Upregulation of lymphoid and renal interferon-gamma mRNA in autoimmune MRL-Fas(lpr) mice with lupus nephritis

Deletion of microRNA-183-96-182 Cluster in Lymphocytes Suppresses Anti-DsDNA Autoantibody Production and IgG Deposition in the Kidneys in C57BL/6-Faslpr/lpr Mice

Dysregulated miRNAs have been implicated in the pathogenesis of systemic lupus erythematosus (SLE). Our previous study reported a substantial increase in three miRNAs located at the miR-183-96-182 cluster (miR-183C) in several autoimmune lupus-prone mice, including MRL/lpr and C57BL/6-lpr (B6/lpr). This study reports that in vitro inhibition of miR-182 alone or miR-183C by specific antagomirs in activated splenocytes from autoimmune-prone MRL/lpr and control MRL mice significantly reduced lupus-related inflammatory cytokines, interferon-gamma (IFNγ), and IL-6 production. To further characterize the role of miR-182 and miR-183C cluster in vivo in lupus-like disease and lymphocyte phenotypes, we used hCD2-iCre to generate B6/lpr mice with conditional deletion of miR-182 or miR-183C in CD2+ lymphocytes (miR-182-/-B6/lpr and miR-183C-/-B6/lpr). The miR-182-/-B6/lpr and miR-183C-/-B6/lpr mice had significantly reduced deposition of IgG immunocomplexes in the kidney when compared to their respective littermate controls, although there appeared to be no remarkable changes in renal pathology. Importantly, we observed a significant reduction of serum anti-dsDNA autoantibodies in miR-183C-/-B6/lpr mice after reaching 24 weeks-of age compared to age-matched miR-183Cfl/flB6/lpr controls. In vitro activated splenocytes from miR-182-/-B6/lpr mice and miR-183C-/-B6/lpr mice showed reduced ability to produce lupus-associated IFNγ. Forkhead box O1(Foxo1), a previously validated miR-183C miRNAs target, was increased in the splenic CD4+ cells of miR-182-/-B6/lpr and miR-183C-/-B6/lpr mice. Furthermore, in vitro inhibition of Foxo1 with siRNA in splenocytes from miR-182-/-B6/lpr and miR-183C-/-B6/lpr mice significantly increased IFNγ expression following anti-CD3/CD28 stimulation, suggesting that miR-182 and miR-183C miRNAs regulate the inflammatory IFNγ in splenocytes via targeting Foxo1. The deletion of either miR-182 alone or the whole miR-183C cluster, however, had no marked effect on the composition of T and B cell subsets in the spleens of B6/lpr mice. There were similar percentages of CD4+, CD8+, CD19+, as well as Tregs, follicular helper T (TFH), germinal center B (GCB), and plasma cells in the miR-183C-/-B6/lpr and miR-182-/-B6/lpr mice and their respective littermate controls, miR-183Cfl/flB6/lpr and miR-182fl/flB6/lpr mice. Together, our data demonstrate a role of miR-183C in the regulation of anti-dsDNA autoantibody production in vivo in B6/lpr mice and the induction of IFNγ in in vitro activated splenocytes from B6/lpr mice.

Suppressor of cytokine signaling-1 mimetic peptides attenuate lymphocyte activation in the MRL/lpr mouse autoimmune model

Autoimmune diseases are driven largely by a pathogenic cytokine milieu produced by aberrantly activated lymphocytes. Many cytokines, including interferon gamma (IFN-γ), utilize the JAK/STAT pathway for signal propagation. Suppressor of Cytokine Signaling-1 (SOCS1) is an inducible, intracellular protein that regulates IFN-γ signaling by dampening JAK/STAT signaling. Using Fas deficient, MRL/MpJ-Faslpr/J (MRL/lpr) mice, which develop lupus-like disease spontaneously, we tested the hypothesis that a peptide mimic of the SOCS1 kinase inhibitory region (SOCS1-KIR) would inhibit lymphocyte activation and modulate lupus-associated pathologies. Consistent with in vitro studies, SOCS1-KIR intraperitoneal administration reduced the frequency, activation, and cytokine production of memory CD8+ and CD4+ T lymphocytes within the peripheral blood, spleen, and lymph nodes. In addition, SOCS1-KIR administration reduced lymphadenopathy, severity of skin lesions, autoantibody production, and modestly reduced kidney pathology. On a cellular level, peritoneal SOCS1-KIR administration enhanced Foxp3 expression in total splenic and follicular regulatory T cells, reduced the effector memory/naïve T lymphocyte ratio for both CD4+ and CD8+ cells, and reduced the frequency of GL7+ germinal center enriched B cells. Together, these data show that SOCS1-KIR treatment reduced auto-reactive lymphocyte effector functions and suggest that therapeutic targeting of the SOCS1 pathway through peptide administration may have efficacy in mitigating autoimmune pathologies.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Mechanisms of tissue injury in lupus nephritis

Systemic lupus erythematosus is a prototypic autoimmune disease characterized by autoantibody production and immune complex formation/deposition in target organs such as the kidney. Resultant local inflammation then leads to organ damage. Nephritis, a major cause of morbidity and mortality in patients with lupus, occurs in approximately 50% of lupus patients. In the present review, we provide an overview of the current research and knowledge concerning mechanisms of renal injury in both lupus-prone mouse models and human lupus patients.

The tumour necrosis factor/TNF receptor superfamily: therapeutic targets in autoimmune diseases

Autoimmune diseases are characterized by the body's ability to mount immune attacks on self. This results from recognition of self-proteins and leads to organ damage due to increased production of pathogenic inflammatory molecules and autoantibodies. Over the years, several new potential therapeutic targets have been identified in autoimmune diseases, notable among which are members of the tumour necrosis factor (TNF) superfamily. Here, we review the evidence that certain key members of this superfamily can augment/suppress autoimmune diseases.

Jak/STAT signaling is involved in the inflammatory infiltration of the kidneys in MRL/lpr mice

Cytokines are known to play an important role in the pathogenesis of lupus nephritis (LN) and the Jak/STAT (Janus kinase-signal transducer and activator of transcription factor) pathway is important in mediating signal transduction of cytokines. This study examined the pathogenic role of Jak/STAT signaling in LN. MRL/lpr mice were either treated with a selective Jak2 inhibitor tyrphostin AG490 or with vehicle alone from 12 weeks of age until being sacrificed at week 20. AG490 significantly inhibited the phosphorylation of Jak2 and STAT1 (p < 0.05). Compared with the vehicle-treated mice, AG490 treatment significantly reduced proteinuria, improved renal function and suppressed histological lesions of the kidneys and salivary glands (p < 0.05). AG490 treatment significantly inhibited the renal expression of monocyte chemotactic protein (MCP)-1, interferon (IFN)-gamma and class II MHC, which was accompanied by reduced renal infiltration of T cells and macrophages (p < 0.05). In addition, AG490 treatment resulted in a decrease in serum anti-double-stranded DNA (anti-dsDNA) antibody and attenuated the deposition of IgG and C3 in the kidneys (p < 0.05). This study demonstrated that Jak/STAT pathway is implicated in the progression of renal inflammation in MRL/lpr mice and targeting this pathway may provide a potential therapeutic approach for LN.

Roles of genetic variations in signalling/immunoregulatory molecules in susceptibility to systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with a complex genetic basis that includes many susceptibility genes on multiple chromosomes. As complex human diseases like SLE involve multiple, interacting genetic and environmental determinants, identifying genes for complex traits is challenging and has had limited success so far. However, recent advances in genetic resources and technology have been providing new tools to identify the novel pathways or the sequence variants that contribute to autoimmune diseases. During the past several years, several new candidate genes have been implicated in development of SLE though association studies. In this article we describe an overview of the latest findings in the genetics of SLE, especially focusing on the genetic variations in the signalling or immunoregulatory molecules including CD28 and IRF family members.

Activation and attenuation of apoptosis of CD4+ T cells following in vivo exposure to two common environmental toxicants, trichloroacetaldehyde hydrate and trichloroacetic acid

Exposure to occupationally relevant concentrations of the environmental pollutant, trichloroethylene (TCE), in the drinking water of autoimmune-prone MRL+/+ mice has been shown to promote the generation of lupus and autoimmune hepatitis in association with the activation of Interferon-gamma (IFN-gamma)-producing CD4+ T cells. Since blocking TCE metabolism suppressed the TCE-induced alteration in immune function, the present study was initiated to determine whether the major metabolites of TCE, trichloroacetaldehyde hydrate (TCAH) and trichloroacetic acid (TCA) could also mediate these immunoregulatory affects in vivo. TCAH and TCA were administered to the drinking water of MRL+/+ mice for 4 weeks. CD4+ T cells from TCAH and TCA-treated MRL+/+ mice, unlike CD4+ T cells from control mice, demonstrated functional and phenotypic signs of activation, as evidenced by increased IFN-gamma production in association with the increased percentage of CD62L(lo) CD4+ T cells. Interestingly, it was also found that the CD4+ T cells from the TCAH and TCA-treated mice showed a decreased susceptibility to the activation-induced cell death (AICD) form of apoptosis following re-stimulation in vitro. By demonstrating that TCAH and TCA can activate CD4+ T cells and inhibit their apoptosis following in vivo exposure represents a mechanism by which environmental toxicants may induce or accelerate the development of autoimmune disease.

Modulation of renal disease in MRL/lpr mice by suberoylanilide hydroxamic acid

Epigenetic regulation of gene expression is involved in the development of many diseases. Histone acetylation is a posttranslational modification of the nucleosomal histone tails that is regulated by the balance of histone deacetylases and histone acetyltransferases. Alterations in the balance of histone acetylation have been shown to cause aberrant expression of genes that are a hallmark of many diseases, including systemic lupus erythematosus. In this study, we determined whether suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor: 1) inhibits inflammatory mediator production in vitro and 2) modulates lupus progression in vivo. Mesangial cells isolated from 10-wk-old MRL/lpr mice were stimulated with LPS/IFN-gamma and incubated with SAHA. TNF-alpha, IL-6, NO, and inducible NO synthase expression were inhibited by SAHA. We then treated MRL/lpr mice with daily injections of SAHA from age 10 to 20 wk. The animals treated with SAHA had decreased spleen size and a concomitant decrease in CD4-CD8- (double-negative) T cells compared with controls. Serum autoantibody levels and glomerular IgG and C3 deposition in SAHA-treated mice were similar to controls. In contrast, proteinuria and pathologic renal disease were significantly inhibited in the mice receiving SAHA. These data indicate that SAHA blocks mesangial cell inflammatory mediator production in vitro and disease progression in vivo in MRL/lpr mice.

Inhibition of lupus by genetic alteration of the interferon-alpha/beta receptor

Type I interferons (IFN-alphabeta) are immunoregulatory cytokines that promote both innate and adaptive immune responses. Although they have been implicated in human SLE, recent studies in mice have helped solidify this connection. By using lupus-prone mice with knockout of the IFN-alphabeta receptor, we and others have documented that lack of IFN-alphabeta leads to a marked reduction in disease manifestations, including autoantibody production, target organ damage and mortality. Furthermore, IFN-alphabeta was found to potentially contribute to several levels of disease pathogenesis. These included the differentiation and activation of dendritic cells, the activation and proliferation of T cells, T cell survival and the activation and survival of autoantibody-producing B cells. These findings strongly support the targeting of IFN-alphabeta in SLE and suggest that definition of the specific pathways critical for disease induction will be important for optimal intervention.

Enhanced expression of interferon-inducible protein 10 associated with Th1 profiles of chemokine receptor in autoimmune pulmonary inflammation of MRL/lpr mice

MRL/Mp-lpr/lpr (MRL/lpr) mice spontaneously develop systemic lupus erythematosus (SLE)-like disease. The natural history of the pulmonary involvement and the underlying mechanism of leukocyte infiltration into the lungs of MRL/lpr mice and SLE patients remains elusive. We aimed to investigate the expression profiles of chemokines and chemokine receptors in the lung of the SLE-prone mouse. We examined the correlation between lung inflammation and expression of IP-10 (interferon-gamma-inducible protein 10), a CXC chemokine, and TARC (thymus- and activation-regulated chemokine), a CC chemokine, in MRL/lpr mice, MRL/Mp-+/+ (MRL/+) mice, and C57BL/6 (B6) control mice. The extent of cell infiltration in the lung was assessed histopathologically. Reverse transcriptase PCR showed up-regulation of IP-10 mRNA expression in the lungs (P < 0.05) of MRL/lpr mice, in comparison with MRL/+ or B6 mice. The increase paralleled increased expression of a specific IP-10 receptor, CXCR3, and correlated with the degree of infiltration of mononuclear lymphocytes. In contrast, lung expression of TARC and its specific receptor, CCR4, were suppressed in MRL/lpr mice. Immunohistology showed that macrophage-like cells were the likely source of IP-10. Flow cytometric analyses revealed that the CXCR3-expressing cells were mainly infiltrating CD4 T cells and macrophages, which correlated with the degree of mononuclear lymphocyte infiltration. Recent data suggest that Th1 cells and Th1-derived cytokines play an important role in the development of SLE-like disease in MRL/lpr mice. Our results suggest that IP-10 expression in the lung is involved, through CXCR3, in the pathogenesis of pulmonary inflammation associated with migration of Th1 cells.

Interferon-gamma augments acute macrophage-mediated renal injury via a glucocorticoid-sensitive mechanism

Macrophages have been implicated in causing renal injury in both human and experimental kidney disease. The aim of the current study was to determine whether modulating the state of macrophage activation directly affects the capacity of these cells to cause renal injury. This was investigated using an adoptive transfer model in which macrophage activation can be manipulated in vitro, using interferon-gamma (IFN-gamma) or dexamethasone (Dex), and then macrophage-mediated renal injury determined in vivo. In this model, rats were made leukopenic by administration of cyclophosphamide (CyPh). Two days later (day 0), animals were injected with sheep anti-GBM serum followed by a single injection of rat NR8383 macrophages on day 1 and then killed 3 or 24 h after cell transfer. NR8383 macrophages were incubated IFN-gamma and/or Dex before adoptive transfer into animals. Induction of proteinuria and glomerular cell proliferation (PCNA+ cells) in this model was dependent on transfer of NR8383 macrophages. Exposure of macrophages to IFN-gamma for 18 h (but not 3 h) before transfer caused a twofold increase in the degree of proteinuria and glomerular cell proliferation compared with unstimulated cells (Nil versus IFN-gamma; P < 0.001). This was due to an increase in the number of transferred macrophages within the glomerulus and a significant increase in degree of renal injury per transferred glomerular macrophage. IFN-gamma increased iNOS and PDGF-B gene expression and upregulated adhesion molecule expression in NR8383 macrophages. In contrast, exposure of NR8383 cells to Dex for 18 h (but not 1 h) abrogated renal injury due to a failure of transferred macrophages to accumulate within the glomerulus. In addition, Dex abrogated renal injury caused by IFN-gamma-stimulated macrophages. In conclusion, activation of macrophages by IFN-gamma, independent of any effect on other leukocytes or renal cells, can substantially augment macrophage-mediated renal injury. This IFN-gamma augmentation of renal injury is sensitive to the action of glucocorticoids, which act directly on macrophages to prevent their recruitment to the inflamed glomerulus. This study provides the first evidence that it is possible to directly modulate macrophage-mediated renal injury.

Modulation of renal disease in MRL/lpr mice by pharmacologic inhibition of inducible nitric oxide synthase

BACKGROUND

MRL-MPJFaslpr (MRL/lpr) mice spontaneously develop lupus-like disease characterized by immune complex glomerulonephritis and overproduction of nitric oxide (NO). Blocking NO production pharmacologically by a non-specific nitric oxide synthase (NOS) inhibitor ameliorated renal disease in MRL/lpr mice while genetically deficient inducible NOS (iNOS) mice developed proliferative glomerulonephritis similar to wild-type controls.

METHODS

To clarify the role of iNOS in the pathogenesis of nephritis in MRL/lpr mice, we treated mice with two different NOS inhibitors. Either NG-monomethyl-l-arginine (L-NMMA), a nonspecific NOS inhibitor, or l-N6-(1-iminoethyl)lysine (L-NIL), an iNOS specific inhibitor, was administered in the drinking water from 10 through 22 weeks of age with disease progression monitored over time. Control mice received water alone.

RESULTS

Both L-NMMA and L-NIL blocked NO production effectively in MRL/lpr mice. As expected, neither L-NNMA nor L-NIL had an effect on antibody production, immune complex deposition or complement activation. Although both NOS inhibitors decreased protein excretion, L-NMMA was more effective than L-NIL. Pathologic renal disease was significantly decreased at 19 weeks in both treatment groups. At 22 weeks the L-NIL treated mice, but not the L-NMMA mice, had significantly reduced renal disease scores compared to controls.

CONCLUSION

These results indicate that specific inhibition of iNOS blocks the development of pathologic renal disease in MRL/lpr mice.

IL-12 enhances lymphoaccumulation by suppressing cell death of T cells in MRL- lpr/lpr mice

Lymphoaccumulation occurs in MRL- lpr/lpr mice, because double-negative T cells (DNT cells) cannot be deleted due to their Fas mutation, i.e., lpr. We show here that IL-12 enhances in lymphoaccumulation by suppressing cell death of DNT cells in [corrected] MRL- lpr/lpr mice. It has been reported that viable DNT cells from MRL- lpr/lpr mice undergo rapid apoptosis in ordinary cell culture without additional stimulation, suggesting that unknown in vivo factors other than lpr suppress the apoptosis. In the present study, we found that plasma IL-12p40 monomer and/or homodimer level increased with age in MRL- lpr/lpr but not in MRL-+/+ mice, and the increase in IL-12 correlated well with lymphoaccumulation. Requirement of IL-12 in lymphoaccumulation and in suppressed cell death of DNT cells of MRL- lpr/lpr mice was assessed. When an antibody neutralizing IL-12 was injected into old MRL- lpr/lpr mice with high plasma IL-12 level, lymphoaccumulation was diminished. When IL-12p40- or IL-12p70-encoding plasmid was administered to young MRL- lpr/lpr mice before the plasma IL-12 level increases, lymphoaccumulation was enhanced. The ordinary cell culture-induced cell death of DNT cells from MRL- lpr/lpr mice was suppressed in the presence of IL-12. Since DNT cells produce IFN-gamma, a potent inducer of IL-12, the INF-gamma induced-IL-12 may enhance lymphoaccumulation in MRL- lpr/lpr mice.

The role of IFN-gamma in systemic lupus erythematosus: a challenge to the Th1/Th2 paradigm in autoimmunity

The classification of T helper cells into type 1 (Th1) and type 2 (Th2) led to the hypothesis that Th1 cells and their cytokines (interleukin [IL]-2, interferon [IFN]-gamma) are involved in cell-mediated autoimmune diseases, and that Th2 cells and their cytokines (IL-4, IL-5, IL-10, IL-13) are involved in autoantibody(humoral)-mediated autoimmune diseases. However, this paradigm has been refuted by recent studies in several induced and spontaneous mouse models of systemic lupus erythematosus, which showed that IFN-gamma is a major effector molecule in this disease. These and additional findings, reviewed here, suggest that these two cross-talking classes of cytokines can exert autoimmune disease-promoting or disease-inhibiting effects without predictability or strict adherence to the Th1-versus-Th2 dualism.

The central and multiple roles of B cells in lupus pathogenesis

A standard view of B cells in systemic autoimmunity is that they promote lupus by producing autoantibodies (autoAb). However, this view is incomplete because recent studies have revealed that autoimmune disease can be dissociated from autoAb deposition. Furthermore, the spontaneous T-cell activation and organ infiltration in systemic lupus erythematosus patients and animal models are difficult to explain entirely via a direct autoAb-mediated mechanism. In this review, we describe work addressing the B-cell functions of autoantigen presentation and autoAb production in lupus pathogenesis. In the JHD-MRL-Faslpr strain (JHD/lpr), a B-cell-deficient version of the lupus-prone MRL-Faslpr (MRL/lpr) mouse, spontaneous nephritis and dermatitis is abrogated, demonstrating that B cells have a primary role in disease. B cells play a similar role in Fas-intact, lupus-prone MRL mice. To address the role of autoantigen presentation, we analyzed transgenic mice which have B cells that cannot secrete immunoglobulin (mIgM transgenic mice). The restoration of B cells without antibody caused substantial interstitial nephritis and vasculitis although less marked than the intact MRL/lpr controls. To address the role of autoAb, we infused serum from aged MRL/lpr mice into JHD/lpr mice. At most, mild to no nephritis was observed in the infused mice. These results indicate that B cells are promoting autoimmunity in mechanisms other than autoAb secretion, and we describe a model depicting these B-cell roles in the context of other inflammatory events in lupus.

Th1 and Th2 T helper cell subsets affect patterns of injury and outcomes in glomerulonephritis

The recognition that human immune responses can be directed by two different subsets of T helper cells (Th1 and Th2) has been an important development in modern immunology. Immune responses polarized by either the Th1 or Th2 subset predominance result in different inflammatory effector pathways and disease outcomes. Many autoimmune diseases are associated with either Th1- or Th2- polarized immune responses. Although these different immune response patterns are relevant to glomerulonephritis (GN), little attention has been paid to the consequences of Th1 or Th2 predominance of nephritogenic immune responses for the pattern and outcome of GN. Unlike other autoimmune conditions, GN results from a variety of different immune responses and has a range of histologic features and immune effectors in glomeruli. This review assesses the data available from studies of experimental and human GN that address the Th1 or Th2 predominance of nephritogenic immune responses and their relevance to the different histopathological patterns and outcomes of GN. In particular, the evidence that Th1-predominant nephritogenic immune responses are associated with severe proliferative and crescentic GN is presented.