Gene expression analysis of CL-20-induced reversible neurotoxicity reveals GABA(A) receptors as potential targets in the earthworm Eisenia fetida

Biological Activity of Hexaazaisowurtzitane Derivatives

Biologically active compounds of natural or synthetic origin have a complex structure and generally contain various structural groups among which polycyclic cage amines are found. Hexaazaisowurtzitanes are representatives of these amines and studies on their biological activity began less than two decades ago, starting with research on the environmental impact of CL-20. This research helped to evaluate the risks of potential pollution in the habitat environments of living organisms and determine whether the chemical compounds in question could be utilized in pesticides, herbicides, fungicides, or medicinal drugs. The nomenclature of hexaazaisowurtzitane compounds has recently been expanded significantly, and some of them have demonstrated promise in the design of medicinal drugs. This paper review studies the pharmacological activity of the acyl derivatives of hexaazaisowurtzitane. Most of the compounds have been found to possess a high analgesic activity, providing a solution to the pressing issue of pain management in current pharmacology. Analgesic drugs currently used in the clinical practice do not meet all of the efficacy and safety requirements (gastro-, nephro-, hepato-, haematotoxicity, etc.). The material presented in the seven sections of this paper highlights information about hexaazaisowurtzitane derivatives. Furthermore, they have been observed to exhibit anti-inflammatory, anticonvulsant, antihypoxic, and antimetastatic activities, which render them highly promising for evaluation in various fields of medicinal practice.

Salidroside protect Chinese hamster V79 cells from genotoxicity and oxidative stress induced by CL-20

Hexanitrohexaazaisowurtzitane (CL-20) is a high-energy elemental explosive widely used in chemical and military fields. CL-20 harms environmental fate, biosafety, and occupational health. However, there is little known about the genotoxicity of CL-20, in particular its molecular mechanisms. Therefore, this study was framed to investigate the genotoxic mechanisms of CL-20 in V79 cells and evaluate whether the genotoxicity could be diminished by pretreating the cells with salidroside. The results showed that CL-20-induced genotoxicity in V79 cells primarily through oxidative damage to DNA and mitochondrial DNA (mtDNA) mutation. Salidroside could significantly reduce the inhibitory effect of CL-20 on the growth of V79 cells and reduce the levels of reactive oxygen species (ROS), 8-hydroxy-2 deoxyguanosine (8-OHdG), and malondialdehyde (MDA). Salidroside also restored CL-20-induced superoxide dismutase (SOD) and glutathione (GSH) in V79 cells. As a result, salidroside attenuated the DNA damage and mutations induced by CL-20. In conclusion, oxidative stress may be involved in CL-20-induced genotoxicity in V79 cells. Salidroside could protect V79 cells from oxidative damage induced by CL-20, mechanism of which may be related to scavenging intracellular ROS and increasing the expression of proteins that can promote the activity of intracellular antioxidant enzymes. The present study for the mechanisms and protection of CL-20-mediated genotoxicity will help further to understand the toxic effects of CL-20 and provide information on the therapeutic effect of salidroside in CL-20-induced genotoxicity.

Toxicity evaluation of pyraclostrobin exposure in farmland soils and co-exposure with nZnO to Eisenia fetida

Although the toxicity of pyraclostrobin (PYRA) to earthworms in artificial soil is well known, the toxicity of PYRA in farmland soils is yet to be explored in detail. Additionally, with more zinc oxide nanoparticles (nZnO) entering the soil environment, the risk of PYRA co-exposure with nZnO is increasing alarmingly. However, toxicity caused by this co-exposure of PYRA and nZnO is still unknown. Therefore, we assessed the biomarkers responses to reveal the toxicity of PYRA (0.1, 1, 2.5 mg/kg) on earthworms in farmland soils (black soil, fluvo-aquic soil, and red clay) and evaluated the biomarkers responses of Eisenia fetida exposed to PYRA (0.5 mg/kg)/PYRA+nZnO (10 mg/kg). Moreover, transcriptomic analysis was performed on E. fetida exposed to PYRA/PYRA+nZnO for 28 days to reveal the mechanism of genotoxicity. The Integrated Biomarker Responses (IBR) showed PYRA induced more severe oxidative stress and damage to E. fetida in farmland soils than that in artificial soil. The oxidative stress and damage induced by PYRA+nZnO were greater than that induced by PYRA. Transcriptomic analysis showed that PYRA and PYRA+nZnO significantly altered gene expression of both biological processes and molecular functions. These results provided toxicological data for PYRA exposure in three typical farmland soils and co-exposure with nZnO.

Biochemical, transcriptomic, gut microbiome responses and defense mechanisms of the earthworm Eisenia fetida to salt stress

The accumulation of sodium chloride (NaCl) in soil is a worldwide problem with detrimental effects on the survival of soil animals. The effects of NaCl on earthworms remain unclear. Here, we show that the growth rate, cocoon production rate, annetocin precursor (ANN) mRNA level, and superoxide dismutase and catalase activities in earthworms were reduced under NaCl stress, whereas the mortality rate, reactive oxygen species (ROS) and malondialdehyde activity level increased. Histological damage to the earthworm body wall and intestine were observed under NaCl stress. NaCl stress increased DNA damage in the seminal vesicle and coelomocytes. The mRNA level of lumbrokinase, 1,3-beta-glucanse, coelomic cytolytic factor (CCF1), and alpha-amylase was significantly down-regulated, whereas that of earthworm excitatory peptides2 (EEP2) was up-regulated. From 16 S rRNA sequencing, the earthworm gut microbiota diversity decreased under NaCl stress. However, Verminephrobacter, Kluyvera, Lactobacillus, and Ochrobactrum increased under NaCl stress. These findings contribute to the risk assessment of the salt stress on soil organisms.

Insights into the mechanisms of organic pollutant toxicity to earthworms: Advances and perspectives

Earthworms play positive ecological roles in soil formation, structure, and fertility, environmental protection, and terrestrial food chains. For this review, we searched the Web of Science database for articles published from 2011 to 2021 using the keywords "toxic" and "earthworm" and retrieved 632 publications. From the perspective of bibliometric analysis, we conducted a co-occurrence network analysis using the keywords "toxic" and "earthworm" to identify the most and least reported topics. "Eisenia fetida," "bioaccumulation," "heavy metals," "oxidative stress," and "pesticides" were the most common terms, and "microbial community," "bacteria," "PFOS," "bioaugmentation," "potentially toxic elements," "celomic fluid," "neurotoxicity," "joint toxicity," "apoptosis," and "nanoparticles" were uncommon terms. Additionally, in this review we highlight the main routes of organic pollutant entry into soil, and discuss the adverse effects on the soil ecosystem. We then systematically review the mechanisms underlying organic pollutant toxicity to earthworms, including oxidative stress, energy and lipid metabolism disturbances, neurological toxicity, intestinal inflammation and injury, gut microbiota dysbiosis, and reproductive toxicity. We conclude by discussing future research perspectives, focusing on environmentally relevant concentrations and conditions, novel data processing approaches, technologies, and detoxification and mitigation methods. This review has implications for soil management in the context of environmental pollution.

The long-term environmental risks from the aging of organochlorine pesticide lindane

Although increased contact time (aging) of pesticides in the soil decreases their bioavailability, this does not mean that the bound residues formed during the aging process pose fewer risk to the soil environment. Here the earthworm Eisenia fetida was exposed to organochlorine pesticide lindane in soil under different durations of lindane aging and exposure. The results of de novo RNA sequencing followed by molecular and biochemical validations demonstrated the aged lindane showed a different tendency to disrupt acetylcholine (ACh) transmission with the effects of fresh lindane to gamma-aminobutyric acid. Using own-developed earthworm activity test, we confirmed aged lindane prompted earthworms to exclusively exhibit a significant hypoactivity in locomotion, which could be explained by the inhibition of Ach system. This study suggested that the toxicity of pesticides would not depend solely on their free state components, and the awareness of long-term environmental risks from the bound states needs to be raised.

Differential histological, cellular and organism-wide response of earthworms exposed to multi-layer graphenes with different morphologies and hydrophobicity

The growing use of graphene-based nanomaterials (GBNs) for various applications increases the probability of their environmental releases and calls for a systematic assessment of their potential impacts on soil invertebrates that serve as an important link along terrestrial food chains. Here, we investigated the response of earthworms (Eisenia fetida) to three types of multi-layer graphenes (MLGs) (G1, G2 and G3 with 12-15 layers) with variable morphology (lateral sizes: 7.4 ± 0.3, 6.4 ± 0.1 and 2.8 ± 0.1 μm; thicknesses: 5.0 ± 0.1, 4.2 ± 0.1 and 4.0 ± 0.2 nm, respectively) and hydrophobicity ((O + N)/C ratios: 0.029, 0.044 and 0.075; contact angles: 122.8, 118.8 and 115.1°, respectively). Exposure to these materials was conducted for 28 days (except for 48-h avoidance test) separately in potting or farm soil at 0.2% and 1% by weight. Earthworms avoided both soils when amended with 1% of the smaller and more hydrophilic MLGs (G2 and G3), leading to a decreased trend in worm cocoon formation. The smallest and most hydrophilic MLG (G3), which was easier to assimilate, also significantly inhibited the viability (20.2-56.0%) and mitochondrial membrane potential (32.0-48.5%) of worm coelomocytes in both soils. In contrast, oxidative damage (indicated by lipid peroxides) was more pronounced upon exposure to more hydrophobic and larger graphenic materials (G1 and G2), which were attributed to facilitated adhesion to and disruption of worm membranes. These findings highlight the importance of MLG morphology and hydrophobicity in their potential toxicity and mode of action, as well as ecological risks associated with incidental and accidental releases.

Enantioselective endocrine-disrupting effects of the phenylpyrazole chiral insecticides in vitro and in silico

The phenylpyrazole chiral insecticides, including the widely used fipronil, ethiprole, and flufiprole, have generated a worldwide interest due to their environmental toxicity. However, up to now,only few studies focused on their their potential endocrine-disrupting effects (EDEs). In this study, we investigated the endocrine hormonal disorder caused by the fipronil, ethiprole, and flufiprole enantiomers in vitro and in silico approach. Results of the luciferase reporter assay indicated that the enantiomers of fipronil, ethiprole, or flufiprole have shown stereoselective endocrine-disrupting effects. S-(-)-ethiprole and S-(-)-flufiprole have anti-thyroidal disorder effects whereas R-(-)-fipronil, R-(+)-ethiprole, and R-(+)-flufiprole showed anti-estrogenic disorder effects. The results of the molecular dynamics simulations revealed that the happened EDEs could be partially attributed to the enantioselective specific receptor binding affinities. It also suggested that Vander Waals interactions plays an important role in the binding procedure. This study could provide helpful information for the explanation of enantioselectivity in the EDEs of chiral phenylpyrazole pesticides at the molecular level.

Right on target: using plants and microbes to remediate explosives

While the immediate effect of explosives in armed conflicts is frequently in the public eye, until recently, the insidious, longer-term corollaries of these toxic compounds in the environment have gone largely unnoticed. Now, increased public awareness and concern are factors behind calls for more effective remediation solutions to these global pollutants. Scientists have been working on bioremediation projects in this area for several decades, characterizing genes, biochemical detoxification pathways, and field-applicable plant species. This review covers the progress made in understanding the fundamental biochemistry behind the detoxification of explosives, including new shock-insensitive explosive compounds; how field-relevant plant species have been characterized and genetically engineered; and the major roles that endophytic and rhizospheric microorganisms play in the detoxification of organic pollutants such as explosives.

Aberrant neurotransmissional mRNAs in cerebral ganglions of rotenone-exposed Lumbricus terrestris exhibiting motor dysfunction and altered cognitive behavior

Rotenone (ROT) was shown to affect cerebral ganglions (CGs) of Lumbricus terrestris as a pioneering observation in our earlier investigation. Though ROT is a well-known neurotoxin causing neurodegeneration (ND), the precipitation of movement dysfunction remains largely unknown. We have designed the current study to analyze motor abnormalities in worms by exposing them to different concentrations (0.0-0.4 ppm) of ROT for 7 days. GABA, cholinergic receptor, serotonin transporter (SERT), acetylcholine esterase (AchE), and dopamine-β-hydroxylase that are well known for their involvement in neuromuscular junctions were investigated by qRT-PCR. Further, neuronal mitochondrial genes (cytochrome C oxidase-2, NADH deydrogenase-1, cytochrome-b) and actin-1 that are essential for regeneration and calreticulin (phagocytosis) were investigated. The levels of neurotransmitters, lipids, ATPase, neuronal behavior analyses, and fluorescence analysis (lipid droplets) were performed in CGs which showed significant variations at 0.3 ppm. Ultrastructural changes in lipid droplet and neuromelatonin were prominent in 0.3 ppm. Dose-dependent effect of ROT on behavior alteration and expression of m-RNAs studied suggested that at 0.3 ppm, it could deteriorate motor and cognitive functions. We predict that perhaps, by virtue of its effect on cerebral ganglionic genes and their neurotransmitting potential, ROT may cause morbidities that resemble features characteristic of hemiparkinsonic degeneration.

Comparative toxicogenomics of three insensitive munitions constituents 2,4-dinitroanisole, nitroguanidine and nitrotriazolone in the soil nematode Caenorhabditis elegans

BACKGROUND

Ecotoxicological studies on the insensitive munitions formulation IMX-101 and its components 2,4-dinitroanisole (DNAN), nitroguanidine (NQ) and nitrotriazolone (NTO) in various organisms showed that DNAN was the main contributor to the overall toxicity of IMX-101 and suggested that the three compounds acted independently. These results motivated this toxicogenomics study to discern toxicological mechanisms for these compounds at the molecular level.

METHODS

Here we used the soil nematode Caenorhabditis elegans, a well-characterized genomics model, as the test organism and a species-specific, transcriptome-wide 44 K-oligo probe microarray for gene expression analysis. In addition to the control treatment, C. elegans were exposed for 24 h to 6 concentrations of DNAN (1.95-62.5 ppm) or NQ (83-2667 ppm) or 5 concentrations of NTO (187-3000 ppm) with ten replicates per treatment. The nematodes were transferred to a clean environment after exposure. Reproduction endpoints (egg and larvae counts) were measured at three time points (i.e., 24-, 48- and 72-h). Gene expression profiling was performed immediately after 24-h exposure to each chemical at the lowest, medium and highest concentrations plus the control with four replicates per treatment.

RESULTS

Statistical analyses indicated that chemical treatment did not significantly affect nematode reproduction but did induce 2175, 378, and 118 differentially expressed genes (DEGs) in NQ-, DNAN-, and NTO-treated nematodes, respectively. Bioinformatic analysis indicated that the three compounds shared both DEGs and DEG-mapped Reactome pathways. Gene set enrichment analysis further demonstrated that DNAN and NTO significantly altered 12 and 6 KEGG pathways, separately, with three pathways in common. NTO mainly affected carbohydrate, amino acid and xenobiotics metabolism while DNAN disrupted protein processing, ABC transporters and several signal transduction pathways. NQ-induced DEGs were mapped to a wide variety of metabolism, cell cycle, immune system and extracellular matrix organization pathways.

CONCLUSION

Despite the absence of significant effects on apical reproduction endpoints, DNAN, NTO and NQ caused significant alterations in gene expression and pathways at 1.95 ppm, 187 ppm and 83 ppm, respectively. This study provided supporting evidence that the three chemicals may exert independent toxicity by acting on distinct molecular targets and pathways.

Intestinal damage, neurotoxicity and biochemical responses caused by tris (2-chloroethyl) phosphate and tricresyl phosphate on earthworm

Organophosphate esters (OPEs) draw growing concern about characterizing the potential risk on environmental health due to its wide usage and distribution. Two typical types of organophosphate esters (OPEs): tris (2-chloroethyl) phosphate (TCEP) and tricresyl phosphate (TCP) were selected to evaluate toxicity of OPEs to the soil organism like earthworm (Eisenia fetida). Histopathological examination (H&E), oxidative stress, DNA damage and RT-qPCR was used to identify the effects and potential mechanism of their toxicity. Hameatoxylin and eosin (H&E) demonstrated that intestinal cells suffered serious damage, and the observed up-regulation of chitinase and cathepsin L in mRNA levels confirmed it. Both TCEP and TCP significantly increased the DNA damage when the concentrations exceeded 1 mg/kg (p < 0.01), and a dose-response relationship was observed. In addition, TCEP and TCP also changed the acetylcholinesterase (AChE) activity and expression of genes associated with neurotoxic effects in earthworms even under exposure to low OPEs concentration (0.1 mg/kg). Moreover, genes associated with nicotinic acetylcholine receptors (nAChR) and carrier protein further demonstrated that highest concentration of TCEP (10 mg/kg) may have an overloading impact on the cholinergic system of E. fetida. Integrated Biological Response index (IBRv2) showed that TCEP exerted stronger toxicity than TCP under the same concentrations. We deduced that the observed intestinal damage, oxidative stress and neurotoxic effect might be the primary mechanisms of TCEP and TCP toxicity. This study provides insight into the toxicological effects of OPEs on earthworm model, and may be useful for risk assessment of OPEs on soil ecosystems.

Rotenone causing dysfunctional mitochondria and lysosomes in cerebral ganglions of Lumbricus terrestris degenerate giant fibers and neuromuscular junctions

Rotenone is well-documented to cause neurodegenerative condition such as Parkinson's, in the exposed systems. However, its detrimental effect on particular sites of neuronal pathway is still under investigation. We aimed at elucidating the impact of rotenone on cerebral ganglions (CG) of Lumbricus terrestris which control movement and behaviour of the worms. Worms were exposed to 0-0.4 ppm/mL of rotenone. Mitochondrial and lysosomal integrities were found to be affected beyond 0.2 ppm/mL of rotenone. Activities of cholinergic enzymes and the expression of tyrosine hydroxylase showed an impaired neuronal transmission in CGs at the dose of 0.2 ppm/mL of rotenone. Histopathological and immunoflourescent analyses showed neuronal apoptosis, reduced nucleic acid content and inhibited of neurosecretion at 0.3 ppm/mL. Electron microscopy showed that the neurons and neuromuscular junctions were affected at 0.2 ppm/mL. Dose-dependent changes were also observed in the motor function such as burrowing behaviours and locomotion. Conduction velocity (CV) and locomotion assessment showed that the CV of lateral giant fiber (LGF) was reduced while that of MGF remains unaffected at 0.2 ppm, the dose at which the burrowing behaviour was also not affected. LGF, cholinergic enzymes and tyrosine hydroxylase are primarily targeted by rotenone affecting locomotion at 0.2 ppm/mL while MGF, neuropile and the burrowing behaviour were affected at 0.3 ppm/mL. We demonstrate, in addition to dose-dependent effects, that the bioaccumulation factors range 0.28-0.32 ppm/μg of rotenone cause degenerative impact on giant fibers affecting neuronal behaviors/locomotion of worms. We also propose worms for studying mechanisms of neuronal pathology caused by chemicals prevailing in earth's atmosphere.

Gene expression profile changes in Eisenia fetida chronically exposed to PFOA

Eisenia fetida is a terrestrial organism, which can be used to diagnose sub-lethal concentrations of PFOA by using molecular biomarkers. In order to identify potential molecular biomarkers, we have exposed E. fetida to 10 mg/kg of PFOA in soil for 8 months. The mRNA isolation, sequencing, transcriptome assembly followed by differential gene expression studies have revealed that genes that are involved in apoptotic process, reproduction, calcium signalling, neuronal development and lipid metabolism are predominantly affected. Highly specific genes that are altered by PFOA can be further validated and used as biomarker to detect sub-lethal concentrations of PFOA in the soil.

Cerebral ganglionic variations and movement behaviors of Lumbricus terrestris on exposure to neurotoxin

BACKGROUND

Invertebrate worms serve as models for understanding the features of neurological functions. Acrylamide (ACR), the well-known neurotoxin, is a water-soluble chemical widely used in various industrial and laboratory processes. ACR is also found in food items which are cooked under high temperature.

PURPOSE

The study attempts to assess the neuropathological changes in cerebral ganglions along with the locomotion and neuronal behavior of Lumbricus terrestris on ACR intoxication.

METHODS

The dosage of acrylamide induced neurotoxicity ranged from 0-17.5 mg/kg body weight for 7 days. The time/dose dependent changes in the oxidant and antioxidant status, activities of Na(+)/K(+)ATPase, Ca(2+)/Mg(2+) ATPase and 5' Nucleotidase were assessed along with the locomotor behavioral analysis.

RESULT

The activities of super oxidase dismutase and catalases were not altered appreciably. However, the glutathione family, lipid peroxide, protein carbonyl content and vitamin C did show significant variations (p<0.001) in a dose-dependent manner, depicting more of oxidative stress, when compared to control worms. The activities of Na(+)/K(+) ATPase was significantly affected (p<0.001) at 3.5 mg/kg bw itself while those of both Ca(2+) and 5' Nucleotidase were found to be affected at 7.0 mg/kg bw of ACR. Mg(2+) ATPase showed significant reduction (p<0.001) in its activity only at 10.5 mg/kg bw of ACR. These dose dependent biochemical variations observed were found to be linked with the behavior of the worms as evident from the latency of movement in a dose-dependent manner which is less pronounced at 7.0 mg and more pronounced at 17.5 mg/kg bw of ACR.

CONCLUSION

The study suggests that ACR disrupts GSSS/GSH balance and perturbs ionic homeostasis in worms and thus affect the motor function highlighting their (GSH-ions) interrelationship in influencing neuromuscular activity. These simple analyses implicate that the cerebral ganglionic variations in the worms may be useful to appreciate the pathology of the neurological diseases (provided sophisticated analyses are employed) especially which involve movement dysfunction, where the brain tissue samples from the affected human patients are scarce.

Non-avoidance behaviour in enchytraeids to boric acid is related to the GABAergic mechanism

Soil invertebrates, e.g. enchytraeids, are known to be able to avoid unfavourable conditions, which gives them an important ecological advantage. These organisms possess chemoreceptors that can detect stressors, which in turn activate responses such as avoidance behaviour. We studied the avoidance behaviour in response to boric acid (BA) using enchytraeids. Results showed not only no avoidance, but that increasing concentrations seemed to have an "attraction" effect. To study the underlying mechanism, a selection of genes targeting for neurotransmission pathways (acetylcholinesterase (AChE) and gamma-aminobutyric acid receptor (GABAr)) were quantified via quantitative real-time polymerase chain reaction (qPCR). Evidences were that BA is neurotoxic via the GABAergic system mechanism where it acts as a GABA-associated protein receptor (GABAAR) antagonist possibly causing anaesthetic effects. This is the first time that (non)avoidance behaviour in invertebrates was studied in relation with the GABAergic system. We strongly recommend the combination of such gene and/or functional assay studies with the avoidance behaviour test as it can bring many advantages and important interpretation lines for ecotoxicity with minor effort.

Short-term effects of Dechlorane Plus on the earthworm Eisenia fetida determined by a systems biology approach

Dechlorane Plus (DP), a chlorinated flame retardant, has been widely detected in environmental matrices, especially in sediment and soil. DP has characteristics similar to persistent organic pollutants. However, no toxicity data of DP on terrestrial invertebrate are available. In this study, earthworms Eisenia fetida were exposed to 0.1, 1, 10, and 50mg/kg DP for 14 days. Lethality, oxidative stress and damage, neurotoxicity, and transcriptomic profiles of E. fetida were assessed on day 7 and day 14 of exposure. Results showed that the acute toxicity of DP was very low. However, DP exposure induced an increase in the oxidative stress markers malonaldehyde (MDA) and 8-Hydroxy-2'-deoxyguanosine (8-OHdG), and altered acetylcholinesterase (AChE) activities. High throughput sequencing-based transcriptomic analysis showed that DP exposure significantly altered gene expression and pathways related to antioxidant enzymes, stress responses, neurological dysfunctions, calcium binding, and signal transduction. The results from different toxicological endpoints indicate that DP toxicity on the earthworm is primarily through oxidative damage and neurotoxicity. Based on these results, we deduce that changes in oxidative stress and neurotoxicity might be the primary mechanisms of DP toxicity. This study provides insight into the toxicological effects of DP on earthworm model, and may be useful for risk assessment of DP on soil ecosystems.