title: Effects of peroxisome proliferator-activated receptor-γ agonists on the generation of microparticles by monocytes/macrophages.
abstract: OBJECTIVE
  Microparticles are membrane vesicles shed by cells upon activation and/or apoptosis. Microparticles are involved in several processes, including blood coagulation and thrombosis. In addition to their role in the regulation of lipid metabolism, peroxisome proliferator-activated receptor-γ (PPAR-γ) agonists exert other effects, both dependent on and independent of PPAR-γ activation. Some PPAR-γ agonists have been linked to an increased risk of thrombotic diseases. We aimed to investigate the potential role of PPAR-γ agonists on the generation of procoagulant microparticles by human monocytes/macrophages.
  
  
  RESULTS
  Monocytes/macrophages were isolated from the buffy coats of normal donors. Cells were incubated with three structurally unrelated PPAR-γ agonists, namely, rosiglitazone, pioglitazone, and 15-deoxy-Δ(12,14)-prostaglandin J(2). Microparticle generation was assessed as phosphatidylserine concentration by a prothrombinase assay, after capturing the microparticles onto annexin V-coated wells. Intracellular calcium concentration was assessed by a fluorescent probe. Extracellular signal-regulated kinase (ERK) phosphorylation was assessed by western blot. Tissue factor expression on microparticles was measured with a one-stage clotting assay. Rosiglitazone and 15-deoxy-Δ(12,14)-prostaglandin J(2), but not pioglitazone, caused a dose-dependent, significant increase in intracellular calcium mobilization and tissue factor-bearing microparticle generation. EGTA inhibited microparticle generation. The specific PPAR-γ inhibitor, GW9662, also inhibited microparticle generation.  Finally, rosiglitazone and 15-deoxy-Δ(12,14)-prostaglandin J(2) caused phosphorylation of ERK; inhibition of ERK by PD98059 inhibited microparticle generation.
  
  
  CONCLUSIONS
  The PPAR-γ agonists rosiglitazone and 15-deoxy-Δ(12,14)-prostaglandin J(2), but not pioglitazone, caused an increase in procoagulant, tissue factor-bearing microparticle generation by human monocytes/macrophages. The effect was dependent on ERK phosphorylation and partly mediated through intracellular calcium mobilization; however, direct activation of the PPAR-γ ligand was also involved.
authors.affiliation: Laboratory of Respiratory Cell Biology, Cardiac, Thoracic and Vascular Department,  University of Pisa, Via Paradisa, 2, 56124 Pisa,  Italy.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Neri
authors.forename: Cinzia
authors.initials: C
authors.lastname: Cordazzo
authors.forename: Yuri
authors.initials: Y
authors.lastname: Carmazzi
authors.forename: Silvia
authors.initials: S
authors.lastname: Petrini
authors.forename: Cristina
authors.initials: C
authors.lastname: Balìa
authors.forename: Fabio
authors.initials: F
authors.lastname: Stefanelli
authors.forename: Angela
authors.initials: A
authors.lastname: Amoruso
authors.forename: Sandra
authors.initials: S
authors.lastname: Brunelleschi
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Breschi
authors.forename: Roberto
authors.initials: R
authors.lastname: Pedrinelli
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Paggiaro
authors.forename: Alessandro
authors.initials: A
authors.lastname: Celi
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D055252:Cell-Derived Microparticles / Q000187:drug effects* / Q000378:metabolism; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D008264:Macrophages / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D047495:PPAR gamma / Q000819:agonists* / Q000378:metabolism*; D000077205:Pioglitazone; D000077154:Rosiglitazone; D015398:Signal Transduction / Q000502:physiology; D045162:Thiazolidinediones / Q000494:pharmacology
chemical_list: D047495:PPAR gamma; D045162:Thiazolidinediones; D000077154:Rosiglitazone; D048049:Extracellular Signal-Regulated MAP Kinases; D020928:Mitogen-Activated Protein Kinases; D000077205:Pioglitazone