title: Effect of proinflammatory cytokines, tumor necrosis factor-alpha and interferon-gamma on epithelial barrier function and matrix metalloproteinase-9 in Madin Darby canine kidney cells.
abstract: BACKGROUND
  Elevated matrix metalloproteinase-9 production during inflammation may be deleterious to epithelial barrier function. Therefore we examined the effect of proinflammatory cytokines on the expression and regulation of matrix metalloproteinase-9 in a model renal epithelial cell system. Tight junctions limit diffusion between compartments and permit directional transport of solutes. Impairment of these junctional complexes by proteolysis may contribute to renal failure through loss of barrier function.
  
  
  METHODS
  The renal epithelial cell model, MDCK cells were employed to examine metalloproteinase activity and mRNA expression. Epithelial barrier function was determined using paracellular flux studies.
  
  
  RESULTS
  We found that matrix metalloproteinase-9 expression (MMP-9) and activity is markedly elevated in response to tumor necrosis factor-alpha exposure through a mitogen-activated protein kinase dependent pathway. The MMP-9 is predominately secreted into the apical compartment and elevated MMP-9 expression correlates with impaired cell barrier function that was restored using a specific inhibitor of MMP activity. Addition of recombinant MMP-9 to the apical compartment of MDCK cultures significantly elevated paracellular flux rate.
  
  
  CONCLUSIONS
  We provide direct evidence for a MMP-9-mediated mechanism that produces junctional disruption. Collectively, these findings support the hypothesis that impaired epithelial barrier function due to activation of tissue/matrix degrading mechanisms occurs in response to specific inflammatory cues.
authors.affiliation: Southwestern Graduate School of Biomedical Sciences, UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, USA.
authors.forename: Amanda K
authors.initials: AK
authors.lastname: Leone
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Chun
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Koehler
authors.forename: Jonathan
authors.initials: J
authors.lastname: Caranto
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: King
mesh_terms: D000818:Animals; D002460:Cell Line; D004285:Dogs; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D007371:Interferon-gamma / Q000494:pharmacology*; D007668:Kidney / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D010539:Permeability / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D048049:Extracellular Signal-Regulated MAP Kinases; D020780:Matrix Metalloproteinase 9