A potential mechanism of triclosan-induced neurotoxicity in zebrafish at environmental Concentrations: Splicing disruption of tecra mediates the circRNA266/miR-214/dapk2-gad2 axis

Abstract

Many environmental pollutants are known to exhibit neurotoxic effects; however, the initiating molecular events and their associated adverse outcome pathways (AOPs) remain largely unclear. This study investigated the role of circRNA266 and its target miRNA in Triclosan (TCS)-induced neurodevelopmental toxicity in zebrafish (Danio rerio) based on candidates circRNAs identified via high-throughput sequencing. Toxicological effects were characterized at multiple levels, including phenotype alterations, motor behavior, neural damage, and the expression of marker genes. TCS exposure was found to upregulate circRNA266, thereby reducing the availability of free miR-214. As a crucial neuroprotective factor, miR-214 downregulation was associated with increased expression of dapk2 and gad2, resulting in elevated inhibitory neurotransmitter levels and neuronal apoptosis. Furthermore, molecular docking analysis suggests that the upregulation of circRNA266 by TCS may occur via its interaction with U2AF1, thereby disrupting the splicing of the tecra gene. While high concentrations of TCS caused marked neurotoxic phenotypes and behavioral impairments, environmentally relevant concentrations did not elicit overt symptoms. Nonetheless, the activation of key molecular events within the AOP framework suggests a potential neurotoxic risk even at low exposure levels. This study is the first to confirm that TCS induces neurotoxicity in zebrafish by interfering with the splicing of the tecra gene and mediating the regulatory role of the circRNA266/miR-214/dapk2-gad2 signaling axis. These findings provide novel insights into the molecular mechanisms of TCS-induced neurotoxicity and propose a potential new AOP model for environmental risk assessment.