Dose but not sex determines inflammatory responses to acute diesel exhaust particle exposure in mice

Background:Currently diesel exhaust particles (DEP), produced from the combustion of fossil fuels by diesel powered motor vehicles, are the major contributor to particulate pollution in urban areas. Due to the small size of DEPs the particles remain suspended for long periods of time, are easily inhaled and they are able to penetrate deeply into the lungs, indicating that exposure to these particles may have potentially serious consequences on respiratory health. We examined this possibility and determined whether dose and sex had an effect on DEP induced inflammation.

Methods:Eight-week BALB/c mice were given 10 lg, 30 lg or 100 lg of DEP in 50 lL saline and 0.05% Tween-80 (or saline and Tween-80 alone) under light methoxyflurane anaesthesia. Following exposure cellular inflammation was examined at 3, 6, 12 and 24 hours via bronchoalveolar lavage (BAL). Total (TCC) and differential cell counts were performed on all BAL fluid.

Results: There was no increase in TCC in mice exposed to 10 or 30 lg DEP for either sex. In contrast, both male (p < 0.001) and female (p < 0.001) mice exposed to 100 lg DEP had an increase in TCC which peaked at 6 hours. The response was reduced but still detectable after 24 hours. This inflammatory response was entirely comprised of macrophages and neutrophils with the macrophage response appearing to peak earlier than the neutrophil response. There did not appear to be any sex related difference in response.

Conclusions: This study showed that exposure to diesel exhaust particles induced cellular inflammation in the lungs, and that it was primarily dose rather than sex that determined the response. This increase in cellular inflammation that was still apparent after 24 hours indicated that exposure to these and other fossil fuel products has the potential to impact on respiratory health and the exacerbation of respiratory illness.