Plasma protein profiling reveals dynamic immunomodulatory changes in multiple sclerosis patients during pregnancy

Multiple sclerosis (MS) is a chronic autoimmune neuroinflammatory and neurodegenerative disorder of the central nervous system. Pregnancy represents a natural modulation of the disease course, where the relapse rate decreases, especially in the 3^rd trimester, followed by a transient exacerbation after delivery. Although the exact mechanisms behind the pregnancy-induced modulation are yet to be deciphered, it is likely that the immune tolerance established during pregnancy is involved. In this study, we used the highly sensitive and specific proximity extension assay technology to perform protein profiling analysis of 92 inflammation-related proteins in MS patients (n=15) and healthy controls (n=10), longitudinally sampled before, during, and after pregnancy. Differential expression analysis was performed using linear models and p-values were adjusted for false discovery rate due to multiple comparisons. Our findings reveal gradual dynamic changes in plasma proteins that are most prominent during the 3^rd trimester while reverting post-partum. Thus, this pattern reflects the disease activity of MS during pregnancy. Among the differentially expressed proteins in pregnancy, several proteins with known immunoregulatory properties were upregulated, such as PD-L1, LIF-R, TGF-β1, and CCL28. On the other hand, inflammatory chemokines such as CCL8, CCL13, and CXCL5, as well as members of the tumor necrosis factor family, TRANCE and TWEAK, were downregulated. Further in-depth studies will reveal if these proteins can serve as biomarkers in MS and whether they are mechanistically involved in the disease amelioration and worsening. A deeper understanding of the mechanisms involved may identify new treatment strategies mimicking the pregnancy milieu.

Pro-Inflammatory and B Cell Regulating Capacities of TWEAK in Rainbow Trout (Oncorhynchus mykiss)

Tumor necrosis factor (TNF)-like weak inducer of apoptosis or TWEAK is a member of the TNF superfamily involved in the regulation of many biological processes. In mammals, TWEAK has been shown to play a role in some autoimmune or inflammatory conditions, but its immune role is not yet clearly defined. In teleost fish, although a few studies have identified homologues to mammalian TWEAK, their biological effects have never been investigated. In the current study, we have studied the transcriptional regulation of two TWEAK homologues (TWEAK 1 and 2) identified in rainbow trout (Oncorhynchus mykiss) throughout different tissues, in response to parasitic or viral infections, or in head kidney (HK) leukocytes stimulated with different stimuli. Although the transcription of both homologues was modulated when HK leukocytes were exposed to several immune stimuli, only TWEAK 1 was significantly modulated upon pathogenic exposure. Thus, we performed a characterization of the functions exerted by this cytokine in HK leukocytes. Recombinant TWEAK 1 strongly up-regulated the transcription of pro-inflammatory genes and antimicrobial peptides in HK leukocytes, with differential transcriptional effects in IgM⁺ B cells, IgM^- lymphocytes and myeloid cells. TWEAK 1 also increased the survival and promoted the differentiation of B cells in HK leukocyte cultures. Our results demonstrate that in teleost fish, TWEAK 1 is involved in the response to different types of pathogens, through the modulation of antimicrobial and pro-inflammatory genes in different leukocytes subsets. Furthermore, a role for TWEAK as a B cell differentiation factor has also been established in rainbow trout.

Serum tumor necrosis factor-like weak inducer of apoptosis levels are elevated in schizophrenia

OBJECTIVE

The purpose of this study was to assess serum Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) concentrations to determine whether changes in patients with schizophrenia could have etiopathogenetic importance. Since very little research has addressed the connection between the inflammatory marker TWEAK and schizophrenia, we wanted to examine alterations of TWEAK and investigate the possible correlation between clinical symptomatology and serum concentrations.

METHODS

A total of 45 schizophrenia patients and 40 healthy controls were included in this study. The Positive Symptom Assessment scale and the Negative Symptom Assessment scale were administered to determine symptom severity. Venous blood samples were collected and serum TWEAK levels were measured.

RESULTS

Serum TWEAK levels were significantly higher in the schizophrenia group than the control group, independently of potential confounders, including sex, age, body mass index and smoking status.

CONCLUSION

The results indicate that TWEAK is elevated in schizophrenia patients, which could deepen our understanding of the role of inflammation in the pathogenesis of schizophrenia.

Is serum TWEAK a useful biomarker of neuropsychiatric systemic lupus erythematosus?

The aim of this study was to determine the role of the tumor necrosis factor like weak inducer of apoptosis (TWEAK) as a serum biomarker of neuropsychiatric involvement in systemic lupus erythematosus (NPSLE). Levels of TWEAK levels were measured in sera of 92 patients with systemic lupus erythematosus (SLE), including 28 patients with neuropsychiatric lupus, and in 59 healthy controls using ELISA. All SLE patients underwent rheumatological, neurological and psychiatric assessment. We found no significant differences in TWEAK levels, between SLE patients and the healthy controls (p=0.2411). Similarly, no difference was observed between subgroup of NPSLE and healthy controls (p=0.7658). The mean SLE disease activity (SLEDAI) was 13.25. No correlations between TWEAK levels with disease activity (SLEDAI, r=0.2113, p=0.2805) or the most common NPSLE manifestations such as headache (r=0.2079), seizures (r=0.1101), cerebrovascular disease (r= 0.2347), cognitive dysfunction (r=0.1597) and anxiety (r=0.1397) were observed. Our data do not support the use of serum TWEAK as a discriminating biomarker for NPSLE. The role of the TWEAK in NPSLE remains to be investigated.

High fat diet consumption results in mitochondrial dysfunction, oxidative stress, and oligodendrocyte loss in the central nervous system

Metabolic syndrome is a key risk factor and co-morbidity in multiple sclerosis (MS) and other neurological conditions, such that a better understanding of how a high fat diet contributes to oligodendrocyte loss and the capacity for myelin regeneration has the potential to highlight new treatment targets. Results demonstrate that modeling metabolic dysfunction in mice with chronic high fat diet (HFD) consumption promotes loss of oligodendrocyte progenitors across the brain and spinal cord. A number of transcriptomic and metabolomic changes in ER stress, mitochondrial dysfunction, and oxidative stress pathways in HFD-fed mouse spinal cords were also identified. Moreover, deficits in TCA cycle intermediates and mitochondrial respiration were observed in the chronic HFD spinal cord tissue. Oligodendrocytes are known to be particularly vulnerable to oxidative damage, and we observed increased markers of oxidative stress in both the brain and spinal cord of HFD-fed mice. We additionally identified that increased apoptotic cell death signaling is underway in oligodendrocytes from mice chronically fed a HFD. When cultured under high saturated fat conditions, oligodendrocytes decreased both mitochondrial function and differentiation. Overall, our findings show that HFD-related changes in metabolic regulators, decreased mitochondrial function, and oxidative stress contribute to a loss of myelinating cells. These studies identify HFD consumption as a key modifiable lifestyle factor for improved myelin integrity in the adult central nervous system and in addition new tractable metabolic targets for myelin protection and repair strategies.

High levels of serum soluble TWEAK are associated with neuroinflammation during multiple sclerosis

Background

Inflammation and demyelination are the main processes in multiple sclerosis. Nevertheless, to date, blood biomarkers of inflammation are lacking. TWEAK, a transmembrane protein that belongs to the TNF ligand family, has been previously identified as a potential candidate.

Methods

Twenty-eight patients (9 males, 19 females) were prospectively included after a first clinical episode suggestive of multiple sclerosis and clinically followed during 3 years. Fifty-seven healthy controls were also included. TWEAK serum levels and MRI exams including magnetization transfer imaging were performed at baseline, 6- and 12-month follow-up.

Results

TWEAK serum levels were significantly increased in the patient group (mean baseline = 1086 ± 493 pg/mL, mean M6 = 624 ± 302 pg/mL and mean M12 = 578 ± 245 pg/mL) compared to healthy controls (mean = 467 ± 177 pg/mL; respectively p < 0.0001, 0.01 and 0.06). Serum levels of soluble TWEAK were significantly increased during relapses, compared to time periods without any relapse (respectively 935 ± 489 pg/mL and 611 ± 292 pg/mL, p = 0.0005). Moreover, patients presenting at least one gadolinium-enhanced CNS lesion at baseline (n = 7) displayed significantly increased serum TWEAK levels in comparison with patients without any gadolinium-enhanced lesion at baseline (n = 21) (respectively 1421 ± 657 pg/mL vs 975 ± 382 pg/mL; p = 0.02). Finally, no correlation was evidenced between TWEAK serum levels and the extent of brain tissue damage assessed by magnetization transfer ratio.

Conclusions

The present study showed that TWEAK serum levels are increased in MS patients, in relation to the disease activity. This simple and reproducible serum test could be used as a marker of ongoing inflammation, contributing in the follow-up and the care of MS patients. Thus, TWEAK is a promising serum marker of the best window to perform brain MRI, optimizing the disease control in patients.

Role of the tumour necrosis factor-like weak inducer of apoptosis (TWEAK)/fibroblast growth factor-inducible 14 (Fn14) axis in autoimmune thyroid disease

BACKGROUND

TNF-like weak inducer of apoptosis (TWEAK), its receptor fibroblast growth factor-inducible 14 (Fn14) and its scavenger receptor CD163 (sCD163) have known associations with many autoimmune diseases. However, the role of the TWEAK axis in autoimmune thyroid disease (AITD) remains unclear. Therefore, the aim of this study was to investigate the role of the TWEAK-Fn14 axis in the pathogenesis of AITD.

METHODS

Serum levels of soluble TWEAK (sTWEAK) and sCD163 were measured in 38 patients with Graves' disease (GD), 40 patients with Hashimoto's thyroiditis (HT) and 40 healthy controls (HCs). Additionally, the mRNA expression of TWEAK and Fn14 in peripheral blood mononuclear cells (PBMCs) was explored, and the protein expression of TWEAK and Fn14 in thyroid glands surgically removed from 10 patients with GD, 10 patients with HT and 10 HCs was studied by immunohistochemical staining.

RESULTS

The results showed that the serum levels of sTWEAK were significantly reduced in patients with HT and inversely correlated with antithyroid peroxidase antibody (TPOAb) levels. Additionally, high levels of sCD163 and a high sCD163/sTWEAK ratio were positively associated with the TPOAb levels in patients with HT and the thyrotropin receptor antibody (TRAb) levels in patients with GD. TWEAK mRNA expression and protein expression were upregulated in thyroid glands and PBMCs from patients with HT.

CONCLUSION

Expression of the TWEAK-Fn14 axis was upregulated in patients with AITD and might play a role in the pathogenesis of AITD.

Regulation of Neuroinflammation: What Role for the Tumor Necrosis Factor-Like Weak Inducer of Apoptosis/Fn14 Pathway?

Observed in many central nervous system diseases, neuroinflammation (NI) proceeds from peripheral immune cell infiltration into the parenchyma, from cytokine secretion and from oxidative stress. Astrocytes and microglia also get activated and proliferate. NI manifestations and consequences depend on its context and on the acute or chronic aspect of the disease. The tumor necrosis factor-like weak inducer of apoptosis (TWEAK)/Fn14 pathway has been involved in chronic human inflammatory pathologies such as neurodegenerative, autoimmune, or malignant diseases. New data now describe its regulatory effects in tissues or fluids from patients with neurological diseases. In this mini-review, we aim to highlight the role of TWEAK/Fn14 in modulating NI in multiple sclerosis, neuropsychiatric systemic lupus erythematosus, stroke, or glioma. TWEAK/Fn14 can modulate NI by activating canonical and non-canonical nuclear factor-κB pathways but also by stimulating mitogen-activated protein kinase signaling. These downstream activations are associated with (i) inflammatory cytokine, chemokine and adhesion molecule expression or release, involved in NI propagation, (ii) matrix-metalloproteinase 9 secretion, implicated in blood–brain barrier disruption and tissue remodeling, (iii) astrogliosis and microgliosis, and (iv) migration of tumor cells in glioma. In addition, we report several animal and human studies pointing to TWEAK as an attractive therapeutic target.

TWEAK-binding autoantibodies are generated during psoriatic arthritis and are not influenced by anti-TNF therapy

BACKGROUND

TNF weakly inducer of apoptosis (TWEAK) is member of the TNF ligand superfamily. Various data support that TWEAK produced by synovial macrophages may contribute to synovitis observed in psoriatic arthritis (PsoA). In PsoA, anti-TNF therapy has been successful in agreement with the key role of TNF in the pathogenesis and the generation by PsoA patients of anti-TNF autoantibodies referred as "beneficial autoimmunity to pro-inflammatory mediators". However, the role of TNF-alpha in the regulation of TWEAK modulation of inflammation during PsoA remains unknown.

METHODS

We have studied level course during anti-TNF therapy of serum soluble TWEAK. In the same cohort, we have investigated the generation of TWEAK-binding autoantibodies by PsoA patients before and after anti-TNF therapy.

RESULTS

Patients with PsoA had significantly higher serum levels of TWEAK compared with controls [respective means (±SEM) were 645 pg/ml (64) and 467 pg/ml (23); (p = 0.006)] but serum soluble TWEAK levels were not correlated with BASDAI (Spearman's coefficients <0.003, p > 0.05). Our study showed that soluble TWEAK levels were not modulated by etanercept therapy [respective Means (±SEM) were 605 (95) (week 12) and 744 (97) (week 24) pg/ml; (p > 0.23)]. Anti-TWEAK autoantibodies were detected in 9/13 (69.2 %) PsoA patients at inclusion and only in 3/57 (5.3 %) healthy blood donors (p < 0.0001). These circulating antibodies were persistent in PsoA patients and detected at similar levels during etanercept therapy. Moreover we showed that they had a down regulating effect on CCL-2 secretion by endothelial cells stimulated by rh TWEAK in vitro.

CONCLUSION

Our study revealed that during psoriatic arthritis (1) serum TWEAK was up regulated and (2) TWEAK-binding autoantibodies are generated. Both parameters were not influenced by anti-TNF therapy and persisted at high levels during anti-TNF therapy. For the first time we described here TWEAK-binding IgG autoantibodies with a down regulating effect on CCL-2 secretion by endothelial cells stimulated by rh TWEAK in vitro. Finally, our results suggest that TWEAK may be involved in PsoA pathogeny. Trial registration This clinical trial was approved by the local Ethics Committee "Comité de Protection des Personnes Sud-Méditerranée V" with the registration number: 2011-002954-29, and French health minister registration number AFSSAPS A110784-42 obtained the 08/22/2011. This clinical trial is registered in Clinical trial.gov under the number: NCT02164214.

Utility of TWEAK to assess neuropsychiatric disease activity in systemic lupus erhytematosus

OBJECTIVE

The purpose of this study was to assess the utility of tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) in serum and cerebrospinal fluid (CSF) as a biomarker in neuropsychiatric systemic lupus erythematosus (NPSLE).

METHODS

Thirty three NPSLE patients were evaluated at hospitalization and six months later. As controls, five SLE patients with septic meningitis, 51 hospitalized SLE patients without a history of neuropsychiatric (NP) manifestations and without infections, 16 SLE patients without NP manifestations (surgical-SLE), four patients with primary neuropsychiatric disorders, and 25 patients with non-autoimmune diseases were also studied. Serum and CSF samples were drawn at hospitalization, except non-NPSLE patients, in whom only serum was studied, and six months later in 19 NPSLE and 27 non-NPSLE patients. Serum and CSF TWEAK levels were measured by ELISA; values are expressed in pg/mL.

RESULTS

The mean ± SD age of NPSLE patients was 31 ± 13.1 years, which was similar across study groups (p = 0.54). TWEAK levels in serum were not different across the study groups. In CSF, TWEAK levels were higher in NPSLE, surgical-SLE and primary neuropsychiatric groups than in non-autoimmune patients: median (IQR) 159.2 (94.1-374.9), 172.3 (125.3-421.9), 371.3 (143-543) vs. 122.1 (76.1-212.4), respectively; all p < 0.05. Six months later, when the neuropsychiatric manifestations were clinically in remission, serum or CSF TWEAK did not vary from baseline in NPSLE patients.

CONCLUSIONS

TWEAK levels are slightly elevated in CSF in SLE patients compared with non-autoimmune controls, irrespective of the presence of NP manifestations. TWEAK levels in serum and CSF do not seem to be a useful biomarker of CNS involvement in SLE.

TWEAK and the progression of renal disease: clinical translation

Tumour necrosis factor-like weak inducer of apoptosis (TWEAK) activates the fibroblast growth factor-inducible-14 (Fn14) receptor. TWEAK has actions on intrinsic kidney cells and on inflammatory cells of potential pathophysiological relevance. The effects of TWEAK in tubular cells have been explored in most detail. In cultured murine tubular cells TWEAK induces the expression of inflammatory cytokines, downregulates the expression of Klotho, is mitogenic, and in the presence of sensitizing agents promotes apoptosis. Similar actions were observed on glomerular mesangial cells. In vivo TWEAK actions on healthy kidneys mimic cell culture observations. Increased expression of TWEAK and Fn14 was reported in human and experimental acute and chronic kidney injury. The role of TWEAK/Fn14 in kidney injury has been demonstrated in non-inflammatory compensatory renal growth, acute kidney injury and chronic kidney disease of immune and non-immune origin, including hyperlipidaemic nephropathy, lupus nephritis (LN) and anti-GBM nephritis. The nephroprotective effect of TWEAK or Fn14 targeting in immune-mediated kidney injury is the result of protection from TWEAK-induced injury of renal intrinsic cells, not from interference with the immune response. A phase I dose-ranging clinical trial demonstrated the safety of anti-TWEAK antibodies in humans. A phase II randomized placebo-controlled clinical trial exploring the efficacy, safety and tolerability of neutralizing anti-TWEAK antibodies as a tissue protection strategy in LN is ongoing. The eventual success of this trial may expand the range of kidney diseases in which TWEAK targeting should be explored.

The TWEAK-Fn14 system as a potential drug target

Fibroblast growth factor-inducible 14 (Fn14) is a member of the tumour necrosis factor (TNF) receptor family that is induced in a variety of cell types in situations of tissue injury. Fn14 becomes activated by TNF-like weak inducer of apoptosis (TWEAK), a typical member of the TNF ligand family. TWEAK is constitutively expressed by monocytes and some tumour cell lines and also shows cytokine inducible expression in various other cell types. Fn14 activation results in stimulation of signalling pathways culminating in the activation of NFκB transcription factors and various MAPKs but might also trigger the PI3K/Akt pathway and GTPases of the Rho family. In accordance with its tissue damage-associated expression pattern and its pleiotropic proinflammatory signalling capabilities, the TWEAK-Fn14 system has been implicated in a huge number of pathologies. The use of TWEAK- and Fn14-knockout mice identified the TWEAK-Fn14 system as a crucial player in muscle atrophy, cerebral ischaemia, kidney injury, atherosclerosis and infarction as well as in various autoimmune scenarios including experimental autoimmune encephalitis, rheumatoid arthritis and inflammatory bowel disease. Moreover, there is increasing preclinical evidence that Fn14 targeting is a useful option in tumour therapy. Based on a discussion of the signalling capabilities of TWEAK and Fn14, this review is focused on two major issues. On the one hand, on the molecular and cellular basis of the TWEAK/Fn14-related pathological outcomes in the aforementioned diseases and on the other hand, on the preclinical experience that have been made so far with TWEAK and Fn14 targeting drugs.

Is TWEAK a Biomarker for Autoimmune/Chronic Inflammatory Diseases?

The TWEAK/Fn14 pathway is now well-known for its involvement in the modulation of inflammation in various human autoimmune/chronic inflammatory diseases (AICID) including lupus, rheumatoid arthritis, and multiple sclerosis. A panel of data is now available concerning TWEAK expression in tissues or biological fluids of patients suffering from AICID, suggesting that it could be a promising biological marker in these diseases. Evidences from several teams support the hypothesis that blocking TWEAK/Fn14 pathway is an attractive new therapeutic lead in such diseases and clinical trials with anti-TWEAK-blocking antibodies are in progress. In this mini-review we discuss the potential use of TWEAK quantification in AICD management in routine practice and highlight the challenge of standardizing data collection to better estimate the clinical utility of such a biological parameter.

BAFF, APRIL, TWEAK, BCMA, TACI and Fn14 proteins are related to human glioma tumor grade: immunohistochemistry and public microarray data meta-analysis

Gliomas are common and lethal tumors of the central nervous system (CNS). Genetic alterations, inflammatory and angiogenic processes have been identified throughout tumor progression; however, treatment still remains palliative for most cases. Biological research on parameters influencing cell survival, invasion and tumor heterogeneity identified several cytokines interfering in CNS inflammation, oxidative stress and malignant transformation, including TNF-superfamily (TNFSF) members. In this report we performed a meta-analysis of public gene-array data on the expression of a group of TNFSF ligands (BAFF, APRIL, TWEAK) and their receptors (BAFF-R, TACI, BCMA, Fn14) in gliomas. In addition, we investigated by immunohistochemistry (IHC) the tumor cells' expression of these ligands and receptors in a series of 56 gliomas of different grade. We show that in IHC, BAFF and APRIL as well as their cognate receptors (BCMA, TACI) and Fn14 expression correlate with tumor grade. This result was not evidenced in micro-arrays meta-analysis. Finally, we detected for the first time Fn14, BAFF, BCMA and TACI in glioma-related vascular endothelium. Our data, combined with our previous report in glioma cell lines, suggest a role for these receptors and ligands in glioma biology and advance these molecules as potential markers for the classification of these tumors to the proliferative, angiogenic or stem-like molecular subtype.

A further TWEAK to multiple sclerosis pathophysiology

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) is a member of the TNF super family that controls many cellular activities including proliferation, migration, differentiation, apoptosis, and inflammation by binding to fibroblast growth factor-inducible 14 (Fn14), a highly inducible cell surface receptor. Recent studies have indicated that TWEAK-Fn14 axis signaling may contribute to chronic autoimmune diseases. TWEAK expression via microglia in cortical lesions, presence of TWEAK(+) macrophages in inflamed leptomeninges, and absence of TWEAK/Fn14 expression in healthy brain implicates importance of this pathway in pathogenesis of multiple sclerosis lesions. TWEAK-Fn14 axis blockade has also shown promise in various multiple sclerosis animal models. Stimulation of the TWEAK/Fn14 pathway can result in activation of both canonical and noncanonical NF-κB signaling and could also stimulate mitogen-activated protein kinase (MAPK) signaling pathways. Here, we have reviewed evidence of the possible role of TWEAK-Fn14 axis in pathophysiology of multiple sclerosis and experimental autoimmune encephalomyelitis (EAE) via neuroinflammation, tissue remodeling, blood-brain barrier (BBB) disruption, neurodegeneration, and astrogliosis.

Crystal structure of human TWEAK in complex with the Fab fragment of a neutralizing antibody reveals insights into receptor binding

The tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is a multifunctional cytokine playing a key role in tissue regeneration and remodeling. Dysregulation of TWEAK signaling is involved in various pathological processes like autoimmune diseases and cancer. The unique interaction with its cognate receptor Fn14 makes both ligand and receptor promising targets for novel therapeutics. To gain insights into this important signaling pathway, we determined the structure of soluble human TWEAK in complex with the Fab fragment of an antibody selected for inhibition of receptor binding. In the crystallized complex TWEAK is bound by three Fab fragments of the neutralizing antibody. Homology modeling shows that Fab binding overlaps with the putative Fn14 binding site of TWEAK. Docking of the Fn14 cysteine rich domain (CRD) to that site generates a highly complementary interface with perfectly opposing charged and hydrophobic residues. Taken together the presented structure provides new insights into the biology of TWEAK and the TWEAK/Fn14 pathway, which will help to optimize the therapeutic strategy for treatment of related cancer types and autoimmune diseases.

TWEAK/Fn14 pathway modulates properties of a human microvascular endothelial cell model of blood brain barrier

BACKGROUND

The TNF ligand family member TWEAK exists as membrane and soluble forms and is involved in the regulation of various human inflammatory pathologies, through binding to its main receptor, Fn14. We have shown that the soluble form of TWEAK has a pro-neuroinflammatory effect in an animal model of multiple sclerosis and we further demonstrated that blocking TWEAK activity during the recruitment phase of immune cells across the blood brain barrier (BBB) was protective in this model. It is now well established that endothelial cells in the periphery and astrocytes in the central nervous system (CNS) are targets of TWEAK. Moreover, it has been shown by others that, when injected into mice brains, TWEAK disrupts the architecture of the BBB and induces expression of matrix metalloproteinase-9 (MMP-9) in the brain. Nevertheless, the mechanisms involved in such conditions are complex and remain to be explored, especially because there is a lack of data concerning the TWEAK/Fn14 pathway in microvascular cerebral endothelial cells.

METHODS

In this study, we used human cerebral microvascular endothelial cell (HCMEC) cultures as an in vitro model of the BBB to study the effects of soluble TWEAK on the properties and the integrity of the BBB model.

RESULTS

We showed that soluble TWEAK induces an inflammatory profile on HCMECs, especially by promoting secretion of cytokines, by modulating production and activation of MMP-9, and by expression of cell adhesion molecules. We also demonstrated that these effects of TWEAK are associated with increased permeability of the HCMEC monolayer in the in vitro BBB model.

CONCLUSIONS

Taken together, the data suggest a role for soluble TWEAK in BBB inflammation and in the promotion of BBB interactions with immune cells. These results support the contention that the TWEAK/Fn14 pathway could contribute at least to the endothelial steps of neuroinflammation.

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) mediates p38 mitogen-activated protein kinase activation and signal transduction in peripheral blood mononuclear cells from patients with lupus nephritis

Forty-two patients with systemic lupus erythematosus (SLE), including 26 patients with renal damage and 16 without, and 20 healthy controls were included in the study. The isolated peripheral blood mononuclear cells (PBMCs) were treated with a p38 inhibitor (SB203580) or anti-tumor necrosis factor-like weak inducer of apoptosis (TWEAK) mAb, with or without phytohemagglutinin/phorbol myristate acetate (PHA/PMA) stimulation. Western blot experiments were used to evaluate the protein expression of TWEAK and p38 MAPK in PBMCs .Next, the contents of interleukin-10 (IL-10) and monocyte chemoattractant protein-1 (MCP-1) in the supernatant were measured by ELISA. The results showed that expression of TWEAK protein in PBMCs from lupus nephritis patients was significantly higher than that from SLE patients without renal damage and healthy controls. PHA/PMA simulation could upregulate the productions of TWEAK and p-p38MAPK in PBMCs from patients with SLE. Anti-TWEAK mAb treatment downregulated both TWEAK and p-p38 MAPK expression in PBMCs, as well as IL-10 and MCP-1 in the supernatant; SB203580 had the same effect on cytokine production in PBMC, but had no effect on the expression of TWEAK. Our results suggested that TWEAK-p38 MAPK-IL-10, MCP-1 signaling pathway in PBMC played an important pathogenic role in lupus nephritis.

TWEAK/Fn14 pathway: an immunological switch for shaping tissue responses

Our immune system performs the vital function of recognizing and eliminating invading pathogens and malignancies. There is an increasing appreciation that the immune system also actively mediates tissue responses under both physiological and pathological conditions, significantly impacting the inflammatory, fibrogenic, and regenerative components. Likewise, there is a growing understanding of how epithelial, endothelial, and other non-hematopoietic tissue cell types actively contribute to the interplay that shapes tissue responses. While much of the molecular basis underlying the immune regulation of tissue responses remains to be delineated, the tumor necrosis factor (TNF) superfamily ligand/receptor pair of TNF-like weak inducer of apoptosis (TWEAK) and fibroblast growth factor-inducible molecule 14 (Fn14) has now emerged as a key piece of this puzzle. In this review, we first discuss how the usually 'dormant' TWEAK/Fn14 pathway becomes activated specifically in injury and disease contexts. We then summarize how TWEAK-mediated Fn14 signaling triggers a wide range of activities in tissue parenchymal and stromal cells as well as progenitor cells. Finally, we review recent experimental evidence that further supports the functional dichotomy of TWEAK/Fn14 activation in physiological versus pathological tissue responses and its potential therapeutic implications. Whereas transient TWEAK/Fn14 activation promotes productive tissue responses after injury, excessive or persistent TWEAK/Fn14 activation drives pathological tissue responses, leading to progressive damage and degeneration.

TWEAK in inclusion-body myositis muscle: possible pathogenic role of a cytokine inhibiting myogenesis

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor Fn14 exert pleiotropic effects, including regulation of myogenesis. Sporadic inclusion-body myositis (IBM) is the most common muscle disease of the elderly population and leads to severe disability. IBM mesoangioblasts, different from mesoangioblasts in other inflammatory myopathies, display a myogenic differentiation defect. The objective of the present study was to investigate TWEAK-Fn14 expression in IBM and other inflammatory myopathies and explore whether TWEAK modulation affects myogenesis in IBM mesoangioblasts. TWEAK, Fn14, and NF-κB expression was assessed by immunohistochemistry and Western blot in cell samples from both muscle biopsies and primary cultures. Mesoangioblasts isolated from samples of IBM, dermatomyositis, polymyositis, and control muscles were treated with recombinant human TWEAK, Fn14-Fc chimera, and anti-TWEAK antibody. TWEAK-RNA interference was performed in IBM and dermatomyositis mesoangioblasts. TWEAK levels in culture media were determined by enzyme-linked immunosorbent assay. In IBM muscle, we found increased TWEAK-Fn14 expression. Increased levels of TWEAK were found in differentiation medium from IBM mesoangioblasts. Moreover, TWEAK inhibited myogenic differentiation of mesoangioblasts. Consistent with this evidence, TWEAK inhibition by Fn14-Fc chimera or short interfering RNA induced myogenic differentiation of IBM mesoangioblasts. We provide evidence that TWEAK is a negative regulator of human mesoangioblast differentiation. Dysregulation of the TWEAK-Fn14 axis in IBM muscle may induce progressive muscle atrophy and reduce activation and differentiation of muscle precursor cells.

Elevation of human tumor necrosis factor-like weak inducer of apoptosis in peripheral blood mononuclear cells is correlated with disease activity and lupus nephritis in patients with systemic lupus erythematosus

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) is a recently identified proinflammatory cytokine of the TNF superfamily. Studies have indicated that TWEAK plays an important role in renal, vascular injury and immune disease. The aim of this study was to explore the expression of the TWEAK in peripheral blood mononuclear cells (PBMCs) and analyze the correlation between TWEAK and disease activity and renal damage of SLE. The expression of TWEAK in PBMCs was determined by RT-PCR and western blot. SLE disease activity was evaluated by Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) 2000 score. Next were analyzed the correlations of TWEAK mRNA and protein to serum IL-10, MCP-1 and some laboratory parameters of SLE disease activity. Subjects comprised 48 patients with SLE including 25 patients with renal damage and 23 without, 20 patients with rheumatoid arthrithis (RA) and 15 healthy controls. The results showed that TWEAK expressions in PBMCs from SLE patients were significantly higher than that in RA patients or healthy controls, especially higher in those patients with renal disease. Elevated production of TWEAK is correlated positively and significantly with SLEDAI, proteinuria, serum anti-dsDNA, IL-10 and MCP-1, but inversely associated with serum complements. Our results suggested that TWEAK in PBMCs is positively related to SLE disease activity and might be involved in the pathogenesis of SLE.

Full-length, membrane-anchored TWEAK can function as a juxtacrine signaling molecule and activate the NF-kappaB pathway

Tumor necrosis factor (TNF) family members are initially synthesized as type II transmembrane proteins, but some of these proteins are substrates for proteolytic enzymes that generate soluble cytokines with biological activity. TWEAK (TNF-like weak inducer of apoptosis), a member of the TNF family, is a multifunctional cytokine that acts via binding to a cell surface receptor named Fn14 (fibroblast growth factor-inducible 14). Studies conducted to date indicate that TWEAK-producing cells can co-express both membrane-anchored and soluble TWEAK isoforms, but there is little information on TWEAK proteolytic processing. Also, it is presently unclear whether membrane-anchored TWEAK, like soluble TWEAK, is biologically active. Here we show that full-length human TWEAK is processed intracellularly by the serine protease furin and identify TWEAK amino acid residues 90-93 as the predominant furin recognition site. In addition, we report that full-length, membrane-anchored TWEAK can bind the Fn14 receptor on neighboring cells and activate the NF-kappaB signaling pathway. Thus, TWEAK can act in a juxtacrine manner to initiate cellular responses, and this property may be important for TWEAK function during physiological wound repair and disease pathogenesis.

Fibroblast growth factor-inducible 14 (Fn14) is expressed in the lower genital tract and may play a role in amplifying inflammation during infection

TNF-like weak inducer of apoptosis (TWEAK) is a member of the tumor necrosis factor (TNF) cytokine superfamily which regulates a number of cellular responses, including inflammation and proliferation. TWEAK is primarily secreted by phagocytic cells and its receptor, fibroblast growth factor-inducible 14 (Fn14), is expressed on non-lymphoid cells, including epithelial, endothelial and mesenchymal cells. The TWEAK/Fn14 pathway is highly conserved from an evolutionary standpoint, and has been shown to play a role in tissue regeneration and inflammation in the liver, kidney, lung and skeletal muscle. We hypothesized that TWEAK/Fn14 might have a physiological role in regulating infection-induced inflammation in the lower female genital tract. To test this hypothesis, we examined expression of the receptor Fn14 in relevant cells and tissue. Receptor function was tested by treating cells with recombinant TWEAK, with and without other known proinflammatory stimuli. Flow cytometric analysis of vaginal and cervical epithelial cells revealed that Fn14 was highly expressed at the cell surface. We also detected both Fn14 and TWEAK in whole cervical tissue by RT-PCR. Treatment of vaginal and cervical epithelial cells with recombinant TWEAK led to a weak induction of the chemokine IL-8. However, TWEAK potentiated the effects of IL-1ss, the TLR2 ligand Pam(3)CysSK(4), and live Neisseria gonorrhoeae in a synergistic manner. These data reveal a novel pathway for regulation of microbial-induced inflammation in the female reproductive tract and suggest that interference with the TWEAK/Fn14 pathway might be an approach to abrogate excessive infection-induced inflammation caused by sexually transmitted pathogens.