RESUMEN
Metabolism is a critical determinant of immune cell functionality. Immunometabolism, by definition, is a multidisciplinary area of immunology research that integrates the knowledge of energy transduction mechanisms and biochemical pathways. An important concept in the field is metabolic switch, a transition of immune cells upon activation to preferential utilization of select catabolic pathways for their energy needs. Mitochondria are not inert in this process and contribute to the metabolic adaptation by different mechanisms which include increasing ATP production to match dynamic bioenergetic demands and serving as a signaling platform. The latter involves generation of reactive oxygen species (ROS), one of the most intensively studied mitochondrial processes. While the role of mitochondrial ROS in the context of oxidative stress is well established, ROS signaling in immunity is an emerging and quickly changing field. In this review, we discuss ROS signaling and immunometabolism concepts from the standpoint of bioenergetics. We also provide a critical insight into the methodology for ROS assessment, outlining current challenges in the field. Finally, based on our analysis of the literature data, we hypothesize that regulatory ROS production, as opposed to oxidative stress, is controlled by mitochondrial biogenesis rather than metabolic switches.
Asunto(s)
Metabolismo Energético , Sistema Inmunológico/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Transducción de Señal , Animales , Humanos , Mitocondrias/metabolismo , Estrés OxidativoRESUMEN
The role of mitochondria in oxidative stress is well recognized, but many questions are still to be answered. This article is intended to update our comprehensive review in 2005 by highlighting the progress in understanding of mitochondrial reactive oxygen species (ROS) metabolism over the past 10 years. We review the recently identified or re-appraised sources of ROS generation in mitochondria, such as p66(shc) protein, succinate dehydrogenase, and recently discovered properties of the mitochondrial antioxidant system. We also reflect upon some controversies, disputes, and misconceptions that confound the field.
Asunto(s)
Antioxidantes/metabolismo , Mitocondrias/metabolismo , Proteínas Mitocondriales/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Animales , HumanosRESUMEN
Optic atrophy 1 (OPA1) mutations cause dominant optic atrophy (DOA) with retinal ganglion cell (RGC) and optic nerve degeneration. The mechanism for the selective degeneration of RGCs in DOA remains elusive. To address the mechanism, we reduced OPA1 protein expression in cell lines and RGCs by RNA interference. OPA1 loss results in mitochondrial fragmentation, deficiency in oxidative phosphorylation, decreased ATP levels, decreased mitochondrial Ca(2+) retention capacity, reduced mtDNA copy numbers, and sensitization to apoptotic insults. We demonstrate profound cristae depletion and loss of crista junctions in OPA1 knockdown cells, whereas the remaining crista junctions preserve their normal size. OPA1-depleted cells exhibit decreased agonist-evoked mitochondrial Ca(2+) transients and corresponding reduction of NAD(+) to NADH, but the impairment in NADH oxidation leads to an overall more reduced mitochondrial NADH pool. Although in our model OPA1 loss in RGCs has no apparent impact on mitochondrial morphology, it decreases buffering of cytosolic Ca(2+) and sensitizes RGCs to excitotoxic injury. Exposure to glutamate triggers delayed calcium deregulation (DCD), often in a reversible manner, indicating partial resistance of RGCs to this injury. However, when OPA1 is depleted, DCD becomes irreversible. Thus, our data show that whereas OPA1 is required for mitochondrial fusion, maintenance of crista morphology and oxidative phosphorylation, loss of OPA1 also results in defective Ca(2+) homeostasis.
Asunto(s)
Calcio/metabolismo , GTP Fosfohidrolasas/metabolismo , Apoptosis , ADN Mitocondrial/metabolismo , GTP Fosfohidrolasas/antagonistas & inhibidores , GTP Fosfohidrolasas/genética , Células HeLa , Histamina/farmacología , Humanos , Mitocondrias/efectos de los fármacos , Mitocondrias/metabolismo , NAD/química , NAD/metabolismo , Atrofia Óptica Autosómica Dominante/metabolismo , Atrofia Óptica Autosómica Dominante/patología , Oxidación-Reducción , Fosforilación Oxidativa , Interferencia de ARN , ARN Interferente Pequeño/metabolismo , Células Ganglionares de la Retina/citología , Células Ganglionares de la Retina/metabolismoRESUMEN
This study tested the hypothesis that mitochondrial precursor targeting peptides can elicit the release of cytochrome c from both liver and brain mitochondria by a mechanism distinct from that mediated by the classical, Ca2+-activated permeability transition pore. Human cytochrome oxidase subunit IV signal peptide (hCOXIV1-22) at concentrations from 15 to 100 microM induced swelling, a decrease in membrane potential, and cytochrome c release in both types of mitochondria. Although cyclosporin A and bongkrekic acid were without effect, dibucaine, propanolol, dextran, and the uncoupler FCCP were each able to inhibit signal peptide-induced swelling and cytochrome c release. Adenylate kinase was coreleased with cytochrome c, arguing against a signal peptide-induced cytochrome c-specific pathway of efflux across the outer membrane. Taken together, the data indicate that a human mitochondrial signal peptide can evoke the release of cytochrome c from both liver and brain mitochondria by a unique permeability transition that differs in several characteristics from the classical mitochondrial permeability transition.
Asunto(s)
Encéfalo/citología , Grupo Citocromo c/metabolismo , Canales Iónicos , Mitocondrias Hepáticas/efectos de los fármacos , Mitocondrias/efectos de los fármacos , Precursores de Proteínas/farmacología , Señales de Clasificación de Proteína/fisiología , Adenosina Trifosfato/farmacología , Adenilato Quinasa/metabolismo , Animales , Dextranos/farmacología , Dibucaína/farmacología , Relación Dosis-Respuesta a Droga , Complejo IV de Transporte de Electrones/química , Humanos , Magnesio/farmacología , Potenciales de la Membrana/efectos de los fármacos , Proteínas de la Membrana/antagonistas & inhibidores , Proteínas de la Membrana/metabolismo , Mitocondrias/enzimología , Mitocondrias/metabolismo , Mitocondrias Hepáticas/enzimología , Mitocondrias Hepáticas/metabolismo , Proteínas de Transporte de Membrana Mitocondrial , Poro de Transición de la Permeabilidad Mitocondrial , Dilatación Mitocondrial/efectos de los fármacos , Permeabilidad/efectos de los fármacos , Propranolol/farmacología , Precursores de Proteínas/química , Transporte de Proteínas/efectos de los fármacos , Ratas , Desacopladores/farmacologíaAsunto(s)
Apoptosis , Mitocondrias/fisiología , Mitocondrias/ultraestructura , Animales , Calcio/metabolismo , Fraccionamiento Celular/métodos , Línea Celular , Permeabilidad de la Membrana Celular , Digitonina , Membranas Intracelulares/fisiología , Potenciales de la Membrana/efectos de los fármacos , Neuronas , Células PC12 , Ratas , terc-Butilhidroperóxido/farmacologíaRESUMEN
Mitochondria can be induced by a variety of agents/conditions to undergo a permeability transition (MPT), which nonselectively increases the permeability of the inner membrane (i.m.) to small (<1500 Da) solutes. Prooxidants are generally considered to trigger the MPT, but some investigators suggest instead that prooxidants open a Ca(2+)-selective channel in the inner mitochondrial membrane and that the opening of this channel, when coupled with Ca(2+) cycling mediated by the Ca(2+) uniporter, leads ultimately to the observed increase in mitochondrial permeability [see, e.g., Schlegel et al. (1992) Biochem. J. 285, 65]. S. A. Novgorodov and T. I. Gudz [J. Bioenerg. Biomembr. (1996) 28, 139] propose that the i.m. contains a pore that, upon exposure to prooxidants, can open to two states, one of which conducts only H(+) and one of which is the classic MPT pore. Given the current interest in increased mitochondrial permeability as a factor in apoptotic cell death, it is important to determine whether i.m. permeability is regulated in one or multiple ways and, in the latter event, to characterize each regulatory mechanism in detail. This study examined the effects of the prooxidants diamide and t-butylhydroperoxide (t-BuOOH) on the permeability of isolated rat liver mitochondria. Under the experimental conditions used, t-BuOOH induced mitochondrial swelling only in the presence of exogenous Ca(2+) (>2 microM), whereas diamide was effective in its absence. In the absence of exogenous inorganic phosphate (P(i)), (1) both prooxidants caused a collapse of the membrane potential (DeltaPsi) that preceded the onset of mitochondrial swelling; (2) cyclosporin A eliminated the swelling induced by diamide and dramatically slowed that elicited by t-BuOOH, without altering prooxidant-induced depolarization; (3) collapse of DeltaPsi was associated with Ca(2+) efflux but not with efflux of glutathione; (4) neither Ca(2+) efflux nor DeltaPsi collapse was sensitive to ruthenium red; (5) collapse of DeltaPsi was accompanied by an increase in matrix pH; no stimulation of respiration was observed; (6) Sr(2+) was able to substitute for Ca(2+) in supporting t-BuOOH-induced i.m. depolarization, but not swelling; (7) in addition to being insensitive to CsA, the collapse of DeltaPsi was also resistant to trifluoperazine, spermine, and Mg(2+), all of which block the MPT; and (8) DeltaPsi was restored (and its collapse was inhibited) upon addition of dithiothreitol, ADP, ATP or EGTA. We suggest that these results indicate that prooxidants open two channels in the i.m.: the classic MPT and a low-conductance channel with clearly distinct properties. Opening of the low-conductance channel requires sulfhydryl group oxidation and the presence of a divalent cation; both Ca(2+) and Sr(2+) are effective. The channel permits the passage of cations, including Ca(2+), but not of protons. It is insensitive to inhibitors of the classic MPT.
Asunto(s)
Membranas Intracelulares/metabolismo , Activación del Canal Iónico/efectos de los fármacos , Canales Iónicos/metabolismo , Mitocondrias Hepáticas/metabolismo , Oxidantes/farmacología , Animales , Calcio/metabolismo , Calcio/farmacología , Ciclosporina/farmacología , Diamida/farmacología , Ditiotreitol/farmacología , Glutatión/metabolismo , Concentración de Iones de Hidrógeno , Membranas Intracelulares/efectos de los fármacos , Canales Iónicos/antagonistas & inhibidores , Masculino , Potenciales de la Membrana/efectos de los fármacos , Mitocondrias Hepáticas/efectos de los fármacos , Dilatación Mitocondrial/efectos de los fármacos , Permeabilidad/efectos de los fármacos , Fosfatos/farmacología , Ratas , Ratas Sprague-Dawley , Rojo de Rutenio/farmacología , Estroncio/metabolismo , Estroncio/farmacología , terc-Butilhidroperóxido/antagonistas & inhibidores , terc-Butilhidroperóxido/farmacologíaRESUMEN
We have reported that the signal presequence of cytochrome oxidase subunit IV from Neurospora crassa increases the permeability of isolated rat liver mitochondria [P. M. Sokolove and K. W. Kinnally (1996) Arch. Biochem. Biophys. 336, 69] and regulates the behavior of the mutiple conductance channel (MCC) of yeast inner mitochondrial membrane [T. A. Lohret and K. W. Kinnally (1995) J. Biol. Chem. 270, 15950]. Here we examine in greater detail the action of a number of mitochondrial presequences from various sources and of several control peptides on the permeability of isolated rat liver mitochondria and on MCC activity monitored via patch-clamp techniques in both mammalian mitoplasts and a reconstituted yeast system. The data indicate that the ability to alter mitochondrial permeability is a property of most, but not all, signal peptides. Furthermore, it is clear that, although signal peptides are characterized by positive charge and the ability to form amphiphilic alpha helices, these two characteristics are not sufficient to guarantee mitochondrial effects. Finally, the results reveal a strong correlation between peptide effects on the permeability of isolated mitochondria and on MCC activity: peptides that induced swelling of mouse and rat mitochondria also activated the quiescent MCC of mouse mitoplasts and induced flickering of active MCC reconstituted from yeast mitochondrial membranes. Moreover, relative peptide efficacies were very similar for mitochondrial swelling and both types of patch-clamp experiments. We propose that patch-clamp recordings of MCC activity and the high-amplitude swelling induced by signal peptides reflect the opening of a single channel. Based on the selective responsiveness of that channel to signal peptides and the dependence of its opening in isolated mitochondria on membrane potential, we further suggest that the channel is involved in the mitochondrial protein import process.
Asunto(s)
Canales Iónicos/efectos de los fármacos , Mitocondrias Hepáticas/efectos de los fármacos , Señales de Clasificación de Proteína/farmacología , Secuencia de Aminoácidos , Animales , Carbonil Cianuro p-Trifluorometoxifenil Hidrazona/farmacología , Masculino , Ratones , Datos de Secuencia Molecular , Permeabilidad/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Partículas Submitocóndricas/efectos de los fármacosRESUMEN
Under a variety of conditions, the permeability of the inner mitochondrial membrane to small solutes can be nonselectively increased. A classic mitochondrial permeability transition (MPT) was originally identified based on its dependence on matrix Ca2+ and its extreme sensitivity to cyclosporin A (CsA). It is now clear, however, that several additional and distinct processes can also produce increases in mitochondrial permeability. Both mitochondrial signal peptides (P. M. Sokolove and K. W. Kinnally, 1996, Arch. Biochem. Biophys. 336, 69-76) and butylated hydroxytoluene (BHT) (P. M. Sokolove and L. M. Haley, 1996, J. Bioenerg. Biomembr. 28, 199-206), for example, induce permeability increases that are relatively CsA insensitive and that persist in the presence of EGTA. Inorganic phosphate (Pi) appears to play a key role in each of these permeability increases. High (>1 mM) Pi levels facilitate the classic MPT, while Pi concentrations below 1 mM stimulate the permeability increase induced by signal peptides and inhibit that triggered by BHT. The effect of high Pi concentrations can most probably be explained by exchange of the anion for matrix ADP and the resulting alleviation of ADP-mediated inhibition of the MPT (R. G. Lapidus and P. M. Sokolove, 1994, J. Biol. Chem. 269, 18931-18936). In the experiments reported here, the mechanisms underlying the effects of low Pi concentrations on mitochondrial permeability were investigated, by monitoring mitochondrial volume, with the following results: (1) A hitherto unrecognized ability of Pi (<1 mM) to increase the lag preceding induction of the classic MPT by diamide, phenylarsine oxide, and t-butylhydroperoxide was identified. (2) Data were obtained suggesting that all of the effects of low Pi concentration, stimulation of signal peptide-induced swelling, blockade of BHT-induced swelling, and delay of the classic MPT, can be attributed to the capacity of the anion to complex Ca2+ in the mitochondrial matrix. (3) Differences in the responses of these three systems for enhancing mitochondrial permeability to experimental manipulation indicate that matrix Ca2+ plays more than one role in the regulation of mitochondrial permeability. An additional important finding is the observation that failure of EGTA to alter a mitochondrial process need not mean that the process is Ca2+ independent. In a multicompartment system, absence of EGTA action may instead reflect failure of the chelator to gain access to regulatory Ca2+.
Asunto(s)
Calcio/metabolismo , Mitocondrias Hepáticas/metabolismo , Fosfatos/metabolismo , Fosfatos/fisiología , Acetatos/farmacología , Aminoquinolinas/farmacología , Animales , Antioxidantes/farmacología , Hidroxitolueno Butilado/farmacología , Calcimicina/farmacología , Quelantes/farmacología , Diamida/farmacología , Ácido Egtácico/farmacología , Membranas Intracelulares/metabolismo , Ionóforos/farmacología , Masculino , Potenciales de la Membrana/efectos de los fármacos , Dilatación Mitocondrial/efectos de los fármacos , Permeabilidad , Señales de Clasificación de Proteína/farmacología , Ratas , Ratas Sprague-Dawley , Reactivos de Sulfhidrilo/farmacología , terc-Butilhidroperóxido/farmacologíaRESUMEN
The evolutionary theory of aging predicts that the equilibrium gene frequency for deleterious mutations should increase with age at onset of mutation action because of weaker (postponed) selection against later-acting mutations. According to this mutation accumulation hypothesis, one would expect the genetic variability for survival (additive genetic variance) to increase with age. The ratio of additive genetic variance to the observed phenotypic variance (the heritability of longevity) can be estimated most reliably as the doubled slope of the regression line for offspring life span on paternal age at death. Thus, if longevity is indeed determined by late-acting deleterious mutations, one would expect this slope to become steeper at higher paternal ages. To test this prediction of evolutionary theory of aging, we computerized and analyzed the most reliable and accurate genealogical data on longevity in European royal and noble families. Offspring longevity for each sex (8409 records for males and 3741 records for females) was considered as a dependent variable in the multiple regression model and as a function of three independent predictors: paternal age at death (for estimation of heritability of life span), paternal age at reproduction (control for parental age effects), and cohort life expectancy (control for cohort and secular trends and fluctuations). We found that the regression slope for offspring longevity as a function of paternal longevity increases with paternal longevity, as predicted by the evolutionary theory of aging and by the mutation accumulation hypothesis in particular.
Asunto(s)
Evolución Biológica , Personajes , Variación Genética/genética , Longevidad/genética , Mutación/genética , Adulto , Anciano , Envejecimiento/genética , Europa (Continente) , Femenino , Genealogía y Heráldica , Humanos , Masculino , Persona de Mediana Edad , Edad Paterna , Linaje , Análisis de Regresión , Selección GenéticaRESUMEN
Since paternal age at reproduction is considered to be the main factor determining human spontaneous mutation rate (Crow, J. (1993) Environ. Mol. Mutagenesis, 21, 122-129), the effect of paternal age on human longevity was studied on 8,518 adult persons (at age 30 and above) from European aristocratic families with well-known genealogy. The daughters born to old fathers (50-59 years) lose about 4.4 years of their life compared to daughters of young fathers (20-29 years) and these losses are highly statistically significant, while sons are not significantly affected. Since only daughters inherit the paternal X chromosome, this sex-specific decrease in daughters' longevity might indicate that human longevity genes (crucial, house-keeping genes) sensitive to mutational load might be located in this chromosome.
Asunto(s)
Longevidad/genética , Mutación , Edad Paterna , Cromosoma X/genética , Adulto , Anciano , Europa (Continente) , Femenino , Humanos , Masculino , Persona de Mediana Edad , Núcleo Familiar , Reproducción/genética , Reproducción/fisiología , Factores SexualesRESUMEN
A protonophore-induced delta psi decrease in a 180-140 mV range causes an increase in the lag-period of Ca(2+)-induced mitochondrial permeabilization but has little effect on the cumene hydroperoxide-induced permeability transition of mitochondria. Suppression of the non-specific permeability induction seems to be mediated by an increase in [ADP] in the mitochondrial matrix. A further decrease in delta psi leads to additional suppression of the non-specific permeability as a result of a partial ruthenium red-sensitive efflux of the previously accumulated Ca2+. On the other hand, complete dissipation of delta psi causes immediate induction of the non-specific permeability. It is concluded that only complete dissipation of delta psi caused by H+ leakages may act as a trigger for non-specific permeability induction.
Asunto(s)
Derivados del Benceno/farmacología , Cloruro de Calcio/farmacología , Membranas Intracelulares/fisiología , Mitocondrias Hepáticas/fisiología , Partículas Submitocóndricas/fisiología , Animales , Atractilósido/análogos & derivados , Atractilósido/farmacología , Carbonil Cianuro p-Trifluorometoxifenil Hidrazona/farmacología , Membranas Intracelulares/efectos de los fármacos , Cinética , Potenciales de la Membrana/efectos de los fármacos , Mitocondrias Hepáticas/efectos de los fármacos , Dilatación Mitocondrial/efectos de los fármacos , Permeabilidad , Ratas , Rojo de Rutenio/farmacología , Partículas Submitocóndricas/efectos de los fármacosRESUMEN
The effect of antioxidants on the nonspecific permeability of the inner mitochondrial membrane induced by cumene hydroperoxide or Ca(2+) has been studied. Butylated hydroxytoluene, butylated hydroxyanisole and 2,2,5,7,8-pentamethyl-6-chromanol, taken at a concentration up to 50 microM, suppress the cumene hydroperoxide-induced accumulation of lipid peroxidation products. In the same range of concentrations, these antioxidants inhibit the activation of nonspecific permeability by cumene hydroperoxide or Ca(2+). Propyl gallate, being less effective under such conditions, fails to affect the induction of nonspecific permeability. Additionally, 2,2,5,7,8-pentamethyl-6-chromanol at a concentration decreasing the accumulation of lipid peroxidation products by 70% has been shown not to increase the lag period of nonspecific permeability induction. Higher antioxidant concentrations, while leading to an increase in the lag period of nonspecific permeability induction, cause but minor suppression of lipid peroxidation. From the results obtained we can assume that free radicals formed in the course of hydroperoxide decomposition or on mitochondrial redox complex interact directly with a system responsible for nonspecific permeability or with regulating components of this system.
Asunto(s)
Peróxido de Hidrógeno/farmacología , Membranas Intracelulares/efectos de los fármacos , Mitocondrias Hepáticas/efectos de los fármacos , Animales , Antioxidantes/farmacología , Hidroxianisol Butilado/farmacología , Hidroxitolueno Butilado/farmacología , Calcio/metabolismo , Cromanos/farmacología , Antagonismo de Drogas , Peroxidación de Lípido/efectos de los fármacos , Mitocondrias Hepáticas/metabolismo , Oxígeno/metabolismo , Permeabilidad/efectos de los fármacos , RatasRESUMEN
The influence of the conformational state of ADP/ATP antiporter on the efficiency of the inhibitory effect of cyclosporine A on the Ca2(+)-induced nonspecific permeability of the inner mitochondrial membrane has been studied. Carboxyatractiloside, the inhibitor of ADP/ATP-antiporter, was shown to prevent the cyclosporine A-induced suppression of the nonspecific permeability. The carboxyatractiloside effect was displayed only in mitochondria depleted of adenine nucleotides. Bifunctional SH reagent, phenylarsine oxide, was also able to reverse the effect of cyclosporine A. The data are consistent with the suggestion that cyclosporine A causes suppression of the nonspecific permeability due to its effect on the ADP/ATP antiporter conformation.
Asunto(s)
Ciclosporinas/farmacología , Mitocondrias Hepáticas/efectos de los fármacos , Translocasas Mitocondriales de ADP y ATP/metabolismo , Animales , Arsenicales/farmacología , Calcio/farmacología , Técnicas In Vitro , Membranas Intracelulares/efectos de los fármacos , Potenciales de la Membrana , Permeabilidad/efectos de los fármacos , Conformación Proteica , Ratas , Reactivos de Sulfhidrilo/farmacologíaRESUMEN
The effect of oligomycin and cyclosporine A on the induction of non-specific permeability of the inner mitochondrial membrane by Ca2+ was under study. Both oligomycin and cyclosporine A were able to prevent the activation of non-specific permeability, but cyclosporine A was the only agent which could restore initial permeability of the inner mitochondrial membrane. The effect of cyclosporine A was shown not to be mediated through redistribution of Ca2+ between different mitochondrial subpopulations.