Abstract
We investigated the role of Ca2+-independent phospholipase A2 (iPLA2) as well as cytosolic phospholipase A2 (cPLA2) in hypoxia-inducible factor-1 (HIF-1)-dependent gene expression. An inhibitor of both iPLA2 and cPLA2, methyl arachidonyl fluorophosphonate (MAFP), prevented hypoxia-induced erythropoietin mRNA expression without affecting HIF-1alpha accumulation in Hep3B cells. The DNA-binding of HIF-1alpha was suppressed by MAFP as confirmed by luciferase reporter gene assays with the hypoxia response element. Translocation of HIF-1alpha to the nucleus assessed by its presence in the nuclear extracts of cells exposed to hypoxia, was diminished by MAFP. However, hypoxia-dependent gene expression was not affected in mesangial cells obtained from cPLA2alpha null mice. Furthermore, a specific iPLA2 inhibitor, bromoenol lactone, suppressed erythropoietin mRNA expression and HIF-1alpha translocation to the nucleus under hypoxic conditions. Thus, iPLA2, but not cPLA2alpha, may play an important role in regulating the transport of HIF-1alpha to the nucleus.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Active Transport, Cell Nucleus / drug effects
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Animals
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Arachidonic Acids / pharmacology
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Calcium / metabolism*
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Cell Hypoxia / physiology
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Cell Line, Tumor
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Cell Nucleus / drug effects
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Cell Nucleus / metabolism*
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Cells, Cultured
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Cytosol / enzymology
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Dose-Response Relationship, Drug
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Erythropoietin / genetics
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Erythropoietin / metabolism
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Gene Expression / genetics
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Humans
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Hypoxia-Inducible Factor 1, alpha Subunit / genetics
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Hypoxia-Inducible Factor 1, alpha Subunit / metabolism*
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Immunoblotting
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Luciferases / genetics
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Luciferases / metabolism
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Mesangial Cells / cytology
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Mesangial Cells / metabolism
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Mice
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Mice, Inbred C57BL
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Mice, Knockout
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Organophosphonates / pharmacology
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Phospholipases A / genetics
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Phospholipases A / metabolism*
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Phospholipases A2
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RNA, Messenger / genetics
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RNA, Messenger / metabolism
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Reverse Transcriptase Polymerase Chain Reaction
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Vascular Endothelial Growth Factor A / genetics
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Vascular Endothelial Growth Factor A / metabolism
Substances
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Arachidonic Acids
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Hypoxia-Inducible Factor 1, alpha Subunit
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Organophosphonates
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RNA, Messenger
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Recombinant Fusion Proteins
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Vascular Endothelial Growth Factor A
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methyl arachidonylfluorophosphonate
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Erythropoietin
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Luciferases
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Phospholipases A
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Phospholipases A2
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Calcium