Ozone exposure enhances mast-cell inflammation in asthmatic airways despite inhaled corticosteroid therapy

Abstract

Asthmatics are recognised to be more susceptible than healthy individuals to adverse health effects caused by exposure to the common air pollutant ozone. Ozone has been reported to induce airway neutrophilia in mild asthmatics, but little is known about how it affects the airways of asthmatic subjects on inhaled corticosteroids. We hypothesised that ozone exposure would exacerbate the pre-existent asthmatic airway inflammation despite regular inhaled corticosteroid treatment. Therefore, we exposed subjects with persistent asthma on inhaled corticosteroid therapy to 0.2 ppm ozone or filtered air for 2 h, on 2 separate occasions. Lung function was evaluated before and immediately after exposure, while bronchoscopy was performed 18 h post exposure. Compared to filtered air, ozone exposure increased airway resistance. Ozone significantly enhanced neutrophil numbers and myeloperoxidase levels in airway lavages, and induced a fourfold increase in bronchial mucosal mast cell numbers. The present findings indicate that ozone worsened asthmatic airway inflammation and offer a possible biological explanation for the epidemiological findings of increased need for rescue medication and hospitalisation in asthmatic people following exposure to ambient ozone.

Keywords::

• Airway inflammation
• air pollution
• BAL
• bronchial mucosa
• myeloperoxidase
• neutrophil

Acknowledgments

The authors thank Ann-Britt Lundström, Lena Skedebrant, Maj-Cari Ledin, Annika Hagenbjörk-Gustafsson, Ulf Hammarström, Gerd Lindén, and Helén Bertilsson for expert technical assistance. This work was generously supported by grants from the Swedish Heart-Lung Foundation, Swedish Asthma and Allergy Association, Vårdal Foundation, and Umeå University.

Declaration of interest: The authors report no conflict of interest.