The TNFR1 antagonist Atrosimab reduces neuronal loss, glial activation and memory deficits in an acute mouse model of neurodegeneration

Tumor necrosis factor alpha (TNF-α) and its key role in modulating immune responses has been widely recognized as a therapeutic target for inflammatory and neurodegenerative diseases. Even though inhibition of TNF-α is beneficial for the treatment of certain inflammatory diseases, total neutralization of TNF-α largely failed in the treatment of neurodegenerative diseases. TNF-α exerts distinct functions depending on interaction with its two TNF receptors, whereby TNF receptor 1 (TNFR1) is associated with neuroinflammation and apoptosis and TNF receptor 2 (TNFR2) with neuroprotection and immune regulation. Here, we investigated the effect of administering the TNFR1-specific antagonist Atrosimab, as strategy to block TNFR1 signaling while maintaining TNFR2 signaling unaltered, in an acute mouse model for neurodegeneration. In this model, a NMDA-induced lesion that mimics various hallmarks of neurodegenerative diseases, such as memory loss and cell death, was created in the nucleus basalis magnocellularis and Atrosimab or control protein was administered centrally. We showed that Atrosimab attenuated cognitive impairments and reduced neuroinflammation and neuronal cell death. Our results demonstrate that Atrosimab is effective in ameliorating disease symptoms in an acute neurodegenerative mouse model. Altogether, our study indicates that Atrosimab may be a promising candidate for the development of a therapeutic strategy for the treatment of neurodegenerative diseases.

Glycine is a competitive antagonist of the TNF receptor mediating the expression of inflammatory cytokines in 3T3-L1 adipocytes

OBJECTIVE

To determine the involvement of TNF-α and glycine receptors in the inhibition of pro-inflammatory adipokines in 3T3-L1 cells.

METHODS

RT-PCR evidenced glycine receptors in 3T3-L1 adipocytes. 3T3-L1 cells were transfected with siRNA for the glycine (Glrb) and TNF1a (Tnfrsf1a) receptors and confirmed by confocal microscopy. Transfected cells were treated with glycine (10 mM). The expressions of TNF-α and IL-6 mRNA were measured by qRT-PCR, while concentrations were quantified by ELISA.

RESULTS

Glycine decreased the expression and concentration of TNF-α and IL-6; this effect did not occur in the absence of TNF-α receptor due to siRNA. In contrast, glycine produced only slight changes in the expression of TNF-α and IL-6 in the absence of the glycine receptor due to siRNA. A docking analysis confirmed the possibility of binding glycine to the TNF-α1a receptor.

CONCLUSION

These findings support the idea that glycine could partially inhibit the binding of TNF-α to its receptor and provide clues about the mechanisms by which glycine inhibits the secretion of pro-inflammatory adipokines in adipocytes through the TNF-α receptor.

Alleviation of Ultraviolet-B Radiation-Induced Photoaging by a TNFR Antagonistic Peptide, TNFR2-SKE

Ultraviolet (UV) radiation of the sunlight, especially UVA and UVB, is the primary environmental cause of skin damage, including topical inflammation, premature skin aging, and skin cancer. Previous reports show that activation of nuclear factor-κB (NF-κB) in human skin fibroblasts and keratinocytes after UV exposure induces the expression and release of proinflammatory cytokines, such as interleukin-1 (IL-1) and tumor necrosis factor-α (TNF-α), and subsequently leads to the production of matrix metalloproteases (MMPs) and growth factor basic fibroblast growth factor (bFGF). Here, we demonstrated that TNFR2-SKEE and TNFR2-SKE, oligopeptides from TNF receptor-associated factor 2 (TRAF2)-binding site of TNF receptor 2 (TNFR2), strongly inhibited the interaction of TNFR1 as well as TNFR2 with TRAF2. In particular, TNFR2-SKE suppressed UVB- or TNF-α-induced nuclear translocalization of activated NF-κB in mouse fibroblasts. It decreased the expression of bFGF, MMPs, and COX2, which were upregulated by TNF-α, and increased procollagen production, which was reduced by TNF-α. Furthermore, TNFR2-SKE inhibited the UVB-induced proliferation of keratinocytes and melanocytes in the mouse skin and the infiltration of immune cells into inflamed tissues. These results suggest that TNFR2-SKE may possess the clinical potency to alleviate UV-induced photoaging in human skin.

Monovalent TNF receptor 1-selective antibody with improved affinity and neutralizing activity

Selective inhibition of tumor necrosis factor (TNF) signaling through the proinflammatory axis of TNF-receptor 1 (TNFR1) while leaving pro-survival and regeneration-promoting signals via TNFR2 unaffected is a promising strategy to circumvent limitations of complete inhibition of TNF action by the approved anti-TNF drugs. A previously developed humanized antagonistic TNFR1-specific antibody, ATROSAB, showed potent inhibition of TNFR1-mediated cellular responses. Because the parental mouse antibody H398 possesses even stronger inhibitory potential, we scrutinized the specific binding parameters of the two molecules and revealed a faster dissociation of ATROSAB compared to H398. Applying affinity maturation and re-engineering of humanized variable domains, we generated a monovalent Fab derivative (13.7) of ATROSAB that exhibited increased binding to TNFR1 and superior inhibition of TNF-mediated TNFR1 activation, while lacking any agonistic activity even in the presence of cross-linking antibodies. In order to improve its pharmacokinetic properties, several Fab13.7-derived molecules were generated, including a PEGylated Fab, a mouse serum albumin fusion protein, a half-IgG with a dimerization-deficient Fc, and a newly designed Fv-Fc format, employing the knobs-into-holes technology. Among these derivatives, the Fv13.7-Fc displayed the best combination of improved pharmacokinetic properties and antagonistic activity, thus representing a promising candidate for further clinical development.

Novel anti-tumour necrosis factor receptor-1 (TNFR1) domain antibody prevents pulmonary inflammation in experimental acute lung injury

BACKGROUND

Tumour necrosis factor alpha (TNF-α) is a pleiotropic cytokine with both injurious and protective functions, which are thought to diverge at the level of its two cell surface receptors, TNFR1 and TNFR2. In the setting of acute injury, selective inhibition of TNFR1 is predicted to attenuate the cell death and inflammation associated with TNF-α, while sparing or potentiating the protective effects of TNFR2 signalling. We developed a potent and selective antagonist of TNFR1 (GSK1995057) using a novel domain antibody (dAb) therapeutic and assessed its efficacy in vitro, in vivo and in a clinical trial involving healthy human subjects.

METHODS

We investigated the in vitro effects of GSK1995057 on human pulmonary microvascular endothelial cells (HMVEC-L) and then assessed the effects of pretreatment with nebulised GSK1995057 in a non-human primate model of acute lung injury. We then tested translation to humans by investigating the effects of a single nebulised dose of GSK1995057 in healthy humans (n=37) in a randomised controlled clinical trial in which subjects were subsequently exposed to inhaled endotoxin.

RESULTS

Selective inhibition of TNFR1 signalling potently inhibited cytokine and neutrophil adhesion molecule expression in activated HMVEC-L monolayers in vitro (P<0.01 and P<0.001, respectively), and also significantly attenuated inflammation and signs of lung injury in non-human primates (P<0.01 in all cases). In a randomised, placebo-controlled trial of nebulised GSK1995057 in 37 healthy humans challenged with a low dose of inhaled endotoxin, treatment with GSK1995057 attenuated pulmonary neutrophilia, inflammatory cytokine release (P<0.01 in all cases) and signs of endothelial injury (P<0.05) in bronchoalveolar lavage and serum samples.

CONCLUSION

These data support the potential for pulmonary delivery of a selective TNFR1 dAb as a novel therapeutic approach for the prevention of acute respiratory distress syndrome.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT01587807.

Pharmacokinetic and Pharmacodynamic Characterisation of an Anti-Mouse TNF Receptor 1 Domain Antibody Formatted for In Vivo Half-Life Extension

Tumour Necrosis Factor-α (TNF-α) inhibition has been transformational in the treatment of patients with inflammatory disease, e.g. rheumatoid arthritis. Intriguingly, TNF-α signals through two receptors, TNFR1 and TNFR2, which have been associated with detrimental inflammatory and beneficial immune-regulatory processes, respectively. To investigate if selective TNFR1 inhibition might provide benefits over pan TNF-α inhibition, tools to investigate the potential impact of pharmacological intervention are needed. Receptor-deficient mice have been very insightful, but are not reversible and could distort receptor cross-talk, while inhibitory anti-TNFR1 monoclonal antibodies have a propensity to induce receptor agonism. Therefore, we set out to characterise a monovalent anti-TNFR1 domain antibody (dAb) formatted for in vivo use. The mouse TNFR1 antagonist (DMS5540) is a genetic fusion product of an anti-TNFR1 dAb with an albumin-binding dAb (AlbudAb). It bound mouse TNFR1, but not human TNFR1, and was an antagonist of TNF-α-mediated cytotoxicity in a L929 cell assay. Surprisingly, the dAb did not compete with TNF-α for TNFR1-binding. This was supported by additional data showing the anti-TNFR1 epitope mapped to a single residue in the first domain of TNFR1. Pharmacokinetic studies of DMS5540 in mice over three doses (0.1, 1.0 and 10 mg/kg) confirmed extended in vivo half-life, mediated by the AlbudAb, and demonstrated non-linear clearance of DMS5540. Target engagement was further confirmed by dose-dependent increases in total soluble TNFR1 levels. Functional in vivo activity was demonstrated in a mouse challenge study, where DMS5540 provided dose-dependent inhibition of serum IL-6 increases in response to bolus mouse TNF-α injections. Hence, DMS5540 is a potent mouse TNFR1 antagonist with in vivo pharmacokinetic and pharmacodynamic properties compatible with use in pre-clinical disease models and could provide a useful tool to dissect the individual contributions of TNFR1 and TNFR2 in homeostasis and disease.

TNFα causes thrombin-dependent vagal neuron apoptosis in inflammatory bowel disease

BACKGROUND

The role of peripheral tumor necrosis factor alpha (TNFα) in inflammatory bowel disease (IBD) is well established, but its central nervous system (CNS) effects are not understood. Thrombin, another mediator of inflammation in IBD, has been implicated in CNS vagal neuron apoptosis in the dorsal motor nucleus of the vagus (DMV). This study evaluates DMV TNFα exposure, characterizes effects of TNFα on DMV neurons, and identifies a relationship between DMV TNFα and thrombin in IBD.

METHODS

2,4,6-Trinitrobenzene sulfonic acid was administered via enema to induce colonic inflammation in rats. TNFα in serum, cerebrospinal fluid (CSF), and DMV tissues were determined by ELISA and DMV TNFα expression by quantitative reverse transcription PCR (RT-PCR). TNFα was administered into the fourth intracerebral ventricle (4 V) adjacent to the DMV, with and without blockade of TNF receptor 1 (TNFR1) and the thrombin receptor proteinase-activated receptor 1 (PAR1). Immunofluorescence was used to evaluate microglial activation (Cd11b) and prothrombin presence in DMV sections. Apoptosis was examined using terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling (TUNEL) and activated caspase-3 immunofluorescence.

RESULTS

IBD is associated with increased TNFα protein in serum, CSF, and DMV tissue; DMV TNFα transcription is also increased. TNFα (4 V) caused a 54 % increase in microglial activation, a 27 % increase in DMV prothrombin protein, and a 31 % increase in vagal neuron apoptosis by TUNEL. There was a 52 % increase in activated caspase-3 immunofluorescence in TNFα-treated animals (p < 0.05). All effects of 4 V TNFα were prevented by TNFR1 blockade. TNFα-induced apoptosis was prevented by PAR1 blockade.

CONCLUSIONS

IBD is associated with DMV exposure to TNFα, causing excess DMV prothrombin and vagal apoptosis.

A novel role for the apoptosis inhibitor ARC in suppressing TNFα-induced regulated necrosis

TNFα signaling can promote apoptosis or a regulated form of necrosis. ARC (apoptosis repressor with CARD (caspase recruitment domain)) is an endogenous inhibitor of apoptosis that antagonizes both the extrinsic (death receptor) and intrinsic (mitochondrial/ER) apoptosis pathways. We discovered that ARC blocks not only apoptosis but also necrosis. TNFα-induced necrosis was abrogated by overexpression of wild-type ARC but not by a CARD mutant that is also defective for inhibition of apoptosis. Conversely, knockdown of ARC exacerbated TNFα-induced necrosis, an effect that was rescued by reconstitution with wild-type, but not CARD-defective, ARC. Similarly, depletion of ARC in vivo exacerbated necrosis caused by infection with vaccinia virus, which elicits severe tissue damage through this pathway, and sensitized mice to TNFα-induced systemic inflammatory response syndrome. The mechanism underlying these effects is an interaction of ARC with TNF receptor 1 that interferes with recruitment of RIP1, a critical mediator of TNFα-induced regulated necrosis. These findings extend the role of ARC from an apoptosis inhibitor to a regulator of the TNFα pathway and an inhibitor of TNFα-mediated regulated necrosis.

Antibody-mediated inhibition of TNFR1 attenuates disease in a mouse model of multiple sclerosis

Tumour necrosis factor (TNF) is a proinflammatory cytokine that is known to regulate inflammation in a number of autoimmune diseases, including multiple sclerosis (MS). Although targeting of TNF in models of MS has been successful, the pathological role of TNF in MS remains unclear due to clinical trials where the non-selective inhibition of TNF resulted in exacerbated disease. Subsequent experiments have indicated that this may have resulted from the divergent effects of the two TNF receptors, TNFR1 and TNFR2. Here we show that the selective targeting of TNFR1 with an antagonistic antibody ameliorates symptoms of the most common animal model of MS, experimental autoimmune encephalomyelitis (EAE), when given following both a prophylactic and therapeutic treatment regime. Our results demonstrate that antagonistic TNFR1-specific antibodies may represent a therapeutic approach for the treatment of MS in the future.

Screening bicyclic peptide libraries for protein-protein interaction inhibitors: discovery of a tumor necrosis factor-α antagonist

Protein-protein interactions represent a new class of exciting but challenging drug targets, because their large, flat binding sites lack well-defined pockets for small molecules to bind. We report here a methodology for chemical synthesis and screening of large combinatorial libraries of bicyclic peptides displayed on rigid small-molecule scaffolds. With planar trimesic acid as the scaffold, the resulting bicyclic peptides are effective for binding to protein surfaces such as the interfaces of protein-protein interactions. Screening of a bicyclic peptide library against tumor necrosis factor-α (TNFα) identified a potent antagonist that inhibits the TNFα-TNFα receptor interaction and protects cells from TNFα-induced cell death. Bicyclic peptides of this type may provide a general solution for inhibition of protein-protein interactions.

Amelioration of liver injury by continuously targeted intervention against TNFRp55 in rats with acute-on-chronic liver failure

Background

Acute-on-chronic liver failure (ACLF) is an acute deterioration of established liver disease. Blocking the TNF (tumor necrosis factor)/TNFR (tumor necrosis factor receptor) 1 pathway may reduce hepatocyte apoptosis/necrosis, and subsequently decrease mortality during development of ACLF. We demonstrated that a long-acting TNF antagonist (soluble TNF receptor: IgG Fc [sTNFR:IgG-Fc]) prevented/reduced development of acute liver failure by blocking the TNF/TNFR1 (TNFRp55) pathway. However, it is still unclear if sTNFR:IgG-Fc can inhibit hepatocyte damage during development of ACLF.

Methodology

Chronic liver disease (liver fibrosis/cirrhosis) was induced in Wistar rats by repeatedly challenging with human serum albumin (HSA), and confirmed by histopathology. ACLF was induced with D-galactosamine (D-GalN)/lipopolysaccharide (LPS) i.p. in the rats with chronic liver disease. Serum and liver were collected for biochemical, pathological and molecular biological examinations.

Principal Findings

Reduced mortality was observed in sTNFR:IgG-Fc treated ACLF rats, consistent with reduced interleukin (IL)-6 levels in serum and liver, as well as reduced hepatic caspase-3 activity, compared to that of mock treated group. Reduced hepatic damage was confirmed with histopathology in the sTNFR:IgG-Fc treated group, which is consistent with reduced Bcl-2 and Bax, at mRNA and protein levels, but increased hepatocyte proliferation (PCNA). This is also supported by the findings that caspase-3 production was up-regulated significantly in ACLF group compared to the mock treated group. Moreover, up-regulated caspase-3 was inhibited following sTNFR:IgG-Fc treatment. Finally, there was up-regulation of hepatic IL-22R in sTNFR:IgG-Fc treated ACLF rats.

Conclusions

sTNFR:IgG-Fc improved survival rate during development of ACLF via ameliorating liver injury with a potential therapeutic value.

Lymphotoxin-α is a novel adiponectin expression suppressor following myocardial ischemia/reperfusion

Recent clinical observations demonstrate adiponectin (APN), an adipocytokine with potent cardioprotective actions, is significantly reduced following myocardial ischemia/reperfusion (MI/R). However, mechanisms responsible for MI/R-induced hypoadiponectinemia remain incompletely understood. Adult male mice were subjected to 30-min MI followed by varying reperfusion periods. Adipocyte APN mRNA and protein expression and plasma APN and TNFα concentrations were determined. APN expression/production began to decline 3 h after reperfusion (reaching nadir 12 h after reperfusion), returning to control levels 7 days after reperfusion. Plasma TNFα levels began to increase 1 h after reperfusion, peaking at 3 h and returning to control levels 24 h after reperfusion. TNFα knockout significantly increased plasma APN levels 12 h after reperfusion but failed to improve APN expression/production 72 h after reperfusion. In contrast, TNF receptor-1 (TNFR1) knockout significantly restored APN expression 12 and 72 h after reperfusion, suggesting that other TNFR1 binding cytokines contribute to MI/R-induced APN suppression. Among many cytokines increased after MI/R, lymphotoxin-α (LTα) was the only cytokine remaining elevated 24-72 h after reperfusion. LTα knockout did not augment APN levels 12 h post-reperfusion, but did so by 72 h. Finally, in vitro treatment of adipocytes with TNFα and LTα at concentrations seen in MI/R plasma additively inhibited APN expression/production in TNFR1-dependent fashion. Our study demonstrates for the first time that LTα is a novel suppressor of APN expression and contributes to the sustained hypoadiponectinemia following MI/R. Combining anti-TNFα with anti-LTα strategies may achieve the best effects restoring APN in MI/R patients.

Japonicone A antagonizes the activity of TNF-α by directly targeting this cytokine and selectively disrupting its interaction with TNF receptor-1

Anti-TNF biologics are effective therapies for various inflammatory diseases. Unfortunately, their clinical use is associated with an increased risk of infections. Selectively inhibiting TNF receptor-1 (TNFR1)-mediated signaling while preserving TNFR2 signaling may reduce inflammation yet maintain host immune response to pathogens. However, few small molecules that selectively target the TNF/TNFR system have been discovered. In the present study, we identified Japonicone A (Jap A), a nature compound derived from Inula japonica Thunb, as a novel TNF-α antagonist, as it reduced the TNF-α-mediated cytotoxicity on L929 cells and inhibited the binding of (125)I-labeled TNF-α to L929 cell surface. Furthermore, Jap A could directly bind to TNF-α rather than TNFR1 as determined by surface plasmon resonance. More importantly, Jap A could effectively inhibit the binding of TNF-α to TNFR1, while displaying only marginal inhibitory effects on that to TNFR2. Jap A also could block TNFR1-mediated signaling as it inhibited TNF-α-induced NF-κB activation in 293 cells. In addition, Jap A suppressed TNF-α-induced expressions of adhesion molecules (ICAM-1, VCAM-1) and chemokine (MCP-1) in the endothelial cells by blocking TNF-α-triggered multiple signaling pathways. Data from in vivo experiments demonstrated that Jap A protected mice from acute hepatitis induced by TNF-α/d-galactosamine, but did not compromise host antiviral immunity in adenovirus-infected mice. These results indicate that Jap A can directly target TNF-α, selectively disrupt its interaction with TNFR1, and antagonize its pro-inflammatory activities without compromising host defense against virus, thus emphasizing the potential of Jap A as an interesting lead compound for development of new anti-inflammatory drugs.

Creation of an improved mutant TNF with TNFR1-selectivity and antagonistic activity by phage display technology

Tumor necrosis factor-alpha (TNF), which binds two types of TNF receptors (TNFR1 and TNFR2), regulates the onset and exacerbation of autoimmune diseases such as rheumatoid arthritis and Crohn's disease. In particular, TNFR1-mediated signals are predominantly related to the induction of inflammatory responses. We have previously generated a TNFR1-selective antagonistic TNF-mutant (mutTNF) and shown that mutTNF efficiently inhibits TNFR1-mediated bioactivity in vitro and attenuates inflammatory conditions in vivo. In this study, we aimed to improve the TNFR1-selectivity of mutTNF This was achieved by constructing a phage library displaying mutTNF-based variants, in which the amino acid residues at the predicted receptor binding sites were substituted to other amino acids. From this mutant TNF library, 20 candidate TNFR1-selective antagonists were isolated. Like mutTNF, all 20 candidates were found to have an inhibitory effect on TNFR1-mediated bioactivity. However, one of the mutants, N7, displayed significantly more than 40-fold greater TNFR1-selectivty than mutTNF. Therefore, N7 could be a promising anti-autoimmune agent that does not interfere with TNFR2-mediated signaling pathways.

TNFR1 and TNFR2 Signaling Interplay in Cardiac Myocytes

Tumor necrosis factor alpha (TNFalpha) plays a major role in chronic heart failure, signaling through two different receptor subtypes, TNFR1 and TNFR2. Our aim was to further delineate the functional role and signaling pathways related to TNFR1 and TNFR2 in cardiac myocytes. In cardiac myocytes isolated from control rats, TNFalpha induced ROS production, exerted a dual positive and negative action on [Ca(2+)] transient and cell fractional shortening, and altered cell survival. Neutralizing anti-TNFR2 antibodies exacerbated TNFalpha responses on ROS production and cell death, arguing for a major protective role of the TNFR2 pathway. Treatment with either neutralizing anti-TNFR1 antibodies or the glutathione precursor, N-acetylcysteine (NAC), favored the emergence of TNFR2 signaling that mediated a positive effect of TNFalpha on [Ca(2+)] transient and cell fractional shortening. The positive effect of TNFalpha relied on TNFR2-dependent activation of the cPLA(2) activity, independently of serine 505 phosphorylation of the enzyme. Together with cPLA(2) redistribution and AA release, TNFalpha induced a time-dependent phosphorylation of ERK, MSK1, PKCzeta, CaMKII, and phospholamban on the threonine 17 residue. Taken together, our results characterized a TNFR2-dependent signaling and illustrated the close interplay between TNFR1 and TNFR2 pathways in cardiac myocytes. Although apparently predominant, TNFR1-dependent responses were under the yoke of TNFR2, acting as a critical limiting factor. In vivo NAC treatment proved to be a unique tool to selectively neutralize TNFR1-mediated effects of TNFalpha while releasing TNFR2 pathways.

SLE serum induces classical caspase-dependent apoptosis independent of death receptors

The main source of autoantigens in systemic lupus erythematosus (SLE) is most likely apoptotic material. We have previously shown that sera from SLE patients can induce apoptosis in monocytes and lymphocytes, and here we characterized mechanisms of apoptosis induced by SLE serum. SLE serum seems to induce caspase-dependent classical apoptosis since cells exposed to SLE serum displayed morphology consistent with classical apoptosis as demonstrated by confocal microscopy, and pan-caspase inhibitor Z-VAD.fmk significantly reduced SLE serum-induced apoptosis. Death-receptor-independent pathways seemed to be involved since SLE serum induced apoptosis equally in FADD-mutant and wild-type Jurkat cell lines, and blocking of Fas and TNFR1 did not reduce apoptosis induction. Importantly, apoptosis was significantly reduced in a Bcl-2 overexpressing Jurkat cell line indicating involvement of mitochondrial pathways. Thus, based on morphology and caspase inhibition experiments, we have demonstrated that SLE serum induce classical caspase-dependent apoptosis, and this was independent of death receptor pathways.

Use of tumor necrosis factor inhibitors in uveitis

PURPOSE OF REVIEW

Use of tumor necrosis factor-alpha blocking agents to treat chronic pediatric uveitis is becoming recognized as an important therapeutic modality. This review summarizes the rationale for this use, highlighting new studies of these agents in pediatric uveitis.

RECENT FINDINGS

The majority of patients with pediatric uveitis either have idiopathic uveitis or uveitis associated with juvenile idiopathic arthritis. Ophthalmologic morbidity among these children is common. Most studies evaluating tumor necrosis factor-alpha blockade in pediatric uveitis are retrospective case series, with attendant limitations that are inherent to any retrospective study. Study of uveitis has been hampered by lack of standardization of disease and outcome measures, which has been addressed by uveitis experts with publication of consensus measures. Data to date suggest that tumor necrosis factor-alpha blockade is efficacious in refractory uveitis. Agents with direct tumor necrosis factor-alpha membrane receptor binding activity may be the most efficacious. There remain many unanswered questions in the treatment of pediatric uveitis, including optimal dosing regimen and long-term efficacy.

SUMMARY

Tumor necrosis factor-alpha blocking agents play an important role in the treatment of chronic pediatric uveitis. Prospective comparative studies are needed so that we may better understand this role.

Interaction between Transmembrane TNF and TNFR1/2 Mediates the Activation of Monocytes by Contact with T Cells

Monocytes and monocytic cells produce proinflammatory cytokines upon direct cell contact with activated T cells. In the autoimmune disease rheumatoid arthritis, the pivotal role of TNF-alpha implies that the interaction between transmembrane TNF-alpha (mTNF) and the TNF receptors (TNFR1 and TNFR2) might participate in the T cell contact-dependent activation of monocytes. Accordingly, treatment of rheumatoid arthritis by administration of a TNF-alpha-blocking Ab was found to significantly decrease TNF-alpha production by monocytes. Several lines of evidence indicated that signaling through TNFR1/2 and through mTNF (reverse signaling) is involved in TNF-alpha production by monocytes after T cell contact: 1) blocking mTNF on activated T cells leads to a significant reduction in TNF-alpha production; 2) down-regulation of TNFR1/2 on monocytes by transfection with small interfering RNA results in diminished TNF-alpha production; 3) blocking or down-regulating TNFR2 on activated T cells inhibits TNF-alpha production, indicating that mTNF on the monocyte surface mediates signaling; 4) ligation of mTNF on monocytes by surface TNFR2 transfected into resting T cells induces TNF-alpha production due to reverse signaling by mTNF; and 5) ligation of mTNF on monocytes by a soluble TNFR2:Ig receptor construct induces TNF-alpha production due to reverse signaling. In conclusion, we identified mTNF and TNFR1/2 as interaction partners contributing to TNF-alpha production in monocytes. Both pathways initiated by mTNF-TNFR interaction are likely to be inhibited by treatment with anti-TNF-alpha Abs.

Tumor necrosis factor receptor 1/c-Jun-NH2-kinase signaling promotes human neoplasia

The tumor necrosis factor alpha receptor (TNFR1) activates downstream effectors that include the mitogen-activated protein kinase kinase 7 (MKK7)/c-Jun-NH(2)-kinase (JNK)/activator protein 1 (AP1) cascade. Here, we report that JNK is activated in a majority of spontaneous human squamous cell carcinomas (SCC). JNK pathway induction bypassed cell cycle restraints induced by oncogenic Ras and cooperated with Ras to convert normal human epidermis into tumors indistinguishable from SCC, confirming its oncogenic potency in human tissue. Inhibiting MKK7, JNK, and AP1 as well as TNFR1 itself using genetic, pharmacologic, or antibody-mediated approaches abolished invasive human epidermal neoplasia in a tumor cell autonomous fashion. The TNFR1/MKK7/JNK/AP1 cascade thus promotes human neoplasia and represents a potential therapeutic target for human epithelial cancers.

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.

Simvastatin potentiates tumor necrosis factor α-mediated apoptosis of human vascular endothelial cells via the inhibition of the geranylgeranylation of RhoA

HMG-CoA reductase inhibitors (statins) are widely used in the treatment and prevention of atherosclerosis. Here we demonstrate that the HMG-CoA reductase inhibitor simvastatin potentiates TNFalpha-mediated apoptosis and TNFalpha signaling in human umbilical vein endothelial cells (HUVECs). While 2.5 microM simvastatin or 40 ng/ml TNFalpha alone had only a small effect on apoptosis in HUVECs, co-incubation with simvastatin and TNFalpha markedly increased apoptosis in a time- and dose-dependent manner as measured by FACS analysis of propidium iodide-stained cells. Geranylgeraniol, which serves as a substrate for the geranylgeranylation of small GTP binding proteins such as RhoA, which is required for the function and membrane localization of Rho, reversed the effect of simvastatin on apoptosis. GGTI, an inhibitor of protein geranylgeranylation, mimicked the effect of simvastatin on apoptosis and interfered with the membrane localization of RhoA. Furthermore, simvastatin increased the expression of the TNFalpha type I receptor (TNFalphaRI) with a dose dependence and a dependence on geranylgeranylation similar to that demonstrated for the potentiation of TNFalpha-mediated apoptosis. Adenoviral expression of a dominant-negative RhoA mimicked the effect of simvastatin on the expression of TNFalphaRI, while adenoviral expression of a dominant-activating RhoA mutant reversed the effect of simvastatin on the expression of TNFalphaRI. Simvastatin also potentiated TNFalpha signaling as determined by increased TNFalpha-mediated E-selectin expression. These data support the conclusion that TNFalpha signaling is under the negative control of RhoA and that statins potentiate TNFalpha signaling at least in part via interference with RhoA inhibition of TNFalpha type I receptor expression.

Antisense oligonucleotide inhibition of tumor necrosis factor receptor 1 protects the liver from radiation-induced apoptosis

PURPOSE

Liver damage by radiation limits its efficacy in cancer treatment. As radiation can generate apoptotic signals, we wished to examine the potential to protect the liver by inhibiting apoptosis through two key mediators, FAS and tumor necrosis factor receptor 1 (TNFR1).

EXPERIMENTAL DESIGN

Radiation-induced liver damage was assessed by serum aspartate aminotransferase and alanine aminotransferase, hepatocyte micronucleus formation, and apoptosis assays (terminal nucleotidyl transferase-mediated nick end labeling and caspase-3 cleavage) in mice. Protection was evaluated by pretreating mice with antisense oligonucleotides (ASO) for FAS or TNFR1 prior to radiation. TNF-alpha production in liver and in Kupffer cells were determined by ELISA.

RESULTS

Radiation increased liver FAS and TNFR1 transcription in a dose- and time-dependent manner (maximized at 25 Gy and 8 hours postirradiation). Pretreatment with ASOs for FAS and TNFR1 resulted in the inhibition of liver FAS and TNFR1 by 78% and 59%, respectively. Inductions of serum aspartate aminotransferase and alanine aminotransferase were observed at 2 hours after radiation and could be reduced by pretreating mice with ASO for TNFR1 but not FAS or control oligonucleotide. Radiation-induced liver apoptosis (terminal nucleotidyl transferase-mediated nick end labeling staining and caspase-3 activation on Western blot) and hepatocyte micronucleus formation were reduced by pretreatment with ASO for TNFR1. In addition, radiation stimulated TNF-alpha production both in irradiated liver and in cultured Kupffer cells by >50% and 100%, respectively.

CONCLUSION

This study suggests that ionizing radiation activates apoptotic signaling through TNFR1 in the liver, and thus provides a rationale for anti-TNFR1 apoptotic treatment to prevent radiation-induced liver injury.

Human periodontal ligament cells secrete macrophage colony-stimulating factor in response to tumor necrosis factor-alpha in vitro

BACKGROUND

Human periodontal ligament (HPDL) cells may support osteoclastogenesis by expressing receptor activator of nuclear factor-kappa B ligand (RANKL) in response to periopathogenic factors and inflammatory cytokines. Because osteoclastogenesis requires the presence of macrophage colony-stimulating factor (M-CSF), we examined whether HPDL cells secrete M-CSF in response to tumor necrosis factor-alpha (TNF-alpha).

METHODS

Cultured HPDL cells were treated with TNF-alpha in serum-free condition. The expression of M-CSF and RANKL was determined by reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. Inhibitors and anti-TNF receptor (TNFR) neutralizing antibodies were used for the inhibitory experiments. A migration assay was performed.

RESULTS

TNF-alpha upregulated M-CSF and RANKL in HPDL cells. The effect on M-CSF expression could be partially blocked by pyrrolidine-dithiocarbamate ammonium salt and LY294002 but not by NS398. Neutralizing antibody to TNFR1 could diminish the effect of TNF-alpha. In addition, TNF-treated culture medium exhibited chemotactic effect for RAW264.7.

CONCLUSIONS

HPDL cells are capable of secreting M-CSF and expressing RANKL in response to TNF-alpha. The upregulation of M-CSF is possibly one of the mechanisms essential for periodontal tissue destruction in response to inflammatory cytokines. The upregulation is partly through nuclear factor-kappa B (NF-kappaB) and phosphatidylinositol 3'-kinase and possibly involves TNFR1.

Histone Deacetylase Inhibitors Suppress the Inducibility of Nuclear Factor-κB by Tumor Necrosis Factor-α Receptor-1 Down-regulation

Recently, the inhibition of histone deacetylase (HDAC) enzymes has attracted attention in the oncologic community as a new therapeutic opportunity for hematologic and solid tumors including non-small cell lung cancer (NSCLC). In hematologic malignancies, such as diffuse large B-cell lymphoma, the HDAC inhibitor (HDI), suberoylanilide hydroxamic acid (SAHA), has recently entered phase II and III clinical trials. To further advance our understanding of their action on tumor cells, we investigated the possible effect of HDI treatment on the functionality of the nuclear factor-kappaB (NF-kappaB) pathway in NSCLC. We found that in the NSCLC cell lines, A549 and NCI-H460, the NF-kappaB pathway was strongly inducible, for example, by stimulation with tumor necrosis factor-alpha (TNF-alpha). Incubation of several NSCLC cell lines with HDIs resulted in greatly reduced gene expression of TNF-alpha receptor-1. HDI-treated A549 and NCI-H460 cells down-regulated TNF-alpha receptor-1 mRNA and protein levels as well as surface exposure, and consequently responded to TNF-alpha treatment with reduced IKK phosphorylation and activation, delayed IkappaB-alpha phosphorylation, and attenuated NF-kappaB nuclear translocation and DNA binding. Accordingly, stimulation of NF-kappaB target gene expression by TNF-alpha was strongly decreased. In addition, we observed that SAHA displayed antitumor efficacy in vivo against A549 xenografts grown on nude mice. HDIs, therefore, might beneficially contribute to tumor treatment, possibly by reducing the responsiveness of tumor cells to the TNF-alpha-mediated activation of the NF-kappaB pathway. These findings also hint at a possible use of HDIs in inflammatory diseases, which are associated with the overproduction of TNF-alpha, such as rheumatoid arthritis or Crohn's disease.

Differential effects of NF-kappaB on apoptosis induced by DNA-damaging agents: the type of DNA damage determines the final outcome

The transcription factor nuclear factor kappa-B (NF-kappaB) is generally regarded as an antiapoptotic factor. Accordingly, NF-kappaB activation inhibits death ligand-induced apoptosis. In contrast, ultraviolet light B (UVB)-induced apoptosis is not inhibited but even enhanced upon NF-kappaB activation by interleukin-1 (IL-1). This study was performed to identify the molecular mechanisms underlying this switch of NF-kappaB. Enhancement of UVB-induced apoptosis was always associated with increased release of tumour necrosis factor-alpha (TNF-alpha), which was dependent on NF-kappaB activation. The same was observed when UVA and cisplatin were used, which like UVB induce base modifications. In contrast, apoptosis caused by DNA strand breaks was not enhanced by IL-1, indicating that the type of DNA damage is critical for switching the effect of NF-kappaB on apoptosis. Surprisingly, activated NF-kappaB induced TNF-alpha mRNA expression in the presence of all DNA damage-inducing agents. However, in the presence of DNA strand breaks, there was no release of the TNF-alpha protein, which is so crucial for enhancing apoptosis. Together, this indicates that induction of DNA damage may have a significant impact on biological effects but it is the type of DNA damage that determines the final outcome. This may have implications for the role of NF-kappaB in carcinogenesis and for the application of NF-kappaB inhibitors in anticancer therapy.

Phorbol ester-induced apoptosis in prostate cancer cells via autocrine activation of the extrinsic apoptotic cascade: a key role for protein kinase C delta

It is well established that activation of protein kinase C (PKC) by phorbol esters promotes apoptosis in androgen-dependent prostate cancer cells. However, there is limited information regarding the cellular mechanisms involved in this effect. In this report we identified a novel autocrine pro-apoptotic loop triggered by PKCdelta activation in prostate cancer cells that is mediated by death receptor ligands. The apoptotic effect of phorbol 12-myristate 13-acetate in LNCaP cells was impaired by inhibition or depletion of tumor necrosis factor alpha-converting enzyme, the enzyme responsible for tumor necrosis factor alpha (TNFalpha) shedding. Moreover, the apoptogenic effect of conditioned medium collected after phorbol 12-myristate 13-acetate treatment could be inhibited by blocking antibodies against TNFalpha and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), but not FasL, as well as by RNA interference depletion of TNFalpha and TRAIL receptors. Moreover, depletion or inhibition of death receptor downstream effectors, including caspase-8, FADD, p38 MAPK, and JNK, significantly reduced the apoptogenic effect of the conditioned medium. PKCdelta played a major role in this autocrine loop, both in the secretion of autocrine factors as well as a downstream effector. Taken together, our results demonstrate that activation of PKCdelta in prostate cancer cells causes apoptosis via the release of death receptor ligands and the activation of the extrinsic apoptotic cascade.

Amelioration of inflammatory arthritis by targeting the pre-ligand assembly domain of tumor necrosis factor receptors

Tumor necrosis factor (TNF)-alpha has an important role in the pathogenesis of autoimmune and inflammatory diseases such as rheumatoid and septic arthritis. The biological effects of TNF-alpha are mediated by binding to TNF receptors TNFR1 (also known as P60) or TNFR2 (also known as P80). The pre-ligand assembly domain (PLAD) is a portion of the extracellular region of TNFRs that mediates receptor-chain association essential for signaling. We found that soluble versions of PLAD, especially those derived from P60, block the biochemical effects of TNF-alpha in vitro and potently inhibit arthritis in animal models. Thus, targeting the PLAD may have clinical value in the treatment of human arthritis and other disorders involving receptors of the TNFR superfamily.

Disabling TNF receptor signaling by induced conformational perturbation of tryptophan-107

We have disabled TNF receptor (TNFR) function by inducing allosteric modulation of tryptophan-107 (W107) in the receptor. The allosteric effect operates by means of an allosteric cavity found a short distance from a previously identified loop involved in ligand binding. Occupying this cavity by small molecules leads to perturbation of distal W107 and disables functions of the TNFR, a molecule not known to undergo conformational change upon binding TNF-alpha. TNF-alpha-induced NF-kappaB and p38 kinase activities and clinical symptoms of collagen-induced arthritis in mice were all diminished. Thus, disabling receptor function by induced conformational changes of active binding surfaces represents an innovative paradigm in structure-based drug design.

Inhibition of tumor necrosis factor-alpha-induced RANTES secretion by alkaline protease in A549 cells

Pseudomonas aeruginosa is a gram-negative bacterium that is an opportunistic pathogen in patients with cystic fibrosis and in immunocompromised hosts. This bacterium produces a variety of proteolytic enzymes, including alkaline protease (AP), which has multiple biological effects. This study investigated the effects of AP on the A549 pulmonary epithelial cell line. Results demonstrate that AP inhibited tumor necrosis factor (TNF)-alpha-induced RANTES gene expression and secretion in a concentration-dependent manner. The TNF-alpha-induced RANTES gene expression and secretion was attenuated with a neutralizing monoclonal antibody directed against the TNF receptor type 1 (TNFR1). Conversely, a neutralizing monoclonal antibody directed against TNF receptor type II had no effect, suggesting that these events were regulated through the TNFR1 receptor. In addition, we observed that soluble TNF receptor type 1 (sTNFR1) levels were significantly increased in culture supernatants of AP-treated cells in a concentration-dependent manner. Finally, membrane-associated TNFR1 was decreased after AP exposures. In these studies, the enzymatically inactive form of AP had no effect on TNF-alpha-induced RANTES secretion, shedding of sTNFR1, or membrane-associated TNFR1. These results demonstrate that AP stimulates shedding of cell-surface TNFR1, resulting in an increase in sTNFR1. Consequently, these events decrease the cells' ability to stimulate RANTES gene expression and secretion through TNFR1.

Prenatal blockage of lymphotoxin beta receptor and TNF receptor p55 signaling cascade resulted in the acceleration of tissue genesis for isolated lymphoid follicles in the large intestine

Signaling by lymphotoxin (LT) and TNF is essential for the organogenesis of secondary lymphoid tissues in systemic and mucosal compartments. In this study, we demonstrated that the progeny of mice treated with fusion protein of LTbetaR and IgGFc (LTbetaR-Ig) or LTbetaR-Ig plus TNFR55-Ig (double Ig) showed significantly increased numbers of isolated lymphoid follicles (ILF) in the large intestine. Interestingly, double Ig treatment accelerated the maturation of large intestinal ILF. Three-week-old progeny of double Ig-treated mice showed increased numbers of ILF in the large intestine, but not in the small intestine. Furthermore, alteration of intestinal microflora by feeding of antibiotic water did not affect the increased numbers of ILF in the large intestine of double Ig-treated mice. Most interestingly, mice that developed numerous ILF also had increased levels of activation-induced cytidine deaminase expression and numbers of IgA-expressing cells in the lamina propria of the large intestine. Taken together, these results suggest that ILF formation in the large intestine is accelerated by blockage of LTbetaR and TNFR55 signals in utero, and ILF, like colonic patches, might play a role in the induction of IgA response in the large intestine.

CCR5 chemokine receptor mediates recruitment of MHC class II-positive Langerhans cells in the mouse corneal epithelium

PURPOSE

To characterize the chemokines and chemokine receptors that mediate the effect of proinflammatory cytokines, interleukin (IL)-1 and tumor necrosis factor (TNF)-alpha, on the recruitment of MHC class II(+) Langerhans cells (LCs) in the corneal epithelium.

METHODS

A standard model for corneal LC recruitment, application of cautery to the central corneal surface was used, and the differential gene expression levels of a panel of chemokines and chemokine receptors were determined by RNase protection assay. Chemokine receptor-knockout mice were used to evaluate the recruitment of MHC class II(+) LCs to the corneal epithelium. To determine the sensitivity of selected chemokines to IL-1 and TNF-alpha stimulation, the chemokine gene expression pattern was analyzed after blockade of IL-1 and TNF receptors.

RESULTS

CCR1, -2, and -5 were overexpressed in corneas after cauterization. Topical administration of soluble TNF receptor I and IL-1 receptor antagonist, which abrogated corneal LC recruitment, significantly suppressed the gene transcription levels of the ligands of CCR1 and/or -5, regulated on activation normal T-cell expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1alpha, and MIP-1beta. The recruitment of major histocompatibility complex (MHC) class II(+) LC was significantly suppressed in CCR5(-/-) mice and blockade of RANTES and MIP-1beta, but not in CCR1(-/-), CCR2(-/-)/MIP-1alpha(-/-), or MIP-1alpha(-/-) mice. The evaluation of epithelial CD11c(+) LC cells by confocal microscopy revealed coexpression for CCR5 primarily among B7(-) (CD80(-)/CD86(-)) subsets of these LCs but not among the mature B7(+) subsets of CD11c(+) LCs.

CONCLUSIONS

These data suggest that CCR5 plays a critical role in mediating recruitment and mobilization of MHC class II(+) LCs into the corneal epithelium. Targeting CCR5 and its ligands may be a new strategy for modulating immunity.

Induction of apoptosis by TNF receptor 2 in a T-cell hybridoma is FADD dependent and blocked by caspase-8 inhibitors

Previously we reported that both human TNFR1 and TNFR2 mediate TNF-induced apoptosis in the transfected rat/mouse T cell hybridoma PC60. We show here that TNFR2-mediated apoptosis in PVC60 cells can be blocked by the broad-spectrum caspase inhibitor zVAD-fmk, the caspase-8 inhibitor zIETD-fmk and by CrmA, a viral inhibitor of caspase-1 and caspase-8. This suggests an involvement of caspase-8 in TNFR2-mediated apoptosis. The upstream adaptor of caspase-8, FADD, is also involved in TNFR2-induced cell death, since transient overexpression of a dominant negative deletion mutant of FADD inhibited apoptosis induced by this receptor. TNFR2-induced apoptosis is independent of endogenous TNF or other death-inducing ligand production and subsequent activation of TNFR1 or other death receptors. Furthermore, TNFR2 stimulation does not enhance sensitivity for a subsequent TNFR1-induced apoptotic signal, as has been reported for Jurkat cells. TRAF2 downregulation, which has been proposed as the mechanism by which TNFR2 enhances TNFR1 signaling, was observed in PC60 cells, but the TNRF1 signal was not modulated. These data confirm the capacity of TNFR2 to generate an apoptotic cell death signal independent of TNFR1.

Cross-linking of CD40 using anti-CD40 antibody, 5C11, has different effects on XG2 multiple myeloma cells

A multiple myeloma (MM) cell line, XG2, has high-level expression of CD40, a tumor necrosis factor receptor (TNFR) family member. CD40 is present on the surfaces of a large variety of cells, including B cells, endothelial cells, dendritic cells and some carcinoma cells, and delivers signals regulating diverse cellular responses, such as proliferation, differentiation, growth suppression, cell death. In this research, we study the effects of cross-linking of CD40 on myeloma cells using different concentrations of anti-CD40 monoclonal antibody (mAb), 5C11. We found that low concentrations of 5C11 induced proliferation of XG2, while high concentrations of 5C11 resulted in homotypic aggregation of XG2, and strongly suppression of its proliferation and apoptosis after 24 h of treatment. These dose-dependent effects of 5C11 were verified by flow cytometry, Western blotting and immunoprecipitation. Autocrine or paracrine induction of IL-6, and up-regulation of membrane TNF and phosphorylation of TNFR1 may partially explain the contradictory biological effects of CD40 cross-linking on XG2 by anti-CD40 mAb.