Interferon-γ and tumor necrosis factor-α act synergistically to up-regulate tissue factor in alveolar epithelial cells

• Published in: Experimental lung research Vol. 37; no. 8; pp. 509 - 517
• Main Authors: Bastarache, Julie A., Sebag, Sara C., Grove, Brandon S., Ware, Lorraine B.
• Format: Journal Article
• Language: English
• Published: England Informa Healthcare 01-10-2011; Taylor & Francis
• Subjects: acute lung injury; acute respiratory distress syndrome; Alveolar Epithelial Cells - drug effects; Alveolar Epithelial Cells - metabolism; Cell Line; Cell-Derived Microparticles - drug effects; Cell-Derived Microparticles - metabolism; coagulation; Drug Synergism; Humans; Interferon-gamma - administration & dosage; microparticles; Receptors, Tumor Necrosis Factor, Type I - metabolism; Receptors, Tumor Necrosis Factor, Type II - metabolism; RNA, Messenger - genetics; RNA, Messenger - metabolism; Thromboplastin - genetics; Thromboplastin - metabolism; TNFR1; TNFR2; tumor necrosis factor alpha receptor; Tumor Necrosis Factor-alpha - administration & dosage; Up-Regulation - drug effects
• ISSN: 0190-2148; 1521-0499
• DOI: 10.3109/01902148.2011.605512

ABSTRACT
Fibrin deposition mediated through activation of tissue factor (TF) in the airspace is central to the pathogenesis of acute lung injury. Defining the mechanisms of TF regulation in the lung is critical to understanding pulmonary fibrin formation. Tumor necrosis factor-α (TNF-α) up-regulates TF in the injured lung, and there is emerging evidence that another cytokine, interferon-γ (IFN-γ), also modulates expression. The effects of TNF-α and IFN-γ on regulation of TF were studied in alveolar epithelial A549 cells. In addition, potential mechanisms of modulation of TF expression by the 2 cytokines were analyzed with the hypothesis that IFN-γ acts synergistically with TNF-α to up-regulate alveolar epithelial TF through modulation of TNF receptor (TNFR) expression. TNF-α but not IFN-γ treatment increased TF mRNA, protein, and cell surface TF activity. The combination of IFN-γ and TNF-α treatment augmented the effects of TNF-α on TF up-regulation and also increased release of procoagulant microparticles (MPs) from A549 cells. IFN-γ modulated expression of both TNF-α receptors. Studies utilizing neutralizing antibodies against the two TNF receptors showed that the TF effects were mediated primarily through augmentation of TNFR1-dependent cellular responses. These findings have important implications for regulation of fibrin formation in the lung in the setting of acute inflammation.