References of "Sluse, Francis"
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See detailFatty acid efficiency profile in uncoupling of Acanthamoeba castellanii mitochondria.
Swida, A.; czarna, M.; Woyda-Polszczyca, A. et al

in Journal of Bioenergetics & Biomembranes (2006), 39

A profile of free fatty acid (FFA) specificity in Acanthamoeba castellanii mitochondrial uncoupling is described. The FFA uncoupling specificity was observed as different abilities to stimulate resting ... [more ▼]

A profile of free fatty acid (FFA) specificity in Acanthamoeba castellanii mitochondrial uncoupling is described. The FFA uncoupling specificity was observed as different abilities to stimulate resting respiration, to decrease resting membrane potential, and to decrease oxidative phosphorylation efficiency. Tested unsaturated FFA (C18-20) were more effective as uncouplers and protonophores when compared to tested saturated FFA (C8-18), with palmitic acid (C16:0) as the most active. As FFA efficiency in mitochondrial uncoupling is related to physiological changes of fatty acid composition (and thereby FFA availability) during growth of amoeba cells, it could be a way to regulate the activity of an uncoupling protein and thereby the efficiency of oxidative phosphorylation during a cell life of this unicellular organism. [less ▲]

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See detailMitochondrial uncoupling proteins: new insights from functional and proteomic studies.
Douette, P.; Sluse, Francis ULg

in Free Radical Biology & Medicine (2006), 40

Mitochondria are the major sites of ATP synthesis through oxidative phosphorylation, a process that is weakened by proton leak. Uncoupling proteins are mitochondrial membrane proteins specialized in ... [more ▼]

Mitochondria are the major sites of ATP synthesis through oxidative phosphorylation, a process that is weakened by proton leak. Uncoupling proteins are mitochondrial membrane proteins specialized in inducible proton conductance. They dissipate the proton electrochemical gradient established by the respiratory chain at the expense of reducing substrates. Several physiological roles have been suggested for uncoupling proteins, including roles in the control of the cellular energy balance and in preventive action against oxidative stress. This review focuses on new leads emerging from comparative proteomics about the involvement of uncoupling protein in the mitochondrial physiology. A brief overview on uncoupling proteins and on proteomics applied to mitochondria is also presented herein. [less ▲]

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See detailProton leak induced by reactive oxygen species produced during in vitro anoxia/reoxygenation in rat skeletal muscle mitochondria.
Navet, R.; Mouithys-mickalad, A.; Douette, P. et al

in Journal of Bioenergetics & Biomembranes (2006), 38

Superoxide anion generation and the impairment of oxidative phosphorylation yield were studied in rat skeletal muscle mitochondria submitted to anoxia/reoxygenation in vitro. Production of superoxide ... [more ▼]

Superoxide anion generation and the impairment of oxidative phosphorylation yield were studied in rat skeletal muscle mitochondria submitted to anoxia/reoxygenation in vitro. Production of superoxide anion was detected after several cycles of anoxia/reoxygenation. Concomitantly, a decrease of state 3 respiration and phosphorylation yield (ADP/O) were observed. The latter resulted from a proton leak. The presence of palmitic acid during anoxia/reoxygenation cycles led to a dose-dependent inhibition of superoxide anion production together with a partial protection of the ADP/O ratio measured after anoxia/reoxygenation. The ADP/O decrease was shown to be due to a permeability transition pore-sustained proton leak, as it was suppressed by cyclosporine A. The permeability transition pore activation was induced during anoxia/reoxygenation by superoxide anion, as it was cancelled by the spin trap (POBN), which scavenges superoxide anion and by palmitic acid, which induces mitochondrial uncoupling. It can be proposed that the palmitic acid-induced proton leak cancels the production of superoxide anion by mitochondria during anoxia/reoxygenation and therefore prevents the occurrence of the superoxide anion-induced permeability transition pore-mediated proton leak after anoxia/reoxygenation [less ▲]

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See detailRegulation of uncoupling protein activity in phosphorylating potato tuber mitochondria.
Navet, R.; Douette, P.; Puttique-Marique, F. et al

in FEBS Letters (2005), 579

In isolated potato tuber mitochondria, palmitic acid (PA) can induce a H+ leak inhibited by GTP in the phosphorylating (state 3) respiration but not in the resting (state 4) respiration. The PA-induced H ... [more ▼]

In isolated potato tuber mitochondria, palmitic acid (PA) can induce a H+ leak inhibited by GTP in the phosphorylating (state 3) respiration but not in the resting (state 4) respiration. The PA-induced H+ leak is constant when state 3 respiration is decreased by an inhibition of the succinate uptake with n-butyl malonate (nBM). We show that the efficiency of inhibition by GTP is decreased when state 3 respiration is progressively inhibited by antimycin A (AA) and is restored following subsequent addition of nBM. We propose that in phosphorylating potato tuber mitochondria, the redox state of ubiquinone, which can antagonistically be varied with AA and nBM, modulates inhibition of the PA-activated UCP-sustained H+ leak by GTP. [less ▲]

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See detailSubstrate kinetics of the Acanthamoeba castellanii alternative oxidase and the effects of GMP.
Jarmuszkiewicz, W.; Czarna, M.; Sluse, Francis ULg

in Biochimica et Biophysica Acta-Bioenergetics (2005), 1708

In Acanthamoeba castellanii mitochondria, the apparent affinity values of alternative oxidase for oxygen were much lower than those for cytochrome c oxidase. For unstimulated alternative oxidase, the K ... [more ▼]

In Acanthamoeba castellanii mitochondria, the apparent affinity values of alternative oxidase for oxygen were much lower than those for cytochrome c oxidase. For unstimulated alternative oxidase, the K(Mox) values were around 4-5 microM both in mitochondria oxidizing 1 mM external NADH or 10 mM succinate. For alternative oxidase fully stimulated by 1 mM GMP, the KK(Mox) values were markedly different when compared to those in the absence of GMP and they varied when different respiratory substrates were oxidized (K(Mox) was around 1.2 microM for succinate and around 11 microM for NADH). Thus, with succinate as a reducing substrate, the activation of alternative oxidase (with GMP) resulted in the oxidation of the ubiquinone pool, and a corresponding decrease in K(Mox). However, when external NADH was oxidized, the ubiquinone pool was further reduced (albeit slightly) with alternative oxidase activation, and the K(Mox) increased dramatically. Thus, the apparent affinity of alternative oxidase for oxygen decreased when the ubiquinone reduction level increased either by changing the activator or the respiratory substrate availability. [less ▲]

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See detailIn phosphorylating Acanthamoeba castellanii mitochondria the sensitivity of uncoupling protein activity to GTP depends on the redox state of quinone.
Jarmuszkiewicz, W.; Swida, A.; czarna, M. et al

in Journal of Bioenergetics & Biomembranes (2005), 37

In isolated Acanthamoeba castellanii mitochondria respiring in state 3 with external NADH or succinate, the linoleic acid-induced purine nucleotide-sensitive uncoupling protein activity is able to ... [more ▼]

In isolated Acanthamoeba castellanii mitochondria respiring in state 3 with external NADH or succinate, the linoleic acid-induced purine nucleotide-sensitive uncoupling protein activity is able to uncouple oxidative phosphorylation. The linoleic acid-induced uncoupling can be inhibited by a purine nucleotide (GTP) when quinone (Q) is sufficiently oxidized, indicating that in A. castellanii mitochondria respiring in state 3, the sensitivity of uncoupling protein activity to GTP depends on the redox state of the membranous Q. Namely, the inhibition of the linoleic acid-induced uncoupling by GTP is not observed in uninhibited state 3 respiration as well as in state 3 respiration progressively inhibited by complex III inhibitors, i.e., when the rate of quinol (QH(2))-oxidizing pathway is decreased. On the contrary, the progressive decrease of state 3 respiration by declining respiratory substrate availability (by succinate uptake limitation or by decreasing external NADH concentration), i.e., when the rate of Q-reducing pathways is decreased, progressively leads to a full inhibitory effect of GTP. Moreover, in A. castellanii mitochondria isolated from cold-treated cells, where a higher uncoupling protein activity is observed, the inhibition of the linoleic acid-induced proton leak by GTP is revealed for the same low values of the Q reduction level. [less ▲]

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See detailEscherichia coli fusion carrier proteins act as solubilizing agents for recombinant uncoupling protein 1 through interactions with GroEL.
Douette, P.; Navet, R.; Gerkens, P. et al

in Biochemical and Biophysical Research Communications (2005), 333

Fusing recombinant proteins to highly soluble partners is frequently used to prevent aggregation of recombinant proteins in Escherichia coli. Moreover, co-overexpression of prokaryotic chaperones can ... [more ▼]

Fusing recombinant proteins to highly soluble partners is frequently used to prevent aggregation of recombinant proteins in Escherichia coli. Moreover, co-overexpression of prokaryotic chaperones can increase the amount of properly folded recombinant proteins. To understand the solubility enhancement of fusion proteins, we designed two recombinant proteins composed of uncoupling protein 1 (UCP1), a mitochondrial membrane protein, in fusion with MBP or NusA. We were able to express soluble forms of MBP-UCP1 and NusA-UCP1 despite the high hydrophobicity of UCP1. Furthermore, the yield of soluble fusion proteins depended on co-overexpression of GroEL that catalyzes folding of polypeptides. MBP-UCP1 was expressed in the form of a non-covalent complex with GroEL. MBP-UCP1/GroEL was purified and characterized by dynamic light scattering, gel filtration, and electron microscopy. Our findings suggest that MBP and NusA act as solubilizing agents by forcing the recombinant protein to pass through the bacterial chaperone pathway in the context of fusion protein. [less ▲]

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See detailSteatosis-induced proteomic changes in liver mitochondria evidenced by two-dimensional differential in-gel electrophoresis
Douette, Pierre ULg; Navet, Rachel ULg; Gerkens, Pascal et al

in Journal of Proteome Research (2005), 4(6), 2024-2031

Steatosis encompasses the accumulation of droplets of fats into hepatocytes. In this work, we performed a comparative analysis of mitochondrial protein patterns found in wild-type and steatosis-affected ... [more ▼]

Steatosis encompasses the accumulation of droplets of fats into hepatocytes. In this work, we performed a comparative analysis of mitochondrial protein patterns found in wild-type and steatosis-affected liver using the novel technique two-dimensional differential in-gel electrophoresis (2D-DIGE). A total of 56 proteins exhibiting significant difference in their abundances were unambiguously identified. Interestingly, major proteins that regulate generation and consumption of the acetyl-CoA pool were dramatically changed during steatosis. Many proteins involved in the response to oxidative stress were also affected. [less ▲]

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See detailSecondary-structure characterization by far-UV CD of highly purified uncoupling protein 1 expressed in yeast
Douette, Pierre ULg; Navet, Rachel ULg; Bouillenne, Fabrice ULg et al

in Biochemical Journal (2004), 380(Pt 1), 139-145

The rat UCP1 (uncoupling protein 1) is a mitochondrial inner-membrane carrier involved in energy dissipation and heat production. We expressed UCP1 carrying a His(6) epitope at its C-terminus in ... [more ▼]

The rat UCP1 (uncoupling protein 1) is a mitochondrial inner-membrane carrier involved in energy dissipation and heat production. We expressed UCP1 carrying a His(6) epitope at its C-terminus in Saccharomyces cerevisiae mitochondria. The recombinant-tagged UCP1 was purified by immobilized metal-ion affinity chromatography to homogeneity (>95 %). This made it suitable for subsequent biophysical characterization. Fluorescence resonance energy transfer experiments showed that n-dodecyl-beta-D-maltoside-solubilized UCPI-His(6) retained its PN (purine nucleotide)-binding capacity. The far-UV CD spectrum of the functional protein clearly indicated the predominance of a-helices in the UCP1 secondary structure. The UCP1 secondary structure exhibited an alpha-helical degree of approx. 68 %, which is at least 25 % higher than the previously reported estimations based on computational predictions. Moreover, the helical content remained unchanged in free and PN-loaded UCP1. A homology model of the first repeat of UCP1, built on the basis of X-ray-solved close parent, the ADP/ATP carrier, strengthened the CD experimental results. Our experimental and computational results indicate that (i) alpha-helices are the major component of UCP1 secondary structure; (ii) PN-binding mechanism does not involve significant secondary-structure rearrangement; and (iii) UCP1 shares similar secondary-structure characteristics with the ADP/ATP carrier, at least for the first repeat. [less ▲]

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See detailEffects of COX-2 inhibitors on ROS produced by Chlamydia pneumoniae-primed human promonocytic cells (THP-1)
Mouithys-Mickalad, Ange ULg; Deby, Ginette ULg; Dogné, Jean-Michel ULg et al

in Biochemical and Biophysical Research Communications (2004), 325(4), 1122-1130

Chronic inflammation through foam cells and macrophages is important in atherosclerosis development, and can be considered as therapeutic targets. Cyclooxygenase and NADPH-oxidase were expressed within ... [more ▼]

Chronic inflammation through foam cells and macrophages is important in atherosclerosis development, and can be considered as therapeutic targets. Cyclooxygenase and NADPH-oxidase were expressed within atherosclerotic lesions. Reactive oxygen species produced by NADPH oxidase were found to trigger the cyclooxygenase-2 expression. The effects of preferential COX-2 inhibitors on ROS produced by Chlamydia-primed human monocytes (THP-1 cells) were evaluated by fluorescence, chemiluminescence, oxymetry, and EPR spin trapping. Fluorescence assays showed an increased production of ROS with Chlamydia versus cells primed by 10(-8) M PMA. COX-2 inhibitors inhibited in a dose-dependent manner the luminol-enhanced CL while ibuprofen and diclofenac increased the chemiluminescence response. By EPR spin trapping, COX-2 inhibitors, ibuprofen, and diclofenac, exhibited a dose-dependent inhibiting effect (10 and 100 muM) on the EPR signal appearance. Our cell model combining EPR, chemiluminescence, and oxymetry appeared relevant to study the modulating effects of preferential COX-2 inhibitors on the cell oxidant activity and chronic inflammatory diseases. (C) 2004 Elsevier Inc. All rights reserved. [less ▲]

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See detailMitochondrial respiratory chain complex patterns from Acanthamoeba castellanii and Lycopersicon esculentum: comparative analysis by BN-PAGE and evidence of protein-protein interaction between alternative oxidase and complex III.
Navet, R.; Jarmuszkiewicz, W.; Douette, P. et al

in Journal of Bioenergetics & Biomembranes (2004), 36(5), 471-479

We have previously shown that a kinetic interplay exists between the cytochrome pathway and the alternative oxidase in mitochondria from amoeba Acanthamoeba castellanii . Native interaction analyses using ... [more ▼]

We have previously shown that a kinetic interplay exists between the cytochrome pathway and the alternative oxidase in mitochondria from amoeba Acanthamoeba castellanii . Native interaction analyses using blue native gel electrophoresis coupled to denaturating electrophoresis and immunodetection have indicated associations between alternative oxidase and oxidative phosphorylation complexes in both amoeba and tomato mitochondria. These associations are dependent on the expression level of alternative oxidase according to the physiological state in both organisms. Alternative oxidase associates broadly with large complexes of the respiratory chain when it is expressed in large amount, i.e., in ripe tomato and exponentially growing amoeba. On the contrary, alternative oxidase interacts specifically with complex III even if expression of the oxidase is low, i.e., in green tomato and stationary phase amoeba. This specific interaction represents a higher level of regulation driven by protein-protein interactions leading to a direct kinetic interplay between the cytochrome pathway and alternative oxidase in both plant and amoeba mitochondria. [less ▲]

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See detailThe effect of growth at low temperature on the activity and expression of the uncoupling protein in Acanthamoeba castellanii mitochondria.
Jarmuszkiewicz, W.; Antos, N.; swida, A. et al

in FEBS Letters (2004), 569

Mitochondria of amoeba Acanthamoeba castellanii, a non-photosynthetic soil amoeboid protozoon, possess an uncoupling protein (AcUCP) that mediates free fatty acid-activated proton re-uptake dissipating ... [more ▼]

Mitochondria of amoeba Acanthamoeba castellanii, a non-photosynthetic soil amoeboid protozoon, possess an uncoupling protein (AcUCP) that mediates free fatty acid-activated proton re-uptake dissipating the proton electrochemical gradient built up by respiration. The present study provides the first evidence that UCP could be a cold response protein in unicellulars. In mitochondria isolated from an amoeba batch culture grown temporarily at low temperature (6 degrees C), the content of AcUCP was increased and correlated with an increase in the linoleic acid (LA)-stimulated UCP-mediated carboxyatractyloside-resistant state 4 respiration, as compared to a control culture (routinely grown at 28 degrees C). Moreover, the cytochrome pathway activity was found to be insensitive to the cold exposure of amoeba cells, as indicated by respiration and membrane potential measurements as well as by an absence of change in the adenine nucleotide translocator and cytochrome oxidase expression levels. Furthermore, in mitochondria from the low-temperature-grown cells, at fixed LA concentration, the increased contribution of AcUCP activity to total mitochondrial phosphorylating respiration accompanied by lower coupling parameters was found, as was confirmed by calculation of this contribution using ADP/O measurements. [less ▲]

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See detailThe contribution of uncoupling protein and ATP synthase to state 3 respiration in Acanthamoeba castellanii mitochondria.
Jarmuszkiewicz, W.; Czarna, M.; Sluse-Goffart, C. et al

in Acta Biochimica Polonica. Polish. (2004), 51

Mitochondria of the amoeba Acanthamoeba castellanii possess a free fatty acid-activated uncoupling protein (AcUCP) that mediates proton re-uptake driven by the mitochondrial proton electrochemical ... [more ▼]

Mitochondria of the amoeba Acanthamoeba castellanii possess a free fatty acid-activated uncoupling protein (AcUCP) that mediates proton re-uptake driven by the mitochondrial proton electrochemical gradient. We show that AcUCP activity diverts energy from ATP synthesis during state 3 mitochondrial respiration in a fatty acid-dependent way. The efficiency of AcUCP in mitochondrial uncoupling increases when the state 3 respiratory rate decreases as the AcUCP contribution is constant at a given linoleic acid concentration while the ATP synthase contribution decreases with respiratory rate. Respiration sustained by this energy-dissipating process remains constant at a given linoleic acid concentration until more than 60% inhibition of state 3 respiration by n-butyl malonate is achieved. The present study supports the validity of the ADP/O method to determine the actual contributions of AcUCP (activated with various linoleic acid concentrations) and ATP synthase in state 3 respiration of A.castellanii mitochondria fully depleted of free fatty acid-activated and describes how the two contributions vary when the rate of succinate dehydrogenase is decreased by succinate uptake limitation [less ▲]

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See detailProtective effect of EGB 761 against oxidative phosphorylation damages of brain mitochondria after Anoxia/reoxygenation in vivo and in vitro
Du, G.; Willet, K.; Jarmuszkiewicz, W. et al

in Toxicology Mechanisms & Methods (2004), 14

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See detailRedox state of endogenous coenzyme q modulates the inhibition of linoleic acid-induced uncoupling by guanosine triphosphate in isolated skeletal muscle mitochondria.
Jarmuszkiewicz, W.; Navet, R.; Alberici, L. et al

in Journal of Bioenergetics & Biomembranes (2004), 36

The skeletal muscle mitochondria contain two isoforms of uncoupling protein, UCP2 and mainly UCP3, which had been shown to be activated by free fatty acids and inhibited by purine nucleotides in ... [more ▼]

The skeletal muscle mitochondria contain two isoforms of uncoupling protein, UCP2 and mainly UCP3, which had been shown to be activated by free fatty acids and inhibited by purine nucleotides in reconstituted systems. On the contrary in isolated mitochondria, the protonophoretic action of muscle UCPs had failed to be demonstrated in the absence of superoxide production. We showed here for the first time that muscle UCPs were activated in state 3 respiration by linoleic acid and dissipated energy from oxidative phosphorylation by decreasing the ADP/O ratio. The efficiency of UCPs in mitochondrial uncoupling increased when the state 3 respiratory rate decreased. The inhibition of the linoleic acid-induced uncoupling by a purine nucleotide (GTP), was not observed in state 4 respiration, in uninhibited state 3 respiration, as well as in state 3 respiration inhibited by complex III inhibitors. On the contrary, the progressive inhibition of state 3 respiration by n -butyl malonate, which inhibits the uptake of succinate, led to a full inhibitory effect of GTP. Therefore, as the inhibitory effect of GTP was observed only when the reduced state of coenzyme Q was decreased, we propose that the coenzyme Q redox state could be a metabolic sensor that modulates the purine nucleotide inhibition of FFA-activated UCPs in muscle mitochondria. [less ▲]

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See detailEFFECTS OF O2 TENSION AND GLUCOSE CONCENTRATION ON THE CELLULAR RESPIRATION OF EQUINE ARTICULAR CHONDROCYTES IN CULTURE.
Schneider, Nicole ULg; Lejeune, Jean-Philippe ULg; Duyckaerts, Claire ULg et al

Poster (2003)

In vivo, articular chondrocytes are exposed to 5 to 10% O2. Chondrocytes are also suspected to produce reactive oxygen species when submitted to anoxia/re-oxygenation. We were interested to study the ... [more ▼]

In vivo, articular chondrocytes are exposed to 5 to 10% O2. Chondrocytes are also suspected to produce reactive oxygen species when submitted to anoxia/re-oxygenation. We were interested to study the effects of O2 and glucose variations on cellular respiration, glucose consumption and lactate production. Equine articular chondrocytes were cultured in suspension for 2 days under 5 or 21 % O2 in the gaseous phase, and with 0, 1.0 or 4.5 g/L glucose. The viable cells were then counted and the respiration rate (O2 consumption) of 10.106 cells was monitored by oxymetry for 2 hours; after oxymetry, glucose and lactate were measured in the medium (enzymatic assays). After 2 days, the cell viability was the best at 5% O2 and 1g/L glucose; it decreased at 4.5 g/L glucose and was the worst at 0g/L glucose, for the two O2 tensions (n=3). There was no obvious difference of the respiration rate between cells cultured at 5 and 21% O2, but respiration of chondrocytes was surprisingly low. When cells were submitted to 20 min anoxia at 0% O2, the O2 consumption was doubled at re-oxygenation for cells previously cultured at 21% O2. Glucose and lactate values found in the medium after oxymetry: lactate release in medium was similar (36.23 and 34.57 mg/L respectively) for cells cultured with 1g glucose and 5 or 21% O2 conditions; lactate values were low (2.03 and 8,63 mg/L respectively) for 4.5 g glucose and 5 or 21% O2. Glucose uptake was not different whatever the culture conditions. These results indicate a low cellular respiration with a lactate production linked to the glucose concentrationin the medium, and raise the question of the capacity of chondrocytes to produce ROS in vivo starting from the mitochondrial chain. [less ▲]

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See detailEffects of O2 tension and glucose concentration on the cellular respiration of equine articular chondrocytes in culture.
Schneider, Nicole ULg; Lejeune, Jean-Philippe ULg; Mouithys-Mickalad, Ange ULg et al

Poster (2003)

In vivo, articular chondrocytes are exposed to 5 to 10% O21,2. Chondrocytes are also suspected to produce reactive oxygen species when submitted to anoxia/re-oxygenation3,4. We were interested to study ... [more ▼]

In vivo, articular chondrocytes are exposed to 5 to 10% O21,2. Chondrocytes are also suspected to produce reactive oxygen species when submitted to anoxia/re-oxygenation3,4. We were interested to study the effects of O2 and glucose variations on cellular respiration, glucose consumption and lactate production. Equine articular chondrocytes were cultured in suspension for 2 days under 5 or 21 % O2 in the gaseous phase, and with 0, 1.0 or 4.5 g/L glucose. The viable cells were then counted and the respiration rate (O2 consumption) of 10.106 cells was monitored by oxymetry for 2 hours; after oxymetry, glucose and lactate were measured in the medium (enzymatic assays). After 2 days, the cell viability was the best at 5% O2 and 1g/L glucose; it decreased at 4.5 g/L glucose and was the worst at 0g/L glucose, for the two O2 tensions (n=3). There was no obvious difference of the respiration rate between cells cultured at 5 and 21% O2, but respiration of chondrocytes was surprisingly low. When cells were submitted to 20 min anoxia at 0% O2, the O2 consumption was doubled at re-oxygenation for cells previously cultured at 21% O2. Glucose and lactate values found in the medium after oxymetry : lactate release in medium was similar (36.23 and 34.57 mg/L respectively) for cells cultured with 1g glucose and 5 or 21% O2 conditions; lactate values were low (2.03 and 8,63 mg/L respectively) for 4.5 g glucose and 5 or 21% O2. Glucose uptake was not different whatever the culture conditions. These results indicate a low cellular respiration with a lactate production linked to the glucose concentration in the medium, and raise the question of the capacity of chondrocytes to produce ROS in vivo starting from the mitochondrial chain. [less ▲]

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See detailEnergy conservation and dissipation in mitochondria isolated from developing tomato fruit of ethylene-defective mutants failing normal ripening: the effect of ethephon, a chemical precursor of ethylene.
Navet, R.; Jarmuszkiewicz, W.; Almeida, A. et al

in Journal of Bioenergetics & Biomembranes (2003), 35(2), 157-168

Alternative oxidase (AOX) and uncoupling protein (UCP) are present simultaneously in tomato fruit mitochondria. In a previous work, it has been shown that protein expression and activity of these two ... [more ▼]

Alternative oxidase (AOX) and uncoupling protein (UCP) are present simultaneously in tomato fruit mitochondria. In a previous work, it has been shown that protein expression and activity of these two energy-dissipating systems exhibit large variations during tomato fruit development and ripening on the vine. It has been suggested that AOX and UCP could be responsible for the respiration increase at the end of ripening and that the cytochrome pathway could be implicated in the climacteric respiratory burst before the onset of ripening. In this study, the use of tomato mutants that fail normal ripening because of deficiencies in ethylene perception or production as well as the treatment of one selected mutant with a chemical precursor of ethylene have revealed that the bioenergetics of tomato fruit development and ripening is under the control of this plant hormone. Indeed, the evolution pattern of bioenergetic features changes with the type of mutation and with the introduction of ethylene into an ethylene-synthesis-deficient tomato fruit mutant during its induced ripening. [less ▲]

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See detailTransient modifications of respiratory capacity in thymic cells during murine radioleukemogenesis
Verlaet, Myriam ULg; Duyckaerts, Claire ULg; Rahmouni, Souad ULg et al

in Free Radical Biology & Medicine (2002), 33(1), 76-82

The evolution of mitochondrial oxidative phosphorylation was studied during cancer induction in a model of thymic radiolymphomagenesis in C57BL/Ka mice. During the preneoplastic period, thymuses displayed ... [more ▼]

The evolution of mitochondrial oxidative phosphorylation was studied during cancer induction in a model of thymic radiolymphomagenesis in C57BL/Ka mice. During the preneoplastic period, thymuses displayed an increase of the cytochrome c oxidase activity and oxygen consumption together with oxidative DNA damage assessed by the presence of the 8-hydroxydeoxyguanine DNA base modification. These transient changes in mitochondrial functional activity were not observed in thymuses of mice rescued from lymphoma development by a bone marrow graft, suggesting an important role of mitochondria for neoplastic transformation in this model. which might therefore be of interest to test the utilization of antioxidants for the prevention of radiation-induced malignancies. (C) 2002 Elsevier Science Inc. [less ▲]

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See detailUncoupling protein and alternative oxidase of Dictyostelium discoideum: occurrence, properties and protein expression during vegetative life and starvation-induced early development.
Jarmusszkiewicz, W.; Behrendt, M.; Navet, R. et al

in FEBS Letters (2002), 532

In this study we show that mitochondria of Dictyostelium discoideum contain both alternative oxidase (AOX) and uncoupling protein (UCP). AOX was stimulated by purine mononucleoside and was monomeric. UCP ... [more ▼]

In this study we show that mitochondria of Dictyostelium discoideum contain both alternative oxidase (AOX) and uncoupling protein (UCP). AOX was stimulated by purine mononucleoside and was monomeric. UCP was stimulated by free fatty acids and was poorly sensitive to GTP. Both proteins collaborated in energy dissipation when activated together. AOX expression in free-living ameboid cells decreased strongly from exponential to stationary phase of growth but much less during starvation-induced aggregation. In contrast, UCP expression was constant in all conditions indicating permanent need. Our results suggest that AOX could play a role in cell differentiation, mainly by protecting prespore cells from programmed cell death. [less ▲]

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