In vivo and in vitro effects of acrylamide on synaptosomal neurotransmitter uptake and release

Richard M. LoPachin, Aron I. Schwarcz, Christopher L. Gaughan, Shirley Mansukhani, Soma Das

Research output: Contribution to journalArticle

66 Scopus citations

Abstract

Evidence suggests acrylamide (ACR) neurotoxicity is mediated by impaired presynaptic transmission. To assess the effects of ACR on nerve terminal function, [3H]glutamate release and uptake were determined in brain synaptosomes isolated from intoxicated rats (50mg/kg per day×8 days, i.p. or 21mg/kg per day×21 days, p.o.). Regardless of ACR dose-rate, a significant reduction in synaptosomal K+-stimulated, Ca 2+-dependent release was detected, whereas kinetic analysis of Na+-dependent uptake did not reveal consistent changes. Immunoblot analysis showed normal protein levels (e.g. SNAP-25) in dysfunctional synaptosomes isolated from ACR-intoxicated rats. This suggests that defective release does not involve changes in protein synthesis and/or anterograde delivery of presynaptic constituents. To identify potential targets, synaptosomes were exposed in vitro to [14C]-ACR and radiolabeled proteins were separated by gel electrophoresis and detected by autoradiography. [14C]-ACR labeling of distinct synaptosomal protein bands (10.5-154,000kDa) was blocked by the sulfhydryl alkylating agent, N-ethylmaleimide (NEM; 4mM) but not by the non-neurotoxic structural analog propionamide (10mM). In vitro characterization of synaptosomal [ 3H]glutamate uptake and release showed that ACR, NEM and iodoacetic acid (IAA) produced concentration-dependent decreases in each parameter that were highly correlated to reductions in free sulfhydryl content. All three chemicals were equiefficacious with respect to reducing sulfhydryl content and neurotransmitter uptake/release, although the relative potencies differed; NEM>IAA>ACR. Kinetic analysis of uptake showed that in vitro exposure to ACR, IAA or NEM at their respective IC50's caused similar reductions in Vmax. These data suggest that ACR-induced synaptic dysfunction involves adduction of presynaptic protein thiol groups and subsequent reduction in neurotransmitter release.

Original languageEnglish (US)
Pages (from-to)349-363
Number of pages15
JournalNeurotoxicology
Volume25
Issue number3
DOIs
StatePublished - Mar 1 2004

Keywords

  • Acrylamide
  • Distal axonopathy
  • Neurotransmitter release
  • Protein thiol groups
  • SNARE core complexes
  • Synaptosomes
  • Uptake

ASJC Scopus subject areas

  • Neuroscience(all)
  • Toxicology

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