scholarly journals Concurrent absorption and secretion of airway surface liquids and bicarbonate secretion in human bronchioles

2019 ◽  
Vol 316 (5) ◽  
pp. L953-L960 ◽  
Author(s):  
A. K. M. Shamsuddin ◽  
Paul M. Quinton
Keyword(s):  
Ussing Chamber ◽  
Small Airway ◽  
Small Airways ◽  
Airway Surface Liquid ◽  
Tissue Architecture ◽  
Airway Epithelia ◽  
Conducting Airway ◽  
Human Lungs ◽  
Bronchiolar Epithelium ◽  
Surface Liquid

Although small airways account for the largest fraction of the total conducting airway surfaces, the epithelial fluid and electrolyte transport in small, native airway epithelia has not been well characterized. Investigations have been limited, no doubt, by the complex tissue architecture as well as by its inaccessibility, small dimensions, and lack of applicable assays, especially in human tissues. To better understand how the critically thin layer of airway surface liquid (ASL) is maintained, we applied a “capillary”-Ussing chamber (area ≈1 mm2) to measure ion transport properties of bronchioles with diameters of ~2 mm isolated from resected specimens of excised human lungs. We found that the small human airway, constitutively and concurrently, secretes and absorbs fluid as observed in porcine small airways (50). We found that the human bronchiolar epithelium is also highly anion selective and constitutively secretes bicarbonate ([Formula: see text]), which can be enhanced pharmacologically by cAMP as well as Ca2+-mediated agonists. Concurrent secretion and absorption of surface liquid along with [Formula: see text] secretion help explain how the delicate volume of the fluid lining the human small airway is physiologically buffered and maintained in a steady state that avoids desiccating or flooding the small airway with ASL.

Airway surface liquid thickness as a function of lung volume in small airways of the guinea pig

1994 ◽  
Vol 77 (5) ◽  
pp. 2333-2340 ◽  
Author(s):  
D. Yager ◽  
T. Cloutier ◽  
H. Feldman ◽  
J. Bastacky ◽  
J. M. Drazen ◽  
...  
Keyword(s):  
Surface Tension ◽  
Epithelial Cells ◽  
Guinea Pig ◽  
Cross Sections ◽  
Lung Volume ◽  
Longitudinal Direction ◽  
Small Airways ◽  
Airway Surface Liquid ◽  
Residual Capacity ◽  
Surface Liquid

The average thickness and distribution of airway surface liquid (ASL) on the luminal surface of peripheral airways were measured in normal guinea pig lungs frozen at functional residual capacity (FRC) and total lung capacity (TLC). Tissue blocks containing cross sections of airways of internal perimeter 0.188–3.342 mm were cut from frozen lungs and imaged by low-temperature scanning electron microscopy (LTSEM). Measurements made from LTSEM images were found to be independent of freezing rate by comparison of measurements at rapid and slow freezing rates. At both lung volumes, the ASL was not uniformly distributed in either the circumferential or longitudinal direction; there were regions of ASL where its thickness was < 0.1 micron, whereas in other regions ASL collected in pools. Discernible liquid on the surfaces of airways frozen at FRC followed the contours of epithelial cells and collected in pockets formed by neighboring cells, a geometry consistent with a low value of surface tension at the air-liquid interface. At TLC airway liquid collected to cover epithelial cells and to form a liquid meniscus, a geometry consistent with a higher value of surface tension. The average ASL thickness (h) was approximately proportional to the square root of airway internal perimeter, regardless of lung volume. For airways of internal perimeter 250 and 1,800 microns, h was 0.9 and 1.8 microns at FRC and 1.7 and 3.7 microns at TLC, respectively. For a given airway internal perimeter, h was 1.99 times thicker at TLC than at FRC; the difference was statistically significant (P < 0.01; 95% confidence interval 1.29–3.08).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Paracellular bicarbonate flux across human cystic fibrosis airway epithelia tempers changes in airway surface liquid pH

2020 ◽  
Vol 598 (19) ◽  
pp. 4307-4320 ◽  
Author(s):  
Ian M. Thornell ◽  
Tayyab Rehman ◽  
Alejandro A. Pezzulo ◽  
Michael J. Welsh
Keyword(s):  
Cystic Fibrosis ◽  
Airway Surface Liquid ◽  
Airway Epithelia ◽  
Cystic Fibrosis Airway ◽  
Surface Liquid

scholarly journals Thick airway surface liquid volume and weak mucin expression in pendrin-deficient human airway epithelia

2015 ◽  
Vol 3 (8) ◽  
pp. e12480 ◽  
Author(s):  
Hyun Jae Lee ◽  
Jee Eun Yoo ◽  
Wan Namkung ◽  
Hyung-Ju Cho ◽  
Kyubo Kim ◽  
...  
Keyword(s):  
Liquid Volume ◽  
Airway Surface Liquid ◽  
Airway Epithelia ◽  
Human Airway ◽  
Mucin Expression ◽  
Surface Liquid ◽  
Human Airway Epithelia

scholarly journals Inhibition of ATP hydrolysis restores airway surface liquid production in cystic fibrosis airway epithelia

2020 ◽  
Vol 318 (2) ◽  
pp. L356-L365 ◽  
Author(s):  
Catharina van Heusden ◽  
Brian Button ◽  
Wayne H. Anderson ◽  
Agathe Ceppe ◽  
Lisa C. Morton ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Steady State ◽  
Atp Hydrolysis ◽  
Fluid Secretion ◽  
Pathological Feature ◽  
Airway Surface Liquid ◽  
Airway Epithelial ◽  
Airway Epithelia ◽  
Atp Levels ◽  
Surface Liquid

Airway surface dehydration is a pathological feature of cystic fibrosis (CF) lung disease. CF is caused by mutations in the CF transmembrane conductance regulator (CFTR), a cyclic AMP-regulated Cl− channel controlled in part by the adenosine A2B receptor. An alternative CFTR-independent mechanism of fluid secretion is regulated by ATP via the P2Y2 receptor (P2Y2R) that activates Ca2+-regulated Cl− channels (CaCC/TMEM16) and inhibits Na+ absorption. However, due to rapid ATP hydrolysis, steady-state ATP levels in CF airway surface liquid (ASL) are inadequate to maintain P2Y2R-mediated fluid secretion. Therefore, inhibiting airway epithelial ecto-ATPases to increase ASL ATP levels constitutes a strategy to restore airway surface hydration in CF. Using [γ32P]ATP as radiotracer, we assessed the effect of a series of ATPase inhibitory compounds on the stability of physiologically occurring ATP concentrations. We identified the polyoxometalate [Co4(H2O)2(PW9O34)2]10− (POM-5) as the most potent and effective ecto-ATPase inhibitor in CF airway epithelial cells. POM-5 caused long-lasting inhibition of ATP hydrolysis in airway epithelia, which was reversible upon removal of the inhibitor. Importantly, POM-5 markedly enhanced steady-state levels of released ATP, promoting increased ASL volume in CF cell surfaces. These results provide proof of concept for ecto-ATPase inhibitors as therapeutic agents to restore hydration of CF airway surfaces. As a test of this notion, cell-free sputum supernatants from CF subjects were studied and found to have abnormally elevated ATPase activity, which was markedly inhibited by POM-5.

scholarly journals Small Molecule Anion Carriers Correct Abnormal Airway Surface Liquid Properties in Cystic Fibrosis Airway Epithelia

2020 ◽  
Vol 21 (4) ◽  
pp. 1488 ◽  
Author(s):  
Ambra Gianotti ◽  
Valeria Capurro ◽  
Livia Delpiano ◽  
Marcin Mielczarek ◽  
María García-Valverde ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Epithelial Cells ◽  
Fluid Composition ◽  
Airway Surface Liquid ◽  
Airway Epithelia ◽  
Drug Candidates ◽  
Cystic Fibrosis Airway ◽  
Functional Models ◽  
Cftr Protein ◽  
Surface Liquid

Cystic fibrosis (CF) is a genetic disease characterized by the lack of cystic fibrosis transmembrane conductance regulator (CFTR) protein expressed in epithelial cells. The resulting defective chloride and bicarbonate secretion and imbalance of the transepithelial homeostasis lead to abnormal airway surface liquid (ASL) composition and properties. The reduced ASL volume impairs ciliary beating with the consequent accumulation of sticky mucus. This situation prevents the normal mucociliary clearance, favouring the survival and proliferation of bacteria and contributing to the genesis of CF lung disease. Here, we have explored the potential of small molecules capable of facilitating the transmembrane transport of chloride and bicarbonate in order to replace the defective transport activity elicited by CFTR in CF airway epithelia. Primary human bronchial epithelial cells obtained from CF and non-CF patients were differentiated into a mucociliated epithelia in order to assess the effects of our compounds on some key properties of ASL. The treatment of these functional models with non-toxic doses of the synthetic anionophores improved the periciliary fluid composition, reducing the fluid re-absorption, correcting the ASL pH and reducing the viscosity of the mucus, thus representing promising drug candidates for CF therapy.

scholarly journals TNFα and IL-17 alkalinize airway surface liquid through CFTR and pendrin

2020 ◽  
Vol 319 (2) ◽  
pp. C331-C344 ◽  
Author(s):  
Tayyab Rehman ◽  
Ian M. Thornell ◽  
Alejandro A. Pezzulo ◽  
Andrew L. Thurman ◽  
Guillermo S. Romano Ibarra ◽  
...  
Keyword(s):  
Defense Mechanisms ◽  
Defense Mechanism ◽  
Primary Cultures ◽  
Secretory Cells ◽  
Airway Surface Liquid ◽  
Airway Epithelia ◽  
Airway Diseases ◽  
Key Factor ◽  
Surface Liquid ◽  
And Function

The pH of airway surface liquid (ASL) is a key factor that determines respiratory host defense; ASL acidification impairs and alkalinization enhances key defense mechanisms. Under healthy conditions, airway epithelia secrete base ([Formula: see text]) and acid (H+) to control ASL pH (pHASL). Neutrophil-predominant inflammation is a hallmark of several airway diseases, and TNFα and IL-17 are key drivers. However, how these cytokines perturb pHASL regulation is uncertain. In primary cultures of differentiated human airway epithelia, TNFα decreased and IL-17 did not change pHASL. However, the combination (TNFα+IL-17) markedly increased pHASL by increasing [Formula: see text] secretion. TNFα+IL-17 increased expression and function of two apical [Formula: see text] transporters, CFTR anion channels and pendrin Cl−/[Formula: see text] exchangers. Both were required for maximal alkalinization. TNFα+IL-17 induced pendrin expression primarily in secretory cells where it was coexpressed with CFTR. Interestingly, significant pendrin expression was not detected in CFTR-rich ionocytes. These results indicate that TNFα+IL-17 stimulate [Formula: see text] secretion via CFTR and pendrin to alkalinize ASL, which may represent an important defense mechanism in inflamed airways.

scholarly journals Electrolyte transport properties in distal small airways from cystic fibrosis pigs with implications for host defense

2016 ◽  
Vol 310 (7) ◽  
pp. L670-L679 ◽  
Author(s):  
Xiaopeng Li ◽  
Xiao Xiao Tang ◽  
Luis G. Vargas Buonfiglio ◽  
Alejandro P. Comellas ◽  
Ian M. Thornell ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Transport Properties ◽  
Host Defense ◽  
Bacterial Colonization ◽  
Short Circuit ◽  
Airway Epithelial Cells ◽  
Small Airway ◽  
Small Airways ◽  
Bacterial Killing ◽  
Airway Epithelia

While pathological and clinical data suggest that small airways are involved in early cystic fibrosis (CF) lung disease development, little is known about how the lack of cystic fibrosis transmembrane conductance regulator (CFTR) function contributes to disease pathogenesis in these small airways. Large and small airway epithelia are exposed to different airflow velocities, temperatures, humidity, and CO2 concentrations. The cellular composition of these two regions is different, and small airways lack submucosal glands. To better understand the ion transport properties and impacts of lack of CFTR function on host defense function in small airways, we adapted a novel protocol to isolate small airway epithelial cells from CF and non-CF pigs and established an organotypic culture model. Compared with non-CF large airways, non-CF small airway epithelia cultures had higher Cl− and bicarbonate (HCO3−) short-circuit currents and higher airway surface liquid (ASL) pH under 5% CO2 conditions. CF small airway epithelia were characterized by minimal Cl− and HCO3− transport and decreased ASL pH, and had impaired bacterial killing compared with non-CF small airways. In addition, CF small airway epithelia had a higher ASL viscosity than non-CF small airways. Thus, the activity of CFTR is higher in the small airways, where it plays a role in alkalinization of ASL, enhancement of antimicrobial activity, and lowering of mucus viscosity. These data provide insight to explain why the small airways are a susceptible site for the bacterial colonization.

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