32 ENDOTHELIN 1 DECREASES LUNG EDEMA CLEARANCE IN ALVEOLAR EPITHELIAL CELLS VIA ENDOTHELIAL ET-B RECEPTOR ACTIVATION AND NITRIC OXIDE GENERATION.

Patients with interstitial lung diseases, such as idiopathic pulmonary fibrosis (IPF) and bronchopulmonary dysplasia (BPD), suffer from lung fibrosis secondary to myofibroblast-mediated excessive ECM deposition and destruction of lung architecture. Transforming growth factor (TGF)-β1 induces epithelial-mesenchymal transition (EMT) of alveolar epithelial cells (AEC) to myofibroblasts both in vitro and in vivo. Inhaled nitric oxide (NO) attenuates ECM accumulation, enhances lung growth, and decreases alveolar myofibroblast number in experimental models. We therefore hypothesized that NO attenuates TGF-β1-induced EMT in cultured AEC. Studies of the capacity for endogenous NO production in AEC revealed that endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) are expressed and active in AEC. Total NOS activity was 1.3 pmol·mg protein−1·min−1 with 67% derived from eNOS. TGF-β1 (50 pM) suppressed eNOS expression by more than 60% and activity by 83% but did not affect iNOS expression or activity. Inhibition of endogenous NOS with l-NAME led to spontaneous EMT, manifested by increased α-smooth muscle actin (α-SMA) expression and a fibroblast-like morphology. Provision of exogenous NO to TGF-β1-treated AEC decreased stress fiber-associated α-SMA expression and decreased collagen I expression by 80%. NO-treated AEC also retained an epithelial morphology and expressed increased lamellar protein, E-cadherin, and pro-surfactant protein B compared with those treated with TGF-β alone. These findings indicate that NO serves a critical role in preserving an epithelial phenotype and in attenuating EMT in AEC. NO-mediated regulation of AEC fate may have important implications in the pathophysiology and treatment of diseases such as IPF and BPD.

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Cl-channel activation is necessary for stimulation of Na transport in adult alveolar epithelial cells

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.2000.278.2.l239 ◽

2000 ◽

Vol 278 (2) ◽

pp. L239-L244 ◽

Cited By ~ 34

Author(s):

Scott M. O'Grady ◽

Xinpo Jiang ◽

David H. Ingbar

Keyword(s):

Epithelial Cells ◽

Adrenergic Receptor ◽

Apical Membrane ◽

Receptor Activation ◽

Alveolar Epithelial Cells ◽

Na Channels ◽

Channel Activation ◽

Alveolar Epithelial ◽

Cl Channel ◽

Stimulation Of

In this review, we discuss evidence that supports the hypothesis that adrenergic stimulation of transepithelial Na absorption across the alveolar epithelium occurs indirectly by activation of apical Cl channels, resulting in hyperpolarization and an increased driving force for Na uptake through amiloride-sensitive Na channels. This hypothesis differs from the prevailing idea that adrenergic-receptor activation increases the open probability of Na channels, leading to an increase in apical membrane Na permeability and an increase in Na and fluid uptake from the alveolar space. We review results from cultured alveolar epithelial cell monolayer experiments that show increases in apical membrane Cl conductance in the absence of any change in Na conductance after stimulation by selective β-adrenergic-receptor agonists. We also discuss possible reasons for differences in Na-channel regulation in cells grown in monolayer culture compared with that in dissociated alveolar epithelial cells. Finally, we describe some preliminary in vivo data that suggest a role for Cl-channel activation in the process of amiloride-sensitive alveolar fluid absorption.

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Macrophage Control of Phagocytosed Mycobacteria Is Increased by Factors Secreted by Alveolar Epithelial Cells through Nitric Oxide Independent Mechanisms

PLoS ONE ◽

10.1371/journal.pone.0103411 ◽

2014 ◽

Vol 9 (8) ◽

pp. e103411 ◽

Cited By ~ 8

Author(s):

Dagbjort H. Petursdottir ◽

Olga D. Chuquimia ◽

Raphaela Freidl ◽

Carmen Fernández

Keyword(s):

Nitric Oxide ◽

Epithelial Cells ◽

Alveolar Epithelial Cells ◽

Alveolar Epithelial

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Mechanical stretching of alveolar epithelial cells increases Na+-K+-ATPase activity

Journal of Applied Physiology ◽

10.1152/jappl.1999.87.2.715 ◽

1999 ◽

Vol 87 (2) ◽

pp. 715-721 ◽

Cited By ~ 53

Author(s):

Christopher M. Waters ◽

Karen M. Ridge ◽

G. Sunio ◽

K. Venetsanou ◽

Jacob Iasha Sznajder

Keyword(s):

Epithelial Cells ◽

Atpase Activity ◽

Basolateral Membrane ◽

Alveolar Epithelial Cells ◽

Lung Epithelial Cells ◽

Cyclic Stretch ◽

Lung Edema ◽

Alveolar Epithelial ◽

A Cell

Alveolar epithelial cells effect edema clearance by transporting Na+ and liquid out of the air spaces. Active Na+ transport by the basolaterally located Na+-K+-ATPase is an important contributor to lung edema clearance. Because alveoli undergo cyclic stretch in vivo, we investigated the role of cyclic stretch in the regulation of Na+-K+-ATPase activity in alveolar epithelial cells. Using the Flexercell Strain Unit, we exposed a cell line of murine lung epithelial cells (MLE-12) to cyclic stretch (30 cycles/min). After 15 min of stretch (10% mean strain), there was no change in Na+-K+-ATPase activity, as assessed by86Rb+uptake. By 30 min and after 60 min, Na+-K+-ATPase activity was significantly increased. When cells were treated with amiloride to block amiloride-sensitive Na+ entry into cells or when cells were treated with gadolinium to block stretch-activated, nonselective cation channels, there was no stimulation of Na+-K+-ATPase activity by cyclic stretch. Conversely, cells exposed to Nystatin, which increases Na+ entry into cells, demonstrated increased Na+-K+-ATPase activity. The changes in Na+-K+-ATPase activity were paralleled by increased Na+-K+-ATPase protein in the basolateral membrane of MLE-12 cells. Thus, in MLE-12 cells, short-term cyclic stretch stimulates Na+-K+-ATPase activity, most likely by increasing intracellular Na+ and by recruitment of Na+-K+-ATPase subunits from intracellular pools to the basolateral membrane.

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Hypercapnia induces injury to alveolar epithelial cells via a nitric oxide-dependent pathway

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.2000.279.5.l994 ◽

2000 ◽

Vol 279 (5) ◽

pp. L994-L1002 ◽

Cited By ~ 71

Author(s):

John D. Lang ◽

Phillip Chumley ◽

Jason P. Eiserich ◽

Alvaro Estevez ◽

Thad Bamberg ◽

...

Keyword(s):

Nitric Oxide ◽

Epithelial Cells ◽

Cell Injury ◽

Inflammatory Responses ◽

Alveolar Epithelial Cells ◽

No Production ◽

Inflammatory Reactions ◽

Alveolar Epithelial ◽

And Function ◽

The Impact

Ventilator strategies allowing for increases in carbon dioxide (CO2) tensions (hypercapnia) are being emphasized to ameliorate the consequences of inflammatory-mediated lung injury. Inflammatory responses lead to the generation of reactive species including superoxide (O2 −), nitric oxide (·NO), and their product peroxynitrite (ONOO−). The reaction of CO2 and ONOO− can yield the nitrosoperoxocarbonate adduct ONOOCO2 −, a more potent nitrating species than ONOO−. Based on these premises, monolayers of fetal rat alveolar epithelial cells were utilized to investigate whether hypercapnia would modify pathways of ·NO production and reactivity that impact pulmonary metabolism and function. Stimulated cells exposed to 15% CO2 (hypercapnia) revealed a significant increase in ·NO production and nitric oxide synthase (NOS) activity. Cell 3-nitrotyrosine content as measured by both HPLC and immunofluorescence staining also increased when exposed to these same conditions. Hypercapnia significantly enhanced cell injury as evidenced by impairment of monolayer barrier function and increased induction of apoptosis. These results were attenuated by the NOS inhibitor N-monomethyl-l-arginine. Our studies reveal that hypercapnia modifies ·NO-dependent pathways to amplify cell injury. These results affirm the underlying role of ·NO in tissue inflammatory reactions and reveal the impact of hypercapnia on inflammatory reactions and its potential detrimental influences.

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Effect of the adenovirus E1A gene on nitric oxide production in alveolar epithelial cells

Clinical Microbiology and Infection ◽

10.1111/j.1469-0691.2005.01188.x ◽

2005 ◽

Vol 11 (8) ◽

pp. 644-650 ◽

Cited By ~ 3

Author(s):

Y. Higashimoto ◽

M. Ohata ◽

Y. Yamagata ◽

T. Iwata ◽

M. Masuda ◽

...

Keyword(s):

Nitric Oxide ◽

Epithelial Cells ◽

Alveolar Epithelial Cells ◽

Nitric Oxide Production ◽

Alveolar Epithelial ◽

Adenovirus E1a ◽

Oxide Production ◽

E1a Gene

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The Fas/FasL pathway impairs the alveolar fluid clearance in mouse lungs

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00271.2012 ◽

2013 ◽

Vol 305 (5) ◽

pp. L377-L388 ◽

Cited By ~ 15

Author(s):

Raquel Herrero ◽

Mishie Tanino ◽

Lincoln S. Smith ◽

Osamu Kajikawa ◽

Venus A. Wong ◽

...

Keyword(s):

Epithelial Cells ◽

Fas Ligand ◽

Alveolar Epithelium ◽

Alveolar Epithelial Cells ◽

Critical Event ◽

Lung Edema ◽

Adrenergic Stimulation ◽

Epithelial Damage ◽

Alveolar Epithelial ◽

Mouse Lungs

Alveolar epithelial damage is a critical event that leads to protein-rich edema in acute lung injury (ALI), but the mechanisms leading to epithelial damage are not completely understood. Cell death by necrosis and apoptosis occurs in alveolar epithelial cells in the lungs of patients with ALI. Fas activation induces apoptosis of alveolar epithelial cells, but its role in the formation of lung edema is unclear. The main goal of this study was to determine whether activation of the Fas/Fas ligand pathway in the lungs could alter the function of the lung epithelium, and the mechanisms involved. The results show that Fas activation alters the alveolar barrier integrity and impairs the ability of the lung alveolar epithelium to reabsorb fluid from the air spaces. This result was dependent on the presence of a normal Fas receptor and was not affected by inflammation induced by Fas activation. Alteration of the fluid transport properties of the alveolar epithelium was partially restored by β-adrenergic stimulation. Fas activation also caused apoptosis of alveolar endothelial cells, but this effect was less pronounced than the effect on the alveolar epithelium. Thus, activation of the Fas pathway impairs alveolar epithelial function in mouse lungs by mechanisms involving caspase-dependent apoptosis, suggesting that targeting apoptotic pathways could reduce the formation of lung edema in ALI.

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