Insights into the disinfection byproduct bromochloroacetamide-induced cardiotoxicity of zebrafish embryo-larvae: A multiomics approach and comparison of biomarker responsiveness.

Bromochloroacetamide (BCAcAm), an inevitable byproduct of the water treatment disinfection process, is widely detected in drinking water. Previous toxicological and in silico results suggested that developmental effects are associated with analogous chemical exposure; however, the key molecular events and underlying mechanisms remain unclear, especially in the early stages of aquatic organisms. In the present study, a zebrafish larval model was used to comprehensively assess the developmental toxicity of BCAcAm via transcriptional, metabolic, biochemical and morphological tests. Integration analyses of RNA sequencing and untargeted metabolomic data revealed crucial biological processes related to drug metabolism, cardiac muscle contraction and oxidative phosphorylation, which started from the initial stage, and ferroptosis progressed to the advanced stage in validated cardiac defects. Biochemical assays further verified ATP depletion, ROS and MDA accumulation, and hyperactivation of detoxification (increased GST activity) and the antioxidative system (increased GSH and GSSG levels). Transcriptionally, BCAcAm led to gpx4 downregulation, iron homeostasis perturbation (upregulated tfr and tf and downregulated fth) and lipid peroxidation (elevated alox12 and lpcat3), suggesting the involvement of ferroptosis. Moreover, the application of Fer-1 (a ferroptosis inhibitor) reversed BCAcAm-induced mitochondrial dysfunction and subsequent cardiotoxicity. In addition, the BMD and IBRv2 indices were derived from molecules across various biological levels. The general ranking of the different biomarkers in terms of better responsiveness and sensitivity performance is as follows: transcriptomics > metabolomics > biochemical assays. In the present study, an approach to detecting chemical-induced adverse outcomes and deciphering the underlying mechanisms through high-throughput data analysis is applied. This study provides valuable insights into the responsiveness and sensitivity of biomarkers, which may be instrumental for evaluating the ecological and health risks associated with newly emerged contaminants.