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Kell DB. A protet-based, protonic charge transfer model of energy coupling in oxidative and photosynthetic phosphorylation. Adv Microb Physiol 2021; 78:1-177. [PMID: 34147184 DOI: 10.1016/bs.ampbs.2021.01.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Textbooks of biochemistry will explain that the otherwise endergonic reactions of ATP synthesis can be driven by the exergonic reactions of respiratory electron transport, and that these two half-reactions are catalyzed by protein complexes embedded in the same, closed membrane. These views are correct. The textbooks also state that, according to the chemiosmotic coupling hypothesis, a (or the) kinetically and thermodynamically competent intermediate linking the two half-reactions is the electrochemical difference of protons that is in equilibrium with that between the two bulk phases that the coupling membrane serves to separate. This gradient consists of a membrane potential term Δψ and a pH gradient term ΔpH, and is known colloquially as the protonmotive force or pmf. Artificial imposition of a pmf can drive phosphorylation, but only if the pmf exceeds some 150-170mV; to achieve in vivo rates the imposed pmf must reach 200mV. The key question then is 'does the pmf generated by electron transport exceed 200mV, or even 170mV?' The possibly surprising answer, from a great many kinds of experiment and sources of evidence, including direct measurements with microelectrodes, indicates it that it does not. Observable pH changes driven by electron transport are real, and they control various processes; however, compensating ion movements restrict the Δψ component to low values. A protet-based model, that I outline here, can account for all the necessary observations, including all of those inconsistent with chemiosmotic coupling, and provides for a variety of testable hypotheses by which it might be refined.
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Affiliation(s)
- Douglas B Kell
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative, Biology, University of Liverpool, Liverpool, United Kingdom; The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark.
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2
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Jindal S, Yang L, Day PJ, Kell DB. Involvement of multiple influx and efflux transporters in the accumulation of cationic fluorescent dyes by Escherichia coli. BMC Microbiol 2019; 19:195. [PMID: 31438868 PMCID: PMC6704527 DOI: 10.1186/s12866-019-1561-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 07/31/2019] [Indexed: 12/11/2022] Open
Abstract
Background It is widely believed that most xenobiotics cross biomembranes by diffusing through the phospholipid bilayer, and that the use of protein transporters is an occasional adjunct. According to an alternative view, phospholipid bilayer transport is negligible, and several different transporters may be involved in the uptake of an individual molecular type. We recognise here that the availability of gene knockout collections allows one to assess the contributions of all potential transporters, and flow cytometry based on fluorescence provides a convenient high-throughput assay for xenobiotic uptake in individual cells. Results We used high-throughput flow cytometry to assess the ability of individual gene knockout strains of E coli to take up two membrane-permeable, cationic fluorescent dyes, namely the carbocyanine diS-C3(5) and the DNA dye SYBR Green. Individual strains showed a large range of distributions of uptake. The range of modal steady-state uptakes for the carbocyanine between the different strains was 36-fold. Knockouts of the ATP synthase α- and β-subunits greatly inhibited uptake, implying that most uptake was ATP-driven rather than being driven by a membrane potential. Dozens of transporters changed the steady-state uptake of the dye by more than 50% with respect to that of the wild type, in either direction (increased or decreased); knockouts of known influx and efflux transporters behaved as expected, giving credence to the general strategy. Many of the knockouts with the most reduced uptake were transporter genes of unknown function (‘y-genes’). Similarly, several overexpression variants in the ‘ASKA’ collection had the anticipated, opposite effects. Similar results were obtained with SYBR Green (the range being approximately 69-fold). Although it too contains a benzothiazole motif there was negligible correlation between its uptake and that of the carbocyanine when compared across the various strains (although the membrane potential is presumably the same in each case). Conclusions Overall, we conclude that the uptake of these dyes may be catalysed by a great many transporters of putatively broad and presently unknown specificity, and that the very large range between the ‘lowest’ and the ‘highest’ levels of uptake, even in knockouts of just single genes, implies strongly that phospholipid bilayer transport is indeed negligible. This work also casts serious doubt upon the use of such dyes as quantitative stains for representing either bioenergetic parameters or the amount of cellular DNA in unfixed cells (in vivo). By contrast, it opens up their potential use as transporter assay substrates in high-throughput screening. Electronic supplementary material The online version of this article (10.1186/s12866-019-1561-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Srijan Jindal
- Department of Chemistry, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK.,Manchester Institute of Biotechnology, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK.,Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK
| | - Lei Yang
- Novo Nordisk Foundation Centre for Biosustainability, Technical University of Denmark, Building 220, Kemitorvet, 2800 Kgs, Lyngby, Denmark
| | - Philip J Day
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK.,Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK
| | - Douglas B Kell
- Department of Chemistry, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK. .,Manchester Institute of Biotechnology, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK. .,Novo Nordisk Foundation Centre for Biosustainability, Technical University of Denmark, Building 220, Kemitorvet, 2800 Kgs, Lyngby, Denmark. .,Department of Biochemistry, Institute of Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Crown St, Liverpool, L69 7ZB, UK.
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Diamandakis D, Zieminska E, Siwiec M, Tokarski K, Salinska E, Lenart J, Hess G, Lazarewicz JW. Tetrabromobisphenol A-induced depolarization of rat cerebellar granule cells: ex vivo and in vitro studies. CHEMOSPHERE 2019; 223:64-73. [PMID: 30769291 DOI: 10.1016/j.chemosphere.2019.02.032] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 02/05/2019] [Accepted: 02/07/2019] [Indexed: 06/09/2023]
Abstract
The brominated flame retardant tetrabromobisphenol A (TBBPA) is toxic to cultured brain neurons, and glutamate receptors partially mediate this effect; consequently, the depolarizing effect of TBBPA on neurons is to be expected, but it is yet to be actually demonstrated. The aim of this study was to detect TBBPA-evoked depolarization and identify the underlying mechanisms. The plasma membrane potential of rat cerebellar granule cells (CGC) in cerebellar slices or in primary cultures was measured using whole-cell current clamp recordings, or the fluorescent probe oxonol VI, respectively. The contribution of NMDA and AMPA receptors, voltage-gated sodium channels and intracellular calcium mobilization was tested using their selective antagonists or inhibitors. Direct interactions of TBBPA with NMDARs were tested by measuring the specific binding of radiolabeled NMDAR ligands to isolated rat cortical membrane fraction. TBBPA (25 μM) strongly depolarized CGC in cerebellar slices, and at ≥ 7.5 μM concentration-dependently depolarized primary CGC cultures. Depolarization of the primary CGC by 25 μM TBBPA was partly reduced when MK-801 was applied alone or in combination with either TTX or CNQX, or where bastadin 12 was applied in combination with ryanodine, whereas depolarization was completely prevented when MK-801, CNQX and TTX where combined. TBBPA had no effect on the specific binding of NMDAR radio-ligands to isolated cortical membranes. These results demonstrate the depolarizing effect of TBBPA on CGC, which is mainly mediated by ionotropic glutamate receptors, while voltage-gated sodium channels are also involved. We found no evidence for the direct activation of NMDARs by TBBPA.
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Affiliation(s)
- Dominik Diamandakis
- Department of Neurochemistry, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawinskiego 5, 02-106, Warsaw, Poland.
| | - Elzbieta Zieminska
- Department of Neurochemistry, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawinskiego 5, 02-106, Warsaw, Poland.
| | - Marcin Siwiec
- Department of Physiology, Institute of Pharmacology, Polish Academy of Sciences, Smetna 12, 31-343, Krakow, Poland.
| | - Krzysztof Tokarski
- Department of Physiology, Institute of Pharmacology, Polish Academy of Sciences, Smetna 12, 31-343, Krakow, Poland.
| | - Elzbieta Salinska
- Department of Neurochemistry, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawinskiego 5, 02-106, Warsaw, Poland.
| | - Jacek Lenart
- Department of Neurochemistry, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawinskiego 5, 02-106, Warsaw, Poland.
| | - Grzegorz Hess
- Department of Physiology, Institute of Pharmacology, Polish Academy of Sciences, Smetna 12, 31-343, Krakow, Poland.
| | - Jerzy W Lazarewicz
- Department of Neurochemistry, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawinskiego 5, 02-106, Warsaw, Poland.
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Control of transmembrane charge transfer in cytochrome c oxidase by the membrane potential. Nat Commun 2018; 9:3187. [PMID: 30093670 PMCID: PMC6085328 DOI: 10.1038/s41467-018-05615-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 07/09/2018] [Indexed: 11/08/2022] Open
Abstract
The respiratory chain in mitochondria is composed of membrane-bound proteins that couple electron transfer to proton translocation across the inner membrane. These charge-transfer reactions are regulated by the proton electrochemical gradient that is generated and maintained by the transmembrane charge transfer. Here, we investigate this feedback mechanism in cytochrome c oxidase in intact inner mitochondrial membranes upon generation of an electrochemical potential by hydrolysis of ATP. The data indicate that a reaction step that involves proton uptake to the catalytic site and presumably proton translocation is impaired by the potential, but electron transfer is not affected. These results define the order of electron and proton-transfer reactions and suggest that the proton pump is regulated by the transmembrane electrochemical gradient through control of internal proton transfer rather than by control of electron transfer.
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Sundaram GSM, Binz K, Sharma V, Yeung M, Sharma V. Live-cell fluorescence imaging: assessment of thioflavin T uptake in human epidermal carcinoma cells. MEDCHEMCOMM 2018; 9:946-950. [PMID: 30108983 PMCID: PMC6072315 DOI: 10.1039/c8md00101d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 03/14/2018] [Indexed: 11/21/2022]
Abstract
Thioflavin T (ThT), a positively charged heterocyclic small molecule, is a widely used fluorescent marker of amyloid pathophysiology to confirm the cause of death in post mortem brain tissue of Alzheimer's disease (AD) patients. Literature precedents indicate that current positron emission tomography (PET) agents, such as 11C-PIB and 18F-flutemetamol, share significant structural similarity with ThT, a lipophilic dye which does not traverse the blood-brain barrier (BBB) to enable the detection of Aβ plaques in vivo. While vital for maintaining normal physiology and healthy brain function, the BBB comprises brain endothelial cells sealed via paracellular protein complexes, bound by an extracellular matrix forming tight junctions thus controlling the delivery of molecules into the brain. The human P-glycoprotein (Pgp/ABCB1, 170 kD plasma membrane protein), belonging to the ABC family of efflux transporter proteins, also lines the luminal surface of brain endothelial cells thus poised to secrete its recognized substrates into the blood. Herein, we postulate that thioflavin T (ThT), due to its physico-chemical attributes, such as moderate lipophilicity and protonated nitrogen, could very well be recognized as a transport substrate of Pgp (P-glycoprotein, ABCB1) thus restricting its permeation into the brain. To evaluate whether or not ThT is indeed recognized by Pgp as its transport substrate thus limiting its BBB permeability, herein, we evaluate cellular accumulation profiles of ThT and PiB (a similar structural uncharged mimetic) in human epidermal carcinoma KB-3-1 (Pgp-) and MDR KB-8-5 (Pgp+) cells, using live-cell fluorescence imaging. While ThT penetrates KB-3-1 cells, it gets excluded from KB-8-5 cells, and also indicates LY335979-induced uptake in Pgp-expressing cells. Furthermore, the cellular uptake profiles of PiB are not impacted by the expression of Pgp under identical conditions. These data show that uptake profiles of ThT have been modified by the expression of Pgp in these cells, and are inversely proportional to the expression of the transporter protein located on the plasma membrane of these cells. Combined data demonstrate that ThT is efficiently recognized by Pgp as its transport substrate.
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Affiliation(s)
- G S M Sundaram
- ICCE Institute , Molecular Imaging Center , Mallinckrodt Institute of Radiology , Washington University School of Medicine , St. Louis , MO 63110 , USA .
| | - Kristen Binz
- ICCE Institute , Molecular Imaging Center , Mallinckrodt Institute of Radiology , Washington University School of Medicine , St. Louis , MO 63110 , USA .
| | - Vedica Sharma
- ICCE Institute , Molecular Imaging Center , Mallinckrodt Institute of Radiology , Washington University School of Medicine , St. Louis , MO 63110 , USA .
| | - Melany Yeung
- Students and Teachers as Research Scientists (STARS) Program , USA
| | - Vijay Sharma
- ICCE Institute , Molecular Imaging Center , Mallinckrodt Institute of Radiology , Washington University School of Medicine , St. Louis , MO 63110 , USA .
- Students and Teachers as Research Scientists (STARS) Program , USA
- Department of Neurology , Washington University School of Medicine , St. Louis , MO 63110 , USA
- Department of Biomedical Engineering , School of Engineering & Applied Science , Washington University , St. Louis 63105 , USA
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Southall J, Henry SL, Gardiner AT, Roszak AW, Mullen W, Carey AM, Kelly SM, de Percin Northumberland CO, Cogdell RJ. Characterisation of a pucBA deletion mutant from Rhodopseudomonas palustris lacking all but the pucBA d genes. PHOTOSYNTHESIS RESEARCH 2018; 135:9-21. [PMID: 28567613 PMCID: PMC5783997 DOI: 10.1007/s11120-017-0386-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 04/08/2017] [Indexed: 06/01/2023]
Abstract
Rhodopseudomonas palustris is a species of purple photosynthetic bacteria that has a multigene family of puc genes that encode the alpha and beta apoproteins, which form the LH2 complexes. A genetic dissection strategy has been adopted in order to try and understand which spectroscopic form of LH2 these different genes produce. This paper presents a characterisation of one of the deletion mutants generated in this program, the pucBAd only mutant. This mutant produces an unusual spectroscopic form of LH2 that only has a single large NIR absorption band at 800 nm. Spectroscopic and pigment analyses on this complex suggest that it has basically a similar overall structure as that of the wild-type HL LH2 complex. The mutant has the unique phenotype where the mutant LH2 complex is only produced when cells are grown at LL. At HL the mutant only produces the LH1-RC core complex.
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Affiliation(s)
- June Southall
- Institute of Molecular Cell and Systems Biology, University of Glasgow, 126 University Place, Glasgow, G12 8TA, Scotland, UK.
| | - Sarah L Henry
- Biomedical Engineering, School of Engineering, University of Glasgow, 126 University Place, Glasgow, G12 8TA, Scotland, UK
| | - Alastair T Gardiner
- Institute of Molecular Cell and Systems Biology, University of Glasgow, 126 University Place, Glasgow, G12 8TA, Scotland, UK
| | - Aleksander W Roszak
- Institute of Molecular Cell and Systems Biology, University of Glasgow, 126 University Place, Glasgow, G12 8TA, Scotland, UK
| | - William Mullen
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, 126 University Place, Glasgow, G12 8TA, Scotland, UK
| | - Anne-Marie Carey
- Center for Innovations in Medicine, The Biodesign Institute, Arizona State University, 1001 S. McAllister Ave., Tempe, AZ, 85287-5001, USA
| | - Sharon M Kelly
- Institute of Molecular Cell and Systems Biology, University of Glasgow, 126 University Place, Glasgow, G12 8TA, Scotland, UK
| | | | - Richard J Cogdell
- Institute of Molecular Cell and Systems Biology, University of Glasgow, 126 University Place, Glasgow, G12 8TA, Scotland, UK
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Renauld S, Cortes S, Bersch B, Henry X, De Waard M, Schaack B. Functional reconstitution of cell-free synthesized purified Kv channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:2373-2380. [DOI: 10.1016/j.bbamem.2017.09.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 08/29/2017] [Accepted: 09/05/2017] [Indexed: 12/11/2022]
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de la Fuente-Herreruela D, Gónzalez-Charro V, Almendro-Vedia VG, Morán M, Martín MÁ, Lillo MP, Natale P, López-Montero I. Rhodamine-based sensor for real-time imaging of mitochondrial ATP in living fibroblasts. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017; 1858:999-1006. [PMID: 28947254 PMCID: PMC5656571 DOI: 10.1016/j.bbabio.2017.09.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 09/05/2017] [Accepted: 09/20/2017] [Indexed: 11/24/2022]
Abstract
Mitochondria are essential for the production and maintenance of ATP in the eukaryotic cell. To image and monitor intracellular ATP level without cell breakage, biological and chemical sensors were developed in the last years. Here, we have internalized a rhodamine-based sensor RSL+ into living cells and monitored the mitochondrial ATP levels in cultured mouse embryonic fibroblasts. To evaluate the robustness of the sensor we imaged the changes of the mitochondrial ATP levels under non-physiological conditions upon incubation with FCCP, oligomycin, azide, deoxyglucose or phosphoenolpyruvate; all compounds that interfere with ATP homeostasis of the cell. The ATP sensor allowed us to determine the mitochondrial ATP levels in human skin fibroblasts where we observe a similar amount of ATP compared to mouse embryonic fibroblasts. We propose the RSL+ to be a valuable tool for the assessment of mitochondrial dysfunction in human cells derived from mitochondrial OXPHOS patients and for basic studies on bioenergetics metabolism. The rhodamine-based sensor RSL+ permeates efficiently eukaryotic plasma membrane and accumulates in mitochondria. RSL+ detects mitochondrial ATP levels in human and mouse skin fibroblasts. RSL+ detects real-time variations of mitochondrial ATP levels under non-physiological conditions.
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Affiliation(s)
- Diego de la Fuente-Herreruela
- Dto. Química Física I, Universidad Complutense de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain; Instituto de Investigación Hospital "12 de Octubre" (i+12), Avenida de Córdoba, s/n, 28041 Madrid, Spain
| | - Vicente Gónzalez-Charro
- Dto. Química Física I, Universidad Complutense de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain; Instituto de Investigación Hospital "12 de Octubre" (i+12), Avenida de Córdoba, s/n, 28041 Madrid, Spain
| | - Víctor G Almendro-Vedia
- Dto. Química Física I, Universidad Complutense de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain; Instituto de Investigación Hospital "12 de Octubre" (i+12), Avenida de Córdoba, s/n, 28041 Madrid, Spain
| | - María Morán
- Instituto de Investigación Hospital "12 de Octubre" (i+12), Avenida de Córdoba, s/n, 28041 Madrid, Spain; U723, Centro de Investigación Biomédica en Red en Enfermedades Raras (CIBERER), Madrid, Spain
| | - Miguel Ángel Martín
- Instituto de Investigación Hospital "12 de Octubre" (i+12), Avenida de Córdoba, s/n, 28041 Madrid, Spain; U723, Centro de Investigación Biomédica en Red en Enfermedades Raras (CIBERER), Madrid, Spain
| | - M Pilar Lillo
- Grupo de Fluorescencia y Biofísica Molecular, Instituto Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain
| | - Paolo Natale
- Dto. Química Física I, Universidad Complutense de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain; Instituto de Investigación Hospital "12 de Octubre" (i+12), Avenida de Córdoba, s/n, 28041 Madrid, Spain
| | - Iván López-Montero
- Dto. Química Física I, Universidad Complutense de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain; Instituto de Investigación Hospital "12 de Octubre" (i+12), Avenida de Córdoba, s/n, 28041 Madrid, Spain.
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Gianpiero C, Anis D, Aikaterini R, Eirini T, Ioannis VS, Dimitrios FG, John T. Boron-containing delocalised lipophilic cations for the selective targeting of cancer cells. MEDCHEMCOMM 2017; 8:67-72. [PMID: 30108691 PMCID: PMC6072302 DOI: 10.1039/c6md00383d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 10/26/2016] [Indexed: 11/25/2022]
Abstract
To limit the incidence of relapse, cancer treatments must not promote the emergence of drug resistance in tumour and cancer stem cells. Under the proviso that a therapeutic amount of boron is selectively delivered to cancer cells, Boron Neutron Capture Therapy (BNCT) may represent one approach that meets this requirement. To this end, we report the synthesis and pharmacology of several chemical entities, based on boron-rich carborane moieties that are functionalised with Delocalized Lipophilic Cations (DLCs), which selectively target the mitochondria of tumour cells. The treatment of tumour and cancer stem cells (CSCs) with such DLC-functionalized carboranes (DLC-carboranes) induces cell growth arrest that is both highly cancer-cell-selective and permanent. Experiments involving cultures of normal and cancer cells show that only normal cells exhibit recapitulation of their proliferation potential upon removal of the DLC-carborane treatment. At the molecular level, the pharmacological effect of DLC-carboranes is exerted through activation of the p53/p21 axis.
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Affiliation(s)
- Calabrese Gianpiero
- School of Life Science, Pharmacy and Chemistry , Kingston University London , Penrhyn Road , Kingston-upon-Thames , Surrey KT1 2EE , UK .
| | - Daou Anis
- School of Life Science, Pharmacy and Chemistry , Kingston University London , Penrhyn Road , Kingston-upon-Thames , Surrey KT1 2EE , UK .
| | - Rova Aikaterini
- Department of Pharmacology , School of Pharmacy , Aristotle University of Thessaloniki , GR-54124 Thessaloniki , Greece
| | - Tseligka Eirini
- Department of Pharmacology , School of Pharmacy , Aristotle University of Thessaloniki , GR-54124 Thessaloniki , Greece
| | - Vizirianakis S Ioannis
- Department of Pharmacology , School of Pharmacy , Aristotle University of Thessaloniki , GR-54124 Thessaloniki , Greece
| | - Fatouros G Dimitrios
- Department of Pharmaceutical Technology , School of Pharmacy , Aristotle University of Thessaloniki , GR-54124 Thessaloniki , Greece
| | - Tsibouklis John
- School of Pharmacy and Biomedical Sciences , University of Portsmouth , Portsmouth , PO1 2DT , UK
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Sautrey G, El Khoury M, Dos Santos AG, Zimmermann L, Deleu M, Lins L, Décout JL, Mingeot-Leclercq MP. Negatively Charged Lipids as a Potential Target for New Amphiphilic Aminoglycoside Antibiotics: A BIOPHYSICAL STUDY. J Biol Chem 2016; 291:13864-74. [PMID: 27189936 DOI: 10.1074/jbc.m115.665364] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Indexed: 11/06/2022] Open
Abstract
Bacterial membranes are highly organized, containing specific microdomains that facilitate distinct protein and lipid assemblies. Evidence suggests that cardiolipin molecules segregate into such microdomains, probably conferring a negative curvature to the inner plasma membrane during membrane fission upon cell division. 3',6-Dinonyl neamine is an amphiphilic aminoglycoside derivative active against Pseudomonas aeruginosa, including strains resistant to colistin. The mechanisms involved at the molecular level were identified using lipid models (large unilamellar vesicles, giant unilamelllar vesicles, and lipid monolayers) that mimic the inner membrane of P. aeruginosa The study demonstrated the interaction of 3',6-dinonyl neamine with cardiolipin and phosphatidylglycerol, two negatively charged lipids from inner bacterial membranes. This interaction induced membrane permeabilization and depolarization. Lateral segregation of cardiolipin and membrane hemifusion would be critical for explaining the effects induced on lipid membranes by amphiphilic aminoglycoside antibiotics. The findings contribute to an improved understanding of how amphiphilic aminoglycoside antibiotics that bind to negatively charged lipids like cardiolipin could be promising antibacterial compounds.
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Affiliation(s)
- Guillaume Sautrey
- From the Université Catholique de Louvain, Louvain Drug Research Institute, Pharmacologie Cellulaire et Moléculaire, Avenue E. Mounier 73, UCL B1.73.05 Bruxelles, Belgium
| | - Micheline El Khoury
- From the Université Catholique de Louvain, Louvain Drug Research Institute, Pharmacologie Cellulaire et Moléculaire, Avenue E. Mounier 73, UCL B1.73.05 Bruxelles, Belgium
| | - Andreia Giro Dos Santos
- From the Université Catholique de Louvain, Louvain Drug Research Institute, Pharmacologie Cellulaire et Moléculaire, Avenue E. Mounier 73, UCL B1.73.05 Bruxelles, Belgium
| | - Louis Zimmermann
- the Département de Pharmacochimie Moléculaire, Université de Grenoble, Alpes/CNRS, UMR 5063, ICMG FR 2607, 470 Rue de la Chimie, BP 53, F-38041 Grenoble, France, and
| | - Magali Deleu
- the Laboratoire de Biophysique Moleculaire aux Interfaces, Université de Liège, Gembloux Agro-Bio Tech, Passage des Déportés, 2, B-5030 Gembloux, Belgium
| | - Laurence Lins
- the Laboratoire de Biophysique Moleculaire aux Interfaces, Université de Liège, Gembloux Agro-Bio Tech, Passage des Déportés, 2, B-5030 Gembloux, Belgium
| | - Jean-Luc Décout
- the Département de Pharmacochimie Moléculaire, Université de Grenoble, Alpes/CNRS, UMR 5063, ICMG FR 2607, 470 Rue de la Chimie, BP 53, F-38041 Grenoble, France, and
| | - Marie-Paule Mingeot-Leclercq
- From the Université Catholique de Louvain, Louvain Drug Research Institute, Pharmacologie Cellulaire et Moléculaire, Avenue E. Mounier 73, UCL B1.73.05 Bruxelles, Belgium,
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11
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Skarabahatava AS, Lukyanenko LM, Slobozhanina EI, Falcioni ML, Orlando P, Silvestri S, Tiano L, Falcioni G. Plasma and mitochondrial membrane perturbation induced by aluminum in human peripheral blood lymphocytes. J Trace Elem Med Biol 2015; 31:37-44. [PMID: 26004890 DOI: 10.1016/j.jtemb.2015.02.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 02/06/2015] [Accepted: 02/12/2015] [Indexed: 01/31/2023]
Abstract
Aluminum is a redox-inert element that could induce cell damage via activation of oxidative stress. In this work, the effect of aluminum on different cellular compartments of human peripheral blood lymphocytes was studied. The presence of aluminum induced a lipid peroxidation and physico-chemical modifications at the membrane level. A decrease in fluorescence anisotropy of TMA-DPH and in the polarity of the lipid bilayer with a concomitant shift toward a gel phase was observed, while the pyrene excimerization coefficient (Kex) increased. Flow cytometry measurements, using JC-1, Rhodamine 123 and H2-DCFDA as fluorescent probes, indicated that aluminum induces a slight mitochondrial membrane depolarization that was associated with a moderate increase in reactive oxygen species production. A significative influence on these parameters was measured only at high aluminum concentration.
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Affiliation(s)
| | | | | | | | - Patrick Orlando
- Department of Clinical Dental Sciences, Polytechnic University of Marche, via Ranieri 60131, Ancona, Italy
| | - Sonia Silvestri
- Department of Clinical Dental Sciences, Polytechnic University of Marche, via Ranieri 60131, Ancona, Italy
| | - Luca Tiano
- Department of Clinical Dental Sciences, Polytechnic University of Marche, via Ranieri 60131, Ancona, Italy.
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12
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Shrestha JP, Subedi YP, Chen L, Chang CWT. A mode of action study of cationic anthraquinone analogs: a new class of highly potent anticancer agents. MEDCHEMCOMM 2015. [DOI: 10.1039/c5md00314h] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Previously, we reported the synthesis and structure–activity relationship (SAR) study of a series of novel 4,9-dioxo-4,9-dihydro-1H-naphtho[2,3-d][1,2,3]triazol-3-ium salts, which had very potent anti-proliferative activities (low μM to nM GI50) against a broad range of cancer cells.
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Affiliation(s)
- Jaya P. Shrestha
- Department of Chemistry and Biochemistry
- Utah State University
- Logan
- USA
| | | | - Liaohai Chen
- Department of Chemistry and Biochemistry
- Utah State University
- Logan
- USA
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13
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Abstract
In the past decade, optical mapping provided crucial mechanistic insight into electromechanical function and the mechanism of ventricular fibrillation. Therefore, to date, optical mapping dominates experimental cardiac electrophysiology. The first cardiac measurements involving optics were done in the early 1900s using the fast cinematograph that later evolved into methods for high-resolution activation and repolarization mapping and stimulation of specific cardiac cell types. The field of "optocardiography," therefore, emerged as the use of light for recording or interfering with cardiac physiology. In this review, we discuss how optocardiography developed into the dominant research technique in experimental cardiology. Furthermore, we envision how optocardiographic methods can be used in clinical cardiology.
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14
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Detection of proton movement directly across viral membranes to identify novel influenza virus M2 inhibitors. J Virol 2013; 87:10679-86. [PMID: 23885079 DOI: 10.1128/jvi.01190-13] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The influenza virus M2 protein is a well-validated yet underexploited proton-selective ion channel essential for influenza virus infectivity. Because M2 is a toxic viral ion channel, existing M2 inhibitors have been discovered through live virus inhibition or medicinal chemistry rather than M2-targeted high-throughput screening (HTS), and direct measurement of its activity has been limited to live cells or reconstituted lipid bilayers. Here, we describe a cell-free ion channel assay in which M2 ion channels are incorporated into virus-like particles (VLPs) and proton conductance is measured directly across the viral lipid bilayer, detecting changes in membrane potential, ion permeability, and ion channel function. Using this approach in high-throughput screening of over 100,000 compounds, we identified 19 M2-specific inhibitors, including two novel chemical scaffolds that inhibit both M2 function and influenza virus infectivity. Counterscreening for nonspecific disruption of viral bilayer ion permeability also identified a broad-spectrum antiviral compound that acts by disrupting the integrity of the viral membrane. In addition to its application to M2 and potentially other ion channels, this technology enables direct measurement of the electrochemical and biophysical characteristics of viral membranes.
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15
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Ahyayauch H, Arnulphi C, Sot J, Alonso A, Goñi FM. The onset of Triton X-100 solubilization of sphingomyelin/ceramide bilayers: effects of temperature and composition. Chem Phys Lipids 2013; 167-168:57-61. [PMID: 23453949 DOI: 10.1016/j.chemphyslip.2013.02.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Accepted: 02/06/2013] [Indexed: 12/01/2022]
Abstract
The early stages of Triton X-100 solubilization of bilayers consisting of sphingomyelin/ceramide (SM/Cer) mixtures have been studied using a combination of calorimetric and spectroscopic techniques. Compositions based on sphingomyelin, containing up to 30 mol% Cer, at 4, 20 and 50°C have been examined. The presence of Cer does not modify the affinity (in terms of ΔG of binding per mol total lipid) of the SM-based bilayers for Triton X-100, although it does increase the amount of detergent required for the onset of solubilization. At 50°C more detergent was required to solubilize the SM/Cer bilayers than at 20°C. The data can be rationalized in terms of lipid and detergent geometries and interactions (Lichtenberg et al., 2013).
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Affiliation(s)
- Hasna Ahyayauch
- Unidad de Biofísica (Centro Mixto CSIC, UPV/EHU), Departamento de Bioquímica, Universidad del País Vasco, Bilbao, Spain
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16
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FLOW CYTOMETRIC MONITORING OF RHODAMINE 123 AND A CYANINE DYE UPTAKE BY YEAST DURING CIDER FERMENTATION. JOURNAL OF THE INSTITUTE OF BREWING 2013. [DOI: 10.1002/j.2050-0416.1996.tb00910.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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17
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Monitoring of real changes of plasma membrane potential by diS-C3(3) fluorescence in yeast cell suspensions. J Bioenerg Biomembr 2012; 44:559-69. [DOI: 10.1007/s10863-012-9458-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Accepted: 06/21/2012] [Indexed: 11/27/2022]
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18
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Ahyayauch H, Collado MI, Alonso A, Goñi FM. Lipid bilayers in the gel phase become saturated by triton X-100 at lower surfactant concentrations than those in the fluid phase. Biophys J 2012; 102:2510-6. [PMID: 22713566 DOI: 10.1016/j.bpj.2012.04.041] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 04/18/2012] [Accepted: 04/24/2012] [Indexed: 11/30/2022] Open
Abstract
It has been repeatedly observed that lipid bilayers in the gel phase are solubilized by lower concentrations of Triton X-100, at least within certain temperature ranges, or other nonionic detergents than bilayers in the fluid phase. In a previous study, we showed that detergent partition coefficients into the lipid bilayer were the same for the gel and the fluid phases. In this contribution, turbidity, calorimetry, and 31P-NMR concur in showing that bilayers in the gel state (at least down to 13-20°C below the gel-fluid transition temperature) become saturated with detergent at lower detergent concentrations than those in the fluid state, irrespective of temperature. The different saturation may explain the observed differences in solubilization.
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Affiliation(s)
- Hasna Ahyayauch
- Unidad de Biofísica (Centro Mixto CSIC-UPV/EHU) and Departamento de Bioquímica, Universidad del País Vasco, Bilbao, Spain
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19
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Das TK, Periasamy N, Krishnamoorthy G. Mechanism of response of potential-sensitive dyes studied by time-resolved fluorescence. Biophys J 2010; 64:1122-32. [PMID: 19431883 DOI: 10.1016/s0006-3495(93)81478-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The mechanism of response of two potential-sensitive dyes, diOC(2)(5) (3,3'-diethyloxadicarbocyanine iodide) and oxonol V (bis-[3-phenyl-5-oxoisoxazol-4-yl]pentamethine oxonol), were studied by using steady-state and time-resolved fluorescence techniques. The lipid concentration dependence of the Deltapsi (membrane potential)-induced change in total fluorescence intensity was quite different for these two dyes. Time-resolved fluorescence measurements showed that the fluorescence decay of these dyes in membranes could be resolved into at least three exponentials. Deltapsi-induced changes in the levels of these three populations were also measured under a variety of conditions. In the case of diOC(2)(5) an inside negative Deltapsi increased the levels of the bound forms. This shows that diOC(2)(5) responds to Deltapsi mainly by an "on-off" mechanism whereby Deltapsi perturbs the membrane-water partition coefficient of the dye. The Deltapsi-induced changes approached zero when the dye was totally membrane bound. In contrast, the Deltapsi-induced response of oxonol V increased with increased membrane binding. An inside negative Deltapsi decreased the level of the bound form with a longer lifetime. This shows that the mechanism of response of oxonol V is a Deltapsi-induced shift in the equilibrium between bound forms of the dye.
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Affiliation(s)
- T K Das
- Chemical Physics Group, Tata Institute of Fundamental Research, Homi Bhabha Road, Bombay 400 005, India
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20
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Shoup TM, Elmaleh DR, Brownell AL, Zhu A, Guerrero JL, Fischman AJ. Evaluation of (4-[18F]Fluorophenyl)triphenylphosphonium Ion. A Potential Myocardial Blood Flow Agent for PET. Mol Imaging Biol 2010; 13:511-517. [DOI: 10.1007/s11307-010-0349-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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21
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Juárez O, Athearn K, Gillespie P, Barquera B. Acid residues in the transmembrane helices of the Na+-pumping NADH:quinone oxidoreductase from Vibrio cholerae involved in sodium translocation. Biochemistry 2009; 48:9516-24. [PMID: 19694431 DOI: 10.1021/bi900845y] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Vibrio cholerae and many other marine and pathogenic bacteria possess a unique respiratory complex, the Na(+)-pumping NADH:quinone oxidoreductase (Na(+)-NQR), which pumps Na(+) across the cell membrane using the energy released by the redox reaction between NADH and ubiquinone. To function as a selective sodium pump, Na(+)-NQR must contain structures that (1) allow the sodium ion to pass through the hydrophobic core of the membrane and (2) provide cation specificity to the translocation system. In other sodium-transporting proteins, the structures that carry out these roles frequently include aspartate and glutamate residues. The negative charge of these residues facilitates binding and translocation of sodium. In this study, we have analyzed mutants of acid residues located in the transmembrane helices of subunits B, D, and E of Na(+)-NQR. The results are consistent with the participation of seven of these residues in the translocation process of sodium. Mutations at NqrB-D397, NqrD-D133, and NqrE-E95 produced a decrease of approximately >or=10-fold in the apparent affinity of the enzyme for sodium (Km(app)(Na+)), which suggests that these residues may form part of a sodium-binding site. Mutation at other residues, including NqrB-E28, NqrB-E144, NqrB-E346, and NqrD-D88, had a strong effect on the quinone reductase activity of the enzyme and its sodium sensitivity, but a weaker effect on the apparent sodium affinity, consistent with a possible role in sodium conductance pathways.
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Affiliation(s)
- Oscar Juárez
- Department of Biology and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
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22
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Chen LD, Liu J, Yu XF, He M, Pei XF, Tang ZY, Wang QQ, Pang DW, Li Y. The biocompatibility of quantum dot probes used for the targeted imaging of hepatocellular carcinoma metastasis. Biomaterials 2008; 29:4170-6. [PMID: 18691751 DOI: 10.1016/j.biomaterials.2008.07.025] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Accepted: 07/11/2008] [Indexed: 02/04/2023]
Abstract
Semiconductor quantum dots (QDs) have several photo-physical advantages over organic dyes making them good markers in biomedical application. We used CdSe/ZnS QDs with maximum emission wavelength of 590nm (QD590) linked to alpha-fetoprotein (AFP) monoclonal antibody (Ab) to detect AFP in cytoplasm of human hepatocellular carcinoma (HCC) cell line HCCLM6. For the in vivo studies, we used QD-AFP-Ab probes for targeted imaging of human HCC xenograft growing in nude mice by injecting them into the tail vein. In addition, the cytotoxicity in vitro, the acute toxicity in vivo, the hemodynamics and tissue distribution of these probes were also investigated. The results in vitro and in vivo indicate that our QD-based probes have good stability, specificity and biocompatibility for ultrasensitive fluorescence imaging of molecular targets in our liver cancer model system.
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Affiliation(s)
- Liang-Dong Chen
- Department of Oncology, Zhongnan Hospital of Wuhan University, Hubei Key Laboratory of Tumor Biological Behaviors, No. 169 Donghu Road, Wuchang District, Wuhan 430071, China
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23
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Abstract
Small-molecule fluorescent probes embody an essential facet of chemical biology. Although numerous compounds are known, the ensemble of fluorescent probes is based on a modest collection of modular "core" dyes. The elaboration of these dyes with diverse chemical moieties is enabling the precise interrogation of biochemical and biological systems. The importance of fluorescence-based technologies in chemical biology elicits a necessity to understand the major classes of small-molecule fluorophores. Here, we examine the chemical and photophysical properties of oft-used fluorophores and highlight classic and contemporary examples in which utility has been built upon these scaffolds.
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Affiliation(s)
| | - Ronald T. Raines
- Department of Chemistry
- Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706
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24
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Calabrese G, Gomes ACNM, Barbu E, Nevell TG, Tsibouklis J. Carborane-based derivatives of delocalised lipophilic cations for boron neutron capture therapy: synthesis and preliminary in vitro evaluation. ACTA ACUST UNITED AC 2008. [DOI: 10.1039/b806197a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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25
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Amoroso AJ, Arthur RJ, Coogan MP, Court JB, Fernández-Moreira V, Hayes AJ, Lloyd D, Millet C, Pope SJA. 3-Chloromethylpyridyl bipyridine fac-tricarbonyl rhenium: a thiol-reactive luminophore for fluorescence microscopy accumulates in mitochondria. NEW J CHEM 2008. [DOI: 10.1039/b802215a] [Citation(s) in RCA: 135] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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26
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Jilkina O, Kong HJ, Hwi L, Kuzio B, Xiang B, Manley D, Jackson M, Kupriyanov VV. Interaction of a mitochondrial membrane potential-sensitive dye, rhodamine 800, with rat mitochondria, cells, and perfused hearts. JOURNAL OF BIOMEDICAL OPTICS 2006; 11:014009. [PMID: 16526886 DOI: 10.1117/1.2159449] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Fluorescence, absorbance, and binding of a mitochondrial membrane potential-sensitive probe, rhodamine 800 (rhod800), were measured in isolated rat mitochondria, hepatocytes, cardiomyocytes, and hearts in the presence or absence of mitochondrial uncouplers. Excitation of rhod800 was achieved with laser diodes (690 or 670 nm) and resulted in a fluorescence peak at 720 nm. Greater than 99% of rhod800 (1 microM) was taken up from the buffer by energized mitochondria. This resulted in a fluorescence decrease by 77% (13% in de-energized mitochondria). Sixty-seven percent of rhod800 was taken up by cardiomyocytes and 75% by hepatocytes resulting in the fluorescence decrease by 16% and 37%, respectively, which were reversed by approximately 10% upon cell uncoupling. In hearts, binding, absorbance, and fluorescence were almost uncoupler-insensitive possibly due to rhod800 interaction outside of mitochondria. Fluorescence of the hearts perfused with 27.5 and 55 nM rhod800 was measured in orthogonal and reflection modes. The former provided deep tissue penetration (approximately a centimeter); however, nonlinearity between absorbance and fluorescence was evident. In the latter setting, depth of tissue penetration was approximately a millimeter, which eliminated an inner filter effect and restored linearity. We concluded that excessive hydrophobicity of rhod800 complicates detection of energy-dependent fluorescence changes in myocardium.
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Affiliation(s)
- Olga Jilkina
- National Research Council of Canada, Institute for Biodiagnostics, Winnipeg, Manitoba, Canada.
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27
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Plásek J, Vojtísková A, Houstek J. Flow-cytometric monitoring of mitochondrial depolarisation: from fluorescence intensities to millivolts. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2005; 78:99-108. [PMID: 15664496 DOI: 10.1016/j.jphotobiol.2004.09.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2004] [Revised: 09/23/2004] [Accepted: 09/24/2004] [Indexed: 11/16/2022]
Abstract
Redistribution potentiometric dyes represent a powerful tool for monitoring membrane potential of mitochondria, especially when these dyes are used with flow cytometry. In particular, tetramethylrhodamine methyl ester proved to be suitable for the screening of mitochondrial membrane potential in cultured human skin fibroblasts from patients suffering from different defects of oxidative phosphorylation. We have developed a method that makes it possible to measure the changes in mitochondrial membrane potential, or to assess the differences between respective mitochondrial membrane potentials in investigated cells and controls in the absolute scale of millivolts. Our approach employs the fact that a logarithmic transformation of Nernst equation-controlled intensity of fluorescence from potentiometric dyes accumulated in mitochondria leads to a linear scale for mitochondrial membrane potentials.
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Affiliation(s)
- J Plásek
- Faculty of Mathematics and Physics, Institute of Physics, Charles University, Ke Karlovu 5, 121 16 Prague, Czech Republic.
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28
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Lloyd D, Harris JC, Biagini GA, Hughes MR, Maroulis S, Bernard C, Wadley RB, Edwards MR. The plasma membrane of microaerophilic protists: oxidative and nitrosative stress. Microbiology (Reading) 2004; 150:1183-1190. [PMID: 15133079 DOI: 10.1099/mic.0.26834-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The trans-plasma-membrane electrochemical potential of microaerophilic protists was monitored by the use of voltage-sensitive charged lipophilic fluorophores; of the many available probes, the anionic oxonol dye bis(1,3-dibarbituric acid)-trimethine oxonol [DiBAC4(3)] is an example of one which has been successfully employed using fluorescence microscopy, confocal laser-scanning microscopy and flow cytometry. Several microaerophilic protists have been investigated with this dye; these were Giardia intestinalis, Trichomonas vaginalis, Tritrichomonas foetus, Hexamita inflata and Mastigamoeba punctachora. Under conditions where they exhibit normal vitality, these organisms exclude DiBAC4(3) by virtue of their maintenance of a plasma-membrane potential (negative inside). Uptake of the fluorophore is indicative of disturbance to this membrane (i.e. by inhibition of pump/leak balance, blockage of channels or generation of ionic leaks), and is indicative of metabolic perturbation or environmental stress. Here, it is shown that oxidative or nitrosative stress depolarizes the plasma membranes of the aforementioned O2-sensitive organisms and allows DiBAC4(3) influx. Oxonol uptake thereby provides a sensitive and early indication of plasma-membrane perturbation by agents that may lead to cytotoxicity and eventually to cell death by necrotic or apoptotic pathways.
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Affiliation(s)
- D Lloyd
- Microbiology (BIOSI 1) Main Building, Cardiff University, PO Box 915, Cardiff CF10 3TL, UK
| | - J C Harris
- Microbiology (BIOSI 1) Main Building, Cardiff University, PO Box 915, Cardiff CF10 3TL, UK
| | - G A Biagini
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, 2052, Australia
| | - M R Hughes
- Department of Chemistry, King's College University of London, Strand, London WC2R 2LS, UK
| | - S Maroulis
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, 2052, Australia
| | - C Bernard
- School of Science, Parramatta Campus, University of Western Sydney, Australia
| | - R B Wadley
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, 2052, Australia
| | - M R Edwards
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, 2052, Australia
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29
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Baracca A, Sgarbi G, Solaini G, Lenaz G. Rhodamine 123 as a probe of mitochondrial membrane potential: evaluation of proton flux through F0 during ATP synthesis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2003; 1606:137-46. [PMID: 14507434 DOI: 10.1016/s0005-2728(03)00110-5] [Citation(s) in RCA: 376] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Rhodamine 123 (RH-123) was used to monitor the membrane potential of mitochondria isolated from rat liver. Mitochondrial energization induces quenching of RH-123 fluorescence and the rate of fluorescence decay is proportional to the mitochondrial membrane potential. Exploiting the kinetics of RH-123 fluorescence quenching in the presence of succinate and ADP, when protons are both pumped out of the matrix driven by the respiratory chain complexes and allowed to diffuse back into the matrix through ATP synthase during ATP synthesis, we could obtain an overall quenching rate proportional to the steady-state membrane potential under state 3 condition. We measured the kinetics of fluorescence quenching by adding succinate and ADP in the absence and presence of oligomycin, which abolishes the ADP-driven potential decrease due to the back-flow of protons through the ATP synthase channel, F(0). As expected, the initial rate of quenching was significantly increased in the presence of oligomycin, and conversely preincubation with subsaturating concentrations of the uncoupler carbonyl cyanide p-trifluoro-metoxyphenilhydrazone (FCCP) induced a decreased rate of quenching. N,N'-dicyclohexylcarbodiimide (DCCD) behaved similarly to oligomycin in increasing the rate of quenching. These findings indicate that RH-123 fluorescence quenching kinetics give reliable and sensitive evaluation of mitochondrial membrane potential, complementing steady-state fluorescence measurements, and provide a mean to study proton flow from the mitochondrial intermembrane space to the matrix through the F(0) channel.
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Affiliation(s)
- Alessandra Baracca
- Department of Biochemistry "G Moruzzi" Alma Mater Studiorum-University of Bologna, Via Irnerio 48, I-40126, Bologna, Italy.
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30
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Sapra R, Bagramyan K, Adams MWW. A simple energy-conserving system: proton reduction coupled to proton translocation. Proc Natl Acad Sci U S A 2003; 100:7545-50. [PMID: 12792025 PMCID: PMC164623 DOI: 10.1073/pnas.1331436100] [Citation(s) in RCA: 230] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Oxidative phosphorylation involves the coupling of ATP synthesis to the proton-motive force that is generated typically by a series of membrane-bound electron transfer complexes, which ultimately reduce an exogenous terminal electron acceptor. This is not the case with Pyrococcus furiosus, an archaeon that grows optimally near 100 degrees C. It has an anaerobic respiratory system that consists of a single enzyme, a membrane-bound hydrogenase. Moreover, it does not require an added electron acceptor as the enzyme reduces protons, the simplest of acceptors, to hydrogen gas by using electrons from the cytoplasmic redox protein ferredoxin. It is demonstrated that the production of hydrogen gas by membrane vesicles of P. furiosus is directly coupled to the synthesis of ATP by means of a proton-motive force that has both electrochemical and pH components. Such a respiratory system enables rationalization in this organism of an unusual glycolytic pathway that was previously thought not to conserve energy. It is now clear that the use of ferredoxin in place of the expected NAD as the electron acceptor for glyceraldehyde 3-phosphate oxidation enables energy to be conserved by hydrogen production. In addition, this simple respiratory mechanism readily explains why the growth yields of P. furiosus are much higher than could be accounted for if ATP synthesis occurred only by substrate-level phosphorylation. The ability of microorganisms such as P. furiosus to couple hydrogen production to energy conservation has important ramifications not only in the evolution of respiratory systems but also in the origin of life itself.
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Affiliation(s)
- Rajat Sapra
- Department of Biochemistry and Molecular Biology, Center for Metalloenzyme Studies, University of Georgia, Athens, GA 30602-7229, USA
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31
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Cunderlíková B, Sikurová L, Moan J. pH, serum proteins and ionic strength influence the uptake of merocyanine 540 by WiDr cells and its interaction with membrane structures. Bioelectrochemistry 2003; 59:1-10. [PMID: 12699813 DOI: 10.1016/s1567-5394(02)00155-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
It has been suggested that selective uptake of photosensitizers is due to significantly lower pH of the interstitial fluid in tumors compared to normal tissue. Therefore, the cellular uptake of merocyanine 540 (MC 540) was examined at two pH values: 6.8+/-0.1 and 7.4+/-0.1. There was no difference in spectral properties (absorption and fluorescence maxima positions, fluorescence intensity) of the drug in the presence of increasing amounts of either human blood plasma or FCS (0-2%) at the two pH values investigated. Nevertheless, significantly higher amounts of the drug were taken up by WiDr cells at pH 6.8+/-0.1, both in the presence of 10% FCS and in the absence of FCS. The absorption spectra of MC 540 in the presence of egg phosphatidylcholine (PC) liposomes turned out to be NaCl concentration-dependent (0.00-0.30 mol l(-1)). Membrane fluidity, as measured by fluorescence anisotropy of diphenylhexatriene (DPH), was unchanged within the experimental error in the NaCl concentration range 0.01-0.30 mol l(-1). The spectral changes indicated an enhancement of the incorporation of MC 540 into lipid membranes with increasing ionic strength. Such a salt concentration dependence suggests a possible involvement of the surface potential in the interaction of MC 540 with lipid membranes. The results might provide an explanation of the pH dependency of the cellular uptake of MC 540 observed in this study.
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Affiliation(s)
- Beata Cunderlíková
- Department of Biophysics, Institute for Cancer Research, Montebello, N-0310 Oslo, Norway.
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32
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Armada SP, Farto R, Pérez MJ, Nieto TP. Effect of temperature, salinity and nutrient content on the survival responses of Vibrio splendidus biotype I. MICROBIOLOGY (READING, ENGLAND) 2003; 149:369-375. [PMID: 12624199 DOI: 10.1099/mic.0.25574-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The aim of this study was to evaluate the survival responses of two strains of Vibrio splendidus, both in natural and in defined media. For this purpose, freshwater and defined media containing different salinities (3.3-0.9 %) and nutrient concentrations (17-0.005 mg x l(-1)) were assayed. The incubation temperatures were established at 4, 10 and 22 degrees C. The acridine orange staining technique was used for total cell enumeration and the number of viable cells was determined using two direct assays, nalidixic acid and tetrazolium salt reduction and plate spreading. Resuscitation assays of viable but non-culturable (VBNC) cells were conducted. According to the counting procedures employed, at least four different subpopulations were found: (i). active (positive response in both nalidixic acid and tetrazolium assays) culturable cells; (ii). active non-culturable cells; (iii). tetrazolium-salt-responsive non-culturable cells and (iv). non-active (responsive to none of the direct viable assays) non-culturable cells. Long-term survival was found at salinities and nutrient concentrations of seawater environments (3.3 % and 5 mg x l(-1) or 1 g l(-1)), whereas the strains entered a VBNC state in freshwater and in brackish (0.9 or 1.6 % salinities) or high nutrient content (17 g x l(-1)) defined medium. The recovery of VBNC cells was not achieved.
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Affiliation(s)
- Susana P Armada
- Microbiología, Departamento de Biología Funcional y Ciencias de la Salud, Facultad de Ciencias, Universidad de Vigo, Lagoas-Marcosende s/n, 36200 Vigo, Spain
| | - Rosa Farto
- Microbiología, Departamento de Biología Funcional y Ciencias de la Salud, Facultad de Ciencias, Universidad de Vigo, Lagoas-Marcosende s/n, 36200 Vigo, Spain
| | - María J Pérez
- Microbiología, Departamento de Biología Funcional y Ciencias de la Salud, Facultad de Ciencias, Universidad de Vigo, Lagoas-Marcosende s/n, 36200 Vigo, Spain
| | - Teresa P Nieto
- Microbiología, Departamento de Biología Funcional y Ciencias de la Salud, Facultad de Ciencias, Universidad de Vigo, Lagoas-Marcosende s/n, 36200 Vigo, Spain
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Dzioba J, Häse CC, Gosink K, Galperin MY, Dibrov P. Experimental verification of a sequence-based prediction: F(1)F(0)-type ATPase of Vibrio cholerae transports protons, not Na(+) ions. J Bacteriol 2003; 185:674-8. [PMID: 12511516 PMCID: PMC145325 DOI: 10.1128/jb.185.2.674-678.2003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The membrane energetics of the intestinal pathogen Vibrio cholerae involves both H(+) and Na(+) as coupling ions. The sequence of the c subunit of V. cholerae F(0)F(1) ATPase suggested that this enzyme is H(+) specific, in contrast to the results of previous studies on the Na(+)-dependent ATP synthesis in closely related Vibrio spp. Measurements of the pH gradient and membrane potential in membrane vesicles isolated from wild-type and DeltaatpE mutant V. cholerae show that the F(1)F(0) ATPase of V. cholerae is an H(+), not Na(+), pump, confirming the bioinformatics assignments that were based on the Na(+)-binding model of S. Rahlfs and V. Müller (FEBS Lett. 404:269-271, 1999). Application of this model to the AtpE sequences from other bacteria and archaea indicates that Na(+)-specific F(1)F(0) ATPases are present in a number of important bacterial pathogens.
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Affiliation(s)
- Judith Dzioba
- Department of Microbiology, University of Manitoba, Winnipeg, Canada
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34
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Waczulikova I, Rozalski M, Rievaj J, Nagyova K, Bryszewska M, Watala C. Phosphatidylserine content is a more important contributor than transmembrane potential to interactions of merocyanine 540 with lipid bilayers. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1567:176-82. [PMID: 12488051 DOI: 10.1016/s0005-2736(02)00614-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Several factors, including the exposure of the negatively charged PL and transmembrane potential (TMP), may affect the binding of merocyanine 540 dye (MC540) to membrane lipids. Our aim was to quantify the significance of each of these two determinants in MC540 interactions with phosphatidylserine:phosphatidylcholine (PS/PC) vesicles. The effects of the altered PS content (PS/PC molar ratio: 5:95, 10:90 and 20:80) and TMP on MC540 binding were monitored using flow cytometry. Rapid [K(+)] flux across the vesicle membrane lipid bilayer was generated using valinomycin. We showed that the increased PS content leads to attenuated MC540 binding, while having no influence on the dynamic parameters of PS/PC vesicle membranes (electron spin resonance (ESR) spectrometry). Higher [K(+)](out) makes PS/PC liposomes bind more MC540, which implies that TMP-which becomes more positive inside the vesicles-favours the interactions of MC540 with the PL bilayer. Overall, the variability attributed to MC540-PL interactions is explained only to a minor extent by the generated TMP (7%) and largely by the variations in PS content (by up to 60%). In conclusion, the content of negatively charged PL is more important than TMP in determining the interactions of MC540 with PS/PC membranes.
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Affiliation(s)
- Iveta Waczulikova
- Department of Biophysics and Chemical Physics, Comenius University, Bratislava, Slovak Republic
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35
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Wong A, Cortopassi GA. High-throughput measurement of mitochondrial membrane potential in a neural cell line using a fluorescence plate reader. Biochem Biophys Res Commun 2002; 298:750-4. [PMID: 12419317 DOI: 10.1016/s0006-291x(02)02546-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Mutations in mitochondrial genes cause mitochondrial genetic disease, which is often associated with deficiency of the mitochondrial membrane potential (MMP). We present a high-throughput method for measuring MMP in intact neural cells using TMRM, a well-known potentiometric dye, in a 48-well plate format. Addition of known MMP depolarizing agents, FCCP or DNP, resulted in a time- and concentration-dependent decrease in fluorescence, which was saturable, whereas the addition of drugs that affect non-mitochondrial properties did not. A cell line deficient in mtDNA had decreased fluorescence, which was not further depleted by a depolarizing agent. The high-throughput results are similar to those produced by more time-consuming and low-throughput flow cytometry or microscopy methods. This plate-based system could facilitate the identification of cell-permeant small molecules (i.e., drugs) that modify MMP, which could be used to enhance mitochondrial function, and also for screening small populations of neural cells for mutations in nuclear or mtDNA genes that decrease MMP.
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Affiliation(s)
- Alice Wong
- Department of Molecular Biosciences, University of California, Davis 95616, USA
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36
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Larrarte E, Margareto J, Novo FJ, Marti A, Alfredo Martínez J. UCP1 muscle gene transfer and mitochondrial proton leak mediated thermogenesis. Arch Biochem Biophys 2002; 404:166-71. [PMID: 12127082 DOI: 10.1016/s0003-9861(02)00201-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Mitochondrial uncoupling protein 1 (UCP1) mediates the thermogenic transport of protons through the inner mitochondrial membrane. This proton leak uncouples respiration from ATP synthesis. The current study assessed the possible contribution of UCP1 muscle gene transfer to impair mitochondrial respiration in a tissue lacking UCP1 gene expression. Rats received an intramuscular injection of plasmid pXC1 containing UCP1 cDNA in the right tibialis muscles, while left tibialis muscles were injected with empty plasmid as control. Ten days after DNA injection, mitochondria from tibialis anterior muscles were isolated and analyzed. UCP1 gene transfer resulted in protein expression as analyzed by inmunoblotting. Mitochondria isolated from UCP1-injected muscles showed a significant increase in state 2 and state 4 oxygen consumption rates and a decreased respiration control ratio in comparison to mitochondria from control muscles. Furthermore, UCP1-containing mitochondria had a lower membrane potential in those states (2 and 4) when compared with control mitochondria. Our results revealed that UCP1 muscle gene transfer is associated with an induced mitochondrial proton leak, which could contribute to increase energy expenditure.
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Affiliation(s)
- Eider Larrarte
- Department of Physiology and Nutrition, University of Navarra, 31008 Pamplona, Spain
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37
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Affiliation(s)
- M Degli Esposti
- Cancer Research Campaign Molecular Pharmacology Group, School of Biological Sciences, University of Manchester, Manchester, M13 9PT, United Kingdom
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38
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Teuber M, Rögner M, Berry S. Fluorescent probes for non-invasive bioenergetic studies of whole cyanobacterial cells. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1506:31-46. [PMID: 11418095 DOI: 10.1016/s0005-2728(01)00178-5] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Fluorescent DeltapH and DeltaPsi indicators have been screened for the non-invasive monitoring of bioenergetic processes in whole cells of the cyanobacterium Synechocystis sp. PCC 6803. Acridine yellow and Acridine orange proved to be the best DeltapH indicators for the investigation of thylakoid and cytoplasmic membrane energization: While Acridine yellow indicated only cytosolic energization, Acridine orange showed signals from both the thylakoid lumen and the cytosol that could be separated kinetically. Both indicators were applied successfully to monitor cellular energetics, such as the interplay of linear and cyclic photosynthetic electron transport, osmotic adaptation and solute transport across the cytoplasmic membrane. In contrast, useful membrane potential indicators were more difficult to find, with Di-4-ANEPPS and Brilliant cresyl blue being the only promising candidates for further studies. Finally, Acridine yellow and Acridine orange could also be applied successfully for the thermophilic cyanobacterium Synechococcus elongatus. Different from Synechocystis sp. PCC 6803, where both respiration and ATP hydrolysis could be utilized for cytoplasmic membrane energization, proton extrusion at the cytoplasmic membrane in Synechococcus elongatus was preferentially driven by ATP hydrolysis.
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Affiliation(s)
- M Teuber
- Lehrstuhl Biochemie der Pflanzen, Ruhr-Universität Bochum, D-44780, Bochum, Germany
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39
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Das TK, Mazumdar S. Effect of Adriamycin on the boundary lipid structure of cytochrome c oxidase: pico-second time-resolved fluorescence depolarization studies. Biophys Chem 2000; 86:15-28. [PMID: 11011696 DOI: 10.1016/s0301-4622(00)00158-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The fluorescence dynamics of the dye 3,3'-diethyloxadicarbocyanine iodide (DODCI) was used to probe the microenvironment of cytochrome c oxidase (CcO) and cardiolipin. The dye was partitioned between an aqueous and a hydrophobic phase. The 'bound' and 'free' populations of DODCI could be separated by analysis of the time-resolved fluorescence decay of the dye. The anisotropy decay of the DODCI bound to CcO showed a unique 'dip and rise' shape that was analyzed by a combination of rotational correlation times with time-dependent weight factors for each lifetime component. Rotational dynamics studies revealed the existence of a restricted motion of the dye bound at the enzyme surface. Adriamycin, an anticancer, albeit cardiotoxic drug, was previously proposed to affect the surface structure of CcO, most likely by causing a disorder to the surface lipid arrangement. A drastic change in the rotational correlation time of the dye bound to the enzyme surface was observed, which suggested a depletion of cardiolipin layer due to complexation with the drug. The effect of Adriamycin on cardiolipin was drastic, leading to its phase separation. The present study suggests that the effect of Adriamycin on CcO is primarily a segregation of the cardiolipins.
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Affiliation(s)
- T K Das
- Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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40
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Mishra A, Behera RK, Behera PK, Mishra BK, Behera GB. Cyanines during the 1990s: A Review. Chem Rev 2000; 100:1973-2012. [PMID: 11749281 DOI: 10.1021/cr990402t] [Citation(s) in RCA: 954] [Impact Index Per Article: 39.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- A Mishra
- Centre of Studies in Surface Science and Technology, Department of Chemistry, Sambalpur University, Jyoti Vihar 768 019, Orissa, India
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41
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Abstract
Mitochondrial oxidative damage and dysfunction contributes to a number of cell pathologies. To investigate how this damage affects cell function we have developed mitochondrially targeted antioxidants and thiol reagents by covalently linking them to lipophilic cations. The cation drives the selective accumulation of these reagents into mitochondria within cells where the antioxidants decrease oxidative damage and the thiol reagents enable measurement of the redox status of thiol proteins. In conjunction with cell and animal models of apoptosis, oxidative damage, and nitric oxide signaling, these molecules may provide new insights into the roles of mitochondria in human pathologies.
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Abstract
The major function of mitochondria in human cells is to provide ATP by oxidative phosphorylation. However, mitochondria have many other roles including the modulation of intracellular calcium concentration and the regulation of apoptotic cell death. Furthermore, the mitochondrial respiratory chain is a major source of damaging free radicals. Consequently, mitochondrial dysfunction contributes to a number of human diseases, ranging from neurodegenerative diseases and ischaemia-reperfusion injury to obesity and diabetes. In addition, mutations to nuclear or mitochondrial DNA cause a number of human diseases. Therefore, strategies to prevent mitochondrial damage or to manipulate mitochondrial function in clinically useful ways may provide new therapies for a range of human disorders. Here we outline why mitochondria are a potentially important target for drug delivery and discuss how to deliver bioactive molecules selectively to mitochondria within cells.
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Affiliation(s)
- M P Murphy
- Department of Biochemistry, University of Otago, Box 56, Dunedin, New Zealand.
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43
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Krishna MM, Periasamy N. Location and orientation of DODCI in lipid bilayer membranes: effects of lipid chain length and unsaturation. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1461:58-68. [PMID: 10556488 DOI: 10.1016/s0005-2736(99)00149-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The location and orientation of a linear dye molecule, DODCI, in lipid bilayer membrane were determined by the effect of viscosity and refractive index of the aqueous medium on the fluorescence properties of the dye bound to the membrane. The membrane-bound dye is solubilized in two sites, one near the surface (short fluorescence lifetime) and another in the interior of the membrane (long lifetime). The ratio of the dye in the two locations and the orientation of the dye (parallel or perpendicular to the membrane) are sensitive to the lipid chain length and unsaturation in the alkyl chain. The fraction of the dye in the interior region is higher for short alkyl chains (C12>C14>C16>>C18C20) and in unsaturated lipids (C14:1>C14:0, C16:1>C16:0). These experimental results are consistent with the general principle that the penetration of an amphiphilic organic molecule in the interior region of the membrane is more when the structure of th bilayer is more fluid-like.
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Affiliation(s)
- M M Krishna
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai, India
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44
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Barakat AI, Leaver EV, Pappone PA, Davies PF. A flow-activated chloride-selective membrane current in vascular endothelial cells. Circ Res 1999; 85:820-8. [PMID: 10532950 DOI: 10.1161/01.res.85.9.820] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Shear stress-induced activation of endothelial ion channels, one of the earliest responses to flow, is implicated in mechano-signal transduction that results in the regulation of vascular tone. The effects of laminar flow on endothelial membrane potential were studied in vitro using both fluorescent potentiometric dye measurements and whole-cell patch-clamp recordings. The application of flow stimulated membrane hyperpolarization, which was reversed to depolarization within 35 to 160 seconds. The depolarization was caused by a Cl(-)-selective membrane current activated by flow independently of the K(+) channel-mediated hyperpolarization. Thus, flow activated both K(+) and Cl(-) currents, with the net membrane potential being determined by the balance of the responses. Membrane potential sensitivity to flow was unchanged by flow preconditioning that elongated and aligned the cells.
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Affiliation(s)
- A I Barakat
- Department of Mechanical and Aeronautical Engineering, University of California, Davis, CA 95616, USA.
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45
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Bkaily G, Jacques D, Pothier P. Use of confocal microscopy to investigate cell structure and function. Methods Enzymol 1999; 307:119-35. [PMID: 10506971 DOI: 10.1016/s0076-6879(99)07010-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- G Bkaily
- Department of Anatomy and Cell Biology, Faculty of Medicine, University of Sherbrooke, Québec, Canada
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46
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Bae J, Stuenkel EL, Loch-Caruso R. Stimulation of oscillatory uterine contraction by the PCB mixture Aroclor 1242 may involve increased [Ca2+]i through voltage-operated calcium channels. Toxicol Appl Pharmacol 1999; 155:261-72. [PMID: 10079212 DOI: 10.1006/taap.1998.8614] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Polychlorinated biphenyls (PCBs) are persistent environmental pollutants associated with spontaneous abortion and shortened gestation length in women and animals. In previous studies, we showed that PCB mixtures and noncoplanar ortho-substituted PCB congeners increased contractions in pregnant rat uterus. In the present study, we hypothesized that the PCB mixture Aroclor 1242 (A1242) stimulates oscillatory uterine contraction in pregnant uterus by increasing intracellular calcium concentration ([Ca2+]i). Pretreatment of uterine strips with ryanodine or thapsigargin, to deplete specific intracellular calcium stores, did not prevent the increased frequency of oscillatory contraction due to 50 microM A1242, whereas thapsigargin effectively blocked carbachol-induced stimulation of uterine contraction. However, 100 microM A1242 was unable to increase contraction in the absence of extracellular calcium or in the presence of the voltage-operated L-type calcium channel blocker nifedipine. A1242 (100 microM) was observed to partially depolarize the cell membrane of myometrial cells from pregnant rats, as measured with a potential-sensitive carbocyanine dye. Changes of [Ca2+]i were monitored in single myometrial cells loaded with the fluorescent calcium-sensitive probe fura-2. Cells exposed to 100 microM A1242 showed a delayed and sustained increase of [Ca2+]i, and this increase was completely blocked in the absence of extracellular calcium or the presence of nifedipine. Therefore, the data suggest that depolarization of the cell membrane by A1242 enabled myometrial cells to increase [Ca2+]i through activation of voltage-operated calcium channels, and the increased [Ca2+]i consequently stimulated contraction of uterine smooth muscle.
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Affiliation(s)
- J Bae
- Department of Environmental and Industrial Health, The University of Michigan, Ann Arbor, Michigan, 48109-2029, USA
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47
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Novo D, Perlmutter NG, Hunt RH, Shapiro HM. Accurate flow cytometric membrane potential measurement in bacteria using diethyloxacarbocyanine and a ratiometric technique. CYTOMETRY 1999; 35:55-63. [PMID: 10554181 DOI: 10.1002/(sici)1097-0320(19990101)35:1<55::aid-cyto8>3.0.co;2-2] [Citation(s) in RCA: 195] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Membrane potential (MP) plays a critical role in bacterial physiology. Existing methods for MP estimation by flow cytometry are neither accurate nor precise, due in part to the heterogeneity of size of the particles analyzed. The ratio of a size- and MP-sensitive measurement, and an MP-independent, size-sensitive measurement, should provide a better estimate of MP. METHODS Flow cytometry and spectrofluorometry were used to detect red (488 --> 600 nm) fluorescence associated with aggregates of diethyloxacarbocyanine (DiOC2(3)), which, in the monomeric state, is normally green (488 --> 530 nm) fluorescent. RESULTS In bacteria incubated with 30 microM dye, aggregate formation increases with the magnitude of the interior-negative membrane potential. Green fluorescence from stained bacteria predominantly reflects particle size, and is relatively independent of MP, whereas red fluorescence is highly dependent on both MP and size. The ratio of red to green fluorescence provides a measure of MP that is largely independent of cell size, with a low coefficient of variation (CV). Calibration with valinomycin and potassium demonstrates that the method is accurate over the range from -50 mV through -120 mV; it also accurately tracks reversible reductions in MP produced by incubation at 4 degrees C and washing in glucose-free medium. CONCLUSIONS The ratiometric technique for MP estimation using DiOC2(3) is substantially more accurate and precise than those previously available, and may be useful in studies of bacterial physiology and in investigations of the effects of antibiotics and other agents on microorganisms.
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Affiliation(s)
- D Novo
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada
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48
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Scaduto RC, Grotyohann LW. Measurement of mitochondrial membrane potential using fluorescent rhodamine derivatives. Biophys J 1999; 76:469-77. [PMID: 9876159 PMCID: PMC1302536 DOI: 10.1016/s0006-3495(99)77214-0] [Citation(s) in RCA: 934] [Impact Index Per Article: 37.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We investigated the use of rhodamine 123 (R123), tetramethylrhodamine methyl ester (TMRM), and tetramethylrhodamine ethyl ester (TMRE) as fluorescent probes to monitor the membrane potential of mitochondria. These indicator dyes are lipophilic cations accumulated by mitochondria in proportion to DeltaPsi. Upon accumulation, all three dyes exhibit a red shift in both their absorption and fluorescence emission spectra. The fluorescence intensity is quenched when the dyes are accumulated by mitochondria. These properties have been used to develop a method to dynamically monitor DeltaPsi of isolated rat heart mitochondria using a ratio fluorescence approach. All three dyes bound to the inner and outer aspects of the inner mitochondrial membrane and, as a result, were accumulated by mitochondria in a greater quantity than predicted by the Nernst equation. Binding to mitochondria was temperature-dependent and the degree of binding was in the order of TMRE > R123 > TMRM. The internal and external partition coefficients for binding were determined to correct for binding in the calculation of DeltaPsi. All three dyes suppressed mitochondrial respiratory control to some extent. Inhibition of respiration was greatest with TMRE, followed by R123 and TMRM. When used at low concentrations, TMRM did not suppress respiration. The use of these dyes and ratio fluorescence techniques affords a simple method for measurement of DeltaPsi of isolated mitochondria. We also applied this approach to the isolated perfused heart to determine whether DeltaPsi could be monitored in an intact tissue. Wavelength scanning of the surface fluorescence of the heart under various conditions after accumulation of TMRM indicated that the mitochondrial matrix-induced wavelength shift of TMRM also occurs in the heart cytosol, eliminating the use of this approach in the intact heart.
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Affiliation(s)
- R C Scaduto
- Department of Cellular and Molecular Physiology, College of Medicine, The Pennsylvania State University, Hershey, Pennsylvania 17033 USA.
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49
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Abstract
The pineal hormone melatonin is involved in photic regulations of various kinds, including adaptation to light intensity, daily changes of light and darkness, and seasonal changes of photoperiod lengths. The melatonin effects are mediated by the specific high-affinity receptors localized on plasma membrane and coupled to GTP-binding protein. Two different G proteins coupled to the melatonin receptors have been described, one sensitive to pertussis toxin and the other sensitive to cholera toxin. On the basis of the molecular structure, three subtypes of the melatonin receptors have been described: Mel1A, Mel1B, and Mel1C. The first two subtypes are found in mammals and may be distinguished pharmacologically using selective antagonists. Melatonin receptor regulates several second messengers: cAMP, cGMP, diacylglycerol, inositol trisphosphate, arachidonic acid, and intracellular Ca2+ concentration ([Ca2+]i). In many cases, its effect is inhibitory and requires previous activation of the cell by a stimulatory agent. Melatonin inhibits cAMP accumulation in most of the cells examined, but the indole effects on other messengers have been often observed only in one type of the cells or tissue, until now. Melatonin also regulates the transcription factors, namely, phosphorylation of cAMP-responsive element binding protein and expression of c-Fos. Molecular mechanisms of the melatonin effects are not clear but may involve at least two parallel transduction pathways, one inhibiting adenylyl cyclase and the other regulating phospholipide metabolism and [Ca2+]i.
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Affiliation(s)
- J Vanecek
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague
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50
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Fluorescence of organic dyes in lipid membranes: Site of solubilization and effects of viscosity and refractive index on lifetimes. J Fluoresc 1998. [DOI: 10.1007/bf02758241] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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