Influences and mechanisms of nanoparticles on pentachloronitrobenzene accumulation by earthworms

Bioresponses of earthworm-microbiota symbionts to polychlorinated biphenyls in the presence of nano zero valent iron in soil

Both earthworms and nano zero-valent iron (nZVI) have been recently regarded as important approaches for in-situ remediation of polychlorinated biphenyls (PCBs) in soil. However, the combined action of earthworms and nZVI toward PCBs, and the biological responses of earthworm-microbiota symbionts to nZVI-PCBs co-exposure in soil remediation systems remain unclear. In this study, a 28-d exposure with different levels of polychlorinated biphenyls (PCBs) and nZVI was applied to earthworm Eisenia fetida in an agricultural soil. Both physiological responses of earthworms and their surrounding microbiota in gut and soil were examined. Kinetic modelling parameters showed a doubled PCB accumulation in earthworms with the presence of nZVI. Meanwhile, nZVI-PCBs coexposure synergistically stimulated the activities of superoxide dismutase (SOD) and catalase (CAT), along with the elevated levels of reactive oxygen species (ROS), malondialdehyde (MDA) and glutathione (GSH) in earthworms. Based on integrated metabolomic and 16S rRNA analysis, it was found that earthworms provided certain metabolites, e.g., S-(2-hydroxyethyl)glutathione, 16-hydroxypalmitic acid, and formamide, beneficial to PCB-degrading microbiota (Novosphingobium and Achromobacter) in the intestine. Our findings of nZVI-enhanced PCB bioaccumulation and the defense mechanism afforded by the earthworm-microbiota symbionts toward PCB-nZVI exposure show the promise of combining earthworms with nZVI for the remediation of PCBs-contaminated soil.

Pentachloronitrobenzene Reduces the Proliferative Capacity of Zebrafish Embryonic Cardiomyocytes via Oxidative Stress

Pentachloronitrobenzene (PCNB) is an organochlorine protective fungicide mainly used as a soil and seed fungicide. Currently, there are few reports on the toxicity of PCNB to zebrafish embryo. Here, we evaluated the toxicity of PCNB in aquatic vertebrates using a zebrafish model. Exposure of zebrafish embryos to PCNB at concentrations of 0.25 mg/L, 0.5 mg/L, and 0.75 mg/L from 6 hpf to 72 hpf resulted in abnormal embryonic development, including cardiac malformation, pericardial edema, decreased heart rate, decreased blood flow velocity, deposition at yolk sac, shortened body length, and increased distance between venous sinus and arterial bulb (SV-BA). The expression of genes related to cardiac development was disordered. However, due to the unstable embryo status in the 0.75 mg/L exposure concentration group, the effect of PCNB on the expression levels of cardiac-related genes was not concentration-dependent. We found that PCNB increased reactive oxygen species stress levels in zebrafish, increased malondialdehyde (MDA) content and catalase (CAT) activity, and decreased superoxide dismutase (SOD) activity. The increased level of oxidative stress reduced the proliferation ability of zebrafish cardiomyocytes, and the expressions of zebrafish proliferation-related genes such as cdk-2, cdk-6, ccnd1, and ccne1 were significantly down-regulated. Astaxanthin (AST) attenuates PCNB-induced reduction in zebrafish cardiomyocyte proliferation by reducing oxidative stress levels. Our study shows that PCNB can cause severe oxidative stress in zebrafish, thereby reducing the proliferative capacity of cardiomyocytes, resulting in zebrafish cardiotoxicity.