Responses of zebrafish to phthalate exposure and recovery: Insights into transcriptome-based molecular mechanisms

Phthalate acid esters (PAEs), widely used as plasticizers, are frequently detected in the environments and are known to exert toxic effects on aquatic organisms. However, whether these effects are recoverable after exposure-and the mechanisms underlying any recovery-remains poorly understood, limiting accurate risk assessment for these toxicants. In this study, zebrafish were exposed to three representative PAEs-dimethyl phthalate (DMP), dibutyl phthalate (DBP), and di-n-octyl phthalate (DNOP)-for 4 days, followed by a 7-day recovery in PAEs-free water. By combining accumulation assessment, survival analysis, and transcriptomic sequencing, we investigated the molecular mechanisms underlying these toxic effects and recovery. All three PAEs were detected in zebrafish during exposure and recovery periods. While no changes were observed in survival, transcriptomic sequencing revealed distinct molecular patterns: DMP interfered with PPAR signaling and tryptophan metabolism, leading to lipid dysregulation, neurotransmitter imbalance, and oxidative stress. DBP influenced glutathione metabolism, reducing antioxidant and detoxification capacity. DNOP suppressed the expressions of genes related to cell cycle and DNA replication, inhibiting cell proliferation and tissue repair. After 7-day recovery, PAE residues were still at high levels, and molecular alterations were aggravated: tryptophan metabolism was further inhibited in the DMP exposure, glutathione pathway remained downregulated under DBP, and DNOP-induced cell cycle arrest became more severe. Our results suggest that PAE exposures can induce persistent and compound-specific transcriptomic toxicity in zebrafish, even after toxicant removal. These findings highlight the importance of including post-exposure periods in future toxicological studies and provide molecular insights for improving environmental risk assessments for PAEs.