title: Leptin induces the generation of procoagulant, tissue factor bearing microparticles by human peripheral blood mononuclear cells.
abstract: BACKGROUND
  Obesity is linked to increased thrombotic risk. Circulating leptin concentration correlates with body mass index. Microparticles are small (.05-1 μm) vesicles shed by activated and apoptotic cells, involved in numerous pathophysiologically relevant phenomena including blood coagulation and thrombosis. We tested the hypothesis that leptin induces the shedding of procoagulant, tissue factor bearing microparticles by human peripheral blood mononuclear cells, and investigated the intracellular mechanisms leading to microparticle release upon incubation with leptin.
  
  
  METHODS
  Peripheral blood mononuclear cells were isolated from healthy donors. Cells were incubated with leptin in the presence or in the absence of a phospholipase C inhibitor, U73122, a calmodulin inhibitor, W-7, and three inhibitors of mitogen activated protein kinases. Microparticle generation was assessed as phosphatidylserine concentration with a prothrombinase assay and by cytofluorimetric analysis. Tissue factor expression on microparticles was measured with a one-stage clotting assay. Intracellular calcium concentration was assessed by a fluorescent probe.
  
  
  RESULTS
  Leptin increased intracellular calcium mobilization and stimulated the generation of tissue factor-bearing MP by peripheral blood mononuclear cells, as assessed by phosphatidylserine quantification, clotting tests and flow-cytometry. U73122, PD98059 (an extracellular signal-regulated kinase1/2 inhibitor), and W-7, significantly inhibited leptin-induced MP release. SB203580 (a p38 inhibitor), and SP600125 (a c-Jun N-terminal kinase inhibitor) had no effect.
  
  
  CONCLUSIONS
  Leptin-induced generation of procoagulant microparticles might represent a link between obesity and atherothrombotic risk. Inhibition of leptin-induced microparticle generation might prove a viable strategy for the reduction of such risk in obese individuals.
authors.affiliation: Laboratorio di Biologia Cellulare Respiratoria, Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, Università di Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Petrini
authors.affiliation: Laboratorio di Biologia Cellulare Respiratoria, Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, Università di Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Neri
authors.affiliation: SSD Analisi ChimicoCliniche ed ImmunoAllergologia, USL 1, Massa e Carrara, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Lombardi
authors.affiliation: Laboratorio di Biologia Cellulare Respiratoria, Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, Università di Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Cordazzo
authors.affiliation: Laboratorio di Biologia Cellulare Respiratoria, Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, Università di Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Balìa
authors.affiliation: Laboratorio di Biologia Cellulare Respiratoria, Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, Università di Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Scalise
authors.affiliation: Laboratorio di Biologia Cellulare Respiratoria, Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, Università di Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Paggiaro
authors.affiliation: Laboratorio di Biologia Cellulare Respiratoria, Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, Università di Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Pedrinelli
authors.affiliation: Laboratorio di Biologia Cellulare Respiratoria, Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, Università di Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy. Electronic address: alessandro.celi@med.unipi.it.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Celi
mesh_terms: D001779:Blood Coagulation Factors / Q000096:biosynthesis*; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000502:physiology; D055252:Cell-Derived Microparticles / Q000187:drug effects* / Q000502:physiology; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D020738:Leptin / Q000494:pharmacology*; D007963:Leukocytes, Mononuclear / Q000378:metabolism*; D013925:Thromboplastin / Q000096:biosynthesis*; D010738:Type C Phospholipases / Q000502:physiology
chemical_list: D001779:Blood Coagulation Factors; D002147:Calmodulin; D020738:Leptin; C045071:leukocyte procoagulant activity; D013925:Thromboplastin; D048049:Extracellular Signal-Regulated MAP Kinases; D010738:Type C Phospholipases; D002118:Calcium
keywords: Leptin; Microparticles; Monocytes; Obesity; Thrombosis; Tissue factor