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Faura G, Studenovska H, Sekac D, Ellederova Z, Petrovski G, Eide L. The Effects of the Coating and Aging of Biodegradable Polylactic Acid Membranes on In Vitro Primary Human Retinal Pigment Epithelium Cells. Biomedicines 2024; 12:966. [PMID: 38790928 PMCID: PMC11117638 DOI: 10.3390/biomedicines12050966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 04/17/2024] [Accepted: 04/24/2024] [Indexed: 05/26/2024] Open
Abstract
Age-related macular degeneration (AMD) is the most frequent cause of blindness in developed countries. The replacement of dysfunctional human retinal pigment epithelium (hRPE) cells by the transplantation of in vitro-cultivated hRPE cells to the affected area emerges as a feasible strategy for regenerative therapy. Synthetic biomimetic membranes arise as powerful hRPE cell carriers, but as biodegradability is a requirement, it also poses a challenge due to its limited durability. hRPE cells exhibit several characteristics that putatively respond to the type of membrane carrier, and they can be used as biomarkers to evaluate and further optimize such membranes. Here, we analyze the pigmentation, transepithelial resistance, genome integrity, and maturation markers of hRPE cells plated on commercial polycarbonate (PC) versus in-house electrospun polylactide-based (PLA) membranes, both enabling separate apical/basolateral compartments. Our results show that PLA is superior to PC-based membranes for the cultivation of hRPEs, and the BEST1/RPE65 maturation markers emerge as the best biomarkers for addressing the quality of hRPE cultivated in vitro. The stability of the cultures was observed to be affected by PLA aging, which is an effect that could be partially palliated by the coating of the PLA membranes.
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Affiliation(s)
- Georgina Faura
- Department of Medical Biochemistry, Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, 0372 Oslo, Norway
- CIDETEC, Basque Research and Technology Alliance (BRTA), 20014 Donostia-San Sebastián, Spain
| | - Hana Studenovska
- Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 00 Prague, Czech Republic;
| | - David Sekac
- Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, 277 21 Libechov, Czech Republic; (D.S.); (Z.E.)
- Department of Cell Biology, Faculty of Science, Charles University, 128 00 Prague, Czech Republic
| | - Zdenka Ellederova
- Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, 277 21 Libechov, Czech Republic; (D.S.); (Z.E.)
| | - Goran Petrovski
- Center for Eye Research and Innovative Diagnostics, Department of Ophthalmology, Oslo University Hospital and Institute for Clinical Medicine, University of Oslo, 0424 Oslo, Norway;
- Norwegian Center for Stem Cell Research, Oslo University Hospital, 0424 Oslo, Norway
- Department of Ophthalmology, University Hospital Centre, University of Split School of Medicine, 21000 Split, Croatia
- UKLO Network, University St. Kliment Ohridski, 7000 Bitola, North Macedonia
| | - Lars Eide
- Department of Medical Biochemistry, Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, 0372 Oslo, Norway
- Department of Medical Biochemistry, Oslo University Hospital, 0424 Oslo, Norway
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Hansman D, Ma Y, Thomas D, Smith J, Casson R, Peet D. Metabolic reprogramming of the retinal pigment epithelium by cytokines associated with age-related macular degeneration. Biosci Rep 2024; 44:BSR20231904. [PMID: 38567515 PMCID: PMC11043024 DOI: 10.1042/bsr20231904] [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: 11/22/2023] [Revised: 03/17/2024] [Accepted: 04/02/2024] [Indexed: 04/04/2024] Open
Abstract
The complex metabolic relationship between the retinal pigment epithelium (RPE) and photoreceptors is essential for maintaining retinal health. Recent evidence indicates the RPE acts as an adjacent lactate sink, suppressing glycolysis in the epithelium in order to maximize glycolysis in the photoreceptors. Dysregulated metabolism within the RPE has been implicated in the pathogenesis of age-related macular degeneration (AMD), a leading cause of vision loss. In the present study, we investigate the effects of four cytokines associated with AMD, TNFα, TGF-β2, IL-6, and IL-1β, as well as a cocktail containing all four cytokines, on RPE metabolism using ARPE-19 cells, primary human RPE cells, and ex vivo rat eyecups. Strikingly, we found cytokine-specific changes in numerous metabolic markers including lactate production, glucose consumption, extracellular acidification rate, and oxygen consumption rate accompanied by increases in total mitochondrial volume and ATP production. Together, all four cytokines could potently override the constitutive suppression of glycolysis in the RPE, through a mechanism independent of PI3K/AKT, MEK/ERK, or NF-κB. Finally, we observed changes in glycolytic gene expression with cytokine treatment, including in lactate dehydrogenase subunit and glucose transporter expression. Our findings provide new insights into the metabolic changes in the RPE under inflammatory conditions and highlight potential therapeutic targets for AMD.
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Affiliation(s)
- David S. Hansman
- School of Biological Sciences, University of Adelaide, Adelaide, SA, Australia
| | - Yuefang Ma
- College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Daniel Thomas
- South Australian Health and Medical Research Institute (SAHMRI), Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | - Justine R. Smith
- College of Medicine and Public Health, Flinders University, Adelaide, SA, Australia
| | - Robert J. Casson
- Discipline of Ophthalmology and Visual Science, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | - Daniel J. Peet
- School of Biological Sciences, University of Adelaide, Adelaide, SA, Australia
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3
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Rizwan S, Toothman B, Li B, Engel AJ, Lim RR, Lu J, Chao JR, Du J. Metabolic phenotyping of healthy and diseased human RPE cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.28.582405. [PMID: 38464098 PMCID: PMC10925320 DOI: 10.1101/2024.02.28.582405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Purpose Metabolic defects in retinal pigment epithelium (RPE) are underlying many retinal degenerative diseases. This study aims to identify the nutrient requirements of healthy and diseased human RPE cells. Methods We profiled the utilization of 183 nutrients in human RPE cells: 1) differentiated and dedifferentiated fetal RPE (fRPE), 2) induced pluripotent stem cell derived-RPE (iPSC RPE), 3) Sorsby fundus dystrophy (SFD) patient-derived iPSC RPE and its CRISPR-corrected isogenic SFD (cSFD) iPSC RPE, and 5) ARPE-19 cell lines cultured under different conditions. Results Differentiated fRPE cells and healthy iPSC RPE cells can utilize 51 and 48 nutrients respectively, including sugars, intermediates from glycolysis and tricarboxylic acid (TCA) cycle, fatty acids, ketone bodies, amino acids, and dipeptides. However, when fRPE cells lose epithelial phenotype through dedifferentiated, they can only utilize 17 nutrients, primarily sugar and glutamine-related amino acids. SFD RPE cells can utilize 37 nutrients; however, Compared to cSFD RPE and healthy iPSC RPE, they are unable to utilize lactate, some TCA cycle intermediates, and short-chain fatty acids. Nonetheless, they show increased utilization of branch-chain amino acids (BCAAs) and BCAA-containing dipeptides. The dedifferentiated ARPE-19 cells in traditional culture media cannot utilize lactate and ketone bodies. In contrast, nicotinamide supplementation promotes differentiation into epithelial phenotype, restoring the ability to use these nutrients. Conclusions Epithelial phenotype confers metabolic flexibility to the RPE for utilizing various nutrients. SFD RPE cells have reduced metabolic flexibility, relying on the oxidation of BCAAs. Our findings highlight the importance of nutrient availability and utilization in RPE differentiation and diseases.
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Affiliation(s)
- Saira Rizwan
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
| | - Beverly Toothman
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
| | - Bo Li
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
- Department of Ophthalmology, Affiliated Hospital of Yangzhou University, Yangzhou University, Yangzhou, Jiangsu Province 225100, China
| | - Abbi J. Engel
- Department of Ophthalmology, University of Washington, Seattle, WA 98109, United States
| | - Rayne R Lim
- Department of Ophthalmology, University of Washington, Seattle, WA 98109, United States
| | - Jinyu Lu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
| | - Jennifer R. Chao
- Department of Ophthalmology, University of Washington, Seattle, WA 98109, United States
| | - Jianhai Du
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
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Sturgis J, Singh R, Caron Q, Samuels IS, Shiju TM, Mukkara A, Freedman P, Bonilha VL. Modeling aging and retinal degeneration with mitochondrial DNA mutation burden. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.30.569464. [PMID: 38076962 PMCID: PMC10705408 DOI: 10.1101/2023.11.30.569464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2023]
Abstract
Somatic mitochondrial DNA (mtDNA) mutation accumulation has been observed in individuals with retinal degenerative disorders. To study the effects of aging and mtDNA mutation accumulation in the retina, a Polymerase gamma (POLG) deficiency model, the POLGD257A mutator mice (PolgD257A), was used. POLG is an enzyme responsible for regulating mtDNA replication and repair. Retinas of young and older mice with this mutation were analyzed in vivo and ex vivo to provide new insights into the contribution of age-related mitochondrial dysfunction due to mtDNA damage. Optical coherence tomography (OCT) image analysis revealed a decrease in retinal and photoreceptor thickness starting at 6 months of age in mice with the POLGD257A mutation compared to wild-type (WT) mice. Electroretinography (ERG) testing showed a significant decrease in all recorded responses at 6 months of age. Sections labeled with markers of different types of retinal cells, including cones, rods, and bipolar cells, exhibited decreased labeling starting at 6 months. However, electron microscopy analysis revealed differences in retinal pigment epithelium (RPE) mitochondria morphology beginning at 3 months. Interestingly, there was no increase in oxidative stress observed in the retina or RPE of POLGD257A mice. Additionally, POLGD257A RPE exhibited an accelerated rate of autofluorescence cytoplasmic granule formation and accumulation. Mitochondrial markers displayed decreased abundance in protein lysates obtained from retina and RPE samples. These findings suggest that the accumulation of mitochondrial DNA mutations leads to impaired mitochondrial function and accelerated aging, resulting in retinal degeneration.
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Affiliation(s)
- John Sturgis
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Rupesh Singh
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Quinn Caron
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Ivy S. Samuels
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
- Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH
| | - Thomas Micheal Shiju
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Aditi Mukkara
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
- College of Arts and Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Paul Freedman
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
- Debusk College of Osteopathic Medicine, Knoxville, TN, USA
| | - Vera L. Bonilha
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
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5
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Zhu S, Xu R, Engel AL, Wang Y, McNeel R, Hurley JB, Chao JR, Du J. Proline provides a nitrogen source in the retinal pigment epithelium to synthesize and export amino acids for the neural retina. J Biol Chem 2023; 299:105275. [PMID: 37741457 PMCID: PMC10616405 DOI: 10.1016/j.jbc.2023.105275] [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: 04/19/2023] [Revised: 09/07/2023] [Accepted: 09/11/2023] [Indexed: 09/25/2023] Open
Abstract
It is known that metabolic defects in the retinal pigment epithelium (RPE) can cause degeneration of its neighboring photoreceptors in the retina, leading to retinal degenerative diseases such as age-related macular degeneration. However, how RPE metabolism supports the health of the neural retina remains unclear. The retina requires exogenous nitrogen sources for protein synthesis, neurotransmission, and energy metabolism. Using 15N tracing coupled with mass spectrometry, we found human RPE can utilize the nitrogen in proline to produce and export 13 amino acids, including glutamate, aspartate, glutamine, alanine, and serine. Similarly, we found this proline nitrogen utilization in the mouse RPE/choroid but not in the neural retina of explant cultures. Coculture of human RPE with the retina showed that the retina can take up the amino acids, especially glutamate, aspartate, and glutamine, generated from proline nitrogen in the RPE. Intravenous delivery of 15N proline in vivo demonstrated 15N-derived amino acids appear earlier in the RPE before the retina. We also found proline dehydrogenase, the key enzyme in proline catabolism is highly enriched in the RPE but not the retina. The deletion of proline dehydrogenase blocks proline nitrogen utilization in RPE and the import of proline nitrogen-derived amino acids in the retina. Our findings highlight the importance of RPE metabolism in supporting nitrogen sources for the retina, providing insight into understanding the mechanisms of the retinal metabolic ecosystem and RPE-initiated retinal degenerative diseases.
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Affiliation(s)
- Siyan Zhu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA; Department of Pharmaceutical and Pharmacological Sciences, West Virginia University, Morgantown, West Virginia, USA
| | - Rong Xu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA
| | - Abbi L Engel
- Department of Ophthalmology, University of Washington, Seattle, Washington, USA
| | - Yekai Wang
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA
| | - Rachel McNeel
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA
| | - James B Hurley
- Department of Ophthalmology, University of Washington, Seattle, Washington, USA; Department of Biochemistry, University of Washington, Seattle, Washington, USA
| | - Jennifer R Chao
- Department of Ophthalmology, University of Washington, Seattle, Washington, USA.
| | - Jianhai Du
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, USA; Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, USA.
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6
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Grumbine MK, Kamat V, Bao K, Crupi T, Mokate K, Lim R, Chao JR, Robbings BM, Hass DT, Hurley JB, Sweet IR. Maintaining and Assessing Various Tissue and Cell Types of the Eye Using a Novel Pumpless Fluidics System. J Vis Exp 2023:10.3791/65399. [PMID: 37522735 PMCID: PMC10791547 DOI: 10.3791/65399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/01/2023] Open
Abstract
Many in vitro models used to investigate tissue function and cell biology require a flow of media to provide adequate oxygenation and optimal cell conditions required for the maintenance of function and viability. Toward this end, we have developed a multi-channel flow culture system to maintain tissue and cells in culture and continuously assess function and viability by either in-line sensors and/or collection of outflow fractions. The system combines 8-channel, continuous optical sensing of oxygen consumption rate with a built-in fraction collector to simultaneously measure production rates of metabolites and hormone secretion. Although it is able to maintain and assess a wide range of tissue and cell models, including islets, muscle, and hypothalamus, here we describe its operating principles and the experimental preparations/protocols that we have used to investigate bioenergetic regulation of isolated mouse retina, mouse retinal pigment epithelium (RPE)-choroid-sclera, and cultured human RPE cells. Innovations in the design of the system, such as pumpless fluid flow, have produced a greatly simplified operation of a multi-channel flow system. Videos and images are shown that illustrate how to assemble, prepare the instrument for an experiment, and load the different tissue/cell models into the perifusion chambers. In addition, guidelines for selecting conditions for protocol- and tissue-specific experiments are delineated and discussed, including setting the correct flow rate to tissue ratio to obtain consistent and stable culture conditions and accurate determinations of consumption and production rates. The combination of optimal tissue maintenance and real-time assessment of multiple parameters yields highly informative data sets that will have great utility for research in the physiology of the eye and drug discovery for the treatment of impaired vision.
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Affiliation(s)
| | - Varun Kamat
- UW Medicine Diabetes Institute, University of Washington
| | | | | | - Kedar Mokate
- UW Medicine Diabetes Institute, University of Washington
| | - Rayne Lim
- Department of Ophthalmology, University of Washington
| | | | | | - Daniel T Hass
- Department of Biochemistry, University of Washington
| | | | - Ian R Sweet
- EnTox Sciences, Inc; UW Medicine Diabetes Institute, University of Washington;
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7
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Liu Q, Zhang X, Huang H, Chen Y, Wang F, Hao A, Zhan W, Mao Q, Hu Y, Han L, Sun Y, Zhang M, Liu Z, Li GL, Zhang W, Shu Y, Sun L, Chen Z. Asymmetric pendrin homodimer reveals its molecular mechanism as anion exchanger. Nat Commun 2023; 14:3012. [PMID: 37230976 DOI: 10.1038/s41467-023-38303-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 04/23/2023] [Indexed: 05/27/2023] Open
Abstract
Pendrin (SLC26A4) is an anion exchanger expressed in the apical membranes of selected epithelia. Pendrin ablation causes Pendred syndrome, a genetic disorder associated with sensorineural hearing loss, hypothyroid goiter, and reduced blood pressure. However its molecular structure has remained unknown, limiting our understanding of the structural basis of transport. Here, we determine the cryo-electron microscopy structures of mouse pendrin with symmetric and asymmetric homodimer conformations. The asymmetric homodimer consists of one inward-facing protomer and the other outward-facing protomer, representing coincident uptake and secretion- a unique state of pendrin as an electroneutral exchanger. The multiple conformations presented here provide an inverted alternate-access mechanism for anion exchange. The structural and functional data presented here disclose the properties of an anion exchange cleft and help understand the importance of disease-associated variants, which will shed light on the pendrin exchange mechanism.
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Affiliation(s)
- Qianying Liu
- The Fifth People's Hospital of Shanghai and Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China
| | - Xiang Zhang
- The Fifth People's Hospital of Shanghai and Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China
| | - Hui Huang
- The Fifth People's Hospital of Shanghai and Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China
| | - Yuxin Chen
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, 200031, China
- MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China
- NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, 200031, China
| | - Fang Wang
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, 200031, China
- MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China
- NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, 200031, China
| | - Aihua Hao
- The Fifth People's Hospital of Shanghai and Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China
| | - Wuqiang Zhan
- The Fifth People's Hospital of Shanghai and Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China
| | - Qiyu Mao
- The Fifth People's Hospital of Shanghai and Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China
| | - Yuxia Hu
- The Fifth People's Hospital of Shanghai and Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China
| | - Lin Han
- The Fifth People's Hospital of Shanghai and Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China
| | - Yifang Sun
- The Fifth People's Hospital of Shanghai and Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China
| | - Meng Zhang
- The Fifth People's Hospital of Shanghai and Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China
| | - Zhimin Liu
- The Fifth People's Hospital of Shanghai and Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China
| | - Geng-Lin Li
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, 200031, China
- MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China
- NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, 200031, China
| | - Weijia Zhang
- The Fifth People's Hospital of Shanghai and Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China
| | - Yilai Shu
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, 200031, China.
- MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China.
- NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, 200031, China.
- Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China.
| | - Lei Sun
- The Fifth People's Hospital of Shanghai and Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China.
- Shanghai Institute of Infectious Disease and Biosecurity, Shanghai, 200032, China.
- Shanghai Key Laboratory of Medical Epigenetics, Shanghai, 200032, China.
| | - Zhenguo Chen
- The Fifth People's Hospital of Shanghai and Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China.
- Shanghai Institute of Infectious Disease and Biosecurity, Shanghai, 200032, China.
- Shanghai Key Laboratory of Medical Epigenetics, Shanghai, 200032, China.
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8
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Eade KT, Ansell BRE, Giles S, Fallon R, Harkins-Perry S, Nagasaki T, Tzaridis S, Wallace M, Mills EA, Farashi S, Johnson A, Sauer L, Hart B, Diaz-Rubio ME, Bahlo M, Metallo C, Allikmets R, Gantner ML, Bernstein PS, Friedlander M. iPSC-derived retinal pigmented epithelial cells from patients with macular telangiectasia show decreased mitochondrial function. J Clin Invest 2023; 133:e163771. [PMID: 37115691 PMCID: PMC10145939 DOI: 10.1172/jci163771] [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: 07/21/2022] [Accepted: 03/14/2023] [Indexed: 04/29/2023] Open
Abstract
Patient-derived induced pluripotent stem cells (iPSCs) provide a powerful tool for identifying cellular and molecular mechanisms of disease. Macular telangiectasia type 2 (MacTel) is a rare, late-onset degenerative retinal disease with an extremely heterogeneous genetic architecture, lending itself to the use of iPSCs. Whole-exome sequencing screens and pedigree analyses have identified rare causative mutations that account for less than 5% of cases. Metabolomic surveys of patient populations and GWAS have linked MacTel to decreased circulating levels of serine and elevated levels of neurotoxic 1-deoxysphingolipids (1-dSLs). However, retina-specific, disease-contributing factors have yet to be identified. Here, we used iPSC-differentiated retinal pigmented epithelial (iRPE) cells derived from donors with or without MacTel to screen for novel cell-intrinsic pathological mechanisms. We show that MacTel iRPE cells mimicked the low serine levels observed in serum from patients with MacTel. Through RNA-Seq and gene set enrichment pathway analysis, we determined that MacTel iRPE cells are enriched in cellular stress pathways and dysregulation of central carbon metabolism. Using respirometry and mitochondrial stress testing, we functionally validated that MacTel iRPE cells had a reduction in mitochondrial function that was independent of defects in serine biosynthesis and 1-dSL accumulation. Thus, we identified phenotypes that may constitute alternative disease mechanisms beyond the known serine/sphingolipid pathway.
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Affiliation(s)
- Kevin T. Eade
- The Lowy Medical Research Institute, La Jolla, California, USA
- Department of Molecular Medicine, The Scripps Research Institute (TSRI), La Jolla, California, USA
| | - Brendan Robert E. Ansell
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Sarah Giles
- The Lowy Medical Research Institute, La Jolla, California, USA
- Department of Molecular Medicine, The Scripps Research Institute (TSRI), La Jolla, California, USA
| | - Regis Fallon
- The Lowy Medical Research Institute, La Jolla, California, USA
- Department of Molecular Medicine, The Scripps Research Institute (TSRI), La Jolla, California, USA
| | - Sarah Harkins-Perry
- The Lowy Medical Research Institute, La Jolla, California, USA
- Department of Molecular Medicine, The Scripps Research Institute (TSRI), La Jolla, California, USA
| | - Takayuki Nagasaki
- Department of Ophthalmology and
- Department of Pathology and Cell Biology, Columbia University, New York, New York, USA
| | - Simone Tzaridis
- The Lowy Medical Research Institute, La Jolla, California, USA
- Department of Molecular Medicine, The Scripps Research Institute (TSRI), La Jolla, California, USA
| | - Martina Wallace
- Institute of Food and Health, School of Agriculture and Food Science, University College Dublin, Dublin, Ireland
| | - Elizabeth A. Mills
- The Lowy Medical Research Institute, La Jolla, California, USA
- Department of Molecular Medicine, The Scripps Research Institute (TSRI), La Jolla, California, USA
| | - Samaneh Farashi
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Alec Johnson
- The Lowy Medical Research Institute, La Jolla, California, USA
| | - Lydia Sauer
- Moran Eye Center, University of Utah School of Medicine, Salt Lake City, Utah, USA
| | - Barbara Hart
- Moran Eye Center, University of Utah School of Medicine, Salt Lake City, Utah, USA
| | - M. Elena Diaz-Rubio
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California, USA
| | - Melanie Bahlo
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Christian Metallo
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California, USA
- Department of Bioengineering, University of California San Diego, La Jolla, California, USA
| | - Rando Allikmets
- Department of Ophthalmology and
- Department of Pathology and Cell Biology, Columbia University, New York, New York, USA
| | - Marin L. Gantner
- The Lowy Medical Research Institute, La Jolla, California, USA
- Department of Molecular Medicine, The Scripps Research Institute (TSRI), La Jolla, California, USA
| | - Paul S. Bernstein
- Moran Eye Center, University of Utah School of Medicine, Salt Lake City, Utah, USA
| | - Martin Friedlander
- The Lowy Medical Research Institute, La Jolla, California, USA
- Department of Molecular Medicine, The Scripps Research Institute (TSRI), La Jolla, California, USA
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9
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Zhu S, Xu R, Engel AL, Wang Y, McNeel R, Hurley JB, Chao JR, Du J. Proline provides a nitrogen source in the retinal pigment epithelium to synthesize and export amino acids for the neural retina. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.18.537355. [PMID: 37131780 PMCID: PMC10153141 DOI: 10.1101/2023.04.18.537355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
It is known that metabolic defects in the retinal pigment epithelium (RPE) can cause degeneration of its neighboring photoreceptors in the retina, leading to retinal degenerative diseases such as age-related macular degeneration. However, how RPE metabolism supports the health of the neural retina remains unclear. The retina requires exogenous nitrogen sources for protein synthesis, neurotransmission, and energy metabolism. Using 15N tracing coupled with mass spectrometry, we found human RPE can utilize the nitrogen in proline to produce and export 13 amino acids, including glutamate, aspartate, glutamine, alanine and serine. Similarly, we found this proline nitrogen utilization in the mouse RPE/choroid but not in the neural retina of explant cultures. Co-culture of human RPE with the retina showed that the retina can take up the amino acids, especially glutamate, aspartate and glutamine, generated from proline nitrogen in the RPE. Intravenous delivery of 15N proline in vivo demonstrated 15N-derived amino acids appear earlier in the RPE before the retina. We also found proline dehydrogenase (PRODH), the key enzyme in proline catabolism is highly enriched in the RPE but not the retina. The deletion of PRODH blocks proline nitrogen utilization in RPE and the import of proline nitrogen-derived amino acids in the retina. Our findings highlight the importance of RPE metabolism in supporting nitrogen sources for the retina, providing insight into understanding the mechanisms of the retinal metabolic ecosystem and RPE-initiated retinal degenerative diseases.
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Affiliation(s)
- Siyan Zhu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
- Department of Pharmaceutical and Pharmacological Sciences, West Virginia University, Morgantown, WV 26506
| | - Rong Xu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
| | - Abbi L. Engel
- Department of Ophthalmology, University of Washington, Seattle, WA 98109
| | - Yekai Wang
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
| | - Rachel McNeel
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
| | - James B. Hurley
- Department of Ophthalmology, University of Washington, Seattle, WA 98109
- Department of Biochemistry, University of Washington, Seattle, WA 98109
| | - Jennifer R. Chao
- Department of Ophthalmology, University of Washington, Seattle, WA 98109
| | - Jianhai Du
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV 26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506
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10
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Saravanan M, Xu R, Roby O, Wang Y, Zhu S, Lu A, Du J. Tissue-Specific Sex Difference in Mouse Eye and Brain Metabolome Under Fed and Fasted States. Invest Ophthalmol Vis Sci 2023; 64:18. [PMID: 36892534 PMCID: PMC10010444 DOI: 10.1167/iovs.64.3.18] [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: 01/09/2023] [Accepted: 02/13/2023] [Indexed: 03/10/2023] Open
Abstract
Purpose Visual physiology and various ocular diseases demonstrate sexual dimorphisms; however, how sex influences metabolism in different eye tissues remains undetermined. This study aims to address common and tissue-specific sex differences in metabolism in the retina, RPE, lens, and brain under fed and fasted conditions. Methods After ad libitum fed or being deprived of food for 18 hours, mouse eye tissues (retina, RPE/choroid, and lens), brain, and plasma were harvested for targeted metabolomics. The data were analyzed with both partial least squares-discriminant analysis and volcano plot analysis. Results Among 133 metabolites that cover major metabolic pathways, we found 9 to 45 metabolites that are sex different in different tissues under the fed state and 6 to 18 metabolites under the fasted state. Among these sex-different metabolites, 33 were changed in 2 or more tissues, and 64 were tissue specific. Pantothenic acid, hypotaurine, and 4-hydroxyproline were the top commonly changed metabolites. The lens and the retina had the most tissue-specific, sex-different metabolites enriched in the metabolism of amino acid, nucleotide, lipids, and tricarboxylic acid cycle. The lens and the brain had more similar sex-different metabolites than other ocular tissues. The female RPE and female brain were more sensitive to fasting with more decreased metabolites in amino acid metabolism, tricarboxylic acid cycles, and glycolysis. The plasma had the fewest sex-different metabolites, with very few overlapping changes with tissues. Conclusions Sex has a strong influence on eye and brain metabolism in tissue-specific and metabolic state-specific manners. Our findings may implicate the sexual dimorphisms in eye physiology and susceptibility to ocular diseases.
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Affiliation(s)
- Meghashri Saravanan
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, United States
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States
| | - Rong Xu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, United States
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States
| | - Olivia Roby
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, United States
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States
| | - Yekai Wang
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, United States
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States
| | - Siyan Zhu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, United States
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States
| | - Amy Lu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, United States
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States
| | - Jianhai Du
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, West Virginia, United States
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, West Virginia, United States
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11
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Fooks K, Galicia-Vazquez G, Gife V, Schcolnik-Cabrera A, Nouhi Z, Poon WWL, Luo V, Rys RN, Aloyz R, Orthwein A, Johnson NA, Hulea L, Mercier FE. EIF4A inhibition targets bioenergetic homeostasis in AML MOLM-14 cells in vitro and in vivo and synergizes with cytarabine and venetoclax. JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH : CR 2022; 41:340. [PMID: 36482393 PMCID: PMC9733142 DOI: 10.1186/s13046-022-02542-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Accepted: 11/21/2022] [Indexed: 12/13/2022]
Abstract
BACKGROUND Acute myeloid leukemia (AML) is an aggressive hematological cancer resulting from uncontrolled proliferation of differentiation-blocked myeloid cells. Seventy percent of AML patients are currently not cured with available treatments, highlighting the need of novel therapeutic strategies. A promising target in AML is the mammalian target of rapamycin complex 1 (mTORC1). Clinical inhibition of mTORC1 is limited by its reactivation through compensatory and regulatory feedback loops. Here, we explored a strategy to curtail these drawbacks through inhibition of an important effector of the mTORC1signaling pathway, the eukaryotic initiation factor 4A (eIF4A). METHODS We tested the anti-leukemic effect of a potent and specific eIF4A inhibitor (eIF4Ai), CR-1-31-B, in combination with cytosine arabinoside (araC) or the BCL2 inhibitor venetoclax. We utilized the MOLM-14 human AML cell line to model chemoresistant disease both in vitro and in vivo. In eIF4Ai-treated cells, we assessed for changes in survival, apoptotic priming, de novo protein synthesis, targeted intracellular metabolite content, bioenergetic profile, mitochondrial reactive oxygen species (mtROS) and mitochondrial membrane potential (MMP). RESULTS eIF4Ai exhibits anti-leukemia activity in vivo while sparing non-malignant myeloid cells. In vitro, eIF4Ai synergizes with two therapeutic agents in AML, araC and venetoclax. EIF4Ai reduces mitochondrial membrane potential (MMP) and the rate of ATP synthesis from mitochondrial respiration and glycolysis. Furthermore, eIF4i enhanced apoptotic priming while reducing the expression levels of the antiapoptotic factors BCL2, BCL-XL and MCL1. Concomitantly, eIF4Ai decreases intracellular levels of specific metabolic intermediates of the tricarboxylic acid cycle (TCA cycle) and glucose metabolism, while enhancing mtROS. In vitro redox stress contributes to eIF4Ai cytotoxicity, as treatment with a ROS scavenger partially rescued the viability of eIF4A inhibition. CONCLUSIONS We discovered that chemoresistant MOLM-14 cells rely on eIF4A-dependent cap translation for survival in vitro and in vivo. EIF4A drives an intrinsic metabolic program sustaining bioenergetic and redox homeostasis and regulates the expression of anti-apoptotic proteins. Overall, our work suggests that eIF4A-dependent cap translation contributes to adaptive processes involved in resistance to relevant therapeutic agents in AML.
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Affiliation(s)
- Katie Fooks
- grid.414980.00000 0000 9401 2774Lady Davis Institute for Medical Research, Montreal, Canada ,grid.14709.3b0000 0004 1936 8649Department of Medicine, McGill University, Montreal, Canada
| | | | - Victor Gife
- grid.414216.40000 0001 0742 1666Maisonneuve-Rosemont Hospital Research Centre, Montreal, Canada ,grid.14848.310000 0001 2292 3357Present Address: Département de Biochimie et Médecine Moléculaire, Université de Montréal, Montreal, Canada
| | | | - Zaynab Nouhi
- grid.414216.40000 0001 0742 1666Maisonneuve-Rosemont Hospital Research Centre, Montreal, Canada
| | - William W. L. Poon
- grid.414980.00000 0000 9401 2774Lady Davis Institute for Medical Research, Montreal, Canada ,grid.14709.3b0000 0004 1936 8649Department of Medicine, McGill University, Montreal, Canada
| | - Vincent Luo
- grid.414980.00000 0000 9401 2774Lady Davis Institute for Medical Research, Montreal, Canada ,grid.14709.3b0000 0004 1936 8649Department of Medicine, McGill University, Montreal, Canada
| | - Ryan N. Rys
- grid.414980.00000 0000 9401 2774Lady Davis Institute for Medical Research, Montreal, Canada ,grid.14709.3b0000 0004 1936 8649Department of Physiology, McGill University, Montreal, Canada
| | - Raquel Aloyz
- grid.414980.00000 0000 9401 2774Lady Davis Institute for Medical Research, Montreal, Canada ,grid.14709.3b0000 0004 1936 8649Department of Medicine, McGill University, Montreal, Canada ,grid.14709.3b0000 0004 1936 8649Gerald Bronfman Department of Oncology, McGill University, Montreal, Canada
| | - Alexandre Orthwein
- grid.414980.00000 0000 9401 2774Lady Davis Institute for Medical Research, Montreal, Canada ,grid.14709.3b0000 0004 1936 8649Department of Medicine, McGill University, Montreal, Canada ,grid.14709.3b0000 0004 1936 8649Gerald Bronfman Department of Oncology, McGill University, Montreal, Canada ,grid.189967.80000 0001 0941 6502Present Address: Department of Radiation Oncology, Emory School of Medicine, Atlanta, USA
| | - Nathalie A. Johnson
- grid.414980.00000 0000 9401 2774Lady Davis Institute for Medical Research, Montreal, Canada ,grid.14709.3b0000 0004 1936 8649Department of Medicine, McGill University, Montreal, Canada ,grid.14709.3b0000 0004 1936 8649Gerald Bronfman Department of Oncology, McGill University, Montreal, Canada
| | - Laura Hulea
- grid.414216.40000 0001 0742 1666Maisonneuve-Rosemont Hospital Research Centre, Montreal, Canada ,grid.14848.310000 0001 2292 3357Present Address: Département de Biochimie et Médecine Moléculaire, Université de Montréal, Montreal, Canada ,grid.14848.310000 0001 2292 3357Département de Médecine, Université de Montréal, Montreal, Canada
| | - Francois E. Mercier
- grid.414980.00000 0000 9401 2774Lady Davis Institute for Medical Research, Montreal, Canada ,grid.14709.3b0000 0004 1936 8649Department of Medicine, McGill University, Montreal, Canada
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12
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Li X, Cai S, He Z, Reilly J, Zeng Z, Strang N, Shu X. Metabolomics in Retinal Diseases: An Update. BIOLOGY 2021; 10:944. [PMID: 34681043 PMCID: PMC8533136 DOI: 10.3390/biology10100944] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 09/16/2021] [Accepted: 09/18/2021] [Indexed: 12/17/2022]
Abstract
Retinal diseases are a leading cause of visual loss and blindness, affecting a significant proportion of the population worldwide and having a detrimental impact on quality of life, with consequent economic burden. The retina is highly metabolically active, and a number of retinal diseases are associated with metabolic dysfunction. To better understand the pathogenesis underlying such retinopathies, new technology has been developed to elucidate the mechanism behind retinal diseases. Metabolomics is a relatively new "omics" technology, which has developed subsequent to genomics, transcriptomics, and proteomics. This new technology can provide qualitative and quantitative information about low-molecular-weight metabolites (M.W. < 1500 Da) in a given biological system, which shed light on the physiological or pathological state of a cell or tissue sample at a particular time point. In this article we provide an extensive review of the application of metabolomics to retinal diseases, with focus on age-related macular degeneration (AMD), diabetic retinopathy (DR), retinopathy of prematurity (ROP), glaucoma, and retinitis pigmentosa (RP).
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Affiliation(s)
- Xing Li
- School of Basic Medical Sciences, Shaoyang University, Shaoyang 422000, China; (X.L.); (Z.H.)
| | - Shichang Cai
- Department of Human Anatomy, School of Medicine, Hunan University of Medicine, Huaihua 418000, China;
| | - Zhiming He
- School of Basic Medical Sciences, Shaoyang University, Shaoyang 422000, China; (X.L.); (Z.H.)
| | - James Reilly
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University, Glasgow G4 0BA, UK;
| | - Zhihong Zeng
- College of Biological and Environmental Engineering, Changsha University, Changsha 410022, China;
| | - Niall Strang
- Department of Vision Science, Glasgow Caledonian University, Glasgow G4 0BA, UK;
| | - Xinhua Shu
- School of Basic Medical Sciences, Shaoyang University, Shaoyang 422000, China; (X.L.); (Z.H.)
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University, Glasgow G4 0BA, UK;
- Department of Vision Science, Glasgow Caledonian University, Glasgow G4 0BA, UK;
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13
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Du J, Zhu S, Lim RR, Chao JR. Proline metabolism and transport in retinal health and disease. Amino Acids 2021; 53:1789-1806. [PMID: 33871679 PMCID: PMC8054134 DOI: 10.1007/s00726-021-02981-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 04/10/2021] [Indexed: 12/11/2022]
Abstract
The retina is one of the most energy-demanding tissues in the human body. Photoreceptors in the outer retina rely on nutrient support from the neighboring retinal pigment epithelium (RPE), a monolayer of epithelial cells that separate the retina and choroidal blood supply. RPE dysfunction or cell death can result in photoreceptor degeneration, leading to blindness in retinal degenerative diseases including some inherited retinal degenerations and age-related macular degeneration (AMD). In addition to having ready access to rich nutrients from blood, the RPE is also supplied with lactate from adjacent photoreceptors. Moreover, RPE can phagocytose lipid-rich outer segments for degradation and recycling on a daily basis. Recent studies show RPE cells prefer proline as a major metabolic substrate, and they are highly enriched for the proline transporter, SLC6A20. In contrast, dysfunctional or poorly differentiated RPE fails to utilize proline. RPE uses proline to fuel mitochondrial metabolism, synthesize amino acids, build the extracellular matrix, fight against oxidative stress, and sustain differentiation. Remarkably, the neural retina rarely imports proline directly, but it uptakes and utilizes intermediates and amino acids derived from proline catabolism in the RPE. Mutations of genes in proline metabolism are associated with retinal degenerative diseases, and proline supplementation is reported to improve RPE-initiated vision loss. This review will cover proline metabolism in RPE and highlight the importance of proline transport and utilization in maintaining retinal metabolism and health.
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Affiliation(s)
- Jianhai Du
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV, 26506, USA. .,Department of Biochemistry, West Virginia University, Morgantown, WV, 26506, USA. .,One Medical Center Dr, WVU Eye Institute, PO Box 9193, Morgantown, WV, 26505, USA.
| | - Siyan Zhu
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV, 26506, USA.,Department of Biochemistry, West Virginia University, Morgantown, WV, 26506, USA
| | - Rayne R Lim
- Department of Ophthalmology, University of Washington, Seattle, WA, 98109, USA
| | - Jennifer R Chao
- Department of Ophthalmology, University of Washington, Seattle, WA, 98109, USA
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