Chronic exposure to triadimenol at environmentally relevant concentration adversely affects aging biomarkers in Caenorhabditis elegans associated with insulin/IGF-1 signaling pathway

Comparative Assessment of Short- and Long-Term Effects of Triadimenol Fungicide on Danio rerio Erythrocytes Using the Micronucleus and Erythrocyte Nuclear Abnormality Assays

Triadimenol is a systemic fungicide widely used in agriculture to manage plant diseases, especially fungal infections. This study aims to evaluate the short-term (24, 48, 72 and 96 h) and long-term (10, 20, and 30 days) genotoxic effects of different concentrations of triadimenol on zebrafish (Danio rerio) erythrocytes using micronucleus (MN) and erythrocyte nuclear abnormal (ENA) assay. Fish were treated with 1.5, 3, and 6 mg/L concentrations of triadimenol for short and long-term periods. After the treatment period, blood was collected with heparin syringe, smears were prepared, the preparations were fixed and stained. For MN assay in short-term treatments, statistically significant MN formation was found at all concentrations of triadimenol for 24 h treatment, at the highest triadimenol concentration for 48 h, at 1.5 and 3 mg/L concentrations for 72 h, and at 3 mg/L concentrations for 96 h, compared to the negative control. In long-term treatments, significant increases in MN formation were observed at all concentrations of triadimenol for 10 and 20 days of treatment compared to the negative control. Mortality occurred at 3 and 6 mg/L concentrations in the 30-day treatment. The most frequently detected abnormalities included echinocytes and binuclear cells. For ENA assay, abnormalities such as echinocytes, binuclear cells, segmented cells, and kidney-shaped nuclei were detected in fish erythrocytes treated with different concentrations of triadimenol. All concentrations of triadimenol caused an increase in the total abnormality level in Danio rerio erythrocytes at all treatment times. These increases were concentration dependent for both short-term and long-term treatments. In conclusion, this study emphasized the potential genotoxic risks of triadimenol fungicide for aquatic organisms in both short-term and long-term treatments and the need for further ecotoxicological evaluation.

Early life long-term exposure to aflatoxin B1 induces aging and alters innate immunity associated with SKN-1/Nrf2 in Caenorhabditis elegans

Aflatoxin B1 (AFB1), a known human carcinogen, represents the most toxic aflatoxin metabolite. Exposure to AFB1 causes increased oxidative stress and immunotoxicity, which are important factors contributing to aging. However, the role of AFB1-induced toxicity in altered innate immunity and aging remains largely unclear. The nematode Caenorhabditis elegans is a suitable model organism for studying aging and toxicology due to its well-studied molecular mechanisms and short life cycle. Effects of AFB1 at 1, 2.5, and 5 μM (312, 781, and 1561 μg/L) on growth, reproduction, and lifespan were examined. The Pseudomonas aeruginosa PA14 slow-killing assay was performed to investigate innate immunity, followed by studying the possible mechanisms using transgenic strains and qPCR analysis. The results showed that early life long-term AFB1 exposure (2.5 and 5 μM) delayed development, reduced reproduction, and shortened lifespan in C. elegans. Furthermore, in aged worms, AFB1 exposure caused a dose-dependent decrease in survival of C. elegans against P. aeruginosa PA14 infection. At adulthood day 4 in the presence of live Escherichia coli OP50, AFB1 (2.5 μM) significantly increased lipofuscin levels (a hallmark of aging) compared to adult day 0, whereas no increase in lipofuscin was observed in nematodes (adulthood day 4) fed with dead E. coli OP50. Additionally, the increased lipofuscin was abolished in the skn-1 mutant with either live or dead E. coli OP50. Furthermore, AFB1 suppressed intestinal SKN-1::GFP translocation. Two-way ANOVA analysis revealed that the activity of E. coli OP50 and AFB1 interactively affected the expression of genes: skn-1, gst-4, hsp-16.1, hsp-16.49, and hsp-70. Our findings highlight the role of AFB1-induced toxicity in altered innate immunity and aging through the involvement of the transcription factor SKN-1/Nrf2.

Exposure to 6-PPD quinone enhances glycogen accumulation in Caenorhabditiselegans

Glycogen metabolism is an important biological process for organisms. In Caenorhabditis elegans, effect of 6-PPD quinone (6-PPDQ) on glycogen accumulation and underlying mechanism were examined. Exposure to 6-PPDQ (1 and 10 μg/L) increased glycogen accumulation. Meanwhile, exposure to 6-PPDQ (1 and 10 μg/L) increased expression of gsy-1 encoding glycogen synthase and decreased expression of pygl-1 encoding glycogen phosphorylase. In 6-PPDQ exposed animals, glycogen content and glycogen accumulation were inhibited by RNAi of gsy-1 and enhanced by RNAi of pygl-1. RNAi of gsy-1 increased pygl-1 expression, and RNAi of pygl-1 increased gsy-1 expression after 6-PPDQ exposure. In 6-PPDQ exposed nematodes, daf-16 and aak-2 expressions were decreased and glycogen accumulation was suppressed by RNAi of daf-16 and aak-2, suggesting alteration in daf-16 and aak-2 expressions did not mediate glycogen accumulation. Moreover, resistance to 6-PPDQ toxicity on locomotion and brood size was observed in gsy-1(RNAi) animals, and susceptibility to 6-PPDQ toxicity was found in pygl-1(RNAi) animals. Therefore, glycogen accumulation could be enhanced by exposure to 6-PPDQ in nematodes. In addition, alteration in expressions of gsy-1 and pygl-1 governing this enhancement in glycogen accumulation mediated induction of 6-PPDQ toxicity.

Polyethylene nanoparticles at environmentally relevant concentrations enhances neurotoxicity and accumulation of 6-PPD quinone in Caenorhabditis elegans

The exposure risk of 6-PPD quinone (6-PPDQ) has aroused increasing concern. In the natural environment, 6-PPDQ could interact with other pollutants, posing more severe environmental problems and toxicity to organisms. We here examined the effect of polyethylene nanoplastic (PE-NP) on 6-PPDQ neurotoxicity and the underling mechanisms in Caenorhabditis elegans. In nematodes, PE-NP (1 and 10 μg/L) decreased locomotion behavior, but did not affect development of D-type neurons. Exposure to PE-NP (1 and 10 μg/L) strengthened neurotoxicity of 6-PPDQ (10 μg/L) on the aspect of locomotion and neurodegeneration induction of D-type motor neurons. Exposure to PE-NPs (10 μg/L) caused increase in expressions of mec-4, asp-3, and asp-4 governing neurodegeneration in 10 μg/L 6-PPDQ exposed nematodes. Moreover, exposure to PE-NP (10 μg/L) increased expression of some neuronal genes (daf-7, dbl-1, jnk-1, and mpk-1) in 6-PPDQ exposed nematodes, and RNAi of these genes resulted in susceptibility to neurotoxicity of PE-NP and 6-PPDQ. 6-PPDQ could be adsorbed by PE-NPs, and resuspension of PE-NP and 6-PPDQ after adsorption equilibrium exhibited similar neurotoxicity to co-exposure of PE-NP and 6-PPDQ. In addition, exposure to PE-NP (1 and 10 μg/L) increased 6-PPDQ accumulation in body of nematodes and increased defecation cycle length in 6-PPDQ exposed nematodes. Therefore, 6-PPDQ could be adsorbed on nanoplastics (such as PE-NPs) and enhance both neurotoxicity and accumulation of 6-PPDQ in organisms.

DEHP and DINP accelerate aging effects in male and female of Drosophila melanogaster depend on AKT/FOXO pathway

Phthalates are commonly used as plasticizers. Numerous studies have focused on endocrine, reproductive, and developmental toxicity of phthalates exposure to male organisms. In recent years, some studies looking into the aging effects of phthalates exposure in D. melanogaster showed discrepant results. In this study, we compared the different concentrations of Di(2-ethylhexyl) phthalate (DEHP) and di-isononyl phthalate (DINP) for acute and chronic treatment for different gender D. melanogaster and explored the potential mechanism of DEHP and DINP exposure. The results showed that acute exposure to DEHP or DINP at a high dose significantly decreased the lifespan of female and male D. melanogaster under HFD stress. Chronic exposure significantly decreased the lifespan of flies in all exposure groups except for the low-dose DINP exposure female group. Among them, in the normal feeding group, we found that female flies seemed to be more resistant to DEHP or DINP exposure. Meanwhile, the locomotion ability and fertility of flies exhibited a dose-dependent decline. Furthermore, phthalates did not significantly reduce the lifespan or health status of akt and foxo mutant flies in the mutant fly assays, and real-time quantitative-PCR (q-PCR) data revealed akt and foxo significant change with 10 μM DEHP or DINP treatment. This suggests that akt and foxo played a role in the process by which DEHP and DINP caused age-related declines in D. melanogaster.

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.

Exposure to 6-PPD quinone enhances lipid accumulation through activating metabolic sensors of SBP-1 and MDT-15 in Caenorhabditis elegans

Although it has been shown that exposure to 6-PPDQ can cause toxicity on environmental organisms, its possible effects on metabolic state remain largely unclear. We here determined the effect of 6-PPDQ exposure on lipid accumulation in Caenorhabditis elegans. We observed increase in triglyceride content, enhancement in lipid accumulation, and increase in size of lipid droplets in 6-PPDQ (1-10 μg/L) exposed nematodes. This detected lipid accumulation was associated with both increase in fatty acid synthesis reflected by increased expressions of fasn-1 and pod-2 and inhibition in mitochondrial and peroxisomal fatty acid β-oxidation indicated by decreased expressions of acs-2, ech-2, acs-1, and ech-3. The observed lipid accumulation in 6-PPDQ (1-10 μg/L) exposed nematodes was also related to the increase in synthesis of monounsaturated fatty acylCoAs reflected by altered expressions of fat-5, fat-6, and fat-7. Exposure to 6-PPDQ (1-10 μg/L) further increased expressions of sbp-1 and mdt-15 encoding two metabolic sensors to initiate the lipid accumulation and to regulate the lipid metabolism. Moreover, the observed increase in triglyceride content, enhancement in lipid accumulation, and alterations in fasn-1, pod-2, acs-2, and fat-5 expressions in 6-PPDQ exposed nematodes were obviously inhibited by sbp-1 and mdt-15 RNAi. Our observations demonstrated the risk of 6-PPDQ at environmentally relevant concentration in affecting lipid metabolic state in organisms.

Long-term exposure to 6-PPD quinone reduces reproductive capacity by enhancing germline apoptosis associated with activation of both DNA damage and cell corpse engulfment in Caenorhabditis elegans

Recently, 6-PPD quinone (6-PPDQ), a derivative of tire antioxidant 6-PPD, was reported to have acute toxicity for organisms. However, the possible reproductive toxicity of 6-PPDQ is still largely unclear. In this study, the reproductive toxicity of 6-PPDQ after long-term exposure was further investigated in Caenorhabditis elegans. Exposure to 1 and 10 μg/L 6-PPDQ reduced the reproductive capacity. Meanwhile, exposure to 1 and 10 μg/L 6-PPDQ enhanced the germline apoptosis, which was accompanied by upregulation of ced-3, ced-4, and egl-1 expressions and downregulation of ced-9 expression. The observed increase in germline apoptosis in 1 and 10 μg/L 6-PPDQ exposed nematodes was associated with the enhancement in DNA damage and increase in expressions of related genes of cep-1, clk-2, hus-1, and mrt-2. The detected enhancement in germline apoptosis in 1 and 10 μg/L 6-PPDQ exposed nematodes was further associated with the increase in expressions of ced-1 and ced-6 governing the cell corpse engulfment process. Molecular docking analysis indicated the binding potentials of 6-PPDQ with three DNA damage checkpoints (CLK-2, HUS-1, and MRT-2) and corpse-recognizing phagocytic receptor CED-1. Therefore, our data suggested the toxicity on reproductive capacity by 6-PPDQ at environmentally relevant concentrations by enhancing DNA damage- and cell corpse engulfment-induced germline apoptosis in organisms.

Toxicity of Per- and Polyfluoroalkyl Substances to Nematodes

Per- and polyfluoroalkyl substances (PFASs) are a class of compounds that persist in the environment globally. Besides being transported to the soil and sediments, which act as their sinks, PFASs can be transferred to several species of higher organisms directly or via bacteria, eliciting a wide range of adverse effects. Caenorhabditis elegans has been widely used in toxicological studies and life science research owing to its numerous advantages over traditional vertebrate models; notably, C. elegans has 65% conserved human-disease-associated genes and does not require ethical approvals for experimental use. This review covers a range of topics, from reported accumulation characteristics and lethal concentrations of PFAS in C. elegans to the mechanisms underlying the toxicity of PFAS at different levels, including reproductive, developmental, cellular, neurologic, oxidative, metabolic, immune, and endocrine toxicities. Additionally, the toxicity levels of some PFAS substitutes are summarized. Lastly, we discuss the toxicological mechanisms of these PFAS substitutes and the importance and promising potential of nematodes as in vivo models for life science research, epidemiological studies (obesity, aging, and Alzheimer's disease research), and toxicological investigations of PFASs and other emerging pollutants compared with other soil animals or model organisms.

Exposure to polystyrene nanoparticles at predicted environmental concentrations enhances toxic effects of Acinetobacter johnsonii AC15 infection on Caenorhabditis elegans

Nanoplastics and microbial pathogens are both widely distributed in the environment; however, their combined toxicity remains largely unclear. Using Caenorhabditis elegans as an animal model, we examined the possible effect of exposure to polystyrene nanoparticle (PS-NP) in Acinetobacter johnsonii AC15 (a bacterial pathogen) infected animals. Exposure to PS-NP at the concentrations of 0.1-10 μg/L significantly enhanced the toxicity of Acinetobacter johnsonii AC15 infection on lifespan and locomotion behaviors. In addition, after exposure to 0.1-10 μg/L PS-NP, the accumulation of Acinetobacter johnsonii AC15 in body of nematodes was also increased. Meanwhile, the innate immune response indicated by the increase of antimicrobial gene expressions in Acinetobacter johnsonii AC15 infected nematodes was suppressed by exposure to 0.1-10 μg/L PS-NP. Moreover, expressions of egl-1, dbl-1, bar-1, daf-16, pmk-1, and elt-2 governing the bacterial infection and immunity in Acinetobacter johnsonii AC15 infected nematodes were further inhibited by exposure to 0.1-10 μg/L PS-NP. Therefore, our data suggested the possible exposure risk of nanoplastic at predicted environmental concentrations in enhancing the toxic effects of bacterial pathogens on environmental organisms.

Microbial colonization of microplastics in wastewater accelerates the aging process associated with oxidative stress and the insulin/IGF1 signaling pathway

Although polystyrene (PS)-induced toxicity in organisms has been documented, adverse effects on lifespan and molecular mechanisms underlying microbial colonization of PS remain elusive. Herein, physicochemical properties of biofilm-developed PS (B-PS) incubated in wastewater were altered compared with virgin PS (V-PS). Bacterial community adherence to the B-PS surface were also impacted. Acute exposure to V-PS (100 μg/L) and B-PS (10 μg/L) significantly altered the mean lifespan and lipofuscin accumulation of Caenorhabditis elegans, suggesting that B-PS exposure at environmentally relevant concentrations could more severely accelerate the aging process than V-PS. Generation of ROS, gst-4::GFP expression, and oxidative stress-related gene expression were significantly altered following B-PS exposure. Moreover, B-PS exposure increased the nucleus-cytoplasm translocation of DAF-16 and altered the expression of genes encoding the insulin/IGF1 signaling (IIS) pathway. Compared with wild-type nematodes, the daf-16 mutation markedly enhanced lipofuscin accumulation and reduced mean lifespan, whereas daf-2, age-1, pdk-1, and akt-1 mutants could recover lipofuscin accumulation and mean lifespan. Accordingly, B-PS exposure accelerated the aging process associated with oxidative stress and the IIS pathway, and the DAF-2-AGE-1-PDK-1-AKT-1-DAF-16 signaling cascade may play a critical role in regulating the lifespan of C. elegans. This study provides new insights into the potential risks associated with microbial colonization of microplastics.

Exposure to 6-PPD Quinone at Environmentally Relevant Concentrations Causes Abnormal Locomotion Behaviors and Neurodegeneration in Caenorhabditis elegans

6-PPD quinone (6-PPDQ) can be transformed from 6-PPD through ozonation. Nevertheless, the potential neurotoxicity of 6-PPDQ after long-term exposure and the underlying mechanism are largely unclear. In Caenorhabditis elegans, we here observed that 0.1-10 μg/L of 6-PPDQ caused several forms of abnormal locomotion behaviors. Meanwhile, the neurodegeneration of D-type motor neurons was observed in 10 μg/L of 6-PPDQ-exposed nematodes. The observed neurodegeneration was associated with the activation of the Ca²⁺ channel DEG-3-mediated signaling cascade. In this signaling cascade, expressions of deg-3, unc-68, itr-1, crt-1, clp-1, and tra-3 were increased by 10 μg/L of 6-PPDQ. Moreover, among genes encoding neuronal signals required for the control of stress response, expressions of jnk-1 and dbl-1 were decreased by 0.1-10 μg/L of 6-PPDQ, and expressions of daf-7 and glb-10 were decreased by 10 μg/L of 6-PPDQ. RNAi of jnk-1, dbl-1, daf-7, and glb-10 resulted in the susceptibility to 6-PPDQ toxicity in decreasing locomotory ability and in inducing neurodegeneration, suggesting that JNK-1, DBL-1, DAF-7, and GLB-10 were also required for the induction of 6-PPDQ neurotoxicity. Molecular docking analysis further demonstrated the binding potential of 6-PPDQ to DEG-3, JNK-1, DBL-1, DAF-7, and GLB-10. Together, our data suggested the exposure risk of 6-PPDQ at environmentally relevant concentrations in causing neurotoxicity in organisms.

Exposure to multi-walled carbon nanotubes causes suppression in octopamine signal associated with transgenerational toxicity induction in C.elegans

Multi-walled carbon nanotube (MWCNT), a kind of carbon-based nanomaterials, has been extensively utilized in a variety of fields. In Caenorhabditis elegans, MWCNT exposure can result in toxicity not only at parental generation (P0-G) but also in the offspring. However, the underlying mechanisms remain still largely unknown. DAF-12, a transcriptional factor (TF), was previously found to be activated and involved in transgenerational toxicity control after MWCNT exposure. In this study, we observed that exposure to 0.1-10 μg/L MWCNTs caused the significant decrease in expression of tbh-1 encoding a tyramine beta-hydroxylase with the function to govern the octopamine synthesis, suggesting the inhibition in octopamine signal. After exposure to 0.1 μg/L MWCNT, the decrease in tbh-1 expression could be also detected in F1-G and F2-G. Moreover, in germline cells, the TF DAF-12 regulated transgenerational MWCNT toxicity by suppressing expression and function of TBH-1. Meanwhile, exposure to 0.1-10 μg/L MWCNTs induced the increase in octr-1 expression and the decrease in ser-6 expression. After exposure to 0.1 μg/L MWCNT, the increased octr-1 expression and the decreased ser-6 expression were further observed in F1-G and F2-G. Germline TBH-1 controlled transgenerational MWCNT toxicity by regulating the activity of octopamine receptors (SER-6 and OCTR-1) in offspring. Furthermore, in the offspring, SER-6 and OCTR-1 affected the induction of MWCNT toxicity by upregulating or downregulating the level of ELT-2, a GATA TF. Taken together, these findings suggested possible link between alteration in octopamine related signals and MWCNT toxicity induction in offspring in organisms.

Exposure to fluopimomide at sublethal doses causes oxidative stress in Caenorhabditis elegans regulated by insulin/insulin-like growth factor 1-like signaling pathway

Fluopimomide is an innovative pesticide, widely used for agricultural pest management; however, little is known about its effect on non-target organisms. This study was designed to assess the potential risk of fluopimomide and the molecular mechanisms using Caenorhabditis elegans, a common model animal. The oxidative stress-related indicators were analyzed in C. elegans after exposure to fluopimomide for 24 h at three sublethal doses (0.2, 1.0, and 5.0 mg/L). The results demonstrated that sublethal exposure to fluopimomide adversely affected the nematodes growth, locomotive behaviors, reproduction, and lifespan, accompanying with enhanced of reactive oxygen species (ROS) generation, lipid and lipofuscin accumulation, and malondialdehyde content. In addition, exposure to fluopimomide significantly inhibited antioxidant systems including superoxide dismutase, catalase, glutathione S-transferase, and glutathione in the nematodes. Moreover, the expression of oxidative stress-related genes of sod-3, hsp-16.1, gst-4, ctl-2, daf-16, and daf-2 were significantly down-regulated, while the expression of skn-1 was significantly up-regulated. Further evidence revealed that daf-16 and skn-1 mutant strains of C. elegans significantly decreased ROS production upon fluopimomide exposure compared with the wild-type nematodes. Overall, our findings indicated that exposure to fluopimomide at sublethal doses caused oxidative damage, mainly associated with insulin/IGF-1-like signaling pathway in C. elegans. This is the first report of potential toxic effects of fluopimomide even at low concentrations, providing a new insight into the mechanisms of toxicity to C. elegans by fluopimomide.

Lipid metabolism and ageing in Caenorhabditis elegans: a complex interplay

Life expectancy in Western countries is increasing, with concomitant rise in ageing-related pathologies, including Parkinson's and Alzheimer's disease, as well as other neurodegenerative diseases. Consequently, the medical, psychological and economic burden to society is increasing. Thus, understanding the cellular and molecular mechanisms underlying the association of ageing with elevated vulnerability to disease is crucial towards promoting quality of life in old age. Caenorhabditis elegans has emerged as a versatile model to study ageing, due to its simplicity, fast life cycle, and the availability of a wide range of biological tools to target specific genes and cells. Indeed, recent studies in C. elegans have revealed that lipid metabolism plays a key role in controlling longevity by impinging on a plethora of molecular pathways and cell types. Here, we summarise findings relevant to the interplay between lipid metabolism and ageing in C. elegans, and discuss the implications for the pathogenesis of age-related disorders in humans.

Transgenerational reproductive toxicity of 2,4,6-trinitrotoluene (TNT) and its metabolite 4-ADNT in Caenorhabditis elegans

2,4,6-trinitrotoluene (TNT) as an energetic compound widely used in military applications has aroused great concerns in recent years due to its large-scale contamination in soil and water; however, its toxicity is still largely unknown. In this study, we investigated the reproductive toxicity and the transgenerational effects of TNT on Caenorhabditis elegans (C. elegans). Our data showed that exposure to TNT at concentrations ranging from 10 to 100 ng/mL resulted in decreasing the lifespan, brood size, number of oocytes and eggs in uterus, while increasing the number of germ cell apoptosis in C. elegans. The apoptotic effects of TNT were blocked in mutants of cep-1 (w40), egl-1 (n487), and hus-1 (op241), indicating conserved genotoxic response genes was involved in mediating TNT-induced germ cell apoptosis. Parental exposure to TNT significantly increased the germ cell apoptosis from P0 to F2 generation, but the toxicity faded away in F3 and F4 generations. Furthermore, TNT was rapidly metabolized in P0, and the accumulation of 4-aminodinitrotoluene (4-ADNT), the main metabolite of TNT in C. elegans, showed a significant decrease from P0 to F1 and a slow decrease in the subsequent generations. Our results demonstrated that ingested TNT can cause severe transgenerational reproductive toxicity and be rapidly converted to 4-ADNT in the nematodes. These data provided basis for future studies on the effects of energetic compounds across generations.

The effect of krill oil on longevity and locomotion: a pilot study

Krill oil as a dietary supplement is popular with consumers. Several experimental and clinical trials have suggested that krill oil is beneficial for longevity and locomotion, but the underlying mechanisms for this have remained largely elusive. In this study, we investigated alleviation of impairment of Caenorhabditis elegans by polar compounds from frying oil with the use of krill oil. Observations of life span and locomotion demonstrated that the intake of krill oil increased median survival by 17.86%, head thrashes by 27.79% and body bends by 20.78% for impaired C. elegans. Metabolomic analysis revealed that krill oil could significantly restore the negative alterations caused by polar compounds, including upregulation of serine, tyrosine, palmitic acid and stearic acid, and downregulation of maltose 6'-phosphate, UDP-glucose, glutamic acid, phosphoserine and 25-hydroxyvitamin D3. Additionally, intake of krill oil also changed some metabolites that were irrelevant to impairment by polar compounds, but were beneficial for health for C. elegans. Metabolomics investigations indicated that krill oil ameliorates energy metabolism and alleviates oxidative stress and excitotoxicity caused by polar compounds on C. elegans. The data obtained in this study will facilitate future functional studies of krill oil.

The use of different sublethal endpoints to monitor atrazine toxicity in nematode Caenorhabditis elegans

In this work, Caenorhabditis elegans was employed as an in vivo model to determine the toxic effects of atrazine at different concentrations. After the exposure period from the larval stage L1 to adulthood day 1, atrazine (10 mg/L) significantly decreased the body length and lifespan of nematodes. In addition, exposure to ≥0.01 mg/L atrazine remarkably increased the intestinal reactive oxygen species (ROS) levels and reduced locomotion behavior of nematodes, while exposure to ≥ 1 mg/L atrazine decreased the brood size of nematodes. Moreover, atrazine (0.001-0.1 mg/L) upregulated the expression levels of hsp-6::GFP and hsp-6/60 in nematodes, indicating the activation of mitochondrial unfolded protein response (mtUPR). On the contrary, atrazine (1-10 mg/L) downregulated the expression levels of hsp-6::GFP and hsp-6/60 in nematodes. Furthermore, mtUPR induction governed by the RNAi knockdown of atfs-1 could increase the vulnerability of nematodes against atrazine toxicity. Overall, our findings highlighted the dynamic responses of nematodes toward different concentrations of atrazine, which could be monitored using different sublethal endpoints as bioindicators.

Epigenetic response to nanopolystyrene in germline of nematode Caenorhabditis elegans

microRNAs (miRNAs) provide an epigenetic regulation mechanism for the response to environmental toxicants. mir-38, a germline miRNA, was increased by exposure to nanopolystyrene (100 nm). In this study, we further found that germline overexpression of mir-38 decreased expressions of nhl-2 encoding a miRISC cofactor, ndk-1 encoding a homolog of NM23-H1, and wrt-3 encoding a homolog of PPIL-2. Meanwhile, germline-specific RNAi knockdown of nhl-2, ndk-1, or wrt-3 caused the resistance to nanopolystyrene toxicity. Additionally, mir-38 overexpression suppressed the resistance of nematodes overexpressing germline nhl-2, ndk-1, or wrt-3 containing 3'UTR, suggesting the role of NHL-2, NDK-1, and WRT-3 as the targets of germline mir-38 in regulating the response to nanopolystyrene. Moreover, during the control of response to nanopolystyrene, EKL-1, a Tudor domain protein, was identified as the downstream target of germline NHL-2, kinase suppressors of Ras (KSR-1 and KSR-2) were identified as the downstream targets of germline NDK-1, and ASP-2, a homolog of BACE1, was identified as the downstream target of germline WRT-3. Our results raised a mir-38-mediated molecular network in the germline in response to nanopolystyrene in nematodes. Our data provided an important basis for our understanding the response of germline of organisms to nanoplastic exposure.

Response of DBL-1/TGF-β signaling-mediated neuron-intestine communication to nanopolystyrene in nematode Caenorhabditis elegans

TGF-β signaling pathway is important for the regulation of stress response in organisms. We here used Caenorhabditis elegans to determine the function of DBL-1/TGF-β signaling pathway in the control of response to nanopolystyrene (100 nm). In DBL-1/TGF-β signaling pathway, exposure to 1-1000 μg/L nanopolystyrene significantly increased the expressions of dbl-1 encoding a TGF-β ligand, sma-6 encoding a TGF-β receptor, sma-4 encoding a Co-Smad, and two genes (mab-31 and sma-9) encoding transcriptional factors. DBL-1 acted in the neurons to control the response to nanopolystyrene. In the neurons, the expression and the function of DBL-1 were under the control of two signaling cascades (SMOC-1-ZAG-1 and SMOC-1-ADT-2). TGF-β receptor SMA-6 acted in the intestine to control the response to nanopolystyrene. The downstream Co-Smad/SMA-4 and two transcriptional factors (MAB-31 and SMA-9) of SMA-6 in the intestine were further identified to be required for the control of response to nanopolystyrene. In nanopolystyrene exposed nematodes, intestinal MAB-31 activated the mitochondrial Mn-SOD/SOD-3 by modulating DAF-16 activity, and intestinal SMA-9 activated the mitochondrial unfolded protein response by affecting ELT-2 activity. Therefore, the DBL-1/TGF-β signaling pathway mediated an important neuron-intestine communication in nanopolystyrene exposed nematodes.

Effect of chronic exposure to nanopolystyrene on nematode Caenorhabditis elegans

Nanoplastic exposure could cause toxicity to Caenorhabditis elegans at various aspects. Nevertheless, the effects of chronic exposure to nanoplastics remain largely unclear in nematodes. In this study, we employed C. elegans as an animal model to determine the effects of nanopolystyrene (30 nm) exposure from adult day-1 for 8-day. After the exposure, only 1000 μg/L nanopolystyrene reduced the lifespan. In contrast, nanopolystyrene ≥1 μg/L decreased locomotion behavior and activated oxidative stress. Meanwhile, in 10 μg/L nanopolystyrene exposed nematodes, both expression of SOD-3, a Mn-SOD, and autophagy induction as indicated by LGG-1:GFP expression were significantly increased. RNAi knockdown of daf-2 encoding an insulin receptor enhanced the autophagy induction, and RNAi knockdown of daf-16 encoding a FOXO transcriptional factor in insulin signaling pathway suppressed the autophagy induction in 10 μg/L nanopolystyrene exposed nematodes. Moreover, DAF-16 acted upstream of LGG-1, an ortholog of Atg8/LC3, to regulate the toxicity of nanopolystyrene toxicity in inducing ROS production and in decreasing locomotion behavior at adult day-9. Our data implied the potential toxicity of chronic exposure to nanoplastics at predicted environmental concentrations on organisms.

Intestinal mir-794 responds to nanopolystyrene by linking insulin and p38 MAPK signaling pathways in nematode Caenorhabditis elegans

Caenorhabditis elegans is sensitive to toxicity of environmental pollutants. The alteration in expression of mir-794, a microRNA (miRNA) molecule, mediated a protective response to nanopolystyene (100 nm) at predicted environmental concentration (1 μg/L) in nematodes. However, the underlying molecular basis for mir-794 function in regulating the response to nanopolystyrene remains largely unclear. In this study, we found that intestinal overexpression of mir-794 caused the susceptibility to nanopolystyrene toxicity, suggesting that mir-794 acted in the intestine to regulate the response to nanopolystyrene. Intestinal overexpression of mir-794 further decreased the expressions of daf-16 encoding a FOXO transcriptional factor in insulin signaling pathway, skn-1 encoding a Nrf transcriptional factor in p38 MAPK signaling pathway, and mdt-15 encoding a lipid metabolic sensor acting downstream of SKN-1 in nanopolystyrene exposed nematodes. Meanwhile, intestinal overexpression of mir-794 could suppress the resistance of nematodes overexpressing intestinal daf-16, skn-1, or mdt-15 containing the corresponding 3' untranslated region (3' UTR) to nanopolystyrene toxicity. Therefore, DAF-16, SKN-1, and MDT-15 acted as the downstream targets of intestinal mir-794 to regulate the response to nanopolystyrene. In the intestine, DAF-16 functioned synergistically with SKN-1 or MDT-15 to regulate the response to nanopolystyrene. Our results suggested that the intestinal mir-794 provided an important epigenetic regulation mechanism to control the response to nanopolystyrene by linking insulin and p38 MAPK signaling pathways in nematodes.

Potential toxicity of nanopolystyrene on lifespan and aging process of nematode Caenorhabditis elegans

In the environment, nanoplastic particles, such as nanopolystyrene, potentially cause toxicity on organisms at various aspects. We here employed endpoints of lifespan and aging-related phenotypes to further investigate the possible long-term effects of nanopolystyrene (100 nm) in Caenorhabditis elegans. After exposure from L1-larvae to adult day-3, nanopolystyrene at high concentrations (100 and 1000 μg/L) reduced the lifespan. Although nanopolystyrene (1 or 10 μg/L) did not affect the lifespan, nanopolystyrene (1 or 10 μg/L) could induce the more severe intestinal reactive oxygen species (ROS) production and decrease in locomotion behavior during the aging process compared with control. Moreover, nanopolystyrene exposure could cause the severe decrease in expressions of some immune response genes, hsp-6 gene, and genes encoding manganese-superoxide dismutases (Mn-SODs) during aging process, suggesting the severe suppression in innate immune response, inhibition in antioxidation defense system, and suppression in mitochondrial unfolded protein response (mt UPR) by nanopolystyrene. Our results highlight the potential of long-term nanopolystyrene exposure in reducing longevity and in affecting health state during the aging process in environmental organisms.

Nanopolystyrene-induced microRNAs response in Caenorhabditis elegans after long-term and lose-dose exposure

microRNAs (miRNAs) usually act post-transcriptionally to suppress the expression of many targeted genes. However, the response of miRNAs to nanoplastics is still unclear. We here employed Caenorhabditis elegans to investigate the response of miRNAs to 100 nm nanopolystyrene at a predicted environmental concentration (1 μg/L). After exposure from L1-larvae to adult day-3, we found that 7 miRNAs (4 down-regulated (mir-39, mir-76, mir-794, and mir-1830) and 3 up-regulated (mir-35, mir-38, and mir-354)) were dysregulated by nanopolystyrene. Expressions of these 7 miRNAs were dose-dependent in nematodes exposed to 1-100 μg/L nanopolystyrene. Among these 7 miRNAs, we found that only mir-35, mir-38, mir-76, mir-354, and mir-794 were involved in the regulation of response to nanopolystyrene based on phenotypic analysis of both transgenic strains and mutant nematodes. Overexpression of mir-35, mir-38, or mir-354 induced a resistance to nanopolystyrene toxicity, and overexpression of mir-76 or mir-794 induced a susceptibility to nanopolystyrene toxicity, which suggested that these 5 miRNAs mediated a protective response to nanopolystyrene. Gene ontology and KEGG analysis further implied that mir-35, mir-38, mir-76, mir-354, and mir-794 were associated with various biological processes and signaling pathways. Our results suggest the crucial role of a certain number of miRNAs in response to nanopolystyrene after long-term and low-dose exposure in organisms.

Identification of long non-coding RNAs in response to nanopolystyrene in Caenorhabditis elegans after long-term and low-dose exposure

The potential adverse effects of nanoplastics, such as nanopolystyrene, have received the great attention recently. However, the molecular response of organisms to nanoplastics is still largely unknown. In this study, we employed Caenorhabditis elegans as an animal model to investigate the long non-coding RNAs (lncRNAs) in response to long-term exposure to low-dose nanopolystyrene (100 nm). Based on Hiseq 2000 sequencing and qRT-PCR confirmation, we identified 36 lncRNAs (21 down-regulated lncRNAs and 15 up-regulated lncRNAs) in response to nanopolystyrene (1 μg/L). Using intestinal reactive oxygen species (ROS) production and locomotion behavior as endpoints, we found that RNAi knockdown of linc-2, linc-9, or linc-61 induced a susceptibility to nanopolystyrene toxicity, and RNAi knockdown of linc-18 or linc-50 induced a resistance to nanopolystyrene toxicity. Meanwhile, nanopolystyrene (1 μg/L) increased expressions of linc-2, linc-9, linc-18, and linc-61 and decreased linc-50 expression, suggesting that these 5 lncRNAs mediated two different responses to nanopolystyrene exposure. Bioinformatical analysis implied that these 5 lncRNAs were associated with multiple biological processes and signaling pathways. Our results demonstrated the crucial roles of lncRNAs in response to long-term exposure to low-dose nanopolystyrene in organisms.

Metabolomics and phenotype assessment reveal cellular toxicity of triclosan in Caenorhabditis elegans

Triclosan (TCS) is an antibiotic that is added to household and personal care products. Recently, it has become more popular, turning into one of the major contaminants of the environment. This raises a dawning awareness regarding health and environmental issues. In this study, the toxicity of TCS to Caenorhabditis elegans was evaluated using a metabolomics approach. Additionally, the lifespan, locomotion, and reproduction of C. elegans were monitored for a better interpretation of toxic effects. In C. elegans exposed to TCS at the concentration of 1 mg/L, the average lifespan decreased in approximately 3 days. Reproduction and locomotion were also decreased with TCS exposure. The number of progenies, head thrashes, and body bends decreased to 45.15 ± 11.63, 39.60 ± 5.90, and 9.20 ± 1.56 with the exposure to TCS, respectively. Oxidative stress was induced by TCS exposure, which was confirmed by using DAF-16:GFP strain and H₂DCF-DA-based ROS assay. Metabolomics analysis revealed that carbohydrates and amino acids related to energy production were considerably affected by TCS exposure. Additionally, levels of tyrosine, serine, and polyamines, responsible for neurotransmitter and stress response, were significantly altered. Collectively, our findings suggest that TCS induces toxic effects by various mechanisms and exerts a strong influence in various phenotypes of the tested model.

Early life exposure to di(2-ethylhexyl)phthalate causes age-related declines associated with insulin/IGF-1-like signaling pathway and SKN-1 in Caenorhabditis elegans

Di(2-ethylhexyl)phthalate (DEHP) is an ubiquitous and emerging contaminant that is widely present in food, agricultural crop, and the environment, posing a potential risk to human health. This study utilized the nematode Caenorhabditis elegans to decipher the toxic effects of early life exposure to DEHP on aging and its underlying mechanisms. The results showed that exposure to DEHP at 0.1 and 1.5 mg/L inhibited locomotive behaviors. In addition, DEHP exposure significantly shortened the mean lifespan of the worms and further adversely affected pharyngeal pumping rate and defecation cycle in aged worms. Moreover, DEHP exposure also further enhanced accumulation of age-related biomarkers including lipofuscin, lipid peroxidation, and intracellular reactive oxygen species in aged worms. In addition, exposure to DEHP significantly suppressed gene expression of hsp-16.1, hsp-16.49, and hsp-70 in aged worms. Further evidences showed that mutation of genes involved in insulin/IGF-1-like signaling (IIS) pathway (daf-2, age-1, pdk-1, akt-1, akt-2, and daf-16) restored lipid peroxidation accumulation upon DEHP exposure in aged worms, whereas skn-1 mutation resulted in enhanced lipid peroxidation accumulation. Therefore, IIS and SKN-1 may serve as an important molecular basis for DEHP-induced age-related declines in C. elegans. Since IIS and SKN-1 are highly conserved among species, the age-related declines caused by DEHP exposure may not be exclusive in C. elegans, leading to adverse human health consequences due to widespread and persistent DEHP contamination in the environment.