Mouse Model for Assessing Endotoxin Involvement in the Lung Inflammation and Cytokine Production Resulting from Inhaled Organic Dust

Abstract

The involvement of endotoxin in the development of acute pulmonary inflammation and tumor necrosis factor (TNF) release following inhalation of cotton dust was demonstrated using endotoxin-sensitive C3HeB/FeJ and endotoxin-resistant C3H/Hel mice. These mice were exposed for a maximum of 6 h to atmospheres of either 45 mg/m³ cotton dust or 2.4 μg/m³ lipopolysaccharide (LPS) from Enterobacter agglomerans. Inflammation was assessed from bronchoalveolar lavage (BAL) cell morphology and lung histology. Release of TNF into BAL fluid was measured using a bioassay employing WEHI 13VAR cells and neutralization with rabbit anti-mouse TNF antiserum. Neutrophil influx and TNF release were maximal at 6 in C3HeB/FeJ mice following cotton dust exposure and at 3 h following LPS exposure. By 24 h after the beginning of cotton dust exposure, TNF in C3HeB/FeJ BAL was no longer detectable, whereas neutrophils were still elevated above control values. In endotoxin-resistant C3H/Hel mice, no inflammation or TNF release resulted from inhalation of LPS, and minimal inflammation and TNF release were noted at 9 h following exposure to cotton dust for 3 or 9 h. These results suggest a major role for endotoxin in acute inflammation and TNF release induced by cotton dust inhalation, with a minor role for other components in cotton dust. The TNF release coincided with the inflammatory response to cotton dust or LPS inhalation, suggesting, but not proving, an etiologic role of TNF in these inflammatory reactions.