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Dao CV, Shiraishi M, Miyamoto A. The MARCKS protein amount is differently regulated by calpain during toxic effects of methylmercury between SH-SY5Y and EA.hy926 cells. J Vet Med Sci 2017; 79:1931-1938. [PMID: 29046508 PMCID: PMC5745167 DOI: 10.1292/jvms.17-0473] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Methylmercury (MeHg) is an environmental pollutant that shows severe toxicity to humans and animals. However, the molecular mechanisms mediating MeHg toxicity are not completely understood. We have previously reported that the MARCKS protein is involved in the MeHg toxicity to SH-SY5Y neuroblastoma and EA.hy926 vascular endothelial cell lines. In addition, calpain, a Ca2+-dependent protease, is suggested to be associated with the MeHg toxicity. Because MARCKS is known as a substrate of calpain, we studied the relation between calpain activation and cleavage of MARCKS and its role in MeHg toxicity. In SH-SY5Y cells, MeHg decreased cell viability along with increased calcium mobilization, calpain activation and a decrease in MARCKS amounts. However, pretreatment with calpain inhibitors attenuated the decrease in cell viability and MARCKS amount induced only by 1 µM but not by 3 µM MeHg. In cells with a MARCKS knockdown, calpain inhibitors failed to attenuate the decrease in cell viability caused by MeHg. In EA.hy926 cells, although MeHg caused calcium mobilization and a decrease in MARCKS levels, calpain activation was not observed. These results indicate that the participation of calpain in the regulation of MARCKS amounts is dependent on the cell type and concentration of MeHg. In SH-SY5Y cells, calpain-mediated proteolysis of MARCKS is involved in cytotoxicity induced by a low concentration of MeHg.
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Affiliation(s)
- Cuong Van Dao
- Department of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan.,Department of Veterinary Pharmacology, Faculty of Animal Husbandry and Veterinary Medicine, Thai Nguyen University of Agriculture and Forestry, Group 10, Quyet Thang Commune, Thai Nguyen City, Thai Nguyen, Vietnam
| | - Mitsuya Shiraishi
- Department of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan
| | - Atsushi Miyamoto
- Department of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan
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Methylmercury Increases and Eicosapentaenoic Acid Decreases the Relative Amounts of Arachidonic Acid-Containing Phospholipids in Mouse Brain. Lipids 2015; 51:61-73. [DOI: 10.1007/s11745-015-4087-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 10/02/2015] [Indexed: 12/29/2022]
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Biamonte F, Latini L, Giorgi FS, Zingariello M, Marino R, De Luca R, D'Ilio S, Majorani C, Petrucci F, Violante N, Senofonte O, Molinari M, Keller F. Associations among exposure to methylmercury, reduced Reelin expression, and gender in the cerebellum of developing mice. Neurotoxicology 2014; 45:67-80. [PMID: 25305366 DOI: 10.1016/j.neuro.2014.09.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 09/24/2014] [Accepted: 09/28/2014] [Indexed: 12/30/2022]
Abstract
Genetic risk factors acting during pregnancy or early after birth have been proposed to account for the exponential increase of autism diagnoses in the past 20 years. In particular, a potential link with exposure to environmental mercury has been suggested. Male sex constitutes a second risk factor for autism. A third potential genetic risk factor is decreased Reelin expression. Male heterozygous reeler (rl(+/-)) mice show an autism-like phenotype, including Purkinje cells (PCs) loss and behavioral rigidity. We evaluated the complex interactions between 3 risk factors, i.e. genetic status, sex, and exposure to methylmercury (MeHg), in rl(+/-) mice. Mice were exposed to MeHg during the prenatal and early postnatal period, either at a subtoxic dose (2 ppm in Dams' drinking water), or at a toxic dose (6 ppm Dams' drinking water), based on observations in other rodent species and mice strains. We show that: (a) 2 ppm MeHg does not cause PCs loss in the different animal groups, and does not enhance PCs loss in rl(+/-) males; consistent with a lack of overt neurotoxicity, 2 ppm MeHg per se does not cause behavioral alterations (separation-induced ultrasonic calls in newborns, or sociability and social preference in adults); (b) in stark contrast, 6 ppm MeHg causes a dramatic reduction of PCs number in all groups, irrespective of genotype and sex. Cytochrome C release from mitochondria of PCs is enhanced in 6 ppm MeHg-exposed groups, with a concomitant increase of μ-calpain active subunit. At the behavioral level, 6 ppm MeHg exposure strongly increases ultrasonic vocalizations in all animal groups. Notably, 6 ppm MeHg significantly decreases sociability in rl(+/-) male mice, while the 2 ppm group does not show such as decrease. At a subtoxic dose, MeHg does not enhance the autism-like phenotype of male rl(+/-) mice. At the higher MeHg dose, the scenario is more complex, with some "autism-like" features (loss of sociability, preference for sameness) being evidently affected only in rl(+/-) males, while other neuropathological and behavioral parameters being altered in all groups, independently from genotype and sex. Mitochondrial abnormalities appear to play a crucial role in the observed effects.
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Affiliation(s)
- Filippo Biamonte
- Laboratory of Developmental Neuroscience and Neural Plasticity, University Campus Biomedico, Via A. del Portillo 21, 00198 Rome, Italy
| | - Laura Latini
- Santa Lucia Foundation, I.R.C.C.S., Via del Fosso di Fiorano 64, 00143 Rome, Italy
| | - Filippo Sean Giorgi
- Section of Neurology, Department of Clinical and Experimental Medicine, University of Pisa, Via Roma 67, 56126 Pisa, Italy
| | | | - Ramona Marino
- Laboratory of Developmental Neuroscience and Neural Plasticity, University Campus Biomedico, Via A. del Portillo 21, 00198 Rome, Italy
| | - Roberto De Luca
- Laboratory of Developmental Neuroscience and Neural Plasticity, University Campus Biomedico, Via A. del Portillo 21, 00198 Rome, Italy
| | - Sonia D'Ilio
- Istituto Superiore di Sanità, Centro Nazionale Sostanze Chimiche, Viale Regina Elena 299, Rome, Italy
| | - Costanza Majorani
- Istituto Superiore di Sanità, Dipartimento di Ambiente e Prevenzione Primaria, Viale Regina Elena 299, Rome, Italy
| | - Francesco Petrucci
- Istituto Superiore di Sanità, Dipartimento di Ambiente e Prevenzione Primaria, Viale Regina Elena 299, Rome, Italy
| | - Nicola Violante
- Istituto Superiore di Sanità, Dipartimento di Ambiente e Prevenzione Primaria, Viale Regina Elena 299, Rome, Italy
| | - Oreste Senofonte
- Istituto Superiore di Sanità, Dipartimento di Ambiente e Prevenzione Primaria, Viale Regina Elena 299, Rome, Italy
| | - Marco Molinari
- Santa Lucia Foundation, I.R.C.C.S., Via del Fosso di Fiorano 64, 00143 Rome, Italy.
| | - Flavio Keller
- Laboratory of Developmental Neuroscience and Neural Plasticity, University Campus Biomedico, Via A. del Portillo 21, 00198 Rome, Italy.
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Hassauer M, Kaiser E, Schneider K, Schuhmacher‐Wolz U. Collate the literature on toxicity data on mercury in experimental animals and humans (Part I – Data on organic mercury). ACTA ACUST UNITED AC 2012. [DOI: 10.2903/sp.efsa.2012.en-297] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Martin Hassauer
- Forschungs‐ und Beratungsinstitut Gefahrstoffe GmbH (FoBiG) Freiburg Germany
| | - Eva Kaiser
- Forschungs‐ und Beratungsinstitut Gefahrstoffe GmbH (FoBiG) Freiburg Germany
| | - Klaus Schneider
- Forschungs‐ und Beratungsinstitut Gefahrstoffe GmbH (FoBiG) Freiburg Germany
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Zakharov VV, Abramova YK, Mosevitsky MI. On the activation of calcium-dependent proteolysis in brain neurons of spontaneously hypertensive rats (SHR strain). Bull Exp Biol Med 2012; 150:587-9. [PMID: 22235391 DOI: 10.1007/s10517-011-1197-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Females of spontaneously hypertensive (SHR strain) and normotensive rats (WKY strain and Wistar) received drinking water with normal (80 mg/liter) or reduced concentration of Ca(2+)(8 mg/liter). Activity of calcium-dependent calpain protease in neurons did not differ in 18-day-old rat pups born and suckled by these animals. Our results are consistent with published data on normal metabolism of SHR rats up to the age of 30 days.
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Affiliation(s)
- V V Zakharov
- Department of Molecular and Radiational Biophysics, B. P. Konstantinov Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, Russia.
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Black P, Niu L, Sachdeva M, Lean D, Poon R, Bowers WJ, Chan HM, Arnason JT, Pelletier G. Modulation of the effects of methylmercury on rat neurodevelopment by co-exposure with Labrador Tea (Rhododendron tomentosum ssp. subarcticum). Food Chem Toxicol 2011; 49:2336-42. [DOI: 10.1016/j.fct.2011.06.035] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Revised: 06/14/2011] [Accepted: 06/15/2011] [Indexed: 02/07/2023]
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Berg K, Puntervoll P, Valdersnes S, Goksøyr A. Responses in the brain proteome of Atlantic cod (Gadus morhua) exposed to methylmercury. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2010; 100:51-65. [PMID: 20701987 DOI: 10.1016/j.aquatox.2010.07.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 06/27/2010] [Accepted: 07/04/2010] [Indexed: 05/29/2023]
Abstract
The molecular mechanisms underlying the neurotoxicity of methylmercury (MeHg), a ubiquitous environmental contaminant, are not yet fully understood. Furthermore, there is a lack of biomarkers of MeHg neurotoxicity for use in environmental monitoring. We have undertaken a proteomic analysis of brains from Atlantic cod (Gadus morhua) exposed to 0, 0.5 and 2 mg/kg MeHg administered by intraperitoneal injection. The doses were given in two injections, half of the dose on the first day and the second half after 1 week, and the total exposure period lasted 2 weeks. Using 2-DE coupled with MALDI-TOF MS and MS/MS, we observed the level of 71 protein spots to be 20% or more significantly altered following MeHg exposure, and successfully identified 40 of these protein spots. Many of these proteins are associated with main known molecular targets and mechanisms of MeHg-induced neurotoxicity in mammals, such as mitochondrial dysfunction, oxidative stress, altered calcium homeostasis and tubulin/disruption of microtubules. More interestingly, several of the affected proteins, with well-established or recently demonstrated critical functions in nervous system-specific processes, have not previously been associated with MeHg exposure in any species. These proteins include the strongest up-regulated protein, pyridoxal kinase (essential for synthesis of several neurotransmitters), G protein (coupled to neurotransmitter receptors), nicotinamide phosphoribosyl-transferase (protection against axonal degeneration), dihydropyrimidinase-like 5 (or collapsin response mediator protein 5, CRMP-5) (axon guidance and regeneration), septin (dendrite development), phosphatidylethanolamine binding protein (precursor for hippocampal cholinergic neurostimulating peptide) and protein phosphatase 1 (control of brain recovery by synaptic plasticity). The results of the present study aid our understanding of molecular mechanisms underlying MeHg neurotoxicity and defense responses, and provide a large panel of protein biomarker candidates for aquatic environmental monitoring.
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Affiliation(s)
- Karin Berg
- Department of Molecular Biology, University of Bergen, PB 7803, N-5020 Bergen, Norway
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Sakamoto M, Miyamoto KI, Wu Z, Nakanishi H. Possible involvement of cathepsin B released by microglia in methylmercury-induced cerebellar pathological changes in the adult rat. Neurosci Lett 2008; 442:292-6. [PMID: 18638529 DOI: 10.1016/j.neulet.2008.07.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2008] [Revised: 07/04/2008] [Accepted: 07/08/2008] [Indexed: 11/24/2022]
Abstract
There is increasing evidence that cathepsin B (CB), a lysosomal cysteine protease, is one of the toxic molecules that are secreted by activated microglia. We herein provide evidence that CB released by activated microglia may play a role in the methylmercury (MeHg)-induced pathological changes observed in the cerebellum of the adult rat. Pathological changes tended to progress slowly after treatment with MeHg (5 mg/kg) for 12 consecutive days. At 5 days after the final treatment of MeHg, there was a mild pyknotic change of the granule cells, whereas a marked accumulation of activated microglia was observed in the granule cell layer of the lingual and central lobe. At 8 days after the final treatment, intense pyknotic changes of the granule cells and the accumulation of activated microglia were observed throughout the cerebellar vermis. CB first significantly increased at 3 days after the final treatment of MeHg as the mature form. CB mainly increased in activated microglia which accumulated in the granule cell layer. The coadministration of CA074, an irreversible CB inhibitor, with MeHg significantly reduced the severity of pyknotic changes of the granule cells. Furthermore, primary cultured microglia secreted the mature CB in the culture medium following cellular activation. These observations strongly suggest that CB secreted by activated microglia is thus closely associated with the MeHg-induced severe pyknotic changes of the cerebellar granule cells. The treatment of CA074 could be a potentially effective therapeutic intervention to prevent the pathological changes in the cerebellum caused by ingestion of MeHg-contaminated food.
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Affiliation(s)
- Misao Sakamoto
- Laboratory of Oral Aging Science, Faculty of Dental Sciences, Kyushu University, Maidashi 3-1-1, Fukuoka 812-8582, Japan
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Hwang IK, Yoo KY, Kim DW, Li H, Park OK, Lee CH, Choi JH, Won MH. αII-Spectrin breakdown product increases in principal cells in the gerbil main olfactory bulb following transient ischemia. Neurosci Lett 2008; 435:251-6. [DOI: 10.1016/j.neulet.2008.02.050] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2007] [Revised: 02/05/2008] [Accepted: 02/20/2008] [Indexed: 11/16/2022]
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de Melo Reis RA, Herculano AM, da Silva MCC, dos Santos RM, do Nascimento JLM. In vitro toxicity induced by methylmercury on sympathetic neurons is reverted by l-cysteine or glutathione. Neurosci Res 2007; 58:278-84. [PMID: 17482303 DOI: 10.1016/j.neures.2007.03.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2007] [Revised: 03/25/2007] [Accepted: 03/26/2007] [Indexed: 11/17/2022]
Abstract
Methylmercury (MeHg) is related to several deleterious effects on the vertebrate nervous system and part of these effects are through interaction with sulfhydryl (-SH) group found in cellular proteins. We decided to characterize the dose-dependent effect of MeHg on the neurotoxicity and the neurite outgrowth induced effects on chick sympathetic neurons dissociated and purified in culture. In this model, MeHg inhibited neurite outgrowth (1-10 microM) and induced cell death (1-10 microM) after 48 h in culture. Since metal toxicity often generates reactive oxygen species, we tested if antioxidant compounds such as glutathione (GSH) or L-cysteine (L-cys) could block the deleterious effects promoted by MeHg. L-methionine, another sulfur-containing amino acid, but without a SH group, was also used in this work. We show that GSH (10-100 microM) and L-cys (100 microM), but not L-methionine (100 microM), fully blocked neurite degeneration and sympathetic neuron cell death in culture.
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Mao X, Yang SH, Simpkins JW, Barger SW. Glutamate receptor activation evokes calpain-mediated degradation of Sp3 and Sp4, the prominent Sp-family transcription factors in neurons. J Neurochem 2007; 100:1300-14. [PMID: 17316402 PMCID: PMC1949346 DOI: 10.1111/j.1471-4159.2006.04297.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Sp-family transcription factors (Sp1, Sp3 and Sp4) contain a zinc-finger domain that binds to DNA sequences rich in G-C/T. As assayed by RT-PCR analysis of mRNA, western-blot analysis, immunofluorescence, and antibody-dependent "supershift" of DNA-binding assays, the prominent Sp-family factors in cerebral neurons were identified as Sp3 and Sp4. By contrast, glial cells were found to express Sp1 and Sp3. We previously showed that the pattern of G-C/T binding activity of Sp-family factors is rapidly and specifically altered by the calcium influx accompanying activation of glutamate receptors. Here, we demonstrate that Sp-factor activity is also lost after a cerebral ischemia/reperfusion injury in vivo. Consistent with its calcium-dependent nature, we found that glutamate's effect on Sp-family factors could be blocked by inhibitors of calpains, neutral cysteine proteases activated by calcium. Purified calpain I cleaved Sp3 and Sp4 into products that retained G-C/T-binding activity, consistent with species observed in glutamate-treated neurons. These data provide details of an impact of glutamate-receptor activation on molecular events connected to gene expression.
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Affiliation(s)
- Xianrong Mao
- Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
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Kamei H, Saito T, Ozawa M, Fujita Y, Asada A, Bibb JA, Saido TC, Sorimachi H, Hisanaga SI. Suppression of Calpain-dependent Cleavage of the CDK5 Activator p35 to p25 by Site-specific Phosphorylation. J Biol Chem 2007; 282:1687-94. [PMID: 17121855 DOI: 10.1074/jbc.m610541200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cdk5 is a proline-directed Ser/Thr protein kinase predominantly expressed in postmitotic neurons together with its activator, p35. N-terminal truncation of p35 to p25 by calpain results in deregulation of Cdk5 and contributes to neuronal cell death associated with several neurodegenerative diseases. Previously we reported that p35 occurred as a phosphoprotein, phospho-p35 levels changed with neuronal maturation, and that phosphorylation of p35 affected its vulnerability to calpain cleavage. Here, we identify the p35 residues Ser(8) and Thr(138) as the major sites of phosphorylation by Cdk5. Mutagenesis of these sites to unphosphorylatable Ala increased susceptibility to calpain in cultured cells and neurons while changing them to phosphomimetic glutamate-attenuated cleavage. Furthermore, phosphorylation state-specific antibodies to these sites revealed that Thr(138) was dephosphorylated in adult rat, although both Ser(8) and Thr(138) were phosphorylated in prenatal brains. In cultured neurons, inhibition of protein phosphatases converted phosho-Ser(8) p35 to dual phospho-Ser(8)/Thr(138) p35 and conferred resistance to calpain cleavage. These results suggest phosphorylation of Thr(138) predominantly defines the susceptibility of p35 to calpain-dependent cleavage and that dephosphorylation of this site is a critical determinant of Cdk5-p25-induced cell death associated with neurodegeneration.
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Affiliation(s)
- Hirotsugu Kamei
- Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachiohji, Tokyo 192-0397, Japan
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Aikman J, O'Steen B, Silver X, Torres R, Boslaugh S, Blackband S, Padgett K, Wang KKW, Hayes R, Pineda J. Alpha-II-spectrin after controlled cortical impact in the immature rat brain. Dev Neurosci 2006; 28:457-65. [PMID: 16943668 DOI: 10.1159/000094171] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Accepted: 04/10/2006] [Indexed: 01/12/2023] Open
Abstract
Proteolytic processing plays an important role in regulating a wide range of important cellular functions, including processing of cytoskeletal proteins. Loss of cytoskeletal proteins such as spectrin is an important characteristic in a variety of acute central nervous system injuries including ischemia, spinal cord injury and traumatic brain injury (TBI). The literature contains extensive information on the proteolytic degradation of alpha-II-spectrin after TBI in the adult brain. By contrast, there is limited knowledge on the characteristics and relevance of these important processes in the immature brain. The present experiments examine TBI-induced proteolytic processing of alpha-II-spectrin after TBI in the immature rat brain. Distinct proteolytic products resulting from the degradation of the cytoskeletal protein alpha-II-spectrin by calpain and caspase 3 were readily detectable in cortical brain parenchyma and cerebrospinal fluid after TBI in immature rats.
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Affiliation(s)
- J Aikman
- Center for Traumatic Brain Injury Studies, Evelyn F. & William L. McKnight Brain Institute of the University of Florida, Gainesville, FL, USA
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Zhang Y, Bhavnani BR. Glutamate-induced apoptosis in neuronal cells is mediated via caspase-dependent and independent mechanisms involving calpain and caspase-3 proteases as well as apoptosis inducing factor (AIF) and this process is inhibited by equine estrogens. BMC Neurosci 2006; 7:49. [PMID: 16776830 PMCID: PMC1526740 DOI: 10.1186/1471-2202-7-49] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Accepted: 06/15/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Glutamate, a major excitatory amino acid neurotransmitter, causes apoptotic neuronal cell death at high concentrations. Our previous studies have shown that depending on the neuronal cell type, glutamate-induced apoptotic cell death was associated with regulation of genes such as Bcl-2, Bax, and/or caspase-3 and mitochondrial cytochrome c. To further delineate the intracellular mechanisms, we have investigated the role of calpain, an important calcium-dependent protease thought to be involved in apoptosis along with mitochondrial apoptosis inducing factor (AIF) and caspase-3 in primary cortical cells and a mouse hippocampal cell line HT22. RESULTS Glutamate-induced apoptotic cell death in neuronal cells was associated with characteristic DNA fragmentation, morphological changes, activation of calpain and caspase-3 as well as the upregulation and/or translocation of AIF from mitochondria into cytosol and nuclei. Our results reveal that primary cortical cells and HT22 cells display different patterns of regulation of these genes/proteins. In primary cortical cells, glutamate induces activation of calpain, caspase-3 and translocation of AIF from mitochondria to cytosol and nuclei. In contrast, in HT22 cells, only the activation of calpain and upregulation and translocation of AIF occurred. In both cell types, these processes were inhibited/reversed by 17beta-estradiol and Delta8,17beta-estradiol with the latter being more potent. CONCLUSION Depending upon the neuronal cell type, at least two mechanisms are involved in glutamate-induced apoptosis: a caspase-3-dependent pathway and a caspase-independent pathway involving calpain and AIF. Since HT22 cells lack caspase-3, glutamate-induced apoptosis is mediated via the caspase-independent pathway in this cell line. Kinetics of this apoptotic pathway further indicate that calpain rather than caspase-3, plays a critical role in the glutamate-induced apoptosis. Our studies further indicate that glutamate- induced changes of these proteins can be inhibited by estrogens, with Delta8,17beta-estradiol, a novel equine estrogen being more potent than 17beta-estradiol. To our knowledge, this is the first demonstration that glutamate-induced apoptosis involves regulation of multiple apoptotic effectors that can be inhibited by estrogens. Whether these observations can help in the development of novel therapeutic approaches for the prevention of neurodegenerative diseases with estrogens and calpain inhibitors remains to be investigated.
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Affiliation(s)
- YueMei Zhang
- Department of Obstetrics and Gynecology, University of Toronto, Institute of Medical Sciences, University of Toronto, Department of Obstetrics and Gynecology, St. Michael's Hospital, Toronto, Ontario, Canada
| | - Bhagu R Bhavnani
- Department of Obstetrics and Gynecology, University of Toronto, Institute of Medical Sciences, University of Toronto, Department of Obstetrics and Gynecology, St. Michael's Hospital, Toronto, Ontario, Canada
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Sakaue M, Okazaki M, Hara S. Very low levels of methylmercury induce cell death of cultured rat cerebellar neurons via calpain activation. Toxicology 2005; 213:97-106. [PMID: 15982794 DOI: 10.1016/j.tox.2005.05.013] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Revised: 05/18/2005] [Accepted: 05/19/2005] [Indexed: 10/25/2022]
Abstract
Methylmercury, an environmental neurotoxicant, induces the apoptotic death of cerebellar granule cells in vitro at a low concentration. To further understand the mechanism of cell death, we used a rat cerebellar granule cell culture system to investigate whether the calpain/cyclin-dependent kinase 5 (cdk5)/p35 cascade, an important cascade for neuronal apoptosis, is involved in the methylmercury-induced death. A noteworthy finding was that the cerebellar granular cell death was increased at a very low concentration of methylmercury, 30 nM, which is lower than that previously reported. The high sensitivity to methylmercury indicates that this culture system is useful for studying methylmercury toxicity at very low concentrations. Using this system, we here found that the methylmercury-induced death was inhibited by the calpain inhibitor II. Furthermore, it was shown that, in methylmercury-exposed cells, alpha-fodrin and tau, calpain substrates, were cleaved to the fragments that disappeared by treatment with the calpain inhibitor II. We next assayed and showed that the intracellular Ca(2+) concentration in cerebellar granule cells increased after methylmercury exposure in a time- and dose-dependent manner, significantly even at 30 nM. These results indicated that a very low concentration of methylmercury causes the intracellular Ca(2+) concentration to increase, activates calpain in the cells, and then induces cell death. We further found that the p35 protein was also processed to p25 that forms the cdk5-p25 complex, a hyperactive kinase for tau. However, an immunoblot using the anti-phosphorylated tau antibody showed that there was no increase of phosphorylated tau in methylmercury-exposed cells. These results suggested that methylmercury-induced cell death via calpain activation should not involve the stimulation of tau phosphorylation activity.
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Affiliation(s)
- Motoharu Sakaue
- Department of Public Health, School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
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Takamure M, Murata KY, Tamada Y, Azuma M, Ueno S. Calpain-dependent α-fodrin cleavage at the sarcolemma in muscle diseases. Muscle Nerve 2005; 32:303-9. [PMID: 15948206 DOI: 10.1002/mus.20362] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
To clarify the involvement of calpains in sarcolemmal remodeling, we examined the expression of calpains and their substrate, alpha-fodrin, in various disorders of muscle. Although immunohistological reactions for alpha-fodrin and calpains were weak in normal control muscles, intense immunoreactivity for alpha-fodrin at the sarcolemma and for calpains throughout the cytoplasm were detected in small muscle fibers from patients with inflammatory myositis (IM), rhabdomyolysis (Rhab), and Duchenne muscular dystrophy (DMD). Most of the calpain-alpha-fodrin double-positive muscle fibers in IM and Rhab also expressed the developmental form of myosin heavy chain. The sarcolemma of these small muscle fibers reacted with an antibody that specifically recognizes the 150-kDa fragments of alpha-fodrin (SBDP 150s) cleaved by calpain, but not caspase 3. Western blot analysis confirmed these results. These observations indicate that calpain is activated and reacts with alpha-fodrin as a substrate at the sarcolemma, and plays a key role in modulating sarcolemmal proteins to adapt to the specific conditions in each myopathy.
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Affiliation(s)
- Miwa Takamure
- Department of Neurology, Nara Medical University, Kashihara, Nara 634-8521, Japan
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