Abstract
The non-protein amino acid (NPAA) ß-methylamino-l-alanine (BMAA) is produced by a diverse range of cyanobacteria, diatoms and dinoflagellates, and is present in both aquatic and terrestrial ecosystems globally. Exposure to BMAA has been implicated in the development of neurodegenerative diseases including amyotrophic lateral sclerosis (ALS), Alzheimer’s disease (AD) and Parkinson’s disease (PD). BMAA is often found in nature along with its structural isomers 2,4-diaminobutyric acid (2,4-DAB) and aminoethylglycine (AEG); however, the toxicity of these NPAAs in combination has not been examined. We have previously demonstrated that BMAA induces endoplasmic reticulum (ER) stress and increases caspase and cathepsin activity in human neuroblastoma cells (SH-SY5Y), effects consistent with proteotoxic stress due to disturbances in protein synthesis, folding or turnover. The current study investigates whether 2,4-DAB and AEG share a similar mechanism of toxicity to BMAA, and if simultaneous exposure of cells to BMAA and its isomers results in increased toxicity in vitro. We show that a 48-h treatment with both 500 μM BMAA and 2,4-DAB decreases cell viability in vitro whereas AEG was not cytotoxic under the same conditions. Treatment of SH-SY5Y cells with 2,4-DAB did not increase expression of ER stress markers. Combined treatment of cells with BMAA and 2,4-DAB resulted in increased caspase activity and increased apoptosis above that of BMAA or 2,4-DAB on their own. These results suggest that 2,4-DAB does not share the same mechanism of toxicity as BMAA but the presence of 2,4-DAB increases the toxicity of BMAA to human cells in vitro.
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Funding was from the Motor Neurone Disease Research Institute of Australia (Grant-in-aid); This research is supported by an Australian Government Research Training Program Scholarship.
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This manuscript represents original research, and has not been published in part or in whole elsewhere. This publication is not currently being considered for publication elsewhere. All authors have actively been involved in work leading to this manuscript, and have read and agreed with its publication. This article does not contain any studies with human participants or animals performed by any of the authors.
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Main, B.J., Rodgers, K.J. Assessing the Combined Toxicity of BMAA and Its Isomers 2,4-DAB and AEG In Vitro Using Human Neuroblastoma Cells. Neurotox Res 33, 33–42 (2018). https://doi.org/10.1007/s12640-017-9763-4
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DOI: https://doi.org/10.1007/s12640-017-9763-4