Targeting transcription factor Stat4 uncovers a role for interleukin-18 in the pathogenesis of severe lupus nephritis in mice

Downregulated GPX4 in salivary gland epithelial cells contributes to salivary secretion dysfunction in Sjogren's syndrome via lipid ROS/pSTAT4/AQP5 axis

Sjogren's syndrome (SS) is an autoimmune disease characterized by dysfunction of exocrine glands, such as salivary glands. However, the molecular mechanism of salivary secretion dysfunction in SS is still unclear. Given the significance of glutathione peroxidase 4 (GPX4) in cellular redox homeostasis, we hypothesized that dysregulation of GPX4 may play a pivotal role in the pathogenesis of salivary secretion dysfunction observed in SS. The salivary gland of SS patients and the SS mouse model exhibited reduced expression of the ferroptosis inhibitor GPX4 and the important protein aquaporin 5 (AQP5), which is involved in salivary secretion. GPX4 overexpression upregulated and GPX4 knockdown downregulated AQP5 expression in salivary gland epithelial cells (SGECs) and salivary secretion. Bioinformatics analysis of GSE databases from SS patients' salivary glands revealed STAT4 as a key intermediary regulator between GPX4 and AQP5. A higher level of nuclear pSTAT4 was observed in the salivary gland of the SS mouse model. GPX4 overexpression inhibited and GPX4 knockdown promoted STAT4 phosphorylation and nuclear translocation in SGECs. CHIP assay confirmed the binding of pSTAT4 within the promoter of AQP5 inhibiting AQP5 transcription. GPX4 downregulation accumulates intracellular lipid ROS in SGECs. Lipid ROS inhibitor ferrostatin-1 treatment during in vitro and in vivo studies confirmed that lipid ROS activates STAT4 phosphorylation and nuclear translocation in SGECs. In summary, the downregulated GPX4 in SGECs contributes to salivary secretion dysfunction in SS via the lipid ROS/pSTAT4/AQP5 axis. This study unraveled novel targets to revitalize the salivary secretion function in SS patients.

The macrocyclic lactone oxacyclododecindione reduces fibrosis progression

Background: Renal fibrosis is one of the most important triggers of chronic kidney disease (CKD), and only a very limited number of therapeutic options are available to stop fibrosis progression. As fibrosis is characterized by inflammation, myofibroblast activation, and extracellular matrix (ECM) deposition, a drug that can address all these processes might be an interesting therapeutic option. Methods: We tested in vivo in an ischemia-reperfusion (I/R) model in C57BL/6 mice and in kidney tubular epithelial cells (TEC) (HK2 cell line and primary cells) whether the natural product oxacyclododecindione (Oxa) reduces fibrosis progression in kidney disease. This was evaluated by Western blot, mRNA expression, and mass spectrometry secretome analyses, as well as by immunohistochemistry. Results: Indeed, Oxa blocked the expression of epithelial-mesenchymal transition marker proteins and reduced renal damage, immune cell infiltration, and collagen expression and deposition, both in vivo and in vitro. Remarkably, the beneficial effects of Oxa were also detected when the natural product was administered at a time point of established fibrotic changes, a situation close to the clinical situation. Initial in vitro experiments demonstrated that a synthetic Oxa derivative possesses similar features. Conclusion: Although open questions such as possible side effects need to be investigated, our results indicate that the combination of anti-inflammatory and anti-fibrotic effects of Oxa make the substance a promising candidate for a new therapeutic approach in fibrosis treatment, and thus in the prevention of kidney disease progression.

The role of upadacitinib in the treatment of ulcerative colitis

The JAK signaling pathway plays a major role in the immunopathology of autoimmune diseases, including inflammatory bowel disease. JAK enzymes provide novel targets for rapidly effective inflammatory bowel disease therapy, particularly in ulcerative colitis. Upadacitinib is a targeted JAK1 inhibitor. In multiple phase III clinical trials, upadacitinib has demonstrated significant improvement in clinical and endoscopic outcomes and quality of life for patients with moderate-to-severe ulcerative colitis. In this drug evaluation we describe the role of the JAK signaling pathway in ulcerative colitis, the mechanism of action of upadacitinib and the current clinical evidence for its use in ulcerative colitis; we also review its safety and tolerability, including for special populations.

Reduced Renal CSE/CBS/H2S Contributes to the Progress of Lupus Nephritis

The molecular mechanisms underlying lupus nephritis (LN) pathogenesis are not fully understood. Hydrogen sulfide (H2S) is involved in many pathological and physiological processes. We sought to investigate the roles of H2S in LN pathogenesis. H2S synthase cystathionine-lyase (CSE) and cystathionine-synthetase (CBS) expression was downregulated in renal tissues of patients with LN and their levels were associated with LN's prognosis using the Nephroseq database. Reduced CSE and CBS protein expression in kidney tissues of LN patients and MRL/lpr mice were confirmed by immunohistochemistry. CSE and CBS mRNA levels were reduced in MRL/lpr and pristine- and R848-induced lupus mice. Given that H2S exerts an anti-inflammatory role partly via regulating inflammatory transcription factors (TFs), we analyzed hub TFs by using a bioinformatics approach. It showed that STAT1, RELA, and T-cell-related signaling pathways were enriched in LN. Increased STAT1 and RELA expression were confirmed in renal tissues of LN patients. Treatment of MRL/lpr and pristine mice with H2S donors alleviated systemic lupus erythematosus (SLE) phenotypes and renal injury. H2S donors inhibited RELA level and T-cell infiltration in the kidneys of MRL/lpr and pristine mice. Our data indicated that CSE/CBS/H2S contributes to LN pathogenesis. Supplementation of H2S would be a potential therapeutic strategy for LN.

Blockage of TIM-3 relieves lupus nephritis by expanding Treg cells and promoting their suppressive capacity in MRL/lpr mice

T Cell Immunoglobulin and Mucin Containing Protein-3 (TIM-3) is an important immune checkpoint protein that is expressed in Tregs and affects their function. However, the expression and role of TIM-3 in modulating regulatory T cells (Tregs) in lupus nephritis (LN) are still unknown. In this study, we found that the percentage of TIM-3⁺ cells among spleen lymphocytes, CD4⁺ T cells and Tregs was higher in MRL/lpr mice than in MpJ mice. TIM-3^high CD4⁺ T cells and TIM-3^high Tregs were mainly responsible for the increase. The percentage of Tregs in TIM-3^high CD4⁺ T cells was lower than that in TIM-3^low CD4⁺ T cells, and the expression of CTLA-4 and IL-10 was lower in TIM-3^high Tregs than in the TIM-3^low Tregs in MRL/lpr mice. Blockade of TIM-3 in vivo significantly increased the Treg population and the expression of CTLA-4 and IL-10 in Tregs, thus relieving the LN symptoms and pathology in MRL/lpr mice. Additionally, bioinformatics analysis indicated that TIM-3 regulates Treg cells in LN mainly through cytokine-cytokine receptor interactions, the PI3K-Akt signaling pathway, the T cell receptor signaling pathway, Th17 cell differentiation and the FoxO signaling pathway. Together, our study has demonstrated that TIM-3 regulates Tregs in LN and that overexpression of TIM-3 in CD4⁺ T cells and Tregs leads to Treg quantity and quality deficiency in MRL/lpr mice. Blockade of TIM-3 protects against LN by expanding Tregs and enhancing their suppressive capacity. Finally, TIM-3 might be a potential therapeutic target for the treatment of LN.

Restoration of Follicular T Regulatory/Helper Cell Balance by OX40L-JAG1 Cotreatment Suppresses Lupus Nephritis in NZBWF1/j Mice

Class-switched antinuclear autoantibodies produced by T follicular helper (TFH) cell-dependent germinal center (GC) B cell response play an essential pathogenic role in lupus nephritis (LN). The role of T follicular regulatory (TFR) cells, an effector subset of CD4⁺Foxp3⁺ T regulatory cells (Tregs), which are specialized in suppressing TFH-GC response and Ab production, remains elusive in LN. Contrasting reports have shown increased/reduced circulating TFR cells in human lupus that might not accurately reflect their presence in the GCs of relevant lymphoid organs. In this study, we report a progressive reduction in TFR cells and decreased TFR/TFH ratio despite increased Tregs in the renal lymph nodes of NZBWF1/j mice, which correlated with increased GC-B cells and proteinuria onset. Cotreatment with soluble OX40L and Jagged-1 (JAG1) proteins increased Tregs, TFR cells, and TFR/TFH ratio, with a concomitant reduction in TFH cells, GC B cells, and anti-dsDNA IgG Ab levels, and suppressed LN onset. Mechanistic studies showed attenuated TFH functions and diminished GC events such as somatic hypermutation and isotype class-switching in OX40L-JAG1-treated mice. RNA sequencing studies revealed inhibition of hypoxia-inducible factor 1-α (HIF-1a) and STAT3 signaling in T conventional cells from OX40L-JAG1-treated mice, which are critical for the glycolytic flux and differentiation into TFH cell lineage. Therefore, the increased TFR/TFH ratio seen in OX40L-JAG1-treated mice could involve both impaired differentiation of TFH cells from T conventional cells and expansion of TFR cells. We show a key role for GC-TFR/TFH imbalance in LN pathogenesis and how restoring homeostatic balance can suppress LN.

Rapamycin relieves lupus nephritis by regulating TIM-3 and CD4+CD25+Foxp3+ Treg cells in an MRL/lpr mouse model

Lupus nephritis (LN) is a severe consequence of systemic lupus erythematosus (SLE) and is an important driver of morbidity and mortality in SLE. Treg cells and TIM-3 play an important role in the pathogenesis of LN. The beneficial effect of rapamycin on LN has been confirmed in both mouse models and patients, but the effect of rapamycin on Treg cells and TIM-3 is not yet completely understood. In this study, rapamycin treatment attenuated proteinuria, histological damage, and renal deposition of C3, and improved renal function. Spleen and renal draining lymph node weight and serum levels of anti-dsDNA antibodies were also improved by rapamycin. Furthermore, the frequency of Treg cells and Treg functional molecules, such as cytotoxic T cell antigen 4 (CTLA-4), interleukin 10 (IL-10), and transforming growth factor β1 (TGF-β1), increased significantly after treatment with rapamycin in MRL/lpr mice. We also found that expression of TIM-3 was significantly decreased in CD4+ T cells and Treg cells in mice treated with rapamycin. In summary, the study demonstrated that rapamycin treatment induced preferential expansion of CD4+CD25+Foxp3+ Tregs with increased expression of CTLA-4, IL-10, and TGF-β1, and decreased TIM-3 expression, thereby ameliorating lupus nephritis in the MRL/lpr mouse model.

STAT4: an immunoregulator contributing to diverse human diseases

Signal transducer and activator of transcription 4 (STAT4) is a member of the STAT family and localizes to the cytoplasm. STAT4 is phosphorylated after a variety of cytokines bind to the membrane, and then dimerized STAT4 translocates to the nucleus to regulate gene expression. We reviewed the essential role played by STAT4 in a wide variety of cells and the pathogenesis of diverse human diseases, especially many kinds of autoimmune and inflammatory diseases, via activation by different cytokines through the Janus kinase (JAK)-STAT signaling pathway.

IL-34-Dependent Intrarenal and Systemic Mechanisms Promote Lupus Nephritis in MRL-Faslpr Mice

BACKGROUND

In people with SLE and in the MRL-Fas^lpr lupus mouse model, macrophages and autoantibodies are central to lupus nephritis. IL-34 mediates macrophage survival and proliferation, is expressed by tubular epithelial cells (TECs), and binds to the cFMS receptor on macrophages and to a newly identified second receptor, PTPRZ.

METHODS

To investigate whether IL-34-dependent intrarenal and systemic mechanisms promote lupus nephritis, we compared lupus nephritis and systemic illness in MRL-Fas^lpr mice expressing IL-34 and IL-34 knockout (KO) MRL-Fas^lpr mice. We also assessed expression of IL-34 and the cFMS and PTPRZ receptors in patients with lupus nephritis.

RESULTS

Intrarenal IL-34 and its two receptors increase during lupus nephritis in MRL-Fas^lpr mice. In knockout mice lacking IL-34, nephritis and systemic illness are suppressed. IL-34 fosters intrarenal macrophage accumulation via monocyte proliferation in bone marrow (which increases circulating monocytes that are recruited by chemokines into the kidney) and via intrarenal macrophage proliferation. This accumulation leads to macrophage-mediated TEC apoptosis. We also found suppression of circulating autoantibodies and glomerular antibody deposits in the knockout mice. This is consistent with fewer activated and proliferating intrarenal and splenic B cells in mice lacking IL-34, and with our novel discovery that PTPRZ is expressed by macrophages, B and T cells. These findings appear translatable to human patients with lupus nephritis, whose expression of IL-34, cFMS, and PTPRZ is similar to that seen in the MRL-Fas^lpr lupus mouse model. Moreover, expression of IL-34 in TECs correlates with disease activity.

CONCLUSIONS

IL-34 is a promising novel therapeutic target for patients with lupus nephritis.

Renal tubular epithelial cell-derived BAFF expression mediates kidney damage and correlates with activity of proliferative lupus nephritis in mouse and men

B-cell activating factor of the tumour necrosis factor family (BAFF) is a cytokine, mainly produced by hematopoietic cells (e.g. monocytes/macrophages, dendritic cells), indispensable for B-cell maturation. The BLISS studies have demonstrated that blocking BAFF by the human monoclonal antibody belimumab is a valuable therapeutic approach in patients with clinically and serologically active systemic lupus erythematosus (SLE). However, the defined sources of BAFF, which contributes to SLE, are still unclear. Recent findings show that BAFF expression is not restricted to myeloid cells. Since lupus nephritis is the main cause of morbidity and mortality for SLE patients, the aim of this study was to investigate whether renal tubular epithelial cells (TEC) are an important source of BAFF and thus may contribute to the pathogenesis and progression of SLE. We found BAFF expression both in cultured murine and human TEC. These results could be verified with in situ data from the kidney. Moreover, BAFF expression in the kidneys of lupus-prone MRL- Fas^lpr mice correlated with disease activity, and BAFF expression on TEC in biopsies of patients with diffuse proliferative lupus nephritis showed a correlation with the histopathological activity index. In vitro functional assays revealed an autocrine loop of BAFF with its binding receptors on TEC, resulting in a strong induction of colony stimulating factor-1. Finally, we identified divergent effects of BAFF on TEC depending on the surrounding milieu ('inflammatory versus non-inflammatory'). Taken together, our findings indicate that renal-derived BAFF may play an important role in the pathophysiology of the systemic autoimmune disease SLE.

Re-Examining Neutrophil Participation in GN

Significant advances in understanding the pathogenesis of GN have occurred in recent decades. Among those advances is the finding that both innate and adaptive immune cells contribute to the development of GN. Neutrophils were recognized as key contributors in early animal models of GN, at a time when the prevailing view considered neutrophils to function as nonspecific effector cells that die quickly after performing antimicrobial functions. However, advances over the past two decades have shown that neutrophil functions are more complex and sophisticated. Specifically, research has revealed that neutrophil survival is regulated by the inflammatory milieu and that neutrophils demonstrate plasticity, mediate microbial killing through previously unrecognized mechanisms, demonstrate transcriptional activity leading to the release of cytokines and chemokines, interact with and regulate cells of the innate and adaptive immune systems, and contribute to the resolution of inflammation. Therefore, neutrophil participation in glomerular diseases deserves re-evaluation. In this review, we describe advances in understanding classic neutrophil functions, review the expanded roles of neutrophils in innate and adaptive immune responses, and summarize current knowledge of neutrophil contributions to GN.

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.

Granulocyte colony-stimulating factor treatment ameliorates lupus nephritis through the expansion of regulatory T cells

Background

Granulocyte colony-stimulating factor (G-CSF) can induce regulatory T cells (Tregs) as well as myeloid-derived suppressor cells (MDSCs). Despite the immune modulatory effects of G-CSF, results of G-CSF treatment in systemic lupus erythematosus are still controversial. We therefore investigated whether G-CSF can ameliorate lupus nephritis and studied the underlying mechanisms.

Methods

NZB/W F1 female mice were treated with G-CSF or phosphate-buffered saline for 5 consecutive days every week from 24 weeks of age, and were analyzed at 36 weeks of age.

Results

G-CSF treatment decreased proteinuria and serum anti-dsDNA, increased serum complement component 3 (C3), and attenuated renal tissue injury including deposition of IgG and C3. G-CSF treatment also decreased serum levels of BUN and creatinine, and ultimately decreased mortality of NZB/W F1 mice. G-CSF treatment induced expansion of CD4⁺CD25⁺Foxp3⁺ Tregs, with decreased renal infiltration of T cells, B cells, inflammatory granulocytes and monocytes in both kidneys and spleen. G-CSF treatment also decreased expression levels of MCP-1, IL-6, IL-2, and IL-10 in renal tissues as well as serum levels of MCP-1, IL-6, TNF-α, IL-10, and IL-17. When Tregs were depleted by PC61 treatment, G-CSF-mediated protective effects on lupus nephritis were abrogated.

Conclusions

G-CSF treatment ameliorated lupus nephritis through the preferential expansion of CD4⁺CD25⁺Foxp3⁺ Tregs. Therefore, G-CSF has a therapeutic potential for lupus nephritis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-016-0380-x) contains supplementary material, which is available to authorized users.

Intrarenal macrophage infiltration induced by T cells is associated with podocyte injury in lupus nephritis patients

Proteinuria is the hallmark of clinical manifestation of disease activity in lupus nephritis (LN) patients, which arises from direct or indirect podocyte injury. This study is to explore the relationship between intrarenal T cell infiltration and podocyte injury in lupus nephritis (LN), and to understand the potential mechanisms of podocyte injury induced by intrarenal T cells. Sixty renal biopsies from patients diagnosed with LN were included in the present study. Histological changes in LN patients were detected by light and electron microscopy. Podocyte-specific nephrin expression in renal tissues was detected by immunofluorescence. Infiltration of T cells (CD3+ cells), infiltration of macrophages (CD68+ cells) and the expression of osteopontin (OPN) in renal tissues were examined by immunohistochemical staining. Pearson or Spearman’s tests were used to perform correlation analysis. Morphologic lesions of podocytes were more severe in LN patients than in normal control subjects. Compared with normal control subjects, nephrin expression was significantly decreased in LN patients. The expression level of nephrin was significantly lower in active LN patients than in the inactive group of patients ( P < 0.05). Compared with normal control subjects, the number of infiltrated intrarenal T cells and macrophages was significantly increased in LN patients. T cells were mainly distributed in renal interstitium, with very few being in glomeruli, while macrophages were mainly located in glomeruli. The number of intrarenal infiltrated T cells and macrophages in active LN patients was more than that in the inactive group ( P < 0.05). Compared with normal control subjects, OPN expression in LN patients was increased significantly. The expression level of OPN in active LN patients was significantly higher than that in the inactive group ( P < 0.05). Podocyte-specific nephrin was negatively correlated with 24-hour proteinuria, intrarenal T cells infiltration and intrarenal OPN expression in LN patients ( P < 0.001). Intrarenal macrophages had significantly positive correlation with intrarenal OPN expression ( P < 0.001). The present study provides possible links between intrarenal T cells, OPN, macrophages with reduced podocyte-nephrin and podocytopathy in systemic lupus erythematosus. In addition, infiltration of macrophages in glomeruli induced by OPN that is induced by T cells may be a crucial mechanism for podocyte injury.

The role of IL-18 in type 1 diabetic nephropathy: The problem and future treatment

Diabetic vascular complication is a leading cause of diabetic nephropathy, a progressive increase in urinary albumin excretion coupled with elevated blood pressure leading to declined glomerular filtration and eventually end stage renal failure. There is growing evidence that activated inflammation is contributing factor to the pathogenesis of diabetic nephropathy. Meanwhile, IL-18, a member of the IL-1 family of inflammatory cytokines, is involved in the development and progression of diabetic nephropathy. However, the benefits derived from the current therapeutics for diabetic nephropathy strategies still provide imperfect protection against renal progression. This imperfection points to the need for newer therapeutic agents that have potential to affect primary mechanisms contributing to the pathogenesis of diabetic nephropathy. Therefore, the recognition of IL-18 as significant pathogenic mediators in diabetic nephropathy leaves open the possibility of new potential therapeutic targets.

Contribution of the STAT4 rs7574865 gene polymorphism to the susceptibility to autoimmune thyroiditis in healthy Turk population and psoriatic subgroups

Introduction

STAT4 is an important transcription factor that activates gene transcription as a response to cytokines. Recently, the influence of STAT4 gene on autoimmune disease has been widely studied in many different immune-related diseases. Autoimmune, metabolic and cardiovascular disorders are more common in psoriatic patients. STAT4 may be a unique gene that switches on in autoimmune-related thyroid disease in psoriatic patients.

The aim of the study: To explore the association of a STAT4 rs7574865 polymorphism to autoimmune thyroid diseases in the general Turkish population and psoriatic subgroups.

Material and methods

A total of 132 psoriatic patients and 118 non-psoriatic volunteers were genotyped for STAT4 rs7574865 using real time PCR. Twenty-four of the psoriatic patients and 15 of the non-psoriatic volunteers have autoimmune-related thyroid diseases.

Results

The prevalence of the T allele [OR = 4.37; 95% CI: 1.05-19; p = 0.03] of the STAT4 rs7574865 was higher in individuals with autoimmune-related thyroid diseases among the all non-psoriatic volunteers. The volunteers with autoimmune-related thyroid diseases has an increased allele positivity and carriers having at least one of the risk allele was significantly higher than in counterparts with a GG wild genotype [ORGT/TT vs. GG: 1.73; 95% CI: 0.09-32; p = 0.03]. Yet, there was no evidence of an association between rs7574865 and autoimmune-related thyroid disease in psoriatic patients.

Conclusions

The STAT4 rs7574865 polymorphism increases autoimmune-related thyroid disease susceptibility among the general population but not in psoriatic patients.

Targeting the inflammasome in rheumatic diseases

Activation of the inflammasome, a protein complex responsible for many cellular functions, including the activation of the proinflammatory cytokines interleukin (IL)-1β and IL-18, has been identified as a key participant in many rheumatic diseases including autoimmune, inflammatory, and autoinflammatory syndromes. This review will discuss the recent advances in understanding the role of this complex in various rheumatic diseases. Furthermore, it will focus on available therapies, which directly and indirectly target the inflammasome and its downstream cytokines to quiet inflammation and possibly dampen autoimmune processes.

Deletion of IL-18 Expression Ameliorates Spontaneous Kidney Failure in MRLlpr Mice

The role of IL-18 in the pathogenesis of systemic lupus erythematosus is still not definitively solved. In this study, we generated MRL^lpr mice, which develop a disease resembling systemic lupus erythematosus, genetically devoid of IL-18 expression. These mice in comparison to IL-18-competent MRL^lpr mice show reduced signs of renal pathogenesis, while other parameters such as mean survival time, lymphadenopathy, constitutive interferon-γ production, and frequency of CD3⁺B220⁺ abnormal T cells were without differences. We conclude that in the systemic lupus erythematosus syndrom IL-18 is involved specifically in the renal pathogenesis.

Genetics and novel aspects of therapies in systemic lupus erythematosus

Autoimmune diseases, such as rheumatoid arthritis, multiple sclerosis, autoimmune hepatitis and inflammatory bowel disease, have complex pathogeneses and the factors which cause these disorders are not well understood. But all have in common that they arise from a dysfunction of the immune system, interpreting self components as foreign antigens. Systemic lupus erythematosus (SLE) is one of these complex inflammatory disorders that mainly affects women and can lead to inflammation and severe damage of virtually any tissue and organ. Recently, the application of advanced techniques of genome-wide scanning revealed more genetic information about SLE than previously possible. These case-control or family-based studies have provided evidence that SLE susceptibility is based (with a few exceptions) on an individual accumulation of various risk alleles triggered by environmental factors and also help to explain the discrepancies in SLE susceptibility between different populations or ethnicities. Moreover, during the past years new therapies (autologous stem cell transplantation, B cell depletion) and improved conventional treatment options (corticosteroids, traditional and new immune-suppressants like mycophenolate mofetile) changed the perspective in SLE therapeutic approaches. Thus, this article reviews genetic aspects of this autoimmune disease, summarizes clinical aspects of SLE and provides a general overview of conventional and new therapeutic approaches in SLE.

The inflammasome and lupus: another innate immune mechanism contributing to disease pathogenesis?

PURPOSE OF REVIEW

The role of innate immunity in systemic lupus erythematosus (SLE) has been a rapidly expanding area of research over the last decade. Included in this rubric is the concept that activation of the inflammasome, a molecular complex that activates caspase-1 and in turn the cytokines IL-1β and IL-18, is important in lupus pathogenesis. This review will summarize the recent discoveries exploring the role of the inflammasome machinery in SLE.

RECENT FINDINGS

Immune complexes can activate the NLRP3 inflammasome, and SLE-derived macrophages are hyper-responsive to innate immune stimuli, leading to enhanced activation of the inflammasome and production of inflammatory cytokines. Work in several murine models suggests an important role for the NLRP3 inflammasome in mediating lupus nephritis. Caspase-1, the central enzyme of the inflammasome, is essential for the development of type I interferon responses, autoantibody production, and nephritis in the pristane model of lupus. The absence of melanoma 2 inflammasome may have protective and pathogenic roles in SLE.

SUMMARY

Recent evidence suggests that the inflammasome machinery is dysregulated in SLE, plays an important role in promotion of organ damage, and may mediate cross-talk between environmental triggers and the development of lupus. Further research should focus on whether inhibition of inflammasome components may serve as a viable target for therapeutic development in SLE.

Comparative screening and validation as a novel tool to identify STAT-specific inhibitors

Signal transducers and activators of transcription (STATs) facilitate action of cytokines, growth factors and pathogens. STAT activation is mediated by a highly conserved SH2 domain, which interacts with phosphotyrosine (pTyr) motifs for specific STAT-receptor contacts and STAT dimerization. The active dimers induce gene transcription in the nucleus by binding to specific DNA-response elements of target genes. Abnormal activation of STAT signaling pathways is implicated in many human diseases, like cancer, inflammation and auto-immunity. STAT inhibitory strategies mostly focus on inhibiting STAT dimerization using small molecules identified by molecular modeling, virtual or library screening, or natural products. Searches for STAT-targeting compounds, exploring the pTyr-SH2 interaction area, yielded many small molecules for STAT3 but sparsely for other STATs. So far, no STAT-targeting drug is approved by the FDA. Moreover, many of these inhibitors do not seem STAT-specific, thereby questioning the present selection strategies of SH2 domain-based STAT inhibitors. This illustrates the need for better models, and screening and validation tools for more druggable STAT inhibitors with high specificity, potency and excellent bioavailability. Based on newly developed 3D structure models for all human (h)STATs, we propose a pipeline approach that combines comparative in silico docking of STAT-SH2 models with an in vitro STAT phosphorylation assay, as a novel tool to screen multi-million compound libraries and identify specific inhibitors for different STATs. Identification of specific and effective STAT inhibitory compounds could provide a tool to increase our understanding of their functional role in different diseases, and serve as therapeutic strategies in cancer, inflammation and auto-immunity.

Therapeutic potential of STAT4 in autoimmunity

INTRODUCTION

STAT4, which acts as the major signaling transducing STATs in response to IL-12, is a central mediator in generating inflammation during protective immune responses and immune-mediated diseases.

AREAS COVERED

This review summarizes that STAT4 is essential for the differentiation and function of a wide variety of immune cells, including natural killer cells, mast cells, dendritic cells and T helper cells. In addition, STAT4-mediated signaling promoted the production of autoimmune-associated components, which are implicated in the pathogenesis of autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis and psoriasis.

EXPERT OPINION

Due to its crucial roles in inflammation and autoimmunity, STAT4 may have promise as an effective therapeutic target for autoimmune diseases. Understanding the molecular mechanisms driving STAT4, together with knowledge on the ability of current immunosuppressive treatment to target this process, may open an avenue to novel therapeutic options.

Therapeutic modulators of STAT signalling for human diseases

The signal transducer and activator of transcription (STAT) proteins have important roles in biological processes. The abnormal activation of STAT signalling pathways is also implicated in many human diseases, including cancer, autoimmune diseases, rheumatoid arthritis, asthma and diabetes. Over a decade has passed since the first inhibitor of a STAT protein was reported and efforts to discover modulators of STAT signalling as therapeutics continue. This Review discusses the outcomes of the ongoing drug discovery research endeavours against STAT proteins, provides perspectives on new directions for accelerating the discovery of drug candidates, and highlights the noteworthy candidate therapeutics that have progressed to clinical trials.

The role of cytokines in the pathogenesis of systemic lupus erythematosus - from bench to bedside

The pathogenesis of systemic lupus erythematosus (SLE) entails a complex interaction between the different arms of the immune system. While autoantibodies production and immune complex deposition are cornered as hallmark features of SLE, there is growing evidence to propose the pathogenic role of cytokines in this disease. Examples of these cytokines include BLys, interleukin-6, interleukin-17, interleukin-18, type I interferons and tumour necrosis factor alpha. These cytokines all assume pivotal functions to orchestrate the differentiation, maturation and activation of various cell types, which would mediate local inflammatory process and tissue injury. The knowledge on these cytokines not only fosters our understanding of the disease, but also provides insights in devising biomarkers and targeted therapies. In this review, we focus on cytokines which have substantial pathogenic significance and also highlight the possible clinical applications of these cytokines.

Biomarker profiling for lupus nephritis

Lupus nephritis (LN) is one of the most severe manifestations of systemic lupus erythematosus (SLE), which is associated with significant morbidity and mortality of SLE patients. The pathogenesis of LN involves multiple factors, including genetic predisposition, epigenetic regulation and environmental interaction. Over the last decade, omics-based techniques have been extensively utilized for biomarker screening and a wide variety of variations which are associated with SLE and LN have been identified at the levels of genomics, transcriptomics and proteomics. These studies and discoveries have expanded our understanding of the molecular basis of the disease and are important for identification of potential therapeutic targets for disease prediction and early treatment. In this review, we summarize some of the recent studies targeted at the identification of LN-associated biomarkers using genomics and proteomic approaches.

Cytokine inhibition as a strategy for treating systemic lupus erythematosus

Cytokines regulate and control the immune system. In systemic lupus erythematosus, several of these cytokines are overexpressed and contribute to the pathogenesis of the disease. Cytokine inhibition has been successfully used to treat other rheumatic and autoimmune diseases, and several cytokines are currently being investigated to determine whether inhibition would be therapeutic in lupus. The cytokines discussed in this review have all undergone clinical trials, and include TNF-α, IL-1, IL-6, IL-10, IL-15, IL-17, IL-18 and IL-23. Inhibition of the majority of these targets was safe and showed some efficacy in treating lupus. Cytokine inhibition strategies have just started to realize their potential for the treatment of this difficult disease, and show great promise for the future.

Definition of IFN-γ-related pathways critical for chemically-induced systemic autoimmunity

IFN-γ is essential for idiopathic and murine mercury-induced systemic autoimmunity (mHgIA), and heterozygous IFN-γ(+/-) mice also exhibit reduced disease. This suggests that blocking specific IFN-γ-related pathways that may only partially inhibit IFN-γ production or function will also suppress autoimmunity. To test this hypothesis, mice deficient in genes regulating IFN-γ expression (Casp1, Nlrp3, Il12a, Il12b, Stat4) or function (Ifngr1, Irf1) were examined for mHgIA susceptibility. Absence of either Ifngr1 or Irf1 resulted in a striking reduction of disease, while deficiency of genes promoting IFN-γ expression had modest to no effect. Furthermore, both Irf1- and Ifng-deficiency only modestly reduced the expansion of CD44(hi) and CD44(hi)CD55(lo) CD4(+) T cells, indicating that they are not absolutely required for T cell activation. Thus, there is substantial redundancy in genes that regulate IFN-γ expression in contrast to those that mediate later signaling events. These findings have implications for the therapeutic targeting of IFN-γ pathways in systemic autoimmunity.

Mechanisms of tissue injury in lupus nephritis

Systemic lupus erythematosus is a prototypic autoimmune disease characterized by autoantibody production and immune complex formation/deposition in target organs such as the kidney. Resultant local inflammation then leads to organ damage. Nephritis, a major cause of morbidity and mortality in patients with lupus, occurs in approximately 50% of lupus patients. In the present review, we provide an overview of the current research and knowledge concerning mechanisms of renal injury in both lupus-prone mouse models and human lupus patients.

Autocrine CSF-1 and CSF-1 receptor coexpression promotes renal cell carcinoma growth

Renal cell carcinoma is increasing in incidence but the molecular mechanisms regulating its growth remain elusive. Coexpression of the monocytic growth factor colony-stimulating factor (CSF)-1 and its receptor CSF-1R on renal tubular epithelial cells (TEC) will promote proliferation and antiapoptosis during regeneration of renal tubules. Here, we show that a CSF-1-dependent autocrine pathway is also responsible for the growth of renal cell carcinoma (RCC). CSF-1 and CSF-1R were coexpressed in RCCs and TECs proximally adjacent to RCCs. CSF-1 engagement of CSF-1R promoted RCC survival and proliferation and reduced apoptosis, in support of the likelihood that CSF-1R effector signals mediate RCC growth. In vivo CSF-1R blockade using a CSF-1R tyrosine kinase inhibitor decreased RCC proliferation and macrophage infiltration in a manner associated with a dramatic reduction in tumor mass. Further mechanistic investigations linked CSF-1 and epidermal growth factor signaling in RCCs. Taken together, our results suggest that budding RCC stimulates the proximal adjacent microenvironment in the kidney to release mediators of CSF-1, CSF-1R, and epidermal growth factor expression in RCCs. Furthermore, our findings imply that targeting CSF-1/CSF-1R signaling may be therapeutically effective in RCCs.

Making sense of therapeutics using antisense technology

INTRODUCTION

Antisense oligonucleotides (ASOs) are short synthetic single-stranded DNA sequences that bind to and induce the cleavage of homologous stretches of mRNA sequences. These result in targeted destruction of mRNA and correction of genetic aberrations. ASOs thus can act as drug molecules and potentially rectify many disease conditions. The broad range of applications reported in the literature highlights the advances in the field.

AREAS COVERED

This review covers different areas in which use of ASOs has been shown to have therapeutic effects. Some drugs in different stages of preclinical and clinical trials are discussed in detail. The problems faced and the strategies to surmount them are also described. The readers will gain an understanding of the recent developments in the field of ASOs with emphasis on their therapeutic applications. They will also become aware of the different strategies used for targeted delivery of ASOs and their stabilization, which may be useful for their work in this field, or in the area of nucleic acid therapeutics in general.

EXPERT OPINION

The design and application of ASOs for recognition of target mRNA sequences have become a fairly straightforward protocol. The main problem lies in designing ASOs which are stable in in vivo milieu. The delivery and bioavailability of the oligonucleotide to the site of action continue to be hurdles in the development of ASOs and therapeutic molecules.