title: In vivo and in vitro effects of acrylamide on synaptosomal neurotransmitter uptake and release.
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 x 8 days, i.p. or 21 mg/kg per day x 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 (10.5-154000 kDa) 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; [3H]. Kinetic analysis of uptake showed that in vitro exposure to ACR, IAA or NEM at their respective IC(50)'s caused similar reductions in V(max). These data suggest that ACR-induced synaptic dysfunction involves adduction of presynaptic protein thiol groups and subsequent reduction in neurotransmitter release.
authors.affiliation: Department of Anesthesiology, Albert Einstein College of Medicine, Montefiore Medical Center, Moses Research Tower-7, 111 E 210th Street, Bronx, NY 10467, USA. lopachin@aecom.yu.edu
authors.forename: Richard M
authors.initials: RM
authors.lastname: LoPachin
authors.forename: Aron I
authors.initials: AI
authors.lastname: Schwarcz
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Gaughan
authors.forename: Shirley
authors.initials: S
authors.lastname: Mansukhani
authors.forename: Soma
authors.initials: S
authors.lastname: Das
mesh_terms: D020106:Acrylamide / Q000493:pharmacokinetics* / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D018698:Glutamic Acid / Q000378:metabolism*; D008297:Male; D018377:Neurotransmitter Agents / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
chemical_list: D018377:Neurotransmitter Agents; D020106:Acrylamide; D018698:Glutamic Acid