Type I interferons inhibition of inflammatory T helper cell responses in systemic lupus erythematosus

High salt diet accelerates the progression of murine lupus through dendritic cells via the p38 MAPK and STAT1 signaling pathways

The increased incidence of systemic lupus erythematosus (SLE) in recent decades might be related to changes in modern dietary habits. Since sodium chloride (NaCl) promotes pathogenic T cell responses, we hypothesize that excessive salt intake contributes to the increased incidence of autoimmune diseases, including SLE. Given the importance of dendritic cells (DCs) in the pathogenesis of SLE, we explored the influence of an excessive sodium chloride diet on DCs in a murine SLE model. We used an induced lupus model in which bone marrow-derived dendritic cells (BMDCs) were incubated with activated lymphocyte-derived DNA (ALD-DNA) and transferred into C57BL/6 recipient mice. We observed that a high-salt diet (HSD) markedly exacerbated lupus progression, which was accompanied by increased DC activation. NaCl treatment also stimulated the maturation, activation and antigen-presenting ability of DCs in vitro. Pretreatment of BMDCs with NaCl also exacerbated BMDC-ALD-DNA-induced lupus. These mice had increased production of autoantibodies and proinflammatory cytokines, more pronounced splenomegaly and lymphadenopathy, and enhanced pathological renal lesions. The p38 MAPK–STAT1 pathway played an important role in NaCl-induced DC immune activities. Taken together, our results demonstrate that HSD intake promotes immune activation of DCs through the p38 MAPK–STAT1 signaling pathway and exacerbates the features of SLE. Thus, changes in diet may provide a novel strategy for the prevention or amelioration of lupus or other autoimmune diseases.

Major depressive disorders accompanying autoimmune diseases - Response to treatment

MDDs (major depressive disorders) belong to the most frequently diagnosed mental diseases and affect approximately 350 million people all over the world. A growing body of evidence suggests that inflammatory processes may play a significant role in the pathophysiology and progression of the disease. The comorbidity of MDDs with many other medical conditions, for example autoimmune diseases (ADs) caused by inflammation, has been observed on numerous occasions. In both cases, increased levels of pro-inflammatory cytokines, chemokines and other inflammatory agents are observed. Furthermore, higher rates of inflammatory markers are associated with a poorer response to antidepressant treatment. Additionally, the presence of any AD is associated with higher prevalence of depression and may reduce the chance of effective therapy. Interestingly, the administration of several anti-inflammatory agents used in AD treatment is positively correlated with a reduction of depressive symptoms. In conclusion, the factors contributing to the coexistence of depression as well as affecting antidepressant treatment effectiveness may lead to an alteration of the cytokine profiles in many autoimmune diseases.

Infection and Lupus: Which Causes Which?

Infection is a leading cause of morbidity and mortality among patients with systemic lupus erythematous (SLE). Dysfunction of the innate and adaptive immune systems increases the risk of infection in patients with SLE. Infectious agents have also been theorized to play a role in the pathogenesis of SLE. This article summarizes our current knowledge of the infectious risk SLE patients face as a result of their underlying disease including abnormal phagocytes and T cells as well as the increased risk of infection associated with immunosuppressive agents used to treat disease. Pathogens thought to play a role in the pathogenesis of disease including EBV, CMV, human endogenous retroviruses (HERVs), and tuberculosis will also be reviewed, as well as the pathologic potential of microbial amyloids and the microbiome.

Breakdown of Immune Tolerance in Systemic Lupus Erythematosus by Dendritic Cells

Dendritic cells (DC) play an important role in the pathogenesis of systemic lupus erythematosus (SLE), an autoimmune disease with multiple tissue manifestations. In this review, we summarize recent studies on the roles of conventional DC and plasmacytoid DC in the development of both murine lupus and human SLE. In the past decade, studies using selective DC depletions have demonstrated critical roles of DC in lupus progression. Comprehensive in vitro and in vivo studies suggest activation of DC by self-antigens in lupus pathogenesis, followed by breakdown of immune tolerance to self. Potential treatment strategies targeting DC have been developed. However, many questions remain regarding the mechanisms by which DC modulate lupus pathogenesis that require further investigations.

Role of IL-33 and its receptor in T cell-mediated autoimmune diseases

Interleukin-33 (IL-33) is a new cytokine of interleukin-1 family, whose specific receptor is ST2. IL-33 exerts its functions via its target cells and plays different roles in diseases. ST2 deletion and exclusion of IL-33/ST2 axis are accompanied by enhanced susceptibility to dominantly T cell-mediated organ-specific autoimmune diseases. It has been reported that IL-33/ST2 pathway plays a key role in host defense and immune regulation in inflammatory and infectious diseases. This review focuses on new findings in the roles of IL-33 and ST2 in several kinds of T cell-mediated autoimmune diseases.

High multi-cytokine levels are not a predictive marker of alloimmunization in transfused sickle cell disease patients

Patients with sickle cell disease (SCD) receive multiple red blood cell (RBC) transfusions for both prevention of and therapy for disease-related complications. In some patients, transfusion results in development of both allo- and auto-antibodies to RBC antigens. What precipitates the antibody formation is currently unclear. It has been hypothesized that a pro-inflammatory state preceding the therapeutic transfusion may be a predisposing factor. Plasma levels of ten cytokines were evaluated upon recruitment to the study of 83 children with SCD undergoing therapeutic RBC transfusions. The levels of cytokines were correlated with development of anti-RBC antibodies prior, or during seven years post recruitment. Twelve subjects displayed significantly higher levels of all cytokines examined, with pro-, as well as anti-inflammatory properties. Surprisingly, the elevated levels of cytokines were preferentially found in patients without anti-RBC allo- and/or auto-antibodies. Further, presence of high cytokine levels was not predictive of anti-RBC antibody development during the subsequent seven year follow up. These data suggest that the increased concentration of multiple cytokines is not a biomarker of either the presence of or susceptibility to the development of RBC alloimmunization.

Interferon alpha inhibits antigen-specific production of proinflammatory cytokines and enhances antigen-specific transforming growth factor beta production in antigen-induced arthritis

Introduction

Interferon alpha (IFN-α) has a complex role in autoimmunity, in that it may both enhance and prevent inflammation. We have previously shown that the presence of IFN-α at sensitization protects against subsequent antigen-triggered arthritis. To understand this tolerogenic mechanism, we performed a descriptive, hypothesis-generating study of cellular and humoral responses associated with IFN-α-mediated protection against arthritis.

Methods

Arthritis was evaluated at day 28 in mice given a subcutaneous injection of methylated bovine serum albumin (mBSA), together with Freund adjuvant and 0 to 5,000 U IFN-α at days 1 and 7, followed by intraarticular injection of mBSA alone at day 21. The effect of IFN-α on mBSA-specific IgG1, IgG2a, IgG2b, IgA, and IgE was evaluated by enzyme-linked immunosorbent assay (ELISA). Cytokines in circulation and in ex vivo cultures on mBSA restimulation was evaluated with ELISA and Luminex, and the identity of cytokine-producing cells by fluorescence-activated cell sorting (FACS) analysis.

Results

Administration of IFN-α protected mice from arthritis in a dose-dependent manner but had no effect on antigen-specific antibody levels. However, IFN-α did inhibit the initial increase of IL-6, IL-10, IL-12, and TNF, and the recall response induced by intraarticular mBSA challenge of IL-1β, IL-10, IL-12, TNF, IFN-γ, and IL-17 in serum. IFN-α decreased both macrophage and CD4⁺ T cell-derived IFN-γ production, whereas IL-17 was decreased only in CD4⁺ T cells. Ex vivo, in mBSA-restimulated spleen and lymph node cell cultures, the inhibitory effect of in vivo administration of IFN-α on proinflammatory cytokine production was clearly apparent, but had a time limit. An earlier macrophage-derived, and stronger activation of the antiinflammatory cytokine transforming growth factor beta (TGF-β) was observed in IFN-α-treated animals, combined with an increase in CD4⁺ T cells producing TGF-β when arthritis was triggered by mBSA (day 21). Presence of IFN-α at immunizations also prevented the reduction in TGF-β production, which was induced by the intraarticular mBSA injection triggering arthritis in control animals.

Conclusions

Administration of IFN-α has a profound effect on the cellular response to mBSA plus adjuvant, but does not affect antigen-specific Ig production. By including IFN-α at immunizations, spleen and lymph node cells inhibit their repertoire of antigen-induced proinflammatory cytokines while enhancing antiinflammatory TGF-β production, first in macrophages, and later also in CD4⁺ T cells. On intraarticular antigen challenge, this antiinflammatory state is reenforced, manifested as inhibition of proinflammatory recall responses and preservation of TGF-β levels. This may explain why IFN-α protects against antigen-induced arthritis.

Differential oxidative modification of proteins in MRL+/+ and MRL/lpr mice: Increased formation of lipid peroxidation-derived aldehyde-protein adducts may contribute to accelerated onset of autoimmune response

Even though reactive oxygen species (ROS) have been implicated in SLE pathogenesis, the contributory role of ROS, especially the consequences of oxidative modification of proteins by lipid peroxidation-derived aldehydes (LPDAs) such as malondialdehyde (MDA) and 4-hydroxynonenal (HNE) in eliciting an autoimmune response and disease pathogenesis remains largely unexplored. MRL/lpr mice, a widely used model for SLE, spontaneously develop a condition similar to human SLE, whereas MRL+/+ mice with the same MRL background, show much slower onset of SLE. To assess if the differences in the onset of SLE in the two substrains could partly be due to differential expression of LPDAs and to provide evidence for the role of LPDA-modified proteins in SLE pathogenesis, we determined the serum levels of MDA-/HNE-protein adducts, anti-MDA-/HNE-protein adduct antibodies, MDA-/HNE-protein adduct specific immune complexes, and various autoantibodies in 6-, 12- and 18-week old mice of both substrains. The results show age-related increases in the formation of MDA-/HNE-protein adducts, their corresponding antibodies and MDA-/HNE-specific immune complexes, but MRL/lpr mice showed greater and more accelerated response. Interestingly, a highly positive correlation between increased anti-MDA-/HNE-protein adduct antibodies and autoantibodies was observed. More importantly, we further observed that HNE-MSA caused significant inhibition in antinuclear antibodies (ANA) binding to nuclear antigens. These findings suggest that LPDA-modified proteins could be important sources of autoantibodies and CICs in these mice, and thus contribute to autoimmune disease pathogenesis. The observed differential responses to LPDAs in MRL/lpr and MRL+/+ mice may, in part, be responsible for accelerated and delayed onset of the disease, respectively.

LY294002 inhibits TLR3/4-mediated IFN-β production via inhibition of IRF3 activation with a PI3K-independent mechanism

TLR3 and TLR4 utilize adaptor TRIF to activate interferon regulatory factor 3 (IRF3), resulting in interferon β (IFN-β) production to mediate anti-viral infection. In this report, we analyzed the effect of two known phosphatidylinositol 3-kinase (PI3K) inhibitors LY294002 and wortmannin on LPS- and poly(I:C)-induced IFN-β production in peritoneal macrophages. LY294002 inhibited LPS- and poly(I:C)-induced IFN-β transcription and secretion. In contrast, wortmannin could not inhibit IFN-β production. Furthermore, IRF3 transcriptional activation and binding to IFN-β promoter were found to be inhibited by LY294002. Therefore, our findings demonstrate LY294002 negatively regulates LPS- and poly(I:C)-induced IFN-β production through inhibition of IRF3 activation in a PI3K-independent manner.

Basophils and autoreactive IgE in the pathogenesis of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a heterogeneous disease that can affect multiple organs. A hallmark of this disease, as is the case for other autoimmune diseases, is the presence of large numbers of autoantibodies. As such, SLE is considered to be a B-cell disease perpetuated by the expansion of autoreactive T and B cells. The T cells involved have long been considered to be T-helper type 1 (Th1) and Th17 cells, as these potent proinflammatory cells can be found in the tissues of SLE patients. Recent advances point to a role for the Th2 environment in contributing to SLE through promotion of autoantibody production. Here we describe the recent work focusing on autoreactive IgE and the activation of basophils as promoting the production of autoantibodies in SLE. The findings, both in a murine model of SLE and in humans with SLE, support the concept that the activation of the basophil by autoreactive IgE-containing immune complexes serves to amplify the production of autoantibodies and contributes to the pathogenesis of disease. We propose that therapeutic targeting of this amplification loop by reducing the levels of circulating autoreactive IgE may have benefit in SLE.

Counter-regulation in the IKK family

The human IKK [IκB (inhibitor of NF-κB) kinase] family has four members; they are the central kinases of innate immunity. Two members, IKKα and IKKβ, the so-called canonical members, phosphoryate IκBα, leading to activation of the transcription factor NF-κB (nuclear factor κB), which controls the expression of many immune and inflammatory genes. The IKK-related proteins TBK-1 (TANK-binding kinase 1) and IKKϵ have a different substrate--IRF3 (interferon regulatory factor 3)--which regulates a different set of genes, the products of which include Type I interferons. Toll-like receptors (TLRs) such as the lipopolysaccharide receptor TLR4 or the poly(I:C) receptor TLR3 activate each of the IKKs, but the pro-inflammatory cytokine IL-1 (interleukin 1), which signals in a broadly similar way to the TLRs, has so far been shown to activate only the canonical IKKs. In this issue of the Biochemical Journal, Clark et al. bring new insights into the regulation of IKKs. They demonstrate that IL-1 is in fact able to activate IKKϵ/TBK-1, which occurs via IKKα/IKKβ. The consequence of this is not IRF3 activation, but a negative feedback effect on IKKα/IKKβ. This provides us with yet another regulatory feedback loop in a system already replete with control mechanisms. It attests yet again to the importance of keeping these innate immune pathways in check, since if they proceed uncontrolled, inflammatory diseases can occur. Importantly, this study utilized new and specific inhibitors of these kinases, suggesting that the interpretation of any effects the compound might have in vivo may be complex, since for example the inhibition of IKKϵ/TBK-1 might actually have a pro-inflammatory effect.

Peroxisome proliferator-activated receptor gamma negatively regulates IFN-beta production in Toll-like receptor (TLR) 3- and TLR4-stimulated macrophages by preventing interferon regulatory factor 3 binding to the IFN-beta promoter

Toll-like receptors 3 and 4 utilize adaptor TRIF to activate interferon regulatory factor 3 (IRF3), resulting in IFN-β production to mediate anti-viral and bacterial infection. Peroxisome proliferator-activated receptor (PPAR)-γ is a ligand-activated transcription factor expressed in various immune cells and acts as a transcriptional repressor to inhibit the transcription of many proinflammatory cytokines. But, the function of PPAR-γ in TLR3- and -4-mediated IFN-β production is not well elucidated. Here, we have analyzed the effect of the PPAR-γ agonists on IFN-β production in peritoneal primary macrophages in response to LPS and poly(I:C). PPAR-γ agonists inhibited LPS and poly(I:C)-induced IFN-β transcription and secretion. siRNA knockdown of PPAR-γ expression and transfection of PPAR-γ expression plasmid demonstrated that PPAR-γ agonist inhibits IFN-β production in a PPAR-γ-dependent manner. The ability of the PPAR-γ agonist to inhibit IFN-β production was confirmed in vivo as mice treated with troglitazone exhibited decreased levels of IFN-β upon LPS and poly(I:C) challenge. Chromatin immunoprecipitation (CHIP) assay and electrophoretic mobility shift assay (EMSA) demonstrated that troglitazone treatment impaired IRF3 binding to the IFN-β promoter. Furthermore, troglitazone could inhibit LPS and poly(I:C)-induced STAT1 phosphorylation and subsequent ISRE activation. These results demonstrate that PPAR-γ negatively regulates IFN-β production in TLR3- and 4-stimulated macrophages by preventing IRF3 binding to the IFN-β promoter.

Macrophage pro-inflammatory cytokine secretion is enhanced following interaction with autologous platelets

BACKGROUND

Macrophages are the dominant phagocyte at sites of wound healing and inflammation, and the cellular and acellular debris encountered by macrophages can have profound effects on their inflammatory profile. Following interaction with apoptotic cells, macrophages are known to switch to an anti-inflammatory phenotype. Activated platelets, however, are also a major component of inflammatory lesions and have been proposed to be pro-inflammatory mediators. In the present study, we tested the hypothesis that macrophage interaction with activated platelets results in an inflammatory response that differs from the response following phagocytosis of apoptotic cells.

METHODS

Human monocyte-derived macrophages (hMDMs) were co-incubated with autologous activated platelets (AAPs) and the platelet-macrophage interaction was examined by electron microscopy and flow cytometry. The cytokines TNF-α, IL-6, and IL-23 were also measured during LPS-activated hMDM co-incubation with AAPs, which was compared to co-incubation with apoptotic lymphocytes. Cytokine secretion was also compared to platelets pre-treated with the gluococorticoid dexamethasone.

RESULTS

Macrophages trapped and phagocytized AAPs utilizing a mechanism that was significantly inhibited by the scavenger receptor ligand fucoidan. LPS-induced macrophage secretion of TNF-α, IL-6, and IL-23 was inhibited by co-incubation with apoptotic cells, but enhanced by co-incubation with AAPs. The platelet-dependent enhancement of LPS-induced cytokines could be reversed by pre-loading the platelets with the glucocorticoid dexamethasone.

CONCLUSIONS

The interaction of human macrophages with autologous platelets results in scavenger-receptor-mediated platelet uptake and enhancement of LPS-induced cytokines. Therefore, the presence of activated platelets at sites of inflammation may exacerbate pro-inflammatory macrophage activation. The possibility of reversing macrophage activation with dexamethasone-loaded platelets is a promising therapeutic approach to treating unresolved inflammation.

Serum levels of IL-33 and soluble ST2 and their association with disease activity in systemic lupus erythematosus

OBJECTIVE

IL-33 has recently been found to be the specific ligand of ST2, an IL-1 receptor family member that is selectively expressed in Th2 cells and mediates Th2 response. This study aims to measure the serum levels of soluble ST2 (sST2) and IL-33 in patients with SLE and to examine their association with disease activity.

METHODS

Seventy SLE patients were evaluated for disease activity, determined by SLEDAI, levels of anti-dsDNA antibody, C3 and C4. Fifty-seven patients were evaluated longitudinally on a second occasion. IL-33 and sST2 were measured by sandwich ELISA in the 127 SLE serum samples and compared with 28 age- and sex-matched healthy controls.

RESULTS

Serum sST2 level was significantly higher in active SLE patients [0.51 (0.18) ng/ml] compared with inactive patients [0.42 (0.08) ng/ml] (P = 0.006) and normal controls [0.36 (0.13) ng/ml] (P < 0.001). sST2 level correlated significantly with SLEDAI, anti-dsDNA antibody and prednisolone dosage, and negatively with C3. Linear regression analysis showed that serum sST2 level was an independent predictive factor for modified SLEDAI, excluding anti-dsDNA and complement score after controlling for age, sex, glomerular filtration rate and prednisolone dosage (regression coefficient: 8.5; 95% CI 2.6, 14.3) (P = 0.005). Serum sST2 level was sensitive to change in disease activity longitudinally, with an effect size of 0.29. Elevated serum IL-33 was comparable in frequency (4.3 vs 7.1%; P = 0.62) and levels (P = 0.53) between SLE patients and controls.

CONCLUSIONS

Elevated serum sST2 level in SLE patients was found to correlate with disease activity and was sensitive to change, suggesting a potential role as a surrogate marker of disease activity.

Dendritic cells as danger-recognizing biosensors

Dendritic cells (DCs) are antigen presenting cells that are characterized by a potent capacity to initiate immune responses. DCs comprise several subsets with distinct phenotypes. After sensing any danger(s) to the host via their innate immune receptors such as Toll-like receptors, DCs become mature and subsequently present antigens to CD4⁺ T cells. Since DCs possess the intrinsic capacity to polarize CD4⁺ helper cells, it is critical to understand the immunological roles of DCs for clinical applications. Here, we review the different DC subsets, their danger-sensing receptors and immunological functions. Furthermore, the cytokine reporter mouse model for studying DC activation is introduced.

FLT3 inhibitors for the treatment of autoimmune disease

BACKGROUND

Autoimmune diseases encompass a broad range of illnesses with a variety of underlying causes, some of which are known and some of which remain elusive.

OBJECTIVE

The focus of this review will be on describing the development of a new type of therapy that could potentially treat T cell-mediated autoimmune diseases. Unlike traditional therapies, which have primarily focused on suppressing T cells directly, targeting the step of antigen presentation may allow a less toxic therapy in which autoimmunity is lessened without compromising the entire immune system. This review will outline the science behind the development of the therapy, the roles of dendritic cells in generating autoimmune disease, and the function of the FLT3 receptor in this process.

A risk haplotype of STAT4 for systemic lupus erythematosus is over-expressed, correlates with anti-dsDNA and shows additive effects with two risk alleles of IRF5

Systemic lupus erythematosus (SLE) is the prototype autoimmune disease where genes regulated by type I interferon (IFN) are over-expressed and contribute to the disease pathogenesis. Because signal transducer and activator of transcription 4 (STAT4) plays a key role in the type I IFN receptor signaling, we performed a candidate gene study of a comprehensive set of single nucleotide polymorphism (SNPs) in STAT4 in Swedish patients with SLE. We found that 10 out of 53 analyzed SNPs in STAT4 were associated with SLE, with the strongest signal of association (P = 7.1 x 10(-8)) for two perfectly linked SNPs rs10181656 and rs7582694. The risk alleles of these 10 SNPs form a common risk haplotype for SLE (P = 1.7 x 10(-5)). According to conditional logistic regression analysis the SNP rs10181656 or rs7582694 accounts for all of the observed association signal. By quantitative analysis of the allelic expression of STAT4 we found that the risk allele of STAT4 was over-expressed in primary human cells of mesenchymal origin, but not in B-cells, and that the risk allele of STAT4 was over-expressed (P = 8.4 x 10(-5)) in cells carrying the risk haplotype for SLE compared with cells with a non-risk haplotype. The risk allele of the SNP rs7582694 in STAT4 correlated to production of anti-dsDNA (double-stranded DNA) antibodies and displayed a multiplicatively increased, 1.82-fold risk of SLE with two independent risk alleles of the IRF5 (interferon regulatory factor 5) gene.