Adverse outcome pathway (AOP)-based approach for assessing the combined neurotoxic effects of multiple pesticides

<p>One of the challenges in the current risk assessment for chemicals is that conventional toxicity assessment systems for assessing individual chemicals cannot evaluate the risk of combined exposure to chemical mixtures. Based on the concept of adverse outcome pathway (AOP), common key events in toxic mechanisms could be used as indexes to assess the combined effects of multiple chemicals. At the last conference, we reported a novel neurotoxic mechanism in which a pyrethroid deltamethrin caused an imbalance in the proteolytic system via the activation of mitophagy and inhibition of proteasome activity. In this study, we examined the neurotoxic effects of multiple pesticides by evaluating these endpoints as key events. We exposed 10 pesticides to mouse neuroblastoma Neuro-2a cells and measured mitochondrial membrane potential and proteolytic activities. The combined effects of pesticides on cell viability were measured by wst-8 assay and analyzed by CompuSyn software. Our data showed that a pyrethroid pesticide, permethrin or deltamethrin, and a phenylpyrazole pesticide, fipronil, shared common key events, such as mitochondrial dysfunction and accumulation of p62, an autophagy substrate marker. Combined exposure to these pesticides induced a further decrease in cell viability compared to single exposure, which showed synergistic effects with a combination index < 1. These data constitute the first analysis of synergistic neurotoxicity caused by combined exposure to different pesticides relation to the common key events of AOP for neurotoxicity.</p>