title: Transforming growth factor-beta type 1 receptor (ALK5) and Smad proteins mediate TIMP-1 and collagen synthesis in experimental intestinal fibrosis.
abstract: Transforming growth factor β (TGF-β) is known to play a key role in intestinal fibrosis; however, the underlying mechanisms are not well understood. TGF-β signal transduction is through TGF-β receptors, including the TGF-β type 1 receptor. Most cell types contain a TGF-β type 1 receptor form known as activin receptor-like kinase 5 (ALK5), which propagates the signal to the nucleus through the phosphorylation of Smad2 and Smad3 proteins. Therefore, we assessed the effect of the disruption of TGF-β/ALK5/Smad signalling by an ALK5 inhibitor (SD-208) in two experimental animal models of intestinal fibrosis: anaerobic bacteria- and trinitrobenzensulphonic acid-induced colitis. In addition, isolated myofibroblasts were pretreated with SD-208 and exposed to recombinant TGF-β1. Finally, myofibroblasts were transfected with ALK5, Smad2, and Smad3-specific siRNA. Up-regulation of ALK5 and TIMP-1, phosphorylation of Smad2 and Smad3 proteins, and increased intestinal wall collagen deposition were found in both experimental animal models. These effects were decreased by SD-208. TGF-β1 treatment also induced phosphorylation of Smad2 and Smad3 and up-regulation of ALK5 protein, TIMP-1, and α2 type 1 collagen gene expression in isolated myofibroblasts. Again these effects were inhibited by SD-208. Also, ALK5, Smad2, and Smad3 siRNA abolished the induction of TIMP-1 and α2 type 1 collagen. Our findings provide evidence that the TGF-β/ALK5/Smad pathway participates in the pathogenesis of experimental intestinal fibrosis. These data show promise for the development of an effective therapeutic intervention in this condition.
authors.affiliation: Department of Pharmacology, Trinity College Dublin, Dublin 2, Ireland. carlos.medina@tcd.ie
authors.forename: Carlos
authors.initials: C
authors.lastname: Medina
authors.forename: Maria Jose
authors.initials: MJ
authors.lastname: Santos-Martinez
authors.forename: Alfredo
authors.initials: A
authors.lastname: Santana
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Paz-Cabrera
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Johnston
authors.forename: Marisabel
authors.initials: M
authors.lastname: Mourelle
authors.forename: Antonio
authors.initials: A
authors.lastname: Salas
authors.forename: Francisco
authors.initials: F
authors.lastname: Guarner
mesh_terms: D000818:Animals; D001421:Bacteria, Anaerobic; D001424:Bacterial Infections / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D003092:Colitis / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D003094:Collagen / Q000096:biosynthesis*; D003106:Colon / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D005355:Fibrosis; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D058628:Myofibroblasts / Q000378:metabolism / Q000473:pathology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000502:physiology*; D051785:Smad Proteins / Q000502:physiology*; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000096:biosynthesis*; D014301:Trinitrobenzenes / Q000494:pharmacology
chemical_list: D018125:Receptors, Transforming Growth Factor beta; D051785:Smad Proteins; D019715:Tissue Inhibitor of Metalloproteinase-1; D014301:Trinitrobenzenes; C029222:sym-trinitrobenzene; D003094:Collagen; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625843:Tgfbr1 protein, rat