Work

Disruption of surfactant homeostasis leads to impaired inflation of zebrafish posterior swim bladder by non-dioxin-like PCB40

Year: 2025

Type: article

Abstract: Detected in various environmental matrices and organisms, polychlorinated biphenyls (PCBs) pose a significant threat to animal health. PCBs are categorized into two groups, dioxin-like (DL) and non-DL (NDL), based on their structure and toxicity. While the toxic effects and mechanisms of DL-PCBs are well-documented, the effects of NDL-PCBs are less studied. Moreover, the effects of PCBs on the swim bladder, a gas-filled organ crucial for buoyancy in fish, are not well understood. In this study, zebrafish embryos were subjected to continuous exposure to nine NDL-PCBs. Among these, 2,2′,3,3′-tetrachlorobiphenyl (PCB40) caused significant defects in zebrafish swim bladder inflation at 120 h post-fertilization (hpf). To elucidate the deeper effects and mechanisms of PCB40 toxicity on the swim bladder, we exposed zebrafish embryos to 2.5 μM, 5 μM, and 10 μM PCB40 using the same method. We observed that PCB40 did not induce any significant changes in hatching rates or survival rates across the three exposure concentrations. However, embryos exposed to 5 μM and 10 μM PCB40 exhibited a high incidence of uninflated swim bladders, along with a marked reduction in the swim bladder size. PCB40 down-regulated the mRNA levels of swim bladder marker genes, including pbx1a , fgf10a , acta2 , and anxa5b , but the tissue layers showed no observable defects. Given that surfactant, composed of lipids and proteins, is essential for swim bladder expansion, we investigated its status. Oil Red O staining demonstrated that PCB40 disrupted surfactant lipid distribution, and levels of surfactant proteins were decreased in comparison to the control. These results indicate that PCB40 impairs zebrafish swim bladder inflation in zebrafish through disruption of the surfactant system. Our data provide new evidence regardingthe toxicity of NDL-PCBs and enhance the overall understanding of the toxicities of PCBs. • Exposure to the non-doxin-like PCB40 impaired posterior swim bladder inflation and compromised its function in zebrafish. • PCB40 down-regulated the transcriptional levels of swim bladder marker genes, as shown by qRT-PCR and WISH. • PCB40 did not affect the formation of swim bladder tissue layers and pneumatic duct. • PCB40 disrupted surfactant-lipid metabolism in the swim bladder and markedly down-regulated surfactant proteins.

Source: Environmental Chemistry and Ecotoxicology

DOI: 10.1016/j.enceco.2025.10.008