The effects of polyethylene microplastics on the growth, reproduction, metabolic enzymes, and metabolomics of earthworms Eisenia fetida.

The existing data regarding the effects of polyethylene (PE) microplastics (MPs) smaller than 5 mm in size on earthworms are insufficient to fully comprehend their toxicity. In this study, earthworms Eisenia fetida were exposed to artificially added PE at a concentration ranging from 0.05 to 20 g/kg soil (0.005%-2%) for 60 days to determine the concentration range causing negative effects on earthworms and to uncover the potential toxic mechanisms. The individual growth, reproduction, and metabolic enzyme activities, including phase I enzymes (cytochrome P450 [CYP] 1A2, 2B6, 2C9, and 3A4), and phase II metabolic enzymes (superoxide dismutase (SOD), catalase (CAT), and glutathione sulfotransferase (GST)), and metabolomics were measured. The observed variations in responses of multiple cross-scale endpoints indicated that individual indices are less responsive to PE MPs than metabolic enzymes or metabolomics. Despite the absence of significant alterations in growth inhibition based on body weight, PE MPs at concentrations equal to or exceeding 2.5 g/kg were found to exert a toxic effect on earthworms, which was evidenced by significant changes in metabolic enzyme activities (CYP1A2, 2B6, 2C9, and 3A4, SOD, CAT, and GST) and important small molecule metabolites screened based on metabolomics, likely due to the bioaccumulation of PE. The toxicity of PE MPs to earthworms is inferred to be associated with neurotoxicity, oxidative damage, decreased detoxification capacity, energy metabolism imbalance, and impaired amino acid and purine metabolism due to bioaccumulation. The findings of this study will enhance our understanding of the molecular toxicity mechanisms of PE MPs and contribute to a more accurate assessment of the ecological risks posed by PE MPs in soil.

Effects of multi-walled carbon nanotubes in soil on earthworm growth and reproduction, enzymatic activities, and metabolomics.

Increased production and environmental release of multi-walled carbon nanotubes (MWCNTs) increase soil exposure and potential risk to earthworms. However, MWCNT toxicity to earthworms remains unclear, with some studies identifying negative effects and others negligible effects. In this study, to determine whether exposure to MWCNTs negatively affects earthworms and to elucidate possible mechanisms of toxicity, earthworms were exposed to sublethal soil concentrations of MWCNTs (10, 50, and 100 mg/kg) for 28 days. Earthworm growth and reproduction, activities of cytochrome P450 (CYP) isoforms (1A2, 2C9, and 3A4) and antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), and glutathione-s-transferase (GST)), and metabolomics were determined. Effects of MWCNTs on earthworms depended on exposure concentration. Exposure to MWCNTs did not significantly affect growth and reproduction of individual earthworms. Exposure to 50 mg/kg MWCNTs significantly increased activities of CYP2C9, CYP3A4, SOD, CAT, and GST but clearly reduced levels of L-aspartate, L-asparagine, and glutamine. With exposure to 100 mg/kg MWCNTs, toxic effects on earthworms were observed, with significant inhibition in activities of CYP isoenzymes and SOD, significant reductions in L-aspartate, L-asparagine, glutamine, and tryptophan, and simultaneous accumulations of citrate, isocitrate, fumarate, 2-oxoglutarate, pyruvate, D-galactose, carbamoyl phosphate, formyl anthranilate, hypoxanthine, and xanthine. Results suggest that toxicity of MWCNTs to earthworms is associated with reduced detoxification capacity, excessive oxidative stress, and disturbance of multiple metabolic pathways, including amino acids metabolism, the tricarboxylic acid cycle, pyruvate metabolism, D-galactose metabolism, and purine metabolism. The study provides new insights to better understand and predict the toxicity of MWCNTs in soil.

[Toxic effects of sublethal acetochlor with sublethal doses on earthworms in soil using multi-endpoints system]. / äºšè‡´æ­»å‰‚é‡ä¹™è‰èƒºå¯¹èš¯èš“çš„æ¯’æ€§æ•ˆåº”åŠæ•æ„Ÿç”Ÿç‰©æ ‡è®°ç‰©.

In this study, we examined the toxic effect of sublethal doses of acetochlor (1, 2, 4, 8 mg·kg-1) on earthworms by exogenous addition. The growth inhibition rate, cytochrome P450 isozymes (CYP1A2, 2C9 and 3A4) activities and the metabolomics were analyzed after seven days of exposure, to infer the toxicity threshold of acetochlor, screen the sensitive biomarkers from the levels of the individual, detoxified enzymes and small molecular metabolites, and elucidate the underlying toxicity mechanism. The results showed that CYP1A2, 2C9 and 3A4 activities were all significantly inhibited, and that the levels of ten metabolites (fructose-6-diphosphate, cytosine monophosphate, uridine monophosphate, adenosine monophosphate, adenosine, xanthine, fumaric acid, dihydroxyglutaric acid, ornithine and 16-hydroxyeicosatetraenoic acid) were significantly decreased by acetochlor exposure. The levels of six metabolites (adenosine succinic acid, succinic acid, arginine, tryptophan, asparagine and phenylalanine) were significantly increased when earthworms being exposed to 2-8 mg·kg-1 acetochlor. Acetochlor exposure caused oxidative damage to earthworms, weakened the glycolysis, disturbed the tricarboxylic acid cycle, disordered the purine and pyrimidine metabolism, and impaired the amino acids metabolism. Compared with the end point at individual level, the above 16 small molecule metabolites and CYP isozymes activities were more sensitive to acetochlor exposure. It was thus recommended that CYP isozymes (1A2, 2C9, and 3A4) activities and small molecular metabolites could be used as a set of biomarkers to diagnose the acetochlor pollution, given their high sensitivity and accuracy.

Evaluation of the combined toxicity of multi-walled carbon nanotubes and cadmium on earthworms in soil using multi-level biomarkers.

The coexistence of multi-walled carbon nanotubes (MWCNTs) with cadmium (Cd) in soil may cause the combined biological effects, but few study reported about their joint toxic effects on earthworms. Therefore, this study investigated the effects of sub-lethal levels of MWCNTs (10, 50, 100 mg/kg) and Cd (2.0, 10 mg/kg) on earthworms Eisenia fetida for 14 days. The changes in multi-level biomarkers of growth inhibition rate, cytochrome P450 isoenzymes (CYP1A2, 2C9 and 3A4), and small molecular metabolites (metabolomics) were determined. The toxic interaction between MWCNTs and Cd was characterized by the combination of the biomarker integration index (BRI), joint effect index concentration addition index (CAI), and the effect concentration addition index (EAI). The results showed that the single MWCNTs exposure caused insignificant change in most biomarkers, while the combined exposure of MWCNTs (50-100 mg/kg) and 10 mg/kg Cd led to significant changes in ten most important metabolites identified by metabolomics and activities of CYP1A2, 2C9, and 3A4. Compared with the toxicity of Cd alone, the combined toxicity of the mixture was significantly reduced. According to the integration of BRI and CAI/EAI, a clearly antagonistic interaction at relatively low effects was observed between MWCNTs and Cd. The responses of multiple biomarkers suggest the toxic action mode of the mixture on earthworms was related to the oxidative injury, and the disruption of amino acid, purine, and pyrimidine metabolism, and the urea cycle.

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.