title: Sphingosine 1-phosphate counteracts the effects of interleukin-1β in human chondrocytes.
abstract: OBJECTIVE
  The lipid mediator sphingosine 1-phosphate (S1P) is found in the synovial fluid of osteoarthritis (OA) patients. S1P protects bovine cartilage by counteracting the effects of interleukin-1β (IL-1β). This study was undertaken to examine the interaction of S1P and IL-1β in human OA chondrocytes.
  
  
  METHODS
  Human cartilage was obtained from patients undergoing total knee joint replacement. Chondrocytes were cultured in monolayer and treated with IL-1β and S1P. Expression of S1P receptor subtypes and genes involved in cartilage degradation was evaluated using real-time polymerase chain reaction, immunohistochemistry, and Western blotting. S1P signaling was evaluated using inhibitors of S1P receptors and small interfering RNA (siRNA) knockdown of the S1P2 receptor. Phosphorylation of MAP kinases and NF-κB in response to IL-1β and S1P was detected by Western blotting.
  
  
  RESULTS
  S1P2 was identified as the most prevalent S1P receptor subtype in human OA cartilage and chondrocytes in vitro. S1P reduced expression of inducible nitric oxide synthase (iNOS) in IL-1β-treated chondrocytes. Reduction of ADAMTS-4 and matrix metalloproteinase 13 expression by S1P correlated with S1P2 expression. Pharmacologic inhibition of the S1P2 receptor, but not the S1P1 and S1P3 receptors, abrogated the inhibition of iNOS expression. Similar results were observed using siRNA knockdown. S1P signaling inhibited IL-1β-induced phosphorylation of p38 MAPK.
  
  
  CONCLUSIONS
  In human chondrocytes, S1P reduces the induction of catabolic genes in the presence of IL-1β. Activation of the S1P2 receptor counteracts the detrimental phosphorylation of p38 MAPK by IL-1β.
authors.affiliation: University of California at San Diego, La Jolla, California; Medical University of Graz, Graz, Austria. mstradner@ucsd.edu
authors.forename: Martin H
authors.initials: MH
authors.lastname: Stradner
authors.forename: Gerald
authors.initials: G
authors.lastname: Gruber
authors.forename: Hannes
authors.initials: H
authors.lastname: Angerer
authors.forename: Verena
authors.initials: V
authors.lastname: Huber
authors.forename: Daniela
authors.initials: D
authors.lastname: Setznagl
authors.forename: Marie-Luise
authors.initials: ML
authors.lastname: Kremser
authors.forename: Florentine C
authors.initials: FC
authors.lastname: Moazedi-Fürst
authors.forename: Reinhard
authors.initials: R
authors.lastname: Windhager
authors.forename: Winfried B
authors.initials: WB
authors.lastname: Graninger
mesh_terms: D051722:ADAM Proteins / Q000378:metabolism; D000071121:ADAMTS4 Protein; D002358:Cartilage, Articular / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D004336:Drug Antagonism; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D006801:Humans; D053583:Interleukin-1beta / Q000378:metabolism / Q000494:pharmacology*; D008246:Lysophospholipids / Q000494:pharmacology*; D053509:Matrix Metalloproteinase 13 / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D011348:Procollagen N-Endopeptidase / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D049349:Receptors, Lysosphingolipid / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000081025:Sphingosine-1-Phosphate Receptors; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D053583:Interleukin-1beta; D008246:Lysophospholipids; D016328:NF-kappa B; D034741:RNA, Small Interfering; D049349:Receptors, Lysosphingolipid; C477522:S1PR2 protein, human; D000081025:Sphingosine-1-Phosphate Receptors; C060506:sphingosine 1-phosphate; D052247:Nitric Oxide Synthase Type II; D048051:p38 Mitogen-Activated Protein Kinases; D051722:ADAM Proteins; D053509:Matrix Metalloproteinase 13; D011348:Procollagen N-Endopeptidase; D000071121:ADAMTS4 Protein; C000603918:ADAMTS4 protein, human; D013110:Sphingosine