Procoagulant, tissue factor-bearing microparticles in bronchoalveolar lavage of interstitial lung disease patients: an observational study.
Coagulation factor Xa appears involved in the pathogenesis of pulmonary fibrosis. Through its interaction with protease activated receptor-1, this protease signals myofibroblast differentiation in lung fibroblasts. Although fibrogenic stimuli induce factor X synthesis by alveolar cells, the mechanisms of local posttranslational factor X activation are not fully understood. Cell-derived microparticles are submicron vesicles involved in different physiological processes, including blood coagulation; they potentially activate factor X due to the exposure on their outer membrane of both phosphatidylserine and tissue factor. We postulated a role for procoagulant microparticles in the pathogenesis of interstitial lung diseases. Nineteen patients with interstitial lung diseases and 11 controls were studied. All subjects underwent bronchoalveolar lavage; interstitial lung disease patients also underwent pulmonary function tests and high resolution CT scan. Microparticles were enumerated in the bronchoalveolar lavage fluid with a solid-phase assay based on thrombin generation. Microparticles were also tested for tissue factor activity. In vitro shedding of microparticles upon incubation with H₂O₂ was assessed in the human alveolar cell line, A549 and in normal bronchial epithelial cells. Tissue factor synthesis was quantitated by real-time PCR. Total microparticle number and microparticle-associated tissue factor activity were increased in interstitial lung disease patients compared to controls (84±8 vs. 39±3 nM phosphatidylserine; 293±37 vs. 105±21 arbitrary units of tissue factor activity; mean±SEM; p<.05 for both comparisons). Microparticle-bound tissue factor activity was inversely correlated with lung function as assessed by both diffusion capacity and forced vital capacity (r² = .27 and .31, respectively; p<.05 for both correlations). Exposure of lung epithelial cells to H₂O₂ caused an increase in microparticle-bound tissue factor without affecting tissue factor mRNA. Procoagulant microparticles are increased in interstitial lung diseases and correlate with functional impairment. These structures might contribute to the activation of factor X and to the factor Xa-mediated fibrotic response in lung injury.
Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, University of Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
Federica
F
Novelli
Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, University of Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
Tommaso
T
Neri
Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, University of Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
Laura
L
Tavanti
Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, University of Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
Chiara
C
Armani
Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, University of Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
Concettina
C
Noce
U.O. Radiodiagnostica 2 SSN, Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
Fabio
F
Falaschi
Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, University of Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
Maria Laura
ML
Bartoli
Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, University of Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
Federica
F
Martino
Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, University of Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
Antonio
A
Palla
Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, University of Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
Alessandro
A
Celi
Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, University of Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
Pierluigi
P
Paggiaro
D000368:Aged; D018893:Bronchoalveolar Lavage; D002460:Cell Line; D055252:Cell-Derived Microparticles / Q000378:metabolism*; D015951:Factor Xa / Q000378:metabolism*; D005260:Female; D006801:Humans; D017563:Lung Diseases, Interstitial / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D011658:Pulmonary Fibrosis / Q000378:metabolism / Q000473:pathology; D013925:Thromboplastin / Q000378:metabolism*
D013925:Thromboplastin; D015951:Factor Xa