AB16942 Sigma-AldrichAnti-DR5 Antibody, CT

OBJECTIVE: Studies in mice suggest a protective role for the TNF-related apoptosis-inducing ligand (TRAIL) in arthritis. We investigated the role of TRAIL in rheumatoid arthritis (RA) patients.METHODS: In the present study, we compared RA Fibroblast-like synoviocytes (FLS) resistant and RAFLS-sensible to TRAIL-induced apoptosis, including levels of the TRAIL receptors (TRAIL-R) and clinical features of respective patient. Furthermore, we evaluated TRAIL and its soluble decoy receptor osteoprotegerin (OPG) levels in RA patients, osteoarthritis (OA) and spondylarthritis (SpA).RESULTS: Sensitivity to TRAIL-induced apoptosis varied in FLS from different patients and disease severity of RA patients inversely correlated with susceptibility of FLS to TRAIL-induced apoptosis. TRAIL-sensitive cells expressed significantly lower levels of TRAIL-R1 and silencing of TRAIL-R1 increased TRAIL-induced apoptosis in RA FLS. TRAIL levels were elevated in the arthritic joints of patients with established RA and synovial fluids displayed elevated TRAIL levels compared to OA and SpA patients. A low ratio of the soluble decoy receptor OPG to TRAIL in sera of early RA patients at baseline was associated with a better evolution of disease activity, but high serum levels of TRAIL at follow-up were associated with joint damages.CONCLUSION: These findings suggest a dual role for TRAIL in RA and resistance of RA FLS to TRAIL-induced apoptosis is associated with a disease promoting activity of TRAIL in RA.Copyright © 2011 by the American College of Rheumatology.

While CD8 subsets activate hepatic fibrosis, natural killer (NK) cells exhibit antifibrotic activity. Glatiramer acetate (GA) is an immune modulator for multiple sclerosis. We assessed the potential impact of GA on mouse hepatic fibrogenesis. Hepatic fibrosis was induced in C57BL/6 mice by intraperitoneal administration of carbon tetrachloride (CCl(4)) for 6 wk. During the last 2 wk, animals were also treated with either GA (200 mu/day ip) or medium and compared with naive and fibrotic mice (8 animals/group). GA markedly attenuated fibrosis without altering reactive oxygen species production. By morphometric measurement of Sirius red-stained tissue sections, the relative fibrosis area decreased from 5.28 +/- 0.32% (mean +/- SE) in the untreated CCl(4) group to 2.01 +/- 0.28% in CCl(4)+GA-treated animals, compared with 0.38 +/- 0.07% in naive mice. alpha-Smooth muscle actin immunoblotting and mRNA expression revealed a similar pattern. Serum aminotransferase and Ishak-Knodell necroinflammatory score were markedly elevated, to the same extent, in both CCl(4)-treated groups. Fibrosis induction was associated with significant increase in CD8 subsets and decrease in CD4 T cells. After GA treatment, however, NK content, CD4(+)CD25(+)FoxP3(+) cells, hepatic expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), and apoptosis of hepatic stellate cells were all increased. Serum interleukin (IL)-10 levels markedly rose, whereas IL-4 fell. In vitro activation of human hepatic stellate cells cocultured with hepatitis C virus-derived peripheral blood lymphocytes decreased when lymphocytes were preincubated with GA before coculture. In an animal model of hepatic fibrosis, GA has an antifibrotic effect associated with decreased CD8 cells and reduced serum IL-4 levels and increased NK cells, CD4(+)CD25(+)FoxP3(+) cells, TRAIL, and elevated serum IL-10 levels.

Here, we provide evidence for a detrimental role of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in neural death in T cell-induced experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). Clinical severity and neuronal apoptosis in brainstem motor areas were substantially reduced upon brain-specific blockade of TRAIL after induction of EAE through adoptive transfer of encephalitogenic T cells. Furthermore, TRAIL-deficient myelin-specific lymphocytes showed reduced encephalitogenicity when transferred to wild-type mice. Conversely, intracerebral delivery of TRAIL to animals with EAE increased clinical deficits, while naive mice were not susceptible to TRAIL. Using organotypic slice cultures as a model for living brain tissue, we found that neurons were susceptible to TRAIL-mediated injury induced by encephalitogenic T cells. Thus, in addition to its known immunoregulatory effects, the death ligand TRAIL contributes to neural damage in the inflamed brain.

The death ligand, TRAIL (tumor necrosis factor-related apoptosis-inducing ligand), has shown great promise for inducing apoptosis selectively in tumors. Although many tumor cells are resistant to TRAIL-induced apoptosis alone, they can often be sensitized by co-treatment with DNA-damaging agents such as etoposide. However, the molecular mechanism underlying this therapeutically important synergy is unknown. We explored the mechanism mediating TRAIL-DNA damage apoptotic synergy in human mesothelioma cells, a tumor type particularly refractory to existing therapies. We show that Bid, a cytoplasmic Bcl-2 homology domain 3-containing protein activated by caspase 8 in response to TRAIL ligation, is essential for TRAIL-etoposide apo-ptotic synergy and, furthermore, that exposure to DNA damage primes cells to induction of apoptosis by otherwise sublethal levels of activated Bid. Finally, we show that the extensive caspase 8 cleavage seen during TRAIL-etoposide synergy is a consequence and not a cause of the apoptotic cascade activated downstream of Bid. These data indicate that TRAIL-etoposide apoptotic synergy arises because DNA damage increases the inherent sensitivity of cells to levels of TRAIL-activated Bid that would otherwise be insufficient for apoptosis. Such studies indicate how the adroit combination of differing proapoptotic and sublethal signals can provide an effective strategy for treating refractory tumors.

In this study, we searched for murine analogues of the four death-receptor types (TRAIL-R1 to R4), targeted by the tumour necrosis factor related apoptosis inducing ligand (TRAIL), which were recently identified in the human brain. The expression of TRAIL-receptors in the normal murine brain was investigated using antibodies directed against different epitopes of the human TRAIL-receptors. Mouse mutants, in particular weaver and Lurcher with their well defined spatio-temporal patterns of neurodegeneration in the cerebellum, the inferior olive and the substantia nigra, were used as a model for investigating a potential contribution of TRAIL-receptors to the genetically determined cell death observed in these mutants. Although all antibodies used, recognized the respective human antigens, only the murine analogue of the human TRAIL-R2 epitope was also identified in the mouse brain. Antisera against human TRAIL-R1, TRAIL-R3 and TRAIL-R4 failed to reveal any other murine TRAIL-receptor analogue. In normal mice, TRAIL-R2 is not universally expressed throughout the brain but rather restricted to specific neuronal populations predominantly consisting of large neurons. In weaver, the spatial patterns and relative densities of TRAIL-R2 labelling were virtually identical to those seen in wild-types during the period of cell death in the cerebellum and the substantia nigra. In Lurcher, TRAIL-R2 expression in cerebellar granule cells and inferior olivary neurons was identical to that in wildtypes but significantly reduced in Purkinje cells undergoing degeneration. Thus, although TRAIL-R2 is found to be expressed in various cell types of the murine brain, cell death in weaver and Lurcher mutants is apparently not accompanied by an upregulation of TRAIL-receptors.

TRAIL (also known as Apo-2L) is a member of the tumor necrosis factor (TNF) ligand family that rapidly induces apoptosis in a variety of transformed cell lines. The human receptor for TRAIL was found to be an undescribed member of the TNF-receptor family (designated death receptor-4, DR4) that contains a cytoplasmic "death domain" capable of engaging the cell suicide apparatus but not the nuclear factor kappa B pathway in the system studied. Unlike Fas, TNFR-1, and DR3, DR4 could not use FADD to transmit the death signal, suggesting the use of distinct proximal signaling machinery. Thus, the DR4-TRAIL axis defines another receptor-ligand pair involved in regulating cell suicide and tissue homeostasis.

TRAIL (also called Apo2L) belongs to the tumor necrosis factor family, activates rapid apoptosis in tumor cells, and binds to the death-signaling receptor DR4. Two additional TRAIL receptors were identified. The receptor designated death receptor 5 (DR5) contained a cytoplasmic death domain and induced apoptosis much like DR4. The receptor designated decoy receptor 1 (DcR1) displayed properties of a glycophospholipid-anchored cell surface protein. DcR1 acted as a decoy receptor that inhibited TRAIL signaling. Thus, a cell surface mechanism exists for the regulation of cellular responsiveness to pro-apoptotic stimuli.

A subset of the tumour necrosis factor (TNF) receptor family contain a conserved intracellular motif, the death domain. Engagement of these receptors by their respective ligands initiates a signalling cascade that rapidly leads to cell death by apoptosis. We have cloned a new member of this family, TRICK2, the TRAIL (TNF-related apoptosis-inducing ligand) receptor inducer of cell killing 2. TRICK2 is expressed in a number of cell types, and to particularly high levels in lymphocytes and spleen. Two isoforms of the TRICK2 mRNA are generated by alternative pre-mRNA splicing and differ by a 29 amino-acid extension to the extracellular domain. Overexpression of TRICK2 rapidly induced apoptosis in 293T cells; this induction was dependent upon the presence of the death domain of TRICK2. Using a soluble molecule containing the TRICK2 extracellular domain, we demonstrated that TRICK2, like DR4 [1], is a receptor for TRAIL/APO-2L [2,3] and could inhibit TRAIL-induced killing of lymphocyte lines, such as the Jurkat T-cell line. TRAIL is upregulated upon lymphocyte activation, as is the intensively studied ligand for Fas, FasL [4]. TRAIL and its receptors might therefore provide another system for the regulation of lymphocyte selection and proliferation, as well as providing an additional weapon in the armoury of cytotoxic lymphocytes.

TRAIL is a member of the tumor necrosis factor (TNF) family of cytokines and induces apoptosis in a wide variety of cells. Based on homology searching of a private database, a receptor for TRAIL (DR4 or TRAIL-R1) was recently identified. Here we report the identification of a distinct receptor for TRAIL, TRAIL-R2, by ligand-based affinity purification and subsequent molecular cloning. TRAIL-R2 was purified independently as the only receptor for TRAIL detectable on the surface of two different human cell lines that undergo apoptosis upon stimulation with TRAIL. TRAIL-R2 contains two extracellular cysteine-rich repeats, typical for TNF receptor (TNFR) family members, and a cytoplasmic death domain. TRAIL binds to recombinant cell-surface-expressed TRAIL-R2, and TRAIL-induced apoptosis is inhibited by a TRAIL-R2-Fc fusion protein. TRAIL-R2 mRNA is widely expressed and the gene encoding TRAIL-R2 is located on human chromosome 8p22-21. Like TRAIL-R1, TRAIL-R2 engages a caspase-dependent apoptotic pathway but, in contrast to TRAIL-R1, TRAIL-R2 mediates apoptosis via the intracellular adaptor molecule FADD/MORT1. The existence of two distinct receptors for the same ligand suggests an unexpected complexity to TRAIL biology, reminiscent of dual receptors for TNF, the canonical member of this family.

Death receptor 4 (DR4) is a recently described receptor for the cytotoxic ligand TRAIL that reportedly uses a FADD-independent pathway to induce apoptosis and does not activate the NF-kappaB pathway. We have isolated a new member of the tumor necrosis factor receptor (TNFR) family, designated DR5, which bears a high degree of sequence homology to DR4. However, contrary to the previous reports, both DR4- and DR5-induced apoptosis can be blocked by dominant-negative FADD, and both receptors can activate NF-kappaB using a TRADD-dependent pathway. Finally, both receptors can interact with FADD, TRADD, and RIP. Thus, both DR5 and DR4 use FADD, TRADD, and RIP in their signal transduction pathways, and FADD is the common mediator of apoptosis by all known death domain-containing receptors.