title: Differential expressions of NOD-like receptors and their associations with inflammatory responses in rheumatoid arthritis.
abstract: OBJECTIVE
  To determine the differential expressions of nucleotide oligomerisation domain (NOD)-like receptors (NLRs) and to investigate their association with inflammatory responses in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS).
  
  
  METHODS
  Gene expression and protein levels of various NLRs, including NOD1, NOD2, NLRP1, NLRP3, NLRP12, NLRX1, and NLRC3, were determined in FLS and synovial tissues from patients with RA and patients with osteoarthritis (OA) using quantitative real-time PCR and immunohistochemistry. After transfection of NOD2 RNAi plasmids or a pcDNA3.1-NLRX1 vector, gene expression levels of pro-inflammatory cytokines in RA FLS and the protein levels of these cytokines in culture supernatants were determined using quantitative real-time PCR and enzyme-linked immunosorbent assays. The effects of NLR gene regulation on NF-κB and caspase-1 were evaluated using Western blot analysis.
  
  
  RESULTS
  Gene expression levels of NOD1, NLRP1, NLRP3, NLRP12, and NLRC3 were not different between RA and OA samples. NOD2 gene expression and protein levels were significantly increased in RA samples, whereas the levels of NLRX1 were significantly decreased. Downregulation of NOD2 gene expression by transfection with NOD2 RNAi plasmid significantly reduced pro-inflammatory cytokine levels in RA FLS, while transfection with adenoviral vectors encoding NLRX1 had no effect on pro-inflammatory cytokine levels. Downregulation of NOD2 gene expression significantly decreased NF-κB, TRAF6, and IKK levels, but not caspase-1 levels, in RA FLS.
  
  
  CONCLUSIONS
  NOD2 is upregulated in RA FLS; moreover, downregulation of NOD2 gene expression reduces pro-inflammatory cytokine and NF-κB levels in RA FLS. These findings provide evidence that NOD2 exerts pro-inflammatory effects in RA.
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Hye Won
authors.initials: HW
authors.lastname: Kim
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Yong-Jin
authors.initials: YJ
authors.lastname: Kwon
authors.affiliation: Chadwick International School, Songdo, Incheon, South Korea.
authors.forename: Byung Wook
authors.initials: BW
authors.lastname: Park
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Jason Jungsik
authors.initials: JJ
authors.lastname: Song
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Yong-Beom
authors.initials: YB
authors.lastname: Park
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, South Korea. mcpark@yuhs.ac.
authors.forename: Min Chan
authors.initials: MC
authors.lastname: Park
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D001172:Arthritis, Rheumatoid / Q000235:genetics* / Q000378:metabolism / Q000601:surgery; D019645:Arthroplasty, Replacement, Knee; D015153:Blotting, Western; D016022:Case-Control Studies; D020170:Caspase 1 / Q000378:metabolism; D015536:Down-Regulation; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein / Q000235:genetics / Q000378:metabolism; D000070576:NLR Proteins; D053474:Nod1 Signaling Adaptor Protein / Q000235:genetics / Q000378:metabolism; D053473:Nod2 Signaling Adaptor Protein / Q000235:genetics / Q000378:metabolism; D020370:Osteoarthritis, Knee / Q000235:genetics / Q000378:metabolism / Q000601:surgery; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D013583:Synovial Membrane / Q000378:metabolism*; D000070918:Synoviocytes / Q000378:metabolism*; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D016328:NF-kappa B; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D000070576:NLR Proteins; C503285:NLRC3 protein, human; C427903:NLRP1 protein, human; C476731:NLRP12 protein, human; C453881:NLRP3 protein, human; C527006:NLRX1 protein, human; C119067:NOD1 protein, human; C429018:NOD2 protein, human; D053474:Nod1 Signaling Adaptor Protein; D053473:Nod2 Signaling Adaptor Protein; D012333:RNA, Messenger; D048029:TNF Receptor-Associated Factor 6; C000604754:Tifab protein, human; D051550:I-kappa B Kinase; D020170:Caspase 1