Ferroptosis involvement in the neurotoxicity of flunitrazepam in zebrafish

Study on the alleviation of reactive oxygen species-mediated flunitrazepam toxicity in zebrafish (Danio rerio) by vitamin C and its mechanism

The frequent detection of psychoactive drugs in aquatic environments has caused various toxic effects on aquatic organisms, highlighting the urgent need to explore remediation methods and mechanisms. Against the backdrop of toxicity induced by the typical benzodiazepine (BZD) flunitrazepam (FLZ) in zebrafish, this study evaluates the mitigating effects of vitamin C (VC) on FLZ-induced embryonic developmental toxicity, larval behavioral anomalies, apoptosis, oxidative stress, and mitochondrial dysfunction at environmentally relevant concentrations through reactive oxygen species (ROS)-mediated pathways. Furthermore, molecular dynamics simulations were utilized to decipher the mechanism underlying ROS inhibition. Results demonstrated that co-exposure to 0.5 μg/L VC with FLZ (0.05 μg/L and 0.2 μg/L) significantly elevated the hatching rate of zebrafish embryos at 72 hpf and decreased the larval malformation rate at 96 hpf. In terms of physiological and biochemical indicators, VC significantly inhibited the FLZ-induced increase in ROS and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels. VC also upregulated the activity of mitochondrial uncoupling protein 2 (UCP2), a key regulator of ROS production. Molecular docking and dynamics simulations revealed that VC competitively binds to the LYS 38 and LYS 240 sites of UCP2, destabilizing FLZ-UCP2 interactions via steric hindrance and hydrogen bond competition. With the restoration of UCP2 activity, its proton leak function was enhanced, suppressing excessive ROS generation. Consequently, uqcr2b, cox4i1l, and atp5g3b were normalized, restoring ATP synthesis capacity and significantly alleviating FLZ-induced mitochondrial dysfunction. This study elucidates the mechanism by which VC counteracts ROS-mediated FLZ toxicity, providing critical insights for assessing environmental risks and formulating protective strategies against pollutants.

Developmental neurotoxicity of anesthetic etomidate in zebrafish larvae: Alterations in motor function, neurotransmitter signaling, and lipid metabolism

Etomidate (ETO), a widely used anesthetic, has emerged as a concerning environmental contaminant due to its increasing misuse and demonstrated neurotoxicity in aquatic organisms. This study employed an integrated multi-omics strategy to investigate the developmental neurotoxic effects of ETO in zebrafish (Danio rerio). ETO exposure induced dose-dependent toxicity in zebrafish embryos, characterized by decreased hatching rates (10-20 %), elevated mortality (up to 30 %), and morphological abnormalities such as scoliosis and pericardial edema. Behavioral assays revealed marked locomotor suppression (40-65 % reduction) and disrupted circadian rhythmicity. Neurochemical profiling indicated a 2.1-fold increase in dopamine levels, accompanied by significant reductions in GABAergic (38 %) and serotonergic (42 %) signaling, consistent with transcriptomic downregulation of related pathway genes. Metabolomic analysis revealed dysregulated lipid metabolism, including a 3.2-fold increase in eicosapentaenoic acid (EPA), and perturbations in phenylalanine metabolism. Transgenic zebrafish models (Tg(hb9:eGFP), Tg(coro1a:DsRed), Tg(elavl3:GCaMP6f)) further demonstrated motor neuron damage, inflammatory cell infiltration in the brain, and disrupted Ca2 + dynamics, indicating blood-brain barrier disruption and neuroinflammation responses. Molecular docking analysis confirmed ETO's binding affinity for GABA-A receptors, aligning with observed neurotransmitter imbalances. These findings elucidate ETO's neurotoxic mechanisms, involving neurotransmitter imbalance, metabolic disruption, and neuroinflammatory. The results underscore the dual threat of ETO as both an emerging aquatic pollutant and a developmental neurotoxicant, highlighting the urgent need for stricter environmental monitoring and a reevaluation of its safety profile, particularly during critical developmental windows.