1
|
Dietl P, Frick M. Channels and Transporters of the Pulmonary Lamellar Body in Health and Disease. Cells 2021; 11:45. [PMID: 35011607 PMCID: PMC8750383 DOI: 10.3390/cells11010045] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 12/20/2021] [Accepted: 12/22/2021] [Indexed: 02/06/2023] Open
Abstract
The lamellar body (LB) of the alveolar type II (ATII) cell is a lysosome-related organelle (LRO) that contains surfactant, a complex mix of mainly lipids and specific surfactant proteins. The major function of surfactant in the lung is the reduction of surface tension and stabilization of alveoli during respiration. Its lack or deficiency may cause various forms of respiratory distress syndrome (RDS). Surfactant is also part of the innate immune system in the lung, defending the organism against air-borne pathogens. The limiting (organelle) membrane that encloses the LB contains various transporters that are in part responsible for translocating lipids and other organic material into the LB. On the other hand, this membrane contains ion transporters and channels that maintain a specific internal ion composition including the acidic pH of about 5. Furthermore, P2X4 receptors, ligand gated ion channels of the danger signal ATP, are expressed in the limiting LB membrane. They play a role in boosting surfactant secretion and fluid clearance. In this review, we discuss the functions of these transporting pathways of the LB, including possible roles in disease and as therapeutic targets, including viral infections such as SARS-CoV-2.
Collapse
Affiliation(s)
- Paul Dietl
- Institute of General Physiology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Manfred Frick
- Institute of General Physiology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| |
Collapse
|
2
|
The biology of the ABCA3 lipid transporter in lung health and disease. Cell Tissue Res 2016; 367:481-493. [PMID: 28025703 DOI: 10.1007/s00441-016-2554-z] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 11/29/2016] [Indexed: 01/10/2023]
Abstract
The lipid transporter, ATP-binding cassette class A3 (ABCA3), is a highly conserved multi-membrane-spanning protein that plays a critical role in the regulation of pulmonary surfactant homeostasis. Mutations in ABCA3 have been increasingly recognized as one of the causes of inherited pulmonary diseases. These monogenic disorders produce familial lung abnormalities with pathological presentations ranging from neonatal surfactant-deficiency-induced respiratory failure to childhood or adult diffuse parenchymal lung diseases for which specific treatment modalities remain limited. More than 200 ABCA3 mutations have been reported to date with approximately three quarters of patients presenting as compound heterozygotes. Recent advances in our understanding of the molecular basis underlying normal ABCA3 biosynthesis and processing and of the mechanisms of alveolar epithelial cell dysregulation caused by the expression of its mutant forms are beginning to emerge. These insights and the role of environmental factors and modifier genes are discussed in the context of the considerable variability in disease presentation observed in patients with identical ABCA3 gene mutations. Moreover, the opportunities afforded by an enhanced understanding of ABCA3 biology for targeted therapeutic strategies are addressed.
Collapse
|
3
|
van der Kant R, Zondervan I, Janssen L, Neefjes J. Cholesterol-binding molecules MLN64 and ORP1L mark distinct late endosomes with transporters ABCA3 and NPC1. J Lipid Res 2013; 54:2153-2165. [PMID: 23709693 DOI: 10.1194/jlr.m037325] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Cholesterol is an essential lipid in eukaryotic cells and is present in membranes of all intracellular compartments. A major source for cellular cholesterol is internalized lipoprotein particles that are transported toward acidic late endosomes (LE) and lysosomes. Here the lipoprotein particles are hydrolyzed, and free cholesterol is redistributed to other organelles. The LE can contain over half of the cellular cholesterol and, as a major sorting station, can contain many cholesterol-binding proteins from the ABCA, STARD, and ORP families. Here, we show that metastatic lymph node 64 (MLN64, STARD3) and oxysterol-binding protein-related protein 1L (ORP1L) define two subpopulations of LE. MLN64 is present on a LE containing the cholesterol transporter ABCA3, whereas ORP1L localizes to another population of LE containing Niemann Pick type C1 (NPC1), a cholesterol exporter. Endocytosed cargo passes through MLN64/ABCA3-positive compartments before it reaches ORP1L/NPC1-positive LE. The MLN64/ABCA3 compartments cycle between LE and plasma membrane and frequently contact "later" ORP1L/NPC1-containing LE. We propose two stages of cholesterol handling in late endosomal compartments: first, cholesterol enters MLN64/ABCA3-positive compartments from where it can be recycled to the plasma membrane, and later, cholesterol enters ORP1L/NPC1 endosomes that mediate cholesterol export to the endoplasmic reticulum.
Collapse
Affiliation(s)
- Rik van der Kant
- Division of Cell Biology, Netherlands Cancer Institute, Amsterdam, Netherlands
| | - Ilse Zondervan
- Division of Cell Biology, Netherlands Cancer Institute, Amsterdam, Netherlands
| | - Lennert Janssen
- Division of Cell Biology, Netherlands Cancer Institute, Amsterdam, Netherlands
| | - Jacques Neefjes
- Division of Cell Biology, Netherlands Cancer Institute, Amsterdam, Netherlands.
| |
Collapse
|
4
|
Grek CL, Newton DA, Qiu Y, Wen X, Spyropoulos DD, Baatz JE. Characterization of alveolar epithelial cells cultured in semipermeable hollow fibers. Exp Lung Res 2009; 35:155-74. [PMID: 19263283 DOI: 10.1080/01902140802495870] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Cell culture methods commonly used to represent alveolar epithelial cells in vivo have lacked airflow, a 3-dimensional air-liquid interface, and dynamic stretching characteristics of native lung tissue--physiological parameters critical for normal phenotypic gene expression and cellular function. Here the authors report the development of a selectively semipermeable hollow fiber culture system that more accurately mimics the in vivo microenvironment experienced by mammalian distal airway cells than in conventional or standard air-liquid interface culture. Murine lung epithelial cells (MLE-15) were cultured within semipermeable polyurethane hollow fibers and introduced to controlled airflow through the microfiber interior. Under these conditions, MLE-15 cells formed confluent monolayers, demonstrated a cuboidal morphology, formed tight junctions, and produced and secreted surfactant proteins. Numerous lamellar bodies and microvilli were present in MLE-15 cells grown in hollow fiber culture. Conversely, these alveolar type II cell characteristics were reduced in MLE-15 cells cultured in conventional 2D static culture systems. These data support the hypothesis that MLE-15 cells grown within our microfiber culture system in the presence of airflow maintain the phenotypic characteristics of type II cells to a higher degree than those grown in standard in vitro cell culture models. Application of our novel model system may prove advantageous for future studies of specific gene and protein expression involving alveolar epithelial or bronchiolar epithelial cells.
Collapse
Affiliation(s)
- Christina L Grek
- Department of Pediatrics, Medical University of South Carolina, Charleston, South Carolina 29425, USA
| | | | | | | | | | | |
Collapse
|
5
|
Abstract
Mutations in the genes encoding the surfactant proteins B and C (SP-B and SP-C) and the phospholipid transporter, ABCA3, are associated with respiratory distress and interstitial lung disease in the pediatric population. Expression of these proteins is regulated developmentally, increasing with gestational age, and is critical for pulmonary surfactant function at birth. Pulmonary surfactant is a unique mixture of lipids and proteins that reduces surface tension at the air-liquid interface, preventing collapse of the lung at the end of expiration. SP-B and ABCA3 are required for the normal organization and packaging of surfactant phospholipids into specialized secretory organelles, known as lamellar bodies, while both SP-B and SP-C are important for adsorption of secreted surfactant phospholipids to the alveolar surface. In general, mutations in the SP-B gene SFTPB are associated with fatal respiratory distress in the neonatal period, and mutations in the SP-C gene SFTPC are more commonly associated with interstitial lung disease in older infants, children, and adults. Mutations in the ABCA3 gene are associated with both phenotypes. Despite this general classification, there is considerable overlap in the clinical and histologic characteristics of these genetic disorders. In this review, similarities and differences in the presentation of these disorders with an emphasis on their histochemical and ultrastructural features will be described, along with a brief discussion of surfactant metabolism. Mechanisms involved in the pathogenesis of lung disease caused by mutations in these genes will also be discussed.
Collapse
Affiliation(s)
- Susan E. Wert
- Perinatal Institute, Section of Neonatology, Perinatal and Pulmonary Biology, Cincinnati Children’s Hospital Medical Center, and the Department of Pediatrics, University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, USA
| | - Jeffrey A. Whitsett
- Perinatal Institute, Section of Neonatology, Perinatal and Pulmonary Biology, Cincinnati Children’s Hospital Medical Center, and the Department of Pediatrics, University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, USA
| | - Lawrence M. Nogee
- Division of Neonatology, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| |
Collapse
|
6
|
Bates SR, Dodia C, Tao JQ, Fisher AB. Surfactant protein-A plays an important role in lung surfactant clearance: evidence using the surfactant protein-A gene-targeted mouse. Am J Physiol Lung Cell Mol Physiol 2007; 294:L325-33. [PMID: 18083768 DOI: 10.1152/ajplung.00341.2007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous studies with the isolated perfused rat lung showed that both clathrin- and actin-mediated pathways are responsible for endocytosis of dipalmitoylphosphatidylcholine (DPPC)-labeled liposomes by granular pneumocytes in the intact lung. Using surfactant protein-A (SP-A) gene-targeted mice, we examined the uptake of [(3)H]DPPC liposomes by isolated mouse lungs under basal and secretagogue-stimulated conditions. Unilamellar liposomes composed of [(3)H]DPPC: phosphatidylcholine:cholesterol:egg phosphatidylglycerol (10:5:3:2 mol fraction) were instilled into the trachea of anesthetized mice, and the lungs were perfused (2 h). Uptake was calculated as percentage of instilled disintegrations per minute in the postlavaged lung. Amantadine, an inhibitor of clathrin and, thus, receptor-mediated endocytosis via clathrin-coated pits, decreased basal [(3)H]DPPC uptake by 70% in SP-A +/+ but only by 20% in SP-A -/- lung, data compatible with an SP-A/receptor-regulated lipid clearance pathway in the SP-A +/+ mice. The nonclathrin, actin-dependent process was low in the SP-A +/+ lung but accounted for 55% of liposome endocytosis in the SP-A -/- mouse. With secretagogue (8-bromoadenosine 3',5'-cyclic monophosphate) treatment, both clathrin- and actin-dependent lipid clearance were elevated in the SP-A +/+ lungs while neither pathway responded in the SP-A -/- lungs. Binding of iodinated SP-A to type II cells isolated from both genotypes of mice was similar indicating a normal SP-A receptor status in the SP-A -/- lung. Inclusion of SP-A with instilled liposomes served to "rescue" the SP-A -/- lungs by reestablishing secretagogue-dependent enhancement of liposome uptake. These data are compatible with a major role for receptor-mediated endocytosis of DPPC by granular pneumocytes, a process critically dependent on SP-A.
Collapse
Affiliation(s)
- Sandra R Bates
- Institute for Environmental Medicine, University of Pennsylvania School of Medicine, 3620 Hamilton Walk, Philadelphia, PA 19104-6068, USA.
| | | | | | | |
Collapse
|
7
|
Andreeva AV, Kutuzov MA, Voyno-Yasenetskaya TA. Regulation of surfactant secretion in alveolar type II cells. Am J Physiol Lung Cell Mol Physiol 2007; 293:L259-71. [PMID: 17496061 DOI: 10.1152/ajplung.00112.2007] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Molecular mechanisms of surfactant delivery to the air/liquid interface in the lung, which is crucial to lower the surface tension, have been studied for more than two decades. Lung surfactant is synthesized in the alveolar type II cells. Its delivery to the cell surface is preceded by surfactant component synthesis, packaging into specialized organelles termed lamellar bodies, delivery to the apical plasma membrane and fusion. Secreted surfactant undergoes reuptake, intracellular processing, and finally resecretion of recycled material. This review focuses on the mechanisms of delivery of surfactant components to and their secretion from lamellar bodies. Lamellar bodies-independent secretion is also considered. Signal transduction pathways involved in regulation of these processes are discussed as well as disorders associated with their malfunction.
Collapse
Affiliation(s)
- Alexandra V Andreeva
- Department of Pharmacology, University of Illinois College of Medicine, Center for Lung and Vascular Biology, Chicago, IL, USA
| | | | | |
Collapse
|
8
|
Gupta N, Manevich Y, Kazi AS, Tao JQ, Fisher AB, Bates SR. Identification and characterization of p63 (CKAP4/ERGIC-63/CLIMP-63), a surfactant protein A binding protein, on type II pneumocytes. Am J Physiol Lung Cell Mol Physiol 2006; 291:L436-46. [PMID: 16556726 DOI: 10.1152/ajplung.00415.2005] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Surfactant protein A (SP-A) binds to alveolar type II cells through a specific high-affinity cell membrane receptor, although the molecular nature of this receptor is unclear. In the present study, we have identified and characterized an SP-A cell surface binding protein by utilizing two chemical cross-linkers: profound sulfo-SBED protein-protein interaction reagent and dithiobis(succinimidylpropionate) (DSP). Sulfo-SBED-biotinylated SP-A was cross-linked to the plasma membranes isolated from rat type II cells, and the biotin label was transferred from SP-A to its receptor by reduction. The biotinylated SP-A-binding protein was identified on blots by using streptavidin-labeled horseradish peroxidase. By using DSP, we cross-linked SP-A to intact mouse type II cells and immunoprecipitated the SP-A-receptor complex using anti-SP-A antibody. Both of the cross-linking approaches showed a major band of 63 kDa under reduced conditions that was identified as the rat homolog of the human type II transmembrane protein p63 (CKAP4/ERGIC-63/CLIMP-63) by matrix-assisted laser desorption ionization and nanoelectrospray tandem mass spectrometry of tryptic fragments. Thereafter, we confirmed the presence of p63 protein in the cross-linked SP-A-receptor complex by immunoprobing with p63 antibody. Coimmunoprecipitation experiments and functional assays confirmed specific interaction between SP-A and p63. Antibody to p63 could block SP-A-mediated inhibition of ATP-stimulated phospholipid secretion. Both intracellular and membrane localized pools of p63 were detected on type II cells by immunofluorescence and immunobloting. p63 colocalized with SP-A in early endosomes. Thus p63 closely interacts with SP-A and may play a role in the trafficking or the biological function of the surfactant protein.
Collapse
Affiliation(s)
- Nisha Gupta
- Institute for Environmental Medicine, University of Pennsylvania School of Medicine, Philadelphia, 19104, USA
| | | | | | | | | | | |
Collapse
|
9
|
Fehrenbach H, Tews S, Fehrenbach A, Ochs M, Wittwer T, Wahlers T, Richter J. Improved lung preservation relates to an increase in tubular myelin-associated surfactant protein A. Respir Res 2005; 6:60. [PMID: 15969762 PMCID: PMC1187923 DOI: 10.1186/1465-9921-6-60] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2004] [Accepted: 06/21/2005] [Indexed: 12/15/2022] Open
Abstract
Background Declining levels of surfactant protein A (SP-A) after lung transplantation are suggested to indicate progression of ischemia/reperfusion (IR) injury. We hypothesized that the previously described preservation-dependent improvement of alveolar surfactant integrity after IR was associated with alterations in intraalveolar SP-A levels. Methods Using immuno electron microscopy and design-based stereology, amount and distribution of SP-A, and of intracellular surfactant phospholipids (lamellar bodies) as well as infiltration by polymorphonuclear leukocytes (PMNs) and alveolar macrophages were evaluated in rat lungs after IR and preservation with EuroCollins or Celsior. Results After IR, labelling of tubular myelin for intraalveolar SP-A was significantly increased. In lungs preserved with EuroCollins, the total amount of intracellular surfactant phospholipid was reduced, and infiltration by PMNs and alveolar macrophages was significantly increased. With Celsior no changes in infiltration or intracellular surfactant phospholipid amount occurred. Here, an increase in the number of lamellar bodies per cell was associated with a shift towards smaller lamellar bodies. This accounts for preservation-dependent changes in the balance between surfactant phospholipid secretion and synthesis as well as in inflammatory cell infiltration. Conclusion We suggest that enhanced release of surfactant phospholipids and SP-A represents an early protective response that compensates in part for the inactivation of intraalveolar surfactant in the early phase of IR injury. This beneficial effect can be supported by adequate lung preservation, as e.g. with Celsior, maintaining surfactant integrity and reducing inflammation, either directly (via antioxidants) or indirectly (via improved surfactant integrity).
Collapse
Affiliation(s)
- Heinz Fehrenbach
- Clinical Research Group "Chronic Airway Diseases", Department of Internal Medicine (Respiratory Medicine), Philipps-University, Baldingerstrasse, D-35043 Marburg, Germany
| | - Sebastian Tews
- Division of Electron Microscopy, Centre of Anatomy, University of Göttingen, Kreuzbergring 36, D-37075 Göttingen, Germany
| | - Antonia Fehrenbach
- Division of Electron Microscopy, Centre of Anatomy, University of Göttingen, Kreuzbergring 36, D-37075 Göttingen, Germany
- Clinical Research Group "Chronic Airway Diseases", Department of Internal Medicine (Respiratory Medicine), Philipps-University, Baldingerstrasse, D-35043 Marburg, Germany
| | - Matthias Ochs
- Division of Electron Microscopy, Centre of Anatomy, University of Göttingen, Kreuzbergring 36, D-37075 Göttingen, Germany
- Institute of Anatomy, University of Bern, Baltzerstrasse 2, CH-3000 Bern 9, Switzerland
| | - Thorsten Wittwer
- Department of Cardiothoracic and Vascular Surgery, Friedrich Schiller University Jena, Bachstrasse 18, D-07740 Jena, Germany
| | - Thorsten Wahlers
- Department of Cardiothoracic and Vascular Surgery, Friedrich Schiller University Jena, Bachstrasse 18, D-07740 Jena, Germany
| | - Joachim Richter
- Division of Electron Microscopy, Centre of Anatomy, University of Göttingen, Kreuzbergring 36, D-37075 Göttingen, Germany
| |
Collapse
|
10
|
Salaun B, de Saint-Vis B, Pacheco N, Pacheco Y, Riesler A, Isaac S, Leroux C, Clair-Moninot V, Pin JJ, Griffith J, Treilleux I, Goddard S, Davoust J, Kleijmeer M, Lebecque S. CD208/dendritic cell-lysosomal associated membrane protein is a marker of normal and transformed type II pneumocytes. THE AMERICAN JOURNAL OF PATHOLOGY 2004; 164:861-71. [PMID: 14982840 PMCID: PMC1613301 DOI: 10.1016/s0002-9440(10)63174-4] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 11/12/2003] [Indexed: 02/05/2023]
Abstract
Dendritic cell-lysosomal associated membrane protein (DC-LAMP)/CD208, a member of the lysosomal associated membrane protein (LAMP) family, is specifically expressed by human DCs on activation. However, its mouse counterpart could not be detected in mature DCs. The present study demonstrates that DC-LAMP is constitutively expressed by mouse, sheep, and human type II pneumocytes. Confocal and immunoelectron microscopy showed that mouse DC-LAMP protein co-localizes with lbm180, a specific marker for the limiting membrane of lamellar bodies that contain surfactant protein B, as well as with intracellular MHC class II molecules that accumulate in the same organelles. Expression of DC-LAMP was also occasionally detected at the cell surface of type II pneumocytes. Interestingly, human bronchioloalveolar carcinoma tumor cells, which correspond to transformed type II pneumocytes, express DC-LAMP. Similar observations were made in the Jaagsiekte sheep retrovirus-associated ovine pulmonary adenocarcinoma, a model of human bronchioloalveolar carcinoma. This study establishes that DC-LAMP is constitutively expressed in normal type II pneumocytes. Furthermore, DC-LAMP appears to be a marker of transformed type II pneumocytes as well, an observation that may help the study and the classification of human lung adenocarcinomas.
Collapse
MESH Headings
- Adenocarcinoma, Bronchiolo-Alveolar/metabolism
- Adenocarcinoma, Bronchiolo-Alveolar/pathology
- Animals
- Antigens, CD/biosynthesis
- Antigens, CD/ultrastructure
- Biomarkers, Tumor/analysis
- Blotting, Northern
- Cell Transformation, Neoplastic
- Cells, Cultured
- Dendritic Cells/immunology
- Dendritic Cells/metabolism
- Dendritic Cells/ultrastructure
- Disease Models, Animal
- Female
- Flow Cytometry
- Humans
- Immunohistochemistry
- Lung/cytology
- Lung/ultrastructure
- Lung Neoplasms/metabolism
- Lung Neoplasms/pathology
- Lysosomal Membrane Proteins
- Mice
- Microscopy, Confocal
- Microscopy, Immunoelectron
- Species Specificity
Collapse
Affiliation(s)
- Bruno Salaun
- Laboratory for Immunological Research, Schering Plough Research Institute, Dardilly, France
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Bates SR, Tao JQ, Notarfrancesco K, DeBolt K, Shuman H, Fisher AB. Effect of surfactant protein A on granular pneumocyte surfactant secretion in vitro. Am J Physiol Lung Cell Mol Physiol 2003; 285:L1055-65. [PMID: 12882765 DOI: 10.1152/ajplung.00271.2002] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Surfactant secretion by lung type II cells occurs when lamellar bodies (LBs) fuse with the plasma membrane and surfactant is released into the alveolar lumen. Surfactant protein A (SP-A) blocks secretagogue-stimulated phospholipid (PL) release, even in the presence of surfactant-like lipid. The mechanism of action is not clear. We have shown previously that an antibody to LB membranes (MAb 3C9) can be used to measure LB membrane trafficking. Although the ATP-stimulated secretion of PL was blocked by SP-A, the cell association of iodinated MAb 3C9 was not altered, indicating no effect on LB movement. FM1-43 is a hydrophobic dye used to monitor the formation of fusion pores. After secretagogue exposure, the threefold enhancement of the number of FM1-43 fluorescent LBs (per 100 cells) was not altered by the presence of SP-A. Finally, there was no evidence of a large PL pool retained on the cell surface through interaction with SP-A. Thus SP-A exposure does not affect these stages in the surfactant secretory pathway of type II cells.
Collapse
Affiliation(s)
- Sandra R Bates
- Institute for Environmental Medicine, University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania 19104-6068, USA.
| | | | | | | | | | | |
Collapse
|
12
|
Rückert P, Bates SR, Fisher AB. Role of clathrin- and actin-dependent endocytotic pathways in lung phospholipid uptake. Am J Physiol Lung Cell Mol Physiol 2003; 284:L981-9. [PMID: 12611816 DOI: 10.1152/ajplung.00392.2002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We evaluated the contribution of endocytotic pathways to pulmonary uptake of surfactant lipids from the alveolar space. Resting and stimulated 8-bromoadenosine 3',5'-cyclic monophosphate (8-Br-cAMP) uptake of unilamellar liposomes labeled with either [(3)H]dipalmitoylphosphatidylcholine ([(3)H]DPPC) or 1-palmitoyl-2-[12-(7-nitro-2-1,3-benzoxadiazol-4-yl) amino] dodecanoyl-phosphatidylcholine (NBD-PC) was studied in isolated perfused rat lungs and isolated type II cells. Amantadine and phenylarsine oxide, inhibitors of clathrin-mediated endocytosis, each decreased [(3)H]DPPC uptake under resting conditions by approximately 40%; their combination had no additional effect. Cytochalasin D, an inhibitor of actin-dependent processes, reduced liposome uptake by 55% and potentiated the effect of either clathrin inhibitor alone. Relative inhibition for all agents was higher in the presence of 8-Br-cAMP. The effect of inhibitors was similar for liposomes labeled with [(3)H]DPPC or NBD-PC. By fluorescence microscopy, NBD-PC taken up by lungs was localized primarily to alveolar type II cells and was localized to lamellar bodies in both lungs and isolated cells. These studies indicate that both clathrin-mediated and actin-mediated pathways are responsible for endocytosis of DPPC-labeled liposomes by alveolar type II cells in the intact lung.
Collapse
Affiliation(s)
- Peter Rückert
- Institute for Environmental Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | | | | |
Collapse
|
13
|
Fehrenbach A, Bube C, Hohlfeld JM, Stevens P, Tschernig T, Hoymann HG, Krug N, Fehrenbach H. Surfactant homeostasis is maintained in vivo during keratinocyte growth factor-induced rat lung type II cell hyperplasia. Am J Respir Crit Care Med 2003; 167:1264-70. [PMID: 12574070 DOI: 10.1164/rccm.200112-132oc] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Keratinocyte growth factor (KGF) induces transient proliferation of alveolar type II cells (AEII) associated with surfactant alterations. To test the hypothesis that homeostasis of intracellular phospholipid stores is maintained under KGF-induced hyperplasia, we (1) collected tissue from adult rat lungs, fixed for light and electron microscopy 3 days after intratracheal instillation of 5 mg recombinant human (rHu) KGF/kg body weight or phosphate-buffered saline (PBS), and from untreated control animals (five animals/group) for design-based stereology of AEII and lamellar body (LB) ultrastructure; and (2) we analyzed uptake and distribution of instilled radiolabeled phospholipids. After rHuKGF, AEII-coverage of alveolar walls (PBS:8.3 +/- 3.0%; rHuKGF:30.6 +/- 4.8%) and number of AEII/ml lung volume (PBS:28.5 +/- 6.5 x 10(6); rHuKGF:48.2 +/- 5.8 x 10(6)) were increased (p < 0.008). Number (PBS:97 +/- 25; rHuKGF:54 +/- 7) and volume (PBS:45.3 +/- 13.8 microm(3); rHuKGF:21.0 +/- 4.7 microm(3)) of LBs per cell were decreased (p < 0.008), but not total amount/ml lung volume (PBS:128 +/- 46. 4 x 10(7) microm(3); rHuKGF:103 +/- 34. 7 x 10(7) microm(3)). This was paralleled by a shift to larger LBs. After rHuKGF, radiolabeled phospholipids accumulated in whole lung tissue relative to lavage fluid (p < 0.01). However, less radiolabel was incorporated per cell (p < 0.01). We conclude that under rHuKGF-induced AEII proliferation intracellular surfactant was decreased per single cell, whereas a constant amount was maintained per unit lung volume. We suggest that surfactant homeostasis is regulated at the level of phospholipid transport processes, for example, secretion and reuptake.
Collapse
Affiliation(s)
- Antonia Fehrenbach
- Division of Electron Microscopy, Center of Anatomy, University of Göttingen, Göttingen, Germany
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Bates SR, Gonzales LW, Tao JQ, Rueckert P, Ballard PL, Fisher AB. Recovery of rat type II cell surfactant components during primary cell culture. Am J Physiol Lung Cell Mol Physiol 2002; 282:L267-76. [PMID: 11792631 DOI: 10.1152/ajplung.00227.2001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A culture system designed to maintain the differentiated characteristics of rat type II cells based on protocols used for human fetal lung pneumocytes was investigated. Type II cells were isolated either from adult rats with elastase (adult type II cells) or from young rats (4-11 days postnatal) with collagenase and trypsin (young type II cells) and were incubated with dexamethasone (Dex, 10 nM) and cAMP (0.1 mM). By day 4 of culture with hormone treatment, the mRNA levels in adult type II cells were less than 3% of day 0 values, whereas surfactant protein (SP)-A protein content was 26%. However, young type II cells maintained lamellar bodies and microvilli and secreted phospholipid in response to ATP. SP-A, -B, and -C mRNA levels were elevated to 159, 350, and 39%, respectively, of day 0 values with a synergistic response to Dex and cAMP, whereas SP-A protein content rose to 119%. Surfactant mRNA and protein did not recover in cells cultured without hormones. This cell culture system restored surfactant components in rat type II cells.
Collapse
Affiliation(s)
- Sandra R Bates
- The Institute for Environmental Medicine, University of Pennsylvania, 19104, USA.
| | | | | | | | | | | |
Collapse
|
15
|
Savani RC, Godinez RI, Godinez MH, Wentz E, Zaman A, Cui Z, Pooler PM, Guttentag SH, Beers MF, Gonzales LW, Ballard PL. Respiratory distress after intratracheal bleomycin: selective deficiency of surfactant proteins B and C. Am J Physiol Lung Cell Mol Physiol 2001; 281:L685-96. [PMID: 11504697 DOI: 10.1152/ajplung.2001.281.3.l685] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Intratracheal bleomycin in rats is associated with respiratory distress of uncertain etiology. We investigated the expression of surfactant components in this model of lung injury. Maximum respiratory distress, determined by respiratory rate, occurred at 7 days, and surfactant dysfunction was confirmed by increased surface tension of the large-aggregate fraction of bronchoalveolar lavage (BAL). In injured animals, phospholipid content and composition were similar to those of controls, mature surfactant protein (SP) B was decreased 90%, and SP-A and SP-D contents were increased. In lung tissue, SP-B and SP-C mRNAs were decreased by 2 days and maximally at 4--7 days and recovered between 14 and 21 days after injury. Immunostaining of SP-B and proSP-C was decreased in type II epithelial cells but strong in macrophages. By electron microscopy, injured lungs had type II cells lacking lamellar bodies and macrophages with phagocytosed lamellar bodies. Surface activity of BAL phospholipids of injured animals was restored by addition of exogenous SP-B. We conclude that respiratory distress after bleomycin in rats results from surfactant dysfunction in part secondary to selective downregulation of SP-B and SP-C.
Collapse
Affiliation(s)
- R C Savani
- Division of Neonatology, Department of Pediatrics, The Children's Hospital of Philadelphia and University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-4399, USA.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|