Inhalation of swine dust induces cytokine release in the upper and lower airways

In healthy subjects, acute inhalation of swine dust causes an influx of inflammatory cells into the airways and increased bronchial responsiveness. The exposure may also cause fever and generalized symptoms. It seems likely that proinflammatory cytokines are involved in the response to inhaled swine dust. Nasal and bronchoalveolar lavage (BAL) were performed before, and 7 and 24 h after the start of 3 h exposure to swine dust, during a period of work in a swine confinement building, in 22 healthy subjects. Lavage fluids were analysed with regard to the cellular response and concentrations of interleukin (IL)-1 alpha, IL-1 beta, IL-6 and tumour necrosis factor-alpha (TNF-alpha). Each subject carried personal samplers for exposure measurements. Inhalable dust and airborne endotoxin, 3-hydroxylated (2-OH) fatty acid and muramic acid were measured. Bronchial responsiveness to methacholine was investigated 1-2 weeks before and 7 h after the start of the exposure. Exposure caused fever (> 38 degrees C) in three subjects, and approximately 25% of the subjects experienced symptoms. Bronchial responsiveness to methacholine increased by 3.5 (1.6-4.8) doubling doses (median (25th-75th percentile)). Following exposure, granulocytes increased more than 50 fold in BAL fluid and more than 40 fold in nasal lavage fluid. IL-1 alpha and IL-1 beta increased significantly in BAL fluid (p < 0.05) and nasal lavage fluid (p < 0.01). IL-6 increased 25 fold in BAL and 15 fold in nasal lavage fluid (p < 0.001). TNF-alpha was below detection limit (0.25 ng.L-1) in most subjects before exposure and increased following exposure to 3.8 (2.4-5.7) and 1.3 (0.6-2.3) ng.L-1 in BAL and nasal lavage fluid, respectively, (p < 0.001). Total inhalable dust was 20.5 (14.6-30.0) mg.m-3 and the concentrations of airborne endotoxin, 3-OH fatty acid and muramic acid were 1.2 (0.8-1.4), 3.5 (2.2-4.5) and 0.9 (0.3-1.9) microgram.m-3, respectively. There was a significant correlation between the IL-6 response in BAL fluid and exposure to dust endotoxin activity and 3-OH fatty acids (p < 0.05). Otherwise, no significant correlations were found between exposure and the cytokine response. We conclude that exposure to swine dust causes an intense upper and lower airway inflammation, which involves the proinflammatory cytokines interleukin-1, interleukin-6 and tumour necrosis factor-alpha.