Supplementary Material for: Sputum Eicosanoid Profiling in Exacerbations of Chronic Obstructive Pulmonary Disease

Background: Eicosanoids are small lipid molecules with diverse biological functions in the airways. Objectives: The aim of this study was to investigate changes in leukotriene B₄ (LTB₄), 8-isoprostane, prostaglandin E₂ (PGE₂) and cysteinyl-leukotriene (cys-LT) levels in the sputum of patients with chronic obstructive pulmonary disease (COPD) at the onset of a severe exacerbation and during the course of recovery. Methods: Thirty-seven ex-smoker COPD patients suffering an episode of acute exacerbation were enrolled. Samples were taken (i) on hospital admission and (ii) after regular treatment. Twenty-five stable ex-smoker COPD patients served as controls. Eicosanoids were determined by enzyme immunoassay. Results: Sputum PGE₂ [39.8 (13.3-103.3) vs. 5.05 (2.3-12.1) pg/ml, p < 0.001], 8-isoprostane [89.5 (36.9-184.7) vs. 29.7 (13.8-68.8) pg/ml, p < 0.01] and LTB₄ [587.7 (252.9-774.8) vs. 276.1 (105.4-594.7) pg/ml, p < 0.05] levels were increased in patients with exacerbation compared to stable subjects. After treatment only PGE₂ levels decreased significantly [at discharge: 19.6 (4.6-52.5) pg/ml, p < 0.01], the levels of other eicosanoids remained elevated (p = NS). Sputum cys-LT levels were similar in stable patients and in those with exacerbation and treatment did not influence cys-LTs either. There was a significant correlation between PGE₂ and sputum neutrophil and lymphocyte cell counts in patients with exacerbation. Conclusions: Our results suggest that 8-isoprostane, LTB₄ and PGE₂ but not cys-LTs may be involved in exacerbation-associated inflammatory processes in the airways of patients with COPD. Validation of PGE₂ for use as a biomarker of recovery from an exacerbation requires further studies.