[en] Partitioning tissue metal concentration into subcellular compartments reflecting toxicologically available pools may provide good descriptors of the toxicological effects of metals on organisms. Here we investigated the relationships between internal compartmentalization of Cd, Pb and Zn and biomarker responses in a model soil organism: the earthworm. The aim of this study was to identify metal fractions reflecting the toxic pressure in an endogeic, naturally occurring earthworm species (Aporrectodea caliginosa) exposed to realistic field-contaminated soils. After a 21 days exposure experiment to 31 field-contaminated soils, Cd, Pb and Zn concentrations in earthworms and in three subcellular fractions (cytosol, debris and granules) were quantified. Different biomarkers were measured: the expression of a metallothionein gene (mt), the activity of catalase (CAT) and of glutathione-s-transferase (GST), and the protein, lipid and glycogen reserves. Biomarkers were further combined into an integrated biomarker index (IBR). The subcellular fractionation provided better predictors of biomarkers than the total internal contents hence supporting its use when assessing toxicological bioavailability of metals to earthworms. The most soluble internal pools of metals were not always the best predictors of biomarker responses. metallothionein expression responded to increasing concentrations of Cd in the insoluble fraction (debris + granules). Protein and glycogen contents were also mainly related to Cd and Pb in the insoluble fraction. On the other hand, GST activity was better explained by Pb in the cytosolic fraction. CAT activity and lipid contents variations were not related to metal subcellular distribution. The IBR was best explained by both soluble and insoluble fractions of Pb and Cd. This study further extends the scope of mt expression as a robust and specific biomarker in an ecologically representative earthworm species exposed to field-contaminated soils. The genetic lineage of the individuals, assessed by DNA barcoding with cytochrome c oxidase subunit I, did not influence mt expression. - • Aporrectodea caliginosa was exposed for 21 days to 31 field-contaminated soils. • Cd, Pb and Zn partitioning into subcellular compartments was studied in exposed worms. • Six biomarkers were analyzed and related to the internal metal concentrations. • Subcellular fractionation provided better predictors than the total internal contents. • metallothionein expression increased with Cd concentration in the insoluble fraction.

[en] Past activities of 2 smelters (Metaleurop Nord and Nyrstar) led to the accumulation of high amounts of Metal Trace Elements (TEs) in top soils of the Noyelles-Godault/Auby area, Northern France. Earthworms were exposed to polluted soils collected in this area to study and better understand the physiological changes, the mechanisms of acclimation, and detoxification resulting from TE exposure. Previously we have cloned and transcriptionally characterized potential biomarkers from immune cells of the ecotoxicologically important earthworm species Eisenia fetida exposed in vivo to TE-spiked standard soils. In the present study, analysis of expression kinetics of four candidate indicator genes (Cadmium-metallothionein, coactosin like protein, phytochelatin synthase and lysenin) was performed in E. fetida after microcosm exposures to natural soils exhibiting an environmental cadmium (Cd) gradient in a kinetic manner. TE body burdens were also measured. This microcosm study provided insights into: (1) the ability of the 4 tested genes to serve as expression biomarkers, (2) detoxification processes through the expression analysis of selected genes, and (3) influence of land uses on the response of potential biomarkers (gene expression or TE uptake). - Highlights: → Expression biomarkers in animals exposed to Cadmium-contaminated field soils. → Expression kinetics to test the ability of genes to serve as expression biomarkers. → Study of detoxification processes through the expression analysis of selected genes.

[en] Diverse anthropogenic activities often lead to the accumulation of inorganic and organic residues in topsoils. Biota living in close contact with contaminated soils may experience stress at different levels of biological organisation throughout the continuum from the molecular-genetic to ecological and community levels. To date, the relationship between changes at the molecular (mRNA expression) and biochemical/physiological levels evoked by exposures to chemical compounds has been partially established in a limited number of terrestrial invertebrate species. Recently, the advent of a family of transcriptomic tools (e.g. Real-time PCR, Subtractive Suppressive Hybridization, Expressed Sequence Tag sequencing, pyro-sequencing technologies, Microarray chips), together with supporting informatic and statistical procedures, have permitted the robust analyses of global gene expression changes within an ecotoxicological context. This review focuses on how transcriptomics is enlightening our understanding of the molecular-genetic responses of three contrasting terrestrial macroinvertebrate taxa (nematodes, earthworms, and springtails) to inorganics, organics, and agrochemicals. - Environmental toxicology and transcriptomics in soil macroinvertebrates.

[en] Anthropogenic activities may lead to the accumulation of inorganic and organic compounds in topsoils. Biota living in close contact with contaminated soils may experience stress at different levels of biological organization throughout the continuum from molecular to community level. Biological responses observed at the individual or infra-individual level of biological organization led to the development of biomarkers. The development of biomarkers consists often in evidencing biological modifications following a contaminant stress in laboratory conditions, using naïve organisms and it is sometime proposed to use the biological state of individuals from sentinel species collected in the field to evaluate the level of environmental exposure. However, considering the possibility of local adaptation following long-term exposure, organisms response sampled in the field may substantially differ from laboratory specimens. In this review, we discuss this point focusing on the definition and validity of molecular biomarkers of metal pollution using earthworms of the Lumbricidae family. -- Considering the possibility of adaptation into the biomarker concept

[en] Yellow-lupin (Lupinus luteus L.) was grown on soils contaminated with heavy metals during two parallel studies. In the first one, the soil was contaminated by industrial activities whereas, in the second one, the soil was artificially contaminated with a single metal including Cd, Pb, Zn, Ni (in nitrate form), and Ag (in nitrate and nanoparticles form). The study was performed to assess a plant’s response to contamination including its antioxidative response and molecular mechanisms involved in metal detoxification through the expression level of metallothioneins (MTs). Overall, the study provided insights into identification and validation of housekeeping genes (HKG) in L. luteus under exposure to metal stress and showed the effects of selected heavy metals and silver nanoparticles on the expression of metallothioneins, the activity of guaiacol peroxidase (GPX) and bioaccumulation of metals in leaves of L. luteus. As such, HKG validation using BestKeeper, NormFinder, and geNorm software allowed for the selection of four most stable reference genes in a context metal contamination for the selected plant. Moreover, a significant increase in the expression levels of MT was observed in plants grown under heavy metal stress and none on plants grown on 25 mg kg⁻¹ of silver nanoparticles. Also, the GPX activity and MT expression showed statistically significant changes between different conditions and doses which means that they can be used as highly sensitive stress markers for planning the phytoremediation process on a large scale.

[en] Highlights: • Bioaccumulation of Ag by plants was species-dependent. • Snails accumulated Ag when they can access contaminated soil. • Sulfidized Ag were less bioavailable than manufactured Ag nanoparticles. • Sulfidized Ag accumulated in the studied trophic chain during chronic exposure. Consumer products containing silver nanoparticles (AgNPs) release silver (Ag) to the environment, particularly wastewater. Sewage sludge (SS), which contains numerous contaminants including Ag, is recycled by spreading on agricultural land. Although slight impacts and bioaccumulation of Ag sulfide (Ag₂S, the main species found in SS) in terrestrial organisms have been demonstrated, possible trophic transfer into plants and subsequently animal species has not been examined. Accordingly, the present study experimentally measured the transfer of Ag from AgNPs and sulfidized Ag into plants and primary consumers and compared their bioavailability. Nine plant cultivars were grown in soil mixed with SS containing Ag, which revealed that bioaccumulation of Ag by plants is species-dependent. Ryegrass (the plant species with the greatest accumulation – up to 0.2 mg kg⁻¹) was then cultivated on a larger scale to expose snails and locusts for several weeks. While locusts did not accumulate Ag after two weeks of exposure, snails exhibited Ag bioaccumulation after 5 weeks when soil was accessible. Sulfidized Ag derived from AgNPs were less available (bioaccumulation up to 2.5 mg kg⁻¹) than the Ag from the original AgNPs (bioaccumulation up to 15 mg kg⁻¹). This transfer potential of Ag could have consequences for food webs due to chronic exposure linked to SS spreading practices. This study shows that transformations of AgNPs in treatment plants attenuate but do not completely eliminate the risk of Ag to plant and animal species SS.