Acute cytokine responses to inhaled swine confinement building dust

Abstract

Inhalation of swine house dust (swine dust) may cause an acute inflammatory reaction Organic Dust Toxic Syndrome (ODTS). The reaction does not require sensitisafion and is associated with airway inflammation, general symptoms, and slight spirometric changes. The agents and causing this reaction are not known. The purpose of this study was to investigate the release of pro-inflammatory cytokines in the airways and peripheral blood following acute exposure to swine dust, the correlation between markers for microbial contaminants in the dust, cytokine responses and health effects, and the release of those cytokines from an epithelial cell line (EP) and from human alveolar macrophages (AM) stimulated by swine dust and LPS.

Healthy subjects, previously unengaged in farm work were exposed to swine dust for 3-4 hours. Interleukin(IL)-6,IL-I receptor antagonist(ra) andtumour necrosis factor(TNF)-a in serum, and IL-Ib in peripheral blood mononuclear cell(PBMC)were measured prior to and rear to exposure. IL-Ia, IL-IB, IL-6 and TNF-a were also measured in nasal lavage (NAL) fluid and bronchoalveolar lavage (BAL) before and after exposure. The time curve were done for IL-6, TNF-a and IL- IB . The mass of inhaled dust, the endotoxin concentration and two markers (muramic acid is a marker for total peptidoglycan content and 3 -(OH)-fatty acid is a marker for total lipopolysaccharide content.) for microbial exposure were quantified. Spirometry and a methacholine bronchial challenge were performed before and 7h after exposure to swine dust. Granulocytes, monocytes, and Iymphocytes were measured in blood widh flow cytometry. NAL, BAL and PBMC cells were measured with colour stain. The oral temperature and general symptoms were recorded.

Exposure to swine dust caused fever, headache, malaise, increased bronchial responsiveness, and a slight decrease in FEVI and VC. IL-Ira, IL-6 and TNF-a increased significantly in serum, IL- IB increased signficantly in PBMC and plasma, IL- I, IL-6 and TNF-a increased significantly in BAL and NAL fluids.Therewas a marked influx of inflammatory cells, especially, of granulocytes. In peripheral blood, TNF-a, IL-6 and IL-IB increased and peaked during 3-5h, 5-7h and 3-7h respectively, after dhe start of exposure. The leukocytes doubled and monocytes increased slightly 6-8h after exposure. Endotoxin, muramic acid, and 3-OH fatty acid correlated signficantly with increase in serum IL-6. Inhalable dust correlated with increase in serum IL-Ira, and endotoxin correlated with increase IL-IB in PBMC. Endotoxin and 3-OH fatty acids also correlated significantly widh the IL-6 increase in BAL. Bacterial markers showed better correlation widh IL 6 changes than total dust concentrations. LPS correlated with symptoms and with lung function changes. Peptidoglycan correlated widh increase in blood granulocytes and body temperature. Swine dust caused a dose-dependent increase of IL-IB, IL-6 and TNF-a in AM. No increase of IL- IB or TNF-a, but a clear increase in IL-6 was found in EP. LPS caused a clear increase in all three cytokines in AM, but none of cytokines in EP.

In conclusion, acute inhalation of dust contaminated with bacterial debris increased the concentration of pro-inflammatory cytokines in BAL, NAL, PBMC and peripheral blood. The changes in cytokines and inflammatory parameters correlated better with markers of bacterial contaminants than with total dust. A markers for bacterial peptidoglycan showed better correlation widh some changes than endotoxin suggesting that several bacterial constituents may play a role in ODTS. The results in vitro test suggest dhat swine dust activated a cytokine response in EP and AM. The EP had more limited cytokine response profile than AM. The swine dust is a more potent stimulus for cytokine release than LPS in EP. Both cells can contribute to inflammatory reaction after inhalation swine dust, and several agents including LPS may play important role in those cytokine release.