Trichlorocarban induces developmental and immune toxicity to zebrafish (Danio rerio) by targeting TLR4/MyD88/NF-κB signaling pathway

Trichlorocarban (TCC) is ubiquitously detected in environmental matrices, while there is a paucity of information regarding its systemic toxicity. In the present study, we observed that TCC exposure led to high embryo mortality, delayed hatching and yolk absorption, as well as increased malformations, such as closure of swim sac and yolk sac edema. Meanwhile, TCC affected the formation and branch of sub-intestinal veins (SIVs), intersegmental vessels and posterior cardinal veins. Especially, the SIVs were shrunk, and their branches were reduced or even broken along with reduced coverage area. TCC-induced oxidative stress and excessive apoptosis resulted from abnormal expression of the anti/pro-apoptotic genes. Significant reduction in the number and aggregation function of immune cells proved that TCC had prominent immunotoxicity to zebrafish. TCC-targeted TLR4 signaling pathway was demonstrated by abnormal expression of the marker genes (tlr4, MyD88 and nf-kappa b) and release of the downstream inflammatory factors (TNF-alpha, IL-6, etc.). Inhibition of TLR4/MyD88/NF-kappa B pathway by an inhibitor (CA-4948) rescued the decreasing trend of the immune cells induced by TCC. Molecular docking results demonstrated that TCC could stably bind to TLR4 receptor to form hydrogen bonds and hydrophobic interactions with amino acids. Overall, these findings reveal the underlying molecular mechanisms on TCC-induced developmental and immune toxicity to zebrafish. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Exposure to TCC results in high embryonic toxicity and immunotoxicity in zebrafish, characterized by abnormal vascular development, increased oxidative stress and apoptosis, as well as reduction in immune cell number and function. The TCC-induced effects are mediated through the TLR4 signaling pathway, which can be rescued by inhibition of TLR4/MyD88/NF-kappa B pathway. Molecular docking studies show stable binding of TCC to TLR4 receptor.