Contribution of endotoxin in macrophage cytokine response to ambient particles in vitro

Ambient particles may cause pulmonary inflammation with ensuing morbidity. Particle-induced production of proinflammatory cytokines in vitro has been used as an indicator of particle toxicity. To identify particle components that were related to particle toxicity, Andersen dichotomous impactors were used to collect ambient fine (PM2.5) and coarse (PM2.5-10) particles in central Taiwan with extraction in endotoxin-free water. Mouse monocyte-macrophage cell line RAW 264.7 cells were exposed to particle extracts at 40 mug/ml for 16 h, and tumor necrosis factor-alpha (TNF-alpha) was measured in the medium by enzyme-linked immunosorbent assay (ELISA). Cell viabilities were all greater than 82%. Coarse particles stimulated higher TNF-alpha production than fine particles, and this was associated with greater particulate endotoxin content. Polymyxin B inhibited 42% of TNF-alpha production elicited by coarse particles and 32 % of TNF-alpha production elicited by fine particles. In fine particles, TNF-alpha production was negatively correlated with Zn content, while no element in coarse particles correlated with TNF-alpha production. Results suggest that endotoxin and other components may be important factors for TNF-alpha production by macrophages in vitro.