Enhanced type I interferon signalling promotes Th1-biased inflammation in cutaneous lupus erythematosus

Recent studies have suggested that type I interferons (IFN) play a role in the pathogenesis of lupus erythematosus (LE), an autoimmune disease of unknown aetiology. Natural interferon-producing plasmacytoid cells have been demonstrated in cutaneous LE (CLE) lesions, along with elevated levels of IFN-alpha mRNA. The hypothesis in the current study was that local production of type I IFNs in CLE induces Th1-biased inflammation via induction of IFN-inducible chemokines such as IP10/CXCL10 leading to the recruitment of chemokine receptor CXCR3 expressing T-cells into skin lesions. Skin biopsies from 21 patients suffering from different types of active cutaneous LE were analysed for the expression of MxA, a protein specifically induced by type I interferons, the IFN-inducible protein IP10/CXCL10, and the chemokine receptor CXCR3, characteristic for Th1 cells, by immunohistochemistry. Additionally, peripheral CD4+ and CD8+ T-cells were investigated for the expression of MxA and CXCR3 by flow cytometry. Cutaneous LE lesions were characterized by strong expression of MxA indicating the induction of localized type I IFN signalling in the skin. Large numbers of infiltrating CXCR3 positive lymphocytes were detected in CLE skin lesions, and correlated closely with lesional MxA expression (epidermis: Spearman's rho = 0.56, p < 0.001; dermis: rho = 0.82, p < 0.001). Intracellular MxA levels of circulating CD4+ and CD8+ T-cells were significantly enhanced in patients with active CLE lesions. The percentage of peripheral T-cells expressing CXCR3 was significantly decreased in specific CLE subtypes. Expression of IP10/CXCL10 in the epidermis links type I IFN signalling and recruitment of CXCR3+ T cells. These results suggest an important role for type I interferon signalling in the pathogenesis of cutaneous lupus erythematosus. It is proposed that type I IFNs induce a Th1-biased inflammatory immune response, with recruitment of CXCR3-expressing T-lymphocytes into the skin.     

Type I Interferon Modulation of Cellular Responses to Cytokines and Infectious Pathogens: Potential Role in SLE Pathogenesis

Type I interferons (IFNs) are pleiotropic cytokines that have been implicated in the pathogenesis of systemic lupus erythematosus (SLE). A key aspect of type I IFN biology is that previous exposure to type I IFNs alters subsequent cellular responses to extracellular stimuli. Type I IFNs may either prime cells for stronger responses to viruses, bacterial pathogens and cytokines such as IL-6 and IFNγ, or may suppress cellular responses to LPS and TNFα. Herein, we review type I IFN signal transduction via the Jak-STAT pathway, and mechanisms by which type I IFNs prime or suppress responses to environmental factors. We develop a hypothesis that type I IFN-dependent priming/enhancement of cellular responses to pro-inflammatory cytokines such as IFNγ and IL-6 contributes to pathogenesis of SLE. In addition, cross-regulation between type I IFNs and TNFα and its potential role in SLE pathogenesis is discussed.     

Pathogenetic role of glomerular CXCL13 expression in lupus nephritis

Podocytes maintain the structure and function of the glomerular filtration barrier. However, podocytes have recently been implicated in the innate immune response, and their function as non‐haematopoietic antigen‐presenting cells was highlighted. We have shown previously that excessive expression of the chemokine CXCL13 is a distinctive early event for nephritis in a murine model of systemic lupus erythematosus (SLE). Furthermore, we found that CXCL13 is elevated significantly in the serum of patients with SLE‐nephritis. In this study, we were able to show for the first time that (i) CXCL13 is expressed locally in glomeruli in a model for SLE‐nephritis in mice and that (ii) incubation of human podocytes with CXCL13 induces receptor stimulation of CXCR5 with activation of signalling pathways, resulting in (iii) secretion of proinflammatory cytokines and chemokines in culture supernatant. This cytokine/chemokine cocktail can lead to (iv) a neutrophil respiratory burst in isolated human granulocytes. Taken together, our results provide further evidence that CXCL13 is involved in the pathogenesis of glomerulonephritis and that podocytes can play an active role in local proinflammatory immune responses. Thus, CXCL13 could be a direct target for the therapy of glomerulonephritis in general and for SLE‐nephritis in particular.     

Expression and Function of Dectin-1 is Defective in Monocytes from Patients with Systemic Lupus Erythematosus and Rheumatoid Arthritis

The aim of this work was to study the expression and function of the innate immune receptor dectin-1 in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). We studied twenty-six patients with SLE not receiving immunosuppressive therapy, twenty-six patients with RA, and fifteen controls. We found that monocytes from SLE patients showed a diminished expression of dectin-1 compared to healthy controls, and an inverse correlation between percent of dectin-1⁺ cells and the disease activity score was detected. In addition, cells from SLE patients showed an abnormal calcium flux response induced by dectin-1 ligands as well as an enhanced release of IL-1β, IL-6 and TNF-α, but not IL-23, upon dectin-1 engagement. Monocytes from patients with RA also showed a diminished expression, and a defective function of dectin-1. Our data suggest that dectin-1 receptor defects could contribute to the pathogenesis of autoimmune inflammatory conditions.     

Sjögren's syndrome autoantibodies provoke changes in gene expression profiles of inflammatory cytokines triggering a pathway involving TACE/NF-κB

We explore the association of the inflammatory gene expression profile observed in the chronic inflammatory autoimmune disorder Sj?gren's syndrome (SS) with changes in TNF-α converting enzyme (TACE), tumor necrosis factor (TNF)-α and nuclear factor (NF)-κB levels showing that pathways that include TNF-α signaling converge on NF-κB contributing to exacerbate the diseases. The treatment of human salivary gland epithelial cells (SGECs) with SS anti-Ro/SSA autoantibodies (Abs) result in a progressive increase in NF-κB-DNA binding, that includes a marked enhancement in NF-κB subunit p65 protein-DNA binding. A human cytokine multi-analyte array demonstrated that the NF-κB proinflammatory target genes, increased by anti-Ro/SSA Abs treatment, includes CXC chemokines (CXCL1, CXCL6 and CXCL9), CC chemokines (CCL2, CCL13 and CCL20), interleukins (IL-1α, IL-1β, IL-1F8, IL-6, IL-8, IL-9, IL-13, IL-17 and IL-22) and their receptors (IL-1RN, IL-10Rα, IL-13Rα, CCR1, CCR2, CCR3, CCR4 and CXCR1). Blockade of TACE through the use of the specific inhibitor TAPI-1 regulates proinflammatory cytokines production in SGEC treated with anti-Ro/SSA Abs inhibiting NF-κB nuclear translocation and activation. To further investigate the role of NF-κB on anti-Ro/SSA Abs-determined proinflammatory gene expression, we used the inhibitory protein IκB-α dominant negative super-repressor as inhibitor of NF-κB-DNA binding, demonstrating that transfection with dominant-negative IκB-α in anti-Ro/SSA-treated SGEC determined a marked reduction of proinflammatory cytokines gene expression. Although further studies are needed to clarify the mechanisms underlying SS, our results demonstrate that SS Abs exert their pathogenic effects via triggering the TACE/TNF-α/NF-κB axis.     

Infiltrating CD8+ T cells in oral lichen planus predominantly express CCR5 and CXCR3 and carry respective chemokine ligands RANTES/CCL5 and IP-10/CXCL10 in their cytolytic granules: a potential self-recruiting mechanism

Lichen planus is a chronic inflammatory disease of the skin and oral mucosa in which the cell-mediated cytotoxicity is regarded as a major mechanism of pathogenesis. To understand its pathophysiology further, the present study examined the in situ expression of chemokines and chemokine receptors in oral lichen planus. Immunohistochemical analysis of 15 cases has consistently revealed that infiltrating CD4(+) and CD8(+) T cells in the submucosa predominantly expressed CCR5 and CXCR3. Furthermore, infiltrating T cells, particularly CD8(+) T cells, were positive for RANTES/CCL5 and IP-10/CXCL10, the ligands of CCR5 and CXCR3, respectively. By immunoelectron microscopy, these chemokines were localized in the cytolytic granules of CD8(+) T cells. Lesional keratinocytes also overexpressed the ligands of CXCR3, namely, MIG/CXCL9, CXCL10, and I-TAC/CXCL11. Our data suggest that the chemokines signaling via CCR5 and CXCR3, which are known to be selectively expressed by type 1 T cells, are predominantly involved in T-cell infiltration of oral lichen planus. Furthermore, the presence of CCL5 and CXCL10 in the cytolytic granules of tissue-infiltrating CD8(+) T cells expressing CCR5 and CXCR3 reveals a potential self-recruiting mechanism involving activated effector cytotoxic T cells.     

Photosensitivity,Apoptosis, and Cytokines in the Pathogenesis of Lupus Erythematosus: a Critical Review

The underlying pathomechanisms of lupus erythematosus (LE), a multifactorial autoimmune disease, remain elusive. Due to the clinical evidence demonstrating a clear relationship between ultraviolet (UV) light exposure and skin lesions of LE, photosensitivity has been proven to be an important factor in the pathogenesis of the disease. Standardised photoprovocation with UVA and UVB irradiation has been shown to be a reliable model for evaluating photosensitivity in patients with cutaneous LE (CLE) and analysing the underlying medical conditions of the disease. In this respect, UV irradiation can cause aberrant induction of apoptosis in keratinocytes and contribute to the appearance of excessive apoptotic cells in the skin of CLE patients. Moreover, apoptotic cells that cannot be cleared by phagocytes may undergo secondary necrosis and release proinflammatory compounds and potential autoantigens, which may contribute to the inflammatory micromilieu that leads to formation of skin lesions in the disease. In addition to UV-mediated induction of apoptosis, the molecular and cellular factors that may cause the abnormal long-lasting photoreactivity in CLE include mediators of inflammation, such as cytokines and chemokines. In particular, interferons (IFNs) are important players in the early activation of the immune system and have a specific role in the immunological interface between the innate and the adaptive immune system. The fact that treatment with recombinant type I IFNs (α and β) can induce not only systemic organ manifestations but also LE-like skin lesions provides additional evidence for a pathogenetic role of these IFNs in the disease.     

Type I interferon modulation of cellular responses to cytokines and infectious pathogens: potential role in SLE pathogenesis

Type I interferons (IFNs) are pleiotropic cytokines that have been implicated in the pathogenesis of systemic lupus erythematosus (SLE). A key aspect of type I IFN biology is that previous exposure to type I IFNs alters subsequent cellular responses to extracellular stimuli. Type I IFNs may either prime cells for stronger responses to viruses, bacterial pathogens and cytokines such as IL-6 and IFN-gamma, or may suppress cellular responses to LPS and TNFalpha. Herein, we review type I IFN signal transduction via the Jak-STAT pathway, and mechanisms by which type I IFNs prime or suppress responses to environmental factors. We develop a hypothesis that type I IFN-dependent priming/enhancement of cellular responses to pro-inflammatory cytokines such as IFNgamma and IL-6 contributes to pathogenesis of SLE. In addition, cross-regulation between type I IFNs and TNFalpha and its potential role in SLE pathogenesis is discussed.     

Immunologic and genetic considerations of cutaneous lupus erythematosus: A comprehensive review

Cutaneous lupus erythematosus (CLE) refers to those subtypes of lupus erythematosus (LE) that have predominantly skin manifestations. Discoid lupus erythematosus (DLE), subacute cutaneous lupus erythematosus (SCLE), LE panniculitis (LEP) and lupus erythematosus tumidus (LET) all fall into the category of CLE. The pathogenesis of CLE is likely multifactorial. UV irradiation has been shown to induce keratinocyte apoptosis. Impaired clearance of apoptotic cells is a potential mechanism for the development of CLE. UV irradiation can also induce externalization of autoantigens such as Ro/SSA, exposing them to circulating autoantibodies. Some drugs have been associated with CLE. Possible mechanisms include stimulation of an immune response through disruption of central tolerance and altered T cell function. T17 cells may also play a role in the pathogenesis of CLE as they have been detected in skin lesions of LE. Treg cells have been found to be decreased in LE lesions, which may contribute to the breakdown of self-tolerance. Epidermal Langerhans cells are reduced in CLE while plasmacytoid DCs are increased in the lesions of CLE, suggesting that DCs may also play an important role in the pathogenesis of CLE. Type I IFN- and TNF-α are both upregulated in lesions of CLE. Other cytokines such as IL-6 and IL-17 are also implicated in the pathogenesis of CLE. Cellular and cytokine networks can be impacted by environmental factors and genetic variations and this can result in an increased risk of developing autoimmune diseases such as CLE.     

Emerging roles for the interferon-inducible p200-family proteins in sex bias in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease involving multiple organs. The disease is characterized by the production of pathogenic autoantibodies to DNA and certain nuclear antigens, chronic inflammation, and immune dysregulation. Genetic studies involving SLE patients and mouse models have indicated that multiple lupus susceptible genes contribute to the disease phenotype. Notably, the development of SLE in patients and in certain mouse models exhibits a strong sex bias. In addition, several lines of evidence indicates that activation of interferon-α (IFN-α) signaling in immune cells and alterations in the expression of certain immunomodulatory cytokines contribute to lupus pathogenesis. Studies have implicated factors, such as the X chromosomal gene dosage effect and the sex hormones, in gender bias in SLE. However, the molecular mechanisms remain unclear. Additionally, it remains unclear whether these factors influence the "IFN-signature," which is associated with SLE. In this regard, a mutually positive regulatory feedback loop between IFNs and estrogen receptor-α (ERα) has been identified in immune cells. Moreover, studies indicate that the expression of certain IFN-inducible p200-family proteins that act as innate immune sensors for cytosolic DNA is differentially regulated by sex hormones. In this review, we discuss how the modulation of the expression of the p200-family proteins in immune cells by sex hormones and IFNs contributes to sex bias in SLE. An improved understanding of the regulation and roles of the p200-family proteins in immune cells is critical to understand lupus pathogenesis as well as response (or the lack of it) to various therapies.     

Differential expression of CXCR3 targeting chemokines CXCL10, CXCL9, and CXCL11 in different types of skin inflammation

Recruitment of activated T-cells to the skin is a common feature in a wide variety of inflammatory skin diseases. As CXCR3 activating chemokines CXCL10 (IP-10), CXCL9 (Mig), and CXCL11 (IP-9/I-TAC) specifically attract activated T-cells, this study addressed the question of whether differences in the expression of these chemokines correlate with the site and cellular composition of the skin infiltrates in different types of inflammatory skin disease. Skin biopsies from lichen planus, chronic discoid lupus erythematosus, allergic patch test reactions, psoriasis, and Jessner's lymphocytic infiltration of the skin were investigated for chemokine expression using RNA in situ hybridization, and for the expression of CXCR3 using immunohistochemistry. The results showed differential expression of CXCL10, CXCL9, and CXCL11, which correlated with differences in the localization and cellular composition of the infiltrates. Whereas CXCL10 and CXCL11 were mainly expressed by basal keratinoctyes, CXCL9 mRNA expression was located predominantly in the dermal infiltrates. Correlation with immunohistochemical data suggested that macrophages and activated keratinocytes were the main producers of these chemokines. CXCR3 was expressed by a majority of both CD4+ and CD8+ infiltrating T-cells, suggesting a functional interaction between locally produced chemokines and CXCR3-expressing T-cells. In conclusion, these findings indicate that these CXCR3 activating chemokines play a significant role in the recruitment and maintenance of T-cell infiltrates in the inflammatory skin diseases studied.     

CXCR5 is critically involved in progression of lupus through regulation of B cell and double‐negative T cell trafficking

The recruitment of immune cells to sites of tissue inflammation is orchestrated by chemokine/chemokine receptor networks. Among these, the CXCL13/CXCR5 axis is thought to be involved critically in systemic lupus erythematosus (SLE) and lupus nephritis pathogenesis. Beyond B cell abnormalities, another hallmark of SLE disease is the occurrence of aberrant T cell responses. In particular, double‐negative (DN) T cells are expanded in the peripheral blood of patients with SLE and in lupus‐prone mice. DN T cells induce immunoglobulin production, secrete proinflammatory cytokines and infiltrate inflamed tissue, including kidneys. We aimed to investigate how CXCR5 deficiency changes immune cell trafficking in murine lupus. We therefore crossed CXCR5^–/– mice with B6/lpr mice, a well‐established murine lupus model. B cell numbers and B cellular immune responses were diminished in CXCR5‐deficient B6/lpr mice. In addition, we observed reduced accumulation of DN T cells in spleen and lymph nodes, paralleled by reduced splenomegaly and lymphadenopathy. In‐vivo migration assays revealed reduced migration of CXCR5‐deficient DN T cells into lymph nodes, and ex‐vivo‐activated CXCR5‐deficient DN T cells failed to infiltrate kidneys of recipients. Moreover, DN T cells and B cells of CXCR5‐deficient B6/lpr mice failed to migrate towards CXCL13 in vitro. We propose that CXCR5 is involved critically in B cell trafficking and germinal cell (GC) formation in murine lupus and in guiding pathogenic DN T cells into lymphoid organs and kidneys, and we therefore describe new pathomechanisms for the CXCL13/CXCR5 axis in SLE.     

Microarray Analysis of Interferon-regulated Genes in SLE

Altered regulation of interferon-α (IFNα) in systemic lupus erythematosus (SLE) was first demonstrated nearly 25 years ago. However, only recently has due attention been directed towards the central role of this cytokine family in SLE. Several laboratories have used large-scale microarray technology to study global gene expression patterns in heterogeneous populations of peripheral blood cells from lupus patients and control subjects. The results of these studies demonstrate that IFN-regulated genes are among the most significantly overexpressed in SLE mononuclear cells. In view of the protean effects of IFNs on immune system function, increased activity of IFNs may account for many of the immune system alterations that characterize SLE and contribute to autoimmunity. Definition of the nature of the major IFNs, or other factors, that drive the IFN-regulated gene expression signature noted in SLE is an important area for investigation that may lead to new approaches to targeted therapy of SLE.     

The pathogenesis of cutaneous lupus erythematosus: The aberrant distribution and function of different cell types in skin lesions

Cutaneous lupus erythematosus (CLE) is an autoimmune disease with a broad range of cutaneous manifestations. In skin lesions of CLE, keratinocytes primarily undergo apoptosis. Interferon‐κ(IFN‐κ) is belonged to type I interferons (type I IFNs) and is selectively produced by keratinocytes. Recently, keratinocytes selectively produced IFN‐κ is identified to be a key to trigger type I interferon responses in CLE. Other immune cells such as plasmacytoid dendritic cells (pDCs) are identified to be relevant origin of type I interferons (type I IFNs) which are central to the development of CLE lesions and responsible for mediating Th1 cell activity. Other types of cells such as neutrophils, B cells and Th17 cells also are involved in the development of this disease. The close interaction of those cells composes a comprehensive and complicated network in CLE. In this review, we discussed the aberrant distribution and function of different cells types involved in this disease and will offer a new direction for research and therapy in the near future.     

IgG opsonized nuclear remnants from dead cells cause systemic inflammation in SLE

Deficiencies in the recognition and engulfment of apoptotic cells have been reported in patients with systemic lupus erythematosus (SLE). If dying cells are not promptly cleared, they undergo secondary necrosis and release nuclear autoantigens. Secondarily necrotic cell-derived material (SNEC) can be generated in vitro employing various methods. SNEC generated by either methods shows similar DNA content, light scatter characteristics, and binding pattern of dead and dying cell ligands and is readily recognized by autoantibodies (AAb) of many patients with SLE. In whole blood, AAb opsonize SNEC and foster its uptake by blood-borne non-professional phagocytes. We observed a significant secretion of the inflammatory cytokines IL-8 and TNF-α by phagocytes which had engulfed different types of opsonized SNEC. Phagocytosis of SNEC and the subsequent production of inflammatory cytokines were strongly influenced by the presence of DNA in this prey, since DNase I treatment reduced both the uptake of SNEC and the induction of IL-8 and TNF-α production. In conclusion, the proinflammatory phagocytosis by circulating phagocytes of IgG-opsonized cellular remnants fosters systemic inflammation in SLE.     

雷公藤内酯醇对系统性红斑狼疮患者DC细胞功能及成熟的影响

目的 通过体外实验研究雷公藤内酯醇(triptolide)对系统性红斑狼疮(systemic lupus erythematosus,SLE)患者树突状细胞(dendritic cell,DC)功能及成熟的影响,为进一步阐明雷公藤内酯醇的免疫学活性提供依据.方法 从SLE患者外周血分离单个核细胞,流式细胞仪分选DC,加入0、5、10、30μg/L的雷公藤内酯醇共孵育,24h后收集上清液,ELISA检测IFN-α、IL-6、TNF-α量,5d后收集细胞,流式细胞仪检测DC表型CD11c、CD80、CD86阳性率,光镜观察DC的形态,扫描电镜观察DC的超微结构.结果 雷公藤内酯醇显著减低活动期与非活动期SLE患者IFN-α、IL-6、TNF-α量,并呈雷公藤内酯醇浓度依赖性(P＜0.05);雷公藤内酯醇可抑制SLE患者DC的分化和成熟,并呈雷公藤内酯醇浓度依赖性(P＜0.05).结论 雷公藤内酯醇能够减弱SLE患者DC的功能,并抑制其分化和成熟.     

Tumor-associated macrophages promote the metastasis of ovarian carcinoma cells by enhancing CXCL16/CXCR6 expression

This study investigated the underlying mechanism by which C-X-C motif chemokine ligand 16 (CXCL16)/C-X-C motif chemokine receptor 6 (CXCR6) signaling is activated by tumor-associated macrophages and assists in regulating the metastasis of ovarian carcinoma. Specimens of ovarian carcinoma tissue and adjacent tissue were collected from 20 ovarian carcinoma patients. Human THP-1 cells were induced to differentiate into macrophages, which were then co-cultured with SKOV3 cells and low concentrations of tumor necrosis factor-α (TNF-α) to simulate the inflammatory microenvironment of ovarian carcinoma. Additionally, small interfering RNA (siRNA) targeting CXCR6 was transfected into SKOV3 cells; after which, the levels of nuclear factor kappa B p65 (NF-κB p65) protein and phosphorylated PI3K and Akt were measured. The migration and invasion abilities of the SKOV3 cells were also tested. The levels of TNF-α, interluekin-6 (IL-6), NF-κB p65, CXCL16, and CXCR6 expression in the ovarian carcinoma tissues were higher than those in the precancerous tissues. CXCR6 expression was positively correlated with TNF-α, IL-6, and CXCL16 expression. Co-culture of SKOV3 cells with macrophages significantly promoted CXCL16, CXCR6, NF-κB, and p65 expression by the SKOV3 cells, increased their levels of phosphorylated PI3K and Akt, and increased the migration and invasion abilities of SKOV3 cells. Silencing of CXCR6 or blocking the PI3K/Akt signal pathway markedly attenuated the expression of NF-κB p65 and phosphorylation of PI3K and Akt, as well as the migration and invasion abilities of SKOV3 cells. These findings demonstrate that macrophages can promote the migration and invasion of ovarian carcinoma cells by affecting the CXCL16/CXCR6 pathway.