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Hubbard WB, Spry ML, Gooch JL, Cloud AL, Vekaria HJ, Burden S, Powell DK, Berkowitz BA, Geldenhuys WJ, Harris NG, Sullivan PG. Clinically relevant mitochondrial-targeted therapy improves chronic outcomes after traumatic brain injury. Brain 2021; 144:3788-3807. [PMID: 34972207 PMCID: PMC8719838 DOI: 10.1093/brain/awab341] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 07/28/2021] [Accepted: 08/04/2021] [Indexed: 11/14/2022] Open
Abstract
Pioglitazone, an FDA-approved compound, has been shown to target the novel mitochondrial protein mitoNEET and produce short-term neuroprotection and functional benefits following traumatic brain injury. To expand on these findings, we now investigate the dose- and time-dependent effects of pioglitazone administration on mitochondrial function after experimental traumatic brain injury. We then hypothesize that optimal pioglitazone dosing will lead to ongoing neuroprotection and cognitive benefits that are dependent on pioglitazone-mitoNEET signalling pathways. We show that delayed intervention is significantly more effective than early intervention at improving acute mitochondrial bioenergetics in the brain after traumatic brain injury. In corroboration, we demonstrate that mitoNEET is more heavily expressed, especially near the cortical contusion, in the 18 h following traumatic brain injury. To explore whether these findings relate to ongoing pathological and behavioural outcomes, mice received controlled cortical impact followed by initiation of pioglitazone treatment at either 3 or 18 h post-injury. Mice with treatment initiation at 18 h post-injury exhibited significantly improved behaviour and tissue sparing compared to mice with pioglitazone initiated at 3 h post-injury. Further using mitoNEET knockout mice, we show that this therapeutic effect is dependent on mitoNEET. Finally, we demonstrate that delayed pioglitazone treatment improves serial motor and cognitive performance in conjunction with attenuated brain atrophy after traumatic brain injury. This study illustrates that mitoNEET is the critical target for delayed pioglitazone intervention after traumatic brain injury, mitochondrial-targeting is highly time-dependent after injury and there is an extended therapeutic window to effectively treat mitochondrial dysfunction after brain injury.
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Affiliation(s)
- W Brad Hubbard
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, KY 40536, USA
- Department of Neuroscience, University of Kentucky, Lexington, KY 40508, USA
- Department of Physiology, University of Kentucky, Lexington, KY 40508, USA
- Lexington VA Healthcare System, Lexington, KY 40502, USA
| | - Malinda L Spry
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, KY 40536, USA
| | - Jennifer L Gooch
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, KY 40536, USA
| | - Amber L Cloud
- College of Medicine, University of Kentucky, Lexington, KY 40508, USA
| | - Hemendra J Vekaria
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, KY 40536, USA
| | - Shawn Burden
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, KY 40536, USA
| | - David K Powell
- Department of Neuroscience, University of Kentucky, Lexington, KY 40508, USA
| | - Bruce A Berkowitz
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, MI 48202, USA
| | - Werner J Geldenhuys
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV 26506, USA
| | - Neil G Harris
- UCLA Brain Injury Research Center, Department of Neurosurgery, and Intellectual Development and Disabilities Research Center, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Patrick G Sullivan
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, KY 40536, USA
- Department of Neuroscience, University of Kentucky, Lexington, KY 40508, USA
- Lexington VA Healthcare System, Lexington, KY 40502, USA
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Abstract
The field of mitochondrial ion channels has recently seen substantial progress, including the molecular identification of some of the channels. An integrative approach using genetics, electrophysiology, pharmacology, and cell biology to clarify the roles of these channels has thus become possible. It is by now clear that many of these channels are important for energy supply by the mitochondria and have a major impact on the fate of the entire cell as well. The purpose of this review is to provide an up-to-date overview of the electrophysiological properties, molecular identity, and pathophysiological functions of the mitochondrial ion channels studied so far and to highlight possible therapeutic perspectives based on current information.
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Choi S, Yu E, Rabello G, Merlo S, Zemmar A, Walton KD, Moreno H, Moreira JE, Sugimori M, Llinás RR. Enhanced synaptic transmission at the squid giant synapse by artificial seawater based on physically modified saline. Front Synaptic Neurosci 2014; 6:2. [PMID: 24575037 PMCID: PMC3921564 DOI: 10.3389/fnsyn.2014.00002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 01/21/2014] [Indexed: 11/30/2022] Open
Abstract
Superfusion of the squid giant synapse with artificial seawater (ASW) based on isotonic saline containing oxygen nanobubbles (RNS60 ASW) generates an enhancement of synaptic transmission. This was determined by examining the postsynaptic response to single and repetitive presynaptic spike activation, spontaneous transmitter release, and presynaptic voltage clamp studies. In the presence of RNS60 ASW single presynaptic stimulation elicited larger postsynaptic potentials (PSP) and more robust recovery from high frequency stimulation than in control ASW. Analysis of postsynaptic noise revealed an increase in spontaneous transmitter release with modified noise kinetics in RNS60 ASW. Presynaptic voltage clamp demonstrated an increased EPSP, without an increase in presynaptic ICa++ amplitude during RNS60 ASW superfusion. Synaptic release enhancement reached stable maxima within 5–10 min of RNS60 ASW superfusion and was maintained for the entire recording time, up to 1 h. Electronmicroscopic morphometry indicated a decrease in synaptic vesicle density and the number at active zones with an increase in the number of clathrin-coated vesicles (CCV) and large endosome-like vesicles near junctional sites. Block of mitochondrial ATP synthesis by presynaptic injection of oligomycin reduced spontaneous release and prevented the synaptic noise increase seen in RNS60 ASW. After ATP block the number of vesicles at the active zone and CCV was reduced, with an increase in large vesicles. The possibility that RNS60 ASW acts by increasing mitochondrial ATP synthesis was tested by direct determination of ATP levels in both presynaptic and postsynaptic structures. This was implemented using luciferin/luciferase photon emission, which demonstrated a marked increase in ATP synthesis following RNS60 administration. It is concluded that RNS60 positively modulates synaptic transmission by up-regulating ATP synthesis, thus leading to synaptic transmission enhancement.
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Affiliation(s)
- Soonwook Choi
- Marine Biological Laboratory Woods Hole, MA, USA ; Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA
| | - Eunah Yu
- Marine Biological Laboratory Woods Hole, MA, USA ; Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA
| | - Guilherme Rabello
- Marine Biological Laboratory Woods Hole, MA, USA ; Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA
| | - Suelen Merlo
- Department of Cell and Molecular Biology, Riberão Preto School of Medicine, University of São Paulo Ribeirão Preto, Brazil
| | - Ajmal Zemmar
- Marine Biological Laboratory Woods Hole, MA, USA
| | - Kerry D Walton
- Marine Biological Laboratory Woods Hole, MA, USA ; Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA
| | - Herman Moreno
- Marine Biological Laboratory Woods Hole, MA, USA ; Departments of Neurology and Physiology/Pharmacology, The Robert F. Furchgott Center for Neural and Behavioral Science, SUNY Downstate Medical Center Brooklyn, NY, USA
| | - Jorge E Moreira
- Marine Biological Laboratory Woods Hole, MA, USA ; Department of Cell and Molecular Biology, Riberão Preto School of Medicine, University of São Paulo Ribeirão Preto, Brazil
| | - Mutsuyuki Sugimori
- Marine Biological Laboratory Woods Hole, MA, USA ; Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA
| | - Rodolfo R Llinás
- Marine Biological Laboratory Woods Hole, MA, USA ; Department of Neuroscience and Physiology, New York University School of Medicine New York, NY, USA
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Shutov LP, Kim MS, Houlihan PR, Medvedeva YV, Usachev YM. Mitochondria and plasma membrane Ca2+-ATPase control presynaptic Ca2+ clearance in capsaicin-sensitive rat sensory neurons. J Physiol 2013; 591:2443-62. [PMID: 23381900 DOI: 10.1113/jphysiol.2012.249219] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The central processes of primary nociceptors form synaptic connections with the second-order nociceptive neurons located in the dorsal horn of the spinal cord. These synapses gate the flow of nociceptive information from the periphery to the CNS, and plasticity at these synapses contributes to centrally mediated hyperalgesia and allodynia. Although exocytosis and synaptic plasticity are controlled by Ca(2+) at the release sites, the mechanisms underlying presynaptic Ca(2+) signalling at the nociceptive synapses are not well characterized. We examined the presynaptic mechanisms regulating Ca(2+) clearance following electrical stimulation in capsaicin-sensitive nociceptors using a dorsal root ganglion (DRG)/spinal cord neuron co-culture system. Cytosolic Ca(2+) concentration ([Ca(2+)]i) recovery following electrical stimulation was well approximated by a monoexponential function with a ∼2 s. Inhibition of sarco-endoplasmic reticulum Ca(2+)-ATPase did not affect presynaptic [Ca(2+)]i recovery, and blocking plasmalemmal Na(+)/Ca(2+) exchange produced only a small reduction in the rate of [Ca(2+)]i recovery (∼12%) that was independent of intracellular K(+). However, [Ca(2+)]i recovery in presynaptic boutons strongly depended on the plasma membrane Ca(2+)-ATPase (PMCA) and mitochondria that accounted for ∼47 and 40%, respectively, of presynaptic Ca(2+) clearance. Measurements using a mitochondria-targeted Ca(2+) indicator, mtPericam, demonstrated that presynaptic mitochondria accumulated Ca(2+) in response to electrical stimulation. Quantitative analysis revealed that the mitochondrial Ca(2+) uptake is highly sensitive to presynaptic [Ca(2+)]i elevations, and occurs at [Ca(2+)]i levels as low as ∼200-300 nm. Using RT-PCR, we detected expression of several putative mitochondrial Ca(2+) transporters in DRG, such as MCU, Letm1 and NCLX. Collectively, this work identifies PMCA and mitochondria as the major regulators of presynaptic Ca(2+) signalling at the first sensory synapse, and underlines the high sensitivity of the mitochondrial Ca(2+) uniporter in neurons to cytosolic Ca(2+).
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Affiliation(s)
- Leonid P Shutov
- Y. M. Usachev: Department of Pharmacology, University of Iowa Carver College of Medicine, 2-340F BSB, 51 Newton Road, Iowa City, IA 52242, USA
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Sanchez V, Feinstein SD, Lunardi N, Joksovic PM, Boscolo A, Todorovic SM, Jevtovic-Todorovic V. General Anesthesia Causes Long-term Impairment of Mitochondrial Morphogenesis and Synaptic Transmission in Developing Rat Brain. Anesthesiology 2011; 115:992-1002. [PMID: 21909020 PMCID: PMC3203321 DOI: 10.1097/aln.0b013e3182303a63] [Citation(s) in RCA: 138] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
BACKGROUND Clinically used general anesthetics, alone or in combination, are damaging to the developing mammalian brain. In addition to causing widespread apoptotic neurodegeneration in vulnerable brain regions, exposure to general anesthesia at the peak of synaptogenesis causes learning and memory deficiencies later in life. In vivo rodent studies have suggested that activation of the intrinsic (mitochondria-dependent) apoptotic pathway is the earliest warning sign of neuronal damage, suggesting that a disturbance in mitochondrial integrity and function could be the earliest triggering events. METHODS Because proper and timely mitochondrial morphogenesis is critical for brain development, the authors examined the long-term effects of a commonly used anesthesia combination (isoflurane, nitrous oxide, and midazolam) on the regional distribution, ultrastructural properties, and electron transport chain function of mitochondria, as well as synaptic neurotransmission, in the subiculum of rat pups. RESULTS This anesthesia, administered at the peak of synaptogenesis, causes protracted injury to mitochondria, including significant enlargement of mitochondria (more than 30%, P < 0.05), impairment of their structural integrity, an approximately 28% increase in their complex IV activity (P < 0.05), and a twofold decrease in their regional distribution in presynaptic neuronal profiles (P < 0.05), where their presence is important for the normal development and functioning of synapses. Consequently, the authors showed that impaired mitochondrial morphogenesis is accompanied by heightened autophagic activity, decrease in mitochondrial density (approximately 27%, P < 0.05), and long-lasting disturbances in inhibitory synaptic neurotransmission. The interrelation of these phenomena remains to be established. CONCLUSION Developing mitochondria are exquisitely vulnerable to general anesthesia and may be important early target of anesthesia-induced developmental neurodegeneration.
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Affiliation(s)
- Victoria Sanchez
- Dept. of Anesthesiology, University of Virginia, Charlottesville, Virginia
- Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia
| | - Shawn D. Feinstein
- Dept. of Anesthesiology, University of Virginia, Charlottesville, Virginia
| | - Nadia Lunardi
- Dept. of Anesthesiology, University of Virginia, Charlottesville, Virginia
- Dept. of Anesthesiology and Pharmacology, University of Padova, Padova, Italy
| | - Pavle M. Joksovic
- Dept. of Anesthesiology, University of Virginia, Charlottesville, Virginia
- Dept. of Psychiatry, Yale University, New Haven, Connecticut
| | - Annalisa Boscolo
- Dept. of Anesthesiology, University of Virginia, Charlottesville, Virginia
- Dept. of Anesthesiology and Pharmacology, University of Padova, Padova, Italy
| | - Slobodan M. Todorovic
- Dept. of Anesthesiology, University of Virginia, Charlottesville, Virginia
- Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia
| | - Vesna Jevtovic-Todorovic
- Dept. of Anesthesiology, University of Virginia, Charlottesville, Virginia
- Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia
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Rueda N, Flórez J, Martínez-Cué C. The Ts65Dn mouse model of Down syndrome shows reduced expression of the Bcl-X(L) antiapoptotic protein in the hippocampus not accompanied by changes in molecular or cellular markers of cell death. Int J Dev Neurosci 2011; 29:711-6. [PMID: 21684326 DOI: 10.1016/j.ijdevneu.2011.06.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 05/20/2011] [Accepted: 06/02/2011] [Indexed: 11/19/2022] Open
Abstract
The Ts65Dn (TS) mouse, the most widely used model of Down syndrome (DS), has a partial trisomy of a segment of chromosome 16 that is homologous to the distal part of human chromosome 21. This mouse shares many phenotypic characteristics with people with DS including neuromorphological, neurochemical, and cognitive disturbances. Both TS and DS brains show earlier aging and neurodegeneration. Since fibroblast cultures from TS mice and human DS hippocampal regions show increased apoptotic cell death it has been suggested that alterations in cerebral apoptosis might be implicated in the cognitive deficits found in TS mice and in people with DS. In the present study we have evaluated brain expression levels of several proapoptotic and antiapoptotic proteins from the mitochondrial (Bcl-2, Bcl-X(L), Bax and Bad) and the extrinsic (Fas-R and Fas-L) apoptotic pathways as well as the final executioner caspase-3, in the cortex and hippocampus of TS mice. No significant alterations in the expression levels of the proapoptotic Bad and Bax or the antiapoptotic Bcl-2 proteins in the cortex or hippocampus were found in TS mice. However, TS mice showed downregulation of Bcl-X(L) in the hippocampus. In the extrinsic pathway we found unchanged levels of Fas-L in both structures and also in the expression levels of Fas-R in the hippocampus. Although Bcl-X(L) downregulation suggests that the hippocampus of TS mice is less protected against programmed cell death, we did not find any evidence for increased apoptosis in TS mice since neither TUNEL-positive cells nor active caspase-3 expression were found in cortex or hippocampus of TS or CO mice.
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Affiliation(s)
- Noemí Rueda
- Department of Physiology and Pharmacology, University of Cantabria, Spain
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7
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General anesthesia causes long-lasting disturbances in the ultrastructural properties of developing synapses in young rats. Neurotox Res 2009; 17:179-88. [PMID: 19626389 DOI: 10.1007/s12640-009-9088-z] [Citation(s) in RCA: 142] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2008] [Revised: 05/12/2009] [Accepted: 06/11/2009] [Indexed: 10/20/2022]
Abstract
Common general anesthetics administered to young rats at the peak of brain development cause widespread apoptotic neurodegeneration in their immature brain. Behavioral studies have shown that this leads to learning and memory deficiencies later in life. The subiculum, a part of the hippocampus proper and Papez's circuit, is involved in cognitive development and is vulnerable to anesthesia-induced developmental neurodegeneration. This degeneration is manifested by acute substantial neuroapoptotic damage and permanent neuronal loss in later stages of synaptogenesis. Since synapse formation is a critical component of brain development, we examined the effects of highly neurotoxic anesthesia combination (isoflurane, nitrous oxide, and midazolam) on ultrastructural development of synapses in the rat subiculum. We found that this anesthesia, when administered at the peak of synaptogenesis, causes long-lasting injury to the subicular neuropil. This is manifested as neuropil scarcity and disarray, morphological changes indicative of mitochondria degeneration, a decrease in the number of neuronal profiles with multiple synaptic boutons and significant decreases in synapse volumetric densities. We believe that observed morphological disturbances of developing synapses may, at least in part, contribute to the learning and memory deficits that occur later in life after exposure of the immature brain to general anesthesia.
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8
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Jonas EA. Molecular participants in mitochondrial cell death channel formation during neuronal ischemia. Exp Neurol 2009; 218:203-12. [PMID: 19341732 DOI: 10.1016/j.expneurol.2009.03.025] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2009] [Revised: 03/11/2009] [Accepted: 03/14/2009] [Indexed: 12/30/2022]
Abstract
Mitochondrial ion channels are involved in numerous cellular processes. Membrane pores and transporters regulate the influx and efflux of calcium, sodium, potassium, zinc and determine the membrane compartmentalization of numerous cytosolic metabolites. The permeability of the inner membrane to ions and solutes helps determine the membrane potential of the inner membrane, but the permeability of the outer membrane, controlled in part by VDAC and the BCL-2 family proteins, regulates the release of important signaling molecules that determine the onset of programmed cell death. BCL-2 family proteins have properties of ion channels and perform specialized physiological functions, for example, regulating the strength and pattern of synaptic transmission, in addition to their well known role in cell death. The ion channels of the inner and outer membranes may come together in a complex of proteins during programmed cell death, particularly during neuronal ischemia, where elevated levels of the divalents calcium and zinc activate inner membrane ion channel conductances. The variety of possible molecular participants within the ion channel complex may be matched only by the variety of different types of programmed cell death.
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Affiliation(s)
- Elizabeth Ann Jonas
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, USA.
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Skalska J, Bednarczyk P, Piwońska M, Kulawiak B, Wilczynski G, Dołowy K, Kudin AP, Kunz WS, Szewczyk A. Calcium ions regulate K⁺ uptake into brain mitochondria: the evidence for a novel potassium channel. Int J Mol Sci 2009; 10:1104-20. [PMID: 19399240 PMCID: PMC2672021 DOI: 10.3390/ijms10031104] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Revised: 03/06/2009] [Accepted: 03/10/2009] [Indexed: 11/28/2022] Open
Abstract
The mitochondrial response to changes of cytosolic calcium concentration has a strong impact on neuronal cell metabolism and viability. We observed that Ca(2+) additions to isolated rat brain mitochondria induced in potassium ion containing media a mitochondrial membrane potential depolarization and an accompanying increase of mitochondrial respiration. These Ca(2+) effects can be blocked by iberiotoxin and charybdotoxin, well known inhibitors of large conductance potassium channel (BK(Ca) channel). Furthermore, NS1619 - a BK(Ca) channel opener - induced potassium ion-specific effects on brain mitochondria similar to those induced by Ca(2+). These findings suggest the presence of a calcium-activated, large conductance potassium channel (sensitive to charybdotoxin and NS1619), which was confirmed by reconstitution of the mitochondrial inner membrane into planar lipid bilayers. The conductance of the reconstituted channel was 265 pS under gradient (50/450 mM KCl) conditions. Its reversal potential was equal to 50 mV, which proved that the examined channel was cation-selective. We also observed immunoreactivity of anti-beta(4) subunit (of the BK(Ca) channel) antibodies with ~26 kDa proteins of rat brain mitochondria. Immunohistochemical analysis confirmed the predominant occurrence of beta(4) subunit in neuronal mitochondria. We hypothesize that the mitochondrial BK(Ca) channel represents a calcium sensor, which can contribute to neuronal signal transduction and survival.
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Affiliation(s)
- Jolanta Skalska
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur st., 02–093 Warsaw, Poland; E-Mails:
(J.S.);
(P.B.);
(M.P.);
(B.K.);
(A.S.)
| | - Piotr Bednarczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur st., 02–093 Warsaw, Poland; E-Mails:
(J.S.);
(P.B.);
(M.P.);
(B.K.);
(A.S.)
- Department of Biophysics, Agricultural University SGGW, 159 Nowoursynowska St., 02–776 Warsaw, Poland; E-Mail:
| | - Marta Piwońska
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur st., 02–093 Warsaw, Poland; E-Mails:
(J.S.);
(P.B.);
(M.P.);
(B.K.);
(A.S.)
| | - Bogusz Kulawiak
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur st., 02–093 Warsaw, Poland; E-Mails:
(J.S.);
(P.B.);
(M.P.);
(B.K.);
(A.S.)
| | - Grzegorz Wilczynski
- Laboratory of Molecular and Systemic Neuromorphology, Nencki Institute of Experimental Biology, 3 Pasteur st., 02–093 Warsaw, Poland; E-Mail:
| | - Krzysztof Dołowy
- Department of Biophysics, Agricultural University SGGW, 159 Nowoursynowska St., 02–776 Warsaw, Poland; E-Mail:
| | - Alexei P. Kudin
- Division of Neurochemistry, Department of Epileptology and Life&Brain Center, University Bonn Medical Center, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany; E-Mail:
| | - Wolfram S. Kunz
- Division of Neurochemistry, Department of Epileptology and Life&Brain Center, University Bonn Medical Center, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany; E-Mail:
- Author to whom correspondence should be addressed; E-Mail:
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, 3 Pasteur st., 02–093 Warsaw, Poland; E-Mails:
(J.S.);
(P.B.);
(M.P.);
(B.K.);
(A.S.)
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Mechanisms of prolonged presynaptic Ca2+ signaling and glutamate release induced by TRPV1 activation in rat sensory neurons. J Neurosci 2008; 28:5295-311. [PMID: 18480286 DOI: 10.1523/jneurosci.4810-07.2008] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Transient receptor potential vanilloid receptor 1 (TRPV1)-mediated release of neuroactive peptides and neurotransmitters from the peripheral and central terminals of primary sensory neurons can critically contribute to nociceptive processing at the periphery and in the CNS. However, the mechanisms that link TRPV1 activation with Ca2+ signaling at the release sites and neurosecretion are poorly understood. Here we demonstrate that a brief stimulation of the receptor using either capsaicin or the endogenous TRPV1 agonist N-arachidonoyl-dopamine induces a prolonged elevation of presynaptic [Ca2+](i) and a concomitant enhancement of glutamate release at sensory synapses. Initiation of this response required Ca2+ entry, primarily via TRPV1. The sustained phase of the response was independent of extracellular Ca2+ and was prevented by inhibitors of mitochondrial Ca2+ uptake and release mechanisms. Measurements using a mitochondria-targeted Ca2+ indicator, mtPericam, revealed that TRPV1 activation elicits a long-lasting Ca2+ elevation in presynaptic mitochondria. The concentration of TRPV1 agonist determined the duration of mitochondrial and cytosolic Ca2+ signals in presynaptic boutons and, consequently, the period of enhanced glutamate release and action potential firing by postsynaptic neurons. These data suggest that mitochondria control vanilloid-induced neurotransmission by translating the strength of presynaptic TRPV1 stimulation into duration of the postsynaptic response.
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Tiede LM, Rocha-Sanchez SM, Hallworth R, Nichols MG, Beisel K. Determination of hair cell metabolic state in isolated cochlear preparations by two-photon microscopy. JOURNAL OF BIOMEDICAL OPTICS 2007; 12:021004. [PMID: 17477711 PMCID: PMC1992521 DOI: 10.1117/1.2714777] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Currently there is no accepted method to measure the metabolic status of the organ of Corti. Since metabolism and mitochondrial dysfunction are expected to play a role in many different hearing disorders, here for the first time we employ two-photon metabolic imaging to assess the metabolic status of the cochlea. When excited with ultrashort pulses of 740-nm light, both inner and outer hair cells in isolated murine cochlear preparations exhibited intrinsic fluorescence. This fluorescence is characterized and shown to be consistent with a mixture of oxidized flavoproteins (Fp) and reduced nicotinamide adenine dinucleotide (NADH). The location of the fluorescence within hair cells is also consistent with the different mitochondrial distributions in these cell types. Treatments with cyanide and mitochondrial uncouplers show that hair cells are metabolically active. Both NADH and Fp in inner hair cells gradually become completely oxidized within 50 min from the time of death of the animal. Outer hair cells show similar trends but are found to have greater variability. We show that it is possible to use two-photon metabolic imaging to assess metabolism in the mouse organ of Corti.
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Affiliation(s)
- Leann M Tiede
- Creighton University, Department of Biomedical Sciences, Omaha, Nebraska 68178, USA.
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12
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Abstract
Mitochondria are central for various cellular processes that include ATP production, intracellular Ca(2+) signaling, and generation of reactive oxygen species. Neurons critically depend on mitochondrial function to establish membrane excitability and to execute the complex processes of neurotransmission and plasticity. While much information about mitochondrial properties is available from studies on isolated mitochondria and dissociated cell cultures, less is known about mitochondrial function in intact neurons in brain tissue. However, a detailed description of the interactions between mitochondrial function, energy metabolism, and neuronal activity is crucial for the understanding of the complex physiological behavior of neurons, as well as the pathophysiology of various neurological diseases. The combination of new fluorescence imaging techniques, electrophysiology, and brain slice preparations provides a powerful tool to study mitochondrial function during neuronal activity, with high spatiotemporal resolution. This review summarizes recent findings on mitochondrial Ca(2+) transport, mitochondrial membrane potential (DeltaPsi(m)), and energy metabolism during neuronal activity. We will first discuss interactions of these parameters for experimental stimulation conditions that can be related to the physiological range. We will then describe how mitochondrial and metabolic dysfunction develops during pathological neuronal activity, focusing on temporal lobe epilepsy and its experimental models. The aim is to illustrate that 1) the structure of the mitochondrial compartment is highly dynamic in neurons, 2) there is a fine-tuned coupling between neuronal activity and mitochondrial function, and 3) mitochondria are of central importance for the complex behavior of neurons.
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Affiliation(s)
- Oliver Kann
- Institut für Neurophysiologie, Charité-Universitätsmedizin Berlin, Tucholskystrasse 2, 10117 Berlin, Germany.
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Li J, Imitola J, Snyder EY, Sidman RL. Neural stem cells rescue nervous purkinje neurons by restoring molecular homeostasis of tissue plasminogen activator and downstream targets. J Neurosci 2006; 26:7839-48. [PMID: 16870729 PMCID: PMC6674224 DOI: 10.1523/jneurosci.1624-06.2006] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neural stem cells (NSCs) offer special therapeutic prospects because they can be isolated from the CNS, expanded ex vivo, and re-implanted into diseased CNS where they not only migrate and differentiate according to cues from host tissue but also appear to be capable of affecting host cells. In nervous (nr) mutant mice Purkinje neuron (PN) mitochondria become abnormal by the second postnatal week, and a majority of PNs die in the fourth to fifth weeks. We previously identified in nr cerebellum a 10-fold increase in tissue plasminogen activator (tPA) as a key component of the mechanism causing nr PN death. Here we report that undifferentiated wild-type murine NSCs, when transplanted into the newborn nr cerebellar cortex, do not replace host PNs but contact imperiled PNs and support their mitochondrial function, dendritic growth, and synaptogenesis, subsequently leading to the rescue of host PNs and restoration of motor coordination. This protection of nr PNs also is verified by an in vitro organotypic slice model in which nr cerebellar slices are cocultured with NSCs. Most importantly, the integrated NSCs in young nr cerebellum rectify excessive tPA mRNA and protein to close to normal levels and protect the mitochondrial voltage-dependent anion channel and neurotrophins, downstream targets of the tPA/plasmin proteolytic system. This report demonstrates for the first time that NSCs can rescue imperiled host neurons by rectifying their gene expression, elevating somatic stem cell therapeutic potential beyond solely cell replacement strategy.
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Li J, Ma Y, Teng YD, Zheng K, Vartanian TK, Snyder EY, Sidman RL. Purkinje neuron degeneration in nervous (nr) mutant mice is mediated by a metabolic pathway involving excess tissue plasminogen activator. Proc Natl Acad Sci U S A 2006; 103:7847-52. [PMID: 16682647 PMCID: PMC1472533 DOI: 10.1073/pnas.0602440103] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Purkinje neurons (PNs), the central cells in cerebellar circuitry and function, constitute a vulnerable population in many human genetic, malignant, hypoxic, and toxic diseases. In the nervous (nr) mutant mouse, the majority of PNs die in the fourth to fifth postnatal weeks, but the responsible molecules are unknown. We first disclose a remarkable increase in mRNA expression and protein concentration in the nr cerebellum of tissue plasminogen activator (tPA), a gene closely linked to the mapped but as-yet-uncloned nr locus. Evidence that excessive tPA triggers nr PN death was obtained with organotypic slice cultures expressing the nr PN phenotype, in which an inhibitor of tPA led to increased nr PN survival. An antagonist of protein kinase C, a downstream component in the tPA pathway, also increased nr PN survival. Additional downstream targets in the tPA pathway (the mitochondrial voltage-dependent anion channel, brain-derived neurotrophic factor, and neurotrophin 3) were also abnormal, in parallel with the alterations in PN mitochondrial morphology, dendritic growth, and synaptogenesis that culminate in nr PN death and motor incoordination. We thus propose a molecular pathway by which the excessive tPA in nr cerebellum mediates PN degeneration.
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Affiliation(s)
- Jianxue Li
- *Department of Neurology, Beth Israel Deaconess Medical Center, and
| | - Yinghua Ma
- *Department of Neurology, Beth Israel Deaconess Medical Center, and
| | - Yang D. Teng
- Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115; and
| | - Kangni Zheng
- *Department of Neurology, Beth Israel Deaconess Medical Center, and
| | | | - Evan Y. Snyder
- Stem Cell and Regeneration Program, The Burnham Institute for Medical Research, La Jolla, CA 92037
- To whom correspondence may be addressed. E-mail:
or
| | - Richard L. Sidman
- *Department of Neurology, Beth Israel Deaconess Medical Center, and
- To whom correspondence may be addressed. E-mail:
or
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