scholarly journals Inhibition of the sodium-dependent HCO3 -transporter SLC4A4, produces a cystic fibrosis-like airway disease phenotype.

2021 ◽  
Author(s):  
Vinciane Saint-Criq ◽  
Anita Guequen ◽  
Amber R Philp ◽  
Sandra Villanueva ◽  
Tábata Apablaza ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Current Model ◽  
Basolateral Membrane ◽  
Protein S ◽  
Chloride Secretion ◽  
Airway Epithelial Cells ◽  
Bicarbonate Transport ◽  
Bicarbonate Secretion ◽  
Anion Secretion ◽  
Sodium Dependent

Bicarbonate secretion is a fundamental process involved in maintaining acid-base homeostasis. Disruption of bicarbonate entry into airway lumen, as has been observed in cystic fibrosis, produces several defects in lung function due to thick mucus accumulation. Bicarbonate is critical for correct mucin deployment and there is increasing interest in understanding its role in airway physiology, particularly in the initiation of lung disease in children affected by cystic fibrosis, in the absence of detectable bacterial infection. The current model of anion secretion in mammalian airways consists of CFTR and TMEM16A as apical anion exit channels, with limited capacity for bicarbonate transport compared to chloride. However, both channels can couple to SLC26A4 anion exchanger to maximise bicarbonate secretion. Nevertheless, current models lack any details about the identity of the basolateral protein(s) responsible for bicarbonate uptake into airway epithelial cells. We report herein that the electrogenic, sodium-dependent, bicarbonate cotransporter, SLC4A4, is expressed in the basolateral membrane of human and mouse airways, and that it’s pharmacological inhibition or genetic silencing reduces bicarbonate secretion. In fully differentiated primary human airway cells, SLC4A4 inhibition induced an acidification of the airways surface liquid and markedly reduced the capacity of cells to recover from an acid load. Studies in the Slc4a4-null mice revealed a previously unreported lung phenotype, characterized by mucus accumulation and reduced mucociliary clearance. Collectively, our results demonstrate that the reduction of SLC4A4 function induced a CF-like phenotype, even when chloride secretion remained intact, highlighting the important role SLC4A4 plays in bicarbonate secretion and mammalian airway function.

scholarly journals Interleukin-17A induces bicarbonate secretion in normal human bronchial epithelial cells

2009 ◽  
Vol 296 (2) ◽  
pp. L257-L266 ◽  
Author(s):  
James L. Kreindler ◽  
Carol A. Bertrand ◽  
Robert J. Lee ◽  
Thomas Karasic ◽  
Shean Aujla ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Ion Transport ◽  
Antimicrobial Peptide ◽  
Basolateral Membrane ◽  
Chloride Secretion ◽  
Bicarbonate Secretion ◽  
Immune Functions ◽  
Bronchial Epithelial ◽  
Interleukin 17A ◽  
Well Differentiated

The innate immune functions of human airways include mucociliary clearance and antimicrobial peptide activity. Both functions may be affected by changes in epithelial ion transport. Interleukin-17A (IL-17A), which has a receptor at the basolateral membrane of airway epithelia, is a T cell cytokine that has been shown to increase mucus secretion and antimicrobial peptide production by human bronchial epithelial (HBE) cells. Furthermore, IL-17A levels are increased in sputum from patients during pulmonary exacerbations of cystic fibrosis. Therefore, we investigated the effects of IL-17A on basal, amiloride-sensitive, and forskolin-stimulated ion transport in mature, well-differentiated HBE cells. Exposure of HBE monolayers to IL-17A for 48 h induced a novel forskolin-stimulated bicarbonate secretion in addition to forskolin-stimulated chloride secretion and resulted in alkalinization of liquid on the mucosal surface of polarized cells. IL-17A-induced bicarbonate secretion was cystic fibrosis transmembrane conductance regulator (CFTR)-dependent, mucosal chloride-dependent, partially Na+-dependent, and sensitive to serosal, but not mucosal, stilbene inhibition. These data suggest that IL-17A modulates epithelial bicarbonate secretion and implicate a mechanism by which airway surface liquid pH changes may be abnormal in cystic fibrosis.

Na-K-Cl cotransport in nystatin-treated tracheal cells: regulation by isoproterenol, apical UTP, and [Cl]i

1994 ◽  
Vol 266 (5) ◽  
pp. C1440-C1452 ◽  
Author(s):  
M. Haas ◽  
D. G. McBrayer
Keyword(s):  
Epithelial Cells ◽  
Plasma Membranes ◽  
Basolateral Membrane ◽  
Primary Cultures ◽  
Chloride Secretion ◽  
Airway Epithelial Cells ◽  
Tracheal Epithelial Cells ◽  
Cl Transport ◽  
Monovalent Ions ◽  
Stimulation Of

Chloride secretion in mammalian airway epithelia is stimulated by beta-adrenergic agonists via an adenosine 3',5'-cyclic monophosphate (cAMP)-dependent mechanism and by apical triphosphate nucleotides (ATP, UTP) via a cAMP-independent mechanism. Both types of secretagogues are known to stimulate apical Cl channels in airway cells; however, to maintain a stimulated rate of secretion, basolateral Cl influx via Na-K-Cl cotransport must be upregulated in parallel with apical Cl efflux. To examine the regulation of basolateral cotransport activity and its relationship to apical Cl efflux, we examined Cl transport in confluent primary cultures of dog tracheal epithelial cells treated with nystatin, an antibiotic that increases the permeability of plasma membranes to small monovalent ions, including Cl. By applying nystatin to the apical membrane of these cultures, apical Cl permeability could be increased to the point where transepithelial Cl transport is limited by transport across the basolateral membrane, which reflects primarily the activity of the cotransporter. In cultures of tracheal cells not treated with nystatin, transepithelial (basolateral-to-apical) 36Cl flux was increased two- to threefold by exposure to isoproterenol (5 microM, basolateral) or apical UTP (10 microM). Apical application of nystatin (400 units/ml) increased the basal level of transepithelial 36Cl flux approximately 1.5-fold and eliminated UTP stimulation of this flux, although an approximately twofold stimulation by isoproterenol persisted. Nystatin treatment also abolished UTP stimulation of saturable, basolateral [3H]bumetanide binding, a measure of functioning Na-K-Cl cotransporters in these cells; isoproterenol stimulation of binding was only mildly inhibited by nystatin treatment. Lowering intracellular Cl concentration ([Cl]i) by incubating cultures with apical media containing nystatin and reduced [Cl] (NO3 replacement) increased both basolateral-to-apical 36Cl flux and [3H]bumetanide binding in the absence of secretagogues or cell shrinkage. The results support our previous suggestion, based entirely on [3H]bumetanide binding [M. Haas, D. G. McBrayer, and J. R. Yankaskas. Am. J. Physiol. 264 (Cell. Physiol. 32): C189-C200, 1993], that UTP stimulation of basolateral Na-K-Cl cotransport in airway epithelial cells is entirely secondary to, and requires, an increase in apical Cl efflux, and further suggest that a decrease in [Cl]i may be a signal for cotransport activation in response to UTP. In addition, a cAMP-dependent cascade initiated by isoproterenol appears to directly stimulate the cotransporter.

scholarly journals Lubiprostone activates non-CFTR-dependent respiratory epithelial chloride secretion in cystic fibrosis mice

2008 ◽  
Vol 295 (5) ◽  
pp. L933-L940 ◽  
Author(s):  
Kelvin D. MacDonald ◽  
Karen R. McKenzie ◽  
Mark J. Henderson ◽  
Charles E. Hawkins ◽  
Neeraj Vij ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Chloride Channels ◽  
Chloride Secretion ◽  
Airway Epithelial Cells ◽  
Sodium Reabsorption ◽  
Airway Epithelial ◽  
Wild Type ◽  
Voltage Dependent ◽  
Clear Dose Response ◽  
Apical Membranes

Periciliary fluid balance is maintained by the coordination of sodium and chloride channels in the apical membranes of the airways. In the absence of the cystic fibrosis transmembrane regulator (CFTR), chloride secretion is diminished and sodium reabsorption exaggerated. ClC-2, a pH- and voltage-dependent chloride channel, is present on the apical membranes of airway epithelial cells. We hypothesized that ClC-2 agonists would provide a parallel pathway for chloride secretion. Using nasal potential difference (NPD) measurements, we quantified lubiprostone-mediated Cl− transport in sedated cystic fibrosis null (gut-corrected), C57Bl/6, and A/J mice during nasal perfusion of lubiprostone (a putative ClC-2 agonist). Baseline, amiloride-inhibited, chloride-free gluconate-substituted Ringer with amiloride and low-chloride Ringer plus lubiprostone (at increasing concentrations of lubiprostone) were perfused, and the NPD was continuously recorded. A clear dose-response relationship was detected in all murine strains. The magnitude of the NPD response to 20 μM lubiprostone was −5.8 ± 2.1 mV (CF, n = 12), −8.1 ± 2.6 mV (C57Bl/6 wild-type, n = 12), and −5.3 ± 1.2 mV (AJ wild-type, n = 8). A cohort of ClC-2 knockout mice did not respond to 20 μM lubiprostone ( n = 6, P = 0.27). In C57Bl/6 mice, inhibition of CFTR with topical application of CFTR inhibitor-172 did not abolish the lubiprostone response, thus confirming the response seen is independent of CFTR regulation. RT-PCR confirmed expression of ClC-2 mRNA in murine lung homogenate. The direct application of lubiprostone in the CF murine nasal airway restores nearly normal levels of chloride secretion in nasal epithelia.

Chloride secretory response to extracellular ATP in human normal and cystic fibrosis nasal epithelia

1992 ◽  
Vol 263 (2) ◽  
pp. C348-C356 ◽  
Author(s):  
L. L. Clarke ◽  
R. C. Boucher
Keyword(s):  
Cystic Fibrosis ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Chloride Secretion ◽  
Extracellular Atp ◽  
Nasal Epithelium ◽  
Secretory Process ◽  
Cl Secretion ◽  
Epithelial Cultures ◽  
Cl Conductance

Chloride secretion across cystic fibrosis (CF) airway epithelia is effectively regulated by pathways associated with intracellular Ca2+ metabolism, but not by mechanisms dependent on protein kinase A or C. In a search for therapeutically useful agonists, we investigated the effects of extracellular ATP on the Cl- secretory process in human normal and CF nasal epithelial cultures with double-barreled Cl- selective microelectrodes. When applied to the basolateral membrane of normal, but not CF, nasal epithelium, extracellular ATP (10(-4) M) stimulated a small increase in Cl- secretion that was primarily associated with a hyperpolarizing conductance in the basolateral membrane. In contrast, ATP applied to the apical (luminal) membrane of either normal or CF nasal epithelium stimulated a greater increase in Cl- secretion that was associated with activation of an apical membrane Cl- conductance. The increases in Cl- current and apical conductance were greater in CF tissues and attained maximal values similar to normal nasal epithelium. We conclude 1) that basolateral application of ATP indirectly induces Cl- secretion by activating a basolateral (K+) conductance and is an effective secretagogue only in normal nasal epithelium and 2) that luminally applied ATP is an effective Cl- secretagogue that activates the apical membrane Cl- conductance of normal and CF nasal epithelia to an equivalent level.

Impaired chloride secretion, as well as bicarbonate secretion, underlies the fluid secretory defect in the cystic fibrosis pancreas

1988 ◽  
Vol 95 (2) ◽  
pp. 349-355 ◽  
Author(s):  
Hinda Kopelman ◽  
Mary Corey ◽  
Kevin Gaskin ◽  
Peter Durie ◽  
Zvi Weizman ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Chloride Secretion ◽  
Bicarbonate Secretion

Heat stable toxin of E. coli (STa) stimulates duodenal mucosal bicarbonate secretion in cystic fibrosis knockout mice

2001 ◽  
Vol 120 (5) ◽  
pp. A137-A137
Author(s):  
D CHILDS ◽  
D CROMBIE ◽  
V PRATHA ◽  
Z SELLERS ◽  
D HOGAN ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Knockout Mice ◽  
Bicarbonate Secretion ◽  
E Coli ◽  
Heat Stable

Differential expression of ORCC and CFTR induced by low temperature in CF airway epithelial cells

1995 ◽  
Vol 268 (1) ◽  
pp. C243-C251 ◽  
Author(s):  
M. E. Egan ◽  
E. M. Schwiebert ◽  
W. B. Guggino
Keyword(s):  
Cystic Fibrosis ◽  
Epithelial Cells ◽  
Incubation Temperature ◽  
Cell Types ◽  
Airway Epithelial Cells ◽  
Airway Epithelial ◽  
Channel Activity ◽  
Patch Clamp Recording ◽  
Cl Channel ◽  
Channel Expression

When nonepithelial cell types expressing the delta F508-cystic fibrosis transmembrane conductance regulator (CFTR) mutation are grown at reduced temperatures, the mutant protein can be properly processed. The effect of low temperatures on Cl- channel activity in airway epithelial cells that endogenously express the delta F508-CFTR mutation has not been investigated. Therefore, we examined the effect of incubation temperature on both CFTR and outwardly rectifying Cl- channel (ORCC) activity in normal, in cystic fibrosis (CF)-affected, and in wild-type CFTR-complemented CF airway epithelia with use of a combination of inside-out and whole cell patch-clamp recording, 36Cl- efflux assays, and immunocytochemistry. We report that incubation of CF-affected airway epithelial cells at 25-27 degrees C is associated with the appearance of a protein kinase A-stimulated CFTR-like Cl- conductance. In addition to the appearance of CFTR Cl- channel activity, there is, however, a decrease in the number of active ORCC when cells are grown at 25-27 degrees C, suggesting that the decrease in incubation temperature may be associated with multiple alterations in ion channel expression and/or regulation in airway epithelial cells.

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