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Translation of pulmonary protein therapy from bench to bedside: Addressing the bioavailability challenges. J Drug Deliv Sci Technol 2021. [DOI: 10.1016/j.jddst.2021.102664] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Akasaka K, Tanaka T, Maruyama T, Kitamura N, Hashimoto A, Ito Y, Watanabe H, Wakayama T, Arai T, Hayashi M, Moriyama H, Uchida K, Ohkouchi S, Tazawa R, Takada T, Yamaguchi E, Ichiwata T, Hirose M, Arai T, Inoue Y, Kobayashi H, Nakata K. A mathematical model to predict protein wash out kinetics during whole-lung lavage in autoimmune pulmonary alveolar proteinosis. Am J Physiol Lung Cell Mol Physiol 2015; 308:L105-17. [PMID: 25398988 DOI: 10.1152/ajplung.00239.2014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Whole-lung lavage (WLL) remains the standard therapy for pulmonary alveolar proteinosis (PAP), a process in which accumulated surfactants are washed out of the lung with 0.5-2.0 l of saline aliquots for 10-30 wash cycles. The method has been established empirically. In contrast, the kinetics of protein transfer into the lavage fluid has not been fully evaluated either theoretically or practically. Seventeen lungs from patients with autoimmune PAP underwent WLL. We made accurate timetables for each stage of WLL, namely, instilling, retaining, draining, and preparing. Subsequently, we measured the volumes of both instilled saline and drained lavage fluid, as well as the concentrations of proteins in the drained lavage fluid. We also proposed a mathematical model of protein transfer into the lavage fluid in which time is a single variable as the protein moves in response to the simple diffusion. The measured concentrations of IgG, transferrin, albumin, and β2-microglobulin closely matched the corresponding theoretical values calculated through differential equations. Coefficients for transfer of β2-microglobulin from the blood to the lavage fluid were two orders of magnitude higher than those of IgG, transferrin, and albumin. Simulations using the mathematical model showed that the cumulative amount of eliminated protein was not affected by the duration of each cycle but dependent mostly on the total time of lavage and partially on the volume instilled. Although physicians have paid little attention to the transfer of substances from the lung to lavage fluid, WLL seems to be a procedure that follows a diffusion-based mathematical model.
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Affiliation(s)
- Keiichi Akasaka
- Bioscience Medical Research Center, Niigata University Medical and Dental Hospital, Niigata, Japan
| | - Takahiro Tanaka
- Bioscience Medical Research Center, Niigata University Medical and Dental Hospital, Niigata, Japan
| | - Takashi Maruyama
- Disaster Prevention Research Institute, Kyoto University, Kyoto, Japan
| | - Nobutaka Kitamura
- Bioscience Medical Research Center, Niigata University Medical and Dental Hospital, Niigata, Japan
| | - Atsushi Hashimoto
- Bioscience Medical Research Center, Niigata University Medical and Dental Hospital, Niigata, Japan
| | - Yuko Ito
- Bioscience Medical Research Center, Niigata University Medical and Dental Hospital, Niigata, Japan
| | - Hiroyoshi Watanabe
- Department of Respiratory Medicine, Dokkyo Medical University Koshigaya Hospital, Saitama, Japan
| | - Tomoshige Wakayama
- Department of Respiratory Medicine, Dokkyo Medical University Koshigaya Hospital, Saitama, Japan
| | - Takero Arai
- Department of Anesthesiology, Dokkyo Medical University Koshigaya Hospital, Saitama, Japan
| | - Masachika Hayashi
- Division of Respiratory Medicine, Niigata University Medical and Dental Hospital, Niigata, Japan
| | - Hiroshi Moriyama
- Division of Respiratory Medicine, Niigata University Medical and Dental Hospital, Niigata, Japan
| | - Kanji Uchida
- Department of Anesthesiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Shinya Ohkouchi
- Department of Respiratory Medicine, Tohoku University Graduate school of Medicine, Miyagi, Japan
| | - Ryushi Tazawa
- Bioscience Medical Research Center, Niigata University Medical and Dental Hospital, Niigata, Japan
| | - Toshinori Takada
- Uonuma Institute of Community Medicine, Niigata University Medical and Dental Hospital, Niigata, Japan
| | - Etsuro Yamaguchi
- Department of Respiratory and Allergy Medicine, Aichi Medical University, Aichi, Japan
| | - Toshio Ichiwata
- Department of Pulmonary Medicine, Tokyo Medical University Hachioji Medical Center, Tokyo, Japan
| | - Masaki Hirose
- Clinical Research Center, NHO Kinki-Chuo Chest Medical Center, Osaka, Japan; and
| | - Toru Arai
- Clinical Research Center, NHO Kinki-Chuo Chest Medical Center, Osaka, Japan; and
| | - Yoshikazu Inoue
- Clinical Research Center, NHO Kinki-Chuo Chest Medical Center, Osaka, Japan; and
| | - Hirosuke Kobayashi
- Graduate School of Medical Sciences, Kitasato University, Kanagawa, Japan
| | - Koh Nakata
- Bioscience Medical Research Center, Niigata University Medical and Dental Hospital, Niigata, Japan;
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Takano M, Kawami M, Aoki A, Yumoto R. Receptor-mediated endocytosis of macromolecules and strategy to enhance their transport in alveolar epithelial cells. Expert Opin Drug Deliv 2014; 12:813-25. [DOI: 10.1517/17425247.2015.992778] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Mechanisms of absorption and elimination of drugs administered by inhalation. Ther Deliv 2013; 4:1027-45. [PMID: 23919477 DOI: 10.4155/tde.13.67] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Pulmonary drug delivery is an effective route for local or systemic drug administration. However, compared with other routes of administration, there is a scarcity of information on how drugs are absorbed from the lung. The different cell composition lining the airways and alveoli makes this task extremely complicated. Lung cell lines and primary culture cells are useful in studying the absorption mechanisms. However, it is imperative that these cell cultures express essential features required to study these mechanisms such as intact tight junctions and transporters. In vivo, the drug has to face defensive physical and immunological barriers such as mucociliary clearance and alveolar macrophages. Knowledge of the physicochemical properties of the drug and aerosol formulation is required. All of these factors interact together leading to either successful drug deposition followed by absorption or drug elimination. These aspects concerning drug transport in the lung are addressed in this review.
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Liu X, Jin L, Upham JW, Roberts MS. The development of models for the evaluation of pulmonary drug disposition. Expert Opin Drug Metab Toxicol 2013; 9:487-505. [DOI: 10.1517/17425255.2013.754009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Evans SE, Kottom TJ, Pagano RE, Limper AH. Primary alveolar epithelial cell surface membrane microdomain function is required for Pneumocystis β-glucan-induced inflammatory responses. Innate Immun 2012; 18:709-16. [PMID: 22334619 DOI: 10.1177/1753425912436763] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Intense lung inflammation characterizes respiratory failure associated with Pneumocystis pneumonia. Our laboratory has previously demonstrated that alveolar epithelial cells (AECs) elaborate inflammatory cytokines and chemokines in response to the Pneumocystis carinii cell wall constituent β-(1→3)-glucan (PCBG), and that these responses require lactosylceramide, a prominent glycosphingolipid constituent of certain cell membrane microdomains. The relevance of membrane microdomains, also termed plasma membrane lipid rafts, in cell signaling and macromolecule handling has been increasingly recognized in many biologic systems, but their role in P. carinii-induced inflammation is unknown. To investigate the mechanisms of microdomain-dependent P. carinii-induced inflammation, we challenged primary rat AECs with PCBG with or without pre-incubation with inhibitors of microdomain function. Glycosphingolipid and cholesterol rich microdomain inhibition resulted in significant attenuation of P. carinii-induced expression of TNF-α and the rodent C-X-C chemokine MIP-2, as well as their known inflammatory secondary signaling pathways. We have previously shown that protein kinase C (PKC) is activated by PCBG challenge and herein show that PKC localizes to AEC microdomains. We also demonstrate by conventional microscopy, fluorescence microscopy, confocal microscopy and spectrophotofluorimetry that AECs internalize fluorescently-labeled PCBG by microdomain-mediated mechanisms, and that anti-microdomain pretreatments prevent internalization. Taken together, these data suggest an important role for AEC microdomain function in PCBG-induced inflammatory responses. This offers a potential novel target for therapeutics for a condition that continues to exert unacceptable morbidity and mortality among immunocompromised populations.
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Affiliation(s)
- Scott E Evans
- Thoracic Diseases Research Unit and the Division of Pulmonary Critical Care and Internal Medicine, Mayo Clinic and Foundation, MN 55905, USA
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Andrade F, Videira M, Ferreira D, Sarmento B. Nanocarriers for pulmonary administration of peptides and therapeutic proteins. Nanomedicine (Lond) 2011; 6:123-41. [DOI: 10.2217/nnm.10.143] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Peptides and therapeutic proteins have been the target of intense research and development in recent years by the pharmaceutical and biotechnology industry. Preferably, they are administered through the parenteral route, which is associated with reduced patient compliance. Formulations for noninvasive administration of peptides and therapeutic proteins are currently being developed. Among them, inhalation appears as a promising alternative for the administration of such products. Several formulations for pulmonary delivery are in various stages of development. Despite positive results, conventional formulations have some limitations such as reduced bioavailability and side effects. Nanocarriers may be an alternative way to overcome the problems of conventional formulations. Some nanocarrier-based formulations of peptides and therapeutic proteins are currently under development. The results obtained are promising, revealing the usefulness of these systems in the delivery of such drugs.
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Affiliation(s)
- Fernanda Andrade
- Department of Pharmaceutical Technology, Faculty of Pharmacy, University of Porto, Rua Aníbal Cunha 164 4050-047, Portugal
| | - Mafalda Videira
- iMed.UL – Research Institute for Medicines and Pharmaceutical Sciences, Faculty of Pharmacy, University of Lisbon, Portugal
| | - Domingos Ferreira
- Department of Pharmaceutical Technology, Faculty of Pharmacy, University of Porto, Rua Aníbal Cunha 164 4050-047, Portugal
| | - Bruno Sarmento
- Centro de Investigação em Ciências da Saúde (CICS), Department of Pharmaceutical Sciences, Instituto Superior de Ciências da Saúde – Norte, Gandra, Portugal
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Fernandes CA, Vanbever R. Preclinical models for pulmonary drug delivery. Expert Opin Drug Deliv 2009; 6:1231-45. [DOI: 10.1517/17425240903241788] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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van den Bogaard EHJ, Dailey LA, Thorley AJ, Tetley TD, Forbes B. Inflammatory Response and Barrier Properties of a New Alveolar Type 1-Like Cell Line (TT1). Pharm Res 2009; 26:1172-80. [DOI: 10.1007/s11095-009-9838-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2008] [Accepted: 01/20/2009] [Indexed: 12/15/2022]
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Patel LN, Uchiyama T, Kim KJ, Borok Z, Crandall ED, Shen WC, Lee VHL. Molecular and Functional Expression of Multidrug Resistance-Associated Protein-1 in Primary Cultured Rat Alveolar Epithelial Cells. J Pharm Sci 2008; 97:2340-9. [PMID: 17854063 DOI: 10.1002/jps.21134] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Multidrug resistance-associated protein-1 (MRP1) is an integral membrane efflux protein that is implicated in multidrug resistance in cancer, but it is also expressed in normal tissues. The objective of this study was to determine the expression, localization and functional activity of MRP1 in primary cultured rat alveolar epithelial cells of types I- and II cell-like phenotypes. RT-PCR data showed 550-base pair fragments in both types I- and II-like pneumocytes that exhibited 99% identity to the rat MRP1 isoform. Significant levels of MRP1 protein were detected by western analysis of immunoprecipitates in both cell types, and immunofluorescence combined with confocal laser scanning microscopy indicated basolateral localization of MRP1. Indomethacin (0-100 microM) increased fluorescein basolateral-to-apical transport, and accumulation of fluorescein in the cells, in a dose-dependent manner. We therefore conclude that the MRP1 gene is present in primary cultured rat epithelial cells of both types I- and II-like phenotypes and its corresponding protein (MRP1) is localized in the basolateral membrane of these cells. Primary cultured monolayers of rat type II-like pneumocytes appear to be a useful tool for screening MRP1 substrates designed for pulmonary delivery/targeting.
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Affiliation(s)
- Leena N Patel
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, California 90089-9121, USA
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Ikehata M, Yumoto R, Nakamura K, Nagai J, Takano M. Comparison of Albumin Uptake in Rat Alveolar Type II and Type I-like Epithelial Cells in Primary Culture. Pharm Res 2007; 25:913-22. [PMID: 17851738 DOI: 10.1007/s11095-007-9426-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Accepted: 07/31/2007] [Indexed: 10/22/2022]
Abstract
PURPOSE To elucidate and compare the activity and mechanism of albumin uptake in primary cultured alveolar type II and type I-like epithelial cells. MATERIALS AND METHODS Type II epithelial cells isolated from rat lungs were cultured for 2 days at 5 x 10(6) cells/35-mm dish or for 6 days at 2 x 10(6) cells/35-mm dish. The mRNA expression of marker genes and FITC-albumin uptake were examined. RESULTS The cells cultured for 2 days exhibited cuboidal type II epithelial morphology with lamellar bodies inside the cells, while the cells cultured for 6 days exhibited squamous type I epithelial morphology. These morphological characteristics were consistent with the changes in mRNA expression pattern of marker genes. FITC-albumin uptake in both cells was temperature-dependent and was inhibited by metabolic inhibitors and bafilomycin A1. The rate of uptake was much higher in type II cells than type I-like cells. In both cells, FITC-albumin uptake was inhibited by clathrin mediated-endocytosis inhibitors, but not by caveolae mediated-endocytosis inhibitors. CONCLUSIONS These findings indicate that albumin in alveolar lining fluid is internalized into type II and type I epithelial cells via clathrin-mediated endocytosis, and the rate of albumin uptake is higher in type II cells than type I cells.
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Affiliation(s)
- Mika Ikehata
- Department of Pharmaceutics and Therapeutics, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8553, Japan
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12
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Bahhady R, Kim KJ, Borok Z, Crandall ED, Shen WC. Enhancement of insulin transport across primary rat alveolar epithelial cell monolayers by endogenous cellular factor(s). Pharm Res 2007; 24:1713-9. [PMID: 17443400 DOI: 10.1007/s11095-007-9301-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2006] [Accepted: 03/20/2007] [Indexed: 11/24/2022]
Abstract
PURPOSE To characterize factor(s) contained in apical medium of primary cultured rat alveolar epithelial type II cell-like monolayers (RAECM-II) that enhance insulin absorption across alveolar epithelial cells. MATERIALS AND METHODS Primary rat alveolar epithelial cell monolayers cultured on Transwells in the presence and absence of 10 ng/ml keratinocyte growth factor for 6 days were dosed from the apical compartment with radiolabeled insulin in: newborn bovine serum-containing medium (SM), conditioned medium from apical compartment of rat alveolar epithelial type I cell-like monolayers (RAECM-I) (CMI), or conditioned medium from apical compartment of RAECM-II (CMII). At the end of 2 h incubation, basolateral medium was collected and amounts of transported radiolabeled insulin were determined using a gamma counter. In order to determine the molecular size range of the enhancing factor(s), CMII was centrifuged in 50 kDa molecular weight cut-off Centricon tubes, and both retentate and filtrate were used as separate dosing solutions. Heat denaturation and ammonium sulphate precipitation were used to determine if the involved factor(s) represent proteins or other smaller soluble factors. Transalveolar transport rates of a paracellular marker, (14)C-mannitol, and fluid-phase marker, horseradish peroxidase, were determined in the presence and absence of the factors. Effects of temperature (4, 16 and 37 degrees C) on radiolabeled insulin fluxes were also measured. RESULTS Conditioned medium obtained from the apical compartment of RAECM-II, CMII, increased transport of insulin across the monolayers when compared to SM or CMI. The enhancing effect of CMII was retained in the precipitate following ammonium sulfate treatment and in the retentate after Centricon filtration. The enhancing effect of CMII was significantly decreased when heated at 80 degrees C for 15 min. CMII did not affect the transport of (14)C-mannitol or HRP, while its effect on insulin transport was decreased by 87% when temperature was lowered to 4 degrees C from 37 degrees C. CONCLUSIONS Conditioned medium from type II cell-like monolayer cultures appears to contain protein factor(s) which seem to be involved in facilitating active transcellular transport of insulin across primary cultured RAECM-II.
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Affiliation(s)
- Rana Bahhady
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, California 90089-9121, USA
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Hussain A, Ahsan F. Indication of transcytotic movement of insulin across human bronchial epithelial cells. J Drug Target 2006; 14:181-90. [PMID: 16777678 DOI: 10.1080/10611860600649633] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
This study was performed to evaluate insulin permeability across human bronchial epithelial cell lines and investigate if insulin is transported via the paracellular or transcellular pathway. The movement of insulin across two bronchial epithelial cells, 16HBE14o- and Calu-3, was studied in the presence or absence of octylmaltoside. Mannitol and propanolol have been used as paracellular and transcellular marker, respectively, and transepithelial electrical resistance (TEER) was determined to investigate the tight junctional integrity of the monolayers. The possible endocytotic mechanism of insulin across these two cell lines was studied by confocal laser scanning microscopy after incubating the cells with fluorescent-labeled insulin. The TEER values for both cell monolayers were >400 Omega cm2 at confluency. There was a decrease in the TEER values when octylmaltoside was added to the apical side of transwells. Similarly, the apparent permeability coefficient (P(app)) values of insulin, mannitol and propanolol, showed an increase with the rise in the concentration of octylmaltoside. In the absence of octylmaltoside, the P(app) values for insulin and the markers were in the following order: propanolol > mannitol > insulin. Confocal microscopic studies revealed that the uptake of insulin by the bronchial epithelial cells perhaps occurs via translocation across the cell. The data presented in this study demonstrate that insulin perhaps moves across the bronchial cells via both paracellular and transcellular pathways.
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Affiliation(s)
- Alamdar Hussain
- Department of Pharmaceutical Sciences, School of Pharmacy, Health Sciences Center, Texas Tech University, 1300 Coulter Drive, Amarillo, TX 79106, USA
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Steimer A, Laue M, Franke H, Haltner-Ukomado E, Lehr CM. Porcine alveolar epithelial cells in primary culture: morphological, bioelectrical and immunocytochemical characterization. Pharm Res 2006; 23:2078-93. [PMID: 16952001 DOI: 10.1007/s11095-006-9057-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2005] [Accepted: 05/08/2006] [Indexed: 10/24/2022]
Abstract
PURPOSE The purpose of this study was to establish a primary culture of porcine lung epithelial cells as an alternative to the currently existing cell cultures from other species, such as e.g., rat or human. Primary porcine lung epithelial cells were isolated, cultivated and analyzed at distinct time points after isolation. MATERIALS AND METHODS The main part of the work focused on the morphology of the cells and the detection of alveolar epithelial cell markers by using electron microscopy, immunofluorescence microscopy and immunoblotting. Regarding a later use for in vitro pulmonary drug absorption studies the barrier properties of the cell monolayer were evaluated by monitoring bioelectrical parameters and by marker transport. RESULTS Epithelial cells isolated from porcine lung grew to confluent monolayers with typical intercellular junctions within a few days. Maximum transepithelial resistance of about 2,000 Omega cm2 was achieved and demonstrated the formation of a tight epithelial barrier. Permeability data of sodium fluorescein recommended a minimal transepithelial resistance of 600 Omega cm2 for transport studies. The cell population changed from a heterogeneous morphology and marker distribution (caveolin-1, pro-SP-C, surface sugars) towards a monolayer consisting of two cell types resembling type I and type II pneumocytes. CONCLUSIONS The porcine alveolar epithelial primary cell culture holds promise for drug transport studies, because it shares major hallmarks of the mammalian alveolar epithelium and it is easily available and scaled up for drug screening.
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Affiliation(s)
- Anne Steimer
- Across Barriers GmbH, Department R&D Cell & Tissue based Systems, Science Park Saar, Saarbrücken, Germany
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Bur M, Huwer H, Lehr CM, Hagen N, Guldbrandt M, Kim KJ, Ehrhardt C. Assessment of transport rates of proteins and peptides across primary human alveolar epithelial cell monolayers. Eur J Pharm Sci 2006; 28:196-203. [PMID: 16533597 DOI: 10.1016/j.ejps.2006.02.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2005] [Revised: 01/30/2006] [Accepted: 02/04/2006] [Indexed: 11/21/2022]
Abstract
In this study, we investigated bi-directional fluxes (i.e., in absorptive and secretive directions) of human serum proteins [albumin (HSA), transferrin (TF), and immunoglobulin G (IgG)] and peptides/proteins of potential therapeutic relevance [insulin (INS), glucagon-like peptide-1 (GLP-1), growth hormone (GH), and parathyroid hormone (PTH)] across tight monolayers of human alveolar epithelial cells (hAEpC) in primary culture. Apparent permeability coefficients (P(app); x10(-7)cm/s, mean+/-S.D.) for GLP-1 (6.13+/-0.87 (absorptive) versus 1.91+/-0.51 (secretive)), HSA (2.45+/-1.02 versus 0.21+/-0.31), TF (0.88+/-0.15 versus 0.30+/-0.03), and IgG (0.36+/-0.22 versus 0.15+/-0.16) were all strongly direction-dependent, i.e., net absorptive, while PTH (2.20+/-0.30 versus 1.80+/-0.77), GH (8.33+/-1.24 versus 9.02+/-3.43), and INS (0.77+/-0.15 versus 0.72+/-0.36) showed no directionality. Trichloroacetic acid precipitation analysis of tested molecules collected from donor and receiver fluids exhibited very little degradation. This is the first study on permeability data for a range of peptides and proteins across an in vitro model of the human alveolar epithelial barrier. These data indicate that there is no apparent size-dependent transport conforming to passive restricted diffusion for the tested substances across human alveolar barrier, in part confirming net absorptive transcytosis. The obtained data differ significantly from previously published reports utilising monolayers from different species. It can be concluded that the use of homologous tissue should be preferred to avoid species differences.
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Affiliation(s)
- Michael Bur
- Saarland University, Biopharmaceutics and Pharmaceutical Technology, 66123 Saarbrücken, Germany
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Cavanaugh KJ, Cohen TS, Margulies SS. Stretch increases alveolar epithelial permeability to uncharged micromolecules. Am J Physiol Cell Physiol 2005; 290:C1179-88. [PMID: 16282193 PMCID: PMC2980812 DOI: 10.1152/ajpcell.00355.2004] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
We measured stretch-induced changes in transepithelial permeability in vitro to uncharged tracers 1.5-5.5 A in radius to identify a critical stretch threshold associated with failure of the alveolar epithelial transport barrier. Cultured alveolar epithelial cells were subjected to a uniform cyclic (0.25 Hz) biaxial 12, 25, or 37% change in surface area (DeltaSA) for 1 h. Additional cells served as unstretched controls. Only 37% DeltaSA (100% total lung capacity) produced a significant increase in transepithelial tracer permeability, with the largest increases for bigger tracers. Using the permeability data, we modeled the epithelial permeability in each group as a population of small pores punctuated by occasional large pores. After 37% DeltaSA, increases in paracellular transport were correlated with increases in the radii of both pore populations. Inhibition of protein kinase C and tyrosine kinase activity during stretch did not affect the permeability of stretched cells. In contrast, chelating intracellular calcium and/or stabilizing F-actin during 37% DeltaSA stretch reduced but did not eliminate the stretch-induced increase in paracellular permeability. These results provide the first in vitro evidence that large magnitudes of stretch increase paracellular transport of micromolecules across the alveolar epithelium, partially mediated by intracellular signaling pathways. Our monolayer data are supported by whole lung permeability results, which also show an increase in alveolar permeability at high inflation volumes (20 ml/kg) at the same rate for both healthy and septic lungs.
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Affiliation(s)
- Kenneth J Cavanaugh
- Department of Bioengineering, 3320 Smith Walk, University of Pennsylvania, Philadelphia, 19104-6392, USA
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von Wichert P, Seifart C. The Lung, an Organ for Absorption? Respiration 2005; 72:552-8. [PMID: 16210898 DOI: 10.1159/000087685] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2004] [Accepted: 02/02/2005] [Indexed: 11/19/2022] Open
Abstract
This review summarizes information concerning the mechanisms of absorption of substances across the pulmonary epithelium. Inhalation is now increasingly used as a route of administration, although the scientific understanding of these mechanisms is rather limited. The aim of this study is to draw attention to these questions.
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Affiliation(s)
- Peter von Wichert
- Department of Medicine, Division of Respiratory and Intensive Care Medicine, Philipps University of Marburg, Marburg, Germany.
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Steimer A, Haltner E, Lehr CM. Cell culture models of the respiratory tract relevant to pulmonary drug delivery. ACTA ACUST UNITED AC 2005; 18:137-82. [PMID: 15966771 DOI: 10.1089/jam.2005.18.137] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The respiratory tract holds promise as an alternative site of drug delivery due to fast absorption and rapid onset of drug action, with avoidance of hepatic and intestinal first-pass metabolism as an additional benefit compared to oral drug delivery. At present, the pharmaceutical industry increasingly relies on appropriate in vitro models for the faster evaluation of drug absorption and metabolism as an alternative to animal testing. This article reviews the various existing cell culture systems that may be applied as in vitro models of the human air-blood barrier, for instance, in order to enable the screening of large numbers of new drug candidates at low cost with high reliability and within a short time span. Apart from such screening, cell culture-based in vitro systems may also contribute to improve our understanding of the mechanisms of drug transport across such epithelial tissues, and the mechanisms of action how advanced drug carriers, such as nanoparticles or liposomes, can help to overcome these barriers. After all, the increasing use and acceptance of such in vitro models may lead to a significant acceleration of the drug development process by facilitating the progress into clinical studies and product registration.
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Affiliation(s)
- A Steimer
- Across Barriers GmbH, Department R&D Cell & Tissue Based Systems, Science Park Saar, Saarbrücken, Germany
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Forbes B, Ehrhardt C. Human respiratory epithelial cell culture for drug delivery applications. Eur J Pharm Biopharm 2005; 60:193-205. [PMID: 15939233 DOI: 10.1016/j.ejpb.2005.02.010] [Citation(s) in RCA: 228] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2004] [Revised: 02/01/2005] [Accepted: 02/02/2005] [Indexed: 11/24/2022]
Abstract
Recent developments in delivering drugs to the lung are driving the need for in vitro methods to evaluate the fate of inhaled medicines. Constraints on experimentation using animals have promoted the use of human respiratory epithelial cell cultures to model the absorption barrier of the lung; with two airway cell lines, 16HBE14o- and Calu-3, and primary cultured human alveolar type I-like cells (hAEpC) gaining prominence. These in vitro models develop permeability properties which are comparable to those reported for native lung epithelia. This is in contrast to the high permeability of the A549 human alveolar cell line, which is unsuitable for use in drug permeability experiments. Tabulation of apparent permeability coefficients (Papp) of compounds measured in 'absorptive' and 'secretory' directions reveals that fewer compounds (< 15) have been evaluated in 16HBE14o- cells and hAEpC compared to Calu-3 cells (> 50). Vectorial (asymmetric) transport of compounds is reported in the three cell types with P-glycoprotein, the most studied transport mechanism, being reported in all. Progress is being made towards in vitro-in vivo-correlation for pulmonary absorption and in the use of cultured respiratory cells to evaluate drug metabolism, toxicity and targeting strategies. In summary, methods for the culture of human respiratory epithelial cell layers have been established and data regarding their permeability characteristics and suitability to model the lung is becoming available. Discerning the circumstances under which the use of human respiratory cell models will be essential, or offers advantages over non-organ, non-species specific cell models, is the next challenge.
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Affiliation(s)
- Ben Forbes
- Pharmaceutical Sciences Research Division, King's College London, London, UK.
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20
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Cooney D, Kazantseva M, Hickey AJ. Development of a size-dependent aerosol deposition model utilising human airway epithelial cells for evaluating aerosol drug delivery. Altern Lab Anim 2005; 32:581-90. [PMID: 15757496 DOI: 10.1177/026119290403200609] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Aerosol delivery to the airways of the human respiratory tract, followed by absorption, constitutes an alternative route of administration for compounds unsuitable for delivery by conventional oral and parenteral routes. The target for aerosol drug delivery is the airways epithelium, i.e. tracheal, bronchial, bronchiolar and alveolar cells, which become the site of drug deposition. These epithelial layers also serve as a barrier to the penetration of inhaled material. An in vitro model for aerosol deposition and transport across epithelia in the human airways may be a good predictor of in vivo disposition. The present preliminary studies begin an investigation that blends the dynamics of aerosol delivery and the basis of an in vitro simulated lung model to evaluate the transport properties of a series of molecular weight marker compounds across human-derived bronchiolar epithelial cell monolayers. An Andersen viable cascade impactor was used as a delivery apparatus for the deposition of size-segregated particles onto monolayers of small airway epithelial cells and Calu-3 cells. It was shown that these cell layers can withstand placement in the impactor, and that permeability can be tested subsequent to removal from the impactor.
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Affiliation(s)
- Daniel Cooney
- Department of Biomedical Engineering, University of North Carolina, Chapel Hill, NC 27599-7360, USA
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Kim KJ, Fandy TE, Lee VHL, Ann DK, Borok Z, Crandall ED. Net absorption of IgG via FcRn-mediated transcytosis across rat alveolar epithelial cell monolayers. Am J Physiol Lung Cell Mol Physiol 2004; 287:L616-22. [PMID: 15169676 DOI: 10.1152/ajplung.00121.2004] [Citation(s) in RCA: 53] [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
We characterized immunoglobulin G (IgG) transport across rat alveolar epithelial cell monolayers cultured on permeable supports. Unidirectional fluxes of biotin-labeled rat IgG (biot-rIgG) were measured in the apical-to-basolateral ( ab) and opposite ( ba) directions as functions of [rIgG] in upstream fluids at 37 and 4°C. We explored specificity of IgG transport by measuring fluxes in the presence of excess Fc, Fab, F(ab′)2, or chicken Ig (IgY). Expression of the IgG receptor FcRn and the effects of dexamethasone on FcRn expression and biot-rIgG fluxes were determined. Results show that ab flux of biot-rIgG is about fivefold greater than ba flux at an upstream concentration of 25 nM biot-rIgG at 37°C. Both ab and ba fluxes of rIgG saturate, resulting in net absorption with half-maximal concentration and maximal flow of 7.1 nM and 1.3 fmol·cm−2·h−1. At 4°C, both ab and ba fluxes significantly decrease, nearly collapsing net absorption. The presence of excess unlabeled Fc [but not Fab, F(ab′)2, or IgY] significantly reduces biot-rIgG fluxes. RT-PCR demonstrates expression of α- and β-subunits of rat FcRn. Northern analysis further confirms the presence of α-subunit of rat FcRn mRNA of ∼1.6 kb. Dexamethasone exposure for 72 h decreases the steady-state level of mRNA for rat FcRn α-subunit and the ab (but not ba) flux of biot-rIgG. These data indicate that IgG transport across alveolar epithelium takes place via regulable FcRn-mediated transcytosis, which may play an important role in alveolar homeostasis in health and disease.
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Affiliation(s)
- Kwang-Jin Kim
- Dept. of Medicine, USC Keck School of Medicine, 2011 Zonal Ave., Los Angeles, CA 90033, USA.
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22
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Mager S, Sloan J. Possible role of amino acids, peptides, and sugar transporter in protein removal and innate lung defense. Eur J Pharmacol 2004; 479:263-7. [PMID: 14612156 DOI: 10.1016/j.ejphar.2003.08.075] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This review presents the hypothesis that removal of polypeptides and glycoproteins from the alveolar space and airways is mediated in part by enzymatic degradation, followed by transporter mediated transepithelial transport of amino acids, peptides and sugar residues. Furthermore, the activity of these transporters ensures low availability of nutrients, and decrease bacterial growth. Thus, airway epithelial transporters for sugar, amino acids, peptides and other nutrients can contribute to the innate lung defense.
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Affiliation(s)
- Sela Mager
- Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, 630 Medical Biomolecular Research Building, Campus Box 7545, Chapel Hill, NC 27599-7545, USA.
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Hastings RH, Folkesson HG, Matthay MA. Mechanisms of alveolar protein clearance in the intact lung. Am J Physiol Lung Cell Mol Physiol 2004; 286:L679-89. [PMID: 15003932 DOI: 10.1152/ajplung.00205.2003] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Transport of protein across the alveolar epithelial barrier is a critical process in recovery from pulmonary edema and is also important in maintaining the alveolar milieu in the normal healthy lung. Various mechanisms have been proposed for clearing alveolar protein, including transport by the mucociliary escalator, intra-alveolar degradation, or phagocytosis by macrophages. However, the most likely processes are endocytosis across the alveolar epithelium, known as transcytosis, or paracellular diffusion through the epithelial barrier. This article focuses on protein transport studies that evaluate these two potential mechanisms in whole lung or animal preparations. When protein concentrations in the air spaces are low, e.g., albumin concentrations <0.5 g/100 ml, protein transport demonstrates saturation kinetics, temperature dependence indicating high energy requirements, and sensitivity to pharmacological agents that affect endocytosis. At higher concentrations, the protein clearance rate is proportional to protein concentration without signs of saturation, inversely related to protein size, and insensitive to endocytosis inhibition. Temperature dependence suggests a passive process. Based on these findings, alveolar albumin clearance occurs by receptor-mediated transcytosis at low protein concentrations but proceeds by passive paracellular mechanisms at higher concentrations. Because protein concentrations in pulmonary edema fluid are high, albumin concentrations of 5 g/100 ml or more, clearance of alveolar protein occurs by paracellular pathways in the setting of pulmonary edema. Transcytosis may be important in regulating the alveolar milieu under nonpathological circumstances. Alveolar degradation may become important in long-term protein clearance, clearance of insoluble proteins, or under pathological conditions such as immune reactions or acute lung injury.
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Affiliation(s)
- Randolph H Hastings
- VA Medical Center (125 3350 La Jolla Village D., San Diego, CA 92161-5085, USA.
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24
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Lombry C, Edwards DA, Préat V, Vanbever R. Alveolar macrophages are a primary barrier to pulmonary absorption of macromolecules. Am J Physiol Lung Cell Mol Physiol 2003; 286:L1002-8. [PMID: 14695119 DOI: 10.1152/ajplung.00260.2003] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We demonstrate that a primary source of elimination of inhaled macromolecules after delivery to the lungs and before absorption into the systemic circulation owes to clearance by alveolar macrophages (AM). Depletion of AM by liposome-encapsulated dichloromethylene diphosphonate is shown to cause severalfold enhancement in systemic absorption of IgG and human chorionic gonadotropin after intratracheal instillation in rats. Lowering the doses of IgG delivered to the lungs alleviates local degradation and results in a dramatic increase in systemic absorption of the protein as well. Chemical and physical means of minimizing uptake of macromolecules by AM are proposed as novel methods for enhancing protein absorption from the lungs. Such strategies may have important ramifications on the development of inhalation as an attractive mode of administration of therapeutic proteins to the bloodstream.
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Affiliation(s)
- Catherine Lombry
- Dept. of Pharmaceutical Technology, School of Pharmacy, Université Catholique de Louvain, Ave. E. Mounier 73 UCL 73.20, 1200 Brussels, Belgium
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25
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Gumbleton M, Hollins AJ, Omidi Y, Campbell L, Taylor G. Targeting caveolae for vesicular drug transport. J Control Release 2003; 87:139-51. [PMID: 12618030 DOI: 10.1016/s0168-3659(02)00358-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Caveolae are morphologically evident as omega-shaped invaginations of the plasma membrane with a diameter of 50-100 nm. They may also exist in a variety of other forms including flattened domains indistinguishable from the plasma membrane itself. At least in some cell types caveolae undertake transport functions including that of the endocytic and transcytotic movement of macromolecules, and indeed microbes and microbial toxins. Opportunities exist for basic and applied investigators working within the pharmaceutical sciences to exploit caveolae membrane interactions with the aim to develop of novel cellular or transcellular drug delivery strategies. This overview article will provide: pertinent information on the biology of the caveolae membrane system; review the various caveolae isolation methods; highlight some of the literature evidence showing that caveolae are functional with regard to macromolecule transport; discuss the role that caveolae could fulfill in the pulmonary absorption of therapeutic proteins from alveolar airspace to capillary blood following inhalational drug delivery, and finally review some very recent work showing proof-of-principle that caveolae domains can be targeted in a tissue-specific manner with highly selective ligands.
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Affiliation(s)
- Mark Gumbleton
- Pharmaceutical Cell Biology, Welsh School of Pharmacy, Cardiff University, Redwood Building, King Edward VII Avenue, Cardiff CF10 3XF, UK.
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26
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Abstract
Alveolar lining fluid normally contains proteins of important physiological, antioxidant, and mucosal defense functions [such as albumin, immunoglobulin G (IgG), secretory IgA, transferrin, and ceruloplasmin]. Because concentrations of plasma proteins in alveolar fluid can increase in injured lungs (such as with permeability edema and inflammation), understanding how alveolar epithelium handles protein transport is needed to develop therapeutic measures to restore alveolar homeostasis. This review provides an update on recent findings on protein transport across the alveolar epithelial barrier. The use of primary cultured rat alveolar epithelial cell monolayers (that exhibit phenotypic and morphological traits of in vivo alveolar epithelial type I cells) has shown that albumin and IgG are absorbed via saturable processes at rates greater than those predicted by passive diffusional mechanisms. In contrast, secretory component, the extracellular portion of the polymeric immunoglobulin receptor, is secreted into alveolar fluid. Transcytosis involving caveolae and clathrin-coated pits is likely the main route of alveolar epithelial protein transport, although relative contributions of these internalization steps to overall protein handling of alveolar epithelium remain to be determined. The specific pathways and regulatory mechanisms responsible for translocation of proteins across lung alveolar epithelium and regulation of the cognate receptors (e.g., 60-kDa albumin binding protein and IgG binding FcRn) expressed in alveolar epithelium need to be elucidated.
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Affiliation(s)
- Kwang-Jin Kim
- Department of Medicine, Physiology, and Biophysics, Will Rogers Institute Pulmonary Research Center, Keck School of Medicine, University of Southern California, 2011 Zonal Avenue, Los Angeles, CA 90033, USA.
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27
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Sloan JL, Grubb BR, Mager S. Expression of the amino acid transporter ATB 0+ in lung: possible role in luminal protein removal. Am J Physiol Lung Cell Mol Physiol 2003; 284:L39-49. [PMID: 12388375 DOI: 10.1152/ajplung.00164.2002] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Normal lung function requires transepithelial clearance of luminal proteins; however, little is known about the molecular mechanisms of protein transport. Protein degradation followed by transport of peptides and amino acids may play an important role in this process. We previously cloned and functionally characterized the neutral and cationic amino acid transporter ATB(0+) and showed expression in the lung by mRNA analysis. In this study, the tissue distribution, subcellular localization, and function of the transporter in native tissue were investigated. Western blots showed expression of the ATB(0+) protein in mouse lung, stomach, colon, testis, blastocysts, and human lung. Immunohistochemistry revealed that ATB(0+) is predominantly expressed on the apical membrane of ciliated epithelial cells throughout mouse airways from trachea to bronchioles and in alveolar type I cells. Electrical measurements from mouse trachea preparations showed Na(+)- and Cl(-)-dependent, amino acid-induced short-circuit current consistent with the properties of ATB(0+). We hypothesize that, by removing amino acids from the airway lumen, the transporter contributes to protein clearance and, by maintaining a low nutrient environment, plays a role in lung defense.
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Affiliation(s)
- Jennifer L Sloan
- Department of Cell and Molecular Physiology and the Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, NC 27599, USA
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28
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Matthay MA, Folkesson HG, Clerici C. Lung epithelial fluid transport and the resolution of pulmonary edema. Physiol Rev 2002; 82:569-600. [PMID: 12087129 DOI: 10.1152/physrev.00003.2002] [Citation(s) in RCA: 490] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The discovery of mechanisms that regulate salt and water transport by the alveolar and distal airway epithelium of the lung has generated new insights into the regulation of lung fluid balance under both normal and pathological conditions. There is convincing evidence that active sodium and chloride transporters are expressed in the distal lung epithelium and are responsible for the ability of the lung to remove alveolar fluid at the time of birth as well as in the mature lung when pathological conditions lead to the development of pulmonary edema. Currently, the best described molecular transporters are the epithelial sodium channel, the cystic fibrosis transmembrane conductance regulator, Na+-K+-ATPase, and several aquaporin water channels. Both catecholamine-dependent and -independent mechanisms can upregulate isosmolar fluid transport across the distal lung epithelium. Experimental and clinical studies have made it possible to examine the role of these transporters in the resolution of pulmonary edema.
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Affiliation(s)
- Michael A Matthay
- Cardiovascular Research Institute and Department of Medicine, University of California, San Francisco, California 94143-0624, USA.
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29
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Gumbleton M. Caveolae as potential macromolecule trafficking compartments within alveolar epithelium. Adv Drug Deliv Rev 2001; 49:281-300. [PMID: 11551400 DOI: 10.1016/s0169-409x(01)00142-9] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
With inhalational delivery the alveolar epithelium appears to be the appropriate lung surface to target for the systemic delivery of macromolecules, such as therapeutic proteins. The existence of a high numerical density of smooth-coated or non-coated plasma membrane vesicles or invaginations within the alveolar epithelial type I cell has long been recognised. The putative function of these vesicles in macromolecule transport remains the focus of research in both pulmonary physiology and pharmaceutical science disciplines. These vesicles, or subpopulations thereof, have been shown to biochemically possess caveolin, a marker protein for caveolae. This review considers the morphometric and biochemical studies that have progressed the characterisation of the vesicle populations within alveolar type I epithelium. Parallel research findings from the endothelial literature have been considered to contrast the state of progress of caveolae research in alveolar epithelium. Speculation is made on a model of caveolae vesicle-mediated transport that may satisfy some of the pulmonary pharmacokinetic data that has been generated for macromolecule absorption. The putative transport function of caveolae within alveolar epithelium is reviewed with respect to in-situ tracer studies conducted within the alveolar airspace. Finally, the functional characterisation of in-vitro alveolar epithelial cell cultures is considered with respect to the role of caveolae in macromolecule transport. A potentially significant role for alveolar caveolae in mediating the alveolar airspace to blood transport of macromolecules cannot be dismissed. Considerable research is required, however, to address this issue in a quantitative manner. A better understanding of the membrane dynamics of caveolae in alveolar epithelium will help resolve the function of these vesicular compartments and may lead to the development of more specific drug targeting approaches for promoting pulmonary drug delivery.
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Affiliation(s)
- M Gumbleton
- Pharmaceutical Cell Biology, Welsh School of Pharmacy, Redwood Building, Cardiff University, Cardiff CF10 3XF, UK.
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30
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Crandall ED, Matthay MA. Alveolar epithelial transport. Basic science to clinical medicine. Am J Respir Crit Care Med 2001; 163:1021-9. [PMID: 11282783 DOI: 10.1164/ajrccm.163.4.2006116] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Affiliation(s)
- E D Crandall
- Department of Medicine, University of Southern California, Los Angeles, USA
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