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Dias C, Fernandes E, Barbosa RM, Laranjinha J, Ledo A. Astrocytic aerobic glycolysis provides lactate to support neuronal oxidative metabolism in the hippocampus. Biofactors 2023; 49:875-886. [PMID: 37070143 DOI: 10.1002/biof.1951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 03/23/2023] [Indexed: 04/19/2023]
Abstract
Under physiological conditions, the energetic demand of the brain is met by glucose oxidation. However, ample evidence suggests that lactate produced by astrocytes through aerobic glycolysis may also be an oxidative fuel, highlighting the metabolic compartmentalization between neural cells. Herein, we investigate the roles of glucose and lactate in oxidative metabolism in hippocampal slices, a model that preserves neuron-glia interactions. To this purpose, we used high-resolution respirometry to measure oxygen consumption (O2 flux) at the whole tissue level and amperometric lactate microbiosensors to evaluate the concentration dynamics of extracellular lactate. We found that lactate is produced from glucose and transported to the extracellular space by neural cells in hippocampal tissue. Under resting conditions, endogenous lactate was used by neurons to support oxidative metabolism, which was boosted by exogenously added lactate even in the presence of excess glucose. Depolarization of hippocampal tissue with high K+ significantly increased the rate of oxidative phosphorylation, which was accompanied by a transient decrease in extracellular lactate concentration. Both effects were reverted by inhibition of the neuronal lactate transporter, monocarboxylate transporters 2 (MCT2), supporting the concept of an inward flux of lactate to neurons to fuel oxidative metabolism. We conclude that astrocytes are the main source of extracellular lactate which is used by neurons to fuel oxidative metabolism, both under resting and stimulated conditions.
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Affiliation(s)
- Cândida Dias
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
- Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal
| | - Eliana Fernandes
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
- Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal
| | - Rui M Barbosa
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
- Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal
| | - João Laranjinha
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
- Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal
| | - Ana Ledo
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
- Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal
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2
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Dominguez-Lopez S, Ahn B, Sataranatarajan K, Ranjit R, Premkumar P, Van Remmen H, Beckstead MJ. Long-term methamphetamine self-administration increases mesolimbic mitochondrial oxygen consumption and decreases striatal glutathione. Neuropharmacology 2023; 227:109436. [PMID: 36693561 PMCID: PMC10080784 DOI: 10.1016/j.neuropharm.2023.109436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 12/26/2022] [Accepted: 01/20/2023] [Indexed: 01/22/2023]
Abstract
Neurotoxic regimens of methamphetamine (METH) are known to increase reactive oxygen species (ROS), affect redox homeostasis, and lead to damage in dopamine neurons. Functional changes induced by long-term METH self-administration on mitochondrial respiratory metabolism and redox homeostasis are less known. To fill this gap, we implanted a jugular catheter into adult male mice and trained them to nose poke for METH infusions. After several weeks of METH exposure, we collected samples of the ventral striatum (vST) and the ventral midbrain (vMB). We used HPLC to determine the levels of the ROS scavenger glutathione in its reduced (GSH) and oxidized forms. Then, we used high-resolution respirometry to determine the oxygen consumption rate (OCR) of mitochondrial complexes. Finally, using in vivo electrophysiology, we assessed changes in dopamine neuron firing activity in the VTA. METH self-administration produced a decrease of the GSH pool in vST, correlating with lifetime METH intake. We observed increased mitochondrial respiration across the two mesolimbic regions. METH self-administration decreases firing rate and burst activity but increases the number of spontaneously active dopamine neurons per track. We conclude that METH self-administration progressively decreased the antioxidant pool in sites of higher dopamine release and produced an increase in mitochondrial metabolism in the mesolimbic areas, probably derived from the increased number of dopamine neurons actively firing. However, dopamine neuron firing activity is decreased by METH self-administration, reflecting a new basal level of dopamine neurotransmission.
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Affiliation(s)
- Sergio Dominguez-Lopez
- Department of Anatomy and Neurobiology, University of Maryland, School of Medicine, Baltimore, MD, 21201, USA; Aging and Metabolism Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA.
| | - Bumsoo Ahn
- Aging and Metabolism Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA
| | | | - Rojina Ranjit
- Aging and Metabolism Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA
| | - Pavithra Premkumar
- Aging and Metabolism Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA
| | - Holly Van Remmen
- Aging and Metabolism Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA; Oklahoma City Veterans Affairs Medical Center, Oklahoma City, OK, 73104, USA
| | - Michael J Beckstead
- Aging and Metabolism Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA; Oklahoma City Veterans Affairs Medical Center, Oklahoma City, OK, 73104, USA
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3
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Dias C, Lourenço CF, Laranjinha J, Ledo A. Modulation of oxidative neurometabolism in ischemia/reperfusion by nitrite. Free Radic Biol Med 2022; 193:779-786. [PMID: 36403737 DOI: 10.1016/j.freeradbiomed.2022.11.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 11/08/2022] [Accepted: 11/12/2022] [Indexed: 11/19/2022]
Abstract
Nitrite has been viewed essentially as an inert metabolic endpoint of nitric oxide (•NO). However, under certain conditions, nitrite can be a source of •NO. In the brain, this alternative source of •NO production independent of nitric oxide synthase activity may be particularly relevant in ischemia/reperfusion (I/R), where low oxygen availability limits enzymatic production of •NO. Notably, in vivo concentration of nitrite can be easily increased with diet, through the ingestion of nitrate-rich foods, opening the window for a therapeutic intervention based on diet. Considering the modulation of mitochondrial respiration by •NO, we have hypothesized that the protective action of nitrite in I/R may also result from modulation of mitochondrial function. We used high-resolution respirometry to evaluate the effects of nitrite in two in vitro models of I/R. In both cases, an increase in oxygen flux was observed following reoxygenation, a phenomenon that has been coined "oxidative burst". The amplitude of this "oxidative burst" was decreased by nitrite in a concentration-dependent manner. Additionally, a pilot in vivo study in which animals received a nitrate-rich diet as a strategy to increase circulating and tissue levels of nitrite also revealed that the "oxidative burst" was decreased in the nitrate-treated animals. These results may provide mechanistic support to the observation of a protective effect of nitrite in situations of brain ischemia.
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Affiliation(s)
- C Dias
- Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal; Center for Neuroscience and Cell Biology, Coimbra, Portugal
| | - C F Lourenço
- Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal; Center for Neuroscience and Cell Biology, Coimbra, Portugal
| | - J Laranjinha
- Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal; Center for Neuroscience and Cell Biology, Coimbra, Portugal
| | - A Ledo
- Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal; Center for Neuroscience and Cell Biology, Coimbra, Portugal.
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Dias C, Fernandes E, Barbosa RM, Ledo A. A Platinized Carbon Fiber Microelectrode-Based Oxidase Biosensor for Amperometric Monitoring of Lactate in Brain Slices. Sensors (Basel) 2022; 22:7011. [PMID: 36146360 PMCID: PMC9501957 DOI: 10.3390/s22187011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 09/12/2022] [Accepted: 09/14/2022] [Indexed: 06/16/2023]
Abstract
BACKGROUND Direct and real-time monitoring of lactate in the extracellular space can help elucidate the metabolic and modulatory role of lactate in the brain. Compared to in vivo studies, brain slices allow the investigation of the neural contribution separately from the effects of cerebrovascular response and permit easy control of recording conditions. METHODS We have used a platinized carbon fiber microelectrode platform to design an oxidase-based microbiosensor for monitoring lactate in brain slices with high spatial and temporal resolution operating at 32 °C. Lactate oxidase (Aerococcus viridans) was immobilized by crosslinking with glutaraldehyde and a layer of polyurethane was added to extend the linear range. Selectivity was improved by electropolymerization of m-phenylenediamine and concurrent use of a null sensor. RESULTS The lactate microbiosensor exhibited high sensitivity, selectivity, and optimal analytical performance at a pH and temperature compatible with recording in hippocampal slices. Evaluation of operational stability under conditions of repeated use supports the suitability of this design for up to three repeated assays. CONCLUSIONS The microbiosensor displayed good analytical performance to monitor rapid changes in lactate concentration in the hippocampal tissue in response to potassium-evoked depolarization.
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Affiliation(s)
- Cândida Dias
- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
- Faculty of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal
| | - Eliana Fernandes
- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
- Faculty of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal
| | - Rui M. Barbosa
- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
- Faculty of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal
| | - Ana Ledo
- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
- Faculty of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal
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Mancini G, Dias C, Lourenço CF, Laranjinha J, de Bem A, Ledo A. A High Fat/Cholesterol Diet Recapitulates Some Alzheimer's Disease-Like Features in Mice: Focus on Hippocampal Mitochondrial Dysfunction. J Alzheimers Dis 2021; 82:1619-1633. [PMID: 34219714 DOI: 10.3233/jad-210122] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Ample evidence from clinical and pre-clinical studies suggests mid-life hypercholesterolemia as a risk factor for developing Alzheimer's disease (AD) at a later age. Hypercholesterolemia induced by dietary habits can lead to vascular perturbations that increase the risk of developing sporadic AD. OBJECTIVE To investigate the effects of a high fat/cholesterol diet (HFCD) as a risk factor for AD by using a rodent model of AD and its correspondent control (healthy animals). METHODS We compared the effect of a HFCD in normal mice (non-transgenic mice, NTg) and the triple transgenic mouse model of AD (3xTgAD). We evaluated cognitive performance in relation to changes in oxidative metabolism and neuron-derived nitric oxide (•NO) concentration dynamics in hippocampal slices as well as histochemical staining of markers of the neurovascular unit. RESULTS In NTg, the HFCD produced only moderate hypercholesterolemia but significant decline in spatial memory was observed. A tendency for decrease in •NO production was accompanied by compromised mitochondrial function with decrease in spare respiratory capacity. In 3xTgAD mice, a robust increase in plasma cholesterol levels with the HFCD did not worsen cognitive performance but did induce compromise of mitochondrial function and significantly decreased •NO production. We found increased staining of biomarkers for astrocyte endfeet and endothelial cells in 3xTgAD hippocampi, which was further increased by the HFCD. CONCLUSION A short term (8 weeks) intervention with HFCD can produce an AD-like phenotype even in the absence of overt systemic hypercholesterolemia and highlights mitochondrial dysfunction as a link between hypercholesterolemia and sporadic AD.
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Affiliation(s)
- Gianni Mancini
- Departamento de Bioquímica, Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | - Candida Dias
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal
| | - Catia F Lourenço
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal
| | - Joao Laranjinha
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal
| | - Andreza de Bem
- Departamento de Bioquímica, Universidade Federal de Santa Catarina, Florianópolis, Brazil.,Department of Physiological Sciences, Institute of Biological Sciences, University of Brasília, Brasília, Brazil.,Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Ana Ledo
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal
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Abstract
Metabolic insufficiency and neuronal dysfunction occur in normal aging but is exaggerated in dementia and Alzheimer's disease (AD). Metabolic insufficiency includes factors important for both substrate supply and utilization in the brain. Metabolic insufficiency occurs through a number of serial mechanisms, particularly changes in cerebrovascular supply through blood vessel abnormalities (ie, small and large vessel vasculopathy, stroke), alterations in neurovascular coupling providing dynamic blood flow supply in relation to neuronal demand, abnormalities in blood brain barrier including decreased glucose and amino acid transport, altered glymphatic flow in terms of substrate supply across the extracellular space to cells and drainage into CSF of metabolites, impaired transport into cells, and abnormal intracellular metabolism with more reliance on glycolysis and less on mitochondrial function. Recent studies have confirmed abnormal neurovascular coupling in a mouse model of AD in response to metabolic challenges, but the supply chain from the vascular system into neurons is disrupted much earlier in dementia than in equivalently aged individuals, contributing to the progressive neuronal degeneration and cognitive dysfunction associated with dementia. We discuss several metabolic treatment approaches, but these depend on characterizing patients as to who would benefit the most. Surrogate biomarkers of metabolism are being developed to include dynamic estimates of neuronal demand, sufficiency of neurovascular coupling, and glymphatic flow to supplement traditional static measurements. These surrogate biomarkers could be used to gauge efficacy of metabolic treatments in slowing down or modifying dementia time course.
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Affiliation(s)
- Dennis A Turner
- Neurosurgery, Neurobiology, and Biomedical Engineering, Duke University Medical Center, Durham, NC 27710, USA.
- Research and Surgery Services, Durham Veterans Affairs Medical Center, Durham, NC 27705, USA.
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Liput M, Magliaro C, Kuczynska Z, Zayat V, Ahluwalia A, Buzanska L. Tools and approaches for analyzing the role of mitochondria in health, development and disease using human cerebral organoids. Dev Neurobiol 2021; 81:591-607. [PMID: 33725382 DOI: 10.1002/dneu.22818] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Revised: 03/08/2021] [Accepted: 03/09/2021] [Indexed: 12/16/2022]
Abstract
Mitochondria are cellular organelles involved in generating energy to power various processes in the cell. Although the pivotal role of mitochondria in neurogenesis was demonstrated (first in animal models), very little is known about their role in human embryonic neurodevelopment and its pathology. In this respect human-induced pluripotent stem cells (hiPSC)-derived cerebral organoids provide a tractable, alternative model system of the early neural development and disease that is responsive to pharmacological and genetic manipulations, not possible to apply in humans. Although the involvement of mitochondria in the pathogenesis and progression of neurodegenerative diseases and brain dysfunction has been demonstrated, the precise role they play in cell life and death remains unknown, compromising the development of new mitochondria-targeted approaches to treat human diseases. The cerebral organoid model of neurogenesis and disease in vitro provides an unprecedented opportunity to answer some of the most fundamental questions about mitochondrial function in early human neurodevelopment and neural pathology. Largely an unexplored territory due to the lack of tools and approaches, this review focuses on recent technological advancements in fluorescent and molecular tools, imaging systems, and computational approaches for quantitative and qualitative analyses of mitochondrial structure and function in three-dimensional cellular assemblies-cerebral organoids. Future developments in this direction will further facilitate our understanding of the important role or mitochondrial dynamics and energy requirements during early embryonic development. This in turn will provide a further understanding of how dysfunctional mitochondria contribute to disease processes.
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Affiliation(s)
- Michał Liput
- Department of Stem Cell Bioengineering, Mossakowski Medical Research Institute Polish Academy of Sciences, Warsaw, Poland
| | - Chiara Magliaro
- Research Centre "E. Piaggio", and Department of Information Engineering, University of Pisa, Pisa, Italy
| | - Zuzanna Kuczynska
- Department of Stem Cell Bioengineering, Mossakowski Medical Research Institute Polish Academy of Sciences, Warsaw, Poland
| | - Valery Zayat
- Department of Stem Cell Bioengineering, Mossakowski Medical Research Institute Polish Academy of Sciences, Warsaw, Poland
| | - Arti Ahluwalia
- Research Centre "E. Piaggio", and Department of Information Engineering, University of Pisa, Pisa, Italy
| | - Leonora Buzanska
- Department of Stem Cell Bioengineering, Mossakowski Medical Research Institute Polish Academy of Sciences, Warsaw, Poland
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Ledo A, Lourenço CF, Cadenas E, Barbosa RM, Laranjinha J. The bioactivity of neuronal-derived nitric oxide in aging and neurodegeneration: Switching signaling to degeneration. Free Radic Biol Med 2021; 162:500-513. [PMID: 33186742 DOI: 10.1016/j.freeradbiomed.2020.11.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 11/02/2020] [Accepted: 11/05/2020] [Indexed: 12/22/2022]
Abstract
The small and diffusible free radical nitric oxide (•NO) has fascinated biological and medical scientists since it was promoted from atmospheric air pollutant to biological ubiquitous signaling molecule. Its unique physical chemical properties expand beyond its radical nature to include fast diffusion in aqueous and lipid environments and selective reactivity in a biological setting determined by bioavailability and reaction rate constants with biomolecules. In the brain, •NO is recognized as a key player in numerous physiological processes ranging from neurotransmission/neuromodulation to neurovascular coupling and immune response. Furthermore, changes in its bioactivity are central to the molecular pathways associated with brain aging and neurodegeneration. The understanding of •NO bioactivity in the brain, however, requires the knowledge of its concentration dynamics with high spatial and temporal resolution upon stimulation of its synthesis. Here we revise our current understanding of the role of neuronal-derived •NO in brain physiology, aging and degeneration, focused on changes in the extracellular concentration dynamics of this free radical and the regulation of bioenergetic metabolism and neurovascular coupling.
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Affiliation(s)
- A Ledo
- Center for Neuroscience and Cell Biology, University of Coimbra, Rua Larga, 3004-504, Coimbra, Portugal; University of Coimbra, Faculty of Pharmacy, Azinhaga de Santa Comba, 3000-548, Coimbra, Portugal.
| | - C F Lourenço
- Center for Neuroscience and Cell Biology, University of Coimbra, Rua Larga, 3004-504, Coimbra, Portugal; University of Coimbra, Faculty of Pharmacy, Azinhaga de Santa Comba, 3000-548, Coimbra, Portugal
| | - E Cadenas
- Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, 90089, CA, USA
| | - R M Barbosa
- Center for Neuroscience and Cell Biology, University of Coimbra, Rua Larga, 3004-504, Coimbra, Portugal; University of Coimbra, Faculty of Pharmacy, Azinhaga de Santa Comba, 3000-548, Coimbra, Portugal
| | - J Laranjinha
- Center for Neuroscience and Cell Biology, University of Coimbra, Rua Larga, 3004-504, Coimbra, Portugal; University of Coimbra, Faculty of Pharmacy, Azinhaga de Santa Comba, 3000-548, Coimbra, Portugal
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9
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Laranjinha J, Nunes C, Ledo A, Lourenço C, Rocha B, Barbosa RM. The Peculiar Facets of Nitric Oxide as a Cellular Messenger: From Disease-Associated Signaling to the Regulation of Brain Bioenergetics and Neurovascular Coupling. Neurochem Res 2020; 46:64-76. [PMID: 32193753 DOI: 10.1007/s11064-020-03015-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 03/07/2020] [Accepted: 03/12/2020] [Indexed: 12/13/2022]
Abstract
In this review, we address the regulatory and toxic role of ·NO along several pathways, from the gut to the brain. Initially, we address the role on ·NO in the regulation of mitochondrial respiration with emphasis on the possible contribution to Parkinson's disease via mechanisms that involve its interaction with a major dopamine metabolite, DOPAC. In parallel with initial discoveries of the inhibition of mitochondrial respiration by ·NO, it became clear the potential for toxic ·NO-mediated mechanisms involving the production of more reactive species and the post-translational modification of mitochondrial proteins. Accordingly, we have proposed a novel mechanism potentially leading to dopaminergic cell death, providing evidence that NO synergistically interact with DOPAC in promoting cell death via mechanisms that involve GSH depletion. The modulatory role of NO will be then briefly discussed as a master regulator on brain energy metabolism. The energy metabolism in the brain is central to the understanding of brain function and disease. The core role of ·NO in the regulation of brain metabolism and vascular responses is further substantiated by discussing its role as a mediator of neurovascular coupling, the increase in local microvessels blood flow in response to spatially restricted increase of neuronal activity. The many facets of NO as intracellular and intercellular messenger, conveying information associated with its spatial and temporal concentration dynamics, involve not only the discussion of its reactions and potential targets on a defined biological environment but also the regulation of its synthesis by the family of nitric oxide synthases. More recently, a novel pathway, out of control of NOS, has been the subject of a great deal of controversy, the nitrate:nitrite:NO pathway, adding new perspectives to ·NO biology. Thus, finally, this novel pathway will be addressed in connection with nitrate consumption in the diet and the beneficial effects of protein nitration by reactive nitrogen species.
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Affiliation(s)
- João Laranjinha
- Faculty of Pharmacy, University of Coimbra, Azinhaga Sta. Comba, 3000-548, Coimbra, Portugal. .,Center for Neuroscience and Cell Biology, University of Coimbra, Pólo 1, 3000-504, Coimbra, Portugal.
| | - Carla Nunes
- Faculty of Pharmacy, University of Coimbra, Azinhaga Sta. Comba, 3000-548, Coimbra, Portugal.,Center for Neuroscience and Cell Biology, University of Coimbra, Pólo 1, 3000-504, Coimbra, Portugal
| | - Ana Ledo
- Center for Neuroscience and Cell Biology, University of Coimbra, Pólo 1, 3000-504, Coimbra, Portugal
| | - Cátia Lourenço
- Center for Neuroscience and Cell Biology, University of Coimbra, Pólo 1, 3000-504, Coimbra, Portugal
| | - Bárbara Rocha
- Faculty of Pharmacy, University of Coimbra, Azinhaga Sta. Comba, 3000-548, Coimbra, Portugal.,Center for Neuroscience and Cell Biology, University of Coimbra, Pólo 1, 3000-504, Coimbra, Portugal
| | - Rui M Barbosa
- Faculty of Pharmacy, University of Coimbra, Azinhaga Sta. Comba, 3000-548, Coimbra, Portugal.,Center for Neuroscience and Cell Biology, University of Coimbra, Pólo 1, 3000-504, Coimbra, Portugal
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Ricke KM, Paß T, Kimoloi S, Fährmann K, Jüngst C, Schauss A, Baris OR, Aradjanski M, Trifunovic A, Eriksson Faelker TM, Bergami M, Wiesner RJ. Mitochondrial Dysfunction Combined with High Calcium Load Leads to Impaired Antioxidant Defense Underlying the Selective Loss of Nigral Dopaminergic Neurons. J Neurosci 2020; 40:1975-86. [PMID: 32005765 DOI: 10.1523/JNEUROSCI.1345-19.2019] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 10/15/2019] [Accepted: 11/24/2019] [Indexed: 12/13/2022] Open
Abstract
Mitochondrial dysfunction is critically involved in Parkinson's disease, characterized by loss of dopaminergic neurons (DaNs) in the substantia nigra (SNc), whereas DaNs in the neighboring ventral tegmental area (VTA) are much less affected. In contrast to VTA, SNc DaNs engage calcium channels to generate action potentials, which lead to oxidant stress by yet unknown pathways. To determine the molecular mechanisms linking calcium load with selective cell death in the presence of mitochondrial deficiency, we analyzed the mitochondrial redox state and the mitochondrial membrane potential in mice of both sexes with genetically induced, severe mitochondrial dysfunction in DaNs (MitoPark mice), at the same time expressing a redox-sensitive GFP targeted to the mitochondrial matrix. Despite mitochondrial insufficiency in all DaNs, exclusively SNc neurons showed an oxidized redox-system, i.e., a low reduced/oxidized glutathione (GSH-GSSG) ratio. This was mimicked by cyanide, but not by rotenone or antimycin A, making the involvement of reactive oxygen species rather unlikely. Surprisingly, a high mitochondrial inner membrane potential was maintained in MitoPark SNc DaNs. Antagonizing calcium influx into the cell and into mitochondria, respectively, rescued the disturbed redox ratio and induced further hyperpolarization of the inner mitochondrial membrane. Our data therefore show that the constant calcium load in SNc DaNs is counterbalanced by a high mitochondrial inner membrane potential, even under conditions of severe mitochondrial dysfunction, but triggers a detrimental imbalance in the mitochondrial redox system, which will lead to neuron death. Our findings thus reveal a new mechanism, redox imbalance, which underlies the differential vulnerability of DaNs to mitochondrial defects.SIGNIFICANCE STATEMENT Parkinson's disease is characterized by the preferential degeneration of dopaminergic neurons (DaNs) of the substantia nigra pars compacta (SNc), resulting in the characteristic hypokinesia in patients. Ubiquitous pathological triggers cannot be responsible for the selective neuron loss. Here we show that mitochondrial impairment together with elevated calcium burden destabilize the mitochondrial antioxidant defense only in SNc DaNs, and thus promote the increased vulnerability of this neuron population.
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