beta-Methylamino-L-alanine

"BMAA" redirects here. For other uses, see BMAA (disambiguation).
beta-Methylamino-L-alanine
Names
IUPAC names
(2S)-2-Amino-3-(methylamino)propanoic acid[1]
Other names
2-Amino-3-methylaminopropanoic acid
Identifiers
15920-93-1 YesY
ChEBI CHEBI:73169 N
ChEMBL ChEMBL11488 N
ChemSpider 94816 N
Jmol 3D model Interactive image
KEGG C08291 N
MeSH alpha-amino-beta-methylaminopropionate
PubChem 105089
Properties
C4H10N2O2
Molar mass 118.14 g·mol−1
log P −0.1
Acidity (pKa) 1.883
Basicity (pKb) 12.114
Related compounds
Related alkanoic acids
Related compounds
 Dimethylacetamide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

β-Methylamino-L-alanine, or BMAA, is a non-proteinogenic amino acid produced by cyanobacteria. BMAA is a neurotoxin and its potential role in various neurodegenerative disorders is the subject of scientific research.

Structure and properties

BMAA is a derivative of the amino acid alanine with a methylamino group on the side chain. This non-proteinogenic amino acid is classified as a polar base.

Sources and detection

BMAA is produced by cyanobacteria in marine, freshwater and terrestrial environments.[2][3] In cultured non-nitrogen-fixing cyanobacteria, BMAA production increases in nitrogen depleted medium.[4] BMAA has been found in aquatic organisms and in plants with cyanobacterial symbionts such as certain lichens, the floating fern Azolla, the leaf petioles of the tropical flowering plant Gunnera, cycads as well as in animals that eat the fleshy covering of cycad seeds, including flying foxes.[5][6][7][8]

High concentrations of BMAA are present in shark fins.[9] Because BMAA is a neurotoxin, consumption of shark fin soup and cartilage pills may therefore pose a health risk.[10] The toxin can be detected via several laboratory methods, including liquid chromatography, high-performance liquid chromatography, mass spectrometry, amino acid analyzer, capillary electrophoresis and NMR spectroscopy.[11]

Neurotoxicity

Mechanisms

Although the mechanisms by which BMAA causes motor neuron dysfunction and death are not entirely understood, current research suggests that there are multiple mechanisms of action. Acutely, BMAA can act as an excitotoxin on glutamate receptors such as NMDA, calcium dependent AMPA and kainate receptors.[12][13] The activation of the metabotropic glutamate receptor 5 is believed to induce oxidative stress in the neuron by depletion of glutathione.[14]

BMAA may also misincorporate into nascent proteins in place of L-serine, possibly causing protein misfolding and aggregation, both hallmarks of tangle diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis (ALS), progressive supranuclear palsy (PSP), and Lewy body disease. In vitro research has shown that protein association of BMAA can be inhibited in presence of excess L-serine.[15]

Effects

A study performed in 2015 with green monkey subjects found that animals orally administered BMAA developed hallmark histopathology features of Alzheimer's Disease including amyloid beta plaques and neurofibrillary tangle accumulation. Animal subjects in the trial fed smaller doses of BMAA were found to have correlative decreases in these pathology features. Additionally, animals that were co-administered BMAA with serine were found to have 70% less beta-amyloid plaques and neurofibrillary tangles than those administered BMAA alone, suggesting that serine may be protective against the neurotoxic effects of BMAA. This experiment represents the first in-vivo model of Alzheimer's Disease that features both beta-amyloid plaques and hyperphosphorylated tau protein. This study also demonstrates that BMAA, an environmental toxin, can trigger neurodegenerative disease.[16]

Degenerative loco-motor diseases have been described in animals grazing on cycad species, fueling interest in a possible link between the plant and the etiology of ALS/PDC. Subsequent laboratory investigations discovered the presence of BMAA. BMAA induced severe neurotoxicity in rhesus macaques, including.[17]

There are reports that low BMAA concentrations can selectively kill cultured motor neurons from mouse spinal cords and produce reactive oxygen species.[13][18]

Scientists have also found that newborn rats treated with BMAA show a progressive neurodegeneration in the hippocampus, including intracellular fibrillar inclusions, and impaired learning and memory as adults.[19][20] [21] In addition BMAA has been reported to be excreted into rodent breast milk, and subsequently transferred to the suckling offspring, suggesting mothers and cows milk might be other possible exposure routes.[22]

Human cases

BMAA is considered a possible cause of the amyotrophic lateral sclerosis/parkinsonism–dementia complex (ALS/PDC) that had an extremely high rate of incidence among the Chamorro people of Guam.[23] The Chamorro call the condition lytico-bodig.[24] In the 1950s, ALS/PDC prevalence ratios and death rates for Chamorro residents of Guam and Rota were 50–100 times that of developed countries, including the United States.[24] No demonstrable heritable or viral factors were found for the disease, and a subsequent decline of ALS/PDC after 1963 on Guam led to the search for responsible environmental agents.[25] The use of cycad (Cycas micronesica[26]) seeds in food decreased as that plant became rarer and the Chamorro population became more Americanized following World War II.[27]

In addition to eating the seeds directly, BMAA may be ingested by humans through biomagnification. Flying foxes, a Chamorro delicacy, may feed on cycad seeds and concentrate the toxin in their flesh. Twenty-four specimens of flying foxes from museum collections were tested for BMAA and BMAA was found in large concentrations in the flying foxes from Guam.[28]

Studies on human brain tissue of ALS/PDC, ALS, Alzheimer's disease, Parkinson's disease, Huntington's disease and neurological controls indicated that BMAA is present in non-genetic progressive neurodegenerative disease but not in controls or genetic-based Huntington's disease.[29][30][31][32]

There is currently ongoing research into the role of BMAA as an environmental factor in neurodegenerative disease.[33][34]

Clinical trials

Safe and effective ways of reducing levels of BMAA in ALS patients have been goals of clinical trials sponsored by Phoenix Neurological Associates and the Institute for Ethnomedicine.[35][36]

See also

References

  1. ↑ "alpha-amino-beta-methylaminopropionate - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 19 August 2005. Identification. Retrieved 25 April 2012.
  2. ↑ Cox, PA, Banack, SA, Murch, SJ, Rasmussen, U, Tien, G, Bidigare, RR, Metcalf, JS, Morrison, LF, Codd, GA, Bergman, B. (2005). "Diverse taxa of cyanobacteria produce b-N-methylamino-L-alanine, a neurotoxic amino acid". PNAS 102 (14): 5074–5078. doi:10.1073/pnas.0501526102. PMC 555964. PMID 15809446.
  3. ↑ Esterhuizen, M, Downing, TG. (2008). "β-N-methylamino-L-alanine (BMAA) in novel South African cyanobacterial isolates". Ecotoxicology and Environmental Safety 71 (2): 309–313. doi:10.1016/j.ecoenv.2008.04.010.
  4. ↑ Downing, S, Banack, SA, Metcalf, JS, Cox, PA, Downing, TG. (2011). "Nitrogen starvation of cyanobacteria results in the production of β-N-methylamino-L-alanine". Toxicon 58: 187–194. doi:10.1016/j.toxicon.2011.05.017.
  5. ↑ Vega, A, Bell, A. (1967). "a-amino-β-methylaminopropionic acid, a new amino acid from seeds of cycas circinalis". Phytochemistry 6: 759–762. doi:10.1016/s0031-9422(00)86018-5.
  6. ↑ Banack, SA, Cox, PA. (2003). "Biomagnification of cycad neurotoxins in flying foxes: implications for ALS-PDC in Guam". Neurology 61 (3): 387–9. doi:10.1212/01.wnl.0000078320.18564.9f.
  7. ↑ Masseret, E, Banack, S, Boumédiène, F, Abadie, E, Brient, L, Pernet, F, Juntas-Morales, R, Pageot, N, Metcalf, J, Cox, P, Camu, W. (2013). "Dietary BMAA exposure in an amyotrophic lateral sclerosis cluster from Southern France". PLOS ONE 8 (12): e83406. doi:10.1371/journal.pone.0083406.
  8. ↑ Field, NC, Metcalf, JS, Caller, TA, Banack, SA, Cox, PA, Stommel, EW. (2013). "Linking β-methylamino-L-alanine exposure to sporadic amyotrophic lateral sclerosis in Annapolis, MD". Toxicon 70: 179–183. doi:10.1016/j.toxicon.2013.04.010.
  9. ↑ Kiyo Mondo, Neil Hammerschlag, Margaret Basile, John Pablo, Sandra A. Banack, Deborah C. Mash (2012). "Cyanobacterial Neurotoxin β-N-Methylamino-L-alanine (BMAA) in Shark Fins". Marine Drugs 10 (2): 509–520. doi:10.3390/md10020509.
  10. ↑ "Neurotoxins in shark fins: A human health concern". Science Daily. February 23, 2012.
  11. ↑ Cohen, SA. (2012). "Analytical techniques for the detection of a-amino- β-methylaminopropionic acid". Analyst 137: 1991. doi:10.1039/c2an16250d.
  12. ↑ Weiss, JH, Koh, J, Choi. D. (1989). "Neurotoxicity of β -N-methylamino-L-alanine (BMAA) and β-N-oxalylamino-L-alanine (BOAA) on cultured cortical neurons". Brain Research 497: 64–71. doi:10.1016/0006-8993(89)90970-0.
  13. 1 2 Lobner, D, Piana, PM, Salous, AK, Peoples, RW. (2007). "β-N-methylamino-L-alanine enhances neurotoxicity through multiple mechanisms". Neurobiology of Disease 25 (2): 360–366. doi:10.1016/j.nbd.2006.10.002.
  14. ↑ Rush, T, Liu, X, Lobner, D. (2012). "Synergistic toxicity of the environmental neurotoxins methylmercury and β-N-methylamino-L-alanine". Neuropharmacology and neurotoxicology 23: 216–219. doi:10.1097/WNR.0b013e32834fe6d6.
  15. ↑ Dunlop, R.A., Cox, P.A., Banack, S.A., Rodgers, J.K. (2013). "The Non-Protein Amino Acid BMAA Is Misincorporated into Human Proteins in Place of l-Serine Causing Protein Misfolding and Aggregation". PLOS ONE 8 (9): e75376. doi:10.1371/journal.pone.0075376. PMC 3783393. PMID 24086518.
  16. ↑ Cox, PA, Davis, DA, Mash, DC, Metcalf, JS, Banack, SA. (2015). "Dietary exposure to an environmental toxin triggers neurofibrillary tangles and amyloid deposits in the brain". Proceedings of the Royal Society B 283 (1823): 20152397. doi:10.1098/rspb.2015.2397.
  17. ↑ Spencer, PS, Hugon, J, Ludolph, A, Nunn, PB, Ross, SM, Roy, DN, Schaumburg, HH. (1987). "Discovery and partial characterization of primate motor-system toxins". Ciba foundation symposium.
  18. ↑ Rao, SD, Banack, SA, Cox, PA, Weiss, JH. (2006). "BMAA selectively injures motor neurons via AMPA/kainate receptor activations". Experimental Neurology 201 (1): 244–52. doi:10.1016/j.expneurol.2006.04.017. PMID 16764863.
  19. ↑ Karlsson, Oskar; Berg, Anna-Lena; Hanrieder, Jörg; Arnerup, Gunnel; Lindström, Anna-Karin; Brittebo, Eva B. (2014). "Intracellular fibril formation, calcification, and enrichment of chaperones, cytoskeletal, and intermediate filament proteins in the adult hippocampus CA1 following neonatal exposure to the nonprotein amino acid BMAA". Archives of Toxicology 89 (3): 423–436. doi:10.1007/s00204-014-1262-2. ISSN 0340-5761.
  20. ↑ Karlsson, O.; Roman, E.; Brittebo, E. B. (2009). "Long-term Cognitive Impairments in Adult Rats Treated Neonatally with -N-Methylamino-L-Alanine". Toxicological Sciences 112 (1): 185–195. doi:10.1093/toxsci/kfp196. ISSN 1096-6080.
  21. ↑ Karlsson, O. (2011). Distribution and Long-term Effects of the Environmental Neurotoxin β-N-methylamino-L-alanine (BMAA): Brain changes and behavioral impairments following developmental exposure. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-140785
  22. ↑ Andersson, Marie; Karlsson, Oskar; Bergström, Ulrika; Brittebo, Eva B.; Brandt, Ingvar (2013). "Maternal Transfer of the Cyanobacterial Neurotoxin β-N-Methylamino-L-Alanine (BMAA) via Milk to Suckling Offspring". PLOS ONE 8 (10): e78133. doi:10.1371/journal.pone.0078133. ISSN 1932-6203. Missing |last1= in Authors list (help)
  23. ↑ Cox, PA, Sacks, OW. (2002). "Cycad neurotoxins, consumption of flying foxes, and ALS-PDC disease in Guam". Neurology 58 (6): 956–9. doi:10.1212/wnl.58.6.956. PMID 11914415.
  24. 1 2 Kurland, LK, Mulder, DW. (1954). "Epidemiologic investigations of amyotrophic lateral sclerosis". Neurology 4: 355. doi:10.1212/wnl.4.5.355.
  25. ↑ Galasko, D, Salmon, DP, Craig, UK, Thal, LJ, Schellenberg, G, Wiederholt, W. (2002). "Clinical features and changing patterns of neurodegenerative disorders on Guam, 1997-2000". Neurology 58: 90–7. doi:10.1212/wnl.58.1.90.
  26. ↑ Hill, KD. (1994). "The cycas rumphii complex (Cycadeceae) in New Guinea and the Western Pacific". Australian Systematic Botany 7: 543–567. doi:10.1071/sb9940543.
  27. ↑ Whiting, MG. (1963). "Toxicity of cycads". Economic Botany 17 (4): 270–302. doi:10.1007/bf02860136.
  28. ↑ Banack, SA, Murch, SJ, Cox, PA. (2006). "Neurotoxic flying foxes as dietary items for the Chamorro people, Mariana Islands". Ethnopharmacology 106: 97–104. doi:10.1016/j.jep.2005.12.032.
  29. ↑ Murch, SJ, Cox, PA, Banack, SA. (2004). "A mechanism for slow release of biomagnified cyanobacterial neurotoxins and neurodegenerative disease in Guam". PNAS 101 (33): 12228–12231. doi:10.1073/pnas.0404926101.
  30. ↑ Murch, SJ, Cox, PA, Banack, SA, Steele, JC, Sacks, OW. (2004). "Occurrence of b-methylamino-L-alanine (BMAA) in ALS/PDC patients from Guam". Acta Neurologica Scandinavica 110 (4): 267–9. doi:10.1111/j.1600-0404.2004.00320.x. PMID 15355492.
  31. ↑ Pablo, J, Banack, SA, Cox, PA, Johnson, TE, Papapetropoulos, Bradley, WG, Buck, A, Mash, DC. (2009). "Cyanobacterial neurotoxin BMAA in ALS and Alzheimer’s disease". Acta neurologica scandinavica 120: 215–225. doi:10.1111/j.1600-0404.2008.01150.x.
  32. ↑ Bradley, WG, Mash, DC. (2009). "Beyond Guam: the cyanobacterial/BMAA hypothesis of the cause of ALS and other neurodegenerative diseases". ALS 10: 7–20. doi:10.3109/17482960903286009.
  33. ↑ Banack, SA, Caller, TA, Stommel, EW. (2010). "The cyanobacteria derived toxin beta-n-methylamino-L-alanine and Amyotrophic Lateral Sclerosis". Toxins 2: 2837–2850. doi:10.3390/toxins2122837.
  34. ↑ Holtcamp, W. (2012). "The emerging science of BMAA: do cyanobacteria contribute to neurodegenerative disease?". Environmental Health Perspectives 120 (3): a110–a116. doi:10.1289/ehp.120-a110. PMC 3295368. PMID 22382274.
  35. ↑ Determining the Safety of L-serine in ALS.
  36. ↑ Safety Study of High Doses of Zinc in ALS Patients (completed).
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