Hypoxic preconditioning and tolerance via hypoxia inducible factor (HIF) 1α-linked induction of P450 2C11 epoxygenase in astrocytes

Mingyue Liu, Nabil J. Alkayed

Research output: Contribution to journalArticle

76 Scopus citations

Abstract

The brain's adaptive response to ischemic preconditioning (IPC) is mediated in part via hypoxia inducible factor (HIF)-responsive genes. We previously showed that IPC induces cytochrome P450 2C11 expression in the brain, associated with protection from stroke. Cytochrome P450 2C11 is an arachidonic acid (AA) epoxygenase expressed in astrocytes, which metabolizes AA to epoxyeico-satrienoic acids (EETs). We tested the hypotheses that hypoxic preconditioning (HPC) induces 2C11 expression in astrocytes via HIF-1α, and that the P450 epoxygenase pathway contributes to enhanced astrocyte tolerance to ischemia-like injury induced by oxygen-glucose deprivation (OGD). Primary cultured astrocytes were incubated under normoxic or hypoxic conditions for 1, 3, 6, 24, or 48 h, and protein levels of P450 2C11 and HIF-1α were measured by Western blotting. Additionally, 2C11 mRNA was measured by Northern blotting, and binding of HIF-1α to 2C11 promoter was evaluated using electrophoretic mobility shift assay (EMSA) with 2C11 promoter DNA containing putative HIF-binding sites. Levels of 2C11 mRNA and protein were significantly increased starting at 3 and 6 h of hypoxia, respectively. The increase in 2C11 expression was preceded by an increase in HIF-1α protein at 1 h of hypoxia, and EMSA showed a specific and direct interaction between 2C11 promoter DNA and HIF-1α in nuclear extracts from astrocytes. HPC and EETs reduced astrocyte cell death, and P450 epoxygenase inhibition prevented protection by HPC. We conclude that HPC induces tolerance in astrocytes, at least in part, via HIF-1α-linked upregulation of P450 2C11.

Original languageEnglish (US)
Pages (from-to)939-948
Number of pages10
JournalJournal of Cerebral Blood Flow and Metabolism
Volume25
Issue number8
DOIs
StatePublished - Aug 1 2005

Keywords

  • Arachidonic acid
  • Astrocytes
  • EET
  • Hypoxia preconditioning (HPC)
  • Hypoxia-inducible factor (HIF)
  • Oxygen glucose deprivation (OGD)
  • P450 2C11 epoxygenase
  • Tolerance

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology
  • Cardiology and Cardiovascular Medicine

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