1
|
Italiano CJ, Pu L, Violi JP, Duggin IG, Rodgers KJ. Cysteine biosynthesis contributes to β-methylamino-l-alanine tolerance in Escherichia coli. Res Microbiol 2021; 172:103852. [PMID: 34246779 DOI: 10.1016/j.resmic.2021.103852] [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: 03/14/2021] [Revised: 06/26/2021] [Accepted: 06/29/2021] [Indexed: 11/25/2022]
Abstract
In contrast to mammalian cells, bacteria such as Escherichia coli have been shown to display tolerance towards the neurotoxin β-methylamino-l-alanine (BMAA) suggesting that these prokaryotes possess a way to metabolise BMAA or its products, resulting in their export, degradation, or detoxification. Single gene deletion mutants of E. coli K-12 with inactivated amino acid biosynthesis pathways were treated with 500 μg/ml BMAA and the resulting growth was monitored. Wild type E. coli and most of the gene deletion mutants displayed unaltered growth in the presence of BMAA over 12 h. Conversely, deletion of genes in the cysteine biosynthesis pathway, cysE, cysK or cysM resulted in a BMAA dose-dependent growth delay in minimal medium. Through further studies of the ΔcysE strain, we observed increased susceptibility to oxidative stress from H2O2 in minimal medium, and disruptions in glutathione levels and oxidation state. The cysteine biosynthesis pathway is therefore linked to the tolerance of BMAA and oxidative stress in E. coli, which potentially represents a mechanism of BMAA detoxification.
Collapse
Affiliation(s)
- Carly J Italiano
- School of Life Sciences, University of Technology Sydney, Ultimo, NSW 2007, Australia.
| | - Lisa Pu
- School of Life Sciences, University of Technology Sydney, Ultimo, NSW 2007, Australia.
| | - Jake P Violi
- School of Life Sciences, University of Technology Sydney, Ultimo, NSW 2007, Australia.
| | - Iain G Duggin
- The iThree Institute, University of Technology Sydney, Ultimo, NSW 2007, Australia.
| | - Kenneth J Rodgers
- School of Life Sciences, University of Technology Sydney, Ultimo, NSW 2007, Australia.
| |
Collapse
|
2
|
Quinn AW, Phillips CR, Violi JP, Steele JR, Johnson MS, Westerhausen MT, Rodgers KJ. β-Methylamino-L-alanine-induced protein aggregation in vitro and protection by L-serine. Amino Acids 2021; 53:1351-1359. [PMID: 34283312 DOI: 10.1007/s00726-021-03049-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Accepted: 07/12/2021] [Indexed: 10/20/2022]
Abstract
The cyanobacterial non-protein amino acid α-amino-β-methylaminopropionic acid, more commonly known as BMAA, was first discovered in the seeds of the ancient gymnosperm Cycad circinalis (now Cycas micronesica Hill). BMAA was linked to the high incidence of neurological disorders on the island of Guam first reported in the 1950s. BMAA still attracts interest as a possible causative factor in amyotrophic lateral sclerosis (ALS) following the identification of ALS disease clusters associated with living in proximity to lakes with regular cyanobacterial blooms. Since its discovery, BMAA toxicity has been the subject of many in vivo and in vitro studies. A number of mechanisms of toxicity have been proposed including an agonist effect at glutamate receptors, competition with cysteine for transport system xc_ and other mechanisms capable of generating cellular oxidative stress. In addition, a wide range of studies have reported effects related to disturbances in proteostasis including endoplasmic reticulum stress and activation of the unfolded protein response. In the present studies we examine the effects of BMAA on the ubiquitin-proteasome system (UPS) and on chaperone-mediated autophagy (CMA) by measuring levels of ubiquitinated proteins and lamp2a protein levels in a differentiated neuronal cell line exposed to BMAA. The BMAA induced increases in oxidised proteins and the increase in CMA activity reported could be prevented by co-administration of L-serine but not by the two antioxidants examined. These data provide further evidence of a protective role for L-serine against the deleterious effects of BMAA.
Collapse
Affiliation(s)
- Adam W Quinn
- Neurotoxin Research Group, School of Life Sciences, University of Technology Syd, ney, Faculty of Science, Building 4, Level 7, room 329. Thomas Street, Sydney, NSW, 2007, Australia
| | - Connor R Phillips
- Neurotoxin Research Group, School of Life Sciences, University of Technology Syd, ney, Faculty of Science, Building 4, Level 7, room 329. Thomas Street, Sydney, NSW, 2007, Australia
| | - Jake P Violi
- Neurotoxin Research Group, School of Life Sciences, University of Technology Syd, ney, Faculty of Science, Building 4, Level 7, room 329. Thomas Street, Sydney, NSW, 2007, Australia
| | - Joel R Steele
- Neurotoxin Research Group, School of Life Sciences, University of Technology Syd, ney, Faculty of Science, Building 4, Level 7, room 329. Thomas Street, Sydney, NSW, 2007, Australia
| | - Michael S Johnson
- Neurotoxin Research Group, School of Life Sciences, University of Technology Syd, ney, Faculty of Science, Building 4, Level 7, room 329. Thomas Street, Sydney, NSW, 2007, Australia
| | - Mika T Westerhausen
- Neurotoxin Research Group, School of Life Sciences, University of Technology Syd, ney, Faculty of Science, Building 4, Level 7, room 329. Thomas Street, Sydney, NSW, 2007, Australia
| | - Kenneth J Rodgers
- Neurotoxin Research Group, School of Life Sciences, University of Technology Syd, ney, Faculty of Science, Building 4, Level 7, room 329. Thomas Street, Sydney, NSW, 2007, Australia.
| |
Collapse
|
3
|
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.
Collapse
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..
| |
Collapse
|
4
|
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.
Collapse
|
5
|
Production of β-methylamino-L-alanine (BMAA) and Its Isomers by Freshwater Diatoms. Toxins (Basel) 2019; 11:toxins11090512. [PMID: 31480725 PMCID: PMC6784237 DOI: 10.3390/toxins11090512] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 08/23/2019] [Accepted: 08/29/2019] [Indexed: 12/14/2022] Open
Abstract
β-methylamino-L-alanine (BMAA) is a non-protein amino acid that has been implicated as a risk factor for motor neurone disease (MND). BMAA is produced by a wide range of cyanobacteria globally and by a small number of marine diatoms. BMAA is commonly found with two of its constitutional isomers: 2,4-diaminobutyric acid (2,4-DAB), and N-(2-aminoethyl)glycine (AEG). The isomer 2,4-DAB, like BMAA, has neurotoxic properties. While many studies have shown BMAA production by cyanobacteria, few studies have looked at other algal groups. Several studies have shown BMAA production by marine diatoms; however, there are no studies examining freshwater diatoms. This study aimed to determine if some freshwater diatoms produced BMAA, and which diatom taxa are capable of BMAA, 2,4-DAB and AEG production. Five axenic diatom cultures were established from river and lake sites across eastern Australia. Cultures were harvested during the stationary growth phase and intracellular amino acids were extracted. Using liquid chromatography triple quadrupole mass spectrometry (LC-MS/MS), diatom extracts were analysed for the presence of both free and protein-associated BMAA, 2,4-DAB and AEG. Of the five diatom cultures analysed, four were found to have detectable BMAA and AEG, while 2,4-DAB was found in all cultures. These results show that BMAA production by diatoms is not confined to marine genera and that the prevalence of these non-protein amino acids in Australian freshwater environments cannot be solely attributed to cyanobacteria.
Collapse
|
6
|
Cell death and mitochondrial dysfunction induced by the dietary non-proteinogenic amino acid L-azetidine-2-carboxylic acid (Aze). Amino Acids 2019; 51:1221-1232. [PMID: 31302779 DOI: 10.1007/s00726-019-02763-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 07/08/2019] [Indexed: 02/07/2023]
Abstract
In addition to the 20 protein amino acids that are vital to human health, hundreds of naturally occurring amino acids, known as non-proteinogenic amino acids (NPAAs), exist and can enter the human food chain. Some NPAAs are toxic through their ability to mimic protein amino acids and this property is utilised by NPAA-containing plants to inhibit the growth of other plants or kill herbivores. The NPAA L-azetidine-2-carboxylic acid (Aze) enters the food chain through the use of sugar beet (Beta vulgaris) by-products as feed in the livestock industry and may also be found in sugar beet by-product fibre supplements. Aze mimics the protein amino acid L-proline and readily misincorporates into proteins. In light of this, we examined the toxicity of Aze to mammalian cells in vitro. We showed decreased viability in Aze-exposed cells with both apoptotic and necrotic cell death. This was accompanied by alterations in endosomal-lysosomal activity, changes to mitochondrial morphology and a significant decline in mitochondrial function. In summary, the results show that Aze exposure can lead to deleterious effects on human neuron-like cells and highlight the importance of monitoring human Aze consumption via the food chain.
Collapse
|
7
|
Davis DA, Mondo K, Stern E, Annor AK, Murch SJ, Coyne TM, Brand LE, Niemeyer ME, Sharp S, Bradley WG, Cox PA, Mash DC. Cyanobacterial neurotoxin BMAA and brain pathology in stranded dolphins. PLoS One 2019; 14:e0213346. [PMID: 30893348 PMCID: PMC6426197 DOI: 10.1371/journal.pone.0213346] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 02/20/2019] [Indexed: 12/29/2022] Open
Abstract
Dolphin stranding events occur frequently in Florida and Massachusetts. Dolphins are an excellent sentinel species for toxin exposures in the marine environment. In this report we examine whether cyanobacterial neurotoxin, β-methylamino-L-alanine (BMAA), is present in stranded dolphins. BMAA has been shown to bioaccumulate in the marine food web, including in the muscles and fins of sharks. Dietary exposure to BMAA is associated with the occurrence of neurofibrillary tangles and β-amyloid plaques in nonhuman primates. The findings of protein-bound BMAA in brain tissues from patients with Alzheimer’s disease has advanced the hypothesis that BMAA may be linked to dementia. Since dolphins are apex predators and consume prey containing high amounts of BMAA, we examined necropsy specimens to determine if dietary and environmental exposures may result in the accumulation of BMAA in the brains of dolphins. To test this hypothesis, we measured BMAA in a series of brains collected from dolphins stranded in Florida and Massachusetts using two orthogonal analytical methods: 1) high performance liquid chromatography, and 2) ultra-performance liquid chromatography with tandem mass spectrometry. We detected high levels of BMAA (20–748 μg/g) in the brains of 13 of 14 dolphins. To correlate neuropathological changes with toxin exposure, gross and microscopic examinations were performed on cortical brain regions responsible for acoustico-motor navigation. We observed increased numbers of β-amyloid+ plaques and dystrophic neurites in the auditory cortex compared to the visual cortex and brainstem. The presence of BMAA and neuropathological changes in the stranded dolphin brain may help to further our understanding of cyanotoxin exposure and its potential impact on human health.
Collapse
Affiliation(s)
- David A. Davis
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, Florida, United States of America
- * E-mail: (DM); (DD)
| | - Kiyo Mondo
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, Florida, United States of America
| | - Erica Stern
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, Florida, United States of America
| | - Ama K. Annor
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, Florida, United States of America
| | - Susan J. Murch
- Department of Chemistry, University of British Columbia, Kelowna, British Columbia, Canada
| | - Thomas M. Coyne
- Office of the District 21 Medical Examiner, Fort Myers, Florida, United States of America
| | - Larry E. Brand
- Divisions of Marine Biology and Fisheries and NSF/NIEHS Oceans and Human Health Center, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, United States of America
| | - Misty E. Niemeyer
- Marine Mammal Rescue and Research, International Fund for Animal Welfare (IFAW), Yarmouth Port, Massachusetts, United States of America
| | - Sarah Sharp
- Marine Mammal Rescue and Research, International Fund for Animal Welfare (IFAW), Yarmouth Port, Massachusetts, United States of America
| | - Walter G. Bradley
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, Florida, United States of America
| | - Paul Alan Cox
- Brain Chemistry Labs, Institute for Ethnomedicine, Jackson Hole, Wyoming, United States of America
| | - Deborah C. Mash
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, Florida, United States of America
- Department of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, Florida, United States of America
- * E-mail: (DM); (DD)
| |
Collapse
|