Molecular Mechanism of Acrylamide Neurotoxicity: Lessons Learned from Organic Chemistry

Richard M. LoPachin¹ and Terrence Gavin²

¹Department of Anesthesiology, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York, USA; ²Department of Chemistry, Iona College, New Rochelle, New York, USA

Abstract

Background: Acrylamide (ACR) produces cumulative neurotoxicity in exposed humans and laboratory animals through a direct inhibitory effect on presynaptic function.

Objectives: In this review, we delineate how knowledge of chemistry provided an unprecedented understanding of the ACR neurotoxic mechanism. We also show how application of the hard and soft, acids and bases (HSAB) theory led to the recognition that the α,β-unsaturated carbonyl structure of ACR is a soft electrophile that preferentially forms covalent bonds with soft nucleophiles.

Methods: In vivo proteomic and in chemico studies demonstrated that ACR formed covalent adducts with highly nucleophilic cysteine thiolate groups located within active sites of presynaptic proteins. Additional research showed that resulting protein inactivation disrupted nerve terminal processes and impaired neurotransmission.

Discussion: ACR is a type-2 alkene, a chemical class that includes structurally related electrophilic environmental pollutants (e.g., acrolein) and endogenous mediators of cellular oxidative stress (e.g., 4-hydroxy-2-nonenal). Members of this chemical family produce toxicity via a common molecular mechanism. Although individual environmental concentrations might not be toxicologically relevant, exposure to an ambient mixture of type-2 alkene pollutants could pose a significant risk to human health. Furthermore, environmentally derived type-2 alkenes might act synergistically with endogenously generated unsaturated aldehydes to amplify cellular damage and thereby accelerate human disease/injury processes that involve oxidative stress.

Conclusions: These possibilities have substantial implications for environmental risk assessment and were realized through an understanding of ACR adduct chemistry. The approach delineated here can be broadly applied because many toxicants of different chemical classes are electrophiles that produce toxicity by interacting with cellular proteins.

Key words: HSAB theory, oxidative stress, protein adducts, soft electrophile, toxic axonopathy, type-2 alkenes, α,β-unsaturated carbonyl derivatives. 

Environ Health Perspect 120:1650–1657 (2012). http://dx.doi.org/10.1289/ehp.1205432 [Online 11 October 2012]

Address correspondence to R.M. LoPachin, Department of Anesthesiology, Montefiore Medical Center, 111 E. 210th St., Bronx, New York 10467 USA. Telephone: (718) 920-5054. Fax: (718) 515-4902. E-mail: richard.lopachin@einstein.yu.edu

This research was supported by grants RO1 ESO3830-25 and RO1 ES07912-11 from the National Institute of Environmental Health Sciences, National Institutes of Health.

The authors declare that they have no actual or potential competing financial interests.

Received 4 May 2012; Accepted 24 September 2012; Online 11 October 2012.