Innate immune airway responses after exposure to ultrafine and ambient particles : in vivo and in vitro models

Abstract

Inhalation of ultrafine and ambient particles in the air triggers a response in the innate immune system of the airways. This thesis explores measures to reduce exposure to organic dust, to dampen the adverse immune effects of chronic organic swine dust exposure and develop a refined in vitro bronchial mucosa model to reduce in vivo toxicity testing on humans and animals.

In Paper I, the aim was to reduce particulate matter exposure by installing particle separators in swine buildings and to explore the respiratory effects in healthy subjects after acute exposure. Exposure measurements including organic dust including endotoxins in both swine building environments (with and without particle separation) were performed and the particle separators reduced mainly particles sized 0.3-0.5 μm. The adverse acute symptoms like headache and increased body temperature in the volunteers were reduced when exposed to the particle separated swine building environment compared to the conventional swine building environment. The particle separators reduced the pro-inflammatory responses (IL-6 and CXCL8) in the upper respiratory tract compared to the conventional swine building environment.

In Paper II, the aim was to investigate the host innate immune response in vivo in chronically organic dust exposed swine farmers after short-term glucocorticosteriods therapy. Swine farmers inhaled budesonide for two weeks which increased their release of soluble TLR2 in the airways. Systemic effects included increased number of circulating leucocytes and TLR4 expression on lymphocytes, and decreased cytotoxic T-cell production of IL-13 and IL-4. The second aim of Paper II was to elucidate the cellular immune response of alveolar macrophages from chronically exposed swine farmers to ex vivo co-stimulation of glucocorticosteroids and TLR ligands. In alveolar macrophages, mRNA TLR2 expression increased and CXCL8 decreased after ex vivo co-stimulation with LPS/peptidoglycan/TNF-α and budesonide. The mRNA expression of CD14, IL-13 and GPx in alveolar macrophages increased after the in vivo steroid treatment of swine farmers. In all, this study showed that inhalation of a glucocorticosteroid strengthens the immune defense pathways in subjects with occupational chronic exposure to organic dust.

In Paper III, the aim was to develop an organotypic in vitro exposure system; combining bronchial models with XposeALI® for exposure of nano-sized palladium. Here we established a viable and robust in vitro bronchial mucosa co-culture model using human primary bronchial epithelial cells and a fibroblast cell line showing in vivo characteristics. By stimulation with IL-13, the model differentiated into a chronic bronchitis-like model. It was successfully combined with the advanced aerosol exposure system PreciseInhale™ and the in vitro module XposeALI® and exposed to palladium nanoparticles, which induced inflammatory responses in the 3D models.