ACTIVATED EOSINOPHILS EVOKE CHLORIDE SECRETION IN MODEL INTESTINAL EPITHELIA PRIMARILY VIA REGULATED RELEASE OF 5'-AMP

Eosinophils may be prominent in intestinal diseases including allergic gastroenteritis, inflammatory bowel disease, enteritis associated wit h hypereosinophilic syndromes (HES), and parasitic diseases. Unlike no rmal blood eosinophils, those that circulate in HES and those that inf iltrate inflamed tissue exhibit an ''activated'' phenotype. To model i ntestinal epithelial-eosinophil interactions, we used peripheral blood eosinophils and human crypt-like T84 epithelial cell-line monolayers. Eosinophils from normal, mildly atopic donors, only if activated by P MA or primed with granulocyte-macrophage-CSF for 48 h, as well as eosi nophils from HES patients elicited a short circuit current when applie d apically to T84 monolayers. This eosinophil-derived bioactivity, whi ch was transferable in cell-free supernatants and in <1000 m.w. ultraf iltrates, stimulated electrogenic Cl- secretion, as indicated by inhib ition with basolateral bumetanide or gluconate substitution and by enh ancement of the rate constant for I-125 efflux from preloaded T84 cell s. This secretagogue activity was blocked in both intact activated eos inophils and in eosinophil-conditioned supernatants, by 8-phenyl-theop hylline, indicating involvement of an adenosine receptor. Ion exchange and reversed-phase HPLC analyses demonstrated that eosinophil superna tant ultrafiltrates contained elevated levels of 5'-AMP that was conve rted to adenosine after incubation with epithelium. Inhibition of epit helial apical membrane ecto-5'-nucleotidase ablated the conversion to adenosine. These studies establish that activated eosinophils elicit C l- secretion from intestinal epithelia and that 5'-AMP released by eos inophils followed by its conversion to adenosine at the epithelial sur face is the basis for this response.