Induction of interleukin-6 gene expression by pro-inflammatory cytokines and black-pigmented Bacteroides in human pulp cell cultures

Ability of Lactobacillus kefiri LKF01 (DSM32079) to colonize the intestinal environment and modify the gut microbiota composition of healthy individuals

BACKGROUND

Probiotics have been observed to positively influence the host's health, but to date few data about the ability of probiotics to modify the gut microbiota composition exist.

AIMS

To evaluate the ability of Lactobacillus kefiri LKF01 DSM32079 (LKEF) to colonize the intestinal environment of healthy subjects and modify the gut microbiota composition.

METHODS

Twenty Italian healthy volunteers were randomized in pre-prandial and post-prandial groups. Changes in the gut microbiota composition were detected by using a Next Generation Sequencing technology (Ion Torrent Personal Genome Machine).

RESULTS

L. kefiri was recovered in the feces of all volunteers after one month of probiotic administration, while it was detected only in three subjects belonging to the pre-prandial group and in two subjects belonging to the post-prandial group one month after the end of probiotic consumption. After one month of probiotic oral intake we observed a reduction of Bilophila, Butyricicomonas, Flavonifractor, Oscillibacter and Prevotella. Interestingly, after the end of probiotic administration Bacteroides, Barnesiella, Butyricicomonas, Clostridium, Haemophilus, Oscillibacter, Salmonella, Streptococcus, Subdoligranolum, and Veillonella were significantly reduced if compared to baseline samples.

CONCLUSION

L. kefiri LKF01 showed a strong ability to modulate the gut microbiota composition, leading to a significant reduction of several bacterial genera directly involved in the onset of pro-inflammatory response and gastrointestinal diseases.

L-mimosine increases the production of vascular endothelial growth factor in human tooth slice organ culture model

AIM

To assess the pro-angiogenic and pro-inflammatory capacity of the dentine-pulp complex in response to the prolyl hydroxylase inhibitor L-mimosine in a tooth slice organ culture model.

METHODOLOGY

Human teeth were sectioned transversely into 600-μm-thick slices and cultured in medium supplemented with serum and antibiotics. Then, pulps were stimulated for 48 h with L-mimosine. Pulps were subjected to viability measurements based on formazan formation in MTT assays. In addition, histological evaluation of pulps was performed based on haematoxylin and eosin staining. Culture supernatants were subjected to immunoassays for vascular endothelial growth factor (VEGF) to determine the pro-angiogenic capacity and to immunoassays for interleukin (IL)-6 and IL-8 to assess the pro-inflammatory response. Interleukin-1 served as pro-inflammatory control. Echinomycin was used to inhibit hypoxia-inducible factor-1 (HIF-1) alpha activity. Data were analysed using Student's t-test and Mann-Whitney U test.

RESULTS

Pulps within tooth slices remained vital upon L-mimosine stimulation as indicated by formazan formation and histological evaluation. L-mimosine increased VEGF production when normalized to formazan formation in the pulp tissue of the tooth slices (P < 0.05). This effect on VEGF was reduced by echinomycin (P < 0.01). Changes in normalized IL-6 and IL-8 levels upon treatment with L-mimosine did not reach the level of significance (P > 0.05), whilst treatment with IL-1, which served as positive control, increased IL-6 (P < 0.05) and IL-8 levels (P < 0.05).

CONCLUSIONS

The prolyl hydroxylase inhibitor L-mimosine increased VEGF production via HIF-1 alpha in the tooth slice organ culture model whilst inducing no prominent increase in IL-6 and IL-8. Pre-clinical studies will reveal if these in vitro effects translate into dental pulp regeneration.

Anti-inflammatory effects of glutamine on LPS-stimulated human dental pulp cells correlate with activation of MKP-1 and attenuation of the MAPK and NF-κB pathways

AIM

To evaluate the anti-inflammatory effects of glutamine and the underlying signal pathway mechanisms in lipopolysaccharide (LPS)-stimulated human dental pulp cells (HDPCs).

METHODS

Human dental pulp cells were exposed to 10 μg mL(-1) LPS and various concentrations of glutamine for 24 h. The production of PGE2 and nitric oxide was determined by enzyme-linked immunosorbent assay (ELISA) and Griess reagent kit, respectively. Cytokines were examined by ELISA, reverse transcriptase-polymerase chain reaction (RT-PCR) and real-time PCR. iNOS and COX protein expression as well as signal pathways were accessed by Western blot. The data were analysed by anova with Bonferroni's test (α = 0.05).

RESULTS

Glutamine reduced LPS-induced iNOS and COX-2 protein expression as well as production of NO and PGE2 in a dose-dependent fashion. Additionally, glutamine suppressed the production and mRNA expression of inflammatory cytokines including interleukin-1β (IL-1β), TNF-α, and IL-8. Furthermore, glutamine attenuated phosphorylation of extracellular signal-regulated kinase (ERK), p38, c-Jun N-terminal kinase (JNK) and IκB-α, and nuclear translocation of NF-κB p65, but enhanced mitogen-activated protein kinase phosphatase-1 (MKP-1) expression in LPS-treated HDPCs.

CONCLUSION

Glutamine exerted an anti-inflammatory effect via activation of MKP-1 and inhibition of the NF-κB and MAPK pathways in LPS-treated HDPCs.

CCL3 and CXCL12 production in vitro by dental pulp fibroblasts from permanent and deciduous teeth stimulated by Porphyromonas gingivalis LPS

OBJECTIVE

The aim of this study was to compare the production of the chemokines CCL3 and CXCL12 by cultured dental pulp fibroblasts from permanent (PDPF) and deciduous (DDPF) teeth under stimulation by Porphyromonas gingivalis LPS (PgLPS).

MATERIAL AND METHODS

Primary culture of fibroblasts from permanent (n=3) and deciduous (n=2) teeth were established using an explant technique. After the fourth passage, fibroblasts were stimulated by increasing concentrations of PgLPS (0-10 µg/mL) at 1, 6 and 24 h. The cells were tested for viability through MTT assay, and production of the chemokines CCL3 and CXCL12 was determined through ELISA. Comparisons among samples were performed using One-way ANOVA for MTT assay and Two-way ANOVA for ELISA results.

RESULTS

Cell viability was not affected by the antigen after 24 h of stimulation. PgLPS induced the production of CCL3 by dental pulp fibroblasts at similar levels for both permanent and deciduous pulp fibroblasts. Production of CXCL12, however, was significantly higher for PDPF than DDPF at 1 and 6 h. PgLPS, in turn, downregulated the production of CXCL12 by PDPF but not by DDPF.

CONCLUSION

These data suggest that dental pulp fibroblasts from permanent and deciduous teeth may present a differential behavior under PgLPS stimulation.

Camphorquinone inhibits odontogenic differentiation of dental pulp cells and triggers release of inflammatory cytokines

INTRODUCTION

Camphorquinone (CQ) is a photoinitiator that triggers polymerization of light-curing materials such as dental adhesives and composites. CQ does not become a part of the polymer network, suggesting that CQ can be leached out into surrounding environment including dental pulp and exert adversary effects on tissues. In order to understand the mechanisms of CQ-induced side effects, we investigated the effect of CQ on cell viability, cytokine secretion, and odontogenic differentiation of dental pulp stem cells in vitro.

METHODS

Cell viability was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay after CQ exposure. Western blotting was performed for p16(INK4A), p21(WAF1), and p53. Secretory cytokines were evaluated using the membrane-enzyme-linked immunosorbent assay as well as conventional and quantitative reverse-transcription polymerase chain reaction. The effects of CQ on odontogenic differentiation were evaluated using alkaline phosphatase and alizarin red S staining methods.

RESULTS

CQ treatment suppressed the proliferation of DPSCs and induced the expression of p16(INK4A), p21(WAF1), and p53. Levels of proinflammatory cytokines (eg, interleukin 6, interleukin 8, and matrix metalloproteinase-3 [MMP3]) were increased by CQ treatment. CQ also inhibited odontogenic differentiation and mineralization capacities of DPSC and MC3T3-E1 cells.

CONCLUSIONS

Our study showed that CQ may trigger pulpal inflammation by inducing proinflammatory cytokine production from the pulpal cells and may impair odontogenic differentiation of dental pulp cells, resulting in pulpal irritation and inflammation.

Anti-inflammatory effect of catechin on cultured human dental pulp cells affected by bacteria-derived factors

Catechins (bioactive polyphenols in green tea) are known to exhibit potent anti-inflammatory properties. However, the anti-inflammatory effects of catechins on inflamed dental pulp tissue are not known. In this study, we investigated the effect of epigallocatechin-3-gallate (EGCG) and epicatechin gallate (ECG), the major components of green tea catechins, on the expression of pro-inflammatory cytokines and adhesion molecules in human dental pulp cells stimulated with bacteria-derived factors such as lipopolysaccharide (LPS) and peptidoglycan (PG). The expression of interleukin (IL)-6 and of IL-8 was examined using the reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assays. The expression of intercellular adhesion molecule-1 (ICAM-1) and of vascular cell adhesion molecule-1 (VCAM-1) on dental pulp cells was analyzed using flow cytometry. The presence of EGCG and ECG significantly reduced, in a concentration-dependent manner, the expression of IL-6 and IL-8 in dental pulp cells exposed to LPS or PG. Increased expression of ICAM-1 and VCAM-1 on the dental pulp cells in response to bacterial components was also decreased by treatment with EGCG and ECG. These findings suggest that green tea catechins may prevent the exacerbation of pulpitis.

Cytotoxicity and biocompatibility of direct and indirect pulp capping materials

There are several studies about the cytotoxic effects of dental materials in contact with the pulp tissue, such as calcium hydroxide (CH), adhesive systems, resin composite and glass ionomer cements. The aim of this review article was to summarize and discuss the cytotoxicity and biocompatibility of materials used for protection of the dentin-pulp complex, some components of resin composites and adhesive systems when placed in direct or indirect contact with the pulp tissue. A large number of dental materials present cytotoxic effects when applied close or directly to the pulp, and the only material that seems to stimulate early pulp repair and dentin hard tissue barrier formation is CH.

Synergy of TLR2 and H1R on Cox-2 Activation in Pulpal Cells

Although pulp fibroblasts are a major cell type in dental pulp, their roles in microbial recognition and pulpal inflammation are not well-understood. Considering the pivotal role of Toll-like receptors (TLRs) in the recognition of micro-organisms, we hypothesized that TLRs on pulp fibroblasts may induce inflammatory signals in dental pulp. In human pulp fibroblasts, TLR2, 3, 4, and 5 were constitutively expressed. Stimulation of TLR2 and 3 induced the expression of pro-inflammatory genes such as CXCL10, CCL5, and/or Cox-2 in pulp fibroblasts. Interestingly, histamine synergistically activated TLR2-mediated Cox-2 expression and PGE(2) production. The synergistic effect of histamine is mediated by histamine receptor-1 (H1R). Studies on the intra-cellular signaling pathways revealed that p38 activation is required for the synergistic activation of Cox-2 by TLR2 and histamine. Analysis of these data suggests that TLR2 on pulp fibroblasts, in concert with H1R, can induce an inflammatory response during microbial infection in dental pulp.

Expression of nucleotide-binding oligomerization domain 2 in normal human dental pulp cells and dental pulp tissues

INTRODUCTION

The nucleotide-binding oligomerization domain (NOD) proteins belong to a distinct family of proteins that are implicated in the intracellular recognition of bacterial components. NOD2 appears to be a sensor of bacterial peptidoglycans because it recognizes a minimal motif present in all peptidoglycans. The interaction of NOD2 with downstream signaling molecules ultimately results in the activation of NF-kappaB and production of inflammatory mediators in innate immunity. As such, NOD2 may play an important role in the detection of bacterial pathogens and the initiation of inflammation within the dental pulp. This study was designed to evaluate the expression of NOD2 in normal human dental pulp cells (HDPCs) and human pulp tissues.

METHODS

Human pulp tissue samples were collected from freshly extracted human wisdom teeth, and HDPCs were prepared from the explants of normal human dental pulp tissues. Nested reverse-transcription polymerase chain reaction (Nested RT-PCR) and Western blotting were performed to detect the expression of NOD2 messenger RNA and protein, respectively. Immunohistochemical staining was used to determine the distribution of NOD2 in the pulp tissues.

RESULTS

The NOD2 messenger RNA and protein were present in normal human dental pulp tissues, with most NOD2 protein expression being localized to odontoblasts and some pulp vascular endothelial cells. In contrast, HDPCs only showed a low level of NOD2 protein expression.

CONCLUSIONS

Our results suggest that NOD2 protein expressed in HDPCs and pulp tissues may play an important role in dental immune defense.

Porphyromonas gingivalis RgpA-Kgp proteinase-adhesin complexes penetrate gingival tissue and induce proinflammatory cytokines or apoptosis in a concentration-dependent manner

The RgpA-Kgp proteinase-adhesin complexes of Porphyromonas gingivalis were observed, using immunostaining, in human gingival tissue associated with periodontitis but not in healthy tissue. The staining pattern suggested a concentration gradient from the subgingival plaque into the subjacent gingival connective tissue. Intense immunostaining was observed in areas displaying gross disturbance of tissue architecture. P. gingivalis cells and the RgpA-Kgp complexes at low concentrations were shown to stimulate secretory intercellular adhesion molecule 1, interleukin-8 (IL-8), IL-6, and macrophage chemoattractant protein secretion from cultured human epithelial (KB) and fibroblast (MRC-5) cells. However, at high concentrations a reduction in the level of these mediators was observed. In contrast, macrophage inflammatory protein 1alpha and IL-1alpha were stimulated only at high P. gingivalis cell concentrations. P. gingivalis cells and the RgpA-Kgp complexes were shown to induce apoptosis in KB and MRC-5 cells in a time- and dose-dependent manner. These data suggest that the RgpA-Kgp complexes penetrate the gingival connective tissue; at low concentrations distal from the plaque the complexes stimulate the secretion of proinflammatory mediators, while at high concentrations proximal to the plaque they induce apoptosis and attenuate the secretion of proinflammatory mediators.

Cytokine-induced prostaglandin E2production and cyclooxygenase-2 expression in dental pulp cells: downstream calcium signalling via activation of prostaglandin EP receptor

AIM

To determine whether (i) proinflammatory cytokines stimulate prostaglandin E(2) (PGE(2)) production and cyclooxygenase (COX) gene expression in dental pulp cells, and (ii) pulp cells that express different prostaglandin E(2) receptor (EP) isoforms and their activation by PGE(2) leads to downstream Ca(2+) signalling.

METHODOLOGY

Cultured human dental pulp cells were exposed to interleukin (IL)-1beta and tumour necrotic factor-alpha (TNF-alpha). The expression of COX-1 and COX-2 was measured with reverse transcriptase-polymerase chain reaction (RT-PCR). The production of PGE(2) was measured using an enzyme-linked immunosorbent assay. Expression of prostaglandin EP receptor isoforms was studied by RT-PCR, whereas fura-2 fluorescence was used to measure calcium mobilization. The Kruskal-Wallis test and Wilcoxon sum rank test with Bonferroni correction were used for statistical analysis.

RESULTS

Interleukin-1beta and TNF-alpha stimulate PGE(2) production of human dental pulp cells (P < 0.05). IL-1beta stimulated the COX-2 but not COX-1 mRNA expression. Pulp cells express mainly EP2, EP3 and EP1 receptors as analysed by RT-PCR. PGE(2) (0.25-2 micromol L(-1)) stimulated the Ca(2+) mobilization as indicated by increase in fura-2 fluorescence.

CONCLUSIONS

Interleukin-1beta and TNF-alpha may stimulate PGE(2) production in dental pulp cells. Activation of prostaglandin EP receptors in dental pulp cells by PGE(2) may induce Ca(2+) signalling to regulate cellular biological activity during inflammation.

The effects of tumor necrosis factor-alpha, interleukin-1beta, interleukin-6, and transforming growth factor-beta1 on pulp fibroblast mediated collagen degradation

Dental pulp destruction is believed to be regulated, in part, by the matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs). Cytokines are believed to be important in the pathogenesis of pulpitis. This study examined the effects that TNF-alpha, IL-1beta, IL-6, and TGF-beta1 have on the collagen degradation mediated by pulp fibroblasts utilizing a cell-mediated collagen degradation assay. Reverse transcriptase-polymerase chain reaction, Western blot analyses, and zymography were utilized to examine multiple MMPs and TIMPs. The collagen degradation mediated by these cells was stimulated by these cytokines. TNF-alpha, IL-1beta, and IL-6 increased the mRNA and/or protein expression of MMP-1, MMP-2, and MMP-3. TGF-beta1 decreased MMP-1 mRNA expression, while only slightly affecting the MMP-2 and MMP-3 mRNA and/or protein. These cytokines did not affect the expression of TIMP-1 or TIMP-2. These results suggest that these cytokines affect pulp destruction, in part, by differentially regulating the MMPs and TIMPs.

Induction of Interleukin-6 and Interleukin-8 Gene Expression by Root Canal Sealers in Human Osteoblastic Cells

Histological investigations have demonstrated that root canal sealers can induce mild to severe inflammatory alternations. However, there is little information on the precise mechanisms about root canal sealers-induced inflammatory reaction. Dysregulated cytokine productions at local disease sites have been considered to be major contributors to the development of inflammatory diseases. Interleukin (IL)-6 and IL-8 released have been reported to play an important role in the pathogenesis of inflammation. The aim of this study was to investigate the effects of root canal sealers N2 (zinc-oxide eugenol based) and AH Plus (epoxy resin based) on the expression of IL-6 and IL-8 mRNA gene in human osteoblastic cell line U2OS cells. The levels of mRNAs were measured by the semi-quantitative reverse-transcriptase polymerase chain reaction analysis. The exposure of quiescent U2OS cells to N2 and AH Plus resulted in the induction of IL-6 and IL-8 mRNA gene expression (p < 0.05). The intensity of IL-8 mRNA gene was found to be significant higher than IL-6 mRNA gene (p < 0.05). Taken together, the activation of IL-6 and IL-8 mRNA gene expression may be one of the pathogenesis of zinc oxide-eugenol based and epoxy resin based root canal sealers-induced periapical inflammation.

Neuropeptide release from dental pulp cells by RgpB via proteinase-activated receptor-2 signaling

Dental pulp inflammation often results from dissemination of periodontitis caused mostly by Porphyromonas gingivalis infection. Calcitonin gene-related peptide and substance P are proinflammatory neuropeptides that increase in inflamed pulp tissue. To study an involvement of the periodontitis pathogen and neuropeptides in pulp inflammation, we investigated human dental pulp cell neuropeptide release by arginine-specific cysteine protease (RgpB), a cysteine proteinase of P. gingivalis, and participating signaling pathways. RgpB induced neuropeptide release from cultured human pulp cells (HPCs) in a proteolytic activity-dependent manner at a range of 12.5-200 nM. HPCs expressed both mRNA and the products of calcitonin gene-related peptide, substance P, and proteinase-activated receptor-2 (PAR-2) that were also found in dental pulp fibroblast-like cells. The PAR-2 agonists, SLIGKV and trypsin, also induced neuropeptide release from HPCs, and HPC PAR-2 gene knockout by transfection of PAR-2 antisense oligonucleotides inhibited significantly the RgpB-elicited neuropeptide release. These results indicated that RgpB-induced neuropeptide release was dependent on PAR-2 activation. The kinase inhibitor profile on the RgpB-neuropeptide release from HPC revealed a new PAR-2 signaling pathway that was mediated by p38 MAPK and activated transcription factor-2 activation, in addition to the PAR-2-p44/42 p38MAPK and -AP-1 pathway. This new RgpB activity suggests a possible link between periodontitis and pulp inflammation, which may be modulated by neuropeptides released in the lesion.

Induction of vascular endothelial growth factor gene expression by proinflammatory cytokines in human pulp and gingival fibroblasts

Vascular endothelial growth factor (VEGF) enhances the permeability of blood vessels, which is an important vascular change observed during inflammatory processes. The purpose of this in vitro study was to investigate the effect of proinflammatory cytokines on the expression of VEGF mRNA gene in human pulp and gingival fibroblasts. Interlukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha) were used to evaluate VEGF mRNA gene expression in human pulp and gingival fibroblasts. The levels of mRNAs were measured by quantitative reverse-transcriptase polymerase chain reaction analysis. Both IL-1alpha and TNF-alpha induced significantly high levels of VEGF mRNA gene expression in human pulp and gingival fibroblasts (p < 0.05). In addition, TNF-alpha was found to be more effective in the induction of VEGF mRNA gene expression in pulp than gingival fibroblasts (p < 0.05). Moreover, IL-1alpha was found to be more effective in the induction of VEGF mRNA gene expression than TNF-alpha in gingival fibroblast cultures (p < 0.05). These results indicate that proinflammatory cytokines can induce VEGF mRNA gene expression, and such an effect may partially contribute to the destruction of pulpal and periapical tissues through promoting expansion of the vascular network coincident to progression of the inflammation.

Regulation of interleukin-6 expression by arecoline in human buccal mucosal fibroblasts is related to intracellular glutathione levels

OBJECTIVES

Cytokines play an important role in regulating fibroblast function and is likely to play a key role in regulating the initiation and progression of scarring in any fibrotic disease. Interleukin-6 (IL-6) has been implicated in the development of a variety of fibrotic diseases. The aim of this study was to compare IL-6 expression in fibroblasts cultured from normal human buccal mucosa and oral submucous fibrosis (OSF) specimens and further explore the potential mechanism that may lead to induce IL-6 expression.

METHODS

mRNA level of IL-6 in fibroblasts from OSF was compared with normal buccal mucosa. The effects of arecoline, the major areca nut alkaloid, on IL-6 expression in normal human buccal mucosa fibroblasts (BMFs) were measured in vitro. mRNA was quantified with AlphaImager 2000. To determine whether glutathione (GSH) levels were important in the induction of IL-6 by arecoline, we pretreated cells with 2-oxothiazolidine-4-carboxylic acid (OTZ) to boost GSH levels or with buthionine sulfoximine (BSO) to deplete GSH.

RESULTS

Fibroblasts derived from OSF exhibited higher IL-6 gene expression than BMF in mRNA levels (P < 0.05). The exposure of quiescent BMF to arecoline resulted in the elevation of IL-6 mRNA expression in a dose-dependent manner (P < 0.05). IL-6 gene regulated by arecoline correlated with intracellular GSH levels in BMF. Arecoline at a concentration of 129 muM induced about 2.7-fold IL-6 mRNA levels over the 6-h incubation period. However, BSO enhanced the IL-6 mRNA levels by 3.9-fold (P < 0.05). In addition, OTZ was found to marginally reduce the arecoline-induced IL-6 expression by about 1.7-fold (P < 0.05).

CONCLUSIONS

Taken together, these results suggest that IL-6 expression is significantly upregulated in OSF fibroblasts in areca quid chewers and arecoline may be responsible for the enhanced IL-6 expression. In addition, the regulation of IL-6 expression induced by arecoline is critically dependent on the intracellular GSH concentrations.

Induction of vascular endothelial growth factor expression in human pulp fibroblasts stimulated with black-pigmented Bacteroides

AIM

To investigate the effect of black-pigmented Bacteroides on the expression of vascular endothelial growth factor (VEGF) gene in human pulp fibroblasts.

METHODOLOGY

The supernatants of Porphyromonas endodontalis, Porphyromonas gingivalis and Prevotella intermedia were used to evaluate VEGF gene expression in human pulp fibroblasts. The levels of mRNAs were measured by the quantitative reverse-transcriptase polymerase chain reaction analysis.

RESULTS

Black-pigmented Bacteroides induced significantly high levels of VEGF mRNA gene expression in human pulp fibroblasts (P < 0.05). In addition, the expression of VEGF depended on the bacteria tested.

CONCLUSIONS

Black-pigmented Bacteroides may be involved in developing pulpal disease through the stimulation of VEGF production that would lead to the expansion of the vascular network coincident to progression of the inflammation.

Induction of interleukin-8 gene expression by black-pigmented Bacteroides in human pulp fibroblasts and osteoblasts

AIM

To investigate the effect of black-pigmented Bacteroides on the expression of interleukin (IL)-8 gene in human pulp fibroblasts and osteoblasts.

METHODOLOGY

The supernatants of Porphyromonas endodontalis, P. gingivalis and Prevotella intermedia were used to evaluate IL-8 gene expression in human pulp fibroblasts and osteoblasts. The levels of mRNAs were measured by the quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis.

RESULTS

Investigations of the time-dependence of IL-8 mRNA expression in black-pigmented Bacteroides-treated pulp fibroblasts and osteoblasts revealed a rapid accumulation of the transcript after 2 h of exposure, and remained elevated throughout the 24-h incubation period. In addition, IL-8 mRNA gene expression was also found in human osteoblasts stimulated with black-pigmented Bacteroides. However, black-pigmented Bacteroides was found to be more effective in the induction of IL-8 mRNA gene expression in osteoblasts than in pulp fibroblasts (P < 0.05).

CONCLUSIONS

Black-pigmented Bacteroides are capable of amplifying the local immune response and promoting pulpal/periapical tissue inflammation by stimulating pulp fibroblasts and osteoblasts to express IL-8.