Altered intracellular pH regulation in neutrophils from patients with cystic fibrosis

Abstract

Cystic fibrosis (CF) is a condition characterized by neutrophil-mediated lung damage and bacterial colonization. The physiological basis for reported functional alterations in CF neutrophils, including increased release of neutrophil elastase, myeloperoxidase, and oxidants, is unknown. These processes are, however, regulated by intracellular pH (pHi). We demonstrate here that pHiregulation is altered in neutrophils from CF patients. Although resting pHiis similar, pHiafter acid loading and activation ( N-formyl-methionyl-leucyl-phenylalanine and phorbol 12-myristate 13-acetate) is more acidic in CF cells than in normal cells. Furthermore, patients with non-CF-related bronchiectasis handle acid loading and activation in a fashion similar to subjects with normal neutrophils, suggesting that chronic pulmonary inflammation alone does not explain the difference in pHi. This is further supported by data showing that normal neutrophils exposed to the CF pulmonary milieu respond by increasing pHias opposed to decreasing pHias seen in activated CF neutrophils. These pHidifferences in activated or acid-loaded CF neutrophils are abrogated by ZnCl2but not by amiloride and bafilomycin A1, suggesting that passive proton conductance is abnormal in CF. In addition, DIDS, which inhibits HCO3−/Cl−exchange, causes alkalinization of control but not of CF neutrophils, suggesting that anion transport is also abnormal in CF neutrophils. In summary, we have shown that pHiregulation in CF neutrophils is intrinsically abnormal, potentially contributing to the pulmonary manifestations of the condition.