruction were examined. Periodontal ligament cells (PDLCs) were stimulated by inflammatory cytokines and periodontal pathogens. The expression and function of PD-L1 on the surface of PDLCs was investigated using flow cytometry in vitro. Periodontal disease was induced by the injection of Porphyromonas gingivalis in mouse models. The expression levels of PD-L1 in the periodontal tissues of the mice were analyzed using flow cytometry and immunohistochemistry. PD-L1 was inducibly expressed on the PDLCs by the inflammatory cytokines and periodontal pathogens. The inflammation-induced expression of PD-L1 was shown to cause the apoptosis of activated T lymphocytes and improve the survival of PDLCs. Furthermore, in the mouse model of experimental periodontitis, the expression of PD-L1 in severe cases of periodontitis was significantly lower, compared with that in mild cases. By contrast, no significant differences were observed between the healthy control and severe periodontitis groups. The results of the present study showed that the expression of PD-L1 may inhibit the destruction of periodontal tissues, indicating the involvement of a possible protective feedback mechanism against periodontal infection.

Epstein-Barr virus infection in chronically inflamed periapical granulomas

Periapical granulomas are lesions around the apex of a tooth caused by a polymicrobial infection. Treatment with antibacterial agents is normally performed to eliminate bacteria from root canals; however, loss of the supporting alveolar bone is typically observed, and tooth extraction is often selected if root canal treatment does not work well. Therefore, bacteria and other microorganisms could be involved in this disease. To understand the pathogenesis of periapical granulomas more precisely, we focused on the association with Epstein-Barr virus (EBV) using surgically removed periapical granulomas (n = 32). EBV DNA was detected in 25 of 32 periapical granulomas (78.1%) by real-time PCR, and the median number of EBV DNA copies was approximately 8,688.01/μg total DNA. In contrast, EBV DNA was not detected in healthy gingival tissues (n = 10); the difference was statistically significant according to the Mann-Whitney U test (p = 0.0001). Paraffin sections were also analyzed by in situ hybridization to detect EBV-encoded small RNA (EBER)-expressing cells. EBER was detected in the cytoplasm and nuclei of B cells and plasma cells in six of nine periapical granulomas, but not in healthy gingival tissues. In addition, immunohistochemical analysis for latent membrane protein 1 (LMP-1) of EBV using serial tissue sections showed that LMP-1-expressing cells were localized to the same areas as EBER-expressing cells. These data suggest that B cells and plasma cells in inflamed granulomas are a major source of EBV infection, and that EBV could play a pivotal role in controlling immune cell responses in periapical granulomas.

Immune Response Profile against Persistent Endodontic Pathogens Candida albicans and Enterococcus faecalis In Vitro

INTRODUCTION

Persistent microorganisms such as Candida albicans and Enterococcus faecalis might be directly related to endodontic treatment failure. The host response to these microorganisms impairs the reestablishment of intraradicular and periradicular health.

METHODS

The present investigation evaluated the expression of inflammatory mediators produced by RAW 264.7 cells in the presence of heat-killed antigens (HK) C. albicans and E. faecalis. Cultures of RAW cells were stimulated with both antigens in the presence or absence of recombinant interferon (rIFN)-γ. Parameters of cell viability, production of nitric oxide (NO), as well as the synthesis of interleukin (IL)-1α, IL-6, IL-10, IL-12, monocyte chemotactic protein-1, and tumor necrosis factor (TNF)-α were analyzed.

RESULTS

Results demonstrated that cell viability was especially reduced in antigens and rIFN-γ-stimulated groups. Groups stimulated with HK C. albicans upregulated IL-10 production. Otherwise, the addition of rIFN-γ to HK C. albicans upregulated TNF-α and NO production. Groups stimulated with HK E. faecalis upregulated TNF-α production. HK E. faecalis and rIFN-γ upregulated TNF-α and NO synthesis. The production of other cytokines remained unchanged by all stimuli.

CONCLUSIONS

Knowledge regarding the host mechanism of response to microorganisms that perpetuate endodontic infection and the periradicular lesions can contribute to optimization of endodontic therapy. The mentioned inflammatory mediators and virulence factors involved in endodontic failure might guide lesion progression and also be targets in the development of disinfectant and immunomodulatory agents.

ST2 deletion increases inflammatory bone destruction in experimentally induced periapical lesions in mice

INTRODUCTION

ST2 is a member of the interleukin (IL)-1 receptor family, and IL-33 is its natural ligand. ST2 signaling promotes Th2 immune response in allergy, autoimmunity, and chronic inflammatory disorders, but its role in the pathogenesis of periapical lesions is unknown. The purpose of this study was to investigate whether ST2 gene deletion affects the development of experimentally induced periapical lesions in mice.

METHODS

Pulps of mandibular molars from wild-type (WT) and ST2 knockout (ST2(-)/(-)) BALB/c mice were exposed and left open to the oral environment. After death, hemi-mandibles were isolated and prepared for histologic, immunohistochemical, and flow cytometric analysis.

RESULTS

The expression of IL-33 and its receptor ST2 was higher in periapical lesions in WT mice compared with normal root apices (both P < .05). The increased periapical bone loss observed in ST2(-)/(-) mice was associated with enhanced influx of neutrophils, CD3+ CXCR3+ Th1 cells, and CD3+ CCR6+ Th17 cells and increased number of tartrate-resistant acid phosphatase+ osteoclasts (all P < .05). Furthermore, periapical lesions in ST2(-)/(-) mice contained increased percentages of T cells expressing interferon-γ, IL-17, tumor necrosis factor-α, and IL-6 (all P < .05). In comparison with WT mice, CD3+ receptor activator of nuclear factor kappa B ligand+ T cells were increased, whereas CD3+ osteoprotegerin+ T cells were decreased in the lesions of ST2(-)/(-) mice (both P < .05).

CONCLUSIONS

ST2 deletion increases inflammatory bone loss in experimental periapical lesions in mice, which is associated with enhanced Th1/Th17 cell mediated periapical immune responses and increased osteoclastogenesis.

Periapical cytokine expression in sickle cell disease

INTRODUCTION

Sickle cell anemia (SCA) is the most prevalent genetic disease worldwide. Patients with SCA exhibit increased levels of proinflammatory mediators as part of a permanently activated immunoinflammatory status.

METHODS

The aim of this study was to evaluate the mRNA expression levels of the cytokines interferon (IFN-γ), tumor necrosis factor, interleukin (IL-1β, IL-17A, IL-10), receptor activator for nuclear factor kappa B ligand, and the chemokines CCL2/MCP-1 and CCL5 in the periapical interstitial fluid from SCA individuals compared with healthy individuals. Samples were collected from 12 teeth of SCA patients and 12 non-SCA patients with apical periodontitis. In addition, 12 teeth were sampled from the periapical region of healthy patients with vital pulp (control). The expression of cytokine mRNA was detected by using real-time polymerase chain reaction.

RESULTS

The expression of mRNA for the Th1-associated cytokines IFN-γ, tumor necrosis factor-α, and IL-1β were significantly higher in SCA individuals than in the control individuals (P < .05). Among Th1-associated cytokines, only IFN-γ was significantly increased in non-SCA compared with control patients (vital pulp). The expression of IL-17A mRNA was significant higher in SCA cases than in control samples (P < .05), whereas the IL-10 mRNA expression was significantly increased in SCA and non-SCA individuals when compared with the control group. Similar levels of receptor activator for nuclear factor kappa B ligand, CCL2, and CCL5 mRNA expression were observed in all samples. However, no significant differences were observed in the expression of cytokine or chemokine mRNA between SCA and non-SCA individuals (P > .05).

CONCLUSIONS

The results were able to demonstrate that SCA patients presented prone proinflammatory ability, despite the fact that any differences in periapical immune responses between SCA and non-SCA individuals were not observed.

Antimicrobial peptide-based treatment for endodontic infections--biotechnological innovation in endodontics

The presence/persistence of microorganisms in the pulp and periapical area corresponds to the maintenance of an exacerbated immune response that leads to the start of periradicular bone resorption and its perpetuation. In endodontic treatment, the available intracanal medications do not have all the desirable properties in the context of endodontic infection and apical periodontitis; they need to include not only strong antimicrobial performance but also an immunomodulatory and reparative activity, without host damage. In addition, there are various levels of resistance to root canal medications. Thus, antimicrobial agents that effectively eliminate resistant species in root canals could potentially improve endodontic treatment. In the emergence of new therapies, an increasing number of studies on antimicrobial peptides (AMPs) have been seen over the past few years. AMPs are defense biomolecules produced in response to infection, and they have a wide spectrum of action against many oral microorganisms. There are some studies that correlate peptides and oral infections, including oral peptides, neuropeptides, and bacterial, fish, bovine and synthetic peptides. So far, there are around 120 published studies correlating endodontic microbiota with AMPs but, according to our knowledge, there are no registered patents in the American patent database. There are a considerable number of AMPs that exhibit excellent antimicrobial activity against endodontic microbiota at a small inhibitory concentration and modulate an exacerbated immune response, down-regulating bone resorption. All these reasons indicate the antimicrobial peptide-based endodontic treatment as an emerging and promising option.

Immunological profile of periapical endodontic infections from HIV- and HIV+ patients

AIM

To evaluate CD4(+) CD28(+) and CD8(+) T-cell genes and the gene expression of IFN-γ, TNF-α, IL-1-β, IL-17A, IL-10, CCL-2/MCP-1, CCL-4, CCL-5 (RANTES), CXCR4, CCR5 and RANKL from cells in the periapical interstitial fluid from root canal infections in healthy patients (HIV-) and HIV-positive individuals (HIV+).

METHODOLOGY

Subjects included 20 HIV- and 23 HIV+ patients referred to the School of Dentistry at the Universidade Federal de Minas Gerais (Belo Horizonte, MG, Brazil). Almost all HIV+ patients were undergoing highly active antiretroviral therapy (HAART). Clinical samples were taken from teeth with pulp necrosis, and no patients had acute periapical symptoms at the time of the appointments. After cleaning and drying, 3 paper points were introduced into the root canal, passing passively through the root apex (2 mm) into the periapical tissues for 1 min. The samples were collected immediately after root canal cleaning and 7 days later (restrained root canal bacterial load) to characterize those gene expressions using real-time PCR.

RESULTS

Significantly higher levels of CD4(+) CD28(+) and CD8(+) T cells in teeth with restrained bacterial loads (second collection) compared with the first collection were observed in both HIV- and HIV+ samples. In HIV- patients, an increase in IL-10 and CXCR4 expression was demonstrated as well as a decrease in pro-inflammatory cytokines such as RANKL, IFN-γ, IL1-β and CCL5. However, in HIV+ patients an increase in cytokines IFN-γ, IL-1-β, TNF-α and IL-17A, and chemokines CCL-2, CXCR4 and CCR5 were observed. The chemokine CCL-5 was not detected in HIV+ individuals.

CONCLUSIONS

These findings suggest that after reducing the root canal bacterial load in HIV- individuals an anti-inflammatory response is generated whilst in HIV+ patients a pro-inflammatory response is sustained in the periapical area.