Inhibition of Neural Crest Cell Migration by Strobilurin Fungicides and Other Mitochondrial Toxicants

Area of Science:

• Toxicology
• Developmental Biology
• Biochemistry

Background:

• Cell-based assays are crucial for toxicity screening but lack validation and integration guidance for risk assessment.
• Neural crest cells (NCCs) are sensitive to developmental toxicants, making them a valuable model.
• Picoxystrobin, a strobilurin fungicide, inhibits mitochondrial complex III and is a potential developmental toxicant.

Purpose of the Study:

• To present a procedure for validating cell-based toxicity screening hits and integrating data for risk assessment.
• To exemplify this procedure with a case study on the developmental toxicity of picoxystrobin using NCCs.
• To pave the way for next-generation risk assessment by bridging in vitro testing and in vivo predictions.

Main Methods:

• Screening of environmental toxicants using the UKN2 assay for NCC migration and cytotoxicity.
• Confirmatory testing and development of an adverse outcome pathway for picoxystrobin.
• Mechanistic studies on oxygen consumption, migration inhibition, and biokinetic modeling for intracellular concentration prediction.
• Physiologically based kinetic modeling to predict brain concentrations following oral intake.

Main Results:

• Picoxystrobin specifically inhibited NCC migration and cytotoxicity in the UKN2 assay.
• Inhibition of oxygen consumption occurred at sub-µM concentrations, and migration was inhibited at 100 nM.
• Biokinetic modeling predicted brain concentrations of 0.1-1 µM at acceptable daily intake levels.
• A margin of exposure ≥ 80 was calculated, indicating a low risk.

Conclusions:

• The study provides a validated hit follow-up strategy for cell-based toxicity testing.
• The developed procedure integrates in vitro hazard data with toxicokinetic modeling for robust risk assessment.
• This approach contributes to the advancement of next-generation risk assessment methodologies.