title: Regulation of inflammatory arthritis by the upstream kinase mitogen activated protein kinase kinase 7 in the c-Jun N-terminal kinase pathway.
abstract: BACKGROUND
  The c-Jun N-terminal kinase (JNK) is a key regulator of matrix metalloproteinase (MMP) and cytokine production in rheumatoid arthritis (RA) and JNK deficiency markedly protects mice in animal models of arthritis. Cytokine-induced JNK activation is strictly dependent on the mitogen-activated protein kinase kinase 7 (MKK7) in fibroblast-like synoviocytes (FLS). Therefore, we evaluated whether targeting MKK7 using anti-sense oligonucleotides (ASO) would decrease JNK activation and severity in K/BxN serum transfer arthritis.
  
  
  METHODS
  Three 2'-O-methoxyethyl chimeric ASOs for MKK7 and control ASO were injected intravenously in normal C57BL/6 mice. PBS, control ASO or MKK7 ASO was injected from Day -8 to Day 10 in the passive K/BxN model. Ankle histology was evaluated using a semi-quantitative scoring system. Expression of MKK7 and JNK pathways was evaluated by quantitative PCR and Western blot analysis.
  
  
  RESULTS
  MKK7 ASO decreased MKK7 mRNA and protein levels in ankles by about 40% in normal mice within three days. There was no effect of control ASO on MKK7 expression and MKK7 ASO did not affect MKK3, MKK4 or MKK6. Mice injected with MKK7 ASO had significantly less severe arthritis compared with control ASO (P < 0.01). Histologic evidence of synovial inflammation, bone erosion and cartilage damage was reduced in MKK7 ASO-treated mice (P < 0.01). MKK7 deficiency decreased phospho-JNK and phospho-c-Jun in ankle extracts (P < 0.05), but not phospho-MKK4. Interleukin-1beta (IL-1β), MMP3 and MMP13 gene expression in ankle joints were decreased by MKK7 ASO (P < 0.01).
  
  
  CONCLUSIONS
  MKK7 plays a critical regulatory role in the JNK pathway in a murine model of arthritis. Targeting MKK7 rather than JNK could provide site and event specificity when treating synovitis.
authors.affiliation: Division of Rheumatology, Allergy and Immunology, UCSD School of Medicine, La Jolla, CA, USA.
authors.forename: Sang-il
authors.initials: SI
authors.lastname: Lee
authors.forename: David L
authors.initials: DL
authors.lastname: Boyle
authors.forename: Andres
authors.initials: A
authors.lastname: Berdeja
authors.forename: Gary S
authors.initials: GS
authors.lastname: Firestein
mesh_terms: D000818:Animals; D000843:Ankle Joint / Q000378:metabolism / Q000473:pathology; D001172:Arthritis, Rheumatoid / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D015153:Blotting, Western; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D007275:Injections, Intravenous; D053583:Interleukin-1beta / Q000235:genetics; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism; D048688:MAP Kinase Kinase 7 / Q000235:genetics* / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000235:genetics*; D053509:Matrix Metalloproteinase 13 / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D016376:Oligonucleotides, Antisense / Q000008:administration & dosage / Q000235:genetics; D010766:Phosphorylation; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012720:Severity of Illness Index; D013583:Synovial Membrane / Q000378:metabolism / Q000473:pathology; D013585:Synovitis / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
chemical_list: D053583:Interleukin-1beta; D016376:Oligonucleotides, Antisense; D048031:JNK Mitogen-Activated Protein Kinases; D048688:MAP Kinase Kinase 7; C482570:Map2k7 protein, mouse; D053509:Matrix Metalloproteinase 13; C507081:Mmp13 protein, mouse