Abstract
Coal workers' pneumoconiosis results from the inhalation of coal mine dust that usually contains small amounts of free crystalline silica. The most important health effect associated with the inhalation of these dusts is pulmonary fibrosis. The alveolar macrophage plays a significant role in mediating pulmonary fibrosis. On activation, the alveolar macrophage releases growth factors and cytokines, including the extracellular matrix protein fibronectin. Fibronectin influences fibroblast function, which is central to pulmonary fibrosis. The objectives of this study were to demonstrate: 1) that fibronectin is present in primate bronchoalveolar lavage fluid (BALF) from control lungs, as well as lungs exposed to generic coal dusts; and 2) that BALF from monkeys whose lungs were exposed to generic quartz dust have significantly higher levels of fibronectin compared to monkeys whose lungs were exposed to generic coal dusts. Bronchoscopy was used to instill known quantities of the characterized mineral dusts into a single lung lobe of Macaca nemestrina. Bronchoalveolar lavage (BAL) was used to recover alveolar lining materials from both the dust-exposed and unexposed lung lobes of the same animals. Fibronectin was demonstrated in BALF from both the dust-exposed and unexposed lungs. Fibronectin levels were significantly higher in BALF from lungs exposed to 500 mg generic quartz dust than in lungs exposed to similar amounts of generic coal dusts. The results suggest that fibronectin is a normal constituent of the lower respiratory tract in primates and is present in significantly increased amounts during exposure to fibrogenic dusts.