Phenotypic and behavioral defects induced by iron exposure can be transferred to progeny in Caenorhabditis elegans

Ferrostatin-1 mitigates cellular damage in a ferroptosis-like environment in Caenorhabditis elegans

Although iron (Fe) is the most biologically abundant transition metal, it is highly toxic when it accumulates as Fe2+, forming a labile Fe pool and favoring the Fenton reaction. This oxidative scenario leads to a type of caspase-independent programmed cell death, referred to as ferroptosis, where following processes take place: (i) Fe2+ overload, (ii) glutathione peroxidase 4 inactivation, (iii) lipid peroxidation, and (iv) glutathione depletion. The present study sought to evaluate the consequences of Fe2+ administration on ferroptosis induction in Caenorhabditis elegans. We demonstrated higher mortality, increased lipid peroxidation, reduced glutathione peroxidase activity, and morphological damage in dopaminergic neurons upon Fe2+ overload. Pharmacological intervention at the level of lipid peroxidation with ferrostatin-1 (250 μM) mitigated the damage and returned the biochemical parameters to basal levels, revealing the potential of this therapeutical approach. Finally, to assess the relationship between ferroptosis and dopamine in a Parkinsonian background, we evaluated the UA44 worm strain which overexpresses the alpha-synuclein protein in cherry-labeled dopaminergic neurons. We demonstrated that Fe2+ administration reduced lethality associated with similar alterations in biochemical and dopaminergic morphological parameters in wild-type animals. These experiments provide mechanistic-based evidence on the efficacy of a pharmacological approach to mitigate the physiological, biochemical, and morphological consequences of Fe2+ overload. At the same time, they encourage further research on the impact of the combined effects resulting from the genetic background and dopamine signaling in a Parkinsonian phenotype.

Impaired Physiological Responses and Neurotoxicity Induced by a Chlorpyrifos-Based Formulation in Caenorhabditis elegans are not Solely Dependent on the Active Ingredient

The current massive and indiscriminate agrochemicals usage, which is inexorably linked to the toxic consequences to the environment and people, represents a great concern. Our work aimed to compare the toxicity induced by chlorpyrifos in its pure form (CPF) with that of a commercial formulation containing allegedly inert ingredients (CBCF) using Caenorhabditis elegans as in vivo model. After a 48h exposure period, CBCF was 14 times more lethal than CPF; Hatching, brood size, body length and motor-related behavioral parameters were decreased, but these effects were significantly higher in CBCF-exposed worms. Additionally, CBCF induced significant morphological changes in cholinergic neurons, which are associated with the motor-related behavioral parameters. Finally, by analyzing the CBCF, were detected the presence of potentially-toxic metals that were not specified in the label. The presented results highlight the toxicological relevance of components present in the commercial formulations of pesticides, which have been claimed as inert compounds.

Ecotoxicity induced by total, water soluble and insoluble components of atmospheric fine particulate matter exposure in Caenorhabditis elegans

Although PM_2.5 could cause toxicity in environmental organisms, the toxicity difference of PM_2.5 under different solubilities is still poorly understood. To acquire a better knowledge of the ecotoxicity of PM_2.5 under different solubilities, the model animal Caenorhabditis elegans (C. elegans) was exposed to Total-PM_2.5, water insoluble components of PM_2.5 (WIS-PM_2.5) and water soluble components of PM_2.5 (WS-PM_2.5). The physiological (growth, locomotion behavior, and reproduction), biochemical (germline apoptosis, and reactive oxygen species (ROS) production) indices, and the related gene expression were examined. According to the findings, acute exposure to these three components caused adverse physiological effects on growth and locomotion behavior, and significantly induced germline apoptosis or ROS production. In contrast, prolonged exposure showed stronger adverse effects than acute exposure. Additionally, the results of multiple toxicological endpoints showed that the toxicity effects of WIS-PM_2.5 are more intense than WS-PM_2.5, which means that insoluble components contributed more to the toxicity of PM_2.5. Prolonged exposure to 1000 mg/L WS-PM_2.5, WIS-PM_2.5, and Total-PM_2.5 dramatically altered the expression of stress-related genes, which further indicated that apoptosis, DNA damage and oxidative stress play a crucial part in toxicity induced by PM_2.5.

A review of transgenerational and multigenerational toxicology in the in vivo model animal Caenorhabditis elegans

A large number of pollutants existing in the environment can last for a long time, and their potential toxic effects can transfer from parents to their offspring. Thus, it is necessary to investigate the toxicity of environmental pollutants across multigenerations and the underlying mechanisms in organisms. Due to its short life cycle and sensitivity to environmental exposures, Caenorhabditis elegans is an important animal model for toxicity assessment of environmental pollutants across multigenerations. In this review, we introduced the transgenerational and multigenerational toxicity caused by various environmental pollutants in C. elegans. Moreover, we discussed the underlying mechanisms for the observed transgenerational and multigenerational toxicity of environmental contaminants in C. elegans.

Reproductive toxicity and underlying mechanisms of fine particulate matter (PM2.5) on Caenorhabditis elegans in different seasons

Although numerous studies have investigated that atmospheric fine particulate matter (PM_2.5) can be toxic to environmental organisms, the research on the reproductive toxicity of PM_2.5 is limited, and the key toxic components and underlying mechanisms remain unknown. In this work, PM_2.5 samples of four seasons in Nanjing from March 1, 2021, to February 28, 2022 were collected and the chemical components were analyzed. Caenorhabditis elegans (C. elegans) was employed to conduct the toxicological testing. The reproductive toxicity of PM_2.5 to C. elegans in different seasons was evaluated by multiple reproductive endpoints. Exposure to high concentrations of PM_2.5 significantly decreased the brood size and the number of fertilized eggs in utero. PM_2.5 exposure also increased the number of germ cell corpses and caused abnormal expression of apoptosis-related genes (ced-9, ced-4, and ced-3), which confirmed that PM_2.5 induced germline apoptosis. In addition, PM_2.5 exposure significantly increased the production of reactive oxygen species (ROS) in C. elegans and the fluorescence intensity of HUS-1 protein in of transgenic strain WS1433. Meanwhile, the expression of genes related to DNA damage (cep-1, clk-2, egl-1, and hus-1) and oxidative stress (mev-1, isp-1, and gas-1) also significantly altered in C. elegans, suggesting induction of DNA damage and oxidative stress. According to Pearson correlation analyses, DNA damage and oxidative stress were significantly correlated with multiple reproductive endpoints in C. elegans. Thus, it was speculated that PM_2.5 caused reproductive dysfunction and germ cell apoptosis in C. elegans may be by inducing ROS and DNA damage. In addition, heavy metals in PM_2.5 were significantly correlated with multiple endpoints at physiological and biochemical, suggesting that the heavy metals might be an important contributor to the reproductive toxicity induced by PM_2.5.

L-threonine promotes healthspan by expediting ferritin-dependent ferroptosis inhibition in C. elegans

The pathways that impact longevity in the wake of dietary restriction (DR) remain still ill-defined. Most studies have focused on nutrient limitation and perturbations of energy metabolism. We showed that the L-threonine was elevated in Caenorhabditis elegans under DR, and that L-threonine supplementation increased its healthspan. Using metabolic and transcriptomic profiling in worms that were fed with RNAi to induce loss of key candidate mediators. L-threonine supplementation and loss-of-threonine dehydrogenaseincreased the healthspan by attenuating ferroptosis in a ferritin-dependent manner. Transcriptomic analysis showed that FTN-1 encoding ferritin was elevated, implying FTN-1 is an essential mediator of longevity promotion. Organismal ferritin levels were positively correlated with chronological aging and L-threonine supplementation protected against age-associated ferroptosis through the DAF-16 and HSF-1 pathways. Our investigation uncovered the role of a distinct and universal metabolite, L-threonine, in DR-mediated improvement in organismal healthspan, suggesting it could be an effective intervention for preventing senescence progression and age-induced ferroptosis.

Iron overload and neurodegenerative diseases: What can we learn from Caenorhabditis elegans?

Iron (Fe) is an essential trace element required for several physiological processes. It plays important roles in mitochondrial function, synthesis, and metabolism of the neurotransmitter, as well as oxygen transport. However, excess Fe can cause toxicity. Particularly, Fe overload may result in neurotoxicity, contributing to the development and progression of neurodegenerative diseases, although the molecular mechanisms underlying Fe-induced neurodegeneration have yet to be entirely understood. Alternative (non-rodent) experimental models have been pointed as important approaches to elucidate molecular and physiological events mediating Fe-induced pathology. Among such alternative strategies, an advantageous experimental worm-model system, Caenorhabditis elegans ( C. elegans), has been used to investigate Fe-induced neurotoxicity and neurodegenerative disorders. Its genome has been fully sequenced, corroborating that it shares significant homology with mammalians, and has approximately 40% of human disease-related genes. As part of this review, we discuss studies using the C. elegans model to study molecular mechanisms such as oxidative stress, mitochondrial dysfunction, disturbed homeostasis, and its potential contribution to the study of metal-induced neurodegenerative diseases such as Parkinson’s disease (PD) and Alzheimer’s disease (AD).

Metal contamination and toxicity of soils and river sediments from the world's largest platinum mining area

Mining activities in the world's largest platinum mining area in South Africa have resulted in environmental contamination with Pt (e.g., the Hex River's vicinity). The present study compared a Pt mining area with a non-mining area along this river in terms of (1) metal concentrations in different grain size fractions from soils and aquatic sediments; (2) the toxicological potential of aquatic sediments based on the Consensus-Based Sediment Quality Guideline (CBSQG); and (3) the chronic toxicity of aqueous eluates from soils and sediments to Caenorhabditis elegans. Platinum concentrations were higher in the mining area than in the non-mining area. For most metals, the sediment silt and clay fraction contained the highest metal concentrations. Based on the CBSQG, most sampling sites exhibited a high toxicological potential, driven by Cr and Ni. Eluate toxicity testing revealed that C. elegans growth, fertility, and reproduction inhibition were not dependent on mining activities or the CBSQG predictions. Toxicity was instead likely due to Cd, Fe, Mn, Ni, Pt, and Pb. In conclusion, the investigated region is loaded with a high geogenic background resulting in high reproduction inhibition. The mining activities lead to additional environmental metal contamination (particularly Pt), contributing to environmental soil and sediment toxicity.

Conjugates of desferrioxamine and aromatic amines improve markers of iron-dependent neurotoxicity

Alzheimer's Disease (AD) is a complex neurodegenerative disorder associated in some instances with dyshomeostasis of redox-active metal ions, such as copper and iron. In this work, we investigated whether the conjugation of various aromatic amines would improve the pharmacological efficacy of the iron chelator desferrioxamine (DFO). Conjugates of DFO with aniline (DFOANI), benzosulfanylamide (DFOBAN), 2-naphthalenamine (DFONAF) and 6-quinolinamine (DFOQUN) were obtained and their properties examined. DFOQUN had good chelating activity, promoted a significant increase in the inhibition of β-amyloid peptide aggregation when compared to DFO, and also inhibited acetylcholinesterase (AChE) activity both in vitro and in vivo (Caenorhabditis elegans). These data indicate that the covalent conjugation of a strong iron chelator to an AChE inhibitor offers a powerful approach for the amelioration of iron-induced neurotoxicity symptoms.

High throughput fluorimetric assessment of iron traffic and chelation in iron-overloaded Caenorhabditis elegans

The nematode Caenorhabditis elegans (C. elegans) is a convenient tool to evaluate iron metabolism as it shares great orthology with human proteins involved in iron transport, in addition to being transparent and readily available. In this work, we describe how wild-type (N2) C. elegans nematodes in the first larval stage can be loaded with acetomethoxycalcein (CAL-AM) and study it as a whole-organism model for both iron speciation and chelator permeability of the labile iron pool (LIP). This model may be relevant for high throughput assessment of molecules intended for chelation therapy of iron overload diseases.

Changes in ferrous iron and glutathione promote ferroptosis and frailty in aging Caenorhabditis elegans

All eukaryotes require iron. Replication, detoxification, and a cancer-protective form of regulated cell death termed ferroptosis, all depend on iron metabolism. Ferrous iron accumulates over adult lifetime in Caenorhabditis elegans. Here, we show that glutathione depletion is coupled to ferrous iron elevation in these animals, and that both occur in late life to prime cells for ferroptosis. We demonstrate that blocking ferroptosis, either by inhibition of lipid peroxidation or by limiting iron retention, mitigates age-related cell death and markedly increases lifespan and healthspan. Temporal scaling of lifespan is not evident when ferroptosis is inhibited, consistent with this cell death process acting at specific life phases to induce organismal frailty, rather than contributing to a constant aging rate. Because excess age-related iron elevation in somatic tissue, particularly in brain, is thought to contribute to degenerative disease, post-developmental interventions to limit ferroptosis may promote healthy aging.

Assessing the influence of the genetically modified factor on mixture toxicological interactions in Caenorhabditis elegans: Comparison between wild type and a SOD type

How to evaluate the ecological risk of transgenic technology is a focus of scientists because of the safety concerns raised by genetically modified (GM) organisms. Nevertheless, most studies are based on individual chemicals and always analyze the GM organism as a type of toxicant. In this study, we changed the approach and used GM organisms as the test objects with normal chemical exposure. Three types of chemicals (two substituted phenols, 4-chlorophenol and 4-nitrophenol; two ionic liquids, 1-butylpyridinium chloride and 1-butylpyridinium bromide; two pesticides, dichlorvos and glyphosate) were used to construct a six-component mixture system. The lethality to wild-type (N2) and sod-3::GFP (SOD-3) Caenorhabditis elegans was determined when they were exposed to the same mixture system after 12 and 24 h. The results showed that the pEC50 values of all of the single chemicals on SOD-3 were greater than those on N2 at 24 h. The toxicities of the single chemicals and nine mixture rays on the two strains increased with time. Notably, we discovered a significant difference between the two strains; time-dependent synergism occurred in mixtures on N2, but time-dependent antagonism occurred in mixtures on SOD-3. Finally, the strength of the synergism or antagonism turned to additive action on the two strains as the exposure time increased. These findings illustrated that the GM factor of the nematode influenced the mixture toxicological interaction at some exposure times. Compared with N2, SOD-3 were more sensitive to stress or toxic reactions. Therefore, the influence of the GM factor on mixture toxicological interactions in environmental risk assessment must be considered.

Neurodegeneration Induced by Metals in Caenorhabditis elegans

Metals are a component of a variety of ecosystems and organisms. They can generally be divided into essential and nonessential metals. The essential metals are involved in physiological processes once the deficiency of these metals has been associated with diseases. Although iron, manganese, copper, and zinc are important for life, it has been evidenced that they are also involved in neuronal damage in many neurodegenerative disorders. Nonessential metals, which are metals without physiological functions, are present in trace or higher levels in living organisms. Occupational, environmental, or deliberate exposures to lead, mercury, aluminum, and cadmium are clearly correlated with the increase of toxicity and varied kinds of pathological situations. Actually, the field of neurotoxicology needs to satisfy two opposing demands: the testing of a growing list of chemicals and resource limitations and ethical concerns associated with testing using traditional mammalian species. Toxicological assays using alternative animal models may relieve some of this pressure by allowing testing of more compounds while reducing expenses and using fewer mammals. The nervous system is by far the more complex system in C. elegans. Almost a third of their cells are neurons (302 neurons versus 959 cells in adult hermaphrodite). It initially underwent extensive development as a model organism in order to study the nervous system, and its neuronal lineage and the complete wiring diagram of its nervous system are stereotyped and fully described. The neurotransmission systems are phylogenetically conserved from nematodes to vertebrates, which allows for findings from C. elegans to be extrapolated and further confirmed in vertebrate systems. Different strains of C. elegans offer a new perspective on neurodegenerative processes. Some genes have been found to be related to neurodegeneration induced by metals. Studying these interactions may be an effective tool to slow neuronal loss and deterioration.

Nanoscale zerovalent iron (nZVI) at environmentally relevant concentrations induced multigenerational reproductive toxicity in Caenorhabditis elegans

Nanoscale zerovalent iron (nZVI) is widely used with large scale for environmental remediation for in situ or ex situ applications. The potential impact of nZVI on biota at environmentally relevant concentrations needs to be elucidated. In this study, the reproductive toxicities of three irons species: carboxymethyl cellulose (CMC)-stabilized nZVI, nanoscale iron oxide (nFe3O4), and ferrous ion (Fe(II)aq) in the soil-dwelling nematode Caenorhabditis elegans were examined. In addition, the generational transfer of reproductive toxicity of CMC-nZVI on C. elegans was investigated. The results showed that CMC-nZVI, nFe3O4, and Fe(II)aq did not cause significant mortality after 24 h exposure at the examined concentrations. Reproductive toxicity assays revealed that CMC-nZVI, nFe3O4, and Fe(II)aq significantly decreased offsprings in parental generation (F0) in accompany with the increased intracellular reactive oxygen species (ROS). Furthermore, the reproductive toxicity of CMC-nZVI at environmentally relevant concentrations was transferrable from the F0 to the F1 and F2 generations, but then recovered in the F3 and F4 generations. Further evidence showed that total irons were accumulated in the F0 and F1 generations of C. elegans after CMC-nZVI parental exposure. This study demonstrated that environmentally relevant concentrations of CMC-nZVI induced multigenerational reproductive toxicity which can be ascribed to its high production of ROS in F0 generation, toxicity of Fe(II)aq, and iron accumulation in C. elegans. Since nZVI is widely used for environmental remediation, considering the multigenerational toxicity, this study thus implicates a potential environmental risk of nZVI-induced nanotoxicity in the environment.

Contribution of heavy metals to toxicity of coal combustion related fine particulate matter (PM2.5) in Caenorhabditis elegans with wild-type or susceptible genetic background

Contribution of chemical components in coal combustion related fine particulate matter (PM2.5) to its toxicity is largely unclear. We focused on heavy metals in PM2.5 to investigate their contribution to toxicity formation in Caenorhabditis elegans. Among 8 heavy metals examined (Fe, Zn, Pb, As, Cd, Cr, Cu, and Ni), Pb, Cr, and Cu potentially contributed to PM2.5 toxicity in wild-type nematodes. Combinational exposure to any two of these three heavy metals caused higher toxicity than exposure to Pb, Cr, or Cu alone. Toxicity from the combinational exposure to Pb, Cr, and Cu at the examined concentrations was higher than exposure to PM2.5 (100 mg/L). Moreover, mutation of sod-2 or sod-3 gene encoding Mn-SOD increased susceptibility in nematodes exposed to Fe, Zn, or Ni, although Fe, Zn, or Ni at the examined concentration did not lead to toxicity in wild-type nematodes. Our results highlight the potential contribution of heavy metals to PM2.5 toxicity in environmental organisms.

Caenorhabditis elegans, a Biological Model for Research in Toxicology

Caenorhabditis elegans is a nematode of microscopic size which, due to its biological characteristics, has been used since the 1970s as a model for research in molecular biology, medicine, pharmacology, and toxicology. It was the first animal whose genome was completely sequenced and has played a key role in the understanding of apoptosis and RNA interference. The transparency of its body, short lifespan, ability to self-fertilize and ease of culture are advantages that make it ideal as a model in toxicology. Due to the fact that some of its biochemical pathways are similar to those of humans, it has been employed in research in several fields. C. elegans' use as a biological model in environmental toxicological assessments allows the determination of multiple endpoints. Some of these utilize the effects on the biological functions of the nematode and others use molecular markers. Endpoints such as lethality, growth, reproduction, and locomotion are the most studied, and usually employ the wild type Bristol N2 strain. Other endpoints use reporter genes, such as green fluorescence protein, driven by regulatory sequences from other genes related to different mechanisms of toxicity, such as heat shock, oxidative stress, CYP system, and metallothioneins among others, allowing the study of gene expression in a manner both rapid and easy. These transgenic strains of C. elegans represent a powerful tool to assess toxicity pathways for mixtures and environmental samples, and their numbers are growing in diversity and selectivity. However, other molecular biology techniques, including DNA microarrays and MicroRNAs have been explored to assess the effects of different toxicants and samples. C. elegans has allowed the assessment of neurotoxic effects for heavy metals and pesticides, among those more frequently studied, as the nematode has a very well defined nervous system. More recently, nanoparticles are emergent pollutants whose toxicity can be explored using this nematode. Overall, almost every type of known toxicant has been tested with this animal model. In the near future, the available knowledge on the life cycle of C. elegans should allow more studies on reproduction and transgenerational toxicity for newly developed chemicals and materials, facilitating their introduction in the market. The great diversity of endpoints and possibilities of this animal makes it an easy first-choice for rapid toxicity screening or to detail signaling pathways involved in mechanisms of toxicity.

Adverse effects of coal combustion related fine particulate matter (PM2.5) on nematode Caenorhabditis elegans

The toxic effects of coal combustion related fine particulate matter (PM2.5), collected from Datong, Shanxi province, China, on nematode Caenorhabditis elegans were investigated. Exposure to PM2.5 resulted in deficits in development, reproduction, locomotion behavior, and lifespan, and induction of intestinal autofluorescence or reactive oxygen species (ROS) production. Prolonged exposure to PM2.5 led to more severe toxicity on nematodes than acute exposure. In addition, exposure to PM2.5 induced altered expression patterns of genes required for the control of oxidative stress. Reduction in mean defecation cycle length and developmental deficits in AVL and DVB neurons, which are involved in the control of defecation behavior, were also triggered by PM2.5 exposure. Thus, oxidative stress and abnormal defecation behavior may contribute greatly to the toxicity of coal combustion related PM2.5 in nematodes. The results also imply that the long-term adverse effects of coal combustion related PM2.5 on environmental organisms should be carefully considered.

Effects of nutritional components on aging

Nutrients including carbohydrates, proteins, lipids, vitamins, and minerals regulate various physiological processes and are essential for the survival of organisms. Reduced overall caloric intake delays aging in various organisms. However, the role of each nutritional component in the regulation of lifespan is not well established. In this review, we describe recent studies focused on the regulatory role of each type of nutrient in aging. Moreover, we will discuss how the amount or composition of each nutritional component may influence longevity or health in humans.

Behavioral and dopaminergic damage induced by acute iron toxicity in Caenorhabditis elegans

Iron (Fe) exposure, results in multiple biological defects in C. elegans, including reproductive and motor impairment, which may be related to oxidative stress and neuronal damage.

Iron promotes protein insolubility and aging in C. elegans

Many late-onset proteotoxic diseases are accompanied by a disruption in homeostasis of metals (metallostasis) including iron, copper and zinc. Although aging is the most prominent risk factor for these disorders, the impact of aging on metallostasis and its role in proteotoxic disease remain poorly understood. Moreover, it is not clear whether a loss of metallostasis influences normal aging. We have investigated the role of metallostasis in longevity ofCaenorhabditis elegans. We found that calcium, copper, iron, and manganese levels increase as a function of age, while potassium and phosphorus levels tend to decrease. Increased dietary iron significantly accelerated the age-related accumulation of insoluble protein, a molecular pathology of aging. Proteomic analysis revealed widespread effects of dietary iron in multiple organelles and tissues. Pharmacological interventions to block accumulation of specific metals attenuated many models of proteotoxicity and extended normal lifespan. Collectively, these results suggest that a loss of metallostasis with aging contributes to age-related protein aggregation.

Full toxicity assessment of Genkwa Flos and the underlying mechanism in nematode Caenorhabditis elegans

Genkwa Flos (GF), the dried flower bud from Daphne genkwa Sieb. et Zucc. (Thymelaeaceae), is a well-known and widely used traditional Chinese medicine. However, we know little about the in vivo mechanism of GF toxicity. Nematode Caenorhabditis elegans has been considered as a useful toxicity assay system by offering a system best suited for asking the in vivo questions. In the present study, we employed the prolonged exposure assay system of C. elegans to perform the full in vivo toxicity assessment of raw-processed GF. Our data show that GF exposure could induce the toxicity on lifespan, development, reproduction, and locomotion behavior. GF exposure not only decreased body length but also induced the formation of abnormal vulva. The decrease in brood size in GF exposed nematodes appeared mainly at day-1 during the development of adult nematodes. The decrease of locomotion behavior in GF exposed nematodes might be due to the damage on development of D-type GABAergic motor neurons. Moreover, we observed the induction of intestinal reactive oxygen species (ROS) production and alteration of expression patterns of genes required for development of apical domain, microvilli, and apical junction of intestine in GF exposed nematodes, implying the possible dysfunction of the primary targeted organ. In addition, GF exposure induced increase in defecation cycle length and deficits in development of AVL and DVB neurons controlling the defecation behavior. Therefore, our study implies the usefulness of C. elegans assay system for toxicity assessment from a certain Chinese medicine or plant extract. The observed toxicity of GF might be the combinational effects of oxidative stress, dysfunction of intestine, and altered defecation behavior in nematodes.

Adverse effects from clenbuterol and ractopamine on nematode Caenorhabditis elegans and the underlying mechanism

In the present study, we used Caenorhabditis elegans assay system to investigate in vivo toxicity from clentuberol and ractopamine and the possible underlying mechanism. Both acute and prolonged exposures to clentuberol or ractopamine decreased brood size and locomotion behavior, and induced intestinal autofluorescence and reactive oxygen species (ROS) production. Although acute exposure to the examined concentrations of clentuberol or ractopamine did not induce lethality, prolonged exposure to 10 µg/L of clentuberol and ractopamine reduced lifespan. At relatively high concentrations, ractopamine exhibited more severe toxicity than clentuberol on nematodes. Overexpression of sod-2 gene encoding a Mn-SOD to prevent induction of oxidative stress effectively inhibited toxicity from clentuberol or ractopamine. Besides oxidative stress, we found that clentuberol might reduce lifespan through influencing insulin/IGF signaling pathway; however, ractopamine might reduce lifespan through affecting both insulin/IGF signaling pathway and TOR signaling pathway. Ractopamine more severely decreased expression levels of daf-16, sgk-1, skn-1, and aak-2 genes than clentuberol, and increased expression levels of daf-2 and age-1 genes at the examined concentration. Therefore, the C. elegans assay system may be useful for assessing the possible toxicity from weight loss agents, and clentuberol and ractopamine may induce toxicity through different molecular mechanisms.

Crucial role of the biological barrier at the primary targeted organs in controlling the translocation and toxicity of multi-walled carbon nanotubes in the nematode Caenorhabditis elegans

Multi-walled carbon nanotubes (MWCNTs) can be translocated into the targeted organs of organisms. We employed a model organism of the nematode Caenorhabditis elegans to investigate the role of a biological barrier at the primary targeted organs in regulating the translocation and toxicity formation of MWCNTs. A prolonged exposure to MWCNTs at predicted environmental relevant concentrations caused adverse effects associated with both the primary and secondary targeted organs on nematodes. The function of PEGylated modification in reducing MWCNTs toxicity might be mainly due to the suppression of their translocation into secondary targeted organs through the primary targeted organs. A biological barrier at the primary targeted organs contributed greatly to the control of MWCNTs translocation into secondary targeted organs, as indicated by functions of Mn-SODs required for prevention of oxidative stress in the primary targeted organs. Over-expression of Mn-SODs in primary targeted organs effectively suppressed the translocation and toxicity of MWCNTs. Our work highlights the crucial role of the biological barrier at the primary targeted organs in regulating the translocation and toxicity formation of MWCNTs. Our data also shed light on the future development of engineered nanomaterials (ENMs) with improved biocompatibility and design of prevention strategies against ENMs toxicity.

Biosafety assessment of titanium dioxide nanoparticles in acutely exposed nematode Caenorhabditis elegans with mutations of genes required for oxidative stress or stress response

We used Caenorhabditis elegans to investigate whether acute exposure to TiO2-NPs at the concentration of 20 μg L(-1) reflecting predicted environmental relevant concentration and 25 mg L(-1) reflecting concentration in food can cause toxicity on nematodes with mutations of susceptible genes. Among examined mutants associated with oxidative stress and stress response, we found that genes of sod-2, sod-3, mtl-2, and hsp-16.48 might be susceptible for TiO2-NPs toxicity. Mutations of these genes altered functions of both possible primary and secondary targeted organs in nematodes exposed to 25 mg L(-1) of TiO2-NPs for 24-h. Mutations of these genes caused similar expression patterns of genes required for oxidative stress in TiO2-NPs exposed mutant nematodes, implying their similar mechanisms to form the susceptible property. Nevertheless, acute exposure to 20 μg L(-1) of TiO2-NPs for 24-h and 25 mg L(-1) of TiO2-NPs for 0.48-h or 5.71-h did not influence functions of both possible primary and secondary targeted organs in sod-2, sod-3, mtl-2, and hsp-16.48 mutants. Therefore, our results suggest the relatively safe property of acute exposure to TiO2-NPs with certain durations at predicted environmental relevant concentrations or concentrations comparable to those in food in nematodes with mutations of some susceptible genes.

Contributions of altered permeability of intestinal barrier and defecation behavior to toxicity formation from graphene oxide in nematode Caenorhabditis elegans

Graphene oxide (GO) has been extensively studied for potential biomedical applications. Meanwhile, potential GO toxicity arises in both biomedical applications and non-biomedical products where environmental exposures may occur. In the present study, we examined the potential adverse effects of GO and the underlying mechanism using nematode Caenorhabditis elegans as the assay system. We compared the in vivo effects of GO between acute exposure and prolonged exposure, and found that prolonged exposure to 0.5-100 mg L(-1) of GO caused damage on functions of both primary (intestine) and secondary (neuron and reproductive organ) targeted organs. In the intestine, ROS production was significantly correlated with the formation of adverse effects on functions of both primary and secondary targeted organs. GO could be translocated into intestinal cells with loss of microvilli, and distributed to be adjacent to or surrounding mitochondria. Prolonged exposure to GO resulted in a hyper-permeable state of the intestinal barrier, an increase in mean defecation cycle length, and alteration of genes required for intestinal development and defecation behavior. Thus, our data suggest that prolonged exposure to GO may cause potential risk to environmental organisms after release into the environment. GO toxicity may be due to the combinational effects of oxidative stress in the intestinal barrier, enhanced permeability of the biological barrier, and suppressed defecation behavior in C. elegans.

High concentration of vitamin E decreases thermosensation and thermotaxis learning and the underlying mechanisms in the nematode Caenorhabditis elegans

α-tocopherol is a powerful liposoluble antioxidant and the most abundant isoform of vitamin E in the body. Under normal physiological conditions, adverse effects of relatively high concentration of vitamin E on organisms and the underlying mechanisms are still largely unclear. In the present study, we used the nematode Caenorhabditis elegans as an in vivo assay system to investigate the possible adverse effects of high concentration of vitamin E on thermosensation and thermotaxis learning and the underlying mechanisms. Our data show that treatment with 100-200 µg/mL of vitamin E did not noticeably influence both thermosensation and thermotaxis learning; however, treatment with 400 µg/mL of vitamin E altered both thermosensation and thermotaxis learning. The observed decrease in thermotaxis learning in 400 µg/mL of vitamin E treated nematodes might be partially due to the moderate but significant deficits in thermosensation, but not due to deficits in locomotion behavior or perception to food and starvation. Treatment with 400 µg/mL of vitamin E did not noticeably influence the morphology of GABAergic neurons, but significantly decreased fluorescent intensities of the cell bodies in AFD sensory neurons and AIY interneurons, required for thermosensation and thermotaxis learning control. Treatment with 400 µg/mL of vitamin E affected presynaptic function of neurons, but had no remarkable effects on postsynaptic function. Moreover, promotion of synaptic transmission by activating PKC-1 effectively retrieved deficits in both thermosensation and thermotaxis learning induced by 400 µg/mL of vitamin E. Therefore, relatively high concentrations of vitamin E administration may cause adverse effects on thermosensation and thermotaxis learning by inducing damage on the development of specific neurons and presynaptic function under normal physiological conditions in C. elegans.

Carboxylic acid functionalization prevents the translocation of multi-walled carbon nanotubes at predicted environmentally relevant concentrations into targeted organs of nematode Caenorhabditis elegans

Carboxyl (-COOH) surface modified multi-walled carbon nanotubes (MWCNTs-COOH) can be used for targeted delivery of drugs and imaging. However, whether MWCNTs-COOH at environmentally relevant concentrations exert certain toxic effects on multicellular organisms and the underlying mechanisms are still largely unclear. In the present study, we applied the nematode Caenorhabditis elegans to evaluate the properties of MWCNTs-COOH at environmentally relevant concentrations by comparing the effects of MWCNTs and MWCNTs-COOH exposure on C. elegans from L1-larvae to adult at concentrations of 0.001-1000 μg L(-1). Exposure to MWCNTs could potentially damage the intestine (primary targeted organ) at concentrations greater than 0.1 μg L(-1) and functions of neurons and reproductive organ (secondary targeted organs) at concentrations greater than 0.001 μg L(-1). Carboxyl modification prevented the toxicity of MWCNTs on the primary and the secondary targeted organs at concentrations less than 100 μg L(-1), suggesting that carboxyl modification can effectively prevent the adverse effects of MWCNTs at environmentally relevant concentrations. After exposure, MWCNTs-COOH (1 mg L(-1)) were translocated into the spermatheca and embryos in the body through the primary targeted organs. However, MWCNTs-COOH (10 μg L(-1)) were not observed in spermatheca and embryos in the body of nematodes. Moreover, relatively high concentrations of MWCNTs-COOH exposed nematodes might have a hyper-permeable intestinal barrier, whereas MWCNTs-COOH at environmentally relevant concentrations effectively sustained the normally permeable state for the intestinal barrier. Therefore, we elucidated the cellular basis of carboxyl modification to prevent toxicity of MWCNTs at environmentally relevant concentrations. Our data highlights the key role of biological barriers in the primary targeted organs to block toxicity formation from MWCNTs, which will be useful for the design of effective prevention strategies against MWCNTs toxicity.

Metal-induced neurodegeneration in C. elegans

The model species, Caenorhabditis elegans, has been used as a tool to probe for mechanisms underlying numerous neurodegenerative diseases. This use has been exploited to study neurodegeneration induced by metals. The allure of the nematode comes from the ease of genetic manipulation, the ability to fluorescently label neuronal subtypes, and the relative simplicity of the nervous system. Notably, C. elegans have approximately 60-80% of human genes and contain genes involved in metal homeostasis and transport, allowing for the study of metal-induced degeneration in the nematode. This review discusses methods to assess degeneration as well as outlines techniques for genetic manipulation and presents a comprehensive survey of the existing literature on metal-induced degeneration studies in the worm.

Transgenerational effects of heavy metals on L3 larva of Caenorhabditis elegans with greater behavior and growth inhibitions in the progeny

Heavy metals are ubiquitous environmental pollutants, and their toxic effects have been widely studied. However, their transgenerational effects between parent and progeny at environmental relevant concentrations need further investigations. Currently, L3 stage of Caenorhabditis elegans was exposed to aqueous metals (Cd, Cu, Pb and Zn) at environmentally realistic concentrations for 96 h. The whole exposure time covered the formation of sperm, ovum and eggs. Subsequently the behavior and growth indicators were measured. The parent nematodes were then bleached to gain synchronized eggs, which were cultured under non-toxic conditions to L3 stage when the same indicators were measured in the progeny. The parent suffered concentration-dependent inhibitions on behavior and growth. Based on the median effective concentration (EC(50)) values, body bending frequency showed relatively higher sensitivity than other behavior indicators. The inhibitions on growth and behavior of progeny were more severe than those of the parent, based on their respective EC(50) values. Interestingly, Cd was not the most toxic metal in either parent or progeny according to EC(50) values, but its EC(50) ratios between parent and progeny (EC(50, parent)/EC(50, progeny)) were the most significant, indicating its greatest transgenerational effects. The results demonstrated the higher sensitivity of L3 larva stage of C. elegans in the transgenerational effect studies than other life stages used before. Our findings suggested that parental exposure to heavy metals can multiply their harmful effects in following generations.

Small sizes of TiO2-NPs exhibit adverse effects at predicted environmental relevant concentrations on nematodes in a modified chronic toxicity assay system

In Caenorhabditis elegans, although acute toxicity of TiO(2) nanoparticles (TiO(2)-NPs) at high concentrations has been investigated, we still know little about chronic toxicity of TiO(2)-NPs. Our data here showed that acute TiO(2)-NPs exposure in the range of μg/L had no obviously adverse effects on nematodes, but the chronic toxicities of large sizes (60 nm and 90 nm) of TiO(2)-NPs in the range of μg/L were detected in nematodes in a modified chronic toxicity assay system. Moreover, chronic toxicities of small sizes (4 nm and 10nm) of TiO(2)-NPs in the range of ng/L were observed in nematodes with locomotion behavior and ROS production as endpoints. In nematodes chronically exposed to small sizes of TiO(2)-NPs at predicted environmental relevant concentrations, locomotion behavior was significantly (P<0.01) correlated with ROS production. Furthermore, treatment with antioxidants (ascorbate and N-acetyl-l-cysteine) inhibited both the induction of ROS production and the decrease of locomotion behaviors observed in nematodes chronically exposed to small sizes of TiO(2)-NPs at predicted environmental relevant concentrations. Therefore, chronic exposure to small sizes of TiO(2)-NPs at predicted environmental relevant concentrations can cause adverse effects on nematodes, and formation of such adverse effects may be largely due to the induction of oxidative stress.

Molecular control of TiO₂-NPs toxicity formation at predicted environmental relevant concentrations by Mn-SODs proteins

With growing concerns of the safety of nanotechnology, the in vivo toxicity of nanoparticles (NPs) at environmental relevant concentrations has drawn increasing attentions. We investigated the possible molecular mechanisms of titanium nanoparticles (Ti-NPs) in the induction of toxicity at predicted environmental relevant concentrations. In nematodes, small sizes (4 nm and 10 nm) of TiO₂-NPs induced more severe toxicities than large sizes (60 nm and 90 nm) of TiO₂-NPs on animals using lethality, growth, reproduction, locomotion behavior, intestinal autofluorescence, and reactive oxygen species (ROS) production as endpoints. Locomotion behaviors could be significantly decreased by exposure to 4-nm and 10-nm TiO₂-NPs at concentration of 1 ng/L in nematodes. Among genes required for the control of oxidative stress, only the expression patterns of sod-2 and sod-3 genes encoding Mn-SODs in animals exposed to small sizes of TiO₂-NPs were significantly different from those in animals exposed to large sizes of TiO₂-NPs. sod-2 and sod-3 gene expressions were closely correlated with lethality, growth, reproduction, locomotion behavior, intestinal autofluorescence, and ROS production in TiO₂-NPs-exposed animals. Ectopically expression of human and nematode Mn-SODs genes effectively prevented the induction of ROS production and the development of toxicity of TiO₂-NPs. Therefore, the altered expression patterns of Mn-SODs may explain the toxicity formation for different sizes of TiO₂-NPs at predicted environmental relevant concentrations. In addition, we demonstrated here a strategy to investigate the toxicological effects of exposure to NPs upon humans by generating transgenic strains in nematodes for specific human genes.

Evaluation of environmental safety concentrations of DMSA Coated Fe2O3-NPs using different assay systems in nematode Caenorhabditis elegans

Dimercaptosuccinic acid (DMSA) coating improves the uptake efficiency presumably by engendering the Fe(2)O(3)-NPs. In the present study, we investigated the possible environmental safety concentrations of Fe(2)O(3)-NPs using different assay systems in nematode Caenorhabditis elegans with lethality, development, reproduction, locomotion behavior, pharyngeal pumping, defecation, intestinal autofluorescence and reactive oxygen species (ROS) production as the endpoints. After exposure from L4-larvae for 24-hr, DMSA coated Fe(2)O(3)-NPs at concentrations more than 50 mg/L exhibited adverse effects on nematodes. After exposure from L1-larvae to adult, DMSA coated Fe(2)O(3)-NPs at concentrations more than 500 μg/L had adverse effects on nematodes. After exposure from L1-larvae to day-8 adult, DMSA coated Fe(2)O(3)-NPs at concentrations more than 100 μg/L resulted in the adverse effects on nematodes. Accompanied with the alterations of locomotion behaviors, ROS production was pronouncedly induced by exposure to DMSA coated Fe(2)O(3)-NPs in the examined three assay systems, and the close associations of ROS production with lethality, growth, reproduction, locomotion behavior, pharyngeal pumping, defecation, or intestinal autofluorescence in nematodes exposed to DMSA coated Fe(2)O(3)-NPs were confirmed by the linear regression analysis. Moreover, mutations of sod-2 and sod-3 genes, encoding Mn-SODs, showed more susceptible properties than wild-type when they were used for assessing the DMSA coated Fe(2)O(3)-NPs-induced toxicity, and the safety concentrations for DMSA coated Fe(2)O(3)-NPs should be defined as concentrations lower than 10 μg/L in sod-2 and sod-3 mutant nematodes.

Inhibition of ROS elevation and damage to mitochondrial function prevents lead-induced neurotoxic effects on structures and functions of AFD neurons in Caenorhabditis elegans

Here we investigated the possible roles of oxidative stress in the formation of decreased thermotaxis to cultivation temperature in lead (Pb)-exposed nematodes Caenorhabditis elagans. Exposure to Pb at the examined concentrations decreased thermotaxis behaviors, and induced severe deficits in the structural properties of AFD sensory neurons. Meanwhile, Pb exposure caused the induction of severe oxidative damage, reactive oxygen species (ROS) production, and mitochondrial dysfunction in young adults. Moreover, pre-treatment with the antioxidants dimethyl sulfoxide (DMSO), ascorbate and N-acetyl-L-cysteine (NAC), used to inhibit both the ROS elevation and the mitochondrial dysfunction caused by Pb exposure, at the L2-larval stage prevented the induction of oxidative damage and the formation of severe deficits in thermotaxis and structural properties of AFD sensory neurons in Pb-exposed young adults. Therefore, the formation of oxidative stress caused by Pb exposure may be due to both the induction of ROS elevation and damage to mitochondrial function, and oxidative stress may play a key role in inducing the neurotoxic effects on the structures and function of AFD sensory neurons in Pb-exposed nematodes.

Aluminum nanoparticle exposure in L1 larvae results in more severe lethality toxicity than in L4 larvae or young adults by strengthening the formation of stress response and intestinal lipofuscin accumulation in nematodes

Toxicity of Al(2)O(3)-NPs, as compared to that of Al(2)O(3), to L1-larval, L4-larval or young adult nematodes was evaluated. When exposure was performed at L1-larval stage, the significant increases of lethality, stress response, and intestinal lipofuscin autofluorescence were observed in 6.3-203.9 mg/L of Al(2)O(3)-NPs exposed nematodes. In contrast, when exposure was performed at L4-larval or young adult stage, the significant increases of lethality and intestinal lipofuscin autofluorescence were observed in 12.7-203.9 mg/L of Al(2)O(3)-NPs exposed nematodes, and the significant inductions of stress response were detected in 25.5-203.9 mg/L of Al(2)O(3)-NPs exposed nematodes. Moreover, the lethality was significantly correlated with the stress response and the intestinal lipofuscin autofluorescence in Al(2)O(3)-NPs exposed nematodes. These data imply that Al(2)O(3)-NPs exposure in L1 larvae causes more severe lethality toxicity than in L4 larvae or young adults by strengthening the formation of stress response and intestinal lipofuscin accumulation in nematodes.

The Caenorhabiditis elegans model as a reliable tool in neurotoxicology

Caenorhabiditis elegans (C. elegans) offers an attractive experimental platform as it has a short life cycle, is inexpensive to maintain and most importantly has high degree of evolutionary conservation with higher eukaryotes. Understanding the contribution of inherent genes that regulate neurotoxicity and antioxidant stress responses in the worm provides critical insight into mechanisms of mammalian neurotoxicity. The C. elegans model readily enables multi-gene approach, allowing for combinatorial genetic variation to be studied within the context of the influence of multigenic polymorphisms in environmental risk and vulnerability. This review provides a synopsis of recent studies on metal and pesticides toxicity in C. elegans, highlighting the utility of the model system in understanding molecular mechanisms that underlie developmental, reproductive and neuronal damage. The continuation of these investigations combining basic toxicological experimentation with novel genetic and high throughput methods will continue to make C. elegans an invaluable tool for future research, providing insight into molecular and cellular mechanisms of toxicity.

Overview of developmental and reproductive toxicity research in China: history, funding mechanisms, and frontiers of the research

Reproductive and developmental toxicology (DART) is the discipline that deals with adverse effects on male and female resulting from exposures to harmful chemical and physical agents. DART research in China boasted a long history, but presently has fallen behind the western world in education and research. The funding mechanisms for DART research in China were similar to that for other toxicological disciplines, and the funding has come from research grants and fellowships provided by national, ministerial, and provincial institutions. Finally, the frontiers of DART research in China could be summarized as follows: (1) use of model animals such as the zebrafish and roundworm, and use of cutting-edge techniques such as stem cell culture, as well as transgenic, metabonomic, and virtual screening to study the mechanisms of developmental toxicity for some important toxicants in China; (2) use of model animals and other lower-level sentinel organisms to evaluate and monitor the developmental toxicogical risk of environmental chemicals or pollutants; (3) epidemiological studies of some important reproductive hazards; (4) in-depth studying of the reproductive and developmental toxicity of some important environmental chemicals; and (5) evaluation and study of the reproductive and developmental toxicity of traditional Chinese medicines.

Exposure to lead and mercury in young larvae induces more severe deficits in neuronal survival and synaptic function than in adult nematodes

In the present study, we investigated the possibly neurotoxic effects of metal (Pb and Hg) exposure at different developmental stages on neuronal loss in the GABAergic nervous system and synaptic functions in the nematode Caenorhabditis elegans. Our data suggest that neuronal survival in GABAergic neurons and cholinergic transmission were relatively stable during development in nematodes. Moreover, neurodegeneration, as shown by the neuronal loss and dorsal/ventral cord gaps, was more severely induced by Pb and Hg exposure at the L1 through L3 larval stages than at the L4 larval and young-adult stages. Similarly, pre- and postsynaptic functions were more severely impaired by Pb and Hg exposure at the L1 through L3 larval stages than at the L4 larval and young-adult stages. Furthermore, both aldicarb and levamisole resistance were significantly correlated with neuronal loss, dorsal cord gap, and ventral cord gap in Pb- and Hg-exposed nematodes, suggesting that neuronal survival was noticeably correlated with synaptic function in metal-exposed nematodes during development. Therefore, younger (L1-L3) larvae show more sensitivity to neurotoxicity of neuronal survival and synaptic function than L4 larvae and young adult nematodes.