Mechanisms of toxicity of triphenyltin chloride (TPTC) determined by a live cell reporter array

Organotin compounds (OTs) in surface sediments, bivalves and algae from the Russian coast of the Barents Sea (Kola Peninsula) and the Fram Strait (Svalbard Archipelago)

Organotin pollution in components of benthic ecosystems was investigated in 2019 in the Barents Sea (South shore, Kola Peninsula) and the Fram Strait (Icefjord, Svalbard Archipelago). Six species of organotin compounds (OTs), including monobutyltin, dibutyltin, tributyltin, tetrabutyltin, triphenyltin and tricyclohexyltin, were measured in the surface sediments, bivalve molluscs (Ciliatocardium ciliatum, Macoma calcarea, Chlamys islandica) and macrophyte algae (Saccharina latissima, Palmaria palmata, Ulvaria obscura, Fucus serratus, Fucus distichus). The results obtained showed moderate contamination of the studied samples with OTs. The total content of six tin compounds was in the ranges 35-139 ng g-1, 13-108 ng g-1 and 2.9-75 ng g-1 (dry weight) in the samples of sediments, bivalves and algae, respectively. In most cases, the concentrations of tributyltin in bottom sediments and mollusc tissues did not exceed the established international regulations. The degradation indices analysis of butyl tin derivatives indicated the active transformation of tributyltin and tetrabutyltin in bottom sediments and macrophyte algae and the accumulation of these compounds in the soft tissues of molluscs. The sediment and mollusc concentrations of OTs measured in this study were comparable to those reported for other areas of the Arctic region.

Screening of metallic pollution in complex environmental samples through a transcriptomic fingerprint method

Characterizing waste ecotoxicity is laborious because of both the undefined nature of environmental samples and the diversity of contaminants that can be present. With regard to these limitations, traditional approaches do not provide information about the nature of the pollution encountered. To improve such assessments, a fluorescent library of 1870 transcriptomic reporters from Escherichia coli K12 MG1655 was used to report the ecotoxic status of environmental samples. The reliability of the approach was evaluated with 6 metallic pollutants (As, Cu, Cd, Hg, Pb, Zn) used alone and in mixture in pure and complex matrices. A total of 18 synthetic samples were used to characterize the specificity of the resulting metallic contamination fingerprints. Metallic contamination impacted 4.5 to 10.2% of the whole transcriptomic fingerprint of E. coli. The analysis revealed that a subset of 175 transcriptomic reporters is sufficient to characterize metallic contamination, regardless of the nature of the sample. A statistical model distinguished patterns due to metallic contamination and provided information about the level of toxicity with 93 to 98% confidence. The use of the transcriptomic assessment was validated for 17 complex matrices with various toxicities and metal contaminants, such as activated sludge, wastewater effluent, soil, wood and river water. The presence of metals and their associated toxicity, which seems linked to their bioavailabilities, were thereby determined. This method constitutes a possible tool to screen unknown complex samples for their metallic status and identify those for which a deeper characterization must be achieved by the use of traditional biosensors and analytical methods.

Toxic effects of benzovindiflupyr, a new SDHI-type fungicide on earthworms (Eisenia fetida)

Benzovindiflupyr has received increasing attention as a new novel succinate dehydrogenase inhibitor (SDHI)-type fungicide. Nonetheless, its traces remaining in soil potentially trigger an ecotoxicological threat to soil organisms including earthworms. This paper evaluates the eco-toxicity of different benzovindiflupyr doses (0.1, 1, 5, and 10 mg kg-1) on earthworms (Eisenia fetida) after long-term exposure. Consequently, benzovindiflupyr at higher doses significantly inhibited the activities of respiratory chain complex II and succinate dehydrogenase (SDH) in E. fetida. Besides, the reactive oxygen species (ROS) and lipid peroxidation (LPO) were significantly induced in earthworms when treated with this fungicide. After benzovindiflupyr exposure, activities of antioxidant enzymes including catalase, peroxidase, and superoxide dismutase were activated. However, glutathione S-transferase activity in E. fetida was initially induced then inhibited in earthworms after treatment. Furthermore, benzovindiflupyr exposure induced the protein carbonylation (PCO) level in cells indicating oxidative damage to the cellular protein. Due to the destruction of the normal function in the coelomocytes, the phagocytic activity was initially activated, then inhibited when earthworms were treated at 5 and 10 mg kg-1 concentrations. Additionally, DNA damage was induced (larger olive tail moment (OTM) values) with the increase of benzovindiflupyr doses and exposure time. The weight was significantly decreased after benzovindiflupyr exposure on days 21 and 28. Benzovindiflupyr at higher doses significantly decreased the reproduction (number of cocoons and juveniles) of E. fetida. These findings reveal that benzovindiflupyr potentially induces a potential toxicological risk to earthworms when applied in the mentioned above dosages.

Organotin Compounds (OTCs) in Saccharina latissima (Phaeophyceae) from the Barents Sea

The degree of contamination of Saccharina latissima, the dominant species among macrophyte algae in the sublittoral zones of the Kola Bay and Eastern Murman of the Barents Sea, with organotin compounds (monobutyltin, dibutyltin, tributyltin, tetrabutyltin, triphenyltin, and tricyclohexyltin) has been assessed. The results show a moderate degree of contamination of the studied samples with organotin compounds. The total concentration of six tin compounds was 17-74 ng/g (dry weight) in algal samples. Analysis of the indices of degradation of butyl tin derivatives showed active processes of tributyltin and tetrabutyltin transformation in algae.

Growth, DNA damage and biochemical toxicity of cyantraniliprole in earthworms (Eisenia fetida)

Cyantraniliprole is a second-generation diamide insecticide that exhibited excellent biological efficacy against a variety of pests. To assess the toxic impact of cyantraniliprole on earthworms, the levels of reactive oxygen species (ROS) and malondialdehyde (MDA), activities of superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST), as well as DNA damage were measured after exposed to five cyantraniliprole concentrations ranging from 0 to 10.00 mg/kg for 7, 14, 21 and 28 days. In most treatment groups, the ROS levels increased significantly before exposure time of 14 days and then returned to normal levels. However, the SOD and CAT activities showed different response with activities were first significantly decreased and subsequently increased. The peroxidase (POD) activity showed no significant differences between treatment and control groups at first and then significantly increased. However, the opposite pattern characterized the GST activity. Also, maybe being dose-dependent before 14 days. The MDA concentration was used as a measure of lipid peroxidation (LPO). During experiment period, the MDA concentrations significantly increased when treated by this pesticide. The olive tail moment (OTM) was used as a measure of DNA damage. At higher concentrations of cyantraniliprole and longer exposure times, the OTM gradually increased, and DNA damage in the earthworms gradually increased. The weight of the high-dose (i.e., 5 mg/kg, 10 mg/kg) earthworms showed a significant trend of decrease phenomenon. Overall, the results suggest that sub-chronic exposure to cyantraniliprole causes DNA damage and LPO, weight loss and growth inhibition, leading to antioxidant defence responses in earthworms.

Bioaccumulation and toxicity of pentachloronitrobenzene to earthworm (Eisenia fetida)

Pentachloronitrobenzene (PCNB) has been widely utilized as a fungicide to control diseases. However, toxic effect data of PCNB on terrestrial invertebrate are not available till now. Herein, the earthworms (Eisenia fetida) were exposed to soil containing different levels of PCNB. Mortality, weight, accumulation, and physiological indexes of earthworms were determined on certain days. PCNB inhibited the growth of earthworms and induced a significant increase in the activity of antioxidative enzymes. ROS, SOD, and MDA of earthworms in the highest treatment group were 6.8, 4.4, and 3.8 times higher than those in the control group, respectively. In addition, earthworm coelomocytes were successfully extracted, cultured, and innovatively employed in in-vitro toxicity test to evaluate the toxic effect of PCNB. The biomarkers utilized in in-vitro toxicity test, including cell viability, intracellular ROS and extracellular LDH showed significant correlations with the PCNB in the culture media, indicating that the in-vitro toxicity test may serve as a useful tool for toxic assessment of pollutants to earthworms and other organisms.

Growth, reproduction and biochemical toxicity of chlorantraniliprole in soil on earthworms (Eisenia fetida)

Diamide insecticides have become the fourth most commonly used insecticide class in the world. Chlorantraniliprole (CAP) is a first-generation diamide insecticide with broad application potential. In this experiment, the eco-toxicity of CAP in soil at 0.1, 1.0, 5.0 and 10.0mg/kg on earthworms (Eisenia fetida) was evaluated during a 42 d exposure. More specifically, the environmental fate and transport of CAP between soil and earthworms was monitored during the exposure period. The present results indicated that the CAP contents of 0.1, 1.0, 5.0 and 10.0mg/kg treatments decreased to no more than 20% in the soil after 42 d of exposure. The accumulation of CAP in earthworms was 0.03, 0.58, 4.28 and 7.21mg/kg earthworm (FW) at 0.1, 1.0, 5.0 and 10.0mg/kg after 42 d of exposure. At 0.1mg/kg and 1.0mg/kg, CAP had no effect on earthworms during the exposure period. The weight of earthworms was significantly reduced at 5.0 and 10.0mg/kg at 28 and 42 days after CAP application. After the 14th day, CAP induced excess production of reactive oxygen species (ROS) at 5.0 and 10.0mg/kg, resulting in oxidative damage to biomacromolecules. We believe that CAP has a high risk potential for earthworms when used at 5.0 and 10.0mg/kg.

Functional genomics assessment of narcotic and specific acting chemical pollutants using E. coli

The knowledge of gene-chemical interaction can be used to derive toxicological mechanism of chemical pollutants, therefore, it might be useful to discriminate chemicals with different mechanisms. In this study, three narcotic chemicals (4-chlorophenol (4-CP), 3, 4-dichloroaniline (DCA) and 2, 2, 2-trichloroethanol (TCE)) and three specific acting chemicals (triclosan (TCS), clarithromycin (CLARY), sulfamethoxazole (SMX)) were assessed by Escherichia coli (E. coli) genome-wide knockout screening. 66, 97, 88, 144, 198 and 180 initial robust hits were identified by exposure to 4-CP, DCA, TCE, TCS, CLARY and SMX with two replicates at the concentration of IC50, respectively. The average fold change values of responsive mutants to the three narcotic chemicals were smaller than the three specific acting chemicals. The common gene ontology (GO) term of biological process enriched by the three narcotic chemicals was "response to external stimulus" (GO: 0009605). Other GO terms like "lipopolysaccharide biosynthetic process" (induced by 4-CP) and "purine nucleotide biosynthetic process" (induced by DCA) were also influenced by the narcotic chemicals. The toxic target of three known specific acting chemicals could be validated by GSEA of responsive genes. Four genes (flhC, fliN, fliH and flhD) might serve as potential biomarkers to distinguish narcotic chemicals and specific acting chemicals. The E. coli functional genomic approach presented here has shown great potential not only for the molecular mechanistic screening of chemicals, rather it can discriminate chemicals based on their mode-of-action.

Reporter Gene Assays in Ecotoxicology

The need for simple and rapid means for evaluating the potential toxic effects of environmental samples has prompted the development of reporter gene assays, based on tester cells (bioreporters) genetically engineered to report on sample toxicity by producing a readily quantifiable signal. Bacteria are especially suitable to serve as bioreporters owing to their fast responses, low cost, convenient preservation, ease of handling, and amenability to genetic manipulations. Various bacterial bioreporters have been introduced for general toxicity and genotoxicity assessment, and the monitoring of endocrine disrupting and dioxin-like compounds has been mostly covered by similarly engineered eukaryotic cells. Some reporter gene assays have been validated, standardized, and accredited, and many others are under constant development. Efforts are aimed at broadening detection spectra, lowering detection thresholds, and combining toxicity identification capabilities with characterization of the toxic effects. Taking advantage of bacterial robustness, attempts are also being made to incorporate bacterial bioreporters into field instrumentation for online continuous monitoring or on-site spot checks. However, key hurdles concerning test validation, cell preservation, and regulatory issues related to the use of genetically modified organisms still remain to be overcome.

Searching for novel modes of toxic actions of oil spill using E. coli live cell array reporter system - A Hebei Spirit oil spill study

Oil is a complex mixture of numerous compounds. Therefore, oil spills near shore can cause various adverse effects on coastal ecosystems. However, most toxicological assessments conducted on oil spill sites have focused on limited modes of toxic actions. In the present study, we utilized the Escherichia coli (E. coli) live cell array system (LCA) to identify novel modes of toxicities of the oil spill-affected sediments. For this purpose, sediment samples were collected from an area heavily polluted by Hebei Spirit oil spill (HSOS) incident of 2007. A total of 93 E. coli reporter genes were used to study responses to the chemicals in the mixture. E. coli K12 strains were exposed to extracts of oil or the sediment, and changes in gene expression were measured. Exposure to extracts of crude and weathered oil resulted in decreased expression in ∼30% of tested genes. However, changes in expression observed after exposure to sediment extracts varied. Sediment extracts containing large concentrations of polycyclic aromatic hydrocarbons (PAH) caused down-regulation of >70% of the genes, while extracts containing lesser total concentrations of PAHs exhibited different trends: genes involved in drug resistance were generally up-regulated, while genes responsive to DNA damage were up-regulated in only two extracts. Results suggest that oil pollution can modulate several toxic response pathways related to DNA repair and antibiotic responses. Results from LCA obtained from the sediment and oil samples were different from those observed in the H4IIE-luc assay. Toxicological implications of such observations deserve further examination. Overall, LCA is a promising tool for screening samples and identifying potential modes of toxicities of environmental samples associated with oil spills.

Classification and toxicity mechanisms of novel flame retardants (NFRs) based on whole genome expression profiling

Recently some novel alternative flame retardants (NFRs), which have been widely applied to meet demands for mandated flame retardation of products, have been detected in various matrices of the environment. However, knowledge on toxic effects and associated molecular mechanisms of these chemicals was limited. Here, toxic mechanisms of action of six NFRs, bis (2-ethylhexyl) phosphate (BEHP), chlorendic acid (Het acid), 2,2-bis (bromomethyl)-1,3-propanediol (BMP), tris (2-butoxyethyl) phosphate (TBEP), triethyl phosphate (TEP), tributyl phosphate (TBP) were investigated by use of a library containing ∼1820 modified green fluorescent protein (GFP) expressing promoter reporter vectors constructed from Escherichia coli K12(E.coli). BEHP, Het acid, BMP, TBEP, TEP, TBP inhibited growth of E. coli with 4 h 10%-inhibition concentrations of 53.0-3102.3 μM. A total of 119, 44, 26, 131, 62, 103 genes out of 336 genes selected during preliminary screening were significantly altered with fold-changes greater than 1.5 by BEHP, Het acid, BMP, TBEP, TEP and TBP, respectively. GO analyses of responsive genes suggested that RNA and primary metabolism process were involved in molecular mechanisms of toxicity. Chemical clustering based on expression of 62 multi-responsive genes showed that BEHP, TBP and TBEP were grouped together, which is consistent with similarity of their chemical structures, especially for BEHP and TBP. Clustering by molecular descriptors and molecular activity by use of the multivariate classification system ToxCast was consistent with that by profiles of multi-responsive genes. The results of this study demonstrated the utility of the E. coli, whole-cell assay for determining mechanisms of toxic action of chemicals.

Microbial reporter gene assay as a diagnostic and early warning tool for the detection and characterization of toxic pollution in surface waters

Surface water samples constantly receive a vast mixture of micropollutants mainly originating from wastewater treatment plants (WWTPs). High-throughput live cell arrays provide a promising method for the characterization of the effects of chemicals and the associated molecular mechanisms. In the present study, this test system was evaluated for the first time for the characterization of a set of typical surface water extracts receiving effluent from WWTPs. The extracts containing complex mixtures of micropollutants were analyzed for the expression of 90 stress responsive genes in the Escherichia coli reporter gene assay. The most affected pathways and the genes most sensitive to surface water samples suggested prominent stress-responsive pathways for wastewater-impacted surface water, such as oxidative stress, DNA damage, and drug resistance. Samples strongly affecting particular pathways were identified by statistical analysis of gene expression. Transcription data were correlated with contamination data from chemical screening and percentages of wastewater in the samples. Samples with particular effects and outstanding chemical composition were analyzed. For these samples, hypotheses on the alteration of the transcription of genes involved in drug resistance and DNA repair attributable to the presence of pharmaceuticals were drawn.

Comparison on the molecular response profiles between nano zinc oxide (ZnO) particles and free zinc ion using a genome-wide toxicogenomics approach

Increasing production and applications of nano zinc oxide particles (nano-ZnO) enhances the probability of its exposure in occupational and environmental settings, but toxicity studies are still limited. Taking the free Zn ion (Zn(2+)) as a control, cytotoxicity of a commercially available nano-ZnO was assessed with a 6-h exposure in Escherichia coli (E. coli). The fitted dose-cytotoxicity curve for ZnCl2 was significantly sharper than that from nano-ZnO. Then, a genome-wide gene expression profile following exposure to nano-ZnO was conducted by use of a live cell reporter assay system with library of 1820 modified green fluorescent protein (GFP)-expressing promoter reporter vectors constructed from E. coli K12 strains, which resulted in 387 significantly altered genes in bacterial (p < 0.001). These altered genes were enriched into ten biological processing and two cell components (p < 0.05) terms through statistical hypergeometric testing, strongly suggesting that exposure to nano-ZnO would result a great disturbance on the functional gene product synthesis processing, such as translation, gene expression, RNA modification, and structural constituent of ribosome. The pattern of expression of 37 genes altered by nano-ZnO (fold change>2) was different from the profile following exposure to 6 mg/L of free zinc ion. The result indicates that these two Zn forms might cause toxicity to bacterial in different modes of action. Our results underscore the importance of understanding the adverse effects elicited by nano-ZnO after entering aquatic environment.

2013 Lush Science Prize

The annual Lush Science Prize is designed to reward outstanding contributions to 21st Century Toxicology Research. A Background Paper is prepared each year prior to the judging process, in order to provide the judging panel with a brief overview of current developments in the field of Replacement alternatives, particularly those relevant to the concept of toxicity pathways. The Background Paper includes information on some key institutional developments in the area--such as the OECD's Adverse Outcome Pathway Project, the Hamner Institute's work, and the Human Toxome Project, and on the phenomenon of collaborative computer systems relevant to the field. From the literature review that was also performed as part of the background research, the two papers receiving the highest score were recommended for consideration by the judges for the 2013 Science Prize.