Alveolar epithelial cells regulate the induction of endothelial cell apoptosis

1994 ◽  
Vol 267 (4) ◽  
pp. C893-C900 ◽  
Author(s):  
C. H. Wendt ◽  
V. A. Polunovsky ◽  
M. S. Peterson ◽  
P. B. Bitterman ◽  
D. H. Ingbar
Keyword(s):  
Endothelial Cells ◽  
Epithelial Cells ◽  
Cell Apoptosis ◽  
Mesenchymal Cell ◽  
Alveolar Epithelial Cells ◽  
Tnf Alpha ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Epithelial ◽  
Induced Apoptosis

Mesenchymal cell apoptosis is important during development, tissue homeostasis, and repair. We sought to determine whether type II alveolar epithelial cells influence mesenchymal cell apoptosis, using the model of tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis of endothelial cells. Apoptosis was quantified by morphology and confirmed by electrophoretic DNA size analysis. Endothelial cells exposed to 20 ng/ml of TNF-alpha for 16 h exhibited apoptosis in 14.4 +/- 1.4% (SE) of the cells, whereas serum-free conditioned media (CM) from primary cultures of rat type II cells reduced TNF-alpha-induced apoptosis by 52% to 7.5 +/- 0.9% (P < 0.01). Flow cytometric analysis of subdiploid DNA content per cell also showed that CM reduced the percentage of cells with TNF-alpha-induced DNA degradation by 48 +/- 1.7%. The protective effect of CM was concentration dependent and also was effective across a range of TNF concentrations. This CM factor was trypsin sensitive and stable at 65 degrees C for 1 h. It bound to a Mono-Q anion-exchange resin, eluting in a discrete peak at 1.18 M NaCl and pH 8.5. Therefore alveolar type II cells release a heat-stable peptide(s) that protects endothelial cells against apoptosis induced by TNF. Our results suggest that alveolar epithelial cells regulate the response of mesenchymal cells to factors that induce apoptosis during injury and repair.

Disparate cytokine regulation of ICAM-1 in rat alveolar epithelial cells and pulmonary endothelial cells in vitro

1995 ◽  
Vol 269 (1) ◽  
pp. L127-L135 ◽  
Author(s):  
W. W. Barton ◽  
S. Wilcoxen ◽  
P. J. Christensen ◽  
R. Paine
Keyword(s):  
Endothelial Cells ◽  
Epithelial Cells ◽  
Inflammatory Cytokines ◽  
Alveolar Epithelial Cells ◽  
Normal Lung ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Epithelial

Intercellular adhesion molecule-1 (ICAM-1) is expressed at high levels on type I alveolar epithelial cells in the normal lung and is induced in vitro as type II cells spread in primary culture. In contrast, in most nonhematopoetic cells ICAM-1 expression is induced in response to inflammatory cytokines. We have formed the hypothesis that the signals that control ICAM-1 expression in alveolar epithelial cells are fundamentally different from those controlling expression in most other cells. To test this hypothesis, we have investigated the influence of inflammatory cytokines on ICAM-1 expression in isolated type II cells that have spread in culture and compared this response to that of rat pulmonary artery endothelial cells (RPAEC). ICAM-1 protein, determined both by a cell-based enzyme-linked immunosorbent assay and by Western blot analysis, and mRNA were minimally expressed in unstimulated RPAEC but were significantly induced in a time- and dose-dependent manner by treatment with tumor necrosis factor-alpha, interleukin-1 beta, or interferon-gamma. In contrast, these cytokines did not influence the constitutive high level ICAM-1 protein expression in alveolar epithelial cells and only minimally affected steady-state mRNA levels. ICAM-1 mRNA half-life, measured in the presence of actinomycin D, was relatively long at 7 h in alveolar epithelial cells and 4 h in RPAEC. The striking lack of response of ICAM-1 expression by alveolar epithelial cells to inflammatory cytokines is in contrast to virtually all other epithelial cells studied to date and supports the hypothesis that ICAM-1 expression by these cells is a function of cellular differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of ICAM-1 with the cytoskeleton in rat alveolar epithelial cells in primary culture

1996 ◽  
Vol 271 (5) ◽  
pp. L707-L718 ◽  
Author(s):  
W. W. Barton ◽  
S. E. Wilcoxen ◽  
P. J. Christensen ◽  
R. Paine
Keyword(s):  
Endothelial Cells ◽  
Epithelial Cell ◽  
Epithelial Cells ◽  
Alveolar Epithelial Cell ◽  
Inflammatory Cells ◽  
Alveolar Epithelial Cells ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Epithelial

Intercellular adhesion molecule-1 ICAM-1) is a transmembrane adhesion protein that is expressed constitutively on the apical surface of type I cells in vivo and on type II cells in vitro as they spread in culture, assuming type I cell-like characteristics. To investigate the possible interaction of ICAM-1 with the alveolar epithelial cell cytoskeleton, rat type II cells in primary culture were extracted with nonionic detergent, and residual ICAM-1 associated with the cytoskeletal remnants was determined using immunofluorescence microscopy, immunoprecipitation, and cell-based enzyme-linked immunosorbent assay. A large fraction of alveolar epithelial cell ICAM-1 remained associated with the cytoskeleton after detergent extraction, whereas two other transmembrane molecules, transferrin receptor and class II major histocompatibility complex, were completely removed. ICAM-1 was redistributed on the cell surface after the disruption of actin filaments with cytochalasin B, suggesting interaction with the actin cytoskeleton. In contrast, ICAM-1 was completely detergent soluble in rat pulmonary artery endothelial cells, human umbilical vein endothelial cells, and rat alveolar macrophages. The association of ICAM-1 with the alveolar epithelial cell cytoskeleton was not altered after stimulation with inflammatory cytokines. However, detergent resistant ICAM-1 was significantly increased after crosslinking of ICAM-1 on the cell surface, suggesting that this cytoskeletal association may be modulated by interactions of alveolar epithelial cells with inflammatory cells. The association of ICAM-1 with the cytoskeleton in alveolar epithelial cells may provide a fixed intermediary between mobile inflammatory cells and the alveolar surface.

Secretion of cytokines by rat alveolar epithelial cells: possible regulatory role for SP-A

1994 ◽  
Vol 266 (2) ◽  
pp. L148-L155 ◽  
Author(s):  
H. Blau ◽  
S. Riklis ◽  
V. Kravtsov ◽  
M. Kalina
Keyword(s):  
Epithelial Cells ◽  
Alveolar Epithelial Cells ◽  
Alveolar Type ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Type Ii Cells ◽  
Long Term Culture ◽  
Alveolar Epithelial ◽  
Gm Csf

Cultured alveolar type II cells and pulmonary epithelial (PE) cells in long-term culture were found to secrete colony-stimulating factors (CSF) into the medium in similar fashion to alveolar macrophages. CSF activity was determined by using the in vitro assay for myeloid progenitor cells [colony-forming units in culture (CFU-C)]. Both lipopolisaccharide (LPS) and interleukin-1 alpha (IL-1 alpha) were found to upregulate the secretion 6.5- to 8-fold from alveolar type II cells and macrophages. However, no stimulatory effect of these factors was observed in PE cells that release CSF into the medium constitutively, possibly due to the conditions of long-term culture. The CSF activity was partially neutralized (70% inhibition) by antibodies against murine granulocyte/macrophage (GM)-CSF and IL-3, thus indicating the presence of both GM-CSF and IL-3-like factors in the CSF. However, the presence of other cytokines in the CSF is highly probable. Surfactant-associated protein A (SP-A), which is known to play a central role in surfactant homeostasis and function, was also found to upregulate secretion of CSF (at concentrations of 0.1-5 micrograms/ml) from alveolar type II cells and macrophages. Control cells such as rat peritoneal macrophages, alveolar fibroblasts, and 3T3/NIH cell line could not be elicited by SP-A to release CSF. The results are discussed in relation to the possible participation of the alveolar epithelial cells in various intercellular signaling networks. Our studies suggest that alveolar type II cells and SP-A may play an important regulatory role in the modulation of immune and inflammatory effector cells within the alveolar space.

scholarly journals Lectin binding patterns to terminal sugars of rat lung alveolar epithelial cells.

1990 ◽  
Vol 38 (2) ◽  
pp. 233-244 ◽  
Author(s):  
D J Taatjes ◽  
L A Barcomb ◽  
K O Leslie ◽  
R B Low
Keyword(s):  
Epithelial Cells ◽  
Lectin Binding ◽  
Alveolar Epithelial Cells ◽  
Gold Complex ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Rat Lung ◽  
Alveolar Epithelial ◽  
I Cells

We used post-embedding cytochemical techniques to investigate the lectin binding profiles of rat lung alveolar epithelial cells. Sections from rat lung embedded in the hydrophilic resin Lowicryl K4M were incubated either directly with a lectin-gold complex or with an unlabeled lectin followed by a specific glycoprotein-gold complex. The binding patterns of the five lectins used could be divided into three categories according to their reactivity with alveolar epithelial cells: (a) the Limax flavus lectin and Ricinus communis I lectin bound to both type I and type II cell plasma membranes; (b) the Helix pomatia lectin and Sambucus nigra L. lectin bound to type II but not type I cells; and (c) the Erythrina cristagalli lectin reacted with type I cells but was unreactive with type II cells. The specificity of staining was assessed by control experiments, including pre-absorption of the lectins with various oligosaccharides and enzymatic pre-treatment of sections with highly purified glycosidases to remove specific sugar residues. The results demonstrate that these lectins can be used to distinguish between type I and type II cells and would therefore be useful probes for investigating cell dynamics during lung development and remodeling.

Hyperoxia-induced apoptosis and Fas/FasL expression in lung epithelial cells

2005 ◽  
Vol 289 (4) ◽  
pp. L647-L659 ◽  
Author(s):  
Monique E. De Paepe ◽  
Quanfu Mao ◽  
Yvonne Chao ◽  
Jessica L. Powell ◽  
Lewis P. Rubin ◽  
...  
Keyword(s):  
Cell Death ◽  
Epithelial Cells ◽  
Protein Expression ◽  
Cell Apoptosis ◽  
Receptor Activation ◽  
Type Ii ◽  
Fasl Expression ◽  
Alveolar Epithelial ◽  
Type Ii Cell ◽  
Induced Apoptosis

Alveolar epithelial apoptosis is an important feature of hyperoxia-induced lung injury in vivo and has been described in the early stages of bronchopulmonary dysplasia (chronic lung disease of preterm newborn). Molecular regulation of hyperoxia-induced alveolar epithelial cell death remains incompletely understood. In view of functional involvement of Fas/FasL system in physiological postcanalicular type II cell apoptosis, we speculated this system may also be a critical regulator of hyperoxia-induced apoptosis. The aim of this study was to investigate the effects of hyperoxia on apoptosis and apoptotic gene expression in alveolar epithelial cells. Apoptosis was studied by TUNEL, electron microscopy, DNA size analysis, and caspase assays. Fas/FasL expression was determined by Western blot analysis and RPA. We determined that in MLE-12 cells exposed to hyperoxia, caspase-mediated apoptosis was the first morphologically and biochemically recognizable mode of cell death, followed by necrosis of residual adherent cells. The apoptotic stage was associated with a threefold upregulation of Fas mRNA and protein expression and increased susceptibility to direct Fas receptor activation, concomitant with a threefold increase of FasL protein levels. Fas gene silencing by siRNAs significantly reduced hyperoxia-induced apoptosis. In murine fetal type II cells, hyperoxia similarly induced markedly increased Fas/FasL protein expression, confirming validity of results obtained in transformed MLE-12 cells. Our findings implicate the Fas/FasL system as an important regulator of hyperoxia-induced type II cell apoptosis. Elucidation of regulation of hyperoxia-induced lung apoptosis may lead to alternative therapeutic strategies for perinatal or adult pulmonary diseases characterized by dysregulated type II cell apoptosis.

Injury of rat pulmonary alveolar epithelial cells by H2O2: dependence on phenotype and catalase

1991 ◽  
Vol 260 (4) ◽  
pp. L318-L325 ◽  
Author(s):  
R. H. Simon ◽  
J. A. Edwards ◽  
M. M. Reza ◽  
R. G. Kunkel
Keyword(s):  
Epithelial Cells ◽  
Catalase Activity ◽  
Lung Diseases ◽  
Alveolar Epithelial Cell ◽  
Alveolar Epithelial Cells ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Epithelial

In a variety of inflammatory lung diseases, type I alveolar epithelial cells are more likely to be injured than are type II cells. Because oxidants have been implicated as a cause of injury in various inflammatory lung diseases, we evaluated the effects of differentiation on alveolar epithelial cell susceptibility to H2O2-induced injury. With the use of isolated rat type II cells in culture, we found that the cytotoxic effect of H2O2 increased between days 2 and 7, when type II cells are known to lose their distinctive type II properties and assume a more type I-like appearance. We previously reported that type II cells utilized both intracellular catalase and glutathione-dependent reactions to protect against H2O2. We therefore examined whether alterations in either of these protective mechanisms were responsible for the differentiation-dependent changes in sensitivity to H2O2. We found that catalase activity within alveolar epithelial cells decreased between 2 and 7 days in culture, whereas no changes were detected in glutathione-dependent systems. We then used a histochemical technique that detects catalase activity and found that type II cells within rat lungs possessed numerous catalase-containing peroxisomes, whereas very few were detected in type I cells. These findings demonstrate that as type II cells assume a type I-like phenotype, they become more susceptible to H2O2-induced injury. This increased susceptibility is associated with reductions in intracellular catalase activity, both in vitro and in vivo.

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.

pH-induced calcium transients in type II alveolar epithelial cells

1993 ◽  
Vol 264 (5) ◽  
pp. L448-L457 ◽  
Author(s):  
G. D. Gerboth ◽  
R. M. Effros ◽  
R. J. Roman ◽  
E. R. Jacobs
Keyword(s):  
Epithelial Cells ◽  
Fluorescent Dyes ◽  
Cultured Cells ◽  
Alveolar Epithelial Cells ◽  
Metabolic Effects ◽  
Type Ii Cells ◽  
Type Ii ◽  
Intracellular Acidification ◽  
Isolated Cells ◽  
Alveolar Epithelial

Although both intracellular pH (pHi) and intracellular Ca2+ concentration ([Ca2+]i) are highly regulated and have important metabolic effects in alveolar epithelial cells, little is known about the interrelationship between these two ions in alveolar epithelial cells. The present study examined changes in [pH]i and [Ca2+]i in isolated alveolar epithelial cells using the fluorescent dyes SNARF-1 and fura-2. Basal pHi values in freshly isolated and cultured alveolar epithelial cells were 7.27 and 7.24, respectively. Resting [Ca2+]i values in freshly isolated cells (53 +/- 5 nM) were lower than those in cultured type II cells (107 +/- 21 nM). pHi increased rapidly after addition of 25 mM NH4Cl in both cultured and freshly isolated cells and then decreased back toward baseline over the following 10 min. The rise in pHi was associated with a transient increase in [Ca2+]i. Resuspension of cells in an NH4Cl-free solution resulted in rapid intracellular acidification, which recovered over the subsequent 10 min. Removal of sodium or addition of 1 mM amiloride to the external solution slowed the rate of recovery from intracellular acidification, consistent with the participation of Na(+)-H+ exchanger in this process. In freshly isolated cells, [Ca2+]i increased following acidification and then decreased as the cells recovered from an acid load. In cultured cells, [Ca2+]i also increased following acidification but then remained elevated over the subsequent 10 min. The recovery of [Ca2+]i toward baseline values in fresh cells following acidification was dependent on the presence of external sodium. These data demonstrate that both increases and decreases in pHi of alveolar epithelial cells are associated with increases in [Ca2+]i and suggest that some of the metabolic effects of altering pHi may be secondary to increases in [Ca2+]i. The dependency of [Ca2+]i recovery following acidification on external sodium raises the possibility that freshly isolated type II cells have Na(+)-Ca2+ exchangers that contribute to the regulation of [Ca2+]i.

gamma-Glutamyl transpeptidase is a polarized alveolar epithelial membrane protein

1995 ◽  
Vol 269 (2) ◽  
pp. L261-L271 ◽  
Author(s):  
D. H. Ingbar ◽  
K. Hepler ◽  
R. Dowin ◽  
E. Jacobsen ◽  
J. M. Dunitz ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Alveolar Epithelial Cells ◽  
Type I ◽  
Type Ii Cells ◽  
Apical Surface ◽  
Type Ii ◽  
Gamma Glutamyl Transpeptidase ◽  
Western Blots ◽  
Alveolar Epithelial ◽  
Glutamyl Transpeptidase

In many diseases the lung is injured by oxidants. gamma-Glutamyl transpeptidase (GGT) is an ectoenzyme on the apical plasma membrane of many epithelial cells that protects against oxidants by replenishing intracellular glutathione. We sought to localize GGT within rat lungs in vivo and in cultured alveolar epithelial cells. In the adult rat lung, indirect immunofluorescence (IF) with a polyclonal antibody to triton-solubilized GGT revealed linear staining outlining the alveoli. Immunoelectron microscopy (IEM) localized the protein on the apical surface of the alveolar epithelial cells, but more densely on type I cells than type II cells, as well as on the apical surface of some ciliated bronchial cells. On Western blots of whole lung and isolated type II cell membrane proteins, the antibody predominantly recognized a broad protein band of 110-120 kDa, consistent with the uncleaved, glycosylated form of GGT. Over time in culture, isolated rat type II cells had increasing immunoreactivity on Western blots and indirect IF but decreasing enzyme activity. At 2 days in culture, confocal laser scanning microscopy demonstrated that GGT was polarized to the apical surface of nonconfluent type II cells. Thus GGT is a polarized apical membrane protein in type I and II cells, suggesting a role in the metabolic functions of these cells. The increased immunoreactive GGT of cultured type II cells is consistent with their acquisition of properties similar to type I cells, but the lack of correlation between immunoreactive protein and enzyme activity awaits explanation.

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