TWEAK and the Central Nervous System

Evaluation Expression of the Caspase-3 and Caspase-9 Apoptotic Genes in Schizophrenia Patients

Objective

Apoptosis is programmed cell death that occurs by several pathways. Caspase-3 is induced by active caspase-9 via the intrinsic pathway. The aim of this research was to explore the expression of caspase-3 and caspase-9 in schizophrenia patients and healthy samples.

Methods

RNA was isolated from the peripheral blood of 39 schizophrenia patients' and healthy samples. After cDNA synthesis, real time PCR (RT-PCR) was used to analyse caspase-3 and caspase-9 gene expression. The severity of psychopathological symptoms of schizophrenia was evaluated using the Positive and Negative Symptoms Scale for schizophrenia (PANSS) and Clinical Global Impressions (CGI).

Results

The expression of caspase-3 and caspase-9 genes was higher in schizophrenia patients than in healthy samples (p = 0.012, p = 0.002, respectively). The increase in caspase-3 gene expression was significant with being male, smoking and with a duration of less than 6 years (p = 0.047, p = 0.049, p = 0.034, respectively). On the other hand, the increase in caspase-9 gene expression was significant in patients who is smoke, have children, and are under 33 years old (p = 0.040, p = 0.043, p = 0.045, respectively). A significant positive correlation was detected between the caspase-3 and caspase-9 gene expression (r = 0.3218, p = 0.049).

Conclusion

Our findings indicate that caspase-3 and caspase-9 gene expression may activate cell death mechanisms by intrinsic apoptotic genes. Furthermore, caspase-3 and caspase-9 may play essential roles in different ways in schizophrenia. Hence there is a need to further study the apoptotic mechanism with expanded patient populations.

Plasma protein alterations during human large vessel stroke: A controlled comparison study

BACKGROUND

Stroke is a major cause of death and disability in the United States. Mechanical thrombectomy (MT) ¹ and tissue plasminogen activator are the current treatments for ischemic stroke, which have improved clinical outcomes. Despite these treatments, functional and cognitive deficits still occur demonstrating a need for predictive biomarkers for beneficial clinical outcomes which can be used as therapeutic targets for pharmacotherapy. The aim of this study compares the proteomic expression of systemic arterial blood collected at the time of MT to those from a matched cerebrovascular disease (CVD) control cohort.

METHODS

The Blood and Clot Thrombectomy Registry and Collaboration (BACTRAC) (clinicaltrials.gov NCT03153683) collects and banks arterial blood, both distal and proximal to the thrombus, from ischemic stroke subjects undergoing MT. Arterial blood from patients undergoing a diagnostic angiogram was also collected and banked as CVD controls. Changes in cardiometabolic and inflammatory proteins between stroke and CVD controls were analyzed via Olink Proteomics.

RESULTS

Proteins including ARTN, TWEAK, HGF, CCL28, FGF-5, CXCL9, TRANCE and GDNF were found to be decreased in stroke subjects when compared to CVD controls. CXCL1, CCL5, OSM, GP1BA, IL6, MMP-1, and CXCL5 were increased in stroke subjects when compared to CVD controls. These proteins were also significantly correlated to stroke outcome metrics such as NIHSS, infarct volume and MoCA scoring.

CONCLUSION

Overall, acute stroke patients had an increase in inflammatory proteins with a decrease in trophic proteins systemically compared to matched CVD controls. Using our CVD controls, proteins of interest were directly compared to stroke patients with the same cerebrovascular risk factors instead of statistically controlling for comorbidities. The novel methodology of matching an arterial blood CVD control group to a stroke group, as well as controlling for age and comorbid status add to the literature on prognostic stroke biomarkers, which are specific targets for future therapeutics.

TNF-like weak inducer of apoptosis / nuclear factor κB axis feedback loop promotes spinal cord injury by inducing astrocyte activation

Non-canonical signaling pathways have been proved to act as potent sites of astrocytes osmotic expanding or proliferation, which promotes the regeneration of axons in areas with non-neural spinal cord injury (SCI). However, the relevant signal pathway that induces autophagic cell death in astrocytes and its function relative to the TNF-like weak inducer of apoptosis/nuclear factor κB (TWEAK/NF-κB) axis remains elusive. The SCI model was established by vertically striking the spinal cord according to Allen’s model. Astrocytes and neuronal cells were prepared from spinal cells extracted from spinal cord tissues of SCI or normal C57BL/6 newborn mice. After co-culturing astrocytes and neurons, cell viability and autophagy were determined by CCK-8, transmission electron microscopy (TEM), and western blot. The expression of TWEAK, NF-κB and inflammatory cytokines was confirmed by qRT-PCR, western blot, Immunofluorescence and ELISA assay. Chromatin immunoprecipitation (CHIP) was used to evaluate the interaction between TWEAK and NF-κB. Our results demonstrated that knockdown of TWEAK and NF-κB inhibited secretion of high levels of TNF-α/IL-1β, partially counteracted by adding Rap. TWEAK/NF-κB was the positive correlation feedback loop regulating the proliferation and autophagy of astrocytes involved in SCI. Moreover, restraining the excess growth of astrocytes was beneficial to the growth of neurons. Collectively, our findings illustrated that the TWEAK/NF-κB pathway might act as a positive modulator of SCI by inducing astrocyte activation, shedding new insights for SCI treatment.

Neuroinflammation in Autoimmune Disease and Primary Brain Tumors: The Quest for Striking the Right Balance

According to classical dogma, the central nervous system (CNS) is defined as an immune privileged space. The basis of this theory was rooted in an incomplete understanding of the CNS microenvironment, however, recent advances such as the identification of resident dendritic cells (DC) in the brain and the presence of CNS lymphatics have deepened our understanding of the neuro-immune axis and revolutionized the field of neuroimmunology. It is now understood that many pathological conditions induce an immune response in the CNS, and that in many ways, the CNS is an immunologically distinct organ. Hyperactivity of neuro-immune axis can lead to primary neuroinflammatory diseases such as multiple sclerosis and antibody-mediated encephalitis, whereas immunosuppressive mechanisms promote the development and survival of primary brain tumors. On the therapeutic front, attempts are being made to target CNS pathologies using various forms of immunotherapy. One of the most actively investigated areas of CNS immunotherapy is for the treatment of glioblastoma (GBM), the most common primary brain tumor in adults. In this review, we provide an up to date overview of the neuro-immune axis in steady state and discuss the mechanisms underlying neuroinflammation in autoimmune neuroinflammatory disease as well as in the development and progression of brain tumors. In addition, we detail the current understanding of the interactions that characterize the primary brain tumor microenvironment and the implications of the neuro-immune axis on the development of successful therapeutic strategies for the treatment of CNS malignancies.

A feasibility trial of gamma sensory flicker for patients with prodromal Alzheimer's disease

INTRODUCTION

We and collaborators discovered that flickering lights and sound at gamma frequency (40 Hz) reduce Alzheimer's disease (AD) pathology and alter immune cells and signaling in mice. To determine the feasibility of this intervention in humans we tested the safety, tolerability, and daily adherence to extended audiovisual gamma flicker stimulation.

METHODS

Ten patients with mild cognitive impairment due to underlying AD received 1-hour daily gamma flicker using audiovisual stimulation for 4 or 8 weeks at home with a delayed start design.

RESULTS

Gamma flicker was safe, tolerable, and adherable. Participants' neural activity entrained to stimulation. Magnetic resonance imaging and cerebral spinal fluid proteomics show preliminary evidence that prolonged flicker affects neural networks and immune factors in the nervous system.

DISCUSSION

These findings show that prolonged gamma sensory flicker is safe, tolerable, and feasible with preliminary indications of immune and network effects, supporting further study of gamma stimulation in AD.

sTWEAK as Predictor of Stroke Recurrence in Ischemic Stroke Patients Treated With Reperfusion Therapies

Aim: The purpose of this study was to investigate clinical and neuroimaging factors associated with stroke recurrence in reperfused ischemic stroke patients, as well as the influence of specific biomarkers of inflammation and endothelial dysfunction.

Methods: We conducted a retrospective analysis on a prospectively registered database. Of the 875 patients eligible for this study (53.9% males; mean age 69.6 ± 11.8 years vs. 46.1% females; mean age 74.9 ± 12.6 years), 710 underwent systemic thrombolysis, 87 thrombectomy and in 78, systemic or intra-arterial thrombolysis together with thrombectomy was applied. Plasma levels of interleukin 6 (IL-6) and tumor necrosis factor alpha (TNFα) were analyzed as markers of inflammation, and soluble tumor necrosis factor-like inducer of apoptosis (sTWEAK) as an endothelial dysfunction marker. The main outcome variables of the study were the presence and severity of leukoaraiosis (LA) and stroke recurrence.

Results: The average follow-up time of the study was 25 ± 13 months, during which 127 patients (14.5%) showed stroke recurrence. The presence and severity of LA was more severe in the second stroke episode (Grade III of the Fazekas 28.3 vs. 52.8%; p < 0.0001). IL-6 levels at the first admission and before reperfusion treatment in patients with and without subsequent recurrence were similar (9.9 ± 10.4 vs. 9.1 ± 7.0 pg/mL, p = 0.439), but different for TNFα (14.7 ± 5.6 vs. 15.9 ± 5.7 pg/mL, p = 0.031) and sTWEAK (5,970.8 ± 4,330.4 vs. 8,660.7 ± 5,119.0 pg/mL, p < 0.0001). sTWEAK values ≥7,000 pg/mL determined in the first stroke were independently associated to recurrence (OR 2.79; CI 95%: 1.87–4.16, p < 0.0001).

Conclusions: The severity and the progression of LA are the main neuroimaging factors associated with stroke recurrence. Likewise, sTWEAK levels were independently associated to stroke recurrence, so further studies are necessary to investigate sTWEAK as a therapeutic target.

LncRNA Snhg3 contributes to dysfunction of cerebral microvascular cells in intracerebral hemorrhage rats by activating the TWEAK/Fn14/STAT3 pathway

LncRNA small nucleolar RNA host gene 3 (Snhg3) has been involved in cell proliferation and migration in malignant cells. However, its role in regulating functions of non-malignant cells has been hardly reported. Here, we found Snhg3 expression was sharply induced in primary brain microvascular endothelial cells (BMVECs) treated with oxygen-and-glucose-deprivation (OGD) plus hemin, an in vitro model of intracerebral hemorrhage (ICH). Downregulation of Snhg3 by siRNA transfection improved cell proliferation and migration abilities and reduced cell apoptosis and monolayer permeability in BMVECs under treatment with OGD plus hemin. Snhg3 overexpression suppressed cell proliferation and migration and increased cell apoptosis and monolayer permeability under normal condition. In ICH rats, downregulation of Snhg3 by siRNA injection improved behavioral and histological manifestations, including number of right turns, limb placement score, integrity of blood-brain barrier (BBB), brain water content and cell apoptosis in vivo. In the mechanism exploration, we found that, TWEAK and Snhg3 displayed a positive correlation with each other. Snhg3 overexpression increased expression of TWEAK protein and its receptor Fn14, that were also induced by OGD plus hemin, activating the downstream neuroinflammatory pathway STAT3 and enhancing the secretion of MMP-2/9. Finally, the TWEAK-siRNA, the Fn14 inhibitor ATA and the STAT3 blocker AG490 were respectively used to treat BMVECs under treatment with OGD plus hemin. Our results showed either TWEAK downregulation, Fn14 inhibition, or STAT3 blockade, could rescue Snhg3-induced impairment of BMVEC functions. In conclusion, the lncRNA Snhg3 contributes to dysfunction of cerebral microvascular cells in ICH rats by activating the TWEAK/Fn14/STAT3 pathway.

Serum soluble TWEAK levels in severe traumatic brain injury and its prognostic significance

BACKGROUND

Severe traumatic brain injury (sTBI) is characterized by a high mortality. Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) participates in inflammation. We determined serum soluble TWEAK (sTWEAK) levels with respect to its prognostic ability.

METHODS

This was a single-center prospective, observational study that was performed from December 2014 to December 2017. A total of 114 sTBI patients who met the inclusion criteria and 114 randomly selected healthy controls were included in the study. Serum sTWEAK levels were gauged. Patients were followed-up until death or completion of 6 months. Poor outcome was referred to as Glasgow outcome scale score of 1-3.

RESULTS

In comparison with controls, patients displayed predominantly higher serum sTWEAK levels. Serum sTWEAK levels were strongly correlated with Glasgow coma scale scores and serum C-reactive protein levels. 32 patients (28.1%) died and 60 patients (52.6%) suffered from a poor outcome. Receiver operating characteristic curve analysis clearly showed that serum sTWEAK levels had substantially high predictive performance for 6-month mortality and poor outcome. Serum sTWEAK emerged as an independent predictor for 6-month mortality, overall survival and poor outcome.

CONCLUSIONS

Raised serum sTWEAK levels are closely related to increasing inflammatory response, elevated trauma severity and worse clinical outcome after sTBI.

Fn14 Participates in Neuropathic Pain Through NF-κB Pathway in Primary Sensory Neurons

Fibroblast growth factor-inducible-14 (Fn14), a receptor for tumor necrosis-like weak inducer of apoptosis, is expressed in the neurons of dorsal root ganglion (DRG). Its mRNA is increased in the injured DRG following peripheral nerve injury. Whether this increase contributes to neuropathic pain is unknown. We reported here that peripheral nerve injury caused by spinal nerve ligation (SNL) increased the expression of Fn14 at both protein and mRNA levels in the injured DRG. Blocking this increase attenuated the development of SNL-induced mechanical, thermal, and cold pain hypersensitivities. Conversely, mimicking this increase produced the increases in the levels of phosphorylated extracellular signal-regulated kinase ½ and glial fibrillary acidic protein in ipsilateral dorsal horn and the enhanced responses to mechanical, thermal, and cold stimuli in the absence of SNL. Mechanistically, the increased Fn14 activated the NF-κB pathway through promoting the translocation of p65 into the nucleus of the injured DRG neurons. Our findings suggest that Fn14 may be a potential target for the therapeutic treatment of peripheral neuropathic pain.

Endothelial cells and lymphatics at the interface between the immune and central nervous systems: implications for multiple sclerosis

PURPOSE OF REVIEW

The central nervous system (CNS) has a unique relationship with the immune system. This review highlights the distinct roles of lymphatic vessels and endothelial cells in the interface between CNS and immune cells and invites to revisit the concept of CNS immune privilege.

RECENT FINDINGS

T cells can follow several routes to penetrate the CNS parenchyma but may also benefit, together with antigen-loaded presenting cells, from the newly described lymphatic network to exit the CNS. CNS endothelial cells (EC) critically positioned at the interface between circulating immune cells and the CNS regulate the multistep cascade for immune cell trafficking into the CNS. They can also be considered as semiprofessional antigen-presenting cells through their ability to present antigens to T cells and to regulate their activation through co-stimulatory and inhibitory molecules.

SUMMARY

The lymphatic network linking the CNS to draining lymph nodes may contribute to the inflammatory reaction occurring in multiple sclerosis (MS). The abundance and strategic positioning of endothelial cells at the blood-brain barrier level most likely endow them with an important role in controlling local adaptive immune responses, rendering them potential therapeutic targets in neuro-inflammatory such as MS.

Biomeasures and mechanistic modeling highlight PK/PD risks for a monoclonal antibody targeting Fn14 in kidney disease

Discovery of the upregulation of fibroblast growth factor-inducible-14 (Fn14) receptor following tissue injury has prompted investigation into biotherapeutic targeting of the Fn14 receptor for the treatment of conditions such as chronic kidney diseases. In the development of monoclonal antibody (mAb) therapeutics, there is an increasing trend to use biomeasures combined with mechanistic pharmacokinetic/pharmacodynamic (PK/PD) modeling to enable decision making in early discovery. With the aim of guiding preclinical efforts on designing an antibody with optimized properties, we developed a mechanistic site-of-action (SoA) PK/PD model for human application. This model incorporates experimental biomeasures, including concentration of soluble Fn14 (sFn14) in human plasma and membrane Fn14 (mFn14) in human kidney tissue, and turnover rate of human sFn14. Pulse-chase studies using stable isotope-labeled amino acids and mass spectrometry indicated the sFn14 half-life to be approximately 5 hours in healthy volunteers. The biomeasures (concentration, turnover) of sFn14 in plasma reveals a significant hurdle in designing an antibody against Fn14 with desired characteristics. The projected dose (>1 mg/kg/wk for 90% target coverage) derived from the human PK/PD model revealed potential high and frequent dosing requirements under certain conditions. The PK/PD model suggested a unique bell-shaped relationship between target coverage and antibody affinity for anti-Fn14 mAb, which could be applied to direct the antibody engineering towards an optimized affinity. This investigation highlighted potential applications, including assessment of PK/PD risks during early target validation, human dose prediction and drug candidate optimization.

TWEAK-Fn14 Influences Neurogenesis Status via Modulating NF-κB in Mice with Spinal Cord Injury

The aim of our research is to investigate the regulatory role of TNF-like weak inducer of apoptosis- fibroblast growth factor-inducible 14 (TWEAK-Fn14) pathway in nuclear factor-kappa B (NF-κB) expression and neurogenesis status after spinal cord injury (SCI). We constructed a mice model of spinal cord injury and injected different lentiviral vectors which were transfected with TWEAK, TWEAK small interfering RNA (siRNA) and Fn14 siRNA into different groups of mice. Locomotor functional recovery status of the hind limb in mice was assessed using the Basso, Beattie and Bresnahan (BBB) test. Apoptosis status in the injured area was examined via TDT-mediated dUTP-biotin nick end-labeling (TUNEL) staining, the expression of GAP-43 in injured spinal cord was quantified by immunohistochemistry and expressions of TWEAK, Fn14, NF-κB, TNF-α, and IL-1β were evaluated by either western blot or ELISA. The expressions of TWEAK, Fn14, and NF-κB in the model group were significantly higher compared with those in the control group. Furthermore, the TWEAK group in which TWEAK was overexpressed exhibited significantly higher expressions of TWEAK, Fn14, and NF-κB, TNF-α and IL-1β in relation to those in the model group (P < 0.05 for all). Moreover, the transfection of Fn14 siRNA antagonized the above effect of TWEAK transfection on injured mice. On the other hand, the TWEAK siRNA group in which the expression of TWEAK was inhibited exhibited significantly lower expressions of TWEAK, Fn14, NF-κB, TNF-α, and IL-1β (P < 0.05 for all). Moreover, the transfection of TWEAK siRNA enhanced the locomotor functional recovery status in injured mice and suppressed the apoptosis of injured areas (P < 0.05 for all). In conclusion, stimulating the TWEAK-Fn14 pathway may elevate the expression of NF-κB, thereby slow the function recovery of SCI mice whereas inhibiting the TWEAK-Fn14 pathway may improve the neurogenesis status in mice with spinal cord injuries.

Soluble Fn14 Is Detected and Elevated in Mouse and Human Kidney Disease

The cytokine TWEAK and its cognate receptor Fn14 are members of the TNF/TNFR superfamily and are upregulated in tissue injury to mediate local tissue responses including inflammation and tissue remodeling. We found that in various models of kidney disease, Fn14 expression (mRNA and protein) is upregulated in the kidney. These models include: lupus nephritis mouse models (Nephrotoxic serum Transfer Nephritis and MRL.Faslpr/lpr), acute kidney injury models (Ischemia reperfusion injury and Folic acid injury), and a ZSF-1 diabetic nephropathy rat model. Fn14 expression levels correlate with disease severity as measured by disease histology. We have also shown for the first time the detection of soluble Fn14 (sFn14) in the urine and serum of mice. Importantly, we found the sFn14 levels are markedly increased in the diseased mice and are correlated with disease biomarkers including proteinuria and MCP-1. We have also detected sFn14 in human plasma and urine. Moreover, sFn14 levels, in urine are significantly increased in DN patients and correlated with proteinuria and MCP-1 levels. Thus our data not only confirm the up-regulation of Fn14/TWEAK pathway in kidney diseases, but also suggest a novel mechanism for its regulation by the generation of sFn14. The correlation of sFn14 levels and disease severity suggest that sFn14 may serve as a potential biomarker for both acute and chronic kidney diseases.

TNF-related weak inducer of apoptosis (TWEAK) levels in schizophrenia

Members of tumor necrosis factor (TNF) superfamily have roles in many biological events and pathogenesis of central nervous system (CNS) diseases. A relatively recently found member of this family, TNF-related weak inducer of apoptosis (TWEAK) have importance both in development of pathological CNS processes and as a target for the treatment of these diseases. The aim of this study was to investigate whether TWEAK's plasma levels are different in patients with schizophrenia. For this purpose plasma TWEAK levels of 44 patients diagnosed with schizophrenia and control group of 40 healthy individuals were compared. Although numerical difference was found between TWEAK levels of patients and controls it was not statistically significant. When we tested for female and male patients and controls seperately, TWEAK levels of male patients were significantly lower than male controls. As far as we know this is the first study that investigates levels of TWEAK in patients with schizophrenia. Although we did not find statistically significant results in our study, we believe that difference could be found in future studies with higher number of subjects. Researches with non-studied TNF superfamily members like TWEAK and TNF-related apoptosis-inducing ligand (TRAIL) could contribute to the understanding of immune-cytokine related hypotheses of schizophrenia.

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.

TNF-like weak inducer of apoptosis promotes blood brain barrier disruption and increases neuronal cell death in MRL/lpr mice

Neuropsychiatric disease is one of the most common manifestations of human systemic lupus erythematosus, but the mechanisms remain poorly understood. In human brain microvascular endothelial cells in vitro, TNF-like weak inducer of apoptosis (TWEAK) decreases tight junction ZO-1 expression and increases the permeability of monolayer cell cultures. Furthermore, knockout (KO) of the TWEAK receptor, Fn14, in the MRL/lpr lupus mouse strain markedly attenuates neuropsychiatric disease, as demonstrated by significant reductions in depressive-like behavior and improved cognitive function. The purpose of the present study was to determine the mechanisms by which TWEAK signaling is instrumental in the pathogenesis of neuropsychiatric lupus (NPSLE). Evaluating brain sections of MRL/lpr Fn14WT and Fn14KO mice, we found that Fn14KO mice displayed significantly decreased cellular infiltrates in the choroid plexus. To evaluate the integrity of the blood brain barrier (BBB) in MRL/lpr mice, Western blot for fibronectin, qPCR for iNOS, and immunohistochemical staining for VCAM-1/ICAM-1 were performed. We found preserved BBB permeability in MRL/lpr Fn14KO mice, attributable to reduced brain expression of VCAM-1/ICAM-1 and iNOS. Additionally, administration of Fc-TWEAK intravenously directly increased the leakage of a tracer (dextran-FITC) into brain tissue. Furthermore, MRL/lpr Fn14KO mice displayed reduced antibody (IgG) and complement (C3, C6, and C4a) deposition in the brain. Finally, we found that MRL/lpr Fn14KO mice manifested reduced neuron degeneration and hippocampal gliosis. Our studies indicate that TWEAK/Fn14 interactions play an important role in the pathogenesis of NPSLE by increasing the accumulation of inflammatory cells in the choroid plexus, disrupting BBB integrity, and increasing neuronal damage, suggesting a novel target for therapy in this disease.

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) promotes glioma cell invasion through induction of NF-κB-inducing kinase (NIK) and noncanonical NF-κB signaling

BACKGROUND

High-grade gliomas are one of the most invasive and therapy-resistant cancers. We have recently shown that noncanonical NF-κB/RelB signaling is a potent driver of tumorigenesis and invasion in the aggressive, mesenchymal subtype of glioma. However, the relevant signals that induce activation of noncanonical NF-κB signaling in glioma and its function relative to the canonical NF-κB pathway remain elusive.

METHODS

The ability of tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) to regulate NF-κB signaling and promote tumor progression was investigated in both established and primary high-grade glioma tumor lines using a three-dimensional (3-D) collagen invasion assay. The roles of specific NF-κB proteins in regulating glioma cell invasion and expression of Matrix Metalloproteinase 9 (MMP9) in response to TWEAK were evaluated using shRNA-mediated loss-of-function studies. The ability of NF-κB-inducing kinase (NIK) to promote glioma growth in vivo was investigated using an orthotopic xenograft mouse model.

RESULTS

In glioma cells that display elevated noncanonical NF-κB signaling, loss of RelB attenuates invasion without affecting RelA expression or phosphorylation and RelB is sufficient to promote invasion in the absence of RelA. The cytokine TWEAK preferentially activates the noncanonical NF-κB pathway through induction of p100 processing to p52 and nuclear accumulation of both RelB and p52 without activating the canonical NF-κB pathway. Moreover, TWEAK, but not TNFα, significantly increases NIK mRNA levels. TWEAK also promotes noncanonical NFκB-dependent MMP9 expression and glioma cell invasion. Finally, expression of NIK is sufficient to increase gliomagenesis in vivo.

CONCLUSIONS

Our data establish a key role for NIK and noncanonical NF-κB in mediating TWEAK-induced, MMP-dependent glioma cell invasion. The findings also demonstrate that TWEAK induces noncanonical NF-κB signaling and signal-specific regulation of NIK mRNA expression. Together, these studies reveal the important role of noncanonical NF-κB signaling in regulating glioma invasiveness and highlight the therapeutic potential of targeting activation of NIK in this deadly disease.

TWEAK/Fn14 Axis-Targeted Therapeutics: Moving Basic Science Discoveries to the Clinic

The TNF superfamily member TWEAK (TNFSF12) is a multifunctional cytokine implicated in physiological tissue regeneration and wound repair. TWEAK is initially synthesized as a membrane-anchored protein, but furin cleavage within the stalk region can generate a secreted TWEAK isoform. Both TWEAK isoforms bind to a small cell surface receptor named Fn14 (TNFRSF12A) and this interaction stimulates various cellular responses, including proliferation and migration. Fn14, like other members of the TNF receptor superfamily, is not a ligand-activated protein kinase. Instead, TWEAK:Fn14 engagement promotes Fn14 association with members of the TNFR associated factor family of adapter proteins, which triggers activation of various signaling pathways, including the classical and alternative NF-κB pathways. Numerous studies have revealed that Fn14 gene expression is significantly elevated in injured tissues and in most solid tumor types. Also, sustained Fn14 signaling has been implicated in the pathogenesis of cerebral ischemia, chronic inflammatory diseases, and cancer. Accordingly, several groups are developing TWEAK- or Fn14-targeted agents for possible therapeutic use in patients. These agents include monoclonal antibodies, fusion proteins, and immunotoxins. In this article, we provide an overview of some of the TWEAK/Fn14 axis-targeted agents currently in pre-clinical animal studies or in human clinical trials and discuss two other potential approaches to target this intriguing signaling node.

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.

Neuropsychiatric disease in murine lupus is dependent on the TWEAK/Fn14 pathway

Given the early onset of neuropsychiatric disease and the potential response to immunosuppressive therapy, neuropsychiatric disease is considered a primary disease manifestation in systemic lupus erythematosus (SLE). However, the pathogenesis is not fully understood and optimal treatment has yet to be determined. TWEAK is a TNF family ligand that mediates pleotropic effects through its receptor Fn14, including the stimulation of inflammatory cytokine production by astrocytes, endothelial cells, and other non-hematopeotic cell types, and induction of neuronal death. Furthermore, TWEAK-inducible mediators are implicated in neuropsychiatric lupus. Thus, we hypothesized that the TWEAK/Fn14 pathway may be involved in the pathogenesis of neuropsychiatric SLE. We generated MRL-lpr/lpr (MRL/lpr) mice deficient for Fn14, the sole known signaling receptor for TWEAK. Neuropsychiatric disease was compared in age- and gender-matched MRL/lpr Fn14 wild type (WT) and knockout (KO) mice, using a comprehensive battery of neurobehavioral tests. We found that MRL/lpr Fn14WT mice displayed profound depression-like behavior as seen by increased immobility in a forced swim test and loss of preference for sweetened fluids, which were significantly ameliorated in Fn14KO mice. Similarly, MRL/lpr Fn14WT mice had impaired cognition, and this was significantly improved in Fn14KO mice. To determine the mechanism by which Fn14 deficiency ameliorates neuropsychiatric disease, we assessed the serum levels of autoantibodies and local expression of cytokines in the cortex and hippocampus of lupus mice. No significant differences were found in the serum levels of antibodies to nuclear antigens, or autoantibodies specifically associated with neuropsychiatric disease, between MRL/lpr Fn14WT and KO mice. However, MRL/lpr Fn14KO mice had significantly decreased brain expression of RANTES, C3, and other proinflammatory mediators. Furthermore, MRL/lpr Fn14KO mice displayed improved blood brain barrier integrity. In conclusion, several central manifestations of neuropsychiatric lupus, including depression-like behavior and altered cognition, are normalized in MRL/lpr mice lacking Fn14. Our results are the first to indicate a role for the TWEAK/Fn14 pathway in the pathogenesis of neuropsychiatric lupus, and suggest this ligand-receptor pair as a potential therapeutic target for a common and dangerous disease manifestation.

TWEAK enhances E-selectin and ICAM-1 expression, and may contribute to the development of cutaneous vasculitis

Our previous work indicated that TWEAK is associated with various types of cutaneous vasculitis (CV). Herein, we investigate the effects of TWEAK on vascular injury and adhesion molecule expression in CV mice. We showed that TWEAK priming in mice induced a local CV. Furthermore, TWEAK priming also increased the extravasation of FITC-BSA, myeloperoxidase activity and the expression of E-selectin and ICAM-1. Conversely, TWEAK blockade ameliorated the LPS-induced vascular damage, leukocyte infiltrates and adhesion molecules expression in LPS-induced CV. In addition, TWEAK treatment of HDMECs up-regulated E-selectin and ICAM-1 expression at both mRNA and protein levels. TWEAK also enhanced the adhesion of PMNs to HDMECs. Finally, western blot data revealed that TWEAK can induce phosphorylation of p38, JNK and ERK in HDMECs. These data suggest that TWEAK acted as an inducer of E-selectin and ICAM-1 expression in CV mice and HDMECs, may contribute to the development of CV.

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.

TWEAK/Fn14 promotes the proliferation and collagen synthesis of rat cardiac fibroblasts via the NF-кB pathway

We wished to elucidate a potential role of the tumor necrosis factor-like weak inducer of apoptosis (TWEAK)/fibroblast growth factor-inducible molecule 14 (Fn14) axis in myocardial fibrosis. Stimulation of neonatal rat cardiac fibroblasts (CFs) with TWEAK could increase CFs numbers and collagen synthesis. Conversely, when CFs were pretreated with siRNA against Fn14, induction of cell proliferation and collagen synthesis by TWEAK were inhibited. Pretreatment with TWEAK on CFs induced activation of the nuclear factor-kappaB (NF-кB) pathway and subsequently increased the production of metalloproteinase-9 (MMP-9). Cell treatment with siRNA against Fn14 led to inhibition of the NF-кB pathway. Additionally, after stimulation of cell with ammonium pyrrolidine dithiocarbamate, cell proliferation and collagen synthesis induced by NF-кB and the upregulation of MMP-9 production were inhibited. The present study suggested that the TWEAK/Fn14 axis increased cell proliferation and collagen synthesis by activating the NF-кB pathway and increasing MMP-9 activity. This axis may be important for regulating myocardial fibrosis.

Expression of human tumor necrosis factor-like weak inducer of apoptosis in patients with systemic lupus erythematosus

The aim of this study was to compare the mRNA and serum expression of tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) in patients with systemic lupus erythematosus (SLE) and healthy controls. Sixty-two SLE patients and 15 healthy controls were recruited in the study. TWEAK messenger RNA (mRNA) expression in peripheral blood mononuclear cells (PBMCs) from 33 of 62 patients was detected by relative quantification RT-PCR. TWEAK concentrations in the sera of all 62 patients were measured by ELISA. TWEAK mRNA expressions in PBMCs were decreased in SLE patients compared with healthy controls. Lower TWEAK mRNA expression was also found in the active SLE patients when compared to inactive ones. However, there was no significant difference between patients with lupus nephritis (LN) and those without. The level of serum TWEAK (sTWEAK) in SLE patients was increased when compared to healthy controls. In addition, the sTWEAK level was higher in SLE patients with vasculitis than those without vasculitis, and so was in comparison between patients with and without headache. Nevertheless, no significant differences were found between active SLE patients and inactive patients, or between LN patients and non-LN SLE patients. In this study, patients with SLE express low levels of TWEAK mRNA but high levels of sTWEAK. Additionally, sTWEAK level was associated with several clinical manifestations of SLE, indicating that TWEAK may play a complex role in SLE.

Tumour necrosis factor-like weak inducer of apoptosis (TWEAK), an important mediator of endothelial inflammation, is associated with the pathogenesis of Henoch-Schonlein purpura

Tumour necrosis factor-like weak inducer of apoptosis (TWEAK), a member of the tumour necrosis factor (TNF) family, has been implicated as a proinflammatory cytokine in many types of autoimmune and infectious diseases. However, information about TWEAK in dermatological diseases is limited. Herein, we investigated the role of TWEAK in patients with Henoch-Schonlein purpura (HSP) and the ability of TWEAK on chemokine production in the human dermal microvascular endothelial cell line (HMEC-1). Serum TWEAK levels in patients with HSP, together with patients with psoriasis vulgaris (PV) and atopic dermatitis (AD), were detected by enzyme-linked immunosorbent assay (ELISA). HMEC-1 cells were treated with TWEAK at concentrations ranging from 1 ng/ml to 100 ng/ml. Serum levels of TWEAK were elevated in patients with HSP in the acute stage but not in patients with PV or AD. Moreover, TWEAK levels were correlated with the severity of HSP. TWEAK markedly induced CCL5 and CXCL8 production at both mRNA and protein levels in HMEC-1 cells. In addition, TWEAK-stimulated HMEC-1 supernatant enhanced HL-60 or human acute monocytic leukaemia cell line (THP-1) cell migration. Finally, Western blot data revealed that TWEAK can induce rapid phosphorylation of inhibitor of κB-α (IκBα) in HMEC-1 cells. In conclusion, we show that serum levels of TWEAK were elevated in patients with acute stage HSP. TWEAK may act as a regulator of nuclear factor-κB (NF-κB) activation and chemokine production in human dermal microvascular endothelial cells, thus promoting leucocyte migration in cutaneous vasculitis.

TWEAK as a target for therapy in systemic lupus erythematosus

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) is a recently identified proinflammatory cytokine of the TNF superfamily. Through activation of the fibroblast growth factor-inducible 14 (Fn14) receptor, TWEAK regulates cell proliferation, cell death and inflammation. The available evidences have indicated that TWEAK might be a target for therapeutic intervention in renal, vascular injury and neuropathy. Since renal, vascular and neuropsychiatric complications are frequently encountered in systemic lupus erythematosus (SLE)--a systemic autoimmune disease, TWEAK-Fn14 pathway may be implicated in the pathogenesis of SLE. In this review, we will discuss the TWEAK-Fn14 pathway and the therapeutic potential of modulating this pathway in SLE.

TWEAK is a positive regulator of cardiomyocyte proliferation

AIMS

Proliferation of mammalian cardiomyocytes stops during the first weeks after birth, preventing the heart from regenerating after injury. Recently, several studies have indicated that induction of cardiomyocyte proliferation can be utilized to regenerate the mammalian heart. Thus, it is important to identify novel factors that can induce proliferation of cardiomyocytes. Here, we determine the effect of TNF-related weak inducer of apoptosis (TWEAK) on cardiomyocytes, a cytokine known to regulate proliferation in several other cell types.

METHODS AND RESULTS

Stimulation of neonatal rat cardiomyocytes with TWEAK resulted in increased DNA synthesis, increased expression of the proliferative markers Cyclin D2 and Ki67, and downregulation of the cell cycle inhibitor p27KIP1. Importantly, TWEAK stimulation resulted also in mitosis (H3P), cytokinesis (Aurora B), and increased cardiomyocyte numbers. Loss of function experiments revealed that re-induction of proliferation was dependent on tumour necrosis factor receptor superfamily member 12A (FN14) signalling. Downstream signalling was mediated through activation of extracellular signal-regulated kinases and phosphatidylinositol 3-kinase as well as inhibition of glycogen synthase kinase-3beta. In contrast to neonatal cardiomyocytes, TWEAK had no effect on adult rat cardiomyocytes due to developmental downregulation of its receptor FN14. However, adenoviral expression of FN14 enabled efficient induction of cell cycle re-entry in adult cardiomyocytes after TWEAK stimulation.

CONCLUSION

Our data establish TWEAK as a positive regulator of cardiomyocyte proliferation.

TNF-like weak inducer of apoptosis inhibits proinflammatory TNF receptor-1 signaling

Soluble TNF-like weak inducer of apoptosis (TWEAK) trimers induce, in a variety of cell lines, translocation of cytosolic tumor necrosis factor (TNF) receptor-associated factor-2 (TRAF2) to a triton X-100-insoluble compartment without changes in the total cellular TRAF2 content. TWEAK-induced TRAF2 translocation is paralleled by a strong increase in nuclear factor kappaB 2 (NFkappaB2)/p100 processing to p52, indicating that TRAF2 redistribution is sufficient for activation of the alternative NFkappaB pathway. In accordance with the crucial role of TRAF2 in proinflammatory, anti-apoptotic TNF receptor-1 (TNFR1) signaling, we observed that TWEAK-primed cells have a reduced capacity to activate the classical NFkappaB pathway or JNK (cJun N-terminal kinase) in response to TNF. Furthermore, TWEAK-primed cells are sensitized for the TNFR1-mediated induction of apoptotic and necrotic cell death. Notably, the expression of the NFkappaB-regulated, TRAF2-interacting TRAF1 protein can attenuate TWEAK-induced depletion of the triton X-100-soluble TRAF2 fraction and improve TNFR1-induced NFkappaB signaling in TWEAK-primed cells. Taken together, we demonstrate that soluble TWEAK desensitizes cells for proinflammatory TNFR1 signaling and thus identify TWEAK as a modifier of TNF signaling.

The TWEAK-Fn14 cytokine-receptor axis: discovery, biology and therapeutic targeting

TWEAK is a multifunctional cytokine that controls many cellular activities including proliferation, migration, differentiation, apoptosis, angiogenesis and inflammation. TWEAK acts by binding to Fn14, a highly inducible cell-surface receptor that is linked to several intracellular signalling pathways, including the nuclear factor-kappaB (NF-kappaB) pathway. The TWEAK-Fn14 axis normally regulates various physiological processes, in particular it seems to play an important, beneficial role in tissue repair following acute injury. Furthermore, recent studies have indicated that TWEAK-Fn14 axis signalling may contribute to cancer, chronic autoimmune diseases and acute ischaemic stroke. This Review provides an overview of TWEAK-Fn14 axis biology and summarizes the available data supporting the proposal that both TWEAK and Fn14 should be considered as potential targets for the development of novel therapeutics.