Age-related increase in mitochondrial proton leak and decrease in ATP turnover reactions in mouse hepatocytes

Harper, Mary Ellen; Monemdjou, Shadi; Ramsey, Jon J.; Weindruch, Richard

doi:10.1152/ajpendo.1998.275.2.e197

Cited by 68 publications

(72 citation statements)

References 46 publications

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“…Our observation supports a recent report which shows an increase in the in situ oxygen consumption due to proton leak in hepatocytes isolated from young 3 month) and old (30 month) C57BLaJ mice. 32 The results are also consistent with results of Hagen et al 33 who showed a reduced mitochondrial membrane potential in resting hepatocytes from old rats. On facevalue there would appear to be a contradiction, in terms of proton leak, between the in situ and isolated mitochondrial observations.…”

Section: Measuring Proton Leak Rk Porter Et Alsupporting

confidence: 90%

Indirect measurement of mitochondrial proton leak and its application

et al. 1999

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In mitochondria, ATP synthesis is coupled to oxygen consumption by the proton electrochemical gradient established across the mitochondrial inner membrane in a process termed oxidative phosphorylation. It has long been known from stoichiometric studies that ATP synthesis is not perfectly coupled to oxygen consumption. The major inef®ciency in the system is leakage of protons across the mitochondrial inner membrane driven by the proton electrochemical gradient. The kinetics of the proton leak can be determined indirectly, by measuring the oxygen consumption of mitochondria under non-phosphorylating conditions (plus oligomycin) as a function of the proton electrochemical gradient. This experimental system provides a convenient means to investigate inner membrane permeability to protons and the effect of factors that may effect that permeability. In this paper we review some results from our laboratory of indirect measurement of mitochondrial proton leak and how it has been applied to investigate the effect of aging, obesity and thyroid status on proton leak. The results show that (i) proton leak in isolated liver mitochondria is not signi®cantly different in a comparison of young and old rats, in contrast (ii) there is an apparent increase in proton leak in in situ mitochondria in hepatocytes from old rats when compared to those from young rats, (iii) proton leak in neuronal mitochondria in situ in synaptosomes is not signi®cantly different in young and old rats, (iv) proton leak is greater in isolated liver mitochondria from obaob mice compared to lean controls, (v) acute leptin (OB protein) administration restores the increased leak rate in isolated liver mitochondria from obaob mice to that of lean controls, (vi) administration of thyroid hormone (T 3 ) increases proton leak in rat muscle mitochondria, and (vii) proton leak in muscle mitochondria is insensitive to the presence of GDP. It is proposed that the experimental system described here for measuring proton leak, is an ideal functional assay for determining whether the novel uncoupling proteins increase inner membrane permeability to protons.

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Section: Measuring Proton Leak Rk Porter Et Alsupporting

confidence: 90%

Indirect measurement of mitochondrial proton leak and its application

et al. 1999

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“…47), an increase in mitochondrial proton leak, and a decreased oxygen consumption (25). To address this question, we examined the mitochondrial genome copies relative to nuclear genome, the total cellular oxygen consumption, and cellular ATP content on a per cell basis.…”

Section: Discussionmentioning

confidence: 99%

Endothelial cells maintain a reduced redox environment even as mitochondrial function declines

Carlisle

Rhoads

et al. 2002

American Journal of Physiology-Cell Physiology

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. Endothelial cells maintain a reduced redox environment even as mitochondrial function declines. Am J Physiol Cell Physiol 283: C1675-C1686, 2002. First published August 22, 2002 10.1152/ajpcell.00092.2002 are an endothelial model of replicative senescence. Oxidative stress, possibly due to dysfunctional mitochondria, is believed to play a key role in replicative senescence and atherosclerosis, an age-related vascular disease. In this study, we determined the effect of cell division on genomic instability, mitochondrial function, and redox status in HUVECs that were able to replicate for ϳ60 cumulative population doublings (CPD). After 20 CPD, the nuclear genome deteriorated and the protein content of the cell population increased. This indicated an increase in cell size, which was accompanied by an increase in oxygen consumption, ATP production, and mitochondrial genome copy number and ϳ10% increase in mitochondrial mass. The antioxidant capacity increased, as seen by an increase in reduced glutathione, glutathione peroxidase, GSSG reductase, and glucose-6-phosphate dehydrogenase. However, by CPD 52, the latter two enzymes decreased, as well as the ratio of mitochondrial-to-nuclear genome copies, the mitochondrial mass, and the oxygen consumption per milligram of protein. Our results signify that HUVECs maintain a highly reducing (GSH) environment as they replicate despite genomic instability and loss of mitochondrial function. replicative senescence; glutathione; cell size changes; genomic instability; human umbilical vein endothelial cells HUMAN UMBILICAL VEIN ENDOTHELIAL CELLS (HUVECs) replicate a finite number of times in culture and are an endothelial model of replicative senescence. Reactive oxygen species (ROS) and oxidative damage to DNA (24), protein (7), and lipid (45) increase with age and have been implicated in aging and replicative senescence (19,48). Oxidative stress has also been implicated in atherosclerosis, an age-related vascular disease, and homocysteine, a contributing factor to atherosclerosis that induces oxidative stress, accelerates endothelial senescence in culture (52). Atherosclerosis is hypothesized to be the result of a "response to injury" of the endothelium. The endothelium must constantly respond to changes in the vascular environment and experiences frequent insults from mechanical, hemodynamic, and inflammatory stresses, all of which enhance oxygen free radical production. In response to injury, endothelial cells must replicate to repair blood vessels. Telomere length is shorter in endothelial cells derived from vessels where there is greater hemodynamic stress, and presumably more endothelial cell replication to repair injury, than in cells isolated from areas of lower stress (10). Injury induced by balloon catheter denudation of rabbit carotid arteries has been shown to result in the accumulation of senescent endothelial cells (18). Studies of the endothelium at atherosclerotic lesions (9, 50) and in vessels from elderly people (30, 50) have detected multinucleated cells ...

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“…Considerable evidence supports the idea that mitochondria are a major target of the aging process (17, 18). Progressive loss of mitochondrial function is a common feature of aging in several tissues and organisms (19)(20)(21), and accumulation of deletions and point mutations in mitochondrial DNA has been described in aged individuals (22,23). Mitochondrial dysfunction and ROS have been implicated in a wide range of age-related neurodegenerative disorders, including Alzheimer's disease and Parkinson's disease (24,25).…”

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confidence: 99%

Mitochondrial “swirls” induced by oxygen stress and in theDrosophilamutanthyperswirl

Walker

Benzer

2004

Proc. Natl. Acad. Sci. U.S.A.

105

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Mitochondrial dysfunction and reactive oxygen species have been implicated in the aging process as well as a wide range of hereditary and age-related diseases. Identifying primary events that result from acute oxidative stress may provide targets for therapeutic interventions that preclude aging. By using electron microscopy, we have discovered a striking initial pattern of degeneration of the mitochondria in Drosophila flight muscle under hyperoxia (100% O2). Within individual mitochondria, the cristae become locally rearranged in a pattern that we have termed a ''swirl.'' Serial sections through individual mitochondria reveal the reorganization of the cristae in three dimensions. The cristae involved in a swirl are deficient in respiratory enzyme cytochrome c oxidase activity, within an otherwise cytochrome c oxidase-positive mitochondrion. In addition, under hyperoxia cytochrome c undergoes a conformational change, manifested by display of an otherwise hidden epitope. The conformational change is correlated with widespread apoptotic cell death in the flight muscle, as revealed by in situ terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling. In normal flies, mitochondrial swirls accumulate slowly with age. To investigate the molecular mechanisms involved in oxygen toxicity, we conducted a genetic screen for mutants that display altered survival under hyperoxia, and we identified both sensitive and resistant mutants. We describe a mutant, hyperswirl, which displays an overabundance of swirls with associated respiratory and flight defects and a greatly reduced lifespan. Such mutants can identify genes that are needed to maintain mitochondrial homeostasis throughout the lifespan.hyperoxia ͉ aging ͉ cytochrome c ͉ apoptosis ͉ muscle M olecular oxygen is a biradical that, upon single electron addition, sequentially generates O 2 Ϫ , H 2 O 2 , and• OH, which, by means of further reactions, can generate an array of additional reactive oxygen species (ROS). D. Harman (1) proposed that free radicals produced during aerobic respiration cause cumulative oxidative damage, resulting in aging and death. Several lines of evidence that support this hypothesis have been established (2-4). It has been shown that ROS can damage cellular macromolecules, including DNA, lipids, and proteins (5-8). Mutations that lead to extended lifespan have been identified in yeast, worm, fly, and mouse, and there is a correlation between increased longevity and enhanced resistance to oxidative stress in these mutants (9, 10). Treatment of WT Caenorhabditis elegans with synthetic superoxide dismutase͞ catalase mimetics increases the mean lifespan by 44% (11), providing direct evidence for the role of oxygen radicals in determining the aging rate in the nematode. In Drosophila, transgenic technology has been used to directly test the freeradical theory of aging. Overexpression of the mitochondrial manganese superoxide dismutase significantly extends adult lifespan (12), the degree of extension in different transgenic lines, being c...

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Age-related increase in mitochondrial proton leak and decrease in ATP turnover reactions in mouse hepatocytes

Cited by 68 publications

References 46 publications

Indirect measurement of mitochondrial proton leak and its application

Indirect measurement of mitochondrial proton leak and its application

Endothelial cells maintain a reduced redox environment even as mitochondrial function declines

Mitochondrial “swirls” induced by oxygen stress and in theDrosophilamutanthyperswirl

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