Hui-Rong Jiang

IL-33 exacerbates antigen-induced arthritis by activating mast cells

IL-33, a cytokine of the IL-1 family, is closely associated with type II T cell responses. Here, we report an unexpected proinflammatory role of IL-33 in inflammatory arthritis. IL-33 was expressed in synovial fibroblasts from patients with rheumatoid arthritis (RA). Expression was markedly elevated in vitro by inflammatory cytokines. Mice lacking ST2, the IL-33 receptor α-chain, developed attenuated collagen-induced arthritis (CIA) and reduced ex vivo collagen-specific induction of proinflammatory cytokines (IL-17, TNFα, and IFNγ), and antibody production. Conversely, treatment of wild-type (WT) but not ST2−/− mice with IL-33 exacerbated CIA and elevated production of both proinflammatory cytokines and anti-collagen antibodies. Mast cells expressed high levels of ST2 and responded directly to IL-33 to produce a spectrum of inflammatory cytokines and chemokines in vitro. In vivo, IL-33 treatment exacerbated CIA in ST2−/− mice engrafted with mast cells from WT but not from ST2−/− mice. Disease exacerbation was accompanied by elevated expression levels of proinflammatory cytokines. Our results demonstrate that IL-33 is a critical proinflammatory cytokine for inflammatory joint disease that integrates fibroblast activation with downstream immune activation mainly via an IL-33-driven, mast-cell-dependent pathway. Thus, this IL-1 superfamily member represents a therapeutic target for RA.

IL-33 attenuates EAE by suppressing IL-17 and IFN-γ production and inducing alternatively activated macrophages

Interleukin (IL)‐33, a member of the IL‐1 cytokine family, is an important modulator of the immune system associated with several immune‐mediated disorders. High levels of IL‐33 are expressed by the central nervous system (CNS) suggesting a potential role of IL‐33 in autoimmune CNS diseases. We have investigated the expression and function of IL‐33 in the development of experimental autoimmune encephalomyelitis (EAE) in mice. We report here that IL‐33 and its receptor ST2 (IL‐33Rα) are highly expressed in spinal cord tissue, and ST2 expression is markedly increased in the spinal cords of mice with EAE. Furthermore, ST2‐deficient (ST2−/−) mice developed exacerbated EAE compared with wild‐type (WT) mice while WT, but not ST2−/− EAE mice treated with IL‐33 developed significantly attenuated disease. IL‐33‐treated mice had reduced levels of IL‐17 and IFN‐γ but produced increased amounts of IL‐5 and IL‐13. Lymph node and splenic macrophages of IL‐33‐treated mice showed polarization toward an alternatively activated macrophage (M2) phenotype with significantly increased frequency of MR+PD‐L2+ cells. Importantly, adoptive transfer of these IL‐33‐treated macrophages attenuated EAE development. Our data therefore demonstrate that IL‐33 plays a therapeutic role in autoimmune CNS disease by switching a predominantly pathogenic Th17/Th1 response to Th2 activity, and by polarization of anti‐inflammatory M2 macrophages.

Galectin-3 Deficiency Reduces the Severity of Experimental Autoimmune Encephalomyelitis

Galectin-3 (Gal-3) is a member of the β-galactoside-binding lectin family and plays an important role in inflammation. However, the precise role of Gal-3 in autoimmune diseases remains obscure. We have investigated the functional role of Gal-3 in experimental autoimmune encephalomyelitis (EAE) following immunization with myelin oligodendrocyte glycoprotein (MOG)35–55 peptide. Gal-3 deficient (Gal-3−/−) mice developed significantly milder EAE and markedly reduced leukocyte infiltration in the CNS compared with similarly treated wild-type (WT) mice. Gal-3−/− mice also contained fewer monocytes and macrophages but more apoptotic cells in the CNS than did WT mice. Following Ag stimulation in vitro, lymph node cells from the immunized Gal-3−/− mice produced less IL-17 and IFN-γ than did those of the WT mice. In contrast, Gal-3−/− mice produced more serum IL-10, IL-5, and IL-13 and contained higher frequency of Foxp3+ regulatory T cells in the CNS than did the WT mice. Furthermore, bone marrow-derived dendritic cells from Gal-3−/− mice produced more IL-10 in response to LPS or bacterial lipoprotein than did WT marrow-derived dendritic cells. Moreover, Gal-3−/− dendritic cells induced Ag-specific T cells to produce more IL-10, IL-5, and IL-12, but less IL-17, than did WT dendritic cells. Taken together, our data demonstrate that Gal-3 plays an important disease-exacerbating role in EAE through its multifunctional roles in preventing cell apoptosis and increasing IL-17 and IFN-γ synthesis, but decreasing IL-10 production.

IL-33 Exacerbates Autoantibody-Induced Arthritis

Rheumatoid arthritis pathogenesis comprises dysregulation in both innate and adaptive immunity. There is therefore intense interest in the factors that integrate these immunologic pathways in rheumatoid arthritis. In this paper, we report that IL-33, a novel member of the IL-1 family, can exacerbate anti–glucose-6-phosphate isomerase autoantibody-induced arthritis (AIA). Mice lacking ST2 (ST2−/−), the IL-33 receptor α-chain, developed attenuated AIA and reduced expression of articular proinflammatory cytokines. Conversely, treatment of wild-type mice with rIL-33 significantly exacerbated AIA and markedly enhanced proinflammatory cytokine production. However, IL-33 failed to increase the severity of the disease in mast cell-deficient or ST2−/− mice. Furthermore, mast cells from wild-type, but not ST2−/−, mice restored the ability of ST2−/− recipients to mount an IL-33–mediated exacerbation of AIA. IL-33 also enhanced autoantibody-mediated mast cell degranulation in vitro and in synovial tissue in vivo. Together these results demonstrate that IL-33 can enhance autoantibody-mediated articular inflammation via promoting mast cell degranulation and proinflammatory cytokine production. Because IL-33 is derived predominantly from synovial fibroblasts, this finding provides a novel mechanism whereby a host tissue-derived cytokine can regulate effector adaptive immune response via enhancing innate cellular activation in inflammatory arthritis.

MAP kinase phosphatase 2 deficient mice develop attenuated experimental autoimmune encephalomyelitis through regulating dendritic cells and T cells

Mitogen-activated protein kinase phosphatases (MKPs) play key roles in inflammation and immune mediated diseases. Here we investigated the mechanisms by which MKP-2 modulates central nervous system (CNS) inflammation in experimental autoimmune encephalomyelitis (EAE). Our results show that MKP-2 mRNA levels in the spinal cord and lymphoid organs of EAE mice were increased compared with naive controls, indicating an important role for MKP-2 in EAE development. Indeed, MKP-2−/− mice developed reduced EAE severity, associated with diminished CNS immune cell infiltration, decreased proinflammatory cytokine production and reduced frequency of CD4+ and CD8+ T cells in spleens and lymph nodes. In addition, MKP-2−/− CD11c+ dendritic cells (DCs) had reduced expression of MHC-II and CD40 compared with MKP-2+/+ mice. Subsequent experiments revealed that CD4+ T cells from naïve MKP-2−/− mice had decreased cell proliferation and IL-2 and IL-17 production relative to wild type controls. Furthermore, co-culture experiments showed that bone marrow derived DCs of MKP-2−/− mice had impaired capability in antigen presentation and T cell activation. While MKP-2 also modulates macrophage activation, our study suggests that MKP-2 is essential to the pathogenic response of EAE, and it acts mainly via regulating the important antigen presenting DC function and T cell activation.

Role of sphingosine 1-phosphate receptors, sphingosine kinases and sphingosine in cancer and inflammation

Sphingosine kinase (there are two isoforms, SK1 and SK2) catalyses the formation of sphingosine 1-phosphate (S1P), a bioactive lipid that can be released from cells to activate a family of G protein-coupled receptors, termed S1P1-5. In addition, S1P can bind to intracellular target proteins, such as HDAC1/2, to induce cell responses. There is increasing evidence of a role for S1P receptors (e.g. S1P4) and SK1 in cancer, where high expression of these proteins in ER negative breast cancer patient tumours is linked with poor prognosis. Indeed, evidence will be presented here to demonstrate that S1P4 is functionally linked with SK1 and the oncogene HER2 (ErbB2) to regulate mitogen-activated protein kinase pathways and growth of breast cancer cells. Although much emphasis is placed on SK1 in terms of involvement in oncogenesis, evidence will also be presented for a role of SK2 in both T-cell and B-cell acute lymphoblastic leukemia. In patient T-ALL lymphoblasts and T-ALL cell lines, we have demonstrated that SK2 inhibitors promote T-ALL cell death via autophagy and induce suppression of c-myc and PI3K/AKT pathways. We will also present evidence demonstrating that certain SK inhibitors promote oxidative stress and protein turnover via proteasomal degradative pathways linked with induction of p53-and p21-induced growth arrest. In addition, the SK1 inhibitor, PF-543 exacerbates disease progression in an experimental autoimmune encephalomyelitis mouse model indicating that SK1 functions in an anti-inflammatory manner. Indeed, sphingosine, which accumulates upon inhibition of SK1 activity, and sphingosine-like compounds promote activation of the inflammasome, which is linked with multiple sclerosis, to stimulate formation of the pro-inflammatory mediator, IL-1β. Such compounds could be exploited to produce antagonists that diminish exaggerated inflammation in disease. The therapeutic potential of modifying the SK-S1P receptor pathway in cancer and inflammation will therefore, be reviewed.

Recruitment of IFN-γ-Producing (Th1-Like) Cells into the Inflamed Retina In Vivo Is Preferentially Regulated by P-Selectin Glycoprotein Ligand 1:P/E-Selectin Interactions

Although there is evidence that altering the Th1/Th2 balance toward Th2 cells may be important in the resolution of Th1-type autoimmune disease, adoptive transfer of Th2 cells is not effective in protecting against Th1-type disease and may cause disease. Therefore, we examined the recruitment of Th1- and Th2-like cells into the retina in the murine autoimmune disease experimental autoimmune uveoretinitis. CD4 T cells were polarized in vitro to IFN-γ-producing Th1-like cells and non-IFN-γ-producing Th2-like cells, labeled, and adoptively transferred. Trafficking to the retina in vivo was evaluated by scanning laser ophthalmoscopy and infiltration by confocal microscopy. There were more rolling and adherent Th1-like cells and they rolled more slowly than did Th2-like cells. Th1-like cells were preferentially recruited into the retinal parenchyma at both initiation and resolution. Surface P-selectin glycoprotein ligand 1 (PSGL-1) and LFA-1 were up-regulated on both populations but were expressed at higher levels on Th1-like cells. Up-regulation of CD44 expression was higher on Th2-like cells. P-selectin, E-selectin, and ICAM-1 are up-regulated on postcapillary venules in the retina. Pretreatment of Th1-like cells with anti-PSGL-1 inhibited rolling and infiltration of Th1-like cells but not Th2-like cells, providing direct in vivo evidence for the inability of Th2 to respond to P/E-selectin despite increased expression of PSGL-1. Anti-LFA-1 pretreatment inhibited infiltration of both Th1- and Th2-like cells, but more so Th-1. We suggest that random trafficking of activated T cells (both Th1 and Th2) across the blood-retina barrier is mediated by CD44:CD44R and LFA-1:ICAM-1, whereas preferential recruitment of Th1 cells is mediated by PSGL-1:P/E-selectin.

Sialoadhesin Promotes the Inflammatory Response in Experimental Autoimmune Uveoretinitis

Macrophages are a prominent component of the effector cell compartment in a number of CD4+ T cell-mediated organ-specific autoimmune diseases. In this study, we investigated the role of the sialic acid binding Ig-like lectin sialoadhesin (Sn, Siglec-1) in a model of interphotoreceptor retinal binding protein peptide-induced experimental autoimmune uveoretinitis in mice with targeted deletion of Sn. Our data show that compared with wild-type mice, experimental autoimmune uveoretinitis is reduced in severity in the initial stages in the Sn knockout (KO) mice. In addition, there is a reduction in the proliferative capacity of T cells from the KO mice draining lymph nodes after immunization with interphotoreceptor retinal binding protein peptides, which is manifest some days before disease onset and persists for the duration of disease. Furthermore, activated T cells from the draining lymph nodes of Sn KO mice secrete lower levels of IFN-γ. The data suggest a role for Sn in “fine tuning” the immune response to autoantigens by modulating T cell priming.

Emerging role of interleukin‐33 in autoimmune diseases

Interleukin‐33 (IL‐33) is a member of the IL‐1 cytokine family. It predominantly induces type 2 immune responses and thus is protective against atherosclerosis and nematode infections but contributes to allergic airway inflammation. Interleukin‐33 also plays a pivotal role in the development of many autoimmune diseases through mechanisms that are still not fully understood. In this review, we focus on the recent advances in understanding of the expression and function of IL‐33 in some autoimmune disorders, aiming to provide insight into its potential role in disease development.

Reduction in shear stress, activation of the endothelium, and leukocyte priming are all required for leukocyte passage across the blood-retina barrier

The passage of leukocytes across the blood‐retina barrier at the early stages of an inflammatory reaction is influenced by a complex series of interactions about which little is known. In particular, the relationship between hydrodynamic factors, such as shear stress and leukocyte velocity, to the adherence and subsequent extravasation of leukocytes into the retina is unclear. We have used a physiological method, scanning laser ophthalmoscopy, to track labeled leukocytes circulating in the retina, followed by confocal microscopy of retinal flatmounts to detect infiltrating cells at the early stage of experimental autoimmune uveitis. This has shown that retinal vessels are subjected to high shear stress under normal circumstances. During the inflammatory reaction, shear stress in retinal veins is reduced 24 h before leukocyte infiltration. This reduction is negatively correlated with leukocyte rolling and sticking in veins and postcapillary venules, the sites of leukocyte extravasation. Activation of vascular endothelial cells is also a prerequisite for leukocyte rolling and infiltration. In addition, antigen priming of leukocytes is influential at the early stage of inflammation, and this is seen clearly in the reduction in rolling velocity and adherence of the primed leukocytes in activated retinal venules, 9 days postimmunization.