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Kronstadt SM, Pottash AE, Levy D, Wang S, Chao W, Jay SM. Therapeutic Potential of Extracellular Vesicles for Sepsis Treatment. ADVANCED THERAPEUTICS 2021; 4:2000259. [PMID: 34423113 PMCID: PMC8378673 DOI: 10.1002/adtp.202000259] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Indexed: 12/14/2022]
Abstract
Sepsis is a deadly condition lacking a specific treatment despite decades of research. This has prompted the exploration of new approaches, with extracellular vesicles (EVs) emerging as a focal area. EVs are nanosized, cell-derived particles that transport bioactive components (i.e., proteins, DNA, and RNA) between cells, enabling both normal physiological functions and disease progression depending on context. In particular, EVs have been identified as critical mediators of sepsis pathophysiology. However, EVs are also thought to constitute the biologically active component of cell-based therapies and have demonstrated anti-inflammatory, anti-apoptotic, and immunomodulatory effects in sepsis models. The dual nature of EVs in sepsis is explored here, discussing their endogenous roles and highlighting their therapeutic properties and potential. Related to the latter component, prior studies involving EVs from mesenchymal stem/stromal cells (MSCs) and other sources are discussed and emerging producer cells that could play important roles in future EV-based sepsis therapies are identified. Further, how methodologies could impact therapeutic development toward sepsis treatment to enhance and control EV potency is described.
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Affiliation(s)
- Stephanie M Kronstadt
- Fischell Department of Bioengineering, University of Maryland, 3102 A. James Clark Hall, College Park, MD 20742, USA
| | - Alex E Pottash
- Fischell Department of Bioengineering, University of Maryland, 3102 A. James Clark Hall, College Park, MD 20742, USA
| | - Daniel Levy
- Fischell Department of Bioengineering, University of Maryland, 3102 A. James Clark Hall, College Park, MD 20742, USA
| | - Sheng Wang
- Translational Research Program, Department of Anesthesiology and Center for Shock Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Wei Chao
- Translational Research Program, Department of Anesthesiology and Center for Shock Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Steven M Jay
- Fischell Department of Bioengineering and Program in Molecular and, Cell Biology, University of Maryland, 3102 A. James Clark Hall, College Park, MD 20742, USA
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Discovery of An Orally Effective Factor IX-Transferrin Fusion Protein for Hemophilia B. Int J Mol Sci 2019; 21:ijms21010021. [PMID: 31861459 PMCID: PMC6981973 DOI: 10.3390/ijms21010021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 12/13/2019] [Accepted: 12/16/2019] [Indexed: 01/12/2023] Open
Abstract
Hemophilia B is a severe blood clotting disorder caused by the deficiency of factor IX (FIX). FIX is not bioavailable when given orally due to poor stability and permeability in the gastrointestinal tract. The feasibility of fusing FIX with transferrin (Tf) to enhance the oral bioavailability of FIX is explored. Seven recombinant fusion proteins (rFIX-Tf) with different linkers were constructed and expressed in HEK293 cells and characterized by in vitro transcytosis and transferrin receptor (TfR) binding assay in Caco-2 cells and a one-stage clotting assay. The in vivo efficacy study was performed using a tail-bleeding model in hemophilia B mice. Fusion proteins rFIX-Tf/G2 and rFIX-Tf/SVSQ were most permeable and showed a specific binding ability to TfR in Caco-2 cells. Both proteins retained FIX activity in clotting generation. The in vivo efficacy study showed that both proteins by intravenous injection significantly reduced blood loss. Most significantly, rFIX-Tf/G2 demonstrated anti-bleeding activity when administered orally. Our results showed that the fusion protein technique with Tf could be potentially used for oral delivery of FIX and the linker between FIX and Tf in the fusion protein is crucial. rFIX-Tf/G2 appears to be the most promising fusion protein as potential oral therapeutics for hemophilia B.
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Gukasyan HJ, Uchiyama T, Kim KJ, Ehrhardt C, Wu SK, Borok Z, Crandall ED, Lee VHL. Oligopeptide Transport in Rat Lung Alveolar Epithelial Cells is Mediated by Pept2. Pharm Res 2017; 34:2488-2497. [PMID: 28831683 DOI: 10.1007/s11095-017-2234-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 07/20/2017] [Indexed: 11/25/2022]
Abstract
PURPOSE Studies were conducted in primary cultured rat alveolar epithelial cell monolayers to characterize peptide transporter expression and function. METHODS Freshly isolated rat lung alveolar epithelial cells were purified and cultured on permeable support with and without keratinocyte growth factor (KGF). Messenger RNA and protein expression of Pept1 and Pept2 in alveolar epithelial type I- and type II-like cell monolayers (±KGF, resp.) were examined by RT-PCR and Western blotting. 3H-Glycyl-sarcosine (3H-gly-sar) transmonolayer flux and intracellular accumulation were evaluated in both cell types. RESULTS RT-PCR showed expression of Pept2, but not Pept1, mRNA in both cell types. Western blot analysis revealed presence of Pept2 protein in type II-like cells, and less in type I-like cells. Bi-directional transmonolayer 3H-gly-sar flux lacked asymmetry in transport in both types of cells. Uptake of 3H-gly-sar from apical fluid of type II-like cells was 7-fold greater than that from basolateral fluid, while no significant differences were observed from apical vs. basolateral fluid of type I-like cells. CONCLUSIONS This study confirms the absence of Pept1 from rat lung alveolar epithelium in vitro. Functional Pept2 expression in type II-like cell monolayers suggests its involvement in oligopeptide lung disposition, and offers rationale for therapeutic development of di/tripeptides, peptidomimetics employing pulmonary drug delivery.
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Affiliation(s)
- Hovhannes J Gukasyan
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California, USA
- Allergan plc, Irvine, California, USA
| | - Tomomi Uchiyama
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California, USA
- Oozora Pharmacy, Hamamatsu, Shizuoka, Japan
| | - Kwang-Jin Kim
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California, USA
- Will Rogers Institute Pulmonary Research Center, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, California, USA
| | - Carsten Ehrhardt
- School of Pharmacy and Pharmaceutical Sciences, Trinity College Dublin, Dublin 2, Ireland
| | - Sharon K Wu
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California, USA
- Amgen, Inc., Thousand Oaks, California, USA
| | - Zea Borok
- Will Rogers Institute Pulmonary Research Center, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Edward D Crandall
- Will Rogers Institute Pulmonary Research Center, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
- Mork Family Department of Chemical Engineering and Materials Science, Viterbi School of Engineering, University of Southern California, Los Angeles, California, USA
| | - Vincent H L Lee
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California, USA.
- School of Pharmacy, Faculty of Medicine, The Chinese University of Hong Kong, 8/F, Lo Kwee-Seong Integrated Biomedical Sciences Building, Area 39, Shatin, N.T. Hong Kong SAR, China.
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Zhang Z, Pu Y, Pan Q, Xu X, Yan X. Influences of keratinocyte growth factor - mesenchymal stem cells on chronic liver injury in rats. ARTIFICIAL CELLS NANOMEDICINE AND BIOTECHNOLOGY 2015; 44:1810-1817. [DOI: 10.3109/21691401.2015.1105237] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Yacobi NR, Fazllolahi F, Kim YH, Sipos A, Borok Z, Kim KJ, Crandall ED. Nanomaterial interactions with and trafficking across the lung alveolar epithelial barrier: implications for health effects of air-pollution particles. AIR QUALITY, ATMOSPHERE, & HEALTH 2011; 4:65-78. [PMID: 25568662 PMCID: PMC4283834 DOI: 10.1007/s11869-010-0098-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Studies on the health effects of air-pollution particles suggest that injury may result from inhalation of airborne ultrafine particles (<100 nm in diameter). Engineered nanomaterials (<100 nm in at least one dimension) may also be harmful if inhaled. Nanomaterials deposited on the respiratory epithelial tract are thought to cross the air-blood barrier, especially via the expansive alveolar region, into the systemic circulation to reach end organs (e.g., myocardium, liver, pancreas, kidney, and spleen). Since ambient ultrafine particles are difficult to track, studies of defined engineered nanomaterials have been used to obtain valuable information on how nanomaterials interact with and traffic across the air-blood barrier of mammalian lungs. Since specific mechanistic information on how nanomaterials interact with the lung is difficult to obtain using in vivo or ex vivo lungs due to their complex anatomy, in vitro alveolar epithelial models have been of considerable value in determining nanomaterial-lung interactions. In this review, we provide information on mechanisms underlying lung alveolar epithelial injury caused by various nanomaterials and on nanomaterial trafficking across alveolar epithelium that may lead to end-organ injury.
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Affiliation(s)
- Nazanin R. Yacobi
- Will Rogers Institute Pulmonary Research Center, University of Southern California, Los Angeles, CA 90033, USA. Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90033, USA
| | - Farnoosh Fazllolahi
- Will Rogers Institute Pulmonary Research Center, University of Southern California, Los Angeles, CA 90033, USA. Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90033, USA
| | - Yong Ho Kim
- Will Rogers Institute Pulmonary Research Center, University of Southern California, Los Angeles, CA 90033, USA. Department of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Arnold Sipos
- Will Rogers Institute Pulmonary Research Center, University of Southern California, Los Angeles, CA 90033, USA. Department of Medicine, University of Southern California, Los Angeles, CA 90033, USA
| | - Zea Borok
- Will Rogers Institute Pulmonary Research Center, University of Southern California, Los Angeles, CA 90033, USA. Department of Medicine, University of Southern California, Los Angeles, CA 90033, USA. Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, CA 90033, USA
| | - Kwang-Jin Kim
- Will Rogers Institute Pulmonary Research Center, University of Southern California, Los Angeles, CA 90033, USA. Department of Medicine, University of Southern California, Los Angeles, CA 90033, USA. Department of Physiology and Biophysics, University of Southern California, Los Angeles, CA 90033, USA. Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, CA 90033, USA. Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90033, USA
| | - Edward D. Crandall
- Will Rogers Institute Pulmonary Research Center, University of Southern California, Los Angeles, CA 90033, USA. Department of Medicine, University of Southern California, Los Angeles, CA 90033, USA. Department of Medicine, University of Southern California, IRD 620, 2020 Zonal Avenue, Los Angeles, CA 90033, USA. Department of Pathology, University of Southern California, Los Angeles, CA 90033, USA. Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90033, USA
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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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Fra MD GP, Avanzi MD GC. Haemopoietic growth factors in the treatment of myelodysplastic syndrome. Expert Opin Ther Pat 2006. [DOI: 10.1517/13543776.16.11.1557] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Bai Y, Shen WC. Improving the Oral Efficacy of Recombinant Granulocyte Colony-Stimulating Factor and Transferrin Fusion Protein by Spacer Optimization. Pharm Res 2006; 23:2116-21. [PMID: 16952003 DOI: 10.1007/s11095-006-9059-5] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2006] [Accepted: 05/08/2006] [Indexed: 10/24/2022]
Abstract
PURPOSE To improve the oral efficacy of the recombinant fusion protein containing granulocyte colony-stimulating factor (G-CSF) and transferrin (Tf) by inserting a linker between the two protein domains. MATERIALS AND METHODS Oligonucleotides encoding flexible and helix-forming peptides were inserted to the recombinant plasmids. The fusion protein without linker insertion was used for comparison. The G-CSF cell-proliferation and Tf receptor-binding activities of the fusion proteins were tested in NFS-60 cells and Caco-2 cells, respectively, and in vivo myelopoietic assay with both subcutaneous and oral administration was performed in BDF1 mice. RESULTS All fusion proteins produced from transfected HEK293 cells were positive in Western-blotting assay with anti-G-CSF and anti-Tf antibodies. Among them, the fusion protein with a long helical (H4-2) linker showed the highest activity in NFS-60 cell proliferation assay, with an EC50 about ten-fold lower than that of the non-linker fusion protein. The fusion protein with H4-2 linker also showed a significantly higher myelopoietic effect when administered either subcutaneously or orally in BDF1 mice. CONCLUSION The insertion of a linker peptide, such as the helix linker H4-2, between G-CSF and Tf domains in the recombinant fusion protein can improve significantly both in vitro and in vivo myelopoietic activity over the non-linker fusion protein.
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Affiliation(s)
- Yun Bai
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California 90033, USA
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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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Bai Y, Ann DK, Shen WC. Recombinant granulocyte colony-stimulating factor-transferrin fusion protein as an oral myelopoietic agent. Proc Natl Acad Sci U S A 2005; 102:7292-6. [PMID: 15870205 PMCID: PMC1129103 DOI: 10.1073/pnas.0500062102] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
An expression construct harboring granulocyte colony-stimulating factor (G-CSF)-transferrin (Tf) fusion protein (G-CSF-Tf) was engineered by fusing human cDNAs encoding G-CSF and Tf to explore the feasibility of using Tf as a carrier moiety for oral delivery of therapeutic proteins. The recombinant protein, G-CSF-Tf, was harvested from protein-free, conditioned medium of transfected HEK293 cells. The in vitro studies demonstrated that the purified G-CSF-Tf fusion protein possesses the activity of both Tf receptor (TfR) binding in Caco-2 cells and G-CSF-dependent stimulation of NFS-60 cell proliferation. Subcutaneous administration of G-CSF-Tf fusion protein to BDF1 mice demonstrated a pharmacological effect comparable to the commercial G-CSF on the increase of absolute neutrophil counts (ANC). However, the fusion protein elicited a significant increase in ANC upon oral administration to BDF1 mice, whereas G-CSF had no effect. This study also showed that orally administered G-CSF-Tf elicits a sustained myelopoietic effect up to 3 days, whereas the s.c. administered G-CSF or G-CSF-Tf lasts only 1 day. Furthermore, coadministration of free Tf abolished the increase of ANC by orally delivered G-CSF-Tf, suggesting that the recombinant protein is absorbed via a TfR-mediated process in the gastrointestinal tract. Taken together, we conclude that the Tf-based recombinant fusion protein technology represents a promising approach for future development of orally effective peptide and protein drugs.
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Affiliation(s)
- Yun Bai
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA 90033, USA
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Widera A, Norouziyan F, Shen WC. Mechanisms of TfR-mediated transcytosis and sorting in epithelial cells and applications toward drug delivery. Adv Drug Deliv Rev 2003; 55:1439-66. [PMID: 14597140 DOI: 10.1016/j.addr.2003.07.004] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Transferrin receptor has been an important protein for many of the advances made in understanding the intricacies of the intramolecular sorting pathways of endocytosed molecules. The unique internalization and recycling functions of transferrin receptor have also made it an attractive choice for drug targeting and delivery of large protein-based therapeutics and toxins. Recent advances in elucidating the role of the intracellular controllers of transferrin recycling and sorting, such as Rab proteins and their effectors, have led to enhancement of transferrin receptor as a drug delivery vehicle. This review focuses on the use of transferrin receptor as an agent for facilitating drug delivery and targeting, and the role that mechanisms of transferrin receptor sorting and transcytosis play in these events.
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Affiliation(s)
- A Widera
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Southern California, PSC 404B, 1985 Zonal Avenue, Los Angeles, CA 90033, USA
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Widera A, Kim KJJ, Crandall ED, Shen WC. Transcytosis of GCSF-transferrin across rat alveolar epithelial cell monolayers. Pharm Res 2003; 20:1231-8. [PMID: 12948021 DOI: 10.1023/a:1025005232421] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE The purpose of this study was to use primary cultured rat alveolar epithelial cell monolayers to examine the potential of using transferrin receptor (TfR)-mediated transcytosis for noninvasive systemic protein drug delivery via the pulmonary route. METHODS Freshly isolated rat type II pneumocytes were plated onto tissue culture-treated polycarbonate 12-mm Transwells. AEC monolayers (> or = 2500 omega(cm2)) were treated with keratinocyte growth factor (10 ng/mL) for maintenance of type II cell-like characteristics. Filgrastim (GCSF)-Tf conjugates were prepared using the linkers SPDP and DPDPB. TfR-specific binding and uptake were determined using 125I-Tf and 59Fe-Tf treatment, respectively. Apical-to-basolateral (A-to-B) transferrin receptor (TfR)-mediated transcytosis was determined by dosing the apical compartment with 1.5 microg/mL of 125I-Tf or 125I-GCSF-Tf. Nonspecific TfR-independent transport of 125I-Tf and 125I-GCSF-Tf was determined in parallel by including 150 microg/mL of nonradiolabeled Tf. Basolateral samples (500 microL) were taken at 2, 4, and 6 h post-dosing, subjected to 15% trichloroacetic acid precipitation, and assayed in a Packard gamma counter. TfR-specific transport was determined as the difference between total and nonspecifc transport. The effects of brefeldin-A (BFA) on TfR distribution and (A-to-B) transport of 125I-Tf, 125I-GCSF and 125I-GCSF-Tf was studied by including the agent in the apical fluid at 1 microg/mL. RESULTS BFA treatment resulted in a small significant reduction in TfR at the basolateral surface of type II cell-like monolayers, while it had no effect on TfR distribution in type I cell-like monolayers. In contrast, BFA treatment significantly altered the endocytosis of TfR, reducing the basolateral uptake of 59Fe-Tf while greatly increasing the apical uptake of 59Fe-Tf. BFA treatment, however, did not affect the TfR-specific uptake of 59Fe-Tf in type I cell-like monolayers. TfR-specific apical-to-basolateral transcytosis of 125I-Tf and 126I-GCSF-Tf conjugates was significantly enhanced in the presence of BFA in type II cell-like monolayers, whereas it had no effect on apical-to-basolateral transport of 125I-GCSF. BFA-enhanced transport of 125I-GCSF-Tf was approximately 3-fold higher than that of 125I-GCSF in the presence or absence of BFA. Moreover, 125I-GCSF transport in the presence of BFA was not significantly different from non-specific 125I-GCSF-Tf transport. Chromatographic analyses and bio-assays revealed that GCSF-Tf was not degraded during transport via TfR-specific processes, and that GCSF retained biologic activity when liberated from the conjugate via dithiothreitol reduction. CONCLUSION This study suggests the possibility of using TfR-mediated transcytosis for systemic delivery of therapeutic proteins via the alveolar epithelium.
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Affiliation(s)
- Adam Widera
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California 90033, USA
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