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

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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 2004

Fingerprint

Acrylamide
Neurotransmitter Agents
Iodoacetic Acid
Synaptosomes
Proteins
Rats
Glutamic Acid
In Vitro Techniques
Kinetics
Ethylmaleimide
Alkylating Agents
Electrophoresis
Autoradiography
Sulfhydryl Compounds
Labeling
Inhibitory Concentration 50
Brain
Gels

Keywords

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

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience
  • Neuroscience(all)
  • Toxicology

Cite this

In vivo and in vitro effects of acrylamide on synaptosomal neurotransmitter uptake and release. / LoPachin, Richard M.; Schwarcz, Aron I.; Gaughan, Christopher L.; Mansukhani, Shirley; Das, Soma.

In: NeuroToxicology, Vol. 25, No. 3, 03.2004, p. 349-363.

Research output: Contribution to journalArticle

LoPachin, Richard M. ; Schwarcz, Aron I. ; Gaughan, Christopher L. ; Mansukhani, Shirley ; Das, Soma. / In vivo and in vitro effects of acrylamide on synaptosomal neurotransmitter uptake and release. In: NeuroToxicology. 2004 ; Vol. 25, No. 3. pp. 349-363.
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