Toxicological effects on earthworms (Eisenia fetida) exposed to sub-lethal concentrations of BDE-47 and BDE-209 from a metabolic point

Modified zero-valent iron nanoparticles enhanced remediation of PCBs-contaminated soil

The high toxicity and persistence of polychlorinated biphenyls (PCBs) in the environment require effective remediation of PCBs-contaminated soil. This study used polylactic acid (PLA) and polyethylene glycol 4000 (PEG-4000) to modify zero-valent iron nanoparticles (nZVI) and conducted characterization analysis. It was found that when the addition amount of PLA was 2 %, the dispersion of modified nZVI was better. The initial pH and water to soil ratio were subjected to single factor experiments and fitted using RSM response surface methodology. The optimal reaction conditions were obtained as follows: the addition amount was 84 g·kg-1, the initial pH was 5.41, and the optimal removal rate was 74 % when the ratio of water to soil was 1.8:1. PLA and PEG-4000 were biodegradable substances that played crucial roles in enhancing the effectiveness of nZVI for PCBs-contaminated soil. By encapsulating nZVI with PLA, we significantly reduced its oxidation when exposed to air. Additionally, the inclusion of PEG-4000 helped prevent the particles from clumping together. The synergistic effect of them increased the effective reaction of nZVI and PCBs and ultimately leading to more efficient remediation. This study offered a new pathway for the efficient green remediation of PCBs-contaminated soil.

Nickel oxide nanoparticles decrease the accumulation of atrazine in earthworms

Nickel oxide nanoparticles (NiO-NPs) are common nanomaterials that may be released into the environment, affecting the toxicity of other contaminants. Atrazine (ATZ) is a commonly used herbicide that can harm organisms due to its persistence and bioaccumulation in the environment. Although the toxicity of ATZ to earthworms is well-documented, the risk of co-exposure with NiO-NPs increases as more nanoparticles accumulate in the soil. In this study, we investigated the effects and mechanisms of NiO-NPs on the accumulation of ATZ in earthworms. The results showed that after day 21, the antioxidant system of the cells under ATZ treatment alone was adversely affected, with ROS content 36.05 % higher than that of the control (CK) group. However, the addition of NiO-NPs reduced the ROS contents in the earthworms by 0.6 %- 32.3 %. Moreover, analysis of earthworm intestinal sections indicates that NiO-NPs mitigated cellular and tissue damage caused by ATZ. High-throughput sequencing revealed that NiO-NPs in earthworm intestines increased the abundance of Pseudomonas aeruginosa and Aeromonas aeruginosa. Additionally, the enhanced function of the ABC transport system in the gut resulted in lower accumulation of ATZ in earthworms. In summary, NiO-NPs can reduce the accumulation and thus the toxicity of ATZ in earthworms. Our study contributes to a deeper understanding of the effects of NiO-NPs on co-existing pollutants.

Endocrine system, cell growth and death, and energy metabolism induced by Sb(III) exposure in earthworm (Pheretima guillemi) revealed by transcriptome and metabolome analysis

Antimony (Sb) is known for its severe and extensive toxicity, and earthworms are considered important indicator organisms in soil ecosystems. Therefore, the present study investigated the mechanism of toxicity of the Sb at different concentrations (50, 200 mg/kg) on earthworms using biochemical indicators, pathological sections, as well as metabolomics and transcriptomics analyses. The results showed that as the exposure concentration increased, both the antioxidant system of earthworms, extent of intestinal damage, and their metabolomic characteristics were significantly enhanced. In the 50 and 200 mg/kg Sb treatment group, 30 and 177 significant differentially changed metabolites (DCMs) were identified, respectively, with the most DCMs being down- and up-regulated, respectively. Metabolomics analysis showed that the contents of dl-tryptophan, glutamic acid, glycine, isoleucine, l-methionine, involved in the protein digestion and absorption as well as aminoacyl-tRNA biosynthesis were significantly up-regulated under the 200 mg/kg treatment. At the transcriptional level, Sb mainly affected the immune system, nervous system, amino acid metabolism, endocrine system, and carbohydrate metabolism in earthworms. The integration of transcriptomic and metabolomic data indicated that high doses of Sb regulated the metabolites and genes related to the oxidative phosphorylation pathway in earthworms. Overall, these results revealed global responses beyond the scope of conventional toxicity endpoints and facilitated a more in-depth and comprehensive assessment of the toxic effects of Sb.

Combined exposure to decabromodiphenyl ether and nano zero-valent iron aggravated oxidative stress and interfered with metabolism in earthworms

Decabromodiphenyl ether (BDE-209) is a common brominated flame retardant in electronic waste, and nano zero-valent iron (nZVI) is a new material in the field of environmental remediation. Little is known about how BDE-209 and nZVI combined exposure influences soil organisms. During the 28 days study, we determined the effects of single and combined exposures to BDE-209 and nZVI on the oxidative stress and metabolic response of earthworms (Eisenia fetida). On day 7, compared to CK, malondialdehyde (MDA) content increased in most combined exposure groups. To remove MDA and reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities were induced in most combined exposure groups. On day 28, compared to CK, the activities of SOD and CAT were inhibited, while POD activity was significantly induced, indicating that POD plays an important role in scavenging ROS. Combined exposure to BDE-209 and nZVI significantly affected amino acid biosynthesis and metabolism, purine metabolism, and aminoacyl-tRNA biosynthesis pathways, interfered with energy metabolism, and aggravated oxidative stress in earthworms. These findings provide a basis for assessing the ecological impacts of using nZVI to remediate soils contaminated with BDE-209 from electronic waste.

Global environmental and toxicological impacts of polybrominated diphenyl ethers versus organophosphate esters: A comparative analysis and regrettable substitution dilemma

The prevalence of organophosphate esters (OPEs) in the global environment is increasing, which aligns with the decline in the usage of polybrominated diphenyl ethers (PBDEs). PBDEs, a category of flame retardants, were banned and classified as persistent organic pollutants (POPs) through the Stockholm Convention due to their toxic and persistent properties. Despite a lack of comprehensive understanding of their ecological and health consequences, OPEs were adopted as replacements for PBDEs. This research aims to offer a comparative assessment of PBDEs and OPEs in various domains, specifically focusing on their persistence, bioaccumulation, and toxicity (PBT) properties. This study explored physicochemical properties (such as molecular weight, octanol-water partition coefficient, octanol-air partition coefficient, Henry's law constant, and vapor pressures), environmental behaviors, global concentrations in environmental matrices (air, water, and soil), toxicities, bioaccumulation, and trophic transfer mechanisms of both groups of compounds. Based on the comparison and analysis of environmental and toxicological data, we evaluate whether OPEs represent another instance of regrettable substitution and global contamination as much as PBDEs. Our findings indicate that the physical and chemical characteristics, environmental behaviors, and global concentrations of PBDEs and OPEs, are similar and overlap in many instances. Notably, OPE concentrations have even surged by orders of several magnitude compared to PBDEs in certain pristine regions like the Arctic and Antarctic, implying long-range transport. In many instances, air and water concentrations of OPEs have been increased than PBDEs. While the bioaccumulation factors (BAFs) of PBDEs (ranging from 4.8 to 7.5) are slightly elevated compared to OPEs (-0.5 to 5.36) in aquatic environments, both groups of compounds exhibit BAF values beyond the threshold of 5000 L/kg (log10 BAF > 3.7). Similarly, the trophic magnification factors (TMFs) for PBDEs (ranging from 0.39 to 4.44) slightly surpass those for OPEs (ranging from 1.06 to 3.5) in all cases. Metabolic biotransformation rates (LogKM) and hydrophobicity are potentially major factors deciding their trophic magnification potential. However, many compounds of PBDEs and OPEs show TMF values higher than 1, indicating biomagnification potential. Collectively, all data suggest that PBDEs and OPEs have the potential to bioaccumulate and transfer through the food chain. OPEs and PBDEs present a myriad of toxicity endpoints, with notable overlaps encompassing reproductive issues, oxidative stress, developmental defects, liver dysfunction, DNA damage, neurological toxicity, reproductive anomalies, carcinogenic effects, and behavior changes. Based on our investigation and comparative analysis, we conclude that substituting PBDEs with OPEs is regrettable based on PBT properties, underscoring the urgency for policy reforms and effective management strategies. Addressing this predicament before an exacerbation of global contamination is imperative.

Co-exposure of butyl benzyl phthalate and TiO2 nanomaterials (anatase) in Metaphire guillelmi: Gut health implications by transcriptomics

During the COVID-19 pandemic, an abundance of plastic face masks has been consumed and disposed of in the environment. In addition, substantial amounts of plastic mulch film have been used in intensive agriculture with low recovery. Butyl benzyl phthalate (BBP) and TiO2 nanomaterials (nTiO2) are widely applied in plastic products, leading to the inevitable release of BBP and nTiO2 into the soil system. However, the impact of co-exposure of BBP and nTiO2 at low concentrations on earthworms remains understudied. In the present study, transcriptomics was applied to reveal the effects of individual BBP and nTiO2 exposures at a concentration of 1 mg kg-1, along with the combined exposure of BBP and nTiO2 (1 mg kg-1 BBP + 1 mg kg-1 nTiO2 (anatase)) on Metaphire guillelmi. The result showed that BBP and nTiO2 exposures have the potential to induce neurodegeneration through glutamate accumulation, tau protein, and oxidative stress in the endoplasmic reticulum and mitochondria, as well as metabolism dysfunction. The present study contributes to our understanding of the toxic mechanisms of emerging contaminants at environmentally relevant levels and prompts consideration of the management of BBP and nTiO2 within the soil ecosystems.

Hepatotoxicity evaluation and possible mechanisms of decabrominated diphenyl ethers (BDE-209) in broilers: Oxidative stress, inflammatory, and transcriptomics

Decabrominated diphenyl ether (BDE-209), a persistent organic pollutant, is linked to a great number of health problems, the most severe of which impact the liver due to its role in the elimination and degradation of exogenous harmful substances. Though the hepatotoxicity of BDE-209 has been observed, its underlying mechanism is yet unknown. The purpose of this study is to thoroughly investigate the hepatotoxicity of BDE-209 and its molecular processes in broilers by subjecting 120 male broilers to varied concentrations of BDE-209 for 42 days. We observed that the bioaccumulation of BDE-209 in the liver in a dose-dependent manner, and that BDE-209 exposure can raise the concentrations of ALT, AST, and GGT, accompanied by hepatocyte fatty degeneration and inflammatory foci. In the hepatic homogenates, oxidative stress was evidenced by elevated levels of MDA and ROS and decreased activies of SOD and CAT. Additionally, pro-inflammatory cytokines including IL-1, IL-1β, TNF-α, IL-8 levels were increased, whereas anti-inflammatory cytokine IL-4 level was declined. Furthermore, RNA sequencing revealed that genes involved in inflammation were considerably dysregulated, and real-time PCR verified the expressed alterations of numerous genes related to the MAPK and WNT signaling pathways. The protein concentrations of NF-κB, β-catenin, and WNT5A, and the phosphorylation levels of JNK and ERK were all dramatically enhanced. The current study indicates that BDE-209 exposure can cause hepatotoxicity in broilers via bioaccumulation and oxidative stress, which then activates the MAPK and WNT signaling pathways, subsequently generating inflammation and hepatic injury.

Heavy metals in five commonly consumed fish species from River Swat, Pakistan, and their implications for human health using multiple risk assessment approaches

This study analyzed the levels of heavy metals bioaccumulation in commonly consumed riverine fish species, including G. cavia, T. macrolepis, G. gotyla, S. plagiostomus, and M. armatus from River Swat in Pakistan, and quantify their potential risk to children and adults in general and fisherfolk communities using multiple pollution and risk assessment approaches. The highest metal detected by inductive coupled plasma mass spectrometry (ICP-MS) was Zn, which ranged from 49.61 to 116.83 mg/kg, followed by Fe (19.25-101.33 mg/kg) > Mn (5.25-40.35 mg/kg) > Cr (3.05-14.59 mg/kg) > Ni (4.26-11.80 mg/kg) > Al (1.59-12.25 mg/kg) > Cu (1.24-8.59 mg/kg) > Pb (0.29-1.95 mg/kg) > Co (0.08-0.46 mg/kg) > Cd (0.01-0.29 mg/kg), demonstrating consistent fluctuation with the safe recommendations of global regulatory bodies. The average bioaccumulation factor (BAF) values in the examined fish species were high (BAF > 5000) for Pb, Zn, Mn, Cu, Cr, Ni, and Cd, bioaccumulate (1000 > BAF < 5000) for Co, and probable accumulative (BAF <1000) for Fe, and Al, while the overall ∑heavy metals pollution index (MPI) values were greater than one (MPI > 1) indicating sever heavy metals toxicity in G. cavia, followed by S. plagiostomus, M. armatus, G. gotyla, and T. macrolepis. The multivariate Pearson's correlation analysis identified the correlation coefficients between heavy metal pairs (NiCr, CuCr, PbCr, AlCo, CuNi, and PbNi), the hierarchical cluster analysis (CA) determined the origin by categorizing heavy metal accumulation into Cluster-A, Cluster-B, and Cluster-C, and the principal component analysis (PCA) discerned nearby weathering, mining, industrial, municipal, and agricultural activities as the potential sources of heavy metals bioaccumulation in riverine fish. As per human risk perspective, S.plagiostomus contributed significantly to the estimated daily intake (EDI) of heavy metals, followed by G.cavia > M.armatus > G.gotyla > T.macrolepis in dependent children and adults of the fisherfolk followed by the general population. The non-carcinogenic target hazard quotient (THQ) and hazard index (HI) values for heavy metal intake through fish exposure were < 1, while the carcinogenic risk (CR) for individual metal intake and the total carcinogenic risk (TCR) for cumulative Cr, Cd, and Pb intake were within the risk threshold of 10-6-10-4, suggesting an acceptable to high non-carcinogenic and carcinogenic risk for both children and adults in the fisherfolk, followed by the general population.

Stress response and tolerance mechanisms of spirobudiclofen exposure based on multiomics in Panonychus citri (Acari: Tetranychidae)

The toxicity of insecticides used in the field decreases gradually to sublethal concentrations over time. Therefore, it is necessary to study sublethal effects of pesticides for controlling population explosion. Panonychus citri is a global pest which control is based on insecticides. This study explores the stress responses of spirobudiclofen on the P. citri. Spirobudiclofen significantly inhibited survival and reproduction of P. citri, and the effects aggravated as concentration increased. The transcriptomes and metabolomes of spirobudiclofen-treated and control were compared to characterize spirobudiclofen molecular mechanism. Transcriptomics indicated stress induced by spirobudiclofen stimulated immune defense, antioxidative system, cuticle formation, and lipid metabolism, as deduced from RNA-seq analysis. Meanwhile, our study found that tolerance metabolism in P. citri was regulated by promoting the metabolism of glycerophospholipids, glycine, serine, and threonine. The results of this study can provide a basis for exploring the adaptation strategies of P. citri to spirobudiclofen stress.

Hemocytes in blue mussel Mytilus edulis adopt different energy supply modes to cope with different BDE-47 exposures

The energetic response of blue mussel Mytilus edulis when coping with tetrabromodiphenyl ether (BDE-47) exposure was evaluated from the perspective of alterations in energy supply mode, and the possible regulating mechanism was discussed based on a 21-day bioassay. The results showed that the energy supply mode changed with concentration: 0.1 μg/L BDE-47 decreased the activity of isocitrate dehydrogenase (IDH), succinate dehydrogenase (SDH), malate dehydrogenase and oxidative phosphorylation, suggesting inhibition of the tricarboxylic (TCA) acid cycle and aerobic respiration. The coincident increase in phosphofructokinase and the decrease in lactate dehydrogenase (LDH) indicated that glycolysis and anaerobic respiration were increased. When exposed to 1.0 μg/L BDE-47, M. edulis mainly utilized aerobic respiration, but lowered glucose metabolism as indicated by the decrease in glutamine and l-leucine was suggested to be involved in this process, which was differed from that in the control. The reoccurrence of IDH and SDH inhibition as well as LDH elevation indicated attenuation of aerobic and anaerobic respiration when the concentration increased to 10 μg/L, but severe protein damage was evidenced based on the elevation of amino acids and glutamine. Under the 0.1 μg/L BDE-47, activation of the AMPK-Hif-1a signaling pathway promoted the expression of glut1, which was the potential mechanism for the improvement of anaerobic respiration, and further activated glycolysis and anaerobic respiration. This study shows that the energy supply mode experienced a conversion from aerobic respiration under normal conditions to anaerobic mode in the low BDE-47 treatment and back to aerobic respiration with increasing BDE-47 concentrations, which may represent a potential mechanism for mussel physiological responses when faced with different levels of BDE-47 stress.

Oxidative stress and gene expression induced by biodegradable microplastics and imidacloprid in earthworms (Eisenia fetida) at environmentally relevant concentrations

The environmental issues caused by biodegradable microplastics (BMPs) from polylactic acid (PLA) as well as pesticides are of increasing concern nowadays. In this study, the toxicological effects of the single and combined exposure of PLA BMPs and imidacloprid (IMI), a neonicotinoid insecticide, on earthworms (Eisenia fetida) were investigated in terms of oxidative stress, DNA damage, and gene expression, respectively. The results showed that compared with the control, SOD, CAT and AChE activities in the single and combined treatments decreased significantly, and POD activity showed an "inhibition-activation" trend. SOD and CAT activities of combined treatments on day 28 and AChE activity of combined treatment on day 21 were significantly higher than those of the single treatments. For the rest of the exposure period, SOD, CAT and AChE activities in the combined treatments were lower than those in the single treatments. POD activity in the combined treatment was significantly lower than those of single treatments at day 7 and higher than that of single treatments at day 28. MDA content showed an "inhibition-activation-inhibition" trend, and the ROS level and 8-OHdG content increased significantly in both the single and combined treatments. This shows that both single and combined treatments led to oxidative stress and DNA damage. ANN and HSP70 were expressed abnormally, while the SOD and CAT mRNA expression changes were generally consistent with the corresponding enzyme activities. The integrated biomarker response (IBR) values were higher under combined exposures than single exposures at both biochemical and molecular levels, indicating that combined treatment exacerbated the toxicity. However, the IBR value of the combined treatment decreased consistently at the time axis. Overall, our results suggest that PLA BMPs and IMI induce oxidative stress and gene expression in earthworms at environmentally relevant concentrations, thereby increasing the risk of earthworms.

PBDEs disrupt homeostasis maintenance and regeneration of planarians due to DNA damage, proliferation and apoptosis anomaly

Polybrominated diphenyl ethers (PBDEs) are widely used as brominated flame retardants in the manufacturing industry, belonging to persistent organic pollutants in the environment. Planarians are the freshwater worms, with strong regenerative ability and extreme sensitivity to environmental toxicants. This study aimed to evaluate the potential acute comprehensive effects of PBDE-47/-209 on freshwater planarians. Methods to detect the effects include: detection of oxidative stress, observation of morphology and histology, detection of DNA fragmentation, and detection of cell proliferation and apoptosis. In the PBDE-47 treatment group, planarians showed increased oxidative stress intensity, severe tissue damage, increased DNA fragmentation level, and increased cell proliferation and apoptosis. In the PBDE-209 treatment group, planarians showed decreased oxidative stress intensity, slight tissue damage, almost unchanged DNA fragmentation level and apoptosis, proliferation increased only on the first day after treatment. In conclusion, both PBDE-47 and PBDE-209 are dangerous environmental hazardous material that can disrupt planarians homeostasis, while the toxicity of PBDE-47 is sever than PBDE-209 that PBDE-47 can lead to the death of planarians.

The effect of 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47) on locomotor behaviour and muscle physiology of the sea cucumber Apostichopus japonicus

The 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) is the predominant congener of polybrominated diphenyl ethers, and it is also a persistent organic pollutant that with a higher detection rate in samples from environment and animals. To date, there have been few studies of the effects of BDE-47 on locomotion in sea cucumbers. In this study, we investigated the influence of different concentrations of BDE-47 (low: 0.1 μg/L; moderate: 1.0 μg/L; high: 10.0 μg/L) on locomotion of Apostichopus japonicus and evaluated changes in their muscle physiology using ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry. The behavioural studies showed that the average and maximum velocity of movement decreased significantly in both the moderate and high BDE-47 groups after 1 day of exposure. In addition, levels of 55 metabolites were identified and characterized in the longitudinal muscle of A. japonicus exposed to BDE-47. The alteration of taurine and norepinephrine levels indicated that BDE-47 had drastic physiological effects on the longitudinal muscle of A. japonicus.

Integration of transcriptomic and metabolomic reveals metabolic pathway alteration in earthworms (Eisenia fetida) under copper exposure

Copper is a trace element that necessary for plant growth in the soil. However, in recent years, due to human activities, the content of copper in soil exceeds the standard seriously, which is threatening the safety of soil animals, plants and even human beings. In this study, we investigated the effects and molecular mechanisms of 60 days long-term copper exposure on earthworms (Eisenia fetida) at 67.58 mg/kg, 168.96 mg/kg and 337.92 mg/kg concentration by using transcriptome and metabolomics. Transcriptome analysis showed that the expression of energy metabolism related genes (LDH, GYS, ATP6N, GAPDH, COX17), immune system related genes (E3.2.1.14) and detoxification related genes (UGT, CYP2U1, CYP1A1) were down-regulated, the expression of antioxidant system related genes (GCLC, HPGDS) were up-regulated in copper exposure experiment of earthworms. Similarly, metabolomics analysis revealed that the expression of energy metabolism related metabolites (Glucose-1-phosphate, Glucose-6-phosphate), TCA cycle related metabolites (fumaric acid, allantoic acid, malate, malic acid) were down-regulated, digestion and immune system related metabolites (Trehalose-6-phosphate) were up-regulated. Integrating transcriptome and metabolomics data, it was found that higher antioxidant capacity and accelerated TCA cycle metabolism may be an adaptive strategy for earthworms to adapt to long-term copper stress. Collectively, the results of this study will greatly contribute to incrementally understand the stress responses on copper exposure to earthworms and supply molecular level support for evaluating the environmental effects of copper on soil organisms.

Is selenium beneficial or detrimental to earthworm? Growth and metabolism responses of Eisenia Fetida to Na2SeO3 exposure

Se unevenly distributed in soils due to variations of geology and anthropogenic input, which results in different effects on earthworms. The effects of Se were characterized by analyzing the growth and metabolism responses of earthworms after exposure to three different concentrations of Na₂SeO₃. The results showed that except the possible growth promotion at 5 mg/kg, low and middle-level exposure to Na₂SeO₃ (0.3-10 mg/kg) did not significantly affect the growth of earthworms. While a significant inhibition effect on growth was observed in the high-level exposure group (30-70 mg/kg). There was an inflection point for Se performing promotion to inhibition effects on earthworm growth. To investigate the metabolic response of earthworms, a novel HPLC-ESI-MS (High Performance Liquid Chromatography-Electrospray Ionization-Mass Spectrometry) method was used to determine sensitive biomarkers. Selenium exposure significantly altered the metabolism of seven essential amino acids, namely tyrosine, leucine, phenylalanine, valine, alanine, glycine, and lysine, and two selenoamino acids, namely selenomethionine and methylselenocysteine. The overall metabolism level of earthworms was not affected at low exposure concentrations, but was affected at medium and high exposure concentrations. The metabolic pathways that integrated the selenocompound metabolism and the tricarboxylic acid cycle from the perspective of energy supply and demand were affected by Na₂SeO₃ exposure. The derived reactive oxygen species at high exposure concentrations were probably the reason for the growth inhibition effect of Se on earthworms. This study provides biochemical insights into the effects of Na₂SeO₃ on earthworms and suggests that an Se concentration of about 2.3 mg/kg is appropriate for soil organism health.

Size effects of polystyrene microplastics on the accumulation and toxicity of (semi-)metals in earthworms

Microplastics (MPs) are plastic fragments less than 5 mm, which may have adverse impacts on organisms. In this study, we investigated the impacts and mechanisms of polystyrene MPs (10 μm and 100 μm) and nanoplastics (NPs, 100 nm) with different concentrations (10 mg/kg and 100 mg/kg) in soil on the uptake of metal Cd and semi-metal As in earthworms, Eisenia fetida. MPs facilitated the accumulation of (semi-)metals via damaging the integrity of earthworm intestine, and earthworms accumulated more (semi-)metals in MP treatment groups than NP treatment groups, especially in group of 100 mg/kg of 10 μm MP with concentrations of 1.13 mg/kg and 32.7 mg/kg of Cd and As, respectively. Higher genotoxicity to earthworms was observed for MPs than NPs. Antioxidant enzymes activity and their mRNA gene relative expression levels indicated that MPs with high concentration induced severer damage to earthworms, thus resulting in the increased accumulation of (semi-)metals by earthworms. In addition, proteomic and metabolomic analysis revealed that MPs (100 ppm of 10 μm) disturbed the earthworm immune and metabolic systems, resulting in the highest accumulation of (semi-)metals in earthworms. This study clarifies the influence mechanisms of MPs with different sizes and levels on the accumulation of (semi-)metals by terrestrial invertebrates.

Metabolomic Studies for the Evaluation of Toxicity Induced by Environmental Toxicants on Model Organisms

Environmental pollution causes significant toxicity to ecosystems. Thus, acquiring a deeper understanding of the concentration of environmental pollutants in ecosystems and, clarifying their potential toxicities is of great significance. Environmental metabolomics is a powerful technique in investigating the effects of pollutants on living organisms in the environment. In this review, we cover the different aspects of the environmental metabolomics approach, which allows the acquisition of reliable data. A step-by-step procedure from sample preparation to data interpretation is also discussed. Additionally, other factors, including model organisms and various types of emerging environmental toxicants are discussed. Moreover, we cover the considerations for successful environmental metabolomics as well as the identification of toxic effects based on data interpretation in combination with phenotype assays. Finally, the effects induced by various types of environmental toxicants in model organisms based on the application of environmental metabolomics are also discussed.

Combined toxic effects of dioxin-like PCB77 with Fe-based nanoparticles in earthworm Eisenia fetida

Iron-based nanomaterials hold promise for in situ remediation of persistent halogenated contaminants such as dioxin-like polychlorinated biphenyls, however, their complex interactions and joint toxicity toward beneficial soil biological functions remain unknown. This study examined the effects of nano-zero valent iron (nZVI) on the physiological and morphological changes, on the bioaccumulation of co-existed dioxin-like 3,3',4,4'-tetrachloro-biphenyls (PCB77), and the joint toxicity of nZVI and PCB77 in earthworms Eisenia fetida. An orthogonally designed experiment was conducted through the exposure of E. fetida to the combined and separate nZVI and PCB77 at various concentrations in soil for 28 days (nZVI at the levels of g-Fe/kg-soil and PCB77 at the levels of mg-PCB/kg-soil). Results indicated that both nZVI and PCB77 inhibited the growth and reproduction of earthworms, and the combined exposure resulted in a synergistic effect. The addition of 10 g/kg nZVI decreased the contents of PCB77 and significantly increased the accumulation of PCB77 to a level ranging 14-97 mg/kg in earthworms in a nZVI dose dependent manner. The observed synergism might relate to the aggravated damage of earthworm epidermis in the presence of nZVI. PCB77 and nZVI at their corresponding high levels (10 mg/kg and 10 g/kg) induced oxidative stress and lipid peroxidation in the earthworms through the increased levels of reactive oxygen species and the subsequent inhibition of antioxidant enzymes including superoxide dismutase and catalase. Further metabolomics analyses revealed that the normal glutamic acid metabolism and tricarboxylic acid cycle were disturbed in earthworms exposed to the combined treatment of 10 mg/kg PCB77 and 10 g/kg nZVI. Our findings suggested that earthworms as a sentinel species could be readily employed in toxicity and tolerance studies to succeed the safe applications of nZVI and interestingly earthworms themselves also hold promise for vermiremediation owing to the high bioaccumulation potential of PCBs from contaminated soils.

Study on molecular level toxicity of Sb(V) to soil springtails: using a combination of transcriptomics and metabolomics

To date, numerous studies have focused on the toxicity of antimony (Sb) to soil-dwelling organisms at the individual level. However, little is known about Sb-caused molecular level toxicity. Here, an integrated transcriptomics and metabolomics approach was used to better reveal toxicity of Sb(V) to springtails Folsomia candida considering environmentally relevant speciation of Sb. No significant effects of Sb(V) on survival, reproduction and growth of springtails were observed using the ISO standard test. Transcriptomics analysis identified 1015 and 3367 differentially expressed genes (DEGs) after 2 and 7 d of exposure, indicating an increasing transcriptomal changes with time. Significantly enriched top GO (Gene Ontology) terms (chitin metabolic process, chitin binding and extracellular region) were shared between the two time exposure groups. However, no enriched KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway was shared, with fatty acid metabolism and apoptosis-fly being the most significant pathway, respectively. Metabolomics analysis identified 155 differential changed metabolites (DCMs) in springtails after 7 d of exposure. Antifolate resistance was the most significantly enriched pathway, in which dihydrofolic acid was up-regulated and three purine nucleotides (adenosine 5'-monophosphate, inosine 5'-monophosphate, guanosine 5'-monophosphate) were down-regulated. This indicated obvious repression of DNA replication, which was also observed by transcriptomics. Additionally, metabolites level related to chitin, oxidative stress, and protein metabolism significantly changed, and these metabolites could also support and confirm main transcriptomic results. Thus, the combination of multiomics facilitated better understanding of the molecular level of toxicity of Sb(V) in Collembola.

The responses of the growth, cytochrome P450 isoenzymes activities and the metabolomics in earthworms to sublethal doses of dichlorvos in soil

In this paper, earthworms (Eisenia fetida) were exposed to sublethal doses of dichlorvos (spiked concentration of 0.1, 1.0, 10 mg/kg) in soil for 14 days, the metabolomics and activities of cytochrome P450 (CYP) isoenzymes (CYP1A2, CYP2C9 and CYP3A4) of earthworms were analyzed aiming to identify sensitive biomarkers and reveal possible mode of toxic action. The results showed that CYP1A2 and CYP2C9 activity appeared to be more sensitive than CYP3A4 activity in response to dichlorvos, and that metabolic responses based on the metabolomics depended on both of the length of exposure and exposure dose. Malate, ornithine, glucose, inosine, myo-inositol and some amino acids (glutamine, tryptophan, phenylalanine, tyrosine, leucine, histidine, glutamate, lysine) and CYP isozenzymes may be biomarkers to reveal the toxic effect of dichlorvos on earthworms. Compared to controls, when dichlorvos dose reached 1.0 and 10 mg/kg on day 14, glucose and ornithine increased significantly, malate and some amino acids (glutamine, tryptophan, phenylalanine, tyrosine, leucine) decreased significantly, and activities of CYP1A2 and CYP2C9 were inhibited significantly. The current results suggested that 1.0 and 10 mg/kg dichlorvos for 14 days of exposure blocked energy metabolism, disordered Krebs cycle, interfered amino acids metabolism and evoked toxic effects on earthworms.

Ecological and toxicological assessments of anthropogenic contaminants based on environmental metabolomics

There has long been a great concern with growing anthropogenic contaminants and their ecological and toxicological effects on living organisms and the surrounding environment for decades. Metabolomics, a functional readout of cellular activity, can capture organismal responses to various contaminant-related stressors, acquiring direct signatures to illustrate the environmental behaviours of anthropogenic contaminants better. This review entails the application of metabolomics to profile metabolic responses of environmental organisms, e.g. animals (rodents, fish, crustacean and earthworms) and microorganisms (bacteria, yeast and microalgae) to different anthropogenic contaminants, including heavy metals, nanomaterials, pesticides, pharmaceutical and personal products, persistent organic pollutants, and assesses their ecotoxicological impacts with regard to literature published in the recent five years. Contaminant-induced metabolism alteration and up/down-regulation of metabolic pathways are revealed in typical organisms. The obtained insights of variations in global metabolism provide a distinct understanding of how anthropogenic contaminants exert influences on specific metabolic pathways on living organisms. Thus with a novel ecotechnique of environmental metabolomics, risk assessments of anthropogenic contaminants are profoundly demonstrated.

Metabolite changes associated with earthworms (Eisenia fetida) graphene exposure revealed by matrix-assisted laser desorption/ionization mass spectrometry imaging

The increased production and environmental release of graphene nanoparticles has raised concerns about its environmental impact, but the effects of graphene on living organisms at the metabolic level remain unknown. In this study, we used matrix assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI)-based untargeted metabolomics to investigate the metabolic response of juvenile earthworms (Eisenia fetida) to graphene exposure in soil tests for the first time. Our results reveal that graphene-exposure significantly disturbs earthworm metabolome, and graphene toxicity on earthworm shows non-concentration-dependent effect. Alanine, phenylalanine, proline, glutamate, arginine, histidine, maltose, glucose, malate, succinate, myo-inositol, and spermidine were successfully screened as significantly change compounds in earthworms for the exposure of graphene. The heterogeneous distributions of these metabolites in earthworm were also clearly imaged by MALDI-MSI. Our MSI results fully showed that the metabolite expression levels in juvenile earthworms significantly changed (up-/down-regulation) after exposure to graphene nanoparticles. This work improves our understanding of graphene nanoparticle toxicity to juvenile earthworms and also enables the continued progression of MALDI-MSI-based metabolomics as an emerging, reliable, and rapid ecotoxicological tool for assessing contaminant toxicity.

Tri-n-butyl phosphate induced earthworm intestinal damage by influencing nutrient absorption and energy homeostasis of intestinal epithelial cells

Tri-n-butyl phosphate (TnBP) is a typical alkyl organophosphate ester that has been used for decades in various products. However, toxicity on terrestrial organisms induced by TnBP has been rarely reported though soil is a predominant sink for hydrophobic organic compounds. The objective of this study was to investigate the TnBP-induced intestinal toxicity mechanism on earthworm Eisenia fetida as well as the potential role of gut bacteria on host's health. TnBP was found to have high bioconcentrations in earthworm intestinal tract. Digestive tract degradation and digestive enzyme activities disruption associated with nutrients absorption were noticed. Using multi-omics approaches, detailed intestinal toxic mechanism of earthworms under TnBP exposure was provided. Tight junctions between small intestinal epithelial cells and osmotic equilibrium were destroyed under 10 mg/kg TnBP, leading to nutrient absorption disturbance. To satisfy the excessive energy requirements induced by TnBP, amino acids gluconeogenesis and protein degradation were detected. Moreover, TnBP significantly decreased the diversity of gut microbiota and changed their structure and function involved in hosts' health and nutrients supply. Overall, this study provides insight into the molecular mechanism of intestinal toxicity by which earthworms respond to TnBP exposure and offer important information for risk assessment of organophosphate esters on soil ecosystems.

Insights into the mechanisms underlying the remediation potential of earthworms in contaminated soil: A critical review of research progress and prospects

In recent years, soil pollution is a major global concern drawing worldwide attention. Earthworms can resist high concentrations of soil pollutants and play a vital role in removing them effectively. Vermiremediation, using earthworms to remove contaminants from soil or help to degrade non-recyclable chemicals, is proved to be an alternative, low-cost technology for treating contaminated soil. However, knowledge about the mechanisms and framework of the vermiremediation various organic and inorganic contaminants is still limited. Therefore, we reviewed the research progress of effects of soil contaminants on earthworms and potential of earthworm used for remediation soil contaminated with heavy metals, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), pesticides, as well as crude oil. Especially, the possible processes, mechanisms, advantages and limitations, and how to boost the efficiency of vermiremediation are well addressed in this review. Finally, future prospects of vermiremediation soil contamination are listed to promote further studies and application of vermiremediation in contaminated soils.

Bioaccumulation and toxic effects of penconazole in earthworms (Eisenia fetida) following soil exposure

As an agricultural fungicide, penconazole (PEN) is widely used and has adverse effects on various organisms. In order to evaluate the ecological safety risks of PEN, the bioaccumulation and toxic effects of PEN in earthworms were studied. Specifically, the results show that the biota-sediment accumulation factor (BSAF) of PEN in earthworms reaches its maximum within 1 day, and then decreases slowly. It reached its lowest value after 14 days of PEN exposure and then rose again. In addition, oxidative stress and metabolic disorder of the earthworm with PEN exposure were assessed. After PEN exposure, the related indicators of oxidative stress involved in the activities of SOD and CAT and the contents of GSH and MDA all changed significantly in earthworms. Moreover, metabolomics analysis of earthworms showed disturbed metabolic profiles following PEN exposure. Respectively, PEN exposure significantly altered the relative abundances of 14 metabolites in earthworms. In general, exposure to PEN caused oxidative stress and metabolic profile disorders of earthworms. The results of this study will be helpful for further evaluation of soil ecological security of PEN.

Occurrence of Halogenated Pollutants in Domestic and Occupational Indoor Dust

The occurrence of halogenated organic pollutants in indoor dust can be high due to the presence of textile, electronic devices, furniture, and building materials treated with these chemicals. In this explorative study, we focused on emerging organic pollutants, such as novel brominated flame retardants (nBFRs) and some perfluoroalkyl substances, together with legacy polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (BDEs) in settled dust collected in houses and workplaces such as one office and two electrotechnical and mechanical workshops. The total contribution of the investigated pollutants was lower in house and in office dusts except for few nBFRs (such as bis (2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate at a concentration of 464.5 ng/g in a house and hexachlorocyclopentadienyldibromocyclooctane at 40.4 ng/g in the office), whereas in electrotechnical and mechanical workshops a high incidence of PCBs, BDEs, and nBFRs occurred (for example, BDE 209 at a concentration of 2368.0 ng/g and tetrabromobisphenol A at 32,320.1 ng/g in electrotechnical and mechanical workshops). Estimated daily intakes were also calculated, showing that domestic and occupational environments can lead to a similar contribution in terms of human exposure. The higher exposure contribution was associated to nBFRs, whose EDIs were in the range of 3968.2–555,694.2 pg/kg bw/day. To provide a complete view about the indoor contamination, in this investigation, we also included polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and nitrated derivatives. Definitely, dust collection represents a simple, fast, and cost-effective sampling and dust contamination level can be a useful indicator of environment healthiness. Besides, the presented method can be a smart tool to provide a time and money saving technique to characterize 99 pollutants thanks to a single sample treatment.

Accumulation and Transformation of 2,2',4,4'-Tetrabrominated Diphenyl Ether (BDE47) by the Earthworm Metaphire vulgaris in Soil

The accumulation and transformation of 2,2',4,4'-tetrabrominated diphenyl ether (BDE47), one congener of the flame retardants polybrominated diphenyl ethers (PBDEs), in soil-feeding fauna are still unknown. Using radioactivity tracer, we incubated ¹⁴C-labelled BDE47 in soil for 21 days in the presence and absence of the geophagous earthworm Metaphire vulgaris. BDE47 accumulated in the earthworm predominantly via oral ingestion of soil, giving a biota-soil accumulation factor (BSAF) value of 1.3 for radioactivity at the end of incubation, and was mostly located in intestine, followed by clitellum (organs region) and skin of earthworms. Accumulation was accompanied by significant decrease of BDE47 concentration in soil porewater and BDE47 mineralization in soil. BDE47 was transformed in the earthworm gut into two metabolites with higher polarities than BDE47. The results provide for the first time insights into accumulation and transformation of lower-brominated congeners of PBDEs in geophagous earthworms, being helpful for environmental risk assessment of PBDEs.

Antioxidant defenses and metabolic responses of blue mussels (Mytilus edulis) exposed to various concentrations of erythromycin

Erythromycin, one of the most widely used macrolide antibiotics, has been detected in various aquatic environments, so erythromycin ecotoxicity should deserve more attention. In this study, blue mussels (Mytilus edulis) were exposed to erythromycin to explore its potential physiological toxicity. After 2d acute and 7d sub-acute exposure to erythromycin, blue mussel glutathione S-transferase (GST) and catalase (CAT) activities were determined with microplate methods and metabolic responses were analyzed using ¹H nuclear magnetic resonance (¹H NMR). The results revealed that GST was approximately 1.6 times higher in exposed mussels at 200 mg/L and higher concentrations. CAT was about 1.9 times higher in exposed mussels at 200 mg/L, indicating that erythromycin exposure led that blue mussels enhanced antioxidant responses. Low doses of erythromycin exposure had a relatively small impact on the metabolism, while high doses of erythromycin exposure (200 and 400 mg/L) disturbed metabolic balance. With the increase of erythromycin concentrations, the individual metabolic differences within the same treatment groups also increased. The significant increase in alanine, glutamate, taurine, glycine and betaine were observed after acute and subacute exposure. Betaine played an important role in protecting antioxidant enzyme activities through adjusting osmotic pressure. The metabolomic results also showed the modes of erythromycin acted on the energy metabolism, osmoregulation, nerve activities and amino acid metabolism. This study highlighted how metabolomics can provide a comprehensive picture of metabolic responses, although significant antioxidant and metabolic responses were observed at high exposure concentrations.

Metabolomics and transcriptomics reveal defense mechanism of rice (Oryza sativa) grains under stress of 2,2',4,4'-tetrabromodiphenyl ether

2,2',4,4'-Tetrabromodiphenyl ether (BDE-47), a predominant polybrominated diphenyl ether (PBDE), has received extensive attention for its potential environmental impact. An integrated study of metabolomics and transcriptomics was conducted on two rice (Oryza sativa) cultivars, Lianjing-7 (LJ-7) and Yongyou-9 (YY-9), which have been identified as tolerant and sensitive cultivars to BDE-47, respectively. The objective was to investigate the molecular mechanisms of their different ability to tolerate BDE-47. Both rice plants were cultivated to maturity in soils containing three concentrations of BDE-47 (10, 20, and 50 mg/kg). Metabolomic analyses of rice grains identified 65 metabolites in LJ-7 and 45 metabolites in YY-9, including amino acids, saccharides, organic acids, fatty acids, and secondary metabolites. In the tolerant cultivar LJ-7 exposed to 50 mg/kg BDE-47, concentrations of most of the metabolites increased significantly, with α-ketoglutaric acid increased by 20-fold and stigmastanol increased by 12-fold. In the sensitive cultivar YY-9, the concentrations of most metabolites increased after the plant was exposed to 1 and 10 mg/kg BDE-47 but decreased after the plant was exposed to 50 mg/kg BDE-47. Transcriptomic data demonstrated that regulation of gene expressions was affected most in LJ-7 exposed to 50 mg/kg BDE-47 (966 genes up-regulated and 620 genes down-regulated) and in YY-9 exposed to 10 mg/kg BDE-47 (85 genes up-regulated and 291 genes down-regulated), in good accordance with the observed metabolic alternation in the two cultivars. Analyses of metabolic pathways and KEGG enrichment revealed that many biological processes, including energy consumption and biosynthesis, were perturbed in the two rice cultivars by BDE-47. A majority of metabolites and genes involved in dominating pathways of energy consumption (e.g., tricarboxylic acid cycle) and the biosynthesis (e.g., metabolism of saccharides and amino acids) were enhanced in LJ-7 by BDE-47. In contrast, energy consumption was increased while biosynthetic processes were inhibited in YY-9 by BDE-47, which could lead to the sensitivity of YY-9 to BDE-47. The combined results suggest that the different defensive abilities of these two rice cultivars in response to BDE-47 could be attributed to their differences in energy-consumption strategy and biosynthesis of nutritional components in grains. This study provides a useful reference for rice cultivation in PBDE-polluted areas.

Mortality, growth and metabolic responses by 1H-NMR-based metabolomics of earthworms to sodium selenite exposure in soils

The rapid development of selenium-enriched agriculture leads to the accumulation of selenium in the soil, which has an adverse impact on terrestrial ecosystems. In the present study, the mortality, growth inhibition rate and metabolism of earthworms were examined to investigate the toxicological effects of sodium selenite (Na₂SeO₃) on earthworms (Eisenia fetida) after exposuring for 14 days (d). We used ¹H-NMR-based metabolomics to identify sensitive biomarkers and explored the metabolic responses of earthworms exposed to Na₂SeO₃. The mortality and growth inhibition rate of earthworms exposed to 70 and 90 mg/kg Na₂SeO₃ were significantly higher than the rate of control group. The LC₅₀ (the median lethal concentration) of Na₂SeO₃ was 57.4 mg/kg in this artificial soil test of E. fetida exposed to Na₂SeO₃ for 14 d. However, there was no significant differences when earthworms were exposed to different concentrations of Na₂SeO₃. The selected metabolic markers were ATP, lactic acid, leucine, alanine, valine, glycine, glutamic acid, lysine, α-glucose and betaine. Na₂SeO₃ affected the metabolic level of earthworms, as the percentage of metabolic markers in the earthworm changes when exposed to different concentrations of Na₂SeO₃. The metabolic disturbances were greater with increasing concentrations of Na₂SeO₃. The differential metabolic markers were significantly changed when exposed to Na₂SeO₃ comparing to those in the control group, affecting the tricarboxylic acid cycle process and breaking the metabolic balance. This study showed that Na₂SeO₃ had toxic effect on the growth and development of earthworms. In addition, this study provided a biochemical insights for the development of selenium-enriched agriculture.

A comparison of the thyroid disruption induced by decabrominated diphenyl ethers (BDE-209) and decabromodiphenyl ethane (DBDPE) in rats

In recent years, decabromodiphenyl ethane (DBDPE), a new alternative flame retardant to the decabrominated diphenyl ethers (BDE-209), is widely used in a variety of products. Previous studies have indicated that DBDPE, like BDE-209, could disrupt thyroid function. However, compared with BDE-209, the degrees of thyrotoxicosis induced by DBDPE were not clear. In addition, the mechanism of thyrotoxicosis induced by DBDPE or BDE-209 was still under further investigation. In this study, male rats as a model were orally exposed to DBDPE or BDE-209 by 5, 50, 500 mg/kg bw/day for 28 days. Then, we assessed the thyrotoxicosis of DBDPE versus BDE-209 and explored the mechanisms of DBDPE and BDE-209-induced thyrotoxicosis. Results showed that decreased free triiodothyronine (FT3) and increased thyroid-stimulating hormone (TSH) and thyrotropin-releasing hormone (TRH) in serum were observed in both 500 mg/kg bw/day BDE-209 and DBDPE group. Decreased total thyroxine (TT4), total T3 (TT3), and free T4 (FT4) were only observed in BDE-209 group but not in DBDPE group. Histological examination and transmission electron microscope examination showed that high level exposure to BDE-209 and DBDPE both caused significant changes in histological structure and ultrastructure of the thyroid gland. Additionally, oxidative damages of thyroid gland (decreased SOD and GSH activities, and increased MDA content) were also observed in both BDE-209 and DBDPE groups. TG contents in the thyroid gland was reduced in BDE-209 group but not in DBDPE group. Both BDE-209 and DBDPE affected the expression of hypothalamic-pituitary-thyroid (HPT) axis related genes. These findings suggested that both BDE-209 and DBDPE exposure could disrupt thyroid function in the direction of hypothyroidism and the underlying mechanism was likely to be oxidative stress and perturbations of HPT axis. However, DBDPE was found to be less toxic than BDE-209.