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Chen Y, Wu XL, Hu HB, Yang SN, Zhang ZY, Fu GL, Zhang CT, Li ZM, Wu F, Si KW, Ma YB, Ji SF, Zhou JS, Ren XY, Xiao XL, Liu JX. Neuronal MeCP2 in the dentate gyrus regulates mossy fiber sprouting of mice with temporal lobe epilepsy. Neurobiol Dis 2023; 188:106346. [PMID: 37931884 DOI: 10.1016/j.nbd.2023.106346] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 11/02/2023] [Accepted: 11/03/2023] [Indexed: 11/08/2023] Open
Abstract
Sprouting of mossy fibers, one of the most consistent findings in tissue from patients with mesial temporal lobe epilepsy, exhibits several uncommon axonal growth features and has been considered a paradigmatic example of circuit plasticity that occurs in the adult brain. Clarifying the mechanisms responsible may provide new insight into epileptogenesis as well as axon misguidance in the central nervous system. Methyl-CpG-binding protein 2 (MeCP2) binds to methylated genomic DNA to regulate a range of physiological functions implicated in neuronal development and adult synaptic plasticity. However, exploring the potential role of MeCP2 in the documented misguidance of axons in the dentate gyrus has not yet been attempted. In this study, a status epilepticus-induced decrease of neuronal MeCP2 was observed in the dentate gyrus (DG). An essential regulatory role of MeCP2 in the development of functional mossy fiber sprouting (MFS) was confirmed through stereotaxic injection of a recombinant adeno-associated virus (AAV) to up- or down-regulate MeCP2 in the dentate neurons. Chromatin immunoprecipitation sequencing (ChIP-seq) was performed to identify the binding profile of native MeCP2 using micro-dissected dentate tissues. In both dentate tissues and HT22 cell lines, we demonstrated that MeCP2 could act as a transcription repressor on miR-682 with the involvement of the DNA methylation mechanism. Further, we found that miR-682 could bind to mRNA of phosphatase and tensin homolog (PTEN) in a sequence specific manner, thus leading to the suppression of PTEN and excessive activation of mTOR. This study therefore presents a novel epigenetic mechanism by identifying MeCP2/miR-682/PTEN/mTOR as an essential signal pathway in regulating the formation of MFS in the temporal lobe epileptic (TLE) mice. SIGNIFICANCE STATEMENT: Understanding the mechanisms that regulate axon guidance is important for a better comprehension of neural disorders. Sprouting of mossy fibers, one of the most consistent findings in patients with mesial temporal lobe epilepsy, has been considered a paradigmatic example of circuit plasticity in the adult brain. Although abnormal regulation of DNA methylation has been observed in both experimental rodents and humans with epilepsy, the potential role of DNA methylation in this well-documented example of sprouting of dentate axon remains elusive. This study demonstrates an essential role of methyl-CpG-binding protein 2 in the formation of mossy fiber sprouting. The underlying signal pathway has been also identified. The data hence provide new insight into epileptogenesis as well as axon misguidance in the central nervous system.
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Affiliation(s)
- Yu Chen
- Institute of Neurobiology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China; Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China; Institute of Neuroscience, Translational Medicine Institute, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City 710061, China
| | - Xiao-Lin Wu
- Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China
| | - Hai-Bo Hu
- Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China
| | - Shu-Nan Yang
- Institute of Neurobiology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China; Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China; Institute of Neuroscience, Translational Medicine Institute, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City 710061, China
| | - Zi-Yi Zhang
- Institute of Neurobiology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China; Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China; Institute of Neuroscience, Translational Medicine Institute, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City 710061, China
| | - Guan-Ling Fu
- Institute of Neurobiology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China; Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China; Institute of Neuroscience, Translational Medicine Institute, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City 710061, China
| | - Chu-Tong Zhang
- Qide College, Xi'an Jiaotong University Health Science Center, Xi'an, China
| | - Zi-Meng Li
- Zonglian College, Xi'an Jiaotong University Health Science Center, Xi'an, China
| | - Feng Wu
- Center of Teaching and Experiment for Medical Postgraduates, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an 710061, China
| | - Kai-Wei Si
- Department of Pathogenic Biology and Immunology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an 710061, China
| | - Yan-Bing Ma
- Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China
| | - Sheng-Feng Ji
- Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China
| | - Jin-Song Zhou
- Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China
| | - Xiao-Yong Ren
- Department of Otolaryngology Head and Neck Surgery, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710004, China
| | - Xin-Li Xiao
- Department of Human Anatomy, Histology and Embryology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China.
| | - Jian-Xin Liu
- Institute of Neurobiology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City, 710061, China; Institute of Neuroscience, Translational Medicine Institute, Xi'an Jiaotong University Health Science Center, 76 West Yanta Road, Xi'an City 710061, China.
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Xu F, Zhang X, Wang J, Li X, He B, Xiao F, Yan T, Wu B, Jia Y, Wang Z. Spinosin protects N2a cells from H 2 O 2 -induced neurotoxicity through inactivation of p38MAPK. J Pharm Pharmacol 2020; 72:1607-1614. [PMID: 32667705 DOI: 10.1111/jphp.13334] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 06/14/2020] [Accepted: 06/21/2020] [Indexed: 01/26/2023]
Abstract
OBJECTIVES Previous studies have suggested that spinosin (SPI) exerted neuroprotective effects through inhibition of oxidative damage, but the underlying mechanisms are still unclear. Herein, the mechanisms underlying the protective effects of SPI against oxidative stress induced by hydrogen peroxide (H2 O2 ) were examined in neuro-2a (N2a) mouse neuroblastoma cells. METHODS N2a cells were pretreated with H2 O2 for 2 h, followed by a 24-h incubation with SPI. Intracellular reactive oxygen species (ROS) production was analysed by flow cytometry. Levels of Aβ1-42 production were determined by ELISA assay. Levels of expression of c-Jun N-terminal kinase (JNK), p-JNK, extracellular signal-regulated kinase (ERK), p-ERK, p38 mitogen-activated protein kinase (p38MAPK), p-p38MAPK, p-Tau (Ser199), p-Tau (Ser202), p-Tau (Ser396), synaptophysin (SYP) and postsynaptic scaffold postsynaptic density-95 (PSD-95) were detected by Western blot analysis. KEY FINDINGS Our results showed that H2 O2 treatment enhanced intracellular ROS production in N2a cells. SPI prevented H2 O2 -induced oxidative damage via inhibiting Aβ1-42 production, decreasing Tau phosphorylation and improving synaptic structural plasticity. Notably, H2 O2 -increased p38MAPK activation was attenuated by SPI administration, and p38MAPK inhibitor BIRB796 markedly reduced H2 O2 -induced oxidative damage in N2a cells. CONCLUSIONS Our findings suggest that SPI protects N2a cells from H2 O2 -induced oxidative damage through inactivation of p38MAPK.
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Affiliation(s)
- Fanxing Xu
- Jiangsu Kanion Pharmaceutical Co., Ltd., Lianyungang, China.,Wuya College of Innovation, Shenyang Pharmaceutical University, Shenyang, China.,State Key Laboratory of New-tech for Chinese Medicine Pharmaceutical Process, Lianyungang, China
| | - Xiaoying Zhang
- School of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, Shenyang, China
| | - Jinyu Wang
- School of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, Shenyang, China
| | - Xu Li
- Jiangsu Kanion Pharmaceutical Co., Ltd., Lianyungang, China.,State Key Laboratory of New-tech for Chinese Medicine Pharmaceutical Process, Lianyungang, China
| | - Bosai He
- Faculty of Functional Food and Wine, Shenyang Pharmaceutical University, Shenyang, China
| | - Feng Xiao
- Faculty of Functional Food and Wine, Shenyang Pharmaceutical University, Shenyang, China
| | - Tingxu Yan
- Faculty of Functional Food and Wine, Shenyang Pharmaceutical University, Shenyang, China
| | - Bo Wu
- Faculty of Functional Food and Wine, Shenyang Pharmaceutical University, Shenyang, China
| | - Ying Jia
- Faculty of Functional Food and Wine, Shenyang Pharmaceutical University, Shenyang, China
| | - Zhenzhong Wang
- Jiangsu Kanion Pharmaceutical Co., Ltd., Lianyungang, China.,State Key Laboratory of New-tech for Chinese Medicine Pharmaceutical Process, Lianyungang, China
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Gill S, Kumara VMR. Detecting Neurodevelopmental Toxicity of Domoic Acid and Ochratoxin A Using Rat Fetal Neural Stem Cells. Mar Drugs 2019; 17:md17100566. [PMID: 31590222 PMCID: PMC6835907 DOI: 10.3390/md17100566] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 10/01/2019] [Accepted: 10/02/2019] [Indexed: 12/12/2022] Open
Abstract
Currently, animal experiments in rodents are the gold standard for developmental neurotoxicity (DNT) investigations; however, testing guidelines for these experiments are insufficient in terms of animal use, time, and costs. Thus, alternative reliable approaches are needed for predicting DNT. We chose rat neural stem cells (rNSC) as a model system, and used a well-known neurotoxin, domoic acid (DA), as a model test chemical to validate the assay. This assay was used to investigate the potential neurotoxic effects of Ochratoxin A (OTA), of which the main target organ is the kidney. However, limited information is available regarding its neurotoxic effects. The effects of DA and OTA on the cytotoxicity and on the degree of differentiation of rat rNSC into astrocytes, neurons, and oligodendrocytes were monitored using cell-specific immunofluorescence staining for undifferentiated rNSC (nestin), neurospheres (nestin and A2B5), neurons (MAP2 clone M13, MAP2 clone AP18, and Doublecortin), astrocytes (GFAP), and oligodendrocytes (A2B5 and mGalc). In the absence of any chemical exposure, approximately 46% of rNSC differentiated into astrocytes and neurons, while 40% of the rNSC differentiated into oligodendrocytes. Both non-cytotoxic and cytotoxic concentrations of DA and OTA reduced the differentiation of rNSC into astrocytes, neurons, and oligodendrocytes. Furthermore, a non-cytotoxic nanomolar (0.05 µM) concentration of DA and 0.2 µM of OTA reduced the percentage differentiation of rNSC into astrocytes and neurons. Morphometric analysis showed that the highest concentration (10 μM) of DA reduced axonal length. These indicate that low, non-cytotoxic concentrations of DA and OTA can interfere with the differentiation of rNSC.
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Affiliation(s)
- S Gill
- Regulatory Toxicology Research Division, Health Products and Food Branch, Tunney's Pasture, Health Canada, 251 Sir Frederick Banting Driveway, Ottawa, ON K1A 0K9, Canada.
| | - V M Ruvin Kumara
- Regulatory Toxicology Research Division, Health Products and Food Branch, Tunney's Pasture, Health Canada, 251 Sir Frederick Banting Driveway, Ottawa, ON K1A 0K9, Canada.
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Moyer CE, Hiolski EM, Marcinek DJ, Lefebvre KA, Smith DR, Zuo Y. Repeated low level domoic acid exposure increases CA1 VGluT1 levels, but not bouton density, VGluT2 or VGAT levels in the hippocampus of adult mice. HARMFUL ALGAE 2018; 79:74-86. [PMID: 30420019 PMCID: PMC6237202 DOI: 10.1016/j.hal.2018.08.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Domoic acid (DA) is a neurotoxin produced during harmful algal blooms that accumulates in marine organisms that serve as food resources for humans. While acute DA neurotoxicity can cause seizures and hippocampal lesions, less is known regarding how chronic, subacute DA exposure in adulthood impacts the hippocampus. With more frequent occurrences of harmful algal blooms, it is important to understand the potential impact of repeated, low-level DA exposure on human health. To model repeated, low-dose DA exposure, adult mice received a single low-dose (0.75 ± 0.05 μg/g) of DA or vehicle weekly for 22 consecutive weeks. Quantitative immunohistochemistry was performed to assess the effects of repeated, low-level DA exposure on hippocampal cells and synapses. Vesicular glutamate transporter 1 (VGluT1) immunoreactivity within excitatory boutons in CA1 of DA-exposed mice was increased. Levels of other vesicular transporter proteins (i.e., VGluT2 and the vesicular GABA transporter (VGAT)) within boutons, and corresponding bouton densities, were not significantly altered in CA1, CA3, or dentate gyrus. There were no significant changes in neuron density or glial fibrillary acidic protein (GFAP) immunoreactivity following chronic, low-dose exposure. This suggests that repeated low doses of DA, unlike high doses of DA, do not cause neuronal loss or astrocyte activation in hippocampus in adult mice. Instead, these findings demonstrate that repeated exposure to low levels of DA leads to subtle changes in VGluT1 expression within CA1 excitatory boutons, which may alter glutamatergic transmission in CA1 and disrupt behaviors dependent on spatial memory.
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Affiliation(s)
- Caitlin E Moyer
- Department of Molecular, Cell, and Developmental Biology, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, United States
| | - Emma M Hiolski
- Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, United States
| | - David J Marcinek
- Departments of Radiology, Pathology, and Bioengineering, University of Washington, South Lake Union Campus, 850 Republican St., Brotman 142, Box 358050, Seattle, WA, 98109, United States
| | - Kathi A Lefebvre
- Environmental and Fisheries Science Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd. East, Seattle, WA 98112, United States
| | - Donald R Smith
- Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, United States
| | - Yi Zuo
- Department of Molecular, Cell, and Developmental Biology, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, United States.
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5
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Rubio-Casillas A, Fernández-Guasti A. The dose makes the poison: from glutamate-mediated neurogenesis to neuronal atrophy and depression. Rev Neurosci 2018; 27:599-622. [PMID: 27096778 DOI: 10.1515/revneuro-2015-0066] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 03/04/2016] [Indexed: 12/21/2022]
Abstract
Experimental evidence has demonstrated that glutamate is an essential factor for neurogenesis, whereas another line of research postulates that excessive glutamatergic neurotransmission is associated with the pathogenesis of depression. The present review shows that such paradox can be explained within the framework of hormesis, defined as biphasic dose responses. Low glutamate levels activate adaptive stress responses that include proteins that protect neurons against more severe stress. Conversely, abnormally high levels of glutamate, resulting from increased release and/or decreased removal, cause neuronal atrophy and depression. The dysregulation of the glutamatergic transmission in depression could be underlined by several factors including a decreased inhibition (γ-aminobutyric acid or serotonin) or an increased excitation (primarily within the glutamatergic system). Experimental evidence shows that the activation of N-methyl-D-aspartate receptor (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors (AMPAR) can exert two opposite effects on neurogenesis and neuron survival depending on the synaptic or extrasynaptic concentration. Chronic stress, which usually underlies experimental and clinical depression, enhances glutamate release. This overactivates NMDA receptors (NMDAR) and consequently impairs AMPAR activity. Various studies show that treatment with antidepressants decreases plasma glutamate levels in depressed individuals and regulates glutamate receptors by reducing NMDAR function by decreasing the expression of its subunits and by potentiating AMPAR-mediated transmission. Additionally, it has been shown that chronic treatment with antidepressants having divergent mechanisms of action (including tricyclics, selective serotonin reuptake inhibitors, and ketamine) markedly reduced depolarization-evoked glutamate release in the hippocampus. These data, taken together, suggest that the glutamatergic system could be a final common pathway for antidepressant treatments.
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Models of progressive neurological dysfunction originating early in life. Prog Neurobiol 2017; 155:2-20. [DOI: 10.1016/j.pneurobio.2015.10.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Revised: 09/11/2015] [Accepted: 10/11/2015] [Indexed: 01/01/2023]
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Hiolski EM, Ito S, Beggs JM, Lefebvre KA, Litke AM, Smith DR. Domoic acid disrupts the activity and connectivity of neuronal networks in organotypic brain slice cultures. Neurotoxicology 2016; 56:215-224. [PMID: 27506300 DOI: 10.1016/j.neuro.2016.08.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 08/04/2016] [Accepted: 08/05/2016] [Indexed: 12/22/2022]
Abstract
Domoic acid is a neurotoxin produced by algae and is found in seafood during harmful algal blooms. As a glutamate agonist, domoic acid inappropriately stimulates excitatory activity in neurons. At high doses, this leads to seizures and brain lesions, but it is unclear how lower, asymptomatic exposures disrupt neuronal activity. Domoic acid has been detected in an increasing variety of species across a greater geographical range than ever before, making it critical to understand the potential health impacts of low-level exposure on vulnerable marine mammal and human populations. To determine whether prolonged domoic acid exposure altered neuronal activity in hippocampal networks, we used a custom-made 512 multi-electrode array with high spatial and temporal resolution to record extracellular potentials (spikes) in mouse organotypic brain slice cultures. We identified individual neurons based on spike waveform and location, and measured the activity and functional connectivity within the neuronal networks of brain slice cultures. Domoic acid exposure significantly altered neuronal spiking activity patterns, and increased functional connectivity within exposed cultures, in the absence of overt cellular or neuronal toxicity. While the overall spiking activity of neurons in domoic acid-exposed cultures was comparable to controls, exposed neurons spiked significantly more often in bursts. We also identified a subset of neurons that were electrophysiologically silenced in exposed cultures, and putatively identified those neurons as fast-spiking inhibitory neurons. These results provide evidence that domoic acid affects neuronal activity in the absence of cytotoxicity, and suggest that neurodevelopmental exposure to domoic acid may alter neurological function in the absence of clinical symptoms.
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Affiliation(s)
- E M Hiolski
- Department of Microbiology & Environmental Toxicology, University of California, Santa Cruz, CA, USA
| | - S Ito
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, CA, USA
| | - J M Beggs
- Department of Physics, Indiana University, Bloomington, IN, USA
| | - K A Lefebvre
- Northwest Fisheries Science Center, NOAA Fisheries, Seattle, WA, USA
| | - A M Litke
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, CA, USA
| | - D R Smith
- Department of Microbiology & Environmental Toxicology, University of California, Santa Cruz, CA, USA
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Abstract
In mammals, the period shortly before and shortly after birth is a time of massive brain growth, plasticity and maturation. It is also a time when the developing brain is exquisitely sensitive to insult, often with long-lasting consequences. Many of society's most debilitating neurological diseases arise, at least in part, from trauma around the time of birth but go undetected until later in life. For the past 15 years, we have been studying the consequences of exposure to the AMPA/kainate agonist domoic acid (DOM) on brain development in the rat. Domoic acid is a naturally occurring excitotoxin that enters the food chain and is known to produce severe neurotoxicity in humans and other adult wildlife. Our work, and that of others, however, has demonstrated that DOM is also toxic to the perinatal brain and that toxicity occurs at doses much lower than those required in adults. This raises concern about the current regulatory limit for DOM contamination that is based on data in adult animals, but has also allowed creation of a novel model of neurological disease progression. Herein, we review briefly the toxicity of DOM in adults, including humans, and describe features of the developing nervous system relevant to enhanced risk. We then review the data on DOM as a prenatal neuroteratogen and describe in detail the work of our respective laboratories to characterize the long-term behavioural and neuropathological consequences of exposure to low-dose DOM in the newborn rat.
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Affiliation(s)
- Tracy A Doucette
- Department of Psychology, University of Prince Edward Island, 550 University Avenue, Charlottetown, PE, C1A4P3, Canada
| | - R Andrew Tasker
- Department of Biomedical Sciences, University of Prince Edward Island, 550 University Avenue, Charlottetown, PE, C1A4P3, Canada.
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Kirkley KS, Madl JE, Duncan C, Gulland FM, Tjalkens RB. Domoic acid-induced seizures in California sea lions (Zalophus californianus) are associated with neuroinflammatory brain injury. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2014; 156:259-68. [PMID: 25286249 DOI: 10.1016/j.aquatox.2014.09.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 09/04/2014] [Accepted: 09/08/2014] [Indexed: 05/16/2023]
Abstract
California sea lions (CSLs) exposed to the marine biotoxin domoic acid (DA) develop an acute or chronic toxicosis marked by seizures and act as sentinels of the disease. Experimental evidence suggests that oxidative stress and neuroinflammation are important mechanisms underlying the seizurogenic potential of environmental toxicants but these pathways are relatively unstudied in CSLs. In the current study, we investigated the role of glutamate-glutamine changes and gliosis in DA-exposed CSLs to better understand the neurotoxic mechanisms occurring during DA toxicity. Sections from archived hippocampi from control and CSLs diagnosed with DA toxicosis were immunofluorescently stained for markers of gliosis, oxidative/nitrative stress and changes in glutamine synthetase (GS). Quantitative assessment revealed increasing loss of microtubule associated protein-2 positive neurons with elevations in 4-hydroxynonenal correlating with chronicity of exposure, whereas the pattern of activated glia expressing nitric oxide synthase 2 and tumor necrosis factor followed pathological severity. There was no significant change in the amount of GS positive cells but there was increased 3-nitrotyrosine in GS expressing cells and in neurons, particularly in animals with chronic DA toxicosis. These changes were consistently seen in the dentate gyrus and in the cornu ammonis (CA) sectors CA3, CA4, and CA1. The results of this study indicate that gliosis and resultant changes in GS are likely important mechanisms in DA-induced seizure that need to be further explored as potential therapies in treating exposed wildlife.
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Affiliation(s)
- Kelly S Kirkley
- Center for Environmental Medicine, Colorado State University, Fort Collins, CO, USA
| | - James E Madl
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Colleen Duncan
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, USA
| | - Frances M Gulland
- The Marine Mammal Center, 1065 Fort Cronkhite, Sausalito, CA 94965, USA
| | - Ronald B Tjalkens
- Center for Environmental Medicine, Colorado State University, Fort Collins, CO, USA.
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