CONTRACTION OF HUMAN BRONCHIAL SMOOTH-MUSCLE CAUSED BY ACTIVATED HUMAN EOSINOPHILS

We assessed the effect of activated eosinophils isolated from human pe ripheral blood in causing contraction of explanted human bronchi in vi tro. Sixty-three epithelium-intact fifth generation airway sections we re obtained from 16 subjects undergoing lung resection for carcinoma. Eosinophils were isolated by negative immunoselection, and activation with 10(-7) M platelet-activating factor (PAF) was confirmed by measur ements of eosinophil peroxidase (EPO) secretion and superoxide (O-2(-) .) generation. EPO secretion increased from 68.6 +/- 13.4 ng/10(6) cel ls to 420 +/- 125 ng/10(6) cells after activation with PAF (P < 0.05). Similarly, PAF-induced O-2(-). generation increased from 15.3 +/- 4.6 4 nmol cytochrome c reduced/10(5) cells to 44.2 +/- 8.50 nmol cytochro me c reduced/10(5) cells (P < 0.05). Cells were instilled into an isol ated airway pouch preparation, and, 60 min later, airway contractile r esponses were determined by optical micrometry as percent decrease in lumenal diameter (%decrease) and percent increase in wall thickness (% increase) using a calibrated magnifying lens. Treatment with either ve hicle, PAF alone, or untreated eosinophils had no effect on airway cal iber or thickness. PAF-activated cells caused a 30.5 +/- 1.52% decreas e in airway caliber (P < 0.001 vs. untreated cells) and a 36.6 +/- 2.5 4% increase in wall thickness (P < 0.001 vs. untreated cells). Preincu bation with A63162, a 5-lipoxygenase inhibitor, caused concentration-d ependent inhibition of airway narrowing. After 10(-5) M A63162, decrea se in airway diameter caused by PAF was 8.00 +/- 0.10% vs. 30.5 +/- 1. 52% for PAF alone (P < 0.01). Cyclooxygenase inhibition with indometha cin caused a lesser inhibition of airway narrowing to 22.4 +/- 1.85% ( P < 0.05 vs. PAF-treated cells). We demonstrate that PAF-activated eos inophils cause direct contraction of human airway smooth muscle predom inantly, but not solely, through activation of the 5-lipoxygenase path way in these cells. We further demonstrate that this airway contractio n is accompanied by increase in wall thickness and not related to chan ges in wet-to-dry weight ratio in contracted airways.