Angiopoietins: a link between angiogenesis and inflammation

Trends Immunol. 2006 Dec;27(12):552-8. doi: 10.1016/ Epub 2006 Oct 12.


The angiopoietin (Ang)-Tie ligand-receptor system has a key regulatory role in regulating vascular integrity and quiescence. Besides its role in angiogenesis, it is an important regulator in numerous diseases including inflammation. Ang-1-mediated Tie2 activation is required to maintain the quiescent resting state of the endothelium. Agonistic Ang-1 functions are antagonized by Ang-2, which is believed to inhibit Ang-1-Tie2 signaling. Ang-2 destabilizes the quiescent endothelium and primes it to respond to exogenous stimuli, thereby facilitating the activities of inflammatory (tumor necrosis factor and interleukin-1) and angiogenic (vascular endothelial growth factor) cytokines. Intriguingly, Ang-2 is expressed weakly by the resting endothelium but becomes strongly upregulated following endothelial activation. Moreover, endothelial cells store Ang-2 in Weibel-Palade bodies from where it can be made available quickly following stimulation, suggesting a role of Ang-2 in controlling rapid vascular adaptive processes. This suggests that Ang-2 is the dynamic regulator of the Ang-Tie2 axis, thereby functioning as a built-in switch controlling the transition of the resting quiescent endothelium towards the activated responsive endothelium.

Publication types

  • Review

MeSH terms

  • Angiopoietin-2 / physiology
  • Angiopoietins / genetics
  • Angiopoietins / metabolism*
  • Angiopoietins / physiology
  • Animals
  • Endothelium, Vascular / metabolism
  • Endothelium, Vascular / physiology*
  • Homeostasis
  • Humans
  • Inflammation / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Models, Biological
  • Neovascularization, Physiologic*
  • Receptors, TIE / metabolism


  • Angiopoietin-2
  • Angiopoietins
  • Receptors, TIE