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 µm (PM(2.5)) 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 PM(2.5) (PPP(2.5)), which are composed primarily of carbon, are responsible for the toxicity caused by ambient particulate matter (original PM(2.5) particles, OPP(2.5)) is currently unclear. The present study assessed the acute toxic effects of OPP(2.5) sampled in Beijing, China and of its PPP(2.5) fraction in male BALB/c mice. The mice were intratracheally instilled with a single dose of aerosolized OPP(2.5) or PPP(2.5). 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 OPP(2.5) and PPP(2.5) 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. OPP(2.5) induced a stronger inflammatory response than PPP(2.5). The complex components adsorbed into the solid core granules of OPP(2.5) and the granules themselves contributed to the toxic effects.