Altered intracellular pH regulation in neutrophils from patients with cystic fibrosis

Cystic fibrosis (CF) is a condition characterized by neutrophil-mediated lu ng damage and bacterial colonization. The physiological basis for reported functional alterations in CF neutrophils, including increased release of ne utrophil elastase, myeloperoxidase, and oxidants, is unknown. These process es are, however, regulated by intracellular pH (pH(i)). We demonstrate here that pH(i) regulation is altered in neutrophils from CF patients. Although resting pH(i) is similar, pH(i) after acid loading and activation (N-formy l-methionyl-leucyl-phenylalanine and phorbol 12-myristate 13-acetate) is mo re acidic in CF cells than in normal cells. Furthermore, patients with non- CF-related bronchiectasis handle acid loading and activation in a fashion s imilar to subjects with normal neutrophils, suggesting that chronic pulmona ry inflammation alone does not explain the difference in pH(i). This is fur ther supported by data showing that normal neutrophils exposed to the CF pu lmonary milieu respond by increasing pH(i) as opposed to decreasing pH(i) a s seen in activated CF neutrophils. These pH(i) differences in activated or acid-loaded CF neutrophils are abrogated by ZnCl2 but not by amiloride and bafilomycin A(1), suggesting that passive proton conductance is abnormal i n CF. In addition, DIDS, which inhibits HCO3-/Cl- exchange, causes alkalini zation of control but not of CF neutrophils, suggesting that anion transpor t is also abnormal in CF neutrophils. In summary, we have shown that pH(i) regulation in CF neutrophils is intrinsically abnormal, potentially contrib uting to the pulmonary manifestations of the condition.