Metal composition of ambient PM2.5 influences severity of allergic airways disease in mice

Children living in Hettstedt in eastern Germany have been reported to have a higher prevalence of sensitization to common aeroallergens than another cohort living in the neighboring city of Zerbst; these differences correlated with the presence of industrial air pollution. Samples of fine particulate matter (< 2.5 mum aerodynamic diameter; PM2.5) collected in Hettstedt in 1999 had several-fold higher levels of zinc, magnesium, lead, copper, and cadmium than samples from Zerbst. To determine if the results from epidemiologic studies could be repeated in an animal model, we administered PM2.5 from Hettstedt and Zerbst to ovalbumin-allergic mice. In Balb/c mice, PM2.5 from Hettstedt, but not PM2.5 from Zerbst or control filter extract, caused a significant increase in immediate responses to ovalbumin challenge when aspirated 2 hr before challenge, but not when aspirated immediately before sensitization 2 weeks earlier. Antigen-specific IgE was increased by Flettstedt PM2.5 whether administered before sensitization or challenge. Airway responsiveness to methacholine aerosol and lung inflammatory cell numbers were significantly increased only, in allergic mice exposed to Hettstedt PM2.5 before challenge. Both Hettstedt and Zerbst PM2.5 significantly increased lung injury parameters and proinflammatory cytokines. These results are consistent with epidemiologic findings and show that metal composition of ambient PM, 5 influences the severity of allergic respiratory disease.