Tumour necrosis factor (TNF) is a cytokine belonging to a family of trimeric proteins; it has been shown to be a key mediator in autoimmune diseases such as rheumatoid arthritis and Crohn's disease. ...While TNF is the target of several successful biologic drugs, attempts to design small molecule therapies directed to this cytokine have not led to approved products. Here we report the discovery of potent small molecule inhibitors of TNF that stabilise an asymmetrical form of the soluble TNF trimer, compromising signalling and inhibiting the functions of TNF in vitro and in vivo. This discovery paves the way for a class of small molecule drugs capable of modulating TNF function by stabilising a naturally sampled, receptor-incompetent conformation of TNF. Furthermore, this approach may prove to be a more general mechanism for inhibiting protein-protein interactions.
TNF is a pleiotropic cytokine with important functions in homeostasis and disease pathogenesis. Recent discoveries have provided insights into TNF biology that introduce new concepts for the ...development of therapeutics for TNF-mediated diseases. The model of TNF receptor signalling has been extended to include linear ubiquitination and the formation of distinct signalling complexes that are linked with different functional outcomes, such as inflammation, apoptosis and necroptosis. Our understanding of TNF-induced gene expression has been enriched by the discovery of epigenetic mechanisms and concepts related to cellular priming, tolerization and induction of 'short-term transcriptional memory'. Identification of distinct homeostatic or pathogenic TNF-induced signalling pathways has introduced the concept of selectively inhibiting the deleterious effects of TNF while preserving its homeostatic bioactivities for therapeutic purposes. In this Review, we present molecular mechanisms underlying the roles of TNF in homeostasis and inflammatory disease pathogenesis, and discuss novel strategies to advance therapeutic paradigms for the treatment of TNF-mediated diseases.
Nuclear factor κB (NF-κB) essential modulator (NEMO), a regulatory component of the IκB kinase (IKK) complex, controls NF-κB activation through its interaction with ubiquitin chains. We show here ...that stimulation with interleukin-1 (IL-1) and TNF induces a rapid and transient recruitment of NEMO into punctate structures that are anchored at the cell periphery. These structures are enriched in activated IKK kinases and ubiquitinated NEMO molecules, which suggests that they serve as organizing centers for the activation of NF-κB. These NEMO-containing structures colocalize with activated TNF receptors but not with activated IL-1 receptors. We investigated the involvement of nondegradative ubiquitination in the formation of these structures, using cells deficient in K63 ubiquitin chains or linear ubiquitin chain assembly complex (LUBAC)-mediated linear ubiquitination. Our results indicate that, unlike TNF, IL-1 requires K63-linked and linear ubiquitin chains to recruit NEMO into higher-order complexes. Thus, different mechanisms are involved in the recruitment of NEMO into supramolecular complexes, which appear to be essential for NF-κB activation.
► TNF-α has both immunoregulatory and a proinflammatory function on a variety of cells of the innate and adaptive immune system. ► TNF-α level have been associated with disease activity in SLE and ...certain clinical features such as nephritis. ► Genetic studies suggest that the TNF-α gene polymorphism is involved in the susceptibility of SLE. ► However the role of TNF-α in SLE is still controversial.
The Tumor Necrosis Factor-alpha (TNF-α) is a pleiotropic cytokine that produces different stimuli in various physiological and pathological conditions. TNF-α contributes importantly to the development of T cells, B cells, and dendritic cells. However, TNF-α is also a potent inflammatory mediator and apoptosis inducer. The significance of the TNF-α involvement in the pathogenesis of systemic lupus erythematosus (SLE) remains controversial. From the genetic standpoint, a number of studies suggest that the TNF-α gene polymorphism is involved in the susceptibility of SLE. Moreover, there is a close association between the TNF-α gene expression and clinical manifestations. In addition, the increased serum level of TNF-α is observed in SLE patients and associated with disease activity and certain systemic manifestations. Treatment with anti-TNF agents is, however, controversial in SLE since induction of antinuclear antibodies, anti-dsDNA, anticardiolipin antibodies, and cases of drug-induced lupus have been observed in rheumatoid arthritis patients. In this context, this study reviewed the importance of TNF-α in the pathogenesis of SLE.
TNF-α is a cytokine involved in systemic inflammation and regulation of immune cells. It is produced chiefly by activated macrophages as a membrane or secreted form. In rainbow trout, two TNF-α ...molecules were described previously. In this article, we report a third TNF-α (TNF-α3) that has only low identities to known trout molecules. Phylogenetic tree and synteny analyses of trout and other fish species suggest that two types (named I and II) of TNF-α exist in teleost fish. The fish type-II TNF-α has a short stalk that may impact on its enzymatic release or restrict it to a membrane-bound form. The constitutive expression of trout TNF-α3 was generally lower than the other two genes in tissues and cell lines, with the exception of the macrophage RTS-11 cell line, in which expression was higher. Expression of all three TNF-α isoforms could be modulated by crude LPS, peptidoglycan, polyinosinic:polycytidylic acid, and rIFN-γ in cell lines and primary macrophages, as well as by bacterial and viral infections. TNF-α3 is the most responsive gene at early time points post-LPS stimulation and can be highly induced by the T cell-stimulant PHA, suggesting it is a particularly important TNF-α isoform. rTNF-α3 produced in CHO cells was bioactive in different cell lines and primary macrophages. In the latter, it induced the expression of proinflammatory cytokines (IL-1β, IL-6, IL-8, IL-17C, and TNF-αs), negative regulators (SOCS1-3, TGF-β1b), antimicrobial peptides (cathelicidin-1 and hepcidin), and the macrophage growth factor IL-34, verifying its key role in the inflammatory cytokine network and macrophage biology of fish.
Necroptosis is a form of programmed cell death that depends on the activation of receptor interacting protein kinase-1 (RIPK1) and RIPK3 by receptors such as tumor necrosis factor (TNF) receptor-1. ...Structural studies indicate that activation of RIPK3 by RIPK1 involves the formation of oligomers via interactions of the RIP homotypic interaction motif (RHIM) domains shared by both proteins; however, the molecular mechanisms by which this occurs are not fully understood. To gain insight into this process, we constructed versions of RIPK3 that could be induced to dimerize or oligomerize in response to a synthetic drug. Using this system, we find that although the formation of RIPK3 dimers is itself insufficient to trigger cell death, this dimerization seeds a RHIM-dependent complex, the propagation and stability of which is controlled by caspase-8 and RIPK1. Consistent with this idea, we find that chemically enforced oligomerization of RIPK3 is sufficient to induce necroptosis, independent of the presence of the RHIM domain, TNF stimulation or RIPK1 activity. Further, although RIPK1 contributes to TNF-mediated RIPK3 activation, we find that RIPK1 intrinsically suppresses spontaneous RIPK3 activation in the cytosol by controlling RIPK3 oligomerization. Cells lacking RIPK1 undergo increased spontaneous RIPK3-dependent death on accumulation of the RIPK3 protein, while cells containing a chemically inhibited or catalytically inactive form of RIPK1 are protected from this form of death. Together, these data indicate that RIPK1 can activate RIPK3 in response to receptor signaling, but also acts as a negative regulator of spontaneous RIPK3 activation in the cytosol.
A novel nanomedicine, CYT-6091, constructed by simultaneously binding recombinant human tumor necrosis factor alpha (rhTNF) and thiolyated polyethylene glycol to the surface of 27-nm colloidal gold ...particles, was tested in a phase I dose escalation clinical trial in advanced stage cancer patients.
CYT-6091, whose dosing was based on the amount of rhTNF in the nanomedicine, was injected intravenously, and 1 cycle of treatment consisted of 2 treatments administered 14 days apart.
Doses from 50 μg/m(2) to 600 μg/m(2) were well tolerated, and no maximum tolerated dose (MTD) was reached, as the highest dose exceeded the target dosage of 1-mg rhTNF per treatment, exceeding the previous MTD for native rhTNF by 3-fold. The first 2 patients on the study, each receiving 50 μg/m(2), did not receive any prophylactic antipyretics or H2 blockade. A predicted, yet controllable fever occurred in these patients, so all subsequently treated patients received prophylactic antipyretics and H2 blockers. However, even at the highest dose rhTNF's dose-limiting toxic effect of hypotension was not seen. Using electron microscopy to visualize nanoparticles of gold in patient biopsies of tumor and healthy tissue showed that patient biopsies taken 24 hours after treatment had nanoparticles of gold in tumor tissue.
These data indicate that rhTNF formulated as CYT-6091 may be administered systemically at doses of rhTNF that were previously shown to be toxic and that CYT-6091 may target to tumors. Future clinical studies will focus on combining CYT-6091 with approved chemotherapies for the systemic treatment of nonresectable cancers.
Monocyte/macrophage recruitment correlates strongly with the progression of diabetic nephropathy. Tumor necrosis factor-α (TNF-α) is produced by monocytes/macrophages but the direct role of TNF-α ...and/or macrophage-derived TNF-α in the progression of diabetic nephropathy remains unclear. Here we tested whether inhibition of TNF-α confers kidney protection in diabetic nephropathy via a macrophage-derived TNF-α-dependent pathway. Compared to vehicle-treated mice, blockade of TNF-α with a murine anti-TNF-α antibody conferred kidney protection in Ins2Akita mice as indicated by reductions in albuminuria, plasma creatinine, histopathologic changes, kidney macrophage recruitment, and plasma inflammatory cytokine levels at 18 weeks of age. To assess the direct role of macrophage-derived TNF-α in diabetic nephropathy, we generated macrophage-specific TNF-α-deficient mice (CD11bCre/TNF-αFlox/Flox). Conditional ablation of TNF-α in macrophages significantly reduced albuminuria, the increase in plasma creatinine and blood urea nitrogen, histopathologic changes, and kidney macrophage recruitment compared to diabetic TNF-αFlox/Flox control mice after 12 weeks of streptozotocin-induced diabetes. Thus, production of TNF-α by macrophages plays a major role in diabetic renal injury. Hence, blocking TNF-α could be a novel therapeutic approach for treatment of diabetic nephropathy.
Macrophages contribute to the pathogenesis of rheumatoid arthritis (RA). They can display different states of activation or "polarization," notably the so-called inflammatory "M1" and the various ...alternative "M2" polarizations, characterized by distinct functions. Data regarding the effects of RA anti-cytokine biological disease-modifying anti-rheumatic drugs (bDMARDs) on macrophage polarization are scarce. We aimed to assess
modulation of macrophage polarization by bDMARDs targeting pro-inflammatory cytokines in RA. We generated monocyte derived macrophages using blood samples from 20 RA patients with active RA and 30 healthy controls. We evaluated
the impact on M1 inflammatory macrophages of: etanercept (ETA), adalimumab (ADA), certolizumab (CZP), tocilizumab (TCZ), and rituximab (RTX). We assessed the impact on macrophage polarization using flow cytometry and RTqPCR to study the expression of surface markers and perform functional studies of cytokine production, phagocytosis, and negative feedback control of inflammation. Among evaluated bDMARDs, anti-TNF agents modulated the polarization of inflammatory macrophages by decreasing inflammatory surface markers (CD40, CD80) and favoring alternative markers (CD16, CD163, MerTK). Anti-TNF agents also induced alternative functions in macrophages activated in inflammatory condition with (i) the inhibition of inflammatory cytokines (TNF, IL-6, IL-12), (ii) an increase in phagocytosis. These findings were mechanistically related to an increase in early IL-10 production, responsible for higher negative feedback control of inflammation involving SOCS3 and Gas6. This IL-10 effect was STAT3-dependent. Anti-TNF agents not only inhibit
inflammatory functions of macrophages, but also favor resolution of inflammation through polarization toward alternative features specifically involving the IL-10/STAT3 axis.
The aging inflammatory microenvironment surrounding Leydig cells is linked to reduced testosterone levels in males. Tumor necrosis factor alpha-induced protein 3 (TNFAIP3) acts as a critical ...anti-inflammatory factor in various aging-related diseases. This study aims to investigate the protective effect of TNFAIP3 on testosterone production in Leydig cells under an aging inflammatory microenvironment.
Bioinformatics analysis examined TNFAIP3 expression differences in aging rat testes and validated the findings in aging mouse testes. In vitro models of inflammation were established using two Leydig cell lines, with tumor necrosis factor alpha (TNF-α) as the inflammatory factor. Lentiviral transduction was utilized to manipulate TNFAIP3 expression in these cell lines. Transcriptomic sequencing identified differentially expressed genes in TNFAIP3-overexpressing cells.
Bioinformatics analysis and validation experiments revealed increased inflammatory signaling and elevated TNFAIP3 expression in aging rat and mouse testes. TNFAIP3 knockdown worsened testosterone synthesis inhibition and apoptosis in cells, while TNFAIP3 overexpression reversed these effects. Transcriptome analysis identified alterations in the P38MAPK pathway following TNFAIP3 overexpression. TNFAIP3 knockdown enhanced TNF-induced P38MAPK signaling, whereas its overexpression attenuated this effect. TNFAIP3 was found to regulate testosterone synthesis by upregulating CEBPB expression.
TNFAIP3 exhibits inhibitory effects on apoptosis and promotes testosterone production in Leydig cells. The protective influence of TNFAIP3 on Leydig cells within an inflammatory microenvironment is likely mediated through by inhibiting the P38MAPK pathway and upregulating CEBPB expression.
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