Glibenclamide blockade of CFTR chloride channels

Abstract

The cystic fibrosis transmembrane conductance regulator (CFTR) is a protein kinase A- and ATP-regulated Cl- channel located in the apical membranes of epithelial cells. Previously Sheppard and Welsh (J. Gen. Physiol. 100: 573-591, 1992) showed that glibenclamide, a compound which binds to the sulfonylurea receptor and thus blocks nucleotide-dependent K+ channels, reduced CFTR whole cell current. The aim of this study was to identify the mechanism underlying this inhibition in cell-free membrane patches containing CFTR Cl- channels. Exposure to gliben-clamide caused a reversible reduction in current carried by CFTR which was paralleled by a decrease in channel open probability (Po). The decrease in Po was concentration dependent, and half-maximum inhibition (ki) occurred at 30 microM. Fluctuation analysis indicated a flickery-type block of open CFTR channels. Event duration analysis supported this notion by showing that the glibenclamide-induced decrease in Po was accompanied by interruptions of open bursts [i.e., an apparent reduction in the burst duration (Tburst)] with only a slight reduction in closed time (Tc). The plot of the corresponding open-to-closed (Tburst-1) and closed-to-open (Tc-1) rates as a function of glibenclamide concentration were consistent with a pseudo-first-order open-blocked mechanism and provided estimates of the on rate (kon = 1.17 microM-1S-1), the off rate (koff = 16 s-1), and the dissociation constant (Kd = 14 microM). The difference between the Ki (30 microM) and the Kd (14 microM) is the result expected for a closed-open-blocked model with an initial Po of 0.47. Since the initial Po was 0.50 +/- 0.02 (n = 12), we can conclude that glibenclamide blocks CFTR by a closed-open-blocked mechanism.

Activating Cystic Fibrosis Transmembrane Conductance Regulator Channels with Pore Blocker Analogs

“…3B) and (ii) inhibition by higher doses of NPPB (Fig. 1, E and F) or by 200 M glibenclamide, another CFTR blocker (17). (At lower doses, glibenclamide could partially mimic the stimulatory effect of NPPB (data not shown).)…”

Fluid Secretion Caused by Aerolysin-Like Hemolysin of Aeromonas sobria in the Intestines Is Due to Stimulation of Production of Prostaglandin E 2 via Cyclooxygenase 2 by Intestinal Cells

“…To elucidate whether the CFTR channel, a plasma membrane Cl Ϫ channel, is involved in fluid accumulation caused by hemolysin, the effects of H-89, a cAMP-dependent protein kinase A (PKA) inhibitor (7,27), and glibenclamide, a selective CFTR inhibitor (34,35), were examined. For the control experiment, CT, which causes diarrhea through the activation of CFTR (18,23), was used.…”

Evidence for Up-regulation of the Endogenous Na-K-2Cl Co-transporter by Molecular Interactions with the Anion Exchanger tAE1 Expressed in Xenopus Oocyte

“…Classical inhibitors of tAE1 anion conductance such as NPPB or niflumic acid could not be used to distinguish tAE1 conductance and activation of the co-transporter because these two compounds also inhibit with high efficiency the NKCC co-transport stimulated by hyperosmolarity (5 ϫ 10 Ϫ4 M of NPPB inhibited 100 Ϯ 0.3% of the Cl-dependent Rb influx activated by hyperosmolarity (n ϭ 8) and niflumic acid at 5 ϫ 10 Ϫ4 M inhibited this Rb influx by 90 Ϯ 3%, n ϭ 8). So we used glybenclamide, inhibitor of the CFTR as well as other anion conductances (23,24). As illustrated in Fig.…”