The search for new drugs capable of blocking the metabolic vulnerabilities of human tumors has now entered the clinical evaluation stage, but several projects already failed in phase I or phase II. ...In particular, very promising in vitro studies could not be translated in vivo at preclinical stage and beyond. This was the case for most glycolysis inhibitors that demonstrated systemic toxicity. A more recent example is the inhibition of glutamine catabolism in lung adenocarcinoma that failed in vivo despite a strong addiction of several cancer cell lines to glutamine in vitro. Such contradictory findings raised several questions concerning the optimization of drug discovery strategies in the field of cancer metabolism. For instance, the cell culture models in 2D or 3D might already show strong limitations to mimic the tumor micro- and macro-environment. The microenvironment of tumors is composed of cancer cells of variegated metabolic profiles, supporting local metabolic exchanges and symbiosis, but also of immune cells and stroma that further interact with and reshape cancer cell metabolism. The macroenvironment includes the different tissues of the organism, capable of exchanging signals and fueling the tumor ‘a distance’. Moreover, most metabolic targets were identified from their increased expression in tumor transcriptomic studies, or from targeted analyses looking at the metabolic impact of particular oncogenes or tumor suppressors on selected metabolic pathways. Still, very few targets were identified from in vivo analyses of tumor metabolism in patients because such studies are difficult and adequate imaging methods are only currently being developed for that purpose. For instance, perfusion of patients with 13C-glucose allows deciphering the metabolomics of tumors and opens a new area in the search for effective targets. Metabolic imaging with positron emission tomography and other techniques that do not involve 13C can also be used to evaluate tumor metabolism and to follow the efficiency of a treatment at a preclinical or clinical stage. Relevant descriptors of tumor metabolism are now required to better stratify patients for the development of personalized metabolic medicine.
In this review, we discuss the current limitations in basic research and drug discovery in the field of cancer metabolism to foster the need for more clinically relevant target identification and validation. We discuss the design of adapted drug screening assays and compound efficacy evaluation methods for the discovery of innovative anti-cancer therapeutic approaches at the level of tumor energetics. This article is part of a Special Issue entitled Mitochondria in Cancer, edited by Giuseppe Gasparre, Rodrigue Rossignol and Pierre Sonveaux.
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•Clinical trials database including the keywords ‘cancer’ and ‘metabolism’ identified 2358 studies.•The metabolic flexibility of cancer cells alters the development of anti-cancer approaches.•Microenvironment and macroenvironment control tumor metabolism in vivo.•Targeting mitochondrial function could alter tumor survival, stem cells viability, metastasis and drug resistance.•Tumor metabolic stratification and relevant biomarkers are prerequisite to develop successful clinical trials on metabolic drugs.
The RAS pathway is a highly conserved cascade of protein-protein interactions and phosphorylation that is at the heart of signalling networks that govern proliferation, differentiation and cell ...survival. Recent findings indicate that the RAS pathway plays a role in the regulation of energy metabolism via the control of mitochondrial form and function but little is known on the participation of this effect in RAS-related rare human genetic diseases. Germline mutations that hyperactivate the RAS pathway have been discovered and linked to human developmental disorders that are known as RASopathies. Individuals with RASopathies, which are estimated to affect approximately 1/1000 human birth, share many overlapping characteristics, including cardiac malformations, short stature, neurocognitive impairment, craniofacial dysmorphy, cutaneous, musculoskeletal, and ocular abnormalities, hypotonia and a predisposition to developing cancer. Since the identification of the first RASopathy, type 1 neurofibromatosis (NF1), which is caused by the inactivation of neurofibromin 1, several other syndromes have been associated with mutations in the core components of the RAS-MAPK pathway. These syndromes include Noonan syndrome (NS), Noonan syndrome with multiple lentigines (NSML), which was formerly called LEOPARD syndrome, Costello syndrome (CS), cardio-facio-cutaneous syndrome (CFC), Legius syndrome (LS) and capillary malformation–arteriovenous malformation syndrome (CM-AVM). Here, we review current knowledge about the bioenergetics of the RASopathies and discuss the molecular control of energy homeostasis and mitochondrial physiology by the RAS pathway.
•Germline mutations in the RAS-MAPK pathway trigger rare diseases: RASopathies.•RASopathies affect approximately 1/1000 human birth but no therapy is available.•RAS controls energy metabolism and mitochondrial physiology.•Bioenergetic alterations are observed in RASopathy patients and related cell and mouse models.•Bioenergetic modulation is under investigation in preclinical studies on various RASopathy models.
Mitochondria are dynamic cellular organelles responsible for a large variety of biochemical processes as energy transduction, REDOX signaling, the biosynthesis of hormones and vitamins, inflammation ...or cell death execution. Cell biology studies established that 1158 human genes encode proteins localized to mitochondria, as registered in MITOCARTA. Clinical studies showed that a large number of these mitochondrial proteins can be altered in expression and function through genetic, epigenetic or biochemical mechanisms including the interaction with environmental toxics or iatrogenic medicine. As a result, pathogenic mitochondrial genetic and functional defects participate to the onset and the progression of a growing number of rare diseases. In this review we provide an exhaustive survey of the biochemical, genetic and clinical studies that demonstrated the implication of mitochondrial dysfunction in human rare diseases. We discuss the striking diversity of the symptoms caused by mitochondrial dysfunction and the strategies proposed for mitochondrial therapy, including a survey of ongoing clinical trials.
•Mitochondria participate to variegated cellular functions.•Primary or secondary mitochondrial defects trigger rare diseases.•Environmental factors can induce mitochondrial dysfunction.•The molecular pathophysiology of mitochondrial diseases is very complex.•A too limited number of drugs is available to modulate mitochondrial function in human therapy.
The expanding universe of mitochondrial research Rossignol, R.
The international journal of biochemistry & cell biology,
January 2013, 2013-Jan, 2013-01-00, 20130101, Letnik:
45, Številka:
1
Journal Article
In this review we discuss the structure and functions of the aspartate/glutamate carriers (AGC1-aralar and AGC2-citrin). Those proteins supply the aspartate synthesized within mitochondrial matrix to ...the cytosol in exchange for glutamate and a proton. A structure of an AGC carrier is not available yet but comparative 3D models were proposed. Moreover, transport assays performed by using the recombinant AGC1 and AGC2, reconstituted into liposome vesicles, allowed to explore the kinetics of those carriers and to reveal their specific transport properties. AGCs participate to a wide range of cellular functions, as the control of mitochondrial respiration, calcium signaling and antioxydant defenses. AGC1 might also play peculiar tissue-specific functions, as it was found to participate to cell-to-cell metabolic symbiosis in the retina. On the other hand, AGC1 is involved in the glutamate-mediated excitotoxicity in neurons and AGC gene or protein alterations were discovered in rare human diseases. Accordingly, a mice model of AGC1 gene knock-out presented with growth delay and generalized tremor, with myelinisation defects. More recently, AGC was proposed to play a crucial role in tumor metabolism as observed from metabolomic studies showing that the asparate exported from the mitochondrion by AGC1 is employed in the regeneration of cytosolic glutathione. Therefore, given the central role of AGCs in cell metabolism and human pathology, drug screening are now being developed to identify pharmacological modulators of those carriers. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.
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•AGC1 and AGC2 export aspartate from mitochondria in exchange for cytosolic glutamate and a proton.•The kinetic properties of AGCs were extensively studied in proteoliposomes.•AGCs participate to cellular REDOX homeostasis and the calcium-mediated control of mitochondrial respiration via the malate-aspartate shuttle.•AGCs gene deficiencies are responsible for rare diseases.•AGC1 is central to neuronal physiology and also plays a role in glutamate-induced excitotoxicity.•AGCs are overexpressed in several types of human tumors.•In silico and in vitro screenings of chemical libraries for identifying new AGC pharmacological modulators are in progress
Mitochondrial dysfunction in the spinal cord is a hallmark of amyotrophic lateral sclerosis (ALS), but the neurometabolic alterations during early stages of the disease remain unknown. Here, we ...investigated the bioenergetic and proteomic changes in ALS mouse motor neurons and patients' skin fibroblasts. We first observed that SODG93A mice presymptomatic motor neurons display alterations in the coupling efficiency of oxidative phosphorylation, along with fragmentation of the mitochondrial network. The proteome of presymptomatic ALS mice motor neurons also revealed a peculiar metabolic signature with upregulation of most energy-transducing enzymes, including the fatty acid oxidation (FAO) and the ketogenic components HADHA and ACAT2, respectively. Accordingly, FAO inhibition altered cell viability specifically in ALS mice motor neurons, while uncoupling protein 2 (UCP2) inhibition recovered cellular ATP levels and mitochondrial network morphology. These findings suggest a novel hypothesis of ALS bioenergetics linking FAO and UCP2. Lastly, we provide a unique set of data comparing the molecular alterations found in human ALS patients' skin fibroblasts and SODG93A mouse motor neurons, revealing conserved changes in protein translation, folding and assembly, tRNA aminoacylation and cell adhesion processes.
1 INSERM, U688 Physiopathologie Mitochondriale, Université Victor Segalen-Bordeaux 2, Bordeaux, France; and 2 IFR 31, Institut Louis Bugnard, BP 84225, UMR 5018 CNRS UPS, Toulouse, France
Submitted ...20 April 2006
; accepted in final form 7 June 2006
To investigate the physiological diversity in the regulation and control of mitochondrial oxidative phosphorylation, we determined the composition and functional features of the respiratory chain in muscle, heart, liver, kidney, and brain. First, we observed important variations in mitochondrial content and infrastructure via electron micrographs of the different tissue sections. Analyses of respiratory chain enzyme content by Western blot also showed large differences between tissues, in good correlation with the expression level of mitochondrial transcription factor A and the activity of citrate synthase. On the isolated mitochondria, we observed a conserved molar ratio between the respiratory chain complexes and a variable stoichiometry for coenzyme Q and cytochrome c , with typical values of 11.5:30135:3:935:6.57.5 for complex II:coenzyme Q:complex III:cytochrome c :complex IV in the different tissues. The functional analysis revealed important differences in maximal velocities of respiratory chain complexes, with higher values in heart. However, calculation of the catalytic constants showed that brain contained the more active enzyme complexes. Hence, our study demonstrates that, in tissues, oxidative phosphorylation capacity is highly variable and diverse, as determined by different combinations of 1 ) the mitochondrial content, 2 ) the amount of respiratory chain complexes, and 3 ) their intrinsic activity. In all tissues, there was a large excess of enzyme capacity and intermediate substrate concentration, compared with what is required for state 3 respiration. To conclude, we submitted our data to a principal component analysis that revealed three groups of tissues: muscle and heart, brain, and liver and kidney.
respiratory chain; tissues; stoichiometry; cytochrome c ; coenzyme Q
Address for reprint requests and other correspondence: R. Rossignol, INSERM U688, Physiopathologie mitochondriale, Université Victor Segalen-Bordeaux 2, 146 rue Léo-Saignat, F-33076 Bordeaux Cedex, France (e-mail: rossig{at}u-bordeaux2.fr )
With the extraordinary progress of mitochondrial science and cell biology, novel biochemical pathways have emerged as strategic points of bioenergetic regulation and control. They include ...mitochondrial fusion, fission and organellar motility along microtubules and microfilaments (mitochondrial dynamics), mitochondrial turnover (biogenesis and degradation), and mitochondrial phospholipids synthesis. Yet, much is still unknown about the mutual interaction between mitochondrial energy state, biogenesis, dynamics and degradation. Meanwhile, clinical research into metabolic abnormalities in tumors as diverse as renal carcinoma, glioblastomas, paragangliomas or skin leiomyomata, has designated new genes, oncogenes and oncometabolites involved in the regulation of cellular and mitochondrial energy production. Furthermore, the examination of rare neurological diseases such as Charcot-Marie Tooth type 2a, Autosomal Dominant Optic Atrophy, Lethal Defect of Mitochondrial and Peroxisomal Fission, or Spastic Paraplegia suggested involvement of MFN2, OPA1/3, DRP1 or Paraplegin, in the auxiliary control of mitochondrial energy production. Lastly, advances in the understanding of mitochondrial apoptosis have suggested a supplementary role for Bcl2 or Bax in the regulation of mitochondrial respiration and dynamics, which has fostered the investigation of alternative mechanisms of energy regulation. In this review, we discuss the regulatory mechanisms of cellular and mitochondrial energy production, and we emphasize the importance of the study of rare neurological diseases in addition to more common disorders such as cancer, for the fundamental understanding of cellular and mitochondrial energy production.
► One-pot mitochondria brain preparation. ► Dietary methylmercury inhibits zebrafish muscle mitochondrial respiration. ► Dietary gold nanoparticles inhibit zebrafish brain mitochondrial respiration. ...► Waterborne uranium decreases zebrafish muscle mitochondria respiratory control ratio.
Mercury, anthropogenic release of uranium (U), and nanoparticles constitute hazardous environmental pollutants able to accumulate along the aquatic food chain with severe risk for animal and human health. The impact of such pollutants on living organisms has been up to now approached by classical toxicology in which huge doses of toxic compounds, environmentally irrelevant, are displayed through routes that never occur in the lifespan of organisms (for instance injecting a bolus of mercury to an animal although the main route is through prey and fish eating). We wanted to address the effect of such pollutants on the muscle and brain mitochondrial bioenergetics under realistic conditions, at unprecedented low doses, using an aquatic model animal, the zebrafish Danio rerio.
We developed an original method to measure brain mitochondrial respiration: a single brain was put in 1.5mL conical tube containing a respiratory buffer. Brains were gently homogenized by 13 strokes with a conical plastic pestle, and the homogenates were immediately used for respiration measurements. Skinned muscle fibers were prepared by saponin permeabilization.
Zebrafish were contaminated with food containing 13μg of methylmercury (MeHg)/g, an environmentally relevant dose. In permeabilized muscle fibers, we observed a strong inhibition of both state 3 mitochondrial respiration and cytochrome c oxidase activity after 49 days of MeHg exposure. We measured a dramatic decrease in the rate of ATP release by skinned muscle fibers. Contrarily to muscles, brain mitochondrial respiration was not modified by MeHg exposure although brain accumulated twice as much MeHg than muscles.
When zebrafish were exposed to 30μg/L of waterborne U, the basal mitochondrial respiratory control ratio was decreased in muscles after 28 days of exposure. This was due to an increase of the inner mitochondrial membrane permeability.
The impact of a daily ration of food containing gold nanoparticles of two sizes (12 and 50nm) was investigated at a very low dose for 60 days (40ng gold/fish/day). Mitochondrial dysfunctions appeared in brain and muscle for both tested sizes.
In conclusion, at low environmental doses, dietary or waterborne heavy metals impinged on zebrafish tissue mitochondrial respiration. Due to its incredible simplicity avoiding tedious and time-consuming mitochondria isolation, our one-pot method allowing brain respiratory analysis should give colleagues the incentive to use zebrafish brain as a model in bioenergetics.
This article is part of a Directed Issue entitled: Bioenergetic dysfunction, adaptation and therapy.
Little is known on the metabolic profile of lung tumors and the reminiscence of embryonic features. Herein, we determined the bioenergetic profiles of human fibroblasts taken from lung epidermoid ...carcinoma (HLF-a) and fetal lung (MRC5). We also analysed human lung tumors and their surrounding healthy tissue from four patients with adenocarcinoma. On these different models, we measured functional parameters (cell growth rates in oxidative and glycolytic media, respiration, ATP synthesis and PDH activity) as well as compositional features (expression level of various energy proteins and upstream transcription factors). The results demonstrate that both the lung fetal and cancer cell lines produced their ATP predominantly by glycolysis, while oxidative phosphorylation was only capable of poor ATP delivery. This was explained by a decreased mitochondrial biogenesis caused by a lowered expression of PGC1α (as shown by RT-PCR and Western blot) and mtTFA. Consequently, the relative expression of glycolytic versus OXPHOS markers was high in these cells. Moreover, the re-activation of mitochondrial biogenesis with resveratrol induced cell death specifically in cancer cells. A consistent reduction of mitochondrial biogenesis and the subsequent alteration of respiratory capacity was also observed in lung tumors, associated with a lower expression level of bcl2. Our data give a better characterization of lung cancer cells’ metabolic alterations which are essential for growth and survival. They designate mitochondrial biogenesis as a possible target for anti-cancer therapy.
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