Human effector B lymphocytes express ARID3a and secrete interferon alpha

Arid3c identifies an uncharacterized subpopulation of V2 interneurons during embryonic spinal cord development

Motor activity is organized by neuronal networks composed of motor neurons and a wide variety of pre-motor interneuron populations located in the brainstem and spinal cord. Differential expression and single-cell RNA sequencing studies recently unveiled that these populations subdivide into multiple subsets. However, some interneuron subsets have not been described yet, and the mechanisms contributing to this neuronal diversification have only been partly deciphered. In this study, we aimed to identify additional markers to further describe the diversity of spinal V2 interneuron populations. Here, we compared the transcriptome of V2 interneurons with that of the other cells of the embryonic spinal cord and extracted a list of genes enriched in V2 interneurons, including Arid3c. Arid3c identifies an uncharacterized subset of V2 that partially overlaps with V2c interneurons. These two populations are characterized by the production of Onecut factors and Sox2, suggesting that they could represent a single functional V2 unit. Furthermore, we show that the overexpression or inactivation of Arid3c does not alter V2 production, but its absence results in minor defects in locomotor execution, suggesting a possible function in subtle aspects of spinal locomotor circuit formation.

ARID3C Acts as a Regulator of Monocyte-to-Macrophage Differentiation Interacting with NPM1

ARID3C is a protein located on human chromosome 9 and expressed at low levels in various organs, yet its biological function has not been elucidated. In this study, we investigated both the cellular localization and function of ARID3C. Employing a combination of LC-MS/MS and deep learning techniques, we identified NPM1 as a binding partner for ARID3C's nuclear shuttling. ARID3C was found to predominantly localize with the nucleus, where it functioned as a transcription factor for genes STAT3, STAT1, and JUNB, thereby facilitating monocyte-to-macrophage differentiation. The precise binding sites between ARID3C and NPM1 were predicted by AlphaFold2. Mutating this binding site prevented ARID3C from interacting with NPM1, resulting in its retention in the cytoplasm instead of translocation to the nucleus. Consequently, ARID3C lost its ability to bind to the promoters of target genes, leading to a loss of monocyte-to-macrophage differentiation. Collectively, our findings indicate that ARID3C forms a complex with NPM1 to translocate to the nucleus, acting as a transcription factor that promotes the expression of the genes involved in monocyte-to-macrophage differentiation.

A+T rich interaction domain protein 3a (Arid3a) impairs Mertk-mediated efferocytosis in cholestasis

BACKGROUND & AIMS

Macrophages are key elements in the pathogenesis of cholestatic liver diseases. Arid3a plays a prominent role in the biologic properties of hematopoietic stem cells, B lymphocytes and tumor cells, but its ability to modulate macrophage function during cholestasis remains unknown.

METHODS

Gene and protein expression and cellular localization were assessed by q-PCR, immunohistochemistry, immunofluorescence staining and flow cytometry. We generated myeloid-specific Arid3a knockout mice and established three cholestatic murine models. The transcriptome was analyzed by RNA-seq. A specific inhibitor of the Mertk receptor was used in vitro and in vivo. Promoter activity was determined by chromatin immunoprecipitation-seq against Arid3a and a luciferase reporter assay.

RESULTS

In cholestatic murine models, myeloid-specific deletion of Arid3a alleviated cholestatic liver injury (accompanied by decreased accumulation of macrophages). Arid3a-deficient macrophages manifested a more reparative phenotype, which was eliminated by in vitro treatment with UNC2025, a specific inhibitor of the efferocytosis receptor Mertk. Efferocytosis of apoptotic cholangiocytes was enhanced in Arid3a-deficient macrophages via upregulation of Mertk. Arid3a negatively regulated Mertk transcription by directly binding to its promoter. Targeting Mertk in vivo effectively reversed the protective phenotype of Arid3a deficiency in macrophages. Arid3a was upregulated in hepatic macrophages and circulating monocytes in primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). Mertk was correspondingly upregulated and negatively correlated with Arid3a expression in PBC and PSC. Mertk+ cells were located in close proximity to cholangiocytes, while Arid3a+ cells were scattered among immune cells with greater spatial distances to hyperplastic cholangiocytes in PBC and PSC.

CONCLUSIONS

Arid3a promotes cholestatic liver injury by impairing Mertk-mediated efferocytosis of apoptotic cholangiocytes by macrophages during cholestasis. The Arid3a-Mertk axis is a promising novel therapeutic target for cholestatic liver diseases.

IMPACT AND IMPLICATIONS

Macrophages play an important role in the pathogenesis of cholestatic liver diseases. This study reveals that macrophages with Arid3a upregulation manifest a pro-inflammatory phenotype and promote cholestatic liver injury by impairing Mertk-mediated efferocytosis of apoptotic cholangiocytes during cholestasis. Although we now offer a new paradigm to explain how efferocytosis is regulated in a myeloid cell autonomous manner, the regulatory effects of Arid3a on chronic liver diseases remain to be further elucidated.

Single cell transcriptome analyses reveal the roles of B cells in fructose-induced hypertension

Rationale

While the immune system plays a crucial role in the development of hypertension, the specific contributions of distinct immune cell populations remain incompletely understood. The emergence of single-cell RNA-sequencing (scRNA-seq) technology enables us to analyze the transcriptomes of individual immune cells and to assess the significance of each immune cell type in hypertension development.

Objective

We aimed to investigate the hypothesis that B cells play a crucial role in the development of fructose-induced hypertension.

Methods and Results

Eight-week-old Dahl salt-sensitive (SS) male rats were divided into two groups and given either tap water (TW) or a 20% fructose solution (HFS) for 4 weeks. Systolic blood pressure was measured using the tail-cuff method. ScRNA-seq analysis was performed on lamina propria cells (LPs) and peripheral blood mononuclear cells (PBMCs) obtained from SS rats subjected to either TW or HFS. The HFS treatment induced hypertension in the SS rats. The analysis revealed 27 clusters in LPs and 28 clusters in PBMCs, allowing for the identification and characterization of various immune cell types within each cluster. Specifically, B cells and follicular helper T (Tfh) cells were prominent in LPs, while B cells and M1 macrophages dominated PBMCs in the HFS group. Moreover, the HFS treatment triggered an increase in the number of B cells in both LPs and PBMCs, accompanied by activation of the interferon pathway.

Conclusions

The significant involvement of B cells in intestinal and PBMC responses indicates their pivotal contribution to the development of hypertension. This finding suggests that targeting B cells could be a potential strategy to mitigate high blood pressure in fructose-induced hypertension. Moreover, the simultaneous increase in follicular B cells and Tfh cells in LPs, along with the upregulation of interferon pathway genes in B cells, underscores a potential autoimmune factor contributing to the pathogenesis of fructose-induced hypertension in the intestine.

Exploration of common genomic signatures of systemic juvenile rheumatoid arthritis and type 1 diabetes

To explore the genetic characteristics of systemic juvenile rheumatoid arthritis (sJRA) and type 1 diabetes mellitus (T1D). The microarray data of sJRA and T1D from Gene Expression Omnibus (GEO) were analyzed. The shared differentially expressed genes (SDEGs) were identified by the Meta-analysis, and genes of extracellular proteins were identified. Then, transcription factors (TFs) and their target genes in SDEGs were obtained by comparing databases from HumanTFDB, and hTFtarget. After that, functional enrichment analyses of the previously identified gene sets were performed by metascape tool. Finally, immune infiltration was analysed by CIBERSORT. We found 175 up-regulated and 245 down-regulated SDEGs, and by constructing a TFs-targeted SDEGs network, 3 key TFs (ARID3A, NEF2, RUNX3) were screened. Functional enrichment analyses and immune infiltration results suggested not only the adaptive immune system but also the innate immune system, and signaling pathways like JAK-STAT are important in the pathogenesis of sJRA and T1D, involving biological processes such as CD4 T cell functions and neutrophil degranulation. This work suggests that innate immune abnormalities also play important roles in sJRA and T1D, CD4 T cell functions, neutrophil degranulation and the JAK-STAT pathway may be involved. The regulatory roles of ARID3A, NEF2, and RUNX3 in this network need to be further investigated.

A regulatory variant at 19p13.3 is associated with primary biliary cholangitis risk and ARID3A expression

Genome-wide association studies have identified 19p13.3 locus associated with primary biliary cholangitis (PBC). Here we aim to identify causative variant(s) and initiate efforts to define the mechanism by which the 19p13.3 locus variant(s) contributes to the pathogenesis of PBC. A genome-wide meta-analysis of 1931 PBC subjects and 7852 controls in two Han Chinese cohorts confirms the strong association between 19p13.3 locus and PBC. By integrating functional annotations, luciferase reporter assay and allele-specific chromatin immunoprecipitation, we prioritize rs2238574, an AT-Rich Interaction Domain 3A (ARID3A) intronic variant, as a potential causal variant at 19p13.3 locus. The risk allele of rs2238574 shows higher binding affinity of transcription factors, leading to an increased enhancer activity in myeloid cells. Genome-editing demonstrates the regulatory effect of rs2238574 on ARID3A expression through allele-specific enhancer activity. Furthermore, knock-down of ARID3A inhibits myeloid differentiation and activation pathway, and overexpression of the gene has the opposite effect. Finally, we find ARID3A expression and rs2238574 genotypes linked to disease severity in PBC. Our work provides several lines of evidence that a non-coding variant regulates ARID3A expression, presenting a mechanistic basis for association of 19p13.3 locus with the susceptibility to PBC.

CD4+ T-cell cooperation promoted pathogenic function of activated naïve B cells of patients with SLE

Objective

To explore cooperation between activated naïve (aNAV) B cells and CD4⁺ T cells in the pathogenesis of SLE through autoantibody production, T-cell differentiation and inflammatory cytokine secretion.

Methods

Peripheral blood mononuclear cell samples were obtained from 31 patients with SLE and used to characterise phenotype of aNAV B cells (n=14) and measured the phosphorylation of B-cell receptor (BCR) signalling molecules (n=5). Upregulation of T-cell costimulatory molecules after BCR and toll-like receptor (TLR)-7/TLR-8 stimulation was detected in cells from four subjects. To explore the role of these cells in SLE pathogenesis via T cell-dependent mechanisms, four subjects were analysed to detect the promotion of CD4⁺ T-cell activation and antibody-secreting cell (ASC) differentiation after CD4⁺ T-cell–B-cell cocultures. The aNAV B cells from four patients were used to assess cytokine secretion.

Results

The aNAV B cells of patients with SLE had increased expression of surface CD40, HLA-DR and interleukin-21 receptor (IL-21R) and FCRL5 molecules. With BCR stimulation, these cells greatly increased PLCγ2 phosphorylation. Integrated BCR and TLR-7/TLR-8 signals induced overexpression of CD40, CD86, IL-21R and HLA-DR on lupus aNAV B cells. In T-cell–B-cell cocultures, lupus aNAV B cells (with upregulated costimulatory molecules) promoted CD4⁺ T-cell proliferation and polarisation toward effector Th₂ and Th₁₇ cells. Importantly, in this coculture system, CD4⁺ T-cell signals enhanced aNAV B-cell differentiation into auto-ASCs and produced anti-DNA antibodies. The interaction between CD4⁺ T cell and aNAV B cell increased production of inflammatory cytokines (IL-6, IL-8 and IL-23).

Conclusion

Cooperation between aNAV B cells and CD4⁺ T cells contributed to SLE pathogenesis by promoting both differentiation of pathogenic T cells (Th₂ and Th₁₇) and autoantibody secretion.

Bruton's Tyrosine Kinase Inhibition as an Emerging Therapy in Systemic Autoimmune Disease

Systemic autoimmune disorders are complex heterogeneous chronic diseases involving many different immune cells. A significant proportion of patients respond poorly to therapy. In addition, the high burden of adverse effects caused by "classical" anti-rheumatic or immune modulatory drugs provides a need to develop more specific therapies that are better tolerated. Bruton's tyrosine kinase (BTK) is a crucial signaling protein that directly links B-cell receptor (BCR) signals to B-cell activation, proliferation, and survival. BTK is not only expressed in B cells but also in myeloid cells, and is involved in many different signaling pathways that drive autoimmunity. This makes BTK an interesting therapeutic target in the treatment of autoimmune diseases. The past decade has seen the emergence of first-line BTK small-molecule inhibitors with great efficacy in the treatment of B-cell malignancies, but with unfavorable safety profiles for use in autoimmunity due to off-target effects. The development of second-generation BTK inhibitors with superior BTK specificity has facilitated the investigation of their efficacy in clinical trials with autoimmune patients. In this review, we discuss the role of BTK in key signaling pathways involved in autoimmunity and provide an overview of the different inhibitors that are currently being investigated in clinical trials of systemic autoimmune diseases, including rheumatoid arthritis and systemic lupus erythematosus, as well as available results from completed trials.

Preclinical to clinical translation of cenerimod, a novel S1P1 receptor modulator, in systemic lupus erythematosus

Objectives:

SLE is an autoimmune disease characterised by aberrant lymphocyte activation and autoantibody production. This study provides an in-depth preclinical and clinical characterisation of the treatment effect of cenerimod, a sphingosine-1-phosphate receptor type 1 (S1P₁) modulator, in SLE.

Methods:

Cenerimod effect on lymphocyte numbers, organ pathology, inflammation, and survival was evaluated in the MRL/lpr lupus mouse model. Lymphocytes from healthy subjects and patients with SLE were assessed for cenerimod-induced S1P₁ receptor internalisation. Lymphocyte subsets and inflammatory biomarkers were characterised in a 12-week phase 2 clinical study (NCT-02472795), where patients with SLE were treated with multiple doses of cenerimod or placebo.

Results:

In MRL/lpr mice treated with cenerimod, blood lymphocytes were reduced, leading to reduced immune infiltrates into tissue, and decreased tissue pathology, proteinuria, and inflammation, resulting in increased survival. Cenerimod was potent and efficacious in inducing S1P₁ receptor internalisation in lymphocytes in both healthy subjects and patients with SLE. In patients with SLE, 12-week cenerimod treatment resulted in a dose-dependent reduction of blood lymphocytes, antibody-secreting cells (ASC), and plasma IFN-α.

Conclusion:

Cenerimod significantly ameliorated systemic and organ-specific pathology and inflammation in a mouse model of SLE. In lymphocytes from patients with SLE, the S1P₁ receptor remained functional despite concomitant background medication. The preclinical lymphocyte reduction translated to patients with SLE and resulted in the normalisation of ASC and the reduction of IFN-associated biomarkers. The efficacy and safety of cenerimod is being further investigated in a long-term clinical study in patients with SLE (CARE; NCT-03742037).

IFN-I Mediates Dysfunction of Endothelial Progenitor Cells in Atherosclerosis of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a multi-system autoimmune disease including the cardiovascular system. Atherosclerosis is the most common cardiovascular complication of SLE and a significant risk factor for morbidity and mortality. Vascular damage/protection mechanism in SLE patients is out of balance, caused by the cascade reaction among oxidative stress, proinflammatory cytokines, Neutrophil Extracellular Traps, activation of B cells and autoantibodies and abnormal T cells. As a precursor cell repairing vascular endothelium, endothelial progenitor cells (EPCs) belong to the protective mechanism and show the reduced number and impaired function in SLE. However, the pathological mechanism of EPCs dysfunction in SLE remains ill-defined. This paper reviews the latest SLE epidemiology and pathogenesis, discusses the changes in the number and function of EPCs in SLE, expounds the role of EPCs in SLE atherosclerosis, and provides new guidance and theoretical basis for exploring novel targets for SLE treatment.

TLR engagement induces ARID3a in human blood hematopoietic progenitors and modulates IFNα production

The DNA binding protein AT-rich interacting domain 3a (ARID3a)2 is expressed in healthy human hematopoietic cord blood progenitors where its modulation influences myeloid versus B lineage development. ARID3a is also variably expressed in subsets of adult peripheral blood hematopoietic progenitors where the consequences of ARID3a expression are unknown. In B lymphocytes, Toll-like receptor (TLR)3 signaling induces ARID3a expression in association with Type I interferon inflammatory cytokines. We hypothesized that TLR ligand stimulation of peripheral blood hematopoietic progenitors would induce ARID3a expression resulting in interferon production, and potentially influencing lineage decisions. Our data revealed that the TLR9 agonist CpG induces ARID3a expression with interferon alpha synthesis in human hematopoietic progenitors. However, ARID3a expression was not associated with increased B lineage development. These results demonstrate the need for further experiments to better define how pathogen-associated responses influence hematopoiesis.

ARID3a expression in human hematopoietic stem cells is associated with distinct gene patterns in aged individuals

Background

Immunologic aging leads to immune dysfunction, significantly reducing the quality of life of the elderly. Aged-related defects in early hematopoiesis result in reduced lymphoid cell development, functionally defective mature immune cells, and poor protective responses to vaccines and pathogens. Despite considerable progress understanding the underlying causes of decreased immunity in the elderly, the mechanisms by which these occur are still poorly understood. The DNA-binding protein ARID3a is expressed in a subset of human hematopoietic progenitors. Inhibition of ARID3a in bulk human cord blood CD34⁺ hematopoietic progenitors led to developmental skewing toward myeloid lineage at the expense of lymphoid lineage cells in vitro. Effects of ARID3a expression in adult-derived hematopoietic stem cells (HSCs) have not been analyzed, nor has ARID3a expression been assessed in relationship to age. We hypothesized that decreases in ARID3a could explain some of the defects observed in aging.

Results

Our data reveal decreased frequencies of ARID3a-expressing peripheral blood HSCs from aged healthy individuals compared with young donor HSCs. Inhibition of ARID3a in young donor-derived HSCs limits B lineage potential, suggesting a role for ARID3a in B lymphopoiesis in bone marrow-derived HSCs. Increasing ARID3a levels of HSCs from aged donors in vitro alters B lineage development and maturation. Finally, single cell analyses of ARID3a-expressing HSCs from young versus aged donors identify a number of differentially expressed genes in aged ARID3A-expressing cells versus young ARID3A-expressing HSCs, as well as between ARID3A-expressing and non-expressing cells in both young and aged donor HSCs.

Conclusions

These data suggest that ARID3a-expressing HSCs from aged individuals differ at both molecular and functional levels compared to ARID3a-expressing HSCs from young individuals.

Type-I interferons in atherosclerosis

Chen et al. review the effects of type-I IFNs and the potential of anti–type-I IFN therapies in atherosclerosis.

The contribution of dyslipidemia and inflammation in atherosclerosis is well established. Along with effective lipid-lowering treatments, the recent success of clinical trials with anti-inflammatory therapies and the accelerated atherosclerosis in many autoimmune diseases suggest that targeting inflammation may open new avenues for the prevention and the treatment for cardiovascular diseases (CVDs). In the past decades, studies have widened the role of type-I interferons (IFNs) in disease, from antivirus defense to autoimmune responses and immuno-metabolic syndromes. While elevated type-I IFN level in serum is associated with CVD incidence in patients with interferonopathies, experimental data have attested that type-I IFNs affect plaque-residing macrophages, potentiate foam cell and extracellular trap formation, induce endothelial dysfunction, alter the phenotypes of dendritic cells and T and B lymphocytes, and lead to exacerbated atherosclerosis outcomes. In this review, we discuss the production and the effects of type-I IFNs in different atherosclerosis-associated cell types from molecular biology studies, animal models, and clinical observations, and the potential of new therapies against type-I IFN signaling for atherosclerosis.

DNA methylation changes on immune cells in Systemic Lupus Erythematosus

DNA methylation as a process that regulates gene expression is crucial in immune cells biology. Global and gene specific methylation changes have been described in autoimmunity, especially in Systemic Lupus Erythematosus. These changes not only contribute to the understanding of the disease, but also some have been proposed as diagnostic or disease activity biomarkers. The present review compiles the most recent discoveries on this field on each type of immune cells, including specific changes in signalling pathways, genes of interest and its possible applications on diagnosis or treatment.

Autoreactive B cells in SLE, villains or innocent bystanders?

The current concepts for development of autoreactive B cells in SLE (systemic lupus erythematosus) focus on extrinsic stimuli and factors that provoke B cells into tolerance loss. Traditionally, major tolerance loss pathways are thought to be regulated by factors outside the B cell including autoantigen engagement of the B-cell receptor (BCR) with simultaneous type I interferon (IFN) produced by dendritic cells, especially plasmacytoid dendritic cells (pDCs). Later, in autoreactive follicles, B-cells encounter T-follicular helper cells (Tfh) that produce interleukin (IL)-21, IL-4 and pathogenic cytokines, IL-17 and IFN gamma (IFNɣ). This review discusses these mechanisms and also highlights recent advances pointing to the peripheral transitional B-cell stage as a major juncture where transient autocrine IFNβ expression by developing B-cells imprints a heightened susceptibility to external factors favoring differentiation into autoantibody-producing plasmablasts. Recent studies highlight transitional B-cell heterogeneity as a determinant of intrinsic resistance or susceptibility to tolerance loss through the shaping of B-cell responsiveness to cytokines and other environment factors.

New Frontiers: ARID3a in SLE

Systemic lupus erythematosus (SLE) is a devastating and heterogeneous autoimmune disease that affects multiple organs, and for which the underlying causes are unknown. The majority of SLE patients produce autoantibodies, have increased levels of type-I inflammatory cytokines, and can develop glomerulonephritis. Recent studies indicate an unexpected but strong association between increased disease activity in SLE patients and the expression of the DNA-binding protein ARID3a (A + T rich interaction domain protein 3a) in a number of peripheral blood cell types. ARID3a expression was first associated with autoantibody production in B cells; however, more recent findings also indicate associations with expression of the inflammatory cytokine interferon alpha in SLE plasmacytoid dendritic cells and low-density neutrophils. In addition, ARID3a is expressed in hematopoietic stem cells and some adult kidney progenitor cells. SLE cells expressing enhanced ARID3a levels show differential gene expression patterns compared with homologous healthy control cells, identifying new pathways potentially regulated by ARID3a. The associations of ARID3a expression with increased disease severity in SLE, suggest that it, or its downstream targets, may provide new therapeutic targets for SLE.

Metformin Inhibits the Type 1 IFN Response in Human CD4+ T Cells

In systemic lupus erythematosus, defective clearance of apoptotic debris and activation of innate cells result in a chronically activated type 1 IFN response, which can be measured in PBMCs of most patients. Metformin, a widely used prescription drug for Type 2 diabetes, has a therapeutic effect in several mouse models of lupus through mechanisms involving inhibition of oxidative phosphorylation and a decrease in CD4⁺ T cell activation. In this study, we report that in CD4⁺ T cells from human healthy controls and human systemic lupus erythematosus patients, metformin inhibits the transcription of IFN-stimulated genes (ISGs) after IFN-α treatment. Accordingly, metformin inhibited the phosphorylation of pSTAT1 (Y701) and its binding to IFN-stimulated response elements that control ISG expression. These effects were independent of AMPK activation or mTORC1 inhibition but were replicated using inhibitors of the electron transport chain respiratory complexes I, III, and IV. This indicates that mitochondrial respiration is required for ISG expression in CD4⁺ T cells and provides a novel mechanism by which metformin may exert a therapeutic effect in autoimmune diseases.

ARID3a gene profiles are strongly associated with human interferon alpha production

Type I interferons (IFN) causes inflammatory responses to pathogens, and can be elevated in autoimmune diseases such as systemic lupus erythematosus (SLE). We previously reported unexpected associations of increased numbers of B lymphocytes expressing the DNA-binding protein ARID3a with both IFN alpha (IFNα) expression and increased disease activity in SLE. Here, we determined that IFNα producing low density neutrophils (LDNs) and plasmacytoid dendritic cells (pDCs) from SLE patients exhibit strong associations between ARID3a protein expression and IFNα production. Moreover, SLE disease activity indices correlate most strongly with percentages of ARID3a⁺ LDNs, but were also associated, less significantly, with IFNα expression in LDNs and pDCs. Hierarchical clustering and transcriptome analyses of LDNs and pDCs revealed SLE patients with low ARID3a expression cluster with healthy controls and identified gene profiles associated with increased proportions of ARID3a- and IFNα-expressing cells of each type. These data identify ARID3a as a potential transcription regulator of IFNα-related inflammatory responses and other pathways important for SLE disease activity.

Cutting Edge: Intracellular IFN-β and Distinct Type I IFN Expression Patterns in Circulating Systemic Lupus Erythematosus B Cells

In systemic lupus erythematosus (SLE), type I IFNs promote induction of type I IFN-stimulated genes (ISG) and can drive B cells to produce autoantibodies. Little is known about the expression of distinct type I IFNs in lupus, particularly high-affinity IFN-β. Single-cell analyses of transitional B cells isolated from SLE patients revealed distinct B cell subpopulations, including type I IFN producers, IFN responders, and mixed IFN producer/responder clusters. Anti-Ig plus TLR3 stimulation of SLE B cells induced release of bioactive type I IFNs that could stimulate HEK-Blue cells. Increased levels of IFN-β were detected in circulating B cells from SLE patients compared with controls and were significantly higher in African American patients with renal disease and in patients with autoantibodies. Together, the results identify type I IFN-producing and -responding subpopulations within the SLE B cell compartment and suggest that some patients may benefit from specific targeting of IFN-β.

Cutting Edge: Endogenous IFN-β Regulates Survival and Development of Transitional B Cells

The transitional stage of B cell development is a formative stage in the spleen where autoreactive specificities are censored as B cells gain immune competence, but the intrinsic and extrinsic factors regulating survival of transitional stage 1 (T1) B cells are unknown. We report that B cell expression of IFN-β is required for optimal survival and TLR7 responses of transitional B cells in the spleen and was overexpressed in T1 B cells from BXD2 lupus-prone mice. Single-cell gene expression analysis of B6 Ifnb^+/+ versus B6 Ifnb^-⁄- T1 B cells revealed heterogeneous expression of Ifnb in wild-type B cells and distinct gene expression patterns associated with endogenous IFN-β. Single-cell analysis of BXD2 T1 B cells revealed that Ifnb is expressed in early T1 B cell development with subsequent upregulation of Tlr7 and Ifna1 Together, these data suggest that T1 B cell expression of IFN-β plays a key role in regulating responsiveness to external factors.

Bone Marrow-Derived Mesenchymal Stem Cells From Patients With Systemic Lupus Erythematosus Have a Senescence-Associated Secretory Phenotype Mediated by a Mitochondrial Antiviral Signaling Protein-Interferon-β Feedback Loop

OBJECTIVE

Bone marrow-derived mesenchymal stem cells (BM-MSCs) create a special microenvironment for hematopoiesis and immunity and display robust immunomodulatory properties that are impaired in systemic lupus erythematosus (SLE). This study was undertaken to identify the mechanisms of defects in human SLE BM-MSCs.

METHODS

Patients fulfilling SLE classification criteria and healthy controls (n = 6 per group) were recruited according to an institutional review board-approved protocol. BM-MSCs were isolated with low-density Ficoll-Hypaque, verified by flow cytometry, and studied using immunocytochemistry, real-time polymerase chain reaction, Western blotting, comet assay, β-galactosidase assay, and RNA interference.

RESULTS

SLE BM-MSCs had a senescent phenotype characterized by a reduced proliferation rate, increased production of reactive oxygen species, increased DNA damage and repair, increased expression of p53 and p16, which block the cell cycle, and altered cytokine production (increased proinflammatory cytokine production and decreased immunomodulatory cytokine production). Moreover, SLE BM-MSCs had a 5-fold increase in interferon-β (IFNβ) levels (P < 0.05 versus healthy controls) and increased IFNβ-induced messenger RNAs (mRNAs), including mRNA for the intracellular nucleic acid-sensing adaptor protein mitochondrial antiviral signaling protein (MAVS), whose expression was highly correlated with IFNβ levels (r > 0.9, P < 0.01). Since MAVS is known to induce IFNβ production, we hypothesized that there is a positive feedback loop between MAVS and IFNβ. Notably, silencing of MAVS markedly decreased IFNβ, p53, and p16 protein levels and expression of mRNAs for proinflammatory cytokines.

CONCLUSION

This study demonstrates a novel pathway for elevated IFNβ signaling in SLE that is not dependent on stimulation by immune complexes but rather is cell intrinsic and critically mediated by IFNβ and MAVS, implicating new pathways as potential therapeutic targets.

Expression and methylation data from SLE patient and healthy control blood samples subdivided with respect to ARID3a levels

Previously published studies revealed that variation in expression of the DNA-binding protein ARID3a in B lymphocytes from patients with systemic lupus erythematosus (SLE) correlated with levels of disease activity (“Disease activity in systemic lupus erythematosus correlates with expression of the transcription factor AT-rich-interactive domain 3A” (J.M. Ward, K. Rose, C. Montgomery, I. Adrianto, J.A. James, J.T. Merrill et al., 2014) [1]). The data presented here compare DNA methylation patterns from SLE peripheral blood mononuclear cells obtained from samples with high numbers of ARID3a expressing B cells (ARID3a^H) versus SLE samples with normal numbers of ARID3a⁺ B cells (ARID3a^N). The methylation data is available at the gene expression omnibus (GEO) repository, “Gene Expression Omnibus: NCBI gene expression and hybridization array data repository” (R. Edgar, M. Domrachev, A.E. Lash, 2002) [2]. Isolated B cells from SLE ARID3a^H and ARID3a^N B samples were also evaluated via qRT-PCR for Type I interferon (IFN) signature and pathway gene expression levels by qRT-PCR. Similarly, healthy control B cells and B cells stimulated to express ARID3a with the TLR agonist, CpG, were also compared via qRT-PCR. Primers designed to detect 6 IFNa subtype mRNAs were tested in 4 IFNa, Epstein-Barr Virus-transformed B cell lines (“Reduced interferon-alpha production by Epstein-Barr virus transformed B-lymphoblastoid cell lines and lectin-stimulated lymphocytes in congenital dyserythropoietic anemia type I” (S.H. Wickramasinghe, R. Hasan, J. Smythe, 1997) [3]). The data in this article support the publication, “Human effector B lymphocytes express ARID3a and secrete interferon alpha” (J.M. Ward, M.L. Ratliff, M.G. Dozmorov, G. Wiley, J.M. Guthridge, P.M. Gaffney, J.A. James, C.F. Webb, 2016) [4].