preparation of zebrafish embryos and chemicals for testing neuromuscular and general toxicity on embryos

Ensaio de Sobressalto para Avaliação de Toxicidade em Embrião de Peixe-Zebra

In recent years, zebrafish have become highly popular model organisms for the evaluation of chemical compound effects, encompassing research areas from drug development to environmental toxicology1. As vertebrates, zebrafish share many aspects of their genetic makeup and overall physiology with humans2,3. Therefore, results obtained in this model often are directly relevant to human health. Several drug candidates currently in clinical trials have been identified in compound screens using zebrafish4.
Toxicity assessment is one major application where tests using zebrafish embryonic stages are of interest. Various Organisation for Economic Co-operation and Development (OECD) test guidelines exist for the use of zebrafish in environmental toxicity testing5,6. The small size and rapid development of zebrafish embryos make them highly suitable for screening approaches on a medium to high throughput scale1,3,4. Toxicological endpoints targeted by such screens include embryonic malformations and lethality7, endocrine disruption8, organ toxicity9, and behavioral assessments indicative of neural toxicity10,11. The behavioral assays are possible because zebrafish embryos show various types of locomotor responses to different stimuli depending on their stage of development. For example, 1 day post fertilization (dpf) embryos show spontaneous tail coiling12 and respond to a sequence of light pulses with a typical sequence of movements, the so-called photomotor response (PMR)10. After hatching, typically occurring around 48-72 hours post fertilization (hpf), the freely swimming eleutheroembryos13 gradually develop startle and escape responses to vibrational stimuli starting around 4 dpf14. These responses are characterized by a distinctive bend to the direction opposite the direction of the stimulus (the so-called C-bend or C-start), which is followed by a smaller counter bend and swimming behavior14,15,16,17. Notably, embryonic behaviors are governed by neural circuits using various neurotransmitter systems, allowing for probing chemical compound effects targeting these systems. For example, the PMR assay revealed the effects of compounds interfering with cholinergic, adrenergic, and dopaminergic signaling10, while the startle response involves cholinergic, glutamatergic, and glycinergic neurons16,18. Furthermore, compounds that damage the muscles or the neuro-muscular interface will also affect these behaviors, as will compounds toxic to the inner ear/lateral line hair cells19,20. Observing zebrafish locomotor behavior in response to a stimulus is thus a suitable means to assess not only neurotoxicity but equally ototoxicity and myotoxicity. Scoring locomotor behavior also serves as a proxy for general toxicity/lethality assessment since dead embryos do not move. Thereby, embryonic locomotion behaviors represent an integrative readout for a first-tier toxicity screening approach, which indicates lethal and neuromuscular compound effects in one setup. Given that the eleutheroembryos are already capable of metabolizing compounds, the approach may also detect the effects of metabolic transformation products7,21,22. Importantly, zebrafish embryos are not considered as protected life stage under some animal protection legislations until the stage of free feeding after 120 hpf13. Therefore, they are regarded as an alternative to animal toxicity testing.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/66153/66153fig01.jpg" /> 
Figure 1: Vibration startle response system setup. (A) Overview of the system. Plates with embryos exposed to the test compounds are placed on the electrodynamic transducer array (&#34;loudspeakers&#34;). The camera is sequentially moved by the belt-driven linear drive into the recording position above the targeted transducer. (B) Detailed view of the transducer/loudspeaker with tissue culture dish inserted on top. The plates are illuminated from below by an LED light sheet at 4000-5000 lux. An LED light next to the speaker lights up while the stimulus is given. (C) Still image of video recorded by the camera upon stimulation of the embryos. (D) Screenshot of the configuration file. (E) Screenshot of the recording software interface. <a href="https://www.jove.com/files/ftp_upload/66153/66153fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Here, we describe a testing protocol for the evaluation of compound effects on the vibration startle response using an in-house build simple testing device based on vibration stimuli generated by electrodynamic transducers coupled with an automated video recording of several freely moving embryos in a tissue culture dish23. The system is modular and allows for sequential recording from several tissue culture dishes in parallel. In the setup currently used, five electrodynamic transducers provide a vibrational stimulus (500 Hz, duration 1 ms) to tissue culture dishes containing 20 embryos placed on top of them (Figure 1). The plates are illuminated from below at 4000-5000 lux with LED light sheets. An LED light next to each transducer indicates periods of stimulus application, and an oscilloscope indicates waveforms and frequency of the applied stimulus (for details, see Ref. 23). The behavior of the embryos is recorded by a high-speed camera (Table of Materials) at 1000 frames per second (fps), which is moved above the targeted speaker by a belt-driven linear drive. This recording speed is required to reliably resolve the startle response. The system provides a low-cost, individually adaptable alternative to current commercial systems. The precise workflow detailed below is currently performed in the framework of the Precision Toxicology initiative24 in order to determine suitable exposure conditions for OMICS data acquisition from zebrafish embryos treated with a selected set of toxicants.

Autor em destaque: Triagem de toxicidade de alto rendimento usando ensaio de resposta de sobressalto de embrião de peixe-zebra

Avaliando a toxicidade de produtos químicos usando um sistema de triagem de resposta de sobressalto de vibração de peixe-zebra

Preparação de embriões de peixe-zebra e produtos químicos para testes de toxicidade neuromuscular e geral em embriões

Para começar, colete embriões em estágios de clivagem, especificamente do estágio de duas células para oito células da desova natural, em uma placa de Petri de 10 centímetros. Remova ovos, detritos e escamas não fertilizados da placa de Petri para limpá-la. Colocar 60 embriões por uma placa de Petri contendo 15 mililitros de meio E3.Posicione todos os pratos contendo embriões em uma câmara umidificada preparada com papel toalha embebido em água. Em seguida, incubá-los 72 horas após a fertilização em uma incubadora fixada a 28,5 graus Celsius. Em seguida, recupere as soluções de estoque químico desejadas do freezer de menos 20 graus Celsius e deixe descongelar.Preparar a diluição em série de cada produto químico em meio E3 em um frasco de vidro. Inspecione a solução quanto à precipitação e, se houver, registre-a. Em seguida, dilua ainda mais para atingir a próxima concentração mais alta.Verifique e repita até que não haja precipitação. Em seguida, verifique e registre o pH da solução de exposição. Se ficar fora da faixa de pH 7,0 a 8,5, ajuste para 7,4 com ácido clorídrico ou hidróxido de sódio.Eliminar qualquer meio de exposição não utilizado de acordo com as regulamentações locais.

preparation-zebrafish-embryos-chemicals-for-testing-neuromuscular

Research

JoVE Journal

Biology

Preparation of Zebrafish Embryos and Chemicals for Testing Neuromuscular and General Toxicity on Embryos

260 visualizações. Para começar, colete embriões em estágios de clivagem, especificamente do estágio de duas células para oito células da desova natural, em uma placa de Petri de 10 centímetros. Remova ovos, detritos e escamas não fertilizados da placa de Petri para limpá-la. Colocar 60 embriões por uma placa de Petri contendo 15 mililitros de meio E3.Posicione todos os pratos contendo embriões em uma câmara umidificada preparada com papel toalha embebido em água. Em seguida, incubá-los 72 ...

Vídeo: Preparação de embriões de peixe-zebra e produtos químicos para testes de toxicidade neuromuscular e geral em embriões

Evaluating Toxicity of Chemicals using a Zebrafish Vibration Startle Response Screening System

We developed a simple screening system for the evaluation of neuromuscular and general toxicity in zebrafish embryos. The modular system consists of electrodynamic transducers above which tissue culture dishes with embryos can be placed. Multiple such loudspeaker-tissue culture dish pairs can be combined. Vibrational stimuli generated by the electrodynamic transducers induce a characteristic startle and escape response in the embryos. A belt-driven linear drive sequentially positions a camera above each loudspeaker to record the movement of the embryos. In this way, alterations to the startle response due to lethality or neuromuscular toxicity of chemical compounds can be visualized and quantified. We present an example of the workflow for chemical compound screening using this system, including the preparation of embryos and treatment solutions, operation of the recording system, and data analysis to calculate benchmark concentration values of compounds active in the assay. The modular assembly based on commercially available simple components makes this system both economical and flexibly adaptable to the needs of particular laboratory setups and screening purposes.

We describe a screening system's workflow and data analysis for evaluating chemical compound toxicity based on the zebrafish embryo vibration startle response. The system records the movements of zebrafish embryos upon exposure to a vibration stimulus and allows for an integrated evaluation of general toxicity/lethality and neuromuscular toxicity.

We developed a simple screening system for the evaluation of neuromuscular and general toxicity in zebrafish embryos. The modular system consists of ...