Effects of pesticide compounds (chlorothalonil and mancozeb) and benzo[a]pyrene mixture on aryl hydrocarbon receptor, p53 and ubiquitin gene expression levels in haemocytes of soft-shell clams (Mya arenaria)

Ecogenotoxicity assessment with land snails: A mini-review

In the context of the increasing environmental and sanitary crisis, it is accepted that soil pollution can cause health alterations and disturb natural population dynamics. Consequently, the assessment of the genotoxic potential of compounds found in contaminated soils is important. Indeed, the alteration of genomic integrity may increase the risk of cancer development and may impair reproduction and long-term population dynamics. Among the methodologies to assess terrestrial genotoxic potential, there has been growing interest during the last decade in monitoring alterations of the genome in bioindicators of soil quality. As some land snail species are recognized bioindicators of soil quality, especially to assess the environmental and toxicological bioavailability of compounds, this review focuses on current knowledge regarding the genotoxicology of land snails. Classical biomarkers to assess genotoxic effects have been used (e.g., DNA breakage, micronuclei, random amplification polymorphic DNA) at various stages of the life cycle, including embryos. The studies were performed in vitro, in vivo, in situ and ex situ and covered a diverse set of contaminants (nanoparticles, metal(loid)s, pesticides, polycyclic aromatic hydrocarbons) and snail species (Cantareus aspersus, Eobania vermiculata, Theba pisana, Helix lucorum). Based on recent studies reviewed here, the use of land snails to map soil genotoxic potential is promising due to their ability to reveal pollution and subsequent environmental risks. Moreover, the position of snails in the trophic chain and the existing bridges between contaminant bioavailability to snails and bioaccessibility to humans reinforce the value of land snail-based ecotoxicological assessment.

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.

Fucoidan ameliorates acute and sub-chronic in vivo toxicity of the fungicide cholorothalonil in Oreochromis niloticus (Nile tilapia)

Fucoidans are sulfated glycans from marine algae that have both anti-cancer and anti-microbial properties. Chlorothalonil is a fungicide and insecticide commonly used in agriculture. Chlorothalonil is relatively toxic to fish and can potentially affect the aquaculture practices. In this study, we determined whether fucoidan administration would offer any protection from acute and subchronic toxicity of chlorothalonil on Nile tilapia. First, we tested the effect of chlorothalonil (20 to 140 μg/L, water-applied) on Nile tilapia in an acute exposure (six days). Survival analysis was performed, together with assessment of histopathology, oxidative stress (i.e., antioxidant status, hydrogen peroxide levels, malondialdehyde and nitric oxide levels) and immunohistochemistry to measure indicators of hepatic damage (i.e., caspase 3, p53, mini-chromosome maintenance proteins (MCM), and glutathione peroxidase). Chlorothalonil induced mild to severe histopathological alterations that were dose-dependent in various tissues of Nile tilapia. Chlorothalonil also induced oxidative stress as indicated by elevated biochemical markers. The highest recorded mortalities were associated with p53 expression. Additional feeding experiments were conducted with fucoidan (8 g/kg diet), following acute (40 μg/L for seven days) and sub-chronic (20 μg/L for six weeks) chlorothalonil application in Nile tilapia. Many of these same biochemical biomarkers of stress, oxidative damage response, and tissue pathology (evidence for hepatic neoplasm) were ameliorated by fucoidan, suggesting a protective effect of the compound. Agrochemicals are ubiquitous on a global scale, and the use of fucoidan as a feed additive may be beneficial for protecting aquatic animal health and aquaculture species from the impacts of chemical run-off.

First evidence of transcriptional modulation by chlorothalonil in mussels Perna perna

Gills are considered a key player in organism defenses against environmental pollutants. Since it is the major site of uptake of waterborne chemicals, the modulation of important cellular defenses is expected in this tissue. Chlorothalonil, a fungicide presented in herbicides and antifouling paints, might be responsible for toxicity in marine biota. In this context, mussels were exposed to 0.1 μgL^-1 and 10 μgL^-1 of chlorothalonil for 24 h and 96 h. Genes from biotransformation and antioxidant defense pathways were investigated. Overall, we report, for the first time, an increase in the transcripts of the AhR-like, SULT1A1-like, CYP1A2-like, GSTO-like, MGST-like and SOD-like genes in the gills of the brown mussel Perna perna. This up-regulation was observed mostly after 96 h of exposure to chlorothalonil. Those results reinforce the important role of gills in xenobiotic metabolism and suggest the involvement of the mentioned genes in the detoxification of the compound. Throughout biotransformation and antioxidant defenses pathway, mussels exposed to chlorothalonil are activating mechanisms of defense against this contaminant.

A verification of correlation between chemical monitoring and multi-biomarker approach using clam Ruditapes philippinarum and scallop Chlamys farreri to assess the impact of pollution in Shandong coastal area of China

Biogeochemical monitoring coupled with multi-biomarker approach were performed for the assessment of marine environment, using clam Ruditapes philippinarum and scallop Chlamys farreri to indicate contamination status in sediments and seawater respectively. The bivalves were collected from three stations, Jiaozhou Bay, Rushan Bay and Laizhou Bay, of Shandong coastal area. A series of contaminants (PAHs and TBBPA) and biomarkers (AhR, EROD, GST, SOD, GPx, CAT, DNA damage) were measured. Multi-biomarker pollution index (MPI) and integrated biomarker response (IBR) were carried out to evaluate contamination status and both indexes showed that Rushan Bay was most polluted, where the pollution level of sediments reached "highly polluted" in August, followed by Jiaozhou Bay and Rushan Bay which reached "lightly polluted". The correlation of IBR values with contaminants' concentrations was verified through the Pearson correlation coefficient (p < 0.05), consolidating this scientific assessment method for marine environment.

Protective effects of lupeol against mancozeb-induced genotoxicity in cultured human lymphocytes

BACKGROUND

Lup-20(29)-en-3H-ol (Lupeol), a dietary pentacyclic triterpenoid has been shown to possess multiple medicinal activities including anti-inflammatory, anti-oxidant and anti-carcinogenic effects. Mancozeb is a widely used broad-spectrum fungicide with well-known carcinogenic hazards in rodents.

PURPOSE

The present study has been designed to investigate the protective effects of lupeol against mancozeb-induced genotoxicity and apoptosis in cultured human lymphocytes (CHLs).

METHODS

The genotoxic effect of mancozeb was evaluated by chromosomal aberration and micronucleus assays. The cell cycle kinetics and intracellular reactive oxygen species (ROS) generation was measured by flow cytometry. The levels of anti-oxidant enzymes and lipid peroxidation (LPO) were estimated by enzymatic assays. The localization of p65NF-κB was measured by immunocytochemical analysis. The differential expression of genes associated with genotoxicity was measured by qRT-PCR.

RESULTS

Mancozeb exposure (5µg/ml) for 24h caused significant induction of chromosomal aberrations (CAs) and micronuclei (MN) formation in CHLs. Pre-and post-treatment (25 and 50µg/ml) of lupeol for 24h significantly (p<0.05) reduced the frequency of CAs and MN induction, in a dose-dependent manner in mancozeb treated CHLs. Concomitantly, lupeol pre-treatment for 24h significantly increased the levels of anti-oxidant enzymes, superoxide dismutase (SOD) and catalase and decreased ROS generation and LPO. Additionally, lupeol pre-treatment significantly reduced mancozeb-induced apoptosis as shown by Sub-G1 peak analysis and annexin V-PI assay, in a dose dependent manner. Moreover, pre-treatment with lupeol attenuated mancozeb-induced NF-κB activation in CHLs. Furthermore, the results of qRT-PCR showed that lupeol pre-treatment significantly (p<0.05) decreased mancozeb-induced expression of DNA damage (p53, MDM2, COX-2, GADD45α and p21) and increased expression of DNA repair responsive genes (hOGG1 and XRCC1) in CHLs.

CONCLUSION

Taken together, our findings suggest that lupeol could attenuate mancozeb-induced oxidative stress, which in turn could inhibit NF-κB activation and thus provide protection against mancozeb-induced genotoxicity and apoptosis. So, lupeol could be used as a potent anti-oxidant regimen against pesticide induced genotoxicity in agricultural farm workers.

Proteomic and metabolomic analysis on the toxicological effects of Benzo[a]pyrene in pearl oyster Pinctada martensii

Benzo[a]pyrene (BaP) is one of the typical toxic polycyclic aromatic hydrocarbons (PAHs) that are widely present in marine environment. BaP has diverse toxic effects, including teratogenic, carcinogenic, mutagenic effects and so on, in various organisms. In this work, we focused on the differential proteomic and metabolomic responses in the digestive gland of pearl oyster Pinctada martensii exposed to two doses of BaP (1 and 10μg/L). Metabolic responses revealed that the high dose of BaP (10μg/L) mainly caused disturbances in osmotic regulation and energy metabolism in the digestive gland. Proteomic responses indicated that both doses of BaP induced disturbances in energy metabolism, cytoskeleton, cell injury, oxidative stress and signal transduction based on the differential proteomic biomarkers. Overall, these results demonstrated a number of potential biomarkers that were characterized by an integrated proteomic and metabolomic approach and provided a useful insight into the toxicological effects on pearl oyster P. martensii.

Disruptive environmental chemicals and cellular mechanisms that confer resistance to cell death

Cell death is a process of dying within biological cells that are ceasing to function. This process is essential in regulating organism development, tissue homeostasis, and to eliminate cells in the body that are irreparably damaged. In general, dysfunction in normal cellular death is tightly linked to cancer progression. Specifically, the up-regulation of pro-survival factors, including oncogenic factors and antiapoptotic signaling pathways, and the down-regulation of pro-apoptotic factors, including tumor suppressive factors, confers resistance to cell death in tumor cells, which supports the emergence of a fully immortalized cellular phenotype. This review considers the potential relevance of ubiquitous environmental chemical exposures that have been shown to disrupt key pathways and mechanisms associated with this sort of dysfunction. Specifically, bisphenol A, chlorothalonil, dibutyl phthalate, dichlorvos, lindane, linuron, methoxychlor and oxyfluorfen are discussed as prototypical chemical disruptors; as their effects relate to resistance to cell death, as constituents within environmental mixtures and as potential contributors to environmental carcinogenesis.

Mechanisms of environmental chemicals that enable the cancer hallmark of evasion of growth suppression

As part of the Halifax Project, this review brings attention to the potential effects of environmental chemicals on important molecular and cellular regulators of the cancer hallmark of evading growth suppression. Specifically, we review the mechanisms by which cancer cells escape the growth-inhibitory signals of p53, retinoblastoma protein, transforming growth factor-beta, gap junctions and contact inhibition. We discuss the effects of selected environmental chemicals on these mechanisms of growth inhibition and cross-reference the effects of these chemicals in other classical cancer hallmarks.

Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: focus on the cancer hallmark of tumor angiogenesis

One of the important 'hallmarks' of cancer is angiogenesis, which is the process of formation of new blood vessels that are necessary for tumor expansion, invasion and metastasis. Under normal physiological conditions, angiogenesis is well balanced and controlled by endogenous proangiogenic factors and antiangiogenic factors. However, factors produced by cancer cells, cancer stem cells and other cell types in the tumor stroma can disrupt the balance so that the tumor microenvironment favors tumor angiogenesis. These factors include vascular endothelial growth factor, endothelial tissue factor and other membrane bound receptors that mediate multiple intracellular signaling pathways that contribute to tumor angiogenesis. Though environmental exposures to certain chemicals have been found to initiate and promote tumor development, the role of these exposures (particularly to low doses of multiple substances), is largely unknown in relation to tumor angiogenesis. This review summarizes the evidence of the role of environmental chemical bioactivity and exposure in tumor angiogenesis and carcinogenesis. We identify a number of ubiquitous (prototypical) chemicals with disruptive potential that may warrant further investigation given their selectivity for high-throughput screening assay targets associated with proangiogenic pathways. We also consider the cross-hallmark relationships of a number of important angiogenic pathway targets with other cancer hallmarks and we make recommendations for future research. Understanding of the role of low-dose exposure of chemicals with disruptive potential could help us refine our approach to cancer risk assessment, and may ultimately aid in preventing cancer by reducing or eliminating exposures to synergistic mixtures of chemicals with carcinogenic potential.

The effect of different polychlorinated biphenyls on two aquatic models, the green alga Pseudokirchneriella subcapitata and the haemocytes from the European abalone Haliotis tuberculata

The present study was conducted to determine the toxicity of different polychlorinated biphenyls (PCBs) on the green algae, Pseudokirchneriella subcapitata and the haemocytes from the European abalone, Haliotis tuberculata. Using the algal growth inhibition test, the green algae median Effective Concentration (EC50) values ranged from 0.34μM for PCB28 to more than 100μM for PCBs 101 and 153. Considering the MTT viability test, the abalone EC50 values ranged from 1.67μM for PCB153 to 89μM for PCB28. Our results in contrast to previous observation in vertebrates did not show significant differences between the dioxin like- and non dioxin like-PCBs toxicities regardless of the model used. However, our results demonstrated that the toxicities of PCBs were species dependent. For example, PCB28 was the most toxic compound for P. subcapitata whereas PCBs 1, 180 and 153 were less toxic for that species. On the contrary, PCB153 was reported as the most toxic for H. tuberculata haemocytes and PCB28 the least toxic. To investigate the mode of action of these compounds, we used an in silico method. Our results suggested that PCBs have a non-specific mode of action (e.g., narcosis) on green algae, and another mode of action, probably more specific than narcosis, was reported for PCBs on the abalone haemocytes.

Transcriptome analysis of neoplastic hemocytes in soft-shell clams Mya arenaria: Focus on cell cycle molecular mechanism

In North America, a high mortality of soft-shell clams Mya arenaria was found to be related to the disease known as disseminated neoplasia (DN). Disseminated neoplasia is commonly recognized as a tetraploid disorder related to a disruption of the cell cycle. However, the molecular mechanisms by which hemocytes of clams are transformed in the course of DN remain by far unknown. This study aims at identifying the transcripts related to DN in soft shell clams' hemocytes using next generation of sequencing (Illumina HiSeq2000). This study mainly focuses on transcripts and molecular mechanisms involved in cell cycle. Using Illumina next generation of sequencing, more than 95,399,159 reads count with an average length of 45  bp was generated from three groups of hemocytes: (1) a healthy group with less than 10% of tetraploid cells; (2) an intermediate group with tetraploid hemocytes ranging between 10% and 50% and (3) a diseased group with more than 50% of tetraploid cells. After the reads were cleaned by removing the adapters, de novo assembly was performed on the sequences and more than 73,696 contigs were generated with a mean contig length estimated at 585 bp ranging from 189 bp to 14,773 bp. Once a Blastx search against NCBI Non Redundant database was performed and the duplicates removed, 18,378 annotated sequences matched known sequences, 3078 were hypothetical and 9002 were uncharacterized sequences. Fifty percent and 41% of known sequences match sequences from Mollusca and Gastropoda respectively. Among the bivalvia, 33%, 17%, 17% and 15% of the contigs match sequences from Ostreoida, Veneroida, Pectinoida and Mytiloida respectively. Gene ontology analysis showed that metabolic, cellular, transport, cell communication and cell cycle represent 33%, 15%, 9%, 8.5% and 7% respectively of the total biological process. Approximately 70% of the component process is related to intracellular process and 15% is linked to protein and ribonucleoprotein complex. Catalytic activities and binding molecular processes represent 39% and 33% of the total molecular functions. Interestingly, nucleic acid binding represents more than 18% of the total protein class. Transcripts involved in the molecular mechanisms of cell cycle are discussed providing new avenues for future investigations.

Effects of polycyclic aromatic hydrocarbons (PAHs) on an aquatic ecosystem: acute toxicity and community-level toxic impact tests of benzo[a]pyrene using lake zooplankton community

We estimated acute toxicity of benzo[a]pyrene (B[a]P) using two cladoceran species, Ceriodaphnia reticulata and Daphnia magna, and also analyzed its impact on zooplankton community throughout an exposure experiment using small-scale mesocosms. LC(50) of B[a]P for C. reticulata and D. magna was 4.3 and 4.7 µg/l, respectively. However, individuals fed with Chlorella showed higher LC(50), 6.1 µg/l for C. reticulata and 8.0 µg/l for D. magna. In the exposure experiment, we examined the impact of B[a]P on zooplankton community using conceivable concentrations in the environment (5 and 10 µg/l) using typical zooplankton community in eutrophicated systems. Despite the residence time of B[a]P in the water column was short as < 4 days, application of B[a]P induced decrease of zooplankton abundance. However, the recovery pattern was different among cladocerans and rotifers. Consequently, B[a]P showed insecticide-like impacts, suppressing cladoceran populations and inducing the dominance of rotifers particularly under high concentration (10 µg/l). Results have suggested that, even such short duration of B[a]P in the water body can have impact on zooplankton abundance and community structure. Since B[a]P easily precipitate to the bottom and rapidly disappears from the water body, careful monitoring and further assessment of the potential toxicity of polycyclic aromatic hydrocarbons are necessary.