EFFECTS OF ACTIVATED EOSINOPHILS CULTURED FROM HUMAN UMBILICAL-CORD BLOOD ON GUINEA-PIG TRACHEALIS

We studied the biochemical indexes and corresponding induction of airw ay smooth muscle contraction and hyperresponsiveness in guinea pig tra chealis in situ caused by cultured eosinophils derived from mononuclea r cell fractions of human umbilical cord blood. A method was developed that permitted isolation of large numbers of cells (approximately 2.6 x 10(6)/ml cord blood) having morphological and immunohistological ch aracteristics of human peripheral blood eosinophils. After activation with 10(-6) M formyl-Met-Leu-Phe + 5 mug/ml cytochalasin B (fMLP + B), in situ application to the epithelial surface of 6 X 10(6) cord-deriv ed eosinophils (CDE)/surface area (CM2) caused 1.46 +/- 0.24 g/cm maxi mal active tracheal tension in guinea pig tracheal smooth muscle (P < 0.005 vs. zero baseline). Muscarinic responsiveness also was augmented in situ in trachealis preparations treated with activated 3-wk CDE. C ontraction caused by 3 x 10(-7) Mol/k g iv methacholine (MCh) was 0.94 +/- 0.18 g/cm at baseline vs. 1.80 +/- 0.24 g/cm after activated CDE (P = 0.02). Control (sham-activated) 3-wk CDE caused neither significa nt contraction [0.41 +/- 0.16 g/cm active tension (AT); P < 0.05 vs. f MLP + B] nor augmented muscarinic responsiveness. Cells cultured for 5 wk contained fewer granules than 3-wk CDE and also caused less direct contraction of trachealis (0.73 +/- 0.14 g/cm AT) after activation (P < 0.01 vs. 3-wk CDE). Both contraction and muscarinic augmentation we re blocked in 3-wk CDE after blockade of leukotriene C4 (LTC4) synthes is by pretreatment with the 5-lipoxygenase inhibitor, A63162 (50 muM). Treatment with A63162 had no effect on the stimulated release of eosi nophil peroxidase. Application of exogenous LTC4 (100-300 pg/ml) cause d similar contractile responses. We demonstrate that eosinophils, whic h can be derived in large numbers and high purity by culture from huma n cord blood, cause airway smooth muscle contraction and augmentation of muscarinic responsiveness. This results from activation of the 5-li poxygenase pathway caused by stimulation with fMLP + B. Physiological activation of guinea pig trachealis is not correlated with the secreti on of the granular protein, eosinophil peroxidase.