Endocrine Disruptor 2,7-Dibromocarbazole Disrupts Energy Metabolism and Alters Locomotor Behavior in Juvenile Zebrafish

Polyhalogenated carbazoles (PHCZs) are emerging environmental contaminants in aquatic ecosystems. Despite their reported endocrine-disrupting potential, the adverse effects of PHCZs on aquatic organisms and their underlying mechanisms remain poorly understood. In this study, we employed 2,7-dibromocarbazole (2,7-DBCZ) as a representative PHCZ to evaluate its detrimental effects on zebrafish and reveal the underlying mechanisms. Exposure to 2,7-DBCZ led to inhibited locomotor activity in zebrafish larvae. Mechanistically, 2,7-DBCZ significantly elevated embryonic estrogen (E₂) and triiodothyronine (T₃) levels, disrupting the normal transcription of E₂-related genes. Moreover, 2,7-DBCZ disrupted energy expenditure homeostasis by affecting energy metabolism-related metabolites, particularly carbohydrates (glucose 1-phosphate and fructose 6-phosphate) and amino acids (glutamine and serine). These findings suggest that the suppression of locomotor behavior in zebrafish larvae induced by 2,7-DBCZ could be attributed to its endocrine-disrupting potential, which triggers disturbances in energy metabolism. The data provide a comprehensive understanding of the ecological risks posed by PHCZs, supporting regulatory decisions regarding these emerging contaminants.