Oxidative stress, intestinal damage, and cell apoptosis: Toxicity induced by fluopyram in Caenorhabditis elegans

Gelsenicine disrupted the intestinal barrier of Caenorhabditis elegans

Gelsemium elegans Benth. (G. elegans) is a traditional medicinal herb that has anti-inflammatory, analgesic, sedative, and detumescence effects. However, it can also cause intestinal side effects such as abdominal pain and diarrhea. The toxicological mechanisms of gelsenicine are still unclear. The objective of this study was to assess enterotoxicity induced by gelsenicine in the nematodes Caenorhabditis elegans (C. elegans). The nematodes were treated with gelsenicine, and subsequently their growth, development, and locomotion behavior were evaluated. The targets of gelsenicine were predicted using PharmMapper. mRNA-seq was performed to verify the predicted targets. Intestinal permeability, ROS generation, and lipofuscin accumulation were measured. Additionally, the fluorescence intensities of GFP-labeled proteins involved in oxidative stress and unfolded protein response in endoplasmic reticulum (UPRER) were quantified. As a result, the treatment of gelsenicine resulted in the inhibition of nematode lifespan, as well as reductions in body length, width, and locomotion behavior. A total of 221 targets were predicted by PharmMapper, and 731 differentially expressed genes were screened out by mRNA-seq. GO and KEGG enrichment analysis revealed involvement in redox process and transmembrane transport. The permeability assay showed leakage of blue dye from the intestinal lumen into the body cavity. Abnormal mRNAs expression of gem-4, hmp-1, fil-2, and pho-1, which regulated intestinal development, absorption and catabolism, transmembrane transport, and apical junctions, was observed. Intestinal lipofuscin and ROS were increased, while sod-2 and isp-1 expressions were decreased. Multiple proteins in SKN-1/DAF-16 pathway were found to bind stably with gelsenicine in a predictive model. There was an up-regulation in the expression of SKN-1:GFP, while the nuclear translocation of DAF-16:GFP exhibited abnormality. The UPRER biomarker HSP-4:GFP was down-regulated. In conclusion, the treatment of gelsenicine resulted in the increase of nematode intestinal permeability. The toxicological mechanisms underlying this effect involved the disruption of intestinal barrier integrity, an imbalance between oxidative and antioxidant processes mediated by the SKN-1/DAF-16 pathway, and abnormal unfolded protein reaction.

Comparative antioxidant and metabolomic analysis for the identification of differential response of mussel (Mytilus coruscus) to four succinate dehydrogenase inhibitor fungicides

Succinate dehydrogenase inhibitor fungicides (SDHIs) are frequently detected in the marine environment. However, studies on the toxicity of SDHIs to marine organisms, Mytilus coruscus (M. coruscus), are poorly reported. Therefore, the antioxidant activities and metabolomic response of four SDHIs, namely, boscalid (BC), thifluzamide (TF), fluopyram (FO), and bixafen (BIX), to (M. coruscus), were comprehensively investigated. The antioxidant activity of BC and TF was significantly increased (p<0.05), whereas those of FO and BIX were significantly decreased. Furthermore, metabolite discriminations among M. coruscus to four SDHIs were illustrated by an untargeted metabolomics approach. A total of 52, 50, 93, and 129 differential metabolites were obtained for BC, TF, FO, and BIX. KEGG of the different metabolites show that the four SDHIs had differential effects on the metabolic pathways of M. coruscus. The current study demonstrated four SDHIs triggered glucose metabolism, lipid metabolism, tricarboxylic acid cycle, and oxidative phosphorylation processes and caused the disruption of nutrient and energy conversion processes in mussels. Finally, five biomarkers were screened by analyzing common differential metabolites that emerged from the four SDHI exposures, which could be used for risk assessment of marine ecosystem exposure to SDHIs. Our results demonstrated the use of metabolomics to understand the potential mechanisms of toxicity of four SDHIs to mussels and to identify potential targets for future targeted risk assessment.

Combined toxicity of trifloxystrobin and fluopyram to zebrafish embryos and the effect on bone development

Trifloxystrobin (TRI) is a methacrylate fungicide, and fluopyram (FLU) is a new pyridylethylbenzamide fungicide and nematicide. Both are often detected in water bodies and may be highly toxic to many aquatic organisms. Unfortunately, the aquatic biological risks of single FLU or a mixture of trifloxystrobin and fluopyram have not been reported. In this study, zebrafish was selected as the test organism to investigate the combined toxicity of trifloxystrobin and fluopyram to zebrafish. After zebrafish embryos exposed to three pesticide solutions, Alcian-blue staining, Alizarin-red staining and quantitative PCR (qPCR) were performed. The results indicated that 96h-LC50 of TRI was 0.159 mg·L-1 to zebrafish embryo, which was highly toxic. The 96h-LC50 of FLU to zebrafish embryos was 4.375 mg·L-1, being moderately toxic. The joint toxicity to zebrafish embryos(FLU at 96h-LC50 and TRI at 96h-LC50 in a 1:1 weight ratio to form a series of concentration treatment groups) was antagonistic. Both trifloxystrobin and fluopyram also inhibited the skeletal development of zebrafish and showed to be antagonistic. The results of qPCR indicated upregulations of different genes upon three different treatments. TRI mainly induced Smads up-expression, which may affect the BMP-smads pathway. FLU mainly induced an up-expression of extracellular BMP ligands and type I receptor (Bmpr-1a), which may affect the BMP ligand receptor pathway. The 1:1 mixture (weight ratio) of trifloxystrobin and fluopyram induced a reduction of the genes of extracellular BMP ligand (Smads) and type I receptor (Bmpr1ba), which may down-regulate BMP signaling and thus attenuating cartilage hyperproliferation, hypertrophy and mineralization. The results warren an interest in further studying the effect of the two fungicides in a mixture on zebrafish.

Effect of Fluopyram on Pratylenchus penetrans on Corn in the Field and In Vitro

The effects of a fluopyram seed treatment on lesion nematodes (Pratylenchus spp.) and other plant-parasitic nematodes (PPNs) were evaluated on corn in multiple field locations in 2020 and 2021. The highest rate of fluopyram seed treatment (0.15 mg seed-1) reduced early season population density of lesion nematodes compared with the base treatment control in 2020 only. However, fluopyram did not affect late season lesion nematode population density and corn yields. Fluopyram seed treatment also had minimal or nonsignificant effects on other PPN species. Based on these results, the effects of fluopyram were tested in vitro on Pratylenchus penetrans. Results demonstrated that fluopyram severely affected motility in P. penetrans. The sensitivity of P. penetrans second-stage juveniles (J2s) to fluopyram was significantly higher than at J4 and adult, suggesting that sensitivity to fluopyram is dependent on developmental stage. In addition, the effects of fluopyram were reversible at an EC50 but were irreversible at the maximum concentration (25 μg/ml). Overall, our results indicate that fluopyram has potential for controlling P. penetrans, but its efficacy is variable depending on nematode developmental stage and chemical concentration. Further research is needed to determine if these impacts can translate to field scenarios.

Discovery of Trifluorobutene Amide Derivatives as Potential Nematicides: Design, Synthesis, Nematicidal Activity Evaluation, SAR, and Mode of Action Study

Plant-parasitic nematodes are one of the major threats to crop protection. However, only limited nematicides are currently available and are confronted with a growing resistance problem, which necessitates the development of novel nematicides. In this study, a series of trifluorobutene amide derivatives was synthesized through the strategy of amide bond reversal, and their nematicidal activity against Meloidogyne incognita was evaluated. The bioassay showed that compounds C2, C10, and C18 and some analogues thereof exhibited good nematicidal activity. Among them, the derivatives of compound C2 containing a benzene ring [C26 (R = 2-CH3) and C33 (R = 2-Cl)] exhibited excellent bioactivity against M. incognita in vitro. The LC50/72h values reached 14.13 and 14.71 mg·L-1, respectively. Moreover, analogues of compounds C10 and C18 containing a thiophene ring [C43 (R = 5-CH3), C44 (R = 4-CH3), and C50 (R = 5-Cl)] exhibited significant bioactivity against M. incognita in vivo with inhibition rates of 68.8, 65.5, and 69.8% at 2.5 mg·L-1 in a matrix, respectively. Meanwhile, C44 and C50 also showed excellent control effects against M. incognita in both cups and microplots. The structure-activity relationship (SAR) of synthesized compounds was discussed in detail. Comparative molecular field analysis (CoMFA) was also conducted to develop the SAR profile. The preliminary mode of action investigation showed that compound C33 exhibited strong inhibition on egg hatching, motility, feeding behavior, and growth of Caenorhabditis elegans. At the same time, the impact of active compounds on biochemical indicators related to oxidative stress showed that compound C33 influenced the production of ROS (reactive oxygen species), and the accumulation of lipofuscin and lipids on C. elegans.

Synergistic toxicity induced by the co-exposure of tenuazonic acid and patulin in Caenorhabditis elegans: Daf-16 plays an important regulatory role

Tenuazonic acid (TeA) and patulin (PAT), as the naturally occurring mycotoxins with various toxic effects, are often detected in environment and food chain, has attracted more and more attention due to their widespread and high contaminations as well as the coexistence, which leads to potential human and animals' risks. However, their combined toxicity has not been reported yet. In our study, C. elegans was used to evaluate the type of combined toxicity caused by TeA+PAT and its related mechanisms. The results showed that TeA and PAT can induce synergistic toxic effects based on Combination Index (CI) evaluation model (Chou-Talalay method), that is, the body length, brood size as well as the levels of ROS, CAT and ATP were significantly affected in TeA+PAT-treated group compared with those in TeA- or PAT-treated group. Besides, the expressions of oxidative (daf-2, daf-16, cyp-35a2, ctl-1, ctl-3, pmk-1, jnk-1, skn-1) and intestinal (fat-5, pod-2, egl-8, pkc-3, ajm-1, nhx-2) stress-related genes were disrupted, among which daf-16 displayed the most significant alternation. Further study on daf-16 gene defective C. elegans showed that the damages to the mutant nematodes were significantly attenuated. Since daf-2, daf-16, jnk-1 and pmk-1 are evolutionarily conserved, our findings could hint synergistic toxic effects of TeA+PAT on higher organisms.

Design, Synthesis, Nematicidal Activity, and Mechanism of Novel Amide Derivatives Containing an 1,2,4-Oxadiazole Moiety

To discover new nematicides, a series of novel amide derivatives containing 1,2,4-oxadiazole were designed and synthesized. Several compounds showed excellent nematicidal activity. The LC50 values of compounds A7, A18, and A20-A22 against pine wood nematode (Bursaphelenchus xylophilus), rice stem nematode (Aphelenchoides besseyi), and sweet potato stem nematode (Ditylenchus destructor) were 1.39-3.09 mg/L, which were significantly better than the control nematicide tioxazafen (106, 49.0, and 75.0 mg/L, respectively). Compound A7 had an outstanding inhibitory effect on nematode feeding, reproductive ability, and egg hatching. Compound A7 effectively promoted the oxidative stress of nematodes and caused intestinal damage to nematodes. Compound A7 significantly inhibited the activity of succinate dehydrogenase (SDH) in nematodes, leading to blockage of electron transfer in the respiratory chain and thereby hindering the synthesis of adenosine triphosphate (ATP), which consequently affects the entire oxidative phosphorylation process to finally cause nematode death. Therefore, compound A7 can be used as a potential SDH inhibitor in nematicide applications.

Evaluation of the toxic effects of fluindapyr, a novel SDHI fungicide, to the earthworms Eisenia fetida

The emergence of resistance to existing succinate dehydrogenase inhibitor fungicides (SDHIs) calls for the urgent innovation of novel formulations, but also results in an increase information gap on the ecological risks of novel SDHIs especially to non-target organisms. Herein, the environmental behavior and toxicological effects of a novel SDHI, fluindapyr (FIP), were evaluated using earthworm as model non-target organism. Results showed that FIP had a relatively shorter half-live (about 28 days) in artificial soil compared with traditional SDHIs. Besides, FIP exhibited a rapid uptake and bioaccumulation trend in earthworms. For the toxicological effects, FIP suppressed earthworm growth (≥ 5 mg/kg) and reproduction (≥ 1 mg/kg) whereas no lethal effects were observed up to the highest tested concentration of 25 mg/mg. FIP of high exposure concentrations also induced serious epidermis and intestines damage as well as oxidative stress to earthworms after 28-day exposure. In addition, expression of oxidative damage related genes (CAT, CRT, GST, HSP70, SOD) was further verified after FIP exposure. The earthworm Tier 1 RQ also indicated a potential risk for earthworm reproduction. Data presented here may be useful for the risk assessments of FIP in soil ecosystems and help to set appropriate precautions to ensure protection against novel SDHIs.

The New Nematicide Cyclobutrifluram Targets the Mitochondrial Succinate Dehydrogenase Complex in Caenorhabditis elegans

Today, agriculture around the world is challenged by parasitic nematode infections. Plant-parasitic nematodes (PPNs) can cause significant damage and crop loss and are a threat to food security. For a long time, the management of PPN infection has relied on nematicides that impact not only parasitic nematodes but also other organisms. More recently, new nematicides have been developed that appear to specifically target PPN. Cyclobutrifluram belongs to this new category of nematicides. Using the nematode Caenorhabditis elegans as a model organism, we show here that cyclobutrifluram strongly impacts the survival and fertility rates of the worm by decreasing the number of germ cells. Furthermore, using a genetic approach, we demonstrate that cyclobutrifluram functions by inhibiting the mitochondrial succinate dehydrogenase (SDH) complex. Transcriptomic analysis revealed a strong response to cyclobutrifluram exposure. Among the deregulated genes, we found genes coding for detoxifying proteins, such as cytochrome P450s and UDP-glucuronosyl transferases (UGTs). Overall, our study contributes to the understanding of the molecular mode of action of cyclobutrifluram, to the finding of new approaches against nematicide resistance, and to the discovery of novel nematicides. Furthermore, this study confirms that C. elegans is a suitable model organism to study the mode of action of nematicides.

Lentinan protects Caenorhabditis elegans against fluopyram-induced toxicity through DAF-16 and SKN-1 pathways

Fluopyram, a SDH inhibitor fungicide, is widely used in agriculture to control fungi and nematodes. However, fluopyram has been proved toxic that caused damage to organs through oxidative stress. The development of natural extracts that can reduce oxidative damage is a promising method. Lentinan is isolated from Lentinus edodes and has been verified its antioxidant activity. In this study, Caenorhabditis elegans was used to evaluate the protective effects of lentinan against fluopyram-induced toxicity and the possible mechanisms. Results showed that lentinan pretreatment notably increased the survival rate of N2 nematodes by 15.0 % and extended the lifespan by 91.5 %, compared with the fluopyram treatment. Lentinan pretreatment reverted the inhibition of the locomotion and reproduction of C. elegans under the fluopyram stress. In addition, lentinan pretreatment significantly decreased the contents of ROS and MDA in N2 nematodes. Moreover, pretreated with lentinan significantly recovered the decreased activities of CAT, SOD, GST and SDH induced by fluopyram. Lentinan pretreatment enhanced the mRNA levels of daf-16 and skn-1 and their downstream genes in the nematodes compared with the fluopyram group. In daf-16 and skn-1 mutants, the lifespan, ROS and related genes expression were not significantly changed in lentinan pretreatment. Pretreated with lentinan significantly enhanced the fluorescence intensity of SOD-3::GFP and GST-4::GFP, and promoted the nuclear translocation of DAF-16 and SKN-1 under the fluopyram stress. In summary, these findings indicated that lentinan protected C. elegans from fluopyram-induced toxicity via DAF-16 and SKN-1.

The concentration-dependent physiological damage, oxidative stress, and DNA lesions in Caenorhabditis elegans by subacute exposure to landfill leachate

The leakage of landfill leachate (LL) into environmental media would be happened even in the sanitary/controlled landfill, due to the deterioration of geomembrane and the blockage of drainage system after long-term operation. Considering the complex composition and high concentration of pollutants in LL, its toxicity assessment should be conducted as a whole liquid contaminant. Therefore, the impacts of LL on Caenorhabditis elegans (C. elegans) were investigated under the condition of different exposure time and exposure volume fraction (EVF). The stimulating effects on locomotion behavior and growth of C. elegans were observed after acute (24 h) exposure to LL, which were increased firstly and then decreased with the increase of EVF. Meanwhile, the intestinal barrier was not affected by LL, and levels of reactive oxygen species (ROS) and cell apoptosis significantly decreased. However, stimulation and inhibition effects on locomotion behavior and growth of C. elegans were observed when subacute (72 h) exposure to 0.25%-0.5% and 1%-4% of LL, respectively. The intestinal injury index and levels of ROS and cell apoptosis significantly increased when EVF were 2% and 4%. Although the acute exposure of LL had resulted in obviously biological adaptability and antioxidant defense in C. elegans, the protective mechanisms failed to be induced as the exposure time increased (subacute exposure). The toxic effects were confirmed by the down-regulation of genes associated with antioxidant defense and neurobehavior, accompanied by the up-regulation of intestinal injury and cell apoptosis related genes. Moreover, the disturbance of metabolic pathways that associated with locomotion behaviors, growth, and antioxidant defense provided good supplementary evidence for the confirmation of oxidative stress in C. elegans. The research results verified the potential of C. elegans as model organism to determine the complex toxic effects of LL.

Discovery of 2-Naphthol from the Leaves of Actephila merrilliana as a Natural Nematicide Candidate

To identify natural nematicides that can replace chemical nematicides, 2-naphthol with high activity against Meloidogyne incognita was isolated from Actephila merrilliana. The nematicidal activity of 2-naphthol against M. incognita was 100% at 100 μg/mL with an EC50 value of 38.00 μg/mL. Moreover, 2-naphthol had a significant negative effect on egg incubation. 2-Naphthol effectively inhibited the invasion of M. incognita into crops in both a pot experiment and field trial. In addition, the structure-activity relationship indicated that the naphthalene ring and its β-site hydroxyl group were the key pharmacophores for the nematicidal activity of 2-naphthol. Nematodes were stimulated by 2-naphthol to produce excessive reactive oxygen species, which may be the underlying mechanism of 2-naphthol nematicidal activity. A systemic evaluation of 2-naphthol in tomato plants demonstrated that 2-naphthol remained mainly fixed in the roots after being absorbed by the crop and was not transported to the stems or leaves. Thus, 2-naphthol can be developed as a natural nematicide candidate.

Biocontrol Efficacy of Bacillus methylotrophicus TA-1 Against Meloidogyne incognita in Tomato

Root-knot nematodes (RKNs) are harmful plant-parasitic nematodes of tomatoes which can cause significant yield losses. Therefore, there is increasing interest in exploring the application of bacterial nematicides. The bacterium Bacillus methylotrophicus TA-1 is a broad-spectrum biological control agent; however, its effect on RKNs control remains largely unclear. In this study, the toxicity of B. methylotrophicus TA-1 against Meloidogyne incognita was investigated in vitro, and the potential of B. methylotrophicus TA-1 to decrease infection of RKNs in tomato were evaluated in pot and field trials. Results showed that B. methylotrophicus TA-1 exhibited high nematicidal activity against second-stage juveniles (J2s) and eggs of M. incognita with 50% lethal concentration (LC50) values of 5.80 and 7.00 × 108 colony forming units (CFU)/ml, respectively. In the pot experiments and field trials conducted in 2020 and 2021, tomato plants treated with B. methylotrophicus TA-1 soil drench applied once at 3, 6, and 9 × 108 CFU/plant had significantly higher plant height and greater yield compared with the untreated control. Tomato yields of the treated plots with B. methylotrophicus TA-1 in 2 consecutive years' field trials were between 53.4 to 66.1 and 52.8 to 61.5 t/ha, while they were 49.7 and 48.2 t/ha in the untreated control for each year, respectively. The lowest population densities of M. incognita at 30 and 60 days after treatment were 119 and 135 J2s per 100 g soil in 2020 and 43 and 118 J2s in 2021 in TA-1-treated plots. The lowest gall index of 4.7 and 3.3 in 2020 and 2021, respectively, and the highest yield were all observed in the TA-1 at 9 × 108 CFU/plant treated plants, with no significant differences with the commercial control abamectin. These results provided a basis for further studies of B. methylotrophicus TA-1 formulations, application doses, frequencies, and mechanisms of action, which are necessary before it could be used as a component of integrated management programs to manage RKNs in tomato production.

Esterification with a Long-Chain Fatty Acid Elevates the Exposure Toxicity of Tigliane Diterpenoids from Euphorbia fischeriana Roots against Nematodes

In this study, two tigliane diterpenoids, 12-deoxyphorbol-13-hexadecanoate and 12-deoxyphorbol-13-acetate (prostratin), were identified from the methanol extract of the roots of Euphorbia fischeriana and were found to have the ability to significantly reduce the survival of Caenorhabditis elegans. It was determined that exposure to these two compounds had toxic effects on the growth, reproduction, locomotion behavior, and accumulation of lipids and lipofuscin of the nematodes. Moreover, the transcription levels of the genes associated with lipid accumulation, apoptosis, insulin, and nuclear hormone synthesis in C. elegans were significantly influenced. Interestingly, 12-deoxyphorbol-13-hexadecanoate produced exposure toxicity at lower concentrations than that of prostratin. Pearson correlation analysis indicates that the elevated exposure toxicity of 12-deoxyphorbol-13-hexadecanoate may be the result of differing transcription levels, which result from the differential expression of fat-6, egl-38, and cep-1. These results reveal that esterification with a long-chain fatty acid elevates the exposure toxicity of this tigliane diterpenoid, thus providing a basis for the application of tigliane diterpenoids in plant-derived nematicides.

Mitochondria in the Spotlight: C. elegans as a Model Organism to Evaluate Xenobiotic-Induced Dysfunction

Mitochondria play a crucial role in cellular respiration, ATP production, and the regulation of various cellular processes. Mitochondrial dysfunctions have been directly linked to pathophysiological conditions, making them a significant target of interest in toxicological research. In recent years, there has been a growing need to understand the intricate effects of xenobiotics on human health, necessitating the use of effective scientific research tools. Caenorhabditis elegans (C. elegans), a nonpathogenic nematode, has emerged as a powerful tool for investigating toxic mechanisms and mitochondrial dysfunction. With remarkable genetic homology to mammals, C. elegans has been used in studies to elucidate the impact of contaminants and drugs on mitochondrial function. This review focuses on the effects of several toxic metals and metalloids, drugs of abuse and pesticides on mitochondria, highlighting the utility of C. elegans as a model organism to investigate mitochondrial dysfunction induced by xenobiotics. Mitochondrial structure, function, and dynamics are discussed, emphasizing their essential role in cellular viability and the regulation of processes such as autophagy, apoptosis, and calcium homeostasis. Additionally, specific toxins and toxicants, such as arsenic, cadmium, and manganese are examined in the context of their impact on mitochondrial function and the utility of C. elegans in elucidating the underlying mechanisms. Furthermore, we demonstrate the utilization of C. elegans as an experimental model providing a promising platform for investigating the intricate relationships between xenobiotics and mitochondrial dysfunction. This knowledge could contribute to the development of strategies to mitigate the adverse effects of contaminants and drugs of abuse, ultimately enhancing our understanding of these complex processes and promoting human health.

Oxidative stress and mitochondrial damage induced by a novel pesticide fluopimomide in Caenorhabditis elegans

Fluopimomide is a novel pesticide intensively used in agricultural pest control; however, its excessive use may have toxicological effects on non-target organisms. In this study, Caenorhabditis elegans was used to evaluate the toxic effects of fluopimomide and its possible mechanisms. The effects of fluopimomide on the growth, pharyngeal pumping, and antioxidant systems of C. elegans were determined. Furthermore, the gene expression levels associated with mitochondria in the nematodes were also investigated. Results indicated that fluopimomide at 0.2, 1.0, and 5.0 mg/L notably (p < 0.001) decreased body length, pharyngeal pumping, and body bends in the nematodes compared to the untreated control. Additionally, fluopimomide at 0.2, 1.0, and 5.0 mg/L notably (p < 0.05) increased the content of malondialdehyde by 3.30-, 21.24-, and 33.57-fold, respectively, while fluopimomide at 1.0 and 5.0 mg/L significantly (p < 0.001) increased the levels of reactive oxygen species (ROS) by 49.14% and 77.06% compared to the untreated control. In contrast, fluopimomide at 1.0 and 5.0 mg/L notably reduced the activities of target enzyme succinate dehydrogenase and at 5.0 mg/L reduced the activities of antioxidant enzyme superoxide dismutase. Further evidence revealed that fluopimomide at 1.0 and 5.0 mg/L significantly inhibited oxygen consumption and at 0.2, 1.0, and 5.0 mg/L significantly inhibited ATP level in comparison to the untreated control. The expression of genes related to the mitochondrial electron transport chain mev-1 and isp-1 was significantly downregulated. ROS levels in the mev-1 and isp-1 mutants after fluopimomide treatments did not change significantly compared with the untreated mutants, suggesting that mev-1 and isp-1 may play critical roles in the toxicity induced by fluopimomide. Overall, the results demonstrate that oxidative stress and mitochondrial damage may be involved in toxicity of fluopimomide in C. elegans.

Combined Effects of Micro- and Nanoplastics at the Predicted Environmental Concentration on Functional State of Intestinal Barrier in Caenorhabditis elegans

The possible toxicity caused by nanoplastics or microplastics on organisms has been extensively studied. However, the unavoidably combined effects of nanoplastics and microplastics on organisms, particularly intestinal toxicity, are rarely clear. Here, we employed Caenorhabditis elegans to investigate the combined effects of PS-50 (50 nm nanopolystyrene) and PS-500 (500 nm micropolystyrene) at environmentally relevant concentrations on the functional state of the intestinal barrier. Environmentally, after long-term treatment (4.5 days), coexposure to PS-50 (10 and 15 μg/L) and PS-500 (1 μg/L) resulted in more severe formation of toxicity in decreasing locomotion behavior, in inhibiting brood size, in inducing intestinal ROS production, and in inducting intestinal autofluorescence production, compared with single-exposure to PS-50 (10 and 15 μg/L) or PS-500 (1 μg/L). Additionally, coexposure to PS-50 (15 μg/L) and PS-500 (1 μg/L) remarkably caused an enhancement in intestinal permeability, but no detectable abnormality of intestinal morphology was observed in wild-type nematodes. Lastly, the downregulation of acs-22 or erm-1 expression and the upregulation expressions of genes required for controlling oxidative stress (sod-2, sod-3, isp-1, clk-1, gas-1, and ctl-3) served as a molecular basis to strongly explain the formation of intestinal toxicity caused by coexposure to PS-50 (15 μg/L) and PS-500 (1 μg/L). Our results suggested that combined exposure to microplastics and nanoplastics at the predicted environmental concentration causes intestinal toxicity by affecting the functional state of the intestinal barrier in organisms.

Mulberry leaves attenuate D-galactose-induced aging in vivo and in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Mulberry leaves contain many bioactive compounds and have been widely used in traditional medicines and functional foods for prevention and treatment of age-related diseases, such as diabetes, cognitive impairment and obesity-mediated liver cancer. Aging has an irreversible negative impact on human health for many years, even decades, before death, which is a social and economic burden on society.

AIM OF THE STUDY

The objective of this study was to investigate the antioxidant and anti-aging effects of mulberry leaf extract (MLE) in vivo and in vitro.

MATERIALS AND METHODS

The Caenorhabditis elegans (C. elegans) was used as a model organism to observe the effects of different concentrations of MLE (1, 2, 4, 8 mg/mL) on nematodes' healthy lifespan, reproductive capacity, locomotion, stress resistance, and antioxidation. In addition, D-galactose (D-gal) induced liver aging in mice and L-02 cells were established. The antioxidant and anti-aging effects of MLE were evaluated by body weight, organ indexes, malondialdehyde (MDA), total superoxide dismutase (T-SOD), total antioxidant capacity (T-AOC), aspartate and alanine aminotransferases (AST and ALT), reactive oxygen species (ROS), mitochondrial membrane potential (MMP), hematoxylin and eosin (H&E), senescence-associated β-galactosidase (SA-β-Gal). Besides, the expressions of AMPK/SIRT1/PGC-1α and Nrf2-Keap1 were detected by Western blotting.

RESULTS

MLE could significantly prolonged nematodes' average life span and improved most physiological indicators related to aging of C. elegans. Moreover, Treatment with MLE ameliorated the decreased body weight and organ index (weight of organ/body weight) in model mice, and protected against oxidative stress in mice and liver cells, in a dose-dependent manner, up-regulating T-SOD and T-AOC, while reducing ROS and MDA levels. MLE decreased both liver and cell levels of AST and ALT, and enhanced the mitochondrial membrane potential. MLE activated the AMPK/SIRT1/PGC-1α pathways, participated in mitochondrial biosynthesis and oxidative metabolism and delayed D-gal-induced aging. MLE promoted the accumulation of Nrf2 in the nucleus, indicating that the improved oxidative stress response was mediated by the Nrf2-Keap1 pathway in vivo and in vitro.

CONCLUSION

MLE appeared to have great potential for stimulating the oxidative stress response and attenuating the aging process of in vivo and in vitro, and provide a novel health-promoting resource against aging and aging-related diseases.

Curcumin supplementation increases longevity and antioxidant capacity in Caenorhabditis elegans

Curcumin is well known as a potent antioxidant and free radical scavenger and has great potential for anti-aging applications. In this study, we investigate the molecular mechanism of curcumin in prolonging the lifespan of C. elegans. Four concentrations of curcumin (10, 25, 50, and 100 µM) were administered, and the optimal treatment concentration was determined by analyzing the nematode lifespan, physiology, and biochemistry. Additionally, RNA-seq and qRT-PCR were performed to explore the antioxidant effect of curcumin and its underlying mechanism. Results revealed that curcumin could significantly improve the survival capacity of C. elegans without influencing its growth. Curcumin was observed to significantly decrease the levels of reactive oxygen species (ROS) under extreme conditions such as heat stress and paraquat stress. In addition, curcumin increased the amount of nematode mitochondrial DNA (mtDNA) replication. RNA-seq results revealed that the underlying mechanism of curcumin in C. elegans is related to the mitogen-activated protein kinase (MAPK) pathway. qRT-PCR results confirmed that the expression of oxidative stress-related genes (sod-1, sod-2, sod-3, gst-4) was increased, and the expression of MAPK signaling pathway-related genes (sek-1, pmk-1, nsy-1) was significantly downregulated. Furthermore, the administration of curcumin extended the lifespan of nematodes, potentially through the enhancement of oxidative stress resistance and the downregulation of the MAPK signaling pathway. These findings improve our understanding of both lifespan extension and the potential mechanism of curcumin in C. elegans.

Isolation, Identification and Molecular Mechanism Analysis of the Nematicidal Compound Spectinabilin from Newly Isolated Streptomyces sp. DT10

Plant parasitic nematodes (PPNs) are highly destructive and difficult to control, while conventional chemical nematicides are highly toxic and cause serious environmental pollution. Additionally, resistance to existing pesticides is becoming increasingly common. Biological control is the most promising method for the controlling of PPNs. Therefore, the screening of nematicidal microbial resources and the identification of natural products are of great significance and urgency for the environmentally friendly control of PPNs. In this study, the DT10 strain was isolated from wild moss samples and identified as Streptomyces sp. by morphological and molecular analysis. Using Caenorhabditis elegans as a model, the extract of DT10 was screened for nematicidal activity, which elicited 100% lethality. The active compound was isolated from the extracts of strain DT10 using silica gel column chromatography and semipreparative high-performance liquid chromatography (HPLC). The compound was identified as spectinabilin (chemical formula C28H31O6N) using liquid chromatography mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR). Spectinabilin exhibited a good nematicidal activity on C. elegans L1 worms, with a half-maximal inhibitory concentration (IC50) of 2.948 μg/mL at 24 h. The locomotive ability of C. elegans L4 worms was significantly reduced when treated with 40 μg/mL spectinabilin. Further analysis of spectinabilin against known nematicidal drug target genes in C. elegans showed that it acts via target(s) different from those of some currently used nematicidal drugs such as avermectin and phosphine thiazole. This is the first report on the nematicidal activity of spectinabilin on C. elegans and the southern root-knot nematode Meloidogyne incognita. These findings may pave the way for further research and application of spectinabilin as a potential biological nematicide.

Genotoxicity of organic contaminants in the soil: A review based on bibliometric analysis and methodological progress

Organic contaminants (OCs) are ubiquitous in the environment, posing severe threats to human health and ecological balance. In particular, OCs and their metabolites could interact with genetic materials to induce genotoxicity, which has attracted considerable attention. In this review, bibliometric analysis was executed to analyze the publications on the genotoxicity of OCs in soil from 1992 to 2021. The result indicated that significant contributions were made by China and the United States in this field and the research hotspots were biological risks, damage mechanisms, and testing methods. Based on this, in this review, we summarized the manifestations and influencing factors of genotoxicity of OCs to soil organisms, the main damage mechanisms, and the most commonly utilized testing methods. OCs can induce genotoxicity and the hierarchical response of soil organisms, which could be influenced by the physicochemical properties of OCs and the properties of soil. Specific mechanisms of genotoxicity can be classified into DNA damage, epigenetic toxicity, and chromosomal aberrations. OCs with different molecular weights lead to genetic material damage by inducing the generation of ROS or forming adducts with DNA, respectively. The micronucleus test and the comet test are the most commonly used testing methods. Moreover, this review also pointed out that future studies should focus on the relationships between bioaccessibilities and genotoxicities, transcriptional regulatory factors, and potential metabolites of OCs to elaborate on the biological risks and mechanisms of genotoxicity from an overall perspective.

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.

Oxidation and Antioxidation of Natural Products in the Model Organism Caenorhabditiselegans

Natural products are small molecules naturally produced by multiple sources such as plants, animals, fungi, bacteria and archaea. They exert both beneficial and detrimental effects by modulating biological targets and pathways involved in oxidative stress and antioxidant response. Natural products’ oxidative or antioxidative properties are usually investigated in preclinical experimental models, including virtual computing simulations, cell and tissue cultures, rodent and nonhuman primate animal models, and human studies. Due to the renewal of the concept of experimental animals, especially the popularization of alternative 3R methods for reduction, replacement and refinement, many assessment experiments have been carried out in new alternative models. The model organism Caenorhabditis elegans has been used for medical research since Sydney Brenner revealed its genetics in 1974 and has been introduced into pharmacology and toxicology in the past two decades. The data from C. elegans have been satisfactorily correlated with traditional experimental models. In this review, we summarize the advantages of C. elegans in assessing oxidative and antioxidative properties of natural products and introduce methods to construct an oxidative damage model in C. elegans. The biomarkers and signaling pathways involved in the oxidative stress of C. elegans are summarized, as well as the oxidation and antioxidation in target organs of the muscle, nervous, digestive and reproductive systems. This review provides an overview of the oxidative and antioxidative properties of natural products based on the model organism C. elegans.

Lentinan extends lifespan and increases oxidative stress resistance through DAF-16 and SKN-1 pathways in Caenorhabditis elegans

Lentinan, extracted from Lentinus edodes, exhibits bioactive properties in vitro; however, little is known about the antioxidant potential in vivo. In this study, the effects of lentinan at 0.05, 0.25 and 1.25 mg/mL on the lifespan, locomotion, reproductive capacity, and oxidative stress resistance in Caenorhabditis elegans were determined. Compared to the untreated control, lentinan at 0.05, 0.25 and 1.25 mg/mL significantly prolonged the lifespan by 17.6%, 35.3% and 25.3% (p < 0.001), respectively, and improved the brood size, locomotion and stress resistance of the nematodes. Furthermore, lentinan at 0.25 mg/mL significantly reduced accumulation of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) by 38.1% (p = 0.013) and 49.7% (p = 0.028), respectively. In addition, lentinan at all tested concentrations significantly increased the activities of superoxide dismutase (SOD) and catalase (CAT). The expression of skn-1 and daf-16 in the treatments with lentinan at 0.25 and 1.25 mg/mL was significantly (p < 0.005) up-regulated compared with the untreated control, whereas that of the daf-2 gene was significantly down-regulated. Further evidence revealed that ROS production in lentinan-treated daf-16 and skn-1 mutant strains was similar to the untreated control. Consistent with the aforementioned results, lentinan enhanced the nuclear translocation of DAF-16 and SKN-1. Our results demonstrated that lentinan could increase lifespan and protect the nematodes from oxidative stress through DAF-16 and SKN-1.

Reproductive Toxicity of Furfural Acetone in Meloidogyne incognita and Caenorhabditis elegans

Furfural acetone (FAc) is a promising alternative to currently available nematicides, and it exhibits equivalent control efficiency on root-knot nematodes with avermectin in fields. However, its effect on the reproduction of root-knot nematode is poorly understood. In this study, the natural metabolite FAc was found to exhibit reproductive toxicity on Meloidogyne incognita and Caenorhabditis elegans. The number of germ cells of C. elegans was observed to decrease after exposure to FAc, with a reduction of 59.9% at a dose of 200 mg/L. FAc in various concentrations induced the germ-cell apoptosis of C. elegans, with an increase over six-fold in the number of apoptotic germ cells at 200 mg/L. These findings suggested that FAc decreased the brood size of nematode by inducing germ-cell apoptosis. Moreover, FAc-induced germ-cell apoptosis was suppressed by the mutation of gene hus-1, clk-2, cep-1, egl-1, ced-3, ced-4, or ced-9. The expression of genes spo-11, cep-1, and egl-1 in C. elegans was increased significantly after FAc treatment. Taken together, these results indicate that nematode exposure to FAc might inflict DNA damage through protein SPO-11, activate CEP-1 and EGL-1, and induce the core apoptosis pathway to cause germ-cell apoptosis, resulting in decreased brood size of C. elegans.