title: Neutrophil extracellular traps promote differentiation and function of fibroblasts.
abstract: Neutrophil activation by inflammatory stimuli and the release of extracellular chromatin structures (neutrophil extracellular traps - NETs) have been implicated in inflammatory disorders. Herein, we demonstrate that NETs released by neutrophils treated either with fibrosis-related agents, such as cigarette smoke, magnesium silicate, bleomycin, or with generic NET inducers, such as phorbol 12-myristate 13-acetate, induced activation of lung fibroblasts (LFs) and differentiation into myofibroblast (MF) phenotype. Interestingly, the aforementioned agents or IL-17 (a primary initiator of inflammation/fibrosis) had no direct effect on LF activation and differentiation. MFs treated with NETs demonstrated increased connective tissue growth factor expression, collagen production, and proliferation/migration. These fibrotic effects were significantly decreased after degradation of NETs with DNase1, heparin or myeloperoxidase inhibitor, indicating the key role of NET-derived components in LF differentiation and function. Furthermore, IL-17 was expressed in NETs and promoted the fibrotic activity of differentiated LFs but not their differentiation, suggesting that priming by DNA and histones is essential for IL-17-driven fibrosis. Additionally, autophagy was identified as the orchestrator of NET formation, as shown by inhibition studies using bafilomycin A1 or wortmannin. The above findings were further supported by the detection of NETs in close proximity to alpha-smooth muscle actin (α-SMA)-expressing fibroblasts in biopsies from patients with fibrotic interstitial lung disease or from skin scar tissue. Together, these data suggest that both autophagy and NETs are involved not only in inflammation but also in the ensuing fibrosis and thus may represent potential therapeutic targets in human fibrotic diseases.
authors.affiliation: Laboratory of Molecular Hematology, Democritus University of Thrace, Alexandroupolis, Greece.
authors.forename: Akrivi
authors.initials: A
authors.lastname: Chrysanthopoulou
authors.forename: Ioannis
authors.initials: I
authors.lastname: Mitroulis
authors.forename: Eirini
authors.initials: E
authors.lastname: Apostolidou
authors.forename: Stella
authors.initials: S
authors.lastname: Arelaki
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Mikroulis
authors.forename: Theocharis
authors.initials: T
authors.lastname: Konstantinidis
authors.forename: Efthimios
authors.initials: E
authors.lastname: Sivridis
authors.forename: Maria
authors.initials: M
authors.lastname: Koffa
authors.forename: Alexandra
authors.initials: A
authors.lastname: Giatromanolaki
authors.forename: Dimitrios T
authors.initials: DT
authors.lastname: Boumpas
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Ritis
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Kambas
mesh_terms: D000199:Actins / Q000378:metabolism; D001343:Autophagy; D002454:Cell Differentiation / Q000187:drug effects; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D002843:Chromatin / Q000378:metabolism*; D002921:Cicatrix / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D018920:Coculture Techniques; D003094:Collagen / Q000378:metabolism; D055513:Connective Tissue Growth Factor / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005355:Fibrosis; D006801:Humans; D020381:Interleukin-17 / Q000378:metabolism; D008168:Lung / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D058628:Myofibroblasts / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D018375:Neutrophil Activation; D020556:Neutrophil Infiltration; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D019899:Paracrine Communication / Q000187:drug effects; D009195:Peroxidase / Q000378:metabolism; D010641:Phenotype; D011658:Pulmonary Fibrosis / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D012867:Skin / Q000276:immunology / Q000378:metabolism / Q000473:pathology
chemical_list: C541116:ACTA2 protein, human; D000199:Actins; C526317:CCN2 protein, human; D002843:Chromatin; D004791:Enzyme Inhibitors; D020381:Interleukin-17; D055513:Connective Tissue Growth Factor; D003094:Collagen; D009195:Peroxidase
keywords: IL-17; autophagy; fibroblast; fibrosis; neutrophil extracellular traps