Role of Interleukin 17 in Arthritis Chronicity through Survival of Synoviocytes via Regulation of Synoviolin Expression Myew-Ling Toh 1 , Gaelle Gonzales1, Marije I. Koenders2, Anne Tournadre1, David Boyle3, Erik Lubberts2, Yuan Zhou 1 , Gary S. Firestein3, Wim B. van den Berg2, Pierre Miossec1* 1 Research Unit Immunogenomics and Inflammation, EA 4130, Hospital Edouard Herriot, University of Lyon, Lyon, France, 2 Rheumatology Research and Advanced Therapeutics, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands, 3 Division of Rheumatology, Allergy and Immunology, Department of Medicine, University of California San Diego, La Jolla, California, United States of America Abstract Background: The use of TNF inhibitors has been a major progress in the treatment of chronic inflammation. However, not all patients respond. In addition, response will be often lost when treatment is stopped. These clinical aspects indicate that other cytokines might be involved and we focus here on the role of IL-17. In addition, the chronic nature of joint inflammation may contribute to reduced response and enhanced chronicity. Therefore we studied the capacity of IL-17 to regulate synoviolin, an E3 ubiquitin ligase implicated in synovial hyperplasia in human rheumatoid arthritis (RA) FLS and in chronic reactivated streptococcal cell wall (SCW)-induced arthritis. Methodology/Principal Findings: Chronic reactivated SCW-induced arthritis was examined in IL-17R deficient and wild-type mice. Synoviolin expression was analysed by real-time RT-PCR, Western Blot or immunostaining in RA FLS and tissue, and p53 assessed by Western Blot. Apoptosis was detected by annexin V/propidium iodide staining, SS DNA apoptosis ELISA kit or TUNEL staining and proliferation by PCNA staining. IL-17 receptor A (IL-17RA), IL-17 receptor C (IL-17-RC) or synoviolin inhibition were achieved by small interfering RNA (siRNA) or neutralizing antibodies. IL-17 induced sustained synoviolin expression in RA FLS. Sodium nitroprusside (SNP)-induced RA FLS apoptosis was associated with reduced synoviolin expression and was rescued by IL-17 treatment with a corresponding increase in synoviolin expression. IL-17RC or IL-17RA RNA interference increased SNP-induced apoptosis, and decreased IL-17-induced synoviolin. IL-17 rescued RA FLS from apoptosis induced by synoviolin knockdown. IL-17 and TNF had additive effects on synoviolin expression and protection against apoptosis induced by synoviolin knowndown. In IL-17R deficient mice, a decrease in arthritis severity was characterized by increased synovial apoptosis, reduced proliferation and a marked reduction in synoviolin expression. A distinct absence of synoviolin expressing germinal centres in IL-17R deficient mice contrasted with synoviolin positive B cells and Th17 cells in synovial germinal centre-like structures. Conclusion/Significance: IL-17 induction of synoviolin may contribute at least in part to RA chronicity by prolonging the survival of RA FLS and immune cells in germinal centre reactions. These results extend the role of IL-17 to synovial hyperplasia. Citation: Toh M-L, Gonzales G, Koenders MI, Tournadre A, Boyle D, et al. (2010) Role of Interleukin 17 in Arthritis Chronicity through Survival of Synoviocytes via Regulation of Synoviolin Expression. PLoS ONE 5(10): e13416. doi:10.1371/journal.pone.0013416 Editor: Derya Unutmaz, New York University, United States of America Received September 22, 2009; Accepted August 12, 2010; Published October 15, 2010 Copyright: 2010 Toh et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work has been supported by research grants from the Hospices Civils de Lyon and the Region Rhone-Alpes and in part by the Me´rieux Institute. Ling Toh and Yuan Zhou were supported by a post-doctoral fellowship of the Region Rhone-Alpes. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: pierre.miossec@univ-lyon1.fr Introduction Anti-TNF therapies have an established role in rheumatoid arthritis (RA) treatment however in the clinic RA remains a chronic disease with up to 40% nonresponders and subsequent flares when TNF inhibitors are ceased. RA is characterised by chronic synovial inflammation and hyperplasia. Synovial hyper- plasia is a consequence of an imbalance between proliferation and apoptosis of resident fibroblast-like synoviocytes (FLS). Resistance of cells to apoptosis is partly due to the upregulation of molecules counteracting the apoptosis cascade. There is substantial evidence that synovial hypertrophy contributes to the chronicity of RA with ultimately destructive consequences. Joint synovectomy by surgi- cal, chemical or radiation measures, removes the pathologic synovial tissue burden leading to cessation of arthritis and more prolonged remission [1]. Similarly to cancer cells, RA FLS demonstrate dysregulated proliferation and apoptosis, anchorage independent growth, intrinsically express proto-oncogenes and functional mutations in tumour suppressor genes such as p53 and are capable of spontaneously invading human cartilage [2]. Up to 40% of RA patients are nonresponders to current anti- TNF biologics suggesting that other molecules implicated in PLoS ONE | www.plosone.org 1 October 2010 | Volume 5 | Issue 10 | e13416