Decoy receptor 3 (DcR3) induces osteoclast formation from monocyte/macrophage lineage precursor cells

The role of decoy receptor 3 in inflammation and atherosclerosis in patients with chronic kidney disease and renal transplant patients

INTRODUCTION

The cardiovascular risk has been increased in chronic kidney disease associated with chronic inflammation and atherosclerosis. Decoy receptor 3, is a member of the TNF receptor superfamily and associated with inflammation and atherosclerosis. The aim of our study is to determine the relationship, between serum DcR3 levels and inflammatory markers in patients with renal transplantation, those receiving dialysis treatment and cases with chronic renal failure that did not receive replacement therapy, and to evaluate their correlation with USG findings.

MATERIAL AND METHODS

A total of 150 patients aged between 22-86 years, consisting of 4 groups, namely renal transplantation, dialysis, predialysis chronic kidney disease and control groups, were included in the study. Serum decoy receptor 3, VCAM-1, ICAM-1 and IL-8 measured with ELISA method. Carotid intima-media thickness and presence of carotis arter plaque performed by ultrasound probe, non-invasively.

RESULTS

All serum markers were higher in dialysis and pre-dialysis chronic kidney disease groups compared to renal transplant and control groups (p<0.05). Serum decoy receptor 3 level (median(min-max)) of renal transplant group (0.49ng/mL (0.19-1.65)) was higher than control group (0.35ng/mL (0.19-2.22)). There was no difference between patients receiving dialysis (0.89ng/mL (0.41-4.98)) and patients with pre-dialysis chronic kidney disease (0.71ng/mL (0.29-1.68)). There was no difference between patient groups in terms of the presence of plaque.

CONCLUSION

Although renal transplantation provides a significant improvement in the inflammatory process, not return completely. Inflammatory process associated with uremic milieu may predispose to atherosclerosis in patients with pre-dialysis chronic kidney disease and hemodialysis patients.

Recent Advances in Osteoclast Biological Behavior

With the progress of the aging population, bone-related diseases such as osteoporosis and osteoarthritis have become urgent problems. Recent studies have demonstrated the importance of osteoclasts in bone homeostasis, implying these will be an important mediator in the treatment of bone-related diseases. Up to now, several reviews have been performed on part of osteoclast biological behaviors such as differentiation, function, or apoptosis. However, few reviews have shown the complete osteoclast biology and research advances in recent years. Therefore, in this review, we focus on the origin, differentiation, apoptosis, behavior changes and coupling signals with osteoblasts, providing a simple but comprehensive overview of osteoclasts for subsequent studies.

RNA-Based Analysis Reveals High Diversity of Plant-Associated Active Fungi in the Atmosphere

Fungi are ubiquitous in nature; that is, they are present everywhere on the planet; understanding the active state and functional capacity of airborne microbes associated with health of human, animal, and plant is critical for biosafety management. Here, we firstly and directly proved that there were about 40% active fungi in the air via rRNA amplicon sequencing and imaging flow cytometry simultaneously. Amplicon sequencing analysis showed differences between structures of active and total fungal community; Ascomycota were dominant in the active community, while Basidiomycota have low transcriptional activity across all samples. Notably, plant pathogenic fungi were predominant in the air, and more than 50% were active, including not only several common plant pathogens but also biotrophic fungi (Erysiphe sp. and Microbotryum sp.) and host-specific pathogens, which were generally considered to be inactive after leaving the host. Putative plant pathogens of eight genera were found active across the sampling season, indicating their superior ability to obtain nutrients even in barren nutrient environments. Interestingly, we detected several potentially active unrecorded fungi in China (Diatrype prominens, Septofusidium herbarum, Pseudomicrostroma glucosiphilum, and Uromycladium tepperianum), which suggested that they spread over a long distance by air and may cause diseases under favorable conditions. Our results suggested that maintaining transmission in air is an essential feature of many fungi including plant pathogens regardless of being a biotrophic, hemibiotrophic, or necrotrophic group. Moreover, two potentially active human pathogens and one animal pathogen were captured, which indicated their potential risks. This study provided a new perspective for more comprehensive understanding of airborne fungi, including their multidimensional lifestyle, state, functioning, and potential pathogenic risk. It also laid the foundation for further prediction and management of airborne microbial communities, which would be of interest for public health and agriculture.

Protective Effect of TNFRSF11A rs7239667 G > C Gene Polymorphism on Coronary Outcome of Kawasaki Disease in Southern Chinese Population

Background

The main symptoms of Kawasaki disease (KD) are inflammatory vasculitis characterized by fever lasting 1–2 weeks, failure to respond to antibiotic treatment, conjunctivitis, redness of the lips and mouth, strawberry tongue, and painless enlargement of the neck lymph nodes. Studies have been shown that tumor necrosis factor (TNF) and TNF receptor family members are abnormally expressed in the acute phase of Kawasaki disease, also revealing that these two play a significant role in the pathogenesis of KD. The purpose of our study is to determine the relationship between TNFRSF11A rs7239667 and the pathogenesis of KD and Coronary artery lesions in KD.

Methods and Results

In this study, TNFRSF11A (rs7239667) genotyping was performed in 1396 patients with KD and 1673 healthy controls. Our results showed that G > C polymorphism of TNFRSF11A (rs7239667) was not associated with KD susceptibility. In addition, the patients with KD were divided into CAA and NCAA groups according to whether they had coronary artery aneurysm (CAA) or not, and the TNFRSF11A rs7239667 genotyping was performed in the two groups. After gender and age calibration, We found that genotype CC of TNFRSF11A may be a protective factor in KD coronary artery damage (adjusted OR = 0.69 95% CI = 0.49–0.99 P = 0.0429) and is more significant in children with KD ≤ 60 months (adjusted OR = 0.49 95% CI = 0.49–0.93 P = 0.0173).

Conclusion

Our study suggests that TNFRSF11A rs7239667 G > C polymorphism maybe play a protective gene role for the severity of KD coronary artery injury and is related to age, which has not been previously revealed.

Decoy Receptor 3 Inhibits Monosodium Urate-Induced NLRP3 Inflammasome Activation via Reduction of Reactive Oxygen Species Production and Lysosomal Rupture

Gout is a common inflammatory arthritis caused by the deposition of monosodium urate (MSU) crystals in the joints. This activates the macrophages into a proinflammatory state by inducing NLRP3-dependent interleukin-1β (IL-1β) secretion, resulting in neutrophil recruitment. Soluble decoy receptor 3 (DcR3) is an immune modulator and can exert biological functions via decoy and non-decoy actions. Previously, we showed that DcR3 suppresses lipopolysaccharides (LPS)- and virus-induced inflammatory responses in the macrophages and promotes the macrophages into the M2 phenotype. In this study, we clarified the actions of DcR3 and its non-decoy action motif heparin sulfate proteoglycan (HSPG) binding domain (HBD) in the MSU crystal-induced NLRP3 inflammasome activation in the macrophages and in mice. In bone marrow-derived macrophages, THP-1 and U937 cells, we found that the MSU crystal-induced secretion of IL-1β and activation of NLRP3 were suppressed by both DcR3.Fc and HBD.Fc. The suppression of the MSU-induced NLRP3 inflammasome activation is accompanied by the inhibition of lysosomal rupture, mitochondrial production of the reactive oxygen species (ROS), expression of cathepsins, and activity of cathepsin B, without affecting the crystal uptake and the expression of NLRP3 or pro-IL-1β. In the air pouch mice model of gout, MSU induced less amounts of IL-1β and chemokines secretion, an increased M2/M1 macrophage ratio, and a reduction of neutrophil recruitment in DcR3-transgenic mice, which expresses DcR3 in myeloid cells. Similarly, the mice intravenously treated with DcR3.Fc or HBD.Fc displayed less inflammation response. These findings indicate that HBD of DcR3 can reduce MSU crystal-induced NLRP3 inflammasome activation via modulation of mitochondrial and lysosomal functions. Therefore, we, for the first time, demonstrate a new therapeutic potential of DcR3 for the treatment of gout.

Decoy Receptor 3 Promotes Preosteoclast Cell Death via Reactive Oxygen Species-Induced Fas Ligand Expression and the IL-1α/IL-1 Receptor Antagonist Pathway

Purpose

Interleukin-1α (IL-1α) is a potent cytokine that plays a role in inflammatory arthritis and bone loss. Decoy receptor 3 (DCR3) is an immune modulator of monocytes and macrophages. The aim of this study was to investigate the mechanism of DCR3 in IL-1α-induced osteoclastogenesis.

Methods

We treated murine macrophages with DCR3 during receptor activator of nuclear factor kappa Β ligand- (RANKL-) plus IL-1α-induced osteoclastogenesis to monitor osteoclast formation by tartrate-resistant acid phosphatase (TRAP) staining. Osteoclast activity was assessed using a pit formation assay. The mechanisms of inhibition were studied by biochemical analyses, including RT-PCR, immunofluorescent staining, flow cytometry, an apoptosis assay, immunoblotting, and ELISA.

Results

DCR3 suppresses IL-1α-induced osteoclastogenesis in both primary murine bone marrow-derived macrophages (BMM) and RAW264.7 cells as it inhibits bone resorption. DCR3 induces RANKL-treated osteoclast precursor cells to express IL-1α, secretory IL-1ra (sIL-1ra), intracellular IL-1ra (icIL-1ra), reactive oxygen species (ROS), and Fas ligand and to activate IL-1α-induced interleukin-1 receptor-associated kinase 4 (IRAK4). The suppression of DCR3 during RANKL- or IL-1α-induced osteoclastogenesis may be due to the abundant secretion of IL-1ra, accumulation of ROS, and expression of Fas ligand in apoptotic osteoclast precursor cells.

Conclusions

We concluded that there is an inhibitory effect of DCR3 on osteoclastogenesis via ROS accumulation and ROS-induced Fas ligand, IL-1α, and IL-1ra expression. Our results suggested that the upregulation of DCR3 in preosteoclasts might be a therapeutic target in inflammatory IL-1α-induced bone resorption.

Reverse Signaling of Tumor Necrosis Factor Superfamily Proteins in Macrophages and Microglia: Superfamily Portrait in the Neuroimmune Interface

The tumor necrosis factor (TNF) superfamily (TNFSF) is a protein superfamily of type II transmembrane proteins commonly containing the TNF homology domain. The superfamily contains more than 20 protein members, which can be released from the cell membrane by proteolytic cleavage. Members of the TNFSF function as cytokines and regulate diverse biological processes, including immune responses, proliferation, differentiation, apoptosis, and embryogenesis, by binding to TNFSF receptors. Many TNFSF proteins are also known to be responsible for the regulation of innate immunity and inflammation. Both receptor-mediated forward signaling and ligand-mediated reverse signaling play important roles in these processes. In this review, we discuss the functional expression and roles of various reverse signaling molecules and pathways of TNFSF members in macrophages and microglia in the central nervous system (CNS). A thorough understanding of the roles of TNFSF ligands and receptors in the activation of macrophages and microglia may improve the treatment of inflammatory diseases in the brain and periphery. In particular, TNFSF reverse signaling in microglia can be exploited to gain further insights into the functions of the neuroimmune interface in physiological and pathological processes in the CNS.

Molecular signaling in bone cells: Regulation of cell differentiation and survival

The achievement of proper bone mass and architecture, and their maintenance throughout life requires the concerted actions of osteoblasts, the bone forming cells, and osteoclasts, the bone resorbing cells. The differentiation and activity of osteoblasts and osteoclasts are regulated by molecules produced by matrix-embedded osteocytes, as well as by cross talk between osteoblasts and osteoclasts through secreted factors. In addition, it is likely that direct contact between osteoblast and osteoclast precursors, and the contact of these cells with osteocytes and cells in the bone marrow, also modulates bone cell differentiation and function. With the advancement of molecular and genetic tools, our comprehension of the intracellular signals activated in bone cells has evolved significantly, from early suggestions that osteoblasts and osteoclasts have common precursors and that osteocytes are inert cells in the bone matrix, to the very sophisticated understanding of a network of receptors, ligands, intracellular kinases/phosphatases, transcription factors, and cell-specific genes that are known today. These advances have allowed the design and FDA-approval of new therapies to preserve and increase bone mass and strength in a wide variety of pathological conditions, improving bone health from early childhood to the elderly. We have summarized here the current knowledge on selected intracellular signal pathways activated in osteoblasts, osteocytes, and osteoclasts.

TRAIL inhibits RANK signaling and suppresses osteoclast activation via inhibiting lipid raft assembly and TRAF6 recruitment

Human osteoclast formation from mononuclear phagocyte precursors involves interactions between members of the tumor necrosis factor (TNF) ligand superfamily and their receptors. Recent evidence indicated that TNF-α-related apoptosis-inducing ligand (TRAIL) induces osteoclast differentiation via a TRAF6-dependent signaling pathway; but paradoxically, it inhibits RANK ligand (RANKL)-induced osteoclast differentiation. Although a number of signaling pathways were linked to the RANK and osteoclastogenesis, it is not known how TRAIL regulates RANK signaling. In this study, we demonstrate that TRAIL regulates RANK-induced osteoclastogenesis in terms of the assembly of lipid raft-associated signaling complexes. RANKL stimulation induced recruitment of TRAF6, c-Src, and DAP-12 into lipid rafts. However, the RANKL-induced assembly of lipid raft-associated signaling complexes and TRAF6 recruitment was abolished in the presence of TRAIL. TRAIL-induced dissociation of RANKL-induced lipid raft signaling complexes was reversed by treatment with TRAIL receptor (TRAIL-R) siRNA or an anti-TRAIL-R blocking antibody, indicating that TRAIL mediates suppression of RANKL-induced lipid raft signaling via interactions with TRAIL-R. Finally, we demonstrated that TRAIL suppressed inflammation-induced bone resorption and osteoclastogenesis in a collagen-induced arthritis (CIA) rat animal model. Our results provide a novel apoptosis-independent role of TRAIL in regulating RANK signaling and suppresses osteoclast activation via inhibiting lipid raft assembly and TRAF6 recruitment.

Mechanisms of the prevention and inhibition of the progression and development of non-alcoholic steatohepatitis by genetic and pharmacological decoy receptor 3 supplementation

AIMS

Treatment of non-alcoholic steatohepatitis (NASH) is difficult due to the absence of a proven treatment and its comprehensive mechanisms. In the NASH animal model, upregulated hepatic inflammation and oxidative stress, with the resultant M1 polarization of macrophages as well as imbalanced adipocytokines, all accelerate NASH progression. As a member of the tumor necrosis factor receptor superfamily, decoy receptor 3 (DcR3) not only neutralizes the death ligands, but also performs immune modulations. In this study, we aimed to investigate the possible non-decoy effects of DcR3 on diet-induced NASH mice.

METHODS

Methionine- and choline-deficient (MCD) diet feeding for 9 weeks was applied to induce NASH in BALB/c mice. Decoy receptor 3 heterozygous transgenesis or pharmacological pretreatment with DcR3a for 1 month were designed as interventions. Intrahepatic inflammatory status as well as macrophage polarization, oxidative stress, and steatosis as well as lipogenic gene expression and fibrotic status were analyzed. Additionally, acute effects of DcR3a on HepG2 cells, Hep3B cells, and primary mouse hepatocytes in various MCD medium-stimulated changes were also evaluated.

RESULTS

Both DcR3 genetic and pharmacologic supplement significantly reduced MCD diet-induced hepatic M1 polarization. In addition, DcR3 supplement attenuated MCD diet-increased hepatic inflammation, oxidative stress, adipocytokine imbalance, steatosis, and fibrogenesis. Moreover, acute DcR3a incubation in HepG2 cells, Hep3B cells, and mouse hepatocytes could normalize the expression of genes related to lipid oxidation along with inflammation and oxidative stress.

CONCLUSION

The ability of DcR3 to attenuate hepatic steatosis and inflammation through its non-decoy effects of immune modulation and oxidative stress attenuation makes it a potential treatment for NASH.

Decoy receptor 3 down-regulates centrosomal protein 70 kDa specifically in rheumatoid synovial fibroblasts

OBJECTIVES

Decoy receptor 3 (DcR3) competitively binds to Fas ligand, lymphotoxin-related inducible ligand that competes for glycoprotein D binding to herpes virus entry mediator on T cells (LIGHT) and TNF-like ligand 1A (TL1A), thereby preventing their effects. Using a microarray assay, we previously newly identified centrosomal protein 70 kDa (CEP70) as one of the genes whose expression in fibroblast-like synoviocytes from patients with rheumatoid arthritis (RA-FLS) is reduced by DcR3. Here, we investigated the significance of DcR3 regulation of CEP70 for RA-FLS.

METHODS

Synovial samples were obtained from RA patients who had never been treated with biologics and from osteoarthritis (OA) patients. CEP70 mRNA expression was quantified using RT-qPCR analysis. CEP70 protein expression was assessed using immunohistochemical and western blot analyses.

RESULTS

CEP70 was expressed predominantly in the superficial lining layer in RA synovial tissue. CEP70 expression was dose-dependently downregulated by DcR3-Fc in RA-FLS but was not downregulated in OA-FLS. TL1A antibody prevented the DcR3-Fc inhibitory effects on CEP70 expression in RA-FLS.

CONCLUSIONS

These results indicated that DcR3 reduces CEP70 expression in RA-FLS by binding to membrane-bound TL1A and may suppress RA-FLS proliferation. The reduction in CEP70 expression by DcR3/TL1A signaling may control the hyperplasia of RA synovium.

Decoy receptor 3: an endogenous immunomodulator in cancer growth and inflammatory reactions

Decoy receptor 3 (DcR3), also known as tumor necrosis factor receptor (TNFR) superfamily member 6b (TNFRSF6B), is a soluble decoy receptor which can neutralize the biological functions of three members of tumor necrosis factor superfamily (TNFSF): Fas ligand (FasL), LIGHT, and TL1A. In addition to ‘decoy’ function, recombinant DcR3.Fc is able to modulate the activation and differentiation of dendritic cells (DCs) and macrophages via ‘non-decoy’ action. DcR3-treated DCs skew T cell differentiation into Th2 phenotype, while DcR3-treated macrophages behave M2 phenotype. DcR3 is upregulated in various cancer cells and several inflammatory tissues, and is regarded as a potential biomarker to predict inflammatory disease progression and cancer metastasis. However, whether DcR3 is a pathogenic factor or a suppressor to attenuate inflammatory reactions, has not been discussed comprehensively yet. Because mouse genome does not have DcR3, it is not feasible to investigate its physiological functions by gene-knockout approach. However, DcR3-mediated effects in vitro are determined via overexpressing DcR3 or addition of recombinant DcR3.Fc fusion protein. Moreover, CD68-driven DcR3 transgenic mice are used to investigate DcR3-mediated systemic effects in vivo. Upregulation of DcR3 during inflammatory reactions exerts negative-feedback to suppress inflammation, while tumor cells hijack DcR3 to prevent apoptosis and promote tumor growth and invasion. Thus, ‘switch-on’ of DcR3 expression may be feasible for the treatment of inflammatory diseases and enhance tissue repairing, while ‘switch-off’ of DcR3 expression can enhance tumor apoptosis and suppress tumor growth in vivo.

Dual growth factor delivery from biofunctionalized allografts: Sequential VEGF and BMP-2 release to stimulate allograft remodeling

Autografts have been shown to stimulate osteogenesis, osteoclastogenesis, and angiogenesis, and subsequent rapid graft incorporation. Large structural allografts, however, suffer from limited new bone formation and remodeling, both of which are directly associated with clinical failure due to non-unions, late graft fractures, and infections, making it a priority to improve large structural allograft healing. We have previously shown the osteogenic ability of a polymer-coated allograft that delivers bone morphogenetic protein-2 both in vitro and in vivo through both burst release and sustained release kinetics. In this study, we have demonstrated largely sequential delivery of bone morphogenetic protein-2 and vascular endothelial growth factor from the same coated allograft. Release data showed that loading both growth factors onto a polymeric coating with two different techniques resulted in short-term (95% release within 2 weeks) and long-term (95% release within 5 weeks) delivery kinetics. We have also demonstrated how released VEGF, traditionally associated with angiogenesis, can also provide a stimulus for allograft remodeling via resorption. Bone marrow derived mononuclear cells were co-cultured with VEGF released from the coated allograft and showed a statistically significant (p < 0.05) and dose dependent increase in the number of tartrate-resistant acid phosphatase-positive multinucleated osteoclasts. Functionality of these osteoclasts was assessed quantitatively and qualitatively by evaluating resorption pit area from both osteo-assay plates and harvested bone. Data indicated a statistically significant higher resorption area from the cells exposed to VEGF released from the allografts over controls (p < 0.05). These results indicate that by using different loading protocols temporal control can be achieved when delivering multiple growth factors from a polymer-coated allograft. Further, released VEGF can also stimulate osteoclastogenesis that may enhance allograft incorporation, and thus mitigate long-term clinical complications. © 2017 Orthopedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1086-1095, 2017.

Non-Canonical (RANKL-Independent) Pathways of Osteoclast Differentiation and Their Role in Musculoskeletal Diseases

Osteoclasts are multinucleated cells derived from mononuclear phagocyte precursors (monocytes, macrophages); in the canonical pathway of osteoclastogenesis, these cells fuse and differentiate to form specialised bone-resorbing osteoclasts in the presence of receptor activator for nuclear factor kappa B ligand (RANKL). Non-canonical pathways of osteoclastogenesis have been described in which several cytokines and growth factors are able to substitute for RANKL. These humoral factors can generally be divided into those which, like RANKL, are tumour necrosis family (TNF) superfamily members and those which are not; the former include TNFα lymphotoxin exhibiting inducible expression and competing with herpes simplex virus glycoprotein D for herpesvirus entry mediator, a receptor expressed by T lymphocytes (LIGHT), a proliferation inducing ligand (APRIL) and B cell activating factor (BAFF); the latter include transforming growth factor beta (TGF-β), interleukin-6 (IL-6), IL-8, IL-11, nerve growth factor (NGF), insulin-like growth factor-I (IGF-I) and IGF-II. This review summarises the evidence for these RANKL substitutes in inducing osteoclast differentiation from tissue-derived and circulating mononuclear phagocytes. It also assesses the role these factors are likely to play in promoting the pathological bone resorption seen in many inflammatory and neoplastic lesions of bone and joint including rheumatoid arthritis, aseptic implant loosening and primary and secondary tumours of bone.

BMP Signaling Mediated by BMPR1A in Osteoclasts Negatively Regulates Osteoblast Mineralization Through Suppression of Cx43

Osteoblasts and osteoclasts are well orchestrated through different mechanisms of communication during bone remodeling. Previously, we found that osteoclast-specific disruption of one of the BMP receptors, Bmpr1a, results in increased osteoblastic bone formation in mice. We hypothesized that BMPR1A signaling in osteoclasts regulates production of either membrane bound proteins or secreted molecules that regulated osteoblast differentiation. In our current study, we co-cultured wild-type osteoblasts with either control osteoclasts or osteoclasts lacking BMPR1A signaling activity. We found that loss of Bmpr1a in osteoclasts promoted osteoblast mineralization in vitro. Further, we found that the expression of Cx43/Gja1 in the mutant osteoclasts was increased, which encoded for one of the gap junction proteins connexin 43/gap junction alpha 1. Knockdown of Gja1 in the mutant osteoclasts for Bmpr1a reduced osteoblastic mineralization when co-cultured. Our findings suggest that GJA1 may be one of the downstream targets of BMPR1A signaling in osteoclasts that mediates osteoclast-osteoblast communication during bone remodeling. J. Cell. Biochem. 118: 605-614, 2017. © 2016 Wiley Periodicals, Inc.

Tumor necrosis factor α-induced protein 8-like 1 promotes apoptosis by regulating B-cell leukemia/lymphoma-2 family proteins in RAW264.7 cells

Although the newly identified protein tumor necrosis factor α-induced protein 8-like 1 (TNFAIP8L1), also known as TIPE1, has been reported to be able to induce apoptosis in human hepatocellular carcinoma cells, the involvement of TIPE1 in apoptosis remains to be elucidated. The present study investigated the pro-apoptotic effect of TIPE1 in an murine macrophage cell line, RAW264.7. The cell apoptosis rate was detected by flow cytometry. The results revealed that overexpressed TIPE1 could directly enhance the apoptosis and the cisplatin-induced cell death of RAW264.7 cells in vitro. Meanwhile, TIPE1 overexpression could suppress tumor growth in vivo. Furthermore, western blotting revealed that overexpressed TIPE1 could upregulate the expression of B-cell leukemia/lymphoma (Bcl)-2 associated X protein (Bax), Bcl-2 interacting killer (Bik) and p53 upregulated modulator of apoptosis (Puma), and activate the mitogen activated protein kinases (MAPKs) signaling pathway. However, western blotting demonstrated that inhibitors of the MAPKs pathway could not decrease the expression of Bax, Bik or Puma. These results indicated that TIPE1 could promote the apoptosis of RAW264.7 cells by upregulating the pro-apoptotic members of the Bcl-2 family of proteins, and that the MAPKs signaling pathway was not involved in the pro-apoptotic effect of TIPE1.

CLEC5A is critical for dengue virus-induced osteoclast activation and bone homeostasis

Abstract

Osteoclasts are bone tissue macrophages critical to maintain bone homeostasis. However, whether osteoclasts are susceptible to flaviviral infections and involved in dengue virus (DV)-induced disease pathogenesis is still unknown. In this study, we found that osteoclasts were preferentially susceptible to DV infection and produced similar amounts of cytokines and infectious virions as macrophages. Interestingly, DV-induced cytokine secretion and nuclear translocation of the transcription factor NFATc1 in osteoclast via the Syk-coupled myeloid C-type lectin member 5A (CLEC5A). Moreover, DV caused transient inflammatory reaction in bone tissue and upregulated osteolytic activity to release C-telopeptide of type I collagen (CTX-1) from bone tissue. Furthermore, DV-induced osteolytic activity was attenuated in CLEC5A-deficient mice, and administration of antagonistic anti-CLEC5A mAb inhibited DV-activated osteolytic activity and reduced CTX-1 serum level in vivo. This observation suggests that osteoclasts serve as a novel target for DV, and transient upregulation of osteolytic activity may contribute to the clinical symptoms in dengue patients.

Key messages

Cultured osteoclasts were susceptible to DV infection.

Osteoclasts produced similar amounts of cytokines and infectious virions as macrophages.

DV induced nuclear translocation of NFATc1 in osteoclast via CLEC5A.

DV caused transient inflammatory reaction in bone tissue and upregulated osteolytic activity.

Antagonistic anti-CLEC5A mAb inhibited DV-activated osteolytic activity in vivo.

Electronic supplementary material

The online version of this article (doi:10.1007/s00109-016-1409-0) contains supplementary material, which is available to authorized users.

Interleukin‑12B is upregulated by decoy receptor 3 in rheumatoid synovial fibroblasts

Decoy receptor 3 (DcR3) competitively binds to three ligands, Fas ligand, lymphotoxin‑related inducible ligand that competes for glycoprotein D binding to herpesvirus entry mediator on T cells and tumor necrosis factor‑like ligand 1A (TL1A), to prevent their effects. Recent studies have suggested that DcR3 directly affects cells as a ligand. Using a microarray assay, our group newly identified interleukin (IL)‑12B, which encodes the p40 subunit common to IL‑12 and IL‑23, as one of the genes for which expression in fibroblast‑like synoviocytes from patients with rheumatoid arthritis (RA‑FLS) is induced by DcR3. The present study demonstrated that IL‑12B mRNA expression was upregulated by DcR3‑Fc in RA‑FLS in a dose‑dependent manner, but not in OA‑FLS. IL‑12B p40 protein in RA‑FLS was increased when stimulated with DcR3‑Fc. Pre‑treatment with anti‑TL1A antibody suppressed the upregulation of IL‑12B mRNA in RA‑FLS stimulated with DcR3‑Fc. DcR3 mRNA expression in RA‑FLS was induced by IL‑23, but not by IL‑12. These results indicated that DcR3 may increase IL‑12 or IL‑23 by inducing IL‑12B p40 expression via membrane‑bound TL1A on RA‑FLS and that IL‑23 reciprocally induces DcR3 expression in RA‑FLS. DcR3 and IL‑23 may interact in a feedback loop that aggravates local inflammation in patients with RA.

Bu-Shen-Ning-Xin decoction: inhibition of osteoclastogenesis by abrogation of the RANKL-induced NFATc1 and NF-κB signaling pathways via selective estrogen receptor α

INTRODUCTION

Bu-Shen-Ning-Xin decoction (BSNXD) is a traditional Chinese medicinal composition that has been used as a remedy for postmenopausal osteoporosis, but the mechanisms affecting bone metabolism are not fully understood.

PURPOSE

We investigated the molecular mechanism and signaling pathway underlying the effect of BSNXD on osteoclastogenesis.

MATERIALS AND METHODS

A postmenopausal osteoporosis animal model generated by ovariectomy was administered BSNXD and drug-derived serum was prepared. An enzyme immunoassay was conducted to measure the 17-β-estradiol (E2) concentration in the drug-derived serum. Bone marrow-derived monocyte/macrophage precursor cells were treated with drug-derived serum, and tartrate-resistance acid phosphatase staining was conducted to observe osteoclastogenesis. A bone resorption assay was performed to analyze the effect on osteoclastic resorptive function. Real-time PCR, flow cytometry, Western blotting, transfection, and luciferase assays were conducted to explore the related mechanism.

RESULTS

E2 was not elevated in BSNXD-derived serum. BSNXD-derived serum suppressed receptor activation of nuclear factor κB ligand (RANKL)-activated osteoclastogenesis in a dose-dependent manner; this effect could be reversed by estrogen receptor α antagonist methyl-piperidino-pyrazole. The serum suppressed RANKL-induced NF-κB transcription and inhibited the accumulation of nuclear factor of activated T-cells, cytoplasmic 1 in osteoclast precursor cells; the inhibitory effect was abolished by methyl-piperidino-pyrazole but not the estrogen receptor β antagonist or androgen receptor antagonist.

CONCLUSION

These results collectively suggest that administration of BSNXD presents inhibitory effects on osteoclast differentiation by abrogating the RANKL-induced nuclear factor of activated T-cells, cytoplasmic 1 and NF-κB signaling pathways downstream of estrogen receptor α, thereby contributing to the inhibitory effect on bone resorption.

Decoy receptor 3 regulates the expression of tryptophan hydroxylase 1 in rheumatoid synovial fibroblasts

Decoy receptor 3 (DcR3) is expressed in rheumatoid arthritis fibroblast‑like synoviocytes (RA‑FLS) and downregulates the expression of tryptophan hydroxylase 1 (TPH1), which is the rate‑limiting enzyme in serotonin synthesis. The aim of the present study was to determine the specificity of the effects of DcR3 on TPH1 in RA‑FLS, and therefore determine whether DcR3 had the potential to modulate the pathogenesis of RA. The present study also aimed to compare the effects of DcR3 and inflammatory cytokines on the expression of TPH1 in RA‑FLS and osteoarthritis (OA)‑FLS. Primary cultured RA‑ or OA‑FLS were incubated with 1.0 µg/ml DcR3‑Fc protein or 1.0 µg/ml control immunoglobulin G (IgG)1 for 12 h, or with 1.0 ng/ml tumor necrosis factor (TNF)α, 1.0 ng/ml interleukin (IL)‑1β or serum‑free Opti‑MEM only, for 24 h. The relative mRNA expression levels of TPH1 were subsequently quantified using reverse transcription‑polymerase chain reaction. The expression of serotonin in RA or OA synovial tissue was detected using immunohistochemistry. The mRNA expression of TPH1 was observed in both RA‑ and OA‑FLS and was significantly decreased following treatment with DcR3 in the RA‑FLS, however, not in the OA‑FLS. The mRNA expression of TPH1 was significantly decreased following treatment with TNFα or IL‑1β in both the RA‑ and OA‑FLS. The expression of serotonin in the multi‑layered lining synovial cells of RA and the outer layer lining synovial cells of OA was detected using immunohistochemistry. The present study is the first, to the best of our knowledge, to demonstrate that the expression of TPH1 in FLS is downregulated by inflammatory cytokines, and that DcR3 suppressed the expression of TPH1 in RA‑FLS in a disease‑specific manner. These results suggested that synovial serotonin may be involved in the pathogenesis of RA, and that TPH1 and DcR3 may be potential therapeutic targets for the treatment of RA.

DcR3 suppresses influenza virus-induced macrophage activation and attenuates pulmonary inflammation and lethality

Influenza A virus (IAV) infects macrophages and stimulates innate immunity receptors and sensors to produce proinflammatory cytokines and chemokines, which are responsible for IAV-induced pulmonary inflammation and injury. Decoy receptor 3 (DcR3) is a soluble protein belonging to the tumor necrosis factor receptor superfamily (TNFRSF), and is able to skew macrophage differentiation into an M2 phenotype. We demonstrated that DcR3 attenuated IAV-induced secretion of proinflammatory cytokines and chemokine from macrophages, and mitigated pulmonary infiltration and reduce lethality. Proteome-wide phosphoproteomic mapping revealed that DcR3 not only activated STK10, a negative regulator of cell migration, but also inactivated PKC-α, which are crucial for the activation of ERK and JNK in human macrophages. Furthermore, less pulmonary infiltration with lower levels of proinflammatory cytokines and chemokine in bronchoalveolar lavage fluid (BALF) were observed in DcR3-transgenic mice. Moreover, recombinant DcR3.Fc and heparan sulfate proteoglycan binding domain of DcR3.Fc (HBD.Fc) fusion proteins attenuated weight loss and protected mice from IAV-induced lethality. Thus, DcR3-mediated protection is not only via suppression of proinflammatory cytokine and chemokine release, but also via activation of STK10 to inhibit cell infiltration. DcR3 fusion proteins may become therapeutic agents to protect host from IAV-induced lethality in the future.

KEY MESSAGE

• DcR3 suppresses IAV-induced cytokine secretion.• DcR3 inhibits IAV-induced JNK and ERK activation in human macrophages.• DcR3 downregulates TLR3 and 7 expressions in human macrophages.• DcR3 protects mice from IAV-induced lethality.

The soluble Decoy Receptor 3 is regulated by a PI3K-dependent mechanism and promotes migration and invasion in renal cell carcinoma

Background

Overexpression of Decoy Receptor 3 (DcR3), a soluble member of the tumor necrosis factor receptor superfamily, is a common event in several types of cancer. In renal cell carcinoma (RCC), DcR3 overexpression is associated with lymph node and distant metastasis as well as a poor prognosis. However, the functional role and regulation of DcR3 expression in RCC is so far unknown.

Methods

Modulation of DcR3 expression by siRNA and ectopic gene expression, respectively, was performed in ACHN and 769-P RCC cell lines. Functional effects of a modulated DcR3 expression were analyzed with regard to migration, invasion, adhesion, clonogenicity, and proliferation. Furthermore, quantitative RT-PCR and immunoblot analyses were performed to evaluate the expression of downstream mediators of DcR3. In further experiments, luciferase assays, quantitative RT-PCR and immunoblot analyses were applied to study the regulation of DcR3 expression in RCC. Additionally, an ex vivo tissue slice culture technique combined with immunohistochemistry was used to study the regulation of DcR3 expression in human RCC specimens.

Results

Here, we show that DcR3 promotes adhesion, migration and invasiveness of RCC cells. The DcR3-dependent increase in cellular invasiveness is accompanied with an up-regulation of integrin alpha 4, matrixmetalloproteinase 7 and urokinase plasminogen activator (uPA). Further, we identified a signaling pathway regulating DcR3 expression in RCC. Using in vitro experiments as well as an ex vivo RCC tissue slice culture model, we demonstrate that expression of DcR3 is regulated in a PI3K/AKT-dependent manner involving the transcription factor nuclear factor of activated T-cells (NFAT).

Conclusions

Taken together, our results identify DcR3 as a key driver of tumor cell dissemination and suggest DcR3 as a promising target for rational therapy of RCC.

A small shared epitope-mimetic compound potently accelerates osteoclast-mediated bone damage in autoimmune arthritis

We have recently proposed that the shared epitope (SE) may contribute to rheumatoid arthritis pathogenesis by acting as a ligand that activates proarthritogenic signal transduction events. To examine this hypothesis, in this study we characterized a novel small SE-mimetic compound, c(HS4-4), containing the SE primary sequence motif QKRAA, which was synthesized using a backbone cyclization method. The SE-mimetic c(HS4-4) compound interacted strongly with the SE receptor calreticulin, potently activated NO and reactive oxygen species production, and markedly facilitated osteoclast differentiation and function in vitro. The pro-osteoclastogenic potency of c(HS4-4) was 100,000- to 1,000,000-fold higher than the potency of a recently described linear SE peptidic ligand. When administered in vivo at nanogram doses, c(HS4-4) enhanced Th17 expansion, and in mice with collagen-induced arthritis it facilitated disease onset, increased disease incidence and severity, enhanced osteoclast abundance in synovial tissues and osteoclastogenic propensities of bone marrow-derived cells, and augmented bone destruction. In conclusion, c(HS4-4), a highly potent small SE-mimetic compound enhances bone damage and disease severity in inflammatory arthritis. These findings support the hypothesis that the SE acts as a signal transduction ligand that activates a CRT-mediated proarthritogenic pathway.

'Decoy' and 'non-decoy' functions of DcR3 promote malignant potential in human malignant fibrous histiocytoma cells

Decoy receptor 3 (DcR3) is a soluble secreted protein that belongs to the tumor necrosis factor receptor (TNFR) superfamily. DcR3 inhibits the Fas ligand (FasL)/Fas apoptotic pathway by binding to FasL, competitively with Fas receptor. Previous studies have reported that overexpression of DcR3 has been detected in various human malignancies and that DcR3 functions as a ‘decoy’ for FasL to inhibit FasL-induced apoptosis. In addition, recent studies have revealed that DcR3 has ‘non-decoy’ functions to promote tumor cell migration and invasion, suggesting that DcR3 may play important roles in tumor progression by decoy and non-decoy functions. We have previously reported that overexpression of DcR3 was observed in human malignant fibrous histiocytoma (MFH), however, the roles of DcR3 in MFH have not been studied. In the present study, to elucidate the roles of DcR3 in tumor progression of MFH, we examined the effects of DcR3 inhibition on cell apoptosis, migration and invasion in human MFH cells. siRNA knockdown of DcR3 enhanced the FasL-induced apoptotic activity and significantly decreased cell migration and invasion with a decrease in the activation of phosphatidylinositol 3 kinase (PI3K)/Akt and matrix metalloproteinase (MMP)-2. The findings in this study strongly suggest that DcR3 plays important roles in tumor progression of human MFH by decoy as well as non-decoy functions and that DcR3 may serve as a potent therapeutic target for human MFH.

Cellular mechanisms of multiple myeloma bone disease

Multiple myeloma (MM) is a hematologic malignancy of differentiated plasma cells that accumulates and proliferates in the bone marrow. MM patients often develop bone disease that results in severe bone pain, osteolytic lesions, and pathologic fractures. These skeletal complications have not only a negative impact on quality of life but also a possible effect in overall survival. MM osteolytic bone lesions arise from the altered bone remodeling due to both increased osteoclast activation and decreased osteoblast differentiation. A dysregulated production of numerous cytokines that can contribute to the uncoupling of bone cell activity is well documented in the bone marrow microenvironment of MM patients. These molecules are produced not only by malignant plasma cells, that directly contribute to MM bone disease, but also by bone, immune, and stromal cells interacting with each other in the bone microenvironment. This review focuses on the current knowledge of MM bone disease biology, with particular regard on the role of bone and immune cells in producing cytokines critical for malignant plasma cell proliferation as well as in osteolysis development. Therefore, the understanding of MM pathogenesis could be useful to the discovery of novel agents that will be able to both restore bone remodelling and reduce tumor burden.

EGFR-driven up-regulation of decoy receptor 3 in keratinocytes contributes to the pathogenesis of psoriasis

Decoy receptor 3 (DcR3) is a soluble receptor of Fas ligand (FasL), LIGHT (TNFSF14) and TNF-like molecule 1A (TL1A) and plays pleiotropic roles in many inflammatory and autoimmune disorders and malignant diseases. In cutaneous biology, DcR3 is expressed in primary human epidermal keratinocytes and is upregulated in skin lesions in psoriasis, which is characterized by chronic inflammation and angiogenesis. However, the regulatory mechanisms of DcR3 over-expression in skin lesions of psoriasis are unknown. Here, we demonstrate that DcR3 can be detected in both dermal blood vessels and epidermal layers of psoriatic skin lesions. Analysis of serum samples showed that DcR3 was elevated, but FasL was downregulated in psoriatic patients compared with normal individuals. Additional cell studies revealed a central role of epidermal growth factor receptor (EGFR) in controlling the basal expression of DcR3 in keratinocytes. Activation of EGFR by epidermal growth factor (EGF) and transforming growth factor (TGF)-α strikingly upregulated DcR3 production. TNF-αenhanced DcR3 expression in both keratinocytes and endothelial cells compared with various inflammatory cytokines involved in psoriasis. Additionally, TNF-α-enhanced DcR3 expression in keratinocytes was inhibited when EGFR was knocked down or EGFR inhibitor was used. The NF-κB pathway was critically involved in the molecular mechanisms underlying the action of EGFR and inflammatory cytokines. Collectively, the novel regulatory mechanisms of DcR3 expression in psoriasis, particularly in keratinocytes and endothelial cells, provides new insight into the pathogenesis of psoriasis and may also contribute to the understanding of other diseases that involve DcR3 overexpression.

Investigation of osteoclastogenic signalling of the RANKL substitute LIGHT

LIGHT (TNFSF14) is a member of the TNF superfamily and is known to substitute for RANKL to induce osteoclast differentiation. LIGHT binds HVEM and LTβR, but it is not known whether these receptors play a role in osteoclast formation or whether LIGHT acts via RANKL signalling pathways. We found that both RANKL and LIGHT strongly induced phosphorylation of Akt and NFκB but not JNK in mouse osteoclast precursor cells. The addition of an Akt inhibitor showed decreased osteoclast differentiation and resorption mediated by both RANKL and LIGHT. RT-PCR and FACS analysis showed that CD14(+) human osteoclast precursors expressed HVEM and LTβR; expression levels of HVEM increased in the course of osteoclastogenesis and a decrease in LIGHT expression was associated with an increase in HVEM suggesting that there is a feedback loop related to this receptor. Our findings show that LIGHT is not inhibited by the soluble RANKL receptor OPG and that LIGHT is a potent osteoclastogenesis factor that activates the Akt, NFκB and JNK pathways.

An HLA-DRB1-coded signal transduction ligand facilitates inflammatory arthritis: a new mechanism of autoimmunity

Particular alleles of HLA contribute to disease susceptibility and severity in many autoimmune conditions, but the mechanisms underlying these associations are often unknown. In this study, we demonstrate that the shared epitope (SE), an HLA-DRB1-coded sequence motif that is the single most significant genetic risk factor for erosive rheumatoid arthritis, acts as a signal transduction ligand that potently activates osteoclastogenesis, both in vitro and in vivo. The SE enhanced the production of several pro-osteoclastogenic factors and facilitated osteoclast (OC) differentiation in mouse and human cells in vitro. Transgenic mice expressing a human HLA-DRB1 allele that code the SE motif demonstrated markedly higher propensity for osteoclastogenesis and enhanced bone degradation capacity ex vivo. In addition, the SE enhanced the differentiation of Th17 cells expressing the receptor activator for NF-κB ligand. When the two agents were combined, IL-17 and the SE enhanced OC differentiation synergistically. When administered in vivo to mice with collagen-induced arthritis, the SE ligand significantly increased arthritis severity, synovial tissue OC abundance, and bone erosion. Thus, the SE contributes to arthritis severity by activating an OC-mediated bone-destructive pathway. These findings suggest that besides determining the target specificity of autoimmune responses, HLA molecules may influence disease outcomes by shaping the pathogenic consequences of such responses.

Absence of herpes virus entry mediator (HVEM) increases bone mass by attenuating receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis

Herpes virus entry mediator (HVEM), which is constitutively expressed at a high level on myeloid lineage cells, is also expressed on bone marrow-derived macrophages, suggesting that it may play a role in bone metabolism by affecting osteoclasts (OC) derived from bone marrow-derived macrophages. To address this question, we evaluated bone mass by micro-computed tomography and the number and activity of OC by tartrate-resistant acid phosphatase (TRAP) and pit formation on dentine slices, comparing HVEM-knockout mice with wild-type mice. The absence of HVEM led to a higher bone mass and to decreased levels of serum collagen type I fragments and serum TRACP5b in vivo. In vitro HVEM deficiency resulted in a reduced number and activity of OC and an impaired receptor activator of nuclear factor-κB ligand signaling through reduced activation of nuclear factor-κB and of nuclear factor of activated T-cells cytoplasmic 1. Exogenous soluble HVEM decreased expression of TRAP, whereas soluble LIGHT (a ligand of HVEM) increased it, indicating the occurrence of a positive signaling through HVEM during osteoclastogenesis. Our findings indicate that HVEM regulates bone remodeling via action on OC. The higher bone mass in the femurs of HVEM-knockout mice could be, at least in part, due to attenuated osteoclastogenesis and bone resorption resulting from decreased receptor activator of nuclear factor-κB ligand signaling in the OC.

TRAF-6 dependent signaling pathway is essential for TNF-related apoptosis-inducing ligand (TRAIL) induces osteoclast differentiation

Human osteoclast formation from mononuclear phagocyte precursors involves interactions between tumor necrosis factor (TNF) ligand superfamily members and their receptors. Recent evidence indicates that in addition to triggering apoptosis, the TNF-related apoptosis-inducing ligand (TRAIL) induces osteoclast differentiation. To understand TRAIL-mediated signal transduction mechanism in osteoclastogenesis, we demonstrated that TRAIL induces osteoclast differentiation via a Tumor necrosis factor receptor-associated factor 6 (TRAF-6)-dependent signaling pathway. TRAIL-induced osteoclast differentiation was significantly inhibited by treatment with TRAF-6 siRNA and TRAF6 decoy peptides in both human monocytes and murine RAW264.7 macrophage cell lines, as evaluated in terms of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells and bone resorption activity. Moreover, TRAIL-induced osteoclast differentiation was also abolished in TRAF6 knockout bone marrow macrophages. In addition to induction of NFATc1, treatment of TRAIL also induced ubiquitination of TRAF6 in osteoclast differentiation. Thus, our data demonstrate that TRAIL induces osteoclastic differentiation via a TRAF-6 dependent signaling pathway. This study suggests TRAF6-dependent signaling may be a central pathway in osteoclast differentiation, and that TNF superfamily molecules other than RANKL may modify RANK signaling by interaction with TRAF6-associated signaling.

Significance of decoy receptor 3 (Dcr3) and external-signal regulated kinase 1/2 (Erk1/2) in gastric cancer

Background

Decoy receptor 3 (DcR3), a member of the tumor necrosis factor receptor (TNFR) superfamily, is associated with anti-tumor immunity suppression. It is highly expressed in many tumors, and its expression can be regulated by the MAPK/MEK/ERK signaling pathway. The MAPK/MEK/ERK pathway has been reported to be a regulator in tumor occurrence, development and clonal expansion. External-signal regulated kinase (ERK) is a vital member of this pathway.

Results

The expression of DcR3 and ERK1/2 in tumor tissues of gastric cancer patients was significantly higher than the non-cancerous group (P < 0.05). There was no statistical difference among tumor tissues from patients with different ages or gender, and even of different differentiation (P > 0.05). However, in patients with stage I gastric cancer, the DcR3 and ERK1/2 levels were significantly lower than patients with more advanced stages.

Conclusions

DcR3 and ERK1/2 play a vital role in the development of gastric cancer, and they may be new markers for indicating the efficiency of gastric cancer treatment in the future.

DcR3 binds to ovarian cancer via heparan sulfate proteoglycans and modulates tumor cells response to platinum with corresponding alteration in the expression of BRCA1

BACKGROUND

Overcoming platinum resistance is a major obstacle in the treatment of Epithelial Ovarian Cancer (EOC). In our previous work Decoy Receptor 3 (DcR3) was found to be related to platinum resistance. The major objective of this work was to define the cellular interaction of DcR3 with EOC and to explore its effects on platinum responsiveness.

METHODS

We studied cell lines and primary cultures for the expression of and the cells ability to bind DcR3. Cells were cultured with DcR3 and then exposed to platinum. Cell viability was determined by MTT assay. Finally, the cells molecular response to DcR3 was studied using real time RT-PCR based differential expression arrays, standard RT-PCR, and Western blot.

RESULTS

High DcR3 in the peritoneal cavity of women with EOC is associated with significantly shorter time to first recurrence after platinum based therapy (p = 0.02). None-malignant cells contribute DcR3 in the peritoneal cavity. The cell lines studied do not secrete DcR3; however they all bind exogenous DcR3 to their surface implying that they can be effected by DcR3 from other sources. DcR3s protein binding partners are minimally expressed or negative, however, all cells expressed the DcR3 binding Heparan Sulfate Proteoglycans (HSPGs) Syndecans-2, and CD44v3. DcR3 binding was inhibited by heparin and heparinase. After DcR3 exposure both SKOV-3 and OVCAR-3 became more resistant to platinum with 15% more cells surviving at high doses. On the contrary CaOV3 became more sensitive to platinum with 20-25% more cell death. PCR array analysis showed increase expression of BRCA1 mRNA in SKOV-3 and OVCAR-3 and decreased BRCA1 expression in CaOV-3 after exposure to DcR3. This was confirmed by gene specific real time PCR and Western blot analysis.

CONCLUSIONS

Non-malignant cells contribute to the high levels of DcR3 in ovarian cancer. DcR3 binds readily to EOC cells via HSPGs and alter their responsiveness to platinum chemotherapy. The paradoxical responses seen were related to the expression pattern of HSPGs available on the cells surface to interact with. Although the mechanism behind this is not completely known alterations in DNA repair pathways including the expression of BRCA1 appear to be involved.

Decoy receptor 3 attenuates collagen-induced arthritis by modulating T cell activation and B cell expansion

OBJECTIVE

To investigate the immune-modulated effects of decoy receptor 3 (DCR3) in an experimental model of rheumatoid arthritis (RA).

METHODS

We delivered DCR3 plasmid into collagen-induced arthritis (CIA) mice using the hydrodynamic method and evaluated the serum level of DCR3 protein by ELISA. After immunization, we assessed disease severity of arthritis incidence, arthritis scores, paw thickness, and means of arthritic limbs, and used hematoxylin and eosin staining to observe synovial hyperplasia. We analyzed numbers of murine splenocytes and inguinal lymphocyte cells, cell populations, and serum proinflammatory cytokines by flow cytometry. We investigated B cell proliferation by carboxyfluorescein succinimidyl ester assay. We evaluated serum levels of total IgG2a and type II collagen-specific IgG and IgG2a using ELISA.

RESULTS

DCR3 expression in sera significantly attenuated disease severity in CIA mice. We found that DCR3 inhibited the volume of inguinal lymph nodes, numbers of CD19+ B cells, and populations of interferon-γ, interleukin 4 (IL-4), IL-17A, and Foxp3-producing CD4+ T cell in vivo. We found that DCR3 inhibited Pam3CSK4 (Toll-like receptor 1/2 ligand)-induced B220+ B cell proliferation in vitro. DCR3 treatment reduced the serum level of IL-6, total IgG2a, and CII-specific IgG2a antibody.

CONCLUSION

We postulated that the protective effects of DCR3 in CIA resulted from modulation of the immune system by maintaining the B/T cell balance and decreasing lymphocyte expansion. We suggest DCR3 as a prophylactic and potential therapeutic agent in the treatment of RA.

DcR3 induces cell proliferation through MAPK signaling in chondrocytes of osteoarthritis

INTRODUCTION

Decoy receptor 3 (DcR3), a soluble receptor belonging to the tumor necrosis factor (TNF) receptor superfamily, competitively binds and inhibits the TNF family including Fas-ligand (Fas-L), lymphotoxin-like inducible protein that competes with glycoprotein D for binding herpesvirus entry mediator on T-cells (LIGHT) and TNF-like ligand 1A (TL1A). In this study, we investigated the functions of DcR3 on osteoarthritis (OA) chondrocytes.

METHODS

Expressions of DcR3 in chondrocytes were measured by realtime Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR). Expression of DcR3 in sera and joint fluids was measured by enzyme-linked immunosorbent assay (ELISA). Chondrocytes were incubated with DcR3-Fc chimera protein (DcR3-Fc) before induction of apoptosis by Fas-L and apoptosis was detected with terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labelling labeling (TUNEL) staining and Western blotting of caspase 8 and poly (ADP-ribose) polymerase (PARP). Chondrocytes were incubated with DcR3-Fc and the proliferation was analyzed by 4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate (WST) assay. Phosphorylation of Extracellular Signal-Regulated Kinase (ERK), P38 mitogen-activated protein kinase (MAPK) and Jun N-terminal Kinase (JNK) in chondrocytes was measured by Western blotting after incubation with DcR3-Fc, Mitogen-activated protein kinase kinase (MEK1/2) inhibitor, or P38 MAPK inhibitor. Chondrocytes were treated with DcR3-Fc after pre-incubation with blocking antibody of Fas-L, LIGHT and TL1A, and proliferation or phosphorylation of ERK was analyzed.

RESULTS

DcR3 was expressed in OA and normal chondrocytes. DcR3-Fc protects chondrocytes from Fas-induced apoptosis. DcR3-Fc increased chondrocytes proliferation and induced the phosphorylation of ERK specifically. DcR3-induced chondrocytes proliferation was inhibited by pre-incubation of PD098059 or blocking Fas-L antibody. DcR3 increased chondrocytes proliferation in OA chondrocytes, but did not in normal.

CONCLUSION

DcR3 regulates the proliferation of OA chondrocytes via ERK signaling and Fas-induced apoptosis.

Ribosome inactivating protein B-chain induces osteoclast differentiation from monocyte/macrophage lineage precursor cells

Human osteoclast formation from mononuclear phagocyte precursors involves interactions between lectins and their receptors. A type-2 ribosome inactivating protein consists of an A chain and a B chain. The glycosylated B chain binds specifically to galactose moieties of sugar molecules. In this study we showed that the recombinant ribosome inactivating protein B-chain (rRBC) could induce osteoclast formation from human monocytes and murine RAW264.7 macrophages. Tartrate-resistant acid phosphatase (TRAP) staining and bone resorption assays demonstrated that differentiation of osteoclast-like cells was induced in the presence of rRBC in a dose-dependent manner. The rRBC-induced osteoclast differentiation was independent of caspase activation and apoptosis induction activity; however, rRBC-induced osteoclastogenesis was dependent on activation of NF-κB, ERK1/2, and p38 MAP kinase. Thus, our data demonstrated that rRBC induced osteoclast differentiation through a non-apoptotic signaling pathway. In addition to triggering apoptosis, the rRBC also induced osteoclast differentiation. According to this study, a novel role is proposed for rRBC in regulating osteoclast differentiation and in osteoimmunology.

Decoy receptor 3: a pleiotropic immunomodulator and biomarker for inflammatory diseases, autoimmune diseases and cancer

Recently, several decoy molecules belonging to tumor necrosis factor receptor superfamily (TNFRSF) have been identified, including decoy receptor 1 (DcR1), decoy receptor 2 (DcR2), and decoy receptor 3 (DcR3). One of the tumor necrosis factor superfamily (TNFSF) members, TNF-related apoptosis-inducing ligand (TRAIL), binds to DcR1 and DcR2, which are membranous receptors with a truncated cytoplasmic domain, thus unable to transduce TRAIL-mediated signaling. In contrast to DcR1 and DcR2, DcR3 is a soluble receptor capable of neutralizing the biological effects of three other TNFSF members: Fas ligand (FasL/TNFSF6/CD95L), LIGHT (TNFSF14) and TNF-like molecule 1A (TL1A/TNFSF15). Since FasL is a potent apoptosis- and inflammation-inducing factor, LIGHT is involved in apoptosis and inflammation, and TL1A is a T cell costimulator and is involved in gut inflammation, DcR3 can be defined as an immunomodulator on the basis of its neutralizing effects on FasL, LIGHT, and TL1A. Initial studies demonstrated that DcR3 expression is elevated in tumors cells; however, later work showed that DcR3 expression is also upregulated in inflammatory diseases, where serum DcR3 levels correlate with disease progression. In addition to its neutralizing effect, DcR3 also acts as an effector molecule to modulate cell function via 'non-decoy' activities. This review focuses on the immunomodulatory effects of DcR3 via 'decoy' and 'non-decoy' functions, and discusses the potential of DcR3 as a biomarker to predict cancer invasion and inflammation progression. We also discuss the possible utility of recombinant DcR3 as a therapeutic agent to control autoimmune diseases, as well as the potential to attenuate tumor progression by inhibiting DcR3 expression.

Phospholipase D signaling pathway is involved in lung cancer-derived IL-8 increased osteoclastogenesis

Bone is a frequent target of lung cancer metastasis, which is associated with significant morbidity and a dismal prognosis. This study analyzed the soluble factors secreted by lung cancer cells, which are responsible for increasing osteoclast differentiation. Addition of recombinant human interleukin-8 (rhIL-8), present in large amounts in A549-conditioned medium (CM) and NCI-H460-CM, mimicked the inductive effect of A549-CM and NCI-H460-CM on osteoclastogenesis. In contrast, depletion of interleukin-8 (IL-8) from A549-CM and NCI-H460-CM decreased the osteoclastogenesis-inductive properties of A549-CM and NCI-H460-CM. Induction of osteoclast differentiation by lung cancer-derived-CM and rhIL-8 was associated with increased phospholipase D (PLD) activation, and the activations of protein kinase C (PKC) alpha/betaII, extracellular signal-regulated kinase (ERK) 1/2 and AKT/the mammalian target of rapamycin (mTOR). Blocking PLD by a specific inhibitor significantly decreased osteoclast formation by inhibiting PKCs activation and subsequently attenuating the phosphorylation of ERK1/2. PLD inhibitor also completely decreased AKT and mTOR phosphorylation, whereas phosphatidylinositol-3-kinase (PI3K) inhibitor only partially decreased mTOR phosphorylation, suggesting that mTOR activation by PLD is through both PI3K/AKT-dependent and PI3K/AKT-independent manner. In addition, blocking AKT and ERK1/2 by a specific inhibitor also suppressed lung cancer-derived-CM and rhIL-8-induced osteoclast differentiation. Moreover, treatment of peripheral blood mononuclear cells with sera from invasive lung cancer patients increased the formation of osteoclasts. Our study suggests that IL-8 or IL-8-mediated PLD/PKC/ERK1/2 or PLD/AKT signaling is an attractive therapeutic target for osteolytic bone metastases in lung cancer patients.