Mechanism-Driven Risk Assessment of 1,3,6-Tribromocarbazole: An Integrated Strategy Implicates ESR1-Associated Cardiovascular Toxicity

Abstract

Polyhalogenated carbazoles (PHCZs) are globally distributed emerging persistent organic pollutants, yet their cardiovascular hazards remain largely uncharacterized. We therefore built an adverse outcome pathway (AOP)-guided prediction-to-validation strategy─coupling environmental occurrence mining, feature-assisted network toxicology, and zebrafish testing─for 1,3,6-tribromocarbazole (1,3,6-BCZ), one of the most frequently detected congeners. Compiled data from 24 sites on three continents confirmed multimedia contamination (water, 0.3–2.69 ng/L; sediment, 0.09–3.45 ng/g) and framed a multiconcentration design anchored by measured aqueous concentrations (up to 43.60 μg/L) and larval body burdens. LASSO/SVM-RFE prioritization of the chemical–target network nominated estrogen receptor 1 (ESR1) as the candidate molecular initiating event, supported by docking (−7.61 kcal/mol) to a ligand-binding domain conserved between human and zebrafish. Sublethal exposure impaired angiogenic sprouting, enlarged the common cardinal vein, reduced subintestinal vessel area, and produced pericardial edema. Transcriptomics and network prediction converged on 18 shared pathways, notably NF-κB signaling and endothelial junctions; ESR1 expression fell while NF-κB subunits, proinflammatory genes, neutrophil infiltration, and oxidative stress rose. 17β-Estradiol cotreatment partially reversed these responses, supporting ESR1-associated, NF-κB-linked cardiovascular injury and providing a transferable framework for data-poor halogenated contaminants.