title: Mechanisms of transforming growth factor beta(1)/Smad signalling mediated by mitogen-activated protein kinase pathways in keloid fibroblasts.
abstract: BACKGROUND
  Keloids are recognized as benign tumours characterized by fibroblastic proliferation and accumulation of extracellular matrix, especially collagen deposition. The transforming growth factor (TGF)-beta(1)/Smad pathway plays an important role in keloid pathogenesis; however the underlying mechanisms are not fully understood.
  
  
  OBJECTIVE
  To define further the mechanisms of TGF-beta(1)/Smad signal transduction mediated by mitogen-activated protein kinases (MAPKs), including the extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK) and p38 pathways, in keloid fibroblasts.
  
  
  METHODS
  In the absence or presence of three MAPK (ERK, JNK and p38)-specific inhibitors, keloid fibroblasts were stimulated with exogenous TGF-beta(1) to activate Smad signalling. Smad protein expression was measured by immunoprecipitation/immunoblotting and immunofluorescence; plasminogen activator inhibitor (PAI)-1 transcriptional activity was measured by real-time reverse transcriptase-polymerase chain reaction analysis.
  
  
  RESULTS
  TGF-beta(1) induced Smad2/3 phosphorylation at both the C-terminal and the linker region, thus promoting formation of the Smad2/3/4 complex and nuclear translocation, and PAI-1 mRNA expression in keloid fibroblasts; in addition, TGF-beta(1) decreased inhibitory Smad7 expression. Meanwhile, the p38 inhibitor significantly inhibited Smad2/3 phosphorylation, especially at the linker region, and furthermore blocked Smad2/3/4 complex formation, and thus decreased PAI-1 mRNA expression; decreased Smad7 expression induced by TGF-beta(1) was also reversed by the p38 inhibitor. The ERK and JNK inhibitors interrupted Smad2/3/4 complex translocation into the nucleus and consequently decreased PAI-1 mRNA expression.
  
  
  CONCLUSIONS
  These results suggested that the ERK, JNK and p38 pathways mediate TGF-beta(1)/Smad signal transduction and might be considered as specific targets of drug therapy for keloids.
authors.affiliation: Department of Pharmacology, Anhui Medical University, Hefei 230032, China.
authors.forename: S
authors.initials: S
authors.lastname: He
authors.forename: X
authors.initials: X
authors.lastname: Liu
authors.forename: Y
authors.initials: Y
authors.lastname: Yang
authors.forename: W
authors.initials: W
authors.lastname: Huang
authors.forename: S
authors.initials: S
authors.lastname: Xu
authors.forename: S
authors.initials: S
authors.lastname: Yang
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: M S
authors.initials: MS
authors.lastname: Roberts
mesh_terms: D000704:Analysis of Variance; D005347:Fibroblasts / Q000378:metabolism*; D015200:Fluoroimmunoassay; D006801:Humans; D015151:Immunoblotting; D007627:Keloid / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051785:Smad Proteins / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D051785:Smad Proteins; D016212:Transforming Growth Factor beta; D020928:Mitogen-Activated Protein Kinases