Elsevier

Cytokine

Volume 55, Issue 2, August 2011, Pages 237-244
Cytokine

IL-27-producing CD14+ cells infiltrate inflamed joints of rheumatoid arthritis and regulate inflammation and chemotactic migration

https://doi.org/10.1016/j.cyto.2011.04.020Get rights and content

Abstract

Interleukin (IL)-27, a heterodimeric cytokine, has been reported to be involved in the pathogenesis of autoimmune diseases through mediating differentiation of Th1 or Th17 cells and immune cell activity or survival. However, the origin and effects of IL-27 in joints of rheumatoid arthritis (RA) remain unclear. In this study, we investigated the distribution and anti-inflammatory roles of IL-27 in RA synovium. The IL-27 levels in plasma of RA patients, osteoarthritis (OA) patients, or healthy volunteers (n = 15 per group) were equivalent and were at most 1 ng/ml, but the IL-27 level in synovial fluid of RA patients (n = 15, mean 0.13 ng/ml; range 0.017–0.37 ng/ml) was significantly higher than that in synovial fluid of OA patients (n = 15, mean 0.003 ng/ml; range 0–0.033 ng/ml) and potentially lower than in plasma. We analyzed the protein level of IL-27 produced by RA fibroblast-like synoviocytes (FLSs) or mononuclear cells (MNCs) from RA or OA synovial fluid or peripheral blood and showed that IL-27 in RA joints was derived from MNCs but not from FLSs. We also found by flow cytometry that IL-27-producing MNCs were CD14+, and that these CD14+IL-27+ cells were clearly detected in RA synovium but rarely in OA synovium by immunohistochemistry. Furthermore, we demonstrated that a relatively physiological concentration of IL-27 below 10 ng/ml suppressed the production of IL-6 and CCL20 from RA FLSs induced by proinflammatory cytokines through the IL-27/IL-27R axis. In the synovial fluid of RA, the IL-27 level interestingly had positive correlation with the IFN-γ level (r = 0.56, p = 0.03), but weak negative correlation with the IL-17A level (r = −0.30, p = 0.27), implying that IL-27 in inflammatory joints of RA induces Th1 differentiation and suppresses the development or the migration of Th17 cells. These findings indicate that circulating IL-27-producing CD14+ cells significantly infiltrate into inflamed regions such as RA synovium and have anti-inflammatory effects in several ways: both directly through the reduction of IL-6 production, and possibly through the induction of Th1 development and the suppression of Th17 development; and indirectly by regulation of recruitment of CCR6+ cells, such as Th17 cells, through the suppression of CCL20 production. Our results suggest that such a serial negative feedback system could be applied to RA therapy.

Highlights

► The IL-27 level in synovial fluid of RA is significantly higher than that of OA. ► IL-27 in RA joints is derived from CD14+ cells. ► IL-27+CD14+ cells significantly infiltrate into RA synovium. ► WSX-1 is ubiquitously expressed on RA synovium. ► IL-27 suppresses the production of IL-6 or CCL20 from RA fibroblast-like synoviocytes.

Introduction

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease, manifesting as systemic inflammatory arthritis with hypertrophy of the synovium followed by the destruction of cartilage, bone, and joint structures. Several in vivo experimental autoimmune animal models and in vitro human studies have suggested that interleukin (IL)-17-secreting helper T (Th17) cells can be considered a critical mediator of RA with respect to tissue inflammation or bone resorption [1], [2], [3], [4]. Th17 cells specifically express chemokine receptor CCR6, and its ligand CCL20 recruits Th17 cells [1], [5]. An association of the dinucleotide polymorphism of the CCR6 gene (CCR6DNP) with RA susceptibility has been suggested [6].

IL-27 is a recently identified cytokine, which is structurally related to IL-12 as a heterodimeric cytokine, similar to IL-23 and IL-35. IL-27 is composed of Epstein–Barr virus-induced gene 3 (EBI3), a p40-related molecule, and IL-27p28, a p35-related molecule [7]. IL-27 is produced by antigen presenting cells (APCs) including dendritic cells (DCs) and monocytes, and is secreted as a heterodimer [8]. IL-27 is reported to be expressed at chronic inflammatory sites, such as synovial tissues in RA [9], skin lesions in psoriasis [10], inflamed intestine in Crohn’s disease, and granulomas in tuberculosis or sarcoidosis [11]. IL-27 suppresses the development of Th17 cells and the production of cytokines including IL-17A from activated CD4+ T cells by blocking RAR-related orphan receptor C (RORC) expression in humans and in several experimental animal models, while it induces Th1 differentiation [9], [12], [13], [14], [15].

IL-27 receptor (IL-27R) is also a heterodimer of WSX-1 (IL-27Rα), a homologue of IL-12Rβ2, and gp130, a component of the IL-6 receptor [16], [17]. Both components are coexpresssed in various human cell types, including monocytes, DCs, T cells, B cells, natural killer cells, mast cells and endothelial cells, and both components are required for the signal transduction of IL-27 [17]. Downstream of IL-27R, mainly STAT1 and STAT3 are activated [17], [18].

In a murine collagen-induced arthritis (CIA) model, administration of IL-27 reduces the amount of serum IL-6, cellular infiltration to the joints, synovial hyperplasia and joint erosion at the onset of the disease [9]. IL-27 also inhibits human receptor of NF-κB ligand (RANKL)-mediated osteoclastogenesis [19], [20]. These reports suggest protective roles for IL-27 in the pathogenesis of arthritis. In contrast, it is also reported that IL-27 possesses pathogenic roles in RA. In experimental animal models of adjuvant-induced arthritis and proteoglycan-induced arthritis, IL-27 is critically involved with the development of arthritis by inducing the differentiation of naïve T cells into interferon (IFN)-γ-producing Th1 cells [21], [22]. In humans, high concentrations of IL-27 induce the production of IL-6 and inflammatory chemokines from FLSs of established RA [23]. These conflicting reports reflect the complex functions of IL-27 in human immunology.

In this study, we investigated the source and role of IL-27 in RA. We show that IL-27-producing CD14+ cells significantly infiltrate RA synovium, and that physiological concentrations of IL-27 could have anti-inflammatory effects in several ways: both directly through the suppression of IL-6 production and possibly through Th1 differentiation; and indirectly by regulating recruitment of CCR6+ cells including Th17 cells through the suppression of CCL20 production. Our results suggest that IL-27 might be a potential therapeutic agent for RA.

Section snippets

Cytokines and reagents

Human recombinant tumor necrosis factor (TNF)-α, human recombinant IL-1β, human recombinant IL-6, human recombinant soluble IL-6 receptor (sIL-6R), and human recombinant IL-17A were purchased from PeproTech USA (Rocky Hill, NJ, USA). The following reagents were purchased from R&D Systems (Minneapolis, MN, USA): human recombinant IL-27, anti-human TCCR/WSX-1 antibody, isotype control IgG, human TCCR/WSX-1 Fc chimera, human IgG1 Fc, anti-human IL-27 antibody and isotype control IgG. Anti-human

IL-27 is expressed similarly in plasma of RA and OA patients and HV, but is significantly higher in RA synovial fluid than in OA synovial fluid

To investigate the possible contribution of IL-27 to the pathogenesis of RA, we measured the concentration of IL-27 in the synovial fluid from patients with RA or OA, and in plasma from HV or patients with RA or OA. The IL-27 level in synovial fluid of RA patients (mean 0.13 ng/ml; range 0.017–0.37 ng/ml) was significantly higher (P < 0.0005) than that in OA patients (mean 0.003 ng/ml; range 0–0.033 ng/ml) (Fig. 1). However, the concentrations of plasma IL-27 in RA patients (mean 0.45 ng/ml; range

Discussion

In this study, we showed that the concentration of IL-27 in plasma of RA and OA patients and HV was at most 1 ng/ml, while that in synovial fluid of RA and OA was at most 400 and 40 pg/ml, respectively (Fig. 1). Recently, IL-27 at 10–100 ng/ml was reported to activate RA FLSs as an inflammatory cytokine [23]. In our laboratory, a high concentration (100 ng/ml) of IL-27 tended to induce IL-6 production from RA FLSs. However, based on the detected concentration of IL-27 in plasma or synovial fluid,

Acknowledgments

This study was supported by health and Labor Science Research Grants for Research on Allergic Disease and Immunology from the Ministry of Health, Labor and Welfare (Grant No. 10103190). We thank J. Toguchida, T. Aoyama, and K. Yamamoto for technical support.

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