Axel J. Hueber

IL-35 is a novel cytokine with therapeutic effects against collagen-induced arthritis through the expansion of regulatory T cells and suppression of Th17 cells

Epstein‐Barr virus‐induced gene 3 (EBI3) and the p35 subunit of IL‐12 have been reported to form a heterodimeric hematopoietin in human and mouse. We have constructed a heterodimeric protein covalently linking EBI3 and p35, to form a novel cytokine which we now call IL‐35. The Fc fusion protein of IL‐35 induced proliferation of murine CD4+CD25+ and CD4+CD25– T cells when stimulated with immobilized anti‐CD3 and anti‐CD28 antibodies in vitro. The IL‐35‐expanded CD4+CD25+ T cell population expressed Foxp3 and produced elevated levels of IL‐10, whereas the IL‐35‐induced CD4+CD25– T cells produced IFN‐γ but not IL‐4. The in vitro expanded CD4+CD25+ T cells retained their suppressive functions against CD4+CD25– effector cells. Furthermore, when cultured with soluble anti‐CD3 antibody and antigen‐presenting cells, IL‐35 suppressed the proliferation of CD4+CD25– effector cells. Moreover, IL‐35 inhibited the differentiation of Th17 cells in vitro. In vivo, IL‐35 effectively attenuated established collagen‐induced arthritis in mice, with concomitant suppression of IL‐17 production but enhanced IFN‐γ synthesis. Thus, IL‐35 is a novel anti‐inflammatory cytokine suppressing the immune response through the expansion of regulatory T cells and suppression of Th17 cell development.

Cutting Edge: Mast Cells Express IL-17A in Rheumatoid Arthritis Synovium

The proinflammatory cytokine IL-17A is considered a crucial player in rheumatoid arthritis (RA) pathogenesis. In experimental models of autoimmune arthritis, it has been suggested that the cellular source of IL-17A is CD4+ T cells (Th17 cells). However, little is known about the source of IL-17 in human inflamed RA tissue. We explored the cellular sources of IL-17A in human RA synovium. Surprisingly, only a small proportion of IL-17–expressing cells were T cells, and these were CCR6 negative. Unexpectedly, the majority of IL-17A expression colocalized within mast cells. Furthermore, we demonstrated in vitro that mast cells produced RORC-dependent IL-17A upon stimulation with TNF-α, IgG complexes, C5a, and LPS. These data are consistent with a crucial role for IL-17A in RA pathogenesis but suggest that in addition to T cells innate immune pathways particularly mediated via mast cells may be an important component of the effector IL-17A response.

MicroRNA-155 as a proinflammatory regulator in clinical and experimental arthritis

MicroRNA (miRNA) species (miR) regulate mRNA translation and are implicated as mediators of disease pathology via coordinated regulation of molecular effector pathways. Unraveling miR disease-related activities will facilitate future therapeutic interventions. miR-155 recently has been identified with critical immune regulatory functions. Although detected in articular tissues, the functional role of miR-155 in inflammatory arthritis has not been defined. We report here that miR-155 is up-regulated in synovial membrane and synovial fluid (SF) macrophages from patients with rheumatoid arthritis (RA). The increased expression of miR-155 in SF CD14+ cells was associated with lower expression of the miR-155 target, Src homology 2-containing inositol phosphatase-1 (SHIP-1), an inhibitor of inflammation. Similarly, SHIP-1 expression was decreased in CD68+ cells in the synovial lining layer in RA patients as compared with osteoarthritis patients. Overexpression of miR-155 in PB CD14+ cells led to down-regulation of SHIP-1 and an increase in the production of proinflammatory cytokines. Conversely, inhibition of miR-155 in RA synovial CD14+ cells reduced TNF-α production. Finally, miR-155–deficient mice are resistant to collagen-induced arthritis, with profound suppression of antigen-specific Th17 cell and autoantibody responses and markedly reduced articular inflammation. Our data therefore identify a role of miR-155 in clinical and experimental arthritis and suggest that miR-155 may be an intriguing therapeutic target.

Interleukin-33 Induces Protective Effects in Adipose Tissue Inflammation During Obesity in Mice

Rationale: Chronic low-grade inflammation involving adipose tissue likely contributes to the metabolic consequences of obesity. The cytokine interleukin (IL)-33 and its receptor ST2 are expressed in adipose tissue, but their role in adipose tissue inflammation during obesity is unclear. Objective: To examine the functional role of IL-33 in adipose tissues and investigate the effects on adipose tissue inflammation and obesity in vivo. Methods and Results: We demonstrate that treatment of adipose tissue cultures in vitro with IL-33 induced production of Th2 cytokines (IL-5, IL-13, IL-10) and reduced expression of adipogenic and metabolic genes. Administration of recombinant IL-33 to genetically obese diabetic (ob/ob) mice led to reduced adiposity, reduced fasting glucose and improved glucose and insulin tolerance. IL-33 also induced accumulation of Th2 cells in adipose tissue and polarization of adipose tissue macrophages toward an M2 alternatively activated phenotype (CD206+), a lineage associated with protection against obesity-related metabolic events. Furthermore, mice lacking endogenous ST2 fed high-fat diet had increased body weight and fat mass and impaired insulin secretion and glucose regulation compared to WT controls fed high-fat diet. Conclusions: In conclusion, IL-33 may play a protective role in the development of adipose tissue inflammation during obesity.

High level of functional dickkopf-1 predicts protection from syndesmophyte formation in patients with ankylosing spondylitis

Introduction The molecular mechanisms of syndesmophyte formation in ankylosing spondylitis (AS) are yet to be characterised. Molecules involved in bone formation such as Wnt proteins and their antagonists probably drive syndesmophyte formation in AS. Methods This study investigated sequential serum levels of functional dickkopf-1 (Dkk1), a potent Wnt antagonist involved in bone formation in arthritis, by capture ELISA with its receptor LRP6 in 65 AS patients from the German Spondyloarthritis Inception Cohort. Dkk1 levels were then related to structural progression (syndesmophyte formation) as well as sclerostin and C-reactive protein (CRP) levels. Results Functional Dkk1 levels were significantly (p=0.025) higher in patients with no syndesmophyte growth (6.78±5.48 pg/ml) compared with those with syndesmophyte growth (4.13±2.10 pg/ml). Dkk1 levels were highly correlated to serum sclerostin levels (r=0.71, 95% CI 0.53 to 0.82; p<0.001) but not to CRP (r=0.15, 95% CI −0.10 to 0.38; p=0.23). Conclusion AS patients with no syndesmophyte formation show significantly higher functional Dkk1 levels suggesting that blunted Wnt signalling suppresses new bone formation and consequently syndesmophyte growth and spinal ankylosis. Similar to serum sclerostin levels, the functional Dkk1 level thus emerges as a potential biomarker for structural progression in patients with AS

Bone loss before the clinical onset of rheumatoid arthritis in subjects with anticitrullinated protein antibodies

Objective Anticitrullinated protein antibodies (ACPA) are a major risk factor for bone loss in rheumatoid arthritis (RA). We have recently shown that ACPA directly induce bone loss by stimulating osteoclast differentiation. As ACPA precede the clinical onset of RA by years, we hypothesised that ACPA positive healthy individuals may already show skeletal changes. Methods We performed a comparative micro-CT analysis of the bone microstructure in the metacarpophalangeal joints of ACPA positive and ACPA negative healthy individuals without clinical signs of arthritis. Results ACPA positive (n=15) and negative (n=15) healthy individuals were not different in age (48.2±4.1 vs 51.4±3.8 years, p=0.57) or gender (eight women and two men in both groups). Bone mineral density was significantly reduced in ACPA positive individuals (mean±SEM 280±11 mg/cm3) compared with controls (327±6). Bone loss was based on cortical bone changes, with significant (p=0.044) reduction in cortical thickness in the ACPA positive group (mean±SEM 0.22±0.03 mm) compared with controls (0.32±0.03 mm). Areas of cortical porosity were significantly (p=0.0005) more widespread in ACPA positive (mean±SEM 7.4±1.4%) than in ACPA negative individuals (1.0±0.3%). Discussion Structural bone damage starts before the clinical onset of arthritis in subjects with ACPA. These findings revise the concept that bone damage is an exclusive consequence of synovitis in patients with RA.

Inflammation is Present in Early Human Tendinopathy

Background The cellular mechanisms of tendinopathy remain unclear particularly with respect to the role of inflammation in early disease. The authors previously identified increased levels of inflammatory cytokines in an early human model of tendinopathy and sought to extend these studies to the cellular analysis of tissue. Purpose To characterize inflammatory cell subtypes in early human tendinopathy, the authors explored the phenotype and quantification of inflammatory cells in torn and control tendon samples. Design Controlled laboratory study. Methods Torn supraspinatus tendon and matched intact subscapularis tendon samples were collected from 20 patients undergoing arthroscopic shoulder surgery. Control samples of subscapularis tendon were collected from 10 patients undergoing arthroscopic stabilization surgery. Tendon biopsy samples were evaluated immunohistochemically by quantifying the presence of macrophages (CD68 and CD206), T cells (CD3), mast cells (mast cell tryptase), and vascular endothelium (CD34). Results Subscapularis tendon samples obtained from patients with a torn supraspinatus tendon exhibited significantly greater macrophage, mast cell, and T-cell expression compared with either torn supraspinatus samples or control subscapularis-derived tissue (P < .01). Inflammatory cell infiltrate correlated inversely (r = .5; P < .01) with rotator cuff tear size, with larger tears correlating with a marked reduction in all cell lineages. There was a modest but significant correlation between mast cells and CD34 expression (r = .4; P < .01) in matched subscapularis tendons from shoulders with supraspinatus ruptures. Conclusion This study provides evidence for an inflammatory cell infiltrate in early mild/moderate human tendinopathy. In particular, the authors demonstrate significant infiltration of mast cells and macrophages, suggesting a role for innate immune pathways in the events that mediate early tendinopathy. Clinical Relevance Further mechanistic studies to evaluate the net contribution and hence therapeutic utility of these cellular lineages and their downstream processes may reveal novel therapeutic approaches to the management of early tendinopathy.

IL-33 induces skin inflammation with mast cell and neutrophil activation

Psoriasis is a common chronic autoimmune condition of the skin characterized by hyperplasia of epidermal keratinocytes associated with pro‐inflammatory cytokines. IL‐33 is a new member of the IL‐1 superfamily that signals through the ST2 receptor and was originally defined as an inducer of T helper 2 (Th2) cytokines. Recently, broader immune activatory potential has been defined for IL‐33 particularly via mast cell activation and neutrophil migration. Here, we show that ST2−/− mice exhibit reduced cutaneous inflammatory responses compared with WT mice in a phorbol ester‐induced model of skin inflammation. Furthermore, injections of IL‐33 into the ears of mice induce an inflammatory skin lesion. This inflammatory response was partially dependent on mast cells as mast cell‐deficient mice (KitW‐sh/W‐sh) showed delayed responses to IL‐33. IL‐33 also recruited neutrophils to the ear, an effect mediated in part by increased production of the chemokine KC (CXCL1). Finally, we show that IL‐33 expression is up‐regulated in the epidermis of clinical psoriatic lesions, compared with healthy skin. These results therefore demonstrate that IL‐33 may play a role in psoriasis‐like plaque inflammation. IL‐33 targeting may provide a new treatment strategy for psoriasis.

Combined Inhibition of Tumor Necrosis Factor α and Interleukin‐17 As a Therapeutic Opportunity in Rheumatoid Arthritis: Development and Characterization of a Novel Bispecific Antibody

Rheumatoid arthritis therapies that are based on inhibition of a single cytokine, e.g., tumor necrosis factor α (TNFα) or interleukin‐6 (IL‐6), produce clinically meaningful responses in only about half of the treated patients. This study was undertaken to investigate whether combined inhibition of TNFα and IL‐17 has additive or synergistic effects in the suppression of mesenchymal cell activation in vitro and inflammation and tissue destruction in arthritis in vivo.

Interleukin‐33: a novel mediator with a role in distinct disease pathologies

Kurowska‐Stolarska M, Hueber A, Stolarski B, McInnes IB (Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK). IL‐33 – a novel mediator with a role in distinct disease pathologies (Key Symposium). J Intern Med 2011; 269: 29–35.