Differences in allergic inflammatory responses in murine lungs: comparison of PM2.5 and coarse PM collected during the hazy events in a Chinese city.

Urban particulate matter (PM) is associated with an increase in asthma. PM2.5 (<PM2.5 μm) and coarse PM (CPM: PM2.5-PM10 μm) were collected from the air in a Chinese city during haze events. The amounts of polycyclic aromatic hydrocarbons (PAHs) were higher in PM2.5 than in CPM. Conversely, microbial elements LPS and β-glucan were much higher in CPM than in PM2.5. Concentrations of Si, Al, Fe, and Ti in CPM were greater than in PM2.5, while Pb, Cu and As concentrations were lower than in PM2.5. When RAW264.7 cells were treated with PM2.5 and CPM, the pro-inflammatory response in the cells was associated with the microbial element levels and attenuated partly by both polymyxin B (PMB) and N-acetylcystein (NAC). The expression of the oxidative stress response gene heme oxygenase1 was associated with PAHs levels. The exacerbating effects of the two-types of PM on murine lung eosinophilia were compared to clarify the role of toxic materials. When BALB/c mice were intratracheally instilled with PM2.5 or CPM (total 0.4 mg) + ovalbumin (OVA), both exacerbated lung eosinophilia along with allergy-relevant biological indicators, such as OVA-specific IgE in serum; enhancement of lung pathology when compared with counterpart samples without OVA. The exacerbating effects were greater in microbial element-rich CPM than in organic chemical-rich PM2.5. These results indicate that microbial elements have more potently exacerbating effects on the development of lung eosinophilia than do organic chemicals. In addition, oxidative stress and transition metals might be associated with the exacerbation of this negative effect.