Abstract
Hypoxia is a common environmental stress that influences signaling pathways and cells function, which through initiating intracellular signaling pathways and hence leading to the activation of the transcription factor hypoxia-inducible factor-1 (HIF-1). In this study, we initially confirm that hypoxia activates HIF-1alpha protein expression in a time-dependent manner with a maximum reached at 60 min in vitro and 4h in vivo in gastric mucosa epithelial cells. The expression of HIF-1alpha is correlated with the activation of HIF-1 DNA binding and transcriptional activity. Hypoxia dose not affect HIF-1alpha mRNA transcription but regulates HIF-1alpha protein expression through a translation-dependent pathway to regulate protein synthesis. Hypoxia could induce phosphorylation of Akt, MAPK (ERK), and target of p70S6K1. PI3K and MAPK inhibitor, LY294002 and U0126 could inhibit hypoxia-induced HIF-1 and VEGF expression. We also investigated the role of reactive oxygen species (ROS) involved in HIF-1 and VEGF expression Exogenous addition of H2O2 was sufficient to activate Akt and ERK, scavengers of H2O2 significantly inhibited hypoxia-induced Akt and ERK, and subsequent HIF-lax expression and transcriptional activity. In conclusion, our data suggested that hypoxia- PI3K signaling through Akt and ERK kinases regulated ROS-dependent, hypoxia- induced HIF-1 activation and VEGF expression in gastric mucosa epithelial cells.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Cell Hypoxia / drug effects
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Cell Line, Transformed
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Epithelial Cells / metabolism*
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Epithelial Cells / pathology
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Gastric Mucosa / metabolism*
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Gastric Mucosa / pathology
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Gene Expression Regulation / drug effects
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Hydrogen Peroxide / pharmacology
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Hypoxia / metabolism*
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Hypoxia / pathology
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Hypoxia-Inducible Factor 1, alpha Subunit / biosynthesis*
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MAP Kinase Signaling System / drug effects
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Mice
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Mitogen-Activated Protein Kinase 1 / antagonists & inhibitors
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Mitogen-Activated Protein Kinase 1 / metabolism*
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Mitogen-Activated Protein Kinase 3 / antagonists & inhibitors
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Mitogen-Activated Protein Kinase 3 / metabolism*
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Oxidants / pharmacology
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Phosphatidylinositol 3-Kinases / metabolism*
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Phosphoinositide-3 Kinase Inhibitors
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Protein Biosynthesis / drug effects
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Protein Kinase Inhibitors / pharmacology
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Proto-Oncogene Proteins c-akt / antagonists & inhibitors
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Proto-Oncogene Proteins c-akt / metabolism*
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Ribosomal Protein S6 Kinases, 70-kDa / antagonists & inhibitors
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Ribosomal Protein S6 Kinases, 70-kDa / metabolism
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Transcription, Genetic / drug effects
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Vascular Endothelial Growth Factor A / biosynthesis*
Substances
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Hif1a protein, mouse
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Hypoxia-Inducible Factor 1, alpha Subunit
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Oxidants
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Phosphoinositide-3 Kinase Inhibitors
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Protein Kinase Inhibitors
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Vascular Endothelial Growth Factor A
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vascular endothelial growth factor A, mouse
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Hydrogen Peroxide
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Proto-Oncogene Proteins c-akt
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Ribosomal Protein S6 Kinases, 70-kDa
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3