Nitric oxide inhibits Na<sup>+</sup>absorption across cultured alveolar type II monolayers

Guo, Yi; DuVall, Michael D.; Crow, John P.; Matalon, Sadis

doi:10.1152/ajplung.1998.274.3.l369

Cited by 107 publications

(128 citation statements)

References 40 publications

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“…In hydrostatic stress, epithelial Na + uptake becomes impaired as a result of pressure-induced endothelial NO production (6) and subsequent NO-dependent inhibition of Na + absorption (2,38). Notably, endothelial NO production may simultaneously activate CFTR, which was indicated by the fact that alveolar fluid secretion was associated with NO-dependent CFTR phosphorylation and blocked by cGKII inhibition.…”

Section: Discussionmentioning

confidence: 99%

Chloride transport-driven alveolar fluid secretion is a major contributor to cardiogenic lung edema

Solymosi

Kaestle-Gembardt

Vadász

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Alveolar fluid clearance driven by active epithelial Na + and secondary Cl − absorption counteracts edema formation in the intact lung. Recently, we showed that impairment of alveolar fluid clearance because of inhibition of epithelial Na + channels (ENaCs) promotes cardiogenic lung edema. Concomitantly, we observed a reversal of alveolar fluid clearance, suggesting that reversed transepithelial ion transport may promote lung edema by driving active alveolar fluid secretion. We, therefore, hypothesized that alveolar ion and fluid secretion may constitute a pathomechanism in lung edema and aimed to identify underlying molecular pathways. In isolated perfused lungs, alveolar fluid clearance and secretion were determined by a double-indicator dilution technique. Transepithelial Cl − secretion and alveolar Cl − influx were quantified by radionuclide tracing and alveolar Cl − imaging, respectively. Elevated hydrostatic pressure induced ouabain-sensitive alveolar fluid secretion that coincided with transepithelial Cl − secretion and alveolar Cl − influx. Inhibition of either cystic fibrosis transmembrane conductance regulator (CFTR) or Na + -K + -Cl − cotransporters (NKCC) blocked alveolar fluid secretion, and lungs of CFTR −/− mice were protected from hydrostatic edema. Inhibition of ENaC by amiloride reproduced alveolar fluid and Cl − secretion that were again CFTR-, NKCC-, and Na + -K + -ATPase-dependent. Our findings show a reversal of transepithelial Cl − and fluid flux from absorptive to secretory mode at hydrostatic stress. Alveolar Cl − and fluid secretion are triggered by ENaC inhibition and mediated by NKCC and CFTR. Our results characterize an innovative mechanism of cardiogenic edema formation and identify NKCC1 as a unique therapeutic target in cardiogenic lung edema.epithelial Cl − transport | pulmonary edema T raditionally, the formation of cardiogenic pulmonary edema has been attributed to passive fluid filtration across an intact alveolocapillary barrier along an increased hydrostatic pressure gradient. However, recent studies show that cardiogenic edema is critically regulated by active signaling processes. Activation of mechanosensitive endothelial ion channels increases lung vascular permeability (1), whereas alveolar epithelial cells lose their physiological ability to clear the distal airspaces from excess fluid by their capacity to actively transport ions across the epithelial barrier (2-4).In the intact lung, the predominant force driving alveolar fluid clearance is an active transepithelial Na + transport from the alveolar into the interstitial space. A major portion of the apical Na + entry is mediated by the amiloride-inhibitable epithelial Na + channel (ENaC), with basolateral Na + extrusion through the Na + -K + -ATPase (5). Cl − and water are considered to follow paracellularly for electroneutrality and osmotic balance. In cardiogenic lung edema, the physiological protection against alveolar flooding provided by an intact alveolar fluid clearance is largely attenuated (3, 4). Previously, ...

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Section: Discussionmentioning

confidence: 99%

Chloride transport-driven alveolar fluid secretion is a major contributor to cardiogenic lung edema

Solymosi

Kaestle-Gembardt

Vadász

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…Type 1 and 2 cells were isolated from rats (22, 23) and mice as described (24); purity was assessed by morphologic analysis and immunostaining for AT1 (RTI40) and AT2 (RTI70) cell markers. Electrophysiologic studies of rat AT2 cells were performed in Ussing chambers as described (21,25).…”

Section: Methodsmentioning

confidence: 99%

Adenosine regulation of alveolar fluid clearance

Factor

Mutlu

Chen

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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Adenosine is a purine nucleoside that regulates cell function through G protein-coupled receptors that activate or inhibit adenylyl cyclase. Based on the understanding that cAMP regulates alveolar epithelial active Na ؉ transport, we hypothesized that adenosine and its receptors have the potential to regulate alveolar ion transport and airspace fluid content. Herein, we report that type 1 (A1R), 2a (A2aR), 2b (A2bR), and 3 (A3R) adenosine receptors are present in rat and mouse lungs and alveolar type 1 and 2 epithelial cells (AT1 and AT2). Rat AT2 cells generated and produced cAMP in response to adenosine, and micromolar concentrations of adenosine were measured in bronchoalveolar lavage fluid from mice. Ussing chamber studies of rat AT2 cells indicated that adenosine affects ion transport through engagement of A1R, A2aR, and/or A3R through a mechanism that increases CFTR and amiloride-sensitive channel function. Intratracheal instillation of low concentrations of adenosine (<10 ؊8 M) or either A2aR-or A3R-specific agonists increased alveolar fluid clearance (AFC), whereas physiologic concentrations of adenosine (>10 ؊6 M) reduced AFC in mice and rats via an A1R-dependent pathway. Instillation of a CFTR inhibitor (CFTRinh-172) attenuated adenosine-mediated down-regulation of AFC, suggesting that adenosine causes Cl ؊ efflux by means of CFTR. These studies report a role for adenosine in regulation of alveolar ion transport and fluid clearance. These findings suggest that physiologic concentrations of adenosine allow the alveolar epithelium to counterbalance active Na ؉ absorption with Cl ؊ efflux through engagement of the A1R and raise the possibility that adenosine receptor ligands can be used to treat pulmonary edema.active sodium transport ͉ adenosine receptors ͉ cystic fibrosis transmembrane conductance regulator P ulmonary edema is due to increased fluid flux into the airspace and impairment of the active Na ϩ transport that clears it (1-4). A variety of approaches to improve alveolar epithelial cell active Na ϩ transport for purposes of accelerating alveolar fluid clearance (AFC) have been explored in experimental systems. Of particular interest are receptor-ligand interactions that increase cAMP production in alveolar epithelial cells. Adenosine is a purine nucleoside that signals through four distinct G protein-coupled receptors, type 1 (A 1 R), type 2a (A 2a R), type 2b (A 2b R), and type 3 (A 3 R). In most cell systems, the A 1 R and A 3 R receptors inhibit adenylyl cyclase and/or lead to signaling through inositol-3-phosphate and phospholipase C. Engagement of type 2 receptors activates adenylyl cyclase by means of Gs␣ and increases cAMP levels. The ability of adenosine receptors (ARs) to couple to adenylyl cyclase led us to hypothesize that ARs might participate in regulation of alveolar epithelial active Na ϩ transport. We approached this hypothesis in rats and mice by testing whether adenosine and its receptors are present in the distal airspace and whether they affect AFC in vivo and vectorial Na ϩ...

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“…Experiments were also undertaken to measure sodium influx through apical amiloride-sensitive channels in basolaterally permeabilized cells, as previously described by Guo et al (13 , 10 mM glucose (pH 7.4) and 120 N-methyl-D-glucamine (an impermeant cation) for 20 min, before the basolateral membrane was permeabilized by basolateral addition of amphotericin B (10 M), a monovalent ionophore. This induced a slowly developing (3-6 min) rise in I sc .…”

Section: Methodsmentioning

confidence: 99%

Hypoxia and β2-Agonists Regulate Cell Surface Expression of the Epithelial Sodium Channel in Native Alveolar Epithelial Cells

Planès

Blot‐Chabaud

Matthay

et al. 2002

Journal of Biological Chemistry

151

145

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Alveolar hypoxia may impair sodium-dependent alveolar fluid transport and induce pulmonary edema in rat and human lung, an effect that can be prevented by the inhalation of ␤ 2 -agonists. To investigate the mechanism of ␤ 2 -agonist-mediated stimulation of sodium transport under conditions of moderate hypoxia, we examined the effect of terbutaline on epithelial sodium channel (ENaC) expression and activity in cultured rat alveolar epithelial type II cells exposed to 3% O 2 for 24 h. Hypoxia reduced transepithelial sodium current and amiloridesensitive sodium channel activity without decreasing ENaC subunit mRNA or protein levels. The functional decrease was associated with reduced abundance of ENaC subunits (especially ␤ and ␥) in the apical membrane of hypoxic cells, as quantified by biotinylation. cAMP stimulation with terbutaline reversed the hypoxia-induced decrease in transepithelial sodium transport by stimulating sodium channel activity and markedly increased the abundance of ␤-and ␥-ENaC in the plasma membrane of hypoxic cells. The effect of terbutaline was prevented by brefeldin A, a blocker of anterograde transport. These novel results establish that hypoxiainduced inhibition of amiloride-sensitive sodium channel activity is mediated by decreased apical expression of ENaC subunits and that ␤ 2 -agonists reverse this effect by enhancing the insertion of ENaC subunits into the membrane of hypoxic alveolar epithelial cells.

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Nitric oxide inhibits Na⁺absorption across cultured alveolar type II monolayers

Cited by 107 publications

References 40 publications

Chloride transport-driven alveolar fluid secretion is a major contributor to cardiogenic lung edema

Chloride transport-driven alveolar fluid secretion is a major contributor to cardiogenic lung edema

Adenosine regulation of alveolar fluid clearance

Hypoxia and β2-Agonists Regulate Cell Surface Expression of the Epithelial Sodium Channel in Native Alveolar Epithelial Cells

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Nitric oxide inhibits Na+absorption across cultured alveolar type II monolayers

Cited by 107 publications

References 40 publications

Chloride transport-driven alveolar fluid secretion is a major contributor to cardiogenic lung edema

Chloride transport-driven alveolar fluid secretion is a major contributor to cardiogenic lung edema

Adenosine regulation of alveolar fluid clearance

Hypoxia and β2-Agonists Regulate Cell Surface Expression of the Epithelial Sodium Channel in Native Alveolar Epithelial Cells

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Product

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Nitric oxide inhibits Na⁺absorption across cultured alveolar type II monolayers