The accelerated development of atherosclerosis with increased risk of cardiovascular disease in systemic lupus erythematosus (SLE) patients is not well understood. An appropriate mouse model would greatly help to understand the mechanisms of this association. We have therefore combined the ApoE-/- model of atherosclerosis with three different murine models of SLE. We found that induction of cGVH in B6.ApoE-/- mice, breeding a Fas null gene onto these B6/lpr.ApoE-/- mice, and breeding the ApoE-/- defect onto MRL/lpr mice all caused a modest increase of atherosclerosis at 24 weeks of age compared to B6.ApoE-/- controls. B cells in B6.ApoE-/- mice had certain phenotypic differences compared to congenic C57BL/6 mice, as indicated by high expression of MHC II, Fas, CD86, and by increased number of cells bearing marginal-zone phenotype. Furthermore, B6ApoE-/- mice had significant titers of anti-oxLDL and anti-cardiolipin autoantibodies compared to their B6 counterparts. Our studies also indicate that, following induction of cGVH, marginal zone B cells in B6.ApoE-/- are depleted, and there is considerable increase in anti-oxLDL and anti-cardiolipin abs along with secretion of lupus-specific autoantibodies, such as anti-dsDNA and anti-chromatin abs. Histological sections showed that cGVH and/or Fas deficiency could exacerbate atherosclerosis. The production of anti-oxLDL and anti-cardiolipin in ApoE-/- mice was also increased. These observations define a connection between induction of lupus-like symptoms and development of severe atherosclerosis in apoE deficient lupus mouse models.
Autoimmunity; Atherosclerosis; Apolipoprotein E; Graft Versus Host Disease; lpr; Systemic Lupus Erythematosus
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-Tnfrsf6lpr [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.
PMID: 21229240 CAMSID: cams2361
Rodent; Autoimmunity; Lupus; Macrophage; Diabetes; Apoptosis
Prolactin is secreted from the pituitary gland and other organs, as well as by cells such as lymphocytes. Prolactin has an immunostimulatory effect and is associated with autoimmune diseases that are characterised by abnormal B cell activation, such as systemic lupus erythematosus (SLE). Our aim was to determine if different splenic B cell subsets express the prolactin receptor and if the presence of prolactin influences these B cell subsets and correlates with development of lupus.
Using real-time PCR and flow cytometry, we found that different subsets of immature (transitional) and mature (follicular, marginal zone) B cells express different levels of the prolactin receptor and are differentially affected by hyperprolactinaemia. We found that transitional B cells express the prolactin receptor at higher levels compared to mature B cells in C57BL/6 mice and the lupus-prone MRL/lpr and MRL mouse strains. Transitional-1 (T1) B cells showed a higher level of prolactin receptor expression in both MRL/lpr and MRL mice compared to C57BL/6 mice. Hyperprolactinaemia was induced using metoclopramide, which resulted in the development of early symptoms of SLE. We found that T1 B cells are the main targets of prolactin and that prolactin augments the absolute number of T1 B cells, which reflects the finding that this B cell subpopulation expresses the highest level of the prolactin receptor.
We found that all B cell subsets express the prolactin receptor but that transitional B cells showed the highest prolactin receptor expression levels. Hyperprolactinaemia in mice susceptible to lupus accelerated the disease and increased the absolute numbers of T1 and T3 B cells but not of mature B cells, suggesting a primary effect of prolactin on the early stages of B cell maturation in the spleen and a role of prolactin in B cell differentiation, contributing to SLE onset.
Production of thromboxane (TX) A2 and PG I2/prostacyclin (PGI2) is increased in patients with atherosclerosis. However, their roles in atherogenesis have not been critically defined. To examine this issue, we cross-bred atherosclerosis-prone apoE-deficient mice with mice deficient in either the TXA receptor (TP) or the PGI receptor (IP). Although they showed levels of serum cholesterol and triglyceride similar to those of apoE-deficient mice, apoE–/–TP–/– mice exhibited a significant delay in atherogenesis, and apoE–/–IP–/– mice exhibited a significant acceleration in atherogenesis compared with mice deficient in apoE alone. The plaques in apoE–/–IP–/– mice showed partial endothelial disruption and exhibited enhanced expression of ICAM-1 and decreased expression of platelet endothelial cell adhesion molecule 1 (PECAM-1) in the overlying endothelial cells compared with those of apoE–/–TP–/– mice. Platelet activation with thrombin ex vivo revealed higher and lower sensitivity for surface P-selectin expression in platelets of apoE–/–IP–/– and apoE–/–TP–/– mice, respectively, than in those of apoE–/– mice. Intravital microscopy of the common carotid artery revealed a significantly greater number of leukocytes rolling on the vessel walls in apoE–/–IP–/– mice than in either apoE–/–TP–/– or apoE–/– mice. We conclude that TXA2 promotes and PGI2 prevents the initiation and progression of atherogenesis through control of platelet activation and leukocyte-endothelial cell interaction.
apoE deficiency causes hyperlipidemia and premature atherosclerosis. To determine if macrophage-specific expression of apoE would decrease the extent of atherosclerosis, we expressed human apoE in macrophages of apoE-null mice (apoE-/-) and assessed the effect on lipid accumulation in cells of the arterial wall. Macrophage-specific expression of human apoE in normal mice was obtained by use of the visna virus LTR. These animals were bred with apoE-/- mice to produce animals hemizygous for expression of human apoE in macrophages in the absence of murine apoE (apoE-/-,hTgE+/0). Low levels of human apoE mRNA were present in liver and spleen and high levels in lung and peritoneal macrophages. Human apoE was secreted by peritoneal macrophages and was detected in Kupffer cells of the liver. Human apoE in the plasma of apoE-/-,hTgE+/0 mice (n = 30) was inversely correlated (P < 0.005) with the plasma cholesterol concentration. After 15 wk on a normal chow diet, atherosclerosis was assessed in apoE-/-,hTgE+/0 animals and in apoE-/-,hTgE0/0 littermates matched for plasma cholesterol level (approximately 450 mg/dl) and lipoprotein profile. There was significantly less atherosclerosis in both the aortic sinus and in the proximal aorta (P < 0.0001) in the animals expressing the human apoE transgene. In apo-E-/-,hTgE+/0 animals, which had detectable atherosclerotic lesions, human apoE was detected in the secretory apparatus of macrophage-derived foam cells in the arterial wall. The data demonstrate that expression of apoE by macrophages is antiatherogenic even in the presence of high levels of atherogenic lipoproteins. The data suggest that apoE prevents atherosclerosis by promoting cholesterol efflux from cells of the arterial wall.
Systemic lupus erythematosus (SLE) T cells display a hyperactive calcineurin-NFAT pathway. The aim of this study is to answer whether this pathway is responsible for the aberrant SLE T cell function and test the effectiveness of the recently recognized calcineurin inhibitor dipyridamole in limiting SLE related pathology.
T and mononuclear cells were isolated from the peripheral blood of patients with SLE and healthy individuals. Murine cells were isolated from the spleens and lymph nodes of lupus prone MRL/lpr mice and control MRL/MpJ mice. Cells were treated in vitro with tacrolimus, dipyridamole or control. MRL/lpr mice were injected intraperitoneally with dipyridamole 50 mg/kg three times a week for 3 weeks.
MRL/lpr T cells, especially CD3+CD4-CD8- displayed a robust calcium influx upon activation and increased levels of NFATc1. MRL/lpr T cells (both CD4+ and CD3+CD4-CD8- cells) provided help to B cells to produce immunoglobulin in a calcineurin-dependent fashion. Dipyridamole treatment of SLE T cells inhibited significantly the expression of CD154, the production of IFN-γ, IL-17, IL-6, and the T cell dependent B cell immunoglobulin secretion. Treatment of MRL/lpr mice with dipyridamole alleviated lupus nephritis and prevented the appearance of skin ulcers.
NFAT activation is a key step in the activation of SLE T cells and the production of immunoglobulin. Dipyridamole inhibits SLE T cell function and improves disease pathology in lupus-prone mice. We propose that dipyridamole can be used in treatment regimens of SLE patients.
Patients with systemic lupus erythematosus (SLE) have a striking increase in atherothrombotic cardiovascular disease (CVD), not explained by the Framingham risk equation. In vitro studies indicate that type-I Interferons (IFNs) may play prominent roles in increased CV risk in SLE. However, the in vivo relevance of these findings, with regards to the development of CVD, has not been characterized. We examined the role of type-I IFNs in endothelial dysfunction, aberrant vascular repair, and atherothrombosis in murine models of lupus and atherosclerosis.
Lupus-prone New Zealand Mixed-2328 mice (NZM) and atherosclerosis-prone Apolipoprotein-E-knockout mice (ApoE−/−) were compared to mice lacking type-I IFN-receptor (INZM and ApoEIFNR−/−, respectively) in their endothelial vasodilatory function, endothelial progenitor cell (EPC) function, in vivo neoangiogenesis, plaque development and occlusive thrombosis. Similar experiments were performed when NZM and ApoE−/− received an IFN-α-containing or an empty adenovirus.
Loss of type IIFN-receptor signaling improves endothelium-dependent vasorelaxation, lipoprotein parameters, EPC numbers and function and neoangiogenesis in lupus-prone mice, independent of disease activity or gender. Further, acute exposure to IFN-α impairs endothelial vasorelaxation and EPC function in lupus-prone and non-lupus-prone mice. ApoEIFNR−/− mice have decreased atherosclerosis severity and arterial inflammatory infiltrates and increased neoangiogenesis, compared to ApoE−/− mice, while NZM and ApoE−/− mice exposed to IFN-α develop accelerated thrombosis and platelet activation.
These results support the hypothesis that type I-IFNs play key roles in the development of premature CVD in SLE and, potentially, in the general population, through pleiotropic deleterious effects on the vasculature.
Angiogenesis; atherosclerosis; systemic lupus erythematosus
In the studies reported here, we have analyzed the production and consumption of T cell growth factor, more recently termed interleukin 2 (IL-2), as well as some cell-mediated immune functions, in murine strains [MRL, BXSB, NZB, and (NZB x NZWF1] manifesting systemic lupus erythematosus (SLE)-like syndromes. Young (4-6 wk) or old (4-8 mo) autoimmune or normal mice were studied and compared with regard to the following T cell functions in vitro after stimulation with concanavalin A (Con A): (a) mitogenic response; (b) IL-2 levels in culture supernates; and (c) the ability to respond to and adsorb IL-2. In addition, proliferative activity in the allogeneic mixed leukocyte culture and frequency of alloreactive cytotoxic T lymphocyte precursors (CTLp) were analyzed in some of these strains. Reduced Con A-induced mitogenic responses and IL-2 production appeared at 3-6 wk of age in the early, severe SLE developing strains MRL-Mp-lpr/lpr (MRL/l) and male BXSB and progressed thereafter. Similar defects appeared at a later stage in MRL/Mp-+/+ and (NZB x NZW)F1 hybrid mice, which develop late disease. Detailed analysis of cells from the enlarged lymph nodes and spleens of older MRL/l mice demonstrated that such cells: (a) responded poorly to Con A or allogeneic stimulator cells, even in the presence of exogenous IL-2; (b) did not suppress IL-2 production by normal spleen cells; (c) were relatively incapable of adsorbing or inactivating IL-2; and (d) had a markedly reduced anti-H-2b CTLp frequency in the mesenteric lymph nodes but a normal one in spleen. These results indicate that the proliferating Thy-1.2+, Lyt-1+ T cells in MRL/l mice are defective in their responses to mitogenic stimuli, in IL-2 production, and in expression of acceptor sites for IL-2. The relevance of these defects to the MRL/l disease as well as to the role of IL-2 in autoimmunity in general remains to be determined.
B cell hyperactivity, a feature common to all lupus-prone murine strains, may be caused by hyperresponsiveness to, overproduction of, or bypassing of certain signals required for B cell activation, proliferation, and differentiation. In this study, we have compared the responses of B cells from three lupus-prone strains of mice (BXSB males, MRL and NZB/W females) and normal strains in a number of assays for which two or more signals are required to obtain a response. In medium to low density cultures of B cells from BXSB and NZB/W but not MRL/l lupus mice, the cells' proliferation induced by bacterial lipopolysaccharide (LPS) or anti-mu antibody was much higher than that of B cells from normal controls. At low B cell density, polyclonal activation by these substances and subsequent Ig secretion were dependent on accessory signals present in supernatants of concanavalin A-treated normal lymphocytes (CAS) or on the MRL/l proliferating T cell- derived B cell differentiation factor (L-BCDF) in both lupus-prone and immunologically normal mice. However, the responses of B cells from BXSB and NZB/W, but not MRL/l, mice to these accessory signals were higher than those of normal mice. Ig synthesis by fresh B cells of BXSB and NZB/W mice cultured in the absence of mitogens but in the presence of CAS or L-BCDF was higher than by similar cells from other strains, suggesting an increased frequency of B cells activated in vivo in these two autoimmune strains of mice. The patterns of IgG subclass secretion in response to LPS (without added CAS or L-BCDF) were abnormal in all lupus strains, with a predominance of IgG2b and/or IgG2a and low levels of IgG3, contrary to normal B cells for which IgG3 synthesis predominated. However, IgG1 synthesis in vitro by autoimmune and normal B cells alike was highly dependent on T cell-derived soluble mediators. Antigen-specific responses to SRBC in vitro of B cells from all lupus strains, like those of B cells from normal strains, required a minimum of three signals (antigen, LPS, T cell-derived antigen nonspecific helper factors). Yet, once triggered, B cells of BXSB and NZB/W mice gave higher responses than those of the other strains. We conclude that B cells of lupus mice have signal requirements similar to those of normal mice. Nevertheless, B cells of BXSB and NZB/W, but not MRL/l, lupus mice hyperrespond or process some accessory signals abnormally.
Systemic lupus erythematosus (SLE) is a chroni c autoimmune disease characterized by loss of tolerance to self-antigens and activation of autoreactive T cells. Regulatory T cells (Treg) play a critical role in controlling the activation of autoreactive T cells. Here, we investigated mechanisms of potential Treg defects in SLE using MRL-Faslpr/lpr (MRL/lpr) and MRL-Fas+/+ (MRL+/+) mouse models. We found a significant increase in CD4+CD25+Foxp3+ Treg cells, albeit with an altered phenotype (CD62L–CD69+) and with a reduced suppressive capacity, in the lymphoid organs of MRL strains compared to non-autoimmune C3H mice. A search for mechanisms underlying the altered Treg phenotype in MRL/lpr mice led us to find a profound reduction in Dicer expression and an altered microRNA (miRNA, miR) profile in MRL/lpr Treg cells. Despite having a reduced level of Dicer, MRL/lpr Treg cells exhibited a significant overexpression of several miRNAs including let-7a, let-7f, miR-16, miR-23a, miR-23b, miR-27a and miR-155. Using computational approaches, we identified one of the upregulated miRNAs, miR-155 that can target CD62L and may thus confer the altered Treg phenotype in MRL/lpr mice. In fact, the induced overexpression of miR-155 in otherwise normal (C3H) Treg cells reduced their CD62L expression, which mimics the altered Treg phenotype in MRL/lpr mice. These data suggest a role of Dicer and miR-155 in regulating Treg cell phenotype. Furthermore, simultaneous appearance of Dicer insufficiency and miR-155 overexpression in diseased mice suggests a Dicer-independent alternative mechanism of miRNA regulation under inflammatory conditions.
Lupus; Treg cells; Dicer; miRNA
Apolipoprotein E (apoE) plays a key role in lipoprotein metabolism and may have other important biological functions. In humans, there are three common, naturally occurring isoforms of apoE that are associated with differences in lipid levels and atherosclerosis. However, the direct in vivo effects of the apoE isoforms on lipoprotein metabolism and atherosclerosis are not yet fully understood. To investigate the effect of the apoE isoforms in vivo, we constructed second-generation recombinant adenoviruses encoding each of the apoE isoforms. These recombinant adenoviruses were injected intravenously into apoE-deficient mice fed a Western diet (mean baseline cholesterol level 1401 mg/dl) in order to study their effects in the absence of endogenous mouse apoE. Hepatic expression of apoE3 and apoE4 completely normalized the lipoprotein profile; 3 d after injection, mean plasma cholesterol levels were 194 and 217 mg/ dl, respectively, and this effect was maintained for at least 6 wk. Expression of apoE2 had much less effect on lipoprotein levels (mean cholesterol level 752 mg/dl 3 d after injection), despite much higher plasma levels of apoE2 compared with apoE3 and apoE4; by 6 wk after injection the cholesterol levels had returned to baseline levels in the apoE2-expressing mice. Expression of all three isoforms significantly increased HDL cholesterol levels by approximately threefold and was independent of the cholesterol-lowering effect. ApoE transgene expression was substantially prolonged compared with that achieved using a first generation adenovirus and apoE was readily detected in plasma 3 mo after virus injection. These studies demonstrate: (a) prolonged in vivo expression of human apoE isoforms in apoE deficient mice after second-generation recombinant adenovirus-mediated somatic gene transfer; and (b) significantly impaired ability of apoE2 in vivo to mediate clearance of remnant lipoproteins in apoE-deficient mice fed a Western diet compared with apoE3 and apoE4.
Three independent mutations involving the apoptosis-1 (APO-1)/Fas receptor or its putative ligand have led to lupuslike diseases associated with lymphadenopathy in different strains of mice. To determine whether humans with SLE also have a defect in this apotosis pathway, we analyzed the expression of APO-1 on freshly isolated blood mononuclear cells and on lymphocytes activated in vitro using flow cytometry and the monoclonal antibody anti-APO-1. Significantly higher level of APO-1 expression were detected on freshly isolated peripheral B cells and both CD4+ and CD8+ T lymphocyte populations obtained from lupus patients when compared with normal controls (P < 0.001). Almost 90% of the cells that stained positive for APO-1 also expressed the CD29 antigen, suggesting that APO-1 was upregulated after lymphocyte activation in vivo. No defect in APO-1 regulation was detected after activation of SLE T (with anti-CD3) or B (with Staphylococcus aureus Cowan 1) lymphocytes in the presence of IL-2 in vitro. Similarly, the anti-APO-1 antibody induced apoptosis in 74 +/- 5% of activated SLE T cells in vitro compared with 79 +/- 6% of the normal controls (P > 0.05). These results reveal that, while APO-1/Fas may play an important role in the regulation of lymphocyte survival in SLE, no consistent defect in the expression or function of the receptor could be detected in these studies.
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-γ-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.
autoimmune disease; interferon-γ-inducible protein 10; Th1/Th2; CCR4; CXCR3
Dysfunction of immune systems, including innate and adaptive immunity, is responsible for the immunopathogenesis of systemic lupus erythematosus (SLE). NK cells are a major part of the innate immune system, and diminished populations of NK cells have been reported in SLE patients. However, the mechanisms behind this decrease and the role of NK cells in SLE pathogenesis remain poorly understood. In this study, we found that a deficiency of NK cells, especially CD226+ NK cells, is prominent in patients with active SLE. Meanwhile, expression of the CD226 ligands CD112 and CD155 on plasmacytoid dendritic cells is observed in SLE patients; thus, activation of CD226+ NK cells may be induced by CD226–ligand interactions. Furthermore, IFN-α, which is mainly produced by plasmacytoid dendritic cells, can mediate the activation-induced cell death of NK cells. Therefore, these processes likely contribute to the loss of NK cells in patients with active SLE. Despite the impaired cytotoxicity of peripheral NK cells in human SLE patients and mouse SLE models, we provide evidence that CD226+ NK cells infiltrate the kidneys of predisease MRL-lpr/lpr mice. Kidney-infiltrating NK cells displayed an activated phenotype and a marked ability to produce cytotoxic granules. These results suggest that, before apoptosis, activated NK cells can infiltrate tissues and, to some extent, mediate tissue injury by producing cytotoxic granules and immunoregulatory cytokines.
Dendritic cells (DCs) are capable of inducing immunity or tolerance. Previous studies have suggested plasmacytoid DCs (pDCs) are pathogenic in systemic lupus erythematosus (SLE). However, the functional characteristics of directly isolated peripheral circulating blood pDCs in SLE have not been evaluated previously.
Peripheral blood pDCs from 62 healthy subjects and 58 SLE patients were treated with apoptotic cells derived from polymorphonuclear cells (PMNs). Antigen loaded or unloaded pDCs were then co-cultured with autologous or allogenous T cells. Changes in T cell proliferation, cell surface CD25 expression, intracellular Foxp3 expression and cytokine production were evaluated. pDCs that had captured apoptotic PMNs (pDCs + apoPMNs were also studied for their cytokine production (interferon (IFN)-alpha, interleukin (IL)-6, IL-10, IL-18) and toll like receptor (TLR) expression.
Circulating pDCs from SLE patients had an increased ability to stimulate T cells when compared with control pDCs. Using allogenous T cells as responder cells, SLE pDCs induced T cell proliferation even in the absence of apoptotic PMNs. In addition, healthy pDCs + apoPMNs induced suppressive T regulatory cell features with increased Foxp3 expression in CD4 + CD25 + cells while SLE pDCs + apoPMNs did not. There were differences in the cytokine profile of pDCs that had captured apoptotic PMNs between healthy subjects and patients with SLE. Healthy pDCs + apoPMNs showed decreased production of IL-6 but no significant changes in IL-10 and IL-18. These pDCs + apoPMNs also showed increased mRNA transcription of TLR9. On the other hand, while SLE pDCs + apoPMNs also had decreased IL-6, there was decreased IL-18 mRNA expression and persistent IL-10 protein synthesis. In addition, SLE pDCs lacked TLR9 recruitment.
We have demonstrated that peripheral circulating pDCs in patients with SLE were functionally abnormal. They lacked TLR9 expression, were less capable of inducing regulatory T cell differentiation and had persistent IL-10 mRNA expression following the capture of apoptotic PMNs. We suggest circulating pDCs may be pathogenically relevant in SLE.
In addition to its effects on cholesterol levels, apoE3 has lipid-independent effects that contribute to cardiovascular protection; one of these effects is the ability to inhibit cell cycling in VSMCs. The goal of this study was to identify and characterize cell cycle-regulatory mechanisms responsible for the anti-mitogenic effect of apoE.
Methods and results
Primary VSMCs were stimulated with serum in the absence or presence of apoE3. apoE3 upregulated expression of the cdk inhibitor, p27kip1, in primary VSMCs, and this effect required Cox2 and activation of PGI2-IP signaling. The microRNA family, miR221/222 has recently been identified as a post-translational regulator of p27, and apoE3 inhibited miR221/222 expression in a Cox2- and PGI2/IP-dependent manner. Moreover, reconstituted miR222 expression was sufficient to override the effects of apoE on p27 expression and S phase entry. The ability to repress expression of miR221/222 is shared by apoE3-containing HDL but is absent from apoA-1, LDL and apoE-depleted HDL. All three apoE isoforms regulate miR221/222, and the effect is independent of the C-terminal lipid-binding domain. miR221/222 levels are increased in the aortae of apoE3-null mice and reduced when apoE3 expression is reconstituted by adeno-associated virus infection. Thus, regulation of miR221/222 by apoE3 occurs in vivo as well as in vitro.
poE inhibits VSMC proliferation by regulating p27 through miR221/222. Control of cell cycle-regulatory microRNAs adds a new dimension to the spectrum of cardiovascular protective effects afforded by apoE and apoE-HDL.
ApoE3; HDL; PGI2; p27; miR221/222; VSMC proliferation
Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the production of an array of pathogenic autoantibodies, including high-affinity anti-dsDNA IgG antibodies. These autoantibodies are mutated and class-switched, mainly to IgG, indicating that immunoglobulin (Ig) gene somatic hypermutation (SHM) and class switch DNA recombination (CSR) are important in their generation. Lupus-prone MRL/faslpr/lpr mice develop a systemic autoimmune syndrome that shares many features with human SLE. We found that Ig genes were heavily mutated in MRL/faslpr/lpr mice and contained long stretches of DNA deletions and insertions. The spectrum of mutations in MRL/faslpr/lpr B cells was significantly altered, e.g., increased dG/dC transitions, and increased targeting of the RGYW/WRCY mutational hotspot and the WGCW AID-targeting hotspot. We also showed that MRL/faslpr/lpr greatly upregulated CSR, particularly to IgG2a and IgA in B cells of the spleen, lymph nodes and Peyer’s patches. In MRL/faslpr/lpr mice, the significant upregulation of SHM and CSR was associated with significantly increased expression of AID, which mediates DNA lesion, the first step in SHM and CSR, and translesion DNA synthesis (TLS) polymerase (pol) θ, pol η and pol ζ, which are involved in DNA synthesis/repair process associated with SHM and, possibly, CSR. Thus, in lupus-prone mice, SHM and CSR are dysregulated, as a result of enhanced AID expression and, therefore, DNA lesions, and dysregulated DNA repair factors, including TLS polymerases, which are involved in the repair process of AID-mediated DNA lesions.
activation-induced cytidine deaminase (AID); antibody; autoantibody; B cell; class switch DNA recombination (CSR); DNA deletion; DNA insertion; lupus; somatic hypermutation (SHM)
Systemic lupus erythematosus (SLE) is an autoimmune disorder affecting multiple organ systems. It is characterized by the presence of autoantibodies reactive against various self-antigens. Susceptibility to SLE is found to be associated with many major histocompatibility complex (MHC) and non-MHC genes, one of which is APO-1/Fas gene, which is present on chromosome 10 in humans. The APO-1/Fas promoter contains consensus sequences for binding of several transcription factors that affect the intensity of Fas expression in cells. The mutations in the APO-1/Fas promoter are associated with risk and severity in various autoimmune diseases and other malignancies. The APO-1/Fas receptor is expressed by many cell types. Two forms of APO-1/Fas protein that are involved in regulation of apoptosis have been identified. Fas receptor-mediated apoptosis plays a physiological and pathological role in killing of infected cell targets. In this review, we have focused on APO-1/Fas gene structure, promoter variants and its association with SLE and other autoimmune diseases. Functional aspects of Fas receptor in apoptosis are also discussed.
APO-1/Fas promoter; autoimmune diseases; systemic lupus erythematosus
To investigate whether ginkgolide B (a platelet-activating factor inhibitor) affects vascular inflammation in atherosclerosis-prone apolipoprotein E-deficient (ApoE−/−) mice.
Methods and Results
Human platelets were used to evaluate the effects of ginkgolide B on platelet aggregation and signal transduction. Ginkgolide B attenuated platelet aggregation and inhibited phosphatidylinositol 3 kinase (PI3K) activation and Akt phosphorylation in thrombin- and collagen-activated platelets. ApoE−/− mice were administered a high-cholesterol diet for 8 weeks. Plasma platelet factor 4 (PF4) and RANTES (regulated upon activation, normal T-cell expressed, and secreted protein) were then measured using an enzyme-linked immunosorbent assay. Scanning electron microscopy and immunohistochemistry were used to determine atherosclerotic lesions. Ginkgolide B decreased plasma PF4 and RANTES levels in ApoE−/− mice. Scanning electron microscopic examination showed that ginkgolide B reduced aortic plaque in ApoE−/− mice. Immunohistochemistry analysis demonstrated that ginkgolide B diminished P-selectin, PF4, RANTES, and CD40L expression in aortic plaque in ApoE−/− mice. Moreover, ginkgolide B suppressed macrophage and vascular cell adhesion protein 1 (VCAM-1) expression in aorta lesions in ApoE−/− mice. Similar effects were observed in aspirin-treated ApoE−/− mice.
Ginkgolide B significantly reduced atherosclerotic lesions and P-selectin, PF4, RANTES, and CD40L expression in aortic plaque in ApoE−/− mice. The efficacy of ginkgolide B was similar to aspirin. These results provide direct evidence that ginkgolide B inhibits atherosclerosis, which may be associated with inhibition of the PI3K/Akt pathway in activated platelets.
Systemic Lupus erythematosus (SLE) is an autoimmune disease caused, in part, by abnormalities in cells of the immune system including B and T cells. Genetically reducing globally the expression of the ETS transcription factor FLI1 by 50% in two lupus mouse models significantly improves disease measures and survival through an unknown mechanism. In this study we analyze the effects of reducing FLI1 in the MRL/lpr lupus prone model on T cell function. We demonstrate that adoptive transfer of MRL/lpr Fli1+/+ or Fli1+/- T cells and B cells into Rag1-deficient mice results in significantly decreased serum immunoglobulin levels in animals receiving Fli1+/- lupus T cells compared to animals receiving Fli1+/+ lupus T cells regardless of the genotype of co-transferred lupus B cells. Ex vivo analyses of MRL/lpr T cells demonstrated that Fli1+/- T cells produce significantly less IL-4 during early and late disease and exhibited significantly decreased TCR-specific activation during early disease compared to Fli1+/+ T cells. Moreover, the Fli1+/- T cells expressed significantly less neuraminidase 1 (Neu1) message and decreased NEU activity during early disease and significantly decreased levels of glycosphingolipids during late disease compared to Fli1+/+ T cells. FLI1 dose-dependently activated the Neu1 promoter in mouse and human T cell lines. Together, our results suggest reducing FLI1 in lupus decreases the pathogenicity of T cells by decreasing TCR-specific activation and IL-4 production in part through the modulation of glycosphingolipid metabolism. Reducing the expression of FLI1 or targeting the glycosphingolipid metabolic pathway in lupus may serve as a therapeutic approach to treating lupus.
B cells have many different roles in systemic lupus erythematosus (SLE), ranging from autoantigen recognition and processing to effector functions (for example, autoantibody and cytokine secretion). Recent studies have shown that intracellular nucleic acid-sensing receptors, Toll-like receptor (TLR) 7 and TLR9, play an important role in the pathogenesis of SLE. Dual engagement of rheumatoid factor-specific AM14 B cells through the B-cell receptor (BCR) and TLR7/9 results in marked proliferation of autoimmune B cells. Thus, strategies to preferentially block innate activation through TLRs in autoimmune B cells may be preferred over non-selective B-cell depletion.
We have developed a new generation of DNA-like compounds named class R inhibitory oligonucleotides (INH-ODNs). We tested their effectiveness in autoimmune B cells and interferon-alpha-producing dendritic cells in vitro and in lupus-prone MRL-Faslpr/lpr mice in vivo.
Class R INH-ODNs have 10- to 30-fold higher inhibitory potency when autoreactive B cells are synergistically activated through the BCR and associated TLR7 or 9 than when stimulation occurs via non-BCR-engaged TLR7/9. Inhibition of TLR9 requires the presence of both CCT and GGG triplets in an INH-ODN, whereas the inhibition of the TLR7 pathway appears to be sequence-independent but dependent on the phosphorothioate backbone. This difference was also observed in the MRL-Faslpr/lpr mice in vivo, where the prototypic class R INH-ODN was more effective in curtailing abnormal autoantibody secretion and prolonging survival.
The increased potency of class R INH-ODNs for autoreactive B cells and dendritic cells may be beneficial for lupus patients by providing pathway-specific inhibition yet allowing them to generate protective immune response when needed.
The aim of this study is to investigate the expression of apolipoprotein E (apoE)
and the relationship between apoE and disease activity of SLE, and the possible
effects of glucocorticoid on apoE and other cytokines activities in SLE
Forty treatment-naïve SLE patients and forty matched healthy controls were
studied. All the SLE patients received prednisone 1 mg/kg/day for 28
consecutive days. The sera levels of apoE and related cytokines were evaluated by
ELISA. The expression of apoE mRNA in peripheral blood mononuclear cells (PBMCs)
was determined by real-time PCR.
Compared with healthy controls, the relative expression levels of ApoE proteins
and sera levels were significantly up-regulated in active SLE patients. ApoE sera
concentrations positively correlated with SLEDAI, anti-dsDNA antibody and the
related cytokines including IL-6, IFN-γ and IL-10, and uncorrelated with the
concentration of total cholesterol (TC) and triglyceride (TG) in SLE patients.
After 4 weeks prednisone treatment, the relative mRNA expression of apoE and
the serum levels of apoE and related cytokines decreased.
ApoE correlated with disease activity and related cytokines in SLE patients.
Glucocorticoid can down-regulate the expressions of apoE and related
The virtual slide(s) for this article can be found
Systemic lupus erythematosus; Apolipoprotein E; Anti-inflammatory cytokine; SLEDAI
In young adulthood, MRL/Mp-lpr/lpr mice develop severe systemic lupus erythematosus (SLE)-like syndrome associated with massive T cell proliferation. The congenic MRL/Mp- mice lack the lpr gene and develop chronic SLE late in life. We have exchanged thymic transplants between these substrains so as to determine the role of the thymus in the development of early, severe SLE and of lymphoproliferation. The median survival times of unmanipulated lpr/lpr and mice were 160 and 510 d, respectively. The lpr/lpr and mice thymectomized when newborn and transplanted at 1 mo with the opposite type of thymus retained the diseases phenotype of their unmanipulated counterparts with 50% mortality at 186 and 498 d, respectively. In contrast, lpr/lpr mice thymectomized when newborn but not transplanted with thymus did not develop lymphoid hyperplasia and glomerulonephritis, and 100% of them were alive at 390 d. Serologically, the thymectomized but untransplanted lpr/lpr mice had significantly reduced levels of autoantibodies, whereas thymectomized and transplanted mice of either substrain were similar to unmanipulated controls. The results indicate that: (a) a thymus is essential for expression of lymphoproliferation and early SLE-like disease in the lpr/lpr phenotype; (b) the lpr/lpr disease is not a result of a unique hormonal or microenvironmental defect(s) of the thymus of this substrain because the genotype of the thymus is irrelevant for the development of T cell proliferation and early SLE; (c) differentiation of stem cells under the hormonal or microenvironmental influences of a thymus that possesses the lpr genotype does not lead to abnormal T cell differentiation or early autoimmunity; and (d) the lpr/lpr disease cannot be caused exclusively by an intrinsic B cell defect or environmental stimuli that cause B cell polyclonal activation.
To characterize modifications of high-density lipoprotein (HDL) in autoimmune gld (generalized lymphoproliferative disorder) mice that may be relevant to premature atherosclerosis in systemic lupus erythematosus and assess their relationship to specific aspects of autoimmune disease.
HDL-cholesterol (HDL-C), apolipoprotein-A1 (ApoA1), paraoxonase-1 (PON1) activity, hepatic gene expression and HDL biogenesis were measured in ageing female gld and wild-type (WT) congenic mice. Autoantibodies, lymphoid organs and cytokines were analyzed by enzyme-linked immunosorbent assay, flow cytometry and multiplex assay respectively.
Plasma HDL-C, HDL-ApoA1 and HDL-associated PON1 activity were reduced in ageing gld mice in association with the development of autoimmunity independently of changes in hepatic ApoA1 and PON1 expression or HDL biogenesis. Hepatic induction of the acute phase reactant, serum amyloid A-1, resulted in its incorporation onto HDL in gld mice. Deletion of the lipid-sensitive receptor, G2A, in gld mice (G2A-/-gld) attenuated reductions in HDL-C and PON1 activity without altering hepatic ApoA1 and PON1 expression, HDL biogenesis or levels of acute phase pro-inflammatory cytokines. Plasma anti-ApoA1 autoantibodies were elevated in ageing gld mice commensurate with detectable increases in ApoA1 immune complexes. Autoantibodies were lower in ageing G2A-/-gld mice compared to gld mice and anti-ApoA1 autoantibody levels were significantly related to HDL-C concentration (r=-0.645, p<0.00004) and PON1 activity (r=-0.555, p<0.0007) amongst autoimmune gld and G2A-/-gld mice.
Autoantibodies against ApoA1 contribute to reducing HDL-C and PON1 activity in autoimmune gld mice independently of hepatic HDL biogenesis, suggesting that functional impairment and premature clearance of HDL immune complexes may be principal mechanisms involved.
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.