Search

In eukaryotic cells, mitochondria are involved in a large array of metabolic and bioenergetic processes that are vital for cell survival. Phospholipids are the main building blocks of mitochondrial membranes. Cardiolipin (CL) is a unique phospholipid which is localized and synthesized in the inner mitochondrial membrane (IMM). It is now widely accepted that CL plays a central role in many reactions and processes involved in mitochondrial function and dynamics. Cardiolipin interacts with and is required for optimal activity of several IMM proteins, including the enzyme complexes of the electron transport chain (ETC) and ATP production and for their organization into supercomplexes. Moreover, CL plays an important role in mitochondrial membrane morphology, stability and dynamics, in mitochondrial biogenesis and protein import, in mitophagy, and in different mitochondrial steps of the apoptotic process. It is conceivable that abnormalities in CL content, composition and level of oxidation may negatively impact mitochondrial function and dynamics, with important implications in a variety of pathophysiological situations and diseases. In this review, we focus on the role played by CL in mitochondrial function and dynamics in health and diseases and on the potential of pharmacological modulation of CL through several agents in attenuating mitochondrial dysfunction.

Mitochondrial dysfunction plays a central role in myocardial ischemia-reperfusion (I/R) injury. Increased reactive oxygen species production, impaired electron transport chain activity, aberrant mitochondrial dynamics, Ca 2+ overload, and opening of the mitochondrial permeability transition pore have been proposed as major contributory factors to mitochondrial dysfunction during myocardial I/R injury. Cardiolipin (CL), a mitochondria-specific phospholipid, plays a pivotal role in multiple mitochondrial bioenergetic processes, including respiration and energy conversion, in mitochondrial morphology and dynamics as well as in several steps of the apoptotic process. Changes in CL levels, species composition, and degree of oxidation may have deleterious consequences for mitochondrial function with important implications in a variety of pathophysiological conditions, including myocardial I/R injury. In this review, we focus on the role played by CL alterations in mitochondrial dysfunction in myocardial I/R injury. Pharmacological strategies to prevent myocardial injury during I/R targeting mitochondrial CL are also examined.

Nonalcoholic fatty liver disease (NAFLD) is today considered the most common form of chronic liver disease, affecting a high proportion of the population worldwide. NAFLD encompasses a large spectrum of liver damage, ranging from simple steatosis to steatohepatitis, advanced fibrosis and cirrhosis. Obesity, hyperglycemia, type 2 diabetes and hypertriglyceridemia are the most important risk factors. The pathogenesis of NAFLD and its progression to fibrosis and chronic liver disease is still unknown. Accumulating evidence indicates that mitochondrial dysfunction plays a key role in the physiopathology of NAFLD, although the mechanisms underlying this dysfunction are still unclear. Oxidative stress is considered an important factor in producing lethal hepatocyte injury associated with NAFLD. Mitochondrial respiratory chain is the main subcellular source of reactive oxygen species (ROS), which may damage mitochondrial proteins, lipids and mitochondrial DNA. Cardiolipin, a phospholipid located at the level of the inner mitochondrial membrane, plays an important role in several reactions and processes involved in mitochondrial bioenergetics as well as in mitochondrial dependent steps of apoptosis. This phospholipid is particularly susceptible to ROS attack. Cardiolipin peroxidation has been associated with mitochondrial dysfunction in multiple tissues in several physiopathological conditions, including NAFLD. In this review, we focus on the potential roles played by oxidative stress and cardiolipin alterations in mitochondrial dysfunction associated with NAFLD.

Cardiolipin (CL) is a unique phospholipid that is almost exclusively localized at the level of the inner mitochondrial membrane (IMM), where it is biosynthesized. This phospholipid is associated with membranes which are designed to generate an electrochemical gradient that is used to produce ATP. Such membranes include the bacterial plasma membrane and IMM. This ubiquitous and intimate association between CL and energy-transducing membranes suggests an important role for CL in mitochondrial bioenergetic processes. CL has been shown to interact with a number of IMM proteins, including the respiratory chain complexes and substrate carriers. Moreover, CL is involved in different stages of the mitochondrial apoptosis process as well as in mitochondrial membrane stability and dynamics. Alterations in CL structure, content, and acyl chain composition have been associated with mitochondrial dysfunction in multiple tissues in several physiopathological conditions and aging. In this review, we provide an overview of the roles of CL in mitochondrial function and bioenergetics in health and disease.

Cardiolipin is a unique phospholipid which is almost exclusively located in the inner mitochondrial membrane where it is biosynthesized. Considerable progress has recently been made in understanding the role of cardiolipin in mitochondrial function and bioenergetics. This phospholipid is associated with membranes designed to generate an electrochemical gradient that is used to produce ATP, such as bacterial plasma membranes and inner mitochondrial membrane. This ubiquitous and intimate association between cardiolipin and energy transducing membranes indicates an important role for cardiolipin in mitochondrial bioenergetic processes. Cardiolipin has been shown to interact with a number of proteins, including the respiratory chain complexes and substrate carrier proteins. Over the past decade, the significance of cardiolipin in the organization of components of the electron transport chain into higher order assemblies, termed respiratory supercomplexes, has been established. Moreover, cardiolipin is involved in different stages of the mitochondrial apoptotic process, as well as in mitochondrial membrane stability and dynamics. This review discusses the current understanding of the functional role that cardiolipin plays in several reactions and processes involved in mitochondrial bioenergetics. This article is part of a Special Issue entitled: Dynamic and ultrastructure of bioenergetic membranes and their components., (© 2013 Elsevier B.V. All rights reserved.)

Reactive oxygen species (ROS) are considered a key factor in mitochondrial dysfunction associated with brain aging process. Mitochondrial respiration is an important source of ROS and hence a potential contributor to brain functional changes with aging. In this study, we examined the effect of aging on cytochrome c oxidase activity and other bioenergetic processes such as oxygen consumption, membrane potential and ROS production in rat brain mitochondria. We found a significant age-dependent decline in the cytochrome c oxidase activity which was associated with parallel changes in state 3 respiration, membrane potential and with an increase in H2O2 generation. The cytochrome aa3 content was practically unchanged in mitochondria from young and aged animals. The age-dependent decline of cytochrome c oxidase activity could be restored, in situ, to the level of young animals, by exogenously added cardiolipin. In addition, exposure of brain mitochondria to peroxidized cardiolipin resulted in an inactivation of this enzyme complex. It is suggested that oxidation/depletion of cardiolipin could be responsible, at least in part, for the decline of cytochrome c oxidase and mitochondrial dysfunction in brain aging. Melatonin treatment of old animals largely prevented the age-associated alterations of mitochondrial bioenergetic parameters. These results may prove useful in elucidating the molecular mechanisms underlying mitochondrial dysfunction associated with brain aging process, and may have implications in etiopathology of age-associated neurodegenerative disorders and in the development of potential treatment strategies.

Aging is a biological process characterized by impairment of cellular bioenergetic function, increased oxidative stress, attenuated ability to respond to stresses, increased risk of contracting age-associated disorders that affects many tissues, with a more marked effect on brain and heart function. Oxidative stress is widely thought to underpin many aging processes. The mitochondrion is considered the most important cellular organelle to contribute to the aging process, mainly through respiratory chain dysfunction and formation of reactive oxygen species, leading to damage to mitochondrial proteins, lipids and mitochondrial DNA. Furthermore, exposure to oxidants, especially in the presence of Ca(2+), can induce the mitochondrial permeability transition with deleterious effects on mitochondrial function. Cardiolipin plays a central role in several mitochondrial bioenergetic processes as well as in mitochondrial-dependent steps in apoptosis and mitochondrial membrane stability and dynamics. Alterations to cardiolipin structure, content and acyl chain profile have been associated with mitochondrial dysfunction in multiple tissues in several physiopathological conditions and aging. In this review, we focus on the role played by oxidative stress and cardiolipin in mitochondrial bioenergetic alterations associated with brain aging., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Aging is a natural, complex, and multifactorial biological process associated with impairment of bioenergetic function, increased oxidative stress, attenuated ability to respond to stresses, and increased risk of contracting age-associated diseases. Oxidative stress is widely thought to underpin many aging processes. The mitochondrion, the powerhouse of the cell, is considered the most important cellular organelle to contribute to the aging process, mainly through respiratory chain dysfunction and formation of reactive oxygen species, leading to damage to mitochondrial proteins, lipids, and mitochondrial DNA. Cardiolipin, a phospholipid located at the level of the inner mitochondrial membrane, is known to be intimately involved in several mitochondrial bioenergetic processes as well as mitochondrial-dependent steps in apoptosis and mitochondrial membrane stability and dynamics. Alterations to cardiolipin structure, content, and acyl chain composition have been associated with mitochondrial dysfunction in multiple tissues in several physiopathological conditions and aging. In this review, we discuss several aspects of mitochondrial bioenergetic alterations in aging and the role played by reactive oxygen species and cardiolipin in these alterations., (Copyright 2010 Elsevier Inc. All rights reserved.)

Melatonin is a natural occurring compound with well-known antioxidant properties. Melatonin is ubiquitously distributed and because of its small size and amphiphilic nature, it is able to reach easily all cellular and subcellular compartments. The highest intracellular melatonin concentrations are found in mitochondria, raising the possibility of functional significance for this targeting with involvement in situ in mitochondrial activities. Mitochondria, the powerhouse of the cell, are considered to be the most important cellular organelles to contribute to degenerative processes mainly through respiratory chain dysfunction and formation of reactive oxygen species, leading to damage to mitochondrial proteins, lipids and DNA. Therefore, protecting mitochondria from oxidative damage could be an effective therapeutic strategy against cellular degenerative processes. Many of the beneficial effects of melatonin administration may depend on its effect on mitochondrial physiology. Cardiolipin, a phospholipid located at the level of inner mitochondrial membrane is known to be intimately involved in several mitochondrial bioenergetic processes as well as in mitochondrial-dependent steps of apoptosis. Alterations to cardiolipin structure, content and acyl chain composition have been associated with mitochondrial dysfunction in multiple tissues in several physiopathological situations and aging. Recently, melatonin was reported to protect the mitochondria from oxidative damage by preventing cardiolipin oxidation and this may explain, at least in part, the beneficial effect of this molecule in mitochondrial physiopathology. In this review, we discuss the role of melatonin in preventing mitochondrial dysfunction and disease.

Cardiolipin oxidation is emerging as an important factor in mitochondrial dysfunction as well as in the initial phase of the apoptotic process. We have previously shown that exogenously added peroxidized cardiolipin sensitizes mitochondria to Ca(2+)-induced mitochondrial permeability transition (MPT) pore opening and promotes the release of cytochrome c. In this work, the effects of intramitochondrial cardiolipin peroxidation on Ca(2+)-induced MPT and on the cytochrome c release from mitochondria were studied. The effects of melatonin, a compound known to protect the mitochondria from oxidative damage, on both of these processes were also tested. tert-Butylhydroperoxide (t-BuOOH), a lipid-soluble peroxide that promotes lipid peroxidation, was used to induce intramitochondrial cardiolipin peroxidation. Exposure of heart mitochondria to t-BuOOH resulted in the oxidation of cardiolipin, associated with an increased sensitivity of mitochondria to Ca(2+)-induced MPT and with the release of cytochrome c from the mitochondria. All these processes were inhibited by micromolar concentrations of melatonin. It is proposed that melatonin inhibits cardiolipin peroxidation in mitochondria, and this effect seems to be responsible for the protection afforded by this agent against the MPT induction and cytochrome c release. Thus, manipulating the oxidation sensitivity of cardiolipin with melatonin may help to control MPT and cytochrome c release, events associated with cell death, and thus, be used for treatment of those disorders characterized by mitochondrial cardiolipin oxidation and Ca(2+) overload.

Cardiolipin is a unique phospholipid which is almost exclusively located at the level of the inner mitochondrial membrane where it is biosynthesized. This phospholipid is known to be intimately involved in several mitochondrial bioenergetic processes. In addition, cardiolipin also has active roles in several of the mitochondrial-dependent steps of apoptosis and in mitochondrial membrane dynamics. Alterations in cardiolipin structure, content and acyl chains composition have been associated with mitochondrial dysfunction in multiple tissues in several physiopathological conditions, including ischemia/reperfusion, different thyroid states, diabetes, aging and heart failure. Cardiolipin is particularly susceptible to ROS attack due to its high content of unsaturated fatty acids. Oxidative damage to cardiolipin would negatively impact the biochemical function of the mitochondrial membranes altering membrane fluidity, ion permeability, structure and function of components of the mitochondrial electron transport chain, resulting in reduced mitochondrial oxidative phosphorylation efficiency and apoptosis. Diseases in which mitochondrial dysfunction has been linked to cardiolipin peroxidation are described. Ca(2+), particularly at high concentrations, appears to have several negative effects on mitochondrial function, some of these effects being linked to CL peroxidation. Cardiolipin peroxidation has been shown to participate, together with Ca(2+), in mitochondrial permeability transition. In this review, we provide an overview of the role of CL peroxidation and Ca(2+) in mitochondrial dysfunction and disease.

Reactive oxygen species (ROS) are considered a key factor in the heart aging process. Mitochondrial respiration is an important site of ROS generation and a potential contributor to heart functional changes with aging. We have examined the effects of aging on various parameters related to mitochondrial bioenergetics in rat heart, such as complex I activity, oxygen consumption, membrane potential, ROS production, and cardiolipin content and oxidation. A loss in complex I activity, state 3 respiration, and membrane potential was found in mitochondria with aging. The capacity of mitochondria to produce H(2)O(2) was significantly increased in aged rats. The mitochondrial content of cardiolipin, a phospholipid required for optimal activity of complex I, significantly decreased as a function of aging, whereas there was a significant increase in the level of oxidized cardiolipin. The lower complex I activity in mitochondria from aged rats could be almost completely restored to the level of young heart by exogenously added cardiolipin, but not by other phospholipids nor by peroxidized cardiolipin. It is proposed that aging causes heart mitochondrial complex I deficiency, which can be attributed to ROS-induced cardiolipin peroxidation. These results may prove useful in elucidating the mechanism underlying mitochondrial dysfunction associated with heart aging.

Reactive oxygen species (ROS) are considered a key factor in brain aging process. Complex I of the mitochondrial respiration chain is an important site of ROS production and hence a potential contributor to brain functional changes with aging. Appropriate antioxidant strategies could be particularly useful to limit this ROS production and associated mitochondrial dysfunction. Melatonin has been shown to possess antioxidant properties and to reduce oxidant events in brain aging. The mechanism underlying this protective effect of melatonin is not well established. In the present study, we examined the effects of long-term treatment of aged rats with melatonin on various parameters related to mitochondrial bioenergetics in brain tissue. After isolation of mitochondria from control, aged, and melatonin-treated young and aged rats, various bioenergetic parameters were evaluated such as complex I activity, rates of state 3 respiration, mitochondrial hydrogen peroxide (H2O2) production, and membrane potential. The mitochondrial content of normal and oxidized cardiolipin was also evaluated. We found that all these mitochondrial parameters were significantly altered with aging, and that melatonin treatment completely prevented these age-related alterations. These effects appear to be due, at least in part, to melatonin's ability to preserve the content and structural integrity of cardiolipin molecules, which play a pivotal role in mitochondrial bioenergetics. The melatonin's ability to prevent complex I dysfunction and cardiolipin peroxidation was also demonstrated by in vitro experiments on brain mitochondria treated with tert-butyl hydroperoxide. In summary, this study documents a decline of mitochondrial bioenergetic functions in brain with aging and the beneficial effect of melatonin.

The effect of peroxidized cardiolipin on the mitochondrial pore transition (MPT) induction and cytochrome c release in rat heart mitochondria was studied. Treatment of mitochondria with cardiolipin hydroperoxide (CLOOH) promoted matrix swelling and release of cytochrome c. Both these processes were inhibited by cyclosporine A and bongkrekic acid, indicating that peroxidized cardiolipin behaves as an inducer of MPT. Ca2+ accumulation was required for this effect. ANT (ADP/ATP carrier) is involved in the CLOOH-dependent MPT induction as suggested by the modulation by ligands and inhibitors of ANT. These results indicate that CLOOH lowers the threshold of Ca2+ for MPT induction. This synergistic effect of Ca2+ and CLOOH on MPT induction and cytochrome c release in mitochondria might have important implications in the apoptotic process as well as in several pathophysiological situations.

Mitochondrial dysfunction and oxidative stress play a central role in the pathophysiology of nonalcoholic fatty liver disease (NAFLD). This study aimed to elucidate the mechanism(s) responsible for mitochondrial dysfunction in nonalcoholic fatty liver. Fatty liver was induced in rats with a choline-deficient (CD) diet for 30 days. We examined the effect of CD diet on various parameters related to mitochondrial function such as complex I activity, oxygen consumption, reactive oxygen species (ROS) generation and cardiolipin content and oxidation. The activity of complex I was reduced by 35% in mitochondria isolated from CD livers compared with the controls. These changes in complex I activity were associated with parallel changes in state 3 respiration. Hydrogen peroxide (H(2)O(2)) generation was significantly increased in mitochondria isolated from CD livers. The mitochondrial content of cardiolipin, a phospholipid required for optimal activity of complex I, decreased by 38% as function of CD diet, while there was a significantly increase in the level of peroxidized cardiolipin. The lower complex I activity in mitochondria from CD livers could be completely restored to the level of control livers by exogenously added cardiolipin. This effect of cardiolipin could not be replaced by other phospholipids nor by peroxidized cardiolipin. It is concluded that CD diet causes mitochondrial complex I dysfunction which can be attributed to ROS-induced cardiolipin oxidation. These findings provide new insights into the alterations underlying mitochondrial dysfunction in NAFLD.

Cardiolipin peroxidation plays a critical role in mitochondrial cytochrome c release and subsequent apoptotic process. Mitochondrial pore transition (MPT) is considered as an important step in this process. In this work, the effect of peroxidized cardiolipin on MPT induction and cytochrome c release in rat heart mitochondria was investigated. Treatment of mitochondria with micromolar concentrations of cardiolipin hydroperoxide (CLOOH) resulted in a dose-dependent matrix swelling, DeltaPsi collapse, release of preaccumulated Ca2+ and release of cytochrome c. All these events were inhibited by cyclosporin A and bongkrekic acid, indicating that peroxidized cardiolipin behaves as an inducer of MPT. Ca2+ accumulation by mitochondria was required for this effect. ANT (ADP/ATP translocator) appears to be involved in the CLOOH-dependent MPT induction, as suggested by the modulation by ligands and inhibitors of adenine nucleotide translocator (ANT). Together, these results indicate that peroxidized cardiolipin lowers the threshold of Ca2+ for MPT induction and cytochrome c release. This synergistic effect of Ca2+ and peroxidized cardiolipin on MPT induction and cytochrome c release in mitochondria, might be important in regulating the initial phase of apoptosis and also may have important implications in those physiopathological situations, characterized by both Ca2+ and peroxidized cardiolipin accumulation in mitochondria, such as aging, ischemia/reperfusion and other degenerative diseases.

Release of cytochrome c from mitochondria is considered a critical, early event in the induction of an apoptosis cascade that ultimately leads to programmed cell death. Mitochondrial Ca(2+) loading is a trigger for the release of cytochrome c, although the molecular mechanism underlying this effect is not fully clarified. This study tested the hypothesis that distinct Ca(2+) thresholds may induce cytochrome c release from rat liver mitochondria by membrane permeability transition (MPT)-dependent and independent mechanisms. The involvement of reactive oxygen species (ROS) and cardiolipin in the Ca(2+)-induced cytochrome c release was also investigated. Cytochrome c was quantitated by a new, very sensitive, and rapid reverse-phase high performance liquid chromatography method with a detection limit of 0.1 pmol/sample. We found that a low extramitochondrial Ca(2+) level (2 microM) promoted the release of approximately 13% of the total alamethicin releasable pool of cytochrome c from mitochondria. This release was not depending of MPT; it was mediated by Ca(2+)-induced ROS production and cardiolipin peroxidation and appears to involve the voltage-dependent anion channel. High extramitochondrial Ca(2+) level (20 microM) promoted approximately 45% of the total releasable pool of cytochrome c. This process was MPT-dependent and was also mediated by ROS and cardiolipin. It is suggested that distinct Ca(2+) levels may determine the mode and the amount of cytochrome c release from rat liver mitochondria. The data may help to clarify the molecular mechanism underlying the Ca(2+)-induced release of cytochrome c from rat liver mitochondria and the role played by ROS and cardiolipin in this process.

Reactive oxygen species (ROS) are considered an important factor in ischemia/reperfusion injury to cardiac myocytes. Mitochondrial respiration is an important source of ROS production and hence a potential contributor to cardiac reperfusion injury. In this study, we have examined the effect of ischemia and ischemia followed by reperfusion of rat hearts on various parameters related to mitochondrial function, such as complex I activity, oxygen consumption, ROS production, and cardiolipin content. The activity of complex I was reduced by 25% and 48% in mitochondria isolated from ischemic and reperfused rat heart, respectively, compared with the controls. These changes in complex I activity were associated with parallel changes in state 3 respiration. The capacity of mitochondria to produce H2O2 increased on reperfusion. The mitochondrial content of cardiolipin, which is required for optimal activity of complex I, decreased by 28% and 50% as function of ischemia and reperfusion, respectively. The lower complex I activity in mitochondria from reperfused rat heart could be completely restored to the level of normal heart by exogenous added cardiolipin. This effect of cardiolipin could not be replaced by other phospholipids nor by peroxidized cardiolipin. It is proposed that the defect in complex I activity in ischemic/reperfused rat heart could be ascribed to a ROS-induced cardiolipin damage. These findings may provide an explanation for some of the factors responsible for myocardial reperfusion injury.

Several lines of evidence indicate that mitochondria-mediated reactive oxygen species (ROS) generation is a major source of oxidative stress in the cell. Release of cytochrome c from mitochondria is a central event in apoptosis induction and appears to be mediated by ROS. Dissociation of cytochrome c from the IMM, where it is bound to cardiolipin, represents a necessary first step for cytochrome c release. In the present study, the role of ROS and cardiolipin in the release of cytochrome c from rat liver mitochondria was investigated. ROS were produced by mitochondria oxidizing succinate in the nonphosphorylating state. Cytochrome c was quantitated by a new, very sensitive and rapid reverse-phase HPLC method. We found that succinate-supported ROS production resulted in a release of cytochrome c from mitochondria and a parallel loss of cardiolipin content. These effects were directly and significantly correlated and also abolished by ADP, which prevents succinate-mediated ROS production. The ROS-induced cytochrome c release was independent from MPT and appears to involve VDAC. It is suggested that mitochondrial-induced ROS production promotes cytochrome c release from mitochondria by a two-steps process, consisting of the dissociation of this protein from cardiolipin, followed by permeabilization of the outer membrane, probably by interaction with VDAC. The data may help clarify the molecular mechanism underlying the release of cytochrome c from the mitochondria to the cytosol and the role of ROS and cardiolipin in this release.

The aim of this study was to investigate the influence of reactive oxygen species (ROS) on the activity of complex I and on the cardiolipin content in bovine heart submitochondrial particles (SMP). ROS were generated through the use of xanthine/xanthine oxidase (X/XO) system. Treatment of SMP with X/XO resulted in a large production of superoxide anion, detected by acetylated cytochrome c method, which was blocked by superoxide dismutase (SOD). Exposure of SMP to ROS generation resulted in a marked loss of complex I activity and to parallel loss of mitochondrial cardiolipin content. Both these effects were completely abolished by SOD+catalase. Exogenous added cardiolipin was able to almost completely restore the ROS-induced loss of complex I activity. No restoration was obtained with other major phospholipid components of the mitochondrial membrane such as phosphatidylcholine and phosphatidylethanolamine, nor with peroxidized cardiolipin. These results demonstrate that ROS affect the mitochondrial complex I activity via oxidative damage of cardiolipin which is required for the functioning of this multisubunit enzyme complex. These results may prove useful in probing molecular mechanisms of ROS-induced peroxidative damage to mitochondria, which have been proposed to contribute to those pathophysiological conditions characterized by an increase in the basal production of reactive oxygen species such as aging, ischemia/reperfusion and chronic degenerative diseases.