Selective Modulation of TNF-TNFRs Signaling: Insights for Multiple Sclerosis Treatment

Kupffer cell inactivation ameliorates immune liver injury via TNF-α/TNFR1 signal pathway in trichloroethylene sensitized mice

METHODS

36 female BALB/c mice were selected and randomly divided the mice into four groups. We established a BALB/c mouse model of TCE sensitization and pretreatment with GdCl3 (40 mg/kg) by intraperitoneal injection during the during the 17th and 19th days.

RESULTS

We found F4/80, the marker of Kupffer cell, was increased in TCE positive group. GdCl3 treatment successfully blocked the activation of Kupffer cell. TNF-α was increased significantly in liver of TCE sensitized mice and decreased significantly when low-dose GdCl3 was used. We found TNF receptor 1 (TNFR1) was increased significantly and GdCl3 treatment resumed the expression of TNFR1 to normal level, as well as the F4/80, TNF-α and TNFR1 mRNA. We also found both caspase-8 and caspase-3 increased in TCE positive group and decreased in TCE + GdCl3 positive group. The number of apoptotic cells in TCE sensitized mice increased by TUNEL staining, and GdCl3 treatment alleviated this increase. Some cells showed edema and inflammatory cell aggregation in liver of TCE positive group, while in the TCE + GdCl3 positive group, the cytoplasm became loose and vacuole-like degeneration occurred.

CONCLUSION

Our study unveils cross-talk between Kupffer cell activation and TNFR1 which mediate apoptosis in liver of TCE sensitized mice.

Connecting Immune Cell Infiltration to the Multitasking Microglia Response and TNF Receptor 2 Induction in the Multiple Sclerosis Brain

Signaling from central nervous system (CNS)-infiltrating lymphocytes and macrophages is critical to activate microglia and cause tissue damage in multiple sclerosis (MS). We combined laser microdissection with high-throughput real time RT-PCR to investigate separately the CNS exogenous and endogenous inflammatory components in postmortem brain tissue of progressive MS cases. A previous analysis of immune infiltrates isolated from the white matter (WM) and the meninges revealed predominant expression of genes involved in antiviral and cytotoxic immunity, including IFNγ and TNF. Here, we assessed the expression of 71 genes linked to IFN and TNF signaling and microglia/macrophage activation in the parenchyma surrounding perivascular cuffs at different stages of WM lesion evolution and in gray matter (GM) lesions underlying meningeal infiltrates. WM and GM from non-neurological subjects were used as controls. Transcriptional changes in the WM indicate activation of a classical IFNγ-induced macrophage defense response already in the normal-appearing WM, amplification of detrimental (proinflammatory/pro-oxidant) and protective (anti-inflammatory/anti-oxidant) responses in actively demyelinating WM lesions and persistence of these dual features at the border of chronic active WM lesions. Transcriptional changes in chronic subpial GM lesions indicate skewing toward a proinflammatory microglia phenotype. TNF receptor 2 (TNFR2) mediating TNF neuroprotective functions was one of the genes upregulated in the MS WM. Using immunohistochemistry we show that TNFR2 is highly expressed in activated microglia in the normal-appearing WM, at the border of chronic active WM lesions, and in foamy macrophages in actively demyelinating WM and GM lesions. In lysolecithin-treated mouse cerebellar slices, a model of demyelination and remyelination, TNFR2 RNA and soluble protein increased immediately after toxin-induced demyelination along with transcripts for microglia/macrophage-derived pro- and anti-inflammatory cytokines. TNFR2 and IL10 RNA and soluble TNFR2 protein remained elevated during remyelination. Furthermore, myelin basic protein expression was increased after selective activation of TNFR2 with an agonistic antibody. This study highlights the key role of cytotoxic adaptive immunity in driving detrimental microglia activation and the concomitant healing response. It also shows that TNFR2 is an early marker of microglia activation and promotes myelin synthesis, suggesting that microglial TNFR2 activation can be exploited therapeutically to stimulate CNS repair.

Receptor-interacting protein kinase 1 (RIPK1) as a therapeutic target

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is a key mediator of cell death and inflammation. The unique hydrophobic pocket in the allosteric regulatory domain of RIPK1 has enabled the development of highly selective small-molecule inhibitors of its kinase activity, which have demonstrated safety in preclinical models and clinical trials. Potential applications of these RIPK1 inhibitors for the treatment of monogenic and polygenic autoimmune, inflammatory, neurodegenerative, ischaemic and acute conditions, such as sepsis, are emerging. This article reviews RIPK1 biology and disease-associated mutations in RIPK1 signalling pathways, highlighting clinical trials of RIPK1 inhibitors and potential strategies to mitigate development challenges.

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) — a key mediator of cell death and inflammation — is activated in human diseases. Here, Yuan and colleagues discuss current understanding of RIPK1 biology and its association with diseases including inflammatory and autoimmune disorders, neurodegenerative diseases and sepsis. The clinical development of small-molecule RIPK1 inhibitors and associated challenges are discussed.

Selective Targeting of TNF Receptors as a Novel Therapeutic Approach

Tumor necrosis factor (TNF) is a central regulator of immunity. Due to its dominant pro-inflammatory effects, drugs that neutralize TNF were developed and are clinically used to treat inflammatory and autoimmune diseases, such as rheumatoid arthritis, inflammatory bowel disease and psoriasis. However, despite their clinical success the use of anti-TNF drugs is limited, in part due to unwanted, severe side effects and in some diseases its use even is contraindicative. With gaining knowledge about the signaling mechanisms of TNF and the differential role of the two TNF receptors (TNFR), alternative therapeutic concepts based on receptor selective intervention have led to the development of novel protein therapeutics targeting TNFR1 with antagonists and TNFR2 with agonists. These antibodies and bio-engineered ligands are currently in preclinical and early clinical stages of development. Preclinical data obtained in different disease models show that selective targeting of TNFRs has therapeutic potential and may be superior to global TNF blockade in several disease indications.

Effectiveness and safety profile of anakinra in a HLA-B27 positive patient with multiple sclerosis-associated uveitis

Multiple sclerosis (MS) is a chronic demyelinating disorder of central nervous system (CNS) leading to neurological disability. A wide variety of ophthalmic and neuro-ophthalmic manifestations have been associated with MS. Although this link is well recognized, controversial is still the risk of developing MS in patients with ophthalmic manifestations. Intermediate uveitis followed by panuveitis are the most common manifestations among the ophthalmic involvement in MS. Timely management of uveitis, is a crucial step to prevent irreversible visual impairment. A multidisciplinary team including ophthalmologists together with other specialists is required in the majority of cases for an adequate diagnostic and therapeutic approach of uveitis. Corticosteroids represent the mainstay of therapy in the acute phase, whereas conventional immunosuppressive drugs such as azathioprine may allow a steroid sparing effect. Increasing evidence from anti-CD 20 monoclonal antibodies such as rituximab have proven the efficacy on clinical and radiological outcomes in MS, on the contrary anti-Tumor Necrosis Factor (TNF) monoclonal antibodies such as infliximab and adalimumab are contraindicated in patients with demyelinating disorders, as they seem to worsen disease and neurological clinical symptoms. On this basis, MS-associated uveitis may deeply influence the therapeutic choices suggesting targeting inflammatory cytokines different from TNF. Recently, interleukin (IL)-1 blockade has been investigated as possible therapeutic tool in several inflammatory eye conditions such as Behcet's disease related uveitis, strengthening that IL-1 is also critical for the development of uveitis. Herein, we report our experience in a HLA-B27 positive patient with MS-associated uveitis successfully treated with the short-acting IL-1 receptor antagonist anakinra.

Structural optimization of a TNFR1-selective antagonistic TNFα mutant to create new-modality TNF-regulating biologics

Excessive activation of the proinflammatory cytokine tumor necrosis factor-α (TNFα) is a major cause of autoimmune diseases, including rheumatoid arthritis. TNFα induces immune responses via TNF receptor 1 (TNFR1) and TNFR2. Signaling via TNFR1 induces proinflammatory responses, whereas TNFR2 signaling is suggested to suppress the pathophysiology of inflammatory diseases. Therefore, selective inhibition of TNFR1 signaling and preservation of TNFR2 signaling activities may be beneficial for managing autoimmune diseases. To this end, we developed a TNFR1-selective, antagonistic TNFα mutant (R1antTNF). Here, we developed an R1antTNF derivative, scR1antTNF-Fc, which represents a single-chain form of trimeric R1antTNF with a human IgG-Fc domain. scR1antTNF-Fc had properties similar to those of R1antTNF, including TNFR1-selective binding avidity, TNFR1 antagonistic activity, and thermal stability, and had a significantly extended plasma t _1/2 in vivo In a murine rheumatoid arthritis model, scR1antTNF-Fc and 40-kDa PEG-scR1antTNF (a previously reported PEGylated form) delayed the onset of collagen-induced arthritis, suppressed arthritis progression in mice, and required a reduced frequency of administration. Interestingly, with these biologic treatments, we observed an increased ratio of regulatory T cells to conventional T cells in lymph nodes compared with etanercept, a commonly used TNF inhibitor. Therefore, scR1antTNF-Fc and 40-kDa PEG-scR1antTNF indirectly induced immunosuppression. These results suggest that selective TNFR1 inhibition benefits the management of autoimmune diseases and that R1antTNF derivatives hold promise as new-modality TNF-regulating biologics.

Inflammation and Oxidative Stress in Multiple Sclerosis: Consequences for Therapy Development

CNS inflammation is a major driver of MS pathology. Differential immune responses, including the adaptive and the innate immune system, are observed at various stages of MS and drive disease development and progression. Next to these immune-mediated mechanisms, other mediators contribute to MS pathology. These include immune-independent cell death of oligodendrocytes and neurons as well as oxidative stress-induced tissue damage. In particular, the complex influence of oxidative stress on inflammation and vice versa makes therapeutic interference complex. All approved MS therapeutics work by modulating the autoimmune response. However, despite substantial developments in the treatment of the relapsing-remitting form of MS, approved therapies for the progressive forms of MS as well as for MS-associated concomitants are limited and much needed. Here, we summarize the contribution of inflammation and oxidative stress to MS pathology and discuss consequences for MS therapy development.

Selective inhibition of Tumor necrosis factor receptor-1 (TNFR1) for the treatment of autoimmune diseases

Anti-TNF biologics have achieved great success in the treatment of autoimmune diseases and have been the most selling biologics on market. However, the anti-TNF biologics have shown some disadvantages such as poor efficacy to some patients and high risk of infection and malignancies during clinical application. Current anti-TNF biologics are antibodies or antibody fragments that bind to TNF-α and subsequently block both TNF-TNFR1 and TNF-TNFR2 signaling. Transgenic animal studies indicate that TNFR1 signaling is responsible for chronic inflammation and cell apoptosis whereas TNFR2 signaling regulates tissue regeneration and inflammation. Recent studies propose to selectively inhibit TNFR1 to enhance efficacy and avoid side effects. In this review, we introduce the biology of TNF-TNFR1 and TNF-TNFR2 signaling, the advantages of selective inhibition of TNF-TNFR1 signaling and research updates on the development of selective inhibitors for TNF-TNFR1 signaling. Antibodies, small molecules and aptamers that selectively inhibit TNFR1 have showed therapeutic potential and less side effects in preclinical studies. Development of selective inhibitors for TNFR1 is a good strategy to enhance the efficacy and reduce the side effects of anti-TNF inhibitors and will be a trend for next-generation of anti-TNF inhibitors.

Discriminative expression of CD39 and CD73 in Cerebrospinal fluid of patients with Multiple Sclerosis and Neuro-Behçet's disease

Treg-mediated immune suppression involves many molecular mechanisms including the cleavage of inflammatory extracellular ATP to adenosine by CD39 ectoenzyme. In the peripheral blood of Multiple Sclerosis (MS) patients, it has been suggested that CD39+ Treg cells have the potential to suppress pro-inflammatory IL-17 secreting cells. Herein, we studied cellular phenotype and mRNA expression of CD39 and CD73 ectoenzymes in the Cerebrospinal fluid (CSF) of MS patients and another neuro-inflammatory disease: the Neuro-behçet's disease (NBD). Using qRT-PCR, we assessed mRNA expression of CD39 and CD73 as well as anti-inflammatory (IL-10) and pro-inflammatory (IL-6, TNF-α, IL-1β) cytokines in patients Peripheral blood mononuclear cells (PBMCs) and CSF of 28 relapsing-remitting multiple sclerosis (RRMS), 20 NBD and 22 controls with non inflammatory neurological disorders (NIND). The most substantial result in the CSF was the higher expression of CD39 in both RRMS and NBD patients compared to NIND. While, the expression of CD73 in CSF samples of NBD was low. In RRMS samples, we detected a significant positive correlation of both CD39 and CD73 with IL-10 expression. Moreover, results by flow cytometry revealed a high percentage of CD39 Treg cells in RRMS CSF. CD39 was preferentially expressed on B cells of NBD. Regarding inflammatory response, we showed a significant increase of IL-6 mRNA expression in NBD patients CSF while in RRMS this increase concerned TNF-α. These results bring evidence that CD39 correlates positively with an anti-inflammatory IL-10 response in RRMS. In contrast, no such association was observed in CSF of NBD patients and CD39 was preferentially expressed on B cells.

A Systematic Test of Receptor Binding Kinetics for Ligands in Tumor Necrosis Factor Superfamily by Computational Simulations

Ligands in the tumor necrosis factor (TNF) superfamily are one major class of cytokines that bind to their corresponding receptors in the tumor necrosis factor receptor (TNFR) superfamily and initiate multiple intracellular signaling pathways during inflammation, tissue homeostasis, and cell differentiation. Mutations in the genes that encode TNF ligands or TNFR receptors result in a large variety of diseases. The development of therapeutic treatment for these diseases can be greatly benefitted from the knowledge on binding properties of these ligand–receptor interactions. In order to complement the limitations in the current experimental methods that measure the binding constants of TNF/TNFR interactions, we developed a new simulation strategy to computationally estimate the association and dissociation between a ligand and its receptor. We systematically tested this strategy to a comprehensive dataset that contained structures of diverse complexes between TNF ligands and their corresponding receptors in the TNFR superfamily. We demonstrated that the binding stabilities inferred from our simulation results were compatible with existing experimental data. We further compared the binding kinetics of different TNF/TNFR systems, and explored their potential functional implication. We suggest that the transient binding between ligands and cell surface receptors leads into a dynamic nature of cross-membrane signal transduction, whereas the slow but strong binding of these ligands to the soluble decoy receptors is naturally designed to fulfill their functions as inhibitors of signal activation. Therefore, our computational approach serves as a useful addition to current experimental techniques for the quantitatively comparison of interactions across different members in the TNF and TNFR superfamily. It also provides a mechanistic understanding to the functions of TNF-associated cell signaling pathways.

Astrocyte and Oligodendrocyte Cross-Talk in the Central Nervous System

Over the last decade knowledge of the role of astrocytes in central nervous system (CNS) neuroinflammatory diseases has changed dramatically. Rather than playing a merely passive role in response to damage it is clear that astrocytes actively maintain CNS homeostasis by influencing pH, ion and water balance, the plasticity of neurotransmitters and synapses, cerebral blood flow, and are important immune cells. During disease astrocytes become reactive and hypertrophic, a response that was long considered to be pathogenic. However, recent studies reveal that astrocytes also have a strong tissue regenerative role. Whilst most astrocyte research focuses on modulating neuronal function and synaptic transmission little is known about the cross-talk between astrocytes and oligodendrocytes, the myelinating cells of the CNS. This communication occurs via direct cell-cell contact as well as via secreted cytokines, chemokines, exosomes, and signalling molecules. Additionally, this cross-talk is important for glial development, triggering disease onset and progression, as well as stimulating regeneration and repair. Its critical role in homeostasis is most evident when this communication fails. Here, we review emerging evidence of astrocyte-oligodendrocyte communication in health and disease. Understanding the pathways involved in this cross-talk will reveal important insights into the pathogenesis and treatment of CNS diseases.

Sustained hyperammonemia induces TNF-a IN Purkinje neurons by activating the TNFR1-NF-κB pathway

Background

Patients with liver cirrhosis may develop hepatic encephalopathy. Rats with chronic hyperammonemia exhibit neurological alterations mediated by peripheral inflammation and neuroinflammation. Motor incoordination is due to increased TNF-a levels and activation of its receptor TNFR1 in the cerebellum.

The aims were to assess (a) whether peripheral inflammation is responsible for TNF-a induction in hyperammonemic rats, (b) the cell type(s) in which TNF-a is increased, (c) whether this increase is associated with increased nuclear NF-κB and TNFR1 activation, (d) the time course of TNF-a induction, and (e) if TNF-a is induced in the Purkinje neurons of patients who die with liver cirrhosis.

Methods

We analyzed the level of TNF-a mRNA and NF-κB in microglia, astrocytes, and Purkinje neurons in the cerebellum after 1, 2, and 4 weeks of hyperammonemia. We assessed whether preventing peripheral inflammation by administering an anti-TNF-a antibody prevents TNF-a induction. We tested whether TNF-a induction is reversed by R7050, which inhibits the TNFR1-NF-κB pathway, in ex vivo cerebellar slices.

Results

Hyperammonemia induced microglial and astrocyte activation at 1 week. This was followed by TNF-a induction in both glial cell types at 2 weeks and in Purkinje neurons at 4 weeks. The level of TNF-a mRNA increased in parallel with the TNF-a protein level, indicating that TNF-a was synthesized in Purkinje cells. This increase was associated with increased NF-κB nuclear translocation. The nuclear translocation of NF-κB and the increase in TNF-a were reversed by R7050, indicating that they were mediated by the activation of TNFR1. Preventing peripheral inflammation with an anti-TNF-a antibody prevents TNF-a induction.

Conclusion

Sustained (4 weeks) but not short-term hyperammonemia induces TNF-a in Purkinje neurons in rats. This is mediated by peripheral inflammation. TNF-a is also increased in the Purkinje neurons of patients who die with liver cirrhosis. The results suggest that hyperammonemia induces TNF-a in glial cells and that TNF-a released by glial cells activates TNFR1 in Purkinje neurons, leading to NF-κB nuclear translocation and the induction of TNF-a expression, which may contribute to the neurological alterations observed in hyperammonemia and hepatic encephalopathy.

[Pathological and protective effects of tumor necrosis factor-alpha in multiple sclerosis]

The immunomodulatory cytokine tumor necrosis factor-alpha (TNF-α) is involved in the regulation of both physiological and pathological processes in the central nervous system (CNS). The effects of TNF-α on CNS reported in clinical trials and experimental studies, evidence of involvement of this cytokine in the pathogenesis of multiple sclerosis are analyzed. Possible causes of failures of non-selective pharmacological inhibition of TNF-α effects in MS are considered in view of current concepts on mechanisms of TNF-α action.

Antioxidant and Anti-inflammatory Diagnostic Biomarkers in Multiple Sclerosis: A Machine Learning Study

An imbalance of inflammatory/anti-inflammatory and oxidant/antioxidant molecules has been implicated in the demyelination and axonal damage in multiple sclerosis (MS). The current study aimed to evaluate the plasma levels of tumor necrosis factor (TNF)-α, soluble TNF receptor (sTNFR)1, sTNFR2, adiponectin, hydroperoxides, advanced oxidation protein products (AOPP), nitric oxide metabolites, total plasma antioxidant capacity using the total radical-trapping antioxidant parameter (TRAP), sulfhydryl (SH) groups, as well as serum levels of zinc in 174 MS patients and 182 controls. The results show that MS is characterized by lowered levels of zinc, adiponectin, TRAP, and SH groups and increased levels of AOPP. MS was best predicted by a combination of lowered levels of zinc, adiponectin, TRAP, and SH groups yielding an area under the receiver operating characteristic (AUC/ROC) curve of 0.986 (±0.005). The combination of these four antioxidants with sTNFR2 showed an AUC/ROC of 0.997 and TRAP, adiponectin, and zinc are the most important biomarkers for MS diagnosis followed at a distance by sTNFR2. Support vector machine with tenfold validation performed on the four antioxidants showed a training accuracy of 92.9% and a validation accuracy of 90.6%. The results indicate that lowered levels of those four antioxidants are associated with MS and that these antioxidants are more important biomarkers of MS than TNF-α signaling and nitro-oxidative biomarkers. Adiponectin, TRAP, SH groups, zinc, and sTNFR2 play a role in the pathophysiology of MS, and a combination of these biomarkers is useful for predicting MS with high sensitivity, specificity, and accuracy. Drugs that increase the antioxidant capacity may offer novel therapeutic opportunities for MS.

A computational model for understanding the oligomerization mechanisms of TNF receptor superfamily

By recognizing members in the tumor necrosis factor (TNF) receptor superfamily, TNF ligand proteins function as extracellular cytokines to activate various signaling pathways involved in inflammation, proliferation, and apoptosis. Most ligands in TNF superfamily are trimeric and can simultaneously bind to three receptors on cell surfaces. It has been experimentally observed that the formation of these molecular complexes further triggers the oligomerization of TNF receptors, which in turn regulate the intracellular signaling processes by providing transient compartmentalization in the membrane proximal regions of cytoplasm. In order to decode the molecular mechanisms of oligomerization in TNF receptor superfamily, we developed a new computational method that can physically simulate the spatial-temporal process of binding between TNF ligands and their receptors. The simulations show that the TNF receptors can be organized into hexagonal oligomers. The formation of this spatial pattern is highly dependent not only on the molecular properties such as the affinities of trans and cis binding, but also on the cellular factors such as the concentration of TNF ligands in the extracellular area or the density of TNF receptors on cell surfaces. Moreover, our model suggests that if TNF receptors are pre-organized into dimers before ligand binding, these lateral interactions between receptor monomers can play a positive role in stabilizing the ligand-receptor interactions, as well as in regulating the kinetics of receptor oligomerization. Altogether, this method throws lights on the mechanisms of TNF ligand-receptor interactions in cellular environments.

Two-Photon Probe for TNF-α. Assessment of the Transmembrane TNF-α Level in Human Colon Tissue by Two-Photon Microscopy

We developed Pyr1-infliximab: a two-photon probe for TNF-α. Pyr1-infliximab showed absorption maxima at 280 and 438 nm and an emission maximum at 610 nm in an aqueous buffer and effective two-photon action cross-section values of (520-2830) × 10^-50 cm⁴s/photon in RAW 264.7 cells. After this probe was labeled, it was possible to detect Pyr1-infliximab-transmembrane TNF-α complexes in a live cell and to determine the relative proportion of these complexes in human colon tissues. This proportion among healthy, possibly inflamed, and inflamed tissues of patients with ulcerative colitis was found to be 1.0/4.5/10. This probe may find useful applications for selective detection of transmembrane TNF-α in a live cell or tissue, for quantification of inflammation in human colon tissue or of antidrug antibodies in patients who stop responding to anti-TNF therapy, and for monitoring of the response to this therapy.

Tumor Necrosis Factor (TNF) Receptor Expression Determines Keratinocyte Fate upon Stimulation with TNF-Like Weak Inducer of Apoptosis

The interaction between tumor necrosis factor- (TNF-) like weak inducer of apoptosis (TWEAK) and fibroblast growth factor-inducible 14 (Fn14) regulates the fate of keratinocytes, depending on the relative expression of TNF receptor (TNFR) 1 or TNFR2. However, the precise mechanism underlying this TWEAK-mediated regulation remains unclear. The aim of this study was to provide comprehensive insight into the roles of Fn14, TNFR1/2, and other relevant molecules in the fate of keratinocytes. Further, we sought to elucidate the structural basis for the interaction of TWEAK and Fn14 in regulating cellular outcomes. Normal keratinocytes (mainly expressing TNFR1) and TNFR2-overexpressing keratinocytes were stimulated with TWEAK. Through immunoprecipitation and Western blotting of keratinocyte lysates, we elucidated the associations between Fn14, TNFR-associated factor 2 (TRAF2), cellular inhibitor of apoptosis protein 1 (cIAP1), and TNFR1/2 molecules. Additionally, we found that TRAF2 exhibited binding to Fn14, cIAP1, and TNFR1/2. Our data suggest that TWEAK induces apoptosis in normal keratinocytes and proliferation in TNFR2-overexpressing keratinocytes in a TNF-α-independent manner; however, inhibition of TRAF2 appears to reverse this effect. Interestingly, the interaction between TWEAK and Fn14 increased TNFR1-associated death domain protein and caspase-8 expression in normal keratinocytes and promoted cytoplasmic import of cIAP1 in TNFR2-overexpressing keratinocytes. In conclusion, we found that the Fn14-TRAF2-TNFR signaling axis mediates TWEAK's regulation of the fate of keratinocytes, possibly in a manner involving the TNF-α-independent TNFR signal transduction.

Neuroinflammation as a Factor of Neurodegenerative Disease: Thalidomide Analogs as Treatments

Neuroinflammation is initiated when glial cells, mainly microglia, are activated by threats to the neural environment, such as pathogen infiltration or neuronal injury. Although neuroinflammation serves to combat these threats and reinstate brain homeostasis, chronic inflammation can result in excessive cytokine production and cell death if the cause of inflammation remains. Overexpression of tumor necrosis factor-α (TNF-α), a proinflammatory cytokine with a central role in microglial activation, has been associated with neuronal excitotoxicity, synapse loss, and propagation of the inflammatory state. Thalidomide and its derivatives, termed immunomodulatory imide drugs (IMiDs), are a class of drugs that target the 3'-untranslated region (3'-UTR) of TNF-α mRNA, inhibiting TNF-α production. Due to their multi-potent effects, several IMiDs, including thalidomide, lenalidomide, and pomalidomide, have been repurposed as drug treatments for diseases such as multiple myeloma and psoriatic arthritis. Preclinical studies of currently marketed IMiDs, as well as novel IMiDs such as 3,6'-dithiothalidomide and adamantyl thalidomide derivatives, support the development of IMiDs as therapeutics for neurological disease. IMiDs have a competitive edge compared to similar anti-inflammatory drugs due to their blood-brain barrier permeability and high bioavailability, with the potential to alleviate symptoms of neurodegenerative disease and slow disease progression. In this review, we evaluate the role of neuroinflammation in neurodegenerative diseases, focusing specifically on the role of TNF-α in neuroinflammation, as well as appraise current research on the potential of IMiDs as treatments for neurological disorders.

Attenuating Neurogenic Sympathetic Hyperreflexia Robustly Improves Antibacterial Immunity After Chronic Spinal Cord Injury

Spinal cord injury (SCI) disrupts critical physiological systems, including the cardiovascular and immune system. Plasticity of spinal circuits below the injury results in abnormal, heightened sympathetic responses, such as extreme, sudden hypertension that hallmarks life-threatening autonomic dysreflexia. Moreover, such sympathetic hyperreflexia detrimentally impacts other effector organs, including the spleen, resulting in spinal cord injury-induced immunodeficiency. Consequently, infection is a leading cause of mortality after SCI. Unfortunately, there are no current treatments that prophylactically limit sympathetic hyperreflexia to prevent subsequent effector organ dysfunction. The cytokine soluble tumor necrosis factor α (sTNFα) is upregulated in the CNS within minutes after SCI and remains elevated. Here, we report that commencing intrathecal administration of XPro1595, an inhibitor of sTNFα, at a clinically feasible, postinjury time point (i.e., 3 d after complete SCI) sufficiently diminishes maladaptive plasticity within the spinal sympathetic reflex circuit. This results in less severe autonomic dysreflexia, a real-time gauge of sympathetic hyperreflexia, for months postinjury. Remarkably, delayed delivery of the sTNFα inhibitor prevents sympathetic hyperreflexia-associated splenic atrophy and loss of leukocytes to dramatically improve the endogenous ability of chronic SCI rats to fight off pneumonia, a common cause of hospitalization after injury. The improved immune function with XPro1595 correlates with less noradrenergic fiber sprouting and normalized norepinephrine levels in the spleen, indicating that heightened, central sTNFα signaling drives peripheral, norepinephrine-mediated organ dysfunction, a novel mechanism of action. Thus, our preclinical study supports intrathecally targeting sTNFα as a viable strategy to broadly attenuate sympathetic dysregulation, thereby improving cardiovascular regulation and immunity long after SCI.SIGNIFICANCE STATEMENT Spinal cord injury (SCI) significantly disrupts immunity, thus increasing susceptibility to infection, a leading cause of morbidity in those living with SCI. Here, we report that commencing intrathecal administration of an inhibitor of the proinflammatory cytokine soluble tumor necrosis factor α days after an injury sufficiently diminishes autonomic dysreflexia, a real time gauge of sympathetic hyperreflexia, to prevent associated splenic atrophy. This dramatically improves the endogenous ability of chronically injured rats to fight off pneumonia, a common cause of hospitalization. This preclinical study could have a significant impact for broadly improving quality of life of SCI individuals.

Resolution of inflammation during multiple sclerosis

Multiple sclerosis (MS) is a frequent autoimmune demyelinating disease of the central nervous system (CNS). There are three clinical forms described: relapsing-remitting multiple sclerosis (RRMS), the most common initial presentation (85%) among which, if not treated, about half will transform, into the secondary progressive multiple sclerosis (SPMS) and the primary progressive MS (PPMS) (15%) that is directly progressive without superimposed clinical relapses. Inflammation is present in all subsets of MS. The relapsing/remitting form could represent itself a particular interest for the study of inflammation resolution even though it remains incomplete in MS. Successful resolution of acute inflammation is a highly regulated process and dependent on mechanisms engaged early in the inflammatory response that are scarcely studied in MS. Moreover, recent classes of disease-modifying treatment (DMTs) that are effective against RRMS act by re-establishing the inflammatory imbalance, taking advantage of the pre-existing endogenous suppressor. In this review, we will discuss the active role of regulatory immune cells in inflammation resolution as well as the role of tissue and non-hematopoietic cells as contributors to inflammation resolution. Finally, we will explore how DMTs, more specifically induction therapies, impact the resolution of inflammation during MS.

Exogenous activation of tumor necrosis factor receptor 2 promotes recovery from sensory and motor disease in a model of multiple sclerosis

Tumor necrosis factor receptor 2 (TNFR2) is a transmembrane receptor that promotes immune modulation and tissue regeneration and is recognized as a potential therapeutic target for multiple sclerosis (MS). However, TNFR2 also contributes to T effector cell function and macrophage-TNFR2 recently was shown to promote disease development in the experimental autoimmune encephalomyelitis (EAE) model of MS. We here demonstrate that systemic administration of a TNFR2 agonist alleviates peripheral and central inflammation, and reduces demyelination and neurodegeneration, indicating that protective signals induced by TNFR2 exceed potential pathogenic TNFR2-dependent responses. Our behavioral data show that systemic treatment of female EAE mice with a TNFR2 agonist is therapeutic on motor symptoms and promotes long-term recovery from neuropathic pain. Mechanistically, our data indicate that TNFR2 agonist treatment follows a dual mode of action and promotes both suppression of CNS autoimmunity and remyelination. Strategies based on the concept of exogenous activation of TNFR2 therefore hold great promise as a new therapeutic approach to treat motor and sensory disease in MS as well as other inflammatory diseases or neuropathic pain conditions.

Different origins of paralogues of salmonid TNR1 and TNFR2: Characterisation and expression analysis of four TNF receptor genes in rainbow trout Oncorhynchus mykiss

Mammalian TNFR1 and TNFR2 bind TNFα and TNFβ, and provide key communication signals to a variety of cell types during development and immune responses that are crucial for cell survival, proliferation and apoptosis. In teleost fish TNFβ is absent but TNFα has been expanded by the third whole genome duplication (3R WGD) and again by a 4R WGD in some lineages, leading to the four TNFα paralogues known in salmonids. Two paralogues for each of TNFR1 and TNFR2 have been cloned in rainbow trout in this study and are present in other salmonid genomes. Whilst the TNFR2 paralogues were generated via the 4R salmonid WGD, the TNFR1 paralogues arose from a local en bloc duplication. Functional diversification of TNFR paralogues was evidenced by differential gene expression and modulation, upstream ATGs affecting translation, ATTTA motifs in the 3'-UTR regulating mRNA stability, and post-translational modification by N-glycosylation. Trout TNFR are highly expressed in immune tissues/organs, and other tissues, in a gene- and tissue-specific manner. Furthermore, their expression is differentially modulated by PAMPs and cytokines in a cell type- and stimulant-specific manner. Such findings suggest an important role of the TNF/TNFR axis in the immune response and other physiological processes in fish.

Tumor necrosis factor alpha (TNF-α) and its soluble receptors are associated with disability, disability progression and clinical forms of multiple sclerosis

BACKGROUND

The association between tumor necrosis factor (TNF)-α, soluble TNF receptor (sTNFR)1 and sTNFR2 with clinical characteristics of multiple sclerosis (MS) remains unclear.

OBJECTIVE

To examine whether TNF-α, sTNFR1 and sTNFR2 are associated with MS diagnosis, disability, disability progression and clinical forms of MS.

MATERIALS AND SUBJECTS

The study included 147 patients with relapsing-remitting MS (RRMS), 21 with progressive clinical forms (ProgMS) and 70 controls. Expanded Disability Status Scale (EDSS) evaluated disability as mild (EDSS < 3.0) or moderate/high (EDSS ≥ 3.0). Multiple Sclerosis Severity Score (MSSS) evaluated disability progression as no progression (MSSS < 5) and progression (MSSS ≥ 5). Baseline data of subjects and plasma levels of TNF-α, sTNFR1, sTNFR2 were obtained.

RESULTS

The MS diagnosis explained 44.6% and 12.3% of TNF-α and sTNFR2 levels, respectively. Moderate/high disability and disability progression were best predicted by sTNFR1 and age (positively) and ProgMS were best predicted by sTNFR1 (positively) and sTNFR2 (negatively), coupled with age and sex. A composite score reflecting the sTNFR1/sTNFR2 ratio showed a positive association with ProgMS after adjusting for age and sex.

CONCLUSION

Increased sTNFR1 and age were positively associated with disability and disability progression, whereas increased sTNFR1 (positively) and sTNFR2 (negatively) were associated with ProgMS, suggesting a distinct role of them in the immunopathological mechanisms of MS.

Experimental autoimmune encephalomyelitis accelerates remyelination after lysophosphatidylcholine-induced demyelination in the corpus callosum

Experimental autoimmune encephalomyelitis (EAE) and lysophosphatidylcholine (LPC)-induced demyelination were combined to study remyelination in a pro-inflammatory context. Two groups of female C57BL/6 mice were subjected either to EAE (EAE mice) or injected with just complete Freund's adjuvant (CFA) and pertussis toxin (PTX) followed by bilateral LPC and phosphate buffered saline injections in the corpus callosum on day 7 (CFA controls). Relative to CFA controls, EAE accelerated remyelination and increased innate immune cell activation, lymphocyte infiltration and cytokine gene expression in the LPC lesions. However, compared to CFA mice, remyelination was reduced (day 14) suggesting this aggressive immune response also compromised myelin repair in EAE mice.

Necrostatin-1 ameliorates the pathogenesis of experimental autoimmune encephalomyelitis by suppressing apoptosis and necroptosis of oligodendrocyte precursor cells

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system characterized by neuronal demyelination. MS pathogenesis occurs via multiple mechanisms, and is mediated in part by oligodendrocyte apoptosis and a robust inflammatory response. In the present study, Necrostatin-1 (Nec-1), a specific inhibitor of the receptor-interacting protein 1 kinase domain, was revealed to effectively alleviate the severity and pathological damage associated with experimental autoimmune encephalomyelitis (EAE), a commonly used mouse model of MS. In addition, treatment with Nec-1 significantly decreased the number of lesions and inflammatory cell infiltrates in spinal cord tissues, as well as the production of associated pro-inflammatory cytokines, including tumor necrosis factor α (TNFα), interferon-γ and interleukin-1β. Nec-1 also suppressed TNFα + zVAD-fmk-induced apoptosis and necroptosis in primary oligodendrocyte precursor cells. The present study revealed that Nec-1 effectively attenuated the progression of EAE by suppressing apoptosis and necroptosis in oligodendrocytes, and represents a potential novel therapeutic agent for the treatment of MS.

Remicade® (infliximab): 20 years of contributions to science and medicine

On August 24, 1998, Remicade^® (infliximab), the first tumor necrosis factor-α (TNF) inhibitor, received its initial marketing approval from the US Food and Drug Administration for the treatment of Crohn’s disease. Subsequently, Remicade was approved in another five adult and two pediatric indications both in the USA and across the globe. In the 20 years since this first approval, Remicade has made several important contributions to the advancement of science and medicine: 1) clinical trials with Remicade established the proof of concept that targeted therapy can be effective in immune-mediated inflammatory diseases; 2) as the first monoclonal antibody approved for use in a chronic condition, Remicade helped in identifying methods of administering large, foreign proteins repeatedly while limiting the body’s immune response to them; 3) the need to establish Remicade’s safety profile required developing new methods and setting new standards for postmarketing safety studies, specifically in the real-world setting, in terms of approach, size, and duration of follow-up; 4) the study of Remicade has improved our understanding of TNF’s role in the immune system, as well as our understanding of the pathophysiology of a range of diseases characterized by chronic inflammation; and 5) Remicade and other TNF inhibitors have transformed treatment practices in these chronic inflammatory diseases: remission has become a realistic goal of therapy and long-term disability resulting from structural damage can be prevented. This paper reviews how, over the course of its development and 20 years of use in clinical practice, Remicade was able to make these contributions.

RhoA as a Key Regulator of Innate and Adaptive Immunity

RhoA is a ubiquitously expressed cytoplasmic protein that belongs to the family of small GTPases. RhoA acts as a molecular switch that is activated in response to binding of chemokines, cytokines, and growth factors, and via mDia and the ROCK signaling cascade regulates the activation of cytoskeletal proteins, and other factors. This review aims to summarize our current knowledge on the role of RhoA as a general key regulator of immune cell differentiation and function. The contribution of RhoA for the primary functions of innate immune cell types, namely neutrophils, macrophages, and conventional dendritic cells (DC) to (i) get activated by pathogen-derived and endogenous danger signals, (ii) migrate to sites of infection and inflammation, and (iii) internalize pathogens has been fairly established. In activated DC, which constitute the most potent antigen-presenting cells of the immune system, RhoA is also important for the presentation of pathogen-derived antigen and the formation of an immunological synapse between DC and antigen-specific T cells as a prerequisite to induce adaptive T cell responses. In T cells and B cells as the effector cells of the adaptive immune system Rho signaling is pivotal for activation and migration. More recently, mutations of Rho and Rho-modulating factors have been identified to predispose for autoimmune diseases and as causative for hematopoietic malignancies.

Targeting RIPK1 for the treatment of human diseases

RIPK1 plays a critical role in mediating deleterious responses downstream of TNFR1. RIPK1 inhibitors have been progressed successfully past human phase I clinical studies. This paper discusses why RIPK1 inhibitors present an opportunity for developing oral drugs for a range of human degenerative and inflammatory diseases, especially CNS pathologies, including ALS, Alzheimer’s disease, Parkinson’s disease, traumatic brain injury, stroke, and lysosomal storage diseases.

RIPK1 kinase has emerged as a promising therapeutic target for the treatment of a wide range of human neurodegenerative, autoimmune, and inflammatory diseases. This was supported by extensive studies which demonstrated that RIPK1 is a key mediator of apoptotic and necrotic cell death as well as inflammatory pathways. Furthermore, human genetic evidence has linked the dysregulation of RIPK1 to the pathogenesis of ALS as well as other inflammatory and neurodegenerative diseases. Importantly, unique allosteric small-molecule inhibitors of RIPK1 that offer high selectivity have been developed. These molecules can penetrate the blood–brain barrier, thus offering the possibility to target neuroinflammation and cell death which drive various neurologic conditions including Alzheimer’s disease, ALS, and multiple sclerosis as well as acute neurological diseases such as stroke and traumatic brain injuries. We discuss the current understanding of RIPK1 regulatory mechanisms and emerging evidence for the pathological roles of RIPK1 in human diseases, especially in the context of the central nervous systems.

Tumor necrosis factor receptor-2 (TNFR2): an overview of an emerging drug target

INTRODUCTION

Tumor necrosis factor (TNF) receptor 2 (TNFR2) is one of two receptors of the cytokines, TNF and lymphotoxin-α. TNFR1 is a strong inducer of proinflammatory activities. TNFR2 has proinflammatory effects too, but it also elicits strong anti-inflammatory activities and has protective effects on oligodendrocytes, cardiomyocytes, and keratinocytes. The protective and anti-inflammatory effects of TNFR2 may explain why TNF inhibitors failed to be effective in diseases such as heart failure or multiple sclerosis, where TNF has been strongly implicated as a driving force. Stimulatory and inhibitory TNFR2 targeting hence attracts considerable interest for the treatment of autoimmune diseases and cancer. Areas covered: Based on a brief description of the pathophysiological importance of the TNF-TNFR1/2 system, we discuss the potential applications of TNFR2 targeting therapies. We also debate TNFR2 activation as a way forward in the search for TNFR2-specific agents. Expert opinion: The use of TNFR2 to target regulatory T-cells is attractive, but this approach is just one amongst many suitable targets. With respect to its preference for Treg stimulation and protection of non-immune cells, TNFR2 is more unique and thus offers opportunities for translational success.

Leukemia Inhibitory Factor Represses GnRH Gene Expression via cFOS during Inflammation in Male Mice

BACKGROUND

The mechanisms whereby neuroinflammation negatively affects neuronal function in the hypothalamus are not clear. Our previous study determined that obesity-mediated chronic inflammation elicits sex-specific impairment in reproductive function via reduction in spine density in gonadotropin-releasing hormone (GnRH) neurons. Neuroinflammation and subsequent decrease in GnRH neuron spine density was specific for male mice, while protection in females was independent of ovarian estrogens.

METHODS

To examine if neuroinflammation-induced cytokines can directly regulate GnRH gene expression, herein we examined signaling pathways and mechanisms in males in vivo and in GnRH-expressing cell line, GT1-7.

RESULTS

GnRH neurons express cytokine receptors, and chronic or acute neuroinflammation represses GnRH gene expression in vivo. Leukemia inhibitory factor (LIF) in particular represses GnRH expression in GT1-7 cells, while other cytokines do not. STAT3 and MAPK pathways are activated following LIF treatment, but only MAPK pathway, specifically p38α, is sufficient to repress the GnRH gene. LIF induces cFOS that represses the GnRH gene via the -1,793 site in the enhancer region. In vivo, following high-fat diet, cFOS is induced in GnRH neurons and neurons juxtaposed to the leaky blood brain barrier of the organum vasculosum of the lamina terminalis, but not in the neurons further away.

CONCLUSION

Our results indicate that the increase in LIF due to neuroinflammation induces cFOS and represses the GnRH gene. Therefore, in addition to synaptic changes in GnRH neurons, neuroinflammatory cytokines directly regulate gene expression and reproductive function, and the specificity for neuronal targets may stem from the proximity to the fenestrated capillaries.