Acetylcholinesterase in zebrafish embryos as a tool to identify neurotoxic effects in sediments

Abstract

In order to clarify the suitability of zebrafish (Danio rerio) embryos for the detection of neurotoxic compounds, the acetylcholinesterase assay was adapted and validated with a series of priority pollutants listed as relevant for the European water policy (Aroclor 1254, 2,3-benzofuran, bisphenol A, chlorpyrifos, paraoxon-methyl, quinoline, and methyl mercury chloride) as well as acetonic extracts from three sediments of known contamination. The acute toxicities of the model substances and the sediment extracts were determined by means of the fish embryo test as specified in OECD TG 236, and concentrations as low as the effective concentration at 10% inhibition (EC10) were used as the highest test concentration in the acetylcholinesterase test in order to avoid nonspecific systemic effects mimicking neurotoxicity. Among the model compounds, only the known acetylcholinesterase inhibitors paraoxon-methyl and chlorpyrifos produced a strong inhibition to about 20 and 33%, respectively, of the negative controls. For the sediment extracts, a reduction of acetylcholinesterase activity to about 60% could only be shown for the Vering Canal sediment extracts; this could be correlated to high contents of acetylcholinesterase-inhibiting polycyclic aromatic hydrocarbons (PAHs) as identified by chemical analyses. Co-incubation of the Vering Canal sediment extracts with chlorpyrifos at EC10 concentrations each did not significantly increase the inhibitory effect of chlorpyrifos, indicating that the mode of action of acetylcholinesterase inhibition by the sediment-borne PAHs is different to that of the typical acetylcholinesterase blocker chlorpyrifos. Overall, the study documents that zebrafish embryos represent a suitable model not only to reveal acetylcholinesterase inhibition, but also to investigate various modes of neurotoxic action.

Automated high-throughput in vitro screening of the acetylcholine esterase inhibiting potential of environmental samples, mixtures and single compounds

“…Designed to suppress the abundance of selected organisms, pesticides inhibiting AChE are usually also toxic for non-targeted species (Bocquené and Galgani, 1998). Furthermore, it has been recently shown that other type of compounds, such as polychlorinated biphenyls or polycyclic aromatic hydrocarbon (PAHs), can inhibit AChE in environmental samples (Kang and Fang, 1997;Kais et al, 2015). This assay was chosen for the development of a new EDA procedure because of the effects AChE inhibitors can have on organisms such as fish and seabirds (Bocquené and Galgani, 1998;Oropesa et al, 2007) and furthermore because apart from selected pesticides (such as organophosphates and carbamates), only a few classes of compounds have been previously tested.…”

Toxicity and Antitumor Activity of a Thiophene–Acridine Hybrid

“…AChE is responsible for the enzymatic degradation of acetylcholine (ACh), and its absence or low activity causes high levels of systemic ACh, which acts as a neurotransmitter [32]. Herein, we observed an increase in AChE activity, which is in general associated to neurotoxicity [33]; however, the literature also suggests that AChE may display antitumor activity, in addition to correlating tumor malignancy with low activity of AChE [34][35][36]. GSTs are vital in the Phase II detoxification enzymes pathway in humans, and they provide protection against toxins by catalyzing toxin conjugation with Glutathione (GSH) or passively binding to various exogenous/endogenous toxic molecules, including environmental toxins, carcinogens, chemotherapeutic agents, and products of oxidative stress [37,38].…”

Danio rerio as a model in aquatic toxicology and sediment research

“…Within the DanTox project (funded by the German Federal Ministry of Education and Research, BMBF from 2010 to 2013), existing assays could be developed further (Garcia-Käufer et al 2015, Hafner et al 2015), and novel mechanism-specific contact assays were introduced for a comprehensive assessment of the bioavailable toxicity in sediments Keiter et al 2010;Kais et al 2015;Schiwy et al 2015). New and valuable knowledge concerning the application of such bioassays and the underlying cellular mechanisms have been gained.…”