[Show abstract][Hide abstract] ABSTRACT: The alveolar compartment in acute lung injury contains high levels of tissue factor (TF) procoagulant activity favoring fibrin deposition. We previously reported that the alveolar epithelium can release TF procoagulant activity in response to a proinflammatory stimulus. To test the hypothesis that the alveolar epithelium further modulates intra-alveolar fibrin deposition through secretion of an endogenous inhibitor to TF, tissue factor pathway inhibitor (TFPI), we measured TFPI levels in edema fluid (EF) from patients with acute respiratory distress syndrome. To determine whether the alveolar epithelium can release TFPI, both full-length TFPI and truncated TFPI were measured (ELISA) in pulmonary edema fluid from patients with acute respiratory distress syndrome (ARDS) and a control group of patients with hydrostatic pulmonary edema (HYDRO). TFPI protein was also measured in conditioned media (CM) and cell lysates (CL) from human alveolar epithelial cells (A549) after exposure to cytomix (TNF-alpha, IL-1 beta, IFN-gamma). TFPI protein levels were higher in pulmonary edema fluid from patients with ARDS vs. HYDRO. TFPI protein was increased in CM and did not change in CL after cytomix treatment; TFPI mRNA levels (RT-PCR) did not change. Despite the high levels of TFPI, both the EF and CM retained significant TF procoagulant activity as measured by plasma recalcification time. The majority of intra-alveolar TFPI was in a truncated, inactive form, whereas the majority of TFPI released from cells was full length, suggesting different mechanisms of inactivation. In summary, the alveolar epithelium releases TFPI in response to an inflammatory stimulus but does not increase TFPI gene transcription or protein production. Levels of intra-alveolar TFPI in ARDS are not sufficient to block intra-alveolar TF procoagulant activity due to truncation and inactivation of intra-alveolar TFPI.
Full-text · Article · Jun 2008 · AJP Lung Cellular and Molecular Physiology
[Show abstract][Hide abstract] ABSTRACT: Intravascular and extravascular fibrin formation are characteristic findings in patients with sepsis, suggesting that the activation of coagulation and the inhibiton of fibrinolysis are important in the pathogenesis of sepsis. Activation of coagulation during sepsis is primarily driven by the tissue factor (TF) pathway, while inhibition of fibrinolysis is primarily due to increases in plasminogen activator inhibitor -1(PAI-1). Downregulation of the anticoagulant Protein C pathway also plays an important role in the modulation of coagulation and inflammation in sepsis. Recent advances in the understanding of pathogenetic mechanisms of coagulation and fibrinolysis in sepsis may have therapeutic implications. Recombinant human activated protein C (rhAPC) is currently the only pharmacologic therapy that has been shown to reduce mortality in adults with severe sepsis, highlighting the importance of coagulation and fibrinolysis as a therapeutic target in sepsis. This review summarizes recent basic and clinical findings with regard to the role of the coagulation cascade in sepsis and explores potential therapeutic targets in the coagulation and fibrinolytic pathways in the management of sepsis.
No preview · Article · Feb 2008 · Current pharmaceutical design
[Show abstract][Hide abstract] ABSTRACT: The alveolar compartment is a procoagulant antifibrinolytic environment in acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS). A study was undertaken to test the hypothesis that the alveolar epithelium can initiate intra-alveolar coagulation by expressing active tissue factor (TF).
Using an in vitro cell surface TF assay and TF ELISA, the activity and production of TF in cultured alveolar epithelial (A549) cells following exposure to cytomix (tumour necrosis factor alpha, interleukin 1beta and interferon gamma) was measured. TF gene transcription was measured by semi-quantitative reverse-transcription PCR. Immunohistochemistry for TF was performed on lung sections from patients with ARDS and controls. TF protein levels were measured by ELISA in undiluted pulmonary oedema fluid from patients with ALI/ARDS and compared with control patients with hydrostatic pulmonary oedema.
TF activity, mRNA and protein levels increased in A549 cells after stimulation with cytomix. Increased TF activity was also seen in A549 cells following incubation with pulmonary oedema fluid from patients with ALI/ARDS. Immunohistochemistry for TF in human lung tissue from patients with ARDS showed prominent TF staining in alveolar epithelial cells as well as intra-alveolar macrophages and hyaline membranes. TF antigen levels in oedema fluid (median 37 113 (IQR 14 956-73 525) pg/ml) were significantly higher than in plasma (median 336 (IQR 165-669) pg/ml, p<0.001) in patients with ALI/ARDS, and TF procoagulant activity in oedema fluid was much higher than in plasma of these patients. Higher plasma levels were associated with mortality.
The alveolar epithelium is capable of modulating intra-alveolar coagulation through upregulation of TF following exposure to inflammatory stimuli and may contribute to intra-alveolar fibrin deposition in ARDS.
[Show abstract][Hide abstract] ABSTRACT: Intra-alveolar fibrin deposition is a common response to localized and diffuse lung infection and acute lung injury (ALI). We hypothesized that the alveolar epithelium modulates intra-alveolar fibrin deposition through activation of protein C. Our objectives [corrected] were to determine whether components of the protein C activation pathway are present in the alveolar compartment in ALI and whether alveolar epithelium is a potential source. In patients with ALI, pulmonary edema fluid levels of endothelial protein C receptor (EPCR) were higher than plasma, suggesting a source in the lung. To determine whether alveolar epithelial cells are a potential source, protein C activation by A549, small airway epithelial, and primary human alveolar epithelial type II cells was measured. All three cell types express thrombomodulin (TM) and EPCR, and activate protein C on the cell surface. Activation of protein C was inhibited by cytomix (TNF-alpha, IL-1beta, and IFN-gamma). Release of EPCR and TM into the conditioned medium was inhibited by the metalloproteinase inhibitors tumor necrosis factor protease inhibitor (TAPI) and GM6001, indicating that the shedding of EPCR and TM from the alveolar epithelium is mediated by a metalloproteinase. These findings provide new evidence that the alveolar epithelium can modulate the protein C pathway and thus could be an important determinant of alveolar fibrin deposition. Local fibrin deposition may be a fundamental mechanism for the lung to localize and confine injury, thus limiting the risk of dissemination of injury or infection to the systemic circulation.
Full-text · Article · May 2007 · American Journal of Respiratory Cell and Molecular Biology
[Show abstract][Hide abstract] ABSTRACT: Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common, life-threatening causes of acute respiratory failure that arise from a variety of local and systemic insults. The need for new specific therapies has led a number of investigators to examine the role of altered coagulation and fibrinolysis in the pathogenesis of ALI/ARDS. This review summarizes our current understanding of coagulation and fibrinolysis in human ALI/ARDS with an emphasis on pathways that could be potential therapeutic targets including the tissue factor pathway, the protein C pathway and modulation of fibrinolysis via plasminogen activator inhibitor-1. The available data suggest that clinical ALI and ARDS are characterized by profound alterations in both systemic and intra-alveolar coagulation and fibrinolysis. Fibrin deposition in the airspaces and lung microvasculature likely results from both activation of the coagulation cascade and impaired fibrinolysis, triggered by inflammation. Modulation of fibrin deposition in the lung through targeting activation and modulation of coagulation as well as fibrinolysis may be an important therapeutic target in clinical ALI/ARDS that deserves further exploration.
Full-text · Article · Oct 2005 · The Keio Journal of Medicine
[Show abstract][Hide abstract] ABSTRACT: The objective of this study was to evaluate the cardiopulmonary effects of a dual-endothelin (ET) receptor antagonist, Tezosentan, on oleic acid (OA)-induced acute lung injury with pulmonary arterial hypertension in dogs. Twelve pentobarbital-anesthetized dogs with intravenous OA-induced acute lung injury (ALI) were divided into 2 groups. The control group (n=6) received saline treatment, whereas the treatment group (n=6) received the ET receptor antagonist, Tezosentan (1 mg/kg intravenous [i.v.]+1 mg/kg/h i.v. infusion). Cardiopulmonary parameters were monitored continuously for 1 hour. OA administration resulted in a significant increase in mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance (PVR) and a decrease in mean systemic arterial pressure (MSAP), systemic vascular resistance (SVR), and cardiac output (CO) in all dogs. Tezosentan treatment markedly attenuated the pulmonary hypertension, with a 32% decrease in MPAP (from 23 +/- 2 mm Hg to 15 +/- 2 mm Hg; P<.01) and a 22% decrease in PVR (from 860 +/- 105 dyn.s.cm(-5) to 670 +/- 96 dyn.s.cm(-5); P<.01) at the end of study. MSAP and SVR were unchanged after Tezosentan treatment, and there was an increase in cardiac output and a decline in peak inspiratory pressure (PIP) in the Tezosentan group compared with the control group. These results indicate that the dual-ET receptor antagonist, Tezosentan, can attenuate the pulmonary hypertension induced by OA. Thus, dual-ET receptor antagonists such as Tezosentan may be useful in the management of acute pulmonary arterial hypertension, complicating the course of OA-induced lung injury.
No preview · Article · Jan 2004 · Experimental Lung Research
[Show abstract][Hide abstract] ABSTRACT: The aim of this study is to investigate whether ambroxol inhibits inflammatory responses in a murine model of lipopolysaccharide-induced acute lung injury (ALI).
Mice (n=295) were first intratracheally instilled with lipopolysaccharide (LPS) to induce ALI and then received an intraperitoneal (i.p.) injection of either normal saline (NS), ambroxol (30 or 90 mg/kg per day) or dexamethasone (2.5 or 5 mg/kg per day) for 7 days. Metabolism (n=10, each), lung morphology (n=5, each) and wet-to-dry lung weight ratio (n=10, each) were studied. The levels of tumor necrosis factor (TNF-alpha), interleukin-6 (IL-6) and transforming growth factor (TGF-beta1) and the protein concentration (n=5 or 7, each) in bronchoalveolar lavage (BAL) were measured.
Mice with LPS-induced ALI that were treated with ambroxol at a dosage of 90 mg/kg per day significantly gained weight compared to the control and dexamethasone-treated groups. Ambroxol and dexamethasone significantly reduced the lung hemorrhage, edema, exudation, neutrophil infiltration and total lung injury histology score at 24 and 48 h. In addition, ambroxol and dexamethasone significantly attenuated the lung wet-to-dry weight ratio at 24 and 48 h (p<0.05). Compared to the control group, TNF-alpha, IL-6 and TGF-beta1 levels in the BAL in both ambroxol- and dexamethasone-treated groups were significantly reduced at 24 and 48 h. The protein in BAL, an index of vascular permeability, was also significantly decreased in the ambroxol- and dexamethasone-treated groups (p<0.05).
Ambroxol inhibited proinflammatory cytokines, reduced lung inflammation and accelerated recovery from LPS-induced ALI.
Full-text · Article · Jan 2004 · Intensive Care Medicine