Death receptors induce apoptosis by intracellular signaling transmission and relate to body growth, development, disease and death. This paper reviews the structural character of death receptors, and the mechanisms by which apoptosis is induced. The biology and pathobiology of these death receptors in liver are discussed as well.
Apoptosis ; physiology ; GPI-Linked Proteins ; Humans ; Liver ; pathology ; physiology ; Receptors, TNF-Related Apoptosis-Inducing Ligand ; Receptors, Tumor Necrosis Factor ; physiology ; Receptors, Tumor Necrosis Factor, Member 10c ; Tumor Necrosis Factor Decoy Receptors ; fas Receptor ; physiology

OX40 is a costimulatory receptor that is expressed primarily on activated CD4⁺, CD8⁺, and regulatory T cells. The ligation of OX40 to its sole ligand OX40L potentiates T cell expansion, differentiation, and activation and also promotes dendritic cells to mature to enhance their cytokine production. Therefore, the use of agonistic anti-OX40 antibodies for cancer immunotherapy has gained great interest. However, most of the agonistic anti-OX40 antibodies in the clinic are OX40L-competitive and show limited efficacy. Here, we discovered that BGB-A445, a non-ligand-competitive agonistic anti-OX40 antibody currently under clinical investigation, induced optimal T cell activation without impairing dendritic cell function. In addition, BGB-A445 dose-dependently and significantly depleted regulatory T cells in vitro and in vivo via antibody-dependent cellular cytotoxicity. In the MC38 syngeneic model established in humanized OX40 knock-in mice, BGB-A445 demonstrated robust and dose-dependent antitumor efficacy, whereas the ligand-competitive anti-OX40 antibody showed antitumor efficacy characterized by a hook effect. Furthermore, BGB-A445 demonstrated a strong combination antitumor effect with an anti-PD-1 antibody. Taken together, our findings show that BGB-A445, which does not block OX40-OX40L interaction in contrast to clinical-stage anti-OX40 antibodies, shows superior immune-stimulating effects and antitumor efficacy and thus warrants further clinical investigation.
Mice ; Animals ; Receptors, Tumor Necrosis Factor/physiology* ; Receptors, OX40 ; Membrane Glycoproteins ; Ligands ; Antibodies, Monoclonal/pharmacology* ; Antineoplastic Agents/pharmacology*

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) is a member of the TNF superfamily of structurally related cytokines and is known to induce proliferation, migration, differentiation, apoptotic cell death, inflammation, and angiogenesis. These physiological processes are induced by the binding of TWEAK to fibroblast growth factor-inducible 14 (Fn14), a highly inducible cell-surface receptor that is linked to several intracellular signaling pathways, including the nuclear factor-κB (NF-κB) pathway. This review discusses the role of the TWEAK-Fn14 axis in several rheumatic diseases and the potential therapeutic benefits of modulation of the TWEAK-Fn14 pathway.
Arthritis, Rheumatoid ; etiology ; Cytokine TWEAK ; Humans ; Lupus Erythematosus, Systemic ; etiology ; Receptors, Tumor Necrosis Factor ; physiology ; Rheumatic Diseases ; etiology ; Scleroderma, Systemic ; etiology ; TWEAK Receptor ; Tumor Necrosis Factors ; physiology

Progranulin (PGRN) is a growth factor implicated in various pathophysiological processes, including wound healing, inflammation, tumorigenesis, and neurodegeneration. It was previously reported that PGRN binds to tumor necrosis factor receptors (TNFR) and has therapeutic effects in inflammatory arthritis (Tang et. al, in Science 332:478-484, 2011); however, Chen et al. reported their inability to demonstrate the PGRN-TNFR interactions under their own conditions (Chen et. al, in J Neurosci 33:9202-9213, 2013). A letter-to-editor was then published by the original group in response to the Chen et al. paper that discussed the reasons for the latter's inability to recapitulate the interactions. In addition, the group published follow-up studies that further reinforced and dissected the interactions of PGRN-TNFR. Recently, the dispute about the legitimacy of PGRN-TNFR interactions appears to be finally settled with independent confirmations of these interactions in various conditions by numerous laboratories. This review presents a chronological update on the story of PGRN-TNFR interactions, highlighting the independent confirmations of these interactions in various diseases and conditions.
Animals ; Humans ; Intercellular Signaling Peptides and Proteins ; metabolism ; Progranulins ; Receptors, Tumor Necrosis Factor ; metabolism ; Signal Transduction ; physiology ; Tumor Necrosis Factor-alpha ; metabolism

TNF-related apoptosis-inducing ligand (TRAIL) is a newly identified member of the tumor necrosis factor (TNF) family. TRAIL induces apoptosis by activating caspase cascades, stimulating a loss of mitochondrial membrane potential (Delta Psim) and cytochrome C release in the FADD/caspase-8 dependent pathway. However, TRAIL can also trigger transcriptional activations of the pro-oncogene of c-fos, JNK, and NF-kappaB by other signaling pathways downstream of FADD/caspase-8. MAPK/ERK activation has a dominant protecting effect over apoptotic signaling from the death receptors. The functional expression of TRAIL by leukemic cells may be involved in tumor cells evasion of immunosurveillance. Somatic mutations of TRAIL-R1 and TRAIL-R2 genes may play a role in the pathogenesis of some tumors. TRAIL can induce apoptosis on various continuous transformed cell lines and primary tumor cells, including several of hematopoietic origin, displaying minimal toxic effects on normal tissues. Because of the abilities of induction of both cytotoxic (apoptosis) and cytostatic (cell cycle perturbation) effects on the leukemic cells, TRAIL is currently considered as a potential(co) therapeutic drug against tumors.
Animals ; Apoptosis Regulatory Proteins ; Hematologic Neoplasms ; etiology ; therapy ; Humans ; Membrane Glycoproteins ; physiology ; Mutation ; Receptors, TNF-Related Apoptosis-Inducing Ligand ; Receptors, Tumor Necrosis Factor ; genetics ; physiology ; Signal Transduction ; TNF-Related Apoptosis-Inducing Ligand ; Tumor Necrosis Factor-alpha ; physiology

Current therapies for autoimmune diseases are not cures but merely palliatives, aimed at reducing symptoms. For the most part, these treatments provide nonspecific suppression of the immune system and thus do not distinguish between a pathogenic autoimmune response and a protective immune response. Recently emerging evidence not only has indicated the involvement of members of the TNF receptor/ligand superfamilies but also has revealed exciting innovative strategies for the treatment of autoimmune diseases and other chronic inflammatory diseases without depressing the immune response in general. In this review, we will discuss the regulatory mechanisms of TNF receptor/ligand family members, such as HVEM/ LIGHT, 4-1BB/4-1BBL, and GITR/GITRL that regulate T and B cell functions and participate in the process of inflammatory diseases. We will also discuss how intervening in the costimulatory pathways mediated by these molecules might have some potential as a therapeutic approach to immune disorders.
Animals ; Apoptosis ; Autoimmune Diseases/immunology/metabolism/pathology ; B-Lymphocytes/immunology/physiology ; Dendritic Cells/physiology ; Human ; Inflammation/*immunology ; Lymphocyte Activation/immunology ; Models, Biological ; Receptors, Tumor Necrosis Factor/*physiology ; T-Lymphocytes/immunology/physiology ; Tumor Necrosis Factor/immunology/*physiology

OBJECTIVETo investigate the gene expression of 4-1BB in peripheral blood mononuclear cells (PBMCs) and the possible significance of the 4-1BB pathway after clinical orthotopic liver transplantation (OLT).

METHODS4-1BB mRNA levels in PBMCs from 22 OLT patients were analyzed by RT-PCR. 4-1BB protein expressed on the surface of CD(4)(+) and CD(8)(+) T cells were detected by flow cytometry, and visualized with direct immunofluorescence and confocal fluorescence microscopy. Patients with primary liver cancer (PLC) and healthy volunteers served as controls. Six cases of recently performed liver transplantation were also observed in this study.

RESULTS4-1BB mRNA was detected in PBMCs from both liver transplant patients with long-term graft acceptance (22 cases) and from transplant patients on day 1 to day 3 post-transplantation (6 cases), but was not found in PBMCs from transplant patients on day 7 to day 30 post-transplantation (6 cases). 4-1BB mRNA was also not found in samples from 8 of the healthy controls and 7 of the PLC patients, though very low expression was detected in the other 4 healthy volunteers and 6 PLC patients. Simultaneously, 4-1BB protein was expressed at nearly undetectable levels on CD(4)(+) and CD(8)(+) T cells from healthy controls, PLC patients, as well as OLT patients within the first month post-transplantation (6 cases). However, 4-1BB expression was found on the surface of CD(4)(+) and CD(8)(+) T cells from liver transplant patients with long-term graft acceptance. Direct immunofluorescent staining and confocal fluorescence microscopy clearly revealed evidence of 4-1BB protein on cell membranes of CD(4)(+) and CD(8)(+) T cells from liver transplant patients with long-term graft acceptance. Simultaneously, a significantly higher percentage of CD(3)(+) CD(25)(+) T cells were found in liver transplant patients with long-term graft acceptance group as compared with the healthy control group (P < 0.05). The expression of 4-1BB protein on T cells did not correlate with the survival time of OLT patients postoperation.

CONCLUSIONSThis study demonstrates that although patients remain in stable condition after liver transplantation under the treatment of immunosuppressants, activated T cells are present to some extent and 4-1BB protein may be involved in this process. Effector T-cells can exert permanent immunoresponses against grafts under these circumstances. Therefore, we conclude that a new immune response balance is established under the combination of both treatment with immunosuppressants and natural immune responses against alloantigens. Manipulation of the 4-1BB/4-1BBL pathway may provide a therapeutic technique for prolonging graft survival.

Adult ; Antigens, CD ; Female ; Gene Expression ; Humans ; Leukocytes, Mononuclear ; chemistry ; Liver Transplantation ; Male ; Middle Aged ; Receptors, Nerve Growth Factor ; genetics ; physiology ; Receptors, Tumor Necrosis Factor ; genetics ; physiology ; Tumor Necrosis Factor Receptor Superfamily, Member 9

Tumor necrosis factor (TNF) -alpha induces pleiotropic cellular effects through a 55kDa, type 1 receptor (TNFR1) and a 75kDa type 2 receptor (TNFR2). Moreover, it participates in the pathogenesis of several CNS diseases, including demyelinating diseases. TNF- receptors are differentially expressed and are regulated in many cell types. However, data regarding the TNF-alpha receptor expression and regulation in human astrocytes is limited to date. We investigated TNF-alpha receptor expression, its regulation by cytokines, and its functional role in primary cultured human fetal astrocytes, which are the most abundant cellular population in the central nervous system and are known to be immunologically active. In this study, astrocytes were found to constitutively and predominantly transcribe, translate and shed TNFR1 rather than TNFR2, but TNFR2 expression was increased by adding TNF-alpha, IL-1, and IFN-gamma, but not by adding LPS. To determine the functional roles of TNFR1 and TNFR2 on TNF induction, we investigated NF-kappaB activation and TNF-alpha induction after neutralizing TNFR1 and TNFR2 by an antibody treatment. We found that NF-kappaB activation and TNF-alpha induction are blocked by TNFR1 neutralizing antibody treatments.
Receptors, Tumor Necrosis Factor, Type II/genetics/*metabolism/physiology ; Receptors, Tumor Necrosis Factor, Type I/genetics/*metabolism/physiology ; RNA, Messenger/metabolism ; NF-kappa B/metabolism ; Humans ; Gene Expression Regulation ; Fetus/cytology ; Cytokines/*pharmacology ; Cells, Cultured ; Astrocytes/drug effects/*metabolism

BACKGROUNDRev is necessary for exporting unspliced and incompletely spliced intron containing HIV mRNAs and for HIV replication. The aim of this study is to develop a kind of selective suicide construct that can specifically and directly induce HIV infected cells into apoptosis based on the high affinity of Rev and Rev response element (RRE).

METHODSMolecular-cloning technique was used to synthesis Rev dependent TNF-R1 expression construct pDM128-TNF-R1 (pT128) that contains RRE and TNFR1 gene. Restriction digestion, Polymerase Chain Reaction (PCR) and DNA sequencing were processed and the exactness and correctness of the inserted TNF-R1 gene in pT128 were confirmed repeatedly. The expression of pT128 co-transfected with different combination of other plasmids by calcium phosphate-DNA co-precipitation in Helas and by gene gun transfection in keratinocytes was further tested by flow-cytometry and cell counted under microscope.

RESULTSThe new plasmid specifically expressed TNF-R1 in Helas when co-transfected with pRev but did not when without pRev. Indirect expression of TNF-R1 from pT128 was slower than the direct expression of that from Hu p60 TNFR1 in pDC302 (pT60), but all those pT60 or pT128 transfected cells showed apoptosis at last while TNF-R1 was sufficiently expressed. Other kinds of Rev expression construct such as pAD8 and a chimeric HIV vaccine also can switched on the selective expression of pT128. Not only Rev-dependent expression in Helas, pT128 also normally expressed its TNF-R1 in keratinocytes. Co-transfected with pRev or pAD8 that expressed Rev, pT128 expressed TNF-R1 and induced apoptosis of green fluorescent keratinocytes in skin explant. The number of green fluorescent keratinocytes co-transfected by pT128 plus pRev or pAD8 was gradually outnumbered by that co-transfected by pT128 only. The difference was more significant after culturing for 72 hours.

CONCLUSIONSRev dependent pT128 is able to selectively induce apoptosis of HIV-infected or Rev-expressed target cells by expression of TNF-R1. The new strategy based on manipulation of the regulatory protein of HIV may be valuable in design of new HIV vaccine.

AIDS Vaccines ; immunology ; Apoptosis ; Biolistics ; Cell Line, Tumor ; Gene Products, rev ; physiology ; Genes, env ; physiology ; Genetic Vectors ; Humans ; Keratinocytes ; metabolism ; Plasmids ; Receptors, Tumor Necrosis Factor, Type I ; genetics

Regulation of P2X7 receptor expression is of interest because activation of this receptor by extracellular ATP triggers a wide variety of cell functions in leukocytes. However, its expression and modulation in human peripheral blood mononuclear cells (PBMC) and monocytes remain unclear. RT-PCR was used to detect the constitutive level of P2X7 receptor and the levels upon stimulation with bacteria, bacterial product, mitogen and various cytokines in human PBMC and monocytes. P2X7 receptor mRNA was detected in PBMC and monocytes. P2X7 receptor expression in PBMC was up-regulated by interleukin-2, -4, -6 (IL-2, IL-4, IL-6) tumour necrosis factor-alpha (TNF-alpha), lipopolysaccharide (LPS) and heat-inactivated Staphylococcus aureus Cowan strain I (SAC). However, interferon-gamma (IFN-gamma), granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF) and phytohemagglutinin-M (PHA-M) had little effect on the expression of P2X7 receptor. Furthermore, LPS and M-CSF could up-regulate P2X7 receptor expression in monocytes, while IFN-gamma, TNF-alpha and GM-CSF had weak effects, but pretreatment with these inducers could not further enhance LPS-stimulated P2X7 receptor expression in monocytes. The results obtained demonstrate that inflammatory stimuli drive P2X7 expression, thus supporting the hypothesis that P2X7 receptor may play a role in the inflammatory responses against bacteria infection, which need further verification.
Humans ; Interleukin-2 ; physiology ; Interleukin-4 ; physiology ; Leukocytes, Mononuclear ; drug effects ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Receptors, Purinergic P2X7 ; genetics ; metabolism ; Tumor Necrosis Factor-alpha ; physiology