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Samartsev VN, Belosludtsev KN, Pavlova EK, Pavlova SI, Semenova AA, Dubinin MV. Theoretical and Experimental Study of the Interaction of Protonophore Uncouplers and Decoupling Agents with Functionally Active Mitochondria. Cell Biochem Biophys 2024:10.1007/s12013-024-01343-4. [PMID: 38856833 DOI: 10.1007/s12013-024-01343-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/29/2024] [Indexed: 06/11/2024]
Abstract
The purpose of this work was to quantitatively characterize the effectiveness of oxidative phosphorylation uncouplers and decoupling agents in functionally active mitochondria, taking into account their content in the hydrophobic region of the inner membrane of these organelles. When conducting theoretical studies, it is accepted that uncouplers and decouplers occupy part of the volume of mitochondria to exhibit their activity, which is defined as the effective volume. The following quantities characterizing the action of these reagents are considered: (1) concentrations of reagents that cause double stimulation of mitochondrial respiration in state 4 (C 200 ); (2) effective distribution coefficient (E MW ) - the ratio of the amount of reagents in the effective volume of mitochondria and the water volume; (3) the relative amount of reagents associated with the effective volume of mitochondria (U M / U T ); (4) specific activity of reagents localized in the effective volume of mitochondria (A M ). We have developed methods for determining these values, based on an analysis of the dependence of the rate of mitochondrial respiration on the concentration of uncouplers and decoupling agents at two different concentrations of mitochondrial protein in the incubation medium. During experimental studies, we compared the effects of the classical protonophore uncouplers 2,4-dinitrophenol (DNP) and сarbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP), the natural uncouplers lauric and palmitic acids, and the natural decouplers α,ω-tetradecanedioic (TDA) and α,ω-hexadecanedioic (HDA) acids that differ both in the structure of the molecule and in the degree of solubility in lipids. Using the developed methods, we have clarified the dependence of the degree of activity of these uncouplers and decoupling agents on the distribution of their molecules between the effective volume of mitochondria and the water volume.
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Affiliation(s)
- Victor N Samartsev
- Mari State University, pl. Lenina 1, Yoshkar-Ola, Mari El, 424001, Russia
| | - Konstantin N Belosludtsev
- Mari State University, pl. Lenina 1, Yoshkar-Ola, Mari El, 424001, Russia
- Institute of theoretical and experimental biophysics, Russian Academy of Sciences, Pushchino, 142290, Russia
| | - Evgenia K Pavlova
- Mari State University, pl. Lenina 1, Yoshkar-Ola, Mari El, 424001, Russia
| | - Svetlana I Pavlova
- Mari State University, pl. Lenina 1, Yoshkar-Ola, Mari El, 424001, Russia
| | - Alena A Semenova
- Mari State University, pl. Lenina 1, Yoshkar-Ola, Mari El, 424001, Russia
| | - Mikhail V Dubinin
- Mari State University, pl. Lenina 1, Yoshkar-Ola, Mari El, 424001, Russia.
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2
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Rokitskaya TI, Kirsanov RS, Khailova LS, Panteleeva AA, Lyamzaev KG, Korshunova GA, Kotova EA, Antonenko YN. Methylation of Phenyl Rings in Ester-Stabilized Phosphorus Ylides Vastly Enhances Their Protonophoric Activity. Chembiochem 2024; 25:e202300848. [PMID: 38353515 DOI: 10.1002/cbic.202300848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 02/08/2024] [Indexed: 03/05/2024]
Abstract
We have recently discovered that ester-stabilized phosphorus ylides, resulting from deprotonation of a phosphonium salt such as [Ph3PCH2COOR], can transfer protons across artificial and biological membranes. To create more effective cationic protonophores, we synthesized similar phosphonium salts with one ((heptyloxycarbonylmethyl)(p-tolyl)bromide) or two ((butyloxycarbonylmethyl)(3,5-xylyl)osphonium bromide) methyl substituents in the phenyl groups. The methylation enormously augmented both protonophoric activity of the ylides on planar bilayer lipid membrane (BLM) and uncoupling of mammalian mitochondria, which correlated with strongly accelerated flip-flop of their cationic precursors across the BLM.
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Affiliation(s)
- Tatyana I Rokitskaya
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Roman S Kirsanov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Ljudmila S Khailova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Alisa A Panteleeva
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Konstantin G Lyamzaev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Galina A Korshunova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Elena A Kotova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Yuri N Antonenko
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
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Abstract
Quantitative structure-activity relationships (QSARs) have been derived which relate skin corrosivity data on organic chemicals (acids, bases, phenols and neutral chemicals) to their log P (log [octanol/water partition coefficient]) values, molecular volumes, melting points and pKa/ pKb values. Data sets were analysed using principal components analysis. For each group of chemicals, plots of the first two principal components of the above parameters, which broadly model skin permeability and cytotoxicity, showed that the analysis was able to discriminate well between corrosive and non-corrosive chemicals. The QSARs derived should be useful for predicting the skin corrosivity potentials of new or untested chemicals within these categories.
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Affiliation(s)
- Martin D. Barratt
- Environmental Safety Laboratory, Unilever Research, Colworth House, Sharnbrook, Bedford MK44 1LQ, UK
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Tang W, Chen J, Hong H. Discriminant models on mitochondrial toxicity improved by consensus modeling and resolving imbalance in training. CHEMOSPHERE 2020; 253:126768. [PMID: 32464767 DOI: 10.1016/j.chemosphere.2020.126768] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 04/08/2020] [Accepted: 04/08/2020] [Indexed: 06/11/2023]
Abstract
Humans and animals may be exposed to tens of thousands of natural and synthetic chemicals during their lifespan. It is difficult to assess risk for all the chemicals with experimental toxicity tests. An alternative approach is to use computational toxicology methods such as quantitative structure-activity relationship (QSAR) modeling. Mitochondrial toxicity is involved in many diseases such as cancer, neurodegeneration, type 2 diabetes, cardiovascular diseases and autoimmune diseases. Thus, it is important to rapidly and efficiently identify chemicals with mitochondrial toxicity. In this study, five machine learning algorithms and twelve types of molecular fingerprints were employed to generate QSAR discriminant models for mitochondrial toxicity. A threshold moving method was adopted to resolve the imbalance issue in the training data. Consensus of the models by an averaging probability strategy improved prediction performance. The best model has correct classification rates of 81.8% and 88.3% in ten-fold cross validation and external validation, respectively. Substructures such as phenol, carboxylic acid, nitro and arylchloride were found informative through analysis of information gain and frequency of substructures. The results demonstrate that resolving imbalance in training and building consensus models can improve classification rates for mitochondrial toxicity prediction.
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Affiliation(s)
- Weihao Tang
- Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian, 116024, China
| | - Jingwen Chen
- Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian, 116024, China.
| | - Huixiao Hong
- National Center for Toxicological Research, U.S. Food and Drug Administration, 3900 NCTR Rd, Jefferson, AR, 72079, USA
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Enoch SJ, Schultz TW, Popova IG, Vasilev KG, Mekenyan OG. Development of a Decision Tree for Mitochondrial Dysfunction: Uncoupling of Oxidative Phosphorylation. Chem Res Toxicol 2018; 31:814-820. [DOI: 10.1021/acs.chemrestox.8b00132] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Steven J. Enoch
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, L3 3AF Liverpool, England
| | - Terry W. Schultz
- College of Veterinary Medicine, The University of Tennessee, 2407 River Drive, Knoxville, Tennessee 37996-4500, United States
| | - Ioanna G. Popova
- Laboratory of Mathematical Chemistry (LMC), As. Zlatarov University, Bourgas 8000, Bulgaria
| | - Krasimir G. Vasilev
- Laboratory of Mathematical Chemistry (LMC), As. Zlatarov University, Bourgas 8000, Bulgaria
| | - Ovanes G. Mekenyan
- Laboratory of Mathematical Chemistry (LMC), As. Zlatarov University, Bourgas 8000, Bulgaria
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Luz AL, Rooney JP, Kubik LL, Gonzalez CP, Song DH, Meyer JN. Mitochondrial Morphology and Fundamental Parameters of the Mitochondrial Respiratory Chain Are Altered in Caenorhabditis elegans Strains Deficient in Mitochondrial Dynamics and Homeostasis Processes. PLoS One 2015; 10:e0130940. [PMID: 26106885 PMCID: PMC4480853 DOI: 10.1371/journal.pone.0130940] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 05/27/2015] [Indexed: 12/28/2022] Open
Abstract
Mitochondrial dysfunction has been linked to myriad human diseases and toxicant exposures, highlighting the need for assays capable of rapidly assessing mitochondrial health in vivo. Here, using the Seahorse XFe24 Analyzer and the pharmacological inhibitors dicyclohexylcarbodiimide and oligomycin (ATP-synthase inhibitors), carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (mitochondrial uncoupler) and sodium azide (cytochrome c oxidase inhibitor), we measured the fundamental parameters of mitochondrial respiratory chain function: basal oxygen consumption, ATP-linked respiration, maximal respiratory capacity, spare respiratory capacity and proton leak in the model organism Caenhorhabditis elegans. Since mutations in mitochondrial homeostasis genes cause mitochondrial dysfunction and have been linked to human disease, we measured mitochondrial respiratory function in mitochondrial fission (drp-1)-, fusion (fzo-1)-, mitophagy (pdr-1, pink-1)-, and electron transport chain complex III (isp-1)-deficient C. elegans. All showed altered function, but the nature of the alterations varied between the tested strains. We report increased basal oxygen consumption in drp-1; reduced maximal respiration in drp-1, fzo-1, and isp-1; reduced spare respiratory capacity in drp-1 and fzo-1; reduced proton leak in fzo-1 and isp-1; and increased proton leak in pink-1 nematodes. As mitochondrial morphology can play a role in mitochondrial energetics, we also quantified the mitochondrial aspect ratio for each mutant strain using a novel method, and for the first time report increased aspect ratios in pdr-1- and pink-1-deficient nematodes.
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Affiliation(s)
- Anthony L. Luz
- Nicholas School of the Environment, Duke University, Durham, North Carolina, United States of America
| | - John P. Rooney
- Nicholas School of the Environment, Duke University, Durham, North Carolina, United States of America
| | - Laura L. Kubik
- Nicholas School of the Environment, Duke University, Durham, North Carolina, United States of America
| | - Claudia P. Gonzalez
- Nicholas School of the Environment, Duke University, Durham, North Carolina, United States of America
| | - Dong Hoon Song
- Simulation Group, Samsung SDI, Suwon-si, Gyeonggi-do, Republic of Korea
| | - Joel N. Meyer
- Nicholas School of the Environment, Duke University, Durham, North Carolina, United States of America
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Silachev DN, Khailova LS, Babenko VA, Gulyaev MV, Kovalchuk SI, Zorova LD, Plotnikov EY, Antonenko YN, Zorov DB. Neuroprotective effect of glutamate-substituted analog of gramicidin A is mediated by the uncoupling of mitochondria. Biochim Biophys Acta Gen Subj 2014; 1840:3434-42. [PMID: 25218694 DOI: 10.1016/j.bbagen.2014.09.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 08/05/2014] [Accepted: 09/01/2014] [Indexed: 01/25/2023]
Abstract
BACKGROUND Reactive oxygen species are grossly produced in the brain after cerebral ischemia and reperfusion causing neuronal cell death. Mitochondrial production of reactive oxygen species is nonlinearly related to the value of the mitochondrial membrane potential with significant increment at values exceeding 150mV. Therefore, limited uncoupling of oxidative phosphorylation could be beneficial for cells exposed to deleterious oxidative stress-associated conditions by preventing excessive generation of reactive oxygen species. METHODS Protonophoric and uncoupling activities of different peptides were measured using pyranine-loaded liposomes and isolated mitochondria. To evaluate the effect of glutamate-substituted analog of gramicidin A ([Glu1]gA) administration on the brain ischemic damage, we employed the in vitro model of neuronal hypoxia using primary neuronal cell cultures and the in vivo model of cerebral ischemia induced in rats by the middle cerebral artery occlusion. RESULTS [Glu1]gA was the most effective in proton-transferring activity among several N-terminally substituted analogs of gramicidin A tested in liposomes and rat brain and liver mitochondria. The peptides were found to be protective against ischemia-induced neuronal cell death and they lowered mitochondrial membrane potential in cultured neurons and diminished reactive oxygen species production in isolated brain mitochondria. The intranasal administration of [Glu1]gA remarkably diminished the infarct size indicated in MR-images of a brain at day 1 after the middle cerebral artery occlusion. In [Glu1]gA-treated rats, the ischemia-induced brain swelling and behavioral dysfunction were significantly suppressed. CONCLUSIONS The glutamate-substituted analogs of gramicidin A displaying protonophoric and uncoupling activities protect neural cells and the brain from the injury caused by ischemia/reperfusion. GENERAL SIGNIFICANCE [Glu1]gA may be potentially used as a therapeutic agent to prevent neuron damage after stroke.
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Affiliation(s)
- Denis N Silachev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119991, Russia
| | - Ljudmila S Khailova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119991, Russia
| | - Valentina A Babenko
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119991, Russia
| | - Mikhail V Gulyaev
- Lomonosov Moscow State University, Faculty of Fundamental Medicine, Moscow 117192, Russia
| | - Sergey I Kovalchuk
- Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russia
| | - Ljubava D Zorova
- International Laser Center, Lomonosov Moscow State University, Moscow 119992, Russia
| | - Egor Y Plotnikov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119991, Russia
| | - Yuri N Antonenko
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119991, Russia.
| | - Dmitry B Zorov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119991, Russia.
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8
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Denisov SS, Kotova EA, Khailova LS, Korshunova GA, Antonenko YN. Tuning the hydrophobicity overcomes unfavorable deprotonation making octylamino-substituted 7-nitrobenz-2-oxa-1,3-diazole (n-octylamino-NBD) a protonophore and uncoupler of oxidative phosphorylation in mitochondria. Bioelectrochemistry 2014; 98:30-8. [DOI: 10.1016/j.bioelechem.2014.02.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 01/21/2014] [Accepted: 02/23/2014] [Indexed: 11/15/2022]
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9
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Klamt A, Huniar U, Spycher S, Keldenich J. COSMOmic: a mechanistic approach to the calculation of membrane-water partition coefficients and internal distributions within membranes and micelles. J Phys Chem B 2008; 112:12148-57. [PMID: 18754634 DOI: 10.1021/jp801736k] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new approach for the modeling of molecules in micellar systems and especially in biomembranes, COSMOmic, is presented, and its performance is validated on the example of the partitioning of molecules between water and biological membranes. Starting from quantum chemical calculations of the surfactant, solvent, and solute molecules, and being based on the COSMO-RS method for fluid-phase thermodynamic properties, COSMOmic is essentially free of additional adjustable parameters. The inclusion of an elastic energy correction into the COSMOmic model did not turn out to yield any significant improvement. The novel COSMOmic method allows for the efficient prediction of the distribution of molecules in micellar systems.
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Affiliation(s)
- Andreas Klamt
- COSMOlogic GmbH&COKG, Burscheider Strasse 515, 51381 Leverkusen, Germany.
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10
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Sibille B, Keriel C, Fontaine E, Catelloni F, Rigoulet M, Leverve XM. Octanoate Affects 2,4-Dinitrophenol Uncoupling in Intact Isolated Rat Hepatocytes. ACTA ACUST UNITED AC 2008. [DOI: 10.1111/j.1432-1033.1995.0498e.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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11
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Ozaki S, Kano K, Shirai O. Electrochemical elucidation on the mechanism of uncoupling caused by hydrophobic weak acids. Phys Chem Chem Phys 2008; 10:4449-55. [DOI: 10.1039/b803458c] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Spycher S, Netzeva TI, Worth AP, Escher BI. Mode of action-based classification and prediction of activity of uncouplers for the screening of chemical inventories. SAR AND QSAR IN ENVIRONMENTAL RESEARCH 2008; 19:433-463. [PMID: 18853296 DOI: 10.1080/10629360802348803] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A new approach for classification of uncouplers of oxidative and photophosphorylation, also suitable for screening of large chemical inventories, is introduced. Earlier fragment-based approaches for this mode of toxic action are limited to phenols but weak acids of extremely diverse chemical classes can act as uncouplers. The proposed approach overcomes the limitation to phenolic uncouplers by combining structural fragments with the global information of physico-chemical descriptors. In a top-down approach to reduce the number of candidate chemicals, firstly substructure definitions for the detection of weak acids were applied. Subsequently, conservative physico-chemical thresholds for the two most important properties for the uncoupling activity were defined: an acid dissociation constant (pK(a)) between 3 and 9, and a sufficiently low energy barrier for the internal permeability of anions (17 kcal/mol). The later was derived from a novel approach to calculate the distribution of compounds across membranes. The combination of structural and physico-chemical criteria allowed a good separation of active from inactive chemicals with high sensitivity (95%) and slightly lower (more than 75%) specificity. Applying this approach to several thousand high and low production volume chemicals retrieved a surprisingly small number of 10 compounds with a predicted excess toxicity above 10. Nevertheless, uncoupling can be an important mode of action as highlighted with several examples ranging from pesticide metabolites to persistent organic compounds.
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Affiliation(s)
- S Spycher
- Department of Environmental Toxicology, UTOX, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
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Staniek K, Rosenau T, Gregor W, Nohl H, Gille L. The protection of bioenergetic functions in mitochondria by new synthetic chromanols. Biochem Pharmacol 2005; 70:1361-70. [PMID: 16150421 DOI: 10.1016/j.bcp.2005.07.030] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Revised: 07/29/2005] [Accepted: 07/29/2005] [Indexed: 10/25/2022]
Abstract
alpha-Tocopherol is the most important lipophilic antioxidant of the chromanol type protecting biomembranes from lipid peroxidation (LPO). Therefore, alpha-tocopherol and its derivatives are frequently used in the therapy or prevention of oxygen radical-derived diseases. In the present study, novel chromanol-type antioxidants (twin-chromanol, cis- and trans-oxachromanol) as well as the well-known short-chain analogue of alpha-tocopherol, pentamethyl-chromanol, were tested for their antioxidative potency in rat heart mitochondria (RHM). Our experiments revealed that the bioenergetic parameters of mitochondria were not deteriorated in the presence of chromanols (up to 50 nmol/mg protein). Exposure of RHM to cumene hydroperoxide and Fe2+ (final concentrations 50 microM each), inducing LPO, significantly affected their bioenergetic parameters which were determined in the presence of glutamate and malate (substrates of mitochondrial complex I). Alterations of the bioenergetic parameters were partially prevented in a concentration-dependent manner by preincubating RHM with antioxidants before adding the radical-generating system. In the lower concentration range, twin-chromanol turned out to be more efficient than pentamethyl-chromanol, both being far more protective than cis- and trans-oxachromanol. Measurement of protein-bound SH groups and thiobarbituric acid-reactive substances revealed that this protective effect was due to their antioxidative action. Furthermore, HPLC measurements of alpha-tocopherol and alpha-tocopheryl quinone in rat liver mitochondria demonstrated an alpha-tocopherol-sparing effect of twin-chromanol. In conclusion, new chromanol-type antioxidants, especially twin-chromanol, were able to improve bioenergetic and biochemical parameters of mitochondria exposed to oxidative stress.
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Affiliation(s)
- Katrin Staniek
- Research Institute for Biochemical Pharmacology and Toxicology, University of Veterinary Medicine Vienna, Veterinärplatz 1, A-1210 Vienna, Austria
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Moridani MY, Siraki A, Chevaldina T, Scobie H, O'Brien PJ. Quantitative structure toxicity relationships for catechols in isolated rat hepatocytes. Chem Biol Interact 2004; 147:297-307. [PMID: 15135085 DOI: 10.1016/j.cbi.2004.02.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2003] [Revised: 01/08/2004] [Accepted: 02/02/2004] [Indexed: 11/26/2022]
Abstract
One- and two-parameter quantitative structure toxicity relationship (QSTR) equations were obtained to describe the cytotoxicity of isolated rat hepatocytes induced by 23 catechols in which LD(50) represents the catechol concentration required to induce 50% cytotoxicity in 2 h. A QSTR equation logLD(50) (microM = - 0.464(+/-0.065) log P + 3.724(+/-0.114) (n = 20, r(2) = 0.740, s(y,x) = 0.372, P < 1 x 10(-6), outliers: 4-methoxycatechol, 3-methoxycatechol, L-dopa) was derived where logP represents octanol/water partitioning. Outliers were determined by adopting a statistical method to standardize the identification of outliers. When pK(a1), the first ionization constant, was considered as a contributing parameter a two-parameter QSTR equation was derived: logLD(50) (microM = - 0.343(+/-0.058) log P - 0.116(+/-0.041) pK(a1)+4.389 (+/-0.315) (n = 22, r(2) = 0.738, s(y,x) = 0.375, P < 0.01, outlier: 4-methoxycatechol). Replacing logP with logD(7.4), the partition coefficient at pH 7.4, improved the first correlation by limiting the outlier to 4-methoxycatechol: logLD(50) (microM)=-0.252(+/-0.039) logD(7.4)+3.168(+/-0.090) (n = 22, r(2) = 0.671, s(y,x) = 0.420, P < 1 x 10(-5). In this study, 4-methoxycatechol (readily autooxidizable) was found to be an outlier for all QSTR equations derived. These findings point to lipophilicity and pK(a1) as two important characteristics of catechols that can be used to predict their cytotoxicity towards isolated rat hepatocytes. The catechols with the higher lipophilicity/distribution coefficient, the lower degree of ionization and the higher pK(a(catechol)) were more toxic towards hepatocytes than the other catechols.
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Affiliation(s)
- Majid Y Moridani
- Faculty of Pharmacy, University of Toronto, 19 Russell Street, Toronto, Ont., Canada M5S 2S2
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15
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Moridani MY, Siraki A, O'Brien PJ. Quantitative structure toxicity relationships for phenols in isolated rat hepatocytes. Chem Biol Interact 2003; 145:213-23. [PMID: 12686497 DOI: 10.1016/s0009-2797(02)00258-2] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Quantitative structure toxicity relationship (QSTR) equations were obtained to predict and describe the cytotoxicity of 31 phenols using logLD(50) as a concentration to induce 50% cytotoxicity of isolated rat hepatocytes in 2 h and logP as octanol/water partitioning: logLD(50) (microM)=-0.588(+/-0.059)logP+4.652(+/-0.153) (n=27, r(2)=0.801, s=0.261, P<1 x 10(-9)). Hydroquinone, catechol, 4-nitrophenol, and 2,4-dinitrophenol were outliers for this equation. When the ionization constant pK(a) was considered as a contributing factor a two-parameter QSTR equation was derived: logLD(50) (microM)=-0.595(+/-0.051)logP+0.197(+/-0.029)pK(a)+2.665(+/-0.281) (n=28, r(2)=0.859, s=0.218, P<1 x 10(-6)). Using sigma+, the Brown variation of the Hammet electronic constant, as a contributing parameter, the cytotoxicity of phenols towards hepatocytes were defined by logLD(50) (microM)=-0.594(+/-0.052)logP-0.552(+/-0.085)sigma+ +4.540(+/-0.132) (n=28, r(2)=0.853, s=0.223, P<1 x 10(-6)). Replacing sigma+ with the homolytic bond dissociation energy (BDE) for (X-PhOH+PhO.-->X-PhO.+PhOH) led to logLD(50) (microM)=-0.601(+/-0.066)logP-0.040(+/-0.018)BDE+4.611(+/-0.166) (n=23, r(2)=0.827, s=0.223, P<0.05). Hydroquinone, catechol and 2-nitrophenol were outliers for the above equations. Using redox potential and logP led to a new correlation: logLD(50) (microM)=-0.529(+/-0.135)logP+2.077(+/-0.892)E(p/2)+2.806(+/-0.592) (n=15, r(2)=0.561, s=0.383, P<0.05) with 4-nitrophenol as an outlier. Our findings indicate that phenols with higher lipophilicity, BDE, or sigma+ values or with lower pK(a) and redox potential were more toxic towards hepatocytes. We also showed that a collapse of hepatocyte mitochondrial membrane potential preceded the cytotoxicity of most phenols. Our study indicates that one or a combination of mechanisms; i.e. mitochondrial uncoupling, phenoxy radicals, or phenol metabolism to quinone methides and quinones, contribute to phenol cytotoxicity towards hepatocytes depending on the phenol chemical structure.
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Affiliation(s)
- Majid Y Moridani
- Faculty of Pharmacy, University of Toronto, 19 Russell Street, Toronto, Ontario, Canada M5S 2S2
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Quantitative structure–activity relationships (QSARs) in toxicology: a historical perspective. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s0166-1280(02)00614-0] [Citation(s) in RCA: 178] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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17
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Abstract
Mitochondria have long been recognized as the generators of energy for the cell. Like any other power source, however, mitochondria are highly vulnerable to inhibition or uncoupling of the energy harnessing process and run a high risk for catastrophic damage to the cell. The exquisite structural and functional characteristics of mitochondria provide a number of primary targets for xenobiotic-induced bioenergetic failure. They also provide opportunities for selective delivery of drugs to the mitochondrion. In light of the large number of natural, commercial, pharmaceutical, and environmental chemicals that manifest their toxicity by interfering with mitochondrial bioenergetics, it is important to understand the underlying mechanisms. The significance is further underscored by the recent identification of bioenergetic control points for cell replication and differentiation and the realization that mitochondria play a determinant role in cell signaling and apoptotic modes of cell death.
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Affiliation(s)
- K B Wallace
- Department of Biochemistry and Molecular Biology, University of Minnesota School of Medicine, Duluth 55812, USA.
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18
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Siddiqui A, McGuigan C, Ballatore C, Srinivasan S, De Clercq E, Balzarini J. Enhancing the aqueous solubility of d4T-based phosphoramidate prodrugs. Bioorg Med Chem Lett 2000; 10:381-4. [PMID: 10714505 DOI: 10.1016/s0960-894x(99)00701-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A range of polyether para-substituted phosphoramidates were synthesised and found to have substantially elevated aqueous solubilities compared to the underivatised parent prodrug. A 30-fold increase in aqueous solubility could be achieved without a substantial decrease of in vitro activity against HIV-1. Replacement of the aryl (i.e. phenolic) moiety by tyrosine led to a substantial enhancement in aqueous solubility but also to a decrease in antiviral potency. A previously unobserved trend was identified, relating increased aryl substituent steric bulk to decreased antiviral activity.
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Affiliation(s)
- A Siddiqui
- Welsh School of Pharmacy, Cardiff University, UK
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19
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Hayashi M, Nakamura Y, Higashi K, Kato H, Kishida F, Kaneko H. A quantitative structure–Activity relationship study of the skin irritation potential of phenols. Toxicol In Vitro 1999; 13:915-22. [DOI: 10.1016/s0887-2333(99)00077-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/20/1999] [Indexed: 10/16/2022]
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20
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Rigoulet M, Devin A, Espié P, Guérin B, Fontaine E, Piquet MA, Nogueira V, Leverve X. Flux-force relationships in intact cells: a helpful tool for understanding the mechanism of oxidative phosphorylation alterations? BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1365:117-24. [PMID: 9693730 DOI: 10.1016/s0005-2728(98)00051-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
On isolated mitochondria, numerous studies of the relationships between fluxes and their associated forces have led to the description of some properties of the oxidative phosphorylation pathway. However whether such an approach can be applied to understanding the actual situation in intact living cells needs further consideration. In this study on isolated hepatocytes, we describe the dependence of the respiratory rate on the three thermodynamic forces linked to oxidative phosphorylation (i.e. the redox span over the respiratory chain, the electrical potential difference across the inner mitochondrial membrane and the free energy of ATP synthesis reaction). Even if this description is phenomenological and some objections may be raised regarding the relevance of such a bulk-phase force estimation, we present some results showing that the study of flux-force relationships in intact cells may be a helpful approach for understanding the mechanisms by which oxidative phosphorylation activity is changed.
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Affiliation(s)
- M Rigoulet
- Institut de Biochimie et Génétique Cellulaires du C.N.R.S., Université de Bordeaux, Bordeaux, France.
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21
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Barratt M, Dixit M, Jones P. The use of in vitro cytotoxicity measurements in QSAR methods for the prediction of the skin corrosivity potential of acids. Toxicol In Vitro 1996; 10:283-90. [DOI: 10.1016/0887-2333(96)00014-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/12/1996] [Indexed: 11/25/2022]
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22
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Carneiro de Melo AM, Cook GM, Miles RJ, Poole RK. Nisin stimulates oxygen consumption by Staphylococcus aureus and Escherichia coli. Appl Environ Microbiol 1996; 62:1831-4. [PMID: 8633884 PMCID: PMC167960 DOI: 10.1128/aem.62.5.1831-1834.1996] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Nisin stimulated oxygen consumption by nongrowing, glucose-metabolizing Staphylococcus aureus and Escherichia coli cells, indicating a protonophore mode of action. A similar stimulation in E. coli cells osmotically stressed to disrupt the outer cell membrane confirmed the cytoplasmic membrane as the site of nisin action and showed that nisin uptake was not prevented by the outer membrane.
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23
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Sibille B, Keriel C, Fontaine E, Catelloni F, Rigoulet M, Leverve XM. Octanoate affects 2,4-dinitrophenol uncoupling in intact isolated rat hepatocytes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 231:498-502. [PMID: 7635161 DOI: 10.1111/j.1432-1033.1995.tb20724.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
When intact isolated rat hepatocytes, either incubated or perifused, were uncoupled by 2,4-dinitrophenol, we found that the effect on glucose and lactate+pyruvate fluxes, cytosolic and mitochondrial redox states and ATP/ADP ratios were dependent on the nature of the exogenous substrate added. 2,4-Dinitrophenol addition (0.25 mmol/l) to cells perifused with dihydroxyacetone (10 mmol/l) resulted in a modest and transient activation of oxygen uptake accompanied by a surprising rise in lactate/pyruvate ratio indicating an increase in the cytosolic NADH/NAD+ ratio. In addition, such uncoupling, fully abolished glucose production, enhanced lactate+pyruvate flux, and strongly decreased cytosolic and mitochondrial ATP/ADP ratios. In these steady-state conditions, further addition of octanoate (0.4 mmol/l) induced a large and sustained enhancement of respiration with a concomitant decrease in the lactate/pyruvate ratio, whereas glucose flux was restored to some extent and cytosolic and mitochondrial ATP/ADP ratios increased. Inhibition of the malate-aspartate shuttle by the transaminase inhibitor aminooxyacetate (0.3 mmol/l) did not modify the effect of 2,4-dinitrophenol with dihydroxyacetone alone whereas it decreased the maximal stimulation of oxygen uptake after octanoate addition. In view of these results we propose the following conclusions. The uncoupling of intact cells by 2,4-dinitrophenol inhibits the translocation of reducing equivalents into the mitochondrial matrix probably by impairing the malate-aspartate shuttle. This explains the increase in the cytosolic NADH/NAD+ ratio and the transient activation of respiration with dihydroxyacetone. Fatty acid addition to cells uncoupled with 2,4-dinitrophenol appears to restore a mitochondrial membrane potential, probably by providing the respiratory chain with reduced cofactors directly in the matrix, thus allowing the transfer of reducing equivalents across the mitochondrial membrane. The restoration, to some extent, of a protonmotive force to uncoupled cells by fatty acid addition is also supported by an increase in ATP synthesis as evidenced by a glucose synthesis with dihydroxyacetone as gluconeogenic substrate.
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Affiliation(s)
- B Sibille
- Laboratoire de Thérapeutique, Université Joseph Fourier, Grenoble, France
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24
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Barratt MD. Quantitative structure activity relationships for skin corrosivity of organic acids, bases and phenols. Toxicol Lett 1995; 75:169-76. [PMID: 7863523 DOI: 10.1016/0378-4274(94)03177-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Quantitative structure activity relationships (QSARs) have been derived relating skin corrosivity data of organic acids, bases and phenols to their log(octanol/water partition coefficient), molecular volume, melting point and pKa. Datasets were analysed using principal components analysis; plots of the first 2 principal components of the above parameters, which broadly model skin permeability and cytotoxicity, for each group of chemicals showed that the analysis was able to discriminate well between corrosive and non-corrosive chemicals. The derived QSARs should be useful for the prediction of the skin corrosivity potential of new or untested chemicals.
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Affiliation(s)
- M D Barratt
- Unilever Environmental Safety Laboratory, Sharnbrook, Bedford, UK
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25
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Pavani M, Fones E, Oksenberg D, Garcia M, Hernandez C, Cordano G, Muñoz S, Mancilla J, Guerrero A, Ferreira J. Inhibition of tumoral cell respiration and growth by nordihydroguaiaretic acid. Biochem Pharmacol 1994; 48:1935-42. [PMID: 7986205 DOI: 10.1016/0006-2952(94)90592-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The effects of nordihydroguaiaretic acid (NDGA), best known as an inhibitor of lipoxygenase activities, on the culture growth, oxygen consumption, ATP level, viability, and redox state of some electron carriers of intact TA3 and 786A ascites tumor cells have been studied. NDGA inhibited the respiration rate of these two tumor cell lines by preventing electron flow through the respiratory chain. Consequently, ATP levels, cell viability and culture growth rates were decreased. NDGA did not noticeably inhibit electron flow through both cytochrome oxidase and ubiquinone-cytochrome b-c1 complex. Also, the presence of NDGA changed to redox state of NAD(P)+ to a more reduced level, and the redox states of ubiquinone, cytochrome b and cytochromes c + c1 changed to a more oxidized level. These observations suggest that the electron transport in the tumor mitochondria was inhibited by NDGA at the NADH-dehydrogenase-ubiquinone level (energy-conserving site 1). As a consequence, mitochondrial ATP synthesis would be interrupted. This event could be related to the cytotoxic effect of NDGA.
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Affiliation(s)
- M Pavani
- Department of Biochemistry and Chemistry, Faculty of Medicine, Universidad de Chile, Santiago
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26
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Abstract
The toxicity of nine chlorophenols to V79 Chinese hamster cells was determined in a survival assay which gives a direct measure of reproductive cell death by measuring single-cell cloning efficiency. Quantitative analyses of the structure-activity relationships showed that the toxicity was linearly related not only to hydrophobicity, as suggested by previous mammalian-cell studies, but also to electronic (electron-withdrawing) substituent effects. The extent electronic factors were related to the toxicity was assessed apart from their influence on partition and transport. The results suggest a relationship between the toxicity and the well-known ability of chlorophenols to induce proton permeability in membranes.
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Affiliation(s)
- K Jansson
- Department of Cell Biology, University of Jyväkylä, Finland
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27
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Barstad AW, Peyton DH, Smejtek P. AHA- heterodimer of a class-2 uncoupler: pentachlorophenol. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1140:262-70. [PMID: 8417778 DOI: 10.1016/0005-2728(93)90065-n] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
AHA- heterodimers formed by association of neutral molecules of weak acid (HA) with its conjugate anion (A-) have been proposed to be the charged membrane-permeable species of class-2 uncouplers. Past attempts to extract and identify AHA- heterodimers failed. We have measured optical spectra of HA+A- (1:1) solutions of pentachlorophenol (PCP) in various solvents and in the presence of PC liposomes. Optical studies were supplemented by nuclear magnetic resonance measurements of HA+A- (1:1) solutions of PCP in dichloroethane to gain insight into the formation of AHA- species in lipid membranes. From these experiments, we found evidence for AHA- formation in non-hydrogen-bonding solvents, then reported the AHA- formation constant Kf and the molar absorptivity epsilon AHA-(lambda). Kf decreases with increasing dielectric constant, kappa, from 1210 +/- 130 M-1 for dichloroethane (kappa 10.7), to 340 +/- 34 M-1 for acetonitrile (kappa 37.5); Kf also decreases with increasing concentration of water. In hydrogen-bonding solvents, octanol (kappa 10.3) and methanol (kappa 33.5) and in liposomes, AHA- heterodimers are not observed optically. We estimate Kf for PCP in lipid bilayers from a combination of data on membrane electrical conductivity and surface density of adsorbed PCP. Our estimate for lipid bilayer, 0.005 < Kf < 0.5 M-1, is consistent with our inability to detect the AHA- species optically in liposome suspensions. We propose that penetration of water into the membrane inhibits formation of AHA- in lipid bilayers.
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Affiliation(s)
- A W Barstad
- Physics Department, Portland State University, OR 97207-0751
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28
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Saitoh I, Miyoshi H, Shimizu R, Iwamura H. Comparison of structure of quinone redox site in the mitochondrial cytochrome-bc1 complex and photosystem II (QB site). EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 209:73-9. [PMID: 1327783 DOI: 10.1111/j.1432-1033.1992.tb17262.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A series of nitrophenolic electron-transport inhibitors (2-substituted 4,6-dinitrophenols) of rat liver mitochondrial cytochrome-bc1 complex and of photosystem II (QB site) of spinach thylakoids was synthesized. The structure/inhibitory-activity relationship was examined to elucidate differences in the three-dimensional structure of the quinone redox site in the two systems. These inhibitors occupy the ubiquinone redox site of cytochrome-bc1 complex competitively with natural ubiquinol, probably at a Qo reaction center. The inhibitory activity tended to increase with the length of the 2-substituent, which may correspond to the isoprenoid side chain of ubiquinone and plastoquinone, increased in both experimental systems. However, the strict structural requirements of the 2-substituent for binding to the ubiquinone or plastoquinone redox site were not identical. The alkyl substituents with a branching structure at the alpha-position to the benzene ring were favorable for inhibition of the cytochrome-bc1 complex, but not of photosystem II. Molecular-orbital calculations indicated that the main chain of 2-substituents with an alpha-branching structure was almost perpendicular to the benzene-ring plane because of steric congestion between the alpha-methyl and phenolic OH groups. The main chain of 2-substituents without an alpha-branching structure was flexible. Molecular-orbital studies indicated that ubiquinol was most stable when the portion of the isoprenoid side chain adjacent to the quinol ring was perpendicular to the quinol-ring plane, because of steric congestion by the vicinal OH and methyl groups. The side chain of plastoquinol was flexible because of the lack of a vicinal methyl group. Thus, the difference in the inhibitory activities between the two systems seemed to reflect the difference in the configuration of the isoprenoid side chain of ubiquinone and plastoquinone. These results suggested that the quinone redox site of the cytochrome-bc1 complex may recognize the configuration of the side chain near the quinone ring in the strict sense, whereas that of photosystem II (QB site) may recognize it in a loose sense.
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Affiliation(s)
- I Saitoh
- Department of Agricultural Chemistry, Kyoto University, Japan
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29
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Branca D, Roberti MS, Vincenti E, Scutari G. Uncoupling effect of the general anesthetic 2,6-diisopropylphenol in isolated rat liver mitochondria. Arch Biochem Biophys 1991; 290:517-21. [PMID: 1656882 DOI: 10.1016/0003-9861(91)90575-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
2,6-Diisopropylphenol, a general anesthetic, was previously reported to reduce the transmembrane electrical potential in isolated rat liver mitochondria without affecting the rate of ATP production. This effect appeared to contrast with the generally accepted chemiosmotic mechanism for oxidative phosphorylation. In this study we further examined the influence of 2,6-diisopropylphenol on the production of ATP by isolated mitochondria and we studied its effect on the permeability of the inner mitochondrial membrane to protons. In order to clarify the effects of 2,6-diisopropylphenol on mitochondrial ATP production the activities of the adenine nucleotide translocator and the ATP synthetase were evaluated. The results obtained indicate that the depression of the transmembrane electrical potential elicited by 2,6-diisopropylphenol decreased the activity of the ATP synthetase (as expected in the chemiosmotic model for energy coupling), but not that of the adenine nucleotide translocator. The decrease of the ATP synthetase activity, however, did not result in an apparent inhibition of the overall rate of ATP production in isolated mitochondria due to the rate-limiting effect of the adenine nucleotide translocator in this process. Moreover 2,6-diisopropylphenol was found to increase the permeability to protons of the inner mitochondrial membrane; this effect became more marked as the pH of the incubation medium was increased, demonstrating that it involved the dissociated form of 2,6-diisopropylphenol. These observations suggested that 2,6-diisopropylphenol affected oxidative phosphorylation by acting as a mild protonophore and that its effectiveness was limited by the low fraction of phenol dissociated at near-physiological pH.
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Affiliation(s)
- D Branca
- Dipartimento di Chimica Biologica, Università di Padova, Italy
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30
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Quantitative analysis with physicochemical substituent and molecular parameters of uncoupling activity of substituted diarylamines. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1991. [DOI: 10.1016/s0005-2728(05)80190-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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31
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Branca D, Roberti MS, Lorenzin P, Vincenti E, Scutari G. Influence of the anesthetic 2,6-diisopropylphenol on the oxidative phosphorylation of isolated rat liver mitochondria. Biochem Pharmacol 1991; 42:87-90. [PMID: 2069600 DOI: 10.1016/0006-2952(91)90684-w] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Isolated rat liver mitochondria have been incubated in the presence of the general anesthetic 2,6-diisopropylphenol (0-100 microM) and the efficiency of oxidative phosphorylation has been evaluated by measuring the respiratory rates, the rates of ATP synthesis or hydrolysis and the magnitude of the transmembrane electrical potential. The results obtained indicate that: (a) in mitochondria energized either by succinate or by ATP, 2,6-diisopropylphenol decreased the transmembrane electrical potential and increased the rates of either electron transfer or ATP hydrolysis; (b) in succinate-energized mitochondria 2,6-diisopropylphenol, at concentrations causing substantial depression of the transmembrane electrical potential, did not modify either the rate of phosphorylation of added ADP or the rate of ADP-stimulated respiration: (c) in succinate-energized mitochondria 2,6-diisopropylphenol caused a concentration-dependent inhibition of the uncoupler-stimulated rate of succinate oxidation. These findings suggest that under the experimental conditions reported 2,6-diisopropylphenol affected the generation and/or maintenance of the transmembrane electrical potential while leaving unchanged the coupling between the electron flow in the respiratory chain and the synthesis of ATP.
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Affiliation(s)
- D Branca
- Department of Biological Chemistry, University of Padova, Italy
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32
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Uncoupling activity of a newly developed fungicide, fluazinam [3-chloro-N-(3-chloro-2,6-dinitro-4-trifluoromethylphenyl)-5-trifluoromethyl-2-pyridinamine]. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1991. [DOI: 10.1016/s0005-2728(05)80077-5] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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33
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Rottenberg H. Decoupling of oxidative phosphorylation and photophosphorylation. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1018:1-17. [PMID: 1695856 DOI: 10.1016/0005-2728(90)90103-b] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- H Rottenberg
- Pathology Department, Hahnemann University School of Medicine, Philadelphia, PA
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34
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Miyoshi H, Tsujishita H, Tokutake N, Fujita T. Quantitative analysis of uncoupling activity of substituted phenols with a physicochemical substituent and molecular parameters. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1016:99-106. [PMID: 2310745 DOI: 10.1016/0005-2728(90)90011-r] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The uncoupling potency of a series of substituted phenols with rat-liver mitochondria was analyzed quantitatively with physicochemical substituent and molecular parameters such as log P, P being the partition coefficient in a phosphatidylcholine liposome/water system, log KA, KA being the acid dissociation constant, and the Taft-Kutter-Hansch steric constant, Es, for ortho-substituents. The potency evaluated from the concentration in the medium required for a defined response was analyzed, showing that the incorporation of compounds in terms of log P, a certain balance between neutral and ionized forms expressible by a parabolic function of log KA and the steric shielding effect of the ortho-substituents on the negatively charged center of ionized form are highly significant factors governing the variations in potency. The potency was also quantitatively separated into the intrinsic potency as the protonophore inside the inner mitochondrial membrane and the incorporation factor in terms of log P. Some phenols found as outliers from the correlations and some others distorting the quality of the correlations were shown to have inhibitory effects on the respiratory chain by specific and non-specific modes of action, respectively, besides uncoupling activity.
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Affiliation(s)
- H Miyoshi
- Department of Agricultural Chemistry, Kyoto University, Japan
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35
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Abstract
The chemiosmotic model of energy transduction offers a satisfying and widely confirmed understanding of the action of uncouplers on such processes as oxidative phosphorylation; the uncoupler, by facilitating the transmembrane movement of protons or other compensatory ions, reduces the electrochemical proton gradient that is posited as the energy intermediate for many kinds of bioenergetic work. In connection with this formulation, uncoupler-resistant mutants of bacteria that neither exclude nor inactivate these agents represent a bioenergetic puzzle. Uncoupler-resistant mutants of aerobic Bacillus species are, in fact, membrane lipid mutants with bioenergetic properties that are indeed challenging in connection with the chemiosmotic model. By contrast, uncoupler-resistant mutants of Escherichia coli probably exclude uncouplers, sometimes only under rather specific conditions. Related phenomena in eucaryotic and procaryotic systems, as well as various observations on uncouplers, decouplers, and certain other membrane-active agents, are also briefly considered.
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Affiliation(s)
- T A Krulwich
- Department of Biochemistry, Mount Sinai School of Medicine, City University of New York, New York 10029
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36
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Schönfeld P, Schild L, Kunz W. Long-chain fatty acids act as protonophoric uncouplers of oxidative phosphorylation in rat liver mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 977:266-72. [PMID: 2556180 DOI: 10.1016/s0005-2728(89)80080-5] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The effect of long-chain fatty acids (LCFA) on respiration and transmembrane potential (delta psi) in the resting state, and the rate of delta psi dissipation [d delta psi/dt)i) was investigated with oligomycin-inhibited rat liver mitochondria using succinate (plus rotenone) as substrate. The results obtained were compared with those of classical protonophores such as 2,4-dinitrophenol (DNP) and 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole (TTFB). The effects of oleate or palmitate and that of DNP or TTFB on respiration and delta psi can be described by a common force-flow relationship. These facts all in all are not compatible with a decoupler-type uncoupling mechanism of LCFA; still, they indicate that the latter are protonophores. Moreover, the oleate-induced increase in the rate of delta psi dissipation closely correlates with that in respiration, suggesting that the uncoupling activity and the protonophoric activity of LCFA are interrelated. Carboxyatractyloside (CAT) exerted only a small inhibitory effect on oleate-induced respiration and delta psi dissipation, indicating that the adenine nucleotide translocase contributes to the uncoupling effect of LCFA to a minor extent only. Proton transport through the lipid region of the membrane as mediated by permeation of the protonated and deprotonated forms of LCFA is interpreted as the main process of the uncoupling of LCFA.
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Affiliation(s)
- P Schönfeld
- Institut für Biochemie der Medizinischen Akademie Magdeburg, G.D.R
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37
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Terada H, Goto S, Yamamoto K, Takeuchi I, Hamada Y, Miyake K. Structural requirements of salicylanilides for uncoupling activity in mitochondria: quantitative analysis of structure-uncoupling relationships. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 936:504-12. [PMID: 3196713 DOI: 10.1016/0005-2728(88)90027-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The uncoupling activities of more than 20 salicylanilides were measured in rat liver mitochondria. The activities, expressed as the minimum concentrations required for full release of state-4 respiration, ranged over three orders of magnitude. The acid dissociation constant, pKA, and the partition coefficient between octanol and water (Poct) of some of the salicylanilides were determined. These two parameters were found to be well expressed in terms of the Hammett constant, sigma, and the hydrophobic substituent coefficient, II, respectively. The pKA and log Poct values of all the salicylanilides were predicted according to these relationships. Furthermore, the capacity factor, k', on high-performance liquid chromatography was determined on glyceryl-coated-controlled pore glass (gly-CPG). Values of log k' correlated well with those of log Poct. The uncoupling activities of the salicylanilides were analyzed in terms of these three parameters. Both hydrophobic and electron-withdrawing properties were found to be essential for induction of potent uncoupling activity. The correlations using log k' were better than those using log Poct.
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Affiliation(s)
- H Terada
- Faculty of Pharmaceutical Sciences, University of Tokushima, Japan
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38
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Miyoshi H, Fujita T. Quantitative analyses of the uncoupling activity of substituted phenols with mitochondria from flight muscles of house flies. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 935:312-21. [PMID: 2844258 DOI: 10.1016/0005-2728(88)90226-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Uncoupling activity with flight-muscle mitochondria from house flies was measured for a series of weakly acidic uncouplers (substituted phenols) and compared with the protonophoric potency across lecithin liposomal membranes. The activity was linearly related to the protonophoric potency when such factors as the stability of anionic species in the membrane phase and the difference in the pH conditions of the extramembranous aqueous phase were taken into account. Relationships of the flight-muscle activity with activities measured previously with rat-liver mitochondria and spinach chloroplasts were linear. Our findings were further evidence for the shuttle-type mechanism of the uncoupling action of weakly acidic uncouplers.
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Affiliation(s)
- H Miyoshi
- Department of Agricultural Chemistry, Faculty of Agriculture, Kyoto University, Japan
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Terada H, Fukui Y, Shinohara Y, Ju-ichi M. Unique action of a modified weakly acidic uncoupler without an acidic group, methylated SF 6847, as an inhibitor of oxidative phosphorylation with no uncoupling activity: possible identity of uncoupler binding protein. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 933:193-9. [PMID: 2894856 DOI: 10.1016/0005-2728(88)90070-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The potent weakly acidic uncoupler SF 6847 was modified by methylation of its phenolic OH group, and the effect of the resulting derivative, with no acid-dissociable group, on oxidative phosphorylation in rat liver mitochondria was examined. The methylated SF 6847 did not induce uncoupling at up to 40 microM, while SF 6847 uncoupled oxidative phosphorylation completely at about 20 nM, indicating that the acid-dissociable group is essential for uncoupling. The O-methylated SF 6847 at 20 microM did, however, inhibit state 3 respiration of mitochondria, although it did not inhibit electron-flow through the respiratory chain, ATPase activated by weakly acidic uncouplers or Pi-ATP exchange. At the same concentration, it also inhibited ATP synthesis in submitochondrial particles. These features are different from those of known inhibitors of oxidative phosphorylation. Thus, O-methylated SF 6847 is a unique inhibitor of oxidative phosphorylation. The possible identity of the uncoupler binding protein is discussed on the basis of these results.
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Affiliation(s)
- H Terada
- Faculty of Pharmaceutical Sciences, University of Tokushima, Japan
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Miyoshi H, Maeda H, Tokutake N, Fujita T. Quantitative Analysis of Partition Behavior of Substituted Phenols from Aqueous Phase into Liposomes Made of Lecithin and Various Lipids. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 1987. [DOI: 10.1246/bcsj.60.4357] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Miyoshi H, Fujita T. Quantitative analyses of uncoupling activity of SF6847 (2,6-di-t-butyl-4-(2,2-dicyanovinyl)phenol) and its analogs with spinach chloroplasts. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1987. [DOI: 10.1016/0005-2728(87)90204-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Miyoshi H, Nishioka T, Fujita T. Quantitative relationship between protonophoric and uncoupling activities of analogs of SF6847 (2,6-di-t-butyl-4-(2',2'-dicyanovinyl)phenol). BIOCHIMICA ET BIOPHYSICA ACTA 1987; 891:293-9. [PMID: 3567180 DOI: 10.1016/0005-2728(87)90224-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Uncoupling activity with rat liver mitochondria and protonophoric activity across the lecithin liposomal membranes were measured for a series of non-classical uncouplers related to the most potent uncoupler known until now, SF6847 (2,6-di-t-butyl-4-(2',2'-dicyanovinyl)phenol). The correlation between uncoupling and protonophoric activities for a number of uncouplers, both non-classical and classical (simply substituted phenols), was examined quantitatively. Correlation was excellent when such factors as the stability of anionic species in the membrane phase and the difference in the pH conditions of the extramembranous aqueous phase were taken into account. Carbonylcyanide m-chlorophenylhydrazone (CCCP) and carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), which are structurally different, were correlated in a way that resembled the correlation of phenolic compounds, so we think that the mode of action of weakly acidic uncouplers was the same regardless of the structural type. Our findings were evidence for the shuttle-type mechanism of uncoupling action.
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