Acute ozone (O3) exposure potentiates early phase response to allergen in sensitized brown norway rats

The photochemical air pollutant ozone has been shown to exacerbate the severity of asthma. This exacerbation of asthma may in part be due to 1) the greater bronchoconstrictive response to ozone inhalation observed in asthmatic subjects and 2) increased responsiveness to allergen challenge in atopic asthmatics. Eight to 10 week old, male Brown‐Norway rats were sensitized and challenged with house dust mite (HDM) allergen using the protocol of Singh et al (Am J Physiol Lung Cell Mol Physiol 284:L588–L598, 2003). The night before the 3 rd HDM or saline challenge, rats were exposed for 8 hours to 1.0 ppm O3 (or filtered air, FA) followed by 8 hr of FA. Following exposure rats were anesthetized and instrumented. Airway resistance (RAW) was monitored continuously. Once baseline measurements were completed the animal was given it's 3 rd HDM or saline challenge and data were averaged every 30 minutes for the next 6 hours. O3 exposure in sensitized and challenged rats (SC/O3) resulted in significantly greater bronchoconstriction compared to all the other groups (p ≤ 0.05). Thirty minutes following allergen and/or saline challenge there was an increase in RAW with the increase in the SC/O3 rats being significantly greater than all other groups (p ≤ 0.05). A late‐phase response was not observed in any of the groups. HDM sensitization and challenge resulted in a significant increase of bronchoalveolar lavage eosinophils (p ≤ 0.05) with no effect of O3 exposure. These data demonstrate that O3 exposure results in a greater increase in RAW and early phase response to HDM allergen in sensitized and challenged Brown‐Norway rats. Funded by NIEHS RO1 ES06791.