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Sini P, Galleri G, Ciampelli C, Galioto M, Padedda BM, Lugliè A, Iaccarino C, Crosio C. Evaluation of cyanotoxin L-BMAA effect on α-synuclein and TDP43 proteinopathy. Front Immunol 2024; 15:1360068. [PMID: 38596666 PMCID: PMC11002123 DOI: 10.3389/fimmu.2024.1360068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Accepted: 03/14/2024] [Indexed: 04/11/2024] Open
Abstract
The complex interplay between genetic and environmental factors is considered the cause of neurodegenerative diseases including Parkinson's disease (PD) and Amyotrophic Lateral Sclerosis (ALS). Among the environmental factors, toxins produced by cyanobacteria have received much attention due to the significant increase in cyanobacteria growth worldwide. In particular, L-BMAA toxin, produced by diverse taxa of cyanobacteria, dinoflagellates and diatoms, has been extensively correlated to neurodegeneration. The molecular mechanism of L-BMAA neurotoxicity is still cryptic and far from being understood. In this research article, we have investigated the molecular pathways altered by L-BMAA exposure in cell systems, highlighting a significant increase in specific stress pathways and an impairment in autophagic processes. Interestingly, these changes lead to the accumulation of both α-synuclein and TDP43, which are correlated with PD and ALS proteinopathy, respectively. Finally, we were able to demonstrate specific alterations of TDP43 WT or pathological mutants with respect to protein accumulation, aggregation and cytoplasmic translocation, some of the typical features of both sporadic and familial ALS.
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Affiliation(s)
- Paola Sini
- Laboratory of Molecular Biology, Department of Biomedical Sciences, University of Sassari, Sassari, Italy
| | - Grazia Galleri
- Laboratory of Molecular Biology, Department of Biomedical Sciences, University of Sassari, Sassari, Italy
| | - Cristina Ciampelli
- Laboratory of Molecular Biology, Department of Biomedical Sciences, University of Sassari, Sassari, Italy
| | - Manuela Galioto
- Laboratory of Molecular Biology, Department of Biomedical Sciences, University of Sassari, Sassari, Italy
| | - Bachisio Mario Padedda
- Laboratory of Ecology, Department of Architecture, Design and Urban Planning, University of Sassari, Sassari, Italy
| | - Antonella Lugliè
- Laboratory of Ecology, Department of Architecture, Design and Urban Planning, University of Sassari, Sassari, Italy
| | - Ciro Iaccarino
- Laboratory of Molecular Biology, Department of Biomedical Sciences, University of Sassari, Sassari, Italy
| | - Claudia Crosio
- Laboratory of Molecular Biology, Department of Biomedical Sciences, University of Sassari, Sassari, Italy
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2
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van Onselen R, Downing TG. Uptake of β-N-methylamino-L-alanine (BMAA) into glutamate-specific synaptic vesicles: Exploring the validity of the excitotoxicity mechanism of BMAA. Neurosci Lett 2024; 821:137593. [PMID: 38103629 DOI: 10.1016/j.neulet.2023.137593] [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: 09/28/2023] [Revised: 12/01/2023] [Accepted: 12/07/2023] [Indexed: 12/19/2023]
Abstract
The first mechanism of toxicity proposed for the cyanobacterial neurotoxin β-N-methylamino-L-alanine (BMAA) was excitotoxicity, and this was supported by numerous in vitro studies in which overactivation of both ionotropic and metabotropic glutamate receptors was reported. However, the excitotoxicity of BMAA is weak in comparison with other known excitotoxins and on par with that of glutamate, implying that to achieve sufficient synaptic concentrations of BMAA to cause classical in vivo excitotoxicity, BMAA must either accumulate in synapses to allow persistent glutamate receptor activation or it must be released in sufficiently high concentrations into synapses to cause the overexcitation. Since it has been shown that BMAA can be readily removed from synapses, release of high concentrations of BMAA into synapses must be shown to confirm its role as an excitotoxin in in vivo systems. This study therefore sought to evaluate the uptake of BMAA into synaptic vesicles and to determine if BMAA affects the uptake of glutamate into synaptic vesicles. There was no evidence to support uptake of BMAA into glutamate-specific synaptic vesicles but there was some indication that BMAA may affect the uptake of glutamate into synaptic vesicles. The uptake of BMAA into synaptic vesicles isolated from areas other than the cerebral cortex should be investigated before definite conclusions can be drawn about the role of BMAA as an excitotoxin.
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Affiliation(s)
- Rianita van Onselen
- Biomedical Research and Innovation Platform, South African Medical Research Council, Cape Town, South Africa; Department of Biochemistry and Microbiology, Nelson Mandela University, Gqeberha, South Africa
| | - Tim G Downing
- Department of Biochemistry and Microbiology, Nelson Mandela University, Gqeberha, South Africa.
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3
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Weeks RD, Banack SA, Howell S, Thunga P, Metcalf JS, Green AJ, Cox PA, Planchart A. The Effects of Long-term, Low-dose β-N-methylamino-L-alanine (BMAA) Exposures in Adult SOD G93R Transgenic Zebrafish. Neurotox Res 2023; 41:481-495. [PMID: 37552461 PMCID: PMC11216512 DOI: 10.1007/s12640-023-00658-z] [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: 09/22/2022] [Revised: 06/07/2023] [Accepted: 07/01/2023] [Indexed: 08/09/2023]
Abstract
β-N-Methylamino-L-alanine (BMAA) is a non-proteinogenic amino acid produced by cyanobacteria, which has been implicated in several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). It is postulated that chronic exposure to BMAA can lead to formation of protein aggregates, oxidative stress, and/or excitotoxicity, which are mechanisms involved in the etiology of ALS. While specific genetic mutations are identified in some instances of ALS, it is likely that a combination of genetic and environmental factors, such as exposure to the neurotoxin BMAA, contributes to disease. We used a transgenic zebrafish with an ALS-associated mutation, compared with wild-type fish to explore the potential neurotoxic effects of BMAA through chronic long-term exposures. While our results revealed low concentrations of BMAA in the brains of exposed fish, we found no evidence of decreased swim performance or behavioral differences that might be reflective of neurodegenerative disease. Further research is needed to determine if chronic BMAA exposure in adult zebrafish is a suitable model to study neurodegenerative disease initiation and/or progression.
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Affiliation(s)
- Ryan D. Weeks
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
- Program in Toxicology, North Carolina State University, Raleigh, NC 27695, USA
- Center for Human Health and the Environment, North Carolina State University, Raleigh, NC 27695, USA
| | - Sandra A. Banack
- Brain Chemistry Labs, Institute for Ethnomedicine, Box 3464, Jackson, WY 83001, USA
| | - Shaunacee Howell
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Preethi Thunga
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - James S. Metcalf
- Brain Chemistry Labs, Institute for Ethnomedicine, Box 3464, Jackson, WY 83001, USA
| | - Adrian J. Green
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
- Program in Toxicology, North Carolina State University, Raleigh, NC 27695, USA
- Center for Human Health and the Environment, North Carolina State University, Raleigh, NC 27695, USA
| | - Paul A. Cox
- Brain Chemistry Labs, Institute for Ethnomedicine, Box 3464, Jackson, WY 83001, USA
| | - Antonio Planchart
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
- Program in Toxicology, North Carolina State University, Raleigh, NC 27695, USA
- Center for Human Health and the Environment, North Carolina State University, Raleigh, NC 27695, USA
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4
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Courtier A, Potheret D, Giannoni P. Environmental bacteria as triggers to brain disease: Possible mechanisms of toxicity and associated human risk. Life Sci 2022; 304:120689. [DOI: 10.1016/j.lfs.2022.120689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 05/11/2022] [Accepted: 06/01/2022] [Indexed: 11/24/2022]
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5
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Cyanobacteria, Cyanotoxins, and Neurodegenerative Diseases: Dangerous Liaisons. Int J Mol Sci 2021; 22:ijms22168726. [PMID: 34445429 PMCID: PMC8395864 DOI: 10.3390/ijms22168726] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 08/03/2021] [Accepted: 08/05/2021] [Indexed: 02/06/2023] Open
Abstract
The prevalence of neurodegenerative disease (ND) is increasing, partly owing to extensions in lifespan, with a larger percentage of members living to an older age, but the ND aetiology and pathogenesis are not fully understood, and effective treatments are still lacking. Neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis are generally thought to progress as a consequence of genetic susceptibility and environmental influences. Up to now, several environmental triggers have been associated with NDs, and recent studies suggest that some cyanotoxins, produced by cyanobacteria and acting through a variety of molecular mechanisms, are highly neurotoxic, although their roles in neuropathy and particularly in NDs are still controversial. In this review, we summarize the most relevant and recent evidence that points at cyanotoxins as environmental triggers in NDs development.
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6
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Wang C, Yan C, Qiu J, Liu C, Yan Y, Ji Y, Wang G, Chen H, Li Y, Li A. Food web biomagnification of the neurotoxin β-N-methylamino-L-alanine in a diatom-dominated marine ecosystem in China. JOURNAL OF HAZARDOUS MATERIALS 2021; 404:124217. [PMID: 33129020 DOI: 10.1016/j.jhazmat.2020.124217] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Revised: 09/25/2020] [Accepted: 10/05/2020] [Indexed: 06/11/2023]
Abstract
The neurotoxin β-N-methylamino-L-alanine (BMAA) reported in some cyanobacteria and eukaryote microalgae is a cause of concern due to its potential risk of human neurodegenerative diseases. Here, BMAA distribution in phytoplankton, zooplankton, and other marine organisms was investigated in Jiaozhou Bay, China, a diatom-dominated marine ecosystem, during four seasons in 2019. Results showed that BMAA was biomagnified in the food web from phytoplankton to higher trophic levels. Trophic magnification factors (TMFs) for zooplankton, bivalve mollusks, carnivorous crustaceans and carnivorous gastropod mollusks were ca. 4.58, 30.1, 42.5, and 74.4, respectively. Putative identification of β-amino-N-methylalanine (BAMA), an isomer of BMAA, was frequently detected in phytoplankton samples. A total of 56 diatom strains of the genera Pseudo-nitzschia, Thalassiosira, Chaetoceros, Planktoniella, and Minidiscus isolated from the Chinese coast were cultured in the laboratory, among which 21 strains contained BMAA mainly in precipitated bound form at toxin concentrations ranging from 0.11 to 3.95 µg/g dry weight. Only 2,4-diaminobutyric acid (DAB) but not BMAA or BAMA was detected in seven species of bacteria isolated from the gut of gastropod Neverita didyma, suggesting that this benthic vector of BMAA may have accumulated this compound via trophic transfer.
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Affiliation(s)
- Chao Wang
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Chen Yan
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Jiangbing Qiu
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Chao Liu
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Yeju Yan
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Ying Ji
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Guixiang Wang
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Hongju Chen
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Yang Li
- Guangdong Provincial Key Laboratory of Healthy and Safe Aquaculture, College of Life Science, South China Normal University, Guangzhou 510631, China
| | - Aifeng Li
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China.
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7
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Ra D, Sa B, Sl B, Js M, Sj M, DA D, Ew S, O K, Eb B, Ad C, Vx T, Gg G, Pa C, Dc M, Wg B. Is Exposure to BMAA a Risk Factor for Neurodegenerative Diseases? A Response to a Critical Review of the BMAA Hypothesis. Neurotox Res 2021; 39:81-106. [PMID: 33547590 PMCID: PMC7904546 DOI: 10.1007/s12640-020-00302-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 10/19/2020] [Accepted: 10/20/2020] [Indexed: 12/15/2022]
Abstract
In a literature survey, Chernoff et al. (2017) dismissed the hypothesis that chronic exposure to β-N-methylamino-L-alanine (BMAA) may be a risk factor for progressive neurodegenerative disease. They question the growing scientific literature that suggests the following: (1) BMAA exposure causes ALS/PDC among the indigenous Chamorro people of Guam; (2) Guamanian ALS/PDC shares clinical and neuropathological features with Alzheimer's disease, Parkinson's disease, and ALS; (3) one possible mechanism for protein misfolds is misincorporation of BMAA into proteins as a substitute for L-serine; and (4) chronic exposure to BMAA through diet or environmental exposures to cyanobacterial blooms can cause neurodegenerative disease. We here identify multiple errors in their critique including the following: (1) their review selectively cites the published literature; (2) the authors reported favorably on HILIC methods of BMAA detection while the literature shows significant matrix effects and peak coelution in HILIC that may prevent detection and quantification of BMAA in cyanobacteria; (3) the authors build alternative arguments to the BMAA hypothesis, rather than explain the published literature which, to date, has been unable to refute the BMAA hypothesis; and (4) the authors erroneously attribute methods to incorrect studies, indicative of a failure to carefully consider all relevant publications. The lack of attention to BMAA research begins with the review's title which incorrectly refers to BMAA as a "non-essential" amino acid. Research regarding chronic exposure to BMAA as a cause of human neurodegenerative diseases is emerging and requires additional resources, validation, and research. Here, we propose strategies for improvement in the execution and reporting of analytical methods and the need for additional and well-executed inter-lab comparisons for BMAA quantitation. We emphasize the need for optimization and validation of analytical methods to ensure that they are fit-for-purpose. Although there remain gaps in the literature, an increasingly large body of data from multiple independent labs using orthogonal methods provides increasing evidence that chronic exposure to BMAA may be a risk factor for neurological illness.
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Affiliation(s)
- Dunlop Ra
- Brain Chemistry Labs, Institute for Ethnomedicine, Jackson, WY, USA.
| | - Banack Sa
- Brain Chemistry Labs, Institute for Ethnomedicine, Jackson, WY, USA
| | - Bishop Sl
- Lewis Research Group, Faculty of Science, University of Calgary, Alberta, Canada
| | - Metcalf Js
- Brain Chemistry Labs, Institute for Ethnomedicine, Jackson, WY, USA
| | - Murch Sj
- Department of Chemistry, University of British Columbia, Kelowna, BC, Canada
| | - Davis DA
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Stommel Ew
- Department of Neurology, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA
| | - Karlsson O
- Department of Environmental Science, Stockholm University, Stockholm, Sweden
| | - Brittebo Eb
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | | | - Tan Vx
- Department of Biological Sciences, Macquarie University Centre for Motor Neuron Disease Research, Macquarie University, Ryde, Australia
| | - Guillemin Gg
- Department of Biological Sciences, Macquarie University Centre for Motor Neuron Disease Research, Macquarie University, Ryde, Australia
| | - Cox Pa
- Brain Chemistry Labs, Institute for Ethnomedicine, Jackson, WY, USA
| | - Mash Dc
- Nova Southeastern University, Fort Lauderdale, FL, USA
| | - Bradley Wg
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, FL, USA
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8
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Silva DF, Candeias E, Esteves AR, Magalhães JD, Ferreira IL, Nunes-Costa D, Rego AC, Empadinhas N, Cardoso SM. Microbial BMAA elicits mitochondrial dysfunction, innate immunity activation, and Alzheimer's disease features in cortical neurons. J Neuroinflammation 2020; 17:332. [PMID: 33153477 PMCID: PMC7643281 DOI: 10.1186/s12974-020-02004-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 10/20/2020] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND After decades of research recognizing it as a complex multifactorial disorder, sporadic Alzheimer's disease (sAD) still has no known etiology. Adding to the myriad of different pathways involved, bacterial neurotoxins are assuming greater importance in the etiology and/or progression of sAD. β-N-Methylamino-L-alanine (BMAA), a neurotoxin produced by some microorganisms namely cyanobacteria, was previously detected in the brains of AD patients. Indeed, the consumption of BMAA-enriched foods has been proposed to induce amyotrophic lateral sclerosis-parkinsonism-dementia complex (ALS-PDC), which implicated this microbial metabolite in neurodegeneration mechanisms. METHODS Freshly isolated mitochondria from C57BL/6 mice were treated with BMAA and O2 consumption rates were determined. O2 consumption and glycolysis rates were also measured in mouse primary cortical neuronal cultures. Further, mitochondrial membrane potential and ROS production were evaluated by fluorimetry and the integrity of mitochondrial network was examined by immunofluorescence. Finally, the ability of BMAA to activate neuronal innate immunity was quantified by addressing TLRs (Toll-like receptors) expression, p65 NF-κB translocation into the nucleus, increased expression of NLRP3 (Nod-like receptor 3), and pro-IL-1β. Caspase-1 activity was evaluated using a colorimetric substrate and mature IL-1β levels were also determined by ELISA. RESULTS Treatment with BMAA reduced O2 consumption rates in both isolated mitochondria and in primary cortical cultures, with additional reduced glycolytic rates, decrease mitochondrial potential and increased ROS production. The mitochondrial network was found to be fragmented, which resulted in cardiolipin exposure that stimulated inflammasome NLRP3, reinforced by decreased mitochondrial turnover, as indicated by increased p62 levels. BMAA treatment also activated neuronal extracellular TLR4 and intracellular TLR3, inducing p65 NF-κB translocation into the nucleus and activating the transcription of NLRP3 and pro-IL-1β. Increased caspase-1 activity resulted in elevated levels of mature IL-1β. These alterations in mitochondrial metabolism and inflammation increased Tau phosphorylation and Aβ peptides production, two hallmarks of AD. CONCLUSIONS Here we propose a unifying mechanism for AD neurodegeneration in which a microbial toxin can induce mitochondrial dysfunction and activate neuronal innate immunity, which ultimately results in Tau and Aβ pathology. Our data show that neurons, alone, can mount inflammatory responses, a role previously attributed exclusively to glial cells.
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Affiliation(s)
- Diana F Silva
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517, Coimbra, Portugal.,IIIUC-Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Emanuel Candeias
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517, Coimbra, Portugal.,Ph.D. Programme in Biomedicine and Experimental Biology (PDBEB), Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - A Raquel Esteves
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517, Coimbra, Portugal.,IIIUC-Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - João D Magalhães
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517, Coimbra, Portugal.,Ph.D. Programme in Biomedicine and Experimental Biology (PDBEB), Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - I Luísa Ferreira
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517, Coimbra, Portugal.,IIIUC-Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Daniela Nunes-Costa
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517, Coimbra, Portugal.,Ph.D. Programme in Biomedicine and Experimental Biology (PDBEB), Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - A Cristina Rego
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517, Coimbra, Portugal.,Institute of Biochemistry, Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Nuno Empadinhas
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517, Coimbra, Portugal.,IIIUC-Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Sandra M Cardoso
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517, Coimbra, Portugal. .,Institute of Cellular and Molecular Biology, Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
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9
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Soto T, Buzzi ED, Rotstein NP, German OL, Politi LE. Damaging effects of BMAA on retina neurons and Müller glial cells. Exp Eye Res 2020; 202:108342. [PMID: 33144094 DOI: 10.1016/j.exer.2020.108342] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 10/23/2020] [Accepted: 10/27/2020] [Indexed: 10/23/2022]
Abstract
B-N-methylamino-L-alanine (BMAA), a cyanotoxin produced by most cyanobacteria, has been proposed to cause long term damages leading to neurodegenerative diseases, including Amyotrophic Lateral Sclerosis/Parkinsonism Dementia complex (ALS/PDC) and retinal pathologies. Previous work has shown diverse mechanisms leading to BMAA-induced degeneration; however, the underlying mechanisms of toxicity affecting retina cells are not fully elucidated. We here show that BMAA treatment of rat retina neurons in vitro induced nuclear fragmentation and cell death in both photoreceptors (PHRs) and amacrine neurons, provoking mitochondrial membrane depolarization. Pretreatment with the N-Methyl-D-aspartate (NMDA) receptor antagonist MK-801 prevented BMAA-induced death of amacrine neurons, but not that of PHRs, implying activation of NMDA receptors participated only in amacrine cell death. Noteworthy, BMAA stimulated a selective axonal outgrowth in amacrine neurons, simultaneously promoting growth cone destabilization. BMAA partially decreased the viability of Müller glial cells (MGC), the main glial cell type in the retina, induced marked alterations in their actin cytoskeleton and impaired their capacity to protect retinal neurons. BMAA also induced cell death and promoted axonal outgrowth in differentiated rat pheochromocytoma (PC12) cells, implying these effects were not limited to amacrine neurons. These results suggest that BMAA is toxic for retina neurons and MGC and point to the involvement of NMDA receptors in amacrine cell death, providing new insight into the mechanisms involved in BMAA neurotoxic effects in the retina.
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Affiliation(s)
- Tamara Soto
- Instituto de Investigaciones Bioquímicas, Depto. de Biología, Bioquímica y Farmacia, Universidad Nacional Del Sur (UNS)-CONICET, 8000, Bahía Blanca, Buenos Aires, Argentina
| | - Edgardo D Buzzi
- Instituto de Investigaciones Bioquímicas, Depto. de Biología, Bioquímica y Farmacia, Universidad Nacional Del Sur (UNS)-CONICET, 8000, Bahía Blanca, Buenos Aires, Argentina; Department of Biology, Biochemistry and Pharmacy, Universidad Nacional Del Sur (UNS)-CONICET, Argentina
| | - Nora P Rotstein
- Instituto de Investigaciones Bioquímicas, Depto. de Biología, Bioquímica y Farmacia, Universidad Nacional Del Sur (UNS)-CONICET, 8000, Bahía Blanca, Buenos Aires, Argentina; Department of Biology, Biochemistry and Pharmacy, Universidad Nacional Del Sur (UNS)-CONICET, Argentina
| | - O Lorena German
- Instituto de Investigaciones Bioquímicas, Depto. de Biología, Bioquímica y Farmacia, Universidad Nacional Del Sur (UNS)-CONICET, 8000, Bahía Blanca, Buenos Aires, Argentina; Department of Biology, Biochemistry and Pharmacy, Universidad Nacional Del Sur (UNS)-CONICET, Argentina
| | - Luis E Politi
- Instituto de Investigaciones Bioquímicas, Depto. de Biología, Bioquímica y Farmacia, Universidad Nacional Del Sur (UNS)-CONICET, 8000, Bahía Blanca, Buenos Aires, Argentina.
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10
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van Onselen R, Scott LL, Downing TG. Evaluating amino acids as protectants against β-N-methylamino-l-alanine-induced developmental neurotoxicity in a rat model. Toxicol Appl Pharmacol 2020; 403:115140. [PMID: 32682829 DOI: 10.1016/j.taap.2020.115140] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 06/15/2020] [Accepted: 07/13/2020] [Indexed: 12/28/2022]
Abstract
With accumulating evidence that supports the role of β-N-methylamino-l-alanine (BMAA) in neurodegeneration, it is necessary to elucidate the mechanisms and modes of BMAA toxicity so as to facilitate the search for potential preventative/therapeutic strategies. Daily supplementation with l-serine was suggested as a possible therapy to treat BMAA-induced neurotoxicity, based on the hypothesized mechanism of BMAA misincorporation into proteins for l-serine. As an alternative to misincorporation, it was hypothesized that BMAA toxicity may, in part, be due to its high affinity for associating with hydroxyl group-containing amino acids, and that a dietary excess of the hydroxyl-containing l-serine might offer protection by binding to BMAA and reducing its toxicity. Additionally, l-serine can also reduce the uptake of BMAA into human cells by competitive uptake at ASCT2, and l-phenylalanine, by competitive uptake at LAT1, and l-alanine, by competitive uptake at SNAT2, can also reduce BMAA uptake into human cells. The aim of this study was therefore to determine the protective value of l-serine, l-phenylalanine and l-alanine in reducing the effects of neonatal exposure to BMAA in a Sprague Dawley rat model. Pre-treatment with l-phenylalanine reduced the observed behavioral abnormalities and neuropathologies by 60-70% in most cases. l-serine was also effective in reducing some of the behavioral abnormalities and neuropathologies, most markedly spinal cord neuronal loss. However, the protective effect of l-serine was obfuscated by neuropathies that were observed in l-serine-treated control male rats. l-alanine had no effect in protecting against BMAA-induced neurotoxicity, suggesting that competitive amino acid uptake plays a minor role in protecting against BMAA-induced neurotoxicity.
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Affiliation(s)
- Rianita van Onselen
- Department of Biochemistry and Microbiology, Nelson Mandela University, P.O. Box 77000, Port Elizabeth, 6031, South Africa
| | - Laura Louise Scott
- Department of Biochemistry and Microbiology, Nelson Mandela University, P.O. Box 77000, Port Elizabeth, 6031, South Africa
| | - Tim G Downing
- Department of Biochemistry and Microbiology, Nelson Mandela University, P.O. Box 77000, Port Elizabeth, 6031, South Africa..
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11
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Behavior and gene expression in the brain of adult self-fertilizing mangrove rivulus fish (Kryptolebias marmoratus) after early life exposure to the neurotoxin β-N-methylamino-l-alanine (BMAA). Neurotoxicology 2020; 79:110-121. [DOI: 10.1016/j.neuro.2020.04.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 04/16/2020] [Accepted: 04/21/2020] [Indexed: 12/11/2022]
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How the Neurotoxin β- N-Methylamino-l-Alanine Accumulates in Bivalves: Distribution of the Different Accumulation Fractions among Organs. Toxins (Basel) 2020; 12:toxins12020061. [PMID: 31972955 PMCID: PMC7076761 DOI: 10.3390/toxins12020061] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 12/30/2019] [Accepted: 01/14/2020] [Indexed: 01/07/2023] Open
Abstract
The environmental neurotoxin β-methylamino-l-alanine (BMAA) may represent a risk for human health. BMAA accumulates in freshwater and marine organisms consumed by humans. However, few data are available about the kinetics of BMAA accumulation and detoxification in exposed organisms, as well as the organ distribution and the fractions in which BMAA is present in tissues (free, soluble bound or precipitated bound cellular fractions). Here, we exposed the bivalve mussel Dreissena polymorpha to 7.5 µg of dissolved BMAA/mussel/3 days for 21 days, followed by 21 days of depuration in clear water. At 1, 3, 8, 14 and 21 days of exposure and depuration, the hemolymph and organs (digestive gland, the gills, the mantle, the gonad and muscles/foot) were sampled. Total BMAA as well as free BMAA, soluble bound and precipitated bound BMAA were quantified by tandem mass spectrometry. Free and soluble bound BMAA spread throughout all tissues from the first day of exposure to the last day of depuration, without a specific target organ. However, precipitated bound BMAA was detected only in muscles and foot from the last day of exposure to day 8 of depuration, at a lower concentration compared to free and soluble bound BMAA. In soft tissues (digestive gland, gonad, gills, mantle and muscles/foot), BMAA mostly accumulated as a free molecule and in the soluble bound fraction, with variations occurring between the two fractions among tissues and over time. The results suggest that the assessment of bivalve contamination by BMAA may require the quantification of total BMAA in whole individuals when possible.
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Iron and other metals in the pathogenesis of Parkinson's disease: Toxic effects and possible detoxification. J Inorg Biochem 2019; 199:110717. [DOI: 10.1016/j.jinorgbio.2019.110717] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 05/08/2019] [Accepted: 05/13/2019] [Indexed: 12/24/2022]
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Metabolism of the neurotoxic amino acid β-N-methylamino-L-alanine in human cell culture models. Toxicon 2019; 168:131-139. [PMID: 31330193 DOI: 10.1016/j.toxicon.2019.07.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 07/12/2019] [Accepted: 07/16/2019] [Indexed: 12/12/2022]
Abstract
Human dietary exposure to the environmental neurotoxin β-N-methylamino-L-alanine (BMAA) has been implicated in an increased risk of developing sporadic neurodegenerative diseases like Alzheimer's and amyotrophic lateral sclerosis. Evidence suggests that humans are exposed to BMAA globally, but very little is known about BMAA metabolism in mammalian systems, let alone in humans. The most plausible, evidence-based mechanisms of BMAA toxicity rely on the metabolic stability of the amino acid and that, following ingestion, it enters the circulatory system unmodified. BMAA crosses from the intestinal lumen into the circulatory system, and the small intestine and liver are the first sites for dietary amino acid metabolism. Both tissues have substantial amino acid metabolic needs, which are largely fulfilled by dietary amino acids. Metabolism of BMAA in these tissues has been largely overlooked, yet is important in gauging the true human exposure risk. Here we investigate the potential for BMAA metabolism by the human liver and small intestine, using in vitro cell systems. Data show that BMAA metabolism via common proteinogenic amino acid metabolic pathways is negligible, and that in the presence of other amino acids cellular uptake of BMAA is substantially reduced. These data suggest that the majority of ingested BMAA remains unmodified following passage through the small intestine and liver. This not only supports oral BMAA exposure as a plausible exposure route to toxic doses of BMAA, but also supports previous notions that protein deficient diets or malnutrition may increase an individual's susceptibility to BMAA absorption and subsequent toxicity.
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Insufficient evidence for BMAA transfer in the pelagic and benthic food webs in the Baltic Sea. Sci Rep 2019; 9:10406. [PMID: 31320701 PMCID: PMC6639344 DOI: 10.1038/s41598-019-46815-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2018] [Accepted: 07/01/2019] [Indexed: 02/06/2023] Open
Abstract
The evidence regarding BMAA occurrence in the Baltic Sea is contradictory, with benthic sources appearing to be more important than pelagic ones. The latter is counterintuitive considering that the identified sources of this compound in the food webs are pelagic primary producers, such as diatoms, dinoflagellates, and cyanobacteria. To elucidate BMAA distribution, we analyzed BMAA in the pelagic and benthic food webs in the Northern Baltic Proper. As potential sources, phytoplankton communities were used. Pelagic food chain was represented by zooplankton, mysids and zooplanktivorous fish, whereas benthic invertebrates and benthivorous fish comprised the benthic chain. The trophic structure of the system was confirmed by stable isotope analysis. Contrary to the reported ubiquitous occurrence of BMAA in the Baltic food webs, only phytoplankton, zooplankton and mysids tested positive, whereas no measurable levels of this compound occurred in the benthic invertebrates and any of the tested fish species. These findings do not support the widely assumed occurrence and transfer of BMAA to the top consumers in the Baltic food webs. More controlled experiments and field observations are needed to understand the transfer and possible transformation of BMAA in the food web under various environmental settings.
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Manolidi K, Triantis TM, Kaloudis T, Hiskia A. Neurotoxin BMAA and its isomeric amino acids in cyanobacteria and cyanobacteria-based food supplements. JOURNAL OF HAZARDOUS MATERIALS 2019; 365:346-365. [PMID: 30448548 DOI: 10.1016/j.jhazmat.2018.10.084] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 10/26/2018] [Accepted: 10/27/2018] [Indexed: 06/09/2023]
Abstract
Cyanobacteria are photosynthetic microorganisms distributed globally in aquatic and terrestrial environments. They are also industrially cultivated to be used as dietary supplements, as they have a high nutritional value; however, they are also known to produce a wide range of toxic secondary metabolites, called cyanotoxins. BMAA (β-methylamino-l-alanine) and its most common structural isomers, DAB (2,4-diaminobutyric acid) and AEG (N-2-aminoethylglycine) produced by cyanobacteria, are non-proteinogenic amino acids that have been associated with neurodegenerative diseases. A possible route of exposure to those amino acids is through consumption of food supplements based on cyanobacteria. The review critically discusses existing reports regarding the occurrence of BMAA, DAB and AEG in cyanobacteria and cyanobacteria-based food supplements. It is shown that inconsistencies in reported results could be attributed to performance of different methods of extraction and analysis applied and in ambiguities regarding determination of soluble and bound fractions of the compounds. The critical aspect of this review aims to grow awareness of human intake of neurotoxic amino acids, while results presented in literature concerning dietary supplements aim to promote further research, quality control as well as development of guidelines for cyanotoxins in food products.
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Affiliation(s)
- Korina Manolidi
- Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "DEMOKRITOS", Patriarchou Grigoriou E' & Neapoleos 27, 15341, Athens, Greece; National and Kapodistrian University of Athens, Faculty of Chemistry, 15784, Panepistimiopolis, Athens, Greece.
| | - Theodoros M Triantis
- Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "DEMOKRITOS", Patriarchou Grigoriou E' & Neapoleos 27, 15341, Athens, Greece.
| | - Triantafyllos Kaloudis
- Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "DEMOKRITOS", Patriarchou Grigoriou E' & Neapoleos 27, 15341, Athens, Greece; Water Quality Control Department, Athens Water Supply and Sewerage Company - EYDAP SA, Athens, Greece.
| | - Anastasia Hiskia
- Institute of Nanoscience and Nanotechnology, National Center for Scientific Research "DEMOKRITOS", Patriarchou Grigoriou E' & Neapoleos 27, 15341, Athens, Greece.
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van Onselen R, Downing TG. β- N-methylamino-L-alanine Inhibits Human Catalase Activity: Possible Implications for Neurodegenerative Disease Development. Int J Toxicol 2019; 38:129-134. [PMID: 30663459 DOI: 10.1177/1091581818821921] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The naturally produced, nonprotein amino acid β- N-methylamino-l-alanine (BMAA) has been proposed as a significant contributor to sporadic neurodegenerative disease development worldwide. However, the existing hypothesized mechanisms of toxicity do not adequately explain the role of BMAA in neurodegenerative disease development. There is evidence for BMAA-induced enzyme inhibition, but the effect of BMAA on human stress response enzymes has received little attention, despite the well-described role of oxidative stress in neurodegenerative disease development. The aim of this study was therefore to investigate the effect of BMAA on human catalase activity and compare it to the known inhibitor 3-amino-1,2,4-triazole. BMAA inhibited human erythrocyte catalase in a cell-free exposure to the same extent as the known inhibitor. Based on enzyme kinetics, the inhibition appears to be noncompetitive, possibly as a result of BMAA binding in the nicotinamide adenine dinucleotide phosphate (NADPH) binding site. BMAA-induced catalase inhibition was also observed in a human cell line culture. We therefore propose that BMAA-induced enzyme inhibition, specifically catalase inhibition, is a mechanism of toxicity that may contribute to the neurotoxicity of BMAA, further supporting the role of BMAA in neurodegenerative disease development.
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Affiliation(s)
- Rianita van Onselen
- 1 Department of Biochemistry and Microbiology, Nelson Mandela University, Port Elizabeth, South Africa
| | - Tim G Downing
- 1 Department of Biochemistry and Microbiology, Nelson Mandela University, Port Elizabeth, South Africa
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Ubiquity of the neurotoxin β-N-methylamino-L-alanine and its isomers confirmed by two different mass spectrometric methods in diverse marine mollusks. Toxicon 2018; 151:129-136. [DOI: 10.1016/j.toxicon.2018.07.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 05/24/2018] [Accepted: 07/05/2018] [Indexed: 12/11/2022]
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Cellular and Molecular Aspects of the β-N-Methylamino-l-alanine (BMAA) Mode of Action within the Neurodegenerative Pathway: Facts and Controversy. Toxins (Basel) 2017; 10:toxins10010006. [PMID: 29271898 PMCID: PMC5793093 DOI: 10.3390/toxins10010006] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 12/19/2017] [Accepted: 12/20/2017] [Indexed: 12/12/2022] Open
Abstract
The implication of the cyanotoxin β-N-methylamino-l-alanine (BMAA) in long-lasting neurodegenerative disorders is still a matter of controversy. It has been alleged that chronic ingestion of BMAA through the food chain could be a causative agent of amyotrophic lateral sclerosis (ALS) and several related pathologies including Parkinson syndrome. Both in vitro and in vivo studies of the BMAA mode of action have focused on different molecular targets, demonstrating its toxicity to neuronal cells, especially motoneurons, and linking it to human neurodegenerative diseases. Historically, the hypothesis of BMAA-induced excitotoxicity following the stimulation of glutamate receptors has been established. However, in this paradigm, most studies have shown acute, rather than chronic effects of BMAA. More recently, the interaction of this toxin with neuromelanin, a pigment present in the nervous system, has opened a new research perspective. The issues raised by this toxin are related to its kinetics of action, and its possible incorporation into cellular proteins. It appears that BMAA neurotoxic activity involves different targets through several mechanisms known to favour the development of neurodegenerative processes.
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Investigating β-N-Methylamino-l-alanine Misincorporation in Human Cell Cultures: A Comparative Study with Known Amino Acid Analogues. Toxins (Basel) 2017; 9:toxins9120400. [PMID: 29240689 PMCID: PMC5744120 DOI: 10.3390/toxins9120400] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 12/12/2017] [Accepted: 12/13/2017] [Indexed: 11/16/2022] Open
Abstract
Misincorporation of β-N-methylamino-l-alanine (BMAA) into proteins has been proposed to be a mechanism of toxicity to explain the role of BMAA in neurodegenerative disease development. However, studies have shown that all detectable BMAA can be removed from proteins by SDS-PAGE purification and that the toxicity of l-canavanine cannot be reproduced in prokaryotes or in a rat pheochromocytoma cell line, strongly indicating that the misincorporation hypothesis of BMAA should be re-investigated. The aim of this study was therefore to determine if BMAA misincorporates into proteins in cells of human origin with subsequent misincorporation-type toxicity. Almost complete loss of viability in response to exposure to l-4-fluorophenylalanine and l-m-tyrosine was observed in all of the cell lines, corresponding to a concentration-dependent increase of the analogues in protein extracts from exposed cells. In contrast, BMAA exposure resulted in slight toxicity in one of the cell lines but the observed toxicity was not the result of misincorporation of BMAA into proteins, as no BMAA was detected in any of the SDS-PAGE purified protein extracts that were obtained from the cells following BMAA exposure. The results show that BMAA is not misincorporated into human proteins and that misincorporation is not a valid mechanism of toxicity.
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