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Li Y, Kinting S, Höppner S, Forstner ME, Uhl O, Koletzko B, Griese M. Metabolic labelling of choline phospholipids probes ABCA3 transport in lamellar bodies. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1864:158516. [DOI: 10.1016/j.bbalip.2019.158516] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 08/21/2019] [Accepted: 08/26/2019] [Indexed: 01/09/2023]
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Osanai K. Rab38 Mutation and the Lung Phenotype. Int J Mol Sci 2018; 19:E2203. [PMID: 30060521 PMCID: PMC6122074 DOI: 10.3390/ijms19082203] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2018] [Revised: 07/21/2018] [Accepted: 07/23/2018] [Indexed: 12/12/2022] Open
Abstract
Rab38 is highly expressed in alveolar type II cells, melanocytes, and platelets. These cells are specifically-differentiated cells and contain characteristic intracellular organelles called lysosome-related organelles, i.e., lamellar bodies in alveolar type II cells, melanosomes in melanocytes, and dense granules in platelets. There are Rab38-mutant rodents, i.e., chocolate mice and Ruby rats. While chocolate mice only show oculocutaneous albinism, Ruby rats show oculocutaneous albinism and prolonged bleeding time and, hence, are a rat model of Hermansky-Pudlak syndrome (HPS). Most patients with HPS suffer from fatal interstitial pneumonia by middle age. The lungs of both chocolate mice and Ruby rats show remarkably increased amounts of lung surfactant and conspicuously enlarged lysosome-related organelles, i.e., lamellar bodies, which are also characteristic of the lungs in human HPS. There are 16 mutant HPS-mouse strains, of which ten mutant genes have been identified to be causative in patients with HPS thus far. The gene products of eight of the ten genes constitute one of the three protein complexes, i.e., biogenesis of lysosome-related organelle complex-1, -2, -3 (BLOC-1, -2, -3). Patients with HPS of the mutant BLOC-3 genotype develop interstitial pneumonia. Recently, BLOC-3 has been elucidated to be a guanine nucleotide exchange factor for Rab38. Growing evidence suggests that Rab38 is an additional candidate gene of human HPS that displays the lung phenotype.
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Affiliation(s)
- Kazuhiro Osanai
- Department of Life Science, Medical Research Institute, Kanazawa Medical University, 1-1 Uchinada-Daigaku, Kahokugun, Ishikawa 920-0293, Japan.
- Department of Respiratory Medicine, Kanazawa Medical University, 1-1 Uchinada-Daigaku, Kahokugun, Ishikawa 920-0293, Japan.
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Osanai K, Nakase K, Sakuma T, Nishiki K, Nojiri M, Kato R, Saito M, Fujimoto Y, Mizuno S, Toga H. Exogenous gene transfer of Rab 38 small GTPase ameliorates aberrant lung surfactant homeostasis in Ruby rats. Respir Res 2017; 18:70. [PMID: 28438206 PMCID: PMC5402648 DOI: 10.1186/s12931-017-0549-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 04/11/2017] [Indexed: 11/25/2022] Open
Abstract
Background Rab38 small GTPase regulates intracellular transport in melanocytes and alveolar type II epithelial cells. Ruby rats carrying Rab38 and other gene mutations exhibit oculocutaneous albinism, bleeding diathesis, and hence, are a rat model of human Hermansky-Pudlak syndrome (HPS). We previously showed that Long Evans Cinnamon (LEC) rats, one strain of the Ruby rats, developed aberrant lung surfactant homeostasis with remarkably enlarged lamellar bodies in alveolar type II cells. Methods A replication-deficient recombinant adenovirus expressing rat Rab38 (Ad-Rab38) was constructed. Alveolar type II cells were isolated from the LEC rats and tested for lung surfactant phosphatidylcholine secretion. The rats were also examined whether exogenous expression of Ad- Rab38 could rescue the altered lung surfactant homeostasis in the lungs. Results Isolated type II cells infected with Ad-Rab38 exhibited improved secretion patterns of [3H]phosphatidylcholine, i.e. increased basal hyposecretion and decreased agonist-induced hypersecretion. Endobronchial administration of Ad-Rab38 improved the morphology of type II cells and lamellar bodies, reducing their sizes close to those of wild-type rats. The increased amounts of phosphatidylcholine and surfactant protein B in the lamellar body fractions were decreased in the Ad-Rab38 infected lungs. Conclusions These results provide strong evidence that the aberrant lung surfactant homeostasis in the LEC rats is caused by Rab38 deficit, and suggest that endobronchial delivery of the responsive transgene could be an effective method to ameliorate the abnormal lung phenotype in the animal model of HPS.
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Affiliation(s)
- Kazuhiro Osanai
- Department of Respiratory Medicine, Kanazawa Medical University, 1-1 Uchinada-Daigaku, Kahokugun, Ishikawa, 920-0293, Japan.
| | - Keisuke Nakase
- Department of Respiratory Medicine, Kanazawa Medical University, 1-1 Uchinada-Daigaku, Kahokugun, Ishikawa, 920-0293, Japan
| | - Takashi Sakuma
- Department of Respiratory Medicine, Kanazawa Medical University, 1-1 Uchinada-Daigaku, Kahokugun, Ishikawa, 920-0293, Japan
| | - Kazuaki Nishiki
- Department of Respiratory Medicine, Kanazawa Medical University, 1-1 Uchinada-Daigaku, Kahokugun, Ishikawa, 920-0293, Japan
| | - Masafumi Nojiri
- Department of Respiratory Medicine, Kanazawa Medical University, 1-1 Uchinada-Daigaku, Kahokugun, Ishikawa, 920-0293, Japan
| | - Ryo Kato
- Department of Respiratory Medicine, Kanazawa Medical University, 1-1 Uchinada-Daigaku, Kahokugun, Ishikawa, 920-0293, Japan
| | - Masatoshi Saito
- Department of Respiratory Medicine, Kanazawa Medical University, 1-1 Uchinada-Daigaku, Kahokugun, Ishikawa, 920-0293, Japan
| | - Yuki Fujimoto
- Department of Respiratory Medicine, Kanazawa Medical University, 1-1 Uchinada-Daigaku, Kahokugun, Ishikawa, 920-0293, Japan
| | - Shiro Mizuno
- Department of Respiratory Medicine, Kanazawa Medical University, 1-1 Uchinada-Daigaku, Kahokugun, Ishikawa, 920-0293, Japan
| | - Hirohisa Toga
- Department of Respiratory Medicine, Kanazawa Medical University, 1-1 Uchinada-Daigaku, Kahokugun, Ishikawa, 920-0293, Japan
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Marcinkiewicz MM, Baker ST, Wu J, Hubert TL, Wolfson MR. A Novel Approach for Ovine Primary Alveolar Epithelial Type II Cell Isolation and Culture from Fresh and Cryopreserved Tissue Obtained from Premature and Juvenile Animals. PLoS One 2016; 11:e0152027. [PMID: 26999050 PMCID: PMC4801353 DOI: 10.1371/journal.pone.0152027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 03/08/2016] [Indexed: 11/19/2022] Open
Abstract
The in vivo ovine model provides a clinically relevant platform to study cardiopulmonary mechanisms and treatments of disease; however, a robust ovine primary alveolar epithelial type II (ATII) cell culture model is lacking. The objective of this study was to develop and optimize ovine lung tissue cryopreservation and primary ATII cell culture methodologies for the purposes of dissecting mechanisms at the cellular level to elucidate responses observed in vivo. To address this, we established in vitro submerged and air-liquid interface cultures of primary ovine ATII cells isolated from fresh or cryopreserved lung tissues obtained from mechanically ventilated sheep (128 days gestation-6 months of age). Presence, abundance, and mRNA expression of surfactant proteins was assessed by immunocytochemistry, Western Blot, and quantitative PCR respectively on the day of isolation, and throughout the 7 day cell culture study period. All biomarkers were significantly greater from cells isolated from fresh than cryopreserved tissue, and those cultured in air-liquid interface as compared to submerged culture conditions at all time points. Surfactant protein expression remained in the air-liquid interface culture system while that of cells cultured in the submerged system dissipated over time. Despite differences in biomarker magnitude between cells isolated from fresh and cryopreserved tissue, cells isolated from cryopreserved tissue remained metabolically active and demonstrated a similar response as cells from fresh tissue through 72 hr period of hyperoxia. These data demonstrate a cell culture methodology using fresh or cryopreserved tissue to support study of ovine primary ATII cell function and responses, to support expanded use of biobanked tissues, and to further understanding of mechanisms that contribute to in vivo function of the lung.
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Affiliation(s)
- Mariola M. Marcinkiewicz
- Department of Thoracic Medicine and Surgery, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
- Center for Inflammation, Translational and Clinical Lung Research, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
- CENTRe: Collaborative for Environmental and Neonatal Therapeutics, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
| | - Sandy T. Baker
- Department of Thoracic Medicine and Surgery, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
- Center for Inflammation, Translational and Clinical Lung Research, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
- CENTRe: Collaborative for Environmental and Neonatal Therapeutics, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
| | - Jichuan Wu
- Department of Thoracic Medicine and Surgery, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
- Center for Inflammation, Translational and Clinical Lung Research, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
- CENTRe: Collaborative for Environmental and Neonatal Therapeutics, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
| | - Terrence L. Hubert
- Department of Thoracic Medicine and Surgery, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
- Center for Inflammation, Translational and Clinical Lung Research, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
- CENTRe: Collaborative for Environmental and Neonatal Therapeutics, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
| | - Marla R. Wolfson
- Department of Thoracic Medicine and Surgery, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
- Department of Physiology, Pediatrics and Medicine, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
- Center for Inflammation, Translational and Clinical Lung Research, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
- CENTRe: Collaborative for Environmental and Neonatal Therapeutics, Katz School of Medicine at Temple University, Philadelphia, PA, United States of America
- * E-mail:
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Hishikawa D, Shindou H, Harayama T, Ogasawara R, Suwabe A, Shimizu T. Identification of Sec14‐like 3 as a novel lipid‐packing sensor in the lung. FASEB J 2013; 27:5131-40. [DOI: 10.1096/fj.13-237941] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Daisuke Hishikawa
- Department of Lipid SignalingResearch InstituteNational Center for Global Health and MedicineTokyoJapan
| | - Hideo Shindou
- Department of Lipid SignalingResearch InstituteNational Center for Global Health and MedicineTokyoJapan
| | - Takeshi Harayama
- Department of Lipid SignalingResearch InstituteNational Center for Global Health and MedicineTokyoJapan
| | - Rie Ogasawara
- Department of Laboratory MedicineSchool of MedicineIwate Medical UniversityUchimaruMoriokaJapan
| | - Akira Suwabe
- Department of Laboratory MedicineSchool of MedicineIwate Medical UniversityUchimaruMoriokaJapan
| | - Takao Shimizu
- Department of Lipid SignalingResearch InstituteNational Center for Global Health and MedicineTokyoJapan
- Department of Biochemistry and Molecular BiologyFaculty of MedicineThe University of TokyoTokyoJapan
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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.
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Affiliation(s)
- Christina L Grek
- Department of Pediatrics, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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Sun K, Brockman D, Campos B, Pitzer B, Myatt L. Induction of surfactant protein A expression by cortisol facilitates prostaglandin synthesis in human chorionic trophoblasts. J Clin Endocrinol Metab 2006; 91:4988-94. [PMID: 17003084 DOI: 10.1210/jc.2006-1472] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
CONTEXT Surfactant protein A (SP-A) may be an important link between the maturation of fetal organs and the initiation of parturition. However, the local expression of SP-A and the effect of SP-A on prostaglandin synthesis in human fetal membranes have not been resolved. OBJECTIVE Our objective was to examine SP-A expression and the effect of SP-A on prostaglandin synthesis in human fetal membranes. DESIGN SP-A expression was examined with immunohistochemistry and PCR. The effect of SP-A on prostaglandin synthesis was investigated in cultured human chorionic trophoblasts. PATIENTS Patients were normal-term pregnant women undergoing elective cesarean sections. RESULTS Both SP-A protein and mRNA were present in amnion epithelial cells, fibroblasts, and chorionic trophoblasts. Cortisol (10(-7) and 10(-6) M, 24 h) induced SP-A expression in cultured chorionic trophoblasts, which could be blocked by the glucocorticoid receptor antagonist RU486. Treatment of chorionic trophoblasts with SP-A (10-100 microg/ml, 24 h) caused a dose-dependent increase of prostaglandin E2 release and an induction of cyclooxygenase type 2 but not cytosolic phospholipase A2 and microsomal prostaglandin E synthase expression. CONCLUSIONS SP-A can be synthesized locally in human fetal membranes, which can be induced by glucocorticoids. SP-A appeared to induce prostaglandin E2 synthesis in chorionic trophoblasts via induction of cyclooxygenase type 2 expression.
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Affiliation(s)
- Kang Sun
- Department of Obstetrics and Gynecology, College of Medicine, University of Cincinnati, 231 Albert Sabin Way, Cincinnati, Ohio 45267, USA.
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8
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Kuzmenko AI, Wu H, McCormack FX. Pulmonary collectins selectively permeabilize model bacterial membranes containing rough lipopolysaccharide. Biochemistry 2006; 45:2679-85. [PMID: 16489761 PMCID: PMC3156245 DOI: 10.1021/bi0522652] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We have reported that Gram-negative organisms decorated with rough lipopolysaccharide (LPS) are particularly susceptible to the direct antimicrobial actions of the pulmonary collectins, surfactant proteins A (SP-A) and D (SP-D). In this study, we examined the lipid and LPS components required for the permeabilizing effects of the collectins on model bacterial membranes. Liposomes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), with or without rough Escherichia coli LPS (J5), smooth E. coli LPS (B5), or cholesterol, were loaded with self-quenching probes and exposed to native or oxidatively modified SP-A. Fluorescence that resulted from permeabilization of liposomes and diffusion of dyes was assessed by microscopy or fluorimetry. Human SP-A and melittin increased the permeability of J5 LPS/POPE liposomes, but not B5 LPS/POPE liposomes or control (POPE only) liposomes. At a human SP-A concentration of 100 microg/mL, the permeability of the J5 LPS/POPE membranes increased 4.4-fold (p < 0.02) compared to the control with no added SP-A. Rat SP-A and SP-D also permeabilized the J5-containing liposomes. Incorporation of cholesterol into J5 LPS/POPE liposomes at a POPE:cholesterol molar ratio of 1:0.15 blocked human SP-A or melittin-induced permeability (p < 0.05) compared to cholesterol-free liposomes. Exposure of human SP-A to surfactant lipid peroxidation blocked the permeabilizing activity of the protein. We conclude that SP-A permeabilizes phospholipid membranes in an LPS-dependent and rough LPS-specific manner, that the effect is neither SP-A- nor species-specific, and that oxidative damage to SP-A abolishes its membrane destabilizing properties. Incorporation of cholesterol into the membrane enhances resistance to permeabilization by SP-A, most likely by increasing the packing density and membrane rigidity.
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Affiliation(s)
| | | | - Francis X. McCormack
- Corresponding Author Footnote: Prof. Francis X. McCormack, University of Cincinnati, MSB Room 6053, 231 Albert Sabin Way, Cincinnati, OH 45267-0564, Tel. 513-558-4831, FAX 513-558-4858, E-mail:
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9
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Feng NH, Lin HI, Wang JS, Chou ST, Ma HK, Rooney SA, Lu JF. Differential expression of a V-type ATPase C subunit gene, Atp6v1c2, during culture of rat lung type II pneumocytes. J Biomed Sci 2005; 12:899-911. [PMID: 16283434 DOI: 10.1007/s11373-005-9020-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2005] [Accepted: 08/03/2005] [Indexed: 01/05/2023] Open
Abstract
The lung alveolar epithelium consists of type I and type II pneumocytes. In vivo, the type II cell is the progenitor cell from which the type I cell originates. When freshly-isolated type II cells are cultured under conventional conditions they rapidly lose their phenotypic properties and attain characteristics of type I cells. Taking advantage of this transdifferentiation, we sought to identify genes that are differentially expressed during culture of rat type II cells. Using suppression subtractive hybridization (SSH), a vacuolar-type H+-ATPase (V-ATPase) C2 subunit gene (Atp6v1c2) was found to be enriched in freshly isolated rat type II cells compared to those cultured for 4 days. Northern blotting and reverse-transcription polymerase chain reaction (RT-PCR) confirmed the differential expression of Atp6v1c2 during in vitro culture of isolated type II cells. Expression ofAtp6v1c2 was significantly reduced early during in vitro culture: almost 90% reduction was observed after 24 h of incubation as determined by real-time PCR. In situ hybridization showed that Atp6v1c2 is expressed in both bronchiolar and alveolar lung epithelial cells, an expression pattern similar to that of surfactant protein B (SP-B). Multi-tissue Northern blotting revealed a unique tissue distribution with Atp6v1c2 expression limited to lung, kidney and testis. The presence and expression of Atp6v1c2 gene transcript isoforms, resulting from alternative splicing, were also investigated. Elucidation of differential expression of Atp6v1c2 in type II cells and further studies of its regulation may provide information useful in understanding the molecular mechanism underlying phenotypic and functional changes during transdifferentiation of alveolar epithelial cells.
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MESH Headings
- Alternative Splicing
- Amino Acid Sequence
- Animals
- Blotting, Northern
- Blotting, Western
- Cell Culture Techniques
- Cell Differentiation
- Cells, Cultured
- Cloning, Molecular
- DNA, Complementary/metabolism
- Expressed Sequence Tags
- Gene Expression Regulation, Enzymologic
- In Situ Hybridization
- Lung/cytology
- Lung/metabolism
- Macrophages/metabolism
- Molecular Sequence Data
- Nucleic Acid Hybridization
- Oligonucleotides/chemistry
- Phenotype
- Protein Isoforms
- Pulmonary Alveoli/metabolism
- Pulmonary Surfactant-Associated Protein B/metabolism
- RNA/metabolism
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Time Factors
- Tissue Distribution
- Vacuolar Proton-Translocating ATPases/biosynthesis
- Vacuolar Proton-Translocating ATPases/genetics
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Affiliation(s)
- Nan-Hsiung Feng
- Department of Internal Medicine, Kaohsiung Military General Hospital, Kaohsiung, Taiwan, ROC
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10
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Patel AS, Reigada D, Mitchell CH, Bates SR, Margulies SS, Koval M. Paracrine stimulation of surfactant secretion by extracellular ATP in response to mechanical deformation. Am J Physiol Lung Cell Mol Physiol 2005; 289:L489-96. [PMID: 15908478 DOI: 10.1152/ajplung.00074.2005] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We developed a heterologous system to study the effect of mechanical deformation on alveolar epithelial cells. First, isolated primary rat alveolar type II (ATII) cells were plated onto silastic substrata coated with fibronectin and maintained in culture under conditions where they become alveolar type I-like (ATI) cells. This was followed by a second set of ATII cells labeled with the nontransferable, vital fluorescent stain 5-chloromethylfluorescein diacetate to distinguish them from ATI cells. By morphometric analysis, equibiaxial deformation (stretch) of the silastic substratum induced comparable changes in cell surface area for both ATII and ATI cells. Surfactant lipid secretion was measured using cells metabolically labeled with [(3)H]choline. In response to 21% tonic stretch for 15 min, ATII cells seeded with ATI cells secreted nearly threefold more surfactant lipid compared with ATII cells seeded alone. ATI cells did not secrete lipid in response to stretch. The enhanced lipid secretion by ATII plus ATI cocultures was inhibited by treatment with apyrase and adenosine deaminase, suggesting that ATP release by ATI cells enhanced surfactant lipid secretion at 21% stretch. This was confirmed using a luciferase assay where, in response to 21% stretch, ATI cells released fourfold more ATP than ATII cells. Because ATI cells release significantly more ATP at a lower level of stretch than ATII cells, this supports the hypothesis that ATI cells are mechanosensors in the lung and that paracrine stimulation of ATII cells by extracellular ATP released from ATI cells plays a role in regulating surfactant secretion.
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Affiliation(s)
- Anand S Patel
- Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, USA
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11
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Kuzmenko AI, Wu H, Wan S, McCormack FX. Surfactant protein A is a principal and oxidation-sensitive microbial permeabilizing factor in the alveolar lining fluid. J Biol Chem 2005; 280:25913-9. [PMID: 15890661 DOI: 10.1074/jbc.m411344200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have reported that surfactant protein A kills some Gram-negative organisms by increasing membrane permeability. In this study, we investigated the physiologic importance of this activity and the effect of oxidative stress on the antimicrobial functions of SP-A in vitro and in vivo. Concentrated bronchoalveolar lavage fluids from SP-A+/+ mice increased the permeability of the Escherichia coli K12 cell membrane to a greater extent than lavage from SP-A-/- animals. Similarly, calcium-dependent surfactant-binding proteins of SP-A+/+ mice increased membrane permeability more than those from SP-A-/- mice and produced greater zonal killing of agar-embedded bacteria in a radial diffusion assay. Exposure of human SP-A to copper-initiated surfactant phospholipid peroxidation or to free radicals generated by human neutrophils in vitro increased the level of SP-A-associated carbonyl moieties and blocked the permeabilizing function of the protein. We also found that exposure of mice to 90% O2 for 4 days, sufficient to lead to consumption of glutathione, oxidation of protein thiols, and accumulation of airspace protein-associated carbonyl moieties, blocked the permeabilizing activity of lavage fluid from SP-A+/+ mice. We conclude that SP-A is a major microbial permeablizing factor in lavage fluid and that oxidative stress inhibits the antibacterial activity of SP-A by a mechanism that includes oxidative modification and functional inactivation of the protein.
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Affiliation(s)
- Alexander I Kuzmenko
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Cincinnati School of Medicine, Cincinnati, Ohio 45267-0564, USA
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12
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Rice WR, Conkright JJ, Na CL, Ikegami M, Shannon JM, Weaver TE. Maintenance of the mouse type II cell phenotype in vitro. Am J Physiol Lung Cell Mol Physiol 2002; 283:L256-64. [PMID: 12114186 DOI: 10.1152/ajplung.00302.2001] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The purpose of this study was to identify culture conditions for maintenance of isolated mouse type II cells with intact surfactant protein (SP) and phospholipid production. Type II cells were isolated from 6-wk-old mice and cultured on Matrigel matrix-rat tail collagen (70:30 vol/vol) in bronchial epithelial cell growth medium minus hydrocortisone plus 5% charcoal-stripped FBS and 10 ng/ml keratinocyte growth factor. Under these conditions, type II cells actively produced surfactant phospholipids and proteins for at least 7 days. Synthesis and secretion of surfactant phospholipids and SP-A, -B, -C, and -D declined on day 1 of culture but recovered by day 3, reaching levels comparable to or exceeding freshly isolated cells by day 5. Abundant lamellar bodies were readily apparent in cells examined on days 5 and 7, and a surfactant pellet was recovered by centrifugation of media harvested on each day of culture. Secretion of SP-B, SP-C, and phosphatidylcholine was stimulated by phorbol 12-myristate 13-acetate and was inhibited by compound 48/80. When tested with a bubble surfactometer, surfactant secreted by type II cells on day 5 of culture lowered surface tension to 5.2 +/- 2.3 mN/m. This is the first description of the synthesis and secretion of a functional surfactant complex by mouse type II cells after 7 days in primary culture.
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Affiliation(s)
- Ward R Rice
- Division of Pulmonary Biology, Children's Hospital Medical Center, Cincinnati, Ohio 45229-3039, USA.
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13
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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.
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Affiliation(s)
- Sandra R Bates
- The Institute for Environmental Medicine, University of Pennsylvania, 19104, USA.
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Gobran LI, Rooney SA. Regulation of SP-B and SP-C secretion in rat type II cells in primary culture. Am J Physiol Lung Cell Mol Physiol 2001; 281:L1413-9. [PMID: 11704537 DOI: 10.1152/ajplung.2001.281.6.l1413] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
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.
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Affiliation(s)
- L I Gobran
- Division of Perinatal Medicine, Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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15
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Gonzales LW, Angampalli S, Guttentag SH, Beers MF, Feinstein SI, Matlapudi A, Ballard PL. Maintenance of differentiated function of the surfactant system in human fetal lung type II epithelial cells cultured on plastic. PEDIATRIC PATHOLOGY & MOLECULAR MEDICINE 2001; 20:387-412. [PMID: 11552739 DOI: 10.1080/15513810109168622] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
We report a simplified culture system for human fetal lung type II cells that maintains surfactant expression. Type II cells isolated from explant cultures of hormone-treated lungs (18-22 wk gestation) by collagenase + trypsin digestion were cultured on plastic for 4 days in serum-free medium containing dexamethasone (Dex, 10 nM) + 8-bromo-cAMP (0.1 mM + isobutylmethylxanthine (0.1 mM) or were untreated (control). Surfactant protein (SP) mRNAs decreased markedly in control cells between days 1 and 4 of culture, but mRNA levels were high in treated cells on day) 4 (SP-A, SP-B, SP-C, SP-D; 600%, 100%, 85%, 130% of day 0 content, respectively). Dex or cAMP alone increased SP-B, SP-C, and SP-D mRNAs and together had additive effects. The greatest increase in SP-A mRNA occurred with cAMP alone. Treated cells processed pro-SP-B and pro-SP-C proteins to mature forms and had a higher rate of phosphatidylcholine (PC) synthesis (2-fold) and higher saturation of PC (approximately 34% versus 27%) than controls. Only treated cells maintained secretagogue-responsive phospholipid synthesis. By electron microscopy, the treated cells retained lamellar bodies and extensive microvilli. We conclude that Dex and cAMP additively stimulate expression of surfactant components in isolated fetal type II cells, providing a simplified culture system for investigation of surfactant-related, and perhaps other, type II cell functions.
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Affiliation(s)
- L W Gonzales
- Department of Pediatrics, Children's Hospital of Philadelphia, Pennsylvania, USA.
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16
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Osanai K, Iguchi M, Takahashi K, Nambu Y, Sakuma T, Toga H, Ohya N, Shimizu H, Fisher JH, Voelker DR. Expression and localization of a novel Rab small G protein (Rab38) in the rat lung. THE AMERICAN JOURNAL OF PATHOLOGY 2001; 158:1665-75. [PMID: 11337364 PMCID: PMC1891947 DOI: 10.1016/s0002-9440(10)64122-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The Rab small G protein family participates in intracellular vesicle transport, including exocytosis and endocytosis. The cDNA encoding a novel Rab-related small G protein (Rab38) has been cloned from rat lung cDNA library and recorded in GenBank (accession no. M94043). However, the expression and localization of the protein in the lung remains primarily unknown. We produced polyhistidine-tagged recombinant Rab38 and a polyclonal antibody with a synthetic peptide. Immunohistochemistry demonstrated that the protein is specifically localized in alveolar type II cells and in bronchial epithelial cells. In situ hybridization using a digoxygenin-labeled RNA riboprobe clearly showed that the mRNA of the protein is localized in alveolar type II cells and bronchial epithelial cells, especially terminal airway epithelial cells. Western blot and reverse transcriptase-polymerase chain reaction showed distinct expression of the protein and mRNA in isolated alveolar type II cells, but not in alveolar macrophages. The native protein was predominantly hydrophobic and was enriched in a high-density vesicle fraction but was barely detectable in nuclear and lamellar body fractions in alveolar type II cells. Immunofluorescence cytochemistry performed on cultured alveolar type II cells showed that Rab38 distributed extensively in the cytoplasm with a distribution pattern similar to endoplasmic reticulum rather than other subcellular organelles. These results suggest that this novel rab small G protein (Rab38) mediates vesicular transport in terminal airway epithelium.
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Affiliation(s)
- K Osanai
- Department of Internal Medicine, Division of Respiratory Disease, Kanazawa Medical University, Ishikawa, Japan.
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17
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Osanai K, Mason RJ, Voelker DR. Pulmonary surfactant phosphatidylcholine transport bypasses the brefeldin A sensitive compartment of alveolar type II cells. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1531:222-9. [PMID: 11325613 DOI: 10.1016/s1388-1981(01)00104-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Brefeldin A (BFA) causes disassembly of the Golgi apparatus and blocks protein transport to this organelle from the endoplasmic reticulum. However, there still remains considerable ambiguity regarding the involvement of the Golgi apparatus in glycerolipid transport pathways. We examined the effects of BFA upon the intracellular translocation of phosphatidylcholine in alveolar type II cells, that synthesize, transport, store and secrete large amounts of phospholipid for regulated exocytosis. BFA at concentrations as high as 10 microg/ml failed to alter the assembly of phosphatidylcholine into lamellar bodies, the specialized storage organelles for pulmonary surfactant. The same concentration of BFA was also ineffective at altering the secretion of newly synthesized phosphatidylcholine from alveolar type II cells. In contrast, concentrations of the drug of 2.5 microg/ml completely arrested newly synthesized lysozyme secretion from the same cells, indicating that BFA readily blocked protein transport processes in alveolar type II cells. The disassembly of the Golgi apparatus in alveolar type II cells following BFA treatment was also demonstrated by showing the redistribution of the resident Golgi protein MG-160 to the endoplasmic reticulum. These results indicate that intracellular transport of phosphatidylcholine along the secretory pathway in alveolar type II cells proceeds via a BFA insensitive route and does not require a functional Golgi apparatus.
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Affiliation(s)
- K Osanai
- National Jewish Medical and Research Center, 1400 Jackson St., Denver, CO 80206, USA
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18
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Affiliation(s)
- A J McCabe
- Buffalo Institute of Fetal Therapy (BIFT), The Children's Hospital of Buffalo, Departments of Surgery, Pediatrics, and OBGYN, The State University of New York at Buffalo, School of Medicine and Biomedical Sciences, Buffalo, NY, USA
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19
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Bates SR, Tao JQ, Schaller S, Fisher AB, Shuman H. Lamellar body membrane turnover is stimulated by secretagogues. Am J Physiol Lung Cell Mol Physiol 2000; 278:L443-52. [PMID: 10710515 DOI: 10.1152/ajplung.2000.278.3.l443] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Lamellar bodies are specialized cellular organelles used for storage of surfactant by alveolar type II cells of the lung. We utilized monoclonal antibody (MAb) 3C9, which recognizes an integral lamellar body-limiting membrane protein of 180 kDa, to follow lamellar body trafficking. (125)I-labeled MAb 3C9 bound to the surface of type II cells and was internalized by the cells in a time- and concentration-dependent manner that was inhibitable by excess unlabeled antibody. The internalized antibody remained undegraded over a 4-h time period. The L2 rat lung cell line that does not have lamellar bodies did not bind iodinated 3C9. Exposure of type II cells to the secretagogues ATP, phorbol 12-myristate 13-acetate, and cAMP resulted in a 1.5- to 2-fold enhancement of binding and uptake of MAb 3C9. Calphostin C inhibited phorbol 12-myristate 13-acetate-stimulated phospholipid secretion and also reduced binding and uptake of MAb 3C9 by type II cells. Treatment of type II cells with phenylarsine oxide to obstruct clathrin-mediated endocytosis had no effect on the internalization of MAb 3C9 while markedly blocking the uptake of surfactant protein A and transferrin. An actin-mediated process was important for lamellar body membrane uptake because incubation with cytochalasin D partially inhibited MAb 3C9 incorporation by type II cells. These studies are compatible with enhanced lamellar body membrane turnover associated with surfactant secretion and indicate that this process can be monitored by the trafficking of the antigen reporter MAb 3C9.
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Affiliation(s)
- S R Bates
- Institute for Environmental Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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20
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Chander A, Sen N, Wadsworth S, Spitzer AR. Coordinate packaging of newly synthesized phosphatidylcholine and phosphatidylglycerol in lamellar bodies in alveolar type II cells. Lipids 2000; 35:35-43. [PMID: 10695922 DOI: 10.1007/s11745-000-0492-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Methylamine, a weak base, inhibits packaging of newly synthesized phosphatidylcholine (PC) in lamellar bodies in 20-22 h cultured alveolar type II cells, suggesting a role for acidic pH of lamellar bodies. In this study, we tested if (i) the packaging of PC is similarly regulated in freshly isolated type II cells and (ii) methylamine also inhibits the packaging of other surfactant phospholipids, particularly, phosphatidylglycerol (PG). The latter would suggest coordinated packaging so as to maintain the phospholipid composition of lung surfactant. During the short-term metabolic labeling experiments in freshly isolated type II cells, methylamine treatment decreased the incorporation of radioactive precursors into PC, disaturated PC (DSPC), and PG of lamellar bodies but not of the microsomes, when compared with controls. The calculated packaging (the percentage of microsomal lipid packaged in lamellar bodies) of each phospholipid was similarly decreased (approximately 50%) in methylamine-treated cells, suggesting coordinated packaging of surfactant phospholipids in lamellar bodies. Equilibrium-labeling studies with freshly isolated type II cells (as is routinely done for studies on surfactant secretion) +/- methylamine showed that in methylamine-treated cells, the secretion of PC and PG was decreased (possibly due to decreased packaging), but the phospholipid composition of released surfactant (measured by radioactivity distribution) was unchanged; and the PC content (measured by mass or radioactivity) of lamellar bodies was lower, but the PC composition (as percentage of total phospholipids) was unchanged when compared with control cells. We speculate that the newly synthesized surfactant phospholipids, PC, DSPC, and PG, are coordinately transported into lamellar bodies by a mechanism requiring the acidic pH, presumably, of lamellar bodies.
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Affiliation(s)
- A Chander
- Department of Pediatrics, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
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21
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Osanai K, Mason RJ, Voelker DR. Trafficking of newly synthesized surfactant protein A in isolated rat alveolar type II cells. Am J Respir Cell Mol Biol 1998; 19:929-35. [PMID: 9843927 DOI: 10.1165/ajrcmb.19.6.3292] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
We examined the synthesis, transport, and localization of surfactant protein A (SP-A) in primary cultures of alveolar type II cells. In type II cells maintained in culture for 6 h, 39% of the SP-A pool detected with an enzyme-linked immunosorbent assay (ELISA) was found in lamellar bodies (LBs). After 24 h in culture, 53% of the cellular SP-A pool was found in LBs. The absolute amount of SP-A in the LB compartment was almost identical at 6 and 24 h of culture. In contrast to the results obtained with ELISA, 35S labeling of newly synthesized SP-A revealed that less than 7% of the cellular SP-A pool was in LBs at either 6 or 24 h of culture. In the 6-h cultures, 17% of the total (i.e., cells and media) [35S]SP-A pool was extracellular. In the 24-h cultures, 70% of the [35S]SP-A pool was extracellular. The secretion of [35S]SP-A was blocked by brefeldin A at all times. When medium containing newly secreted [35S]SP-A was incubated with alveolar type II cells maintained in culture for 24 h, the protein was taken up and incorporated into the LB fraction. More than 80% of the internalized SP-A was associated with the LB compartment after a 6 h incubation. The uptake of [35S]SP-A was blocked at 4 degrees C and was promoted by addition of unlabeled SP-A at 37 degrees C. These findings support a pathway of extracellular routing of SP-A prior to its accumulation in LBs in cultured type II cells.
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Affiliation(s)
- K Osanai
- National Jewish Medical and Research Center; and Department of Medicine, Anna Perahia Adatto Clinical Research Center, Denver, Colorado, USA
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22
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Abstract
Surfactant secretion is a critical regulated process in the metabolism of pulmonary surfactant. Presumably, because this process is vital to the survival of the organism, there are several independent pathways for stimulating secretion which work through different cell surface receptors and signaling mechanisms. In addition, there is apparent homeostatic regulation in that two components of surfactant, namely SP-A and dipalmitoylphosphatidylcholine, can inhibit secretion. Although secretion of surfactant has been studied for over two decades, there remains some important issues to be resolved. In vivo secretion can be stimulated by hyperventilation or even a single large breath. However, we do not know the biochemical mechanism for this physiologically important form of stimulation. In vitro, we know many of the proximal events in signaling, but we do not know how the lamellar bodies move within a cell or the docking mechanism at the plasma membrane. Many investigators have demonstrated that SP-A will inhibit secretion in vitro, but the mechanism is not known. Finally, there is a route of secretion of SP-A independent of lamellar bodies, but we do not know details of this pathway nor its regulation.
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Affiliation(s)
- R J Mason
- Department of Medicine, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, CO 80206, USA.
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23
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Batenburg JJ, Haagsman HP. The lipids of pulmonary surfactant: dynamics and interactions with proteins. Prog Lipid Res 1998; 37:235-76. [PMID: 10193527 DOI: 10.1016/s0163-7827(98)00011-3] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- J J Batenburg
- Laboratory of Veterinary Biochemistry, Graduate School of Animal Health, Utrecht University, The Netherlands.
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24
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Xu X, McCormick-Shannon K, Voelker DR, Mason RJ. KGF increases SP-A and SP-D mRNA levels and secretion in cultured rat alveolar type II cells. Am J Respir Cell Mol Biol 1998; 18:168-78. [PMID: 9476903 DOI: 10.1165/ajrcmb.18.2.2824] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Studies of secretion of surfactant proteins by alveolar type II cells have been limited because the expression of the genes for these proteins decreases rapidly in primary culture. We developed a culture system to investigate the regulation of lipid and protein secretion by alveolar type II cells and the genes involved in these processes. Rat type II cells were plated on membrane inserts coated with rat-tail collagen in medium containing 10% fetal bovine serum (FBS) for 1 d before being changed to medium containing 5 ng/ml keratinocyte growth factor (KGF) and 2% serum for 3 d and to medium with 5% Engelbreth-Holm-Swarm tumor matrix (EHS) but without serum for 2 d. From this time forward, the cells were placed on a rocking platform and cultured with 0.4 ml medium on the apical surface at the air-liquid interface (A/L) in four different, serum-free media: basal Dulbecco's modified Eagle's medium (DMEM)/F12 medium (DF12), basal medium plus EHS (DF12/EHS), basal medium plus KGF (DF12/KGF), and basal medium plus EHS and KGF (DF12/EHS/KGF). Cells cultured in DF12 and DF12/EHS assumed an attenuated, flattened morphology, whereas those in DF12/KGF and DF12/EHS/KGF were more cuboidal, contained numerous lamellar bodies, and had apical microvilli. Cells cultured in DF12 and DF12/EHS produced a relatively weak signal for the surfactant protein mRNAs (surfactant proteins [SP]-A, SP-B, SP-C, and SP-D, respectively), and secretion of SP-A and SP-D remained low. In contrast, cells maintained for 3 d at A/L and cultured in the presence of KGF showed strong signals for SP-A, SP-B, and SP-D mRNAs, and secreted SP-A, SP-D, and lysozyme into the apical medium. The combination of 12-O-tetradecanoyl-phorbol-11-acetate (TPA) and terbutaline stimulated secretion of [3H]phosphatidylcholine ([3H]PC), SP-A, and lysozyme, but not SP-D. This primary culture system should prove useful for mechanistic studies of the secretion of SP-A, SP-D, and surfactant lipids.
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Affiliation(s)
- X Xu
- Department of Medicine, National Jewish Medical and Research Center, Denver, Colorado 80206, USA
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25
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Bhandari V, Lu H, Pachter J, Kresch MJ. Actin depolymerization is developmentally regulated in rat type II cells exposed to terbutaline. Pediatr Res 1997; 41:166-71. [PMID: 9029633 DOI: 10.1203/00006450-199702000-00002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The type II alveolar epithelial cell synthesizes and secretes pulmonary surfactant. Terbutaline enhances phospholipid release from adult and fetal type II cells. Our hypothesis is that the actin network of microfilaments regulates the secretory activity of the type II cell. To examine the developmental regulation of the changes in actin subfractions associated with secretory activity, cultures of type II cells derived from adult and 19-d fetal rat lung were incubated with or without 10 microM terbutaline for 1, 30, and 60 min. Dose-response effects of terbutaline were examined in adult type II cells. Effects of phorbol ester were also examined Globular (G-actin) and filamentous (F-actin) fractions were extracted from the cells and analyzed separately. Specified cellular equivalent volumes of each subfraction were analyzed by Western blotting, visualized by a color reaction, and quantified by densitometry. There was a decrease in the cytoskeletal F-actin pool along with an increase in the G-actin fraction within I min in adult type II cells exposed to terbutaline, indicating that depolymerization of F-actin occurs. Values returned to control levels by 60 min. In contrast, the decrease in F-actin, with a concomitant increase in G-actin, was maximal at 60 min in fetal cells exposed to terbutaline. There was a dose-dependent increase in actin depolymerization with maximal effects at 10 microM terbutaline. Phorbol ester also caused an increase in actin depolymerization. Depolymerization of the actin microfilament network may regulate transport and exocytosis of lamellar bodies in type II cells. We speculate that there is an early secretory mechanism that involves depolymerization of actin microfilaments and a late, actin-independent secretory mechanism present in adult type II cells. The timing of the response of the actin-dependent pathway is developmentally regulated. This may explain the developmental differences in the secretion of surfactant that we have previously shown.
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Affiliation(s)
- V Bhandari
- Department of Pediatrics, University of Connecticut School of Medicine, Farmington 06030-2203, USA
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26
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Lin S, Akinbi HT, Breslin JS, Weaver TE. Structural requirements for targeting of surfactant protein B (SP-B) to secretory granules in vitro and in vivo. J Biol Chem 1996; 271:19689-95. [PMID: 8702672 DOI: 10.1074/jbc.271.33.19689] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Human surfactant protein B (SP-B) is synthesized by type II cells as a 381-residue preproprotein which is proteolytically processed to a 79-residue mature peptide and targeted to lamellar bodies for secretion. To identify secretory granule targeting determinants, constructs encoding the SP-B preproprotein (SP-B), COOH-terminally deleted SP-B (SP-BDeltaC), the NH2-terminal propeptide (SP-BN), and a chimeric molecule consisting of albumin and the mature peptide (ALB/SP-BM) were transfected into AtT-20 and PC12 cells. Pulse-chase studies demonstrated that 10-30% of SP-B and SP-BDeltaC remained in cells in an endoglycosidase H-resistant form. Secretion of stored SP-B was stimulated by forskolin/12-O-tetradecanoylphorbol-13-acetate and intracellular SP-B was localized to secretory granules by immunoelectron microscopy. In contrast, SP-BN and ALB/SP-BM were constitutively secreted and not detected in secretory granules. Specific processing of SP-B was not detected in either AtT-20 or PC12 cells. Expression of SP-BDeltaC in transgenic mice resulted in secretion of fully processed mature SP-B, indicating correct processing and targeting of this construct in vivo. We conclude that 1) SP-B processing occurs in a cell-specific manner, 2) the proprotein contains secretory granule targeting determinants that are not cell-specific, 3) the NH2-terminal propeptide and the mature peptide are required for targeting SP-B to lamellar body, and 4) the COOH-terminal propeptide is not required for processing or sorting of SP-B.
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Affiliation(s)
- S Lin
- Division of Pulmonary Biology, Children's Hospital Medical Center, Cincinnati, Ohio 45229-3039, USA
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27
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Chander A, Sen N, Wu AM, Higgins S, Wadsworth S, Spitzer AR. Methylamine decreases trafficking and packaging of newly synthesized phosphatidylcholine in lamellar bodies in alveolar type II cells. Biochem J 1996; 318 ( Pt 1):271-8. [PMID: 8761482 PMCID: PMC1217618 DOI: 10.1042/bj3180271] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Lung lamellar bodies, the storage organelles for lung surfactant phosphatidylcholine (PC), maintain an acidic pH that can be increased with weak bases. This study investigates the effect of a weak base, methylamine, on the pH in lamellar bodies and on the trafficking and packaging of newly synthesized PC in lamellar bodies. Methylamine increased the pH of isolated lung lamellar bodies and of lamellar bodies in intact cells. Metabolic labelling of isolated type II cells with [methyl-3H]choline showed that although methylamine (2.5-10 mM) did not alter the labelling of cellular or microsomal PC and disaturated PC, it decreased the labelling of the PC and disaturated PC in lamellar bodies. The packaging of PC in lamellar bodies (the specific activities ratio between the PC in lamellar bodies and the microsomal PC) also decreased in a time- and concentration-dependent manner. The cellular synthesis of PC or its packaging into lamellar bodies was unaltered by brefeldin A, suggesting that the Golgi was not involved in PC packaging. Although methylamine also increased surfactant secretion, the inhibition of PC packaging in lamellar bodies seems unrelated to the secretagogue effect, (1) on the basis of metabolic consequences of increased secretion and (2) because ATP, another secretagogue, did not inhibit PC packaging. Methylamine seems to inhibit PC packaging by inhibiting trafficking of PC to lipid-rich light subcellular fractions. Together our results suggest that the trafficking of surfactant PC into lamellar bodies might be sensitive to changes in the pH of lamellar bodies.
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Affiliation(s)
- A Chander
- Department of Pediatrics, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA
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