In vivo imaging visualizes discoid platelet aggregations without endothelium disruption and implicates contribution of inflammatory cytokine and integrin signaling

Blood. 2012 Feb 23;119(8):e45-56. doi: 10.1182/blood-2011-09-381400. Epub 2011 Nov 16.

Abstract

The mechanism by which thrombotic vessel occlusion occurs independently of plaque development or endothelial cell (EC) disruption remains unclear, largely because of an inability to visualize the formation of thrombus, especially at the single-platelet level in real time. Here we demonstrate that rapidly developing thrombi composed of discoid platelets can be induced in the mesenteric capillaries, arterioles, and large-sized arteries of living mice, enabling characterization of the kinetics of thrombosis initiation and the multicellular interrelationships during thrombus development. Platelet aggregation without EC disruption was triggered by reactive oxygen species (ROS) photochemically induced by moderate power laser irradiation. The inflammatory cytokines TNF-α and IL-1 could be key components of the EC response, acting through regulation of VWF mobilization to the cell surface. Thrombus formation was then initiated by the binding of platelet GPIbα to endothelial VWF in our model, and this effect was inhibited by the ROS scavenger N-acetylcysteine. Actin linker talin-dependent activation of alphaIIb-beta3 integrin or Rac1 in platelets was required for late-phase thrombus stability. Our novel imaging technology illustrates the molecular mechanism underlying inflammation-based thrombus formation by discoid platelets on undisrupted ECs and suggests control of ROS could be a useful therapeutic target for the prevention of thrombotic diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcysteine / pharmacology
  • Animals
  • Blood Platelets / metabolism
  • Cells, Cultured
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / metabolism*
  • Flow Cytometry
  • Human Umbilical Vein Endothelial Cells / metabolism
  • Humans
  • Interleukin-1 / genetics
  • Interleukin-1 / metabolism*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mice, Transgenic
  • Microscopy, Confocal / methods
  • Platelet Aggregation*
  • Platelet Glycoprotein GPIIb-IIIa Complex / genetics
  • Platelet Glycoprotein GPIIb-IIIa Complex / metabolism*
  • Platelet Glycoprotein GPIb-IX Complex / metabolism
  • Protein Binding / drug effects
  • Reactive Oxygen Species / metabolism
  • Receptors, Tumor Necrosis Factor / genetics
  • Receptors, Tumor Necrosis Factor / metabolism
  • Signal Transduction*
  • Thrombosis / genetics
  • Thrombosis / metabolism
  • Tumor Necrosis Factor-alpha / genetics
  • Tumor Necrosis Factor-alpha / metabolism*
  • rac1 GTP-Binding Protein / genetics
  • rac1 GTP-Binding Protein / metabolism
  • von Willebrand Factor / metabolism

Substances

  • Interleukin-1
  • Platelet Glycoprotein GPIIb-IIIa Complex
  • Platelet Glycoprotein GPIb-IX Complex
  • Reactive Oxygen Species
  • Receptors, Tumor Necrosis Factor
  • Tumor Necrosis Factor-alpha
  • von Willebrand Factor
  • rac1 GTP-Binding Protein
  • Acetylcysteine