Molecular and Cellular Biochemistry

, Volume 312, Issue 1–2, pp 121–129 | Cite as

Expression of Nrf2 and its downstream gene targets in hibernating 13-lined ground squirrels, Spermophilus tridecemlineatus

  • Pier Jr Morin
  • Zhouli Ni
  • David C. McMullen
  • Kenneth B. Storey


Mammalian hibernation is associated with wide variation in heart rate, blood flow, and oxygen delivery to tissues and is used as a model of natural ischemia/reperfusion. In non-hibernators, ischemia/reperfusion is typically associated with oxidative stress but hibernators seem to deal with potential oxidative damage by enhancing antioxidant defenses in an anticipatory manner. The present study assesses the role of the Nrf2 transcription factor in the regulation of antioxidant defenses during hibernation. Nrf2 mRNA and protein expression were enhanced in selected organs of 13-lined ground squirrels, Spermophilus tridecemlineatus during hibernation. Furthermore, Nrf2 protein in heart was elevated by 1.4–1.5 fold at multiple stages over a torpor–arousal bout including during entry, long term torpor, and early arousal. Levels returned to euthermic values when squirrels were fully aroused in interbout. Protein levels of selected downstream target genes under Nrf2 control were also measured via immunoblotting over the torpor–arousal cycle in heart. Cu/Zn superoxide dismutase and aflatoxin aldehyde reductase levels increased significantly during entry into torpor and then gradually declined falling to control levels or below in fully aroused animals. Heme oxygenase-1 also showed the same trend. This suggests a role for Nrf2 in regulating the antioxidant defenses needed for hibernation success. Heart nrf2 was amplified by PCR and sequenced. The deduced amino acid sequence showed high identity with the sequence from other mammals but with selected unique substitutions (e.g., proline residues at positions 111 and 230) that might be important for conformational stability of the protein at near 0°C body temperatures in the torpid state.


Oxidative stress Antioxidant defense Ischemia resistance Torpor–arousal cycle NF-E2-related factor-2 Superoxide dismutase Heme oxygenase Aflatoxin aldehyde reductase Heart 



We thank Dr. J.M. Hallenbeck, National Institute of Neurological Disorders and Stroke, for supplying us with samples of ground squirrel tissues and Dr. John D. Hayes, University of Dundee, for providing the AFAR1 antibody. Thanks also to J.M. Storey for editorial review of the manuscript. Supported by a discovery grant from the Natural Sciences and Engineering Research Council of Canada; KBS holds the Canada Research Chair in Molecular Physiology.


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Copyright information

© Springer Science+Business Media, LLC. 2008

Authors and Affiliations

  • Pier Jr Morin
    • 1
  • Zhouli Ni
    • 1
  • David C. McMullen
    • 1
  • Kenneth B. Storey
    • 1
  1. 1.Institute of Biochemistry and Departments of Chemistry and BiologyCarleton UniversityOttawaCanada

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