URINARY EOSINOPHIL-DERIVED NEUROTOXIN PROTEIN-X - A SIMPLE METHOD FORASSESSING EOSINOPHIL DEGRANULATION IN-VIVO/

Background: Eosinophil-derived neurotoxin/protein X (EDN/EPX), one of the cationic granule proteins released by polymorphonuclear eosinophil s, can be detected in human urine. Objective: We sought to evaluate wh ether the urinary release of EDN/EPX was dependent on the blood eosino phil cell count, the bronchoalveolar eosinophil cell count, or both an d on the clinical diagnosis, We also attempted to determine the precis e kinetics of decrease of EDN excretion and eosinophil counts after th e onset of corticosteroid treatment. Methods: Daily urinary release of EDN/EPX was measured by radioimmunoassay in 28 patients with high hyp ereosinophilia (group 1), 32 patients with moderate hypereosinophilia (group 2), 26 patients without hypereosinophilia at the time of the st udy but with a known pulmonary disease involving eosinophils (group 3) , and 13 control patients (group 4). Results: The urinary excretion of EDN/EPX was significantly higher in patients from groups 1 or 2 than in patients from groups 3 or 4. Particularly high levels of EDN/EPX ex cretion were observed in patients from groups 1 or 2 with chronic eosi nophilic pneumonia (chronic eosinophilic pneumonia: 4.7 +/- 8.1 mg/day , control subjects: 0.39 +/- 0.33 mg/day, p < 0.001), Urinary excretio n of EDN/EPX was significantly correlated with blood (r = 0.66, p < 0. 001) and differential bronchoalveolar (r = 0.62, p = 0.04) eosinophil cell counts in patients from group 1 but not from the other groups, Co rticosteroid treatment was followed by a significant decrease in EDN/E PX excretion. The kinetics of decrease in EDN/EPX were delayed as comp ared with the dramatic drop in peripheral eosinophil counts, Distinct kinetics between urinary EDN/EPX and eosinophil counts differentiated the recurrence of chronic eosinophilic pneumonia from an asthma attack in one patient. Conclusion: Measurement of urinary EDN/EPX excretion may be a useful indicator of eosinophil degranulation in vivo.