Fumitaka Terabe

IL-6 blockade inhibits the induction of myelin antigen-specific Th17 cells and Th1 cells in experimental autoimmune encephalomyelitis

The development of Th17 cells is a key event in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), a murine model of human multiple sclerosis (MS). Previous studies have demonstrated that an IL-6-dependent pathway is involved in the differentiation of Th17 cells from naïve CD4-positive T cells in vitro. However, the role of IL-6 in vivo in the development of Th17 cells in EAE has remained unclear. In the present study, we found that IL-6 blockade by treatment with an anti-IL-6 receptor monoclonal antibody (anti-IL-6R mAb) inhibited the development of EAE and inhibited the induction of myelin oligodendrocyte glycoprotein (MOG) peptide-specific CD4-positive, CD8-positive, and Th17 T cells, in inguinal lymph nodes. Thus, the protective effect of IL-6 blockade in EAE is likely to be mediated via the inhibition of the development of MOG-peptide-specific Th17 cells and Th1 cells, which in turn leads to reduced infiltration of T cells into the CNS. These findings indicate that anti-IL-6R mAb treatment might represent a novel therapy for human MS.

The Influence of Excessive IL-6 Production In Vivo on the Development and Function of Foxp3+ Regulatory T Cells

IL-6 is a proinflammatory cytokine and its overproduction is implicated in a variety of inflammatory disorders. Recent in vitro analyses suggest that IL-6 is a key cytokine that determines the balance between Foxp3+ regulatory T cells (Tregs) and Th17 cells. However, it remains unclear whether excessive IL-6 production in vivo alters the development and function of Foxp3+ Tregs. In this study, we analyzed IL-6 transgenic (Tg) mice in which serum IL-6 levels are constitutively elevated. Interestingly, in IL-6 Tg mice, whereas peripheral lymphoid organs were enlarged, and T cells exhibited activated phenotype, Tregs were not reduced but rather increased compared with wild-type mice. In addition, Tregs from Tg mice normally suppressed proliferation of naive T cells in vitro. Furthermore, Tregs cotransferred with naive CD4 T cells into SCID–IL-6 Tg mice inhibited colitis as successfully as those transferred into control SCID mice. These results indicate that overproduction of IL-6 does not inhibit development or function of Foxp3+ Tregs in vivo. However, when naive CD4 T cells alone were transferred, Foxp3+ Tregs retrieved from SCID–IL-6 Tg mice were reduced compared with SCID mice. Moreover, the Helios− subpopulation of Foxp3+ Tregs, recently defined as extrathymic Tregs, was significantly reduced in IL-6 Tg mice compared with wild-type mice. Collectively, these results suggest that IL-6 overproduced in vivo inhibits inducible Treg generation from naive T cells, but does not affect the development and function of natural Tregs.

iTRAQ-based proteomic identification of leucine-rich α-2 glycoprotein as a novel inflammatory biomarker in autoimmune diseases

Objective To identify a novel serum biomarker of disease activity in inflammatory autoimmune disorders. Methods Sera obtained from rheumatoid arthritis (RA) patients before and after anti-TNF therapy were analysed by iTRAQ (isobaric tags for relative and absolute quantitation) quantitative proteomic analysis and further validated by ELISA. Results Of 326 proteins identified by proteomic analysis, increased serum levels of leucine-rich α-2 glycoprotein (LRG) was identified in RA patients before therapy. Serum LRG concentrations were significantly elevated in RA patients compared with healthy controls and decreased after anti-TNF therapy. Furthermore, serum LRG concentrations correlated with disease activity in RA and Crohns disease (CD). Interestingly, in a subpopulation of patients with active CD and normal C-reactive protein levels, serum LRG concentrations were elevated. Conclusions LRG represents a novel serum biomarker for monitoring disease activity during therapy in autoimmune patients, particularly useful in patients with active disease but normal CRP levels.

Blockade of interleukin-6 signaling suppresses experimental autoimmune uveoretinitis by the inhibition of inflammatory Th17 responses.

The aim of this study was to investigate the effect of anti-mouse IL-6 receptor monoclonal antibody (MR16-1) treatment on CD4 T cell differentiation and compared it to the effect of anti-TNF mAb treatment with using a murine model of experimental autoimmune uveoretinitis (EAU). C57BL/6 mice were immunized with interphotoreceptor retinoid-binding protein (IRBP) to induce ocular inflammation treatment with control IgG or MR16-1 or anti-TNF mAb. Helper T cells differentiation was analyzed during the development of EAU. Immunization with IRBP increased the frequency of Th17 cells rather than Th1 cells in the early stage of EAU. Treatment with MR16-1 on the same day as immunization (day 0) or one day after (day 1) suppressed ocular inflammation in EAU mice. Treatment with MR16-1 on day 0 inhibited the induction of Th17 cells in vivo, and inhibited not only IRBP-responsive Th17 cells but also their Th1 counterparts and induced IRBP-responsive regulatory T (Treg) cells in vitro. The administration of anti-TNF mAb had no significant protective effect in EAU mice. The protective effect of anti-IL-6R mAb treatment, but not anti-TNF mAb treatment on EAU correlated with the inhibition of Th17 differentiation. This finding suggests that IL-6 blockade may have a therapeutic effect on human ocular inflammation which is mediated via mechanisms distinct from those of TNF blockade. IL-6 blockade may thus represent an alternative therapy for patients with ocular inflammation who are refractory to anti-TNF mAb therapy.

Blockade of interleukin-6 receptor alleviates disease in mouse model of scleroderma.

Activation of fibroblasts by interleukin-6 (IL-6) is implicated in the pathogenesis of scleroderma, suggesting that the inhibition of fibroblast activation may be a promising scleroderma treatment. In this study, we used an IL-6 blocking antibody (Ab) and Il-6 knockout (Il-6KO) mice to examine the role of IL-6 in the bleomycin (BLM)-induced mouse model of scleroderma. BLM was administered to C57BL/6 and Il-6KO mice to induce dermal sclerosis. BLM-treated and control phosphate-buffered saline-treated mice were treated with anti-mouse IL-6 receptor monoclonal Ab (MR16-1). Disease severity was evaluated by measuring dermal thickness and skin hardness, by counting the numbers of α-smooth muscle actin-positive cells and mast cells, and by examining the cutaneous draining lymph nodes. C57BL/6 mice with BLM induced scleroderma had elevated serum IL-6 levels and more severe dermal sclerosis than Il-6KO mice. Weekly administration of MR16-1, but not control Ab, prevented and improved dermal sclerosis, and also attenuated swelling of the draining lymph nodes. MR16-1 suppressed α-smooth muscle actin induction in IL-6-stimulated Il-6KO fibroblasts. Our results indicate that IL-6 contributes to BLM induced dermal sclerosis and that IL-6 receptor-specific monoclonal Ab may improve the symptoms of scleroderma by suppressing fibroblast activation.

Suppressor of cytokine signaling-1 ameliorates dextran sulfate sodium-induced colitis in mice

Inflammatory bowel disease (IBD) is a chronic disorder of the gastrointestinal tract. Although the etiology and pathogenesis of IBD remain unknown, pro-inflammatory cytokines including IFN-gamma play an important role in the development of IBD. Suppressor of cytokine signaling-1 (SOCS-1) is a crucial inhibitor of cytokine signaling, particularly of IFN-gamma. In this study, we investigated the role of SOCS-1 in the development of murine dextran sulfate sodium (DSS)-induced colitis, a model of colitis resembling human IBD. SOCS-1 heterozygous (SOCS-1(+/-)) and wild-type (WT) mice were given 3% DSS dissolved in drinking water for 5 days. Activation and expression of signal transducers and activators of transcription (STAT) in colonic tissues were assessed by western blot analysis. The expression of CD4, IFN-gamma, IL-4, IL-17 and Forkhead box P3 (Foxp3) in colonic lamina propria lymphocytes was analyzed by flow cytometry and cytokine concentrations in serum were measured. DSS-treated SOCS-1(+/-) mice developed more severe colitis than DSS-treated WT mice. Enhanced activation of STAT1, a higher ratio of CD4(+)IFN-gamma(+) T cells and a lower frequency of Foxp3(+) regulatory T (Treg) cells, were observed in the colon of DSS-treated SOCS-1(+/-) mice compared with DSS-treated WT mice. DSS-treated SOCS-1(+/-) mice showed higher levels of IFN-gamma in sera than did DSS-treated WT mice. Furthermore, T cell-specific SOCS-1-conditional knockout mice developed more severe colitis than control mice after DSS administration. Our findings suggest that SOCS-1, particularly in T cells, prevents the development of DSS-induced colitis in mice by inhibiting IFN-gamma/STAT1 signaling and by subsequently regulating Treg cell development.

Blockade of interleukin-6 signaling suppresses not only th17 but also interphotoreceptor retinoid binding protein-specific Th1 by promoting regulatory T cells in experimental autoimmune uveoretinitis.

PURPOSE. Both Th17 and Th1 cells contribute to experimental autoimmune uveoretinitis (EAU). Interleukin-6 (IL-6) blockade inhibits Th17 differentiation in EAU and potently suppresses ocular inflammation, although its effect on Th1 cells is unknown. To clarify the mechanism of IL-6 blockade, the authors investigated T helper cells with particular focus on Th1 and regulatory T cells (Treg) in EAU of IL-6 gene knockout (KO) mice. METHODS. EAU was induced in wild-type (WT) mice and in mice lacking IL-6 (IL-6KO), IL-17 (IL-17KO), and IFN-γ (GKO) on a C57BL/6 background. Clinical scores of EAU, cytokine levels in supernatants from ocular tissue homogenates, and T helper cell differentiation in lymph nodes in each mouse were examined. To study the roles of Treg cells, EAU was induced in IL-6KO mice treated with anti-CD25 monoclonal antibody (mAb) to deplete Treg cells in vivo. RESULTS. Inflammation was comparable between WT, IL-17KO, and GKO mice but was absent in IL-6KO mice. Th17 and interphotoreceptor retinoid binding protein (IRBP)-specific Th1 cells were increased in GKO and IL-17KO mice, respectively, whereas both populations were reduced in IL-6KO mice. Th1-dominant EAU in IL-17KO mice was suppressed by anti-IL-6R mAb treatment. Treg cell depletion in vivo induced EAU in IL-6KO mice. CONCLUSIONS. After the induction of EAU, IL-6 deficiency resulted in the inhibition of the IRBP-specific Th1 response and enhanced the generation of IRBP-specific Treg cells. Furthermore, Treg was needed to inhibit Th1 responses and ocular inflammation in IL-6KO mice. Protective effects of IL-6 signaling blockade in EAU involve not only Th17 cell inhibition but also IRBP-specific Treg cell promotion.

Serum leucine-rich alpha-2 glycoprotein is a disease activity biomarker in ulcerative colitis

Background: Reliable biomarkers for monitoring disease activity have not been clinically established in ulcerative colitis (UC). This study aimed to investigate whether levels of serum leucine‐rich alpha‐2 glycoprotein (LRG), identified recently as a potential disease activity marker in Crohns disease and rheumatoid arthritis, correlate with disease activity in UC. Methods: Serum LRG concentrations were determined by enzyme‐linked immunosorbent assay (ELISA) in patients with UC and healthy controls (HC) and were evaluated for correlation with disease activity. Expression of LRG in inflamed colonic tissues from patients with UC was analyzed by western blotting and immunohistochemistry. Interleukin (IL)‐6‐independent induction of LRG was investigated using IL‐6‐deficient mice by lipopolysaccharide (LPS)‐mediated acute inflammation and dextran sodium sulfate (DSS)‐induced colitis. Results: Serum LRG concentrations were significantly elevated in active UC patients compared with patients in remission (P < 0.0001) and HC (P < 0.0001) and were correlated with disease activity in UC better than C‐reactive protein (CRP). Expression of LRG was increased in inflamed colonic tissues in UC. Tumor necrosis factor alpha (TNF‐&agr;), IL‐6, and IL‐22, serum levels of which were elevated in patients with active UC, could induce LRG expression in COLO205 cells. Serum LRG levels were increased in IL‐6‐deficient mice with LPS‐mediated acute inflammation and DSS‐induced colitis. Conclusions: Serum LRG concentrations correlate well with disease activity in UC. LRG induction is robust in inflamed colons and is likely to involve an IL‐6‐independent pathway. Serum LRG is thus a novel serum biomarker for monitoring disease activity in UC and is a promising surrogate for CRP. (Inflamm Bowel Dis 2012;)

Imatinib mesylate inhibited rat adjuvant arthritis and PDGF-dependent growth of synovial fibroblast via interference with the Akt signaling pathway

Overgrowth of the synovium plays an important role in the pathogenesis of rheumatoid arthritis (RA). Platelet-derived growth factor (PDGF) is one of the most potent mitogenic factors of synovial cells, and imatinib mesylate (imatinib) is a specific inhibitor of the PDGF receptor tyrosine kinase. The aim of this study was to elucidate the anti-rheumatic activity of imatinib. The in vivo effects of imatinib were assessed by evaluating the sequential manifestation of adjuvant-induced arthritis in rats using paw volume and clinical scores. Imatinib was found to inhibit rat adjuvant-induced arthritis, but the inhibitory effects were incomplete. To confirm the mechanism of anti-rheumatic-activity of imatinib, we assessed the in vitro effects of imatinib on the proliferation of RA synovial fibroblast-like cells (RASFs) using a MTT assay. Intracellular signaling of PDGF was evaluated by Western blot analysis. Platelet-derived growth factor was found to induce a significant proliferation of RASFs, while imatinib inhibited PDGF-induced proliferation of RASF. Imatinib also inhibited PDGF-induced phosphorylation of the PDGF receptor and Akt, whereas constitutive activated extracellular signal-regulated kinase was not inhibited by imatinib. In contrast, imatinib did not inhibit transforming growth factor β- and basic fibroblast growth factor-induced proliferation of RASF. Oral administration of imatinib ameliorated adjuvant-induced arthritis in rats, and it inhibited PDGF-induced RASF proliferation through disruption of the PDGF-R to Akt kinase signaling pathway. Because imatinib cannot inhibit the non-PDGF-dependent proliferation of RASFs, the anti-rheumatic effect of imatinib may be incomplete. The development of inhibitors of RASF proliferation may lead to the successful treatment of RA.

Green tea polyphenol epigallocatechin gallate inhibits cell signaling by inducing SOCS1 gene expression

Therapeutic effects of green tea involve an inhibitory function of its constituent polyphenol epigallocatechin gallate (EGCG) on cell signaling. The specificity and mechanism(s) by which EGCG inhibits cell signaling have remained unclear. Here, we demonstrate that green tea and EGCG induce suppressor of cytokine signaling 1 (SOCS1) gene expression, a negative regulator of specific cell signaling pathways. In mouse immune cells, EGCG induces SOCS1 expression via an oxidative (superoxide) pathway and activation of the signal transducer and activator of transcription 5 transcription factor. EGCG inhibited SOCS1-regulated cell signaling, but this inhibitory effect was abrogated in cells deficient in SOCS1. These findings identify a mechanism by which EGCG inhibits cell signaling with specificity, mediated by induction of the negative regulator SOCS1.