Impacts of Different Exposure Scenarios on Transcript Abundances in Danio rerio Embryos when Investigating the Toxicological Burden of Riverine Sediments

Abstract

PurposeRecently, a proof-of-concept study revealed the suitability of transcriptome analyses to obtain and assess changes in the abundance of transcripts in zebrafish (Danio rerio) embryos after exposure to organic sediment extracts. The present study investigated changes in the transcript abundance in zebrafish embryos exposed to whole sediment samples and corresponding organic extracts in order to identify the impact of different exposure pathways on sediment toxicity.Materials and Methods Danio rerio embryos were exposed to sublethal concentrations of three sediment samples from the Danube River, Germany. The sediment samples were investigated both as freeze-dried samples and as organic extracts. Silica dust and a process control of the extraction procedure were used as references. After exposure, mRNA was isolated and changes in profiles of gene expression levels were examined by an oligonucleotide microarray. The microarray results were compared with bioassays, chemical analysis of the sediments and profiles of gene expression levels induced by several single substances.Results and DiscussionThe microarray approach elucidated significant changes in the abundance of transcripts in exposed zebrafish embryos compared to the references. Generally, results could be related to Ah-receptor-mediated effects as confirmed by bioassays and chemical analysis of dioxin-like contaminants, as well as to exposure to stress-inducing compounds. Furthermore, the results indicated that mixtures of chemicals, as present in sediment and extract samples, result in complex changes of gene expression level profiles difficult to compare with profiles induced by single chemical substances. Specifically, patterns of transcript abundances were less influenced by the chemical composition at the sampling site compared t the method of exposure (sediment/extract). This effect might be related to different bioavailability of chemicals.ConclusionsThe apparent difference between the exposure scenarios is an important aspect that needs to be addressed when conducting analyses of alterations in the expression level of mRNA.

A Reduced Transcriptome Approach to Assess Environmental Toxicants Using Zebrafish Embryo Test

“…29 We selected a minimum number of genes playing central roles in biological pathways, which may significantly represent the maximum number of biological pathways. Additionally, a list of toxicology-relevant genes was curated to include the following: (1) genes measured as endpoints in ToxCast 1 , (2) genes corresponding to molecular initiating events (MIEs) and key events (KEs) associated with adverse outcome pathways (AOPs) described in the AOP-Wiki (https://aopwiki.org/wiki/index.php/Main_Page), (3) genes listed in graphical model of the fish hypothalamic−pituitary−gonadal (HPG) axis 30 and (4) a set of manually retrieved genes associated with development [31][32][33][34][35][36][37][38] (Table 1). Finally, to avoid potential amplification bias during mRNA quantification, the combined genes were submitted for online multiplex primers design by Ion Ampliseq Designer, where the genes with high transcript abundance across zebrafish transcriptome were removed from the RZT gene set.…”

Essential Oils as Stress-Reducing Agents for Fish Aquaculture: A Review

“…The stress response is initiated and controlled by two hormonal systems, which lead to the production of catecholamines (such as adrenaline and noradrenaline, and their precursor dopamine) by the hypothalamus-sympathetic-chromaffin (HSC) axis, and corticosteroids (mainly cortisol) by the hypothalamus-pituitary-interrenal (HPI) axis (Wendelaar Bonga, 1997, 2011; Flik et al, 2006; Martos-Sitcha et al, 2014). Behavioral changes are used by the organism to overcome this situation, subsequently generating several responses to the stressor, including gene, metabolic, energetic, immune, endocrine, and neural changes (Schreck and Tort, 2016; Figure 1). Long-term consequences of repeated or prolonged stressful exposures are maladaptive by negatively affecting other necessary life functions, such as growth, development, disease resistance, behavior or reproduction and may even culminate in fish death (Wendelaar Bonga, 1997; Schreck and Tort, 2016).…”

Pollution by metals and toxicity assessment using Caenorhabditis elegans in sediments from the Magdalena River, Colombia

“…The relationship between river sediment contaminants and toxicity has been reported using different biological models, including HepG2 cells (Pinto et al, 2015), Danio rerio (Bluhm et al, 2014), Daphnia magna (De Castro-Catala et al, 2015), and the nematode Caenorhabditis elegans (Menzel et al, 2009;Turner et al, 2013). The later has been used as a model to assess toxicity of soils (Baderna et al, 2014;Harmon and Wyatt, 2008;H€ oss et al, 2009;Huguier et al, 2013), water (Ju et al, 2014), wastewater (Wang et al, 2008(Wang et al, , 2010, particulate matter (Sun et al, 2015;Zhao et al, 2014), sewage sludge (McLaggan et al, 2012), and river sediments (H€ oss et al, 2010;Tuikka et al, 2011;Wolfram et al, 2012).…”