Hidetake Nagahara

Myeloid-Derived Suppressor Cells Play Crucial Roles in the Regulation of Mouse Collagen-Induced Arthritis

Myeloid-derived suppressor cells (MDSCs) are of myeloid origin and are able to suppress T cell responses. The role of MDSCs in autoimmune diseases remains controversial, and little is known about the function of MDSCs in autoimmune arthritis. In this study, we clarify that MDSCs play crucial roles in the regulation of proinflammatory immune response in a collagen-induced arthritis (CIA) mouse model. MDSCs accumulated in the spleens of mice with CIA when arthritis severity peaked. These MDSCs inhibited the proliferation of CD4+ T cells and their differentiation into Th17 cells in vitro. Moreover, MDSCs inhibited the production of IFN-γ, IL-2, TNF-α, and IL-6 by CD4+ T cells in vitro, whereas they promoted the production of IL-10. Adoptive transfer of MDSCs reduced the severity of CIA in vivo, which was accompanied by a decrease in the number of CD4+ T cells and Th17 cells in the draining lymph nodes. However, depletion of MDSCs abrogated the spontaneous improvement of CIA. In conclusion, MDSCs in CIA suppress the progression of CIA by inhibiting the proinflammatory immune response of CD4+ T cells. These observations suggest that MDSCs play crucial roles in the regulation of autoimmune arthritis, which could be exploited in new cell-based therapies for human rheumatoid arthritis.

The rapid efficacy of abatacept in a patient with rheumatoid vasculitis

We report a case of rheumatoid vasculitis (RV) that responded well to abatacept, a cytotoxic T lymphocyte-associated antigen 4 (CTLA4)-immunoglobulin fusion protein. A 38-year-old woman developed RV despite treatment with methotrexate and tumor necrosis factor (TNF) inhibitors. The effects of steroid therapy, immunoabsorption plasmapheresis, and interleukin-6 inhibitor were insufficient, however, administration of abatacept rapidly improved her clinical symptoms with almost normalization of the immunological findings. This is the first published case report of the successful treatment of RV with abatacept.

Knock out of S1P3 receptor signaling attenuates inflammation and fibrosis in bleomycin-induced lung injury mice model.

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid metabolite involved in many critical cellular processes, including proliferation, migration, and angiogenesis, through interaction with a family of five G protein–coupled receptors (S1P1–5). Some reports have implicated S1P as an important inflammatory mediator of the pathogenesis of airway inflammation, but the role of S1P3 in the pathogenesis of lung diseases is not completely understood. We used S1P3-deficient (knockout (KO)) mice to clarify the role of S1P3 receptor signaling in the pathogenesis of pulmonary inflammation and fibrosis using a bleomycin-induced model of lung injury. On the seventh day after bleomycin administration, S1P3 KO mice exhibited significantly less body weight loss and pulmonary inflammation than wild-type (WT) mice. On the 28th day, there was less pulmonary fibrosis in S1P3 KO mice than in WT mice. S1P3 KO mice demonstrated a 56% reduction in total cell count in bronchoalveolar lavage fluid (BALF) collected on the seventh day compared with WT mice; however, the differential white blood cell profiles were similar. BALF analysis on the seventh day showed that connective tissue growth factor (CTGF) levels were significantly decreased in S1P3 KO mice compared with WT mice, although no differences were observed in monocyte chemotactic protein-1 (MCP-1) or transforming growth factor β1 (TGF-β1) levels. Finally, S1P levels in BALF collected on the 7th day after treatment were not significantly different between WT and S1P3 KO mice. Our results indicate that S1P3 receptor signaling plays an important role in pulmonary inflammation and fibrosis and that this signaling occurs via CTGF expression. This suggests that this pathway might be a therapeutic target for pulmonary fibrosis.

Monocarboxylate Transporter 4, Associated With the Acidification of Synovial Fluid, Is a Novel Therapeutic Target for Inflammatory Arthritis

Synovial fluid pH is decreased in patients with rheumatoid arthritis (RA); however, the underlying mechanisms are unclear. We undertook this study to examine the mechanism by which synovial fluid pH is regulated and to explore the possibility of a therapeutic strategy by manipulating this mechanism.

Allograft inflammatory factor-1 in the pathogenesis of bleomycin-induced acute lung injury

Allograft inflammatory factor-1 (AIF-1) is a protein expressed by macrophages infiltrating the area around the coronary arteries of rats with an ectopic cardiac allograft. Some studies have shown that expression of AIF-1 increased in a mouse model of trinitrobenzene sulfonic acid-induced acute colitis and in acute cellular rejection of human cardiac allografts. These results suggest that AIF-1 is related to acute inflammation. The current study used bleomycin-induced acute lung injury to analyze the expression of AIF-1 and to examine its function in acute lung injury. Results showed that AIF-1 was significantly expressed in lung macrophages and increased in bronchoalveolar lavage fluid from mice with bleomycin-induced acute lung injury in comparison to control mice. Recombinant AIF-1 increased the production of IL-6 and TNF-α from RAW264.7 (a mouse macrophage cell line) and primary lung fibroblasts, and it also increased the production of KC (CXCL1) from lung fibroblasts. These results suggest that AIF-1 plays an important role in the mechanism underlying acute lung injury.

Roles of high-mobility group box 1 and thrombin in murine pulmonary fibrosis and the therapeutic potential of thrombomodulin

Cross talk between inflammation and coagulation plays important roles in acute or subacute progressive pulmonary fibrosis characterized by diffuse alveolar damage. Thrombomodulin is a physiological inhibitor of high-mobility group box 1 (HMGB1), and thrombin and may be effective for this condition. This study investigated the roles of HMGB1 and thrombin in the pathophysiology of bleomycin-induced pulmonary fibrosis and the efficacy of recombinant human soluble thrombomodulin (rhTM). Pulmonary fibrosis was induced in wild-type C57BL/6 mice by intratracheal instillation of bleomycin. We first assessed HMGB1, thrombin, transforming growth factor (TGF)-β1, and α-smooth muscle actin (SMA) levels in bronchoalveolar lavage fluid and lung tissue sections over time. Expression of HMGB1 and thrombin was elevated before that of TGF-β1 and α-SMA and remained high during the fibrotic phase after bleomycin instillation. We next examined whether in vitro stimulation with HMGB1 and thrombin induced expression of TGF-β1 and α-SMA in cultured alveolar macrophages and lung fibroblasts, respectively, by performing quantitative PCR, enzyme-linked immunosorbent assay, Western blot, and immunofluorescence analyses. HMGB1 and thrombin stimulation induced TGF-β1 production by alveolar macrophages, and thrombin stimulation also induced α-SMA expression in lung fibroblasts. Finally, we evaluated the effect of rhTM on bleomycin-induced pulmonary fibrosis. Compared with the vehicle control, both early and late-phase administration of rhTM suppressed the fibrotic process. Our results suggest that HMGB1 and thrombin were involved in the pathophysiology of pulmonary fibrosis via production of profibrotic proteins and that rhTM attenuated bleomycin-induced pulmonary fibrosis. rhTM may be a therapeutic option for acute or subacute pulmonary fibrosis.

AB0256 Very Early Response To Abatacept Could Be A Predictive Factor for Repair of Bone Erosion in Patients with Rheumatoid Arthritis Assessed by MRI

Background There is no report investigating predictive factors for MRI erosion change in treatment of rheumatoid arthritis (RA) with abatacept (ABT), because very little data are available on the efficacy of ABT assessed by MRI. Objectives The aim of this study is to examine the efficacy of ABT in patients with RA assessed by MRI and identify factors associated with change of bone erosion score. Methods Thirty-five RA patients were included in this prospective study. MRI of bilateral hands and conventional radiographs (CR) of bilateral hands and feet were performed at baseline and month 12 of treatment with intravenous ABT. MRI images were scored for synovitis, osteitis and bone erosion according to the Rheumatoid Arthritis MRI Scoring System. CR images were assessed according to the van der Heijde modified total Sharp score. Results Thirty-one patients completed this study. Mean Simplified Disease Activity Index (SDAI) and Health Assessment Questionnaire Disability Index (HAQ-DI) at baseline were 23.4±12.0 and 1.1±0.6 respectively. At the group level, mean MRI synovitis and osteitis scores showed statistically significant reductions through 12 months of treatment with ABT (from 17.1±7.0 to 11.4±6.2 (p<0.0001) and from 5.1±8.2 to 1.9±2.5 (p=0.003), respectively). On the other hand, mean MRI erosion scores showed no change throughout the study period (from 28.2±38.6 to 28.7±39.2). Mean CR erosion scores also showed no change (from 17.3±42.5 to 17.6±42.6). However, at the patient level, reductions of MRI erosion score were observed in 13% of patients, whereas no patient showed reduction of CR erosion score. The functional remission rates, which is defined as HAQ-DI≤0.5, of patients with regressive, unchanged and progressive MRI erosion score were 100%, 71% and 33%, respectively. On multiple regression analysis, SDAI response rate at month 1 and CRP at baseline were identified as the predicting factors for changes of erosion score (regression coefficient; -0.70 (p<0.001)/0.42 (p=0.02), respectively). Optimal cutoff value of SDAI response rate at month 1 was 0.524 (p=0.019). It is interesting that patients with regression of MRI erosion had high titer of rheumatoid factor (median: 591IU/ml) and anti-CCP antibody (median: 254U/ml) at baseline. Conclusions This study demonstrated ABT has a strong inhibitory effect on joint damage reducing synovitis and osteitis and not progressing bone erosion in RA patients. Over 10% patients showed repair of bone erosion assessed by MRI, which resulted in functional remission. SDAI response rate at month 1 could be a predictive factor for repair of bone erosion. Disclosure of Interest Y. Kukida Grant/research support from: Bristol-Myers Squibb, A. Kasahara: None declared, T. Seno: None declared, T. Inoue: None declared, N. Kamio: None declared, R. Sagawa: None declared, T. Kida: None declared, A. Nakabayashi: None declared, H. Nagahara: None declared, A. Yamamoto: None declared, S. Morita: None declared, H. Ito: None declared, M. Kohno: None declared, Y. Kawahito Grant/research support from: Bristol-Myers Squibb

THU0112 Myeloid-Derived Suppressor Cells have Regulatory Roles in Mouse Collagen-Induced Arthritis

Background Myeloid-derived suppressor cells (MDSCs) are of myeloid origin and are able to suppress T cell responses. MDSCs are characterized by the co-expression of the myeloid differentiation antigens Gr-1 and CD11b in mice (1). MDSCs in cancer have been studied in detail and are known to play roles in tumor associated immune suppression. However, the roles of MDSCs in autoimmune disease remain controversial and little is known about MDSCs in autoimmune arthritis. Objectives We investigate the roles of MDSCs in autoimmune arthritis using collagen-induced arthritis (CIA) mouse models. Methods We determined the number of Gr-1+ CD11b+ MDSCs in the spleens of CIA mice by flow cytometry. Next, we isolated MDSCs from CIA mice by magnetic cell sorting and cultured with CD4+ T cells to analyze the functions of MDSCs. We investigated the proliferation of CD4+ T cells by CFSE dye dilution assay and estimated cytokine levels produced by CD4+ T cells using ELISA. Furthermore, we investigated CD4+ T cell differentiation into Th17 cells by flow cytometry. Finally, we performed adoptive transfer of MDSCs into CIA mice and investigated the severity of arthritis. Results MDSCs significantly accumulated in the spleens of mice with CIA when arthritis severity peaked. These MDSCs inhibited CD4+ T cell proliferation and differentiation into Th17 cells. Moreover, MDSCs inhibited the production of IFNγ, IL-2, TNFα, and IL-6 by CD4+ T cells in vitro, whereas they promoted the production of IL-10. Adoptive transfer of MDSCs reduced both clinical (Image A) and histological arthritis scores (Image B) in vivo, which was accompanied by a decrease in the number of CD4+ T cells and Th17 cells in the draining lymph nodes. Image/graph Conclusions MDSCs in CIA suppress the progression of CIA by inhibiting the pro-inflammatory immune response of CD4+ T cells. These observations suggest that MDSCs play crucial roles in the regulation of autoimmune arthritis, which could be exploited in new cell-based therapies for human rheumatoid arthritis (RA). References Gabrilovich, D. I., and S. Nagaraj. 2009. Myeloid-derived suppressor cells as regulators of the immune system. Nat. Rev. Immunol. 9: 162-174. Disclosure of Interest None Declared

Role of allograft inflammatory factor-1 in bleomycin-induced lung fibrosis

Allograft inflammatory factor-1 (AIF-1) is a protein expressed by macrophages infiltrating the area around the coronary arteries in a rat ectopic cardiac allograft model. We previously reported that AIF-1 is associated with the pathogenesis of rheumatoid arthritis and skin fibrosis in sclerodermatous graft-versus-host disease mice. Here, we used an animal model of bleomycin-induced lung fibrosis to analyze the expression of AIF-1 and examine its function in lung fibrosis. The results showed that AIF-1 was expressed on lung tissues, specifically macrophages, from mice with bleomycin-induced lung fibrosis. Recombinant AIF-1 increased the production of TGF-β which plays crucial roles in the mechanism of fibrosis by mouse macrophage cell line RAW264.7. Recombinant AIF-1 also increased both the proliferation and migration of lung fibroblasts compared with control group. These results suggest that AIF-1 plays an important role in the mechanism underlying lung fibrosis, and may provide an attractive new therapeutic target.

Efficacy of abatacept in patients with rheumatoid arthritis, as assessed by magnetic resonance imaging of bilateral hands

To examine the efficacy of abatacept in patients with rheumatoid arthritis (RA) using magnetic resonance imaging (MRI) of bilateral hands.