Abstract
Swine Confinement Facility (SCF) dust consists of a complex mixture of feed grain particles, bacterial components, organic particulates and gases. When these particles are inhaled they deposit along the respiratory tract and mediate respiratory symptoms and disease in swine farmers and facility workers. Macrophages ingest and eliminate microbes and debris under chronic conditions; however, the role of macrophages in agricultural-related respiratory dis ease has not been fully elucidated. The goal was to evaluate the hypothesis that chronic exposure to SC F dust causes inflammation by modulating pulmonary protein levels and macrophage function. Balb/c mice were exposed to 5, 12.5 and 25% SCF Dust Extract (DE) via nebulization 30 min/day five days a week, for eight weeks with weekends excluded. Bronchoalveolar Lavage Fluid (BALF) was collected and analyzed for protein concentration, leukocyte distribution and macrophage morphology. For comparison, THP-1 monocytic cells were exposed to 0.110% DE overnight and evaluated for phagocytosis and reactive oxygen species production. Repeated exposure to DE via nebulizer caused a significant i ncrease in protein concentration and inflammatory c ell number, namely macrophages, in a dose-dependent manner within the lung as compared to controls. Macrophages with pseudopods and vacuoles were the most abundant leukocytes within BALF of mice exposed to DE. Similarly, in vitro studies with 10% DE treated THP-1 cells revealed e nhanced phagocytosis (p<0.05), pseudopodia and vacuolization following e xposure to compared to control cells. In addition, there were time- and dose-dependent increases of intracel lular ROS production by THP-1 cells exposed to 5 and 10% DE compared to control (p<0.01). These findings indicate repeated, long-term inhalation of swine confinement facility dust may mediate chronic airwa y and lung inflammation through modulation of protein concentration and macrophage function. The aerosolized dust-mouse inhalation model presented here may offer a good tool for studying particle mediated ch ronic inflammation of the tracheobronchial tree and lungs.
Highlights
In an effort to meet growing consumer demand, animal production has shifted from pasture-based approached to large Concentrated Animal Feeding Operations (CAFOs)
There was a significant increase in Bronchoalveolar Lavage Fluid (BALF) protein concentration in 12.5% Dust Extract (DE) exposed mice compared to Phosphate Buffer Saline (PBS)-control (Fig. 1A)
Delivery of aerosolized substances to mice via nebulizer is not novel; to our knowledge this is the first report documenting an increase in macrophages with vacuoles and pseudopods following long-term, repeated exposure to aerosolized swine housing dust extract using an in vivo mouse model
Summary
In an effort to meet growing consumer demand, animal production has shifted from pasture-based approached to large Concentrated Animal Feeding Operations (CAFOs). Inhalation of endotoxins and carbon dioxide at levels above the recommended health threshold limits (McDonnell et al, 2008) can lead to acute and chronic. Pender et al / American Journal of Immunology 10 (1): 35-45, 2014 airway inflammation can occur (Schierl et al, 2007) which may lead to loss of lung function, as measured by the decrease in forced expiratory air in one second or less (Costa et al, 2007). Inhalation of endotoxins and carbon dioxide at levels above the recommended health threshold limits (McDonnell et al, 2008) chronic airway inflammation can occur (Schierl et al, 2007) which may lead to loss of lung function, as measured by the decrease in forced expiratory air in one second or less (Costa et al, 2007). After frequent exposure to Swine Confinement Facility (SCF) dust, physiological effects can develop, including pulmonary inflammation, severe asthma, chronic respiratory diseases and bronchoconstriction (Demanche et al, 2009)
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