title: Activated platelets stimulate tissue factor expression in smooth muscle cells.
abstract: Tissue factor (TF)-induced activation of the coagulation plays a key role in the pathophysiology of acute coronary syndromes. Because TF represents the initial trigger of the coagulation cascade, its expression in the arterial wall is tightly regulated.
  
  
  OBJECTIVE
  To determine whether and which soluble mediators released during platelet activation may upregulate TF expression in smooth muscle cells (SMCs).
  
  
  RESULTS
  Rabbit SMCs were challenged with collagen-activated platelets and their effects on TF mRNA transcription and protein expression were evaluated at different time points (30 min, 1, 2, 4, 8, 12 and 24 h) by RT-PCR, immunofluorescence and a two-stage colorimetric assay. A progressive increase in TF mRNA, peaking at 2 h, was evident in SMCs stimulated with activated platelets with respect to baseline. The increase in TF mRNA expression was associated with a parallel increase in TF protein, as demonstrated by immunofluorescence and by colorimetric assay. In a different set of experiments, selected platelet-derived soluble mediators were shown to induce TF mRNA expression.
  
  
  CONCLUSIONS
  Activated platelets upregulate TF, via release of several soluble mediators, in a cell population widely expressed in the vessel wall and in atherosclerotic plaques, such as SMCs. This phenomenon might play an important role in sustaining thrombus formation in vivo.
authors.affiliation: Division of Cardiology, University of Naples Federico II, Naples, Italy.
authors.forename: Plinio
authors.initials: P
authors.lastname: Cirillo
authors.forename: Paolo
authors.initials: P
authors.lastname: Golino
authors.forename: Paolo
authors.initials: P
authors.lastname: Calabrò
authors.forename: Massimo
authors.initials: M
authors.lastname: Ragni
authors.forename: Lavinia
authors.initials: L
authors.lastname: Forte
authors.forename: Orlando
authors.initials: O
authors.lastname: Piro
authors.forename: Salvatore
authors.initials: S
authors.lastname: De Rosa
authors.forename: Mario
authors.initials: M
authors.lastname: Pacileo
authors.forename: Massimo
authors.initials: M
authors.lastname: Chiariello
mesh_terms: D000818:Animals; D001011:Aorta / Q000502:physiology; D001792:Blood Platelets / Q000502:physiology*; D002478:Cells, Cultured; D006801:Humans; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000098:blood supply* / Q000502:physiology*; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D015539:Platelet Activation / Q000502:physiology*; D011817:Rabbits; D013925:Thromboplastin / Q000378:metabolism*
chemical_list: D013925:Thromboplastin