RESUMO
CONTEXT: The toxicity of atractyloside/carboxyatractyloside is generally well recognized and commonly ascribed to the inhibition of mitochondrial ADP/ATP carriers, which are pivotal for oxidative phosphorylation. However, these glycosides may 'paralyze' additional target proteins. OBJECTIVE: This review presents many facts about atractyloside/carboxyatractyloside and their plant producers, such as Xanthium spp. (Asteraceae), named cockleburs. METHODS: Published studies and other information were obtained from databases, such as 'CABI - Invasive Species Compendium', 'PubMed', and 'The World Checklist of Vascular Plants', from 1957 to December 2022. The following major keywords were used: 'carboxyatractyloside', 'cockleburs', 'hepatotoxicity', 'mitochondria', 'nephrotoxicity', and 'Xanthium'. RESULTS: In the third decade of the twenty first century, public awareness of the severe toxicity of cockleburs is still limited. Such toxicity is often only perceived by specialists in Europe and other continents. Interestingly, cocklebur is among the most widely distributed invasive plants worldwide, and the recognition of new European stands of Xanthium spp. is provided here. The findings arising from field and laboratory research conducted by the author revealed that (i) some livestock populations may instinctively avoid eating cocklebur while grazing, (ii) carboxyatractyloside inhibits ADP/GDP metabolism, and (iii) the direct/indirect target proteins of carboxyatractyloside are ambiguous. CONCLUSIONS: Many aspects of the Xanthium genus still require substantial investigation/revision in the future, such as the unification of the Latin nomenclature of currently distinguished species, bur morphology status, true fruit (achene) description and biogeography of cockleburs, and a detailed description of the physiological roles of atractyloside/carboxyatractyloside and the toxicity of these glycosides, mainly toward mammals. Therefore, a more careful interpretation of atractyloside/carboxyatractyloside data, including laboratory tests using Xanthium-derived extracts and purified toxins, is needed.
Assuntos
Núcleosídeo-Difosfato Quinase , Animais , Atractilosídeo/toxicidade , Glicosídeos/toxicidade , Difosfato de Adenosina , MamíferosRESUMO
Sixteen adult, 4-month-old male Wistar rats were randomly assigned to the training group (n = 8) or the control group (n = 8). We elucidated the effects of 8 weeks of endurance training on coenzyme Q (Q) content and the formation of reactive oxygen species (ROS) at the tissue level and in isolated mitochondria of the rat heart, liver and brain. We demonstrated that endurance training enhanced mitochondrial biogenesis in all tested organs, while a significant increase in the Q redox state was observed in the heart and brain, indicating an elevated level of QH2 as an antioxidant. Moreover, endurance training increased the mQH2 antioxidant pool in the mitochondria of the heart and liver, but not in the brain. At the tissue and isolated mitochondria level, an increase in ROS formation was only observed in the heart. ROS formation observed in the mitochondria of individual rat tissues after training may be associated with changes in the activity/amount of individual components of the oxidative phosphorylation system and its molecular organization, as well as with the size of the oxidized pool of mitochondrial Q acting as an electron carrier in the respiratory chain. Our results indicate that tissue-dependent changes induced by endurance training in the cellular and mitochondrial QH2 pool acting as an antioxidant and in the mitochondrial Q pool serving the respiratory chain may serve important roles in energy metabolism, redox homeostasis and the level of oxidative stress.
Assuntos
Transporte de Elétrons , Mitocôndrias/fisiologia , Oxirredução , Fosforilação Oxidativa , Espécies Reativas de Oxigênio/metabolismo , Ubiquinona/análogos & derivados , Animais , Encéfalo/metabolismo , Treino Aeróbico , Coração , Peróxido de Hidrogênio/metabolismo , Fígado/metabolismo , Miocárdio/metabolismo , Especificidade de Órgãos , Estresse Oxidativo , Ratos , Ubiquinona/metabolismoRESUMO
Uncoupling proteins (UCPs) belong to the mitochondrial anion carrier protein family and mediate regulated proton leak across the inner mitochondrial membrane. Free fatty acids, aldehydes such as hydroxynonenal, and retinoids activate UCPs. However, there are some controversies about the effective action of retinoids and aldehydes alone; thus, only free fatty acids are commonly accepted positive effectors of UCPs. Purine nucleotides such as GTP inhibit UCP-mediated mitochondrial proton leak. In turn, membranous coenzyme Q may play a role as a redox state-dependent metabolic sensor that modulates the complete activation/inhibition of UCPs. Such regulation has been observed for UCPs in microorganisms, plant and animal UCP1 homologues, and UCP1 in mammalian brown adipose tissue. The origin of UCPs is still under debate, but UCP homologues have been identified in all systematic groups of eukaryotes. Despite the differing levels of amino acid/DNA sequence similarities, functional studies in unicellular and multicellular organisms, from amoebae to mammals, suggest that the mechanistic regulation of UCP activity is evolutionarily well conserved. This review focuses on the regulatory feedback loops of UCPs involving free fatty acids, aldehydes, retinoids, purine nucleotides, and coenzyme Q (particularly its reduction level), which may derive from the early stages of evolution as UCP first emerged.
Assuntos
Aldeídos/metabolismo , Eucariotos/metabolismo , Ácidos Graxos não Esterificados/metabolismo , Mamíferos/metabolismo , Proteínas de Desacoplamento Mitocondrial/metabolismo , Nucleotídeos de Purina/metabolismo , Ubiquinona/metabolismo , AnimaisRESUMO
The biogenesis of the cauliflower curd mitochondrial proteome was investigated under cold, heat and the recovery. For the first time, two dimensional fluorescence difference gel electrophoresis was used to study the plant mitochondrial complexome in heat and heat recovery. Particularly, changes in the complex I and complex III subunits and import proteins, and the partial disintegration of matrix complexes were observed. The presence of unassembled subunits of ATP synthase was accompanied by impairment in mitochondrial translation of its subunit. In cold and heat, the transcription profiles of mitochondrial genes were uncorrelated. The in-gel activities of respiratory complexes were particularly affected after stress recovery. Despite a general stability of respiratory chain complexes in heat, functional studies showed that their activity and the ATP synthesis yield were affected. Contrary to cold stress, heat stress resulted in a reduced efficiency of oxidative phosphorylation likely due to changes in alternative oxidase (AOX) activity. Stress and stress recovery differently modulated the protein level and activity of AOX. Heat stress induced an increase in AOX activity and protein level, and AOX1a and AOX1d transcript level, while heat recovery reversed the AOX protein and activity changes. Conversely, cold stress led to a decrease in AOX activity (and protein level), which was reversed after cold recovery. Thus, cauliflower AOX is only induced by heat stress. In heat, contrary to the AOX activity, the activity of rotenone-insensitive internal NADH dehydrogenase was diminished. The relevance of various steps of plant mitochondrial biogenesis to temperature stress response and recovery is discussed.
Assuntos
Brassica/fisiologia , Respiração Celular/fisiologia , Regulação da Expressão Gênica de Plantas , Proteínas Mitocondriais/metabolismo , Renovação Mitocondrial/fisiologia , Oxirredutases/metabolismo , Proteínas de Plantas/metabolismo , Estresse Fisiológico , Western Blotting , Transporte de Elétrons , Eletroforese em Gel Bidimensional , Membranas Mitocondriais/metabolismo , Proteínas Mitocondriais/genética , NADH Desidrogenase/genética , NADH Desidrogenase/metabolismo , Oxirredução , Fosforilação Oxidativa , Estresse Oxidativo , Oxirredutases/genética , Proteínas de Plantas/genética , Proteômica , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , TemperaturaRESUMO
Endurance training enhances mitochondrial oxidative capacity, but its effect on mitochondria functioning is poorly understood. In the present study, the influence of an 8-week endurance training on the bioenergetic functioning of rat skeletal muscle mitochondria under different assay temperatures (25, 35, and 42 °C) was investigated. The study was performed on 24 adult 4-month-old male Wistar rats, which were randomly assigned to either a treadmill training group (n = 12) or a sedentary control group (n = 12). In skeletal muscles, endurance training stimulated mitochondrial biogenesis and oxidative capacity. In isolated mitochondria, endurance training increased the phosphorylation rate and elevated levels of coenzyme Q. Moreover, a decrease in mitochondrial uncoupling, including uncoupling protein-mediated proton leak, was observed after training, which could explain the increased reactive oxygen species production (in nonphosphorylating mitochondria) and enhanced oxidative phosphorylation efficiency. At all studied temperatures, endurance training significantly augmented H2O2 production (and coenzyme Q reduction level) in nonphosphorylating mitochondria and decreased H2O2 production (and coenzyme Q reduction level) in phosphorylating mitochondria. Endurance training magnified the hyperthermia-induced increase in oxidative capacity and attenuated the hyperthermia-induced decline in oxidative phosphorylation efficiency and reactive oxygen species formation of nonphosphorylating mitochondria via proton leak enhancement. Thus, endurance training induces both quantitative and qualitative changes in muscle mitochondria that are important for cell signaling as well as for maintaining muscle energy homeostasis, especially at high temperatures.
Assuntos
Mitocôndrias Musculares/metabolismo , Músculo Esquelético/metabolismo , Condicionamento Físico Animal , Animais , Peróxido de Hidrogênio/metabolismo , Masculino , Músculo Esquelético/fisiologia , Fosforilação Oxidativa , Resistência Física , Esforço Físico , Ratos , Ratos Wistar , Ubiquinona/metabolismoRESUMO
The influence of 4-hydroxy-2-nonenal (HNE), a lipid peroxidation end product, on the activity of the amoeba Acanthamoeba castellanii uncoupling protein (AcUCP) in isolated phosphorylating mitochondria was studied. Under phosphorylating conditions, exogenously added HNE induced GTP-sensitive AcUCP-mediated mitochondrial uncoupling. The HNE-induced proton leak decreased the yield of oxidative phosphorylation in an HNE concentration-dependent manner. The present study describes how the contributions of ATP synthase and HNE-induced AcUCP in phosphorylating respiration vary when the rate of succinate oxidation is decreased by limiting succinate uptake or inhibiting complex III activity within the range of a constant membrane potential. In phosphorylating mitochondria, at a given HNE concentration (100 µM), the efficiency of AcUCP in mitochondrial uncoupling increased as the respiratory rate decreased because the AcUCP contribution remained constant while the ATP synthase contribution decreased with the respiratory rate. HNE-induced uncoupling can be inhibited by GTP only when ubiquinone is sufficiently oxidized, indicating that in phosphorylating A. castellanii mitochondria, the sensitivity of AcUCP activity to GTP depends on the redox state of the membranous ubiquinone.
Assuntos
Acanthamoeba castellanii/metabolismo , Aldeídos/farmacologia , Canais Iônicos/metabolismo , Mitocôndrias/metabolismo , Proteínas Mitocondriais/metabolismo , Proteínas de Protozoários/metabolismo , Acanthamoeba castellanii/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Oxirredução , Fosforilação Oxidativa , Proteína Desacopladora 1RESUMO
We compared the influence of different adenine and guanine nucleotides on the free fatty acid-induced uncoupling protein (UCP) activity in non-phosphorylating Acanthamoeba castellanii mitochondria when the membranous ubiquinone (Q) redox state was varied. The purine nucleotides exhibit an inhibitory effect in the following descending order: GTP>ATP>GDP>ADPâ«GMP>AMP. The efficiency of guanine and adenine nucleotides to inhibit UCP-sustained uncoupling in A. castellanii mitochondria depends on the Q redox state. Inhibition by purine nucleotides can be increased with decreasing Q reduction level (thereby ubiquinol, QH2 concentration) even with nucleoside monophosphates that are very weak inhibitors at the initial respiration. On the other hand, the inhibition can be alleviated with increasing Q reduction level (thereby QH2 concentration). The most important finding was that ubiquinol (QH2) but not oxidised Q functions as a negative regulator of UCP inhibition by purine nucleotides. For a given concentration of QH2, the linoleic acid-induced GTP-inhibited H(+) leak was the same for two types of A. castellanii mitochondria that differ in the endogenous Q content. When availability of the inhibitor (GTP) or the negative inhibition modulator (QH2) was changed, a competitive influence on the UCP activity was observed. QH2 decreases the affinity of UCP for GTP and, vice versa, GTP decreases the affinity of UCP for QH2. These results describe the kinetic mechanism of regulation of UCP affinity for purine nucleotides by endogenous QH2 in the mitochondria of a unicellular eukaryote.
Assuntos
Acanthamoeba castellanii/metabolismo , Canais Iônicos/metabolismo , Proteínas Mitocondriais/metabolismo , Nucleotídeos de Purina/farmacologia , Ubiquinona/análogos & derivados , Acanthamoeba castellanii/fisiologia , Nucleotídeos de Adenina/farmacologia , Benzoquinonas/metabolismo , Ácidos Graxos não Esterificados/farmacologia , Nucleotídeos de Guanina/farmacologia , Homeostase , Canais Iônicos/antagonistas & inibidores , Potenciais da Membrana/fisiologia , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Proteínas Mitocondriais/antagonistas & inibidores , Oxirredução , Consumo de Oxigênio/efeitos dos fármacos , Ribonucleotídeos/farmacologia , Ubiquinona/fisiologia , Proteína Desacopladora 1RESUMO
The endothelium is considered to be relatively independent of the mitochondrial energy supply. The goals of this study were to examine mitochondrial respiratory functions in endothelial cells and isolated mitochondria and to assess the influence of chronic high glucose exposure on the aerobic metabolism of these cells. A procedure to isolate of bioenergetically active endothelial mitochondria was elaborated. Human umbilical vein endothelial cells (EA.hy926 line) were grown in medium containing either 5.5 or 25 mM glucose. The respiratory response to elevated glucose was observed in cells grown in 25 mM glucose for at least 6 days or longer. In EA.hy926 cells, growth in high glucose induced considerably lower mitochondrial respiration with glycolytic fuels, less pronounced with glutamine, and higher respiration with palmitate. The Crabtree effect was observed in both types of cells. High glucose conditions produced elevated levels of cellular Q10, increased ROS generation, increased hexokinase I, lactate dehydrogenase, acyl-CoA dehydrogenase, uncoupling protein 2 (UCP2), and superoxide dismutase 2 expression, and decreased E3-binding protein of pyruvate dehydrogenase expression. In isolated mitochondria, hyperglycaemia induced an increase in the oxidation of palmitoylcarnitine and glycerol-3-phosphate (lipid-derived fuels) and a decrease in the oxidation of pyruvate (a mitochondrial fuel); in addition, increased UCP2 activity was observed. Our results demonstrate that primarily glycolytic endothelial cells possess highly active mitochondria with a functioning energy-dissipating pathway (UCP2). High-glucose exposure induces a shift of the endothelial aerobic metabolism towards the oxidation of lipids and amino acids.
Assuntos
Respiração Celular/fisiologia , Células Endoteliais/metabolismo , Glucose/metabolismo , Mitocôndrias/metabolismo , Acil-CoA Desidrogenases/metabolismo , Linhagem Celular , Ácidos Graxos/metabolismo , Glutamina/metabolismo , Hexoquinase/metabolismo , Humanos , Canais Iônicos/metabolismo , L-Lactato Desidrogenase/metabolismo , Proteínas Mitocondriais/metabolismo , Oxirredução , Palmitatos/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Superóxido Dismutase/metabolismo , Ubiquinona/análogos & derivados , Ubiquinona/metabolismo , Veias Umbilicais/metabolismo , Proteína Desacopladora 2RESUMO
We studied the influence of exogenously generated superoxide and exogenous 4-hydroxy-2-nonenal (HNE), a lipid peroxidation end product, on the activity of the Acanthamoeba castellanii uncoupling protein (AcUCP). The superoxide-generating xanthine/xanthine oxidase system was insufficient to induce mitochondrial uncoupling. In contrast, exogenously added HNE induced GTP-sensitive AcUCP-mediated mitochondrial uncoupling. In non-phosphorylating mitochondria, AcUCP activation by HNE was demonstrated by increased oxygen consumption accompanied by a decreased membrane potential and ubiquinone (Q) reduction level. The HNE-induced GTP-sensitive proton conductance was similar to that observed with linoleic acid. In phosphorylating mitochondria, the HNE-induced AcUCP-mediated uncoupling decreased the yield of oxidative phosphorylation. We demonstrated that the efficiency of GTP to inhibit HNE-induced AcUCP-mediated uncoupling was regulated by the endogenous Q redox state. A high Q reduction level activated AcUCP by relieving the inhibition caused by GTP while a low Q reduction level favoured the inhibition. We propose that the regulation of UCP activity involves a rapid response through the endogenous Q redox state that modulates the inhibition of UCP by purine nucleotides, followed by a late response through lipid peroxidation products resulting from an increase in the formation of reactive oxygen species that modulate the UCP activation.
Assuntos
Acanthamoeba castellanii/metabolismo , Aldeídos/farmacologia , Inibidores de Cisteína Proteinase/farmacologia , Guanosina Trifosfato/metabolismo , Canais Iônicos/metabolismo , Mitocôndrias/metabolismo , Proteínas Mitocondriais/metabolismo , Proteínas de Protozoários/metabolismo , Ubiquinona/metabolismo , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Oxirredução/efeitos dos fármacos , Proteína Desacopladora 1RESUMO
Uncoupling proteins (UCPs) are members of the mitochondrial anion carrier protein family that are present in the mitochondrial inner membrane and mediate free fatty acid (FFA)-activated, purine nucleotide (PN)-inhibited proton conductance. Since 1999, the presence of UCPs has been demonstrated in some non-photosynthesising unicellular eukaryotes, including amoeboid and parasite protists, as well as in non-fermentative yeast and filamentous fungi. In the mitochondria of these organisms, UCP activity is revealed upon FFA-induced, PN-inhibited stimulation of resting respiration and a decrease in membrane potential, which are accompanied by a decrease in membranous ubiquinone (Q) reduction level. UCPs in unicellular eukaryotes are able to divert energy from oxidative phosphorylation and thus compete for a proton electrochemical gradient with ATP synthase. Our recent work indicates that membranous Q is a metabolic sensor that might utilise its redox state to release the PN inhibition of UCP-mediated mitochondrial uncoupling under conditions of phosphorylation and resting respiration. The action of reduced Q (QH2) could allow higher or complete activation of UCP. As this regulatory feature was demonstrated for microorganism UCPs (A. castellanii UCP), plant and mammalian UCP1 analogues, and UCP1 in brown adipose tissue, the process could involve all UCPs. Here, we discuss the functional connection and physiological role of UCP and alternative oxidase, two main energy-dissipating systems in the plant-type mitochondrial respiratory chain of unicellular eukaryotes, including the control of cellular energy balance as well as preventive action against the production of reactive oxygen species.
Assuntos
Eucariotos/metabolismo , Canais Iônicos/metabolismo , Proteínas Mitocondriais/metabolismo , Acanthamoeba castellanii/genética , Acanthamoeba castellanii/metabolismo , Tecido Adiposo Marrom/metabolismo , Animais , Eucariotos/genética , Evolução Molecular , Ácidos Graxos não Esterificados/metabolismo , Canais Iônicos/antagonistas & inibidores , Canais Iônicos/genética , Peroxidação de Lipídeos , Mitocôndrias/metabolismo , Proteínas Mitocondriais/antagonistas & inibidores , Proteínas Mitocondriais/genética , Modelos Biológicos , Oxirredutases/metabolismo , Proteínas de Plantas , Nucleotídeos de Purina/farmacologia , Espécies Reativas de Oxigênio/metabolismo , Especificidade da Espécie , Ubiquinona/metabolismo , Proteína Desacopladora 1RESUMO
Addition of a moderate (1.4 mM) concentration of H(2)O(2) to protozoon Acanthamoeba castellanii cell cultures at different growth phases caused a different response to oxidative stress. H(2)O(2) treatment of exponentially growing cells significantly delayed their growth; however, in mitochondria isolated from these cells, no damage to their bioenergetic function was observed. In contrast, addition of H(2)O(2) to A. castellanii cells approaching the stationary phase did not influence their growth and viability while seriously affecting mitochondrial bioenergetic function. Although mitochondrial integrity was maintained, oxidative damage was revealed in the reduction of cytochrome pathway activity, uncoupling protein activity, and the efficiency of oxidative phosphorylation as well as the membrane potential and the endogenous ubiquinone reduction level of the resting state. An increase in the alternative oxidase protein level and activity as well as an increase in the membranous ubiquinone content were observed in mitochondria isolated from late H(2)O(2)-treated cells. For the first time, the regulation of ubiquinone content in the inner mitochondrial membrane is shown to play a role in the response to oxidative stress. A physiological role for the higher activity of the alternative oxidase in response to oxidative stress in unicellular organisms, such as amoeba A. castellanii, is discussed.
Assuntos
Acanthamoeba castellanii/citologia , Acanthamoeba castellanii/metabolismo , Mitocôndrias/metabolismo , Acanthamoeba castellanii/enzimologia , Metabolismo Energético , Humanos , Estresse Oxidativo/fisiologia , Oxigênio/metabolismoRESUMO
The effects of different adenine and guanine nucleotides on the cyanide-resistant respiration (i.e. alternative oxidase (AcAOX) activity) of mitochondria from the amoeba A. castellanii mitochondria were studied. We found that guanine nucleotides activate AcAOX to a greater degree than adenine nucleotides, and that nucleoside monophosphates were more efficient activators than nucleoside di- or triphosphates. The extent of the nucleotides' influence on AcAOX was dependent on the medium's pH and was more pronounced at pH 6.8, which is optimal for AcAOX activity. In contrast to other purine nucleosides, we demonstrate, for the first time, that ATP has an inhibitory effect on AcAOX activity. Since we also observed the inhibition by ATP in the mitochondria of another protozoon, such as Dictyostelium discoideum, and the yeast, Candida maltosa, it may be a regulatory feature common to all purine nucleotide-modulated non-plant AOXs. The physiological importance of this discovery is discussed. Kinetic data show that the binding of GMP (a positive allosteric effector) and the binding of ATP (a negative allosteric effector) to AcAOX are mutually exclusive. ATP's inhibition of the enzyme can be overcome by sufficiently high concentrations of GMP, and conversely, GMP's stimulation can be overcome by sufficiently high concentrations of ATP. However, an approximately three times lower concentration of GMP compared to ATP gives a half maximal effect on AcAOX activity. This is indicative of a higher binding affinity for the positive effector at the same or, at least overlapping, nucleotide-binding sites on AcAOX. These results suggest that AcAOX activity in A. castellanii mitochondria might be controlled by the relative intracellular concentrations of purine nucleotides.
Assuntos
Acanthamoeba castellanii/efeitos dos fármacos , Acanthamoeba castellanii/enzimologia , Trifosfato de Adenosina/farmacologia , Guanosina Monofosfato/farmacologia , Oxirredutases/antagonistas & inibidores , Acanthamoeba castellanii/citologia , Regulação Alostérica/efeitos dos fármacos , Animais , Candida/efeitos dos fármacos , Candida/enzimologia , Respiração Celular/efeitos dos fármacos , Cianetos/farmacologia , Dictyostelium/efeitos dos fármacos , Dictyostelium/enzimologia , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/enzimologia , Proteínas Mitocondriais , Modelos Biológicos , Fosforilação/efeitos dos fármacos , Proteínas de Plantas , Solubilidade/efeitos dos fármacos , Especificidade por Substrato/efeitos dos fármacosRESUMO
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%.
Assuntos
Canais Iônicos/metabolismo , Proteínas Mitocondriais/metabolismo , Nucleotídeos de Purina/metabolismo , Ubiquinona/metabolismo , Adipócitos Marrons/metabolismo , Animais , Ácidos Graxos não Esterificados/metabolismo , Canais Iônicos/genética , Masculino , Mitocôndrias/metabolismo , Proteínas Mitocondriais/genética , Oxirredução , Fosforilação , Ligação Proteica , Ratos , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteína Desacopladora 1RESUMO
We studied FFA (free fatty acid)-induced uncoupling activity in Acanthamoeba castellanii mitochondria in the non-phosphorylating state. Either succinate or external NADH was used as a respiratory substrate to determine the proton conductance curves and the relationships between respiratory rate and the quinone reduction level. Our determinations of the membranous quinone reduction level in non-phosphorylating mitochondria show that activation of UCP (uncoupling protein) activity leads to a PN (purine nucleotide)-sensitive decrease in the quinone redox state. The gradual decrease in the rate of quinone-reducing pathways (using titration of dehydrogenase activities) progressively leads to a full inhibitory effect of GDP on LA (linoleic acid) induced proton conductance. This inhibition cannot be attributed to changes in the membrane potential. Indeed, the lack of GDP inhibitory effect observed when the decrease in respiratory rate is accompanied by an increase in the quinone reduction level (using titration of the quinol-oxidizing pathway) proves that the inhibition by nucleotides can be revealed only for a low quinone redox state. It must be underlined that, in A. castellanii non-phosphorylating mitochondria, the transition of the inhibitory effect of GDP on LA-induced UCP-mediated uncoupling is observed for the same range of quinone reduction levels (between 50% and 40%) as that observed previously for phosphorylating conditions. This observation, drawn from the two different metabolic states of mitochondria, indicates that quinone could affect UCP activity through sensitivity to PNs.
Assuntos
Acanthamoeba castellanii/metabolismo , Benzoquinonas/química , Canais Iônicos/química , Proteínas Mitocondriais/química , Oxirredução , Nucleotídeos de Purina/química , Animais , Guanosina Difosfato/química , Ácido Linoleico/química , Potenciais da Membrana , Mitocôndrias/metabolismo , NAD/química , Fosforilação Oxidativa , Oxigênio/química , Fosforilação , Prótons , Proteína Desacopladora 1RESUMO
The purpose of this study was establishing the basic energetic parameters of amoeba Acanthamoeba castellanii mitochondria respiring with malate and their response to oxidative stress caused by hydrogen peroxide in the presence of Fe(2+) ions. It appeared that, contrary to a previous report (Trocha LK, Stobienia O (2007) Acta Biochim Polon 54: 797), H(2)O(2)-treated mitochondria of A. castellanii did not display any substantial impairment. No marked changes in cytochrome pathway activity were found, as in the presence of an inhibitor of alternative oxidase no effects were observed on the rates of uncoupled and phosphorylating respiration and on coupling parameters. Only in the absence of the alternative oxidase inhibitor, non-phosphorylating respiration progressively decreased with increasing concentration of H(2)O(2), while the coupling parameters (respiratory control ratio and ADP/O ratio) slightly improved, which may indicate some inactivation of the alternative oxidase. Moreover, our results show no change in membrane potential, Ca(2+) uptake and accumulation ability, mitochondrial outer membrane integrity and cytochrome c release for 0.5-25 mM H(2)O(2)-treated versus control (H(2)O(2)-untreated) mitochondria. These results indicate that short (5 min) incubation of A. castellanii mitochondria with H(2)O(2) in the presence of Fe(2+) does not damage their basic energetics.
Assuntos
Acanthamoeba castellanii/metabolismo , Acanthamoeba castellanii/efeitos dos fármacos , Animais , Cálcio/metabolismo , Citocromos c/metabolismo , Metabolismo Energético/efeitos dos fármacos , Peróxido de Hidrogênio/farmacologia , Membranas Intracelulares/efeitos dos fármacos , Membranas Intracelulares/metabolismo , Transporte de Íons/efeitos dos fármacos , Malatos/metabolismo , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Estresse Oxidativo/efeitos dos fármacosRESUMO
Uncoupling proteins (UCPs), members of mitochondrial carrier family, are present in mitochondrial inner membrane and mediate free fatty acid-activated, purine-nucleotide-inhibited H+ re-uptake. UCPs can modulate the tightness of coupling between mitochondrial respiration and ATP synthesis. A physiological function of the first described UCP, UCP1 or termogenin, present in mitochondria of mammalian brown adipose tissues is well established. UCP1 plays a role in nonshivering thermogenesis in mammals. The widespread presence of UCPs in eukaryotes, in non-thermogenic tissues of animals, plants and in unicellular organisms implies that these proteins may elicit other functions than thermogenesis. However, the physiological functions of UCP1 homologues are still under debate. They can regulate energy metabolism through modulation of the electrochemical proton gradient and production of ROS. Functional activation of UCPs is proposed to decrease ROS production. Moreover, products of lipid peroxidation can activate UCPs and promote feedback down-regulation of mitochondrial ROS production.
Assuntos
Canais Iônicos/fisiologia , Proteínas Mitocondriais/fisiologia , Desacopladores/metabolismo , Tecido Adiposo Marrom/metabolismo , Animais , Biotransformação , Regulação para Baixo , Células Eucarióticas/metabolismo , Humanos , Canais Iônicos/química , Proteínas Mitocondriais/química , Espécies Reativas de Oxigênio/metabolismo , Proteína Desacopladora 1RESUMO
Enormous interest in mitochondrial uncoupling proteins (UCPs) is caused by relevant impact of these energy-dissipating systems on cellular energy transduction. A key role of UCPs in regulation of mitochondrial metabolism is supported by existence of their different isoforms in various mammalian tissues. Recent studies have shown that UCPs have an important part in pathogenesis of various disorders, such as obesity, type-2 diabetes, cachexia, aging or tumor. The obscure roles of UCPs in normal physiology and their emerging role in pathophysiology, provide exciting potential for further investigation. However, neither the exact physiological nor biochemical roles of UCP homologues are well understood. Therefore, providing mechanistic explanation of their functions in cellular physiology may be the basis for potential farmacological targeting of UCPs in future on clinical scale.
Assuntos
Tecido Adiposo/metabolismo , Metabolismo Energético/fisiologia , Canais Iônicos/metabolismo , Mitocôndrias/metabolismo , Proteínas Mitocondriais/metabolismo , Envelhecimento/metabolismo , Animais , Caquexia/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Metabolismo Energético/efeitos dos fármacos , Ácidos Graxos/metabolismo , Humanos , Canais Iônicos/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Proteínas Mitocondriais/efeitos dos fármacos , Neoplasias/metabolismo , Obesidade/metabolismo , Proteína Desacopladora 1 , Proteína Desacopladora 2 , Proteína Desacopladora 3RESUMO
We studied the effects of various assay temperatures, representing hypothermia (25°C), normothermia (35°C), and hyperthermia (42°C), on the oxidation of lipid-derived fuels in rat skeletal muscle mitochondria of untrained and endurance-trained rats. Adult 4-month-old male Wistar rats were assigned to a training group (rats trained on a treadmill for 8 weeks) or a sedentary control group. In skeletal muscle mitochondria of both control and trained rats, an increase in the assay temperature from 25°C to 42°C was accompanied by a consistent increase in the oxidation of palmitoylcarnitine and glycerol-3-phosphate. Moreover, endurance training increased mitochondrial capacity to oxidize the lipid-derived fuels at all studied temperatures. The endurance training-induced increase in mitochondrial capacity to oxidize fatty acids was accompanied by an enhancement of mitochondrial biogenesis, as shown by the elevated expression levels of Nrf2, PGC1α, and mitochondrial marker and by the elevated expression levels of mitochondrial proteins involved in fatty acid metabolism, such as fatty acid transporter CD36, carnitine palmitoyltransferase 1A (CPT1A), and acyl-CoA dehydrogenase (ACADS). We conclude that hyperthermia enhances but hypothermia attenuates the rate of the oxidation of fatty acids and glycerol-3-phosphate in rat skeletal muscle mitochondria isolated from both untrained and trained rats. Moreover, our results indicate that endurance training up-regulates mitochondrial biogenesis markers, lipid-sustained oxidative capacity, and CD36 and CPT1A proteins involved in fatty acid transport, possibly via PGC1α and Nrf2 signaling pathways.
Assuntos
Ácidos Graxos/metabolismo , Mitocôndrias Musculares/metabolismo , Músculo Esquelético/metabolismo , Condicionamento Físico Animal , Temperatura , Animais , Masculino , Oxirredução , Ratos , Ratos WistarRESUMO
Mitochondrial respiratory and phosphorylation activities, mitochondrial uncoupling, and hydrogen peroxide formation were studied in isolated rat skeletal muscle mitochondria during experimentally induced hypothermia (25 °C) and hyperthermia (42 °C) compared to the physiological temperature of resting muscle (35 °C). For nonphosphorylating mitochondria, increasing the temperature from 25 to 42 °C led to a decrease in membrane potential, hydrogen peroxide production, and quinone reduction levels. For phosphorylating mitochondria, no temperature-dependent changes in these mitochondrial functions were observed. However, the efficiency of oxidative phosphorylation decreased, whereas the oxidation and phosphorylation rates and oxidative capacities of the mitochondria increased, with increasing assay temperature. An increase in proton leak, including uncoupling protein-mediated proton leak, was observed with increasing assay temperature, which could explain the reduced oxidative phosphorylation efficiency and reactive oxygen species production.
Assuntos
Febre/fisiopatologia , Hipotermia/fisiopatologia , Mitocôndrias Musculares/metabolismo , Músculo Esquelético/metabolismo , Fosforilação Oxidativa , Estresse Oxidativo , Espécies Reativas de Oxigênio/metabolismo , Animais , Citrato (si)-Sintase/metabolismo , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Peróxido de Hidrogênio/metabolismo , Masculino , Potencial da Membrana Mitocondrial , Proteínas Mitocondriais/metabolismo , Oxirredução , Consumo de Oxigênio , Ratos , Ratos Wistar , TemperaturaRESUMO
Using isolated potato tuber mitochondria possessing uncoupling protein (StUCP), we found that, under non-phosphorylating conditions, the sensitivity of aldehyde (all trans-retinal or 4-hydroxy-2-nonenal)-induced and fatty acid (linoleic acid)-induced StUCP-mediated proton leaks to GTP is controlled by the endogenous ubiquinone (Q) reduction level. The action of StUCP activators was abolished by GTP only when Q was sufficiently oxidized, but no inhibitory effect was observed when Q was highly reduced. Thus, the Q reduction level-dependent regulation of StUCP inhibition functions independently of the type of UCP activation and could be an important physiological factor affecting the efficiency of UCP-catalyzed uncoupling in plant mitochondria.