Genotoxic effects and gene expression changes in larval zebrafish after exposure to ZnCl2 and ZnO nanoparticles

Abstract

Engineered nanoparticles (NPs) can potentially generate adverse effects at the tissue, organ, cellular, subcellular, DNA, and protein levels due to their unique physico-chemical properties. Dissoluble NPs (e.g. nZnO) can be toxic in aquatic organisms. We compared effects of nZnO and corresponding concentrations of released Zn(II) by water-soluble ZnCl 2 on larval zebrafish Danio rerio (72 h post fertilization) by analyzing changes in expression levels of stressrelated genes ( p53, rad51, mt2) by qRT-PCR. Additionally, genotoxicity of nZnO and Zn(II) was assessed. The lethal concentrations for 50% mortality (LC 50 ) in larval zebrafish exposed for 96 h to 0 to 70 mg l −1 nZnO and Zn(II) were 21.37 ± 1.81 mg l −1 (95% CI) and 4.66 ± 0.11 mg l −1 , respectively. A concentration-dependent increase in DNA strand breaks was detected in cells from larvae exposed (96 h) to nZnO and Zn(II). DNA damage was higher in Zn(II)-than nZnO-exposed larvae. Induction of stress-related genes in larvae was complex and was not directly related to nZnO and Zn(II) concentrations, although there was significant induction in the mt2 gene of larvae exposed to Zn(II) and nZnO relative to controls. mt2 induction of 20.5 ± 1.9-fold and 2.5 ± 0.8-fold change (mean ± SEM) was observed in larvae at the highest Zn(II) and nZnO concentrations (3 and 6 mg l −1 ), respectively. The results suggest that toxicity associated with nZnO is primarily due to the release of Zn(II).KEY WORDS: Nanoscale ZnO · Zinc chloride · Genotoxicity · Stress-related genes · Danio rerio Resale or republication not permitted without written consent of the publisherDis Aquat Org 117: [205][206][207][208][209][210][211][212][213][214] 2016 for a number of enzymes. However, when present in excessive concentrations, this metal can cause adverse effects (Regoli & Principato 1995, Wilson et al. 2012. nZnO can partially but relatively rapidly dissolve in water, and the release of free Zn ions is the primary source of toxicity (Franklin et al. 2007, Blinova et al. 2010, Buerki-Thurnherr et al. 2013. Several studies have indicated that nZnO are toxic to fish: mortality, hatching inhibition, retarded growth, tissue injuries, and malformation have been reported in embryonic and larval zebrafish Danio rerio exposed to nZnO (Zhu et al. 2009, Bai et al. 2010, Zhao et al. 2013. Although some studies found that toxicity of nZnO could be mainly attributed to dissolved Zn ions (Franklin et al. 2007, Wong et al. 2010, toxicity of nZnO cannot always be explained by the dissolved Zn ions (Bai et al. 2010.Particle-induced generation of reactive oxygen species (ROS) and dissolution to ionic Zn represent the primary modes of action for nZnO toxicity across all species tested (Ma et al. 2013). Indeed, ROS induction triggering an oxidative stress response has become a widely accepted paradigm for cellular effects of NPs (Nel et al. 2006, Zhu et al. 2009, Song et al. 2010, Sharma et al. 2012. Excessive production of ROS can induce pro-inflammatory and cytotoxic effects (Nel et al. 200...

Zinc Chloride Exposure Inhibits Brain Acetylcholine Levels, Produces Neurotoxic Signatures, and Diminishes Memory and Motor Activities in Adult Zebrafish

“…The United States Environmental Protection Agency (USEPA) established a system as an initial screen that applied zebrafish as a model for rapid identification of chemical toxicity to evaluate the effects from myriad chemical pollutants [ 38 ]. However, the biological effects of ZnCl 2 on neurobehavioral development in a vertebrate model are not well characterized in research ( Table A1 ).…”

Potential Harm of Maltodextrin‐Coated Cadmium Sulfide Quantum Dots in Embryos and Fetuses

“…It has been shown that CdS-maltodextrin QDs are able to induce cytotoxicity and cell death, alter cell proliferation and induce the production of radical oxygen species (ROS) in a dose-dependent manner [14]. QD-induced perturbations of cellular mechanisms may cause different pathophysiological processes depending on concentration and duration of exposure [49][50][51].…”

Influence of calcium and EDTA on copper ion bioavailability in copper nanoparticle toxicity tests improves understanding of nano-specific effects

“…To determine LC 50 values of CuSO 4 and Cu-NPs, stock solutions were added to each 400 mL and 2 L exposure beakers at eight different nominal concentrations (0, 40, 80, 160, 300, 600, 1200, and 3000 mg/L) for Cu 2þ and six different nominal concentrations (0, 40, 200, 500, 1000, and 3000 mg/L) for Cu-NPs, respectively, and for each experiment at least three beakers were included without Cu 2þ and Cu-NPs as an experimental control. Thirty larval zebrafish (72 hpf) were put in each beaker and tried to determine the mortality of larvae (LC 50 ) at 96 h period of time at different concentrations (Boran and Ulutas, 2016). After determination of lethal and sublethal concentration of Cu 2þ and Cu-NPs, gene expression experiments were conducted to compare Cu 2þ and Cu-NPs.…”

“…cDNA was synthesized in the following conditions: annealing at 25 C, extending at 42 C, and heat-inactivating transcriptase at 70 C (GeneAmp ® PCR System, 9700, Applied Biosystems, California, USA). cDNA was stored at À80 C until quantitative RT-PCR (qRT-PCR) transcriptional analysis (Boran and Ulutas, 2016).…”