Department of Matrix Medicine, Oita University, 1-1 Idaigaoka Hasama-machi, Yufu, Oita 879-5593, Japan.
Biochem Biophys Res Commun. 2012 Feb 17;418(3):457-63. doi: 10.1016/j.bbrc.2012.01.039. Epub 2012 Jan 18.
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.
辐射诱导的纤维化发生在正常组织接受治疗或意外辐射后。组织纤维化是胶原和其他细胞外基质成分的过度积累。本研究探讨了电离辐射如何影响 I 型胶原的表达水平和信号通路。实时 RT-PCR 显示，在 NIH3T3 细胞中用 10Gy 照射后，I 型胶原的α1和α2链的 mRNA 从 48 小时开始升高。两种基因和 I 型胶原标志物的相对荧光素酶活性在 72 小时升高。TGF-β1 mRNA 的升高早于 I 型胶原基因。Western blot 分析显示，Smad 磷酸化在 72 小时升高。相反，用 TGF-β 受体抑制剂处理抑制了 I 型胶原的 mRNA 和相对荧光素酶活性。用 Smad 结合位点的突变型构建体抑制 Smad 的磷酸化，并用抑制剂抑制荧光素酶活性。然而，MAPK 途径，p38、ERK1/2 和 JNK，不受特定抑制剂或 siRNA 的影响。数据表明，Smad 途径介导了辐射诱导纤维化中 I 型胶原的表达。
