Eosinophil-derived neurotoxin (EDN) in healthy and asthmatic volunteers

Abstract

Introduction: Released from eosinophils, EDN is a biomarker of eosinophilia and eosinophil activation. EDN has potential clinical utility in identifying asthma and COPD patients with an eosinophilic phenotype who may benefit from anti-eosinophilic treatment. Aims and objectives: We established normal EDN concentrations and stability in healthy volunteers, and hypothesised EDN would be elevated in asthmatics and associated with eosinophil activation. Methods: (1) Venous blood samples were collected from 10 healthy volunteers on 3 occasions over 28 days and plasma EDN was measured by ELISA. (2) Blood from an additional 3 healthy volunteers was stored at room temperature for 0, 4, 24, 48 and 72 h before EDN measurement. (3) Blood from an additional 3 healthy volunteers was stimulated with fMLP and CD11b expression and EDN were measured. (4) Plasma EDN was measured in 10 mild to moderate asthma patients with a history of >300 eosinophils/uL. Results: EDN concentrations (mean ±SD) in healthy volunteers on Days 0, 14, and 28 were 6.1 ±1.6, 6.6 ±3.0 and 5.5 ±2.1ng/mL. EDN concentrations in whole blood were stable ≤24 hours. fMLP induced a 190% rise in EDN and a 230% increase in CD11b expression. EDN in asthmatics was 31.7±20.6ng/mL, significantly greater than for healthy volunteers. Conclusions: EDN concentrations were low in healthy volunteers with little variability over 28 days. EDN was stable in whole blood for up to 24h. EDN concentrations were elevated in mild asthmatics. Stimulation of eosinophils caused EDN release and an increase in CD11b expression. EDN is a potential biomarker of eosinophil activation in asthma patients.