Role of eosinophils in airway inflammation of chronic obstructive pulmonary disease

Abstract

COPD is a significant cause of morbidity and mortality. In some patients with COPD, eosinophils contribute to inflammation that promotes airway obstruction; approximately a third of stable COPD patients have evidence of eosinophilic inflammation. Although the eosinophil threshold associated with clinical relevance in patients with COPD is currently subject to debate, eosinophil counts hold potential as biomarkers to guide therapy. In particular, eosinophil counts may be useful in assessing which patients may benefit from inhaled corticosteroid therapy, particularly regarding exacerbation prevention. In addition, several therapies targeting eosinophilic inflammation are available or in development, including monoclonal antibodies targeting the IL5 ligand, the IL5 receptor, IL4, and IL13. The goal of this review was to describe the biologic characteristics of eosinophils, their role in COPD during exacerbations and stable disease, and their use as biomarkers to aid treatment decisions. We also propose an algorithm for inhaled corticosteroid use, taking into consideration eosinophil counts and pneumonia history, and emerging eosinophil-targeted therapies in COPD.

Inhaled corticosteroids for chronic obstructive pulmonary disease: what is their role in therapy?

“…Skin bruising and oral candidiasis were increased with ICS therapy in most studies 7,8,10,43,58. In a subset of patients from the Lung Health Study, no effect of ICSs on adrenal function was observed over the 3-year study duration 59.…”

“…Moreover, therapeutic agents targeting eosinophils, namely anti-IL5 and anti-IL5-receptor monoclonal antibodies, have been evaluated to reduce the risk of exacerbations in COPD patients with high eosinophil counts and a history of exacerbations despite optimized standard-of-care therapy;43 however, results have been inconsistent 93–95…”

Clinical differences between eosinophilic and non-eosinophilic acute exacerbation of chronic obstructive pulmonary disease (AECOPD), a multicenter cross-sectional study

“…In recent years, amount of studies showed that blood eosinophil is an effective, stable, and available biomarker in COPD, which can be used to de ne the phenotypes of COPD [17,25,34,35]. However, the cut-off value of blood EOS is still in debate, ranging from 150 to 400 cells/μL and/or 2% to 4% in different studies [17,18,22,24,25,[34][35][36]. Then, in this study, both 200 cells/μL and 300 cells/ μL, and, 2% and 3% were considered as the cut-off values of blood EOS counts and EOS% in AECOPD patients (Figure 1).…”

“…Many studied showed that blood EOS was considered to be a reasonably good predictor of EOS in airways in COPD patients [22,37,38]. Eltboli O et al showed that the strong correlations between blood EOS% and the submucosal eosinophil counts (r = 0.57) and reticular basement membrane (RBM) thickness (r = 0.59) were found in COPD [37].…”

“…However, mounting evidence reported that sputum and blood eosinophils also increased in a subset of COPD patients [17,21,22]. Several studies showed that higher blood eosinophil counts were associated with an increased risk of readmission, severe lung function impairment, and longer length hospital stay (LHS) in COPD [23][24][25][26].…”