The Liquid Crystal Monomer 3cH2B Affects the Visual System via Neural-Cell-Specific Retinoic Acid Disruption in the Optic Tectum

As a newly recognized type of emerging contaminant, liquid crystal monomers (LCMs) are widely distributed in the environment and human consumptions and their effects on visual systems and the underlying mechanisms are yet to be elucidated. Therefore, this study investigated the visual-neuro influence of 3cH2B (a frequently detected LCM) under environmentally relevant concentrations in zebrafish. The findings revealed that 40 μg/L 3cH2B induced visual behaviors after 40 days of exposure, which was accompanied by decreased retinoic acid (RA) levels and retinal structural deformation in the eyes. Simultaneously, a decline in the number of synaptic vesicles and loss of neurons were observed in the central nervous system (CNS). In addition, downregulation of RA metabolism pathways was identified in inhibitory neurons of the CNS. Spatial transcriptomic analysis showed that 3cH2B exposure reduced both the proportion of inhibitory neurons and the expression of RA-related genes in the optic tectum of the midbrain. Furthermore, RA supplementation significantly alleviated the behavioral alterations and retinal damage induced by 3cH2B, highlighting the critical role of RA in regulating these effects.