Influence of fine particulate matter and its pure particulate fractions on pulmonary immune cells and cytokines in mice

Particulate matter with a diameter <= 2.5 mu m (PM2.5) has a complex composition and has been associated with the incidence of cardiopulmonary disease and premature death in humans. However, whether pure particulate fractions of PM2.5 (PPP2.5), which are composed primarily of carbon, are responsible for the toxicity caused by ambient particulate matter (original PM2.5 particles, OPP2.5) is currently unclear. The present study assessed the acute toxic effects of OPP2.5 sampled in Beijing, China and of its PPP2.5 fraction in male BALB/c mice. The mice were intratracheally instilled with a single dose of aerosolized OPP2.5 or PPP2.5. Blood, lungs and bronchoalveolar lavage fluid were collected after 24 h for histopathology, flow cytometry and the measurement of pro-inflammatory cytokines/chemokines and other biochemical factors. Both OPP2.5 and PPP2.5 caused acute toxicity, particularly inflammatory responses, including an increase in the levels of pro-inflammatory cytokines and an accumulation of numerous immune cells in the lungs. OPP2.5 induced a stronger inflammatory response than PPP2.5. The complex components adsorbed into the solid core granules of OPP2.5 and the granules themselves contributed to the toxic effects.