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Al-Samir S, Prill M, Supuran CT, Gros G, Endeward V. CO 2 permeability of the rat erythrocyte membrane and its inhibition. J Enzyme Inhib Med Chem 2021; 36:1602-1606. [PMID: 34261373 PMCID: PMC8282279 DOI: 10.1080/14756366.2021.1952194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
We have studied the CO2 permeability of the erythrocyte membrane of the rat using a mass spectrometric method that employs 18 O-labelled CO2. The method yields, in addition, the intraerythrocytic carbonic anhydrase activity and the membrane HCO3- permeability. For normal rat erythrocytes, we find at 37 °C a CO2 permeability of 0.078 ± 0.015 cm/s, an intracellular carbonic anhydrase activity of 64,100, and a bicarbonate permeability of 2.1 × 10-3 cm/s. We studied whether the rat erythrocyte membrane possesses protein CO2 channels similar to the human red cell membrane by applying the potential CO2 channel inhibitors pCMBS, Dibac, phloretin, and DIDS. Phloretin and DIDS were able to reduce the CO2 permeability by up to 50%. Since these effects cannot be attributed to the lipid part of the membrane, we conclude that the rat erythrocyte membrane is equipped with protein CO2 channels that are responsible for at least 50% of its CO2 permeability.
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Affiliation(s)
- Samer Al-Samir
- AG Vegetative Physiologie 4220, Zentrum Physiologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - Maximilian Prill
- AG Vegetative Physiologie 4220, Zentrum Physiologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - Claudiu T Supuran
- Neurofarba Department, Section of Pharmaceutical and Nutritional Sciences, University of Florence, Florence, Italy
| | - Gerolf Gros
- AG Vegetative Physiologie 4220, Zentrum Physiologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - Volker Endeward
- AG Vegetative Physiologie 4220, Zentrum Physiologie, Medizinische Hochschule Hannover, Hannover, Germany
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Phenotype-Based High-Content Screening Using Fluorescent Chemical Bioprobes: Lipid Droplets and Glucose Uptake Quantification in Live Cells. Methods Mol Biol 2018. [PMID: 29736722 DOI: 10.1007/978-1-4939-7847-2_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Phenotypic screening in live cells has emerged as a promising strategy for drug discovery in pharmaceutical communities. For relevant phenotype-based screening setups, it is critical to develop adequate reporters in order to selectively visualize subcellular compartments or phenotypic changes that represent disease-related characteristics during compound screening. In this chapter, we introduce two phenotype-based high-content/high-throughput assays using fluorescent bioprobes that have been designed and refined to selectively stain cellular lipid droplets (LDs) and to show cellular glucose uptake. In conjunction with target identification process for the hit compounds from phenotypic screening, these fluorescent chemical probe-based screening techniques are expected to drive a great advancement for the discovery of novel first-in-class therapeutics.
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Jo A, Jung J, Kim E, Park SB. A high-content screening platform with fluorescent chemical probes for the discovery of first-in-class therapeutics. Chem Commun (Camb) 2016; 52:7433-45. [PMID: 27166145 DOI: 10.1039/c6cc02587k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Phenotypic screening has emerged as a promising approach to discover novel first-in-class therapeutic agents. Rapid advances in phenotypic screening systems facilitate a high-throughput unbiased evaluation of compound libraries. However, limited sets of phenotypic changes are utilized in high-content screening, which require extensive genetic engineering. Therefore, it is critical to develop new chemical probes that can reflect phenotypic changes in any type of cells, especially primary cells, tissues, and organisms. Herein, we introduce our continuous efforts in the development of fluorescent bioprobes and their application to phenotypic screening. In addition, we emphasize the importance of the phenotype-based approach in conjunction with target identification at an early stage of research to accelerate the discovery of therapeutics with new modes of action.
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Affiliation(s)
- Ala Jo
- Department of Chemistry, Seoul National University, Seoul, 08826, Korea.
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Jo A, Park J, Park SB. Exploiting the mechanism of cellular glucose uptake to develop an image-based high-throughput screening system in living cells. Chem Commun (Camb) 2013; 49:5138-40. [PMID: 23628794 DOI: 10.1039/c3cc41529e] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Biophysical understanding of cellular glucose uptake led us to the development of an image-based high-throughput screening system by using a fluorescent glucose bioprobe, GB2. The accuracy, robustness, and practicality of our image-based HTS system were demonstrated through the pilot screening and the subsequent in vitro confirmation.
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Affiliation(s)
- Ala Jo
- Department of Chemistry, Seoul National University, Seoul, Korea
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Henkin AH, Ortegon AM, Cho S, Shen WJ, Falcon A, Kraemer FB, Lee SJ, Stahl A. Evidence for protein-mediated fatty acid efflux by adipocytes. Acta Physiol (Oxf) 2012; 204:562-70. [PMID: 21951599 DOI: 10.1111/j.1748-1716.2011.02367.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
AIM The hormonally controlled mobilization and release of fatty acids from adipocytes into the circulation is an important physiological process required for energy homeostasis. While uptake of fatty acids by adipocytes has been suggested to be predominantly protein-mediated, it is unclear whether the efflux of fatty acids also requires membrane proteins. METHODS We used fluorescent fatty acid efflux assays and colorimetric assays for free fatty acids and glycerol to identify inhibitors with effects on fatty acid efflux, but not lipolysis, in 3T3-L1 adipocytes. We assessed the effect of these inhibitors on a fibroblast-based cell line expressing fatty acid transport protein 1, hormone-sensitive lipase and perilipin, which presumably lacks adipocyte-specific proteins for fatty acid efflux. RESULTS We identified 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) as an inhibitor of fatty acid efflux that did not impair lipolysis or the cellular exit of glycerol but lead to an accumulation of intracellular fatty acids. In contrast, fatty acid efflux by the reconstituted cellular model for fatty acid efflux was responsive to lipolytic stimuli, but insensitive to DIDS inhibition. CONCLUSION We propose that adipocytes specifically express an as yet unidentified DIDS-sensitive protein that enhances the efflux of fatty acids and therefore may lead to novel treatment approaches for obesity-related disorders characterized by abnormal lipid fluxes and ectopic triglyceride accumulation.
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Affiliation(s)
- A H Henkin
- Department of Nutritional Sciences and Toxicology, University of California at Berkeley, USA
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Stojanov K, de Vries EF, Hoekstra D, van Waarde A, Dierckx RA, Zuhorn IS. [
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F]FDG Labeling of Neural Stem Cells for in Vivo Cell Tracking with Positron Emission Tomography: Inhibition of Tracer Release by Phloretin. Mol Imaging 2012. [DOI: 10.2310/7290.2011.00021] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Katica Stojanov
- From the Departments of Cell Biology/Membrane Cell Biology and Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Erik F.J. de Vries
- From the Departments of Cell Biology/Membrane Cell Biology and Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Dick Hoekstra
- From the Departments of Cell Biology/Membrane Cell Biology and Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Aren van Waarde
- From the Departments of Cell Biology/Membrane Cell Biology and Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Rudi A.J.O. Dierckx
- From the Departments of Cell Biology/Membrane Cell Biology and Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Inge S. Zuhorn
- From the Departments of Cell Biology/Membrane Cell Biology and Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
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Abstract
There are two classes of glucose transporters involved in glucose homeostasis in the body, the facilitated transporters or uniporters (GLUTs) and the active transporters or symporters (SGLTs). The energy for active glucose transport is provided by the sodium gradient across the cell membrane, the Na(+) glucose cotransport hypothesis first proposed in 1960 by Crane. Since the cloning of SGLT1 in 1987, there have been advances in the genetics, molecular biology, biochemistry, biophysics, and structure of SGLTs. There are 12 members of the human SGLT (SLC5) gene family, including cotransporters for sugars, anions, vitamins, and short-chain fatty acids. Here we give a personal review of these advances. The SGLTs belong to a structural class of membrane proteins from unrelated gene families of antiporters and Na(+) and H(+) symporters. This class shares a common atomic architecture and a common transport mechanism. SGLTs also function as water and urea channels, glucose sensors, and coupled-water and urea transporters. We also discuss the physiology and pathophysiology of SGLTs, e.g., glucose galactose malabsorption and familial renal glycosuria, and briefly report on targeting of SGLTs for new therapies for diabetes.
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Affiliation(s)
- Ernest M Wright
- Department of Physiology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California 90095-1751, USA.
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Katsori AM, Hadjipavlou-Litina D. Recent progress in therapeutic applications of chalcones. Expert Opin Ther Pat 2011; 21:1575-96. [PMID: 21711087 DOI: 10.1517/13543776.2011.596529] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
INTRODUCTION Chalcones are a group of plant-derived polyphenolic compounds belonging to the flavonoids family that possess a wide variety of cytoprotective and modulatory functions, which may have therapeutic potential for multiple diseases. Their physicochemical properties seem to define the extent of their biological activity. AREAS COVERED A comprehensive synopsis of recent patent literature (2005 - 2011) describing chalcones and their derivatives on selected activities (e.g., anti-inflammatory, antimitotic, cytotoxic, antioxidant, anti-infection) is provided in this paper. Synthesis, combinatorial techniques, biological evaluation in vitro/in vivo, and new biological assays are discussed. In addition to selected biological data, a wide range of pharmaceutical applications and pharmaceutical compositions are also summarized. EXPERT OPINION Several natural and synthetic chalcones and their derivatives appear as promising anti-inflammatory and anticancer activities. Their clinical evaluation will be critical to assess their therapeutic utility. Those for which the mechanism of action is well defined can serve as lead compounds for the design of new, more promising molecules.
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Affiliation(s)
- Anna-Maria Katsori
- Aristotle University of Thessaloniki, School of Pharmacy, Department of Pharmaceutical Chemistry, Thessaloniki 54124, Greece
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Ostroumova OS, Malev VV, Ilin MG, Schagina LV. Surfactin activity depends on the membrane dipole potential. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:15092-15097. [PMID: 20828112 DOI: 10.1021/la102691y] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The effect of dipole modifying agents phloretin and RH 421 on the membrane conductance induced by surfactin, a lipopeptide antibiotic from Bacillus subtilis, was studied. Surfactin added on both sides of a bilayer formed from diphytanoylphosphocholine in 1 M KCl (pH 6.5) leads to the formation of voltage-independent channels of different conductance levels. The conductance of different states of SA channels varies from tens of picosiemens for small pores up to tens of nanosiemens for large ones. Small channels demonstrate pronounced cationic selectivity, whereas large ones practically lose their K(+)/Cl(-) selectivity, most probably because of their large effective radii. The addition of phloretin to the bilayer bathing solution, the agent known to decrease the membrane dipole potential, results in a decrease in the surfactin-induced membrane conductance. At the same time, increasing the membrane dipole potential because of the introduction of RH 421 leads to a rise in the steady-state conductance. Increasing dipole potential is accompanied by increases in both the number of open channels and their conductance. The observed changes in the channel-forming activity of surfactin might be caused by varying the partition coefficient of lipopeptide between the lipid and aqueous phases.
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Affiliation(s)
- Olga S Ostroumova
- Institute of Cytology of the Russian Academy of Sciences, St. Petersburg 194064, Russia.
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Decreased [18F]fluoro-2-deoxy-d-glucose incorporation and increased glucose transport are associated with resistance to 5FU in MCF7 cells in vitro. Nucl Med Biol 2007; 34:955-60. [DOI: 10.1016/j.nucmedbio.2007.07.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2007] [Revised: 07/10/2007] [Accepted: 07/12/2007] [Indexed: 11/23/2022]
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Martin HJ, Kornmann F, Fuhrmann GF. The inhibitory effects of flavonoids and antiestrogens on the Glut1 glucose transporter in human erythrocytes. Chem Biol Interact 2004; 146:225-35. [PMID: 14642735 DOI: 10.1016/j.cbi.2003.06.001] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Flavonoids and isoflavonoids are potent inhibitors of glucose efflux in human erythrocytes. Net changes of sugars inside the cells were measured by right angle light scattering. The inhibitory potency of hydroxylated flavonoids depends on the pH of the medium. The apparent affinity is maximal at low pH where the molecule is in the undissociated form. The following K(i)-values at pH 6.5 in microM have been obtained: phloretin 0.37+/-0.03, myricetin 0.76+/-0.42, quercetin 0.93+/-0.28, kaempferol 1.33+/-0.17, isoliquiritigenin 1.96, genistein 3.92+/-0.62, naringenin 8.88+/-1.88, 7-hydroxyflavone 17.58+/-3.15 and daidzein 18.62+/-2.85. Flavonoids carrying hydroxyl groups are weak acids and are deprotonated at high pH-values. From spectral changes pK-values between 6.80 (naringenin) and 7.73 (myricetin) have been calculated. No such pK-value could be obtained from quercetin which was rather unstable at alkaline pH. Flavone itself without a hydroxyl group does not demonstrate any absorbance changes at different pH-values and no significant change in inhibition of glucose transport with pH (K(i)-value around 35 microM). In this respect it is similar to the antiestrogens diethylstilbestrol, tamoxifen and cyclofenil with K(i)-values for glucose efflux inhibition of 2.61+/-0.30, 6.75+/-2.03 and 3.97+/-0.54 microM. Except for phloretin, the flavonoids investigated have planar structures. The inhibitory activity in glucose efflux of planar flavonoids increases exponentially with the number of hydroxyl groups in the molecule.
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Affiliation(s)
- Hans-Jörg Martin
- Department of Pharmacology and Toxicology, School of Medicine, Philipps-University of Marburg, Karl-von-Frisch-Strasse 1, D-35033 Marburg, Germany.
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12
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Cseh R, Benz R. Interaction of phloretin with lipid monolayers: relationship between structural changes and dipole potential change. Biophys J 1999; 77:1477-88. [PMID: 10465758 PMCID: PMC1300435 DOI: 10.1016/s0006-3495(99)76995-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Phloretin is known to adsorb to lipid surfaces and alters the dipole potential of lipid monolayers and bilayers. Its adsorption to biological and artificial membranes results in a change of the membrane permeability for a variety of charged and neutral compounds. In this respect phloretin represents a model substance to study the effect of dipole potentials on membrane permeability. In this investigation we studied the interaction of phloretin with monolayers formed of different lipids in the liquid-expanded and the condensed state. Phloretin integrated into the monolayers as a function of the aqueous concentration of its neutral form, indicated by an increase of the surface pressure in the presence of phloretin. Simultaneous recording of the surface potential of the monolayers allowed us to correlate the degree of phloretin integration and the phloretin-induced dipole potential change. Increasing the surface pressure decreased the phloretin-induced shift of the isotherms, but did not influence the phloretin-induced surface potential change. This means that phloretin adsorption to the lipid surface can occur without affecting the lipid packing. The surface potential effect of phloretin is accompanied by a change of the lipid dipole moment vector dependent on the lipid packing. This means that the relation between the surface potential change and the lipid packing cannot be described by a static model alone. Taking into account the deviations of the surface potential change versus molecular area isotherms of the experimental data to the theoretically predicted course, we propose a model that relates the area change to the dipole moment in a dynamic manner. By using this model the experimental data can be described much better than with a static model.
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Affiliation(s)
- R Cseh
- Lehrstuhl für Biotechnologie, Theodor-Boveri-Institut (Biozentrum) der Universität Würzburg, D-97074 Würzburg, Germany
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Panayotova-Heiermann M, Loo DD, Kong CT, Lever JE, Wright EM. Sugar binding to Na+/glucose cotransporters is determined by the carboxyl-terminal half of the protein. J Biol Chem 1996; 271:10029-34. [PMID: 8626557 DOI: 10.1074/jbc.271.17.10029] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
d-Glucose is absorbed across the proximal tubule of the kidney by two Na+/glucose cotransporters (SGLT1 and SGLT2). The low affinity SGLT2 is expressed in the S1 and S2 segments, has a Na+:glucose coupling ratio of 1, a K0.5 for sugar of approximately 2 mM, and a K0.5 for Na+ of approximately 1 mM. The high affinity SGLT1, found in the S3 segment, has a coupling ratio of 2, and K0.5 for sugar and Na+ of approximately 0.2 and 5 mM, respectively. We have constructed a chimeric protein consisting of amino acids 1-380 of porcine SGLT2 and amino acids 381-662 of porcine SGLT1. The chimera was expressed in Xenopus oocytes, and steady-state kinetics were characterized by a two-electrode voltage-clamp. The K0.5 for alpha-methyl-d-glucopyranoside (0.2 mM) was similar to that for SGLT1, and like SGLT1 the chimera transported D-galactose and 3-O-methylglucose. In contrast, SGLT2 transports poorly D-galactose and excludes 3-O-methylglucose. The apparent K0.5Na was 3.5 mM (at -150 mV), and the Hill coefficient ranged between 0.8 and 1.5. We conclude that recognition/transport of organic substrate is mediated by interactions distal to amino acid 380, while cation binding is determined by interactions arising from the amino- and carboxyl-terminal halves of the transporters. Surprisingly, the chimera transported alpha-phenyl derivatives of D-glucose as well as the inhibitors of sugar transport: phlorizin, deoxyphlorizin, and beta-D-glucopyranosylphenyl isothiocyanate are transported with high affinity (K0.5 for phlorizin was 5 microM). Thus, the pocket for organic substrate binding is increased from 10 x 5 x 5 (A) for SGLT1 to 11 x 18 x 5 (A) for the chimera.
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Affiliation(s)
- M Panayotova-Heiermann
- Department of Physiology, UCLA School of Medicine, Los Angeles, California 90095-1751, USA
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