Procoagulant, tissue factor-bearing microparticles in bronchoalveolar lavage of interstitial lung disease patients: an observational study.

Federica Novelli,Federica Martino,Maria Laura Bartoli,Antonio Palla,Concettina Noce,Fabio Falaschi,Pierluigi Paggiaro,Alessandro Celi,Chiara Armani,Tommaso Neri,Laura Tavanti,Yulia Komarova

doi:10.1371/journal.pone.0095013

Federica Novelli, Federica Martino + Show 10 more

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https://doi.org/10.1371/journal.pone.0095013

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Abstract

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.

Highlights

Interstitial lung diseases (ILDs) are a group of diseases resulting from damage to the lung parenchyma by a combination of inflammation and fibrosis [1]
A large number of ILDs are of unknown cause and are called idiopathic interstitial pneumonias (IIPs); the most frequent form of IIP, called idiopathic pulmonary fibrosis (IPF), is associated with a characteristic histopathologic and/or radiologic pattern called usual interstitial pneumonia (UIP) [2]
Since FX must be converted to FXa in order to participate in the coagulation cascade and to function as a signaling molecule via protease activated receptors (PAR)-1, in an attempt to further clarify the mechanisms of FX activation in the context of PF, we investigated the potential implication of tissue factor (TF)-bearing MP in the pathogenesis of the disease

Summary

Introduction

Interstitial lung diseases (ILDs) are a group of diseases resulting from damage to the lung parenchyma by a combination of inflammation and fibrosis [1]. A large number of ILDs are of unknown cause and are called idiopathic interstitial pneumonias (IIPs); the most frequent form of IIP, called idiopathic pulmonary fibrosis (IPF), is associated with a characteristic histopathologic and/or radiologic pattern called usual interstitial pneumonia (UIP) [2]. According to the classical model, blood coagulation is initiated through the so called extrinsic pathway by the contact of circulating factor (F) VIIa with membrane-associated tissue factor (TF) expressed by non vascular cells ( extrinsic to blood) and exposed upon tissue injury; the FVIIa/TF complex activates FX to FXa, which in turn activates prothrombin to thrombin [3]. One proposed alternate mechanism for the activation of the extrinsic pathway of blood coagulation is represented by circulating TFbearing microparticles (MP) [5,6]. Bastarache and coll. have demonstrated a role for procoagulant, alveolar epithelial cell-derived MP in the pathogenesis of the acute respiratory distress syndrome [12]

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