Special neutrophil elastase inhibitory activity in BAL fluid from patients with silicosis and asbestosis

Pneumoconiosis is defined as the disease resulting from a chronic exposure to different inorganic dusts. In order to assess the lung defence against the effects of dust exposure, we studied the bronchoalveolar lavage (BAL) fluids from 30 silicotic patients (9 of them having a diagnosis of progressive massive fibrosis (PMF)) and 8 subjects with a diagnosis of asbestosis. Total protein content, N-acetyl-beta-D-glucosaminidase activity, free elastase-like activity, immunoreactive alpha 1-proteinase inhibitor (alpha 1PI) and neutrophil elastase inhibitory capacity (NEIC) were determined, and the values obtained were compared to those of 14 control BAL fluids. In all of the patients, our data showed a significant increase of total protein content and free elastase-like activity. In contrast, N-acetyl-beta-D-glucosaminidase activities did not reach statistical significance. Values concerning immunoreactive alpha 1PI and NEIC were significantly raised only in patients with PMF and with asbestosis. When the ratio NEIC/immunoreactive alpha 1PI was calculated, a significant difference was noticed in the asbestosis group; on the other hand, this ratio was significantly reduced in the group of PMF patients. After neutrophil elastase addition, an electrophoretic study by SDS-PAGE and immunoblotting was carried out; it showed more proteolysed alpha 1PI in the BAL fluids having a lowered NEIC/alpha 1PI ratio. These facts could be explained by the presence of inhibitors of neutrophil elastase different from alpha 1PI.