Lupus-prone MRL Research Articles

Benzo[a]pyrene Exposure Reduces Cell-Type Diversity and Stimulates Sex-Biased Damage Pathways in End Organs of Lupus-Prone Mice.

Studies indicate that genetic factors only account for approximately thirty percent of all autoimmune diseases, while the rest of autoimmune pathogenesis is attributed to environmental factors including toxic chemicals. To understand if and how environmental pollutants trigger autoimmunity, we investigated the effect of benzo[a]pyrene (BaP) exposure on the development of autoimmune phenotypes in the lupus-prone MRL strain. The exposure of MRL mice to BaP over the course of 8 weeks before lupus onset resulted in total body weight loss in males, while marginal changes in anti-dsDNA levels occurred. Multi-organ analyses of BaP-treated and control MRL mice suggested that the kidney is a major organ directly affected by the metabolism of benzene-containing compounds, with increased expression of BaP-target genes including Cyp4b1 and Hao2. Intriguingly, spatial transcriptomic data showed that BaP caused a drastic reduction in cell-type diversity in both the kidneys and spleen of MRL mice. Further analysis of the molecular pathways affected suggested a sex-biased effect of BaP treatment, with the upregulated expression of angiogenesis genes in the lungs and an increased deposition of C3 in the kidneys of male mice. While SLE is more common in women, the disease is more severe in male patients, with an increased risk of disease progression to renal failure and lung cancer. Our results reveal sex-biased molecular pathways stimulated by BaP which may help explain the increased likelihood of end organ damage in males with lupus.

Silica Exposure Differentially Modulates Autoimmunity in Lupus Strains and Autoantibody Transgenic Mice.

Inhalational exposure to crystalline silica is linked to several debilitating systemic autoimmune diseases characterized by a prominent humoral immune component, but the mechanisms by which silica induces autoantibodies is poorly understood. To better understand how silica lung exposure breaks B cell tolerance and unleashes autoreactive B cells, we exposed both wildtype mice of healthy C57BL/6 and lupus-prone BXSB, MRL, and NZB strains and mice carrying an autoantibody transgene on each of these backgrounds to instilled silica or vehicle and monitored lung injury, autoimmunity, and B cell fate. Silica exposure induced lung damage and pulmonary lymphoid aggregates in all strains, including in genetically diverse backgrounds and in autoantibody transgenic models. In wildtype mice strain differences were observed in specificity of autoantibodies and site of enhanced autoantibody production, consistent with genetic modulation of the autoimmune response to silica. The unique autoantibody transgene reporter system permitted the in vivo fate of autoreactive B cells and tolerance mechanisms to be tracked directly, and demonstrated the presence of transgenic B cells and antibody in pulmonary lymphoid aggregates and bronchoalveolar lavage fluid, respectively, as well as in spleen and serum. Nonetheless, B cell enumeration and transgenic antibody quantitation indicated that B cell deletion and anergy were intact in the different genetic backgrounds. Thus, silica exposure sufficient to induce substantial lung immunopathology did not overtly disrupt central B cell tolerance, even when superimposed on autoimmune genetic susceptibility. This suggests that silica exposure subverts tolerance at alternative checkpoints, such as regulatory cells or follicle entry, or requires additional interactions or co-exposures to induce loss of tolerance. This possibility is supported by results of differentiation assays that demonstrated transgenic autoantibodies in supernatants of Toll-like receptor (TLR)7/TLR9-stimulated splenocytes harvested from silica-exposed, but not vehicle-exposed, C57BL/6 mice. This suggests that lung injury induced by silica exposure has systemic effects that subtly alter autoreactive B cell regulation, possibly modulating B cell anergy, and that can be unmasked by superimposed exposure to TLR ligands or other immunostimulants.

Age-associatedBcells expanded in autoimmune mice are memory cells sharing H-CDR3-selected repertoires.

Age-associated Bcells (ABCs) represent a distinct cell population expressing low levels of CD21 (CD21-/low ). The Ig repertoire expressed by ABCs in aged mice is diverse and exhibits signs of somatic hypermutation (SHM). A CD21-/low B-cell population is expanded in autoimmune diseases, e.g. systemic lupus erythematosus, as well as in lupus-prone NZB/W mice and in mice lacking a pre-Bcell receptor (SLC-/- ). However, the nature of the CD21-/low Bcells (hereafter ABCs) in autoimmunity is not well understood. Here we show that in young SLC-/- mice, the vast majority of the ABCs express memory B-cell (MBC) markers in contrast to wild-type controls. A similar population is present in lupus-prone MRL mice before and at disease onset. In SLC-/- mice, a majority of the ABCs are IgM+ , their VH genes have undergone SHM, show clonal diversification and clonal restriction at the H-CDR3 level. ABC hybridomas, established from SLC-/- mice, secrete typical lupus autoantibodies, e.g. anti-Smith antigen, and some of those that bind to DNA comprise a H-CDR3 that is identical to previously described IgM anti-DNA antibodies from lupus-prone mice. Together, these results reveal that ABCs in autoimmune mice are comprised of autoreactive MBCs expressing highly restricted H-CDR3 repertoires.

Renal tubular epithelial cell-derived BAFF expression mediates kidney damage and correlates with activity of proliferative lupus nephritis in mouse and men.

B-cell activating factor of the tumour necrosis factor family (BAFF) is a cytokine, mainly produced by hematopoietic cells (e.g. monocytes/macrophages, dendritic cells), indispensable for B-cell maturation. The BLISS studies have demonstrated that blocking BAFF by the human monoclonal antibody belimumab is a valuable therapeutic approach in patients with clinically and serologically active systemic lupus erythematosus (SLE). However, the defined sources of BAFF, which contributes to SLE, are still unclear. Recent findings show that BAFF expression is not restricted to myeloid cells. Since lupus nephritis is the main cause of morbidity and mortality for SLE patients, the aim of this study was to investigate whether renal tubular epithelial cells (TEC) are an important source of BAFF and thus may contribute to the pathogenesis and progression of SLE. We found BAFF expression both in cultured murine and human TEC. These results could be verified with in situ data from the kidney. Moreover, BAFF expression in the kidneys of lupus-prone MRL- Faslpr mice correlated with disease activity, and BAFF expression on TEC in biopsies of patients with diffuse proliferative lupus nephritis showed a correlation with the histopathological activity index. Invitro functional assays revealed an autocrine loop of BAFF with its binding receptors on TEC, resulting in a strong induction of colony stimulating factor-1. Finally, we identified divergent effects of BAFF on TEC depending on the surrounding milieu ('inflammatory versus non-inflammatory'). Taken together, our findings indicate that renal-derived BAFF may play an important role in the pathophysiology of the systemic autoimmune disease SLE.

Inhaled silica induces autoimmunity in a strain-dependent manner

Abstract Background Respiratory exposure to crystalline silica in man is associated with autoimmunity that includes a prominent humoral component. We hypothesize that autoimmune B cell recruitment and regulation are altered in silica-exposed lungs in genetically susceptible individuals. Methods Wildtype and autoAb transgenic (Tg+) mice of B6 and lupus-prone NZB, MRL, and BXSB backgrounds were exposed to silica dust or vehicle by oropharyngeal aspiration. After 1–3 months, lung pathology and lymphocytic infiltrates were scored. Lupus and vasculitis autoAb levels were measured in bronchoalveolar lavage fluid (BALF), serum, and supernatants from cultured lung and spleen cells. Results All silica-exposed strains showed extensive lung pathology and focal B and T cell infiltrates consistent with ectopic lymphoid structures (ELS). In wildtype mice, % lung area containing ELS after silica exposure varied by strain (BXSB>MRL>B6>NZB, p=0.03). Significant increases in autoAb production with silica exposure were observed in BALF, lung cell supernatants, and serum, and varied by genetic background. Among Tg+ mice, Tg+ Ig levels in BALF were higher in silica- vs vehicle-exposed mice in B6 and BXSB strains (p<0.05). Conclusions Respiratory exposure to silica leads to pulmonary B and T cell accumulation with ELS formation and enhanced autoAb production. This occurs in a strain-dependent manner, highlighting the impact of genetic influences on silica-induced autoimmunity. Evidence of local autoAb secretion implicates dysregulated control of autoreactive B cells at the environment/lung interface, possibly through the intermediary of silica-induced ELS.

Toll-like receptor 9 suppresses lupus disease in Fas-sufficient MRL Mice.

Genetic deficiency in TLR9 accelerates pathogenesis in the spontaneous polygenic MRL.Faslpr murine model of systemic lupus erythematosus, despite the absence of anti-nucleosome autoantibodies. However, it could be argued that this result was dependent on Fas-deficiency rather than lupus-promoting genes in the MRL genetic background. Here we report the effects of TLR9 deficiency on autoimmune disease independent of the lpr mutation in Fas by characterizing Tlr9-/- and Tlr9+/+ mice on the Fas-intact MRL/+ genetic background. By 30 weeks of age, Tlr9-deficient MRL/+ had more severe renal disease, increased T cell activation, and higher titers of anti-Sm and anti-RNA autoantibodies than Tlr9-intact animals, as had been the case in the MRL.Faslpr model. In addition, Tlr9-deficient MRL/+ mice had increased numbers of germinal center phenotype B cells and an increase in splenic neutrophils and conventional dendritic cell populations. Thus, the disease accelerating effects of Tlr9 deficiency are separable from those mediated by the Fas mutation in the lupus-prone MRL genetic background. Nonetheless, disease acceleration in Tlr9-deficient MRL/+ mice was phenotypically distinct from that in Fas-deficient counterparts, which has important implications.

Trichloroethylene Exposure Reduces Liver Injury in a Mouse Model of Primary Biliary Cholangitis.

Trichloroethylene (TCE) is a persistent environmental contaminant proposed to contribute to autoimmune disease. Experimental studies in lupus-prone MRL+/+ mice have suggested that TCE exposure can trigger autoimmune hepatitis. The vast majority of studies examining the connection between TCE and autoimmunity utilize this model, and the impact of TCE exposure in other established models of autoimmune liver disease is not known. We tested the hypothesis that TCE exposure exacerbates experimental hepatic autoimmunity in dominant negative transforming growth factor beta receptor type II (dnTGFBRII) mice, which develop serological and histological features resembling human primary biliary cholangitis. Female 8-week-old wild-type and dnTGFBRII mice were exposed to TCE (0.5 mg/ml) or vehicle (1% ethoxylated castor oil) in the drinking water for 12 or 22 weeks. Liver histopathology in 20- and 30-week-old wild-type mice was unremarkable irrespective of treatment. Mild portal inflammation was observed in vehicle-exposed 20-week-old dnTGFBRII mice and was not exacerbated by TCE exposure. Vehicle-exposed 30-week-old dnTGFBRII mice developed anti-mitochondrial antibodies, marked hepatic inflammation with necrosis, and hepatic accumulation of both B and T lymphocytes. To our surprise, TCE exposure dramatically reduced hepatic parenchymal inflammation and injury in 30-week-old dnTGFBRII mice, reflected by changes in hepatic proinflammatory gene expression, serum chemistry, and histopathology. Interestingly, TCE did not affect hepatic B cell accumulation or induction of the anti-inflammatory cytokine IL10. These data indicate that TCE exposure reduces autoimmune liver injury in female dnTGFBRII mice and suggests that the precise effect of environmental chemicals in autoimmunity depends on the experimental model.

Involvement of infiltrating macrophage-derived activin A in the progression of renal damage in MRL-lpr mice.

Lupus nephritis is a life-threatening complication of systemic lupus erythematosus (SLE). Various growth factors, cytokines, and chemokines are implicated in the development of SLE. However, the pathophysiological processes involved in the development of lupus nephritis still remain unclear. In this study, we examined the involvement of activin A, a member of the transforming growth factor β (TGF-β) superfamily, in the progression of renal damage in lupus-prone MRL-lpr mice. Activin A was not expressed in the kidneys of control MRL-MpJ mice but was detectable in perivascular infiltrating cluster of differentiation 68 (CD68)-positive cells in the kidneys of MRL-lpr mice. Urinary activin A, which was also absent in MRL-MpJ mice, was detectable in MRL-lpr mice from 16 wk onward. Urinary activin A levels were significantly correlated with the number of perivascular inflammatory cell layers, the number of crescentic glomeruli, and the percentage of Elastica van Gieson (EVG)-positive fibrotic areas, but not with urinary protein levels or serum activin A. When activin action was blocked in vivo by the intraperitoneal administration of an activin antagonist, follistatin, the number of crescentic glomeruli, percentage of EVG-positive fibrotic areas, CD68-positive cell infiltration, and proteinuria were significantly reduced in a dose-dependent manner. These data suggest that infiltrating macrophage-derived activin A is involved in the progression of renal damage in MRL-lpr mice.

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.

Toxicogenomic analysis reveals profibrogenic effects of trichloroethylene in autoimmune-mediated cholangitis in mice.

Epidemiological studies suggest that exposure to environmental chemicals increases the risk of developing autoimmune liver disease. However, the identity of specific chemical perpetrators and the mechanisms whereby environmental chemicals modify liver disease is unclear. Previous studies link exposure to trichloroethylene (TCE) with the development of autoimmune liver disease and exacerbation of autoimmunity in lupus-prone MRL mice. In this study, we utilized NOD.c3c4 mice, which spontaneously develop autoimmune cholangitis bearing resemblance to some features of primary biliary cirrhosis. Nine-week-old female NOD.c3c4 mice were given TCE (0.5 mg/ml) or its vehicle (1% Cremophor-EL) in drinking water for 4 weeks. TCE had little effect on clinical chemistry, biliary cyst formation, or hepatic CD3+ T-cell accumulation. Hepatic microarray profiling revealed a dramatic suppression of early growth response 1 (EGR1) mRNA in livers of TCE-treated mice, which was verified by qPCR and immunohistochemical staining. Consistent with a reported link between reduced EGR1 expression and liver fibrosis, TCE increased hepatic type I collagen (COL1A1) mRNA and protein levels in livers of NOD.c3c4 mice. In contrast, TCE did not increase COL1A1 expression in NOD.ShiLtJ mice, which do not develop autoimmune cholangitis. These results suggest that in the context of concurrent autoimmune liver disease with a genetic basis, modification of hepatic gene expression by TCE may increase profibrogenic signaling in the liver. Moreover, these studies suggest that NOD.c3c4 mice may be a novel model to study gene-environment interactions critical for the development of autoimmune liver disease.

Endogenous Tim-1 promotes severe systemic autoimmunity and renal disease MRL-Faslprmice

The T-cell immunoglobulin mucin 1, also known as kidney injury molecule-1, modulates CD4+ T-cell responses and is also expressed by damaged proximal tubules within the kidney. Both Th subset imbalance (Th1/Th2/Th17) and regulatory T-cell and B-cell alterations contribute to the pathogenesis of autoimmune disease. This study investigated the effects of an inhibitory anti-T-cell immunoglobulin mucin 1 antibody (RMT1-10) in lupus-prone MRL-Fas(lpr) mice. MRL-Fas(lpr) mice were treated with RMT1-10 or a control antibody intraperitoneally twice weekly from 3 mo of age for 16 wk. RMT1-10 treatment significantly improved survival, limited the development of lymphadenopathy and skin lesions, preserved renal function and decreased proteinuria, reduced serum anti-DNA antibody levels, and attenuated renal leukocyte accumulation. Th1 and Th17 cellular responses systemically and intrarenally were reduced, but regulatory T and B cells were increased. RMT1-10 treatment also reduced glomerular immunoglobulin and C3 deposition and suppressed cellular proliferation and apoptosis. Urinary excretion and renal expression of kidney injury molecule-1 was reduced, reflecting diminished interstitial injury. As RMT1-10 attenuated established lupus nephritis, manipulating immune system T-cell immunoglobulin mucin 1 may represent a therapeutic strategy in autoimmune diseases affecting the kidney.

Protective role for CCR5 in murine lupus nephritis

Leukocyte infiltration is a characteristic feature of human and experimental lupus nephritis and is closely correlated with loss of renal function. The chemokine receptor CCR5 is expressed on monocyte and T cell subsets and is thought to play an important role in recruiting these cells into inflamed organs. To investigate the functional role of CCR5 in lupus nephritis, CCR5-deficient mice were backcrossed onto the lupus-prone MRL-Fas(lpr) (MRL/lpr) genetic background. Unexpectedly, CCR5(-/-) MRL/lpr mice developed an aggravated course of lupus nephritis in terms of glomerular tissue injury and albuminuria. Deterioration of the nephritis was associated with an overall increase in mononuclear cell infiltration into the kidney, whereas renal leukocyte subtype balance, systemic T cell response, and autoantibody formation were unaffected by CCR5 deficiency. Renal and systemic protein levels of the CCR5 ligand CCL3, which can also attract leukocytes via its alternate receptor CCR1, were significantly increased in nephritic CCR5(-/-) MRL/lpr mice. Further studies revealed that the systemic increase in the CCR5/CCR1 ligand is also observed in nonimmune CCR5(-/-) C57BL/6 mice and that this increase was due to a reduced clearance, rather than an overproduction, of CCL3. Taken together, our data support the hypothesis that CCR5-dependent consumption of its own ligands may act as a negative feedback loop to restrain local chemokine levels within inflamed tissues, thereby limiting inflammatory cell influx.

Macrophages from lupus-prone MRL mice have a conditional signaling abnormality that leads to dysregulated expression of numerous genes.

Macrophages (mϕ) from pre-diseased mice of the major murine inbred models of spontaneous autoimmunity (AI), including multiple lupus-prone strains and the type I diabetes-prone NOD (non-obese diabetic) strain, have identical apoptotic target-dependent abnormalities. This characteristic feature of mϕ from AI-prone mice suggests that abnormal signaling events induced within mϕ following their interaction with apoptotic targets may predispose to AI. Such signaling abnormalities would affect predominantly the processing and presentation of self-antigen (i.e., derived from apoptotic targets), while sparing the processing and presentation of foreign antigen (i.e., derived from non-apoptotic sources). Here, we used DNA microarrays to test the hypothesis that mϕ from AI-prone mice (MRL/MpJ [MRL/+] or MRL/MpJ-Tnfrsf6 ( lpr ) [MRL/lpr]) differentially express multiple genes in comparison to non-AI mϕ (BALB/c), but do so in a largely apoptotic cell-dependent manner. Mϕ were stimulated with lipopolysaccharide, a potent innate stimulus, in the presence or absence of serum (an experimental surrogate for apoptotic targets). In accord with our hypothesis, the number of genes differentially expressed by MRL mϕ was significantly increased in the presence vs. the absence of serum, the apoptotic target surrogate (n = 401 vs. n = 201). Notably, for genes differentially expressed by MRL mϕ in the presence of serum, serum-free culture normalized their expression to a level statistically indistinguishable from that by non-AI mϕ. Comparisons of mϕ from AI-prone NOD and non-AI C57BL/6 mice corroborated these findings. Together, these data support the hypothesis that mϕ from MRL and other AI-prone mice are characterized by a conditional abnormality elicited by serum lipids or apoptotic targets.

Dominant epitope p21-40 of snRNP D protein recognized by both autoreactive T and B cells in lupus-prone MRL lpr/lpr mice (135.22)

Abstract Aberrant T and B cell responses to multiple nuclear and cytoplasmic Ags such as small nuclear ribonucleoparticles (snRNPs) are a hallmark of systemic lupus erythematosus. Although Th1 response is considered to be predominant in lupus pathogenesis, the identification of Th17 cells may challenge Th1 paradigm. To investigate the respective roles of Th1, Th17, and Treg cells in lupus development, we analyzed different T cell subsets in spleen and kidney of lupus-prone MRL lpr/lpr mice. With increasing age and disease severity, the IFN-gamma-producing T cells were significantly increased. No significant change was observed in the IL-17-secreting CD4 T cells. Furthermore, the ration of Th1/Treg was significantly increased when mice aged while Th17/Treg ratio remained unchanged. To determine the antigenic epitopes recognized by autoreactive T and B cells, synthesized peptides of autoAg snRNP D protein were used. Two epitopes were recognized by autoreactive T cells while three epitopes were recognized by autoantibodies in MRL lpr/lpr mice. Interestingly, peptide 21-40 of snRNP D protein was recognized by both autoantibodies and T cells. Furthermore, one of T cell hybridomas generated from snRNP D-immunized B10.A Tg mice was also responsive to peptide 21-40. Taken together, our studies demonstrate that Th1 response remains dominant in lupus-prone MRL lpr/lpr mice and p21-40 of snRNP D protein appears to be a pathogenic epitope that can be recognized by both autoreactive B and T cells.

Dendritic cells in the skin of autoimmune mice display an inability to migrate: a novel mechanism and role in skin inflammation (135.12)

Abstract Tissue-resident DC carry antigens to tissue-draining lymph nodes (LN) to induce immunity. To investigate the role of this DC function in the pathogenesis of autoimmune disease, we analyzed the migration of skin-resident DC, namely Langerhans cells (LC) and dermal DC, in lupus dermatitis. LC and dermal DC, but not blood-derived DC, from lupus-prone MRL-lpr and MRL+/+ mice exhibited defects in their ability to emigrate from the epidermis, to migrate through dermal lymphatics, and to immigrate into LN (JI 2008). Since conventional DC migration assays require DC activation, we used Lang-EGFP knock-in (KI) mice to visualize LC at steady-state. EGFP+ cells (LC) were lower in LN of KI MRL mice than of KI B6 mice, thus confirming what we found using inbred mice. Importantly, skin DC migration defect precedes disease and correlates with the severity of dermatitis. Conversely, treatment with αGalCer restores skin DC migration and ameliorates dermatitis. Surprisingly, αGalCer-mediated increase in skin DC migration does not require NKT cells, but is associated with epidermal γδ T cell (eγδT) expansion in a CD1d-dependent manner. Finally, eγδT are reduced in MRL mice, and deficiency of CD1d or eγδT, but not of NKT, reduces skin DC migration and worsens dermatitis. Thus, we elucidate a novel mechanism, whereby CD1d-dependent eγδT normally facilitate skin DC migration. This regulatory mechanism is impaired in lupus dermatitis, providing evidence for a novel mechanism of autoimmune disease.

Overexpression of interferon-activated gene 202 (Ifi202) correlates with the progression of autoimmune glomerulonephritis associated with the MRL chromosome 1

B6.MRLc1(82-100) congenic mice carrying the telomeric region of lupus-prone MRL chromosome 1 develop autoimmune glomerulonephritis (GN). The GN susceptibility locus of B6.MRLc1(82-100) contains the interferon activated gene 200 (Ifi200) family, which consists of Ifi202, 203, 204, and 205. Recently, Ifi202 was suggested as a candidate gene for murine lupus. In this study, we assessed the association between Ifi200 family and GN in several disease models. We compared the expression of Ifi200 family members in 24 organs between the C57BL/6 and B6.MRLc1(82-100). The expressions of Ifi200 family members differed between strains, and the most dramatic differences appeared in Ifi202 expression. Briefly, in the blood, immune organs, lungs, and testes mRNA expression was higher in B6.MRLc1(82-100) mice. In the kidney and immune organs, only Ifi202 expression increased with the development of GN in B6.MRLc1(82-100), and significant differences from C57BL/6 were observed even before disease onset. Ifi202 expression in the kidneys of BXSB, NZB/WF1, and MRL/lpr was also significantly high in the early- and late-disease stages. Furthermore, laser microdissection-reverse-transcriptase-polymerase chain reaction analysis confirmed the high Ifi202 expression in all areas of B6.MRLc1(82-100) kidneys. In conclusion, in the Ifi200 family, Ifi202 expressions in the kidney and immune organs significantly increased with GN progression.

Severe tissue trauma triggers the autoimmune state systemic lupus erythematosus in the MRL/++ lupus-prone mouse

Tissue damage associated with a severe injury can result in profound inflammatory responses that may trigger autoimmune development in lupus-prone individuals. In this study, we investigated the role of a large full-thickness cutaneous burn injury on the early onset of autoimmune disease in lupus-prone MRL/++ mice. MRL/++ mice (chronic model) exhibit autoimmune symptoms at >70 weeks of age, whereas MRL/-Fas(lpr) mice (acute model) develop autoimmune disease in 17-22 weeks due to a lymphoproliferative mutation. Autoimmune disease developed in MRL/++ mice (4-15 weeks post injury) is manifested by skin lesions, vasculitis, epidermal ulcers, cellular infiltration, splenomegaly, lymphadenopathy, hypergammaglobulinemia, elevated autoantibodies and renal pathologies including proteinuria, glomerulonephritis and immune complex deposition; complications that contribute to reduced survival. Transcription studies of wound margin tissue show a correlation between the pathogenic effects of dysregulated IL-1beta, IL-6, TNF-alpha and PGE(2) synthesis during early wound healing and early onset of autoimmune disease. Interestingly, MRL/++ mice with healed wounds (30-40 days post burn) strongly rejected skin isografts. Conversely, skin isografts transplanted onto naive age-matched MRL/++ littermates achieved long-term survival. Collectively, these findings suggest that traumatic injury exacerbates inflammatory skin disease and severe multi-organ pathogenesis in lupus-prone mice.

Mechanisms behind flare of renal lupus during murine pregnancy

The outcome of pregnancy in systemic lupus erythematosus is still controversial. The authors recently reported the disappearance of the manifestation of the skin disease but a diminished survival rate in lupus-prone animals undergoing several pregnancies. It was postulated that lupus-prone animals must have subclinical renal symptoms at an early age and that immune and hormonal changes during pregnancy exacerbate immune reactions in the kidneys, leading to a shortened life span. Here, the authors analysed changes at day 14 of pregnancy in lupus-prone LPR (MRL/lpr) mice and MRL controls regarding cytokines, regulatory T (Treg) cells and deposition of immunocomplexes. Worsened kidney function was observed during pregnancy, even in the absence of lupus signs. This was accompanied by renal inflammation and higher interferon-γ and interleukin-10 levels. C3 and immunoglobulin G deposition was enhanced in kidney and placenta from lupus-prone pregnant animals. Pregnancy enhanced the levels of Treg cells in control animals but not in lupus-prone animals. As pregnancy-induced Treg cells were shown to be specific for paternal antigens it is not to be expected that these Treg cells can help to destroy autoreactive cells. The authors conclude that early subclinical kidney disease in lupus-prone animals exacerbates during pregnancy. Albeit obtained with an experimental animal model, their data are potentially of importance for lupus patients of reproductive age.

Ability of Trichloroethylene Metabolite to Promote Immune Pathology is Strain-Specific

Chronic low-level exposure to the environmental pollutant trichloroethylene has been shown to promote autoimmune disease in association with CD4+ T-lymphocyte activation in lupus-prone MRL+/+ mice. One of the primary metabolites of trichloroethylene, trichloroacetaldehyde hydrate (TCAH), was similarly shown to increase the percentage of IFNγ-producing CD4+ T-lymphocytes when added to the drinking water of MRL+/+ mice. In addition, TCAH-treated MRL+/+ mice developed skin inflammation and alopecia. In the present study TCAH was tested for its ability to accelerate the development of alopecia in C3H/HeJ mice which tend to develop the disorder spontaneously late in life. In contrast to MRL+/+ mice, C3H/HeJ mice treated with TCAH did not develop alopecia at an increased rate. In addition, TCAH did not promote the expansion of activated IFNγ-producing CD4+ T-lymphocytes in C3H/HeJ mice. CD4+ T-lymphocytes from TCAH-treated C3H/HeJ mice, unlike their MRL+/+ counterparts, did not become resistant to activation-induced apoptosis following in vivo exposure to TCAH. Taken together, it appears that the ability of TCAH to promote immune-mediated pathology is strain-specific and may require an autoimmune-prone genetic background.

Inflammatory modulation of PPARγ expression and activity

Nitric oxide (NO) production increases with age in the lupus-prone MRL/ lpr mouse, paralleling disease activity. One mechanism for excess NO production in MRL/ lpr mice may be a defect in down-regulatory mechanisms of the iNOS pathway. A potential modulator of NO is the nuclear hormone receptor peroxisome proliferation activated receptor gamma (PPARγ). We demonstrate that renal PPARγ protein expression was altered as disease progressed in MRL/ lpr mice, which paralleled increased iNOS protein expression. Additionally, MRL/ lpr-derived primary mesangial cells expressed less PPARγ than BALB/c mesangial cells and produced more NO in response to LPS and IFNγ. Furthermore, PPARγ activity was reduced in mesangial cells following exposure to inflammatory mediators. This activity was restored with the addition of a NOS enzyme inhibitor. These results indicate that the activation of inflammatory pathways may lead to reduced activity and expression of PPARγ, further exacerbating the disease state.