title: Smad, but not MAPK, pathway mediates the expression of type I collagen in radiation induced fibrosis.
abstract: Radiation induced fibrosis occurs following a therapeutic or accidental radiation exposure in normal tissues. Tissue fibrosis is the excessive accumulation of collagen and other extracellular matrix components. This study investigated how ionizing radiation affects the expression level and signal pathway of type I collagen. Real time RT-RCR showed that both α1 and α2 chain of type I collagen mRNA were elevated from 48 h after irradiation with 10 Gy in NIH3T3 cells. The relative luciferase activities of both genes and type I collagen marker were elevated at 72 h. TGF-β1 mRNA was elevated earlier than those of type I collagen genes. A Western blot analysis showed the elevation of Smad phosphorylation at 72 h. Conversely, treatment with TGF-β receptor inhibitor inhibited the mRNA and relative luciferase activity of type I collagen. The phosphorylation of Smad was repressed with the inhibitor, and the luciferase activity was cancelled using a mutant construct of Smad binding site of α2(I) collagen gene. However, the MAPK pathways, p38, ERK1/2 and JNK, were not affected with specific inhibitors or siRNA. The data showed that the Smad pathway mediated the expression of type I collagen in radiation induced fibrosis.
authors.affiliation: Department of Matrix Medicine, Oita University, 1-1 Idaigaoka Hasama-machi, Yufu, Oita 879-5593, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yano
authors.forename: Ryoji
authors.initials: R
authors.lastname: Hamanaka
authors.forename: Miki
authors.initials: M
authors.lastname: Nakamura
authors.forename: Hideaki
authors.initials: H
authors.lastname: Sumiyoshi
authors.forename: Noritaka
authors.initials: N
authors.lastname: Matsuo
authors.forename: Hidekatsu
authors.initials: H
authors.lastname: Yoshioka
mesh_terms: D000818:Animals; D024042:Collagen Type I / Q000096:biosynthesis* / Q000235:genetics; D005355:Fibrosis; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D041681:NIH 3T3 Cells; D011833:Radiation Injuries, Experimental / Q000378:metabolism* / Q000473:pathology*; D011839:Radiation, Ionizing; D051785:Smad Proteins / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000096:biosynthesis / Q000235:genetics; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D024042:Collagen Type I; D051785:Smad Proteins; D053773:Transforming Growth Factor beta1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases