Prostaglandin E2 and cysteinyl leukotriene concentrations in sputum: association with asthma severity and eosinophilic inflammation

Background Inflammation of the airways in asthma is associated with the production of cysteinyl leukotrienes (cysLT), prostaglandin (PG)E₂, 8‐isoprostane, nitric oxide and other mediators. However, the relationship between asthma severity or eosinophilic inflammation and the concentrations of mediators in sputum is unclear. Objective To assess sputum PGE₂, cysLT, 8‐isoprostane and nitrate concentrations, as well as urinary leukotriene (LT)E₄ and 9α,11β‐prostaglandin (PG)F₂ concentrations, in patients with differing severities of asthma and eosinophilic or non‐eosinophilic airway inflammation. Methods Inflammatory cells in sputum were assessed in 12 patients with mild, 14 with moderate and 12 with severe persistent asthma, as well as in 13 control subjects. Asthmatic patients were categorized into those with eosinophilic or non‐eosinophilic airway inflammation. Sputum PGE₂, cysLT and 8‐isoprostane, and urinary LTE₄ were extracted on immunoaffinity sorbents, and the concentrations of all mediators were measured using enzyme immunoassays. Sputum nitrate concentrations were measured on a chemiluminescence analyzer. Results Sputum PGE₂ concentrations were higher in both moderate (1710 pg/mL) and severe asthmatic (1590 pg/mL) compared with control subjects (827 pg/mL) (P<0.05). CysLT concentrations were higher in moderate asthmatic compared with control or severe asthmatic subjects (P<0.05). Sputum PGE₂ concentrations were lower in patients with eosinophilic (1180 pg/mL) compared with non‐eosinophilic airway inflammation (2520 pg/mL) (P=0.02). In contrast, sputum cysLT and urinary LTE₄ concentrations were higher in those with eosinophilic airway inflammation (P<0.05). Forced expiratory volume in 1 s was inversely correlated with sputum eosinophils in all asthmatic patients (r_s=?0.5, P=0.002). There were no significant differences in sputum 8‐isoprostane or nitrate concentrations. Conclusions Increased airway concentrations of PGE₂ are consistent with the hypothesis that PGE₂ has a bronchoprotective and anti‐inflammatory role in patients with more severe asthma. A reduced PGE₂ to cysLT ratio in the airways may adversely affect lung function and contribute to persistence of symptoms and airway remodelling in patients with eosinophilic airway inflammation. Cite this as: S. Aggarwal, Y. P. Moodley, P. J. Thompson and N. L. Misso, Clinical & Experimental Allergy, 2010 (40) 85–93.