Contents lists available at ScienceDirect Molecular Immunology journal homepage: www.elsevier.com/locate/molimm Inactivation of the KSRP gene modifies collagen antibody induced arthritis Rudolf Käfer a,1 , Katharina Schrick a,1 , Lisa Schmidtke a , Evelyn Montermann b , Dominika Hobernik b , Matthias Bros b , Ching-Yi Chen c , Hartmut Kleinert a, ⁎ , Andrea Pautz a, ⁎ a Department of Pharmacology, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany b Department of Dermatology, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany c Department of Biochemistry & Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, USA ARTICLE INFO Keywords: Rheumatoid arthritis CAIA KSRP Pro-inflammatory mediators Gene expression ABSTRACT The KH type splicing regulatory protein (KSRP) is a nucleic acid binding protein, which negatively regulates the stability and/or translatability of many mRNA species encoding immune-relevant proteins. As KSRP is expressed in immune cells including T and B cells, neutrophils, macrophages and dendritic cells, we wanted to analyze its importance for the development of autoimmune diseases. We chose collagen antibody-induced arthritis (CAIA) as an appropriate autoimmune disease mouse model in which neutrophils and macrophages constitute the main effector cell populations. We compared arthritis induction in wild type (WT) and KSRP -/- mice and paws were taken for histological sections and qPCR analysis. Furthermore, we determined the frequencies of spleen immune cells by flow cytometry. Cytokine levels in spleen cell supernatants were determined by cytometric bead array analyses (CBA). After CAIA induction we unexpectedly observed in WT animals much stronger swelling of the paws than in KSRP -/- mice. In accordance, histological staining of paw sections of KSRP -/- animals revealed much lower frequencies of infiltrating immune cells in the joints compared to WT animals. Furthermore, CAIA-treatment resulted in reduced expression of several inflammatory factors (like CXCL-1, iNOS, TNF-α and S100A8) as well as immune cell marker genes (e.g. LFA-1, CD68, Ly6G) in the joints of KSRP -/- mice. Spleen cells of KSRP -/- mice showed lower frequencies of myeloid cells. On cytokine level IFN-γ production was increased in spleen cells of KSRP -/- mice compared to WT samples. These data surprisingly suggest that the absence of KSRP protects against the induction of inflammatory arthritis. 1. Introduction Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune and destructive joint disease affecting 1% of the population. RA is characterized by abnormal accumulation of immune cells (macro- phages, dendritic cells, mast cells, eosinophils, neutrophils, T cells and B cells). These immune cells together with endothelial cells, fibroblasts and chondrocytes express and export numerous pro-inflam- matory mediators like cytokines (TNF-α, IL-1, IL-6 etc.), chemokines (MCP-1/CCL2 etc.), lipids, growth factors and destructive enzymes (e.g. matrix metalloproteinases), which are critically involved in local tissue destruction and fibrotic processes (McInnes and Schett, 2007). These inflammation-induced changes in the expression of pro-inflammatory genes result from the activation/inhibition of different transcription factors (like NF-κB, STATs, AP-1; transcriptional regulation) and RNA binding proteins (RBPs; like TTP, KSRP, PABP; post-transcriptional regulation) (Okamoto et al., 2008; Carrick et al., 2004). Collagen-induced arthritis (CIA) is a widely-used animal model for RA (Caplazi et al., 2015). Immunization with native collagen type II (CII) in adjuvant induces autoimmune polyarthritis in susceptible rodents and primates. In accordance to the murine system CII seems to be also a relevant autoantigen in humans and there is evidence that in both, human and mice, the disease is driven by CII-specific T- and B- cells and their secreted cytokines (Caplazi et al., 2015; Kim et al., http://dx.doi.org/10.1016/j.molimm.2017.05.003 Received 24 March 2017; Received in revised form 27 April 2017; Accepted 1 May 2017 ⁎ Corresponding authors at: Department of Pharmacology, University Medical Center of the Johannes Gutenberg University, Obere Zahlbacher Str. 67, D55101 Mainz, Germany. 1 These authors contributed equally to this work. E-mail addresses: kleinert@mail.uni-mainz.de (H. Kleinert), pautz@uni-mainz.de (A. Pautz). Abbreviations: 3′-UTR, 3′-untranslated region; AI, arthritis index; ARE, AU-rich element; ARE-BP, ARE binding protein; CAIA, collagen antibody induced arthritis; CBA, cytometric bead array; CIA, collagen induced arthritis; CII, collagen type II; FACS, fluorescent activated cell sorting; KSRP, KH-type splicing regulatory protein; iNOS, inducible NO synthase; mAB, monoclonal antibody; PBMC, peripheral blood monocytes; qRT-PCR, quantitative real time reverse transcription polymerase chain reaction; RA, rheumatoid arthritis; RBP, RNA-binding protein; Pol2A, RNA polymerase II Molecular Immunology 87 (2017) 207–216 0161-5890/ © 2017 Elsevier Ltd. All rights reserved. MARK