Zebrafish (Danio rerio) Reproduction Is Affected by Life-Cycle Exposure to Differently Charged Polystyrene Nanoplastics with Sex-Specific Responses

While nanoplastics (NPs) are distributed ubiquitously in the environment, limited information is available for assessing the effects of different charges on their surfaces on the reproduction of aquatic vertebrates, especially at environmentally realistic concentrations. In this study, starting with embryos, zebrafish (Danio rerio) were exposed to 10 μg/L polystyrene (PS, no charge), PS–NH2 (positive charge), or PS-COOH (negative charge) nanoplastics during a full life cycle (120 days) and their effects on reproductive performances, sex hormones, and expression of genes associated with steroidogenic pathways were investigated. Alterations of vitellogenin (VTG) and DNA methylation, as well as the development of offspring (F1) without subsequent chemical exposure, were further examined. The fecundity of females was significantly decreased by exposure to 10 μg/L PS or PS-COOH. In females, testosterone content was significantly higher along with down-regulation of cyp19a1a upon treatment with differently charged PS. The significant decrease of 11-ketotestosterone (11-KT) in male plasma reduced the proportion of mature spermatocytes in the testis. Parental exposure to differently charged PS resulted in the abnormal development of F1 in clean water. Comprehensive analysis showed that life-cycle exposure of zebrafish to differently charged PS affects reproductive performance in a sex-specific manner and impairs the development of F1. This study provides a theoretical foundation for risk management measures of differently charged nanoplastics.