CpG ODN-induced matrix metalloproteinase-13 expression is mediated via activation of the ERK and NF-κB signalling pathways in odontoblast cells

ERK is involved in the regulation of CpG ODN 2395 on the expression levels of anti-lipopolysaccharide factors in Chinese mitten crab, Eriocheir sinensis

CpG oligodeoxynucleotides (ODN), as an effective adjuvant or immunopotentiator, activate the immune system and induce various immune responses. Recently, it has also been reported that high dose of CpG ODN can lead to immunosuppression. However, the underlying mechanism of CpG ODN-mediated immune response remains largely unknown in invertebrates. In the present study, the role of ERK in regulating expression levels of anti-lipopolysaccharide factors (ALFs) induced by different doses of CpG ODN 2395 was analyzed in Chinese mitten crab, Eriocheir sinensis. The mRNA expression levels of EsALFs (EsALF1, EsALF2 and EsALF3) and EsERK in haemocytes were observed to increase from 6 h to 48 h post low doses of CpG ODN 2395 (0.5 μg and 2.5 μg) stimulation, while they were suppressed after high dose of CpG ODN 2395 (12.5 μg) injection. Meanwhile, the phosphorylation levels of ERK in haemocytes were significantly promoted after low doses of CpG ODN 2395 injection, and a reduce level of ERK phosphorylation was observed after high dose of CpG ODN 2395 injection. Further investigation showed that the expression levels of EsALFs induced by CpG ODN 2395 were markedly down-regulated after knocking down the expression of EsERK. Similarly, the EsALFs mRNA expression were also inhibited post different doses of CpG ODN 2395 stimulation in PD98059 (ERK inhibitor) injection crabs. These results collectively suggest that ERK is involved in regulating the expression level of EsALFs induced by different dose of CpG ODN 2395 in Chinese mitten crab, which contribute to the understanding of the regulation of CpG ODN involving in immune response in crustaceans.

Potentiality and Inflammatory Marker Expression Are Maintained in Dental Pulp Cell Cultures from Carious Teeth

Objectives: This investigation aimed to isolate and culture human dental pulp cells from carious teeth (cHDPCs) and compare their growth characteristics, colony-forming efficiency, mineralization potential and gene expression of Toll-like receptors (TLR)-2, TLR-4, TLR-9, tumour necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-8, IL-17A, 1L-17R, IL-23A, nuclear factor-kappa B (NF-κB), mitogen-activated protein kinase (MAPK1), dentin matrix protein (DMP)-1, dentin sialophospho protein (DSPP), sex determining region Y-box 2 (SOX2) and marker of proliferation Ki-67 (MKi67) with cells isolated from healthy or non-carious teeth (ncHDPCs). Methods: Pulp tissues were obtained from both healthy and carious teeth (n = 5, each) to generate primary cell lines using the explant culture technique. Cell cultures studies were undertaken by generating growth curves, a colony forming unit and a mineralization assay analysis. The expression of vimentin was assessed using immunocytochemistry (ICC), and the gene expression of above-mentioned genes was determined using quantitative real-time reverse-transcription polymerase chain reaction. Results: ncHDPCs and cHDPCs were successfully isolated and cultured from healthy and inflamed human dental pulp tissue. At passage 4, both HDPC types demonstrated a typical spindle morphology with positive vimentin expression. No statistical difference was observed between ncHDPCs and cHDPCs in their growth characteristics or ability to differentiate into a mineralizing phenotype. ncHDPCs showed a statistically significant higher colony forming efficiency than cHDPCs. The gene expression levels of TLR-2, TLR-4, TLR-9, TNF-α, IL-6, IL-8, IL-17R, IL-23A, NF-κB, MAPK1, DMP1, DSPP and SOX2 were significantly higher in cHDPCs compared with ncHDPC cultures. Conclusion: cHDPCs retain their differentiation potential and inflammatory phenotype in vitro. The inflamed tooth pulp contains viable stem/progenitor cell populations which have the potential for expansion, proliferation and differentiation into a mineralizing lineage, similar to cells obtained from healthy pulp tissue. These findings have positive implications for regenerative endodontic procedures.

The Role of Dendritic Cells during Physiological and Pathological Dentinogenesis

The dental pulp is a soft connective tissue of ectomesenchymal origin that harbors distinct cell populations, capable of interacting with each other to maintain the vitality of the tooth. After tooth injuries, a sequence of complex biological events takes place in the pulpal tissue to restore its homeostasis. The pulpal response begins with establishing an inflammatory reaction that leads to the formation of a matrix of reactionary or reparative dentin, according to the nature of the exogenous stimuli. Using several in vivo designs, antigen-presenting cells, including macrophages and dendritic cells (DCs), are identified in the pulpal tissue before tertiary dentin deposition under the afflicted area. However, the precise nature of this phenomenon and its relationship to inherent pulp cells are not yet clarified. This literature review aims to discuss the role of pulpal DCs and their relationship to progenitor/stem cells, odontoblasts or odontoblast-like cells, and other immunocompetent cells during physiological and pathological dentinogenesis. The concept of “dentin-pulp immunology” is proposed for understanding the crosstalk among these cell types after tooth injuries, and the possibility of immune-based therapies is introduced to accelerate pulpal healing after exogenous stimuli.

Laminin-Modified Dental Pulp Extracellular Matrix for Dental Pulp Regeneration

Native dental pulp extracellular matrix (DPEM) has proven to be an effective biomaterial for dental pulp regeneration. However, as a significant extracellular matrix glycoprotein, partial laminins were lost during the decellularization process, which were essential for odontoblast differentiation. Thereby, this study investigated the feasibility of LN supplementation to improve the surface of DPEM for odontoblast layer regeneration. The influences of laminin on cell adhesion and odontogenic differentiation were evaluated in vitro. Then, we fabricated laminin-modified DPEM based on the physical coating strategy and observed the location and persistency of laminin coating by immunofluorescent staining. Finally, laminin-modified DPEM combined with treated dentin matrix (TDM) was transplanted in orthotopic jaw bone of beagles (n = 3) to assess the effect of LNs on dental pulp tissue regeneration. The in vitro results showed that laminins could improve the adhesion of dental pulp stem cells (DPSCs) and promoted DPSCs toward odontogenic differentiation. Continuous odontoblastic layer-like structure was observed in laminin-modified DPEM group, expressing the markers for odontoblastogenesis, dentine matrix protein-1 (DMP-1) and dentin sialophosphoprotein (DSPP). Overall, these studies demonstrate that the supplementation of laminins to DPEM contributes to the odontogenic differentiation of cells and to the formation of odontoblast layer in dental pulp regeneration.

Knockdown of NRAGE induces odontogenic differentiation by activating NF-κB signaling in mouse odontoblast-like cells

PURPOSE

Neurotrophin receptor-interacting MAGE homologue (Nrage) plays an important role in bone development and the metabolism of normal skeletal structures. Our previous study showed that Nrage inhibited the odontogenic differentiation of mouse dental pulp cells. However, the potential roles and mechanism of Nrage in regulating odontogenic differentiation are unknown. The aim of this study was to investigate the molecular mechanism of Nrage in odontogenic differentiation of mouse odontoblast-like cells.

MATERIALS AND METHODS

Endogenous expression of Nrage was stably downregulated by lentivirus-mediated shRNA. Mineralized nodules formation was detected by alizarin red S staining. Dmp-1, Dspp, and ALP mRNA and protein levels were detected by qRT-PCR and western blotting, respectively. In addition, ALPase activity was detected. Confocal microscopy and co-immunoprecipitation (co-IP) were used to analyze the interactions between NRAGE and NF-κB signaling molecules. An IKK inhibitor was also used in the study.

RESULTS

NRAGE expression in odontoblasts was downregulated during mouse first maxillary molar development. Moreover, NRAGE expression was downregulated during odontogenic differentiation of odontoblast-like cells. NRAGE knockdown significantly upregulated DMP1 and DSP expression, increased ALPase activity, and promoted mineralized nodule formation. In addition, NRAGE knockdown increased the translocation of NF-κB1 to the nucleus and phosphorylation levels of p65. Co-IP results showed that NRAGE bound to IKKβ. Most importantly, the promoting effect of Nrage knockdown on odontoblastic differentiation was reduced after treatment with an IKK inhibitor.

CONCLUSIONS

Our data confirmed that NRAGE is an important regulator of odontogenic differentiation of odontoblasts by inhibiting the NF-κB signaling pathway through binding to IKKβ.

ABBREVIATIONS

Nrage: neurotrophin receptor-interacting MAGE homologue; DSP: dentin sialophospho protein; DMP-1: dentin matrix protein-1; BMP: bone morphogenetic protein; Wnt: wingless; NF-κB: nuclear factor of activated B cells; DAPI: 4',6-diamidino-2-phenylindole; KO: knockout; DPCs: dental pulp cells; AA: ascorbic acid; β-Gly: β-glycerophosphate; Dex: dexamethasone; co-IP: co-immunoprecipitation; IκB: inhibitor of NF-κB; IKK: IκB kinase.

The roles of odontoblasts in dental pulp innate immunity

Odontoblasts located in the outermost layer of dental pulp form a natural barrier between mineralized tissues, dentin, and soft tissues, dental pulp, of the vital tooth, and they first recognize caries-related pathogens and sense external irritations. Therefore, odontoblasts possess a specialized innate immune system to fight oral pathogens invading into dentin. Generally, the rapid initial sensing of microbial pathogens, especially pathogen-associated molecular patterns (PAMPs) shared by microorganisms, are mediated by pattern recognition receptors (PRRs), such as Toll-like receptor and the nucleotide-binding oligomerization domain (NOD). The innate immune responses in odontoblasts initiated by sensing oral pathogens provide host protective events, such as inflammatory reactions, to produce a variety of pro-inflammatory mediators, including chemokines and cytokines. These attract various inflammatory cells and cause antibacterial reactions, such as the production of defensins, to kill microorganisms in the proximal region of the odontoblast layer. This review focuses on innate immunity, especially cellular and molecular mechanisms regarding the sensing of PAMPs from oral pathogens by PRRs, in odontoblasts and provides information for future studies for the development of novel therapeutic strategies, including diagnosis and treatment, to prevent exceeding dental pulp inflammation and preserve the dental pulp tissues.

The Histone-Deacetylase-Inhibitor Suberoylanilide Hydroxamic Acid Promotes Dental Pulp Repair Mechanisms Through Modulation of Matrix Metalloproteinase-13 Activity

Direct application of histone-deacetylase-inhibitors (HDACis) to dental pulp cells (DPCs) induces chromatin changes, promoting gene expression and cellular-reparative events. We have previously demonstrated that HDACis (valproic acid, trichostatin A) increase mineralization in dental papillae-derived cell-lines and primary DPCs by stimulation of dentinogenic gene expression. Here, we investigated novel genes regulated by the HDACi, suberoylanilide hydroxamic acid (SAHA), to identify new pathways contributing to DPC differentiation. SAHA significantly compromised DPC viability only at relatively high concentrations (5 μM); while low concentrations (1 μM) SAHA did not increase apoptosis. HDACi-exposure for 24 h induced mineralization-per-cell dose-dependently after 2 weeks; however, constant 14d SAHA-exposure inhibited mineralization. Microarray analysis (24 h and 14 days) of SAHA exposed cultures highlighted that 764 transcripts showed a significant >2.0-fold change at 24 h, which reduced to 36 genes at 14 days. 59% of genes were down-regulated at 24 h and 36% at 14 days, respectively. Pathway analysis indicated SAHA increased expression of members of the matrix metalloproteinase (MMP) family. Furthermore, SAHA-supplementation increased MMP-13 protein expression (7 d, 14 days) and enzyme activity (48 h, 14 days). Selective MMP-13-inhibition (MMP-13i) dose-dependently accelerated mineralization in both SAHA-treated and non-treated cultures. MMP-13i-supplementation promoted expression of several mineralization-associated markers, however, HDACi-induced cell migration and wound healing were impaired. Data demonstrate that short-term low-dose SAHA-exposure promotes mineralization in DPCs by modulating gene pathways and tissue proteases. MMP-13i further increased mineralization-associated events, but decreased HDACi cell migration indicating a specific role for MMP-13 in pulpal repair processes. Pharmacological inhibition of HDAC and MMP may provide novel insights into pulpal repair processes with significant translational benefit. J. Cell. Physiol. 231: 798-816, 2016. © 2015 Wiley Periodicals, Inc.

CpG Oligodeoxynucleotides Induce Differential Cytokine and Chemokine Gene Expression Profiles in Dapulian and Landrace Pigs

Oligodeoxynucleotides containing unmethylated CpG motifs (CpG ODN) mimic the immunostimulatory activity of microbial DNA by interacting with Toll-like receptor 9 (TLR9) to activate both the innate and adaptive immune responses in different species. However, few studies have been published to compare the effects of CpG ODN on different pig breeds. Therefore, in this study, whole blood gene expression profiles of DPL and Landrace pigs treated with CpG ODN were studied using RNA-seq technology. Five Hundred differentially expressed genes (DEGs) were identified between the two breeds. DPL pigs had significantly higher number of immune-relevant DEGs than the Landrace pigs after CpG ODN treatment. Pathway analysis showed that cytokine-cytokine receptor interaction and chemokine signaling pathway were the major enriched pathways of the immune-relevant DEGs. Further in vitro experiments showed that PBMCs of the DPL pigs had significantly higher levels of TLR9 mRNA than those of the Landrace pigs, both before and after CpG ODN stimulation. Cytokine and chemokine induction in the PBMCs of both breeds were also measured after CpG ODN stimulation. Our data showed that mRNA levels of cytokines (IFNα, IL8, IL12 p40) and chemokines (CXCL9, CXCL13) were significantly higher in the PBMCs of the DPL pigs than those of the Landrace pigs. Taken together, our data provide new information regarding the pig breed difference in response to CpG ODN stimulation and that higher levels of TLR9 mRNA in DPL pigs may be a major contributor for disease resistance.

Osteopontin Promotes Expression of Matrix Metalloproteinase 13 through NF-κB Signaling in Osteoarthritis

Osteopontin (OPN) is associated with the severity and progression of osteoarthritis (OA); however, the mechanism of OPN in the pathogenesis of OA is unknown. In this study, we found that OA patients had higher abundance of OPN and matrix metalloproteinase 13 (MMP13). In chondrocytes, we showed that OPN promoted the production of MMP13 and activation of NF-κB pathway by increasing the abundance of p65 and phosphorylated p65 and translocation of p65 protein from cytoplasm to nucleus. Notably, inhibition of NF-κB pathway by inhibitor suppressed the production of MMP13 induced by OPN treatment. In conclusion, OPN induces production of MMP13 through activation of NF-κB pathway.

An Overview of Pathogen Recognition Receptors for Innate Immunity in Dental Pulp

Pathogen recognition receptors (PRRs) are a class of germ line-encoded receptors that recognize pathogen-associated molecular patterns (PAMPs). The activation of PRRs is crucial for the initiation of innate immunity, which plays a key role in first-line defense until more specific adaptive immunity is developed. PRRs differ in the signaling cascades and host responses activated by their engagement and in their tissue distribution. Currently identified PRR families are the Toll-like receptors (TLRs), the C-type lectin receptors (CLRs), the nucleotide-binding oligomerization domain-like receptors (NLRs), the retinoic acid-inducible gene-I-like receptors (RLRs), and the AIM2-like receptor (ALR). The environment of the dental pulp is substantially different from that of other tissues of the body. Dental pulp resides in a low compliance root canal system that limits the expansion of pulpal tissues during inflammatory processes. An understanding of the PRRs in dental pulp is important for immunomodulation and hence for developing therapeutic targets in the field of endodontics. Here we comprehensively review recent finding on the PRRs and the mechanisms by which innate immunity is activated. We focus on the PRRs expressed on dental pulp and periapical tissues and their role in dental pulp inflammation.

Extracellular Signal-regulated Kinase Mitogen-activated Protein Kinase and Phosphatidylinositol 3-Kinase/Akt Signaling Are Required for Lipopolysaccharide-mediated Mineralization in Murine Odontoblast-like Cells

INTRODUCTION

Odontoblasts play an important role in post-developmental control of mineralization in response to external stimuli in the tooth. The present study investigated whether lipopolysaccharide (LPS), a major bacterial cell wall component, influenced mineralization in a murine odontoblast-like cell (OLC) line and the related intracellular signaling pathways involved.

METHODS

Alizarin red S staining was used to assess mineralized nodule formation in OLCs in response to LPS. The effects of LPS on gene expression of odontoblastic markers were investigated by using quantitative real-time reverse-transcriptase polymerase chain reaction. The potential involvement of toll-like receptor 4 (TLR4), nuclear factor kappa B (NF-κB), mitogen-activated protein kinase (MAPK), or phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathways in the mineralized nodule formation, and mRNA expression of several odontoblastic markers of OLCs induced by LPS was assessed by using alizarin red S staining and quantitative real-time reverse-transcriptase polymerase chain reaction. Moreover, LPS stimulation resulted in phosphorylation of protein that was determined by Western blot analysis.

RESULTS

OLCs showed reduced mineralized nodule formation and several odontoblastic markers expression in response to LPS exposure. Furthermore, inhibition of TLR4, extracellular signal-regulated kinase (ERK), and PI3K/Akt signaling noticeably antagonized LPS-mediated mineralization in OLCs. However, p38 MAPK, c-Jun N-terminal kinase, and NF-κB signaling inhibitors did not affect LPS-mediated mineralization in OLCs. Notably, LPS treatment resulted in a time-dependent phosphorylation of ERK and PI3K/Akt in OLCs, which was abrogated by their specific inhibitors.

CONCLUSIONS

LPS decreased mineralization in OLCs via TLR4, ERK MAPK, and PI3K/Akt signaling pathways, but not p38, c-Jun N-terminal kinase, or NF-κB signaling.

Identification of Toll-like receptor 9 as parapoxvirus ovis-sensing receptor in plasmacytoid dendritic cells

Parapoxvirus ovis (PPVO) is known for its immunostimulatory capacities and has been successfully used to generate vector vaccines effective especially in non-permissive host species. Murine conventional and plasmacytoid dendritic cells (cDC and pDC) are able to recognize PPVO. The PPVO-sensing receptor on pDC is hitherto unknown. In this study we aimed to define the pattern recognition receptor responsible for the activation of murine pDC by inactivated and replication-competent PPVO. We show that PPVO-induced expression of type I and type III interferons, pro-inflammatory cytokines, and co-stimulatory CD86 by bone marrow-derived pDC but not cDC is blocked by chloroquine, an inhibitor of endosomal maturation. The activation of pDC is independent of viral replication and depends mainly on TLR9. Moreover, the use of phosphatidylinositol 3-kinase inhibitor wortmannin or C-Jun-N-terminal kinase inhibitor SP600125 results in significant reduction of PPVO-induced pDC activation. Taken together, our data identify endosomal TLR9 as PPVO-sensing receptor in pDC.

A critical role for suppressors of cytokine signaling 3 in regulating LPS-induced transcriptional activation of matrix metalloproteinase-13 in osteoblasts

Suppressor of cytokine signaling 3 (SOCS3) is a key regulator of cytokine signaling in macrophages and T cells. Although SOCS3 seems to contribute to the balance between the pro-inflammatory actions of IL-6 family of cytokines and anti-inflammatory signaling of IL-10 by negatively regulating gp130/Jak/Stat3 signal transduction, how and the molecular mechanisms whereby SOCS3 controls the downstream impact of TLR4 are largely unknown and current data are controversial. Furthermore, very little is known regarding SOCS3 function in cells other than myeloid cells and T cells. Our previous study demonstrates that SOCS3 is expressed in osteoblasts and functions as a critical inhibitor of LPS-induced IL-6 expression. However, the function of SOCS3 in osteoblasts remains largely unknown. In the current study, we report for the first time that LPS stimulation of osteoblasts induces the transcriptional activation of matrix metalloproteinase (MMP)-13, a central regulator of bone resorption. Importantly, we demonstrate that SOCS3 overexpression leads to a significant decrease of LPS-induced MMP-13 expression in both primary murine calvariae osteoblasts and a mouse osteoblast-like cell line, MC3T3-E1. Our findings implicate SOCS3 as an important regulatory mediator in bone inflammatory diseases by targeting MMP-13.