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Ramsay E, Montaser AB, Niitsu K, Urtti A, Auriola S, Huttunen KM, Uchida Y, Kidron H, Terasaki T. Transporter Protein Expression of Corneal Epithelium in Rabbit and Porcine: Evaluation of Models for Ocular Drug Transport Study. Mol Pharm 2024; 21:3204-3217. [PMID: 38809137 PMCID: PMC11474527 DOI: 10.1021/acs.molpharmaceut.3c01210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 05/14/2024] [Accepted: 05/15/2024] [Indexed: 05/30/2024]
Abstract
The transcorneal route is the main entry route for drugs to the intraocular parts, after topical administration. The outer surface, the corneal epithelium (CE), forms the rate-limiting barrier for drug permeability. Information about the role and protein expression of drug and amino acid transporter proteins in the CE is sparse and lacking. The aim of our study was to characterize transporter protein expression in rabbit and porcine CE to better understand potential drug and nutrient absorption after topical administration. Proteins, mainly Abc and Slc transporters, were characterized with quantitative targeted absolute proteomics and global untargeted proteomics methods. In the rabbit CE, 24 of 48 proteins were detected in the targeted approach, and 21 of these were quantified. In the porcine CE, 26 of 58 proteins were detected in the targeted approach, and 20 of these were quantified. Among these, 15 proteins were quantified in both animals: 4f2hc (Slc3a2), Aqp0, Asct1 (Slc1a4), Asct2 (Slc1a5), Glut1 (Slc2a1), Hmit (Slc2a13), Insr, Lat1 (Slc7a5), Mct1 (Slc16a1), Mct2 (Slc16a7), Mct4 (Slc16a3), Mrp 4 (Abcc4), Na+/K+-ATPase, Oatp3a1 (Slco3a1), and Snat2 (Slc38a2). Overall, the global proteomics results supported the targeted proteomics results. Organic anion transporting polypeptide Oatp3a1 was detected and quantified for the first time in both rabbit (1.4 ± 0.4 fmol/cm2) and porcine (11.1 ± 5.3 fmol/cm2) CE. High expression levels were observed for L-type amino acid transporter, Lat1, which was quantified with newly selected extracellular domain peptides in rabbit (48.9 ± 11.8 fmol/cm2) and porcine (37.6 ± 11.5 fmol/cm2) CE. The knowledge of transporter protein expression in ocular barriers is a key factor in the successful design of new ocular drugs, pharmacokinetic modeling, understanding ocular diseases, and the translation to human.
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Affiliation(s)
- Eva Ramsay
- Drug
Research Programme, Division of Pharmaceutical Biosciences, Faculty
of Pharmacy, University of Helsinki, 00014 Helsinki, Finland
| | - Ahmed B. Montaser
- School
of Pharmacy, University of Eastern Finland, Yliopistonranta 1 C, 70211 Kuopio, Finland
| | - Kanako Niitsu
- School
of Pharmacy, University of Eastern Finland, Yliopistonranta 1 C, 70211 Kuopio, Finland
| | - Arto Urtti
- Drug
Research Programme, Division of Pharmaceutical Biosciences, Faculty
of Pharmacy, University of Helsinki, 00014 Helsinki, Finland
- School
of Pharmacy, University of Eastern Finland, Yliopistonranta 1 C, 70211 Kuopio, Finland
| | - Seppo Auriola
- School
of Pharmacy, University of Eastern Finland, Yliopistonranta 1 C, 70211 Kuopio, Finland
| | - Kristiina M. Huttunen
- School
of Pharmacy, University of Eastern Finland, Yliopistonranta 1 C, 70211 Kuopio, Finland
| | - Yasuo Uchida
- Department
of Molecular Systems Pharmaceutics, Graduate School of Biomedical
and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-0037, Japan
| | - Heidi Kidron
- Drug
Research Programme, Division of Pharmaceutical Biosciences, Faculty
of Pharmacy, University of Helsinki, 00014 Helsinki, Finland
| | - Tetsuya Terasaki
- School
of Pharmacy, University of Eastern Finland, Yliopistonranta 1 C, 70211 Kuopio, Finland
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2
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Misawa N, Honda S. Increased sodium fluorescein transport by corticosteroids is inhibited by a LAT-1 specific inhibitor in retinal pigment epithelial cells in vitro. Sci Rep 2023; 13:22981. [PMID: 38151501 PMCID: PMC10752866 DOI: 10.1038/s41598-023-50196-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 12/16/2023] [Indexed: 12/29/2023] Open
Abstract
To investigate whether aldosterone (ALD) and hydrocortisone (HC) change the gene expression of SLC7A5, which encodes the large neutral amino acid transporter small subunit 1 (LAT1), and the transport activity of LAT1 in the retinal pigment epithelium (RPE) in vitro. ARPE-19 cells were grown to confluence. After withdrawing the serum, ALD or HC was added with several doses and incubated, and SLC7A5 gene expression was measured. The influx and efflux transport of sodium fluorescein (Na-F) were evaluated using the Transwell culture system. SLC7A5 gene expression was upregulated by ALD and downregulated by HC in a dose-dependent manner. Both ALD and HC significantly increased the influx and efflux Na-F transport of RPE cells at a dose that did not change the expression of SLC7A5. JPH203, a specific inhibitor of LAT1, significantly reduced accelerated Na-F transport. Both ALD and HC increased the gene expression of zonula occludin-1 (ZO-1) although they did not change the immunoreactivity of ZO-1 in RPE cells. LAT1 may play an important role in increasing Na-F transport associated with ALD and HC administration. A specific LAT1 inhibitor may effectively regulate the increased material transport of RPE induced by ALD and HC.
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Affiliation(s)
- Norihiko Misawa
- Department of Ophthalmology and Visual Sciences, Osaka Metropolitan University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan
| | - Shigeru Honda
- Department of Ophthalmology and Visual Sciences, Osaka Metropolitan University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan.
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3
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Taurino G, Chiu M, Bianchi MG, Griffini E, Bussolati O. The SLC38A5/SNAT5 amino acid transporter: from pathophysiology to pro-cancer roles in the tumor microenvironment. Am J Physiol Cell Physiol 2023; 325:C550-C562. [PMID: 37458433 DOI: 10.1152/ajpcell.00169.2023] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 07/11/2023] [Accepted: 07/11/2023] [Indexed: 08/09/2023]
Abstract
SLC38A5/SNAT5 is a system N transporter that can mediate net inward or outward transmembrane fluxes of neutral amino acids coupled with Na+ (symport) and H+ (antiport). Its preferential substrates are not only amino acids with side chains containing amide (glutamine and asparagine) or imidazole (histidine) groups, but also serine, glycine, and alanine are transported by the carrier. Expressed in the pancreas, intestinal tract, brain, liver, bone marrow, and placenta, it is regulated at mRNA and protein levels by mTORC1 and WNT/β-catenin pathways, and it is sensitive to pH, nutritional stress, inflammation, and hypoxia. SNAT5 expression has been found to be altered in pathological conditions such as chronic inflammatory diseases, gestational complications, chronic metabolic acidosis, and malnutrition. Growing experimental evidence shows that SNAT5 is overexpressed in several types of cancer cells. Moreover, recently published results indicate that SNAT5 expression in stromal cells can support the metabolic exchanges occurring in the tumor microenvironment of asparagine-auxotroph tumors. We review the functional role of the SNAT5 transporter in pathophysiology and propose that, due to its peculiar operational and regulatory features, SNAT5 may play important pro-cancer roles when expressed either in neoplastic or in stromal cells of glutamine-auxotroph tumors.NEW & NOTEWORTHY The transporter SLC38A5/SNAT5 provides net influx or efflux of glutamine, asparagine, and serine. These amino acids are of particular metabolic relevance in several conditions. Changes in transporter expression or activity have been described in selected types of human cancers, where SNAT5 can mediate amino acid exchanges between tumor and stromal cells, thus providing a potential therapeutic target. This is the first review that recapitulates the characteristics and roles of the transporter in physiology and pathology.
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Affiliation(s)
- Giuseppe Taurino
- Laboratory of General Pathology, Department of Medicine and Surgery, University of Parma, Parma, Italy
- MRH-Microbiome Research Hub, University of Parma, Parma, Italy
| | - Martina Chiu
- Laboratory of General Pathology, Department of Medicine and Surgery, University of Parma, Parma, Italy
| | - Massimiliano G Bianchi
- Laboratory of General Pathology, Department of Medicine and Surgery, University of Parma, Parma, Italy
- MRH-Microbiome Research Hub, University of Parma, Parma, Italy
| | - Erika Griffini
- Laboratory of General Pathology, Department of Medicine and Surgery, University of Parma, Parma, Italy
| | - Ovidio Bussolati
- Laboratory of General Pathology, Department of Medicine and Surgery, University of Parma, Parma, Italy
- MRH-Microbiome Research Hub, University of Parma, Parma, Italy
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Sennoune SR, Nandagopal GD, Ramachandran S, Mathew M, Sivaprakasam S, Jaramillo-Martinez V, Bhutia YD, Ganapathy V. Potent Inhibition of Macropinocytosis by Niclosamide in Cancer Cells: A Novel Mechanism for the Anticancer Efficacy for the Antihelminthic. Cancers (Basel) 2023; 15:759. [PMID: 36765717 PMCID: PMC9913174 DOI: 10.3390/cancers15030759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 01/17/2023] [Accepted: 01/23/2023] [Indexed: 01/28/2023] Open
Abstract
Niclosamide, a drug used to treat tapeworm infection, possesses anticancer effects by interfering with multiple signaling pathways. Niclosamide also causes intracellular acidification. We have recently discovered that the amino acid transporter SLC38A5, an amino acid-dependent Na+/H+ exchanger, activates macropinocytosis in cancer cells via amino acid-induced intracellular alkalinization. Therefore, we asked whether niclosamide will block basal and SLC38A5-mediated macropinocytosis via intracellular acidification. We monitored macropinocytosis in pancreatic and breast cancer cells using TMR-dextran and the function of SLC38A5 by measuring Li+-stimulated serine uptake. The peptide transporter activity was measured by the uptake of glycylsarcosine. Treatment of the cancer cells with niclosamide caused intracellular acidification. The drug blocked basal and serine-induced macropinocytosis with differential potency, with an EC50 of ~5 μM for the former and ~0.4 μM for the latter. The increased potency for amino acid-mediated macropinocytosis is due to direct inhibition of SLC38A5 by niclosamide in addition to the ability of the drug to cause intracellular acidification. The drug also inhibited the activity of the H+-coupled peptide transporter. We conclude that niclosamide induces nutrient starvation in cancer cells by blocking macropinocytosis, SLC38A5 and the peptide transporter. These studies uncover novel, hitherto unknown, mechanisms for the anticancer efficacy of this antihelminthic.
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Affiliation(s)
- Souad R. Sennoune
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | | | - Sabarish Ramachandran
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Marilyn Mathew
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Sathish Sivaprakasam
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Valeria Jaramillo-Martinez
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Yangzom D. Bhutia
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Vadivel Ganapathy
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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5
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Wang Z, Yemanyi F, Blomfield AK, Bora K, Huang S, Liu CH, Britton WR, Cho SS, Tomita Y, Fu Z, Ma JX, Li WH, Chen J. Amino acid transporter SLC38A5 regulates developmental and pathological retinal angiogenesis. eLife 2022; 11:e73105. [PMID: 36454214 PMCID: PMC9714971 DOI: 10.7554/elife.73105] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 11/17/2022] [Indexed: 12/03/2022] Open
Abstract
Amino acid (AA) metabolism in vascular endothelium is important for sprouting angiogenesis. SLC38A5 (solute carrier family 38 member 5), an AA transporter, shuttles neutral AAs across cell membrane, including glutamine, which may serve as metabolic fuel for proliferating endothelial cells (ECs) to promote angiogenesis. Here, we found that Slc38a5 is highly enriched in normal retinal vascular endothelium, and more specifically, in pathological sprouting neovessels. Slc38a5 is suppressed in retinal blood vessels from Lrp5-/- and Ndpy/- mice, both genetic models of defective retinal vascular development with Wnt signaling mutations. Additionally, Slc38a5 transcription is regulated by Wnt/β-catenin signaling. Genetic deficiency of Slc38a5 in mice substantially delays retinal vascular development and suppresses pathological neovascularization in oxygen-induced retinopathy modeling ischemic proliferative retinopathies. Inhibition of SLC38A5 in human retinal vascular ECs impairs EC proliferation and angiogenic function, suppresses glutamine uptake, and dampens vascular endothelial growth factor receptor 2. Together these findings suggest that SLC38A5 is a new metabolic regulator of retinal angiogenesis by controlling AA nutrient uptake and homeostasis in ECs.
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Affiliation(s)
- Zhongxiao Wang
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Felix Yemanyi
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Alexandra K Blomfield
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Kiran Bora
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Shuo Huang
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Chi-Hsiu Liu
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - William R Britton
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Steve S Cho
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Yohei Tomita
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Zhongjie Fu
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Jian-xing Ma
- Department of Biochemistry, Wake Forest University School of MedicineWinston-SalemUnited States
| | - Wen-hong Li
- Departments of Cell Biology and of Biochemistry, University of Texas Southwestern Medical CenterDallasUnited States
| | - Jing Chen
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
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6
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Impact of Inhibition of Glutamine and Alanine Transport on Cerebellar Glial and Neuronal Metabolism. Biomolecules 2022; 12:biom12091189. [PMID: 36139028 PMCID: PMC9496060 DOI: 10.3390/biom12091189] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Revised: 08/21/2022] [Accepted: 08/24/2022] [Indexed: 11/16/2022] Open
Abstract
The cerebellum, or “little brain”, is often overlooked in studies of brain metabolism in favour of the cortex. Despite this, anomalies in cerebellar amino acid homeostasis in a range of disorders have been reported. Amino acid homeostasis is central to metabolism, providing recycling of carbon backbones and ammonia between cell types. Here, we examined the role of cerebellar amino acid transporters in the cycling of glutamine and alanine in guinea pig cerebellar slices by inhibiting amino acid transporters and examining the resultant metabolism of [1-13C]d-glucose and [1,2-13C]acetate by NMR spectroscopy and LCMS. While the lack of specific inhibitors of each transporter makes interpretation difficult, by viewing results from experiments with multiple inhibitors we can draw inferences about the major cell types and transporters involved. In cerebellum, glutamine and alanine transfer is dominated by system A, blockade of which has maximum effect on metabolism, with contributions from System N. Inhibition of neural system A isoform SNAT1 by MeAIB resulted in greatly decreased metabolite pools and reduced net fluxes but showed little effect on fluxes from [1,2-13C]acetate unlike inhibition of SNAT3 and other glutamine transporters by histidine where net fluxes from [1,2-13C]acetate are reduced by ~50%. We interpret the data as further evidence of not one but several glutamate/glutamine exchange pools. The impact of amino acid transport inhibition demonstrates that the cerebellum has tightly coupled cells and that glutamate/glutamine, as well as alanine cycling, play a major role in that part of the brain.
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7
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Bhutia YD, Mathew M, Sivaprakasam S, Ramachandran S, Ganapathy V. Unconventional Functions of Amino Acid Transporters: Role in Macropinocytosis (SLC38A5/SLC38A3) and Diet-Induced Obesity/Metabolic Syndrome (SLC6A19/SLC6A14/SLC6A6). Biomolecules 2022; 12:biom12020235. [PMID: 35204736 PMCID: PMC8961558 DOI: 10.3390/biom12020235] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 01/24/2022] [Accepted: 01/27/2022] [Indexed: 02/06/2023] Open
Abstract
Amino acid transporters are expressed in mammalian cells not only in the plasma membrane but also in intracellular membranes. The conventional function of these transporters is to transfer their amino acid substrates across the lipid bilayer; the direction of the transfer is dictated by the combined gradients for the amino acid substrates and the co-transported ions (Na+, H+, K+ or Cl−) across the membrane. In cases of electrogenic transporters, the membrane potential also contributes to the direction of the amino acid transfer. In addition to this expected traditional function, several unconventional functions are known for some of these amino acid transporters. This includes their role in intracellular signaling, regulation of acid–base balance, and entry of viruses into cells. Such functions expand the biological roles of these transporters beyond the logical amino acid homeostasis. In recent years, two additional unconventional biochemical/metabolic processes regulated by certain amino acid transporters have come to be recognized: macropinocytosis and obesity. This adds to the repertoire of biological processes that are controlled and regulated by amino acid transporters in health and disease. In the present review, we highlight the unusual involvement of selective amino acid transporters in macropinocytosis (SLC38A5/SLC38A3) and diet-induced obesity/metabolic syndrome (SLC6A19/SLC6A14/SLC6A6).
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8
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Sniegowski T, Korac K, Bhutia YD, Ganapathy V. SLC6A14 and SLC38A5 Drive the Glutaminolysis and Serine-Glycine-One-Carbon Pathways in Cancer. Pharmaceuticals (Basel) 2021; 14:ph14030216. [PMID: 33806675 PMCID: PMC8000594 DOI: 10.3390/ph14030216] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 02/24/2021] [Accepted: 02/25/2021] [Indexed: 02/06/2023] Open
Abstract
The glutaminolysis and serine–glycine–one-carbon pathways represent metabolic reactions that are reprogramed and upregulated in cancer; these pathways are involved in supporting the growth and proliferation of cancer cells. Glutaminolysis participates in the production of lactate, an oncometabolite, and also in anabolic reactions leading to the synthesis of fatty acids and cholesterol. The serine–glycine–one-carbon pathway is involved in the synthesis of purines and pyrimidines and the control of the epigenetic signature (DNA methylation, histone methylation) in cancer cells. Methionine is obligatory for most of the methyl-transfer reactions in the form of S-adenosylmethionine; here, too, the serine–glycine–one-carbon pathway is necessary for the resynthesis of methionine following the methyl-transfer reaction. Glutamine, serine, glycine, and methionine are obligatory to fuel these metabolic pathways. The first three amino acids can be synthesized endogenously to some extent, but the need for these amino acids in cancer cells is so high that they also have to be acquired from extracellular sources. Methionine is an essential amino acid, thus making it necessary for cancer cells to acquire this amino acid solely from the extracellular milieu. Cancer cells upregulate specific amino acid transporters to meet this increased demand for these four amino acids. SLC6A14 and SLC38A5 are the two transporters that are upregulated in a variety of cancers to mediate the influx of glutamine, serine, glycine, and methionine into cancer cells. SLC6A14 is a Na+/Cl− -coupled transporter for multiple amino acids, including these four amino acids. In contrast, SLC38A5 is a Na+-coupled transporter with rather restricted specificity towards glutamine, serine, glycine, and methionine. Both transporters exhibit unique functional features that are ideal for the rapid proliferation of cancer cells. As such, these two amino acid transporters play a critical role in promoting the survival and growth of cancer cells and hence represent novel, hitherto largely unexplored, targets for cancer therapy.
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9
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Pfeiffer RL, Marc RE, Jones BW. Müller Cell Metabolic Signatures: Evolutionary Conservation and Disruption in Disease. Trends Endocrinol Metab 2020; 31:320-329. [PMID: 32187524 PMCID: PMC7188339 DOI: 10.1016/j.tem.2020.01.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 12/05/2019] [Accepted: 01/09/2020] [Indexed: 01/21/2023]
Abstract
Müller cells are glia that play important regulatory roles in retinal metabolism. These roles have been evolutionarily conserved across at least 300 million years. Müller cells have a tightly locked metabolic signature in the healthy retina, which rapidly degrades in response to insult and disease. This variation in metabolic signature occurs in a chaotic fashion, involving some central metabolic pathways. The cause of this divergence of Müller cells, from a single class with a unique metabolic signature to numerous separable metabolic classes, is currently unknown and illuminates potential alternative metabolic pathways that may be revealed in disease. Understanding the impacts of this heterogeneity on degenerate retinas and the implications for the metabolic support of surrounding neurons will be critical to long-term integration of retinal therapeutics for the restoration of visual perception following photoreceptor degeneration.
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Affiliation(s)
- Rebecca L Pfeiffer
- Moran Eye Center, University of Utah Department of Ophthalmology and Visual Sciences, 65 Mario Capecchi Drive, Salt Lake City, UT 84132, USA. *
| | - Robert E Marc
- Moran Eye Center, University of Utah Department of Ophthalmology and Visual Sciences, 65 Mario Capecchi Drive, Salt Lake City, UT 84132, USA; Signature Immunologics, Torrey, UT, USA
| | - Bryan W Jones
- Moran Eye Center, University of Utah Department of Ophthalmology and Visual Sciences, 65 Mario Capecchi Drive, Salt Lake City, UT 84132, USA.
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10
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Miki A, Sakurada Y, Tanaka K, Semba K, Mitamura Y, Yuzawa M, Tajima A, Nakatochi M, Yamamoto K, Matsuo K, Imoto I, Honda S. Genome-Wide Association Study to Identify a New Susceptibility Locus for Central Serous Chorioretinopathy in the Japanese Population. ACTA ACUST UNITED AC 2018; 59:5542-5547. [DOI: 10.1167/iovs.18-25497] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- Akiko Miki
- Department of Surgery, Division of Ophthalmology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yoichi Sakurada
- Department of Ophthalmology, Faculty of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Koji Tanaka
- Department of Ophthalmology, Nihon University School of Medicine, Tokyo, Japan
| | - Kentaro Semba
- Department of Ophthalmology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan
| | - Yoshinori Mitamura
- Department of Ophthalmology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan
| | - Mitsuko Yuzawa
- Department of Ophthalmology, Nihon University School of Medicine, Tokyo, Japan
| | - Atsushi Tajima
- Department of Bioinformatics and Genomics, Graduate School of Advanced Preventive Medical Sciences, Kanazawa University, Kanazawa, Japan
| | - Masahiro Nakatochi
- Statistical Analysis Section, Center for Advanced Medicine and Clinical Research, Nagoya University Hospital, Nagoya, Japan
| | - Ken Yamamoto
- Department of Medical Biochemistry, Kurume University School of Medicine, Kurume, Japan
| | - Keitaro Matsuo
- Division of Molecular and Clinical Epidemiology, Aichi Cancer Center Research Institute, Nagoya, Japan
- Division of Epidemiology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Issei Imoto
- Division of Molecular Genetics, Aichi Cancer Center Research Institute, Nagoya, Japan
| | - Shigeru Honda
- Department of Surgery, Division of Ophthalmology, Kobe University Graduate School of Medicine, Kobe, Japan
- Department of Ophthalmology and Visual Sciences, Osaka City University Graduate School of Medicine, Osaka, Japan
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11
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Swarup A, Samuels IS, Bell BA, Han JYS, Du J, Massenzio E, Abel ED, Boesze-Battaglia K, Peachey NS, Philp NJ. Modulating GLUT1 expression in retinal pigment epithelium decreases glucose levels in the retina: impact on photoreceptors and Müller glial cells. Am J Physiol Cell Physiol 2018; 316:C121-C133. [PMID: 30462537 DOI: 10.1152/ajpcell.00410.2018] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The retina is one of the most metabolically active tissues in the body and utilizes glucose to produce energy and intermediates required for daily renewal of photoreceptor cell outer segments. Glucose transporter 1 (GLUT1) facilitates glucose transport across outer blood retinal barrier (BRB) formed by the retinal pigment epithelium (RPE) and the inner BRB formed by the endothelium. We used conditional knockout mice to study the impact of reducing glucose transport across the RPE on photoreceptor and Müller glial cells. Transgenic mice expressing Cre recombinase under control of the Bestrophin1 ( Best1) promoter were bred with Glut1flox/flox mice to generate Tg-Best1-Cre:Glut1flox/flox mice ( RPEΔGlut1). The RPEΔGlut1 mice displayed a mosaic pattern of Cre expression within the RPE that allowed us to analyze mice with ~50% ( RPEΔGlut1m) recombination and mice with >70% ( RPEΔGlut1h) recombination separately. Deletion of GLUT1 from the RPE did not affect its carrier or barrier functions, indicating that the RPE utilizes other substrates to support its metabolic needs thereby sparing glucose for the outer retina. RPEΔGlut1m mice had normal retinal morphology, function, and no cell death; however, where GLUT1 was absent from a span of RPE greater than 100 µm, there was shortening of the photoreceptor cell outer segments. RPEΔGlut1h mice showed outer segment shortening, cell death of photoreceptors, and activation of Müller glial cells. The severe phenotype seen in RPEΔGlut1h mice indicates that glucose transport via the GLUT1 transporter in the RPE is required to meet the anabolic and catabolic requirements of photoreceptors and maintain Müller glial cells in a quiescent state.
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Affiliation(s)
- Aditi Swarup
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University , Philadelphia, Pennsylvania
| | - Ivy S Samuels
- Louis Stokes Cleveland VA Medical Center , Cleveland, Ohio.,Cole Eye Institute, Cleveland Clinic , Cleveland, Ohio
| | - Brent A Bell
- Department of Ophthalmology, University of Pennsylvania , Philadelphia, Pennsylvania
| | - John Y S Han
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University , Philadelphia, Pennsylvania
| | - Jianhai Du
- Department of Ophthalmology, Department of Biochemistry, West Virginia University Eye Institute , Morgantown, West Virginia
| | - Erik Massenzio
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University , Philadelphia, Pennsylvania
| | - E Dale Abel
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa , Iowa City, Iowa.,Division of Endocrinology and Metabolism, Carver College of Medicine, University of Iowa , Iowa City, Iowa
| | - Kathleen Boesze-Battaglia
- Department of Biochemistry, Penn Dental Medicine, University of Pennsylvania , Philadelphia, Pennsylvania
| | - Neal S Peachey
- Louis Stokes Cleveland VA Medical Center , Cleveland, Ohio.,Cole Eye Institute, Cleveland Clinic , Cleveland, Ohio.,Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University , Cleveland, Ohio
| | - Nancy J Philp
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University , Philadelphia, Pennsylvania
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Toft-Kehler AK, Skytt DM, Kolko M. A Perspective on the Müller Cell-Neuron Metabolic Partnership in the Inner Retina. Mol Neurobiol 2017; 55:5353-5361. [PMID: 28929338 DOI: 10.1007/s12035-017-0760-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 08/31/2017] [Indexed: 10/18/2022]
Abstract
The Müller cells represent the predominant macroglial cell in the retina. In recent decades, Müller cells have been acknowledged to be far more influential on neuronal homeostasis in the retina than previously assumed. With its unique localization, spanning the entire retina being interposed between the vessels and neurons, Müller cells are responsible for the functional and metabolic support of the surrounding neurons. As a consequence of major energy demands in the retina, high levels of glucose are consumed and processed by Müller cells. The present review provides a perspective on the symbiotic relationship between Müller cells and inner retinal neurons on a cellular level by emphasizing the essential role of energy metabolism within Müller cells in relation to retinal neuron survival.
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Affiliation(s)
- A K Toft-Kehler
- Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark
| | - D M Skytt
- Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark
| | - Miriam Kolko
- Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark. .,Department of Ophthalmology, Zealand University Hospital, Vestermarksvej 23, 4000, Roskilde, Denmark. .,Department of Ophthalmology, Copenhagen University Hospital, Rigshospitalet, Nordre Ringvej 57, 2600, Glostrup, Denmark.
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Ji HP, Xiong Y, Song WT, Zhang ED, Gao ZL, Yao F, Su T, Zhou RR, Xia XB. MicroRNA-28 potentially regulates the photoreceptor lineage commitment of Müller glia-derived progenitors. Sci Rep 2017; 7:11374. [PMID: 28900179 PMCID: PMC5595954 DOI: 10.1038/s41598-017-11112-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 08/18/2017] [Indexed: 12/29/2022] Open
Abstract
Retinal degenerative diseases ultimately result into irreversible photoreceptor death or loss. At present, the most promising treatment for these diseases is cell replacement therapy. Müller glia are the major glia in the retina, displaying cardinal features of retinal progenitor cells, and can be candidate of seed cells for retinal degenerative diseases. Here, mouse retinal Müller glia dissociated and cultured in vitro amplified and were dedifferentiated into Müller glia-derived progenitors (MGDPs), demonstrating expression of stem/progenitor cell markers Nestin, Sox2 and self-renewal capacity. MicroRNAs (miRNAs) play unique roles in the retinogenesis, so we hypothesized miRNAs would contribute to photoreceptor lineage commitment of MGDPs. By TargetScan, Miranda, and Pictar bioinformatics, gain/loss-of-function models, dual luciferase assay, we identified and validated that miR-28 targeted the photoreceptor-specific CRX transcription factor. Anti-miR-28 could induce MGDPs to differentiate into neurons strongly expressing CRX and Rhodopsin, while miR-28 mimic suppressed CRX and Rhodopsin expression. Knockdown of CRX by siRNA blocked the expression of CRX and Rhodospin upregulated by anti-miR-28, indicating that anti-miR-28 potentially induced photoreceptor commitment of MGDPs by targeting CRX, but more experiments are necessary to confirm their role in differentiation.
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Affiliation(s)
- Hong-Pei Ji
- Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, 410008, China.,Departemnt of Ophthalmology, The People's Hospital of Guizhou Province, Guiyang, 550002, China
| | - Yu Xiong
- Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, 410008, China
| | - Wei-Tao Song
- Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, 410008, China
| | - En-Dong Zhang
- Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, 410008, China
| | - Zhao-Lin Gao
- Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, 410008, China
| | - Fei Yao
- Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, 410008, China
| | - Tao Su
- Department of Institute of Medical Sciences, Xiangya Hospital, Central South University, Changsha, 410008, China
| | - Rong-Rong Zhou
- Department of Oncology, Xiangya Hospital, Central South University, Changsha, 410008, China.
| | - Xiao-Bo Xia
- Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, 410008, China.
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Wang J, Cui X, Roon P, Saul A, Smith SB. The Role of Sigma1R in Mammalian Retina. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 964:267-284. [PMID: 28315277 DOI: 10.1007/978-3-319-50174-1_18] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
This review article focuses on studies of Sigma 1 Receptor (Sigma1R) and retina . It provides a brief overview of the earliest pharmacological studies performed in the late 1990s that provided evidence of the presence of Sigma1R in various ocular tissues. It then describes work from a number of labs concerning the location of Sigma1R in several retinal cell types including ganglion, Müller glia , and photoreceptors . The role of Sigma1R ligands in retinal neuroprotection is emphasized. Early studies performed in vitro clearly showed that targeting Sigma1R could attenuate stress-induced retinal cell loss. These studies were followed by in vivo experiments. Data about the usefulness of targeting Sigma1R to prevent ganglion cell loss associated with diabetic retinopathy are reviewed. Mechanisms of Sigma1R-mediated retinal neuroprotection involving Müller cells , especially in modulating oxidative stress are described along with information about the retinal phenotype of mice lacking Sigma1R (Sigma1R -/- mice). The retina develops normally in Sigma1R -/- mice, but after many months there is evidence of apoptosis in the optic nerve head, decreased ganglion cell function and eventual loss of these cells. Additional studies using the Sigma1R -/- mice provide strong evidence that in the retina, Sigma1R plays a key role in modulating cellular stress. Recent work has shown that targeting Sigma1R may extend beyond protection of ganglion cells to include photoreceptor cell degeneration as well.
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Affiliation(s)
- Jing Wang
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15th Street, CB 1114, Augusta, GA, 30912-2000, USA
- The James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA
| | - Xuezhi Cui
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15th Street, CB 1114, Augusta, GA, 30912-2000, USA
- The James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA
| | - Penny Roon
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15th Street, CB 1114, Augusta, GA, 30912-2000, USA
| | - Alan Saul
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1120 15th Street, CB 1114, Augusta, GA, 30912-2000, USA
- The James and Jean Culver Vision Discovery Institute, Augusta University, Augusta, GA, USA
| | - Sylvia B Smith
- Departments of Cellular Biology and Anatomy and Ophthalmology and the James and Jean Culver Vision Discovery Institute, Medical College of Georgia at Augusta University, Augusta, GA, 30912, USA.
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Bhutia YD, Ganapathy V. Glutamine transporters in mammalian cells and their functions in physiology and cancer. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1863:2531-9. [PMID: 26724577 DOI: 10.1016/j.bbamcr.2015.12.017] [Citation(s) in RCA: 197] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 12/19/2015] [Accepted: 12/22/2015] [Indexed: 01/17/2023]
Abstract
The SLC (solute carrier)-type transporters (~400 in number) in mammalian cells consist of 52 distinct gene families, grouped solely based on the amino acid sequence (primary structure) of the transporter proteins and not on their transport function. Among them are the transporters for amino acids. Fourteen of them, capable of transporting glutamine across the plasma membrane, are found in four families: SLC1, SLC6, SLC7, and SLC38. However, it is generally thought that the members of the SLC38 family are the principal transporters for glutamine. Some of the glutamine transporters are obligatory exchangers whereas some function as active transporters in one direction. While most glutamine transporters mediate the influx of the amino acid into cells, some actually mediate the efflux of the amino acid out of the cells. Glutamine transporters play important roles in a variety of tissues, including the liver, brain, kidney, and placenta, as clearly evident from the biological and biochemical phenotypes resulting from the deletion of specific glutamine transporters in mice. Owing to the obligatory role of glutamine in growth and proliferation of tumor cells, there is increasing attention on glutamine transporters in cancer biology as potential drug targets for cancer treatment. Selective blockers of certain glutamine transporters might be effective in preventing the entry of glutamine and other important amino acids into tumor cells, thus essentially starving these cells to death. This could represent the beginning of a new era in the discovery of novel anticancer drugs with a previously unexplored mode of action. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.
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Affiliation(s)
- Yangzom D Bhutia
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Vadivel Ganapathy
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
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Shanmugam AK, Mysona BA, Wang J, Zhao J, Tawfik A, Sanders A, Markand S, Zorrilla E, Ganapathy V, Bollinger KE, Smith SB. Progesterone Receptor Membrane Component 1 (PGRMC1) Expression in Murine Retina. Curr Eye Res 2015; 41:1105-1112. [PMID: 26642738 DOI: 10.3109/02713683.2015.1085579] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE Sigma receptors 1 (σR1) and 2 (σR2) are thought to be two distinct proteins which share the ability to bind multiple ligands, several of which are common to both receptors. Whether σR1 and σR2 share overlapping biological functions is unknown. Recently, progesterone receptor membrane component 1 (PGRMC1) was shown to contain the putative σR2 binding site. PGRMC1 has not been studied in retina. We hypothesize that biological interactions between σR1 and PGRMC1 will be evidenced by compensatory upregulation of PGRMC1 in σR1-/- mice. METHODS Immunofluorescence, RT-PCR, and immunoblotting methods were used to analyze expression of PGRMC1 in wild-type mouse retina. Tissues from σR1-/- mice were used to investigate whether a biological interaction exists between σR1 and PGRMC1. RESULTS In the eye, PGRMC1 is expressed in corneal epithelium, lens, ciliary body epithelium, and retina. In retina, PGRMC1 is present in Müller cells and retinal pigment epithelium. This expression pattern is similar, but not identical to σR1. PGRMC1 protein levels in neural retina and eye cup from σR1-/- mice did not differ from wild-type mice. Nonocular tissues, lung, heart, and kidney showed similar Pgrmc1 gene expression in wild-type and σR1-/- mice. In contrast, liver, brain, and intestine showed increased Pgrmc1 gene expression in σR1-/- mice. CONCLUSION Despite potential biological overlap, deletion of σR1 did not result in a compensatory change in PGRMC1 protein levels in σR1-/- mouse retina. Increased Pgrmc1 gene expression in organs with high lipid content such as liver, brain, and intestine indicates a possible tissue-specific interaction between σR1 and PGRMC1. The current studies establish the presence of PGRMC1 in retina and lay the foundation for analysis of its biological function.
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Affiliation(s)
- Arul K Shanmugam
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA.,b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA
| | - Barbara A Mysona
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA.,b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA
| | - Jing Wang
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA.,b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA
| | - Jing Zhao
- b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA.,c Department of Ophthalmology , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA
| | - Amany Tawfik
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA.,b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA
| | - A Sanders
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA
| | - Shanu Markand
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA.,b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA
| | - Eric Zorrilla
- d Harold L. Dorris Neurological Research Institute , The Scripps Research Institute , La Jolla , CA , USA
| | - Vadivel Ganapathy
- b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA.,e Department of Cell Biology and Biochemistry , Texas Tech University Health Sciences Center , Lubbock , TX , USA
| | - Kathryn E Bollinger
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA.,b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA.,c Department of Ophthalmology , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA
| | - Sylvia B Smith
- a Department of Cellular Biology and Anatomy , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA.,b James & Jean Culver Vision Discovery Institute , Georgia Regents University , Augusta , GA , USA.,c Department of Ophthalmology , Medical College of Georgia, Georgia Regents University , Augusta , GA , USA
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17
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Fu S, Dong S, Zhu M, Sherry DM, Wang C, You Z, Haigh JJ, Le YZ. Müller Glia Are a Major Cellular Source of Survival Signals for Retinal Neurons in Diabetes. Diabetes 2015; 64:3554-63. [PMID: 26068541 PMCID: PMC4587642 DOI: 10.2337/db15-0180] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 05/26/2015] [Indexed: 12/22/2022]
Abstract
To dissect the role of vascular endothelial growth factor receptor-2 (VEGFR2) in Müller cells and its effect on neuroprotection in diabetic retinopathy (DR), we disrupted VEGFR2 in mouse Müller glia and determined its effect on Müller cell survival, neuronal integrity, and trophic factor production in diabetic retinas. Diabetes was induced with streptozotocin. Retinal function was measured with electroretinography. Müller cell and neuronal densities were assessed with morphometric and immunohistochemical analyses. Loss of VEGFR2 caused a gradual reduction in Müller glial density, which reached to a significant level 10 months after the onset of diabetes. This observation was accompanied by an age-dependent decrease of scotopic and photopic electroretinography amplitudes and accelerated loss of rod and cone photoreceptors, ganglion cell layer cells, and inner nuclear layer neurons and by a significant reduction of retinal glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor. Our results suggest that VEGFR2-mediated Müller cell survival is required for the viability of retinal neurons in diabetes. The genetically altered mice established in this study can be used as a diabetic animal model of nontoxin-induced Müller cell ablation, which will be useful for exploring the cellular mechanisms of neuronal alteration in DR.
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Affiliation(s)
- Shuhua Fu
- Department of Ophthalmology, The Second Affiliated Hospital of Nanchang University, Nanchang, China Section of Endocrinology and Diabetes, Department of Medicine, The University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Shuqian Dong
- Section of Endocrinology and Diabetes, Department of Medicine, The University of Oklahoma Health Sciences Center, Oklahoma City, OK Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, China
| | - Meili Zhu
- Section of Endocrinology and Diabetes, Department of Medicine, The University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - David M Sherry
- Department of Cell Biology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Changyun Wang
- Department of Ophthalmology, The Second Affiliated Hospital of Nanchang University, Nanchang, China
| | - Zhipeng You
- Department of Ophthalmology, The Second Affiliated Hospital of Nanchang University, Nanchang, China
| | - Jody J Haigh
- Vascular Cell Biology Unit, VIB Inflammation Research Center, Ghent University, Ghent, Belgium Department for Biomedical Molecular Biology, Ghent University, Ghent, Belgium Mammalian Functional Genetics Laboratory, Division of Blood Cancers, Australian Centre for Blood Diseases, Monash University and Alfred Health Centre, Melbourne, Victoria, Australia Department of Clinical Haematology, Monash University and Alfred Health Centre, Melbourne, Victoria, Australia
| | - Yun-Zheng Le
- Section of Endocrinology and Diabetes, Department of Medicine, The University of Oklahoma Health Sciences Center, Oklahoma City, OK Department of Cell Biology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK Department of Ophthalmology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK Harold Hamm Diabetes Center, The University of Oklahoma Health Sciences Center, Oklahoma City, OK
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18
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Wang J, Shanmugam A, Markand S, Zorrilla E, Ganapathy V, Smith SB. Sigma 1 receptor regulates the oxidative stress response in primary retinal Müller glial cells via NRF2 signaling and system xc(-), the Na(+)-independent glutamate-cystine exchanger. Free Radic Biol Med 2015; 86:25-36. [PMID: 25920363 PMCID: PMC4554890 DOI: 10.1016/j.freeradbiomed.2015.04.009] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 04/02/2015] [Accepted: 04/07/2015] [Indexed: 01/18/2023]
Abstract
Oxidative stress figures prominently in retinal diseases, including diabetic retinopathy, and glaucoma. Ligands for σ1R, a unique transmembrane protein localized to the endoplasmic reticulum, mitochondria, and nuclear and plasma membranes, have profound retinal neuroprotective properties in vitro and in vivo. Studies to determine the mechanism of σ1R-mediated retinal neuroprotection have focused mainly on neurons. Little is known about the effects of σ1R on Müller cell function, yet these radial glial cells are essential for homeostatic support of the retina. Here we investigated whether σ1R mediates the oxidative stress response of Müller cells using wild-type (WT) and σ1R-knockout (σ1RKO) mice. We observed increased endogenous reactive oxygen species (ROS) levels in σ1RKO Müller cells compared to WT, which was accompanied by decreased expression of Sod1, catalase, Nqo1, Hmox1, Gstm6, and Gpx1. The protein levels of SOD1, CAT, NQO1, and GPX1 were also significantly decreased. The genes encoding these antioxidants contain an antioxidant response element (ARE), which under stress is activated by NRF2, a transcription factor that typically resides in the cytoplasm bound by KEAP1. In the σ1RKO Müller cells Nrf2 expression was decreased significantly at the gene (and protein) level, whereas Keap1 gene (and protein) levels were markedly increased. NRF2-ARE binding affinity was decreased markedly in σ1RKO Müller cells. We investigated system xc(-), the cystine-glutamate exchanger important for synthesis of glutathione (GSH), and observed decreased function in σ1RKO Müller cells compared to WT as well as decreased GSH and GSH/GSSG ratios. This was accompanied by decreased gene and protein levels of xCT, the unique component of system xc(-). We conclude that Müller glial cells lacking σ1R manifest elevated ROS, perturbation of antioxidant balance, suppression of NRF2 signaling, and impaired function of system xc(-). The data suggest that the oxidative stress-mediating function of retinal Müller glial cells may be compromised in the absence of σ1R. The neuroprotective role of σ1R may be linked directly to the oxidative stress-mediating properties of supportive glial cells.
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Affiliation(s)
- Jing Wang
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA 30912-2000, USA; James and Jean Culver Vision Discovery Institute, Augusta, GA 30912-2000, USA
| | - Arul Shanmugam
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA 30912-2000, USA; James and Jean Culver Vision Discovery Institute, Augusta, GA 30912-2000, USA
| | - Shanu Markand
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA 30912-2000, USA; James and Jean Culver Vision Discovery Institute, Augusta, GA 30912-2000, USA
| | - Eric Zorrilla
- Harold L. Dorris Neurological Research Institute, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Vadivel Ganapathy
- James and Jean Culver Vision Discovery Institute, Augusta, GA 30912-2000, USA; Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912-2000, USA
| | - Sylvia B Smith
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA 30912-2000, USA; James and Jean Culver Vision Discovery Institute, Augusta, GA 30912-2000, USA; Department of Ophthalmology, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912-2000, USA.
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Shanmugam A, Wang J, Markand S, Perry RL, Tawfik A, Zorrilla E, Ganapathy V, Smith SB. Sigma receptor 1 activation attenuates release of inflammatory cytokines MIP1γ, MIP2, MIP3α, and IL12 (p40/p70) by retinal Müller glial cells. J Neurochem 2015; 132:546-58. [PMID: 25439327 PMCID: PMC4451448 DOI: 10.1111/jnc.13002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 11/25/2014] [Indexed: 12/27/2022]
Abstract
The high-affinity sigma receptor 1 (σR1) ligand (+)-pentazocine ((+)-PTZ) affords profound retinal neuroprotection in vitro and in vivo by a yet-unknown mechanism. A common feature of retinal disease is Müller cell reactive gliosis, which includes cytokine release. Here, we investigated whether lipopolysaccharide (LPS) stimulates cytokine release by primary mouse Müller cells and whether (+)-PTZ alters release. Using a highly sensitive inflammatory antibody array we observed significant release of macrophage inflammatory proteins (MIP1γ, MIP2, MIP3α) and interleukin-12 (IL12 (p40/p70)) in LPS-treated cells compared to controls, and a significant decrease in secretion upon (+)-PTZ treatment. Müller cells from σR1 knockout mice demonstrated increased MIP1γ, MIP2, MIP3α and IL12 (p40/p70) secretion when exposed to LPS compared to LPS-stimulated WT cells. We investigated whether cytokine secretion was accompanied by cytosolic-to-nuclear NFκB translocation and whether endothelial cell adhesion/migration was altered by released cytokines. Cells exposed to LPS demonstrated increased NFκB nuclear location, which was reduced significantly in (+)-PTZ-treated cells. Media conditioned by LPS-stimulated-Müller cells induced leukocyte-endothelial cell adhesion and endothelial cell migration, which was attenuated by (+)-PTZ treatment. The findings suggest that release of certain inflammatory cytokines by Müller cells can be attenuated by σR1 ligands providing insights into the retinal neuroprotective role of this receptor.
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Affiliation(s)
- Arul Shanmugam
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, USA
- James and Jean Culver Vision Discovery Institute, Georgia Regents University, Augusta, Georgia, USA
| | - Jing Wang
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, USA
- James and Jean Culver Vision Discovery Institute, Georgia Regents University, Augusta, Georgia, USA
| | - Shanu Markand
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, USA
- James and Jean Culver Vision Discovery Institute, Georgia Regents University, Augusta, Georgia, USA
| | - Richard L Perry
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, USA
- James and Jean Culver Vision Discovery Institute, Georgia Regents University, Augusta, Georgia, USA
| | - Amany Tawfik
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, USA
- James and Jean Culver Vision Discovery Institute, Georgia Regents University, Augusta, Georgia, USA
| | - Eric Zorrilla
- Harold L. Dorris Neurological Research Institute, The Scripps Research Institute, La Jolla, California, USA
| | - Vadivel Ganapathy
- James and Jean Culver Vision Discovery Institute, Georgia Regents University, Augusta, Georgia, USA
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, USA
| | - Sylvia B Smith
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, USA
- James and Jean Culver Vision Discovery Institute, Georgia Regents University, Augusta, Georgia, USA
- Department of Ophthalmology, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, USA
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Ananth S, Gnana-Prakasam JP, Bhutia YD, Veeranan-Karmegam R, Martin PM, Smith SB, Ganapathy V. Regulation of the cholesterol efflux transporters ABCA1 and ABCG1 in retina in hemochromatosis and by the endogenous siderophore 2,5-dihydroxybenzoic acid. Biochim Biophys Acta Mol Basis Dis 2014; 1842:603-12. [PMID: 24462739 DOI: 10.1016/j.bbadis.2014.01.010] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 01/08/2014] [Accepted: 01/13/2014] [Indexed: 01/19/2023]
Abstract
Hypercholesterolemia and polymorphisms in the cholesterol exporter ABCA1 are linked to age-related macular degeneration (AMD). Excessive iron in retina also has a link to AMD pathogenesis. Whether these findings mean a biological/molecular connection between iron and cholesterol is not known. Here we examined the relationship between retinal iron and cholesterol using a mouse model (Hfe(-/-)) of hemochromatosis, a genetic disorder of iron overload. We compared the expression of the cholesterol efflux transporters ABCA1 and ABCG1 and cholesterol content in wild type and Hfe(-/-) mouse retinas. We also investigated the expression of Bdh2, the rate-limiting enzyme in the synthesis of the endogenous siderophore 2,5-dihydroxybenzoic acid (2,5-DHBA) in wild type and Hfe(-/-) mouse retinas, and the influence of this siderophore on ABCA1/ABCG1 expression in retinal pigment epithelium. We found that ABCA1 and ABCG1 were expressed in all retinal cell types, and that their expression was decreased in Hfe(-/-) retina. This was accompanied with an increase in retinal cholesterol content. Bdh2 was also expressed in all retinal cell types, and its expression was decreased in hemochromatosis. In ARPE-19 cells, 2,5-DHBA increased ABCA1/ABCG1 expression and decreased cholesterol content. This was not due to depletion of free iron because 2,5-DHBA (a siderophore) and deferiprone (an iron chelator) had opposite effects on transferrin receptor expression and ferritin levels. We conclude that iron is a regulator of cholesterol homeostasis in retina and that removal of cholesterol from retinal cells is impaired in hemochromatosis. Since excessive cholesterol is pro-inflammatory, hemochromatosis might promote retinal inflammation via cholesterol in AMD.
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Affiliation(s)
- Sudha Ananth
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA 30912, USA
| | - Jaya P Gnana-Prakasam
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA 30912, USA
| | - Yangzom D Bhutia
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA 30912, USA
| | | | - Pamela M Martin
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA 30912, USA
| | - Sylvia B Smith
- Department of Cellular Biology and Anatomy, Georgia Regents University, Augusta, GA 30912, USA
| | - Vadivel Ganapathy
- Department of Biochemistry and Molecular Biology, Georgia Regents University, Augusta, GA 30912, USA.
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22
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The SLC38 family of sodium-amino acid co-transporters. Pflugers Arch 2013; 466:155-72. [PMID: 24193407 DOI: 10.1007/s00424-013-1393-y] [Citation(s) in RCA: 160] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 10/16/2013] [Accepted: 10/20/2013] [Indexed: 12/13/2022]
Abstract
Transporters of the SLC38 family are found in all cell types of the body. They mediate Na(+)-dependent net uptake and efflux of small neutral amino acids. As a result they are particularly expressed in cells that grow actively, or in cells that carry out significant amino acid metabolism, such as liver, kidney and brain. SLC38 transporters occur in membranes that face intercellular space or blood vessels, but do not occur in the apical membrane of absorptive epithelia. In the placenta, they play a significant role in the transfer of amino acids to the foetus. Members of the SLC38 family are highly regulated in response to amino acid depletion, hypertonicity and hormonal stimuli. SLC38 transporters play an important role in amino acid signalling and have been proposed to act as transceptors independent of their transport function. The structure of SLC38 transporters is characterised by the 5 + 5 inverted repeat fold, which is observed in a wide variety of transport proteins.
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Križaj D, Ryskamp DA, Tian N, Tezel G, Mitchell CH, Slepak VZ, Shestopalov VI. From mechanosensitivity to inflammatory responses: new players in the pathology of glaucoma. Curr Eye Res 2013; 39:105-19. [PMID: 24144321 DOI: 10.3109/02713683.2013.836541] [Citation(s) in RCA: 130] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
PURPOSE OF THE STUDY Many blinding diseases of the inner retina are associated with degeneration and loss of retinal ganglion cells (RGCs). Recent evidence implicates several new signaling mechanisms as causal agents associated with RGC injury and remodeling of the optic nerve head. Ion channels such as Transient receptor potential vanilloid isoform 4 (TRPV4), pannexin-1 (Panx1) and P2X7 receptor are localized to RGCs and act as potential sensors and effectors of mechanical strain, ischemia and inflammatory responses. Under normal conditions, TRPV4 may function as an osmosensor and a polymodal molecular integrator of diverse mechanical and chemical stimuli, whereas P2X7R and Panx1 respond to stretch- and/or swelling-induced adenosine triphosphate release from neurons and glia. Ca(2+) influx, induced by stimulation of mechanosensitive ion channels in glaucoma, is proposed to influence dendritic and axonal remodeling that may lead to RGC death while (at least initially) sparing other classes of retinal neuron. The secondary phase of the retinal glaucoma response is associated with microglial activation and an inflammatory response involving Toll-like receptors (TLRs), cluster of differentiation 3 (CD3) immune recognition molecules associated with the T-cell antigen receptor, complement molecules and cell type-specific release of neuroactive cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). The retinal response to mechanical stress thus involves a diversity of signaling pathways that sense and transduce mechanical strain and orchestrate both protective and destructive secondary responses. CONCLUSIONS Mechanistic understanding of the interaction between pressure-dependent and independent pathways is only beginning to emerge. This review focuses on the molecular basis of mechanical strain transduction as a primary mechanism that can damage RGCs. The damage occurs through Ca(2+)-dependent cellular remodeling and is associated with parallel activation of secondary ischemic and inflammatory signaling pathways. Molecules that mediate these mechanosensory and immune responses represent plausible targets for protecting ganglion cells in glaucoma, optic neuritis and retinal ischemia.
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Deletion of LRP5 in VLDLR knockout mice inhibits retinal neovascularization. PLoS One 2013; 8:e75186. [PMID: 24058663 PMCID: PMC3772893 DOI: 10.1371/journal.pone.0075186] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 08/12/2013] [Indexed: 11/19/2022] Open
Abstract
The development and maintenance of retinal vasculature require a precise balance between pro-angiogenic and anti-angiogenic factors. However, mechanisms underlying normal homeostasis of retinal vasculature and pathological changes of disrupted retinal vessel development are not fully understood. Recent studies of the low-density lipoprotein receptor-related protein 5 (LRP5) and the very low-density lipoprotein receptor (VLDLR) mutant mice indicate that LRP5 mediates a pro-angiogenic signal while VLDLR mediates an anti-angiogenic signal in retinal vasculature. Mice with a loss of LRP5 display underdeveloped intraretinal vasculature associated with endothelial cell (EC) clustering and failed EC migration into deep retinal layers. In contrast, VLDLR knockout mice show overgrown intraretinal vasculature and subretinal neovascularization. To understand the mechanisms for the opposite retinal vascular abnormalities between LRP5 and VLDLR mutant mice and to test how a loss of LRP5 perturbs subretinal neovascularization caused by a loss of VLDLR, we have generated and characterized the retinal vasculature in LRP5/VLDLR double knockout (DKO) mice. Our data show that DKO mice develop substantial EC clustering without subretinal neovascularization. The absence of subretinal neovascularization in DKO mice is associated with inhibited migration of ECs into the photoreceptor cell layer. In addition, the transcription level of Slc38a5, which encodes a Müller cell specific glutamine transporter, is significantly reduced in DKO mice, similar to previously reported changes in LRP5 single knockout mice. Thus, LRP5 signaling is a prerequisite for neovascularization in VLDLR knockout mice. LRP5 may be an effective target for inhibiting intraretinal neovascularization.
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Wang LL, Chen H, Huang K, Zheng L. Elevated histone acetylations in Müller cell contribute to inflammation: A novel inhibitory effect of minocycline. Glia 2012; 60:1896-905. [DOI: 10.1002/glia.22405] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2012] [Accepted: 07/24/2012] [Indexed: 11/10/2022]
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Chen J, Stahl A, Krah NM, Seaward MR, Joyal JS, Juan AM, Hatton CJ, Aderman CM, Dennison RJ, Willett KL, Sapieha P, Smith LEH. Retinal expression of Wnt-pathway mediated genes in low-density lipoprotein receptor-related protein 5 (Lrp5) knockout mice. PLoS One 2012; 7:e30203. [PMID: 22272305 PMCID: PMC3260226 DOI: 10.1371/journal.pone.0030203] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Accepted: 12/12/2011] [Indexed: 01/13/2023] Open
Abstract
Mutations in low-density lipoprotein receptor-related protein 5 (Lrp5) impair retinal angiogenesis in patients with familial exudative vitreoretinopathy (FEVR), a rare type of blinding vascular eye disease. The defective retinal vasculature phenotype in human FEVR patients is recapitulated in Lrp5 knockout (Lrp5−/−) mouse with delayed and incomplete development of retinal vessels. In this study we examined gene expression changes in the developing Lrp5−/− mouse retina to gain insight into the molecular mechanisms that underlie the pathology of FEVR in humans. Gene expression levels were assessed with an Illumina microarray on total RNA from Lrp5−/− and WT retinas isolated on postnatal day (P) 8. Regulated genes were confirmed using RT-qPCR analysis. Consistent with a role in vascular development, we identified expression changes in genes involved in cell-cell adhesion, blood vessel morphogenesis and membrane transport in Lrp5−/− retina compared to WT retina. In particular, tight junction protein claudin5 and amino acid transporter slc38a5 are both highly down-regulated in Lrp5−/− retina. Similarly, several Wnt ligands including Wnt7b show decreased expression levels. Plasmalemma vesicle associated protein (plvap), an endothelial permeability marker, in contrast, is up-regulated consistent with increased permeability in Lrp5−/− retinas. Together these data suggest that Lrp5 regulates multiple groups of genes that influence retinal angiogenesis and may contribute to the pathogenesis of FEVR.
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Affiliation(s)
- Jing Chen
- Department of Ophthalmology, Harvard Medical School, Children's Hospital Boston, Boston, Massachusetts, United States of America
| | - Andreas Stahl
- Department of Ophthalmology, Harvard Medical School, Children's Hospital Boston, Boston, Massachusetts, United States of America
- University Eye Hospital Freiburg, Freiburg, Germany
| | - Nathan M. Krah
- Department of Ophthalmology, Harvard Medical School, Children's Hospital Boston, Boston, Massachusetts, United States of America
| | - Molly R. Seaward
- Department of Ophthalmology, Harvard Medical School, Children's Hospital Boston, Boston, Massachusetts, United States of America
| | - Jean-Sebastian Joyal
- Department of Ophthalmology, Harvard Medical School, Children's Hospital Boston, Boston, Massachusetts, United States of America
| | - Aimee M. Juan
- Department of Ophthalmology, Harvard Medical School, Children's Hospital Boston, Boston, Massachusetts, United States of America
| | - Colman J. Hatton
- Department of Ophthalmology, Harvard Medical School, Children's Hospital Boston, Boston, Massachusetts, United States of America
| | - Christopher M. Aderman
- Department of Ophthalmology, Harvard Medical School, Children's Hospital Boston, Boston, Massachusetts, United States of America
| | - Roberta J. Dennison
- Department of Ophthalmology, Harvard Medical School, Children's Hospital Boston, Boston, Massachusetts, United States of America
| | - Keirnan L. Willett
- Department of Ophthalmology, Harvard Medical School, Children's Hospital Boston, Boston, Massachusetts, United States of America
| | - Przemyslaw Sapieha
- Department of Ophthalmology, Harvard Medical School, Children's Hospital Boston, Boston, Massachusetts, United States of America
- Department of Ophthalmology, Maisonneuve-Rosemont Hospital Research Centre, University of Montreal, Montreal, Canada
| | - Lois E. H. Smith
- Department of Ophthalmology, Harvard Medical School, Children's Hospital Boston, Boston, Massachusetts, United States of America
- * E-mail:
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Gnana-Prakasam JP, Reddy SK, Veeranan-Karmegam R, Smith SB, Martin PM, Ganapathy V. Polarized distribution of heme transporters in retinal pigment epithelium and their regulation in the iron-overload disease hemochromatosis. Invest Ophthalmol Vis Sci 2011; 52:9279-86. [PMID: 22058337 DOI: 10.1167/iovs.11-8264] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE FLVCR, BCRP, and PCFT/HCP-1 represent the three heme transporters identified thus far in mammalian cells, but there is very little known about their expression and regulation in the retina. In this study, the expression of these transporters in mouse retina and retinal pigment epithelium (RPE) and their regulation in the iron-overload disease hemochromatosis were examined. METHODS The expression of FLVCR, BCRP, and PCFT in mouse retina and primary mouse RPE cells was studied by RT-PCR and immunofluorescence. Polarized localization of the transporters in RPE was studied by co-localization using a specific marker of the RPE apical membrane. Uptake of heme in primary RPE cells was determined using zinc-mesoporphyrin, a fluorescent heme analogue. The regulation of heme transporters by iron overload was studied in two genetic models of hemochromatosis (HFE-null mouse and HJV-null mouse) and in two nongenetic models of iron overload (cytomegalovirus infection and treatment with ferric ammonium citrate). RESULTS All three heme transporters were expressed in the retina and RPE. In the RPE, the expression of FLVCR was restricted to the apical membrane, and the expression of BCRP and PCFT was restricted to the basolateral membrane. In all cases of iron overload, the expression of FLVCR and PCFT was upregulated and that of BCRP was downregulated. CONCLUSIONS Hemochromatosis is associated not only with excessive accumulation of free iron in the retina and RPE but also with excessive accumulation of heme. Since heme is toxic at high levels, as is free iron, heme-induced oxidative damage may also play a role in hemochromatosis-associated retinal pathology.
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Affiliation(s)
- Jaya P Gnana-Prakasam
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Georgia Health Sciences University, Augusta, Georgia 30912, USA
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Shatanawi A, Romero MJ, Iddings JA, Chandra S, Umapathy NS, Verin AD, Caldwell RB, Caldwell RW. Angiotensin II-induced vascular endothelial dysfunction through RhoA/Rho kinase/p38 mitogen-activated protein kinase/arginase pathway. Am J Physiol Cell Physiol 2011; 300:C1181-92. [PMID: 21289285 DOI: 10.1152/ajpcell.00328.2010] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Enhanced vascular arginase activity impairs endothelium-dependent vasorelaxation by decreasing l-arginine availability to endothelial nitric oxide (NO) synthase, thereby reducing NO production. Elevated angiotensin II (ANG II) is a key component of endothelial dysfunction in many cardiovascular diseases and has been linked to elevated arginase activity. We determined signaling mechanisms by which ANG II increases endothelial arginase function. Results show that ANG II (0.1 μM, 24 h) elevates arginase activity and arginase I expression in bovine aortic endothelial cells (BAECs) and decreases NO production. These effects are prevented by the arginase inhibitor BEC (100 μM). Blockade of ANG II AT(1) receptors or transfection with small interfering RNA (siRNA) for Gα12 and Gα13 also prevents ANG II-induced elevation of arginase activity, but siRNA for Gαq does not. ANG II also elevates active RhoA levels and induces phosphorylation of p38 MAPK. Inhibitors of RhoA activation (simvastatin, 0.1 μM) or Rho kinase (ROCK) (Y-27632, 10 μM; H1152, 0.5 μM) block both ANG II-induced elevation of arginase activity and phosphorylation of p38 MAPK. Furthermore, pretreatment of BAECs with p38 inhibitor SB-202190 (2 μM) or transfection with p38 MAPK siRNA prevents ANG II-induced increased arginase activity/expression and maintains NO production. Additionally, inhibitors of p38 MAPK (SB-203580, 5 μg·kg(-1)·day(-1)) or arginase (ABH, 8 mg·kg(-1)·day(-1)) or arginase gene knockout in mice prevents ANG II-induced vascular endothelial dysfunction and associated enhancement of arginase. These results indicate that ANG II increases endothelial arginase activity/expression through Gα12/13 G proteins coupled to AT(1) receptors and subsequent activation of RhoA/ROCK/p38 MAPK pathways leading to endothelial dysfunction.
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Affiliation(s)
- Alia Shatanawi
- Dept. of Pharmacology and Toxicology, Georgia Health Sciences University, Augusta, GA 30912, USA
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LRP5 is required for vascular development in deeper layers of the retina. PLoS One 2010; 5:e11676. [PMID: 20652025 PMCID: PMC2907392 DOI: 10.1371/journal.pone.0011676] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Accepted: 06/28/2010] [Indexed: 11/19/2022] Open
Abstract
Background The low-density lipoprotein receptor-related protein 5 (LRP5) plays an important role in the development of retinal vasculature. LRP5 loss-of-function mutations cause incomplete development of retinal vessel network in humans as well as in mice. To understand the underlying mechanism for how LRP5 mutations lead to retinal vascular abnormalities, we have determined the retinal cell types that express LRP5 and investigated specific molecular and cellular functions that may be regulated by LRP5 signaling in the retina. Methods and Findings We characterized the development of retinal vasculature in LRP5 mutant mice using specific retinal cell makers and a GFP transgene expressed in retinal endothelial cells. Our data revealed that retinal vascular endothelial cells predominantly formed cell clusters in the inner-plexiform layer of LRP5 mutant retina rather than sprouting out or migrating into deeper layers to form normal vascular network in the retina. The IRES-β-galactosidase (LacZ) report gene under the control of the endogenous LRP5 promoter was highly expressed in Müller cells and was also weakly detected in endothelial cells of the retinal surface vasculature. Moreover, the LRP5 mutant mice had a reduction of a Müller cell-specific glutamine transporter, Slc38a5, and showed a decrease in b-wave amplitude of electroretinogram. Conclusions LRP5 is not only essential for vascular endothelial cells to sprout, migrate and/or anastomose in the deeper plexus during retinal vasculature development but is also important for the functions of Müller cells and retinal interneurons. Müller cells may utilize LRP5-mediated signaling pathway to regulate vascular development in deeper layers and to maintain the function of retinal interneurons.
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Liu X, Li Y, Liu Y, Luo Y, Wang D, Annex BH, Goldschmidt-Clermont PJ. Endothelial progenitor cells (EPCs) mobilized and activated by neurotrophic factors may contribute to pathologic neovascularization in diabetic retinopathy. THE AMERICAN JOURNAL OF PATHOLOGY 2009; 176:504-15. [PMID: 19948824 DOI: 10.2353/ajpath.2010.081152] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Diabetic retinopathy is characterized by pathological retinal neovascularization. Accumulating evidence has indicated that high levels of circulating endothelial progenitor cells (EPCs) are an important risk factor for neovascularization. Paradoxically, the reduction and dysfunction of circulating EPCs has been extensively reported in diabetic patients. We hypothesized that EPCs are differentially altered in the various vasculopathic complications of diabetes mellitus, exhibiting distinct behaviors in terms of angiogenic response to ischemia and growth factors and potentially playing a potent role in motivating vascular precursors to induce pathological neovascularization. Circulating levels of EPCs from diabetic retinopathy patients were analyzed by flow cytometry and by counting EPC colony-forming units, and serum levels of neurotrophic factors were measured by enzyme-linked immunosorbent assay. We found increased levels of nerve growth factor and brain-derived neurotrophic factor in the blood of diabetic retinopathy patients; this increase was correlated with the levels of circulating EPCs. In addition, we demonstrated that retinal cells released neurotrophic factors under hypoxic conditions to enhance EPC activity in vitro and to increase angiogenesis in a mouse ischemic hindlimb model. These results suggest that neurotrophic factors may induce neoangiogenesis through EPC activation, leading to the pathological retinal neovascularization. Thus, we propose that neovascularization in the ischemic retina might be regulated by overexpression of neurotrophic factors.
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Affiliation(s)
- Xialin Liu
- Zhongshan Ophthalmic Center, State Key Laboratory of Ophthalmology, Sun Yat-sen University, Guangzhou 510060, China.
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Okamoto M, Akanuma SI, Tachikawa M, Hosoya KI. Characteristics of glycine transport across the inner blood-retinal barrier. Neurochem Int 2009; 55:789-95. [PMID: 19666071 DOI: 10.1016/j.neuint.2009.08.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Revised: 07/28/2009] [Accepted: 08/01/2009] [Indexed: 10/20/2022]
Abstract
Although glycine plays a pivotal role in neurotransmission and neuromodulation in the retina and is present in high concentration in the retina, the source of retinal glycine is still unclear. The purpose of the present study was to investigate glycine transport across the inner blood-retinal barrier (inner BRB). [(14)C]Glycine transport at the inner BRB was characterized using a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2 cells) as an in vitro model of the inner BRB and in vivo vascular injection techniques. [(14)C]Glycine uptake by TR-iBRB2 cells was Na(+)- and Cl(-)-dependent, and concentration-dependent with Michaelis-Menten constants of 55.4 microM and 8.02 mM, and inhibited by glycine transporter 1 (GlyT1) and system A inhibitors. These uptake studies suggest that GlyT1 and system A are involved in [(14)C]glycine uptake by TR-iBRB2 cells. RT-PCR analysis demonstrated that GlyT1 and system A (encoding ATA 1 and ATA2) mRNA are expressed in TR-iBRB2 cells. An in vivo study suggested that [(14)C]glycine is transported from blood to the retina whereas [(14)C]alpha-methylaminoisobutyric acid, a selective substrate for system A, is not. In conclusion, GlyT1 most likely mediates glycine transport at the inner BRB and is expected to play an important role in regulating the glycine concentration in the neural retina.
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Affiliation(s)
- Masashi Okamoto
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
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Expression of the iron-regulatory protein haemojuvelin in retina and its regulation during cytomegalovirus infection. Biochem J 2009; 419:533-43. [PMID: 19191760 DOI: 10.1042/bj20082240] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Haemochromatosis is a genetic disorder of iron overload resulting from loss-of-function mutations in genes coding for the iron-regulatory proteins HFE [HLA-like protein involved in iron (Fe) homoeostasis], transferrin receptor 2, ferroportin, hepcidin and HJV (haemojuvelin). Expression of the first four genes coding for these proteins in retina has been established. Here we report on the expression of HJV. Since infection of retina with CMV (cytomegalovirus) causes blindness, we also investigated the expression of HJV and other iron-regulatory proteins in retina during CMV infection. HJV (HJV gene) mRNA was expressed in RPE (retinal pigment epithelium)/eyecup and neural retina in mouse. In situ hybridization and immunohistochemistry confirmed the presence of HJV mRNA and protein in RPE, outer and inner nuclear layers, and ganglion cell layer. Immunocytochemistry with cell lines and primary cell cultures showed HJV expression in RPE and Müller cells. In RPE, the expression was restricted to apical membrane. Infection of primary cultures of mouse RPE with CMV increased HJV mRNA and protein levels. Under similar conditions, HFE (HFE gene) mRNA levels were not altered, but HFE protein was decreased. Hepcidin expression was, however, not altered. These findings were demonstrable in vivo with CMV-infected mouse retina. The CMV-induced up-regulation of HJV in RPE was independent of changes in HFE because the phenomenon was also seen in HFE-null RPE cells. CMV-infected primary RPE cells showed evidence of iron accumulation and oxidative stress, as indicated by increased levels of ferritin and hydroxynonenal. The observed changes in HJV expression and iron status during CMV infection in retina may have significance in the pathophysiology of CMV retinitis.
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Role of retinal glial cells in neurotransmitter uptake and metabolism. Neurochem Int 2009; 54:143-60. [DOI: 10.1016/j.neuint.2008.10.014] [Citation(s) in RCA: 171] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2008] [Revised: 10/15/2008] [Accepted: 10/20/2008] [Indexed: 11/30/2022]
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Effects of hyperglycemia and oxidative stress on the glutamate transporters GLAST and system xc- in mouse retinal Müller glial cells. Cell Tissue Res 2009; 335:477-88. [PMID: 19156441 DOI: 10.1007/s00441-008-0742-1] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Accepted: 12/09/2008] [Indexed: 10/21/2022]
Abstract
Elevated glutamate levels have been reported in humans with diabetic retinopathy. Retinal Müller glial cells regulate glutamate levels via the GLAST transporter and system x(c)(-) (cystine-glutamate exchanger). We have investigated whether transporter function and gene and/or protein expression are altered in mouse Müller cells cultured under conditions of hyperglycemia or oxidative stress (two factors implicated in diabetic retinopathy). Cells were subjected to hyperglycemic conditions (35 mM glucose) over an 8-day period or to oxidative stress conditions (induced by exposure to various concentrations of xanthine:xanthine oxidase) for 6 h. The Na(+)-dependent and -independent uptake of [(3)H] glutamate was assessed as a measure of GLAST and system x(c)(-) function, respectively. Hyperglycemia did not alter the uptake of [(3)H] glutamate by GLAST or system x(c)(-); neither gene nor protein expression decreased. Oxidative stress (70:14 or 100:20 microM xanthine:mU/ml xanthine oxidase) decreased GLAST activity by approximately 10% but increased system x(c)(-) activity by 43% and 89%, respectively. Kinetic analysis showed an oxidative-stress-induced change in V(max), but not K(m). Oxidative stress caused a 2.4-fold increase in mRNA encoding xCT, the unique component of system x(c)(-). Of the two isoforms of xCT (40 and 50 kDa), oxidative stress induced a 3.6-fold increase in the 40-kDa form localized to the plasma membrane. This is the first report of the differential expression and localization of xCT isoforms as caused by cellular stress. Increased system x(c)(-) activity in Müller cells subjected to conditions associated with diabetic retinopathy may be beneficial, as this exchanger is important for the synthesis of the antioxidant glutathione.
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Umapathy NS, Dun Y, Martin PM, Duplantier JN, Roon P, Prasad P, Smith SB, Ganapathy V. Expression and function of system N glutamine transporters (SN1/SN2 or SNAT3/SNAT5) in retinal ganglion cells. Invest Ophthalmol Vis Sci 2008; 49:5151-60. [PMID: 18689705 DOI: 10.1167/iovs.08-2245] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
PURPOSE Glutamine transport is essential for the glutamate-glutamine cycle, which occurs between neurons and glia. System N, consisting of SN1 (SNAT3) and SN2 (SNAT5), is the principal mediator of glutamine transport in retinal Müller cells. Mediators of glutamine transport in retinal ganglion cells were investigated. METHODS The relative contributions of various transport systems for glutamine uptake (systems N, A, L, y+L, ASCT, and ATB(0,+)) were examined in RGC-5 cells based on differential features of the individual transport systems. mRNA for the genes encoding members of these transport systems were analyzed by RT-PCR. Based on these data, SN1 and SN2 were analyzed in mouse retina, RGC-5 cells, and primary mouse ganglion cells (GCs) by in situ hybridization (ISH), immunofluorescence (IF), and Western blotting. RESULTS Three transport systems--N, A, and L--participated in glutamine uptake in RGC-5 cells. System N was the principal contributor; systems A and L contributed considerably less. ISH and IF revealed SN1 and SN2 expression in the ganglion, inner nuclear, and photoreceptor cell layers. SN1 and SN2 colocalized with the ganglion cell marker Thy 1.2 and with the Müller cell marker vimentin, confirming their presence in both retinal cell types. SN1 and SN2 proteins were detected in primary mouse GCs. CONCLUSIONS These findings suggest that in addition to its role in glutamine uptake in retinal glial cells, system N contributes significantly to glutamine uptake in ganglion cells and, hence, contributes to the retinal glutamate-glutamine cycle.
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Affiliation(s)
- Nagavedi S Umapathy
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia 30912, USA
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Hepcidin expression in mouse retina and its regulation via lipopolysaccharide/Toll-like receptor-4 pathway independent of Hfe. Biochem J 2008; 411:79-88. [PMID: 18042040 DOI: 10.1042/bj20071377] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Hepcidin is a hormone central to the regulation of iron homeostasis in the body. It is believed to be produced exclusively by the liver. Ferroportin, an iron exporter, is the receptor for hepcidin. This transporter/receptor is expressed in Müller cells, photoreceptor cells and the RPE (retinal pigment epithelium) within the retina. Since the retina is protected by the retinal-blood barriers, we asked whether ferroportin in the retina is regulated by hepcidin in the circulation or whether the retina produces hepcidin for regulation of its own iron homeostasis. Here we show that hepcidin is expressed robustly in Müller cells, photoreceptor cells and RPE cells, closely resembling the expression pattern of ferroportin. We also show that bacterial LPS (lipopolysaccharide) is a regulator of hepcidin expression in Müller cells and the RPE, both in vitro and in vivo, and that the regulation occurs at the transcriptional level. The action of LPS on hepcidin expression is mediated by the TLR4 (Toll-like receptor-4). The upregulation of hepcidin by LPS occurs independent of Hfe (human leukocyte antigen-like protein involved in Fe homeostasis). The increase in hepcidin levels in retinal cells in response to LPS treatment is associated with a decrease in ferroportin levels. The LPS-induced upregulation of hepcidin and consequent down-regulation of ferroportin is associated with increased oxidative stress and apoptosis within the retina in vivo. We conclude that retinal iron homeostasis may be regulated in an autonomous manner by hepcidin generated within the retina and that chronic bacterial infection/inflammation of the retina may disrupt iron homeostasis and retinal function.
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Jiang G, Mysona B, Dun Y, Gnana-Prakasam JP, Pabla N, Li W, Dong Z, Ganapathy V, Smith SB. Expression, subcellular localization, and regulation of sigma receptor in retinal muller cells. Invest Ophthalmol Vis Sci 2006; 47:5576-82. [PMID: 17122151 PMCID: PMC3724475 DOI: 10.1167/iovs.06-0608] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Sigma receptors (sigmaRs) are nonopioid, nonphencyclidine binding sites with robust neuroprotective properties. Type 1 sigmaR1 (sigmaR1) is expressed in brain oligodendrocytes, but its expression and binding capacity have not been analyzed in retinal glial cells. This study examined the expression, subcellular localization, binding activity, and regulation of sigmaR1 in retinal Müller cells. METHODS Primary mouse Müller cells (MCs) were analyzed by RT-PCR, immunoblotting, and immunocytochemistry for the expression of sigmaR1, and data were compared with those of the rat Müller cell line (rMC-1) and the rat ganglion cell line (RGC-5). Confocal microscopy was used to determine the subcellular sigmaR1 location in primary mouse MCs. Membranes prepared from these cells were used for binding assays with [3H]-pentazocine (PTZ). The kinetics of binding, the ability of various sigmaR1 ligands to compete with sigmaR1 binding, and the effects of donated nitric oxide (NO) and reactive oxygen species (ROS) on binding were examined. RESULTS sigmaR1 is expressed in primary mouse MCs and is localized to the nuclear and endoplasmic reticulum membranes. Binding assays showed that in primary mouse MCs, rMC-1, and RGC-5, the binding of PTZ was saturable. [3H]-PTZ bound with high affinity in RGC-5 and rMC-1 cells, and the binding was similarly robust in primary mouse MCs. Competition studies showed marked inhibition of [3H]-PTZ binding in the presence of sigmaR1-specific ligands. Incubation of cells with NO and ROS donors markedly increased sigmaR1 binding activity. CONCLUSIONS MCs express sigmaR1 and demonstrate robust sigmaR1 binding activity, which is inhibited by sigmaR1 ligands and is stimulated during oxidative stress. The potential of Müller cells to bind sigmaR1 ligands may prove beneficial in retinal degenerative diseases such as diabetic retinopathy.
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Affiliation(s)
- Guoliang Jiang
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
| | - Barbara Mysona
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
| | - Ying Dun
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
| | - Jaya P. Gnana-Prakasam
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA
| | - Navjotsin Pabla
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
| | - Weiguo Li
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
| | - Zheng Dong
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
| | - Vadivel Ganapathy
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA
| | - Sylvia B. Smith
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
- Department of Ophthalmology, Medical College of Georgia, Augusta, GA
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Dun Y, Mysona B, Itagaki S, Martin-Studdard A, Ganapathy V, Smith S. Functional and molecular analysis of D-serine transport in retinal Müller cells. Exp Eye Res 2006; 84:191-9. [PMID: 17094966 PMCID: PMC3773703 DOI: 10.1016/j.exer.2006.09.015] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Revised: 09/21/2006] [Accepted: 09/22/2006] [Indexed: 12/31/2022]
Abstract
D-serine, an endogenous co-agonist of NMDA receptors in vertebrate retina, may modulate glutamate sensitivity of retinal neurons. This study determined at the functional and molecular level the transport process responsible for D-serine in retinal Müller cells. RT-PCR and immunoblotting showed that serine racemase (SR), the synthesizing enzyme for D-serine, is expressed in the rMC-1 Müller cell line and primary cultures of mouse Müller cells (1 degrees MCs). The relative contributions of different amino acid transport systems to d-serine uptake were determined based on differential substrate specificities and ion dependencies. D-serine uptake was obligatorily dependent on Na+, eliminating Na+-independent transporters (asc-1 and system L) for D-serine in Müller cells. The Na+:substrate stoichiometry for the transport process was 1:1. D-serine transport was inhibited by alanine, serine, cysteine, glutamine, and asparagine, but not anionic amino acids or cationic amino acids, suggesting that D-serine transport in Müller cells occurs via ASCT2 rather than ASCT1 or ATB0,+. The expression of mRNAs specific for ASCT1, ASCT2, and ATB0,+ was analyzed by RT-PCR confirming the expression of ASCT2 (and ASCT1) mRNA, but not ATB0,+, in Müller cells. Immunoblotting detected ASCT2 in neural retina and in 1 degrees MCs; immunohistochemistry confirmed these data in retinal sections and in cultures of 1 degrees MCs. The efflux of D-serine via ASCT2 by ASCT2 substrates was demonstrable using the Xenopus laevis oocyte heterologous expression system. These data provide the first molecular evidence for SR and ASCT2 expression in a Müller cell line and in 1 degrees MCs and suggest that D-serine, synthesized in Müller cells by SR, is effluxed via ASCT2 to regulate NMDA receptors in adjacent neurons.
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Affiliation(s)
- Y. Dun
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
| | - B. Mysona
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
| | - S. Itagaki
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA
| | - A. Martin-Studdard
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
| | - V. Ganapathy
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA
| | - S.B. Smith
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA
- Department of Ophthalmology, Medical College of Georgia, Augusta, GA
- Please send correspondence to: Sylvia B. Smith, Ph.D., Department of Cellular Biology and Anatomy, Medical College of Georgia, 1459 Laney-Walker Blvd., CB 2820, Augusta, GA 30912-2000, 706-721-7392 (phone), 706-721-6839 (fax),
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Kutty RK, Samuel W, Chen S, Vijayasarathy C, Dun Y, Mysona B, Wiggert B, Smith SB. Immunofluorescence analysis of the expression of Norpeg (Rai14) in retinal Müller and ganglion cells. Neurosci Lett 2006; 404:294-8. [PMID: 16806700 DOI: 10.1016/j.neulet.2006.06.006] [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] [Received: 04/04/2006] [Revised: 05/31/2006] [Accepted: 06/01/2006] [Indexed: 10/24/2022]
Abstract
Novel retinal pigment epithelial cell gene (Norpeg, Rai14), a developmentally regulated mouse gene, encodes a protein containing six ankyrin repeats and a coiled-coil domain. The objective of the present study was to characterize the Norpeg protein and to analyze its expression in mouse retina using an antibody preparation that we developed. The approximately 110kDa Norpeg was immunoprecipitated and characterized by mass spectrometry. Primary cultures of Müller and ganglion cells isolated from the mouse retina were found to express Norpeg when analyzed by immunoblotting and immunofluorescence microscopy. Immunofluorescence analysis of normal mouse retina sections demonstrated that Norpeg is expressed in cells of the ganglion cell layer, inner nuclear layer as well as in the retinal pigment epithelium. Immunoreactivity was also evident in the radial glial (Müller) cell fibers.
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Affiliation(s)
- R Krishnan Kutty
- Section on Biochemistry, Laboratory of Retinal Cell and Molecular Biology, 7/329, National Eye Institute, National Institutes of Health, Bethesda, MD 20892-0706, USA.
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Papapetropoulos S, FFrench-Mullen J, McCorquodale D, Qin Y, Pablo J, Mash DC. Multiregional gene expression profiling identifies MRPS6 as a possible candidate gene for Parkinson's disease. Gene Expr 2006; 13:205-15. [PMID: 17193926 PMCID: PMC6032441 DOI: 10.3727/000000006783991827] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Combining large-scale gene expression approaches and bioinformatics may provide insights into the molecular variability of biological processes underlying neurodegeneration. To identify novel candidate genes and mechanisms, we conducted a multiregional gene expression analysis in postmortem brain. Gene arrays were performed utilizing Affymetrix HG U133 Plus 2.0 gene chips. Brain specimens from 21 different brain regions were taken from Parkinson's disease (PD) (n = 22) and normal aged (n = 23) brain donors. The rationale for conducting a multiregional survey of gene expression changes was based on the assumption that if a gene is changed in more than one brain region, it may be a higher probability candidate gene compared to genes that are changed in a single region. Although no gene was significantly changed in all of the 21 brain regions surveyed, we identified 11 candidate genes whose pattern of expression was regulated in at least 18 out of 21 regions. The expression of a gene encoding the mitochondria ribosomal protein S6 (MRPS6) had the highest combined mean fold change and topped the list of regulated genes. The analysis revealed other genes related to apoptosis, cell signaling, and cell cycle that may be of importance to disease pathophysiology. High throughput gene expression is an emerging technology for molecular target discovery in neurological and psychiatric disorders. The top gene reported here is the nuclear encoded MRPS6, a building block of the human mitoribosome of the oxidative phosphorylation system (OXPHOS). Impairments in mitochondrial OXPHOS have been linked to the pathogenesis of PD.
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Affiliation(s)
| | | | - Donald McCorquodale
- *Department of Neurology, University of Miami, Miller School of Medicine, Miami, FL, USA
| | - Yujing Qin
- *Department of Neurology, University of Miami, Miller School of Medicine, Miami, FL, USA
| | - John Pablo
- *Department of Neurology, University of Miami, Miller School of Medicine, Miami, FL, USA
| | - Deborah C. Mash
- *Department of Neurology, University of Miami, Miller School of Medicine, Miami, FL, USA
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