PBA increases CFTR expression but at high doses inhibits Cl⁻secretion in Calu-3 airway epithelial cells

Abstract

Sodium 4-phenylbutyrate (PBA), a short-chain fatty acid, has been approved to treat patients with urea cycle enzyme deficiencies and is being evaluated in the management of sickle cell disease, thalassemia, cancer, and cystic fibrosis (CF). Because relatively little is known about the effects of PBA on the expression and function of the wild-type CF transmembrane conductance regulator (wt CFTR), the goal of this study was to examine the effects of PBA and related compounds on wt CFTR-mediated Cl(-) secretion. To this end, we studied Calu-3 cells, a human airway cell line that expresses endogenous wt CFTR and has a serous cell phenotype. We report that chronic treatment of Calu-3 cells with a high concentration (5 mM) of PBA, sodium butyrate, or sodium valproate but not of sodium acetate reduced basal and 8-(4-chlorophenylthio)-cAMP-stimulated Cl(-) secretion. Paradoxically, PBA enhanced CFTR protein expression 6- to 10-fold and increased the intensity of CFTR staining in the apical plasma membrane. PBA also increased protein expression of Na(+)-K(+)-ATPase. PBA reduced CFTR Cl(-) currents across the apical membrane but had no effect on Na(+)-K(+)-ATPase activity in the basolateral membrane. Thus a high concentration of PBA (5 mM) reduces Cl(-) secretion by inhibiting CFTR Cl(-) currents across the apical membrane. In contrast, lower therapeutic concentrations of PBA (0.05-2 mM) had no effect on cAMP-stimulated Cl(-) secretion across Calu-3 cells. We conclude that PBA concentrations in the therapeutic range are unlikely to have a negative effect on Cl(-) secretion. However, concentrations >5 mM might reduce transepithelial Cl(-) secretion by serous cells in submucosal glands in individuals expressing wt CFTR.

The Chemopreventive Agent Resveratrol Stimulates Cyclic AMP–Dependent Chloride SecretionIn vitro

“…As shown earlier, short-chain fatty acids inhibit cAMPmediated chloride secretion in rat and rabbit colon (15,40). In Madin-Darby canine kidney cells and Calu-3 cells, butyrate (5 mmol/L) reduced basal as well as cAMP-stimulated I sc (41,42). In contrast, lower concentrations of phenylbutyrate (<2 mmol/L) had no effect on cAMP-stimulated Cl À secretion across Calu-3 cells (42).…”

“…In Madin-Darby canine kidney cells and Calu-3 cells, butyrate (5 mmol/L) reduced basal as well as cAMP-stimulated I sc (41,42). In contrast, lower concentrations of phenylbutyrate (<2 mmol/L) had no effect on cAMP-stimulated Cl À secretion across Calu-3 cells (42). In several studies, the effect of butyrate on Cl À secretion in T 84 cells was investigated.…”

ThePseudomonas aeruginosaSecreted Protein PA2934 Decreases Apical Membrane Expression of the Cystic Fibrosis Transmembrane Conductance Regulator

“…The basolateral bath solution contained 120 mM NaCl, 25 mM NaHCO 3 , 3.3 mM KH 2 PO 4 , 0.8 mM K 2 HPO 4 , 1.0 mM MgCl 2 , 1.0 mM CaCl 2 , and 10 mM glucose. Short-circuit current (I sc ) was measured by clamping the transepithelial voltage across the monolayers to 0 mV by using a voltage clamp (model VCC MC6; Physiological Instruments) as described previously (20,31,48). Current output from the clamp was digitized using an analog-to-digital converter (iWorx, Dover, NH).…”

Surface Expression of ASIC2 Inhibits the Amiloride-sensitive Current and Migration of Glioma Cells

“…11B). To validate that we were working with plasma membrane proteins, Western blots were probed for Na (27). To corroborate that the obtained plasma membrane fraction was not contaminated with other membranes, control Western blots were done using a mouse anti-GM130 antibody (BD Transduction Laboratories), which is a marker of Golgi membranes (Fig.…”