scholarly journals Airway Surface Liquid Osmolality Measured Using Fluorophore-Encapsulated Liposomes

2001 ◽  
Vol 117 (5) ◽  
pp. 423-430 ◽  
Author(s):  
Sujatha Jayaraman ◽  
Yuanlin Song ◽  
A.S. Verkman
Keyword(s):  
Epithelial Cells ◽  
Water Loss ◽  
Airway Epithelial Cells ◽  
Evaporative Water Loss ◽  
Airway Surface Liquid ◽  
Airway Epithelial ◽  
Evaporative Water ◽  
Dry Air ◽  
Surface Liquid ◽  
Sulforhodamine 101

The airway surface liquid (ASL) is the thin layer of fluid coating the luminal surface of airway epithelial cells at an air interface. Its composition and osmolality are thought to be important in normal airway physiology and in airway diseases such as asthma and cystic fibrosis. The determinants of ASL osmolality include epithelial cell solute and water transport properties, evaporative water loss, and the composition of secreted fluids. We developed a noninvasive approach to measure ASL osmolality using osmotically sensitive 400-nm-diam liposomes composed of phosphatidylcholine/cholesterol/polyethylene glycol-phosphatidylcholine (1:0.3:0.08 molar ratio). Calcein was encapsulated in the liposomes at self-quenching concentrations (30 mM) as a volume-sensitive marker, together with sulforhodamine 101 (2 mM) as a volume-insensitive reference. Liposome calcein/sulforhodamine 101 fluorescence ratios responded rapidly (<0.2 s) and stably to changes in solution osmolality. ASL osmolality was determined from calcein/sulforhodamine 101 fluorescence ratios after addition of microliter quantities of liposome suspensions to the ASL. In bovine airway epithelial cells cultured on porous supports at an air–liquid interface, ASL thickness (by confocal microscopy) was 22 μm and osmolality was 325 ± 12 mOsm. In anesthetized mice in which a transparent window was created in the trachea, ASL thickness was 55 μm and osmolality was 330 ± 36 mOsm. ASL osmolality was not affected by pharmacological inhibition of CFTR in airway cell cultures or by genetic deletion of CFTR in knockout mice. ASL osmolality could be increased substantially to >400 mOsm by exposure of the epithelium to dry air; the data were modeled mathematically using measured rates of osmosis and evaporative water loss. These results establish a ratio imaging method to map osmolality in biological compartments. ASL fluid is approximately isosmolar under normal physiological conditions, but can become hyperosmolar when exposed to dry air, which may induce cough and airway reactivity in some patients.

Erythromycin increases bactericidal activity of surface liquid in human airway epithelial cells

2005 ◽  
Vol 289 (4) ◽  
pp. L565-L573 ◽  
Author(s):  
Kota Ishizawa ◽  
Tomoko Suzuki ◽  
Mutsuo Yamaya ◽  
Yu Xia Jia ◽  
Seiichi Kobayashi ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Bactericidal Activity ◽  
Culture Medium ◽  
Airway Epithelial Cells ◽  
Airway Surface Liquid ◽  
Airway Epithelial ◽  
Tracheal Epithelial Cells ◽  
Tracheal Epithelial ◽  
Surface Liquid ◽  
Number Of Bacteria

Macrolide antibiotics have clinical benefits in patients with diffuse panbronchiolitis and in patients with cystic fibrosis. Although many mechanisms have been proposed, the precise mechanisms are still uncertain. We examined the effects of erythromycin on bactericidal activity of airway surface liquid secreted by cultured human tracheal epithelial cells. Airway surface liquid was collected by washing the surface of human tracheal epithelial cells with a sodium solution (40 meq/l). Methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa were incubated with airway surface liquid, and the number of surviving bacteria was examined. The number of bacteria in airway surface liquid from the cells cultured in medium alone was significantly lower than that in the sodium solution. Furthermore, the number of bacteria in airway surface liquid from the cells treated with erythromycin was significantly lower than that in airway surface liquid from the cells treated with solvent alone. The production of mRNA and protein of human β-defensin-1 and human β-defensin-2 was significantly increased by erythromycin. Bactericidal activity of airway surface liquid was observed at low concentrations (40 meq/l) of sodium but not at higher concentrations (≥80 meq/l). Airway surface liquid did not contain significant amounts of antibiotics supplemented in the culture medium. Erythromycin at the levels in airway surface liquid and in culture medium did not inhibit bacterial growth. These results suggest that erythromycin may increase bactericidal activity of airway surface liquid in human airway epithelial cells through human β-defensins production and reduce susceptibility of the airway to bacterial infection.

Regional differences in airway surface liquid composition

1981 ◽  
Vol 50 (3) ◽  
pp. 613-620 ◽  
Author(s):  
R. C. Boucher ◽  
M. J. Stutts ◽  
P. A. Bromberg ◽  
J. T. Gatzy
Keyword(s):  
Water Loss ◽  
Regional Differences ◽  
Regional Difference ◽  
Liquid Composition ◽  
Evaporative Water Loss ◽  
Osmotic Gradient ◽  
Airway Surface Liquid ◽  
Evaporative Water ◽  
Surface Liquid ◽  
Electrochemical Equilibrium

Liquid from canine airway surfaces was absorbed onto filter paper strips and analyzed. In resting conditions, tracheal surface liquid was hyperosmolal (330 mosmol/kg H2O) compared to plasma with raised Na+ (158 meq/l), Cl- (134 meq/l), K+ (28 meq/l), and HCO3- (32 meq/l) concentrations. The volume collected was increased by repetitive sampling, a response blocked by atropine, or by methacholine injection. Compared to nose breathing, tracheal surface liquid osmolality was increased by 10 min of mouth breathing (410 mosmol/kg H2O). Surface liquid from 0.5-cm diameter bronchi was nearly isosmolal (304 mosmol/kg H2O) with plasma in resting conditions, with Na and Cl concentrations lower than plasma (120 and 106 meq/l, respectively), and K+ (52 meq/l), and HCO3- (50 meq/l) concentrations higher than those of plasma or tracheal liquid. Although the K+ in tracheal fluid approaches the value for electrochemical equilibrium, K+ in fluid from the bronchi and HCO3- in both regions cannot be accounted for by passive forces. The regional difference in osmolality supports the concept that the higher osmolality of tracheal liquid reflects evaporative water loss from this site. The transepithelial osmotic gradient generated by evaporative water loss may be a driving force for hydration of the tracheal surface.

scholarly journals Functional Apical Large Conductance, Ca2+-activated, and Voltage-dependent K+ Channels Are Required for Maintenance of Airway Surface Liquid Volume

2011 ◽  
Vol 286 (22) ◽  
pp. 19830-19839 ◽  
Author(s):  
Dahis Manzanares ◽  
Carlos Gonzalez ◽  
Pedro Ivonnet ◽  
Ren-Shiang Chen ◽  
Monica Valencia-Gattas ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Ion Transport ◽  
Apical Membrane ◽  
Airway Epithelial Cells ◽  
Bk Channels ◽  
Liquid Volume ◽  
Airway Surface Liquid ◽  
Airway Epithelial ◽  
Voltage Dependent ◽  
Surface Liquid

Large conductance, Ca2+-activated, and voltage-dependent K+ (BK) channels control a variety of physiological processes in nervous, muscular, and renal epithelial tissues. In bronchial airway epithelia, extracellular ATP-mediated, apical increases in intracellular Ca2+ are important signals for ion movement through the apical membrane and regulation of water secretion. Although other, mainly basolaterally expressed K+ channels are recognized as modulators of ion transport in airway epithelial cells, the role of BK in this process, especially as a regulator of airway surface liquid volume, has not been examined. Using patch clamp and Ussing chamber approaches, this study reveals that BK channels are present and functional at the apical membrane of airway epithelial cells. BK channels open in response to ATP stimulation at the apical membrane and allow K+ flux to the airway surface liquid, whereas no functional BK channels were found basolaterally. Ion transport modeling supports the notion that apically expressed BK channels are part of an apical loop current, favoring apical Cl− efflux. Importantly, apical BK channels were found to be critical for the maintenance of adequate airway surface liquid volume because continuous inhibition of BK channels or knockdown of KCNMA1, the gene coding for the BK α subunit (KCNMA1), lead to airway surface dehydration and thus periciliary fluid height collapse revealed by low ciliary beat frequency that could be fully rescued by addition of apical fluid. Thus, apical BK channels play an important, previously unrecognized role in maintaining adequate airway surface hydration.

scholarly journals Transport properties in CFTR−/− knockout piglets suggest normal airway surface liquid pH and enhanced amiloride-sensitive Na+ absorption

2020 ◽  
Vol 472 (10) ◽  
pp. 1507-1519 ◽  
Author(s):  
Roberta Benedetto ◽  
Raquel Centeio ◽  
Jiraporn Ousingsawat ◽  
Rainer Schreiber ◽  
Melanie Janda ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Transport Properties ◽  
Airway Epithelial Cells ◽  
Small Contribution ◽  
Mrna Levels ◽  
Lung Pathology ◽  
Airway Epithelial ◽  
Contrast Enhanced ◽  
Surface Liquid ◽  
A Minor

Abstract Previous analysis of CFTR-knockout (CFTR−/−) in piglets has provided important insights into the pathology of cystic fibrosis. However, controversies exist as to the true contribution of CFTR to the pH balance in airways and intestine. We therefore compared ion transport properties in newborn wild-type (CFTR+/+) and CFTR-knockout (CFTR−/− piglets). Tracheas of CFTR−/− piglets demonstrated typical cartilage malformations and muscle cell bundles. CFTR−/− airway epithelial cells showed enhanced lipid peroxidation, suggesting inflammation early in life. CFTR was mainly expressed in airway submucosal glands and was absent in lungs of CFTR−/− piglets, while expression of TMEM16A was uncompromised. mRNA levels for TMEM16A, TMEM16F, and αβγENaC were unchanged in CFTR−/− airways, while mRNA for SLC26A9 appeared reduced. CFTR was undetectable in epithelial cells of CFTR−/− airways and intestine. Small intestinal epithelium of CFTR−/− piglets showed mucus accumulation. Secretion of both electrolytes and mucus was activated by stimulation with prostaglandin E2 and ATP in the intestine of CFTR+/+, but not of CFTR−/− animals. pH was measured inside small bronchi using a pH microelectrode and revealed no difference between CFTR+/+ and CFTR−/− piglets. Intracellular pH in porcine airway epithelial cells revealed only a small contribution of CFTR to bicarbonate secretion, which was absent in cells from CFTR−/− piglets. In contrast to earlier reports, our data suggest a minor impact of CFTR on ASL pH. In contrast, enhanced amiloride-sensitive Na+ absorption may contribute to lung pathology in CFTR−/− piglets, along with a compromised CFTR- and TMEM16A-dependent Cl− transport.

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