title: Catabolic and proinflammatory effects of leptin in chondrocytes are regulated by suppressor of cytokine signaling-3.
abstract: Previous studies provide evidence that adipokine leptin increases production of catabolic and proinflammatory factors in chondrocytes and serves as a link between obesity and osteoarthritis (OA). However, the magnitude of the response to leptin treatment varies greatly between chondrocytes from different donor patients. In the present study, we investigated the regulatory role of suppressor of cytokine signaling-3 (SOCS-3) in the leptin-induced responses in OA cartilage.
  
  
  
  Cartilage and synovial fluid samples from 97 patients with OA undergoing knee replacement surgery were collected. Cartilage samples were cultured with leptin (10 μg/ml), and the levels of proinflammatory and catabolic factors in synovial fluid and in the cartilage culture media, and SOCS-3 expression in the cartilage were measured. The role of SOCS-3 in leptin signaling was further studied in H4 murine chondrocytes by downregulating SOCS-3 with siRNA.
  
  
  
  Leptin-induced expression of matrix metalloproteinases MMP-1, MMP-3, MMP-13, interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were higher in the cartilage samples with low SOCS-3 expression. Accordingly, downregulation of SOCS-3 by siRNA in H4 chondrocytes led to enhanced leptin-induced expression of MMP-3, MMP-13, IL-6 and iNOS. Synovial fluid leptin was associated positively, and cartilage SOCS-3 negatively with synovial fluid levels of MMPs in a multivariate model in obese (body mass index (BMI) >30 kg/m2) but not in non-obese (BMI <30 kg/m2) patients.
  
  
  
  Our results show, for the first time, that SOCS-3 regulates leptin-induced responses in cartilage, and could thus be a future drug target in the treatment or prevention of OA, especially in obese patients.
authors.affiliation: The Immunopharmacology Research Group, University of Tampere School of Medicine and Tampere University Hospital, Tampere, Finland.
authors.forename: Anna
authors.initials: A
authors.lastname: Koskinen-Kolasa
authors.affiliation: The Immunopharmacology Research Group, University of Tampere School of Medicine and Tampere University Hospital, Tampere, Finland.
authors.forename: Katriina
authors.initials: K
authors.lastname: Vuolteenaho
authors.affiliation: The Immunopharmacology Research Group, University of Tampere School of Medicine and Tampere University Hospital, Tampere, Finland.
authors.forename: Riku
authors.initials: R
authors.lastname: Korhonen
authors.affiliation: The Immunopharmacology Research Group, University of Tampere School of Medicine and Tampere University Hospital, Tampere, Finland.|Coxa Hospital for Joint Replacement, Tampere, Finland.
authors.forename: Teemu
authors.initials: T
authors.lastname: Moilanen
authors.affiliation: The Immunopharmacology Research Group, University of Tampere School of Medicine and Tampere University Hospital, Tampere, Finland. eeva.moilanen@uta.fi.
authors.forename: Eeva
authors.initials: E
authors.lastname: Moilanen
mesh_terms: D000368:Aged; D000818:Animals; D015153:Blotting, Western; D002358:Cartilage, Articular / Q000378:metabolism; D019902:Chondrocytes / Q000378:metabolism*; D005260:Female; D055785:Gene Knockdown Techniques; D006801:Humans; D007118:Immunoassay; D020738:Leptin / Q000378:metabolism*; D008297:Male; D051379:Mice; D008875:Middle Aged; D009765:Obesity / Q000150:complications; D020370:Osteoarthritis, Knee / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D050826:Suppressor of Cytokine Signaling Proteins / Q000378:metabolism*
chemical_list: D020738:Leptin; D050826:Suppressor of Cytokine Signaling Proteins
keywords: Adipokine; Chondrocytes; Leptin; Obesity; Osteoarthritis; SOCS-3