Biochemical responses of earthworm Eisenia fetida exposed to cadmium-contaminated soil with long duration

Exploring the Toxicity of Oxytetracycline in Earthworms (Eisenia fetida) Based on the Integrated Biomarker Response Method

Antibiotic contamination has become a global environmental issue of widespread concern, among which oxytetracycline contamination is very severe. In this study, earthworm (Eisenia fetida) was exposed to oxytetracycline to study its impact on the soil environment. The total protein (TP), catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), malondialdehyde (MDA), glutathione S-transferase (GST), and glutathione peroxidase (GPX) oxidative stress indicators in earthworms were measured, and the integrated biomarker response (IBR) approach was used to evaluate the toxic effect of oxytetracycline on earthworms. A Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) and a path analysis model were used to explore the physiological and metabolic processes of earthworms after stress occurs. The results showed that SOD, GPX, and GST play important roles in resisting oxytetracycline stress. In addition, stress injury showed a good dose-effect relationship, and long-term stress from pollutants resulted in the most serious damage to the head tissue of earthworms. These results provide a theoretical basis for understanding the toxic effect of oxytetracycline on soil animals, monitoring the pollution status of oxytetracycline in soil, and conducting ecological security risk assessment.

Resveratrol protects against cadmium-induced cerebrum toxicity through modifications of the cytochrome P450 enzyme system in microsomes

BACKGROUND

Cadmium (Cd), known as a vital contaminant in the environment, penetrates the blood-brain barrier and accumulates in the cerebrum. Acute toxicosis of Cd, which leads to lethal cerebral edema, intracellular accumulation and cellular dysfunction, remains to be illuminated with regard to the exact molecular mechanism of cerebral toxicity. Resveratrol (RES), present in the edible portions of numerous plants, is a simply acquirable and correspondingly less toxic natural compound with neuroprotective potential, which provides some theoretical bases for antagonizing Cd-induced cerebral toxicity.

RESULTS

This work was executed to research the protective effects of RES against Cd-induced toxicity in chicken cerebrum. Markedly, these lesions were increased in the Cd group, which also exhibited a thinner cortex, reduced granule cells, vacuolar degeneration, and an enlarged medullary space in the cerebrum. Furthermore, Cd induced CYP450 enzyme metabolism disorders by disrupting the nuclear xenobiotic receptor response (NXRs), enabling the cerebrum to reduce the ability to metabolize exogenous substances, eventually leading to Cd accumulation. Meanwhile, accumulated Cd promoted oxidative damage and synergistically promoted the damage to neurons and glial cells.

CONCLUSION

RES initiated NXRs (especially for aromatic receptor and pregnancy alkane X receptor), decreasing the expression of CYP450 genes, changing the content of CYP450, maintaining CYP450 enzyme normal activities, and exerting antagonistic action against the Cd-induced abnormal response of nuclear receptors. These results suggest that the cerebrum toxicity caused by Cd was reduced by pretreatment with RES. © 2023 Society of Chemical Industry.

Bioaccumulation of Silver and Impairment of Vital Organs in Clarias gariepinus from Co-Exposure to Silver Nanoparticles and Cow Dung Contamination

This study reports the implications of silver nanoparticles (AgNPs) and cow-dung contamination on water quality and oxidative perturbations in antioxidant biomarkers in the exposed Clarias gariepinus. Sixteen samples of C. gariepinus were exposed to fresh-water, 0.75 mg/mL each of AgNPs, cow-dung and a mixture of AgNPs-cow dung dosed water for 10 days. Cow-dung significantly (p < 0.05) depleted dissolved oxygen (DO) and increased biochemical oxygen demand (BOD) by 14% and 75% respectively. The trends of abundance and bioaccumulation of Ag in C. gariepinus exposed to different treatments followed kidney > muscle > gill > liver, implying the kidney was the worst affected organ. The AgNPs significantly (p < 0.05) perturbed vital organs in C. gariepinus by altering activities of antioxidant biomarkers, whereas AgNPs-cow dung had reduced perturbations implying organic matter bound Ag⁺ to reduce toxicity. These results conclude that AgNPs posed a challenging environment for C. gariepinus to thrive.

Effects of combined treatment of cadmium and oxytetracycline on the terrestrial isopod Porcellio leavis

The influence of pharmaceutical residues and heavy metals on living organisms has received global attention. The present study assessed the interactive effect of antibiotic residues and heavy metals in soil, as contaminated food with cadmium (Cd) and oxytetracycline (OTC) on the isopod Porcellio leavis. It was fed on fresh plant leaves contaminated with different concentrations of cadmium, Cd+OTC1000 ppm, Cd+OTC2000 ppm and Cd+OTC3000 ppm for 4 weeks. The changes in the feeding patterns, protein, lipid peroxidation (LPO), catalase activity (CAT), and total free amino acids (TFAA) were recorded. There were significant differences in the obtained results where Cd reduced the egestion ratio (ER) however, OTC enhanced this ratio. Biochemical analysis illustrated that combination between OTC and Cd inhibits the toxic effects of Cd at low concentration (1000 ppm), while at high concentration (3000 ppm) raise the toxicity. Detailed studies are required for further understanding of the interaction between OTC and heavy metals, and also its impact on soil animals and for improving soil risk evaluation.

Formation of perfluorocarboxylic acids (PFCAs) during the exposure of earthworms to 6:2 fluorotelomer sulfonic acid (6:2 FTSA)

6:2 fluorotelomer sulfonic acid (6:2 FTSA) is a novel perfluorooctane sulfonate (PFOS) alternative used globally in aqueous film forming foams (AFFFs). Although 6:2 FTSA has been recently detected in the environment, its fate in terrestrial invertebrates remains unclear. The uptake, elimination and biotransformation of 6:2 FTSA in earthworms (Eisenia fetida) were investigated after in vivo and in vitro exposure. 6:2 FTSA could be biodegraded by microorganisms in soil to trifluoroacetic acid (TFA), perfluoropropionic acid (PFPrA), perfluorobutanoic acid (PFBA), perfluoropentanoic acid (PFPeA) and perfluorohexanoic acid (PFHxA). The uptake rate constant (k_u) and biota-to-soil accumulation factor (BSAF) of 6:2 FTSA in earthworms were 0.185 g_oc/g_ww/d and 0.685 g_oc/g_ww, respectively, indicating high bioaccumulative ability in earthworms. Five terminal perfluorocarboxylic acids (PFCAs) metabolites, including TFA, PFPrA, PFBA, PFPeA and PFHxA were observed in both in vivo and in vitro exposure tests, with TFA as the predominant metabolite. However, no perfluoroheptanoic acid (PFHpA) was observed in the present study. The elimination rate constants (k_e) increased in the order: 6:2 FTSA (0.057/d) < TFA (0.058/d) < PFPrA (0.071/d) < PFBA (0.084/d) < PFHxA (0.182/d) < PFPeA (0.193/d). Biodegradation of 6:2 FTSA in the earthworm homogenates, cytolchrome P450 (CYP450) enzyme solutions and glutathione-s-transferase (GST) enzyme solutions fitted well with the first order kinetics. The biotransformation rate constants (k) were in the following order: homogenates (0.012/h) > CYP450 (0.009/h) > GST (0.007/h), implying that CYP450 and GST were involved in biotransformation of 6:2 FTSA in earthworms. This study provides important theoretical evidence for the fate of 6:2 FTSA in earthworms.

Toxicological effect of Parthenium hysterophorus and milk processing industry sludge on earthworms, Eisenia fetida

Production of large quantities of organic waste all over the world poses major environmental and disposal problems. The present study was conducted to explore the deleterious effects of Parthenium hysterophorus and milk processing industry sludge on the health of earthworm, Eisenia fetida. Earthworms were allowed to grow in the mixture of cow dung:Parthenium hysterophorus (75:25) and cow dung:milk processing industry sludge (60:40) for 60 days. The biochemical markers viz. superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and malondialdehyde (MDA) levels and histological changes in earthworm's intestine were assessed after 15, 30, 45, and 60 days of exposure. The results revealed increased MDA level, while SOD, CAT, and GPx activities showed variation in both treatments. Furthermore, histopathological changes revealed damage in the intestinal tissue in both treatments during all intervals. More severe effects were registered in P. hysterophorus treatment. Obtained results may contribute to the understanding of P. hysterophorus and milk processing industry sludge induced toxic effects on earthworms and to identify defense mechanism of Eisenia fetida.

Mechanism underlying earthworm on the remediation of cadmium-contaminated soil

Cadmium (Cd) contamination of soil becomes a potential agricultural and global environmental problem due to the need to ensure safe food. In this study, earthworms (Eisenia fetida) and plants (vetiver grass) were prepared for removal Cd from soil. The results showed the Cd concentration in the soil of all experimental groups decreased, notably by 17.60% in the group with 20 mg/kg Cd concentration. In the roots of vetiver, the content of Cd increased by 57% after earthworms were added and the transfer coefficient of Cd was also significantly increased. Moreover, Cd in the soil was generally absorbed by the intestinal tract of earthworms and became concentrated, mainly in the midgut and hindgut accounting for >77.78% of the total. In addition, enteric microorganism analysis demonstrated that the bacterial community structure played an important role in Cd enrichment and metabolism regulation. There was a significant correlation between some bacteria and Cd concentration. Among these bacteria, Pseudomonas brenneri, were involved in the adsorption and metabolism of Cd to reduce the toxicity of Cd to the earthworms. On the other hand, in order to cope with the external Cd stress, the malondialdehyde (MDA) and hydrogen critically (CAT) enzymes in the earthworms increased with the concentration. Therefore, the high tolerance of earthworms to Cd is related to its physiological adjustment and the balance of intestinal bacteria. The combination of earthworms, microorganisms and plants can result a good alternative to diminish the impact of Cd in soils.

`Cadmium induced cardiac inflammation in chicken (Gallus gallus) via modulating cytochrome P450 systems and Nrf2 mediated antioxidant defense

Cadmium (Cd) has been implicated in the pathogenesis of inflammation, myocardial infarction, angiocardiopathy, even cancers. However, it is unknown that Cd-induced cardiac toxicity through Nrf2-mediate antioxidant defense and Cytochrome P450 (CYP450) system. To ascertain the chemoprevention of Cd-induced cardiac toxicity, total 60 newborn chicks were fed with different doses of Cd (0 mg/kg, 35 mg/kg and 70 mg/kg) for a period of 90 days feed administration. Results indicated Cd exposure caused cardiac histopathology changed and functions abnormal, induced NOS activities raised and cardiac inflammation, triggering inflammation factors (IL-6, IL-8, TNF-α, and NF-κb) upregulation and inhabitation of IL-10. Cd caused increase of total CYP450 and Cytochrome b5 (Cyt b5) contents, while erythromycin N-demethylase (ERND), aminopyrin N-demethylase (APND), aniline-4-hydeoxylase (AH) and NADPH-cytochrome c reductase (NCR) indicated opposite situations with different degrees of reduction in microsomes. The mRNA level of most CYP450s isoforms (CYP1A1, CYP1A2, CYP1A5, CYP1B1, CYP2C18, CYP2C45, CYP3A4, CYP3A7 and CYP3A9) were significantly increase but CYP2D6 expression level changed not obvious. Furthermore, Cd treatment caused increased the peroxidation product (MDA) and H₂O₂ over accumulation, the decreased of T-AOC accompanied by decreased activity of antioxidant enzymes (T-SOD, GST and GPX). Over accumulation of Cd lead to oxidative stress and activated Nrf2 signal pathway through upregulating pivotal target genes (HO-1, NQO1, GCLC, GCLM and SOD). These findings suggested Cd exposure caused cardiotoxicity through CYP450s enzymes homeostasis disturbance and Nrf2-mediated oxidative stress signal pathways defense. These results may provide new evidence on molecular mechanism of Cd-induced cardiac toxicity.

Use of integrated biomarker response for studying the resistance strategy of the earthworm Metaphire californica in Cd-contaminated field soils in Hunan Province, South China

Research was conducted to study the response and detoxification mechanisms of earthworms collected from Cd-contaminated areas in Hunan Province, South China. Metaphire californica, the dominant earthworm species in fields, referred as earthworm-A and -B that collected from low- (0.81 mg kg^-1) and high-Cd soil (13.3 mg kg^-1), respectively, for exchanging incubation in laboratory. The results showed that earthworm-A gradually accumulated higher Cd when exposed in the high-Cd soil, whereas Cd concentration of earthworm-B decreased after being transferred to low-Cd soil (albeit BAF_Cd >20). The integrated biomarker response index was calculated with the biomarkers of antioxidant systems (e.g., superoxide dismutase (SOD), peroxidase (POD), glutathione (GSH), glutathione peroxidase (GPx), glutathione-S transferase (GST), and malondialdehyde (MDA)) and energy index (e.g., protein and glycogen) in M. californica. GSH, GPx, and GST contributed the most to the integrated biomarker response (IBR) in earthworm-A when exposed in high-Cd soil for 14 d. Earthworm-B responded with higher GST and GPx activities and decreased protein content in low-Cd soil. For 28 d, the response of earthworm-A was not evident in either low- or high-Cd soil, and the inductive effect of metal stress on earthworm-B tended to be stable, except for the higher MDA content (p < 0.05) when exposed in low-Cd soil. The IBR index of earthworm-B (2.93 and 3.40) in low- and high-Cd soil, respectively, was higher than that of earthworm-A (0.89 and 1.0). Overall, earthworm-A exhibited a detoxification process to resist high-Cd toxicity from low-to high-Cd soil. Earthworm-B exhibited a physiological resilience once its habitat had changed to a normal or low-Cd soil environment, possibly owing to the cost of its resistance adaptation to the historical highly contaminated soil in fields.

Evaluation of combined toxicity of Siduron and cadmium on earthworm (Eisenia fetida) using Biomarker Response Index

Agrochemicals and heavy metals are widespread contaminants in urban soil and could co-exist as mixture, which could cause unexpected risk to terrestrial organism. To assess the joint effect of herbicide Siduron and Cd, a battery of sub-lethal biomarkers was studied using earthworm ecotoxicological assay. Most selected biomarkers appeared significant but complicated responses with the increasing concentration of contaminants after 28-day exposure. In order to quantify the overall effect of the mixture contaminants, Biomarker Response Index (BRI) was used to integrate the multiple responses. Concentration Addition Index (CAI) and Effect Addition Index (EAI) were introduced to assess types of joint effect. Results showed significantly dose-effect responses between BRI and contaminant exposure concentrations. Integrated toxicity increased obviously under joint treatments of Siduron and Cd compared to their individual treatments. According to CAI, a clear antagonism was observed at relatively lower effects and gradually transformed to slight synergism with an increase of effects, while EAI showed the joint effect of addition at the whole range of effect levels. Thus, compared to the simple analysis of those complicated responses, BRI is an effective method to determine the integrated toxicity of mixture and its combination with joint effect indices (CAI and EAI) provides more worthy risk assessment on toxicity interaction among compounds.

Enrofloxacin at environmentally relevant concentrations enhances uptake and toxicity of cadmium in the earthworm Eisenia fetida in farm soils

Individual and combined effects of enrofloxacin (EF) and cadmium (Cd) on the earthworm Eisenia fetida at environmentally relevant concentrations were investigated. EF is a veterinary antibiotic; Cd is an impurity in phosphatic fertiliser. For both, residues may accumulate in farm soils. In laboratory tests, over 98% of spiked EF was adsorbed by farm soils, with a half-life >8 weeks. However, earthworms absorbed less than 20% of spiked EF. Earthworms in soil with EF concentration 10 mg kg(-1) soil experienced transient oxidative stress and exhibited reduced burrowing activity and respiration after an 8-week exposure; EF at 0.1 and 1.0 mg kg(-1) soil did not elicit toxicity symptoms. When both were added, Cd did not affect EF uptake, but each increment of spiked EF increased Cd bioaccumulation and associated oxidative stress of earthworms, and also caused decreased burrow length and CO2 production. However, metallothionein induction was not affected. The enhanced toxicity of Cd to earthworms in the presence of EF at low environmental concentrations may have implications for the health and reproductive success of earthworm populations and highlights the importance of understanding effects of antibiotic contamination of farm soils, and of awareness of environmental effects from interaction between multiple contaminants.

Toxicological effects of soil contaminated with spirotetramat to the earthworm Eisenia fetida

The aim of this study was to evaluate the potential toxicity of spirotetramat to the earthworm Eisenia fetida in a natural soil environment. Many biochemical markers, viz., superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), glutathione S-transferase (GST), cellulase, and malondialdehyde (MDA) contents were measured after exposure to 0.25, 1.25, and 2.5mgkg(-1) for 2, 7, 14, 21, and 28days. In addition, the comet assay was performed on earthworm coelomocytes to assess the level of genetic damage. The results demonstrate that the SOD activity and MDA content were significantly stimulated by the highest dose (2.5mgkg(-1)) of spirotetramat for the entire period of exposure. The activities of CAT and POD increased significantly by 2d and 21d, respectively, but the activities of both were significantly inhibited after prolonged exposure (28d). After an initial increase on the 2nd day, the cellulase activity in the high-dose treatment group was significantly inhibited for the entire remaining exposure period. The comet assay results demonstrate that spirotetramat (⩽2.5mgkg(-1)) can induce low and intermediate degrees of DNA damage in earthworm coelomocytes. The results indicate that spirotetramat may pose potential biochemical and genetic toxicity to earthworms (E. fetida), and this information is helpful for understanding the ecological toxicity of spirotetramat on soil invertebrate organisms.

Effects of soil organic matter content on cadmium toxicity in Eisenia fetida: implications for the use of biomarkers and standard toxicity tests

Bioavailability is affected by soil physicochemical characteristics such as pH and organic matter (OM) content. In addition, OM constitutes the energy source of Eisenia fetida, a well established model species for soil toxicity assessment. The present work aimed at assessing the effects of changes in OM content on the toxicity of Cd in E. fetida through the measurement of neutral red uptake (NRU) and mortality, growth, and reproduction (Organisation for Economic Co-operation and Development [OECD] Nos. 207 and 222). Complementarily, metallothionein (MT) and catalase transcription levels were measured. To decrease variability inherent to natural soils, artificial soils (Organization for Economic Cooperation and Development 1984) with different OM content (6, 10, and 14%) and spiked with Cd solutions at increasing concentrations were used. Low OM in soil decreased soil ingestion and Cd bioaccumulation but also increased Cd toxicity causing lower NRU of coelomocytes, 100 % mortality, and stronger reproduction impairment, probably due to the lack of energy to maintain protection mechanisms (production of MT).Cd bioaccumulation did not reflect toxicity, and OM played a pivotal role in Cd toxicity. Thus, OM content should be taken into account when using E. fetida in in vivo exposures for soil health assessment.

Zonation in the digestive tract of Eisenia fetida: implications in biomarker measurements for toxicity assessment

Eisenia fetida is a model species for soil health assessment and different biomarkers that detect either the presence of bioavailable contaminants or their biological effect have been developed. These parameters are performed in a target tissue or whole earthworm, without considering the marked zonation in histological organisation, enzyme activities and gene expression pattern existing along the body. Thus, the present work was aimed at (a) characterising the morphofunctional heterogeneity along the digestive tract of E. fetida in tissue morphology and turnover, lysosomal enzyme markers (β-glucuronidase, β-GUS; hexosaminidase, HEX), lipofuscin contents (LPF) and metallothionein (MT) and catalase (CAT) gene expression; and (b) determining whether the responsiveness to Cd exposure varies among tissues and along the digestive tract. HEX and β-GUS exhibited a heterogeneous distribution pattern along and across the digestive tract and Cd exposure caused a marked decrease of HEX and an increase of β-GUS activity. Likewise, the significant decrease of cell turnover and the induction of MT transcription were was zone-dependent. Therefore, in was concluded that the consideration of the zonation when applying biomarker for toxicity assessment would reduce the intrinsic variability that results from overlooking the marked morphofunctional heterogeneity that exists in annelids along their body axis.