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Kang B, Wang J, Guo S, Yang L. Mercury-induced toxicity: Mechanisms, molecular pathways, and gene regulation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 943:173577. [PMID: 38852866 DOI: 10.1016/j.scitotenv.2024.173577] [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: 11/30/2023] [Revised: 03/01/2024] [Accepted: 05/25/2024] [Indexed: 06/11/2024]
Abstract
Mercury is a well-known neurotoxicant for humans and wildlife. The epidemic of mercury poisoning in Japan has clearly demonstrated that chronic exposure to methylmercury (MeHg) results in serious neurological damage to the cerebral and cerebellar cortex, leading to the dysfunction of the central nervous system (CNS), especially in infants exposed to MeHg in utero. The occurrences of poisoning have caused a wide public concern regarding the health risk emanating from MeHg exposure; particularly those eating large amounts of fish may experience the low-level and long-term exposure. There is growing evidence that MeHg at environmentally relevant concentrations can affect the health of biota in the ecosystem. Although extensive in vivo and in vitro studies have demonstrated that the disruption of redox homeostasis and microtube assembly is mainly responsible for mercurial toxicity leading to adverse health outcomes, it is still unclear whether we could quantitively determine the occurrence of interaction between mercurial and thiols and/or selenols groups of proteins linked directly to outcomes, especially at very low levels of exposure. Furthermore, intracellular calcium homeostasis, cytoskeleton, mitochondrial function, oxidative stress, neurotransmitter release, and DNA methylation may be the targets of mercury compounds; however, the primary targets associated with the adverse outcomes remain to be elucidated. Considering these knowledge gaps, in this article, we conducted a comprehensive review of mercurial toxicity, focusing mainly on the mechanism, and genes/proteins expression. We speculated that comprehensive analyses of transcriptomics, proteomics, and metabolomics could enhance interpretation of "omics" profiles, which may reveal specific biomarkers obviously correlated with specific pathways that mediate selective neurotoxicity.
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Affiliation(s)
- Bolun Kang
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012 Beijing, China
| | - Jinghan Wang
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012 Beijing, China
| | - Shaojuan Guo
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012 Beijing, China
| | - Lixin Yang
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, 100012 Beijing, China.
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2
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Ke T, Santamaria A, Barbosa F, Rocha JBT, Skalny AV, Tinkov AA, Bowman AB, Aschner M. Developmental Methylmercury Exposure Induced and Age-Dependent Glutamatergic Neurotoxicity in Caenorhabditis elegans. Neurochem Res 2023; 48:920-928. [PMID: 36385214 DOI: 10.1007/s11064-022-03816-5] [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] [Received: 05/07/2022] [Revised: 10/12/2022] [Accepted: 11/03/2022] [Indexed: 11/17/2022]
Abstract
Developmental methylmercury (MeHg) exposures cause latent neurotoxic effects in adults; however, the mechanisms underlying the latent neurotoxicity are not fully understood. In the current study, we used C. elegans as an animal model to investigate the latent neurotoxic effects of developmental MeHg exposures on glutamatergic neurons. The young larvae stage 1 worms were exposed to MeHg (0.05 ~ 5 µM) for 48 h. The morphological and behavioral endpoints of glutamatergic neurons were compared when worms reached to adult stages including the young adult stage (day 1 adult) and the old adult stage (day 10 adult). Here, we showed that C. elegans glutamatergic neurons were morphologically intact following low or medium MeHg exposures (0.05 ~ 0.5 µM). The morphological damage of glutamatergic neurons appeared to be pronounced in day 10 adults developmentally exposed to 5 µM MeHg. Behavioral assays also showed an age-dependent latent effect of MeHg. In the nose touch response assay, only day 10 adult worms exhibited a functional decline following prior 5 µM MeHg exposure. Moreover, the disruption of NaCl memory appeared only in day 1 adults following MeHg exposures but not in day 10 adults. The expression of C. elegans homologs of mammalian vesicular glutamate transporter (eat-4) was repressed in day 1 adults, while the glutamate receptor homolog (glr-1) was upregulated in day 10 adults with 5 µM MeHg. In the comparison of age-dependent changes in the insulin-like pathway (daf-2/age-1/daf-16) following MeHg exposures, we showed that the daf-2/age-1/daf-16 pathway was mobilized in day 1 adults but repressed in day 10 adults. Collectively, our data supports a conclusion that MeHg-induced glutamatergic neurotoxicity exhibits an age-dependent pattern, possibly related to the prominent changes in age-dependent modulation in the glutamatergic neurotransmission and metabolic pathways.
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Affiliation(s)
- Tao Ke
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Abel Santamaria
- Laboratorio de Aminoácidos Excitadores/Laboratorio de Neurofarmacología Molecular y Nanotecnología, Instituto Nacional de Neurología y Neurocirugía, 14269, Mexico City, Mexico
| | - Fernando Barbosa
- Faculty of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, 14040-900, Brazil
| | - João B T Rocha
- Departamento de Bioquímica e Biologia Molecular, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, RS, 97105900, Brazil
| | - Anatoly V Skalny
- IM Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia
| | - Alexey A Tinkov
- IM Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia
- Yaroslavl State University, Yaroslavl, Russia
| | - Aaron B Bowman
- School of Health Sciences, Purdue University, West Lafayette, IN, 47907-2051, USA
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.
- , Forchheimer Building, Room 209, 1300 Morris Park Avenue, Bronx, NY, 10461, USA.
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3
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Bjørklund G, Antonyak H, Polishchuk A, Semenova Y, Lesiv M, Lysiuk R, Peana M. Effect of methylmercury on fetal neurobehavioral development: an overview of the possible mechanisms of toxicity and the neuroprotective effect of phytochemicals. Arch Toxicol 2022; 96:3175-3199. [PMID: 36063174 DOI: 10.1007/s00204-022-03366-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 08/17/2022] [Indexed: 11/25/2022]
Abstract
Methylmercury (MeHg) is a global environmental pollutant with neurotoxic effects. Exposure to MeHg via consumption of seafood and fish can severely impact fetal neurobehavioral development even when MeHg levels in maternal blood are as low as about 5 μg/L, which the mother tolerates well. Persistent motor dysfunctions and cognitive deficits may result from trans-placental exposure. The present review summarizes current knowledge on the mechanisms of MeHg toxicity during the period of nervous system development. Although cerebellar Purkinje cells are MeHg targets, the actions of MeHg on thiol components in the neuronal cytoskeleton as well as on mitochondrial enzymes and induction of disturbances of glutamate signaling can impair extra-cerebellar functions, also at levels well tolerated by adult individuals. Numerous herbal substances possess neuroprotective effects, predominantly represented by natural polyphenolic molecules that might be utilized to develop natural drugs to alleviate neurotoxicity symptoms caused by MeHg or other Hg compounds.
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Affiliation(s)
- Geir Bjørklund
- Council for Nutritional and Environmental Medicine, Toften 24, 8610, Mo i Rana, Norway.
| | | | | | | | - Marta Lesiv
- Ivan Franko National University of Lviv, Lviv, Ukraine
| | - Roman Lysiuk
- Danylo Halytsky Lviv National Medical University, Lviv, Ukraine
- CONEM Ukraine Life Science Research Group, Danylo Halytsky Lviv National Medical University, Lviv, Ukraine
| | - Massimiliano Peana
- Department of Chemical, Physics, Mathematics and Natural Sciences, University of Sassari, Sassari, Italy
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4
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Sahu R, Mehan S, Kumar S, Prajapati A, Alshammari A, Alharbi M, Assiri MA, Narula AS. Effect of alpha-mangostin in the prevention of behavioural and neurochemical defects in methylmercury-induced neurotoxicity in experimental rats. Toxicol Rep 2022; 9:977-998. [PMID: 35783250 PMCID: PMC9247835 DOI: 10.1016/j.toxrep.2022.04.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 04/17/2022] [Accepted: 04/20/2022] [Indexed: 12/11/2022] Open
Abstract
Methylmercury (MeHg+) is a known neurotoxin that causes progressive motor neuron degeneration in the central nervous system. Axonal degeneration, oligodendrocyte degeneration, and myelin basic protein (MBP) deficits are among the neuropathological abnormalities caused by MeHg+ in amyotrophic lateral sclerosis (ALS). This results in demyelination and motor neuron death in both humans and animals. Previous experimental studies have confirmed that overexpression of the extracellular signalling regulated kinase (ERK1/2) signalling contributes to glutamate excitotoxicity, inflammatory response of microglial cells, and oligodendrocyte (OL) dysfunction that promotes myelin loss. Alpha-mangostin (AMG), an active ingredient obtained from the tree "Garcinia mangostana Linn," has been used in experimental animals to treat a variety of brain disorders, including Parkinson's and Huntington's disease memory impairment, Alzheimer's disease, and schizophrenia, including Parkinson's disease and Huntington's disease memory impairment, Alzheimer's disease, and schizophrenia. AMG has traditionally been used as an antioxidant, anti-inflammatory, and neuroprotective agent.Accordingly, we investigated the therapeutic potential of AMG (100 and 200 mg/kg) in experimental rats with methylmercury (MeHg+)-induced neurotoxicity. The neuroprotective effect of AMG on behavioural, cellular, molecular, and other gross pathological changes, such as histopathological alterations in MeHg+ -treated rat brains, is presented. The neurological behaviour of experimental rats was evaluated using a Morris water maze (MWM), open field test (OFT), grip strength test (GST), and force swim test (FST). In addition, we investigate AMG's neuroprotective effect by restoring MBP levels in cerebral spinal fluid and whole rat brain homogenate. The apoptotic, pro-inflammatory, and oxidative stress markers were measured in rat blood plasma samples and brain homogenate. According to the findings of this study, AMG decreases ERK-1/2 levels and modulates neurochemical alterations in rat brains, minimising MeHg+ -induced neurotoxicity.
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Affiliation(s)
- Rakesh Sahu
- Neuropharmacology Division, Department of Pharmacology, ISF College of Pharmacy, Moga, Punjab, India
| | - Sidharth Mehan
- Neuropharmacology Division, Department of Pharmacology, ISF College of Pharmacy, Moga, Punjab, India
| | - Sumit Kumar
- Neuropharmacology Division, Department of Pharmacology, ISF College of Pharmacy, Moga, Punjab, India
| | - Aradhana Prajapati
- Neuropharmacology Division, Department of Pharmacology, ISF College of Pharmacy, Moga, Punjab, India
| | - Abdulrahman Alshammari
- Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Post Box 2455, Riyadh 11451, Saudi Arabia
| | - Metab Alharbi
- Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Post Box 2455, Riyadh 11451, Saudi Arabia
| | - Mohammed A. Assiri
- Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Post Box 2455, Riyadh 11451, Saudi Arabia
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Komuro Y, Galas L, Morozov YM, Fahrion JK, Raoult E, Lebon A, Tilot AK, Kikuchi S, Ohno N, Vaudry D, Rakic P, Komuro H. The Role of Galanin in Cerebellar Granule Cell Migration in the Early Postnatal Mouse during Normal Development and after Injury. J Neurosci 2021; 41:8725-8741. [PMID: 34462307 PMCID: PMC8528496 DOI: 10.1523/jneurosci.0900-15.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2015] [Revised: 08/16/2021] [Accepted: 08/19/2021] [Indexed: 11/21/2022] Open
Abstract
Galanin, one of the most inducible neuropeptides, is widely present in developing brains, and its expression is altered by pathologic events (e.g., epilepsy, ischemia, and axotomy). The roles of galanin in brain development under both normal and pathologic conditions have been hypothesized, but the question of how galanin is involved in fetal and early postnatal brain development remains largely unanswered. In this study, using granule cell migration in the cerebellum of early postnatal mice (both sexes) as a model system, we examined the role of galanin in neuronal cell migration during normal development and after brain injury. Here we show that, during normal development, endogenous galanin participates in accelerating granule cell migration via altering the Ca2+ and cAMP signaling pathways. Upon brain injury induced by the application of cold insults, galanin levels decrease at the lesion sites, but increase in the surroundings of lesion sites. Granule cells exhibit the following corresponding changes in migration: (1) slowing down migration at the lesion sites; and (2) accelerating migration in the surroundings of lesion sites. Experimental manipulations of galanin signaling reduce the lesion site-specific changes in granule cell migration, indicating that galanin plays a role in such deficits in neuronal cell migration. The present study suggests that manipulating galanin signaling may be a potential therapeutic target for acutely injured brains during development.SIGNIFICANCE STATEMENT Deficits in neuronal cell migration caused by brain injury result in abnormal development of cortical layers, but the underlying mechanisms remain to be determined. Here, we report that on brain injury, endogenous levels of galanin, a neuropeptide, are altered in a lesion site-specific manner, decreasing at the lesion sites but increasing in the surroundings of lesion sites. The changes in galanin levels positively correlate with the migration rate of immature neurons. Manipulations of galanin signaling ameliorate the effects of injury on neuronal migration and cortical layer development. These results shed a light on galanin as a potential therapeutic target for acutely injured brains during development.
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Affiliation(s)
- Yutaro Komuro
- Department of Neurosciences, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195
| | - Ludovic Galas
- Regional Platform for Cell Imaging of Normandy, INSERM, Université de Rouen Normandie, 76000 Rouen, France
| | - Yury M Morozov
- Department of Neuroscience, Yale University School of Medicine, New Haven, Connecticut 06510
| | - Jennifer K Fahrion
- Department of Neurosciences, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195
| | - Emilie Raoult
- Regional Platform for Cell Imaging of Normandy, INSERM, Université de Rouen Normandie, 76000 Rouen, France
| | - Alexis Lebon
- Regional Platform for Cell Imaging of Normandy, INSERM, Université de Rouen Normandie, 76000 Rouen, France
| | - Amanda K Tilot
- Department of Genomic Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195
| | - Shin Kikuchi
- Department of Neurosciences, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195
| | - Nobuhiko Ohno
- Department of Neurosciences, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195
- Division of Neurobiology and Bioinformatics, National Institute for Physiological Sciences, Aichi 444-8787, Japan
- Department of Anatomy, Division of Histology and Cell Biology, School of Medicine, Jichi Medical University, Tochigi 329-0498, Japan
| | - David Vaudry
- Regional Platform for Cell Imaging of Normandy, INSERM, Université de Rouen Normandie, 76000 Rouen, France
- Neuropeptides, Neuronal Death and Cell Plasticity Team, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, INSERM U1239, Université de Rouen Normandie, 76000 Rouen, France
| | - Pasko Rakic
- Department of Neuroscience, Yale University School of Medicine, New Haven, Connecticut 06510
- Kavli Institute for Neuroscience, Yale School of Medicine, New Haven, Connecticut 06510
| | - Hitoshi Komuro
- Department of Neurosciences, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195
- Department of Neuroscience, Yale University School of Medicine, New Haven, Connecticut 06510
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6
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Minj E, Upadhayay S, Mehan S. Nrf2/HO-1 Signaling Activator Acetyl-11-keto-beta Boswellic Acid (AKBA)-Mediated Neuroprotection in Methyl Mercury-Induced Experimental Model of ALS. Neurochem Res 2021; 46:2867-2884. [PMID: 34075522 DOI: 10.1007/s11064-021-03366-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Revised: 04/28/2021] [Accepted: 05/27/2021] [Indexed: 12/12/2022]
Abstract
Methylmercury (MeHg) is a potent neurotoxin that causes neurotoxicity and neuronal cell death. MeHg exposure also leads to oligodendrocyte destruction, glial cell overactivation, and demyelination of motor neurons in the motor cortex and spinal cord. As a result, MeHg plays an important role in the progression of amyotrophic lateral sclerosis (ALS)-like neurocomplications. ALS is a fatal neurodegenerative disorder in which neuroinflammation is the leading cause of further CNS demyelination. Nuclear factor erythroid-2-related factor-2 (Nrf2)/Heme oxygenase-1 (HO-1) signaling pathway was thought to be a potential target for neuroprotection in ALS. Acetyl-11-keto-beta-boswellic acid (AKBA) is a multi-component pentacyclic triterpenoid mixture derived from Boswellia serrata with anti-inflammatory and antioxidant properties. The research aimed to investigate whether AKBA, as a Nrf2 / HO-1 activator, can provide protection against ALS. Thus, we explored the role of AKBA on the Nrf2/HO-1 signaling pathway in a MeHg-induced experimental ALS model. In this study, ALS was induced in Wistar rats by oral gavage of MeHg 5 mg/kg for 21 days. An open field test, force swim test, and grip strength were performed to observe experimental rats' motor coordination behaviors. In contrast, a morris water maze was performed for learning and memory. Administration of AKBA 50 mg/kg and AKBA 100 mg/kg continued from day 22 to 42. Neurochemical parameters were evaluated in the rat's brain homogenate. In the meantime, post-treatment with AKBA significantly improved behavioral, neurochemical, and gross pathological characteristics in the brain of rats by increasing the amount of Nrf2/HO-1 in brain tissue. Collectively, our findings indicated that AKBA could potentially avoid demyelination and encourage remyelination.
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Affiliation(s)
- Elizabeth Minj
- Neuropharmacology Division, Department of Pharmacology, ISF College of Pharmacy, Moga, 142001, Punjab, India
| | - Shubham Upadhayay
- Neuropharmacology Division, Department of Pharmacology, ISF College of Pharmacy, Moga, 142001, Punjab, India
| | - Sidharth Mehan
- Neuropharmacology Division, Department of Pharmacology, ISF College of Pharmacy, Moga, 142001, Punjab, India.
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7
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Masood MI, Hauke NT, Nasim MJ, Sarfraz M, Naseem M, Schäfer KH. Neural stem cell-based in vitro bioassay for the assessment of neurotoxic potential of water samples. J Environ Sci (China) 2021; 101:72-86. [PMID: 33334539 DOI: 10.1016/j.jes.2020.07.028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 07/26/2020] [Accepted: 07/31/2020] [Indexed: 06/12/2023]
Abstract
Intensive agriculture activities, industrialization and growing numbers of wastewater treatment plants along river banks collectively contribute to the elevated levels of neurotoxic pollutants in natural water reservoirs across Europe. We established an in vitro bioassay based upon neural stem cells isolated from the subventricular zone of the postnatal mouse to evaluate the neurotoxic potential of raw wastewater, treated sewage effluent, groundwater and drinking water. The toxic potential of water samples was evaluated employing viability, proliferation, differentiation and migration assays. We found that raw wastewater could reduce the viability and proliferation of neural stem cells, and decreased the neuronal and astrocyte differentiation, neuronal neurite growth, astrocyte growth and cell migration. Treated sewage water also showed inhibitory effects on cell proliferation and migration. Our results indicated that relatively high concentrations of nitrogenous substances, pesticides, mercuric compounds, bisphenol-A, and phthalates, along with some other pollutants in raw wastewater and treated sewage water, might be the reason for the neuroinhibitory effects of these water samples. Our model successfully predicted the neurotoxicity of water samples collected from different sources and also revealed that the incomplete removal of contaminants from wastewater can be problematic for the developing nervous system. The presented data also provides strong evidence that more effective treatments should be used to minimize the contamination of water before release into major water bodies which may be considered as water reservoirs for human usage in the future.
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Affiliation(s)
- Muhammad Irfan Masood
- Division of Bioorganic Chemistry, School of Pharmacy, Saarland University, D-66123 Saarbrücken, Germany; ENS Group, University of Applied Sciences Kaiserslautern, 66482 Zweibrücken, Germany; Institute of Pharmaceutical Sciences, University of Veterinary and Animal Sciences, 54000 Lahore, Pakistan.
| | - Natalie Tamara Hauke
- Applied Life Sciences, University of Applied Sciences Kaiserslautern, 66482 Zweibrücken, Germany; Abwasserverband Bergstrasse, Altau 10, 69469 Weinheim, Germany
| | - Muhammad Jawad Nasim
- Division of Bioorganic Chemistry, School of Pharmacy, Saarland University, D-66123 Saarbrücken, Germany
| | - Muhammad Sarfraz
- Division of Bioorganic Chemistry, School of Pharmacy, Saarland University, D-66123 Saarbrücken, Germany
| | - Mahrukh Naseem
- Department of Zoology, University of Balochistan, Quetta 87550, Pakistan
| | - Karl Herbert Schäfer
- ENS Group, University of Applied Sciences Kaiserslautern, 66482 Zweibrücken, Germany.
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Aaseth J, Wallace DR, Vejrup K, Alexander J. Methylmercury and developmental neurotoxicity: A global concern. CURRENT OPINION IN TOXICOLOGY 2020. [DOI: 10.1016/j.cotox.2020.01.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Hwang HM, Ku RY, Hashimoto-Torii K. Prenatal Environment That Affects Neuronal Migration. Front Cell Dev Biol 2019; 7:138. [PMID: 31380373 PMCID: PMC6652208 DOI: 10.3389/fcell.2019.00138] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 07/08/2019] [Indexed: 11/22/2022] Open
Abstract
Migration of neurons starts in the prenatal period and continues into infancy. This developmental process is crucial for forming a proper neuronal network, and the disturbance of this process results in dysfunction of the brain such as epilepsy. Prenatal exposure to environmental stress, including alcohol, drugs, and inflammation, disrupts neuronal migration and causes neuronal migration disorders (NMDs). In this review, we summarize recent findings on this topic and specifically focusing on two different modes of migration, radial, and tangential migration during cortical development. The shared mechanisms underlying the NMDs are discussed by comparing the molecular changes in impaired neuronal migration under exposure to different types of prenatal environmental stress.
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Affiliation(s)
- Hye M Hwang
- Center for Neuroscience Research, Children's National Medical Center, The Children's Research Institute, Washington, DC, United States.,The Institute for Biomedical Sciences, School of Medicine and Health Sciences, The George Washington University, Washington, DC, United States
| | - Ray Y Ku
- Center for Neuroscience Research, Children's National Medical Center, The Children's Research Institute, Washington, DC, United States
| | - Kazue Hashimoto-Torii
- Center for Neuroscience Research, Children's National Medical Center, The Children's Research Institute, Washington, DC, United States.,Departments of Pediatrics, and Pharmacology & Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, DC, United States
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10
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Cho HJ, Shan Y, Whittington NC, Wray S. Nasal Placode Development, GnRH Neuronal Migration and Kallmann Syndrome. Front Cell Dev Biol 2019; 7:121. [PMID: 31355196 PMCID: PMC6637222 DOI: 10.3389/fcell.2019.00121] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 06/14/2019] [Indexed: 12/22/2022] Open
Abstract
The development of Gonadotropin releasing hormone-1 (GnRH) neurons is important for a functional reproduction system in vertebrates. Disruption of GnRH results in hypogonadism and if accompanied by anosmia is termed Kallmann Syndrome (KS). From their origin in the nasal placode, GnRH neurons migrate along the olfactory-derived vomeronasal axons to the nasal forebrain junction and then turn caudally into the developing forebrain. Although research on the origin of GnRH neurons, their migration and genes associated with KS has identified multiple factors that influence development of this system, several aspects still remain unclear. This review discusses development of the olfactory system, factors that regulate GnRH neuron formation and development of the olfactory system, migration of the GnRH neurons from the nose into the brain, and mutations in humans with KS that result from disruption of normal GnRH/olfactory systems development.
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Affiliation(s)
- Hyun-Ju Cho
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - Yufei Shan
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - Niteace C Whittington
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - Susan Wray
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
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11
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Tolcos M, McDougall A, Shields A, Chung Y, O'Dowd R, Turnley A, Wallace M, Rees S. Intrauterine Growth Restriction Affects Cerebellar Granule Cells in the Developing Guinea Pig Brain. Dev Neurosci 2018; 40:162-174. [PMID: 29763885 DOI: 10.1159/000487797] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 02/15/2018] [Indexed: 01/02/2023] Open
Abstract
Intrauterine growth restriction (IUGR) can lead to adverse neurodevelopmental sequelae in postnatal life. However, the effects of IUGR on the cerebellum are still to be fully elucidated. A major determinant of growth and development of the cerebellum is proliferation and subsequent migration of cerebellar granule cells. Our objective was to determine whether IUGR, induced by chronic placental insufficiency (CPI) in guinea pigs, results in abnormal cerebellar development due to deficits suggestive of impaired granule cell proliferation and/or migration. CPI was induced by unilateral ligation of the uterine artery at mid-gestation, producing growth-restricted (GR) foetuses at 52 and 60 days of gestation (dg), and neonates at 1 week postnatal age (term approx. 67 dg). Controls were from sham-operated animals. In GR foetuses compared with controls at 52 dg, the external granular layer (EGL) width and internal granular layer (IGL) area were similar. In GR foetuses compared with controls at 60 dg: (a) the EGL width was greater (p < 0.005); (b) the IGL area was smaller (p < 0.005); (c) the density of Ki67-negative (postmitotic) granule cells in the EGL was greater (p < 0.01); (d) the somal area of Purkinje cells was reduced (p < 0.005), and (e) the linear density of Bergmann glia was similar. The EGL width in GR foetuses at 60 dg was comparable to that of 52 dg control and GR foetuses. The pattern of p27-immunoreactivity in the EGL was the inverse of Ki67-immunoreactivity at both foetal ages; there was no difference between control and GR foetuses at either age in the width of p27-immunoreactivity, or in the percentage of the EGL width that it occupied. In the molecular layer of GR neonates compared with controls there was an increase in the areal density of granule cells (p < 0.05) and in the percentage of migrating to total number of granule cells (p < 0.01) at 1 week but not at 60 dg (p > 0.05). Thus, we found no specific evidence that IUGR affects granule cell proliferation, but it alters the normal program of migration to the IGL and, in addition, the development of Purkinje cells. Such alterations will likely affect the development of appropriate circuitry and have implications for cerebellar function.
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Affiliation(s)
- Mary Tolcos
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, Victoria, Australia.,Department of Obstetrics and Gynaecology, Monash University, Clayton, Victoria, Australia.,School of Health and Biomedical Sciences, RMIT University, Bundoora, Victoria, Australia
| | - Annie McDougall
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, Victoria, Australia.,Department of Obstetrics and Gynaecology, Monash University, Clayton, Victoria, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
| | - Amy Shields
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, Victoria, Australia
| | - Yoonyoung Chung
- Department of Anatomy, School of Medicine, Chosun University, Gwangju, Republic of Korea
| | - Rachael O'Dowd
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Victoria, Australia
| | - Ann Turnley
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Victoria, Australia
| | - Megan Wallace
- The Ritchie Centre, Hudson Institute of Medical Research, Clayton, Victoria, Australia.,Department of Obstetrics and Gynaecology, Monash University, Clayton, Victoria, Australia
| | - Sandra Rees
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Victoria, Australia
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12
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Tucker EK, Nowak RA. Methylmercury alters proliferation, migration, and antioxidant capacity in human HTR8/SV-neo trophoblast cells. Reprod Toxicol 2018; 78:60-68. [PMID: 29581082 DOI: 10.1016/j.reprotox.2018.03.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 03/01/2018] [Accepted: 03/22/2018] [Indexed: 12/19/2022]
Abstract
Methylmercury, a potent neurotoxin, is able to pass through the placenta, but its effects on the placenta itself have not been elucidated. Using an immortalized human trophoblast cell line, HTR8/SV-neo, we assessed the in vitro toxicity of methylmercury. We found that 1 μg/mL methylmercury decreased viability, proliferation, and migration; and it had effects on antioxidant genes similar to those seen in neural cells. However, methylmercury led to decreased expression of superoxide dismutase 1 and increased expression of surfactant protein D. HTR cells treated 0.01 or 0.1 μg/mL methylmercury had increased migration rates along with decreased expression of an adhesion gene, cadherin 3, suggesting that low doses of methylmercury promote migration in HTR cells. Our results indicate that trophoblast cells react differently to methylmercury relative to neural cell lines, and thus investigation of methylmercury toxicity in placental cells is needed to understand the effects of this heavy metal on the placenta.
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Affiliation(s)
- Emily K Tucker
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, 1207, W. Gregory Dr., Urbana, Illinois, USA.
| | - Romana A Nowak
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, 1207, W. Gregory Dr., Urbana, Illinois, USA
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13
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Hernández AJA, Reyes VL, Albores-García D, Gómez R, Calderón-Aranda ES. MeHg affects the activation of FAK, Src, Rac1 and Cdc42, critical proteins for cell movement in PDGF-stimulated SH-SY5Y neuroblastoma cells. Toxicology 2017; 394:35-44. [PMID: 29197552 DOI: 10.1016/j.tox.2017.11.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 10/16/2017] [Accepted: 11/28/2017] [Indexed: 01/05/2023]
Abstract
Methylmercury (MeHg) is an environmental neurotoxicant that inhibits neuronal migration. This process requires several cyclic steps involving the formation of membrane protrusions (lamellipodia and filopodia) and focal adhesion turnover. FAK and Src are critical proteins that regulate both processes. The FAK-Src complex promotes the activation of Rac1 and Cdc42, two GTPases involved in the remodeling of the actin cytoskeletal network. Here, we studied the effect of MeHg (1, 10, 100, 500 and 1000nM) on cell migration, the formation of cell protrusions, focal adhesion location and the activation of FAK, Src, Rac1 and Cdc42 using the SH-SY5Y neuroblastoma cell line stimulated with PDGF-BB (PDGF). The data show that MeHg (1-500nM) inhibited PDGF-stimulated cell migration. In PDGF-stimulated cells, MeHg (100-1000nM) decreased protrusions and increased the size of the p-FAKY397 clusters. MeHg also inhibited PDGF-induced FAK and Src activation and, at 100nM, MeHg inhibited the activation of Rac1 and Cdc42. Altogether, the findings show that low concentrations of MeHg inhibit SH-SY5Y cell migration by disrupting the activation and disassembly of FAK. This negatively affects the activation of Src, Rac1 and Cdc42, all of which are critical proteins for the regulation of cell movement. These effects could be related to the MeHg-mediated inhibition of PDGF-induced formation of lamellipodia and filopodia, focal adhesion disassembly and PDGF-induced movement.
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Affiliation(s)
| | | | | | - Rocío Gómez
- Departamento de Toxicologia, Cinvestav, DF. Mexico, Mexico
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14
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Edoff K, Raciti M, Moors M, Sundström E, Ceccatelli S. Gestational Age and Sex Influence the Susceptibility of Human Neural Progenitor Cells to Low Levels of MeHg. Neurotox Res 2017; 32:683-693. [PMID: 28756503 PMCID: PMC5602033 DOI: 10.1007/s12640-017-9786-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 07/09/2017] [Accepted: 07/12/2017] [Indexed: 01/13/2023]
Abstract
The developing nervous system is highly susceptible to methylmercury (MeHg), a widespread environmental neurotoxic contaminant. A wide range of morphological and functional outcomes have been described; however, there are still open questions regarding the mechanisms behind the developmental neurotoxic effects induced by low-level exposure. In the present study, we have examined the effects of nanomolar concentrations of MeHg on primary fetal human progenitor cells (hNPCs) with special focus on the role played by developmental stage and sex on the neurotoxic outcome. We found that neurospheres derived from earlier gestational time points exhibit higher susceptibility to MeHg, as they undergo apoptosis at a much lower dose (25 nM) as compared to neurospheres established from older fetuses (100 nM). At subapoptotic concentrations (10 nM), MeHg inhibited neuronal differentiation and maturation of hNPCs, as shown by a reduced number of Tuj1-positive cells and a visible reduction in neurite extension and cell migration, associated with a misregulation of Notch1 and BDNF signaling pathways. Interestingly, cells derived from male fetuses showed more severe alterations of neuronal morphology as compared to cells from females, indicating that the MeHg-induced impairment of neurite extension and cell migration is sex-dependent. Accordingly, the expression of the CDKL5 gene, a major factor regulating neurite outgrowth, was significantly more downregulated in male-derived cells. Altogether, gestational age and sex appear to be critical factors influencing in vitro hNPC sensitivity to low levels of MeHg.
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Affiliation(s)
- Karin Edoff
- Department of Neuroscience, Karolinska Institutet, Retzius väg 8, SE-171 77, Stockholm, Sweden
| | - Marilena Raciti
- Department of Neuroscience, Karolinska Institutet, Retzius väg 8, SE-171 77, Stockholm, Sweden.
| | - Michaela Moors
- Department of Neuroscience, Karolinska Institutet, Retzius väg 8, SE-171 77, Stockholm, Sweden
| | - Erik Sundström
- Department of Neurobiology, Care Sciences, and Society, Karolinska Institutet, Geriatrik-lab plan 5, SE-141 52, Huddinge, Sweden
| | - Sandra Ceccatelli
- Department of Neuroscience, Karolinska Institutet, Retzius väg 8, SE-171 77, Stockholm, Sweden
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15
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Galas L, Bénard M, Lebon A, Komuro Y, Schapman D, Vaudry H, Vaudry D, Komuro H. Postnatal Migration of Cerebellar Interneurons. Brain Sci 2017; 7:brainsci7060062. [PMID: 28587295 PMCID: PMC5483635 DOI: 10.3390/brainsci7060062] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 05/25/2017] [Accepted: 06/01/2017] [Indexed: 12/26/2022] Open
Abstract
Due to its continuing development after birth, the cerebellum represents a unique model for studying the postnatal orchestration of interneuron migration. The combination of fluorescent labeling and ex/in vivo imaging revealed a cellular highway network within cerebellar cortical layers (the external granular layer, the molecular layer, the Purkinje cell layer, and the internal granular layer). During the first two postnatal weeks, saltatory movements, transient stop phases, cell-cell interaction/contact, and degradation of the extracellular matrix mark out the route of cerebellar interneurons, notably granule cells and basket/stellate cells, to their final location. In addition, cortical-layer specific regulatory factors such as neuropeptides (pituitary adenylate cyclase-activating polypeptide (PACAP), somatostatin) or proteins (tissue-type plasminogen activator (tPA), insulin growth factor-1 (IGF-1)) have been shown to inhibit or stimulate the migratory process of interneurons. These factors show further complexity because somatostatin, PACAP, or tPA have opposite or no effect on interneuron migration depending on which layer or cell type they act upon. External factors originating from environmental conditions (light stimuli, pollutants), nutrients or drug of abuse (alcohol) also alter normal cell migration, leading to cerebellar disorders.
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Affiliation(s)
- Ludovic Galas
- Normandie University, UNIROUEN, INSERM, Regional Cell Imaging Platform of Normandy (PRIMACEN), 76000 Rouen, France.
| | - Magalie Bénard
- Normandie University, UNIROUEN, INSERM, Regional Cell Imaging Platform of Normandy (PRIMACEN), 76000 Rouen, France.
| | - Alexis Lebon
- Normandie University, UNIROUEN, INSERM, Regional Cell Imaging Platform of Normandy (PRIMACEN), 76000 Rouen, France.
| | - Yutaro Komuro
- Department of Neurophysiology, Donders Centre for Neuroscience, Radboud University, Nijmegen 6525 AJ, The Netherlands.
| | - Damien Schapman
- Normandie University, UNIROUEN, INSERM, Regional Cell Imaging Platform of Normandy (PRIMACEN), 76000 Rouen, France.
| | - Hubert Vaudry
- Normandie University, UNIROUEN, INSERM, Regional Cell Imaging Platform of Normandy (PRIMACEN), 76000 Rouen, France.
| | - David Vaudry
- Normandie University, UNIROUEN, INSERM, Regional Cell Imaging Platform of Normandy (PRIMACEN), 76000 Rouen, France.
| | - Hitoshi Komuro
- Department of Neuroscience, School of Medicine, Yale University, New Haven, CT 06510, USA.
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16
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Das S, Paul A, Mumbrekar KD, Rao SBS. Harmonization of Mangiferin on methylmercury engendered mitochondrial dysfunction. ENVIRONMENTAL TOXICOLOGY 2017; 32:630-644. [PMID: 28071871 DOI: 10.1002/tox.22265] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 03/08/2016] [Accepted: 03/09/2016] [Indexed: 06/06/2023]
Abstract
Mangiferin (MGN), a C-glucosylxanthone abundantly found in mango plants, was studied for its potential to ameliorate methylmercury (MeHg) induced mitochondrial damage in HepG2 (human hepatocarcinoma) cell line. Cell viability experiments performed using 3-[4,5-dimethylthiazol-2-yl]-2,5- diphenyltetrazolium bromide (MTT) showed protective property of MGN in annulling MeHg-induced cytotoxicity. Conditioning the cells with optimal dose of MGN (50 µM) lowered MeHg-induced oxidative stress, calcium influx/efflux, depletion of mitochondrial trans-membrane potential and prevented mitochondrial fission as observed by decrease in Mitotracker red fluorescence, expression of pDRP1 (serine 616), and DRP1 levels. MGN pre-treated cells demonstrated elevation in the activities of glutathione (GSH), Glutathione-S-transferase (GST), Glutathione peroxidase (GPx), Glutathione reductase (GR), reduced levels of Aspartate aminotransferase (AST) and Alanine aminotransferase (ALT) and mitochondrial electron transport chain (ETC) enzyme complexes. In addition, the anti-apoptotic effect of MGN was clearly indicated by the reduction in MeHg-induced apoptotic cells analyzed by flowcytometric analysis after Annexin V-FITC/propidium iodide staining. In conclusion, the present work demonstrates the ability of a dietary polyphenol, MGN to ameliorate MeHg-mediated mitochondrial dysfunction in human hepatic cells in vitro. This hepatoprotective potential may be attributed predominantly to the free radical scavenging/antioxidant property of MGN, by facilitating the balancing of cellular Ca2+ ions, maintenance of redox homeostasis and intracellular antioxidant activities, ultimately preserving the mitochondrial function and cell viability after MeHg intoxication. As MeHg intoxication occurs over a period of time, continuous consumption of such dietary compounds may prove to be very useful in promoting human health. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 630-644, 2017.
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Affiliation(s)
- Shubhankar Das
- Department of Radiation Biology and Toxicology, School of Life Sciences, Manipal University, Manipal, Karnataka, India, 576104
| | - Ajanta Paul
- Department of Biotechnology, School of Life Sciences, Manipal University, Manipal, Karnataka, India, 576104
| | - Kamalesh D Mumbrekar
- Department of Radiation Biology and Toxicology, School of Life Sciences, Manipal University, Manipal, Karnataka, India, 576104
| | - Satish B S Rao
- Department of Radiation Biology and Toxicology, School of Life Sciences, Manipal University, Manipal, Karnataka, India, 576104
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17
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Antunes Dos Santos A, Appel Hort M, Culbreth M, López-Granero C, Farina M, Rocha JBT, Aschner M. Methylmercury and brain development: A review of recent literature. J Trace Elem Med Biol 2016; 38:99-107. [PMID: 26987277 PMCID: PMC5011031 DOI: 10.1016/j.jtemb.2016.03.001] [Citation(s) in RCA: 101] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 03/02/2016] [Indexed: 02/02/2023]
Abstract
Methylmercury (MeHg) is a potent environmental pollutant, which elicits significant toxicity in humans. The central nervous system (CNS) is the primary target of toxicity, and is particularly vulnerable during development. Maternal exposure to MeHg via consumption of fish and seafood can have irreversible effects on the neurobehavioral development of children, even in the absence of symptoms in the mother. It is well documented that developmental MeHg exposure may lead to neurological alterations, including cognitive and motor dysfunction. The neurotoxic effects of MeHg on the developing brain have been extensively studied. The mechanism of toxicity, however, is not fully understood. No single process can explain the multitude of effects observed in MeHg-induced neurotoxicity. This review summarizes the most current knowledge on the effects of MeHg during nervous system development considering both, in vitro and in vivo experimental models. Considerable attention was directed towards the role of glutamate and calcium dyshomeostasis, mitochondrial dysfunction, as well as the effects of MeHg on cytoskeletal components/regulators.
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Affiliation(s)
| | - Mariana Appel Hort
- Institute of Biological Sciences, Federal University of Rio Grande, Campus Carreiros, Rio Grande do Sul, Brazil
| | - Megan Culbreth
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Caridad López-Granero
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Marcelo Farina
- Department of Biochemistry, Federal University of Santa Catarina, Florianopolis, Santa Catarina, Brazil
| | - Joao B T Rocha
- Department of Biochemistry, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul, Brazil
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, USA.
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18
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Ling W, Endo T, Kubo KI, Nakajima K, Kakeyama M, Tohyama C. In Utero Bisphenol A Exposure Induces Abnormal Neuronal Migration in the Cerebral Cortex of Mice. Front Endocrinol (Lausanne) 2016; 7:7. [PMID: 26869994 PMCID: PMC4733926 DOI: 10.3389/fendo.2016.00007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 01/15/2016] [Indexed: 01/21/2023] Open
Abstract
Bisphenol A (BPA) has been known to have endocrine-disrupting activity to induce reproductive and behavioral abnormalities in offspring of laboratory animal species. However, morphological basis of this abnormality during brain development is largely unknown. Cerebral cortex plays a crucial role in higher brain function, and its precisely laminated structure is formed by neuronal migration. In the present study, transfecting a plasmid (pCAG-mCherry) by in utero electroporation (IUE), we visualized developing neurons and investigated the possible effects of in utero BPA exposure on neuronal migration. Pregnant mice were exposed to BPA by osmotic pump at estimated daily doses of 0, 40 (BPA-40), or 400 (BPA-400) μg/kg from embryonic day 14.5 (E14.5) to E18.5. IUE was performed at E14.5 and neuronal migration was analyzed at E18.5. Compared with the control group, neuronal migration in the cortical plate was significantly decreased in the BPA-40 group; however, there was no significant difference in the BPA-400 group. Among several neuronal migration-related genes and cortical layer-specific genes, TrkB in the BPA-400 group was found significantly upregulated. In conclusion, in utero exposure to low BPA dose was found to disrupt neuronal migration in the cerebral cortex in a dose-specific manner.
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Affiliation(s)
- Wenting Ling
- Laboratory of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Toshihiro Endo
- Laboratory of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Ken-ichiro Kubo
- Department of Anatomy, Keio University School of Medicine, Tokyo, Japan
| | - Kazunori Nakajima
- Department of Anatomy, Keio University School of Medicine, Tokyo, Japan
| | - Masaki Kakeyama
- Laboratory of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
- Laboratory for Systems Neuroscience and Preventive Medicine, Faculty of Human Sciences, Waseda University, Tokorozawa, Japan
| | - Chiharu Tohyama
- Laboratory of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
- Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
- *Correspondence: Chiharu Tohyama,
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19
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Methylmercury upregulates RE-1 silencing transcription factor (REST) in SH-SY5Y cells and mouse cerebellum. Neurotoxicology 2015; 52:89-97. [PMID: 26610923 DOI: 10.1016/j.neuro.2015.11.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 11/09/2015] [Accepted: 11/11/2015] [Indexed: 01/06/2023]
Abstract
Methylmercury (MeHg) is a highly neurotoxic compound that, in adequate doses, can cause damage to the brain, including developmental defects and in severe cases cell death. The RE-1-silencing transcription factor (REST) has been found to be involved in the neurotoxic effects of environmental pollutants such as polychlorinated biphenyls (PCBs). In this study, we investigated the effects of MeHg treatment on REST expression and its role in MeHg-induced neurotoxicity in neuroblastoma SH-SY5Y cells. We found that MeHg exposure caused a dose- and time- dependent apoptotic cell death, as evidenced by the appearance of apoptotic hallmarks including caspase-3 processing and annexin V uptake. Moreover, MeHg increased REST gene and gene product expression. MeHg-induced apoptotic cell death was completely abolished by REST knockdown. Interestingly, MeHg (1μM/24h) increased the expression of REST Corepressor (Co-REST) and its binding with REST whereas the other REST cofactor mammalian SIN3 homolog A transcription regulator (mSin3A) was not modified. In addition, we demonstrated that the acetylation of histone protein H4 was reduced after MeHg treatment and was critical for MeHg-induced apoptosis. Accordingly, the pan-histone deacetylase inhibitor trichostatin-A (TSA) prevented MeHg-induced histone protein H4 deacetylation, thereby reverting MeHg-induced neurotoxic effect. Male mice subcutaneously injected with 10mg/kg of MeHg for 10 days showed an increase in REST expression in the granule cell layer of the cerebellum together with a decrease in histone H4 acetylation. Collectively, we demonstrated that methylmercury exposure can cause neurotoxicity by activating REST gene expression and H4 deacetylation.
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20
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Bénard M, Lebon A, Komuro H, Vaudry D, Galas L. Ex vivo imaging of postnatal cerebellar granule cell migration using confocal macroscopy. J Vis Exp 2015:e52810. [PMID: 25992599 PMCID: PMC4542730 DOI: 10.3791/52810] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
During postnatal development, immature granule cells (excitatory interneurons) exhibit tangential migration in the external granular layer, and then radial migration in the molecular layer and the Purkinje cell layer to reach the internal granular layer of the cerebellar cortex. Default in migratory processes induces either cell death or misplacement of the neurons, leading to deficits in diverse cerebellar functions. Centripetal granule cell migration involves several mechanisms, such as chemotaxis and extracellular matrix degradation, to guide the cells towards their final position, but the factors that regulate cell migration in each cortical layer are only partially known. In our method, acute cerebellar slices are prepared from P10 rats, granule cells are labeled with a fluorescent cytoplasmic marker and tissues are cultured on membrane inserts from 4 to 10 hr before starting real-time monitoring of cell migration by confocal macroscopy at 37 °C in the presence of CO2. During their migration in the different cortical layers of the cerebellum, granule cells can be exposed to neuropeptide agonists or antagonists, protease inhibitors, blockers of intracellular effectors or even toxic substances such as alcohol or methylmercury to investigate their possible role in the regulation of neuronal migration.
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Affiliation(s)
- Magalie Bénard
- PRIMACEN, Cell Imaging Platform of Normandy, Inserm, IRIB, University of Rouen
| | - Alexis Lebon
- PRIMACEN, Cell Imaging Platform of Normandy, Inserm, IRIB, University of Rouen
| | - Hitoshi Komuro
- Department of Neurobiology, School of Medicine, Yale University
| | - David Vaudry
- PRIMACEN, Cell Imaging Platform of Normandy, Inserm, IRIB, University of Rouen
| | - Ludovic Galas
- PRIMACEN, Cell Imaging Platform of Normandy, Inserm, IRIB, University of Rouen;
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21
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Padhi BK, Rosales M, Pelletier G. Perinatal methylmercury exposure perturbs the expression of Plp1 and Cnp splice variants in cerebellum of rat pups. Neurotoxicology 2015; 48:223-30. [PMID: 25936639 DOI: 10.1016/j.neuro.2015.04.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 03/18/2015] [Accepted: 04/22/2015] [Indexed: 01/01/2023]
Abstract
Early life exposure to environmental chemicals can interfere with myelin formation in the developing brain, leading to neurological disorders. The Proteolipid Protein 1 (Plp1), Myelin Basic Protein (Mbp) and 2',3'-Cyclic Nucleotide 3'Phosphodiesterase (Cnp) genes expressed in oligodendrocytes and involved in myelination processes can be useful biomarkers of potential developmental neurotoxicity. In an earlier study, we concluded that the reduction in the expression levels of Mbp splice variants in juvenile rat cerebellum following perinatal methylmercury (MeHg) exposure were compatible with an overall reduction of mature oligodendrocytes population. This observation prompted us to analyze the expression of Plp1 and Cnp in developing rat cerebellum to further confirm and investigate the toxic effects of MeHg on vulnerable oligodendrocytes. Splice variants of Plp1 in human and of Cnp in mouse are curated in NCBI RefSeq database, but not for rat. Lack of annotation of splice variants can pose significant challenge for the reliable quantification of gene expression levels in toxicological studies. Therefore, we applied a "comparative sequence analysis" approach, relying on annotated splice variants in human/mouse and on evolutionary conservation of intron-exon structures, to identify additional splice variants of Plp1 and Cnp in rat. Then, we confirmed their identity by nucleotide sequencing and characterized their temporal expression patterns during brain development by RT-PCR. The measurement of total transcripts and individual splice variants of Plp1 and Cnp in the cerebellum of MeHg-exposed rat pups revealed a relatively similar level of reduction in their expression levels. This study further confirms that perinatal exposure to MeHg can impact oligodendrocytes in pups. Based on these observations, we conclude that monitoring the expression of these oligodendrocyte-enriched genes can be useful to identify toxic chemicals affecting myelination.
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Affiliation(s)
- Bhaja K Padhi
- Hazard Identification Division, HECSB, Health Canada, Tunney's Pasture, Ottawa, Ontario K1A 0L2, Canada.
| | - Marianela Rosales
- Hazard Identification Division, HECSB, Health Canada, Tunney's Pasture, Ottawa, Ontario K1A 0L2, Canada
| | - Guillaume Pelletier
- Hazard Identification Division, HECSB, Health Canada, Tunney's Pasture, Ottawa, Ontario K1A 0L2, Canada
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22
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Fritsche E, Alm H, Baumann J, Geerts L, Håkansson H, Masjosthusmann S, Witters H. Literature review on in vitro and alternative Developmental Neurotoxicity (DNT) testing methods. ACTA ACUST UNITED AC 2015. [DOI: 10.2903/sp.efsa.2015.en-778] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Ellen Fritsche
- Leibniz Research Institute for Environmental Medicine (IUF), Group of Sphere Models and Risk Assessment, Auf'm Hennekamp 50, 40225 Düsseldorf, Germany
| | - Henrik Alm
- Leibniz Research Institute for Environmental Medicine (IUF), Group of Sphere Models and Risk Assessment, Auf'm Hennekamp 50, 40225 Düsseldorf, Germany
| | - Jenny Baumann
- Leibniz Research Institute for Environmental Medicine (IUF), Group of Sphere Models and Risk Assessment, Auf'm Hennekamp 50, 40225 Düsseldorf, Germany
| | - Lieve Geerts
- Flemish Institute for Technological Research (VITO), Environmental Risk & Health, Boeretang 200, B‐2400 Mol, Belgium
| | - Helen Håkansson
- Karolinska Institute (KI), Institute of Environmental Medicine (IMM), Unit of Environmental Health Risk Assessment, SE‐171 77 Stockholm, Sweden
| | - Stefan Masjosthusmann
- Leibniz Research Institute for Environmental Medicine (IUF), Group of Sphere Models and Risk Assessment, Auf'm Hennekamp 50, 40225 Düsseldorf, Germany
| | - Hilda Witters
- Flemish Institute for Technological Research (VITO), Environmental Risk & Health, Boeretang 200, B‐2400 Mol, Belgium
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23
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Luhmann HJ, Fukuda A, Kilb W. Control of cortical neuronal migration by glutamate and GABA. Front Cell Neurosci 2015; 9:4. [PMID: 25688185 PMCID: PMC4311642 DOI: 10.3389/fncel.2015.00004] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Accepted: 01/06/2015] [Indexed: 11/13/2022] Open
Abstract
Neuronal migration in the cortex is controlled by the paracrine action of the classical neurotransmitters glutamate and GABA. Glutamate controls radial migration of pyramidal neurons by acting primarily on NMDA receptors and regulates tangential migration of inhibitory interneurons by activating non-NMDA and NMDA receptors. GABA, acting on ionotropic GABAA-rho and GABAA receptors, has a dichotomic action on radially migrating neurons by acting as a GO signal in lower layers and as a STOP signal in upper cortical plate (CP), respectively. Metabotropic GABAB receptors promote radial migration into the CP and tangential migration of interneurons. Besides GABA, the endogenous GABAergic agonist taurine is a relevant agonist controlling radial migration. To a smaller extent glycine receptor activation can also influence radial and tangential migration. Activation of glutamate and GABA receptors causes increases in intracellular Ca(2+) transients, which promote neuronal migration by acting on the cytoskeleton. Pharmacological or genetic manipulation of glutamate or GABA receptors during early corticogenesis induce heterotopic cell clusters in upper layers and loss of cortical lamination, i.e., neuronal migration disorders which can be associated with neurological or neuropsychiatric diseases. The pivotal role of NMDA and ionotropic GABA receptors in cortical neuronal migration is of major clinical relevance, since a number of drugs acting on these receptors (e.g., anti-epileptics, anesthetics, alcohol) may disturb the normal migration pattern when present during early corticogenesis.
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Affiliation(s)
- Heiko J Luhmann
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Germany
| | - A Fukuda
- Department of Neurophysiology, Hamamatsu University School of Medicine Hamamatsu, Shizuoka, Japan
| | - W Kilb
- Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Germany
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Wang X, Liu J, Zhu Z, Ou G. The heparan sulfate-modifying enzyme glucuronyl C5-epimerase HSE-5 controls Caenorhabditis elegans Q neuroblast polarization during migration. Dev Biol 2015; 399:306-14. [PMID: 25614236 DOI: 10.1016/j.ydbio.2015.01.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2014] [Revised: 01/05/2015] [Accepted: 01/10/2015] [Indexed: 10/24/2022]
Abstract
Directional cell migration is fundamental for neural development, and extracellular factors are pivotal for this process. Heparan sulfate proteoglycans (HSPGs) that carry long chains of differentially modified sugar residues contribute to extracellular matrix; however, the functions of HSPG in guiding cell migration remain elusive. Here, we used the Caenorhabditis elegans mutant pool from the Million Mutation Project and isolated a mutant allele of the heparan sulfate-modifying enzyme glucuronyl C5-epimerase HSE-5. Loss-of-function of this enzyme resulted in defective Q neuroblast migration. We showed that hse-5 controlled Q cell migration in a cell non-autonomous manner. By performing live cell imaging in hse-5 mutant animals, we found that hse-5 controlled initial polarization during Q neuroblast migration. Furthermore, our genetic epistasis analysis demonstrated that lon-2 might act downstream of hse-5. Finally, rescue of the hse-5 mutant phenotype by expression of human and mouse hse-5 homologs suggested a conserved function for this gene in neural development. Taken together, our results indicated that proper HSPG modification in the extracellular matrix by HSE-5 is essential for neuroblast polarity during migration.
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Affiliation(s)
- Xiangming Wang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, China.
| | - Jianhong Liu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, China
| | - Zhiwen Zhu
- Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Guangshuo Ou
- Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
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25
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Baumann J, Dach K, Barenys M, Giersiefer S, Goniwiecha J, Lein PJ, Fritsche E. Application of the Neurosphere Assay for DNT Hazard Assessment: Challenges and Limitations. METHODS IN PHARMACOLOGY AND TOXICOLOGY 2015. [DOI: 10.1007/7653_2015_49] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Methylmercury exposure during early Xenopus laevis development affects cell proliferation and death but not neural progenitor specification. Neurotoxicol Teratol 2014; 47:102-13. [PMID: 25496965 DOI: 10.1016/j.ntt.2014.11.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2014] [Revised: 11/25/2014] [Accepted: 11/27/2014] [Indexed: 11/23/2022]
Abstract
Methylmercury (MeHg) is a widespread environmental toxin that preferentially and adversely affects developing organisms. To investigate the impact of MeHg toxicity on the formation of the vertebrate nervous system at physiologically relevant concentrations, we designed a graded phenotype scale for evaluating Xenopus laevis embryos exposed to MeHg in solution. Embryos displayed a range of abnormalities in response to MeHg, particularly in brain development, which is influenced by both MeHg concentration and the number of embryos per ml of exposure solution. A TC50 of ~50μg/l and LC50 of ~100μg/l were found when maintaining embryos at a density of one per ml, and both increased with increasing embryo density. In situ hybridization and microarray analysis showed no significant change in expression of early neural patterning genes including sox2, en2, or delta; however a noticeable decrease was observed in the terminal neural differentiation genes GAD and xGAT, but not xVGlut. PCNA, a marker for proliferating cells, was negatively correlated with MeHg dose, with a significant reduction in cell number in the forebrain and spinal cord of exposed embryos by tadpole stages. Conversely, the number of apoptotic cells in neural regions detected by a TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay was significantly increased. These results provide evidence that disruption of embryonic neural development by MeHg may not be directly due to a loss of neural progenitor specification and gene transcription, but to a more general decrease in cell proliferation and increase in cell death throughout the developing nervous system.
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27
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Komuro Y, Galas L, Lebon A, Raoult E, Fahrion JK, Tilot A, Kumada T, Ohno N, Vaudry D, Komuro H. The role of calcium and cyclic nucleotide signaling in cerebellar granule cell migration under normal and pathological conditions. Dev Neurobiol 2014; 75:369-87. [PMID: 25066767 DOI: 10.1002/dneu.22219] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 06/30/2014] [Accepted: 07/25/2014] [Indexed: 11/07/2022]
Abstract
In the developing brain, immature neurons migrate from their sites of origin to their final destination, where they reside for the rest of their lives. This active movement of immature neurons is essential for the formation of normal neuronal cytoarchitecture and proper differentiation. Deficits in migration result in the abnormal development of the brain, leading to a variety of neurological disorders. A myriad of extracellular guidance molecules and intracellular effector molecules is involved in controlling the migration of immature neurons in a cell type, cortical layer and birth-date-specific manner. To date, little is known about how extracellular guidance molecules transfer their information to the intracellular effector molecules, which regulate the migration of immature neurons. In this article, to fill the gap between extracellular guidance molecules and intracellular effector molecules, using the migration of cerebellar granule cells as a model system of neuronal cell migration, we explore the role of second messenger signaling (specifically Ca(2+) and cyclic nucleotide signaling) in the regulation of neuronal cell migration. We will, first, describe the cortical layer-specific changes in granule cell migration. Second, we will discuss the roles of Ca(2+) and cyclic nucleotide signaling in controlling granule cell migration. Third, we will present recent studies showing the roles of Ca(2+) and cyclic nucleotide signaling in the deficits in granule cell migration in mouse models of fetal alcohol spectrum disorders and fetal Minamata disease.
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Affiliation(s)
- Yutaro Komuro
- Department of Neurosciences, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, 44195
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28
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Hutchins BI, Klenke U, Wray S. Calcium release-dependent actin flow in the leading process mediates axophilic migration. J Neurosci 2013; 33:11361-71. [PMID: 23843509 PMCID: PMC3724331 DOI: 10.1523/jneurosci.3758-12.2013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Revised: 02/20/2013] [Accepted: 02/26/2013] [Indexed: 12/22/2022] Open
Abstract
Proper assembly of neural circuits requires newly born neurons to migrate from their place of origin to their final location. Little is known about the mechanisms of axophilic neuronal migration, whereby neurons travel along axon pathways to navigate to their destinations. Gonadotropin-releasing hormone (GnRH)-expressing neurons migrate along olfactory axons from the nose into the forebrain during development, and were used as a model of axophilic migration. After migrating, GnRH neurons are located in the hypothalamus and are essential for puberty and maintenance of reproductive function. To gain a better understanding of the mechanisms underlying axophilic migration, we investigated in mice the regulation of movement from calcium signals to cytoskeletal dynamics. Live imaging revealed robust calcium activity during axophilic migration, and calcium release through IP3 receptors was found to stimulate migration. This occurred through a signaling pathway involving the calcium sensor calcium/calmodulin protein kinase kinase, AMP-activated kinase, and RhoA/ROCK. By imaging GnRH neurons expressing actin-GFP or Lifeact-RFP, calcium release was found to stimulate leading process actin flow away from the cell body. In contrast, actin contractions at the cell rear were unaffected by this calcium signaling pathway. These findings are the first to test the regulation of cytoskeletal dynamics in axophilic migration, and reveal mechanisms of movement that have broad implications for the migration of other CNS populations.
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Affiliation(s)
- B. Ian Hutchins
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-9525, and
- Postdoctoral Research Associate Program, National Institute of General Medical Sciences, National Institutes of Health, Bethesda, Maryland 20892-6200
| | - Ulrike Klenke
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-9525, and
| | - Susan Wray
- Cellular and Developmental Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-9525, and
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29
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Dórea JG, Farina M, Rocha JBT. Toxicity of ethylmercury (and Thimerosal): a comparison with methylmercury. J Appl Toxicol 2013; 33:700-11. [PMID: 23401210 DOI: 10.1002/jat.2855] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 12/10/2012] [Accepted: 12/11/2012] [Indexed: 12/18/2022]
Abstract
Ethylmercury (etHg) is derived from the metabolism of thimerosal (o-carboxyphenyl-thio-ethyl-sodium salt), which is the most widely used form of organic mercury. Because of its application as a vaccine preservative, almost every human and animal (domestic and farmed) that has been immunized with thimerosal-containing vaccines has been exposed to etHg. Although methylmercury (meHg) is considered a hazardous substance that is to be avoided even at small levels when consumed in foods such as seafood and rice (in Asia), the World Health Organization considers small doses of thimerosal safe regardless of multiple/repetitive exposures to vaccines that are predominantly taken during pregnancy or infancy. We have reviewed in vitro and in vivo studies that compare the toxicological parameters among etHg and other forms of mercury (predominantly meHg) to assess their relative toxicities and potential to cause cumulative insults. In vitro studies comparing etHg with meHg demonstrate equivalent measured outcomes for cardiovascular, neural and immune cells. However, under in vivo conditions, evidence indicates a distinct toxicokinetic profile between meHg and etHg, favoring a shorter blood half-life, attendant compartment distribution and the elimination of etHg compared with meHg. EtHg's toxicity profile is different from that of meHg, leading to different exposure and toxicity risks. Therefore, in real-life scenarios, a simultaneous exposure to both etHg and meHg might result in enhanced neurotoxic effects in developing mammals. However, our knowledge on this subject is still incomplete, and studies are required to address the predictability of the additive or synergic toxicological effects of etHg and meHg (or other neurotoxicants).
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Affiliation(s)
- José G Dórea
- Department of Nutrition, Faculty of Health Sciences, Universidade de Brasilia, 70919-970, Brasilia, DF, Brazil.
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Diphenyl diselenide prevents methylmercury-induced mitochondrial dysfunction in rat liver slices. Tetrahedron 2012. [DOI: 10.1016/j.tet.2012.09.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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31
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Scelfo B, Politi M, Reniero F, Palosaari T, Whelan M, Zaldívar JM. Application of multielectrode array (MEA) chips for the evaluation of mixtures neurotoxicity. Toxicology 2012; 299:172-83. [DOI: 10.1016/j.tox.2012.05.020] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Revised: 05/21/2012] [Accepted: 05/23/2012] [Indexed: 01/10/2023]
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32
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Padhi BK, Pelletier G. Perturbation of myelin basic protein (Mbp) splice variant expression in developing rat cerebellum following perinatal exposure to methylmercury. Toxicol Lett 2012; 213:374-80. [PMID: 22835759 DOI: 10.1016/j.toxlet.2012.07.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Revised: 07/12/2012] [Accepted: 07/14/2012] [Indexed: 01/01/2023]
Abstract
Myelin sheaths surrounding axons are essential for saltatory conduction of nerve impulse in the central nervous system. A major protein constituent of myelin sheaths is produced by the myelin basic protein (Mbp) gene, whose expression in oligodendrocytes is conserved across vertebrates. In rat, five Mbp splice variants resulting from alternative splicing of exons 2, 5 and/or 6 are characterized. We developed a PCR-based strategy to quantify individual Mbp splice variants and characterized a sixth Mbp splice variant lacking only exon 5. This newly identified splice variant is predominantly expressed in developing rat brain and has orthologs in mouse and human. Many neurotoxic chemicals can perturb myelination and Mbp gene expression. Regulation of Mbp gene expression at the post-transcriptional level was assessed following perinatal exposure to neurotoxic methylmercury (2 mg/kg b.w./day). Similar reductions in total and individual Mbp splice variant mRNA levels suggest that methylmercury-induced perturbation in Mbp gene expression occurred as a consequence of decreased oligodendrocyte cell population in absence of a significant impact on its post-transcriptional regulation.
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Affiliation(s)
- Bhaja K Padhi
- Hazard Identification Division, HECSB, Health Canada, Tunney's Pasture, Ottawa, ON, K1A 0L2, Canada
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33
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Role of calcium and mitochondria in MeHg-mediated cytotoxicity. J Biomed Biotechnol 2012; 2012:248764. [PMID: 22927718 PMCID: PMC3425894 DOI: 10.1155/2012/248764] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Revised: 06/12/2012] [Accepted: 06/14/2012] [Indexed: 11/17/2022] Open
Abstract
Methylmercury (MeHg) mediated cytotoxicity is associated with loss of intracellular calcium (Ca2+) homeostasis. The imbalance in Ca2+ physiology is believed to be associated with dysregulation of Ca2+ intracellular stores and/or increased permeability of the biomembranes to this ion. In this paper we summarize the contribution of glutamate dyshomeostasis in intracellular Ca2+ overload and highlight the mitochondrial dysfunctions induced by MeHg via Ca2+ overload. Mitochondrial disturbances elicited by Ca2+ may involve several molecular events (i.e., alterations in the activity of the mitochondrial electron transport chain complexes, mitochondrial proton gradient dissipation, mitochondrial permeability transition pore (MPTP) opening, thiol depletion, failure of energy metabolism, reactive oxygen species overproduction) that could culminate in cell death. Here we will focus on the role of oxidative stress in these phenomena. Additionally, possible antioxidant therapies that could be effective in the treatment of MeHg intoxication are briefly discussed.
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