Acrylamide Neurotoxicity Studies in Caenorhabditis elegans Model

Abstract

Acrylamide (ACR), utilized as a precursor for producing polyacrylamide for water purification, has demonstrated neurotoxic properties. However, the mechanisms underlying its neurotoxicity remain inadequately understood. In this investigation, Caenorhabditis elegans were exposed to ACR at concentrations ranging from 250 to 1000 μg/mL and then their locomotor behavior, neuronal development, neurotransmitter concentrations, and gene expression profiles were assessed. Exposure to 250-1000 μg/mL ACR resulted in observable behaviors such as head swiveling and body bending, accompanied by a significant reduction in body size. Furthermore, ACR exposure caused damage to serotonergic, cholinergic, dopaminergic, and glutamatergic neuronal structures. In this context, elevated levels of serotonin, dopamine, acetylcholine, and glutamate were detected, along with notable upregulation of the expression of genes associated with neurotransmitters, including tph-1, cat-4, mod-1, mod-5, cat-1, ser-1, dat-1, dop-1, dop-3, unc-17, cho-1, eat-4, and glr-2. Moreover, ACR exposure elevated reactive oxygen species (ROS), O₂, and H₂O₂ levels while concurrently depleting glutathione (GSH), thereby compromising the antioxidant defense system. This led to a significant upsurge in the expression of genes involved in the nematode ACR detoxification pathway, specifically daf-16, skn-1, mlt-1, sod-3, gst-4, gcs-1, hsf-1, and hsp-16.2. Additionally, Spearman correlation analysis revealed a significant inverse relationship between certain neurotransmitter and antioxidant genes and locomotor activities, highlighting the role of these genes in mediating ACR-induced neurotoxicity in C. elegans. Collectively, this research enhances the understanding of the mechanisms related to ACR neurotoxicity.

Keywords: Caenorhabditis elegans; acrylamide; neurotoxicity; oxidative stress.

Figure 1

Effect of ACR on body length (A), width (B), head swinging (C), body bending (D), swallowing frequency (E) and lipofuscin accumulation (F). Results are presented as means ± SEMs (n = 30 replicates per group) in comparison to the control group. Statistical significance is indicated in the figures as follows: *** p < 0.001.

Figure 2

Effect of ACR on (A) ROS, (B) O₂⁻, (C) H₂O₂, and (D) GSH. Results are presented as means ± SEMs (n = 30 for each group) in comparison to the control group. Statistical significance is indicated in the figures as follows: * p < 0.05, ** p < 0.01, and *** p < 0.001.

Figure 3

Effect of ACR on the foraging behavior and chemotaxis index. (A). Schematic diagram of a test dish for the feeding behavior of C. elegans. (B). Foraging behavior. (C). Schematic diagram of a test dish for chemotaxis index of C. elegans. (D). Chemotaxis index. Data are presented as means ± SEMs (n = 30 for each group) in comparison to the control group. Statistical significance is indicated in the figures as follows: *** p < 0.001.

Figure 4

Effect of ACR on GR1366 (tph-1::GFP), BZ555 (dat-1::GFP), LX929 (unc-17::GFP), EG1285 (unc-47::GFP), DA1240 (eat-4::GFP) and neurotransmitters. (A) Fluorescent images depicting five neurons from nematodes. (B) Relative fluorescence intensity in five neurons in nematodes. (C) The levels of GABA, serotonin, dopamine, acetylcholine, and glutamate in comparison to the control group. Statistical significance is indicated in the figures as follows: * p < 0.05, ** p < 0.01, and *** p < 0.001.

Figure 5

(A) Effects of ACR on the mRNA expression levels of genes associated with serotonin, dopamine, acetylcholine, and glutamate in C. elegans. (B) Effects of ACR on the mRNA levels of genes related to antioxidant function in C. elegans. Data are normalized by the expression of act-1 and are presented as means ± SEMs (n = 3) compared to the control group. Statistical significance is indicated in the figures as follows: * p < 0.05, ** p < 0.01, and *** p < 0.001.

Figure 6

(A) The locations of DAF-16::GFP in the ‘cytosolic’, ‘intermediate’, and ‘nuclear’ regions. (B) Impact of ACR on SOD-3::GFP and GST::GFP. (C) The data are presented as means ± SEMs (n = 30 for each group). * p < 0.05, and *** p < 0.001, in comparison to the control group.

Figure 7

Spearman’s correlation analysis. * p < 0.05, ** p < 0.01, and *** p < 0.001.

Figure 8

Diagram depicting the potential mechanism through which ACR may cause harm to serotonergic, dopaminergic, cholinergic, and glutamatergic neurons.