Calcium Modulated Chloride Pathways Contribute to Chloride Flux in Murine CF-Affected Macrophages

摘要

Cystic Fibrosis (CF), a common lethal inherited disorder defined by ion transport abnormalities, chronic infection and robust inflammation, is the result of mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein, a cAMP-activated chloride (Cl⁻) channel. Macrophages are reported to have impaired activity in CF. Previous studies suggest that Cl⁻ transport is important for macrophage function therefore impaired Cl⁻ secretion may underlie CF macrophage dysfunction. To determine if alterations in Cl⁻ transport exist in CF macrophages, Cl⁻ efflux was measured using N-[ethoxycarbonylmethyl]-6-methoxyquinolinium bromide (MQAE), a fluorescent indicator dye. The contribution of CFTR was assessed by calculating Cl⁻ flux in the presence and absence of cftrinh-172. The contribution of calcium (Ca²⁺) modulated Cl⁻ pathways was assessed by examining Cl⁻ flux with varied extracellular Ca²⁺ concentrations, or following treatment with carbachol or thapsigargin, agents that increase intracellular Ca²⁺ levels. Our data demonstrate that CFTR contributed to Cl⁻ efflux only in WT macrophages, while Ca²⁺-mediated pathways contributed to Cl⁻ transport in CF and WT macrophages. Furthermore, CF macrophages demonstrated augmented Cl⁻ efflux with increases in extracellular Ca²⁺. Taken together, this suggests that Ca²⁺-mediated Cl⁻ pathways are enhanced in CF macrophages compared to WT macrophages.