TGF-α perturbs surfactant homeostasis in vivo

To determine potential relationships between transforming growth factor (TGF)-α and surfactant homeostasis, the metabolism, function, and composition of surfactant phospholipid and proteins were assessed in transgenic mice in which TGF-α was expressed in respiratory epithelial cells. Secretion of saturated phosphatidylcholine was decreased 40–60% by expression of TGF-α. Although SP-A, SP-B, and SP-C mRNA levels were unchanged by expression of TGF-α, SP-A and SP-B content in bronchoalveolar lavage fluid was decreased. The minimum surface tension of surfactant isolated from the transgenic mice was significantly increased. Incubation of cultured normal mice type II cells with TGF-α in vitro did not change secretion of surfactant phosphatidylcholine and SP-B, indicating that TGF-α does not directly influence surfactant secretion. Expression of a dominant negative (mutant) EGF receptor in the respiratory epithelium blocked the TGF-α-induced changes in lung morphology and surfactant secretion, indicating that EGF receptor signaling in distal epithelial cells was required for TGF-α effects on surfactant homeostasis. Because many epithelial cells were embedded in fibrotic lesions caused by TGF-α, changes in surfactant homeostasis may at least in part be influenced by tissue remodeling that results in decreased surfactant secretion. The number of nonembedded type II cells was decreased 30% when TGF-α was expressed during development and was increased threefold by TGF-α expression in adulthood, suggesting possible alteration of type II cells on surfactant metabolism in the adult lung. Abnormalities in surfactant function and decreased surfactant level in the airways may contribute to the pathophysiology induced by TGF-α in both the developing and adult lung.

Download Full-text

Adrenal hormone regulation of fibronectin synthesis by type II pulmonary epithelial cells

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1997.273.1.l86 ◽

1997 ◽

Vol 273 (1) ◽

pp. L86-L92

Author(s):

S. E. Dunsmore ◽

Y. C. Lee ◽

D. E. Rannels

Keyword(s):

Extracellular Matrix ◽

Epithelial Cells ◽

Cell Phenotype ◽

Type Ii Cells ◽

Mrna Levels ◽

Hormone Regulation ◽

Type Ii ◽

Adrenal Hormone ◽

Pulmonary Epithelial Cells ◽

Type Ii Cell

Previous work suggested an association between changes in the alveolar extracellular matrix and epithelial cell growth in lungs of adrenalectomized rats in vivo. Other studies demonstrated that adrenal hormones modulate extracellular matrix synthesis by type II pulmonary epithelial cells in vitro. Adrenal hormone regulation of type II cell fibronectin synthesis was thus examined. Fibronectin synthesis was quantitated by immunoprecipitation of the metabolically labeled molecule from cells, extracellular matrix, and culture medium. On day 1 of primary culture, synthesis of matrix fibronectin by type II cells isolated from the lungs of adrenalectomized animals was more than twice that by cells isolated from control rats. Adrenalectomy elevated steady-state fibronectin mRNA levels in primary isolates of type II cells cultured for 1 or 3 days. These results suggest that altered fibronectin synthesis and deposition into the extracellular matrix accompany changes in type II cell phenotype that occur after adrenalectomy.

Download Full-text

Distribution and surfactant association of carcinoembryonic cell adhesion molecule 6 in human lung

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00055.2011 ◽

2012 ◽

Vol 302 (2) ◽

pp. L216-L225 ◽

Cited By ~ 8

Author(s):

Cheryl Chapin ◽

Nicole A. Bailey ◽

Linda W. Gonzales ◽

Jae-Woo Lee ◽

Robert F. Gonzalez ◽

...

Keyword(s):

Cell Adhesion ◽

Epithelial Cells ◽

Lung Disease ◽

Adhesion Molecule ◽

Cell Adhesion Molecule ◽

Human Lung ◽

Fetal Lung ◽

Type Ii Cells ◽

Type Ii ◽

Adult Lung

Carcinoembryonic cell adhesion molecule 6 (CEACAM6) is a glycosylated, glycophosphatidylinositol-anchored protein expressed in epithelial cells of various primate tissues. It binds gram-negative bacteria and is overexpressed in human cancers. CEACAM6 is associated with lamellar bodies of cultured type II cells of human fetal lung and protects surfactant function in vitro. In this study, we characterized CEACAM6 expression in vivo in human lung. CEACAM6 was present in lung lavage of premature infants at birth and increased progressively in intubated infants with lung disease. Of surfactant-associated CEACAM6, ∼80% was the fully glycosylated, 90-kDa form that contains the glycophosphatidylinositol anchor, and the concentration (3.9% of phospholipid for adult lung) was comparable to that for surfactant proteins (SP)-A/B/C. We examined the affinity of CEACAM6 by purification of surfactant on density gradient centrifugation; concentrations of CEACAM6 and SP-B per phospholipid were unchanged, whereas levels of total protein and SP-A decreased by 60%. CEACAM6 mRNA content decreased progressively from upper trachea to peripheral fetal lung, whereas protein levels were similar in all regions of adult lung, suggesting proximal-to-distal developmental expression in lung epithelium. In adult lung, most type I cells and ∼50% of type II cells were immunopositive. We conclude that CEACAM6 is expressed by alveolar and airway epithelial cells of human lung and is secreted into lung-lining fluid, where fully glycosylated protein binds to surfactant. Production appears to be upregulated during neonatal lung disease, perhaps related to roles of CEACAM6 in surfactant function, cell proliferation, and innate immune defense.

Download Full-text

The MicroRNA 29 Family Promotes Type II Cell Differentiation in Developing Lung

Molecular and Cellular Biology ◽

10.1128/mcb.00096-16 ◽

2016 ◽

Vol 36 (16) ◽

pp. 2141-2141 ◽

Cited By ~ 11

Author(s):

Wei Guo ◽

Houda Benlhabib ◽

Carole R. Mendelson

Keyword(s):

Cell Differentiation ◽

Epithelial Cells ◽

Transforming Growth Factor ◽

Fetal Lung ◽

Transforming Growth Factor Β ◽

Late Gestation ◽

Alveolar Type ◽

Type Ii Cells ◽

Type Ii ◽

Type Ii Cell

Lung alveolar type II cells uniquely synthesize surfactant, a developmentally regulated lipoprotein that is essential for breathing. Expression of the gene (SFTPA) encoding the major surfactant protein, SP-A, in midgestation human fetal lung (HFL) is dramatically induced by cyclic AMP (cAMP). cAMP induction of SP-A expression is repressed by transforming growth factor β (TGF-β) and by hypoxia. In this study, we found that expression of the microRNA 29 (miR-29) family was significantly upregulated in epithelial cells isolated from mouse fetal lung during late gestation and in epithelial cells isolated from HFL explants during type II cell differentiation in culture. miR-29 expression in cultured HFL epithelial cells was increased by cAMP and inhibited by hypoxia, whereas the miR-29 target, TGF-β2, was coordinately decreased. Knockdown of the miR-29 family in cultured HFL type II cells blocked cAMP-induced SP-A expression and accumulation of surfactant-containing lamellar bodies, suggesting their physiological relevance. This occurred through derepression of TGF-β signaling. Notably, cAMP increased binding of endogenous thyroid transcription factor 1 (TTF-1/Nkx2.1) to themiR-29ab1promoter in HFL type II cells, and TTF-1 increasedmiR-29ab1promoter-driven luciferase activity in cotransfection assays. Together, these findings identify miR-29 family members as TTF-1-driven mediators of SP-A expression and type II cell differentiation through repression of TGF-β signaling.

Download Full-text

GM-CSF enhances lung growth and causes alveolar type II epithelial cell hyperplasia in transgenic mice

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1997.273.4.l715 ◽

1997 ◽

Vol 273 (4) ◽

pp. L715-L725 ◽

Cited By ~ 30

Author(s):

Jacquelyn A. Huffman Reed ◽

Ward R. Rice ◽

Zsuzsanna K. Zsengellér ◽

Susan E. Wert ◽

Glenn Dranoff ◽

...

Keyword(s):

Epithelial Cells ◽

Transgenic Mice ◽

Lung Epithelial Cells ◽

Alveolar Type ◽

Type Ii Cells ◽

Type Ii ◽

Cell Hyperplasia ◽

Α Subunit ◽

Gm Csf ◽

Type Ii Cell

The human surfactant protein (SP)-C gene promoter was used to direct expression of mouse granulocyte macrophage colony-stimulating factor (GM-CSF; SP-C-GM mice) in lung epithelial cells in GM-CSF-replete (GM+/+) or GM-CSF null mutant (GM−/−) mice. Lung weight and volume were significantly increased in SP-C-GM mice compared with GM+/+ or GM−/− control mice. Immunohistochemical staining demonstrated marked type II cell hyperplasia, and immunofluorescent labeling for proliferating cell nuclear antigen was increased in type II cells of SP-C-GM mice. Abundance of type II cells per mouse lung was increased three- to fourfold in SP-C-GM mice compared with GM+/+ and GM−/− mice. GM-CSF increased bromodeoxyuridine labeling of isolated type II cells in vitro. Type II cells, alveolar macrophages, and endothelial and bronchiolar epithelial cells were stained by antibodies to the GM-CSF receptor α-subunit in both GM+/+ mice and GM-CSF gene-targeted mice that are also homozygous for the SP-C-GM transgene. High levels of GM-CSF expression in type II cells of transgenic mice increased lung size and caused type II cell hyperplasia, demonstrating an unexpected role for the molecule in the regulation of type II cell proliferation and differentiation.

Download Full-text

Correlation of expression of transcription factor C/EBP alpha and surfactant protein genes in lung cells

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1995.269.2.l241 ◽

1995 ◽

Vol 269 (2) ◽

pp. L241-L247 ◽

Cited By ~ 11

Author(s):

F. Li ◽

E. Rosenberg ◽

C. I. Smith ◽

K. Notarfrancesco ◽

S. R. Reisher ◽

...

Keyword(s):

Transcription Factor ◽

Epithelial Cells ◽

Cell Line ◽

Surfactant Protein ◽

Surfactant Proteins ◽

Type Ii Cells ◽

Mrna Levels ◽

Type Ii ◽

Surfactant System ◽

Factor C

C/EBP alpha is a transcription factor which can stimulate expression of genes in lipid-metabolizing epithelial cells. We have detected an increase in mRNA for C/EBP alpha in lungs of fetal rats between days 18 and 20 of gestation, correlating with events occurring during the maturation of the surfactant system, such as an increase in the amount of surfactant protein A mRNA. We have found that C/EBP alpha mRNA levels are substantially enriched in type II alveolar epithelial cells purified from adult lung and that the C/EBP alpha protein is present in type II cell nuclei. When the type II cells are removed from the lung and purified, the protein is rapidly lost. However, both surfactant protein gene expression and C/EBP alpha reappear when cells are plated on Matrigel. Levels of C/EBP alpha mRNA from purified cells decline much more slowly than the protein and are still detectable 48 h after cells have been plated on standard tissue culture plastic. We have also detected the C/EBP alpha protein in nuclear extracts of NCI-H441, a lung-derived cell line that expresses surfactant proteins A and B, but not in A549, a lung-derived cell line which does not express the surfactant proteins. Our data suggest that C/EBP alpha is involved in the development and maintenance of the surfactant system in lung type II cells.

Download Full-text

Transforming growth factor-beta 1 modulates type II cell fibronectin and surfactant protein C expression

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1994.267.5.l569 ◽

1994 ◽

Vol 267 (5) ◽

pp. L569-L577 ◽

Cited By ~ 9

Author(s):

W. M. Maniscalco ◽

R. A. Sinkin ◽

R. H. Watkins ◽

M. H. Campbell

Keyword(s):

Transforming Growth Factor Beta ◽

Transforming Growth Factor ◽

Surfactant Protein ◽

Type Ii Cells ◽

Mrna Levels ◽

Type Ii ◽

Tgf Beta ◽

Surfactant Protein C ◽

Type Ii Cell ◽

Growth Factor Beta

Extracellular matrix (ECM) deposition by alveolar type II cells is important for repair of a damaged alveolar epithelium. Transforming growth factor-beta (TGF-beta) is abundant in injured lung and has profound effects on ECM production and cell differentiation. We determined the effects of TGF-beta 1 on type II cell expression of fibronectin and surfactant protein C (SP-C) in vitro. TGF-beta 1 increased the proportion of type II cells with detectable mRNA for fibronectin from 9 to 68%, as demonstrated by in situ hybridization, and increased the fibronectin mRNA levels 10-fold. TGF-beta 1-treated cultures had increased immunostaining for fibronectin and increased secretion of metabolically labeled fibronectin. A decreased proportion of type II cells treated with TGF-beta 1 had detectable mRNA for SP-C, and the abundance of this message per cell decreased to 25% of control values. No effects of TGF-beta 1 were noted on the proportion of cells that contained lamellar bodies, which was 87% in both groups. These data indicate that TGF-beta 1 regulates type II cell fibronectin protein an mRNA levels. In addition, the decreased abundance of SP-C mRNA suggests that TGF-beta 1 may also modulate type II cell differentiation in lung injury.

Download Full-text

Mechanisms of Transforming Growth Factor-β Receptor Endocytosis and Intracellular Sorting Differ between Fibroblasts and Epithelial Cells

Molecular Biology of the Cell ◽

10.1091/mbc.12.3.675 ◽

2001 ◽

Vol 12 (3) ◽

pp. 675-684 ◽

Cited By ~ 38

Author(s):

Jules J.E. Doré ◽

Diying Yao ◽

Maryanne Edens ◽

Nandor Garamszegi ◽

Elizabeth L. Sholl ◽

...

Keyword(s):

Growth Factor ◽

Epithelial Cells ◽

Ligand Binding ◽

Transforming Growth Factor ◽

Point Mutations ◽

Type I ◽

Receptor Complex ◽

Type Ii ◽

Down Regulation ◽

Β Receptor

Transforming growth factor-βs (TGF-β) are multifunctional proteins capable of either stimulating or inhibiting mitosis, depending on the cell type. These diverse cellular responses are caused by stimulating a single receptor complex composed of type I and type II receptors. Using a chimeric receptor model where the granulocyte/monocyte colony-stimulating factor receptor ligand binding domains are fused to the transmembrane and cytoplasmic signaling domains of the TGF-β type I and II receptors, we wished to describe the role(s) of specific amino acid residues in regulating ligand-mediated endocytosis and signaling in fibroblasts and epithelial cells. Specific point mutations were introduced at Y182, T200, and Y249 of the type I receptor and K277 and P525 of the type II receptor. Mutation of either Y182 or Y249, residues within two putative consensus tyrosine-based internalization motifs, had no effect on endocytosis or signaling. This is in contrast to mutation of T200 to valine, which resulted in ablation of signaling in both cell types, while only abolishing receptor down-regulation in fibroblasts. Moreover, in the absence of ligand, both fibroblasts and epithelial cells constitutively internalize and recycle the TGF-β receptor complex back to the plasma membrane. The data indicate fundamental differences between mesenchymal and epithelial cells in endocytic sorting and suggest that ligand binding diverts heteromeric receptors from the default recycling pool to a pathway mediating receptor down-regulation and signaling.

Download Full-text

P2-purinoceptors regulate surfactant secretion from rat isolated alveolar Type II cells

British Journal of Pharmacology ◽

10.1111/j.1476-5381.1986.tb11148.x ◽

1986 ◽

Vol 89 (3) ◽

pp. 485-491 ◽

Cited By ~ 43

Author(s):

Ward R. Rice ◽

Fannie M. Singleton

Keyword(s):

Alveolar Type ◽

Type Ii Cells ◽

Type Ii ◽

Alveolar Type Ii Cells ◽

P2 Purinoceptors ◽

Surfactant Secretion

Download Full-text

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

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1995.269.1.l127 ◽

1995 ◽

Vol 269 (1) ◽

pp. L127-L135 ◽

Cited By ~ 5

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)

Download Full-text