title: Inhibition of interleukin 1-induced matrix metalloproteinase 13 expression in human chondrocytes by interferon gamma.
abstract: BACKGROUND
  Despite well-documented immunomodulation by interferon gamma (IFNgamma), its role and mechanism of regulation of matrix metalloproteinase 13 (MMP13) gene expression in human chondrocytes is unknown.
  
  
  OBJECTIVE
  To investigate the ability and mechanism of IFNgamma to suppress interleukin 1 (IL1)-induced MMP13 expression in articular chondrocytes.
  
  
  METHODS
  Human chondrocytes were treated with IFNgamma or IL1beta alone or in combination. MMP13 mRNA was analysed by semiquantitative reverse transcriptase-PCR. MMP13 protein, phospho-signal transducer and activator of transcription 1 (STAT1) and p44/42 mitogen-activated protein kinase levels were measured by western blotting. MMP13 promoter luciferase, cytomegalovirus cyclic AMP response element-binding protein (CBP)/p300 plasmids and STAT1 small interfering RNA (siRNA) were transfected by the calcium phosphate method. IFNgamma receptor was also neutralised. Activator protein (AP) 1 activity was monitored by the TransAM transcription factor kit. STAT1-CBP/p300 interaction was studied by immunoprecipitation.
  
  
  RESULTS
  IFNgamma potently suppressed IL1-induced expression of MMP13 and promoter activity. Blockade with neutralising IFNgamma R1 antibody revealed that MMP13 inhibition by IFNgamma is mediated by the IFN receptor. IFNgamma-stimulated activation of STAT1 was directly correlated with MMP13 suppression. Knockdown of the STAT1 gene by specific siRNA or its inhibition with fludarabine partially restored the IL1beta induction of MMP13 expression and promoter activity. IFNgamma did not alter AP1 binding ability but promoted physical interaction of STAT1 and CBP/p300 coactivator. p300 overexpression reversed IFNgamma inhibition of endogenous MMP13 mRNA expression and exogenous MMP13 promoter activity.
  
  
  CONCLUSIONS
  IFNgamma, through its receptor, activates STAT1, which binds with CBP/p300 coactivator, sequesters it from the cell system, and thus inhibits transcriptional induction of the MMP13 gene in chondrocytes. IFNgamma and its signalling pathways could be targeted therapeutically for diminishing IL1-induced cartilage degradation by MMP13 in patients with arthritis.
authors.affiliation: K-5255 Mailloux, Hôpital Notre-Dame du CHUM, 1560 Sherbrooke East, Montréal, Québec, Canada H2L 4M1. muhammad.zafarullah@umontreal.ca
authors.forename: R
authors.initials: R
authors.lastname: Ahmad
authors.forename: H Y
authors.initials: HY
authors.lastname: Qureshi
authors.forename: M
authors.initials: M
authors.lastname: El Mabrouk
authors.forename: J
authors.initials: J
authors.lastname: Sylvester
authors.forename: M
authors.initials: M
authors.lastname: Ahmad
authors.forename: M
authors.initials: M
authors.lastname: Zafarullah
mesh_terms: D015153:Blotting, Western / Q000379:methods; D002358:Cartilage, Articular / Q000166:cytology / Q000201:enzymology; D019902:Chondrocytes / Q000187:drug effects* / Q000201:enzymology; D050881:E1A-Associated p300 Protein / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D053583:Interleukin-1beta / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D007719:Knee Joint / Q000166:cytology / Q000201:enzymology; D053509:Matrix Metalloproteinase 13 / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D017471:Receptors, Interferon / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D050794:STAT1 Transcription Factor / Q000378:metabolism; D014162:Transfection; D000096743:Interferon gamma Receptor
chemical_list: D050881:E1A-Associated p300 Protein; D007371:Interferon-gamma; D053583:Interleukin-1beta; D053509:Matrix Metalloproteinase 13; D010455:Peptides; D012333:RNA, Messenger; D017471:Receptors, Interferon; D050794:STAT1 Transcription Factor; D000096743:Interferon gamma Receptor; C513345:AP1 peptide; C494079:STAT1 protein, human; C494360:EP300 protein, human