scholarly journals Stimulation of mitochondrial proton conductance by hydroxynonenal requires a high membrane potential

2008 ◽  
Vol 28 (2) ◽  
pp. 83-88 ◽  
Author(s):  
Nadeene Parker ◽  
Antonio Vidal-Puig ◽  
Martin D. Brand
Keyword(s):  
Membrane Potential ◽  
Feedback Loop ◽  
Adenine Nucleotide ◽  
Proton Leak ◽  
Skeletal Muscle Mitochondria ◽  
Mitochondrial Ros ◽  
The Matrix ◽  
High Membrane Potential ◽  
Uncoupling Of Oxidative Phosphorylation ◽  
Mild Uncoupling

Mild uncoupling of oxidative phosphorylation, caused by a leak of protons back into the matrix, limits mitochondrial production of ROS (reactive oxygen species). This proton leak can be induced by the lipid peroxidation products of ROS, such as HNE (4-hydroxynonenal). HNE activates uncoupling proteins (UCP1, UCP2 and UCP3) and ANT (adenine nucleotide translocase), thereby providing a negative feedback loop. The mechanism of activation and the conditions necessary to induce uncoupling by HNE are unclear. We have found that activation of proton leak by HNE in rat and mouse skeletal muscle mitochondria is dependent on incubation with respiratory substrate. In the presence of HNE, mitochondria energized with succinate became progressively more leaky to protons over time compared with mitochondria in the absence of either HNE or succinate. Energized mitochondria must attain a high membrane potential to allow HNE to activate uncoupling: a drop of 10–20 mV from the resting value is sufficient to blunt induction of proton leak by HNE. Uncoupling occurs through UCP3 (11%), ANT (64%) and other pathways (25%). Our findings have shown that exogenous HNE only activates uncoupling at high membrane potential. These results suggest that both endogenous HNE production and high membrane potential are required before mild uncoupling will be triggered to attenuate mitochondrial ROS production.

scholarly journals The regulation of brain mitochondrial calcium-ion transport. The role of ATP in the discrimination between kinetic and membrane-potential-dependent calcium-ion efflux mechanisms

1980 ◽  
Vol 186 (3) ◽  
pp. 833-839 ◽  
Author(s):  
D G Nicholls ◽  
I D Scott
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Calcium Ion ◽  
Adenine Nucleotide ◽  
Brain Mitochondria ◽  
The Matrix ◽  
High Membrane Potential ◽  
Calcium Ion Transport ◽  
Efflux Pathway

Mitochondria from guinea-pig cerebral cortex incubated in the presence of Pi or acetate are unable to regulate the extramitochondrial free Ca2+ at a steady-state which is independent of the Ca2+ accumulated in the matrix. This is due to the superimposition on kinetically regulated Ca2+ cycling of a membrane-potential-dependent reversal of the Ca2+ uniporter. The latter efflux is a consequence of a low membrane potential, which correlates with a loss of adenine nucleotide loss from the matrix, enable the mitochondria to maintain a high membrane potential and allow the mitochondria to buffer the extramitochondrial free Ca2+ precisely when up to 200 nmol of Ca2+/mg of protein is accumulated in the matrix. The steady-state extramitochondrial free Ca2+ is maintained as low as 0.3 microM. The Na+-activated efflux pathway is functional in the presence of ATP and oligomycin and accounts precisely for the change in steady-state free Ca2+ induced by Na+ addition. The need to distinguish carefully between kinetic and membrane-potential-dependent efflux pathways is emphasized and the competence of brain mitochondria to regulate cytosolic free Ca2+ concentrations in vivo is discussed.

scholarly journals High membrane potential promotes alkenal-induced mitochondrial uncoupling and influences adenine nucleotide translocase conformation

2008 ◽  
Vol 413 (2) ◽  
pp. 323-332 ◽  
Author(s):  
Vian Azzu ◽  
Nadeene Parker ◽  
Martin D. Brand
Keyword(s):  
Membrane Potential ◽  
Adenine Nucleotide ◽  
Uncoupling Proteins ◽  
Adenine Nucleotide Translocase ◽  
Oxygen Species ◽  
Proton Conductance ◽  
Mitochondrial Uncoupling ◽  
Mitochondrial Inner Membrane ◽  
High Membrane Potential ◽  
Uncoupling Of Oxidative Phosphorylation

Mitochondria generate reactive oxygen species, whose downstream lipid peroxidation products, such as 4-hydroxynonenal, induce uncoupling of oxidative phosphorylation by increasing proton leak through mitochondrial inner membrane proteins such as the uncoupling proteins and adenine nucleotide translocase. Using mitochondria from rat liver, which lack uncoupling proteins, in the present study we show that energization (specifically, high membrane potential) is required for 4-hydroxynonenal to activate proton conductance mediated by adenine nucleotide translocase. Prolonging the time at high membrane potential promotes greater uncoupling. 4-Hydroxynonenal-induced uncoupling via adenine nucleotide translocase is prevented but not readily reversed by addition of carboxyatractylate, suggesting a permanent change (such as adduct formation) that renders the translocase leaky to protons. In contrast with the irreversibility of proton conductance, carboxyatractylate added after 4-hydroxynonenal still inhibits nucleotide translocation, implying that the proton conductance and nucleotide translocation pathways are different. We propose a model to relate adenine nucleotide translocase conformation to proton conductance in the presence or absence of 4-hydroxynonenal and/or carboxyatractylate.

scholarly journals Control of oxidative phosphorylation during insect metamorphosis

2004 ◽  
Vol 287 (2) ◽  
pp. R314-R321 ◽  
Author(s):  
M. E. Chamberlin
Keyword(s):  
Membrane Potential ◽  
Oxidative Phosphorylation ◽  
Adenine Nucleotide ◽  
Substrate Oxidation ◽  
Proton Leak ◽  
Protonmotive Force ◽  
Control Analysis ◽  
Membrane Area ◽  
Early Stages ◽  
Oxidation System

The midgut of the tobacco hornworm ( Manduca sexta) is a highly aerobic tissue that is destroyed and replaced by a pupal epithelium at metamorphosis. To determine how oxidative phosphorylation is altered during the programmed death of the larval cells, top-down control analysis was performed on mitochondria isolated from the midguts of larvae before and after the commitment to pupation. Oxygen consumption and protonmotive force (measured as membrane potential in the presence of nigericin) were monitored to determine the kinetic responses of the substrate oxidation system, proton leak, and phosphorylation system to changes in the membrane potential. Mitochondria from precommitment larvae have higher respiration rates than those from postcommitment larvae. State 4 respiration is controlled by the proton leak and the substrate oxidation system. In state 3, the substrate oxidation system exerted 90% of the control over respiration, and this high level of control did not change with development. Elasticity analysis, however, revealed that, after commitment, the activity of the substrate oxidation system falls. This decline may be due, in part, to a loss of cytochrome c from the mitochondria. There are no differences in the kinetics of the phosphorylation system, indicating that neither the F1F0 ATP synthase nor the adenine nucleotide translocase is affected in the early stages of metamorphosis. An increase in proton conductance was observed in mitochondria isolated from postcommitment larvae, indicating that membrane area, lipid composition, or proton-conducting proteins may be altered during the early stages of the programmed cell death of the larval epithelium.

scholarly journals The basal proton conductance of mitochondria depends on adenine nucleotide translocase content

2005 ◽  
Vol 392 (2) ◽  
pp. 353-362 ◽  
Author(s):  
Martin D. Brand ◽  
Julian L. Pakay ◽  
Augustine Ocloo ◽  
Jason Kokoszka ◽  
Douglas C. Wallace ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Metabolic Rate ◽  
Adenine Nucleotide ◽  
Adenine Nucleotide Translocase ◽  
Proton Leak ◽  
Proton Conductance ◽  
Wild Type ◽  
Muscle Mitochondria ◽  
Mild Uncoupling ◽  
Molecular Nature

The basal proton conductance of mitochondria causes mild uncoupling and may be an important contributor to metabolic rate. The molecular nature of the proton-conductance pathway is unknown. We show that the proton conductance of muscle mitochondria from mice in which isoform 1 of the adenine nucleotide translocase has been ablated is half that of wild-type controls. Overexpression of the adenine nucleotide translocase encoded by the stress-sensitive B gene in Drosophila mitochondria increases proton conductance, and underexpression decreases it, even when the carrier is fully inhibited using carboxyatractylate. We conclude that half to two-thirds of the basal proton conductance of mitochondria is catalysed by the adenine nucleotide carrier, independently of its ATP/ADP exchange or fatty-acid-dependent proton-leak functions.

Mitochondrial matrix reactive oxygen species production is very sensitive to mild uncoupling

2003 ◽  
Vol 31 (6) ◽  
pp. 1300-1301 ◽  
Author(s):  
S. Miwa ◽  
M.D. Brand
Keyword(s):  
Reactive Oxygen Species ◽  
Membrane Potential ◽  
Complex I ◽  
Electron Flow ◽  
Ros Production ◽  
Oxygen Species ◽  
Inner Membrane ◽  
Reverse Electron Flow ◽  
The Matrix ◽  
Mild Uncoupling

Mitochondria produce ROS (reactive oxygen species) as a by-product of aerobic respiration. Several studies in mammals and birds suggest that the most physiologically relevant ROS production is from complex I following reverse electron flow, and is highly sensitive to membrane potential. A study of Drosophila mitochondria respiring glycerol 3-phosphate revealed that membrane potential-sensitive ROS production from complex I following reverse electron flow was on the matrix side of the inner membrane. A 10 mV decrease in membrane potential was enough to abolish around 70% of the ROS produced by complex I under these conditions. Another important ROS generator in this model, glycerol-3-phosphate dehydrogenase, produced ROS mostly to the cytosolic side; this ROS production was totally insensitive to a small decrease in membrane potential (10 mV). Thus mild uncoupling may be particularly significant for ROS production from complex I on the matrix side of the mitochondrial inner membrane.

scholarly journals Olive oil-supplemented diet alleviates acute heat stress-induced mitochondrial ROS production in chicken skeletal muscle

2009 ◽  
Vol 297 (3) ◽  
pp. R690-R698 ◽  
Author(s):  
Ahmad Mujahid ◽  
Yukio Akiba ◽  
Masaaki Toyomizu
Keyword(s):  
Skeletal Muscle ◽  
Heat Stress ◽  
Membrane Potential ◽  
Oxidative Damage ◽  
Olive Oil ◽  
Ros Production ◽  
Muscle Mitochondria ◽  
Skeletal Muscle Mitochondria ◽  
Mitochondrial Ros ◽  
Acute Heat Stress

We have previously shown that avian uncoupling protein (avUCP) is downregulated on exposure to acute heat stress, stimulating mitochondrial reactive oxygen species (ROS) production and oxidative damage. In this study, we investigated whether upregulation of avUCP could attenuate oxidative damage caused by acute heat stress. Broiler chickens ( Gallus gallus) were fed either a control diet or an olive oil-supplemented diet (6.7%), which has been shown to increase the expression of UCP3 in mammals, for 8 days and then exposed either to heat stress (34°C, 12 h) or kept at a thermoneutral temperature (25°C). Skeletal muscle mitochondrial ROS (measured as H2O2) production, avUCP expression, oxidative damage, mitochondrial membrane potential, and oxygen consumption were studied. We confirmed that heat stress increased mitochondrial ROS production and malondialdehyde levels and decreased the amount of avUCP. As expected, feeding birds an olive oil-supplemented diet increased the expression of avUCP in skeletal muscle mitochondria and decreased ROS production and oxidative damage. Studies on mitochondrial function showed that heat stress increased membrane potential in state 4, which was reversed by feeding birds an olive oil-supplemented diet, although no differences in basal proton leak were observed between control and heat-stressed groups. These results show that under heat stress, mitochondrial ROS production and olive oil-induced reduction of ROS production may occur due to changes in respiratory chain activity as well as avUCP expression in skeletal muscle mitochondria.

The membrane permeability transition in liver mitochondria of the great green goby Zosterisessor ophiocephalus (Pallas)

2000 ◽  
Vol 203 (22) ◽  
pp. 3425-3434 ◽  
Author(s):  
A. Toninello ◽  
M. Salvi ◽  
L. Colombo
Keyword(s):  
Membrane Potential ◽  
Rat Liver ◽  
Adenine Nucleotide ◽  
Respiratory Control ◽  
Permeability Transition ◽  
Liver Mitochondria ◽  
Transport Systems ◽  
Rat Liver Mitochondria ◽  
The Matrix ◽  
Zosterisessor Ophiocephalus

Liver mitochondria from the great green goby Zosterisessor ophiocephalus (Pallas) normally exhibit bioenergetic variables (membrane potential 165+/−7 mV; respiratory control ratio 6.6+/−0.4; ADP/O ratio 1.85+/−0.8; means +/− s.e.m., N=6) and activities of physiological transport systems (phosphate/proton symporter, adenine nucleotide antiporter, Ca(2+) electrophoretic uniporter) comparable with those of rat liver mitochondria. When incubated in the presence of Ca(2+) and an inducer agent such as phosphate, these mitochondria undergo a complete collapse of membrane potential accompanied by a large-amplitude swelling of the matrix, influx of sucrose from the incubation medium, release of endogenous Mg(2+) and K(+) (approximately 90% of the total) and of preaccumulated Ca(2+) and oxidation of endogenous pyridine nucleotides. All these phenomena, which are completely eliminated by cyclosporin A and inhibited with different efficacies by Mg(2+) and spermine, demonstrate that the induction of the permeability transition in this type of mitochondria has characteristics similar to those described in rat liver mitochondria. In contrast, the requirement for very high Ca(2+) concentrations (greater than 100 micromol l(−1) for the induction of the permeability transition represents a very important difference that distinguishes this phenomenon in fish and mammalian mitochondria.

Proton leak induced by reactive oxygen species produced during in vitro anoxia/reoxygenation in rat skeletal muscle mitochondria

2006 ◽  
Vol 38 (1) ◽  
pp. 23-32 ◽  
Author(s):  
Rachel Navet ◽  
Ange Mouithys-Mickalad ◽  
Pierre Douette ◽  
Claudine M. Sluse-Goffart ◽  
Wieslawa Jarmuszkiewicz ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Skeletal Muscle ◽  
Reactive Oxygen ◽  
Proton Leak ◽  
Oxygen Species ◽  
Rat Skeletal Muscle ◽  
Muscle Mitochondria ◽  
Skeletal Muscle Mitochondria

scholarly journals Dose Response of Endotoxin on Hepatocyte and Muscle Mitochondrial Respiration In Vitro

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Victor Jeger ◽  
Sebastian Brandt ◽  
Francesca Porta ◽  
Stephan M. Jakob ◽  
Jukka Takala ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Mitochondrial Respiration ◽  
Hepg2 Cells ◽  
Human Hepatocytes ◽  
Atp Content ◽  
Muscle Mitochondria ◽  
Complex Ii ◽  
Skeletal Muscle Mitochondria ◽  
Reduced Time

Introduction.Results on mitochondrial dysfunction in sepsis are controversial. We aimed to assess effects of LPS at wide dose and time ranges on hepatocytes and isolated skeletal muscle mitochondria.Methods.Human hepatocellular carcinoma cells (HepG2) were exposed to placebo or LPS (0.1, 1, and 10 μg/mL) for 4, 8, 16, and 24 hours and primary human hepatocytes to 1 μg/mL LPS or placebo (4, 8, and 16 hours). Mitochondria from porcine skeletal muscle samples were exposed to increasing doses of LPS (0.1–100 μg/mg) for 2 and 4 hours. Respiration rates of intact and permeabilized cells and isolated mitochondria were measured by high-resolution respirometry.Results.In HepG2 cells, LPS reduced mitochondrial membrane potential and cellular ATP content but did not modify basal respiration. Stimulated complex II respiration was reduced time-dependently using 1 μg/mL LPS. In primary human hepatocytes, stimulated mitochondrial complex II respiration was reduced time-dependently using 1 μg/mL LPS. In isolated porcine skeletal muscle mitochondria, stimulated respiration decreased at high doses (50 and 100 μg/mL LPS).Conclusion.LPS reduced cellular ATP content of HepG2 cells, most likely as a result of the induced decrease in membrane potential. LPS decreased cellular and isolated mitochondrial respiration in a time-dependent, dose-dependent and complex-dependent manner.

Mitochondrial (‘mild’) uncoupling and ROS production: physiologically relevant or not?

2011 ◽  
Vol 39 (5) ◽  
pp. 1305-1309 ◽  
Author(s):  
Irina G. Shabalina ◽  
Jan Nedergaard
Keyword(s):  
Membrane Potential ◽  
Oxidative Damage ◽  
Uncoupling Protein ◽  
Electron Flow ◽  
Ros Production ◽  
Present Evidence ◽  
Beneficial Effects ◽  
Reverse Electron Flow ◽  
Species Production ◽  
Mild Uncoupling

During the last decade, the possibility that ‘mild’ uncoupling could be protective against oxidative damage by diminishing ROS (reactive oxygen species) production has attracted much interest. In the present paper, we briefly examine the evidence for this possibility. It is only ROS production from succinate under reverse electron-flow conditions that is sensitive to membrane potential fluctuations, and so only this type of ROS production could be affected; however, the conditions under which succinate-supported ROS production is observed include succinate concentrations that are supraphysiological. Any decrease in membrane potential, even ‘mild uncoupling’, must necessarily lead to large increases in respiration, i.e. it must be markedly thermogenic. Mitochondria within cells are normally ATP-producing and thus already have a diminished membrane potential, and treatment of cells, organs or animals with small amounts of artificial uncoupler does not seem to have beneficial effects that are explainable via reduced ROS production. Although it has been suggested that members of the uncoupling protein family (UCP1, UCP2 and UCP3) may mediate a mild uncoupling, present evidence does not unequivocally support such an effect, e.g. the absence of the truly uncoupling protein UCP1 is not associated with increased oxidative damage. Thus present evidence does not support mild uncoupling as a physiologically relevant alleviator of oxidative damage.

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