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Maiuri T, Bazan CB, Harding RJ, Begeja N, Kam TI, Byrne LM, Rodrigues FB, Warner MM, Neuman K, Mansoor M, Badiee M, Dasovich M, Wang K, Thompson LM, Leung AKL, Andres SN, Wild EJ, Dawson TM, Dawson VL, Arrowsmith CH, Truant R. Poly ADP-ribose signaling is dysregulated in Huntington disease. Proc Natl Acad Sci U S A 2024; 121:e2318098121. [PMID: 39331414 DOI: 10.1073/pnas.2318098121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/28/2024] Open
Abstract
Huntington disease (HD) is a genetic neurodegenerative disease caused by cytosine, adenine, guanine (CAG) expansion in the Huntingtin (HTT) gene, translating to an expanded polyglutamine tract in the HTT protein. Age at disease onset correlates to CAG repeat length but varies by decades between individuals with identical repeat lengths. Genome-wide association studies link HD modification to DNA repair and mitochondrial health pathways. Clinical studies show elevated DNA damage in HD, even at the premanifest stage. A major DNA repair node influencing neurodegenerative disease is the PARP pathway. Accumulation of poly adenosine diphosphate (ADP)-ribose (PAR) has been implicated in Alzheimer and Parkinson diseases, as well as cerebellar ataxia. We report that HD mutation carriers have lower cerebrospinal fluid PAR levels than healthy controls, starting at the premanifest stage. Human HD induced pluripotent stem cell-derived neurons and patient-derived fibroblasts have diminished PAR response in the context of elevated DNA damage. We have defined a PAR-binding motif in HTT, detected HTT complexed with PARylated proteins in human cells during stress, and localized HTT to mitotic chromosomes upon inhibition of PAR degradation. Direct HTT PAR binding was measured by fluorescence polarization and visualized by atomic force microscopy at the single molecule level. While wild-type and mutant HTT did not differ in their PAR binding ability, purified wild-type HTT protein increased in vitro PARP1 activity while mutant HTT did not. These results provide insight into an early molecular mechanism of HD, suggesting possible targets for the design of early preventive therapies.
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Affiliation(s)
- Tamara Maiuri
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 3Z5, Canada
| | - Carlos Barba Bazan
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 3Z5, Canada
| | - Rachel J Harding
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto ON M5S 3M2, Canada
- Structural Genomics Consortium, University of Toronto, Toronto, ON M5G 1L7, Canada
- Department of Pharmacology and Toxicology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Nola Begeja
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 3Z5, Canada
| | - Tae-In Kam
- Neurodegeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Lauren M Byrne
- University College London Huntington Disease Centre, University College London Queen Square Institute of Neurology, University College London, London WC1N 3BG, United Kingdom
| | - Filipe B Rodrigues
- University College London Huntington Disease Centre, University College London Queen Square Institute of Neurology, University College London, London WC1N 3BG, United Kingdom
| | - Monica M Warner
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 3Z5, Canada
- Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Kaitlyn Neuman
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 3Z5, Canada
| | - Muqtasid Mansoor
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 3Z5, Canada
| | - Mohsen Badiee
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205
| | - Morgan Dasovich
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205
| | - Keona Wang
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697
| | - Leslie M Thompson
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697
- Department of Psychiatry and Human Behavior, University of California, Irvine, CA 92868
| | - Anthony K L Leung
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205
- Department of Molecular Biology and Genetics, School of Medicine, Johns Hopkins University, Baltimore, MD 21205
- Department of Genetic Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205
- Department of Oncology, School of Medicine, Johns Hopkins University, Baltimore, MD 21205
| | - Sara N Andres
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 3Z5, Canada
- Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Edward J Wild
- University College London Huntington Disease Centre, University College London Queen Square Institute of Neurology, University College London, London WC1N 3BG, United Kingdom
| | - Ted M Dawson
- Neurodegeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Valina L Dawson
- Neurodegeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Cheryl H Arrowsmith
- Structural Genomics Consortium, University of Toronto, Toronto, ON M5G 1L7, Canada
- Princess Margaret Cancer Centre, University of Toronto, Toronto, ON M5G 1L7, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 1L7, Canada
| | - Ray Truant
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 3Z5, Canada
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2
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Kraskovskaya N, Koltsova A, Parfenova P, Shatrova A, Yartseva N, Nazarov V, Devyatkina E, Khotin M, Mikhailova N. Dermal Fibroblast Cell Line from a Patient with the Huntington's Disease as a Promising Model for Studying Disease Pathogenesis: Production and Characterization. BIOCHEMISTRY. BIOKHIMIIA 2024; 89:1239-1250. [PMID: 39218021 DOI: 10.1134/s000629792407006x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Revised: 05/21/2024] [Accepted: 06/13/2024] [Indexed: 09/04/2024]
Abstract
Huntington's disease (HD) is an incurable hereditary disease caused by expansion of the CAG repeats in the HTT gene encoding the mutant huntingtin protein (mHTT). Despite numerous studies in cellular and animal models, the mechanisms underlying the biological role of mHTT and its toxicity to striatal neurons have not yet been established and no effective therapy for HD patients has been developed so far. We produced and characterized a new line of dermal fibroblasts (HDDF, Huntington's disease dermal fibroblasts) from a patient with a confirmed HD diagnosis. We also studied the growth characteristics of HDDF cells, stained them for canonical markers, karyotyped these cells, and investigated their phenotype. HDDF cells was successfully reprogrammed into induced striatal neurons via transdifferentiation. The new fibroblast line can be used as a cell model to study the biological role of mHTT and manifestations of HD pathogenesis in both fibroblasts and induced neuronal cells obtained from them by reprogramming techniques.
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Affiliation(s)
- Nina Kraskovskaya
- Institute of Cytology, Russian Academy of Science, St. Petersburg, 194064, Russia.
| | - Anna Koltsova
- Institute of Cytology, Russian Academy of Science, St. Petersburg, 194064, Russia
| | - Polina Parfenova
- Institute of Cytology, Russian Academy of Science, St. Petersburg, 194064, Russia
| | - Alla Shatrova
- Institute of Cytology, Russian Academy of Science, St. Petersburg, 194064, Russia
| | - Natalya Yartseva
- Institute of Cytology, Russian Academy of Science, St. Petersburg, 194064, Russia
| | - Vladimir Nazarov
- Pavlov First St. Petersburg State Medical University, St. Petersburg, 197022, Russia
| | - Ekaterina Devyatkina
- Pavlov First St. Petersburg State Medical University, St. Petersburg, 197022, Russia
| | - Mikhail Khotin
- Institute of Cytology, Russian Academy of Science, St. Petersburg, 194064, Russia
| | - Natalia Mikhailova
- Institute of Cytology, Russian Academy of Science, St. Petersburg, 194064, Russia
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3
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Maiuri T, Hung CL, Suart C, Begeja N, Barba-Bazan C, Peng Y, Savic N, Wong T, Truant R. DNA Repair in Huntington's Disease and Spinocerebellar Ataxias: Somatic Instability and Alternative Hypotheses. J Huntingtons Dis 2021; 10:165-173. [PMID: 33579859 PMCID: PMC7990435 DOI: 10.3233/jhd-200414] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The use of genome wide association studies (GWAS) in Huntington's disease (HD) research, driven by unbiased human data analysis, has transformed the focus of new targets that could affect age at onset. While there is a significant depth of information on DNA damage repair, with many drugs and drug targets, most of this development has taken place in the context of cancer therapy. DNA damage repair in neurons does not rely on DNA replication correction mechanisms. However, there is a strong connection between DNA repair and neuronal metabolism, mediated by nucleotide salvaging and the poly ADP-ribose (PAR) response, and this connection has been implicated in other age-onset neurodegenerative diseases. Validation of leads including the mismatch repair protein MSH3, and interstrand cross-link repair protein FAN1, suggest the mechanism is driven by somatic CAG instability, which is supported by the protective effect of CAA substitutions in the CAG tract. We currently do not understand: how somatic instability is triggered; the state of DNA damage within expanding alleles in the brain; whether this damage induces mismatch repair and interstrand cross-link pathways; whether instability mediates toxicity, and how this relates to human ageing. We discuss DNA damage pathways uncovered by HD GWAS, known roles of other polyglutamine disease proteins in DNA damage repair, and a panel of hypotheses for pathogenic mechanisms.
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Affiliation(s)
- Tamara Maiuri
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Claudia L.K. Hung
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Celeste Suart
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Nola Begeja
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Carlos Barba-Bazan
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Yi Peng
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Natasha Savic
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Timothy Wong
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
| | - Ray Truant
- McMaster University, Department of Biochemistry and Biomedical Sciences, Hamilton, Ontario, Canada
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Smatlikova P, Askeland G, Vaskovicova M, Klima J, Motlik J, Eide L, Ellederová Z. Age-Related Oxidative Changes in Primary Porcine Fibroblasts Expressing Mutated Huntingtin. NEURODEGENER DIS 2019; 19:22-34. [PMID: 31167196 DOI: 10.1159/000500091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 03/30/2019] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Huntington's disease (HD) is a devastating neurodegenerative disorder caused by CAG triplet expansions in the huntingtin gene. Oxidative stress is linked to HD pathology, although it is not clear whether this is an effect or a mediator of disease. The transgenic (TgHD) minipig expresses the N-terminal part of human-mutated huntingtin and represents a unique model to investigate therapeutic strategies towards HD. A more detailed characterization of this model is needed to fully utilize its potential. METHODS In this study, we focused on the molecular and cellular features of fibroblasts isolated from TgHD minipigs and the wild-type (WT) siblings at different ages, pre-symptomatic at the age of 24-36 months and with the onset of behavioural symptoms at the age of 48 months. We measured oxidative stress, the expression of oxidative stress-related genes, proliferation capacity along with the expression of cyclin B1 and D1 proteins, cellular permeability, and the integrity of the nuclear DNA (nDNA) and mitochondrial DNA in these cells. RESULTS TgHD fibroblasts isolated from 48-month-old animals showed increased oxidative stress, which correlated with the overexpression of SOD2 encoding mitochondrial superoxide dismutase 2, and the NEIL3 gene encoding DNA glycosylase involved in replication-associated repair of oxidized DNA. TgHD cells displayed an abnormal proliferation capacity and permeability. We further demonstrated increased nDNA damage in pre-symptomatic TgHD fibroblasts (isolated from animals aged 24-36 months). CONCLUSIONS Our results unravel phenotypic alterations in primary fibroblasts isolated from the TgHD minipig model at the age of 48 months. Importantly, nDNA damage appears to precede these phenotypic alterations. Our results highlight the impact of fibroblasts from TgHD minipigs in studying the molecular mechanisms of HD pathophysiology that gradually occur with age.
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Affiliation(s)
- Petra Smatlikova
- Laboratory of Cell Regeneration and Plasticity, Research Center PIGMOD, Institute of Animal Physiology and Genetics, Czech Academy of Science, Libechov, Czechia.,Department of Cell Biology, Faculty of Science, Charles University in Prague, Prague, Czechia
| | - Georgina Askeland
- Department of Medical Biochemistry, University of Oslo and Oslo University Hospital, Oslo, Norway.,Department of Microbiology, Oslo University Hospital, Oslo, Norway
| | - Michaela Vaskovicova
- Laboratory of DNA Integrity, Research Center PIGMOD, Institute of Animal Physiology and Genetics, Czech Academy of Science, Libechov, Czechia.,Department of Cell Biology, Faculty of Science, Charles University in Prague, Prague, Czechia
| | - Jiri Klima
- Laboratory of Cell Regeneration and Plasticity, Research Center PIGMOD, Institute of Animal Physiology and Genetics, Czech Academy of Science, Libechov, Czechia
| | - Jan Motlik
- Laboratory of Cell Regeneration and Plasticity, Research Center PIGMOD, Institute of Animal Physiology and Genetics, Czech Academy of Science, Libechov, Czechia
| | - Lars Eide
- Department of Medical Biochemistry, University of Oslo and Oslo University Hospital, Oslo, Norway
| | - Zdenka Ellederová
- Laboratory of Cell Regeneration and Plasticity, Research Center PIGMOD, Institute of Animal Physiology and Genetics, Czech Academy of Science, Libechov, Czechia,
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5
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Abstract
Diseases such as Huntington's disease and certain spinocerebellar ataxias are caused by the expansion of genomic cytosine-adenine-guanine (CAG) trinucleotide repeats beyond a specific threshold. These diseases are all characterised by neurological symptoms and central neurodegeneration, but our understanding of how expanded repeats drive neuronal loss is incomplete. Recent human genetic evidence implicates DNA repair pathways, especially mismatch repair, in modifying the onset and progression of CAG repeat diseases. Repair pathways might operate directly on repeat sequences by licensing or inhibiting repeat expansion in neurons. Alternatively, or in addition, because many of the genes containing pathogenic CAG repeats encode proteins that themselves have roles in the DNA damage response, it is possible that repeat expansions impair specific DNA repair pathways. DNA damage could then accrue in neurons, leading to further expansion at repeat loci, thus setting up a vicious cycle of pathology. In this review, we consider DNA damage and repair pathways in postmitotic neurons in the context of disease-causing CAG repeats. Investigating and understanding these pathways, which are clearly relevant in promoting and ameliorating disease in humans, is a research priority, as they are known to modify disease and therefore constitute prevalidated drug targets.
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Affiliation(s)
- Thomas H Massey
- Institute of Psychological Medicine and Clinical Neurosciences, MRC Centre for Neuropsychiatric Genetics and Genomics, Hadyn Ellis Building, Cardiff University, Cardiff, CF24 4HQ, UK
| | - Lesley Jones
- Institute of Psychological Medicine and Clinical Neurosciences, MRC Centre for Neuropsychiatric Genetics and Genomics, Hadyn Ellis Building, Cardiff University, Cardiff, CF24 4HQ, UK
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6
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Pan L, Penney J, Tsai LH. Chromatin regulation of DNA damage repair and genome integrity in the central nervous system. J Mol Biol 2014; 426:3376-88. [PMID: 25128619 DOI: 10.1016/j.jmb.2014.08.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Revised: 08/04/2014] [Accepted: 08/05/2014] [Indexed: 12/17/2022]
Abstract
With the continued extension of lifespan, aging and age-related diseases have become a major medical challenge to our society. Aging is accompanied by changes in multiple systems. Among these, the aging process in the central nervous system is critically important but very poorly understood. Neurons, as post-mitotic cells, are devoid of replicative associated aging processes, such as senescence and telomere shortening. However, because of the inability to self-replenish, neurons have to withstand challenge from numerous stressors over their lifetime. Many of these stressors can lead to damage of the neurons' DNA. When the accumulation of DNA damage exceeds a neuron's capacity for repair, or when there are deficiencies in DNA repair machinery, genome instability can manifest. The increased mutation load associated with genome instability can lead to neuronal dysfunction and ultimately to neuron degeneration. In this review, we first briefly introduce the sources and types of DNA damage and the relevant repair pathways in the nervous system (summarized in Fig. 1). We then discuss the chromatin regulation of these processes and summarize our understanding of the contribution of genomic instability to neurodegenerative diseases.
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Affiliation(s)
- Ling Pan
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jay Penney
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Li-Huei Tsai
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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7
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Mariucci G, Villarini M, Moretti M, Taha E, Conte C, Minelli A, Aristei C, Ambrosini MV. Brain DNA damage and 70-kDa heat shock protein expression in CD1 mice exposed to extremely low frequency magnetic fields. Int J Radiat Biol 2010; 86:701-10. [DOI: 10.3109/09553001003789588] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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8
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Belloni M, Uberti D, Rizzini C, Ferrari-Toninelli G, Rizzonelli P, Jiricny J, Spano P, Memo M. Distribution and kainate-mediated induction of the DNA mismatch repair protein MSH2 in rat brain. Neuroscience 2000; 94:1323-31. [PMID: 10625070 DOI: 10.1016/s0306-4522(99)00380-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
DNA repair is one of the most essential systems for maintaining the inherited nucleotide sequence of genomic DNA over time. Repair of DNA damage would be particularly important in neurons, because these cells are among the longest-living cells in the body. MSH2 is one of the proteins which are involved in the recognition and repair of a specific type of DNA damage that is characterized by pair mismatches. We studied the distribution of MSH2 in rat brain by immunohistochemical analysis. We found the level of MSH2 expression in rat brain to be clearly heterogeneous. The highest intensity of staining was found in the pyramidal neurons of the hippocampus and in the entorhinal and frontoparietal cortices. Positive cells were observed in the substantia nigra pars compacta, in cerebellar granular and Purkinje cells, and in the motor neurons of the spinal cord. We investigated the possible modulation of MSH2 expression after injection of kainate. Systemic administration of kainate induces various behavioural alterations and a typical pattern of neuropathology, with cell death in the hippocampal pyramidal neurons of the CA3/CA4 fields. Kainate injection also resulted in a marked, dose-dependent increase of MSH2 immunoreactivity in the hippocampal neurons of the CA3/CA4 fields. The effect was specific, since no changes in immunoreactivity were detected in the dentate gyrus nor in other brain areas. In summary, our data suggest that a mismatch DNA repair system, of which MSH2 protein is a representative component, is heterogeneously expressed in the rat brain and specifically induced by an experimental paradigm of excitotoxicity.
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Affiliation(s)
- M Belloni
- Department of Biomedical Sciences and Biotechnologies, School of Medicine, University of Brescia, Italy
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9
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Hurd YL, Yakovleva T, Nussenzweig A, Li GC, Terenius L, Bakalkin G. A novel neuron-specific DNA end-binding factor in the murine brain. Mol Cell Neurosci 1999; 14:213-24. [PMID: 10576891 DOI: 10.1006/mcne.1999.0782] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To characterize the distribution of transcription factor AP-1 and YY1 DNA-binding activities in the rat brain, the labeled target oligonucleotides were loaded on brain sections and after incubation and washing, the residual signal was registered by autoradiography. The binding was predominantly associated with neurons and was regionally specific with highest levels in the cerebellum, hippocampus, and piriform cortex. The identified binding factor was not, however, sequence-specific, but apparently recognized DNA ends and was activated by long double-stranded DNA. UV cross-linking identified the molecular mass of the factor to be about 80 kDa. The factor was not found in soluble brain extracts, suggesting its association with membranes or the nuclear matrix. Despite apparent similarities with Ku protein, which targets DNA-ends, the DNA end-binding activity was present in brains of Ku86- and Ku70-deficient mice. Since DNA end-binding factors are generally involved in DNA repair, the same function may be suggested for the novel factor identified in the present study.
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Affiliation(s)
- Y L Hurd
- Section of Psychiatry, Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden
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10
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Belloni M, Uberti D, Rizzini C, Jiricny J, Memo M. Induction of two DNA mismatch repair proteins, MSH2 and MSH6, in differentiated human neuroblastoma SH-SY5Y cells exposed to doxorubicin. J Neurochem 1999; 72:974-9. [PMID: 10037468 DOI: 10.1046/j.1471-4159.1999.0720974.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The MutS homologues MSH2 and MSH6 form a heterodimeric protein complex that is involved in the recognition of base/base mismatches and insertion/deletion loops, as well as some other types of DNA damage. We investigated the expression of these proteins in undifferentiated and retinoic acid-differentiated human neuroblastoma SH-SY5Y cells by immunocytochemistry, western blot analysis, and RT-PCR. Nuclei from undifferentiated SH-SY5Y cells were found to be immunoreactive to anti-MSH2 and anti-MSH6 antibodies. Following differentiation, the cells stop dividing and change morphology to acquire a neuron-like phenotype. Under these conditions, both anti-MSH2 and anti-MSH6 immunoreactivities were still detectable, although the signals were somewhat less intense. When these cells were exposed for 2 h to neurotoxic concentrations of doxorubicin (50 nM), they exhibited a marked and homogeneous increase of both anti-MSH2 and anti-MSH6 immunoreactivities. As revealed by western blot analysis, these effects were associated with increased protein content and were dose-dependent. Using RT-PCR technology, we also found that doxorubicin treatment did not change MSH2 or MSH6 mRNA levels. Our data indicate that human postmitotic, neuron-like cells constitutively express the molecular machinery devoted to recognition of DNA mismatches and that this system is activated by specific treatment leading to cell death. These findings might help clarify the molecular mechanisms underlying various human neurological diseases that are associated with deficiencies in DNA repair and/or a high rate of DNA damage acquisition.
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Affiliation(s)
- M Belloni
- Department of Biomedical Sciences and Biotechnology, School of Medicine, University of Brescia, Italy
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11
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12
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Abstract
To determine whether oxidative stress after cerebral ischemia-reperfusion affects genetic stability in the brain, we studied mutagenesis after forebrain ischemia-reperfusion in Big Blue transgenic mice (male C57BL/6 strain) containing a reporter lacI gene, which allows detection of mutation frequency. The frequency of mutation in this reporter lacI gene increased from 1.5 to 7.7 (per 100,000) in cortical DNA after 30 min of forebrain ischemia and 8 hr of reperfusion and remained elevated at 24 hr reperfusion. Eight DNA lesions that are characteristic of DNA damage mediated by free radicals were detected. Four mutagenic lesions (2,6-diamino-4-hydroxy-5-formamidopyrimidine, 8-hydroxyadenine, 5-hydroxycytosine, and 8-hydroxyguanine) examined by gas chromatography/mass spectrometry and one corresponding 8-hydroxy-2'-deoxyguanosine by a method of HPLC with electrochemical detection increased in cortical DNA two- to fourfold (p < 0.05) during 10-20 min of reperfusion. The damage to gamma-actin and DNA polymerase-beta genes was detected within 20 min of reperfusion based on the presence of formamidopyrimidine DNA N-glycosylase-sensitive sites. These genes became resistant to the glycosylase within 4-6 hr of reperfusion, suggesting a reduction in DNA damage and presence of DNA repair in nuclear genes. These results suggest that nuclear genes could be targets of free radicals.
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13
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Liu PK, Hsu CY, Dizdaroglu M, Floyd RA, Kow YW, Karakaya A, Rabow LE, Cui JK. Damage, repair, and mutagenesis in nuclear genes after mouse forebrain ischemia-reperfusion. J Neurosci 1996; 16:6795-806. [PMID: 8824320 PMCID: PMC2711221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/1996] [Revised: 08/02/1996] [Accepted: 08/13/1996] [Indexed: 02/02/2023] Open
Abstract
To determine whether oxidative stress after cerebral ischemia-reperfusion affects genetic stability in the brain, we studied mutagenesis after forebrain ischemia-reperfusion in Big Blue transgenic mice (male C57BL/6 strain) containing a reporter lacI gene, which allows detection of mutation frequency. The frequency of mutation in this reporter lacI gene increased from 1.5 to 7.7 (per 100,000) in cortical DNA after 30 min of forebrain ischemia and 8 hr of reperfusion and remained elevated at 24 hr reperfusion. Eight DNA lesions that are characteristic of DNA damage mediated by free radicals were detected. Four mutagenic lesions (2,6-diamino-4-hydroxy-5-formamidopyrimidine, 8-hydroxyadenine, 5-hydroxycytosine, and 8-hydroxyguanine) examined by gas chromatography/mass spectrometry and one corresponding 8-hydroxy-2'-deoxyguanosine by a method of HPLC with electrochemical detection increased in cortical DNA two- to fourfold (p < 0.05) during 10-20 min of reperfusion. The damage to gamma-actin and DNA polymerase-beta genes was detected within 20 min of reperfusion based on the presence of formamidopyrimidine DNA N-glycosylase-sensitive sites. These genes became resistant to the glycosylase within 4-6 hr of reperfusion, suggesting a reduction in DNA damage and presence of DNA repair in nuclear genes. These results suggest that nuclear genes could be targets of free radicals.
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Affiliation(s)
- P K Liu
- Laboratory of Neurobiology, Division of Restorative Neurology and Human Neurobiology, Baylor College of Medicine, Houston, Texas 77030, USA
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14
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Lai H, Singh NP. Single- and double-strand DNA breaks in rat brain cells after acute exposure to radiofrequency electromagnetic radiation. Int J Radiat Biol 1996; 69:513-21. [PMID: 8627134 DOI: 10.1080/095530096145814] [Citation(s) in RCA: 225] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We investigated the effects of acute (2-h) exposure to pulsed (2-micros pulse width, 500 pulses s(-1)) and continuous wave 2450-MHz radiofrequency electromagnetic radiation on DNA strand breaks in brain cells of rat. The spatial averaged power density of the radiation was 2mW/cm2, which produced a whole-body average-specific absorption rate of 1.2W/kg. Single- and double-strand DNA breaks in individual brain cells were measured at 4h post-exposure using a microgel electrophoresis assay. An increase in both types of DNA strand breaks was observed after exposure to either the pulsed or continuous-wave radiation, No significant difference was observed between the effects of the two forms of radiation. We speculate that these effects could result from a direct effect of radiofrequency electromagnetic energy on DNA molecules and/or impairment of DNA-damage repair mechanisms in brain cells. Our data further support the results of earlier in vitro and in vivo studies showing effects of radiofrequency electromagnetic radiation on DNA.
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Affiliation(s)
- H Lai
- Bioelectromagetics Research Laboratory, Center for Bioengineering, University of Washington, Seattle, 98195, USA
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15
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Blanchet P, Wellemeyer ML, Burton GV. Case report: retinitis pigmentosa following cytotoxic chemotherapy in Usher's syndrome. Am J Med Sci 1992; 303:319-20. [PMID: 1580321 DOI: 10.1097/00000441-199205000-00010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Ocular toxicity is an uncommon complication of cytotoxic chemotherapy. Retinitis pigmentosa complicating cancer chemotherapy has not been reported. A patient with probable Usher's syndrome (congenital sensorineural deafness) had apparent acceleration of retinitis pigmentosa with blindness following cytotoxic chemotherapy for non-Hodgkin's lymphoma. Retinitis pigmentosa, a feature of Usher's syndrome, usually develops as a slowly progressive process. The rapid acceleration of retinopathy following tumor therapy suggests a possible relationship to the cytotoxic chemotherapy. Lymphocytes and fibroblasts from patients with Usher's syndrome are hypersensitive to the x-ray type of DNA-damaging agents. The DNA-damaging effects of chemotherapy may have accelerated the progression of retinitis pigmentosa in this patient.
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Affiliation(s)
- P Blanchet
- Department of Medicine, Louisiana State University Medical Center-Shreveport 71130-3932
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16
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Hartshorn JN, Scicchitano DA, Robison SH. Measurements of genomic and gene-specific DNA repair of alkylation damage in cultured human T-lymphocytes. BASIC LIFE SCIENCES 1990; 53:233-49. [PMID: 2126430 DOI: 10.1007/978-1-4613-0637-5_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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17
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Robbins JH. A childhood neurodegeneration due to defective DNA repair: a novel concept of disease based on studies xeroderma pigmentosum. J Child Neurol 1989; 4:143-6. [PMID: 2654275 DOI: 10.1177/088307388900400215] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- J H Robbins
- Dermatology Branch, National Cancer Institute, Bethesda, MD 20892
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Robison SH, Munzer JS, Tandan R, Bradley WG. Alzheimer's disease cells exhibit defective repair of alkylating agent-induced DNA damage. Ann Neurol 1987; 21:250-8. [PMID: 3606032 DOI: 10.1002/ana.410210306] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The most common cause of senile and presenile dementia is Alzheimer's disease, a disorder with an undetermined cause. A number of studies have indicated that neurons from patients with Alzheimer's disease have decreased ribonucleic acid levels and reduced protein synthesis. Recent studies using lymphoblasts from patients with Alzheimer's disease have indicated that these cells are more sensitive to deoxyribonucleic acid (DNA)-alkylating agents. We have used cell survival, unscheduled DNA synthesis, and alkaline elution to assess the capacity for DNA repair in skin fibroblasts from normal control subjects, control subjects with central nervous system disease, and patients with Alzheimer's disease. Our results indicate that the Alzheimer's disease cells, unlike normal cells, fail to repair methylmethane sulfonate-induced DNA damage. Both normal and Alzheimer's disease cells are able to ameliorate the effects of ultraviolet light. These results indicate that a specific pathway for DNA repair is affected in Alzheimer's disease. The repair defect may be related to the cause of the disease or may be the cause of the disease.
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19
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Robbins JH, Otsuka F, Tarone RE, Polinsky RJ, Brumback RA, Nee LE. Parkinson's disease and Alzheimer's disease: hypersensitivity to X rays in cultured cell lines. J Neurol Neurosurg Psychiatry 1985; 48:916-23. [PMID: 3876409 PMCID: PMC1028494 DOI: 10.1136/jnnp.48.9.916] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Fibroblast and/or lymphoblastoid lines from patients with several inherited primary neuronal degenerations are hypersensitive to DNA-damaging agents. Therefore, lymphoblastoid lines were irradiated from patients with sporadic Parkinson's disease (PD), Alzheimer's disease, and amyotrophic lateral sclerosis. The mean survival values of the eight Parkinson's disease and of the six Alzheimer's disease lines, but not of the five amyotrophic lateral sclerosis lines, were less than that of the 28 normal lines. Our results with Parkinson's disease and Alzheimer's disease cells can be explained by a genetic defect arising as a somatic mutation during embryogenesis, causing defective repair of the X-ray type of DNA damage. Such a DNA repair defect could cause an abnormal accumulation of spontaneously occurring DNA damage in Parkinson's disease and Alzheimer's disease neurons in vivo, resulting in their premature death.
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Robbins JH, Brumback RA, Polinsky RJ, Wirtschafter JD, Tarone RE, Scudiero DA, Otsuka F. Hypersensitivity to DNA-damaging agents in abiotrophies: a new explanation for degeneration of neurons, photoreceptors, and muscle in Alzheimer, Parkinson and Huntington diseases, retinitis pigmentosa, and Duchenne muscular dystrophy. BASIC LIFE SCIENCES 1985; 35:315-44. [PMID: 2933027 DOI: 10.1007/978-1-4899-2218-2_20] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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22
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Boorstein RJ, Pardee AB. Factors modifying 3-aminobenzamide cytotoxicity in normal and repair-deficient human fibroblasts. J Cell Physiol 1984; 120:335-44. [PMID: 6746752 DOI: 10.1002/jcp.1041200312] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
3-Aminobenzamide (3-AB), an inhibitor of poly(ADP-ribosylation), is lethal to human fibroblasts with damaged DNA. Its cytotoxicity was determined relative to a number of factors including the types of lesions, the kinetics of repair, and the availability of alternative repair systems. A variety of alkylating agents, UV or gamma irradiation, or antimetabolites were used to create DNA lesions. 3-AB enhanced lethality with monofunctional alkylating agents only. Within this class of compounds, methylmethanesulfonate (MMS) treatments made cells more sensitive to 3-AB than did treatment with methylnitrosourea (MNU) or methylnitronitrosoguanidine (MNNG). 3-AB interfered with a dynamic repair process lasting several days, since human fibroblasts remained sensitive to 3-AB for 36-48 hours following MMS treatment. During this same interval, 3-AB caused these cells to arrest in G2 phase. Alkaline elution analysis also revealed that this slow repair was delayed further by 3-AB. Human mutant cells defective in DNA repair differed in their responses to 3-AB. Among mutants sensitive to monofunctional alkylating agents, ataxia telangiectasia cells were slightly more sensitive to 3-AB than control cells, while Huntington's disease cells had a near-normal response. Among UV-sensitive strains, xeroderma pigmentosum variant (XPV) cells were more sensitive to 3-AB after MMS than were XP complementation group A (A) cells, which responded normally. Greater lethality with 3-AB could be dependent on inability of the mutant cells to repair damage by other processes.
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Ohno K, Takeshita K. Patients with tuberous sclerosis have fibroblasts with normal limits for growth characteristics and sensitivities to DNA alkylating agents. JINRUI IDENGAKU ZASSHI. THE JAPANESE JOURNAL OF HUMAN GENETICS 1984; 29:359-69. [PMID: 6442744 DOI: 10.1007/bf01871251] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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24
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Abstract
The contribution of genetic differences to variation in ageing and the relationship of ageing to certain types of dementia are discussed. Neuropathological changes commonly found in the ageing brain are present in more severe form in Alzheimer-type dementia, Down's syndrome, multi-infarct dementia, and a substantial number of patients with Parkinson's disease. An increased frequency of ageing-associated changes outside the brain have been reported in Alzheimer-type dementia, Down's syndrome, and multi-infarct dementia, although the evidence is generally meagre and in many cases requires further corroboration. Genetic studies of Alzheimer-type dementia support the existence of heterogeneity on the basis of family history and age of onset; early onset is associated with greater genetic risk and severity of abnormality. The increasing evidence of an association between DNA damage, premature ageing, and neuronal cell loss may provide insights into the aetiology of these and other forms of dementia.
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Abstract
Huntington disease is a neurological autosomal dominant disease of unknown origin and the search for a suitable diagnostic marker has been extended to the peripheral tissues. It is generally believed that a membrane defect exists in Huntington disease although the evidence is controversial. It is the aim of this review to examine the validity of these claims for each of the peripheral tissues and techniques involved, and it is not intended to include all other aspects of research into Huntington disease.
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Robbins JH, Scudiero DA, Otsuka F, Tarone RE, Brumback RA, Wirtschafter JD, Polinsky RJ, Barrett SF, Moshell AN, Scarpinato RG. Hypersensitivity to DNA-damaging agents in cultured cells from patients with Usher's syndrome and Duchenne muscular dystrophy. J Neurol Neurosurg Psychiatry 1984; 47:391-8. [PMID: 6726265 PMCID: PMC1027781 DOI: 10.1136/jnnp.47.4.391] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Lymphoblastoid lines from nine Usher's syndrome (recessively inherited retinitis pigmentosa and congenital sensorineural deafness) patients (representing eight kindreds) and from ten Duchenne muscular dystrophy patients (representing seven kindreds) showed a small but statistically significant hypersensitivity to the lethal effects of X-rays, as measured by the cellular ability to exclude the vital dye trypan blue, when compared with lines from 26 normal control subjects. Fibroblast lines from the Usher's syndrome patients, treated with X-rays or the radiomimetic, DNA-damaging chemical N-methyl-N'-nitro-N-nitrosoguanidine, also showed a statistically significant hypersensitivity when compared to normal fibroblast lines. These findings are consistent with the possibility that defective DNA repair mechanisms may be involved in the pathogenesis of these degenerative diseases.
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Brennan S, Lewis PD. Studies of cellular radiosensitivity in hereditary disorders of nervous system and muscle. J Neurol Neurosurg Psychiatry 1983; 46:1143-5. [PMID: 6663314 PMCID: PMC491782 DOI: 10.1136/jnnp.46.12.1143] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Skin fibroblasts from patients with familial dysautonomia, Duchenne muscular dystrophy and Charcot-Marie-Tooth disease show normal sensitivity to ionising radiation, as measured by post-irradiation clonal growth. Previous reports of cellular hypersensitivity to ionising radiation and other DNA-damaging agents in familial dysautonomia and Duchenne muscular dystrophy have not been confirmed.
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Robbins JH, Polinsky RJ, Moshell AN. Evidence that lack of deoxyribonucleic acid repair causes death of neurons in xeroderma pigmentosum. Ann Neurol 1983; 13:682-4. [PMID: 6881931 DOI: 10.1002/ana.410130621] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Xeroderma pigmentosum (XP) is an autosomal recessive disorder with hypersensitivity to the lethal effects of ultraviolet radiation caused by inherited defects in deoxyribonucleic acid (DNA) repair processes. Some patients with XP develop a primary neuronal degeneration which has been thought to result from unrepaired damage in neuronal DNA. Five years ago we reported that cultured skin fibroblasts from a 12-year-old girl with XP, who then had only one major neurological abnormality of the disease, had a sensitivity to ultraviolet radiation intermediate between that of XP patients with numerous neurological abnormalities and those with none. Recent neurological studies reveal that she has a slowly but progressively developing sensorineural deafness as well as cerebellar and motor dysfunction typical of XP. The results support the postulate that defective DNA repair is associated with premature neuron death.
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Frommel D, Allain JP, Courouce AM, Derose S, Trepo D, Crivelli O, Rizzetto M. Long-lasting abatement of HBsAg synthesis induced by acute delta infection. Lancet 1983; 1:656-7. [PMID: 6131340 DOI: 10.1016/s0140-6736(83)91835-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Robbins JH, Otsuka F, Tarone RE, Polinsky RJ, Brumback RA, Moshell AN, Nee LE, Ganges MB, Cayeux SJ. Radiosensitivity in alzheimer disease and Parkinson disease. Lancet 1983; 1:468-9. [PMID: 6131182 DOI: 10.1016/s0140-6736(83)91461-7] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Abstract
Figure 2 illustrates a suggested mechanism of carcinogenesis. This scheme takes into account the effect of carcinogens at different integration levels: subcellular, tissue, and organism. Any of these levels may be age dependent. Age-associated changes in the activity of enzymes responsible for activation and inactivation of carcinogens, and variations in concentrations of lipids and proteins contributing to the transport of carcinogenic agents into cells, may play an important role in the modifying effect of age on carcinogenesis. The effects of age-associated changes in DNA repair need clarification. However, they are thought to exert a permissive influence on the age-associated rise in tumor incidence. It seems that proliferative activity of target tissues is the important modifying factor of carcinogenesis. Age-related changes of regulation at tissue and organism levels are also powerful factors in carcinogenesis modification. Age-dependent changes in the neuroendocrine system provide conditions for metabolic immunodepression and promotion of carcinogenesis. On the other hand, carcinogens per se (especially chemical and radiological) may intensify aging processes in the organism. Normalization, by drugs, of age-associated shifts requiring synthetic and energetic changes of a transformed tumor cells, and of immunological shifts, may exert both antitumor and geroprotective effects.
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Scudiero DA, Moshell AN, Scarpinato RG, Meyer SA, Clatterbuck BE, Tarone RE, Robbins JH. Lymphoblastoid lines and skin fibroblasts from patients with tuberous sclerosis are abnormally sensitive to ionizing radiation and to a radiomimetic chemical. J Invest Dermatol 1982; 78:234-8. [PMID: 7057056 DOI: 10.1111/1523-1747.ep12506550] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Lymphoblastoid lines, derived by transforming peripheral blood lymphocytes with Epstein-Barr virus, and skin fibroblast lines were established from two patients with tuberous sclerosis. The number of viable lymphoblastoid cells was determined by their ability to exclude the vital dye trypan blue after their irradiation with x-rays or 254 nm ultraviolet light. The growth of fibroblasts was determined by their ability to form colonies after treatment with the radiomimetic, DNA-damaging chemical N-methyl-N'-nitro-N-nitrosoguanidine. The tuberous sclerosis lymphoblastoid lines were hypersensitive to x-rays but had normal sensitivity to the ultraviolet radiation. The tuberous sclerosis fibroblast lines were hypersensitive to the N-methyl-N'-nitro-N-nitrosoguanidine. The hypersensitivity of tuberous sclerosis cells to x-rays and to N-methyl-N'-nitro-N-nitrosoguanidine is believed to reflect defective repair of DNA damaged by these agents and may provide the basis for in vitro, including prenatal, diagnostic tests for tuberous sclerosis.
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