Blood Journal
Leading the way in experimental and clinical research in hematology

Vitamin C is dispensable for oxygen sensing in vivo

  1. Katarzyna J. Nytko1,
  2. Nobuyo Maeda2,
  3. Philipp Schläfli1,
  4. Patrick Spielmann1,
  5. Roland H. Wenger1, and
  6. Daniel P. Stiehl1
  1. 1Institute of Physiology and Zürich Center for Integrative Human Physiology, University of Zürich, Zürich, Switzerland; and
  2. 2Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC

Abstract

Prolyl-4-hydroxylation is necessary for proper structural assembly of collagens and oxygen-dependent protein stability of hypoxia-inducible transcription factors (HIFs). In vitro function of HIF prolyl-4-hydroxylase domain (PHD) enzymes requires oxygen and 2-oxoglutarate as cosubstrates with iron(II) and vitamin C serving as cofactors. Although vitamin C deficiency is known to cause the collagen-disassembly disease scurvy, it is unclear whether cellular oxygen sensing is similarly affected. Here, we report that vitamin C–deprived Gulo−/− knockout mice show normal HIF-dependent gene expression. The systemic response of Gulo−/− animals to inspiratory hypoxia, as measured by plasma erythropoietin levels, was similar to that of animals supplemented with vitamin C. Hypoxic HIF induction was also essentially normal under serum- and vitamin C–free cell-culture conditions, suggesting that vitamin C is not required for oxygen sensing in vivo. Glutathione was found to fully substitute for vitamin C requirement of all 3 PHD isoforms in vitro. Consistently, glutathione also reduced HIF-1α protein levels, transactivation activity, and endogenous target gene expression in cells exposed to CoCl2. A Cys201Ser mutation in PHD2 increased basal hydroxylation rates and conferred resistance to oxidative damage in vitro, suggesting that this surface-accessible PHD2 cysteine residue is a target of antioxidative protection by vitamin C and glutathione.

  • Submitted September 15, 2010.
  • Accepted February 2, 2011.
View Full Text