Mouse Model Of Systemic Lupus Erythematosus Research Articles

Features of Neuropsychiatric Lupus in Nba2 mouse model

Abstract Background Neuropsychiatric lupus (NPSLE) is a poorly understood manifestation of the autoimmune disease systemic lupus erythematosus (SLE). NPSLE is characterized by symptoms including anxiety and depression, and recent data have suggested a pathogenic role for interferon-alpha (IFNα). Additionally, IFNα can diminish the production of the neurotransmitter serotonin, suggesting a causative link between IFNα and NPSLE. B6.Nba2 mice develop SLE in an IFNα-dependent manner making it a valuable model for the study of NPSLE. Methods Age-matched female B6.Nba2 and B6 mice were tested. Behavioral studies included open field testing (OFT), elevated plus maze (EPM), and fear conditioning (FC) tests for detection of anxiety-like behavior, and forced swim test (FST) for detection of depression-like behavior. Serum serotonin and dopamine levels were measured by ELISA and serotonin receptors were enumerated by IHC. Result Results from both OFT (p=0.001), EPM (p<0.05) and FC (p<0.05) tests supported a strong anxiety phenotype in B6.Nba2 female mice, while data from FST (p<0.05) suggested a depressive phenotype as well. B6.Nba2 females also showed significantly less serum serotonin (p<0.0001) and dopamine (p<0.05) levels than age-matched B6 females. Conclusion Our data suggests that the B6.Nba2 mouse model of SLE expresses an anxiety and depressive phenotype resembling NPSLE. Along with our previous data showing that IFNα levels are upregulated and required for disease development, our results suggest a positive correlation between IFNα, reduced serotonin, and an anxiety phenotype. Current studies are evaluating the effect of genetic IFNα-receptor manipulation in brain cells and the direct relationship between IFNα and NPSLE.

IL-2 Therapy Diminishes Renal Inflammation and the Activity of Kidney-Infiltrating CD4+ T Cells in Murine Lupus Nephritis.

An acquired deficiency of interleukin-2 (IL-2) and related disturbances in regulatory T cell (Treg) homeostasis play an important role in the pathogenesis of systemic lupus erythematosus (SLE). Low-dose IL-2 therapy was shown to restore Treg homeostasis in patients with active SLE and its clinical efficacy is currently evaluated in clinical trials. Lupus nephritis (LN), a challenging organ manifestation in SLE, is characterized by the infiltration of pathogenic CD4+ T cells into the inflamed kidney. However, the role of the Treg-IL-2 axis in the pathogenesis of LN and the mode of action of IL-2 therapy in the inflamed kidneys are still poorly understood. Using the (NZB × NZW) F1 mouse model of SLE we studied whether intrarenal Treg are affected by a shortage of IL-2 in comparison with lymphatic organs and whether and how intrarenal T cells and renal inflammation can be influenced by IL-2 therapy. We found that intrarenal Treg show phenotypic signs that are reminiscent of IL-2 deprivation in parallel to a progressive hyperactivity of intrarenal conventional CD4+ T cells (Tcon). Short-term IL-2 treatment of mice with active LN induced an expansion the intrarenal Treg population whereas long-term IL-2 treatment reduced the activity and proliferation of intrarenal Tcon, which was accompanied by a clinical and histological amelioration of LN. The association of these immune pathologies with IL-2 deficiency and their reversibility by IL-2 therapy provides important rationales for an IL-2-based immunotherapy of LN.

UNC93B1 recruits syntenin-1 to dampen TLR7 signalling and prevent autoimmunity.

At least two members of the Toll-like receptor (TLR) family, TLR7 and TLR9, can recognize self-RNA or DNA, respectively. Despite the structural and functional similarities between these receptors, their contribution to autoimmune diseases such as systemic lupus erythematosus (SLE) can be quite different. For example, TLR7 and TLR9 have opposing effects in mouse models of SLE; disease is exacerbated in TLR9-deficient mice but attenuated in TLR7-deficient mice1. However, mechanisms of negative regulation that differentiate between TLR7 and TLR9 have not been described. Here we report a new function for the TLR trafficking chaperone Unc93b1 that specifically limits signaling of TLR7, but not TLR9, and prevents TLR7-dependent autoimmunity in mice. We find that mutations in Unc93b1 leading to enhanced TLR7 signaling also disrupt binding to Syntenin-1, a protein implicated in exosome biogenesis. Both Unc93b1 and TLR7 are detectable in exosomes, suggesting that Unc93b1 recruitment of Syntenin-1 facilitates sorting of TLR7 into intralumenal vesicles of multivesicular bodies which terminates signaling. Syntenin-1 binding requires phosphorylation of Unc93b1, providing a mechanism for dynamic regulation of TLR7 activation and signaling. Thus, Unc93b1 not only enables proper trafficking of nucleic acid-sensing TLRs but also sets the activation threshold of potentially self-reactive TLR7.

Abstract 128: Leptin Accelerates Autoimmune Disease Progression and the Development of Hypertension in an Experimental Model of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder that predominately affects women and is associated with high rates of hypertension and cardiovascular disease. SLE is characterized by B and T lymphocyte dysfunction and altered cytokine production, including elevated levels of the adipocytokine leptin. Leptin promotes the expansion of proinflammatory T helper (T H ) 1 and T H 17 cells and inhibits the differentiation of regulatory T cells (T REG ). Because T cells are mechanistically linked to the development of hypertension in SLE, we hypothesized that administration of leptin would alter T H subsets and accelerate the development of hypertension in a female mouse model of SLE. To test this hypothesis, 30 week old female SLE (NZBWF1, n=21) and control (NZW, n=25) mice were implanted with minipumps to continuously deliver recombinant mouse leptin (0.5 mg/kg/day) or vehicle for four weeks. At the conclusion of the study, splenic CD4 + T H subsets were analyzed by flow cytometric analyses and no significant alterations in T H 1, T H 2, T H 17, or T REG cells were detected; however, circulating T REG in SLE mice were lower after leptin administration (1.1±0.2% SLE-vehicle vs. 0.52±0.1% SLE-leptin, p<0.05). Circulating IgG isotypes were also analyzed to correlate with T H subset activities and circulating levels of IgG2a were higher in SLE mice administered leptin (0.79±0.2 mg/mL SLE-vehicle vs. 1.2±0.05 mg/mL SLE-leptin, p<0.05), indicating increased T H 1 activity. In further support of inflammatory T cell activity, circulating levels of TNF-α and IL-17 were elevated in SLE mice administered leptin (TNF-α: 18.6±8.4 pg/mL SLE-vehicle vs. 80.5±15.9 pg/mL SLE-leptin, p<0.01) (IL-17: 0.46±0.1 pg/mL SLE-vehicle vs. 1.68±0.5 pg/mL, p<0.01). Mean arterial pressure (MAP; mmHg), measured in conscious mice by carotid catheter, was higher in SLE mice than in control mice (113±3 Control-vehicle vs. 128±3, p=0.06), and leptin further increased blood pressure in SLE mice (SLE-leptin: 134±3; p<0.01 vs. Control-vehicle and Control-leptin). In conclusion, these data suggest that leptin plays a pathogenic role in the development of hypertension in autoimmunity, in part by altering the balance of T H 1, T H 17, and T REG activity.

Characterization of acute TLR-7 agonist-induced hemorrhagic myocarditis in mice by multiparametric quantitative cardiac magnetic resonance imaging.

ABSTRACTHemorrhagic myocarditis is a potentially fatal complication of excessive levels of systemic inflammation. It has been reported in viral infection, but is also possible in systemic autoimmunity. Epicutaneous treatment of mice with the Toll-like receptor 7 (TLR-7) agonist Resiquimod induces auto-antibodies and systemic tissue damage, including in the heart, and is used as an inducible mouse model of systemic lupus erythematosus (SLE). Here, we show that overactivation of the TLR-7 pathway of viral recognition by Resiquimod treatment of CFN mice induces severe thrombocytopenia and internal bleeding, which manifests most prominently as hemorrhagic myocarditis. We optimized a cardiac magnetic resonance (CMR) tissue mapping approach for the in vivo detection of diffuse infiltration, fibrosis and hemorrhages using a combination of T1, T2 and T2* relaxation times, and compared results with ex vivo histopathology of cardiac sections corresponding to CMR tissue maps. This allowed detailed correlation between in vivo CMR parameters and ex vivo histopathology, and confirmed the need to include T2* measurements to detect tissue iron for accurate interpretation of pathology associated with CMR parameter changes. In summary, we provide detailed histological and in vivo imaging-based characterization of acute hemorrhagic myocarditis as an acute cardiac complication in the mouse model of Resiquimod-induced SLE, and a refined CMR protocol to allow non-invasive longitudinal in vivo studies of heart involvement in acute inflammation. We propose that adding T2* mapping to CMR protocols for myocarditis diagnosis improves diagnostic sensitivity and interpretation of disease mechanisms.This article has an associated First Person interview with the first author of the paper.

The Impact of Vitamin D on Cognitive Dysfunction in Mice with Systemic Lupus Erythematosus.

BackgroundA growing body of evidence suggests that systemic lupus erythematosus (SLE) may result in reversible cognitive dysfunction. Vitamin D is considered important for neurons. The therapeutic effect of vitamin D was evaluated in a rat model of SLE.Material/MethodsThere were 20 male MRL/lpr mice randomly divided into the SLE model group and the vitamin D group, in addition, 10 male C57BL 6J mice were used as the control (CON) group. Vitamin D was administered intraperitoneally (2 μg/kg) for 4 weeks. After 4 weeks of continuing intervention, we tested the cognitive function using the Morris water maze. The expression of vitamin D receptor (VDR), amyloid-β, caspase-3, and Bcl-2 were detected by western blot analysis.ResultsIn the present study, we observed that vitamin D treatment alleviated neurobehavioral deficits in the mice with SLE. At the molecular levels, administration of vitamin D activated the expression of VDR and reduced the number of dead cells in the CA1 region of the hippocampus as well as regulated caspase-3 and Bcl-2 expression.ConclusionsIn conclusion, our results indicated that vitamin D played a protective role by suppressing inflammatory cytokines, thereby ultimately inhibiting the progression of apoptosis in a mouse model of SLE. Vitamin D may be promising as a protective intervention in SLE with cognitive dysfunction, and more and more experiments are warranted for its clinical testing in the near future.

Human recombinant relaxin-2 does not attenuate hypertension or renal injury but exacerbates vascular dysfunction in a female mouse model of SLE

Systemic lupus erythematosus (SLE) is an autoimmune disease that disproportionately affects women of reproductive age and increases their risk for developing hypertension, vascular, and renal disease. Relaxin has potential beneficial therapeutic effects in cardiovascular disease through direct actions on the vasculature. The potential therapeutic benefit of relaxin on SLE-associated cardiovascular and renal risk factors like hypertension has not previously been tested. We hypothesized that relaxin would attenuate hypertension, renal injury, and vascular dysfunction in an established female mouse model of SLE (NZBWF1 mice). Serelaxin (human recombinant relaxin-2, 0.5 mg·kg-1·day-1) or vehicle was administered via osmotic mini-pump for 4 wk in female control (NZW) or SLE mice between 28 and 31 wk of age. Serelaxin treatment increased uterine weights in both groups, suggesting that the Serelaxin was bioactive. Mean arterial pressure, measured by carotid artery catheter, was significantly increased in vehicle-treated SLE mice compared with vehicle-treated controls, but was not changed by Serelaxin treatment. Albumin excretion rate, measured by ELISA, was similar between vehicle- and Serelaxin-treated SLE mice and between vehicle- and Serelaxin-treated control mice. Wire myography was performed using isolated carotid arteries to assess endothelial-independent and -dependent vasodilation, and data confirm that SLE mice have impaired endothelium-independent and -dependent relaxation compared with control mice. Serelaxin treatment did not affect endothelium-independent vasodilation, but exacerbated the endothelium-dependent dysfunction. These data suggest that, contrary to our hypothesis, Serelaxin infusion does not attenuate hypertension, renal injury, or vascular dysfunction in SLE, but worsens underlying vascular endothelial dysfunction in this experimental model of SLE. These data do not support the use of human recombinant relaxin-2 as an antihypertensive in the SLE patient population. NEW & NOTEWORTHY Relaxin is a peptide hormone commonly known for its role in pregnancy and for its use in recent clinical trials for the treatment of heart failure. Evidence suggests that relaxin has immunomodulatory effects; however, the potential therapeutic impact of relaxin in chronic immune mediated disease is unclear. This study tests whether recombinant human relaxin (Serelaxin) attenuates the progression of autoimmunity, and the associated cardiovascular consequences, in an experimental model of systemic lupus erythematosus.

Efficacy and Pharmacodynamic Modeling of the BTK Inhibitor Evobrutinib in Autoimmune Disease Models.

Because of its role in mediating both B cell and Fc receptor signaling, Bruton's tyrosine kinase (BTK) is a promising target for the treatment of autoimmune diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Evobrutinib is a novel, highly selective, irreversible BTK inhibitor that potently inhibits BCR- and Fc receptor-mediated signaling and, thus, subsequent activation and function of human B cells and innate immune cells such as monocytes and basophils. We evaluated evobrutinib in preclinical models of RA and SLE and characterized the relationship between BTK occupancy and inhibition of disease activity. In mouse models of RA and SLE, orally administered evobrutinib displayed robust efficacy, as demonstrated by reduction of disease severity and histological damage. In the SLE model, evobrutinib inhibited B cell activation, reduced autoantibody production and plasma cell numbers, and normalized B and T cell subsets. In the RA model, efficacy was achieved despite failure to reduce autoantibodies. Pharmacokinetic/pharmacodynamic modeling showed that mean BTK occupancy in blood cells of 80% was linked to near-complete disease inhibition in both RA and SLE mouse models. In addition, evobrutinib inhibited mast cell activation in a passive cutaneous anaphylaxis model. Thus, evobrutinib achieves efficacy by acting both on B cells and innate immune cells. Taken together, our data show that evobrutinib is a promising molecule for the chronic treatment of B cell-driven autoimmune disorders.

Epoxyeicosatrienoic Acid Analog EET-A Blunts Development of Lupus Nephritis in Mice.

Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disorder that causes life threatening renal disease and current therapies are limited with serious side-effects. CYP epoxygenase metabolites of arachidonic acid epoxyeicosatrienoic acids (EETs) demonstrate strong anti-inflammatory and kidney protective actions. We investigated the ability of an orally active EET analog, EET-A to prevent kidney injury in a mouse SLE model. Twenty-weeks old female NZBWF1 (SLE) and age-matched NZW/LacJ (Non SLE) were treated with vehicle or EET-A (10 mg/kg/d, p.o.) for 14 weeks and urine and kidney tissues were collected at the end of the protocol. SLE mice demonstrated marked renal chemotaxis with 30–60% higher renal mRNA expression of CXC chemokine receptors (CXCR) and CXC chemokines (CXCL) compared to Non SLE mice. In SLE mice, the elevated chemotaxis is associated with 5-15-fold increase in cytokine mRNA expression and elevated inflammatory cell infiltration in the kidney. SLE mice also had elevated BUN, serum creatinine, proteinuria, and renal fibrosis. Interestingly, EET-A treatment markedly diminished renal CXCR and CXCL renal mRNA expression in SLE mice. EET-A treatment also reduced renal TNF-α, IL-6, IL-1β, and IFN-γ mRNA expression by 70–80% in SLE mice. Along with reductions in renal chemokine and cytokine mRNA expression, EET-A reduced renal immune cell infiltration, BUN, serum creatinine, proteinuria and renal fibrosis in SLE mice. Overall, we demonstrate that an orally active EET analog, EET-A prevents renal injury in a mouse model of SLE by reducing inflammation.

Cyclophosphamide treatment for hypertension and renal injury in an experimental model of systemic lupus erythematosus.

Cardiovascular disease is the major cause of mortality among patients with the autoimmune disorder systemic lupus erythematosus (SLE). Our laboratory previously reported that immunosuppression with mycophenolate mofetil, a common therapy in patients with SLE, attenuates the development of hypertension in an experimental model of SLE. Cyclophosphamide (CYC) is another common therapy for patients with SLE that has contributed to improved disease management; however, its impact on the development of hypertension associated with SLE is not clear. We tested whether treatment with CYC (25 mg/kg, once/week, IP injection) for 4 weeks would attenuate hypertension in an established female mouse model of SLE with hypertension (30‐week‐old NZBWF1 females). Plasma anti‐dsDNA IgG levels, pathogenic for the disease, were lower in CYC‐treated SLE mice compared to vehicle‐treated SLE mice, suggesting efficacy of the therapy to suppress aberrant immune system function. Mean arterial pressure (MAP) was assessed by carotid artery catheters in conscious mice. Treatment did not attenuate the development of hypertension when compared to vehicle‐treated SLE mice; however, urinary albumin excretion was lower in CYC‐treated animals. Corresponding with the reduction in autoantibodies, data suggest that CYC treatment lowered circulating CD45R+ B cells. Paradoxically, circulating CD11b+Ly6G+ neutrophils were increased in CYC‐treated SLE mice compared to vehicle treated. Estrus cycling data also suggest that CYC treatment had an impact on ovarian function that may be consistent with reduced circulating estrogen levels. Taken together, these data suggest that CYC treatment attenuates autoantibody production and renal disease during SLE, but that the potential to affect MAP may be blunted by the increase in circulating neutrophils and CYC's impact on ovarian function.

Recombinant Human Relaxin‐2 Treatment in an Experimental Female Mouse Model of Autoimmune Disease with Hypertension

Relaxin is a peptide hormone commonly known for its role during pregnancy; however, it has been postulated to have beneficial therapeutic effects in cardiovascular disease through direct actions on the vasculature. Systemic lupus erythematosus (SLE) is an autoimmune disease that, for reasons that are not completely understood, disproportionately affects women of reproductive age and increases their risk for developing hypertension, cardiovascular and renal disease. The potential therapeutic benefit of relaxin on SLE associated cardiovascular and renal risk factors like hypertension has not previously been tested. The objective of this study was to test the efficacy of relaxin to attenuate hypertension, renal injury, and vascular dysfunction in an established female mouse model of SLE (NZBWF1 mice). To test this, Serelaxin (human recombinant relaxin‐2, 0.5 mg/kg/day) or vehicle (saline) was administered via osmotic mini‐pump (Alzet 1002) for 4 weeks in NZW (Control) or SLE mice between 28 and 31 weeks of age. Mean arterial pressure was measured by carotid artery catheters in conscious mice at the conclusion of the study. Urinary albumin excretion, a marker of renal injury, was determined at the conclusion of the study by albumin ELISA in overnight samples collected in metabolic cages. Wire myography was performed using isolated carotid arteries to assess endothelial‐independent and –dependent vasodilation in response to increasing concentrations of sodium nitroprusside and acetylcholine, respectively (10−8–10−4 M). Serelaxin‐treated control and SLE mice had significantly increased uterine weights (p<0.05) compared to vehicle‐treated mice, suggesting that the Serelaxin was bioactive. Mean arterial pressure was significantly increased in vehicle‐treated SLE mice compared to vehicle treated controls (134 ± 5 mmHg vs. 111 ± 3, n=9–12, p<0.05). Blood pressure was not changed in Serelaxin‐treated SLE (139 ± 5 mmHg, n=12) or control mice (115 ± 3 mmHg, n=10). Albumin excretion rate was similar between vehicle‐(23.6 ± 17.5 mg/day, n =11) and Serelaxin‐treated (35.7 ± 16.1 mg/day, n= 11) SLE mice, and between vehicle (1.1 ± 0.9 mg/day, n=15) and Serelaxin‐treated (0.1 ± 0.1 mg/day, n=13) control mice. Wire myography data confirm previously published studies showing that SLE mice have impaired endothelial‐independent (Figure 1) and ‐dependent (Figure 2) relaxation compared to control mice. Serelaxin treatment did not affect endothelial‐independent vasodilation, but appears to have exacerbated the endothelial‐dependent dysfunction. These data suggest that, contrary to our hypothesis, Serelaxin infusion does not attenuate hypertension, renal injury, or vascular dysfunction in SLE under these experimental conditions. In fact, Serelaxin, through its direct actions on the vasculature, may worsen the underlying vascular endothelial dysfunction in this experimental model of SLE.Support or Funding InformationVA Merit Award (BX002604‐01A2), AHA 18PRE34020108, NIH (P01HL051971, P20GM104357, U54GM115428, R01HL134711, T32HL105324‐05)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

MMP-9/Gelatinase B Degrades Immune Complexes in Systemic Lupus Erythematosus.

Systemic Lupus Erythematosus (SLE) is a common and devastating autoimmune disease, characterized by a dysregulated adaptive immune response against intracellular antigens, which involves both autoreactive T and B cells. In SLE, mainly intracellular autoantigens generate autoantibodies and these assemble into immune complexes and activate the classical pathway of the complement system enhancing inflammation. Matrix metalloproteinase-9 (MMP-9) levels have been investigated in the serum of SLE patients and in control subjects. On the basis of specific studies, it has been suggested to treat SLE patients with MMP inhibitors. However, some of these inhibitors induce SLE. Analysis of LPR−/−MMP-9−/− double knockout mice suggested that MMP-9 plays a protective role in autoantigen clearance in SLE, but the effects of MMP-9 on immune complexes remained elusive. Therefore, we studied the role of MMP-9 in the clearance of autoantigens, autoantibodies and immune complexes and demonstrated that the lack of MMP-9 increased the levels of immune complexes in plasma and local complement activation in spleen and kidney in the LPR−/− mouse model of SLE. In addition, we showed that MMP-9 dissolved immune complexes from plasma of lupus-prone LPR−/−/MMP-9−/− mice and from blood samples of SLE patients. Surprisingly, autoantigens incorporated into immune complexes, but not immunoglobulin heavy or light chains, were cleaved by MMP-9. We discovered Apolipoprotein-B 100 as a new substrate of MMP-9 by analyzing the degradation of immune complexes from human plasma samples. These data are relevant to understand lupus immunopathology and side-effects observed with the use of known drugs. Moreover, we caution against the use of MMP inhibitors for the treatment of SLE.

Expansion of regulatory T cells using low-dose interleukin-2 attenuates hypertension in an experimental model of systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disorder that is characterized by prevalent hypertension, renal injury, and cardiovascular disease. Numerous studies have reported a low prevalence and/or impaired function of regulatory T (TREG) cells in both patients with SLE and murine models of the disease. Evidence suggests that TREG cell dysfunction in SLE results from a deficiency in IL-2. Recent studies have reported that low-dose IL-2 therapy expands TREG cells in mouse models of SLE, but whether expanding TREG cells protects against hypertension and renal injury during SLE is unclear. To examine this question, female SLE (NZBWF1) and control (NZW) mice were injected with vehicle or recombinant mouse IL-2 three times in 24 h followed by single maintenance doses every 5 days for 4 wk. Treatment with IL-2 effectively expanded TREG cell populations in the peripheral blood, spleen, and kidneys. Circulating levels of anti-dsDNA IgG autoantibodies, a marker of SLE disease activity, were higher in SLE mice compared with control mice but were unaffected by IL-2 treatment. As previously reported by our laboratory, mean arterial pressure, measured in conscious mice by a carotid catheter, was higher in SLE mice than in control mice. Mean arterial pressure was significantly lower in IL-2-treated SLE mice compared with vehicle-treated SLE mice, suggesting that expanding TREG cells using low-dose IL-2 attenuates the development of hypertension. While the mechanism for the protection against hypertension is unclear, it does not appear to be related to the delay of SLE disease progression.

Gp49B is a pathogenic marker for auto-antibody-producing plasma cells in lupus-prone BXSB/Yaa mice.

AbstractImmune homeostasis is critically regulated by the balance between activating and inhibitory receptors expressed on various immune cells such as T and B lymphocytes, and myeloid cells. The inhibitory receptors play a fundamental role in the immune checkpoint pathway, thus maintaining peripheral tolerance. We recently found that expression of leukocyte immunoglobulin-like receptor (LILR)B4, an inhibitory member of the human LILR family, is augmented in auto-antibody-producing plasmablasts/plasma cells of systemic lupus erythematosus (SLE) patients. However, the mechanism behind the 'paradoxical' up-regulation of this inhibitory receptor upon pathogenic antibody-secreting cells is yet to be known. To this end, in this study, we examined if glycoprotein 49B (gp49B), the murine counterpart of human LILRB4, is also elevated in auto-antibody-producing cells in several SLE mouse models, and tried to clarify the underlying mechanism. We found that gp49B is expressed on plasma cells of lupus-prone models but not of healthy C57BL/6 mice, and the level was positively correlated to the anti-double-stranded DNA IgG titer in serum. Gp49B genetic deletion, however, did not abolish the serum auto-antibodies or fully ameliorate the lethal glomerulonephritis, indicating that gp49B is not the sole regulator of lupus but a pathogenic element in the disease. We conclude that the elevated expression of this inhibitory receptor on pathogenic plasma cells was also relevant upon the murine SLE model. The mechanism of gp49B underlying the disease progression in lupus-prone mice has been discussed.

Basophil involvement in lupus nephritis: a basis for innovation in daily care.

Lupus nephritis (LN) affects a large proportion of patients with systemic lupus erythematosus (SLE). LN can lead to end-stage renal disease depending on when it is diagnosed and on the adequacy of the treatment administered to the patient based on the class of LN. Determination of the class and activity of LN is only possible by histological analysis of kidney biopsies. In this context, the development of non-invasive early diagnostic tools for determining the class of LN and biomarkers predicting the response to treatment would greatly benefit patients with SLE. Basophils, which are one of the rarest types of circulating leucocytes, are well-established effectors of allergic and parasitic diseases. Recent advances in the understanding of the immune regulatory role of basophils in several auto immune conditions, including SLE and LN, have demonstrated their involvement in the amplification of auto-antibody production and LN pathogenesis in both human SLE and lupus-like mouse models. The present review summarizes the currently available literature describing dysregulation of basophil counts, basophil activation status and basophil activating factors in patients with SLE and the involvement of basophils in the pathogenesis of SLE. We also discuss the potential utility of these biological and immunological parameters as diagnostic and prognostic biomarkers, used alone or in combination with other known SLE and LN activity biomarkers. Finally, considering basophils as contributors to the disease, they may also constitute a future treatment target for the management of SLE and LN.

Epistatic Interactions Between Mutations of Deoxyribonuclease 1-Like 3 and the Inhibitory Fc Gamma Receptor IIB Result in Very Early and Massive Autoantibodies Against Double-Stranded DNA.

Autoantibodies against double-stranded DNA (anti-dsDNA) are a hallmark of systemic lupus erythematosus (SLE). It is well documented that anti-dsDNA reactive B lymphocytes are normally controlled by immune self-tolerance mechanisms operating at several levels. The evolution of high levels of IgG anti-dsDNA in SLE is dependent on somatic hypermutation and clonal selection, presumably in germinal centers from non-autoreactive B cells. Twin studies as well as genetic studies in mice indicate a very strong genetic contribution for the development of anti-dsDNA as well as SLE. Only few single gene defects with a monogenic Mendelian inheritance have been described so far that are directly responsible for the development of anti-dsDNA and SLE. Recently, among other mutations, rare null-alleles for the deoxyribonuclease 1 like 3 (DNASE1L3) and the Fc gamma receptor IIB (FCGR2B) have been described in SLE patients and genetic mouse models. Here, we demonstrate that double Dnase1l3- and FcgR2b-deficient mice in the C57BL/6 background exhibit a very early and massive IgG anti-dsDNA production. Already at 10 weeks of age, autoantibody production in double-deficient mice exceeds autoantibody levels of diseased 9-month-old NZB/W mice, a long established multigenic SLE mouse model. In single gene-deficient mice, autoantibody levels were moderately elevated at early age of the mice. Premature autoantibody production was accompanied by a spontaneous hyperactivation of germinal centers, early expansions of T follicular helper cells, and elevated plasmablasts in the spleen. Anti-dsDNA hybridomas generated from double-deficient mice show significantly elevated numbers of arginines in the CDR3 regions of the heavy-chain as well as clonal expansions and diversification of B cell clones with moderate numbers of somatic mutations. Our findings show a strong epistatic interaction of two SLE-alleles which prevent early and high-level anti-dsDNA autoantibody production. Both genes apparently synergize to keep in check excessive germinal center reactions evolving into IgG anti-dsDNA antibody producing B cells.

C1q restrains autoimmunity and viral infection by regulating CD8+ T cell metabolism.

Deficiency of C1q, the initiator of the complement classical pathway, is associated with the development of systemic lupus erythematosus (SLE). Explaining this association in terms of abnormalities in the classical pathway alone remains problematic because C3 deficiency does not predispose to SLE. Here, using a mouse model of SLE, we demonstrate that C1q, but not C3, restrains the response to self-antigens by modulating the mitochondrial metabolism of CD8+ T cells, which can themselves propagate autoimmunity. C1q deficiency also triggers an exuberant effector CD8+ T cell response to chronic viral infection leading to lethal immunopathology. These data establish a link between C1q and CD8+ T cell metabolism and may explain how C1q protects against lupus, with implications for the role of viral infections in the perpetuation of autoimmunity.

Protection from lethal Flu infections: lessons from a systemic lupus mouse model

Abstract Patients with systemic lupus erythematosus (SLE) are more susceptible to infections than healthy subjects but it is unknown whether this is due to disease or treatment. Using mice expressing three SLE susceptibility loci (triple congenics hereafter called TC mice) we unexpectedly found that these mice are resistant to an otherwise lethal respiratory Flu PR8 (H1N1) infection. At the naïve state, TC mice had not only more activated plasmacytoid dendritic cells, inflammatory monocytes and natural killer cells but also more activated CD8+ and CD4+ T cells with higher TNF and IFNg-producing capacity than C57BL/6J controls. At the primary effector phase following intranasal Flu PR8 infection, TC mice mounted poor antibody responses but their Flu-specific CD8+ T cell responses were greater effectors at the membrane level (higher frequencies of KLRG1+IL7R− and KLRG1+IL7R+) and at the transcriptional level (higher T-bet expression) than CD8+ T cells from C57BL/6J counterparts. PR8-immune TC mice also developed more functional Flu-specific CD8+ T cell responses than C57BL/6J mice following to a heterosubtypic Flu X-31 (H3N2) challenge. While immunosuppressive treatments of SLE in patients might be responsible of mounting poor anti-microbial immune responses, lessons from this SLE mouse model could be taken to prevent and protect against severe Flu infections.

A(1-7) reduces pathologies associated with SLE in MRL-lpr mice

Abstract Patients with Systemic Lupus Erythematosus (SLE) suffer from a chronic inflammatory autoimmune disease that causes damage to various organ systems. Even with the array of current treatments, patients with lupus are still in need of effective therapies to treat this complex, multi-system disease. Recent studies of the Renin Angiotensin System (RAS), widely known for its role in blood pressure regulation, have uncovered immunomodulatory effects. One of the more recently discovered components of RAS, angiotensin (1-7) [A(1-7)], is a bioactive peptides that affects various systems. In our study, MRL-lpr mice were treated daily with saline or A(1-7) for 6 weeks starting at 8 weeks of age. Proteinuria was monitored throughout the duration of the study. MRL-lpr mice treated with saline had higher levels of proteinuria compared to the MRL/MpJ- control mice, and A(1-7) treated MRL-lpr mice. A glomerulonephritis score revealed that the MRL-lpr mice had significant glomerular pathologies compared to MRL-MpJ mice of the same age. A(1-7) treatment significantly reduced the glomerular pathologies in the MRL-lpr mice. Treatment with A(1-7) reduced the size of both inguinal and axillary lymph nodes in MRl-lpr mice, and levels of anti-dsDNA IgG compared to the saline treated MRL-lpr mice. Treatment with A(1-7) also significantly reduced the severity of cutaneous pathologies resulting in only mild inflammation and hair loss compared to the saline treated MRL-lpr mice. Daily systemic treatment with A(1-7) significantly ameliorated disease in one of the most severe mouse models of SLE, making Mas agonists a potential target for future SLE therapies.

Splenic 6‐hydroxydopamine Worsens Renal Inflammation and Injury in a Murine Model of Systemic Lupus Erythematosus

Renal inflammation is prevalent in the chronic autoimmune disease systemic lupus erythematosus (SLE) and drives the progression of kidney injury, which contributes to the morbidity and mortality. Inflammation in SLE results from a loss of self‐tolerance and the production of autoantibodies against nuclear antigens (e.g., anti‐double‐stranded (ds) DNA autoantibodies); however, other immunoregulatory mechanisms such as the cholinergic anti‐inflammatory pathway may also be dysregulated and contribute to aberrant systemic and renal inflammation in the disease. The cholinergic anti‐inflammatory pathway is a protective, neuroimmune mechanism thought to involve neurotransmission between the parasympathetic vagus and the sympathetic splenic nerves. Although a direct anatomical connection between the vagus and the splenic nerve is controversial, stimulation of these nerves results in a decrease in the production and release of pro‐inflammatory cytokines from splenic immune cells. In order to confirm the importance of the splenic nerve in this pathway, others have used 6‐hydroxydopamine (6OHDA), a neurotoxin that depletes catecholamines, to chemically denervate the spleen and thereby dampen the sympathetic component of the cholinergic anti‐inflammatory pathway. We hypothesized that splenic injection of 6OHDA would further disrupt the cholinergic anti‐inflammatory pathway in a mouse model of SLE and result in increased renal inflammation and worsened disease severity, which would highlight the importance of the splenic nerve in quelling renal inflammation. In the current study, female SLE and control mice were injected with 6OHDA (120 μg in 60 μl saline) or vehicle directly into the spleen at 33 weeks of age (n = 6/group). To confirm splenic denervation with 6OHDA, we utilized the glyoxylic acid condensation reaction on 12 μm spleen sections of representative animals and verified that catecholamine histofluorescence was diminished in 6OHDA‐treated mice (205 vs. 111 histofluorescent foci). Renal cortical TNF‐α (normalized to total protein) was increased in SLE mice compared to controls (3.1e6 ± 1.2e5 vs. 7.8e5 ± 1.6e4 intensity units; p = 0.029), and 6OHDA exacerbated this pro‐inflammatory cytokine in SLE mice (7.6e6 ± 2.4 intensity units; p = 0.048) with no effect in controls (1.8e6 ± 7.0e5 intensity units; p = 0.697). Anti‐dsDNA autoantibodies were elevated in SLE mice compared to controls (2.1e4 ± 5.7e3 vs. 1.0e4 ± 4.7e3 activity units; p = 0.013), but 6OHDA did not alter this measure of disease severity in SLE mice (1.8e4 ± 5.2e3 activity units; p = 0.692). Albumin excretion rate (AER) was elevated in SLE mice compared to controls (160.7 ± 28.0 vs. 2.7 ± 2.7 mg/dL; p < 0.001). 6OHDA accentuated the increase in AER in SLE mice (454.2 ± 150.2 mg/dL; p = 0.010) but had no effect in controls (27.5 ± 17.0 mg/dL; p = 0.754). In summary, 6OHDA aggravated renal inflammation and injury in SLE mice indicated by heightened renal cortical TNF‐α and AER. This suggests that chemical splenic denervation may disrupt endogenous, sympathetically‐mediated anti‐inflammatory mechanisms. Further studies are needed to confirm the role of the splenic nerve in regulating renal inflammation.Support or Funding InformationFunded by AHA grants 14SDG18320033 (KWM), 16PRE29910012 (GSP), and UNTHSC Intramural FundingThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.