title: Role of the JNK signaling pathway in downregulation of connexin43 by TNF-α in human corneal fibroblasts.
abstract: OBJECTIVE
  Proinflammatory cytokines such as tumor necrosis factor (TNF)-α contribute to corneal inflammation. Corneal stromal fibroblasts are connected to each other via gap junctions. We have now examined the role of mitogen-activated protein kinase (MAPK) signaling pathways in TNF-α-induced downregulation of the gap junction protein connexin43 (Cx43) in human corneal fibroblasts.
  
  
  METHODS
  Cultured human corneal fibroblasts were exposed to TNF-α in the absence or presence of inhibitors of MAPK signaling pathways. Expression of Cx43 was evaluated by immunofluorescence and immunoblot analyses. Gap-junctional intercellular communication (GJIC) was measured with a dye-coupling assay.
  
  
  RESULTS
  TNF-α reduced the abundance of Cx43 in human corneal fibroblasts (as revealed by immunoblot analysis) as well as induced the loss of specific staining for this protein (as revealed by immunofluorescence analysis). These effects of TNF-α were attenuated by an inhibitor of c-Jun NH₂-terminal kinase (JNK inhibitor II) but not by inhibitors of signaling by extracellular signal-regulated kinase (PD98059) or by p38 MAPK (SB203580). JNK inhibitor II also attenuated the inhibitory effect of TNF-α on GJIC.
  
  
  CONCLUSIONS
  The inhibitory effects of TNF-α on Cx43 expression and GJIC in human corneal fibroblasts are mediated, at least in part, by the JNK signaling pathway, which therefore likely plays a role in corneal inflammation.
authors.affiliation: Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Ube City, Yamaguchi, Japan. k.kimura@yamaguchi-u.ac.jp
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kimura
authors.forename: Tomoko
authors.initials: T
authors.lastname: Orita
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Morishige
authors.forename: Teruo
authors.initials: T
authors.lastname: Nishida
authors.forename: Koh-Hei
authors.initials: KH
authors.lastname: Sonoda
mesh_terms: D002450:Cell Communication / Q000276:immunology; D002478:Cells, Cultured; D018031:Connexin 43 / Q000276:immunology / Q000378:metabolism*; D003315:Cornea / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D015536:Down-Regulation / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D017629:Gap Junctions / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007634:Keratitis / Q000276:immunology / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism*
chemical_list: D018031:Connexin 43; D004791:Enzyme Inhibitors; C500216:GJA1 protein, human; D014409:Tumor Necrosis Factor-alpha