Angiopoietin-2 is critical for cytokine-induced vascular leakage

PLoS One. 2013 Aug 5;8(8):e70459. doi: 10.1371/journal.pone.0070459. Print 2013.

Abstract

Genetic experiments (loss-of-function and gain-of-function) have established the role of Angiopoietin/Tie ligand/receptor tyrosine kinase system as a regulator of vessel maturation and quiescence. Angiopoietin-2 (Ang-2) acts on Tie2-expressing resting endothelial cells as an antagonistic ligand to negatively interfere with the vessel stabilizing effects of constitutive Ang-1/Tie-2 signaling. Ang-2 thereby controls the vascular response to inflammation-inducing as well as angiogenesis-inducing cytokines. This study was aimed at assessing the role of Ang-2 as an autocrine (i.e. endothelial-derived) regulator of rapid vascular responses (within minutes) caused by permeability-inducing agents. Employing two independent in vivo assays to quantitatively assess vascular leakage (tracheal microsphere assay, 1-5 min and Miles assay, 20 min), the immediate vascular response to histamine, bradykinin and VEGF was analyzed in Ang-2-deficient (Ang-2(-/-)) mice. In comparison to the wild type control mice, the Ang2(-/-) mice demonstrated a significantly attenuated response. The Ang-2(-/-) phenotype was rescued by systemic administration (paracrine) of an adenovirus encoding Ang-2. Furthermore, cytokine-induced intracellular calcium influx was impaired in Ang-2(-/-) endothelioma cells, consistent with reduced phospholipase activation in vivo. Additionally, recombinant human Ang-2 (rhAng-2) alone was unable to induce vascular leakage. In summary, we report here in a definite genetic setting that Ang-2 is critical for multiple vascular permeability-inducing cytokines.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angiopoietin-2 / genetics
  • Angiopoietin-2 / metabolism*
  • Animals
  • Blotting, Western
  • Bradykinin / genetics
  • Bradykinin / metabolism
  • Capillary Permeability / drug effects
  • Capillary Permeability / genetics
  • Cells, Cultured
  • Cytokines / pharmacology*
  • Female
  • Human Umbilical Vein Endothelial Cells
  • Lung / cytology
  • Lung / metabolism
  • Mice
  • Mice, Knockout
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Vascular Endothelial Growth Factor A / genetics
  • Vascular Endothelial Growth Factor A / metabolism

Substances

  • Angiopoietin-2
  • Cytokines
  • Recombinant Fusion Proteins
  • Vascular Endothelial Growth Factor A
  • Bradykinin

Grant support

This study was supported by a grant from the German Research Council (DFG, SFB-TR23 [Vascular Differentiation and Remodeling], project A3). The funding agency had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.