Bakery flour dust exposure causes non-allergic inflammation and enhances allergic airway inflammation in mice (1)
Characterized by rhinitis which often accompanies respiratory symptoms such as airflow obstruction and bronchial hyper-responsiveness, baker’s asthma has been shown to develop in work environments in which there is continued exposure to bakery flour dust. Bakery flour dust is a complex mixture of proteins and other organic materials including bacterial endotoxin.
An 8% solution of Italian bakery flour is prepared in phosphate buffer saline/0.15M NaCl, ph 7.2 and shaken overnight at 4° C. This solution is lyophilized and stored at −20° C.
In this attempted sensitization protocol there was no increase in total serum IgE as the measurable levels were consistent with sham sensitized sham challenged mice in an OVA protocol. Both MIP-2 and KC are significantly increased as a result of bakery flour exposure in mice.
Both bakery flour dust and flour dust extract caused a significant, dose-dependent increase in pulmonary neutrophilic inflammation four hours after exposure. Both MIP-2 and KC protein were induced by installation of bakery flour dust or flour dust extract. both flour and flour dust extract caused a significant increase in the overall number of macrophages present in the lung at the high dose, while bakery flour also caused an increase in macrophages at the medium dose.
The absolute number of macrophages in whole lung lavage was increased in both flour and saline instillation groups. This inflammatory response was more pronounced 4 hours after the exposure and both the macrophage and the neutrophilic inflammatory responses were still elevated at 24 hours after instillation.
Endotoxin contamination in the bakery flour used in these experiments (3780 EU/mg) was determined. The biologic response to flour dust is tlr4-independent as both wild-type and tlr4-deficient mice responded similarly to flour dust instillation. These responses are consistent with previous results in which significant increases in total cells, macrophages, neutrophils, TNF-α, MIP-2 and KC when compared with the saline-exposed animals.
Mice pre-treated with LPS in the same amounts found in 1 mg of bakery flour dust were not different in total number of inflammatory cells. Mice pre-exposed to either flour or LPS-free flour had significantly enhanced macrophage and eosinophilic inflammation consequent to OVA challenge. Significantly elevated TNF-α and IL-5 protein in whole lung lavage in mice pre-exposed to LPS, flour, or LPS-free flour but not flour extract. Total serum IgE for all exposures was also significantly elevated although the flour pre-exposed mice did not have enhanced total serum IgE compared to sensitized mice pre-exposed to saline before ova challenge.
