Muramic Acid, Endotoxin, 3-Hydroxy Fatty Acids, and Ergosterol Content Explain Monocyte and Epithelial Cell Inflammatory Responses to Agricultural Dusts

Abstract

In agricultural and other environments, inhalation of airborne microorganisms is linked to respiratory disease development. Bacterial endotoxins, peptidoglycans, and fungi are potential causative agents, but relative microbial characterization and inflammatory comparisons amongst agricultural dusts are not well described. The aim of this study was to determine the distribution of microbial endotoxin, 3-hydroxy fatty acids (3-OHFA), muramic acid, and ergosterol and evaluate inflammatory responses in human monocytes and bronchial epithelial cells with various dust samples. Settled surface dust from 5 environments was obtained: swine facility, dairy barn, grain elevator, domestic home (no pets) and domestic home with dog. Endotoxin concentration was determined by recombinant Factor C (rFC). 3-OHFA, muramic acid and ergosterol were measured using gas chromatography-mass spectrometry. Dust-induced inflammatory cytokine secretion in human monocytes and bronchial epithelial cells was evaluated. Endotoxin-independent dust-induced inflammatory responses were evaluated. Endotoxin and 3-OHFA levels were highest in agricultural dusts. Muramic acid, endotoxin, 3-OHFA and ergosterol were detected in dusts samples. Muramic acid was highest in animal farming dusts. Ergosterol was most significant in grain elevator dust. Agricultural dusts induced monocyte TNFα, IL-6, IL-8 and epithelial cell IL-6 and IL-8 secretion. Monocyte and epithelial IL-6 and IL-8 secretion was not dependent on endotoxin. House dust(s)-induced monocyte TNFα, IL-6, IL-8 secretion. Swine facility dust generally produced elevated responses compared to other dusts. Agricultural dusts are complex with significant microbial component contribution. Large animal farming dust(s)-induced inflammation is not entirely dependent on endotoxin. Addition of muramic acid to endotoxin in large animal farming environment monitoring is warranted.

Air Quality in Horse Stables

“…Dust from large animal farming is a complex mixture, and factors other than endotoxin and glucan, such as muramic acid and 3-hydroxy fatty acid, may contribute to respiratory inflammation and these components should therefore be added to the list of markers (Poole et al, 2010). Regarding the horses being examined, for most management systems in our northern climates stabled horses spend far more time indoors than their keepers on a daily basis.…”

Exposures and Health Outcomes in Relation to Bioaerosol Emissions From Composting Facilities: A Systematic Review of Occupational and Community Studies

“…Elevated inflammatory responses have also been found in humans working in agricultural settings (May et al, 2012;Poole et al, 2010).…”

“…There were no studies identified that would enable the estimation of incidence rates of occupational allergic disease, one of the most frequent occupational respiratory disorders. However, respiratory and allergic disease following elevated exposures to some bioaerosols, such as endotoxin and Aspergillus fumigatus (Rautiala et al, 2003), was noted in other occupations including agricultural workers (May et al, 2012;Poole et al, 2010) and domestic waste collectors that were not considered in this review. The lack of longitudinal studies is most likely due to the practical difficulties of longitudinal studies in these settings, and the difficulty in obtaining historical data due to the relatively recent development of the composting industry.…”

Organic Dust, Lipopolysaccharide, and Peptidoglycan Inhalant Exposures Result in Bone Loss/Disease

“…Farming is also a known occupational hazard for developing musculoskeletal diseases such as osteoarthritis (OA) and rheumatoid arthritis (RA) (8)(9)(10)(11)(12). The organic dust exposure is complex, involving a wide diversity of microbial motifs (e.g., peptidoglycans [PGNs] and endotoxin) and particulate matter, which elicit airway inflammatory responses in mice (7,13). Namely, repetitive organic dust exposures induce the development of lymphoid aggregates and peribronchiolar/ vascular inflammation, comprised of T and B lymphocytes and macrophages with associated neutrophil recruitment (5,14,15).…”