Evaluation of Complex Toxicity of Canbon Nanotubes and Sodium Pentachlorophenol Based on Earthworm Coelomocytes Test.

As a standard testing organism in soil ecosystems, the earthworm Eisenia fetida has been used widely in toxicity studies. However, tests at the individual level are time- and animal-consuming, with limited sensitivity. Earthworm coelomocytes are important for the assimilation and elimination of exogenous compounds and play a key role in the processes of phagocytosis and inflammation. In this study, we explored an optimal condition to culture coelomocytes of E. fetida in vitro and investigated the cytotoxicity of multiwalled carbon nanotubes (MWCNTs) and sodium pentachlorophenol (PCP-Na) using coelomocytes via evaluating lethal toxicity, oxidative stress, membrane damage, and DNA damage. The results showed that coelomocytes can be successfully cultured in vitro in primary under the RPMI-1640 medium with 2-4×104 cells/well (1-2×105 cells/mL) in 96-well plates at 25°C without CO2. Both MWCNTs and PCP-Na could cause oxidative damage and produce ROS, an evidence for lipid peroxidation with MDA generation and SOD and CAT activity inhibition at high stress. The two chemicals could separately damage the cell membrane structure, increasing permeability and inhibiting mitochondrial membrane potential (MMP). In addition, our results indicate that PCP-Na may be adsorbed onto MWCNTs and its toxicity on earthworm was accordingly alleviated, while a synergetic effect was revealed when PCP-Na and MWCNTs were added separately. In summary, coelomocyte toxicity in in vitro analysis is a sensitive method for detecting the adverse effects of carbon nanotubes combined with various pollutants.

Ecotoxicological effects of earthworm following long-term Dechlorane Plus exposure.

Dechlorane Plus (DP), similar to persistent organic pollutants, has been widely detected in environmental matrices, especially in sediment and soil. In this study, earthworms Eisenia fetida were exposed to 0.1, 0.5, 6.25 and 12.5 mg kg(-1) DP for 28 d. Lethality, oxidative stress, neurotoxicity and cellulase of E. fetida were assessed to investigate ecotoxicological effects of DP after long-term exposure. Results showed that the direct toxicity of DP was very low. However, death rate, as well as SOD activity, together with changes in activities of CAT, GSH-Px, and GSH levels, indicating that oxidative stress may play a significant role in DP exposure. In addition, DP also changes the AChE and cellulase activity of earthworms even under low DP concentration after long-term exposure. Moreover, comet assay results showed that DP exposure increased the levels of tDNA significantly (p < 0.05) even in the lowest treatment (0.1 mg kg(-1) DP). Combined with the results of enzyme activity, oxidative damage and comet assay, it can be suggested that earthworms experience more stress of DP during long-time exposure. 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.

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.

Acute toxicity of multi-walled carbon nanotubes, sodium pentachlorophenate, and their complex on earthworm Eisenia fetida.

Laboratory experiments were undertaken to relate biomarker responses to the toxicities of multi-walled carbon nanotubes (MWCNTs) and sodium pentachlorophenate (PCP-Na), both individually and combined. The acute toxicities of MWCNTs and PCP-Na on earthworm Eisenia fetida were studied through different exposure methods (filter paper contact test, immersion contact test, and artificial soil contact test). Enzyme activity and malondialdehyde (MDA) content in the earthworm E. fetida exposed to MWCNTs and PCP-Na in filter paper contact test, both individually and under combined exposure, were determined. After exposure, PCP-Na induced observable acute toxicity while the MWCNTs induced slight toxicity. Interestingly the earthworms exposed to the mixture of MWCNTs and PCP-Na demonstrated different expression of enzymatic biomarkers from those exposed to MWCNTs or PCP-Na alone. Our results indicated that the toxicity of PCP-Na on E. fetida may be alleviated by the appearance of MWCNTs for all exposure methods except for immersion contact test.