Background
Polymorphisms and products of the cyclooxygenase (COX) pathway have been associated with the development of chronic obstructive pulmonary disease (COPD) and adverse outcomes. COX-produced prostaglandin E2 (PGE-2) may play a role in the inflammation observed in COPD, potentially through deleterious airway macrophage polarization. A better understanding of the role of PGE-2 in COPD morbidity may inform trials for therapeutics targeting the COX pathway or PGE-2.
Conclusions
Elevated levels of sputum PGE-2, rather than systemic PGE-2, is associated with increased respiratory symptoms and history of exacerbation among individuals with COPD. Additional studies focused on mechanism of action are warranted.
Methods
Urine and induced sputum were collected from former smokers with moderate-severe COPD. The major urinary metabolite of PGE-2 (PGE-M) was measured, and ELISA was performed on sputum supernatant for PGE-2 airway measurement. Airway macrophages underwent flow cytometry phenotyping (surface CD64, CD80, CD163, CD206, and intracellular IL-1β, TGF-β1). Health information was obtained the same day as the biologic sample collection. Exacerbations were collected at baseline and then monthly telephone calls.
Results
Among 30 former smokers with COPD (mean±SD age 66.4±8.88 years and forced expiratory volume in 1 second [FEV1] 62.4±8.37 percent predicted), a 1 pg/mL increase in sputum PGE-2 was associated with higher odds of experiencing at least one exacerbation in the prior 12 months (odds ratio 3.3; 95% confidence interval: 1.3 to15.0), worse respiratory symptoms and health status. PGE-M was not associated with exacerbations or symptoms. Neither airway PGE-2 nor urinary PGE-M was uniformly associated with an M1 or M2 polarization. Conclusions: Elevated levels of sputum PGE-2, rather than systemic PGE-2, is associated with increased respiratory symptoms and history of exacerbation among individuals with COPD. Additional studies focused on mechanism of action are warranted.