Halobenzoquinone-Induced Developmental Toxicity, Oxidative Stress, and Apoptosis in Zebrafish Embryos

The developmental toxicity of water disinfection byproducts remains unclear. Here we report the study of halobenzoquinone (HBQ)-induced in vivo developmental toxicity and oxidative stress using zebrafish embryos as a model. Embryos were exposed to 0.5-10 μM of individual HBQs and 0.5-5 mM haloacetic acids for up to 120 h postfertilization (hpf). LC₅₀ values of the HBQs at 24 hpf were 4.6-9.8 μM, while those of three haloacetic acids were up to 200 times higher at 1900-2600 μM. HBQ exposure resulted in significant developmental malformations in larvae, including failed inflation of the gas bladder, heart malformations, and curved spines. An increase in reactive oxygen species was observed, together with a decrease in superoxide dismutase activity and glutathione content. Additionally, the antioxidant N-acetyl-l-cysteine significantly mitigated all HBQ-induced effects, supporting that oxidative stress contributes to HBQ toxicity. Further experiments examined HBQ-induced effects on DNA and genes. HBQ exposure increased 8-hydroxydeoxyguanosine levels, DNA fragmentation, and apoptosis in larvae, with apoptosis induction related to changes in the gene expression of p53 and mdm2. These results suggest that HBQs are acutely toxic, causing oxidative damage and developmental toxicity to zebrafish larvae.