Ozone exaggerates nasal allergic inflammation

A double-blind randomised trail design was used to address the effect of ambient ozone on the nasal airways and to evaluate the effects of ozone on allergic mucosa. Ten grass pollen allergic rhinitics were exposed for 2 hours at rest on 2 separate occasions to 400 ppb ozone and filtered air respectively. The exposure to 400 ppb ozone and filtered air was performed prior to the grass pollen season and again during the season. Baseline nasal lavage in which histamine, eosinophil cationic protein (ECP), myeloperoxidase (MPO), total proteins, and albumin were measured and neutrophils, eosinophils and epithelial cells were counted, was made immediately prior to exposure (-120 min). After 2 h of exposure to ozone/filtered air repeated measurements were performed at 0, 30, 60, 120, 240, 360 minutes post exposure. Significant increases were observed when exposed to ozone versus filtered air during the pollen season for histamine (AUC1; p=0.05), MPO (AUC2; p=0.05), ECP (AUC2; p=0.008), total proteins (AUC, p=0.02; AUC1, p=0.007; AUC2, p=0.05), and albumin (AUC, p=0.007; AUC1, p=0.02; AUC2, p=0.005). There was also a significant increase in the total protein level (AUC, p=0.05; AUC1, p=0.02; AUC2 p=0.05) and albumin (AUC, p=0.03; AUC1, p=0.03; AUC2, p=0.04) after ozone exposure versus air out of season. Significant increase of the neutrophils (p=0.01 and p=0.007) in the nasal lavage fluid (NLF) at time points 0 min and 360 min respectively were observed, while eosinophils and epithelial cells significantly increased only at time point 360 min (p=0.02 and p=0.02 respectively) all of them after ozone exposure versus filtered air during the season. Neutrophils also significantly increased in the NLF at time point 0 min and 360 min (p=0.03 and p=0.01) while epithelial cells increased only at time point 360 min (p=0.01) after ozone exposure versus filtered air out of season. We can conclude that ozone induces neutrophil and eosinophil recruitment into the nose and this is accompanied by activation, as evidenced by release of MPO and ECP in NAL. Pre-existing allergic mucosal inflammation during the pollen season, exaggerates the response to ozone, particularly in relationship to the recruitment of eosinophils and neutrophils 6h following exposure.