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Zheng BX, Long W, Zheng W, Zeng Y, Guo XC, Chan KH, She MT, Leung ASL, Lu YJ, Wong WL. Mitochondria-Selective Dicationic Small-Molecule Ligand Targeting G-Quadruplex Structures for Human Colorectal Cancer Therapy. J Med Chem 2024; 67:6292-6312. [PMID: 38624086 DOI: 10.1021/acs.jmedchem.3c02240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
Mitochondria are important drug targets for anticancer and other disease therapies. Certain human mitochondrial DNA sequences capable of forming G-quadruplex structures (G4s) are emerging drug targets of small molecules. Despite some mitochondria-selective ligands being reported for drug delivery against cancers, the ligand design is mostly limited to the triphenylphosphonium scaffold. The ligand designed with lipophilic small-sized scaffolds bearing multipositive charges targeting the unique feature of high mitochondrial membrane potential (MMP) is lacking and most mitochondria-selective ligands are not G4-targeting. Herein, we report a new small-sized dicationic lipophilic ligand to target MMP and mitochondrial DNA G4s to enhance drug delivery for anticancer. The ligand showed marked alteration of mitochondrial gene expression and substantial induction of ROS production, mitochondrial dysfunction, DNA damage, cellular senescence, and apoptosis. The ligand also exhibited high anticancer activity against HCT116 cancer cells (IC50, 3.4 μM) and high antitumor efficacy in the HCT116 tumor xenograft mouse model (∼70% tumor weight reduction).
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Affiliation(s)
- Bo-Xin Zheng
- State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR 999077, China
| | - Wei Long
- State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR 999077, China
| | - Wende Zheng
- The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen 518057, P. R. China
| | - Yaoxun Zeng
- The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen 518057, P. R. China
| | - Xiao-Chun Guo
- School of Biomedical and Pharmaceutical Sciences, Guangdong University of Technology, Guangzhou 510006, P. R. China
| | - Ka-Hin Chan
- State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR 999077, China
| | - Meng-Ting She
- The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen 518057, P. R. China
| | - Alan Siu-Lun Leung
- State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR 999077, China
| | - Yu-Jing Lu
- School of Biomedical and Pharmaceutical Sciences, Guangdong University of Technology, Guangzhou 510006, P. R. China
| | - Wing-Leung Wong
- State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR 999077, China
- The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen 518057, P. R. China
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Age-associated alterations of brain mitochondria energetics. Biochem Biophys Res Commun 2023; 643:1-7. [PMID: 36584587 DOI: 10.1016/j.bbrc.2022.12.070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 11/28/2022] [Accepted: 12/22/2022] [Indexed: 12/25/2022]
Abstract
The study aimed to explore the role of age-associated elevated cytosolic Ca2+ in changes of brain mitochondria energetic processes. Two groups of rats, young adults (4 months) and advanced old (24 months), were evaluated for potential alterations of mitochondrial parameters, the oxidative phosphorylation (OxPhos), membrane potential, calcium retention capacity, activity of glutamate/aspartate carrier (aralar), and ROS formation. We demonstrated that the brain mitochondria of older animals have a lower resistance to Ca2+ stress with resulting consequences. The suppressed complex I OxPhos and decreased membrane potential were accompanied by reduction of the Ca2+ threshold required for induction of mPTP. The Ca2+ binding sites of mitochondrial aralar mediated a lower activity of old brain mitochondria. The altered interaction between aralar and mPTP may underlie mitochondrial dysregulation leading to energetic depression during aging. At the advanced stages of aging, the declined metabolism is accompanied by the diminished oxidative background.
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Bioenergetic consequences from xenotopic expression of a tunicate AOX in mouse mitochondria: Switch from RET and ROS to FET. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2020; 1861:148137. [PMID: 31825809 DOI: 10.1016/j.bbabio.2019.148137] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 12/01/2019] [Accepted: 12/05/2019] [Indexed: 12/23/2022]
Abstract
Electron transfer from all respiratory chain dehydrogenases of the electron transport chain (ETC) converges at the level of the quinone (Q) pool. The Q redox state is thus a function of electron input (reduction) and output (oxidation) and closely reflects the mitochondrial respiratory state. Disruption of electron flux at the level of the cytochrome bc1 complex (cIII) or cytochrome c oxidase (cIV) shifts the Q redox poise to a more reduced state which is generally sensed as respiratory stress. To cope with respiratory stress, many species, but not insects and vertebrates, express alternative oxidase (AOX) which acts as an electron sink for reduced Q and by-passes cIII and cIV. Here, we used Ciona intestinalis AOX xenotopically expressed in mouse mitochondria to study how respiratory states impact the Q poise and how AOX may be used to restore respiration. Particularly interesting is our finding that electron input through succinate dehydrogenase (cII), but not NADH:ubiquinone oxidoreductase (cI), reduces the Q pool almost entirely (>90%) irrespective of the respiratory state. AOX enhances the forward electron transport (FET) from cII thereby decreasing reverse electron transport (RET) and ROS specifically when non-phosphorylating. AOX is not engaged with cI substrates, however, unless a respiratory inhibitor is added. This sheds new light on Q poise signaling, the biological role of cII which enigmatically is the only ETC complex absent from respiratory supercomplexes but yet participates in the tricarboxylic acid (TCA) cycle. Finally, we delineate potential risks and benefits arising from therapeutic AOX transfer.
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Fricker M, Tolkovsky AM, Borutaite V, Coleman M, Brown GC. Neuronal Cell Death. Physiol Rev 2018; 98:813-880. [PMID: 29488822 PMCID: PMC5966715 DOI: 10.1152/physrev.00011.2017] [Citation(s) in RCA: 662] [Impact Index Per Article: 110.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 05/23/2017] [Accepted: 07/10/2017] [Indexed: 02/07/2023] Open
Abstract
Neuronal cell death occurs extensively during development and pathology, where it is especially important because of the limited capacity of adult neurons to proliferate or be replaced. The concept of cell death used to be simple as there were just two or three types, so we just had to work out which type was involved in our particular pathology and then block it. However, we now know that there are at least a dozen ways for neurons to die, that blocking a particular mechanism of cell death may not prevent the cell from dying, and that non-neuronal cells also contribute to neuronal death. We review here the mechanisms of neuronal death by intrinsic and extrinsic apoptosis, oncosis, necroptosis, parthanatos, ferroptosis, sarmoptosis, autophagic cell death, autosis, autolysis, paraptosis, pyroptosis, phagoptosis, and mitochondrial permeability transition. We next explore the mechanisms of neuronal death during development, and those induced by axotomy, aberrant cell-cycle reentry, glutamate (excitoxicity and oxytosis), loss of connected neurons, aggregated proteins and the unfolded protein response, oxidants, inflammation, and microglia. We then reassess which forms of cell death occur in stroke and Alzheimer's disease, two of the most important pathologies involving neuronal cell death. We also discuss why it has been so difficult to pinpoint the type of neuronal death involved, if and why the mechanism of neuronal death matters, the molecular overlap and interplay between death subroutines, and the therapeutic implications of these multiple overlapping forms of neuronal death.
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Affiliation(s)
- Michael Fricker
- Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales , Australia ; Department of Clinical Neurosciences, University of Cambridge , Cambridge , United Kingdom ; Neuroscience Institute, Lithuanian University of Health Sciences , Kaunas , Lithuania ; and Department of Biochemistry, University of Cambridge , Cambridge , United Kingdom
| | - Aviva M Tolkovsky
- Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales , Australia ; Department of Clinical Neurosciences, University of Cambridge , Cambridge , United Kingdom ; Neuroscience Institute, Lithuanian University of Health Sciences , Kaunas , Lithuania ; and Department of Biochemistry, University of Cambridge , Cambridge , United Kingdom
| | - Vilmante Borutaite
- Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales , Australia ; Department of Clinical Neurosciences, University of Cambridge , Cambridge , United Kingdom ; Neuroscience Institute, Lithuanian University of Health Sciences , Kaunas , Lithuania ; and Department of Biochemistry, University of Cambridge , Cambridge , United Kingdom
| | - Michael Coleman
- Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales , Australia ; Department of Clinical Neurosciences, University of Cambridge , Cambridge , United Kingdom ; Neuroscience Institute, Lithuanian University of Health Sciences , Kaunas , Lithuania ; and Department of Biochemistry, University of Cambridge , Cambridge , United Kingdom
| | - Guy C Brown
- Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales , Australia ; Department of Clinical Neurosciences, University of Cambridge , Cambridge , United Kingdom ; Neuroscience Institute, Lithuanian University of Health Sciences , Kaunas , Lithuania ; and Department of Biochemistry, University of Cambridge , Cambridge , United Kingdom
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Abstract
Cerebellar disorders trigger the symptoms of movement problems, imbalance, incoordination, and frequent fall. Cerebellar disorders are shown in various CNS illnesses including a drinking disorder called alcoholism. Alcoholism is manifested as an inability to control drinking in spite of adverse consequences. Human and animal studies have shown that cerebellar symptoms persist even after complete abstinence from drinking. In particular, the abrupt termination (ethanol withdrawal) of long-term excessive ethanol consumption has shown to provoke a variety of neuronal and mitochondrial damage to the cerebellum. Upon ethanol withdrawal, excitatory neurotransmitter molecules such as glutamate are overly released in brain areas including cerebellum. This is particularly relevant to the cerebellar neuronal network as glutamate signals are projected to Purkinje neurons through granular cells that are the most populated neuronal type in CNS. This excitatory neuronal signal may be elevated by ethanol withdrawal stress, which promotes an increase in intracellular Ca(2+) level and a decrease in a Ca(2+)-binding protein, both of which result in the excessive entry of Ca(2+) to the mitochondria. Subsequently, mitochondria undergo a prolonged opening of mitochondrial permeability transition pore and the overproduction of harmful free radicals, impeding adenosine triphosphate (ATP)-generating function. This in turn provokes the leakage of mitochondrial molecule cytochrome c to the cytosol, which triggers a cascade of adverse cytosol reactions. Upstream to this pathway, cerebellum under the condition of ethanol withdrawal has shown aberrant gene modifications through altered DNA methylation, histone acetylation, or microRNA expression. Interplay between these events and molecules may result in functional damage to cerebellar mitochondria and consequent neuronal degeneration, thereby contributing to motoric deficit. Mitochondria-targeting research may help develop a powerful new therapy to manage cerebellar disorders associated with hyperexcitatory CNS disorders like ethanol withdrawal.
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Affiliation(s)
- Marianna E Jung
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center at Fort Worth, 3500 Camp Bowie Blvd., Fort Worth, TX, 76107-2699, USA,
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Huang WC, Tseng TY, Chen YT, Chang CC, Wang ZF, Wang CL, Hsu TN, Li PT, Chen CT, Lin JJ, Lou PJ, Chang TC. Direct evidence of mitochondrial G-quadruplex DNA by using fluorescent anti-cancer agents. Nucleic Acids Res 2015; 43:10102-13. [PMID: 26487635 PMCID: PMC4666356 DOI: 10.1093/nar/gkv1061] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 09/30/2015] [Indexed: 11/26/2022] Open
Abstract
G-quadruplex (G4) is a promising target for anti-cancer treatment. In this paper, we provide the first evidence supporting the presence of G4 in the mitochondrial DNA (mtDNA) of live cells. The molecular engineering of a fluorescent G4 ligand, 3,6-bis(1-methyl-4-vinylpyridinium) carbazole diiodide (BMVC), can change its major cellular localization from the nucleus to the mitochondria in cancer cells, while remaining primarily in the cytoplasm of normal cells. A number of BMVC derivatives with sufficient mitochondrial uptake can induce cancer cell death without damaging normal cells. Fluorescence studies of these anti-cancer agents in live cells and in isolated mitochondria from HeLa cells have demonstrated that their major target is mtDNA. In this study, we use fluorescence lifetime imaging microscopy to verify the existence of mtDNA G4s in live cells. Bioactivity studies indicate that interactions between these anti-cancer agents and mtDNA G4 can suppress mitochondrial gene expression. This work underlines the importance of fluorescence in the monitoring of drug-target interactions in cells and illustrates the emerging development of drugs in which mtDNA G4 is the primary target.
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Affiliation(s)
- Wei-Chun Huang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Ting-Yuan Tseng
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Ying-Ting Chen
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Cheng-Chung Chang
- Institute of Biomedical Engineering, National Chung-Hsing University, Taichung 40227, Taiwan
| | - Zi-Fu Wang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Chiung-Lin Wang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Tsu-Ning Hsu
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan Department of Agricultural Chemistry, National Taiwan University, Taipei 10617, Taiwan
| | - Pei-Tzu Li
- Department of Biochemical Science and Technology, National Taiwan University, Taipei 10617, Taiwan
| | - Chin-Tin Chen
- Department of Biochemical Science and Technology, National Taiwan University, Taipei 10617, Taiwan
| | - Jing-Jer Lin
- Institute of Biochemistry and Molecular Biology, National Taiwan University College of Medicine, Taipei 10051, Taiwan
| | - Pei-Jen Lou
- Department of Otolaryngology, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei 10051, Taiwan
| | - Ta-Chau Chang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
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Gainutdinov T, Molkentin JD, Siemen D, Ziemer M, Debska-Vielhaber G, Vielhaber S, Gizatullina Z, Orynbayeva Z, Gellerich FN. Knockout of cyclophilin D in Ppif⁻/⁻ mice increases stability of brain mitochondria against Ca²⁺ stress. Arch Biochem Biophys 2015; 579:40-6. [PMID: 26032335 DOI: 10.1016/j.abb.2015.05.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Revised: 05/24/2015] [Accepted: 05/25/2015] [Indexed: 01/16/2023]
Abstract
The mitochondrial peptidyl prolyl isomerase cyclophilin D (CypD) activates permeability transition (PT). To study the role of CypD in this process we compared the functions of brain mitochondria isolated from wild type (BMWT) and CypD knockout (Ppif(-/-)) mice (BMKO) with and without CypD inhibitor Cyclosporin A (CsA) under normal and Ca(2+) stress conditions. Our data demonstrate that BMKO are characterized by higher rates of glutamate/malate-dependent oxidative phosphorylation, higher membrane potential and higher resistance to detrimental Ca(2+) effects than BMWT. Under the elevated Ca(2+) and correspondingly decreased membrane potential the dose response in BMKO shifts to higher Ca(2+) concentrations as compared to BMWT. However, significantly high Ca(2+) levels result in complete loss of membrane potential in BMKO, too. CsA diminishes the loss of membrane potential in BMWT but has no protecting effect in BMKO. The results are in line with the assumption that PT is regulated by CypD under the control of matrix Ca(2+). Due to missing of CypD the BMKO can favor PT only at high Ca(2+) concentrations. It is concluded that CypD sensitizes the brain mitochondria to PT, and its inhibition by CsA or CypD absence improves the complex I-related mitochondrial function and increases mitochondria stability against Ca(2+) stress.
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Affiliation(s)
- T Gainutdinov
- Department of Neurology, Otto-von-Guericke-University, Magdeburg D-39120, Germany; Institute of Ecology and Use of Mineral Resources, Academy of Sciences of Tatarstan, Kazan 420087, Russian Federation
| | - J D Molkentin
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Howard Hughes Medical Institute, Cincinnati, OH 45229, USA
| | - D Siemen
- Department of Neurology, Otto-von-Guericke-University, Magdeburg D-39120, Germany
| | - M Ziemer
- Department of Neurology, Otto-von-Guericke-University, Magdeburg D-39120, Germany
| | - G Debska-Vielhaber
- Department of Neurology, Otto-von-Guericke-University, Magdeburg D-39120, Germany
| | - S Vielhaber
- Department of Neurology, Otto-von-Guericke-University, Magdeburg D-39120, Germany
| | - Z Gizatullina
- Leibniz Institute for Neurobiology, Brennecke Str. 6, Magdeburg D-39118, Germany
| | - Z Orynbayeva
- Department of Surgery, Drexel University College of Medicine, Philadelphia, PA 19102, USA.
| | - F N Gellerich
- Department of Neurology, Otto-von-Guericke-University, Magdeburg D-39120, Germany; Leibniz Institute for Neurobiology, Brennecke Str. 6, Magdeburg D-39118, Germany.
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Semi-synthesis of cyclosporins. Biochim Biophys Acta Gen Subj 2015; 1850:2121-44. [PMID: 25707381 DOI: 10.1016/j.bbagen.2015.02.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 02/11/2015] [Accepted: 02/13/2015] [Indexed: 12/28/2022]
Abstract
BACKGROUND Since its isolation in 1970, and discovery of its potent inhibitory activity on T-cell proliferation, cyclosporin A (CsA) has been shown to play a significant role in diverse fields of biology. Furthermore, chemical modification of CsA has led to analogs with distinct biological activities associated with its protein receptor family, cyclophilins. SCOPE OF REVIEW This review systematically collates the synthetic chemistry performed at each of the eleven amino acids, and provides examples of the utility of such transformations. The various modifications of CsA are traced from early, modest chemistry performed at the unique Bmt residue, through the remarkable use of a polyanion enolate that can be stereoselectively manipulated, and onto application of more recently developed olefin metathesis chemistry to prepare new CsA derivatives with unexpected biological activity. MAJOR CONCLUSIONS The myriad biological activities of CsA and its synthetic derivatives have inspired the development of new approaches to modify the CsA ring. In turn, these new CsA derivatives have served as tools in the discovery of new roles for cyclophilins. GENERAL SIGNIFICANCE This review provides information on the types of cyclosporin derivatives that are available to the many biologists working in this field, and should be of value to the medicinal chemist trying to discover drugs based on CsA. This article is part of a Special Issue entitled Proline-directed foldases: Cell signaling catalysts and drug targets.
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Wieduwild R, Lin W, Boden A, Kretschmer K, Zhang Y. A repertoire of peptide tags for controlled drug release from injectable noncovalent hydrogel. Biomacromolecules 2014; 15:2058-66. [PMID: 24825401 DOI: 10.1021/bm500186a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A repertoire of conjugable tags for controlling the release of drugs from biomaterials is highly interesting for the development of combinatorial drug administration techniques. This paper describes such a system of 11 peptide tags derived from our previous work on a physical hydrogel system cross-linked through peptide-heparin interactions. The release kinetics of the tags correlate well with their affinity to heparin and obey Fick's second law of diffusion, with the exception of the ATIII peptide, which displays a stable release profile close to a zero-order reaction. A system for release experiments over seven months was built, using the hydrogel matrix as a barrier between the reservoirs of tagged compounds and supernatant. The gel matrix can be injected without affecting the releasing properties. A tagged cyclosporin A derivative was also tested, and its release was monitored by measuring its biological activity. This work represents a design of biomaterials with an integral system of drug delivery, where both the assembly process of the matrix and affinity capture/release of tagged compounds are based on the noncovalent interaction of heparin with one class of peptides.
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Affiliation(s)
- Robert Wieduwild
- B CUBE Center for Molecular Bioengineering, Technische Universität Dresden , Arnoldstraße 18, 01307 Dresden, Germany
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Oxygen glucose deprivation causes mitochondrial dysfunction in cultivated rat hippocampal slices: Protective effects of CsA, its immunosuppressive congener [D-Ser]8CsA, the novel non-immunosuppressive cyclosporin derivative Cs9, and the NMDA receptor antagonist MK 801. Mitochondrion 2013; 13:539-47. [DOI: 10.1016/j.mito.2012.07.110] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 07/11/2012] [Accepted: 07/15/2012] [Indexed: 02/06/2023]
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Siemen D, Ziemer M. What is the nature of the mitochondrial permeability transition poreand What is it Not? IUBMB Life 2013; 65:255-62. [DOI: 10.1002/iub.1130] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 12/07/2012] [Indexed: 12/23/2022]
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Cytosolic Ca2+ regulates the energization of isolated brain mitochondria by formation of pyruvate through the malate–aspartate shuttle. Biochem J 2012; 443:747-55. [DOI: 10.1042/bj20110765] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The glutamate-dependent respiration of isolated BM (brain mitochondria) is regulated by Ca2+cyt (cytosolic Ca2+) (S0.5=225±22 nM) through its effects on aralar. We now also demonstrate that the α-glycerophosphate-dependent respiration is controlled by Ca2+cyt (S0.5=60±10 nM). At higher Ca2+cyt (>600 nM), BM accumulate Ca2+ which enhances the rate of intramitochondrial dehydrogenases. The Ca2+-induced increments of state 3 respiration decrease with substrate in the order glutamate>α-oxoglutarate>isocitrate>α-glycerophosphate>pyruvate. Whereas the oxidation of pyruvate is only slightly influenced by Ca2+cyt, we show that the formation of pyruvate is tightly controlled by Ca2+cyt. Through its common substrate couple NADH/NAD+, the formation of pyruvate by LDH (lactate dehydrogenase) is linked to the MAS (malate–aspartate shuttle) with aralar as a central component. A rise in Ca2+cyt in a reconstituted system consisting of BM, cytosolic enzymes of MAS and LDH causes an up to 5-fold enhancement of OXPHOS (oxidative phosphorylation) rates that is due to an increased substrate supply, acting in a manner similar to a ‘gas pedal’. In contrast, Ca2+mit (intramitochondrial Ca2+) regulates the oxidation rates of substrates which are present within the mitochondrial matrix. We postulate that Ca2+cyt is a key factor in adjusting the mitochondrial energization to the requirements of intact neurons.
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