Morphogenic protein epimorphin protects intestinal epithelial cells from oxidative stress by the activation of EGF receptor and MEK/ERK, PI3 kinase/Akt signals.
Epimorphin is a mesenchymal protein that regulates morphogenesis of epithelial cells. Our preliminary study suggested a novel function of epimorphin in enhancing survival of intestinal epithelial cells (IEC). Oxidative stress leads to cell injury and death and is suggested to be a key contributor to pathogenesis of inflammatory bowel disease. This study was conducted to determine whether epimorphin protects IEC from oxidative stress. Rat intestinal epithelial cell line IEC-6 was cultured with epimorphin (10 and 20 mug/ml), and the life span of IEC was assessed. The mean life span of IEC-6 cells was prolonged 1.9-fold (P < 0.0006) by treatment with epimorphin. We then examined the epimorphin signaling pathways. Epimorphin phosphorylated epidermal growth factor (EGF) receptor, activated the MEK/extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase and phosphatidylinositol 3 (PI3) kinase/Akt pathways, phosphorylated Bad, and induced Bcl-X(L) and survivin. Hydrogen peroxide (1 mM) induced cell death in 92% of IEC-6 cells, but epimorphin dramatically diminished (88.7%) cell death induced by hydrogen peroxide (P < 0.0001). This protective effect of epimorphin was significantly attenuated by inhibitors of MEK and PI3 kinase (P < 0.0001) or EGF receptor-neutralizing antibody (P = 0.0007). In wound assays, the number of migrated cells in the wound area decreased (72.5%) by treatment with 30 muM hydrogen peroxide, but epimorphin increased the number of migrated cells 3.18-fold (P < 0.0001). These results support a novel function of epimorphin in protecting IEC from oxidative stress. This anti-oxidative function of epimorphin is dramatic and is likely mediated by the activation of EGF receptors and the MEK/extracellular signal-regulated kinase and PI3 kinase/Akt signaling pathways and through the induction of anti-apoptotic factors.
Iizuka
Masahiro
M
Department of Internal Medicine, Akita University School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan. maiizuka@doc.med.akita-u.ac.jp
Sasaki
Kenji
K
Hirai
Yohei
Y
Shindo
Kenichi
K
Konno
Shiho
S
Itou
Hiroaki
H
Ohshima
Shigetoshi
S
Horie
Yasuo
Y
Watanabe
Sumio
S
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D002470:Cell Survival / Q000502:physiology; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000502:physiology*; D007413:Intestinal Mucosa / Q000166:cytology / Q000502:physiology*; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism*; D008562:Membrane Glycoproteins; D018384:Oxidative Stress / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction
D066246:ErbB Receptors; D020930:MAP Kinase Kinase Kinases; D008562:Membrane Glycoproteins; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; C504581:Stx2 protein, rat