text: L-BMAA induced ER stress and enhanced caspase 12 cleavage in human neuroblastoma SH-SY5Y cells at low nonexcitotoxic concentrations.
  The cyanobacterial β-N-methylamino-L-alanine (L-BMAA) is described as a low-potency excitotoxin, possibly a factor in the increased incidence of amyotrophic lateral sclerosis (ALS) and Parkinsonism-dementia complex (PDC) in Guam. The latter association is intensively disputed, as L-BMAA concentrations required for toxic effects exceed those assumed to occur via food. The question thus was raised whether L-BMAA leads to neurodegeneration at nonexcitotoxic conditions. Using human SH-SY5Y neuroblastoma cells, L-BMAA-transport, incorporation into proteins, and subsequent impairment of cellular protein homeostasis were investigated. Binding of L-BMAA to intracellular proteins, but no clear protein incorporation was detected in response to (14)C-L-BMAA exposures. Nevertheless, low L-BMAA concentrations (≥ 0.1mM, 48 h) increased protein ubiquitination, 20S proteasomal and caspase 12 activity, expression of the endoplasmic reticulum (ER) stress marker CHOP, and enhanced phosphorylation of elf2α in SH-SY5Y cells. In contrast, high L-BMAA concentrations (≥ 1mM, 48 h) increased reactive oxygen species and protein oxidization, which were partially ameliorated by coincubation with vitamin E. L-BMAA-mediated cytotoxicity was observable 48 h following ≥ 2mM L-BMAA treatment. Consequently, the data presented here suggest that low L-BMAA concentrations result in a dysregulation of the cellular protein homeostasis with ensuing ER stress that is independent from high-concentration effects such as excitotoxicity and oxidative stress. Thus, the latter could be a contributing factor in the onset and slow progression of ALS/PDC in Guam.
entities.id: T10 T11 T12 T13 T14 T15 T16 T17 T18 T19 T1 T20 T21 T2 T3 T4 T5 T6 T7 T8 T9
entities.type: CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL GENE-N GENE-Y GENE-Y CHEMICAL GENE-Y GENE-Y CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL
entities.text: L-BMAA L-BMAA L-BMAA (14)C L-BMAA L-BMAA L-BMAA 20S proteasomal caspase 12 CHOP L-BMAA elf2α caspase 12 oxygen vitamin E L-BMAA L-BMAA L-BMAA β-N-methylamino-L-alanine L-BMAA L-BMAA