Eosinophilic cytokines and small airway dysfunction in women with COPD: correlation with exposure to biomass smoke versus tobacco smoking

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory disease characterised by progressive airflow obstruction. Tobacco smoking is the leading cause of COPD (COPD-TS); however, chronic exposure to biomass smoke (COPD-BS) is the second risk factor. COPD-TS and COPD-BS are now considered different phenotypes, with COPD-BS having small airway dysfunction (SAD). Our primary aim was to investigate the correlation between SAD and the serum levels of interleukins implicated in the maturation and recruitment of eosinophils in women with COPD-BS and COPD-TS. This cross-sectional study included 25 women with COPD-BS and 25 women with COPD-TS, and the relationship with SAD was assessed by impulse oscillometry (IOS), alongside measurements of interleukins (IL-1ra, IL-2, IL-4, IL-8, IL-9, IL-13, and IL-17) and eotaxin using the multiplex test (Bio-Plex), in addition to eosinophils total blood. Blood eosinophil count, cytokines, and eotaxin were higher in COPD-BS relative to COPD-TS. IOS measurements were higher in COPD-BS than in COPD-TS. R5-R20 positively correlated with the concentrations of all measured cytokines noted if COPD groups were analysed separately (P < 0.01). Eosinophil counts and cytokines in COPD-BS positively correlate with small airway resistance as measured by IOS in R5-R20.