Learning, memory deficits, and impaired neuronal maturation attributed to acrylamide

Low-dose acrylamide induces mitochondrial autophagy and energy metabolism dysfunction in SH-SY5Y cells via BV2 microglial activation

Acrylamide (ACR), a common environmental and food contaminant, can cause neurotoxicity and increase the risk of neurodegenerative diseases. While the neurotoxicity induced by high-dose ACR exposure in occupational workers is evident, the potential adverse effects of low-dose daily exposure remain a subject of debate. In this present study, we aim to explore whether low-dose ACR induces neurotoxicity based on the interactions between microglia and neurons. Results demonstrated that low-dose ACR did not significantly impair mitochondrial homeostasis in SH-SY5Y cells, but induced microglial polarisation towards the M1 pro-inflammatory phenotype at this concentration. Interestingly, the supernatants from ACR pre-activated BV2 microglia were observed to trigger mitochondrial dysfunction, induce autophagy, and disrupt energy metabolism in SH-SY5Y cells, whose effects were not observed in cells solely treated with ACR. Furthermore, muscone, acting as an inhibitor of inflammatory factors, successfully ameliorated the activation of microglia induced by low-dose ACR and notably downregulated the expression levels of IL-1β, IL-6, and TNF-α. In an additional effect, muscone reversed the expression trends of P62 and LC3 proteins, which were perturbed by the activation of microglia in SH-SY5Y cells. In conclusion, our results proved that low-dose ACR induced mitochondrial autophagy and energy metabolism disturbance in SH-SY5Y cells via BV2 microglial activation, which might be significantly influenced by the release of pro-inflammatory factors. Our study emphasized the crucial role of microglia-neuronal interactions, providing novel insights for understanding low-dose ACR induced neurotoxicity.

Intestinal Obstruction and Neurotoxicity Associated With Water Bead Ingestion

Water beads are superabsorbent polymer balls. They were originally marketed for agricultural and decorative applications and are now sold as sensory toys. They can be harmful to children in 2 ways. Upon ingestion, water beads absorb liquid and, because they can increase in volume by more than a hundredfold, intestinal obstruction can result. In addition, they are made of polymerized acrylamide monomer. Acrylamide monomer can be toxic at high levels. Here, we present a case of intestinal obstruction in the setting of water bead ingestion temporarily associated with signs of neurotoxicity. The patient presented to the emergency department at 13 months of age with vomiting, lethargy, weight loss over several weeks, insomnia, and facial dermatitis. Due to worsening clinical signs and imaging findings suggestive of intestinal obstruction, she underwent an exploratory laparotomy. A mass consisting of water beads was removed from the distal small intestine. After removal of the mass, the patient's facial dermatitis resolved; however, the patient's speech, gross and fine motor, sensory, and neurological functions continued to worsen. After reevaluation, a second surgical procedure led to removal of multiple fragments of water bead material from the patient's large intestine. This case highlights the potential dangers of acrylamide in consumer products that may be accessible to children.

The neurotoxicity of acrylamide in ultra-processed foods: interventions of polysaccharides through the microbiota-gut-brain axis

Ultra-processed foods (UPFs) have become popular in recent years, however, the detrimental effects of their excessive consumption have also become evident. Acrylamide (AA), a processing hazard present in UPFs, can further aggravate the harmful effects of UPFs. AA can cause significant damage to both the intestinal barrier and gut microbiota, thereby affecting the nervous system through the microbiota-gut-brain (MGB) axis. Natural polysaccharides have demonstrated the capacity to significantly alleviate the oxidative stress and inflammatory response associated with AA exposure. In addition, they exhibit neuroprotective properties that may be mediated through the MGB axis. This paper reviews literature on the presence of AA in certain UPFs and its potential to inflict serious harm on the human gut microbiota and brain. Moreover, the possibility of utilizing polysaccharides as a preventative measure against AA-induced neurotoxicity was also proposed. These findings provide new insights into the safety risks associated with the overconsumption of UPFs and highlight the potential of polysaccharides to counteract the neurodegeneration induced by AA.

Assessment of the neurotoxicity of monosodium glutamate on neural stem cells and hippocampal neurogenesis in a rodent model

Monosodium glutamate (MSG) is a widely used flavor enhancer in processed foods and valued for its ability to enhance the savory taste known as umami. MSG is classified as non-toxic and recognized as a safe food additive with no specific usage restrictions in many countries. However, neurotoxic studies on MSG have primarily focused on neurons, and the effects of MSG on neural stem cells (NSCs) have not been reported. This study aimed to evaluate the neurotoxic effect of MSG on NSCs and hippocampal neurogenesis in a rodent model. In vitro studies showed that MSG induces cytotoxicity in primary neuron cultures but has no toxic effect on NSCs. Furthermore, in vivo studies on 4-week-old male C57BL/6 mice orally administered MSG and sodium chloride (NaCl) for two weeks revealed that neither MSG nor NaCl induced changes in the expressions of neuronal markers or glutamate receptors in the hippocampus. In addition, no differences in NSC proliferation or survival were detected, and MSG did not adversely affect the neuronal differentiation of NSCs. Moreover, neurobehavioral tests showed that MSG treatment did not impair spatial learning and memory. These findings provide a first assessment of the neurotoxic effects of MSG on NSCs and hippocampal neurogenesis.

Developmental neurotoxicity evaluation of acrylamide based on in vitro to in vivo extrapolation by pregnancy PBTK modelling

Acrylamide (ACR) is a known neurotoxicant that can pass the placenta and has been detected in breast milk. Some in vivo and in vitro studies indicate that ACR exposure might lead to developmental neurotoxicity (DNT). Here, we have developed a physiologically-based toxicokinetic model for a pregnant human population using PK-Sim. We performed an in vitro to in vivo extrapolation (IVIVE) of data collected from human neuroblastoma SH-SY5Y cells exposed during differentiation to ACR. The developed PBTK model was successfully evaluated and predicted fetal plasma concentrations in the low nM range after exposing the model to an estimated average daily intake for pregnant women. The IVIVE showed that low concentrations of ACR (fM-nM) that induced attenuated differentiation of the SH-SY5Y neuronal cell model, were relevant for human exposure to ACR from oral intake. However, doses estimated in the IVIVE from concentrations in the µM range, were found to be unrealistic by exposure through food intake for an average daily intake. However, in case of exposure due to environmental pollution or occupational exposure, these concentrations may be reached in fetal plasma. The findings in this study raise the concern regarding ACR exposure during pregnancy as well as the relevance of testing concentrations in vitro that are several orders of magnitude higher than the predicted fetal plasma concentrations.

Reduction of eEF2 kinase alleviates the learning and memory impairment caused by acrylamide

BACKGROUND

The impact of acrylamide (ACR) on learning and memory has garnered considerable attention. However, the targets and mechanisms are still unclear.

RESULTS

Elongation factor 2 (eEF2) was significantly upregulated in the results of serum proteomics. Results from in vitro and in vivo experiments indicated a notable upregulation of Eukaryotic elongation factor 2 kinase (eEF2K), the sole kinase responsible for eEF2 phosphorylation, following exposure to ACR (P < 0.05). Subsequent in vitro experiments using eEF2K siRNA and in vivo experiments with eEF2K-knockout mice demonstrated significant improvements in abnormal indicators related to ACR-induced learning and memory deficits (P < 0.05). Proteomic analysis of the hippocampus revealed Lpcat1 as a crucial downstream protein regulated by eEF2K. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses indicated that eEF2K may play a role in the process of ACR-induced learning and memory impairment by affecting ether lipid metabolism.

CONCLUSIONS

In summary, eEF2K as a pivotal treatment target in the mechanisms underlying ACR-induced learning and memory impairment, and studies have shown that it provides robust evidence for potential clinical interventions targeting ACR-induced impairments.

Attenuated neuronal differentiation caused by acrylamide is not related to oxidative stress in differentiated human neuroblastoma SH-SY5Y cells

Acrylamide (ACR) is a known neurotoxicant and developmental neurotoxicant. As a soft electrophile, ACR reacts with thiol groups in cysteine. One hypothesis of ACR induced neurotoxicity and developmental neurotoxicity (DNT) is conjugation with reduced glutathione (GSH) leading to GSH depletion, increased reactive oxygen species (ROS) production and further oxidative stress and cellular damage. In this regard, we have investigated the effect of ACR on neuronal differentiation, glutathione levels and ROS production in the human neuroblastoma SH-SY5Y cell model. After 9 days of differentiation and exposure, ACR significantly impaired area neurites per cell at non-cytotoxic concentrations (0.33 μM and 10 μM). Furthermore, 10 μM ACR dysregulated 9 mRNA markers important for neuronal development, 5 of them being associated with cytoskeleton organization and axonal guidance. At the non-cytotoxic concentrations that significantly attenuate neuronal differentiation, ACR did neither decrease the level of GSH or total glutathione levels, nor increased ROS production. In addition, the expression of 5 mRNA markers for cellular stress was assessed with no significant altered regulation after ACR exposure up to 320 μM. Thus, ACR-induced DNT is not due to GSH depletion and increased ROS production, neither at non-cytotoxic nor cytotoxic concentrations, in the SH-SH5Y model during differentiation.

Cationic nanoplastic causes mitochondrial dysfunction in neural progenitor cells and impairs hippocampal neurogenesis

Nanoplastics (NPs) exposure to humans can occur through various routes, including the food chain, drinking water, skin contact, and respiration. NPs are plastics with a diameter of less than 100 nm and have the potential to accumulate in tissues, leading to toxic effects. This study aimed to investigate the neurotoxicity of polystyrene NPs on neural progenitor cells (NPCs) and hippocampal neurogenesis in a rodent model. Toxicity screening of polystyrene NPs based on their charge revealed that cationic amine-modified polystyrene (PS-NH3+) exhibited cytotoxicity, while anionic carboxylate-modified polystyrene (PS-COO-) and neutral NPs (PS) did not. NPCs treated with PS-NH3+ showed a significant reduction in growth rate due to G1 cell cycle arrest. PS-NH3+ increased the expression of cell cycle arrest markers p21 and p27, while decreasing cyclin D expression in NPCs. Interestingly, PS-NH3+ accumulated in mitochondria, leading to mitochondrial dysfunction and energy depletion, which caused G1 cell cycle arrest. Prolonged exposure to PS-NH3+ in C17.2 NPCs increased the expression of p16 and senescence-associated secretory phenotype factors, indicating cellular senescence. In vivo studies using C57BL/6 mice demonstrated impaired hippocampal neurogenesis and memory retention after 10 days of PS-NH3+ administration. This study suggests that NPs could deplete neural stem cell pools in the brain by mitochondrial dysfunction, thereby adversely affecting hippocampal neurogenesis and neurocognitive functions.

The protective effect of Ganoderma atrum polysaccharide on intestinal barrier function damage induced by acrylamide in mice through TLR4/MyD88/NF-κB based on the iTRAQ analysis

The potential mechanism for the protective effect of Ganoderma atrum (G. atrum) polysaccharide (PSG-1) on acrylamide (AA) induced intestinal damage in mice was explored. Results showed that PSG-1 pretreatment prevented AA-induced injury by decreasing intestinal permeability and serum D-lactate acid (D-Lac) levels and increasing the number of small intestinal goblet cells and IgA secreting cells. In addition, PSG-1 pretreatment effectively reduced malondialdehyde (MDA) level and raised superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) activities in the intestine. Furthermore, PSG-1 administration decreased the levels of pro-inflammatory factors including IL-1β, TNF-α, and IL-6, while the anti-inflammatory factor IL-10 was elevated. Meanwhile, PSG-1 could increase the performance of tight junction (TJ) proteins such as Occludin, Claudin-1 and ZO-1. Moreover, according to the isobaric tag for relative and absolute quantitation (iTRAQ) and Western blot results, PSG-1 could reduce AA-induced intestinal injury through TLR4/MyD88/NF-κB signaling pathway. Overall, the present study suggested that PSG-1 protected intestinal permeability and barrier function in mice via reducing inflammation and oxidative stress, and effectively prevented AA-induced intestinal injury in mice.

Administration of Different Doses of Acrylamide Changed the Chemical Coding of Enteric Neurons in the Jejunum in Gilts

Excessive consumption of highly processed foods, such as chips, crisps, biscuits and coffee, exposes the human to different doses of acrylamide. This chemical compound has a multidirectional, adverse effect on human and animal health, including the central and peripheral nervous systems. In this study, we examined the effect of different doses of acrylamide on the enteric nervous system (ENS) of the porcine jejunum. Namely, we took into account the quantitative changes of neurons located in the jejunum wall expressing substance P (SP), galanin (GAL), a neuronal form of nitric oxide synthase (nNOS), the vesicular acetylcholine transporter (VAChT) and cocaine- and amphetamine-regulated transcript (CART). The obtained results indicate that acrylamide causes a statistically significant increase in the number of neurons immunoreactive to SP, GAL, VAChT and CART in all types of examined enteric plexuses and a significant drop in the population of nNOS-positive enteric neurons. Changes were significantly greater in the case of a high dose of acrylamide intoxication. Our results indicate that acrylamide is not indifferent to ENS neurons. A 28-day intoxication with this substance caused marked changes in the chemical coding of ENS neurons in the porcine jejunum.

Developmental neurotoxicity of acrylamide and its metabolite glycidamide in a human mixed culture of neurons and astrocytes undergoing differentiation in concentrations relevant for human exposure

Neural stem cells (NSCs) derived from human induced pluripotent stem cells were used to investigate effects of exposure to the food contaminant acrylamide (AA) and its main metabolite glycidamide (GA) on key neurodevelopmental processes. Diet is an important source of human AA exposure for pregnant women, and AA is known to pass the placenta and the newborn may also be exposed through breast feeding after birth. The NSCs were exposed to AA and GA (1 ×10^-8 - 3 ×10^-3 M) under 7 days of proliferation and up to 28 days of differentiation towards a mixed culture of neurons and astrocytes. Effects on cell viability was measured using Alamar Blue™ cell viability assay, alterations in gene expression were assessed using real time PCR and RNA sequencing, and protein levels were quantified using immunocytochemistry and high content imaging. Effects of AA and GA on neurodevelopmental processes were evaluated using endpoints linked to common key events identified in the existing developmental neurotoxicity adverse outcome pathways (AOPs). Our results suggest that AA and GA at low concentrations (1 ×10^-7 - 1 ×10^-8 M) increased cell viability and markers of proliferation both in proliferating NSCs (7 days) and in maturing neurons after 14-28 days of differentiation. IC₅₀ for cell death of AA and GA was 5.2 × 10^-3 M and 5.8 × 10^-4 M, respectively, showing about ten times higher potency for GA. Increased expression of brain derived neurotrophic factor (BDNF) concomitant with decreased synaptogenesis were observed for GA exposure (10^-7 M) only at later differentiation stages, and an increased number of astrocytes (up to 3-fold) at 14 and 21 days of differentiation. Also, AA exposure gave tendency towards decreased differentiation (increased percent Nestin positive cells). After 28 days, neurite branch points and number of neurites per neuron measured by microtubule-associated protein 2 (Map2) staining decreased, while the same neurite features measured by βIII-Tubulin increased, indicating perturbation of neuronal differentiation and maturation.

Subchronic Acrylamide Exposure Activates PERK-eIF2α Signaling Pathway and Induces Synaptic Impairment in Rat Hippocampus

Acrylamide (ACR), a well-documented neurotoxicant to humans, is extensively found in starchy foods. More than 30% of the typical daily calorie intake comes from ACR-containing foods. Epidemiological and toxicological studies have found that ACR exposure is associated with mild cognitive change in men and experimental animals. However, there is limited information on the mechanisms by which ACR exposure induces memory deficits. The aberrant activation of the PKR-like ER kinase (PERK)-eukaryotic initiation factor 2α (eIF2α) signaling pathway is emerging as a major common theme in cognitive decline. The present study is designed to explore the effect of subchronic ACR exposure on the PERK signaling and the synaptic impairment to elucidate the potential mechanism of ACR-induced cognitive dysfunction in rat. ACR exposure at 5 and 10 (mg/kg)/day by gavage for 14 weeks results in gait abnormality and cognitive impairment in rats, which were accompanied by neuronal loss, glial cell proliferation, and synaptic ultrastructure damage in the hippocampus. ACR reduced the expression of phosphorylated cAMP response element-binding protein (P-CREB), brain-derived neurotrophic factor (BDNF), and synaptic vesicle proteins synapsin-1 and synaptophysin synthesis. ACR also excessively activates the PERK-eIF2α signaling, resulting in overexpression of C/EBP homologous protein (CHOP) and activating transcription factor 4 (ATF4). This work helps to propose a possible mechanism of subchronic exposure of ACR-induced neurotoxicity.

Di-n-butyl phthalate disrupts neuron maturation in primary rat embryo neurons and male C57BL/6 mice

Di-n-butyl phthalate (DBP) is commonly used as a plasticizer and its usage continues to increase in conjunction with plastic consumption. DBP is readily released into air, drinking water, and soil, and unfortunately, is a potent endocrine disrupter that impairs central nervous system functions. Previously DBP was found to (1) arrest the cell cycle of C17.2 neural progenitor cells (NPCs) at the G1 phase, (2) reduce numbers of newly generated neural stem cells in the mouse hippocampus, and (3) adversely affect learning and memory. Other investigators also noted DBP-mediated neurotoxic effects, but as yet, no study has addressed the adverse effects of DBP on neuronal differentiation. Data demonstrated that at 200 μM DBP induced apoptosis in rat embryo primary neurons by increasing reactive oxygen species levels and inducing mitochondrial dysfunction. However, no significant effect was detected on neurons at concentrations of ≤100 μM. In contrast, doublecortin/microtubule associated protein-2 (DCX/MAP2) immunocytochemistry showed that DBP at 100 μM delayed neuronal maturation by increasing protein levels of DCX (an immature neuronal marker), without markedly affecting cell viability. Further in vivo studies confirmed that DCX+ cell numbers were significantly elevated in the hippocampus of DBP-treated mice, indicating that DBP delayed neuronal maturation, which is known to be associated with impaired memory retention. Data demonstrated that DBP might disrupt neuronal maturation, which is correlated with reduced neurocognitive functions.

Paternal acrylamide exposure induces transgenerational effects on sperm parameters and learning capability in mice

Acrylamide (AA) has been shown to have neurological and reproductive toxicities, but little is known about transgenerational effects of AA. In this study, male C57BL/6 mice were exposed to AA (0.01, 1, 10 μg/mL) and its metabolite glycidamide (GA, 10 μg/mL) in drinking water, which were then mated with unexposed female mice to produce F1 and F2 generations. We found that both AA and GA at high concentrations decreased sperm motility in F0 mice and increased sperm malformation rates in mice from all the three generations. In addition, AA and GA increased sperm reactive oxygen species as well as decreased serum testosterone levels, and increased the escape latency time in exposed mice and their offspring. We further found that AA-induced mRNA expression changes in the hippocampus of F0 mice persist to the F2 generation. In the sperm of F0 mice, AA induced significant DNA methylation changes in genes involved in neural and reproduction; the mRNA expression levels of Dnmt3b, a DNA methyltransferase, were dramatically decreased in the testes of F0 and F1 mice. In conclusion, our study indicates that paternal AA exposure leads to DNA methylation-mediated transgenerational adverse effects on sperm parameters and leaning capability in mice.

Neuroprotective and Anti-Inflammatory Effects of Evernic Acid in an MPTP-Induced Parkinson's Disease Model

Oxidative stress, mitochondrial dysfunction, and neuroinflammation are strongly associated with the pathogenesis of Parkinson's disease (PD), which suggests that anti-oxidative and anti-inflammatory compounds might provide an alternative treatment for PD. Here, we evaluated the neuroprotective effects of evernic aid (EA), which was screened from a lichen library provided by the Korean Lichen Research Institute at Sunchon National University. EA is a secondary metabolite generated by lichens, including Ramalina, Evernia, and Hypogymnia, and several studies have described its anticancer, antifungal, and antimicrobial effects. However, the neuroprotective effects of EA have not been studied. We found that EA protected primary cultured neurons against 1-methyl-4-phenylpyridium (MPP+)-induced cell death, mitochondrial dysfunction, and oxidative stress, and effectively reduced MPP+-induced astroglial activation by inhibiting the NF-κB pathway. In vivo, EA ameliorated MPTP-induced motor dysfunction, dopaminergic neuronal loss, and neuroinflammation in the nigrostriatal pathway in C57BL/6 mice. Taken together, our findings demonstrate that EA has neuroprotective and anti-inflammatory effects in PD models and suggest that EA is a potential therapeutic candidate for PD.

Does the food processing contaminant acrylamide cause developmental neurotoxicity? A review and identification of knowledge gaps

There is a worldwide concern on adverse health effects of dietary exposure to acrylamide (AA) due to its presence in commonly consumed foods. AA is formed when carbohydrate rich foods containing asparagine and reducing sugars are prepared at high temperatures and low moisture conditions. Upon oral intake, AA is rapidly absorbed and distributed to all organs. AA is a known human neurotoxicant that can reach the developing foetus via placental transfer and breast milk. Although adverse neurodevelopmental effects have been observed after prenatal AA exposure in rodents, adverse effects of AA on the developing brain has so far not been studied in humans. However, epidemiological studies indicate that gestational exposure to AA impair foetal growth and AA exposure has been associated with reduced head circumference of the neonate. Thus, there is an urgent need for further research to elucidate whether pre- and perinatal AA exposure in humans might impair neurodevelopment and adversely affect neuronal function postnatally. Here, we review the literature with emphasis on the identification of critical knowledge gaps in relation to neurodevelopmental toxicity of AA and its mode of action and we suggest research strategies to close these gaps to better protect the unborn child.

Effect of Acrylamide Supplementation on the Population of Vasoactive Intestinal Peptide (VIP)-Like Immunoreactive Neurons in the Porcine Small Intestine

Acrylamide is one of the harmful substances present in food. The present study aimed to establish the effect of acrylamide supplementation in tolerable daily intake (TDI) dose (0.5 µg/kg b.w./day) and a dose ten times higher than TDI (5 µg/kg b.w./day) on the population of vasoactive intestinal peptide-like immunoreactive (VIP-LI) neurons in the porcine small intestine and the degree of the co-localization of VIP with other neuroactive substances (neuronal nitric oxide synthase (nNOS), substance P (SP), and cocaine- and amphetamine-regulated transcript peptide (CART)). In our work, 15 Danish landrace gilts (5 in each experimental group) received capsules (empty or with low or high doses of acrylamide) for a period of 28 days with their morning feeding. Using double immunofluorescence staining, we established that acrylamide supplementation increased the number of neurons showing immunoreactivity towards VIP in all types of enteric nervous system (ENS) plexuses and fragments of the small intestine studied. Moreover, both doses of acrylamide led to changes in the degree of co-localization of VIP with nNOS, SP, and CART in intramural neurons. The observed changes may be the adaptation of neurons to local inflammation, oxidative stress, or the direct toxic effects of acrylamide on intestinal neurons, also referred to as neuronal plasticity.

Acrylamide alters CREB and retinoic acid signalling pathways during differentiation of the human neuroblastoma SH-SY5Y cell line

Acrylamide (ACR) is a known neurotoxicant which crosses the blood–brain barrier, passes the placenta and has been detected in breast milk. Hence, early-life exposure to ACR could lead to developmental neurotoxicity. The aim of this study was to elucidate if non-cytotoxic concentrations of ACR alter neuronal differentiation by studying gene expression of markers significant for neurodevelopment in the human neuroblastoma SH-SY5Y cell model. Firstly, by using RNASeq we identified two relevant pathways that are activated during 9 days of retinoic acid (RA) induced differentiation i.e. RA receptor (RAR) activation and the cAMP response element-binding protein (CREB) signalling pathways. Next, by qPCR we showed that 1 and 70 µM ACR after 9 days exposure alter the expression of 13 out of 36 genes in the RAR activation pathway and 18 out of 47 in the CREB signalling pathway. Furthermore, the expression of established neuronal markers i.e. BDNF, STXBP2, STX3, TGFB1 and CHAT were down-regulated. Decreased protein expression of BDNF and altered ratio of phosphorylated CREB to total CREB were confirmed by western blot. Our results reveal that micromolar concentrations of ACR sustain proliferation, decrease neurite outgrowth and interfere with signalling pathways involved in neuronal differentiation in the SH-SY5Y cell model.

Exposure to acrylamide decreases noradrenergic axons in rat brain

PURPOSE

Acrylamide is known to induce disorders in the central nervous system in humans and experimental animals. The present study investigated effects of exposure to acrylamide on adult neurogenesis, noradrenergic axons and the level of norepinephrine in the brain of male rats.

METHOD

Four groups of 12 male Wistar rats each were exposed to acrylamide at 0, 0.2, 2 and 20 mg/kg body weight by gavage for 5 weeks. Six rats of each groups were injected with 5-bromo-2'-deoxy-uridine (BrdU) after five-week exposure to acrylamide to examine proliferative cells in the dentate gyrus using immunostaining. Density of noradrenergic and serotonergic axons in the prefrontal cortex, hippocampus and cortex behind the bregma was quantified. Remaining 6 rats were decapitated after the last exposure and brains were dissected out to measure monoamine level in the hippocampus and prefrontal cortex using high performance liquid chromatography.

RESULT

Exposure to acrylamide dose-dependently decreased the density of noradrenergic axons in the prefrontal cortex with a significant change at 20 mg/kg. Norepinephrine level decreased in the hippocampus at 20 mg/kg. Exposure to acrylamide at 20 mg/kg or less did not change the number of BrdU positive cells, but the result should be considered preliminary.

CONCLUSION

The results show that oral exposure to acrylamide induces decrease in noradrenergic axons and norepinephrine level in the brain of rats. Given the similar effects are observed in 1-bromopropane-exposed rats, there may be the common mechanism in the toxicity of soft electrophiles to the central nervous system.

Influence of Acrylamide Administration on the Neurochemical Characteristics of Enteric Nervous System (ENS) Neurons in the Porcine Duodenum

The digestive tract, especially the small intestine, is one of the main routes of acrylamide absorption and is therefore highly exposed to the toxic effect of acrylamide contained in food. The aim of this experiment was to elucidate the effect of low (tolerable daily intake—TDI) and high (ten times higher than TDI) doses of acrylamide on the neurochemical phenotype of duodenal enteric nervous system (ENS) neurons using the pig as an animal model. The experiment was performed on 15 immature gilts of the Danish Landrace assigned to three experimental groups: control (C) group—pigs administered empty gelatine capsules, low dose (LD) group—pigs administered capsules with acrylamide at the TDI dose (0.5 μg/kg body weight (b.w.)/day), and the high dose (HD) group—pigs administered capsules with acrylamide at a ten times higher dose than the TDI (5 μg/kg b.w./day) with a morning feeding for 4 weeks. Administration of acrylamide, even in a low (TDI) dose, led to an increase in the percentage of enteric neurons immunoreactive to substance P (SP), calcitonin gene-related peptide (CGRP), galanin (GAL), neuronal nitric oxide synthase (nNOS), and vesicular acetylcholine transporter (VACHT) in the porcine duodenum. The severity of the changes clearly depended on the dose of acrylamide and the examined plexus. The obtained results suggest the participation of these neuroactive substances in acrylamide-inducted plasticity and the protection of ENS neurons, which may be an important line of defence from the harmful action of acrylamide.

Acrylamide aggravates cognitive deficits at night period via the gut-brain axis by reprogramming the brain circadian clock

Imbalance of the circadian rhythm leads to pathologies including obesity, neurodegenerative diseases, and even cancer. Acrylamide (ACR) is a chronic neurotoxin which can lead to carcinogenicity, reproduction toxicity, teratogenicity, and neurotoxicity. The aim of this study was to reveal a potential mechanism of ACR-triggered neurotoxicity related to circadian clock in mice brain. For this purpose, 80 3-month-old C57/BL6J mice were randomly divided into two groups (n = 40/group): the control group was fed a standard diet (AIN-93M) with pure water, and the ACR group was fed a standard diet (AIN-93M) with 0.003% ACR in drinking water for 16 weeks. In the current study, ACR treatment induced circadian disorder and suppressed the circadian-related protein expressions in mice brain. Furthermore, ACR diet aggravated the cognitive dysfunction and spatial memory loss at night phase. Consistent with these results, ACR caused cognitive defects in the night period by down-regulating the ERK/cAMP response element-binding protein (CREB)/brain-derived neurotrophic factor (BDNF) signaling pathways and the expression of synaptosomal-related protein SNAP-25 and PSD-95. Moreover, excessive autophagy phenomenon also occurred in mice hippocampus in the night phase under ACR administration. Of note, ACR stimulated the brain inflammatory reaction via affecting the intestinal barrier integrity and increasing the levels of circulating LPS, IL-1β and TNF-α. Above all, the present research discovered that ACR is a potential circadian-depressing compound that influences cognitive function in mice brain.

MAPKs and NF-κB-mediated acrylamide-induced neuropathy in rat striatum and human neuroblastoma cells SY5Y

Acrylamide (ACR) is a potent neurotoxin that can be produced during high-temperature food processing, but the underlying toxicological mechanism remains unclear. In this study, the detrimental effects of ACR on the striatal dopaminergic neurons and the roles of mitogen-activated protein kinases (MAPKs) and nuclear factor κB (NF-κB) in ACR-induced neuronal apoptosis were investigated. Acute ACR exposure caused dopaminergic neurons loss and apoptosis as revealed by decreased tyrosine hydroxylase (TH)-positive cells and TH protein level and increased terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive cells in the striatum. ACR-decreased glutathione content, increased levels of malondialdehyde, proinflammatory cytokines tumor necrosis factor α, and interleukin 6. In addition, nuclear NF-κB and MAPKs signaling pathway with c-Jun N-terminal kinase (JNK) and p38 were activated by ACR. Specific inhibitors were used to explore the roles of MAPKs and NF-κB pathways in ACR-induced apoptosis in SH-SY5Y cells. Pretreatment with JNK-specific inhibitors SP600125 markedly upregulated the reduced B-cell lymphoma 2 (Bcl-2) content and downregulated the increased Bcl-2-associated X protein (Bax) level and thereby eventually reduced the proportions of early and late apoptotic cells induced by ACR, while p38 suppression by SB202190 only reversed the decrease in Bcl-2 expression. Inhibition of NF-κB by BAY 11-7082 markedly upregulated Bax level and decreased Bcl-2 expression, and eventually increasing the proportions of neuronal apoptosis compared with that in ACR alone. These results suggested that JNK contributed to ACR-induced apoptosis, while NF-κB acted as a protective regulator in response to ACR-induced neuropathy. This study helps to offer a deeper insight into the mechanism of ACR-induced neuropathy.