Effects of organic chemicals derived from ambient particulate matter on lung inflammation related to lipopolysaccharide

The effects of components of ambient particulate matter (PM) on individuals with predisposing respiratory disorders are not well defined. We have previously demonstrated that airway exposure to diesel exhaust particles (DEP) or organic chemicals (OC) extracted from DEP (DEP-OC) enhances lung inflammation related to bacterial endotoxin (lipopolysaccharide, LPS). The present study aimed to examine the effects of airway exposure to OC extracted from urban PM (PM-OC) on lung inflammation related to LPS. ICR mice were divided into four experimental groups that intratracheally received vehicle, LPS (2.5 mg/kg), PM-OC (4 mg/kg), or PM-OC + LPS. Lung inflammation, lung water content, and lung expression of cytokines were evaluated 24 h after intratracheal administration. LPS challenge elicited lung inflammation evidenced by cellular profiles of bronchoalveolar lavage fluid and lung histology, which was further aggravated by the combined challenge with PM-OC. The combination with PM-OC and LPS did not significantly exaggerate LPS-elicited pulmonary edema. LPS instillation induced elevated lung expression of interleukin-1 beta, macrophage inflammatory protein-1 alpha, macrophage chemoattractant protein-1, and keratinocyte chemoattractant, whereas the combined challenge with PM-OC did not influence these levels. All the results were consistent with our previous reports on DEP-OC. These results suggest that the extracted organic chemicals from PM exacerbate infectious lung inflammation. The mechanisms underlying the enhancing effects are not mediated via the enhanced local expression of proinflammatory cytokines.