Comparison of transfer and effects of Cd on rats exposed in a short experimental snail-rat food chain or to CdCl2 dosed food

From environmental bioavailability of metal(loid)s to their ecogenotoxicological effects in land snails

To date, no study has linked the environmental and the ecogenotoxicological bioavailability of contaminants to land snails. Yet, understanding the specific ecotoxicological mechanisms from bioaccumulation to genotoxicity is necessary e.g., to build an adverse outcome pathway relevant to risk assessment. Consequently, the aim of our study is to look for relationships between accumulated concentrations of As, Cd and Hg in sub-adult snails and ecotoxicological effects at the individual (survival and growth) and molecular (genomic stability) levels. This study combines random amplified polymorphic DNA (RAPD) coupled with high-resolution capillary electrophoresis system (HRS) and micronucleus (MN) assay on haemocytes to consider various types of cytogenomic damage, such as chromosomal aberrations, breakages, adducts and mutations. The results showed alteration of the individual endpoints at higher accumulation quotients (AQs) that reflect the excess of transfers to snails, especially with decreased survival for As. In addition, genotoxic effects were observed with an increased occurrence of MN in haemocytes for the three meta(loid)s considered (R² from 0.57 to 0.61 as a function of the meta(loid)s). No concentration-dependent decrease in genome stability was highlighted by RAPD-HRS in snails exposed to As and Cd but not Hg. Our results demonstrate the complementarity of the RAPD-HRS and the MN assay for understanding the different genotoxic mechanisms of the three metal(loid)s studied in land snails. They show a way to better assess environmental risks of contaminated soils by associating ecotoxicity, genotoxicity and bioaccumulation assays (ISO 24032), i.e., ecogenotoxicological bioavailability. Convergences highlighted here between the bioaccumulation of metal(loid)s in viscera and genotoxic effects in haemocytes constitute a way to better assess the bioavailability of contaminants in soils to the land snail and the subsequent environmental risk.

From bioavailability to risk assessment of polluted soil using snails: link between excess transfer and inhibition of sexual maturation

An accurate assessment of the environmental risk of soils contaminated by metal(loid)s (MEs) requires quantifying exposure and knowing the toxicity of contaminants transferred to biota. For this purpose, two indices have been developed with the bioindicator Cantareus aspersus to assess exposure (SET: sum of the excess of transfer) and risk (ERITME: evaluation of the risk of the transferred metal elements) of multi-contaminated soils. If the SET and ERITME indices allow characterization of exposure and risk based on unspecific toxicity points, then the link between these indices and real effects on some toxicological endpoints, such as growth or sexual maturation, remains to be demonstrated. For this purpose, sub-adult snails were exposed for 28 days to 38 ME-contaminated soils. Relationships between the SET and/or ERITME indices and health alterations in C. aspersus were determined using Spearman correlations, linear regressions, univariate regression trees, and kinetic models. Relationships were determined between the values of the SET and ERITME indices, bioaccumulation as an indicator of ME bioavailability, and the alteration in physiological endpoints, such as the shell development used as a non-invasive indicator of sexual maturation. The results enabled the determination of three levels of risk according to the differences in reaching sexual maturity: no risk, uncertain, and proven risk depended on whether the value of ERITME was below, in, or beyond the interval [2574-22720], respectively. This study provides the first benchmarks with the SET and ERITME indices to interpret the risk of contaminated soils to snails and to relate the environmental and toxicological bioavailability of ME mixtures.

Ex situ environmental risk assessment of polluted soils using threshold guide values for the land snail Cantareus aspersus

Environmental risk assessment of contaminated soils should ideally be carried out with complementary approaches (chemical and biological) conducted in situ and ex situ. While biological methods based on the assessment of effect and bioaccumulation in bioindicators exist for soil fauna organisms, such as land snails, the methodology is currently limited in the field to 14 metallic elements (MEs). To provide new relevant tools to the stakeholders of polluted fields, the aim of this work is to determine ex situ threshold guide values (ex situ TGVs), for 15 MEs, 16 polycyclic aromatic hydrocarbons (PAHs) and 7 polychlorinated biphenyls (PCBs). These ex situ TGVs are the usual concentration of contaminants found in the viscera of the bioindicator Cantareus aspersus after 28 days of exposure to uncontaminated soils. The second objective was to assess and validate the relevance of these ex situ TGVs for the interpretation of contamination levels in various European contaminated soils based on global index calculations: i) The sum of the excess of transfers (SETs) and ii) the weighted SETs based on the general toxicity points of each contaminant used to evaluate the risk of transferred MEs, PAHs and PCBs (ERITMEs, ERITPAHs and ERITPCBs, respectively). In addition, the influence of soil physico-chemical properties on accumulation was modelled to better understand their roles in bioavailability. The presented ex situ TGV and the associated indicators (the global sum of the excess of transfers and global ecotoxicological risk) provide a basis by which stakeholders can prioritize the management of polluted soils depending on the risk they may represent. The determination of ex situ TGVs for organic and inorganic compounds provides new tools to characterize excess contaminant transfers, and it will also allow the use of snails for ERAs, notably for common pollutants, such as PAHs and PCBs for which guide values are not available.

Effects of soil amendments on cadmium transfer along the lettuce-snail food chain: Influence of chemical speciation

Cadmium (Cd) trophic transfer along the soil-lettuce-snail food chain was investigated using the root bags-based pot experiments. Two amendments (corn straw biochar and micro-hydroxyapatite (μHAP)) were investigated on Cd (0, 2.5, and 5 mg/kg soil) availability in soils, chemical distribution in plant cells and accumulation in snails. After 60 days, both the CaCl2 extractable Cd in rhizosphere soil (CdCaCl2,rhizo) and Cd accumulation in lettuce decreased with amendments addition. Biochar had a great capacity to reduce both Cd contents and toxicity-sensitive associated Cd (CdFi+Fii) percentages in lettuce roots at 2.5 mg/kg Cd contaminated soil; while μHAP generates a higher reduction in both Cd contents and chain transfer associated Cd (CdFi+Fii+Fiii) percentages in lettuce shoots at 5 mg/kg Cd contaminated soil. Linear regression showed that both contents of root CdFi+Fii and shoot CdFi+Fii+Fiii are better correlated with the CdCaCl2,rhizo (R2 > 0.70, p < 0.01). After 15 days feeding, almost 90% content of Cd accumulated in snail viscera. μHAP had a higher reduction in snail soft tissues Cd accumulation than biochar. Distributions of Cd in snail tissues are significantly correlated with CdFi+Fii+Fiii in shoots (viscera R2 = 0.835; soft tissue R2 = 0.771). Established quantitative relationships could be used to predict the bioavailability and transfer of Cd in terrestrial food chain in the presence of amendments.

Leaf aging effects on copper and cadmium transfer along the lettuce-snail food chain

Metal bioavailability at root plasma membrane surfaces and chemical forms within cells putatively controls the trophic transfer processes. Accumulation and distribution of Cu or Cd in lettuce were investigated as a function of lettuce leaf aging through soil-solution culture experiments. Metal contents in snail tissues were examined after fed on young (interior) or old (exterior) age leaves for 15d, respectively. In both roots and leaves, Cu accumulation was higher than Cd by 3-90 fold. Regardless of 9.42 μmoL/L CuCl2 exposure, young leaves accumulated more Cu than old leaves, while higher Cu contents are found in snail tissues fed on old leaves. Opposite trends were observed for Cd. Copper as an essential element had a higher transfer factor (TF) than the non-essential element Cd in biomagnification from leaf to snail. Reasons involved in metal chemical forms within leaf cells, where higher percentages of toxicity and migration associated metal (Fi: inorganic form, Fii: water-soluble form and Fiii: pectate- and protein-integrated form) are found for Cu in old leaves (88.3-91.6%) and Cd in young leaves (86.8-94.5%). Metal activities at root plasma membrane surfaces ({M2+}0) and chemical forms in Fi + Fii + Fiii linearly correlated with metal accumulation in lettuce and snail tissues (R2 > 0.900, p < 0.001 for snails fed on old leaves). Our study incorporated both the chemical form approach and {M2+}0 into evaluating the trophic bioavailability of different metals along the lettuce-snail chain, which is important for mechanistic understanding of metal behaviors in the ecosystem.

Uptake and biological responses in land snail Cornu aspersum exposed to vaporized CdCl2

The uptake of Cd and some biomarkers of exposure and effects have been investigated in specimens of land snail Cornu aspersum exposed to vaporized CdCl₂ (10mg/L) for 7 days. The Cd levels quantified in snail's whole bodies confirmed Cd bioavailability trough vaporization and an higher accumulation in the midgut gland compared to the foot. Biological responses investigated showed a reduction of destabilization time of lysosomal membranes (NRRT) in hemocytes and an induction of catalase activities (CAT) in midgut gland. A further evidence of CdCl₂ vaporized exposure was given by an increase in MT protein content as well as induction of Cd-MT gene expression, highlighting the central role of the midgut gland in Cd detoxification. These biomarkers can thus be considered as sensitive tools for the assessment of Cd contamination in the air using land snails as bioindicators. No changes in of GST activity and MDA were observed. From the overall results, the land snail, C. aspersum, could be used as good bioindicator of air quality for pollution monitoring purposes having shown clear signs of exposure and effects due Cd exposure by air.

Green garden snail, Cantareus apertus, as biomonitor and sentinel for integrative metal pollution assessment in roadside soils

The present investigation was conceived to study, in a small scale field study, the potential of the green garden snail, Cantareus apertus, as biomonitor and sentinel for integrative metal pollution assessment in soils. For this purpose, we investigated the association between the trace metal (Cd, Pb, As, Fe, Cr, Cu, Ni, and Zn) concentrations in soil, plants (Trifolium repens), and C. apertus depending on the distance (20, 150, and 700 m) from a main roadside in Tunisia as well as between metal concentrations and biomarkers of oxidative stress, oxidative damage, and neurotoxicity in C. apertus. Results revealed a clear association between the concentration of metals such as Ni, Cu, and Zn in snail digestive gland, both amongst them and with oxidative stress and neurotoxicity biomarkers recorded in the same organ. Interestingly, Ni, Pb, and Zn occurred at the highest concentration in soil, plant, and snails and the association appeared related to the immediacy of the roadside and the concentration of these three metals tended to decrease with distance from the roadside in the soil-plant-snail system. Conversely, Cd and Cu were bioaccumulated in plants and snails but their concentrations in soil were not high and did not show a decline in concentration with distance from the roadside. After PCA analysis, PC-01 (56% of the variance) represented metal bioaccumulation and associated toxic effects in snails in the presence of high levels of metal pollution (nearby the roadside) while PC-02 (35% of the variance) represented stress induced by moderate levels of metal pollution (at intermediate distances from the roadside). The four studied sites were clearly discriminated one from each other, depending on how they are affected by traffic pollution. In summary, this field study reveals that (a) C. apertus can be used as biomonitor for metal pollution in roadside soils and as sentinel for pollution effects assessment based on biochemical biomarkers; and (b) that oxidative stress and neurotoxicity biomarkers endow with a powerful biological tool for metal pollution biomonitoring in soils, especially in combination with chemical analysis of the soil-plant-snail transfer system. Moreover, this study provides some baseline data for future impact assessments concerning trace metal pollution in Tunisia.

Distribution of As, Cd, and Pb in seafood in Southern China and their oral bioavailability in mice

The distribution of the toxic elements As, Cd, and Pb in nine different types of seafood from Shenzhen, China, was investigated by using inductively coupled plasma mass spectrometry (ICP-MS). The results revealed that the concentrations of arsenic (As) in fish (Lutjanus erythropterus, Paralichthys olivaceus) and in bivalve (Meretrix meretrix) and cadmium (Cd) in scallop (Argopecten irradians) exceed the limits established by food safety regulations in China and EU (European Union). Furthermore, the bioavailability of As, Cd, and lead (Pb) in mice after 20-day oral ingestion of Crassostrea rivularis was investigated, and the total rate of absorption of toxic elements in samples from the liver and kidney tissues and blood was determined. The results of this in vivo trial indicated that the oral bioavailability of As, Cd, and Pb was approximately 0.33, 0.45, and 0.74%, respectively.

Internal distribution of Cd in lettuce and resulting effects on Cd trophic transfer to the snail: Achatina fulica

The mechanisms underlying Cd trophic transfer along the soil-lettuce-snail food chain were investigated. The fate of Cd within cells, revealed by assessment of Cd chemical forms and of subcellular partitioning, differed between the two examined lettuce species that we examined (L. longifolia and L. crispa). The species-specific internal Cd fate not only influenced Cd burdens in lettuce, with higher Cd levels in L. crispa, but also affected Cd transfer efficiency to the consumer snail (Achatina fulica). Especially, the incorporation of Cd chemical forms (Cd in the inorganic, water-soluble and pectates and protein-integrated forms) in lettuce could best explain Cd trophic transfer, when compared to dietary Cd levels alone and/or subcellular Cd partitioning. Trophically available metal on the subcellular partitioning base failed to shed light on Cd transfer in this study. After 28-d of exposure, most Cd was trapped in the viscera of Achatina fulica, and cadmium bio-magnification was noted in the snails, as the transfer factor of lettuce-to-snail soft tissue was larger than one. This study provides a first step to apply a chemical speciation approach to dictate the trophic bioavailability of Cd through the soil-plant-snail system, which might be an important pre-requisite for mechanistic understanding of metal trophic transfer.

Toxic effects of two sources of dietborne cadmium on the juvenile cobia, Rachycentron canadum L. and tissue-specific accumulation of related minerals

In the present study, juvenile cobia, Rachycentron canadum L. were fed diets contaminated by two different sources of cadmium: squid viscera meal (SVM-Cd, organic form) and cadmium chloride (CdCl2-Cd, inorganic form). The Cd concentrations in fish diet were approximate 3.0, 5.0 and 10.0mg Cd kg(-1) for both inorganic and organic forms. In the control diet (0.312mg Cd kg(-1) diet, Cd mainly come from fish meal), no cadmium was added. The experiment lasted for 16 weeks and a statistically significant inverse relationship was observed between specific growth rate (SGR) and the concentration of dietary Cd. The SGR of cobia fed a diet with SVM-Cd increased at the lowest doses and decreased with the increasing level of dietary SVM. Fish fed diet contaminated SVM-Cd had significantly higher SGR than those fed diets contaminated CdCl2-Cd among the high Cd level diets treatments. The dietary Cd levels also significantly affected the survival rate of the fish. Among the hematological characteristics and plasma constituents, glutamic-pyruvic transaminase activities and alkaline phosphatase activities in serum and liver increased and hepatic superoxide dismutase activity decreased with the increasing dietary Cd levels. The cobia fed diet contaminated by high level of CdCl2-Cd had significantly higher ALP activity than cobia fed diet contaminated by high level of SVM-Cd. The results from these studies indicate no differences in toxicity response to dietborne SVM-Cd and CdCl2-Cd at a low level of Cd. However, at a higher level, cobia was more sensitive to dietborne CdCl2-Cd than SVM-Cd. Based on quadratic regression of SGR, The Cd concentrations was 3.617mg kg(-1) in the optimal diet, Cd source was SVM (126mg Cd kg(-1) in SVM) which stimulate the growth of cobia and the added level was determined to be 26.7g kg(-1) diet in the present study. Cd accumulations in the kidney of cobia fed both types of Cd were higher than other tissues, and the order of Cd accumulation in tissues were kidney>liver>intestine>gill>muscle. Iron accumulation in liver and kidney and calcium accumulation in vertebra and scale were also significantly affected by dietary Cd levels.

Can the Hyperaccumulating Plant Arabidopsis halleri in Feed Influence a Given Consumer Organism (Rattus norvegicus var. alba)?

Zinc and cadmium concentrations in rat (Rattus norvegicus var. alba) tissues were analyzed by inductively coupled plasma optical emission spectrometry. Rats were fed the zinc and cadmium hyperaccumulating plant, Arabidopsis halleri. When compared to the control group, a Cd increase in all tissues (liver, kidneys, small intestine, spleen, testes, muscle), with the exception of bone tissue was observed. In comparison to the control group, the kidneys, liver and small intestine contained 375, 162, and 80 times more Cd, respectively. Differences between zinc concentrations in rats fed with A. halleri and those of the control group were significant only in the small intestine and kidney tissues. Results suggest using the hyperaccumulating plant A. halleri as a feed stresses the consumer organism not through its Zn content, but through its Cd content.

Cadmium toxicokinetics and bioaccumulation in turtles: trophic exposure of Trachemys scripta elegans

Ecotoxicological data in reptiles are mainly represented by field studies reporting the tissue burden of wild-captured individuals but much less is known regarding the processes of uptake, depuration, accumulation and the effects of inorganic contaminants in these species. In the present study, the accumulation, the path and the effects of exposure to cadmium (Cd) through diet intake were investigated in female red eared slider turtles, Trachemys scripta elegans. In the first phase of the experiment, turtles underwent an acclimatization period during which they were fed a control diet. In the second phase, the turtles were exposed to cadmium through a CdCl(2) supplemented-diet with increased environmentally relevant concentrations for a period of 13 weeks. Following this, the turtles went through a third phase, a recovery phase of 3 weeks, during which they were fed uncontaminated food. Blood and feces were collected during the three phases of the experiment. The turtles were euthanized at the end of the experiment and organ samples collected. The Cd-concentrations in blood remained stable over the course of the experiment while Cd-concentrations in feces increased with time and with the amount of Cd ingested. The proportional accumulation in liver and kidney together was comprised between 0.7 and 6.1% and they represented the main organs of accumulation. Cd accumulated in the organs in the following order of concentration: kidney > liver > pancreas > muscle. In terms of burden in organs, the Cd-burden was the highest in liver followed by kidney and pancreas. The proportional accumulation decreased as Cd ingestion increased, suggesting that at a higher dose of Cd, assimilation decreased. Mineral content of the liver and pancreas became modified according to Cd level; increasing dietary Cd exposure increased concentrations of zinc and iron in liver and copper in pancreas in a dose-dependent manner. Accumulation of Cd had no effect on survival, food consumption, growth, weight or length suggesting no effect of the treatment on female turtle body condition.

Spatially explicit analysis of metal transfer to biota: influence of soil contamination and landscape

Concepts and developments for a new field in ecotoxicology, referred to as “landscape ecotoxicology,” were proposed in the 1990s; however, to date, few studies have been developed in this emergent field. In fact, there is a strong interest in developing this area, both for renewing the concepts and tools used in ecotoxicology as well as for responding to practical issues, such as risk assessment. The aim of this study was to investigate the spatial heterogeneity of metal bioaccumulation in animals in order to identify the role of spatially explicit factors, such as landscape as well as total and extractable metal concentrations in soils. Over a smelter-impacted area, we studied the accumulation of trace metals (TMs: Cd, Pb and Zn) in invertebrates (the grove snail Cepaea sp and the glass snail Oxychilus draparnaudi) and vertebrates (the bank vole Myodes glareolus and the greater white-toothed shrew Crocidura russula). Total and CaCl₂-extractable concentrations of TMs were measured in soils from woody patches where the animals were captured. TM concentrations in animals exhibited a high spatial heterogeneity. They increased with soil pollution and were better explained by total rather than CaCl₂-extractable TM concentrations, except in Cepaea sp. TM levels in animals and their variations along the pollution gradient were modulated by the landscape, and this influence was species and metal specific. Median soil metal concentrations (predicted by universal kriging) were calculated in buffers of increasing size and were related to bioaccumulation. The spatial scale at which TM concentrations in animals and soils showed the strongest correlations varied between metals, species and landscapes. The potential underlying mechanisms of landscape influence (community functioning, behaviour, etc.) are discussed. Present results highlight the need for the further development of landscape ecotoxicology and multi-scale approaches, which would enhance our understanding of pollutant transfer and effects in ecosystems.

Differential liver proteome mapping of control and cadmium-fed rats

A comparative study of proteome maps from control and Cd-exposed rat liver was performed using a new technology of two-dimensional liquid chromatography separation method (PF-2D system, Beckman Coulter). Rats were fed for one month 0 or 100 μg Cd g(-1). The between-replicate and between-sample variations showed good repeatability and suitable reproducibility for the two dimensions of separation of proteins. In this complex mixture, PF-2D led to the separation of two major peaks which differed between control and Cd-exposed rat livers, one being identified by mass spectrometry as Cu/Zn superoxide dismutase (SOD), a well-known biomarker of Cd exposure, the other as phosphatidylethanolamine binding protein (PEBP). SOD content was decreased in Cd-exposed rat liver, compared to the control group which was corroborated by a significant decrease of SOD activity. PEBP content also tended to be decreased after Cd exposure. Present results demonstrate interest but also limitations of proteomic approach using PF-2D system to analyze effects of chemicals on organisms.

Role of Panax ginseng as an antioxidant after cadmium-induced hepatic injuries

Liver, being primary site for biotransformation of foreign compounds is vulnerable to various chemical assaults. Ginseng has a wide range of pharmacological and therapeutical action. In the present study an attempt has been made to study the cadmium chloride (CdCl(2)) induced toxicity in liver and its possible protection by Panax ginseng. Swiss albino mice were divided into four groups: (i) Control group--only vehicle (double distilled water) (ii) Ginseng treated group - 10mg/kg b.wt. orally (iii) CdCl(2) treated group - 1.0mg/kg b.wt. CdCl(2) i.p. (iv) Combination group--Ginseng root extract (10mg/kg b.wt.) and CdCl(2) (1.0mg/kg b.wt.). Activities of alkaline phosphatase, GOT, GPT were measured in serum and lipid peroxidation (LPO) and GSH content were measured in liver. The results indicated a significant increase in LPO, GOT, GPT activities and decrease in GSH and serum alkaline phosphatase activities after CdCl(2) treatment. Ginseng alone did not show any significant alterations except a significant decrease in LPO level. Combined treatment of Ginseng and CdCl(2) showed significant decrease in LPO, GOT, GPT and elevation in GSH and serum alkaline phosphatase as compared to CdCl(2) treated group. Thus, Ginseng is found to be protective against cadmium-induced hepatic injuries.

Does subcellular distribution in plants dictate the trophic bioavailability of cadmium to Porcellio dilatatus (Crustacea, Isopoda)?

The present study examined how subcellular partitioning of Cd in plants with different strategies to store and detoxify Cd may affect trophic transfer of Cd to the isopod Porcellio dilatatus. The plant species used were Lactuca sativa, a horticultural metal accumulator species; Thlaspi caerulescens, a herbaceous hyperaccumulator species; and the nonaccumulator, T. arvense. Taking into account that differences in subcellular distribution of Cd in plants might have an important role in the bioavailability of Cd to a consumer, a differential centrifugation technique was adopted to separate plant leaf tissues into four different fractions: cell debris, organelles, heat-denatured proteins, and heat-stable proteins (metallothionein-like proteins). Plants were grown in replicate hydroponic systems and were exposed for 7 d to 100 microM Cd spiked with 109Cd. After a 14-d feeding trial, net assimilation of Cd in isopods following consumption of T. caerulescens and T. arvense leaves reached 16.0 +/- 2.33 and 21.9 +/- 1.94 microg/g animal, respectively. Cadmium assimilation efficiencies were significantly lower in isopods fed T. caerulescens (10.0 +/- 0.92%) than in those fed T. arvense (15.0 +/- 1.03%). In further experiments, Cd assimilation efficiencies were determined among isopods provided with purified subcellular fractions of the three plants. On the basis of our results, Cd bound to heat-stable proteins was the least bioavailable to isopods (14.4-19.6%), while Cd bound to heat-denatured proteins was the most trophically available to isopods (34.4-52.8%). Assimilation efficiencies were comparable in isopods fed purified subcellular fractions from different plants, further indicating the importance of subcellular Cd distribution in the assimilation. These results point to the ecological relevance of the subcellular Cd distribution in plants, which directly influence the trophic transfer of Cd to the animal consumer.