Neural System Impairment and Involved Microglia-Neuron Regulation of Broflanilide in Zebrafish Larvae

Ecotoxicological risk assessment of the novel psychoactive substance Esketamine: Emphasis on fish skeletal, behavioral, and vascular development

Novel psychoactive substances (NPS), such as Esketamine (Esket), often contaminate the aquatic ecosystems following human consumption, raising concerns about the residues and potential ecological hazards to non-target organisms. The study used zebrafish as a model organism to investigate the developmental toxicity and ecotoxicological effects of acute Esket exposure. Our findings demonstrate that exposure to Esket significantly affected the early development and angiogenesis of zebrafish embryos/larvae. The mandible length was significantly decreased, and the angles between the pharyngeal arch cartilages were narrowed compared to the control group (all P < 0.05). Additionally, Esket resulted in a decrease of 47.6-89.8 % in the number of neural crest cells (NCC). Transcriptome analysis indicated altered expression of genes associated with cartilage and osteoblast growth. Moreover, Esket significantly inhibited swimming ability in zebrafish larvae and was accompanied by behavioral abnormalities and molecular alterations in the brain. Potential mechanisms underlying Esket-induced behavioral disorders involve neurotransmitter system impairment, abnormal cartilage development and function, aberrant vascular development, as well as perturbations in oxidative stress and apoptosis signaling pathways. Notably, the dysregulation of skeleton development through the bone morphogenetic protein (BMP) signaling pathway is identified as the primary mechanistic behind Esket-induced behavioral disorder. This study enhances our understanding of Esket's ecotoxicology profile and provides a comprehensive assessment of the environmental risks associated with NPS.

Post-fertilization 2-ethylhexyl-4-methoxycinnamate (EHMC) exposure affects axonal growth, muscle fiber length, and motor behavior in zebrafish embryos

Organic UV filters, which are often found in the environment, have been the focus of much public health concern. 2-ethylhexyl-4-methoxycinnamate (EHMC) is one of the most common organic UV filters present in the environment. However, few studies have investigated its developmental neurotoxic (DNT) effects and the underlying molecular mechanisms. In the present study, zebrafish embryos were exposed to low concentration of EHMC (0, 0.01, 0.1, 1 mg/L) in static water starting from 6 h post-fertilization (hpf). Results showed that EHMC exposure caused a reduction in somite count at 13 hpf, a diminishment in head-trunk angle at 30 hpf, a delay in hatching at 48 hpf, and a decrease in head depth and head length at both 30 and 48 hpf. Additionally, EHMC led to abnormal motor behaviors at various developmental stages including altered spontaneous movement at both 23 and 24 hpf, and decreased touch response at 30 hpf. Consistent with these morphological changes and motor behavior deficits, EHMC inhibited axonal growth of primary motor neurons at 30 and 48 hpf, and yielded subtle changes in muscle fiber length at 48 hpf, suggesting the functional relevance of structural changes. Moreover, EHMC exposure induced excessive cell apoptosis in the head and spinal cord regions, increased the production of reactive oxygen species (ROS) and malondialdehyde (MDA), and reduced the level of glutathione (GSH). Defects of lateral line system neuromasts were also observed, but no structural deformity of blood vessels was seen in developing zebrafish. Abnormal expression of axonal growth-related genes (gap43, mbp, shha, and α1-tubulin) and apoptosis-related genes (bax/bcl-2 and caspase-3) revealed potential molecular mechanisms regarding the defective motor behaviors and aberrant phenotype. In summary, our findings indicate that EHMC induced developmental neurotoxicity in zebrafish, making it essential to assess its risks and provide warnings regarding EHMC exposure.