title: Advanced glycation end products cause collagen II reduction by activating Janus kinase/signal transducer and activator of transcription 3 pathway in porcine chondrocytes.
abstract: OBJECTIVE
  The major risk factor for OA is ageing; however, the mechanisms remain largely unclear. We investigated the effects and mechanisms of advanced glycation end products (AGEs) that accumulate in aged joints in chondrocytes.
  
  
  METHODS
  Porcine chondrocytes or cartilage fragments were prepared. Gene expression of MMPs and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) was assessed by real-time RT-PCR. Gelatin zymography was used to determine MMP-13 enzyme activity. Histochemistry or immunoblotting analysis was applied to determine the expression of collagen II, proteoglycan and aggrecan. Electrophoretic mobility shift assay and immunoblotting were used to study the activation of signal transducer and activator of transcription 3 (STAT3). Genetic manipulations with short hairpin RNA (shRNA) or dominant negative constructs were applied.
  
  
  RESULTS
  AGE enhanced expression and enzyme activity of MMP and ADAMTS genes and resulted in reduction of collagen II. Both janus kinase 2 (JAK2) and JAK3 inhibitors suppressed AGE-induced MMP-13, ADAMTS-4 and ADAMTS-5 expression and enzyme activity. Inhibition of JAK2 or JAK3 prevented AGE-mediated decrease of collagen II in chondrocytes and proteoglycan (aggrecan) degradation in cartilage fragments. In addition, interference of STAT3 expression inhibited AGE-induced MMP-13 and ADAMTS enzyme activities and mRNA levels. Furthermore, expression of the dominant negative receptor of AGE (DN-RAGE) blocked AGE-induced STAT3 phosphorylation.
  
  
  CONCLUSIONS
  Blocking JAK/STAT3 signalling pathway inhibited AGE-induced activation of MMP-13 and ADAMTS and prevented AGE-mediated decrease of collagen II and proteoglycan (aggrecan). The results indicated that JAK/STAT3 pathway may be a potential target for designing disease-modifying drugs for the treatment of OA.
authors.affiliation: Institute of Cellular and System Medicine, National Health Research Institute, Zhunan, Taiwan, ROC.
authors.forename: Chuan-Yueh
authors.initials: CY
authors.lastname: Huang
authors.forename: Kuan-Yui
authors.initials: KY
authors.lastname: Lai
authors.forename: Li-Feng
authors.initials: LF
authors.lastname: Hung
authors.forename: Wan-Lin
authors.initials: WL
authors.lastname: Wu
authors.forename: Feng-Cheng
authors.initials: FC
authors.lastname: Liu
authors.forename: Ling-Jun
authors.initials: LJ
authors.lastname: Ho
mesh_terms: D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism; D053674:Aggrecans / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism*; D024043:Collagen Type II / Q000378:metabolism*; D019483:Disintegrins / Q000235:genetics / Q000378:metabolism; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D017127:Glycation End Products, Advanced / Q000494:pharmacology*; D053612:Janus Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D053509:Matrix Metalloproteinase 13 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D010003:Osteoarthritis / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013552:Swine
chemical_list: D053674:Aggrecans; D024043:Collagen Type II; D019483:Disintegrins; D017127:Glycation End Products, Advanced; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; D053612:Janus Kinases; D051722:ADAM Proteins; D053509:Matrix Metalloproteinase 13