Quantitative investigation of the mechanisms of microplastics and nanoplastics toward zebrafish larvae locomotor activity

This study investigated the direct and indirect toxic effects of microplastics and nanoplastics toward zebrafish (Danio rerio) larvae locomotor activity. Results showed that microplastics alone exhibited no significant effects except for the upregulated zfrho visual gene expression; whereas nanoplastics inhibited the larval locomotion by 22% during the last darkness period, and significantly reduced larvae body length by 6%, inhibited the acetylcholinesterase activity by 40%, and upregulated gfap, α1-tubulin, zfrho and zfblue gene expression significantly. When co-exposed with 2 μg/L 17 α-ethynylestradiol (EE2), microplastics led to alleviation on EE2’s inhibition effect on locomotion, which was probably due to the decreased freely dissolved EE2 concentration. However, though nanoplastics showed stronger adsorption ability for EE2, the hypoactivity phenomenon still existed in the nanoplastics co-exposure group. Moreover, when co-exposed with a higher concentration of EE2 (20 μg/L), both plastics showed an enhanced effect on the hypoactivity. Principal component analysis was performed to reduce data dimensions and four principal components were reconstituted in terms of oxidative stress, body length, nervous and visual system related genes explaining 84% of total variance. Furthermore, oxidative damage and body length reduction were evaluated to be main reasons for the hypoactivity. Therefore, nanoplastics alone suppressed zebrafish larvae locomotor activity and both plastic particles can change the larvae swimming behavior when co-exposed with EE2. This study provides new insights into plastic particles’ effects on zebrafish larvae, improving the understanding of their environmental risks to the aquatic environment.

Qiqing Chen, Michael Gundlach, Shouye Yang and al., Science of The Total Environment, Volumes 584–585, 15 April 2017, Pages 1022–1031

The article

Assessment of microplastic-sorbed contaminant bioavailability through analysis of biomarker gene expression in larval zebrafish

Microplastics (MPs) are prevalent in marine ecosystems. Because toxicants (termed here “co-contaminants”) can sorb to MPs, there is potential for MPs to alter co-contaminant bioavailability. Our objective was to demonstrate sorption of two co-contaminants with different physicochemistries [phenanthrene (Phe), log10Kow = 4.57; and 17α-ethinylestradiol (EE2), log10Kow = 3.67] to MPs; and assess whether co-contaminant bioavailability was increased after MP settlement. Bioavailability was indicated by gene expression in larval zebrafish. Both Phe and EE2 sorbed to MPs, which reduced bioavailability by a maximum of 33% and 48% respectively. Sorption occurred, but was not consistent with predictions based on co-contaminant physicochemistry (Phe having higher log10Kow was expected to have higher sorption). Contaminated MPs settled to the bottom of the exposures did not lead to increased bioavailability of Phe or EE2. Phe was 48% more bioavailable than predicted by a linear sorption model, organism-based measurements therefore contribute unique insight into MP co-contaminant bioavailability.

Victoria A. Sleight, Adil Bakir, Richard C. Thompson, Theodore B. Henry, Marine Pollution Bulletin, Volume 116, Issues 1–2, 15 March 2017, Pages 291–297

The article

Proteomics analysis of zebrafish brain following chronically exposed to bisphenol A

Bisphenol A, a plastic monomer and plasticizer, is a well-known endocrine disrupter, widely present in the aquatic environment, but little is known regarding its neurotoxicity in fish. Herein, we investigated its effects on male zebrafish brain. Zebrafish were exposed to 10 µg/L BPA for 45 days. An isobaric tags for relative and absolute quantitation approach coupled with nano high-performance liquid chromatography-tandem mass spectrometry analysis was employed to detect and identify differentially expressed proteins. A total of 46 proteins was identified and categorized into functional classes that mostly included metabolism and transport, cytoplasm and organelle, ion and nucleotide binding, indicating that bisphenol A toxicity in fish brain is complex. The biological pathways of starch and sucrose metabolism, calcium signaling, and aminoacyl-tRNA biosynthesis were also induced. Proteomic analyses add new perspectives to bisphenol A neurotoxicity in aquatic organisms.

Xiangyang Wu, Chongwei Lu, Xing Dong, Zhen Zhang, Ming Yang & Hai Xu, Toxicological & Environmental Chemistry, Volume 99, Issue 3, Pages 469-481, 2017

Uptake and accumulation of polystyrene microplastics in zebrafish (Danio rerio) and toxic effects in liver

Microplastics have become an emerging contaminant and caused widespread concern about its potential toxic effects. In this study, the uptake and tissue accumulation of polystyrene microplastics (PS-MPs) in zebrafish were detected, as well as the toxic effects in liver were investigated. The results showed that after 7 days of exposure, 5-μm diameter MPs accumulated in fish gill, liver, and gut, while 20-μm diameter MPs only accumulated in fish gill and gut. Histopathological analysis showed that both sizes of 5-μm and 70-nm PS-MPs caused inflammation and lipid accumulation in fish liver. PS-MPs also induced significantly increased activities of SOD and CAT, indicating oxidative stress was induced after MPs treatment. In addition, metabolomic analysis suggested that MPs exposure induced alterations of metabolic profiles in fish liver and disturbed the lipid and energy metabolism. These findings provide new insights into the toxic effects of MPs on fish.

Yifeng Lu, Yan Zhang, Yongfeng Deng, Wei Jiang, Yanping Zhao, Jinju Geng, Lili Ding, and Hong-qiang Ren, Environ. Sci. Technol., vol. 50 (7), pages 4054-4060, April 2016

Environmentally Relevant Concentrations of the Flame Retardant Tris(1,3-dichloro-2-propyl) Phosphate Inhibit Growth of Female Zebrafish and Decrease Fecundity

Bioconcentrations of tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) in brain, gonad, and liver as well as effects on fecundity and development of zebrafish (Danio rerio) were determined. Zebrafish (1-month old) were exposed to environmentally relevant concentrations of 29 ± 2.1, 600 ± 21, or 6300 ± 130 ng TDCIPP/L. After 120 days of exposure, TDCIPP accumulated in the brain, gonad, and liver with bioconcentration factors of 460, 38, and 87 in females and 26, 55, and 110 in males, respectively. TDCIPP accumulated to a greater extent in brains of females than those of males. Exposure to 6300 ± 130 ng TDCIPP/L resulted in significantly (P < 0.05) fewer eggs being produced, but the histology of the gonad, plasma concentrations of estradiol and 11-ketotestosterone, and expression of genes involved in hypothalamic–pituitary–gonadal–liver axis were not significantly (P > 0.05) different between individuals exposed to TDCIPP and the unexposed control fish. Exposure to TDCIPP resulted in shorter body length, lighter body mass, and lower gonadal–somatic index in females. These effects were possibly due to down-regulation of expression of genes along the growth hormone/insulin-like growth factor (GH/IGF) axis. Correlations between the production of eggs and developmental parameters or expression of genes along the GH/IGF axis further suggested that environmentally relevant concentrations of TDCIPP could have adverse effects on reproduction, possibly due to the inhibition of the growth of females.

Ya Zhu, Xufa Ma, Guanyong Su, Liqin Yu, Robert J. Letcher, Jie Hou, Hongxia Yu, John P. Giesy, and Chunsheng Liu, Environ. Sci. Technol., Article ASAP, October 29, 2015

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Influence of polyethylene microplastic beads on the uptake and localization of silver in zebrafish (Danio rerio)

This study aimed to determine whether the uptake and localization of Ag in zebrafish was affected by the presence of polyethylene microplastic beads (PE MPBs). Zebrafish were exposed to 1 μg Ag L−1 (radiolabelled with 110mAg) for 4 and 24 h in the presence or absence of PE MPBs (10, 100 or 1000 MPBs mL−1), and one treatment in which MPBs (1000 MPBs mL−1) were incubated with Ag to promote adsorption. The presence of MPBs, at any of the tested doses, had no effect on the uptake or localization of Ag. However, exposure to the Ag-incubated MPBs (∽75% of the Ag bound to MPBs) significantly reduced Ag uptake at both time points and also significantly increased the proportion of intestinal Ag. This study demonstrates that microplastics can alter the bioavailability and uptake route of a metal contaminant in a model fish species.

Farhan R. Khan, Kristian Syberg, Yvonne Shashoua, Nicolas R. Bury, Environmental Pollution, Volume 206, Pages 73–79, November 2015

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Long-term effects of Bisphenol AF (BPAF) on hormonal balance and genes of hypothalamus-pituitary-gonad axis and liver of zebrafish (Danio rerio), and the impact on offspring

Bisphenol AF (BPAF) is one of the analogues of bisphenol A (BPA) and is widely used as a raw material in the plastics industry. The potential toxicity to fish from exposure to BPAF in the aquatic environment is largely unknown. In this study, zebrafish (Danio rerio) were exposed to BPAF at 5,25 and 125 mu g L-1, from 4 hour-post-fertilization (hpf) to 120 day-post-fertilization (dpf), representing the period from embryo to adult. The levels of plasma hormones were measured and the expression of selected representative genes along the hypothalamus-pituitary-gonad (HPG) axis and liver were examined. The concentration of 17 beta-estradiol (E2) was significantly increased in male and female fish and a significant decrease of testosterone (T) was observed in male fish. The mRNA expression of genes along the HPG axis and in liver tissues in F0 generation fish demonstrated that the steroid hormonal balances of zebrafish were modulated through the alteration of steroidgenesis. (…)

Jiachen Shi, Zhihao Jiao, Sai Zheng, Ming Li, Jing Zhang, Yixing Feng, Jie Yin, Bing Shao, Chemosphere, Volume 128, Pages 252–257, June 2015

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