Genomic view of systemic autoimmunity in MRLlpr mice

Rare SH2B3 coding variants in lupus patients impair B cell tolerance and predispose to autoimmunity

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease with a clear genetic component. While most SLE patients carry rare gene variants in lupus risk genes, little is known about their contribution to disease pathogenesis. Amongst them, SH2B3-a negative regulator of cytokine and growth factor receptor signaling-harbors rare coding variants in over 5% of SLE patients. Here, we show that unlike the variant found exclusively in healthy controls, SH2B3 rare variants found in lupus patients are predominantly hypomorphic alleles, failing to suppress IFNGR signaling via JAK2-STAT1. The generation of two mouse lines carrying patients' variants revealed that SH2B3 is important in limiting the number of immature and transitional B cells. Furthermore, hypomorphic SH2B3 was shown to impair the negative selection of immature/transitional self-reactive B cells and accelerate autoimmunity in sensitized mice, at least in part due to increased IL-4R signaling and BAFF-R expression. This work identifies a previously unappreciated role for SH2B3 in human B cell tolerance and lupus risk.

Intersection of Immunity, Metabolism, and Muscle Regeneration in an Autoimmune-Prone MRL Mouse Model

Due to the limited capacity of mammals to regenerate complex tissues, researchers have worked to understand the mechanisms of tissue regeneration in organisms that maintain that capacity. One example is the MRL/MpJ mouse strain with unique regenerative capacity in ear pinnae that is absent from other strains, such as the common C57BL/6 strain. The MRL/MpJ mouse has also been associated with an autoimmune phenotype even in the absence of the mutant Fas gene described in its parent strain MRL/lpr. Due to these findings, the differences between the responses of MRL/MpJ versus C57BL/6 strain are evaluated in volumetric muscle injury and subsequent material implantation. One salient feature of the MRL/MpJ response to injury is robust adipogenesis within the muscle. This is associated with a decrease in M2-like polarization in response to biologically derived extracellular matrix scaffolds. In pro-fibrotic materials, such as polyethylene, there are fewer foreign body giant cells in the MRL/MpJ mice. As there are reports of both positive and negative influences of adipose tissue and adipogenesis on wound healing, this model can provide an important lens to investigate the interplay between stem cells, adipose tissue, and immune responses in trauma and material implantation.

B cell-intrinsic Myd88 regulates disease progression in murine lupus

Nucleic acid-specific Toll-like receptors (TLRs) have been implicated in promoting disease pathogenesis in systemic lupus erythematosus (SLE). Whether such TLRs mediate disease onset, progression, or both remains undefined; yet the answer to this question has important therapeutic implications. MyD88 is an essential adaptor that acts downstream of IL-1 family receptors and most TLRs. Both global and B cell-specific Myd88 deficiency ameliorated disease in lupus-prone mice when constitutively deleted. To address whether Myd88 was needed to sustain ongoing disease, we induced B cell-specific deletion of Myd88 after disease onset in MRL.Faslpr mice using an inducible Cre recombinase. B cell-specific deletion of Myd88 starting after disease onset resulted in ameliorated glomerulonephritis and interstitial inflammation. Additionally, treated mice had reduced autoantibody formation and an altered B cell compartment with reduced ABC and plasmablast numbers. These experiments demonstrate the role of MyD88 in B cells to sustain disease in murine lupus. Therefore, targeting MyD88 or its upstream activators may be a viable therapeutic option in SLE.

Ectopic adipogenesis in response to injury and material implantation in an autoimmune mouse model

Due to the limited capacity of mammals to regenerate complex tissues, researchers have worked to understand the mechanisms of tissue regeneration in organisms that maintain that capacity. One example is the MRL/MpJ mouse strain with unique regenerative capacity in ear pinnae that is absent from other strains, such as the common C57BL/6 strain. The MRL/MpJ mouse has also been associated with an autoimmune phenotype even in the absence of the mutant Fas gene described in its parent strain MRL/lpr. Due to these findings, we evaluated the differences between the responses of MRL/MpJ versus C57BL/6 strain in traumatic muscle injury and subsequent material implantation. One salient feature of the MRL/MpJ response to injury was a robust adipogenesis within the muscle. This was associated with a decrease in M2-like polarization in response to biologically derived extracellular matrix scaffolds. In pro-fibrotic materials, such as polyethylene, there were fewer foreign body giant cells in the MRL/MpJ mice. As there are reports of both positive and negative influences of adipose tissue and adipogenesis on wound healing, this model could provide an important lens to investigate the interplay between stem cells, adipose tissue, and immune responses in trauma and materials implantation.

Impaired dynamic X-chromosome inactivation maintenance in T cells is a feature of spontaneous murine SLE that is exacerbated in female-biased models

OBJECTIVE

Systemic lupus erythematosus (SLE) is a highly female-biased systemic autoimmune disease, but the molecular basis for this female bias remains incompletely elucidated. B and T lymphocytes from patients with SLE and female-biased mouse models of SLE exhibit features of epigenetic dysregulation on the X chromosome which may contribute to this strong female bias. We therefore examined the fidelity of dynamic X-chromosome inactivation maintenance (dXCIm) in the pathogenesis of two murine models of spontaneous lupus-NZM2328 and MRL/lpr-with disparate levels of female-bias to determine whether impaired dXCIm contributes to the female bias of disease.

METHODS

CD23+ B cells and CD3+ T cells were purified from age-matched C57BL/6 (B6), MRL/lpr, and NZM2328 male and female mice, activated in vitro, and processed for Xist RNA fluorescence in situ hybridization, H3K27me3 immunofluorescence imaging, qPCR, and RNA sequencing analyses.

RESULTS

The dynamic relocalization of Xist RNA and the canonical heterochromatin mark, H3K27me3, to the inactive X chromosome was preserved in CD23+ B cells, but impaired in activated CD3+ T cells from the MRL/lpr model (p < 0.01 vs. B6), and even more impaired in the heavily female-biased NZM2328 model (p < 0.001 vs. B6; p < 0.05 vs. MRL/lpr). RNAseq of activated T cells from NZM2328 mice revealed the female-biased upregulation of 32 X-linked genes distributed broadly across the X chromosome, many of which have roles in immune function. Many genes encoding Xist RNA-interacting proteins were also differentially expressed and predominantly downregulated, which may account for the observed mislocalization of Xist RNA to the inactive X chromosome.

CONCLUSIONS

Although evident in T cells from both the MRL/lpr and NZM2328 models of spontaneous SLE, impaired dXCIm is more severe in the heavily female-biased NZM2328 model. The aberrant X-linked gene dosage in female NZM2328 mice may contribute towards the development of female-biased immune responses in SLE-prone hosts. These findings provide important insights into the epigenetic mechanisms contributing to female-biased autoimmunity.

Knockdown of KLF5 ameliorates renal fibrosis in MRL/lpr mice via inhibition of MX1 transcription

OBJECTIVE

This study aims to elucidate the role of Kruppel-like factor (KLF5) and myxovirus resistance 1 (MX1) in the progression of renal fibrosis in lupus nephritis (LN).

METHODS

First, the expression of KLF5 and MX1 was assessed in the peripheral blood of LN patients and healthy participants. Next, the pathological changes in renal tissues were evaluated and compared in BALB/c and MRL/lpr mice, by detecting the expression of fibrosis marker proteins (transforming growth factor-β [TGF-β] and CTGF) and α-SMA, the content of urine protein, and the levels of serum creatinine, blood urea nitrogen, and serum double-stranded DNA antibody. In TGF-β1-induced HK-2 cells, the messenger RNA levels of KLF5 and MX1 were tested by qRT-PCR, and the protein expression of α-SMA, type I collagen (Col I), fibronectin (FN), and matrix metalloproteinase 9 (MMP9) was measured by western blot analysis. Moreover, the relationship between KLF5 and MX1 was predicted and verified.

RESULTS

In renal tissues of MRL/lpr mice and the peripheral blood of LN patients, KLF5 and MX1 were highly expressed. Pearson analysis revealed that KLF5 was positively correlated with MX1. Furthermore, KLF5 bound to MX1 promoter and promoted its transcription level. MRL/lpr mice showed substantial renal injury, accompanied by increased expression of α-SMA, TGF-β, CTGF, Col I, FN, and MMP9. Injection of sh-KLF5 or sh-MX1 alone in MRL/lpr mice reduced renal fibrosis in LN, while simultaneous injection of sh-KLF5 and ad-MX1 exacerbated renal injury and fibrosis. Furthermore, we obtained the same results in TGF-β1-induced HK-2 cells.

CONCLUSION

Knockdown of KLF5 alleviated renal fibrosis in LN through repressing the transcription of MX1.

Let’s review the gut microbiota in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic, immune-mediated disease associated with significant morbidity and mortality. New evidence suggests that diet, gut microbiota, intestinal permeability, and endotoxemia may modulate chronic inflammation and disease activity in SLE. This review focus on what is known about the gut microbiota in lupus mouse models and SLE patients and the possible mechanisms that connect the gut microbiota with SLE. It included 29 studies (12 animal studies, 15 human studies, and 2 included data on both), with variable results regarding alpha and beta-diversity and gut microbiota composition between lupus-mouse models and SLE patients. Ruminococcus (R.) gnavus was significantly increased in lupus nephritis (LN) in one study, but this was not corroborated by others. Despite the different results, mechanistic lupus mouse model studies have shown that gut microbiota can modulate disease activity. Interestingly, pathobiont translocation in monocolonized and autoimmune-prone mice induced autoantibodies and caused mortality, which could be prevented by a vaccine targeting the pathobiont. Moreover, studies on fecal transplants and diet on different lupus mouse models showed an effect on disease activity. In SLE patients, a higher adherence to the Mediterranean diet was associated with lower disease activity, which may be explained by the connection between diet and gut microbiota. Although gut dysbiosis has been observed in SLE patients and lupus mouse models, it remains to clarify if it is a cause or a consequence of the disease or its treatments. Further studies with larger and well-characterized populations will undoubtedly contribute to deciphering the role of gut microbiota in SLE development, progression, and outcome.

Polymeric dexamethasone prodrugs attenuate lupus nephritis in MRL/lpr mice with reduced glucocorticoid toxicity

Due to their potent immunosuppressive and anti-inflammatory effects, glucocorticoids (GCs) are the most widely used medications in treating lupus nephritis (LN). Long-term use of GCs, however, is associated with numerous off-target adverse effects. To reduce GCs' adverse effects, we previously developed two polymeric dexamethasone prodrug nanomedicines: N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer-based dexamethasone prodrug (P-Dex), and micelle-forming polyethylene glycol (PEG)-based dexamethasone prodrug (ZSJ-0228). Both P-Dex and ZSJ-0228 provided sustained amelioration of LN in lupus-prone NZB/W F1 mice with reduced GC-associated adverse effects. Here, we have extended our investigation to the MRL/lpr mouse model of LN. Compared to dose equivalent daily dexamethasone sodium phosphate (Dex) treatment, monthly P-Dex or ZSJ-0228 treatments were more effective in reducing proteinuria and extending the lifespan of MRL/lpr mice. Unlike the daily Dex treatment, ZSJ-0228 was not associated with measurable GC-associated adverse effects. In contrast, adrenal gland atrophy was observed in P-Dex treated mice.

Double Negative T Regulatory Cells: An Emerging Paradigm Shift in Reproductive Immune Tolerance?

Immune regulation of female reproductive function plays a crucial role in fertility, as alterations in the relationship between immune and reproductive processes result in autoimmune subfertility or infertility. The breakdown of immune tolerance leads to ovulation dysfunction, implantation failure, and pregnancy loss. In this regard, immune cells with regulatory activities are essential to restore self-tolerance. Apart from regulatory T cells, double negative T regulatory cells (DNTregs) characterized by TCRαβ+/γδ+CD3+CD4–CD8– (and negative for natural killer cell markers) are emerging as effector cells capable of mediating immune tolerance in the female reproductive system. DNTregs are present in the female reproductive tract of humans and murine models. However, their full potential as immune regulators is evolving, and studies so far indicate that DNTregs exhibit features that can also maintain tolerance in the female reproductive microenvironment. This review describes recent progress on the presence, role and mechanisms of DNTregs in the female reproductive system immune regulation and tolerance. In addition, we address how DNTregs can potentially provide a paradigm shift from the known roles of conventional regulatory T cells and immune tolerance by maintaining and restoring balance in the reproductive microenvironment of female fertility.

Sphingosine 1-phosphate receptor-targeted therapeutics in rheumatic diseases

Sphingosine 1-phosphate (S1P), which acts via G protein-coupled S1P receptors (S1PRs), is a bioactive lipid essential for vascular integrity and lymphocyte trafficking. The S1P-S1PR signalling axis is a key component of the inflammatory response in autoimmune rheumatic diseases. Several drugs that target S1PRs have been approved for the treatment of multiple sclerosis and inflammatory bowel disease and are under clinical testing for patients with systemic lupus erythematosus (SLE). Preclinical studies support the hypothesis that targeting the S1P-S1PR axis would be beneficial to patients with SLE, rheumatoid arthritis (RA) and systemic sclerosis (SSc) by reducing pathological inflammation. Whereas most preclinical research and development efforts are focused on reducing lymphocyte trafficking, protective effects of circulating S1P on endothelial S1PRs, which maintain the vascular barrier and enable blood circulation while dampening leukocyte extravasation, have been largely overlooked. In this Review, we take a holistic view of S1P-S1PR signalling in lymphocyte and vascular pathobiology. We focus on the potential of S1PR modulators for the treatment of SLE, RA and SSc and summarize the rationale, pathobiology and evidence from preclinical models and clinical studies. Improved understanding of S1P pathobiology in autoimmune rheumatic diseases and S1PR therapeutic modulation is anticipated to lead to efficacious and safer management of these diseases.

Cenerimod, a selective S1P1 receptor modulator, improves organ-specific disease outcomes in animal models of Sjögren's syndrome

Background

Sjögren’s syndrome is a systemic autoimmune disease characterized by immune cells predominantly infiltrating the exocrine glands and frequently forming ectopic lymphoid structures. These structures drive a local functional immune response culminating in autoantibody production and tissue damage, associated with severe dryness of mucosal surfaces and salivary gland hypofunction. Cenerimod, a potent, selective and orally active sphingosine-1-phosphate receptor 1 modulator, inhibits the egress of lymphocytes into the circulation. Based on the mechanism of action of cenerimod, its efficacy was evaluated in two mouse models of Sjögren’s syndrome.

Methods

Cenerimod was administered in two established models of Sjögren’s syndrome; firstly, in an inducible acute viral sialadenitis model in C57BL/6 mice, and, secondly, in the spontaneous chronic sialadenitis MRL/lpr mouse model. The effects of cenerimod treatment were then evaluated by flow cytometry, immunohistochemistry, histopathology and immunoassays. Comparisons between groups were made using a Mann-Whitney test.

Results

In the viral sialadenitis model, cenerimod treatment reduced salivary gland immune infiltrates, leading to the disaggregation of ectopic lymphoid structures, reduced salivary gland inflammation and preserved organ function. In the MRL/lpr mouse model, cenerimod treatment decreased salivary gland inflammation and reduced T cells and proliferating plasma cells within salivary gland ectopic lymphoid structures, resulting in diminished disease-relevant autoantibodies within the salivary glands.

Conclusions

Taken together, these results suggest that cenerimod can reduce the overall autoimmune response and improve clinical parameters in the salivary glands in models of Sjögren’s syndrome and consequently may reduce histological and clinical parameters associated with the disease in patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02673-x.

Toll-like Receptor Signaling Inhibitory Peptide Improves Inflammation in Animal Model and Human Systemic Lupus Erythematosus

Toll-like receptors (TLRs) play a major role in the innate immune system. Several studies have shown the regulatory effects of TLR-mediated pathways on immune and inflammatory diseases. Dysregulated functions of TLRs within the endosomal compartment, including TLR7/9 trafficking, may cause systemic lupus erythematosus (SLE). TLR signaling pathways are fine-tuned by Toll/interleukin-1 receptor (TIR) domain-containing adapters, leading to interferon (IFN)-α production. This study describes a TLR inhibitor peptide 1 (TIP1) that primarily suppresses the downstream signaling mediated by TIR domain-containing adapters in an animal model of lupus and patients with SLE. The expression of most downstream proteins of the TLR7/9/myeloid differentiation factor 88 (MyD88)/IFN regulatory factor 7 signaling was downregulated in major tissues such as the kidney, spleen, and lymph nodes of treated mice. Furthermore, the pathological analysis of the kidney tissue confirmed that TIP1 could improve inflammation in MRL/lpr mice. TIP1 treatment downregulated many downstream proteins associated with TLR signaling, such as MyD88, interleukin-1 receptor-associated kinase, tumor necrosis factor receptor-associated factor 6, and IFN-α, in the peripheral blood mononuclear cells of patients with SLE. In conclusion, our data suggest that TIP1 can serve as a potential candidate for the treatment of SLE.

The implications of the purinergic signaling throughout pregnancy

Purinergic signaling is a necessary mechanism to trigger or even amplify cell communication. Its ligands, notably adenosine triphosphate (ATP) and adenosine, modulate specific membrane-bound receptors in virtually all human cells. Regardless of the stage of the pregnancy, cellular communication between maternal, placental, and fetal cells is the paramount mechanism to sustain its optimal status. In this review, we describe the crucial role of purinergic signaling on the regulation of the maternal-fetal trophic exchanges, immune control, and endocrine exchanges throughout pregnancy. The nature of the modulation of both ATP and adenosine on the embryo-maternal interface, going through placental invasion until birth delivery depends on the general maternal-fetal health state and consequently on the selective activation of their specific receptors. In addition, an increasing number of studies have been demonstrating the pivotal role of ATP and adenosine in modulating deleterious effects of suboptimal conditions of pregnancy. Here, we discuss the role of purinergic signaling on the balance that coordinates the embryo-maternal exchanges and a promising therapeutic venue in the context of pregnancy disorders.

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).

Intravenous Administration of Toll-Like Receptor Inhibitory Peptide 1 is Effective for the Treatment of Systemic Lupus Erythematosus in a Mus musculus Model

Objective

Systemic lupus erythematosus (SLE) is a common chronic autoimmune inflammatory disease According to recent studies, signaling through Toll-like receptor (TLR) protein, which promotes the production of inflammatory cytokines, leads to the development of SLE TLR-inhibitory peptide 1 (TIP1) has been newly identified for the treatment of autoimmune diseases.

Methods

The effect of TIP1 was analyzed in an SLE mouse model (MRL/lpr) The mice in the control treatment group (n=5) were administered an intravenous injection of phosphate-buffered saline twice weekly, whereas the mice in the TIP1 treatment group (n=6) were administered an intravenous injection of TIP1 (1 nmol/g) twice weekly MRL/mpj mice (n=5) were selected as normal controls The mice were injected for 4 weeks between 14 and 18 weeks of age, followed by assays of their spleen, kidneys, lymph nodes, serum, and urine.

Results

The antinuclear antibody and inflammatory cytokine (interferon-α) in the serum as well as levels of albumin in the urine of the mice in the TIP1 treatment group had decreased when compared to those of mice in the control treatment group Kidney inflammation in mice in the TIP1 treatment group was alleviated The mRNA expression levels of TLR7- or TLR9-related downstream signaling molecules also decreased in all organs of the mice in the TIP1 treatment group.

Conclusion

Intravenous treatment with TIP1 reduces symptoms and markers of inflammation in MRL/lpr mice Hence, TIP1 is a promising medication for the treatment of SLE.

Identification of hub genes, pathways, and related transcription factors in systemic lupus erythematosus: A preliminary bioinformatics analysis

BACKGROUND

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multiple organ damage and the production of a variety of autoantibodies. The pathogenesis of SLE has not been fully defined, and it is difficult to treat. Our study aimed to identify candidate genes that may be used as biomarkers for the screening, diagnosis, and treatment of SLE.

METHODS

We used the GEO2R tool to identify the differentially expressed genes (DEGs) in SLE-related datasets retrieved from the Gene Expression Omnibus (GEO). In addition, we also identified the biological functions of the DEGs by gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. Additionally, we constructed protein-protein interaction (PPI) networks to identify hub genes, as well as the regulatory network of transcription factors related to DEGs.

RESULTS

Two datasets were identified for use from the GEO (GSE50772, GSE4588), and 34 up-regulated genes and 4 down-regulated genes were identified by GEO2R. Pathway analysis of the DEGs revealed enrichment of the interferon alpha/beta signaling pathway; GO analysis was mainly enriched in response to interferon alpha, regulation of ribonuclease activity. PPIs were constructed through the STRING database and 14 hub genes were selected and 1 significant module (score = 12.923) was obtained from the PPI network. Additionally, 11 key transcription factors that interacted closely with the 14 hub DEGs were identified from the gene transcription factor network.

CONCLUSIONS

Bioinformatic analysis is an effective tool for screening the original genomic data in the GEO database, and a large number of SLE-related DEGs were identified. The identified hub DEGs may be potential biomarkers of SLE.

SH3BP2 Deficiency Ameliorates Murine Systemic Lupus Erythematosus

BACKGROUND

The adaptor protein Src homology 3 domain-binding protein 2 (SH3BP2) is widely expressed in immune cells. It controls intracellular signaling pathways. The present study was undertaken to investigate the role of SH3BP2 in a murine systemic lupus erythematosus model.

METHODS

For the lupus model, we used Fas^lpr/lpr mice. Clinical and immunological phenotypes were compared between Fas^lpr/lpr and SH3BP2-deficient Fas^lpr/lpr mice. Splenomegaly and renal involvement were assessed. Lymphocyte subsets in the spleen were analyzed by flow cytometry. To examine the role of SH3BP2 in specific cells, B cell-specific SH3BP2-deficient lupus mice were analyzed; T cells and bone marrow-derived dendritic cells and macrophages were analyzed in vitro.

RESULTS

SH3BP2 deficiency significantly reduced lupus-like phenotypes, presented as splenomegaly, renal involvement, elevated serum anti-dsDNA antibody, and increased splenic B220⁺CD4^-CD8^- T cells. Notably, SH3BP2 deficiency in B cells did not rescue the lupus-like phenotypes. Furthermore, SH3BP2 deficiency did not substantially affect the characteristics of T cells and macrophages in vitro. Interestingly, SH3BP2 deficiency suppressed the differentiation of dendritic cells in vitro and reduced the number of dendritic cells in the spleen of the lupus-prone mice.

CONCLUSIONS

SH3BP2 deficiency ameliorated lupus-like manifestations. Modulating SH3BP2 expression could thus provide a novel therapeutic approach to autoimmune diseases.

Aberrant Gut Microbiome Contributes to Intestinal Oxidative Stress, Barrier Dysfunction, Inflammation and Systemic Autoimmune Responses in MRL/lpr Mice

Microbiome composition and function have been implicated as contributing factors in the pathogenesis of autoimmune diseases (ADs), including systemic lupus erythematosus (SLE), rheumatoid arthritis and autoimmune hepatitis (AIH). Furthermore, dysbiosis of gut microbiome is associated with impaired barrier function and mucosal immune dysregulation. However, mechanisms by which gut microbiome contributes to the ADs and whether antioxidant treatment can restore gut homeostasis and ameliorate the disease outcome are not known. This study was, therefore, focused on examining the involvement of gut microbiome and host responses in the pathogenesis of SLE using unique female mouse models (C57BL/6, MRL+/+ and MRL/lpr) of 6 and 18 weeks with varying degrees of disease progression. Fecal microbiome diversity and composition, gut oxidative stress (OS), barrier function and inflammation, as well as systemic autoimmunity were determined. Interestingly, each mouse strain had distinct bacterial community as revealed by β-diversity. A lower Firmicutes/Bacteroidetes ratio in 6-week-old MRL/lpr mice was observed, evidenced by decrease in Peptostreptococcaceae under Firmicutes phylum along with enrichment of Rikenellaceae under Bacteroidetes phylum. Additionally, we observed increases in colonic OS [4-hydroxynonenal (HNE)-adducts and HNE-specific immune complexes], permeability changes (lower tight junction protein ZO-2; increased fecal albumin and IgA levels) and inflammatory responses (increased phos-NF-κB, IL-6 and IgG levels) in 18-week-old MRL/lpr mice. These changes were associated with markedly elevated AD markers (antinuclear and anti-smooth muscle antibodies) along with hepatic portal inflammation and severe glomerulonephritis. Notably, antioxidant N-acetylcysteine treatment influenced the microbial composition (decreased Rikenellaceae; increased Akkeransiaceae, Erysipelotrichaceae and Muribaculaceae) and attenuated the systemic autoimmunity in MRL/lpr mice. Our data thus show that gut microbiome dysbiosis is associated with increased colonic OS, barrier dysfunction, inflammatory responses and systemic autoimmunity markers. These findings apart from delineating a role for gut microbiome dysbiosis, also support the contribution of gut OS, permeability changes and inflammatory responses in the pathogenesis of ADs.

Niclosamide suppresses the expansion of follicular helper T cells and alleviates disease severity in two murine models of lupus via STAT3

Background

Autoantibody production against endogenous cellular components is pathogenic feature of systemic lupus erythematosus (SLE). Follicular helper T (T_FH) cells aid in B cell differentiation into autoantibody-producing plasma cells (PCs). The IL-6 and IL-21 cytokine-mediated STAT3 signaling are crucial for the differentiation to T_FH cells. Niclosamide is an anti-helminthic drug used to treat parasitic infections but also exhibits a therapeutic effect on autoimmune diseases due to its potential immune regulatory effects. In this study, we examined whether niclosamide treatment could relieve lupus-like autoimmunity by modulating the differentiation of T_FH cells in two murine models of lupus.

Methods

10-week-old MRL/lpr mice were orally administered with 100 mg/kg of niclosamide or with 0.5% methylcellulose (MC, vehicle) daily for 7 weeks. TLR7 agonist, resiquimod was topically applied to an ear of 8-week-old C57BL/6 mice 3 times a week for 5 weeks. And they were orally administered with 100 mg/kg of niclosamide or with 0.5% MC daily for 5 weeks. Every mouse was analyzed for lupus nephritis, proteinuria, autoantibodies, immune complex, immune cell subsets at the time of the euthanization.

Results

Niclosamide treatment greatly improved proteinuria, anti-dsDNA antibody levels, immunoglobulin subclass titers, histology of lupus nephritis, and C3 deposition in MRL/lpr and R848-induced mice. In addition, niclosamide inhibited the proportion of T_FH cells and PCs in the spleens of these animals, and effectively suppressed differentiation of T_FH-like cells and expression of associated genes in vitro.

Conclusions

Niclosamide exerted therapeutic effects on murine lupus models by suppressing T_FH cells and plasma cells through STAT3 inhibition.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02760-2.

Deletion of Mir223 Exacerbates Lupus Nephritis by Targeting S1pr1 in Faslpr/lpr Mice

Objective

The micro RNAs (miRNAs) and their target mRNAs are differentially expressed in various immune-mediated cells. Here, we investigated the role of Mir223 and sphingosine-1-phosphate receptor 1 (S1pr1) in the pathogenesis of systemic lupus erythematosus.

Methods

We analyzed miRNA and mRNA profiling data of CD4+ splenic T cells derived from MRL/MpJ-Faslpr /J mice. We performed 3' untranslated region (UTR) luciferase reporter gene assay using human umbilical vein endothelial cells (HUVECs). We generated the B6-Mir223-/-Faslpr/lpr mice and the lupus phenotypes were analyzed.

Results

In CD4+ splenic T cells, we identified upregulation of miR-223-3p and downregulation of the possible target, S1pr1 by RNA sequencing of MRL/MpJ-Faslpr /J mice. The transfection with miR-223-3p mimic significantly suppressed a luciferase activity in HUVEC treated with a Lentivirus vector containing 3' UTR of S1pr1. The mRNA levels of S1pr1 were significantly decreased after miR-223-3p overexpression. In B6-Mir223-/-Faslpr/lpr mice, the proportion of CD3+ T cells, CD3+CD4-CD8- cells, B cells, plasma cells, and S1PR1+CD4+ T cells in the spleen was significantly increased compared with that in B6-Mir223+/+Faslpr/lpr mice by flow cytometry. B6-Mir223-/-Faslpr/lpr mice demonstrated the elevation of glomerular and renal vascular scores associated with enhanced intraglomerular infiltration of S1PR1+CD4+ T cells.

Conclusion

Unexpectedly, the deletion of Mir223 exacerbated the lupus phenotypes associated with increased population of S1PR1+CD4+ T in spleen and the enhanced infiltration of S1PR1+CD4+ T cells in inflamed kidney tissues, suggesting compensatory role of Mir223 in the pathogenesis of lupus nephritis.

Naringenin mitigates autoimmune features in lupus-prone mice by modulation of T-cell subsets and cytokines profile

Naringenin is flavonoid mainly found in citrus fruits which has shown several biological properties. In this work, we evaluated the therapeutic potential of the flavonoid Naringenin. Five-month-old B6.MRL-Faslpr/J lupus-prone mice were administered daily orally with Naringenin for seven months. We showed that Naringenin treatment at 50 or 100 mg/kg inhibited the splenomegaly and decreased the levels of anti-nuclear and anti-dsDNA autoantibodies. Furthermore, a reduction in serum concentration of TNF-α, IFN-γ and IL-6 was observed in the mice provided with Naringenin. Interestingly, serum levels of IL-10 increased. Naringenin decreased the frequency and absolute numbers of splenic effector memory T cells. Additionally, in order to be able to evaluate whether Naringenin prevented kidney damage, twelve-week-old MRL/MpJ-Faslpr/J mice, an accelerated lupus model, were orally administered with Naringenin at 100 mg/kg for six weeks. Surprisingly, Naringenin treatment prevented kidney damage and reduced the development of fibrosis similar to cyclophosphamide group. Moreover, Naringenin treatment increased the percentage of regulatory T cells in this aggressive model of lupus. Together, these results suggest a potential ability of Naringenin to reduce the autoimmunity in lupus-prone mice by modulation of T-cell subsets and cytokines profile that mitigate the development of important lupus clinical manifestations.

Early and Short-Term Interventions in the Gut Microbiota Affects Lupus Severity, Progression, and Treatment in MRL/lpr Mice

There have been attempts to reveal the possible associations between systemic lupus erythematosus (SLE) and gut microbiota. Using MRL/lpr mice, this study was performed to reveal whether early and short-term interventions in gut microbiota affect lupus. MRL/lpr mice were treated with antibiotics or fecal microbiota transplantation (FMT) before onset. Then, prednisone was used to treat the lupus mice with initially different gut microbiota compositions. The compositions of gut microbiota were assessed by the V3-V4 region of 16S rRNA gene sequence. Early and short-term antibiotics exposure aggravated lupus severity by depleting beneficial gut microbiota for lupus, such as Lactobacillus and Bifidobacterium, and enriching harmful gut microbiota for lupus, such as Klebsiella and Proteus. FMT alleviated lupus severity by renovating the antibiotic-induced dysbiosis of gut microbiota in the following 1 week after antibiotics exposure. Besides, short-term antibiotics exposure before onset imposed no significant effects on lupus progression, but the following one week of FMT suppressed lupus progression. Moreover, the short-term antibiotics or FMT before onset inhibited the therapeutic efficiency of prednisone on lupus from 9 to 13 weeks old of MRL/lpr mice. These data demonstrate that the gut microbiota before onset is important for lupus severity, progression and treatment.

Immune Relevant and Immune Deficient Mice: Options and Opportunities in Translational Research

In 1989 ILAR published a list and description of immunodeficient rodents used in research. Since then, advances in understanding of molecular mechanisms; recognition of genetic, epigenetic microbial, and other influences on immunity; and capabilities in manipulating genomes and microbiomes have increased options and opportunities for selecting mice and designing studies to answer important mechanistic and therapeutic questions. Despite numerous scientific breakthroughs that have benefitted from research in mice, there is debate about the relevance and predictive or translational value of research in mice. Reproducibility of results obtained from mice and other research models also is a well-publicized concern. This review summarizes resources to inform the selection and use of immune relevant mouse strains and stocks, aiming to improve the utility, validity, and reproducibility of research in mice. Immune sufficient genetic variations, immune relevant spontaneous mutations, immunodeficient and autoimmune phenotypes, and selected induced conditions are emphasized.

The IL4I1 Enzyme: A New Player in the Immunosuppressive Tumor Microenvironment

The high metabolic needs of T lymphocytes in response to activation make them particularly vulnerable to modifications of their biochemical milieu. Immunosuppressive enzymes produced in the tumor microenvironment modify nutrient availability by catabolizing essential or semi-essential amino acids and producing toxic catabolites, thus participating in the local sabotage of the antitumor immune response. L-amino-acid oxidases are FAD-bound enzymes found throughout evolution, from bacteria to mammals, and are often endowed with anti-infectious properties. IL4I1 is a secreted L-phenylalanine oxidase mainly produced by inflammatory antigen-presenting cells-in particular, macrophages present in T helper type 1 granulomas and in various types of tumors. In the last decade, it has been shown that IL4I1 is involved in the fine control of B- and T-cell adaptive immune responses. Preclinical models have revealed its role in cancer immune evasion. Recent clinical data highlight IL4I1 as a new potential prognostic marker in human melanoma. As a secreted enzyme, IL4I1 may represent an easily targetable molecule for cancer immunotherapy.

Immune homeostasis and regulation of the interferon pathway require myeloid-derived Regnase-3

The RNase Regnase-1 is a master RNA regulator in macrophages and T cells that degrades cellular and viral RNA upon NF-κB signaling. The roles of its family members, however, remain largely unknown. Here, we analyzed Regnase-3-deficient mice, which develop hypertrophic lymph nodes. We used various mice with immune cell-specific deletions of Regnase-3 to demonstrate that Regnase-3 acts specifically within myeloid cells. Regnase-3 deficiency systemically increased IFN signaling, which increased the proportion of immature B and innate immune cells, and suppressed follicle and germinal center formation. Expression analysis revealed that Regnase-3 and Regnase-1 share protein degradation pathways. Unlike Regnase-1, Regnase-3 expression is high specifically in macrophages and is transcriptionally controlled by IFN signaling. Although direct targets in macrophages remain unknown, Regnase-3 can bind, degrade, and regulate mRNAs, such as Zc3h12a (Regnase-1), in vitro. These data indicate that Regnase-3, like Regnase-1, is an RNase essential for immune homeostasis but has diverged as key regulator in the IFN pathway in macrophages.

CKD-506, a novel HDAC6-selective inhibitor, improves renal outcomes and survival in a mouse model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic multisystemic autoimmune disease with an unknown etiology. Recently, it has been elucidated that dysregulated histone deacetylase (HDAC) activity is related to the pathogenesis of inflammatory and autoimmune diseases. Broad-spectrum HDAC inhibitors are effective for the treatment of allergy, cancer, and autoimmune diseases, but they have several adverse side effects. Thus, the purpose of this study was to evaluate the effects of a novel HDAC 6-specific inhibitor, CKD-506, in a murine SLE model. CKD-506 significantly improved survival rate and significantly decreased the incidence of severe proteinuria, blood urea nitrogen, kidney inflammation, and glomerular infiltration of IgG and C3. In addition, CKD 506 reduced the proportions of CD138⁺ plasma cells, CD4⁻CD8⁻ T cells, and CD25⁺ cells and the Th1/Th2 ratio in the spleen. CKD-506 significantly reduced inflammatory cytokines such as IL-10, IL-15, IL-17, TNF-α, and IFN-inducible protein (IP-10) and significantly increased TGF-β in serum. CKD-506 also significantly reduced IFN-γ, IL-1β, IL-4, IL-6, IP-10, MCP-1, and CCL4 levels in kidney. CKD-506 decreased the production of various pro-inflammatory cytokines and chemokines in the serum and kidneys, resulting in inhibition of cell migration and suppression of lupus nephritis without adverse effects.

Double-Edged Effect of Hydroxychloroquine on Human Umbilical Cord-Derived Mesenchymal Stem Cells Treating Lupus Nephritis in MRL/lpr Mice

Hydroxychloroquine (HCQ) and human umbilical cord-derived mesenchymal stem cells (UC-MSCs) were used to treat systemic lupus erythematosus (SLE), respectively. However, the effect of HCQ on UC-MSCs in lupus nephritis (LN) has not been investigated. In this study, HCQ and UC-MSCs were used in MRL/lpr mice. Surprisingly, although the treatment of both HCQ and UC-MSCs could ameliorate renal damage separately, the presence of HCQ decreased unexpectedly the therapeutic effects of UC-MSCs through interfering expression of IFN-γ. However, HCQ-pretreated UC-MSCs showed significant improvements of renal morphology and function more rapidly than that of UC-MSCs and HCQ alone. To test the role of HCQ in UC-MSCs, MRL/lpr mice and SLE patients' peripheral blood were used in vivo and in vitro. Results showed that after administration of UC-MSCs pretreated by HCQ, CXCR3 expression in renal tissues, serum IL-2, and IgM levels decreased significantly, and serum IL-10 level increased significantly. HCQ pretreatment caused a significant decrease of TNF-α and MCP-1 secretion and an increase of IL-1β and CXCL10 release from UC-MSCs. Our results indicate that HCQ plays a double-edged role in UC-MSCs. It is necessary for clinical treatment to pre-evaluated concomitant application of UC-MSCs with HCQ. More importantly, the alterative expression of IFN-γ, the improvement of migration ability of UC-MSCs, the regulation of Th1/Th2 balance, and the changes of antibodies secretion in B cell might be involved in its mechanisms.

Development of Th17-Associated Interstitial Kidney Inflammation in Lupus-Prone Mice Lacking the Gene Encoding STAT-1

OBJECTIVE

Type I interferon (IFN) signaling is a central pathogenic pathway in systemic lupus erythematosus (SLE), and therapeutics targeting type I IFN signaling are in development. Multiple proteins with overlapping functions play a role in IFN signaling, but the signaling events downstream of receptor engagement are unclear. This study was undertaken to investigate the roles of the type I and type II IFN signaling components IFN-α/β/ω receptor 2 (IFNAR-2), IFN regulatory factor 9 (IRF-9), and STAT-1 in a mouse model of SLE.

METHODS

We used immunohistochemical staining and highly multiplexed assays to characterize pathologic changes in histology, autoantibody production, cytokine/chemokine profiles, and STAT phosphorylation in order to investigate the individual roles of IFNAR-2, IRF-9, and STAT-1 in MRL/lpr mice.

RESULTS

We found that STAT-1(-/-) mice, but not IRF-9(-/-) or IFNAR-2(-/-) mice, developed interstitial nephritis characterized by infiltration with retinoic acid receptor-related orphan nuclear receptor γt-positive lymphocytes, macrophages, and eosinophils. Despite pronounced interstitial kidney disease and abnormal kidney function, STAT-1(-/-) mice had decreased proteinuria, glomerulonephritis, and autoantibody production. Phosphospecific flow cytometry revealed shunting of STAT phosphorylation from STAT-1 to STAT-3/4.

CONCLUSION

We describe unique contributions of STAT-1 to pathology in different kidney compartments in a mouse model, and provide potentially novel insight into tubulointerstitial nephritis, a poorly understood complication that predicts end-stage kidney disease in SLE patients.

The contribution of the programmed cell death machinery in innate immune cells to lupus nephritis

Systemic lupus erythematosus (SLE) is a chronic multi-factorial autoimmune disease initiated by genetic and environmental factors, which in combination trigger disease onset in susceptible individuals. Damage to the kidney as a consequence of lupus nephritis (LN) is one of the most prevalent and severe outcomes, as LN affects up to 60% of SLE patients and accounts for much of SLE-associated morbidity and mortality. As remarkable strides have been made in unlocking new inflammatory mechanisms associated with signaling molecules of programmed cell death pathways, this review explores the available evidence implicating the action of these pathways specifically within dendritic cells and macrophages in the control of kidney disease. Although advancements into the underlying mechanisms responsible for inducing cell death inflammatory pathways have been made, there still exist areas of unmet need. By understanding the molecular mechanisms by which dendritic cells and macrophages contribute to LN pathogenesis, we can improve their viability as potential therapeutic targets to promote remission.

Inhibition of SHP2 ameliorates the pathogenesis of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a devastating multisystemic autoimmune disorder. However, the molecular mechanisms underlying its pathogenesis remain elusive. Some patients with Noonan syndrome, a congenital disorder predominantly caused by gain-of-function mutations in the protein tyrosine phosphatase SH2 domain-containing PTP (SHP2), have been shown to develop SLE, suggesting a functional correlation between phosphatase activity and systemic autoimmunity. To test this directly, we measured SHP2 activity in spleen lysates isolated from lupus-prone MRL/lpr mice and found it was markedly increased compared with that in control mice. Similar increases in SHP2 activity were seen in peripheral blood mononuclear cells isolated from lupus patients relative to healthy patients. To determine whether SHP2 alters autoimmunity and related immunopathology, we treated MRL/lpr mice with an SHP2 inhibitor and found increased life span, suppressed crescentic glomerulonephritis, reduced spleen size, and diminished skin lesions. SHP2 inhibition also reduced numbers of double-negative T cells, normalized ERK/MAPK signaling, and decreased production of IFN-γ and IL-17A/F, 2 cytokines involved in SLE-associated organ damage. Moreover, in cultured human lupus T cells, SHP2 inhibition reduced proliferation and decreased production of IFN-γ and IL-17A/F, further implicating SHP2 in lupus-associated immunopathology. Taken together, these data identify SHP2 as a critical regulator of SLE pathogenesis and suggest targeting of its activity as a potent treatment for lupus patients.

Signal transducer and activator of transcription 5 is implicated in disease activity in adult and juvenile onset systemic lupus erythematosus

The Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway is one of a handful of pleiotropic cascades used to transduce a multitude of signals for development and homeostasis in humans. It is the principal signaling mechanism for a wide array of cytokines and growth factors. Dysregulated cytokine action on immune cells plays an important role in the initiation and progress of systemic lupus erythematosus (SLE). In this study, we tried to assess the role of STAT5 in systemic lupus erythematosus and correlate its phosphorylation level with the disease activity. The activation of the STAT5 was assessed by measuring the level of expression of phosphorylated STAT5 (pSTAT5) using flow cytometry on the peripheral blood T and B cells in 58 SLE patients (40 adult and 18 juvenile onset) and on 23 healthy age- and sex-matched controls for both groups. Serum prolactin level was also assessed in the patients and control by ELISA. The study revealed that the level of pSTAT5 was higher in adult SLE patients than in healthy control (p = 0.001) and in juvenile-onset SLE patients versus age-matched control (p = 0.031). A positive correlation existed between the pSTAT5 levels and Systemic Lupus Activity Measure (SLAM) score and also with multiple clinical manifestations indicating a potential role of STAT5 signaling in pathogenesis SLE. The pSTAT5 signaling is implicated in the disease activity of SLE and may be a useful target of therapy by correcting the dysregulation of cytokines involved in the disease pathogenesis.

Modulatory Effects of Mild Carbon Monoxide Exposure in the Developing Mouse Cochlea

Carbon monoxide (CO) is well known as a highly toxic poison at high concentrations, yet in physiologic amounts it is an endogenous biological messenger in organs such as the internal ear and brain. In this study we tested the hypothesis that chronic very mild CO exposure at concentrations 25-ppm increases the expression of oxidative stress protecting enzymes within the cellular milieu of the developing inner ear (cochlea) of the normal CD-1 mouse. In addition we tested also the hypothesis that CO can decrease the pre-existing condition of oxidative stress in the mouse model for the human medical condition systemic lupus erythematosus by increasing two protective enzymes heme-oxygenase-1 (HO-1), and superoxide dismutase-2 (SOD-2). CD-1 and MRL/lpr mice were exposed to mild CO concentrations (25 ppm in air) from prenatal only and prenatal followed by early postnatal day 5 to postnatal day 20. The expression of cell markers specific for oxidative stress, and related neural/endothelial markers were investigated at the level of the gene products by immunohistochemistry, proteomics and mRNA expression (quantitative real time-PCR). We found that in the CD-1 and MRL/lpr mouse cochlea SOD-2 and HO-1 were upregulated. In this mouse model of autoimmune disease defense mechanism are attenuated, thus mild CO exposure is beneficial. Several genes (mRNA) and proteins detected by proteomics involved in cellular protection were upregulated in the CO exposed CD-1 mouse and the MRL/lpr mouse.

What is damaging the kidney in lupus nephritis?

Despite marked improvements in the survival of patients with severe lupus nephritis over the past 50 years, the rate of complete clinical remission after immune suppression therapy is <50% and renal impairment still occurs in 40% of affected patients. An appreciation of the factors that lead to the development of chronic kidney disease following acute or subacute renal injury in patients with systemic lupus erythematosus is beginning to emerge. Processes that contribute to end-stage renal injury include continuing inflammation, activation of intrinsic renal cells, cell stress and hypoxia, metabolic abnormalities, aberrant tissue repair and tissue fibrosis. A deeper understanding of these processes is leading to the development of novel or adjunctive therapies that could protect the kidney from the secondary non-immune consequences of acute injury. Approaches based on a molecular-proteomic-lipidomic classification of disease should yield new information about the functional basis of disease heterogeneity so that the most effective and least toxic treatment regimens can be formulated for individual patients.

Paradoxical effects of all-trans-retinoic acid on lupus-like disease in the MRL/lpr mouse model

Roles of all-trans-retinoic acid (tRA), a metabolite of vitamin A (VA), in both tolerogenic and immunogenic responses are documented. However, how tRA affects the development of systemic autoimmunity is poorly understood. Here we demonstrate that tRA have paradoxical effects on the development of autoimmune lupus in the MRL/lpr mouse model. We administered, orally, tRA or VA mixed with 10% of tRA (referred to as VARA) to female mice starting from 6 weeks of age. At this age, the mice do not exhibit overt clinical signs of lupus. However, the immunogenic environment preceding disease onset has been established as evidenced by an increase of total IgM/IgG in the plasma and expansion of lymphocytes and dendritic cells in secondary lymphoid organs. After 8 weeks of tRA, but not VARA treatment, significantly higher pathological scores in the skin, brain and lung were observed. These were accompanied by a marked increase in B-cell responses that included autoantibody production and enhanced expression of plasma cell-promoting cytokines. Paradoxically, the number of lymphocytes in the mesenteric lymph node decreased with tRA that led to significantly reduced lymphadenopathy. In addition, tRA differentially affected renal pathology, increasing leukocyte infiltration of renal tubulointerstitium while restoring the size of glomeruli in the kidney cortex. In contrast, minimal induction of inflammation with tRA in the absence of an immunogenic environment in the control mice was observed. Altogether, our results suggest that under a predisposed immunogenic environment in autoimmune lupus, tRA may decrease inflammation in some organs while generating more severe disease in others.

Self DNA from lymphocytes that have undergone activation-induced cell death enhances murine B cell proliferation and antibody production

Systemic lupus erythematosus (SLE) is characterized by prominent autoinflammatory tissue damage associated with impaired removal of dying cells and DNA. Self DNA-containing immune complexes are able to activate both innate and adaptive immune responses and play an important role in the maintenance and exacerbation of autoimmunity in SLE. In this study, we used DNA from lymphocytes that have undergone activation-induced cell death (ALD-DNA) and analyzed its role on the activation and differentiation of B cells from normal BALB/c mice as well as lupus-prone MRL^+/+ and MRL/lpr mice. We found that ALD-DNA directly increased the expression of costimulatory molecules and the survival of naïve B cells in vitro. Although ALD-DNA alone had little effect on the proliferation of naïve B cells, it enhanced LPS-activated B cell proliferation in vitro and in vivo. In addition, ALD-DNA increased plasma cell numbers and IgG production in LPS-stimulated cultures of naïve B cells, in part via enhancing IL-6 production. Importantly, B cells from lupus mice were hyperresponsive to ALD-DNA and/or LPS relative to normal control B cells in terminal plasma cell differentiation, as evidenced by increases in CD138⁺ cell numbers, IgM production, and mRNA levels of B lymphocyte-induced maturation protein-1 (Blimp-1) and the X-box binding protein 1 (XBP1). Furthermore, ALD-DNA enhanced CD40-activated naïve B cell proliferation. Collectively, these data indicate that self DNA can serve as a DAMP (damage-associated molecular pattern) that cooperates with signals from both innate and adaptive immunity to promote polyclonal B cell activation, a common characteristic of autoimmune diseases.

Comparative transcriptional profiling of 3 murine models of SLE nephritis reveals both unique and shared regulatory networks

Objective

To define shared and unique features of SLE nephritis in mouse models of proliferative and glomerulosclerotic renal disease.

Methods

Perfused kidneys from NZB/W F1, NZW/BXSB and NZM2410 mice were harvested before and after nephritis onset. Affymetrix based gene expression profiles of kidney RNA were analyzed using Genomatix Pathway Systems and Ingenuity Pathway Analysis software. Gene expression patterns were confirmed using real-time PCR.

Results

955, 1168 and 755 genes were regulated in the kidneys of nephritic NZB/W F1, NZM2410 and NZW/BXSB mice respectively. 263 genes were regulated concordantly in all three strains reflecting immune cell infiltration, endothelial cell activation, complement activation, cytokine signaling, tissue remodeling and hypoxia. STAT3 was the top associated transcription factor, having a binding site in the gene promoter of 60/263 regulated genes. The two strains with proliferative nephritis shared a macrophage/DC infiltration and activation signature. NZB/W and NZM2410 mice shared a mitochondrial dysfunction signature. Dominant T cell and plasma cell signatures in NZB/W mice reflected lymphoid aggregates; this was the only strain with regulatory T cell infiltrates. NZW/BXSB mice manifested tubular regeneration and NZM2410 mice had the most metabolic stress and manifested loss of nephrin, indicating podocyte loss.

Conclusions

These findings identify shared inflammatory mechanisms of SLE nephritis that can be therapeutically targeted. Nevertheless, the heterogeneity of effector mechanisms suggests that individualized therapy might need to be based on biopsy findings. Some common mechanisms are shared with non-immune–mediated renal diseases, suggesting that strategies to prevent tissue hypoxia and remodeling may be useful in SLE nephritis.

TSPAN33 is a novel marker of activated and malignant B cells

We have identified Tspan33 as a gene encoding a transmembrane protein exhibiting a restricted expression pattern including expression in activated B cells. TSPAN33 is a member of the tetraspanin family. TSPAN33 is not expressed in resting B cells, but is strongly induced in primary human B cells following activation. Human 2E2 cells, a Burkitt's lymphoma-derived B cell model of activation and differentiation, also upregulate TSPAN33 upon activation. TSPAN33 is expressed in several lymphomas including Hodgkin's and Diffuse large B cell lymphoma. TSPAN33 is also expressed in some autoimmune diseases where B cells participate in the pathology, including rheumatoid arthritis patients, systemic lupus erythematosus (SLE), and in spleen B cells from MRL/Fas(lpr/lpr) mice (a mouse model of SLE). We conclude that TSPAN33 may be used as a diagnostic biomarker or as a target for therapeutic antibodies for treatment of certain B cell lymphomas or autoimmune diseases.

Fueling autoimmunity: type I interferon in autoimmune diseases

In recent years, active research using genomic, cellular and animal modeling approaches has revealed the fundamental forces driving the development of autoimmune diseases. Type I interferon imprints unique molecular signatures in a list of autoimmune diseases. Interferon is induced by diverse nucleic acid-containing complexes, which trigger innate immune activation of plasmacytoid dendritic cells. Interferon primes, activates or differentiates various leukocyte populations to promote autoimmunity. Accordingly, interferon signaling is essential for the initiation and/or progression of lupus in several experimental models. However, the heterogeneous nature of systemic lupus erythematosus requires better characterization on how interferon pathways are activated and subsequently promote the advancement of autoimmune diseases. Given the central role of type I interferon, various strategies are devised to target these cytokines or related pathways to curtail the progression of autoimmune diseases.

Anti-IFN-α/β receptor antibody treatment ameliorates disease in lupus-predisposed mice

The demonstration in humans and mice that nucleic acid-sensing TLRs and type I IFNs are essential disease mediators is a milestone in delineating the mechanisms of lupus pathogenesis. In this study, we show that Ifnb gene deletion does not modify disease progression in NZB mice, thereby strongly implicating IFN-α subtypes as the principal pathogenic effectors. We further document that long-term treatment of male BXSB mice with an anti-IFN-α/β receptor Ab of mouse origin reduced serologic, cellular, and histologic disease manifestations and extended survival, suggesting that disease acceleration by the Tlr7 gene duplication in this model is mediated by type I IFN signaling. The efficacy of this treatment in BXSB mice was clearly evident when applied early in the disease process, but only partial reductions in some disease characteristics were observed when treatment was initiated at later stages. A transient therapeutic effect was also noted in the MRL-Fas(lpr) model, although overall mortality was unaffected. The combined findings suggest that IFN-α/β receptor blockade, particularly when started at early disease stages, may be a useful treatment approach for human systemic lupus erythematosus and other autoimmune syndromes.

Beneficial effect of novel proteasome inhibitors in murine lupus via dual inhibition of type I interferon and autoantibody-secreting cells

OBJECTIVE

To investigate the hypothesis that proteasome inhibition may have potential in the treatment of SLE, by targeting plasmacytoid dendritic cells (PDCs) and plasma cells, both of which are critical in disease pathogenesis.

METHODS

Lupus-prone mice were treated with the nonselective proteasome inhibitors carfilzomib and bortezomib, the immunoproteasome inhibitor ONX 0914, or vehicle control. Tissue was harvested and analyzed by flow cytometry using standard markers. Nephritis was monitored by evaluation for proteinuria and by histologic analysis of kidneys. Serum anti-double-stranded DNA (anti-dsDNA) levels were measured by enzyme-linked immunosorbent assay (ELISA), and total IgG and dsDNA antibody-secreting cells (ASCs) by enzyme-linked immunospot assay. Human peripheral blood mononuclear cells or mouse bone marrow cells were incubated with Toll-like receptor (TLR) agonists and proteasome inhibitors, and interferon-α (IFNα) levels were measured by ELISA and flow cytometry.

RESULTS

Early treatment of lupus-prone mice with the dual-targeting proteasome inhibitors carfilzomib or bortezomib or the immunoproteasome-specific inhibitor ONX 0914 prevented disease progression, and treatment of mice with established disease dramatically abrogated nephritis. Treatment had profound effects on plasma cells, with greater reductions in autoreactive than in total IgG ASCs, an effect that became more pronounced with prolonged treatment and was reflected in decreasing serum autoantibody levels. Notably, proteasome inhibition efficiently suppressed production of IFNα by TLR-activated PDCs in vitro and in vivo, an effect mediated by inhibition of both PDC survival and PDC function.

CONCLUSION

Inhibition of the immunoproteasome is equally efficacious as dual targeting agents in preventing lupus disease progression by targeting 2 critical pathways in disease pathogenesis, type I IFN activation and autoantibody production by plasma cells.

Inhibition of the TWEAK/Fn14 pathway attenuates renal disease in nephrotoxic serum nephritis

Previously it was shown that the TNF superfamily member TWEAK (TNFSF12) acts through its receptor, Fn14, to promote proinflammatory responses in kidney cells, including the production of MCP-1, RANTES, IP-10 and KC. In addition, the TWEAK/Fn14 pathway promotes mesangial cell proliferation, vascular cell activation, and renal cell death. To study the relevance of the TWEAK/Fn14 pathway in the pathogenesis of antibody-induced nephritis using the mouse model of nephrotoxic serum nephritis (NTN), we induced NTN by passive transfer of rabbit anti-glomerular antibodies into Fn14 knockout (KO) and wild type (WT) mice. Severe proteinuria as well as renal histopathology were induced in WT but not in Fn14 KO mice. Similarly, a pharmacologic approach of anti-TWEAK mAb administration into WT mice in the NTN model significantly ameliorated proteinuria and improved kidney histology. Anti-TWEAK treatment did not affect the generation of mouse anti-rabbit antibodies; however, within the kidney there was a significant decrease in glomerular immunoglobulin deposition, as well as macrophage infiltrates and tubulointerstitial fibrosis. The mechanism of action is most likely due to reductions in downstream targets of TWEAK/Fn14 signaling, including reduced renal expression of MCP-1, VCAM-1, IP-10, RANTES as well as Fn14 itself, and other molecular pathways associated with fibrosis in anti-TWEAK treated mice. Thus, TWEAK/Fn14 interactions are instrumental in the pathogenesis of nephritis in the NTN model, apparently mediating a cascade of pathologic events locally in the kidney rather than by impacting the systemic immune response. Disrupting TWEAK/Fn14 interactions may be an innovative kidney-protective approach for the treatment of lupus nephritis and other antibody-induced renal diseases.

Role of TWEAK in lupus nephritis: a bench-to-bedside review

There is significant unmet need in the treatment of lupus nephritis (LN) patients. In this review, we highlight the role of the TWEAK/Fn14 pathway in mediating key pathologic processes underlying LN involving both glomerular and tubular injury, and thus the potential for renal protection via blockade of this pathway. The specific pathological mechanisms of TWEAK - namely promoting inflammation, renal cell proliferation and apoptosis, vascular activation and fibrosis - are described, with supporting data from animal models and in vitro systems. Furthermore, we detail the translational relevance of these mechanisms to clinical readouts in human LN. We present the opportunity for an anti-TWEAK therapeutic as a renal protective agent to improve efficacy relative to current standard of care treatments hopefully without increased safety risk, and highlight a phase II trial with BIIB023, an anti-TWEAK neutralizing antibody, designed to assess efficacy in LN patients. Taken together, targeting the TWEAK/Fn14 axis represents a potential new therapeutic paradigm for achieving renal protection in LN patients.

Myeloid dendritic cells from B6.NZM Sle1/Sle2/Sle3 lupus-prone mice express an IFN signature that precedes disease onset

Patients with systemic lupus erythematosus show an overexpression of type I IFN-responsive genes that is referred to as "IFN signature." We found that B6.NZMSle1/Sle2/Sle3 (Sle1,2,3) lupus-prone mice also express an IFN signature compared with non-autoimmune C57BL/6 mice. In vitro, myeloid dendritic cells (mDCs) (GM-CSF bone marrow-derived dendritic cells; BMDCs) from Sle1,2,3 mice constitutively overexpressed IFN-responsive genes such as IFN-β, Oas-3, Mx-1, ISG-15, and CXCL10 and members of the IFN signaling pathway STAT1, STAT2, and IRF7. The IFN signature was similar in Sle1,2,3 BMDCs from young, pre-autoimmune mice and from mice with high titers of autoantibodies, suggesting that the IFN signature in mDCs precedes disease onset and is independent from the autoantibodies. Sle1,2,3 BMDCs hyperresponded to stimulation with IFN-α and the TLR7 and TLR9 agonists R848 and CpGs. We propose that this hyperresponse is induced by the IFN signature and only partially contributes to the signature, as oligonucleotides inhibitory for TLR7 and TLR9 only partially suppressed the constitutive IFN signature, and pre-exposure to IFN-α induced the same hyperresponse in wild-type BMDCs as in Sle1,2,3 BMDCs. In vivo, mDCs and to a lesser extent T and B cells from young prediseased Sle1,2,3 mice also expressed the IFN signature, although they lacked the strength that BMDCs showed in vitro. Sle1,2,3 plasmacytoid DCs expressed the IFN signature in vitro but not in vivo, suggesting that mDCs may be more relevant before disease onset. We propose that Sle1,2,3 mice are useful tools to study the role of the IFN signature in lupus pathogenesis.

From the Large Scale Expression Analysis of Lupus Nephritis to Targeted Molecular Medicine

Lupus nephritis (LN) is one of the most severe complications of systemic lupus erythematosus (SLE). Current treatments for LN lack sufficient efficacy as they do not necessarily target the LN responsible pathways and therapeutic responses vary widely in the patient population. LN mouse models have been useful in delineating disease pathogenesis and for testing novel therapies, but they do not entirely represent the events happening in human LN. This review describes how recently developed systems biology technologies can help to integrate current knowledge with large scale experimental data to generate new hypotheses and insight into the regulatory events occurring in LN.

Female and male sex hormones differentially regulate expression of Ifi202, an interferon-inducible lupus susceptibility gene within the Nba2 interval

Increased expression of IFN-inducible Ifi202 gene in certain strains of female mice is associated with susceptibility to systemic lupus erythematosus (SLE). Although, the development of SLE is known to have a strong sex bias, the molecular mechanisms remain unknown. Here we report that in vivo treatment of orchiectomized (NZB x NZW)F(1) male mice with the female sex hormone 17beta-estradiol significantly increased steady-state levels of Ifi202 mRNA in splenic cells, whereas treatment with the male hormone dihydrotestosterone decreased the levels. Moreover, increased expression of Ifi202 in B6.Nba2 B cells and reduced expression in T cells were associated with increased levels of estrogen receptor-alpha (ERalpha) and androgen receptor, respectively. Furthermore, the steady-state levels of Ifi202 mRNA were higher in splenic cells from C57BL/6, B6.Nba2, NZB, and (NZB x NZW)F(1) female mice as compared with males. 17beta-estradiol treatment of B cells and WT276 cells increased Ifi202 mRNA levels, whereas treatment with dihydrotestosterone decreased the levels. Interestingly, overexpression of ERalpha in WT276 cells increased the expression of Ifi202 and stimulated the activity of the 202-luc-reporter through the c-Jun/AP-1 DNA-binding site. Accordingly, ERalpha preferentially associated with the regulatory region of the Ifi202 gene in female B6.Nba2 B cells than in males. Furthermore, Ifi202 mRNA levels were detectable in splenic cells of wild-type (Esr1(+/+)), but not null (Esr1(-/-)), (NZB x NZW)F(1) female mice. Collectively, our observations demonstrate that the female and male sex hormones differentially regulate the expression of Ifi202, thus providing support for the role of Ifi202 in sex bias in SLE.

Stage dependent aberrant regulation of cytokine-STAT signaling in murine systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease of unknown etiology that involves multiple interacting cell types driven by numerous cytokines and autoimmune epitopes. Although the initiating events leading to SLE pathology are not understood, there is a growing realization that dysregulated cytokine action on immune cells plays an important role in promoting the inflammatory autoimmune state. We applied phospho-specific flow cytometry to characterize the extent to which regulation of cytokine signal transduction through the STAT family of transcription factors is disturbed during the progression of SLE. Using a panel of 10 cytokines thought to have causal roles in the disease, we measured signaling responses at the single-cell level in five immune cell types from the MRLlpr murine model. This generated a highly multiplexed view of how cytokine stimuli are processed by intracellular signaling networks in adaptive and innate immune cells during different stages of SLE pathogenesis. We report that robust changes in cytokine signal transduction occur during the progression of SLE in multiple immune cell subtypes including increased T cell responsiveness to IL-10 and ablation of Stat1 responses to IFNalpha, IFNgamma, IL-6, and IL-21, Stat3 responses to IL-6, Stat5 responses to IL-15, and Stat6 responses to IL-4. We found increased intracellular expression of Suppressor of Cytokine Signaling 1 protein correlated with negative regulation of Stat1 responses to inflammatory cytokines. The results provide evidence of negative feedback regulation opposing inflammatory cytokines that have self-sustaining activities and suggest a cytokine-driven oscillator circuit may drive the periodic disease activity observed in many SLE patients.

Murine B cell response to TLR7 ligands depends on an IFN-beta feedback loop

Type I IFNs play an important, yet poorly characterized, role in systemic lupus erythematosus. To better understand the interplay between type I IFNs and the activation of autoreactive B cells, we evaluated the effect of type I IFN receptor (IFNAR) deficiency in murine B cell responses to common TLR ligands. In comparison to wild-type B cells, TLR7-stimulated IFNAR(-/-) B cells proliferated significantly less well and did not up-regulate costimulatory molecules. By contrast, IFNAR1(-/-) B cells did not produce cytokines, but did proliferate and up-regulate activation markers in response to other TLR ligands. These defects were not due to a difference in the distribution of B cell populations or a failure to produce a soluble factor other than a type I IFN. Instead, the compromised response pattern reflected the disruption of an IFN-beta feedback loop and constitutively low expression of TLR7 in the IFNAR1(-/-) B cells. These results highlight subtle differences in the IFN dependence of TLR7 responses compared with other TLR-mediated B cell responses.

ICOS controls effector function but not trafficking receptor expression of kidney-infiltrating effector T cells in murine lupus

Renal pathology in systemic lupus erythematosus involves both autoantibody deposition and a cellular inflammatory response, both of which are mediated by effector CD4 T cells. MRL(lpr) mice spontaneously develop massive perivascular infiltrates, but the pathways that regulate the development, trafficking, and effector functions of kidney-infiltrating T cells are poorly defined. To address these questions, we first surveyed inflammatory chemokine protein levels in nephritic kidneys from lupus-prone MRL(lpr) mice. After identifying highly elevated levels of the CXCR3 ligand CXCL9, we found that kidney-infiltrating effectors are enriched for expression of CXCR3, as well as P-selectin ligand and ICOS. Using genetic ablation, we demonstrate that ICOS plays an essential role in the establishment of renal perivascular infiltrates, although a small number of infiltrating cells remain around the blood vessels. Interestingly, though IgG autoantibody production is substantially reduced in Icos(-/-) MRL(lpr) mice, the progression of immune complex glomerulonephritis is only modestly diminished and the production of inflammatory chemokines, such as CXCL9, remains high in the kidney. We find that Icos(-/-) effector cell numbers are only slightly reduced and these have normal expression of CXCR3 and P-selectin ligand with intact migration to CXCL9. However, they have impaired production of inflammatory cytokines and fail to show evidence of efficient proliferation in the kidney. Thus, while dispensable for acquisition of renal trafficking receptor expression, ICOS is strictly required for local inflammatory functions of autoreactive CD4 T cells in murine lupus.

Mapping similarities in mTOR pathway perturbations in mouse lupus nephritis models and human lupus nephritis

Introduction

Treatment with sirolimus, a mammalian target of rapamycin (mTOR) inhibitor, has been shown to be efficacious in the MRL/lpr and NZB × NZW F1 mouse models of lupus nephritis, indicating a critical role for the mTOR pathway in both models. This type of demonstration of efficacy in animal models is usually a pre-requisite for advancement into clinical development. However, efficacy in an animal model often has not translated to the desired activity in the clinic. Therefore, a more profound understanding of the mechanistic similarities and differences between various animal models and human diseases is highly desirable.

Methods

Transcriptional profiling was performed on kidneys from mice with lupus nephritis; from mice who had efficacious drug treatment; and from mice before they developed nephritis. Analysis of variance with false discovery rate adjusted to p < 0.05 and an average fold change of two or more was used to identify transcripts significantly associated with disease and response to therapy. Pathway analyses (using various bioinformatics tools) were carried out to understand the basis for drug efficacy in the mouse model. The relevance in human lupus of the pathways identified in the mouse model was explored using information from several databases derived from the published literature.

Results

We identified a set of nephritis-associated genes in mouse kidney. Expression of the majority of these returned to asymptomatic levels on sirolimus treatment, confirming the correlation between expression levels and symptoms of nephritis. Network analysis showed that many of these nephritis genes are known to interact with the mTOR pathway. This led us to ask what human diseases are linked to the mTOR pathway. We constructed the mTOR pathway interactome consisting of proteins that interact with members of the mTOR pathway and identified a strong association between mTOR pathway genes and genes reported in the literature as being involved in human lupus.

Conclusions

Our findings implicate the mTOR pathway as a critical contributor to human lupus. This broad pathway-based approach to understanding the similarities in, and differences between, animal models and human diseases may have broader utility.