Morphological, behavioral, and molecular neurotoxicity of octocrylene in zebrafish larvae

Octocrylene (OC), a prevalent ultraviolet (UV) filter in sunscreens, is frequently detected in soils, sediments, aquatic systems, and food chains, making it an emerging contaminant. Although evidence suggests OC impairs zebrafish larval development, its neurotoxic effects remain incompletely understood. In this study, zebrafish embryos were exposed to OC (0-30 μM) to assess impacts on early neurodevelopment. The results showed that exposure to 30 μM OC reduced the hatching rate of zebrafish and decreased their heart rate at 48 hpf. OC concentrations above 10 μM increased the body length of zebrafish larvae. Moreover, OC exposure significantly reduced various types of neural cells, including neural stem cells, neural progenitor cells, neurons, and glial cells, and led to behavioral abnormalities. Mechanistically, transcriptomic profiling revealed that the differentially expressed genes were mainly enriched in the process of activating apoptosis. Concentration-dependent increases in acridine orange (AO) and reactive oxygen species (ROS) staining confirmed apoptosis in brain tissues. Further analysis suggested that OC-induced neurotoxicity may be mediated by dysregulation of the MDM2-p53 signaling axis. These findings elucidate previously unrecognized mechanisms of OC neurotoxicity, providing critical insights for environmental risk assessment of UV filters.