Unknown,Transcriptomics,Genomics,Proteomics

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Toxicity and transcriptomic analysis in Hyalella azteca suggests increased exposure and susceptibility of epibenthic organisms to Zinc Oxide Nanoparticles

ABSTRACT: Abstract: Nanoparticles (NPs) are expected to make their way into the aquatic environment where sedimentation of particles will likely occur, putting benthic organisms at particular risk. Therefore, organisms such as Hyalella azteca, an epibenthic crustacean which forages at the sediment surface, is likely to have a high potential exposure. Here we show that Zinc Oxide (ZnO) NPs are more toxic to H. azteca compared with the corresponding metal ion, Zn2+. Dissolution of ZnO NPs contributes about 50% of the Zn measured in the ZnO NP suspensions, and cannot account for the toxicity of these particles to H. azteca. However, gene expression analysis is unable to distinguish between the ZnO NP exposures and Zinc Sulfate (ZnSO4) exposures at equitoxic concentrations. These results lead us to hypothesize that ZnO NPs provide and an enhanced exposure route for Zn2+ uptake into H. azteca, and possibly other sediment dwelling organisms. Our study supports the prediction that sediment dwelling organisms are highly susceptible to the effects of ZnO NPs and should be considered in the risk assessment of these nanomaterials. This experiment included four different treatments and an untreated control. Each treatment or control, consisted of ten independent replicates of twenty Hyalella azteca. Of these, six were randomly chosen to be used for the microarray analysis.

ORGANISM(S): Hyalella azteca

SUBMITTER: Helen Poynton

PROVIDER: E-GEOD-49136 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Hormesis is a dose response phenomenon characterized by a stimulation of an organismal response at low doses of a chemical and inhibition of the response (toxicity) at a higher dose. In the present study, Daphnia magna were exposed to the energetic compound 2,4,6-trinitrotoluene (TNT) for 21 days, and the endpoints survival, growth (length and dry weight), and reproduction (number of neonates per survivor) were assesed, identifying hormetic responses at the lower treatment levels. In order to elucidate the mechanisms leading to hormesis, microarray analysis was performed at 0.004 (hormetic), 0.12 (sometimes hormetic), and 1.85 (toxic) mg/L TNT. Functional and transcriptional benchmark dose analyses performed on differentially expressed genes suggested the involvement of lipid metabolism in hormetic responses and subsequently lipidomic analysis was performed on the same treatments. Lipid analysis supported the hypothesis that TNT exposure affected lipid metabolism, and showed that hormetic effects could be related to increases in some polyunsaturated fatty acids and ecosanoids known to be involved in Daphnia growth and reproduction. Chronic toxicity tests was designed to identify the hormetic range of D. magna responses to TNT. Daphnia magna younger than 24 h old and obtained from in-house cultures at the U.S. Army Engineer Research and Development Center, Environmental Laboratory (Vicksburg, MS) were used to initiate the bioassay. The experimental design consisted of one D. magna per test chamber and 10 test chambers per treatment level. In the microarray mass exposure, nominal treatment levels were 0.004, 0.02, 0.12, 0.44, and 1.85 mg/L. Based on the results of the testing in the 50 ml beakers, organisms from three treatments were selected for analysis of gene expression: 0.004, 0.12, and 1.85 mg/L. These treatments were selected to represent a hormetic concentration (0.004 mg/L), a toxic concentration (1.85 mg/L), and an intermediate concentration (0.12 mg/L). A total of 23 arrays used, with 5-6 replicates per each dose (solvent control, 0.004 mg/L, 0.12 mg/L, and 1.85 mg/L).

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Toxicity and transcriptomic analysis in Hyalella azteca suggests increased exposure and susceptibility of epibenthic organisms to Zinc Oxide Nanoparticles

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