Acrylamide induces locomotor defects and degeneration of dopamine neurons in Caenorhabditis elegans

Levels of Amyloid Beta (Aβ) Expression in the Caenorhabditis elegans Neurons Influence the Onset and Severity of Neuronally Mediated Phenotypes

A characteristic feature of Alzheimer's disease (AD) is the formation of neuronal extracellular senile plaques composed of aggregates of fibrillar amyloid β (Aβ) peptides, with the Aβ1-42 peptide being the most abundant species. These Aβ peptides have been proposed to contribute to the pathophysiology of the disease; however, there are few tools available to test this hypothesis directly. In particular, there are no data that establish a dose-response relationship between Aβ peptide expression level and disease. We have generated a panel of transgenic Caenorhabditis elegans strains expressing the human Aβ1-42 peptide under the control of promoter regions of two pan-neuronal expressed genes, snb-1 and rgef-1. Phenotypic data show strong age-related defects in motility, subtle changes in chemotaxis, reduced median and maximum lifespan, changes in health span indicators, and impaired learning. The Aβ1-42 expression level of these strains differed as a function of promoter identity and transgene copy number, and the timing and severity of phenotypes mediated by Aβ1-42 were strongly positively correlated with expression level. The pan-neuronal expression of varying levels of human Aβ1-42 in a nematode model provides a new tool to investigate the in vivo toxicity of neuronal Aβ expression and the molecular and cellular mechanisms underlying AD progression in the absence of endogenous Aβ peptides. More importantly, it allows direct quantitative testing of the dose-response relationship between neuronal Aβ peptide expression and disease for the first time. These strains may also be used to develop screens for novel therapeutics to treat Alzheimer's disease.

Polymer chain extenders induce significant toxicity through DAF-16 and SKN-1 pathways in Caenorhabditis elegans: A comparative analysis

Polymer chain extenders, commonly used in plastic production, have garnered increasing attention due to their potential environmental impacts. However, a comprehensive understanding of their ecological risks remains largely unknown. In this study, we employed the model organism Caenorhabditis elegans to investigate toxicological profiles of ten commonly-used chain extenders. Exposure to environmentally relevant concentrations of these chain extenders (ranging from 0.1 µg L-1 to 10 mg L-1) caused significant variations in toxicity. Lethality assays demonstrated the LC50 values ranged from 92.42 µg L-1 to 1553.65 mg L-1, indicating marked differences in acute toxicity. Sublethal exposures could inhibit nematodes' growth, shorten lifespan, and induce locomotor deficits, neuronal damage, and reproductive toxicity. Molecular analyses further elucidated the involvement of the DAF-16 and SKN-1 signaling pathways, as evidenced by upregulated expression of genes including ctl-1,2,3, sod-3, gcs-1, and gst-4. It implicates these pathways in mediating oxidative stress and toxicities induced by chain extenders. Particularly, hexamethylene diisocyanate and diallyl maleate exhibited markedly high toxicity among the chain extenders, as revealed through a comparative analysis of multiple endpoints. These findings demonstrate the potential ecotoxicological risks of polymer chain extenders, and suggest the need for more rigorous environmental safety assessments.

Can the concentration of environmentally persistent free radicals describe its toxicity to Caenorhabditis elegans? Evidence provided by neurotoxicity and oxidative stress

Environmentally persistent free radicals (EPFRs) are emerging pollutants stabilized on or inside particles. Although the toxicity of EPFR-containing particles has been confirmed, the conclusions are always ambiguous because of the presence of various compositions. A clear dose-response relationship was always challenged by the fact that the concentrations of these coexisted components simultaneously changed with EPFR concentrations. Without these solid dose-response pieces of evidence, we could not confidently conclude the toxicity of EPFRs and the description of potential EPFR risks. In this study, we established a particle system with a fixed catechol concentration but different reaction times to obtain particles with different EPFR concentrations. Caenorhabditis elegans (C. elegans) in response to different EPFR concentrations was systematically investigated at multiple biological levels, including behavior observations and biochemical and transcriptome analyses. Our results showed that exposure to EPFRs disrupted the development and locomotion of C. elegans. EPFRs cause concentration-dependent neurotoxicity and oxidative damage to C. elegans, which could be attributed to reactive oxygen species (ROS) promoted by EPFRs. Furthermore, the expression of key genes related to neurons was downregulated, whereas antioxidative genes were upregulated. Overall, our results confirmed the toxicity from EPFRs and EPFR concentration as a rational parameter to describe the extent of toxicity.

PIEZO mediates a protective mechanism for nematode Caenorhabditis elegans in response to nanoplastics caused dopaminergic neurotoxicity at environmentally relevant concentrations

Studies have probed nanoplastic toxicity on environmental organisms, but the regulatory role of animal PIEZO-type mechanosensitive ion channel component (PIEZO) remains unclear. Herein, we identified the sole PIEZO in Caenorhabditis elegans (C. elegans), utilizing amino acid homology analysis and Trans-Membrane prediction using Hidden Markov Models (TMHMM). In C. elegans, RNAi knockdown of pezo-1 had no impact on lifespan, body length, lethality, locomotion behaviors, or oxidative response (P > 0.05). However, exposure to 15 μg/L nanopolystyrene in the pezo-1 RNAi group resulted in severe locomotion changes: head trashes (P < 0.01), body bends (P < 0.05), forward turns (P < 0.05), backward turns (P < 0.01), and impaired sensory perception, including abnormal chemotaxis to NaCl (P < 0.01) and diacetyl (P < 0.01), as well as aversive responses (P < 0.05) to nanopolystyrene compared to the wild-type group. Dopaminergic neuron damage explains these behaviors, with GST-4 (P < 0.01) and SKN-1/Nrf2 (P < 0.01) activation mitigating nanoplastic-induced damage. Our results emphasize that even at the environmentally relevant concentrations (ERC), nanoplastics can impact neurotoxicity-related endpoints, with PIEZO mediating the regulation of oxidative and antioxidative systems in response to these effects. PIEZO may be applied for assessing the neurotoxicity or oxidative stress induced by other environmental toxicants besides nanoplastics.

Disruption of dopamine metabolism by exposure to 6-PPD quinone in Caenorhabditis elegans

Caenorhabditis elegans is a useful model for examining metabolic processes and related mechanisms. We here examined the effect of exposure to N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6-PPDQ) on dopamine metabolism and underling molecular basis in nematodes. The dopamine content was reduced by 6-PPDQ (1 and 10 μg/L). Meanwhile, dopamine related behaviors (basal slowing response and area restricted searching) were changed by 6-PPDQ (1 and 10 μg/L). Exposure to 6-PPDQ (1 and 10 μg/L) decreased expressions of genes (cat-2 and bas-1) encoding enzymes governing dopamine synthesis and cat-1 encoding dopamine transporter. Development of dopaminergic neurons was also affected by 10 μg/L 6-PPDQ as reflected by decrease in fluorescence intensity, neuronal loss, and defect in dendrite development. Exposure to 6-PPDQ (1 and 10 μg/L) altered expressions of ast-1 and rcat-1 encoding upregulators of cat-2 and bas-1. The dopamine content and expressions of cat-2 and bas-1 were inhibited by RNAi of ast-1 and increased by RNAi of rcat-1 in 6-PPDQ exposed nematodes. Using endpoints of locomotion behavior and brood size, in 6-PPDQ exposed nematodes, the susceptibility to toxicity was caused by RNAi of ast-1, cat-2, bas-1, and cat-1, and the resistance to toxicity was induced by RNAi of rcat-1. Therefore, 6-PPDQ exposure disrupted dopamine metabolism and the altered molecular basis for dopamine metabolism was associated with 6-PPDQ toxicity induction. Moreover, the defects in dopamine related behaviors and toxicity on locomotion and reproduction could be rescued by treatment with 0.1 mM dopamine.

Toxicity, formation, contamination, determination and mitigation of acrylamide in thermally processed plant-based foods and herbal medicines: A review

Thermal processing is one of the important techniques for most of the plant-based food and herb medicines before consumption and application in order to meet the specific requirement. The plant and herbs are rich in amino acids and reducing sugars, and thermal processing may lead to Maillard reaction, resulting as a high risk of acrylamide pollution. Acrylamide, an organic pollutant that can be absorbed by the body through the respiratory tract, digestive tract, skin and mucous membranes, has potential carcinogenicity, neurological, genetic, reproductive and developmental toxicity. Therefore, it is significant to conduct pollution determination and risk assessment for quality assurance and security of medication. This review demonstrates state-of-the-art research of acrylamide focusing on the toxicity, formation, contamination, determination, and mitigation in taking food and herb medicine, to provide reference for scientific processing and ensure the security of consumers.

Automated recognition and analysis of body bending behavior in C. elegans

BACKGROUND

Locomotion behaviors of Caenorhabditis elegans play an important role in drug activity screening, anti-aging research, and toxicological assessment. Previous studies have provided important insights into drug activity screening, anti-aging, and toxicological research by manually counting the number of body bends. However, manual counting is often low-throughput and takes a lot of time and manpower. And it is easy to cause artificial bias and error in counting results.

RESULTS

In this paper, an algorithm is proposed for automatic counting and analysis of the body bending behavior of nematodes. First of all, the numerical coordinate regression method with convolutional neural network is used to obtain the head and tail coordinates. Next, curvature-based feature point extraction algorithm is used to calculate the feature points of the nematode centerline. Then the maximum distance between the peak point and the straight line between the pharynx and the tail is calculated. The number of body bends is counted according to the change in the maximum distance per frame.

CONCLUSION

Experiments are performed to prove the effectiveness of the proposed algorithm. The accuracy of head coordinate prediction is 0.993, and the accuracy of tail coordinate prediction is 0.990. The Pearson correlation coefficient between the results of the automatic count and manual count of the number of body bends is 0.998 and the mean absolute error is 1.931. Different strains of nematodes are selected to analyze differences in body bending behavior, demonstrating a relationship between nematode vitality and lifespan. The code is freely available at https://github.com/hthana/Body-Bend-Count .

Recent advances in the removal of emerging contaminants from water by novel molecularly imprinted materials in advanced oxidation processes-A review

Recently, there has been a global focus on effectively treating emerging contaminants (ECs) in water bodies. Advanced oxidation processes (AOPs) are the primary technology used for ECs removal. However, the low concentrations of ECs make it difficult to overcome the interference of background substances in complex water quality, which limits the practical application of AOPs. To address this limitation, many researchers are developing new catalysts with preferential adsorption. Molecular imprinting technology (MIT) combined with conventional catalysts has been found to effectively enhance the selectivity of catalysts for the targeted catalytic degradation of pollutants. This review presents a comprehensive summary of the progress made in research on molecularly imprinted polymers (MIPs) in the selective oxidation of ECs in water. The preparation methods, principles, and control points of novel MIP catalysts are discussed. Furthermore, the performance and mechanism of the catalysts in photocatalytic oxidation, electrocatalytic oxidation, and persulfate activation are analyzed with examples. The possible ecotoxicological risks of MIP catalysts are also discussed. Finally, the challenges and prospects of applying MIP catalysts in AOP are presented along with proposed solutions. This review provides a better understanding of using MIP catalysts in AOPs to target the degradation of ECs.

Acrylamide induces the activation of BV2 microglial cells through TLR2/4-mediated LRRK2-NFATc2 signaling cascade

Acrylamide (ACR), a potential neurotoxin, is generated from the Maillard reaction between reducing sugars and free amino acids during food processing. Our work focuses on clarifying the role of the leucine-rich repeat kinase 2 (LRRK2) and nuclear factor of activated T cells, cytoplasmic 2 (NFATc2) in the polarization of BV2 cells to the M1 proinflammatory type induced by ACR. Specifically, ACR promoted the phosphorylation of LRRK2 and NFATc2 in BV2 microglia. Furthermore, selectively phosphorylated LRRK2 by ACR induced nuclear translocation of NFATc2 to trigger a neuroinflammatory cascade. Knock-down of LRRK2 by silencing significantly diminished ACR-induced microglial neurotoxic effect with the decline of IL-1β, IL-6, and iNOS levels and the decrease of NFATc2 expression in BV2 cells. After pretreated with Toll-Like Receptor 2 (TLR2) and TLR4 inhibitors separately, both the activation of LRRK2 and the release of pro-inflammatory factors were inhibited in BV2 cells. Gallic acid (GA) is ubiquitous in most parts of the medicinal plant. GA alleviated the increased CD11b expression, IL-6 and iNOS levels induced by ACR in BV2 microglia. In conclusion, this study shows that ACR leads to the cascade activation of LRRK2-NFATc2 mediated by TLR2 and TLR4 to induce microglial toxicity.

Molecular determinants of acrylamide neurotoxicity through covalent docking

Acrylamide (ACR) is formed during food processing by Maillard reaction between sugars and proteins at high temperatures. It is also used in many industries, from water waste treatment to manufacture of paper, fabrics, dyes and cosmetics. Unfortunately, cumulative exposure to acrylamide, either from diet or at the workplace, may result in neurotoxicity. Such adverse effects arise from covalent adducts formed between acrylamide and cysteine residues of several neuronal proteins via a Michael addition reaction. The molecular determinants of acrylamide reactivity and its impact on protein function are not completely understood. Here we have compiled a list of acrylamide protein targets reported so far in the literature in connection with neurotoxicity and performed a systematic covalent docking study. Our results indicate that acrylamide binding to cysteine is favored in the presence of nearby positively charged amino acids, such as lysines and arginines. For proteins with more than one reactive Cys, docking scores were able to discriminate between the primary ACR modification site and secondary sites modified only at high ACR concentrations. Therefore, docking scores emerge as a potential filter to predict Cys reactivity against acrylamide. Inspection of the ACR-protein complex structures provides insights into the putative functional consequences of ACR modification, especially for non-enzyme proteins. Based on our study, covalent docking is a promising computational tool to predict other potential protein targets mediating acrylamide neurotoxicity.

Neurotoxicity of bisphenol A exposure on Caenorhabditis elegans induced by disturbance of neurotransmitter and oxidative damage

Bisphenol A (BPA) is putatively regarded as an environmental neurotoxicant found in everyday plastic products and materials, however, the possible neurobehavioral adverse consequences and molecular mechanisms in animals have not been clearly characterized. The nematode Caenorhabditis elegans has become a promising animal model for neurotoxicological researches. To investigate the dose-effect relationships of BPA-induced neurotoxicity effects, the locomotion behavior and developmental parameters of the nematode were determined after BPA exposure. The present data demonstrated that BPA caused neurobehavioral toxicities, including head thrashes and body bends inhibition. In addition, when C. elegans was exposed to BPA at a concentration higher than 2 μM, growth and survival rate were decreased. The serotonergic, dopaminergic and GABAergic neurons were damaged by BPA. Furthermore, lower levels of mRNA expression related to dopamine, serotonin and GABA were detected in the worms exposed to 50 μM BPA. Increased SOD-3 expression might be adaptive response to BPA exposure. Moreover, oxidative damage triggered by BPA was manifested by changes in GST-4 expression, accompany with abnormity of ATP synthesis, but not nuclear localization of DAF-16/FOXO. Finally, we showed that epigallocatechin-3-gallate partially rescued BPA-induced reactive oxygen species (ROS) production and neurobehavioral toxicity. Altogether, the neurobehavioral and developmental toxicity of BPA may be induced by neurotransmission abnormity and oxidative damage. The present data imply that oxidative stress is linked to neuronal damage and neurobehavioral harm resulting from developmental BPA exposure.

The role of additives on acrylamide formation in food products: a systematic review

Acrylamide (AA) is a toxic substance formed in many carbohydrate-rich food products, whose formation can be reduced by adding some additives. Furthermore, the type of food consumed determines the AA intake. According to the compiled information, the first route causing AA formation is the Maillard reaction. Some interventions, such as reducing AA precursors in raw materials, (i.e., asparagine), reducing sugars, or decreasing temperature and processing time can be applied to limit AA formation in food products. The L-asparaginase is more widely used in potato products. Also, coatings loaded with proteins, enzymes, and phenolic compounds are new techniques for reducing AA content. Enzymes have a reducing effect on AA formation by acting on asparagine; proteins by competing with amino acids to participate in Maillard, and phenolic compounds through their radical scavenging activity. On the other hand, some synthetic and natural additives increase the formation of AA. Due to the high exposure to AA and its toxic effects, it is essential to recognize suitable food additives to reduce the health risks for consumers. In this sense, this study focuses on different additives that are proven to be effective in the reduction or formation of AA in food products.

Cardiotoxicity and neurobehavioral effects induced by acrylamide in Daphnia magna

Acrylamide has neurotoxic and/or cardiotoxic effects on humans however available information regarding the neuro- and cardiotoxicity currently is very limited for freshwater organism models. Using three distinct techniques, thus, we investigated the neuro- and cardiotoxic effects of acrylamide in the freshwater invertebrate model, Daphnia magna. We exposed D. magna to acrylamide at concentrations of 0.3, 2.7, and 11.1 mg/L for 48 h alongside a control group. We then conducted physiological (thoracic limb activity and heart rate) and behavioral tests (including distance moved, velocity, turn angle, moving duration, the distance between subjects, and body contact frequency), as well as gene transcription analyses (related to cardiomyopathy, the serotonergic synapse, neuroactive ligand-receptor interactions, the GABAergic synapse, and acetylcholine receptors). After acrylamide exposure, the thoracic limb activity and heart rates of D. magna showed time- and dose dependent inhibition. From low to high exposure concentrations, both heart rates and thoracic limb activity were decreased. Additionally, the distance between subjects and body contact frequencies was significantly reduced. At the gene transcription level, acrylamide significantly altered the transcription of five genes related to cardiomyopathy and eight genes related to the serotonergic synapse, neuroactive ligand-receptor interactions, and the GABAergic synapse. The signs of hindered neural and cardiac functions were shown in D. magna. This suggests that acrylamide exposure leads to cardiotoxicity and neurobehavior defects in D. magna. Because cardiotoxicity and neurobehavioral changes may cause an ecological imbalance via predation of D. magna, acrylamide may also be considered a threat to freshwater ecosystem.

Acrylamide-induced damage to postsynaptic plasticity is CYP2E1 dependent in an SH-SY5Y co-culture system

Acrylamide (ACR), a neurotoxic substance, is characterized by a range of industrial and population exposures. The effects of ACR on synapses have been examined, but the regulation and molecular mechanism of key proteins related to ACR and its metabolite glycidamide (GA) have not been elucidated. In this study, we constructed two co-culture systems to mimic neurons that do not express and overexpress CYP2E1. In these co-cultures, we observed the effects and relative influence of ACR and GA on cell survival as well as synaptic structural and functional plasticity. Next, we investigated the relationship between ACR-induced nerve damage and key proteins in the postsynaptic membrane. After ACR exposure, cell death and synaptic damage were significantly worse in CYP2E1-overexpressing co-culture systems, suggesting that ACR-induced neurotoxicity may be related to metabolic efficiency (including CYP2E1 activity). Moreover, with increasing doses of ACR, the key postsynaptic membrane proteins PSD-95 expression was reduced and CaMKII and NMDAR-2B phosphorylation was increased. ACR exposure also triggered a rapid dose- and time-dependent increase in intracellular Ca²⁺, whose changes can affect the expression of the above-mentioned key proteins. In summary, we clarified the relationship between ACR exposure, neuronal damage and postsynaptic plasticity and proposed an ACR-CYP2E1-GA: Ca²⁺-PSD-95-NMDAR-Ca²⁺-CaMKII effect chain. This information will further improve the development of an alternative pathway strategy for investigating the risk posed by ACR.

Chronic di(2-ethylhexyl) phthalate exposure leads to dopaminergic neuron degeneration through mitochondrial dysfunction in C. elegans

The plasticizer di(2-ethylhexyl) phthalate (DEHP) is frequently detected in the environment due to the abundance of its use. These levels might be hazardous to human health and ecosystems. Phthalates have been associated with neurological disorders, yet whether chronic DEHP exposure plays a role in Parkinson's disease (PD) or its underlying mechanisms is unknown. We investigated the effects of chronic DEHP exposure less than an environmentally-relevant dose on PD hallmarks, using Caenorhabditis elegans as a model. We show that developmental stage and exposure timing influence DEHP-induced dopaminergic neuron degeneration. In addition, in response to chronic DEHP exposure at 5 mg/L, mitochondrial fragmentation became significantly elevated, reactive oxygen species (ROS) levels increased, and ATP levels decreased, suggesting that mitochondrial dysfunction occurs. Furthermore, the data show that mitochondrial complex I (nuo-1 and gas-1) and complex II (mev-1) are involved in DEHP-induced dopaminergic neuron toxicity. These results suggest that chronic exposure to DEHP at levels less than an environmentally-relevant dose causes dopaminergic neuron degeneration through mitochondrial dysfunction involving mitochondrial complex I and II. Considering the high level of genetic conservation between C. elegans and mammals, chronic DEHP exposure might elevate the risk of developing PD in humans.

Chronic acrylamide exposure resulted in dopaminergic neuron loss, neuroinflammation and motor impairment in rats

Acrylamide (ACR) as a by-product of Maillard reaction is widely present in food. Although ACR is known to exhibit neurotoxicity, most studies about ACR neurotoxicity are currently short-term high-dose providing limited reference value for human exposure. The present study aims to determine the effects of chronic ACR exposure on dopaminergic neurons in rat nigra and the potential mechanism from the perspective of NLRP3 inflammasome-mediated neuroinflammation. The SD rats were maintained on treated drinking water providing dosages of 0, 0.5, or 5 mg/kg/day ACR for 12 months. ACR exposure caused motor dysfunction in rats, which was associated with dopaminergic neuron loss, α-Synuclein (α-Syn) accumulation and decreased brain-derived neurotrophic factor (BDNF) in nigra. ACR activated microglia by increasing Iba-1⁺, Iba-1⁺CD68⁺ positive cells and the percentage of ameboid-shaped ones in rat nigra. ACR markedly upregulated the protein levels of NLRP3 inflammasome constituents NLRP3 and caspase-1 and inflammatory cytokine IL-1β. ACR chronic exposure increased the risk of Parkinson's disease (PD) like dopaminergic neuron depletion in nigra potentially through NLRP3 inflammasome-mediated neuroinflammtion.

Abnormal neurotransmission of GABA and serotonin in Caenorhabditis elegans induced by Fumonisin B1

Fumonisin B1 (FB1) is a neurodegenerative mycotoxin synthesized by Fusarium spp., but the potential neurobehavioral toxicity effects in organisms have not been characterized clearly. Caenorhabditis elegans (C. elegans) has emerged as a promising model organism for neurotoxicological studies due to characteristics such as well-functioning nervous system and rich behavioral phenotypes. To investigate whether FB1 has neurobehavioral toxicity effects on C. elegans, the motor behavior, neuronal structure, neurotransmitter content, and gene expression related with neurotransmission of C. elegans were determined after exposed to 20-200 μg/mL FB1 for 24 h and 48 h, respectively. Results showed that FB1 caused behavioral defects, including body bends, head thrashes, crawling distance, mean speed, mean amplitude, mean wavelength, foraging behavior, and chemotaxis learning ability in a dose-, and time-dependent manner. In addition, when C. elegans was exposed to FB1 at a concentration of 200 μg/mL for 24 h and above 100 μg/mL for 48 h, the GABAergic and serotonergic neurons were damaged, but no effect on dopaminergic, glutamatergic, and cholinergic neurons. The relative content of GABA and serotonin decreased significantly. Furthermore, abnormal expression of mRNA levels associated with GABA and serotonin were found in nematodes treated with FB1, such as unc-30, unc-47, unc-49, exp-1, mod-5, cat-1, and tph-1. The neurobehavioral toxicity effect of FB1 may be mediated by abnormal neurotransmission of GABA and serotonin. This study provides useful information for understanding the neurotoxicity of FB1.

Glutamatergic transmission associated with locomotion-related neurotoxicity to lindane over generations in Caenorhabditis elegans

Organochlorine pesticide lindane in the environment and biota results in the potential risks on ecosystem and human health. Lindane can adversely affect the locomotion and nervous system, yet the potential neurotoxicity of lindane over generations remains uncertain. In this study, the neurotoxicity and underlying mechanisms in Caenorhabditis elegans (C. elegans) were investigated after parental (P0) exposure to lindane at environmentally relevant concentrations over generations. Exposure to lindane at concentrations of 10-100 ng/L significantly decreased body bends and head thrashes in P0 generation. Significant decrease of fluorescence labeled different neurotransmitters, and clear morphological changes by exposure to lindane at 10-100 ng/L suggested that lindane could induce the neuronal damage in C. elegans. During the transgenerational process, decreased locomotive behaviors were also observed in F1-F3 generations, and head thrashes returned to normal levels in F4 generation. Moreover, lindane exposure down-regulated the expression of dat-1, dop-1, glr-1 and mod-1genes, while up-regulated unc-30 gene in P0 generation, which recovered to normal levels in F4 generation. Interestingly, eat-4 continued to be regulated from inhibition to stimulation in P0-F4 generations, suggesting that glutamatergic transmission may more contribute to the neurotoxicity of lindane over generations.

Lipidome reveals the alleviation of krill oil on the impairment of acrylamide

Krill oil has rich content of polyunsaturated fatty acids and various biological functions. Previous researches have demonstrated that krill oil is helpful to improve the locomotion via antioxidation and regulation...

Effects of lanthanum nitrate on behavioral disorder, neuronal damage and gene expression in different developmental stages of Caenorhabditis elegans

Rare earth elements (REEs) are widely used in the industry, agriculture, biomedicine, aerospace, etc, and have been shown to pose toxic effects on animals, as such, studies focusing on their biomedical properties are gaining wide attention. However, environmental and population health risks of REEs are still not very clear. Also, the REEs damage to the nervous system and related molecular mechanisms needs further research. In this study, the L1 and L4 stages of the model organism Caenorhabditis elegans were used to evaluate the effects and possible neurotoxic mechanism of lanthanum(III) nitrate hexahydrate (La(NO₃)₃·6H₂O). For the L1 and L4 stage worms, the 48-h median lethal concentrations (LC₅₀s) of La(NO₃)₃·6H₂O were 93.163 and 648.0 mg/L respectively. Our results show that La(NO₃)₃·6H₂O induces growth inhibition and defects in behavior such as body length, body width, body bending frequency, head thrashing frequency and pharyngeal pumping frequency at the L1 and L4 stages in C. elegans. The L1 stage is more sensitive to the toxicity of lanthanum than the L4 stage worms. Using transgenic strains (BZ555, EG1285 and NL5901), we found that La(NO₃)₃·6H₂O caused the loss or break of soma and dendrite neurons in L1 and L4 stages; and α-synuclein aggregation in L1 stage, indicating that Lanthanum can cause toxic damage to dopaminergic and GABAergic neurons. Mechanistically, La(NO₃)₃·6H₂O exposure inhibited or activated the neurotransmitter transporters and receptors (glutamate, serotonin and dopamine) in C. elegans, which regulate behavior and movement functions. Furthermore, significant increase in the production of reactive oxygen species (ROS) was found in the L4 stage C. elegans exposed to La(NO₃)₃·6H₂O. Altogether, our data show that exposure to lanthanum can cause neuronal toxic damage and behavioral defects in C. elegans, and provide basic information for understanding the neurotoxic effect mechanism and environmental health risks of rare earth elements.

Caenorhabditis elegans to Model the Capacity of Ascorbic Acid to Reduce Acute Nitrite Toxicity under Different Feed Conditions: Multivariate Analytics on Behavioral Imaging

Nitrocompounds are present in the environment and human diet and form part of vegetables and processed meat products as additives. These compounds are related to negative impacts on human and animal health. The protective effect of ascorbic acid has been demonstrated by some biological systems as regards several nitrocompounds. This work focused on studying the possibility of modeling this effect on nitrite toxicity with the model Caenorhabditis elegans. The three factors studied in this work were ascorbic acid concentration, nitrite exposure concentration, and presence/absence of food. The protective effect was evaluated by scoring lethality and its impact on behavior by means of multivariate statistical methods and imaging analytics. The effects of nitrite and the influence of food availability were evidenced. Apart from increasing lethality, nitrite had disruption effects on movements. All the observed symptoms reduced when ascorbic acid was administered, and it diminished lethality in all cases. Ascorbic acid maintained nematodes' postural capacities. The results suggest that nitrites' nonspecific toxicity in C. elegans can be mitigated by ascorbic acid, as previously evidenced in other biological systems. Thus, our results reveal the ability of C. elegans to reproduce the known protective effect of ascorbic acid against nitrite.

Trans-generational effect of neurotoxicity and related stress response in Caenorhabditis elegans exposed to tetrabromobisphenol A

Tetrabromobisphenol A (TBBPA), one of the most common brominated flame retardants, has been associated with immunotoxicity, neurotoxicity, and reproductive toxicity. However, little attention has been focused on understanding the trans-generational effects of TBBPA. The present study used the Caenorhabditis elegans (C. elegans) animal model to evaluate the trans-generational effects of neurotoxicity induced by environmentally relevant concentrations of TBBPA (0, 0.1, 1, 10, 100, and 1000 µg/L). Multiple indicators including physiological effects (body length, brood size, head thrashes, body bends, and crawling trajectory), degree of neuronal damage (dopamine, GABAergic, and glutamatergic neurons), oxidative stress-related biochemical indicators (superoxide dismutase [SOD] activity, catalase [CAT] enzyme, malondialdehyde [MDA] production, and reactive oxygen species [ROS] accumulation), and stress-related gene expressions have been evaluated in the exposed parental C. elegans generation (G₁) and their progeny (G₂) under TBBPA-free conditions. The results showed that TBBPA exposure induced adverse effects on physiological endpoints, among which body bends and head thrashes were the most sensitive ones, detected above 1 µg/L in G₁ and 100 µg/L in G₂ nematodes, respectively. After contaminant exposure, the three neurons revealed damage related to neurobehavioral endpoints, with no hereditary effects in the progeny. The oxidative stress-related biochemical endpoints demonstrated that when the exposure concentrations were above 1 µg/L in maternal worms, impairment can be detected in both generations, but the progeny recovered at low toxicity concentration (1-100 µg/L). The integrated target gene expression profiles were clearly altered in G₁ and G₂ worms at concentrations between 1 and 1000 µg/L, and a more significant difference existed in two generations of nematodes at low levels (1-10 µg/L) of TBBPA. Studing trans-generational neurotoxicity and the underlying mechanism can generate a precise evaluation of the environmental risk of TBBPA.

NLRP3 inflammasome inhibition attenuates subacute neurotoxicity induced by acrylamide in vitro and in vivo

Acrylamide (AA) constitutes an important industrial chemical agent and well-known neurotoxin. However, the mechanism underlying AA-mediated neurotoxicity is extremely complicated and controversial. In this study, we found that activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome and its subsequent downstream inflammatory responses plays an important role in AA-induced neurotoxicity mechanisms. In vitro experiments revealed that AA (2.5 mM) induced BV2 microglial cytotoxicity and triggered NLRP3 inflammasome activation along with downstream proinflammatory cytokine interleukin-1β and interleukin-18 expression. Treatment with inhibitor or NLRP3 siRNA efficiently protected BV2 microglial cells against AA-induced cytotoxicity and reversed NLRP3 inflammasome activation and its mediated inflammatory reaction. Similarly, AA exposure (50 mg/kg) for 10 consecutive days caused significant activation of NLRP3 inflammasomes and neuroinflammation in C57BL/6 mice, whereas inhibiting these effects through specific NLRP3 inflammasome blocker MCC950 (5 mg/kg) intervention or NLRP3 knock-out significantly ameliorated AA-induced ataxia, cerebellar Purkinje cells degeneration, and apoptosis. Furthermore, we demonstrated that antagonism of NLRP3 could also up-regulate the Nrf2 signalling pathway and related antioxidant genes. In conclusion, our findings indicate that activation of the NLRP3 inflammasome pathway is involved in AA-induced neurotoxicity, whereas MCC950 treatment or NLRP3 knock-out could effectively protect against AA-induced neurotoxic injury through the inhibition of neuroinflammation and activation of the Nrf2 antioxidant pathway. Therefore, the NLRP3 inflammasome might serve as a promising therapeutic target, with drugs designed to specifically inhibit this pathway potentially providing new avenues for preventing or ameliorating AA poisoning.

Neuron-specific toxicity of chronic acrylamide exposure in C. elegans

Acrylamide is a food-borne chemical with well-known neurotoxic properties. To date, the toxicity mechanisms of chronic acrylamide exposure are not fully understood. Using the genetic model Caenorhabditis elegans, we found that chronic acrylamide exposure induces a locomotor defect that is characterized by severe uncoordination of muscle movement that is distinct from an overall reduction in activity. C. elegans exhibiting chronic acrylamide-induced locomotor defects show significant degeneration to the dopaminergic and cholinergic, but not GABAergic motor neurons. Degeneration of the dopaminergic and cholinergic neurons are found in 58% to 67% of C. elegans after chronic acrylamide exposure, with the varying degrees of severity ranging from neuronal blebbing to complete dendrite loss. The observed pattern of neurotoxicity does not have a heritable effect, as parental exposure to chronic acrylamide does not lead to neurodegeneration in the developed offspring. Overall, these finding illustrate that chronic acrylamide exposure cause locomotor defects by inducing degeneration of specific neuron types in C. elegans.

Single and simultaneous effects of acrylamide and ethanol on bone microstructure of mice after one remodeling cycle

Background

This study aimed to examine femoral bone microstructure of mice after single and simultaneous administration to acrylamide and ethanol since both substances are often consumed separately and/or together by humans. Interactive effects of these toxins were analysed after one remodeling cycle.

Methods

Twenty clinically healthy adult mice were randomly divided into four groups following 2 weeks administration of toxins: A group - mice were fed with acrylamide (40 mg/kg bw); E group - mice were ethanol-fed (15% ethanol); AE group - mice were simultaneously fed with both toxins, and a C group – control (without acrylamide and/or ethanol supplementation). Generally, 2D and 3D imaging methods were used to determine cortical and trabecular bone tissues microstructure. Biochemical analyses of plasma parameters were also realized using commercially available ELISA tests and spectrophotometrically.

Results

Single and simultaneous exposure to acrylamide and ethanol affected only cortical bone microstructure. No significant changes in trabecular bone morphometry were detected among all groups. In mice from the A group, increased endocortical remodeling associated with a higher level of serum calcium and vasoconstriction of primary osteon’s vascular canals (POVC) were identified. On the contrary, increased cortical porosity consistent with a decreased relative bone volume, bone mineral density (BMD) and lower levels of alkaline phosphatase (ALP), glutathione (GSH), calcium in plasma and also with vasodilation of POVC were observed in the E group. In the AE group, the highest density of secondary osteons associated with a lower BMD and decreased levels of ALP, GSH were documented. The parameters of POVC and Haversian canals approximated to the C group. In addition, single and simultaneous exposure to both toxins caused liver disease consistent with a higher values of alanine aminotransferase (ALT), aspartate aminotransferase (AST) in plasma of all experimental groups.

Conclusions

Single administration to acrylamide and ethanol had negative effects on cortical bone structure of mice after one remodeling cycle. However, we identified possible antagonistic impact of these toxins on the structure of the cortical bone.

Impact of nuclear distribution element genes in the typical and atypical antipsychotics effects on nematode Caenorhabditis elegans: Putative animal model for studying the pathways correlated to schizophrenia

The nuclear distribution element genes are conserved from fungus to humans. The nematode Caenorhabditis elegans expresses two isoforms of nuclear distribution element genes, namely nud-1 and nud-2. While nud-1 was functionally demonstrated to be the worm nudC ortholog, bioinformatic analysis revealed that the nud-2 gene encodes the worm ortholog of the mammalian NDE1 (Nuclear Distribution Element 1 or NudE) and NDEL1 (NDE-Like 1 or NudEL) genes, which share overlapping roles in brain development in mammals and also mediate the axon guidance in mammalian and C. elegans neurons. A significantly higher NDEL1 enzyme activity was shown in treatment non-resistant compared to treatment resistant SCZ patients, who essentially present response to the therapy with atypical clozapine but not with typical antipsychotics. Using C. elegans as a model, we tested the consequence of nud genes suppression in the effects of typical and atypical antipsychotics. To assess the role of nud genes and antipsychotic drugs over C. elegans behavior, we measured body bend frequency, egg laying and pharyngeal pumping, which traits are controlled by specific neurons and neurotransmitters known to be involved in SCZ, as dopamine and serotonin. Evaluation of metabolic and behavioral response to the pharmacotherapy with these antipsychotics demonstrates an important unbalance in serotonin pathway in both nud-1 and nud-2 knockout worms, with more significant effects for nud-2 knockout. The present data also show an interesting trend of mutant knockout worm strains to present a metabolic profile closer to that observed for the wild-type animals after the treatment with the typical antipsychotic haloperidol, but which was not observed for the treatment with the atypical antipsychotic clozapine. Paradoxically, behavioral assays showed more evident effects for clozapine than for haloperidol, which is in line with previous studies with rodent animal models and clinical evaluations with SCZ patients. In addition, the validity and reliability of using this experimental animal model to further explore the convergence between the dopamine/serotonin pathways and neurodevelopmental processes was demonstrated here, and the potential usefulness of this model for evaluating the metabolic consequences of treatments with antipsychotics is also suggested.

Neuroprotective Effects of Betulin in Pharmacological and Transgenic Caenorhabditis elegans Models of Parkinson's Disease

Parkinson’s disease (PD) is the second most common degenerative disorder of the central nervous system in the elderly. It is characterized by progressive loss of dopaminergic neurons in the substantia nigra pars compacta, as well as by motor dysfunction. Although the causes of PD are not well understood, aggregation of α-synuclein (α-syn) in neurons contributes to this disease. Current therapeutics for PD provides satisfactory symptom relief but not a cure. Treatment strategies include attempts to identify new drugs that will prevent or arrest the progressive course of PD by correcting disease-specific pathogenic process. Betulin is derived from the bark of birch trees and possesses anticancer, antimicrobial, and anti-inflammatory properties. The aim of the present study was to evaluate the potential for betulin to ameliorate PD features in Caenorhabditis elegans (C. elegans) models. We demonstrated that betulin diminished α-syn accumulation in the transgenic C. elegans model. Betulin also reduced 6-hydroxydopamine-induced dopaminergic neuron degeneration, reduced food-sensing behavioral abnormalities, and reversed life-span decreases in a pharmacological C. elegans model. Moreover, we found that the enhancement of proteasomes activity by promoting rpn1 expression and downregulation of the apoptosis pathway gene, egl-1, may be the molecular mechanism for betulin-mediated protection against PD pathology. Together, these findings support betulin as a possible treatment for PD and encourage further investigations of betulin as an antineurodegenerative agent.

Biosafety assessment of water samples from Wanzhou watershed of Yangtze Three Gorges Reservior in the quiet season in Caenorhabditis elegans

We here employed a model animal of Caenorhabditis elegans to perform toxicity assessment of original surface water samples collected from Three Gorges Reservoir (TGR) in the quiet season in Wanzhou, Chongqing. Using some sublethal endpoints, including lifespan, body length, locomotion behavior, brood size, and intestinal reactive oxygen species (ROS) induction, we found that the examined five original surface water samples could not cause toxicity on wild-type nematodes. Nevertheless, the surface water sample collected from backwater area induced the significant increase in expressions of genes (sod-2 and sod-3) encoding Mn-SODs in wild-type nematodes. Among the examined five original surface water samples, exposure to the original surface water sample collected from backwater area could further cause the toxicity in decreasing locomotion behavior and in inducing intestinal ROS production in sod-3 mutant nematodes. Moreover, the solid phase of surface water sample collected from backwater area might mainly contribute to the observed toxicity in sod-3 mutant nematodes. Our results are helpful for understanding the potential effects of surface water in the TGR region in the quiet season on environmental organisms.

Insights on the age dependent neurodegeneration induced by Monocrotophos, (an organophosphorous insecticide) in Caenorhabditis elegans fed high glucose: Evidence in wild and transgenic strains

The higher susceptibility of high glucose fed C. elegans to Monocrotophos (MCP, an organophosphorus insecticide) - induced dopaminergic (DA) neuronal degeneration was recently demonstrated. Employing this acute exposure model, the impact of MCP on DA degeneration among worms of two age groups (8 and 13 d old) fed control (CO) and high glucose (GF) diet with specific focus on phenotypic alterations, oxidative impairments and associated molecular perturbations employing both wild (N2) and transgenic strains(BZ555 and NL5901) was investigated. In general, 13 d worms exhibited higher susceptibility to MCP intoxication compared to 8 d old worms. Further, MCP-exposure caused an enhanced degree of DA degeneration among glucose fed (GF) worms as evidenced by lower chemotaxis index, reduced long-term memory and increased nonanone repulsion. Biochemical analysis of 13 d GF worms also revealed a significant increase in ROS, protein carbonyls and reduced ADP/ATP ratio. Interestingly, marked increase in degeneration of dopaminergic neurons and increased in α-synuclein content was evident among 13 d GF worms exposed to MCP. Significant alterations in the mRNA expression levels of daf-2, age-1, sir 2.1 and aak-2 among 13 d GF worms was evident. Collectively these findings suggest that high intake of glucose diet aggravates MCP associated dopaminergic neuronal degeneration and the impact of increasing age under such a condition. Moreover it provides an experimental paradigm to explore the molecular targets and mechanism/s underlying the possible relationship between insecticide exposure-associated dopaminergic degeneration in humans under hyperglycemic conditions.

Mutation of hop-1 and pink-1 attenuates vulnerability of neurotoxicity in C. elegans: the role of mitochondria-associated membrane proteins in Parkinsonism

Mitochondrial dysfunction is considered as a critical mechanism in the pathogenesis of Parkinson's disease (PD). Increasing evidence supports the notion of mitochondria-associated membranes (MAMs) in mitochondrial dysfunction; yet little is known about the role of MAMs-related proteins in the pathogenesis of PD. Herein we exposed the nematode Caenorhabditis elegans to 0.5-10.0 μM rotenone (RO) or 0.2-1.6 mM paraquat (PQ) for 3 days. Our results showed that both RO and PQ induced similar Parkinsonism including motor deficits and dopaminergic degeneration. RO/PQ caused mitochondrial damages characterized by the increase of vacuole areas and autophagy vesicles, but the decrease of mitochondrial cristae. RO/PQ-impacted mitochondrial function was also demonstrated by the decrease of ATP level and mitochondrial membrane potential. Additionally, the attachment or surrounding of endoplasmic reticulum to the damaged mitochondria indicates ultrastructural alterations in MAMs. Using fluorescently labeled transgenic nematodes, we further found that the expression of tomm-7 and genes of Complex I, II and III was reduced, whereas the expression of pink-1 was increased in the exposed animals. To determine MAMs in toxicity toward PD, we investigated the mutants of hop-1 and pink-1, encoding presenilin and PTEN-induced putative kinase 1 (PINK1) in mitochondria-associated membranes, respectively. Results demonstrated that the mutation of both hop-1 and pink-1 reduced the vulnerability of lethal, behavioral, and mitochondrial toxicity induced by RO/PQ. These findings suggest that presenilin and PINK1 play important roles in the RO/PQ-induced neurotoxicity through the mechanisms involved in mitochondria-associated membranes.

Microplastic particles cause intestinal damage and other adverse effects in zebrafish Danio rerio and nematode Caenorhabditis elegans

Microplastics have been frequently detected in aquatic environments, and there are increasing concerns about potential effects on biota. In this study, zebrafish Danio rerio and nematode Caenorhabditis elegans were used as model organisms for microplastic exposure in freshwater pelagic (i.e. water column) and benthic (i.e. sediment) environments. We investigated the toxic effects of five common types of microplastics: polyamides (PA), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC) and polystyrene (PS) particles. Results showed no or low lethality in D. rerio after exposure for 10d at 0.001-10.0mgL^-1 microplastics. The PA, PE, PP and/or PVC microplastics with ~70μm size caused intestinal damage including cracking of villi and splitting of enterocytes. Exposure to 5.0mgm^-2 microplastics for 2d significantly inhibited survival rates, body length and reproduction of C. elegans. Moreover, exposure to microplastics reduced calcium levels but increased expression of the glutathione S-transferase 4 enzyme in the intestine, which indicates intestinal damage and oxidative stress are major effects of microplastic exposure. Among 0.1, 1.0 and 5.0μm sizes of fluorescently labeled PS, 1.0μm particles caused the highest lethality, the maximum accumulation, the lowest Ca²⁺ level in the intestine and the highest expression of glutathione S-transferase 4 in nematodes. Taken together, these findings suggest that intestinal damage is a key effect of microplastics; and that the toxicity of microplastics is closely dependent on their size, rather than their composition.

Agro Waste Utilization for Cost-Effective Production of l-Asparaginase by Pseudomonas plecoglossicida RS1 with Anticancer and Acrylamide Mitigation Potential

Agricultural wastes such as the peels of onion and garlic were used as a supplement along with l-asparagine for the very first time to produce increased yield of l-asparaginase by Pseudomonas plecoglossicida RS1. Statistical optimization strategies such as response surface methodology were used to generate a medium composition containing extracts of 0.9 (v/v) of garlic peel waste and 0.5% (v/v) onion peel waste along with 0.2% (w/w) l-asparagine, which yielded a twofold increase in the enzyme activity compared to the unsupplemented minimal (M-9) medium. The presence of l-asparagine content in the peel extract was confirmed by high-performance liquid chromatography. Further, l-asparaginase was purified to homogeneity, and identity was confirmed by matrix-assisted laser desorption ionization time-of-flight analysis. The application of the purified l-asparaginase as a therapeutic was studied in HeLa cells which showed a p53-mediated G₂ cell cycle arrest. Moreover, the purified l-asparaginase showed effective acrylamide mitigation in vitro, at 6 IU, and its effective degradation was also demonstrated by the effect on chemotactic index of Caenorhabditis elegans and the restoration of the cognitive abilities of C. elegans which was coexposed to acrylamide and l-asparaginase compared to that exposed to acrylamide alone. Thus, l-asparaginase, with multipotent applications, was produced by effective waste utilization for economical commercial production.

Modulation of Alpha-synuclein Expression and Associated Effects by MicroRNA Let-7 in Transgenic C. elegans

Neurodegenerative Parkinson’s disease (PD) is a multi-factorial disorder lacking complete cure. Understanding the complete mechanism of initiation and progression of this disease has been quite challenging; however, progress has been made toward deciphering certain genetic aspects related to the disease condition. Genetics studies have provided clues toward the role of microRNAs (miRNAs) in various disease conditions. One of the crucial miRNA molecules, let-7, is highly conserved miRNA and is known to regulate important functions of development and viability; its altered expression has been reported in C. elegans model of PD. We carried out studies with let-7, employing transgenic C. elegans model expressing ‘human’ alpha-synuclein and developed a let-7 loss-of-function model toward studying the downstream effects related to PD. We observed that let-7 miRNA was upregulated in C. elegans model of PD and figured that loss of let-7 miRNA leads to decreased alpha-synuclein expression, increased autophagy, increased Daf-16 expression, increased oxidative stress and increased lipid content with no effect on dopaminergic/acetylcholinergic neurons. Our findings indicate that let-7 miRNA regulates PD-associated pathways. Our study provides insight toward the role of let-7 in regulating expression of genes associated with these pathways which might have implications on the multi-factorial nature of PD. Potential pharmacological agents modulating the expression of let-7 could be studied toward targeting the multi-factorial aspect of PD.

Acrylamide-induced changes in femoral bone microstructure of mice

Acrylamide (AA) is one of the most common toxins in foods. Its effect on bone microstructure has not been investigated. The aim of our study was to analyze the impact of acute exposure to AA on femoral bone microstructure in mice. Adult animals were treated perorally with 2 doses of AA (E1 group, 1 mg/kg b.w.) in a 24-h period and with 3 doses of AA (E2 group, 1 mg/kg b.w.) in a 48-h period. Mice exposed to AA had smaller sizes of primary osteon's vascular canals. Secondary osteons were significantly smaller in mice from E2 group; however their increased number (from 38 % to 77 %) was identified in both E1 and E2 groups. In these groups, a higher number of resorption lacunae (from 100 % to 122 %) was also found. The values for bone volume, trabecular number were increased and that for trabecular separation was decreased in mice administered AA. Significantly higher value of bone surface was observed in mice from E1 group whereas trabecular thickness was increased in E2 group. The effect of AA on microstructure of compact and trabecular bone tissues is different. In our study, one dose of AA was used and acute effects of AA were investigated. Therefore, further studies are needed to study mechanisms by which AA acts on bone.

A colour preference technique to evaluate acrylamide-induced toxicity in zebrafish

The zebrafish has become a commonly used vertebrate model for toxicity assessment, of particular relevance to the study of toxic effects on the visual system because of the structural similarities shared by zebrafish and human retinae. In this article we present a colour preference-based technique that, by assessing the functionality of photoreceptors, can be used to evaluate the effects of toxicity on behaviour. A digital camera was used to record the locomotor behaviour of individual zebrafish swimming in a water tank consisting of two compartments separated by an opaque perforated wall through which the fish could pass. The colour of the lighting in each compartment could be altered independently (producing distinct but connected environments of white, red or blue) to allow association of the zebrafish's swimming behaviour with its colour preference. The functionality of the photoreceptors was evaluated based on the ability of the zebrafish to sense the different colours and to swim between the compartments. The zebrafish tracking was carried out using our algorithm developed with MATLAB. We found that zebrafish preferred blue illumination to white, and white illumination to red. Acute treatment with acrylamide (2mM for 36h) resulted in a marked reduction in locomotion and a concomitant loss of colour-preferential swimming behaviour. Histopathological examination of acrylamide-treated zebrafish eyes showed that acrylamide exposure had caused retinal damage. The colour preference tracking technique has applications in the assessment of neurodegenerative disorders, as a method for preclinical appraisal of drug efficacy and for behavioural evaluation of toxicity.

Behavioral deficits and neural damage of Caenorhabditis elegans induced by three rare earth elements

Rare earth elements (REEs) are widely used in industry, agriculture, medicine and daily life in recent years. However, environmental and health risks of REEs are still poorly understood. In this study, neurotoxicity of trichloride neodymium, praseodymium and scandium were evaluated using nematode Caenorhabditis elegans as the assay system. Median lethal concentrations (48 h) were 99.9, 157.2 and 106.4 mg/L for NdCl₃, PrCl₃ and ScCl₃, respectively. Sublethal dose (10-30 mg/L) of these trichloride salts significantly inhibited body length of nematodes. Three REEs resulted in significant declines in locomotor frequency of body bending, head thrashing and pharyngeal pumping. In addition, mean speed and wavelength of crawling movement were significantly reduced after chronic exposure. Using transgenic nematodes, we found NdCl₃, PrCl₃ and ScCl₃ resulted in loss of dendrite and soma of neurons, and induced down-expression of dat-1::GFP and unc-47::GFP. It indicates that REEs can lead to damage of dopaminergic and GABAergic neurons. Our data suggest that exposure to REEs may cause neurotoxicity of inducing behavioral deficits and neural damage. These findings provide useful information for understanding health risk of REE materials.

Behavioral Phenotyping and Pathological Indicators of Parkinson's Disease in C. elegans Models

Parkinson's disease (PD) is a neurodegenerative disorder with symptoms that progressively worsen with age. Pathologically, PD is characterized by the aggregation of α-synuclein in cells of the substantia nigra in the brain and loss of dopaminergic neurons. This pathology is associated with impaired movement and reduced cognitive function. The etiology of PD can be attributed to a combination of environmental and genetic factors. A popular animal model, the nematode roundworm Caenorhabditis elegans, has been frequently used to study the role of genetic and environmental factors in the molecular pathology and behavioral phenotypes associated with PD. The current review summarizes cellular markers and behavioral phenotypes in transgenic and toxin-induced PD models of C. elegans.

Chronic exposure to graphene-based nanomaterials induces behavioral deficits and neural damage in Caenorhabditis elegans

Nanomaterials of graphene and its derivatives have been widely applied in recent years, but whose impacts on the environment and health are still not well understood. In the present study, the potential adverse effects of graphite (G), graphite oxide nanoplatelets (GO) and graphene quantum dots (GQDs) on the motor nervous system were investigated using nematode Caenorhabditis elegans as the assay system. After being characterized using TEM, SEM, XPS and PLE, three nanomaterials were chronically exposed to C. elegans for 6 days. In total, 50-100 mg l^-1 GO caused a significant reduction in the survival rate, but G and GDDs showed low lethality on nematodes. After chronic exposure of sub-lethal dosages, three nanomaterials were observed to distribute primarily in the pharynx and intestine; but GQDs were widespread in nematode body. Three graphene-based nanomaterials resulted in significant declines in locomotor frequency of body bending, head thrashing and pharynx pumping. In addition, mean speed, bending angle-frequency and wavelength of the crawling movement were significantly reduced after exposure. Using transgenic nematodes, we found high concentrations of graphene-based nanomaterials induced down-expression of dat-1::GFP and eat-4::GFP, but no significant changes in unc-47::GFP. This indicates that graphene-based nanomaterials can lead to damages in the dopaminergic and glutamatergic neurons. The present data suggest that chronic exposure of graphene-based nanomaterials may cause neurotoxicity risks of inducing behavioral deficits and neural damage. These findings provide useful information to understand the toxicity and safe application of graphene-based nanomaterials. Copyright © 2017 John Wiley & Sons, Ltd.

Can coffee consumption lower the risk of Alzheimer's disease and Parkinson's disease? A literature review

In light of the fact that the number of elderly citizens in society is steadily increasing, the search for dietary factors which might prolong mental agility is growing in significance. Coffee, together with its main ingredient, caffeine, has been the focus of much attention from various researchers, as data on its beneficial effects on human health continue to accumulate. Most reports indicate that moderate coffee consumption may in fact lower the risk for common neurodegenerative conditions, i.e. Alzheimer's and Parkinson's diseases. Regardless, due to their complex pathogenesis as well as methodology of scientific research, the exact impact of coffee consumption remains to be fully elucidated. At present, it seems safe to inform the general public that coffee drinkers need not fear for their health. Possibly, in the future experts will recommend drinking coffee not only to satisfy individual taste preferences but also to decrease age-related mental deterioration.

F-Box Protein XREP-4 Is a New Regulator of the Oxidative Stress Response in Caenorhabditis elegans

The transcription factor SKN-1 (Skinhead family member-1) in Caenorhabditis elegans is a homolog of the mammalian Nrf-2 protein and functions to promote oxidative stress resistance and longevity. SKN-1 mediates protection from reactive oxygen species (ROS) via the transcriptional activation of genes involved in antioxidant defense and phase II detoxification. Although many core regulators of SKN-1 have been identified, much remains unknown about this complex signaling pathway. We carried out an ethyl methanesulfonate (EMS) mutagenesis screen and isolated six independent mutants with attenuated SKN-1-dependent gene activation in response to acrylamide. All six were found to contain mutations in F46F11.6/xrep-4 (xenobiotics response pathways-4), which encodes an uncharacterized F-box protein. Loss of xrep-4 inhibits the skn-1-dependent expression of detoxification genes in response to prooxidants and decreases survival of oxidative stress, but does not shorten life span under standard culture conditions. XREP-4 interacts with the ubiquitin ligase component SKR-1 and the SKN-1 principal repressor WDR-23, and knockdown of xrep-4 increases nuclear localization of a WDR-23::GFP fusion protein. Furthermore, a missense mutation in the conserved XREP-4 F-box domain that reduces interaction with SKR-1 but not WDR-23 strongly attenuates SKN-1-dependent gene activation. These results are consistent with XREP-4 influencing the SKN-1 stress response by functioning as a bridge between WDR-23 and the ubiquitin ligase component SKR-1.

Tris(2-chloroethyl) phosphate (TCEP) and tris(2-chloropropyl) phosphate (TCPP) induce locomotor deficits and dopaminergic degeneration in Caenorhabditis elegans

Organophosphate flame retardants (PFRs) are a new class of flame retardants. The health risks of PFRs have received attention recently. However, little is known about the potential toxicity of PFRs on the nervous system. Herein, we evaluated the neurotoxic effects of two typical PFRs, tris(2-chloroethyl) phosphate (TCEP) and tris(2-chloropropyl) phosphate (TCPP), using Caenorhabditis elegans. Median lethal concentrations of chronic exposure (3 d) were 1578 and 857 mg L-1 for TCEP and TCPP, respectively. The sublethal dose of TCEP or TCPP significantly inhibited the body length and reduced the lifespans of nematodes. 500 mg L-1 and above of TCEP/TCPP led to a significant decline in the locomotor frequency of body bending and head thrashing. Furthermore, their exposure reduced the crawling speed and the frequency of bending oscillation of nematodes. This indicates that TCEP/TCPP induces locomotor deficits, along with Parkinsonian-like movement impairment including bradykinesia and hypokinesia. Using transgenic worms, we found that TCEP/TCPP could induce down-expression of P dat-1 and resulted in the degeneration of dopaminergic neurons, especially PDE neurons. Moreover, TCEP/TCPP induced over-expression of unc-54, which indicates the aggregation of α-synuclein in the process of degeneration. These findings suggest the neurotoxicity risks of organophosphorus flame retardants, which are associated with the locomotor deficits and dopaminergic degeneration.

Freshwater Planarians as an Alternative Animal Model for Neurotoxicology

Traditional toxicology testing has relied on low-throughput, expensive mammalian studies; however, timely testing of the large number of environmental toxicants requires new in vitro and in vivo platforms for inexpensive medium- to high-throughput screening. Herein, we describe the suitability of the asexual freshwater planarian Dugesia japonica as a new animal model for the study of developmental neurotoxicology. As these asexual animals reproduce by binary fission, followed by regeneration of missing body structures within approximately 1 week, development and regeneration occur through similar processes allowing us to induce neurodevelopment "at will" through amputation. This short time scale and the comparable sizes of full and regenerating animals enable parallel experiments in adults and developing worms to determine development-specific aspects of toxicity. Because the planarian brain, despite its simplicity, is structurally and molecularly similar to the mammalian brain, we are able to ascertain neurodevelopmental toxicity that is relevant to humans. As a proof of concept, we developed a 5-step semiautomatic screening platform to characterize the toxicity of 9 known neurotoxicants (consisting of common solvents, pesticides, and detergents) and a neutral agent, glucose, and quantified effects on viability, stimulated and unstimulated behavior, regeneration, and brain structure. Comparisons of our findings with other alternative toxicology animal models, such as zebrafish larvae and nematodes, demonstrated that planarians are comparably sensitive to the tested chemicals. In addition, we found that certain compounds induced adverse effects specifically in developing animals. We thus conclude that planarians offer new complementary opportunities for developmental neurotoxicology animal models.