The Experts below are selected from a list of 192 Experts worldwide ranked by ideXlab platform
Lester Packer - One of the best experts on this subject based on the ideXlab platform.
-
Succinate-Ubiquinone reductase linked recycling of α-tocopherol in reconstituted systems and mitochondria: Requirement for reduced Ubiquinone
Archives of Biochemistry and Biophysics, 2004Co-Authors: John J. Maguire, Valerian E. Kagan, Brian A. C. Ackrell, Elena Serbinova, Lester PackerAbstract:Abstract Studies have demonstrated that accumulation of mitochondrial tocopheroxyl radical, the primary oxidation product of α-tocopherol, accompanies rapid consumption of tocopherol. Enzyme-linked electron flow lowers both the steady-state concentration of the radical and the consumption of tocopherol. Reduction of tocopheroxyl radical by a mitochondrial electron carrier(s) seems a likely mechanism of tocopherol recycling. Succinate-Ubiquinone reductase (complex II) was incorporated into liposomes in the presence of tocopherol and Ubiquinone-10. After inducing formation of tocopheroxyl radical, it was possible to show that reduced Ubiquinone prevents radical accumulation and tocopherol consumption. There was no evidence of direct reduction of tocopheroxyl radical by succinate-reduced complex II. These reactions were also measured using Ubiquinone-1 and α-C-6-chromanol (2,5,7,8-tetramethyl-2-(4′-methylpentyl)-6-chromanol) which are less hydrophobic analogues of Ubiquinone-10 and α-tocopherol. Mitochondrial membranes were made deficient in Ubiquinone but sufficient in α-tocopherol and were reconstituted with added quinone. With these membranes it was shown that mitochondrial enzymelinked reduction of Ubiquinone protects α-tocopherol from consumption, and there is a requirement for Ubiquinone. This complements the observations made in liposomes and we propose that reduced mitochondrial Ubiquinones have a role in α-tocopherol protection, presumably through efficient reduction of the tocopheroxyl radical.
-
Assay of Ubiquinones and ubiquinols as antioxidants.
Methods in Enzymology, 2004Co-Authors: Valerian E. Kagan, Elena Serbinova, Detcho A. Stoyanovsky, S. Khwaja, Lester PackerAbstract:Publisher Summary A diverse range of biological electron-transfer membranes are known to contain a complement of Ubiquinones that can undergo redox changes. In membranes of animals, the role of Ubiquinones in electron transport is unclear with the notable exception of Ubiquinones in mitochondria. In mitochondria, Ubiquinones act as mobile distributors of reducing equivalents among the NADH dehydrogenase, succinate dehydrogenase, and cytochrome b–c1 segment of the electron transport chain and as participants of the protonmotive Q cycle. Ubiquinones are stoichiometrically in excess of electron-transfer chains, additionally, Ubiquinones in their reduced form, ubiquinols, may act as free radical scavengers. In chemical systems, vitamin E (α-tocopherol) has a higher reactivity toward peroxyl radicals than ubiquinols. The Ubiquinone/ubiquinol redox couple may act efficiently as a mediator in the regeneration of vitamin E by electron transport in cellular membranes. Ubiquinols may be necessary for reducing the vitamin E phenoxyl radical to prevent prooxidant effects of vitamin E in low density lipoproteins (LDL).
-
Interactions between Ubiquinones and vitamins in membranes and cells
Molecular Aspects of Medicine, 2003Co-Authors: Anastasia Constantinescu, John J. Maguire, Lester PackerAbstract:Abstract The interaction between Ubiquinones and vitamin E was studied in the inner membranes of rat liver mitochondria, liposomes and human erythrocyte plasma membranes. Free radicals were produced by addition of exogenous oxidants, and their reaction with chromanols and Ubiquinone was followed by ESR and HPLC. Membranes were made deficient in Ubiquinone but sufficient in α-tocopherol and were reconstituted with added Ubiquinone. With these membrane preparations it was shown that (i) in the inner mitochondrial membranes there is a requirement for Ubiquinone in the enzymatic recycling of vitamin E; (ii) succinate-Ubiquinone reductase incorporated in liposomes cannot protect vitamin E in the absence of Ubiquinone and (iii) in human erythrocyte plasma membranes protection against the loss of vitamin E can be provided by NADH-cytochrome-b 5 -dependent enzymatic recycling. We conclude that ubiquinonols (ubisemiquinones) reduce vitamin E through electron transport.
-
sensitive high performance liquid chromatography techniques for simultaneous determination of tocopherols tocotrienols ubiquinols and Ubiquinones in biological samples
Methods in Enzymology, 1999Co-Authors: Maurizio Podda, R Milbradt, Maret G Traber, Christine Weber, Lester PackerAbstract:Publisher Summary Lipophilic antioxidants are responsible for the protection of cell membranes against lipid peroxidation. Vitamin E is the major lipophilic antioxidant in plasma, membranes, and tissues and is the collective name for the eight naturally occurring molecules (four tocopherols and four tocotrienols) that exhibit α-tocopherol activity. This chapter discusses the sensitive high-performance liquid chromatography techniques for simultaneous determination of tocopherols, tocotrienols, ubiquinols, and Ubiquinones in biological samples. The method described in this chapter allows the extraction and detection of the various vitamin E forms along with ubiquinol/Ubiquinone in a single aliquot of tissue. The unexpected distribution of vitamin E forms in different tissues exemplifies that the selective determination of the major lipophilic antioxidants is important for understanding the relationship among diet, oxidative stress, and cellular regulatory processes.
-
simultaneous determination of tissue tocopherols tocotrienols ubiquinols and Ubiquinones
Journal of Lipid Research, 1996Co-Authors: Maurizio Podda, Maret G Traber, Christine Weber, Lester PackerAbstract:A tissue-specific distribution of the various vitamin E forms, tocotrienols and tocopherols, has been found, sug- gesting that these forms have unique roles in cellular func- tions. A sensitive procedure is described for the simultaneous determination of individual tocopherols, tocotrienols, ubiqui- nols, and Ubiquinones using gradient high pressure liquid chromatography (HPLC) and electrochemical detection for vitamin E homologues and ubiquinols, and in-line W detec- tion for Ubiquinones. Using this method, the lipophilic anti- oxidant complement of a variety of hairless mouse tissues was analyzed. Of the vitamin E forms, brain contained virtually only a-tocopherol (5.4 k 0.1 nmol/g; 99.8%) and no detect- able tocotrienols were found. By contrast, skin contained nearly 15% tocotrienols and 1% y-tocopherol. In other tissues, the a-tocopherol content was higher (20 nmol/g), while each of the other forms represented about 1% of the total (ptoco- phero10.2 to 0.4 nmol/g, a-tocotrienol 0.1, ptocotrienolO.2). Ubiquinol-9 concentrations were highest in kidney (81 nmol/g) and in liver (42 nmol/g), while the highest ubiqui- none-9 concentrations were found in kidney (301 k 123 nmol/g) and heart (244 & 22 nmol/g). Liver contained nearly identical concentrations of each of the redox couple (ubiqui- nol-9 (41 k 16 nmovg) and Ubiquinone-9 (46 k 18 nmol/g). I The unique distribution of these various antioxidants in the tissues measured suggests their distribution may be de- pendent upon selective mechanisms for maintaining antioxi- dant defenses in each tissue.-Podda, M., C. Weber, M. G. Traber, and L. Packer. Simultaneous determination of tissue tocopherol, tocotrienols, ubiquinols, and Ubiquinones. J. Lipid Res. 1996. 37: 893-901. Supplementary key words vitamin E coenzyme Q 0 HPLC 0 electrochemical detection tissue method
Wieslawa Jarmuszkiewicz - One of the best experts on this subject based on the ideXlab platform.
-
uncoupling protein 1 inhibition by purine nucleotides is under the control of the endogenous Ubiquinone redox state
Biochemical Journal, 2009Co-Authors: Aleksandra Swidabarteczka, Andrzej Woydaploszczyca, Francis Sluse, Wieslawa JarmuszkiewiczAbstract:We studied non-esterified fatty acid-induced uncoupling of heterologously expressed rat UCP1 (uncoupling protein 1) in yeast mitochondria, as well as UCP1 in rat BAT (brown adipose tissue) mitochondria. The proton-conductance curves and the relationship between the Ubiquinone reduction level and membrane potential were determined in non-phosphorylating BAT and yeast mitochondria. The ADP/O method was applied to determine the ADP phosphorylation rate and the relationship between the Ubiquinone reduction level and respiration rate in yeast mitochondria. Our studies of the membranous Ubiquinone reduction level in mitochondria demonstrate that activation of UCP1 leads to a purine nucleotide-sensitive decrease in the Ubiquinone redox state. Results obtained for non-phosphorylating and phosphorylating mitochondria, as the endogenous Ubiquinone redox state was gradually varied by a lowering rate of the Ubiquinone-reducing or ubiquinol-oxidizing pathways, indicate that the endogenous Ubiquinone redox state has no effect on non-esterified fatty acid-induced UCP1 activity in the absence of GTP, and can only regulate this activity through sensitivity to inhibition by the purine nucleotide. At a given oleic acid concentration, inhibition by GTP diminishes when Ubiquinone is reduced sufficiently. The Ubiquinone redox state-dependent alleviation of UCP1 inhibition by the purine nucleotide was observed at a high Ubiquinone reduction level, when it exceeded 85–88%.
-
Uncoupling protein 1 inhibition by purine nucleotides is under control of the endogenous Ubiquinone redox state
Biochemical Journal, 2009Co-Authors: Aleksandra Swida-barteczka, Francis Sluse, Andrzej Woyda-ploszczyca, Wieslawa JarmuszkiewiczAbstract:We studied free fatty acid-induced uncoupling of heterologously expressed rat UCP1 in yeast mitochondria as well as UCP1 in rat BAT mitochondria. The proton conductance curves and the relationship between Ubiquinone reduction level and membrane potential were determined in non-phosphorylating BAT and yeast mitochondria. The ADP/O method was applied to determine the ADP phosphorylation rate and the relationship between Ubiquinone reduction level and respiration rate in yeast mitochondria. Our studies of membranous Ubiquinone reduction level in mitochondria demonstrate that activation of UCP1 leads to a purine nucleotide-sensitive decrease in the Ubiquinone redox state. Results obtained for non-phosphorylating and phosphorylating mitochondria, as the endogenous Ubiquinone redox state was gradually varied by a lowering rate of the Ubiquinone-reducing or ubiquinol-oxidising pathways, indicate that the endogenous Ubiquinone redox state has no effect on free fatty acid-induced UCP1 activity in the absence of GTP, and can only regulate this activity through sensitivity to inhibition by the purine nucleotide. At a given oleic acid concentration, inhibition by GTP diminishes when Ubiquinone is reduced sufficiently. The Ubiquinone redox state-dependent alleviation of UCP1 inhibition by the purine nucleotide was observed at a high Ubiquinone reduction level, when it exceeded 85-88%.
Eric Fontaine - One of the best experts on this subject based on the ideXlab platform.
-
Ubiquinone analogs: a mitochondrial permeability transition pore-dependent pathway to selective cell death.
PLoS ONE, 2010Co-Authors: Flavien Devun, Ludivine Walter, Julie Belliere, Cécile Cottet-rousselle, Xavier Leverve, Eric FontaineAbstract:BACKGROUND: Prolonged opening of the mitochondrial permeability transition pore (PTP) leads to cell death. Various Ubiquinone analogs have been shown to regulate PTP opening but the outcome of PTP regulation by Ubiquinone analogs on cell fate has not been studied yet. METHODOLOGY/PRINCIPAL FINDINGS: The effects of Ubiquinone 0 (Ub(0)), Ubiquinone 5 (Ub(5)), Ubiquinone 10 (Ub(10)) and decyl-Ubiquinone (DUb) were studied in freshly isolated rat hepatocytes, cultured rat liver Clone-9 cells and cancerous rat liver MH1C1 cells. PTP regulation by Ubiquinones differed significantly in permeabilized Clone-9 and MH1C1 cells from that previously reported in liver mitochondria. Ub(0) inhibited PTP opening in isolated hepatocytes and Clone-9 cells, whereas it induced PTP opening in MH1C1 cells. Ub(5) did not affect PTP opening in isolated hepatocytes and MH1C1 cells, but it induced PTP opening in Clone-9 cells. Ub(10) regulated PTP in isolated hepatocytes, whereas it did not affect PTP opening in Clone-9 and MH1C1 cells. Only DUb displayed the same effect on PTP regulation in the three hepatocyte lines tested. Despite such modifications in PTP regulation, competition between Ubiquinones still occurred in Clone-9 and MH1C1 cells. As expected, Ub(5) induced a PTP-dependent cell death in Clone-9, while it did not affect MH1C1 cell viability. Ub(0) induced a PTP-dependent cell death in MH1C1 cells, but was also slightly cytotoxic in Clone-9 by an oxidative stress-dependent mechanism. CONCLUSIONS/SIGNIFICANCE: We found that various Ubiquinone analogs regulate PTP in different ways depending on the cell studied. We took advantage of this unique property to develop a PTP opening-targeted strategy that leads to cell death specifically in cells where the Ubiquinone analog used induces PTP opening, while sparing the cells in which it does not induce PTP opening.
-
a Ubiquinone binding site regulates the mitochondrial permeability transition pore
Journal of Biological Chemistry, 1998Co-Authors: Eric Fontaine, Francois Ichas, Paolo BernardiAbstract:Abstract We have investigated the regulation of the mitochondrial permeability transition pore (PTP) by Ubiquinone analogues. We found that the Ca2+-dependent PTP opening was inhibited by Ubiquinone 0 and decylUbiquinone, whereas all other tested quinones (Ubiquinone 5, 1,4-benzoquinone, 2-methoxy-1,4-benzoquinone, 2,3-dimethoxy-1,4-benzoquinone, and 2,3-dimethoxy-5,6-dimethyl-1,4-benzoquinone) were ineffective. Pore inhibition was observed irrespective of the method used to induce the permeability transition (addition of Pi or atractylate, membrane depolarization, or dithiol cross-linking). Inhibition of PTP opening by decylUbiquinone was comparable with that exerted by cyclosporin A, whereas Ubiquinone 0 was more potent. Ubiquinone 5, which did not inhibit the PTP per se, specifically counteracted the inhibitory effect of Ubiquinone 0 or decylUbiquinone but not that of cyclosporin A. These findings define a Ubiquinone-binding site directly involved in PTP regulation and indicate that different quinone structural features are required for binding and for stabilizing the pore in the closed conformation. At variance from all other quinones tested, decylUbiquinone did not inhibit respiration. Our results define a new structural class of pore inhibitors and may open new perspectives for the pharmacological modulation of the PTP in vivo.
Maurizio Podda - One of the best experts on this subject based on the ideXlab platform.
-
sensitive high performance liquid chromatography techniques for simultaneous determination of tocopherols tocotrienols ubiquinols and Ubiquinones in biological samples
Methods in Enzymology, 1999Co-Authors: Maurizio Podda, R Milbradt, Maret G Traber, Christine Weber, Lester PackerAbstract:Publisher Summary Lipophilic antioxidants are responsible for the protection of cell membranes against lipid peroxidation. Vitamin E is the major lipophilic antioxidant in plasma, membranes, and tissues and is the collective name for the eight naturally occurring molecules (four tocopherols and four tocotrienols) that exhibit α-tocopherol activity. This chapter discusses the sensitive high-performance liquid chromatography techniques for simultaneous determination of tocopherols, tocotrienols, ubiquinols, and Ubiquinones in biological samples. The method described in this chapter allows the extraction and detection of the various vitamin E forms along with ubiquinol/Ubiquinone in a single aliquot of tissue. The unexpected distribution of vitamin E forms in different tissues exemplifies that the selective determination of the major lipophilic antioxidants is important for understanding the relationship among diet, oxidative stress, and cellular regulatory processes.
-
simultaneous determination of tissue tocopherols tocotrienols ubiquinols and Ubiquinones
Journal of Lipid Research, 1996Co-Authors: Maurizio Podda, Maret G Traber, Christine Weber, Lester PackerAbstract:A tissue-specific distribution of the various vitamin E forms, tocotrienols and tocopherols, has been found, sug- gesting that these forms have unique roles in cellular func- tions. A sensitive procedure is described for the simultaneous determination of individual tocopherols, tocotrienols, ubiqui- nols, and Ubiquinones using gradient high pressure liquid chromatography (HPLC) and electrochemical detection for vitamin E homologues and ubiquinols, and in-line W detec- tion for Ubiquinones. Using this method, the lipophilic anti- oxidant complement of a variety of hairless mouse tissues was analyzed. Of the vitamin E forms, brain contained virtually only a-tocopherol (5.4 k 0.1 nmol/g; 99.8%) and no detect- able tocotrienols were found. By contrast, skin contained nearly 15% tocotrienols and 1% y-tocopherol. In other tissues, the a-tocopherol content was higher (20 nmol/g), while each of the other forms represented about 1% of the total (ptoco- phero10.2 to 0.4 nmol/g, a-tocotrienol 0.1, ptocotrienolO.2). Ubiquinol-9 concentrations were highest in kidney (81 nmol/g) and in liver (42 nmol/g), while the highest ubiqui- none-9 concentrations were found in kidney (301 k 123 nmol/g) and heart (244 & 22 nmol/g). Liver contained nearly identical concentrations of each of the redox couple (ubiqui- nol-9 (41 k 16 nmovg) and Ubiquinone-9 (46 k 18 nmol/g). I The unique distribution of these various antioxidants in the tissues measured suggests their distribution may be de- pendent upon selective mechanisms for maintaining antioxi- dant defenses in each tissue.-Podda, M., C. Weber, M. G. Traber, and L. Packer. Simultaneous determination of tissue tocopherol, tocotrienols, ubiquinols, and Ubiquinones. J. Lipid Res. 1996. 37: 893-901. Supplementary key words vitamin E coenzyme Q 0 HPLC 0 electrochemical detection tissue method
Hideto Miyoshi - One of the best experts on this subject based on the ideXlab platform.
-
oversized Ubiquinones as molecular probes for structural dynamics of the Ubiquinone reaction site in mitochondrial respiratory complex i
Journal of Biological Chemistry, 2020Co-Authors: Shinpei Uno, Masatoshi Murai, Takahiro Masuya, Kyoko Shinzawaitoh, Jonathan Lasham, Outi Haapanen, T Shiba, Daniel Ken Inaoka, Vivek Sharma, Hideto MiyoshiAbstract:NADH-quinone oxidoreductase (complex I) couples electron transfer from NADH to quinone with proton translocation across the membrane. Quinone reduction is a key step for energy transmission from the site of quinone reduction to the remotely located proton-pumping machinery of the enzyme. Although structural biology studies have proposed the existence of a long and narrow quinone-access channel, the physiological relevance of this channel remains debatable. We investigated here whether complex I in bovine heart submitochondrial particles (SMPs) can catalytically reduce a series of oversized Ubiquinones (OS-UQs), which are highly unlikely to transit the narrow channel because their side chain includes a bulky "block" that is ∼13 A across. We found that some OS-UQs function as efficient electron acceptors from complex I, accepting electrons with an efficiency comparable with Ubiquinone-2. The catalytic reduction and proton translocation coupled with this reduction were completely inhibited by different quinone-site inhibitors, indicating that the reduction of OS-UQs takes place at the physiological reaction site for Ubiquinone. Notably, the proton-translocating efficiencies of OS-UQs significantly varied depending on their side-chain structures, suggesting that the reaction characteristics of OS-UQs affect the predicted structural changes of the quinone reaction site required for triggering proton translocation. These results are difficult to reconcile with the current channel model; rather, the access path for Ubiquinone may be open to allow OS-UQs to access the reaction site. Nevertheless, contrary to the observations in SMPs, OS-UQs were not catalytically reduced by isolated complex I reconstituted into liposomes. We discuss possible reasons for these contradictory results.
-
synthetic Ubiquinones specifically bind to mitochondrial voltage dependent anion channel 1 vdac1 in saccharomyces cerevisiae mitochondria
Biochemistry, 2017Co-Authors: Masatoshi Murai, Ayaka Okuda, Takenori Yamamoto, Yasuo Shinohara, Hideto MiyoshiAbstract:The role of the voltage-dependent anion channel (VDAC) as a metabolic gate of the mitochondrial outer membrane has been firmly established; however, its involvement in the regulation of mitochondrial permeability transition (PT) remains extremely controversial. Although some low-molecular-weight chemicals have been proposed to modulate the regulatory role of VDAC in the induction of PT, direct binding between these chemicals and VDAC has not yet been demonstrated. In the present study, we investigated whether the Ubiquinone molecule directly binds to VDAC in Saccharomyces cerevisiae mitochondria through a photoaffinity labeling technique using two photoreactive Ubiquinones (PUQ-1 and PUQ-2). The results of the labeling experiments demonstrated that PUQ-1 and PUQ-2 specifically bind to VDAC1 and that the labeled position is located in the C-terminal region Phe221–Lys234, connecting the 15th and 16th β-strand sheets. Mutations introduced in this region (R224A, Y225A, D228A, and Y225A/D228A) hardly affected ...
-
Probing the Ubiquinone reduction site in bovine mitochondrial complex I using a series of synthetic Ubiquinones and inhibitors.
Journal of Bioenergetics and Biomembranes, 2001Co-Authors: Hideto MiyoshiAbstract:Studies of the structure–activity relationships of Ubiquinones and specific inhibitors are helpful to probe the structural and functional features of the Ubiquinone reduction site of bovine heart mitochondrial complex I. Bulky exogenous short-chain Ubiquinones serve as sufficient electron acceptors from the physiological Ubiquinone reduction site of bovine complex I. This feature is in marked contrast to other respiratory enzymes such as mitochondrial complexes II and III. For various complex I inhibitors, including the most potent inhibitors, acetogenins, the essential structural factors that markedly affect the inhibitory potency are not necessarily obvious. Thus, the loose recognition by the enzyme of substrate and inhibitor structures may reflect the large cavitylike structure of the Ubiquinone (or inhibitor) binding domain in the enzyme. On the other hand, several phenomena are difficult to explain by a simple one-catalytic site model for Ubiquinone.