Induced murine models of systemic lupus erythematosus

Lupus susceptibility gene Pbx1 controls the development, stability, and function of regulatory T cells via Rtkn2 expression

The maintenance of regulatory T (Treg) cells critically prevents autoimmunity. Pre-B cell leukemia transcription factor 1 (Pbx1) variants are associated with lupus susceptibility, particularly through the expression of a dominant negative isoform Pbx1-d in CD4+ T cells. Pbx1-d overexpression impaired Treg cell homeostasis and promoted inflammatory CD4+ T cells. Here, we showed a high expression of Pbx1 in human and murine Treg cells, which is decreased in lupus patients and mice. Pbx1 deficiency or Pbx1-d overexpression reduced the number, stability, and suppressive activity of Treg cells, which increased murine responses to immunization and autoimmune induction. Mechanistically, Pbx1 deficiency altered the expression of genes implicated in cell cycle and apoptosis in Treg cells. Intriguingly, Rtkn2, a Rho-GTPase previously associated with Treg homeostasis, was directly transactivated by Pbx1. Our results suggest that the maintenance of Treg cell homeostasis and stability by Pbx1 through cell cycle progression prevent the expansion of inflammatory T cells that otherwise exacerbates lupus progression in the hosts.

LncRNA IL21-AS1 interacts with hnRNPU protein to promote IL21 overexpression and aberrant differentiation of Tfh cells in systemic lupus erythematosus

BACKGROUND

The aberrant differentiation of T follicular helper (Tfh) cells plays an important role in the pathogenesis of systemic lupus erythematosus (SLE). However, the mechanism of regulating Tfh cells differentiation remains unclear. Long noncoding RNAs (lncRNAs) act as important regulators in the processes of innate and adaptive immune response. Whether lncRNAs are involved in regulating Tfh cell differentiation and autoimmune responses need to be further identified.

METHODS

The characters and functions of human IL21-AS1 and its mouse homologous lncRNA (mIl21-AS) were investigated by a series of biochemical assays and cell transfection assay. mIl21-AS1 regulating humoral immune response in vivo was explored by keyhole limpet haemocyanin (KLH) and chronic graft versus host disease (cGVHD) model.

RESULTS

Human IL21-AS1 and its mouse homologous lncRNA (mIl21-AS) were identified and cloned. We uncovered that IL21-AS1 was highly expressed in CD4+ T cells of SLE patients and Tfh cells, which promoted differentiation of Tfh cells. Mechanistically, IL21-AS1 bound heterogeneous nuclear ribonucleoprotein U and recruited acetyltransferases CREB-binding protein to the promoter of IL21, leading to the transcriptional activation of IL21 and Tfh cells differentiation through increasing Histone H3 acetylation level on IL21 promoter. Moreover, Tfh proportion and antibodies production were significantly increased in mIl21-AS knock-in mice immunized with KLH. mIl21-AS1 overexpression also exacerbated the lupus-like phenotype in cGVHD mice model.

CONCLUSIONS

Our results demonstrate that IL21-AS1 activates IL21 transcription via epigenetic mechanism to promote germinal centre response, adding insight into the molecular regulation of autoimmune pathogenesis and providing a novel target for SLE treatment.

5-aminolevulinic acid combined with sodium ferrous citrate ameliorated lupus nephritis in a mouse chronic graft-versus-host disease model

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by the abnormal activation of immune cells and hypersecretion of autoantibodies and causes irreversible chronic damage, such as lupus nephritis. Chronic graft-versus-host-disease (cGvHD) in mice induced by the injection of parental mouse lymphocytes into F1 hybrids leads to a disease similar to SLE. 5-aminolevulinic acid (5-ALA) is a key progenitor of heme, and its combination with sodium ferrous citrate (SFC) can up-regulate the heme oxygenase (HO-1) expression, resulting in an anti-inflammatory effect. While HO-1 had been reported to be involved in T cell activation and can limit immune-based tissue damage through Treg suppression, which promotes effector response. Thus, we hypothesized that treatment with 5-ALA/SFC could ameliorate lupus nephritis in a mouse cGvHD model. Our results showed that 5-ALA/SFC-treatment significantly decreased the anti-double-stranded DNA (ds-DNA) autoantibodies, blood urea nitrogen (BUN) and creatinine (Cre) levels, reduced kidney inflammatory dendritic cells (DCs) and B cell activation, and increased the regulatory T cells (Tregs) at nine weeks. Furthermore, 5-ALA/SFC suppressed mRNA expression of TNF-α, IL-1β, IFN-γ and markers on DCs. In addition, we also found that 5-ALA/SFC treatment increased the HO-1 expression on donor-derived DCs and Tregs concurrently, increased the number of Tregs, and reduced the population of activated DCs, B cells and CD8+ T cells at three weeks (early stage of the disease). We thus identified a novel role of 5-ALA/SFC for therapeutically improving the symptoms of lupus nephritis in a mouse cGvHD model and expanded the current understanding of how this immunoregulatory agent can be used to generate beneficial immune responses and treat autoimmune disease.

JAK/STAT inhibitor therapy partially rescues the lipodystrophic autoimmune phenotype in Clec16a KO mice

CLEC16A is implicated in multiple autoimmune diseases. We generated an inducible whole-body knockout (KO), Clec16a^ΔUBC mice to address the role of CLEC16A loss of function. KO mice exhibited loss of adipose tissue and severe weight loss in response to defective autophagic flux and exaggerated endoplasmic reticulum (ER) stress and robust cytokine storm. KO mice were glucose tolerant and displayed a state of systemic inflammation with elevated antibody levels, including IgM, IgA, Ig2b and IgG3, significantly reduced circulating insulin levels in the presence of normal food consumption. Metabolic analysis revealed disturbances in the lipid profile, white adipose decreasing concomitantly with enhanced inflammatory response, and energy wasting. Mechanistically, endoplasmic reticulum (ER) stress triggers excessive hormone sensitive lipases (HSL) mediated lipolysis which contributes to adipose inflammation via activation of JAK-STAT, stress kinases (ERK1/2, P38, JNK), and release of multiple proinflammatory mediators. Treatment with a JAK-STAT inhibitor (tofacitinib) partially rescued the inflammatory lipodystrophic phenotype and improved survival of Clec16a^ΔUBC mice by silencing cytokine release and modulating ER stress, lipolysis, mitophagy and autophagy. These results establish a mechanistic link between CLEC16A, lipid metabolism and the immune system perturbations. In summary, our Clec16a^ΔUBC mouse model highlights multifaceted roles of Clec16a in normal physiology, including a novel target for weight regulation and mutation-induced pathophysiology.

D-mannose ameliorates autoimmune phenotypes in mouse models of lupus

BACKGROUND

Systemic lupus erythematosus is an autoimmune disease characterized by an overproduction of autoantibodies resulting from dysregulation in multiple immune cell types. D-mannose is a C- 2 epimer of glucose that exhibits immunoregulatory effects in models of autoimmune diseases, such as type 1 diabetes, induced rheumatoid arthritis, and airway inflammation. This study was conducted to evaluate the efficacy of D-mannose treatment in mouse models of lupus.

RESULTS

Firstly, the effect of D-Mannose was evaluated by flow cytometry on the in vitro activation of non-autoimmune C57BL/6 (B6) bone marrow-derived dendritic cells (BMDCs) and their ability to induce antigen-specific CD4+ T cell proliferation and activation. D-mannose inhibited the maturation of BMDCs and their induction of antigen-specific T cell proliferation and activation. In vivo, D-mannose increased the frequency of Foxp3+ regulatory T cells in unmanipulated B6 mice. To assess the effect of D-mannose in mouse models of lupus, we used the graft-versus-host disease (cGVHD) induced model and the B6.lpr spontaneous model. In the cGVHD model, D-mannose treatment decreased autoantibody production, with a concomitant reduction of the frequency of effector memory and follicular helper T cells as well as germinal center B cells and plasma cells. These results were partially validated in the B6.lpr model of spontaneous lupus.

CONCLUSION

Overall, our results suggest that D-mannose ameliorates autoimmune activation in models of lupus, at least partially due to its expansion of Treg cells, the induction of immature conventional dendritic cells and the downregulation of effector T cells activation. D-Mannose showed however a weaker immunomodulatory effect in lupus than in other autoimmune diseases.

An autoimmune disease variant of IgG1 modulates B cell activation and differentiation

The maintenance of autoreactive B cells in a quiescent state is crucial for preventing autoimmunity. Here we identify a variant of human immunoglobulin G1 (IgG1) with a Gly³⁹⁶→Arg substitution (hIgG1-G396R), which positively correlates with systemic lupus erythematosus. In induced lupus models, murine homolog Gly³⁹⁰→Arg (G390R) knockin mice generate excessive numbers of plasma cells, leading to a burst of broad-spectrum autoantibodies. This enhanced production of antibodies is also observed in hapten-immunized G390R mice, as well as in influenza-vaccinated human G396R homozygous carriers. This variant potentiates the phosphorylation of the IgG1 immunoglobulin tail tyrosine (ITT) motif. This, in turn, alters the availability of phospho-ITT to trigger longer adaptor protein Grb2 dwell times in immunological synapses, leading to hyper-Grb2-Bruton's tyrosine kinase (Btk) signaling upon antigen binding. Thus, the hIgG1-G396R variant is important for both lupus pathogenesis and antibody responses after vaccination.

Protective Role of Myeloid Cells Expressing a G-CSF Receptor Polymorphism in an Induced Model of Lupus

The genetic analysis of the lupus-prone NZM2410 mouse has identified a suppressor locus, Sle2c2, which confers resistance to spontaneous lupus in combination with NZM2410 susceptibility loci, or in the chronic graft-versus-host disease (cGVHD) induced model of lupus in the B6.Sle2c2 congenic strain. The candidate gene for Sle2c2, the Csf3r gene encoding the granulocyte colony-stimulating factor receptor (G-CSF-R/CD114), was validated when cGVHD was restored in B6.Sle2c2 mice after treatment with G-CSF. The goal of the project reported herein was to investigate the myeloid cells that confer resistance to cGVHD and to ascertain if the mechanism behind their suppression involves the G-CSF pathway. We showed that despite expressing the highest levels of G-CSF-R, neutrophils play only a modest role in the autoimmune activation induced by cGVHD. We also found reduced expression levels of G-CSF-R on the surface of dendritic cells (DCs) and a differential distribution of DC subsets in response to cGVHD in B6.Sle2c2 versus B6 mice. The CD8α⁺ DC subset, known for its tolerogenic phenotype, was expanded upon induction of cGVHD in B6.Sle2c2 mice. In addition, the deficiency of CD8α⁺ DC subset enhanced the severity of cGVHD in B6.Batf3^-/- and B6.Sle2c2 mice, confirming their role in suppression of cGVHD. B6.Sle2c2DCs presented lowered activation and antigen presentation abilities and expressed lower levels of genes associated with DC activation and maturation. Exposure to exogenous G-CSF reversed the majority of these phenotypes, suggesting that tolerogenic DCs maintained through a defective G-CSF-R pathway mediated the resistance to cGVHD in B6.Sle2c2 mice.

B lymphocytes confer immune tolerance via cell surface GARP-TGF-β complex

GARP, a cell surface docking receptor for binding and activating latent TGF-β, is highly expressed by platelets and activated Tregs. While GARP is implicated in immune invasion in cancer, the roles of the GARP-TGF-β axis in systemic autoimmune diseases are unknown. Although B cells do not express GARP at baseline, we found that the GARP-TGF-β complex is induced on activated human and mouse B cells by ligands for multiple TLRs, including TLR4, TLR7, and TLR9. GARP overexpression on B cells inhibited their proliferation, induced IgA class-switching, and dampened T cell-independent antibody production. In contrast, B cell-specific deletion of GARP-encoding gene Lrrc32 in mice led to development of systemic autoimmune diseases spontaneously as well as worsening of pristane-induced lupus-like disease. Canonical TGF-β signaling more readily upregulates GARP in Peyer patch B cells than in splenic B cells. Furthermore, we demonstrated that B cells are required for the induction of oral tolerance of T cell-dependent antigens via GARP. Our studies reveal for the first time to our knowledge that cell surface GARP-TGF-β is an important checkpoint for regulating B cell peripheral tolerance, highlighting a mechanism of autoimmune disease pathogenesis.

Toll-like receptor-9 is involved in the development of B cell stimulating factor-induced systemic lupus erythematosus

The objective of the present study was to investigate the role of Toll-like receptor (TLR)-9 in B lymphocyte stimulating factor (BLyS)-induced systemic lupus erythematosus (SLE) in mice. The anti-double stranded (ds)DNA antibody titer, levels of complement proteins (C3 and C4), interleukin (IL)-10 and the disease activity [assessed by the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level] were measured. A total of 21 transgenic female mice (aged 8-10 weeks and weighing 30-40 g) expressing the Epstein-Barr virus membrane antigen, BLLF1, were studied. Mice were randomly divided into the control, the BLyS inhibition and the TLR-9 inhibition groups, with 7 mice in each group. Mice in the blank control group received intraperitoneal injections of normal saline, mice in the BLyS inhibition group received intraperitoneal injections of anti-BR3 monoclonal antibody (5,000 ng/day) and mice in the TLR-9 inhibition group received intraperitoneal injections of anti-human TLR-9 antibody (250 ng/day). The treatment regimens continued for 10 days, followed by the collection of peripheral venous blood. The relative levels of TLR-9 mRNA were measured by reverse transcription-quantitative polymerase chain reaction. Furthermore, the BLyS protein concentration and IL-10 levels were measured by ELISA. TLR-9 mRNA, BLyS, IL-10, anti-dsDNA antibody titer, C3, C4, ESR and CRP levels of the blank control group were significantly higher than those of the other two groups (P<0.05). The differences in comparison of these indexes between the BLyS inhibition and TLR-9 inhibition groups were not statistically significant (P>0.05), with the exception of TLR-9 mRNA and BLyS. In conclusion, the TLR-9 signaling pathway may be important for BLyS-induced SLE, and regulation of the inflammatory immune level.

MicroRNA 155-deficiency leads to decreased autoantibody levels and reduced severity of nephritis and pneumonitis in pristane-induced lupus

Objective

We herein examine the role of endogenous miR155 in the development of systemic manifestations in pristane induced lupus.

Materials and methods

Systemic lupus in miR155-deficient and wild type mice was induced upon injection of pristane and analyzed after 8 months, PBS-injected mice served as controls. Glomerulonephritis and pneumonitis were quantified using the kidney biopsy score and a newly adapted histomorphometric image analysis system; lung tissue was further analyzed by tissue cytometry. Serum levels of anti-dsDNA, anti-histone and anti-chromatin antibodies were measured by ELISA. Frequencies of B cells, activated and regulatory CD4⁺ T cells as well as Th1, Th2, Th17 cells were measured by flow cytometry. RT-qPCR was used to measure expression levels of interferon-signature and T-cell subset related as well as miR155-associated genes.

Results

After induction of lupus, miR155-deficient mice had significant less pulmonary involvement (perivascular inflammatory area in mm2/mm2 lung area 0.00092±0.00015 vs. 0.0027±0.00075, p = 0.0347) and renal disease (glomerular activity score 1.95±0.19 vs 3±0.26, p = 0.0029) compared to wild types. MiR155-deficient mice had significantly lower serum levels of disease-associated auto-antibodies and decreased frequencies of activated CD4⁺CD25⁺ (Foxp3^-) cells. Upon restimulation, CD4⁺ cells showed a less pronounced Th2 and Th17 and a slightly decreased Th1 response in mir155-deficient mice. Pristane-treated wild types showed significantly up-regulated expression of genes related to the INF-signature (MX1, IP10, IRF7, ISG15).

Conclusions

MiR155-deficient mice had less severe organ involvement, lower serum auto-antibody levels, a less prominent T cell response and lower expressions of genes jointly responsible for disease development. Thus, antagonizing miR155 might be a future approach in treating SLE.

Assessing Autophagy in Mouse Models and Patients with Systemic Autoimmune Diseases

Autophagy is a tightly regulated mechanism that allows cells to renew themselves through the lysosomal degradation of proteins, which are misfolded or produced in excess, and of damaged organelles. In the context of immunity, recent research has specially attempted to clarify its roles in infection, inflammation and autoimmunity. Autophagy has emerged as a spotlight in several molecular pathways and trafficking events that participate to innate and adaptive immunity. Deregulation of autophagy has been associated to several autoimmune diseases, in particular to systemic lupus erythematosus. Nowadays, however, experimental data on the implication of autophagy in animal models of autoimmunity or patients remain limited. In our investigations, we use Murphy Roths Large (MRL)/lymphoproliferation (lpr) lupus-prone mice as a mouse model for lupus and secondary Sjögren's syndrome, and, herein, we describe methods applied routinely to analyze different autophagic pathways in different lymphoid organs and tissues (spleen, lymph nodes, salivary glands). We also depict some techniques used to analyze autophagy in lupus patient's blood samples. These methods can be adapted to the analysis of autophagy in other mouse models of autoinflammatory diseases. The understanding of autophagy implication in autoimmune diseases could prove to be very useful for developing novel immunomodulatory strategies. Our attention should be focused on the fact that autophagy processes are interconnected and that distinct pathways can be independently hyper-activated or downregulated in distinct organs and tissues of the same individual.

Recent advances in the understanding of renal inflammation and fibrosis in lupus nephritis

Lupus nephritis is a potentially reversible cause of severe acute kidney injury and is an important cause of end-stage renal failure in Asians and patients of African or Hispanic descent. It is characterized by aberrant exaggerated innate and adaptive immune responses, autoantibody production and their deposition in the kidney parenchyma, triggering complement activation, activation and proliferation of resident renal cells, and expression of pro-inflammatory and chemotactic molecules leading to the influx of inflammatory cells, all of which culminate in destruction of normal nephrons and their replacement by fibrous tissue. Anti-double-stranded DNA (anti-dsDNA) antibody level correlates with disease activity in most patients. There is evidence that apart from mediating pathogenic processes through the formation of immune complexes, pathogenic anti-dsDNA antibodies can bind to resident renal cells and induce downstream pro-apoptotic, pro-inflammatory, or pro-fibrotic processes or a combination of these. Recent data also highlight the critical role of macrophages in acute and chronic kidney injury. Though clinically effective, current treatments for lupus nephritis encompass non-specific immunosuppression and the anti-inflammatory action of high-dose corticosteroids. The clinical and histological impact of novel biologics targeting pro-inflammatory molecules remains to be investigated. Insight into the underlying mechanisms that induce inflammatory and fibrotic processes in the kidney of lupus nephritis could present opportunities for more specific novel treatment options to improve clinical outcomes while minimizing off-target untoward effects. This review discusses recent advances in the understanding of pathogenic mechanisms leading to inflammation and fibrosis of the kidney in lupus nephritis in the context of established standard-of-care and emerging therapies.

In Vivo Therapeutic Success of MicroRNA-155 Antagomir in a Mouse Model of Lupus Alveolar Hemorrhage

OBJECTIVE

Diffuse alveolar hemorrhage (DAH) is a rare but life-threatening complication of systemic lupus erythematosus (SLE). Pristane-treated B6 mice develop severe DAH within 2 weeks of treatment. MicroRNA-155 (miR-155) is a pleiotropic microRNA that plays a crucial role in the regulation of immune responses. Recent studies have revealed a pathogenic role of miR-155 in various autoimmune disorders. The purpose of this study was to examine the role of miR-155 in the development of DAH in pristane-induced lupus using miR-155-knockout (miR-155(-/-)) mice and miR-155 antagomir to silence miR-155.

METHODS

DAH was induced by an intraperitoneal injection of 0.5 ml of pristane. MicroRNA-155 antagomir was administered intravenously to silence miR-155 expression. Lung tissues were collected for RNA extraction and were embedded in paraffin for sectioning. Gene expression profiling data were analyzed using Ingenuity Pathway Analysis. Real-time quantitative polymerase chain reaction analysis was used for single-gene validation. Luciferase reporter assay and argonaute 2 immunoprecipitation were performed for target validation.

RESULTS

MicroRNA-155 expression was significantly increased during the development of DAH. Disease progression was reduced in miR-155(-/-) mice as well as by in vivo silencing of miR-155 using a miR-155 antagomir. MicroRNA-155 silencing dampened pristane-induced ectopic activation of multiple inflammatory pathways and reduced the expression of proinflammatory cytokines. Several negative regulators of NF-κB signaling were inhibited by pristane and were reactivated in miR-155(-/-) mice. In particular, the antiinflammatory factor peroxisome proliferator-activated receptor α was identified as a direct target of miR-155.

CONCLUSION

MicroRNA-155 promotes pristane-induced lung inflammation. It contributes to ectopic activation of NF-κB signaling pathways by targeting multiple negative regulators. MicroRNA-155 antagomir may be a promising therapeutic strategy for treating acute lung inflammation in lupus.

Mechanisms of tumor necrosis factor α antagonist-induced lupus in a murine model

OBJECTIVE

Tumor necrosis factor α (TNFα) antagonists are effective for treating rheumatoid arthritis and other inflammatory diseases, but their use can be complicated by the development of lupus-like phenomena. This study was undertaken to investigate the role of TNFα in a murine model of lupus.

METHODS

Toll-like receptor 7 (TLR-7) ligand-driven lupus was induced by injection of pristane into C57BL/6 (B6) mice deficient in TNFα (TNFα(-/-) ) or TNFα-intact B6 mice as wild-type controls. Autoantibody and type I interferon (IFN) production was measured in each group of mice, and the effects of the presence or absence of TNFα on type I IFN-producing plasmacytoid dendritic cells (PDCs), Ly-6C(high) monocytes, and TNFα-producing neutrophils were determined.

RESULTS

TNFα(-/-) mice did not spontaneously develop autoantibodies or clinical manifestations of lupus, suggesting that TNFα deficiency alone is insufficient to cause lupus. Although the levels of type I IFN were comparable between untreated TNFα(-/-) and wild-type control mice, untreated TNFα(-/-) mice had increased circulating levels of PDCs and PDC-like cells, which enhanced the potential for production of type I IFN. When treated with pristane, TNFα(-/-) mice developed more severe lupus compared to pristane-treated controls, characterized by increased levels of anti-Sm/RNP autoantibodies, type I IFN, PDCs, and peritoneal inflammatory (Ly-6C(high) ) monocytes. In pristane-treated TNFα(-/-) mice, the numbers of neutrophils, a cell type that promotes resolution of inflammation, were decreased considerably, whereas the responses of inflammatory monocytes and PDCs and the production of type I IFN were increased and prolonged.

CONCLUSION

Low levels of TNFα will increase the number of circulating PDCs in mice, thereby enhancing the potential to produce type I IFN. However, this does not necessarily lead to type I IFN production or autoimmunity unless there is concomitant exposure to endogenous TLR-7 ligands, which are released from dead cells following pristane treatment. In humans, the rate of clearance of dead cells, along with the levels of TNFα, may influence who will develop lupus following treatment with TNFα inhibitors.

Normalization of CD4+ T cell metabolism reverses lupus

Systemic lupus erythematosus (SLE) is an autoimmune disease in which autoreactive CD4(+) T cells play an essential role. CD4(+) T cells rely on glycolysis for inflammatory effector functions, but recent studies have shown that mitochondrial metabolism supports their chronic activation. How these processes contribute to lupus is unclear. We show that both glycolysis and mitochondrial oxidative metabolism are elevated in CD4(+) T cells from lupus-prone B6.Sle1.Sle2.Sle3 (TC) mice as compared to non-autoimmune controls. In vitro, both the mitochondrial metabolism inhibitor metformin and the glucose metabolism inhibitor 2-deoxy-d-glucose (2DG) reduced interferon-γ (IFN-γ) production, although at different stages of activation. Metformin also restored the defective interleukin-2 (IL-2) production by TC CD4(+) T cells. In vivo, treatment of TC mice and other lupus models with a combination of metformin and 2DG normalized T cell metabolism and reversed disease biomarkers. Further, CD4(+) T cells from SLE patients also exhibited enhanced glycolysis and mitochondrial metabolism that correlated with their activation status, and their excessive IFN-γ production was significantly reduced by metformin in vitro. These results suggest that normalization of T cell metabolism through the dual inhibition of glycolysis and mitochondrial metabolism is a promising therapeutic venue for SLE.