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Ghosh N, Das A, Biswas N, Mahajan SP, Madeshiya AK, Khanna S, Sen CK, Roy S. MYO-Inositol In Fermented Sugar Matrix Improves Human Macrophage Function. Mol Nutr Food Res 2022; 66:e2100852. [PMID: 35073444 PMCID: PMC9420542 DOI: 10.1002/mnfr.202100852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 12/07/2021] [Indexed: 11/07/2022]
Abstract
SCOPE Reactive oxygen species production by innate immune cells plays a central role in host defense against invading pathogens at wound-site. A weakened hos-defense results in persistent infection leading to wound chronicity. Fermented Papaya Preparation (FPP), a complex sugar matrix, bolstered respiratory burst activity and improved wound healing outcomes in chronic wound patients. The objective of the current study was to identify underlying molecular factor/s responsible for augmenting macrophage host defense mechanisms following FPP supplementation. METHODS AND RESULTS In depth LC-MS/MS analysis of cells supplemented with FPP led to identification of myo-inositol as a key determinant of FPP activity towards improving macrophage function. Myo-inositol, in quantities that is present in FPP, significantly improved macrophage respiratory burst and phagocytosis via de novo synthesis pathway of ISYNA1. Additionally, myo-inositol transporters, HMIT and SMIT1, played a significant role in such activity. Blocking these pathways using siRNA attenuated FPP-induced improved macrophage host defense activities. FPP supplementation emerges as a novel approach to increase intracellular myo-inositol levels. Such supplementation also modified wound microenvironment in chronic wound patients to augment myo-inositol levels in wound fluid. CONCLUSION These observations indicate that myo-inositol in FPP influences multiple aspects of macrophage function critical for host defense against invading pathogens. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Nandini Ghosh
- Department of Surgery, IU Health Comprehensive Wound Center, Indiana Center for Regenerative Medicine and Engineering, Indiana University School of Medicine, Indianapolis, IN, 46202
| | - Amitava Das
- Department of Surgery, IU Health Comprehensive Wound Center, Indiana Center for Regenerative Medicine and Engineering, Indiana University School of Medicine, Indianapolis, IN, 46202
| | - Nirupam Biswas
- Department of Surgery, IU Health Comprehensive Wound Center, Indiana Center for Regenerative Medicine and Engineering, Indiana University School of Medicine, Indianapolis, IN, 46202
| | - Sanskruti P Mahajan
- Department of Surgery, IU Health Comprehensive Wound Center, Indiana Center for Regenerative Medicine and Engineering, Indiana University School of Medicine, Indianapolis, IN, 46202
| | - Amit K Madeshiya
- Department of Surgery, IU Health Comprehensive Wound Center, Indiana Center for Regenerative Medicine and Engineering, Indiana University School of Medicine, Indianapolis, IN, 46202
| | - Savita Khanna
- Department of Surgery, IU Health Comprehensive Wound Center, Indiana Center for Regenerative Medicine and Engineering, Indiana University School of Medicine, Indianapolis, IN, 46202
| | - Chandan K Sen
- Department of Surgery, IU Health Comprehensive Wound Center, Indiana Center for Regenerative Medicine and Engineering, Indiana University School of Medicine, Indianapolis, IN, 46202
| | - Sashwati Roy
- Department of Surgery, IU Health Comprehensive Wound Center, Indiana Center for Regenerative Medicine and Engineering, Indiana University School of Medicine, Indianapolis, IN, 46202
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D'Souza SW, Copp AJ, Greene NDE, Glazier JD. Maternal Inositol Status and Neural Tube Defects: A Role for the Human Yolk Sac in Embryonic Inositol Delivery? Adv Nutr 2020; 12:212-222. [PMID: 32892218 PMCID: PMC7849949 DOI: 10.1093/advances/nmaa100] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 06/10/2020] [Accepted: 07/28/2020] [Indexed: 12/12/2022] Open
Abstract
Supplementation with myo-inositol during the periconceptional period of pregnancy may ameliorate the recurrence risk of having a fetus affected by a neural tube defect (NTD; e.g., spina bifida). This could be of particular importance in providing a means for preventing NTDs that are unresponsive to folic acid. This review highlights the characteristics of inositol and describes the role of myo-inositol in the prevention of NTDs in rodent studies and the evidence for its efficacy in reducing NTD risk in human pregnancy. The possible reduction in NTD risk by maternal myo-inositol implies functional and developmentally important maternal-embryonic inositol interrelationships and also suggests that embryonic uptake of myo-inositol is crucial for embryonic development. The establishment of active myo-inositol cellular uptake mechanisms in the embryonic stages of human pregnancy, when the neural tube is closing, is likely to be an important determinant of normal development. We draw attention to the generation of materno-fetal inositol concentration gradients and relationships, and outline a transport pathway by which myo-inositol may be delivered to the early developing human embryo. These considerations provide novel insights into the mechanisms that may underpin inositol's ability to confer embryonic developmental benefit.
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Affiliation(s)
- Stephen W D'Souza
- Maternal and Fetal Health Research Centre, St. Mary's Hospital, School of Medical Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Andrew J Copp
- Newlife Birth Defects Research Centre, Developmental Biology and Cancer Department, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
| | - Nicholas D E Greene
- Newlife Birth Defects Research Centre, Developmental Biology and Cancer Department, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
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Case KC, Salsaa M, Yu W, Greenberg ML. Regulation of Inositol Biosynthesis: Balancing Health and Pathophysiology. Handb Exp Pharmacol 2020; 259:221-260. [PMID: 30591968 DOI: 10.1007/164_2018_181] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Inositol is the precursor for all inositol compounds and is essential for viability of eukaryotic cells. Numerous cellular processes and signaling functions are dependent on inositol compounds, and perturbation of their synthesis leads to a wide range of human diseases. Although considerable research has been directed at understanding the function of inositol compounds, especially phosphoinositides and inositol phosphates, a focus on regulatory and homeostatic mechanisms controlling inositol biosynthesis has been largely neglected. Consequently, little is known about how synthesis of inositol is regulated in human cells. Identifying physiological regulators of inositol synthesis and elucidating the molecular mechanisms that regulate inositol synthesis will contribute fundamental insight into cellular processes that are mediated by inositol compounds and will provide a foundation to understand numerous disease processes that result from perturbation of inositol homeostasis. In addition, elucidating the mechanisms of action of inositol-depleting drugs may suggest new strategies for the design of second-generation pharmaceuticals to treat psychiatric disorders and other illnesses.
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Affiliation(s)
- Kendall C Case
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA
| | - Michael Salsaa
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA
| | - Wenxi Yu
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Miriam L Greenberg
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA.
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Vazquez-Levin M, Verón G. Myo‐inositol in health and disease: its impact on semen parameters and male fertility. Andrology 2019; 8:277-298. [DOI: 10.1111/andr.12718] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Revised: 10/12/2019] [Accepted: 10/16/2019] [Indexed: 02/06/2023]
Affiliation(s)
- M.H. Vazquez-Levin
- Laboratorio de Estudios de Interacción Celular en Reproducción y Cáncer Instituto de Biología y Medicina Experimental (IBYME)Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)‐ Fundación IBYME (FIBYME) Ciudad Autónoma de Buenos Aires Argentina
| | - G.L. Verón
- Laboratorio de Estudios de Interacción Celular en Reproducción y Cáncer Instituto de Biología y Medicina Experimental (IBYME)Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)‐ Fundación IBYME (FIBYME) Ciudad Autónoma de Buenos Aires Argentina
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Signal Transduction in Astrocytes during Chronic or Acute Treatment with Drugs (SSRIs, Antibipolar Drugs, GABA-ergic Drugs, and Benzodiazepines) Ameliorating Mood Disorders. JOURNAL OF SIGNAL TRANSDUCTION 2014; 2014:593934. [PMID: 24707399 PMCID: PMC3953578 DOI: 10.1155/2014/593934] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Accepted: 12/16/2013] [Indexed: 01/29/2023]
Abstract
Chronic treatment with fluoxetine or other so-called serotonin-specific reuptake inhibitor antidepressants (SSRIs) or with a lithium salt “lithium”, carbamazepine, or valproic acid, the three classical antibipolar drugs, exerts a multitude of effects on astrocytes, which in turn modulate astrocyte-neuronal interactions and brain function. In the case of the SSRIs, they are to a large extent due to 5-HT2B-mediated upregulation and editing of genes. These alterations induce alteration in effects of cPLA2, GluK2, and the 5-HT2B receptor, probably including increases in both glucose metabolism and glycogen turnover, which in combination have therapeutic effect on major depression. The ability of increased levels of extracellular K+ to increase [Ca2+]i is increased as a sign of increased K+-induced excitability in astrocytes. Acute anxiolytic drug treatment with benzodiazepines or GABAA receptor stimulation has similar glycogenolysis-enhancing effects. The antibipolar drugs induce intracellular alkalinization in astrocytes with lithium acting on one acid extruder and carbamazepine and valproic acid on a different acid extruder. They inhibit K+-induced and transmitter-induced increase of astrocytic [Ca2+]i and thereby probably excitability. In several cases, they exert different changes in gene expression than SSRIs, determined both in cultured astrocytes and in freshly isolated astrocytes from drug-treated animals.
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Song D, Li B, Yan E, Man Y, Wolfson M, Chen Y, Peng L. Chronic Treatment with Anti-bipolar Drugs Causes Intracellular Alkalinization in Astrocytes, Altering Their Functions. Neurochem Res 2012; 37:2524-40. [DOI: 10.1007/s11064-012-0837-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 07/03/2012] [Accepted: 07/08/2012] [Indexed: 12/26/2022]
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Munoz C, Sopjani M, Dërmaku-Sopjani M, Almilaji A, Föller M, Lang F. Downregulation of the osmolyte transporters SMIT and BGT1 by AMP-activated protein kinase. Biochem Biophys Res Commun 2012; 422:358-62. [DOI: 10.1016/j.bbrc.2012.04.092] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 04/17/2012] [Indexed: 11/29/2022]
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Fu H, Li B, Hertz L, Peng L. Contributions in astrocytes of SMIT1/2 and HMIT to myo-inositol uptake at different concentrations and pH. Neurochem Int 2012; 61:187-94. [PMID: 22564531 DOI: 10.1016/j.neuint.2012.04.010] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 04/09/2012] [Accepted: 04/11/2012] [Indexed: 12/21/2022]
Abstract
myo-Inositol is important for cell signaling both in cytoplasm and in intracellular organelles. It is required in the plasma membrane and cytoplasm for maintained synthesis of the second messengers, inositoltrisphosphate (IP(3)) and diacylglycerol (DAG) from phosphatidylinositol bisphosphate (PIP(2)), and in organelles as precursor for synthesis of complex signaling phospholipids and inositolphosphates from IP(3) and PIP(2). myo-Inositol must be taken up into the cell where its is used, because neither neurons nor astrocytes synthesize it. It is also an osmolyte, taken up in response to surrounding hyperosmolarity and released during hypo-osmolarity. There are three myo-inositol transporters, the Na(+)-dependent SMIT1 and SMIT2, and HMIT, which co-transports myo-inositol with H(+). Their relative expressions in astrocytes and neurons are unknown. Uptake kinetics for myo-inositol in astrocytes has repeatedly been determined, but always on the assumption of only one component, leaving kinetics for the individual transporters unknown. This paper demonstrates that astrocytes obtained directly from the brain express SMIT1 and HMIT, but little SMIT2, and that all three transporters are expressed in neurons. Cultured mouse astrocytes show a high-affinity/low-capacity myo-inositol uptake (V(max): 60.0 ± 3.0 pmol/min per mg protein; K(m): 16.7 ± 2.6 μM), mediated by SMIT1 and perhaps partly by SMIT2. It was determined in cells pre-treated with HMIT-siRNA and confirmed by specific inhibition of SMIT. However at physiologically relevant myo-inositol concentrations most uptake is by a lower-affinity/higher-capacity uptake, mediated by HMIT (V(max): 358 ± 60 pmol/min per mg protein; K(m): 143 ± 36 μM) and determined by subtraction of SMIT-mediated from total uptake. At high myo-inositol concentrations, its uptake is inhibited by incubation in medium with increased pH, and increased during intracellular acidification with NH(4)Cl. This is in agreement with literature data for HMIT alone. At low concentration, where SMIT1/2 activity gains importance, myo-inositol uptake is reduced by ammonia-induced intracellular acidification, consistent with the transporter's pH sensitivity reported in the literature.
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Affiliation(s)
- Hui Fu
- Department of Clinical Pharmacology, College of Basic Medical Sciences, China Medical University, Shenyang, PR China
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Ma K, Thomason LA, McLaurin J. scyllo-Inositol, Preclinical, and Clinical Data for Alzheimer’s Disease. CURRENT STATE OF ALZHEIMER'S DISEASE RESEARCH AND THERAPEUTICS 2012; 64:177-212. [DOI: 10.1016/b978-0-12-394816-8.00006-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Hosseinzadeh Z, Bhavsar SK, Lang F. Down-Regulation of the Myoinositol Transporter SMIT by JAK2. Cell Physiol Biochem 2012. [DOI: 10.1159/000343335] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Song D, Du T, Li B, Cai L, Gu L, Li H, Chen Y, Hertz L, Peng L. Astrocytic alkalinization by therapeutically relevant lithium concentrations: implications for myo-inositol depletion. Psychopharmacology (Berl) 2008; 200:187-95. [PMID: 18506424 DOI: 10.1007/s00213-008-1194-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/27/2007] [Accepted: 04/27/2008] [Indexed: 11/29/2022]
Abstract
RATIONALE One theory for therapeutic effects of the lithium ion (Li+) in bipolar disorder is that myo-inositol, needed for phospholipase C-mediated signaling, is depleted by Li(+)-induced inhibition of inositolphosphate hydrolysis or of myo-inositol uptake, an effect demonstrated in cultured mouse astrocytes at high myo-inositol concentrations. In contrast, myo-inositol uptake is inhibited at low concentrations, reflecting that it occurs both by the high-affinity Na(+)-dependent myo-inositol transporter (SMIT) and the lower-affinity H(+)-dependent inositol transporter (HMIT). Increased intracellular pH (pHi) stimulates SMIT but inhibits HMIT, suggesting that the effect of Li+ could be caused by intracellular alkalinization. In this study, we therefore investigated Li+ effects on intracellular pH in astrocytes, measured by 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF) fluorescence. RESULTS Chronic treatment with the therapeutically relevant Li+ concentration of 1 mM for 2 or 3 weeks increased pHi by approximately 0.10, whereas 0.5 mM was ineffective, and 2 mM caused a larger increase. The alkalinization resulted from acute stimulation of the Na+/H+ exchanger (NHE) by extracellular Li+, demonstrated after acid load with NH4Cl. In response to continuous stimulation, NHE1 mRNA was down-regulated, but protein was not. CONCLUSIONS Chronic treatment with pharmacologically relevant Li+ concentrations increases pHi in astrocytes, creating conditions for decreased uptake of high myo-inositol concentrations and increased uptake of low concentrations. The pharmacological relevance of this effect is supported by literature data suggesting brain acidosis in bipolar patients and by preliminary observations that carbamazepine and valproate also increase pHi in astrocytes. Stimulation of NHE1-stimulated sodium ion uptake might also trigger uptake of chloride ions and osmotically obliged water.
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Affiliation(s)
- Dan Song
- Department of Clinical Pharmacology, College of Basic Medical Sciences, China Medical University, Shenyang, People's Republic of China
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Schneider S, Schneidereit A, Konrad KR, Hajirezaei MR, Gramann M, Hedrich R, Sauer N. Arabidopsis INOSITOL TRANSPORTER4 mediates high-affinity H+ symport of myoinositol across the plasma membrane. PLANT PHYSIOLOGY 2006; 141:565-77. [PMID: 16603666 PMCID: PMC1475457 DOI: 10.1104/pp.106.077123] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Four genes of the Arabidopsis (Arabidopsis thaliana) monosaccharide transporter-like superfamily share significant homology with transporter genes previously identified in the common ice plant (Mesembryanthemum crystallinum), a model system for studies on salt tolerance of higher plants. These ice plant transporters had been discussed as tonoplast proteins catalyzing the inositol-dependent efflux of Na(+) ions from vacuoles. The subcellular localization and the physiological role of the homologous proteins in the glycophyte Arabidopsis were unclear. Here we describe Arabidopsis INOSITOL TRANSPORTER4 (AtINT4), the first member of this subgroup of Arabidopsis monosaccharide transporter-like transporters. Functional analyses of the protein in yeast (Saccharomyces cerevisiae) and Xenopus laevis oocytes characterize this protein as a highly specific H(+) symporter for myoinositol. These activities and analyses of the subcellular localization of an AtINT4 fusion protein in Arabidopsis and tobacco (Nicotiana tabacum) reveal that AtINT4 is located in the plasma membrane. AtINT4 promoter-reporter gene plants demonstrate that AtINT4 is strongly expressed in Arabidopsis pollen and phloem companion cells. The potential physiological role of AtINT4 is discussed.
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Affiliation(s)
- Sabine Schneider
- Molekulare Pflanzenphysiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany
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Chau JFL, Lee MK, Law JWS, Chung SK, Chung SSM. Sodium/myo-inositol cotransporter-1 is essential for the development and function of the peripheral nerves. FASEB J 2005; 19:1887-9. [PMID: 16174787 DOI: 10.1096/fj.05-4192fje] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Sodium/myo-inositol cotransporter-1 (SMIT-1) is one of the transporters responsible for importing myo-inositol (MI) into the cells. MI is a precursor for a family of signal transduction molecules, phosphatidylinositol, and its derivatives that regulates many cellular functions. SMIT-1 null mice died soon after birth due to respiratory failure, but neonatal lethality was prevented by prenatal maternal MI supplement. Although the lung air sacs were closed, lung development was not significantly affected in the SMIT-1 null mice. The development of the peripheral nerves, including the brachial plexus, facial, vagus, and intercostal nerves, and the phrenic nerve that innervates the diaphragm was severely affected. All of these peripheral nerve abnormalities were corrected by prenatal MI supplement, indicating that MI is essential for the development of peripheral nerve and that neonatal lethality of the SMIT-1 knockout mice is most likely due to abnormal development of the nerves that control breathing. In the adult SMIT-1 deficient mice rescued by MI supplement, MI content in their brain, kidney, skeletal muscle, liver, and sciatic nerve was greatly reduced. The sciatic nerve, in particular, was most dependent on SMIT-1 for the accumulation of MI, and nerve conduction velocity and protein kinase C activity in this tissue were significantly reduced by SMIT-1 deficiency.
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Affiliation(s)
- Jenny F L Chau
- Institute of Molecular Biology, The University of Hong Kong, Hong Kong, SAR, China
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Mongan TP, Ganapasam S, Hobbs SB, Seyfang A. Substrate specificity of the Leishmania donovani myo-inositol transporter: critical role of inositol C-2, C-3 and C-5 hydroxyl groups. Mol Biochem Parasitol 2004; 135:133-41. [PMID: 15287594 DOI: 10.1016/j.molbiopara.2004.01.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Inositol is an essential precursor for the formation of glycosyl-phosphatidylinositol (GPI)-anchors found in the majority of surface molecules in trypanosomatids, in addition to its requirement for phoshatidylinositol signal transduction pathways. In Leishmania donovani, high-affinity inositol transport is catalyzed by the active myo-inositol/H+ transporter MIT, which is driven by a proton gradient across the parasite membrane. We have characterized the substrate specificity and pharmacology of L. donovani MIT in vitro and in promastigote cultures. High substrate specificity of myo-inositol transport was shown in competition studies with 14 different monosaccharides and MIT function was unaffected by the structurally similar pentose sugars or hexoses. L-Fucose and D-xylose, both inhibitors of the Na+-dependent inositol transport system in the human host, did not affect MIT transport function in the parasite. Competition studies with eight different inositol isomers revealed that proton bonds between the C-2, C-3 and C-5 hydroxyl groups of myo-inositol and the transporter protein played a critical role for substrate recognition, and the C-3 hydroxyl oxygen appears to act as an electron donor to form an H-bond with a positive charge of the MIT permease. The cytotoxic inositol analogue 3-fluoro-myo-inositol was recognized by MIT with similar affinity as myo-inositol and showed an IC50 value of 42 +/- 8 microM in L. donovani cultures. Finally, substrate affinities of MIT revealed apparent Km values of 84 +/- 8 microM for myo-inositol and 5.4 +/- 0.9 nM for H+, equal pH 8.27 + 0.08, suggesting that the L. donovani myo-inositol/H+ symporter is fully activated at physiological pH in the sandfly midgut or macrophage phagolysosome. We conclude that Leishmania MIT constitutes an attractive target for delivery of cytotoxic inositol analogues and differs significantly from the sodium-coupled myo-inositol transport system of the human host.
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Affiliation(s)
- Tyler P Mongan
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912-2100, USA
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Jin JH, Seyfang A. High-affinity myo-inositol transport in Candida albicans: substrate specificity and pharmacology. Microbiology (Reading) 2003; 149:3371-3381. [PMID: 14663071 DOI: 10.1099/mic.0.26644-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Inositol is considered a growth factor in yeast cells and it plays an important role inCandidaas an essential precursor for phospholipomannan, a glycophosphatidylinositol (GPI)-anchored glycolipid on the cell surface ofCandidawhich is involved in the pathogenicity of this opportunistic fungus and which binds to and stimulates human macrophages. In addition, inositol plays an essential role in the phosphatidylinositol signal transduction pathway, which controls many cell cycle events. Here, high-affinitymyo-inositol uptake inCandida albicanshas been characterized, with an apparentKmvalue of 240±15 μM, which appears to be active and energy-dependent as revealed by inhibition with azide and protonophores (FCCP, dinitrophenol).Candida myo-inositol transport was sodium-independent but proton-coupled with an apparentKmvalue of 11·0±1·1 nM for H+, equal pH 7·96±0·05, suggesting that theC. albicansmyo-inositol–H+transporter is fully activated at physiological pH.C. albicansinositol transport was not affected by cytochalasin B, phloretin or phlorizin, an inhibitor of mammalian sodium-dependent inositol transport. Furthermore,myo-inositol transport showed high substrate specificity for inositol and was not significantly affected by hexose or pentose sugars as competitors, despite their structural similarity. Transport kinetics in the presence of eight different inositol isomers as competitors revealed that proton bonds between the C-2, C-3 and C-4 hydroxyl groups ofmyo-inositol and the transporter protein play a critical role for substrate recognition and binding. It is concluded thatC. albicansmyo-inositol–H+transport differs kinetically and pharmacologically from the human sodium-dependentmyo-inositol transport system and constitutes an attractive target for delivery of cytotoxic inositol analogues in this pathogenic fungus.
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Affiliation(s)
- Jean Huaqian Jin
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, 1120 15th Street, Augusta, GA 30912-2100, USA
| | - Andreas Seyfang
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, 1120 15th Street, Augusta, GA 30912-2100, USA
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Eladari D, Chambrey R, Pezy F, Podevin RA, Paillard M, Leviel F. pH dependence of Na+/myo-inositol cotransporters in rat thick limb cells. Kidney Int 2002; 62:2144-51. [PMID: 12427139 DOI: 10.1046/j.1523-1755.2002.00690.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND To balance medullary interstitium hypertonicity generated by transepithelial NaCl absorption, medullary thick ascending limb (MTAL) cells accumulate myo-inositol (MI). Expression of Na+-MI cotransporter (SMIT) mRNA in TAL is correlated with the NaCl absorption rate. Our present study aimed to determine the plasma membrane location and functional properties of the Na+-MI cotransporter in MTAL cells. METHODS Preparation of basolateral (BLMV) and luminal (LMV) membrane vesicles were simultaneously isolated from purified rat MTAL suspension, and uptake of [3H]myo-inositol ([3H]MI) was used to assess Na+-MI cotransport activity. RESULTS In the presence of an inside-negative membrane potential, imposing an inwardly-directed Na+-gradient versus tetramethylammonium (TMA) stimulated the initial [3H]MI uptake in BLMV and LMV. Phlorizin inhibited Na+ gradient-dependent initial [3H]MI uptake in both preparations, with IC50 values of 565 and 29 micromol/L in BLMV and LMV, respectively. 2-0,C-methylene myo-inositol (MMI), a competitive inhibitor of MI transport, only inhibited the BLMV Na+-MI cotransporter. Phlorizin-sensitive Na+ gradient-dependent initial [3H]MI uptake showed Michaelis-Menten kinetics in both preparations, with similar Vmax but different Km values of 51 and 107 micromol/L in BLMV and LMV, respectively. Finally, BLMV but not LMV Na+-MI cotransporter exhibited a marked pH dependence with sigmoidal patterns of activation, as intravesicular pH (pHi) was decreased from 8.0 to 6.0 at extravesicular pH (pHe) 8.0, and as pHe was increased from 6.0 to 8.0 at pHi 6.0. Maximal activation was observed at pHi 6.5 and pHe 7.5. CONCLUSIONS In rat MTAL cells, Na+-MI cotransporter activity is present in both BLM and LM, and has markedly different functional properties, indicating the presence of distinct transporters. Basolateral Na+-MI cotransporter activity is maximal at physiological pH values of MTAL cells and interstitium, and a powerful modulation of the transporter activity may be exerted by pHe and pHi.
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Affiliation(s)
- Dominique Eladari
- Institut National de la Santé et de la Recherche Médicale, Unité 356, Université Pierre et Marie Curie, Institut Fédératif de Recherche 58 and Hôpital Européen Georges Pompidou, Assistance-Publique, Hôpitaux de Paris, Paris, France
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Fisher SK, Novak JE, Agranoff BW. Inositol and higher inositol phosphates in neural tissues: homeostasis, metabolism and functional significance. J Neurochem 2002; 82:736-54. [PMID: 12358779 DOI: 10.1046/j.1471-4159.2002.01041.x] [Citation(s) in RCA: 465] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Inositol phospholipids and inositol phosphates mediate well-established functions in signal transduction and in Ca2+ homeostasis in the CNS and non-neural tissues. More recently, there has been renewed interest in other roles that both myo-inositol and its highly phosphorylated forms may play in neural function. We review evidence that myo-inositol serves as a clinically relevant osmolyte in the CNS, and that its hexakisphosphate and pyrophosphorylated derivatives may play roles in such diverse cellular functions as DNA repair, nuclear RNA export and synaptic membrane trafficking.
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Affiliation(s)
- Stephen K Fisher
- Mental Health Research Institute, and Department of Pharmacology, University of Michigan, Ann Arbor, Michigan 48109, USA.
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18
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Chiu TTY, Rogers MS, Law ELK, Briton-Jones CM, Cheung LP, Haines CJ. Follicular fluid and serum concentrations of myo-inositol in patients undergoing IVF: relationship with oocyte quality. Hum Reprod 2002; 17:1591-6. [PMID: 12042283 DOI: 10.1093/humrep/17.6.1591] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The follicular microenvironment is an important determinant of oocyte development. The aim of this study was to examine whether the myo-inositol (MI) content in human follicular fluid (FF) was associated with better oocyte quality. METHODS A total of 53 patients treated with IVF was recruited to a prospective observational study. FF and serum samples collected were divided into two groups: group A consisted of FF associated with matured and fertilized oocytes, whilst group B was from follicles with immature and unfertilized oocytes. RESULTS Patient's age, total ampoules of HMG used, days of stimulation, basal levels of FSH, estradiol (E(2)) levels on the day of HCG, and serum MI content were not significantly different between the two groups. FF volume and its MI content were significantly higher in group A compared with group B (P < 0.05). The levels of MI in FF were positively correlated with the amount of E(2) in their corresponding FF samples and also correlated with embryo quality. CONCLUSIONS We propose that higher concentrations of MI and E(2) in human FF appear to play a role in follicular maturity and provide a marker of good quality oocytes.
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Affiliation(s)
- Tony T Y Chiu
- Department of Obstetrics and Gynaecology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.
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Grunewald RW, Oppermann M, Schettler V, Fiedler GM, Jehle PM, Schuettert JB. Polarized function of thick ascending limbs of Henle cells in osmoregulation. Kidney Int 2001; 60:2290-8. [PMID: 11737602 DOI: 10.1046/j.1523-1755.2001.00070.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Organic osmolytes are necessary for osmoregulation in mammalian kidney. Since renal epithelial cells in many cases possess specific mechanisms both for uptake and osmotically regulated release, we investigated their localization in polarized cells. METHODS An immortalized epithelial cell line derived from the thick ascending limb of Henle's loop (TALH) was used to examine the transport characteristics of the apical and basolateral plasma membranes for osmotic regulation of organic osmolytes. Cells were cultured on filters in a two-compartment chamber. RESULTS In culture under hypertonic conditions the TALH cells accumulated in the following balance: sorbitoverline> betaine = myo-inositoverline> glycerophosphoryl choline (GPC). When extracellular osmolarity was decreased, then sorbitol was released on the apical side, whereas betaine and myo-inositol efflux occurred on the basolateral side. GPC release showed no preference of either side. Taurine did not seem to be necessary for osmoregulation under these conditions. Osmotically regulated myo-inositol and betaine uptake was located on the apical side, and choline uptake took place on both sides equally. CONCLUSION These results show that in renal epithelial cells, both osmotically induced release and the uptake of organic osmolytes are divided between the apical and the basolateral sides. This might be important for volume regulation.
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Affiliation(s)
- R W Grunewald
- Department of Nephrology and Rheumatology, University Hospital Göttingen, Göttingen, Germany.
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20
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Uldry M, Ibberson M, Horisberger JD, Chatton JY, Riederer BM, Thorens B. Identification of a mammalian H(+)-myo-inositol symporter expressed predominantly in the brain. EMBO J 2001; 20:4467-77. [PMID: 11500374 PMCID: PMC125574 DOI: 10.1093/emboj/20.16.4467] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Inositol and its phosphorylated derivatives play a major role in brain function, either as osmolytes, second messengers or regulators of vesicle endo- and exocytosis. Here we describe the identification and functional characterization of a novel H(+)-myo- inositol co-transporter, HMIT, expressed predominantly in the brain. HMIT cDNA encodes a 618 amino acid polypeptide with 12 predicted transmembrane domains. Functional expression of HMIT in Xenopus oocytes showed that transport activity was specific for myo-inositol and related stereoisomers with a Michaelis-Menten constant of approximately 100 microM, and that transport activity was strongly stimulated by decreasing pH. Electrophysiological measurements revealed that transport was electrogenic with a maximal transport activity reached at pH 5.0. In rat brain membrane preparations, HMIT appeared as a 75-90 kDa protein that could be converted to a 67 kDa band upon enzymatic deglycosylation. Immunofluorescence microscopy analysis showed HMIT expression in glial cells and some neurons. These data provide the first characterization of a mammalian H(+)-coupled myo- inositol transporter. Predominant central expression of HMIT suggests that it has a key role in the control of myo-inositol brain metabolism.
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Affiliation(s)
| | | | | | - Jean-Yves Chatton
- Institute of Pharmacology and Toxicology,
Institute of Physiology and Institute of Cell Biology and Morphology, University of Lausanne, Lausanne, Switzerland Corresponding author e-mail:
| | - Beat M. Riederer
- Institute of Pharmacology and Toxicology,
Institute of Physiology and Institute of Cell Biology and Morphology, University of Lausanne, Lausanne, Switzerland Corresponding author e-mail:
| | - Bernard Thorens
- Institute of Pharmacology and Toxicology,
Institute of Physiology and Institute of Cell Biology and Morphology, University of Lausanne, Lausanne, Switzerland Corresponding author e-mail:
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21
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Matskevitch I, Stegen C, Wagner CA, Moschén I, Bindels R, Van Os C, Bröer S, Lang F. Acute regulation of the betaine/GABA transporter BGT-1 expressed in Xenopus oocytes by extracellular pH. Kidney Blood Press Res 2001; 23:356-9. [PMID: 11070414 DOI: 10.1159/000025983] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Besides uptake of Na(+) and Cl(-), mammalian cells counteract osmotic cell shrinkage also by Na(+)-coupled uptake of osmolytes, e. g., myo-inositol, taurine or betaine. The expression of the corresponding transporters is transcriptionally regulated by the ambient pH and osmolarity and is increased upon cell shrinkage, a process requiring hours. The present study has been performed to disclose rapid regulation by pH of osmolyte transport via BGT-1. Transport of GABA was investigated by using the two-electrode voltage-clamp technique with BGT-1 expressing Xenopus oocytes. GABA was used as a substrate, because of the low oocyte endogenous transport activity. Extracellular acidification to pH 5.5 reversibly decreased and extracellular alkalinization to pH 8.5 increased GABA-induced currents. Kinetic analysis revealed that extracellular alkalinization increases the affinity for Cl(-) as reflected by a decrease of the apparent K(m)-value for Cl(-) from >500 mM to 55.8 +/- 4.7 mM upon an increase of the pH from 7.0 to 8.5. The apparent K(m)- values for Na(+) and GABA remained unaltered in the pH range from 6.0 to 8.5. Instead, alkalinization increased the maximal current induced by saturating Na(+) and GABA concentrations. The results are compatible with a model of interference of H(+) ions with Cl(-) binding and a pH-dependent reduction of V(max) for Na(+) and GABA.
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Affiliation(s)
- I Matskevitch
- Department of Physiology, University of Tübingen, Germany
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22
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Forster IC, Biber J, Murer H. Proton-sensitive transitions of renal type II Na(+)-coupled phosphate cotransporter kinetics. Biophys J 2000; 79:215-30. [PMID: 10866949 PMCID: PMC1300927 DOI: 10.1016/s0006-3495(00)76285-0] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the kidney proximal tubule, acidification of the glomerular filtrate leads to an inhibition of inorganic phosphate (P(i)) reabsorption by type II Na(+)-coupled cotransporters (NaPi-II). As external pH also alters the divalent/monovalent P(i) ratio, it has been difficult to separate putative proton interactions with the cotransporter from direct titration of divalent P(i), the preferred species transported. To distinguish between these possibilities and identify pH-sensitive transitions in the cotransport cycle, the pH-dependent kinetics of two NaPi-II isoforms, expressed in Xenopus laevis oocytes, were investigated electrophysiologically. At -50 mV, both isoforms showed >70% suppression of electrogenic response for an external pH change from 8.0 to 6.2, not attributable to titration of divalent P(i). This was accompanied by a progressive removal of steady-state voltage dependence. The NaPi-II-related uncoupled slippage current was unaffected by a pH change from 7.4 to 6.2, with no shift in the reversal potential, which suggested that protons do not function as substrate. The voltage-dependence of pre-steady-state relaxations was shifted to depolarizing potentials in 100 mM and 0 mM Na(ext)(+) and two kinetic components were resolved, the slower of which was pH-dependent. The changes in kinetics are predicted by a model in which protons interact with the empty carrier and final Na(+) binding step.
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Affiliation(s)
- I C Forster
- Institute of Physiology, University of Zurich, Zurich, Switzerland.
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