Impairment of cation transport in A549 cells and rat alveolar epithelial cells by hypoxia

1997 ◽  
Vol 273 (4) ◽  
pp. L797-L806 ◽  
Author(s):  
Heimo Mairbäurl ◽  
Ralf Wodopia ◽  
Sigrid Eckes ◽  
Susanne Schulz ◽  
Peter Bärtsch
Keyword(s):  
Epithelial Cells ◽  
A549 Cells ◽  
Alveolar Epithelium ◽  
Cell Types ◽  
Cation Transport ◽  
Alveolar Epithelial Cells ◽  
Alveolar Type ◽  
Water Reabsorption ◽  
Alveolar Epithelial

A reduced cation reabsorption across the alveolar epithelium decreases water reabsorption from the alveoli and could diminish clearing accumulated fluid. To test whether hypoxia restricts cation transport in alveolar epithelial cells, cation uptake was measured in rat lung alveolar type II pneumocytes (AII cells) in primary culture and in A549 cells exposed to normoxia and hypoxia. In AII and A549 cells, hypoxia caused a[Formula: see text]-dependent inhibition of the Na-K pump, of Na-K-2Cl cotransport, and of total and amiloride-sensitive22Na uptake. Nifedipine failed to prevent hypoxia-induced transport inhibition in both cell types. In A549 cells, the inhibition of the Na-K pump and Na-K-2Cl cotransport occurred within ∼30 min of hypoxia, was stable >20 h, and was reversed by 2 h of reoxygenation. There was also a reduction in cell membrane-associated Na-K-ATPase and a decrease in Na-K-2Cl cotransport flux after full activation with calyculin A, indicating a decreased transport capacity. [14C]serine incorporation into cell proteins was reduced in hypoxic A549 cells, but inhibition of protein synthesis with cycloheximide did not reduce ion transport. In AII and A549 cells, ATP levels decreased slightly, and ADP and the ATP-to-ADP ratio were unchanged after 4 h of hypoxia. In A549 cells, lactate, intracellular Na, and intracellular K were unchanged. These results indicate that hypoxia inhibits apical Na entry pathways and the basolateral Na-K pump in A549 cells and rat AII pneumocytes in culture, indicating a hypoxia-induced reduction of transepithelial Na transport and water reabsorption by alveolar epithelium. If similar changes occur in vivo, the impaired cation transport across alveolar epithelial cells might contribute to the formation of hypoxic pulmonary edema.

Hypoxia decreases proteins involved in epithelial electrolyte transport in A549 cells and rat lung

2000 ◽  
Vol 279 (6) ◽  
pp. L1110-L1119 ◽  
Author(s):  
Ralf Wodopia ◽  
Hyun Soo Ko ◽  
Javiera Billian ◽  
Rudolf Wiesner ◽  
Peter Bärtsch ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Lung Tissue ◽  
A549 Cells ◽  
Alveolar Epithelial Cells ◽  
Alveolar Type ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Type Ii Cells ◽  
Alveolar Epithelial

Fluid reabsorption from alveolar space is driven by active Na reabsorption via epithelial Na channels (ENaCs) and Na-K-ATPase. Both are inhibited by hypoxia. Here we tested whether hypoxia decreases Na transport by decreasing the number of copies of transporters in alveolar epithelial cells and in lungs of hypoxic rats. Membrane fractions were prepared from A549 cells exposed to hypoxia (3% O2) as well as from whole lung tissue and alveolar type II cells from rats exposed to hypoxia. Transport proteins were measured by Western blot analysis. In A549 cells, α1- and β1-Na-K-ATPase, Na/K/2Cl cotransport, and ENaC proteins decreased during hypoxia. In whole lung tissue, α1-Na-K-ATPase and Na/K/2Cl cotransport decreased. α- and β-ENaC mRNAs also decreased in hypoxic lungs. Similar results were seen in alveolar type II cells from hypoxic rats. These results indicate a slow decrease in the amount of Na-transporting proteins in alveolar epithelial cells during exposure to hypoxia that also occurs in vivo in lungs from hypoxic animals. The reduced number of transporters might account for the decreased transport activity and impaired edema clearance in hypoxic lungs.

Discordant regulatory changes in monocrotaline-induced megalocytosis of lung arterial endothelial and alveolar epithelial cells

2006 ◽  
Vol 290 (6) ◽  
pp. L1216-L1226 ◽  
Author(s):  
Somshuvra Mukhopadhyay ◽  
Pravin B. Sehgal
Keyword(s):  
Cell Cycle ◽  
Epithelial Cells ◽  
Dna Synthesis ◽  
A549 Cells ◽  
Cell Types ◽  
Alveolar Epithelial Cells ◽  
Cell Type ◽  
Alveolar Epithelial ◽  
Unfolded Protein ◽  
Cell Cycle Regulatory Proteins

Monocrotaline (MCT) causes pulmonary hypertension in the rat by a mechanism characterized by megalocytosis (enlarged cells with enlarged endoplasmic reticulum and Golgi and a cell cycle arrest) of pulmonary arterial endothelial (PAEC), arterial smooth muscle, and type II alveolar epithelial cells. In cell culture, although megalocytosis is associated with a block in entry into mitosis in both lung endothelial and epithelial cells, DNA synthesis is stimulated in endothelial but inhibited in epithelial cells. The molecular mechanism(s) for this dichotomy are unclear. While MCTP-treated PAEC and lung epithelial (A549) cells both showed an increase in the “promitogenic” transcription factor STAT3 levels and in the IL-6-induced nuclear pool of PY-STAT3, this was transcriptionally inactive in A549 but not in PAEC cells. This lack of transcriptional activity of STAT3 in A549 cells correlated with the cytoplasmic sequestration of the STAT3 coactivators CBP/p300 and SRC1/NcoA in A549 cells but not in PAEC. Both cell types displayed a Golgi trafficking block, loss of caveolin-1 rafts, and increased nuclear Ire1α, but an incomplete unfolded protein response (UPR) with little change in levels of UPR-induced chaperones including GRP78/BiP. There were discordant alterations in cell cycle regulatory proteins in the two cell types such as increase in levels of both cyclin D1 and p21 simultaneously, but with a decrease in cdc2/cdk1, a kinase required for entry into mitosis. While both cell types showed increased cytoplasmic geminin, the DNA synthesis-initiating protein Cdt1 was predominantly nuclear in PAEC but remained cytoplasmic in A549 cells, consistent with the stimulation of DNA synthesis in the former but an inhibition in the latter cell type. Thus differences in cell type-specific alterations in subcellular trafficking of critical regulatory molecules (such as CBP/p300, SRC1/NcoA, Cdt1) likely account for the dichotomy of the effects of MCTP on DNA synthesis in endothelial and epithelial cells.

Tight monolayers of rat alveolar epithelial cells: bioelectric properties and active sodium transport

1989 ◽  
Vol 256 (3) ◽  
pp. C688-C693 ◽  
Author(s):  
J. M. Cheek ◽  
K. J. Kim ◽  
E. D. Crandall
Keyword(s):  
Epithelial Cells ◽  
Sodium Transport ◽  
Short Circuit ◽  
Alveolar Epithelium ◽  
Alveolar Epithelial Cells ◽  
Active Sodium ◽  
Alveolar Epithelial ◽  
Active Sodium Transport ◽  
Complex Anatomy

Because the pulmonary alveolar epithelium separates air spaces from a fluid-filled compartment, it is expected that this barrier would be highly resistant to the flow of solutes and water. Investigation of alveolar epithelial resistance has been limited due to the complex anatomy of adult mammalian lung. Previous efforts to study isolated alveolar epithelium cultured on porous substrata yielded leaky monolayers. In this study, alveolar epithelial cells isolated from rat lungs and grown on tissue culture-treated Nucleopore filters resulted in tight monolayers with transepithelial resistance greater than 2,000 omega.cm2. Changes in bioelectric properties of these alveolar epithelial monolayers in response to ouabain, amiloride, and terbutaline are consistent with active sodium transport across a polarized barrier. 22Na flux measurements under short-circuit conditions directly confirm net transepithelial absorption of sodium by alveolar epithelial cells in the apical to basolateral direction, comparable to the observed short-circuit current (4.37 microA/cm2). The transport properties of these tight monolayers may be representative of the characteristics of the mammalian alveolar epithelial barrier in vivo.

Effect of endocytosis inhibitors on alveolar clearance of albumin, immunoglobulin G, and SP-A in rabbits

1994 ◽  
Vol 266 (5) ◽  
pp. L544-L552 ◽  
Author(s):  
R. H. Hastings ◽  
J. R. Wright ◽  
K. H. Albertine ◽  
R. Ciriales ◽  
M. A. Matthay
Keyword(s):  
Immunoglobulin G ◽  
Protein Transport ◽  
Protein A ◽  
Alveolar Epithelium ◽  
Alveolar Epithelial Cells ◽  
Capillary Endothelium ◽  
Alveolar Type ◽  
Protein Uptake ◽  
Alveolar Epithelial

Protein in the alveolar space may be cleared by endocytosis and degradation inside alveolar epithelial cells, by transcytosis across the alveolar epithelium, or by restricted diffusion through the epithelium. The relative contributions of these three pathways to clearance of large quantities of protein from the air spaces is not known. This study investigated the effects of monensin and nocodazole, agents which inhibit endocytosis in cell culture, on alveolar epithelial protein transport in anesthetized rabbits. There was evidence that monensin and nocodazole inhibited endocytosis by the alveolar epithelium in vivo. Nocodazole increased the number of vesicles in the alveolar epithelium and capillary endothelium. Monensin increased vesicle density in the endothelium. These results suggested that the inhibitors disrupted microtubules or interrupted cellular membrane traffic in the lung. Both inhibitors decreased lung parenchymal uptake of immunoreactive human albumin from the air spaces. Monensin and nocodazole inhibited albumin uptake in cultured alveolar type II cells. Monensin increased the amount of 125I-labeled surfactant protein A associated with the lungs, compared with the quantity remaining in the air space 2 h after instillation. Although the drugs decreased alveolar epithelial protein uptake, they did not decrease alveolar clearance of 125I-labeled immunoglobulin G or 131I-labeled albumin in anesthetized rabbits. Thus monensin- and nocodazole-sensitive protein-uptake pathways do not account for most alveolar protein clearance when the distal air spaces are filled with a protein solution.

Expression of the tyrosine phosphatase LAR-PTP2 is developmentally regulated in lung epithelia

1994 ◽  
Vol 267 (3) ◽  
pp. L263-L270 ◽  
Author(s):  
D. Rotin ◽  
B. J. Goldstein ◽  
C. A. Fladd
Keyword(s):  
Epithelial Cells ◽  
Lung Development ◽  
Tyrosine Phosphatase ◽  
A549 Cells ◽  
Alveolar Epithelial Cells ◽  
Alveolar Type ◽  
Type Ii ◽  
Adult Type ◽  
Alveolar Epithelial

The role of tyrosine kinases in regulating cell proliferation, differentiation, and development has been well documented. In contrast, little is known about the role of protein tyrosine phosphatases (PTPs) in mammalian development. To identify PTPs that may be involved in lung development, we have isolated (by polymerase chain reaction) from rat fetal alveolar epithelial cells a cDNA fragment which was identified as the recently cloned tyrosine phosphatase LAR-PTP2. Analysis of tissue expression of LAR-PTP2 identified a approximately 7.5-kb message in the lung, which is also expressed weakly in brain, and an alternatively spliced approximately 6.0-kb message (LAR-PTP2B) expressed in brain. In the fetal lung, LAR-PTP2 was preferentially expressed in lung epithelial (but not fibroblast) cells grown briefly in primary culture, and its expression was tightly regulated during lung development, peaking at 20 days of gestational age (term = 22 days), when mature alveolar type II epithelium first appears. Accordingly, immunoblot analysis revealed high expression of endogenous LAR-PTP2 protein in alveolar epithelial cells from 21-day gestation fetuses. LAR-PTP2 was also expressed in lungs of newborn rats, but transcripts (and protein) were barely detectable in adult lungs and in the nonproliferating adult alveolar type II cells. Interestingly, expression was restored in the transformed adult type II-like A549 cells. These results suggest that LAR-PTP2 may play a role in the proliferation and/or differentiation of epithelial cells during lung development.

Parathyroid hormone-related protein, an autocrine regulatory factor in alveolar epithelial cells

1996 ◽  
Vol 270 (3) ◽  
pp. L353-L361 ◽  
Author(s):  
R. H. Hastings ◽  
D. Summers-Torres ◽  
T. C. Cheung ◽  
L. S. Ditmer ◽  
E. M. Petrin ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Primary Cultures ◽  
A549 Cells ◽  
Alveolar Epithelial Cells ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Epithelial ◽  
Parathyroid Hormone Related Protein ◽  
Pthrp Receptor

Alveolar epithelial cells in vivo, primary cultures of adult rat type II cells, and human A549 alveolar carcinoma cells express parathyroid hormone-related protein (PTHrP). Here we demonstrated that type II cells and A549 cells also express the PTHrP receptor and that they exhibit differentiation-related responses to the amino-terminal PTHrP fragment, PTHrP-(1-34). PTHrP receptor expression in A549 cells was shown by detection of a 0.3-kb reverse transcriptase polymerase chain reaction product formed by primers specific for PTHrP receptor. In situ hybridization studies localized the site of production of PTHrP and PTHrP receptor mRNA in rat lung cells with morphology and location typical of type II cells. Primary cultures of such type II cells also expressed PTHrP receptor mRNA. Incubation with PTHrP-(1-34) stimulated disaturated phosphatidylcholine (DSPC) synthesis in A549 cells and increased the release of newly synthesized DSPC by cultured type II cells and A549 cells. In addition, PTHrP-(1-34) increased the number of lamellar bodies per type II cell and increased their expression of alkaline phosphatase in a dose-dependent manner. Thus PTHrP-(1-34) promoted a differentiated type II cell phenotype. Since cultured type II cells, alveolar epithelial cells in vivo, and A549 cells express PTHrP and the PTHrP receptor, PTHrP-(1-34) may be an autocrine regulatory factor in type II cells and lung cancer cells.

scholarly journals Methemoglobin-induced signaling and chemokine responses in human alveolar epithelial cells

2014 ◽  
Vol 306 (1) ◽  
pp. L88-L100 ◽  
Author(s):  
Sharon Mumby ◽  
Latha Ramakrishnan ◽  
Timothy W. Evans ◽  
Mark J. D. Griffiths ◽  
Gregory J. Quinlan
Keyword(s):  
Epithelial Cells ◽  
Primary Cultures ◽  
A549 Cells ◽  
Alveolar Epithelial Cells ◽  
Lung Epithelial Cells ◽  
Alveolar Type ◽  
Alveolar Epithelial ◽  
Pathway Activation ◽  
Jnk Activation ◽  
Human Alveolar Epithelial Cells

Diffuse alveolar hemorrhage is characterized by the presence of red blood cells and free hemoglobin in the alveoli and complicates a number of serious medical and surgical lung conditions including the pulmonary vasculitides and acute respiratory distress syndrome. In this study we investigated the hypothesis that exposure of human alveolar epithelial cells to hemoglobin and its breakdown products regulates chemokine release via iron- and oxidant-mediated activation of the transcription factor NF-κB. Methemoglobin alone stimulated the release of IL-8 and MCP-1 from A549 cells via activation of the NF-κB pathway; additionally, IL-8 required ERK activation and MCP-1 required JNK activation. Neither antioxidants nor iron chelators and knockdown of ferritin heavy and light chains affected these responses, indicating that iron and reactive oxygen species are not involved in the response of alveolar epithelial cells to methemoglobin. Incubation of primary cultures of human alveolar type 2 cells with methemoglobin resulted in a similar pattern of chemokine release and signaling pathway activation. In summary, we have shown for the first time that methemoglobin induced chemokine release from human lung epithelial cells independent of iron- and redox-mediated signaling involving the activation of the NF-κB and MAPK pathways. Decompartmentalization of hemoglobin may be a significant proinflammatory stimulus in a variety of lung diseases.

Ectopeptidases of alveolar epithelium: candidates for roles in alveolar regulatory mechanisms

1991 ◽  
Vol 260 (6) ◽  
pp. L381-L385
Author(s):  
J. D. Funkhouser ◽  
S. D. Tangada ◽  
R. D. Peterson
Keyword(s):  
Biological Activity ◽  
Epithelial Cells ◽  
Alveolar Epithelium ◽  
Cell Types ◽  
Alveolar Epithelial Cells ◽  
Regulatory Mechanisms ◽  
Luminal Surface ◽  
Biological Feature ◽  
Alveolar Cells ◽  
Alveolar Epithelial

This commentary discusses the implications of recent observations indicating that at least one, and probably three, ectopeptidases are exhibited on the surface of alveolar epithelial cells. The unique biological feature of the ectopeptidases is that they are expressed on the surface of only selected cell types and at specific stages in the differentiation of those cells. Consequently they are positioned to exert their enzymatic activity in a very restricted locale. Drawing from information derived from studies of this activity on other cells, we develop the proposition that the ectopeptidases on alveolar epithelial cells regulate the biological activity of peptides encountered at this site. These may be peptides produced by the alveolar epithelial cells or cytokines that have the potential of influencing the alveolar cells. Awareness that these ectopeptidases are expressed on the luminal surface of these cells thus opens heretofore unrecognized avenues of investigation.

scholarly journals Role of CXCL16 in BLM-induced epithelial–mesenchymal transition in human A549 cells

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Zhenzhen Ma ◽  
Chunyan Ma ◽  
Qingfeng Zhang ◽  
Yang Bai ◽  
Kun Mu ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Pulmonary Fibrosis ◽  
Epithelial Mesenchymal Transition ◽  
A549 Cells ◽  
Alveolar Epithelial Cells ◽  
Alveolar Type ◽  
Mesenchymal Transition ◽  
Alveolar Epithelial ◽  
Tgf Β1

AbstractAlveolar epithelial cells play an essential role in the initiation and progression of pulmonary fibrosis, and the occurrence of epithelial–mesenchymal transition (EMT) may be the early events of pulmonary fibrosis. Recent studies have shown chemokines are involved in the complex process of EMT, and CXC chemokine ligand 16 (CXCL16) is also associated with many fibrosis-related diseases. However, whether CXCL16 is dysregulated in alveolar epithelial cells and the role of CXCL16 in modulating EMT in pulmonary fibrosis has not been reported. In this study, we found that CXCL16 and its receptor C-X-C motif chemokine receptor 6 (CXCR6) were upregulated in bleomycin induced EMT in human alveolar type II-like epithelial A549 cells. Synergistic effect of CXCL16 and bleomycin in promoting EMT occurrence, extracellular matrix (ECM) excretion, as well as the pro-inflammatory and pro-fibrotic cytokines productions in A549 cells were observed, and those biological functions were impaired by CXCL16 siRNA. We further confirmed that CXCL16 regulated EMT in A549 cells via the TGF-β1/Smad3 pathways. These results indicated that CXCL16 could promote pulmonary fibrosis by promoting the process of EMT via the TGF-β1/Smad3 signaling pathway.

Autoregulation of CCL26 synthesis and secretion in A549 cells: a possible mechanism by which alveolar epithelial cells modulate airway inflammation

2005 ◽  
Vol 289 (3) ◽  
pp. L478-L488 ◽  
Author(s):  
B. O. Abonyo ◽  
M. S. Alexander ◽  
A. S. Heiman
Keyword(s):  
Epithelial Cells ◽  
A549 Cells ◽  
Airway Epithelial Cells ◽  
Alveolar Epithelial Cells ◽  
Alveolar Type ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Receptor System ◽  
Superoxide Anion Production ◽  
Alveolar Epithelial

Eotaxins (CCL11, CCL24, CCL26) originating from airway epithelial cells and leukocytes have been detected in bronchoalveolar lavage of asthmatics. Although the alveolar epithelium is the destination of uncleared allergens and other inflammatory products, scanty information exists on their contribution to the generation and regulation of the eotaxins. We envisioned a state whereby alveolar type II cells, a known source of other inflammatory proteins, could be involved in both the production and regulation of CCL24 and CCL26. Herein, we demonstrated that all three eotaxins are constitutively expressed in A549 cells. IL-4 and IL-13 stimulated a concentration-dependent secretion of CCL24 and CCL26. The cytokines did not act synergistically. Cycloheximide and actinomycin D abrogated IL-4- and IL-13-dependent CCL26 but not CCL24 secretion. Both IL-13 and IL-4 stimulated CCL26 synthesis that was inhibited in a concentration-dependent manner by CCL26 but not CCL24. Only CCL26 reduced expression of CCR3 receptors by 30–40%. On the other hand, anti-CCR3 pretreatment reduced IL-4+IL-13-dependent CCL26 secretion, implying autoregulation. A CCR3-specific antagonist (SB-328437) significantly decreased IL-4-dependent synthesis and release of CCL26. Eosinophils treated with medium from IL-4-stimulated A549 cells preincubated with anti-CCL26 showed a marked decrease of superoxide anion production compared with anti-CCL24 treated. These results suggest that CCL26 is a major eotaxin synthesized and released by alveolar epithelial cells and is involved in autoregulation of CCR3 receptors and other eotaxins. This CCL26-CCR3 ligand-receptor system may be an attractive target for development of therapeutics that limits progress of inflammation in airway disease.

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