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Liu X, Yan Q, Liu X, Wei W, Zou L, Zhao F, Zeng S, Yi L, Ding H, Zhao M, Chen J, Fan S. PKM2 induces mitophagy through the AMPK-mTOR pathway promoting CSFV proliferation. J Virol 2024; 98:e0175123. [PMID: 38319105 PMCID: PMC10949426 DOI: 10.1128/jvi.01751-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 12/14/2023] [Indexed: 02/07/2024] Open
Abstract
Viruses exploit the host cell's energy metabolism system to support their replication. Mitochondria, known as the powerhouse of the cell, play a critical role in regulating cell survival and virus replication. Our prior research indicated that the classical swine fever virus (CSFV) alters mitochondrial dynamics and triggers glycolytic metabolic reprogramming. However, the role and mechanism of PKM2, a key regulatory enzyme of glycolytic metabolism, in CSFV replication remain unclear. In this study, we discovered that CSFV enhances PKM2 expression and utilizes PKM2 to inhibit pyruvate production. Using an affinity purification coupled mass spectrometry system, we successfully identified PKM as a novel interaction partner of the CSFV non-structural protein NS4A. Furthermore, we validated the interaction between PKM2 and both CSFV NS4A and NS5A through co-immunoprecipitation and confocal analysis. PKM2 was found to promote the expression of both NS4A and NS5A. Moreover, we observed that PKM2 induces mitophagy by activating the AMPK-mTOR signaling pathway, thereby facilitating CSFV proliferation. In summary, our data reveal a novel mechanism whereby PKM2, a metabolic enzyme, promotes CSFV proliferation by inducing mitophagy. These findings offer a new avenue for developing antiviral strategies. IMPORTANCE Viruses rely on the host cell's material-energy metabolic system for replication, inducing host metabolic disorders and subsequent immunosuppression-a major contributor to persistent viral infections. Classical swine fever virus (CSFV) is no exception. Classical swine fever is a severe acute infectious disease caused by CSFV, resulting in significant economic losses to the global pig industry. While the role of the metabolic enzyme PKM2 (pyruvate dehydrogenase) in the glycolytic pathway of tumor cells has been extensively studied, its involvement in viral infection remains relatively unknown. Our data unveil a new mechanism by which the metabolic enzyme PKM2 mediates CSFV infection, offering novel avenues for the development of antiviral strategies.
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Affiliation(s)
- Xiaodi Liu
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guang Dong, China
| | - Quanhui Yan
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guang Dong, China
| | - Xueyi Liu
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guang Dong, China
| | - Wenkang Wei
- State Key Laboratory of Swine and Poultry Breeding Industry, Agro-Biological Gene Research Center, Guangdong Academy of Agricultural Sciences, Guangzhou, China
| | - Linke Zou
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guang Dong, China
| | - Feifan Zhao
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guang Dong, China
| | - Sen Zeng
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guang Dong, China
| | - Lin Yi
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guang Dong, China
| | - Hongxing Ding
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guang Dong, China
| | - Mingqiu Zhao
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guang Dong, China
| | - Jinding Chen
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guang Dong, China
| | - Shuangqi Fan
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guang Dong, China
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2
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Gerevich Z, Kovács R, Liotta A, Hasam-Henderson LA, Weh L, Wallach I, Berndt N. Metabolic implications of axonal demyelination and its consequences for synchronized network activity: An in silico and in vitro study. J Cereb Blood Flow Metab 2023; 43:1571-1587. [PMID: 37125487 PMCID: PMC10414014 DOI: 10.1177/0271678x231170746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 02/13/2023] [Accepted: 03/22/2023] [Indexed: 05/02/2023]
Abstract
Myelination enhances the conduction velocity of action potentials (AP) and increases energy efficiency. Thick myelin sheaths are typically found on large-distance axonal connections or in fast-spiking interneurons, which are critical for synchronizing neuronal networks during gamma-band oscillations. Loss of myelin sheath is associated with multiple alterations in axonal architecture leading to impaired AP propagation. While numerous studies are devoted to the effects of demyelination on conduction velocity, the metabolic effects and the consequences for network synchronization have not been investigated. Here we present a unifying computational model for electrophysiology and metabolism of the myelinated axon. The computational model suggested that demyelination not only decreases the AP speed but AP propagation in demyelinated axons requires compensatory processes like mitochondrial mass increase and a switch from saltatory to continuous propagation to rescue axon functionality at the cost of reduced AP propagation speed and increased energy expenditure. Indeed, these predictions were proven to be true in a culture model of demyelination where the pharmacologically-induced loss of myelin was associated with increased oxygen consumption rates, and a significant broadening of bandwidth as well as a decrease in the power of gamma oscillations.
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Affiliation(s)
- Zoltan Gerevich
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Richard Kovács
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Agustin Liotta
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
- Department of Anesthesiology and Intensive Care, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
- Institute of Computer-assisted Cardiovascular Medicine, Deutsches Herzzentrum der Charité (DHZC), Berlin, Germany
| | - Luisa A Hasam-Henderson
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Ludwig Weh
- Institute of Biochemistry, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Iwona Wallach
- Institute of Computer-assisted Cardiovascular Medicine, Deutsches Herzzentrum der Charité (DHZC), Berlin, Germany
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Nikolaus Berndt
- Institute of Computer-assisted Cardiovascular Medicine, Deutsches Herzzentrum der Charité (DHZC), Berlin, Germany
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
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3
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Bai Y, Pei XJ, Ban N, Chen N, Liu SN, Li S, Liu TX. Nutrition-dependent juvenile hormone sensitivity promotes flight-muscle degeneration during the aphid dispersal-reproduction transition. Development 2022; 149:275958. [DOI: 10.1242/dev.200891] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 06/28/2022] [Indexed: 11/20/2022]
Abstract
ABSTRACT
In insects, the loss of flight typically involves a dispersal-reproduction transition, but the underlying molecular mechanisms remain poorly understood. In the parthenogenetic pea aphid Acyrthosiphon pisum, winged females undergo flight-muscle degeneration after flight and feeding on new host plants. Similarly, topical application of a juvenile hormone (JH) mimic to starved aphids also induces flight-muscle degeneration. We found that feeding preferentially upregulated the expression of the JH receptor gene Met and a JH-inducible gene, Kr-h1, in the flight muscles, and, thus, enhanced tissue-specific JH sensitivity and signaling. RNAi-mediated knockdown of Kr-h1 prevented flight-muscle degeneration. Likewise, blocking nutritional signals by pharmacological inhibition of the target of rapamycin complex 1 (TORC1) impaired JH sensitivity of the flight muscles in feeding aphids and subsequently delayed muscle degeneration. RNA-sequencing analysis revealed that enhanced JH signaling inhibited the transcription of genes involved in the tricarboxylic acid cycle, likely resulting in reduction of the energy supply, mitochondrial dysfunction and muscle-fiber breakdown. This study shows that nutrient-dependent hormone sensitivity regulates developmental plasticity in a tissue-specific manner, emphasizing a relatively underappreciated mechanism of hormone sensitivity in modulating hormone signaling.
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Affiliation(s)
- Yu Bai
- Guangdong Provincial Key Laboratory of Insect Development Biology and Applied Technology, Institute of Insect Science and Technology, School of Life Sciences, South China Normal University 1 , Guangzhou 510631 , China
- State Key Laboratory of Crop Stress Biology for Arid Areas and Key Laboratory of Integrated Pest Management on the Loess Plateau of Ministry of Agriculture, Northwest A&F University 2 , Yangling 712100 , China
| | - Xiao-Jin Pei
- Guangdong Provincial Key Laboratory of Insect Development Biology and Applied Technology, Institute of Insect Science and Technology, School of Life Sciences, South China Normal University 1 , Guangzhou 510631 , China
| | - Ning Ban
- Key Lab of Integrated Crop Pest Management of Shandong Province, College of Plant Health and Medicine, Qingdao Agricultural University 3 , Qingdao 266109 , China
| | - Nan Chen
- Guangdong Provincial Key Laboratory of Insect Development Biology and Applied Technology, Institute of Insect Science and Technology, School of Life Sciences, South China Normal University 1 , Guangzhou 510631 , China
| | - Su-Ning Liu
- Guangdong Provincial Key Laboratory of Insect Development Biology and Applied Technology, Institute of Insect Science and Technology, School of Life Sciences, South China Normal University 1 , Guangzhou 510631 , China
| | - Sheng Li
- Guangdong Provincial Key Laboratory of Insect Development Biology and Applied Technology, Institute of Insect Science and Technology, School of Life Sciences, South China Normal University 1 , Guangzhou 510631 , China
| | - Tong-Xian Liu
- Institute of Entomology, Guizhou University 4 , Guiyang 550025 , China
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4
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Lee I, Yang NC. Using Taguchi Method to Determine the Optimum Conditions for Synthesizing Parapyruvate. Molecules 2022; 27:molecules27061870. [PMID: 35335234 PMCID: PMC8954423 DOI: 10.3390/molecules27061870] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 03/09/2022] [Accepted: 03/10/2022] [Indexed: 02/01/2023] Open
Abstract
The synthesis of parapyruvate is important for the analysis of the content in the pyruvate supplements and the study of aging-related neurodegenerative diseases. However, the pure parapyruvate crystal is not, as yet, commercially available. In this study, we applied the Taguchi's L9 orthogonal array to investigate the optimal conditions for the preparation of the pure parapyruvate by the alkaline treatment of the pyruvic acid and then followed it with the solvent crystallization steps. We were also interested in revealing the major factors that affect the yield for the synthesized pure parapyruvate crystals. In addition, the parapyruvate-inhibited enzyme kinetic of α-ketoglutarate dehydrogenase complex (KGDHC) was also investigated. We found that the pure parapyruvate could be obtained in combination with an alkaline treatment and two solvent crystallization steps. The main factors affecting the yield of the pure parapyruvate were the concentration of the pyruvic acid (the reactant), the pH of the alkali treatment, the type of solvent used for the crystallization and the volume ratio of solvent used for crystallization. Finally, the optimal conditions could prepare parapyruvate crystals with a high purity of 99.8% and a high yield of 72.8%. In addition, the results demonstrate that parapyruvate is a reversibly competitive inhibitor for KGDHC.
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Affiliation(s)
- Inn Lee
- Department of Nutrition, Chung Shan Medical University, Taichung 402, Taiwan;
| | - Nae-Cherng Yang
- Department of Nutrition, Chung Shan Medical University, Taichung 402, Taiwan;
- Department of Nutrition, Chung Shan Medical University Hospital, Taichung 402, Taiwan
- Correspondence: ; Tel.: +886-4-2473-0022; Fax: +886-4-2324-8175
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Li WX, Li GH, Tong X, Yang PP, Huang JF, Xu L, Dai SX. Systematic metabolic analysis of potential target, therapeutic drug, diagnostic method and animal model applicability in three neurodegenerative diseases. Aging (Albany NY) 2020; 12:9882-9914. [PMID: 32461378 PMCID: PMC7288927 DOI: 10.18632/aging.103253] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 04/20/2020] [Indexed: 01/10/2023]
Abstract
Considerable evidence suggests that metabolic abnormalities are associated with neurodegenerative diseases. This study aimed to conduct a systematic metabolic analysis of Alzheimer’s disease (AD), Parkinson’s disease (PD) and Huntington’s disease (HD). Human and mouse model microarray datasets were downloaded from the Gene Expression Omnibus database. The metabolic genes and pathways were collected from the Recon 3D human metabolic model. Drug and target information was obtained from the DrugBank database. This study identified ATP1A1, ATP6V1G2, GOT1, HPRT1, MAP2K1, PCMT1 and PLK2 as key metabolic genes that were downregulated in AD, PD and HD. We screened 57 drugs that target these genes, such as digoxin, ouabain and diazoxide. This study constructed multigene diagnostic models for AD, PD and HD by using metabolic gene expression profiles in blood, all models showed high accuracy (AUC > 0.8) both in the experimental and validation sets. Furthermore, analysis of animal models showed that there was almost no consistency among the metabolic changes between mouse models and human diseases. This study systematically revealed the metabolic damage among AD, PD, and HD and uncovered the differences between animal models and human diseases. This information may be helpful for understanding the metabolic mechanisms and drug development for neurodegenerative diseases.
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Affiliation(s)
- Wen-Xing Li
- Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, Yunnan, China.,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming 650204, Yunnan, China
| | - Gong-Hua Li
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, Yunnan, China
| | - Xin Tong
- Yunnan Key Laboratory of Primate Biomedical Research, Institute of Primate Translational Medicine, Kunming University of Science and Technology, Kunming 650500, Yunnan, China
| | - Peng-Peng Yang
- Yunnan Key Laboratory of Primate Biomedical Research, Institute of Primate Translational Medicine, Kunming University of Science and Technology, Kunming 650500, Yunnan, China
| | - Jing-Fei Huang
- Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, Yunnan, China.,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming 650204, Yunnan, China
| | - Lin Xu
- Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, Yunnan, China.,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming 650204, Yunnan, China.,Centre for Excellence in Brain Science and Intelligent Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Shao-Xing Dai
- Yunnan Key Laboratory of Primate Biomedical Research, Institute of Primate Translational Medicine, Kunming University of Science and Technology, Kunming 650500, Yunnan, China
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6
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Liu H, Yu C, Xu T, Zhang X, Dong M. Synergistic protective effect of paeoniflorin and β-ecdysterone against rotenone-induced neurotoxicity in PC12 cells. Apoptosis 2018; 21:1354-1365. [PMID: 27688248 DOI: 10.1007/s10495-016-1293-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
There are several factors, like oxidative stress and neurons loss, involving neurodegenerative diseases such as Parkinson's disease (PD). The combination of antioxidant and anti-apoptotic agent is becoming a promising approach to fight against PD. This study evaluates the hypothesis that paeoniflorin (PF) and β-ecdysterone (β-Ecd) synergize to protect PC12 cells against toxicity induced by PD-related neurotoxin rotenone. The combination of PF and β-Ecd, hereafter referred to as the PF/β-Ecd, at suboptimal concentrations increased the viability of rotenone-exposed PC12 cells in a synergistic manner. PF and β-Ecd cooperate to attenuate the rotenone-induced apoptosis by decrease in Bax expression, caspase-9 activity, and caspase-3 activity. PF or PF/β-Ecd, but not β-Ecd, inhibited rotenone-triggered protein kinase C-δkinase C-δ (PKCδ) upregulation and nuclear factor κB (NF-κB) activation. β-Ecd or PF/β-Ecd, but not PF, enhanced serine/threonine protein kinase (Akt) activation, promoted nuclear factor E2-related factor 2 (Nrf2) nuclear accumulation, suppressed reactive oxygen species (ROS) production. Neuroprotection of PF/β-Ecd could be completely blocked by PKCδ inhibitor rottlerin plus Akt specific inhibitor LY294002. Dual blockade of the PKCδ/NF-κB pathway by PF and activation of Akt/Nrf2 pathway by β-Ecd results in a synergistic neuroprotective effect against rotenone-induced neurotoxicity in vitro. These findings provide the rationale for determining the in vivo activity of combined therapy with PF and β-Ecd against PD.
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Affiliation(s)
- Han Liu
- The Institute of Medicine, Qiqihar Medical University, 333 BuKui Street, JianHua District, Qiqihar, 161006, China
| | - Chunlei Yu
- The Institute of Medicine, Qiqihar Medical University, 333 BuKui Street, JianHua District, Qiqihar, 161006, China
| | - Tianjiao Xu
- The Institute of Medicine, Qiqihar Medical University, 333 BuKui Street, JianHua District, Qiqihar, 161006, China
| | - Xiaojie Zhang
- The Institute of Medicine, Qiqihar Medical University, 333 BuKui Street, JianHua District, Qiqihar, 161006, China
| | - Miaoxian Dong
- The Institute of Medicine, Qiqihar Medical University, 333 BuKui Street, JianHua District, Qiqihar, 161006, China.
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7
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Prajapati P, Sripada L, Singh K, Roy M, Bhatelia K, Dalwadi P, Singh R. Systemic Analysis of miRNAs in PD Stress Condition: miR-5701 Modulates Mitochondrial-Lysosomal Cross Talk to Regulate Neuronal Death. Mol Neurobiol 2017; 55:4689-4701. [PMID: 28710704 DOI: 10.1007/s12035-017-0664-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 06/19/2017] [Indexed: 10/19/2022]
Abstract
Parkinson's disease (PD) is complex neurological disorder and is prevalent in the elderly population. This is primarily due to loss of dopaminergic neurons in the substantia nigra pars compacta (SNc) region of the brain. The modulators of the selective loss of dopaminergic neurons in PD are still not well understood. The small non-coding RNAs specifically miRNAs fine-tune the protein levels by post-transcriptional gene regulation. The role of miRNAs in PD pathogenesis is still not well characterized. In the current study, we identified the miRNA expression pattern in 6-OHDA-induced PD stress condition in SH-SY5Y, dopaminergic neuronal cell line. The targets of top 5 miRNAs both up- and down regulated were analyzed by using StarBase. The putative pathways of identified miRNAs included neurotrophin signaling, neuronal processes, mTOR, and cell death. The level of miR-5701 was significantly downregulated in the presence of 6-OHDA. The putative targets of miR-5701 miRNA include genes involved in lysosomal biogenesis and mitochondrial quality control. The transfection of miR-5701 mimic decreased the transcript level of VCP, LAPTM4A, and ATP6V0D1. The expression of miR-5701 mimic induces mitochondrial dysfunction, defect in autophagy flux, and further sensitizes SH-SY5Y cells to 6-OHDA-induced cell death. To our knowledge, the evidence in the current study demonstrated the dysregulation of specific pattern of miRNAs in PD stress conditions. We further characterized the role of miR-5701, a novel miRNA, as a potential regulator of the mitochondrial and lysosomal function determining the fate of neurons which has important implication in the pathogenesis of PD.
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Affiliation(s)
- Paresh Prajapati
- Department of Biochemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, 390002, India
| | - Lakshmi Sripada
- Department of Biochemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, 390002, India
| | - Kritarth Singh
- Department of Biochemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, 390002, India
| | - Milton Roy
- Department of Biochemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, 390002, India
| | - Khyati Bhatelia
- Department of Biochemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, 390002, India
| | - Pooja Dalwadi
- Department of Biochemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, 390002, India
| | - Rajesh Singh
- Department of Biochemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, 390002, India.
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8
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Delgado-Camprubi M, Esteras N, Soutar MP, Plun-Favreau H, Abramov AY. Deficiency of Parkinson's disease-related gene Fbxo7 is associated with impaired mitochondrial metabolism by PARP activation. Cell Death Differ 2016; 24:120-131. [PMID: 27689878 PMCID: PMC5260490 DOI: 10.1038/cdd.2016.104] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 07/28/2016] [Accepted: 08/31/2016] [Indexed: 12/20/2022] Open
Abstract
The Parkinson's disease (PD)-related protein F-box only protein 7 (Fbxo7) is the substrate-recognition component of the Skp1-Cullin-F-box protein E3 ubiquitin ligase complex. We have recently shown that PD-associated mutations in Fbxo7 disrupt mitochondrial autophagy (mitophagy), suggesting a role for Fbxo7 in modulating mitochondrial homeostasis. Here we report that Fbxo7 deficiency is associated with reduced cellular NAD+ levels, which results in increased mitochondrial NADH redox index and impaired activity of complex I in the electron transport chain. Under these conditions of compromised respiration, mitochondrial membrane potential and ATP contents are reduced, and cytosolic reactive oxygen species (ROS) production is increased. ROS activates poly (ADP-ribose) polymerase (PARP) activity in Fbxo7-deficient cells. PARP inhibitor restores cellular NAD+ content and redox index and ATP pool, suggesting that PARP overactivation is cause of decreased complex I-driven respiration. These findings bring new insight into the mechanism of Fbxo7 deficiency, emphasising the importance of mitochondrial dysfunction in PD.
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Affiliation(s)
- Marta Delgado-Camprubi
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London, UK
| | - Noemi Esteras
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London, UK
| | - Marc Pm Soutar
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London, UK
| | - Helene Plun-Favreau
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London, UK
| | - Andrey Y Abramov
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London, UK
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9
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Millet AMC, Bertholet AM, Daloyau M, Reynier P, Galinier A, Devin A, Wissinguer B, Belenguer P, Davezac N. Loss of functional OPA1 unbalances redox state: implications in dominant optic atrophy pathogenesis. Ann Clin Transl Neurol 2016; 3:408-21. [PMID: 27547769 PMCID: PMC4891995 DOI: 10.1002/acn3.305] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 03/04/2016] [Accepted: 03/05/2016] [Indexed: 12/14/2022] Open
Abstract
Objective OPA1 mutations cause protein haploinsufficiency leading to dominant optic atrophy (DOA), an incurable retinopathy with variable severity. Up to 20% of patients also develop extraocular neurological complications. The mechanisms that cause this optic atrophy or its syndromic forms are still unknown. After identifying oxidative stress in a mouse model of the pathology, we sought to determine the consequences of OPA1 dysfunction on redox homeostasis. Methods Mitochondrial respiration, reactive oxygen species levels, antioxidant defenses, and cell death were characterized by biochemical and in situ approaches in both in vitro and in vivo models of OPA1 haploinsufficiency. Results A decrease in aconitase activity suggesting an increase in reactive oxygene species and an induction of antioxidant defenses was observed in cortices of a murine model as well as in OPA1 downregulated cortical neurons. This increase is associated with a decline in mitochondrial respiration in vitro. Upon exogenous oxidative stress, OPA1‐depleted neurons did not further exhibit upregulated antioxidant defenses but were more sensitive to cell death. Finally, low levels of antioxidant enzymes were found in fibroblasts from patients supporting their role as modifier factors. Interpretation Our study suggests that the pro‐oxidative state induced by OPA1 loss may contribute to DOA pathogenesis and that differences in antioxidant defenses can explain the variability in expressivity. Furthermore, antioxidants may be used as therapy as they could prevent or delay DOA symptoms in patients.
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Affiliation(s)
- Aurélie M C Millet
- Center of Developmental Biology (CBD)/Research Center on Animal Cognition (CRCA) Center for Integrative Biology (CBI) Toulouse University, CNRS, UPS Toulouse France
| | - Ambre M Bertholet
- Center of Developmental Biology (CBD)/Research Center on Animal Cognition (CRCA) Center for Integrative Biology (CBI) Toulouse University, CNRS, UPS Toulouse France
| | - Marlène Daloyau
- Center of Developmental Biology (CBD)/Research Center on Animal Cognition (CRCA) Center for Integrative Biology (CBI) Toulouse University, CNRS, UPS Toulouse France
| | - Pascal Reynier
- CNRS UMR 6214 Inserm UMR 1083 UFR Sciences médicales Rue Haute de Reculee Angers Cedex 01 49045 France
| | - Anne Galinier
- Laboratoire de Biochimie Nutritionnelle "STROMALab" UMR UPS/CNRS/EFS 5273 Inserm U1031, CHU Rangueil 1 avenue Jean Poulhès Toulouse Cedex 9 31059 France
| | - Anne Devin
- Laboratoire métabolisme énergétique cellulaire IBGC du CNRS 1 rue Camille Saint Saëns Bordeaux Cedex 33077 France
| | - Bernd Wissinguer
- Centre for Ophthalmology University of Tübingen Roentgenweg 11 Tübingen D-72076 Germany
| | - Pascale Belenguer
- Center of Developmental Biology (CBD)/Research Center on Animal Cognition (CRCA) Center for Integrative Biology (CBI) Toulouse University, CNRS, UPS Toulouse France
| | - Noélie Davezac
- Center of Developmental Biology (CBD)/Research Center on Animal Cognition (CRCA) Center for Integrative Biology (CBI) Toulouse University, CNRS, UPS Toulouse France
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10
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Pahrudin Arrozi A, Wan Ngah WZ, Mohd Yusof YA, Ahmad Damanhuri MH, Makpol S. Antioxidant modulation in restoring mitochondrial function in neurodegeneration. Int J Neurosci 2016; 127:218-235. [PMID: 27074540 DOI: 10.1080/00207454.2016.1178261] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Alzheimer's disease (AD) and Parkinson's disease (PD) are the leading causes of disability associated with neurodegeneration worldwide. These diseases are influenced by multiple genetic and environmental factors and share similar mechanisms as both are characterized by accumulation and aggregation of misfolded proteins - amyloid-beta (Aβ) in AD and α-synuclein in PD. Over the past decade, increasing evidence has shown that mitochondrial dysfunction and the generation of reactive oxygen species (ROS) are involved in the pathology of these diseases, and the contributions of these defects to the cellular and molecular changes that eventually cause neuronal death have been explored. Using mitochondrial protective agents, such as antioxidants, to combat ROS provides a new strategy for neurodegenerative treatment. In this review, we highlight the potential of multiple types of antioxidants, including vitamins, phytochemicals, fatty acids and minerals, as well as synthetic antioxidants specifically targeting the mitochondria, which can restore mitochondrial function, in the treatment of neurodegenerative disorders at both the pre-clinical and clinical stages by focusing on AD and PD.
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Affiliation(s)
- Aslina Pahrudin Arrozi
- a Department of Biochemistry , Universiti Kebangsaan Malaysia Medical Center , Kuala Lumpur , Malaysia
| | - Wan Zurinah Wan Ngah
- a Department of Biochemistry , Universiti Kebangsaan Malaysia Medical Center , Kuala Lumpur , Malaysia
| | - Yasmin Anum Mohd Yusof
- a Department of Biochemistry , Universiti Kebangsaan Malaysia Medical Center , Kuala Lumpur , Malaysia
| | | | - Suzana Makpol
- a Department of Biochemistry , Universiti Kebangsaan Malaysia Medical Center , Kuala Lumpur , Malaysia
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11
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Krishna G. Aqueous extract of tomato seeds attenuates rotenone-induced oxidative stress and neurotoxicity in Drosophila melanogaster. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2016; 96:1745-1755. [PMID: 26033662 DOI: 10.1002/jsfa.7281] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 04/19/2015] [Accepted: 05/28/2015] [Indexed: 06/04/2023]
Abstract
BACKGROUND Tomato seeds, a major by-product from the food processing industry, constitute a rich source of bioactives and a large population consumes tomato (either in raw or cooked form). In the present study, initially we assessed the antioxidant activity of aqueous extract of tomato seeds (TSE) in selected chemical systems and further explored the neuroprotective effects of TSE utilising the rotenone (ROT) model of neurotoxicity in Drosophila. RESULTS Adult male flies (Oregon K) were fed TSE-enriched medium (0.1-0.2%) with or without ROT (500 µmol L(-1)) for 7 days. The propensity of TSE to protect flies against ROT-induced lethality, locomotor phenotype, oxidative stress and neurotoxicity was investigated. TSE offered marked protection against ROT-induced mortality, while survivors exhibited improved locomotor phenotype. TSE significantly attenuated ROT-induced oxidative stress, mitochondrial dysfunctions, protein carbonyls content, restored the cholinergic function and dopamine levels. CONCLUSION We hypothesise that the efficacy of tomato seed extract to attenuate ROT-mediated neurotoxicity may be largely related to the combined antioxidant activity of bioactives resulting in abrogation of oxidative stress and mitochondrial dysfunction. More importantly, our approach provides an experimental paradigm to rapidly assess the potential neuroprotective effects of common dietary components employing Drosophila, since it corroborates previous evidence in a mouse model.
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Affiliation(s)
- Gokul Krishna
- Department of Biochemistry and Nutrition, CSIR - Central Food Technological Research Institute (CFTRI), Mysore, 570020, India
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Computational Analysis of AMPK-Mediated Neuroprotection Suggests Acute Excitotoxic Bioenergetics and Glucose Dynamics Are Regulated by a Minimal Set of Critical Reactions. PLoS One 2016; 11:e0148326. [PMID: 26840769 PMCID: PMC4740490 DOI: 10.1371/journal.pone.0148326] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 01/15/2016] [Indexed: 11/22/2022] Open
Abstract
Loss of ionic homeostasis during excitotoxic stress depletes ATP levels and activates the AMP-activated protein kinase (AMPK), re-establishing energy production by increased expression of glucose transporters on the plasma membrane. Here, we develop a computational model to test whether this AMPK-mediated glucose import can rapidly restore ATP levels following a transient excitotoxic insult. We demonstrate that a highly compact model, comprising a minimal set of critical reactions, can closely resemble the rapid dynamics and cell-to-cell heterogeneity of ATP levels and AMPK activity, as confirmed by single-cell fluorescence microscopy in rat primary cerebellar neurons exposed to glutamate excitotoxicity. The model further correctly predicted an excitotoxicity-induced elevation of intracellular glucose, and well resembled the delayed recovery and cell-to-cell heterogeneity of experimentally measured glucose dynamics. The model also predicted necrotic bioenergetic collapse and altered calcium dynamics following more severe excitotoxic insults. In conclusion, our data suggest that a minimal set of critical reactions may determine the acute bioenergetic response to transient excitotoxicity and that an AMPK-mediated increase in intracellular glucose may be sufficient to rapidly recover ATP levels following an excitotoxic insult.
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Rao SV, Muralidhara, Yenisetti SC, Rajini PS. Evidence of neuroprotective effects of saffron and crocin in a Drosophila model of parkinsonism. Neurotoxicology 2016; 52:230-42. [DOI: 10.1016/j.neuro.2015.12.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 12/05/2015] [Accepted: 12/10/2015] [Indexed: 01/04/2023]
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van Maarschalkerweerd A, Pedersen MN, Peterson H, Nilsson M, Nguyen T, Skamris T, Rand K, Vetri V, Langkilde AE, Vestergaard B. Formation of covalent di-tyrosine dimers in recombinant α-synuclein. INTRINSICALLY DISORDERED PROTEINS 2015; 3:e1071302. [PMID: 28232892 PMCID: PMC5314896 DOI: 10.1080/21690707.2015.1071302] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 07/02/2015] [Accepted: 07/02/2015] [Indexed: 11/02/2022]
Abstract
Parkinson's disease is associated with fibril deposition in the diseased brain. Misfolding events of the intrinsically disordered synaptic protein α-synuclein are suggested to lead to the formation of transient oligomeric and cytotoxic species. The etiology of Parkinson's disease is further associated with mitochondrial dysfunction and formation of reactive oxygen species. Oxidative stress causes chemical modification of native α-synuclein, plausibly further influencing misfolding events. Here, we present evidence for the spontaneous formation of covalent di-tyrosine α-synuclein dimers in standard recombinant protein preparations, induced without extrinsic oxidative or nitrative agents. The dimers exhibit no secondary structure but advanced SAXS studies reveal an increased structural definition, resulting in a more hydrophobic micro-environment than the highly disordered monomer. Accordingly, monomers and dimers follow distinct fibrillation pathways.
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Affiliation(s)
| | - M N Pedersen
- Department of Drug Design and Pharmacology; University of Copenhagen ; Copenhagen, Denmark
| | - H Peterson
- Department of Drug Design and Pharmacology; University of Copenhagen ; Copenhagen, Denmark
| | - M Nilsson
- Department of Drug Design and Pharmacology; University of Copenhagen ; Copenhagen, Denmark
| | - Ttt Nguyen
- Department of Pharmacy; University of Copenhagen ; Copenhagen, Denmark
| | - T Skamris
- Department of Drug Design and Pharmacology; University of Copenhagen ; Copenhagen, Denmark
| | - K Rand
- Department of Pharmacy; University of Copenhagen ; Copenhagen, Denmark
| | - V Vetri
- Dipartimento di Fisica e Chimica; Universitá di Palermo ; Palermo, Italy
| | - A E Langkilde
- Department of Drug Design and Pharmacology; University of Copenhagen ; Copenhagen, Denmark
| | - B Vestergaard
- Department of Drug Design and Pharmacology; University of Copenhagen ; Copenhagen, Denmark
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15
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Physiology-based kinetic modeling of neuronal energy metabolism unravels the molecular basis of NAD(P)H fluorescence transients. J Cereb Blood Flow Metab 2015; 35:1494-506. [PMID: 25899300 PMCID: PMC4640339 DOI: 10.1038/jcbfm.2015.70] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 02/19/2015] [Accepted: 03/18/2015] [Indexed: 01/06/2023]
Abstract
Imaging of the cellular fluorescence of the reduced form of nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) is one of the few metabolic readouts that enable noninvasive and time-resolved monitoring of the functional status of mitochondria in neuronal tissues. Stimulation-induced transient changes in NAD(P)H fluorescence intensity frequently display a biphasic characteristic that is influenced by various molecular processes, e.g., intracellular calcium dynamics, tricarboxylic acid cycle activity, the malate-aspartate shuttle, the glycerol-3-phosphate shuttle, oxygen supply or adenosine triphosphate (ATP) demand. To evaluate the relative impact of these processes, we developed and validated a detailed physiologic mathematical model of the energy metabolism of neuronal cells and used the model to simulate metabolic changes of single cells and tissue slices under different settings of stimulus-induced activity and varying nutritional supply of glucose, pyruvate or lactate. Notably, all experimentally determined NAD(P)H responses could be reproduced with one and the same generic cellular model. Our computations reveal that (1) cells with quite different metabolic status may generate almost identical NAD(P)H responses and (2) cells of the same type may quite differently contribute to aggregate NAD(P)H responses recorded in brain slices, depending on the spatial location within the tissue. Our computational approach reconciles different and sometimes even controversial experimental findings and improves our mechanistic understanding of the metabolic changes underlying live-cell NAD(P)H fluorescence transients.
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TNF-α regulates miRNA targeting mitochondrial complex-I and induces cell death in dopaminergic cells. Biochim Biophys Acta Mol Basis Dis 2014; 1852:451-61. [PMID: 25481834 DOI: 10.1016/j.bbadis.2014.11.019] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 11/22/2014] [Accepted: 11/26/2014] [Indexed: 01/06/2023]
Abstract
Parkinson's disease (PD) is a complex neurological disorder of the elderly population and majorly shows the selective loss of dopaminergic (DAergic) neurons in the substantia nigra pars compacta (SNpc) region of the brain. The mechanisms leading to increased cell death of DAergic neurons are not well understood. Tumor necrosis factor-alpha (TNF-α), a pro-inflammatory cytokine is elevated in blood, CSF and striatum region of the brain in PD patients. The increased level of TNF-α and its role in pathogenesis of PD are not well understood. In the current study, we investigated the role of TNF-α in the regulation of cell death and miRNA mediated mitochondrial functions using, DAergic cell line, SH-SY5Y (model of dopaminergic neuron degeneration akin to PD). The cells treated with low dose of TNF-α for prolonged period induce cell death which was rescued in the presence of zVAD.fmk, a caspase inhibitor and N-acetyl-cysteine (NAC), an antioxidant. TNF-α alters mitochondrial complex-I activity, decreases adenosine triphosphate (ATP) levels, increases reactive oxygen species levels and mitochondrial turnover through autophagy. TNF-α differentially regulates miRNA expression involved in pathogenesis of PD. Bioinformatics analysis revealed that the putative targets of altered miRNA included both pro/anti apoptotic genes and subunits of mitochondrial complex. The cells treated with TNF-α showed decreased level of nuclear encoded transcript of mitochondrial complexes, the target of miRNA. To our knowledge, the evidences in the current study demonstrated that TNF-α is a potential regulator of miRNAs which may regulate mitochondrial functions and neuronal cell death, having important implication in pathogenesis of PD.
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Cunha MP, Martín-de-Saavedra MD, Romero A, Egea J, Ludka FK, Tasca CI, Farina M, Rodrigues ALS, López MG. Both creatine and its product phosphocreatine reduce oxidative stress and afford neuroprotection in an in vitro Parkinson's model. ASN Neuro 2014; 6:1759091414554945. [PMID: 25424428 PMCID: PMC4357608 DOI: 10.1177/1759091414554945] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Creatine is the substrate for creatine kinase in the synthesis of phosphocreatine (PCr). This energetic system is endowed of antioxidant and neuroprotective properties and plays a pivotal role in brain energy homeostasis. The purpose of this study was to investigate the neuroprotective effect of creatine and PCr against 6-hydroxydopamine (6-OHDA)-induced mitochondrial dysfunction and cell death in rat striatal slices, used as an in vitro Parkinson's model. The possible involvement of the signaling pathway mediated by phosphatidylinositol-3 kinase (PI3K), protein kinase B (Akt), and glycogen synthase kinase-3β (GSK3β) was also evaluated. Exposure of striatal slices to 6-OHDA caused a significant disruption of the cellular homeostasis measured as 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide reduction, lactate dehydrogenase release, and tyrosine hydroxylase levels. 6-OHDA exposure increased the levels of reactive oxygen species and thiobarbituric acid reactive substances production and decreased mitochondrial membrane potential in rat striatal slices. Furthermore, 6-OHDA decreased the phosphorylation of Akt (Serine(473)) and GSK3β (Serine(9)). Coincubation with 6-OHDA and creatine or PCr reduced the effects of 6-OHDA toxicity. The protective effect afforded by creatine or PCr against 6-OHDA-induced toxicity was reversed by the PI3K inhibitor LY294002. In conclusion, creatine and PCr minimize oxidative stress in striatum to afford neuroprotection of dopaminergic neurons.
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Affiliation(s)
- Mauricio Peña Cunha
- Facultad de Medicina, Instituto Teófilo Hernando, Universidad Autónoma de Madrid, Spain Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Spain Departamento de Bioquímica, Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Florianópolis, SC, Brazil
| | - Maria D Martín-de-Saavedra
- Facultad de Medicina, Instituto Teófilo Hernando, Universidad Autónoma de Madrid, Spain Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Spain Department of Physiology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - Alejandro Romero
- Facultad de Medicina, Instituto Teófilo Hernando, Universidad Autónoma de Madrid, Spain Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Spain Departamento de Toxicología y Farmacología, Facultad de Veterinaria, Universidad Complutense de Madrid, Spain
| | - Javier Egea
- Facultad de Medicina, Instituto Teófilo Hernando, Universidad Autónoma de Madrid, Spain Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Spain Instituto de Investigación Sanitaria Hospital de la Princesa, Madrid, Spain
| | - Fabiana K Ludka
- Departamento de Bioquímica, Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Florianópolis, SC, Brazil Department of Pharmacy, Universidade do Contestado, Canoinhas, SC, Brazil
| | - Carla I Tasca
- Facultad de Medicina, Instituto Teófilo Hernando, Universidad Autónoma de Madrid, Spain
| | - Marcelo Farina
- Departamento de Bioquímica, Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Florianópolis, SC, Brazil
| | - Ana Lúcia S Rodrigues
- Departamento de Bioquímica, Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Florianópolis, SC, Brazil
| | - Manuela G López
- Facultad de Medicina, Instituto Teófilo Hernando, Universidad Autónoma de Madrid, Spain Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Spain
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Effects of partial inhibition of respiratory complex I on H2O 2 production by isolated brain mitochondria in different respiratory states. Neurochem Res 2014; 39:2419-30. [PMID: 25287903 DOI: 10.1007/s11064-014-1446-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 09/24/2014] [Accepted: 09/28/2014] [Indexed: 12/21/2022]
Abstract
The aim of this work was to characterize the effects of partial inhibition of respiratory complex I by rotenone on H2O2 production by isolated rat brain mitochondria in different respiratory states. Flow cytometric analysis of membrane potential in isolated mitochondria indicated that rotenone leads to uniform respiratory inhibition when added to a suspension of mitochondria. When mitochondria were incubated in the presence of a low concentration of rotenone (10 nm) and NADH-linked substrates, oxygen consumption was reduced from 45.9 ± 1.0 to 26.4 ± 2.6 nmol O2 mg(-1) min(-1) and from 7.8 ± 0.3 to 6.3 ± 0.3 nmol O2 mg(-1) min(-1) in respiratory states 3 (ADP-stimulated respiration) and 4 (resting respiration), respectively. Under these conditions, mitochondrial H2O2 production was stimulated from 12.2 ± 1.1 to 21.0 ± 1.2 pmol H2O2 mg(-1) min(-1) and 56.5 ± 4.7 to 95.0 ± 11.1 pmol H2O2 mg(-1) min(-1) in respiratory states 3 and 4, respectively. Similar results were observed when comparing mitochondrial preparations enriched with synaptic or nonsynaptic mitochondria or when 1-methyl-4-phenylpyridinium ion (MPP(+)) was used as a respiratory complex I inhibitor. Rotenone-stimulated H2O2 production in respiratory states 3 and 4 was associated with a high reduction state of endogenous nicotinamide nucleotides. In succinate-supported mitochondrial respiration, where most of the mitochondrial H2O2 production relies on electron backflow from complex II to complex I, low rotenone concentrations inhibited H2O2 production. Rotenone had no effect on mitochondrial elimination of micromolar concentrations of H2O2. The present results support the conclusion that partial complex I inhibition may result in mitochondrial energy crisis and oxidative stress, the former being predominant under oxidative phosphorylation and the latter under resting respiration conditions.
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