Screening tools to evaluate the neurotoxic potential of botanicals: building a strategy to assess safety

Abstract

Areas covered: This paper outlines the selection of NAMs, including in vitro assays using primary rat cortical neurons, zebrafish embryos, and Caenorhabditis elegans. These assays aim to assess neurotoxic endpoints such as neuronal activity and behavioral responses. Microelectrode array recordings of rat cortical neurons provide insights into the impact of botanical extracts on neuronal function, while the zebrafish embryos and C. elegans assays evaluate neurobehavioral responses. The paper also provides an account of the selection of botanical case studies based on expert judgment and existing neuroactivity/toxicity information. The proposed battery of assays will be tested with these case studies to evaluate their utility for neurotoxicity screening.

Expert opinion: The complexity of botanicals necessitates the use of multiple NAMs for effective neurotoxicity screening. This paper discusses the evaluation of methodologies to develop a robust framework for evaluating botanical safety, including complex neuronal models and key neurodevelopmental process assays. It aims to establish a comprehensive screening framework.

Keywords: Botanical; NAM; UVCB; complex mixtures; in vitro; neurotoxicity; screening.

Figure 1.

Overview of the model system and experimental setup used to determine the suitability of these assays for botanicals. hpf: hours post-fertilization. Created with BioRender.

Figure 2.

MicroElectrode Array (MEA) recordings rely on 48-well plates that have a 4 × 4 electrode grid on the bottom of each well, on top of which neuronal cells can be cultured (top left). The spontaneous neuronal activity is recorded as local field potentials (bottom left). The neuroactive potential of botanical extracts can be assessed by comparing the neuronal activity before (baseline recording) and after exposure (right).

Figure 3.

Schematic diagram showing the types of neurobehavioral assays performed in zebrafish larvae, such as larval photomotor response (LPR) assays conducted in light and dark phases, and larval startle response (LSR) assays.

Figure 4.

Schematic diagram showing the types of neurobehavioral assays performed with C. elegans larvae, such as the reaction to adverse smell and body movement assays.