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Jagannathan NS, Koh JYP, Lee Y, Sobota RM, Irving AT, Wang LF, Itahana Y, Itahana K, Tucker-Kellogg L. Multi-omic analysis of bat versus human fibroblasts reveals altered central metabolism. eLife 2024; 13:e94007. [PMID: 39037770 PMCID: PMC11262796 DOI: 10.7554/elife.94007] [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: 12/06/2023] [Accepted: 03/07/2024] [Indexed: 07/23/2024] Open
Abstract
Bats have unique characteristics compared to other mammals, including increased longevity and higher resistance to cancer and infectious disease. While previous studies have analyzed the metabolic requirements for flight, it is still unclear how bat metabolism supports these unique features, and no study has integrated metabolomics, transcriptomics, and proteomics to characterize bat metabolism. In this work, we performed a multi-omics data analysis using a computational model of metabolic fluxes to identify fundamental differences in central metabolism between primary lung fibroblast cell lines from the black flying fox fruit bat (Pteropus alecto) and human. Bat cells showed higher expression levels of Complex I components of electron transport chain (ETC), but, remarkably, a lower rate of oxygen consumption. Computational modeling interpreted these results as indicating that Complex II activity may be low or reversed, similar to an ischemic state. An ischemic-like state of bats was also supported by decreased levels of central metabolites and increased ratios of succinate to fumarate in bat cells. Ischemic states tend to produce reactive oxygen species (ROS), which would be incompatible with the longevity of bats. However, bat cells had higher antioxidant reservoirs (higher total glutathione and higher ratio of NADPH to NADP) despite higher mitochondrial ROS levels. In addition, bat cells were more resistant to glucose deprivation and had increased resistance to ferroptosis, one of the characteristics of which is oxidative stress. Thus, our studies revealed distinct differences in the ETC regulation and metabolic stress responses between human and bat cells.
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Affiliation(s)
- N Suhas Jagannathan
- Cancer and Stem Cell Biology Programme, Duke-NUS Medical SchoolSingaporeSingapore
- Centre for Computational Biology, Duke-NUS Medical SchoolSingaporeSingapore
| | - Javier Yu Peng Koh
- Cancer and Stem Cell Biology Programme, Duke-NUS Medical SchoolSingaporeSingapore
| | - Younghwan Lee
- Cancer and Stem Cell Biology Programme, Duke-NUS Medical SchoolSingaporeSingapore
| | - Radoslaw Mikolaj Sobota
- Functional Proteomics Laboratory, Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and ResearchSingaporeSingapore
| | - Aaron T Irving
- Programme in Emerging Infectious Diseases, Duke-NUS Medical SchoolSingaporeSingapore
- Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Zhejiang UniversityHainingChina
| | - Lin-fa Wang
- SingHealth Duke-NUS Global Health InstituteSingaporeSingapore
| | - Yoko Itahana
- Cancer and Stem Cell Biology Programme, Duke-NUS Medical SchoolSingaporeSingapore
| | - Koji Itahana
- Cancer and Stem Cell Biology Programme, Duke-NUS Medical SchoolSingaporeSingapore
| | - Lisa Tucker-Kellogg
- Cancer and Stem Cell Biology Programme, Duke-NUS Medical SchoolSingaporeSingapore
- Centre for Computational Biology, Duke-NUS Medical SchoolSingaporeSingapore
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Rizwan S, Toothman B, Li B, Engel AJ, Lim RR, Niernberger S, Lu J, Ratliff C, Xiang Y, Eminhizer M, 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 the retinal pigment epithelium (RPE) underlie many retinal degenerative diseases. This study aims to identify the nutrient requirements of healthy and diseased human RPE cells. Methods We profiled nutrient utilization of various human RPE cells, including differentiated and dedifferentiated fetal RPE (fRPE), induced pluripotent stem cell derived-RPE (iPSC RPE), Sorsby fundus dystrophy (SFD) patient-derived iPSC RPE, CRISPR-corrected isogenic SFD (cSFD) iPSC RPE, and ARPE-19 cell lines using Biolog Phenotype MicroArray Assays. 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 their epithelial phenotype through dedifferentiation, nutrient utilization becomes restricted to 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. Dedifferentiated ARPE-19 cells grown in traditional culture media cannot utilize lactate and ketone bodies. In contrast, nicotinamide supplementation promotes differentiation towards an epithelial phenotype, restoring the ability to use these nutrients. Conclusions Epithelial phenotype confers metabolic flexibility to healthy RPE for utilizing various nutrients. SFD RPE cells have reduced metabolic flexibility, relying on the oxidation of BCAAs. Our findings highlight the potentially important roles of nutrient availability and utilization in RPE differentiation and diseases.
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Chen M, Wang Y, Dalal R, Du J, Vollrath D. Alternative oxidase blunts pseudohypoxia and photoreceptor degeneration due to RPE mitochondrial dysfunction. Proc Natl Acad Sci U S A 2024; 121:e2402384121. [PMID: 38865272 PMCID: PMC11194566 DOI: 10.1073/pnas.2402384121] [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: 02/05/2024] [Accepted: 05/15/2024] [Indexed: 06/14/2024] Open
Abstract
Loss of mitochondrial electron transport complex (ETC) function in the retinal pigment epithelium (RPE) in vivo results in RPE dedifferentiation and progressive photoreceptor degeneration, and has been implicated in the pathogenesis of age-related macular degeneration. Xenogenic expression of alternative oxidases in mammalian cells and tissues mitigates phenotypes arising from some mitochondrial electron transport defects, but can exacerbate others. We expressed an alternative oxidase from Ciona intestinalis (AOX) in ETC-deficient murine RPE in vivo to assess the retinal consequences of stimulating coenzyme Q oxidation and respiration without ATP generation. RPE-restricted expression of AOX in this context is surprisingly beneficial. This focused intervention mitigates RPE mTORC1 activation, dedifferentiation, hypertrophy, stress marker expression, pseudohypoxia, and aerobic glycolysis. These RPE cell autonomous changes are accompanied by increased glucose delivery to photoreceptors with attendant improvements in photoreceptor structure and function. RPE-restricted AOX expression normalizes accumulated levels of succinate and 2-hydroxyglutarate in ETC-deficient RPE, and counteracts deficiencies in numerous neural retinal metabolites. These features can be attributed to the activation of mitochondrial inner membrane flavoproteins such as succinate dehydrogenase and proline dehydrogenase, and alleviation of inhibition of 2-oxyglutarate-dependent dioxygenases such as prolyl hydroxylases and epigenetic modifiers. Our work underscores the importance to outer retinal health of coenzyme Q oxidation in the RPE and identifies a metabolic network critical for photoreceptor survival in the context of RPE mitochondrial dysfunction.
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Affiliation(s)
- Ming Chen
- Department of Genetics, Stanford University School of Medicine, Palo Alto, CA94305
| | - Yekai Wang
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV26506
| | - Roopa Dalal
- Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA94305
| | - Jianhai Du
- Department of Ophthalmology and Visual Sciences, West Virginia University, Morgantown, WV26506
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV26506
| | - Douglas Vollrath
- Department of Genetics, Stanford University School of Medicine, Palo Alto, CA94305
- Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA94305
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4
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Xue Y, Cepko CL. Gene Therapies for Retinitis Pigmentosa that Target Glucose Metabolism. Cold Spring Harb Perspect Med 2024; 14:a041289. [PMID: 37460158 PMCID: PMC11065158 DOI: 10.1101/cshperspect.a041289] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2024]
Abstract
Retinitis pigmentosa is a blinding disease wherein rod photoreceptors are affected first, due to the expression of a disease gene, leading to the loss of dim light vision. In many cases, cones do not express the disease gene, yet they are also affected and eventually die, typically after most of the rods in their neighborhood have died. The cause of secondary cone death is unclear. Photoreceptors are one of the most energy-demanding cell types in the body and consume a high amount of glucose. At an early stage of degeneration, the cones appear to have a shortage of glucose to fuel their metabolism. This review focuses on gene therapy approaches that address this potential metabolic shortcoming.
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Affiliation(s)
- Yunlu Xue
- Lingang Laboratory, Shanghai 200031, China
| | - Constance L Cepko
- Departments of Genetics and Ophthalmology, Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
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Zorova LD, Abramicheva PA, Andrianova NV, Babenko VA, Zorov SD, Pevzner IB, Popkov VA, Semenovich DS, Yakupova EI, Silachev DN, Plotnikov EY, Sukhikh GT, Zorov DB. Targeting Mitochondria for Cancer Treatment. Pharmaceutics 2024; 16:444. [PMID: 38675106 PMCID: PMC11054825 DOI: 10.3390/pharmaceutics16040444] [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: 02/28/2024] [Accepted: 03/20/2024] [Indexed: 04/28/2024] Open
Abstract
There is an increasing accumulation of data on the exceptional importance of mitochondria in the occurrence and treatment of cancer, and in all lines of evidence for such participation, there are both energetic and non-bioenergetic functional features of mitochondria. This analytical review examines three specific features of adaptive mitochondrial changes in several malignant tumors. The first feature is characteristic of solid tumors, whose cells are forced to rebuild their energetics due to the absence of oxygen, namely, to activate the fumarate reductase pathway instead of the traditional succinate oxidase pathway that exists in aerobic conditions. For such a restructuring, the presence of a low-potential quinone is necessary, which cannot ensure the conventional conversion of succinate into fumarate but rather enables the reverse reaction, that is, the conversion of fumarate into succinate. In this scenario, complex I becomes the only generator of energy in mitochondria. The second feature is the increased proliferation in aggressive tumors of the so-called mitochondrial (peripheral) benzodiazepine receptor, also called translocator protein (TSPO) residing in the outer mitochondrial membrane, the function of which in oncogenic transformation stays mysterious. The third feature of tumor cells is the enhanced retention of certain molecules, in particular mitochondrially directed cations similar to rhodamine 123, which allows for the selective accumulation of anticancer drugs in mitochondria. These three features of mitochondria can be targets for the development of an anti-cancer strategy.
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Affiliation(s)
- Ljubava D. Zorova
- A.N. Belozersky Research Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (L.D.Z.); (P.A.A.); (V.A.B.); (S.D.Z.); (I.B.P.); (V.A.P.); (D.S.S.); (E.I.Y.); (D.N.S.); (E.Y.P.)
- V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatology, 117997 Moscow, Russia
| | - Polina A. Abramicheva
- A.N. Belozersky Research Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (L.D.Z.); (P.A.A.); (V.A.B.); (S.D.Z.); (I.B.P.); (V.A.P.); (D.S.S.); (E.I.Y.); (D.N.S.); (E.Y.P.)
| | - Nadezda V. Andrianova
- A.N. Belozersky Research Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (L.D.Z.); (P.A.A.); (V.A.B.); (S.D.Z.); (I.B.P.); (V.A.P.); (D.S.S.); (E.I.Y.); (D.N.S.); (E.Y.P.)
| | - Valentina A. Babenko
- A.N. Belozersky Research Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (L.D.Z.); (P.A.A.); (V.A.B.); (S.D.Z.); (I.B.P.); (V.A.P.); (D.S.S.); (E.I.Y.); (D.N.S.); (E.Y.P.)
- V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatology, 117997 Moscow, Russia
| | - Savva D. Zorov
- A.N. Belozersky Research Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (L.D.Z.); (P.A.A.); (V.A.B.); (S.D.Z.); (I.B.P.); (V.A.P.); (D.S.S.); (E.I.Y.); (D.N.S.); (E.Y.P.)
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Irina B. Pevzner
- A.N. Belozersky Research Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (L.D.Z.); (P.A.A.); (V.A.B.); (S.D.Z.); (I.B.P.); (V.A.P.); (D.S.S.); (E.I.Y.); (D.N.S.); (E.Y.P.)
- V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatology, 117997 Moscow, Russia
| | - Vasily A. Popkov
- A.N. Belozersky Research Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (L.D.Z.); (P.A.A.); (V.A.B.); (S.D.Z.); (I.B.P.); (V.A.P.); (D.S.S.); (E.I.Y.); (D.N.S.); (E.Y.P.)
- V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatology, 117997 Moscow, Russia
| | - Dmitry S. Semenovich
- A.N. Belozersky Research Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (L.D.Z.); (P.A.A.); (V.A.B.); (S.D.Z.); (I.B.P.); (V.A.P.); (D.S.S.); (E.I.Y.); (D.N.S.); (E.Y.P.)
| | - Elmira I. Yakupova
- A.N. Belozersky Research Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (L.D.Z.); (P.A.A.); (V.A.B.); (S.D.Z.); (I.B.P.); (V.A.P.); (D.S.S.); (E.I.Y.); (D.N.S.); (E.Y.P.)
| | - Denis N. Silachev
- A.N. Belozersky Research Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (L.D.Z.); (P.A.A.); (V.A.B.); (S.D.Z.); (I.B.P.); (V.A.P.); (D.S.S.); (E.I.Y.); (D.N.S.); (E.Y.P.)
| | - Egor Y. Plotnikov
- A.N. Belozersky Research Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (L.D.Z.); (P.A.A.); (V.A.B.); (S.D.Z.); (I.B.P.); (V.A.P.); (D.S.S.); (E.I.Y.); (D.N.S.); (E.Y.P.)
- V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatology, 117997 Moscow, Russia
| | - Gennady T. Sukhikh
- V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatology, 117997 Moscow, Russia
| | - Dmitry B. Zorov
- A.N. Belozersky Research Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; (L.D.Z.); (P.A.A.); (V.A.B.); (S.D.Z.); (I.B.P.); (V.A.P.); (D.S.S.); (E.I.Y.); (D.N.S.); (E.Y.P.)
- V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatology, 117997 Moscow, Russia
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Irerhievwie O, Ichipi-Ifukor PC, Asagba SO. Hepatocellular degeneration in mice co-exposed to in-utero aluminium and cadmium: Implication of a disordered antioxidant and energy homeostatic response in the liver. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2024; 106:104375. [PMID: 38262495 DOI: 10.1016/j.etap.2024.104375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2023] [Revised: 12/08/2023] [Accepted: 01/17/2024] [Indexed: 01/25/2024]
Abstract
The current study comprised four groups of pregnant animals viz; Control (CTR) received 10 ml/kg of normal saline, Al:10 mg/kg of AlCl3, Cd: 1.5 mg/Kg of CdCl2 Al+Cd; 10 mg/kg of AlCl3 and 1.5 mg/Kg of CdCl2. Treatment was done from pregnancy days (PNT) 7-20. After delivery, male animals were weaned on PSD 21 and sacrificed on PSD 78. From the study significant increases on serum liver enzymes in the group exposed to Cd and that exposed to Al+Cd were observed. The study further showed altered serum and hepatic antioxidant balance for the Cd, Al and Al+Cd groups compared to control. Similarly, lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH) activities in the liver were elevated in Cd and Al+Cd groups while an altered liver histological feature in treated groups were also observed. it was concluded that in utero co-exposure to Al and Cd had the ability to alter hepatic functional indices.
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Kumar A, Bellar A, Mishra S, Sekar J, Welch N, Dasarathy S. L-Isoleucine reverses hyperammonemia-induced myotube mitochondrial dysfunction and post-mitotic senescence. J Nutr Biochem 2024; 123:109498. [PMID: 37871767 PMCID: PMC10841977 DOI: 10.1016/j.jnutbio.2023.109498] [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: 03/12/2023] [Revised: 10/16/2023] [Accepted: 10/19/2023] [Indexed: 10/25/2023]
Abstract
Perturbations in the metabolism of ammonia, a cytotoxic endogenous metabolite, occur in a number of chronic diseases, with consequent hyperammonemia. Increased skeletal muscle ammonia uptake causes metabolic, molecular, and phenotype alterations including cataplerosis of (loss of tricarboxylic acid cycle (TCA) cycle intermediate) α-ketoglutarate (αKG), mitochondrial oxidative dysfunction, and senescence-associated molecular phenotype (SAMP). L-Isoleucine (Ile) is an essential, branched-chain amino acid (BCAA) that simultaneously provides acetyl-CoA as an oxidative substrate and succinyl-CoA for anaplerosis (providing TCA cycle intermediates). Our multiomics analyses in myotubes and skeletal muscle from hyperammonemic mice and human patients with cirrhosis showed perturbations in BCAA transporters and catabolism. We, therefore, determined if Ile reverses hyperammonemia-induced impaired mitochondrial oxidative function and SAMP. Studies were performed in differentiated murine C2C12 myotubes that were early passage, late passage (senescent), or those depleted of LAT1/SLC7A5 and human induced pluripotent stem cell-derived myotubes (hiPSCM). Ile reverses hyperammonemia-induced reduction in the maximum respiratory capacity, complex I, II, and III functions in early passage murine myotubes and hiPSCM. Consistently, low ATP content and impaired global protein synthesis (high energy requiring cellular process) during hyperammonemia are reversed by Ile in murine myotubes and hiPSCM. Lower abundance of critical regulators of protein synthesis in mTORC1 signaling, and increased phosphorylation of eukaryotic initiation factor 2α are also reversed by Ile. Genetic depletion studies showed that Ile responses are independent of the amino acid transporter LAT1/SLC7A5. Our studies show that Ile reverses the hyperammonemia-induced impaired mitochondrial oxidative function, cataplerosis, and SAMP in a LAT1/SLC7A5 transporter-independent manner.
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Affiliation(s)
- Avinash Kumar
- Department of Gastroenterology, Hepatology and Nutrition, All India Institute of Medical Sciences, New Delhi, India
| | - Annette Bellar
- Department of Inflammation and Immunity, Lerner Research Institute, Gastroenterology and Hepatology, Cleveland Clinic, Cleveland, Ohio, USA
| | - Saurabh Mishra
- Department of Inflammation and Immunity, Lerner Research Institute, Gastroenterology and Hepatology, Cleveland Clinic, Cleveland, Ohio, USA
| | - Jinendiran Sekar
- Department of Inflammation and Immunity, Lerner Research Institute, Gastroenterology and Hepatology, Cleveland Clinic, Cleveland, Ohio, USA
| | - Nicole Welch
- Department of Inflammation and Immunity, Lerner Research Institute, Gastroenterology and Hepatology, Cleveland Clinic, Cleveland, Ohio, USA
| | - Srinivasan Dasarathy
- Department of Inflammation and Immunity, Lerner Research Institute, Gastroenterology and Hepatology, Cleveland Clinic, Cleveland, Ohio, USA.
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Ritterhoff J, Tian R. Metabolic mechanisms in physiological and pathological cardiac hypertrophy: new paradigms and challenges. Nat Rev Cardiol 2023; 20:812-829. [PMID: 37237146 DOI: 10.1038/s41569-023-00887-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/02/2023] [Indexed: 05/28/2023]
Abstract
Cardiac metabolism is vital for heart function. Given that cardiac contraction requires a continuous supply of ATP in large quantities, the role of fuel metabolism in the heart has been mostly considered from the perspective of energy production. However, the consequence of metabolic remodelling in the failing heart is not limited to a compromised energy supply. The rewired metabolic network generates metabolites that can directly regulate signalling cascades, protein function, gene transcription and epigenetic modifications, thereby affecting the overall stress response of the heart. In addition, metabolic changes in both cardiomyocytes and non-cardiomyocytes contribute to the development of cardiac pathologies. In this Review, we first summarize how energy metabolism is altered in cardiac hypertrophy and heart failure of different aetiologies, followed by a discussion of emerging concepts in cardiac metabolic remodelling, that is, the non-energy-generating function of metabolism. We highlight challenges and open questions in these areas and finish with a brief perspective on how mechanistic research can be translated into therapies for heart failure.
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Affiliation(s)
- Julia Ritterhoff
- Molecular and Translational Cardiology, Department of Internal Medicine III, Heidelberg University Hospital, Heidelberg, Germany.
- Mitochondria and Metabolism Center, Department of Anaesthesiology and Pain Medicine, University of Washington, Seattle, WA, USA.
| | - Rong Tian
- Mitochondria and Metabolism Center, Department of Anaesthesiology and Pain Medicine, University of Washington, Seattle, WA, USA.
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Kamat V, Grumbine MK, Bao K, Mokate K, Khalil G, Cook D, Clearwater B, Hirst R, Harman J, Boeck M, Fu Z, Smith LEH, Goswami M, Wubben TJ, Walker EM, Zhu J, Soleimanpour SA, Scarlett JM, Robbings BM, Hass D, Hurley JB, Sweet IR. A versatile pumpless multi-channel fluidics system for maintenance and real-time functional assessment of tissue and cells. CELL REPORTS METHODS 2023; 3:100642. [PMID: 37963464 PMCID: PMC10694526 DOI: 10.1016/j.crmeth.2023.100642] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 07/24/2023] [Accepted: 10/20/2023] [Indexed: 11/16/2023]
Abstract
To address the needs of the life sciences community and the pharmaceutical industry in pre-clinical drug development to both maintain and continuously assess tissue metabolism and function with simple and rapid systems, we improved on the initial BaroFuse to develop it into a fully functional, pumpless, scalable multi-channel fluidics instrument that continuously measures changes in oxygen consumption and other endpoints in response to test compounds. We and several other laboratories assessed it with a wide range of tissue types including retina, pancreatic islets, liver, and hypothalamus with both aqueous and gaseous test compounds. The setup time was less than an hour for all collaborating groups, and there was close agreement between data obtained from the different laboratories. This easy-to-use system reliably generates real-time metabolic and functional data from tissue and cells in response to test compounds that will address a critical need in basic and applied research.
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Affiliation(s)
- Varun Kamat
- University of Washington Medicine Diabetes Institute, University of Washington, Seattle, WA 98109, USA
| | | | - Khang Bao
- EnTox Sciences, Inc., Mercer Island, WA 98040, USA
| | - Kedar Mokate
- University of Washington Medicine Diabetes Institute, University of Washington, Seattle, WA 98109, USA
| | - Gamal Khalil
- EnTox Sciences, Inc., Mercer Island, WA 98040, USA
| | - Daniel Cook
- EnTox Sciences, Inc., Mercer Island, WA 98040, USA
| | | | - Richard Hirst
- Technical Assembly Service Corporation, Seattle, WA 98109, USA
| | - Jarrod Harman
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Myriam Boeck
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA; Eye Center, Medical Center, Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany
| | - Zhongjie Fu
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Lois E H Smith
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Moloy Goswami
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA
| | - Thomas J Wubben
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA
| | - Emily M Walker
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 98195, USA
| | - Jie Zhu
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 98195, USA
| | - Scott A Soleimanpour
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 98195, USA
| | - Jarrad M Scarlett
- University of Washington Medicine Diabetes Institute, University of Washington, Seattle, WA 98109, USA; Department of Pediatric Gastroenterology and Hepatology, Seattle Children's Hospital, Seattle, WA 98145, USA
| | - Brian M Robbings
- University of Washington Medicine Diabetes Institute, University of Washington, Seattle, WA 98109, USA; Department of Biochemistry, University of Washington, Seattle, WA 98109, USA
| | - Daniel Hass
- Department of Biochemistry, University of Washington, Seattle, WA 98109, USA
| | - James B Hurley
- Department of Biochemistry, University of Washington, Seattle, WA 98109, USA
| | - Ian R Sweet
- University of Washington Medicine Diabetes Institute, University of Washington, Seattle, WA 98109, USA; EnTox Sciences, Inc., Mercer Island, WA 98040, USA.
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10
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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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11
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Hass DT, Zhang Q, Autterson GA, Bryan RA, Hurley JB, Miller JML. Medium Depth Influences O2 Availability and Metabolism in Human RPE Cultures. Invest Ophthalmol Vis Sci 2023; 64:4. [PMID: 37922158 PMCID: PMC10629522 DOI: 10.1167/iovs.64.14.4] [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: 05/14/2023] [Accepted: 10/13/2023] [Indexed: 11/05/2023] Open
Abstract
Purpose Retinal pigment epithelium (RPE) oxidative metabolism is critical for normal retinal function and is often studied in cell culture systems. Here, we show that conventional culture media volumes dramatically impact O2 availability, limiting oxidative metabolism. We suggest optimal conditions to ensure cultured RPE is in a normoxic environment permissive to oxidative metabolism. Methods We altered the availability of O2 to human primary and induced pluripotent stem cell-derived RPE cultures directly via a hypoxia chamber or indirectly via the amount of medium over cells. We measured oxygen consumption rates (OCRs), glucose consumption, lactate production, 13C6-glucose and 13C5-glutamine flux, hypoxia inducible factor 1α (HIF-1α) stability, intracellular lipid droplets after a lipid challenge, transepithelial electrical resistance, cell morphology, and pigmentation. Results Medium volumes commonly employed during RPE culture limit diffusion of O2 to cells, triggering hypoxia, activating HIF-1α, limiting OCR, and dramatically altering cell metabolism, with only minor effects on typical markers of RPE health. Media volume effects on O2 availability decrease acetyl-CoA utilization, increase glycolysis and reductive carboxylation, and alter the size and number of intracellular lipid droplets under lipid-rich conditions. Conclusions Despite having little impact on visible and typical markers of RPE culture health, media volume dramatically affects RPE physiology "under the hood." As RPE-centric diseases like age-related macular degeneration involve oxidative metabolism, RPE cultures need to be optimized to study such diseases. We provide guidelines for optimal RPE culture volumes that balance ample nutrient availability from larger media volumes with adequate O2 availability seen with smaller media volumes.
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Affiliation(s)
- Daniel T. Hass
- Department of Biochemistry, The University of Washington, Seattle, Washington, United States
| | - Qitao Zhang
- Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan, United States
| | | | | | - James B. Hurley
- Department of Biochemistry, The University of Washington, Seattle, Washington, United States
| | - Jason M. L. Miller
- Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan, United States
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, Michigan, United States
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12
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Harman JC, Pivodic A, Nilsson AK, Boeck M, Yagi H, Neilsen K, Ko M, Yang J, Kinter M, Hellström A, Fu Z. Postnatal hyperglycemia alters amino acid profile in retinas (model of Phase I ROP). iScience 2023; 26:108021. [PMID: 37841591 PMCID: PMC10568433 DOI: 10.1016/j.isci.2023.108021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 05/03/2023] [Accepted: 09/19/2023] [Indexed: 10/17/2023] Open
Abstract
Nutritional deprivation occurring in most preterm infants postnatally can induce hyperglycemia, a significant and independent risk factor for suppressing physiological retinal vascularization (Phase I retinopathy of prematurity (ROP)), leading to compensatory but pathological neovascularization. Amino acid supplementation reduces retinal neovascularization in mice. Little is known about amino acid contribution to Phase I ROP. In mice modeling hyperglycemia-associated Phase I ROP, we found significant changes in retinal amino acids (including most decreased L-leucine, L-isoleucine, and L-valine). Parenteral L-isoleucine suppressed physiological retinal vascularization. In premature infants, severe ROP was associated with a higher mean intake of parenteral versus enteral amino acids in the first two weeks of life after adjustment for treatment group, gestational age at birth, birth weight, and sex. The number of days with parenteral amino acids support independently predicted severe ROP. Further understanding and modulating amino acids may help improve nutritional intervention and prevent Phase I ROP.
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Affiliation(s)
- Jarrod C. Harman
- Department of Ophthalmology, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Aldina Pivodic
- The Sahlgrenska Centre for Pediatric Ophthalmology Research, Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Anders K. Nilsson
- The Sahlgrenska Centre for Pediatric Ophthalmology Research, Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Myriam Boeck
- Department of Ophthalmology, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
- Eye Center, Medical Center, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany
| | - Hitomi Yagi
- Department of Ophthalmology, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
- Ophthalmology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Katherine Neilsen
- Department of Ophthalmology, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Minji Ko
- Department of Ophthalmology, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Jay Yang
- Department of Ophthalmology, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Michael Kinter
- Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
| | - Ann Hellström
- The Sahlgrenska Centre for Pediatric Ophthalmology Research, Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Zhongjie Fu
- Department of Ophthalmology, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
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13
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Lee SJ, Emery D, Vukmanic E, Wang Y, Lu X, Wang W, Fortuny E, James R, Kaplan HJ, Liu Y, Du J, Dean DC. Metabolic transcriptomics dictate responses of cone photoreceptors to retinitis pigmentosa. Cell Rep 2023; 42:113054. [PMID: 37656622 PMCID: PMC10591869 DOI: 10.1016/j.celrep.2023.113054] [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: 05/08/2023] [Revised: 06/21/2023] [Accepted: 08/15/2023] [Indexed: 09/03/2023] Open
Abstract
Most mutations in retinitis pigmentosa (RP) arise in rod photoreceptors, but cone photoreceptors, responsible for high-resolution daylight and color vision, are subsequently affected, causing the most debilitating features of the disease. We used mass spectroscopy to follow 13C metabolites delivered to the outer retina and single-cell RNA sequencing to assess photoreceptor transcriptomes. The S cone metabolic transcriptome suggests engagement of the TCA cycle and ongoing response to ROS characteristic of oxidative phosphorylation, which we link to their histone modification transcriptome. Tumor necrosis factor (TNF) and its downstream effector RIP3, which drive ROS generation via mitochondrial dysfunction, are induced and activated as S cones undergo early apoptosis in RP. The long/medium-wavelength (L/M) cone transcriptome shows enhanced glycolytic capacity, which maintains their function as RP progresses. Then, as extracellular glucose eventually diminishes, L/M cones are sustained in long-term dormancy by lactate metabolism.
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Affiliation(s)
- Sang Joon Lee
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA; Department of Ophthalmology, Kosin University College of Medicine, #262 Gamcheon-ro, Seo-gu, Busan 49267, Korea
| | - Douglas Emery
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Eric Vukmanic
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Yekai Wang
- Departments of Ophthalmology and Visual Sciences and Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506, USA
| | - Xiaoqin Lu
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Wei Wang
- Department of Ophthalmology and Visual Sciences, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Enzo Fortuny
- Department of Neurosurgery, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Robert James
- Department of Neurosurgery, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Henry J Kaplan
- Department of Ophthalmology, St. Louis University School of Medicine, St. Louis MO 63110, USA
| | - Yongqing Liu
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA
| | - Jianhai Du
- Departments of Ophthalmology and Visual Sciences and Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV 26506, USA.
| | - Douglas C Dean
- Department of Medicine, Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202, USA.
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14
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Ruocco C, Malavazos AE, Ragni M, Carruba MO, Valerio A, Iacobellis G, Nisoli E. Amino acids contribute to adaptive thermogenesis. New insights into the mechanisms of action of recent drugs for metabolic disorders are emerging. Pharmacol Res 2023; 195:106892. [PMID: 37619907 DOI: 10.1016/j.phrs.2023.106892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 07/28/2023] [Accepted: 08/17/2023] [Indexed: 08/26/2023]
Abstract
Adaptive thermogenesis is the heat production by muscle contractions (shivering thermogenesis) or brown adipose tissue (BAT) and beige fat (non-shivering thermogenesis) in response to external stimuli, including cold exposure. BAT and beige fat communicate with peripheral organs and the brain through a variegate secretory and absorption processes - controlling adipokines, microRNAs, extracellular vesicles, and metabolites - and have received much attention as potential therapeutic targets for managing obesity-related disorders. The sympathetic nervous system and norepinephrine-releasing adipose tissue macrophages (ATM) activate uncoupling protein 1 (UCP1), expressed explicitly in brown and beige adipocytes, dissolving the electrochemical gradient and uncoupling tricarboxylic acid cycle and the electron transport chain from ATP production. Mounting evidence has attracted attention to the multiple effects of dietary and endogenously synthesised amino acids in BAT thermogenesis and metabolic phenotype in animals and humans. However, the mechanisms implicated in these processes have yet to be conclusively characterized. In the present review article, we aim to define the principal investigation areas in this context, including intestinal microbiota constitution, adipose autophagy modulation, and secretome and metabolic fluxes control, which lead to increased brown/beige thermogenesis. Finally, also based on our recent epicardial adipose tissue results, we summarise the evidence supporting the notion that the new dual and triple agonists of glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and glucagon (GCG) receptor - with never before seen weight loss and insulin-sensitizing efficacy - promote thermogenic-like amino acid profiles in BAT with robust heat production and likely trigger sympathetic activation and adaptive thermogenesis by controlling amino acid metabolism and ATM expansion in BAT and beige fat.
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Affiliation(s)
- Chiara Ruocco
- Center for Study and Research on Obesity, Department of Biomedical Technology and Translational Medicine, University of Milan, via Vanvitelli, 32, 20129 Milan, Italy
| | - Alexis Elias Malavazos
- Endocrinology Unit, Clinical Nutrition and Cardiovascular Prevention Service, IRCCS Policlinico San Donato, Piazza Edmondo Malan, 2, San Donato Milanese, 20097 Milan, Italy; Department of Biomedical, Surgical and Dental Sciences, University of Milan, via della Commenda, 10, 20122 Milan, Italy
| | - Maurizio Ragni
- Center for Study and Research on Obesity, Department of Biomedical Technology and Translational Medicine, University of Milan, via Vanvitelli, 32, 20129 Milan, Italy
| | - Michele O Carruba
- Center for Study and Research on Obesity, Department of Biomedical Technology and Translational Medicine, University of Milan, via Vanvitelli, 32, 20129 Milan, Italy
| | - Alessandra Valerio
- Department of Molecular and Translational Medicine, University of Brescia, viale Europa, 11, 25123 Brescia, Italy
| | - Gianluca Iacobellis
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Miami, 1400 NW 12th Ave, Miami, FL, USA
| | - Enzo Nisoli
- Center for Study and Research on Obesity, Department of Biomedical Technology and Translational Medicine, University of Milan, via Vanvitelli, 32, 20129 Milan, Italy.
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15
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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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16
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Park G, Haley JA, Le J, Jung SM, Fitzgibbons TP, Korobkina ED, Li H, Fluharty SM, Chen Q, Spinelli JB, Trivedi CM, Jang C, Guertin DA. Quantitative analysis of metabolic fluxes in brown fat and skeletal muscle during thermogenesis. Nat Metab 2023; 5:1204-1220. [PMID: 37337122 PMCID: PMC10696589 DOI: 10.1038/s42255-023-00825-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 05/15/2023] [Indexed: 06/21/2023]
Abstract
Adaptive thermogenesis by brown adipose tissue (BAT) dissipates calories as heat, making it an attractive anti-obesity target. Yet how BAT contributes to circulating metabolite exchange remains unclear. Here, we quantified metabolite exchange in BAT and skeletal muscle by arteriovenous metabolomics during cold exposure in fed male mice. This identified unexpected metabolites consumed, released and shared between organs. Quantitative analysis of tissue fluxes showed that glucose and lactate provide ~85% of carbon for adaptive thermogenesis and that cold and CL316,243 trigger markedly divergent fuel utilization profiles. In cold adaptation, BAT also dramatically increases nitrogen uptake by net consuming amino acids, except glutamine. Isotope tracing and functional studies suggest glutamine catabolism concurrent with synthesis via glutamine synthetase, which avoids ammonia buildup and boosts fuel oxidation. These data underscore the ability of BAT to function as a glucose and amino acid sink and provide a quantitative and comprehensive landscape of BAT fuel utilization to guide translational studies.
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Affiliation(s)
- Grace Park
- Department of Biological Chemistry, University of California Irvine, Irvine, CA, USA
| | - John A Haley
- Program in Molecular Medicine, UMass Chan Medical School, Worcester, MA, USA
| | - Johnny Le
- Department of Biological Chemistry, University of California Irvine, Irvine, CA, USA
| | - Su Myung Jung
- Department of Biological Sciences, Sungkyunkwan University, Suwon, South Korea
| | - Timothy P Fitzgibbons
- Division of Cardiovascular Medicine, Department of Medicine, UMass Chan Medical School, Worcester, MA, USA
| | | | - Huawei Li
- Program in Molecular Medicine, UMass Chan Medical School, Worcester, MA, USA
| | - Shelagh M Fluharty
- Program in Molecular Medicine, UMass Chan Medical School, Worcester, MA, USA
| | - Qingbo Chen
- Program in Molecular Medicine, UMass Chan Medical School, Worcester, MA, USA
| | - Jessica B Spinelli
- Program in Molecular Medicine, UMass Chan Medical School, Worcester, MA, USA
| | - Chinmay M Trivedi
- Division of Cardiovascular Medicine, Department of Medicine, UMass Chan Medical School, Worcester, MA, USA
- Department of Molecular, Cell and Cancer Biology, UMass Chan Medical School, Worcester, MA, USA
- Li-Weibo Institute for Rare Diseases Research, UMass Chan Medical School, Worcester, MA, USA
| | - Cholsoon Jang
- Department of Biological Chemistry, University of California Irvine, Irvine, CA, USA.
| | - David A Guertin
- Program in Molecular Medicine, UMass Chan Medical School, Worcester, MA, USA.
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17
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Hass DT, Zhang Q, Autterson G, Bryan R, Hurley JB, Miller JM. Medium depth influences O 2 availability and metabolism in cultured RPE cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.01.530623. [PMID: 36909658 PMCID: PMC10002737 DOI: 10.1101/2023.03.01.530623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
Abstract
PURPOSE RPE oxidative metabolism is critical for normal retinal function and is often studied in cell culture systems. Here, we show that conventional culture media volumes dramatically impact O 2 availability, limiting oxidative metabolism. We suggest optimal conditions to ensure cultured RPE is in a normoxic environment permissive to oxidative metabolism. METHODS We altered the availability of O 2 to human primary RPE cultures directly via a hypoxia chamber or indirectly via the amount of medium over cells. We measured oxygen consumption rates (OCR), glucose consumption, lactate production, 13 C-glucose flux, hypoxia inducible factor (HIF-1α) stability, intracellular lipid droplets after a lipid challenge, trans-epithelial electrical resistance, cell morphology, and pigmentation. RESULTS Medium volumes commonly employed during RPE culture limit diffusion of O 2 to cells, triggering hypoxia, activating HIF-1α, limiting OCR, and dramatically altering cell metabolism, with only minor effects on typical markers of RPE health. Media volume effects on O 2 availability decrease acetyl-CoA utilization, increase glycolysis, and alter the size and number of intracellular lipid droplets under lipid-rich conditions. CONCLUSIONS Despite having little impact on visible and typical markers of RPE culture health, media volume dramatically affects RPE physiology ″under the hood″. As RPE-centric diseases like age-related macular degeneration (AMD) involve oxidative metabolism, RPE cultures need to be optimized to study such diseases. We provide guidelines for optimal RPE culture volumes that balance ample nutrient availability from larger media volumes with adequate O 2 availability seen with smaller media volumes.
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18
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Todorova V, Stauffacher MF, Ravotto L, Nötzli S, Karademir D, Ebner LJA, Imsand C, Merolla L, Hauck SM, Samardzija M, Saab AS, Barros LF, Weber B, Grimm C. Deficits in mitochondrial TCA cycle and OXPHOS precede rod photoreceptor degeneration during chronic HIF activation. Mol Neurodegener 2023; 18:15. [PMID: 36882871 PMCID: PMC9990367 DOI: 10.1186/s13024-023-00602-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Accepted: 02/03/2023] [Indexed: 03/09/2023] Open
Abstract
BACKGROUND Major retinal degenerative diseases, including age-related macular degeneration, diabetic retinopathy and retinal detachment, are associated with a local decrease in oxygen availability causing the formation of hypoxic areas affecting the photoreceptor (PR) cells. Here, we addressed the underlying pathological mechanisms of PR degeneration by focusing on energy metabolism during chronic activation of hypoxia-inducible factors (HIFs) in rod PR. METHODS We used two-photon laser scanning microscopy (TPLSM) of genetically encoded biosensors delivered by adeno-associated viruses (AAV) to determine lactate and glucose dynamics in PR and inner retinal cells. Retinal layer-specific proteomics, in situ enzymatic assays and immunofluorescence studies were used to analyse mitochondrial metabolism in rod PRs during chronic HIF activation. RESULTS PRs exhibited remarkably higher glycolytic flux through the hexokinases than neurons of the inner retina. Chronic HIF activation in rods did not cause overt change in glucose dynamics but an increase in lactate production nonetheless. Furthermore, dysregulation of the oxidative phosphorylation pathway (OXPHOS) and tricarboxylic acid (TCA) cycle in rods with an activated hypoxic response decelerated cellular anabolism causing shortening of rod photoreceptor outer segments (OS) before onset of cell degeneration. Interestingly, rods with deficient OXPHOS but an intact TCA cycle did not exhibit these early signs of anabolic dysregulation and showed a slower course of degeneration. CONCLUSION Together, these data indicate an exceeding high glycolytic flux in rods and highlight the importance of mitochondrial metabolism and especially of the TCA cycle for PR survival in conditions of increased HIF activity.
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Affiliation(s)
- Vyara Todorova
- Laboratory for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Wagistrasse 14, 8952, Schlieren, Switzerland
| | - Mia Fee Stauffacher
- Laboratory for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Wagistrasse 14, 8952, Schlieren, Switzerland
| | - Luca Ravotto
- Institute of Pharmacology and Toxicology and Neuroscience Center Zurich, University and ETH Zurich, Winterthurerstr. 190, 8057, Zurich, Switzerland
| | - Sarah Nötzli
- Laboratory for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Wagistrasse 14, 8952, Schlieren, Switzerland
| | - Duygu Karademir
- Laboratory for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Wagistrasse 14, 8952, Schlieren, Switzerland
| | - Lynn J A Ebner
- Laboratory for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Wagistrasse 14, 8952, Schlieren, Switzerland
| | - Cornelia Imsand
- Laboratory for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Wagistrasse 14, 8952, Schlieren, Switzerland
| | - Luca Merolla
- Laboratory for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Wagistrasse 14, 8952, Schlieren, Switzerland
| | - Stefanie M Hauck
- Metabolomics and Proteomics Core, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Ingolstädter Landstraße 1, 85764, Munich, Germany
| | - Marijana Samardzija
- Laboratory for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Wagistrasse 14, 8952, Schlieren, Switzerland
| | - Aiman S Saab
- Institute of Pharmacology and Toxicology and Neuroscience Center Zurich, University and ETH Zurich, Winterthurerstr. 190, 8057, Zurich, Switzerland
| | - L Felipe Barros
- Centro de Estudios Científicos (CECs), Valdivia, Chile.,Universidad San Sebastián, Valdivia, Chile
| | - Bruno Weber
- Institute of Pharmacology and Toxicology and Neuroscience Center Zurich, University and ETH Zurich, Winterthurerstr. 190, 8057, Zurich, Switzerland
| | - Christian Grimm
- Laboratory for Retinal Cell Biology, Department of Ophthalmology, University Hospital Zurich, University of Zurich, Wagistrasse 14, 8952, Schlieren, Switzerland.
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19
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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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20
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Inhibition of Succinate Dehydrogenase by Pesticides (SDHIs) and Energy Metabolism. Int J Mol Sci 2023; 24:ijms24044045. [PMID: 36835457 PMCID: PMC9962667 DOI: 10.3390/ijms24044045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 02/07/2023] [Accepted: 02/14/2023] [Indexed: 02/19/2023] Open
Abstract
Succinate dehydrogenase (SDH) is one of the enzymes of the tricarboxylic acid cycle (Krebs cycle) and complex II of the mitochondrial respiratory chain. A class of fungicides (SDHIs) targets the complex II reaction in the SDH. A large number of those in use have been shown to inhibit SDH in other phyla, including humans. This raises questions about possible effects on human health and non-target organisms in the environment. The present document will address metabolic consequences in mammals; it is neither a review on SDH nor is it about the toxicology of SDHIs. Most clinically relevant observations are linked to a severe decrease in SDH activity. Here we shall examine the mechanisms for compensating a loss of SDH activity and their possible weaknesses or adverse consequences. It can be expected that a mild inhibition of SDH will be compensated by the kinetic properties of this enzyme, but this implies a proportionate increase in succinate concentration. This would be relevant for succinate signaling and epigenetics (not reviewed here). With regard to metabolism, exposure of the liver to SDHIs would increase the risk for non-alcoholic fatty liver disease (NAFLD). Higher levels of inhibition may be compensated by modification of metabolic fluxes with net production of succinate. SDHIs are much more soluble in lipids than in water; consequently, a different diet composition between laboratory animals and humans is expected to influence their absorption.
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21
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Wang R, Liang L, Matsumoto M, Iwata K, Umemura A, He F. Reactive Oxygen Species and NRF2 Signaling, Friends or Foes in Cancer? Biomolecules 2023; 13:biom13020353. [PMID: 36830722 PMCID: PMC9953152 DOI: 10.3390/biom13020353] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 02/03/2023] [Accepted: 02/09/2023] [Indexed: 02/17/2023] Open
Abstract
The imbalance between reactive oxygen species (ROS) production and clearance causes oxidative stress and ROS, which play a central role in regulating cell and tissue physiology and pathology. Contingent upon concentration, ROS influence cancer development in contradictory ways, either stimulating cancer survival and growth or causing cell death. Cells developed evolutionarily conserved programs to sense and adapt redox the fluctuations to regulate ROS as either signaling molecules or toxic insults. The transcription factor nuclear factor erythroid 2-related factor 2 (NRF2)-KEAP1 system is the master regulator of cellular redox and metabolic homeostasis. NRF2 has Janus-like roles in carcinogenesis and cancer development. Short-term NRF2 activation suppresses tissue injury, inflammation, and cancer initiation. However, cancer cells often exhibit constitutive NRF2 activation due to genetic mutations or oncogenic signaling, conferring advantages for cancer cells' survival and growth. Emerging evidence suggests that NRF2 hyperactivation, as an adaptive cancer phenotype under stressful tumor environments, regulates all hallmarks of cancer. In this review, we summarized the source of ROS, regulation of ROS signaling, and cellular sensors for ROS and oxygen (O2), we reviewed recent progress on the regulation of ROS generation and NRF2 signaling with a focus on the new functions of NRF2 in cancer development that reach beyond what we originally envisioned, including regulation of cancer metabolism, autophagy, macropinocytosis, unfolded protein response, proteostasis, and circadian rhythm, which, together with anti-oxidant and drug detoxification enzymes, contributes to cancer development, metastasis, and anticancer therapy resistance.
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Affiliation(s)
- Ruolei Wang
- The Center for Cancer Research, Academy of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China
| | - Lirong Liang
- Department of Respiratory and Critical Care Medicine, Beijing Institute of Respiratory Medicine and Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, China
| | - Misaki Matsumoto
- Department of Pharmacology, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
| | - Kazumi Iwata
- Department of Pharmacology, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
| | - Atsushi Umemura
- Department of Pharmacology, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
- Correspondence: (A.U.); (F.H.); Tel.: +75-251-5332 (A.U.); +86-21-5132-2501 (F.H.)
| | - Feng He
- The Center for Cancer Research, Academy of Integrative Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China
- Correspondence: (A.U.); (F.H.); Tel.: +75-251-5332 (A.U.); +86-21-5132-2501 (F.H.)
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22
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Attaway AH, Bellar A, Mishra S, Karthikeyan M, Sekar J, Welch N, Musich R, Singh SS, Kumar A, Menon A, King J, Langen R, Webster J, Scheraga R, Rochon K, Mears J, Naga Prasad SV, Hatzoglou M, Chakraborty AA, Dasarathy S. Adaptive exhaustion during prolonged intermittent hypoxia causes dysregulated skeletal muscle protein homeostasis. J Physiol 2023; 601:567-606. [PMID: 36533558 PMCID: PMC10286804 DOI: 10.1113/jp283700] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 12/06/2022] [Indexed: 12/23/2022] Open
Abstract
Nocturnal hypoxaemia, which is common in chronic obstructive pulmonary disease (COPD) patients, is associated with skeletal muscle loss or sarcopenia, which contributes to adverse clinical outcomes. In COPD, we have defined this as prolonged intermittent hypoxia (PIH) because the duration of hypoxia in skeletal muscle occurs through the duration of sleep followed by normoxia during the day, in contrast to recurrent brief hypoxic episodes during obstructive sleep apnoea (OSA). Adaptive cellular responses to PIH are not known. Responses to PIH induced by three cycles of 8 h hypoxia followed by 16 h normoxia were compared to those during chronic hypoxia (CH) or normoxia for 72 h in murine C2C12 and human inducible pluripotent stem cell-derived differentiated myotubes. RNA sequencing followed by downstream analyses were complemented by experimental validation of responses that included both unique and shared perturbations in ribosomal and mitochondrial function during PIH and CH. A sarcopenic phenotype characterized by decreased myotube diameter and protein synthesis, and increased phosphorylation of eIF2α (Ser51) by eIF2α kinase, and of GCN-2 (general controlled non-derepressed-2), occurred during both PIH and CH. Mitochondrial oxidative dysfunction, disrupted supercomplex assembly, lower activity of Complexes I, III, IV and V, and reduced intermediary metabolite concentrations occurred during PIH and CH. Decreased mitochondrial fission occurred during CH. Physiological relevance was established in skeletal muscle of mice with COPD that had increased phosphorylation of eIF2α, lower protein synthesis and mitochondrial oxidative dysfunction. Molecular and metabolic responses with PIH suggest an adaptive exhaustion with failure to restore homeostasis during normoxia. KEY POINTS: Sarcopenia or skeletal muscle loss is one of the most frequent complications that contributes to mortality and morbidity in patients with chronic obstructive pulmonary disease (COPD). Unlike chronic hypoxia, prolonged intermittent hypoxia is a frequent, underappreciated and clinically relevant model of hypoxia in patients with COPD. We developed a novel, in vitro myotube model of prolonged intermittent hypoxia with molecular and metabolic perturbations, mitochondrial oxidative dysfunction, and consequent sarcopenic phenotype. In vivo studies in skeletal muscle from a mouse model of COPD shared responses with our myotube model, establishing the pathophysiological relevance of our studies. These data lay the foundation for translational studies in human COPD to target prolonged, nocturnal hypoxaemia to prevent sarcopenia in these patients.
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Affiliation(s)
- Amy H. Attaway
- Department of Pulmonary Medicine, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
| | - Annette Bellar
- Department of Inflammation and Immunity, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
| | - Saurabh Mishra
- Department of Inflammation and Immunity, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
| | - Manikandan Karthikeyan
- Department of Inflammation and Immunity, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
| | - Jinendiran Sekar
- Department of Inflammation and Immunity, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
| | - Nicole Welch
- Department of Inflammation and Immunity, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
- Department of Gastroenterology and Hepatology, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
| | - Ryan Musich
- Department of Inflammation and Immunity, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
| | - Shashi Shekhar Singh
- Department of Inflammation and Immunity, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
| | - Avinash Kumar
- Department of Inflammation and Immunity, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
| | - Aishwarya Menon
- Department of Inflammation and Immunity, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
| | - Jasmine King
- Department of Inflammation and Immunity, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
| | - Ramon Langen
- Department of Respiratory Medicine, Maastricht University Medical Center, Netherlands
| | - Justine Webster
- Department of Respiratory Medicine, Maastricht University Medical Center, Netherlands
| | - Rachel Scheraga
- Department of Inflammation and Immunity, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
| | - Kristy Rochon
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio
| | - Jason Mears
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio
| | - Sathyamangla V Naga Prasad
- Department of Cardiovascular and Metabolic Diseases, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
| | - Maria Hatzoglou
- Department of Genomic Medicine, Case Western Reserve University, Cleveland, Ohio
| | | | - Srinivasan Dasarathy
- Department of Pulmonary Medicine, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
- Department of Gastroenterology and Hepatology, Lerner Research Institute Cleveland Clinic, Cleveland, Ohio
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Ng PQ, Saint-Geniez M, Kim LA, Shu DY. Divergent Metabolomic Signatures of TGFβ2 and TNFα in the Induction of Retinal Epithelial-Mesenchymal Transition. Metabolites 2023; 13:213. [PMID: 36837832 PMCID: PMC9966219 DOI: 10.3390/metabo13020213] [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: 12/31/2022] [Revised: 01/23/2023] [Accepted: 01/23/2023] [Indexed: 02/04/2023] Open
Abstract
Epithelial-mesenchymal transition (EMT) is a dedifferentiation program in which polarized, differentiated epithelial cells lose their cell-cell adhesions and transform into matrix-producing mesenchymal cells. EMT of retinal pigment epithelial (RPE) cells plays a crucial role in many retinal diseases, including age-related macular degeneration, proliferative vitreoretinopathy, and diabetic retinopathy. This dynamic process requires complex metabolic reprogramming to accommodate the demands of this dramatic cellular transformation. Both transforming growth factor-beta 2 (TGFβ2) and tumor necrosis factor-alpha (TNFα) have the capacity to induce EMT in RPE cells; however, little is known about their impact on the RPE metabolome. Untargeted metabolomics using high-resolution mass spectrometry was performed to reveal the metabolomic signatures of cellular and secreted metabolites of primary human fetal RPE cells treated with either TGFβ2 or TNFα for 5 days. A total of 638 metabolites were detected in both samples; 188 were annotated as primary metabolites. Metabolomics profiling showed distinct metabolomic signatures associated with TGFβ2 and TNFα treatment. Enrichment pathway network analysis revealed alterations in the pentose phosphate pathway, galactose metabolism, nucleotide and pyrimidine metabolism, purine metabolism, and arginine and proline metabolism in TNFα-treated cells compared to untreated control cells, whereas TGFβ2 treatment induced perturbations in fatty acid biosynthesis metabolism, the linoleic acid pathway, and the Notch signaling pathway. These results provide a broad metabolic understanding of the bioenergetic rewiring processes governing TGFβ2- and TNFα-dependent induction of EMT. Elucidating the contributions of TGFβ2 and TNFα and their mechanistic differences in promoting EMT of RPE will enable the identification of novel biomarkers for diagnosis, management, and tailored drug development for retinal fibrotic diseases.
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Affiliation(s)
- Pei Qin Ng
- Department of Plant Science, University of Cambridge, Downing Street, Cambridge CB2 3EA, Cambridgeshire, UK
- Schepens Eye Research Institute of Mass Eye and Ear, Boston, MA 02114, USA
- Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA
- School of Biological Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
- South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA 5000, Australia
| | - Magali Saint-Geniez
- Schepens Eye Research Institute of Mass Eye and Ear, Boston, MA 02114, USA
- Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA
| | - Leo A. Kim
- Schepens Eye Research Institute of Mass Eye and Ear, Boston, MA 02114, USA
- Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA
| | - Daisy Y. Shu
- Schepens Eye Research Institute of Mass Eye and Ear, Boston, MA 02114, USA
- Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA
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24
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Hass DT, Bisbach CM, Sadilek M, Sweet IR, Hurley JB. Aerobic Glycolysis in Photoreceptors Supports Energy Demand in the Absence of Mitochondrial Coupling. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1415:435-441. [PMID: 37440069 DOI: 10.1007/978-3-031-27681-1_64] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
Metabolism is adapted to meet energetic needs. Based on the amount of ATP required to maintain plasma membrane potential, photoreceptor energy demands must be high. The available evidence suggests that photoreceptors primarily generate metabolic energy through aerobic glycolysis, though this evidence is based primarily on protein expression and not measurement of metabolic flux. Aerobic glycolysis can be validated by measuring flux of glucose to lactate. Aerobic glycolysis is also inefficient and thus an unexpected adaptation for photoreceptors to make. We measured metabolic rates to determine the energy-generating pathways that support photoreceptor metabolism. We found that photoreceptors indeed perform aerobic glycolysis and this is associated with mitochondrial uncoupling.
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Affiliation(s)
- Daniel T Hass
- Department of Biochemistry, University of Washington, Seattle, WA, USA.
| | - Celia M Bisbach
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Martin Sadilek
- Department of Chemistry, University of Washington, Seattle, WA, USA
| | - Ian R Sweet
- UW Medicine - Diabetes Institute, University of Washington, Seattle, WA, USA
| | - James B Hurley
- Department of Biochemistry, University of Washington, Seattle, WA, USA
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25
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Arnold PK, Finley LW. Regulation and function of the mammalian tricarboxylic acid cycle. J Biol Chem 2022; 299:102838. [PMID: 36581208 PMCID: PMC9871338 DOI: 10.1016/j.jbc.2022.102838] [Citation(s) in RCA: 58] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 12/15/2022] [Accepted: 12/20/2022] [Indexed: 12/27/2022] Open
Abstract
The tricarboxylic acid (TCA) cycle, otherwise known as the Krebs cycle, is a central metabolic pathway that performs the essential function of oxidizing nutrients to support cellular bioenergetics. More recently, it has become evident that TCA cycle behavior is dynamic, and products of the TCA cycle can be co-opted in cancer and other pathologic states. In this review, we revisit the TCA cycle, including its potential origins and the history of its discovery. We provide a detailed accounting of the requirements for sustained TCA cycle function and the critical regulatory nodes that can stimulate or constrain TCA cycle activity. We also discuss recent advances in our understanding of the flexibility of TCA cycle wiring and the increasingly appreciated heterogeneity in TCA cycle activity exhibited by mammalian cells. Deeper insight into how the TCA cycle can be differentially regulated and, consequently, configured in different contexts will shed light on how this pathway is primed to meet the requirements of distinct mammalian cell states.
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Affiliation(s)
- Paige K. Arnold
- Cell Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, New York, USA,Louis V. Gerstner Jr. Graduate School of Biomedical Sciences, Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Lydia W.S. Finley
- Cell Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, New York, USA,For correspondence: Lydia W. S. Finley
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26
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Berkowitz BA, Podolsky RH, Childers KL, Roberts R, Katz R, Waseem R, Robbings BM, Hass DT, Hurley JB, Sweet IR, Goodman C, Qian H, Alvisio B, Heaps S. Transducin-Deficient Rod Photoreceptors Evaluated With Optical Coherence Tomography and Oxygen Consumption Rate Energy Biomarkers. Invest Ophthalmol Vis Sci 2022; 63:22. [PMID: 36576748 PMCID: PMC9804021 DOI: 10.1167/iovs.63.13.22] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Purpose To test the hypothesis that rod energy biomarkers in light and dark are similar in mice without functional rod transducin (Gnat1rd17). Methods Gnat1rd17 and wildtype (WT) mice were studied in canonically low energy demand (light) and high energy demand (dark) conditions. We measured rod inner segment ellipsoid zone (ISez) profile shape, external limiting membrane-retinal pigment epithelium (ELM-RPE) thickness, and magnitude of a hyporeflective band (HB) intensity dip located between photoreceptor tips and apical RPE; antioxidants were given in a subset of mice. Oxygen consumption rate (OCR) and visual performance indexes were also measured. Results The lower energy demand expected in light-adapted wildtype retinas was associated with an elongated ISez, thicker ELM-RPE, and higher HB magnitude, and lower OCR compared to high energy demand conditions in the dark. Gnat1rd17 mice showed a wildtype-like ISez profile shape at 20 minutes of light that became rounder at 60 minutes; at both times, ELM-RPE was smaller than wildtype values, and the HB magnitude was unmeasurable. OCR was higher than in the dark. Light-adapted Gnat1rd17 mice biomarkers were unaffected by anti-oxidants. Gnat1rd17 mice showed modest outer nuclear layer thinning and no reduction in visual performance indexes. Conclusions Light-stimulated changes in all biomarkers in WT mice are consistent with the established light-induced decrease in net energy demand. In contrast, biomarker changes in Gnat1rd17 mice raise the possibility that light increases net energy demand in the absence of rod phototransduction.
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Affiliation(s)
- Bruce A Berkowitz
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Robert H Podolsky
- Biostatistics and Study Methodology, Children's National Hospital, Silver Spring, Maryland, United States
| | - Karen Lins Childers
- Beaumont Research Institute, Beaumont Health, Royal Oak, Michigan, United States
| | - Robin Roberts
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Ryan Katz
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Rida Waseem
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Brian M Robbings
- Department of Biochemistry, Department of Ophthalmology, University of Washington, Seattle, Washington, United States.,Department of Medicine, UW Medicine Diabetes Institute, University of Washington, Seattle, Washington, United States
| | - Daniel T Hass
- Department of Biochemistry, Department of Ophthalmology, University of Washington, Seattle, Washington, United States
| | - James B Hurley
- Department of Biochemistry, Department of Ophthalmology, University of Washington, Seattle, Washington, United States
| | - Ian R Sweet
- Department of Medicine, UW Medicine Diabetes Institute, University of Washington, Seattle, Washington, United States
| | - Cole Goodman
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Haohua Qian
- Visual Function Core, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Bruno Alvisio
- OSIO Bioinformatics Core, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Sam Heaps
- OSIO Bioinformatics Core, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
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27
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Fu Z, Nilsson AK, Hellstrom A, Smith LEH. Retinopathy of prematurity: Metabolic risk factors. eLife 2022; 11:e80550. [PMID: 36420952 PMCID: PMC9691009 DOI: 10.7554/elife.80550] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 11/16/2022] [Indexed: 11/25/2022] Open
Abstract
At preterm birth, the retina is incompletely vascularized. Retinopathy of prematurity (ROP) is initiated by the postnatal suppression of physiological retinal vascular development that would normally occur in utero. As the neural retina slowly matures, increasing metabolic demand including in the peripheral avascular retina, leads to signals for compensatory but pathological neovascularization. Currently, only late neovascular ROP is treated. ROP could be prevented by promoting normal vascular growth. Early perinatal metabolic dysregulation is a strong but understudied risk factor for ROP and other long-term sequelae of preterm birth. We will discuss the metabolic and oxygen needs of retina, current treatments, and potential interventions to promote normal vessel growth including control of postnatal hyperglycemia, dyslipidemia and hyperoxia-induced retinal metabolic alterations. Early supplementation of missing nutrients and growth factors and control of supplemental oxygen promotes physiological retinal development. We will discuss the current knowledge gap in retinal metabolism after preterm birth.
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Affiliation(s)
- Zhongjie Fu
- Department of Ophthalmology, Boston Children’s Hospital, Harvard Medical SchoolBostonUnited States
| | - Anders K Nilsson
- The Sahlgrenska Centre for Pediatric Ophthalmology Research, Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of GothenburgGothenburgSweden
| | - Ann Hellstrom
- The Sahlgrenska Centre for Pediatric Ophthalmology Research, Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of GothenburgGothenburgSweden
| | - Lois EH Smith
- Department of Ophthalmology, Boston Children’s Hospital, Harvard Medical SchoolBostonUnited States
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28
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Oxygen regulation of breathing is abolished in mitochondrial complex III-deficient arterial chemoreceptors. Proc Natl Acad Sci U S A 2022; 119:e2202178119. [PMID: 36122208 PMCID: PMC9522341 DOI: 10.1073/pnas.2202178119] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Oxygen sensing by chemoreceptor glomus cells in the carotid body plays an essential adaptive function in health and disease; however, the underlying mechanisms are not fully understood. Glomus cells survive genetic disruption of mitochondrial complex III, although this results in a functional disconnection between the distal and proximal components of the mitochondrial electron transport chain (ETC). These cells exhibit selective abolition of mitochondrial and cellular responsiveness to hypoxia, as well as altered systemic hyperventilation and acclimatization to hypoxia, indicating that acute oxygen-sensing and -signaling during hypoxia result from the integrated action of mitochondrial ETC components. The mitochondrial ETC emerges as a complex oxygen-sensing and -signaling system of potential pathophysiological relevance in maladaptive responses to hypoxia. Acute oxygen (O2) sensing is essential for adaptation of organisms to hypoxic environments or medical conditions with restricted exchange of gases in the lung. The main acute O2-sensing organ is the carotid body (CB), which contains neurosecretory chemoreceptor (glomus) cells innervated by sensory fibers whose activation by hypoxia elicits hyperventilation and increased cardiac output. Glomus cells have mitochondria with specialized metabolic and electron transport chain (ETC) properties. Reduced mitochondrial complex (MC) IV activity by hypoxia leads to production of signaling molecules (NADH and reactive O2 species) in MCI and MCIII that modulate membrane ion channel activity. We studied mice with conditional genetic ablation of MCIII that disrupts the ETC in the CB and other catecholaminergic tissues. Glomus cells survived MCIII dysfunction but showed selective abolition of responsiveness to hypoxia (increased [Ca2+] and transmitter release) with normal responses to other stimuli. Mitochondrial hypoxic NADH and reactive O2 species signals were also suppressed. MCIII-deficient mice exhibited strong inhibition of the hypoxic ventilatory response and altered acclimatization to sustained hypoxia. These data indicate that a functional ETC, with coupling between MCI and MCIV, is required for acute O2 sensing. O2 regulation of breathing results from the integrated action of mitochondrial ETC complexes in arterial chemoreceptors.
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Tournaire G, Loopmans S, Stegen S, Rinaldi G, Eelen G, Torrekens S, Moermans K, Carmeliet P, Ghesquière B, Thienpont B, Fendt SM, van Gastel N, Carmeliet G. Skeletal progenitors preserve proliferation and self-renewal upon inhibition of mitochondrial respiration by rerouting the TCA cycle. Cell Rep 2022; 40:111105. [PMID: 35905715 PMCID: PMC9380255 DOI: 10.1016/j.celrep.2022.111105] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 04/13/2022] [Accepted: 06/25/2022] [Indexed: 11/25/2022] Open
Abstract
A functional electron transport chain (ETC) is crucial for supporting bioenergetics and biosynthesis. Accordingly, ETC inhibition decreases proliferation in cancer cells but does not seem to impair stem cell proliferation. However, it remains unclear how stem cells metabolically adapt. In this study, we show that pharmacological inhibition of complex III of the ETC in skeletal stem and progenitor cells induces glycolysis side pathways and reroutes the tricarboxylic acid (TCA) cycle to regenerate NAD+ and preserve cell proliferation. These metabolic changes also culminate in increased succinate and 2-hydroxyglutarate levels that inhibit Ten-eleven translocation (TET) DNA demethylase activity, thereby preserving self-renewal and multilineage potential. Mechanistically, mitochondrial malate dehydrogenase and reverse succinate dehydrogenase activity proved to be essential for the metabolic rewiring in response to ETC inhibition. Together, these data show that the metabolic plasticity of skeletal stem and progenitor cells allows them to bypass ETC blockade and preserve their self-renewal. Skeletal stem/progenitor cells can proliferate upon electron transport chain blockade Succinate dehydrogenase is reversed with fumarate functioning as electron acceptor Pyruvate and aspartate are critical for NAD+ regeneration and proliferation Metabolic changes prevent DNA demethylation and preserve self-renewal
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Affiliation(s)
- Guillaume Tournaire
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, KU Leuven, O&N1bis Herestraat 49, 3000 Leuven, Belgium; Prometheus, Division of Skeletal Tissue Engineering, KU Leuven, Leuven, Belgium
| | - Shauni Loopmans
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, KU Leuven, O&N1bis Herestraat 49, 3000 Leuven, Belgium; Prometheus, Division of Skeletal Tissue Engineering, KU Leuven, Leuven, Belgium
| | - Steve Stegen
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, KU Leuven, O&N1bis Herestraat 49, 3000 Leuven, Belgium; Prometheus, Division of Skeletal Tissue Engineering, KU Leuven, Leuven, Belgium
| | - Gianmarco Rinaldi
- Laboratory of Cellular Metabolism and Metabolic Regulation, VIB Center for Cancer Biology, Leuven, Belgium; Laboratory of Cellular Metabolism and Metabolic Regulation, Department of Oncology and Leuven Cancer Institute, KU Leuven, Leuven, Belgium
| | - Guy Eelen
- Laboratory of Angiogenesis and Vascular Metabolism, VIB Center for Cancer Biology, Leuven, Belgium; Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology and Leuven Cancer Institute, KU Leuven, Leuven, Belgium
| | - Sophie Torrekens
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, KU Leuven, O&N1bis Herestraat 49, 3000 Leuven, Belgium
| | - Karen Moermans
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, KU Leuven, O&N1bis Herestraat 49, 3000 Leuven, Belgium
| | - Peter Carmeliet
- Laboratory of Angiogenesis and Vascular Metabolism, VIB Center for Cancer Biology, Leuven, Belgium; Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology and Leuven Cancer Institute, KU Leuven, Leuven, Belgium
| | - Bart Ghesquière
- Metabolomics Expertise Center, Department of Oncology, KU Leuven/VIB Center for Cancer Biology Leuven, Leuven, Belgium
| | - Bernard Thienpont
- Laboratory of Functional Epigenetics, Department of Human Genetics, KU Leuven, Leuven, Belgium
| | - Sarah-Maria Fendt
- Laboratory of Cellular Metabolism and Metabolic Regulation, VIB Center for Cancer Biology, Leuven, Belgium; Laboratory of Cellular Metabolism and Metabolic Regulation, Department of Oncology and Leuven Cancer Institute, KU Leuven, Leuven, Belgium
| | | | - Geert Carmeliet
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, KU Leuven, O&N1bis Herestraat 49, 3000 Leuven, Belgium; Prometheus, Division of Skeletal Tissue Engineering, KU Leuven, Leuven, Belgium.
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Hazim RA, Paniagua AE, Tang L, Yang K, Kim KKO, Stiles L, Divakaruni AS, Williams DS. Vitamin B3, nicotinamide, enhances mitochondrial metabolism to promote differentiation of the retinal pigment epithelium. J Biol Chem 2022; 298:102286. [PMID: 35868562 PMCID: PMC9396405 DOI: 10.1016/j.jbc.2022.102286] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 07/14/2022] [Accepted: 07/15/2022] [Indexed: 01/04/2023] Open
Abstract
In the mammalian retina, a metabolic ecosystem exists in which photoreceptors acquire glucose from the choriocapillaris with the help of the retinal pigment epithelium (RPE). While the photoreceptor cells are primarily glycolytic, exhibiting Warburg-like metabolism, the RPE is reliant on mitochondrial respiration. However, the ways in which mitochondrial metabolism affect RPE cellular functions are not clear. We first used the human RPE cell line, ARPE-19, to examine mitochondrial metabolism in the context of cellular differentiation. We show that nicotinamide induced rapid differentiation of ARPE-19 cells, which was reversed by removal of supplemental nicotinamide. During the nicotinamide-induced differentiation, we observed using quantitative PCR, Western blotting, electron microscopy, and metabolic respiration and tracing assays that (1) mitochondrial gene and protein expression increased, (2) mitochondria became larger with more tightly folded cristae, and (3) mitochondrial metabolism was enhanced. In addition, we show that primary cultures of human fetal RPE cells responded similarly in the presence of nicotinamide. Furthermore, disruption of mitochondrial oxidation of pyruvate attenuated the nicotinamide-induced differentiation of the RPE cells. Together, our results demonstrate a remarkable effect of nicotinamide on RPE metabolism. We also identify mitochondrial respiration as a key contributor to the differentiated state of the RPE and thus to many of the RPE functions that are essential for retinal health and photoreception.
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Affiliation(s)
- Roni A Hazim
- Department of Ophthalmology and Stein Eye Institute
| | | | - Lisa Tang
- Department of Ophthalmology and Stein Eye Institute
| | - Krista Yang
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, CA 90095
| | - Kristen K O Kim
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, CA 90095
| | - Linsey Stiles
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, CA 90095; Department of Medicine, Endocrinology. UCLA David Geffen School of Medicine. Los Angeles, CA, 90095, USA
| | - Ajit S Divakaruni
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, CA 90095
| | - David S Williams
- Department of Ophthalmology and Stein Eye Institute; Department of Neurobiology, David Geffen School of Medicine at UCLA; Molecular Biology Institute; Brain Research Institute, University of California, Los Angeles, CA.
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31
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Kiyama T, Chen CK, Zhang A, Mao CA. Differential Susceptibility of Retinal Neurons to the Loss of Mitochondrial Biogenesis Factor Nrf1. Cells 2022; 11:cells11142203. [PMID: 35883647 PMCID: PMC9321222 DOI: 10.3390/cells11142203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 07/10/2022] [Accepted: 07/13/2022] [Indexed: 12/14/2022] Open
Abstract
The retina, the accessible part of the central nervous system, has served as a model system to study the relationship between energy utilization and metabolite supply. When the metabolite supply cannot match the energy demand, retinal neurons are at risk of death. As the powerhouse of eukaryotic cells, mitochondria play a pivotal role in generating ATP, produce precursors for macromolecules, maintain the redox homeostasis, and function as waste management centers for various types of metabolic intermediates. Mitochondrial dysfunction has been implicated in the pathologies of a number of degenerative retinal diseases. It is well known that photoreceptors are particularly vulnerable to mutations affecting mitochondrial function due to their high energy demand and susceptibility to oxidative stress. However, it is unclear how defective mitochondria affect other retinal neurons. Nuclear respiratory factor 1 (Nrf1) is the major transcriptional regulator of mitochondrial biogenesis, and loss of Nrf1 leads to defective mitochondria biogenesis and eventually cell death. Here, we investigated how different retinal neurons respond to the loss of Nrf1. We provide in vivo evidence that the disruption of Nrf1-mediated mitochondrial biogenesis results in a slow, progressive degeneration of all retinal cell types examined, although they present different sensitivity to the deletion of Nrf1, which implicates differential energy demand and utilization, as well as tolerance to mitochondria defects in different neuronal cells. Furthermore, transcriptome analysis on rod-specific Nrf1 deletion uncovered a previously unknown role of Nrf1 in maintaining genome stability.
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Affiliation(s)
- Takae Kiyama
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School at The University of Texas Health Science Center at Houston (UTHealth), 6431 Fannin St., MSB 7.024, Houston, TX 77030, USA; (T.K.); (A.Z.)
| | - Ching-Kang Chen
- Department of Ophthalmology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA;
| | - Annie Zhang
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School at The University of Texas Health Science Center at Houston (UTHealth), 6431 Fannin St., MSB 7.024, Houston, TX 77030, USA; (T.K.); (A.Z.)
| | - Chai-An Mao
- Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School at The University of Texas Health Science Center at Houston (UTHealth), 6431 Fannin St., MSB 7.024, Houston, TX 77030, USA; (T.K.); (A.Z.)
- The MD Anderson Cancer Center/UTHealth Graduate School of Biomedical Sciences, Houston, TX 77030, USA
- Correspondence:
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32
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Berkowitz BA, Podolsky RH, Childers KL, Burgoyne T, De Rossi G, Qian H, Roberts R, Katz R, Waseem R, Goodman C. Functional Changes Within the Rod Inner Segment Ellipsoid in Wildtype Mice: An Optical Coherence Tomography and Electron Microscopy Study. Invest Ophthalmol Vis Sci 2022; 63:8. [PMID: 35816042 PMCID: PMC9284466 DOI: 10.1167/iovs.63.8.8] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Purpose To test the hypothesis that changing energy needs alter mitochondria distribution within the rod inner segment ellipsoid. Methods In mice with relatively smaller (C57BL/6J [B6J]) or greater (129S6/ev [S6]) retina mitochondria maximum reserve capacity, the profile shape of the rod inner segment ellipsoid zone (ISez) was measured with optical coherence tomography (OCT) under higher (dark) or lower (light) energy demand conditions. ISez profile shape was characterized using an unbiased ellipse descriptor (minor/major aspect ratio). Other bioenergy indexes evaluated include the external limiting membrane-retinal pigment epithelium (ELM-RPE) thickness and the magnitude of the signal intensity of a hyporeflective band located between the photoreceptor tips and apical RPE. The spatial distribution of rod ellipsoid mitochondria were also examined with electron microscopy. Results In B6J mice, darkness produced a greater ISez aspect ratio, thinner ELM-RPE, and a smaller hyporeflective band intensity than in light. In S6 mice, dark and light ISez aspect ratio values were not different and were greater than in light-adapted B6J mice; dark-adapted S6 mice showed smaller ELM-RPE thinning versus light, and negligible hyporeflective band intensity in the light. In B6J mice, mitochondria number in light increased in the distal inner segment ellipsoid and decreased proximally. In S6 mice, mitochondria number in the inner segment ellipsoid were not different between light and dark, and were greater than in B6J mice. Conclusions These data raise the possibility that rod mitochondria activity in mice can be noninvasively evaluated based on the ISez profile shape, a new OCT index that complements OCT energy biomarkers measured outside of the ISez region.
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Affiliation(s)
- Bruce A Berkowitz
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Robert H Podolsky
- Biostatistics and Study Methodology, Children's National Hospital, Silver Spring, Maryland, United States
| | - Karen Lins Childers
- Beaumont Research Institute, Beaumont Health, Royal Oak, Michigan, Unites States
| | - Tom Burgoyne
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
| | - Giulia De Rossi
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
| | - Haohua Qian
- Visual Function Core, National Eye Institute, National Institutes of Health, Bethesda, Maryland, Unites States
| | - Robin Roberts
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Ryan Katz
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Rida Waseem
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Cole Goodman
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
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33
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Bayley JP, Devilee P. Hypothesis: Why Different Types of SDH Gene Variants Cause Divergent Tumor Phenotypes. Genes (Basel) 2022; 13:genes13061025. [PMID: 35741787 PMCID: PMC9222429 DOI: 10.3390/genes13061025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 06/01/2022] [Accepted: 06/02/2022] [Indexed: 11/16/2022] Open
Abstract
Despite two decades of paraganglioma-pheochromocytoma research, the fundamental question of how the different succinate dehydrogenase (SDH)-related tumor phenotypes are initiated has remained unanswered. Here, we discuss two possible scenarios by which missense (hypomorphic alleles) or truncating (null alleles) SDH gene variants determine clinical phenotype. Dysfunctional SDH is a major source of reactive oxygen species (ROS) but ROS are inhibited by rising succinate levels. In scenario 1, we propose that SDH missense variants disrupt electron flow, causing elevated ROS levels that are toxic in sympathetic PPGL precursor cells but well controlled in oxygen-sensing parasympathetic paraganglion cells. We also suggest that SDHAF2 variants, solely associated with HNPGL, may cause the reversal of succinate dehydrogenase to fumarate reductase, producing very high ROS levels. In scenario 2, we propose a modified succinate threshold model of tumor initiation. Truncating SDH variants cause high succinate accumulation and likely initiate tumorigenesis via disruption of 2-oxoglutarate-dependent enzymes in both PPGL and HNPGL precursor tissues. We propose that missense variants (including SDHAF2) cause lower succinate accumulation and thus initiate tumorigenesis only in very metabolically active tissues such as parasympathetic paraganglia, which naturally show very high levels of succinate.
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Affiliation(s)
- Jean-Pierre Bayley
- Department of Human Genetics, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands;
- Correspondence:
| | - Peter Devilee
- Department of Human Genetics, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands;
- Department of Pathology, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands
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34
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Hass DT, Bisbach CM, Robbings BM, Sadilek M, Sweet IR, Hurley JB. Succinate metabolism in the retinal pigment epithelium uncouples respiration from ATP synthesis. Cell Rep 2022; 39:110917. [PMID: 35675773 PMCID: PMC9251713 DOI: 10.1016/j.celrep.2022.110917] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 04/08/2022] [Accepted: 05/12/2022] [Indexed: 11/28/2022] Open
Abstract
Fumarate can be a surrogate for O2 as a terminal electron acceptor in the electron transport chain. Reduction of fumarate produces succinate, which can be exported. It is debated whether intact tissues can import and oxidize succinate produced by other tissues. In a previous report, we showed that mitochondria in retinal pigment epithelium (RPE)-choroid preparations can use succinate to reduce O2 to H2O. However, cells in that preparation could have been disrupted during tissue isolation. We now use multiple strategies to quantify intactness of the isolated RPE-choroid tissue. We find that exogenous 13C4-succinate is oxidized by intact cells then exported as fumarate or malate. Unexpectedly, we also find that oxidation of succinate is different from oxidation of other substrates because it uncouples electron transport from ATP synthesis. Retinas produce and export succinate. Our findings imply that retina succinate may substantially increase O2 consumption by uncoupling adjacent RPE mitochondria. The retina releases succinate, a source of reducing power for mitochondria. Hass et al. outline a pathway by which retina succinate can enter intact RPE-choroid cells and stimulate mitochondrial respiration that is uncoupled from ATP synthesis. Rapid RPE succinate oxidation may limit O2 levels in the retina.
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Affiliation(s)
- Daniel T Hass
- Biochemistry Department, The University of Washington, Seattle, WA 98195, USA
| | - Celia M Bisbach
- Biochemistry Department, The University of Washington, Seattle, WA 98195, USA; Promega Corporation, 2800 Woods Hollow Road, Fitchburg, WI 53711, USA
| | - Brian M Robbings
- Biochemistry Department, The University of Washington, Seattle, WA 98195, USA; Diabetes Institute, The University of Washington, Seattle, WA 98109, USA
| | - Martin Sadilek
- Chemistry Department, The University of Washington, Seattle, WA 98195, USA
| | - Ian R Sweet
- Diabetes Institute, The University of Washington, Seattle, WA 98109, USA; Division of Metabolism, Endocrinology and Nutrition, The University of Washington, Seattle, WA 98195, USA
| | - James B Hurley
- Biochemistry Department, The University of Washington, Seattle, WA 98195, USA; Opthalmology Department, The University of Washington, Seattle, WA 98109, USA.
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35
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Why succinate? Physiological regulation by a mitochondrial coenzyme Q sentinel. Nat Chem Biol 2022; 18:461-469. [PMID: 35484255 PMCID: PMC9150600 DOI: 10.1038/s41589-022-01004-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Accepted: 02/25/2022] [Indexed: 12/15/2022]
Abstract
Metabolites once considered solely in catabolism or anabolism turn out to have key regulatory functions. Among these, the citric acid cycle intermediate succinate stands out owing to its multiple roles in disparate pathways, its dramatic concentration changes and its selective cell release. Here we propose that succinate has evolved as a signaling modality because its concentration reflects the coenzyme Q (CoQ) pool redox state, a central redox couple confined to the mitochondrial inner membrane. This connection is of general importance because CoQ redox state integrates three bioenergetic parameters: mitochondrial electron supply, oxygen tension and ATP demand. Succinate, by equilibrating with the CoQ pool, enables the status of this central bioenergetic parameter to be communicated from mitochondria to the rest of the cell, into the circulation and to other cells. The logic of this form of regulation explains many emerging roles of succinate in biology, and suggests future research questions.
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36
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Gas regulation of complex II reversal via electron shunting to fumarate in the mammalian ETC. Trends Biochem Sci 2022; 47:689-698. [PMID: 35397924 PMCID: PMC9288524 DOI: 10.1016/j.tibs.2022.03.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 02/22/2022] [Accepted: 03/14/2022] [Indexed: 12/24/2022]
Abstract
The electron transport chain (ETC) is a major currency converter that exchanges the chemical energy of fuel oxidation to proton motive force and, subsequently, ATP generation, using O2 as a terminal electron acceptor. Discussed herein, two new studies reveal that the mammalian ETC is forked. Hypoxia or H2S exposure promotes the use of fumarate as an alternate terminal electron acceptor. The fumarate/succinate and CoQH2/CoQ redox couples are nearly iso-potential, revealing that complex II is poised for facile reverse electron transfer, which is sensitive to CoQH2 and fumarate concentrations. The gas regulators, H2S and •NO, modulate O2 affinity and/or inhibit the electron transfer rate at complex IV. Their induction under hypoxia suggests a mechanism for how traffic at the ETC fork can be regulated.
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Bisbach CM, Hass DT, Thomas ED, Cherry TJ, Hurley JB. Monocarboxylate Transporter 1 (MCT1) Mediates Succinate Export in the Retina. Invest Ophthalmol Vis Sci 2022; 63:1. [PMID: 35363247 PMCID: PMC8976921 DOI: 10.1167/iovs.63.4.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 03/12/2022] [Indexed: 11/24/2022] Open
Abstract
Purpose Succinate is exported by the retina and imported by eyecup tissue. The transporters mediating this process have not yet been identified. Recent studies showed that monocarboxylate transporter 1 (MCT1) can transport succinate across plasma membranes in cardiac and skeletal muscle. Retina and retinal pigment epithelium (RPE) both express multiple MCT isoforms including MCT1. We tested the hypothesis that MCTs facilitate retinal succinate export and RPE succinate import. Methods We assessed retinal succinate export and eyecup succinate import in short-term ex vivo culture using gas chromatography-mass spectrometry. We tested the dependence of succinate export and import on pH, proton ionophores, conventional MCT substrates, and the MCT inhibitors AZD3965, AR-C155858, and diclofenac. Results Succinate exits retinal tissue through MCT1 but does not enter the RPE through MCT1 or any other MCT. Intracellular succinate levels are a contributing factor that determines if an MCT1-expressing tissue will export succinate. Conclusions MCT1 facilitates export of succinate from retinas. An unidentified, non-MCT transporter facilitates import of succinate into RPE.
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Affiliation(s)
- Celia M. Bisbach
- Department of Biochemistry, University of Washington, Seattle, Washington, United States
| | - Daniel T. Hass
- Department of Biochemistry, University of Washington, Seattle, Washington, United States
| | - Eric D. Thomas
- Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, Washington, United States
| | - Timothy J. Cherry
- Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, Washington, United States
| | - James B. Hurley
- Department of Biochemistry, University of Washington, Seattle, Washington, United States
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38
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Yazdani M. Uncontrolled Oxygen Levels in Cultures of Retinal Pigment Epithelium: Have We Missed the Obvious? Curr Eye Res 2022; 47:651-660. [PMID: 35243933 DOI: 10.1080/02713683.2022.2050264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Retinal pigment epithelium (RPE) is the outermost layer of retina located between the photoreceptor cells and the choroid. This highly-polarized monolayer provides critical support for the functioning of the other parts of the retina, especially photoreceptors. Methods of culturing RPE have been under development since its establishment in 1920s. Despite considering various factors, oxygen (O2) levels in RPE microenvironments during culture preparation and experimental procedure have been overlooked. O2 is a crucial parameter in the cultures, and therefore, maintaining RPE cells at O2 levels different from their native environment (70-90 mm Hg of O2) could have unintended consequences. Owing to the importance of the topic, lack of sufficient discussion in the literature and to encourage future research, this paper will focus on uncontrolled O2 level in cultures of RPE cells.
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Affiliation(s)
- Mazyar Yazdani
- Department of Medical Biochemistry, Oslo University Hospital, Rikshospitalet, 0027 Oslo, Norway
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39
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Damsgaard C, Country MW. The Opto-Respiratory Compromise: Balancing Oxygen Supply and Light Transmittance in the Retina. Physiology (Bethesda) 2022; 37:101-113. [PMID: 34843655 PMCID: PMC9159541 DOI: 10.1152/physiol.00027.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The light-absorbing retina has an exceptionally high oxygen demand, which imposes two conflicting needs: high rates of blood perfusion and an unobstructed light path devoid of blood vessels. This review discusses mechanisms and physiological trade-offs underlying retinal oxygen supply in vertebrates and examines how these physiological systems supported the evolution of vision.
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Affiliation(s)
- Christian Damsgaard
- 1Aarhus Institute of Advanced Studies, Aarhus University, Aarhus, Denmark,2Zoophysiology, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Michael W. Country
- 3Retinal Neurophysiology Section, National Eye Institute,
National Institutes of Health, Bethesda, Maryland
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40
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Spinelli JB, Rosen PC, Sprenger HG, Puszynska AM, Mann JL, Roessler JM, Cangelosi AL, Henne A, Condon KJ, Zhang T, Kunchok T, Lewis CA, Chandel NS, Sabatini DM. Fumarate is a terminal electron acceptor in the mammalian electron transport chain. Science 2021; 374:1227-1237. [PMID: 34855504 PMCID: PMC8803114 DOI: 10.1126/science.abi7495] [Citation(s) in RCA: 95] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
For electrons to continuously enter and flow through the mitochondrial electron transport chain (ETC), they must ultimately land on a terminal electron acceptor (TEA), which is known to be oxygen in mammals. Paradoxically, we find that complex I and dihydroorotate dehydrogenase (DHODH) can still deposit electrons into the ETC when oxygen reduction is impeded. Cells lacking oxygen reduction accumulate ubiquinol, driving the succinate dehydrogenase (SDH) complex in reverse to enable electron deposition onto fumarate. Upon inhibition of oxygen reduction, fumarate reduction sustains DHODH and complex I activities. Mouse tissues display varying capacities to use fumarate as a TEA, most of which net reverse the SDH complex under hypoxia. Thus, we delineate a circuit of electron flow in the mammalian ETC that maintains mitochondrial functions under oxygen limitation.
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Affiliation(s)
- Jessica B. Spinelli
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Paul C. Rosen
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Hans-Georg Sprenger
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Anna M. Puszynska
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jessica L. Mann
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Julian M. Roessler
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Andrew L. Cangelosi
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Antonia Henne
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
| | - Kendall J. Condon
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Tong Zhang
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Tenzin Kunchok
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
| | - Caroline A. Lewis
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
| | - Navdeep S. Chandel
- Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - David M. Sabatini
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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41
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Du SW, Palczewski K. MicroRNA regulation of critical retinal pigment epithelial functions. Trends Neurosci 2021; 45:78-90. [PMID: 34753606 DOI: 10.1016/j.tins.2021.10.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 10/06/2021] [Accepted: 10/15/2021] [Indexed: 02/08/2023]
Abstract
MicroRNAs are short, evolutionarily conserved noncoding RNAs that are critical for the control of normal cellular physiology. In the retina, photoreceptors are highly specialized neurons that transduce light into electrical signals. Photoreceptors, however, are unable to process visual stimuli without the support of the retinal pigment epithelium (RPE). The RPE performs numerous functions to aid the retina, including the generation of visual chromophore and metabolic support. Recent work has underscored how microRNAs enable vision through their contributions to RPE functions. This review focuses on the biogenesis and control of microRNAs in rodents and humans, the roles microRNAs play in RPE function and degeneration, and how microRNAs could serve as potential therapeutics and biomarkers for visual diseases.
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Affiliation(s)
- Samuel W Du
- Center for Translational Vision Research, University of California, Irvine School of Medicine, CA, USA; Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine School of Medicine, CA, USA; Department of Physiology and Biophysics, University of California, Irvine School of Medicine, CA, USA
| | - Krzysztof Palczewski
- Center for Translational Vision Research, University of California, Irvine School of Medicine, CA, USA; Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine School of Medicine, CA, USA; Department of Physiology and Biophysics, University of California, Irvine School of Medicine, CA, USA; Department of Molecular Biology and Biochemistry, University of California, Irvine School of Medicine, CA, USA; Department of Chemistry, University of California, Irvine School of Medicine, CA, USA.
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42
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Kamat V, Robbings BM, Jung SR, Kelly J, Hurley JB, Bube KP, Sweet IR. Fluidics system for resolving concentration-dependent effects of dissolved gases on tissue metabolism. eLife 2021; 10:e66716. [PMID: 34734803 PMCID: PMC8660022 DOI: 10.7554/elife.66716] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 11/01/2021] [Indexed: 12/15/2022] Open
Abstract
Oxygen (O2) and other dissolved gases such as the gasotransmitters H2S, CO, and NO affect cell metabolism and function. To evaluate effects of dissolved gases on processes in tissue, we developed a fluidics system that controls dissolved gases while simultaneously measuring parameters of electron transport, metabolism, and secretory function. We use pancreatic islets, retina, and liver from rodents to highlight its ability to assess effects of O2 and H2S. Protocols aimed at emulating hypoxia-reperfusion conditions resolved a previously unrecognized transient spike in O2 consumption rate (OCR) following replenishment of O2, and tissue-specific recovery of OCR following hypoxia. The system revealed both inhibitory and stimulatory effects of H2S on insulin secretion rate from isolated islets. The unique ability of this new system to quantify metabolic state and cell function in response to precise changes in dissolved gases provides a powerful platform for cell physiologists to study a wide range of disease states.
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Affiliation(s)
- Varun Kamat
- University of Washington Medicine Diabetes Institute, University of WashingtonSeattleUnited States
| | - Brian M Robbings
- University of Washington Medicine Diabetes Institute, University of WashingtonSeattleUnited States
- Department of Biochemistry, University of WashingtonSeattleUnited States
| | - Seung-Ryoung Jung
- University of Washington Medicine Diabetes Institute, University of WashingtonSeattleUnited States
| | | | - James B Hurley
- Department of Biochemistry, University of WashingtonSeattleUnited States
| | - Kenneth P Bube
- Department of Mathematics, University of WashingtonSeattleUnited States
| | - Ian R Sweet
- University of Washington Medicine Diabetes Institute, University of WashingtonSeattleUnited States
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43
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Tsantilas KA, Cleghorn WM, Bisbach CM, Whitson JA, Hass DT, Robbings BM, Sadilek M, Linton JD, Rountree AM, Valencia AP, Sweetwyne MT, Campbell MD, Zhang H, Jankowski CSR, Sweet IR, Marcinek DJ, Rabinovitch PS, Hurley JB. An Analysis of Metabolic Changes in the Retina and Retinal Pigment Epithelium of Aging Mice. Invest Ophthalmol Vis Sci 2021; 62:20. [PMID: 34797906 PMCID: PMC8606884 DOI: 10.1167/iovs.62.14.20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Purpose The purpose of this study was to present our hypothesis that aging alters metabolic function in ocular tissues. We tested the hypothesis by measuring metabolism in aged murine tissues alongside retinal responses to light. Methods Scotopic and photopic electroretinogram (ERG) responses in young (3–6 months) and aged (23–26 months) C57Bl/6J mice were recorded. Metabolic flux in retina and eyecup explants was quantified using U-13C-glucose or U-13C-glutamine with gas chromatography-mass spectrometry (GC-MS), O2 consumption rate (OCR) in a perifusion apparatus, and quantifying adenosine triphosphatase (ATP) with a bioluminescence assay. Results Scotopic and photopic ERG responses were reduced in aged mice. Glucose metabolism, glutamine metabolism, OCR, and ATP pools in retinal explants were mostly unaffected in aged mice. In eyecups, glutamine usage in the Krebs Cycle decreased while glucose metabolism, OCR, and ATP pools remained stable. Conclusions Our examination of metabolism showed negligible impact of age on retina and an impairment of glutamine anaplerosis in eyecups. The metabolic stability of these tissues ex vivo suggests age-related metabolic alterations may not be intrinsic. Future experiments should focus on determining whether external factors including nutrient supply, oxygen availability, or structural changes influence ocular metabolism in vivo.
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Affiliation(s)
- Kristine A Tsantilas
- Department of Biochemistry, University of Washington, Seattle, Washington, United States
| | - Whitney M Cleghorn
- Department of Biochemistry, University of Washington, Seattle, Washington, United States
| | - Celia M Bisbach
- Department of Biochemistry, University of Washington, Seattle, Washington, United States
| | - Jeremy A Whitson
- Department of Biology, Davidson College, Davidson, North Carolina, United States
| | - Daniel T Hass
- Department of Biochemistry, University of Washington, Seattle, Washington, United States
| | - Brian M Robbings
- Department of Biochemistry, University of Washington, Seattle, Washington, United States.,UW Diabetes Institute, University of Washington, Seattle, Washington, United States
| | - Martin Sadilek
- Department of Chemistry, University of Washington, Seattle, Washington, United States
| | - Jonathan D Linton
- Department of Biochemistry, University of Washington, Seattle, Washington, United States
| | - Austin M Rountree
- UW Diabetes Institute, University of Washington, Seattle, Washington, United States
| | - Ana P Valencia
- Department of Radiology, University of Washington, Seattle, Washington, United States
| | - Mariya T Sweetwyne
- Department of Laboratory Medicine & Pathology, University of Washington, Seattle, Washington, United States
| | - Matthew D Campbell
- Department of Radiology, University of Washington, Seattle, Washington, United States
| | - Huiliang Zhang
- Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
| | - Connor S R Jankowski
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States.,Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States
| | - Ian R Sweet
- UW Diabetes Institute, University of Washington, Seattle, Washington, United States
| | - David J Marcinek
- Department of Radiology, University of Washington, Seattle, Washington, United States
| | - Peter S Rabinovitch
- Department of Laboratory Medicine & Pathology, University of Washington, Seattle, Washington, United States
| | - James B Hurley
- Department of Biochemistry, University of Washington, Seattle, Washington, United States.,Department of Ophthalmology, University of Washington, Seattle, Washington, United States
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44
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Warburg Effect, Glutamine, Succinate, Alanine, When Oxygen Matters. BIOLOGY 2021; 10:biology10101000. [PMID: 34681099 PMCID: PMC8533123 DOI: 10.3390/biology10101000] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 09/27/2021] [Accepted: 09/29/2021] [Indexed: 01/12/2023]
Abstract
Cellular bioenergetics requires an intense ATP turnover that is increased further by hypermetabolic states caused by cancer growth or inflammation. Both are associated with metabolic alterations and, notably, enhancement of the Warburg effect (also known as aerobic glycolysis) of poor efficiency with regard to glucose consumption when compared to mitochondrial respiration. Therefore, beside this efficiency issue, other properties of these two pathways should be considered to explain this paradox: (1) biosynthesis, for this only indirect effect should be considered, since lactate release competes with biosynthetic pathways in the use of glucose; (2) ATP production, although inefficient, glycolysis shows other advantages when compared to mitochondrial respiration and lactate release may therefore reflect that the glycolytic flux is higher than required to feed mitochondria with pyruvate and glycolytic NADH; (3) Oxygen supply becomes critical under hypermetabolic conditions, and the ATP/O2 ratio quantifies the efficiency of oxygen use to regenerate ATP, although aerobic metabolism remains intense the participation of anaerobic metabolisms (lactic fermentation or succinate generation) could greatly increase ATP/O2 ratio; (4) time and space constraints would explain that anaerobic metabolism is required while the general metabolism appears oxidative; and (5) active repression of respiration by glycolytic intermediates, which could ensure optimization of glucose and oxygen use.
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45
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He J, Yamamoto M, Sumiyama K, Konagaya Y, Terai K, Matsuda M, Sato S. Two-photon AMPK and ATP imaging reveals the bias between rods and cones in glycolysis utility. FASEB J 2021; 35:e21880. [PMID: 34449091 DOI: 10.1096/fj.202101121r] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 08/08/2021] [Accepted: 08/11/2021] [Indexed: 12/15/2022]
Abstract
In vertebrates, retinal rod and cone photoreceptor cells rely significantly on glycolysis. Lactate released from photoreceptor cells fuels neighboring retinal pigment epithelium cells and Müller glial cells through oxidative phosphorylation. To understand this highly heterogeneous metabolic environment around photoreceptor cells, single-cell analysis is needed. Here, we visualized cellular AMP-activated protein kinase (AMPK) activity and ATP levels in the retina by two-photon microscopy. Transgenic mice expressing a hyBRET-AMPK biosensor were used for measuring the AMPK activity. GO-ATeam2 transgenic mice were used for measuring the ATP level. Temporal metabolic responses were successfully detected in the live retinal explants upon drug perfusion. A glycolysis inhibitor, 2-deoxy-d-glucose (2-DG), activated AMPK and reduced ATP. These effects were clearly stronger in rods than in cones. Notably, rod AMPK and ATP started to recover at 30 min from the onset of 2-DG perfusion. Consistent with these findings, ex vivo electroretinogram recordings showed a transient slowdown in rod dim flash responses during a 60-min 2-DG perfusion, whereas cone responses were not affected. Based on these results, we propose that cones surrounded by highly glycolytic rods become less dependent on glycolysis, and rods also become less dependent on glycolysis within 60 min upon the glycolysis inhibition.
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Affiliation(s)
- Jiazhou He
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Masamichi Yamamoto
- Department of Research Promotion and Management, National Cerebral and Cardiovascular Center Research Institute, Osaka, Japan
| | - Kenta Sumiyama
- Laboratory for Mouse Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Osaka, Japan
| | - Yumi Konagaya
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Kenta Terai
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Michiyuki Matsuda
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto, Japan.,Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto, Japan.,Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto, Japan
| | - Shinya Sato
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
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Lo Faro V, Ten Brink JB, Snieder H, Jansonius NM, Bergen AA. Genome-wide CNV investigation suggests a role for cadherin, Wnt, and p53 pathways in primary open-angle glaucoma. BMC Genomics 2021; 22:590. [PMID: 34348663 PMCID: PMC8336345 DOI: 10.1186/s12864-021-07846-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 06/18/2021] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND To investigate whether copy number variations (CNVs) are implicated in molecular mechanisms underlying primary open-angle glaucoma (POAG), we used genotype data of POAG individuals and healthy controls from two case-control studies, AGS (n = 278) and GLGS-UGLI (n = 1292). PennCNV, QuantiSNP, and cnvPartition programs were used to detect CNV. Stringent quality controls at both sample and marker levels were applied. The identified CNVs were intersected in CNV region (CNVR). After, we performed burden analysis, CNV-genome-wide association analysis, gene set overrepresentation and pathway analysis. In addition, in human eye tissues we assessed the expression of the genes lying within significant CNVRs. RESULTS We reported a statistically significant greater burden of CNVs in POAG cases compared to controls (p-value = 0,007). In common between the two cohorts, CNV-association analysis identified statistically significant CNVRs associated with POAG that span 11 genes (APC, BRCA2, COL3A1, HLA-DRB1, HLA-DRB5, HLA-DRB6, MFSD8, NIPBL, SCN1A, SDHB, and ZDHHC11). Functional annotation and pathway analysis suggested the involvement of cadherin, Wnt signalling, and p53 pathways. CONCLUSIONS Our data suggest that CNVs may have a role in the susceptibility of POAG and they can reveal more information on the mechanism behind this disease. Additional genetic and functional studies are warranted to ascertain the contribution of CNVs in POAG.
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Affiliation(s)
- Valeria Lo Faro
- Department of Ophthalmology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.,Departments of Clinical Genetics and Ophthalmology, Amsterdam University Medical Center (AMC), Location AMC K2-217
- AMC-UvA, P.O.Box 22700, 1100 DE, Amsterdam, The Netherlands
| | - Jacoline B Ten Brink
- Departments of Clinical Genetics and Ophthalmology, Amsterdam University Medical Center (AMC), Location AMC K2-217
- AMC-UvA, P.O.Box 22700, 1100 DE, Amsterdam, The Netherlands
| | - Harold Snieder
- Department of Epidemiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Nomdo M Jansonius
- Department of Ophthalmology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Arthur A Bergen
- Departments of Clinical Genetics and Ophthalmology, Amsterdam University Medical Center (AMC), Location AMC K2-217
- AMC-UvA, P.O.Box 22700, 1100 DE, Amsterdam, The Netherlands. .,Department of Ophthalmology, Amsterdam UMC, Location AMC, Amsterdam, The Netherlands. .,Netherlands Institute for Neuroscience (NIN-KNAW), Amsterdam, The Netherlands.
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47
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Rowe AA, Patel PD, Gordillo R, Wert KJ. Replenishment of TCA cycle intermediates provides photoreceptor resilience against neurodegeneration during progression of retinitis pigmentosa. JCI Insight 2021; 6:e150898. [PMID: 34292885 PMCID: PMC8492344 DOI: 10.1172/jci.insight.150898] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 07/16/2021] [Indexed: 11/24/2022] Open
Abstract
The metabolic environment is important for neuronal cells, such as photoreceptors. When photoreceptors undergo degeneration, as occurs during retinitis pigmentosa (RP), patients have progressive loss of vision that proceeds to full blindness. Currently, there are no available treatments for the majority of RP diseases. We performed metabolic profiling of the neural retina in a preclinical model of RP and found that TCA cycle intermediates were reduced during disease. We then determined that (a) promoting citrate production within the TCA cycle in retinal neurons during disease progression protected the photoreceptors from cell death and prolonged visual function, (b) supplementation with single metabolites within the TCA cycle provided this therapeutic effect in vivo over time, and (c) this therapeutic effect was not specific to a particular genetic mutation but had broad applicability for patients with RP and other retinal degenerative diseases. Overall, targeting TCA cycle activity in the neural retina promoted photoreceptor survival and visual function during neurodegenerative disease.
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Affiliation(s)
- Ashley A Rowe
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, United States of America
| | - Pinkal D Patel
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, United States of America
| | - Ruth Gordillo
- Department of Internal Medicine, UT Southwestern Medical Center, Dallas, United States of America
| | - Katherine J Wert
- Department of Ophthalmology, UT Southwestern Medical Center, Dallas, United States of America
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48
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Abstract
The outer retina is nourished from the choroid, a capillary bed just inside the sclera. O2, glucose, and other nutrients diffuse out of the choroid and then filter through a monolayer of retinal pigment epithelium (RPE) cells to fuel the retina. Recent studies of energy metabolism have revealed striking differences between retinas and RPE cells in the ways that they extract energy from fuels. The purpose of this review is to suggest and evaluate the hypothesis that the retina and RPE have complementary metabolic roles that make them depend on each other for survival and for their abilities to perform essential and specialized functions. Expected final online publication date for the Annual Review of Vision Science, Volume 7 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- James B Hurley
- Departments of Biochemistry and Ophthalmology, University of Washington, Seattle, Washington 98115, USA;
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49
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George SM, Lu F, Rao M, Leach LL, Gross JM. The retinal pigment epithelium: Development, injury responses, and regenerative potential in mammalian and non-mammalian systems. Prog Retin Eye Res 2021; 85:100969. [PMID: 33901682 DOI: 10.1016/j.preteyeres.2021.100969] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 03/23/2021] [Accepted: 04/07/2021] [Indexed: 12/13/2022]
Abstract
Diseases that result in retinal pigment epithelium (RPE) degeneration, such as age-related macular degeneration (AMD), are among the leading causes of blindness worldwide. Atrophic (dry) AMD is the most prevalent form of AMD and there are currently no effective therapies to prevent RPE cell death or restore RPE cells lost from AMD. An intriguing approach to treat AMD and other RPE degenerative diseases is to develop therapies focused on stimulating endogenous RPE regeneration. For this to become feasible, a deeper understanding of the mechanisms underlying RPE development, injury responses and regenerative potential is needed. In mammals, RPE regeneration is extremely limited; small lesions can be repaired by the expansion of adjacent RPE cells, but large lesions cannot be repaired as remaining RPE cells are unable to functionally replace lost RPE tissue. In some injury paradigms, RPE cells proliferate but do not regenerate a morphologically normal monolayer, while in others, proliferation is pathogenic and results in further disruption to the retina. This is in contrast to non-mammalian vertebrates, which possess tremendous RPE regenerative potential. Here, we discuss what is known about RPE formation during development in mammalian and non-mammalian vertebrates, we detail the processes by which RPE cells respond to injury, and we describe examples of RPE-to-retina and RPE-to-RPE regeneration in non-mammalian vertebrates. Finally, we outline barriers to RPE-dependent regeneration in mammals that could potentially be overcome to stimulate a regenerative response from the RPE.
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Affiliation(s)
- Stephanie M George
- Department of Ophthalmology, Louis J. Fox Center for Vision Restoration, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Fangfang Lu
- Department of Ophthalmology, Louis J. Fox Center for Vision Restoration, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA; Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, 410011, China
| | - Mishal Rao
- Department of Ophthalmology, Louis J. Fox Center for Vision Restoration, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Lyndsay L Leach
- Department of Ophthalmology, Louis J. Fox Center for Vision Restoration, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Jeffrey M Gross
- Department of Ophthalmology, Louis J. Fox Center for Vision Restoration, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA; Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA.
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50
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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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