title: Interleukin-33 acts as a transcriptional repressor and extracellular cytokine in fibroblast-like synoviocytes in patients with rheumatoid arthritis.
abstract: The present study aimed to assess the functions of interleukin (IL)-33 in fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis (RA). Enzyme-linked immunosorbent assays (ELISAs) were used to quantify interleukin (IL)-33 in plasma obtained from patients with RA and osteoarthritis (OA). To evaluate functions of intracellular IL-33, levels of inflammatory mediators and matric metalloproteinases (MMPs) were measured in RA FLS transfected with IL-33 small- interfering RNA (siRNA) or plasmids, and changes in the expression and regulation of nuclear factor kappaB (NF-κB) were determined using western blotting and reporter gene assays. In addition, to examine the extracellular effects of IL-33, IP10 and receptor activator of NF-κB ligand (RANKL) mRNA levels were measured after treatment with IL-33 and blocking antibodies to ST2, the IL-33 receptor. To evaluate whether extracellular IL-33 regulated osteoclastogenesis, human CD14(+) monocytes cocultured with IL-33-stimulated FLS were stained with tartrate-resistant acid phosphatase (TRAP). IL-33 levels were higher in plasma obtained from patients with RA than in those obtained from patients with OA. The expression levels of IL-33 were elevated in RA FLS that had been stimulated with poly I:C, IL-1β, and tumor necrosis factor (TNF)-α. Silencing of IL-33 increased the levels of pro-inflammatory molecules and MMPs, promoted inhibitor of kappaB (IκBα) degradation, and increased NF-κB activity; these effects were reversed in IL-33 plasmid-transfected FLS. Stimulation with exogenous IL-33 increased RANKL and IP-10 mRNA expression. These increases were blocked by anti-ST2 treatment. Furthermore, we confirmed that extracellular IL-33 stimulated the formation of TRAP(+) multinucleated osteoclasts through RA FLS. These results suggested that intracellular IL-33 acted as a transcriptional repressor of NF-κB, which may provide negative feedback against inflammatory responses, whereas, extracellular IL-33 functioned as an activator of osteoclastogenesis. Therefore, increased plasma IL-33 levels in patients with RA could be a possible biomarker to reflect the potential risks of bone erosion.
authors.affiliation: Asan Institute for Life Science, Asan Medical Center, Seoul 138-736, Republic of Korea; Division of Rheumatology, Department of Internal Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul 138-736, Republic of Korea.
authors.forename: Eun-Ju
authors.initials: EJ
authors.lastname: Lee
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Pusan National Yangsan Hospital, Yangsan 626-770, Republic of Korea.
authors.forename: Min Wook
authors.initials: MW
authors.lastname: So
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul 138-736, Republic of Korea.
authors.forename: Seokchan
authors.initials: S
authors.lastname: Hong
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul 138-736, Republic of Korea.
authors.forename: Yong-Gil
authors.initials: YG
authors.lastname: Kim
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul 138-736, Republic of Korea.
authors.forename: Bin
authors.initials: B
authors.lastname: Yoo
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul 138-736, Republic of Korea. Electronic address: cklee@amc.seoul.kr.
authors.forename: Chang-Keun
authors.initials: CK
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000235:genetics / Q000473:pathology; D002478:Cells, Cultured; D054357:Chemokine CXCL10 / Q000235:genetics; D018920:Coculture Techniques; D005260:Female; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D015151:Immunoblotting; D000067596:Interleukin-33 / Q000097:blood / Q000235:genetics / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects; D053245:RANK Ligand / Q000235:genetics; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013583:Synovial Membrane / Q000473:pathology; D014158:Transcription, Genetic / Q000187:drug effects*
chemical_list: C114753:CXCL10 protein, human; D054357:Chemokine CXCL10; D000067596:Interleukin-33; D016328:NF-kappa B; D053245:RANK Ligand; C505688:TNFSF11 protein, human
keywords: Fibroblast-like synoviocytes; Interleukin-33; Osteoclastogenesis; Rheumatoid arthritis; Transcriptional repressor