1
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Patel SH, Bachmann M, Kadow S, Wilson GC, Abdel-Salam MML, Xu K, Keitsch S, Soddemann M, Wilker B, Becker KA, Carpinteiro A, Ahmad SA, Szabo I, Gulbins E. Simultaneous targeting of mitochondrial Kv1.3 and lysosomal acid sphingomyelinase amplifies killing of pancreatic ductal adenocarcinoma cells in vitro and in vivo. J Mol Med (Berl) 2023; 101:295-310. [PMID: 36790532 PMCID: PMC10036429 DOI: 10.1007/s00109-023-02290-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Revised: 01/12/2023] [Accepted: 01/17/2023] [Indexed: 02/16/2023]
Abstract
Pancreas ductal adenocarcinoma (PDAC) remains a malignant tumor with very poor prognosis and low 5-year overall survival. Here, we aimed to simultaneously target mitochondria and lysosomes as a new treatment paradigm of malignant pancreas cancer in vitro and in vivo. We demonstrate that the clinically used sphingosine analog FTY-720 together with PAPTP, an inhibitor of mitochondrial Kv1.3, induce death of pancreas cancer cells in vitro and in vivo. The combination of both drugs results in a marked inhibition of the acid sphingomyelinase and accumulation of cellular sphingomyelin in vitro and in vivo in orthotopic and flank pancreas cancers. Mechanistically, PAPTP and FTY-720 cause a disruption of both mitochondria and lysosomes, an alteration of mitochondrial bioenergetics and accumulation of cytoplasmic Ca2+, events that collectively mediate cell death. Our findings point to an unexpected cross-talk between lysosomes and mitochondria mediated by sphingolipid metabolism. We show that the combination of PAPTP and FTY-720 induces massive death of pancreas cancer cells, thereby leading to a substantially delayed and reduced PDAC growth in vivo. KEY MESSAGES: FTY-720 inhibits acid sphingomyelinase in pancreas cancer cells (PDAC). FTY-720 induces sphingomyelin accumulation and lysosomal dysfunction. The mitochondrial Kv1.3 inhibitor PAPTP disrupts mitochondrial functions. PAPTP and FTY-720 synergistically kill PDAC in vitro. The combination of FTY-720 and PAPTP greatly delays PDAC growth in vivo.
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Affiliation(s)
- Sameer H Patel
- Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Magdalena Bachmann
- Department of Biologyand , CNR Institute of Neurosciences, University of Padua, Padua, Italy
| | - Stephanie Kadow
- Institute of Molecular Biology, University Hospital Essen, University of Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany
| | - Gregory C Wilson
- Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Mostafa M L Abdel-Salam
- Department of Biologyand , CNR Institute of Neurosciences, University of Padua, Padua, Italy
| | - Kui Xu
- Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Simone Keitsch
- Institute of Molecular Biology, University Hospital Essen, University of Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany
| | - Matthias Soddemann
- Institute of Molecular Biology, University Hospital Essen, University of Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany
| | - Barbara Wilker
- Institute of Molecular Biology, University Hospital Essen, University of Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany
| | - Katrin Anne Becker
- Institute of Molecular Biology, University Hospital Essen, University of Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany
| | - Alexander Carpinteiro
- Institute of Molecular Biology, University Hospital Essen, University of Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany
| | - Syed A Ahmad
- Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Ildiko Szabo
- Department of Biologyand , CNR Institute of Neurosciences, University of Padua, Padua, Italy.
| | - Erich Gulbins
- Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
- Institute of Molecular Biology, University Hospital Essen, University of Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany.
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2
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Terry LE, Arige V, Neumann J, Wahl AM, Knebel TR, Chaffer JW, Malik S, Liston A, Humblet-Baron S, Bultynck G, Yule DI. Missense mutations in inositol 1,4,5-trisphosphate receptor type 3 result in leaky Ca 2+ channels and activation of store-operated Ca 2+ entry. iScience 2022; 25:105523. [PMID: 36444295 PMCID: PMC9700043 DOI: 10.1016/j.isci.2022.105523] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 10/10/2022] [Accepted: 11/04/2022] [Indexed: 11/09/2022] Open
Abstract
Mutations in all subtypes of the inositol 1,4,5-trisphosphate receptor Ca2+ release channel are associated with human diseases. In this report, we investigated the functionality of three neuropathy-associated missense mutations in IP3R3 (V615M, T1424M, and R2524C). The mutants only exhibited function when highly over-expressed compared to endogenous hIP3R3. All variants resulted in elevated basal cytosolic Ca2+ levels, decreased endoplasmic reticulum Ca2+ store content, and constitutive store-operated Ca2+ entry in the absence of any stimuli, consistent with a leaky IP3R channel pore. These variants differed in channel function; when stably over-expressed the R2524C mutant was essentially dead, V615M was poorly functional, and T1424M exhibited activity greater than that of the corresponding wild-type following threshold stimulation. These results demonstrate that a common feature of these mutations is decreased IP3R3 function. In addition, these mutations exhibit a novel phenotype manifested as a constitutively open channel, which inappropriately gates SOCE in the absence of stimulation.
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Affiliation(s)
- Lara E. Terry
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642, USA
| | - Vikas Arige
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642, USA
| | - Julika Neumann
- KU Leuven, Department of Microbiology and Immunology, Leuven, Belgium
| | - Amanda M. Wahl
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642, USA
| | - Taylor R. Knebel
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642, USA
| | - James W. Chaffer
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642, USA
| | - Sundeep Malik
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642, USA
| | - Adrian Liston
- KU Leuven, Department of Microbiology and Immunology, Leuven, Belgium
| | | | - Geert Bultynck
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, Leuven, Belgium
| | - David I. Yule
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642, USA
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3
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Jackson J, Wischhof L, Scifo E, Pellizzer A, Wang Y, Piazzesi A, Gentile D, Siddig S, Stork M, Hopkins CE, Händler K, Weis J, Roos A, Schultze JL, Nicotera P, Ehninger D, Bano D. SGPL1 stimulates VPS39 recruitment to the mitochondria in MICU1 deficient cells. Mol Metab 2022; 61:101503. [PMID: 35452878 PMCID: PMC9170783 DOI: 10.1016/j.molmet.2022.101503] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 04/08/2022] [Accepted: 04/15/2022] [Indexed: 01/21/2023] Open
Abstract
Objective Mitochondrial “retrograde” signaling may stimulate organelle biogenesis as a compensatory adaptation to aberrant activity of the oxidative phosphorylation (OXPHOS) system. To maintain energy-consuming processes in OXPHOS deficient cells, alternative metabolic pathways are functionally coupled to the degradation, recycling and redistribution of biomolecules across distinct intracellular compartments. While transcriptional regulation of mitochondrial network expansion has been the focus of many studies, the molecular mechanisms promoting mitochondrial maintenance in energy-deprived cells remain poorly investigated. Methods We performed transcriptomics, quantitative proteomics and lifespan assays to identify pathways that are mechanistically linked to mitochondrial network expansion and homeostasis in Caenorhabditis elegans lacking the mitochondrial calcium uptake protein 1 (MICU-1/MICU1). To support our findings, we carried out biochemical and image analyses in mammalian cells and mouse-derived tissues. Results We report that micu-1(null) mutations impair the OXPHOS system and promote C. elegans longevity through a transcriptional program that is independent of the mitochondrial calcium uniporter MCU-1/MCU and the essential MCU regulator EMRE-1/EMRE. We identify sphingosine phosphate lyase SPL-1/SGPL1 and the ATFS-1-target HOPS complex subunit VPS-39/VPS39 as critical lifespan modulators of micu-1(null) mutant animals. Cross-species investigation indicates that SGPL1 upregulation stimulates VPS39 recruitment to the mitochondria, thereby enhancing mitochondria-lysosome contacts. Consistently, VPS39 downregulation compromises mitochondrial network maintenance and basal autophagic flux in MICU1 deficient cells. In mouse-derived muscles, we show that VPS39 recruitment to the mitochondria may represent a common signature associated with altered OXPHOS system. Conclusions Our findings reveal a previously unrecognized SGPL1/VPS39 axis that stimulates intracellular organelle interactions and sustains autophagy and mitochondrial homeostasis in OXPHOS deficient cells. micu-1(null) nematodes are long-lived mitochondrial mutants. MICU-1/MICU1 deficiency stimulates VPS-39/VPS39 and SPL-1/SGPL1 upregulation. VPS-39 sustains mitochondrial network expansion in micu-1(null) nematodes. VPS39 and SGPL1 expression influences mitochondria-lysosome contact sites in MICU1 deficient cells. VPS39/SGPL1 signaling may be a common signature of mitochondrial deficient cells.
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Affiliation(s)
- Joshua Jackson
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Lena Wischhof
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Enzo Scifo
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Anna Pellizzer
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Yiru Wang
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Antonia Piazzesi
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Debora Gentile
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Sana Siddig
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Miriam Stork
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | | | - Kristian Händler
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany; PRECISE Platform for Single Cell Genomics and Epigenomics, German Center for Neurodegenerative Diseases (DZNE), University of Bonn, Bonn, Germany
| | - Joachim Weis
- Institute of Neuropathology, RWTH Aachen University Hospital, Aachen, Germany
| | - Andreas Roos
- Universitätsklinikum Essen and Universität Duisburg-Essen, Essen, Germany
| | - Joachim L Schultze
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany; PRECISE Platform for Single Cell Genomics and Epigenomics, German Center for Neurodegenerative Diseases (DZNE), University of Bonn, Bonn, Germany; LIMES Institute, Department for Genomics and Immunoregulation, University of Bonn, Bonn, Germany
| | | | - Dan Ehninger
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Daniele Bano
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany.
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4
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Kociszewska D, Chan J, Thorne PR, Vlajkovic SM. The Link between Gut Dysbiosis Caused by a High-Fat Diet and Hearing Loss. Int J Mol Sci 2021; 22:13177. [PMID: 34947974 PMCID: PMC8708400 DOI: 10.3390/ijms222413177] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 12/02/2021] [Accepted: 12/06/2021] [Indexed: 12/17/2022] Open
Abstract
This review aims to provide a conceptual and theoretical overview of the association between gut dysbiosis and hearing loss. Hearing loss is a global health issue; the World Health Organisation (WHO) estimates that 2.5 billion people will be living with some degree of hearing loss by 2050. The aetiology of sensorineural hearing loss (SNHL) is complex and multifactorial, arising from congenital and acquired causes. Recent evidence suggests that impaired gut health may also be a risk factor for SNHL. Inflammatory bowel disease (IBD), type 2 diabetes, diet-induced obesity (DIO), and high-fat diet (HFD) all show links to hearing loss. Previous studies have shown that a HFD can result in microangiopathy, impaired insulin signalling, and oxidative stress in the inner ear. A HFD can also induce pathological shifts in gut microbiota and affect intestinal barrier (IB) integrity, leading to a leaky gut. A leaky gut can result in chronic systemic inflammation, which may affect extraintestinal organs. Here, we postulate that changes in gut microbiota resulting from a chronic HFD and DIO may cause a systemic inflammatory response that can compromise the permeability of the blood-labyrinth barrier (BLB) in the inner ear, thus inducing cochlear inflammation and hearing deficits.
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Affiliation(s)
| | | | | | - Srdjan M. Vlajkovic
- Department of Physiology and The Eisdell Moore Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, Auckland 1142, New Zealand; (D.K.); (J.C.); (P.R.T.)
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5
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Terry LE, Alzayady KJ, Wahl AM, Malik S, Yule DI. Disease-associated mutations in inositol 1,4,5-trisphosphate receptor subunits impair channel function. J Biol Chem 2020; 295:18160-18178. [PMID: 33093175 PMCID: PMC7939385 DOI: 10.1074/jbc.ra120.015683] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 10/21/2020] [Indexed: 01/27/2023] Open
Abstract
The inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs), which form tetrameric channels, play pivotal roles in regulating the spatiotemporal patterns of intracellular calcium signals. Mutations in IP3Rs have been increasingly associated with many debilitating human diseases such as ataxia, Gillespie syndrome, and generalized anhidrosis. However, how these mutations affect IP3R function, and how the perturbation of as-sociated calcium signals contribute to the pathogenesis and severity of these diseases remains largely uncharacterized. Moreover, many of these diseases occur as the result of autosomal dominant inheritance, suggesting that WT and mutant subunits associate in heterotetrameric channels. How the in-corporation of different numbers of mutant subunits within the tetrameric channels affects its activities and results in different disease phenotypes is also unclear. In this report, we investigated representative disease-associated missense mutations to determine their effects on IP3R channel activity. Additionally, we designed concatenated IP3R constructs to create tetrameric channels with a predefined subunit composition to explore the functionality of heteromeric channels. Using calcium imaging techniques to assess IP3R channel function, we observed that all the mutations studied resulted in severely attenuated Ca2+ release when expressed as homotetramers. However, some heterotetramers retained varied degrees of function dependent on the composition of the tetramer. Our findings suggest that the effect of mutations depends on the location of the mutation in the IP3R structure, as well as on the stoichiometry of mutant subunits assembled within the tetrameric channel. These studies provide insight into the pathogenesis and penetrance of these devastating human diseases.
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Affiliation(s)
- Lara E Terry
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, USA
| | - Kamil J Alzayady
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, USA
| | - Amanda M Wahl
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, USA
| | - Sundeep Malik
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, USA
| | - David I Yule
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, USA.
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6
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Dhukhwa A, Bhatta P, Sheth S, Korrapati K, Tieu C, Mamillapalli C, Ramkumar V, Mukherjea D. Targeting Inflammatory Processes Mediated by TRPVI and TNF-α for Treating Noise-Induced Hearing Loss. Front Cell Neurosci 2019; 13:444. [PMID: 31632242 PMCID: PMC6786284 DOI: 10.3389/fncel.2019.00444] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Accepted: 09/18/2019] [Indexed: 12/20/2022] Open
Abstract
Noise trauma is the most common cause of hearing loss in adults. There are no known FDA approved drugs for prevention or rescue of noise-induced hearing loss (NIHL). In this study, we provide evidence that implicates stress signaling molecules (TRPV1, NOX3, and TNF-α) in NIHL. Furthermore, we provide evidence that inhibiting any one of these moieties can prevent and treat NIHL when administered within a window period. Hearing loss induced by loud noise is associated with the generation of reactive oxygen species (ROS), increased calcium (Ca2+) in the endolymph and hair cells, and increased inflammation in the cochlea. Increased (Ca2+) and ROS activity persists for several days after traumatic noise exposure (NE). Chronic increases in (Ca2+) and ROS have been shown to increase inflammation and apoptosis in various tissue. However, the precise role of Ca2+ up-regulation and the resulting inflammation causing a positive feedback loop in the noise-exposed cochlea to generate sustained toxic amounts of Ca2+ are unknown. Here we show cochlear TRPV1 dysregulation is a key step in NIHL, and that inflammatory TNF-α cytokine-mediated potentiation of TRPV1 induced Ca2+ entry is an essential mechanism of NIHL. In the Wistar rat model, noise produces an acute (within 48 h) and a chronic (within 21 days) increase in cochlear gene expression of TRPV1, NADPH oxidase 3 (NOX3) and pro-inflammatory mediators such as tumor necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX2). Additionally, we also show that H2O2 (100 μM) produces a robust increase in Ca2+ entry in cell cultures which is enhanced by TNF-α via the TRPV1 channel and which involves ERK1/2 phosphorylation. Mitigation of NIHL could be achieved by using capsaicin (TRPV1 agonist that rapidly desensitizes TRPV1. This mechanism is used in the treatment of pain in diabetic peripheral neuropathy) pretreatment or by inhibition of TNF-α with Etanercept (ETA), administered up to 7 days prior to NE or within 24 h of noise. Our results demonstrate the importance of the synergistic interaction between TNF-α and TRPV1 in the cochlea and suggest that these are important therapeutic targets for treating NIHL.
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Affiliation(s)
- Asmita Dhukhwa
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - Puspanjali Bhatta
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - Sandeep Sheth
- Department of Pharmaceutical Sciences, College of Pharmacy, Larkin University, Miami, FL, United States
| | - Krishi Korrapati
- Department of Otolaryngology, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - Coral Tieu
- Department of Otolaryngology, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - Chaitanya Mamillapalli
- Department of Internal Medicine, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - Vickram Ramkumar
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - Debashree Mukherjea
- Department of Otolaryngology, Southern Illinois University School of Medicine, Springfield, IL, United States
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7
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Bano D, Jewell SA, Nicotera P. Calcium signaling then and now, via Stockholm. Biochem Biophys Res Commun 2016; 482:384-387. [PMID: 27908727 DOI: 10.1016/j.bbrc.2016.11.151] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Accepted: 11/27/2016] [Indexed: 11/19/2022]
Affiliation(s)
- Daniele Bano
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Sarah A Jewell
- German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
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8
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Finkbeiner S. Calcium-mediated Gene Expression: Mechanism for Neuronal Plasticity and Survival. Neuroscientist 2016. [DOI: 10.1177/107385849500100603] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Calcium plays a central role in many proposed mechanisms of neuronal plasticity as well as neuronal death and degeneration. The observation that certain calcium channel antag onists dramatically protect neurons in a variety of neurological disease models has led to a general strategy for neuroprotection: broadly block calcium entry. However, emerging evidence suggests that calcium can promote neuronal survival and plasticity or death and degeneration, depending on the route of entry. Calcium may partly promote neuronal survival through the autocrine action of neurotrophins such as brain-derived neurotrophic factor. Calcium-mediated neurotrophin secretion may also promote synapse formation during development and in conditions of chronic abnormal neuronal activity such as ep ilepsy. A full understanding of these signal transduction pathways could lead to refined pharmacological strategies that minimize calcium's deadly effects and optimize its growth- and survival-promoting properties. The Neuroscientist 1:317-320,1995
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Abstract
ABSTRACT:In recognition of the 100th anniversary of Charcot’s death we have reviewed possible pathogenic mechanisms in amyotrophic lateral sclerosis (ALS). Advances in the last 5 years in molecular biology and genetics have identified mutations in the cytosolic dismutase (SODI) gene in some patients with familial ALS raising the possibility that oxidative stress may be involved in the pathogenesis. An excitotoxic pathogenesis has been implicated based on elevated plasma and CSF levels of amino acids and altered contents of amino acids in the nervous system of ALS patients and changes in the number of excitatory amino acid receptors. ALS sera containing antibodies to L-type calcium channels and the development of immune mediated lower and upper and lower motor neuron models have revitalized research efforts focusing on an immune basis for ALS. Other pathogenic mechanisms which have been the subject of recent research include elemental toxicity, apoptosis and programmed cell death and possibly a deficiency or abnormality in growth factors. Pathogenic processes for ALS must account for an increasing incidence of ALS, male preponderance, and the selective vulnerability of the corticomotoneuronal system.
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Guerrero-Hernandez A, Verkhratsky A. Calcium signalling in diabetes. Cell Calcium 2014; 56:297-301. [PMID: 25217232 DOI: 10.1016/j.ceca.2014.08.009] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Revised: 08/08/2014] [Accepted: 08/19/2014] [Indexed: 12/31/2022]
Abstract
Molecular cascades responsible for Ca(2+) homeostasis and Ca(2+) signalling could be assembled in highly plastic toolkits that define physiological adaptation of cells to the environment and which are intimately involved in all types of cellular pathology. Control over Ca(2+) concentration in different cellular compartments is intimately linked to cell metabolism, because (i) ATP production requires low Ca(2+), (ii) Ca(2+) homeostatic systems consume ATP and (iii) Ca(2+) signals in mitochondria stimulate ATP synthesis being an essential part of excitation-metabolic coupling. The communication between the ER and mitochondria plays an important role in this metabolic fine tuning. In the insulin resistance state and diabetes this communication has been impaired leading to different disorders, for instance, diminished insulin production by pancreatic β cells, reduced heart and skeletal muscle contractility, reduced NO production by endothelial cells, increased glucose production by liver, increased lipolysis by adipose cells, reduced immune responses, reduced cognitive functions, among others. All these processes eventually trigger degenerative events resulting in overt diabetes due to reduction of pancreatic β cell mass, and different complications of diabetes, such as retinopathy, nephropathy, neuropathy, and different cardiovascular diseases.
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Affiliation(s)
| | - Alexei Verkhratsky
- The University of Manchester, School of Biological Sciences, 1.124 Stopford Building, Oxford Road, Manchester M13 9PT, UK
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11
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Alzayady KJ, Wagner LE, Chandrasekhar R, Monteagudo A, Godiska R, Tall GG, Joseph SK, Yule DI. Functional inositol 1,4,5-trisphosphate receptors assembled from concatenated homo- and heteromeric subunits. J Biol Chem 2013; 288:29772-84. [PMID: 23955339 DOI: 10.1074/jbc.m113.502203] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Vertebrate genomes code for three subtypes of inositol 1,4,5-trisphosphate (IP3) receptors (IP3R1, -2, and -3). Individual IP3R monomers are assembled to form homo- and heterotetrameric channels that mediate Ca(2+) release from intracellular stores. IP3R subtypes are regulated differentially by IP3, Ca(2+), ATP, and various other cellular factors and events. IP3R subtypes are seldom expressed in isolation in individual cell types, and cells often express different complements of IP3R subtypes. When multiple subtypes of IP3R are co-expressed, the subunit composition of channels cannot be specifically defined. Thus, how the subunit composition of heterotetrameric IP3R channels contributes to shaping the spatio-temporal properties of IP3-mediated Ca(2+) signals has been difficult to evaluate. To address this question, we created concatenated IP3R linked by short flexible linkers. Dimeric constructs were expressed in DT40-3KO cells, an IP3R null cell line. The dimeric proteins were localized to membranes, ran as intact dimeric proteins on SDS-PAGE, and migrated as an ∼1100-kDa band on blue native gels exactly as wild type IP3R. Importantly, IP3R channels formed from concatenated dimers were fully functional as indicated by agonist-induced Ca(2+) release. Using single channel "on-nucleus" patch clamp, the channels assembled from homodimers were essentially indistinguishable from those formed by the wild type receptor. However, the activity of channels formed from concatenated IP3R1 and IP3R2 heterodimers was dominated by IP3R2 in terms of the characteristics of regulation by ATP. These studies provide the first insight into the regulation of heterotetrameric IP3R of defined composition. Importantly, the results indicate that the properties of these channels are not simply a blend of those of the constituent IP3R monomers.
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Affiliation(s)
- Kamil J Alzayady
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
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12
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Öztürk G, Cengiz N, Erdoğan E, Him A, Oğuz EK, Yenidünya E, Ayşit N. Two distinct types of dying back axonal degenerationin vitro. Neuropathol Appl Neurobiol 2013; 39:362-76. [DOI: 10.1111/j.1365-2990.2012.01295.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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13
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Jia X, Chen L, Li J, Su R, Shi D, Tang Z. Effect of copper chloride exposure on the membrane potential and cytosolic free calcium in primary cultured chicken hepatocytes. Biol Trace Elem Res 2012; 148:331-5. [PMID: 22447273 DOI: 10.1007/s12011-012-9376-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Accepted: 02/23/2012] [Indexed: 10/28/2022]
Abstract
This study was conducted to examine the effects of copper on membrane potential and cytosolic free calcium in isolated primary chicken hepatocytes which were exposed to different concentration of Cu(2+) (0, 10, 50, 100 μM) or a mixture of Cu(2+) and vitamin C (50 and 50 μM, respectively). Viability, membrane potential, and cytosolic free Ca(2+) of monolayer cultured hepatocytes were investigated at the indicated time point. Results showed that, among the different concentrations of Cu(2+) exposure, the viability of hepatocytes treated with 100 μM Cu(2+) was the worst at the 12th and 24th hours. The effects of Cu(2+) on viability and proliferation were time and dose dependent. Further investigation indicated that Cu(2+) exposure significantly enhanced cytosolic free Ca(2+) in hepatocytes, compared to that in control group, at the 24th hour. Meanwhile, membrane potential was noticeably reduced in hepatocytes increasing concentration of Cu(2+). Taking these results together, we have shown that Cu(2+) can cause toxicity to primary chicken hepatocytes in excessive dose and the effect of Cu(2+) exposure on membrane potential is not site specific, which is probably mediated by the changes of cytosolic free Ca(2+).
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Affiliation(s)
- Xuexia Jia
- College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, China
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Saito Y, Ohguro H, Ohguro I, Sato N, Ishikawa F, Yamazaki H, Metoki T, Ito T, Nakazawa M. Misregulation of rhodopsin phosphorylation and dephosphorylation found in P23H rat retinal degeneration. Clin Ophthalmol 2011; 2:821-8. [PMID: 19668436 PMCID: PMC2699806 DOI: 10.2147/opth.s4359] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
To examine rhodopsin (Rho) functions in P23H rat, kinetics of Rho regeneration and dephosphorylation were investigated by spectrophotometric analysis and immunofluorescence labeling method using specific antibodies toward phosphorylated 334Ser or 338Ser site. Rho dephosphorylation at both sites was extremely delayed in P23H retina as compared to normal ones. Kinetics of Rho regeneration was not altered between normal and P23H rats under dark adaptation. Next, to study the effects of several Ca2+channel blockers on this model, retinal function and morphology were evaluated. Among them, nilvadipine showed a significant protective effect against P23H retinal degeneration. Neurotrophic factor, fibroblast growth factor-2 and Arc, known to suppress the apoptosis in the central nervous system, were significantly upregulated upon administration of nilvadipine. The present study indicates that misregulation of Rho phosphorylation may be involved as an important step in retinal degeneration of P23H and administration of nilvadipine may be a potential therapeutic agent for the retinal degenerations.
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15
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The cytolytic and cytotoxic activities of palytoxin. Toxicon 2011; 57:449-59. [DOI: 10.1016/j.toxicon.2010.12.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2010] [Revised: 12/15/2010] [Accepted: 12/20/2010] [Indexed: 11/18/2022]
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16
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Habib S, Ali A. Biochemistry of nitric oxide. Indian J Clin Biochem 2011; 26:3-17. [PMID: 22211007 PMCID: PMC3068772 DOI: 10.1007/s12291-011-0108-4] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2011] [Accepted: 01/01/2011] [Indexed: 12/21/2022]
Abstract
Nitric oxide (NO) a free radical having both cytoprotective as well as tumor promoting agent is formed from l-arginine by converting it to l-citrulline via nitric oxide synthase enzymes. The reaction product of nitric oxide with superoxide generates potent oxidizing agent, peroxynitrite which is the main mediator of tissue and cellular injury. Peroxynitrite is reactive towards many biomolecules which includes amino acids, nucleic acid bases; metal containing compounds, etc. NO metabolites may play a key role in mediating many of the genotoxic/carcinogenic effects as DNA damage, protein or lipid modification, etc. The basic reactions of nitric oxide can be divided as direct effect of the radical where it alone plays a role in either damaging or protecting the cell milieu and an indirect effect in which the byproducts of nitric oxide formed by convergence of two independent radical generating pathways play the role in biological reactions which mainly involve oxidative and nitrosative stress. Nitric oxide is also capable of directly interacting with mitochondria through inhibition of respiration or by permeability transition. Reaction of nitric oxide with metal ions include its direct interaction with the metals or with oxo complexes thereby reducing them to lower valent state. Excessive production of nitric oxide can be studied by inhibiting the synthetic pathway of nitric oxide using both selective or specific nitric oxide synthase inhibitor or non-selective nitric oxide synthase inhibitor with respect to isoforms of nitric oxide.
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Affiliation(s)
- Safia Habib
- Department of Biochemistry, Faculty of Medicine, Aligarh Muslim University, Aligarh, 202002 India
| | - Asif Ali
- Department of Biochemistry, Faculty of Medicine, Aligarh Muslim University, Aligarh, 202002 India
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17
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Dejeans N, Tajeddine N, Beck R, Verrax J, Taper H, Gailly P, Calderon PB. Endoplasmic reticulum calcium release potentiates the ER stress and cell death caused by an oxidative stress in MCF-7 cells. Biochem Pharmacol 2009; 79:1221-30. [PMID: 20006589 DOI: 10.1016/j.bcp.2009.12.009] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Revised: 12/04/2009] [Accepted: 12/07/2009] [Indexed: 02/01/2023]
Abstract
Increase in cytosolic calcium concentration ([Ca2+](c)), release of endoplasmic reticulum (ER) calcium ([Ca2+](er)) and ER stress have been proposed to be involved in oxidative toxicity. Nevertheless, their relative involvements in the processes leading to cell death are not well defined. In this study, we investigated whether oxidative stress generated during ascorbate-driven menadione redox cycling (Asc/Men) could trigger these three events, and, if so, whether they contributed to Asc/Men cytoxicity in MCF-7 cells. Using microspectrofluorimetry, we demonstrated that Asc/Men-generated oxidative stress was associated with a slow and moderate increase in [Ca2+](c), largely preceding permeation of propidium iodide, and thus cell death. Asc/Men treatment was shown to partially deplete ER calcium stores after 90 min (decrease by 45% compared to control). This event was associated with ER stress activation, as shown by analysis of eIF2 phosphorylation and expression of the molecular chaperone GRP94. Thapsigargin (TG) was then used to study the effect of complete [Ca2+](er) emptying during the oxidative stress generated by Asc/Men. Surprisingly, the combination of TG and Asc/Men increased ER stress to a level considerably higher than that observed for either treatment alone, suggesting that [Ca2+](er) release alone is not sufficient to explain ER stress activation during oxidative stress. Finally, TG-mediated [Ca2+](er) release largely potentiated ER stress, DNA fragmentation and cell death caused by Asc/Men, supporting a role of ER stress in the process of Asc/Men cytotoxicity. Taken together, our results highlight the involvement of ER stress and [Ca2+](er) decrease in the process of oxidative stress-induced cell death in MCF-7 cells.
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Affiliation(s)
- Nicolas Dejeans
- Université Catholique de Louvain, Louvain Drug Research Institute, Toxicology and Cancer Biology Research Group, PMNT Unit, Belgium
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18
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Shin KY, Lee GH, Park CH, Kim HJ, Park SH, Kim S, Kim HS, Lee KS, Won BY, Lee HG, Choi JH, Suh YH. A novel compound, maltolyl p-coumarate, attenuates cognitive deficits and shows neuroprotective effects in vitro and in vivo dementia models. J Neurosci Res 2007; 85:2500-11. [PMID: 17600377 DOI: 10.1002/jnr.21397] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
To develop a novel and effective drug that could enhance cognitive function and neuroprotection, we newly synthesized maltolyl p-coumarate by the esterification of maltol and p-coumaric acid. In the present study, we investigated whether maltolyl p-coumarate could improve cognitive decline in scopolamine-injected rats and in amyloid beta peptide(1-42)-infused rats. Maltolyl p-coumarate was found to attenuate cognitive deficits in both rat models using passive avoidance test and to reduce apoptotic cell death observed in the hippocampus of the amyloid beta peptide(1-42)-infused rats. We also examined the neuroprotective effects of maltolyl p-coumarate in vitro using SH-SY5Y cells. Cells were pretreated with maltolyl p-coumarate, before exposed to amyloid beta peptide(1-42), glutamate or H2O2. We found that maltolyl p-coumarate significantly decreased apoptotic cell death and reduced reactive oxygen species, cytochrome c release, and caspase 3 activation. Taking these in vitro and in vivo results together, our study suggests that maltolyl p-coumarate is a potentially effective candidate against Alzheimer's disease that is characterized by wide spread neuronal death and progressive decline of cognitive function.
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Affiliation(s)
- Ki Young Shin
- Department of Pharmacology, College of Medicine, National Creative Research Initiative Center for Alzheimer's Dementia and Neuroscience Research Institute, MRC, Seoul National University, Seoul, Korea
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19
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Pinton P, Rizzuto R. p66Shc, oxidative stress and aging: importing a lifespan determinant into mitochondria. Cell Cycle 2007; 7:304-8. [PMID: 18235239 DOI: 10.4161/cc.7.3.5360] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The 66 KDa isoform of Shc and its signalling properties have attracted in the past years major interest in aging research. Here, we summarize p66Shc functions and outline a specific signalling route leading to mitochondrial import, that accounts for its pro-apoptotic activity upon oxidative stress. This model, that could explain the alterations of mitochondrial Ca2+ homeostasis observed after oxidative stress, highlights novel pharmacological targets in age-related disorders.
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Affiliation(s)
- Paolo Pinton
- Department of Experimental and Diagnostic Medicine, Section of General Pathology, ER-GenTech Laboratory and Interdisciplinary Center for the Study of Inflammation (ICSI), University of Ferrara, Ferrara, Italy
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20
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Sasaki S, Warita H, Komori T, Murakami T, Abe K, Iwata M. Parvalbumin and calbindin D-28k immunoreactivity in transgenic mice with a G93A mutant SOD1 gene. Brain Res 2006; 1083:196-203. [PMID: 16546142 DOI: 10.1016/j.brainres.2006.01.129] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2005] [Revised: 01/24/2006] [Accepted: 01/28/2006] [Indexed: 11/20/2022]
Abstract
Immunohistochemical study was performed to examine if calcium-binding proteins are involved in the degeneration of motor neurons in the brain stems and the spinal cords of transgenic mice carrying a G93A mutant human SOD1 gene. Specimens from age-matched non-transgenic wild-type mice served as controls. In the spinal cord of the controls, the density of parvalbumin-immunoreactive neurons was highest in the large anterior horn neurons and lower in the posterior horn neurons in the spinal cord. On the other hand, calbindin D-28k immunoreactivity was much less apparent than that observed with parvalbumin antisera. Rexed's lamina II was densely immunostained for calbindin D-28k, whereas, in the anterior horn, calbindin-D-28k-positive small neurons were barely dispersed in a scattered pattern. In transgenic mice, parvalbumin-positive anterior horn neurons were severely reduced, even at the presymptomatic stage, whereas calbindin-positive neurons were largely preserved. At the symptomatic stage, both parvalbumin and calbindin D-28k immunoreactivity markedly diminished or disappeared in the anterior horn. Immunoblotting analysis revealed a significant reduction of immunoreactivity to parvalbumin antibody in transgenic mice compared with the controls. In the brain stem, parvalbumin-positive oculomotor and abducens neurons and the calbindin D-28k-positive sixth nucleus were well-preserved in transgenic mice as well as in the controls. Thus, the diffuse and severe loss of parvalbumin immunoreactivity of large motor neurons even at early stages in SOD1-transgenic mice and the absence of calbindin D-28k immunoreactivity of normal large motor neurons suggest that these calcium-binding proteins may contribute to selective vulnerability and an early loss of function of large motor neurons in this SOD1-transgenic mouse model.
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Affiliation(s)
- Shoichi Sasaki
- Department of Neurology, Neurological Institute, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan.
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Park CH, Choi SH, Koo JW, Seo JH, Kim HS, Jeong SJ, Suh YH. Novel cognitive improving and neuroprotective activities of Polygala tenuifolia Willdenow extract, BT-11. J Neurosci Res 2002; 70:484-92. [PMID: 12391609 DOI: 10.1002/jnr.10429] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We carried out this study to search a new active constituent that had cognitive enhancing activity and low side effects from natural source. We found that the extract of dried root of Polygala tenuifolia Willdenow (BT-11, 10 mg/kg, i.p.) could significantly reverse scopolamine-induced cognitive impairments in rat, using a passive avoidance and a water maze test. We also investigated the effects of BT-11 on neurotoxicity induced by glutamate (Glu) and toxic metabolites of amyloid precursor protein (APP) such as amyloid beta protein (A beta) and C-terminal fragment of APP (CT) in primary cultured neurons of rat. The pretreatment of BT-11 (0.5, 3, and 5 micro g/ml) significantly reduced cell death induced by Glu (1 mM), A beta (10 micro M) and CT105 (10 micro M) in a dose-dependent manner. In addition, BT-11 inhibited acetylcholinesterase (AChE) activity in a dose-dependent and non-competitive manner (IC(50) value; 263.7 micro g/ml). Our novel findings suggest the possibility that this extract may have some protective effects against neuronal death and cognitive impairments in Alzheimer's disease (AD), or other neurodegenerative diseases related to excitotoxicity and central cholinergic dysfunction.
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Affiliation(s)
- Cheol Hyoung Park
- Department of Pharmacology, College of Medicine, National Creative Research Initiative Center for Alzheimer's Dementia and Neuroscience Research Institute, MRC, Seoul National University, Seoul, South Korea
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22
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Molyneux CA, Glyn MC, Ward BJ. Oxidative stress and cardiac microvascular structure in ischemia and reperfusion: the protective effect of antioxidant vitamins. Microvasc Res 2002; 64:265-77. [PMID: 12204651 DOI: 10.1006/mvre.2002.2419] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Reperfusion of the ischemic myocardium results in structural changes in the capillary bed, which may contribute to decreased microcirculatory flow ("no reflow"). This study was designed to correlate the endothelial cell shape changes with both oxidative stress and lipid peroxidation and to evaluate the beneficial potential of Trolox (a hydrophilic analogue of alpha-tocopherol) and ascorbic acid. Isolated buffer-perfused rat hearts were made ischemic for 45 min and then reperfused with 100 microM Trolox and/or 100 microM ascorbic acid. Morphological changes were quantified by measuring capillary cross-sectional areas. Increased myocardial content of oxidized glutathione and its release into the coronary effluent were used as indices of oxidative stress. Myocardial MDA, an end product of lipid peroxidation, was also measured. Luminal membrane blebs and capillary "constriction" in the ischemic groups occurred when there was no change in either glutathione status or MDA concentrations. Reperfusion altered the redox state of the heart sufficiently to induce lipid peroxidation. It also induced endothelial cell swelling and a reduction in luminal area. Ascorbic acid was a more effective antioxidant than Trolox as it significantly reduced both oxidative stress and ultrastructural injury. The combined antioxidant treatment returned both the stress ratio and the capillary measurements to control values. We conclude that endothelial cell swelling correlates with the degree of oxidative stress and that antioxidant vitamins reduce membrane damage by preventing lipid peroxidation.
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Affiliation(s)
- Catherine A Molyneux
- William Harvey Research Institute, St. Bartholomew's and the Royal London School of Medicine and Dentistry, Queen Mary, University of London, London 0E1 4NS, United Kingdom
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23
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Manzl C, Schubert M, Schwarzbaum PJ, Krumschnabel G. Effects of chemical anoxia on adrenergic responses of goldfish hepatocytes and the contribution of ?- and ?-adrenoceptors. ACTA ACUST UNITED AC 2002. [DOI: 10.1002/jez.10048] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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24
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Murphy MP. Development of lipophilic cations as therapies for disorders due to mitochondrial dysfunction. Expert Opin Biol Ther 2001; 1:753-64. [PMID: 11728211 DOI: 10.1517/14712598.1.5.753] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Mitochondrial dysfunction causes or exacerbates a number of diseases. These include genetic disorders such as Friedreich's ataxia where the primary lesion is a defect in a nuclear gene and those diseases caused by mutations to mitochondrial DNA. Mitochondrial damage also contributes to neurodegenerative diseases, diabetes and ischaemia-reperfusion injury. Drug therapies to prevent or alleviate mitochondrial dysfunction use redox active compounds, anti-oxidants or mitochondrial co-factors, however, their effectiveness is limited. A promising approach to increase the selectivity and potency of these compounds is to modify them so that they concentrate within mitochondria. This can be done by incorporating a lipophilic cation which causes the molecules to concentrate several hundred-fold in mitochondria, driven by the membrane potential across the inner membrane. As lipophilic cations cross biological membranes easily, they can be delivered to mitochondria of the heart, brain and skeletal muscle, the organs most affected by mitochondrial damage. Mitochondria-targeted lipophilic cations may lead to improved therapies for diseases involving mitochondrial dysfunction.
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Affiliation(s)
- M P Murphy
- MRC-Dunn Human Nutrition Unit, Wellcome Trust-MRC Building, Hills Road, Cambridge CB2 2XY, UK.
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25
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Pinton P, Ferrari D, Di Virgilio F, Pozzan T, Rizzuto R. Molecular machinery and signaling events in apoptosis. Drug Dev Res 2001. [DOI: 10.1002/ddr.1159] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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26
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Marchi B, Burlando B, Panfoli I, Viarengo A. Interference of heavy metal cations with fluorescent Ca2+ probes does not affect Ca2+ measurements in living cells. Cell Calcium 2000; 28:225-31. [PMID: 11032778 DOI: 10.1054/ceca.2000.0155] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In studies about the effects of heavy metals on intracellular Ca2+, the use of fluorescent probes is debated, as metal cations are known to affect the probe signal. In this study, spectrofluorimetric experiments in free solution, using Fluo-3 and Fura-2, showed that Zn2+ and Cd2+ enhanced the probe signal, Cu2+ quenched it, and Hg2+ had no effect. Addition of GSH prevented most of these effects, suggesting the occurrence of a similar protective role in living cells. Digital imaging of living mussel haemocytes loaded with Fura-2/AM or Fluo-3/AM showed that Hg2+, Cu2+ and Cd2+ induced a rise in probe fluorescence, whereas up to 200 microM Zn2+ had no effect. In particular, Cd2+ produced the strongest probe signal rise in free solution, but the lowest fluorescence increase in cells. Probe calibration yielded [Ca2+]i values characteristic of resting levels in control and Zn2+-exposed cells, and, as expected, indicated Ca2+ homeostasis impairment in cells exposed to Cd2+, Cu2+ and Hg2+. Our results show that Ca2+ probe responses to heavy metals in living cells are completely different from those obtained in free solution, indicating that fluorescent probes can be a suitable tool to record the effects of heavy metals on [Ca2+]i.
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Affiliation(s)
- B Marchi
- Dip. di Biologia Sperimentale Applicata e Ambientale, Università di Genova, Genova, Italy
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27
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Tan Y, Williams EA, Lancia AJ, Zahm DS. On the altered expression of tyrosine hydroxylase and calbindin-D 28kD immunoreactivities and viability of neurons in the ventral tegmental area of Tsai following injections of 6-hydroxydopamine in the medial forebrain bundle in the rat. Brain Res 2000; 869:56-68. [PMID: 10865059 DOI: 10.1016/s0006-8993(00)02348-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Calbindin-D 28kD is a calcium binding protein reported to protect neurons from degeneration by buffering intracellular calcium. It is expressed in midbrain dopaminergic neurons reported to be relatively resistant to degeneration in Parkinson's disease and certain of its animal models. Lesions of the nigrostriatal pathway produced in rats following injection of 6-hydroxydopamine result in a neurochemical profile similar to that seen in patients with Parkinson's disease. In the present study, brains were processed to exhibit tyrosine hydroxylase- and calbindin-D 28kD immunoreactivities in sections through the ventral mesencephalon at 3, 7, 10, 14 and 21 days after 6-hydroxydopamine had been injected into the medial forebrain bundle. Numbers of ventral mesencephalic calbindin-D 28kD immunoreactive neurons were significantly reduced ipsilateral to the lesions at 3 days post-lesion and, following slight recovery, remained significantly depleted through post-lesion day 21. The densities of calbindin-D 28kD and tyrosine hydroxylase immunoreactive neurons were different only at the 3 day post-lesion time point, when the apparent loss of calbindin-D 28 kD immunoreactive profiles was significantly greater. A lesion-induced increase in the proportion of neurons exhibiting both calbindin-D 28kD and tyrosine hydroxylase immunoreactivities, expected if calbindin-D 28kD is neuroprotective, was observed in the substantia nigra, pars compacta, but not in the ventral tegmental area. It is concluded that, while the observed losses of tyrosine hydroxylase and calbindin-D 28kD immunoreactivities do not necessarily reflect neuronal degeneration, they are not consistent with CB confering a neuroprotective advantage in the ventral tegmental area following 6-OHDA lesions as administered in this study.
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Affiliation(s)
- Y Tan
- Department of Anatomy and Neurobiology, School of Medicine, Saint Louis University, 1402 S. Grand Blvd., Saint Louis, MO 63104, USA
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28
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Huang HM, Ou HC, Hsieh SJ. Antioxidants prevent amyloid peptide-induced apoptosis and alteration of calcium homeostasis in cultured cortical neurons. Life Sci 2000; 66:1879-92. [PMID: 10809185 DOI: 10.1016/s0024-3205(00)00511-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Beta-amyloid ((A)beta) is a peptide of 39-42 amino acids that is the primary component of plaques in Alzheimer's disease (AD). The mechanism by which (A)beta expresses its neurotoxic effects may involve induction of reactive oxygen species (ROS) and elevation of intracellular free calcium levels. Cultured cortical cells were utilized to study the alterations in calcium homeostasis underlying the neurotoxic effect of (A)beta. Serum supplement B27 and vitamin E were effective in preventing neuronal death as assessed by lactate dehydrogenase (LDH) release, (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and number of apoptotic nuclei. In addition, (A)beta-induced cytosolic free calcium ([Ca2+]i) was blocked by antioxidants vitamin E and U83836E, but not by N-methyl-D-aspartic acid (NMDA) receptor antagonist MK-801, or by voltage-gated calcium channel blocker nimodipine. Taken together, the results suggest that NMDA receptor and voltage-gated calcium channels are not involved in (A)beta-induced [Ca2+]i increase. This increase appeared to be the result of extracellular calcium influx by some unknown mechanisms. In addition, antioxidants such as B27 were effective in protecting cultured cortical neurons against (A)beta, and correlated with (A)beta attenuation of early calcium response.
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Affiliation(s)
- H M Huang
- Department of Education and Medical Research, Taichung Veterans General Hospital, Taiwan, ROC.
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29
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Bywood PT, Johnson SM. Dendrite loss is a characteristic early indicator of toxin-induced neurodegeneration in rat midbrain slices. Exp Neurol 2000; 161:306-16. [PMID: 10683296 DOI: 10.1006/exnr.1999.7259] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In rat brain substantia nigra catecholamine neurons in vitro, a sensitive indicator of excitatory amino-acid-induced damage is dendritic degeneration that precedes the loss of the cell body. The present study has shown that dendritic loss is not specific for excitatory amino acids and is an early indicator of neurodegeneration produced by numerous agents that initiate damage by different primary cellular actions. Rats were anesthetised by fluothane inhalation and killed, and the brain was rapidly removed. Three-hundred-micrometer-thick slices containing substantia nigra were incubated for 2 h at 35 degrees C in the presence or absence of kainic acid (50 microM), 1-methyl-4-phenylpyridinium ion (10 or 50 microM), ouabain (10 or 30 microM), 6-hydroxydopamine (10 or 100 microM), potassium cyanide (100 microM or 1 mM), or elevated extracellular potassium chloride (25, 50, or 100 mM). The slices were fixed and recut into thin sections (30 micrometer) and substantia nigra dopamine neurons were immunolabeled for tyrosine hydroxylase coupled to diaminobenzidine. Both the cell body and the extensive dendritic projections were immunolabeled. Each agent caused a similar pattern of toxicity including loss of tyrosine-hydroxylase-immunolabeled dendrites at lower concentrations and damage to, or disintegration of, the cell bodies at higher concentrations. For example, 100 microM potassium cyanide reduced the proportion of substantia nigra neurons which exhibited dendrites from 66 +/- 4% (SEM) in controls to 54 +/- 7%, without obvious changes in cell bodies. After 1 mM potassium cyanide, only 13 +/- 2% of substantia nigra neurons retained dendrites and cell bodies were shrunken or disintegrated. Loss of dendrites was also evident in substantia nigra neurons stained with cresyl violet or immunolabeled for microtubule-associated protein 2. The findings suggest that disruption of the dendritic arbor is an early indicator of neurodegeneration, irrespective of how this is initiated. The approach that we have developed may therefore prove valuable in investigating the mechanisms of degeneration of catecholamine neurons.
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Affiliation(s)
- P T Bywood
- Department of Clinical Pharmacology, Flinders University of South Australia, Adelaide, 5001, Australia
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30
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El-Ashmawy IM, Youssef SA. The antagonistic effect of chlorpromazine on cadmium toxicity. Toxicol Appl Pharmacol 1999; 161:34-9. [PMID: 10558921 DOI: 10.1006/taap.1999.8785] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Adult male rats were injected sc with cadmium chloride (CdCl(2)) in a single dose of 7 mg/kg body wt. Twenty-four hours postinjection, exposure to CdCl(2) increased the hemoglobin absorbance of the testes from 0.36 +/- 0.01 to 2.46 +/- 0.02. Pretreatment of rats with chlorpromazine (CPZ) 3 mg/kg ip either for 1 or 2 days before exposure to CdCl(2) significantly (p < 0.05) reduced the testicular damage and the hemoglobin absorbance decreased to 1.03 +/- 0.02 and 0.92 +/- 0.04, respectively. After CdCl(2) injection there was a progressive increase in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities. CdCl(2) injection induced hemorrhage and a diffuse area of coagulative necrosis in liver. Pretreatment with CPZ partially protected liver from the effect of CdCl(2). Two months postinjection, exposure to CdCl(2) significantly decreased the weights of testes, epididymis, and accessory sex organs. Furthermore, CdCl(2) induced a highly significant (p < 0.01) decrease in sperm cell concentration and the percentage of mobile cells. Moreover CdCl(2) induced degenerative changes in testes, epididymis, and seminal vesicles. Pretreatment with CPZ partially protected these organs from the toxic effects of CdCl(2). It could be concluded that chlorpromazine partially antagonized the toxic effects of cadmium on liver, testes, and other male reproductive organs of rats.
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Affiliation(s)
- I M El-Ashmawy
- Faculty of Veterinary Medicine, Alexandria University, Alexandria, Egypt
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31
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Pelletier MR, Wadia JS, Mills LR, Carlen PL. Seizure-induced cell death produced by repeated tetanic stimulation in vitro: possible role of endoplasmic reticulum calcium stores. J Neurophysiol 1999; 81:3054-64. [PMID: 10368420 DOI: 10.1152/jn.1999.81.6.3054] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Seizures may cause brain damage due to mechanisms initiated by excessive excitatory synaptic transmission. One such mechanism is the activation of death-promoting intracellular cascades by the influx and the perturbed homeostasis of Ca2+. The neuroprotective effects of preventing the entry of Ca2+ from voltage-dependent Ca2+ channels, NMDA receptors, and non-NMDA receptors, is well known. Less clear is the contribution to excitotoxicity of Ca2+ released from endoplasmic reticulum (ER) stores. We produced epileptiform discharges in combined entorhinal cortex/hippocampus slices using repeated tetanic stimulation of the Schaffer collaterals and assessed cell death after 1, 3, or 12-14 h with gel electrophoresis of genomic DNA and immunohistologically using terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine 5'-triphosphate (dUTP) nick end labeling (TUNEL) staining. We manipulated ER Ca2+ stores using two conventional drugs, dantrolene, which blocks the Ca2+ release channel, and thapsigargin, which blocks sarco-endoplasmic reticulum Ca2+-ATPases resulting in depletion of ER Ca2+ stores. To monitor epileptogenesis, and to assess effects attributable to dantrolene and thapsigargin on normal synaptic transmission, extracellular potentials were recorded in stratum pyramidale of the CA1 region. Repeated tetanic stimulation reliably produced primary afterdischarge and spontaneous epileptiform discharges, which persisted for 14 h, the longest time recorded. We did not observe indications of cell death attributable to seizures with either method when assessed after 1 or 3 h; however, qualitatively more degraded DNA always was observed in tetanized slices from the 12- to 14-h group compared with time-matched controls. Consistent with these data was a significant, fourfold, increase in the percentage of TUNEL-positive cells in CA3, CA1, and entorhinal cortex in tetanized slices from the 12- to 14-h group (16. 5 +/- 4.4, 33.7 +/- 7.1, 11.6 +/- 2.1, respectively; means +/- SE; n = 7) compared with the appropriate time-matched control (4.1 +/- 2.2, 7.3 +/- 2.0, 2.8 +/- 0.9, respectively; n = 6). Dantrolene (30 microM; n = 5) and thapsigargin (1 microM; n = 4) did not affect significantly normal synaptic transmission, assessed by the amplitude of the population spike after 30 min of exposure. Dantrolene and thapsigargin also were without effect on the induction or the persistence of epileptiform discharges, but both drugs prevented seizure-induced cell death when assessed with gel electrophoresis. We suggest that Ca2+ entering a cell from the outside, in addition to the Ca2+ contributed from ryanodine-sensitive stores (i.e., Ca2+-induced Ca2+ release), may be necessary for seizure-induced cell death.
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Affiliation(s)
- M R Pelletier
- Bloorview Epilepsy Research Laboratory, University of Toronto, Toronto, Ontario M5T 2S8, Canada
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32
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Abstract
Nitric oxide (NO) has several essential roles in mammals, but unregulated NO production can cause cell death through oxidative stress, disrupted energy metabolism, DNA damage, activation of poly(ADP-ribose) polymerase, or dysregulation of cytosolic calcium. Such disturbances can lead to either apoptotic or necrotic cell death, depending on the severity and context of the damage. Here I review the mechanisms by which NO kills cells and discuss how NO thereby contributes to ischaemia-reperfusion injury and neurodegeneration.
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Affiliation(s)
- M P Murphy
- Department of Biochemistry, University of Otago, Box 56, Dunedin, New Zealand.
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Edelfors S, Hass U, Ravn-Jonsen A. The effect of in vitro exposure to white spirit on [Ca2+i] in synaptosomes from rats exposed prenatally to white spirit. PHARMACOLOGY & TOXICOLOGY 1999; 84:197-200. [PMID: 10361975 DOI: 10.1111/j.1600-0773.1999.tb01483.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Female rats were exposed to white spirit (400 and 800 ppm for 6 hr/day) at day 7-20 during pregnancy. Thirty-five days after birth all female offspring were sacrificed, the brains removed, and the synaptosomal fractions prepared for in vitro studies. The cytosolic calcium concentration was measured using the FURA-2 technique. The results show that cytosolic calcium was increased in synaptosomes from rats exposed to white spirit prenatally compared to synaptosomes from unexposed rats. When synaptosomes were exposed to white spirit in vitro, the cytosolic calcium concentration changes were identical in all groups of rats. The membrane leakage measured as FURA-2 leakage from the synaptosomes identical in all three groups of animals. The results suggest that prenatal exposure to white spirit induces long-lasting and possibly irreversible changes in calcium homeostasis in the rat nervous system.
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Affiliation(s)
- S Edelfors
- Department of Pharmacology, Panum Institute, University of Copenhagen, Denmark
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34
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Cassarino DS, Parks JK, Parker WD, Bennett JP. The parkinsonian neurotoxin MPP+ opens the mitochondrial permeability transition pore and releases cytochrome c in isolated mitochondria via an oxidative mechanism. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1453:49-62. [PMID: 9989245 DOI: 10.1016/s0925-4439(98)00083-0] [Citation(s) in RCA: 240] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The mitochondrial transition pore (MTP) is implicated as a mediator of cell injury and death in many situations. The MTP opens in response to stimuli including reactive oxygen species and inhibition of the electron transport chain. Sporadic Parkinson's disease (PD) is characterized by oxidative stress and specifically involves a defect in complex I of the electron transport chain. To explore the possible involvement of the MTP in PD models, we tested the effects of the complex I inhibitor and apoptosis-inducing toxin N-methyl-4-phenylpyridinium (MPP+) on cyclosporin A (CsA)-sensitive mitochondrial swelling and release of cytochrome c. In the presence of Ca2+ and Pi, MPP+ induced a permeability transition in both liver and brain mitochondria. MPP+ also caused release of cytochrome c from liver mitochondria. Rotenone, a classic non-competitive complex I inhibitor, completely inhibited MPP(+)-induced swelling and release of cytochrome c. The MPP(+)-induced permeability transition was synergistic with nitric oxide and the adenine nucleotide translocator inhibitor atractyloside, and additive with phenyl arsine oxide cross-linking of dithiol residues. MPP(+)-induced pore opening and cytochrome c release were blocked by CsA, the Ca2+ uniporter inhibitor ruthenium red, the hydrophobic disulfide reagent N-ethylmaleimide, butacaine, and the free radical scavenging enzymes catalase and superoxide dismutase. MPP+ neurotoxicity may derive from not only its inhibition of complex I and consequent ATP depletion, but also from its ability to open the MTP and to release mitochondrial factors including Ca2+ and cytochrome c known to be involved in apoptosis.
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Affiliation(s)
- D S Cassarino
- Neuroscience Program, University of Virginia Health Sciences Center, Charlottesville 22908, USA
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35
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36
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Cassarino DS, Bennett JP. An evaluation of the role of mitochondria in neurodegenerative diseases: mitochondrial mutations and oxidative pathology, protective nuclear responses, and cell death in neurodegeneration. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 1999; 29:1-25. [PMID: 9974149 DOI: 10.1016/s0165-0173(98)00046-0] [Citation(s) in RCA: 278] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
There is mounting evidence for mitochondrial involvement in neurodegenerative diseases including Alzheimer's and Parkinson's disease and amyotrophic lateral sclerosis. Mitochondrial DNA mutations, whether inherited or acquired, lead to impaired electron transport chain (ETC) functioning. Impaired electron transport, in turn, leads to decreased ATP production, formation of damaging free-radicals, and altered calcium handling. These toxic consequences of ETC dysfunction lead to further mitochondrial damage including oxidation of mitochondrial DNA, proteins, and lipids, and opening of the mitochondrial permeability transition pore, an event linked to cell death in numerous model systems. Although protective nuclear responses such as antioxidant enzymes and bcl-2 may be induced to combat these pathological changes, such a vicious cycle of increasing oxidative damage may insidiously damage neurons over a period of years, eventually leading to neuronal cell death. This hypothesis, a synthesis of the mitochondrial mutations and oxidative stress hypotheses of neurodegeneration, is readily tested experimentally, and clearly points out many potential therapeutic targets for preventing or ameliorating these diseases.
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Affiliation(s)
- D S Cassarino
- Medical Scientist Training Program, University of Virginia Health Sciences Center, Charlottesville 22908, USA
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37
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Li Y, Copin JC, Reola LF, Calagui B, Gobbel GT, Chen SF, Sato S, Epstein CJ, Chan PH. Reduced mitochondrial manganese-superoxide dismutase activity exacerbates glutamate toxicity in cultured mouse cortical neurons. Brain Res 1998; 814:164-70. [PMID: 9838093 DOI: 10.1016/s0006-8993(98)01082-8] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Studies of neuronal injury and death after cerebral ischemia and various neurodegenerative diseases have increasingly focused on the interactions between mitochondrial function, reactive oxygen species (ROS) production and glutamate neurotoxicity. Recent findings suggest that increased mitochondrial ROS production precedes neuronal death after glutamate treatment. It is hypothesized that under pathological conditions when mitochondrial function is compromised, extracellular glutamate may exacerbate neuronal injury. In the present study, we focus on the relationship between mitochondrial superoxide production and glutamate neurotoxicity in cultured cortical neurons with normal or reduced levels of manganese-superoxide dismutase (MnSOD) activity. Our results demonstrate that neurons with reduced MnSOD activity are significantly more sensitive to transient exposure to extracellular glutamate. The increased sensitivity of cultured cortical neurons with reduced MnSOD activity is characteristically subject only to treatment by glutamate but not to other glutamate receptor agonists, such as N-methyl-d-aspartate, kainate and quisqualate. We suggest that the reduced MnSOD activity in neurons may exacerbate glutamate neurotoxicity via a mechanism independent of receptor activation.
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Affiliation(s)
- Y Li
- Department of Neurological Surgery, University of California, School of Medicine, San Francisco, CA 94143-0651, USA
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38
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Swerdlow RH, Parks JK, Cassarino DS, Trimmer PA, Miller SW, Maguire DJ, Sheehan JP, Maguire RS, Pattee G, Juel VC, Phillips LH, Tuttle JB, Bennett JP, Davis RE, Parker WD. Mitochondria in sporadic amyotrophic lateral sclerosis. Exp Neurol 1998; 153:135-42. [PMID: 9743575 DOI: 10.1006/exnr.1998.6866] [Citation(s) in RCA: 139] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mitochondria are abnormal in persons with amyotrophic lateral sclerosis (ALS) for unknown reasons. We explored whether aberration of mitochondrial DNA (mtDNA) could play a role in this by transferring mitochondrial DNA (mtDNA) from ALS subjects to mtDNA-depleted human neuroblastoma cells. Resulting ALS cytoplasmic hybrids (cybrids) exhibited abnormal electron transport chain functioning, increases in free radical scavenging enzyme activities, perturbed calcium homeostasis, and altered mitochondrial ultrastructure. Recapitulation of defects previously observed in ALS subjects and ALS transgenic mice by expression of ALS mtDNA support a pathophysiologic role for mtDNA mutation in some persons with this disease.
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Affiliation(s)
- R H Swerdlow
- Department of Neurology, University of Virginia Health Sciences Center, 1 Hospital Drive, Charlottesville, Virginia 22908, USA
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39
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Huang CQ, Shepherd RK, Seligman PM, Clark GM. Reduction in excitability of the auditory nerve following acute electrical stimulation at high stimulus rates: III. Capacitive versus non-capacitive coupling of the stimulating electrodes. Hear Res 1998; 116:55-64. [PMID: 9508028 DOI: 10.1016/s0378-5955(97)00196-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Safe electrical stimulation of neural tissue is typically achieved using charge-balanced biphasic current pulses, which are designed to minimize the generation of direct current (DC) and the production of harmful electrochemical products. However, due to the kinetics of the charge injection process, neural stimulators must also use capacitive coupling or electrode shorting techniques, to ensure DC levels are minimal. Previous studies have reported a reduction in excitability of the auditory nerve following acute simulation at high rates and intensities. Elevated levels of DC were reported in these studies despite using charge-balanced biphasic pulses and electrode shorting. The present study was designed to investigate the extent to which DC contributed to these stimulus induced reductions in auditory nerve excitability. Adult guinea pigs were bilaterally implanted and unilaterally stimulated for two hours using charge-balanced biphasic current pulses and stimulus rates of 200, 400 or 1000 pulses/s (pps) at a stimulus intensity well above clinical levels (0.34 microC/phase). DC levels were controlled using either electrode shorting, or electrode shorting with capacitive coupling. Electrically evoked auditory brainstem responses (EABRs) were recorded before and periodically following the acute stimulation. It was found that the extent of reduction in the EABR amplitude was a function of stimulus rate. While there was little change in the EABR following stimulation at 200 pps, significant post-stimulus reductions in the EABR amplitude were observed at stimulus rates of 400 and 1000 pps during the three hour post-stimulus monitoring period. Stimulation using capacitively coupled electrodes, which eliminated all DCs, showed reductions in EABR amplitudes similar to those observed following stimulation using electrode shorting alone. While there was no significant difference in the extent of reduction in EABR amplitudes for capacitive coupling versus electrode shorting at stimulus rates of 200 pps (P > 0.05) and 400 pps (P > 0.05), there was a significant difference at 1000 pps (P< 0.001). The present findings indicate that the major component of the stimulus induced reductions observed in auditory nerve excitability appear to be associated with stimulus induced neuronal activity, although elevated levels of DC ( > 2.5 microA) can also contribute to these changes. However, although statistically significant, the effects of DC are very small compared to the effects of high rate, high intensity stimulation per se.
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Affiliation(s)
- C Q Huang
- Department of Otolaryngology, The University of Melbourne, Victoria, Australia
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40
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Peng TI, Jou MJ, Sheu SS, Greenamyre JT. Visualization of NMDA receptor-induced mitochondrial calcium accumulation in striatal neurons. Exp Neurol 1998; 149:1-12. [PMID: 9454610 DOI: 10.1006/exnr.1997.6599] [Citation(s) in RCA: 99] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Ca2+ influx through NMDA receptor-gated channels and the subsequent rise in intracellular Ca2+ concentration ([Ca2+]i) have been implicated in cytotoxic processes that lead to irreversible neuronal injury. While many studies have focused on cytosolic Ca2+ homeostasis, much less is known about Ca2+ fluxes in subcellular organelles, such as mitochondria. The mitochondria play an important role in Ca2+ homeostasis by sequestering cytosolic Ca2+ loads. However, mitochondrial Ca2+ overload can impair ATP synthesis, induce free radical formation, and lead to lipid peroxidation. Thus, it is also important to understand the mitochondrial Ca2+ fluxes induced by NMDA. In this study, changes in mitochondrial Ca2+ concentration ([Ca2+]m) in cultured striatal neurons were monitored with a Ca(2+)-binding fluorescent probe, rhod-2, and laser scanning confocal microscopy. The rhod-2 fluorescence signal was highly localized in mitochondrial areas of confocal images. A rapid increase of [Ca2+]m was observed when neurons were treated with 100 microM NMDA. The increased [Ca2+]m induced by NMDA could not be observed in the presence of ruthenium red, an inhibitor of the mitochondrial Ca2+ uniporter, or CCCP, a protonophore that breaks down the mitochondrial membrane potential necessary for Ca2+ uptake. The magnitude and reversibility of changes in [Ca2+]m induced by NMDA were variable. In neurons receiving multiple pulses of NMDA, [Ca2+]m did not return to baseline. The elevated [Ca2+]m may persist indefinitely and may rise further after successive NMDA exposures. These data demonstrate that Ca2+ accumulates in mitochondria in response to NMDA receptor activation. This Ca2+ accumulation may play a role in the excitotoxic mitochondrial dysfunction induced by NMDA.
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Affiliation(s)
- T I Peng
- Department of Neurology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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41
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42
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Siklós L, Kuhnt U, Párducz A, Szerdahelyi P. Intracellular calcium redistribution accompanies changes in total tissue Na+, K+ and water during the first two hours of in vitro incubation of hippocampal slices. Neuroscience 1997; 79:1013-22. [PMID: 9219964 DOI: 10.1016/s0306-4522(97)00031-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Changes of total tissue water, Ca, Na and K contents were monitored in whole transverse hippocampal slices of the guinea-pig during the first 2 h of in vitro incubation. A brief, 75% increase in tissue Ca was noted during the initial 15 min of maintenance, in contrast to a permanent increase of sodium and water contents, coupled to simultaneous decrease of potassium level. The rate of tissue Na, K and water changes comprised a rapid phase at the first 10-20 min, parallel with the increase of the tissue Ca content, and a slow phase during the rest of the incubation period. Development of specific morphological alterations, representative of ischemic/hypoxic lesions and a translocation of calcium from cytoplasm to mitochondria and endoplasmic reticulum during slice maintenance, was also detected by electron microscopy. A two-step mechanism might explain the development of a new steady-state total calcium content of slices. in which the cellular Ca2+ uptake at the beginning of incubation, likely triggered by hypoxic/ ischemic trauma of slice preparation, is followed by a balanced Ca2+ influx, extrusion and sequestration (predominantly into mitochondria and endoplasmic reticulum) during maintenance.
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Affiliation(s)
- L Siklós
- Laboratory of Molecular Neurobiology, Institute of Biophysics, Biological Research Center, Szeged, Hungary
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43
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Calcium homeostasis and reactive oxygen species production in cells transformed by mitochondria from individuals with sporadic Alzheimer's disease. J Neurosci 1997. [PMID: 9169522 DOI: 10.1523/jneurosci.17-12-04612.1997] [Citation(s) in RCA: 177] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Alzheimer's disease (AD) is associated with defects in mitochondrial function. Mitochondrial-based disturbances in calcium homeostasis, reactive oxygen species (ROS) generation, and amyloid metabolism have been implicated in the pathophysiology of sporadic AD. The cellular consequences of mitochondrial dysfunction, however, are not known. To examine these consequences, mitochondrially transformed cells (cybrids) were created from AD patients or disease-free controls. Mitochondria from platelets were fused to rho0 cells created by depleting the human neuroblastoma line SH-SY5Y of its mitochondrial DNA (mtDNA). AD cybrids demonstrated a 52% decrease in electron transport chain (ETC) complex IV activity but no difference in complex I activity compared with control cybrids or SH-SY5Y cells. This mitochondrial dysfunction suggests a transferable mtDNA defect associated with AD. ROS generation was elevated in the AD cybrids. AD cybrids also displayed an increased basal cytosolic calcium concentration and enhanced sensitivity to inositol-1,4, 5-triphosphate (InsP3)-mediated release. Furthermore, they recovered more slowly from an elevation in cytosolic calcium induced by the InsP3 agonist carbachol. Mitochondrial calcium buffering plays a major role after this type of perturbation. beta-amyloid (25-35) peptide delayed the initiation of calcium recovery to a carbachol challenge and slowed the recovery rate. Nerve growth factor reduced the carbachol-induced maximum and moderated the recovery kinetics. Succinate increased ETC activity and partially restored the AD cybrid recovery rate. These subtle alterations in calcium homeostasis and ROS generation might lead to increased susceptibility to cell death under circumstances not ordinarily toxic.
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44
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Agostinho P, Duarte CB, Carvalho AP, Oliveira CR. Oxidative stress affects the selective ion permeability of voltage-sensitive Ca2+ channels in cultured retinal cells. Neurosci Res 1997; 27:323-34. [PMID: 9152045 DOI: 10.1016/s0168-0102(96)01165-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The effect of ascorbate/Fe2+-induced oxidative stress on the intracellular Ca2+ concentration ([Ca2+]i) and on the voltage-sensitive Ca2+ channels (VSCC) of chick retinal cells was evaluated in this study. We also analyzed the effect of oxidation on the intracellular Na+ concentration ([Na+]i) and on the Ca2+-dependent release of [3H])gamma-aminobutric acid (GABA) evoked by 50 mM KCI. The resting [Ca2+]i was not affected by oxidation, but the [Ca2+]i response (delta[Ca2+]i) to K+-depolarization was significantly inhibited under oxidative stress conditions. The Ca2+ influx stimulated by membrane depolarization was mediated by L- and N-type VSCC, and by N-metyl-D-aspartate (NMDA) receptor channel, activated by endogenous glutamate released by glutamatergic cells. In cultured retinal cells L-type channels are the major route of Ca2+ influx during depolarization and the most affected by oxidative stress. The N-type VSCC seem not to be affected by oxidant conditions; they were found to be involved in glutamatergic transmission and only indirectly in the release of [3H]GABA evoked by K+-depolarization. Although the Ca2+-dependent release of [3H]GABA evoked by 50 mM KCl is mediated by Ca2+ entry through L-type Ca2+ channels, it is not affected by pre-incubation with the oxidant pair. The oxidative stress conditions increased the [Na+]i in Ca2+-free medium, by a process dependent of Na+ entry through L-type VSCC. The increased permeability of L-type VSCC to Na+ may increase the Ca2+-independent release of endogenous glutamate which, by activating the NMDA receptors, induces the release of [3H]GABA by reversal of its transporter. The equilibrium between the release of GABA and glutamate may play an in important role in neuroprotection against excitotoxic insults.
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Affiliation(s)
- P Agostinho
- Center for Neurosciences of Coimbra, University of Coimbra, Portugal
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45
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Allain H, Bentué-Ferrer D, Belliard S, Derouesné C. 1 Pharmacology of Alzheimer's Disease. PROGRESS IN MEDICINAL CHEMISTRY 1997. [DOI: 10.1016/s0079-6468(08)70104-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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46
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Freitas AJ, Rocha JB, Wolosker H, Souza DO. Effects of Hg2+ and CH3Hg+ on Ca2+ fluxes in rat brain microsomes. Brain Res 1996; 738:257-64. [PMID: 8955521 DOI: 10.1016/s0006-8993(96)00781-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A permanent increase in cytosolic Ca2+ levels seems to be associated with various pathological situations which may result in cell death. Hg2+ and CH3Hg+ are potent neurotoxic agents, but the precise molecular mechanism(s) underlying their effects are not sufficiently understood. In the present study we investigated the potential role of Ca(2+)-ATPase located in the endoplasmic reticulum as a molecular target for mercury. Hg2+ and CH3Hg+ inhibited Ca(2+)-ATPase and Ca2+ uptake by brain microsomes with similar potencies. However, the inhibitory potency of Hg2+ was higher than that of CH3Hg+, probably reflecting differences in the affinity for the sulfhydryl groups of these compounds. Passive or unidirectional Ca2+ efflux (measured in the absences of Ca(2+)-ATPase ligands) was increased significantly by CH3Hg+ and Hg2+. Again, the potency of Hg2+ was higher than that of CH3Hg+. Blockers of Ca2+ channels (ruthenium red, procaine, heparin) did not affect the increase in passive Ca2+ efflux induced by mercury compounds, possibly indicating that Ca2+ release occurs through Ca(2+)-ATPase. Addition of physiological concentrations of glutathione (GSH) simultaneously with mercury abolished the inhibitory effects of both forms of Hg on ca(2+)-transport. However, if the enzyme was first inhibited with Hg2+ or CH3Hg+ and subsequently treated with GSH, the reversal of inhibition was about 50%, suggesting that part of the cysteinyl residues involved in the inhibitory actions of mercury in Ca(2+)-transport bind to mercury with an extremely high affinity.
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Affiliation(s)
- A J Freitas
- Departamento de Quimica, Universidade Federal de Santa Maria, RS, Brazil
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47
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Stein MA, Mathers DA, Yan H, Baimbridge KG, Finlay BB. Enteropathogenic Escherichia coli markedly decreases the resting membrane potential of Caco-2 and HeLa human epithelial cells. Infect Immun 1996; 64:4820-5. [PMID: 8890244 PMCID: PMC174450 DOI: 10.1128/iai.64.11.4820-4825.1996] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
It is presumed, but not proven, that enteropathogenic Escherichia coli (EPEC) causes secretory diarrhea by altering ion transport in enterocytes. In this study we used the whole-cell, current clamp variant of the patch clamp technique to demonstrate that EPEC infection of HeLa and Caco-2 human epithelial cells reduces cell resting membrane potential. The observed reduction of resting membrane potential in HeLa cells results from EPEC-mediated signal transduction to the host cell but is not dependent upon EPEC-mediated elevation of levels of intracellular free calcium. These findings indicate that EPEC can directly alter the relative distribution of ions across epithelial host cell membranes. This may be relevant to the etiology of diarrhea caused by EPEC infection.
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Affiliation(s)
- M A Stein
- Biotechnology Laboratory, University of British Columbia, Vancouver, Canada
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48
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Elevation of intracellular calcium levels in outer hair cells by trimethyltin. Toxicol In Vitro 1996; 10:567-76. [DOI: 10.1016/s0887-2333(96)00036-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/12/1995] [Indexed: 11/23/2022]
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49
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Edelfors S, Hass U, Ravn-Jonsen A, Lund SP. The effect of ageing and in vitro exposure to xylene and KCl on [Ca2+]i in synaptosomes from rats exposed prenatally to xylene. PHARMACOLOGY & TOXICOLOGY 1996; 78:409-12. [PMID: 8829202 DOI: 10.1111/j.1600-0773.1996.tb00227.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Female rats (Mol: WIST) were exposed prenatally to 500 p.p.m. of technical xylene on days 7-20. At the age of fourteen months the rats were sacrificed and the synaptosomal fraction prepared for in vitro studies. The cytosolic calcium concentration was measured using the FURA-2 technique. The cytosolic calcium was increased in synaptosomes from old rats compared to those from rats at the age of three months, but no effect of prenatal exposure was seen. When synaptosomes were incubated with xylene, potassium or both, the cytosolic calcium concentration was changed identically in all groups of rats. When synaptosomes were incubated simultaneously to xylene and potassium a dramatical leakage of FURA-2 was observed. The mechanisms behind the membrane leakage are discussed.
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Affiliation(s)
- S Edelfors
- Department of Pharmacology, Panum Institute, University of Copenhagen, Denmark
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50
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Liu Y, Fechter LD. Comparison of the effects of trimethyltin on the intracellular calcium levels in spiral ganglion cells and outer hair cells. Acta Otolaryngol 1996; 116:417-21. [PMID: 8790741 DOI: 10.3109/00016489609137866] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Cochlear impairment by trimethyltin chloride (TMT), a potential contaminant of marine paints and polyvinyl chloride tubing, has been well demonstrated. Its toxic effect on the inner hair cells (IHC)-spiral ganglion cell (SGC) unit occurs almost immediately while disruption of outer hair cell (OHC) function does not occur until several hours after exposure. In this experiment, OHCs and SGCs from pigmented guinea pigs were tested in vitro to determine the role of enhanced intracellular calcium [Ca2+]i levels in TMT ototoxicity and to determine the sources of enhanced [Ca2+]i. The latter was determined by experiments using artificial perilymph without Ca2+ and by use of the Ca2+ channel blocker, nifedipine. The data show that TMT elevates [Ca2+]i in both OHC and SGC. The elevation of [Ca2+]i in SGC is much more rapid and larger than that in OHC. The elevation of [Ca2+]i in SGC can be attenuated by removing Ca2+ from artificial perilymph or pretreating with nifedipine, but neither of these treatments is effective in OHC. The results suggest that TMT disrupts intracellular storage of Ca2+ in OHCs and SGCs, but that is also enhancing influx of Ca2+ from extracellular sources in the SGCs.
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Affiliation(s)
- Y Liu
- College of Pharmacy, Toxicology Program, University of Oklahoma Health Sciences Center, Oklahoma City 73190, USA
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