IBUPROFEN INHIBITS CYSTIC-FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR-MEDIATED CL- SECRETION

We evaluated the acute effects of ibuprofen and salicylic acid on cAMP -mediated Cl- secretion (I-SC) in both colonic and airway epithelia, I n T84 cells, ibuprofen inhibited the forskolin-dependent I-SC in a con centration-dependent manner, having an apparent K-i of 142 mu M. Salic ylic acid inhibited I-SC with an apparent K-i of 646 mu M. We determin ed whether ibuprofen would also inhibit the forskolin-stimulated I-SC in primary cultures of mouse trachea epithelia (MTE) and human bronchi al epithelia (HBE). Similar to our results in T84 cells, ibuprofen (50 0 mu M) inhibited the forskolin-induced I-SC in MTEs and HBEs by 59+/- 4% (n = 11) and 39+/-6% (n = 8), respectively. Nystatin was employed t o selectively permeabilize the basolateral or apical membrane to deter mine the effect of ibuprofen on apical Cl- (I-Cl) and basolateral K+ ( I-K) currents after stimulation by forskolin, After forskolin stimulat ion, ibuprofen (500 mu M) reduced both the I-Cl and I-K; reducing I-Cl and I-K by 60 and 15%, respectively. To determine whether this inhibi tion of I-Cl was due to the inhibition of CFTR, the effects of ibuprof en and salicylic acid on CFTR Cl- channels in excised, inside-out patc hes from L-cells were evaluated. Ibuprofen (300 mu M) reduced CFTR Cl- current by 60+/-16% and this was explained by a short-lived block (si milar to 1.2 ms) which causes an apparent reduction in single channel amplitude from 1.07+/-0.04 pA to 0.59+/-0.04 pA (n = 3), Similarly, sa licylic acid (3 mM) reduced CFTR Cl- current by 50+/-8% with an appare nt reduction in single channel amplitude from 1.08+/-0.03 pA to 0.48+/ -0.06 pA (n = 4), Based on these results, we conclude that the NSAIDs ibuprofen and salicylic acid inhibit cAMP-mediated Cl- secretion in hu man colonic and airway epithelia via a direct inhibition of CFTR Cl- c hannels as well as basolateral membrane K+ channels. This may reduce t heir efficacy in conjunction with other therapeutic strategies designe d to increase CFTR expression and/or function in secretory epithelia.