Triclosan induces cardiac malformations via an estrogen receptor-ERK-mitochondrial apoptotic signaling axis in zebrafish embryos.

Triclosan (TCS), a widely used antimicrobial agent, is persistently detected in aquatic environments (up to 1.14 μM in pore water) and human matrices, raising concerns about its developmental toxicity. However, the molecular mechanisms underlying TCS-induced cardiac malformations remain largely unresolved. Here, we report that exposure of zebrafish embryos to TCS at concentrations including environmentally relevant levels (62.5 nM to 1 μM) induced cardiac morphological abnormalities and cardiomyocyte apoptosis, accompanied by transcriptomic alterations in genes associated with cardiac development and apoptosis. Mechanistic investigations revealed that TCS activated ERα and the membrane estrogen receptor GPER, resulting in sustained ERK1/2 phosphorylation. Pharmacological blockade of ER or ERK signaling, as well as genetic knockdown of esr1/esr2a, effectively rescued TCS-induced cardiac malformations and apoptotic responses, supporting the involvement of ER-ERK signaling in TCS-associated cardiac abnormalities. Notably, ER-ERK activation triggered profound mitochondrial dysfunction, characterized by excessive mitochondrial ROS generation, dissipation of mitochondrial membrane potential, and ultrastructural mitochondrial damage, ultimately leading to cleaved-caspase-3-dependent apoptosis. The mitochondrial-targeted antioxidant MitoQ significantly alleviated ROS generation, mitochondrial injury, and cardiac defects. Furthermore, molecular docking analysis supported strong binding affinities between TCS and key components of the ER-ERK signaling axis, suggesting potential molecular interactions. Overall, this study identifies a previously unrecognized ER-ERK-mitochondrial apoptotic pathway as a central mechanism driving TCS-induced cardiac developmental toxicity, providing mechanistic insight into the cardiovascular developmental risks posed by environmental endocrine disruptors.