IL-17 in rheumatoid arthritis: a new target for treatment or just another cytokine?

Detection and characterization of bacterial nucleic acids in culture-negative synovial tissue and fluid samples from rheumatoid arthritis or osteoarthritis patients

Human intestinal microbes can mediate development of arthritis – Studies indicate that certain bacterial nucleic acids may exist in synovial fluid (SF) and could be involved in arthritis, although the underlying mechanism remains unclear. To characterize potential SF bacterial nucleic acids, we used 16S rRNA gene amplicon sequencing to assess bacterial nucleic acid communities in 15 synovial tissue (ST) and 110 SF samples from 125 patients with rheumatoid arthritis (RA) and 16 ST and 42 SF samples from 58 patients with osteoarthritis (OA). Our results showed an abundant diversity of bacterial nucleic acids in these clinical samples, including presence of Porphyromonas and Bacteroides in all 183 samples. Agrobacterium, Comamonas, Kocuria, Meiothermus, and Rhodoplanes were more abundant in synovial tissues of rheumatoid arthritis (STRA). Atopobium, Phascolarctobacterium, Rhodotorula mucilaginosa, Bacteroides uniformis, Rothia, Megasphaera, Turicibacter, Leptotrichia, Haemophilus parainfluenzae, Bacteroides fragilis, Porphyromonas, and Streptococcus were more abundant in synovial tissues of osteoarthritis (STOA). Veillonella dispar, Haemophilus parainfluenzae, Prevotella copri and Treponema amylovorum were more abundant in synovial fluid of rheumatoid arthritis (SFRA), while Bacteroides caccae was more abundant in the synovial fluid of osteoarthritis (SFOA). Overall, this study confirms existence of bacterial nucleic acids in SF and ST samples of RA and OA lesions and reveals potential correlations with degree of disease.

The role of prostaglandin E2 receptor signaling of dendritic cells in rheumatoid arthritis

Prostaglandin E2 (PGE2), a very potent lipid mediator produced from arachidonic acid (AA) through the action of cyclooxygenase (COX) enzymes, is implicated in the regulation of dendritic cell (DC) functions such as differentiation ability, cytokine-producing capacity, Th-cell polarizing ability, migration and maturation. DCs are the most potent antigen-presenting cells and play major roles in both the induction of primary immune responses and tolerance. It is well established that PGE2 functions significantly in the pathogenesis of rheumatoid arthritis (RA). Although the role of PGE2 in RA has been studied extensively, the effects of PGE2 on DC biology and the role of DCs in RA have not become the focus of investigation until recently. Here, we summarize the latest progress in PGE2 research with respect to DC functions, as well as the role of PGE2 receptor signaling of DCs in the pathogenesis of RA.

A new phenylpyrazoleanilide, y-320, inhibits interleukin 17 production and ameliorates collagen-induced arthritis in mice and cynomolgus monkeys

Interleukin (IL)-15 and IL-17 are thought to play an important role in the pathogenesis of rheumatoid arthritis (RA) because both pro-inflammatory cytokines are found in synovial fluid of RA patients. In this study, we examined the pharmacological profiles of Y-320, a new phenylpyrazoleanilide immunomodulator. Y-320 inhibited IL-17 production by CD4 T cells stimulated with IL-15 with IC₅₀ values of 20 to 60 nM. Oral administration of Y-320 (0.3 to 3 mg/kg) significantly inhibited the development and progression of arthritis and joint destruction with reduction of IL-17 mRNA expression in arthritic joints of type II collagen-induced arthritis (CIA) in DBA/1J mice. Y-320 in combination with anti-murine tumor necrosis factor-α monoclonal antibody showed a synergistic effect on mouse CIA. Moreover, therapeutic treatment with Y-320 (0.3 and 1 mg/kg orally) ameliorated CIA in cynomolgus monkeys. Our results suggest that Y-320, an orally active inhibitor for IL-17 production, provides a useful therapy for RA.

Development of a High-Throughput Cell-Based Assay for Identification of IL-17 Inhibitors

Human interleukin 17 (IL-17) is a proinflammatory cytokine derived mainly from activated T cells. Extensive evidence points to a significant role of IL-17 in many autoimmune and infectious diseases, as well as tumorigenesis and transplant rejection, and suggests that targeting IL-17 could be a promising therapeutic strategy. Robust cell-based assays would thus be essential for lead identification and the optimization of therapeutic candidates. Herein, we report a well-characterized two-step assay, consisting of (a) in vitro activation and stimulation of CD4+ T lymphocytes by a defined complex of antibodies and cytokines, leading to T helper 17 (Th17) cell differentiation and IL-17 production, and (b) IL-17 quantification in cell supernatants using a homogeneous time-resolved fluorescence (HTRF) assay. The system was optimized for and shown to be reliable in high-throughput compatible 96- and 384-well plate formats. The assay is robust (Z′ > 0.5) and simple to perform, yields a stable response, and allows for sufficient discrimination of positive (IL-17–producing cells) and negative controls (uninduced cells). The assay was validated by performing dose-response testing of rapamycin and cyclosporine A, which had previously been reported to inhibit IL-17, and determining, for the first time, their in vitro potencies (IC50s of 80 ± 23 pM and 223 ± 52 nM, respectively). Also, IKK 16, a selective small-molecule inhibitor of IκB kinase, was found to inhibit IL-17 production, with an IC50 of 315 ± 79 nM.

T-lineage cells require the thymus but not VDJ recombination to produce IL-17A and regulate granulopoiesis in vivo

IL-17A and IL-17F regulate granulopoiesis and are produced by memory T cells. Rag1(-/-) recombinase-activating gene-deficient mice cannot produce mature T cells but maintain normal neutrophil counts. Athymic nude mice are neutropenic or have near-normal neutrophil counts, depending on the prevailing intestinal flora, and do not produce IL-17A. By contrast, thymi from Rag1(-/-) mice contain as much IL-17A as those from wild-type (WT) mice. IL-17A-producing cells are found in the double negative DN1 compartment of the Rag1(-/-) thymus and express intracellular CD3. These cells colonize the spleen and mesenteric lymph node and secrete IL-17A in vitro following stimulation with IL-23 at a level similar to that of WT splenocytes. Adoptively transferred Rag1(-/-) or WT thymocytes correct neutrophil counts in neutropenic nude mice. We conclude that the development of IL-17A-producing T-lineage cells requires an intact thymic epithelium, but not V(D)J recombination.

Childhood and teenage stroke

OBJECTIVE

The purpose of this manuscript is to review the various etiologies and to discuss the therapeutic issues in childhood stroke.

METHODS

A PubMed search of literature pertaining to childhood stroke was conducted from 1983 to 2008 using specific key search words pertinent to cerebrovascular disorders in childhood.

RESULTS

The analysis of the multiple causes of childhood stroke including arterial ischemic strokes and cerebral venous thrombosis was presented. Current therapy and outcome data in childhood stroke are also discussed throughout the length of the article.

CONCLUSIONS

With increasing vigilance among physicians and improved neuroimaging modalities, the diagnosis of childhood stroke is now made earlier, with increasing frequency and greater accuracy. However, larger and well-controlled studies regarding the optimal management of childhood stroke in terms of the use of both antithrombotic drugs and anticoagulation are still needed in addition to longitudinal follow-up studies of children with stroke.

Expression of interleukin-17RC protein in normal human tissues

Background

Interleukin-17 (IL-17) cytokines and receptors play an important role in many autoimmune and inflammatory diseases. IL-17 receptors IL-17RA and IL-17RC have been found to form a heterodimer for mediating the signals of IL-17A and IL-17F cytokines. While the function and signaling pathway of IL-17RA has been revealed, IL-17RC has not been well characterized. The function and signaling pathway of IL-17RC remain largely unknown. The purpose of the present study was to systematically examine IL-17RC protein expression in 53 human tissues.

Results

IL-17RC expression in 51 normal human tissues and two benign tumors (i.e., lymphangioma and parathyroid adenoma) on the tissue microarrays was determined by immunohistochemical staining, using two polyclonal antibodies against IL-17RC. IL-17RC protein was expressed in many cell types including the myocardial cells, vascular and lymphatic endothelial cells, glandular cells (of the adrenal, parathyroid, pituitary, thyroid, pancreas, parotid salivary, and subepidermal glands), epithelial cells (of the esophagus, stomach, intestine, anus, renal tubule, breast, cervix, Fallopian tube, epididymis, seminal vesicle, prostate, gallbladder, bronchus, lung, and skin), oocytes in the ovary, Sertoli cells in the testis, motor neurons in the spinal cord, autonomic ganglia and nerves in the intestine, skeletal muscle cells, adipocytes, articular chondrocytes, and synovial cells. High levels of IL-17RC protein expression were observed in most vascular and lymphatic endothelium and squamous epithelium. The epithelium of the breast, cervix, Fallopian tube, kidney, bladder and bronchus also expressed high levels of IL-17RC, so did the glandular cells in the adrenal cortex, parotid salivary and subepidermal glands. In contrast, IL-17RC protein was not detectable in the smooth muscle cells, fibroblasts, antral mucosa of the stomach, mucosa of the colon, endometrium of the uterus, neurons of the brain, hepatocytes, or lymphocytes. Nevertheless, IL-17RC protein was expressed in the vascular endothelium within the tissues where the IL-17RC-negative cells resided.

Conclusion

IL-17RC protein is expressed in most human tissues, the function of which warrants further investigation.

IL-17A inhibits the expansion of IL-17A-producing T cells in mice through "short-loop" inhibition via IL-17 receptor

IL-23 and IL-17A regulate granulopoiesis through G-CSF, the main granulopoietic cytokine. IL-23 is secreted by activated macrophages and dendritic cells and promotes the expansion of three subsets of IL-17A-expressing neutrophil-regulatory T (Tn) cells; CD4(-)CD8(-)alphabeta(low), CD4(+)CD8(-)alphabeta(+) (Th17), and gammadelta(+) T cells. In this study, we investigate the effects of IL-17A on circulating neutrophil levels using IL-17R-deficient (Il17ra(-/-)) mice and Il17ra(-/-)Itgb2(-/-) mice that lack both IL-17R and all four beta(2) integrins. IL-17R deficiency conferred a reduction in neutrophil numbers and G-CSF levels, as did Ab blockade against IL-17A in wild-type mice. Bone marrow transplantation revealed that IL-17R expression on nonhemopoietic cells had the greatest effects on regulating blood neutrophil counts. Although circulating neutrophil numbers were reduced, IL-17A expression, secretion, and the number of IL-17A-producing Tn cells were elevated in Il17ra(-/-) and Il17ra(-/-)Itgb2(-/-) mice, suggesting a negative feedback effect through IL-17R. The negative regulation of IL-17A-producing T cells and IL-17A and IL-17F gene expression through the interactions of IL-17A or IL-17F with IL-17R was confirmed in splenocyte cultures in vitro. We conclude that IL-17A regulates blood neutrophil counts by inducing G-CSF production mainly in nonhemopoietic cells. IL-17A controls the expansion of IL-17A-producing Tn cell populations through IL-17R.

Rheumatoid arthritis synovium contains two subsets of CD83-DC-LAMP- dendritic cells with distinct cytokine profiles

Dendritic cells (DCs) have been proposed to play a pivotal role in the initiation and perpetuation of rheumatoid arthritis (RA) by presentation of arthritogenic antigens to T cells. We investigated the in vivo characteristics of two major DC subsets, myeloid DCs (mDCs) and plasmacytoid DCs (pDCs), in RA synovial tissue (ST) by measuring their frequency, phenotype, distribution, and cytokine expression. ST was obtained by arthroscopy from 20 RA, 8 psoriatic arthritis, and 10 inflammatory osteoarthritis patients. Levels of CD1c(+) mDCs and CD304(+) pDCs present in ST were quantified by digital image analysis, and their distribution was assessed by double immunolabeling with antibodies against CD3 and CD8. The maturation status and cytokine profile of mDCs and pDCs were quantified by double-immunofluorescence microscopy. In RA patients, the number of CD304(+) pDCs exceeded that of CD1c(+) mDCs, with the majority of infiltrating DCs being CD83(-) or DC-LAMP(-). Synovial pDC numbers were especially increased in RA patients who were positive for rheumatoid factor and anti-citrullinated peptide antibody. mDCs and pDCs were localized adjacent to lymphocyte aggregates. In ST from RA patients, both mDCs and pDCs expressed interleukin (IL)-15. IL-18 and interferon (IFN)-alpha/beta were mainly expressed by pDCs whereas IL-12p70 and IL-23p19 expression was predominant in mDCs. These data characterize the phenotypes of mDCs and pDCs in inflammatory synovitis and define for the first time the cytokine expression profile of these DC subsets.

Role of the novel Th17 cytokine IL-17F in inflammatory bowel disease (IBD): upregulated colonic IL-17F expression in active Crohn's disease and analysis of the IL17F p.His161Arg polymorphism in IBD

BACKGROUND

Interleukin (IL)-17F, produced in IL-23R-expressing Th17 cells, is a novel member of the IL-17 cytokine family. Given the association of IL23R with inflammatory bowel disease (IBD), we characterized the role of IL-17F in IBD including its intestinal gene expression and the effect of the IL17F p.His161Arg polymorphism on disease susceptibility and phenotype of Crohn's disease (CD) and ulcerative colitis (UC). In addition, we analyzed the IL17F p.His161Arg polymorphism for potential epistasis with IL23R and NOD2/CARD15 variants.

METHODS

Intestinal IL-17F mRNA expression was measured by quantitative polymerase chain reaction (PCR). Genomic DNA from 1682 individuals (CD: n = 499; UC: n = 216; controls: n = 967) was analyzed for the presence of the IL17F p.His161Arg polymorphism, the 3 NOD2 variants, p.Arg702Trp, p.Gly908Arg, and p.Leu1007fsX1008, and 10 CD-associated IL23R variants.

RESULTS

Intestinal IL-17F mRNA expression was 4.4-fold increased in inflamed colonic lesions compared to uninflamed biopsies in CD (P = 0.016) but not in UC. However, the mean intestinal IL-17F mRNA expression was higher in UC than in CD (P < 0.0001). The IL17F p.His161Arg substitution was observed with similar frequencies in IBD patients and controls and was not associated with a certain disease phenotype, but weakly associated with a low body mass index (BMI; P = 0.009) and an earlier age of disease onset (P = 0.039) in UC. There was no evidence for epistasis between the IL17F p.His161Arg polymorphism and IBD-associated single nucleotide polymorphisms within the IL23R gene.

CONCLUSIONS

Intestinal IL17F gene expression is increased in active CD. The IL17F p.His161Arg polymorphism is not associated with IBD susceptibility and has no epistatic interaction with CD-associated IL23R variants.

Vaccination with cytokines in autoimmune diseases

Most autoimmune diseases have an unknown etiology, but all involve cytokines cascade in their development. At the present time, several cytokines have been identified as major targets in various autoimmune diseases, involving the development of monoclonal antibodies (MAbs) against those cytokines. Even if MAbs are indeed efficient, the passive immunotherapies also present some disadvantages and are expensive. To counter this, several strategies have been developed, including active immunotherapy, based on the vaccination principle. The aim of such a strategy is to induce a B cell response and to obtain autoantibodies able to neutralize the interaction of the self-cytokine with its receptor. To that purpose, cytokines (entire or peptide) are either coupled with a protein-carrier or virus-like particle, or modified with foreign Th cell epitopes. DNA vaccination can also be used with cytokine sequences. This review focuses on the different vaccination strategies with cytokines (including Tumor Necrosis Factor (TNF)alpha, Interleukin-1beta (IL-1beta), IL-17) in different autoimmune diseases in preclinical studies; the benefit/risk ratio of such a strategy and the present development of clinical trials in some autoimmune diseases are also discussed.

Identification of the IL-17 receptor related molecule IL-17RC as the receptor for IL-17F

The proinflammatory cytokines IL-17A and IL-17F have a high degree of sequence similarity and share many biological properties. Both have been implicated as factors contributing to the progression of inflammatory and autoimmune diseases. Moreover, reagents that neutralize IL-17A significantly ameliorate disease severity in several mouse models of human disease. IL-17A mediates its effects through interaction with its cognate receptor, the IL-17 receptor (IL-17RA). We report here that the IL-17RA-related molecule, IL-17RC is the receptor for IL-17F. Notably, both IL-17A and IL-17F bind to IL-17RC with high affinity, leading us to suggest that a soluble form of this molecule may serve as an effective therapeutic antagonist of IL-17A and IL-17F. We generated a soluble form of IL-17RC and demonstrate that it effectively blocks binding of both IL-17A and IL-17F, and that it inhibits signaling in response to these cytokines. Collectively, our work indicates that IL-17RC functions as a receptor for both IL-17A and IL-17F and that a soluble version of this protein should be an effective antagonist of IL-17A and IL-17F mediated inflammatory diseases.

Interferon-gamma regulates susceptibility to collagen-induced arthritis through suppression of interleukin-17

OBJECTIVE

The enhanced expression of experimental arthritis in the absence of interferon-gamma (IFNgamma) suggests that IFNgamma suppresses arthritis. Interleukin-17 (IL-17) is a pivotal T cell cytokine in arthritis, and in vitro studies have indicated that IFNgamma suppresses IL-17 production. We undertook this study to test the hypothesis that resistance to collagen-induced arthritis (CIA) in C57BL/6 (B6) mice is regulated by IFNgamma-mediated suppression of IL-17.

METHODS

Wild-type (WT) B6 mice, IFNgamma-knockout (KO) B6 mice, and DBA/1 mice were immunized with type II collagen (CII) in Freund's complete adjuvant (CFA). Lymphocytes from immunized mice were analyzed for cytokine production ex vivo by intracellular staining or restimulation with CII and enzyme-linked immunosorbent assays. In vivo blockade of IL-17 was achieved with an anti-IL-17 monoclonal antibody (mAb).

RESULTS

CII restimulation of T cells from CII/CFA-immunized mice resulted in an approximately 5-fold increase in IL-17 production in IFNgamma-KO B6 mice compared with WT B6 mice. Neutralization of IFNgamma increased IL-17 production in WT B6 mice, and neutralization of IL-4 had a synergistic effect. Interestingly, the prototypical CIA-susceptible strain DBA/1 also demonstrated a high IL-17 and a low IFNgamma cytokine profile compared with WT B6 mice. Administration of the anti-IL-17 mAb attenuated arthritis in DBA/1 mice and almost completely prevented expression of arthritis in IFNgamma-KO B6 mice.

CONCLUSION

These results indicate that sensitivity of IFNgamma-deficient B6 mice to CIA is associated with high IL-17 production and that this cytokine is required for expression of arthritis in this strain.

Overexpression of synoviolin in peripheral blood and synoviocytes from rheumatoid arthritis patients and continued elevation in nonresponders to infliximab treatment

OBJECTIVE

Synoviolin is a novel E3 ubiquitin ligase that has been implicated in the pathogenesis of rheumatoid arthritis (RA). The purpose of this study was to examine the expression and regulation of synoviolin by tumor necrosis factor alpha (TNFalpha), both in vivo and in vitro.

METHODS

A total of 54 RA patients and 23 healthy control subjects were analyzed before, 4 hours after the first infusion, and at week 22 of infliximab treatment. Clinical response was assessed by the American College of Rheumatology criteria for 20% improvement and the Disease Activity Score in 28 joints (DAS28) at 6 months. Synoviolin messenger RNA expression was measured by real-time reverse transcription-polymerase chain reaction in peripheral blood (PB) and fibroblast-like synoviocytes (FLS) and with and without TNFalpha or interleukin-1beta (IL-1beta) stimulation.

RESULTS

Synoviolin expression was increased in whole PB obtained from RA patients as compared with that from healthy controls and was significantly reduced early and late after infliximab treatment in responders, but in not nonresponders. Reduction in synoviolin expression was associated with reduced levels of markers of disease activity, including C-reactive protein levels. Nonresponders to infliximab therapy had significantly higher synoviolin expression at baseline as compared with responders, and this elevation persisted despite infliximab therapy. PB CD14+ monocytes expressed increased synoviolin levels compared with CD3+ lymphocytes, and TNFalpha or IL-1beta induced a further increase in expression in CD3+ cells. TNFalpha or IL-1beta induced sustained synoviolin expression in RA FLS.

CONCLUSION

Elevated PB levels of synoviolin were identified in circulating PB mononuclear cells and were associated with nonresponse to infliximab treatment. Sustained up-regulation of synoviolin by IL-lbeta and TNFalpha may contribute to prolonged survival of immune cells and dysregulated FLS proliferation, leading to RA chronicity.

Expression of interleukin-17B in mouse embryonic limb buds and regulation by BMP-7 and bFGF

Interleukin-17B (IL-17B) is a member of interleukin-17 family that displays a variety of proinflammatory and immune modulatory activities. In this study, we found that IL-17B mRNA was maximally expressed in the limb buds of 14.5 days post coitus (dpc) mouse embryo and declined to low level at 19.5 dpc. By immunohistochemical staining, the strongest IL-17B signals were observed in the cells of the bone collar in the primary ossification center. The chondrocytes in the resting and proliferative zones were stained moderately, while little staining was seen in the hypertrophic zone. Furthermore, in both C3H10T1/2 and MC3T3-E1 cells, the IL-17B mRNA was up-regulated by recombinant human bone morphogenetic protein-7, but down-regulated by basic fibroblast growth factor via the extracellular signal-regulated kinase pathway. This study provides the first evidence that IL-17B is expressed in the mouse embryonic limb buds and may play a role in chondrogenesis and osteogenesis.