Researcresearch On The Developmental Neurotoxocity And Related Mechanisms Of Tetrabromobisphenol S To Zebrafish

Tetrabromobisphenol S is a new type of brominated flame retardant introduced to the market as an alternative to Tetrabromobisphenol A.At the same time,there is growing recognition of the potential harm of TBBPS to human and environmental health,but data on its biosafety are limited,especially the lack of systematic studies on its development and neurotoxicity,and the impact and mechanism of action of TBBPS on the developing nervous system have not been clarified.Therefore,this paper uses zebrafish as a research model to explore the neurodevelopmental toxicity of TBPS to zebrafish and reveal its potential mechanism at the molecular level,in order to provide a reference for the safe and rational use of TBBPS.The main research contents are as follows:（1）Establish a zebrafish embryo TBBPS exposure model and conduct acute toxicity tests.The results showed that the lethal concentration(LC₅₀)of TBBPS was 5.73 mg/L,and the maximum non-lethal concentration（MNLC）was 3.47 mg/L.Low concentration of TBBBPS causes a series of adverse effects in the development process of zebrafish embryo（0-120 hpf）,which are manifested in hatching rate,decreased heart rate and blood flow activity,and decreased body length.Zebrafish embryos/larvae are able to effectively absorb and accumulate TBBBS in solution and directly affect their toxicity levels.（2）The developmental neurotoxic effect of TBBBS on zebrafish was explored by 1/9（0.386mg/L）,1/6（0.578 mg/L）and 1/3（1.156 mg/L）of embryonic MNLC.The results showed that zebrafish（0-120 hpf）exposure to TBPS may lead to craniofacial development of juvenile fish,abnormal neuroaxon development,and adverse effects on the neural behavior of embryos and larvae.Acridine orange staining found that as TBBPS exposure increased,the degree of apoptosis intensified,consistent with the test results of apoptosis-related enzymes（Caspase-3and Caspase-9）activity.（3）Zebrafish was explored by 1/9（0.386 mg/L）,1/6（0.578 mg/L）and 1/3（1.156 mg/L）of embryonic MNLC.Based on behavioral detection and gene expression analysis of circadian rhythm network,the potential nerve damage of TBBPS to zebrafish larvae and its subsequent adverse reactions were explored.The results showed that TBBPS exposure led to significant changes in the expression of key genes related to circadian rhythm:the expression of the five genes were upregulated compared with the control,and the expression of the six genes were down-regulated.Combined with Western blot analysis and fluorescence in situ hybridization results further confirmed the disruption of TBBPS on circadian rhythm networks.In addition to this,the circadian-driven motor behavior changed significantly.（4）Zebrafish was explored by 1/9（0.386 mg/L）,1/6（0.578 mg/L）and 1/3（1.156 mg/L）of embryonic MNLC.Through transcriptome sequencing analysis,the molecular mechanism of TBBPS exposure to neurodevelopmental toxicity to zebrafish is elucidated from the gene level.Bioinformatics analysis of neurologically relevant genes found that these genes are involved in the biological processes of multiple neurotransmitter systems.The neurotransmitter level test results showed that the content of GABA and its receptors in the neurotransmitter decreased significantly,which was consistent with the change of the down-regulation result of its genes.Taken together,our findings suggest that TBBPS causes abnormal morphology and neuronal development in zebrafish larvae,inducing developmental neurotoxicity in zebrafish by disrupting the neurotransmitter system and circadian network.