Regulation of SP-B and SP-C secretion in rat type II cells in primary culture

2001 ◽  
Vol 281 (6) ◽  
pp. L1413-L1419 ◽  
Author(s):  
Laurice I. Gobran ◽  
Seamus A. Rooney
Keyword(s):  
Lung Surfactant ◽  
Lamellar Body ◽  
Surfactant Protein ◽  
Type Ii Cells ◽  
Type Ii ◽  
Pharmacological Agents ◽  
Hydrophobic Protein ◽  
Surfactant Phospholipids ◽  
Protein Components ◽  
Phosphatidylcholine Secretion

Secretion of lung surfactant phospholipids is a highly regulated process. A variety of physiological and pharmacological agents stimulate surfactant phospholipid secretion in isolated type II cells. Although the lipid and hydrophobic protein components of surfactant are believed to be secreted together by exocytosis of lamellar body contents, regulation of surfactant protein (SP) B and SP-C secretion has not previously been examined. To address the question of whether secretion of SP-B and SP-C is stimulated by the same agonists that stimulate phospholipid secretion, we measured secretion of all four SPs under the same conditions used to measure phosphatidylcholine secretion. Freshly isolated rat type II cells were cultured overnight and exposed to known surfactant phospholipid secretagogues for 2.5 h, after which the amounts of SP-A, SP-B, SP-C, and SP-D in the medium were measured with immunoblotting. Secretion of SP-B and SP-C was stimulated three- to fivefold by terbutaline, 5′-( N-ethylcarboxyamido)adenosine, ATP, 12- O-tetradecanoylphorbol 13-acetate, and ionomycin. Similar to their effects on phospholipid secretion, the stimulatory effects of the agonists were abolished by Ro 31-8220. Secretion of SP-A and SP-D was not stimulated by the secretagogues tested. We conclude that secretion of the phospholipid and hydrophobic protein components of surfactant is similarly regulated, whereas secretion of the hydrophilic proteins is regulated differently.

Early increase in expression of surfactant protein A gene in type II cells from silica-treated rats

1997 ◽  
Vol 273 (2) ◽  
pp. L395-L400
Author(s):  
C. J. Viviano ◽  
S. A. Rooney
Keyword(s):  
Lung Surfactant ◽  
Protein A ◽  
Surfactant Protein ◽  
Type Ii Cells ◽  
Mrna Levels ◽  
Type Ii ◽  
Mrna Content ◽  
Type Ii Cell ◽  
Surfactant Phospholipids ◽  
Two Populations

Silica is known to cause an increase in lung surfactant and to promote type II cell hypertrophy and hyperplasia. Two populations of type II cells can be isolated from silica-treated rats: type IIA cells that are similar to normal type II cells and type IIB cells that are larger, contain more surfactant phospholipids, and have increased rates of phospholipid biosynthesis. As much less is known about the influence of silica on the amounts of surfactant proteins (SPs) in type II cells, we examined expression of the genes for all four SPs in types IIA and IIB cells isolated from rats 1, 3, and 7 days after a single intratracheal injection of silica. There was a rapid increase in expression of the SP-A gene in type II cells from the silica-treated animals. SP-A mRNA content was 8- to 10-fold greater in types IIA and IIB cells isolated 1 day after silica injection than in type II cells from saline-injected animals. SP-A mRNA levels were also elevated in the cells isolated on days 3 and 7 after silica injection, but the extent of the increase was less than in the cells isolated on day 1 and declined with time after injection. SP-B, SP-C, and SP-D mRNA levels were 2.5- to 4-fold greater in type IIA cells on day 3 after silica injection than in control type II cells. However, those mRNA levels were not significantly increased in the type IIA cells isolated on days 1 and 7 or in type IIB cells at any time point. These data show that silica causes a rapid and substantial increase in expression of the SP-A gene in type II cells.

scholarly journals Immunocytochemical localization of lysozyme and surfactant protein A in rat type II cells and extracellular surfactant forms.

1992 ◽  
Vol 40 (10) ◽  
pp. 1491-1500 ◽  
Author(s):  
E M Haller ◽  
S A Shelley ◽  
M R Montgomery ◽  
J U Balis
Keyword(s):  
Lung Surfactant ◽  
Protein A ◽  
Lamellar Body ◽  
Surfactant Protein ◽  
Surfactant Protein A ◽  
Peripheral Compartment ◽  
Type Ii Cells ◽  
Type Ii ◽  
Lamellar Bodies ◽  
Body Protein

Using immunogold labeling of fixed, cryosubstituted tissue sections, we compared the distribution of lysozyme, an oxidant-sensitive lamellar body protein, with that of surfactant protein A (SP-A) in rat Type II cells, extracellular surfactant forms, and alveolar macrophages. Morphometric analysis of gold particle distribution revealed that lysozyme and SP-A were present throughout the secretory and endosomal pathways of Type II cells, with prominent localization of lysozyme in the peripheral compartment of lamellar bodies. All extracellular surfactant forms were labeled for both proteins with preferential labeling of tubular myelin and unilamellar vesicles. Labeling of tubular myelin for SP-A was striking when compared with that of lamellar bodies and other extracellular surfactant forms. Lamellar body-like forms and multilamellar structures were uniformly labeled for lysozyme, suggesting that this protein is rapidly redistributed within these forms after secretion of lysozyme-laden lamellar bodies. By contrast, increased labeling for SP-A was observed over peripheral membranes of lamellar body-like forms and multilamellar structures, apparently reflecting progressive SP-A enrichment of these membranes during tubular myelin formation. The results indicate that lysozyme is an integral component of the lamellar body peripheral compartment and secreted surfactant membranes, and support the concept that lysozyme may participate in the structural organization of lung surfactant.

Regulation of lung surfactant secretion

1990 ◽  
Vol 258 (6) ◽  
pp. L241-L253 ◽  
Author(s):  
A. Chander ◽  
A. B. Fisher
Keyword(s):  
Lung Surfactant ◽  
Protein A ◽  
Lamellar Body ◽  
Surfactant Protein ◽  
Ventilation Rate ◽  
Future Research ◽  
Surfactant Secretion ◽  
Vasopressin Receptors ◽  
Protein Components

Secretion of lung surfactant is the direct step in release of the lipoprotein-like product, synthesized in lung epithelial type II cells, onto the alveolar surface. Release of surfactant phosphatidylcholine (PC) proceeds via formation of surface pores during exocytosis of lamellar bodies. Surfactant secretion is regulated locally in the lung by changes in ventilation rate, possibly mediated by distension and altered intracellular pH. Secretion is also stimulated by various agents, including agonists for beta-adrenergic, purinoceptors, and vasopressin receptors and is associated with increased cytosolic Ca2+, cellular adenosine 3',5'-cyclic monophosphate, and activation of protein kinases. Limited studies suggest that secretion of surfactant protein A may be regulated by both cAMP-dependent and protein kinase C-dependent pathways. The integration of these various mechanisms for the in vivo regulation of surfactant secretion remains largely unexplored. Future research into the mechanisms involved in lamellar body fusion with the plasma membrane, role of protein phosphorylation, transient changes in cAMP and Ca2+, and coordination between the secretion of phospholipid and protein components of surfactant should enhance our understanding of secretion of surfactant “lipoprotein.”

Pulmonary surfactant protein A-mediated uptake of phosphatidylcholine by alveolar type II cells

1993 ◽  
Vol 265 (2) ◽  
pp. L193-L199 ◽  
Author(s):  
A. Tsuzuki ◽  
Y. Kuroki ◽  
T. Akino
Keyword(s):  
Pulmonary Surfactant ◽  
Protein A ◽  
Lamellar Body ◽  
Surfactant Protein ◽  
Surfactant Protein A ◽  
Alveolar Type ◽  
Type Ii Cells ◽  
Type Ii ◽  
Lamellar Bodies ◽  
Pulmonary Surfactant Protein

Pulmonary surfactant protein A (SP-A)-mediated uptake of phosphatidylcholine (PC) by alveolar type II cells was investigated. SP-A enhanced the uptake of liposomes containing dipalmitoylphosphatidylcholine (DPPC), 1-palmitoyl-2-linoleoyl phosphatidylcholine (PLPC), or 1,2-dihexadecyl-sn-glycero-3-phosphocholine (DPPC-ether), a diether analogue of DPPC, but about twice as much DPPC was taken up by type II cells as PLPC or DPPC-ether. When subcellular distribution was analyzed, 51.3 +/- 2.9% (mean +/- SD, n = 3) of cell-associated radiolabeled DPPC was recovered in the lamellar body-rich fraction in the presence of SP-A, whereas only 19.3 +/- 1.9% (mean +/- SD, n = 3) was found to this fraction in the absence of SP-A. When type II cells were incubated either with DPPC at 0 degree C or with DPPC-ether at 37 degrees C, or no cells were included, low proportions of the cell-associated lipids were present in the fractions corresponding to lamellar bodies even in the presence of SP-A. Anti-SP-A antibody significantly reduced the radioactivity incorporated into the lamellar body fraction. Phosphatidylcholine that had been incorporated into lamellar bodies remained largely intact when SP-A was present. Subcellular fractionations of type II cells with radiolabeled SP-A and DPPC revealed that the sedimentation characteristics of cell-associated SP-A are different from those of DPPC, although a small broad peak of radiolabeled SP-A was found in the lamellar body fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Endocytosed SP-A and surfactant lipids are sorted to different organelles in rat type II pneumocytes

2001 ◽  
Vol 281 (2) ◽  
pp. L345-L360 ◽  
Author(s):  
Heide Wissel ◽  
Andrea Lehfeldt ◽  
Petra Klein ◽  
Torsten Müller ◽  
Paul A. Stevens
Keyword(s):  
Cell Surface ◽  
Intracellular Transport ◽  
Protein A ◽  
Lamellar Body ◽  
Surfactant Protein ◽  
Type Ii Cells ◽  
Type Ii ◽  
Lamellar Bodies ◽  
Type Ii Pneumocytes ◽  
Early Endosomes

Intracellular transport of endocytosed surfactant protein A (SP-A) and lipid was investigated in isolated rat type II cells. After internalization, SP-A and lipid are taken up via the coated-pit pathway and reside in a common compartment, positive for the early endosomal marker EEA1 but negative for the lamellar body marker 3C9. SP-A then recycles rapidly to the cell surface via Rab4-associated recycling vesicles. Internalized lipid is transported toward a Rab7-, CD63-, 3C9-positive compartment, i.e., lamellar bodies. Inhibition of calmodulin led to inhibition of uptake and transport out of the EEA1-positive endosome and thus of resecretion of both components. Inhibition of intravesicular acidification (bafilomycin A1) led to decreased uptake of both surfactant components. It inhibited transport out of early endosomes for lipid only, not for SP-A. We conclude that in type II cells, endocytosed SP-A and lipid are transported toward a common early endosomal compartment. Thereafter, both components dissociate. SP-A is rapidly recycled to the cell surface and does not enter classic lamellar bodies. Lipid is transported toward lamellar bodies.

Uptake of pulmonary surfactant protein C into adult rat lung lamellar bodies

1993 ◽  
Vol 74 (3) ◽  
pp. 1005-1011 ◽  
Author(s):  
R. A. Pinto ◽  
J. R. Wright ◽  
D. Lesikar ◽  
B. J. Benson ◽  
J. A. Clements
Keyword(s):  
Protein C ◽  
Lamellar Body ◽  
Surfactant Protein ◽  
Type Ii Cells ◽  
Type Ii ◽  
Lamellar Bodies ◽  
Adult Rats ◽  
Alveolar Air ◽  
Surfactant Protein C ◽  
Air Space

Previous studies have provided evidence that a large proportion of secreted surfactant lipids is taken up from the alveolar air space by type II cells, incorporated into lamellar bodies, and resecreted. Our goal was to characterize the clearance of exogenously administered recombinant surfactant protein C (SP-C) and to determine if SP-C is taken up by type II cells and incorporated into lamellar bodies. SP-C was radiolabeled by alkylation with [3H]iodoacetic acid and retained its ability to enhance phospholipid adsorption to an air-liquid interface. A mixture of 100 micrograms phospholipid radiolabeled with [14C]dipalmitoylphosphatidylcholine and 10 micrograms SP-C was instilled into the lungs of spontaneously breathing anesthetized adult rats. At later times, the lungs were lavaged and subcellular organelles were isolated. The radioactivity of both phospholipids and SP-C (expressed as disintegrations per minute per microgram phospholipid) in lamellar body fractions increased up to 4 h postinstillation and began to decline after approximately 4 h. The results of this study suggest that SP-C and dipalmitoylphosphatidylcholine are taken up promptly from the alveolar air space and are incorporated into lamellar bodies with time courses that do not differ greatly.

Type II pneumocytes secrete vitamin E together with surfactant lipids

1993 ◽  
Vol 265 (2) ◽  
pp. L133-L139 ◽  
Author(s):  
B. Rustow ◽  
R. Haupt ◽  
P. A. Stevens ◽  
D. Kunze
Keyword(s):  
Vitamin E ◽  
Palmitic Acid ◽  
Lung Surfactant ◽  
Protein A ◽  
Specific Radioactivity ◽  
Surfactant Protein ◽  
Lung Lavage ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Surfactant

Lung surfactant is exposed to strongly oxidizing conditions. We examined the hypothesis that in lung, lipophilic antioxidants are secreted together with surfactant to counteract the peroxidation of surfactant constituents. Lung lavage and the subfractions of the alveolar surfactant contain the lipophilic antioxidants vitamin E, vitamin A, and plasmalogens. The specific radioactivity of vitamin E isolated from serum, lung homogenate, lamellar bodies, and lung lavage increased linearly up to 3 h after intraperitoneal application of [3H]tocopherol. [3H]tocopherol was secreted in situ together with [14C]palmitic acid-labeled phospholipid in response to isoproterenol. Type II cells cultured in presence of [3H]tocopherol or of [3H]cholecalciferol and [14C]palmitic acid responded to isoproterenol by a time-dependent increase in secretion of [3H]tocopherol and of 14C-labeled phospholipids but not of [3H]cholecalciferol. The isoproterenol-stimulated secretion of [3H]tocopherol and of 14C-labeled phospholipids by type II cells is inhibited by surfactant protein A. We conclude that the alveolar surfactant contains lipophilic antioxidants as integral constituents. [3H]tocopherol seems to be secreted together with surfactant.

Immunocytochemical localization of lung surfactant proteins by cryoultramicrotomy and freeze-substitution embedding

1990 ◽  
Vol 48 (3) ◽  
pp. 38-39
Author(s):  
W.F. Voorhout ◽  
T. Veenendaal ◽  
H.P. Haagsman ◽  
J.W. Slot
Keyword(s):  
Lung Surfactant ◽  
Protein A ◽  
Freeze Substitution ◽  
Transpulmonary Pressure ◽  
Surfactant Protein ◽  
Apical Plasma Membrane ◽  
Type Ii Cells ◽  
Main Function ◽  
Type Ii ◽  
Lamellar Bodies

Lung surfactant is composed primarily of phospholipids but contains also about 10% proteins. Its main function is to decrease alveolar surface tension at low transpulmonary pressure to prevent alveolar collaps. Surfactant is stored in lamellar bodies in alveo1lar type II cells and is transformed after secretion in tubular myelin, a lattice-like structure.We investigated the biogenesis of surfactant and the pathways that the large hydrophilic surfactant protein A (SP-A) and the small hydrophobic surfactant protein B (SP-B) follow in human lung by using two different immunocytochemical techniques, the cryo-ultramicrotomy method and a new post-embedding method.In the non-embedded, ultrathin cryosections of the lung, prepared and immunolabeled for SP-A and SP-B as described before, it was impossible to achieve a satisfying preservation of lipid-rich structures like lamellar bodies (Fig. 1 and 2). Nevertheless SP-A and SP-B are detected in remnants of lamellar bodies (Fig. 1 and 2) and SP-A is further found to be present throughout the biosynthetic route, in some multivesicular bodies and over the apical plasma membrane of type II cells (Fig. 1).

Surfactant lipid uptake and secretion in type II cells in response to lectins and secretagogues

1991 ◽  
Vol 261 (6) ◽  
pp. L434-L442 ◽  
Author(s):  
M. Griese ◽  
L. I. Gobran ◽  
S. A. Rooney
Keyword(s):  
Primary Cultures ◽  
Type Ii Cells ◽  
Type Ii ◽  
Lipid Uptake ◽  
Dipalmitoyl Phosphatidylcholine ◽  
Maclura Pomifera ◽  
Surfactant Secretion ◽  
Surfactant Lipid ◽  
Surfactant Phospholipids ◽  
Phosphatidylcholine Secretion

Secretion of surfactant phospholipids can be inhibited by the surfactant-associated protein SP-A. SP-A was reported to stimulate lipid uptake by type II cells, whereas surfactant secretagogues were reported to have the same effect in isolated perfused lungs. We examined the effect of such secretagogues on uptake of liposomes containing L-alpha-[2-palmitoyl-9,103H(N)]-dipalmitoyl phosphatidylcholine in primary cultures of type II cells. As SP-A contains a lectinlike domain and other lectins were reported to inhibit surfactant secretion, we also examined the effect of such lectins on lipid uptake. At concentrations at which they maximally stimulate phosphatidylcholine secretion in type II cells, several secretagogues had no effect on liposome uptake. Maclura pomifera agglutinin (MPA) stimulated uptake approximately 10-fold with a concentration eliciting 50% maximum stimulation (EC50) of 17 micrograms/ml. The effect of MPA on uptake was considerably greater than that of SP-A. However, although the stimulatory effect of ATP on phosphatidylcholine secretion was almost completely antagonized by SP-A, it was maximally inhibited only 75% by MPA. The concentration eliciting 50% maximum inhibition (IC50) for MPA inhibition of secretion was 0.5 micrograms/ml. Concanavalin A, another lectin, had no effect on lipid uptake but completely inhibited secretion. These data show that a lectin other than SP-A can stimulate phospholipid uptake by type II cells cultured on plastic and suggest that surfactant secretion and reuptake are independently regulated processes.

scholarly journals Role of Phosphocholine Cytidylyltransferase α in Lung Development

2006 ◽  
Vol 27 (3) ◽  
pp. 975-982 ◽  
Author(s):  
Yong Tian ◽  
Ruobing Zhou ◽  
Jerold E. Rehg ◽  
Suzanne Jackowski
Keyword(s):  
Epithelial Cell ◽  
Lung Development ◽  
Cultured Cells ◽  
Lung Surfactant ◽  
Surfactant Protein ◽  
Alveolar Type ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Lamellar Bodies

ABSTRACT Lung development depends upon the differentiation and expansion of a variety of specialized epithelial cell types, including distal type I and type II pneumocytes in the late term. Previous studies have shown a strict dependence on the choline cytidylyltransferase α isoform (CCTα) to mediate membrane phospholipid formation in cultured cells and during preimplantation embryogenesis. CCTα expression is highest in lung, and there has long been speculation about its precise role, due to the dual requirement for phospholipid in proliferating cell membranes and for lung surfactant production from alveolar type II cells. We investigated the function of CCTα in lung development, using an inducible, epithelial cell-specific CCTα knockout mouse line. Deletion of CCTα beginning at embryonic day 7.5 did not restrict lung development but resulted in severe respiratory failure at birth. Alveolar lavage and lung lipid analyses showed significant decreases in the major surfactant phospholipid, dipalmitoyl-phosphatidylcholine. The fatty acids destined for the surfactant phospholipid were redirected to an expanded triglyceride pool. Transcripts encoding type II cell-specific markers were expressed in the knockout mice, indicating the expected progression of differentiation in lung epithelia. However, surfactant protein levels were reduced, with the exception of that for surfactant protein B, which was elevated. Ultrastructural analysis of the type II cells showed Golgi complex abnormalities and aberrant lamellar bodies, which deliver surfactant lipid and protein to the alveolar lumen. Thus, CCTα was not required for the proliferation or differentiation of lung epithelia but was essential for the secretory component of phospholipid synthesis and critical for the proper formation of lamellar bodies and surfactant protein homeostasis.

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