Ecotoxicogenomic analysis of stress induced on Caenorhabditis elegans in heavy metal contaminated soil after nZVI treatment

Soil contamination by heavy metals (HMs) is an environmental problem, and nanoremediation by using zero-valent iron nanoparticles (nZVI) has attracted increasing interest. We used ecotoxicological test and global transcriptome analysis with DNA microarrays to assess the suitability of C. elegans as a useful bioindicator to evaluate such strategy of nanoremediation in a highly polluted soil with Pb, Cd and Zn. The HMs produced devastating effect on C. elegans. nZVI treatment reversed this deleterious effect up to day 30 after application, but the reduction in the relative toxicity of HMs was lower at day 120. We stablished gene expression profile in C. elegans exposed to the polluted soil, treated and untreated with nZVI. The percentage of differentially expressed genes after treatment decreases with exposure time. After application of nZVI we found decreased toxicity, but increased biosynthesis of defensive enzymes responsive to oxidative stress. At day 14, when a decrease in toxicity has occurred, genes related to specific heavy metal detoxification mechanisms or to response to metal stress, were down regulated: gst-genes, encoding for glutathione-S-transferase, htm-1 (heavy metal tolerance factor), and pgp-5 and pgp-7, related to stress response to metals. At day 120, we found increased HMs toxicity compared to day 14, whereas the transcriptional oxidative and metal-induced responses were attenuated. These findings indicate that the profiled gene expression in C. elegans may be considered as an indicator of stress response that allows a reliable evaluation of the nanoremediation strategy. (C) 2020 Elsevier Ltd. All rights reserved.