Emerging contaminant 1,3,6,8-tetrabromocarbazole induces oxidative damage and apoptosis during the embryonic development of zebrafish (Danio rerio)

Abstract

Since polyhalogenated carbazoles (PHCs) have been widely detected at high concentrations in multiple environmental media in recent years, the health risk of exposure to these compounds has drawn increasing attention. Most studies have mainly focused on their dioxin-like toxicity, which is induced through the AhR pathway, because PHCs have structures similar to those of polychlorinated dibenzofurans (PCDFs). In addition, most xenobiotic compounds induce oxidative stress in organisms, which is a more common mechanism of toxicity induction. However, there is limited information regarding the oxidative stress and damage induced by PHCs in vivo. The PHC 1,3,6,8-tetrabromocarbazole (1368-TBCZ) is detected at high concentration and frequency. In the present study, the toxic effects (acute toxicity, developmental toxicity, oxidative stress, and apoptosis) induced by 1368-TBCZ at three different concentrations were investigated using zebrafish embryos. It was concluded that the 96 h median lethal concentration (LC50) of 1368-TBCZ for zebrafish embryos was greater than 2.0 mg L−1. The results showed that 1368-TBCZ had little effect on the hatching rate of zebrafish embryos. However, 1368-TBCZ at 0.5 and 2.0 mg L−1 inhibited skeletal and cardiac development. It promoted ROS production, CAT enzyme activity, lipid peroxidation, DNA damage, and apoptosis, even at the lowest dose (0.1 mg L−1). In addition, 1368-TBCZ influenced oxidative stress-related gene expression, upregulating the expression of caspase 3 and p53 at 2.0 mg L−1 and inhibiting the expression of caspase 9, FoxO3b, and Bcl-2/Bax. The present study comprehensively evaluated 1368-TBCZ-induced toxicity in zebrafish, providing valuable data for better evaluation of the potential risks posed by this PHC.