Stimulation of interleukin-1beta-independent interleukin-6 production in human dental pulp cells by lipopolysaccharide

Gene expression analysis of toll like receptor 2 and 4, Dectin-1, Osteopontin and inflammatory cytokines in human dental pulp ex-vivo

BACKGROUND

Toll like receptors (TLR) 2 and 4 present on innate immune cells of the dental pulp detect cariogenic bacteria. Along with bacteria, C. albicans may also be present in dental caries. The presence of C. albicans can be detected by Dectin-1 a C type Lectin receptor. Expression of Dectin-1 in human pulpits has not been reported. Similarly, cytokines are released as a consequence of dental pulp inflammation caused by cariogenic bacteria. The T helper (Th) 1 inflammatory response leads to exacerbation of inflammation and its relationship with Osteopontin (OPN) is not known in pulp inflammation.

OBJECTIVE

The aim of this study was to observe the expression of Dectin-1, TLR-2, OPN and pro-inflammatory cytokines in irreversibly inflamed human dental pulp and to observe relationship between Dectin-1/TLR-2 and OPN/Pro-inflammatory cytokines in the presence of appropriate controls.

METHODS

A total of 28 subjects diagnosed with irreversible pulpitis were included in this ex-vivo study. Fifteen samples were subjected to standard hematoxylin and Eosin (H&E) and immunohistochemistry staining. Whereas, gene expression analysis was performed on 13 samples to observe mRNA expression of pro-inflammatory cytokines; tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1 beta (ß), IL-6 Dectin-1, OPN, TLR-2 and TLR-4. SPSS version 21 was used for statistical analysis. One way analysis of variance (ANOVA), Pearson correlation and Chi-square test were used at p ≤ 0.05.

RESULTS

Gene expressions of Dectin-1, TLR-2 and TLR-4 were observed in all samples. Dectin-1 and TLR-2 expressions were significantly correlated (r = 0.5587, p = 0.0002). Similarly, OPN and TNF-α expression showed a significant correlation (r = 0.5860, p = 0001). The agreement between histologic and clinical diagnosis was 69.2% in the cases of irreversible pulpitis.

CONCLUSION

Dectin-1 was expressed by inflamed human dental pulp. Dectin-1 and TLR-2 expression pattern was suggestive of a collaborative receptor response in inflamed pulp environment. OPN and TNF-α expressions showed a positive correlation indicating a possible relationship.

Human Dental Pulp Cells Express Cellular Markers for Inflammation and Hard Tissue Formation in Response to Bacterial Information

INTRODUCTION

Lipopolysaccharide (LPS) is a major component of the outer membranes of gram-negative bacteria associated with deep dental caries and pulpitis. When bacteria invade dentinal tubes and dentin is continually destroyed, tertiary dentin is formed by preexisting odontoblasts. However, the relationship between LPS and tertiary dentin formation remains unclear. We investigated whether LPS stimulation induces the formation of hard tissue in human dental pulp cells (hDPCs).

METHODS

Immortalized hDPCs were cultured, and Escherichia coli-derived LPS (1 μg/mL) was incorporated into the culture medium. Samples were obtained after 0, 1, 3, 7, 14, and 21 days, and messenger RNA expression of IL-1β, IL-6, Wnt5a, Runx2, ALP, and alkaline phosphatase (ALP) activity was investigated.

RESULTS

Quantitative real-time polymerase chain reaction revealed higher messenger RNA expression levels of IL-1β and IL-6 in the LPS group on 1 day (P < .05). The expression levels of dentinogenesis-related markers including Wnt5a, Runx2, and ALP were higher in the LPS group (2.0-, 4.7- and 10.0-fold, respectively) than that in the control group at 14 days (P < .01). ALP activity was significantly stronger in the LPS group than in the control group at 21 days (P < .01). Treatment of Box5, an antagonist of Wnt5a, showed a decreased expression of Runx2 and ALP (P < .05).

CONCLUSIONS

These results indicate that LPS stimulation induces the gene expression of inflammatory cytokines and hard tissue formation through Wnt5a signaling pathways in hDPCs.

Dental Pulp Defence and Repair Mechanisms in Dental Caries

Dental caries is a chronic infectious disease resulting from the penetration of oral bacteria into the enamel and dentin. Microorganisms subsequently trigger inflammatory responses in the dental pulp. These events can lead to pulp healing if the infection is not too severe following the removal of diseased enamel and dentin tissues and clinical restoration of the tooth. However, chronic inflammation often persists in the pulp despite treatment, inducing permanent loss of normal tissue and reducing innate repair capacities. For complete tooth healing the formation of a reactionary/reparative dentin barrier to distance and protect the pulp from infectious agents and restorative materials is required. Clinical and in vitro experimental data clearly indicate that dentin barrier formation only occurs when pulp inflammation and infection are minimised, thus enabling reestablishment of tissue homeostasis and health. Therefore, promoting the resolution of pulp inflammation may provide a valuable therapeutic opportunity to ensure the sustainability of dental treatments. This paper focusses on key cellular and molecular mechanisms involved in pulp responses to bacteria and in the pulpal transition between caries-induced inflammation and dentinogenic-based repair. We report, using selected examples, different strategies potentially used by odontoblasts and specialized immune cells to combat dentin-invading bacteria in vivo.

Interleukin-17/T-helper 17 cells in an atopic dermatitis mouse model aggravate orthodontic root resorption in dental pulp

Interleukin (IL)-17 is an important mediator of orthodontically induced inflammatory root resorption (OIIRR). However, its role in the dental pulp (DP) has not been studied. The aim of this study was to investigate, using an atopic dermatitis (AD) model, how IL-17 contributes to OIIRR in DP. Atopic dermatitis is the most common IL-17-associated allergic disease. Atopic dermatitis model mice (AD group) and wild-type mice (control group) were subjected to an excessive orthodontic force. The localization of T-helper (Th)17 cells, IL-17, IL-6, and keratinocyte chemoattractant (KC; an IL-8-related protein in rodents) were determined in DP. In addition, CD4+ T cells, including IL-17 production cells, were obtained from patients with AD and from healthy donors, and the effects of IL-17 on the production of IL-6 and IL-8 were investigated using a co-culture of CD4+ T cells with human dental pulp (hDP) cells stimulated with substance P (SP). Immunoreactivity for Th17 cells, IL-17, IL-6, and KC was increased in DP tissue subjected to orthodontic force in the AD group compared with DP tissue subjected to orthodontic force in the control group. The cells obtained from the AD patients displayed increased IL-6 and IL-8 production. These results suggest that IL-17 may aggravate OIIRR in DP.

NLRP3 is expressed in human dental pulp cells and tissues

INTRODUCTION

One of the best-characterized Nod-like receptor (NLR) family members is pyrin domain containing 3 (NLRP3). Intracellular NLRP3 is the most versatile innate immune receptor. On activation, NLRP3 assembles into a multiprotein complex, termed an inflammasome, which regulates the secretion and bioactivity of interleukin-1 family cytokines. NLRP3 has broad specificity for mediating an immune response to a wide range of microbial stimuli or danger signals. Therefore, we hypothesize that NLRP3 plays an essential role in the detection of bacterial pathogens and the initiation of inflammation within the dental pulp. Thus, the aim of this study was to evaluate the expression of NLRP3 in normal human dental pulp cells (HDPCs) and pulp tissues.

METHODS

Pulp tissues were collected from freshly extracted human third molars, and HDPCs were prepared from the explants of normal dental pulp tissues. Reverse transcription-polymerase chain reaction and Western blotting were performed to detect the levels of NLRP3 mRNA and protein, respectively. In addition, immunohistochemical staining was used to determine the distribution of NLRP3 in pulp tissues.

RESULTS

Normal human dental pulp tissues displayed high levels of NLRP3 mRNA and protein. NLRP3 proteins were principally expressed in odontoblasts and some pulp vascular endothelial cells. Moreover, HDPCs also expressed NLRP3 but at a relatively low level in comparison with that of dental pulp tissues.

CONCLUSIONS

The expression of NLRP3 in HDPCs and pulp tissues suggests that NLRP3-mediated signaling pathways may play an important role in dental immune defense.

Pressure induces interleukin-6 expression via the P2Y6 receptor in human dental pulp cells

BACKGROUND AND OBJECTIVE

An increase in intrapulpal pressure occurs during inflammation and restorative procedures; however, the role of the pressure on human dental pulp cell (HDPC) is not yet clarified. In this study, the effect of pressure on interleukin-6 (IL-6) expression of HDPCs was examined.

DESIGN

HDPCs were applied with pressure (0.7-1.4 g/cm(2)). The level of IL-6 mRNA and protein release was determined by RT-PCR and ELISA, respectively. The signalling pathways were investigated using inhibitors, antagonists, and small interfering RNA.

RESULTS

The results showed that pressure up-regulated IL-6 mRNA expression and protein release in a time- and dose-dependent manner. The implication of P2Y receptor was exhibited by a significant inhibition of pressure-induced IL-6 expression by suramin, an antagonist for the non-specific purinergic receptor family. Using loss of function experiments, we showed MRS2578 (a specific P2Y6 antagonist), as well as P2Y6 small interfering RNA, abolished pressure-induced IL-6, whilst MRS2179 (a specific P2Y1 antagonist) and NF449 (a P2X1, P2X3, P2Y1, and P2Y2 antagonist) had no effect. Finally, we demonstrated that either the conditioned medium collected from pressurised dental pulp cells or addition of UDP, a selective agonist of P2Y6, up-regulated IL-6 expression in HDPCs.

CONCLUSIONS

These results indicate that pressure could induce IL-6 expression through the P2Y6 receptor in HDPCs, leading to a new insight of the role of pressure on cytokine release during pulpal inflammatory process.

Substance P increases production of proinflammatory cytokines and formation of osteoclasts in dental pulp fibroblasts in patients with severe orthodontic root resorption

INTRODUCTION

The objective of this study was to determine the extent to which substance P (SP) increases proinflammatory cytokine production and osteoclast formation of human dental pulp fibroblasts (HDPF) in patients with severe orthodontically induced inflammatory root resorption (OIIRR).

METHODS

HDPF were obtained from 5 patients with severe apical root resorption after orthodontic treatment. The levels of interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha were determined after 24 hours by using ELISA kits. Furthermore, culture supernatants were added to cultured human osteoclasts, and osteoclast formation was observed after tartrate-resistant acid phosphatase (TRAP) staining and the formation of resorption cavities.

RESULTS

Stimulation with SP increased the levels of IL-1beta, IL-6, and TNF-alpha, in a time- and concentration-dependent manner, although the increase was greater in the severe root resorption (SRR) group than in the nonresorption (NR) group (P < 0.001, 3-way repeated measures ANOVA). As for osteoclast formation, the numbers of TRAP-positive multinucleate cells and resorptive pits were significantly increased in the SRR group compared with the NR group (P < 0.001, 2-way repeated measures ANOVA).

CONCLUSIONS

These results suggest that HDPF stimulated with SP might be deeply involved in the progress of inflammation in pulp tissue and the incidence of SRR during orthodontic treatment.

In vitro characterization of human dental pulp cells: various isolation methods and culturing environments

Our purpose was to characterize human dental pulp cells isolated by various methods and to examine the behavior of cells grown under various conditions for the purpose of pulp/dentin tissue engineering and regeneration. We compared the growth of human pulp cells isolated by either enzyme digestion or the outgrowth method. Expression of dentin sialophosphoprotein, Cbfa1, and two types of collagen (I and III) in these cells was examined by Western blot or reverse transcription/polymerase chain reaction. Growth of pulp cells on dentin and in collagen gel was also characterized. We found that different isolation methods give rise to different populations or lineages of pulp cells during in vitro passage based on their collagen gene expression patterns. Cells isolated by enzymedigestion had a higher proliferation rate than those isolated by outgrowth. Pulp cells did not proliferate or grew minimally on chemically and mechanically treated dentin surface and appeared to establish an odontoblast-like morphology with a cytoplasmic process extending into a dentinal tubule as revealed by scanning electron microscopy. The contraction of the collagen matrix caused by pulp cells was dramatic: down to 34% on day 14. Our data indicate that (1) the choice of the pulp cell isolation method may affect the distribution of the obtained cell populations, (2) a treated dentin surface might still promote odontoblast differentiation, and (3) a collagen matrix may not be a suitable scaffold for pulp tissue regeneration because of the marked contraction caused by pulp cells in the matrix. The present study thus provides important information and a basis for further investigations pre-requisite to establishing pulp tissue engineering/regeneration protocols.

Trigeminal c-Fos expression and behavioral responses to pulpal inflammation in ferrets

Injury to peripheral dental tissues evokes dynamic alternations in central sensory pathways. We have previously reported that transient stimulation of the dental pulp with noxious heat evokes the induction of the immediate early gene product Fos in the transitional region between subnucleus interpolaris and caudalis (Vi/Vc) and subnucleus caudalis (Vc). A question arises as to whether similar changes occur in response to inflammation to the tooth pulp. In this study, the effects of pulpal inflammation produced by bacterial lipopolysaccharide (LPS) on face-grooming behavior and trigeminal Fos expression were examined. Face-grooming behaviors were recorded daily for 3 days pre- and 24, 48 and 72 h post- LPS or saline application. All animals were perfused 72 h post- LPS or saline application. Brainstems were processed for Fos-like immunoreactivity (Fos-LI). Teeth were processed for H&E staining. Histological examination of LPS-treated teeth revealed features of an acute pulpitis. Moreover, LPS-treated animals showed greater face-grooming activity (i.e. tongue protrusions) directed to the injured tooth than the sham-operated group. The number of Fos-positive neurons was greater in the trigeminal subnucleus caudalis (Vc) and the transitional regions (Vi/Vc) in LPS-treated animals compared with sham-operated animals, and greater in the deeper laminae than the superficial laminae of each trigeminal region. LPS treatment did not evoke Fos expression in the rostral trigeminal regions above Vi/Vc. These results demonstrate that LPS-induced pulpal inflammation results in significant alterations in the Vi/Vc and Vc, and such changes may underlie the observed nociceptive behavioral responses and may play an important role in producing a symptomatic pulpitis in humans.

The purification and characterization of an 88-kDa Porphyromonas endodontalis 35406 protease

A Porphyromonas endodontalis ATCC 35406 protease was purified from Triton X-114 cell extracts by preparative SDS-PAGE followed by electroelution. The purified enzyme exhibits a molecular size of 88 kDa and was dissociated into two polypeptides of 43 and 41 kDa upon heating in the presence of sodium dodecyl sulfate with or without a reducing agent. The protease (pH optimum 7.5-8.0) degraded the extracellular matrix proteins fibrinogen and fibronectin. Collagen IV was also degraded at 37 degrees C but not at 28 degrees C. The protease also cleaved the bioactive peptide angiotensin at amino acid residue phenylalanine-8 and tyrosine-4 but failed to hydrolyze bradykinin, vasopressin and synthetic chromogenic substrates with phenylalanine or tyrosine at the P1 position. In addition, two peptidases were detected in P. endodontalis cells: a proline aminopeptidase that remained associated with the cell pellet after detergent extraction and peptidase/s that partitioned into the Triton X-114 phase after phase separation and degraded the bioactive peptides bradykinin and vasopressin. These P. endodontalis peptidases and proteases may play an important role in both the nutrition and pathogenicity of these assacharolytic microorganisms. The inactivation of bioactive peptides and degradation of extracellular matrix proteins by bacterial enzymes may contribute to the damage of host tissues accompanied with endodontic infections.

An immunohistochemical study of osteoprotegerin in the human dental pulp

This study investigated the expression of osteoprotegerin (OPG) in healthy and inflamed dental pulps. Histological sections 7 microm thick of 47 teeth, either caries-free or affected by gross caries, were used. Sections were stained with hematoxylin-eosin, and other sections of the same specimen were subjected to the avidin-biotin peroxidase complex immunohistochemical procedure for detection of OPG. The study focused on the coronal pulp that was divided into peripheral and central regions. In the peripheral pulp healthy and inflamed specimens showed high OPG immunoreactivity of the odontoblastic layer. When no inflammation was present in the central pulp OPG immunoreactivity was light. Fibroblasts and endothelial cells showed immunoreactivity ranging from none to intense. When inflammation was present in the central pulp the chronic inflammatory cells showed intense immunoreactivity.

Serum leptin levels in patients with nonalcoholic steatohepatitis

OBJECTIVE

Leptin is a peptide hormone that mainly regulates food intake and energy expenditure of human body. A close correlation between serum leptin levels and the percentage of body fat stores is well known. Nonalcoholic steatohepatitis (NASH) is a common disorder which causes serum liver enzyme elevation. In this study, the serum leptin levels were investigated in patients with NASH to determine a possible role in the pathogenesis and in patients with chronic viral hepatitis to ascertain the effect of hepatic inflammation on serum leptin level.

METHODS

Forty-nine patients (38 men, 11 women) with NASH diagnosed by biopsy, 32 patients with biopsy-proven chronic viral hepatitis (21 men and 11 women), and 30 healthy adults (17 men, 13 women) enrolled in the study. Fasting blood samples were obtained, and serum leptin levels were measured by ELISA. Body mass index (BMI) was calculated for all subjects, and serum insulin, C-peptide, and lipoprotein levels were also detected.

RESULTS

The mean serum leptin levels (+/-SEM) were 6.62 +/- 0.71, 4.24 +/- 1.0, and 4.02 +/- 0.46 ng/ml in NASH, chronic hepatitis, and the control group, respectively. Mean serum leptin level in the NASH group was significantly higher than those in the other groups tested. BMI was also slightly higher in the NASH group when compared to the other groups (26.7 +/- 0.3, 23.7 +/- 0.6, and 24.6 +/- 0.3, respectively). There was a significant correlation between BMI and serum leptin levels when all the subjects were evaluated together (NASH, hepatitis, and control groups, r = 0.337, p = 0.012) but not in the NASH group when evaluated alone (r = 0.238, p = 0.1). Of the predisposing factors for NASH, obesity was observed in 24% of patients and hyperlipidemia in 67%. Serum cholesterol and triglyceride levels were significantly higher in the NASH group than those in controls (p < 0.05). It has been detected that most of these patients consumed high amounts of fat in their dietary habits.

CONCLUSIONS

The serum leptin levels were significantly higher in patients with NASH, while they were not affected by chronic hepatitis. This elevation is out of proportion to BMI of these patients and may be related to hyperlipidemia in most. Elevated serum leptin levels, therefore, may promote hepatic steatosis and steatohepatitis.

Whole genomic DNA probe for detection of Porphyromonas endodontalis

The purpose of the present study was to develop a DNA probe for Porphyromonas endodontalis. Pure cultures of P. endodontalis were grown in TYP medium, in an anaerobic chamber. DNA was extracted from the P. endodontalis and labeled using the Genius System by Boehringer Mannheim. The labeled P. endodontalis DNA was used in dot-blot hybridization reactions with homologous (P. endodontalis) and unrelated bacterial samples. To determine specificity, strains of 40 other oral bacterial species (e.g. Porphyromonas gingivalis, Porphyromonas asaccharolytica, and Prevotella intermedia) were spotted and reacted with the P. endodontalis DNA probe. None of the panel of 40 oral bacteria hybridized with the P. endodontalis probe, whereas the blot of the homologous organism showed a strong positive reaction. To determine the sensitivity of the probe, dilutions of a P. endodontalis suspension of known concentration were blotted onto a nylon membrane and reacted with the probe. The results of our investigation indicate that the DNA probe that we have prepared specifically detects only P. endodontalis and can detect at least 3 x 10(4) cells.

Plasma leptin levels are associated with abnormal fibrinolysis in men and postmenopausal women

BACKGROUND

Leptin is a crucial mediator of satiety signals and energy balance, and its circulating levels are increased in obesity. It has recently been shown that plasma leptin levels in humans correlate with circulating insulin and to insulin secretion. This indicates that leptin may be an important link in metabolic consequences of the insulin resistance syndrome. Whether this includes abnormalities in fibrinolysis has not been studied.

METHODS AND RESULTS

Healthy subjects (n = 165; 85 men and 80 women) from the Northern Sweden MONICA population were investigated. Anthropometric measurements, oral glucose tolerance tests and sampling for plasma leptin, lipids, fibrinogen and fibrinolytic variables were made. Leptin levels were 342% higher in women than in men and were in both sexes strongly correlated to body mass index (BMI). After adjustments for age and BMI, leptin levels correlated significantly to pre/post glucoseload insulin levels in both sexes. After further adjustment for baseline insulin levels, leptin levels were in males significantly associated with increased waist circumference (P<0.001), low HDL cholesterol (P<0.05), low tPA activity (P<0.01) and high PAI-1 activity (P<0.001). In postmenopausal females, a significant association between leptin and low tPA activity/high PAI-1 activity was seen after adjustment for age and BMI (P<0.05). Conclusions. Circulating levels of leptin are associated with components of the insulin resistance syndrome, including defective fibrinolysis, in men and postmenopausal women. This suggests that leptin may be involved in the mediation of consequences of insulin resistance.