Olfactory toxicity of tetrabromobisphenol A to the goldfish Carassius auratus

Tetrabromobisphenol A (TBBPA) is one of the most extensively used brominated flame retardants and its increasing use in consumer products has raised concerns about its ecotoxicity. Given the ubiquity of TBBPA in aquatic environments, it is inevitable that these chemicals will enter the olfactory chambers of fish via water currents. Nevertheless, the olfactory toxicity of TBBPA to aquatic organisms and the underlying toxic mechanisms have yet to be elucidated. Therefore, we investigated the olfactory toxicity of TBBPA in the goldfish Carassius auratus, a model organism widely used in sensory biology. Results showed that exposure to TBBPA resulted in abnormal olfactory-mediated behaviors and diminished electro-olfactogram (EOG) responses, indicating reduced olfactory acuity. To uncover the underlying mechanisms of action, we examined the structural integrity of the olfactory epithelium (OE), expression levels of olfactory G protein-coupled receptors (GPCRs), enzymatic activities of ion transporters, and fluctuations in neurotransmitters. Additionally, comparative transcriptomic analysis was employed to investigate the molecular mechanisms further. Our study demonstrates for the first time that TBBPA at environmentally relevant levels can adversely affect the olfactory sensitivity of aquatic organisms by interfering with the transmission of aqueous stimuli to olfactory receptors, impeding the binding of odorants to their receptors, disrupting the olfactory signal transduction pathway, and ultimately affecting the generation of action potentials.