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Qi Q, Wei Y, Zhang X, Guan J, Mao S. Challenges and strategies for ocular posterior diseases therapy via non-invasive advanced drug delivery. J Control Release 2023; 361:191-211. [PMID: 37532148 DOI: 10.1016/j.jconrel.2023.07.055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 07/22/2023] [Accepted: 07/31/2023] [Indexed: 08/04/2023]
Abstract
Posterior segment diseases, such as age-related macular degeneration (AMD) and diabetic retinopathy (DR) are vital factor that seriously threatens human vision health and quality of life, the treatment of which poses a great challenge to ophthalmologists and ophthalmic scientists. In particular, ocular posterior drug delivery in a non-invasive manner is highly desired but still faces many difficulties such as rapid drug clearance, limited permeability and low drug accumulation at the target site. At present, many novel non-invasive topical ocular drug delivery systems are under development aiming to improve drug delivery efficiency and biocompatibility for better therapy of posterior segment oculopathy. The purpose of this review is to present the challenges in the noninvasive treatment of posterior segment diseases, and to propose strategies to tackle these bottlenecks. First of all, barriers to ocular administration were introduced based on ocular physiological structure and behavior, including analysis and discussion on the influence of ocular structures on noninvasive posterior segment delivery. Thereafter, various routes of posterior drug delivery, both invasive and noninvasive, were illustrated, along with the respective anatomical obstacles that need to be overcome. The widespread and risky application of invasive drug delivery, and the need to develop non-invasive local drug delivery with alternative to injectable therapy were described. Absorption routes through topical administration and strategies to enhance ocular posterior drug delivery were then discussed. As a follow-up, an up-to-date research advances in non-invasive delivery systems for the therapy of ocular fundus lesions were presented, including different nanocarriers, contact lenses, and several other carriers. In conclusion, it seems feasible and promising to treat posterior oculopathy via non-invasive local preparations or in combination with appropriate devices.
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Affiliation(s)
- Qi Qi
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang 110016, China
| | - Yidan Wei
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang 110016, China
| | - Xin Zhang
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang 110016, China
| | - Jian Guan
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang 110016, China
| | - Shirui Mao
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang 110016, China.
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2
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Zeng S, Chen Y, Zhou F, Zhang T, Fan X, Chrzanowski W, Gillies MC, Zhu L. Recent advances and prospects for lipid-based nanoparticles as drug carriers in the treatment of human retinal diseases. Adv Drug Deliv Rev 2023; 199:114965. [PMID: 37315899 DOI: 10.1016/j.addr.2023.114965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 05/08/2023] [Accepted: 06/09/2023] [Indexed: 06/16/2023]
Abstract
The delivery of cures for retinal diseases remains problematic. There are four main challenges: passing through multiple barriers of the eye, the delivery to particular retinal cell types, the capability to carry different forms of therapeutic cargo and long-term therapeutic efficacy. Lipid-based nanoparticles (LBNPs) are potent to overcome these challenges due to their unique merits: amphiphilic nanoarchitectures to pass biological barriers, vary modifications with specific affinity to target cell types, flexible capacity for large and mixed types of cargos and slow-release formulations for long-term treatment. We have reviewed the latest research on the applications of LBNPs for treating retinal diseases and categorized them by different payloads. Furthermore, we identified technical barriers and discussed possible future development for LBNPs to expand the therapeutic potential in treating retinal diseases.
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Affiliation(s)
- Shaoxue Zeng
- Macula Research Group, Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW 2006, Australia
| | - Yingying Chen
- Macula Research Group, Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW 2006, Australia; Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Fanfan Zhou
- School of Pharmacy, The University of Sydney, Sydney, NSW 2006, Australia
| | - Ting Zhang
- Macula Research Group, Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW 2006, Australia
| | - Xiaohui Fan
- Pharmaceutical Informatics Institute, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | | | - Mark C Gillies
- Macula Research Group, Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW 2006, Australia
| | - Ling Zhu
- Macula Research Group, Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW 2006, Australia.
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Bile Duct Ligation Impairs Function and Expression of Mrp1 at Rat Blood–Retinal Barrier via Bilirubin-Induced P38 MAPK Pathway Activations. Int J Mol Sci 2022; 23:ijms23147666. [PMID: 35887010 PMCID: PMC9318728 DOI: 10.3390/ijms23147666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Revised: 07/04/2022] [Accepted: 07/07/2022] [Indexed: 11/29/2022] Open
Abstract
Liver injury is often associated with hepatic retinopathy, resulting from accumulation of retinal toxins due to blood–retinal barrier (BRB) dysfunction. Retinal pigment epithelium highly expresses MRP1/Mrp1. We aimed to investigate whether liver injury affects the function and expression of retinal Mrp1 using bile duct ligation (BDL) rats. Retinal distributions of fluorescein and 2,4-dinitrophenyl-S-glutathione were used for assessing Mrp1 function. BDL significantly increased distributions of the two substrates and bilirubin, downregulated Mrp1 protein, and upregulated phosphorylation of p38 and MK2 in the retina. BDL neither affected the retinal distribution of FITC-dextran nor expressions of ZO-1 and claudin-5, demonstrating intact BRB integrity. In ARPE-19 cells, BDL rat serum or bilirubin decreased MRP1 expression and enhanced p38 and MK2 phosphorylation. Both inhibiting and silencing p38 significantly reversed the bilirubin- and anisomycin-induced decreases in MRP1 protein. Apparent permeability coefficients of fluorescein in the A-to-B direction (Papp, A-to-B) across the ARPE-19 monolayer were greater than Papp, B-to-A. MK571 or bilirubin significantly decreased Papp, A-to-B of fluorescein. Bilirubin treatment significantly downregulated Mrp1 function and expression without affecting integrity of BRB and increased bilirubin levels and phosphorylation of p38 and MK2 in rat retina. In conclusion, BDL downregulates the expression and function of retina Mrp1 by activating the p38 MAPK pathway due to increased bilirubin levels.
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Schneider-Futschik EK, Reyes-Ortega F. Advantages and Disadvantages of Using Magnetic Nanoparticles for the Treatment of Complicated Ocular Disorders. Pharmaceutics 2021; 13:1157. [PMID: 34452117 PMCID: PMC8400382 DOI: 10.3390/pharmaceutics13081157] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 07/20/2021] [Accepted: 07/22/2021] [Indexed: 01/01/2023] Open
Abstract
Nanomaterials provide enormous opportunities to overcome the limitations of conventional ocular delivery systems, such as low therapeutic efficacy, side effects due to the systemic exposure, or invasive surgery. Apart from the more common ocular disorders, there are some genetic diseases, such as cystic fibrosis, that develop ocular disorders as secondary effects as long as the disease progresses. These patients are more difficult to be pharmacologically treated using conventional drug routes (topically, systemic), since specific pharmacological formulations can be incompatible, display increased toxicity, or their therapeutic efficacy decreases with the administration of different kind of chemical molecules. Magnetic nanoparticles can be used as potent drug carriers and magnetic hyperthermia agents due to their response to an external magnetic field. Drugs can be concentrated in the target point, limiting the damage to other tissues. The other advantage of these magnetic nanoparticles is that they can act as magnetic resonance imaging agents, allowing the detection of the exact location of the disease. However, there are some drawbacks related to their use in drug delivery, such as the limitation to maintain efficacy in the target organ once the magnetic field is removed from outside. Another disadvantage is the difficulty in maintaining the therapeutic action in three dimensions inside the human body. This review summarizes all the application possibilities related to magnetic nanoparticles in ocular diseases.
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Affiliation(s)
- Elena K. Schneider-Futschik
- Department of Biochemistry & Pharmacology, Faculty of Medicine, School of Biomedical Sciences, Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC 3010, Australia;
| | - Felisa Reyes-Ortega
- Visual Quality Research Group, Department of Ophthalmology, Maimonides Biomedical Research Institute of Cordoba (IMIBIC), Reina Sofía University Hospital and University of Cordoba, 14004 Cordoba, Spain
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Verma A, Tiwari A, Saraf S, Panda PK, Jain A, Jain SK. Emerging potential of niosomes in ocular delivery. Expert Opin Drug Deliv 2020; 18:55-71. [PMID: 32903034 DOI: 10.1080/17425247.2020.1822322] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
INTRODUCTION Niosomes have recently grabbed attention as one of the best tools for various site-specific drug delivery systems, including ophthalmic drug delivery. Surfactants (nonionic; tweens and spans) of different HLB values and cholesterol are the fundamental components for these formulations. It is an alternative controlled ocular drug delivery system to liposomes to overcome the problems associated with sterilization, large-scale production, and stability. It also enhances the adhesion or retention ability of drug at the ocular site. Hydrophilic or lipophilic or amphoteric drugs can be easily encapsulated in niosomes. Besides, niosomes are a leading vesicular system compatible with most of the drugs for site-specific delivery. AREAS COVERED This article reveals challenges and barriers for ocular drug delivery, various transporters and receptors present in the ocular region for the transportation of therapeutics as well as nutrients, and various method of preparations, loading methods and application potential of niosomes in ocular drug delivery. EXPERT OPINION Niosomes, a vesicular system offers numerous advantages and applicability because of its good stability, non-immunogenicity, permeation potential, and controlled release ability etc. This drug delivery system has been efficiently used in the treatment of many ocular diseases.
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Affiliation(s)
- Amit Verma
- Pharmaceutics Research Projects Laboratory, Department of Pharmaceutical Sciences, Dr. Harisingh Gour Vishwavidyalaya , Sagar, India
| | - Ankita Tiwari
- Pharmaceutics Research Projects Laboratory, Department of Pharmaceutical Sciences, Dr. Harisingh Gour Vishwavidyalaya , Sagar, India
| | - Shivani Saraf
- Pharmaceutics Research Projects Laboratory, Department of Pharmaceutical Sciences, Dr. Harisingh Gour Vishwavidyalaya , Sagar, India
| | - Pritish Kumar Panda
- Pharmaceutics Research Projects Laboratory, Department of Pharmaceutical Sciences, Dr. Harisingh Gour Vishwavidyalaya , Sagar, India
| | - Ankit Jain
- Pharmaceutics Research Projects Laboratory, Department of Pharmaceutical Sciences, Dr. Harisingh Gour Vishwavidyalaya , Sagar, India.,Department of Materials Engineering, Indian Institute of Science , Bangalore, India
| | - Sanjay K Jain
- Pharmaceutics Research Projects Laboratory, Department of Pharmaceutical Sciences, Dr. Harisingh Gour Vishwavidyalaya , Sagar, India
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Gonzalez-Pizarro R, Parrotta G, Vera R, Sánchez-López E, Galindo R, Kjeldsen F, Badia J, Baldoma L, Espina M, García ML. Ocular penetration of fluorometholone-loaded PEG-PLGA nanoparticles functionalized with cell-penetrating peptides. Nanomedicine (Lond) 2019; 14:3089-3104. [DOI: 10.2217/nnm-2019-0201] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Aim: Development of fluorometholone-loaded PEG-PLGA nanoparticles (NPs) functionalized with cell-penetrating peptides (CPPs) for the treatment of ocular inflammatory disorders. Materials & methods: Synthesized polymers and peptides were used for elaboration of functionalized NPs, which were characterized physicochemically. Cytotoxicity and ability to modulate the expression of proinflammatory cytokines were evaluated in vitro using human corneal epithelial cells (HCE-2). NPs uptake was assayed in both in vitro and in vivo models. Results: NPs showed physicochemical characteristics suitable for ocular administration without evidence of cytotoxicity. TAT-NPs and G2-NPs were internalized and displayed anti-inflammatory activity in both HCE-2 cells and mouse eye. Conclusion: TAT-NPs and G2-NPs could be considered a novel strategy for the treatment of ocular inflammatory diseases of the anterior and posterior segment.
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Affiliation(s)
- Roberto Gonzalez-Pizarro
- Department of Pharmacy, Pharmaceutical Technology & Physical Chemistry, Faculty of Pharmacy & Food Sciences, University of Barcelona, 08028 Catalonia, Spain
- Institute of Nanoscience & Nanotechnology (IN2UB), University of Barcelona, 08028 Catalonia, Spain
| | - Graziella Parrotta
- Department of Biochemistry & Molecular Biology, Faculty of Science, University of Southern Denmark, 5230 Southern Denmark, Denmark
| | - Rodrigo Vera
- Department of Biochemistry & Physiology, Faculty of Pharmacy & Food Sciences, University of Barcelona, 08028 Catalonia, Spain
- Institute of Biomedicine, University of Barcelona (IBUB), 08028 Catalonia, Spain
- Institut de Recerca Sant Joan de Déu (IRSJD), 08950 Catalonia, Spain
| | - Elena Sánchez-López
- Department of Pharmacy, Pharmaceutical Technology & Physical Chemistry, Faculty of Pharmacy & Food Sciences, University of Barcelona, 08028 Catalonia, Spain
- Biomedical Research Networking Center in Neurodegenerative Diseases (CIBERNED), 28031 Madrid, Spain
- Institute of Nanoscience & Nanotechnology (IN2UB), University of Barcelona, 08028 Catalonia, Spain
| | - Ruth Galindo
- Department of Pharmacy, Pharmaceutical Technology & Physical Chemistry, Faculty of Pharmacy & Food Sciences, University of Barcelona, 08028 Catalonia, Spain
| | - Frank Kjeldsen
- Department of Biochemistry & Molecular Biology, Faculty of Science, University of Southern Denmark, 5230 Southern Denmark, Denmark
| | - Josefa Badia
- Department of Biochemistry & Physiology, Faculty of Pharmacy & Food Sciences, University of Barcelona, 08028 Catalonia, Spain
- Institute of Biomedicine, University of Barcelona (IBUB), 08028 Catalonia, Spain
- Institut de Recerca Sant Joan de Déu (IRSJD), 08950 Catalonia, Spain
| | - Laura Baldoma
- Department of Biochemistry & Physiology, Faculty of Pharmacy & Food Sciences, University of Barcelona, 08028 Catalonia, Spain
- Institute of Biomedicine, University of Barcelona (IBUB), 08028 Catalonia, Spain
- Institut de Recerca Sant Joan de Déu (IRSJD), 08950 Catalonia, Spain
| | - Marta Espina
- Department of Pharmacy, Pharmaceutical Technology & Physical Chemistry, Faculty of Pharmacy & Food Sciences, University of Barcelona, 08028 Catalonia, Spain
- Institute of Nanoscience & Nanotechnology (IN2UB), University of Barcelona, 08028 Catalonia, Spain
| | - María L García
- Department of Pharmacy, Pharmaceutical Technology & Physical Chemistry, Faculty of Pharmacy & Food Sciences, University of Barcelona, 08028 Catalonia, Spain
- Biomedical Research Networking Center in Neurodegenerative Diseases (CIBERNED), 28031 Madrid, Spain
- Institute of Nanoscience & Nanotechnology (IN2UB), University of Barcelona, 08028 Catalonia, Spain
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Abstract
Although the eye is an accessible organ for direct drug application, ocular drug delivery remains a major challenge due to multiple barriers within the eye. Key barriers include static barriers imposed by the cornea, conjunctiva, and retinal pigment epithelium and dynamic barriers including tear turnover and blood and lymphatic clearance mechanisms. Systemic administration by oral and parenteral routes is limited by static blood-tissue barriers that include epithelial and endothelial layers, in addition to rapid vascular clearance mechanisms. Together, the static and dynamic barriers limit the rate and extent of drug delivery to the eye. Thus, there is an ongoing need to identify novel delivery systems and approaches to enhance and sustain ocular drug delivery. This chapter summarizes current and recent experimental approaches for drug delivery to the anterior and posterior segments of the eye.
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Affiliation(s)
- Burcin Yavuz
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado, 12850 East Montview Blvd., C238-V20, Aurora, CO, 80045, USA.,Department of Biomedical Engineering, Tufts University, Medford, MA, 02155, USA
| | - Uday B Kompella
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado, 12850 East Montview Blvd., C238-V20, Aurora, CO, 80045, USA.
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8
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Tatke A, Janga KY, Avula B, Wang X, Jablonski MM, Khan IA, Majumdar S. P-glycoprotein Restricts Ocular Penetration of Loperamide across the Blood-Ocular Barriers: a Comparative Study in Mdr1a Knock-out and Wild Type Sprague Dawley Rats. AAPS PharmSciTech 2018. [PMID: 29520587 DOI: 10.1208/s12249-018-0979-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The current research was undertaken to determine the existence and magnitude of P-glycoprotein (P-gp) expression on the blood-ocular barriers by studying the ocular penetration of loperamide, a specific P-gp substrate, in P-gp (Mdr1a) knock-out (KO) and wild type (WT) Sprague Dawley rats. A clear, stable, sterile solution of loperamide (1 mg/mL), for intravenous administration, was formulated and evaluated. Ocular distribution was studied in P-gp KO and WT rats following intravenous administration of loperamide (at two doses). The drug levels in plasma, aqueous humor (AH), and vitreous humor (VH) samples were determined with the aid of UHPLC-Q-TOF-MS/MS, and the AH/plasma (D AH ) and VH/plasma (D VH ) distribution ratios were estimated. Electroretinography (ERG), ultrastructural analyses, and histology studies were carried out, in both KO and WT rats, to detect any drug-induced functional and/or structural alterations in the retina. Dose-related loperamide levels were observed in the plasma of both WT and KO rats. The loperamide concentrations in the AH and VH of KO rats were significantly higher compared to that observed in the WT rats, at the lower dose. However, a marked increase in the D AH and D VH was noted in the KO rats. ERG, ultrastructure, and histology studies did not indicate any drug-induced toxic effects in the retina under the test conditions. The results from these studies demonstrate that P-gp blocks the penetration of loperamide into the ocular tissues from the systemic circulation and that the effect is more pronounced at lower plasma loperamide concentrations.
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9
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Ocular Drug Delivery Barriers-Role of Nanocarriers in the Treatment of Anterior Segment Ocular Diseases. Pharmaceutics 2018; 10:pharmaceutics10010028. [PMID: 29495528 PMCID: PMC5874841 DOI: 10.3390/pharmaceutics10010028] [Citation(s) in RCA: 201] [Impact Index Per Article: 33.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 02/12/2018] [Accepted: 02/23/2018] [Indexed: 12/20/2022] Open
Abstract
Ocular drug delivery is challenging due to the presence of anatomical and physiological barriers. These barriers can affect drug entry into the eye following multiple routes of administration (e.g., topical, systemic, and injectable). Topical administration in the form of eye drops is preferred for treating anterior segment diseases, as it is convenient and provides local delivery of drugs. Major concerns with topical delivery include poor drug absorption and low bioavailability. To improve the bioavailability of topically administered drugs, novel drug delivery systems are being investigated. Nanocarrier delivery systems demonstrate enhanced drug permeation and prolonged drug release. This review provides an overview of ocular barriers to anterior segment delivery, along with ways to overcome these barriers using nanocarrier systems. The disposition of nanocarriers following topical administration, their safety, toxicity and clinical trials involving nanocarrier systems are also discussed.
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10
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Vellonen KS, Hellinen L, Mannermaa E, Ruponen M, Urtti A, Kidron H. Expression, activity and pharmacokinetic impact of ocular transporters. Adv Drug Deliv Rev 2018; 126:3-22. [PMID: 29248478 DOI: 10.1016/j.addr.2017.12.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 10/24/2017] [Accepted: 12/13/2017] [Indexed: 12/13/2022]
Abstract
The eye is protected by several tissues that limit the permeability and entry of potentially harmful substances, but also hamper the delivery of drugs in the treatment of ocular diseases. Active transport across the ocular barriers may affect drug distribution, but the impact of drug transporters on ocular drug delivery is not well known. We have collected and critically reviewed the literature for ocular expression and activity of known drug transporters. The review concentrates on drug transporters that have been functionally characterized in ocular tissues or primary cells and on transporters for which there is available expression data at the protein level. Species differences are highlighted, since these may explain observed inconsistencies in the influence of specific transporters on drug disposition. There is variable evidence about the pharmacokinetic role of transporters in ocular tissues. The strongest evidence for the role of active transport is available for the blood-retinal barrier. We explored the role of active transport in the cornea and blood retinal barrier with pharmacokinetic simulations. The simulations show that the active transport is important only in the case of specific parameter combinations.
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11
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Pelkonen L, Sato K, Reinisalo M, Kidron H, Tachikawa M, Watanabe M, Uchida Y, Urtti A, Terasaki T. LC–MS/MS Based Quantitation of ABC and SLC Transporter Proteins in Plasma Membranes of Cultured Primary Human Retinal Pigment Epithelium Cells and Immortalized ARPE19 Cell Line. Mol Pharm 2017; 14:605-613. [DOI: 10.1021/acs.molpharmaceut.6b00782] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Laura Pelkonen
- School
of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, 70210 Kuopio, Finland
| | - Kazuki Sato
- Division
of Membrane Transport and Drug Targeting, Graduate School of Pharmaceutical
Sciences, Tohoku University, Sendai, Japan
| | - Mika Reinisalo
- School
of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, 70210 Kuopio, Finland
| | - Heidi Kidron
- Centre
for Drug Research, Division of Pharmaceutical Biosciences, Faculty
of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014 Helsinki, Finland
| | - Masanori Tachikawa
- Division
of Membrane Transport and Drug Targeting, Graduate School of Pharmaceutical
Sciences, Tohoku University, Sendai, Japan
| | - Michitoshi Watanabe
- Division
of Membrane Transport and Drug Targeting, Graduate School of Pharmaceutical
Sciences, Tohoku University, Sendai, Japan
| | - Yasuo Uchida
- Division
of Membrane Transport and Drug Targeting, Graduate School of Pharmaceutical
Sciences, Tohoku University, Sendai, Japan
| | - Arto Urtti
- School
of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, 70210 Kuopio, Finland
- Centre
for Drug Research, Division of Pharmaceutical Biosciences, Faculty
of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014 Helsinki, Finland
| | - Tetsuya Terasaki
- Division
of Membrane Transport and Drug Targeting, Graduate School of Pharmaceutical
Sciences, Tohoku University, Sendai, Japan
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13
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Vellonen KS, Malinen M, Mannermaa E, Subrizi A, Toropainen E, Lou YR, Kidron H, Yliperttula M, Urtti A. A critical assessment of in vitro tissue models for ADME and drug delivery. J Control Release 2014; 190:94-114. [DOI: 10.1016/j.jconrel.2014.06.044] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 06/22/2014] [Accepted: 06/23/2014] [Indexed: 12/22/2022]
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14
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Wade JS, Desai TA. Planar microdevices enhance transport of large molecular weight molecules across retinal pigment epithelial cells. Biomed Microdevices 2014; 16:629-38. [PMID: 24789225 PMCID: PMC4082762 DOI: 10.1007/s10544-014-9865-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Large molecular weight drug delivery to the posterior eye is challenging due to cellular barriers that hinder drug transport. Understanding how to enhance transport across the retinal barrier is important for the design of new drug delivery systems. A novel mechanism to enhance drug transport is the use of geometric properties, which has not been extensively explored in the retina. Planar SU-8/Poly(ethyleneglycol)dimethacrylate microdevices were constructed using photolithography to deliver FITC dextran across an in vitro retinal model. The model consists of retinal pigment epithelial (RPE) cells grown to confluence on transwell inserts, which provides an environment to investigate the influence of geometry on paracellular and transcellular delivery of encapsulated large molecules. Planar microdevices enhanced transport of large molecular weight dextrans across different models of RPE in a size dependent fashion. Increased drug permeation across the RPE was observed with the addition of microdevices as compared to a traditional bolus of FITC dextran. This phenomena was initiated by a non-toxic interaction between the microdevices and the retinal tight junction proteins. Suggesting that increased drug transport occurs via a paracellular pathway. These experiments provide evidence to support the future use of planar unidirectional microdevices for delivery of biologics in ocular applications.
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Affiliation(s)
- Jennifer S. Wade
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, California 94158, USA
| | - Tejal A. Desai
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, California 94158, USA
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15
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Abstract
The eye is a highly protected organ, and designing an effective therapy is often considered a challenging task. The anatomical and physiological barriers result in low ocular bioavailability of drugs. Due to these constraints, less than 5% of the administered dose is absorbed from the conventional ophthalmic dosage forms. Further, physicochemical properties such as lipophilicity, molecular weight and charge modulate the permeability of drug molecules. Vision-threatening diseases such as glaucoma, diabetic macular edema, cataract, wet and dry age-related macular degeneration, proliferative vitreoretinopathy, uveitis, and cytomegalovirus retinitis alter the pathophysiological and molecular mechanisms. Understanding these mechanisms may result in the development of novel treatment modalities. Recently, transporter/receptor targeted prodrug approach has generated significant interest in ocular drug delivery. These transporters and receptors are involved in the transport of essential nutrients, vitamins, and xenobiotics across biological membranes. Several influx transporters (peptides, amino acids, glucose, lactate and nucleosides/nucleobases) and receptors (folate and biotin) have been identified on conjunctiva, cornea, and retina. Structural and functional delineation of these transporters will enable more drugs targeting the posterior segment to be successfully delivered topically. Prodrug derivatization targeting transporters and receptors expressed on ocular tissues has been the subject of intense research. Several prodrugs have been designed to target these transporters and enhance the absorption of poorly permeating parent drug. Moreover, this approach might be used in gene delivery to modify cellular function and membrane receptors. This review provides comprehensive information on ocular drug delivery, with special emphasis on the use of transporters and receptors to improve drug bioavailability.
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16
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Sreekumar PG, Spee C, Ryan SJ, Cole SPC, Kannan R, Hinton DR. Mechanism of RPE cell death in α-crystallin deficient mice: a novel and critical role for MRP1-mediated GSH efflux. PLoS One 2012; 7:e33420. [PMID: 22442691 PMCID: PMC3307734 DOI: 10.1371/journal.pone.0033420] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2012] [Accepted: 02/14/2012] [Indexed: 11/26/2022] Open
Abstract
Absence of α-crystallins (αA and αB) in retinal pigment epithelial (RPE) cells renders them susceptible to oxidant-induced cell death. We tested the hypothesis that the protective effect of α-crystallin is mediated by changes in cellular glutathione (GSH) and elucidated the mechanism of GSH efflux. In α-crystallin overexpressing cells resistant to cell death, cellular GSH was >2 fold higher than vector control cells and this increase was seen particularly in mitochondria. The high GSH levels associated with α-crystallin overexpression were due to increased GSH biosynthesis. On the other hand, cellular GSH was decreased by 50% in murine retina lacking αA or αB crystallin. Multiple multidrug resistance protein (MRP) family isoforms were expressed in RPE, among which MRP1 was the most abundant. MRP1 was localized to the plasma membrane and inhibition of MRP1 markedly decreased GSH efflux. MRP1-suppressed cells were resistant to cell death and contained elevated intracellular GSH and GSSG. Increased GSH in MRP1-supressed cells resulted from a higher conversion of GSSG to GSH by glutathione reductase. In contrast, GSH efflux was significantly higher in MRP1 overexpressing RPE cells which also contained lower levels of cellular GSH and GSSG. Oxidative stress further increased GSH efflux with a decrease in cellular GSH and rendered cells apoptosis-prone. In conclusion, our data reveal for the first time that 1) MRP1 mediates GSH and GSSG efflux in RPE cells; 2) MRP1 inhibition renders RPE cells resistant to oxidative stress-induced cell death while MRP1 overexpression makes them susceptible and 3) the antiapoptotic function of α-crystallin in oxidatively stressed cells is mediated in part by GSH and MRP1. Our findings suggest that MRP1 and α crystallin are potential therapeutic targets in pathological retinal degenerative disorders linked to oxidative stress.
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Affiliation(s)
- Parameswaran G. Sreekumar
- Arnold and Mabel Beckman Macular Research Center, Doheny Eye Institute, Los Angeles, California, United States of America
| | - Christine Spee
- Arnold and Mabel Beckman Macular Research Center, Doheny Eye Institute, Los Angeles, California, United States of America
| | - Stephen J. Ryan
- Arnold and Mabel Beckman Macular Research Center, Doheny Eye Institute, Los Angeles, California, United States of America
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, California, United States of America
| | - Susan P. C. Cole
- Division of Cancer Biology and Genetics, Queen's University Cancer Research Institute, Kingston, Canada
| | - Ram Kannan
- Arnold and Mabel Beckman Macular Research Center, Doheny Eye Institute, Los Angeles, California, United States of America
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, California, United States of America
| | - David R. Hinton
- Arnold and Mabel Beckman Macular Research Center, Doheny Eye Institute, Los Angeles, California, United States of America
- Department of Pathology, Keck School of Medicine of the University of Southern California, Los Angeles, California, United States of America
- * E-mail:
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Juuti-Uusitalo K, Vaajasaari H, Ryhänen T, Narkilahti S, Suuronen R, Mannermaa E, Kaarniranta K, Skottman H. Efflux protein expression in human stem cell-derived retinal pigment epithelial cells. PLoS One 2012; 7:e30089. [PMID: 22272278 PMCID: PMC3260202 DOI: 10.1371/journal.pone.0030089] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Accepted: 12/13/2011] [Indexed: 12/02/2022] Open
Abstract
Retinal pigment epithelial (RPE) cells in the back of the eye nourish photoreceptor cells and form a selective barrier that influences drug transport from the blood to the photoreceptor cells. At the molecular level, ATP-dependent efflux transporters have a major role in drug delivery in human RPE. In this study, we assessed the relative expression of several ATP-dependent efflux transporter genes (MRP1, -2, -3, -4, -5, -6, p-gp, and BCRP), the protein expression and localization of MRP1, MRP4, and MRP5, and the functionality of MRP1 efflux pumps at different maturation stages of undifferentiated human embryonic stem cells (hESC) and RPE derived from the hESC (hESC-RPE). Our findings revealed that the gene expression of ATP-dependent efflux transporters MRP1, -3, -4, -5, and p-gp fluctuated during hESC-RPE maturation from undifferentiated hESC to fusiform, epithelioid, and finally to cobblestone hESC-RPE. Epithelioid hESC-RPE had the highest expression of MRP1, -3, -4, and P-gp, whereas the most mature cobblestone hESC-RPE had the highest expression of MRP5 and MRP6. These findings indicate that a similar efflux protein profile is shared between hESC-RPE and the human RPE cell line, ARPE-19, and suggest that hESC-RPE cells are suitable in vitro RPE models for drug transport studies. Embryonic stem cell model might provide a novel tool to study retinal cell differentiation, mechanisms of RPE-derived diseases, drug testing and targeted drug therapy.
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Affiliation(s)
- Kati Juuti-Uusitalo
- The Institute of Biomedical Technology, University of Tampere, Tampere, Finland.
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18
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Hosoya KI, Tomi M, Tachikawa M. Strategies for therapy of retinal diseases using systemic drug delivery: relevance of transporters at the blood-retinal barrier. Expert Opin Drug Deliv 2011; 8:1571-87. [PMID: 22035231 DOI: 10.1517/17425247.2011.628983] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
INTRODUCTION There is an increasing need for managing rapidly progressing retinal diseases because of the potential loss of vision. Although systemic drug administration is one possible route for treating retinal diseases, retinal transfer of therapeutic drugs from the circulating blood is strictly regulated by the blood-retinal barrier (BRB). AREAS COVERED This review discusses the constraints and challenges of drug delivery to the retina. In addition, this article discusses the properties of drugs and the conditions of the BRB that affect drug permeability. The reader will gain insights into the strategies for developing therapeutic drugs that are able to cross the BRB for treating retinal diseases. Further, the reader will gain insights into the role of BRB physiology including barrier functions, and the effect of influx and efflux transporters on retinal drug delivery. EXPERT OPINION When designing and selecting optimal drug candidates, it's important to consider the fact that they should be recognized by influx transporters and that efflux transporters at the BRB should be avoided. Although lipophilic cationic drugs are known to be transported to the brain across the blood-brain barrier, verapamil transport to the retina is substantially higher than to the brain. Therefore, lipophilic cationic drugs do have a great ability to increase influx transport across the BRB.
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Affiliation(s)
- Ken-ichi Hosoya
- University of Toyama, Graduate School of Medicine and Pharmaceutical Sciences, Department of Pharmaceutics, 2630, Sugitani, Toyama 930 0194, Japan.
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19
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Boddu SHS, Jwala J, Chowdhury MR, Mitra AK. In vitro evaluation of a targeted and sustained release system for retinoblastoma cells using Doxorubicin as a model drug. J Ocul Pharmacol Ther 2011; 26:459-68. [PMID: 20874666 DOI: 10.1089/jop.2010.0048] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
PURPOSE The objective of this study was to develop a novel folate receptor-targeted drug delivery system for retinoblastoma cells using doxorubicin (DOX) as a model drug. METHODS Biodegradable DOX-loaded poly(d,l-lactide-co-glycolide)-poly(ethylene glycol)-folate (PLGA-PEG-FOL) micelles (DOXM) were prepared with various solvents (dimethylsulfoxide, acetone, and dimethylformamide). The effects of solvents on entrapment efficiency, particle size, and polydispersity were examined. The effects of thermosensitive gel structure on the release of DOX from the DOXM were also studied. Qualitative and quantitative uptake studies of DOX and DOXM were carried out in Y-79 cell line. Cytotoxicity studies of DOXM were performed on Y-79 cells. RESULTS Based on size, polydispersity, and entrapment efficiency, dimethylformamide was found to be the most suitable solvent for the preparation of DOXM. Dispersion of DOXM in PLGA-PEG-PLGA gel sustained drug release for a period of 2 weeks. Uptake of DOX was ∼4 times higher with DOXM than DOX in Y-79 cells overexpressing folate receptors. This was further confirmed from the quantitative uptake studies. DOXM exhibited higher cytotoxicity in Y-79 cells when compared with pure DOX. CONCLUSION These polymeric micellar systems suspended in thermosensitive gels may provide sustained and targeted delivery of anticancer agents to retinoblastoma cells following intravitreal administration.
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Affiliation(s)
- Sai H S Boddu
- Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri-Kansas City , Kansas City, MO 64108-2718, USA
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20
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Wilson CG, Tan LE, Mains J. Principles of Retinal Drug Delivery from Within the Vitreous. DRUG PRODUCT DEVELOPMENT FOR THE BACK OF THE EYE 2011. [DOI: 10.1007/978-1-4419-9920-7_6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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21
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Tomi M, Hosoya KI. The role of blood–ocular barrier transporters in retinal drug disposition: an overview. Expert Opin Drug Metab Toxicol 2010; 6:1111-24. [DOI: 10.1517/17425255.2010.486401] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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22
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Gaudana R, Ananthula HK, Parenky A, Mitra AK. Ocular drug delivery. AAPS JOURNAL 2010; 12:348-60. [PMID: 20437123 DOI: 10.1208/s12248-010-9183-3] [Citation(s) in RCA: 747] [Impact Index Per Article: 53.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2009] [Accepted: 02/24/2010] [Indexed: 12/11/2022]
Abstract
Ocular drug delivery has been a major challenge to pharmacologists and drug delivery scientists due to its unique anatomy and physiology. Static barriers (different layers of cornea, sclera, and retina including blood aqueous and blood-retinal barriers), dynamic barriers (choroidal and conjunctival blood flow, lymphatic clearance, and tear dilution), and efflux pumps in conjunction pose a significant challenge for delivery of a drug alone or in a dosage form, especially to the posterior segment. Identification of influx transporters on various ocular tissues and designing a transporter-targeted delivery of a parent drug has gathered momentum in recent years. Parallelly, colloidal dosage forms such as nanoparticles, nanomicelles, liposomes, and microemulsions have been widely explored to overcome various static and dynamic barriers. Novel drug delivery strategies such as bioadhesive gels and fibrin sealant-based approaches were developed to sustain drug levels at the target site. Designing noninvasive sustained drug delivery systems and exploring the feasibility of topical application to deliver drugs to the posterior segment may drastically improve drug delivery in the years to come. Current developments in the field of ophthalmic drug delivery promise a significant improvement in overcoming the challenges posed by various anterior and posterior segment diseases.
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Affiliation(s)
- Ripal Gaudana
- Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri-Kansas City, 2464 Charlotte St., Kansas City, Missouri 64108-2718, USA
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23
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Filter-cultured ARPE-19 cells as outer blood-retinal barrier model. Eur J Pharm Sci 2010; 40:289-96. [PMID: 20385230 DOI: 10.1016/j.ejps.2010.04.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2009] [Revised: 04/02/2010] [Accepted: 04/03/2010] [Indexed: 02/03/2023]
Abstract
Retinal pigment epithelium (RPE) regulates drug transfer between posterior eye segment and blood circulation, but there is no established RPE cell model for drug delivery studies. We evaluated ARPE-19 filter culture model for this purpose. Passive permeability of 6-carboxyfluorescein, betaxolol and FITC-dextran (40kDa) and active transport of 6-carboxyfluorescein, sodium fluorescein, rhodamine 123, cyclosporine A and digoxin in ARPE-19 model were investigated and compared with isolated bovine RPE-choroid tissue. In addition, barrier properties, and mRNA expression of RPE-specific and melanogenesis-related genes (RPE65, VMD2, CRALBP, OTX-2, MITF-A, TRP-1, tyrosinase) were measured in various culture conditions. The filter grown ARPE-19 cell model showed reasonable barrier properties (TER close to 100Omegacm(2)), but its permeability was slightly higher than that of isolated bovine RPE/choroid specimens. In active transport studies the ARPE-19 model mimics qualitatively the permeability profile of bovine RPE-choroid, but ARPE-19 model underestimates the importance of active transport relative to passive diffusion. Long-term filter-cultured ARPE-19 cells expressed various RPE-specific and melanogenesis-related genes at higher levels than the ARPE-19 cells cultured short-term in flasks. ARPE-19 model can be used to study drug permeation processes in the RPE.
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24
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Vergarajauregui S, Martina JA, Puertollano R. Identification of the penta-EF-hand protein ALG-2 as a Ca2+-dependent interactor of mucolipin-1. J Biol Chem 2009; 284:36357-36366. [PMID: 19864416 DOI: 10.1074/jbc.m109.047241] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Loss of function mutations in mucolipin-1 (MCOLN1) have been linked to mucolipidosis type IV (MLIV), a recessive lysosomal storage disease characterized by severe neurological and ophthalmological abnormalities. MCOLN1 is an ion channel that regulates membrane transport along the endolysosomal pathway. It has been suggested that MCOLN1 participates in several Ca(2+)-dependent processes, including fusion of lysosomes with the plasma membrane, fusion of late endosomes and autophagosomes with lysosomes, and lysosomal biogenesis. Here, we searched for proteins that interact with MCOLN1 in a Ca(2+)-dependent manner. We found that the penta-EF-hand protein ALG-2 binds to the NH-terminal cytosolic tail of MCOLN1. The interaction is direct, strictly dependent on Ca(2+), and mediated by a patch of charged and hydrophobic residues located between MCOLN1 residues 37 and 49. We further show that MCOLN1 and ALG-2 co-localize to enlarged endosomes induced by overexpression of an ATPase-defective dominant-negative form of Vps4B (Vps4B(E235Q)). In agreement with the proposed role of MCOLN1 in the regulation of fusion/fission events, we found that overexpression of MCOLN1 caused accumulation of enlarged, aberrant endosomes that contain both early and late endosome markers. Interestingly, aggregation of abnormal endosomes was greatly reduced when the ALG-2-binding domain in MCOLN1 was mutated, suggesting that ALG-2 regulates MCOLN1 function. Overall, our data provide new insight into the molecular mechanisms that regulate MCOLN1 activity. We propose that ALG-2 acts as a Ca(2+) sensor that modulates the function of MCOLN1 along the late endosomal-lysosomal pathway.
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Affiliation(s)
- Silvia Vergarajauregui
- Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892
| | - Jose A Martina
- Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892
| | - Rosa Puertollano
- Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892.
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Sunkara G, Ayalasomayajula SP, DeRuiter J, Kompella UB. Probenecid treatment enhances retinal and brain delivery of N-4-benzoylaminophenylsulfonylglycine: an anionic aldose reductase inhibitor. Brain Res Bull 2009; 81:327-32. [PMID: 19761819 DOI: 10.1016/j.brainresbull.2009.09.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2009] [Revised: 09/02/2009] [Accepted: 09/03/2009] [Indexed: 01/21/2023]
Abstract
Anion efflux transporters are expected to minimize target tissue delivery of N-[4-(benzoylaminophenyl)sulfonyl]glycine (BAPSG), a novel carboxylic acid aldose reductase inhibitor, which exists as a monocarboxylate anion at physiological conditions. Therefore, the objective of this study was to determine whether BAPSG delivery to various eye tissues including the retina and the brain can be enhanced by probenecid, a competitive inhibitor of anion transporters. To determine the influence of probenecid on eye and brain distribution of BAPSG, probenecid was administered intraperitoneally (120 mg/kg body weight; i.p.) 20 min prior to BAPSG (50 mg/kg; i.p.) administration. Drug disposition in various eye tissues including the retina and the brain was determined at 15 min, 1, 2 and 4h after BAPSG dose in male Sprauge-Dawley rats. To determine whether probenecid alters plasma clearance of BAPSG, influence of probenecid (120 mg/kg; i.p.) on the plasma pharmacokinetics of intravenously administered BAPSG (15 mg/kg) was studied as well. Finally, the effect of probenecid co-administration on the ocular tissue distribution of BAPSG was assessed in rabbits following topical (eye drop) administration. Following pretreatment with probenecid in the rat study, retinal delivery at 1h was increased by about 11-fold (2580 ng/g vs. 244 ng/g; p<0.05). Further, following probenecid pretreatment, significant BAPSG levels were detectable in the brain (45 + or - 20 ng/g) at 1h, unlike controls where the drug was not detectable. Plasma concentrations, plasma elimination half-life, and total body clearance of intravenously administered BAPSG were not altered by i.p. probenecid pretreatment. In the topical dosing study, a significant decline in BAPSG delivery was observed in the iris-ciliary body but no significant changes were observed in other tissues of the anterior segment of the eye including tears. Thus, inhibition of anion transporters is a useful approach to elevate retinal and brain delivery of BAPSG.
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26
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Martina JA, Lelouvier B, Puertollano R. The calcium channel mucolipin-3 is a novel regulator of trafficking along the endosomal pathway. Traffic 2009; 10:1143-56. [PMID: 19497048 DOI: 10.1111/j.1600-0854.2009.00935.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The varitint-waddler phenotype in mice is caused by gain-of-function mutations in mucolipin-3 (MCOLN3), a member of the mucolipin family of ion channels. These mice are characterized by defects in pigmentation, hearing loss and vestibular defects, suggesting that MCOLN3 might play a role in melanosome trafficking and hair cell maturation. Recent evidence has shown that MCOLN3 is a Ca(2+)-permeable channel and its activity is regulated by pH. Here we show that MCOLN3 primarily localizes to early and late endosomes in human epithelial cells. This distribution at the less acidic portions of the endocytic pathway is consistent with the reported inactivation of the channel by low pH. Furthermore, overexpression of MCOLN3 causes dramatic alterations in the endosomal pathway, including enlargement of Hrs-positive endosomes, delayed degradation of epidermal growth factor (EGF) and EGF receptor (EGFR) and defective autophagosome maturation, whereas depletion of endogenous MCOLN3 enhances EGFR degradation. Finally, we found that endosomal pH is higher in cells overexpressing MCOLN3 and propose a model in which Ca(2+) release from endosomes mediated by MCOLN3 might be important for efficient endosomal acidification. Therefore, MCOLN3 is a novel Ca(2+) channel that plays a crucial role in the regulation of cargo trafficking along the endosomal pathway.
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Affiliation(s)
- Jose A Martina
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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27
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Mannermaa E, Vellonen KS, Ryhänen T, Kokkonen K, Ranta VP, Kaarniranta K, Urtti A. Efflux protein expression in human retinal pigment epithelium cell lines. Pharm Res 2009; 26:1785-91. [PMID: 19384462 DOI: 10.1007/s11095-009-9890-6] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Accepted: 04/02/2009] [Indexed: 12/15/2022]
Abstract
PURPOSE The objective of this study was to characterize efflux proteins (P-glycoprotein (P-gp), multidrug resistance proteins (MRP1-6) and breast cancer resistance protein (BCRP)) of retinal pigment epithelium (RPE) cell lines. METHODS Expression of efflux proteins in two secondary (ARPE-19, D407) and two primary (HRPEpiC and bovine) RPE cell lines was measured by quantitative RT-PCR and western blotting. Furthermore, activity of MRP1 and MRP5 of ARPE-19 cell line was assessed with calcein-AM and carboxydichlorofluorescein (CDCF) probes. RESULTS Similar efflux protein profile was shared between ARPE-19 and primary RPE cells, whereas D407 cell line was notably different. D407 cells expressed MRP2 and BCRP, which were absent in other cell lines and furthermore higher MRP3 transcript expression was found. MRP1, MRP4 and MRP5 were identified from all human RPE cell lines and MRP6 was not expressed in any cell lines. The pattern of efflux protein expression did not change when ARPE-19 cells were differentiated on filters. The calcein-AM and CDCF efflux tests provided evidence supporting MRP1 and MRP5 activity in ARPE-19 cells. CONCLUSIONS MRP1, MRP4 and MRP5 are the main efflux transporters in RPE cell lines. There are differences in efflux protein expression between RPE cell lines.
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Affiliation(s)
- Eliisa Mannermaa
- Department of Pharmaceutics, University of Kuopio, Yliopistonranta 1C, 70210 Kuopio, Finland.
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28
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Intraocular sustained-release delivery systems for triamcinolone acetonide. Pharm Res 2009; 26:770-84. [PMID: 19184374 DOI: 10.1007/s11095-008-9812-z] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Accepted: 12/11/2008] [Indexed: 02/06/2023]
Abstract
Recently, the use of triamcinolone acetonide (TA) injection has increased dramatically in treatment for several ocular diseases. Among them, macular diseases such as macular edema due to diabetic retinopathy, venous occlusive diseases, ocular inflammation and age-related macular degeneration (AMD) are very common vision threatening disorders and are great challenges to treat. In these types of chronic retinal diseases, repeated intraocular injections of TA are often required which increases the likelihood of complications. In order to achieve sustained-release, maintain therapeutic levels of TA over longer times and reduce frequency of intravitreal injections, researchers are investigating different implantable devices or injectable systems. However, as of yet, there is no sustained-release product for TA available on the commercial market. This review discusses and compares different sustained-release devices or injectable systems that are currently being developed.
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29
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Proksch JW, Ward KW. Cassette dosing pharmacokinetic studies for evaluation of ophthalmic drugs for posterior ocular diseases. J Pharm Sci 2008; 97:3411-21. [PMID: 17948915 DOI: 10.1002/jps.21188] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The purpose of this investigation was to evaluate the utility of cassette dosing as a means for increasing throughput and decreasing animal usage for intravitreal ocular pharmacokinetic studies. Pigmented rabbits received a single intravitreal injection of test article containing either a single compound or a mixture of up to five compounds. Samples of vitreous, choroid and retina were collected at predetermined intervals through 7 or 28 days after dosing. Concentrations of each compound were determined by LC/MS/MS, with subsequent pharmacokinetic data analysis. The ocular pharmacokinetic properties of four test compounds administered as a cassette were in agreement with the ocular pharmacokinetics of each compound when administered as a single entity. Cassette dosing was subsequently used to screen an additional 15 compounds, with injection of 5 compounds per study. Based on the results from these cassette-dosing studies, some compounds demonstrated favorable ocular pharmacokinetics, with sustained concentrations above 300 ng/g in retina for at least 1 week after dosing while other compounds showed either considerably less penetration into retina or a shorter residence time in the retina. These findings suggest that the cassette dosing approach can be used in evaluating the intravitreal ocular pharmacokinetic properties of compounds intended for ocular use.
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Affiliation(s)
- Joel W Proksch
- Global Preclinical Development, Bausch & Lomb, 1400 N. Goodman Street, Rochester, New York 14609, USA.
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30
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Hariharan S, Gunda S, Mishra GP, Pal D, Mitra AK. Enhanced corneal absorption of erythromycin by modulating P-glycoprotein and MRP mediated efflux with corticosteroids. Pharm Res 2008; 26:1270-82. [PMID: 18958406 DOI: 10.1007/s11095-008-9741-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Accepted: 09/29/2008] [Indexed: 12/17/2022]
Abstract
PURPOSE The objectives were (i) to test in vivo functional activity of MRP2 on rabbit corneal epithelium and (ii) to evaluate modulation of P-gp and MRP2 mediated efflux of erythromycin when co-administered with corticosteroids. METHODS Cultured rabbit primary corneal epithelial cells (rPCECs) was employed as an in vitro model for rabbit cornea. Cellular accumulation and bi-directional transport studies were conducted across Madin-Darby Canine Kidney (MDCK) cells overexpressing MDR1 and MRP2 proteins to delineate transporter specific interaction of steroids. Ocular pharmacokinetic studies were conducted in rabbits following a single-dose infusion of erythromycin in the presence of specific inhibitors and steroids. RESULTS Bi-directional transport of erythromycin across MDCK-MDR1 and MDCK-MRP2 cells showed significant difference between BL-AP and AP-BL permeability, suggesting that erythromycin is a substrate for P-gp and MRP2. Cellular accumulation of erythromycin in rPCEC was inhibited by steroids in a dose dependent manner. MK571, a specific MRP inhibitor, modulated the aqueous humor concentration of erythromycin in vivo. Even, steroids inhibited P-gp and MRP2 mediated efflux with maximum increase in k(a), AUC(0-infinity), C(max) and C(last) values of erythromycin, observed with 6alpha-methyl prednisolone. CONCLUSION MRP2 is functionally active along with P-gp in effluxing drug molecules out of corneal epithelium. Steroids were able to significantly inhibit both P-gp and MRP2 mediated efflux of erythromycin.
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Affiliation(s)
- Sudharshan Hariharan
- Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri-Kansas City, 5005 Rockhill Road, Kansas City, MO 64110, USA
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31
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Nevala H, Ylikomi T, Tähti H. Evaluation of the selected barrier properties of retinal pigment epithelial cell line ARPE-19 for an in-vitro blood-brain barrier model. Hum Exp Toxicol 2008; 27:741-9. [DOI: 10.1177/0960327107082230] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In-vitro models that maintain complex transport mechanisms and structural properties associated with the blood-brain barrier in vivo would be useful in drug permeability and neurotoxicological studies. To evaluate the suitability of a human retinal pigment epithelial cell line for a blood-brain barrier model, we have compared the barrier properties of the human retinal pigment epithelial cell line ARPE-19, the human colonic adenocarcinoma cell line Caco-2, and primary porcine microvessel endothelial cells. The tight junction proteins occludin and ZO-1 were stained immunocytochemically. The paracellular ionic permeability was evaluated by measuring the trans-epithelial or trans-endothelial electric resistance. To evaluate the active transport mechanisms, the existence and the activity of the efflux transporters, P-glycoprotein and multidrug resistance-associated proteins, were studied. All the cell types in this study stained positively for occludin and ZO-1. However, the trans-endothelial electric resistance of ARPE-19 cells was low compared with that of primary porcine microvessel endothelial cell and Caco-2 cells. In addition, both the P-glycoprotein expression and its activity in ARPE-19 cells were low. In conclusion, the barrier properties of the human ARPE-19 cell line were not satisfactory for a blood-brain barrier model. For future studies, it is important to develop a human brain endothelial cell line with expression of the complex in-vivo properties of the blood-brain barrier.
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Affiliation(s)
- H Nevala
- Medical School, Cell Research Center, University of Tampere, Finland
| | - T Ylikomi
- Medical School, Cell Research Center, University of Tampere, Finland; Tampere University Hospital, Tampere, Finland
| | - H Tähti
- Medical School, Cell Research Center, University of Tampere, Finland
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Abstract
Anatomy and physiology of the eye makes it a highly protected organ. Designing an effective therapy for ocular diseases, especially for the posterior segment, has been considered as a formidable task. Limitations of topical and intravitreal route of administration have challenged scientists to find alternative mode of administration like periocular routes. Transporter targeted drug delivery has generated a great deal of interest in the field because of its potential to overcome many barriers associated with current therapy. Application of nanotechnology has been very promising in the treatment of a gamut of diseases. In this review, we have briefly discussed several ocular drug delivery systems such as microemulsions, nanosuspensions, nanoparticles, liposomes, niosomes, dendrimers, implants, and hydrogels. Potential for ocular gene therapy has also been described in this article. In near future, a great deal of attention will be paid to develop non-invasive sustained drug release for both anterior and posterior segment eye disorders. A better understanding of nature of ocular diseases, barriers and factors affecting in vivo performance, would greatly drive the development of new delivery systems. Current momentum in the invention of new drug delivery systems hold a promise towards much improved therapies for the treatment of vision threatening disorders.
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Meletiadis J, Chanock S, Walsh TJ. Defining targets for investigating the pharmacogenomics of adverse drug reactions to antifungal agents. Pharmacogenomics 2008; 9:561-84. [DOI: 10.2217/14622416.9.5.561] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Adverse drug reactions (ADRs) associated with antifungal therapy are major problems in patients with invasive fungal infections. Whether by clinical history or patterns of genetic variation, the identification of patients at risk for ADRs should result in improved outcomes while minimizing deleterious side effects. A major contributing factor to ADRs with antifungal agents relates to drug distribution, metabolism and excretion. Genetic variation in key genes can alter the structure and expression of genes and gene products (e.g., proteins). Thus far, the effort has focused on identifying polymorphisms with either empirical or predicted in silico functional consequences; the best candidate genes encode phase I and II drug-metabolizing enzymes (e.g., CYP2C19 and N-acetyltransferase), plasma proteins (albumin and lipoproteins) and drug transporters (P-glycoprotein and multidrug resistance proteins), which can affect the disposition of antifungal agents, eventually leading to dose-dependent (type A) toxicity. Less is known regarding the key genes that interact with antifungal agents, resulting in idiosyncratic (type B) ADRs. The possible role of certain gene products and genetic polymorphisms in the toxicities of antifungal agents are discussed in this review. The preliminary data address the following: low-density lipoproteins and cholesteryl ester transfer protein in amphotericin B renal toxicity; toll-like receptor 1 and 2 in amphotericin B infusion-related ADRs; phosphodiesterase 6 in voriconazole visual adverse events; flavin-containing monooxygenase, glutathione transferases and multidrug resistance proteins 1 and 2 in ketoconazole and terbinafine hepatotoxicity; CYP enzymes and P-glycoprotein in drug interactions between azoles and coadministered medications; multidrug resistance proteins 8 and 9 on 5-flucytosine bone marrow toxicity; and mast cell activation in caspofungin histamine release. This will focus on high-priority candidate genes, which could provide a starting point for molecular studies to elucidate the potential mechanisms for understanding toxicity associated with antifungal drugs as well as identifying candidate genes for large population prospective genetic association studies.
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Affiliation(s)
- Joseph Meletiadis
- National Cancer Institute, National Institutes of Health, Pediatric Oncology Branch, Bethesda, MD 20814, USA
- Attikon University General Hospital, Laboratoty for Clinical Microbiology, 1 Rimini Street, Athens 124 62, Greece
| | - Stephen Chanock
- National Cancer Institute, National Institutes of Health, Pediatric Oncology Branch, Bethesda, MD 20814, USA
| | - Thomas J Walsh
- National Cancer Institute, National Institutes of Health, Pediatric Oncology Branch, Bethesda, MD 20814, USA
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Zhang T, Xiang CD, Gale D, Carreiro S, Wu EY, Zhang EY. Drug transporter and cytochrome P450 mRNA expression in human ocular barriers: implications for ocular drug disposition. Drug Metab Dispos 2008; 36:1300-7. [PMID: 18411399 DOI: 10.1124/dmd.108.021121] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Studies were designed to quantitatively assess the mRNA expression of 1) 10 cytochrome P450 (P450) enzymes in human cornea, iris-ciliary body (ICB), and retina/choroid relative to their levels in the liver, and of 2) 21 drug transporters in these tissues relative to their levels in human small intestine, liver, or kidney. Potential species differences in mRNA expression of PEPT1, PEPT2, and MDR1 were also assessed in these ocular tissues from rabbit, dog, monkey, and human. P450 expression was either absent or marginal in human cornea, ICB, and retina/choroid, suggesting a limited role for P450-mediated metabolism in ocular drug disposition. In contrast, among 21 key drug efflux and uptake transporters, many exhibited relative expression levels in ocular tissues comparable with those observed in small intestine, liver, or kidney. This robust ocular transporter presence strongly suggests a significant role that transporters may play in ocular barrier function and ocular pharmacokinetics. The highly expressed efflux transporter MRP1 and uptake transporters PEPT2, OCT1, OCTN1, and OCTN2 may be particularly important in absorption, distribution, and clearance of their drug substrates in the eye. Evidence of cross-species ocular transporter expression differences noted in these studies supports the conclusion that transporter expression variability, along with anatomic and physiological differences, should be taken into consideration to better understand animal ocular pharmacokinetic and pharmacodynamic data and the scalability to human for ocular drugs.
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Affiliation(s)
- Tao Zhang
- College of Pharmacy, the Ohio State University, Columbus, Ohio, USA
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Abstract
Research into treatment modalities affecting vision is rapidly progressing due to the high incidence of diseases such as diabetic macular edema, proliferative vitreoretinopathy, wet and dry age-related macular degeneration and cytomegalovirus retinitis. The unique anatomy and physiology of eye offers many challenges to developing effective retinal drug delivery systems. Historically, drugs have been administered to the eye as liquid drops instilled in the cul-de-sac. However retinal drug delivery is a challenging area. The transport of molecules between the vitreous/retina and systemic circulation is restricted by the blood-retinal barrier, which is made up of retinal pigment epithelium and endothelial cells of the retinal blood vessels. An increase in the understanding of drug absorption mechanisms into the retina from local and systemic administration has led to the development of various drug delivery systems, such as biodegradable and non-biodegradable implants, microspheres, nanoparticles and liposomes, gels and transporter-targeted prodrugs. Such diversity in approaches is an indication that there is still a need for an optimized noninvasive or minimally invasive drug delivery system to the eye. A number of large molecular weight compounds (i.e., oligonucleotides, RNA aptamers, peptides and monoclonal antibodies) have been and continue to be introduced as new therapeutic entities. However, for high molecular weight polar compounds the mechanism of epithelial transport is primarily through the tight junctions in the retinal pigment epithelium, as these agents undergo limited transcellular diffusion. Delivery and administration of these new drugs in a safe and effective manner is still a major challenge facing pharmaceutical scientists. In this review article, the authors discuss various drug delivery strategies, devices and challenges associated with drug delivery to the retina.
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Affiliation(s)
- Kumar G Janoria
- University of Missouri-Kansas City, Department of Pharmaceutical Sciences, School of Pharmacy, 5005 Rockhill Road, Kansas City, MO 64110, USA
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Kim SH, Lutz RJ, Wang NS, Robinson MR. Transport barriers in transscleral drug delivery for retinal diseases. Ophthalmic Res 2007; 39:244-54. [PMID: 17851264 DOI: 10.1159/000108117] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Accepted: 06/06/2007] [Indexed: 12/16/2022]
Abstract
Transscleral delivery has emerged as an attractive method for treating retinal disorders because it offers localized delivery of drugs as a less invasive method compared to intravitreal administration. Numerous novel transscleral drug delivery systems ranging from microparticles to implants have been reported. However, transscleral delivery is currently not as clinically effective as intravitreal delivery in the treatment of retinal diseases. Transscleral drug delivery systems require drugs to permeate through several layers of ocular tissue (sclera, Bruch's membrane-choroid, retinal pigment epithelium) to reach the neuroretina. As a result, a steep drug concentration gradient from the sclera to the retina is established, and very low concentrations of drug are detected in the retina. This steep gradient is created by the barriers to transport that hinder drug molecules from successfully reaching the retina. A review of the literature reveals 3 types of barriers hindering transscleral drug delivery: static, dynamic and metabolic. While static barriers have been examined in detail, the literature on dynamic and metabolic barriers is lacking. These barriers must be investigated further to gain a more complete understanding of the transport barriers involved in transscleral drug delivery.
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Affiliation(s)
- Stephanie H Kim
- Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD 20892-5766, USA.
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Subramanian VS, Mohammed ZM, Molina A, Marchant JS, Vaziri ND, Said HM. Vitamin B1 (thiamine) uptake by human retinal pigment epithelial (ARPE-19) cells: mechanism and regulation. J Physiol 2007; 582:73-85. [PMID: 17463047 PMCID: PMC2075275 DOI: 10.1113/jphysiol.2007.128843] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Accepted: 04/23/2007] [Indexed: 01/19/2023] Open
Abstract
Retinal abnormality and visual disturbances occur in thiamine-responsive megaloblastic anaemia (TRMA), an autosomal recessive disorder caused by mutations in the human thiamine transporter-1 (hTHTR-1). Human retinal pigment epithelial cells play a pivotal role in supplying thiamine to the highly metabolically active retina but nothing is known about the mechanism, regulation or biological processes involved in thiamine transport in these cells. To address these issues, we used human-derived retinal pigment epithelial ARPE-19 cells to characterize the thiamine uptake process. Thiamine uptake is energy- and temperature-dependent, pH-sensitive, Na+-independent, saturable at both the nanomolar (apparent Km, 30 +/- 5 nM) and the micromolar (apparent Km, 1.72 +/- 0.3 microM) concentration ranges, specific for thiamine and sensitive to sulfhydryl group inhibition. The diuretic amiloride caused a concentration-dependent inhibition in thiamine uptake, whereas the anti-trypanosomal drug, melarsoprol, failed to affect the uptake process. Both hTHTR-1 and hTHTR-2 are expressed in ARPE-19 cells as well as in native human retinal tissue with expression of the former being significantly higher than that of the latter. Uptake of thiamine was adaptively regulated by extracellular substrate level via transcriptionally mediated mechanisms that involve both hTHTR-1 and hTHTR-2; it was also regulated by an intracellular Ca2+-calmodulin-mediated pathway. Confocal imaging of living ARPE-19 cells expressing TRMA-associated hTHTR-1 mutants (D93H, S143F and G172D) showed various expression phenotypes. These results demonstrate for the first time the existence of a specialized and regulated uptake process for thiamine in a cellular model of human retinal pigment epithelia that involves hTHTR-1 and hTHTR-2. Further, clinically relevant mutations in hTHTR-1 lead to impaired cell surface expression or function of the transporter in retinal epithelial ARPE-19 cells.
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Becker U, Ehrhardt C, Daum N, Baldes C, Schaefer UF, Ruprecht KW, Kim KJ, Lehr CM. Expression of ABC-transporters in human corneal tissue and the transformed cell line, HCE-T. J Ocul Pharmacol Ther 2007; 23:172-81. [PMID: 17444805 DOI: 10.1089/jop.2006.0095] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
PURPOSE The aim of this study was to elucidate the expression pattern of transport proteins relevant to drug absorption in human cornea and to assess the human corneal epithelial cell line, HCE-T, regarding its use as an in vitro model for drug-absorption studies. METHODS Human corneal tissue and HCE-T cells were examined for the expression of P-glycoprotein (P-gp/MDR1), multidrug resistance-associated protein 1 (MRP1), multidrug resistance-associated protein 2 (MRP2), lung resistance-related protein (LRP), and breast cancer-resistance protein (BCRP), using reverse transcriptase-polymerase chain reaction and immunofluorescence microscopy. Moreover, transporter activity was measured by bi-directional flux studies across excised human cornea and HCE-T cell layers using a P-gp/MDR1 substrate, rhodamine 123 (Rh123). RESULTS Transport studies of Rh123 revealed no significant differences in fluxes in the apical-to-basolateral and basolateral-to-apical directions across excised human corneas or HCE-T cell layers, suggesting the absence or insignificant, if any, participation of P-gp/MDR1 to Rh123 fluxes. Of all the transporter proteins under investigation, only LRP was found in human cornea. By contrast, a signal for LRP was not found in HCE-T, but the expression of MRP1, MRP2, and BCRP could be confirmed. Of note is the lack of P-gp/MDR1 expression in any of the specimens we examined. CONCLUSIONS Only a limited array of ABC-transporters is functionally expressed in human cornea. The expression pattern of HCE-T cells appears to be widely different from that of the native corneal tissue. Hence, the in vitro model of human cornea, HCE-T, should be used with much caution when predicting transport rates across the human corneal epithelial barrier in vivo.
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Affiliation(s)
- Ulrich Becker
- Department of Biopharmaceutics and Pharmaceutical Technology, Saarland University, Saarbrücken, Germany
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Yang JJ, Ann DK, Kannan R, Lee VHL. Multidrug resistance protein 1 (MRP1) in rabbit conjunctival epithelial cells: its effect on drug efflux and its regulation by adenoviral infection. Pharm Res 2007; 24:1490-500. [PMID: 17404811 DOI: 10.1007/s11095-007-9267-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2006] [Accepted: 02/08/2007] [Indexed: 01/02/2023]
Abstract
PURPOSE To evaluate the expression, localization, function, and regulation of multidrug resistance protein (MRP1) in rabbit conjunctival epithelial cells (RCEC). MATERIALS AND METHODS MRP1 gene expression in RCEC was determined by reverse transcription-polymerase chain reaction (RT-PCR), and MRP1 protein expression and its localization were determined by Western blot analysis and immunofluorescence using an anti-MRP1 monoclonal antibody, MRPr1. The effect of MRP1 on the transport and uptake of fluorescein was evaluated in RCEC grown on Transwell filters. Moreover, the effect of adenovirus type 5 (Ad5)-infected RCEC, and cytokines (Interleukin 1 (IL-1), IL-6, and tumor necrosis factor alpha (TNFalpha)) on MRP1 expression and leukotriene C4 (LTC4) uptake were investigated. RESULTS A 652 bp RT-PCR product from rabbit conjunctiva showed a 87% homology to human MRP1. Immunostaining with MRPr1 revealed a predominant basolateral localization of MRP1 in RCEC. Uptake of fluorescein, a MRP1 substrate, was increased (203-290%) in the presence of uricosuric drug probenecid at 100 microM, anti-inflammatory drug indomethacin at 10 microM and diclofenac, flurbiprofen, and ofloxacin at 1 mM, and by ATP depletion, but not influenced by the depletion of GSH, and the presence of antiviral cidofovir and anti-inflammatory drug cromolyn and prednisolone. Apical-to-basolateral facilitated transport of LTC4 was abolished in the presence of probenecid. Western blot analysis with MRPr1 revealed a distinct band at approximately 190 kDa for freshly isolated and cultured RCEC. Both Ad5 and cytokines (IL-1, IL-6, and TNF-alpha) up-regulated MRP1 expression, thereby reducing LTC4 uptake. CONCLUSIONS MRP1 appears to be primarily localized in the basolateral membrane of RCEC and function in the efflux of certain organic anions and inflammatory factors out of cells from the basolateral membrane. The upregulation in the expression of MRP1 by Ad5-infection and cytokines suggests a role of MRP1 in the transport of inflammatory factors during ocular inflammation. Supported by NIH grants EY12578, EY10421, and EY12356.
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Affiliation(s)
- Johnny J Yang
- Department of Pharmaceutical Sciences, University of Southern California, Los Angeles, CA 90089-9121, USA.
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Mannermaa E, Vellonen KS, Urtti A. Drug transport in corneal epithelium and blood-retina barrier: emerging role of transporters in ocular pharmacokinetics. Adv Drug Deliv Rev 2006; 58:1136-63. [PMID: 17081648 DOI: 10.1016/j.addr.2006.07.024] [Citation(s) in RCA: 219] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2006] [Accepted: 07/31/2006] [Indexed: 12/12/2022]
Abstract
Corneal epithelium and blood-retina barrier (i.e. retinal capillaries and retinal pigment epithelium (RPE)) are the key membranes that regulate the access of xenobiotics into the ocular tissues. Corneal epithelium limits drug absorption from the lacrimal fluid into the anterior chamber after eyedrop administration, whereas blood-retina barrier restricts the entry of drugs from systemic circulation to the posterior eye segment. Like in general pharmacokinetics, the role of transporters has been considered to be quite limited as compared to the passive diffusion of drugs across the membranes. As the functional role of transporters is being revealed it has become evident that the transporters are widely important in pharmacokinetics. This review updates the current knowledge about the transporters in the corneal epithelium and blood-retina barrier and demonstrates that the information is far from complete. We also show that quite many ocular drugs are known to interact with transporters, but the studies about the expression and function of those transporters in the eye are still sparse. Therefore, the transporters probably have greater role in ocular pharmacokinetics than we currently realise.
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Affiliation(s)
- Eliisa Mannermaa
- Department of Pharmaceutics, University of Kuopio, FIN-70211 Kuopio, Finland
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Cheruvu NPS, Kompella UB. Bovine and porcine transscleral solute transport: influence of lipophilicity and the Choroid-Bruch's layer. Invest Ophthalmol Vis Sci 2006; 47:4513-22. [PMID: 17003447 PMCID: PMC3324974 DOI: 10.1167/iovs.06-0404] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
PURPOSE To determine the influence of the choroid-Bruch's layer and solute lipophilicity on in vitro transscleral drug permeability in bovine and porcine eyes. METHODS The in vitro permeability of two VEGF inhibitory drugs, budesonide and celecoxib, which are lipophilic and neutral at physiologic pH, and of three marker solutes, 3H-mannitol (hydrophilic, neutral), sodium fluorescein (hydrophilic, anionic), and rhodamine 6G (lipophilic, cationic), were determined across freshly excised scleras, with or without the underlying choroid-Bruch's layer. Select studies were performed using porcine sclera with and without choroid-Bruch's layer. Neural retina was removed by exposure of the eyecup to isotonic buffer and wherever required, the retinal pigment epithelial (RPE) layer of the preparation was disrupted and removed by exposure to hypertonic buffer. Because of the poor solubility of celecoxib and budesonide, permeability studies were conducted with 5% wt/vol of hydroxypropyl-beta-cyclodextrin (HPbetaCD). For other solutes, permeability studies were conducted, with and without HPbetaCD. Partitioning of the solutes into bovine sclera and choroid-Bruch's layer was also determined. RESULTS The calculated log (distribution coefficient) values were -2.89, -0.68, 2.18, 3.12, and 4.02 for mannitol, sodium fluorescein, budesonide, celecoxib, and rhodamine 6G, respectively. Removal of RPE was confirmed by transmission electron microscopy and differences in the transport of mannitol. The order of the permeability coefficients (Papp) across sclera and sclera-choroid-Bruch's layers in bovine and porcine models was 3H-mannitol > fluorescein > budesonide > celecoxib > rhodamine 6G, with HPbetaCD, and 3H-mannitol > fluorescein > rhodamine 6G, without HPbetaCD. The presence of choroid-Bruch's layer reduced the bovine scleral permeability by 2-, 8-, 16-, 36-, and 50-fold and porcine tissue permeability by 2-, 7-, 15-, 33-, and 40-fold, respectively, for mannitol, sodium fluorescein, budesonide, celecoxib, and rhodamine 6G. The partition coefficients measured in bovine tissues correlated positively with the log (distribution coefficient) and exhibited a trend opposite that of transport. The partition coefficient ratio of bovine choroid-Bruch's layer to sclera was approximately 1, 1.5, 1.7, 2, and 3.5, respectively, for the solutes, as listed earlier. CONCLUSIONS The choroid-Bruch's layer is a more significant barrier to drug transport than is sclera. It hinders the transport of lipophilic solutes, especially a cationic solute, more than hydrophilic solutes and in a more dramatic way than does sclera. The reduction in transport across this layer directly correlates with solute binding to the tissue. Understanding the permeability properties of sclera and underlying layers would be beneficial in designing better drugs for transscleral delivery.
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Affiliation(s)
- Narayan P. S. Cheruvu
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, Nebraska
| | - Uday B. Kompella
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, Nebraska
- Department of Ophthalmology, University of Nebraska Medical Center, Omaha, Nebraska
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Constable PA, Lawrenson JG, Dolman DEM, Arden GB, Abbott NJ. P-Glycoprotein expression in human retinal pigment epithelium cell lines. Exp Eye Res 2006; 83:24-30. [PMID: 16530756 DOI: 10.1016/j.exer.2005.10.029] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2005] [Revised: 10/14/2005] [Accepted: 10/21/2005] [Indexed: 12/28/2022]
Abstract
P-Glycoprotein (P-gp), an active efflux transporter encoded by the MDR1 gene, has recently been identified in the human and pig retinal pigment epithelium (RPE) in situ. Efflux pumps such as P-gp are major barriers to drug delivery in several tissues. We wished to establish whether human RPE cell lines express P-gp under the culture conditions recommended for each cell line so as to determine their suitability as in vitro models for predicting drug transport across the outer blood-retinal barrier. Three human RPE cell lines, ARPE19, D407 and h1RPE were investigated. Reverse transcriptase-polymerase chain reaction (RT-PCR) was carried out to determine the expression of MDR1 mRNA. Immunocytochemistry using the P-gp-specific antibody C219 was undertaken to investigate the presence of P-gp protein in each cell type. Uptake of rhodamine 123, a P-gp substrate, in the presence or absence of pre-treatment with a P-gp inhibitor, verapamil, was measured in each cell line to determine functional expression of P-gp. For all experiments, MDCK cells stably transfected with the human MDR1 gene (MDCK-MDR1) were used as a positive control. ARPE19 cells were consistently negative for P-gp as assessed by RT-PCR and immunocytochemistry. By contrast, RT-PCR of D407 and h1RPE samples yielded weak bands corresponding to MDR1; P-gp protein expression, as demonstrated by C219 immunoreactivity, was also present. Rhodamine uptake after treatment with verapamil was significantly greater in D407 and MDCK-MDR1, indicating functional expression of P-gp in these two cell lines. No evidence of functional P-gp was found in ARPE19 and h1RPE. In conclusion, D407 and h1RPE cells express P-gp, though functional activity was demonstrable only in D407 cells. ARPE19 cells do not express P-gp. Of these human RPE cells lines D407 could be considered as a suitable model for in vitro drug transport studies, particularly those involving P-gp substrates, without modification of their usual culture conditions.
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Affiliation(s)
- Paul A Constable
- Department of Optometry and Visual Science, Henry Wellcome Laboratories for Vision Sciences, Applied Vision Research Centre, City University, Northampton Square, London EC1V OHB, UK.
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Attar M, Shen J, Ling KHJ, Tang-Liu D. Ophthalmic drug delivery considerations at the cellular level: drug-metabolising enzymes and transporters. Expert Opin Drug Deliv 2005; 2:891-908. [PMID: 16296785 DOI: 10.1517/17425247.2.5.891] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Ophthalmic drugs typically achieve < 10% ocular bioavailability. A drug applied to the surface of the eye may cross ocular-blood barriers where it may encounter metabolising enzymes and cellular transporters before it distributes to the site of action. Characterisation of ocular enzyme systems and cellular transporters and their respective substrate selectivity have provided new insight into the roles these proteins may play in ocular drug delivery and distribution. Altered metabolism and transport have been proposed to contribute to a number of ocular disease processes including inflammation, glaucoma, cataract, dry eye and neurodegeneration. As ocular enzyme and transport systems are better characterised, their properties become an integral consideration in drug design and development.
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Affiliation(s)
- Mayssa Attar
- Allergan, Inc., Department of Pharmacokinetics and Drug Metabolism, Irvine, CA 92612, USA
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Majumdar S, Gunda S, Pal D, Mitra AK. Functional activity of a monocarboxylate transporter, MCT1, in the human retinal pigmented epithelium cell line, ARPE-19. Mol Pharm 2005; 2:109-17. [PMID: 15804185 DOI: 10.1021/mp0499050] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The purpose of this study was to identify and characterize the functional activity of monocarboxylic acid transporter 1 (MCT1) on the human retinal pigmented epithelium (RPE) cell line, ARPE-19, and to evaluate whether the cell line can function as an in vitro screening tool for intravitreally administered drugs/prodrugs targeted to the MCT1 expressed in RPE. Uptake studies were carried out at 37 degrees C, for 30 s, with ARPE-19 cells. [(14)C]l-Lactic acid was selected as a substrate for this transporter. Uptake of [(14)C]L-lactic acid by ARPE-19 cells was found to exhibit saturable kinetics (K(m) = 3.1 +/- 0.6 mM and V(max) = 63.1 +/- 4.1 pmol/min/mg of protein). Monocarboxylic acids, such as benzoic acid, salicylic acid, and pyruvic acid, inhibited the uptake of [(14)C]L-lactic acid whereas di- and tricarboxylic acids, such as phthalic, succinic, and citric acids, did not demonstrate any inhibitory effect. Uptake was stereospecific where D-lactic acid was less effective in inhibiting [(14)C]L-lactic acid uptake than unlabeled L-lactic acid. ELISA indicated the expression of only MCT1, MCT4, and MCT8 isoforms by ARPE-19 cells. Increase in [(14)C]L-lactic acid uptake was observed as the uptake medium pH was lowered from 7.4 to 5.0. Moreover, inhibition of [(14)C]L-lactic acid uptake was observed in the presence of the protonophore 2,4-dinitrophenol. Uptake was significantly decreased in the presence of sodium azide, ouabain, p-chloromercuribenzoic acid (pCMBA), N-ethylmaleamide, dithiothreitol, and p-chloromercuribenzene sulfonate (pCMBS). However, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and L-thyroxine did not inhibit [(14)C]L-lactic acid. RT-PCR studies and sequence analysis of the PCR product confirmed the expression of MCT1 by ARPE-19 cells. Our results indicate that MCT1 is functionally active and is the only MCT isoform involved in the apical uptake of monocarboxylates by ARPE-19 cells. This cell line may thus be used as an effective screening tool for intravitreally administered drugs/prodrugs targeted toward MCT1 expressed on the RPE.
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Affiliation(s)
- Soumyajit Majumdar
- Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri-Kansas City, 5005 Rockhill Road, Kansas City, MO 64110, USA
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Said HM, Wang S, Ma TY. Mechanism of riboflavin uptake by cultured human retinal pigment epithelial ARPE-19 cells: possible regulation by an intracellular Ca2+-calmodulin-mediated pathway. J Physiol 2005; 566:369-77. [PMID: 15878949 PMCID: PMC1464759 DOI: 10.1113/jphysiol.2005.085811] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In mammalian cells (including those of the ocular system), the water-soluble vitamin B2 (riboflavin, RF) assumes an essential role in a variety of metabolic reactions and is critical for normal cellular functions, growth and development. Cells of the human retinal pigment epithelium (hRPE) play an important role in providing a sufficient supply of RF to the retina, but nothing is known about the mechanism of the vitamin uptake by these cells and its regulation. Our aim in the present study was to address this issue using the hRPE ARPE-19 cells as the retinal epithelial model. Our results show RF uptake in the hRPE to be: (1) energy and temperature dependent and occurring without metabolic alteration in the transported substrate, (2) pH but not Na+ dependent, (3) saturable as a function of concentration with an apparent Km of 80 +/- 14 nM, (4) trans-stimulated by unlabelled RF and its structural analogue lumiflavine, (5) cis-inhibited by the RF structural analogues lumiflavine and lumichrome but not by unrelated compounds, and (6) inhibited by the anion transport inhibitors 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) and 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonic acid (SITS) as well as by the Na+ -H+ exchange inhibitor amiloride and the sulfhydryl group inhibitor p-chloromercuriphenylsulphonate (p-CMPS). Maintaining the hRPE cells in a RF-deficient medium led to a specific and significant up-regulation in RF uptake which was mediated via changes in the number and affinity of the RF uptake carriers. While modulating the activities of intracellular protein kinase A (PKA)-, protein kinase C (PKC)-, protein tyrosine kinase (PTK)-, and nitric oxide (NO)-mediated pathways were found to have no role in regulating RF uptake, a role for the Ca2+ -calmodulin-mediated pathway was observed. These studies demonstrate for the first time the involvement of a specialized carrier-mediated mechanism for RF uptake by hRPE cells and show that the process is adaptively regulated in RF deficiency, and also appears to be under the regulation of an intracellular Ca2+ -calmodulin-mediated pathway.
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Affiliation(s)
- Hamid M Said
- VA Medical Center-151, Long Beach, CA 90822, USA.
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Gandhi MD, Pal D, Mitra AK. Identification and functional characterization of a Na(+)-independent large neutral amino acid transporter (LAT2) on ARPE-19 cells. Int J Pharm 2004; 275:189-200. [PMID: 15081149 DOI: 10.1016/j.ijpharm.2004.01.035] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2003] [Revised: 01/27/2004] [Accepted: 01/27/2004] [Indexed: 12/21/2022]
Abstract
The objective of this study was to investigate the presence of a large neutral amino acid transporter on the ARPE-19 cell line. ARPE-19 cells were grown on 24-well plates for uptake studies. Uptake characteristics of [3H]L-phenylalanine (L-Phe) were determined at various concentrations and pH at 37 degrees C. Inhibition studies were conducted in presence of L- and D-amino acids, metabolic inhibitors, like ouabain, sodium azide, and in presence of sodium-free medium, to delineate the mechanism of uptake. RT-PCR was carried out on total RNA isolated from the ARPE-19 cells. Presence of Na(+)-free buffer did reduce the uptake rate. Hence, all experiments were carried out in Na(+)-free medium to delineate the sodium-independent uptake mechanism. Uptake of L-Phe on ARPE cells was found to be saturable with a Km = 89.35 +/- 14 microM, Vmax = 58.9 +/- 2.5 pmol min(-1) mg protein(-1), and Kd = 0.108 +/- 0.04 microl min(-1) mg protein(-1). Dose-dependent inhibition was observed with increasing concentrations of unlabeled L-Phe. Uptake also was found to be energy independent. Significant inhibition of [3H]L-Phe was observed with large neutral aromatic and aliphatic amino acids as well as small neutral amino acids. System L-specific inhibitor BCH produced partial inhibition of uptake. Neither acidic nor basic amino acids altered the uptake rate. Results obtained were predominantly characteristic of LAT2, particularly with respect to substrate selectivity and pH dependence. Bands for LAT2 were detected by RT-PCR in the ARPE cell line. This study provides biochemical evidence of the presence of a Na(+)-independent, facilitative transport system, LAT2, on the ARPE-19 cells.
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Affiliation(s)
- Mohit D Gandhi
- Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri Kansas City, 5005 Rockhill Road, Kansas City, MO 64110-2499, USA
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Proulx S, Landreville S, Guérin SL, Salesse C. Integrin α5 expression by the ARPE-19 cell line: comparison with primary RPE cultures and effect of growth medium on the α5 gene promoter strength. Exp Eye Res 2004; 79:157-65. [PMID: 15325562 DOI: 10.1016/j.exer.2004.03.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2003] [Accepted: 03/08/2004] [Indexed: 11/22/2022]
Abstract
Primary cultures of human retinal pigment epithelium (RPE) requires young human donors with short post-mortem time and no known retinal diseases. The use of an established human RPE cell line, like ARPE-19, would be a welcomed alternative to primary cultures. This cell line retains many of the characteristics of RPE cells, including cell morphology, functional tight junctions and expression of CRALBP and RPE65. This study was conducted in order to investigate integrin alpha5 expression at both the gene and protein level in the ARPE-19 cell line and compare the results with those obtained with primary cultures of RPE cells. The potential use of this cell line as a substitute for primary cultures of RPE cells was also considered. Integrin alpha5 protein was detected on RPE and ARPE-19 cultures at different confluencies by immunofluorescence and immunoprecipitation analyses. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to study alpha5 mRNA levels. Transient transfections were performed in order to compare alpha5 promoter strength in both types of cells. Immunofluorescence studies showed that both primary RPE and ARPE-19 cells yielded similar alpha5 staining patterns at all cell confluencies. Both immunoprecipitation and RT-PCR analyses provided evidence that sub-confluent and confluent RPE and ARPE-19 cells have similar cell surface alpha5 protein and mRNA levels whereas post-confluent cells had a marked decrease in both protein and transcript levels. ARPE-19 cells show a large increase in promoter strength compared to primary cultures. When compared to primary cultures, the cell line exhibited major differences in the way the alpha5 promoter is regulated, even if both cell types are cultured under identical conditions. This study demonstrates that primary cultures of human RPE and ARPE-19 cells show reductions in both the alpha5 protein and the mRNA when cells reach post-confluency. However, major differences have been observed in the strength of the alpha5 promoter between both cell types. We also show that culturing ARPE-19 cells in a different growth medium alters the transcriptional activity directed by the alpha5 promoter.
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Affiliation(s)
- Stéphanie Proulx
- Unité de Recherche en Ophtalmologie, Centre de Recherche du CHUQ, Pavillon CHUL, Faculté de médecine, Université Laval, Salle S-5, 2705 Boul. Laurier, Ste-Foy, Que., Canada G1V 4G2
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Sunkara G, Ayalasomayajula SP, Rao CS, Vennerstrom JL, DeRuiter J, Kompella UB. Systemic and ocular pharmacokinetics of N-4-benzoylaminophenylsulfonylglycine (BAPSG), a novel aldose reductase inhibitor. J Pharm Pharmacol 2004; 56:351-8. [PMID: 15025860 PMCID: PMC4469078 DOI: 10.1211/0022357022908] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
To better develop N-[4-(benzoylamino)phenylsulfonyl]glycine (BAPSG), a potent and selective aldose reductase inhibitor capable of delaying the progression of ocular diabetic complications, the objective of this study was to assess its pharmacokinetics. The plasma pharmacokinetics of BASPG was assessed in male Sprague-Dawley rats following intravenous, intraperitoneal and oral routes of administration and its distribution to various tissues including those of the eye was studied following intraperitoneal administration. In addition, rat plasma protein binding of BAPSG was studied using ultracentrifugation method and its ocular tissue disposition was assessed following topical administration in rabbits. Plasma and tissue levels of BAPSG were analysed using an HPLC assay. BAPSG exhibited dose-proportionate AUC0 --> infinity (area under the plasma concentration-time curve) following both intravenous and intraperitoneal administration over the dose range (5-50 mg kg(-1)) studied and an erratic oral absorption profile with low oral bioavailability. The fraction bioavailability following oral and intraperitoneal administration was 0.06 and 0.7-1, respectively. BAPSG exhibited short plasma elimination half-lives in the range 0.5-1.5 h. BAPSG was bound to rat plasma proteins and the percent protein binding ranged from 83 to 99.8%. BAPSG was better distributed to cornea, lens and retina than to brain, following intraperitoneal administration in rats. However, the distribution was lower compared with kidney and liver. Following topical administration in rabbits, BAPSG delivery to the surface ocular tissues, cornea and conjunctiva was higher compared with intraocular tissues, aqueous humour, iris-ciliary body and lens. Thus, BAPSG was distributed to ocular tissues following systemic and topical modes of administration.
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Affiliation(s)
- Gangadhar Sunkara
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, NE 68198-6025, USA.
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Ocheltree SM, Keep RF, Shen H, Yang D, Hughes BA, Smith DE. Preliminary investigation into the expression of proton-coupled oligopeptide transporters in neural retina and retinal pigment epithelium (RPE): lack of functional activity in RPE plasma membranes. Pharm Res 2004; 20:1364-72. [PMID: 14567629 DOI: 10.1023/a:1025741723724] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE To determine the expression and functional activity of proton-coupled oligopeptide transporters (POT) in retinal pigment epithelial (RPE) cells. METHODS RT-PCR was used to probe the presence of POT mRNA in freshly isolated bovine RPE (BRPE) and human RPE (HRPE) cells, a human RPE cell line (ARPE-19), and human and bovine neural retina. [14C]GlySar uptake was used to characterize POT activity in cultured ARPE-19 cells and freshly isolated BRPE cell sheet suspensions. RESULTS PHT1 mRNA was expressed in BRPE, HRPE, ARPE-19, and bovine and human neural retina. In contrast, PEPT2 and PHT2 were expressed only in bovine and human retina, and PEPT1 could not be detected. GlySar exhibited a linear uptake over 6 h at pH values of 6.0 and 7.4, with greater uptake at pH 7.4 (p < 0.01). GlySar uptake did not exhibit saturability (5-2000 microM) and was unchanged when studied in the presence of 1 mM L-histidine. In contrast, GlySar uptake was significantly decreased when studied at 4 degrees C or in the presence of endocytic inhibitors at 37 degrees C (p < 0.01). Studies in BRPE cell sheet suspensions validated the results obtained in ARPE-19 cells and strongly suggested the absence of POT on the apical and basolateral membranes of RPE. CONCLUSIONS PHT1 mRNA is present in native bovine and human RPE and a human RPE cell line. However, the data argue against PHT1 being expressed on plasma membranes of RPE. Overall, GlySar appears to be taken up by RPE cells via a low-affinity, endocytic process.
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Affiliation(s)
- Scott M Ocheltree
- Department of Pharmaceutical Sciences, The University of Michigan, Ann Arbor, Michigan 48109-1065, USA
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