Neurotoxicity and cardiotoxicity alleviation by polystyrene microplastics in cadmium sulfide-exposed zebrafish larvae

Our recent study confirmed the polystyrene microplastics (PS MPs) promote the release of Cd^2 + from cadmium sulfide (CdS) pigment under sunlight irradiation, potentially increasing environmental risk. However, despite the anticipated increase in toxicity due to Cd²⁺ release, PS MPs were found to mitigate the toxicity of CdS pigment, although the underlying mechanisms remain unclear. In this study, sunlight irradiation induced significant neurotoxicity and cardiotoxicity in zebrafish larvae exposed to CdS pigment, as evidenced by reduced spontaneous movement, decreased total locomotor distance, and elevated heart rate. Although PS MPs further promoted Cd²⁺ release from CdS pigment, co-exposure nevertheless alleviated neurotoxicity and cardiotoxicity, restoring heart rate and neurobehavioral parameters in zebrafish larvae. This protective effect was associated with PS MPs alleviating oxidative stress, as reflected by reduced reactive oxygen species (ROS) levels and increased antioxidant enzyme activities in zebrafish larvae. Consistent with these physiological changes, co-exposure restored the expression of genes involved in cardiac (tfr1a, f3b and smyd1b) and neural (dnaja1, sec24d and glula) system development. These findings highlighted the importance of understanding the interactions between PS MPs and CdS pigment, emphasizing the necessity of considering environmental realism in environmental risks assessment of co-contaminants.