The apoptotic ligands TRAIL, TWEAK, and Fas ligand mediate monocyte death induced by autologous lupus T cells

Fn14 and TNFR2 as regulators of cytotoxic TNFR1 signaling

Tumor necrosis factor (TNF) receptor 1 (TNFR1), TNFR2 and fibroblast growth factor-inducible 14 (Fn14) belong to the TNF receptor superfamily (TNFRSF). From a structural point of view, TNFR1 is a prototypic death domain (DD)-containing receptor. In contrast to other prominent death receptors, such as CD95/Fas and the two TRAIL death receptors DR4 and DR5, however, liganded TNFR1 does not instruct the formation of a plasma membrane-associated death inducing signaling complex converting procaspase-8 into highly active mature heterotetrameric caspase-8 molecules. Instead, liganded TNFR1 recruits the DD-containing cytoplasmic signaling proteins TRADD and RIPK1 and empowers these proteins to trigger cell death signaling by cytosolic complexes after their release from the TNFR1 signaling complex. The activity and quality (apoptosis versus necroptosis) of TNF-induced cell death signaling is controlled by caspase-8, the caspase-8 regulatory FLIP proteins, TRAF2, RIPK1 and the RIPK1-ubiquitinating E3 ligases cIAP1 and cIAP2. TNFR2 and Fn14 efficiently recruit TRAF2 along with the TRAF2 binding partners cIAP1 and cIAP2 and can thereby limit the availability of these molecules for other TRAF2/cIAP1/2-utilizing proteins including TNFR1. Accordingly, at the cellular level engagement of TNFR2 or Fn14 inhibits TNFR1-induced RIPK1-mediated effects reaching from activation of the classical NFκB pathway to induction of apoptosis and necroptosis. In this review, we summarize the effects of TNFR2- and Fn14-mediated depletion of TRAF2 and the cIAP1/2 on TNFR1 signaling at the molecular level and discuss the consequences this has in vivo.

Muscle Inflammation Susceptibility: A Potential Phenotype for Guiding Precision Rehabilitation After Total Hip Arthroplasty in End-Stage Osteoarthritis

The progression of osteoarthritis of the hip to its end stage and ultimately to total hip arthroplasty (THA) is complex; the multifactorial pathophysiology involves myriad collaborating tissues in and around the diseased joint. We have named the heightened state of periarticular muscle inflammation at the time of surgery "muscle inflammation susceptibility" (MuIS) because it is distinct from systemic inflammation. In this review article, we discuss how MuIS and heightened atrophy-associated signaling in the periarticular skeletal muscles may contribute to reduced muscle mass, impaired muscle quality (ie, through fibrosis), and a muscle microenvironment that challenges regenerative capacity and thus functional recovery from THA. We also review directions for future research that should advance understanding of the key determinants of precision for optimized success of THA for each individual.

Disentangling the Pathogenesis of Systemic Lupus Erythematosus: Close Ties between Immunological, Genetic and Environmental Factors

Systemic Lupus Erythematosus (SLE) is a systemic autoimmune disease that attacks various organ systems with a variety of clinical implications, ranging from mild skin and mucosal manifestations to severe central nervous system manifestations and death. Cases of SLE have been documented nearly two centuries ago when scholars used the terms 'erythema centrifugum' and 'seborrhea congestiva' to describe the discoid skin lesions and the butterfly or malar rash in SLE. Since then, knowledge about this disease has developed rapidly, especially knowledge related to the underlying pathogenesis of SLE. To date, it is known that immune system dysregulation, supported by genetic and environmental predisposition, can trigger the occurrence of SLE in a group of susceptible individuals. Various inflammatory mediators, cytokines and chemokines, as well as intra- and intercellular signaling pathways, are involved in the pathogenesis of SLE. In this review, we will discuss the molecular and cellular aspects of SLE pathogenesis, with a focus on how the immune system, genetics and the environment interact and trigger the various clinical manifestations of SLE.

Targeting fibroblast growth factor (FGF)-inducible 14 (Fn14) for tumor therapy

Fibroblast growth factor-inducible 14 (Fn14) is a member of the tumor necrosis factor (TNF) receptor superfamily (TNFRSF) and is activated by its ligand TNF-like weak inducer of apoptosis (TWEAK). The latter occurs as a homotrimeric molecule in a soluble and a membrane-bound form. Soluble TWEAK (sTWEAK) activates the weakly inflammatory alternative NF-κB pathway and sensitizes for TNF-induced cell death while membrane TWEAK (memTWEAK) triggers additionally robust activation of the classical NF-κB pathway and various MAP kinase cascades. Fn14 expression is limited in adult organisms but becomes strongly induced in non-hematopoietic cells by a variety of growth factors, cytokines and physical stressors (e.g., hypoxia, irradiation). Since all these Fn14-inducing factors are frequently also present in the tumor microenvironment, Fn14 is regularly found to be expressed by non-hematopoietic cells of the tumor microenvironment and most solid tumor cells. In general, there are three possibilities how the tumor-Fn14 linkage could be taken into consideration for tumor therapy. First, by exploitation of the cancer associated expression of Fn14 to direct cytotoxic activities (antibody-dependent cell-mediated cytotoxicity (ADCC), cytotoxic payloads, CAR T-cells) to the tumor, second by blockade of potential protumoral activities of the TWEAK/Fn14 system, and third, by stimulation of Fn14 which not only triggers proinflammtory activities but also sensitizes cells for apoptotic and necroptotic cell death. Based on a brief description of the biology of the TWEAK/Fn14 system and Fn14 signaling, we discuss the features of the most relevant Fn14-targeting biologicals and review the preclinical data obtained with these reagents. In particular, we address problems and limitations which became evident in the preclinical studies with Fn14-targeting biologicals and debate possibilities how they could be overcome.

Identification of Angiogenesis-Related Prognostic Biomarkers Associated With Immune Cell Infiltration in Breast Cancer

Background: This study aimed to explore the prognostic value of angiogenesis-related genes (ARGs) and their association with immune cell infiltration (ICI) in breast cancer (BC).

Methods: Transcriptome data of BC were obtained from the TCGA and GEO databases. Differentially expressed ARGs were identified by the limma package. The identification of key genes and construction of the risk score model were performed by univariate and multivariate Cox regression algorithms. The prognostic value of the risk score was assessed by ROC curves and nomogram. GO, KEGG pathway, and GSEA were used to investigate the biological functions of differentially expressed genes (DEGs), and CIBERSORT, ssGSEA, and xCell algorithms were performed to estimate the ICI in high-risk and low-risk groups. The correlations between prognostic biomarkers and differentially distributed immune cells were assessed. Moreover, a ceRNA regulatory network based on prognostic biomarkers was constructed and visualized by Cytoscape software.

Results: A total of 18 differentially expressed ARGs were identified between tumor and adjacent normal tissue samples. TNFSF12, SCG2, COL4A3, and TNNI3 were identified as key prognostic genes by univariate and multivariate Cox regression analyses. The risk score model was further constructed based on the four-gene signature and validated in GSE7390 and GSE88770 datasets. ROC curves and nomogram indicated that the risk score had good accuracy for determining BC patient survival. Biological function analysis showed that DEGs in high- and low-risk groups had a high enrichment in immune-related biological processes and signaling pathways. Moreover, significantly different ICIs were found between high- and low-risk groups, such as memory B cells, CD8⁺ T cells, resting memory CD4⁺ T cells, follicular helper T cells, regulatory T cells, monocytes, M2 macrophages, and neutrophils, and each prognostic biomarker was significantly correlated with one or more immune cell types.

Conclusion: The current study identified novel prognostic ARGs and developed a prognostic model for predicting survival in patients with BC. Furthermore, this study indicated that ICI may act as a bond between angiogenesis and BC. These findings enhance our understanding of angiogenesis in BC and provide novel guidance on developing therapeutic targets for BC patients.

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.

Towards a better understanding of adult idiopathic epidermal necrolysis: a retrospective study of 19 cases

BACKGROUND

Most cases of Stevens-Johnson syndrome and toxic epidermal necrolysis are drug-induced. A small subset of cases remain with unknown aetiology (idiopathic epidermal necrolysis [IEN]).

OBJECTIVE

We sought to better describe adult IEN and understand the aetiology.

METHODS

This retrospective study was conducted in 4 centres of the French national reference centre for epidermal necrolysis. Clinical data were collected for the 19 adults hospitalized for IEN between January 2015 and December 2019. Wide toxicology analysis of blood samples was performed. Histology of IEN cases was compared with blinding to skin biopsies of drug-induced EN (DIEN, 'controls'). Available baseline skin biopsies were analysed by shotgun metagenomics and transcriptomics and compared to controls.

RESULTS

IEN cases represented 15.6% of all EN cases in these centres. The median age of patients was 38 (range 16-51) years; 68.4% were women. Overall, 63.2% (n = 12) of cases required intensive care unit admission and 15.8% (n = 3) died at the acute phase. Histology showed the same patterns of early- to late-stage EN with no difference between DIEN and IEN cases. One toxicology analysis showed unexpected traces of carbamazepine; results for other cases were negative. Metagenomics analysis revealed no unexpected pathological microorganism. Transcriptomic analysis highlighted a different pro-apoptotic pathway in IEN compared to DIEN, with an overexpression of apoptosis effectors TWEAK/TRAIL.

CONCLUSIONS

IEN affects young people and is a severe form of EN. A large toxicologic investigation is warranted. Different pathways seem involved in IEN and DIEN, leading to the same apoptotic effect, but the primary trigger remains unknown.

The Impact of TRAIL (C1595T and G1525A) and DR4 (rs20576) Gene Polymorphisms on Systemic Lupus Erythematosus

Apoptosis dysregulation is a distinct hallmark of several disorders like systemic lupus erythematosus (SLE). In fact, SLE has two special features for apoptosis: irregular apoptosis and decline in clearing of apoptotic bodies. Tumor Necrosis Factor (TNF)-Related Apoptosis-Inducing Ligand (TRAIL) is a death ligand that causes to apoptosis via attaching to its receptors such as death receptor-4 (DR4). The present study aimed to evaluate the effects of TRAIL G1525A and C1595T and DR4 A683C (rs20576) gene polymorphisms on SLE development. 160 SLE patients and 160 healthy individuals as the control group participated in the study. Genotype analysis was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). With regard to TRAIL (C1595T) polymorphism, the frequency of CT genotype was significantly higher in the case group than the control with 3-fold increase in SLE development risk (P = 0.0001). Furthermore, the frequency of the TT genotype also was higher in the case group than the control group with 3.2-fold increase in SLE development risk. The allelic distribution analysis defined the T allele as a risk factor for SLE development (P = 0.0001). The frequency of AA genotype and allele A of TRAIL (G1525A) polymorphism also was statistically higher in the case group than the control group (P = 0.0001). There was no significant association between DR4 rs20576 polymorphism and SLE development. TRAIL C1595T and G1525A gene polymorphisms are suggested as the risk factors for SLE development, although the results showed no association between DR4 rs20576 polymorphism and SLE.

Tumor Necrosis Factor-Like Weak Inducer of Apoptosis (TWEAK)/Fibroblast Growth Factor-Inducible 14 (Fn14) Axis in Cardiovascular Diseases: Progress and Challenges

Cardiovascular diseases (CVD) are the leading cause of mortality in Western countries. CVD include several pathologies, such as coronary artery disease, stroke, peripheral artery disease, and aortic aneurysm, among others. All of them are characterized by a pathological vascular remodeling in which inflammation plays a key role. Interaction between different members of the tumor necrosis factor superfamily and their cognate receptors induce several biological actions that may participate in CVD. The cytokine tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its functional receptor, fibroblast growth factor-inducible 14 (Fn14), are abundantly expressed during pathological cardiovascular remodeling. The TWEAK/Fn14 axis controls a variety of cellular functions, such as proliferation, differentiation, and apoptosis, and has several biological functions, such as inflammation and fibrosis that are linked to CVD. It has been demonstrated that persistent TWEAK/Fn14 activation is involved in both vessel and heart remodeling associated with acute and chronic CVD. In this review, we summarized the role of the TWEAK/Fn14 axis during pathological cardiovascular remodeling, highlighting the cellular components and the signaling pathways that are involved in these processes.

Programmed Cell Death Pathways in the Pathogenesis of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease characterized by excessive inflammatory and immune responses and tissue damage. Increasing evidence has demonstrated the important role of programmed cell death in SLE pathogenesis. When apoptosis encounters with defective clearance, accumulated apoptotic cells lead to secondary necrosis. Different forms of lytic cell death, including secondary necrosis after apoptosis, NETosis, necroptosis, and pyroptosis, contribute to the release of damage-associated molecular patterns (DAMPs) and autoantigens, resulting in triggering immunity and tissue damage in SLE. However, the role of autophagy in SLE pathogenesis is in dispute. This review briefly discusses different forms of programmed cell death pathways and lay particular emphasis on inflammatory cell death pathways such as NETosis, pyroptosis, and necroptosis and their roles in the inflammatory and immune responses in SLE.

Utilization of Biomarkers in Lupus Nephritis

Lupus nephritis (LN) occurs in up to 60% of SLE patients, and is a leading cause of disability and death. Current treatment of LN consists of a combination of high dose corticosteroids that non-specifically decrease inflammation and cytotoxic medications that reduce auto-antibody production. That combination of therapy is associated with significant side effects while remission rates remain inadequate. Since the introduction of biologics into the pharmacological armamentarium, there has been hope for less toxic and more effective therapies for LN. Unfortunately, after multiple clinical trials, no biologic has improved efficacy over standard of care therapies for LN. This is likely, in part, due to disease heterogeneity. The utilization of biomarkers in LN may provide a way to stratify patients and guide therapeutic options. In this review, we summarize traditional and novel LN biomarkers and discuss how they may be used to diagnose, stratify, and guide therapy in patients with LN, bringing precision medicine to the forefront of LN therapy.

Analysis of extracellular vesicles generated from monocytes under conditions of lytic cell death

Extracellular vesicles (EVs) are an important class of membrane-bound structures that have been widely investigated for their roles in intercellular communication in the contexts of tumor progression, vascular function, immunity and regenerative medicine. Much of the current knowledge on the functions of EVs pertains to those derived from viable cells (e.g. exosomes and microvesicles) or apoptotic cells (e.g. apoptotic bodies) whilst the generation of EVs from dying cells under non-apoptotic conditions remains poorly characterized. Herein, the release of EVs from THP-1 monocytes under conditions of primary necrosis, secondary necrosis and pyroptosis, was investigated. A comprehensive analysis of THP-1-derived EVs revealed that cells undergoing lytic forms of cell death generated a high number of EVs compared with viable or apoptotic cells in vitro. Differential centrifugation via 16,000 g and 100,000 g revealed that dying THP-1 cells release both medium and small EVs, respectively, consistent with the known characteristics of microvesicles and/or exosomes. In addition, large EVs isolated via 2000 g centrifugation were also present in all samples. These findings suggest that lytic cell death under both sterile and non-sterile inflammatory conditions induces monocytes to generate EVs, which could potentially act as mediators of cell-to-cell communication.

Molecular and clinical characterization of CD163 expression via large-scale analysis in glioma

The expression and function of CD163 in glioma are not fully understood. In this report, we collected totally 1323 glioma samples from the Chinese Glioma Genome Atlas (CGGA) dataset, including 325 RNA-seq data and 301 mRNA microarray data, and 697 glioma samples from The Cancer Genome Atlas (TCGA) dataset to characterize the molecular and clinical features of CD163 in glioma by conducting a large-scale study. We found that CD163 expression was positively associated with the grade of malignancy of glioma. CD163 expression was up-regulated in IDH wild-type glioma and mesenchymal subtype. Gene ontology analysis suggested that CD163-related genes were more involved in immune response and angiogenesis in glioma. Moreover, CD163 showed a positive relationship with stromal and immune cell populations. Kaplan-Meier curves analysis revealed that higher CD163 expression indicated significantly poor survival in glioma and glioblastoma multiforme (GBM). Pearson correlation analysis revealed that CD163 was robustly associated with the immune checkpoints and other macrophage markers. These results demonstrated that CD163 predicts poor prognosis in glioma patients. Additionally, combination of CD163 and immune checkpoints may impair angiogenesis and reverse dysfunctional phenotypes of T cells, which suggest that CD163 may be a promising biomarker and target for immunotherapeutic strategies. Abbreviations: CGGA: Chinese Glioma Genome Atlas; TCGA: The Cancer Genome Atlas; TAMs: Tumor associated macrophages; IDH: isocitrate dehydrogenase; GBM: glioblastoma.

Regulation of Cathepsin E gene expression by the transcription factor Kaiso in MRL/lpr mice derived CD4+ T cells

Global DNA hypomethylation in CD4+ cells in systemic lupus erythematosus (SLE) was suggested to play a key role in the pathogenesis. To identify new methylation-sensitive genes, we integrated genome-wide DNA methylation and mRNA profiling data in CD4+ cells of MRL/lpr (MRL) and C57BL6/J (B6) mice. We identified Cathepsin E (Ctse), in which 13 methyl-CpGs within 583 bp region of intron 1 were hypomethylated, and Ctse mRNA upregulated in MRL compared with B6 mice. One of methyl-CpGs, mCGCG was 93.3 ± 2.05% methylated in B6 mice, while 80.0 ± 6.2% methylated and mutated to CGGG in MRL mice. Kaiso is known to bind to mCGCG and we hypothesized that it represses expression of Ctse in B6 mice. The binding of Kaiso to mCGCG site in B6 mice was reduced in MRL mice revealed by ChIP-PCR. EL4 cells treated with 5-azaC and/or Trichostatin A showed the suppression of binding of Kaiso to mCGCG motif by ChIP-PCR and the overexpression of Ctse was demonstrated by qPCR. Ctse gene silencing by siRNA in EL4 cells resulted in reduction of IL-10 secretion. The hypomethylation of mCGCG motif, reduced recruitment of Kaiso, and increased expression of Ctse and Il-10 in CD4+ cells may be involved in the pathogenesis of SLE.

Apoptosis in patients with primary antiphospholipid antibody syndrome

AIM

Dysregulated apoptosis has been implicated in autoimmune diseases. In the present study, we investigated the apoptosis-related cytokines and apoptosis in patients with primary antiphospholipid syndrome (pAPS).

METHOD

We prospectively recruited 12 pAPS patients, 17 antiphospholipid antibody (APA)-positive systemic lupus erythematosus (SLE) patients without APS manifestations (APA⁺ SLE), 13 SLE patients with secondary APS (APS⁺ SLE) and 10 healthy controls (HCs). Plasma levels of soluble apoptosis-inducing ligands and cytokines, and the expression levels of apoptosis-inducing ligands in peripheral blood mononuclear cells, were determined. In addition, blood lymphocytes/monocytes apoptosis were determined in six pAPS patients and six HCs, using flow cytometric analysis of caspase 3, 8 and 9 activities.

RESULTS

There was a trend toward higher plasma levels of soluble tumor necrosis factor (TNF)-related apoptosis-inducing ligand (sTRAIL), interleukin-10 (IL-10) and TNF-α in pAPS patients when compared with HCs. We also observed higher plasma levels of IL-10 and TNF α in APA⁺ SLE and APS⁺ SLE patients when compared with HCs. However, there was no significant difference in blood lymphocytes/monocytes apoptosis between pAPS patients and HCs.

CONCLUSION

There was a trend toward elevated plasma levels of sTRAIL, IL-10 and TNF-α, but no evidence for dysregulated apoptosis in pAPS patients.

Precision medicine in lupus nephritis: can biomarkers get us there?

Patients with systemic lupus erythematosus frequently develop lupus nephritis (LN), a condition that can lead to end-stage kidney disease. Multiple serum and urine biomarkers for LN have been proposed in recent years, yet none have become incorporated into clinical use. The majority of studies have been single center with significant variability in cohorts, assays, and sample storage, leading to inconclusive results. It has become clear that no single biomarker is likely to be sufficient to diagnose LN, identify flares, and define the response to therapy and prognosis. A more likely scenario is a panel of urine, serum, tissue, and genetic biomarkers. In this review, we summarize traditional and novel biomarkers and discuss how they may be utilized in order to bring precision medicine to clinical practice in LN.

Clinical significance of serum interleukin-8 and soluble tumor necrosis factor-like weak inducer of apoptosis levels in patients with diabetic nephropathy

AIMS/INTRODUCTION

Recent studies suggest that chronic inflammatory responses are important in the development of diabetic nephropathy (DN). Various inflammatory and angiogenesis molecules affect the pathogenesis and progression of DN. Inflammation damages the microcirculation and causes kidney damage. In the present study, we studied changes in interleukin-8 (IL-8) and soluble tumor necrosis factor-like weak inducer of apoptosis (sTWEAK) levels in patients with DN, and investigated the clinical significance of these two inflammatory factors.

MATERIALS AND METHODS

Participants were categorized into healthy controls (n = 30) and patients with type 2 diabetes mellitus (n = 124). The type 2 diabetes mellitus group was further subdivided into the normoalbuminuria (n = 34), microalbuminuria (MAU; n = 46,) and proteinuria (MaAU; n = 44,) groups. Patients with DN were included in the MAU and MaAU groups. Total cholesterol, triglyceride, low-density lipoprotein cholesterol, glycosylated hemoglobin, fasting blood glucose, 2-h postprandial blood glucose, blood urea nitrogen, serum creatinine, 24-h urine microalbumin, IL-8 and sTWEAK levels were measured. Logistic regression was used to analyze the factors associated with proteinuria.

RESULTS

In the healthy controls, normoalbuminuria, MAU and MaAU groups, we found that IL-8 levels increased, whereas sTWEAK levels decreased (P < 0.05). IL-8 might be an independent risk factor and serum sTWEAK a protective factor for MAU and MaAU. Serum levels of sTWEAK, IL-8 and microalbumin were significantly correlated in the MAU and MaAU groups.

CONCLUSIONS

Serum IL-8 and sTWEAK levels might be markers that can be used for an early diagnosis of DN.

The lncRNA RHPN1-AS1 downregulation promotes gefitinib resistance by targeting miR-299-3p/TNFSF12 pathway in NSCLC

Although epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) gefitinib has exhibited notable clinical efficacy in non-small cell lung cancer (NSCLC) patients. However, its therapeutic efficacy is ultimately limited by the development of gefitinib resistance. The present study aimed to investigate the effects of the long non-coding RNA, RHPN1-AS1 on gefitinib resistance in NSCLC and explore the underlying mechanisms. In this study, RHPN1-AS1 was observed to be downregulated in gefitinib resistant patients and NSCLC cell lines. Besides, decreased expression of RHPN1-AS1 was found to be associated with poor prognosis of NSCLC patients. RHPN1-AS1 knockdown conferred gefitinib resistance to gefitinib sensitive NSCLC cells, whereas the overexpression of RHPN1-AS1 sensitized gefitinib resistant NSCLC cells to gefitinib treatment. Mechanistically, RHPN1-AS1 was found to positively regulate the expression of TNFSF12 by directly interacting with miR-299-3p. Collectively, RHPN1-AS1 modulates gefitinib resistance through miR-299-3p/TNFSF12 pathway in NSCLC. Our findings indicate that RHPN1-AS1 may serve as not only a prognostic biomarker for gefitinib resistance but also as a promising therapeutic biomarker and target for the treatment of NSCLC patients.

Immune and myodegenerative pathomechanisms in inclusion body myositis

Inclusion Body Myositis (IBM) is a relatively common acquired inflammatory myopathy in patients above 50 years of age. Pathological hallmarks of IBM are intramyofiber protein inclusions and endomysial inflammation, indicating that both myodegenerative and inflammatory mechanisms contribute to its pathogenesis. Impaired protein degradation by the autophagic machinery, which regulates innate and adaptive immune responses, in skeletal muscle fibers has recently been identified as a potential key pathomechanism in IBM. Immunotherapies, which are successfully used for treating other inflammatory myopathies lack efficacy in IBM and so far no effective treatment is available. Thus, a better understanding of the mechanistic pathways underlying progressive muscle weakness and atrophy in IBM is crucial in identifying novel promising targets for therapeutic intervention. Here, we discuss recent insights into the pathomechanistic network of mutually dependent inflammatory and degenerative events during IBM.

Organ-specific biomarkers in lupus

Systemic lupus erythematosus (SLE) is a complex and highly heterogeneous disease, which affects multiple organs, including joints, skin, kidneys, heart, hematopoietic system, and nerve system. While the etiopathogenesis of SLE still remains unclear, genetic susceptibilities and aberrant epigenetic modifications are believed to be involved. For precision therapy, it is necessary to assess accurately and objectively organ involvements and disease activity, which is difficult by current clinical laboratory tests. Biomarkers, which are a biologic, genetic, epigenetic or a chemical characteristic and conveniently detectable, serve as measures of disease diagnosis, activity, prognosis, and manifestation prediction, thereby providing instruction for individualized therapy. In addition, biomarkers differ according to different manifestations, since the disease activity index and treatments vary significantly. For example, unlike other non-renal SLE, lupus nephritis requires significant immunosuppressive drugs. Over the past decades, the research on biomarkers in lupus has been strengthened and numerous promising biomarkers have been identified at levels of genomics, transcriptomics and proteomics. In this review, we summarize the conventional and novel biomarkers in the tissue-specific manner, and discuss their roles in specific organ diagnosis, future manifestation prediction, disease activity assessment and their correlation with histology results. By doing so, it aims to shed a light on individualized treatment.

TWEAK Negatively Regulates Human Dicer

The ribonuclease Dicer plays a central role in the microRNA pathway by processing microRNA precursors (pre-microRNAs) into microRNAs, a class of 19- to 24-nucleotide non-coding RNAs that regulate expression of ≈60% of the genes in humans. To gain further insights into the function and regulation of Dicer in human cells, we performed a yeast two-hybrid (Y2HB) screen using human Dicer double-stranded RNA-binding domain (dsRBD) as bait. This approach identified tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) as a Dicer-interacting protein candidate. Confocal immunofluorescence microscopy revealed the colocalization of Dicer and TWEAK proteins at the perinuclear region of HeLa cells. The Dicer-TWEAK protein interaction was confirmed by coimmunoprecipitation and found not likely to be mediated by RNA. TWEAK dose-dependently reduced pre-microRNA conversion into mature microRNA in Dicer activity assays using extracts of transfected human HEK 293 cells. TWEAK expression also impaired microRNA-guided RNA silencing of a reporter gene induced by a pre-microRNA. These findings suggest a role for TWEAK—a pro-inflammatory cytokine—in regulating Dicer function and microRNA biogenesis, and its possible involvement in regulating gene expression during inflammatory processes and diseases.

Cell death in the pathogenesis of systemic lupus erythematosus and lupus nephritis

Nephritis is one of the most severe complications of systemic lupus erythematosus (SLE). One key characteristic of lupus nephritis (LN) is the deposition of immune complexes containing nucleic acids and/or proteins binding to nucleic acids and autoantibodies recognizing these molecules. A variety of cell death processes are implicated in the generation and externalization of modified nuclear autoantigens and in the development of LN. Among these processes, apoptosis, primary and secondary necrosis, NETosis, necroptosis, pyroptosis, and autophagy have been proposed to play roles in tissue damage and immune dysregulation. Cell death occurs in healthy individuals during conditions of homeostasis yet autoimmunity does not develop, at least in part, because of rapid clearance of dying cells. In SLE, accelerated cell death combined with a clearance deficiency may lead to the accumulation and externalization of nuclear autoantigens and to autoantibody production. In addition, specific types of cell death may modify autoantigens and alter their immunogenicity. These modified molecules may then become novel targets of the immune system and promote autoimmune responses in predisposed hosts. In this review, we examine various cell death pathways and discuss how enhanced cell death, impaired clearance, and post-translational modifications of proteins could contribute to the development of lupus nephritis.

Elevated levels of TRAIL in systemic lupus erythematosus are associated to the presence of anti-SSA/SSB antibodies

The objective of this study was to determine potential relationship between the levels of serum TNF-related apoptosis inducing ligand (TRAIL) and osteoprotegerin (OPG) and clinical markers in systemic lupus erythematosus (SLE) patients. Forty SLE patients with inactive disease were enrolled in this study. For comparison, 20 Sjögren's syndrome (SS) patients and 30 normal controls were also analysed. Serum levels of TRAIL and OPG were determined by ELISA. Serum TRAIL and OPG concentrations in SLE patients were significantly ( P < 0.05) higher than those in healthy volunteers. Of note, serum TRAIL but not OPG was significantly ( P < 0.05) higher in the SLE patient subset characterized by the presence of anti-SSA/SSB antibodies. The relationship between high levels of TRAIL and SSA/SSB antibodies was further supported by the analysis of SS patients characterized by SSA/SSB antibodies positivity, in which TRAIL levels resulted comparable to the subgroup of anti-SSA/SSB positive SLE patients. The presence of SSA/SSB antibodies, targeting a specific subset of SLE and SS patients, is related to increased serum levels of TRAIL but not of OPG. Lupus (2007) 16, 479—482.

Upregulation of TRAIL expression on human T lymphocytes by interferon b and glatiramer acetate

We measured the in vivo and in vitro effects of interferon (IFN)b and glatiramer acetate (GA) on the expression of the regulatory molecule, tumor necrosis factor related apoptosis inducing ligand (TRAIL), in patients with multiple sclerosis (MS). We confirmed the prior observation that TRAIL is enhanced on anti-CD3 activated T cells by the in vitro addition of IFNβ. T cells from IFNβ-treated patients stimulated with anti-CD3 only, had higher levels of TRAIL than untreated patients, suggesting that in vivo IFNβ exposure has an effect on TRAIL expression in association with T cell activation. In vitro IFNβ-induced TRAIL upregulation on anti-CD3 or phytohemagglutinin-activated T cells was comparable for IFNβ-treated and non-treated MS patients and controls, indicating that IFN receptors were neither saturated nor down-regulated by current IFNβ therapy. Although GAin vivo orin vitro did not induce TRAIL, the IFNβ-GA combination in vitro enhanced TRAIL expression to higher levels than IFNβ alone on CD4+ T cells obtained from MS patients, regardless of GA treatment status, and healthy donors, and on GA reactive T cell lines derived from GA-treated patients or controls. Whether any observed therapeutic effects of GA/IFNβ combination therapy will correlate with TRAIL expression and function remains to be determined.

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.

Population pharmacokinetic and pharmacodynamic analysis of BIIB023, an anti-TNF-like weak inducer of apoptosis (anti-TWEAK) monoclonal antibody

AIMS

Tumour necrosis factor-like weak inducer of apoptosis (TWEAK) is implicated in the pathogenesis of lupus nephritis. This study evaluated the pharmacokinetics, using the population approach, and pharmacodynamics of BIIB023, an anti-TWEAK monoclonal antibody, in healthy Chinese, Japanese and Caucasian volunteers.

METHODS

In this single-dose, randomized, double-blind, phase 1 study of BIIB023 in healthy volunteers, BIIB023 was administered by intravenous infusion (3 or 20 mg kg(-1) ) on Day 1; follow-up occurred through Day 71. BIIB023 serum concentration was measured using a validated enzyme-linked immunosorbent assay; BIIB023 concentration-time data were subjected to noncompartmental analysis. Population pharmacokinetic analysis was performed using data from this study and a prior phase 1 study of BIIB023 in subjects with rheumatoid arthritis. Soluble TWEAK and

TWEAK

BIIB023 complex were evaluated.

RESULTS

There were no differences in BIIB023 pharmacokinetics requiring dose adjustment among the three ethnic groups or between healthy volunteers and arthritis patients. BIIB023 central compartment volume (3050 ml) and clearance (7.42 ml h(-1) ) were comparable to those observed for other monoclonal antibody drugs. BIIB023 serum exposure increased in a dose-dependent manner in all groups, but not in direct proportion to dose level; at concentrations below ~10 μg ml(-1) , nonlinear clearance was observed. Soluble TWEAK levels decreased to below the level of quantitation after BIIB023 treatment, with concomitant changes in

TWEAK

BIIB023 complex levels.

CONCLUSIONS

No clinically meaningful differences were observed in BIIB023 pharmacokinetic and pharmacodynamic properties in healthy Chinese, Japanese and Caucasian volunteers; pharmacodynamic measures suggested target engagement. TWEAK may be an attractive therapeutic target for lupus nephritis treatment.

The New Role of CD163 in the Differentiation of Bone Marrow Stromal Cells into Vascular Endothelial-Like Cells

Bone marrow stromal cells (BMSCs) can differentiate into vascular endothelial cells (VECs). It is regarded as an important solution to cure many diseases, such as ischemic diseases and diabetes. However, the mechanisms underlying BMSC differentiation into VECs are not well understood. Recent reports showed that CD163 expression was associated with angiogenesis. In this study, overexpression of CD163 in BMSCs elevated the protein level of the endothelial-associated markers CD31, Flk-1, eNOS, and VE-cadherin, significantly increased the proportion of Alexa Fluor 488-acetylated-LDL-positive VECs, and promoted angiogenesis on Matrigel. Furthermore, we demonstrated that CD163 acted downstream homeobox containing 1 (Hmbox1) and upstream fibroblast growth factor 2 (FGF-2). These data suggested that CD163 was involved in Hmbox1/CD163/FGF-2 signal pathway in BMSC differentiation into vascular endothelial-like cells. We found a new signal pathway and a novel target for further investigating the gene control of BMSC differentiation into a VEC lineage.

Biomarkers in lupus nephritis

Lupus nephritis (LN) has significant impact on the outcome of patients with systemic lupus erythematosus (SLE). In the absence of any new breakthrough for management of LN over the last few years, using existing treatment modalities in a more effective manner is the mainstay of improving outcomes. For effectively using the drugs, disease activity needs to be assessed accurately and more objectively, which is not possible with present clinical assessment tools. Biomarkers help in accurate assessment of disease activity and enable the physician to individualize the therapy. Conventional disease activity markers have limitations which need to be addressed and research in the area of biomarker discovery in LN has immensely expanded over the last two decades as evident by the literature. Moreover, biomarkers for LN should be different from the markers of overall disease activity as LN requires significant immunosuppression, unlike other non-renal manifestations of SLE. Newly discovered biomarkers exhibit qualities pertaining to different aspects of disease activity and damage. In this review, we discuss the established as well as new biomarkers of SLE in the light of their role in LN diagnosis, follow-up, prediction of renal flare and correlation with renal histology findings.

Impaired phagocytosis of apoptotic cell material in serologically active clinically quiescent patients with systemic lupus erythematosis

AIM

Serologically active clinically quiescent (SACQ) patients with systemic lupus erythematosus (SLE) account for 8-12% of all patients with SLE, but there is disagreement about whether such patients are indeed clinically stable. Patients with clinically active SLE have decreased macrophage function, although the status of SACQ patients with SLE is unclear.

METHOD

This study compared 18 patients who met the diagnostic criteria for SACQ SLE with 18 healthy volunteers with regard to the capability of macrophages to clear apoptotic bodies by use of a modified serum-free phagocytosis test. Macrophages that naturally differentiated from monocytes were used to engulf apoptotic cells developed from polymorphonuclear neutrophils.

RESULTS

The results showed that macrophages from SACQ patients with SLE had less phagocytotic capability than those from healthy controls.

CONCLUSION

The significant reduction of macrophage phagocytotic capability in these patients suggests the potential for disease recurrence. The use of a serum-free method confirmed the presence of intrinsic factors that modulate the decrease of macrophage function in SLE.

Cytokines and MicroRNAs as Candidate Biomarkers for Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease, with varied course and symptoms. Its etiology is very complex and not clearly understood. There is growing evidence of the important role of cytokines in SLE pathogenesis, as well as their utility as biomarkers and targets in new therapies. Other potential new SLE biomarkers are microRNAs. Recently, over one hundred different microRNAs have been demonstrated to have a significant impact on the immune system. Various alterations in these microRNAs, associated with disease pathogenesis, have been described. They influence the signaling pathways and functions of immune response cells. Here, we aim to review the emerging new data on SLE etiology and pathogenesis.

Therapy and pharmacological properties of hydroxychloroquine and chloroquine in treatment of systemic lupus erythematosus, rheumatoid arthritis and related diseases

OBJECTIVES

This review examines the pharmacokinetics, modes of action and therapeutic properties of the anti-malarial drugs, hydroxychloroquine (HCQ) and chloroquine (CQ), in the treatment of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and related conditions, as well as osteoarthritis (OA).

KEY FINDINGS

Both HCQ and CQ have historically been employed successfully for the treatment of SLE and RA for over 70 years. HCQ has been used extensively for SLE where it has a good reputation for controlling the dermatological complications in SLE. It has also been reported to effectively control the symptoms of Sjøgren's syndrome, as well as preventing thrombosis in phospholipid antibody (aPL) syndrome. In RA and SLE, HCQ is preferred because of the lower incidence of gastrointestinal adverse reactions compared with CQ and it might have a lower risk of ocular adverse reactions. There is increasing evidence that HCQ may reduce atherosclerosis and risks of cardiovascular disease in rheumatic patients. Both HCQ and CQ have been shown to improve glycaemia and reduce the risks of type II diabetes mellitus. Although both HCQ and CQ are effective in low-moderate RA, HCQ is now preferred as part of combination therapy for more severe disease. The advantages of combination therapy are that the doses of the individual drugs may be lowered so reducing adverse reactions. Both HCQ and CQ are diastereoisomers, have basic properties and are given as the sulphate and phosphate salts. While being relatively well absorbed orally and with good bioavailability, they have long and variable plasma terminal elimination half-lives (approximately 40-60 days). This reflects their high volume of distribution, V D (HCQ 44,000L; CQ 65,000L) which extends into aqueous compartments, long mean residence time (HCQ 1300 h; CQ 900 h) and with about half the drugs (metabolites) undergoing renal clearance. The strong binding to melanin reflects the ocular injury and dermatological properties of these drugs. The consensus is that the occurrence of ocular adverse reactions can be minimised by close attention to the dose (which should be set on a body weight basis) with regular (e.g. quarterly) retinal examination. Although HCQ and CQ can pass through the placenta, the use of these drugs during pregnancy does not appear to risk harm to the baby and might be beneficial to the mother with SLE and her child by controlling the SLE disease activity, which is known to be an important factor affecting pregnancy outcome. The modes of action of HCQ and CQ in these arthritides represent somewhat of an enigma. Undoubtedly, these drugs have multiple actions related, in part, their ability to accumulate in lysosomes and autophagosomes of phagocytic cells as well as affecting MHC Class II expression and antigen presentation; actions of the production of pro-inflammatory cytokines [e.g. interleukin-1 (IL-1) tumour necrosis factor-α (TNFα)]; control of toll-like receptor-9 activation; and leucocyte generation of reactive oxygen species (ROS); i.e. antioxidant activity. The actions of these drugs on T and B cells are less clear but may depend on these leucocyte-mediated actions. Anti-malarials also protect against cytokine-mediated cartilage resorption. This and other actions may underlie the potential benefits in treating OA. The exact relationships of these various actions, mostly determined in vitro, have not been specifically defined in vivo or ex vivo in relation to clinical efficacy.

OUTCOMES

HCQ and CQ have a good reputation for being effective and relatively safe treatments in SLE, mild-moderate RA and Sjøgren's syndrome. There is need for (a) more information on their mode of action in relation to the control of these diseases, (b) scope for developing formulations that have improved pharmacokinetic and therapeutic properties and safety, and (c) further exploring their use in drug combinations not only with other disease modifying agents but also with biologics.

Heat shock protein 27 and its regulatory molecules express differentially in SLE patients with distinct autoantibody profiles

Generation of autoantigens of nuclear origin, like dsDNA and extractable nuclear antigens (ENA) have largely been associated with dysregulated apoptosis and defective clearance of apoptotic debris in SLE. Heat shock protein (HSP) 27 has been reported to have anti-apoptotic properties hence it was of interest to study the expression of HSP27 and its regulatory molecule Brn3a and hsa-miR-939 in SLE patients with distinct autoantibodies specificities. SLE patients were categorized into three subsets based on their distinct sero-positivity for either anti-dsDNA antibody alone (anti-dsDNA(+) group) or anti-ENA antibody alone (anti-ENA(+) group) or both (anti-dsDNA(+) ENA(+) group). We investigated the mRNA and protein expression of HSP27 and Brn3a in peripheral blood leukocytes (PBLs) by real-time reverse transcriptase PCR and Western blotting. Expression of apoptosis markers caspase 3 and poly (ADP-ribose) polymerase (PARP) was determined by Western blotting. Hsa-miR-939 expression was determined using TaqMan(®) miRNA assay. In this study, we report significant downregulation of HSP27 in anti-ENA(+) patients and increased expression of caspase 3 and PARP in both anti-ENA(+) and anti-dsDNA(+) SLE subsets. A negative correlation was observed between the expression of HSP27 and apoptosis markers caspase 3 and PARP. Decreased Brn3a expression was observed in anti-ENA(+) SLE patients, which correlated positively with HSP27 expression. Expression of hsa-miR-939, which has a potential target site for Brn3a 3' UTR, was also elevated specifically in anti-ENA(+) patients. The decreased expressions of HSP27, Brn3a along with elevated levels of hsa-miR-939 are selectively associated with anti-ENA(+) patients and HSP27 was observed to be inversely associated with apoptosis. These findings are suggestive of distinct regulatory processes operative in SLE patient subsets with different autoantibody specificities.

Acetylated histones contribute to the immunostimulatory potential of neutrophil extracellular traps in systemic lupus erythematosus

In addition to disturbed apoptosis and insufficient clearance of apoptotic cells, there is recent evidence for a role of neutrophils in the aetiopathogenesis of systemic lupus erythematosus (SLE). In response to various stimuli, neutrophils can rapidly release DNA fibres decorated with citrullinated histones and anti-microbial peptides. These structures are referred to as neutrophil extracellular traps (NETs). In addition to apoptotic cell-derived microparticles, these NETs may comprise a further source of autoantigens, able to drive the autoimmune response in SLE. Our group recently identified specific histone modifications occurring during apoptosis that play an important role in the autoimmune response in SLE. In the current study, we evaluated the presence and immunostimulatory potential of these previously identified histone modifications in NETs. Compared to NETs from healthy donors, the histones present in NETs formed by SLE-derived neutrophils contain increased amounts of acetylated and methylated residues, which we previously observed to be associated with apoptosis and SLE. Treatment of neutrophils with histone deacetylase (HDAC) inhibitor Trichostatin A (TSA), prior to induction of NETosis, induced NETs containing hyperacetylated histones, endowed with an increased capacity to activate macrophages. This implies that specific histone modifications, in particular acetylation, might enhance the immunostimulatory potential of NETs in SLE.

Deficiency of IRE1 and PERK signal pathways in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease with uncertain pathogenesis. Endoplasmic reticulum (ER) stress has close correlations with inflammation and/or immune diseases. However, it is unknown whether aberrant ER stress is involved in SLE pathogenesis. We aimed to characterize the ER stress-related genes in patients with SLE and analyzed their correlations with the disease. Peripheral blood leucocytes were isolated from 76 well-characterized patients with SLE and 69 healthy controls. ER stress-related genes were determined at transcription level by absolute quantitative real-time polymerase chain reaction. Stepwise regression and correlation analysis were used to analyze the relationships between SLE disease and ER stress. Abnormal unfolded protein responses were found in patients with SLE with the downregulation of inositol-requiring enzyme 1 (IRE1), pancreatic ER kinase (PERK) and CCAAT/enhancer-binding protein homologous protein (CHOP) and upregulation of XBP1, XBP1s and MANF. In the patients with SLE disease activity index (SLEDAI) <12, PERK and MANF expressions were significantly decreased, compared with the patients with severe SLE (SLEDAI ≥ 12). However, there was no significant change in ATF6 mRNA expression in the patients with SLE. Negative correlation between IRE1/XBP1 and SLEDAI was observed in lower SLEDAI score group. Negative correlations between CHOP and anti-dsDNA antibody, MANF and antinuclear antibody were observed in high-SLEDAI score group. We also found that antinuclear antibody and anti-dsDNA antibodies correlated with SLEDAI in a weak positive manner. SLEDAI was negatively related with C3 level. SLEDAI and anti-dsDNA antibody showed modestly positive correlation with urine protein. These findings suggest that the abnormal unfolded protein responses, especially IRE1/XBP1 and PERK/CHOP axes, may contribute to SLE pathogenesis, which may be potential diagnosis indicators or treatment targets.

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.

Pathological activation of canonical nuclear-factor κB by synergy of tumor necrosis factor α and TNF-like weak inducer of apoptosis in mouse acute colitis

Tumor necrosis factor (TNF)-α is a major effector in various inflammatory conditions. TNF-like weak inducer of apoptosis (TWEAK) is a member of the TNF superfamily that promotes inflammatory tissue damage through its receptor, FGF-inducible molecule 14 (Fn14). Since both TWEAK and TNF-α have been shown to mediate pathological responses through inter-dependent or independent pathways by in vitro, the potential interplay of these pathways was investigated in a mouse colitis model. Acute colitis was induced by rectal injection of trinitrobenzene sulfonic acid (TNBS), with administration of control IgG, TNF receptor (TNFR)-Ig chimeric protein, anti-TWEAK monoclonal antibody, or the combination of TNFR-Ig and anti-TWEAK antibody. On day 4, disease severity was evaluated and gene expression profiling was analyzed using whole colon tissue. NF-κB activation was investigated with Western blot. Levels of transcript of TWEAK, Fn14 and NF-κB-related molecules were measured in purified colon epithelial cells (ECs). As a result, activation of the canonical (p50/RelA), but not noncanonical (p100/RelB)-mediated pathway was the hallmark of inflammatory responses in this model. Inflammation induced upregulation of Fn14 only in ECs but not in other cell types. Combination treatment of TNFR-Ig and anti-TWEAK antibody synergistically reduced disease severity in comparison with the control antibody or single agent treatment. Gene expression profile of the colon indicated downregulation of canonical NF-κB pathway with combination treatment. In conclusion, synergistic activation of canonical NF-κB by TWEAK and TNF-α is critical for the induction of inflammatory tissue damage in acute inflammation.

Breaking immunological tolerance in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a fairly heterogeneous autoimmune disease of unknown etiology that mainly affects women in the childbearing age. SLE is a prototype type III hypersensitivity reaction in which immune complex depositions cause inflammation and tissue damage in multiple organs. Two distinct cell death pathways, apoptosis and NETosis, gained a great deal of interest among scientists, since both processes seem to be deregulated in SLE. There is growing evidence that histone modifications induced by these cell death pathways exert a central role in the induction of autoimmunity. In the current review, we discuss how abnormalities in apoptosis, NETosis, and histone modifications may lead to a break of immunological tolerance in SLE.

Concerted action of Nrf2-ARE pathway, MRN complex, HMGB1 and inflammatory cytokines - implication in modification of radiation damage

Whole body exposure to low linear energy transfer (LET) ionizing radiations (IRs) damages vital intracellular bio-molecules leading to multiple cellular and tissue injuries as well as pathophysiologies such as inflammation, immunosuppression etc. Nearly 70% of damage is caused indirectly by radiolysis of intracellular water leading to formation of reactive oxygen species (ROS) and free radicals and producing a state of oxidative stress. The damage is also caused by direct ionization of biomolecules. The type of radiation injuries is dependent on the absorbed radiation dose. Sub-lethal IR dose produces more of DNA base damages, whereas higher doses produce more DNA single strand break (SSBs), and double strand breaks (DSBs). The Nrf2-ARE pathway is an important oxidative stress regulating pathway. The DNA DSBs repair regulated by MRN complex, immunomodulation and inflammation regulated by HMGB1 and various types of cytokines are some of the key pathways which interact with each other in a complex manner and modify the radiation response. Because the majority of radiation damage is via oxidative stress, it is essential to gain in depth understanding of the mechanisms of Nrf2-ARE pathway and understand its interactions with MRN complex, HMGB1 and cytokines to increase our understanding on the radiation responses. Such information is of tremendous help in development of medical radiation countermeasures, radioprotective drugs and therapeutics. Till date no approved and safe countermeasure is available for human use. This study reviews the Nrf2-ARE pathway and its crosstalk with MRN-complex, HMGB1 and cytokines (TNF-a, IL-6, IFN-? etc.). An attempt is also made to review the modification of some of these pathways in presence of selected antioxidant radioprotective compounds or herbal extracts.

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Exposure to low linear energy transfer (LET) ionizing radiation (IR) causes intracellular oxidative stress and activate the Nrf2-ARE antioxidant pathway.

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Irradiation also causes inflammation and DNA damage which affect other pathways related to MRN complex and HMGB1 proteins.

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The antioxidant Keap1-Nrf2-ARE pathway most importantly regulates intracellular oxidative stress.

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The interaction of Keap1-Nrf2-ARE pathway with HMGB1 regulated inflammation; MRN complex regulated DNA repair is reviewed.

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.

TWEAK/Fn14 and Non-Canonical NF-kappaB Signaling in Kidney Disease

The incidence of acute kidney injury (AKI) and chronic kidney disease (CKD) is increasing. However, there is no effective therapy for AKI and current approaches only slow down, but do not prevent progression of CKD. TWEAK is a TNF superfamily cytokine. A solid base of preclinical data suggests a role of therapies targeting the TWEAK or its receptor Fn14 in AKI and CKD. In particular TWEAK/Fn14 targeting may preserve renal function and decrease cell death, inflammation, proteinuria, and fibrosis in mouse animal models. Furthermore there is clinical evidence for a role of TWEAK in human kidney injury including increased tissue and/or urinary levels of TWEAK and parenchymal renal cell expression of the receptor Fn14. In this regard, clinical trials of TWEAK targeting are ongoing in lupus nephritis. Nuclear factor-kappa B (NF-κB) activation plays a key role in TWEAK-elicited inflammatory responses. Activation of the non-canonical NF-κB pathway is a critical difference between TWEAK and TNF. TWEAK activation of the non-canonical NF-κB pathways promotes inflammatory responses in tubular cells. However, there is an incomplete understanding of the role of non-canonical NF-κB activation in kidney disease and on its contribution to TWEAK actions in vivo.

TWEAK/Fn14 pathway promotes a T helper 2-type chronic colitis with fibrosis in mice

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK), a TNF superfamily member, induces damage of the epithelial cells (ECs) and production of inflammatory mediaters through its receptor Fn14 in a model of acute colitis. In our current study of chronic colitis induced by repeated rectal injection of a hapten, we found that inflammation, fibrosis, and T helper 2 (Th2)-type immunity were significantly reduced in Fn14 gene knockout (KO) mice when compared with wild-type (WT) control mice. Expression of thymic stromal lymphopoietin (TSLP) was lower in Fn14 KO colon ECs than in WT ECs. TWEAK potentiates the induction of TSLP by interleukin-13 (IL-13) in colon explants from WT but not in Fn14 KO tissue. TSLP receptor KO mice exhibit milder chronic colitis, similar to that in Fn14 KO mice. TWEAK and IL-13 synergistically promote fibroblast proliferation. Thus we propose an IL-13-TWEAK/Fn14-TSLP axis as a key mechanism underlying chronic colitis with fibrosis.

The peroxisome-proliferator activated receptor-γ agonist pioglitazone modulates aberrant T cell responses in systemic lupus erythematosus

PPAR-γ agonists can suppress autoimmune responses and renal inflammation in murine lupus but the mechanisms implicated in this process remain unclear. We tested the effect of the PPAR-γ agonist pioglitazone in human lupus and control PBMCs with regard to gene regulation and various functional assays. By Affymetrix microarray analysis, several T cell-related pathways were significantly highlighted in pathway analysis in lupus PBMCs. Transcriptional network analysis showed IFN-γ as an important regulatory node, with pioglitazone treatment inducing transcriptional repression of various genes implicated in T cell responses. Confirmation of these suppressive effects was observed specifically in purified CD4+ T cells. Pioglitazone downregulated lupus CD4+ T cell effector proliferation and activation, while it significantly increased proliferation and function of lupus T regulatory cells. We conclude that PPAR-γ agonists selectively modulate CD4+ T cell function in SLE supporting the concept that pioglitazone and related,-agents should be explored as potential therapies in this disease.

Tumor necrosis factor-like weak inducer of apoptosis and its receptor fibroblast growth factor-inducible 14 are expressed in urticarial vasculitis

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK), a member of the TNF family, has been implicated as a pro-inflammatory cytokine in many types of autoimmune and infectious diseases. However, information about TWEAK in dermatological diseases is limited. To date, no studies have investigated the roles of TWEAK in patients with urticarial vasculitis (UV). This study aimed to assess serum TWEAK levels, together with TWEAK and fibroblast growth factor-inducible 14 (Fn14) expressions of skin lesions in patients with UV. Serum TWEAK levels in patients with UV, together with patients with cutaneous leukocytoclastic angiitis (CLA) and healthy controls were detected by enzyme-linked immunosorbent assay; TWEAK and Fn14 expressions of skin lesions were analyzed by immunohistochemistry. Results showed that TWEAK and Fn14 were abundantly expressed in the dermal vessel wall of lesional skin in patients with UV but not healthy controls. Serum TWEAK levels in the acute stage in patients with UV were significantly higher than those in the convalescent stage and healthy controls. Serum TWEAK levels were elevated significantly in patients with CLA compared with those in healthy controls. Our previous study indicated that TWEAK may be an important mediator for the development of vascular inflammation in skin. In addition, we also found that TWEAK blockade substantially reduced vascular damage and perivascular leukocyte infiltrates in lipopolysaccharide-induced cutaneous vasculitis. Our study shows that TWEAK may be associated with the pathogenesis of UV; it is therefore suggested that TWEAK may be a potential therapeutic target for UV and other types of cutaneous vasculitis.

Reduced expressions of Fas and Bcl-2 proteins in CD14+ monocytes and normal CD14 soluble levels in juvenile systemic lupus erythematosus

In order to evaluate Fas and Bcl-2 expressions in CD14+ monocytes, to measure soluble CD14 serum levels and to analyze the relationships with lupus nephritis and disease activity, we enrolled 41 patients with juvenile systemic lupus erythematosus (JSLE) and 27 healthy volunteers. Disease activity was determined by SLEDAI score. Peripheral monocytes were stained for CD14, Fas and Bcl-2 molecules, and cellular expressions were determined by flow cytometry. Soluble CD14 levels were measured by a quantitative ELISA kit. JSLE patients, those with active disease and those with nephritis, presented significantly reduced expressions of Fas and Bcl-2 proteins in CD14+ monocytes compared with healthy controls. Significant inverse correlations between percentages of CD14+Fas+ cells, SLEDAI score and anti-dsDNA antibodies were observed. JSLE patients had soluble CD14 levels similar to controls, although sCD14 levels positively correlated with ESR, but not with SLEDAI score. JSLE patients with nephritis also presented sCD14 levels similar to controls. In conclusion, the reduced expressions of Fas and Bcl-2 proteins in CD14+ monocytes from JSLE patients depict that monocyte apoptotic mechanisms may be important in lupus pathogenesis.

TRAIL mRNA expression in peripheral blood mononuclear cells of Egyptian SLE patients

Although the definite etiopathogenesis of systemic lupus erythematosus (SLE) remains unclear, many different mechanisms may contribute to its pathogenesis. Tumor-necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor (TNF) family with pro-apoptotic activity. The accumulation of apoptotic cell debris has been hypothesized to induce the autoimmune inflammation in SLE, and TRAIL may trigger this programmed cell death. We investigated TRAIL mRNA expression levels in peripheral blood mononuclear cells (PBMCs) from 60 SLE patients and 40 controls using quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR), and we studied the association between the results and clinical and laboratory parameters of the patients. Expression levels of TRAIL mRNAs in SLE patients were significantly higher than in controls (p<0.001). A statistically significant association was detected between TRAIL mRNA expression and SLE activity (p=0.001).

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.

IL-17 stimulates differentiation of human anti-inflammatory macrophages and phagocytosis of apoptotic neutrophils in response to IL-10 and glucocorticoids

Exposure of human monocytes/macrophages to anti-inflammatory agents, such as IL-10 or glucocorticoids, can lead to two separate fates: either Fas/CD95-mediated apoptosis or differentiation into regulatory and efferocytic M2c (CD14(bright)CD16(+)CD163(+)Mer tyrosine kinase(+)) macrophages. We found that the prevalent effect depends on the type of Th cytokine environment and on the stage of monocyte-to-macrophage differentiation. In particular, the presence of IFN-γ (Th1 inflammation) or the prolonged exposure to IL-4 (chronic Th2 inflammation) promotes apoptosis of monocytes/macrophages and causes resistance to M2c differentiation, thus provoking impaired clearance of apoptotic neutrophils, uncontrolled accumulation of apoptotic cells, and persistent inflammation. In contrast, the presence of IL-17 (Th17 environment) prevents monocyte/macrophage apoptosis and elicits intense M2c differentiation, thus ensuring efficient clearance of apoptotic neutrophils and restoration of anti-inflammatory conditions. Additionally, the Th environment affects the expression of two distinct Mer tyrosine kinase isoforms: IL-4 downregulates the membrane isoform but induces an intracellular and Gas6-dependent isoform, whereas IFN-γ downregulates both and IL-17 upregulates both. Our data support an unexpected role for IL-17 in orchestrating resolution of innate inflammation, whereas IFN-γ and IL-4 emerge as major determinants of IL-10 and glucocorticoid resistance.