Modulation of macrophage differentiation and activation by decoy receptor 3

Plasma tumour necrosis factor-alpha-related proteins in prognosis of heart failure with pulmonary hypertension

AIMS

Patients with heart failure (HF) exhibit poor prognosis, which is further deteriorated by pulmonary hypertension (PH), with negative impact on morbidity and mortality. As PH due to left HF (LHF-PH) is among the most common causes of PH, there is an urge according to the 2021 European Society of Cardiology HF guidelines to find new biomarkers that aid in prognostication of this patient cohort. Given the role of tumour necrosis factor-alpha (TNF-α) in HF progression, we aimed to investigate the prognostic value of plasma proteins related to TNF-α in patients with LHF-PH, in relation to haemodynamic changes following heart transplantation (HT).

METHODS AND RESULTS

Twenty TNF-α-related plasma proteins were analysed using proximity extension assay in healthy controls (n = 20) and patients with LHF-PH (n = 67), before and 1 year after HT (n = 19). Plasma levels were compared between the groups, and the prognostic values were determined using Kaplan-Meier and Cox regression analyses. Plasma levels of lymphotoxin-beta receptor (LTBR), TNF receptor superfamily member 6B (TNFRSF6B), and TNF-related apoptosis-inducing ligand receptors 1 and 2 (TRAIL-R1 and TRAIL-R2, respectively) were higher in LHF-PH pre-HT vs. controls (P < 0.0001), as well as higher in pre-HT vs. post-HT (P < 0.001). The elevated pre-HT levels of LTBR, TNFRSF6B, TRAIL-R1, and TRAIL-R2 decreased towards the levels of healthy controls after HT. Higher preoperative levels of LTBR, TNFRSF6B, TRAIL-R1, and TRAIL-R2 in LHF-PH were associated with worse survival rates (P < 0.002). In multivariate Cox regression models, each adjusted for age and sex, LTBR, TNFRSF6B, TRAIL-R1, and TRAIL-R2 predicted mortality (P < 0.002) [hazard ratio (95% confidence interval): 1.12 (1.04-1.19), 1.01 (1.004-1.02), 1.28 (1.14-1.42), and 1.03 (1.02-1.04), respectively].

CONCLUSIONS

Elevated pre-HT plasma levels of the TNF-α-related proteins LTBR, TNFRSF6B, TRAIL-R1, and TRAIL-R2 in LHF-PH decreased 1 year after HT, displaying a normalization pattern towards the levels of the healthy controls. These proteins were also prognostic, where higher levels were associated with worse survival rates in LHF-PH, providing new insight in their potential role as prognostic biomarkers. Larger studies are warranted to validate our findings and to investigate their possible pathobiological mechanisms in LHF-PH.

Evaluation of the role of serum DcR3 levels in the early clinical prognosis of patients with Crimean-Congo hemorrhagic fever

BACKGROUND

Crimean-Congo hemorrhagic fever (CCHF) is a zoonotic disease that is transmitted by Hyalomma ticks and is endemic in many parts of the world. This study aimed to determine the relationship between early serum Decoy receptor-3 (DcR3) level and clinical severity in patients with CCHF.

METHODS

The study included 88 patients hospitalized for CCHF between April and August 2022 and a control group of 40 healthy individuals. The patients were divided according to clinical course as those with mild/moderate (group 1, n=55) and severe (group 2, n=33) CCHF. DcR3 levels were measured by enzyme-linked immunosorbent assay of serum obtained at the time of diagnosis.

RESULTS

Fever, hemorrhage, nausea, headache, diarrhea, and hypoxia were significantly more common among patients with severe CCHF than patients with mild/moderate CCHF (p<0.001, <0.001, 0.02, 0.01, <0.001, and <0.001, respectively). Group 2 had higher serum DcR3 levels than both group 1 and the control group (p<0.001 for both). Serum DcR3 levels were also significantly higher in group 1 than in the control group (p<0.001). Using 98.4 ng/mL as the cut-off value, serum DcR3 had 99% sensitivity and 88% specificity in differentiating patients with severe CCHF from those with mild/moderate CCHF.

CONCLUSION

During the high season in our endemic region, CCHF can present with a severe clinical course independent of age and comorbidities, unlike other infectious diseases. Elevated DcR3 observed early in the disease may allow additional immunomodulatory therapies to be tried in addition to antiviral therapy in CCHF, for which treatment options are limited.

The Role of Decoy Receptor DcR3 in Gastrointestinal Malignancy

Malignancies are among the leading causes of mortality worldwide. Early detection and treatment are the primary targets of clinical and translational research, and may be facilitated by the recognition of novel diagnostic and prognostic biomarkers. Decoy receptor 3 (DcR3) is a soluble receptor of the tumor necrosis factor receptor superfamily of proteins (TNFRSF), which associates with its respective TNF-like ligands, Fas-L, LIGHT, and TL1A. DcR3 has been recognised as a significant anti-apoptotic factor with prominent involvement in various inflammatory and neoplastic conditions. Increased intratumor expression of DcR3 and elevated soluble DcR3 protein content in the sera of patients has been reported for various malignancies. Recent published work has suggested that monitoring of local and systemic DcR3 may provide an attractive biomarker, mainly for defining subgroups of patients with aggressive tumor behaviour and poor prognosis. The aim of the present review is to summarize and critically present existing evidence regarding the potential clinical importance of monitoring DcR3 expression in patients with malignancies of the gastrointestinal tract, as well as liver and pancreatic cancer. We also present a detailed description of the pathophysiological basis that may underlie the involvement of DcR3 in gastrointestinal carcinogenesis. Based on these data, we comment on the potential applicability of DcR3 monitoring in the diagnosis and, most importantly, the prognostic stratification of patients.

Decoy receptor 3 is involved in epidermal keratinocyte commitment to terminal differentiation via EGFR and PKC activation

Decoy receptor 3 (DcR3) is a soluble receptor for Fas ligand, LIGHT and TL1A, but it also exerts effector functions. Previously, we found that DcR3 is upregulated in the serum and lesional skin of patients with psoriasis and is upregulated by EGFR activation in proliferating primary human epidermal keratinocytes. However, the functional role of intracellular DcR3 in keratinocyte differentiation is still incompletely defined. Herein, primary cultured human epidermal keratinocytes were differentiated by phorbol 12-myristate 13-acetate (PMA) treatment, calcium treatment and cell confluence, which are three standard in vitro differentiation models. We found that the constitutive expression of the DcR3 gene and protein was progressively suppressed during terminal differentiation of keratinocytes. These changes were correlated with downregulation of EGFR activation during keratinocyte differentiation. EGFR inhibition by gefitinib further decreased confluence-induced suppression of DcR3 mRNA expression, and, vice versa, knocking down DcR3 expression attenuated EGFR and EGFR ligand expression as well as EGFR activation. Under conditions without a change in cell growth, DcR3 silencing reduced the expression of involucrin and transglutaminase 1 but enhanced the induction of the terminal differentiation markers keratin 10 and loricrin. Of note, DcR3 interacted with PKCα and PKCδ and enhanced PKC activity. In keratinocytes with PKCα and PKCδ silencing, differentiation markers were differentially affected. In conclusion, DcR3 expression in keratinocytes is regulated by EGFR and forms a positive feedback loop to orchestrate constitutive EGFR and PKC activity. During differentiation, DcR3 is downregulated and involved in modulating the pattern of terminal differentiation.

A protein linked to cancer and various inflammatory diseases may also be an important driver for the skin condition in psoriasis. The outer surface of the skin is formed by cells called keratinocytes, which transition from a highly proliferative state to a fully mature state where they no longer divide. This developmental process is disrupted in psoriasis. Researchers led by Wan-Wan Lin at National Taiwan University, Taipei, have now identified a prominent role for a protein called decoy receptor 3 (DcR3), which is a biomarker for a variety of disorders and is also abnormally expressed in keratinocytes in psoriatic lesions. Lin and colleagues demonstrated that DcR3 interacts with multiple cellular signaling pathways that coordinate cell differentiation. These findings reveal how aberrant DcR3 activity might lead to the abnormal keratinocyte developmental behavior observed in psoriasis.

Integrative analysis of TNFRSF6B as a potential therapeutic target for pancreatic cancer

Background

Pancreatic cancer is one of the most lethal malignant tumors worldwide with poor outcomes. Previous studies have shown that tumor necrosis factor receptor superfamily member 6b (TNFRSF6B) plays an important role in cancer progression and immunosuppression. However, the mechanisms by which TNFRSF6B influence pancreatic cancer, and the regulatory networks involved remain to be further studied.

Methods

This study analyzed the mRNA information and clinical data of patients from The Cancer Genome Atlas (TCGA) and the ONCOMINE databases. The gene co-expression data regarding TNFRSF6B was obtained from the c-BioPortal and used to explore the functional network of TNFRSF6B in pancreatic cancer, as well as its function in tumor immunity. Short hairpin (sh) RNA knock-down experiments were performed to examine the functional roles of TNFRSF6B in pancreatic cancer cell lines.

Results

The expression of TNFRSF6B was elevated in pancreatic cancer tissues compared to normal pancreatic tissues, and its high expression was associated with poor prognosis of patients with pancreatic cancer. TNFRSF6B was found to be widely involved in cell cycle processes, apoptosis, apoptosis signaling pathways, immune responses, and responses to interferon. Knock-down of TNFRSF6B expression inhibited pancreatic cancer cell proliferation and invasion in vitro. Moreover, carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) was found to be co-expressed with TNFRSF6B, and there was a positive correlation between these molecules in pancreatic cancer cells.

Conclusions

This report suggested that TNFRSF6B has a critical role in the progression and metastasis of pancreatic cancer. These findings provide novel insights into the role of TNFRSF6B in the functional network of pancreatic cancer, and suggest that TNFRSF6B may be a potential therapeutic target.

Serum decoy receptor 3 (DcR3): a promising biomarker for atopic asthma in children

Bronchial asthma is a common chronic inflammatory disease with high prevalence and morbidity, particularly in school-aged children. Decoy receptor 3 (DcR3) is a soluble decoy receptor that belongs to the tumor necrosis factor receptor superfamily and has been reported to be elevated in several allergic and inflammatory diseases. This study was designed to determine the role of DcR3 in pediatric asthma. The serum DcR3 levels were analyzed in 85 subjects (60 pediatric patients with bronchial asthma and 25 age- and sex-matched healthy control children) using the enzyme-linked immunosorbent assay technique. Patients with asthma had higher serum DcR3 levels than healthy control subjects (p = 0.007). In the atopic group of patients with asthma, the serum DcR3 levels were inversely correlated with the asthma control test score (R =  - 0.392, p = 0.039). Overall, DcR3 could be a promising biomarker of atopic asthma, specifically in pediatric patients.

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.

Whole Transcriptome Analysis of Chicken Bursa Reveals Candidate Gene That Enhances the Host's Immune Response to Coccidiosis

Coccidiosis is a major hazard to the chicken industry, but the host’s immune response to coccidiosis remains unclear. Here, we performed Eimeria coccidia challenge in 28-day-old ROSS 308 broilers and selected the bursa from the three most severely affected individuals and three healthy individuals for RNA sequencing. We obtained 347 DEGs from RNA-seq and found that 7 upregulated DEGs were enriched in Cytokine-cytokine receptor interaction pathway. As the DEGs with the highest expression abundance in these 7 genes, TNFRSF6B was speculated to participate in the process of host’s immune response to coccidiosis. It is showed that TNFRSF6B can polarize macrophages to M1 subtype and promote inflammatory cytokines expression. In addition, the expression of TNFRSF6B suppressed HD11 cells apoptosis by downregulating Fas signal pathway. Besides, TNFRSF6B-mediated macrophages immunity activation can be reversed by apoptosis. Overall, our study indicates that TNFRSF6B upregulated in BAE, is capable of aggravating the inflammatory response by inhibiting macrophages apoptosis via downregulating Fas signal pathway, which may participate in host’s immune response to coccidiosis.

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.

Correlations Between Serum Decoy Receptor 3 and Airflow Limitation and Quality of Life in Male Patients with Stable Stage and Acute Exacerbation of COPD

PURPOSE

Serum decoy receptor 3 (DcR3) level increases in chronic inflammatory diseases. The present study aimed to examine serum DcR3 and IL-6 levels in male patients with stable chronic obstructive pulmonary disease (COPD) and acute exacerbation of the disease and correlations between these markers and airflow limitation.

METHODS

We measured serum DcR3 and IL-6 levels in 60 COPD patients [30 stable COPD (SCOPD), and 30 acute exacerbation of COPD (AECOPD)], and 30 control subjects and assessed their correlations with airflow limitation according to the COPD stage indicated by the global initiative for chronic obstructive pulmonary disease (GOLD) criteria, peripheral O₂ saturation (SpO₂), and COPD assessment test (CAT) score. We also tested associations between serum DcR3 levels and COPD patients' clinical parameters.

RESULTS

Both serum DcR3 and IL-6 levels increased with increasing severity of airflow limitation in SCOPD and AECOPD groups (P < 0.01 to 0.001). These markers also increased in patients with AECOPD compared with subjects in SCOPD group in GOLD stages III-IV (P < 0.05 to 0.001). In addition, there was a significant positive correlation between serum DcR3 level and IL-6, CAT score and smoking history (per year).

CONCLUSION

The study revealed that serum DcR3 level elevated with increasing severity of airflow limitation in male COPD patients, particularly in acute exacerbation phase. This increase was associated with a reduced quality of life and increased severity of hypoxia. These results suggest that DcR3 may be associated with the underlying pathophysiology of COPD in male patients.

Role of prognostic biomarker decoy receptor 3 and immunomodulation in kidney diseases

Decoy receptor 3 (DcR3), also known as tumor necrosis factor receptor superfamily member 6b (TNFRSF6B), was recently identified as a novel biomarker for predicting progression of kidney diseases with potential immune modulation. The purpose of this review is to discuss the current evidence related to DcR3 in kidney diseases and to compare the differences between human and animal studies both in vivo and in vitro. High serum DcR3 predicts the occurrence of peritonitis in patients receiving chronic peritoneal dialysis and is positively correlated with inflammatory markers such as interleukin-6, high-sensitivity C-reactive protein, and adhesion molecules in patients on maintenance hemodialysis (HD). Higher serum DcR3 levels not only independently predict cardiovascular and all-cause mortality in HD patients but also identify older adults on HD at risk of protein-energy wasting in combination with a low geriatric nutritional risk index. Recently, renal tubular epithelial cells (RTECs) expressing DcR3 have also been used to predict progression of chronic kidney disease. Expression of DcR3 was correlated with a 2-fold increase in serum creatinine or failure of kidney allograft. DcR3 could protect renal myofibroblasts against Fas-induced apoptosis and subsequently lead to renal fibrosis. Locally expressed DcR3 in the RTECs may suppress the FasL-Fas-mediated apoptosis of T cells, resulting in an accumulation of allo-reactive T cells. In addition to traditional biological functions, recombinant DcR3.Fc and cytomegalovirus promoter-driven human DcR3 plasmid are able to modulate the activation and differentiation of dendritic cells and macrophages via "non-decoy" action. Both progressive IgA nephropathy and autoimmune crescentic glomerulonephritis in mice can be suppressed after hydrodynamics-based gene delivery of DcR3 plasmid. DcR3-mediated effects in vitro could be surveyed via over-expressing DcR3 or addition of recombinant DcR3.Fc, and CD68-driven DcR3 transgenic mice are suitable for investigating systemic effect in vivo. Inhibition of DcR3 expression in human may be a promising approach for pathomechanism.

Role of TGFβ3-Smads-Sp1 axis in DcR3-mediated immune escape of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a leading cause of tumour-associated mortality worldwide, but no significant improvement in treating HCC has been reported with currently available systemic therapies. Immunotherapy represents a new frontier in tumour therapy. Therefore, the immunobiology of hepatocarcinoma has been under intensive investigation. Decoy receptor 3 (DcR3), a member of the tumour necrosis factor receptor (TNFR) superfamily, is an immune suppressor associated with tumourigenesis and cancer metastasis. However, little is known about the role of DcR3 in the immunobiology of hepatocarcinoma. In this study, we found that overexpression of DcR3 in HCC is mediated by the TGFβ3-Smad-Sp1 signalling pathway, which directly targets DcR3 promoter regions. Moreover, overexpression of DcR3 in HCC tissues is associated with tumour invasion and metastasis and significantly promotes the differentiation and secretion of Th2 and Treg cells while inhibiting the differentiation and secretion of Th1 cells. Conversely, knockdown of DcR3 expression in HCC significantly restored the immunity of CD4⁺ T cells. Inhibition of DcR3 expression may provide a novel immunotherapeutic approach to restoring immunity in HCC patients.

Hepatitis B X protein upregulates decoy receptor 3 expression via the PI3K/NF-κB pathway

Chronic hepatitis B (CHB) is associated with the development of hepatocellular carcinoma (HCC). Decoy receptor 3 (DcR3) is a tumor necrosis factor receptor that promotes tumor cell survival by inhibiting apoptosis and interfering with immune surveillance. Previous studies showed that DcR3 was overexpressed in HCC cells and that short hairpin RNA (shDcR3) sensitizes TRAIL-resistant HCC cells. However, the expression of DcR3 during hepatitis B virus (HBV) infection has not been investigated. Here, we demonstrated that DcR3 was overexpressed in CHB patients and that DcR3 upregulation was positively correlated with the HBV DNA load and liver injury (determined by histological activity index, serum alanine aminotransferase level, and aspartate aminotransferase level). We found that hepatitis B virus X protein (HBx) upregulated DcR3 expression in a dose-dependent manner, but this increase was blocked by NF-κB inhibitors. HBx also induced the activation of NF-κB, and the NF-κB subunits p65 and p50 upregulated DcR3 by directly binding to the DcR3 promoters. Inhibition of PI3K significantly downregulated DcR3 and inhibited the binding of NF-κB to the DcR3 promoters. Our results demonstrate that the HBx induced DcR3 expression via the PI3K/NF-κB pathway; this process may contribute to the development of HBV-mediated HCC.

Hypoxia as a barrier to immunotherapy in pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is a lethal disease with limited response to cytotoxic chemoradiotherapy, as well as newer immunotherapies. The PDA tumor microenvironment contains infiltrating immune cells including cytotoxic T cells; however, there is an overall immunosuppressive milieu. Hypoxia is a known element of the solid tumor microenvironment and may promote tumor survival. Through various mechanisms including, but not limited to, those mediated by HIF-1α, hypoxia also leads to increased tumor proliferation and metabolic changes. Furthermore, epithelial to mesenchymal transition is promoted through several pathways, including NOTCH and c-MET, regulated by hypoxia. Hypoxia-promoted changes also contribute to the immunosuppressive phenotype seen in many different cell types within the microenvironment and thereby may inhibit an effective immune system response to PDA. Pancreatic stellate cells (PSCs) and myofibroblasts appear to contribute to the recruitment of myeloid derived suppressor cells (MDSCs) and B cells in PDA via cytokines increased due to hypoxia. PSCs also increase collagen secretion in response to HIF-1α, which promotes a fibrotic stroma that alters T cell homing and migration. In hypoxic environments, B cells contribute to cytotoxic T cell exhaustion and produce chemokines to attract more immunosuppressive regulatory T cells. MDSCs inhibit T cell metabolism by hoarding key amino acids, modulate T cell homing by cleaving L-selectin, and prevent T cell activation by increasing PD-L1 expression. Immunosuppressive M2 phenotype macrophages promote T cell anergy via increased nitric oxide (NO) and decreased arginine in hypoxia. Increased numbers of regulatory T cells are seen in hypoxia which prevent effector T cell activation through cytokine production and increased CTLA-4. Effective immunotherapy for pancreatic adenocarcinoma and other solid tumors will need to help counteract the immunosuppressive nature of hypoxia-induced changes in the tumor microenvironment. Promising studies will look at combination therapies involving checkpoint inhibitors, chemokine inhibitors, and possible targeting of hypoxia. While no model is perfect, assuring that models incorporate the effects of hypoxia on cancer cells, stromal cells, and effector immune cells will be crucial in developing successful therapies.

CpGs Induce Differentiation of Atlantic Salmon Mononuclear Phagocytes Into Cells With Dendritic Morphology and a Proinflammatory Transcriptional Profile but an Exhausted Allostimulatory Activity

Due to their ability to present foreign antigens and prime naïve T cells, macrophages, and dendritic cells (DCs) are referred to as professional antigen-presenting cells (APCs). Although activated macrophages may function as APCs, these cells are particularly effective at directly engaging pathogens through phagocytosis, and production of antimicrobial compounds. On the other hand, DCs possess superb antigen-presenting and costimulatory capacity and they are essential for commencement and regulation of adaptive immune responses. In in vitro models, development of mature mammalian DCs from monocytes requires sequential exposure to growth factors (including GM-CSF and IL-4) and proinflammatory stimuli such as toll-like receptor (TLR) ligands. Currently, except for IL-4/13, neither orthologs nor functional analogs of the growth factors which are essential for the differentiation of mammalian DCs (including GM-CSF and FLT3) have been identified in teleosts and data about differentiation of piscine APCs is scant. In the present study, primary salmon mononuclear phagocytes (MPs) stimulated in vitro for 5-7 days with a B-class CpG oligodeoxynucleotides (ODN 2006PS) underwent morphological differentiation and developed "dendritic" morphology, characterized by long, branching pseudopodia. Transcriptional profiling showed that these cells expressed high levels of proinflammatory mediators characteristic for M1 polarized MPs. However, the cells treated with CpGs for 7 days downregulated their surface MHCII molecules as well as their capacity to endocytose ovalbumin and exhibited attenuated allostimulatory activity. This concurred with transcriptional downregulation of costimulatory CD80/86 and upregulation of inhibitory CD274 (B7-H1) genes. Despite their exhausted allostimulatory activity, these cells were still responsive to re-stimulation with gardiquimod (a TLR7/8 ligand) and further upregulated a wide array of immune genes including proinflammatory mediators such as intereukin-1 beta and tumor necrosis factor. Overall, the presented data highlight the disparate effects TLR ligands may have on the proinflammatory status of APCs, on one side, and their antigen-presenting/costimulatory functions, on the other. These findings also indicate that despite the poor phylogenetic conservation of the growth factors involved in the differentiation of DCs, some of the processes that orchestrate the development and the differentiation of professional APCs are conserved between teleosts in mammals.

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: 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.

DcR3 promotes hepatoma cell migration by downregulating E-cadherin expression

Decoy receptor 3 (DcR3), a decoy molecule belonging to the tumor necrosis factor receptor superfamily (TNFRSF), is a soluble receptor that can neutralize the biological effects of three other TNFSF members, namely, Fas ligand (FasL/TNFSF6/CD95L), LIGHT (TNFSF14) and TNF-like molecule 1A (TL1A/TNFSF15). DcR3 expression is increased in tumor cells. As such, DcR3 has been considered a potential biomarker to predict cancer invasion and progression of inflammation. However, the molecular mechanisms of DcR3 in tumor progression and metastasis remain poorly described. In the present study, DcR3 induced cytoskeleton remodeling, inhibited E-cadherin expression, and promoted cancer cell migration. Immunofluorescence and flow cytometry demonstrated that DcR3 expression was increased in hepatoma cells, whereas E-cadherin expression was significantly downregulated. Immunohistochemistry revealed that DcR3 and E-cadherin exhibited an opposite expression pattern between normal and cancerous liver tissues. Moreover, DcR3 treatment promoted IκBα degradation and p65 nuclear translocation. Therefore, the present study uncovered the mechanism underlying the function of DcR3 in cancer cell migration and provides evidence that DcR3 may be a potential target for cancer therapy.

Epigenetic mechanisms of myeloid differentiation in the tumor microenvironment

Myeloid cells are extremely plastic as they respond and terminally differentiate into a plethora of functional types, in the blood or tissues, in response to a variety of growth factors, cytokines and pathogenic molecules. This plasticity is also manifested by the subversion of normal differentiation into the aberrant generation of a variety of tolerogenic myeloid cells in the tumoral microenvironment, where a variety of factors are released. Epigenetic mechanisms are in great part responsible for the plasticity of myeloid cells both under physiological and tumoral conditions. The development of compounds that inhibit epigenetic enzymes provides novel therapeutic opportunities to intercept the crosstalk between cancer cells and host myeloid cells. Here, we summarize our current knowledge on the myeloid cell types generated in the cancer environment, the factors and epigenetic enzymes participating in these processes and propose a number of potential targets for future pharmacological use.

The immunomodulator decoy receptor 3 improves locomotor functional recovery after spinal cord injury

Background

Spinal cord injury (SCI) causes loss of neurons and axons and results in motor and sensory function impairments. SCI elicits an inflammatory response and induces the infiltration of immune cells, predominantly macrophages, to the injured site. Decoy receptor 3 (DcR3), also known as tumor necrosis factor receptor superfamily member (TNFRSF)-6B, is a pleiotropic immunomodulator capable of inducing macrophage differentiation into the M2 phenotype and enhancing angiogenesis. Because M2 macrophages are crucial for the recovery of impaired motor functions, we ask whether DcR3 is beneficial for the functional recovery of locomotion in Sprague-Dawley (SD) rats after SCI.

Methods

Contusion injury of the spinal cord was performed using a New York University impactor at the ninth thoracic vertebrae, followed by intrathecal injection of 15 μg recombinant protein comprising DcR3 (DcR3.Fc) in 5 μl of normal saline as the treatment, or 5 μl of normal saline as the control, into the injury epicenter. Functional recovery was evaluated using an open-field test weekly up to 6 weeks after injury. The cavity size and myelin sparing in the rostral-to-caudal region, including the epicenter of the injury, were then examined in SCI rats by histological staining. The expression of anti-inflammatory cytokines and the presence of M2 macrophages were determined by quantitative real-time polymerase chain reaction (qPCR) and immunohistochemistry at 7 day after SCI. Statistical analysis was performed using a two-tailed Student’s t test.

Results

Intrathecal administration of DcR3.Fc significantly improved locomotor function and reduced secondary injury with a smaller wound cavity and increased myelin sparing at the lesion site. Compared with the control group, DcR3.Fc-treated rats had increased vascularization at the injury epicenter along with higher levels of interleukin (IL)-4 and IL-10 and lower level of IL-1β on DcR3.Fc-treated rats at day 7 after SCI. Moreover, higher levels of arginase I (Arg I) and CD206 (M2 macrophage markers) and RECA-1 (endothelial marker) were observed in the epicenter on day 7 after SCI by immunofluorescence staining.

Conclusions

These results indicated that DcR3.Fc may promote the M2 macrophage infiltration and enhanced angiogenesis at the lesion site, thus preserving a greater amount of spinal cord tissues and enhancing functional recovery after SCI.

Decoy Receptor 3 (DcR3) as a Biomarker of Tumor Deterioration in Female Reproductive Cancers: A Meta-Analysis

Background

DcR3 (decoy receptor 3) has been proposed be involved in development and prognosis of female reproductive cancers, including cervical cancer, ovarian cancer, and breast cancer. The purpose of this meta-analysis was to explore the evidence for the correlation between DcR3 and the clinicopathological characteristics, as well as the overall survival time, in female reproductive cancers.

Material/Methods

Relevant studies were searched for in PubMed, Wiley Online Library, Web of Science, Science Direct, Cochrane Central Register of Controlled Trials, Google Scholar, EMBASE, Ovid, LILACS, Chinese CNKI, Chong Qing VIP, Wan Fang, and China Biology Medicine disc up to 30 September 2015. Data on the relationship between DcR3 expression and TNM stage, differentiation, lymph node metastasis, age, and overall survival time were extracted. Pooled odds ratios (ORs) and 95% CIs (confidence intervals) were estimated by forest plot.

Results

Twelve studies with 1127 patients met the inclusion criteria for this meta-analysis. Overexpression of DcR3 was significantly related to the risk of female reproductive cancers (OR=10.69, 95% CI: 6.33–18.05), TNM stage (OR=5.51, 95% CI: 2.83–10.71), differentiation (OR=4.16, 95% CI: 2.28–7.60), lymph node metastasis (OR=5.89, 95% CI: 3.16–10.9), age (OR=0.85, 95% CI: 0.51–1.44), and overall survival time (OR=1.84, 95% CI: 0.58–5.83). Subgroup analyses showed that overexpression of DcR3 in cervical, ovarian, and breast cancer all had similar relationships with these clinicopathological parameters.

Conclusions

Our meta-analysis suggests that overexpression of DcR3 may play vital roles in the tumorigenesis and deterioration of female reproductive cancers. However, the relationship between DcR3 expression and prognosis needs further investigation.

Serum decoy receptor 3 is a biomarker for disease severity in nonatopic asthma patients

BACKGROUND/PURPOSE

Decoy receptor 3 (DcR3), a soluble receptor of the tumor necrosis factor receptor superfamily, is a pleiotropic immunomodulator. The aim of this study was to investigate serum DcR3 levels in atopic and nonatopic asthma patients.

METHODS

The serum DcR3 levels of 70 adults with asthma and 20 healthy controls were determined by enzyme-linked immunosorbent assay (ELISA). The asthma patients were divided into atopic and nonatopic subgroups, based on the presence or absence of immunoglobulin E (IgE) specific to allergen. Correlations between serum DcR3 levels and blood total-eosinophil counts, forced expiratory volume in 1 second (FEV1), FEV1/forced vital capacity (FVC), and Asthma Control Test (ACT) scores were analyzed.

RESULTS

The mean serum DcR3 level was significantly higher in asthma patients than in healthy controls (266.1 ± 60.6 pg/mL vs. 63.7 ± 21.9 pg/mL, p = 0.003), but there was no significant difference between the mean serum DcR3 level of asthma patients with atopy (37 patients) and patients without atopy (33 patients; 298.7 ± 111.2 pg/mL vs. 230.6 ± 38.5 pg/mL, p = 0.064). However, the serum DcR3 level was positively correlated with the total eosinophil count (r = 0.448, p = 0.012) and inversely correlated with the percentages of predicted FEV1, FEV1/FVC, and ACT score (r = 0.409, p = 0.018; r = -0.399, p = 0.021; and r = -0.505, p = 0.003, respectively) in nonatopic asthma patients, but not in atopic patients.

CONCLUSION

High serum DcR3 levels are associated with disease severity in nonatopic asthma patients, which suggests that DcR3 is a potential biomarker that can be used to predict the severity of nonatopic asthma.

Elevated Serum Levels of the Antiapoptotic Protein Decoy-Receptor 3 Are Associated with Advanced Liver Disease

Background. Decoy-receptor 3 (DcR3) exerts antiapoptotic and immunomodulatory function and is overexpressed in neoplastic and inflammatory conditions. Serum DcR3 (sDcR3) levels during the chronic hepatitis/cirrhosis/hepatocellular carcinoma (HCC) sequence have not been explored. Objective. To assess the levels and significance of sDcR3 protein in various stages of chronic liver disease. Methods. We compared sDcR3 levels between healthy controls and patients with chronic viral hepatitis (CVH), decompensated cirrhosis (DC), and HCC. Correlations between sDcR3 levels and various patient- and disease-related factors were analyzed. Results. sDcR3 levels were significantly higher in patients with CVH than in controls (P < 0.01). sDcR3 levels were elevated in DC and HCC, being significantly higher compared not only to controls (P < 0.001 for both) but to CVH patients as well (P < 0.001 for both). In addition, DcR3 protein was detected in large quantities in the ascitic fluid of cirrhotics. In patients with CVH, sDcR3 significantly correlated to fibrosis severity, as estimated by Ishak score (P = 0.019) or by liver stiffness measured with elastography (Spearman r = 0.698, P < 0.001). In cirrhotic patients, significant positive correlations were observed between sDcR3 levels and markers of severity of hepatic impairment, including MELD score (r = 0.653, P < 0.001). Conclusions. Circulating levels of DcR3 are elevated during chronic liver disease and correlate with severity of liver damage. sDcR3 may serve as marker for liver fibrosis severity and progression to end-stage liver disease.

Usefulness of Circulating Decoy Receptor 3 in Predicting Coronary Artery Disease Severity and Future Major Adverse Cardiovascular Events in Patients With Multivessel Coronary Artery Disease

Decoy receptor 3 (DcR3), a member of the tumor necrosis factor receptor superfamily, is an antiapoptotic soluble receptor considered to play an important role in immune modulation and has pro-inflammatory functions. This study was designed to test whether circulating DcR3 levels are associated with coronary artery disease (CAD) severity and predict future major adverse cardiovascular events (MACEs) in patients with CAD. Circulating DcR3 levels and the Syntax score (SXscore) were determined in patients with multivessel CAD. The primary end point was the MACE within 12 months. In total, 152 consecutive patients with angiographically confirmed multivessel CAD who had received percutaneous coronary intervention were enrolled and were divided into 3 groups according to CAD lesion severity. Group 1 was defined as low SXscore (≤13), group 2 as intermediate SXscore (>13 and ≤22), and group 3 as high SXscore (>22). DcR3 levels were significantly higher in the high SXscore group than the other 2 groups (13,602 ± 7,256 vs 8,025 ± 7,789 vs 4,637 ± 4,403 pg/ml, p <0.001). By multivariate analysis, circulating DcR3 levels were identified as an independent predictor for high SXscore (adjusted odds ratio 1.15, 95% confidence interval 1.09 to 1.21; p <0.001). The Kaplan-Meier analysis showed that increased circulating DcR3 levels are associated with enhanced 1-year MACE in patients with multivessel CAD (log-rank p <0.001). In conclusion, increased circulating DcR3 levels are associated with CAD severity and predict future MACE in patients with multivessel CAD.

Elevated serum levels of decoy receptor 3 are associated with disease severity in patients with hemorrhagic fever with renal syndrome

Hemorrhagic fever with renal syndrome (HFRS) is an acute viral infectious disease characterized by fever, hemorrhage and renal failure. HFRS has become a serious public health problem in China. Unfortunately, the pathogenesis of HFRS has not been completely clarified. The aim of this study is to investigate the changes of decoy receptor 3 (DcR3) and to further explore its potential roles in HFRS. The levels of serum DcR3 were measured by sandwich ELISA. We found serum DcR3 levels increased significantly, which reached peak value during the oliguric phase and in the critical group. Moreover, serum DcR3 levels were closely related to the levels of pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and parameters reflecting kidney injury including BUN, creatinine (Cr) and proteinuria. This study indicates that high levels of serum DcR3 have associations with the disease stages, severity and degree of kidney damage. Meanwhile, our results suggest that DcR3 may play a dual role in HFRS pathogenesis. First, DcR3 is involved in the inflammatory cascade response resulting in capillary permeability and kidney injury in the early stage. Secondly, HTNV infection induced DcR3 expression at the convalescent phase may act as a feed-back mechanism in anti-inflammatory response. Thus, a study of DcR3 is essential for a better understanding of HFRS pathogenesis.

Human CLEC18 Gene Cluster Contains C-type Lectins with Differential Glycan-binding Specificity

The human C-type lectin 18 (clec18) gene cluster, which contains three clec18a, clec18b, and clec18c loci, is located in human chromosome 16q22. Although the amino acid sequences of CLEC18A, CLEC18B, and CLEC18C are almost identical, several amino acid residues located in the C-type lectin-like domain (CTLD) and the sperm-coating protein/Tpx-1/Ag5/PR-1/Sc7 (SCP/TAPS) domain, also known as the cysteine-rich secretory proteins/antigen 5/pathogenesis-related 1 proteins (CAP) domain, are distinct from each other. Genotyping by real-time PCR and sequencing further shows the presence of multiple alleles in clec18a/b/c loci. Flow cytometry analysis demonstrates that CLEC18 (CLEC18A, -B, and -C) are expressed abundantly in human peripheral blood cells. Moreover, CLEC18 expression is further up-regulated when monocytes differentiate into macrophages and dendritic cells. Immunofluorescence staining reveals that CLEC18 are localized in the endoplasmic reticulum, Golgi apparatus, and endosome. Interestingly, CLEC18 are also detectable in human sera and culture supernatants from primary cells and 293T cells overexpressing CLEC18. Moreover, CLEC18 bind polysaccharide in Ca(2+)-independent manner, and amino acid residues Ser/Arg(339) and Asp/Asn(421) in CTLD domain contribute to their differential binding abilities to polysaccharides isolated from Ganoderma lucidum (GLPS-F3). The Ser(339) (CLEC18A) → Arg(339) (CLEC18A-1) mutation completely abolishes CLEC18A-1 binding to GLPS-F3, and a sugar competition assay shows that CLEC18 preferentially binds to fucoidan, β-glucans, and galactans. Because proteins with the SCP/TAPS/CAP domain are able to bind sterol and acidic glycolipid, and are involved in sterol transport and β-amyloid aggregation, it would be interesting to investigate whether CLEC18 modulates host immunity via binding to glycolipids, and are also involved in glycolipid transportation and protein aggregation in the future.

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.

Absolute quantification of DcR3 and GDF15 from human serum by LC-ESI MS

Biomarkers are widely used in clinical diagnosis, prognosis and therapy monitoring. Here, we developed a protocol for the efficient and selective enrichment of small and low concentrated biomarkers from human serum, involving a 95% effective depletion of high-abundant serum proteins by partial denaturation and enrichment of low-abundant biomarkers by size exclusion chromatography. The recovery of low-abundance biomarkers was above 97%. Using this protocol, we quantified the tumour markers DcR3 and growth/differentiation factor (GDF)15 from 100 μl human serum by isotope dilution mass spectrometry, using ¹⁵N metabolically labelled and concatamerized fingerprint peptides for the both proteins. Analysis of three different fingerprint peptides for each protein by liquid chromatography electrospray ionization mass spectrometry resulted in comparable concentrations in three healthy human serum samples (DcR3: 27.23 ± 2.49 fmol/ml; GDF15: 98.11 ± 0.49 fmol/ml). In contrast, serum levels were significantly elevated in tumour patients for DcR3 (116.94 ± 57.37 fmol/ml) and GDF15 (164.44 ± 79.31 fmol/ml). Obtained data were in good agreement with ELISA and qPCR measurements, as well as with literature data. In summary, our protocol allows the reliable quantification of biomarkers, shows a higher resolution at low biomarker concentrations than antibody-based strategies, and offers the possibility of multiplexing. Our proof-of-principle studies in patient sera encourage the future analysis of the prognostic value of DcR3 and GDF15 for colon cancer patients in larger patient cohorts.

Systemic and local expression levels of TNF-like ligand 1A and its decoy receptor 3 are increased in primary biliary cirrhosis

BACKGROUND & AIMS

Through a genome-wide association study of a Japanese population, we recently identified TNFSF15, a gene encoding TNF-like ligand 1A (TL1A), as a susceptibility gene for primary biliary cirrhosis (PBC). We investigated the clinical significance of TL1A and one of its receptors, decoy receptor 3 (DcR3), in PBC.

METHODS

We analysed the systemic and local expression of TL1A and DcR3 in 110 PBC patients and 46 healthy controls using enzyme-linked immunosorbent assay, quantitative polymerase chain reaction and immunohistochemical staining.

RESULTS

Serum TL1A levels were significantly increased in PBC patients at both early and late stages as compared with healthy controls, and its levels were significantly decreased in early-stage PBC patients after ursodeoxycholic acid (UDCA) treatment. TL1A was immunohistochemically localized to biliary epithelial cells, Kupffer cells, blood vessels and infiltrating mononuclear cells in the PBC liver. In addition, TL1A messenger RNA expression was increased in the PBC liver as compared with the non-diseased liver. Serum DcR3 levels were also significantly increased in PBC patients, and were significantly decreased after UDCA treatment in early-stage PBC patients.

CONCLUSIONS

These results indicate that TL1A and DcR3 may play an important role in the pathogenesis of PBC.

Decoy receptor 3: Its role as biomarker for chronic inflammatory diseases

Members of the tumor-necrosis factor-α (TNF-α) and TNF-α receptor (TNFR) superfamilies of proteins (TNFSF and TNFRSF, respectively) play important roles in the function of the immune system. Decoy receptor 3 (DcR3, TNFRSF6b) is a decoy receptor that binds to three TNFSF ligands, FasL, LIGHT and TL1A. Association to these ligands competes with the corresponding functional receptors and blocks downstream signaling, leading to immunomodulatory effects, including the prevention of apoptosis. DcR3 lacks a transmembrane region and exists only as a secreted protein, which is detectable in biological fluids. Recent studies have shown that DcR3 is upregulated and may be pathogenetically implicated in several and diverse chronic inflammatory diseases. The strongest associations have been described for rheumatological diseases, mainly systemic lupus erythematosus and rheumatoid arthritis, inflammatory bowel disease, and serious infectious conditions, including systemic inflammatory response syndrome. In the majority of these conditions, DcR3 mRNA and protein expression is elevated both at the target tissues as well as in the systemic circulation. DcR3 concentration in the serum is untraceable in the majority of healthy individuals but can be detected in patients with various inflammatory diseases. In most such cases, soluble DcR3 correlates with disease severity, as patients with severe forms of disease have significantly higher levels than patients with milder or no activity. In addition, effective anti-inflammatory treatment leads to the disappearance of soluble DcR3 from the circulation. Taken together, current evidence suggests that serum DcR3 may become a useful biomarker for chronic inflammatory disorders, as it is upregulated in response to inflammatory stimuli, and may serve both as a prognostic marker for disease severity and as a surrogate indicator of response to treatment.

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.

HLA-dependent tumour development: a role for tumour associate macrophages?

HLA abnormalities on tumour cells for immune escape have been widely described. In addition, cellular components of the tumour microenvironment, in particular myeloid derived suppressor cells (MDSC) and alternatively activated M2 tumour-associated macrophages (TAMs), are involved in tumour promotion, progression, angiogenesis and suppression of anti-tumour immunity. However, the role of HLA in these activities is poorly understood. This review details MHC class I characteristics and describes MHC class I receptors functions. This analysis established the basis for a reflection about the crosstalk among the tumour cells, the TAMs and the cells mediating an immune response.The tumour cells and TAMs exploit MHC class I molecules to modulate the surrounding immune cells. HLA A, B, C and G molecules down-regulate the macrophage myeloid activation through the interaction with the inhibitory LILRB receptors. HLA A, B, C are able to engage inhibitory KIR receptors negatively regulating the Natural Killer and cytotoxic T lymphocytes function while HLA-G induces the secretion of pro-angiogenic cytokines and chemokine thanks to an activator KIR receptor expressed by a minority of peripheral NK cells. The open conformer of classical MHC-I is able to interact with LILRA receptors described as being associated to the Th2-type cytokine response, triggering a condition for the M2 like TAM polarization. In addition, HLA-E antigens on the surface of the TAMs bind the inhibitory receptor CD94/NKG2A expressed by a subset of NK cells and activated cytotoxic T lymphocytes protecting from the cytolysis.Furthermore MHC class II expression by antigen presenting cells is finely regulated by factors provided with immunological capacities. Tumour-associated macrophages show an epigenetically controlled down-regulation of the MHC class II expression induced by the decoy receptor DcR3, a member of the TNFR, which further enhances the M2-like polarization. BAT3, a positive regulator of MHC class II expression in normal macrophages, seems to be secreted by TAMs, consequently lacking its intracellular function, it looks like acting as an immunosuppressive factor.In conclusion HLA could cover a considerable role in tumour-development orchestrated by tumour-associated macrophages.

Toll-like receptor-mediated IRE1α activation as a therapeutic target for inflammatory arthritis

In rheumatoid arthritis (RA), macrophage is one of the major sources of inflammatory mediators. Macrophages produce inflammatory cytokines through toll-like receptor (TLR)-mediated signalling during RA. Herein, we studied macrophages from the synovial fluid of RA patients and observed a significant increase in activation of inositol-requiring enzyme 1α (IRE1α), a primary unfolded protein response (UPR) transducer. Myeloid-specific deletion of the IRE1α gene protected mice from inflammatory arthritis, and treatment with the IRE1α-specific inhibitor 4U8C attenuated joint inflammation in mice. IRE1α was required for optimal production of pro-inflammatory cytokines as evidenced by impaired TLR-induced cytokine production in IRE1α-null macrophages and neutrophils. Further analyses demonstrated that tumour necrosis factor (TNF) receptor-associated factor 6 (TRAF6) plays a key role in TLR-mediated IRE1α activation by catalysing IRE1α ubiquitination and blocking the recruitment of protein phosphatase 2A (PP2A), a phosphatase that inhibits IRE1α phosphorylation. In summary, we discovered a novel regulatory axis through TRAF6-mediated IRE1α ubiquitination in regulating TLR-induced IRE1α activation in pro-inflammatory cytokine production, and demonstrated that IRE1α is a potential therapeutic target for inflammatory arthritis.

Expression of decoy receptor 3 in diffuse sclerosing variant of papillary thyroid carcinoma: correlation with M2 macrophage differentiation and lymphatic invasion

BACKGROUND

The diffuse sclerosing variant of papillary thyroid carcinoma (DSV-PTC) is a unique variant of PTC that is characterized by extensive lymphovascular invasion of tumor cells in a background of lymphocytic thyroiditis. The lymphatic emboli contain tumor cells as well as macrophages, but the recruitment of these macrophages is not well understood. The aim of this study was to determine the relationship between the expression of Decoy receptor 3 (DcR3), the recruitment of tumor-associated macrophages (TAMs), and lymphatic invasion in DSV-PTC.

METHODS

We retrospectively examined 14 cases of DSV-PTC using immunohistochemistry studies. The density of TAMs, lymphatic vessel density, lymphatic invasion, tumor emboli area, and DcR3 expression were assessed. Statistical analyses were performed using Fisher's exact test, unpaired t-test, and linear regression.

RESULTS

The lymphatic tumor emboli contained a relatively higher density of TAMs than stroma and classical PTC (CPTC) areas. In addition, the number of lymphatic invasions and the size of the tumor emboli area were positively correlated with the number of M2 TAMs. A higher density of M2 TAMs was associated with older patients and larger tumor size. Moreover, DcR3 was expressed only in lymphatic tumor cells and squamous metaplastic tumor cells, but not in macrophages and CPTC. In addition, the preferential expression of DcR3 in tumors was associated with higher levels of M2 TAMs and lymphatic invasion.

CONCLUSION

Despite the fact that the exact relationship between DcR3, M2 macrophages, and lymphatic invasion in DSV-PTC remains to be elucidated, our findings suggest that DcR3 expression in DSV-PTC tumor cells may promote the polarized macrophage differentiation toward the M2 phenotype. This phenomenon may further promote lymphatic invasion of DSV-PTC tumor cells.

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.

CLEC5A is critical for dengue virus–induced inflammasome activation in human macrophages

Persistent high fever is one of the most typical clinical symptoms in dengue virus (DV)–infected patients. However, the source of endogenous pyrogen (eg, IL-1β) and the signaling cascade leading to the activation of inflammasome and caspase-1, which are essential for IL-1β and IL-18 secretion, during dengue infection have not been elucidated yet. Macrophages can be polarized into distinct phenotypes under the influence of GM-CSF or M-CSF, denoted as GM-Mφ and M-Mφ, respectively. We found that DV induced high levels of IL-1β and IL-18 from GM-Mφ (inflammatory macrophage) and caused cell death (pyroptosis), whereas M-Mφ (resting macrophage) did not produce IL-1β and IL-18 on DV infection even with lipopolysaccharide priming. This observation demonstrates the distinct responses of GM-Mφ and M-Mφ to DV infection. Moreover, up-regulation of pro-IL-1β, pro-IL-18, and NLRP3 associated with caspase-1 activation was observed in DV-infected GM-Mφ, whereas blockade of CLEC5A/MDL-1, a C-type lectin critical for dengue hemorrhagic fever and Japanese encephalitis virus infection, inhibits NLRP3 inflammasome activation and pyrotopsis in GM-Mφ. Thus, DV can activate NLRP3 inflammasome via CLEC5A, and GM-Mφ plays a more important role than M-Mφ in the pathogenesis of DV infection.

Differential expression of distinct surface markers in early endothelial progenitor cells and monocyte-derived macrophages

Bone marrow-derived endothelial progenitor cells (EPCs) play a fundamental role in postnatal angiogenesis. Currently, EPCs are defined as early and late EPCs based on their biological properties and their time of appearance during in vitro culture. Reports have shown that early EPCs share common properties and surface markers with adherent blood cells, especially CD14+ monocytes. Distinguishing early EPCs from circulating monocytes or monocyte-derived macrophages (MDMs) is therefore crucial to obtaining pure endothelial populations before they can be applied as part of clinical therapies. We compared the gene expression profiles of early EPCs, blood cells (including peripheral blood mononuclear cells, monocytes, and MDMs), and various endothelial lineage cells (including mature endothelial cells, late EPCs, and CD133+ stem cells). We found that early EPCs expressed an mRNA profile that showed the greatest similarity to MDMs than any other cell type tested. The functional significance of this molecular profiling data was explored by Gene Ontology database search. Novel plasma membrane genes that might potentially be novel isolation biomarkers were also pinpointed. Specifically, expression of CLEC5A was high in MDMs, whereas early EPCs expressed abundant SIGLEC8 and KCNE1. These detailed mRNA expression profiles and the identified functional modules will help to develop novel cell isolation approaches that will allow EPCs to be purified; these can then be used to target cardiovascular disease, tumor angiogenesis, and various ischemia-related diseases.

Specific elevation of DcR3 in sera of sepsis patients and its potential role as a clinically important biomarker of sepsis

Because of its potentially important role in the pathogenesis of sepsis, the expression of soluble decoy receptor 3 (DcR3) was investigated in sera of sepsis patients. The serum levels of DcR3 and its tumor necrosis factor-like ligand TL1A and homologous decoy receptor OPG were quantified by ELISA. The values of DcR3 to diagnose sepsis were analyzed by receiver-operating characteristic (ROC) curves. The results showed that DcR3 was significantly elevated in sepsis compared to systemic inflammatory response syndrome (SIRS), a condition similar to sepsis but resulting from noninfectious insults. DcR3 showed superior area under the ROC curve (AUC, 0.958) compared to poor AUCs of TL1A and OPG. At a cut-off of 3.24 ng/mL, DcR3 predicted sepsis from SIRS with 96% sensitivity and 82.6% specificity. DcR3 also predicted sepsis from cancer and inflammatory bowel disease with equally excellent values. Therefore, DcR3 serum level has the potential to serve as a reliable biomarker of sepsis.

Decoy receptor 3, a novel inflammatory marker, and mortality in hemodialysis patients

BACKGROUND AND OBJECTIVES

Inflammation is closely associated with cardiovascular disease, the leading cause of mortality in patients with CKD. Serum decoy receptor 3 (DcR3) is a member of the TNF receptor superfamily. CKD patients have higher levels of DcR3 than the general population, but whether DcR3 predicts mortality in CKD patients on hemodialysis has not been explored.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

DcR3 levels were measured in 316 prevalent hemodialysis patients who were followed up from November 1, 2004, to June 30, 2009, for cardiovascular and all-cause mortality.

RESULTS

The baseline DcR3 concentration showed a strong positive correlation with inflammatory markers including high-sensitivity C-reactive protein, IL-6, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1). During a follow-up period of 54 months, 90 patients died (34 cardiovascular deaths). Kaplan-Meier survival analysis showed higher cardiovascular and all-cause mortality in patients with higher DcR3 levels. The hazard ratios (95% confidence intervals) of the highest versus lowest tertiles of DcR3 were 2.8 (1.1-7.3; P for trend=0.04) for cardiovascular mortality and 2.1 (1.1-3.7; P for trend=0.02) for all-cause mortality, respectively. Based on the minimal increase in the area under the receiver operating characteristic curve from 0.79 to 0.80, the addition of DcR3 to established risk factors including VCAM-1, albumin, and IL-6 does not improve the prediction of mortality.

CONCLUSIONS

Higher DcR3 levels strongly correlate with inflammation and independently predict cardiovascular and all-cause mortality in CKD patients on hemodialysis.

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 enhances tumor progression via induction of tumor-associated macrophages

Tumor-associated macrophages (TAMs) are the major component of tumor-infiltrating leukocytes. TAMs are heterogeneous, with distinct phenotypes influenced by the microenvironment surrounding tumor tissues. Decoy receptor 3 (DcR3), a member of the TNFR superfamily, is overexpressed in tumor cells and is capable of modulating host immunity as either a neutralizing decoy receptor or an effector molecule. Upregulation of DcR3 has been observed to correlate with a poor prognosis in various cancers. However, the mechanisms underlying the DcR3-mediated tumor-promoting effect remain unclear. We previously demonstrated that DcR3 modulates macrophage activation toward an M2-like phenotype in vitro and that DcR3 downregulates MHC class II expression in TAMs via epigenetic control. To investigate whether DcR3 promotes tumor growth, CT26-DcR3 stable transfectants were established. Compared with the vector control clone, DcR3-transfectants grew faster and resulted in TAM infiltration. We further generated CD68 promoter-driven DcR3 transgenic (Tg) mice to investigate tumor growth in vivo. Compared with wild-type mice, macrophages isolated from DcR3-Tg mice displayed higher levels of IL-10, IL-1ra, Ym1, and arginase activity, whereas the expression of IL-12, TNF-α, IL-6, NO, and MHC class II was downregulated. Significantly enhanced tumor growth and spreading were observed in DcR3-Tg mice, and the enhanced tumor growth was abolished by arginase inhibitor N-ω-hydroxy-l-norarginine and histone deacetylase inhibitor sodium valproate. These results indicated that induction of TAMs is an important mechanism for DcR3-mediated tumor progression. Our findings also suggest that targeting DcR3 might help in the development of novel treatment strategies for tumors with high DcR3 expression.

Decoy receptor 3 inhibits renal mononuclear leukocyte infiltration and apoptosis and prevents progression of IgA nephropathy in mice

The progression of IgA nephropathy (IgAN), the most frequent type of primary glomerulonephritis, is associated with high levels of mononuclear leukocyte infiltration into the kidney. These cells consist mainly of T cells and macrophages. Our previous study showed that a decoy receptor 3 (DCR3) gene therapy can prevent the development of a mouse autoimmune glomerulonephritis model by its potent immune modulating effects (Ka SM, Sytwu HK, Chang DM, Hsieh SL, Tsai PY, Chen A. J Am Soc Nephrol 18: 2473-2485, 2007). Here, we tested the hypothesis that DCR3 might prevent the progression of IgAN, an immune complex-mediated primary glomerulonephritis, by inhibiting T cell activation, renal T cell/macrophage infiltration, and protecting the kidney from apoptosis. We used a progressive IgAN (Prg-IgAN) model in B cell-deficient mice, because the mice are characterized by a dramatic proliferation of activated T cells systemically and progressive NF-κB activation in the kidney. We treated the animals with short-term gene therapy with DCR3 plasmids by hydrodynamics-based gene delivery. When the mice were euthanized on day 21, we found that, compared with empty vector-treated (disease control) Prg-IgAN mice, DCR3 gene therapy resulted in 1) systemic inhibition of T cell activation and proliferation; 2) lower serum levels of proinflammatory cytokines; 3) improved proteinuria, renal function, and renal pathology (inhibiting the development of marked glomerular proliferation, crescent formation, glomerulosclerosis, and interstitial inflammation); 5) suppression of T cell and macrophage infiltration into the periglomerular interstitium of the kidney; and 5) a reduction in apoptotic figures in the kidney. On the basis of these findings, DCR3 might be useful therapeutically in preventing the progression of IgAN.

Genome-wide association study identifies two new susceptibility loci for atopic dermatitis in the Chinese Han population

Atopic dermatitis is a chronic, relapsing form of inflammatory skin disorder that is affected by genetic and environmental factors. We performed a genome-wide association study of atopic dermatitis in a Chinese Han population using 1,012 affected individuals (cases) and 1,362 controls followed by a replication study in an additional 3,624 cases and 12,197 controls of Chinese Han ethnicity, as well as 1,806 cases and 3,256 controls from Germany. We identified previously undescribed susceptibility loci at 5q22.1 (TMEM232 and SLC25A46, rs7701890, P(combined) = 3.15 × 10(-9), odds ratio (OR) = 1.24) and 20q13.33 (TNFRSF6B and ZGPAT, rs6010620, P(combined) = 3.0 × 10(-8), OR = 1.17) and replicated another previously reported locus at 1q21.3 (FLG, rs3126085, P(combined) = 5.90 × 10(-12), OR = 0.82) in the Chinese sample. The 20q13.33 locus also showed evidence for association in the German sample (rs6010620, P = 2.87 × 10(-5), OR = 1.25). Our study identifies new genetic susceptibility factors and suggests previously unidentified biological pathways in atopic dermatitis.

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.

Aberrant expression and function of death receptor-3 and death decoy receptor-3 in human cancer

Death receptor-3 (DR3) and death decoy receptor-3 (DcR3) are both members of the tumour necrosis factor receptor (TNFR) superfamily. The TNFR superfamily contains eight death domain-containing receptors, including TNFR1 (also called DR1), Fas (also called DR2), DR3, DR4, DR5, DR6, NGFR and EDAR. Upon the binding of these receptors with their corresponding ligands, the death domain recruits various proteins that mediate both the death and proliferation of cells. Receptor function is negatively regulated by decoy receptors (DcR1, DcR2, DcR3 and OPG). DR3/DcR3 are a pair of positive and negative players with which vascular endothelial growth inhibitor (VEGI) interacts. VEGI has been suggested to be a potential tumour suppressor. The inhibitory effects of VEGI on cancer are manifested in three main areas: a direct effect on cancer cells, an anti-angiogenic effect on endothelial cells, and the stimulation of dendritic cell maturation. A recent study indicated that DR3 may be a new receptor for E-selectin, which has been reported to be associated with cancer metastasis. DcR3 is a soluble receptor, highly expressed in various tumours, which lacks an apparent transmembrane segment, prevents cytokine response through ligand binding and neutralization, and is an inhibitor of apoptosis. DcR3 serves as a decoy receptor for FasL, LIGHT and VEGI. The cytokine LIGHT activates various anti-tumour functions and is expected to be a promising candidate for cancer therapy. Certain tumours may escape FasL-dependent immune-cytotoxic attack by expressing DcR3, which blocks FasL function. DR3/DcR3 play profound roles in regulating cell death and proliferation in cancer. The present review briefly discusses DR3/DcR3 and attempts to elucidate the role of these negative and positive players in cancer.

Emodin suppresses lipopolysaccharide-induced pro-inflammatory responses and NF-κB activation by disrupting lipid rafts in CD14-negative endothelial cells

BACKGROUND AND PURPOSE

Emodin [1,3,8-trihydroxy-6-methylanthraquinone] has been reported to exhibit vascular anti-inflammatory properties. However, the corresponding mechanisms are not well understood. The present study was designed to explore the molecular target(s) of emodin in modifying lipopolysaccharide (LPS)-associated signal transduction pathways in endothelial cells.

EXPERIMENTAL APPROACH

Cultured primary human umbilical vein endothelial cells (HUVECs; passages 3-5) were pre-incubated with emodin (1-50 µg·mL(-1) ). LPS-induced expression of pro-inflammatory cytokines [interleukin (IL)-1β, IL-6] and chemokines (IL-8; CCL2/MCP-1) were determined by reverse transcription-PCR and elisa. Nuclear factor-κB (NF-κB) activation, inhibitor of κB (IκB)α degradation and Toll-like receptor-4 (TLR-4) were detected by immunocytochemistry and Western blotting. Cholesterol depletion [by methyl β-cyclodextrin (MBCD), a specific cholesterol binding agent] and cholesterol replenishment were further used to investigate the roles of lipid rafts in activation of HUVECs.

KEY RESULTS

Emodin inhibited, concentration-dependently, the expression of LPS-induced pro-inflammatory cytokines (IL-1β, IL-6) and chemokines (IL-8, CCL2) and, in parallel, inhibited NF-κB activation and IκBα degradation in HUVECs. However, emodin did not inhibit the NF-κB activation and IκBα degradation induced by IL-1β. The cholesterol binding agent, MBCD, inhibited LPS-induced NF-κB activation in passaged HUVECs [which also lack the LPS receptor, membrane CD14 (mCD14)], showing that lipid rafts played a key role in LPS signalling in mCD14-negative HUVECs. Moreover, emodin disrupted the formation of lipid rafts in cell membranes by depleting cholesterol.

CONCLUSIONS AND IMPLICATIONS

Lipid rafts were crucial in facilitating inflammatory responses of mCD14-negative HUVECs to LPS. Emodin disrupted lipid rafts through depleting cholesterol and, consequently, inhibited inflammatory responses in endothelial cells.

CD4+ CD25+ regulatory T cells suppressed the indirect xenogeneic immune response mediated by porcine epithelial cell pulsed dendritic cells

BACKGROUND

CD4(+) CD25(+) regulatory T cells have been reported to suppress T cell-mediated xenogeneic immune responses. Although the direct T cell response to xenogeneic cells is important, the indirect xenogeneic immune response mediated by dendritic cells (DCs) is also likely involved in rejection. We have generated an in vitro indirect immune reaction model and evaluated the effect of CD4(+) CD25(+) regulatory T cells on this system.

METHODS

Human DCs were generated from peripheral blood and cultured with X-ray-irradiated porcine kidney epithelial cells. Porcine cell-pulsed DCs were mixed with autologous CD4(+) T cells, CD4(+) CD25(-) T cells and/or CD4(+) CD25(+) T cells. After 7 days of culture, T cell proliferation was measured.

RESULTS

The co-culture of human DCs and X-ray-irradiated porcine epithelial cells resulted in observable DC phagocytic activity within 2 days. These porcine cell-pulsed DCs stimulated CD4(+) T cell proliferation much more potently than unpulsed DCs or porcine cells. This proliferation was blocked by CTLA4-Ig or an anti-HLA-DR antibody. CD4(+) CD25(+) regulatory T cells also suppressed CD4(+) CD25(-) T cell proliferation in response to porcine cell-pulsed DCs.

CONCLUSIONS

An in vitro model of the indirect xenogeneic immune response was established. Porcine cell-pulsed DCs stimulated CD4(+) T cells, and CD4(+) CD25(+) regulatory T cells suppressed this response.