Dual Pathway Activated by tert-Butyl Hydroperoxide in Human Airway Anion Secretion

Abstract

We analyzed the mechanisms underlying the ion transport induced by tert-butyl hydroperoxide (t-BOOH), a membranepermeant oxidant that has been widely used as a model of oxidative stress, in human airway epithelial cells (Calu-3). We found that t-BOOH induced a short-circuit current that was composed of two distinct components, a peaked component (PC) and a sustained component (SC). Both components were reduced by the presence of H-89 (N-[2-(4-bromocinnamylamino)ethyl]-5-isoquinoline) [10 M, a protein kinase A (PKA) inhibitor] and clofilium (100 M, a cAMP-dependent K ϩ channel inhibitor) but not by charybdotoxin (50 nM, a human intermediate conductance Ca 2ϩ -activated K ϩ channel inhibitor), suggesting that both PC and SC were generated through a common PKA-dependent/Ca 2ϩ -independent pathway. Notwithstanding, analyses of the physiological properties revealed that PC and SC were attributable to different pathways. PC, but not SC, was correlated with apical membrane Cl Collectively, t-BOOH induces PKA-related anion secretion through two independent pathways: rapid activation of apical anion efflux through a COX-2-dependent/cytoskeleton-independent pathway and relatively delayed activation of NKCC1 for basolateral anion uptake through a COX-2-independent/cytoskeletondependent pathway.