Depressed urokinase activity in bronchoalveolar lavage fluid from patients with sarcoidosis,silicosis or idiopathic pulmonary Rbrosis: relationship to disease severity

Intraalveolar fibrinolysis, is regulated by the concerted actions of plasmin, plasminogen activators (PAs), and their specific inhibitors (PAIs). This event is considered as a critical step in the pathogenesis of pulmonary fibrosis. The aim of this study was to evaluate whether local PA activity can be held as a marker of fibrosis in chronic interstitial lung disorders (ILD). Changes in both PA activity and PA-related proteins (urokinase-type PA (uPA), tissue-type PA (tPA), PAI-1 and PAI-2) were assessed in bronchoalveolar fluid (BALF) of 60 subjects: 18 healthy controls, 18 non-fibrotic sarcoidosis patients, 16 patients with idiopathic pulmonary fibrosis (IPF) and eight silicotic patients with established fibrosis. We observed a significant decrease of BALF PA activity in the three groups of patients as compared with controls. Reduction in BALF PA activity was compatible with lower uPA protein levels associated, especially in IPF patients, with an increased occurrence of PAI-1 and PAI-2 antigens. Soluble tPA antigen was never detected either in control subjects or in patients. Most importantly, the reduction in BALF PA activity and uPA protein levels was found to be most severe in patients with advanced fibrotic disease, namely IPF, while moderate and only weak alterations were found in silicosis and non-fibrotic sarcoidosis, respectively. In addition, significant positive correlations were found between BALF PA activity and functional impairment as assessed by TLC % and DL_CO%. Finally, the reduction in uPA and PA activity levels observed in BALF from sarcoidosis patients was found to be proportional to the degree of BAL lymphocytosis. These findings indicate that an intense reduction in BALF PA activity is associated with severe stages of the parenchymal disease, possibly reflecting the degree of the fibrotic process.