Neuroglobin regulates hypoxic response of neuronal cells through Hif-1α- and Nrf2-mediated mechanism

J Cereb Blood Flow Metab. 2012 Jun;32(6):1046-60. doi: 10.1038/jcbfm.2012.21. Epub 2012 Apr 4.

Abstract

Oxygen sensing in hypoxic neurons has been classically attributed to cytochrome c oxidase and prolyl-4-hydroxylases and involves stabilization of transcription factors, hypoxia-inducible factor-1α (Hif-1α) and nuclear factor erythroid 2-related factor 2 (Nrf2) that mediate survival responses. On the contrary, release of cytochrome c into the cytosol during hypoxic stress triggers apoptosis in neuronal cells. We, here advocate that the redox state of neuroglobin (Ngb) could regulate both Hif-1α and Nrf2 stabilization and cytochrome c release during hypoxia. The hippocampal regions showing higher expression of Ngb were less susceptible to global hypoxia-mediated neurodegeneration. During normoxia, Ngb maintained cytochrome c in the reduced state and prevented its release from mitochondria by using cellular antioxidants. Greater turnover of oxidized cytochrome c and increased utilization of cellular antioxidants during acute hypoxia altered cellular redox status and stabilized Hif-1α and Nrf2 through Ngb-mediated mechanism. Chronic hypoxia, however, resulted in oxidation and degradation of Ngb, accumulation of ferric ions and release of cytochrome c that triggered apoptosis. Administration of N-acetyl-cysteine during hypoxic conditions improved neuronal survival by preventing Ngb oxidation and degradation. Taken together, these results establish a role for Ngb in regulating both the survival and apoptotic mechanisms associated with hypoxia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcysteine / pharmacology
  • Animals
  • Cell Hypoxia
  • Cell Survival / drug effects
  • Cytochromes c / metabolism
  • Free Radical Scavengers / pharmacology
  • Globins / metabolism*
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism*
  • Male
  • NF-E2-Related Factor 2 / metabolism*
  • Nerve Tissue Proteins / metabolism*
  • Neurodegenerative Diseases / metabolism
  • Neuroglobin
  • Neurons / metabolism*
  • Oxidation-Reduction / drug effects
  • Proteolysis*
  • Rats, Sprague-Dawley

Substances

  • Free Radical Scavengers
  • Hif1a protein, rat
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • NF-E2-Related Factor 2
  • Nerve Tissue Proteins
  • Neuroglobin
  • Nfe2l2 protein, rat
  • Globins
  • Cytochromes c
  • Acetylcysteine