In vitro effect of air pollutants on human bronchi

A useful approach for constructing dose-response relationships and for studying the underlying mechanisms by which a xenobiotic agent enhances airway reactivity is to measure the response of an isolated airway following ex vivo exposure to a pollutant. We have in this way determined the dose-response relationship between ex vivo exposure to pollutants such as nitrogen dioxide (NO2), the aldehyde acrolein, and ozone (O3) and the reactivity to agonists in human isolated bronchial smooth muscle. We have also investigated the underlying alteration in the cellular mechanisms of airway smooth-muscle contraction induced by such exposure and found that it is related to alteration in calcium signaling at the site of the airway smooth-muscle cell. Finally, although there is epidemiological evidence that an increase in allergic diseases such as asthma may be linked to air pollution, there are few experimental data to address this issue. The final aim of this study was therefore to investigate the interaction between passive sensitization and exposure to pollutants in human isolated airways. We have examined (i) the effect of a pre-exposure to pollutants on the contraction of sensitized bronchi in response to a specific antigen and (ii) the effect of passive sensitization on the contraction in response to nonspecific agonists in bronchi pre-exposed to pollutants. The results indicate a combined effect of immunological sensitization and exposure to pollutants; that is, passive sensitization and exposure to pollutants act in a synergistic manner on human bronchial smooth-muscle reactivity in response to both specific antigens and nonspecific agonists.