title: Signal transduction of MEK/ERK and PI3K/Akt activation by hypoxia/reoxygenation in renal epithelial cells.
abstract: The extracellular signal-regulated kinase (ERK) and Akt have been reported to be activated by ischemia/reperfusion in vivo. However, the signaling pathways involved in activation of these kinases and their potential roles were not fully understood in the postischemic kidney. In the present study, we observed that these kinases are activated by hypoxia/reoxygenation (H/R), an in vitro model of ischemia/reperfusion, in opossum kidney (OK) cells and elucidated the signaling pathways of these kinases. ERK and Akt were transiently activated during the early phase of reoxygenation following 4-12h of hypoxia. The ERK activation was inhibited by U0126, a specific inhibitor of ERK upstream MAPK/ERK kinase (MEK), but not by LY294002, a specific inhibitor of phosphoinositide 3-kinase (PI3K), whereas Akt activation was blocked by LY294002, but not by U0126. Inhibitors of epidermal growth factor receptor (EGFR) (AG 1478), Ras and Raf, as well as antioxidants inhibited activation of ERK and Akt, while the Src inhibitor PP2 had no effect. PI3K/Akt activation was shown to be associated with up-regulation of X chromosome-linked inhibitor of apoptosis (XIAP), but not survivin. Reoxygenation following 4-h hypoxia-stimulated cell proliferation, which was dependent on ERK and Akt activation and was also inhibited by antioxidants and AG 1478. Taken together, these results suggest that H/R induces activation of MEK/ERK and PI3K/Akt/XIAP survival signaling pathways through the reactive oxygen species-dependent EGFR/Ras/Raf cascade. Activation of these kinases may be involved in the repair process during ischemia/reperfusion.
authors.affiliation: Department of Physiology, Medical Research Institute, MRC for Ischemic Tissue Regeneration, College of Medicine, Pusan National University, Pusan 602-739, Republic of Korea.
authors.forename: Dae Sik
authors.initials: DS
authors.lastname: Kwon
authors.forename: Chae Hwa
authors.initials: CH
authors.lastname: Kwon
authors.forename: Jae Ho
authors.initials: JH
authors.lastname: Kim
authors.forename: Jae Suk
authors.initials: JS
authors.lastname: Woo
authors.forename: Jin Sup
authors.initials: JS
authors.lastname: Jung
authors.forename: Yong Keun
authors.initials: YK
authors.lastname: Kim
mesh_terms: D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D015687:Cell Hypoxia; D049109:Cell Proliferation; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000201:enzymology*; D066246:ErbB Receptors / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D007668:Kidney / Q000166:cytology / Q000201:enzymology*; D020935:MAP Kinase Signaling System; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D009570:Nitriles / Q000494:pharmacology; D009893:Opossums; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015427:Reperfusion Injury / Q000201:enzymology; D015398:Signal Transduction; D014162:Transfection; D018631:ras Proteins / Q000378:metabolism
chemical_list: D002070:Butadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D009570:Nitriles; D017382:Reactive Oxygen Species; C113580:U 0126; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D018631:ras Proteins