Over-expression of the decoy receptor 3 (DcR3) gene in peripheral blood mononuclear cells (PBMC) derived from silicosis patients

Genome-wide mRNA profiling identifies the NRF2-regulated lymphocyte oxidative stress status in patients with silicosis

BACKGROUND

The immunomodulatory abnormalities of silicosis are related to the lymphocyte oxidative stress state. The potential effect of antioxidant therapy on silicosis may depend on the variation in nuclear factor erythroid 2-related factor 2 (NRF2)-regulated antioxidant genes in peripheral blood mononuclear cells (PBMCs). As NRF2 is a redox-sensitive transcription factor, its possible roles and underlying mechanism in the treatment of silicosis need to be clarified.

METHODS

Ninety-two male patients with silicosis and 87 male healthy volunteers were randomly selected. PBMCs were isolated from fresh blood from patients with silicosis and healthy controls. The lymphocyte oxidative stress state was investigated by evaluating NRF2 expression and NRF2-dependent antioxidative genes in PBMCs from patients with silicosis. Key differentially expressed genes (DEGs) and signaling pathways were identified utilizing RNA sequencing (RNA-Seq) and bioinformatics technology. Gene set enrichment analysis was used to identify the differences in NRF2 signaling networks between patients with silicosis and healthy controls.

RESULTS

The number of monocytes was significantly higher in patients with silicosis than that of healthy controls. Furthermore, RNA-Seq findings were confirmed using quantitative polymerase chain reaction and revealed that NRF2-regulated DEGs were associated with glutathione metabolism, transforming growth factor-β, and the extracellular matrix receptor interaction signaling pathway in PBMCs from patients with silicosis. The top 10 hub genes were identified by PPI analysis: SMAD2, MAPK3, THBS1, SMAD3, ITGB3, integrin alpha-V (ITGAV), von Willebrand factor (VWF), BMP4, CD44, and SMAD7.

CONCLUSIONS

These findings suggest that NRF2 signaling regulates the lymphocyte oxidative stress state and may contribute to fibrogenic responses in human PBMCs. Therefore, NRF2 might serve as a novel preventive and therapeutic candidate for silicosis.

T Cell Dysregulation in Non-silicotic Silica Exposed Workers: A Step Toward Immune Tolerance Breakdown

Background: Chronic silica exposure can lead to silicosis, complicated or not by autoimmune diseases (AID). The pathophysiology of silica-induced AID remains not fully understood, especially immune mechanisms that may develop in patients without yet established silicosis. We conducted a prospective clinical study to analyze the impact of crystalline silica (CS) on T cell phenotype and regulatory T cells (Tregs) frequency, as well as on auto-antibodies development in non-silicotic workers exposed to CS.

Methods: Workers with moderate to high exposure level to CS and aged between 30 and 60 years-old were considered for inclusion. Peripheral blood mononuclear cells were analyzed by flow cytometry. Auto-antibodies were screened in serum by immunofluorescence. Blood from 42 and 45 healthy subjects (HC) was used as control for T cell phenotype and serum analyses, respectively.

Results: Among the 63 included workers exposed to CS, 55 had full data available and were analyzed. Ten were exposed to CS for <5 years, 18 for 5–10 years and 27 for more than 10 years. The frequency of Tregs (CD4⁺CD25⁺CD127⁻FoxP3⁺) was significantly lower in CS exposed workers as compared to HC. We found an increased expression of the activation marker HLA-DR on T cells (CD3⁺, CD4⁺, and CD8⁺) of CS exposed workers as compared to HC. Tregs to activated T cells ratio was also lower in exposed subjects. In the latter, HLA-DR expression level and Tregs frequency were significantly associated with CS exposure duration. Serum autoantibody detection was significantly higher in CS exposed workers as compared to HC. Especially, among workers exposed more than 10 years, antinuclear antibodies and ANCA were detected in 44 and 22% among them, as compared to 5 and 2.5% in HC, respectively.

Conclusion: This work shows that CS exposure is associated with a decrease of Tregs frequency, an increase of T cell activation status, and a tolerance breakdown against auto-antigens. These results show that alterations of the T cell compartment can be detected early over the course of CS exposure, preceding silicosis development or AID onset.

An insight into the role of the death receptor CD95 throughout pregnancy: Guardian, facilitator, or foe

The prototype death receptor CD95 (Fas) and its ligand, CD95L (FasL), have been thoroughly studied due to their role in immune homeostasis and elimination of infected and transformed cells. The fact that CD95 is present in female reproductive cells and modulated during embryogenesis and pregnancy has raised interest in its role in immune tolerance to the fetoplacental unit. CD95 has been shown to be critical for proper embryonic formation and survival. Moreover, altered expression of CD95 or its ligand causes autoimmunity and has also been directly involved in recurrent pregnancy losses and pregnancy disorders. The objective of this review is to summarize studies that evaluate the mechanisms involved in the activation of CD95 to provide an updated global view of its effect on the regulation of the maternal immune system. Modulation of the CD95 system components may be the immune basis of several common pregnancy disorders.

Increased circulating levels of tumor necrosis factor-like cytokine 1A and decoy receptor 3 correlate with SYNTAX score in patients undergoing coronary surgery

Objective

Chronic inflammation of the arteries is a critical mechanism responsible for coronary atherosclerosis. We aimed to determine if tumor necrosis factor (TNF)-like cytokine 1A (TL1A) and decoy receptor 3 (DcR3) were involved in promoting atherosclerosis.

Methods

We compared plasma levels of TL1A and DcR3 in patients with coronary artery disease (CAD) undergoing coronary artery bypass grafting (n=40) and patients without CAD group (n=37, normal coronary artery angiogram) by enzyme-linked immunosorbent assay. We also analyzed the correlation between CAD and SYNTAX scores.

Results

Plasma levels of TL1A and DcR3 were significantly higher in the CAD compared with the no-CAD group. Multivariate analysis showed that TL1A and DcR3 were significantly correlated with the presence of CAD, and receiver operating characteristic curve analysis indicated that both TL1A and DcR3 showed high sensitivity and specificity for diagnosing CAD. Furthermore, TL1A was positively and significantly correlated with SYNTAX score in CAD patients.

Conclusions

CAD patients requiring coronary artery bypass grafting have high circulating levels of both TL1A and DcR3, which may thus be useful biomarkers for diagnosing severe CAD. Furthermore, plasma levels of TL1A correlate with SYNTAX score, supporting its potential use as an indicator of the severity of CAD.

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.

Clinical evaluation of CENP-B and Scl-70 autoantibodies in silicosis patients

Silicosis patients (SIL) suffer from respiratory disorders and dysregulation of autoimmunity. Frequent complications such as rheumatoid arthritis, systemic sclerosis (SSc) and vasculitis are known in SIL. Furthermore, we reported previously that some SIL exhibited better respiratory conditions in association with a worse immunological status. In this study, the clinical roles of anti-CENP-B and Scl-70 autoantibodies in SIL were analyzed. The titer index (Log10) of anti-CENP-B autoantibody in SIL was higher than that of healthy volunteers (HV), and that of SSc was higher than those of HV and SIL. This titer index was positively correlated with an assumed immune status of 1 for HV, 2 for SIL, and 3 for SSc. Moreover, although factor analysis revealed that the titer index of the anti-CENP-B autoantibody formed the same factor with the anti-Scl-70 autoantibody, IgG value and age in SIL cases, another extracted factor indicated that the IgA value and anti-Scl-70 antibody were positively related, but anti-CENP-B showed an opposite pattern in the results of the factor analysis. These findings indicated that the titer index of anti-CENP-B autoantibody may be a biomarker for dysregulation in SIL cases. Future clinical follow-up of SIL may therefore require both respiratory and immunological assessment.

Alterations of Fas and Fas-Related Molecules in Patients with Silicosis

Persons with silicosis have not only respiratory disorders but also autoimmune diseases. To clarify the mechanisms involved in the dysregulation of autoimmunity found in patients with silicosis, we have been focusing on Fas and Fas-related molecules in the Fas-mediated apoptotic pathway, because Fas is one of the most important molecules regulating autoimmunity involving T cells. Our findings showed that patients with silicosis exhibited elevated serum soluble Fas levels, an increased relative expression of the soluble fas and dcr3 genes in peripheral blood mononuclear cells, high levels of other variant messages of the fas transcript, relatively decreased expression of genes encoding several physiological inhibitors (such as survivin and toso), and dominancy of lower-membrane Fas expressers in lymphocytes, which transcribe soluble fas dominantly, compared with soluble fas transcription in healthy donors. These findings are consistent with known features regarding immunological factors, such as serum immunogulobulin G levels and the titer of anti-nuclear autoantibodies in silicosis. In addition, anti-caspase 8 autoantibody and anti-Fas autoantibody were detected in serum specimens from patients with silicosis, and a functional assay showed that anti-Fas antibody stimulated Fas-mediated apoptosis. We hypothesize that there are two subpopulations of silicosis lymphocytes. One is a long-term surviving fraction that includes self-recognizing clones showing lower levels of membrane Fas and inhibition of Fas/Fas ligand binding in extracellular spaces. The other subpopulation exhibits apoptosis caused by silica and silicates, is recruited from bone marrow, shows higher levels of membrane Fas, and is sensitive to anti-Fas autoantibody. Further investigation should be performed to confirm the effects of silica and silicates on the human immune system.

Environmental factors and human health: fibrous and particulate substance-induced immunological disorders and construction of a health-promoting living environment

Among the various scientific fields covered in the area of hygiene such as environmental medicine, epidemiology, public health and preventive medicine, we are investigating the immunological effects of fibrous and particulate substances in the environment and work surroundings, such as asbestos fibers and silica particles. In addition to these studies, we have attempted to construct health-promoting living conditions. Thus, in this review we will summarize our investigations regarding the (1) immunological effects of asbestos fibers, (2) immunological effects of silica particles, and (3) construction of a health-promoting living environment. This review article summarizes the 2014 Japanese Society for Hygiene (JSH) Award Lecture of the 85th Annual Meeting of the JSH entitled "Environmental health effects: immunological effects of fibrous and particulate matter and establishment of health-promoting environments" presented by the first author of this manuscript, Prof. Otsuki, Department of Hygiene, Kawasaki Medical School, Kurashiki, Japan, the recipient of the 2014 JSH award. The results of our experiments can be summarized as follows: (1) asbestos fibers reduce anti-tumor immunity, (2) silica particles chronically activate responder and regulatory T cells causing an unbalance of these two populations of T helper cells, which may contribute to the development of autoimmune disorders frequently complicating silicosis, and (3) living conditions to enhance natural killer cell activity were developed, which may promote the prevention of cancers and diminish symptoms of virus infections.

Predictive value of decoy receptor 3 in postoperative nosocomial bacterial meningitis

Nosocomial bacterial meningitis requires timely treatment, but what is difficult is the prompt and accurate diagnosis of this disease. The aim of this study was to assess the potential role of decoy receptor 3 (DcR3) levels in the differentiation of bacterial meningitis from non-bacterial meningitis. A total of 123 patients were recruited in this study, among them 80 patients being with bacterial meningitis and 43 patients with non-bacterial meningitis. Bacterial meningitis was confirmed by bacterial culture of cerebrospinal fluid (CSF) culture and enzyme-linked immunosorbent assay (ELISA) was used to detect the level of DcR3 in CSF. CSF levels of DcR3 were statistically significant between patients with bacterial meningitis and those with non-bacterial meningitis (p < 0.001). A total of 48.75% of patients with bacterial meningitis received antibiotic >24 h before CSF sampling, which was much higher than that of non-bacterial meningitis. CSF leucocyte count yielded the highest diagnostic value, with an area under the receiver operating characteristic curve (ROC) of 0.928, followed by DcR3. At a critical value of 0.201 ng/mL for DcR3, the sensitivity and specificity were 78.75% and 81.40% respectively. DcR3 in CSF may be a valuable predictor for differentiating patients with bacterial meningitis from those with non-bacterial meningitis. Further studies are needed for the validation of this study.

Silica exposure and altered regulation of autoimmunity

Silica particles and asbestos fibers, which are known as typical causatives of pneumoconiosis, induce lung fibrosis. Moreover, silicosis patients often complicate with autoimmune diseases, and asbestos-exposed patients suffer from malignant diseases such as pleural mesothelioma and lung cancer. We have been conducting experimental studies to investigate altered regulation of self-tolerance caused by silica exposure, including analyses using specimens such as plasma and immunocompetent cells obtained from silicosis patients, as a means of examining the supposition that silica exposure induces molecular and cellular biological alterations of immune cells. These approaches have resulted in the detection of several specific autoantibodies, alterations of CD95/Fas and its related molecules, and evidence of chronic activation of responder T cells and regulatory T cells following silica exposure. In this review, we present details of our investigations as an introduction to scientific approaches examining the immunological effects of environmental and occupational substances.

The role of TL1A and DR3 in autoimmune and inflammatory diseases

TNF-like ligand 1A (TL1A), which binds its cognate receptor DR3 and the decoy receptor DcR3, is an identified member of the TNF superfamily. TL1A exerts pleiotropic effects on cell proliferation, activation, and differentiation of immune cells, including helper T cells and regulatory T cells. TL1A and its two receptors expression is increased in both serum and inflamed tissues in autoimmune diseases such as inflammatory bowel disease (IBD), rheumatoid arthritis (RA), and ankylosing spondylitis (AS). Polymorphisms of the TNFSF15 gene that encodes TL1A are associated with the pathogenesis of irritable bowel syndrome, leprosy, and autoimmune diseases, including IBD, AS, and primary biliary cirrhosis (PBC). In mice, blocking of TL1A-DR3 interaction by either antagonistic antibodies or deletion of the DR3 gene attenuates the severity of multiple autoimmune diseases, whereas sustained TL1A expression on T cells or dendritic cells induces IL-13-dependent small intestinal inflammation. This suggests that modulation of TL1A-DR3 interaction may be a potential therapeutic target in several autoimmune diseases, including IBD, RA, AS, and PBC.

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.

The serologic decoy receptor 3 (DcR3) levels are associated with slower disease progression in HIV-1/AIDS patients

BACKGROUND/PURPOSE

The decoy receptor 3 (DcR3) is a member of the tumor necrosis factor receptor (TNFR) super-family. It counteracts the biological effects of Fas ligands and inhibits apoptosis. The goals of this study were to understand the associations between serologic DcR3 (sDcR3) levels and different human immunodeficiency virus type 1 (HIV-1) subtypes, as well as the AIDS disease progression.

METHODS

Serum samples from 61 HIV/AIDS patients, who had been followed up every 6 months for 3 years, were collected. sDcR3 levels were quantified using an enzyme immunoassay (EIA).

RESULTS

The sDcR3 levels in patients with HIV-1 subtype B were significantly higher than those in patients infected with subtype CRF01_AE (p < 0.001). In addition, multivariable linear mixed model analysis demonstrated that HIV-1 subtype B and slow disease progression were associated with higher levels of sDcR3, adjusting for potential predictors (p = 0.0008 and 0.0455, respectively).

CONCLUSION

HIV-1-infected cells may gain a survival advantage by activating DcR3, which prevents infected cell detection by the host immune system. These data indicate that the sDcR3 level is a biomarker for AIDS disease progression.

Silicon, a Possible Link between Environmental Exposure and Autoimmune Diseases: The Case of Rheumatoid Arthritis

Silicon is one of the most common chemicals on earth. Several compounds such as silica, asbestos, silicone or, nanoparticles are built from tetrahedral units with silicon as the central atom. Despite these, structural similarities, they have rarely been analyzed as a group. These compounds generate significant biological alterations that include immune hyperactivation, production of the reactive species of oxygen and tissue injury. These pathological processes may trigger autoimmune responses and lead to the development of rheumatoid arthritis. Populations at risk include those that constantly work in industrial process, mining, and agriculture as well as those that undergo silicone implants. Herein a review on the main features of these compounds and how they may induce autoimmune responses is presented.

Detection of anti-topoisomerase I autoantibody in patients with silicosis

OBJECTIVES

The aim of this study was to detect anti-topoisomerase I (anti-topo I) autoantibodies, which are known to be limited in systemic sclerosis patients, in silicosis patients with no clinical symptoms of autoimmune disease.

METHODS

Serum anti-topo I autoantibodies were detected using ELISA. Differences in clinical parameters between patients with and without anti-topo I autoantibodies were analyzed.

RESULTS

Seven of 69 patients had anti-topo I autoantibodies. These 7 patients showed elevated PaCO(2) values (P=0.0212), and inverse correlations between serum soluble Fas levels and PaCO(2) values were found.

CONCLUSION

Anti-topo I autoantibodies were detected in 10.1% of silicosis patients without any clinical symptoms of autoimmune disease. The findings here suggest that the genesis of anti-topo I autoantibodies might be related to pulmonary involvement or lung fibrosis associated with progression of silicosis.

Keynote lecture in the 13th Japanese Society of Immunotoxicology (JSIT 2006) : -Pathophysiological Development and Immunotoxicology: what we have found from research related to silica and silicate such as asbestos-

Silica and silicates may disturb immune functions such as autoimmunity and tumor immunity, because people who are exposed to the materials sometimes develop autoimmune and malignant diseases, respectively. Although silica-induced disorders of autoimmunity have been explained as adjuvant-type effects of silica, more precise analyses are needed and should reflect the recent progress in immunomolecular findings. A brief summary of our investigations related to the immunological effects of silica/asbestos is presented. Recent advances in immunomolecular studies led to detailed analyses of the immunological effects of asbestos and silica. Both affect immuno-competent cells and these effects may be associated with the pathophysiological development of complications in silicosis and asbestos-exposed patients such as the occurrence of autoimmune disorders and malignant tumors, respectively. In addition, immunological analyses may lead to the development of new clinical tools for the modification of the pathophysiological aspects of diseases such as the regulation of autoimmunity or tumor immunity using cell-mediated therapies, various cytokines, and molecule-targeting therapies. In particular, as the incidence of asbestos-related malignancies is increasing and such malignancies have been a medical and social problem since the summer in 2005 in Japan, efforts should be focused on developing a cure for these diseases to eliminate the nation wide anxiety about these malignancies.

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.

Dysregulation of the immune system caused by silica and asbestos

Silica and asbestos cause pneumoconioses known as silicosis and asbestosis, respectively, that are each characterized by progressive pulmonary fibrosis. While local effects of inhaled silica particles alter the function of alveolar macrophages and sequential cellular and molecular biological events, general systemic immunological effects may also evolve. One well-known health outcome associated with silica exposure/silicosis is an increase in the incidence of autoimmune disorders. In addition, while exposure to silica--in the crystalline form--has also been seen to be associated with the development of lung cancers, it remains unclear as to whether or not silicosis is a necessary condition for the elevation of silica-associated lung cancer risks. Since asbestos is a mineral silicate, it would be expected to also possess generalized immunotoxicological effects similar to those associated with silica particles. However, asbestos-exposed patients are far better known than silicotic patients for development of malignant diseases such as lung cancer and mesothelioma, and less so for the development of autoimmune disorders. With both asbestos and crystalline silica, one important dysregulatory outcome that needs to be considered is an alteration in tumor immunity that allows for silica- or asbestos- (or asbestos-associated agent)-induced tumors to survive and thrive in situ. In this review, the immunotoxicological effects of both silica and asbestos are presented and contrasted in terms of their abilities to induce immune system dysregulation that then are manifest by the onset of autoimmunity or by alterations in host-tumor immunity.

Decoy receptor 3 levels in peripheral blood predict outcomes of acute respiratory distress syndrome

RATIONALE

Acute respiratory distress syndrome (ARDS), a serious inflammatory reaction to acute lung injury, is associated with high mortality rates. Decoy receptor (DcR) 3 is a soluble protein with immunomodulatory effects. Biomarkers that reliably predict outcomes in ARDS are not currently available.

OBJECTIVES

Comparing DcR3 with the Acute Physiology and Chronic Health Evaluation (APACHE) II scores and three other plasma markers to explore the association of DcR3 and the clinical outcome in ARDS.

METHODS

Eighty-eight patients with ARDS were studied. Baseline APACHE II scores and clinical data were recorded. Plasma levels of DcR3, soluble triggering receptor expressed on myeloid cells (sTREM)-1, tumor necrosis factor (TNF)-alpha, and IL-6 were measured on Day 1 and later time points, and correlated with the survival status on Day 28 after the onset of ARDS. For validation, 59 patients with ARDS from another medical center were studied.

MEASUREMENTS AND MAIN RESULTS

Among the biomarkers evaluated, only DcR3 discriminated the survivors and nonsurvivors at all time points in the first week of ARDS. DcR3 independently associated with and best predicted the 28-day mortality of patients with ARDS. Plasma DcR3 levels most correlated to multiple-organ dysfunction and ventilator dependence. Compared with survivors, the nonsurvivors had higher DcR3 levels regardless of the APACHE II scores. Kaplan-Meier survival analysis showed higher mortality in patients with ARDS with higher DcR3 levels. The outcome prediction of patients with ARDS by plasma DcR3 levels was recapitulated by the validation cohort.

CONCLUSIONS

High plasma DcR3 levels correlate with development of multiple-organ dysfunction and independently predict the 28-day mortality in patients with ARDS.

Soluble Interleukin-2 Receptor as an Indicator of Immunological Disturbance Found in Silicosis Patients

Silicosis patients (SILs) possess not only respiratory disorders but also alterations in autoimmunity. To determine an early indicator of immunological disturbance in SILs, the role of serum-soluble interleukin (IL)-2 receptor (sIL-2R) was analyzed. Of ten SILs, immunological clinical parameters such as immunoglobulin (Ig) G, complements, the titer of autoantibodies including anti-nuclear antibodies (ANA), anti-Scl-70 antibody (Ab) and anti-centromere (CM) Ab, and experimental indicators such as serum-soluble Fas, serum IL-2, CD25+ cells in CD4+ or CD8+ fractions, and sIL-2R were divided from respiratory parameters such as % vital capacity (%VC), percentage of forced expiratory volume in 1 second (FEV1.0%) and v25/Ht (liter/second/m(body height) by a correlation assay. Additionally, a stepwise regression test showed that sIL-2R was correlated with Ig G, ANA and anti-CM Ab. Furthermore, factor analysis revealed that sIL-2R contributed to the subpopulation of SILs with poorer immunological status in the absence of alterations in respiratory status. By defining healthy donors as 1, SILs as 2 and patients with systemic sclerosis as 3 for immunopathological progression status as metric variables, sIL2R and ANA showed a strong positive correlation. This suggests that sIL-2R is a good clinical indicator of immunological disturbance found in SILs without clinical manifestations of any disturbance in autoimmunity. Further analysis using a large-scale number of patients should be performed to confirm these findings.

Elevated serum decoy receptor 3 with enhanced T cell activation in systemic lupus erythematosus

Decoy receptor 3 (DcR3/TR6) is a decoy receptor for the Fas ligand (FasL) and can inhibit FasL-induced apoptosis. It has been reported recently that DcR3 can induce T cell activation via co-stimulation of T cells, suggesting that DcR3 may be involved in the pathophysiology of autoimmune diseases. This study aims to analyse the serum DcR3 in patients with systemic lupus erythematosus (SLE) and to investigate the role of DcR3 in the pathogenesis of SLE. Significantly elevated serum DcR3 was observed in SLE patients, and the mean serum DcR3 level was significantly higher for those with active disease [SLE disease activity index (SLEDAI) >/= 10] compared with that in patients with inactive disease (SLEDAI < 10). In addition to reducing activation-induced cell death in activated T cells via neutralization of the FasL, soluble DcR3-Fc enhanced T cell proliferation and increased interleukin-2 and interferon-gamma production via co-stimulation of T cells. Moreover, enhanced T cell reactivity to DcR3-induced co-stimulation was demonstrated in lymphocytes from patients with SLE, suggesting the elevated serum DcR3 may associate with enhanced T cell activation in vivo. These findings are the first to demonstrate that serum DcR3 concentrations are increased in SLE patients, and this may imply a possible role of DcR3 in the pathogenesis of SLE via enhanced T cell hyperreactivity and reduced apoptosis in activated T cells.

Overexpression of human decoy receptor 3 in mice results in a systemic lupus erythematosus-like syndrome

OBJECTIVE

Decoy receptor 3 (DcR3), a tumor necrosis factor receptor family member, is a secreted protein that can enhance cell survival by interfering with multiple apoptosis pathways. This study was undertaken to investigate the role of DcR3 in the pathogenesis of autoimmune disease.

METHODS

We generated transgenic mice with actin promoter-driven expression of human DcR3 and investigated the development of autoimmune disease in these mice.

RESULTS

T cell immune responses were compromised in young DcR3-transgenic mice. Beyond 5-6 months of age, transgenic mice developed a systemic lupus erythematosus (SLE)-like syndrome, with numerous features of the disease. They produced autoantibodies against double-stranded DNA. Their kidneys showed pathologic changes indicative of glomerular nephritis and IgG and C3 deposition, and proteinuria, leukocyturia, and hematuria, were evident. Aged transgenic mice also developed skin lesions and lymphocyte infiltration in the liver, and exhibited leukopenia, anemia, and thrombocytopenia. The SLE-like syndrome penetrance in DcR3-transgenic mice was sex associated, occurring in approximately 60% of females versus 20% of males. Exogenous recombinant DcR3 or endogenous DcR3 produced by transgenic T cells effectively protected T cells against activation-induced apoptosis in vitro. Probably as a consequence of this, CD4 cells with a phenotype of previous activation were increased in the peripheral blood of transgenic mice beyond 6 months of age.

CONCLUSION

These results show that DcR3 overexpression could lead to an SLE-like syndrome in mice.

Decoy receptor 3 ameliorates an autoimmune crescentic glomerulonephritis model in mice

Autoimmune crescentic glomerulonephritis (ACGN) is a variant of crescentic glomerulonephritis. The outcome of treatment of crescentic glomerulonephritis is poor. Binding of decoy receptor 3 (DCR3) to its ligand is capable of downregulating the alloresponsiveness of T cells. DCR3 has also been shown to benefit an experimental autoimmune model of diabetes. This study tested the hypothesis that a potential immune regulator, DCR3, could prevent the evolution of ACGN. With the use of an established ACGN model in mice, mice were treated with 100 microg/10 g body wt human DCR3 by hydrodynamics-based gene delivery at 14-d intervals. The results showed that the gene therapy resulted in (1) suppression of T and B cell activation and T cell proliferation; (2) a reduction in serum levels of proinflammatory cytokines; (3) improvement of proteinuria and renal dysfunction; (4) prevention of glomerular crescent formation, renal interstitial inflammation, and glomerulosclerosis; (5) a reduction in serum levels of autoantibodies and glomerular immune deposits; (6) inhibition of apoptosis in the spleen and kidney; (7) prevention of T cell and macrophage infiltration of the kidney; and (8) suppression of fibrosis-related gene expression in the kidney compared with empty vector-treated (disease control) ACGN mice. On the basis of these findings, it is proposed that human DCR3 exerts its preventive and protective effects on ACGN through modulation of T cell activation/proliferation, B cell activation, protection against apoptosis, and suppression of mononuclear leukocyte infiltration in the kidney.

Parathyroid hormone related protein (PTHrP) inhibits TNFalpha-induced apoptosis by blocking the extrinsic and intrinsic pathways

Parathyroid hormone related protein (PTHrP) is expressed at low levels in many fetal and adult tissues where it plays a central role in regulating cell proliferation, cell death, and tissue homeostasis. In vivo and in vitro, PTHrP has been shown to promote the survival of a variety of cells by regulating expression of the anti-apoptotic protein Bcl2. Additional work has shown that intra-nuclear accumulation of PTHrP in CFK2 (PTH1R positive) and 27m21 (PTH1R negative) condrogenic cells promotes their survival by closing down ribosome biogenesis and promoting quiescence. The current studies were undertaken to examine the role of wild-type PTHrP and a mutant form that cannot translocate to the nucleus in protecting cells from TNFalpha-induced apoptosis. Both forms of the protein were equally effective in blocking the extrinsic pathway by inhibiting expression of the TNF receptor death domain, activating Bid, and promoting cleavage of caspase 8. These observations suggest a direct mechanism of PTHrP action on components of the extrinsic pathway, involving a region of the protein outside of the NTS. PTHrP and M1PTHrP also inhibited the intrinsic pathway by preventing the exchange of anti-apoptotic for pro-apoptotic proteins at the mitochondrial membrane, thus maintaining its integrity and preventing the release of caspase-activating factors into the cytosol. In general, this mitochondrial-related activity was somewhat delayed and was mediated more effectively by PTHrP than by M1PTHrP, suggesting an indirect mechanism of action that might require the presence of an intact NTS.

Parathyroid hormone-related protein (PTHrP) inhibits mitochondrial-dependent apoptosis through CK2

Over the past decade, parathyroid hormone-related protein (PTHrP) has been identified as a key survival factor for cells subjected to apoptotic stimuli. Its anti-apoptotic activity has been attributed to nuclear accumulation of the intact protein, or a synthetic peptide corresponding to its nuclear targeting sequence (NTS), which promotes rapid exit of nutrient deprived cells from the cell cycle. Intracellular PTHrP also inhibited apoptosis by blocking tumor necrosis factor alpha (TNFalpha)-induced apoptosis by blocking signaling from the "death receptor" and preventing damage to the mitochondrial membrane. In both cases, the anti-apoptotic activity was significantly reduced in the presence of a nuclear deficient form of PTHrP with a (88)K/E K/E.K/I(91) mutation in the NTS. The current work was undertaken to determine the mechanism by which nuclear PTHrP blocked mitochondrial-mediated apoptosis. Using sub-cellular fractionation and functional assays we showed that pre-treatment of HEK293 cells with exogenous NTS peptide before inducing apoptosis with TNFalpha was as effective as expression of the full-length protein in inhibiting apoptosis. Inhibition of apoptosis was associated with increased expression of protein kinase casein kinase 2 (CK2) and in sustained CK2 accumulation and activity in the nuclear fraction. In primary chondrogenic cells harvested from the limb buds of PTHrP(+/-) and PTHrP(-/-) embryonic mice, there was a dose-dependent decrease in CK2 expression and activity that correlated with increased susceptibility to apoptosis. Taken together the results indicate that nuclear accumulation of PTHrP effectively inhibits mitochondrial-mediated apoptosis through regulation of the expression, activity, and sub-cellular trafficking of CK2.

Involvement of IL-10 and Bcl-2 in resistance against an asbestos-induced apoptosis of T cells

To analyze the possibility that immunological alteration in asbestos-related diseases (ARDs) such as asbestosis (ASB) and malignant mesothelioma (MM) may affect the progression of cancers, a human adult T cell leukemia virus-immortalized T cell line (MT-2Org) was continuously exposed to 10 mug/ml of chrysotile-B (CB), an asbestos. After at least 8 months of exposure, the rate of apoptosis in the cells became very low and the resultant subline was designated MT-2Rst. The MT-2Rst cells were characterized by (i) enhanced expression of bcl-2, with regain of apoptosis-sensitivity by reduction of bcl-2 by siRNA, (ii) excess IL-10 secretion and expression, and (iii) activation of STAT3 that was inhibited by PP2, a specific inhibitor of Src family kinases. These results suggested that the contact between cells and asbestos may affect the human immune system and trigger a cascade of biological events such as activation of Src family kinases, enhancement of IL-10 expression, STAT3 activation and Bcl-2 overexpression. This speculation was partially confirmed by the detection of elevated bcl-2 expression levels in CD4 + peripheral blood T cells from patients with MM compared with those from patients with ASB or healthy donors. Further studies will be required to verify the role of T cells with enhanced bcl-2 expression in tumor progression induced by asbestos exposure.

Attenuation of bone mass and increase of osteoclast formation in decoy receptor 3 transgenic mice

Decoy receptor 3 (DcR3), a soluble receptor for FasL, LIGHT, and TL1A, induces osteoclast formation from monocyte, macrophage, and bone stromal marrow cells. However, the function of DcR3 on bone formation remains largely unknown. To understand the function of DcR3 in bone formation in vivo, transgenic mice overexpressing DcR3 were generated. Bone mineral density (BMD) and bone mineral content (BMC) of total body were significantly lower in DcR3 transgenic mice as compared with wild-type controls. The difference in BMD and BMC between DcR3 transgenic and control mice was confirmed by histomorphometric analysis, which showed a 35.7% decrease in trabecular bone volume in DcR3 transgenic mice in comparison with wild-type controls. The number of osteoclasts increased in DcR3 transgenic mice. In addition, local administration of DcR3 (30 microg/ml, 10 microl, once/day) into the metaphysis of the tibia via the implantation of a needle cannula significantly decreased the BMD, BMC, and bone volume of secondary spongiosa in tibia. Local injection of DcR3 also increased osteoclast numbers around trabecular bone in tibia. Furthermore, coadminstration of soluble tumor necrosis factor receptor inhibitor/Fc chimera (TNFRSF1A) but not osteoprotegerin inhibited the action of DcR3. In addition, in an assay of osteoclast activity on substrate plates, DcR3 significantly increased the resorption activity of mature osteoclasts. Treatment with higher concentrations of DcR3 slightly increased nodule formation and alkaline phosphatase activity of primary cultured osteoblasts. These results indicate that DcR3 may play an important role in osteoporosis or other bone diseases.

Reduced function of CD4+25+ regulatory T cell fraction in silicosis patients

The quality and quantity of CD4+25+ regulatory T cells (Treg) in silicosis patients (SIL) were examined and compared with results from healthy donors (HD) because SIL often develop autoimmune diseases along with pulmonary disorders. Peripheral blood mononuclear cells from 57 SIL and 50 HD were analyzed for Treg. Treg frequency and clinical parameters were subjected to a factor analysis. Treg and CD4+25- T cells (Tneg) from five HD and five SIL, sorted by flow-cytometer, were used for functional assays of Treg, the expression pattern of Treg specific genes (FoxP3, GITR and CTLA-4) and activation-related genes (CD122 and CD123). Although the actual frequency of Treg did not differ between SIL and HD, the age-corrected level was reduced in SIL. The factor analysis showed that Treg frequency was positively associated with the serum level of IL-2. The inhibitory effect of Treg on Tneg activation was decreased when the Treg:Tneg ratio was 1:1/4 to 1/2. In addition, Treg dominancy of FoxP3 and CTLA-4 expression and Tneg dominancy of CD132 expression found in HD were lost in SIL. These results indicated that the Treg fraction in SIL may be substituted with chronically activated T cells due to recurrent exposure to silica, resulting in a reduction in the frequency and function of Treg. Since the reduction of Treg may precede the clinical manifestation, as silicosis may be a pre-clinical status for autoimmune diseases, control of Treg function using cell and/or gene therapy may be a good way to manage autoimmune disease.

The glycosaminoglycan-binding domain of decoy receptor 3 is essential for induction of monocyte adhesion

Decoy receptor 3 (DcR3), a soluble receptor for Fas ligand, LIGHT (homologous to lymphotoxins shows inducible expression and competes with HSV glycoprotein D for herpes virus entry mediator, a receptor expressed by T lymphocytes), and TNF-like molecule 1A, is highly expressed in cancer cells and in tissues affected by autoimmune disease. DcR3.Fc has been shown to stimulate cell adhesion and to modulate cell activation and differentiation by triggering multiple signaling cascades that are independent of its three known ligands. In this study we found that DcR3.Fc-induced cell adhesion was inhibited by heparin and heparan sulfate, and that DcR3.Fc was unable to bind Chinese hamster ovary K1 mutants defective in glycosaminoglycan (GAG) synthesis. Furthermore, the negatively charged, sulfated GAGs of cell surface proteoglycans, but not their core proteins, were identified as the binding sites for DcR3.Fc. A potential GAG-binding site was found in the C-terminal region of DcR3, and the mutation of three basic residues, i.e., K256, R258, and R259, to alanines abolished its ability to trigger cell adhesion. Moreover, a fusion protein comprising the GAG-binding region of DcR3 with an Fc fragment (DcR3_HBD.Fc) has the same effect as DcR3.Fc in activating protein kinase C and inducing cell adhesion. Compared with wild-type THP-1 cells, cell adhesion induced by DcR3.Fc was significantly reduced in both CD44v3 and syndecan-2 knockdown THP-1 cells. Therefore, we propose a model in which DcR3.Fc may bind to and cross-link proteoglycans to induce monocyte adhesion.

Attenuation of Th1 response in decoy receptor 3 transgenic mice

The soluble decoy receptor 3 (DcR3) is a member of the TNFR superfamily. Because DcR3 is up-regulated in tumor tissues and is detectable in the sera of cancer patients, it is regarded as an immunosuppressor to down-regulate immune responses. To understand the function of DcR3 in vivo, we generated transgenic mice overexpressing DcR3 systemically. In comparison with HNT-TCR (HNT) transgenic mice, up-regulation of IL-4 and IL-10 and down-regulation of IFN-gamma, IL-12, and TNF-alpha were observed in the influenza hemagglutinin(126-138) peptide-stimulated splenocytes of HNT-DcR3 double-transgenic mice. When infected with Listeria monocytogenes, DcR3 transgenic mice show attenuated expression of IFN-gamma as well as increased susceptibility to infection. The Th2 cell-biased phenotype in DcR3 transgenic mice is attributed to decreased IL-2 secretion by T cells, resulting in the suppression of IL-2 dependent CD4(+) T cell proliferation. This suggests that DcR3 might help tumor growth by attenuating the Th1 response and suppressing cell-mediated immunity.

Overexpression of decoy receptor 3 in hepatocellular carcinoma and its association with resistance to Fas ligand-mediated apoptosis

AIM: To characterize the expression and genomic amplification of decoy receptor 3 (DcR3) in hepatocellular carcinoma (HCC) and to evaluate the role of DcR3 in apoptosis.

METHODS: We examined 48 cases of HCC for DcR3 expression by RT-PCR and DcR3 gene amplification by quantitative genomic PCR. DcR3 protein was detected by immunohistochemistry. Terminal deoxynucleotidyl transferase-mediated dUTP digoxigenin nick and labeling (TUNEL) was used to identify the apoptosis cells in tissues. Primary hepatoma cell culture and MTT test were used to evaluate the protection against FasL- and chemical-induced apoptosis by DcR3 expression.

RESULTS: DcR3 mRNA overexpression was detected in 60% HCC (29/48) patients. The occurrence of HCC was not associated with amplification of the gene. One sample base substitution was found in three sites as a sequence in Genbank. The expression of DcR3 in HCC was associated with the apoptotic index (0.067±0.04 vs 0.209±0.12, P<0.01), size of mass, stage, and infiltration or metastasis (41.2% vs 71.0%, 40% vs 75%, 51.8% vs 84.6%, P<0.05). DcR3 expression could protect hepatoma cells against apoptosis induced by FasL, but not by chemicals.

CONCLUSION: These data suggest that in addition to gene amplification there may be another mechanism underlying DcR3 overexpression. The effect of overexpression of DcR3 on the apoptosis of cancer cells may have direct therapeutic implications for the management of HCC.

Induction of CD69 antigen expression in peripheral blood mononuclear cells on exposure to silica, but not by asbestos/chrysotile-A

While cases of silicosis are often complicated by various autoimmune disorders, patients with asbestosis develop malignant tumors such as lung cancer and malignant mesothelioma. These differences may derive from different biological effects, particularly on immunological cells, of silica and asbestos. To find differences between silica and asbestos, the early activation antigen, CD69, on T cells was examined because dysregulated and continuous activation of T cells may promote the survival of self-recognizing T cells. After cultivation of peripheral blood mononuclear cells with or without silica or chrysotile-A, an asbestos, only silica induced CD69 expression on the lymphocytes. This induction of CD69 expression was mediated by protein kinase C activation. In addition, cell-cell contact mediated by HLA-DR was more important than soluble factors secreted from silica-phagocytosed cells such as IL-1beta, IL-6, and IL-8, even though IL-6 and IL-8 were produced during the culture of PBMCs with silica and chrysotile-A. It should be examined how these activated, CD69-expressing lymphocytes affect other immune systems as well as alter themselves in terms of cytokine production and cell-cell interaction, leading to autoimmune disorders in silicosis patients.

Quantification and detection of DcR3, a decoy receptor in TNFR family

A soluble decoy receptor, DcR3, belongs to the tumor necrosis factor receptor (TNFR) family, and this receptor is known to bind to three TNF family ligands, namely Fas ligand (FasL), LIGHT, and TL1A. To aid our understating of the role of DcR3 in the immune system, we have developed quantitative enzyme-linked immunosorbent assay (ELISA) to detect soluble DcR3 in human biological fluids. Two monoclonal antibodies, MD3E2 and MD3B1, that recognized different epitopes on the DcR3 molecule were selected as capture and detection antibodies, respectively, to be paired in ELISA. The assay had a detection limit of 36 pg/ml with a dynamic range of 0.25-16 ng/ml. The recovery range was 91-112% for cell culture supernatant and 90-108% for human sera. Intra- and inter-assay CVs were less than 7.2% and 11.2%, respectively. Among a panel of cell lines tested, colon adenocarcinoma cell line, SW480, secreted the highest levels of DcR3 at 3.2 ng/ml. From the screening of human sera samples, we discovered that 39 healthy individuals, 59 tumor patients, and 46 patients with renal failure expressed an average (mean+/-S.D.) 0.56+/-0.52, 2.3+/-1.6, and 4.6+/-2.8 ng/ml DcR3, respectively. To confirm the specificity of ELISA, we have purified native DcR3 from SW480 cell culture supernatants and identified a native DcR3 in a clinical serum by immunoprecipitation. Taken together, our data demonstrated that the ELISA developed in this study was specific and sensitive to quantify soluble DcR3 in a variety of human biological fluids and that the assay would be useful for studying the regulation of DcR3 in certain pathophysiological conditions.

Enhanced adhesion of monocytes via reverse signaling triggered by decoy receptor 3

Decoy receptor 3 (DcR3), a newly identified soluble protein belonging to the tumor necrosis factor receptor (TNFR) superfamily, is a receptor for Fas ligand (FasL), LIGHT and TL1A. It has been demonstrated that DcR3 is frequently overexpressed by malignant tumors arising from lung, gastrointestinal tract, neuronal glia and virus-associated leukemia. Recently, we demonstrated that DcR3 is able to modulate the differentiation and activation of dendritic cells (DCs), and that DcR3-treated DCs skew naive T cell differentiation towards a Th2 phenotype. In this study, we further demonstrate that DcR3 is able to induce actin reorganization and enhance the adhesion of monocytes and THP-1 cells by activating multiple signaling molecules, such as protein kinase C (PKC), phosphatidylinositol 3-kinase (PI3K), focal adhesion kinase (FAK) and Src kinases. This provides the first evidence that the soluble DcR3, like other immobilized members of TNFR superfamily, is able to trigger 'reverse signaling' to modulate cell function.

Selective induction of tumor necrosis receptor factor 6/decoy receptor 3 release by bacterial antigens in human monocytes and myeloid dendritic cells

Tumor necrosis factor (TNF) receptor 6/decoy receptor 3 (TR6/DcR3) is an antiapoptosis soluble receptor of the TNF family produced by tumor cells. In this study, TR6 expression in human immune cells was investigated. TR6 mRNA and protein were detectable in selected antigen-presenting cells. Monocytes and myeloid-derived dendritic cells (MDC) released the protein exclusively following stimulation of Toll-like receptor 2 (TLR2) and TLR4 by gram-positive and gram-negative bacterial antigens. Plasmacytoid dendritic cells, activated by bacterial antigens via TLR9 or by viral infection, did not produce the protein. Similarly, activated T cells did not release TR6. The release of TR6 by MDC was dependent on the activation of p42/p44 mitogen-activated protein kinases, Src-like protein tyrosine kinases, and phosphatidylinositol 3-kinase, signaling pathways important for MDC maturation and survival. In agreement with the in vitro data, TR6 levels in serum were significantly elevated in patients with bacterial infections. Overall, these data suggest a novel role for TR6 in immune responses to bacteria.

Immunomodulatory effect of decoy receptor 3 on the differentiation and function of bone marrow-derived dendritic cells in nonobese diabetic mice: from regulatory mechanism to clinical implication

To investigate the regulatory effects of decoy receptor 3 (DcR3) on the differentiation and function of dendritic cells (DCs), bone marrow-derived DCs (BM-DCs) from nonobese diabetic (NOD) mice were cultured with recombinant DcR3.Fc protein. Their differentiating phenotypes and T cell-stimulating functions were then evaluated. Expression of CD11c, CD40, CD54, and major histocompatibility complex I-A(g7) was reduced in cells cultured with additional DcR3.Fc, compared with DCs incubated with granulocyte macrophage-colony stimulating factor and interleukin (IL)-4, indicating that DcR3 interferes with the differentiation and maturation of BM-DCs. One of the most striking effects of DcR3.Fc on the differentiation of DCs was the up-regulation of CD86 and down-regulation of CD80, suggesting a modulatory potential to skew the T cell response toward the T helper cell type 2 (Th2) phenotype. Consistent with this, the proliferation of CD4(+) T cells cocultured with DcR3.Fc-treated DCs was significantly reduced compared with that of T cells stimulated by normal DCs. Moreover, the secretion of interferon-gamma from T cells cocultured with DcR3.Fc-treated DCs was profoundly suppressed, indicating that DcR3 exerts a Th1-suppressing effect on differentiating DCs. Furthermore, adoptive transfer experiments revealed that NOD/severe combined immunodeficiency mice received DcR3.Fc-treated DCs, and subsequently, autoreactive T cells showed delayed onset of diabetes and a decrease in diabetic severity compared with mice that received normal DCs and T cells, suggesting a future therapeutic potential in autoimmune diabetes. Data from two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight analysis show an up-regulation of some proteins-such as mitogen-activated protein kinase p38 beta, cyclin-dependent kinase 6, and signal-induced proliferation-associated gene 1-and a down-regulation of the IL-17 precursor; tumor necrosis factor-related apoptosis-inducing ligand family member-associated nuclear factor-kappaB activator-binding kinase 1; and Golgi S-nitroso-N-acetylpenicillamine in cells treated with DcR3, further demonstrating its effect on DC differentiation and function.

Modulation of dendritic cell differentiation and maturation by decoy receptor 3

Decoy receptor 3 (DcR3), a soluble receptor belonging to the TNFR superfamily, is a receptor for both Fas ligand (FasL) and LIGHT. It has been demonstrated that DcR3 is up-regulated in lung and colon cancers, thus promoting tumor growth by neutralizing the cytotoxic effects of FasL and LIGHT. In this study, we found that DcR3.Fc profoundly modulated dendritic cell differentiation and maturation from CD14(+) monocytes, including the up-regulation of CD86/B7.2, and the down-regulation of CD40, CD54/ICAM-1, CD80/B7.1, CD1a, and HLA-DR. Moreover, DcR3-treated dendritic cells suppressed CD4(+) T cell proliferation in an allogeneic MLR and up-regulated IL-4 secretion of CD4(+)CD45RA(+) T cells. This suggests that DcR3.Fc may act not only as a decoy receptor to FasL and LIGHT, but also as an effector molecule to skew T cell response to the Th2 phenotype.

Establishment of CD7+ human myeloma sister cell lines, KMS-21-PE and KMS-21-BM, carrying t(11;14) and t(8;14)

Two new human myeloma cell lines were established from pleural effusion and bone marrow malignant cells derived from a single patient, who manifested hyperammonemia associated with multiple myeloma, and these were characterized. Both lines possess t(11;14)(q13;q32) and t(8;14)(q24;q32) reciprocal translocations and overexpress cyclin D1, but not c-myc. Human myeloma lines including these new lines produced and secreted excess ammonia into culture medium more than non-myelomatous hematological cell lines. In addition, these two lines were revealed to have high surface CD7 expression correlated with relatively high mRNA expression by MP-RT-PCR. Among 8 human myeloma lines, half of them revealed significant surface expression of CD7 and a positive correlation between expression levels of protein and message. CD7 message was also detected in surface negative lines. Consequently, there may be posttranslational regulation of the CD7 molecule, whose cellular biological role in expressing cells has not been elucidated.