Hypoxia-inducible angiopoietin-2 expression is mimicked by iodonium compounds and occurs in the rat brain and skin in response to systemic hypoxia and tissue ischemia

Am J Pathol. 2000 Jun;156(6):2077-89. doi: 10.1016/S0002-9440(10)65079-1.


Angiopoietins are ligands for the endothelial cell tyrosine kinase receptor Tie-2. Ang-1, the major physiological activator of Tie-2, promotes blood vessel maturation and stability. Ang-2 counteracts this effect by competitively inhibiting the binding of Ang-1 to Tie-2. Using a combined RNase protection/semiquantitative reverse transcriptase-polymerase chain reaction approach, we demonstrate that hypoxia up-regulates Ang-2 mRNA levels by up to 3.3-fold in two human endothelial cell lines. In bovine microvascular endothelial (BME) cells, the flavoprotein oxidoreductase inhibitor diphenylene iodonium (DPI) and the related compound iodonium diphenyl mimic induction of Ang-2 but not vascular endothelial growth factor (VEGF) by hypoxia; in combination with hypoxia, DPI further increases Ang-2 expression but has no effect on the induction of VEGF by hypoxia. Neither Ang-2 or VEGF was increased by cyanide or rotenone, suggesting that failure in mitochondrial electron transport is not involved in the oxygen-sensing system that controls their expression. In ischemic rat dorsal skin flaps or in the brain of rats maintained for 12 hours under conditions of hypoxia, Ang-2 mRNA was up-regulated 7.5- or 17.6- fold, respectively. VEGF was concomitantly increased, whereas expression of Ang-1, Tie-2, and the related receptor Tie-1 was unaltered. In situ hybridization localized Ang-2 mRNA to endothelial cells in hypoxic skin. These findings 1) show that up-regulation of Ang-2 by hypoxia occurs widely in endothelial cells in vitro and in vivo; 2) suggest that induction of Ang-2, but not VEGF, by hypoxia in BME cells is controlled by a flavoprotein oxidoreductase that is sensitive to iodonium compounds; and 3) point to Ang-2 and VEGF as independently regulated and selective effectors of hypoxia-induced vascular sprouting.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angiopoietin-2
  • Animals
  • Biphenyl Compounds / pharmacology
  • Brain / metabolism*
  • Cattle
  • Cell Line
  • Endothelial Growth Factors / metabolism
  • Humans
  • Hypoxia / metabolism*
  • Ischemia / metabolism*
  • Lymphokines / metabolism
  • Male
  • Onium Compounds / pharmacology
  • Proteins / metabolism*
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Rats, Wistar
  • Skin / blood supply
  • Skin / metabolism*
  • Up-Regulation
  • Vascular Endothelial Growth Factor A
  • Vascular Endothelial Growth Factors


  • Angiopoietin-2
  • Biphenyl Compounds
  • Endothelial Growth Factors
  • Lymphokines
  • Onium Compounds
  • Proteins
  • RNA, Messenger
  • Vascular Endothelial Growth Factor A
  • Vascular Endothelial Growth Factors
  • diphenyliodonium
  • diphenyleneiodonium