Clinical relevance of circulating anti-ENA and anti-dsDNA secreting cells from SLE patients and their dependence on STAT-3 activation

Dysregulated CXCL12 expression in osteoblasts promotes B-lymphocytes preferentially homing to the bone marrow in MRL/lpr mice

Objective: Todetect the abnormal distribution of B-lymphocytes between peripheral and bone marrow (BM) compartments and explore the mechanism of abnormal chemotaxis of B-lymphocytes in lupus subjects. Methods: The proportions of CXC chemokine receptor (CXCR)4+ B cells and CFDA-labeled MRL/lpr-derived B cells were detected by flow cytometry. The levels of CXC chemokine ligand (CXCL)12in peripheral blood (PB)were measured by ELISA. The migrated B cells to osteoblasts (OBs) was measured by transwell migration assay. The relative spatial position of B cells, OBs and CXCL12 was presented by Immunofluorescence assay. Results: Firstly, we found that the percentage of CXCR4+ B cells was lower in PB and higher in the BM from both MRL/lpr mice and patientswith Systemic lupus erythematosus (SLE). Secondly, OBs from MRL/lpr mice produced more CXCL12 than that from C57BL/6 mice. Besides, MRL/lpr-derived OBs demonstrated more potent chemotactic ability toward B-lymphocytes than control OBs by vitro an vivo. Additionally, more B-lymphocytes were found to co-localize with OBs within the periosteal zone of bone in MRL/lpr mice. Lastly, the percentages of CXCR4+B cells were found to be negatively correlated with serum Immunoglobulin (Ig) G concentration, moreover, BM CXCL12 levels were found to be positively correlated with SLE disease activity index Score and negatively correlated with serum Complement3 (C3) concentration. Conclusions: our results indicated that there is a shifted distribution of B-lymphocytes between BM and peripheral compartments in both SLE patients and MRL/lpr mice. Besides, the up-regulated levels of CXCL12 in OBs was indicated to contribute to the enhanced chemotactic migration and anchorage of B-lymphocytes to OBs.

The role of Interleukin-21 in autoimmune Diseases: Mechanisms, therapeutic Implications, and future directions

IL-21 is a multifunctional cytokine that regulates the functional activity of various immune cells. Initial studies have shown that IL-21 can influence the differentiation, proliferation and function of T and B cells, as well as promote the maturation and increase the cytotoxicity of CD8 + T cells and NK cells. During humoral immune responses, IL-21 has significant effects on B cell activation, differentiation and apoptosis. In addition, IL-21 promotes the differentiation of both naive and memory B cells, ultimately leading to the activation of plasma cells. The function of IL-21 in the immune system is complex, as it has the ability to either stimulate or inhibit immune responses. in addition, IL-21 facilitates the differentiation of naive and memory B cells into plasma cells. The functionality of IL-21 in the immune system is diverse, as it has the ability to stimulate or inhibit immune responses. This cytokine has been implicated in several diseases including cancer, allergies and autoimmune diseases. Research has suggested that this cytokine is involved in the development of autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. Several studies have suggested that inhibition of IL-21 has a therapeutic effect on autoimmune diseases. Therefore, targeting both the cytokine's receptor and IL-21 in autoimmune diseases may be an effective approach to reduce the severity of the disease or to treat it. This review will examine the biological effects of IL-21 on various immune cells and the role of the cytokine in autoimmune diseases.

B cell-targeted polylactic acid nanoparticles as platform for encapsulating jakinibs: potential therapeutic strategy for systemic lupus erythematosus

Background: B cells are pivotal in systemic lupus erythematosus and autoimmune disease pathogenesis. Materials & methods: To address this, Nile Red-labeled polylactic acid nanoparticles (NR-PLA NPs) loaded with the JAK inhibitor baricitinib (BARI), specifically targeting JAK1 and JAK2 in B cells, were developed. Results: Physicochemical characterization confirmed NP stability over 30 days. NR-PLA NPs were selectively bound and internalized by CD19+ B cells, sparing other leukocytes. In contrast to NR-PLA NPs, BARI-NR-PLA NPs significantly dampened B-cell activation, proliferation and plasma cell differentiation in healthy controls. They also inhibited key cytokine production. These effects often surpassed those of equimolar-free BARI. Conclusion: This study underscores the potential of PLA NPs to regulate autoreactive B cells, offering a novel therapeutic avenue for autoimmune diseases.

Role of JAK-STAT signaling pathway in pathogenesis and treatment of primary Sjögren's syndrome

ABSTRACT

Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease with high prevalence and possible poor prognosis. Though the pathogenesis of pSS has not been fully elucidated, B cell hyperactivity is considered as one of the fundamental abnormalities in pSS patients. It has long been identified that Janus kinases-signal transducer and activator of transcription (JAK-STAT) signaling pathway contributes to rheumatoid arthritis and systemic lupus erythematosus. Recently, increasing numbers of studies have provided evidence that JAK-STAT pathway also has an important role in the pathogenesis of pSS via direct or indirect activation of B cells. Signal transducer and activator of transcription 1 (STAT1), STAT3, and STAT5 activated by various cytokines and ribonucleic acid contribute to pSS development, respectively or synergically. These results reveal the potential application of Janus kinase inhibitors for treatment of pSS, which may fundamentally improve the quality of life and prognosis of patients with pSS.

Janus kinase inhibitors in systemic lupus erythematosus: implications for tyrosine kinase 2 inhibition

Aberrant activation of the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) pathway is common in systemic lupus erythematosus (SLE), conferring immune-mediated properties in target tissues. Multiple cytokines activate different combinations of JAKs and STATs to alter the cell fate of target tissue and induce end-organ damage. Thus, the simultaneous blockade of several different cytokines by small molecules acting downstream intracellular signalling has gained traction. JAK inhibitors have been approved for the treatment of several rheumatic diseases, yet hitherto not for SLE. Nevertheless, JAK inhibitors including tofacitinib, baricitinib, and deucravacitinib have shown merit as treatments for SLE. Tofacitinib, a JAK1/3 inhibitor, reduced cholesterol levels, improved vascular function, and decreased the type I interferon signature in SLE patients. Baricitinib, a JAK1/2 inhibitor, demonstrated significant improvements in lupus rashes and arthritis in a phase 2 and a phase 3 randomised controlled trial, but the results were not replicated in another phase 3 trial. Deucravacitinib, a selective tyrosine kinase 2 (TYK2) inhibitor, yielded greater response rates than placebo in a phase 2 trial of SLE and will be investigated in larger phase 3 trials. TYK2 is activated in response to cytokines actively involved in lupus pathogenesis; this review highlights the potential of targeting TYK2 as a promising therapy for SLE.

Targeted Small Molecules for Systemic Lupus Erythematosus: Drugs in the Pipeline

Despite the uncertainty of the pathogenesis of systemic lupus erythematosus, novel small molecules targeting specific intracellular mechanisms of immune cells are being developed to reverse the pathophysiological processes. These targeted molecules have the advantages of convenient administration, lower production costs, and the lack of immunogenicity. The Janus kinases, Bruton's tyrosine kinases, and spleen tyrosine kinases are important enzymes for activating downstream signals from various receptors on immune cells that include cytokines, growth factor, hormones, Fc, CD40, and B-cell receptors. Suppression of these kinases impairs cellular activation, differentiation, and survival, leading to diminished cytokine actions and autoantibody secretion. Intracellular protein degradation by immunoproteasomes, levered by the cereblon E3 ubiquitin ligase complex, is an essential process for the regulation of cellular functions and survival. Modulation of the immunoproteasomes and cereblon leads to depletion of long-lived plasma cells, reduced plasmablast differentiation, and production of autoantibodies and interferon-α. The sphingosine 1-phosphate/sphingosine 1-phosphate receptor-1 pathway is responsible for lymphocyte trafficking, regulatory T-cell/Th17 cell homeostasis, and vascular permeability. Sphingosine 1-phosphate receptor-1 modulators limit the trafficking of autoreactive lymphocytes across the blood-brain barrier, increase regulatory T-cell function, and decrease production of autoantibodies and type I interferons. This article summarizes the development of these targeted small molecules in the treatment of systemic lupus erythematosus, and the future prospect for precision medicine.

Potential Use of Janus Kinase Inhibitors in the Treatment of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic, autoimmune disease with unclear pathogenesis. One characteristic of SLE is pro-inflammatory and anti-inflammatory cytokine imbalance. Janus kinase (JAK) is an intracellular non-receptor tyrosine kinase essential for many cytokine signaling pathways. Dysregulation of the JAK/signal transduction and transcriptional activator (STAT) pathway is an important process in SLE pathogenesis. Targeting JAK/STAT proteins can simultaneously block the functions of multiple cytokines. Current SLE treatment with non-specific corticosteroids and immunosuppressants can cause many adverse reactions. Therefore, treatments designed to control specific molecular targets for SLE are desirable. JAK inhibitors (JAKis) are a potential treatment for rheumatic diseases; however, the use of targeted signaling pathways to treat SLE remains a challenge, and its efficacy has not been determined. JAKis have shown positive results in reducing the use of glucocorticoids and/or non-specific immunosuppressants for SLE. JAKis are currently undergoing several clinical trials and expected to be the next stage in the treatment of SLE. Therefore, inhibition of the JAK/STAT pathway through JAKis may improve traditional treatment strategies for SLE.

HERC6 is upregulated in peripheral blood mononuclear cells of patients with systemic lupus erythematosus and promotes the disease progression

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease. Peripheral blood mononuclear cells (PBMCs) are any peripheral blood cell with round nuclei, including lymphocytes (T cells, B cells) and monocytes, whose physicochemical properties are randomized by obvious immune changes, and are a potentially effective source of SLE blood test samples and therapeutic targets. This study aimed to explore the upregulation molecules of PBMCs in patients with SLE and to explore their biological role. Homologous to the E6-AP carboxyl terminus (HECT) and regulator of chromosome condensation 1 (RCC1)-like domain (RLD) containing E3 ubiquitin protein ligase family member 6 (HERC6) expression was found significantly upregulated in four Gene Expression Omnibus gene sets. Moreover, HERC6 expression was upregulated in PBMCs from SLE patients compared with that in PBMCs from normal donors. HERC6 was significantly associated with SLE clinical phenotypes such as complement C3 content, erythrocyte sedimentation rate, and SLE disease activity index. In vitro, knockdown of HERC6 inhibited PBMC apoptosis, inflammatory response, and janus kinase (JAK)/signal transducer and activator of transcription (STAT) signalling pathway, while overexpression of HERC6 led to the opposite results. In addition, AG490, a JAK/STAT pathway inhibitor, reversed the promoting effect of HERC6 overexpression on PBMC apoptosis and inflammation. In conclusion, the level of HERC6 in PBMCs in patients with SLE was upregulated. Overexpression of HERC6 promoted PBMC apoptosis and inflammatory response, which was involved in the JAK/STAT pathway.

A Selective Neutraligand for CXCL12/SDF-1α With Beneficial Regulatory Functions in MRL/Lpr Lupus Prone Mice

Dysregulation of CXCL12/SDF-1-CXCR4/CD184 signaling is associated with inflammatory diseases and notably with systemic lupus erythematosus. Issued from the lead molecule chalcone-4, the first neutraligand of the CXCL12 chemokine, LIT-927 was recently described as a potent analogue with improved solubility and stability. We aimed to investigate the capacity of LIT-927 to correct immune alterations in lupus-prone MRL/lpr mice and to explore the mechanism of action implemented by this small molecule in this model. We found that in contrast to AMD3100, an antagonist of CXCR4 and agonist of CXCR7, LIT-927 reduces the excessive number of several B/T lymphocyte subsets occurring in the blood of sick MRL/lpr mice (including CD3⁺/CD4^-/CD8^-/B220⁺ double negative T cells). In vitro, LIT-927 downregulated the overexpression of several activation markers on splenic MRL/lpr lymphocytes. It exerted effects on the CXCR4 pathway in MRL/lpr CD4⁺ T spleen cells. The results underline the importance of the CXCL12/CXCR4 axis in lupus pathophysiology. They indicate that neutralizing CXCL12 by the neutraligand LIT-927 can attenuate hyperactive lymphocytes in lupus. This mode of intervention might represent a novel strategy to control a common pathophysiological mechanism occurring in inflammatory diseases.

Targeting the JAK-STAT pathway in autoimmune diseases and cancers: A focus on molecular mechanisms and therapeutic potential

The Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway is characterized by diverse immune regulatory systems involving cell proliferation, survival, and inflammation and immune tolerance. Aberrant JAK/STAT transduction activates proinflammatory cytokine signaling that jeopardize the immune balance and thus contributes to the development of autoimmune diseases and cancer progression. The success of several small-molecule JAK inhibitors in the treatment of rheumatologic diseases demonstrates that targeting the JAK/STAT pathway is efficient in suppressing inflammation and sheds light on their therapeutic potential in several autoimmune diseases and cancers. In this review, we discuss the signal transduction and molecular mechanism involving immune function through the JAK-STAT pathway, outline the role of this pathway in autoimmunity and oncoimmunology, and explain the preclinical and clinical trial evidence for the therapeutic potential of targeting the JAK-STAT signaling pathway. Issues regarding the safety and clinical efficacy of JAK inhibitors are reviewed. Ongoing studies are addressed with a focus on emerging indications for JAK inhibition and explanations of the novel mechanisms of JAK-STAT signaling blockade.

JAK Inhibitors: Prospects in Connective Tissue Diseases

The dysregulation of the JAK-STAT pathway is associated with various immune disorders. Four JAK inhibitors have been approved for rheumatoid arthritis (RA), and numerous JAK inhibitors are currently being tested in phase II and III trials for the treatment of various autoimmune inflammatory diseases. In this narrative review, we elucidate the involvement of the JAK-STAT signaling pathway in the pathogenesis of connective tissue diseases (CTDs). We also discuss the efficacy of the first- and second-generation JAK inhibitors (tofacitinib, baricitinib, ruxolitinib, peficitinib, filgotinib, upadacitinib, solcitinib, itacitinib, decernotinib, R333, and pf-06651600) for CTDs including RA, systemic lupus erythematosus, dermatomyositis, systemic sclerosis, Sjögren's syndrome, and vasculitis, based on laboratory and clinical research findings. JAK inhibitors have great potential for the treatment of various CTDs by reducing multiple cytokine production and suppressing inflammation, with the advantages of rapid onset in an oral formulation and decreased corticosteroid dependence and the associated adverse events, especially in refractory cases. We also highlight the safety of novel JAK inhibitors, which can cause opportunistic infections, especially viral infections. Being a very recent therapeutic option, information regarding the safety of JAK inhibitors during pregnancy and for pediatric use is limited. However, it is recommended that JAK inhibitors should be avoided in pregnant and breastfeeding women. More clinical data, especially on highly selective inhibitors, are required to judge the efficacy and safety of JAK inhibition in CTDs.

Th cytokine profile in childhood-onset systemic lupus erythematosus

Background

Childhood-onset systemic lupus erythematosus (cSLE) is a kind of chronic inflammatory disease characterized by a highly abnormal immune system. This study aimed to detect the serum levels of Th (T helper) cytokines (IL-2, IL-4, IL-5, IL-6, IL-9, IL-10, IL-13, IL-17A, IL-17F, IL-21, IL-22, IFN-γ and TNF-α) in cSLE and healthy controls, and then to elucidate their association with clinical manifestations, disease activity and laboratory parameters. In order to provide clues for early diagnosis and timely intervention treatment of cSLE patients.

Methods

A total of 33 children with cSLE and 30 healthy children were enrolled in this study. Children in the cSLE group were classified into the inactive or active cSLE group according to their SLE disease activity index 2000 (SLEDAI-2 K) score. Th cytokine profiles in the peripheral blood were detected and analysed.

Results

Levels of IL-2, IL-10 and IL-21 in the cSLE group were significantly higher than those in the healthy control group (P < 0.05, P < 0.01 and P < 0.01, respectively). Expression of IL-2, IL-10 and IL-21 in the active cSLE group was significantly higher than that in the healthy control group (P < 0.05, P < 0.01 and P < 0.05, respectively), but that of IL-22 expression was markedly lower in the active cSLE group than in the healthy control group (P < 0.001). IL-21 in the inactive SLE group was significantly higher than that in the healthy control group (P < 0.05), and levels of IL-2 and IL-10 in the active cSLE group were significantly higher than those in the inactive cSLE group (P < 0.01 and P < 0.05). In-depth analysis showed that after excluding age, gender and drug interference, the levels of IL-2 (P < 0.05), IL-6 (P < 0.05) and IL-10 (P < 0.05) were still positively correlated with SLEDAI-2 K scores. However, the levels of IL-6 (P < 0.05) and IFN- γ (P < 0.05) were still negatively correlated with CD4⁺/CD8⁺, and the concentration of IL-6 (P < 0.05) was still positively correlated with the occurrence of nephritis.

Conclusion

This study provides a theoretical basis for the discovery of effective methods to regulate imbalance in T lymphocyte subsets in cSLE, which may lead to new approaches for the diagnosis of cSLE.

Case Report: Reversal of Long-Standing Refractory Diffuse Non-Scarring Alopecia Due to Systemic Lupus Erythematosus Following Treatment With Tofacitinib

The Janus kinases (JAKs) are intracellular tyrosine kinases involved in a broad variety of inflammatory cascades participating in the pathogenesis of systemic lupus erythematosus (SLE). Diffuse non-scarring alopecia is one of the most frequent cutaneous manifestations in SLE, resulting in devastating psychosocial consequences. Although recent studies have shown promising outcomes of the JAK inhibitors in SLE treatment, the efficacy of tofacitinib in diffuse non-scarring alopecia due to SLE has never been reported. Here we present a 29-year-old SLE patient with a 10-year history of refractory severe diffuse non-scarring alopecia who experienced dramatic hair regrowth with tofacitinib. Furthermore, we have made a systematic review regarding the potential effectiveness of tofacitinib in systemic and cutaneous lupus erythematosus. To the best of our knowledge, this is the first case study depicting an SLE patient with refractory alopecia who experienced impressive hair regrowth with the JAK1/3 inhibitor tofacitinib therapy, which contributes to expanding the field of possible uses of tofacitinib in SLE patients with difficult-to-treat cutaneous involvement, including severe alopecia.

Prolactin Rescues Immature B Cells from Apoptosis-Induced BCR-Aggregation through STAT3, Bcl2a1a, Bcl2l2, and Birc5 in Lupus-Prone MRL/lpr Mice

Self-reactive immature B cells are eliminated through apoptosis by tolerance mechanisms, failing to eliminate these cells results in autoimmune diseases. Prolactin is known to rescue immature B cells from B cell receptor engagement-induced apoptosis in lupus-prone mice. The objective of this study was to characterize in vitro prolactin signaling in immature B cells, using sorting, PCR array, RT-PCR, flow cytometry, and chromatin immunoprecipitation. We found that all B cell maturation stages in bone marrow express the prolactin receptor long isoform, in both wild-type and MRL/lpr mice, but its expression increased only in the immature B cells of the latter, particularly at the onset of lupus. In these cells, activation of the prolactin receptor promoted STAT3 phosphorylation and upregulation of the antiapoptotic Bcl2a1a, Bcl2l2, and Birc5 genes. STAT3 binding to the promoter region of these genes was confirmed through chromatin immunoprecipitation. Furthermore, inhibitors of prolactin signaling and STAT3 activation abolished the prolactin rescue of self-engaged MRL/lpr immature B cells. These results support a mechanism in which prolactin participates in the emergence of lupus through the rescue of self-reactive immature B cell clones from central tolerance clonal deletion through the activation of STAT3 and transcriptional regulation of a complex network of genes related to apoptosis resistance.

Effect of interleukin-6, -17, -21, -22, and -23 and STAT3 on signal transduction pathways and their inhibition in autoimmune arthritis

Rheumatic diseases are complex autoimmune diseases which include among others rheumatoid arthritis (RA), juvenile idiopathic arthritis (JIA), and psoriatic arthritis (PsA). These diseases are characterized by prolonged and increased secretion of inflammatory factors, eventually leading to inflammation. This is often accompanied by persistent pain and stiffness in the joint and finally bone destruction and osteoporosis. These diseases can occur at any age, regardless of gender or origin. Autoimmune arthritis is admittedly associated with long-term treatment, and discontinuation of medication is associated with unavoidable relapse. Therefore, it is important to detect the disease at an early stage and apply appropriate preventative measures. During inflammation, pro-inflammatory factors such as interleukins (IL)-6, -17, -21, -22, and -23 are secreted, while anti-inflammatory factors including IL-10 are downregulated. Research conducted over the past several years has focused on inhibiting inflammatory pathways and activating anti-inflammatory factors to improve the quality of life of people with rheumatic diseases. The aim of this paper is to review current knowledge on stimulatory and inhibitory pathways involving the signal transducer and activator of transcription 3 (STAT3). STAT3 has been shown to be one of the crucial factors involved in inflammation and is directly linked with other pro-inflammatory factors and thus is a target of current research on rheumatoid diseases.

STAT3 phosphorylation mediates the stimulatory effects of interferon alpha on B cell differentiation and activation in SLE

OBJECTIVE

Type I IFNs play a well-known role in the pathogenesis of SLE, through activation of CD4 T and antigen-presenting cells. Here, we investigated the effects of IFN alpha (IFNα) on SLE B cell activation and differentiation.

METHODS

Peripheral blood mononuclear cells (PBMCs) and purified total or naïve B cells were obtained from healthy controls and SLE patients. The effects of IFNα on B cell differentiation were studied by flow cytometry. The role of STAT3 in B cell responses to IFNα was studied using pharmacological inhibitors and PBMCs from STAT3-deficient individuals.

RESULTS

Incubation of normal PBMCs with IFNα induces a B cell differentiation pattern as observed spontaneously in SLE PBMCs. IFNα displays direct stimulatory effects on purified naïve B cells from healthy individuals, as evidenced by a significant induction of cell surface CD38 and CD95 in the presence of the cytokine. In purified naïve B cells, IFNα also induces STAT3 phosphorylation. IFNα-induced naïve B cell differentiation in total PBMCs is significantly inhibited in the presence of STAT3 inhibitors, or in PBMCs from individuals with STAT3 loss of function mutations. Spontaneous levels of STAT3, but not STAT1, phosphorylation are significantly higher in total B cells from SLE patients compared with controls. Pharmacological STAT3 inhibition in SLE PBMCs inhibits naïve B cell activation and differentiation.

CONCLUSION

IFNα displays direct stimulatory effects on B cell differentiation and activation in SLE. STAT3 phosphorylation mediates the effects of IFNα stimulation in naïve B cells, an observation that opens new therapeutic perspectives in SLE.

Alterations in peripheral blood B cells in systemic lupus erythematosus patients with renal insufficiency

OBJECTIVE

Systemic lupus erythematosus (SLE) is one of the autoimmune diseases, believed to be closely related to hyperactivity of B cells, overproduction of autoantibodies and immune complex formation and deposition in affected tissue. The autoreactive inflammation leads to multiorgan damage with kidney dysfunction in the forefront. Studies on lupus nephritis (LN), affecting the majority of SLE patients, are mainly focused on cells causing local inflammation. The aim of our work was to detect alterations in more accessible peripheral blood B cells in the course of SLE focusing on the influence of renal insufficiency (RI) on those parameters.

METHODS

We performed a comprehensive flow cytometry analysis of B cell subpopulations, analyzed gene expression patterns with qPCR, and examined serum cytokine levels with multiplex cytokine/chemokine assay.

RESULTS

We discovered distribution of specific B cell subsets, especially CD38⁺ cells, plasmablasts, associated with the presence and severity of the disease. Changes in expression of MBD2, DNMT1 and APRIL genes were not only associated with activity of SLE but also were significantly changed in patients with RI.

CONCLUSIONS

All these results shed new light on the role of circulating B cells, their subpopulations, function, and activity in the SLE with kidney manifestation.

JAK inhibitors for the treatment of autoimmune and inflammatory diseases

Cytokines play a central role in the pathophysiology of autoimmune and inflammatory diseases. Several cytokines signal through the JAK-STAT pathway, which is now recognized as a major target to inhibit the effect of a wide array of cytokines. JAK inhibitors are increasingly used in the setting of inflammatory and autoimmune diseases. While the currently approved drugs are panJAK inhibitors, more selective small molecules are being developed and tested in various rheumatic disorders. In this extensive review, we present evidence- or hypothesis-based perspectives for these drugs in various rheumatologic conditions, such as rheumatoid arthritis, systemic lupus erythematosus, giant cell arteritis, and autoinflammatory diseases.

Pathogenic and Therapeutic Relevance of JAK/STAT Signaling in Systemic Lupus Erythematosus: Integration of Distinct Inflammatory Pathways and the Prospect of Their Inhibition with an Oral Agent

Four Janus kinases (JAKs) (JAK1, JAK2, JAK3, TYK2) and seven signal transducers and activators of transcription (STATs) (STAT1, STAT2, STAT3, STAT4, STAT5A, STAT5B, STAT6) mediate the signal transduction of more than 50 cytokines and growth factors in many different cell types. Located intracellularly and downstream of cytokine receptors, JAKs integrate and balance the actions of various signaling pathways. With distinct panels of STAT-sensitive genes in different tissues, this highly heterogeneous system has broad in vivo functions playing a crucial role in the immune system. Thus, the JAK/STAT pathway is critical for resisting infection, maintaining immune tolerance, and enforcing barrier functions and immune surveillance against cancer. Breakdowns of this system and/or increased signal transduction may lead to autoimmunity and other diseases. Accordingly, the recent development and approval of the first small synthetic molecules targeting JAK molecules have opened new therapeutic avenues of potentially broad therapeutic relevance. Extensive data are now available regarding the JAK/STAT pathway in rheumatoid arthritis. Dysregulation of the cytokines is also a hallmark of systemic lupus erythematosus (SLE), and targeting the JAK/STAT proteins allows simultaneous suppression of multiple cytokines. Evidence from in vitro studies and animal models supports a pivotal role also in the pathogenesis of cutaneous lupus and SLE. This has important therapeutic implications, given the current paucity of targeted therapies especially in the latter. Herein, we summarize the currently available literature in experimental SLE, which has led to the recent promising Phase II clinical trial of a JAK inhibitor.

Autoreactive B-lymphocytes in SLE and RA patients: Isolation and characterisation using extractable nuclear and citrullinated antigens bound to immunobeads

Systemic lupus erythematosus and rheumatoid arthritis are autoimmune diseases characterised by B-cell hyperactivation and production of autoantibodies (AutoAbs) against various self-antigens, including extractable nuclear antigens and citrullinated peptides. Therefore, B lymphocytes and antibody-secreting cells are considered relevant targets for therapies. However, isolation and characterisation of auto-reactive specific B lymphocytes are limited, primarily due to technical issues. In this work, we purified extractable nuclear antigen-specific and citrullinated peptide-specific auto-reactive B lymphocytes by magnetic selection with ENA- and citrullinated peptide-bound immunobeads. We obtained blood auto-reactive B lymphocytes from most patients. Their nature was primarily naïve B cells, some of them in an active status, with low levels of somatic hypermutations in the immunoglobulin heavy-chain variable regions. Their presence correlated with serum levels of autoAb. Auto-reactive B lymphocytes were able to differentiate into auto-reactive antibody-secreting cells under conditions of stimulation. In addition, based on the presence of circulating auto-reactive B cells and/or antibody-secreting cells, four different profiles were described in lupus patients. Thus, tracking auto-reactive B cells and/or antibody-secreting cells in patient blood could represent a biomarker for deciding whether to use therapies blocking either B cells, plasma cells or both, as well as a new tool for monitoring minimal residual autoimmune disease in patients.

Clinical significance and immunobiology of IL-21 in autoimmunity

Interleukin-21 (IL-21), an autocrine cytokine predominantly produced by follicular helper T (Tfh) and T helper 17 (Th17) cells, has been proven to play an important role in the immune system, for example, by promoting proliferation and the development of Tfh and Th17 cells, balancing helper T cell subsets, inducing B cell generation and differentiation into plasma cells, and enhancing the production of immunoglobulin. These effects are mainly mediated by activation of the JAK/STAT, MAPK and PI3K pathways. Some IL-21 target genes, such as B lymphocyte induced maturation protein-1 (Blimp-1), suppressor of cytokine signaling (SOCS), CXCR5 and Bcl-6, play important roles in the immune response. Therefore, IL-21 has been linked to autoimmune diseases. Indeed, IL-21 levels are increased in the peripheral blood and tissues of patients with systematic lupus erythematosus (SLE), rheumatoid arthritis (RA), type 1 diabetes (T1D), immune thrombocytopenia (ITP), primary Sjogren's syndrome (pSS), autoimmune thyroid disease (AITD) and psoriasis. This increased IL-21 even positively associates with Tfh cells, plasma cells, autoantibodies and disease activity in SLE and RA. Additionally, IL-21 has been utilized as a therapeutic target in SLE, RA, T1D and psoriatic mouse models. Profoundly, clinical trials have shown safety and improvement in RA patients. However, tolerance and long-term pharmacodynamics effects with low bioavailability have been found in SLE patients. Therefore, this review aims to summarize the latest progress on IL-21 function and its signaling pathway and discuss the role of IL-21 in the pathogenesis of and therapy for autoimmune diseases, with the hope of providing potential therapeutic and diagnostic strategies for clinical use.

Anti-dsDNA titre in female systemic lupus erythematosus patients: relation to disease manifestations, damage and antiphospholipid antibodies

Background Attempts are ongoing to unveil unresolved queries about anti-double-stranded deoxyribonucleic acid (anti-dsDNA), their precise pathogenic effects and to what extent blocking them would be a useful therapeutic goal. Objectives The aim of the present study was to determine the anti-dsDNA antibodies titre in systemic lupus erythematosus (SLE) patients and investigate their relation to the disease characteristics, activity, damage and antiphospholipid autoantibodies (aPL). Methods Seventy female SLE patients and 35 age- and sex-matched controls were included. The anti-dsDNA level and aPL were measured. Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) and Systemic Lupus International Collaborative Clinics/American College of Rheumatology Damage Index (SLICC/ACR-DI) were assessed. Results The mean age of the patients was 27.5 ± 5.1 years, disease duration 7.7 ± 5.4 years, and SLEDAI and SLICC/ACR-DI scores were 6.8 ± 8.04 and 1.2 ± 1.3, respectively. Anti-dsDNA was positive in 61.4% of the patients and the titre (133.2 ± 100.5 IU/ml) was significantly higher compared to controls (22.03 ± 17.2 IU/ml) ( p < 0.0001). The anti-dsDNA level was significantly increased in those with musculoskeletal manifestations ( p = 0.007) and positive anti-β2 glycoprotein (anti-β2GP) ( p = 0.037) and decreased in those with neuropsychiatric manifestations ( p = 0.004) and those receiving cyclophosphamide (CYC) ( p = 0.013). The anti-dsDNA level tended to be higher in active patients. The anti-dsDNA titre significantly correlated with the erythrocyte sedimentation rate ( p = 0.001), anticardiolipin IgG and IgA antibodies ( p = 0.008) and anti-β2GP IgG ( p = 0.03) and IgA ( p = 0.002) and inversely with the total leucocytic count ( p < 0.0001) and SLICC/ACR-DI ( p = 0.001). Conclusion Anti-dsDNA is remarkably increased in SLE patients especially those with musculoskeletal manifestations and aPL. A protective role seems likely in those with neuropsychiatric manifestations and those receiving CYC and may form a shield against disease tissue damage.