Coagulation factors in the airways in moderate and severe asthma and the effect of inhaled steroids F J H Brims, 1 A J Chauhan, 1 B Higgins, 2 J K Shute 2 c An additional appendix is published online only at http:// thorax.bmj.com/content/vol64/ issue12 1 Respiratory Centre, Queen Alexandra Hospital, Portsmouth Hospitals NHS Trust, UK; 2 Institute of Biomedical and Biomolecular Sciences, University of Portsmouth, UK Correspondence to: Dr J Shute, Institute of Biomedical and Biomolecular Sciences, St Michael’s Building, White Swan Road, Portsmouth PO1 2DT, UK; jan.shute@port. ac.uk Received 11 February 2009 Accepted 24 July 2009 Published Online First 23 August 2009 ABSTRACT Background: There is evidence of activation of the extrinsic coagulation cascade in the asthmatic airway, and both plasma and locally derived factors may be involved. The hypothesis that the normal haemostatic balance of healthy airways sampled by sputum induction favours fibrin formation in asthmatic airways, and that inhaled corticosteroids (ICS) and plasma exudation influence this balance, was tested. Methods: ELISA and activity assays were used to measure a 2 -macroglobulin (an index of plasma leakage) and coagulation factors in hypertonic saline-induced sputum of 30 stable subjects (10 controls, 10 with moderate asthma and 10 with severe asthma). Additionally, the moderate cohort were weaned off their ICS, followed by further sputum induction 5 days after cessation of steroids. Results: ICS wean induced a significant rise in plasminogen (median (interquartile range (IQR)): 13.92 (6.12–16.17) vs 4.82 (2.14–13.32) ng/ml; 95% CI 0.003 to 8.596, p = 0.0499) and tissue plasminogen activator (tPA; 5.57 (3.57–14.35) vs 3.88 (1.74–4.05) ng/ml; 95% CI 0.828 to 9.972, p = 0.0261) levels in sputum, such that tPA in untreated moderate asthma was significantly (p = 0.0029) higher than normal (2.14 (0.0–2.53) ng/ml). Subjects with severe asthma had significantly more a 2 - macroglobulin (p = 0.0003), tissue factor (p = 0.023), plasminogen activator inhibitor (p = 0.0091), thrombin- activatable fibrinolysis inhibitor (p = 0.0031) and fibrin degradation products (p = 0.0293) in their sputum than control subjects. Conclusion: Untreated moderate asthma is associated with increased fibrinolysis that is corrected by ICS. Severe asthma and high dose corticosteroid therapy is associated with a profibrinogenic, antifibrinolytic environment in the airways. This study suggests that inhibition of fibrin deposition in severe asthma may be a therapeutic approach. Asthma is characterised by airway inflammation and variable tissue remodelling. 1 It is influenced by inhaled corticosteroid (ICS) therapy, yet many of those with asthma remain symptomatic, some with severe manifestations of the disease, as structural changes lead to airflow obstruction that may be irreversible. 2 Plasma exudation from the bronchial microvasculature contributes to bron- chial obstruction by fibrin deposition in mucus plugs, bronchial wall thickening, epithelial shed- ding, thickening of the basement membrane, hypertrophy of the smooth muscle and mucus secretion. Fibrin deposition in distal airways is also associated with increased bronchial hyper-respon- siveness. 3 We further reported that fibrin forma- tion by bronchial epithelial cells in vitro is independent of plasma proteins, and is essential for bronchial epithelial repair. 4 Exposure of plasma to cell-bound tissue factor (TF), the principal activator of the extrinsic coagulation cascade, initiates fibrin clot formation within minutes, although the rate of fibrin forma- tion is determined by components of the intrinsic coagulation cascade. 5 Thus, early, physiologically desirable, fibrin formation for normal wound healing, initiated by TF-bearing cells, may propa- gate into exudated bulk plasma, generating exces- sive and physiologically undesirable fibrin that could lead to fibrosis, mucus plug formation, airway narrowing and bronchial hyper-reactivity (BHR). 3 6–8 Levels of TF in induced sputum are higher in patients with mild asthma compared with healthy controls, 9 and after allergen challenge. 10 A TF- dependent increase in coagulation and a plasmino- gen activator inhibitor (PAI-1)-dependent decrease in fibrinolysis is a feature of alveolar fibrin formation in acute respiratory distress syndrome (ARDS) and idiopathic pulmonary fibrosis. 11 There has been recent interest in the role of platelets contributing to the coagulation response in patients with acute lung injury 12 ; however, their role in the regulation of the extrinsic coagulation cascade in the lung, and in those with asthma is not known. Activation of the coagulation cascade has both fibrin-dependent and fibrin-independent influences on tissue fibrosis. Fibrin-dependent effects include neutralisation of surfactant, binding and accumulation of transforming growth factor b (TGFb) and provision of a matrix for fibroblast proliferation. Independent effects include activa- tion of serine proteases, notably thrombin, factor VIIa (FVIIa) and FXa, that activate protease- activated receptors (PARs), present on fibroblasts and bronchial epithelial cells, to stimulate fibrotic and inflammatory processes further in the lung 6 11 13 and also to enhance TF expression further. 14 Thus increased levels of TF are self- amplifying when coagulation is initiated. In the normal lung, the haemostatic balance is antithrombotic and favours fibrinolysis. 6 We sought to test the hypothesis that the normal haemostatic balance changes in favour of coagula- tion in moderate and severe asthma, and that ICS and plasma exudation influence this balance. METHODS Patients Healthy controls and patients with moderate and severe asthma were recruited from the community and from the asthma clinic at Queen Alexandra Hospital, Portsmouth, UK. Asthma was confirmed Asthma Thorax 2009;64:1037–1043. doi:10.1136/thx.2009.114439 1037 group.bmj.com on September 7, 2016 - Published by http://thorax.bmj.com/ Downloaded from