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PI(18:1/18:1) is a SCD1-derived lipokine that limits stress signaling. Nat Commun 2022; 13:2982. [PMID: 35624087 PMCID: PMC9142606 DOI: 10.1038/s41467-022-30374-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 04/27/2022] [Indexed: 02/07/2023] Open
Abstract
Cytotoxic stress activates stress-activated kinases, initiates adaptive mechanisms, including the unfolded protein response (UPR) and autophagy, and induces programmed cell death. Fatty acid unsaturation, controlled by stearoyl-CoA desaturase (SCD)1, prevents cytotoxic stress but the mechanisms are diffuse. Here, we show that 1,2-dioleoyl-sn-glycero-3-phospho-(1’-myo-inositol) [PI(18:1/18:1)] is a SCD1-derived signaling lipid, which inhibits p38 mitogen-activated protein kinase activation, counteracts UPR, endoplasmic reticulum-associated protein degradation, and apoptosis, regulates autophagy, and maintains cell morphology and proliferation. SCD1 expression and the cellular PI(18:1/18:1) proportion decrease during the onset of cell death, thereby repressing protein phosphatase 2 A and enhancing stress signaling. This counter-regulation applies to mechanistically diverse death-inducing conditions and is found in multiple human and mouse cell lines and tissues of Scd1-defective mice. PI(18:1/18:1) ratios reflect stress tolerance in tumorigenesis, chemoresistance, infection, high-fat diet, and immune aging. Together, PI(18:1/18:1) is a lipokine that links fatty acid unsaturation with stress responses, and its depletion evokes stress signaling. Fatty acid unsaturation by stearoyl-CoA desaturase 1 (SCD1) protects against cellular stress through unclear mechanisms. Here the authors show 1,2-dioleoyl-sn-glycero-3-phospho-(1’-myo-inositol) is an SCD1-derived signaling lipid that regulates stress-adaption, protects against cell death and promotes proliferation.
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The antimicrobial and immunomodulatory effects of Ionophores for the treatment of human infection. J Inorg Biochem 2021; 227:111661. [PMID: 34896767 DOI: 10.1016/j.jinorgbio.2021.111661] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Revised: 10/27/2021] [Accepted: 11/03/2021] [Indexed: 12/18/2022]
Abstract
Ionophores are a diverse class of synthetic and naturally occurring ion transporter compounds which demonstrate both direct and in-direct antimicrobial properties against a broad panel of bacterial, fungal, viral and parasitic pathogens. In addition, ionophores can regulate the host-immune response during communicable and non-communicable disease states. Although the clinical use of ionophores such as Amphotericin B, Bedaquiline and Ivermectin highlight the utility of ionophores in modern medicine, for many other ionophore compounds issues surrounding toxicity, bioavailability or lack of in vivo efficacy studies have hindered clinical development. The antimicrobial and immunomodulating properties of a range of compounds with characteristics of ionophores remain largely unexplored. As such, ionophores remain a latent therapeutic avenue to address both the global burden of antimicrobial resistance, and the unmet clinical need for new antimicrobial therapies. This review will provide an overview of the broad-spectrum antimicrobial and immunomodulatory properties of ionophores, and their potential uses in clinical medicine for combatting infection.
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Su Z, Leitch JJ, Sek S, Lipkowski J. Ion-Pairing Mechanism for the Valinomycin-Mediated Transport of Potassium Ions across Phospholipid Bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:9613-9621. [PMID: 34323494 DOI: 10.1021/acs.langmuir.1c01500] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The role of the anion on the ionophore properties of valinomycin was studied in a model floating bilayer lipid membrane (fBLM) using supporting electrolytes containing K+ with four different counter anion species (ClO4-, H2PO4-, Cl-, and F-). The electrochemical impedance spectra indicate that the membrane resistance of the bilayer decreases with the decrease of Gibbs free energy of anion solvation. The IR spectra demonstrate that valinomycin does not readily bind to K+ in the KH2PO4, KCl, and KF electrolyte solutions, but in the presence of KClO4, valinomycin readily binds to K+, forming a valinomycin-K+ complex. The results in the present paper reveal the role of the counter anion on the transport of cations by valinomycin across the lipid bilayer. The valinomycin-cation complex creates an ion pair with the anion, and this ion pair can enter the hydrophobic region of the bilayer transporting the cation across the membrane. Anions with low solvation energies facilitate the formation of the ion pair improving the ion conductivity of valinomycin-incorporated bilayers. This paper sheds new light on the transport mechanism of valinomycin ionophores and provides new information about the bioactivity of this molecule.
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Affiliation(s)
- ZhangFei Su
- Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - J Jay Leitch
- Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Slawomir Sek
- Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Żwirki i Wigury 101, 02-089 Warsaw, Poland
| | - Jacek Lipkowski
- Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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The Potential Role of Lithium as an Antiviral Agent against SARS-CoV-2 via Membrane Depolarization: Review and Hypothesis. Sci Pharm 2021. [DOI: 10.3390/scipharm89010011] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Studies on potential treatments of Coronavirus Disease 2019 (COVID-19) are important to improve the global situation in the face of the pandemic. This review proposes lithium as a potential drug to treat COVID-19. Our hypothesis states that lithium can suppress NOD-like receptor family pyrin domain containing-3 (NLRP3) inflammasome activity, inhibit cell death, and exhibit immunomodulation via membrane depolarization. Our hypothesis was formulated after finding consistent correlations between these actions and membrane depolarization induced by lithium. Eventually, lithium could serve to mitigate the NLRP3-mediated cytokine storm, which is allegedly reported to be the inciting event of a series of retrogressive events associated with mortality from COVID-19. It could also inhibit cell death and modulate the immune system to attenuate its release, clear the virus from the body, and interrupt the cycle of immune-system dysregulation. Therefore, these effects are presumed to improve the morbidity and mortality of COVID-19 patients. As the numbers of COVID-19 cases and deaths continue to rise exponentially without a clear consensus on potential therapeutic agents, urgent conduction of preclinical and clinical studies to prove the efficacy and safety of lithium is reasonable.
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Bondarev NV. Computer Analysis of Stability of Cation Complexes with
Ionophore Antibiotics. RUSS J GEN CHEM+ 2020. [DOI: 10.1134/s1070363220080149] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Cánovas R, Padrell Sánchez S, Parrilla M, Cuartero M, Crespo GA. Cytotoxicity Study of Ionophore-Based Membranes: Toward On-Body and in Vivo Ion Sensing. ACS Sens 2019; 4:2524-2535. [PMID: 31448593 DOI: 10.1021/acssensors.9b01322] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
We present the most complete study to date comprising in vitro cytotoxicity tests of ion-selective membranes (ISMs) in terms of cell viability, proliferation, and adhesion assays with human dermal fibroblasts. ISMs were prepared with different types of plasticizers and ionophores to be tested in combination with assays that focus on the medium-term and long-term leaching of compounds. Furthermore, the ISMs were prepared in different configurations considering (i) inner-filling solution-type electrodes, (ii) all-solid-state electrodes based on a conventional drop-cast of the membrane, (iii) peeling after the preparation of a wearable sensor, and (iv) detachment from a microneedle-based sensor, thus covering a wide range of membrane shapes. One of the aims of this study, other than the demonstration of the biocompatibility of various ISMs and materials tested herein, is to create an awareness in the scientific community surrounding the need to perform biocompatibility assays during the very first steps of any sensor development with an intended biomedical application. This will foster meeting the requirements for subsequent on-body application of the sensor and avoiding further problems during massive validations toward the final in vivo use and commercialization of such devices.
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Affiliation(s)
- Rocío Cánovas
- Department of Chemistry, School of Engineering Science in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Teknikringen 30, SE-100 44 Stockholm, Sweden
| | - Sara Padrell Sánchez
- Department of Clinical Science, Intervention and Technology, Karolinska Institutet, and Division of Obstetrics and Gynecology, Karolinska Universitetssjukhuset, SE-141 86 Stockholm, Sweden
| | - Marc Parrilla
- Department of Chemistry, School of Engineering Science in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Teknikringen 30, SE-100 44 Stockholm, Sweden
| | - María Cuartero
- Department of Chemistry, School of Engineering Science in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Teknikringen 30, SE-100 44 Stockholm, Sweden
| | - Gastón A. Crespo
- Department of Chemistry, School of Engineering Science in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Teknikringen 30, SE-100 44 Stockholm, Sweden
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Delp J, Funke M, Rudolf F, Cediel A, Bennekou SH, van der Stel W, Carta G, Jennings P, Toma C, Gardner I, van de Water B, Forsby A, Leist M. Development of a neurotoxicity assay that is tuned to detect mitochondrial toxicants. Arch Toxicol 2019; 93:1585-1608. [PMID: 31190196 DOI: 10.1007/s00204-019-02473-y] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Accepted: 05/07/2019] [Indexed: 12/18/2022]
Abstract
Many neurotoxicants affect energy metabolism in man, but currently available test methods may still fail to predict mito- and neurotoxicity. We addressed this issue using LUHMES cells, i.e., human neuronal precursors that easily differentiate into mature neurons. Within the NeuriTox assay, they have been used to screen for neurotoxicants. Our new approach is based on culturing the cells in either glucose or galactose (Glc-Gal-NeuriTox) as the main carbohydrate source during toxicity testing. Using this Glc-Gal-NeuriTox assay, 52 mitochondrial and non-mitochondrial toxicants were tested. The panel of chemicals comprised 11 inhibitors of mitochondrial respiratory chain complex I (cI), 4 inhibitors of cII, 8 of cIII, and 2 of cIV; 8 toxicants were included as they are assumed to be mitochondrial uncouplers. In galactose, cells became more dependent on mitochondrial function, which made them 2-3 orders of magnitude more sensitive to various mitotoxicants. Moreover, galactose enhanced the specific neurotoxicity (destruction of neurites) compared to a general cytotoxicity (plasma membrane lysis) of the toxicants. The Glc-Gal-NeuriTox assay worked particularly well for inhibitors of cI and cIII, while the toxicity of uncouplers and non-mitochondrial toxicants did not differ significantly upon glucose ↔ galactose exchange. As a secondary assay, we developed a method to quantify the inhibition of all mitochondrial respiratory chain functions/complexes in LUHMES cells. The combination of the Glc-Gal-NeuriTox neurotoxicity screening assay with the mechanistic follow up of target site identification allowed both, a more sensitive detection of neurotoxicants and a sharper definition of the mode of action of mitochondrial toxicants.
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Affiliation(s)
- Johannes Delp
- Chair for In Vitro Toxicology and Biomedicine, Department of Inaugurated by the Doerenkamp-Zbinden Foundation, University of Konstanz, Universitaetsstr. 10, 78457, Constance, Germany
- Cooperative Doctorate College InViTe, University of Konstanz, Constance, Germany
| | - Melina Funke
- Chair for In Vitro Toxicology and Biomedicine, Department of Inaugurated by the Doerenkamp-Zbinden Foundation, University of Konstanz, Universitaetsstr. 10, 78457, Constance, Germany
| | - Franziska Rudolf
- Chair for In Vitro Toxicology and Biomedicine, Department of Inaugurated by the Doerenkamp-Zbinden Foundation, University of Konstanz, Universitaetsstr. 10, 78457, Constance, Germany
| | - Andrea Cediel
- Swetox Unit for Toxicological Sciences, Karolinska Institutet, Stockholm, Sweden
| | | | - Wanda van der Stel
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Einsteinweg 55, 2333 CC, Leiden, The Netherlands
| | - Giada Carta
- Division of Molecular and Computational Toxicology, Amsterdam Institute for Molecules, Medicines and Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Paul Jennings
- Division of Molecular and Computational Toxicology, Amsterdam Institute for Molecules, Medicines and Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Cosimo Toma
- Laboratory of Environmental Chemistry and Toxicology, Department of Environmental Health Sciences, Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Via la Masa 19, 20156, Milan, Italy
| | | | - Bob van de Water
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Einsteinweg 55, 2333 CC, Leiden, The Netherlands
| | - Anna Forsby
- Swetox Unit for Toxicological Sciences, Karolinska Institutet, Stockholm, Sweden
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Marcel Leist
- Chair for In Vitro Toxicology and Biomedicine, Department of Inaugurated by the Doerenkamp-Zbinden Foundation, University of Konstanz, Universitaetsstr. 10, 78457, Constance, Germany.
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Tian S, Xiong H, Geng P, Yuan Z, Hu X. CesH Represses Cereulide Synthesis as an Alpha/Beta Fold Hydrolase in Bacillus cereus. Toxins (Basel) 2019; 11:E231. [PMID: 31010094 PMCID: PMC6521208 DOI: 10.3390/toxins11040231] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 04/13/2019] [Accepted: 04/20/2019] [Indexed: 12/18/2022] Open
Abstract
Cereulide is notorious as a heat-stable emetic toxin produced by Bacillus cereus and glucose is supposed to be an ingredient supporting its formation. This study showed that glucose addition benefited on cell growth and the early transcription of genes involved in substrate accumulation and toxin synthesis, but it played a negative role in the final production of cereulide. Meanwhile, a lasting enhancement of cesH transcription was observed with the addition of glucose. Moreover, the cereulide production in ΔcesH was obviously higher than that in the wild type. This indicates that CesH has a repression effect on cereulide production. Bioinformatics analysis revealed that CesH was an alpha/beta hydrolase that probably associated with the cell membrane, which was verified by subcellular localization. The esterase activity against para-nitrophenyl acetate (PNPC2) of the recombinant CesH was confirmed. Although no sign of ester bond cleavage in cereulide or valinomycin was demonstrated in in vitro assays, CesH could reverse the cereulide analogue sensitivity of Bacillus subtilis in vivo, by which toxin degradation was facilitated. Moreover, site directed mutations identified that the conserved catalytic triad of CesH might consist of Serine 86, Glutamate 199, and Histidine 227. These results help us to understand the regulation of cereulide production and provide clues for developing control measurements.
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Affiliation(s)
- Shen Tian
- Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China.
- University of the Chinese Academy of Sciences, Beijing 100049, China.
| | - Hairong Xiong
- College of Life Science, South-Central University for Nationalities, Wuhan 430074, China.
| | - Peiling Geng
- Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China.
- University of the Chinese Academy of Sciences, Beijing 100049, China.
| | - Zhiming Yuan
- Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China.
| | - Xiaomin Hu
- Key Laboratory of Special Pathogens and Biosafety, Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China.
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9
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Wang Y, Qin Y, Zhang Y, Wu R, Li P. Antibacterial mechanism of plantaricin LPL-1, a novel class IIa bacteriocin against Listeria monocytogenes. Food Control 2019. [DOI: 10.1016/j.foodcont.2018.10.025] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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10
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Nishimura-Danjobara Y, Oyama K, Yokoigawa K, Oyama Y. Hyperpolarization by N-(3-oxododecanoyl)-l-homoserine-lactone, a quorum sensing molecule, in rat thymic lymphocytes. Chem Biol Interact 2018; 283:91-96. [PMID: 29427588 DOI: 10.1016/j.cbi.2018.02.008] [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: 12/22/2017] [Revised: 01/22/2018] [Accepted: 02/05/2018] [Indexed: 11/25/2022]
Abstract
To study the adverse effects of N-(3-oxododecanoyl)-l-homoserine-lactone (ODHL), a quorum sensing molecule, on mammalian host cells, its effect on membrane potential was examined in rat thymic lymphocytes using flow cytometric techniques with a voltage-sensitive fluorescent probe. As 3-300 μM ODHL elicited hyperpolarization, it is likely that it increases membrane K+ permeability because hyperpolarization is directly linked to changing K+ gradient across membranes, but not Na+ and Cl- gradients. ODHL did not increase intracellular Ca2+ concentration. ODHL also produced a response in the presence of an intracellular Zn2+ chelator. Thus, it is unlikely that intracellular Ca2+ and Zn2+ are attributed to the response. Quinine, a non-specific K+ channel blocker, greatly reduced hyperpolarization. However, because charybdotoxin, tetraethylammonium chloride, 4-aminopyridine, and glibenclamide did not affect it, it is pharmacologically hypothesized that Ca2+-activated K+ channels, voltage-gated K+ channels, and ATP-sensitive K+ channels are not involved in ODHL-induced hyperpolarization. Although the K+ channels responsible for ODHL-induced hyperpolarization have not been identified, it is suggested that ODHL can elicit hyperpolarization in mammalian host cells, disturbing cellular functions.
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Affiliation(s)
- Yumiko Nishimura-Danjobara
- Department of Food Science, Faculty of Bioscience and Bioindustry, Tokushima University, Tokushima 770-8513, Japan
| | - Keisuke Oyama
- Department of Food Science, Faculty of Bioscience and Bioindustry, Tokushima University, Tokushima 770-8513, Japan
| | - Kumio Yokoigawa
- Department of Food Science, Faculty of Bioscience and Bioindustry, Tokushima University, Tokushima 770-8513, Japan
| | - Yasuo Oyama
- Department of Food Science, Faculty of Bioscience and Bioindustry, Tokushima University, Tokushima 770-8513, Japan.
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11
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Song L, Wu X. Development of efflux pump inhibitors in antituberculosis therapy. Int J Antimicrob Agents 2016; 47:421-9. [DOI: 10.1016/j.ijantimicag.2016.04.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 03/25/2016] [Accepted: 04/02/2016] [Indexed: 12/18/2022]
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12
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Roundhill E, Turnbull D, Burchill S. Localization of MRP-1 to the outer mitochondrial membrane by the chaperone protein HSP90β. FASEB J 2015; 30:1712-23. [PMID: 26722004 DOI: 10.1096/fj.15-283408] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 12/08/2015] [Indexed: 12/29/2022]
Abstract
Overexpression of plasma membrane multidrug resistance-associated protein 1 (MRP-1) in Ewing's sarcoma (ES) predicts poor outcome. MRP-1 is also expressed in mitochondria, and we have examined the submitochondrial localization of MRP-1 and investigated the mechanism of MRP-1 transport and role of this organelle in the response to doxorubicin. The mitochondrial localization of MRP-1 was examined in ES cell lines by differential centrifugation and membrane solubilization by digitonin. Whether MRP-1 is chaperoned by heat shock proteins (HSPs) was investigated by immunoprecipitation, immunofluorescence microscopy, and HSP knockout using small hairpin RNA and inhibitors (apoptozole, 17-AAG, and NVPAUY). The effect of disrupting mitochondrial MRP-1-dependent efflux activity on the cytotoxic effect of doxorubicin was investigated by counting viable cell number. Mitochondrial MRP-1 is glycosylated and localized to the outer mitochondrial membrane, where it is coexpressed with HSP90. MRP-1 binds to both HSP90 and HSP70, although only inhibition of HSP90β decreases expression of MRP-1 in the mitochondria. Disruption of mitochondrial MRP-1-dependent efflux significantly increases the cytotoxic effect of doxorubicin (combination index, <0.9). For the first time, we have demonstrated that mitochondrial MRP-1 is expressed in the outer mitochondrial membrane and is a client protein of HSP90β, where it may play a role in the doxorubicin-induced resistance of ES.-Roundhill, E., Turnbull, D., Burchill, S. Localization of MRP-1 to the outer mitochondrial membrane by the chaperone protein HSP90β.
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Affiliation(s)
- Elizabeth Roundhill
- Children's Cancer Research Group, Leeds Institute of Cancer and Pathology, St. James's University Hospital, Leeds, United Kingdom; and
| | - Doug Turnbull
- Wellcome Trust Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Susan Burchill
- Children's Cancer Research Group, Leeds Institute of Cancer and Pathology, St. James's University Hospital, Leeds, United Kingdom; and
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Pule CM, Sampson SL, Warren RM, Black PA, van Helden PD, Victor TC, Louw GE. Efflux pump inhibitors: targeting mycobacterial efflux systems to enhance TB therapy. J Antimicrob Chemother 2015; 71:17-26. [DOI: 10.1093/jac/dkv316] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
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14
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Mattei C, Molgó J, Benoit E. Involvement of both sodium influx and potassium efflux in ciguatoxin-induced nodal swelling of frog myelinated axons. Neuropharmacology 2014; 85:417-26. [PMID: 24950451 DOI: 10.1016/j.neuropharm.2014.06.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 05/09/2014] [Accepted: 06/02/2014] [Indexed: 01/22/2023]
Abstract
Ciguatoxins, mainly produced by benthic dinoflagellate Gambierdiscus species, are responsible for a complex human poisoning known as ciguatera. Previous pharmacological studies revealed that these toxins activate voltage-gated Na+ channels. In frog nodes of Ranvier, ciguatoxins induce spontaneous and repetitive action potentials (APs) and increase axonal volume that may explain alterations of nerve functioning in intoxicated humans. The present study aimed determining the ionic mechanisms involved in Pacific ciguatoxin-1B (P-CTX-1B)-induced membrane hyperexcitability and subsequent volume increase in frog nodes of Ranvier, using electrophysiology and confocal microscopy. The results reveal that P-CTX-1B action is not dependent on external Cl- ions since it was not affected by substituting Cl- by methylsulfate ions. In contrast, substitution of external Na+ by Li+ ions suppressed spontaneous APs and prevented nodal swelling. This suggests that P-CTX-1B-modified Na+ channels are not selective to Li+ ions and/or are blocked by these ions, and that Na+ influx through Na+ channels opened during spontaneous APs is required for axonal swelling. The fact that the K+ channel blocker tetraethylammonium modified, but did not suppress, spontaneous APs and greatly reduced nodal swelling induced by P-CTX-1B indicates that K+ efflux might also be involved. This is supported by the fact that P-CTX-1B, when tested in the presence of both tetraethylammonium and the K+ ionophore valinomycin, produced the characteristic nodal swelling. It is concluded that, during the action of P-CTX-1B, water movements responsible for axonal swelling depend on both Na+ influx and K+ efflux. These results pave the way for further studies regarding ciguatera treatment.
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Affiliation(s)
- César Mattei
- CNRS, Institut de Neurobiologie Alfred Fessard - FRC2118, Laboratoire de Neurobiologie et Développement - UPR3294, 91198 Gif-sur-Yvette cedex, France; Laboratoire Biologie Neurovasculaire et Mitochondriale Intégrée, UMR CNRS 6214 INSERM 1083, Université d'Angers, 49045 Angers cedex 01, France.
| | - Jordi Molgó
- CNRS, Institut de Neurobiologie Alfred Fessard - FRC2118, Laboratoire de Neurobiologie et Développement - UPR3294, 91198 Gif-sur-Yvette cedex, France
| | - Evelyne Benoit
- CNRS, Institut de Neurobiologie Alfred Fessard - FRC2118, Laboratoire de Neurobiologie et Développement - UPR3294, 91198 Gif-sur-Yvette cedex, France
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15
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Structurally diverse natural products that cause potassium leakage trigger multicellularity in Bacillus subtilis. Proc Natl Acad Sci U S A 2008; 106:280-5. [PMID: 19114652 DOI: 10.1073/pnas.0810940106] [Citation(s) in RCA: 248] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We report a previously undescribed quorum-sensing mechanism for triggering multicellularity in Bacillus subtilis. B. subtilis forms communities of cells known as biofilms in response to an unknown signal. We discovered that biofilm formation is stimulated by a variety of small molecules produced by bacteria--including the B. subtilis nonribosomal peptide surfactin--that share the ability to induce potassium leakage. Natural products that do not cause potassium leakage failed to induce multicellularity. Small-molecule-induced multicellularity was prevented by the addition of potassium, but not sodium or lithium. Evidence is presented that potassium leakage stimulates the activity of a membrane protein kinase, KinC, which governs the expression of genes involved in biofilm formation. We propose that KinC responds to lowered intracellular potassium concentration and that this is a quorum-sensing mechanism that enables B. subtilis to respond to related and unrelated bacteria.
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Sun CB, Suresh A, Deng YZ, Naqvi NI. A multidrug resistance transporter in Magnaporthe is required for host penetration and for survival during oxidative stress. THE PLANT CELL 2006; 18:3686-705. [PMID: 17189344 PMCID: PMC1785395 DOI: 10.1105/tpc.105.037861] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
In prokaryotes and eukaryotes, multidrug resistance (MDR) transporters use energy-dependent efflux action to regulate the intracellular levels of antibiotic or xenobiotic compounds. Using mutational analysis of ABC3, we define an important role for such MDR-based efflux during the host penetration step of Magnaporthe grisea pathogenesis. Mutants lacking ABC3 were completely nonpathogenic but were surprisingly capable of penetrating thin cellophane membranes to some extent. The inability of abc3Delta to penetrate the host surface was most likely a consequence of excessive buildup of peroxide and accumulation of an inhibitory metabolite(s) within the mutant appressoria. Treatment with antioxidants partially suppressed the host penetration defects in the abc3Delta mutant. abc3Delta was highly sensitive to oxidative stress and was unable to survive the host environment and invasive growth conditions. ABC3 transcript levels were redox-regulated, and on host surfaces, the activation of ABC3 occurred during initial stages of blast disease establishment. An Abc3-green fluorescent protein fusion localized to the plasma membrane in early appressoria (and in penetration hyphae) but became predominantly vacuolar during appressorial maturity. We propose that ABC3 function helps Magnaporthe to cope with cytotoxicity and oxidative stress within the appressoria during early stages of infection-related morphogenesis and likely imparts defense against certain antagonistic and xenobiotic conditions encountered during pathogenic development.
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Affiliation(s)
- Chuan Bao Sun
- Fungal Patho-Biology Group, Temasek Life Sciences Laboratory and Department of Biological Sciences, National University of Singapore, Singapore 117604
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Rouzaire-Dubois B, Gérard V, Dubois JM. Involvement of K+ channels in the quercetin-induced inhibition of neuroblastoma cell growth. Pflugers Arch 1993; 423:202-5. [PMID: 8321622 DOI: 10.1007/bf00374395] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The effects of the flavonoid quercetin on cell proliferation and voltage-dependent K+ current were studied on mouse neuroblastoma x glioma hybrid cells. In the presence of 1% fetal calf serum, quercetin inhibited both cell proliferation and K+ current with effective doses inducing half-maximum effects of 10 microM and 70 microM respectively. Valinomycin (1 nM) antagonized 80% of the growth-inhibitory effects of 10 microM quercetin. The results suggest that at least a part of the anti-proliferative effect of quercetin is mediated by a K+ channel blockade. They further confirm a role for K+ channels in mitogenesis and cell proliferation.
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Chapter 5 Monovalent Ion Transport and Membrane Potential Changes during Leukocyte Activation: Lymphocytes. ACTA ACUST UNITED AC 1990. [DOI: 10.1016/s0070-2161(08)60077-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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19
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Daoud SS, Juliano RL. In vitro effect of liposome-incorporated valinomycin on growth and macromolecular synthesis of normal and ras-transformed 3T3 cells. Cancer Chemother Pharmacol 1989; 23:151-5. [PMID: 2647310 DOI: 10.1007/bf00267946] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Valinomycin is a depsipeptide antibiotic that selectively translocates potassium ion across biologic membranes. This drug has been reported to display antitumor effects, but its use has been limited by its extreme toxicity. However, its incorporation into lipid vesicles (liposomes) has resulted in a reduction in toxicity and in the enhancement of the drug's therapeutic index. As a preliminary investigation of the mechanistic basis for this enhancement, the in vitro response of normal 3T3 and ras-transformed cells to free (VM) and liposomal valinomycin (VM-MLV) was examined. The incorporation of [3H]-leucine and [methyl-3H]-thymidine was used to assess macromolecular synthesis, and the MTT vital dye assay was used to measure cell survival and growth. Pretreatment of exponentially growing NIH/3T3 cells with 20 nM VM for 1 h decreased [3H]-leucine and [methyl-3H]-thymidine incorporation by 90% and 80%, respectively. However, Ha-ras 3T3 cells showed resistance to VM treatment with inhibitory doses in the range of 200 nM. At equimolar VM concentrations, VM-MLV was found to be less inhibitory than VM for protein and DNA synthesis. Specifically, marked protective activity was apparent with normal 3T3 cells. In this report we also demonstrate that VM selectively killed normal cells compared with ras-transformed cells grown in vitro. However, VM-MLV displayed a modest cytotoxic selectivity (3- to 4-fold) to ras-transformed cells. Our data suggests that first, there is good correlation between growth inhibition and inhibition of DNA and protein synthesis by VM, and second, VM-MLV exhibits a modest, selective toxicity to the ras-transformed 3T3 cell line as compared with nontransformed 3T3 cells, whereas free VM has the opposite selectivity.
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Affiliation(s)
- S S Daoud
- Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill 27599
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20
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Kent RL, Hoober JK, Cooper G. Load responsiveness of protein synthesis in adult mammalian myocardium: role of cardiac deformation linked to sodium influx. Circ Res 1989; 64:74-85. [PMID: 2909303 DOI: 10.1161/01.res.64.1.74] [Citation(s) in RCA: 101] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Exposure of adult mammalian myocardium to increased hemodynamic loads augments cardiac protein synthesis, ultimately leading to hypertrophy of the affected chamber. This established relationship between loading conditions and protein synthesis was examined in terms of two questions. First, is there a basic difference between the anabolic effect of a passive load imposed on diastolic myocardium and that of an active load generated by systolic myocardium? This issue was addressed by measuring [3H]phenylalanine incorporation into muscle protein in either quiescent or contracting ferret papillary muscles, set at known isometric lengths. Myocardial protein synthesis increased in proportion to total muscle tension in each case, with an equivalent relation describing both quiescent and contracting muscles. Synthesis of two contractile proteins, actin and myosin heavy chain, were enhanced by muscle loading. Thus, a quantitative rather than qualitative difference between the anabolic effects of diastolic and systolic loading was demonstrated. Second, since increased sodium influx is an initial cellular response requisite to the growth-inducing activity of many substances, and since sodium entry through stretch-activated ion channels is stimulated by deformation of the sarcolemma, does cardiac deformation during increased loading promote sodium influx as a signal to increase anabolic activity? In either quiescent or contracting papillary muscles, the rate of 24Na+ uptake was found to increase with load. Streptomycin, a cationic blocker of the mechanotransducer ion channels, was without effect on protein synthesis in stimulated but slack muscles; however, it inhibited, in a dose-related manner, the augmented protein synthesis otherwise observed in contracting muscles developing tension. At 500 microM, streptomycin did not reduce active tension, but it did reduce the synthesis of both actin and myosin heavy chain. In a second pharmacologic approach, inotropic agents were chosen which uniformly increased muscle tension development but which had contrasting effects on sodium influx. Protein synthesis increased in the presence of Na+ influx enhancers, monensin or veratridine; however, protein synthesis decreased in the presence of amiloride, a sodium influx inhibitor. Thus, myocardial protein synthesis varied directly with sodium influx despite the positive inotropic effect observed with each of these agents. In addition, inhibition of protein synthesis by ouabain demonstrated that activation of the Na+ pump is required for the anabolic effect of load.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- R L Kent
- VA Medical Center, Charleston, SC 29403
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Matkó J, Szöllösi J, Trón L, Damjanovich S. Luminescence spectroscopic approaches in studying cell surface dynamics. Q Rev Biophys 1988; 21:479-544. [PMID: 3071824 DOI: 10.1017/s0033583500004637] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The major elements of membranes, such as proteins, lipids and polysaccharides, are in dynamic interaction with each other (Albertset al.1983). Protein diffusion in the lipid matrix of the membrane, the lipid diffusion and dynamic domain formation below and above their transition temperature from gel to fluid state, have many functional implications. This type of behaviour of membranes is often summarized in one frequently used word membrane fluidity (coined by Shinitzky & Henkart, 1979). The dynamic behaviour of the cell membrane includes rotational, translational and segmental movements of membrane elements (or their domain-like associations) in the plane of, and perpendicular to the membrane. The ever changing proximity relationships form a dynamic pattern of lipids, proteins and saccharide moieties and are usually described as ‘cell-surface dynamics’ (Damjanovichet al.1981). The knowledge about the above defined behaviour originates from experiments performed mostly on cytoplasmic membranes of eukaryotic cells. Nevertheless numerous data are available also on the mitochondrial and nuclear membranes, as well as endo (sarco-)plasmic reticulum (Martonosi, 1982; Slater, 1981; Siekevitz, 1981).
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Affiliation(s)
- J Matkó
- Department of Biophysics, Medical University of Debrecen, Hungary
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Wilson HA, Chused TM. Lymphocyte membrane potential and Ca2+-sensitive potassium channels described by oxonol dye fluorescence measurements. J Cell Physiol 1985; 125:72-81. [PMID: 2413058 DOI: 10.1002/jcp.1041250110] [Citation(s) in RCA: 140] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A method is described for quantitative measurement of lymphocyte transmembrane electrical potential difference (psi) by flow cytometric recording of the oxonol dye fluorescence of single cells. Both the simultaneous collection and analysis of multiple optical parameters and the use of a negatively charged oxonol probe allowed more accurate measurement of psi than may be obtained by bulk cell suspension techniques employing cationic voltage indicators. Mouse spleen and human blood lymphocyte psi was calculated to be -70 mV. T and B lymphocytes maintain a constant psi as extracellular K+ is varied from 2 to 10 mM and the deviation from K+ equilibrium potentials (EK) is shown to result from Na+ permeability. At [K+]o values greater than 10 mM, lymphocytes behave as K+ electrodes. Examination of lymphocyte subsets showed that hyperpolarization induced by the Ca2+ ionophore A23187 occurs only in T cells. This response was identified as activation of a Ca2+-sensitive K+ channel by pharmacologic manipulations. Hence, T cells depolarized by 4-aminopyridine (4-AP, 10 mM) were observed to return to resting psi by A23187-induced elevation of [Ca2+]i. Cells depolarized by quinine (100 microM) were unaffected by A23187. The Ca2+-activated channel does not contribute to resting psi in T cells since it may be selectively blocked by quinine (20 microM) or modulated by calmodulin antagonists (5 microM trifluperazine) without affecting resting psi.
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Yamanishi K. Effects of valinomycin on hexose transport and cellular ATP pools in mouse fibroblasts. J Cell Physiol 1984; 119:163-71. [PMID: 6715414 DOI: 10.1002/jcp.1041190204] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The K+ ionophore valinomycin at concentrations of 1 X 10(-8) M and over, stimulated 2-deoxy-D-glucose (2DG) and 3-O-methylglucose (3OMG) uptake in Swiss 3T3 fibroblasts. The rate-limiting step of 2DG uptake was transport rather than phosphorylation, in the control or valinomycin-treated cells. Kinetic analysis showed that valinomycin increased the Vmax for 2DG uptake without change of the Km. The valinomycin-stimulated 2DG uptake was insensitive to 10 micrograms/ml cycloheximide, and extracellular K+ concentrations between 0.1 and 50 mM. On the other hand, valinomycin at the concentration of 1 X 10(-8) M and over, induced a rapid decrease in cellular ATP content, followed by stimulation of 2DG uptake and recovery of the ATP content. A similar relationship between the reduction of cellular ATP content and the subsequent stimulation of 2DG uptake was observed when the cells were treated not only with 2,4-dinitrophenol and iodoacetic acid, but also with other monovalent cation ionophores or inhibitors of oxidative phosphorylation. These results suggest that valinomycin may posttranslationally stimulate hexose transport by increasing the number of functional carriers of hexose or changing their mobility, and the rapid decrease in cellular ATP pools by valinomycin may be a trigger of the stimulation of the hexose transport in Swiss 3T3 fibroblasts.
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Monroe JG, Cambier JC. B cell activation. III. B cell plasma membrane depolarization and hyper-Ia antigen expression induced by receptor immunoglobulin cross-linking are coupled. J Exp Med 1983; 158:1589-99. [PMID: 6415207 PMCID: PMC2187138 DOI: 10.1084/jem.158.5.1589] [Citation(s) in RCA: 92] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
We report investigation of the relationship between ligand-induced B cell plasma membrane depolarization and increased expression of membrane-associated, I-A subregion encoded (mI-A) antigens. Results demonstrate that equal frequencies of B cells are stimulated to undergo membrane depolarization and to increase mI-A expression in response to mitogen, anti-Ig, and thymus-independent (TI) or thymus-dependent (TD) antigens. Further, a cause-and-effect relationship between these two events is suggested by results that demonstrate that inhibition of anti-Fab--induced depolarization by valinomycin also inhibits the subsequent increase in mI-A antigen expression and "passive" (non-ligand-mediated) depolarization of murine B cells by K+ results in hyper-mI-A antigen expression. Based upon these results we hypothesize that antigen-mediated receptor cross-linking results in signal transduction via membrane depolarization, which is resultant in increased mI-A antigen synthesis and cell surface expression. This increase in mI-A antigen density may render the B cell more receptive to subsequent interaction with I-region-restricted helper T cells.
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Monroe JG, Cambier JC. B cell activation. I. Anti-immunoglobulin-induced receptor cross-linking results in a decrease in the plasma membrane potential of murine B lymphocytes. J Exp Med 1983; 157:2073-86. [PMID: 6602204 PMCID: PMC2187028 DOI: 10.1084/jem.157.6.2073] [Citation(s) in RCA: 79] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
We report analyses of the effect of anti-Fab antibodies on plasma membrane potential of mouse B lymphocytes. Results indicate that divalent fragments of anti-Fab antibodies mitogenic for B cells stimulate membrane depolarization detectable by cytofluorometric analysis of 3,3'-dipentyloxacarbocyanine iodide-stained cells. Depolarization is detectable within 5 min of exposure to ligand and maximal within 1 h of exposure when greater than or equal to 80% of splenic B cells exhibit decreased membrane potential. The ineffectiveness of monovalent Fab antibody fragments in inducing this event suggests that receptor immunoglobulin cross-linking is essential. Frequencies of cells induced to enter cell cycle, as assessed by acridine orange cell cycle analysis, are equal to those induced to depolarize by lipopolysaccharide plus dextran sulfate or anti-Fab, which suggests a relationship between these events. However, membrane depolarization is itself an insufficient signal to promote subsequent thymidine uptake, as evidenced by the fact that doses of anti-Fab that are suboptimal for thymidine uptake induce maximal depolarization. These results suggest that cross-linking of surface immunoglobulin on B cells may provide an initial signal for activation but is itself insufficient to drive B cell proliferation.
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Felber SM, Brand MD. Valinomycin can depolarize mitochondria in intact lymphocytes without increasing plasma membrane potassium fluxes. FEBS Lett 1982; 150:122-4. [PMID: 7160466 DOI: 10.1016/0014-5793(82)81317-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Trist DG, Weatherall M. Inhibition of human lymphocyte transformation by two aryloxyalkylamidines. J Pharm Pharmacol 1982; 34:97-101. [PMID: 6121888 DOI: 10.1111/j.2042-7158.1982.tb04193.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The incorporation of [3H]thymidine into human lymphocytes stimulated by phytohaemagglutinin (PHA) was inhibited by anilino-N-2-m-chlorophenoxypropylacetamidine (501C) and xylamidine. These amidines antagonize 5-HT, but 5-HT did not alter [3H]thymidine incorporation. 501C inhibited PHA-induced lymphocyte transformation as observed by [3H]thymidine incorporation, [3H]uridine incorporation, [3H]leucine incorporation, DNA content, potassium content, and histological examination. 501C also inhibited increased [3H]thymidine incorporation in human mixed lymphocyte cultures. The IC50 of 501C for inhibition of these processes lay between 4 and 8 microM. When added late in culture (after 6-8 h) 501C was less effective. Possible mechanisms by which 501C inhibits transformation are discussed.
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Arslan P, Miolo A, Montecucco C, Pozzan T. Effect of ionophores on lymphocyte cellular metabolism. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1982; 141:481-9. [PMID: 7090923 DOI: 10.1007/978-1-4684-8088-7_46] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The effect of valinomycin, nigericin, gramicidin S and D, A23187 and X537A on respiration and cellular ATP content of rat spleen lymphocytes is presented. It has been found that while valinomycin and nigericin interfere with mitochondrial functions gramicidin D does not show an appreciable effect. These results are explained in terms of different ability of ionophores to re-distribute among intracellular membranes. A23187 and X537A, added with Ca2+, strongly enhanced O2 consumption and reduced cellular ATP content.
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Alonso MA, Carrasco L. Action of membrane-active compounds on mammalian cells. Permeabilization of human cells by ionophores to inhibitors of translation and transcription. EUROPEAN JOURNAL OF BIOCHEMISTRY 1980; 109:535-40. [PMID: 7408899 DOI: 10.1111/j.1432-1033.1980.tb04825.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Kiefer H, Blume AJ, Kaback HR. Membrane potential changes during mitogenic stimulation of mouse spleen lymphocytes. Proc Natl Acad Sci U S A 1980; 77:2200-4. [PMID: 6929546 PMCID: PMC348680 DOI: 10.1073/pnas.77.4.2200] [Citation(s) in RCA: 104] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
By monitoring differences in accumulation of the lipophilic cation [(3)H]tetraphenylphosphonium in media containing low or high potassium concentrations [Lichtshtein, D., Kaback, H. R. & Blume, A. J. (1979) Proc. Natl. Acad. Sci. USA 76, 650-654], the membrane potential of lymphocytes from various sources has been estimated. On the basis of this method, the potential of normal mouse spleen lymphocytes (T and B cells) is -65 +/- 2 mV (mean +/- SEM, interior negative). During the course of mitogenic stimulation by concanavalin A, lipopolysaccharide, or fetal calf serum, the membrane potential of murine spleen lymphocytes changes systematically according to the following pattern: (i) early depolarization lasting 2-3 hr, (ii) repolarization over the next 7 hr, and (iii) a final hyperpolarization phase during the last 24-48 hr. During repolarization and hyperpolarization, moreover, there is a direct correlation between the membrane potential and DNA synthesis, as judged by [(3)H]thymidine incorporation. By using isolated T and B cells, it is observed that concanavalin A depolarizes T cells only, whereas lipopolysaccharide depolarizes B cells only. Thus, both mitogens exhibit the same specificity for depolarization as for mitogenic stimulation. On the basis of these observations, it is suggested that the transition of lymphocytes from a resting state to mitotic activity is initiated by depolarization of the plasma membrane.
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Mikkelsen RB, Schmidt-Ullrich R, Wallach DF. Concanavalin A induces an intraluminal alkalinization of thymocyte membrane vesicles. J Cell Physiol 1980; 102:113-7. [PMID: 6246125 DOI: 10.1002/jcp.1041020203] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Weak acid distribution methods demonstrate that mitogenic levels of concanavalin A induce an intravesicular alkalinization of isolated thymocyte membrane vesicles. Experiments with chemical reagents that crosslink the high affinity concanavalin A receptor and extensive correlation with known cellular events suggest that a "membrane Bohr effect" may participate in the initiation of mitogenesis.
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Deutsch CJ, Holian A, Holian SK, Daniele RP, Wilson DF. Transmembrane electrical and pH gradients across human erythrocytes and human peripheral lymphocytes. J Cell Physiol 1979; 99:79-93. [PMID: 37251 DOI: 10.1002/jcp.1040990110] [Citation(s) in RCA: 114] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Transmembrane electrical and pH gradients have been measured across human erythrocytes and peripheral blood lymphocytes using equilibrium distributions of radioactively labelled lipophilic ions, and of weak acids and weak bases, respectively. The distributions of methylamine, trimethylamine, acetic acid and trimethylacetic acid give calculated transmembrane pH gradients (pHe-pHi) for erythrocytes of between 0.14-0.21 for extracellular pH values of 7.28-7.16. The distributions of trimethylacetic acid. DMO and trimethylamine were determined for lymphocytes, establishing upper and lower limits of the calculated pH gradient over the external pH range of 6.7 to 7.7. Tritiated triphenylmethyl phosphonium ion (TPMP) and 14C-thiocyanate ion (SCN) equilibrium distributions were measured in order to calculate transmembrane electrical potentials, using tetraphenylboron as a catalyst to facilitate TPMP equilibrium. Transmembrane potentials of -7 to -10 mV were calculated from SCN and TPMP, respectively for red cells, and -35 to -52 mV respectively, in the case of lymphocytes. Distributions of TPMP and potassium ions were determined in the presence of valinomycin over a wide range of extracellular potassium concentrations for red cells and the calculated Nernst potentials for TPMP compared to the calculated potential using the Goldman equation for chloride and potassium ions. Distributions of TPMP, SCN and potassium ions were also determined for lymphocyte suspensions as a function of extracellular potassium and the calculated Nernst potentials for TPMP and SCN compared to the calculated potassium diffusion potential.
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Holian A, Deutsch CJ, Holian SK, Daniele RP, Wilson DF. Lymphocyte response to phytohemagglutinin: intracellular volume and intracellular [K+]. J Cell Physiol 1979; 98:137-44. [PMID: 762191 DOI: 10.1002/jcp.1040980115] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The effect of phytohemagglutinin (PHA) on lymphocytes was examined with respect to free intracellular water volume and intracellular [K+]. At a cell concentration of 30 X 10(6) lymphocytes/ml in modified Hank's Buffered Salt Solution (HBSS) in the presence of 10% human AB serum, addition of PHA at 3 mg/ml resulted in a 24-27% decrease in free intracellular water space within 30 to 60 minutes and a return to control level after three hours. A larger change in intracellular water (44%) was observed under similar conditions in the absence of serum. The absolute intracellular K+ content did not change after PHA addition, but the cell water volume decrease arising from PHA addition resulted in a 29% increase in intracellular [K+] at 60 minutes. The decrease in lymphocyte water volume induced by PHA was also observed for concanavalin A which stimulates lymphocyte proliferation, but not for wheat germ lectin, an agglutinating agent which is not mitogenic. Thus, volume regulation may be closely associated with the mitogenicity of these compounds.
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DeLong J, Civan MM. Dissociation of cellular K+ accumulation from net Na+ transport by toad urinary bladder. J Membr Biol 1978; 42:19-43. [PMID: 97388 DOI: 10.1007/bf01870392] [Citation(s) in RCA: 42] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Daniele RP, Holian SK, Nowell PC. A potassium ionophore (Nigericin) inhibits stimulation of human lymphocytes by mitogens. J Exp Med 1978; 147:571-81. [PMID: 146727 PMCID: PMC2184504 DOI: 10.1084/jem.147.2.571] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Nigericin, an ionophore that exchanges K+ for H+ across most biologic membranes, reversibly inhibited the proliferative response of human lymphocytes to phytohemagglutinin (PHA). Inhibition occurred at nigericin concentrations of 10(-8) M or greater, and only during the early event of mitogenesis. There was no effect if nigericin was added 24 h or later after the initiation of PHA-stimulated cultures. The effect was not the result of toxicity or impaired mitochondrial respiration. At similar concentrations, nigericin also inhibited lymphocyte responses in mixed lymphocyte cultures and to other mitogens including concanavalin A, pokeweed mitogen, and the calcium ionophore A23187. The findings support the view that one or more transmembranous events, mediated by changes in cation flux and/or membrane potential, are critical in the initial stages of lymphocyte mitogenesis.
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A potassium ionophore (valinomycin) inhibits lymphocyte proliferation by its effects on the cell membrane. Proc Natl Acad Sci U S A 1977; 74:392. [PMID: 16592380 PMCID: PMC393268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2023] Open
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