Kinetics of lung tissue factor expression and procoagulant activity in bleomycin induced acute lung injury.

Li Ma,Brittany E Brake,Robert H Carnahan,Tracy L Cooper,Brandon S Grove,Lorraine B Ware,Ciara M Shaver,Julie A Bastarache,Daphne B Mitchell,Nancy E Wickersham

doi:10.1186/s40169-015-0063-4

Li Ma, Brittany E Brake + Show 8 more

Open Access

https://doi.org/10.1186/s40169-015-0063-4

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Abstract

BackgroundActivation of coagulation by expression of tissue factor (TF) in the airspace is a hallmark of acute lung injury (ALI) but the timing of TF activation in relationship to increases in lung permeability and inflammation are unknown.MethodsTo test the hypothesis that TF is upregulated early in the course of acute bleomycin lung injury and precedes increased permeability and inflammation we studied the early course of bleomycin-induced ALI in mice. Mice were treated with 0.04U intratracheal bleomycin or vehicle control and bronchoalveolar lavage (BAL) and lung tissue were collected daily for 7 days. Whole lung TF mRNA was determined by QT-PCR. TF protein was assessed by ELISA and immunostaining. BAL procoagulant activity was measured by BAL clot time and thrombin-antithrombin complexes. Inflammation was assessed by BAL cell count, differentials and CXCL1/KC concentration. Lung permeability was assessed by BAL protein and lung wet to dry weight ratio.ResultsExpression of CXCL1 occurred by day 1. BAL protein and lung wet-to-dry weight ratio increased significantly by day 3. TF mRNA and BAL procoagulant activity peaked on day 4 while whole lung TF protein peaked on day 6. Changes in permeability and procoagulant activity preceded inflammatory cell influx which was maximal at day 6 while whole lung TF protein peaked along with inflammation.ConclusionThese data demonstrate that cytokine upregulation is the earliest response to bleomycin administration, followed by increased lung permeability, upregulation of TF, and recruitment of inflammatory cells.

Highlights

Activation of coagulation by expression of tissue factor (TF) in the airspace is a hallmark of acute lung injury (ALI) but the timing of TF activation in relationship to increases in lung permeability and inflammation are unknown
Staining became more patchy and intense on days 3 and 5 and persisted on day 7. These increases in TF mRNA and protein were paralleled by increased TF procoagulant activity in bronchoalveolar lavage (BAL) fluid (Fig. 3a) which peaked at day 4
In ALI, the lung epithelium upregulates TF mRNA, protein and procoagulant activity [10] and releases TF positive procoagulant microparticles [15] leading to a shift towards procoagulant pathways in the airspace that are not balanced by anticoagulant pathways such as tissue factor pathway inhibitor (TFPI) [16]

Summary

Introduction

Activation of coagulation by expression of tissue factor (TF) in the airspace is a hallmark of acute lung injury (ALI) but the timing of TF activation in relationship to increases in lung permeability and inflammation are unknown. Coagulation and inflammation are linked through protease activated receptors (PAR) and thrombin-mediated signaling through PAR-1 on vascular cells increases production of chemokines such as MCP-1, resulting in the efficient recruitment of leukocytes in a mouse-to-rat heart transplant model [14]. These studies suggest that targeting coagulation pathways in ALI may lead to changes in inflammation.

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